Chandlerella hawkingi: glucose utilization and glycolytic enzymes

Uterine estradiol and progesterone receptor concentration, activities of certain antioxidant enzymes and dehydrogenases and histoarchitecture in relation to time of secretion of nidatory estrogen and high endometrial sensitivity in rat

Alterations in uterine nuclear and cytosolic estradiol (ER) and progesterone (PR) receptor concentration, activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), glucose-6-phosphate dehydrogenase (G-6-PDH) and lactate dehydrogenase (LDH), surface and transmission electron microscopy and histology in relation to the time of secretion of nidatory estrogen and the onset of endometrial sensitivity in the rat were investigated. A significant increase in plasma estradiol (E2) concentration in control rats was observed at 22.00 h on day 4 post-coitum, whereas progesterone (P) concentration increased at 17.00 h on day 4 and was maintained until 17.00 h on day 5. The period of high endometrial sensitivity (10.00 h on day 5) was characterized by elevated uterine cytosolic ER and nuclear and cytosolic PR concentration and POD activity, low columnar luminal epithelium with undulating surface and intercellular membranes, covered with short microvilli and pinopods, and containing numerous electron-transparent apical vesicles, mitochondria, polyribosomes, rough (RER) and smooth (SER) endoplasmic reticulum, well developed Golgi, few lysosomes and lipid droplets and loose edematous antimesometrial stroma. Inhibition in endometrial sensitivity by post-coital centchroman was associated with a marked depletion in uterine cytosolic ER and an increase in nuclear ER concentration, a decrease in POD and G-6-PDH activities, compact fibroblastic stroma, an increase in luminal epithelial cell height with decreased RER, SER, polyribosomes, Golgi, straightening of intercellular membranes, reduced surface undulations and absence of pinopods. Electron-transparent vesicles appeared flattened and clumped in the apical portion of cells, tight junctions were more prominent and lipid droplets were translucent. Nuclear and cytosolic PR and the pattern of secretion or plasma E2 and P remained unaffected. CAT, SOD and LDH activities, although high throughout pre-implantation, did not vary in relation to the secretion of nidatory estrogen, endometrial sensitivity or centchroman treatment.

Mitochondrial NADH oxidase activity of Setaria cervi

The bovine filarial parasite, Setaria cervi, has been found to contain NAD(P)H oxidase activity. The system was predominantly located in the mitochondrial membranes, with very little activity available in the soluble fraction of the organelle. The membrane preparation also exhibited the presence of a reduced pyridine nucleotide transhydrogenase which converted NADPH into NADH by transferring a hydride ion. The oxidase activity was inhibited by all the respiratory inhibitors examined, with the greatest sensitivity to rotenone, a site I-specific inhibitor. The system was also found to be susceptible to exposure to anthelmintics, amongst which levamisole proved the most effective.

Setaria cervi: enzymes in microfilariae and in vitro action of antifilarials

Microfilariae of bovine filarial parasite Setaria cervi are equipped with the enzymes of glycolysis, pentose phosphate and PEP-succinate pathways and thus resemble the adult form in its metabolic pattern. Malate dehydrogenase was the most active enzyme in microfilariae followed by lactic dehydrogenase and fumarase, while phosphoglucoisomerase, PEP-carboxykinase and FDP-aldolase were comparatively less active. The very low ratio of PK/PEPCK in S. cervi microfilariae indicates active fixation of CO2 into PEP to produce oxalacetate. Centperazine and diethylcarbamazine significantly inhibited PEP-carboxykinase, fumarate reductase and succinic dehydrogenase, suggesting that these antifilarials probably exert microfilaricidal action by blocking the PEP-succinate pathway.

Setaria cervi: enzymes of glycolysis and PEP-succinate pathway

Setaria cervi, the filarial parasite inhabiting the Indian water buffalo (Bubalus bubalis Linn.) contained almost all the enzymes involved in glycogen degradation. Significant activities of glycogen phosphorylase, glucokinase, phosphoglucomutase, phosphoglucose isomerase, phosphofructokinase, FDP-aldolase, glyceraldehyde-3-phosphate dehydrogenase, phosphopyruvate hydratase, pyruvate kinase, lactate dehydrogenase glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase were detected in cell-free extracts of whole worms. The presence of PEP-carboxykinase, malate dehydrogenase, fumarase and fumarate reductase revealed the functioning of the PEP-succinate pathway in addition to phosphorylating glycolysis and pentose phosphate pathway in the parasite. Excepting fumarate reductase all other enzymes were localized in the particulate-free cytosol fraction, although small amounts of glycogen phosphorylase, aldolase and lactate dehydrogenase were also detected in the mitochondrial fraction.

