Search PubMed⌕ Search

Biomedical subjects

J F Wilber

Publications and source records attributed to J F Wilber.

At least 55 records · Page 3Linked to original sources
PubMed1987

Thyrotropin-releasing hormone and histidyl-proline diketopiperazine: stimulation of secretion from hypothalamic fragments in vitro by depolarizing agents.

The influence of depolarizing agents on the release of TRH and histidyl-proline diketopiperazine [C(HP)] from rat hypothalami was examined in vitro. Thin hypothalamic fragments from two separate animals were incubated in Krebs-Ringer bicarbonate media. Immunoreactive TRH and C(HP) released into medium were determined by specific RIAs. Potassium and ouabain, a Na+/K+-ATPase inhibitor, stimulated TRH and C(HP) secretion in a graded fashion, but the magnitudes of C(HP) secretory responses were less than those of TRH. The stimulation by KCl and ouabain was inhibited by the addition of verapamil, a Ca2+ channel blocker, or omission of Ca2+ from medium in the presence of EGTA. Veratridine, a Na+ channel activator, also stimulated TRH and C(HP) release from rat hypothalami, and this stimulation was completely blocked by tetrodotoxin, a Na+ channel blocker. The results of this study indicate that TRH and C(HP) release from rat hypothalami are stimulated by membrane depolarization in vitro and depend on Na+ and Ca2+ influx.

Animals↗
PubMed1986

Distribution and characterization of cyclo(His-Pro)-like immunoreactivity in human cerebrospinal fluid.

The distribution of cyclo(His-Pro), thyrotropin-releasing hormone and pyroglutamate aminopeptidase activity was examined in the CSF of human and a number of other mammalian species. Cyclo(His-Pro)-like immunoreactivity was present in the CSF of all species examined, and was immunologically and chromatographically identical with the authentic cyclo(His-Pro). Cyclo(His-Pro) concentration in CSF had no significant correlation with CSF TRH or pyroglutamate aminopeptidase.

Adult↗
PubMed1986

On the mechanism of fasting-associated elevations in hypothalamic cyclo(His-Pro) content.

Potential mechanism(s) underlying the fasting-associated rise in hypothalamic cyclo(His-Pro) content was explored by examining the effects of 24-hour fasting on: (i) cyclo(His-Pro) synthesis from TRH, (ii) cyclo(His-Pro) metabolism, and (iii) cyclo (His-Pro) secretion by hypothalamic tissue in vitro. The data presented here show that none of these three variables were altered due to fasting. Two additional potential changes that could cause cyclo(His-Pro) elevations during fasting are suggested. These include an in vivo decrease in hypothalamic cyclo(His-Pro) secretion that may not be apparent in vitro, and/or an increase in the synthesis of cyclo(His-Pro) from a precursor(s) other than TRH.

Aminopeptidases↗
PubMed1986

Amyotrophic lateral sclerosis: effects of acute intravenous and chronic subcutaneous administration of thyrotropin-releasing hormone in controlled trials.

We performed double-blind crossover trials to assess the effects of thyrotropin-releasing hormone (TRH) on amyotrophic lateral sclerosis patients. For acute intravenous trials, 500 mg TRH or placebo with norepinephrine was given at 1-week intervals (16 patients). CSF TRH concentration increased, and clinical side effects appeared with TRH. For chronic studies, 25 mg TRH and a saline placebo were given subcutaneously every day for 3 months (25 patients). CSF TRH level increased 29-fold after a single TRH injection, and mild transient side effects occurred. Vital signs, respiratory function, semiquantitative and quantitative neurologic function, muscle strength by manual and dynamometer testing, and EMG were studied. With daily TRH, 10 patients noted subjective improvement without objective evidence, and 10 patients complained of worsening of the disease with objective decline after TRH was stopped. Statistical analysis, however, showed no beneficial effects from either acute or chronic TRH trials.

Adult↗
PubMed1985

Biochemical transmethylation of lipids and neuropeptidergic stimulation of pituitary hormone secretion.

S-adenosyl-L-methionine-dependent methylation of membrane phosphatidylethanolamine to phosphatidylcholine has been shown to exist in a number of tissues including pituitary gland and to play important roles in receptor-mediated functions. The possible role of this phospholipid methylation reaction in pituitary hormone secretion has been studied. To this end, the ability of thyrotropin-releasing hormone (TRH) to release thyrotropin (TSH) and prolactin and the ability of luteinizing hormone-releasing hormone (LH-RH) to release luteinizing hormone (LH) were evaluated after inhibition of pituitary phospholipid methylation. Both TRH and LH-RH stimulated the release of their corresponding pituitary hormone in a dose-dependent manner and this stimulatory effect was inhibited in the presence of phospholipid methylation inhibitors. Non-specific stimulation of TSH release by 55 mM KCl or 0.1 mM veratridine, however, was not affected by the methylation inhibitors. The data suggest that phospholipid methylation may participate in receptor-mediated release of pituitary hormones.

