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Biomedical subjects

G Barrera

Publications and source records attributed to G Barrera.

At least 55 records · Page 3Linked to original sources
PubMed1986

Cellular distribution of lysosomal hydrolase activities in the regenerating rat liver.

Cathepsins B and D, beta-galactosidase, and acid phosphatase activities were found to be decreased in the regenerating rat liver, the reduction being maximal around the peak of hepatocyte mitoses (30 h). To investigate whether these changes could be heterogeneously distributed among hepatic cells, total cell populations from control or two-thirds hepatectomized rat livers were dissociated by the collagenase perfusion technique and analysed by different procedures. Isopycnic centrifugation in a Metrizamide gradient satisfactorily resolved hepatocytes and non-parenchymal cells from control animals but was not adequate when applied to 30-h regenerating liver cells. Colchicine treatment of the hepatectomized animals, resulted in substantial accumulation of phase M-hepatocytes. Subpopulations considerably enriched in fast-sedimenting phase M-cells were obtained by sedimentation at 1 g of the total liver cell population, and subsequently analysed by isopycnic equilibration. Phase M-hepatocytes were shown to have markedly reduced levels of beta-galactosidase, acid phosphatase, and cathepsin B activities in comparison, not only with control hepatocytes, but also with those parenchymal cells which were not metaphase-arrested in the same regenerating livers. Therefore, in partially-hepatectomized rats, hepatocytes progressing up to metaphase in the first mitotic cycle exhibited a selective depletion of lysosomal enzyme activities. The mechanism(s) underlying this change remain(s) presently unknown.

Acid Phosphatase↗
PubMed1986

Long-term validation of 1 g of protein per kilogram body weight from a predominantly vegetable mixed diet to meet the requirements of young adult males.

Eight healthy young men participated in a 90-d metabolic balance study designed to assess the adequacy of 1 g of protein (N X 6.25) per kilogram body weight per day provided by a predominantly vegetable diet. The mean gross energy intake of the subjects was 49 kcal/(kg X d). The individuals received the experimental diet for eleven 8-d experimental periods. Three isoenergetic, isonitrogenous meals were served at 0800, 1200 and 1900. Anthropometric measurements and biochemical determinations in blood were made at the beginning of the study and afterwards at regular 15-d intervals. Body weight was measured daily. The mean overall weight change for the group was -0.8 kg. The mean daily urinary nitrogen output decreased from an initial value of 134.6 mg/(kg X d) to a final figure of 115.1 mg/(kg X d) (P less than 0.01), while the daily fecal N decreased from 31.5 to 26.3 mg/(kg X d) (P less than 0.05). Mean cumulative nitrogen balances were slightly positive for seven out of the eight individuals with an overall mean nitrogen balance value of +6.7 mg N/(kg X d). Biochemical and hematological values showed no significant changes throughout the study, except for a decrease in serum cholesterol. It is concluded that the "Chilean" mixed diet fed at the level of 1 g of protein per kilogram body weight per day with sufficient energy meets the long-term protein-energy needs of healthy young men, thus supporting the 1984 FAO/WHO/UNU safe recommended daily protein allowance of 0.75 g of reference protein, with a correction for the lower digestibility of vegetable sources.

Adult↗
PubMed1986

Calmodulin antagonism and growth-inhibiting activity of triphenylethylene antiestrogens in MCF-7 human breast cancer cells.

