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Biomedical subjects

R Benoit

Publications and source records attributed to R Benoit.

At least 55 records · Page 3Linked to original sources
PubMed1989

Influence of albumin and non-esterified fatty acids on serum prostacyclin binding in pregnancy.

We investigated the etiology of the previously documented decrease in serum prostocyclin binding during pregnancy. Addition of albumin to the serum of pregnant women failed to raise binding to non-pregnant levels. Pregnancy serum bound significantly more prostacyclin following the removal of non-esterified fatty acids and the addition of fatty acid free albumin resulted in a rise in binding to non-pregnant levels. We conclude that serum protein prostacyclin binding is affected by both albumin concentration and non-esterified fatty acids.

Blood Proteins↗
PubMed1989

Prosomatostatin-derived antrin is present in gastric D cells and in portal blood.

The three widely distributed peptides derived from prosomatostatin are the original neurohormone somatostatin-14, somatostatin-28, and somatostatin-28(1-12), which are all derived from the COOH terminus of the precursor. Recently a decapeptide derived from the NH2 terminus of the prohormone has been identified in extracts of rat gastric antrum and named antrin. Data now show that in both rats and humans this new molecular form is concentrated in the D cell of the gastrointestinal mucosa together with somatostatin-28(1-12). The highest concentration of antrin immunofluorescent cells is located in the mucosa of the gastric antrum. Ultrastructural studies performed on pyloric D cells using the protein A-gold technique reveals that antrin is present in the same secretory granules as somatostatin-28(1-12) and detectable in one-third of all secretory granules. Acid extracts of rat hepatic portal plasma contain a peptide similar or identical to antrin, indicating that the antral decapeptide circulates in blood.

Amino Acid Sequence↗
PubMed1989

Serum prostacyclin binding and half-life in normal and hypertensive pregnant women.

The effective half-life of prostacyclin in human serum is highly dependent on binding to serum proteins. Abnormalities in prostacyclin binding appear to be important in some patients with thrombotic thrombocytopenic purpura. We investigated prostacyclin binding and half-life in normotensive and hypertensive pregnant women and in nonpregnant controls. Pregnancy was associated with a decrease in serum prostacyclin binding and a shorter prostacyclin half-life. This decrease was even greater in women with hypertensive disorders. The decrease in prostacyclin half-life in hypertensive disorders may play an important role in the pathogenesis of these disorders. Measurement of both production and metabolism, however, will be required to adequately assess the role of prostacyclin in normal and abnormal gestation.

Adult↗
PubMed1988

Immunohistochemical evidence for a possible somatostatin-containing amygdalostriatal pathway in normal and Alzheimer's disease brain.

Somatostatin (SOM) immunohistochemistry was used to map SOM-containing fibers, perikarya and terminal-like structures in the human forebrain of 8 control and 8 Alzheimer's diseased patients. Immunohistochemically processed tissue revealed a somatostatin-immunoreactive amygdalostriatal fiber pathway apparently originating from SOM-positive neurons of the central amygdaloid nucleus. This pathway coursed dorsomedially between the optic tract and the internal segment of the globus pallidus within the ansa peduncularis-ventral amygdalofugal fiber system en route to the substantia innominata-nucleus basalis complex, the bed nucleus of the stria terminalis, the medial preoptic hypothalamic area, the nucleus accumbens and the olfactory tubercle. Somatostatin fibers associated with this pathway appeared as coarse heavily stained 'wooly fibers'. At the light microscopic level, there was no apparent difference in this somatostatin containing amygdalostriatal pathway between neurologically normal and Alzheimer's diseased brains.

Adolescent↗
PubMed1988

Somatostatin-28- and somatostatin-14-like immunoreactivities in the rat pituitary gland.

Endogenous SS14- as well as SS28-like immunoreactive materials were detected in both male and female rats by radioimmunoassay and by immunocytochemistry on ultrathin frozen sections. The content of somatostatin-like immunoreactivity was 0.39 +/- 0.08 pg per mg adenohypophysis. Immunoreactivity was localized by immunocytochemistry in three pituitary cell types: somatotrophs, lactotrophs and thyrotrophs, but not in corticotrophs and gonadotrophs. In these three pituitary cell types the SS28- and the SS14-like immunoreactive materials were localized in the cytoplasm and in the nucleus. In the cytoplasm the immunoreactivity was seen in the cytoplasmic matrix and in the secretory granules. In the nucleus it was present mainly in the euchromatin close to the heterochromatin. In somatotrophs and lactotrophs, SS14- and SS28-like immunoreactive materials have been detected at the plasma membrane level. These results suggest that (1) endogenous SS14 and SS28 are present in adenohypophysis in somatotrophs, lactotrophs and thyrotrophs, and (2) the two peptides act on both the cytoplasmic components and the nucleus.

