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Structural Damage (structural + damage)
Terms modified by Structural Damage Selected AbstractsNanoparticles: Investigations on the Structural Damage in Human Erythrocytes Exposed to Silver, Gold, and Platinum Nanoparticles (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 8 2010Mater. [source] Investigations on the Structural Damage in Human Erythrocytes Exposed to Silver, Gold, and Platinum NanoparticlesADVANCED FUNCTIONAL MATERIALS, Issue 8 2010P. V. Asharani Abstract Human erythrocytes or red blood cells (RBCs), which constitute 99% of blood cells, perform an important function of oxygen transport and can be exposed to nanoparticles (NPs) entering into the human body during therapeutical applications involving such NPs. Hence, the haemocompatibility of the Ag, Au, and Pt NPs on human RBCs is investigated. The parameters monitored include haemolysis, haemagglutination, erythrocyte sedimentation rate, membrane topography, and lipid peroxidation. The findings suggest that platinum and gold NPs are haemocompatible compared to Ag NPs. Erythrocytes exhibit significant lysis, haemagglutination, membrane damage, detrimental morphological variation, and cytoskeletal distortions following exposure to Ag NPs at a concentration of 100,µg,mL,1. Exposure of Ag+ to RBCs shows no lysis or deterioration, implying that the observed toxicity is solely due to NPs. The haemolyzed erythrocyte fraction has the ability to induce DNA damage in nucleated cells. Additionally, multiple pits and depressions are observed on RBC membrane following exposure to Ag NPs (50,µg,mL,1 onwards). Hence, it is apparent that Ag NPs exhibit toxicity on RBCs and on other cells that are exposed to NP-mediated haemolyzed fractions. [source] Expected loss-based alarm threshold set for earthquake early warning systemsEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 9 2007Iunio Iervolino Abstract Earthquake early warning systems (EEWS) seem to have potential as tools for real-time seismic risk management and mitigation. In fact, although the evacuation of buildings requires warning time not available in many urbanized areas threatened by seismic hazard, they may still be used for the real-time protection of critical facilities using automatic systems in order to reduce the losses subsequent to a catastrophic event. This is possible due to the real-time seismology, which consists of methods and procedures for the rapid estimation of earthquake features, as magnitude and location, based on measurements made on the first seconds of the P -waves. An earthquake engineering application of earthquake early warning (EEW) may be intended as a system able to issue the alarm, if some recorded parameter exceeds a given threshold, to activate risk mitigation actions before the quake strikes at a site of interest. Feasibility analysis and design of such EEWS require the assessment of the expected loss reduction due to the security action and set of the alarm threshold. In this paper a procedure to carry out these tasks in the performance-based earthquake engineering probabilistic framework is proposed. A merely illustrative example refers to a simple structure assumed to be a classroom. Structural damage and non-structural collapses are considered; the security action is to shelter occupants below the desks. The cost due to a false alarm is assumed to be related to the interruption of didactic activities. Results show how the comparison of the expected losses, for the alarm-issuance and non-issuance cases, allows setting the alarm threshold on a quantitative and consistent basis, and how it may be a tool for the design of engineering applications of EEW. Copyright © 2007 John Wiley & Sons, Ltd. [source] Comparative response analysis of conventional and innovative seismic protection strategiesEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 5 2002S. Bruno Abstract The paper presents a numerical investigation aimed at evaluating the improvements achievable through devices for passive seismic protection of buildings based on the use of shape memory alloys (SMA) in place of conventional steel or rubber devices. To get some generality in the results, different resisting reinforced concrete plane frames were analysed, either protected or not. ,New' and ,existing' buildings were considered depending on whether seismic provisions are adopted in the building design or not. Base isolation and energy dissipation were equally addressed for both conventional and innovative SMA-based devices. Fragility analyses were performed using specific damage measures to account for comparisons among different damage types; the results were then used to estimate quantitatively the effectiveness of the various protection systems. More specifically, the assessment involved a direct comparison of the damage reduction provided by each protection system with respect to the severe degradation experienced by the corresponding non-protected frame. Structural damage, non-structural damage and damage to contents were used on purpose and included in a subsequent phase of cost analysis to evaluate the expected gains also in terms of economic benefits and life loss prevention. The results indicate that base isolation, when applicable, provides higher degrees of safety than energy dissipation does; moreover, the use of SMA-based devices generally brings about better performances, also in consideration of the reduced functional and maintenance requirements. Copyright © 2002 John Wiley & Sons, Ltd. [source] Indian Ocean tsunamis: environmental and socio-economic impacts in Langkawi, MalaysiaTHE GEOGRAPHICAL JOURNAL, Issue 2 2007MICHAEL BIRD We report the results of a study of the physical characteristics and socio-economic impacts