The influence of ehrlich ascites tumour growth on the turnover of lactate dehydrogenase in tissues of the mouse

• 1.1. The influence of Ehrlich ascites tumour growth on the turnover of total soluble protein and lactate dehydrogenase (LDH) in mouse tissues has been studied.
• 2.2. Turnover parameters were determined by means of double-labelling technique, with the enzyme (LDH) being isolated by affinity chromatography.
• 3.3. Tumour growth was accompanied by a decreased rate of synthesis of total protein in all tissues.
• 4.4. Lactate dehydrogenase by contrast snowed an increased rate of synthesis in all tissues but kidney.
• 5.5. These directions of change, in combination with the lesser response of degradation constants, resulted in a consequent conservation of enzyme activity in all tissues except kidney.
• 6.6. A generalized shift in the LDH isozyme pattern of these tissues was also observed during tumour growth with an increased contribution of A-type subunit.
• 7.7. These results have been discussed in relation to the redirection of protein synthesis and degradation, the occurrence of foetal isozymes, and possible mechanisms involved in the redistribution of protein resources in the animal during tumour development.

     

Lactate dehydrogenase in amoeba,Acanthamoeba sp. in different phases and conditions of culture

• 1.1. The activity and kinetic changes of amoeba LDH in different phases and conditions of culture were investigated.
• 2.2. LDH of the amoeba is specific against d(−)LDH irrespective of the hypoxic conditions created.
• 3.3. In hypoxic conditions it was not possible to visualize the presence of another LDH isozyme of muscle type by kinetic or electrophoretic analysis.
• 4.4. However, the changes in the K_m value and the L:H ratio as well as the decrease of electrophoretic mobility of LDH band indicate the change in kinetic properties of the enzyme from an obviously heart type in oxygenated culture in the direction of a muscle type LDH in strongly hypoxic culture conditions.
• 5.5. The influence of factors producing either environmental or metabolic hypoxia on possible repression or induction of LDH in amoeba is discussed.

     

Comparative dehydrogenase activity during the ontogenesis of the yellow fever mosquito Aedes (Stegomyia) aegypti L. (diptera:culicidae)

• 1.1. α-GPDH in most active in adults, LDH in third instar larvae, and MDH in third instar larvac.
• 2.2. During pre-pupal growth, LDH is the most active enzyme, followed by MDH and α-GPDH; while during post-pupal growth, MDH is most active followed by α-GPDH and LDH.
• 3.3. Increased enzyme activity is in response to changing physiological and physical environments, and is due to temporal activation of new gene loci indicated by the production of new α-GPDH and MDH isozymes. LDH activity is probably controlled by the temporal action of regulatory gene(s).
• 4.4. Dehydrogenase activity profiles during ontogenesis are probably species-specific.

     

Lactate dehydrogenase of goldfish red and white muscle in relation to thermal accumulation

• 1.1. Activities of the red and white muscle LDH from 8°C-acclimated goldfish were about three times higher than those acclimated to 28°C.
• 2.2. Isozyme composition and some kinetic properties of the red muscle LDH differed from those of the white muscle enzyme.
• 3.3. The amount of red muscle as well as LDH activity tended to increase during cold acclimation.

     

Distribution of opine dehydrogenases and lactate dehydrogenase activities in marine animals

• 1.1. Opine dehydrogenases (OpDHs) and lactate dehydrogenase (LDH) activities were determined in various marine animals. OpDHs were detected in six marine invertebrate phyla; Porifera, Coelenterata, Annelida, Mollusca, Arthropoda and Echinodermata in phylogenic sequence.
• 2.2. Among several OpDHs, tauropine dehydrogenase (TaDH) occurred widely in marine invertebrates, from Porifera to Echinodermata.
• 3.3. With a few exceptions, total OpDHs activities exceeded that of LDH activity in the marine invertebrates investigated.
• 4.4. With respect to anaerobic glycolysis, OpDHs are indicated to play an important role in phylogenically lower invertebrates, whereas LDH is more important in higher animals.

     

Phosphonomonoesterase activity in Metridium senile L.

