Immunocytochemical localization of somatostatin in cell bodies of the rat hypothalamus.

Cell bodies of small to moderate-sized neurons in the female rat hypothalamus were stained specifically for somatostatin (SRIF) by means of the unlabeled antibody-peroxidase-antiperoxidase immunocytochemical method. SRIF-positive perikarya were scattered throughout the periventricular nucleus in a limited region extending from the middle of the optic chiasm to the rostral margin of the median eminence. The same neurons were revealed with either rabbit (R) or guinea pig (GP) anti-SRIF antisera. Positive cell bodies were more readily assessed with GP antibodies because nonspecific background staining was much less with these than with R anti-SRIF. Positive perikarya were not observed in other hypothalamic nuclei and ependymal elements were also immunocytochemically negative.     

胰岛淀粉样多肽在豚鼠胰腺分布的免疫组织化学研究

本文用免疫组织化学ＡＢＣ法,研究了胰岛淀粉样多肽（Ｉｓｌｅｔａｍｙｌｏｉｄｐｏｌｙｐｅｐｔｉｄｅ,ＩＡＰＰ或称Ａｍｙｌｉｎ）在豚鼠胰脏的分布,并用邻片免疫组织化学双标记法,观察了ＩＡＰＰ与胰岛素（Ｉｎｓｕｌｉｎ,ＩＮＳ）、生长抑素（ＳｏｍａｔｏｓｔａｔｉｎＳＳ）的共存关系。结果显示,豚鼠胰岛内绝大多数细胞都呈ＩＡＰＰ阳性免疫反应,在胰外分泌部的腺泡和导管内也散在分布有ＩＡＰＰ免疫反应阳性细胞。多数ＩＡＰＰ免疫反应阳性的细胞都显示ＩＮＳ免疫反应阳性,胰岛内少数ＩＡＰＰ阳性细胞也呈ＳＳ免疫反应阳性。说明ＩＡＰＰ主要分布在豚鼠的胰岛内．但也少量存在于外分泌部。ＩＡＰＰ主要和ＩＮＳ共存于Ｂ细胞内。但也和ＳＳ共存于Ｄ细胞内,提示ＩＡＰＰ可能通过自分泌途径调节ＩＮＳ和ＳＳ的分泌。     

Effect of starvation on somatostatin content of pancreas and gastrointestinal tract of the guinea pig

The effect of 48-hour starvation on the somatostatin contents of the pancreas and gastrointestinal tract was studied in the guinea pig. Somatostatin contents were higher in various portions of the stomach and pancreas of fed guinea pigs than in fed rats and unchanged after 48-hour starvation, in spite of the decreased blood glucose level. These results suggest that somatostatin may not play the same physiological role in nutrient homeostasis of guinea pigs as it does in other species.     

Modulation of cholinergic neurotransmitter release from myenteric plexus by somatostatin

Efflux of radiolabeled acetylcholine (Ach) was studied in vitro using myenteric plexus-longitudinal muscle strips from guinea pig small intestine. The data showed that somatostatin (6.0 x 10(-7) M) depressed resting output of Ach from enteric neurons and this inhibition was unaltered in the presence of naloxone (1.0 x 10(-6) M). The inhibition by somatostatin on field-stimulated Ach release was dose-dependent but this inhibition was never complete; there was a 40% fraction of total release remained resistant to somatostatin. Both caerulein (2.85 x 10(-9) M) and guanidine (3.0 x 10(-3) M) stimulated release of [H3]-Ach from plexus neurons. The release of Ach induced by guanidine or caerulein was also susceptible to inhibition by somatostatin (6.0 x 10(-7) M). This study provides functional evidence to further substantiate an inhibitory action on plexus cholinergic neurons by somatostatin.     

Isolation and structure of guinea pig gastric and pancreatic somatostatin

Somatostatin-14 has been isolated from guinea pig pancreas and stomach and purified to homogeneity by gel filtration, ion-exchange chromatography and reverse phase HPLC. Amino acid composition and sequence analysis indicated that guinea pig somatostatin from both tissues has the same structure as somatostatin-14 from all other mammalian species yet studied. The study has demonstrated that somatostatin-14 from gastric tissue has the same structure as the peptide from hypothalamus and pancreas.     

Absence of effect of somatostatin on the guinea pig gallbladder

The effect of somatostatin (GH-RIH) on cholecystokinin octapeptide (OP-CCK) or acetylcholine (ACh) induced contraction of the guinea pig gallbladder was evaluated in vitro. GH-RIH failed to inhibit the muscle contraction induced by OP-CCK or ACh. To correlate with the in vitro results, the effect of GH-RIH on OP-CCK induced contraction of the gallbladder was evaluated in the guinea pig in vivo. GH-RIH did not affect the OP-CCK induced contraction of the gallbladder. Our results suggest that GH-RIH does not have direct inhibitory effect on the contraction of the guinea pig gallbladder induced by OP-CCK or ACh.     

A difference between the proteins conveyed in the fast component of axonal transport in guinea pig hypoglossal and vagus motor neurons.

