Energy production in Entamoeba histolytica: new perspectives in rational drugs design

The amebicidal action of metronidazol is activated when the enzyme pyruvate: ferredoxin oxido reductase transfers reducing equivalents to the nitro group of the drug. The enzyme is present in Entanoeba histolytica and other anaerobic parasites like Giardia and Trichomonas that lack mitochondria. The selectivity of the drug can be ascribed to the absence of the reductasa in the human host. E. histolytica possesses other enzymes involved in glucose catabolism that are interesting for the rational desing of new drugs. It has glycolytic enzymes that are important for the production of energy like phosphofructokinase, pyruvate phosphate dikinase, phosphoenolpyruvate carboxytransphosphorylase and thiokinase, which use pyrophosphate as a phosphate donor and have no human counterparts. The first part of this article describes the reactions by which E. histolytica obtains energy from glucose degradation, and includes recent advances in thecloning of genes for the various participating enzymes. The second part shows an alternative view for the study of target enzymes that are unique to the parasite, and indicates their importance in therapautic research

Modulatory effect of sepia shell extract on activity of glucose-6-phosphatase and alanine amino transferase in diabetic mice.

Alkali extract of sepia shell possesses hypoglycemic effect. The status of glycogen and pyruvate and the activity of glucose-6-phosphatase and alanine amino transferase in liver was studied under the influence of sepia shell extract in both normal and streptozotocin induced diabetic mice. The glycogen concentration was elevated steeply in both and the pyruvate concentration increased substantially in diabetic mice, while the activity of glucose-6-phosphatase and alanine amino transferase was inhibited in normal and diabetic mice. The sepia shell extract enhances glycogenesis and reduces the formation of glucose from metabolic intermediates like pyruvate and glucose-1-phosphate and by suppressing gluconeogenesis.

Metabolism of glucose, glutamine and pyruvate in lymphocytes from Walker 256 tumor bearing rats

This study examined the effect of Walker 256 tumor growth in vivo on the metabolism of glucose, glutamine and pyruvate in lymphocytes. A comparison between the metabolism of Walker 256 tumor cells obtained in vivo with that of lymphocytes was also carried out. Lymphocytes and tumor cells were isolated and incubated for 1 h for the following measurements: lactate production from glucose (5.6 mM) and pyruvate (3 mM), glutamate and aspartate formation from glutamine (3 mM) and decarboxylation of [U-14C]-glucose, [U-14C]-glutamine, [1-14C]-pyruvate and [3-14C]-pyruvate. The presence of the tumor increased lactate production (2.7-fold from glucose and 2-fold from pyruvate), decarboxylation of [U-14C]-glucose (3.7-fold) and [1-14C]-pyruvate (4.4-fold) and the formation of aspartate (6.3-fold) and glutamate (4.6-fold) from glutamine. The conversion of glucose to lactate and CO2 was higher in tumor cells as compared to lymphocytes. Tumor cells also showed a higher production of glutamate and an 8-fold increased decarboxylation rate of [U-14C]-glutamine in tumor cells, which was more active than that of lymphocytes even from tumor-bearing rats. Tumor growth stimulated glucose and glutamine metabolism in lymphocytes; however, the importance of this fact for the function of these cells remains to be elucidated

Fisiopatología del trastorno de ansiedad / The physiopathologyof anxiety disorders

En los últimos años se ha estudiado el trastorno de ansiedad, desde muy diversos enfoques. En el siguiente artículo revisaremos las teorías fisiopatológicas propuestas por los diferentes grupos de investigación en esta área. Abordaremos tres enfoques teóricos: neurobiológico, psicoanalítico asi como del aprendizaje-conductual

Effects of hypotensive anesthesia with sodium nitroprusside or isoflurane on hemodynamic and metabolic changes

The hemodynamic and metabolic changes during induced hypotension with isoflurane (isoflurane group) or sodium nitroprusside (SNP group) were observed in twelve mongrel dogs. These hypotensive effects were evaluated at 30 and 60 minutes after the mean arterial blood pressure was lowered to 50% from the control. Hemodynamic changes were evaluated by measuring systemic arterial blood pressure, heart rate, central venous pressure, pulmonary capillary wedge pressure, cardiac output, systemic vascular resistance and pulmonary vascular resistance. Metabolic changes were evaluated by measuring serum lactate and pyruvate, arterio-venous oxygen content difference and oxygen extraction rate. We also compared the ventilatory effect of hypotensive anesthesia by blood gas analysis. The results were as follows: 1. Isoflurane inhalation 2-4% or SNP infusion 10-20 micrograms/kg/min was required to reduce the mean arterial pressure to 50% of the control. 2. Heart rate was decreased slightly in the isoflurane group but significantly decreased in the SNP group. 3. There were no significant changes in central venous pressure and pulmonary capillary wedge pressure in either group. 4. Cardiac output was reduced in both groups but was more severe in the isoflurane group. 5. Systemic vascular resistance was decreased by 36% in the isoflurane group and 47% in the SNP group. 6. Acidosis was apparent and did not recover to the control until 30 minutes after recovery in the SNP group. 7. Arterio-venous oxygen difference was increased during hypotension in the isoflurane group probably due to decreased cardiac output. 8. The lactate/pyruvate ratio increased slightly in the SNP group.

