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P R Lewis

Publications and source records attributed to P R Lewis.

At least 37 records · Page 2Linked to original sources
PubMed1983

Embryonic neural transplants across a major histocompatibility barrier: survival and specificity of innervation.

The ability of embryonic tissue to survive cross-transplantation between histologically incompatible rat strains was examined by transplanting septal neurons from Sprague Dawley fetuses to adult Wistar rats (Ag-B6 to Ag-B2 histocompatibility haplotype). Transplants were found to survive without rejection over a period of 3 months. Furthermore, the laminar pattern of cholinergic innervation was similar to that of homogenic septal transplants and of intrinsic septal projections. These results suggest that embryonic neural tissue transplanted across major histocompatibility barriers are capable of survival for extended periods of time, and are in support of the concept of the privileged nature of embryonic tissue as a source of material for cross-transplantation.

Animals↗
PubMed1982

The distribution of acetylcholinesterase in the lateral geniculate nucleus of the cat and monkey.

The distribution of acetylcholinesterase (AChe) has been examined histochemically in the lateral geniculate nucleus (LGN) of the cat and the monkey, and in the cat visual cortex. It was found that in the cat, AChE is most concentrated in laminae A and A1. Lamina C-proper possessed a weak band of AChE in its ventral part. Only restricted patches of activity were observed in the medial interlaminar nucleus. Laminae C1-3 and the central interlaminar nucleus possessed very little AChE. This pattern of enzyme distribution suggests that in the cat LGN, AChe activity coincides with the sites of neurophysiologically recorded X-cells, which are predominantly found in laminae A and A1 and are scarce in the C laminae and the medial interlaminar nucleus. The presence of AChE over neurones in layer VI of both areas 17 and 18 of the cerebral cortex in the cat suggests the corticothalamic pathway as one possible source of geniculate AChE activity. In the monkey LGN, AChE activity was observed in the parvocellular and magnocellular layers. The activity was greatest in the magnocellular layers, which are believed to contain neurones driven predominantly by retinal Y-cells. Thus, for this species the correlation between AChE activity and X-cells does not seem to hold.

Acetylcholinesterase↗
PubMed1982

Role of fetal oxytocin in parturition in the rat.

The oxytocin (OT) content of pituitary glands from neonatal rats was reduced by parturition, indicating possible release from fetal glands during labor. The content of fetal glands fell from 2.5 ng/gland in utero to 1 ng/gland immediately after birth. Rabbit serum antibodies against OT were administered to pregnant or fetal rats preceding parturition or to lactating rats on Day 10 of lactation. Antibody administration to lactating rats resulted in a decrease in weight gain of suckling pups, indicating that OT was bound by antibody. Administration of OT antibody to pregnant rats had no effect on the duration of gestation while injection into fetal pups resulted in an 18 h increase in the mean duration of gestation compared to sham-injected controls. These studies indicate that fetal OT might have a role in initiating parturition in the rat.

Animals↗
PubMed1980

Effect of dopamine on length of gestation and on the release of fetal oxytocin in rats.

Oxytocin (OT) release from the maternal posterior pituitary gland has been implicated in the process of spontaneous labor. The possibility that OT release from a fetal source may also be involved in this process was investigated. Administration of dopamine (DA), 150 mg/kg/ui hr, or L-dopa, 200 mg/kg/12 hr, plus carbidopa, 20 mg/kg/12 hr, to pregnant rats beginning on day 16 of gestation delayed the mean delivery time by 10 to 18 hr. These drug treatments also inhibited the release of OT from fetal pituitary glands which normally occurred during parturition. Release of OT from maternal pituitary glands was not affected and no alterations in the duration or outcome of labor were noted. Administration of [3H]DA to pregnant rats resulted in higher amounts of labeled DA in fetal brain tissues than in maternal brain. These studies suggest that fetal OT is involved in the timing of parturition in the rat and that DA may prolong gestation by affecting fetal OT.

Animals↗
PubMed1979

Skin diving fatalities in New Zealand.

A review of skin diving fatalities in New Zealand for the period 1961--1973 revealed 28 deaths of which 21 were scuba divers. Two-thirds of the scuba deaths occurred in water less than 15m deep. Running out of air and lack of essential equipment were frequent contributory factors. The pathological findings are presented and show drowning to be the most common mode of death. Some deficiences in the assessment of these fatalities are discussed.

Adolescent↗
PubMed1978

Investigation of a dopaminergic mechanism for regulating oxytocin release.

The isolated hypothalamo-neurohypophysial system (HNS) of male rats was incubated with putative neurotransmitters in vitro to determine their significance in regulating oxytocin release. Dopamine was found to inhibit the spontaneous release of oxytocin from the HNS in a dose-related manner. The maximum inhibition produced by dopamine (10(-9) M) was significantly different from control values and was blocked by haloperidol (5 x 10(-5) M). Apomorphine (10(-9) M) mimicked the effect of dopamine on this system. The type of receptor involved in the inhibitory effect on oxytocin release is unclear, although a dopaminergic mechanism in vivo. When levodopa plus carbidopa were injected into male rats, the gland content of oxytocin in these animals was significantly increased over control values. When a similar dosage regimen was employed with pregnant rats beginning on day 16 of gestation, levodopa plus carbidopa delayed the average delivery time 12 hr. The results of these studies are also consistent with a dopaminergic mechanism for the regulation of oxytocin release.

