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At least 73 records · Page 4Linked to original sources
PubMed1976

Imported fire ant hypersensitivity. Studies of human reactions to fire ant venom.

It is now apparent that venom and venom components of the Hymenoptera superfamilies of Apida (honeybee) and Vespida (wasps, yellow jackets, and hornets) are becoming increasingly important in the diagnosis and treatment of hypersensitivity reactions. Stings from fire ants (superfamily Formicidae, family Myrmicinae) have also been recognized as causes of systemic reactions in man. Fire ant venom is unique in its composition, consisting mainly of alkaloids in aqueous suspension with only trace amounts of protein. This study compares the skin reactivity of fire ant venom and synthesized alkaloid components with the whole body extract (WBE) of fire ants and other Hymenoptera. The venom as well as the WBE of fire ants was found useful for skin test diagnosis of sensitive individuals. There appear to be cross-reactive or shared antigens between fire ant venom, WBE, and WBE of other Hymenoptera. Successful passive transfer of skin reactivity to nonsensitive individuals was accomplished with sera from sensitive individuals. Loss of this passive transfer by heating sera at 56 degrees C for 4 hr is evidence in favor of IgE mediating the positive skin test to the venom.

Animals↗
PubMed2000

Unilateral lesion of the nigrostriatal pathway induces a transient decrease of firing rate with no change in the firing pattern of neurons of the parafascicular nucleus in the rat.

Electrophysiological recordings of thalamic parafascicular nucleus neurons were done in normal rats and in three groups of rats at different time intervals after injection of 6-hydroxydopamine into the pars compacta of substantia nigra. In normal rats, parafascicular neurons exhibited low firing rates (3.88+/-0.80 spikes/s). Concerning the pattern, 59% of the units discharged irregularly and 41% exhibited bursty pattern. In rats with 6-hydroxydopamine lesions, the firing rate decreased significantly during the first week post-lesion (1.15+/-0.36 spikes/s, P<0.01). During the second week, the firing rate was slightly, but not significantly, lower (2.59+/-0.41 spikes/s, P>0.05) than that of normal rats to return to the basal level three weeks post-lesion (3. 66+/-0.41 spikes/s, P>0.05). In these three groups of 6-hydroxydopamine-lesioned rats, the firing pattern showed no change when compared to control animals. These results show that the lesion of nigral dopaminergic neurons induced a transient decrease of the firing rate of parafascicular neurons with no change in the firing pattern demonstrating the absence of a stable influence of the dopaminergic system on the spontaneous activity of parafascicular neurons.

Action Potentials↗
PubMed2004

Mean instantaneous firing frequency is always higher than the firing rate.

Frequency coding is considered one of the most common coding strategies employed by neural systems. This fact leads, in experiments as well as theoretical studies, to construction of so-called transfer functions, where the output firing frequency is plotted against the input intensity. The term "firing frequency" can be understood differently in different contexts. Basically, it means that the number of spikes over an interval of preselected length is counted and then divided by the length of the interval, but due to the obvious limitations, the length of observation cannot be arbitrarily long. Then firing frequency is defined as reciprocal to the mean interspike interval. In parallel, an instantaneous firing frequency can be defined as reciprocal to the length of current interspike interval, and by taking a mean of these, the definition can be extended to introduce the mean instantaneous firing frequency. All of these definitions of firing frequency are compared in an effort to contribute to a better understanding of the input-output properties of a neuron.

Action Potentials↗
PubMed1984

The control of firing pattern in nigral dopamine neurons: single spike firing.

