Adrenal function in different phases of the estrous cycle in the domesticated silver fox, Vulpes fulvus

Experiments were made on silver foxes from a population which had been selected for 10 to 15 generations for the domestic behaviour and on animals from a control, unselected population. In females from both populations, studies were made of the level of 11-OHCS in the blood serum, in vitro production of 11-OHCS, the size of fascicular zone in the adrenal cortex, the volume of cellular nuclei and nucleoli, as well as the reaction of the adrenals in vitro to 2 doses of ACTH (1 and 5 units/g of the adrenals) during anestrus, proestrus and estrus. In control females, all the characters investigated significantly increased from anestrus to proestrus. In domesticated females, no changes in the production of 11-OHCS in vitro or changes in morphological features of the fascicular zone were observed in the course of estrous cycle. During proestrus, the adrenals of the domesticated animals were not able to increase the production of 11-OHCS in vitro after application of ACTH. The decrease in the reactivity of the adrenals to the effect of ACTH is presumably the main cause why in unselected females the adrenal are not activated during proestrus. Therefore, in the course of selection for the domestication type of behaviour, species specific dynamics of activation of the adrenals during estrous cycle is lost.     

Blood glucose and serum insulin levels in lean and genetically obese mice.

Fed and 24 hour fasted lean and genetically obese mice (ob/ob) were given a fixed glucose load per gm body weight by intraperitoneal and intragastric administration. Intraperitoneal glucose injection into the obese mice produced a prolonged elevated blood glucose level with a concomitant significant decrease of circulating insulin. Possible interpretations of this observation are discussed. In those obese animals in which glucose was administered intragastrically the fed obese mice had a blood glucose concentration of 450-500 mg% for a period of one hour but there was no increase in circulating insulin, however, in the fasted obese mice in which the glucose concentration was about 350 mg% for one hour, there was a significant increase in the circulating insulin levels. The fed and fasted lean mice showed normal glucose tolerance curves and the expected increase in circulating insulin following either intraperitoneal orintragastric glucose loads. It is concluded that hyperglycaemia in the ob/ob mice is unlikely to be the principal cause of hyperinsulinaemia.     

The postnatal ontogenetic characteristics of adrenal function in female water voles Arvicola terrestris with different fur colors

Studies have been made of the effect of colour mutation on the development of the adrenals in female aquatic voles. Colour mutation in homozygote results in retarded growth rate of the whole body and the adrenals, as well as in postnatal changes in the dynamics of corticosteron content in the blood. Obviously, the effect of colour mutation on plasma concentrations of corticosteron is realised mainly via extra-adrenal mechanisms since no differences were found in corticosteron production by the adrenals and in the adrenal reaction to ACTH (5 U/g of the adrenals) in vitro in growing aquatic voles. During postnatal life, mutant black females exhibited lower sensitivity of the adrenals to the inhibitory influence of estradiol (40 ng/100 mg of the adrenals) as compared to wild phenotype animals.     

Effects of hypo and hyperthyroidism on the response to glucose loading of blood glucose, ketones and insulin and liver glycogen as studied in the fasted rat

After receiving an i.p. glucose load, 24 h fasted thyroidectomized rats showed a progressive increase in blood glucose and a slow decrease in blood ketone bodies. Both liver glycogen and plasma insulin levels showed no differences within 60 min of the glucose administration. It is suggested that the glucose intolerance in these animals is partly due to an insulin deficiency. Thyroidectomized rats treated daily with 25 microgram of L-thyroxine/100 g body weight for 40 days responded to the glucose test with a supranormal and more persistent elevation of blood glucose but with a faster and a greater fall in blood ketone bodies, as compared to controls. Sixty min after the glucose loading, liver glucogen levels were lower and plasma insulin were slightly higher than controls. It is suggested that a diminished extraction of glucose during transhepatic passage can be responsible for the impaired glucose tolerance observed in the hyperthyroid animals.     