Animals↗
PubMed1977

Regional distribution of choline acetyltransferase and acetylcholinesterase within the amygdaloid complex and stria terminalis system.

The distribution of "marker" enzymes for cholinergic neurons has been studied in 10 subdivisions of the amygdaloid complex of the rat brain. Choline acetyltransferase activity was measured using a radiochemical method in samples dissected from fresh serial sections. Acetylcholinesterase was studied using a histochemical procedure. Both enzymes had similar patterns of distribution within the amygdaloid complex and were most concentrated in the posterior lateral and basolateral nuclei and in the nucleus of the lateral olfactory tract. These enzymes were much less concentrated in the cortical, medial, central, and basomedial nuclei. Large differences in acetylcholinesterase staining were found within the lateral posterior and the basolateral nuclei and within the pyriform cortex. Biochemical studies showed a parallel distribution of choline acetyltransferase within these nuclei. The results indicate that cholinergic neural elements in the amygdala are concentrated primarily in the basolateral complex and suggest that this region may be innervated by cholinergic fibers traveling in the ventral amygdalo-fugal pathway.

Acetylcholinesterase↗
PubMed1975

Effects of vagotomy on the distribution of cholinesterases in the cat medulla oblongata.

Histochemical study of the distribution of cholinesterases in the cat medulla oblongata reveals that all neurones in the dorsal motor nucleus of the vagus (DMV) contain true cholinesterase (AChE) but, while most contain this enzyme alone, a small proportion of cells contain pseudocholinesterase (BuChE) as well. Cervical vagotomy affects the two types of cell to different degrees of severity. The BuChE-containing neurones lose their enzyme completely within 2-3 weeks and they atrophy and disappear as a result of the operation. On the other hand, the reaction is less severe and is reversible in those cells containing AChE only. Vagotomy also causes reduction of AChE and BuChE staining in the nearby area subpostrema; the depletion here is pronounced at 2-3 weeks and recovery occurs within the year. These findings suggest that some cells in the area subpostrema project peripherally via the vagus and that the area is part of the vagal nuclear complex. Moreover, capilllaries in the area contain AChE and BuChE in the endothelial lining and this is one of the few areas of the cat hindbrain to exhibit such vascular enzyme activity. The ependyma of the area postrema, which overlies the area subpostrema, is heavily stained for BuChE but this is unaffected by vagotomy.

Animals↗
PubMed1975

Cholinesterase activity in the hypoglossal nucleus of the rat and the changes produced by axotomy: a light and electron microscopic study.

Within the hypoglossal nucleus large amounts of acetylcholinesterase (AChE) activity are present in all the neurons, whereas intracellular butyrylcholinesterase (BuChE) activity occurs only within a ventro-caudally situated cluster of cells. AChE activity within the neurons occurs mainly in the cisternae of the granular endoplasmic reticulum but there is some in the intermembranous space of the nuclear envelope and in the Golgi complexes. In the neuropil, reaction product is seen along some axonal and synaptic membranes. The distribution of BuChE in the ventro-caudal cells is identical with that of AChE except that BuChE activity is absent from the neuropil. The level of intraneuronal AChE activity falls rapidly during the first few days after axotomy. The fall is due partly to a dissolution and peripheral migration of the E.R. but also to a decrease in AChE content of the E.R. that remains. Return of staining begins in the 4th week and continues as the E.R. reassembles. Staining in the neuropil falls more slowly, but recovers less completely. The ventro-caudal group of cells shows the same kinds of change, but more dramatically. BuChE activity returns only erratically and never completely. The similarity in normal distribution, and in response to axotomy, of the two cholinesterases suggests that their functions are related.

Acetylcholinesterase↗
PubMed1975

The localization of acetylcholinesterase in the locus coeruleus of the normal rat and after 6-hydroxydopamine treatment.

The locus coerulus is a densely packed group of neurons in the floor of the fourth ventricle, and is the largest aggregate of noradrenaline-containing cells in the mammalian brain. The distribution within the locus of acetylcholinesterase (AChE), which is present in high concentration, has been studied at light and electron microscope level, both in normal rats and in ones treated with 6-hydroxydopamine. Neuronal enzyme activity is entirely intracellular and mainly concentrated in stacks of ER which occupy much of the cell cytoplasm. There are no indications of a cholinergic input. After 6-hydroxydopamine treatment extensive cell death occurs and AChE activity virtually disappears. A majority of the many blood vessels in the locus also stain strongly for AChE, unlike those present in most other areas of the rat brain. The locus coeruleus therefore represents an area of the rat brain with a high content of AChE, but no evidence of a cholinergic mechanism. Some possible explanations for this anomalous presence of AChE are briefly discussed.

Acetylcholinesterase↗