Dietary carbohydrate level and glucose metabolism in turkey poults.

1. Feeding British United turkeys (BUT) and Nicholas turkeys (NT) diets with varying carbohydrate levels for 24 hr post-hatch resulted in lower hepatic glucose-6-phosphatase activity and higher plasma glucose levels as dietary carbohydrate level was increased. 2. There were no differences between the strains in liver weight or glucose-6-phosphatase activity, but BUT exhibited higher plasma glucose values than did NT at the two highest levels of carbohydrate. Plasma glucose did not differ between strains at the lowest level of carbohydrate or in fasted poults. 3. Blood glucose values were consistently higher in both strains when sampled 1 hr after initial sampling of fasted poults. 4. Both strains were able to maintain the 1 hr blood glucose levels through 24 hr when kept at approximately 37 degrees C. 5. When held at approximately 21 C for the first hour and at approximately 37 degrees C through 24 hr fasted NT were able to maintain the initial blood glucose rise while BUT were not.     

Thyroid hormone response to thyrotrophin releasing hormone (TRH) in the sex-linked dwarf chicken

The effect of an injection of thyrotrophin releasing hormone (TRH) on plasma levels of thyroid hormones was studied in dwarf and normal Rhode Island Red chickens with similar genotypes other than for the sex-linked dwarf gene dw. The sex-linked dwarf chickens had different plasma iodothyronine levels from control normal chickens: high thyroxine (T4), low triiodothyronine (T3) and similar reverse T3 (rT3) levels. The injection of TRH (10 micrograms/kg) in 5-day- and 5-week-old normal chickens increased the plasma T4 within 30 min without a significant increase in T3, whereas the injection of TRH in 11-and 26-week-old normal chickens increased plasma T3 60 min later. In dwarfs the response of T4 to TRH was the same as that in normals but no increased T3 response was observed. The plasma level of rT3 was not influenced by the TRH injection in either strain. These results suggest that although in the sex-linked dwarfs thyroidal response to exogenous TRH is similar to that of normals, the dwarf gene dw inhibits the conversion of T4 to T3 in peripheral tissues without any inhibitory effect on rT3 production.     

Growth hormone and seawater adaptation in coho salmon, Oncorhynchus kisutch

1. Effects of growth hormone (GH) were examined on short-term aspects of seawater adaptation in coho salmon smolts. 2. Injection of somatostatin (SRIF) immediately prior to seawater entry suppressed plasma GH levels, but did not have any significant effects at 6 or 12 hr on hematocrits, plasma glucose or plasma Na+ levels. 3. Plasma GH levels increased 250% within 36 hr after seawater exposure. 4. Plasma glucose levels, in contrast, were significantly lower in the seawater fish after 36 hr post-exposure. 5. Plasma Na+ levels increased to 190 mEq/1 by 24 hr but subsequently returned to freshwater levels while hematocrits showed no significant changes over the 72 hr of exposure. 6. The significance of these results is discussed in terms of successful seawater adaptation in coho salmon.     

Variations of Some Physiological and Immunological Parameters in Siberian Sturgeon (Acipenser baerii,Brandt, 1869) Subjected to an Acute Stressor

This study was carried out to investigate the effect of an acute stressor on the variation of some physiological and immunological parameters of Siberian sturgeon (Acipenser baerii) juveniles. Fish, reared in 3 tanks for 10 weeks, were used for this study. The acute stress of fish consisted of 2 min of air exposure stress. Plasma levels of cortisol, glucose, and lactate as well as lysozyme activity in plasma were measured before stress and 1 hr, 3 hr, 6 hr, 9 hr, 12 hr, and 24 hr after stress. The plasma cortisol significantly increased in the highest level 1 hr after stress, yet it gradually declined after 3 hr. The glucose significantly increased only 1 hr after stress. There was no significant difference between plasma lactate prestress and poststress. Moreover, lysozyme activity was enhanced by stress, thus reaching the highest level 9 hr after stress. The results of this study indicate that Siberian sturgeon not only have a rapid response to acute stress, but also a great capacity for recovery from stress, thus returning physiological parameters to prestress levels after 6 hr.     

