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At least 91 records · Page 5Linked to original sources
PubMed1996

Carboxyhemoglobin levels in a series of automobile fires. Death due to crash or fire?

The determination of death by trauma versus fire can be of major consideration, especially in civil product liability litigation. Blood carboxyhemoglobin levels can be instrumental in that differentiation. Twenty-eight fatalities involving fire in automobiles were reviewed. All subjects displayed some degree of body burn, and in 25 severe charring and/or incineration was present at autopsy. In only one case was there a history of explosion or flash fire. Carboxyhemoglobin levels varied from 92% to values of < 10%. In seven cases no collision occurred. In six of these subjects COHb values were > or = 47%. In all 16 cases with carboxyhemoglobin levels of < or = 10% a collision occurred. In 12 of 16 of these subjects, blunt force injury sufficient to cause death was discovered. Data presented in this article indicate that a carboxyhemoglobin level of > 30% strongly suggests inhalation of combustion products as the cause of death. In contrast, a level of < 20% should prompt a search for other causes.

Accidents, Traffic↗
PubMed2005

Physical fitness of an industrial fire department vs. a municipal fire department.

Both industrial and municipal firefighters need to maintain high levels of physical fitness and minimize cardiovascular risk factors. The nature of firefighter responsibilities in industrial and municipal settings may vary, affecting the ability to sustain high levels of physical fitness. We compared the working conditions, physical fitness, and exercise training practices of an industrial fire department (n = 17) to those of a nearby municipal fire department (n = 55). After informed consent, aerobic capacity, muscular strength, muscular endurance, body composition, flexibility, blood lipid concentrations, and blood pressure levels were measured. Exercise training practices and related factors were assessed using a questionnaire. Despite programmatic differences, these departments demonstrated similar, relatively high degrees of physical fitness and similar blood lipid concentrations, blood pressure levels, and cardiac risk factors. It is recommended that fire departments involve appropriately trained staff, schedule on-duty times for exercise, offer well-equipped exercise facilities, and follow National Strength and Conditioning Association (NSCA) and American College of Sports Medicine (ACSM) guidelines for exercise conditioning in order to maintain a high degree of physical fitness.

Adult↗
PubMed2006

Small mammals and forest fuel reduction: national-scale responses to fire and fire surrogates.

Forest fuel reduction treatments are increasingly used by managers to reduce the risk of high-severity wildfire and to manage changes in the ecological function of forests. However, comparative ecological effects of the various types of treatments are poorly understood. We examined short-term patterns in small-mammal responses to mechanical thinning, prescribed-fire, and mechanical thinning/prescribed-fire combination treatments at eight different study areas across the United States as a part of the National Fire and Fire Surrogate (FFS) Project. Research questions included: (1) do treatments differ in their effect on small mammal densities and biomass? and (2) are effects of treatments consistent across study areas? We modeled taxa-specific densities and total small-mammal biomass as functions of treatment types and study area effects and ranked models based on an information-theoretic model selection criterion. Small-mammal taxa examined, including deer mice (Peromyscus maniculatus), yellow-pine chipmunks (Tamias amoenus), and golden-mantled ground squirrels (Spermophilus lateralis), as well as all Peromyscus and Tamias species, had top-ranked models with responses varying both by treatment type and study area. In each of these cases, the top-ranked model carried between 69% and 99% of the total weight in the model set, indicating strong support for the top-ranked models. However, the top-ranked model of total small-mammal biomass was a model with biomass varying only with treatment (i.e., treated vs. untreated), not by treatment type or study area; again, this model had strong support, with 75% of the total model weight. Individual species and taxa appear to have variable responses to fuel reduction treatment types in different areas; however, total small-mammal biomass appears generally to increase after any type of fuel reduction. These results suggest that there is substantial variability in taxa-specific responses to treatments and indicate that adaptive management policies may be necessary when applying fuel reduction treatments in areas where management of small-mammal populations is of interest. Adaptive management can be used by managers who are conducting fuel reduction treatments to reduce uncertainty as to which treatments are locally optimal for meeting objectives for the management of small-mammal populations.

Animals↗
PubMed1979

Fire deaths and drinking: data from the Ontario fire reporting system.

