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Biomedical subjects

J D Dunn

Publications and source records attributed to J D Dunn.

At least 19 recordsLinked to original sources
PubMed1990

Contribution of centrifugal innervation to choline acetyltransferase activity in the cat cochlear nucleus.

Using a quantitative microchemical mapping approach combined with surgical cuts of fiber tracts, the contributions of centrifugal pathways to choline acetyltransferase activity were mapped three-dimensionally in the cat cochlear nucleus. Large reductions of choline acetyltransferase activity, averaging 70%, were measured in almost all parts of the lesion-side nucleus following transection of virtually all its centrifugal connections. More superficial cuts, penetrating just through the olivocochlear bundle, also led to significant reductions of enzyme activity, especially most rostrally in the anteroventral cochlear nucleus and superficial granular region, where the reductions were similar to those following the complete cuts. Lesions encroaching upon the superior olivary complex gave bilateral effects. Transverse cuts between rostral and caudal parts of the cochlear nucleus gave some small effects. The results suggest that, as in rats, most choline acetyltransferase activity in the cat cochlear nucleus is associated with its centrifugal innervation. However, unlike the situation in rats, the enzyme activity in cats is related more to olivocochlear branches than to ventral fibers in the trapezoid body region. Also, the choline acetyltransferase activity related to olivocochlear collateral innervation is much less uniformly distributed within the cochlear nucleus in cats than in rats.

Animals↗
PubMed1989

Effect of septal ablation on choline acetyltransferase in the paraventricular nucleus.

To determine whether there is a cholinergic projection from the lateral septum to the paraventricular nucleus of the hypothalamus (PVH), a quantitative histochemical analysis of the effects of unilateral ablation (0.5 microliter of a 10 micrograms/ml solution of ibotenic acid) of the lateral septum (LSV) on the choline acetyltransferase (ChAT) activity of the PVH and surrounding perinuclear area was undertaken. Comparisons of the ChAT activity of the PVH region ipsilateral to the LSV lesion (lesioned side) with that of the PVH contralateral (nonlesioned side) to the ablated LSV showed a 20% reduction (p less than 0.05) of ChAT activity in 2 areas of the PVH on the lesioned side. When ChAT activity of LSV-ablated and intact control rats was compared, a 20% difference in activity (p less than 0.05) was noted in four areas on the nonlesioned side and a 35% difference (p less than 0.05) of ChAT activity was noted in five regions of the PVH on the lesioned side of LSV-ablated animals. Taken together these data suggest that the pathway from the LSV to the PVH contains a small, bilateral cholinergic component. However, the data also indicate that this is not the only cholinergic projection to the PVH.

Animals↗
PubMed1989

Quality of care.

Explore the source record for details and available documents.

Emergency Service, Hospital↗
PubMed1989

Brain histidine and food intake in rats fed diets deficient in single amino acids.

Histidine (His) is elevated in plasma and brain during protein deficiency as well as in several pathological conditions, leading to the possibility of a direct effect on central nervous system (CNS) function. In this study, groups of weanling rats were fed diets containing graded levels of casein or a single indispensable amino acid (IAA: Leu, Val, Ile, Phe, Trp, Thr, Met or Lys) in order to produce nutritionally-deficient states. Body weight gains and food intakes were recorded daily for 2 wk. Whole brain and serum samples were obtained and analyzed for amino acid (AA) content. All weight gain and food intake responses could be predicted by the Saturation Kinetics Model. The only consistent pattern observed in AA profiles which could be correlated with food intake was an increase in brain His concentrations. Limiting dietary casein or IAA elevated brain His above controls 2.5- and 1.5-fold, respectively. Food intake was generally depressed by 50% at brain His concentrations above 105 nmol/g. Since His is the precursor of the depressant neurotransmitter histamine (HA), systemic increases may be significant in that HA could be a possible cause of the anorexia observed in protein and IAA deficiency.

Amino Acids, Essential↗
PubMed1988

Melittin-evoked increase in plasma corticosterone levels.