Dopamine (DA) neurons have been recorded in vivo in four states of activity: hyperpolarized, nonfiring; single spike firing; burst firing; and depolarization inactivation. Nonfiring DA neurons can be made to fire by iontophoretic application of the excitatory substances glutamate and cholecystokinin, or by depolarizing current injection. Spontaneously active DA cells typically fire in a slow (3 to 8 Hz) irregular pattern. In vivo intracellular recordings revealed that this pattern is sustained by the alternation of two currents: a spontaneously occurring slow depolarization (13 +/- 3 mV amplitude, 78 +/- 40 msec duration) which brings the membrane potential of the DA cell to spike threshold (-42 mV), and an afterhyperpolarization mediated by a calcium-activated potassium conductance (IK(Ca)). The slow depolarization is a pacemaker-like conductance, with a rate of rise proportional to the membrane potential. The regular pacemaker pattern of the spontaneously occurring slow depolarization is interrupted by the IK(Ca) which appears to be triggered by calcium entry during the action potential. Thus, intracellular injection of the calcium chelator EGTA will cause DA cells to fire in a regular, pacemaker pattern. The IK(Ca) is observed after single spikes and trains of spikes with the amplitude of the afterhyperpolarization being proportional to the number of spikes in a train. Both the afterhyperpolarization and the firing accommodation observed during depolarizing current injection can be blocked by intracellular injection of the calcium chelator EGTA.

Action Potentials↗
PubMed1998

A simple model for neural computation with firing rates and firing correlations.

A simple extension of standard neural network models is introduced which provides a model for neural computations that involve both firing rates and firing correlations. Such an extension appears to be useful since it has been shown that firing correlations play a significant computational role in many biological neural systems. Standard neural network models are only suitable for describing neural computations in terms of firing rates. The resulting extended neural network models are still relatively simple, so that their computational power can be analysed theoretically. We prove rigorous separation results, which show that the use of firing correlations in addition to firing rates can drastically increase the computational power of a neural network. Furthermore, one of our separation results also throws new light on a question that involves just standard neural network models: we prove that the gap between the computational power of high-order and first-order neural nets is substantially larger than shown previously.

Neural Networks, Computer↗
PubMedDate not supplied

Buses as fire hazards: a Swedish problem only? Suggestions for fire-prevention measures.

In Sweden, approximately 6% of all human transportation is made via buses. The Swedish Board of Accident Investigation and the Swedish Rescue Services Agency have pointed out repeatedly that buses are potential fire and burn hazards, not only when involved in collisions but also in other circumstances. The number of fire incidents is increasing, especially in newer buses. In conjunction with the Swedish Rescue Services Agency, we examined some of the recent bus fires in Sweden. We did not find any casualties, but the results of our study suggest that casualties as a result of bus fires are imminent unless preventive measures are taken. We also studied experiences from previous bus fires and suggest preventive measures.

Burns↗
PubMedDate not supplied

Working toward the elimination of residential fire deaths: the Centers for Disease Control and Prevention's Smoke Alarm Installation and Fire Safety Education (SAIFE) program.

To address residential fires and related injuries, the Centers for Disease Control and Prevention funds state health departments to deliver a Smoke Alarm Installation and Fire Safety Education (SAIFE) program in high-risk homes in 16 states. This program involves recruiting local communities and community partners, hiring a local coordinator, canvassing neighborhood homes, installing long-lasting lithium-powered smoke alarms, and providing general fire safety education and 6-month follow-up to determine alarm functionality. Local fire departments are vital community partners in delivering this program. Since the program's inception, more than 212,000 smoke alarms have been installed in more than 126,000 high-risk homes. Additionally, approximately 610 lives have potentially been saved as a result of a program alarm that provided early warning to a dangerous fire incident.

Burns↗
PubMed2002

A study of the effects of a Micelle Encapsulator Fire Suppression Agent on dynamic headspace analysis of fire debris samples.

The effects of a Micelle Encapsulator Fire Suppression Agent (F-500, Hazard Control Technologies Inc., Fayetteville, Georgia) on the routine analysis of fire debris samples by Gas Chromatography (GC) were studied. When mixed with water the product can be used in the suppression of Class A and Class B fires. Laboratory tests were performed to determine whether or not the product has any effect on the analysis for ignitable liquids by GC, in particular for gasoline, medium petroleum distillates. and heavy petroleum distillates. Test burns were suppressed using either the micelle encapsulator or water and samples collected from these burns were analyzed. The results of analysis show that use of the micelle encapsulator at a fire scene may affect the chromatographic data obtained from samples collected by the investigator. However, the effect does not prevent the identification of common ignitable liquids in fire debris samples.

