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Active Period (active + period)

Distribution by Scientific Domains

Medical Sciences	35%
Life Sciences	35%
Polymers and Materials Science	14%

Selected Abstracts

Soluble Interleukin-2 Receptors Increase During the Active Periods in Cluster Headache

HEADACHE, Issue 1 2003
M. Empl MD
Objective.,To investigate whether cytokines are altered during the active period of cluster headache. Background.,Patients with cluster headache show activation of the hypothalamus in PET studies and via endocrinologic parameters. Data also suggest an inflammatory process occurs in cluster headache. A connection between the presumed inflammatory cause, an immunological activation, and the hypothalamus could be generated by certain cytokines. Design and Methods.,ELISA was used to determine the serum levels of soluble interleukin-2 receptors, interleukin-1, interleukin-6, and 2 soluble interleukin-6 receptors (sIL-6R and soluble gp130) in 18 patients with cluster headache (6 women and 12 men) during the cluster period and in 17 healthy controls who were headache-free (3 women and 14 men). Results.,Patients with cluster headache had significantly increased soluble interleukin-2 receptors (413.6±223 U/mL vs. 290.0±112 U/mL; P < .05) compared with controls. Serum levels of interleukin-1 (0.29±0.30 pg/mL vs. 0.13±0.13 pg/mL, n.s.), interleukin-6 (0.87±0.6 pg/mL vs. 0.91±0.7 pg/ml; n.s.), soluble interleukin-6 receptors (33,131±8,349 pg/mL vs. 35,063±7,606 pg/mL; n.s.), or soluble gp130 (289±59 pg/mL vs. 283±20 pg/mL; n.s.) did not differ between the 2 groups, although patients with cluster tended to have higher interleukin-1 values. Conclusions.,Because elevated soluble interleukin-2 receptors indicate T cell activation, our findings suggest immune activation during cluster headache. Because interleukin-2 can activate the hypothalamus and stimulate the release of Corticotropin-releasing Factor (CRF), interleukin-2 could link a putative immunological cause of cluster headache with the observed hypothalamic activation. Systemic changes of interleukin-1 or the interleukin-6 system do not seem to play a role in cluster headache, as no alterations of serum levels were observed. Even so, unchanged serum levels do not exclude limited local production. [source]

External urethral sphincter activity in diabetic rats

NEUROUROLOGY AND URODYNAMICS, Issue 5 2008
Guiming Liu
Abstract Aim To examine the temporal effects of diabetes on the bladder and the external urethral sphincter (EUS) activity in rats. Methods Female Sprague-Dawley rats (n,=,24) were divided into two groups: streptozotocin-induced diabetic rats and age-matched controls. Cystometrograms (CMGs) were taken under urethane anesthesia and electromyograms (EMG) of the EUS were evaluated in all rats at 6 and 20 weeks after diabetes induction. After EMG assessment, the tissues of the urethra were harvested for morphological examination. Results Diabetes caused reduction of body weight, but an increase in bladder weight. CMG measurements showed diabetes increased threshold volume, contraction duration, high-frequency oscillations (HFO), and residual volume. Peak contraction amplitude increased in 6-week but not 20-week diabetic rats. EUS-EMG measurements showed increased frequency of EUS-EMG bursting discharge during voiding in 6-week diabetic rats (8.1,±,0.2 vs. 6.9,±,0.6/sec) but not in 20-week (5.8,±,0.3 vs. 6.0,±,0.2/sec) diabetic rats compared with controls. EUS-EMG bursting periods were also increased in both 6-week and 20-week diabetic rats compared with controls. EUS-EMG silent periods were reduced in 6-week diabetic rats, but were not changed in 20-week diabetic rats compared with controls. Active periods did not change in 20-week diabetic rats, but increased in 6-week diabetic rats compared with controls. Morphometric analysis showed atrophy of the EUS after 20 week but not 6 weeks of DM induction. Conclusions Our data indicates diabetes causes functional and anatomical abnormalities of the EUS. These abnormalities may contribute to the time-dependent bladder dysfunction in diabetic rats. Neurourol. Urodynam. 27:429,434, 2008. © 2008 Wiley-Liss, Inc. [source]