The triphenylethylene antiestrogen tamoxifen has been shown previously to inhibit both calmodulin and protein kinase C activities, which are involved in the control of cell proliferation. We have studied the effect of several derivatives of the triphenylethylene antiestrogen family on the inhibition of both calmodulin-dependent cyclic adenosine 3':5'-monophosphate-phosphodiesterase activity and proliferation of breast cancer cells cultured with 0.5 microM estradiol in order to prevent interaction of these drugs with the estrogen receptor. We have observed that hydroxylation of the triphenylethylene molecule significantly decreases its ability to inhibit the calmodulin-dependent phosphodiesterase activity in vitro. Furthermore, the growth-inhibiting activity of several antiestrogens and other calmodulin antagonists [R24571, trifluoperazine, N-(6-aminohexyl)-5-chloronaphthalene-1-sulfonamide, and N-(6-aminohexyl)-1-naphthalenesulfonamide] correlated with their antagonistic effects on calmodulin activity. The level of activity was determined as follows: R24571 greater than tamoxifen = N-demethyltamoxifen = nafoxidine greater than 4-hydroxytamoxifen greater than 3,4-dihydroxytamoxifen = trifluoperazine greater than N-(6-aminohexyl)-5-chloronaphthalene-1-sulfononamide greater than metabolite A greater than N-(6-aminohexyl)-1-naphthalenesulfonamide. On the other hand both protein kinase C-activating and -inhibiting drugs (phorboltetradecanoate-13-acetate and tamoxifen, respectively) have a synergistic inhibitory effect on the growth of MCF-7 cells. Our data suggest that antiestrogen interactions with calmodulin and not protein kinase C may play a role in mediating the drug-induced estrogen-independent inhibition of breast cancer cell growth.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1985

[Anthropometric characteristics of school children graduated from basic and secondary education in the Metropolitan area of Santiago de Chile].

An anthropometric assessment of the nutritional status and growth of students graduating from Basic (8th grade) and Secondary (4th grade) Education was carried out. A group sample of 522 students from the Metropolitan Area of Santiago, Chile, was randomly selected. The same number of students by sex, dependency (public and private schools) from high, medium and low socioeconomic levels (SEL) was chosen. SEL was measured through the Graffar Modified Scale, and the percentage of weight for age (% W/A), height/age (% H/A) and weight/height (% W/H) were evaluated in accordance with the National Center for Health Statistics (NCHS) reference pattern. The % adequacy of head circumference/age (% HC/A) was determined by the Tanner Tables, and the % of upper to lower segment ratio (% US/LS), by the Tables of Muzzo et al. Results revealed that the % of W/A and of H/A were diminished in students of both sexes, while the % of UP/LS, was increased in males of low SEL, from Basic Education; this impact is lost in males graduating from Secondary Education and persists only in the LSE females. No differences in the nutritional status (% W/H) of students according to SEL, were found. Females registered values over 110% of the WHO standard, a finding suggesting a high prevalence of overweight and obesity. We conclude that there is a growth retardation in students graduating from 8th Basic Grade, which persists only in females from 4th grade of Secondary Education. This finding indicates that, in addition to possible environmental factors, other factors, probably of genetic order, also influence the latter. Overweight and obesity, therefore, constitute an important problem that merits measures of preventive nature directed to avoid future consequences.

Adolescent↗
PubMed1984

Effect of Epomediol on the ATPase and adenylate cyclase activities in plasmamembranes isolated from rat liver.

The effect of Epomediol (Clesidren (R)) on the membrane ATPase and Adenylate Cyclase activities has been investigated using highly purified rat liver plasmamembranes. The drug, even at micromolar concentration, showed a significant stimulatory effect on Ca++/Mg++- ATPase, Ca++- ATPase and Adenylate Cyclase activities. In particular the effect on Ca++- ATPase activity suggests that the drug under study may favourably modulate the calcium intracellular homeostasis.

Adenosine Triphosphatases↗
PubMed1982

[Changes in adenosinetriphosphatase activity in rat liver after CC14 poisoning].

Our study shows evidences that CCl4 administration (at the dose of 2,5 ml/kg b.w. "per os") increased ATPase activities in rat liver plasmamembranes 1 and 2 hours after treatment. Conversely we found that CCl4 poisoning decreased ATPase activities in microsomal membranes of rat liver at the same tested times. Therefore we suggest that ATPase activities were differently influenced by CCl4 treatment with respect to different subcellular distribution of those enzymes.

Adenosine Triphosphatases↗
PubMed1982

[Changes in Na+, K+-adenosinetriphosphatase and 5'-nucleotidase activities in cell membrane isolated from rat liver after acute white phosphorus poisoning].

