PubMed Health⌕ Search

Biomedical subjects

C Sakamoto

Publications and source records attributed to C Sakamoto.

At least 109 records · Page 6Linked to original sources
PubMed1986

[Effects of various pancreatic secretagogues on somatostatin binding to rat pancreatic acinar cell plasma membranes].

The effects of pretreatment with pancreatic secretagogues and subsequently activated cellular events on [125I-Tyr1] somatostatin binding to acinar membranes were studied. Pretreatment of pancreatic acini with bombesin at increasing concentrations for 120 min reduced labeled somatostatin binding to the acinar membranes in a dose-dependent fashion with a maximal reduction of binding at 10(-8)M bombesin (44.3 +/- 1.8% of control). The maximal inhibition of labeled somatostatin binding by pretreatment with bombesin was almost comparable to that with COOH-terminal octapeptide cholecystokinin (CCK8) or carbamylcholine (carbachol). Furthermore, pretreatment of acini with vasoactive intestinal peptide (VIP) as well as secretin resulted in a small, but significant decrease of subsequent labeled somatostatin binding. In addition, adenosine 3', 5' cyclic nucleotide derivatives or a phosphodiesterase inhibitor mimicked the effect of VIP or secretin. The effect of simultaneous pretreatment of acini with VIP and carbachol on subsequent labeled somatostatin binding appeared to be almost equal to the calculated additive value for each peptide. These results suggest that the binding of somatostatin to its receptors in the pancreatic acini may be regulated via two functionally distinct pathways.

Animals↗
PubMed1986

[Phorbol ester or diacylglycerol modulates somatostatin binding to its receptors on rat pancreatic acinar cell membranes].

To clarify the precise mechanism by which unrelated peptides, cholecystokinin or carbamylcholine, modulate the somatostatin binding, the effect of a phorbol ester, 12-O-tetradecanoylphorbol-13-acetate (TPA) or a synthetic diacylglycerol analog, 1-oleyl-2-acetylglycerol (OAG) on [125I-Tyr1]somatostatin binding to pancreatic acinar cell membranes was examined. Pretreatment of pancreatic acini for 120 min at 37 degrees C with 100 ng/ml TPA maximally reduced subsequent labeled somatostatin binding to acinar membranes. The inhibitory effect of TPA on the somatostatin binding was dependent on the dose used, or the time and temperature of pretreatment. These effects of TPA were almost mimicked by the treatment of acini with OAG. Scatchard analysis of [125I-Tyr1]somatostatin binding demonstrated that the decrease in the labeled somatostatin binding induced by TPA or OAG pretreatment was due to the decrease in the maximum binding capacity without a significant change in the binding affinity. A specifically labeled single band of the Mr = 90 K obtained with a photoaffinity cross-linking study indicates that the somatostatin binding sites are the same somatostatin receptor as previously described. Moreover, the intensity of the Mr = 90 K band was dramatically decreased when acini were treated with increasing concentrations of TPA, a finding consistent with TPA-induced decrease in binding capacity. Such an inhibitory effect of TPA was abolished when pretreatment of acini with TPA was performed in the presence of Ca2+ chelating compounds such as EDTA and EGTA. Interestingly, the combined treatment of TPA and Ca2+ ionophore A23187 caused synergistic inhibition of the subsequent labeled somatostatin binding to acinar membranes, although Ca2+ ionophore itself almost failed to affect the somatostatin binding. These results suggest, therefore, that TPA or OAG can modulate somatostatin binding to its receptors on rat pancreatic acinar cell membranes, presumably through activation of Ca2+-activated, phospholipid-dependent protein kinase (protein kinase C) and the activated protein kinase C and intracellular Ca2+ mobilization presumably act to modulate pancreatic acinar somatostatin receptors synergistically.

Animals↗
PubMed1986

[CCK and carbachol differently modulate somatostatin binding to rat pancreatic acinar membranes].

