Biomedical subjects

T DeGuzman

Publications and source records attributed to T DeGuzman.

12 recordsLinked to original sources

PubMed1998

Alteration of protease levels in different brain areas of suicide victims.

Numerous recent studies found that proteases play a major role in brain function. In addition to their role in protein turnover, they have modulatory functions and an important role in apoptosis, pathological changes, and other mechanisms. To explore possible differences in brain protein metabolism of suicide victims, we examined the activity of two proteases, cathepsin D and calpain (I and II combined), in eleven discrete areas of postmortem brain tissue of 21 victims of suicide and of 31 age- and sex-matched control subjects without a history of psychiatric or neurological disease. The levels of functionally important amino acids in five of these areas were also measured. Cathepsin D activity was found to be lower in two of eleven regions of brains of suicide victims, the parahippocampal cortex and the medial hypothalamus, by 26% and 27%, respectively. Calpain activity was lower in two different areas tested, 29% in the medulla oblongata and 26% in the lateral prefrontal cortex, and was 18% higher in the midbrain. There were no significant differences in the other areas (globus pallidus, hippocampus, amygdala, caudate nucleus, ventral tegmental area, and nucleus accumbens). Protease distribution was regionally heterogeneous--the levels in the globus pallidus were low, and in the hippocampus high, with about a two-fold difference. The length of the postmortem period for obtaining tissue, the storage time of the frozen tissue, and the age of the subject had no apparent influence on the results obtained. Although there was a tendency toward higher levels of aspartate and glycine in brain areas from suicide victims, the difference was not significant. The variations among individual brains were greater in amino acid levels than in protease levels. The findings indicate the possible role of protein metabolism in depressive or suicidal behavior.

Amino Acids↗

PubMed1996

Changes in brain protease activity in aging.

We measured changes in protease activity with aging, conducting assays of cathepsin D and calpain II activities and the rate of degradation of cytoskeletal proteins, preparing the enzymes and substrates from young and aged brains. Calpain preparations added to the young and to the aged substrates were standardized with casein as substrate so that age-related changes in calpain specificity and substrate susceptibility were measured. Several age-related differences were observed in substrate susceptibility and in enzyme activity. With respect to substrate, the neurofilament protein from young animals was somewhat more susceptible to calpain action than that from older animals. With respect to enzyme activity, calpain from aged brain cleaved neurofilament protein at a faster rate than did calpain from young. With neurofilaments, the most rapid breakdown usually occurred when enzyme from aged tissue was incubated with substrate from young. Kidney enzyme of aged rats incubated with neurofilament substrate of aged rats resulted in a more rapid breakdown than enzyme of young kidney incubated with substrate of young. The age dependence of tubulin breakdown was somewhat different from that of neurofilament breakdown. The most rapid breakdown usually occurred when using enzyme from young with tubulin from young. Incubation of neurofilament protein or tubulin with cathepsin D did not reveal any differences with aging. These studies suggest that an increase in enzyme activity observed previously during aging may also include changes in the properties of the enzyme (substrate specificity) and/or in the properties of their endogenous substrates (susceptibility to breakdown).

Aging↗

PubMed1996

Amino acid distribution in immature rat brain.

We compared the levels of amino acids in the free pool in 6 regions (cerebral cortex, olfactory bulb, substantia nigra, globus pallidus, caudate nucleus, and spinal cord) in the newborn rat brain. The amino acid distribution was heterogeneous, with the area of highest concentration containing 2-3 fold as much as the lowest area. These differences were considerably less than those previously found for adult brain. Although some areas often contained high levels of amino acids, and others mostly low levels, the distribution of the various amino acids was highly variable. This heterogeneity of distribution in the newborn brain was different from that in the adult brain. We conclude that there is significant heterogeneity of amino acid distribution, that it is different for each amino acid, and that it undergoes major changes during development.

Aging↗

PubMed1995

Effect of food deprivation on glutathione and amino acid levels in brain and liver of young and aged rats.

The effect of short-term food deprivation on glutathione (GSH) and amino acid levels in brain regions of young and aged rats was compared with changes observed in liver. Animals aged 3 months and 24 months were deprived of food for 48 h. GSH and amino acid levels from cerebral cortex, cerebellum, pons medulla, and liver were assayed and compared with levels in animals of the same age fed normal diets. In liver in both young and old rats, GSH levels fell 30%, from 13 mumol/g tissue to 8.7 mumol/g tissue. Significant changes were observed in other amino acids, including an increase of 30-50% in methionine, glycine, and glutamine, and a decrease of 30-50% in alanine in liver of both young and aged rats, and a 4-fold increase in taurine in young. In brain, little change was observed upon food deprivation. No decrease was observed in GSH, and only small changes were observed in other amino acids. In the aged animal aspartate, glutamate, and alanine levels were slightly lower; tyrosine in cerebellum was reduced by 30%, and both glycine and tyrosine in the pons medulla were reduced by 20-30%. In the brain areas examined, levels of GSH ranged from 1-2 mumol/g in young and 0.8-1.4 mumol/g in old; with levels in pons medulla being lower than those in cerebral cortex. In brain, in contrast to liver, levels were scarcely affected by short-term food deprivation.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗

PubMed1995

Effect of diet on tissue protease activity.

