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Biomedical subjects

V J Perez

Publications and source records attributed to V J Perez.

At least 19 recordsLinked to original sources
PubMed1988

Weight, corticosterone and glucose: changes with time of day after food deprivation.

The effects of constant food deprivation, terminated at different times of day were examined with respect to percent body weight loss (%BWL), plasma corticosterone (PC) and plasma glucose (PG). A 19-hour food deprivation paradigm schedule staggered around varying times of the day-night cycle was used. Patterns of %BWL related to nocturnal lipogenesis and diurnal lipolysis showed the greatest loss (10%) occurring at 0700 hr, while in evening hours, there was an increasing pattern of weight loss, with the greatest amount (7%) occurring at 2200 hr. A pattern suggestive of neuroregulatory cycles of glucocorticoid release was evident for PC levels; maximum levels for PC (23.2 micrograms%) were reported at 0700 hr and at 1900 hr (16.6 micrograms%). Similar patterns were also noted in PG levels, with respective maximum levels of 138.0 mg% and 125.8 mg% occurring at 0700 hr and 1900 hr. These results indicate that the time of day that a deprivation schedule is initiated and terminated is an important consideration due to the impact of circadian photoperiodism. Time of day should be an essential consideration when utilizing deprivation paradigms.

Animals↗
PubMed1987

Neuromelanogenic and cytotoxic properties of canine brainstem peroxidase.

We have isolated a heme protein from canine midbrains that possesses potent peroxidase activity. This enzyme catalyzes the oxidation of dopamine to neuromelanin in the presence of H2O2. We have further shown that the isolated peroxidase possesses potent cytotoxic activity in the presence of superoxide or H2O2 and Cl-. The enzyme possesses an endogenous NAD(P)H oxidase activity that can promote the cytotoxic activity by virtue of its production of superoxide. Other enzymes such as dihydroorotate dehydrogenase and galactose oxidase, which produce O2- and H2O2, respectively, are also effective in promoting the cytotoxic activity of the brainstem peroxidase. Although rat erythrocytes were routinely used as the target cell, other cell types, including rat hepatoma and mouse neuroblastoma cells, are also susceptible to the toxic action of the peroxidase. The cytotoxic action of the brainstem peroxidase is dramatically enhanced by kainic acid and is significantly enhanced by Mn2+, whereas dopamine was found to be a potent inhibitor of the cytotoxic activity. Based on these findings, we postulate a central role for the brainstem peroxidase in dopamine metabolism as well as in the biochemical and anatomical changes associated with Parkinson's disease.

Animals↗
PubMed1979

Minimal tissue concentrations of glutamate required to produce necrosis of hypothalamic neurons in newborn mice.

Groups of 4-day-old Cox Swiss albino mice were injected once subcutaneously with monosodium glutamate at several doses between 0.2 and 0.5 mg/g body weight. Glutamate, at a dose of 0.35 mg/g, produced neuronal necrosis of a very limited nature in only 60% of the animals and was defined as the minimal effective neurotoxic dose in the 4-day-old mouse. Neuronal loss was not detected in any animals treated with less than 0.35% mg/g of the amino acid whereas lesions became more extensive as the dose was increased to 0.5 mg/g. Glutamate was measured in the arcuate nucleus and plasma 0, 15, 30, 60 and 90 min after injection. These data indicated that duration of glutamate accumulation in the arcuate nucleus may be as important a variable in producing neuronal degeneration in the hypothalamus as concentration of the amino acid in that nucleus.

Animals↗
PubMed1978

S-100 protein: regional CNS concentrations in rats raised in different environments.

The S-100 protein was measured in 7 discrete brain areas from rats raised in an enriched, social, or isolated environment for 21, 42, or 84 days after weaning. S-100 was measured at significantly higher concentrations under enriched than under social environmental conditions in cerebellum and brainstem at 21 days but not thereafter. The protein in corresponding areas of brain in isolates was significantly less concentrated than in social controls. The results suggest changes, in turnover of the protein as a result of stimulation and activation of functionally specific brain regions, of the animals' responses to and interaction with environmental stimuli and adaptation to those stimuli.

Animals↗
PubMed1978

The effect of protein-free diet on blood pressure in the Wistar rat.

The relationship between blood pressure (BP) and an 18 day protein free diet (PFD) was studied in unanesthetized male Wistar rats beginning at 20 weeks of age. Following cessation of the 18 day diet, BP was monitored for 8 weeks. Both the PFD animals and a control diet (CD) group showed a reduction in BP from 20 weeks to 30 weeks. Reduction in BP for PFD animals was 3 times that of the CD animals across the diet period. The authors caution the reader in terms of generalizing across strains for this effect and suggest that a greater data base is needed before a definite statement can be made concerning the effects of a protein free diet on BP.

Aging↗
PubMed1977

Preparation and properties of the brain specific protein 14-3-2.

A brain specific protein, 14-3-2, has been isolated from bovine brain by the use of ammonium sulfate precipitation, gel filtration on Sephadex G-150, and ion exchange chromatography on DEAE-cellulose and DEAE-Sephadex. It is an acidic protein, in agreement with the high content of glutamic and aspartic acid, that is composed of a single polypeptide chain of mol. wt. 50,000. Immunochemical tests using antiserum to purified 14-3-2 showed that the protein is present in at least 100-fold greater amounts in brain than in any other rat tissue. Furthermore, 14-3-2 was found in brains of a number of vertebrate species, although the antigen is apparently not entirely identical in all species tested. The protein 14-3-2 can be considered to be a species non-specific protein which is neuronal in origin.

Amino Acid Sequence↗