Body weight loss during acute hypoxia: effects of increased convective oxygen transport or previous acclimation.

Body weight loss and growth retardation occur in rats exposed to simulated high altitude, which may be related to the hypoxemia-induced reduction in the convective oxygen transport (COT). The present study was thus performed to determine whether transfusion polycythemia, increased affinity of hemoglobin for oxygen, or previous acclimation to hypobaria (factors that increase COT) are able to counteract its effect on body weight during the early period of exposure, which appears to be a suitable parameter to test the effectiveness of acclimatization. Polycythemia was induced in weanling rats by two ip injections of 2.5 ml/100 g b.wt of packed homologous red cells. The rise in hemoglobin O2 affinity was brought about in adult rats by giving them 0.5 g/dl sodium cyanate in the drinking water for 3 weeks. A lower body weight loss during the early period of exposure to hypobaria was seen in treated rats than in controls. However, body weight loss was still important, which would indicate that compensation was probably not complete. When growing rats were acclimated to simulated altitude, a sudden increase in body weight was observed when they were brought back to ground levels. When animals were taken to altitude again, they lost weight at a rate not significantly different to that found in non-acclimated ones. The results obtained indicate that treatments do not prevent the studied effect of hypoxia and suggest that hypophagia and the resultant initial body weight loss and secondary depression of body growth could be considered as protective mechanisms against the environmental challenge, although further investigation will be necessary to confirm the hypothesis.

Body weight loss during acute hypoxia: effects of increased convective oxygen transport or previous acclimation

La pérdida de peso corporal y el retardo del crecimiento corporal que se observan en ratas expuestas a condiciones de altura simulada podrían estar relacionados con la reducción del transporte convectivo de O2 (COT) inducida por hipoxemia. El presente estudio fue realizado para determinar si la policitemia transfusional, el incremento de la afinidad de la hemoglobina por el O2, o la aclimatación previa a hipobaria (factores que incrementan (COT) son capaces de contrarrestar los efectos señalados sobre el peso corporal durante el "período inicial" de la exposición, el que puede se considerado como um parámetro útil para comprobar la efectividad de la aclimatación. La policitemia fue inducida en ratas jóvenes mediante dos inyecciones ip de 2,5 ml/100g de suspensión de eritrócitos homólogos al 80 por ciento. La disminución de la P50 fue inducida en ratas adultas mediante la administración de o.5g/dl de cianato de sodio en el agua de bebida durante 3 semanas. Ambos tratamientos indujeron una menor pérdida de peso lo que sugeriría que la compensación fue probablemente insuficiente. Cuando ratas jóvenes fueron aclimatadas a condiciones de altura simulada, se observó un marcado incremento del peso corporal cuando perdieron peso en la misma proporción que la observada en animales controles no aclimatados previamente. Los resultados obtenidos indican que el incremento del COT no previene los efectos estudiados de la exposición a hipobária y sugieren que la hipofagia y la pérdida inicial de peso, así como la depressión secundaria del crecimiento corporal, podrían ser consideradas como un mecanismo protector contra la hipoxia resultante

Body weight loss during acute hypoxia: effects of increased convective oxygen transport or previous acclimation

La pérdida de peso corporal y el retardo del crecimiento corporal que se observan en ratas expuestas a condiciones de altura simulada podrían estar relacionados con la reducción del transporte convectivo de O2 (COT) inducida por hipoxemia. El presente estudio fue realizado para determinar si la policitemia transfusional, el incremento de la afinidad de la hemoglobina por el O2, o la aclimatación previa a hipobaria (factores que incrementan (COT) son capaces de contrarrestar los efectos señalados sobre el peso corporal durante el "período inicial" de la exposición, el que puede se considerado como um parámetro útil para comprobar la efectividad de la aclimatación. La policitemia fue inducida en ratas jóvenes mediante dos inyecciones ip de 2,5 ml/100g de suspensión de eritrócitos homólogos al 80 por ciento. La disminución de la P50 fue inducida en ratas adultas mediante la administración de o.5g/dl de cianato de sodio en el agua de bebida durante 3 semanas. Ambos tratamientos indujeron una menor pérdida de peso lo que sugeriría que la compensación fue probablemente insuficiente. Cuando ratas jóvenes fueron aclimatadas a condiciones de altura simulada, se observó un marcado incremento del peso corporal cuando perdieron peso en la misma proporción que la observada en animales controles no aclimatados previamente. Los resultados obtenidos indican que el incremento del COT no previene los efectos estudiados de la exposición a hipobária y sugieren que la hipofagia y la pérdida inicial de peso, así como la depressión secundaria del crecimiento corporal, podrían ser consideradas como un mecanismo protector contra la hipoxia resultante (AU)

Body weight loss during acute hypoxia: effects of increased convective oxygen transport or previous acclimation.

Body weight loss and growth retardation occur in rats exposed to simulated high altitude, which may be related to the hypoxemia-induced reduction in the convective oxygen transport (COT). The present study was thus performed to determine whether transfusion polycythemia, increased affinity of hemoglobin for oxygen, or previous acclimation to hypobaria (factors that increase COT) are able to counteract its effect on body weight during the early period of exposure, which appears to be a suitable parameter to test the effectiveness of acclimatization. Polycythemia was induced in weanling rats by two ip injections of 2.5 ml/100 g b.wt of packed homologous red cells. The rise in hemoglobin O2 affinity was brought about in adult rats by giving them 0.5 g/dl sodium cyanate in the drinking water for 3 weeks. A lower body weight loss during the early period of exposure to hypobaria was seen in treated rats than in controls. However, body weight loss was still important, which would indicate that compensation was probably not complete. When growing rats were acclimated to simulated altitude, a sudden increase in body weight was observed when they were brought back to ground levels. When animals were taken to altitude again, they lost weight at a rate not significantly different to that found in non-acclimated ones. The results obtained indicate that treatments do not prevent the studied effect of hypoxia and suggest that hypophagia and the resultant initial body weight loss and secondary depression of body growth could be considered as protective mechanisms against the environmental challenge, although further investigation will be necessary to confirm the hypothesis.