Seasonal distribution and species composition of daytime biting mosquitoes

ENTOMOLOGICAL RESEARCH, Issue 2 2009
Waseem AKRAM
Abstract Adults and immatures of Aedes mosquito populations were collected at temperatures between 40 and 44°C (summer), while larvae were collected at 0°C (winter). Major mosquito activities were observed from February to mid-December at various collection sites that yielded high populations of Aedes spp. from May to September, and high populations of Culex spp. and Anopheles spp. from March to September. In June to July, mosquito activity was suspended because the relative humidity was high (70%); a result of the monsoon rains. In August, with temperature ranging from 38 to 42°C, the populations of Culex, Anopheles and Aedes began to increase (36.8, 32.1 and 26.3%, respectively). Population estimates (through standard prototype Centers for Disease Control (CDC) and Biogents (BG)-sentinel) and species composition of Aedes in forest habitats indicated a rapid increase in the populations of Ae. albopictus (52.3%), Ae. aegypti (19.1%) and Ae. vittatus (28.5%) following the rainy season in July. Areas positive for Ae. albopictus had identical population levels and distribution ranges of Ae. vittatus, however, there were no Ae. aegypti in Ae. albopictus areas from August to September. The population level, seasonal distribution, habitat and areas of adult activity marked by global positioning system (GPS) coordinates are being used for reference and for species composition data of Anopheles spp. (2), Culex spp. (10) and Aedes spp. (5) in addition to associated temperature, relative humidity and physico-chemical factors of larval habitat. Global meteorological changes have caused an expansion of the active period, leading to the mosquito's possibility of being a vector of disease increasing, resulting in the spread of dengue fever. [source]

The Assessment of Land Resources: Achievements and New Challenges

GEOGRAPHICAL RESEARCH, Issue 2 2002
Donald A. Davidson
It is surprising that despite all the pleas and policies regarding the development of sustainable land use systems, there is still considerable ignorance regarding the nature and significance of land resources. This paper traces the development and achievements of land evaluation during the 20th century, with particular reference to soils. The most active period was between 1950 and around 1980 with the development of soil and land capability surveys, methodological advances initiated with the FAO Framework for Land Evaluation, and regional land resource assessments. Thus there were considerable achievements in land evaluation by the early 1980s, and subsequently there have been important advances in the subject through the application of GIS, spatial analysis, modelling and fuzzy set algebra. Since the late 1990s there has been a phenomenal rise in interest in soil quality assessment. Considerable debate has focussed on definition, and methods of assessment and monitoring. The latter part of this paper discusses the major challenges to the development and application of land evaluation. The inadequacy of much soil survey data in terms of variables, quality, spatial coverage and scale is emphasised. Also, there is a continuing need to highlight the centrality of land resource issues in any attempt to develop sustainable land use systems. [source]

Soluble Interleukin-2 Receptors Increase During the Active Periods in Cluster Headache