• 1.1. An esterase which hydrolyzes 4-nitrophenyl(phenyl)phosphonic acid (4-NPPP) was purified from M. senile (sea anemone).
• 2.2. The enzyme showed no 5′-nucleotide phosphodiesterase activity with 5′-(4-nitrophenyl) TMP or phosphomonoesterase activity with 4-nitrophenylphosphate.
• 3.3. Addition of excess Zn²⁺ restored activity after inactivation by EDTA.
• 4.4. Thiol reagents and phenylmenthanesulfonylfluoride did not inactivate, whereas, dithiothreitol inactivated.
• 5.5. Aminoethylphosphonic acid (AEP) was a competitive inhibitor of 4-NPPP indicating possible activity with phosphonomonoesters of AEP.

     

Enzymes of fructose metabolism in the intestinal mucosa of the rat (Rattus norvegicus). Localization along the small intestine; consequences of dietary fructose

• 1.1. The activities of all the eight enzymes of conversion of fructose to glucose, of all the three key enzymes of glycolysis and of the two dehydrogenases of pentose shunt were determined in proximal and distal mucosa of small intestine.
• 2.2. With the exception of hexokinase, all of these enzymes have an activity significantly higher in the proximal than distal mucosa.
• 3.3. The gradient along the intestine is particularly important for the three enzymes which are typical for fructose metabolism (ketohexokinase, triokinase and fructose-1-phosphate aldolase), for glucose-6-phosphatase and for phosphofructokinase.
• 4.4. The effects of fructose diet on the enzyme activities are compatible with the results, described in other papers, concerning the final products of metabolism.
• 5.5. The increase of fructose metabolism appears to result mainly from the stimulation of the activities of ketohexokinase and fructose-1-phosphate aldolase which control all the pathways of ketohexose utilization.
• 6.6. The activation of glucose-6-phosphatase, in comparison with the other enzymes which are involved in glucose-6-phosphate metabolism, explains the appearance of the ability to synthesize glucose with fructose as substrate. This enzyme is the only key enzyme of fructose to glucose conversion which responds to fructose feeding in distal mucosa.
• 7.7. The activities of hexokinase and phosphofructokinase are not increased by fructose feeding.
• 8.8. The activity of pyruvate kinase. the only key glycolytic enzyme which is necessarily implicated when fructose is the substrate, is stimulated but less than the typical enzymes of fructose metabolism.
• 9.9. But, because of its quantitative importance, the glycolytic pathway is responsible for the most part of the observed increase of fructose utilization.
• 10.10. The responses of pyruvate kinase, glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase activities to fructose feeding are similar in the two parts of small intestine.
• 11.11. The activities of ketohexokinase, triokinase and glucose-6-phosphate isomerase are stimulated only in the proximal small intestine mucosa.
• 12.12. The other enzyme activities which are stimulated in proximal segment are also increased in distal segment.
• 13.13. All segments of small bowel show adaptive changes to dietary manipulation but not necessarily for all their functions.
• 14.14. The gradient of enzyme activities from the proximal to the distal small intestine persists despite dietary modification, but the data do not determine that this gradient is intrinsic or that it is not intrinsic.

     

Electrophoretic characterization of a hybrid between Eretmochelys imbricata and Caretta caretta (Cheloniidae)

• 1.1. An intermediate morphotype between Eretmochelys imbricata and Caretta caretta was studied in Praia do Forte, Bahia, Brazil.
• 2.2. Three enzymatic systems were successfully analyzed: SOD, lactate dehydrogenase (LDH) and esterase (EST). Isoelectric focusing of total soluble proteins of muscle and transferrin were shown.
• 3.3. Esterase exhibited nine phenotype patterns, seven in C. caretta and one in the others morphotypes. SOD phenotypes were identical in the three morphotypes. Lactate dehydrogenase and transferrins were characteristic for each species.
• 4.4. Jaccard's measure of similarity was calculated and a phenogram with the three morphotypes were constructed using isoelectric focusing of total soluble proteins.

     

Distribution of serine esterase activity in the lymphoid system of C57bl/6 mice,effect of aging on the enzymatic activity

• 1.1. The activity of serine esterase (SE) was investigated in the lymphoid system of C57BL/6 mice. SE activity increased in the lymphoid tissues with their content of mature T-lymphocytes, except that high levels were also observed in various populations of bone marrow cells.
• 2.2. The maturation of T-lymphocytes in the thymus was accompanied by an increase in their SE activity.
• 3.3. Experiments on the influence of age on SE activity showed that while thymocytes were not affected, a three-fold increase in activity occurs in spleen lymphocytes between the ages of 26 and 78 wk.

