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Biomedical subjects

P A Boxer

Publications and source records attributed to P A Boxer.

At least 37 records · Page 2Linked to original sources
PubMed1993

Polyamine modulation of excitatory amino acid responses in the rat cortical wedge.

Rat neocortex slices in Mg2+ free buffer show spontaneous discharges which have a constant frequency and are dependent on N-methyl-D-aspartate (NMDA) receptor activation. Spermine increased the frequency of discharges at concentrations below 1 mM, had biphasic effects at 1 mM, and only decreased the frequency of discharges at 3 mM. In contrast, the amplitude of these discharges was only reduced by spermine in a concentration dependent manner (300 microM to 3 mM). Spermidine produced similar effects, but was a less potent inhibitor of discharge frequency and amplitude than spermine. Diethylenetriamine (DET) 300 microM did not significantly inhibit polyamine-induced increases in the discharge frequency. Polyamines inhibited direct depolarizations induced by the glutamate agonists NMDA or alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) in a concentration and time dependent manner. The data are consistent with two sites of action for polyamines, one enhancing the frequency of NMDA-mediated spontaneous epileptiform discharges and the other inhibiting direct glutamate responses in rat cortex. The slow onset (time to maximal enhancement or inhibition by polyamines greater than 30 min) and lack of reversibility with polyamine removal suggest that these sites are intracellular and/or presynaptic.

Amino Acids↗
PubMed1993

Assessment of potential violence in the paranoid worker.

Violence in the workplace is sometimes a manifestation of an untreated psychiatric disorder. Paranoid personality disorder, paranoid schizophrenia, and delusional (paranoid) disorder are three psychiatric syndromes in which paranoid ideation is a prominent feature. While the vast majority of people with these conditions are not violent, paranoid workers can exhibit violent behavior as a reaction to beliefs that co-workers or supervisors are threatening or persecuting them. Three cases are described to illustrate the clinical presentation of these disorders and their management in an occupational setting.

Adult↗
PubMed1993

Psychological distress and alcohol use among fire fighters.

Few studies have investigated stressors to which fire fighters are subjected and the potential psychological consequences. One hundred and forty-five fire fighters were studied to enumerate potential occupational stressors, assess psychological distress and problems with alcohol use, and determine whether a relationship exists between these measures and self-reported stressors. Hearing that children are in a burning building was the highest ranked stressor. According to three self-report instruments, between 33 and 41% of the fire fighters were experiencing significant psychological distress, and 29% had possible or probable problems with alcohol use. These figures are significantly higher than would be expected in a typical community or working population. In a logistic regression analysis, no relationship was found between measures of psychological distress and alcohol use and the 10 most highly ranked work stressors.

Adult↗
PubMed1992

Beta-proline analogues as agonists at the strychnine-sensitive glycine receptor.

3-Carboxy-3,4-dehydropyrrolidine was found to bind with affinity equal to that of glycine in a [3H]strychnine binding assay. Simple substitution of the 1-, 2-, 4-, or 5-position resulted in marked loss of affinity. A decline in affinity was also found upon enlargement, contraction, or saturation of the 5-membered ring. However, beta-proline and azetidine-3-carboxylic acid retained significant binding affinity. Despite its good affinity in [3H]strychnine binding, 3-carboxy-3,4-dehydropyrrolidine showed only weak agonist activity in intracellular recordings of cultured murine spinal cord neurons. This apparent lack of correlation between binding and functional results is discussed in light of the current models of the strychnine-sensitive glycine receptor.

Animals↗
PubMed1990

Indoor air quality: a psychosocial perspective.

The incidence of indoor air quality problems has increased dramatically over the past decade. Investigation of these problems has yielded a definitive cause in only one third of the cases. Psychosocial factors may play a key role in the development and propagation of symptoms attributed to poor indoor air quality. Guidelines for managing indoor air quality problems from the organizational perspective are based upon psychosocial principles and elements of risk perception.

Air Pollutants↗
PubMed1990

Comparison of phenytoin with noncompetitive N-methyl-D-aspartate antagonists in a model of focal brain ischemia in rat.

