Effects of serotonergic agents on survival and hemolymph composition of the larval mosquito Aedes aegypti (Diptera: Culicidae, L.) in vivo: does serotonin regulate hemolymph acid-base homeostasis?

The role of serotonin in the regulation of larval Aedes aegypti hemolymph composition was investigated in vivo using two reuptake inhibitors (SSRIs), alaproclate HCl and 6-nitroquipazine maleate, and the receptor antagonist methiothepin mesylate. Larvae were placed in media differing in pH and salinity in the presence and absence of serotonergic agents. The toxicity of each agent was strongly influenced by ambient pH. For each agent, toxicity was negligible in acidic media, intermediate in neutral media and greatest in alkaline media. By contrast, toxicity of all agents was independent of salinity. No effects on mass-specific body water or hemolymph volume were observed whereas hemolymph osmotic pressure, Na(+) concentrations and pH differed significantly among treatments. 6-nitroquipazine caused a decrease in Na(+) from 115+/-1.7 to 103+/-0.9 mmol l(-1), and alaproclate caused alkalosis of the hemolymph from pH 7.55+/-0.026 to pH 7.72+/-0.044. Methiothepin decreased hemolymph osmotic pressure from 329+/-9.9 to 304+/-8.8 and showed the greatest overall toxicity. Control larvae excreted net base in pH 4 media (1.4 micromol g(-1) h(-1)) and net acid in pH 7 (1.2 micromol g(-1) h(-1)) and pH 11 (5.1 micromol g(-1) h(-1)) media. In pH 4 media, alaproclate and methiothepin caused a shift to net H(+) excretion (1.1 and 1.5 micromol g(-1) h(1), respectively) whereas these agents did not influence acid excretion rates in pH 7 or pH 11 media. The hypothesis that serotonin is involved in hemolymph acid-base balance is discussed.

Cyclic nucleotides in pancreatic islets. Tolbutamide- and arginine-induced insulin release.

With the use of isolated rat islet perfusion, levels of the islet cyclic adenosine 3' ,5' -monophosphate (cAMP) were compared with dynamic insulin secretion induced by tolbutamide and arginine. Tolbutamide elevated islet cAMP rapidly and augmented both glucose-induced islet cAMP levels and insulin secretion; arginine, however, did not elevate islet cAMP but did enhance glucose-induced insulin secretion. Since the latter result could have been modulated by cyclic guanosine 3' ,5' -monophosphate, this cyclic nucleotide was also measured and found to remain unchanged during stimulation of insulin secretion by arginine and a combination or arginine and glucose. Thus, the action of tolbutamide appears to be modulated in part by cAMP, whereas arginine appears to augment insulin secretion independently of cyclic nucleotides.

Effect of low-dose somatostatin infusion on pancreatic and gastric endocrine function in lean and obese nondiabetic human subjects.

The present study was designed to compare, in lean and obese nondiabetic subjects, basal and postprandial levels of peripheral venous plasma insulin, glucagon, gastrin, pancreatic polypeptide (PP), glucose, triglycerides, and somatostatin-like immunoreactivity (SLI) during the infusion of synthetic somatostatin-14 or saline. Thirty-five minutes before the ingestion of the test meal, an infusion of synthetic somatostatin-14 was started at a rate of 0.5 ng/kg X min and was increased to 1.0 ng/kg X min 30 min after consumption of the meal and lasted for another 90 min. During the infusion of saline, basal peripheral vein levels of insulin, gastrin, and triglycerides were elevated in obese subjects, whereas basal plasma SLI levels were significantly lower compared with the lean controls. Basal glucagon and PP levels were similar in both groups. After the ingestion of the meal, augmented concentrations of insulin and gastrin were observed in the obese subjects, whereas postprandial SLI and PP levels were reduced. Chromatography of fasting plasma revealed all measurable SLI to be confined to the void volume fractions of a Bio-Gel P-10 column. The rise in SLI after the meal was due to an increase of SLI co-eluting with somatostatin-28 and somatostatin-14. During the infusion of somatostatin, only basal insulin levels were significantly lower in the obese subjects, whereas no change of any basal hormone level was observed in the lean group. During the infusion of somatostatin, SLI levels were elevated by 20-30 pg/ml in both groups compared with the saline controls. During the infusion rate of 0.5 ng/kg X min, only postprandial PP levels were reduced significantly in the obese group, while all the other parameters were unaffected in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence for the detrimental effect of adrenaline infused to healthy dogs in doses imitating spontaneous secretion after coronary occlusion.

