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M C Beinfeld

Publications and source records attributed to M C Beinfeld.

At least 55 records · Page 3Linked to original sources
PubMed1990

Inhibition of potassium-evoked release of cholecystokinin from rat caudate-putamen, cerebral cortex and hippocampus incubated in vitro by phencyclidine and related compounds.

Potassium-evoked release of cholecystokinin (CCK) from slices of caudate-putamen, hippocampus, and cerebral cortex was inhibited in a dose-related fashion by phencyclidine (PCP). In order to further examine this effect, PCP-like ligands (dexoxadrol, levoxadrol, PCMP and MK-801) as well as compounds known to interact with the sigma receptor ((+)-SKF, DTG, (+)-3-PPP, and pentazocine) were tested. While some of these compounds inhibited CCK release, their rank order potency (Dex = Lev greater than PCP = PCMP greater than DTG = MK-801 = (+)-3-PPP) differs from that of known PCP-N-methyl-D-aspartate linked effects or sigma interactions. These results suggest that the mechanism by which PCP acts to inhibit CCK release may involve a novel type of PCP interaction.

Animals↗
PubMed1990

Microdialysis as an approach to quantitate the release of neuropeptides.

1. In vivo microdialysis was performed on anesthetized and awake rats to measured release of cholecystokinin from the posterior nucleus accumbens. 2. Basal levels of cholecystokinin were detectable by radioimmunoassay in some, but not all animals. 3. Recovery through the microdialysis probe ranged from 0.1-2.4% for cholecystokinin, suggesting practical limitations to this approach with present technology.

Animals↗
PubMed1990

Inhibition of carbachol-induced inositol phosphate accumulation by phencyclidine, phencyclidine-like ligands and sigma agonists involves blockade of the muscarinic cholinergic receptor: a novel dioxadrol-preferring interaction.

The effect of phencyclidine (PCP) on carbachol-induced phosphoinositol hydrolysis was examined in rat brain slices taken from cortex, caudate-putamen and hippocampus. In all three regions studied, PCP significantly inhibited carbachol-induced [3H]inositol phosphate accumulation working as low as 10(-6) M in the cerebral cortex. Because PCP has been shown to act at two sites, a PCP-site and a sigma site, various PCP-like agonists [levoxadrol (Lev), dexoxadrol (Dex) and MK-801 [(+)-5-methyl-10,11-dihydro- 5H-dibenzo(a,b)cyclo-hepaten-5, 10-imine maleate]] as well as sigma agonists [(+)-SKF10047 and 1,3-di(2-toly)guanidine (DTG) were examined for their effects on carbachol-induced phosphoinositol hydrolysis. All but MK-801 significantly inhibited the carbachol action; however, their order of potencies, Lev greater than or equal to Dex much greater than PCP greater than or equal to DTG greater than or equal to (+)-SKF10047 differed from those of other known PCP interactions at PCP and sigma sites. Inasmuch as it is known that PCP competes for binding at muscarinic sites, we examined the effects of PCP, Lev, Dex, DTG and MK-801 on the binding of L-[3H]-3-quinuclidinyl benzilate to its muscarinic site. All blocked L-[3H]-3-quinuclidinyl benzilate binding and exhibited a rank order of potency almost identical to that obtained in the inositol studies with Lev greater than Dex much much greater than DTG much greater than PCP MK-801. In addition, the IC50 values obtained from both studies were very similar. It is concluded that PCP, PCP-like compounds and sigma agonists block carbachol-induced inositol-phosphate accumulation by blockade of muscarinic receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Cholecystokinin, dopamine and schizophrenia.

Immunoreactive-cholecystokinin (CCK) in cerebrospinal fluid (CSF) was examined in 11 drug-free DSM-III schizophrenic patients and 6 age-matched controls. CSF CCK was significantly lower (p less than .002) in schizophrenic subjects than in controls and was significantly lower (p less than .01) in male than female schizophrenic subjects. CSF CCK was significantly lower (p less than .04) in schizophrenic subjects whose antipsychotic response was delayed 28 or more days after initiation of haloperidol compared with earlier drug responders. CCK appears to be required for neuroleptic-induced depolarization-inactivation of dopamine neurons and associated antipsychotic response; therefore, schizophrenic patients with low CCK may be resistant to the antipsychotic effects of neuroleptics.