Recent in vitro and in vivo experiments have suggested that excitatory amino acid antagonists, particularly those active at the N-methyl-D-aspartate receptor subtype, are effective in ameliorating ischemic injury due to their antiexcitotoxic activity. However, these drugs are also potent and effective in vivo anticonvulsants. The present experiments compared the noncompetitive N-methyl-D-aspartate antagonists phencyclidine and MK-801 with the anticonvulsant phenytoin in a model of focal brain ischemia. Fisher F-344 rats were subjected to tandem occlusion of the middle cerebral and ipsilateral common carotid arteries under halothane anesthesia. Compounds were administered intravenously 30 minutes and 24 hours after arterial occlusion; infarct size was assessed at 48 hours after occlusion. Phencyclidine had no effect on infarct volume at 1 mg/kg, significantly reduced (by 36%) infarct volume at 3 mg/kg, and produced a nonsignificant 26% decrease at 10 mg/kg. The more potent and selective noncompetitive antagonist MK-801 reduced (by 32%) infarct volume significantly at 0.1 mg/kg, produced a nonsignificant 23% decrease at 0.3 mg/kg, and had no effect at 0.5 mg/kg. Phenytoin, which is not a glutamate antagonist, reduced the infarct volume by 45% at 28 mg/kg. A single dose of phenytoin (28 mg/kg) administered 30 minutes after occlusion was neuroprotective, but delaying drug administration for more than 2 hours was ineffective. These data suggest that blockade of the N-methyl-D-aspartate receptor is effective in reducing the infarct size after focal cerebral ischemia. The neuroprotective activity of phenytoin suggests that this may be related to the common anticonvulsant action.

Animals↗
PubMed1989

Identification and evaluation of O-alkyl substituted hydroxamic acids as potent in vitro inhibitors of the hepatic glycine cleavage system and investigation of their action on in vivo central nervous system glycine concentration.

The identification and evaluation of an extensive series of O-alkyl substituted hydroxamic acids as potent in vitro inhibitors of the hepatic glycine cleavage system is described. An investigation of the action of selected examples on the in vitro brain glycine cleavage system and their influence on in vivo plasma and central nervous system glycine concentrations following systemic administration is also reported.

Animals↗
PubMed1988

Alterations of group Ia-motoneuron monosynaptic EPSPs in aged cats.

The fashion in which the aging process affects synaptic transmission was explored in old cats. The synapses between Ia-afferent fibers and spinal cord alpha-motoneurons were studied employing intracellular recording techniques. The amplitude and time course of Ia-motoneuron monosynaptic excitatory postsynaptic potentials (Ia-EPSPs) recorded from motoneurons of the gastrocnemius medialis motor pool were determined in adult (1-3 years of age) and in old (14-15 years of age) cats. These Ia-EPSPs were evoked by the stimulation of the gastrocnemius medialis nerve in pentobarbital-anesthetized cats. No statistically significant change was found in the amplitude of these synaptic potentials in the old cats compared with the adult controls. In contrast, their time course was markedly modified; both rise-time and half-width were significantly longer in the old cats. In addition, the rate-of-rise of these Ia-EPSPs was significantly slower in the old cats. No breaks or inflections were observed on the rising phase of the potentials in the adult cats, whereas they were present in a subpopulation of potentials in the old cats. There was also a reduction, in the old cats, in the conduction velocity of the peripheral portion of the Ia-afferent fibers. These data indicate that Ia synaptic transmission is considerably affected during old age. It is suggested that these effects in aged cats may be due to modifications in presynaptic as well as postsynaptic processes.

Aging↗
PubMed1987

Basic electrophysiological properties of spinal cord motoneurons during old age in the cat.

