Biomedical subjects

R L Moss

Publications and source records attributed to R L Moss.

283 records · Page 16Linked to original sources

PubMedDate not supplied

Calcitonin and calcitonin gene-related peptide alter the excitability of neurons in rat forebrain.

Individual neurons in the hypothalamus, thalamus, cortex, and other forebrain areas of urethane-anesthetized, male rats were iontophoretically tested for their membrane sensitivity to salmon calcitonin (CT), human CT, and CT gene-related peptide (CGRP). Extracellular recording of unit activity revealed that depression of neuronal firing was the predominant effect of iontophoretically applied salmon CT (35 of 74 cells tested). Few neurons responded to salmon CT with an increase in firing rate (N = 3). When CGRP was iontophoretically applied a pattern of response resembling that of salmon CT was observed. CGRP was predominantly inhibitory and excited those neurons whose firing rate was increased by salmon CT. Inhibition was also the predominant effect of human CT. However, no neurons were excited by human CT. The results clearly demonstrate that a subpopulation of neurons with membrane sensitivity to salmon CT, human CT, and CGRP are present in the rat forebrain. This finding suggests that modulation of neuronal activity may underlie the behavioral and biochemical effects of these peptides when administered centrally. Endogenous CGRP and CT-like peptides in rat brain may be capable of regulating these events as neurotransmitters or neuromodulators.

Action Potentials↗

PubMedDate not supplied

Sensitivity of rat forebrain neurons to growth hormone-releasing hormone.

The effects of iontophoretically applied human pancreatic growth hormone-releasing factor (hpGRF), peptide histidine isoleucine (PHI-27), and somatostatin (SS) on the extracellular activity of single cells in the hypothalamus, thalamus, and cortex of the rat brain were studied in urethane-anesthetized, male rats. Neurons with membrane sensitivity to hpGRF, PHI-27, and SS were present in each brain region. Although neurons excited by these peptides were encountered in thalamus and hypothalamus, depression of neuronal firing was the predominant response observed. Overall, the neurons responding to hpGRF also possessed membrane sensitivity to PHI-27, whereas, the hpGRF sensitive neurons appeared to be more divided as to their ability to respond to SS. The results clearly demonstrate that hpGRF and PHI-27 are capable of affecting the membrane excitability of neurons in several brain regions. The distribution of neurons sensitive to hpGRF suggests that hypothalamic GRF, in addition to its well documented role in the regulation of pituitary growth hormone secretion, may subserve other physiological events in the rat central nervous system as a neurotransmitter and/or neuromodulator.

Action Potentials↗

PubMedDate not supplied

Solitary hypothalamic neurons inherently express vasopressin and tyrosine hydroxylase.

Hypothalamic neurons were grown as single cells in three-dimensional culture. Solitary neurons lacking cell contacts were immunocytochemically examined for inherent expression of vasopressin (VP), tyrosine hydroxylase (TH), and luteinizing hormone releasing hormone (LHRH). Immunoreactive VP and TH were detected within a day. Sixty to eighty-five percent of neurons displayed homogeneously distributed reaction product for VP or TH. One percent exhibited intense punctate staining of somas and varicosities. Few neurons stained for LHRH. Results indicate that hypothalamic neurons can express appropriate neuropeptides and transmitter-specific products without contacting other neurons or nonneuronal cells. Thus, this culture system may provide a useful model to study intrinsic neuronal processes.

Animals↗

PubMedDate not supplied

Specific binding of 125I-LHRH agonist to hippocampal membranes: fluctuations during the estrous cycle.

Specific binding of 125I-[D-Ala6-CH3-Leu7-Pro9,NHET]LHRH, a LHRH agonist, to hippocampal membranes prepared from ovariectomized female rates was examined. One high affinity binding site was observed with a Kd of 0.12 +/- 0.01 nM and an apparent Bmax of 13.0 +/- 3.8 fmol/mg. Luteinizing hormone-releasing hormone and the behaviorally active Ac-LHRH(5-10) were able to compete for the agonist binding site. Native LHRH had an apparent Ki of 1.73 nM, while AC-LHRH(5-10) was 30 times less potent. Competition studies examined over the rat estrous cycle revealed an eighteenfold decrease in apparent affinity during diestrus I and estrus compared with ovariectomized animals. Tissue from animals in proestrus had a Ki of 5.0 nM. Specific binding studies indicate that receptor concentration is highest in proestrus (6.11 +/- 0.90 fmol/mg) and significantly lower during estrus (2.4 +/- 0.29 fmol/mg). These data suggest that at least one fragment of native LHRH can interact with neuronal LHRH receptors and that these receptors, like those in the pituitary, can be modulated by circulating steroid hormones.

Animals↗

PubMedDate not supplied

Effects of a biologically active LHRH fragment on CA1 hippocampal neurons.

