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Aims: The specific objective of this study was to determine acute and long-term effects of cyclo (his–pro) (CHP) plus zinc and l-histidine (CZH) treatment on glucose metabolism in genetically obese (ob/ob), type 2 diabetic mice. Methods: Acute effects of 0.3 mg of CHP plus 10 mg of zinc and 0.5 mg of l-histidine/kg body weight (BW) on fed blood glucose concentrations and 3-h average of above fasting blood glucose concentrations (TAFGCs), an index of oral glucose tolerance test, in lean and ob/ob mice were determined. To evaluate long-term effects of CZH on TAFGCs, lean and ob/ob mice were treated with drinking water containing increasing doses of CHP (0, 0.5, 1.0 or 1.5 mg/l) plus 10 mg zinc and 0.5 mg of l-histidine/l for 3 weeks. During the treatment period, fed blood glucose concentrations, BW and food and water intake were determined. At the end of the treatment, fasting blood glucose concentrations, TAFGC and fed plasma insulin concentrations were determined. Results: Blood glucose concentrations significantly decreased when CZH was administered acutely via gastric gavage in food-deprived ob/ob mice. Similarly, 1.0 mg/l CHP treatment of mice with fixed amounts of 10 mg zinc and 0.5 mg l-histidine/l was optimal to decrease fed blood glucose and plasma insulin concentrations during a 3-week treatment period in ob/ob mice. TAFGC values in these mice also improved most significantly with the same combination of CHP, zinc and l-histidine used to test for fed blood glucose and plasma insulin levels. Fasting blood glucose concentrations and BW gains also decreased in ob/ob mice treated with 1.0 mg of CHP/l plus the same amount of zinc and l-histidine used in the above experiments. No effects of CZH treatment in lean mice were observed. Conclusions: CZH is effective in decreasing blood glucose concentrations in genetically obese (ob/ob), type 2 diabetic mice. These data support our working hypothesis that CZH may be an important anti-hyperglycaemic agent.

Aim: The present study is designed to determine whether arachidonic acid (AA) plus zinc improves clinical signs of diabetes in genetically diabetic ob/ob mice. Methods: In the first study, effects of acute administration of AA plus zinc on glucose disposal were determined in ob/ob and lean mice (n = 6 each). In the second study, ob/ob and lean mice were treated with increasing doses of AA plus zinc for 2 weeks (n = 5 each). Postprandial and fasting blood glucose concentrations, three-hour-area-average above fasting glucose concentration (TAFGC), water and food intake, body weight and plasma insulin concentrations were measured. Results: Acute administration of AA plus zinc significantly increased glucose disposal in ob/ob mice. In the second study, postprandial and fasting blood glucose concentrations, TAFGC, and water and food intake in ob/ob mice treated with AA plus zinc for 2 weeks were significantly decreased compared with those in mice given no AA. Plasma insulin concentrations in both lean and ob/ob mice were not changed by AA treatment in drinking water. Conclusions: AA plus zinc in drinking water is effective in decreasing blood glucose levels in obese mice. These results indicate that use of these compounds should be considered as a dietary supplement to control hyperglycaemia in patients with type II diabetes.

Expression of the long form of the leptin receptor, the isoform that is considered to have full signaling capability, has been reported in the central nervous system and several peripheral cell types. However, only a few cell lines have been shown to express the long form of the receptor. AR42J, a cell line derived from azaserine-treated rat pancreas, is a common model for pancreatic acinar cell secretion. In this study, the presence of leptin-receptor variants and leptin action was evaluated in this cell line. Messenger RNAs for both the long and a short form of the leptin receptor were detected by reverse transcription-polymerase chain reaction (RT-PCR) in AR42J cells, and authenticity of the receptor was confirmed by DNA sequencing. Competitive binding studies demonstrated that binding of radiolabeled leptin was specific and did not cross-react with cholecystokinin (CCK). Biologic effects of leptin on amylase release and intracellular calcium mobilization were further assessed in the presence and the absence of CCK, a known pancreatic secretagogue. Although leptin alone (< or =200 ng/ml) did not affect basal amylase release, it inhibited amylase release stimulated by 1 nM CCK by 48%. Leptin alone had no significant effect on calcium mobilization. However, pretreatment of leptin (10 and 100 ng/ml) enhanced calcium responses stimulated by CCK. These data demonstrate that the rat pancreatic tumor cell line AR42J expresses a functional form of the leptin receptor that modulates the action of CCK in calcium mobilization and amylase release.