We have previously shown that acute coronary occlusion in the dog is often accompanied by increased adrenaline release into the blood. In the present study the consequences of this humoral reaction were studied in anaesthetised healthy mongrel dogs subjected to adrenaline infusion administered at a rate relevant to spontaneous release of this amine in coronary occlusion. Adrenaline was infused in a dose of 1.2 microgram.kg-1.min-1 for 4 h. Dogs receiving saline served as the control. Adrenaline administration led to the decrease in insulin/glucose ratio, to a significant fall in serum triiodothyronine and in blood pH. Free fatty acid levels doubled. Histochemically, a diminution in succinic dehydrogenase and ATPase activity in adrenaline-treated hearts was found. A significant fall in the activity of mitochondrial hexokinase in these hearts was detected spectrophotometrically. Electron microscopic study revealed alterations in the mitochondrial structure. These findings indicate that an excess of adrenaline in ammounts similar to that seen in experimental infarction leads to profound metabolic and hormonal disturbances and exerts a detrimental effect upon myocardium.

[Immunogenicity of semisynthetic human insulin Novo--five year prospective studies]. / Immunogennosc insuliny ludzkiej pólsyntetycznej Novo--5-letnie badania prospektywne.

The aim of the study was to compare the immunogenicity of semisynthetic human and porcine monocomponent (MC) insulin Novo during--5-year observation. Thirty-one diabetic patients, never previously treated with insulin were randomly allocated to treatment with one of the two coded insulin preparations in a double blind trial. 15 patients aged 20-58 years (mean age--36 years) were treated with human insulin and 16 diabetics aged 19-61 years (mean age--34 years) with MC pork insulin. The insulin was injected twice a day (Actrapid plus Monotard). Serum insulin-binding antibodies were determined according to Christiansen (radioimmunoelectrophoretic method). The development of insulin-binding antibodies during the first year of observation was more rapid in patients treated with MC pork insulin but thereafter it was similar in the two studied groups. After 5 years of treatment with human insulin serum insulin-binding antibodies were found in 14 patients. The level of antibodies was very low (< 0.130 mU/ml) in 5 subjects, low (0.171-0.401 mU/ml) in 6 patients and relatively high (0.885; 1.186; 5, 162 mU/ml) in 3 patients. In the group of diabetics treated with MC pork insulin after 5 years of observation serum insulin-binding antibodies were found in 12 patients. The level of antibodies was low (0.131-0.576 mU/ml) in 9 subjects and relatively high (1.034; 3.954; 5.639 mU/ml) in 3 patients. The results obtained after 2-5 years of the study did not differ significantly (Wilcoxon's test, p > 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Controlled study comparing treatment with monocomponent insulin and conventional insulin in patients with lipoatrophy.

Twenty-one patients with evident lipoatrophy treated with conventional (Conv.) insulin were either allocated to continuation of treatment with previously used insulin (Conv. group, n = 10) or were transferred to Lente MC (monocomponent) insulin with or without supplementary Actrapid MC insulin (MC group, n = 11). On entry and after 3, 6 and 12 months of follow-up, serum insulin-, pancreatic polypeptide- and proinsulin-binding IgGs were determined by radioimmunoelectrophoresis according to the method of Christiansen. Prior to determination of proinsulin-binding IgG, the insulin-binding IgG was removed by means of sepharose-bound insulin according to the method of Heding. In both groups a slight decrease in the titer of insulin-binding IgG was observed: in the Conv. group from 5.33 +/- 0.92 (SEM) to 4.66 +/- 1.17 mU/ml after 12 months, and in the MC group from 3.22 +/- 0.64 to 2.66 +/- 0.46 mU/ml, respectively. Due to the small number of patients with pancreatic polypeptide antibody titers above the detection limit no statistical evaluation was carried out. The level of serum proinsulin-binding IgG decreased in the MC group only (from 9.3 +/- 2.2 to 1.9 +/- 0.6 ng/ml after 12 months), and even showed a slight increase in the Conv. group (the respective titers were: 14.0 +/- 4.6 and 14.9 +/- 4.6 ng/ml). In the MC group 10 patients (91%) showed improvement and 7 (64%) complete regression of their lipoatrophy corresponding to 6 (60%) and 2 (20%) in the Conv. group. This finding suggests a possible role of proinsulin-binding antibodies in the pathogenesis of insulin lipoatrophy.

