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Biomedical subjects

M J Brownstein

Publications and source records attributed to M J Brownstein.

At least 145 records · Page 8Linked to original sources
PubMed1978

Successful replantation of two avulsed scalps by microvascular anastomoses.

Two cases of immediate replantation of avulsed scalps by microvascular anastomosis are presented. This method of treatment seems to offer significant economic, social, and psychological advantages over split-skin grafting of the calvarium, or other presently used treatments. The need for secondary reconstructive procedures after a successful replantation is minimal, or nil. The mechanism of scalping is reviewed, and it is related anatomically to the structure of the galea aponeurotica. Specific recommendations are made regarding the immediate care of the avulsed scalp and the denuded calvarium, the value of a team approach in replantation, and various technical aspects of the procedure and postoperative management. The more frequent use of interpositional vein grafts is urged.

Adolescent↗
PubMed1977

On the origin of substance P and glutamic acid decarboxylase (GAD) in the substantia nigra.

Knife cuts in the frontal plane separating the anterior part of the caudate-putamen from the globus pallidus resulted in marked decreases in substances P levels in the reticular part of the substantia nigra. More caudal knife cuts were required in order to effect maximal decreases in nigral glutamic acid decarboxylase levels. Thus, there is a clear anatomical dissociation between the striatal neurons which project to the reticular part of the substantia nigra and which contain SP, and the more caudally located GAD-containing striatal and pallidal neurons, all of which travel through the globus pallidus on their way to the substantia nigra.

Animals↗
PubMed1977

Origin of glutamate-decarboxylase (GAD)-containing cells in discrete hypothalamic nuclei.

Glutamate decarboxylase activity (GAD) was assayed in discrete hypothalamic nuclei in the rat following lesions of the major afferent pathways from hippocampus, amygdala, midbrain, septum, thalamus and globus pallidus. None of these lesions led to a marked decrease in GAD activity in selected nuclei. After total deafferentation of the medial-basal hypothalamus GAD remained unchanged in the median eminence but fell markedly in the ventromedial and arcuate nuclei. In these two nuclei a decrease of GAD still occurred following partial deafferentation from lateral and posterior hypothalamus, but not from anterior and preoptic areas. These results indicated that most GAD-containing cells have their origin inside of the hypothalamus. In this region GABAergic neurons are likely to be short interneurons providing intrahypothalamic connections. Such connections are suggested from lateral and posterior hypothalamus onto the medial basal nuclei.

Afferent Pathways↗
PubMed1977

Serotonergic innervation of the forebrain: effect of lesions on serotonin and tryptophan hydroxylase levels.

Concentrations of serotonin and tryptophan hydroxylase activity in individual hypothalamic and limbic nuclei, as well as cortical regions, were measured by radioenzymatic microassays after dorsal raphe nucleus lesions and various surgical transections of the brain stem. Fourteen days after lesioning of the dorsal raphe nucleus there were 43-65% decreases in 5-HT concentrations of certain hypothalamic and limbic nuclei. More pronounced decreases were found in the parietal cortex and in the locus coeruleus and substantia nigra. Degenerations of nerve terminals in various regions of the hypothalamus and the limbic system were detected by electron microscopic studies 1-8 days after dorsal raphe nucleus lesions. There was no change in the 5-HT concentration of the spinal cord following dorsal raphe nucleus lesions. Surgical transections at the level of mesencephalic-pontine junction caused no significant changes in 5-HT concentrations or tryptophan hydroxylase levels in the hypothalamus, limbic system, cerebral cortex or spinal cord. Serotonergic fibers ascending from the mesencephalic raphe nuclei constitute a well circumscribed bundle dorsal to the interpeduncular nucleus. The axons enter the hypothalamus between the mammillary body and crus cerebri just ventral to the medial forebrain bundle. The ascending pathway contains all the ascending 5-HT fibers innervating the hypothalamus and the rostral limbic and cortical areas.

Animals↗
PubMed1977

Evidence for substance P in the striato-nigral tract.

The highest concentration of substnace P yet found in the mammalian brain is in the reticular part of the substantia nigra. The effect of various lesions on the substance P content of that region has been examined in the rat in order to determine the possible sources and paths of nigropetal substance P-containing fibers. Unilateral knife cuts which transect the medial forebrain bundle and medial portion of the crus cerebri at a premammillary level lead to a 90% reduction in substance P in the ipsilateral reticular part of substantia nigra, with no significant effect on contralateral values. Incomplete electrolytic lesions of the globus pallidus lead to a 50% decrease. These data indicate that descending uncrossed pathways provide most of the substance P in the reticular part of the substantia nigra, with the striato-nigral tract providing an important component.