In vivo effect of glucocorticoids on the rates of pyruvate utilization and lactate formation by incubated lymphocytes

Although the immunosuppressive effect of glucocorticoids has been widely reported, the mechanism of action of these hormones on the immune system has not been fully established. In the present study, the effect of glucocorticoids on the rates of pyruvate utilization and lactate production by lymphocytes obtained from rat mesenteric lymph nodes was investigated. Adult rats were injected withh dexamethasone ( 1 mg/kg, ip) daily for dfays. A stressed group which received a corresponding volume of 0.9% saline and control rats not injected were also included. All treatments were carried out at 17:00 h. Stress or administration of dexamethasone reduced the rate of pyruvate utilization by 505 and 625, respectively. The hormonal injection increased ther rate of lactate production by 575, whereas the stressed group showed a 2.4-fold increase of the conversion of pyruvate to lactate, as compared to control rats. These findings suggest that glucorticoids regulate pyruvate metabolism in lymphocytes and that an additional neurohormonal factor released during stress may also participate in the control of lactate production

Products of non-reductive CO2 assimilation in the halophilic archaebacterium Haloferax mediterranei.

The products of CO2 fixation by heterotrophically grown Haloferax mediterranei were analysed. The main 14C-labelled alpha-ketoacid detected following incubation with NaH14CO3 and pyruvate or propionate was pyruvate. In presence of these organic acids and NH4+, 14CO2 was incorporated into glutamic and aspartic acids and alanine.

Rates of pyruvate utilization and lactate formation by lymphocytes from young and aged rats

The rates of pyruvate utilization and lactate formation were measured in lymphocytes obtained from mesentéric lymph nodes were incubated at-C for 1 h. The conversion of pyruvate to lactate accounted for 92.5% of the total pyruvate utilized by lymphocytes from yung rats and was 34.2% and 44.5% for adult and aged rats, respectively. Wen lymphocytes were stimulated with concanavalin. A there was an increase of 65.5% and 37.1% in the rates of pyruvate utilization by lymphocytes from young and adult rats, respectively. No changes in pyruvate utilization were observed in response to concanavalin A in lymphocytes from aged rats

Lack of hypophosphatemic effect on glucose uptake, lactate and pyruvate release by the normal rat perfused hind-limb

In previous experiments, it was observed that in the perfused hind-limb of phosphorus deficient rats there was a faster utilization of glucose when compared with preparations obtained from ad-libitum fed rats but similar to that obtained from pair-weighed rats. A greater release of lactate under the influence of insulin and a marked spontaneous and insulin induced liberation of pyruvate was registered in the perfused hind-limb of the phosphorus deficient rat. Since a hypophosphatemic medium was employed, we though it would be interesting to study the effect of low perfusate Pi in normal rat hind-limb preparations and, additionally, to observe it fast changes in the level of medium orthophosphate from normal to low values and viceversa were able to determine changes in glucose uptake and lactate and pyruvate release. In one group of experiments, the hind-limb of normal rats was perfused successively with orthophosphate deprived medium for thirty minutes in each stage. In another group of experiments, the first stage was carried out with normal. Pi medium, the second with orthophosphate deprived medium, and the third with normal Pi medium; each stage lasted thirty minutes. In all the experiments there was a gradual release of orthophosphate. The glucose uptake was not modified by the fast changes in the medium Pi nor were significant differences in lactate and pyruvate release observed, which showed clear increases in all stages. It is concluded that hypophosphatemia alone is not sufficient to obtain greater increases of lactate and pyruvate release; it is also required that the hind-limb preparations be obtained from ..

