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Query: UMLS:C0027651 (tumor)
 685,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The membrane potential of the Ehrlich ascites tumor cell was shown to be influenced by its amino acid content and the activity of the Na+ :K+ pump. The membrane potential (monitored by the fluorescent dye, 3,3'-dipropylthiodicarbocyanine iodide) varied with the size of the endogenous amino acid pool and with the concentration of accumulated 2-aminoisobutyrate. When cellular amino acid content was high, the cells were hyperpolarized; as the pool declined in size, the cells were depolarized. The hyperpolarization seen with cellular amino acid required cellular Na+ but not cellular ATP. Na+ efflux was more rapid from cells containing 2-aminoisobutyrate than from cells low in internal amino acids. These observations indicate that the hyperpolarization recorded in cells with high cellular amino acid content resulted from the electrogenic co-efflux of Na+ and amino acids. Cellular ATP levels were found to decline rapidly in the presence of the dye and hence the influence of the pump was seen only if glucose was added to the cells. When the cells contained normal Na+ (approx. 30mM), the Na+ :K+ pump was shown to have little effect on the membrane potential (the addition of ouabain had little effect on the potential). When cellular Na+ was raised to 60mM, the activity of the pump changed the membrane potential from the range -25 to -30 mV to -44 to -63 mV. This hyperpolarization required external K+ and was inhibited by ouabain.
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PMID:The influence of cellular amino acids and the Na+ : K+ pump on the membrane potential of the Ehrlich ascites tumor cell. 21 14

A calcium infusion (4 mg Ca++/kg/hr) significantly increased plasma insulin levels and reduced blood glucose in 4 patients with insulin-secreting pancreatic islet cell tumors. These parameters were not altered by a similar infusion of calcium in normal volunteers, 2 patients with alimentary hypoglycemia, and 2 with functional hypoglycemia. No difference in response was observed between patients with benign and malignant beta-cell tumors. Infusion of diazoxide (600 mg) with calcium blocked the stimulation of the latter on insulin secretion. The results indicate the usefulness of calcium infusion in the diagnosis of insulin-secreting tumor.
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PMID:Insulin release in response to calcium in the diagnosis of insulinoma. 21 87

Implantation of MtT-F4 tumor, a mammotropic tumor that secretes large quantities of ACTH, GH and prolactin, into male Fisher rats induced the development of hyperlipidemia. Free fatty acid, triglyceride and cholesterol levels in the plasma were significantly increased at 31 days after tumor implantation. Blood glucose and glycerol levels remained normal, while uric acid concentration in the blood was significantly decreased. The lipolytic response of isolated adipose tissue cells to ACTH was significantly higher in cells derived from rats bearing an MtT-F4 tumor for 31 days than from their corresponding controls. However, the activity of adenylate cyclase in fat cells stimulated with ACTH was not significantly higher in cells derived from tumor bearing rats than in cells from control rats.
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PMID:Development of hyperlipidemia associated with increased lipolytic response of isolated adipose tissue cells following prolonged stimulation by an ectopic pituitary tumor. 21 11

Pancreatic islet cell tumors were induced in 32 of 49 male Wistar rats (73%) surviving 9 months or longer following treatment with streptozotocin alone, with streptozotocin and nicotinamide, or with streptozotocin and picolinamide. Serial oral glucose tolerance tests in rats treated with streptozotocin and nicotinamide showed that the elevation of blood glucose levels after oral glucose load was depressed significantly 7 months after treatment. Plasma insulin responses were distinctly elevated 9 months after treatment. Blood glucose levels remained lower and plasma insulin levels rose markedly after a glucose load in tumor-bearing rats as compared to the response of tumor-free rats. These findings suggest that pancreatic islet cell tumors induced by streptozotocin with and without combined treatment are insulin-secreting, and that streptozotocin itself has oncogenic effects on the rat pancreas. Mean insulin concentration in islet cell tumors amounted to 401 U/g wet wt, whereas the concentration was 14 U/g wet wt in the pancreatic tissue from tumor-free rats.
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PMID:Biochemical studies on rats with insulin-secreting islet cell tumors induced by streptozotocin: with special reference to physiological response to oral glucose load in the course of and after tumor induction. 21 81

The clinicopathologic aspects of pancreatic islet cell adenocarcinoma in 6 dogs were compared. Diagnosis was based on insulin-glucose ratios in 5 dogs. Surgical excision of the tumor resulted in absence of clinical signs for at least 1 year in 3 dogs.
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PMID:Pancreatic islet cell adenocarcinoma: clinical and diagnostic features of six cases. 21 19

Thirteen cases of bronchopulmonary carcinomas without symptoms of hypercorticoidism, hypopotassemic alkalosis, or intolerance to an overdose of glucose are described. Repeated circadian rhythm and the suppression test with small doses of dexamethasone were practiced on each one. In 7 cases the secretion of cortisol was supressed normally with oral administration of dexametahsone. In the other 6 cases the circadian rhythm was lost and it was imposible to reduce the plasma level of cortisol with dexamethasone. The results help to point out the usefulness of these easy to perform dynamic tests as a means of diagnosing the ectopic production of ACTH by bronchopulmonary tumors. At the same time they show the relatively high incidence of production of this hormone by this type of tumors in patients who have no symptoms of classical hypercorticoidism. The determination of plasma cortisol levels using this test could be valuable in establishing the prognosis and clinical course of the disease. A normalization of the endogenous adrenal secretion of glucocorticoids would indicate a regression of the tumor in response to treatment.
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PMID:[Ectopic ACTH syndrome in bronchopulmonary tumors (author's transl)]. 21 3

