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Biomedical subjects

S E Leeman

Publications and source records attributed to S E Leeman.

At least 109 records · Page 6Linked to original sources
PubMed1981

Effect of capsaicin pretreatment on capsaicin-evoked release of immunoreactive somatostatin and substance P from primary sensory neurons.

Release of immunoreactive somatostatin (I-SRIF) and immunoreactive substance P (I-SP) was studied from slices prepared from upper dorsal horn (UDH) and lower dorsal plus ventral horn (LDH-VH) of rat spinal cord. Superfusion with capsaicin (10 microM) led to release of I-SRIF and I-SP from UDH slices but not from LDH-VH slices. The capsaicin-evoked release of I-SP was 6 fold higher than that of I-SRIF. A pulse of 60 mM K+ applied after the capsaicin pulse caused release of I-SRIF and I-SP from UDH as well as LDH-VH slices. Pretreatment of rats with capsaicin (125 mg/kg, s.c.) led to a nearly 40% depletion of I-SP in slices from UDH only. Capsaicin-evoked release from these slices was reduced by 81% for I-SRIF and by 79% for I-SP. Release evoked by K+ remained unchanged. These results indicate that capsaicin causes release of both I-SRIF and-I-SP and that this release is most likely restricted to primary sensory neurons. The marked reduction of the release of I-SP after systemic capsaicin pretreatment may well represent one of the, or even the reason for the insensitivity of capsaicin pretreated rats towards chemogenic pain.

Animals↗
PubMed1981

Immunoreactive neurotensin levels in pancreas: elevation in diabetic rats and mice.

Neurotensin levels in pancreas, but not other tissues, were increased in diabetic animals. The concentration of pancreatic immunoreactiveneurotensin was 138% higher in streptozotocin-diabetic rats, and 68% higher in genetically diabetic (db/db) mice as compared to their respective control animals. Daily administration of insulin (10-15 IU/kg) to diabetic rats completely reversed this effect, and pancreatic neurotensin levels in these animals returned to control values. These findings suggest that elevated levels of pancreatic neurotensin may contribute to some of the metabolic and hormonal disturbances occurring in diabetes.

Animals↗
PubMed1981

Elevation of plasma neurotensin during lipid perfusion of rat small intestine.

Perfusion of the small intestine with a lipid solution results in elevated plasma neurotensin-like immunoreactivity in blood collected from the superior mesenteric vein. Perfusion of amino acids, glucose, hyperosmotic saline, acidified saline, bile salt and diluted rat bile had no effect. Neurotensin-like immunoreactivity in portal plasma was significantly higher than that measured concomitantly in peripheral arterial plasma. Neurotensin, as identified by high pressure liquid chromatography, rose from 4 to 9 fm/ml (n = 4) and 9 to 18 fm/ml (n = 9) extracted plasma during lipid stimulation as compared to the saline control. These results demonstrate that intraintestinal lipid is an effective and specific stimulus for the release of neurotensin from the small intestine into the portal circulation. However, until a target organ can be shown to respond to these modest levels of plasma neurotensin, it is unsettled whether the peptide is a hormone or whether its elevation in plasma is due to "overflow" of a paracrine agent.

Animals↗
PubMed1980

Isolation of human intestinal neurotensin.

The biologically active peptide neurotensin (NT) has been isolated from fresh postmortem human small intestine and its identity with bovine hypothalamic and intestinal neurotensin has been established. Purification was achieved by gel filtration and two ion exchange chromatography steps; material was detected by radioimmunoassay (RIA). A substance was obtained that had integral molar ratios of amino acids and eluted in a single peak during reverse-phase high pressure liquid chromatography (HPLC). This material had an amino acid composition and COOH-terminal sequence identical with those of bovine NT. Human and bovine neurotensin gave rise to the same fragments when treated with papain; they were indistinguishable in RIAs using three different region-specific antisera and in their hypotensive effect on anesthetized rats. Using mucosal scrapings obtained immediately post-mortem from four subjects, the concentration of immunoreactive neurotensin was found to increase from duodenum to distal ileum, in agreement with results obtained in other mammalian species.

Amino Acids↗
PubMed1980

Primary cultures of dispersed hypothalamic cells from fetal rats: morphology, electrical activity, and peptide content.

Cultures prepared from dispersed fetal hypothalamic tissue have cells which can be identified as neurons by their morphology and electrical activity. The elongation of neuritic processes in these cultures is increased by treatment with 1-beta-D arabinofuranosylcytosine (ara-C). Hypothalamic cultures have measurable quantities of immunoreactive substance P and neurotensin, and the neurons can accumulate (3H)GABA.

Animals↗
PubMed1980

Characterization of neurotensin production by a line of rat medullary thyroid carcinoma cells.

The rMTC 6-23 cell line was derived from a calcitonin-producing rat medullary thyroid carcinoma. During characterization of these cells we discovered that they also synthesize and secrete neurotensin (NT), a tridecapeptide originally isolated from the hypothalamus and not previously associated with C cells. Immunoreactive NT (iNT) was measured with two antisera: HC-8, which recognizes the COOH-terminal eight amino acids, and TG-1, which binds the NH2-terminal region of NT. By use of these antisera, 2 M acetic acid extracts of rMTC 6-23 cells were found to contain 0.7--5.0 pmol of iNT per mg of cell protein. Successive fractionation of iNT from cell extracts by gel filtration, ion-exchange chromatograpy, and reverse-phase high-pressure liquid chromatography showed at each step a peak of iNT that was indistinguishable from synthetic NT in its chromatographic behavior. Biologic activity of the iNT was confirmed by demonstrating the characteristic fall in arterial blood pressure in the rat after intravenous injection of material purified from rMTC 6-23 cells. Calcium (0.5--4.0 mM) stimulated release of iNT in a dose-dependent manner; the effect was maximal at 3--4 mM calcium. K+ (50 mM) stimulated release of iNT that was maximal in the presence of 1.0--1.5 mM calcium. Synthesis and secretion of iNT by these cells were shown during a 16-day growth experiment. These results demonstrate that rMTC 6-23 cells contain NT and suggest the possibility of an association between neurotensin and calcitonin.

