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Biomedical subjects

B J Davis

Publications and source records attributed to B J Davis.

At least 127 records · Page 7Linked to original sources
PubMed1983

Morphological and functional aspects of pancreatic islet innervation.

Pancreatic islets are collections of 4 functionally-related endocrine cells distributed nonrandomly in the pancreas. Their major physiological actions center about the regulation of metabolic homeostasis. Experimental evidence shows that, in addition to circulating substates, the islets are controlled by outflow from the central nervous system communicated through autonomic nerves. Islet cells also interact with one another via hormonal messengers and, possibly, electrotonic impulses producing a complex--yet well-controlled--system for the integration of numerous types of signals. This paper is a brief review of some of the numerous interactions between the autonomic nervous system and the endocrine pancreas. Particular emphasis is placed on the role of recently discovered autonomic factors and newly recognized autonomic centers in the brain.

Animals↗
PubMed1982

Localization of methionine-enkephalin, substance P, and somatostatin immunoreactivities in the main olfactory bulb of the hamster.

Methionine-enkephalin, substance P, and somatostatin immunoreactivities are associated with different classes of neurons in the main olfactory bulb of the hamster. In the glomerular layer, methionine-enkephalin immunoreactivity is observed in the somata and dendrites of periglomerular cells whereas substance P immunoreactivity is present in the somata and dendrites of external tufted cells. Substance P immunoreactivity may also be present in the superficial short axon cells. In the deeper layers, methionine-enkephalin immunoreactivity is observed in a mixed population of neurons which appear to be primarily granule cells, whereas somatostatin immunoreactivity is present only in deep short axon cells. Methionine-enkephalin-, substance P-, and somatostatin-positive fibers of central origin are also observed in the main olfactory bulb.

Animals↗
PubMed1982

Prelimbic cortex, mediodorsal thalamus, septum, and delayed alternation in rats.

Rats were trained preoperatively on contingently reinforced alternation in a T-maze. Then different matched groups of rats received lesions in the prelimbic cortex, mediodorsal thalamus, posterodorsal septum (aimed at transecting the precommissural fornix), and control operations (no brain lesions). Following a 2-week recovery period the rats were retested in the T-maze for retention of delayed alternation. Control rats were unaffected by the control operations and the testing hiatus of the recovery period. Rats with lesions in the prelimbic cortex performed at chance levels on the first postoperative session as did rats with posterodorsal septal lesions, but both groups recovered with continued experience, i.e., they could relearn the task. Rats with lesions in mediodorsal thalamus were only slightly affected by the lesions. The results suggest that a restricted field in the medial pregenual cortex, the prelimbic area, is critically involved in T-maze alternation. However, the data also suggest that a major subcortical source of afferents to prelimbic cortex, the mediodorsal nucleus of the thalamus, is not crucial for retention of contingently reinforced T-maze delayed alternation following interference with septo-hippocampal circuitry is consistent with data previously reported.

Animals↗
PubMed1982

Ultrastructural identification of substance P immunoreactive neurons in the main olfactory bulb of the hamster.

The neurons containing substance P immunoreactivity in the main olfactory bulb of the hamster are located in the glomerular layer. Their cell bodies lie in the periglomerular region and contain spherical or ovoid nuclei which lack invaginations of the nuclear membrane and tend to be positioned eccentrically in the cell body. Dendrites of these neurons extend throughout the periglomerular region and project into the glomerular neuropil. Within the glomerular neuropil, processes with substance P immunoreactivity contain agranular, spherical synaptic vesicles. Primary olfactory axons, and processes of uncertain origin which contain pleomorphic synaptic vesicles, form synaptic contacts with substance P immunoreactive processes. These ultrastructural findings confirm that the substance P immunoreactive neurons are external tufted cells. Their likely physiological properties are considered in relation to the synaptic organization in the glomerular layer of the main olfactory bulb and to the other putative neurotransmitters or neuromodulators located in this layer.

Animals↗
PubMed1982

Digital counter tallys number of tissue sections cut and recycles at selectable intervals.

A digital counter is described for use on any microtome. The counter performs three independent functions: 1) a cumulative count is maintained, 2) a second interval counter recycles each time a preselected number of sections are cut, and 3) a third rounds counter records the number of times the interval counter recycles and also recycles at selected intervals. The digital counter activates relays when recycling and can control motorized microtomes during serial sectioning.

