Carbohydrate metabolism in adult schistosomes of different strains and species

In this comparative study the carbohydrate metabolism of Schistosoma japonicum, S. haematobium, S. intercalatum, S. bovis and three strains of S. mansoni was investigated. No large differences were found in the protein and glycogen contents of all species involved. In all species investigated, lactate was the main end product of carbohydrate breakdown. However, all parasites degraded part of the glucose to CO2 via the Krebs cycle. No difference was observed in the contribution of this aerobic process to energy production in the three strains of S. mansoni investigated. The differences in Krebs-cycle activity between the five schistosome species investigated were very small. Therefore, this study refutes the idea that significant differences exist in the carbohydrate metabolism of various schistosome species or strains.     

Carbohydrate metabolism in fructose-fed and food-restricted running rats

In chronically catheterized rats hepatic glycogen was increased by fructose (approximately 10 g/kg) gavage (FF rats) or lowered by overnight food restriction (FR rats). [3-3H]- and [U-14C]glucose were infused before, during, and after treadmill running. During exercise the increase in glucose production (Ra) was always directly related to work intensity and faster than the increase in glucose disappearance, resulting in increased plasma glucose levels. At identical work-loads the increase in Ra and plasma glucose as well as liver glycogen breakdown were higher in FF and control (C) rats than in FR rats. Breakdown of muscle glycogen was less in FF than in C rats. Incorporation of [14C]glucose in glycogen at rest and mobilization of label during exercise partly explained that 14C estimates of carbohydrate metabolism disagreed with chemical measurements. In some muscles glycogen depletion was not accompanied by loss of 14C and 3H, indicating futile cycling of glucose. In FR rats a postexercise increase in liver glycogen was seen with 14C/3H similar to that of plasma glucose, indicating direct synthesis from glucose. In conclusion, in exercising rats the increase in glucose production is subjected to feedforward regulation and depends on the liver glycogen concentration. Endogenous glucose may be incorporated in glycogen in working muscle and may be used directly for liver glycogen synthesis rather than after conversion to trioses. Fructose ingestion may diminish muscular glycogen breakdown. The [14C]glucose infusion technique for determination of muscular glycogenolysis is of doubtful value in rats.     

Carbohydrate metabolism in erythrocytes of copper deficient rats

Dietary copper deficiency is known to adversely affect the circulatory system of fructose-fed rats. Part of the problem may lie in the effect of copper deficiency on intermediary metabolism. To test this, weanling male Long-Evans rats were fed for 4 or 8 weeks on sucrose-based diets containing low or adequate copper content. Copper deficient rats had significantly lower plasma and tissue copper as well as lower plasma copper, zinc-superoxide dismutase activity. Copper deficient rats also had a significantly higher heart:body weight ratio when compared to pair-fed controls. Direct measurement of glycolysis and pentose phosphate pathway flux in erythrocytes using (13)C NMR showed no differences in carbon flux from glucose or fructose to pyruvate but a significantly higher flux through the lactate dehydrogenase locus in copper deficient rats (approximately 1.3 times, average of glucose and glucose + fructose measurements). Copper-deficient animals had significantly higher erythrocyte concentrations of glucose, fructose, glyceraldehyde 3-phosphate and NAD(+). Liver metabolite levels were also affected by copper deficiency being elevated in glycogen and fructose 1-phosphate content. The results show small changes in carbohydrate metabolism of copper deficient rats.     

Taurine transport across the small intestine of adult and suckling rats

1. Taurine accumulation in intestinal cells of adult and suckling rats reached steady-state after 60 min with an In/Out ratio of 1.46 and 4.66 in the adult and suckling rats respectively. 2. The accumulative capacity of the intestinal strips isolated from suckling rats is almost four times higher than that of adult rats. 3. The steady-state uptake of taurine by the adult and suckling rats intestinal cells is saturable, sodium-dependent and inhibited by ouabain. 4. The calculated Vmax of the mediated component of the steady-state uptake in the suckling rats is three times greater than that of the adult rats, and the affinity is seven fold greater in the suckling as compared to the adult. 5. Taurine influx across the mucosal membrane in the suckling rat is significantly greater than that of the control adult.     