Animals↗
PubMed1980

Release of immunoreactive somatostatin from hypothalamic cells in culture: inhibition by gamma-aminobutyric acid.

Primary cultures of dispersed hypothalamic cells were prepared from embryonic rats to study the release of immunoreactive somatostatin. The immunoreactive somatostatin content of these cultures increased during the first 2 weeks after plating and was readily measurable for several weeks thereafter; this material was characterized by gel permeation and reverse-phase chromatography. Depolarization of the cells with 60 mM K+ or with veratridine resulted in a calcium-dependent release of immunoreactive somatostatin which cochromatographed with synthetic somatostatin on reverse-phase chromatography. Tetrodotoxin blocked the veratridine-evoked release. However, even in the absence of exogenous stimuli, immunoreactive somatostatin was released by the cells into the medium. More than 70% of this tonic release was found to be calcium dependent and to be inhibited by tetrodotoxin, indicating that spontaneous electrical activity in the cultures leads to a release of immunoreactive somatostatin. gamma-Aminobutyric acid inhibited the tonic release of immunoreactive somatostatin and this was reversed by bicuculline. These findings support the hypothesis that gamma-aminobutyric acid inhibits somatostatin release in vivo.

Animals↗
PubMed1980

Neurotensin neurons in the rat hypothalamus: an immunocytochemical study.

Neurotensin was localized in the hypothalamic tissues of adult Sprague-Dawley rats by immunoperoxidase techniques. Visualization of perikarya was greatly enhanced by intraventricular administration of colchicine. Many perikarya containing neurotensin-like immunoreactivity were seen in the medial preoptic area, the periventricular hypothalamus, the parvocellular portion of the paraventricular nucleus, the arcuate nucleus, and the lateral hypothalamus in the perifornical area. There were moderate numbers of cell bodies in the ventral portion of the anterior hypothalamus, the dorsomedial nucleus, and the posterior hypothalamus. No positive cells were seen in the suprachiasmatic, ventromedial, or mammillary nuclei. Reactive fibers were generally distributed in the same regions as cell bodies. Additional dense collections were seen in the lateral part of the zona externa of the median eminence, the pituitary stalk, the posterior mammillary nucleus, and the most lateral portions of the hypothalamus at the medial edge of the crura cerbri. There were smaller numbers of fibers found in the pre-mammillary and posterior hypothalamic nuclei and the posterior pituitary gland. These results indicate that the neurotensin system in the hypothalamus is very extensive and complex, as it is in many other brain regions. Neurons and fibers are found in many hypothalamic areas, including projections to the hypophysial portal system in the median eminence, suggesting that neurotensin may affect neuroendocrine mechanisms at several levels, including the anterior pituitary gland.

Animals↗
PubMed1980

Neurotensin in plasma: immunochemical and chromatographic character of acid/acetone-soluble material.

Using a RIA, we have examined the character of the neurotensin-like (NT-like) peptides present in acid/acetone extracts of animal and human plasma. Plasma immunoreactivity was measured using four antisera with different specificities. Antisera which were directed against the COOH-terminus of NT measured higher levels of plasma immunoreactivity than did antisera with NH2-terminal or mixed specificity. Chromatographic fractionation of bovine plasma extracts revealed the presence of multiple substances, one of which was chromatographically and immunochemically indistinguishable from NT. We estimate the plasma level of this component to be about 15-25 fmol/ml, which is 30-50% of the measurement obtained on unfractionated extracts using antiserum HC-8. Several other components were also identified which behaved as though they were smaller than NT and seemed to share with NT four to eight of its COOH-terminal amono acids. One eluted from Sephadex G-25 in the region of the NT-like peptide previously identified in extracts of gastric mucosa. Infusion of synthetic NT into rats for 30 min did not result in the formation of these COOH-terminal relatives of NT. Our results argue strongly for the presence of NT in plasma and also indicate that other peptides, sharing COOH-terminal homologies with NT, appear in plasma, possibly from the stomach, liver, and other as yet unidentified source(s).

Acetone↗
PubMed1980

Substance P in human cerebrospinal fluid: reductions in peripheral neuropathy and autonomic dysfunction.

Substance P (SP), a putative peptide neurotransmitter, was measured in human lumbar cerebrospinal fluid (CSF) by radioimmunoassay. Substance P-like immunoreactivity (SPLI) was present in the CSF of 18 neurologically normal adults in concentrations ranging from 2.9 to 11.1 fmol per milliliter, with a mean of 7.0 /+- 0.6 fmol per milliliter (mean /+- SE). Slightly more than half of the CSF-SPLI cochromatographed with synthetic SP on Sephadex G-25. There was no apparent gradient in CSF-SPLI concentration over the first 30 ml of CSF removed by lumbar puncture. Mean concentrations CSF-SPLI in patients with Huntington disease, parkinsonism, miscellaneous dyskinesias, progressive supranuclear palsy, myopathy, and amyotrophic lateral sclerosis did not differ significantly from normal. Patients with neuropathy or multiple-system atrophy (Shy-Drager syndrome) had significantly reduced mean CSF-SPLI concentrations. These observations suggest that lumbar CSF-SPLI arises largely from spinal cord, nerve roots, or dorsal root ganglia, and that pathologic processes affecting these structures may be reflected by reduced levels of CSF-SPLI.

Adolescent↗