Cell proliferation and death in the brain of active and hibernating frogs

JOURNAL OF ANATOMY, Issue 2 2009
Silvia Cerri
Abstract ,Binomial' cell proliferation and cell death have been studied in only a few non-mammalian vertebrates, such as fish. We thought it of interest to map cell proliferation/apoptosis in the brain of the frog (Rana esculenta L.) as this animal species undergoes, during the annual cycle, physiological events that could be associated with central nervous system damage. Therefore, we compared the active period and the deep underground hibernation of the frog. Using western blot analysis for proliferating cell nuclear antigen (PCNA), we revealed a positive 36 kDa band in all samples and found higher optical density values in the hibernating frogs than in active frogs. In both active and hibernating frogs, we found regional differences in PCNA-immunoreactive cells and terminal transferase dUTP nick-end labelling apoptotic cells in the ventricular zones and parenchyma areas of the main encephalon subdivisions. During the active period of the frogs, the highest concentration of PCNA-immunoreactive cells was found in the ventricle dorsal zone of the cerebral hemispheres but only some of the cells were apoptotic. By contrast, the tectal and cerebellar ventricular zones had a small or medium amount of PCNA-immunoreactive cells, respectively, and a higher number of apoptotic cells. During hibernation, an increased PCNA-immunoreactive cell number was observed in both the brain ventricles and parenchyma compared with active frogs. This increase was primarily evident in the lateral ventricles, a region known to be a proliferation ,hot spot'. Although differences existed among the brain areas, a general increase of apoptotic cell death was found in hibernating frogs, with the highest number of apoptotic cells being detected in the parenchyma of the cerebral hemispheres and optic tectum. In particular, the increased number of apoptotic cells in the hibernating frogs compared with active frogs in the parenchyma of these brain areas occurred when cell proliferation was higher in the corresponding ventricular zones. We suggest that the high number of dying cells found in the parenchymal regions of hibernating frogs might provide the stimulus for the ventricular zones to proliferate. Hibernating frogs could utilize an increased cell proliferation in the brain areas as a neuroprotective strategy to face cell death and the onset of neurological damages. Therefore, the hibernator promises to be a valuable model for studying the mechanisms naturally carried out by the central nervous system in order to adapt itself or survive adverse conditions. [source]

Mild carbon monoxide exposure impairs the developing auditory system of the rat

JOURNAL OF NEUROSCIENCE RESEARCH, Issue 5 2003
Douglas S. Webber
Abstract The object of this study was to determine if chronic exposure to mild concentrations of CO in air caused changes in the integrity of the inferior colliculus during the most active period of synaptogenesis/auditory development. We examined all subregions of the inferior colliculus (IC) of rats by immunocytochemical approaches after pups were exposed chronically to CO concentrations of, 0, 12.5, 25, and 50 ppm in air starting at Day 8 through 20,22 days of age. Mother-reared pups were compared to the gastrostomy-reared pups with or without CO exposure for basal neural activity, using c-Fos immunoreactivity as a marker. Half the rats were examined at 27 days of age, 5 days after the end of CO exposure, and the other half were examined 50 days later at 75,77 days of age. In the central nucleus of the IC, the number of cells expressing a basal level of c-Fos was decreased significantly in the CO-exposed animals when compared to controls; however, there was little or no difference in the number of cells expressing c-Fos in the other subregions of the IC. We conclude that the central nucleus of the inferior colliculus is affected selectively by mild CO exposure (0.0012% in air) and that this reduction in neuronal activity persists into adulthood. © 2003 Wiley-Liss, Inc. [source]

Fundamental Molecular Weight Distribution of RAFT Polymers

MACROMOLECULAR REACTION ENGINEERING, Issue 5 2008
Hidetaka Tobita
Abstract The molecular weight distribution formed in an ideal reversible addition-fragmentation chain transfer (RAFT)-mediated radical polymerization is considered theoretically. In this polymerization, the addition to the RAFT agent is reversible, and the active period on the same chain could be repeated, via the two-armed intermediate, with probability 1/2. This possible repetition is accounted for by introducing a new concept, the overall active/dormant periods. With this method, the apparent functional form of the molecular weight distribution (MWD) reduces to that proposed for the ideal living radical polymers (Tobita, Macromol. Theory Simul. 2006, 15, 12). The repetition results in a broader MWD than without the repetition. The formulae for the average molecular weights formed in batch and a continuous stirred tank reactor are also presented. [source]

Kinetics of Stable Free Radical Mediated Polymerization inside Submicron Particles

MACROMOLECULAR THEORY AND SIMULATIONS, Issue 9 2007
Hidetaka Tobita
Abstract Controlled/living radical polymerization systems in which the active period is extremely small, ,A,,,1, such as the cases of stable free radical mediated polymerization (or nitroxide mediated polymerization) and atom transfer radical polymerization, are considered theoretically. The polymerization rate, Rp, for such systems increases by lowering the trapping agent concentration [X]. When the polymerization is conducted inside small particles, Rp decreases with D below the diameter Dp,SMC at which a single molecule concentration (SMC) is equal to [X]bulk. On the other hand, when the average number of trapping agents in a particle is smaller than about 10, the fluctuation of nX among particles is significant, which leads to a larger Rp than in the cases where all particles contain the same nX. Because of the effects of SMC and fluctuation, Rp may show an acceleration window, Dp,SMC,<,Dp,<,Dp,Fluct where Rp is slightly larger than that in bulk. [source]