The specific objective of this study was to determine acute and long-term effects of cyclo (his-pro) (CHP) plus zinc and l-histidine (CZH) treatment on glucose metabolism in genetically obese (ob/ob), type 2 diabetic mice.Acute effects of 0.3 mg of CHP plus 10 mg of zinc and 0.5 mg of l-histidine/kg body weight (BW) on fed blood glucose concentrations and 3-h average of above fasting blood glucose concentrations (TAFGCs), an index of oral glucose tolerance test, in lean and ob/ob mice were determined. To evaluate long-term effects of CZH on TAFGCs, lean and ob/ob mice were treated with drinking water containing increasing doses of CHP (0, 0.5, 1.0 or 1.5 mg/l) plus 10 mg zinc and 0.5 mg of l-histidine/l for 3 weeks. During the treatment period, fed blood glucose concentrations, BW and food and water intake were determined. At the end of the treatment, fasting blood glucose concentrations, TAFGC and fed plasma insulin concentrations were determined.Blood glucose concentrations significantly decreased when CZH was administered acutely via gastric gavage in food-deprived ob/ob mice. Similarly, 1.0 mg/l CHP treatment of mice with fixed amounts of 10 mg zinc and 0.5 mg l-histidine/l was optimal to decrease fed blood glucose and plasma insulin concentrations during a 3-week treatment period in ob/ob mice. TAFGC values in these mice also improved most significantly with the same combination of CHP, zinc and l-histidine used to test for fed blood glucose and plasma insulin levels. Fasting blood glucose concentrations and BW gains also decreased in ob/ob mice treated with 1.0 mg of CHP/l plus the same amount of zinc and l-histidine used in the above experiments. No effects of CZH treatment in lean mice were observed.CZH is effective in decreasing blood glucose concentrations in genetically obese (ob/ob), type 2 diabetic mice. These data support our working hypothesis that CZH may be an important anti-hyperglycaemic agent.

In vitro gastric vagal afferents' (GVAs) unit activities were recorded from the ventral GVA nerve strands in rats. The responsiveness of 16 GVA terminals to close intra-arterial injection of vehicle (0.1 ml), leptin (350 pmol), and cholecystokinin (CCK)-8 (10 pmol) was analyzed to generate a spike count-versus-time histogram. Data of 5-min spike counts before and after each treatment were normalized by dividing the latter by the former. A quotient (Q) > 1 indicates an excitatory effect, Q < 1 indicates an inhibitory effect, and Q close to 1 indicates no effect. Two types of GVA terminals were identified. Type 1 (n = 8) responded to leptin with Q > 1; CCK-8 pretreatment did not consistently alter leptin sensitivity. In contrast, Type 2 (n = 8) responded to leptin with Q < 1 or close to 1, and CCK-8 pretreatment increased the leptin sensitivity so that the terminals responded to subsequent leptin with Q > 1. These data suggest that Type 1 and Type 2 GVA terminals may provide afferent neural signals, which, in turn, will be involved in body weight and food intake control systems, respectively.

