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Ovarian hormone secretion is regulated by gonadotropins, and it has been demonstrated that this response is modulated by nitric oxide (NO). The focus of this study was to determine the effect of chronic NO deficiency on the secretion of ovarian steroids. Female rats were given N-nitro-L-arginine (L-NNA; 0.6 g/L) in their drinking water, and vaginal smears were obtained daily. By 4 wk of treatment, all the rats were in constant estrus or proestrus. At 6-8 wk the animals were killed; the ovaries were removed and incubated in the presence of eCG (1 IU/ml) and hCG (1 IU/ml) and/or S-nitroso-L-acetyl penicillamine (an NO donor, S-NAP; 0.1 mM) for 4 h. Medium was collected at 30-min intervals, and estradiol, progesterone, and androstenedione were measured. Ovaries from proestrous rats served as controls. Ovaries from L-NNA-treated animals had a greater basal and gonadotropin-stimulated release of estradiol but not of androstenedione or progesterone in comparison to ovaries from untreated controls. S-NAP decreased the gonadotropin-stimulated estradiol, progesterone, and androstenedione in ovaries from NO-deficient rats. Steroid secretion in controls was not responsive to S-NAP. We conclude that chronic NO inhibition produces constant estrus due to increased estradiol production and that NO acts to inhibit estradiol and androstenedione production.

The effects of acetaldehyde (ACA) were examined in isolated electrically driven papillary muscle preparations from normal and streptozotocin-treated diabetic rats. Muscles from diabetic rats developed greater tension than those from normal rats. In muscles from both groups, ACA caused concentration-dependent negative inotropic effects that were independent of cholinergic or purinergic mechanisms and were not attributable to nitric oxide (NO) release. ACA was three to five times more potent with regard to its negative inotropic effect in diabetic than in normal rat muscles. A propranolol-sensitive, sympathetically mediated positive inotropic effect occurred at certain concentrations. Decreasing [Ca2+]o from 2.7 to 0.5 mM reduced basal developed force to a significantly greater extent in muscles from normal rats than in those from diabetic rats. In low [Ca2+]o, concentration-response curves to CaCl2 in diabetic muscles were displaced to the left of that in normal muscles, suggesting that diabetic muscles are more sensitive to the positive inotropic effect of added CaCl2 at low [Ca2+]o, whereas at higher [Ca2+]o (1 mM), normal muscles developed more force in response to added CaCl2. ACA 10 and 30 mM more readily inhibited CaCl2-induced positive inotropic effect in normal than in diabetic muscles. Force-frequency curves, (negative staircase response) were recorded in both normal and diabetic muscles. In diabetic muscles, the curve exhibited a positive component at the lowest frequencies applied and was displaced to the right of that in normal muscle. ACA concentration-dependently inhibited force development, and diabetic muscles were more susceptible to the negative inotropic effect of ACA, when the stimulation frequency was increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Previous studies from our laboratory showed that diabetes increases platelet aggregation in rats, but only in washed platelets. In the present study, we evaluated platelet aggregation coupled with adenosine triphosphate (ATP) release in normal and diabetic rats using a whole blood electrical aggregometer. Additionally, we investigated the role of endothelium-derived relaxing factor, or nitric oxide, in the platelet reactivity in diabetic rats. Rats were made diabetic using streptozocin, 55 mg/kg. After 1 month the rats were anesthetized, and arterial blood samples were collected directly into sodium citrate solution 3.8%. Platelet counts and mean platelet volumes were determined. Platelet aggregation, disaggregation, and ATP release in response to adenosine diphosphate (ADP), collagen, and arachidonic acid were measured. Platelet aggregation in response to ADP, collagen, and arachidonic acid was not different in diabetic rats when compared with that in controls. However, ATP release in response to ADP was significantly increased in diabetic rats. Platelets from diabetic animals were significantly larger than those of controls. Nitro-L-arginine methyl ester, a nitric oxide synthase inhibitor, decreased platelet aggregation in response to ADP in the normal animals, but not in the diabetic animals. However, arginine-induced nitric oxide production decreased platelet aggregation and enhanced the occurrence of disaggregation in platelets from both normal and diabetic rats. From these studies, we conclude that platelet aggregation in diabetic rats is not different using whole blood electrical aggregation, but platelet ATP secretion is significantly enhanced. Additionally, nitric oxide may modulate the platelet aggregation, disaggregation, and ATP secretory response. However, it does not appear to be a major factor in the altered aggregation responses in diabetic rats.