Autonomic dysfunction in unselected and untreated primary open angle glaucoma patients: a pilot study

OPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 4 2007
Doina Gherghel
Abstract Purpose:, To investigate the presence of silent cardiac ischaemic episodes and the status of autonomic function in consecutive, newly diagnosed and untreated primary open-angle glaucoma patients. Methods:, Twenty-four consecutively diagnosed glaucoma patients and 22 age-matched controls were subjected to ambulatory 24-h blood pressure (BP) and electrocardiogram (ECG) monitoring by using Cardiotens-01 (Meditech Ltd). Based on the ECG recordings, heart rate variability (HRV) frequency domain parameters [low-frequency (LF), high-frequency (HF) and LF/HF ratio] were calculated and analysed in the two study groups. Results:, Glaucoma patients demonstrated higher LF and LF/HF values than normal subjects for both the active period (p = 0.020 and 0.029) and the passive period (p = 0.044 and 0.049 respectively). HRV parameters were similar in patients and controls suffering from silent cardiac ischaemia (p > 0.05); however, glaucoma patients with normal ECG demonstrated higher LF and LF/HF values during the active period of the 24-h measurement period than control subjects characterized by the same cardiac activity (p = 0.010 and 0.021 respectively). Conclusion:, Independent of a history and/or clinical signs of cardiovascular disease, glaucoma patients exhibit abnormal autonomic function. [source]

Effect of weak, interrupted sinusoidal low frequency magnetic field on neural regeneration in rats: Functional evaluation

BIOELECTROMAGNETICS, Issue 5 2005
Marijan Bervar
Abstract A study of the effect of weak, interrupted sinusoidal low frequency magnetic field (ISMF) stimulation on regeneration of the rat sciatic nerve was carried out. In the experiment, 60 Wistar rats were used: 24 rats underwent unilateral sciatic nerve transection injury and immediate surgical nerve repair, 24 rats underwent unilateral sciatic nerve crush injury, and the remaining 12 rats underwent a sham surgery. Half of the animals (n,=,12) with either sciatic nerve lesion were randomly chosen and exposed between a pair of Helmholtz coils for 3 weeks post-injury, 4 h/day, to an interrupted (active period to pause ratio,=,1.4 s/0.8 s) sinusoidal 50 Hz magnetic field of 0.5 mT. The other half of the animals (n,=,12) and six rats with sham surgery were used for two separate controls. Functional recovery was followed for 6 weeks for the crush injuries and 7½ months for the transection injuries by video assisted footprint analysis in static conditions and quantified using a recently revised static sciatic index (SSI) formula. We ascertained that the magnetic field influence was weak, but certainly detectable in both injury models. The accuracy of ISMF influence detection, determined by the one-way repeated measures ANOVA test, was better for the crush injury model: F(1, 198),=,9.0144, P,=,.003, than for the transection injury model: F(1, 198),=,6.4826, P,=,.012. The Student,Newman,Keuls range test for each response day yielded significant differences (P,<,.05) between the exposed and control groups early in the beginning of functional recovery and later on from the points adjacent to the beginning of the plateau, or 95% of functional recovery, and the end of observation. These differences probably reflect the ISMF systemic effect on the neuron cell bodies and increased and more efficient reinnervation of the periphery. Bioelectromagnetics 26:351,356, 2005. © 2005 Wiley-Liss, Inc. [source]

Cluster headache: aetiology, diagnosis and management.