A porcine animal model to mimic the restart of enteral nutrition (refeeding-model)

With the aim towards establishing an animal model of total parenteral nutrition (TPN), 12 piglets aged 9 weeks (mean body weight 21 kg) were surgically provided with central venous catheters. Six piglets were nourished parenterally with the objective to reach a 14-d period of TPN; the other six piglets served as control and were fed normally. Only one animal from each group could be monitored over the whole period. Nine piglets were euthanised on d 13 and one on d 12. No animal showed fever or signs of septicaemia during the study. The levels of Ca, Mg, Na and P in the blood were within the normal range as were those for blood glucose and plasma creatinine. Symptoms of the TPN included: transient diarrhoea, occasional appearance of faecal blood and occasional absence of defecation. A reduced small intestine length and altered mucosal morphology and function were observed. One animal showed bile stasis at the end of the study. All TPN animals showed a remarkably high level of blood urea early in the morning. The intestinal symptoms observed may resemble the human situation during TPN. However, due to the fast growth rate, pigs aged 9 weeks have higher nutrient requirements per kg body weight. Consequently, the osmolality of the nutrient solution was necessarily high. Whether the significantly higher blood urea observed in the TPN group reflected a catabolic metabolism during the starving period at night-time could not be conclusively shown. Alternatively, it could reflect a slower growth rate and a resulting quantitative excess of amino acids (AA), or could have been the consequence of a suboptimal AA composition. A permanent infusion would be favourable in order not to overcharge the capacity for glucose uptake and amino acid metabolism during the infusion.     

Overwinter fasting and re-feeding in rainbow trout: plasma growth hormone and cortisol levels in relation to energy mobilisation

This study investigated the roles of cortisol and growth hormone (GH) during a period of fasting in overwintering salmonid fish. Indices of carbohydrate (plasma glucose, liver glycogen), lipid (plasma free fatty acids (FFAs)) and protein metabolism (plasma protein, total plasma amino acids) were determined, together with plasma GH, cortisol and somatolactin (SL) levels at intervals in three groups of rainbow trout (continuously fed; fasted for 9 weeks then fed; fasted for 17 weeks). In fasted fish, a decline in body weight and condition factor was accompanied by reduced plasma glucose and hepatic glycogen and increased plasma FFA. No consistent elevation of plasma GH occurred until after 8 weeks of fasting when plasma GH levels increased ninefold. No changes were observed in plasma total protein and AA until between weeks 13 and 17 when both were reduced significantly. When previously fasted fish resumed feeding, plasma glucose and FFA, and hepatic glycogen levels rapidly returned to control values and weight gain resumed. No significant changes in plasma cortisol levels, related to feeding regime, were evident at any point during the study and there was no evidence that SL played an active role in the response to fasting. The results suggest that overwinter fasting may not represent a significant nutritional stressor to rainbow trout and that energy mobilisation during fasting may be achieved without the involvement of GH, cortisol or SL.     

Functional characteristics of the adrenals in the ontogeny of male water voles Arvicola terrestris with various fur colorings

Studies have been made of the effect of colour mutations on the adrenal function in growing male voles. In postnatal life, the level of 11-oxycorticosteroids in the blood exhibited similar changes in brown (wild phenotype) and black (mutant) voles. The highest level was found in 1-2-month animals; a decrease took place to the 6th month which was followed by a secondary increase at the age of 8 months. Corticosteron production in vitro is the highest in brown males 5-month. In black voles, after 2 months the production remains unchanged, being rather high. In 5-, 6- and 8-month voles, corticosteron production in vitro increased, but not decreased after prior incubation. In mutant voles, the adrenals are more sensitive to stimulating effect of ACTH (5 units per 1 g of the adrenals) and inhibitory effect of estradiol (40 ng/100 mg) in vitro.     

Effects of human growth hormone on the porto-arterial concentration differences of glucose and amino acids in the newborn piglet.

It is known that growth hormone (GH) increases the mitotic index of duodenal crypt cells. In early life, such an effect could be of particular importance for the functional development of the intestine in terms of absorptive capacity. In this study, osmotic mini pumps were introduced into the abdominal cavity of newborn piglets. The pumps permitted a continuous infusion of either recombinant human growth hormone (rhGH) at a rate of 0.1 IU GH x kg(-1) x 24 h(-1) or of vehicle. After 7 days of treatment, a bolus of amino acids and glucose was infused into the duodenum. Following this bolus, there was a prompt rise in the plasma concentration of both amino acids and glucose, especially in blood withdrawn from the portal vein. Thus, when the differences in concentrations of both amino acids and glucose between portal and arterial blood plasma were calculated, these differences reached maximum values between 30 and 60 minutes after the bolus. In animals treated with GH, maximum values occurred at a lower level than in control animals. These reductions were in the order of 60% (P > 0.01) if calculated over the first hour of absorption. From this study, it might be concluded that GH does not improve the absorptive capacity of the small intestine in newborn piglets. Instead, GH seems to reduce the absorption dynamics of glucose and amino acids. The reason for this is obscure, but could imply a specific effect of GH on enterocyte function.     