Ascaridia galli: lactic acid production, glycogen content, glycolytic enzymes and properties of purified aldolase, enolase and glucose-6-phosphate dehydrogenase

Glycogen reserves of whole worms and their body wall, intestines, ovarian and testicular tubules of the avian intestinal nematode,Ascaridia galli, were assayed and on dry-weight basis found to be 14–20 %, except in the testicular tissue which contained only 7 % glycogen.

Segments of whole male worms or testicular tubules were found to produce more lactic acid than segments of whole female worms or ovarian tubules. The body wall and intestine of the worms had also appreciable glycolytic activity. Whereas in the segments of whole worms, male and female alike, glycolysis was more active under anaerobic conditions, no differences in glycolytic rates were seen between aerobiosis and anaerobiosis when isolated tissues were used. Exogenously added glucose did not stimulate glycolysis either aerobically or anaerobically to any extent greater than observed in the absence of glucose.

Homogenates of whole worms or their different anatomical parts were assayed for enzymic activities associated with the Embden-Meyerhof pathway of glucose assimilation. The crude extracts prior to differential centrifugation, were found to contain glycogen phosphorylase, aldokinases, pyruvate kinase, phosphatases acting on glucose 6-phosphate and hexose diphosphate and 6-phospho-gluconate dehydrogenase. The 105000gparticulate-free supernate was found to have significant activities of the following enzymes: fructokinase, phosphoglucomutase, phosphoglucoseisomerase, phosphofructokinase, aldolase, glyceraldehyde 3-phosphate dehydrogenase, lactic dehydrogenase and glucose-6-phosphate dehydrogenase. This fraction was devoid of NADH or NADPH oxidase activities in the absence of added substrates.

Although there was some indication of a negative correlation between low glycogen reserves and high glycolytic activity in the testicular tubules, in general, there was no relationship between glycogen reserve and glycolytic activity on the one hand or between the rate of glycolysis and the specific activities of some of the key glycolytic enzymes in either whole worm or in tissues other than the testicular tubules.

The 105000gsupernate was fractionated with ammonium sulphate. The fraction precipitating between 25 and 80 % saturation of the salt was recovered, dialysed and chromatographed on DEAE cellulose column. By a step-wise elution schedule using increasing molarity of NaCl in tris-HCl buffer, pH 7·4, three main protein fractions were obtained representing respectively enolase, aldolase and glucose-6-phosphate dehydrogenase.

The recovery of enzyme activity after chromatography on DEAE cellulose was higher than the amount applied to the column suggesting that during the fractionation some naturally occurring inhibitors were removed. About 10- to 20-fold purification of the enzymes was achieved by anion-exchange chromatography.

Some properties of the purified enzymes were studied with respect to the affects of enzyme and substrate concentrations, temperature of preincubation and action of divalent cations, some anions, metal chelating agents and SH reagents. The Kmvalues of enolase, aldolase and glucose-6-phosphate dehydrogenase ofA. galliwere 5·9 × 10−4M, 4·5 × 10−3M and 2·4 × 10−3M respectively. Glucose-6-phosphate dehydrogenase was found to be very sensitive to both heat and cold losing activity rapidly even at 43 °C or by freezing and thawing.

The SH groups of aldolase were readily blocked bypCMB and presumably byo–phenanthroline. No requirement of any divalent cations was shown by this enzyme which was, however, inhibited by borate ions.

Enolase ofA. gallishowed a requirement of Mg2+for full activation. Phosphate, fluoride, EDTA,o–phenanthroline, αα-bipyridyl inhibited the enzyme. Veronal was found to inactivate the enzyme.

Glucose-6-phosphate dehydrogenase ofA. galliwas also found to be sensitive to SH reagents and metal chelating agents. The enzyme was activated by Co2+, Mn2+and Mg2+.

The evidence presented indicates that segments of whole worms ofA. gallior its anatomical parts are equipped with the enzymatic machinery required to mediate anaerobic breakdown of glucose and to derive energy by this mechanism.

The authors are grateful to Dr R. K. Kaushik for help in identifying the worms, to Mr P. A. George for help in the statistical analysis of the data and to Messrs A. C. Kol and S. K. Bose for skilful technical assistance.