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C Sakamoto

Publications and source records attributed to C Sakamoto.

At least 145 records · Page 8Linked to original sources
PubMed1981

Insulin release from the isolated perfused rat pancreas containing insulinomata induced by streptozotocin and nicotinamide: effects of glucose and responses to tumor removal.

The kinetics of insulin secretion in response to glucose were studied in the in vitro perfused rat pancreas before and after removal of islet cell tumors induced by streptozotocin and nicotinamide. In addition, insulin secretion before and after tumor removal was compared with that from normal pancreata before and after sham operations, respectively. Thus, the two pancreas preparations were subjected to repeated perfusions with glucose. Perfusion of pancreata containing tumors with 8.4 mM glucose resulted in biphasic release in a pattern similar to that of normal pancreas. However, both basal and stimulated insulin secretion of tumor-bearing pancreata were greater than either those of pancreata from which tumors had been excluded by ligature or those of normal pancreata before sham operation. A second increase in the concentration of glucose from 2.8 to 8.4 mM also produced a biphasic release of insulin from extratumoral pancreata as well as from sham-operated normal pancreata. However, the insulin secretory response to glucose of extratumoral pancreatic tissue was less than that of control pancreatic tissue. Our findings indicate that pancreatic islet cell tumors induced by streptozotocin and nicotinamide respond to glucose with typical biphasic insulin release. Thus, chemically induced rat insulinomata may provide a readily available and valuable model of insulin-secreting tissue, analogous to normal islets. Furthermore, our study suggests that the B cell function of pancreata containing tumors is inhibited by the preexisting tumor-induced hyperinsulinism or by its metabolic consequences.

Adenoma, Islet Cell↗
PubMed1981

Birth weight assessed by factor analysis.

To investigate the relevancy of birth weight, data on 300 term newborn infants were subjected to a reevaluation of 31 variables related to body measurements of both the mother and child and to the placenta. Factor analysis was introduced to analyze the data obtained. Each group was composed of multiple factor axes, of which factor structures were rather simple in Appropriate for Date (AFD) for approximating the practical images, compared to Heavy for Date (HFD) and Light for Date (LFD). In AFD, the birth weight was thought contributive by the limiting effect of the placenta, independently of the measurements of the mother. We found that the birth weight in itself seems to have a different meaning in each group, and it is difficult to readily categorize the findings on the table of equivalent parameters for labelling of the newborn.

Birth Weight↗
PubMed1980

Effect of somatostatin and calcium deprivation on cholecystokinin or caerulein-induced insulin and glucagon release from the isolated perfused rat pancreas.

The present experiments were undertaken to investigate the effect of alteration in on extracellular calcium concentration and of somatostatin on cholecystokinin-(CCK)- and caerulein-induced insulin and glucagon release from the isolated perfused rat pancreas. In control studies using perfusate containing 2.5 mM CaCl2 and 50 mg/dl glucose, CCK and caerulein caused insulin and glucagon release in a dose-related fashion. During perfusion with calcium free medium, insulin release was markedly inhibited. Subsequent introduction of 2.5 mM CaCl2 to the medium restored insulin response toward control levels. Extracellular calcium depletion, however, had no effect on CCK- or caerulein-induced glucagon release. The output of glucagon in the absence of calcium was comparable to that seen in the control experiments. On the other hand, somatostatin abolished the increase in glucagon secretion, but not the increase in insulin secretion, when perfused simultaneously with CCK or caerulein. However, pretreatment for 10 min with somatostatin blocked even insulin secretion. However, pretreatment for 10 min with somatostatin blocked even insulin secretion. The effects of somatostatin on hormonal discharge are suggested to be related to an alteration in the handling of or response to calcium. Recently, somatostatin has also been shown to inhibit calcium uptake by islets. Thus, the present results indicate a differential sensitivity of CCK- and caerulein-stimulated alpha and beta cell to extracellular calcium depletion and to the effect of somatostatin.

Animals↗
PubMed1979

Discrepancies between the doses of cholecystokinin or caerulein-stimulating exocrine and endocrine responses in perfused isolated rat pancreas.