Comparative changes with age of the fasting response in circulating ketone bodies, glucose and insulin and oral glucose tolerance test in the rat

1. Body weight loss in 48 hr fasted rats decreased with age. 2. Blood glucose and plasma RIA-insulin levels correlated negatively and positively respectively with body weight in fed rats. Fasting produced a greater fall in blood glucose and a smaller decrease in RIA-insulin in young than in old rats. 3. Blood ketone bodies correlated negatively with body weight after 48 hr fasting. 4. In oral glucose tolerance tests, blood glucose rose more in adult and old rats than in prepuberals when both fed and fasted. RIA-insulin levels rose more in prepuberals than in older rats when fed but not when fasted. 5. Changes in body composition and reduced insulin sensitivity with age are discussed.     

Leptin predicts bone and fat mass after accounting for the effects of diet and glucocorticoid treatment in piglets

The role of leptin in neonatal growth and bone metabolism has been investigated, but not simultaneously. The objectives of this study were to determine if leptin relates to bone mass during rapid growth; if consumption of maternal milk is related to elevated circulating concentrations of leptin resulting in higher fat mass; and if glucocorticoids result in higher fat mass and reduced bone mass due to elevated leptin. Thirty-two piglets were randomized to either a suckling or milk substitute plus either dexamethasone (DEX) or placebo injection for 15 days beginning at 5 days of age. Milk and blood samples were obtained at baseline, and after 15 days, blood was sampled again for measurement of leptin and bone biochemistry. Weight at baseline plus weight and length after 15 days were recorded, followed by measurement of whole body bone mineral content, bone area, and fat mass using dual energy x-ray absorptiometry. At baseline, plasma leptin was elevated in suckled piglets. Piglets that suckled had elevated fat mass as did those who received DEX. However, DEX resulted in suppressed weight and length, bone mass, and bone metabolism. Leptin was similar among groups after the 15 days. After accounting for body size and treatment effects, piglet plasma leptin was predictive of bone and fat mass. Leptin circulating early postnatally is linked to body composition, specifically fat and bone mass. Elevations in fat mass and reductions in bone mass observed after 15 days of DEX treatment are not related to leptin metabolism. Both human and porcine neonates share similar characteristics with respect to relationships of leptin with fat and bone mass.     

Hepatic iron content corresponds with the susceptibility of lymphocytes to oxidative stress in neonatal pigs

The pig is born with limited iron supplies. If not supplemented, piglets dramatically loose their body iron stores during the first few days of postnatal life. The aim of this study was to investigate the influence of hepatic iron content on susceptibility of blood cells to oxidative stress. Four 1-day-old and three 7-days-old animals were used in this study. The alkaline version of the comet assay was used to measure DNA damage. As expected, iron body stores of non-supplemented animals decrease significantly during the first 4 days of life. However, no difference in background DNA damage was found between untreated lymphocytes from these two groups of animals, despite the difference in their hepatic iron content. Interestingly, DNA damage induced by H2O2 and X-radiation in lymphocytes taken from 1-day-old piglets was significantly higher than in those taken from 7-days-old animals. In contrast, NaOCl or tert-butyl-hydroxide also induced significant amounts of DNA damage, but no differences between the two groups of piglets were found. Our data show that decreased hepatic iron content corresponds with decreased susceptibility of blood lymphocytes to oxidative stressors.     