We studied the metabolic and cardiovascular responses to insulin-induced hypoglycemia, 2-deoxyglucose-induced glucose cytopenia, and hyperglycemia in normal rats and in rats with streptozocin-induced diabetes. Insulin (2.0 U/kg) was infused intravenously into normal and 4-week diabetic rats, and the cardiovascular responses were monitored for 90 minutes. Insulin infusion decreased plasma glucose and mean arterial pressure by the same relative degree in both groups of animals. Heart rate was significantly decreased only in the diabetic rats. The injection of 2-deoxyglucose was followed by an increase in plasma glucose in both normal and diabetic rats. Heart rate was increased in normal rats, and both mean arterial pressure and heart rate decreased in the diabetic animals. Hyperglycemia induced by infusion of glucose increased plasma glucose and insulin and decreased mean arterial pressure and heart rate in both groups of animals. We concluded that acute insulin or insulin-induced hypoglycemia decreases cardiovascular tone in normals and, to a significantly greater extent, in diabetic rats and that while 2-deoxyglucose-induced glucose cytopenia increases cardiovascular tone in normal rats, it elicits a hypotensive response in diabetic ones. Glucose-induced hyperglycemia is associated with a decrease in cardiovascular tone in both groups of animals.

The autoregulation of insulin secretion was studied using perifused and incubated pancreatic islets of normal (obOb) mice and of their obese-hyperglycemic (obob) littermates. Islets secreted more insulin when they were perifused than when they were incubated and insulin was allowed to accumulate in the medium. When rat insulin was added to the incubation medium in the concentration of 250 μU/ml, the secretory activity of the normal islets was suppressed almost completely. The concentration of exogenous insulin required to inhibit the islets of obese mice was higher and increased with the age of the animals, until it reached a value that was 20 to 30 times greater than that found in the circulating blood. Similar concentrations may well exist in the extracellular fluid of the pancreatic islets. It is possible that while insulin resistance of the peripheral tissues may be responsible for the hyperglycemia of the obob mice, the progressive loss of insulin sensitivity of their pancreatic islets and, consequently, of the normal autoregulation of insulin secretion, may play a role in the progressive hyperinsulinism and, hence, of the obesity characteristic of these animals.

A. Seaweed.—By means of a three-compartment cell with ceramic diaphragms, suspensions of dried ground Laminaria cloustoni stipe were electrodialysed to remove inorganic material. The total-ash content of the seaweed was reduced from 33.4 to 7.4% in 30 minutes, representing a removal of 78% of the ash. Tests were also made on dried, ground frond, and a much smaller removal was effected. The total-ash content was reduced from 28 to 22.8% in 30 minutes, representing a removal of about 18% of the ash. Duplicate tests were made to determine the amount of alkali and chlorine recovered and the energy required. The following figures were obtained (per Ib. of dry seaweed): alkali recovered, 0.053 Ib.; chlorine recovered (estimated), 0.056 Ib.; energy required, 3.03 kw. B. Fish albumen.—A three-compartment cell, with diaphragms of cellulosic material, was used for tests to reduce the ash content of fish albumen. It was found possible to reduce the ash content from 7.7 to 4.0% in 90 minutes, representing a removal of 52.3% of the inorganic material. The fact that not all the inorganic material is removed in either A or B is tentatively attributed to the presence of a certain proportion of it in an insoluble form such as calcium alginate in seaweed and calcium citrate in fish albumen. Electrodialysis of calcium alginate and calcium citrate gave results which supported this view.

Variables affecting the electrodeposition of basic magnesium carbonate and calcium carbonate from suspension in organic liquids have been investigated. Temperature has little effect. Deposition increases linearly, in most cases, with voltage, time, concentration and electrode surface. An unusual effect has been noted with high concentrations of materials containing a hydroxyl group, the amount of deposit increasing very rapidly with increasing concentration. With different organic liquids as suspending media, the amount of deposit increases with increasing dielectric constant in the series ethyl acetate, n-amyl alcohol, n-butyl alcohol, n-propyl alcohol, ethanol and methanol. With acetone and nitrobenzene little or no deposition is obtained, whereas cyclohexanone gives a result in agreement with the first series where magnesium carbonate is deposited, but gives no appreciable deposit with calcium carbonate. In certain cases a break occurs in the relationships when the deposit is heavy, possibly because the weight of the deposit causes a partial breaking-off. The mechanical strength of the deposit appears to depend upon the conditions of deposition. It has also been shown that the presence of small amounts of water or of acid has no apparent effect, but larger amounts cause, in the first case, an increasingly wet deposit and in the second, complete inhibition. The purity of the suspending medium can affect the action greatly. Heavy currents obtained during tests on calcium carbonate suspended in methanol are thought to be due to a reaction between these substances.