Glucose uptake orthophosphate exchange lactate and pyruvaterelease of perfused rat hind-limb during phosphorus deficiency

This experimental work was carried out on perfused skinned hind-limbs from three groups of rats: fed-ad-libitum (FAL), phosphorus deficient (PD) and pair-weighed (PW), all of them fasted for 24 hours before the experiments. The perfusate was prepared using KRB solution to which was added bovine albumin (3 g.%), glucose (180 mg/dl), orthophosphate (0.5 mg/dl) and approximately 16-18 per cent of fresh washed rats erythrocytes. pH was adjusted to 7.40. The medium was bubbled with hunid O2-CO2 gas mixture (95/5%). Initial perfusate volume was 90 ml. 32Pi (0.5*Ci/ml) was incorporated to the medium at -15 minutes time.Parameters measured were: perfusate glucose, perfusate plasma Pi, perfusate 32Pi, perfusate plasma Pi relative specific activity, perfusate lactate and perfusate pyruvate. Samples were obtained every 15 minutes up to 90 minutes. Insulin (200 *U/ml) was added to perfusate as a bolus at 0 minutes time, in the experiments in which the effect to the hormone was appraised. The spontaneous glucose uptake was greater in the PD group than in the FAL group, but no significant difference was found between PD and PW. Insulin increased the glicose uptake in the three groups, but the difference between PD and the other two groups was not significant. The perfusate plasma Pi rose gradually in all groups. In the stage 0-30 minutes hypophosphatemia was still present, and the increase in glucose uptake determined by insulin was not significantly different from the spontaneous incorporation of the hexose to the preparations in the PD group. The spontaneous Pi release to the medium by the preparations was not significantly differ..

Influence of the metabolic environment on oxygen uptake and isometric developed tension of isolated rat portal vein

Se cuantificaron simultáneamente la captación de oxígeno y la tensión contráctil isométrica (TCI) de la vena porta aislada de rata, incubada en medio sin glucosa, luego de la readmisión de sustratos metabólicos y de la adición de 2-deoxi-D-glucosa (2-DG) o insulina. En condiciones controles, la capatación de 02 fue de 0.128 + ou - 0.004 micronl de oxígeno/mg peso seco/m (n = 50). Después de 40 m de incubación en medio sin glucosa, la TCI y la captación de oxígeno fueron deprimidas en grado similar. La adición de glucosa 11 mM o piruvato, acetado, lactado o buricato 5 mM a venas hipodinámicas, provocó diferentes niveles de recuperación de los parámetros mecánico y metabólico, siendo piruvato y acetato los más efectivos. Insulina (0.1 U/ml) añadida 5 m previos a la readmisión de glucosa, incrementó la recuperación de la TCI sin modificar la captación de oxígeno. 2-DG 5.5 mM, cuando se añadió en medio sin glucosa abolió la TCI pero sólo deprimió la respiración celular en un 38% a los 20m; estos efectos fueron atenuados en presencia de glucosa. Los resultados sugieren que la captación de oxígeno en este vaso depende, entre otros factores, del sustrato exógeno. También evidencian relaciones entre la amplitud de la TCI y la actividad metabólica, así como la relevancia de las vías glucolíticas y oxidativas

Glycolytic enzymes in juvenile and adult Angiostrongylus cantonensis.

In extracts of adult Angiostrongylus cantonensis, the activities of enzymes including glucokinase, phosphoglucoisomerase, phosphofructokinase, aldolase, triosepho sphate isomerase, glyceraldehydephosphate dehydrogenase, phosphoglycerokinase, phosphoglyceromutase, enolase, pyruvate kinase, lactate dehydrogenase, pyruvate decarboxylase, alcohol dehydrogenase, glucose 6-phosphate dehydrogenase, glycerophosphate dehydrogenase and pyruvate dehydrogenase complex were demonstrated. The present of significant activity of glycerophosphate dehydrogenase and glucose 6-phosphate dehydrogenase may indicate the possibility of an operative of alpha-glycerophosphate and pentose phosphate pathway.

Effect of acephate (orthene) on tissue levels of thiamine, pyruvic acid, lactic acid, glycogen and blood sugar.

Effect of Acephate, an organophosphorus insecticide, on tissue levels of thiamine, pyruvic acid, lactic acid, glycogen and blood sugar, has been studied. The albino rats, injected subcutaneously with Acephate (25 mg/10 gm body wt./day) for 4 weeks and 8 weeks, showed appreciable depletion of thiamine in liver, heart, kidney, brain and blood. The depletion of thiamine was found to be more after 8 weeks of Acephate injection. There was concomitant increase in pyruvic acid and lactic acid in various tissues. There was enormous depletion of glycogen in liver and slight rise in blood sugar concentration. The animals injected thiamine (120 micrograms/100 gm body wt./day) along with Acephate, showed more or less normal levels of thiamine, pyruvic acid, lactic acid, liver glycogen and blood sugar. The increase in pyruvic acid and lactic acid in tissues has been attributed to depletion of thiamine which is required of pyruvic acid oxidation. The increase in blood sugar has been attributed to the excess breakdown of glycogen.