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Initial Decrease (initial + decrease)
Selected AbstractsEffects of Endotoxin Exposure on Cationic Amino Acid Transporter Function in Ovine Peripheral Blood Mononuclear CellsEXPERIMENTAL PHYSIOLOGY, Issue 2 2003Megan F. Clark Rodent models of sepsis differ from clinical human disease in that humans make substantially less whole-body nitric oxide and have different cellular responses to endotoxin. Sheep, when exposed to endotoxin, behave in a manner more similar to humans. Many studies of rodent peripheral blood mononuclear cells (PBMCs) exposed to endotoxin demonstrate increased cationic amino acid transporter function (particularly through the y+ transporter) to supply arginine substrate to upregulated nitric oxide synthase. Whether this is true in sheep is not known. We have studied cationic amino acid transport in sheep PBMCs stimulated with endotoxin, using labelled lysine. PBMCs stimulated both in vitro and in vivo show an initial reduction in total and y+ lysine transport (after 1-2 h exposure to endotoxin): a previously undescribed effect of endotoxin. In in vitro activated cells, the reduction in y+ transport was prevented by the lipoxygenase inhibitor, nordihydroguaretic acid (NDGA), and the phospholipase inhibitor 4-bromophenacyl bromide (4-BPAB), but not cyclohexamide or a number of other inhibitors of intracellular second-messenger pathways. In contrast after 14 h incubation, the expected increase in total and y+ lysine transport was seen. The increase in y+ transport could be prevented by cyclohexamide, dexamethasone, ibuprofen, the protein kinase C inhibitor sphingosine, NDGA and 4-BPAB. These results suggest that in response to endotoxin exposure there is an initial decrease in y+ activity mediated by a lipoxygenase product, followed by a substantial increase in y+ activity mediated by the products of either cyclo-oxygenase or lipoxygenase. Cyclo-oxygenase and/or lipoxygenase inhibition might be useful in reducing arginine transport, and hence nitric oxide production, in these cells. [source] In vitro change in mechanical strength of ,-tricalcium phosphate/copolymerized poly- L -lactide composites and their application for guided bone regenerationJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2002Masanori Kikuchi Abstract Novel composites of bioactive ,-tricalcium phosphate [Ca3(PO4)2] and biodegradable copolymerized poly- L -lactide (CPLA) were prepared by a heat-kneading method. The mechanical and chemical changes of the composites were evaluated in vitro by soaking in physiological saline and Dulbecco's phosphate buffered saline. When soaked in physiological saline, the 3-point mechanical strength decreased rapidly from 60 to 30 MPa in the initial 4 weeks and then gradually reached a plateau; the initial decrease in the mechanical strength was ascribed to the dissolution of ,-tricalcium phosphate from the surface. The mechanical properties evident at 8,12 weeks were sufficient for the composites to be used as a biodegradable material for regeneration of bone because the hydrolysis of CPLA was inhibited in both physiological saline and phosphate-buffered saline as a result of a pH-buffering effect. Composite membranes 250-,m thick were used to regenerate large bone defects in beagle dogs: 10 × 10 × 10 mm3 in volume in the mandible and 20 mm in length in the tibia. The afflicted areas covered with the composite membranes were almost perfectly filled with new bone 12 weeks after the operation, whereas those covered with a CPLA membrane or without any membranes were invaded by soft tissue. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 62: 265,272, 2002 [source] Evolution of Thermophysical Characteristics in Tin Oxide: From Pressed Powder Compact to Fired Porous BodyJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2008Céline Poulier The thermal response of a ceramic body during firing will be controlled by its thermophysical characteristics. Laser flash measurements have been used to investigate the thermal conductivity of pressed powder compacts of pure tin oxide as a function of temperature. After an initial decrease up to 150°C attributed to removal of surface species, the thermal conductivity increases progressively with thermal treatment up to 1000°C. Because there is almost no variation in the pore volume fraction, the behavior is explained by grain boundary formation and neck growth, which increase the contact area between particles. Supporting evidence is given by an increase in mechanical strength. Finally, thermal treatment above 1000°C increases the thermal conductivity due to a reduction in the number of grain boundaries per unit length of heat path. [source] The effect of storage on the P50 of feline bloodJOURNAL OF VETERINARY