The membrane potential (E(m)) was used as an indicator to evaluate the effect of stem cell factor (SCF) on the membrane integrity of peritoneal mast cells (PMCs). PMCs were harvested from the peritoneal lavage of Sprague-Dawley rats, purified more than 95% and cultured with or without the presence of SCF (2 x 10(-8) M). E(m) values were measured with conventional intracellular recording techniques. Results from day 1 to day 4 in culture were compared. Significant differences in average E(m) (aE(m)) (P < 0.01, analysis of variance) were seen on days 3 and 4 (means +/- SE in millivolts): -67.4 +/- 8.0 and -59.4 +/- 4.8 with SCF vs. -24.8 +/- 7.9 and -7.6 +/- 3.9 without SCF, respectively. Moreover, after culture with SCF for > 1 wk, the aE(m) values of purified PMCs had a tendency to reach plateau values similar to that of unpurified PMCs on day 1 (at -20 mV). The morphological appearances of PMCs can be correlated with the results of aE(m) measurements. PMCs with a smooth spherical shape and highly refractive appearance, and better tolerance to electrode impalement, showed E(m) with greater negative values and lesser fluctuations. These results indicate that SCF can maintain the membrane properties and viability of purified PMCs in a long-term culture.

The human pancreas consists of both exocrine and endocrine components, is responsible for the proper digestion of specific food nutrients, and regulates the metabolism of absorbed nutrients. The exocrine and endocrine pancreas are linked not only anatomically and embryologically but also vascularly and functionally. The gastrointestinal hormones regulate the secretion and synthesis of all digestive enzymes in the pancreatic acini (enteroacinar axis) and the secretions of pancreatic islet hormone, particularly insulin (enteroinsular axis). Recently, many islet vascular studies in experimental animals have provided evidence of a coexisting parallel and serial (insuloacinar) angioarchitecture [38]. This arrangement of the islet capillary blood flow to the periinsular acinar plexus has led to the proposal that exocrine pancreatic function is partly regulated by the endocrine islets and their hormones [16]. This functional relationship, enteroacinar axis, enteroinsular axis, and insuloacinar axis are all affected in chronic pancreatitis and can lead to pancreatic exocrine and endocrine defficiency.

3177 Background: Octreotide acetate (LAR) is commonly used for symptom control in carcinoid tumors. At doses of 20 or 30 mg, up to 40% of carcinoid patients require additional aqueous octreotide se...

The search for tumor markers suitable for use in diagnosis and management of patients with lung cancer has met with limited success because each available marker lacks sufficient sensitivity and specificity. We have begun a collaborative study to evaluate multiple simultaneous serum markers to determine whether there is a combination that will increase both sensitivity and specificity to the degree that noninvasive serologic tests might provide a means for managing patients with lung cancer. The National Cancer Institute, Bethesda, Maryland, has established a Serum Bank which can supply identical aliquots of the same serum sample to several different laboratories to perform quantitative assays for a number of markers. The results of these assays will serve as a data base to be analyzed for selection of the optimal grouping of markers for the different types of lung cancer and for evaluation of different biostatistical techniques to maximize the benefit derived by multiple marker determination. The evaluation of multiple markers will be carried out in several separate steps: (a) determination of a combination of markers that discriminate advanced lung cancer from benign lung disease; (b) demonstration of the ability of that combination to define early or localized lung cancer; (c) selection of a combination that best separates lung cancer from cancer of other sites; (d) testing of combined markers for the ability to predict response to therapy, including detection of early recurrence before clinical signs appear; and (e) evaluation of the combination(s) for effectiveness in detecting lung cancer in asymptomatic individuals. The experimental design and selection of markers will be presented and discussed.

To determine whether the autonomic nervous system has a direct effect on GIP secretion, six normal subjects received a 4-hr intraduodenal perfusion of glucose (225 mg/min) and polyethylene glycol on four successive days. During the latter 2 hr, either normal saline, propranolol, phentolamine, or atropine were infused intravenously. Glucose absorption was calculated by measuring glucose and polyethylene glycol following luminal aspiration distal to the perfusion site. Basal and peak or nadir values in the saline study of plasma glucose, insulin, glucagon, and GIP were similar to the other three studies prior to autonomic blockade. During the latter 2 hr of the glucose perfusion, the plasma glucose and glucagon responses to saline did not differ from responses to the three blocking agents. Phentolamine but not atropine or propranolol resulted in a greater insulin response compared to saline (3247 +/- 762 vs 1348 +/- 388 microU/ml/120 min, P less than 0.01). GIP was not significantly affected by phentolamine (18,146 +/- 4574), propranolol (7585 +/- 5854), or atropine (15,797 +/- 6297) compared to saline (11,717 +/- 5204 pg/ml/120 min). Glucose absorption was unaffected by infusions of saline, phentolamine, and propranolol, but was increased following atropine infusion (5841 +/- 1120 vs 1044 +/- 808 mg/120 min, P less than 0.02). There appears to be no direct effect of the autonomic nervous system on glucose-induced secretion of GIP.