Na+, K+-ATPase and 5'-Nucleotidase activities in rat liver plasmamembranes after "in vivo" intoxication with a single dose of white phosphorus (10 mg/kg b.w. "per os") are investigated. Na+, K+-ATPase activity is significantly increased 1 hour and inhibited 12 hours after intoxication. 5'-Nucleotidase is strongly increased at 1, 2 and 4 hours after poisoning and is significantly decreased at 12 hours. The enhancement of both the enzymatic activities is evident prior to triglyceride accumulation in rat liver. Our results suggest that lipid fluidity of cell membrane is early and mildly affected during white phosphorus poisoning.

5'-Nucleotidase↗
PubMed1982

[Changes in the adenosinetriphosphatase activity in plasma membranes incubated in vitro in the presence of 4-hydroxy-2,3-nonenal].

Cation-dependent ATPase activities of rat liver plasmamembranes incubated "in vitro" with 4-hidroxy-2,3-nonenal (HNE, an aldehyde from peroxidative decomposition of biological membrane lipid moieties) are investigated. Mg++-ATPase activity is inhibited significantly by all the doses of HNE used (13,9, 4,1,1,2, 0,35 and 0,10 microM). Evidences for the inhibition of Mg++- Na+- K+- ATPase activity are also presented. Ca++- ATPase activity is strongly increased when rat liver plasmamembranes are incubated in presence of HNE 13,9 microM. Our results suggest that HNE may play a role in the control of intracellular cation levels acting directly on mechanisms of plasmamembranes ion transport.

Adenosine Triphosphatases↗
PubMed1982

Capacity of the Chilean mixed diet to meet the protein and energy requirements of young adult males.

1. The capacity of the Chilean mixed diet to meet the daily protein and energy needs was tested in eight subjects aged from 20 to 31 years using the nitrogen balance method. This diet was tested at the protein levels of 0.40, 0.55 and 0.70 g/kg body-weight per d. 2. An egg reference diet providing 0.30, 0.45 and 0.60 g protein/kg per d was also assayed. 3. The mean daily energy intake was 207 kJ/kg per d according to subjects' previous intake and activity pattern. 4. The N balance response to each dietary protein level was taken as a measure of adequacy of protein intake, and regression analyses of N balance (Y) v. N intake (X) were calculated to estimate protein needs. The equations found were Y = 0.70X - 68.7 for the egg diet, and Y = 0.74X - 92 for the mixed diet. 5. From these equations the mean protein requirements for equilibrium were estimated to be 0.61 g/kg for egg and 0.78 g/kg for the mixed diet. 6. If the coefficient of variation is 15, the protein requirement for N equilibrium of 97.5% of the population would be 0.8 g/kg per d for egg and 1.0 g/kg per d for the mixed diet.

Adult↗
PubMed1982

Obligatory urinary and faecal nitrogen losses in young Chilean men given two levels of dietary energy intake.

1. The obligatory nitrogen losses were measured in young adult males of the low socio-economic group, consuming an N-free diet at 192 kJ (46 kcal)/kg per d from day 1 to 10 and 243 kJ (58 kcal)/kg per d from day 11 to 18. 2. All subjects, except one, lost weight compatible with N loss. 3. A kinetic evaluation of the results showed that the asymptotically derived urinary N loss after stability had been reached was 35.8 mg N/kg per d. The mean time to stability was 6.5 d. The subjects showed a trend toward decline in N loss while consuming the high-energy N-free diet. 4. The obligatory faecal N loss for days 1-10 was 16.1 mg N/kg per d and 8 mg N/kg per d for days 11-18. 5. Based on the factorial approach the total obligatory N loss of our subjects, for the initial 10 d, was 57.5 mg N/kg per d.

Adult↗
PubMed1981

Effect of methylglyoxal on rat liver lysosome-vacuolar apparatus.

Methylglyoxal (MeG) administration to rats doesn't cause any change in liver lysosome integrity; on the other hand, lysosome osmotic fragility appears highly increased at short times after the treatment. Concomitantly, a significant decrease of the residual latent activity of acid phosphatase (RLA = activity which cannot be unmasked by extensive hypo-osmotic shock) occurs. Cycloheximide (CHM), when administered shortly before MeG, prevents both the changes in RLA and in osmotic fragility. These results point to a big stimulation of autophagy in rat liver by MeG.

Acid Phosphatase↗