     

Plasma lipoprotein profiles and arylesterase activities in two inbred strains of rabbits with high or low response of plasma cholesterol to dietary cholesterol

• 1.1. Cholesterol feeding for 4 weeks of female and male rabbits of two inbred strains increased plasma cholesterol concentrations by about 11 and 48 mmole/I in the hypo- and hyperresponsive strain, respectively.
• 2.2. On the low-cholesterol pre-experimental diet, the hyporesponsive animals had significantly higher plasma HDL (high density protein) cholesterol levels than hyperresponders.
• 3.3. In both strains, cholesterol feeding caused elevations of cholesterol in all lipoprotein classes, the difference between the hypo- and hyperresponsive strains in essence only being observed in the VLDL (very low density lipoprotein) fraction.
• 4.4. Basal plasma total arylesterase activity was significantly higher in the hypo- than in the hyperresponsive rabbits.
• 5.5. Dietary cholesterol caused an increase in plasma esterase activity in both strains.
• 6.6. We suggest that in rabbits a low plasma arylesterase activity and a low concentration of HDL cholesterol are associated with an increased sensitivity to dietary cholesterol.

     

Relationship between brain trehalase activity and trehalosema during direct and diapausing development in Pieris brassicae

• 1.1. Brain trehalase specific activity and trehalosemia were measured during the end of the developmental life cycle in non-diapausing and diapausing insects.
• 2.2. During non-diapausing development, trehalosemia reached maximum values at the beginning of pupal life. Then a constant decrease was observed up to the end of adult life.
• 3.3. The specific activity of brain trehalase was maximum when the insects were in active feeding periods, minimum activity appearing during moulting phases.
• 4.4. During diapausing development, trehalosemia was very high at the beginning of pupal life, particularly when insects were exposed to wintering conditions.
• 5.5. When diapause was broken, trehalosemia fell, announcing adult emergence.
• 6.6. Brain trehalase activity showed the same qualitative variations as in non-diapausing larvae, but with rather lower values.
• 7.7. During pupal life, brain trehalase activity decreased markedly during the long period necessary to obtain diapause breakdown.
• 8.8. Wintering conditions allow a progressive increase of brain trehalase activity, which preceded the fall of trehalosemia.

     

NADPH/NADP ratio could regulate the glyoxylate cycle in Tetrahymena pyriformis

• 1.1. The glyoxylic acid cycle pathway could be regulated through the modulation of the isocitrate dehydrogenase-NADP activity. This enzyme is inhibited by NADPH.
• 2.2. The effect on the glyoxylate cycle flux of variations in the rate of the NADPH-consuming pathways has been studied.
• 3.3. Increase in the rate of NADPH-consuming activity by addition of H₂O₂ produces inhibition of the glyoxylate cycle and decrease in the NADPH/NADP ratio.
• 4.4. These results suggest that the glyoxylate flux in Tetrahymena could be modulated by regulation of NADP-dependent isocitrate dehydrogenase by the NADPH/NADP ratio.

     

Circannual rhythmicity in the hibernating ground squirrel Citellus lateralis under constant light and hyperthermic ambient temperature

• 1.1. In order to elucidate some of the parameters of the circannual rhythm in heterothermichomothermic mammals, the ground squirrel Citellus lateralis was maintained for 3 years under constant. high ambient temperature (34 C).
• 2.2. Results indicate that the ground squirrel continues to exhibit a circannual cycle of body weight fluctuations despite the high temperature.
• 3.3. Furthermore, although alternating periods of heterothermy-homothermy were not possible at 34 C, the body weight cycle did free run under this constant environmental condition, and thus demonstrates the true endogenous nature of the circannual rhythm.

     

Temperature acclimation in amphibians: Changes in lactate dehydrogenase activities and isoenzyme patterns in several tissues from adult Discoglossus pictus pictus (Otth.)

• 1.1. The effect of cold (8 ± 2°C) acclimation on the lactate dehydrogenase activities and isoenzyme patterns from sartorius muscle, liver, heart and brain of adult Discoglossus pictus pictus (Otth.) was studied.
• 2.2. Two groups of animals were studied: one set of animals was trapped in October and another set in December. In both cases some of the animals were sacrificed upon collection and some others subjected to 5 months of acclimation at 8 ± 2°C before being sacrificed for analysis.
• 3.3. A general trend towards a decrease in LDH specific activity was observed during cold acclimation. The magnitude of change, but not the direction, depends on both the tissue examined and the season at which the experiment was initiated.
• 4.4. A complex LDH isoenzyme reorganization was also found in liver, heart and brain. In liver from Experiment 1 and in heart from both experiments, a relative maintenance in M-type LDH activity during cold acclimation was observed. However, in brain there was a relative maintenance of LDH₃ activity in both experiments.
• 5.5. The low behavioral activity (and its metabolic consequences) and the existence of an intrinsic annual rhythm in D. pictus metabolism are suggested as responsible for the observed enzymatic changes.