Although the detailed mechanism of action of NGF as it occurs in vivo still requires considerable clarification, a model in which NGF is generated by end organs of responsive neurons and interacts with these neurons to provide trophic stimulation and maintenance of viability seems highly plausible. The demonstration of NGF synthesis by these cells, including the details of the process, is required, and information regarding the events following the formation of the hormone-receptor complex at the plasma membrane must be obtained. However, the contribution of internalization and the possible role of the internalized receptor as a second messenger for generating the long-term effects of the hormone are particularly appealing. Any findings with NGF will almost certainly provide additional important insights into other polypeptide growth factors, particularly those substances found in the neurotrophic subset.

Hypochondroplasia is an autosomal dominant discrete form of short-limbed dwarfism with roentgenographic changes similar to, but distinctive from, achondroplasia. The patients are normal at birth and in early childhood present with short-limbed dwarfism, thick body build, long trunk, normal head, moderate lumbar lordosis and broad, stubby hands and feet. A high incidence of mental retardation and absence of other neurologic complications is distinctive from achondroplasia. Diagnosis of hypochondroplasia is primarily radiogrpahic. No single diagnostic radiographic sign is present, and thus, a complete radiographic survey of the whole skeleton is required for diagnosis. Pertinent radiographic findings include a normal skull, short, broad long bones with prominent bony sites of muscle attachment, normal growth plate, prominent styloid process of the ulna and lateral malleolus of the fibula, shortened base of the iliac bones, horizontal hypoplastic low-set sacrum and mild narrowing of the interpediculate distance of the lumbar spine. Differential diagnosis is from other types of short-limbed dwarfism, particularly achondroplasia. Kozlowski, an authority on hypochondroplasia, believes this form of short-limbed dwarfism, if carfully searched for, may be more common than achondroplasia.

Glucose, insulin (IRI), pancreatic (IRG) and total (GLI) immunoreactive glucagon were measured in the serum of normal hamsters and of hamsters with an insulin- and glucagon-secreting, transplantable insuloma. The tumor-bearing animals were hypoglycemic, hyperinsulinemic and hyperglucagonemic. The pancreatic islets of tumor-bearing animals secreted less glucagon and insulin in response to arginine or to changes in the glucose concentration of the medium, than did the islets of control hamsters. In addition, the introduction of glucose into the gastro-intestinal tract, which caused a significant rise in the serum GLI concentration of normal hamsters, failed to do so in the tumor-bearing animals. The results suggest that the high levels of serum glucagon and insulin induced by the tumor, suppressed IRI, IRG and GLI secretion in these animals.

Significant quantities of A cell and total glucagon were found in the systemic blood of eviscerated rats, especially following arginine infusion. These findings and the hyperglucagonemia previously observed in depancreatized and in eviscerated animals, prompted us to look for glucagon sources other than the pancreas and the gastrointestinal tract. Significant amounts of immunoreactive glucagon (IRG) were extracted from rat submaxillary and parotid gland tissue using a modification of the method of Kenny. This IRG could be measured with an antiglucagon serum specific for pancreatic or A cell glucagon and with an antiserum that crossreacts with extracts of intestinal mucosa. Intravenous injections of submaxillary gland extracts caused a significant increase in blood glucose in normal, but not in eviscerated rats. A-V differences in glucagon concentration between aorta and facial vein suggest that the salivary glands release glucagon into the circulation. Similarly, A-V differences between the blood of the aorta and of the renal vein suggest that the kidneys remove glucagon from the circulation in normal, but not in eviscerated rats. Indeed, the kidneys of eviscerated rats may release previously stored glucagon into the blood. No glucagon was found in the saliva. Glucagon release by the salivary glands and the kidneys may contribute to the hyperglucagonemia characteristic of depancreatized and eviscerated animals.