Patients with intractable angina: free thyroxine index, immunoreactive insulin and free fatty acids in blood, free adrenaline and noradrenaline in urine.

The activity of adrenergic system, thyroid gland and blood levels of insulin and FFA were studied in 120 patients with intractable angina. Noradrenaline excretion was normal but that of adrenaline was augmented in a vast majority of patients and even doubled in 27% of cases. Free thyroxine index values were abnormally high in 22% of cases and inversely correlated with ergometric performance. A diabetic-like insulin response after 50.0 g oral glucose intake was found in 10 out of 26 examined patients. Abnormally high values of FFA were observed in 66%. The mechanisms likely to account for these alterations and their suspected influence on clinical course of intractable angina are discussed.

[Cholinergic regulation of insulin and glucagon secretion in healthy people and in patients with non-insulin dependent diabetes]. / Cholinerge Regulation der Insulin- und Glukagonsekretion bei Gesunden und Patienten mit nichtinsulinabhängigem Diabetes.

In 10 healthy subjects and in 10 patients with non-insulin-dependent, well controlled diabetes the following three tests were carried out in each persons: 1. the intravenous infusion of 25 g of L-arginine over 30 min, 2. the intravenous infusion of L-arginine plus prostigmin (0.01 mg per kg body weight), and 3. the intravenous infusion of L-arginine plus atropine (0.01 mg per kg body weight). Venous blood glucose, plasma insulin (IRI) and plasma glucagon (IRG) were determined on fasting and throughout the tests. The cholinergic stimulation increased, and the cholinergic blockade decreased the insulin and glucagon secretion during intravenous L-arginine infusion, both in healthy subjects and in diabetics, these effects being less marked (not significantly) in the latter group of test persons. On the other hand, neither prostigmin, nor atropine modified the behavior of blood glucose in comparison to the course of glycaemia observed during the infusion of L-arginine alone. These observations are an evidence of an integrative effect of the cholinergic system on the function of A- and B-cells of the pancreatic islets, which may be of importance for the proper utilization of food substrates.

[Somatostatin-like activity (SLI) in the blood during metformin treatment of obese patients with diabetes mellitus type 2]. / Poziom aktywnosci somatostatynopodobnej (SLI) we krwi podczas leczenia metformina otylych pacjentów z cukrzyca typu 2.

Plasma somatostatin-like activity (SLI) was measured in obese women with type 2 diabetes in fasting condition and after a test meal (714 kcal: 27% carbohydrates, 8% protein, 73% fat). The tests were done twice: first, after a week of dietetic treatment and then 7 days of metformin administration, 1.5 g a day. Blood glucose and insulin concentration (IRI) were also followed throughout the test. The plasma SLI on fasting and after the test meal, before and after treatment with metformin did not show any significant differences. Blood glucose was lower in the fasting state significantly and serum insulin showed a tendency to decrease at the end of the test. These findings contradict the hypothesis of a possible role of somatostatin in peripheral blood in the enteric effect of metformin. The local (paracrine?) action of SLI secreted after metformin administration cannot be excluded.

Serum insulin, pancreatic glucagon and growth hormone levels in response to intravenous infusion of L-arginine in patients with recently detected juvenile diabetes.

The secretion of insulin, glucagon and growth hormone was determined in the serum of patients with recently diagnosed juvenile-type diabetes (10 patients) during stimulation by intravenous infusion of L-arginine and was compared with the results found in a group of five healthy persons. The value of the insulinemia was significantly lower in the diabetics as compared with the healthy controls. Serum glucagon levels were higher in all diabetics when fasting and after L-arginine administration as compared with the controls but a significant difference was observed only at the peck of secretion (5 min after L-arginine administration). Growth hormone concentration was slightly higher in the diabetics after secretory stimulation than in the controls, particularly at the peak of secretion (30 and 45 min) but the difference was statistically no significant.

Patterns of endocrine reactivity in patients with recent myocardial infarction. Clinical and biochemical correlations: trial of endocrine therapy.