1. The electrophysiological properties of alpha-motoneurons in old cats (14-15 yr) were compared with those of adult cats (1-3 yr). These properties were measured utilizing intracellular recording and stimulating techniques. 2. Unaltered in the old cat motoneurons were the membrane potential, action potential amplitude, and slopes of the initial segment (IS) and soma dendritic (SD) spikes, as well as the duration and amplitude of the action potential's afterhyperpolarization. 3. In contrast, the following changes in the electrophysiological properties of lumbar motoneurons were found in the old cats: a decrease in axonal conduction velocity, a shortening of the IS-SD delay, an increase in input resistance, and a decrease in rheobase. 4. In spite of these considerable changes in motoneuron properties in the old cat, normal correlations between different electrophysiological properties were maintained. The following key relationships, among others, were the same in adult and old cat motoneurons: membrane potential polarization versus action potential amplitude, duration of the afterhyperpolarization versus motor axon conduction velocity, and rheobase versus input conductance. 5. A review of the existing literature reveals that neither chronic spinal cord section nor deafferentation (13, 21) in adult animals produce the changes observed in old cats. Thus we consider it unlikely that a loss of synaptic contacts was responsible for the modifications in electrophysiological properties observed in old cat motoneurons. 6. We conclude that during old age there are significant changes in the soma-dendritic portion of cat motoneurons, as indicated by the modifications found in input resistance, rheobase, and IS-SD delay, as well as significant changes in their axons, as indicated by a decrease in conduction velocity.

Action Potentials↗
PubMed1986

Effect of stimulation of the nucleus reticularis gigantocellularis on the membrane potential of cat lumbar motoneurons during sleep and wakefulness.

The present study was performed in order to determine the effect of electrical stimulation of the medullary nucleus reticularis gigantocellularis (NRGc) on the membrane potential of spinal cord motoneurons during sleep and wakefulness. Accordingly, intracellular recordings were obtained from lumbar motoneurons in unanesthetized normally respiring cats during naturally occurring states of wakefulness, quiet sleep and active sleep. Electrical stimuli applied to the NRGc evoked synaptic potentials which occurred at short latency (less than 10 ms) and did not exhibit consistent changes in their waveforms during any states of sleep or wakefulness. During wakefulness and quiet sleep, longer latency (greater than 20 ms) low-amplitude hyperpolarizing potentials occasionally followed NRGc stimulation. However, during active sleep, NRGc stimulation produced, in all motoneurons, relatively large hyperpolarizing potentials that were characterized by a mean amplitude of 3.5 +/- 0.4 mV (mean +/- S.E.M.), a mean latency-to-peak of 43.0 +/- 0.8 ms, and an average duration of 34.4 +/- 1.7 ms. These potentials were capable of blocking the generation of orthodromic spikes elicited by sciatic nerve stimulation. When anodal current or chloride was passed through the recording electrode, the hyperpolarizing potentials decreased in amplitude, and in some cases their polarity was reversed. These results indicate that the active sleep-specific hyperpolarizing potentials were inhibitory postsynaptic potentials. Thus, the NRGc possesses the capability of providing a postsynaptic inhibitory drive that is directed toward lumbar motoneurons which is dependent on the occurrence of the behavioral state of active sleep.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Aging of motoneurons and synaptic processes in the cat.

The aging of spinal cord alpha motoneurons was explored in old cats with intracellular recording techniques to determine the basic membrane properties of these neurons and their monosynaptic response following activation of group Ia afferent fibers. The conduction velocity of the motoneurons' axons decreased in old animals (14 to 15 years of age) compared with adult controls (1 to 3 years of age). The input resistance of the motoneurons increased in the old cats; no change occurred in the resting membrane potential or spike amplitude. There was a reduction in the delay between the initial segment and the somadendritic components of the antidromic spike. The half-width duration of the monosynaptic EPSP in the old cats increased, but its amplitude did not change. These data indicate that a host of different membrane properties of spinal cord motoneurons and their Ia-monosynaptic input are affected by the aging process. Analysis of the results suggests that the degradation of neuronal processes occurs in all motoneurons rather than preferentially affecting a specific population of motoneurons.

Action Potentials↗
PubMed1985

Psychiatric diagnoses of Cuban refugees in the United States: findings of medical review boards.

To assess the reproducibility of psychiatric diagnoses made in immigration proceedings, the authors examined cases of 109 Cuban refugees who had appealed psychiatric diagnoses that precluded their admission to the United States according to the Immigration and Nationality Act. Medical review boards upheld only 23 (42%) of 55 initial diagnoses of antisocial personality disorder but affirmed exclusionary certifications in 39 (72%) of the 54 other cases. Failure to sustain a high proportion of diagnoses of antisocial personality disorder may reflect interviewer biases, cross-cultural inappropriateness of diagnostic criteria, or other deficiencies in the current system of psychiatric evaluation of potential refugees.