Effects of dieldrin on hepatic carbohydrate metabolism in the suckling and adult rat

Hepatic carbohydrate metabolism was studied in adult and suckling rats given age-specific LD50 doses of dieldrin po. These doses in 5-, 10-, and 60-day-old Wistar rats were 38, 28, and 63 mg/kg, respectively. Plasma glucose and free fatty acids (FFA), and hepatic glycogen, phosphoenolpyruvate carboxykinase (PEPCK), fructose-1,6-diphosphatase (FDP), and glucose-6-phosphatase (G6P) were measured 1 and 3 h after administration of the insecticide. Plasma glucose concentrations were elevated (17%) in some 5-day-old rats after 1 h and in all adults after 1 and 3 h (45 and 30%, respectively). Plasma FFA concentrations were decreased (9%) in the 5-day-old rat 1 h after dieldrin. Hepatic glycogen content was reduced in both 5- and 10-day-old pups at 1 hour (22 and 17%, respectively). Hepatic FDP activity was elevated in the 5-day-old rat at 1 h (17%) and was decreased (10%) in the 10-day-old rat at 3 h. Hepatic PEPCK activity was increased in adult animals by 30% 1 h after dieldrin. Furthermore, PEPCK activity was increased at 3 h in rats of all ages (76%, 5-day-old pup; 115%, 10-day-old pup; 56%, 60-day-old adult). Hepatic G6P activity was unaltered by dieldrin. Thus only the activity of hepatic PEPCK is consistently elevated by dieldrin exposure. However, this enhanced PEPCK activity is associated with dieldrin-induced hyperglycemia only in the adult rat.     

Carbohydrate and lipid metabolism in rats during adaptation to cold

Cold adapted rats are shown to have glucose and fatty acids concentration in blood inchanged, lactate concentration increased and triglyceride concentration decreased against the control level. Glucose utilization rate in the tolerance test grows. Glycogen content falls, hexokinase and succinate dehydrogenase activity increases, glucose-6-phosphatase and NAD+-isocytratedehydrogenase activity decreases in the liver of experimental animals. The results indicate that utilization of carbohydrate and lipid substrates for thermogenesis is intensified in cold-adapted rats. The hypothesis is supported by the data of tests dealing with IPNA injection or with bringing the animals back under thermocomfortable conditions.     

Fasciola hepatica: Carbohydrate metabolism of the adult

Glycogen (or exogenous glucose) was the only energy source utilized by adult Fasciola hepatica under a number of different incubation conditions. When exogenous glucose was present in the incubation medium, significant amounts of lactate were excreted. Anaerobically, in the presence of glucose, lactate accounted for 20% of the total end products measured. In the absence of glucose, organic acid production accounted for approximately 60% of glycogen carbon utilized; this value was reduced to 40% in the presence of exogenous glucose. There was no appreciable Pasteur effect.     

Trypsin inhibitors in serum of adult and suckling rats and in rat milk

• 1.1. Trypsin inhibitors in serum from adult and suckling rats and in rat milk were studied by gel filtration and electrophoresis in casein-agarose gels. In addition trypsin binding properties and inhibiting activity in the presence of low mol. wt substrates were studied.
• 2.2. In adult rat serum 6 trypsin inhibitors were found, most of these having not been described before. One inhibitor, di-macroglobulin is a homologue of human α₂-macroglobulin. Two inhibitors in the α₁- and α₂-regions of the electropherogram had a mol. wt of about 200,000. The third group of inhibitors was eluted together with albumin and had electrophoretic mobilities in the di-α₂- and β-region.
• 3.3. In the serum of the newborn rat the inhibitors of the third protein peak dominated, especially that in the α₂-region. In later developmental stages the inhibitor pattern became increasingly similar to that of the adult. A specific inhibitor, α₂-acute phase globulin, was found in the neonatal rat but disappeared in later developmental stages.
• 4.4. The trypsin inhibitors in rat milk were dominated by inhibitors in the third protein peak after gel nitration and had the same electrophoretic mobilities as the inhibitors of the corresponding fraction in serum. No low mol. wt trypsin inhibitors specific for milk were found.
• 5.5. Rat milk trypsin inhibiting activity seems to have a higher resistance to low pH-values than the inhibiting activity of rat serum.
• 6.6. The trypsin inhibitor pattern in the serum of the suckling rat is similar to that of milk, indicating an absorption of inhibitors from milk. The milk inhibitors may have the function of preventing protein breakdown in the intestine of the suckling rat.