Effects of cysteamine administration on plasma concentration of metabolites, pancreatic glucagon and insulin in the chicken

1. The effects of subcutaneous injection of cysteamine (2-mercaptoethylamine, 300 mg/kg) were investigated in 5-6 week-old chickens. 2. In the short term (1 hr), cysteamine increased plasma levels of glucose, free fatty acids and insulin, and decreased that of alpha-amino non protein nitrogen. 3. In a longer term (17-24 hr), cysteamine increased the plasma level of glucose, did not modify those of alpha-amino non protein nitrogen, insulin and glucagon and decreased that of free fatty acids. 4. The disposal of an oral glucose load was impaired and the glucose-induced inhibition of pancreatic glucagon and stimulation of insulin release were blunted 17 hr after cysteamine administration. 5. Therefore, cysteamine exerts multiple effects on chicken pancreatic islet cells.     

Effects of hypophysectomy on plasma levels of pancreatic polypeptide (APP) and insulin in adult chickens

Adenohypophysectomy (hypox) was carried out in adult chickens in an attempt to assess what role, if any, the anterior pituitary gland plays in maintaining basal levels of plasma insulin (IRI) and avian pancreatic polypeptide (APP) both before and immediately after a fast-refeed regimen. Each bird was tube-fed 61 gms twice daily, body weights were taken daily, and blood samples drawn daily just before the second feeding. All birds were fasted for 24 hr on days 4-5, another blood sample taken, and then refed the usual gruel. Blood samples were taken at 5,15,30,90 and 180 min after refeeding. Hypox caused an immediate and sustained decrease in plasma IRI and a significant but transient increase in plasma APP which lasted 3-4 days before returning to normal; plasma glucose was marginally decreased. Refeeding resulted in a trend of less response (increase) in all three parameters studied in the hypox group. It is suggested that in chickens, hypox may lead to a release phenomenon from a normal inhibitory role which the anterior pituitary gland plays on APP release.     

Effect of propranolol and isoproterenol on plasma thyroxine and triiodothyronine concentration in rainbow trout (Salmo gairdneri)

1. Rainbow trout (Salmo gairdneri) given a single intraperioneal injection of propanolol (a β-adrenoceptor inhibitor) had plasma triiodothyronine (T3) levels which were significantly (P < 0.01) lower than in control fish 8 hr after the injection, but not after 24hr; thyroxine (T4) levels and T4/T3 ratios were not significantly affected.2. Isoproterenol (a β-adrenoceptor stimulator) had no effect on T4, T3 or T4/T3 ratios.3. A single intraperitorial injection of TSH and prolactin given together induced a significant increase (P < 0.05) in plasma T3 levels 24 hr after the injection.4. TSH and prolactin given to propanol-treated fish caused a further significant increase in T3 levels compared with TSH + prolactin-, TSH-, prolactin-, or solvent-injected groups (P < 0.01).5. The data suggest that the inhibition of peripheral monodeiodination of T4 to T3 by propranolol, well documented in mammals, does not occur in rainbow trout. On the contrary, T3 levels after propranolol administration are increased in conditions where thyroid simulation occurs.     

How closely do circulating blood glucose levels reflect feeding state in fowls?

1. Amounts of food eaten in 30 min, by fasted-refed immature hens, were not correlated with plasma glucose levels before feeding, or with increases in glucose after feeding. 2. When previously fasted birds were given 0, 5, 10, 15 or 20 g food to eat, their plasma glucose increased by similar amounts with 10, 15 and 20 g, by slightly less with 5 g, and hardly at all with 0 g. 3. When food was removed from free-feeding birds, their plasma glucose levels declined slightly in 2 hr and then remained steady. They declined markedly further overnight, but recovered to a level higher than before deprivation when 10 g food was provided. 4. Four hours darkness during normal daytime had no effect on plasma glucose in fasted-refed birds, but sight of food and presentation of an empty food pan caused slight increases in glucose in 24-hr fasted birds. 5. It is concluded that blood glucose in fowls fluctuates around several "typical" levels, but that there is also much variation between and within birds. Direct (absorbed) and indirect (thermogenic) consequences of feeding probably both contribute to fluctuations in glucose, and these seem more likely to influence regulation of food intake in the longer-term rather than the short-term.     