Antisocial Personality Disorder↗
PubMed1985

Occupational mass psychogenic illness. History, prevention, and management.

Occupational mass psychogenic illness is a poorly understood phenomenon that is probably underreported in the literature. Several recent outbreaks illustrate the main features, including explosive onset usually triggered by a physicochemical stimulus; disproportionate involvement of relatively uneducated, low-paid women who perform highly routine tasks; diverse symptoms with scarcity of physical signs or laboratory findings; frequent absence of usual symptoms caused by the putative contaminant; recurrences in affected individuals when they congregate; and benign morbidity and lack of sequelae. Inappropriate handling of these outbreaks can lead to prolonged employee disability and disrupted production. Though the etiology of epidemic psychogenic illness often remains uncertain, a sufficient body of knowledge exists to plan a rational prevention and management program.

Disease Outbreaks↗
PubMed1984

An epidemic of psychogenic illness in an electronics plant.

We investigated an outbreak of illness in electronics plant workers. Questionnaire data revealed that 98 employees experienced symptoms, including light- headedness , headache, sleepiness, and numbness/tingling of the face or extremities. Attack rates by work station followed no apparent pattern. Extensive medical and environmental evaluation, including air sampling for numerous solvents and gases, provided no physical or chemical explanation for the epidemic. Compared with well employees, ill employees were more commonly female, complained more frequently of bothersome odors, and believed that greater danger existed of the illness recurring. Blood gas analyses of seven of 11 ill workers showed respiratory alkalosis, consistent with hyperventilation. The poorly defined nature of this illness, the absence of exposures to environmental contaminants in concentrations exceeding recommended limits, and the evidence of hyperventilation suggest that this outbreak was an incident of industrial psychogenic illness.

Adult↗
PubMed1984

A new Legionella species, Legionella feeleii species nova, causes Pontiac fever in an automobile plant.

From 15 to 21 August 1981, Pontiac fever affected 317 automobile assembly plant workers. Results of serologic tests were negative for Mycoplasma, Chlamydia, respiratory tract viruses, and previously described legionellae. A gram-negative, rod-shaped organism (WO-44C) that did not grow on blood agar, required L-cysteine for growth, and contained large amounts of branched-chain fatty acids was isolated from a water-based coolant. The organism did not react with antisera against other legionellae, and on DNA hybridization the organism was less than 10% related to other Legionella species. Geometric mean titers found by indirect fluorescent antibody testing to WO-44C were significantly higher in ill employees than in controls (p = 0.0001). Attack rates by department decreased linearly with the department's distance from the implicated coolant system. The etiologic agent apparently was a new Legionella species; we propose the name Legionella feeleii species nova (AATC 35072). This is the first outbreak of nonpneumonic legionellosis in which the etiologic agent is not L. pneumophila, serogroup 1.

Aerosols↗
PubMed1982

Hyperpolarizing membrane responses induced in lumbar motoneurons by stimulation of the nucleus reticularis pontis oralis during active sleep.

Intracellular recordings were obtained from lumbar motoneurons in unanesthetized, undrugged, normally respiring cats during the states of wakefulness, quiet sleep and active sleep. The objective was to examine the state-dependent control of spinal cord motoneurons exerted by the pontomesencephalic reticular formation. Accordingly, electrical stimulation was applied to the nucleus reticularis pontis oralis while the membrane potential of lumbar motoneurons was recorded. Short latency depolarizing and/or hyperpolarizing potentials were observed throughout sleep and wakefulness; no state-dependent pattern was found in the direction of polarization or amplitude for these early potentials. However, a long latency hyperpolarizing potential emerged exclusively during active sleep; it was characterized by a peak latency of 45 +/- 1 (S.E.M.) ms, a duration of 40 +/- 2 ms, and an amplitude of 3 +/- 0.5 mV. This active sleep-selective potential was capable of inhibiting spontaneous motoneuron activity. These and previously obtained data support the notion that excitation of the nucleus reticularis pontis oralis results in somatomotor inhibition at the level of the spinal cord and brainstem selectively during the state of active sleep.

Animals↗