Data Display↗
PubMed1982

Carnosine in primary afferents of the olfactory system: an autoradiographic and biochemical study.

Previous in vivo studies have shown that beta-alanine is incorporated specifically into the dipeptide L-carnosine (beta-alanyl-L-histidine). In the present study, we administered beta-[3H]alanine to the nasal cavity of hamsters and used biochemical analyses to identify the radioactively labeled compounds in the olfactory epithelium and olfactory bulb and autoradiography to demonstrate the localization and transport of the label in the primary afferents of the olfactory system. The olfactory epithelium and lamina propria were labeled intensely 6 hr after intranasal beta-[3H]alanine administration. At this survival time, 61% of the radioactivity in the olfactory epithelium was present in the carnosine fraction, while 37% of the label remained in the beta-alanine fraction. After 24-hr and 4-day survival periods, greater than 82% of the radioactivity was present in the carnosine fraction, and the olfactory receptors and bundles of axons were labeled preferentially. The olfactory nerve and glomerular layers of the main olfactory bulb were labeled intensely at 6 and 24 hr after beta-[3H]alanine administration; much less label was present in these layers at 4 days survival. At all three of these survival times, greater than 84% of the radioactivity in the olfactory bulb was present in the carnosine fraction. No label was present in the olfactory epithelium or bulb 18 days after beta-[3H]alanine administration. While the autoradiographic labeling over the structures of the accessory olfactory system was consistently less intense than that over the main olfactory system structures, the patterns of labeling were similar over the four survival times. Intranasal alpha-[3H]alanine administration resulted in some labeling in the primary afferent fibers, but the labeling did not have the specificity nor the same time course over the four survival times that was observed after beta-[3H]alanine administration. The results are consistent with the hypothesis that carnosine is a neurotransmitter or neuromodulator in the olfactory neurons. The results also suggest that carnosine may play a similar role in the vomeronasal neurons.

Afferent Pathways↗
PubMed1981

The organization of centrifugal projections from the anterior olfactory nucleus, ventral hippocampal rudiment, and piriform cortex to the main olfactory bulb in the hamster: an autoradiographic study.

The centrifugal projections from the various subdivisions of the anterior olfactory nucleus (AON) can be categorized into four groups based on the organization of terminal fields in the main olfactory bulb (MOB). Pars lateralis and dorsalis have bilaterally asymmetric laminar projections to the MOB. The ipsilateral projections terminate primarily in the superficial half of the granule cell layer and in the deep third of the glomerular layer, whereas the contralateral projections terminate primarily in the superficial half of the granule cell layer and do not extend into the glomerular layer. Pars ventralis and posterior have bilaterally symmetric laminar projections with heavy terminations both in the superficial half of the granule cell layer and in the deep third of the glomerular layer. Pars medialis sends predominantly ipsilateral projections to the deep half of the granule cell layer. Pars externa has predominantly contralateral projections with a very narrow terminal field immediately deep to the internal plexiform layer. The projections to the MOB from the ventral hippocampal rudiment (HR) and the piriform cortex (PC) are exclusively ipsilateral. The projections from the ventral HR terminate primarily in the deep half of the granule cell layer. The projections from the PC also terminate predominantly in the granule cell layer, but there is a progressive shifting of terminal fields from the superficial half of this layer toward deeper regions for centrifugal axons arising from progressively more caudal levels of the PC. The laminar termination patterns of cortical afferents to the ipsilateral MOB thus are correlated with the mediolateral axis of the olfactory peduncle and the rostrocaudal axis of the piriform cortex. The centrifugal axons from these various sources enter directly into the granule cell layer of the caudal MOB or pass through the internal plexiform layer of the accessory olfactory bulb to reach the middle and anterior part of the MOB. We have termed these two routes the final common bulb pathway. The centrifugal axons from the laterally situated sources join the anterior and bulbar limbs of the anterior commissure before entering the final common bulbar pathway. In contrast, the centrifugal axons from pars medialis and the ventral HR travel diffusely in the cellular layer of the ipsilateral olfactory peduncle. A small component of the centrifugal projections from the PC travels in association with the lateral olfactory tract.