of the Indian Ocean Tsunami of 26 December 2004 on the tourist island of Langkawi, Malaysia. In comparison with many other locations struck by the tsunami, the immediate physical and socio-economic impacts in Langkawi were relatively minor. A detailed survey of the watermark and ground elevations was undertaken in the worst affected area between Sungei Kuala Teriang and Sungei Kuala Melaka. Here, the tsunami reached a maximum elevation of 4.29 m as it crossed the coast, with a maximum flow depth of 2.0 m and a very consistent run-up elevation relative to mean sea level of 300 ± 10 cm. The tsunami inundated inshore areas for 300 m and penetrated inland along creeks for 500,1000 m. Structural damage to buildings was confined to within 50,150 m of the shoreline where about 10% of the houses were completely destroyed and 60,70% suffered significant structural damage. Damage was particularly severe in areas where there was no engineered coastal protection, but while coastal revetments did provide enhanced protection for houses at the waterfront, the coastline in the study area appeared to be more heavily impacted than elsewhere in Langkawi because wave energy was focused on the area by offshore breakwaters built to protect the Langkawi port and airport. Emergency response after the tsunami was rapid and efficient but would have been improved if the local police station had not been rendered inoperative by the first wave, and if a mechanism had been in place to ensure that informal advance warnings transmitted between Phuket (Thailand), Langkawi and Penang (Malaysia) by tourist operators could have been more widely disseminated. [source] Numerical Treatment of Seismic Accelerograms and of Inelastic Seismic Structural Responses Using Harmonic WaveletsCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 4 2007Pol D. Spanos The effectiveness of the harmonic wavelets for capturing the temporal evolution of the frequency content of strong ground motions is demonstrated. In this regard, a detailed study of important earthquake accelerograms is undertaken and smooth joint time-frequency spectra are provided for two near-field and two far-field records; inherent in this analysis is the concept of the mean instantaneous frequency. Furthermore, as a paradigm of usefulness for aseismic structural purposes, a similar analysis is conducted for the response of a 20-story steel frame benchmark building considering one of the four accelerograms scaled by appropriate factors as the excitation to simulate undamaged and severely damaged conditions for the structure. The resulting joint time-frequency representation of the response time histories captures the influence of nonlinearity on the variation of the effective natural frequencies of a structural system during the evolution of a seismic event. In this context, the potential of the harmonic wavelet transform as a detection tool for global structural damage is explored in conjunction with the concept of monitoring the mean instantaneous frequency of records of critical structural responses. [source] Output-only structural identification in time domain: Numerical and experimental studiesEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 4 2008M. J. Perry Abstract By identifying changes in stiffness parameters, structural damage can be detected and monitored. Although considerable progress has been made in this research area, many challenges remain in achieving robust structural identification based on incomplete and noisy measurement signals. The identification task is made even more difficult if measurement of input force is to be eliminated. To this end, an output-only structural identification strategy is proposed to identify unknown stiffness and damping parameters. A non-classical approach based on genetic algorithms (GAs) is adopted. The proposed strategy makes use of the recently developed GA-based method of search space reduction, which has shown to be able to accurately and reliably identify structural parameters from measured input and output signals. By modifying the numerical integration scheme, input can be computed as the parameter identification task is in progress, thereby eliminating the need to measure forces. Numerical and experimental results demonstrate the power of the strategy in accurate and efficient identification of structural parameters and damage using only incomplete acceleration measurements. Copyright © 2007 John Wiley & Sons, Ltd. [source] Structural damage detection using the optimal weights of the approximating artificial neural networksEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 2 2002Shih-Lin Hung Abstract This work presents a novel neural network-based approach to detect structural damage. The proposed approach comprises two steps. The first step, system identification, involves using neural system identification networks (NSINs) to identify the undamaged and damaged states of a structural system. The partial derivatives of the outputs with respect to the inputs of the NSIN, which identifies the system in a certain undamaged or damaged state, have a negligible variation with different system errors. This loosely defined unique property enables these partial derivatives to quantitatively indicate system damage from the model parameters. The second step, structural damage detection, involves using the neural damage detection network (NDDN) to detect the location and extent of the structural damage. The input to the NDDN is taken as the aforementioned partial derivatives of NSIN, and the output of the NDDN identifies the damage level for each member in the structure. Moreover, SDOF and MDOF examples are presented to demonstrate the feasibility of using the proposed method for damage detection of linear structures. Copyright © 2001 John Wiley & Sons, Ltd. [source] Feasibility of using impedance-based damage assessment for pipeline structuresEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 10 2001Gyuhae Park Abstract This paper presents the feasibility of using an impedance-based health monitoring technique in monitoring a critical civil facility. The objective of this research is to utilize the capability of the impedance method in identifying structural damage in those areas where a very quick condition monitoring is urgently needed, such as in a post-earthquake analysis of a pipeline system. The basic principle behind this technique is to utilize high-frequency structural excitation (typically greater than 30 kHz) through surface-bonded piezoelectric sensors/actuators to detect changes in structural point impedance due to the presence of damage. Real-time damage detection in pipes connected by bolted joints was investigated, and the capability of the impedance method in tracking and monitoring the integrity of the typical civil facility has been demonstrated. Data collected from the tests illustrates the capability of this technology to detect imminent damage under normal operating conditions and immediately after a natural disaster. Copyright © 2001 John Wiley & Sons, Ltd. [source] A preliminary prediction of seismic damage-based degradation in RC structuresEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 7 2001Vinay K. Gupta Abstract Estimation of structural damage from a known increase in the fundamental period of a structure after an earthquake or prediction of degradation of stiffness and strength for a known damage requires reliable correlations between these response functionals. This study proposes a modified Clough,Johnston single-degree-of-freedom oscillator to establish these correlations in the case of a simple elasto-plastic oscillator. It is assumed that the proposed oscillator closely models the response of a given multi-degree-of-freedom system in its fundamental mode throughout the duration of the excitation. The proposed model considers the yield displacement level and ductility supply ratio-related parameter as two input parameters which must be estimated over a narrow range of ductility supply ratio from a frequency degradation curve. This curve is to be identified from a set of recorded excitation and response time-histories. Useful correlations of strength and stiffness degradation with damage have been obtained wherein a simple damage index based on maximum and yield displacements and ductility supply ratio has been considered. As an application, the proposed model has been used to demonstrate that ignoring the effects of aftershocks in the case of impulsive ground motions may lead to unsafe designs. Copyright © 2001 John Wiley & Sons, Ltd. [source] Single-step purification of the recombinant green fluorescent protein from intact Escherichia coli cells using preparative PAGEELECTROPHORESIS, Issue 17 2009Few Ne Chew Abstract Mechanical and non-mechanical breakages of bacterial cells are usually the preliminary steps in intracellular protein purification. In this study, the recombinant green fluorescent protein (GFP) was purified from intact Escherichia coli cells using preparative PAGE. In this purification process, cells disruption step is not needed. The cellular content of E. coli was drifted out electrically from cells and the negatively charged GFP was further electroeluted from polyacrylamide gel column. SEM investigation of the electrophoresed cells revealed substantial structural damage at the cellular level. This integrated purification technique has successfully recovered the intracellular GFP with a yield of 82% and purity of 95%. [source] Seizures in the Developing Brain Cause Adverse Long-term Effects on Spatial Learning and AnxietyEPILEPSIA, Issue 12 2004Umit Sayin Summary:,Purpose: Seizures in the developing brain cause less macroscopic structural damage than do seizures in adulthood, but accumulating evidence shows that seizures early in life can be associated with persistent behavioral and cognitive impairments. We previously showed that long-term spatial memory in the eight-arm radial-arm maze was impaired in rats that experienced a single episode of kainic acid (KA)-induced status epilepticus during early development (postnatal days (P) 1,14). Here we extend those findings by using a set of behavioral paradigms that are sensitive to additional aspects of learning and behavior. Methods: On P1, P7, P14, or P24, rats underwent status epilepticus induced by intraperitoneal injections of age-specific doses of KA. In adulthood (P90,P100), the behavioral performance of these rats was compared with that of control rats that did not receive KA. A modified version of the radial-arm maze was used to assess short-term spatial memory; the Morris water maze was used to evaluate long-term spatial memory and retrieval; and the elevated plus maze was used to determine anxiety. Results: Compared with controls, rats with KA seizures at each tested age had impaired short-term spatial memory in the radial-arm maze (longer latency to criterion and more reference errors), deficient long-term spatial learning and retrieval in the water maze (longer escape latencies and memory for platform location), and a greater degree of anxiety in the elevated plus maze (greater time spent in open arms). Conclusions: These findings provide additional support for the concept that seizures early in life may be followed by life-long impairment of certain cognitive and behavioral functions. These results may have clinical implications, favoring early and aggressive control of seizures during development. [source] Linking structural, metabolic and functional changes in multiple sclerosisEUROPEAN JOURNAL