We compared the proteins transported in the fast component of guinea pig hypoglossal motor neurons with those of guinea pig vagus (preganglionic parasympathetic) neurons. The fast component proteins of hypoglossal and vagus neurons were radioactively labeled by injecting 3H-amino acids into the hypoglossal and vagus motor nuclei. The radioactive fast component proteins obtained from each system were then compared with each other by SDS-polyacrylamide slab gel electrophoresis and fluorography. These analyses revealed at least twenty polypeptides which appear common to the fast component of each neuronal system. In addition, we identified one difference between the proteins comprising the fast component of these neuronal systems. A polypeptide, molecular weight 50,000 daltons, present in the fast component of vagus neurons was not detected in the fast component of hypoglossal motor neurons. These observations are discussed with regard to the similarities and differences between these neuronal systems.     

A difference between the proteins conveyed in the fast component of axonal transport in guinea pig hypoglossal and vagus motor neurons

We compared the proteins transported in the fast component of guinea pig hypoglossal motor neurons with those of guinea pig vagus (preganglionic parasympathetic) neurons. The fast component proteins of hypoglossal and vagus neurons were radioactively labeled by injecting ³H-amino acids into the hypoglossal and vagus motor nuclei. The radioactive fast component proteins obtained from each system were then compared with each other by SDS-polyacrylamide slab gel electrophoresis and fluorography. These analyses revealed at least twenty polypeptides which appear common to the fast component of each neuronal system. In addition, we identified one difference between the proteins comprising the fast component of these neuronal systems. A polypeptide, molecular weight 50,000 daltons, present in the fast component of vagus neurons was not detected in the fast component of hypoglossal motor neurons. These observations are discussed with regard to the similarities and differences between these neuronal systems.     

Prenatal appearance of a short nucleosomal DNA repeat length in neurons of the guinea pig cerebral cortex

The organization of chromatin in neurons of the cerebral cortex of the guinea pig brain was analyzed by digesting isolated nuclei with micrococcal nuclease. During development, cortical neurons were observed to undergo an alteration in chromatin structure which results in an atypically short nucleosomal DNA repeat length of 164 bp. This change in chromatin organization occurs postnatally in certain mammals but in the guinea pig it takes place prior to birth between days 32 and 44 of fetal development. This suggests that the appearance of the short nucleosomal DNA repeat length in cortical neurons correlates to a particular stage of differentiation of cortical neurons rather than to the event of birth.     

Evidence for the presence of dihydro (reduced) somatostatin-14 in the guinea pig brain

Analysis of somatostatin-like immunoreactivity (SLI) in guinea pig brain by HPLC and radioimmunoassay revealed an unexpected peak of SLI eluting at a retention time slightly later than standard somatostatin-14. The following evidence argues that this peak represents dihydro (H2) somatostatin-14. (1) The peak had the same retention time as standard [H2]somatostatin. (2) The possibility of a reduction artefact due to tissue processing was excluded by adding exogenous somatostatin-14 or 125I-labeled N-Tyr-somatostatin-14 to tissue and observing that no corresponding reduced peptides were generated. (3) Mild oxidation of brain extracts with H2O2 decreased, whereas mild reduction with dithiothreitol increased, the proposed peak of [H2]somatostatin. (4) Reaction of tissue extracts with iodoacetamide decreased the size of the proposed [H2]somatostatin peak but resulted in generation of a new peak co-eluting with standard carboxymethylated somatostatin-14. The proportion of the [H2]somatostatin peak in five brain regions, the hypothalamus, amygdala, cerebral cortex, brainstem and cerebellum, ranged from 6 to 20% of total SLI. The probability of somatostatin-14 existing endogenously in reduced or oxidized forms may have implications for its biological function in the guinea pig.     

Participation of capsaicin-sensitive neurons in the cardiovascular effects of neurotensin in guinea pigs

Intravenous (IV) infusions of neurotensin (NT) in anesthetized guinea pigs elicited dose-dependent pressor effects and tachycardia. Both effects were significantly reduced or abolished in guinea pigs given a chronic treatment with the neurotoxin capsaicin. In guinea pig isolated atria NT evoked a positive inotropic and chronotropic effect. Both effects were completely abolished in atria derived from capsaicin-treated guinea pigs. The positive inotropic and chronotropic effects of NT in guinea pig atria were mimicked by capsaicin and calcitonin gene-related peptide (CGRP). These results were interpreted as an indication that NT produces its cardiovascular effects in guinea pigs by activating capsaicin-sensitive sensory neurons.     

Effect of cholecystokinin octapeptide and somatostatin on the motility of guinea pig and canine gallbladder

Species differences have been observed in the effect of cholecystokinin octapeptide (CCK OP) on the canine and guinea pig gallbladder smooth muscle motility. 1. CCK OP was more potent stimulant in canine than in guinea pig gallbladder smooth muscles. Its pD2 values were 10 and 9.2, respectively. 2. The acetylcholine (10(-4) M)-induced maximum contractions in canine gallbladder muscle strips were by 50% lower as compared to the CCK OP (10(-8) M) maximum responses while in guinea pig gallbladder muscle strips the acetylcholine (ACh) maximum responses were by 20% lower than the CCK OP maximum responses. 3. CCK OP increased [3H]ACh release by 27% in canine gallbladder and by 40% in guinea pig gallbladder. 4. Somatostatin (SOM) had not any direct myogenic effect in guinea pig and canine gallbladder but it decreased [3H]ACh release from gallbladder intrinsic cholinergic neurons.     