Fire Extinguishing Systems↗
PubMed1983

In vivo and in vitro comparison of fire ant venom and fire ant whole body extract.

Thirty-four patients with a history of immediate hypersensitivity to the sting of the imported fire ant were evaluated in a study designed to compare the diagnostic usefulness of fire ant whole body extract (WBE) preparations with that of fire ant venom (IFAV). Ninety-one percent (31/34) of the hypersensitive patients skin tested with IFAV at a maximal concentration of 1:5 X 10(3), v/v, demonstrated a wheal equal to or greater than the histamine control. Fifty-three percent (18/34) of the group were skin test positive to a WBE preparation. When the criteria for a positive skin test were relaxed, 82% of the hypersensitive group could be identified with the IFAWBE. A comparison of skin test results in sensitive patients revealed variability in the sensitivity of the WBE preparations utilized in the study. Leukocyte histamine release demonstrated a dose-response release of histamine with both IFAV and SIWBEa preparations. Specific venom antisera produced in rabbits identified a precipitin line of common identity in a gel-diffusion system containing IFAWBE and IFAV. This finding was verified by the competitive inhibition of IFAWBE with IFAV in a solid-phase radioimmunoassay system. Fire ant WBEs contain venom constituents and are effective diagnostic agents in up to 82% of patients with hypersensitivity to the sting of the imported fire ant. Marked variability in the responsiveness of sensitive patients to different WBE preparations mandates standardization of these diagnostic preparations.

Adolescent↗
PubMed1992

Safety and efficacy of fire ant venom in the diagnosis of fire ant allergy.

Thirty-three adult patients who had had systemic allergic reactions to fire ant stings and 33 insect-nonallergic control subjects were skin tested with single lots of Solenopsis invicta (Sol i) fire ant venom (IFAV) and two commercially available imported fire ant whole body extracts (IFA WBEs). All three extracts were analyzed for protein concentration. Sol i II and Sol i III concentrations were each assayed by means of two ELISAs with complementary monoclonal antibodies, one species specific and one cross-reactive. Radioallergosorbent test (RAST) to IFAV and both IFA WBEs was performed on sera from all study subjects. Both IFA WBEs contained high concentrations of fire ant body proteins. Sol i II and III concentrations each varied twofold between the two IFA WBE preparations. Patients were generally more reactive to IFAV than IFA WBE by skin testing and RAST. IFAV RAST appeared to be a more sensitive assay than IFA WBE RAST. No adverse reactions occurred to skin testing with IFAV, but intradermal testing with higher concentrations of IFA WBE caused delayed large local reactions in 16 of 30 (53%) control subjects. These reactions were attributed to the large amounts of extraneous body proteins in IFA WBE. These results (1) demonstrate that skin testing with IFAV is safe, (2) indicate that IFAV is more potent than IFA WBE, and (3) suggest that IFAV may be the superior reagent for diagnosis of fire ant allergy.

Adult↗
PubMed1997

Low genetic diversity in Persoonia mollis (Proteaceae), a fire-sensitive shrub occurring in a fire-prone habitat.

Allozyme frequency data were used to estimate hierarchical levels of genetic diversity within and among the nine subspecies of the morphologically variable shrub Persoonia mollis R. Br. (Proteaceae). This species is a fire-sensitive component of the fire-prone sclerophyllous vegetation of south- eastern Australia. The total gene diversity (H(T)=0.139) within P. mollis was less than half that typically found within angiosperm species. However, P. mollis was typical of angiosperms in the way its gene diversity was distributed, with 78.3 per cent of the total gene diversity found within populations. Of the 21.7 per cent found among populations, 17.9 per cent was attributed to differences among subspecies and only 3.8 per cent attributed to differences among populations within subspecies. Heterozygosity (H(E)) within populations varied 10-fold from 0.023-0.206, with a comparatively low mean over all populations of 0.109. A significant deficit of heterozygotes for the outbreeding P. mollis is consistent with the 'heterozygosity paradox', is caused by a Wahlund effect, and suggests an average genetic neighbourhood size of between 3 and 60 plants. Explanations for these patterns and the weak correlation of these data with morphological variation are discussed. It is suggested that the high frequency and haphazard occurrence of fire plays a major role in affecting the levels and distribution of genetic diversity within P. mollis, and probably within other fire-sensitive plant species also occurring in fire-prone habitats, through relatively frequent localized extinction and subsequent recolonization.