Afferent Pathways↗
PubMed1977

Glutamate decarboxylase (GAD) and gamma-aminobutyric acid (GABA) in discrete nuclei of hypothalamus and substantia nigra.

The distribution of L-glutamate decarboxylase activity (GAD) and gamma-aminobutyric acid (GABA) was investigated in the hypothalamic nuclei and in parts of the substantia nigra in the rat. GAD varied markedly among these areas. The reticular part of the nigra showed the highest activity two-fold higher than any other nucleus. Among the hypothalamic nuclei, a 5-fold difference was found between the poorest and richest nuclei. High GAD was measured in the preoptic, anterior and dorsomedial nuclei. Low activity was found in arcuate and supraoptic nuclei. The lowest GAD activity was measured in the median eminence with only half the activity of the whole brain homogenate. This suggests that GABAergic neurones might not be involved in neuroendocrine regulation at the median eminence level. GABA was determined using the sensitive cycling microassay. The rats were killed by microwaves, procedure which was found to inactivate enzymatic processes within two sec without affecting the level or the distribution of GABA. Postmortem increments during the first 3 min following decapitation ranged up to 5 times the endogenous levels, and were proportional to the GAD activity of the corresponding nucleus. This confirms that GAD is the limiting factor in GABA synthesis and suggests that GABA turnover might be rapid. Endogenous GABA showed a uniform distribution within hypothalamic nuclei and nigra. No relationship appeared between endogenous GABA levels and GAD activities in the various nuclei. These results suggest that while GABA synthesis is likely to occur in non-evenly distributed nerve cells, most GABA may be stored in surrounding cells, presumably glia cells.

Aminobutyrates↗
PubMed1977

Neurophysin biosynthesis: conversion of a putative precursor during axonal transport.

[35S]Cysteine injected adjacent to the supraoptic nucleus of the rat is rapidly incorporated into a 20,000-dalton protein that, in time, is converted to a 12,000-dalton labeled protein, neurophysin. This putative precursor of neurophysin appears to be synthesized in the supraoptic nucleus and transformed to neurophysin and related peptides during axonal transport to the neurohypophysis.

Animals↗
PubMed1977

Presence of corticotropin in brain of normal and hypophysectomized rats.

Immunoreactive and bioreactive corticotropin (ACTH-like) activities have been detected in the median eminence and remaining medial basal hypothalamus of both normal and hypophysectomized adult male rats: bioreactive ACTH (pg/100 mug of protein) 1028 in median eminence and 1289 in medial basal hypothalamus; immunoreactive ACTH (midportion ACTH antibody), 1554 in median eminence and 1887 in medial basal hypothalamus. By use of appropriate antibodies and bioassay, it was demonstrated that immunoreactivity was not due solely to alpha-melanotropin, which has previously been reported to be present in the brain of hypophysectomized animals. The Sephadex G-50 gel filtration patterns determined by immunoassay of column eluates obtained from hypothalamic extracts of normal or hypophysectomized animals were similar but were not identical to the pattern derived from whole pituitary. Immunoreactive (midportion ACTH antibody) ACTH concentrations (pg/100 mug of protein) of other central nervous system areas in normal animals were: cerebellum 34.3, cortex 46.3, thalamus 23.8, and hippocampus 116.3. The total amount of bioreactive ACTH present in the median eminence and medial basal hypothalamus is approximately 1% of that present in the pituitary. The present data suggest that such ACTH may have a diencephalic rather than pituitary origin and raise the question of the functional significance of such ACTH.

Adrenocorticotropic Hormone↗
PubMed1977

Thyrotropin-releasing hormone-like material in the rat retina: changes due to environmental lighting.

Material reacting with an antibody to thyrotropin-releasing hormone (TRH) has been found to be present in the rat retina. The compound present in the retina cochromatographed with authentic TRH and most of its activity was lost when incubated with pyroglutamate aminopeptidase (L-pyroglutamyl-peptide hydrolase, EC 3.4.11.8), an enzyme that degrades TRH. The TRH-like activity in the rat retina was low during the night and high during the day. There was a 4-hr lag period after the lights were turned on before peak TRH levels were attained. A decrease in TRH was seen after 2 hr of darkness and the level of TRH was lowest after 4 hr of darkness. Retinal TRH is elevated by environmental lighting regardless of the time of the day. These findings suggest that TRH may be involved in retinal photorecptive mechanisms.

Animals↗