Hepatic iron content corresponds with the susceptibility of lymphocytes to oxidative stress in neonatal pigs

The pig is born with limited iron supplies. If not supplemented, piglets dramatically loose their body iron stores during the first few days of postnatal life. The aim of this study was to investigate the influence of hepatic iron content on susceptibility of blood cells to oxidative stress. Four 1-day-old and three 7-days-old animals were used in this study. The alkaline version of the comet assay was used to measure DNA damage. As expected, iron body stores of non-supplemented animals decrease significantly during the first 4 days of life. However, no difference in background DNA damage was found between untreated lymphocytes from these two groups of animals, despite the difference in their hepatic iron content. Interestingly, DNA damage induced by H₂O₂ and X-radiation in lymphocytes taken from 1-day-old piglets was significantly higher than in those taken from 7-days-old animals. In contrast, NaOCl or tert-butyl-hydroxide also induced significant amounts of DNA damage, but no differences between the two groups of piglets were found. Our data show that decreased hepatic iron content corresponds with decreased susceptibility of blood lymphocytes to oxidative stressors.     

Gluconeogenesis from glycine and serine in fasted normal and diabetic rats.

1. Non-anaesthetized normal and diabetic rats were fasted for 1 day, and [U-14C]glycine, or [U-14C]serine, or [U-14C]- plus [3-3H]-glucose was injected intra-arterially. The rates of synthesis de novo/irreversible disposal for glycine, serine and glucose, as well as the contribution of carbon atoms by the amino acids to plasma glucose, were calculated from the integrals of the specific-radioactivity-versus-time curves in plasma. 2. The concentrations of both glycine and serine in blood plasma were lower in diabetic than in fasted normal animals. 3. The rates of synthesis de novo/irreversible disposal of both amino acids tended to be lower in diabetic animals, but the decrease was statistically significant only for serine (14.3 compared with 10.5 mumol/min per kg). 4. Of the carbon atoms of plasma glucose, 2.9% arose from glycine in both fasted normal and diabetic rats, whereas 4.46% of glucose carbon originated from serine in fasted normal and 6.77% in diabetic rats. 5. As judged by their specific radioactivities, plasma serine and glycine exchange carbon atoms rapidly and extensively. 6. It was concluded that the turnover of glycine remains essentially unchanged, whereas that of serine is decreased in diabetic as compared with fasted normal rats. The plasma concentration of both amino acids was lower in diabetic rats. Both glycine and serine are glucogenic. In diabetic rats the contribution of carbon atoms from glycine to glucose increases in direct proportion to the increased glucose turnover, whereas the contribution by serine becomes also proportionally higher.     

Function of abnormal corpora lutea in vitro after GnRH-induced ovulation in the anoestrous ewe

Normal and abnormal corpora lutea were recovered from anoestrous Romney Marsh ewes on Days 3, 4, 5 and 6 after treatment with small-dose (250 ng) multiple injections of GnRH followed by a bolus injection (125 micrograms) with (+P) and without (-P) progesterone pretreatment and a study made of their characteristics in vitro. Plasma progesterone concentrations initially rose concurrently in all animals but abnormal luteal function occurred in 70% of the -P ewes and was defined on Day 5 when plasma progesterone concentrations declined relative to those in the +P ewes. All corpora lutea recovered on Days 3 and 4 appeared macroscopically similar and there were no significant differences between the +P and -P groups in terms of luteal weight, progesterone content and binding of 125I-labelled hCG on these days. However, corpora lutea from the -P animals only exhibited a decline in progesterone production in vitro on Day 4 (P less than 0.01), and morphological differences became apparent on Days 5 and 6 when the abnormal corpora lutea from the -P animals also decreased in weight (P less than 0.01) and progesterone content (P less than 0.001). Binding of 125I-labelled hCG increased on Day 5 in the normal corpora lutea only. These results show that, although abnormal luteal function induced by GnRH treatment of anoestrous ewes could not be distinguished from normal corpora lutea before Day 5 by measurement of progesterone in peripheral plasma, a significant decline in progesterone production in vitro occurred on Day 4 in the abnormal corpora lutea. This was followed by significant decreases in weight and progesterone content and a failure to increase 125I-labelled hCG binding. Abnormal corpora lutea are therefore capable of some initial growth and progesterone production, before undergoing a rapid and premature regression from Day 4, which has similar characteristics to natural luteolysis.     