The actions of a behaviorally active luteinizing hormone-releasing hormone fragment, Ac-LHRH(5-10), on CA1 pyramidal cells were studied utilizing conventional intracellular recordings from the in vitro rat hippocampal slice preparation. The behaviorally active fragment (10(-7) M) and the natural decapeptide [LHRH(1-10), 10(-8) M] had similar actions on CA1 neurons: a long-duration depolarization associated with increased input resistance, a reduction in the slow afterhyperpolarization (AHP), and a decrease in accommodation. In contrast, a biologically inactive LHRH fragment [LHRH(1-6) at 10(-7) M] had no effect on electrical properties of CA1 neurons. These data suggest that Ac-LHRH(5-10), like LHRH(1-10), may have a modulatory action on hippocampal neurons.

Animals↗

PubMedDate not supplied

Midbrain central gray: LHRH infusion enhances lordotic behavior in estrogen-primed ovariectomized rats.

Ovariectomized rats were implanted with 23 gauge stainless steel cannulae in the ventrolateral midbrain central gray. Twelve sexually active rats were estrone-primed and infused with saline and 50 ng luteinizing hormone-releasing hormone (LHRH) in counterbalanced order. Infusion of luteinizing hormone-releasing hormone significantly enhanced the lordotic response to coital stimulation compared to saline infusion. These results support the role of hypothalamo-mesencephalic LHRH-containing pathways in modulating lordotic behavior in estrogen-primed ovariectomized rats.

Animals↗

PubMedDate not supplied

Effects of hypothalamic peptide hormones on the electrical activity of Aplysia neurons.

The effect of luteinizing hormone-releasing hormone (LHRH) and thyrotropin-releasing hormone (TRH) on the electrical activity of neurons in the abdominal ganglion of Aplysia californica was studied. Where tested, TRH had no effect. The neurosecretory white-cell neurons were the most responsive of the neurons tested with LHRH. Bath applications of 1 micro M LHRH increased firing rates in 4 of 5 white cells for extended periods of time. The increased rates persisted in an LHRH-deficient bath. A similar result was obtained with bath applications of the LHRH agonist analog D-Ala6, des-Gly10-LHRH-ethylamide. The iontophoresis of LHRH onto white-cell somata either produced no change in electrical activity or initiated an increase in firing rate and bursting patterns which outlasted the application period. Two types of white cells are suggested by the white-cell responsiveness to LHRH. The white cells responsive to the decapeptide are candidate model neurons for studying the membrane actions of LHRH.

Animals↗

PubMedDate not supplied

Estrogen: mechanisms for a rapid action in CA1 hippocampal neurons.

Estrogen modulates a variety of functions, most of which can be explained by the classical genomic mechanism of action. However, a number of estrogen's actions appear to be incompatible with this mechanism and fall into the category of nongenomic. In the hippocampus, application of 17beta-estradiol rapidly enhances the amplitude of kainate-induced currents of CA1 neurons. The potentiation resulted from a cyclic adenosine monophosphate-dependent phosphorylation process rather than a direct allosteric modulation of AMPA/kainate receptors. To initiate this potentiation, estrogen is required on both sides of the plasma membrane. Extracellularly, estrogen appears to activate a G-protein-coupled receptor, whereas the intracellular action of estrogen appears to be a modulation of the balance between phosphorylation and dephosphorylation. The binding sites responsible for the potentiation are genetically or pharmacologically distinct from both estrogen receptors alpha and beta. These findings provide support for the concept of a novel mechanism of action for estrogen.

Animals↗

PubMedDate not supplied

Vital signs records omissions on prehospital patient encounter forms.

INTRODUCTION: A reported in-field, prospective evaluation of 227 prehospital patient assessments by advanced life support (ALS) emergency medical technicians (EMTs) found a frequent failure to measure vital signs. The objective of this retrospective review was to report the omission frequency of vital signs found in a centralized emergency medical services (EMS) data collection system. METHODS: The EMS database contained information from 90,480 optically scanned, prehospital patient encounter forms. Each record identified EMT skill levels, response times, dispatch type, vital signs, medical and trauma information, treatment, and patient disposition. Records for 1989 and 1990 were collected from 92 rural EMS providers who responded to emergency medical and trauma events. RESULTS: Of 90,480 emergency responses, 14,129 (15.6%) were false alarms, deceased, or canceled without vital patient contact. Valid encounters were documented for 76,351 (84.4%) patient contacts. Systolic blood pressure measurements were not recorded for 13,262 (17.4%) patients. Diastolic blood pressure was not recorded for 14,272 (18.7%) patients. A pulse record was not recorded for 12,125 (15.9%) patients. A ventilatory rate was absent in 12,958 (17.0%) patient records. CONCLUSION: This study found a frequent failure by non-metropolitan basic life support (BLS) and advanced life support (ALS) EMTs to record vital signs on prehospital emergency patient encounter forms. It supports a previous report of direct in-field observations of ALS EMTs failing to measure vital signs during patient assessment. The impact of vital sign omissions upon individual patient care can be assessed only by receiving medical control physicians. In the absence of effective emergency physician networking, the statewide magnitude of the problem among BLS and ALS EMTs has not been recognized as a system issue.

Ambulances↗

PubMedDate not supplied

Therapeutic agents utilized in urban/rural prehospital care.