Animals↗
PubMed1981

Cholinergic and catecholaminergic afferents to the olfactory bulb in the hamster: a neuroanatomical, biochemical, and histochemical investigation.

A series of neuroanatomical, biochemical, and histochemical studies have been conducted to determine the sources of cholinergic afferents to the main olfactory bulb (MOB) in the hamster. Following horseradish peroxidase (HRP) injections that are restricted to the MOB, retrograde neuronal labeling is observed bilaterally in the anterior olfactory nucleus, locus coeruleus, and raphe nuclei, and ipsilaterally in the ventral hippocampal rudiment, dorsal peduncular cortex, piriform cortex, nucleus of the lateral olfactory tract, anterior pole of the medial septal area and vertical limb of the diagonal band, nucleus of the horizontal limb of the diagonal band (HDB), and hypothalamus. Spread of HRP into the accessory olfactory bulb results in additional neuronal labeling ipsilaterally in the bed nucleus of the accessory olfactory tract, medial amygdaloid nucleus, and bed nucleus of the stria terminalis, and bilaterally in the posteromedial cortical amygdaloid nucleus. Retrograde tracing studies also have been conducted in cases with lesions in the basal forebrain or hypothalamus to assess the extent to which such lesions interrupt fibers of passage from other sources of centrifugal afferents, and the effects of such lesions on choline acetyltransferase (CAT) activity and catecholamine content in the MOB and on acetylcholinesterase (AChE) activity in the forebrain have been evaluated. Lesions in the basal forebrain reduce or eliminate CAT and AChE activity in the MOB in direct relationship to the extent of damage to the HDB. Norepinephrine (NE) content in the MOB also is reduced by basal forebrain lesions, but in relationship to damage of the medial forebrain bundle (MFB). The hypothalamic lesions have no effect on AChE activity in the forebrain or on CAT activity in the MOB, but they eliminate retrograde labeling in the locus coeruleus and raphe nuclei and reduce the NE content of the MOB to undetectable levels. The dopamine content of the MOB is not reduced by any of the lesions. Anterograde tracing studies have been conducted to compare the rostral projection patterns of the HDB with the distribution of AChE activity. Most of the rostrally directed axons travel in association with the MFB. A small component of axons travels in association with the lateral olfactory tract. Within the MOB, the axons terminate predominantly in the glomerular layer and in the vicinity of the internal plexiform layer. The projection and termination patterns of the HDB correspond well with the distribution of AChE activity. These various results indicate that the HDB is the major source of cholinergic afferents to the MOB.

Animals↗
PubMed1980

Treatment of Syphacia obvelata in the Syrian hamster (Mesocricetus auratus) with piperazine citrate.

The effective dose for eradication of Syphacia obvelata infestation in Syrian hamsters (Mesocricetus auratus) was determined and a colony of 2,278 hamsters housed in 751 cages were treated. Two treatment courses with 10 mg of piperazine citrate/ml of drinking water for 7 days, separated by 5 days without treatment, achieved eradication of parasites previously demonstrated by perianal fecal smears containing ova.

Administration, Oral↗
PubMed1975

Prostaglandin-induced regression of porcine corpora lutea maintained by estrogen.

Corpora lutea were marked with suture in 24 crossbred gilts on day 7 to 9 of the estrous cycle (first day of estrus equals 0). All gilts were injected with 5 mg of estradiol benzoate (EB) daily from day 10 to 15 to extend the lifespan of corpora tutea, then the gilts were randomly assigned to two groups. On day 20, the 12 gilts of Group 1 were injected with 10 mg PGF-2ALPHA, and the 12 gilts of Group 2 were injected with saline. Ovaries were recovered 10 to 13 days after PGF-2ALPHA or saline injection. Ten gilts in Group 1 displayed estrus 5 plus or minus 0.7 days after PGF-2ALPHA injection, but only two gilts in Group 2 displayed estrus during the experimental period. In gilts that displayed estrus, all marked CL had regressed. Marked CL were still present in all 12 gilts that failed to exhibit estrus during the experimental period. These results show that in the pig, PGF-2ALPHA caused regression of CL that were maintained beyond the normal luteal phase of the estrous cycel by EB treatment.

Animals↗