Sulphonylureas-induced increase in insulin binding and glucose metabolism by isolated rat adipocytes

The effects of oral hypoglycaemic drugs, SPC-703 (n-/p-toluenesulphonyl/-5-methyl-2-pirazoline-1-carbonami de) and tolbutamide on insulin binding and glucose metabolism by isolated adipocytes were studied. After 10 days of administration of both sulphonylurea derivatives, no differences were observed in insulin concentration between both experimental and the control groups of animals, despite a significant fall in blood glucose level. SPC-703 and tolbutamide in concentrations of 1 mM added in vitro to the suspension of adipocytes had no effect on insulin binding or on basal and insulin simulated glucose metabolism. Daily administration of 300 mg/kg body weight of SPC-703 or tolbutamide for 10 days resulted in 48% and 34% increase of specific binding of insulin by adipocytes, respectively. From the Scatchard plot analysis we noted that the increase of binding resulted from increased affinity of insulin receptors for hormone. Simultaneous increase in basal and insulin stimulated glucose metabolism by adipocytes, as measured by 14CO2 production and 14C incorporation into cellular lipids, was observed. The results indicate that hypoglycaemic action of sulphonylureas may be explained by increased affinity of insulin receptors and the stimulating action of these compounds on peripheral glucose metabolism.     

Body size and composition of Crabeater seals (Lobodon carcinophagus), with observations on tissue and organ size in Ross seals (Ommatophoca rossi)

Linear body measurements and body weights of 17 Crabeater seals and four Ross seals were recorded, and the relationships of weight to linear dimensions were calculated. There were no significant differences between sexes of these relationships in Crabeater seals. All Ross seals were males.
The major body components (blood, fat, skin, muscle, bone, connective tissue and viscera) of seven Crabeater seals were weighed after dissection.
Blood, fat and skin of two Ross seals were weighed. Weights of 22 visceral organs of the same animals, and linear bone dimensions of eight Crabeater seals and skull measurements of five Ross seals were recorded.
There was no significant difference between sexes or ages in body composition of Crabeater seals. Relatively, Crabeater and Ross seals had less blood (9–10% body weight) than Elephant seals, and less fat (21–22% body weight) than most other marine mammals. The low body fat content may have been attributable to season and physiological status of the animals when dissected. The percentages of body weight represented by the other major components of Crabeater seals were: skin 8%, muscle 44%, bone 10%, connective tissue 0.7% and total viscera 8%. These figures, and the relative sizes of individual organs, were discussed in relation to their possible function in Crabeater and Ross seals.     

Effects of 24-hour starvation period on metabolic parameters of 20-day-old rats

The effects of a 24-hour starvation period upon 20-day-old rat pups were studied both in animals kept in the presence of their starved dams and in their absence. The relative loss of body weight was more intense in the rats that received no milk, being however, severe in both groups. There was a significant maintenance of both plasma glucose levels and total amino acids, with differences in blood glucose compartmentation and a remarkable uniformity in the effects of starvation upon individual amino-acid concentrations. A significant increase in plasma urea was observed, higher in the rats kept in the presence of the dam. Ketone bodies increased with starvation but their final levels were lower than in adults. The general pattern of metabolic change observed suggests a situation, after 24-h food deprivation, similar to that of long term starvation in adults; with an active protein amino-acid catabolism but with a remarkable maintenance of circulating foodstuff levels.     

Cerebral Acid Buffering Capacity at Different Ages Measured In Vivo by 31P and 1H Nuclear Magnetic Resonance Spectroscopy

Cerebral acidosis occurring during ischemia has been proposed as one determinant of tissue damage. Newborn animals appear to be less susceptible to ischemic tissue damage than adults. One possible component of ischemic tolerance could derive from maturational differences in the extent of acid production and buffering in newborns compared to adults. The purpose of this study was to measure the dependency of acid production on the blood plasma glucose concentrations and acid buffering capacity of piglets at different stages of development. Complete ischemia was induced in 29 piglets ranging in postconceptual age from 111 to 156 days (normal term conception, 115 days). Brain buffering capacity during the first 30 min of ischemia was quantified in vivo, via 31P and 1H nuclear magnetic resonance (NMR) spectroscopy, by measuring the change in intracellular brain pH for a given change in the concentration of compounds that contribute to the production of hydrogen ions. Animals from all four age groups showed a similar linear correlation between preischemia blood glucose concentration and intracellular pH after 30 min of ischemia. For each animal the slope of the plot of intracellular pH versus cerebral buffer base deficit was used to calculate the buffer capacity. Using data obtained over the entire 30 min of ischemia, there was no difference in the mean buffer capacity of the different age groups, nor was there a significant correlation between buffer capacity and age. However, there was a significant increase in buffer capacity for the intracellular pH range 6.6-6.0, compared to 7.0-6.6, for all age groups. No significant differences in buffer capacity for these two pH ranges were observed between any of the age groups. Acid buffering capacity was also measured by performing pH titrations on brain tissue homogenized in the presence of inhibitors of glycolysis and creatine kinase. Plots of homogenate pH versus buffer base deficit showed a nonlinear trend similar to that seen in vivo, indicating an increase in buffer capacity as intracellular pH decreases. A comparison of newborn and 1-month-old brain tissue frozen under control conditions or after 45 min of ischemia revealed no differences that could be attributed to age and a slight decrease in buffer capacity of ischemic brain compared to control brain tissue homogenates. There was no difference between the brain buffering capacity measured in vivo using 31P and 1H NMR and that measured in vitro using brain homogenates.     