Gastric inhibitory polypeptide (GIP) concentrations may be influenced by obesity, diabetes, and glucagon deficiency and be under feedback inhibition by insulin. To assess these factors, insulin-dependent diabetic, totally pancreatectomized diabetic, and lean and obese noninsulin-dependent diabetic patients were studied twice, once during partial insulin withdrawal and again when euglycemia was achieved before and after mixed meal ingestion, using an artificial endocrine pancreas. The results were compared to those from weight-matched lean and obese nondiabetic subjects. No significant differences in postprandial GIP responses were found between lean and obese nondiabetic subjects. Despite basal and postprandial hyperglycemia, the GIP responses to the mixed meal were not significantly different between insulin-deficient (insulin-dependent and totally pancreatectomized) patients and lean nondiabetic subjects. In addition, there were no significant differences in postprandial GIP responses between insulin-dependent and totally pancreatectomized patients. In contrast, lean and obese noninsulin-dependent diabetic patients had reduced GIP responses compared to weight-matched nondiabetic subjects (mean +/- SE, 37.9 +/- 5.4 vs. 67.1 +/- 10.8 ng ml-1 240 min-1, respectively; P less than 0.05). This difference was entirely due to the reduced GIP responses in obese noninsulin-dependent diabetic patients compared to those in obese nondiabetic subjects (32.1 +/- 7.9 vs. 76.9 +/- 18.2 ng ml-1 240 min-1, respectively; P less than 0.05); the postprandial GIP responses were not significantly different between lean noninsulin-dependent diabetic patients and lean nondiabetic subjects. Insulin infusion by an artificial endocrine pancreas resulted in postprandial insulin and glucose profiles that approximated those of nondiabetics, but did not significantly alter GIP responses to the mixed meal (48.2 +/- 5.5 ng ml-1 240 min-1) in the 18 diabetic patients compared to results obtained with sc insulin treatment (42.2 +/- 5.2 ng ml-1 240 min-1). In conclusion, postprandial GIP responses are normal in obese nondiabetic subjects and insulin-deficient diabetic patients and are blunted in obese, but not in lean, noninsulin-dependent diabetic patients. In addition, GIP does not appear to be under feedback inhibition by insulin or influenced by glucagon deficiency in diabetes.

The isolation of the human form of PHI (peptide HI) is described. The peptide was purified from human colonic extracts by using a chemical method for the detection of its C-terminal amidated structure. Human PHI consists of 27 amino acid residues and the complete amino acid sequence is: His-Ala-Asp-Gly-Val-Phe-Thr-Ser-Asp-Phe-Ser-Lys-Leu-Leu-Gly-Gln-Leu-Ser-Ala-Lys-Lys-Tyr-Leu-Glu-Ser-Leu-Met-NH2. The differences between the structures of porcine and human PHI are at position 12 (Arg/Lys replacement) and at position 27 (Ile/Met). Human PHIPorcine PHIBovine PHIBrain peptideGut peptideC-terminal amideVIP/PHI precursor