The ATPase inhibitor quercetin, which inhibits tumor glycolysis, was shown to be a glucose transport inhibitor like the chemically related compound phloretin. Rat thymocyte glucose transport stimulated by the mitogens concanavalin A or ionophore A 23187 was more sensitive than unstimulated transport to quercetin inhibition. The partial inhibition of Na+-, K+- ATPase activity by quercetin observed in tumor cells was confirmed in thymocyte plasma membranes. The specific Na+-, K+- ATPase inhibitor ouabain did not mimic the effect of quercetin on mitogen-stimulated glucose transport but did reduce the effectiveness of concanavalin A as a stimulator of mitochondrial pyruvate oxidation. The results support the idea that glycolytic flux and the activity of plasma membrane ATPase are related but suggest that glucose transport, rather than the Na+-, K+-ATPase, is the rate-limiting reaction in lymphocytes.
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PMID:Preferential inhibition by quercetin of mitogen-stimulated thymocyte glucose transport. 22 Apr 48

The gamma-aminobutyric acid (GABA) concentration of pancreatic islets in rats treated with streptozotocin (STZ) and of human insulinoma tissue was studied. Seven hours after the administration of 65 mg/kg body weight of STZ, a distinct increase in serum insulin concentration and at the same time a decrease in blood glucose level were seen. Twenty-four hours after the injection of STZ, however, the level of serum insulin decreased much, whereas that of blood glucose increased considerably. On the other hand, the GABA concentration of the islet was reduced dramatically to about one-tenth the control level after both 7 and 24 h. The histologic investigations of the islets revealed the destruction of B cells but no changes in A and D cells 7 and 24 h after the treatment of STZ. Nerve fibers and nerve endings in the islets were preserved intact all through the study. The GABA and insulin contents of the two cases of human insulinoma were determined. One insulinoma, which was compactly occupied with B cells according to its histologic features, contained a high concentration of GABA. The other tumor, having a rather sparse distribution of B cells in it as compared with the former case, possessed a lower concentration of GABA, but it was still high compared with that of its surrounding tissues. The present observations indicate that a large amount of GABA is available in the B cells of the pancreatic islets.
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PMID:High concentration of gamma-aminobutyric acid in pancreatic beta cells. 22 Dec 97

A glucose-controlled insulin and glucose infusion system (Biostator system, Miles Laboratories Inc., Elkhart, Ind.) was used during operation for removal of four suspected insulinomas. In two patients the Biostator system continuously monitored plasma glucose levels and, through a computer-controlled feedback mechanism, automatically infused insulin or glucose as needed. In this way plasma glucose could be kept at approximately 110 mg/dl throughout the procedure. In one patient a rise in insulin infusion rate and a fall in glucose infusion rate followed removal of the tumor. In the other, absence of these findings was consistent with the clinical suspicion that the source of hypoglycemia had not been removed. In two other patients the Biostator system continuously monitored the patient's plasma glucose, without feedback-controlled administration of insulin or glucose. This demonstrated that, in these patients, tumor manipulation and removal did not lead to severe hypoglycemia, and thus eliminated any need to prophylactically infuse large amounts of glucose. Successful tumor removal was followed by a rise in blood glucose levels in both of these individuals. The glucose-controlled insulin and glucose infusion system appears to be a useful instrument for intraoperative management of patients with suspected insulinomas.
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PMID:Continuous monitoring and control of plasma glucose during operation for removal of insulinomas. 22

Implantation of MtT-F4 tumor, a mammotropic tumor that secretes large quantities of ACTH, GH and prolactin, into male Fisher rats induced the development of hyperlipidemia. Free fatty acid, triglyceride and cholesterol levels in the plasma were significantly increased at 31 days after tumor implantation. Blood glucose and glycerol levels remained normal, while uric acid concentration in the blood was significantly decreased. The concentrations of the serum lipoproteins were significantly increased, while, only small changes in the distribution of the serum lipids and the composition of the lipoproteins were observed. Following stimulation of isolated adipose tissue cells with ACTH, the lipolytic response and the accumulation of cyclic AMP was higher in cells derived from the rats with the tumor, although the accumulation of cyclic GMP was not different from control adipocytes. Further, when the isolated adipose tissue cells were stimulated with dibutyryl cyclic AMP no difference was observed between the control and tumor bearing groups. Clofibrate administered in the diet resulted in a complete elimination of the tumor effect on serum triglycerides and to a great extent prevented the rise in serum cholesterol. The tumor-induced increase in the concentration of the high density lipoproteins was not affected, but the elevation of the d less than 1.063 lipoproteins was not affected, but the elevation of the d less than 1.063 lipoproteins was partially reversed. The increased lipolytic response and accumulation of cyclic AMP following stimulation by ACTH was not altered in adipocytes derived from tumor bearing rats. However, clofibrate treatment resulted in a significantly greater accumulation of cyclic GMP in fat cells stimulated with ACTH from both control and tumor bearing rats. Clofibrate in the diet did not alter the levels of GH or prolactin or serum lipids in the control rats nor were the elevated hormone levels of the tumor bearing rats changed.
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PMID:Experimental hyperlipidemia in rats. 22 51


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