OF NEUROLOGY, Issue 4 2001Massimo Filippi In patients with multiple sclerosis (MS), conventional magnetic resonance imaging (MRI) has markedly improved our ability to detect the macroscopic abnormalities of the brain and spinal cord. New quantitative magnetic resonance (MR) approaches with increased sensitivity to subtle normal-appearing white matter (NAWM) and grey matter changes and increased specificity to the heterogeneous pathological substrates of MS may give information complementary to conventional MRI. Magnetization transfer imaging (MTI) and diffusion-weighted imaging (DWI) have the potential to provide important information on the structural changes occurring within and outside T2-visible lesions. Magnetic resonance spectroscopy (MRS) adds information on the biochemical nature of such changes. Functional MRI might quantify the efficiency of brain plasticity in response to MS injury and improve our understanding of the link between structural damage and clinical manifestations. The present review summarizes how the application of these MR techniques to the study of MS is dramatically changing our understanding of how MS causes irreversible neurological deficits. [source] Dangers relating to fires in carbon-fibre based composite materialFIRE AND MATERIALS, Issue 4 2005Tommy Hertzberg Abstract Inhalable carbon fibres have been suspected to pose similar threats to human health as asbestos fibres. It is well-known that fibres having a diameter of less than 3 µm might be inhaled and transported deep into the human respiratory system. Some composite materials use carbon fibres as structural reinforcement. These fibres do not pose any risks as such as they are firmly connected to the laminate and surrounded by a polymer matrix. Also, these fibres typically have diameters >6 µm and thus, are not inhalable. However, if the material is exposed to a fire, the carbon material might be oxidized and fractionated and thereby, inhalable fibres might be generated into the fire smoke. The capability of carbon fibre-based composite material to produce dangerous inhalable fibres from different combustion scenarios has been investigated. It was found that the risk of fires generating inhalable carbon fibres is related to the surface temperature, the oxygen level and the airflow field close to the material surface. The temperatures necessary for oxidation of the carbon fibre is so high that it is possible that only a flashover situation will pose any real danger. Other possible danger scenarios are highly intense fires (e.g. a liquid fuel fire), or situations where structural damage is part of the fire scenario. Copyright © 2005 John Wiley & Sons, Ltd. [source] IL-6 inhibition in the treatment of rheumatoid arthritisFUTURE PRESCRIBER, Issue 3 2007FRCP Professor of experimental rheumatology, Peter Taylor MA, honorary consultant rheumatologist The armentarium of potential therapeutics for rheumatoid arthritis (RA) has grown with the identification of relevant disease molecules. Of these, biologic therapeutics targeting tumour necrosis factor-alpha (TNF-alpha), particularly when used in combination with oral methotrexate, have enjoyed notable success in suppressing inflammation and markedly inhibiting the progression of structural damage previously thought to be an unavoidable characteristic of RA.1,2 However, despite the unprecedented clinical and commercial successes of TNF inhibitors, their availability is restricted by high costs and the failure of a substantial proportion of patients to demonstrate significant clinical responses. Copyright © 2007 John Wiley & Sons, Ltd. [source] Sensorimotor network rewiring in mild cognitive impairment and Alzheimer's diseaseHUMAN BRAIN MAPPING, Issue 4 2010Federica Agosta Abstract This study aimed at elucidating whether (a) brain areas associated with motor function show a change in functional magnetic resonance imaging (fMRI) signal in amnestic mild cognitive impairment (aMCI) and Alzheimer's disease (AD), (b) such change is linear over the course of the disease, and (c) fMRI changes in aMCI and AD are driven by hippocampal atrophy, or, conversely, reflect a nonspecific neuronal network rewiring generically associated to brain tissue damage. FMRI during the performance of a simple motor task with the dominant right-hand, and structural MRI (i.e., dual-echo, 3D T1-weighted, and diffusion tensor [DT] MRI sequences) were acquired from 10 AD patients, 15 aMCI patients, and 11 healthy controls. During the simple-motor task, aMCI patients had decreased recruitment of the left (L) inferior frontal gyrus compared to controls, while they showed increased recruitment of L postcentral gyrus and head of L caudate nucleus, and decreased activation of the cingulum compared with AD patients. Effective connectivity was altered between primary sensorimotor cortices (SMC) in aMCI patients vs. controls, and between L SMC, head of L caudate nucleus, and cingulum in AD vs. aMCI patients. Altered fMRI activations and connections were correlated with the hippocampal atrophy in aMCI and with the overall GM microstructural damage in AD. Motor-associated functional cortical changes in aMCI and AD mirror fMRI changes of the cognitive network, suggesting the occurrence of a widespread brain rewiring with increasing structural damage rather than a specific response of cognitive network. Hum Brain Mapp, 2010. © 2009 Wiley-Liss, Inc. [source] Is major depressive disorder a metabolic encephalopathy?HUMAN PSYCHOPHARMACOLOGY: CLINICAL AND EXPERIMENTAL, Issue 5 2008Brian H Harvey Abstract Metabolic encephalopathy is an acute disturbance in cellular metabolism in the brain evoked by conditions of hypoxia, hypoglycaemia, oxidative stress and/or inflammation. It usually develops acutely or subacutely and is