Animals↗
PubMed1985

Distribution and characterization of cyclo (His-Pro)-like immunoreactivity in the human gastrointestinal tract.

Cyclo (His-Pro) [C(HP)] has been measured by radioimmunoassay in perchloric acid extracts of human gastrointestinal (GI) tract structures derived from autopsy sources and fresh colonic biopsies. C(HP) was identified in all regions of the human GI tract, ranging in concentrations from 599 +/- 102 pg/mg protein in stomach, to 127 +/- 26 pg/mg protein in esophagus. The mean concentration of C(HP) from colonic biopsies was 335 +/- 30 pg/mg protein, statistically similar to values derived from postmortem sources. Since C(HP) concentrations are within the range of other gut peptide modulators, cyclo (His-Pro) is speculated to play a role as a new paracrine modulator of human GI tract function(s).

Animals↗
PubMed1985

Brain thyrotropin-releasing hormone matures independently of the hypothalamus in the rat.

To evaluate the relationship of the extrahypothalamic brain thyrotropin-releasing hormone (TRH) to its hypothalamic counterpart, we studied the maturation of hypothalamic and extrahypothalamic TRH in the rat. The absolute increase of TRH in the whole brain and the extrahypothalamus reached adult levels at 7 days of age, whereas the hypothalamic TRH concentrations did not differ from the adult levels at 23 days. Moreover, the TRH concentrations at 7 days were greater than the adult levels in the striatum, hippocampus, pons-medulla and cerebellum, and similar to the adult levels in the midbrain and cortex. These data indicate the developmental divergency of hypothalamic and extrahypothalamic TRH, implying that the maturation of extrahypothalamic TRH is independent of the hypothalamus. The present study suggests that extrahypothalamic TRH may play a neurophysiological role in the central nervous system at an early infantile age, at which hypothalamic TRH is not ripe for its endocrinological action.

Age Factors↗
PubMed1985

Alteration by liquid protein diet of TRH and cyclo(His-Pro) in the young rat brain.

Effects of liquid protein diet (LPD), known to be poor in protein quality, on brain thyrotropin-releasing hormone (TRH) and histidylproline diketopiperazine (cyclo(His-Pro] were examined in young male rats. At day 23 of weaning, the animals were fed either a 20% casein diet ad libitum or a 20% LPD, or were pair-fed with a 20% casein diet. They were decapitated at day 48. The body weight of those in the LPD and pair-fed groups decreased significantly, and the loss was sustained in comparison with that in the ad libitum group. Cyclo(His-Pro) concentrations in the whole brain were significantly greater in the LPD group than in the pair-fed and ad libitum groups, whereas its concentrations were similar in the pair-fed and ad libitum groups. No significant differences were observed in concentrations of brain TRH in the three groups. These findings indicate that quality of the protein component in the diet contributes to alterations in the neuropeptide, cyclo(His-Pro), in the young rat brain.

Animals↗
PubMed1984

Protein-energy malnutrition during pregnancy alters caffeine's effect on brain tissue of neonate rats.

We studied whether protein-energy malnutrition changed brain susceptibility to a small dose of caffeine in newborn rats. Since we had demonstrated previously that caffeine intake during lactation increased the brain neuropeptide on newborns, we investigated further the effects of the prenatal administration of caffeine on TRH and cyclo (His-Pro). From day 13 of gestation to delivery day, pregnant rats in one group were fed either a 20% or a 6% protein diet ad libitum, and those in the other group were pair-fed with each protein diet supplemented with caffeine at an effective dose of 2 mg/100 g body weight. Upon delivery, brain weight, brain protein, RNA, DNA and the neuropeptides thyrotropin-releasing hormone (TRH) and cyclo (His-Pro) were measured in the newborn rats. A 6% protein without caffeine diet caused reductions in brain weights and brain protein, RNA and DNA contents, but did not alter brain TRH and cyclo (His-Pro) concentrations in the newborn animals. In the offspring from dams fed a 6% protein diet, caffeine administration significantly elevated brain weights and brain contents of protein, RNA and DNA. In contrast, these values were similar between noncaffeine and caffeine-supplemented animals in a 20% protein diet group. Brain TRH and cyclo (His-Pro) concentrations were not changed by caffeine administration. These data suggest that caffeine augments protein synthesis in the newborn rat brain when malnourished, but that the same dose of caffeine did not affect protein synthesis in brains of newborn rats from normally nourished dams. Therefore, the present findings indicate that the nutritional status of mothers during pregnancy has important implication in the impact of caffeine on their offspring's brains.