Animals↗
PubMed1988

GABAergic neurons containing somatostatin-like immunoreactivity in the rat hippocampus and dentate gyrus.

The distribution of somatostatin-like immunoreactive (SS-LI) material and its colocalization with glutamic acid decarboxylase (GAD)-like immunoreactivity were studied in the rat hippocampus and dentate gyrus neurons using immunohistochemistry. In the dentate gyrus and CA1 region, SS-LI perikarya were concentrated in the hilus and in the stratum oriens, respectively, whereas immunoreactive cell bodies were rarely seen in other layers. Approximately half of the SS-LI neurons of the CA3 region were situated in the stratum oriens, the other half being scattered in strata pyramidale, lucidum and radiatum. About 90% of SS-LI neurons were also GAD-like immunoreactive, whereas about 14% of GAD-like immunoreactive (GAD-LI) neurons were SS-like immunoreactive. The percentage of GAD-LI neurons which were also immunoreactive for SS varied from one layer to the other. This percentage was about 30% in the hilus of the dentate gyrus and in the stratum oriens of the CA1 and CA3 regions; it was 5-10% in the strata pyramidale, lucidum and radiatum of the CA3 region and reached only 2% in the granule cell layer and molecular layer of the dentate gyrus and in the stratum pyramidale and stratum radiatum in the CA1 region. These observations indicate that the majority of SS-LI neurons in the rat hippocampal formation are a subpopulation of GABAergic neurons.

Animals↗
PubMed1988

Serum prostacyclin binding and half-life in the umbilical circulation.

Serum prostacyclin binding and half-life was measured in twenty pairs of maternal and umbilical venous samples and in twenty non-pregnant controls. When compared to non-pregnant values both umbilical and maternal samples demonstrated significantly lower albumin concentrations, percentage of prostacyclin binding and shorter prostacyclin half-life.

Epoprostenol↗
PubMed1988

Ontogeny of pituitary responsiveness to corticotropin-releasing hormone in rat.

The ontogeny of the pituitary's responsiveness to synthetic rat corticotropin-releasing hormone (CRH) in the late prenatal and early postnatal periods of rats was studied by a superfusion system using whole pituitaries. A significant increase of immunoreactive beta-endorphin (IR-beta-Ep) secretion in response to 10(-10) M CRH but not to 10(-11) M CRH was observed in pituitaries from the 15th day of gestation, the earliest day that we tested, whereas 10(-11) M CRH stimulated IR-beta-Ep release from the pituitaries of 17.5-day-old fetuses. Dose-related IR-beta-Ep secretions induced by 10(-12) M to 10(-10) M CRH were observed in pituitaries of 19.5- and 21.5-day-old fetuses, and 1-, 3- and 9-day-old newborn pups. CRH stimulated not only IR-beta-Ep and IR-adrenocorticotropic hormone (ACTH) but also IR-alpha-melanocyte-stimulating hormone (IR-alpha-MSH) secretions from fetal pituitaries. The content of IR-CRH in the hypothalamic extract from 15-day-old fetus was 6.6 +/- 3.6 pg/hypothalamus (mean +/- S.E.M.) and it gradually increased to reach 212.7 +/- 20.3 pg/hypothalamus on the 21.5th day of gestation. However, the content of IR-CRH in the hypothalamus dramatically decreased just after birth and then rapidly increased again from the 5th day after birth. These data indicate that the responsiveness of corticotrophs to CRH is already present on the 15th day of gestation, when the content of IR-CRH in the hypothalamus is extremely low and that the amount of hypothalamic IR-CRH dramatically dropped for several days just after birth in rats.

Animals↗
PubMed1987

A new prosomatostatin-derived peptide reveals a pattern for prohormone cleavage at monobasic sites.

Cleavage of the peptide bonds of preprosomatostatin at basic residues near the carboxyl terminus yields somatostatin-14, somatostatin-28, and somatostatin-28 (1-12). However, little is known about the molecular forms derived from the amino terminal portion of the precursor, even though this part of the prohormone is highly conserved through evolution. By using an antibody against the amino terminus of prosomatostatin, a decapeptide with the structure Ala-Pro-Ser-Asp-Pro-Arg-Leu-Arg-Gln-Phe, corresponding to preprosomatostatin (25-34), was isolated from the endocrine portion of the rat stomach, the gastric antrum. The antral decapeptide may represent a bioactive product generated from prosomatostatin after a monobasic cleavage similar to that involved in the formation of somatostatin-28. In fact, a monobasic cleavage requires two basic residues and a domain containing nonpolar amino acids such as alanine or leucine, or both.