reversible if the systemic disorder is treated. If left untreated, however, metabolic encephalopathy may result in secondary structural damage to the brain. Most encephalopathies are present with neuropsychiatric symptoms, one in particular being depression. However, mood disorders are often co-morbid with cardiovascular, liver, kidney and endocrine disorders, while increasing evidence concurs that depression involves inflammatory and neurodegenerative processes. This would suggest that metabolic disturbances resembling encephalopathy may underscore the basic neuropathology of depression at a far deeper level than currently realized. Viewing depression as a form of encephalopathy, and exploiting knowledge gleaned from our understanding of the neurochemistry and treatment of metabolic encephalopathy, may assist in our understanding of the neurobiology of depression, but also in realizing new ideas in the pharmacotherapy of mood disorders. Copyright © 2008 John Wiley & Sons, Ltd. [source] Nerve perforation with pencil point or short bevelled needles: histological outcomeACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 8 2010T. STEINFELDT Background: In the case of needle nerve contact during peripheral blocks, pencil point needles are considered less traumatic compared with bevelled needles. However, there are not enough data to prove this notion. Therefore, the aim of this study was to challenge the hypothesis that nerve perforation with short bevelled needles is associated with major nerve damage compared with pencil point needles. Methods: In five anaesthetised pigs, the brachial plexus was exposed bilaterally. Up to eight nerves underwent needle nerve perforation using a pencil point needles cannula or an short bevelled needle. After 48 h, the nerves were resected. The specimens were processed for visual examination and the detection of inflammatory cells (haematoxylin,eosin, i.e. CD68-immunohistochemistry to detect macrophages), myelin damage (Kluver,Barrera staining) and intraneural haematoma. The grade of nerve injury was characterised by an objective score ranging from 0 (no injury) to 4 (severe injury). Results: Fifty nerves were examined. According to the injury score applied, there was no significant difference between the pencil point needles [median (inter-quartile range) 2.0 (2.0,2.0)] and the short bevelled-needle group [median 2.0 (2.0,2.0) P=0.23]. No myelin damage was observed. Signs of post-traumatic inflammation were equally distributed among both groups. Conclusions: In the present study, the magnitude of nerve injury after needle nerve perforation was not related to one of the applied needle types. Post-traumatic inflammation rather than structural damage of nerve tissue is the only notable sign of nerve injury after needle nerve perforation with either needle type. However, neither the pencil point- nor the short bevelled needle can be designated a less traumatic device. [source] Responses of ants to selective logging of a central Amazonian forestJOURNAL OF APPLIED ECOLOGY, Issue 3 2000H.L. Vasconcelos Summary 1.,Relatively little information exists on the effects of logging on rain forest organisms, particularly in the Neotropics where logging operations have increased dramatically in recent years. In this study we determined experimentally the effects of selective logging of a central Amazonian forest on ground-living ants. 2.,The experimental design consisted of three 4-ha replicated plots representing control unlogged forest, forest logged 10 years prior to the start of the study (1987), and forest logged 4 years prior to the start of the study (1993). The logging operation removed 50% of the basal area of trees of commercial value, or about eight trees per hectare. This resulted in a significant decrease in canopy cover, and an increase in understorey vegetation density in logged plots relative to controls. 3.,Collection and identification of ants from a total of 360 1-m2 samples of leaf-litter revealed 143 ant species, of which 97 were found in the control plots, 97 in the plots logged in 1987, and 106 in those logged in 1993. Species richness, evenness and mean abundance (ants m,2) per plot did not vary among treatments. Most of the species found in the control plots were also present in the logged plots. However, population density of many species changed as a result of logging, an effect that persisted for at least 10 years after logging. Species commonly found in sites that were directly disturbed by logging (gaps and tracks) were rare in the undisturbed forest, as revealed by an additional collection of ants. 4.,These results suggest that the persistence of ant assemblages typical of undisturbed forest is likely to depend on the amount of structural damage incurred by logging. Thus management techniques that minimize logging impacts on forest structure are likely to help maintain the conservation value of logged forests for ground-dwelling ants. It is particularly important to minimize the extent of logging roads and tracks created by heavy machinery because these areas appear more prone to invasion by non-forest species. [source] Mechanisms underlying the inhibition of the cytochrome P450 system by copper ionsJOURNAL OF APPLIED TOXICOLOGY, Issue 8 2009M. E. Letelier Abstract Copper toxicity has been associated to the capacity of free copper ions to catalyze the production of superoxide anion and hydroxyl radical, reactive species that modify the structure and/or function of biomolecules. In addition, nonspecific Cu2+ -binding to thiol enzymes, which modifies their catalytic activities, has been reported. Cytochrome P450 (CYP450) monooxygenase is a thiol protein that binds substrates in the first and limiting step of CYP450 system catalytic cycle, necessary