The following endocrine function parameters were studied serially in a group of 10 patients with recent myocardial infarction: blood and urinary levels of epinephrine and norepinephrine, urinary excretion of vanillyl-mandelic acid; protein-bound iodine, Hamolsky test (Hamolsky, Stein, and Freedberg, 1957); blood insulin; 24-hour urinary excretion of 17-hydroxycorticoids, sodium, and potassium. The acute phase of myocardial infarction, especially in those patients with a severe clinical course (rhythm disturbances, coronary insufficiency, circulatory failure), was associated with disturbed endocrine reactivity. The most frequent and the earliest feature was the increased level of the 24-hour urinary excretion of epinephrine, combined with a pronounced decrease in blood insulin level. Later in the course of the disease, as the adrenergic reactivity returned to normal, there was an increase in blood insulin to normal levels. In 3 patients with severe clinical symptoms of acute myocardial infarction, there were, in addition to the increased 24-hour urinary excretion of catecholamines, a decreased blood insulin, higher than normal levels of protein-bound iodine, and of the Hamolsky test. One of these patients developed hypoadrenia. It is possible that the abnormal endocrine reactions accelerate the catabolic processes within cardiac tissue (catecholamines, thyroid hormones), especially when there is a possible functional deficiency of hormones, occurring as a general adaptation reaction to stress (cortisol, insulin). The disturbances that follow may be dangerous for the patient.

Insulin secretion. Interrelationships of glucose, cyclic adenosine 3:5-monophosphate, and calcium.

Glucose elevates both cyclic adenosine 3:5-monophosphate (cyclic AMP) and insulin secretion rapidly and in a parallel dose-dependent fashion in perifused rat islets. Theophylline stimulates cyclic AMP much more than glucose, yet secretion is much less. When the two agents are combined, cyclic AMP is similar to theophylline alone yet secretion is augmented synergistically. Glucose-induced cyclic AMP generation and insulin secretion are dependent on extracellular calcium. Theophylline-induced insulin secretion is also extracellular calcium-dependent; however, theophylline-induced cyclic AMP elevation is independent of extracellular calcium. Thus, extracellular calcium has multiple effects on insulin secretion, some of which appear unrelated to a terminal secretory process. When glucose is combined with theophylline at physiologic levels of extracellular calcium, both the first and second phases of secretion are prominent. At extracellular calcium levels of 0.05 mM, only the second phase is prominent whereas at 10 nM extracellular calcium (ethylene glycol bis(beta-aminoethyl ether)-N,-tetraacetic acid) only the first phase is prominent. A divalent cation ionophore (a23187, Eli Lilly), which transports calcium and magnesium ions across biological membranes, was used to elucidate further the role of calcium and magnesium. If the ionophore (10 muM) is perifused for 5 min at low extracellular calcium and magnesium, and physiologic calcium is then added, a sudden spike of insulin release occurs in the absence of cyclic AMP generation. Similar results were obtained with magnesium. When the ionophore is perifused for 30 min at low calcium and magnesium, insulin secretion again occurs in the absence of cyclic AMP generation. Electron microscopic examination of the B cells following perifusion with the ionophore shows no specific alterations. These observations suggest that: (a) glucose elevates cyclic AMP, but the latter acts primarily as a positive feed-forward modulator of glucose-induced insulin release; and (b) extracellular calcium has multiple effects on insulin secretion both upon, and independent of, the cyclic AMP system.

The effect of phenformin on amino acid-induced insulin secretion in diabetics.

Twenty-one patients with mild maturity-onset diabetes were given introduodenal infusions of an amino acid mixture (0.5 g amino acids per kg body weight). In 9 other patients L-arginine was infused intravenously in a constant dose of 25 g. Alpha-amino nitrogen, blood glucose and plasma insulin levels were assayed under control conditions and after three days of treatment with phenformin, 150 mg daily, plus the same 150 mg dose 60 min before the second loading. Intraduodenal infusion of the amino acid mixture provoked a greater increase in plasma insulin than intravenous infusion of L-arginine, this increase being significantly inhibited by phenformin only in the first case. Since no evident influence of phenformin on the intestinal absorption of amino acids could be demonstrated, this effect may be explained by a local action on the intestinal wall exposed to high concentrations of the drug, resulting in the inhibition of the insulin secretion stimulating activity of the gut.