Somatostatin binding to its receptors on rat pancreatic acinar membranes was characterized with [125I-Tyr1]somatostatin. The COOH-terminal octapeptide of cholecystokinin (CCK8), when present at various concentrations in the reaction mixture for the binding study, reduced labeled somatostatin binding in a dose-dependent manner, whereas carbachol or Ca2+ ionophore did not affect the binding. By contrast, when pancreatic acini were first treated with carbachol and thereafter [125I-Tyr1]somatostatin binding to membranes prepared from these acini was examined, carbachol reduced subsequent somatostatin binding in a dose-dependent manner. Scatchard analysis of the labeled somatostatin binding revealed that carbachol pretreatment decreased the maximum binding capacity from 142 +/- 20 fmol/mg of membrane protein to 63.5 +/- 3.5 fmol/mg of membrane protein without significantly affecting the binding affinity. To test for the possibility that CCK8 also may affect labeled somatostatin binding through an intracellular process, pancreatic acini were first treated with CCK8 and then the membrane bound CCK8 was washed out. Subsequent labeled somatostatin binding to membranes from these acini was also decreased. When 1 mM EDTA was present in the pretreatment medium, the inhibitory effect of carbachol or CCK8 was partially abolished, suggesting that an intracellular process to modulate somatostatin binding is dependent on Ca2+. On the other hand, pretreatment of acini with Ca2+ ionophore almost failed to affect subsequent labeled somatostatin binding. Results therefore suggest that CCK8 can modulate labeled somatostatin binding to pancreatic acinar membranes not only acting through an intracellular process but also at membrane sites and carbachol- or CCK8-activated intracellular process to modulate somatostatin binding is dependent on Ca2+, but Ca2+ mobilization itself is not sufficient to affect subsequent somatostatin binding.

Animals↗
PubMed1986

[Open laparoscopy, a report of 12 cases in gynecology--with special reference to the diagnosis and treatment of infertility].

Open laparoscopies were performed on patients with eleven infertilities and one ectopic pregnancy in our gynecology clinic. Eight cases of endometriosis were revealed in eleven severe infertile patients. There were three cases of different findings between preoperative hysterosalpingograms and chromotubations under laparoscopies. One case of ectopic pregnancy was cured by salpingectomy after diagnostic laparoscopy. All 12 patients had N2O gas pneumoperitoneum under endo-tracheal intubated anesthesia. One case with both halothane and N2O anesthesia became temporarily hypothermic during open laparoscopy. Indications of gynecologic laparoscopy, characteristics of open laparoscopy and its comparison with closed laparoscopy are discussed.

Adult↗
PubMed1986

Difference in effects of pirenzepine and atropine on carbachol-induced pepsinogen secretion from isolated gastric glands.

The effect of pirenzepine on carbamylcholine (carbachol)-stimulated pepsinogen secretion was compared with that of atropine in the isolated guinea pig gastric glands. Pirenzepine and atropine caused a dose dependent inhibition of carbachol-stimulated pepsinogen secretion. Moreover, pirenzepine as well as atropine produced a rightward shift in the dose response curve of carbachol-stimulated pepsinogen secretion but did not alter the maximum increase in pepsinogen secretion. Results therefore demonstrate that pirenzepine acts as a specific receptor antagonist in the interaction of carbachol with its receptor on gastric chief cells. However, pirenzepine was 50 times less potent than atropine in inhibiting pepsinogen secretion. Half maximal inhibitory concentration of pirenzepine was 2 X 10(-5) M when a maximally effective concentration of carbachol was used, while that of atropine was 4 X 10(-7) M. Results, therefore, suggest that muscarinic receptor on gastric chief cells to which pirenzepine binds may be an intermediate affinity type.

Animals↗
PubMed1986

Phorbol ester or diacylglycerol modulates somatostatin binding to its receptors on rat pancreatic acinar cell membranes.

