Search PubMed⌕ Search

Biomedical subjects

J Mendez

Publications and source records attributed to J Mendez.

At least 55 records · Page 3Linked to original sources
PubMed1995

A tactile sensory system of Myxococcus xanthus involves an extracellular NAD(P)(+)-containing protein.

CsgA is a cell surface protein that plays an essential role in tactile responses during Myxococcus xanthus fruiting body formation by producing the morphogenic C-signal. The primary amino acid sequence of CsgA exhibits homology with members of the short-chain alcohol dehydrogenase (SCAD) family and several lines of evidence suggest that NAD(P)+ binding is essential for biological activity. First, the predicted CsgA secondary structure based on the 3 alpha/20 beta-hydroxysteroid dehydrogenase crystal structure suggests that the amino-terminal portion of the protein contains an NAD(P)+ binding pocket. Second, strains with csgA alleles encoding amino acid substitutions T6A and R10A in the NAD(P)+ binding pocket failed to develop. Third, exogenous MalE-CsgA rescues csgA development, whereas MalE-CsgA with the amino acid substitution CsgA T6A does not. Finally, csgA spore yield increased approximately 20% when containing 100 nM of MalE-CsgA was supplemented with 10 microM of NAD+ or NADP+. Conversely, 10 microM of NADH or NADPH delayed development for approximately 24 hr and depressed spore levels approximately 10%. Together, these results argue that NAD(P)+ binding is critical for C-signaling. S135 and K155 are conserved amino acids in the catalytic domain of SCAD members. Strains with csgA alleles encoding the amino acid substitutions S135T or K155R failed to develop. Furthermore, a MalE-CsgA protein containing CsgA S135T was not able to restore development to csgA cells. In conclusion, amino acids conserved in the coenzyme binding pocket and catalytic site are essential for C-signaling.

Amino Acid Sequence↗
PubMed1994

Coping with ambiguity in multi-ethnic children of alcoholics.

Visual field dependence in 292 multi-ethnic adult children of alcoholics (ACAs) and nonalcoholics (NACAs) was assessed, using the Hidden Figures Test (Ekstrom, French, & Harmon, 1976). There were no differences among ethnic groups, but ACAs achieved a significantly lower percentage of correct answers and more incorrect answers and attempted more questions relative to NACAs. These findings suggest that ACAs' visuospatial deficits are not related to ethnic and cultural factors.

Adaptation, Psychological↗
PubMed1994

Growth hormone and cortisol secretion before and after erythropoietin therapy in CAPD patients.

Correction of anemia with recombinant human erythropoietin (rHuEPO) in patients with end-stage renal disease (ESRD) has been associated with improvement of several endocrine abnormalities. However, long-term effects of this therapy on pituitary secretion in patients undergoing continuous ambulatory peritoneal dialysis (CAPD) is not known. The aim of the present work was to assess the growth hormone (GH) and cortisol responses to insulin-induced hypoglycemia before and after the correction of anemia with rHuEPO therapy in CAPD patients. Five well-nourished and clinically stable patients were studied before and after 12-24 weeks of rHuEPO treatment. Seven normal volunteers were studied as controls. Insulin-induced hypoglycemia tests were performed prior to starting rHuEPO therapy and again after partial correction of anemia. Blood samples for GH, cortisol, and glucose were collected between -30 and 120 min after insulin (0.1 U/kg bw) administration. GH responses to hypoglycemic stress were characterized by marked differences in single patients when compared with the control group. However, the GH peak and the area under the secretory curves (AUC) of GH responses in CAPD patients (10.6 +/- 4.8 micrograms/L and 15.4 +/- 6.1 micrograms h/L, respectively) did not differ from those obtained in control subjects (14.3 +/- 4.1 micrograms/L and 19.4 +/- 3.5 micrograms h/L, respectively). The study, after correction of anemia, showed an evident decrease of GH values at each time point on the response curve in 4 patients, and no modification in 1 patient. Mean values of GH peak and AUC were 8.8 +/- 2.8 micrograms/L and 9.6 +/- 2.3 micrograms h/L.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Sarcosporidian infection in pigs in Uruguay.

Examination of enzymatic digests of samples of the crux diaphragm obtained at abbatoirs in Montevideo, Uruguay, indicated that 57.2% of 269 pigs weighing 90-140 kg were infected with Sarcocystis sp. The morphology of sarcocystis in H & E stained sections indicated that they were Sarcocystis miescheriana.

Abattoirs↗
PubMed1984

Fat-free mass as a function of maximal oxygen consumption and 24-hour urinary creatinine, and 3-methylhistidine excretion.