Adult↗
PubMed1989

Characterization of a somatostatin-28 generating metallo-endoprotease from rat brain cytosol.

Brain cytosol contains a neutral metallo-protease of about 80,000 which cleaves a substrate containing the site at which mammalian prosomatostatin is cleaved to generate somatostatin 28 in vivo. This represents a cleavage on the carboxyl side of a single arginine residue at an Arg-Ser bond. The enzyme was unable to cleave several other substrates containing single arginine residues or two substrates containing an Arg-Lys or Lys-Arg pair. When it was incubated with anglerfish pancreatic prosomatostatin, it produced significant quantities of a peptide which co-eluted with somatostatin 28 II. Based on the ability of this enzyme to cleave small and large substrates related to somatostatin, it is a potential candidate for the enzymes which cleaves prosomatostatin in vivo.

Amino Acid Sequence↗
PubMed1989

Characterization of an endoprotease from rat small intestinal mucosal secretory granules which generates somatostatin-28 from prosomatostatin by cleavage after a single arginine residue.

We have extracted, characterized, and partially purified an enzyme from secretory granules from rat small intestinal mucosa which cleaves a synthetic prosomatostatin substrate on the carboxyl side of a single arginine residue. This substrate Leu-Gln-Arg-Ser-Ala-Asn-Ser-NH2 contains the monobasic site at which mammalian prosomatostatin is cleaved in vivo to generate somatostatin-28. This activity was released from the granules by osmotic shock followed by extraction with 500 mM KCl. The enzyme had a molecular weight of about 55,000, a pH optimum of about 7.5, and a Km for the synthetic substrate of 20 microM. It was partially inhibited by diisopropyl fluorophosphate, phenylmethanesulfonyl fluoride, iodoacetate, soybean trypsin inhibitor, and EDTA. It was also very sensitive to aprotinin (complete inhibition at 25 micrograms/ml) but was not inhibited by bestatin, pepstatin, or p-chloromercuribenzoate. This endoprotease was unable to cleave three small trypsin and kallikrein substrates (N alpha-benzoyl-L-arginine ethyl ester, N alpha-benzoyl-DL-arginine p-nitroanilide, and N alpha-benzoyl-L-arginine 7-amido-4-methylcoumarin). It was unable to cleave either the Arg-Asp bond in CCK 12 or the Arg-Glu and Arg-Met bonds of synthetic peptides corresponding to sequences of anglerfish prosomatostatin II situated upstream from the somatostatin-28 domain. These observations together suggest that adjacent amino acids play a role in determining the conformational specificity of the monobasic cleavage. This soluble enzyme was also able to cleave three synthetic substrates containing dibasic residues (Arg-Lys or Lys-Arg) on the carboxyl side of the arginine, although it did so less rapidly than at the monobasic cleavage sites. When incubated with partially purified prosomatostatin from anglerfish pancreas, significant quantities of somatostatin-28 II were produced. All these cleavages were completely blocked by preincubation with aprotinin. Although further work is required to clarify the physiological role of this enzyme, it appears, in view of its catalytic properties, this endoprotease could be involved in the conversion of prosomatostatin to somatostatin-28 in intestine mucosal secretory cells.

Amino Acid Sequence↗
PubMed1989

Effects of short- and long-term haloperidol administration and withdrawal on regional brain cholecystokinin and neurotensin concentrations in the rat.