Isoleucine, a potent plasma glucose-lowering amino acid, stimulates glucose uptake in C2C12 myotubes

To examine which branched-chain amino acids affect the plasma glucose levels, we investigated the effects of leucine, isoleucine, and valine (0.3 g/kg body weight p.o.) in normal rats using the oral glucose tolerance test (OGTT, 2 g/kg). A single oral administration of isoleucine significantly reduced plasma glucose levels 30 and 60 min after the glucose bolus, whereas administration of leucine and valine did not produce a significant decrease. Oral administration of valine significantly enhanced the plasma glucose level at 30 min after the glucose administration and leucine had a similar effect at 120 min. At each measurement timepoint, the insulin levels of the treated groups were lower than that of the control group. We then investigated the effects of leucine, isoleucine or valine at the same concentration (1 mM) on glucose metabolism in C(2)C(12) myotubes in the absence of insulin. Glucose consumption was elevated by 16.8% in the presence of 1 mM isoleucine compared with the control. Conversely, 1 mM leucine or valine caused no significant changes in glucose consumption in the C(2)C(12) myotubes. The 2-deoxyglucose uptake of C(2)C(12) myotubes significantly increased upon exposure to 1-10 mM isoleucine and 5-10 mM leucine. However, isoleucine caused no significant difference in glycogen synthesis in C(2)C(12) myotubes, although leucine and valine caused a significant increase in intracellular glycogen compared with the control. The isoleucine effect on glucose uptake was mediated by phosphatidylinositol 3-kinase (PI3K), but was independent of mammalian target of rapamycin (mTOR). These results suggest that isoleucine stimulates the insulin-independent glucose uptake in skeletal muscle cells, which may contribute to the plasma glucose-lowering effect of isoleucine in normal rats.     

Gluconeogenesis in perfused chicken kidney. Effects of feeding and starvation

1. Starvation for 48 hr doubled the rate of gluconeogenesis from lactate and pyruvate in perfused chicken kidney, but did not change the rate of production of glucose from malate, succinate, or alpha-ketoglutarate. 2. Amino-oxyacetate and D-malate inhibited the production of glucose from lactate and from pyruvate by 55% in each case. Quinolinate reduced the production of glucose from lactate and from pyruvate by 50% in both fed and starved chickens, but had no effect on the production of glucose from intermediates in the citric acid cycle. 3. Starvation increased the rate of formation of mitochondrial phosphoenolpyruvate from pyruvate, but had no effect on the rate of formation of mitochondrial phosphoenolpyruvate from malate.     

Regulation of glucose transport and transporter 4 (GLUT-4) in muscle and adipocytes of sucrose-fed rats: effects of N-3 poly- and monounsaturated fatty acids.