Amino Acid Sequence↗
PubMed1987

Platelet inhibitory activity in placentas from normal and abnormal pregnancies.

Retroplacental blood flow requires inhibition of coagulation in the absence of an endothelial lining. We confirmed that trophoblast releases an inhibitor of platelet aggregation which functions via degradation of adenosine diphosphate. This inhibitor appears to be deficient in some pregnancies with abruptio placentae and intrauterine growth retardation. Unimpeded retroplacental blood flow may depend upon the local inhibition of platelet aggregation. Placental tissue contains an inhibitor of platelet aggregation which appears to be an adenosine diphosphatase distinct from heat-stable alkaline phosphatase. Placental tissue from patients with abruptio placentae contains abnormally low amounts of this enzyme.

Abruptio Placentae↗
PubMed1987

Regional heterogeneity in the distribution of somatostatin-28- and somatostatin-28(1-12)-immunoreactive profiles in monkey neocortex.

The distribution of the prosomatostatin-derived peptides (PSDP), somatostatin-28 and somatostatin-28(1-12), in the cynomolgus monkey (Macaca fascicularis) neocortex was characterized in quantitative immunohistochemical studies of 3 visual areas (V1, primary visual cortex; V2, the adjacent visual association area; and AIT, a visual association area in anterior inferior temporal cortex), 2 auditory areas (AI, primary auditory cortex; and T1, an adjacent auditory association area) and anterior cingulate cortex (Area 24). The results of similar quantitative analyses in 3 homologous areas in rat neocortex (primary visual, primary auditory, and anterior cingulate) are also presented. Primate cortical areas differed significantly in both density and laminar distribution of PSDP-immunoreactive profiles. Area 24, the most densely labeled area, had nearly 6 times as many PSDP-immunoreactive neurons as V1. Both auditory areas contained approximately two-thirds the number of PSDP-immunoreactive neurons found in Area 24; however, both had nearly 4 times as many immunoreactive neurons as V1. The 3 visual areas showed incremental increases in the number of PSDP-immunoreactive neurons; V2 contained nearly twice and AIT nearly 3 times the number of immunoreactive neurons present in V1. Both the supra- and infragranular layers were densely labeled in Area 24 and Area T1, however, in AI, V1, V2, and AIT the infragranular layers were relatively sparsely labeled. In contrast to the regional heterogeneity found in the primate neocortex, the distribution of immunoreactive neurons was quite uniform across the 3 rat cortical areas. The rat cortical areas contained substantially fewer immunoreactive neurons than most of the monkey cortical areas, and a majority of these immunoreactive neurons were located in the infragranular layers. These findings suggest that the regional specialization of primate neocortex involves the selective distribution of PSDP-immunoreactive neurons. They also suggest that chemically specified intrinsic organization of neocortex is not likely to be uniform across species or across cortical areas in the primate. The distinctive regional distribution patterns of PSDP-immunoreactive profiles appear to parallel that of the long corticocortical projections (contralateral and distant ipsilateral projections), suggesting an association between these presumed inhibitory interneurons and this important extrinsic system.

Animals↗
PubMed1986

Somatostatin-28(1-12)-like immunoreactivity is reduced in Alzheimer's disease cerebral cortex.

A deficiency in somatostatin is the most consistently described neurochemical alteration in Alzheimer's disease (AD) attributable to intrinsic cortical neurons. Somatostatin-28 (SOM-28), an N-terminal-extended form of somatostatin, can be cleaved to form somatostatin-28(1-12)(SOM-28(1-12) ) and somatostatin-14 (SOM-14). We have measured concentrations of SOM-28(1-12)-like immunoreactivity in 8 cortical regions from 12 patients with AD and 13 controls. Significant reductions (P less than 0.001) were found in all cortical regions examined with the largest decrease in temporal lobe. Reductions were significantly correlated with decreases in somatostatin-14-like immunoreactivity in the same regions. The similar reductions of two prosomatostatin-derived peptides in AD cerebral cortex supports the contention that decreased somatostatin immunoreactivity in AD is caused by a degeneration of somatostatin cortical neurons and terminals.

Aged↗
PubMed1986

Somatostatin-containing D cells exhibit immunoreactivity for rat somatostatin cryptic peptide in six mammalian species. An electron-microscopical study.