HEADACHE, Issue 3 2003
K Ekbom
Drugs. 2002;62(1):61-69 Cluster headache is characterised by repeated attacks of strictly unilateral pain in the orbital region associated with local autonomic symptoms or signs. The attacks are brief but of a very severe, almost excruciating intensity. For unknown reasons males are affected more often than females. Recent studies suggest that an autosomal dominant gene has a role in some families with cluster headache. Hormonal studies indicate a dysfunction in the central nervous system. Neuroimaging has revealed primary defects in the hypothalamic grey matter. Local homolateral dilatation in the intracranial segment of the internal carotid and ophthalmic arteries during attacks is the result of a generic neurovascular activation, probably mediated by trigeminal parasympathetic reflexes. Sumatriptan 6mg subcutaneously is the drug of choice in the treatment of acute attacks. Inhalation of 100% oxygen can also be recommended. In the prophylactic treatment, verapamil is the first option. Other drugs that can be considered are corticosteroids, which may induce a remission of frequent, severe attacks, and lithium. Oral ergotamine tartrate may be sufficient for patients with night attacks and/or short, rather mild to moderately severe cluster headache periods. Third line drugs are serotonin inhibitors (methysergide and pizotifen) and valproic acid. Patients should be encouraged to keep headache diaries and be carefully instructed about the nature and treatment of the headaches. Alcohol can bring on extra attacks and should not be consumed during active periods of cluster headache. Comment: A useful review of clinical options. Given the effectiveness of injectable sumatriptan and the prophylactic use of ergotamine mentioned, one might speculate that the new intranasal formulations of triptans (eg, zolmitriptan) and triptans with a longer half-life (eg, frovatriptan) may prove to be effective in the treatment of cluster headache. DSM [source]

A new traffic model for backbone networks and its application to performance analysis

INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 6 2008
Ming Yu
Abstract In this paper, we present a new traffic model constructed from a random number of shifting level processes (SLP) aggregated over time, in which the lengths of the active periods of the SLP are of Pareto or truncated Pareto distribution. For both cases, the model has been proved to be asymptotically second-order self-similar. However, based on extensive traffic data we collected from a backbone network, we find that the active periods of the constructing SLPs can be approximated better by a truncated Pareto distribution, instead of the Pareto distribution as assumed in existing traffic model constructions. The queueing problem of a single server fed with a traffic described by the model is equivalently converted to a problem with a traffic described by Norros' model. For the tail probability of the queue length distribution, an approximate expression and upper bound have been found in terms of large deviation estimates and are mathematically more tractable than existing results. The effectiveness of the traffic model and performance results are demonstrated by our simulations and experimental studies on a backbone network. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Light use efficiency of dry matter gain in five macro-lichens: relative impact of microclimate conditions and species-specific traits

PLANT CELL & ENVIRONMENT, Issue 1 2000
K. Palmqvist
ABSTRACT Relations between irradiance (I) and lichen growth were investigated for five macro-lichens growing at two sites in Sweden. The lichens represented different mycobiont,photobiont associations, two morphologies (foliose, fruticose) and two life forms (epiphytic, terricolous). The lichens were transplanted at two geographically distant sites in Sweden (1000 km apart) from Sept 1995 to Sept 1996 in their typical microhabitats, where microclimate and growth were followed. Between April/May and Sept 96, the terricolous species had a dry matter gain of 0·2 to 0·4 g (g DW),1 and the epiphytes 0·01 to 0·02 g (g DW),1. When related to area, growth amounted to 30 to 70 g m,2 for the terricolous species and to 1 to 4 g m,2 for the epiphytes. There was a strong correlation between growth and intercepted irradiance when the lichens were wet (Iwet), with 0·2 to 1·1 g lichen dry matter being produced per MJ solar energy. Across the 10 sets of transplants, light use efficiencies of dry matter yield (e) ranged between 0·5 and 2%, using an energy equivalent of 17·5 kJ g,1 of lichen dry matter. The higher productivity of the terricolous species was due to longer periods with thallus water contents sufficient for metabolic activity and because of the higher mean photon flux densities of their microhabitat. A four-fold difference in photosynthetic capacity among the species was also important. It is concluded that lichen dry matter gain was primarily related to net carbon gain during metabolically active periods, which was determined by light duration, photon flux density and photosynthetic capacity. [source]