Data on recorded alcohol impairment of 264 victims of fatal fires in Ontario in 1976 are analyzed. Male victims were twice as likely to be impaired as females, and impairment was more common among those under 50 years of age. Alcohol impairment was most often noted in victims of fires at night and on weekends. Overall, 31% of adult victims were reported as alcohol impaired. The Ontario data suggests alcohol involvement in victims was not associated with smoking as a cause of the fire.

Alcohol Drinking↗
PubMed1987

Neuronal firing in the pallidal region: firing patterns during sleep-wakefulness cycle in cats.

Neuronal activity was investigated by extracellular microelectrodes in the pallidal region of freely moving cats during wakefulness (W), slow-wave sleep (SWS) and paradoxical sleep (PS). The firing of 150 units from 35 points was examined. On the basis of the modifications of firing rates and patterns during the sleep-wakefulness cycle, 5 groups of neurons were distinguished. Two of these groups were characterized by strong increase of firing rate in W and PS and in one of them this increase preceded the cortical activation at the SWS-PS transition by an average of 26 sec. The role played by the basal forebrain area in the regulation of the sleep-wakefulness cycle is discussed.

Action Potentials↗
PubMed1989

Survey of fatal anaphylactic reactions to imported fire ant stings. Report of the Fire Ant Subcommittee of the American Academy of Allergy and Immunology.

A physician questionnaire survey was conducted by the Fire Ant Subcommittee of the American Academy of Allergy and Immunology to document deaths caused by imported fire ant stings. From the 29,300 physicians surveyed, reports of 83 fatal and two near-fatal fire ant-sting reactions were received. Most anaphylactic deaths were reported from Florida (22) and Texas (19). After excluding duplicate reports, four confirmed deaths were documented in Alabama, 10 in Florida, two in Georgia, two in Louisiana, and 14 in Texas.

Adult↗
PubMed2005

Effect of an exponentially decaying threshold on the firing statistics of a stochastic integrate-and-fire neuron.

We study a white-noise driven integrate-and-fire (IF) neuron with a time-dependent threshold. We give analytical expressions for mean and variance of the interspike interval assuming that the modification of the threshold value is small. It is shown that the variability of the interval can become both smaller or larger than in the case of constant threshold depending on the decay rate of threshold. We also show that the relative variability is minimal for a certain finite decay rate of the threshold. Furthermore, for slow threshold decay the leaky IF model shows a minimum in the coefficient of variation whenever the firing rate of the neuron matches the decay rate of the threshold. This novel effect can be seen if the firing rate is changed by varying the noise intensity or the mean input current.

Animals↗
PubMed2004

Fire-diffuse-fire calcium waves in confined intracellular spaces.

The propagation of fire-diffuse-fire Ca(2+) waves through a three-dimensional rectangular domain is considered. The domain is infinite in extent in the direction of propagation but with lateral barriers to diffusion which contain Ca(2+) pumps. The Ca(2+) concentration profile due to the firing of a release site (spark) is derived analytically based on the Green's function for the diffusion equation on the domain. The existence, stability and speed of these waves is shown to be critically dependent on the dimensions of the domain and the Ca(2+) pump rate. It is shown that the smaller the dimensions of the region, the lower the Ca(2+) release flux required for wave propagation, and the higher the wave speed. Also it is shown that the region may support multiple Ca(2+) wavefronts of varying wave speed. This model is relevant to subsarcolemmal waves in atrial myocytes (Kockskämper et al., 2001, Biophys. J. 81, 2590-2605), and the results may be of importance in understanding the roles of the endoplasmic/sarcoplasmic reticulum, surface membranes and Ca(2+) pumps in the intracellular Ca(2+) dynamics of cells.

Calcium↗
PubMed2000

Conjoint control of hippocampal place cell firing by two visual stimuli. I. The effects of moving the stimuli on firing field positions.

To better understand how hippocampal place cell activity is controlled by sensory stimuli, and to further elucidate the nature of the environmental representation provided by place cells, we have made recordings in the presence of two distinct visual stimuli under standard conditions and after several manipulations of these stimuli. In line with a great deal of earlier work, we find that place cell activity is constant when repeated recordings are made in the standard conditions in which the centers of the two stimuli, a black card and a white card, are separated by 135 degrees on the wall of a cylindrical recording chamber. Rotating the two stimuli by 45 degrees causes equal rotations of place cell firing fields. Removing either card and rotating the other card also causes fields to rotate equally, showing that the two stimuli are individually salient. Increasing or decreasing the card separation (card reconfiguration) causes a topological distortion of the representation of the cylinder floor such that field centers move relative to each other. We also found that either kind of reconfiguration induces a position-independent decrease in the intensity of place cell firing. We argue that these results are not compatible with either of two previously stated views of the place cell representation; namely, a nonspatial theory in which each place cell is tuned to an arbitrarily selected subset of available stimuli or a rigid map theory. We propose that our results imply that the representation is map-like but not rigid; it is capable of undergoing stretches without altering the local arrangement of firing fields.