The general hormonal requirements for the restoration of spermatogenesis in regressed hypophysectomized rats were investigated. With the aid of the Staput fractionation technique, it was established that thymidine-3H was readily incorporated into spermatogonia and resting spermatocytes. Labeled cells did not progress to form appreciable numbers of primary spermatocytes or spermatids in the absence of hormonal replacement. The inhibition of formation of pachytene primary spermatocytes in hypophysectomized rats was overcome by administration of follicle-stimulating hormone (FSH), luteinizing hormone (LH), or testosterone, but a combination of either FSH plus LH, or FSH plus testosterone, was required for the progression of pachytene primary spermatocytes to spermatids and spermatozoa. Carnitine acetyltransferase (CAT) measurements in testes from various groups of animals provided ancillary evidence consistent with the conclusion that either FSH, LH, or testosterone was required for the normal restoration of pachytene-diplotene spermatocyte formation. However, one or more additional blocks in spermatogenesis existed in hypophysectomized animals, since elevation of depressed testicular CAT levels in hypophysectomized rats to normal levels required FSH plus LH, or FSH plus testosterone. Cortisone and thyroxin treatment had no measurable effects on testicular function in hypophysectomized rats.

Levels of carnitine acetyltransferase (CAT) in testes from neonatal rats were approximately 5% of those obtained in testes from adult rats. The changing activities measured during development indicated that maximal rates of increase were achieved at a time when mature primary spermatocytes were being generated. Spermatogonia had lowest CAT levels (0.16 unit/108 cells) while diplotene primary spermatocytes had highest CAT activities (6.1 units/108 cells). The apparent specific activities of other mitochondrial enzymes measured (glutamic dehydrogenase, carnitine palmitoyltransferase, and cytochrome oxidase) in testis did not increase at a time when CAT levels were elevated by over sevenfold.In adult hypophysectomized rats, CAT levels in testes decreased during the regression period, with most rapid rates of loss of activities at times corresponding to the diminution of spermatids and spermatocytes. The CAT activities in testes of fully regressed hypophysectomized rats were low, but were slightly higher than values obtained in testes from 7- and 14-day-old rats. The data were discussed in relation to the use of CAT levels as a biochemical indicator of the relative number of spermatogonia and spermatocytes in rat testes.

Sera from 171 patients with advanced lung cancer, from 110 normals, and from 123 subjects with benign respiratory diseases were analyzed for 10 substances to detect lung cancer: ferritin, lipid-bound sialic acid, total sialic acid, beta 2-microglobulin, lipotropin, the alpha and beta subunits of human chorionic gonadotropin, calcitonin (two assays), parathyroid hormone, and carcinoembryonic antigen. Individual markers were studied, and optimal combinations of markers were sought for discriminating lung cancer patients from normals and from patients with benign lung disease. Numerous methods for combining the markers were examined, but the methods of logistic regression and recursive partitioning were finally adopted. The best discrimination rules we could find used only carcinoembryonic antigen (CEA) and total sialic acid (TSA). The performance of these rules was validated on an independent serum panel containing sera from 68 patients with advanced lung cancer, from 40 normals, and from 52 patients with benign respiratory disease. The combination rules based on TSA and CEA performed better than a rule based on CEA alone. Logistic discrimination rules with TSA and CEA that were designed to have 95% specificity achieved 54% sensitivity for discriminating advanced lung cancer from normal controls and 52% sensitivity for discriminating advanced lung cancer from controls with benign disease. Some aspects of clinical applicability are discussed, including planned studies for localized lung cancer and the requirement for further testing in specific clinical settings.

As part of a prospective diagnostic protocol, patients suspected of having pancreatic cancer had systemic and portal venous blood samples assayed, in coded batches, for peptide hormones and enzymes thought to be of potential value as tumor markers. An average of 111 patients were tested for each candidate marker. Results were analyzed by dividing patients into three groups according to the definitive diagnoses. These were pancreatic cancer (32% of patients), other cancers (27%), and benign diseases (41%). Although elevated mean levels of fasting plasma glucose and serum alkaline phosphatase were found in the pancreatic cancer group, there were no significant differences in the mean levels of any of the candidate markers studied in the three groups. The diagnostic values of normal and elevated levels of each candidate marker studied have been calculated. None has proven to be as useful as the serum level of pancreatic oncofetal antigen, fasting plasma glucose, or serum alkaline phosphatase in the diagnosis or exclusion of pancreatic cancer.