The effects of oral administration of the neuroleptic, haloperidol, on regional brain concentrations of cholecystokinin (CCK) and neurotensin were examined in the rat. Both short-term (3 weeks) and long-term (8 months) haloperidol administration increased the concentration of CCK in the substantia nigra. While short-term administration significantly increased the concentration of CCK in the ventral tegmental area and decreased the concentration of CCK in the cortex, including the medial prefrontal cortex, these effects were not observed following long-term drug administration. In contrast, long-term, but not short-term, haloperidol administration decreased the concentration of CCK in the olfactory tubercle. Withdrawal from long-term haloperidol did not alter CCK concentrations in any of the brain regions examined. Short-term haloperidol administration significantly increased the concentration of neurotensin in the caudate-putamen. Both short- and long-term administration increased the concentration of neurotensin in the nucleus accumbens, but only the increased following long-term administration reached statistical significance. Withdrawal from long-term haloperidol administration slightly decreased the concentrations of neurotensin in the caudate-putamen and nucleus accumbens. These results indicate that dopamine receptor blockade can affect both CCK- and neurotensin-containing neural systems. Furthermore, these two neuropeptides are affected differently depending upon the duration of haloperidol administration and withdrawal from this drug. The results raise the possibility that chronic administration of haloperidol may be toxic to some neurotensin-containing neurons in the basal ganglia.

Administration, Oral↗
PubMed1989

Response to exogenous cholecystokinin of six human gastrointestinal cancers xenografted in nude mice.

Gastrointestinal hormones regulate growth of cancers as well as normal tissues. We investigated whether long-term cholecystokinin (CCK) administration might affect growth or metabolism of human tumors xenografted in nude mice. In each experiment, approximately 20 nude mice bearing subcutaneous xenografts of the particular cancer line being studied were used. Half received CCK and half received saline solution intraperitoneally twice daily for 14 days. Tumor volume and body weight were measured every 3 days. If the tumors produced marker substances, these were measured in nude mouse serum and also in the xenografts. Tumor growth was significantly retarded by CCK in two of the six cancers studied. In each case, DNA, RNA, and protein reflected tumor volumes. In one of these tumors (SLU 077), serum carcinoembryonic antigen (CEA) levels paralleled the tumor volumes. In another tumor (SLU 132), serum CEA levels and tumor immunolabeling for CEA and pancreatic oncofetal antigen increased in response to CCK administration, whereas tumor volumes did not. These findings suggest that exogenous highdose CCK altered the growth and metabolism in two of six human cancers studied.

Animals↗
PubMed1989

Role of peptide histidine isoleucine in relaxation of cat lower esophageal sphincter.

Vasoactive intestinal peptide (VIP) is a candidate as an inhibitory neurotransmitter mediating relaxation of the lower esophageal sphincter (LES) because VIP antiserum reduces LES relaxation in response to neural stimulation. Vasoactive intestinal peptide antiserum, however, does not completely block LES relaxation. Thus it is possible that other neurotransmitters may be involved. Peptide histidine isoleucine has structural homologies with VIP, is synthesized with VIP from a common precursor protein, coexists in some nerve cells, and is coproduced with VIP in some tumors. In numerous organ systems VIP and peptide histidine isoleucine (PHI) produce similar effects, with PHI being less potent than VIP by approximately one log number. In the LES both VIP and PHI produce tetrodotoxin-resistant dose-dependent relaxation, with PHI being almost equipotent with VIP. We therefore tested the hypothesis that PHI may be a second neurotransmitter, partly responsible for relaxation of the cat LES, by using a highly specific rabbit PHI antiserum that exhibits minimal cross-binding with VIP, secretin, and glucagon. In 3 animals, LES and brain tissue were extracted in 0.1 N HCl and assayed with a PHI radioimmunoassay. The antiserum cross-reacted with cat brain and LES showing PHI concentrations greater than 100 ng/g, with the LES containing equal or greater concentrations of PHI than brain tissue. In other animals consecutive LES circular muscle strips were cut, mounted in 1-ml muscle chambers, and stimulated with 6-s square-wave trains of 0.1-, 0.2-, 0.4-, and 0.8-ms pulses at 1, 2, and 5 Hz. These parameters produced relaxation that was completely blocked by tetrodotoxin, and reduced by VIP antiserum, but not affected by adrenergic or cholinergic receptor antagonists. Some strips were incubated in 5% or 10% PHI antiserum, whereas others were incubated in the same concentration of preimmunization serum from the same animal. Incubation in normal serum did not significantly affect relaxation, whereas in the antiserum-treated strips, LES relaxation was reduced by a significant amount (20%-30%) at all parameters of stimulation tested. Incubation in antiserum however had no effect on relaxation induced by VIP (10(-8)-10(-6) M). These data suggest that PHI may play a role in LES relaxation induced by electrical stimulation.