We and others have suggested previously that the binding of somatostatin to its receptors in the pancreas is regulated by not only somatostatin analogs but also cholecystokinin analogs in proportion to their known biological potencies. To clarify the precise mechanism by which unrelated peptides modulate somatostatin binding, the effect of a phorbol ester, 12-O-tetradecanoylphorbol 13-acetate (TPA), or a synthetic diacylglycerol analog, 1-oleyl-2-acetylglycerol (OAG), on [125I-Tyr1]somatostatin binding to pancreatic acinar cell membranes was examined. Pretreatment of pancreatic acini for 120 min at 37 degrees C with 100 ng/ml TPA maximally reduced subsequent labeled somatostatin binding to acinar membranes. The inhibitory effect of TPA on the somatostatin binding was dependent on the dose used or the time and temperature of pretreatment. These effects of TPA were almost mimicked by the treatment of acini with OAG. Scatchard analysis of [125I-Tyr1]somatostatin binding demonstrated that the decrease in the labeled somatostatin binding induced by TPA or OAG pretreatment was due to the decrease in the maximum binding capacity without a significant change in the binding affinity. A specifically labeled single band of Mr = 90,000 obtained with a photoaffinity cross-linking study indicates that the somatostatin-binding sites are the same somatostatin receptor as previously described. Moreover, the intensity of the Mr = 90,000 band was dramatically decreased when acini were treated with increasing concentrations of TPA, a finding consistent with TPA-induced decrease in binding capacity. Such an inhibitory effect of TPA was abolished when pretreatment of acini with TPA was performed in the presence of Ca2+-chelating compounds such as EDTA and EGTA or phospholipid-interacting drugs such as chlorpromazine and tetracaine. Interestingly, the combined treatment of TPA and Ca2+ ionophore A23187 caused synergistic inhibition of the subsequent labeled somatostatin binding to acinar membranes, although Ca2+ ionophore itself almost failed to affect the somatostatin binding. These results suggest, therefore, that TPA or OAG can modulate somatostatin binding to its receptors on rat pancreatic acinar cell membranes, presumably through activation of Ca2+-activated, phospholipid-dependent protein kinase (protein kinase C); and the activated protein kinase C and intracellular Ca2+ mobilization presumably act to modulate the pancreatic acinar somatostatin receptors synergistically.

Animals↗
PubMed1985

Combined effect of phorbol ester and, A23187 or dibutyryl cyclic AMP on pepsinogen secretion from isolated gastric glands.

In isolated guinea pig gastric glands, pepsinogen secretion was stimulated by the phorbol ester, 12-0-tetradecanoyl-phorbol-13-acetate (TPA) in a dose dependent manner. Calcium-deprivation from the medium resulted in the decrease in TPA-induced pepsinogen secretion. The combination of 0.4 microM Ca2+ionophore A23187 and TPA stimulated pepsinogen secretion slightly higher than the calculated additive value for each agent. This synergistic effect of the agents supports a role of calcium-activated, phospholipid-dependent protein Kinase (protein Kinase C) in gastric pepsinogen secretion. Furthermore, pepsinogen secretion was also stimulated by dibutyryl cyclic AMP (dbc AMP) and dbc AMP slightly enhanced TPA-induced pepsinogen secretion. Results suggest that gastric chief cells possess at least two different secretory pathways for pepsinogen which are probably dependent on protein kinase C and cyclic AMP, respectively.

Animals↗
PubMed1985

Exocrine pancreatic function in rats after acute trypsin inhibitor treatment.

A single oral dose of synthetic trypsin inhibitor (TI, 20 mg/100 g) was given to rats by orogastric tube 6, 12, 18, or 24 hr before the removal of the pancreas and the preparation of isolated perfused pancreas. TI treatment induced no significant changes in body weight and total amount of DNA content in the pancreas, but pancreatic wet weight, total pancreatic protein and amylase, and the concentration of total protein and amylase relative to DNA were significantly decreased at 6 or 12 hr posttreatment, with a partial return toward control values at 18-24 hr after TI treatment. In isolated perfused pancreas, basal amylase output was similar in the control and in all 4 groups of TI-pretreated rats, while basal rate of flow of pancreatic juice was significantly increased at 12-24 hr posttreatment. Caerulein (0.1 ng/ml; 64 pM) stimulated pancreatic juice flow was greatly increased in rats pretreated with TI 12-24 hr earlier. In contrast, caerulein-stimulated amylase output was significantly lower in TI-pretreated groups compared with the control. However, when amylase output was related to the total content in the pancreas, the secretory responsiveness for amylase release was significantly higher in rats at 6-18 hr posttreatment compared with the control. The present study indicates that a single oral administration of TI modulates biological response to caerulein in the isolated perfused pancreas. The enhanced responsiveness of amylase release to subsequent stimulation is seen in early periods, while that of pancreatic juice flow is observed in late periods.

Amylases↗
PubMed1985

Sonographic criteria of phasic changes in human endometrial tissue.

Sonographic criteria of endometrial tissue were obtained following serial observations in normally ovulating women, and a prospective identification of a specific phase was made in those with regular menstrual cycles. This may be the first report of endometrial tissue characterization. Clinical management of infertility and monitoring of follicular growth will thus be facilitated.

Endometrium↗
PubMed1985

Relationship between the severity of diabetes mellitus and pancreatic exocrine dysfunction in rats.