for the metabolism of lipophilic xenobiotics. Therefore, copper ions have the potential to oxidize and bind to cysteinyl residues of this monooxygenase, altering the CYP450 system activity. To test this postulate, we studied the effect of Cu2+ alone and Cu2+/ascorbate in rat liver microsomes, to independently evaluate its nonspecific binding and its pro-oxidant effects, respectively. We assessed these effects on the absorbance spectrum of the monooxygenase, as a measure of structural damage, and p -nitroanisole O -demethylating activity of CYP450 system, as a marker of functional impairment. Data obtained indicate that Cu2+ could both oxidize and bind to some amino acid residues of the CYP450 monooxygenase but not to its heme group. The differences observed between the effects of Cu2+ and Cu2+/ascorbate show that both mechanisms are involved in the catalytic activity inhibition of CYP450 system by copper ions. The significance of these findings on the pharmacokinetics and pharmacodynamics of drugs is discussed. Copyright © 2009 John Wiley & Sons, Ltd. [source] Structural response of Caribbean dry forests to hurricane winds: a case study from Guánica Forest, Puerto RicoJOURNAL OF BIOGEOGRAPHY, Issue 3 2006Skip J. Van Bloem Abstract Aim, Tropical dry forests in the Caribbean have an uniquely short, shrubby structure with a high proportion of multiple-stemmed trees compared to dry forests elsewhere in the Neotropics. Previous studies have shown that this structure can arise without the loss of main stems from cutting, grazing, or other human intervention. The Caribbean has a high frequency of hurricanes, so wind may also influence forest stature. Furthermore, these forests also tend to grow on soils with low amounts of available phosphorus, which may also influence structure. The objective of this study was to assess the role of high winds in structuring dry forest, and to determine whether soil nutrient pools influence forest response following hurricane disturbance. Location, Guánica Forest, Puerto Rico. Methods, Over 2000 stems in five plots were sampled for hurricane effects within 1 week after Hurricane Georges impacted field sites in 1998. Sprout initiation, growth, and mortality were analysed for 1407 stems for 2 years after the hurricane. Soil nutrient pools were measured at the base of 456 stems to assess association between nutrients and sprout dynamics. Results, Direct effects of the hurricane were minimal, with stem mortality at < 2% and structural damage to stems at 13%, although damage was biased toward stems of larger diameter. Sprouting response was high , over 10 times as many trees had sprouts after the hurricane as before. The number of sprouts on a stem also increased significantly. Sprouting was common on stems that only suffered defoliation or had no visible effects from the hurricane. Sprout survival after 2 years was also high (> 86%). Soil nutrient pools had little effect on forest response as a whole, but phosphorus supply did influence sprout dynamics on four of the more common tree species. Main conclusions, Hurricanes are able to influence Caribbean tropical dry forest structure by reducing average stem diameter and basal area and generating significant sprouting responses. New sprouts, with ongoing survival, will maintain the high frequency of multi-stemmed trees found in this region. Sprouting is not limited to damaged stems, indicating that trees are responding to other aspects of high winds, such as short-term gravitational displacement or sway. Soil nutrients play a secondary role in sprouting dynamics of a subset of species. The short, shrubby forest structure common to the Caribbean can arise naturally as a response to hurricane winds. [source] Drugs Used to Treat Osteoporosis: The Critical Need for a Uniform Nomenclature Based on Their Action on Bone Remodeling,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 2 2005B Lawrence Riggs MD Abstract There continues to be uncertainty about the classification of available drugs for treating osteoporosis. We find that grouping them into anti-catabolic and anabolic classes based on the mechanisms of their action on bone remodeling and fracture reduction removes ambiguities and provides a relatively straightforward classification. The recent introduction of teriparatide into clinical practice initiated the era of anabolic therapy for osteoporosis, but it is still unclear how to define an anabolic drug. All drugs that increase bone mass do so by affecting bone remodeling. When their mechanisms of action on bone remodeling and on fracture reduction are considered, we find that anti-osteoporotic drugs fall naturally into either anti-catabolic or anabolic classes. Anti-catabolic drugs increase bone strength and reduce fractures mainly by decreasing the number of bone multicellular units (BMUs). This reduces perforative resorption and preserves skeletal microarchitecture (by preventing further structural damage to trabecular bone and increased porosity in cortical bone induced by high bone remodeling). Reduction in bone remodeling by anti-catabolic drugs may increase bone mass moderately during the interval in which previously initiated BMUs are completing mineralization. Some anti-catabolic drugs may also enhance the formation phase of the remodeling cycle, but their major action is to reduce overall bone turnover (i.e., the number of BMUs in bone). In contrast, anabolic drugs increase bone strength and reduce fractures by substantially increasing bone mass as a result of an overall increase in the number of BMUs combined with a positive BMU balance (the magnitude of the formation phase is greater than that of the resorption phase). Some anabolic drugs also induce renewed modeling, increase periosteal apposition and repair of