The goal of this study was to compare the short-term effects of dietary n-3 polyunsaturated (fish oil) and monounsaturated (olive oil) fatty acids on glucose transport, plasma glucose and lipid controls in a dietary insulin resistance model using sucrose-fed rats. The underlying cellular and molecular mechanisms were also determined in the muscle and adipose tissue. Male Sprague-Dawley rats (5 weeks old) were randomized for diets containing 57.5 % (w/w) sucrose and 14 % lipids as either fish oil (SF), olive oil (SO) or a mixture of standard oils (SC) for 3 weeks. A fourth control group (C) was fed a diet containing 57.5 % starch and 14 % standard oils. After three weeks on the diet, body weight was comparable in the four groups. The sucrose-fed rats were hyperglycemic and hyperinsulinemic in response to glucose load. The presence of fish oil in the sucrose diet prevented sucrose-induced hyperinsulinemia and hypertriglyceridemia, but had no effect on plasma glucose levels. Insulin-stimulated glucose transport in adipocytes increased after feeding with fish oil (p < 0.005). These modifications were associated with increased Glut-4 protein (p < 0.05) and mRNA levels in adipocytes. In the muscle, no effect was found on Glut-4 protein levels. Olive oil, however, could not bring about any improvement in plasma insulin, plasma lipids or Glut-4 protein levels. We therefore conclude that the presence of fish oil, in contrast to olive oil, prevents insulin resistance and hypertriglyceridemia in rats on a sucrose diet, and restores Glut-4 protein quantity in adipocytes but not in muscle at basal levels. Dietary regulation of Glut-4 proteins appears to be tissue specific and might depend on insulin stimulation and/or duration of dietary interventions.     

The serum ferroxidase activity and the iron mobilization by estrogens

The serum ferroxidase activity and the iron mobilization of estrogens were studied in chickens and turkeys. Serum iron and copper were determined in 20 male chickens, 5 adult females (not laying), 12 laying chickens, 13 male turkeys, 5 adult females (not laying), and 4 laying turkeys. Serum iron and copper increased simultaneously during the laying period as a consequence of a higher estrogen level during this period. Evidence of this was obtained by injecting estradiol benzoate (3 mg estradiol, 3 times/week for 2 weeks) which produced a 6-fold increase of serum iron and copper. The levels dropped to base line values after a third week without treatment. A maximum ferroxidase activity was noted during the laying period representing a 20-fold incre ase while iron showed a 7-fold increase. 2 mg diethylstilbestrol/kg adm inistered to 6 immature pullets demonstrated an increase in the ferroxid ase activity with a peak at 36 hours and a peak of iron at 60 hours. Serum mare gonadotrophin caused a significant increase in ferroxidase activity by Day 14 (p less than .0001). These results suggest that the ferroxidase induction by exogenous estrogens or by endogenous estrogens is an identical effect.     

The effect of islet amyloid polypeptide (amylin) and calcitonin gene-related peptide on glucose removal in the anaesthetized rat and on insulin secretion from rat pancreatic isletsin vitro

The effect of intravenous infusion of islet amyloid polypeptide (IAPP/amylin) and calcitonin gene-related peptide (CGRP) on blood glucose and plasma insulin in the basal and glucose-stimulated state was investigated in the anaesthetized rat. Both peptides had no effect on basal blood glucose or plasma insulin but following an intravenous bolus of glucose, CGRP-treated rats were hyperglycaemic and hyperinsulinaemic compared with control animals which were similar to IAPP-treated rats. IAPP had no effect on glucose-stimulated islet insulin secretion. These results suggest that CGRP, but not IAPP, alters glucose removalin vivo.     

Plasma Insulin in Response to Enterostatin and Effect of Adrenalectomy in Rats

Enterostatin has previously been reported to alter serum insulin and corticosterone levels after central administration of the peptide. The purpose of the present study was to investigate the effect of peripheral administration of enterostatin on insulin and corticosterone levels as well as the response of plasma insulin to enterostatin administration in adrena-lectomized rats. Female Sprague-Dawley rats were given a bolus injection intravenously with enterostatin alone or together with glucose. Enterostatin increased basal plasma levels of insulin, but significantly inhibited the increase in plasma insulin stimulated by glucose. Plasma corticosterone levels were not altered after a single intravenous injection of enterostatin. In rats infused chronically with enterostatin, plasma insulin levels were significantly reduced and plasma corticosterone levels were increased. The daily food intake was lower in these rats, but there was no effect on body weight. After adrenalectomy, the responsiveness of plasma insulin to enterostatin infusion was completely abolished. Furthermore, adrenalectomy itself reduced basal plasma levels of insulin and increased plasma levels of endogenous enterostatin. These results suggest that peripheral enterostatin administration produces a similar effect as central infusion of the peptide, and that the glucocorticoid hormones are involved in the regulation of plasma insulin by enterostatin.     