Intrauterine growth restriction alters the metabonome of the serum and jejunum in piglets

Intrauterine growth restriction (IUGR) is not only an underlying factor for stunted postnatal growth and newborn deaths, but also associated with disease prevalence, such as hypertension and diabetes, in both adult humans and animals. To investigate the metabolic status of IUGR, the differences in serum and jejunal tissue metabonome were examined in IUGR and normal weight 21 day old piglets. IUGR piglets had a significantly lower birth weight (785 ± 42 g vs. 1451 ± 124 g), weaned weight (3053 ± 375 g vs. 6489 ± 545 g) and average daily gain (108 ± 16 g vs. 240 ± 21 g) than normal weight piglets (p < 0.05). IUGR piglets also had a shorter villus height and smaller villus height to crypt depth ratio (p < 0.05) in jejunum. An NMR-based metabonomic study found that serum levels of glycoprotein, albumin and threonine were higher in IUGR than in normal weight piglets, while serum levels of HDL, lipids, unsaturated lipids, glycerophosphorylcholine, myo-inositol, citrate, glutamine and tyrosine were lower in IUGR piglets (p < 0.05). In addition, marked changes in jejunal metabolites, including elevated levels of lipids and unsaturated lipids, and decreased levels of valine, alanine, glutamine, glutamate, choline, glycerophosphorylcholine, trimethylamine-N-oxide, scyllo-inositol, lactate, creatine, glucose, galactose, phenylalanine, tyrosine, glutathione, inosine and taurine were observed in IUGR piglets (p < 0.05). These novel findings indicate that IUGR piglets have a distinctive metabolic status compared to normal weight piglets, including changes in lipogenesis, lipid oxidation, energy supply and utilization, amino acid and protein metabolism, and antioxidant ability; these changes could contribute to impaired growth and jejunal function.     

Effect of cold exposure on energy metabolism in the young pig

Twenty-four piglets were weaned at 3 weeks of age and received 615 kJ metabolizable energy/(kg body weight X day). The temperature was reduced from 29 to 25 degrees C by 4 weeks of age. Six pigs were exposed to cold by reducing the temperature to 10 degrees C by 5 weeks of age while the other six were exposed to 23 degrees C. These two temperatures were maintained for 3 weeks. Each week the three pigs closest to the mean weight of each group were used for measurements of heat production for 23 h by open-circuit calorimetry and glucose turnover by continuous infusion of [6-3H]- and [U-14C]-glucose. The animals were sacrificed at 8 weeks of age, a sample of their intercostal muscle was used for in vitro measurement of muscle respiration, and the carcass was analyzed. There was no change in heat production, glucose turnover, and rectal temperature during the 3 weeks of cold exposure, so the data were pooled. Cold exposure increased heat production by 50%, forced mobilization of fat reserves (1000 g over the 3 weeks), and increased glucose replacement rate by 20%. The decline in rectal temperature to 37.6 from 38.8 degrees C could be regarded as a strategy to reduce energy needed to regulate body temperature. In the cold, heat production equalled metabolizable energy intake, but protein deposition was maintained at the same level as that in the pigs at the thermoneutral temperature, using the energy derived from the mobilization of body fat. The increase in Na+-K+ ATPase dependent respiration accounted for 70% of the increase in O2 consumption of muscle from cold-exposed pigs and thus is potentially an important component of cold-induced thermogenesis in the pig.