EMERGENCY AND CRITICAL CARE, Issue 1 2007Chris Wong DVM Abstract Objective: To determine the effect of storage on the P50 of feline hemoglobin. Design: Prospective, in vitro, laboratory study. Subjects: Venous blood from 4 clinically healthy cats. Measurements: Blood was collected into CPDA-1 anticoagulant/preservative and maintained at 4°C for 5 weeks. Measurements were made on Days 0, 2, 4, 7, 14, 21, 28, and 35. The blood samples were equilibrated in a tonometer to gas mixtures containing 2.5%, 4%, 5%, or 8% oxygen, with 5% carbon dioxide balance nitrogen; pH was adjusted to 7.4. Chloride, partial pressure of oxygen, and hemoglobin saturation were measured; P50 was calculated. Results: Chloride decreased from 124.3±2.1 to 88.5±1.9 mEq/L immediately after dilution with CPDA-1, and did not change for the 5 weeks thereafter. The P50 decreased from an average of 35.0±1.2 to between 31 and 32 mmHg after 7 days, and did not change further for 4 weeks thereafter. Conclusions: The decrease in P50 of feline hemoglobin was minor compared with that of blood from species in which 2,3-diphosphoglycerate (2,3-DPG) is a major modifier of hemoglobin affinity for oxygen. The decrease in P50 in the present study was attributed to an initial decrease in chloride and a subsequent loss of modest quantities of red cell 2,3-DPG. [source] Interaction of UV Radiation and Inorganic Carbon Supply in the Inhibition of Photosynthesis: Spectral and Temporal Responses of Two Marine Picoplankters,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 2 2005Cristina Sobrino ABSTRACT The effect of ultraviolet radiation (UVR) on inhibition of photosynthesis was studied in two species of marine picoplankton with different carbon concentration mechanisms: Nannochloropsis gaditana Lubián possesses a bicarbonate uptake system and Nannochloris atomus Butcher a CO2 active transport system. Biological weighting functions (BWFs) for inhibition of photosynthesis by UVR and photosynthesis vs irradiance (PI) curves for photosynthetically active radiation (PAR) were estimated for both species grown with an enriched CO2 supply (high dissolved inorganic carbon [DIC]: 1% CO2 in air) and in atmospheric CO2 levels (low DIC: 0.03% CO2). The response to UVR and PAR exposures was different in each species depending on the DIC treatment. Under PAR exposure, rates of maximum photosynthesis were similar between treatments in N. gaditana. However, the cultures growing in high DIC had lower sensitivity to UVR than the low DIC cultures. In contrast, N. atomus had higher rates of photosynthesis under PAR exposure with high DIC, but the BWFs were not significantly different between treatments. The results suggest that one or more processes in N. gaditana associated with HCO3, transport are target(s) for UV photodamage because there was relatively less UV inhibition of the high DIC-grown cultures in which inorganic carbon fixation is supplied by passive CO2 diffusion. Time courses of photochemical efficiency in PAR, during UV exposure and during subsequent recovery in PAR, were determined using a pulse amplitude modulated fluorometer. The results were consistent with the BWFs. In all time courses, a steady state was obtained after an initial decrease, consistent with a dynamic balance between damage and repair as found for other phytoplankton. However, the relationship of response to exposure showed a steep decline in activity that is consistent with a constant rate of repair. A novel feature of a model developed from a constant repair rate is an explicit threshold for photosynthetic response to UV. [source] Environmental neurotoxin-induced progressive model of parkinsonism in ratsANNALS OF NEUROLOGY, Issue 1 2010Wei-Bin Shen PhD Objective Exposure to a number of drugs, chemicals, or environmental factors can cause parkinsonism. Epidemiologic evidence supports a causal link between the consumption of flour made from the washed seeds of the plant Cycas micronesica by the Chamorro population of Guam and the development of amyotrophic lateral sclerosis/parkinsonism dementia complex. Methods We now report that consumption of washed cycad flour pellets by Sprague-Dawley male rats induces progressive parkinsonism. Results Cycad-fed rats displayed motor abnormalities after 2 to 3 months of feeding such as spontaneous unilateral rotation, shuffling gait, and stereotypy. Histological and biochemical examination of brains from cycad-fed rats revealed an initial decrease in the levels of dopamine and its metabolites in the striatum (STR), followed by neurodegeneration of dopaminergic (DAergic) cell bodies in the substantia nigra (SN) pars compacta (SNc). ,-Synuclein (,-syn; proteinase K-resistant) and ubiquitin aggregates were found in the DAergic neurons of the SNc and neurites in the STR. In addition, we