Effects of pH on the gill ATPase activity and blood composition of whitefish (Coregonus peled) and trout (Salmo trutta fario)

1. The effects of pH on blood composition and gill (Na+ + Mg2+) ATPase activity were studied in 142 whitefish and trout kept for 3 to 17 hr in tanks at pH 3.0-9.5 in Northern Finland. 2. pH clearly influenced all blood values, except plasma alanine and aspartate aminotransferases. Blood haemoglobin and packed cell volume of whitefish and trout were lower at pH 9.5 but higher at pH 3.0 than those of controls at pH 6.5. 3. Both fishes had lowest plasma sodium and chloride values in groups kept for 9 to 17 hr in tanks with water acidified to pH 3.0 to 3.5. Changes in the plasma chloride concentration were associated with plasma sodium (r = 0.92, n = 102, P less than 0.001). 4. The gill (Na+ + K+ + Mg2+) ATPase of trout showed high activity over wide ranges of pH (6.0-7.5) at 13 degrees C having a distinct optimum at pH 7.0. 5. Blood glucose and lactate concentrations of whitefish and trout increased after exposure to acid and base. High values at pH 3.0 to 3.5 suggested hypoxic stress due to acidaemia.     

Effect of atrial natriuretic factor on plasma vasopressin in conscious rats

An intravenous (IV) bolus injection (10 μg) of synthetic rat atrial natriuretic factor [ANF (Arg 101-Tyr 126)] into normal conscious Sprague-Dawley rats produced a significant decrease of plasma arginine vasopressin (AVP) while 1-, 2-, and 5-μg doses exerted no such effect. Mean arterial blood pressure (MAP) was lowered about 15 mmHg by an IV 10 μg bolus injection of ANF. When plasma AVP rose significantly in rats exposed to such osmotic stimuli as 600 mM NaCl and 900 mM mannitol intraperitoneally (IP), subsequent IV injection of ANF (10 μg) markedly depressed this parameter. Lower doses of ANF were ineffective against 600 mM NaCl IP. The significant elevation of plasma AVP levels by hypertonic sucrose 900 mM IP was not modified by ANF (10 μg). Blood pressure remained unchanged after IP administration of various osmotic stimuli, except mannitol, and in all these experiments an IV bolus of ANF exerted a lowering effect on MAP. Seventy-two hr water deprivation (mixed osmotic and volume stimulus) resulted in elevated plasma AVP levels which were unaffected by an IV bolus injection of ANF at doses of 0.06–10 μg. Immunoreactive ANF (IR-ANF) rose in plasma to 39.3±13 ng/ml 1 min after an IV bolus injection of 10 μg ANF, dropping to 1.01±0.2 ng/ml after 5 min and to 0.32±0.01 ng/ml after 10 min (when ANF and AVP interactions were studied), but still remained approximately six times higher than in control rats. These results suggest that, in the conscious rat, only pharmacological levels of ANF observed after an IV bolus infusion may influence both resting and osmotically-stimulated AVP levels.     

Glucoregulatory effects of bombesin in lean and genetically obese hyperglycaemic (ob/ob) mice

1. Plasma glucose and insulin responses to bombesin were examined in 12-15-week-old 12 hr fasted lean and genetically obese hyperglycaemic (ob/ob) mice. 2. Bombesin (1 mg/kg ip) produced a prompt but transient increase of plasma insulin in lean mice (maximum increase of 50% at 5 min), and a more slowly generated but protracted insulin response in ob/ob mice (maximum increase of 80% at 30 min). Plasma glucose concentrations of both groups of mice were increased by bombesin (maximum increases of 40 and 48% respectively in lean and ob/ob mice at 15 min). 3. When administered with glucose (2 g/kg ip), bombesin (1 mg/kg ip) rapidly increased insulin concentrations of lean and ob/ob mice (maximum increases of 39 and 63% respectively at 5 min). Bombesin did not significantly alter the rise of plasma glucose after exogenous glucose administration to these mice. 4. The results indicate that bombesin exerts an insulin-releasing effect in lean and ob/ob mice. The greater insulin-releasing effect in ob/ob mice renders bombesin a possible component of the overactive entero-insular axis in the ob/ob mutant, especially if it acts within the islets as a neurotransmitter or paracrine agent.     