Journal Article↗
PubMed2003

Firing-rate resonance in a generalized integrate-and-fire neuron with subthreshold resonance.

Neurons that exhibit a peak at finite frequency in their membrane potential response to oscillatory inputs are widespread in the nervous system. However, the influence of this subthreshold resonance on spiking properties has not yet been thoroughly analyzed. To this end, generalized integrate-and-fire models are introduced that reproduce at the linear level the subthreshold behavior of any given conductance-based model. A detailed analysis is presented of the simplest resonant model of this kind that has two variables: the membrane potential and a supplementary voltage-gated resonant variable. The firing-rate modulation created by a noisy weak oscillatory drive, mimicking an in vivo environment, is computed numerically and analytically when the dynamics of the resonant variable is slow compared to that of the membrane potential. The results show that the firing-rate modulation is shaped by the subthreshold resonance. For weak noise, the firing-rate modulation has a minimum near the preferred subthreshold frequency. For higher noise, such as that prevailing in vivo, the firing-rate modulation peaks near the preferred subthreshold frequency.

Action Potentials↗
PubMed1999

House fire injury prevention update. Part I. A review of risk factors for fatal and non-fatal house fire injury.

OBJECTIVE: To summarize house fire injury risk factor data, using relative risk estimation as a uniform method of comparison. METHODS: Residential fire risk factor studies were identified as follows: MEDLINE (1983 to March 1997) was searched using the keywords fire*/burn*, with etiology/cause*, prevention, epidemiology, and smoke detector* or alarm*. ERIC (1966 to March 1997) and PSYCLIT (1974 to June 1997) were searched by the above keywords, as well as safety, skills, education, and training. Other sources included: references of retrieved publications, review articles, and injury prevention books; Injury Prevention journal hand search; government documents; and internet sources. When not provided by the authors, relative risk (RR), odds ratio, and standardized mortality ratios were calculated, to enhance comparison between studies. RESULTS: Fifteen relevant articles were retrieved, including two case-control studies. Non-modifiable risk factors included young age (RR 1.8-7.5), old age (RR 2.6-3.6), male gender (RR 1.4-2.9), non-white race (RR 1.3-15.0), low income (RR 3.4), disability (RR 2.5-6.5), and late night/early morning occurrence (RR 4.1). Modifiable risk factors included place of residence (RR 2.1-4.2), type of residence (RR 1.7-10.5), smoking (RR 1.5 to 7.7), and alcohol use (RR 0.7-7.5). Mobile homes and homes with fewer safety features, such as a smoke detector or a telephone, presented a higher risk of fatal injury. CONCLUSIONS: Risk factor data should be used to assist in the development, targeting, and evaluation of preventive strategies. Development of a series of quantitative systematic reviews could synthesize existing data in areas such as house fire injury prevention.

Accidents, Home↗
PubMed1993

Determination of firing distance and firing angle by neutron activation analysis in a case involving gunshot wounds.

This paper reports the determination of the firing distance and a method for the evaluation of the firing angle in a fatal incident caused by two gunshots. Neutron Activation Analysis (NAA) was used to determine the Sb pattern around the bullet entrance holes on a garment of the victim, and around bullet holes produced by different shots on test targets from the gun and ammunition under investigation. The calibration curves obtained at various distances and firing angles enabled the determination of the firing distances and angles of the crime shots with a standard deviation of +/- 2 cm and +/- 5 degrees, respectively.

Axilla↗
PubMed2004

Assessment of application-rate dependent effects of a long-term fire retardant chemical (Fire Trol 934) on Typha domingensis germination.

