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T De Guzman

Publications and source records attributed to T De Guzman.

6 recordsLinked to original sources
PubMed1991

Effects of brief starvation on brain protease activity.

Changes in the activity of proteases (cathepsin D and calpains) caused by 48-h food withdrawal were studied in the brain, liver, kidney, spleen, and heart of 3-, 12-, and 24-month-old Fischer rats. Cathepsin D activity was similar in brain, liver, and heart of control animals; in kidney it was 5-fold higher and in spleen about 10-fold higher. With age, activity increased in all organs tested except spleen. Brief starvation caused no change of cathepsin D activity in brain, but caused an increase in liver and a decrease in spleen. Neutral proteolytic activity in control was highest in the pons-medulla-cerebellum fraction of brain, and activity in liver and heart was below that in brain. Activity increased with age in brain and decreased in other organs. Brief starvation in young animals caused an increase in activity in brain, and a decrease in liver and spleen. Isolated calpain II activity was high in control brain. It increased with age in the cerebrum. Brief starvation resulted in a decrease in the brain. The results indicate that the protease content of the brain is altered with age and in malnutrition, with changes not being the same for all proteases, and changes in brain being different from those in other organs.

Aging↗
PubMed1983

Dietary lithium during development: changes in amino acid levels, ionic content, and [3H]spiperone binding in the brain of rats.

We found that chronic lithium diet affects the sensitivity of neuroleptic receptors and the content of amino acids in the brain, and that the changes in adult animals differ from those in young rats. Pregnant rats were kept on lithium diet (pellets with 0.21% Li2CO3 and 0.21% NaCl) during the gestation period and the offspring were kept on lithium for six weeks after delivery. Control rats were kept on normal diet under identical conditions. In corpus striatum and cerebral cortex of lithium-treated young rats a reduction in apparent dissociation constant and no change in (3H)spiperone total binding sites were found, suggesting a sensitization of the neuroleptic receptor; this result was unlike that obtained with adult lithium-treated rats, where the total number of binding sites was decreased. The lithium content of brain was very high (2.32 meq/kg of wet weight), whereas in the serum only 0.75 meq/l was recorded. K+ and Na+ levels increased by 20% and 9% respectively in the brain and remained at normal levels in the serum. Analysis of free amino acids in the cerebral cortex, midbrain, and cerebellum showed increases in GABA and glycine levels in all three regions, a significant increase in taurine in midbrain, and an increase in lysine in cerebral cortex and cerebellum. The results indicate that the effect of chronic dietary lithium given during pregnancy on the neuroleptic receptor in young rats is different from that in adult animals. It produces an increase in the number of the neuroleptic receptor sites instead of the decline in the number of binding sites found in adult rats. It remains to be established whether this effect is related more to the age of the animal tested or to the stage of development of the CNS at which the lithium was administered.

Amino Acids↗
PubMed1978

Decrease in cerebral protein synthesis on a low protein diet.

When rats are put on a diet that is low in protein or contains no protein, decrease in brain weight can be observed. Changes in adults are minimal. In the young there is a 10--30% decrease in cell number and protein content; the cell size (protein per cell) does not change significantly. The change is greater, the earlier the diet is started and the more severe the protein dificiency is. The longer the malnutrition period lasts, the smaller is the recovery to normal values on subsequent control diets. Amino acid incorporation in the brain decreased 10--30% under these experimental conditions; it seems the decrease was to a great extent in the more slowly metabolized protein pool. Changes in other organs were greater; for example, in liver the decrease was up to 75% under similar conditions. The changes in the brain were heterogeneous; there were regional differences, and not all proteins were affected to the same degree; choline acetyltransferase was not affected. Cellular amino acid transport as studied with incubated slices of brain was not altered under these conditions.

Animals↗
PubMed1974

Drug uptake by brain. II. Barbiturate uptake alters the transport of amino acids in vitro(1).

1. Valine and leucine uptake into mouse brain slices was stimulated by 1 to 4 mM phenobarbital and pentobarbital. Greater concentrations of these two barbiturates inhibited the transport of these amino acids. Barbital, isobarbituric acid, and 5-nitrobarbituric acid had no effect, while amobarbital and secobarbital produced only inhibition of uptake. 2. Transport of glutamate and aspartate was unaffected by phenobarbital concentrations that inhibited uptake of lysine and alpha-aminoisobutyric acid. 3. Changes in the Na+ and K+ content of the slices were not related to stimulation of valine or leucine uptake. 4. There was no concentrative uptake of phenobarbital by brain slices. The partially saturable uptake of pentobarbital was not by active transport, because the uptake increased after heating brain, liver, or kidney slices to 95 degrees for 10 min. 5. This study shows that individual members of a pharmacologically related group may have specific effects on a composite physiological function (amino acid transport) of brain tissue.

Amino Acids↗