• The rate of disappearance from the circulation of exogenous heptadecapeptide gastrin was studied before and after 50% distal small-bowel resection in four rhesus monkeys. For each study, venous blood samples were drawn during, and at frequent intervals after, a one-hour peripheral venous infusion of synthetic human gastrin 1 given at a constant rate within the range of 0.4 to 2.4 μg/hr/kg of body weight. The rate of disappearance of infused gastrin was not affected by small-bowel resection (mean half-time before operation, 2.50 minutes; mean half-time after operation, 2.47 minutes). These data indicate that in the rhesus monkey, the rate of catabolism of exogenous gastrin is not decreased after distal small-bowel resection, and indicate that other mechanisms are responsible for the hypergastrinemia and gastric acid hypersecretion observed in this animal model. (Arch Surg1981;116:297-300)

Restoration of testicular function in long-term hypo-physectomized rats given different hormonal treatments during the various cycles of the seminiferous epithelium was evaluated on the basis of the weights of testes, epididymides, and other accessory sexual glands, histological examination of testes, and determination of the numbers of spermatozoa/epididymis. The staput fractionation technique for the separation of classes of germinal cells was employed to provide a measure of the advancing front of pulse-labelled cells following the intratesticular administration of (3-H)thymidinemthe results suggested that during the first two cycles, in which spermatogonia develop into pachytene spermatocytes, either LH or testosterone alone was sufficient for partial restoration. During the third cycle of the seminiferous epithelium, LH and FSH were required to allow previously labelled pachytene spermatocytes to progress efficiently to stage 7 spermatids. Administration of LH alone during the final cycle was sufficient to permit stage 7 spermatids to develop into spermatozoa, provided LH plus H had been given during the previous three cycles. Injection of LH during the entire period and of FSH during the third cycle of the seminiferous epithelium was required to achieve Staput profiles characteristic of a normal advancing front of pulse-labelled cells, and to allow partial restoration of spermatogenesis. More complete restoration was obtained in rats given FSH and LH during the first three cycles but, with the doses employed, the number of spermatoza/testis remained subnormal. Efficient completion of each cycle of the seminiferous epithelium appeared to be hormone-dependent. The data are discussed in relation to the possibility that hormones may affect the general development of germinal cells in an indirect manner by their influence on Sertoli cell function.

The human vasoactive intestinal polypeptide (VIP) has been isolated from colonic tissue. The amino acid composition and N-terminus (histidine) of the human VIP are identical to those previously reported for bovine and porcine VIP.

We have shown previously the presence of a non-cholinergic, non-adrenergic excitatory innervation in the muscularis mucosa of the canine colon. Immunoreactive-like substance P was released in response to nerve stimulation. This release was reduced in the presence of tetrodotoxin and in a calcium-free solution. Bombesin, another peptide present in this muscle, was excitatory when applied exogenously. Excitation with bombesin was blocked by tetrodotoxin. The aims of this study therefore were to determine if bombesin is released during nerve stimulation and if bombesin causes contraction by releasing substance P. Strips of muscularis mucosa were placed in a superfusion apparatus to record contractile activity. Intramural nerves were stimulated by two platinum wire electrodes. The superfusate which passed over each strip was collected and assayed for bombesin-and substance P-like immunoreactivity. Under control conditions, the concentration of bombesin was 6.0 ± 0.9 pg/ml (mean ± SEM). Following nerve stimulation (10 Hz, 10 V, 200 µs) the concentration of bombesin in the superfusate increased significantly (p < 0.02) to 9.41 ± 0.98 pg/ml (mean ± SEM). In the presence of tetrodotoxin (10-6 M) and in a calcium-free bathing solution, the increase in immunoreactive-like bombesin in the superfusate was no longer observed (respectively: 6.37 ± 1.07 pg/m1 and 7.5 ± 1.4 pg/ml). Furthermore, applied bombesin (10-6 M) increased substance P levels (28 ± 1.7 pg/ml) in the superfusate. This increase was reduced significantly (p < 0.05) by tetrodotoxin (11.4 ± 6.5 pg/ml). Finally, with substance P-antiserum in the superfusate (dilution 1:75), the excitatory response induced by either nerve stimulation or exogenous bombesin was decreased. We conclude from these observations that transmural stimulation releases bombesin from intramural nerves and that bombesin acts on substance P-containing nerves to release substance P, thereby causing contraction. (Supported by NIH Grant AM 17238.)