Antisera raised against rat somatostatin cryptic peptide (RSCP; corresponding to amino acids 63-77 of rat pro-somatostatin), somatostatin-28-(1-12) and somatostatin-28-(17-28) were used to compare the morphological distribution of these pro-somatostatin-derived sequences within the gastroenteropancreatic system of six mammalian species, including man. Using the immunogold staining procedure, RSCP, SS28-(1-12) and SS28-(17-28) immunoreactivity was found to be present in all the D cells of the tissues investigated. Extra-islet RSCP and SS28-(1-12) immunoreactive cells were also identified in some species. RSCP, SS28-(1-12) and SS-28-(17-28) immunoreactivities were also present in a single case of human duodenal somatostatinoma. Immunostaining of serial ultrathin sections from all specimens in this study revealed that RSCP and both somatostatin immunoreactivities were co-localised in a majority of the reactive cells. Corroborative evidence was obtained by double immunogold staining which further showed that RSCP, SS28-(1-12) and SS28-(17-28) immunoreactivities were co-localised to individual secretory granules in D type cells, both normal and tumour. RSCP and SS28-(17-28) immunoreactivities were invariably co-localised, whereas SS28-(1-12) immunoreactivity was restricted to a sub-population of secretory granules. Our findings suggest that RSCP immunoreactivity is conserved in a number of mammalian species and is stored in each secretory granule type. Consequently, detection of the RSCP sequence may serve as a useful marker for somatostatin-producing systems throughout the diffuse neuroendocrine system.

Colon↗
PubMed1985

Blood pressure following microinjection of somatostatin related peptides into the rat nucleus tractus solitarii.

The possible role of medullary somatostatin as a neurotransmitter involved in blood pressure regulation was examined. Blood pressure and heart rate were measured in pentobarbital anesthetized rats while pmol quantities of somatostatin-28 (SS28), SS28-(15-28) (somatostatin-14), SS28-(1-12) or SS28-(1-10) were injected into the caudal nucleus tractus solitarii (NTS). Injection of artificial cerebrospinal fluid (ACSF; 500 nl/10 s) alone was followed by a small (2 mmHg) statistically insignificant decrease in blood pressure. SS28, SS28-(15-28) or SS28-(1-12) induced an immediate and statistically significant decrease in blood pressure as compared to vehicle alone. SS28-(1-10) had no significant effect. SS28 was tested at three doses. The lowest dose of SS28 (2.5 pmol) induced an 8 mmHg drop in blood pressure, the medium dose (25 pmol), an 11 mmHg drop and the highest dose (250 pmol) a 16 mmHg drop. The other peptide fragments were tested only at the higher 250 pmol dose. SS28-(1-12) induced a significantly (P less than 0.01) less drop in blood pressure (10 mmHg) when compared to either SS28 or SS28-(15-28) (18-19 mmHg). The hypotensive and bradycardiac effects of SS28 were prevented by pretreatment with methylscopolamine (5 mg/kg i.p.) 10 min prior to SS28. The cardiovascular effects of intramedullary injected SS28 were also blocked with an ipsilateral NTS injection of yohimbine or tolazoline 10 min prior to SS28.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Immunoreactive somatostatin-28(1-12) is increased in Huntington's disease.

Somatostatin-28(1-12) concentrations were measured in Huntington's disease (HD) postmortem tissue using a specific radioimmunoassay. Concentrations of immunoreactive somatostatin-28(1-12) were significantly increased in the caudate and putamen but were unchanged in cortical areas A9 and A17. Since somatostatin-28(1-12) terminates with the amino acids Arg-Glu-OH, we examined whether this dodecapeptide compound might exert a neurotoxic effect. Injections of somatostatin-28(1-12) into rat striatum showed no evidence of histologic damage.

Adolescent↗
PubMed1985

The somatostatin-28 convertase of rat brain cortex generates both somatostatin-14 and somatostatin-28.

The products generated after addition of the ARG-LYS esteropeptidase activity purified from rat brain to synthetic somatostatin-28 were analyzed using radioimmunoassay, HPLC and amino acid analysis. In addition to somatostatin-14, both free arginine and free Lysine were identified together with somatostatin-28. The dipeptide ARG-LYS was not present, which indicates that three peptide bonds were hydrolyzed in order to achieve excision of the doublet. Since it is likely that the octacosapeptide is a precursor for both somatostatin-14 and somatostatin-28, these observations add further support to the hypothesis that the convertase is also involved in the in vivo processing of endogenous somatostatin-28.

Animals↗