identified ,-syn aggregates in neurons of the locus coeruleus and cingulate cortex. No loss of motor neurons in the spinal cord was found after chronic consumption of cycad flour. In an organotypic slice culture of the rat SN and the striatum, an organic extract of cycad causes a selective loss of dopamine neurons and ,-syn aggregates in the SN. Interpretation Cycad-fed rats exhibit progressive behavioral, biochemical, and histological hallmarks of parkinsonism, coupled with a lack of fatality. ANN NEUROL 2010;68:70,80 [source] Pre-steady state kinetics of ATP hydrolysis by Na,K-ATPaseCELL BIOCHEMISTRY AND FUNCTION, Issue 3 2009Nikhat Manzoor Abstract Fast reaction kinetics of ATP hydrolysis by Na,K-ATPase has been investigated by following absorption pattern of pH sensitive dye in stopped flow spectrophotometer. Distinct pre-steady state phase signal could be recorded with an initial decrease in acidity followed by increase in acidity. Average half time for H+ absorption and peak alkalinity was, respectively, 30,ms and 60,ms. Under optimal Na+ (120,mM) and K+ (30,mM) concentrations, magnitude of both H+ absorption and H+ release are found to be about 1.0,H+/ATPase molecule. H+ absorption and release decreased with decrease in Na+ concentration, H+ release was more affected. Both H+ absorption and H+ release are found to be independent of K+ concentration in the pre-steady state phase. No H+ absorption or release was observed following mixing of either ADP, Na+ or K+ alone with ATPase. Effect of delayed mixing of Na+ or K+ on two phases of pre-steady state cycle indicates that ATP hydrolytic cycle starts without K+ ions if optimal Na+ is present. ATP hydrolytic cycle does not start in the absence of Na+ ions. Results obtained have been interpreted in terms of an extended kinetic scheme for Na,K-ATPase. Copyright © 2009 John Wiley & Sons, Ltd. [source] Report of a Case Receiving Full-Arch Rehabilitation in Both Jaws Using Immediate Implant Loading Protocols: A 1-Year Resonance Frequency Analysis Follow-UpCLINICAL IMPLANT DENTISTRY AND RELATED RESEARCH, Issue 1 2006Michael Portmann DDS ABSTRACT Background:, Immediate occlusal implant loading has been documented as a viable treatment option for various indications. However, documentations related to full-arch rehabilitation are usually limited to treatment of one jaw at a time, thereby leaving the opposing dentition unchanged. Furthermore, clinical documentation using traditional, well-accepted measuring techniques may not be adequate when it comes to short-term evaluation of the success or failure of implants subjected to immediate occlusal loading. Purpose:, The purpose of this case report is to (1) present an implant stability follow-up of a patient receiving an immediate, implant-supported full-arch rehabilitation in both jaws and (2) evaluate the patient's acceptance of this rehabilitation. Materials and Methods:, A 68-year-old patient scheduled for implant treatment was selected for an immediate implant loading protocol in both jaws. During two surgical events 3 weeks apart, eight maxillary and four mandibular Brĺnemark System® Mk IV TiUniteTM fixtures (Nobel Biocare AB, Göteborg, Sweden) were inserted and subsequently used to immediately support a cross-arch fixed prosthesis in the maxilla and a bar-retained overdenture in the mandible. Implant stability was recorded from the day of surgery periodically during a 1-year follow-up using resonance frequency analysis (RFA). Results:, At the 1-year follow-up, based on clinical, RFA, and radiographic evaluations, all implants and the reconstructions were classified as successful. All maxillary implants showed a decrease in the implant stability quotient (ISQ) value from the measurement at the time of surgery to the first follow-up, whereas two of four mandibular implants revealed an initial drop in stability. Irrespective of a specific ISQ level measured at implant surgery (ISQ range 53,74) and despite an initial decrease in stability, measurements recorded at the 12-month follow-up indicated similar stability levels for all maxillary implants (ISQ range 64,68) or the group of mandibular implants (ISQ range 72,75) but with a higher ISQ level for mandibular implants. Furthermore, the patient's acceptance of the immediate full-arch rehabilitation in both jaws was high. Conclusions:, The present case report demonstrates that a slightly staged approach for full-arch rehabilitation in both jaws using immediate implant loading protocols is a realistic treatment option. Furthermore, RFA follow-up indicates that immediately occlusally loaded implants placed in reduced bone quality and quantity are more prone to loose stability in the early healing period compared with implants placed in dense bone quality. [source] | ||||||||||||||||