Additive effects of dietary protein and energy deficiencies on mandibular growth in the weanling rat.

Dietary protein restriction adversely affects mandibular growth in the weanling rat. Protein deficiency is usually accompanied by reduced food intake which, in turn, induces energy deficiency. The present study was thus designed to dissociate the effects of dietary protein and energy deficiencies on the growth of the mandible in rapidly growing rats. Four groups of Sprague-Dawley rats aged 30 days were fed a normal diet, a low-energy diet, a low protein diet, and a low-protein and low-energy diet for 20 days. Rats were sacrificed at the end of experimental period and body weight and mandibular dimensions were recorded to evaluate body growth and mandibular growth. The growth of the mandible was affected almost in the same order of magnitude by both protein and energy restrictions. When both were applied together, mandibular growth was even more severely affected. Two way analysis of variance revealed the absence of synergism between variables, indicating that the negative effects of dietary protein and energy restrictions on mandibular growth could be considered to be additive.

Additive effects of dietary protein and energy deficiencies on mandibular growth in the weanling rat

Dietary protein restriction adversely affects mandibular growth in the weanling rat. Protein deficiency is usually accompanied by reduced food intake which, in turn, induces energy deficiency. The present study was thus designed to dissociate the effects of dietary protein and energy deficiencies on the growth of the mandible in rapidly growing rats. Four groups of Sprague-Dawley rats aged 30 days were fed a normal diet, a low-energy diet, a low protein diet, and a low-protein and low-energy diet for 20 days. Rats were sacrificed at the end of experimental period and body weight and mandibular dimensions were recorded to evaluate body growth and mandibular growth. The growth of the mandible was affected almost in the same order of magnitude by both protein and energy restrictions. When both were applied together, mandibular growth was even more severely affected. Two way analysis of variance revealed the absence of synergism between variables, indicating that the negative effects of dietary protein and energy restrictions on mandibular growth could be considered to be additive.

Additive effects of dietary protein and energy deficiencies on mandibular growth in the weanling rat.

Dietary protein restriction adversely affects mandibular growth in the weanling rat. Protein deficiency is usually accompanied by reduced food intake which, in turn, induces energy deficiency. The present study was thus designed to dissociate the effects of dietary protein and energy deficiencies on the growth of the mandible in rapidly growing rats. Four groups of Sprague-Dawley rats aged 30 days were fed a normal diet, a low-energy diet, a low protein diet, and a low-protein and low-energy diet for 20 days. Rats were sacrificed at the end of experimental period and body weight and mandibular dimensions were recorded to evaluate body growth and mandibular growth. The growth of the mandible was affected almost in the same order of magnitude by both protein and energy restrictions. When both were applied together, mandibular growth was even more severely affected. Two way analysis of variance revealed the absence of synergism between variables, indicating that the negative effects of dietary protein and energy restrictions on mandibular growth could be considered to be additive.

The mechanism of the transient depression of the erythropoietic rate induced in the rat by a single injection of uranyl nitrate.

With the purpose of assessing the effect of uranyl nitrate (UN) on the rate of erythropoiesis, 1 mg/kg of the compound was injected iv to adult female Wistar rats. The dosing vehicle was injected into control animals. A single injection of UN induced a transient depression of the rate of red cell volume 59Fe uptake, which reached its lowest value (68% depression) by the seventh postinjection day. By 14 days, 59Fe incorporation had returned to normal. The amount of iron going to erythroid tissue per hour, reticulocyte count, and immunoreactive erythropoietin concentration in both plasma and kidney extracts were also significantly depressed in UN-treated rats in relation to these values in vehicle-injected rats by the seventh postinjection day. Dose-response curves for exogenous erythropoietin (Epo) performed in polycythemic intact and UN-treated rats 7 days after drug injection revealed a significant depression of the response in UN-injected animals. Moreover, bone marrow cells obtained from rats pretreated with UN formed a reduced number of erythroid colonies in vitro in response to Epo. Therefore, possible mechanisms for the observed transient depression in the rate of erythropoiesis associated with acute UN treatment include decreased Epo production and direct or indirect damage of erythroid progenitor cells.

The concentration of dietary casein required for normal mandibular growth in the rat.

To determine a suitable casein concentration for normal, undeformed mandibular growth, we placed weanling male rats on diets containing graded levels of casein between 0% and 30% for 19 days. Some weanlings were killed so that initial values could be established. Ten linear dimensions corresponding to the six skeletal units of the mandible were evaluated so that their growth rates at the end of the experimental period could be established. Other dimensions were also evaluated for study of the growth rate of the bone as a whole. The macroscopic growth of the mandible showed a sigmoidal relationship with dietary casein concentration, most of the measurements reaching a plateau at 20% casein. Within the skeletal units, four dimensions corresponding to the alveolar and symphyseal regions did not change with age and were not affected by the casein content of the diet. The remaining six dimensions-corresponding to condylar, coronoid, angular, and basal regions of the mandible-increased with age and were related positively to dietary casein concentration. Their growth patterns were not uniform, although all of them reached maximal values when the diet contained 20% casein. Therefore, deformation of the mandible appears to occur in rats fed diets with a casein concentration lower than 20%. It appears that a dietary casein concentration of 20% is required for normal, undeformed mandibular growth.