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L Benavides

Publications and source records attributed to L Benavides.

10 recordsLinked to original sources
PubMed1997

Changes in gravity influence rat postnatal motor system development: from simulation to space flight.

Our research examines the role of the environment in postnatal nervous system development. Recently we have been studying the effects of changes in gravity on the motor system of rats from postnatal day (P) 2 to 31 using kinematic analysis of swimming, walking, and righting reflexes. Using the tail suspension model of weightlessness we identified sensitive and critical periods of motor system development corresponding to the time during which a motor skill is first achieved. Motor performance in suspended animals was marked by slow swimming, walking, and air-righting, all of which were characterized by hindlimb extension. (Walton et al, Neurosci. 52,763,1992). The critical periods identified in these studies contributed to determining the age of animals for a small payload, NIH.R3. This 9-day mission (STS-72) included 2 litters at P5, P7, or P15 at launch. The P7-16 and P15-24 groups were studied post-flight. On the landing day (R+0) surface righting, swimming and walking were slower in flight compared to control animals. Differences were more marked in the younger animals and the hindlimbs were more affected than the forelimbs with marked, prolonged extension of, at least, the ankle joint angle. Readaptation to 1G was slower in the P7-16 group with righting reflexes adapting first, walking last. We have shown that gravity is an important factor in postnatal nervous system development and that its affect depends on the age of the animal, duration of the perturbation, and the motor function studied.

Animals↗
PubMed1992

A study of erythropoiesis and iron metabolism in the rabbit in vivo. II. Dependence of the response on iron storage and transport.

Rabbits subjected to a daily bloodletting schedule of 10 ml blood per kg body weight increase four- or fivefold their erythropoietic production compared to normal non-bled animals. The maximum response they can reach under these conditions mobilizes more than 9 mg of iron per day per rabbit into hemoglobin. When fed ad libitum with their regular diet, they do not need any further iron supplement for full erythropoiesis. The experimental increment in iron body stores and/or serum iron levels does not enhance their erythropoietic response, demonstrating that iron is not rate limiting under the conditions studied. Furthermore, although serum iron levels are elevated onefold in the controls under chronic anemia with respect to non-bled animals, the concentration of serum transferrin is only slightly increased; hence, the iron saturation of this protein changes from a 50% to an 80% level. In the absence of an extra supplement of iron, rabbits subjected to chronic bloodletting show no signs of body iron depletion, as judged by their continuous macrocytic RBC production.

Anemia↗
PubMed1979

The rate limiting step in the reticulocyte uptake of transferrin and transferrin iron. Effects of some incubation variables.

Reticulocytes incubated in an isotonic NaCl saline medium containing glucose, glutamine and amino acids, were able to detach both iron atoms from all the transferrin incorporated by them. In the absence of these metabolites, although transferrin uptake was the same, the reticulocytes failed to remove completely the iron from the transferrin which they incorporated. It has been shown before that there is unspecific as well as specific binding of transferrin to the reticulocyte. By incubating the cells in the presence of a high concentration of bovine serum albumin, we have been able to prevent the unsepcific attachment of transferrin. At least 94% of the iodinated transferrin was capable of donating its iron to the reticulocytes.

Amino Acids↗