Although long-term fire retardants (LTR) gain increasingly acceptance as effective tools for wildfire management, recent studies indicate their potential harmfulness in the environment, especially in aquatic ecosystems. This study comprises a first laboratory impact assessment of LTR action in temporal Mediterranean wetlands, using seed germination of Typha domingensis as indicator of impact. Our aim was to identify application rates upon which seed germination could be significantly affected. We tested for low (1 l m(-2)) and high (3 l m(-2)) application rates of Fire Trol 934 which are recommended by the manufacturers as a function of fuel characteristics. In addition, we simulated the impact of a higher application rate of 5 l m(-2) because inhomogeneous dispersal of the LTR during fire control and prevention operations can result in locally elevated applications. Results of a microcosm experiment indicate that application rates of 1 or 3 l m(-2) can impact Typha germination rates in the short-term via indirect LTR-mediated effects on water quality, which suppressed necessary cues for germination. However, a subsequent experiment with Petri dishes, using seeds isolated from the LTR treated sediments did not show significantly different germination rates between the control and the treatments with application rates of 1 or 3 l m(-2). This suggests that retardant pre-application germination success could be recovered in nature once the retardant is eliminated. By contrast, seeds almost completely failed to germinate in the microcosm experiment and the subsequent Petri dish essay when an application rate of 5 l m(-2) was used. This suggests a critical level upon which Typha seed germination may be perpetually limited. Research should be extended to other plant species to provide fire managers with guidelines for environmentally safe use of LTR in the Mediterranean region.

Dose-Response Relationship, Drug↗
PubMed2006

Neuron firing in driven nonlinear integrate-and-fire models.

Statistical properties of neuron firing are studied in the framework of a nonlinear leaky integrate-and-fire model that is driven by a slow periodic subthreshold signal. The firing events are characterized by first passage time densities. The experimentally better accessible interspike interval density generally depends on the sojourn times in a refractory state of the neuron. This aspect is not part of the integrate-and-fire model and must be modelled additionally. For a large class of refractory dynamics, a general expression for the interspike interval density is given and further evaluated for the two cases with an instantaneous resetting (i.e. no refractory state) and a refractory state possessing a deterministic lifetime. First passage time densities and interspike interval densities following from the proposed theory compare favorably with precise numerical simulations.

Action Potentials↗
PubMed2002

Dynamics of the firing probability of noisy integrate-and-fire neurons.

Cortical neurons in vivo undergo a continuous bombardment due to synaptic activity, which acts as a major source of noise. Here, we investigate the effects of the noise filtering by synapses with various levels of realism on integrate-and-fire neuron dynamics. The noise input is modeled by white (for instantaneous synapses) or colored (for synapses with a finite relaxation time) noise. Analytical results for the modulation of firing probability in response to an oscillatory input current are obtained by expanding a Fokker-Planck equation for small parameters of the problem - when both the amplitude of the modulation is small compared to the background firing rate and the synaptic time constant is small compared to the membrane time constant. We report here the detailed calculations showing that if a synaptic decay time constant is included in the synaptic current model, the firing-rate modulation of the neuron due to an oscillatory input remains finite in the high-frequency limit with no phase lag. In addition, we characterize the low-frequency behavior and the behavior of the high-frequency limit for intermediate decay times. We also characterize the effects of introducing a rise time to the synaptic currents and the presence of several synaptic receptors with different kinetics. In both cases, we determine, using numerical simulations, an effective decay time constant that describes the neuronal response completely.

Action Potentials↗
PubMed1977

Carboxyhemoglobin concentrations in flash fire victims: report of six simultaneous fire fatalities without elevated carboxyhemoglobin.

Eight people died in a traffic accident involving a tractor-trailer and ten autos. The accident caused a series of flash fires from ruptured gas tanks. Complete autopsies established that six of the victims died exclusively from thermal trauma; none showed an elevated blood carboxyhemoglobin concentration. Flash fire victims are exceptions to the axiom that elevation of blood carboxyhemoglobin is a sine qua non for concluding that a decedent recovered from the scene of a conflagration was alive in the fire.

Accidents, Traffic↗