The relationship between the severity of diabetes mellitus and pancreatic exocrine function was investigated in rats made diabetic by injecting 3 different doses of streptozotocin (30, 45 or 60 mg/kg body weight). The expected correlation was obtained between the dose of streptozotocin and degree of elevation of blood glucose and decrease in pancreatic insulin content. Pancreatic amylase content of the diabetic rats was less than that of control rats and was in parallel with less values in pancreatic insulin content. On the other hand, trypsinogen content of diabetic rats was greater than that of control. Basal and caerulein-stimulated flow rates of pancreatic juice and protein output were similar in the control and in all 3 groups of diabetic rats. In contrast, there was a graded response of amylase and trypsinogen, depending upon the content of each enzyme in the pancreas. Both basal and caerulein-stimulated amylase outputs from diabetic rat pancreas were significantly reduced in parallel with the severity of diabetic state, but were similar to those from the control rats when related to the total pancreatic content. The present findings indicate that pancreatic exocrine dysfunction in diabetes mellitus is closely related to the severity of the disease, but the secretory dynamics in the perfused pancreas are not altered.

Amylases↗
PubMed1985

Interaction of caerulein, glucose, and amino acids on insulin secretion from the perfused rat pancreas.

The effect of caerulein on insulin response to graded amounts of glucose from the isolated perfused rat pancreas was investigated in the presence or absence of an amino acids mixture. Caerulein at a concentration of 0.1 ng/ml which is a submaximal concentration for an effect on exocrine pancreatic secretion potentiated insulin responses to glucose concentrations less than 200 mg/dl, but produced no further increase when added to a glucose stimulus over a 200 mg/dl. However, in the presence of amino acids the insulin response to 200 mg/dl glucose was significantly potentiated by the stimulation of 0.1 ng/ml caerulein. The effectiveness of caerulein as an insulinotropic agent depended on the glucose concentration only when amino acids were present. These results indicate that caerulein, at a concentration which stimulate pancreatic exocrine secretion, has a synergistic effect on insulin response to glucose and amino acids and therefore raises the possibility that endogenously released CCK may contribute to the entero-insular axis.

Amino Acids↗
PubMed1985

Localization of saturable CCK binding sites in rat pancreatic islets by light and electron microscope autoradiography.

Cholecystokinin (CCK) is a known stimulus for the release of insulin and other islet hormones. To localize islet cell CCK binding sites, we measured the uptake of 125I-CCK by the isolated, perfused rat pancreas. Light microscope autoradiographs revealed uptake of label over both the endocrine islets of Langerhans and the exocrine acini. This uptake of 125I-CCK was saturable, as it decreased markedly when a large excess of unlabeled CCK8 was included in the perfusion solution. To define which cells in the islets bound CCK, electron microscope autoradiographs were prepared. The majority of silver grains in islets were localized over beta cells (69%), although saturable uptake was also observed over alpha (12%) and other islet cells. When grain densities were analyzed (grains/micron 2), the highest density was observed over islet blood vessel cells. In contrast to islet blood vessels, there was no localization of 125I-CCK over acinar blood vessels. This study supports the concept, therefore, that there is a direct regulation of islet endocrine cells by CCK, and also raises the possibility that CCK influences islet hormone release via an indirect effect on the islet vascular endothelium.

Animals↗
PubMed1984

Brain CCK receptors are structurally distinct from pancreas CCK receptors.

Brain and pancreas cholecystokinin (CCK) receptors differ markedly in their selectivity for CCK analogs. To determine the size and subunit structure of the brain CCK receptor and compare it to that of the pancreas, 125I-CCK33 was covalently cross-linked with ultraviolet light to its receptor on mouse brain particles and purified pancreatic plasma membranes. When CCK was crosslinked to brain membranes, a single consistent major labeled protein band of Mr = 55,000 was observed in both the presence and the absence of DTT. These data with brain receptors contrast to results with pancreatic receptors where two bands of Mr = 120,000 and 80,000 are labeled in the absence and presence of DTT, respectively. These studies indicate, therefore, that the brain and pancreas CCK receptors are structurally and functionally distinct.

Animals↗
PubMed1984

The somatostatin receptor on isolated pancreatic acinar cell plasma membranes. Identification of subunit structure and direct regulation by cholecystokinin.