trabecular microstructure. We hope that this classification will serve as a starting point for continued discussion on the important issue of nomenclature. [source] Melatonin protects against taurolithocholic-induced oxidative stress in rat liverJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 5 2010Lorena Fuentes-Broto Abstract Cholestasis, encountered in a variety of clinical disorders, is characterized by intracellular accumulation of toxic bile acids in the liver. Furthermore, oxidative stress plays an important role in the pathogenesis of bile acids. Taurolithocholic acid (TLC) was revealed in previous studies as the most pro-oxidative bile acid. Melatonin, a well-known antioxidant, is a safe and widely used therapeutic agent. Herein, we investigated the hepatoprotective role of melatonin on lipid and protein oxidation induced by TLC alone and in combination with FeCl3 and ascorbic acid in rat liver homogenates and hepatic membranes. The lipid peroxidation products, malondialdehyde and 4-hydroxyalkenals (MDA,+,4-HDA), and carbonyl levels were quantified as indices of oxidative damage to hepatic lipids and proteins, respectively. In the current study, the rise in MDA,+,4-HDA levels induced by TLC was inhibited by melatonin in a concentration-dependent manner in both liver homogenates and in hepatic membranes. Melatonin also had protective effects against structural damage to proteins induced by TLC in membranes. These results suggest that the indoleamine melatonin may potentially act as a protective agent in the therapy of those diseases that involve bile acid toxicity. J. Cell. Biochem. 110: 1219,1225, 2010. Published 2010 Wiley-Liss, Inc. [source] Tracing the route of Sphaerospora truttae from the entry locus to the target organ of the host, Salmo salar L., using an optimized and specific in situ hybridization techniqueJOURNAL OF FISH DISEASES, Issue 11-12 2003A S Holzer Abstract Sphaerospora truttae is an important pathogen of Atlantic salmon parr in Scottish aquaculture. To trace the early development of S. truttae and to overcome the common problem of detecting low numbers of cryptic, early myxosporean stages, a DNA-based approach was applied in this study. Specific primers were designed for S. truttae from Atlantic salmon, based on 18S rDNA sequences, obtained from isolated myxosporean spores. These were 5, biotin-labelled and used in an optimized and rapid in situ hybridization (ISH) protocol, which provided a strong and specific signal of the parasite within host tissue sections and, at the same time, minimized structural damage to tissues due to processing. This methodology provided a reliable tool enabling the detection of S. truttae stages down to single cell level. Using ISH the epithelium of the gills was identified as the predominant entry locus of the parasite. By 3 days after infection S. truttae had penetrated the vascular epithelia and thereafter proliferated in the blood for at least 10 days before exiting the vascular system through capillary walls. From day 12 post-infection onwards, the kidney, as well as the spleen and the liver, were invaded. Numbers of S. truttae invading the kidney (37.3%) differed little from numbers found in the spleen (35.3%) and the liver (27.4%). The latter organs represented a dead end in the development of S. truttae as all stages in these organs degenerated and sporogony was found to take place exclusively inside the renal tubules. Early sporogonic stages were found from day 25 post-infection but mature spores only developed after at least 15 days of proliferation within the tubules. [source] In vivo vascular hallmarks of diffuse leukoaraiosisJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 1 2010Jinsoo Uh PhD Abstract Purpose: To characterize multiple patterns of vascular changes in leukoaraiosis using in vivo magnetic resonance imaging (MRI) techniques. Materials and Methods: We measured cerebral blood flow (CBF), cerebrovascular reactivity (CVR), and blood,brain-barrier (BBB) leakage in a group of 33 elderly subjects (age: 72.3 ± 6.8 years, 17 males, 16 females). Leukoaraiosis brain regions were identified in each subject using fluid-attenuated inversion-recovery (FLAIR) MRI. Vascular parameters in the leukoaraiosis regions were compared to those in the normal-appearing white matter (NAWM) regions. Vascular changes in leukoaraiosis were also compared to structural damage as assessed by diffusion tensor imaging. Results: CBF and CVR in leukoaraiosis regions were found to be 39.7 ± 5.2% (P < 0.001) and 52.5 ± 11.6% (P = 0.005), respectively, of those in NAWM. In subjects who did not have significant leukoaraiosis, CBF and CVR in regions with high risk for leukoaraiosis showed a slight reduction compared to the other white matter regions. Significant BBB leakage was also detected (P = 0.003) in leukoaraiosis and the extent of BBB leakage was positively correlated with mean diffusivity. In addition, CVR in NAWM was lower than that in white matter of subjects without significant leukoaraiosis. Conclusion: Leukoaraiosis was characterized by reduced CBF, CVR, and a leakage in the BBB. J. Magn. Reson. Imaging 2010;32:184,190. © 2010 Wiley-Liss, Inc. [source] Molecular and Cellular Events in Alcohol-Induced Muscle DiseaseALCOHOLISM, Issue 12 2007Joaquim Fernandez-Solŕ Alcohol consumption induces a dose-dependent noxious effect on skeletal muscle, leading to progressive functional and structural damage of myocytes, with concomitant reductions in lean body mass. Nearly half of high-dose chronic alcohol consumers develop alcoholic skeletal myopathy. The pathogenic mechanisms that lie between alcohol intake and loss of muscle tissue involve multiple pathways, making the elucidation of the disease somewhat difficult. This review discusses the