     

Changes in glycolytic and associated enzyme activities during rana ridibunda oocyte development

• 1.1. Most of glycolytic and associated enzymes in the oocytes of the frog Rana ridibunda exhibit a higher activity at the early growth stages; the activity declines by the time the oocyte reaches full growth. Citrate syntase follows a similar pattern.
• 2.2. Enzymes related to gluconeogenesis have non-detectable activity.
• 3.3. It is suggested that at the early stages of oocyte growth glycogen could contribute as a fuel mainly for the pentose phosphate pathway; in the full-grown oocyte glycogen could serve mainly as a fuel for the glycolytic pathway.

     

Diurnal temperature sensitivity of dairy cattle in a naturally cycling environment

• 1.1.|Vaginal temperatures of 15 Bos taurus cattle were monitored for 17 days in daily pens exposed to normal environmental fluctuations.
• 2.2.|Regressions of vaginal temperature on ambient temperature were made for each collection time in the 24 h cycle. Slopes of regressions provided an index of animal sensitivity to environmental temperature.
• 3.3.|Fluctuations in sensitivity occurred throughout the day with positive slopes excepts at 0630 h.

     

Temperature acclimation in the teleost,Blennius pholis: Changes in enzyme activity and cell structure

• 1.1. The effect of thermal acclimation on the activity of liver enzymes of B. pholis and on the ultrastructure of the liver was studied.
• 2.2. Significant increases in the activities of SDH and G6PDH, but not of LDH were found after cold-acclimation.
• 3.3. E.M. measurements suggested that cold-acclimation resulted in an increase in the size of liver cells and their nuclei, and in the number, but not the size of liver mitochondria.

     

Allozyme variation in a dimeric esterase of the oriental fruit fly,Dacus dorsalis (insecta: tephritidae), from peninsular malaysia

• 1.1. Seven natural populations of Dacus dorsalis were analyzed for a dimeric esterase by means of horizontal starch-gel electrophoresis.
• 2.2. The electrophoretic phenotypes were governed by nine codominant Est-D alleles.
• 3.3. The commonest allele in all seven population samples was Est-D¹⁰⁰ which encoded an electrophoretic band with intermediate mobility.
• 4.4. The distribution of EST-D phenotypes were in accordance with Hardy-Weinberg expectations.
• 5.5. There was no geographic variation in the distribution of Est-D alleles.

     

Phosphatase activity in the hepatopancreas of Helix aspersa

• 1.1. Phosphatase acid (PhA) activity in the digestive gland (hepatopancreas) of the common garden snail Helix aspersa has been investigated using cytochemical methods.
• 2.2. All the cells composing this gland show PhA activity, the distribution pattern differing according to the cell type.
• 3.3. The digestive cells show the most widely distributed reaction product (brush border, phagolysosomes, multivesicular bodies and autophagic vacuoles).
• 4.4. In the excretory cells this activity appears in large sacs, while in the calcium cells the reaction product is abundant in the calcium granules.
• 5.5. Cellular digestion processes performed by each of these cell types is discussed together with their role in the detoxification of heavy elements derived from the environment.

     

A comparison of aspartate transcarbamylase activity in juvenile pacific oysters (Crassostrea gigas) when fed various diets

• 1.1. The optimum pH for measurement of aspartate transcarbamylase activity in oyster tissue was determined to be 9.35 while the optimum temperature was 39.5°C.
• 2.2. Aspartate transcarbamylase activity varied significantly over short periods of time (hr) possibly due to fluctuations in the amount of food digested.
• 3.3. The composition of the oyster's diet also affected the levels of aspartate transcarbamylase activity in oyster tissues.
• 4.4. Those oysters fed an egg yolk-starch diet contained significantly lower aspartate transcarbamylase activity than oysters fed an egg yolk-starch-salmon oil diet or a casein-starch-salmon oil diet.
• 5.5. The aspartate transcarbamylase activities in oysters fed Phacedactylum tricornutum or a starch diet were not significantly different from the activities in oysters fed the egg yolk-starch diet.