The effects of highly purified natural porcine cholecystokinin (CCK) and synthetic caerulein on the rate of flow of pancreatic juice, the rate of output of amylase, and the rate of release of immunoreactive insulin (IRI) and immunoreactive glucagon (IRG) were simultaneously investigated in the isolated perfused rat pancreas. The maximal flow rate of pancreatic juice was obtained with concentrations of CCK ranging from 0.5 to 10 mU/ml, whereas amylase output was maximal at CCK concentrations from 1 to 10 mU/ml. Caerulein at concentrations of 0.05-1 ng/ml induced a similar maximal flow rate and amylase secretion. Supramaximal stimulatory concentrations of these peptides resulted in lower rates of release of fluid and amylase than with the maximally effective concentrations. Stimulation of IRI and IRG release was elicited only with concentrations of peptides supramaximal for effects on the exocrine responses. The demonstration of very similar discrepancies between the doses of caerulein required to elicit maximal exocrine responses and those required to elicit endocrine responses provide strong evidence that the pattern of the effect of the porcine CCK is accounted for by CCK itself. Although caerulein had no influence on IRI response when superimposed on 100 or 150 mg/100 ml glucose stimulation, preperfusion of caerulein led to a significant enhancement of IRI response to a subsequent glucose stimulation in both phases. The augmentation effect was completely separate from the direct IRI-stimulating effect of caerulein, because the CCK-like peptide requires no glucose for insulinotropic action. Because the concentrations of the peptides necessary for stimulation of endocrine responses were inhibitory in their effects on exocrine responses, it may be inferred that it is unlikely that the endocrine effect is physiologically important, though the results of caerulein for augmenting glucose-stimulated IRI release suggests a possible role for CCK in carbohydrate metabolism.

Amylases↗
PubMed1979

Effect of caerulein on exocrine and endocrine pancreas in the rat.

The secretion of insulin, glucagon, pancreatic juice, and amylase in response to a 20-min iv infusion of synthetic caerulein were studied simultaneously in the anesthetized rat. Caerulein, a chemical analogue of cholecystokinin, was used in doses of 1-1000 ng/kg.min. The maximum stimulatory effect of caerulein on pancreatic juice volume and amylase output was obtained with doses of 10 ng/kg.min. With increasing doses, the effect decreased progressively. On the other hand, the release of insulin and glucagon was stimulated only by supramaximal doses of caerulein, which had little or no effect on pancreatic exocrine secretions. These results raised the question of whether, under physiological conditions, cholecystokinin regulates the secretory activity of the endocrine pancreas.

Amylases↗
PubMed1978

Pancreatitis-like isoamylase pattern in normal persons.

On the assumption that a rise in the pancreatic type isoamylases may not necessarily indicate underlying pancreatitis, genetic studies of human serum and urinary amylase isoenzymes have been performed with the use of electrophoresis. Although the preponderant increase in the two principal pancreatic isoamylases Amylase-1 and 2 has been accepted to be a specific index of pancreatic involvement, 1.68% of normal persons had Amylase-2 with an elevated amylase activity (named "Dominant Amylase-2") up to the same levels as the major isoenzymes. Results of pancreozymin-secretin test and other laboratory findings of these persons with Dominant Amylase-2 were all within normal ranges. Pedigree studies confirmed an autosomal dominant mode of inheritance for this variant. The important of serial determination and pedigree investigations has been shown to distinguish normal persons having Dominant Amylase-2 from patients with pancreatitis without elevated amylase activity. The existence of an inherited trait of pancreatitis-like isoamylase pattern in healthy individuals must be born in mind before coming to a conclusion when amylase isoenzymes are used for clinical medicine, though preponderance of the pancreatic type isoenzymes in serum and urine has been revealed to be a characteristic finding in pancreatitis. Knowledge of amylase genetic polymorphism provides a scientific basis for amylase isoenzyme interpretation.

Acute Disease↗
PubMed1978

[Effect of caerulein on pancreatic endocrine and exocrine secretion from the perfused rat pancreas (author's transl)].

Several investigations in vivo and in vitro have shown that gastro-intestinal hormones stimulate insulin secretion. However, the reports on the insulinotropic activity of pancreozymin are contradictory. The conflicting results are probably due to the fact that pure native preparation of this hormone has not been obtained in "physiologic" doses. In the present study this problem has been investigated by exposing rat pancreas to caerulein in vitro. Caerulein, an active decapeptide isolated from the skin of the Australian amphibia Hyla caerulea, resembles pancreozymin in chemical structure, including C-terminus. This active polypeptide of nonmammalian origin has been shown to possess all the biological activities of pancreozymin. The present investigation was undertaken to evaluate the significance of the interactions of exocrine and endocrine pancreas using perfused rat pancreas in vitro. Biphasic insulin release was demonstrated with caerulein at concentrations higher than 1 ng/ml. Insulin response of the first phase was proportional to the dose up to 1 microgram/ml. The second phase of insulin release was, however, almost constant, regardless of the concentrations of caerulein. Release of glucagon was stimulated by the same concentrations of caerulein which stimulated insulin release. Maximal response of the pancreatic amylase and pancretic juice output were observed with 1 ng/ml of caerulein. With higher doses, significantly less secretory responses were observed. The dissociation of the response to caerulein between endocrine and exocrine pancreas was found.

Amylases↗