Somatostatin binding to its receptors on rat pancreatic acinar membranes was characterized with [125I-Tyr1]somatostatin. Binding at 24 degrees C was rapid reaching a maximum after 60 min and was reversible upon the addition of 1 microM unlabeled ligand. Scatchard analysis revealed a single class of binding sites, with a Kd of 0.32 +/- 0.03 nM and a binding capacity of 600 +/- 54 fmol/mg of protein. Specificity for the somatostatin was demonstrated with the inhibition of labeled hormone binding by somatostatin analogs in proportion to their biological activities. When [125I-Tyr1]somatostatin was cross-linked to its receptors with the photoreactive cross-linker n-hydroxysuccinimidyl-4-azidobenzoate, the hormone was associated with Mr = 90,000 protein. Similar mobilities of the radioactive band were observed in the presence and absence of dithiothreitol. In contrast to other unrelated peptides, cholecystokinin (CCK) and its analogs directly reduced [125I-Tyr1] somatostatin binding to isolated membranes. The effect of CCK was one-half-maximal at 3 nM and maximal at 100 nM. In the presence of 3 nM CCK8, the binding capacity for somatostatin was decreased to 237 +/- 39 fmol/mg of protein without a significant change in affinity. Dibutyryl cyclic GMP, a CCK receptor antagonist, blocked this action of CCK8 indicating that the CCK receptor mediated the decrease in [125-Tyr1]somatostatin binding. In contrast cerebral cortex membranes, which also possess a somatostatin receptor, were not regulated by CCK. These results indicate, therefore, that 1) purified pancreatic acinar plasma membranes contain specific receptors for somatostatin, 2) the receptor has an apparent Mr of about 90,000, and 3) the binding of somatostatin to its receptor on pancreatic plasma membranes is regulated by CCK analogs acting via the CCK receptor.

Animals↗
PubMed1984

Pancreatic CCK receptors: characterization of covalently labeled subunits.

125I-CCK was crosslinked with ultraviolet light to its receptor on pancreatic plasma membranes. The predominant labeled species following polyacrylamide gel electrophoresis had a molecular weight of 120,000 in the absence, and 80,000 in the presence of the reducing agent dithiothreitol. The M = 120,000 labeled band could be extracted, reduced and converted to Mr = 80,000. Moreover, peptide mapping with Staph aureus V8 protease showed a similar pattern for the 120,000 and 80,000 dalton bands. The crosslinked receptor could be solubilized with Triton X-100, absorbed to wheat germ agglutinin and eluted with N-acetylglucosamine. The results indicate, therefore, that the CCK receptor is a glycoprotein with subunits coupled by disulfide bonds.

Animals↗
PubMed1984

Exocrine and endocrine secretion from isolated perfused rat pancreas with islet cell tumors induced by streptozotocin and nicotinamide.

Pancreatic exocrine and endocrine function in the rat with islet cell tumors induced by streptozotocin and nicotinamide was studied in the in vitro isolated perfused pancreas. The tumor-bearing pancreas secreted significant amounts of insulin even at 2.8 mM glucose stimulation. Further, insulin response to 8.3 mM glucose stimulation was greater in the tumor-bearing pancreas than in the control. Not only endocrine, but also exocrine, disorders were found in the rat pancreas bearing islet cell tumors. In contrast to the increased response of insulin, amylase output in response to 0.1 ng/ml cerulein was significantly lower in the tumor-bearing than in the control pancreas, although there was no difference in pancreatic juice flows from both groups. These results suggest that enzyme secretory function of the pancreas with islet cell tumors may be suppressed in the presence of some interrelationship between the exocrine and endocrine portion of the pancreas with islet cell tumors.

Adenoma, Islet Cell↗
PubMed1984

Effect of short-term peroral administration of synthetic trypsin inhibitor on endocrine secretion in the isolated perfused rat pancreas.

The effects of peroral treatment with synthetic trypsin inhibitor on endocrine secretion in response to four different stimuli were investigated in the isolated perfused rat pancreas. After 10 days' treatment pancreatic wet weights and protein and amylase contents in the pancreas were significantly increased. On the other hand, total contents of IRI and IRG in the T.I.-treated and control pancreas were nearly the same. In spite of the lack of alteration in hormone contents, a lower initial phase of IRI response to 8.3 mM glucose, glucose plus 0.1 ng/ml caerulein or 20 mM arginine was observed in the T.I.-treated pancreas. Furthermore, the IRI response to 10 mM theophylline was both slower and the most reduced in the T.I.-treated pancreas. From these observations, it is suggested that short-term peroral administration of synthetic trypsin inhibitor not only has no trophic effect on pancreatic B-cell and A-cell in the rat but also may affect some pathway of insulin secretion from the B-cell to reduce IRI responses to secretagogues.

Amylases↗