The influence of streptozotocin diabetes on adrenal function in male rats.

Male Wistar rats were treated with an i.v. dose of 100 mg/kg of Streptozotocin (STZ). Either 5 days or 1, 2 or 3 months after induction of diabetes, the adrenal function of these animals was studied. Short course diabetes (5 days) was accompanied by adrenal hypertrophy and high plasma corticosterone levels; during later periods the diabetic rats consistenly showed signs of adrenal hyperactivity, yet both adrenal weight and plasma corticosterone tended to be lower than in the 5 day-treated animals. Adrenal incubations with 14C-progesterone showed that 5 days and one month diabetic animals synthesized more deoxycorticosterone than controls; production of corticosterone and 18-hydroxydeoxycorticosterone was normal at all time periods studied. Synthesis of 18-hydroxycorticosterone, a compound which affects sodium metabolism, was increased in 5 day-treated rats; thereafter, the function of the zona glomerulosa seemed to be impaired in diabetic rats. These results suggest that early after induction of diabetes there is adrenal hyperfunction of the mixed type (i.e. gluco and mineralcorticoid), and that in the later periods (2-3 months), the deranged metabolism of the diabetic rat acts as a chronic stress.     

On hepatic and extrahepatic postheparin serum lipase activities and the influence of experimental hypercortisolism and diabetes on these activities.

This paper shows that the palmitoyl-CoA hydrolase activity of postheparin serum of the rat is mainly derived from the liver. The identity of this activity with the heparin-releasable hepatic triacylglycerol hydrolase activity is established. The consequences of the different substrate specificities of the hepatic and extrahepatic enzymes for the measurement of the overall postheparin serum lipase activity are discussed. Treatment of the rats with either a corticosteroid or with streptozotocin was found to lower the lipolytic activity from the liver and to enhance the extrahepatic activity. Also in human postheparin serum, palmitoyl-CoA hydrolase activity is shown to behave identical with hepatic triacylglycerol hydrolase activity. The possible function of the liver in the serum triacylglycerol metabolism is discussed in connection with the proposed mechanism for the role of extrahepatic lipoprotein lipase in atherogenesis.     

The influence of experimental deformation on craniofacial development in rats

Cranial deformation was produced experimentally in rats 8 to 40 days old for the purpose of studying the rotation of the craniofacial bones and the modification of the growth rates of the functional cranial components. One hundred and twenty four skulls (65 males and 59 females) were employed, classified as: deformed , deformed-hydrocephalic, sham-operated and controls. A midsagittal diagram was drawn for each skull and the angle subtended by each bone with respect to the vestibular plane was measured. Growth indices were worked out for both the neural skull and the facial skull. Deformation altered the rotation of the parietal, interparietal and basisphenoidal bones and restricted the rotation of the fronto-ethmo-facial complex. Alteration of the longitudinal growth rates of the dorsal and basilar components of the neurocranium and the splanchnocranium produced the persistence of the klinorynchal state.     

The influence of experimental deformation on neurocranial Wormian bones in rats

Two hundred and twenty crania of Wistar rats were experimentally deformed. The growth of the anterior vault was restricted in one subgroup and the growth of the posterior vault was restricted in the second subgroup. Seventy-seven deformed animals survived up to the thirtieth day of age and were sacrificed. Both subgroups were compared with each other as well as with 37 surviving sham-operated animals and 51 controls, all samples being 30 days of age (group A). Additionally, 33 normal crania of animals sacrificed at 1, 10 and 20 days as well as 19 deformed crania of 10 and 20 days old were observed (group B). Chi-square and Z tests were employed. Wormian bones found in the skulls of normal growing rats apparently represent an epigenetic polymorphism. Higher frequencies of wormian bones were found in deformed crania than in sham-operated ones and controls. Experimental deformation may be an extra-genetic factor that affects the normal genetic expression of wormian bones. This concept is relevant to studies of human population differences based on discontinuous cranial traits.     

The influence of serum separators on biochemical values in experimental animals]

The influence of three serum separators, A, B and C, on biochemical values was examined. With A or B, changes in the values of ChE, LAP, UN, K, P, Cl and Ca in rat serum; ChE, UN, Cl and Ca in dog serum; and K and P in monkey serum took place over a period of 20 min after blood collection. Therefore, the biochemical values of whole blood were considered to be stable after 20 min. Thus, biochemical tests were conducted on serum from the three serum separators after allowing the blood to stand 20 min. The values obtained for each separator were not markedly different from those of the control. These results suggest that a serum separator is useful for separation of serum of experimental animals under the proper conditions.     

Increased serum apoA-IV concentrations in experimental uremic rats.