INTRODUCTION: Objectives of this study were to determine the number of prehospital emergency patients who were given advanced life support (ALS) drugs and to compare utilization rates for ALS drugs in urban and rural environments. Certified ALS emergency medical technicians (Arizona) have 29 therapeutic agents authorized for prehospital administration. These agents may be administered only under direction of a medical control authority or by following standing orders. METHODS: A retrospective review was made of prehospital emergency encounter records. They were acquired by the Arizona Office of Emergency Medical Services (OEMS) from rural EMS providers who used optically scannable forms and from a metropolitan fire department's medical emergency response records. RESULTS: In 1989 and 1990, 273,611 emergency patient encounter records were entered into the EMS database; 197,260 were urban responses and 76,351 were rural responses. Drugs (ALS) were administered to 16,730 (8.5%) urban emergency patients and to 5,359 (7%) rural emergency patients at the incident site or during transport to a medical care facility. Nitrostat, 0.4 mg sublingual tablet, was the drug most frequently administered to emergency patients in the prehospital setting. Utilization rates found in the urban and the rural data sets were consistent for the individual agents. Variations in use frequency between urban and rural setting were noted for some drugs. Of the 29 approved ALS drugs, seven (24%) were administered to 10% or more urban patients who received drugs. In the rural areas, eight (27.6%) were administered to 10% or more patients who received drugs. There were nine (31%) agents administered to less than 1% of all patients who received drugs. A majority of the approved drugs, 17 (59%) were administered at a rate below 5% of all patients receiving medications. CONCLUSION: Severity of illness or injury prompted administration of ALS drugs to 8.1% of patients receiving prehospital emergency care. The most frequently utilized medication in the urban/rural areas was for treatment of cardiac symptoms. Variations between urban/rural drug utilization reflected the drugs of choice which are compatible with long transport times to a medical facility.

Arizona↗

PubMedDate not supplied

Prevalence of postburn depression following burn injury.

We examined the prevalence of depression after burn injury in 139 adults treated at a major burn center. Interviews were held from one to eight years following the burn. Our subsample, taken from 882 patients treated over a six-year period, comprised all patients with 30% total body surface area burns and a random sample of those with burns of lesser severity. We considered 17 possible predictors of depression (including the severity and placement of the burn and the patient's age, educational background, medical history, employment status, income level, and emotional and psychiatric history). We found that it is the person, rather than the injury, that best predicts postburn depression. The factor most strongly linked with depression was a past history of emotional disturbance. However, after being burned, a significant number of even previously well-adjusted patients show clinical postburn depression.

Adjustment Disorders↗

PubMedDate not supplied

A randomized study of a pH sensor feeding tube vs a standard feeding tube in patients requiring enteral nutrition.

Postpyloric feedings are a widely practiced form of enteral nutrition. We prospectively randomized two groups of hospital patients to receive a standard feeding tube or a feeding tube that uses a pH sensor to facilitate postpyloric placement and compared placement speed and accuracy, displacement detection, and costs for the two groups. Thirty-nine patients were randomized, with 20 receiving a pH sensor feeding tube and 19 an identical non-pH sensor feeding tube. An x-ray of the kidneys, ureter, and bladder was taken at 1, 6, and 48 hours after placement in both groups. Separate cost-benefit analyses were done by using retrospective chart review of costs for a separate 20-patient standard feeding tube group and calculated costs for a 20-patient hypothetical pH sensor group. At 1 hour, the duodenum was reached in 53% of the pH sensor feeding tube patients and 45% of the standard feeding tube patients (the difference was not significant). At 48 hours, 93% of the pH sensor feeding tubes reached the duodenum vs 67% of the standard feeding tubes (p < .08). Thirty percent of the pH sensor patients had an initial gastric pH > or = 4, negating pH sensor benefit in tube placement. In the remaining 70% of the patients, placement with the pH sensor had a 100% specificity compared with the x-ray of the kidneys, ureter, and bladder. Displacement was easily detected with routine pH monitoring in three of the pH sensor feeding tube patients and corrected. It was detected in two standard feeding tube patients, one of whom aspirated.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗

PubMedDate not supplied

Parenteral feeding alters the fatty acid composition of serum phospholipids of rabbits.

BACKGROUND: Cholestatic liver disease develops in 30% to 70% of neonates receiving total parental nutrition (TPN). We analyzed the fatty acid composition of serum phospholipids from control and TPN-fed rabbits to determine if TPN altered the fatty acid profile. METHODS: Eleven male New Zealand White rabbits aged 9 to 11 weeks received TPN, whereas 11 other rabbits were offered standard laboratory rabbit chow ad libitum. After 14 days on the prescribed diet, serum samples were analyzed for their phospholipid fatty acid content by gas chromatography. RESULTS: The proportions of palmitolenic (16:2n7), alpha-linolenic (18:3n3), arachidic (20:0), and eicosaenoic (20:1n9) acids were significantly lower in the serum phospholipids of the TPN-fed animals compared with the control group. The proportion of docosahexaenoic acid (22:6n3), a fatty acid that is critical to the development of the nervous system, was increased two- to threefold. CONCLUSIONS: The differences in proportions of fatty acids observed between control and TPN-fed animals indicate that a fatty acid elongation and desaturation pathways are perturbed in rabbits on TPN.

Amino Acids↗