The release of glucagon from pancreatic and extrapancreatic sources was studied in normal rats and in rats carrying transplants of a MtT-W-15 tumor which secretes large quantities of growth hormone and prolactin. The tumor-bearing rats had high serum levels of A cell immunoreactive glucagon (IRGa), total immunoreactive glucagon (IRGT) and immunoreactive insulin (IRI) and an increased total glucagon and insulin content of the pancreas. Pancreatic islets isolated from tumor-bearing rats secreted more glucagon under basal conditions but did not respond significantly to low glucose stimulation. However, they contained more insulin per islet and secreted more insulin under basal and stimulated conditions. The serum IRGa response to arginine infusion in vivo was lower in the tumor-bearing than in the normal rats. The introduction of a 5% glucose solution into the small intestine caused similar increases in the level of serum IRGT in the two groups of rats. Thus, the tumor increased the total pancreatic glucagon content and basal secretion, blunted the A cell response to stimulation, but did not significantly alter the secretion of glucagon by the intestine. We attribute these responses to tumor-induced hypersomatotropinism although we cannot rule out an effect of the large amounts of circulating prolactin.

The ability of dispersed islet cells in a perifusion system to secrete glucagon and insulin in response to physiologic stimuli was investigated. Normal hamster islets were isolated by coUagenase digestion and the cells dispersed by sequential digestion with coUagenase and trypsin. Following a 50-min period of equilibrium in buffer with high glucose concentrations (5.0 mg/ml), glucagon secretion was stimulated by glucopenia and subsequently, inhibited by increasing the concentration of glucose. The responsiveness to glucose inhibition was significantly less in dispersed islet cells than in intact islets. However, the dispersed islet cells showed a significantly greater response to arginine. Glucagon secretion by dispersed islet cells was stimulated to tolbutamide and epinephrine but somatostatin had no effect. Dispersed islet cell preparations did not augment insulin secretion in response to glucose but did secrete more insulin in response to arginine. Intact islets secreted insulin in response to glucose but not arginine. We conclude that A cells in cell suspension do not need direct contact or an intact intra-islet environment in order to respond to glucose, arginine, epinephrine, or tolbutamide but the extent of response may be influenced by paracrine effects. However, paracrine relationships may be important in determining the response of B cells to secretagogues.

Somatostatin (SRIF) given intravenously, either as a single bolus or as a 2 hr infusion caused a significant prolongation of partial thromboplastin time (PTT) and depressed platelet counts and platelet aggregation in the rat. Following daily injections of protamin-zinc SRIF for 2 weeks the platelet count returned to normal, PTT remained prolonged and platelet aggregation was enhanced. The doses of SRIF used in this work were adequate to suppress the secretion of insulin and glucagon by the isolated pancreatic islets of treated animals.

The effect of acute and chronic ingestion of aspartame was studied in normal and streptozotocin-induced diabetic rats. In both groups, a single dose of aspartame caused an increase of approximately 12% in liver tryptophan oxygenase (TO) activity. In diabetic animals, the sweetener caused a decrease in blood and brain tryptophan and an increase in serum glucose and glucagon. Chronic ingestion of aspartame also caused increase in TO activity in both groups. It caused a decrease in fasting serum insulin in normal animals and an increase in serum glucose in diabetic animals. Aspartame may adversely affect the capacity to control glucose metabolism in the diabetic.

Tolbutamide and glibenclamide (glyburide) were administered to normal hamsters, mice or rats in daily doses proportional to their body weight and equivalent to those used in human therapy. The animals were sacrificed after 6 to 8 weeks of treatment. Pieces of pancreas or isolated pancreatic islets were incubated or perifused in a medium containing glucose or tolbutamide, with or without Ieucine-114C or glucose-U-14C. The results indicate that the B cells of sulfonylurea treated animals synthesized and released less insulin and oxidized less glucose than those of insulin or saline treated controls. Accordingly, at least in the glibenclamide treated animals, the tolerance for glucose and the insulinogenic response to a glucose load in vivo were suppressed. Although insular function tended to return, to normal after treatment was discontinued, the results reported in this paper do not support the generally accepted view that the lasting therapeutic effectiveness of the sulfonylureas is due to a beta-cytotrophic action.