Gastric inhibitory polypeptide (GIP) is considered to be the principal mediator of the enteroinsular axis. A glucose-insulin clamp technique was used to study the effects of differing blood glucose levels on the insulinotropic and glucagonotropic actions of fat-stimulated GIP in seven healthy subjects, as well as the effect of physiologic hyperinsulinemia on GIP secretion. Blood glucose levels were clamped for 4 h at 43+/-2 mg/dl (hypoglycemic clamp), 88+/-1 mg/dl (euglycemic clamp), and 141+/-2 mg/dl (hyperglycemic clamp) in the presence of a constant insulin infusion (100 m U/kg per h). Under hypoglycemic clamp conditions there was no increase in C-peptide nor glucagon after Lipomul ingestion, despite an increase of GIP of 51.7+/-8.7 ng/ml per 120 min. Under euglycemic clamp conditions, small and inconsistent increases in C-peptide and glucagon were observed after fat ingestion and a concomitant increase of GIP of 35.2+/-9.4 ng/ml per 120 min. Under hyperglycemic clamp conditions after fat ingestion and a GIP increase of 24.0+/-5.7 ng/ml per 120 min, C-peptide increased from 6.4+/-5 ng/ml to 11.0+/-1.1 ng/ml (P0.01) but glucagon did not change. These findings confirm that in healthy man GIP exerts its insulinotropic properties only under hyperglycemic conditions and indicate that GIP is not glucagonotropic. Under euglycemic clamp conditions (plasma glucose, 89+/-1 mg/dl) and physiologic hyperinsulinemia (serum immunoreactive insulin, 137+/-3 muU/ml) GIP responses to fat ingestion (39.7+/-9.8 ng/ml per 120 min) were not different from the GIP responses to fat ingestion in the absence of hyperinsulinemia (39.7+/-11.1 ng/ml per 120 min). Therefore, insulin under normoglycemic conditions does not exert an inhibitory effect on fat-stimulated GIP secretion. The higher GIP response to oral fat in the hypoglycemic clamp, and the lower GIP response in the hyperglycemic clamp compared to the response in the euglycemic clamp suggests an effect of glycemia itself on GIP secretion in the presence of hyperinsulinemia.

The intracellular microelectrode technique was used to determine the effects of pentagastrin, G-17 (synthetic human gastrin I) and G-34 (natural human G-34 I) on the electrical activity of single cells of the circular layer of canine antral muscles. Mechanical activity of the cells was simultaneously monitored by attaching a transducer to measure tension in the direction of the long axis of the circular fibres. The preparation measured approximately 2 × 7 mm. In this tissue, the action potential consists of an upstroke potential followed by a plateau potential. Changes in the strength of contraction are related to changes in the size of the plateau potential. All three forms of gastrin increased the action potential frequency and the amplitude and duration of the action potential plateau. Similarly, the frequency and force of contractions were increased. Dose-response curves for the effects on electrical activity were determined for single cells. The mean ED50 for the effect of pentagastrin on plateau amplitude was 5 × 10−12 ± 1.5 × 10−12 M (n = 4) and on frequency was 5.5 × 10−10 ± 2.5 × 10−10 M (n = 3). G-17 was found to be slightly less potent, with ED50 for plateau amplitude and frequency being 3.9 × 10−11 ± 2.1 × 10−11M (n = 4) and 2.0 × 10−9± 0.4 × 10−9M (n = 3), respectively. This difference in potency was confirmed by determining the dose-response curves for both agents in a single cell. Although there is a difference in potency, the comparison of both agents in a single cell indicates that the efficacies are similar. For both G-17 and pentagastrin, the effects on the size of the action potential plateau occurred in a lower concentration range than the effect on frequency. The effects on the plateau occur within the range of concentrations of gastrin present in the blood after a meal, whereas the effects on frequency are probably relevant only with respect to conditions of hypergastrinaemia. A sufficient quantity of G-34 was available for a single dose (3 × 10−10 M) but not for an entire dose-response curve. This dose was effective in increasing the size of the action potential plateau, action potential frequency, and the frequency and force of contraction. The effects of this dose were compared with the dose-response curve for G-17 obtained from the same cell. The results indicate that G-34 may have a greater biological activity than G-17 both on electrical and mechanical activity. We conclude that both G-17 and G-34 have physiological actions on canine gastric antral motility.