Adult↗
PubMed1984

Identification of immunoreactive thyrotropin-releasing hormone in human neoplasia.

Immunoreactive TRH (IR-TRH) was identified in extracts derived from seven human cancer tissues, including two oat cell carcinomas. The IR-TRH concentrations ranged from 29-189 pg/g. Tumor IR-TRH exhibited immunological identity with synthetic pyroglu-his-proamide and coeluted with synthetic [3H]TRH after high pressure liquid chromatography on a mu Bondapak C-18 column. These data extend the number of hypothalamic peptide hormones identified in human neoplastic tissues.

Adenocarcinoma↗
PubMed1983

Protein-energy malnutrition alters brain thyrotropin-releasing hormone and cyclo (His-Pro) in the neonatal rat.

To evaluate effects of protein-energy malnutrition on the brain neuropeptides thyrotropin-releasing hormone (TRH) and cyclo (His-Pro) in the cerebellum and the remainder brain, we studied neonatal rats in the lactational period. Protein-energy malnutrition caused an increase in cyclo (His-Pro) concentrations, but not in TRH concentrations, in the neonatal cerebellum. In the remainder brain, a reduction in cyclo (His-Pro) concentrations occurred with an increase in TRH concentrations. These data indicate that protein-energy malnutrition affects both brain TRH and cyclo (His-Pro) in the neonatal rats during lactation.

Animals↗
PubMed1983

Descending serotonergic, peptidergic and cholinergic pathways from the raphe nuclei: a multiple transmitter complex.

The localization of serotonergic, various peptidergic and possibly cholinergic neurons in the medullary raphe nuclei that project to the lumbosacral spinal cord have been studied using a retrograde transport method combined with immunocytochemical and histochemical techniques. Spinally projecting neurons stained for serotonin-like, substance P-like, enkephalin-like and thyrotropin-releasing hormone-like immunoreactivity and for the histochemical marker acetylcholinesterase were all observed in each of the raphe nuclei of the medulla, as well as in the adjacent ventrolateral reticular formation. The similar distributions of the descending serotonergic and peptidergic neurons in the raphe nuclei as well as quantitative data on their relative numbers suggest that a large fraction of raphe-spinal neurons contain serotonin co-existing with one or more peptides in the same cell.

Acetylcholine↗
PubMed1983

Influences of maternal caffeine on the neonatal rat brains vary with the nutritional states.

The potential effect of maternal caffeine ingestion upon total brain protein and the concentration of two prototype neuropeptides, thyrotropin-releasing hormone (TRH) and its derivative, cyclo (His-Pro) in neonates was examined during the nursing period in the context of variable maternal protein intake. Maternal caffeine intake (2 mg/100 g body weight) significantly increased the total brain protein of neonates derived from dams fed a 6% casein diet, but not from dams fed a 12%- or 20%-casein diet. Maternal caffeine consumption significantly increased the amount of cyclo (His-Pro) in the neonatal brains in all groups. The percent increments in pups from dams fed 6%, 12%, and 20% casein diets were respectively 137%, 131%, and 120%. By contrast, no significant alterations were observed in TRH concentrations between caffeine and control groups. It is concluded that maternal caffeine can influence neonatal brain protein and cyclo (His-Pro) during nursing under conditions of protein-energy malnutrition.

Animals↗
PubMed1983

Brain TRH and Cyclo (His-Pro) and brain protein in the newborn rat are altered by maternal liquid protein feeding.

Liquid protein diet (LPD) has been shown previously to produce maternal and fetal weight loss and fetal congenital anomalies, including cataracts and craniofacial malformations. Therefore, to examine the effects of LPD in pregnancy upon the central nervous system of pups, pregnant dams were fed either a 20% casein diet ad libitum, a 20% LPD, or pair-fed with a 20% casein diet. LPD was associated with significant maternal weight loss, and pups had significantly lower birth weights (5.14 +/- 0.64) than pups from the pair-fed controls (5.70 +/- 0.46, p less than 0.05). Total brain protein content was reduced significantly in pups of both sexes from pregnant fed LPD. Moreover, the concentrations of two brain peptides neurotransmitters, thyrotropin-releasing hormone (TRH), and its biologically active metabolite, histidyl-proline diketopiperazine Cyclo (His-Pro), were elevated in the pups from LPD-fed mothers. In contrast, there was no significant difference in brain protein or brain peptides in pups from pair-fed mothers vs. pups from mothers fed ad libitum. These data suggest that qualitative alterations of the protein component in maternal dietary composition have deleterious effects upon the ontogeny of the rat fetal CNS, as reflected by reduced total protein and elevated concentrations of TRH and Cyclo (His-Pro).

Animals↗