Animals↗
PubMed2002

Firing sequence storage using inhibitory synapses in networks of pulsatil nonhomogeneous integrate-and-fire neural oscillators.

We discuss a nonhomogeneous population of pulsatil integrate-and-fire neural oscillators, coupled through purely inhibitory synapses. For instantaneous communication, we provide a strategy to generate synaptic couplings to obtain simple periodic and stable firing patterns. We provide restrictions under which each stored firing pattern is a unique attractor for the population dynamics. In the case of Peskin's leaky integrator we show results obtained from numerical simulations.

Journal Article↗
PubMed2005

Slow oscillatory firing: a major firing pattern of dopamine neurons in the ventral tegmental area.

Using spectral analysis and in vivo single-unit recording in rats, the present study revealed a pronounced slow oscillation (SO) in the firing activity of about half the dopamine (DA) neurons recorded in the ventral tegmental area. DA neurons in this group tended to fire repetitive spike clusters, making them appear to be rhythmic bursting cells. However, only some of these burst-like events met the traditional "80/160 ms" burst criteria entirely. The observation that the SO could be found in nonbursting DA cells, occurred at frequencies different from those of bursts, and persisted after bursts were digitally removed from spike trains further supports the suggestion that the SO is different from the traditionally defined bursting. Interspike intervals (ISIs) had been thought to be bimodally distributed in bursting DA neurons. This study found that some nonbursting DA cells also had a bimodal ISI distribution and a significant number of bursting cells did not. In the majority of cells where less than half the spikes occurred in bursts, a bimodal ISI distribution was highly predictive of the presence of the SO. Results further showed that the generation of the SO required forebrain inputs to DA neurons but not the adrenergic alpha1 receptor activation responsible for psychostimulant-induced increases in the SO. Taken together, these results suggest that the SO is distinct from the traditionally defined bursting and represents a major firing pattern of DA neurons in the ventral tegmental area.

Action Potentials↗
PubMed2005

Resuspension and redistribution of radionuclides during grassland and forest fires in the Chernobyl exclusion zone: part I. Fire experiments.

Controlled burning of experimental plots of forest or grassland in the Chernobyl exclusion zone has been carried out in order to estimate the parameters of radionuclide resuspension, transport and deposition during forest and grassland fires and to evaluate the working conditions of firemen. An increase of several orders of magnitude of the airborne radionuclide concentration was observed in the territory near the fire area. The resuspension factor for (137)Cs and (90)Sr was determined to range from 10(-6) to 10(-5) m(-1), and for the plutonium radionuclides from 10(-7) to 10(-6) m(-1) (related to the nuclides in the combustible biomass). These values are 2 orders of magnitude lower if they are calculated relatively to the total contamination density (including the nuclides in the soil). The radionuclide fallout along the plume axis is negligible in comparison to the existing contamination. However, the additional inhalation dose for firemen exposed in the affected area can reach the level of the additional external irradiation in the period of their mission. The plutonium nuclides constitute the dominating contribution to the inhalation dose.

Adult↗
PubMed2005

Fire, rain and the selection of seeder and resprouter life-histories in fire-recruiting, woody plants.

Several Cape species of the genus Erica are known to present seeder and resprouter phenotypes, and this variation seems to have a genetic basis. Therefore, this genus provides ideal model systems for using to elucidate the evolution of nonsprouting or seeder and resprouter life-histories in woody, fire-recruiting plants. A simple simulation model was developed to identify, under life-history optimality, the ecological conditions (viz. rainfall conditions and fire frequency) that conferred a selective advantage to the seeder phenotype over the resprouter in a given Cape Erica species. The model illustrated that the seeder life-history was able to invade and replace a resprouter population only under a mild mediterranean climate, with short, moderate summer droughts. This simulation approach will contribute to a better understanding of the biogeographical pattern of seeder and resprouter lineages of one of the paradigmatic fynbos woody taxa throughout the Cape floristic region.