Rats 1, 3, 12, and 24 months old were fed diets low in protein (8% casein), and proteolytic activity in tissue from brain, liver, and lung was determined. After a low-protein diet was fed for 4 weeks to 1-month-old rats, there was a significant increase in cathepsin D activity in liver, and calpain activity was increased in lung. Little change was seen in proteolytic activity in brain. In 12-month-old rats, there was an increase in cathepsin D activity in brain and liver. In 24-month-old rats, cathepsin D activity in the liver and calpain activity in lung were increased. There was no change in proteolytic activity in the brain. When animals were fed diets supplemented with fatty acids or antioxidants for 2 months, in 3-month-old rats calpain activity was increased in brain but decreased in lung. Cathepsin D activity was significantly increased in young and adult animals in brain and in liver. These observations suggest that diet changes result in significant alteration in tissue calpain and cathepsin D levels, and possibly activity, in vivo. Generally, changes are greater for cathepsin D than for calpain, and are smaller in brain than in other tissues.

Aging↗

PubMed1994

Calpain activity in adult and aged human brain regions.

We assayed calpain activity in 27 human brain regions from adult (43-65 years of age) and aged (66-83 years of age) postmortem tissue samples. Calpain I (microM Ca-requiring) activity was 10% or less of the total activity; it was below detectable levels in a number of areas, and so data are are expressed as total (microM + mM Ca-dependent) calpain activity. The distribution of the enzyme was regionally heterogeneous. Highest activity was found in the spinal cord, followed by the amygdala, and levels in mesencephalic areas and in cerebellar grey matter were also high. Levels in cerebellar white matter, tegmentum, pons, and putamen were low, and activity in cortical areas was also relatively low. Although in some areas activity seemed higher with aging, the differences were not statistically significant. We previously found that the regional distribution of cathepsin D in human and in rat brain is similar, this seems to be true for calpain activity as well. The increase of protease activity with age found in rat brain is not found in human areas, as was shown previously with cathepsin D, and in the present study with calpain.

Adult↗

PubMed1992

The distribution of cathepsin D activity in adult and aging human brain regions.

We measured the activity of cathepsin D, the major cerebral protease, in 50 separate areas of the central nervous system of adult and aged humans, using hemoglobin as the substrate. The activity showed significant regional heterogeneity, with average differences of 50-100% between the lower and higher level areas, and a more than threefold difference between the lowest and highest levels. The forebrain, midbrain, and hindbrain each had areas of high and low activity; cerebellum and cord areas were among those with low activity. Cathepsin levels tended to increase with age in about half of the areas analyzed, and the increases were significant in 14. Statistically significant decreases with aging were observed in two areas. The increases varied between 30 and 60%, and the decreases were 20%. Enzyme activity in thalamus, hypothalamus, pons, medulla, and cerebellum increased with age. In the ventrolateral medulla, which contains the major portion of the cerebral noradrenergic cells, the cathepsin D levels increased with age; in the dorsal raphe area, which contains the major portion of the cerebral serotonergic cells, the enzyme levels decreased. The change with age in human brain seems to be less than what we observed in rat brain, where activity more than doubled in most areas. The changes in enzyme levels need to be tested at more ages to establish a pattern of changes in activity throughout life.

Adult↗

PubMed1990

Calpain II activity and calpastatin content in brain regions of 3- and 24-month-old rats.

In previous studies, we found a significantly higher (100% or more) content of cathepsin D in the aging brain. In the present study, we determined activity of Ca2(+)-activated neutral protease requiring millimolar Ca2+ (calpain II, CANP II) and amount of its endogenous inhibitor, calpastatin, in extracts of various brain regions of 3-month-old and 24-month-old male Fischer-344 rats. Calpain II was separated from calpastatin in a single step (chromatography) and its activity was tested using as substrates [methyl-14C]alpha-casein, the cytoskeletal proteins desmin and actin, and a mixture of neurofilament triplet proteins and glial fibrillary acidic proteins (GFAP). We found no changes in calpain II activity in pons-medulla and spinal cord, but significant increases were detected in cortex (72%) and striatum (63%) of the 24-month-old rats using [methyl-14C]alpha-casein as substrate. The profile of desmin and actin breakdown showed regional variations somewhat different from those of [methyl-14C]alpha-casein. With desmin, the greatest increases with age were in the striatum (82%) and hypothalamus (46%), but there were no alterations in cortex, cerebellum, and pons-medulla. With actin, slightly enhanced activity in cortex and cerebellum was noticeable. Calpastatin content in brain regions was also increased, with the regional pattern of increase fairly similar to the pattern of enzyme activity increase. The causes and the physiological consequences of increased calpain and calpastatin content in the aged brain are being investigated. That changes with age are somewhat different with the various brain protein substrates indicates that some of the properties of the enzyme also undergo alteration with age.(ABSTRACT TRUNCATED AT 250 WORDS)