Immunoelectron microscopic demonstration of pancreatic polypeptide in midgut epithelium of hematophagous dipterans

Midguts of mosquitoes, Aedes aegypti and Anopheles stephensi, and of the tsetse fly, Glossina morsitans morsitans, as well as guinea pig pancreas, were prepared for electron microscopy by using low-temperature embedding in Lowicryl K4M. Rabbit antiserum to bovine pancreatic polypeptide (PP) crossreacted with secretory granules of pancreatic PP-producing cells and of the clear cells in mosquito gut. Rabbit antiserum to human somatostatin crossreacted with the control tissue, guinea pig pancreas D-cells, but not with the mosquito clear cells. None of the antisera used showed a distinct reaction with the endocrine-like cells of tsetse fly midgut. Positive reactions were revealed by gold as electron-dense marker. The gold particles were coated with protein A-gold or goat antibodies to rabbit immunoglobulin.     

Studies on hormonal regulation of lipolysis and lipogenesis in fat cells of various mammalian species

1. Corticotropin-stimulated lipolysis in adipocytes of rats, mice, hamsters, guinea pigs and rabbits. Melanotropins elicited high lipolytic activity only in guinea pig and rabbit adipocytes. Opiate peptides were active only in rabbit adipocytes. Pituitary and chorionic gonadotropins and somatotropin were lipolytic in guinea pig adipocytes. Other hormones tested including prolactin, somatostatin, substance P, neurotensin, angiotensin II, thyrotropin releasing hormone and pancreatic polypeptide were devoid of lipolytic activity in all of the adipocytes studied. 2. In the rabbit adipocytes gamma-melanotropin was lipolytic only at high doses. At these doses the peptide inhibited the lipolytic response to a high dose of corticotropin. 3. Lipolysis stimulated by vasoactive intestinal peptide and epinephrine in rat adipocytes was antagonized by insulin. The lipolytic hormones corticotropin, epinephrine, vasoactive intestinal peptide and secretin suppressed basal and insulin-stimulated lipogenesis.     

Somatostatin inhibits adrenergic and cholinergic neurotransmission in smooth muscle.

Somatostatin reduced the response to field stimulation in the guinea pig ileum and reduced the spontaneous contractions in the rabbit jejunum, an effect that was blocked by tetrodotoxin. Somatostatin also inhibited field stimulated alpha adrenergic contractions in the rat vas deferens and rabbit ear artery. However, the responses to direct application of either acetylcholine in the ileum or to norepinephrine in the ear artery or vas deferens were not affected by somatostatin. These results strongly suggest that somatostatin inhibits neuronal release of cholinergic and adrenergic transmitter substances in smooth muscle.     

Beta-endorphin and somatostatin in the pancreatic D-cell colocalization by immunocytochemistry

Utilizing highly specific antisera, beta-endorphin and somatostatin immunoreactivity were identified simultaneously in the D-cell of the pancreas of the rat, guinea pig, and man by the fluorescence-immunocytochemical technique. Our observations are consistent with a modulating role of beta-endorphin either within the D-cell or upon A and B cells, thereby regulating the secretion of insulin and glucagon.     

Comparative distribution of nitric oxide synthase- and serotonin-containing neurons in the raphe nuclei of four mammalian species

 Monoclonal antibodies were generated against serotonin (5-HT) and the C-terminal portion of the neuronal form of nitric oxide synthase (nNOS), the enzyme producing nitric oxide in neurons. These antibodies were used to compare the distribution of 5-HT- and nNOS-containing neurons in the raphe nuclei of four animal species (rat, mouse, guinea pig, and cat). It was found that the rat was the only species in which the raphe nuclei contain a substantial number of nNOS-immunoreactive (IR) cell bodies. In this species and as observed by other authors, all mesencephalic raphe nuclei contained nNOS-IR cells, the largest group being located in the nucleus raphe dorsalis. The coexistence of nNOS and 5-HT immunoreactivities in these nuclei was visualized by double labeling. In the medulla, the nuclei raphe magnus and obscurus displayed a rather low number of nNOS-IR neurons. In the other species, nNOS-IR cell bodies were found in very low numbers, whatever raphe nucleus was considered. The rostral pole of the nucleus raphe dorsalis and the nuclei raphe magnus and obscurus contained a few nNOS-IR neurons which did not show any coincidence with the 5-HT neurons. In addition, nNOS-IR axons were rare. It is concluded that in the mouse, guinea pig, and cat the involvement of nitric oxide in functions subserved by 5-HT within the raphe nuclei might be minimal. Accepted: 5 May 1998