Animals↗
PubMed1989

Mechanism of pressor response to posterior hypothalamic injection of neuropeptide Y.

Unilateral microinjection of neuropeptide Y (NPY) into the posterior hypothalamic nucleus was previously found to evoke an increase in mean arterial pressure (MAP) in urethan-anesthetized rats. In this study, the mechanism by which this increase occurs was examined. Pretreatment of rats with 2.0 mg/kg (iv) of phenoxybenzamine, or 7.5 mg/kg (iv) of pentolinium, resulted in a significant reduction in the peak MAP evoked by microinjection of NPY (2.35 nmol) into the posterior hypothalamic nucleus. Administration of the vasopressin V1-receptor antagonist [d(CH2)5Tyr(Me)]AVP (10 micrograms/kg iv) before microinjection of NPY failed to attenuate the increase in MAP. Similar results were obtained with respect to the effect of these three antagonists on the increase in MAP evoked by injection of the cholinergic muscarinic agonist carbachol (5.48 nmol) into the posterior hypothalamic nucleus. Furthermore, microinjection of NPY or carbachol elicited a significant elevation of renal sympathetic nerve activity and an increase in resistance of the hindquarter vascular bed. However, NPY elicited a decrease and carbachol an increase in the resistance of the mesenteric bed, whereas NPY elicited an increase and carbachol a decrease in the resistance of the renal bed. These results suggest that NPY elicits an increase in MAP via centrally mediated sympathetic excitation. Furthermore, NPY and carbachol differentially affect sympathetic outflow to peripheral vascular beds after microinjection into the posterior hypothalamic nucleus.

Animals↗
PubMed1989

Establishment of a cholecystokinin-producing rat medullary thyroid carcinoma cell line.

A rat medullary thyroid carcinoma, which was previously shown to produce high levels of immunoreactive cholecystokinin (CCK), was used to establish a stable cell line. Transplantable tumors were subjected to four series of alternate in vitro and in vivo passages. Cells were prepared from the fourth series of tumors under serum-free medium conditions that prevent fibroblast growth. Subcloning of these cells yielded several propagatable clonal cell lines. One cell line with immunoreactive CCK-8 production was selected for further studies. This high CCK cell line, WE4/2, produces and secretes a CCK-immunoreactive product that coelutes with synthetic CCK-8 sulfate during Sephadex chromatography and HPLC. Northern analysis with a rat CCK cDNA revealed that the cultured cells produce a CCK RNA the same size and with the same 5' end as that previously reported for brain and intestines. In addition, a recombinant plasmid containing about 800 basepairs of 5' flanking sequence of the rat CCK gene linked to the coding sequence of the bacterial chloramphenicol acetyltransferase gene elicited a high level of chloramphenicol acetyltransferase activity when transfected into the WE4/2 cell line. Therefore, the WE4/2 cell line provides a model system for studying CCK gene expression and biosynthesis.

Animals↗
PubMed1988

Phorbol esters stimulate the potassium-induced release of cholecystokinin from slices of cerebral cortex, caudato-putamen and hippocampus incubated in vitro.

Incubation of slices of caudato-putamen, cerebral cortex and hippocampus for 5 to 15 minutes with phorbol 12,13-dibutyrate (PDB) or phorbol 12-myristate 13-acetate (PMA) increased potassium evoked cholecystokinin (CCK) release from 139% to 296% of control. The inactive 4 alpha phorbol and 4 alpha PDB did not alter CCK release. None of the active or inactive phorbols tested altered basal CCK release. These results suggest that there may be similarities in the regulation of CCK release in different brain regions. Although the physiological factors which regulate CCK release may differ in these tissues, it is possible that their common action is mediated by the products of inositol phospholipid turnover.