Actins↗

PubMed1989

Increase in cathepsin D activity in rat brain in aging.

Cathepsin D-like activity in homogenates of five brain areas of 3-month-old and 24-month-old Fischer 344 rats was measured. With hemoglobin as substrate at pH 3.2, more than 90% of the activity was inhibited by pepstatin. In each area studied, activity was more than twice as high in the old rat brain: 140-160% higher in the cortex, cerebellum, pons-medulla, and striatum and 90-100% higher in the hippocampus and spinal cord. The greatly increased metabolic capacity in the absence of an increase in protein turnover may have a role in age-related pathological degeneration in the brain.

Aging↗

PubMed1983

Developmental changes in the breakdown of brain tubulin by cerebral cathepsin D.

The activity of cathepsin D on hemoglobin and on cytoplasmic tubulin was measured in brain preparations at different ages--in newborn, 10- and 21-day-old, and young adult rats. Enzyme activity increased after birth, reaching a maximum at around 21 days, and then declined. This increase was not parallel with decreased turnover of proteins during development, but was parallel with decreasing level and increasing microheterogeneity and rate of assembly of tubulin during development. The breakdown of tubulin was heterogeneous, with initial fast breakdown of a large portion, followed by breakdown at a lower rate. This heterogeneity in breakdown persisted throughout development. The breakdown of tubulin, unlike that of hemoglobin, was at all ages greater at pH 5.8 than at pH 3.2. The possible role of cathepsin D in tubulin metabolism and the developmental changes under physiological conditions need further exploration.

Aging↗

PubMed1982

Lithium: effect on [3H]spiperone binding, ionic content, and amino acid levels in the brain of rats.

After prolonged treatment of rats with lithium (pellets, 0.21% lithium carbonate, or 0.5 mg/ml lithium chloride in drinking water) for three months, the level of lithium in plasma was 0.87 meq/liter; in several brain regions, between 1.06-1.39 mueq/g wet weight. The content of sodium and potassium inthe plasma was normal. The level of potassium in the brain regions tested increased by 13-30% and that of sodium by about 10%. Glycine levels increased significantly in all the regions (cerebral cortex, midbrain, cerebellum, and spinal cord). In the cerebellum GABA was also increased, while glutamine was decreased. In midbrain, apart from increases in glycine levels, alanine, valine, GABA and lysine were also increased. In the spinal cord, glutamic acid was also increased. Changes were largely in the putative neurotransmitters. Long-term treatment with lithium also influenced the high-affinity binding of [3H] spiperone in the cerebral cortex and corpus striatum. Two specific binding sites were found in both brain regions; the main change was the reduction in the lower affinity binding site (B max 2).

Amino Acids↗

PubMedDate not supplied

Enkephalin-containing polypeptides are potent inhibitors of enkephalin degradation.

Enkephalin-containing polypeptides derived from pro-enkephalin A, pro-enkephalin B, or pro-opiomelanocortin were inhibitors of enkephalin degradation by aminoenkephalinases purified from cytosol or membranes. Of the peptides, Argo-Met-enkephalin was the most potent inhibitor for the aminoenkephalinases, with an IC50 of about 0.6 microM, it was more effective than bestatin (IC50 = 0.8-1.0 microM). This inhibition was partly due to substrate competition. Argo-Met-enkephalin was hydrolyzed by aminoenkephalinases to form Arg, Tyr, and Gly-Gly-Phe-Met in a substrate-inhibited manner. The hexapeptide also inhibited the breakdown of Arg- and Tyr-beta-naphthylamide by the membrane aminoenkephalinase. Since Argo-Met-enkephalin did not inhibit leucine aminopeptidase, it was a more selective inhibitor than bestatin of Met-enkephalin breakdown by aminopeptidases. Argo-Met-enkephalin inhibited enkephalin breakdown by synaptosomal plasma membranes but not by brain slices. Our data suggest that in addition to their possible role as opioids, the enkephalin-containing polypeptides may be regulators of enkephalin levels.

Aminopeptidases↗