The present study was undertaken to systematically evaluate the effect of melittin on nonstress pituitary-adrenal function of the adult female rat. In the first study rats were given melittin (0.5 mg.kg-1) or saline (0.5 ml) intraperitoneally at 0800 hr. Blood for determining plasma corticosterone levels was collected by decapitation at 4, 8, 24 or 48 hrs post-injection. Corticosterone levels of rapidly decapitated rats provided basal corticosterone levels. In general, plasma corticosterone levels of melittin-treated animals were higher than those of saline-injected rats at 4, 24, and 48 hrs but significant differences (p less than 0.05) occurred only at 4 and 48 hrs. A second study showed the melittin-evoked corticosterone response to be present at 3 days but by 6 days the response was absent. However, the duration of the increase in plasma corticosterone levels was extended to 8 days by using a double injection protocol (0.5mg.kg-1 melittin on day 1 and day 4). In all studies melittin-evoked increases in corticosterone levels were observed only in the AM and the melittin-induced increases in plasma corticosterone levels were suppressed with dexamethasone (DECADRON, 100 micrograms.kg-1, s.c.). These data indicate that a 0.5mg.kg-1 dose of melittin evokes a significant increase in adrenocortical activity and the evoked response is feedback sensitive.

Animals↗
PubMed1988

Effect of melittin on pituitary-adrenal responsiveness to stress.

We previously have shown that melittin evokes a sustained increase in plasma corticosterone levels of the female rat. Significant increases occurred only during the morning and the duration of the response was increased from 48 h to 8 days by a second milittin injection 3 days after initial exposure to melittin. To further evaluate the effect of melittin on adrenocortical function, rats were given melittin at 09.00 h on days 1 and 4 and on day 8 rats were subjected to a variety of different stresses. Saline-injected rats served as controls. Blood for determining non-stress and stress levels of corticosterone concentration (RIA) was collected by decapitation. In all cases morning but not afternoon non-stress plasma corticosterone levels of melittin-injected rats were higher than those of saline-injected controls; afternoon non-stress corticosterone levels did not differ between groups. Melittin- and saline-treated rats showed comparable corticosterone responses to a morning 2-min restraint stress. In contrast, melittin treatment facilitated the pituitary-adrenal response to rotational and surgical stress as well as the stress of removing one rat from a cage of two. Fifteen min after removal of the first rat of a cage of two, plasma corticosterone levels of the melittin-injected rat were significantly higher than those of saline-injected rats. Likewise, plasma corticosterone levels of melittin-treated rats were higher (P less than 0.05) than those of saline-injected rats 15 min after rotational (10 rpm) and surgical (jugular cutdown and blood withdrawal) stress.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenocorticotropic Hormone↗
PubMed1987

Plasma corticosterone responses to electrical stimulation of the bed nucleus of the stria terminalis.

The effect of ventral septal stimulation on pituitary-adrenal function was assessed by evaluating plasma corticosterone obtained prior to and following sham or electrical stimulation of the bed nucleus of the stria terminalis (BNST) of female rats anesthetized with urethane (1.3 g X kg-1). Hippocampal EEG, ECG, heart rate, blood pressure and respiration were routinely monitored; timed blood samples (0.2 ml) for determining plasma corticosterone (RIA) were obtained from a catheterized tail artery. Samples were taken at 0.5 min prior to and at 5, 10, 15 and 30 min after initiation of stimulation. Whereas increased plasma corticosterone levels followed stimulation of the medial aspect of the BNST, lateral stimulation resulted in decreased plasma corticosterone levels. The overall increase in plasma corticosterone following medial stimulation was 24%; the overall decrease was 13%. The largest increase in plasma corticosterone (36%) occurred at 30 min poststimulation; the largest decrease (22%) occurred at 15 min. Stimulation of the most rostral aspect of the BNST produced plasma corticosterone responses similar to that observed following medial stimulation. In contrast, no changes in corticosterone levels were observed following either sham stimulation or stimulation of the corpus callosum, fornix or anterior commissure.

Amygdala↗
PubMed1987

Effect of olivocochlear bundle transection on choline acetyltransferase activity in the rat cochlear nucleus.

Using a microdissection and quantitative microassay approach, choline acetyltransferase activities were mapped in the cochlear nuclei of rats having complete transections of the olivocochlear bundle on one side in the brain stem. In rats in which the trapezoid body was not significantly damaged by the lesion, consistent reductions of choline acetyltransferase activity in subregions of the lesion-side cochlear nucleus, as compared to the control side, averaged about 20%. Nevertheless, a profound lesion-side reduction of choline acetyltransferase activity was found in a branch connection from the olivocochlear bundle to the cochlear nucleus. The results suggest that branches from the olivocochlear bundle are cholinergic, but contribute a relatively minor proportion of the cholinergic synapses in all regions of the rat cochlear nucleus. In the light of previous results with more extensive lesions, it can be proposed that synapses in all regions of the rat cochlear nucleus. In the light of previous results with more extensive lesions, it can be proposed that most cholinergic input into the rat cochlear nucleus enters by a ventral route along the trapezoid body. It is noted that this represents a quantitatively somewhat different situation from that in the cat.