Fordtran [1] und Barreras [2] haben als Erste gezeigt, das orales Calciumcarbonat in pharmakologischen Dosen die Magensauresekretion in Patienten mit Duodenalulcus stimuliert.

A sedimentation velocity chamber at unit gravity (Staput fractionation) was employed to separate cells obtained from suspensions of testes from adult rats, and the differential cell count was determined to estimate the sedimentation profiles of cell populations in various fractions. The incorporation of thymidine-3H into acid-insoluble portions of cell fractions was measured at varying times following the intratesticular administration of thymidine. The kinetic profiles of thymidine-3H incorporation into spermatogonia, primary spermatocytes, spermatids, and spermatozoa were compared with radioautographs prepared from histological sections of testes obtained from the same animals. Good correlations were observed between radioactivity peaks in Staput fractions and grain localization in cells of the spermatogenesis cycle at varying time periods after thymidine-3H injection. Data obtained with the Staput technique can be rapidly quantitated. The limits of the Staput fractionation technique for the separation of cells from the rat testis were evaluated with respect to the possible isolation of homogeneous populations for biochemical studies, and to the currently more amenable separation of heterogeneous classes of cells for kinetic studies. The usefulness of the method was validated for application to subsequent investigations.

The pattern of intercellular cytoplasmic bridges between rat spermatogonia and between spermatocytes is illustrated from electron microscopy of serial sections. Clones, or syncytia, containing as many as 22 connected spermatogonia and as many as 74 connected spermatocytes were observed. The absence of closed rings of cells agrees with the observation that intercellular bridges are the result of incomplete cell division, rather than cell fusion. The bridges thus are a record of spermatogonial divisions within a clone. In early spermatogonial generations there is a predominantly linear arrangement. The groups of spermatocytes have more side branches. From the presence of synaptonemal complexes it is concluded that the connected spermatocytes of a given clone are in about the same developmental stage. The pattern of intercellular bridges indicates, however, that not all nuclei in a clone undergo mitosis in the same cycle. The connected cells of a clone are therefore not all of the same generation. From unconnected bridges it is assumed that new clones originate from single cells or groups of spermatogonia which separate from an existing clone.

Intracellular microelectrode and standard organ bath techniques were used to study in vitro the effects of three molecular forms of the peptide cholecystokinin on the electrical and mechanical activities of canine antral circular muscle. Three forms were studied: the carboxyl-terminal octapeptide of cholecystokinin (CCK-OP), the molecule containing 33 amino acid residues (CCK33), and the peptide termed "cholecystokinin variant" that contains 39 amino acids (CCK39). All three forms increased the force and frequency of spontaneous contractions. They also increased the frequency and the amplitude and duration of the plateau of the gastric action potential. Atropine did not block any of these effects, suggesting that the action of these peptides was largely due to a direct action on the smooth muscle. Complete dose-response curves were determined for the effect of these peptides on the force and frequency of contraction for muscle strips and for the effect on amplitude of the plateau and frequency of the action potential for single cells. CCK39 and CCK-OP had similar potencies and both forms were more potent than CCK33.