     

Metabolism of intracerebrally injected mevalonate in brain of suckling and young adult rats

We have investigated the in vivo metabolism via sterol and nonsterol pathways of intracerebrally injected mevalonate (MVA) in brains from suckling (10-day-old) and young adult (60-day-old) rats. Results of our study indicated that increasing the amounts of MVA injected increased MVA incorporation into all the lipid fractions examined. The incorporation of MVA into nonsaponiable lipids (NSF) and digitonin precipitable sterols (DPS) was similar in brains from adult and suckling rats. In brain tissue from both suckling and young adult rats the synthesis of dolichol from MVA varied with the amounts of MVA injected. Significant amounts of MVA were recovered in phosphorylated and free polyprenols (farnesol and geraniol) in brain tissue from rats of both ages. Also in both groups of animals, the amounts of MVA incorporated in phosphorylated and free farnesol were higher than the amounts recovered in either, phosphorylated or free geraniol. The amounts of MVA incorporated into the prenoic/fatty acid fraction by brain tissue from both suckling and young adult rats were less than 1% of the total MVA incorporated (nonsaponifiable and saponifiable lipids). Incorporation of MVA into the prenoic/fatty acid fraction by brain tissue was higher in suckling than in young adult rats. These data indicate that the brain tissue from suckling and young adult rats do not differ in their capacity to metabolize MVA into squalene and sterols and that in brain, metabolism of MVA by a shunt pathway is minimal. This suggests that in vivo regulation of cholesterol synthesis during brain development must occur at a step(s) in the sterol synthetic pathway prior to mevalonate, and that metabolism of mevalonate by shunt pathway did not play a role in the developmental regulation of brain sterol synthesis. The data also suggest that in both groups of animals the synthesis of squalene by synthetase may in part control brain sterol synthesis and the synthesis of dolichol is regulated by MVA concentration in the tissue.     

Increased lipoprotein lipase content in the adipose tissue of suckling and weaning obese Zucker rats.

The aim of this study was to determine whether the increase in lipoprotein lipase activity displayed by the adipose tissue of obese (fa/fa) rats as compared with that of lean (Fa/fa) rats could be ascribed to a change in the content or in the catalytic properties of the enzyme. The question was addressed in rats of two ages: in 7-day-old suckling and in 30-day-old post-weaning pups. Inguinal fat-pads were removed surgically (7 days of age) or after killing (30 days of age), and acetone-extract powders were prepared. The relative quantity of enzyme was assessed by immunotitration using an antiserum raised in goat against purified lipoprotein lipase from rat adipose tissue. The results indicate that increases in enzyme activity in obese animals were strictly paralleled by increases in the amount of enzyme in suckling as well as in post-weaning pups. Moreover, the apparent Km values of lipoprotein lipase for its substrate triacylglycerol were identical in the two genotypes. In conclusion, the genotype-mediated increase in lipoprotein lipase activity in adipose tissue of obese Zucker rats was fully accounted for by an increase in the content of the enzyme. In addition, this work documents the mechanism of the increase in lipoprotein lipase activity during weaning, which is mediated mainly through changes in the adipose-tissue enzyme content.     

Carbohydrate and nitrogenous metabolism condition in the rat tissue under experimental rhabdomyolysis

Some effects of glycerol injection on indices of the condition of the thiol-disulfide system as well as carbohydrate and nitrogen metabolism in rats in vivo were studied. A decrease was revealed in levels of non-protein SH-groups in the liver, kidney and heart, as well as of protein SH-groups in the kidney and heart of rats following glycerol injection. That might be connected with SH-group oxidation under the excessive arrival of free haem into tissues under rhabdomyolysis. A decrease in glycogen and increase in tyrosine aminotransferase activity in the liver were observed. Activation of nitrogenous metabolism following glycerol injection is indicated by the increase of aminotransferase activity in organs, and concentration of blood urea. High concentration of creatinine in the rat serum can reflect malfiltration in kidneys.