Normal histochemical analysis localizes apoA-IV within renal proximal tubules, which suggests that the kidney is a major catabolic site. In clinical renal failure and animal models of decreased renal function, low molecular weight proteins cannot be efficiently filtered through the glomerular basement membrane, and therefore they accumulate in plasma. In normal plasma, apoA-IV exists as both lipoprotein associated and lipoprotein-free, low molecular weight forms. To examine this further, uremic serum apolipoprotein and mRNA levels were examined in surgically 5/6 nephrectomized rats. Compared to sham-operated controls, uremic serum apoA-IV was elevated twofold and was distributed to a greater extent in the lipoprotein-free subfraction. Serum triglycerides were unchanged. Despite finding no correlation between serum apoA-IV and triglyceride levels (in either the d less than 1.006 g/ml or 1.006 less than d less than 1.019 g/ml fraction), serum apoA-IV was positively correlated with the renal function parameters of blood urea nitrogen (r = 0.949, P less than 0.001), creatinine (r = 0.952, P less than 0.001), and uric acid (r = 0.903, P less than 0.001). In addition, the concentration of apoA-IV per milligram of renal homogenate protein in uremic rats was significantly higher than that of control rats, whereas there was no difference in the content of apoA-I between the two groups. ApoA-I, apoA-IV, and apoB mRNA levels in hepatic and in intestinal tissue were undistinguishable between the uremic and surgical sham rats.(ABSTRACT TRUNCATED AT 250 WORDS)     

The influence of prolonged cimetidine administration on serum gastrin levels and gastric acid secretion in rats.

The correlation between serum gastrin levels and gastric acid secretion during 4 weeks of cimetidine administration (once daily) was investigated. Serum gastrin levels and gastric acid secretion were estimated on the 7th, 14th, 21st and 28th day after cimetidine administration (25 mg.kg-1, intragastrically). At the mentioned time intervals gastric acid secretion stimulated by histamine and pentagastrin was also studied. It was found that on the 14th and 21st day after cimetidine administration serum gastrin levels were significantly elevated. Basal gastric acid secretion after cimetidine administration was significantly decreased at all the observed time intervals. Histamine-stimulated gastric acid secretion was increased on the 14th, 21st and 28th day after cimetidine administration. Hypoacidity was not followed at all time intervals by hypergastrinaemia (only on day 14 and 21 after cimetidine).     

Renal hypertrophy in experimental diabetes. Effect of diabetes on the pathways of glucose metabolism: differential response in adult and immature rats.

The effect of short-term diabetes, 5 days after the administration of streptozotocin, on renal growth and the activity of alternative pathways of glucose metabolism was studied in immature (21-day-old) rats and in adult rats. The kidney weight increased by 28% in the adult diabetic rats, but by only 10% in the immature diabetic rats, relative to their age-matched control groups. The flux of glucose via the pentose phosphate pathway was increased 2-3-fold in the adult diabetic rats, but was unchanged in the immature diabetic group. Enzymes of this pathway (glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase) increased by 29% and 77% respectively in adult diabetic rats; in the immature group they showed changes of +5% and +28% respectively. The rate of glucose phosphorylation increased significantly in both groups of diabetic rats; only minor changes were observed in oxidation via the tricarboxylic acid cycle. Increases of 40-50% were found in the activity of enzymes involved in UDP-glucose metabolism (phosphoglucomutase, UDPglucose pyrophosphorylase and UDPglucose dehydrogenase) and in lactate dehydrogenase in both young and adult animals. The results suggest a differential renal response to streptozotocin-diabetes according to the stage of renal growth and development, and it is proposed that the difference is related to the developmental emergence of aldose reductase. Enzymes involved in formation of ribose 5-phosphate and NADPH are strikingly increased in the adult diabetic, whereas metabolic functions dependent on a high ambient glucose concentration, e.g. synthesis of glycogen and glucuronate, are similarly affected in adult and immature diabetic groups, both showing certain aspects of 'glucose overutilization'.     

The influence of feed restriction and subsequent re-feeding on gonadotrophin secretion and serum testosterone levels in male rats.

Male rats at 3 months were fully fed or were restricted to 50% of normal feed intake for 10 or 20 days. Underfeeding for either period resulted in reduced (P less than 0-05) body weight and pituitary weight but did not affect testicular weight. Underfeeding for 20 days resulted in reduced (P less than 0-05) weights of the seminal vesicles and ventral prostate. The serum concentration of LH was depressed (P less than 0-05) after 10 days of underfeeding and the pituitary concentration of LH was elevated (P less than 0-05) after 20 days of underfeeding. Neither serum nor pituitary concentration of FSH was influenced by feed level. Serum testosterone concentration was reduced in rats underfed for 20 days. In a second study, 2-month-old males were fully fed, underfed (15 days) or underfed and then re-fed (full feed) for 1, 2, 3 or 7 days. Underfeeding produced effects similar to those noted in the first experiment. Re-feeding of underfed rats resulted in body and ventral prostate weights returning to levels similar to those of fully fed controls by Day 7. The serum level of FSH was elevated (P less than 0-05) above the control level on Days 1, 3 and 7 of re-feeding, while the serum level of LH appeared to return to the control level. Serum testosterone level rebounded and exceeded (P less than 0-05) the control level on Days 1 and 2 of re-feeding.     

The influence of clenbuterol on growth in rats.

1. The influence was studied of a beta 2-agonist, clenbuterol, on mean gain of body weight, feed efficiency and growth of muscle tissue in female Wistar rats of three different weights (70, 150 and 200 g). 2. Clenbuterol significantly increases mean gain of body weight and feed efficiency in all the studies realised, but much more effectively in animals of greater age/weight (200 g). 3. In addition, it favours protein deposition in muscle, given that it increases significantly (P less than 0.001) the muscle/body weight ratio in all of the experiments.