Acetylcholinesterase↗
PubMed1987

Effects of trapezoid body and superior olive lesions on choline acetyltransferase activity in the rat cochlear nucleus.

Using a microdissection and quantitative microassay approach, choline acetyltransferase activities were mapped in the cochlear nuclei of rats having either transection of the trapezoid body or destruction of the superior olivary complex on one side in the brain stem. Lateral trapezoid body transection resulted in dramatic loss of choline acetyltransferase activity in all parts of the ipsilateral cochlear nucleus, while more medial transection had little effect. Destruction of the superior olivary complex resulted in dramatic loss of choline acetyltransferase activity in the ipsilateral cochlear nucleus, and detectable loss also contralaterally. The results suggest that most of the centrifugal cholinergic projections to the rat cochlear nucleus derive from or traverse the vicinity of the superior olivary complex bilaterally and enter the cochlear nucleus ventrally from the region of the trapezoid body.

Animals↗
PubMed1987

Differential plasma corticosterone responses to electrical stimulation of the medial and lateral septal nuclei.

To pursue the possibility that subdivisions within the medial and lateral septal nuclei are differentially involved in adrenocortical function, plasma samples obtained prior to and following electrical stimulation of the septal nuclei of urethane (1.30 g/kg)-anesthetized female rats were assessed for corticosterone concentration. Hippocampal EEG, ECG, heart rate (HR), mean arterial pressure (MAP) and respiration were routinely monitored, and timed blood samples (0.15 ml) were obtained from a catheterized tail artery. Blood samples were taken 0.5 min prior to and at 5, 10, 15 and 30 min after initiation of stimulation. Whereas no change in Cpd B levels were observed following sham stimulation or stimulation of the corpus callosum, fornix or anterior commissure, stimulation of the medial septal nuclei produced differential responses. Decreased plasma Cpd B responses followed stimulation of the medial septal nucleus (MS); increases in plasma Cpd B followed stimulation of the dorsal (LSD) and ventral (LSV) division of the lateral septal nucleus. The overall increase in plasma Cpd B levels following LSD and LSV stimulation was 16 and 32%, respectively. The overall decrease in corticosterone concentration subsequent to MS stimulation was 18%. The largest increases in Cpd B levels occurred at 5 min (36%) and 10 min (24%) for LSV and LSD groups, respectively; the largest decrease was noted at 15 min (25%). Plasma Cpd B responses to stimulation of the intermediate area of the lateral septal nucleus produced varying and inconsistent responses. Collectively, these data support the hypothesis that subdivisions within the septal nuclei are differentially involved in adrenocortical function.

Animals↗
PubMed1987

Characteristics of the frequent visitor to the industrial medical department and implications for health promotion.

The number of visits to an in-house industrial medical clinic, of absences in three categories, and of late arrivals found in 1,505 employees of an automobile assembly plant were compared with respect to the age, sex, race, department, and shift characteristics of the employees. Less than 16% of the work force was found to account for over 50% of the medical visits. Those 235 frequent visitors were found to have significantly more absences and more tardiness compared with the rest of the plant population. The frequent visitors who completed a health risk appraisal had significantly greater health risks compared with a responding sample of nonfrequent visitors.

Absenteeism↗
PubMed1987

Risk management in emergency medicine.

This article discusses risk management and control of malpractice risk in the Emergency Department. Particular emphasis is placed on actuarial information related to Emergency Department losses.

Emergency Service, Hospital↗
PubMed1986

Differential cytolysis of murine spleen, bone-marrow and leukemia cells by melittin reveals differences in membrane topography.

L1210 leukemia cells are 2-4 fold more sensitive to the cytolytic effects of melittin, the membrane-active toxin of bee venom, than normal DBA/2 mouse spleen and bone-marrow cells. Lysis of the normal cells was abolished when either 75 mM galactosamine, glucosamine or 100 microM beta-lactoglobulin was added to the melittin-cell reaction, but lysis of the leukemia cells was unaffected. The amino-groups appeared necessary for blocking melittin-mediated lysis since glucose, galactose and the N-acetyl derivatives were not inhibitory. Bone-marrow cells were more readily protected from lysis than spleen cells. Since melittin-inhibitor complexes were not detected by gel chromatography and the inhibitor could be added to the cell suspension after melittin, the evidence suggests that bone-marrow cells are rich in membrane binding sites for carbohydrates that decrease in mature spleen cells and are virtually absent after neoplastic transformation.

Animals↗