recent advances in basic and clinical research on the molecular and cellular events involved in the development of alcohol-induced muscle disease. The main areas of recent research interest on this field are as follows: (i) molecular mechanisms in alcohol exposed muscle in the rat model; (ii) gene expression changes in alcohol exposed muscle; (iii) the role of trace elements and oxidative stress in alcoholic myopathy; and (iv) the role of apoptosis and preapoptotic pathways in alcoholic myopathy. These aforementioned areas are crucial in understanding the pathogenesis of this disease. For example, there is overwhelming evidence that both chronic alcohol ingestion and acute alcohol intoxication impair the rate of protein synthesis of myofibrillar proteins, in particular, under both postabsorptive and postprandial conditions. Perturbations in gene expression are contributory factors to the development of alcoholic myopathy, as ethanol-induced alterations are detected in over 400 genes and the protein profile (i.e., the proteome) of muscle is also affected. There is supportive evidence that oxidative damage is involved in the pathogenesis of alcoholic myopathy. Increased lipid peroxidation is related to muscle fibre atrophy, and reduced serum levels of some antioxidants may be related to loss of muscle mass and muscle strength. Finally, ethanol induces skeletal muscle apoptosis and increases both pro- and antiapoptotic regulatory mechanisms. [source] Housing and Mental Health: A Review of the Evidence and a Methodological and Conceptual CritiqueJOURNAL OF SOCIAL ISSUES, Issue 3 2003Gary W. Evans Despite the fact that people invest more financial, temporal, and psychological resources in their homes than in any other material entity, research on housing and mental health is remarkably underdeveloped. We critically review existing research on housing and mental health, considering housing type (e.g., single-family detached versus multiple dwelling), floor level, and housing quality (e.g., structural damage). We then discuss methodological and conceptual shortcomings of this literature and provide a theoretical framework for future research on housing quality and mental health. [source] Brain structural damage in spinocerebellar ataxia type 2.MOVEMENT DISORDERS, Issue 6 2008A voxel-based morphometry study Abstract Voxel-based morphometry (VBM) enables an unbiased in-vivo whole-brain quantitative analysis of differences in gray matter (GM), white matter (WM) and cerebro-spinal fluid (CSF) volumes. We assessed with VBM 20 spinocerebellar ataxia Type 2 (SCA2) patients with mild or moderate cerebellar deficit and 20 age and sex-matched healthy controls. SCA2 patients showed a significant (P < 0.05 corrected for multiple comparison) symmetric loss of GM in the cerebellar vermis and hemispheres sparing lobules I,II, Crus II,VII, and X, and of the WM in the peridentate region, middle cerebellar peduncles, dorsal pons, and cerebral peduncles. The CSF volume was increased in the posterior cranial fossa. No GM, WM or CSF volume changes were observed in the supratentorial compartment. A mild (P < 0.05, >0.01) correlation was observed between the GM and WM loss and severity of the neurological deficit. In SCA2 patients with mild to moderate cerebellar deficit, GM and WM volume loss and CSF volume increase are confined to the posterior cranial fossa. © 2008 Movement Disorder Society [source] Diffusion tensor imaging in spinal cord: methods and applications , a reviewNMR IN BIOMEDICINE, Issue 7-8 2002Chris A. Clark Abstract The spinal cord is a clinically eloquent site within the central nervous system, containing important sensorimotor tracts confined within a small cross-sectional area. Damage to the spinal cord may be caused by a wide range of pathologies, and can result in profound functional disability. Characterization of the structural integrity of the spinal cord can be assessed using diffusion tensor imaging methods. Development and application of this technique may improve our understanding of the nature and evolution of structural damage in spinal cord disease. Possible developments include improved detection of ischaemic lesions, clarification of the relationship between clinical disability and structural damage to the cord and monitoring of anti-inflammatory or neuroprotective therapies. In this review current technical aspects, clinical applications and the suggested future development of spinal cord diffusion imaging are discussed. Copyright © 2002 John Wiley & Sons, Ltd. [source] MULTIDISCIPLINARY PAIN ABSTRACTS: 50PAIN PRACTICE, Issue 1 2004Article first published online: 15 MAR 200 Degenerative disease of the spine is one of the most common clinical entities and affects the intervertebral discs, including opposing vertebral endplates, the intervertebral posterior joints and the ligaments. The most severe primary spinal degenerative changes are found in the lower cervical and lumbar spine regions. The spine contains three different types of joints, each of which presents its own pattern of degenerative disease: cartilaginous joints, synovial joints, and fibrous joints. With regard to radicular pain, root compression alone does not fully account for root pain following disc-root conflict, but it is, nevertheless, considered to be the main cause of pain. The authors pointed out that the origin of pain is multi-factorial and that inflammation probably predominates over merely mechanical mechanisms. They also considered whether vertebral arthrosis can be construed as the body's decision to favor the spine's static function over its dynamic role when joint "hypermobility" linked to chronic load in old age could cause severe structural damage to the bony vertebral structures. [source] | ||||||||||||||||||||||