Animals↗
PubMed1988

Heterogeneity of motilin immunoreactivity in mammalian tissue.

Motilin is a 22 amino acid peptide first isolated and sequenced from porcine gut. The use of antisera directed to the synthetic porcine gut motilin sequence has produced conflicting results as to regional distribution and histological localization of motilin in mammalian brain and gut. Motilin immunoreactivity has been detected (by RIA) in brain regions where no immunostaining is discernible. Variations in the patterns of staining are also observed with different antisera. These discrepancies have been explained by postulating species-, tissue-, and region-specific variations in peptide immunoreactivity, and variable cross reactivities of the independent antisera with these forms. The use of cloned porcine cDNA encoding gut prepromotilin in Northern blot analysis of brain regions expressing motilin-like immunoreactivity has also failed to reveal a homologous message, questioning the true nature of the immunoreactive material in the brain. Physiological studies, however, have suggested central roles for motilin in a variety of CNS (feeding behavior, bladder control, cerebral and brain stem modulation, pituitary growth hormone release) and gastrointestinal (gastric emptying, intestinal motility) functions. The motilin immunoreactive material detected in brain may be encoded by a distinct non-homologous gene, and still share amino acid homologies with the motilin sequence. Molecular biological characterization of the cell systems which contain motilin and motilin-like immunoreactivity should allow a better definition of their roles in these tissues.

Adrenal Medulla↗
PubMed1988

Alterations in blood pressure of normotensive and hypertensive rats following intrathecal injections of neuropeptide Y.

The effect of the intrathecal administration of neuropeptide Y (NPY) on blood pressure and heart rate of anesthetized normotensive and hypertensive rats was studied. Neuropeptide Y was observed to produce a decrease in the blood pressure of Sprague-Dawley, Wistar Kyoto (WKY), DOCA-salt, and DOCA-sham control rats. The maximum percent decrease in blood pressure of Sprague-Dawley rats was 12.8 and 15.2% in response to 0.1 and 1.0 nmol NPY, respectively. Similar changes in heart rate were observed. The depressor effect of intrathecal NPY was attenuated by prior treatment with yohimbine and propranolol but not prazosin. The depressor effect of intrathecal NPY observed in normotensive and DOCA-salt hypertensive rats was not seen in the spontaneously hypertensive rat (SHR). The studies extend to the spinal cord the list of regions and tissues where NPY can produce physiological effects. It is concluded that the effects of NPY are closely associated with sympathetic preganglionic neurons in the spinal cord that the depressor effect of NPY involves alpha 2 and beta adrenoceptors, and that a loss of the depressor effect of NPY may contribute to the development or maintenance of hypertension in the SHR.

Adrenergic alpha-Antagonists↗
PubMed1988

Role of glucagon in cholecystokinin-stimulated bile flow in dogs.

Although many choleretic agents are known, their physiological roles and interrelationships in increasing bile flow remain largely undetermined. Exogenous cholecystokinin (CCK), glucagon, and insulin are stimulants of hepatic bile flow in animals and humans. Of possible importance in the choleresis produced by CCK is the stimulation by exogenous CCK of glucagon and insulin release from the pancreas. This research evaluates the role of glucagon and insulin in the choleresis produced by CCK. Dogs with chronic biliary and gastric fistulas were used. The synthetic octapeptide of CCK (CCK-8) administered in increasing doses produced progressive increases in bile volume, bile bicarbonate secretion, and bile chloride concentration and output. The choleresis produced by CCK-8 was qualitatively similar to that produced by intravenous glucagon. CCK-8 administration in increasing doses produced progressive increases in plasma glucagon. When bile flow changes during CCK-8 administration were correlated with changes in plasma glucagon, significant correlation existed. CCK-8 significantly increased serum insulin concentration only at the highest dose of CCK-8 administered. Somatostatin is an inhibitor of hormone release. Administration of somatostatin, along with CCK-8, inhibited the choleresis and the increased plasma glucagon produced by CCK-8 administration alone. During acute experiments in anesthetized dogs, the pancreas and stomach were removed to eliminate endogenous glucagon and insulin release. (ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