Hypoglycemic activity of Cajanus cajan (seeds) in mice.

The effect of roasted and unroasted seeds of C. cajan on serum glucose levels of normal and alloxan diabetic mice were studied. Single doses of unroasted seeds (60% and 80%) on administration to normal as well as alloxanized mice showed significant reduction in the serum glucose levels after 1-2 hr and a significant rise at 3 hr. In case of roasted seeds, on other hand there was a significant increase in serum glucose levels during 3 hr experimental period. It is therefore concluded that roasting of seeds at high temperature for an half hour period resulted in the total loss of hypoglycemic principle but not the hyperglycemic principle present in the seeds.     

Dynamics of plasma Ca and calcitonin levels in stonefish (Inimicus japonicus) administered a high-Ca solution into the stomach

In stonefish, changes in plasma total Ca and calcitonin levels were examined after administration of a high-Ca solution into the stomach. Blood was taken successively at 0, 1, 3, 9, 33, and 81 hr from a fine tube cannulated into the aortic bulb. Plasma Ca levels increased acutely at 1 hr and attained the peak after 3-9 hr of the administration. Although plasma calcitonin levels did not exhibit conspicuous changes for 1-3 hr, they began to rise significantly at 33 hr. The plasma Ca level began to decline significantly at 33 hr, although the level was still significantly higher than the initial level. At 33 hr, however, the plasma calcitonin level still continued to increase. At 81 hr, the plasma Ca level had returned to the initial level. At that time, the plasma calcitonin level was also significantly lower than that at 33 hr. These results suggest that, in stonefish, the ultimobranchial gland has the ability to respond physiologically to rises in plasma Ca levels, to secrete calcitonin, and to cease the secretion when the plasma Ca levels return to the initial level.     

Antihyperglycemic effects of 3-O-methyl-D-chiro-inositol and D-chiro-inositol associated with manganese in streptozotocin diabetic rats.

The acute effects after administration of 3-O-Methyl-D-Chiro-inositol, D-Chiro-inositol and manganese, components of the pH 2.0 putative mediator of insulin action, on plasma glucose were examined in low dose streptozotocin-treated rats. 3-O-Methyl-D-Chiro-inositol at a bolus dose of 5 mg/kg decreased plasma glucose 6% at 120 min (p < 0.05). A higher bolus dose of 3-O-Methyl-D-Chiro-inositol (15 mg/kg) promoted a more persistent hypoglycemic effect of 22% at 120 min (p < 0.05). Infusion of 8.3 microg/min of manganese chloride lowered plasma glucose by 23% (p < 0.05). 3-O-Methyl-D-Chiro-inositol (15 mg/kg) together with manganese chloride (8.3 microg/min) promoted a reduction of 49% in 120 min (p < 0.05). D-Chiro-inositol at a bolus dose of 5 mg/kg had no effect. A single dose of 15 mg/kg produced a reduction of 21% (p < 0.05) in 120 min. D-Chiro-inositol (15 mg/kg) associated with manganese chloride (8.3 microg/min) decreased elevated plasma glucose 47% (p < 0.05) in 120 min. D-Chiro-inositol coadministered with manganese reduced glucose concentrations during the final 60 min (p < 0.05). 3-O-Methyl-D-Chiro-inositol and D-chiro-inositol are components of the mediator structure. Manganese is also a presumed component of the mediator, having an important role in glucose uptake, insulin release and mediator generation. These compounds have also been identified in the literature as hypoglycemic agents.