Biological Evolution↗
PubMed2001

The effect of ion pumps on the speed of travelling waves in the fire-diffuse-fire model of Ca2+ release.

The fire-diffuse-fire model provides an idealized model of Ca2+ release within living cells. The effect of calcium pumps, which drive Ca2+ back into internal stores, is often neglected for mathematical simplicity. Here we show how to explicitly analyse such effects by extending the work of Keizer et al. [Keizer, J. E., G. D. Smith, S. Ponce Dawson and J. Pearson (1998). Saltatory propagation of Ca2+ waves by Ca2+ sparks. Biophys. J. 75, 595-600.]. For travelling waves, in which release events occur sequentially, we construct the speed of waves in terms of the time-scale at which pumps operate. An immediate consequence of this analysis is that the inclusion of calcium pumps leads to multiple solutions. A linear stability analysis determines those solution branches in parameter space which are stable. Numerical continuation is used to provide explicit examples of the bifurcation diagrams of the speed of waves as a function of physiologically significant system parameters.

Calcium↗
PubMed1998

Firing frequency of leaky intergrate-and-fire neurons with synaptic current dynamics.

We consider a model of an integrate-and-fire neuron with synaptic current dynamics, in which the synaptic time constant tau' is much smaller than the membrane time constant tau. We calculate analytically the firing frequency of such a neuron for inputs described by a random Gaussian process. We find that the first order correction to the frequency due to tau' is proportional to the square root of the ratio between these time constants radicaltau'/tau. This implies that the correction is important even when the synaptic time constant is small compared with that of the potential. The frequency of a neuron with tau'>0 can be reduced to that of the basic IF neuron (corresponding to tau'=1) using an "effective" threshold which has a linear dependence on radical tau'/tau. Numerical simulations show a very good agreement with the analytical result, and permit an extrapolation of the "effective" threshold to higher orders in radical tau'/tau. The obtained frequency agrees with simulation data for a wide range of parameters.

Animals↗
PubMed1979

The spontaneous firing patterns of forebrain neurons. IV. Effects of bilateral and unilateral frontal cortical ablations on firing of caudate, globus pallidus and thalamic neurons.

To assess the effects of partial deafferentation of the neostriatum on spontaneous neuronal activity in the basal ganglia and related thalamic nuclei, ablations of frontal cortex were carried out in adult cats. Postoperative measures of interspike intervals of single neurons in the caudate nucleus, globus pallidus and ventral anterior-ventral lateral complex of the thalamus revealed a slowing of neuronal firing in these structures as compared with non-lesioned controls. The fact that deafferentation by cortical damage produces changes in neuronal firing in target neurons of the striatum (globus pallidus) and in thalamic neurons at least two synapses removed from the striatum is noteworthy. The possible extent to which these results might have been influenced by reduction of cortical inputs to or denervation of the thalamus is discussed.

Afferent Pathways↗
PubMedDate not supplied

Receptors, sparks and waves in a fire-diffuse-fire framework for calcium release.

Calcium ions are an important second messenger in living cells. Indeed calcium signals in the form of waves have been the subject of much recent experimental interest. It is now well established that these waves are composed of elementary stochastic release events (calcium puffs or sparks) from spatially localised calcium stores. The aim of this paper is to analyse how the stochastic nature of individual receptors within these stores combines to create stochastic behaviour on long time-scales that may ultimately lead to waves of activity in a spatially extended cell model. Techniques from asymptotic analysis and stochastic phase-plane analysis are used to show that a large cluster of receptor channels leads to a release probability with a sigmoidal dependence on calcium density. This release probability is incorporated into a computationally inexpensive model of calcium release based upon a stochastic generalisation of the fire-diffuse-fire (FDF) threshold model. Numerical simulations of the model in one and two dimensions (with stores arranged on both regular and disordered lattices) illustrate that stochastic calcium release leads to the spontaneous production of calcium sparks that may merge to form saltatory waves. Illustrations of spreading circular waves, spirals and more irregular waves are presented. Furthermore, receptor noise is shown to generate a form of array enhanced coherence resonance whereby all calcium stores release periodically and simultaneously.

Animals↗