The relationships between maximal oxygen consumption (VO2max) with fat-free mass (FFM), and with 24-h urinary excretion of 3-methylhistidine (3MH) and creatinine (Cr), were studied in 12 active men age 31.4 +/- 9 yr (mean +/- SD). FFM, VO2max and VO2maxWt-1 were 50.9 +/- 9.1 kg, 3.8 +/- 0.9 L X min-1, and 54.8 +/- 9.4 ml X kg-1 X min-1, respectively. Urinary 3MH and Cr after 3 days on a meat-free diet were 213.9 +/- 30.8 mumol X day-1 and 1.60 +/- 0.3 g X day-1, respectively. 3MH X Cr-1 was 135.3 +/- 16.8 mumol X g-1 or 15.3 +/- 1.9 molar ratio X 10(3). The strongest (p less than 0.01) associations found were 3MH versus FFM, FFM versus VO2max, and 3MH versus VO2max. Other significant (p less than 0.05) relationships were Cr versus FFM, Cr versus 3MH, and Cr versus VO2max. Nonsignificant correlations were found for 3MH X Cr-1 versus VO2max X kg-1 X min-1 versus FFM, 3MH X Cr-1 versus VO2max, and FFM versus VO2max X kg-1 X min-1. The best predictor of FFM was 3MH. It was concluded that endogenous urinary 3MH excretion is a valid method to study human body composition and that 3MH is more closely related to FFM (r = 0.93) than VO2max (r = 0.78).

Adult↗
PubMed1984

Sports science and body composition analysis: emphasis on cell and muscle mass.

Because we are unsure of many of the constants that we use in the calculation of components of body composition, there is a need for a greater number of postmortem analyses in order to prepare better equations for more accurate utilization of indirect noninvasive measurements. At present, most investigators who study active people (including athletes) use techniques that only provide an approximation of body fatness. Because excess fat serves as a burden to the body during transport in the performance of many physical activities, fatness constitutes a variable of concern. Fat-free body weight is usually calculated by difference and serves as a reference for some physiological functions. Although fat-free weight and lean body mass are not the same, most investigators calculate fat-free weight and many use the terms interchangeably. Some of the assumptions and problems in utilizing hydrodensitometry in the calculation of body fatness remain unresolved, such as the true densities of the different gross components of body composition in the young, aged, physically fit, etc. A variety of body composition profiles of different athletes have been published in recent years, which substantially augment efforts initiated in the 1940s and 1950s. The regular employment of a total body water assessment along with hydrodensitometry would improve the accuracy of calculation of body fatness, but the procedure is somewhat expensive in cost and time of subject involvement. In order to extend our knowledge of body composition and to quantitatively ascertain the mass of skeletal muscle, some of the procedures for calculating cell and muscle mass are reviewed including total body potassium, total body nitrogen, creatinine excretion, and 3-methylhistidine excretion. These procedures reveal important information, but require further investigation before we are confident that we are measuring cell or muscle mass. We have focused on 3-methylhistidine excretion because preliminary investigation suggests that it may reveal differences in muscle mass not detected by densitometry.

Adipose Tissue↗
PubMed1982

Exercise intensity, dietary intake, and high-density lipoprotein cholesterol in young female competitive swimmers.

Plasma high-density and low-density lipoprotein cholesterol (HDL-C and LDL-C) and dietary intake were compared in female competitive swimmers (CS, n = 7), synchronized swimmers (SS, n = 11), and sedentary controls (C, n = 6). CS tended to be taller, heavier, and leaner than C; SS were intermediate. The caloric intake of CS was 21.5% greater than C (2468 +/- 534 versus 2030 +/- 668, p less than 0.001). Dietary composition for all groups was 49% carbohydrate, 35% fat, and 15% protein. Total plasma cholesterol (TC) and LDL-C were not significantly different among groups. HDL-C, and HDL-C/TC were increased in CS compared with SS and C. HDL-C was 17 and 22% higher for CS than SS or C (82.0 +/- 14.6 versus 70.0 +/- 10.9 versus 67.2 +/- 14.0 mg/dl, p less than 0.05, respectively). The results of the current study indicate that plasma HDL-C is significantly elevated in young women who participate in an intensive, but not moderate, exercise regimen.

Adult↗
PubMed1982

Effects of exercise in cool water on body weight loss.

Seven obese women (greater than 30 per cent body fat, mean = 43 per cent) performed moderate exercise (30 to 40 per cent of maximal oxygen consumption) for 90 min during head-out immersion in cool water (17 to 22 degrees C) five times per week for eight weeks to determine if cold exposure and the attendant caloric deficit in body heat stores would lead to body weight loss. Exercise was on a cycle ergometer that was modified for underwater use. Body weight, body fat, fat-free body weight, and caloric intake did not change significantly as a result of the exercise program in cool water. The significant heat debts incurred were presumably repaid without an increase in energy expenditure. The caloric balance and the thermal data obtained suggest that body heat stores were slowly repaid during recovery by resting metabolic heat production associated with a reduced rate of body heat loss. Maximal oxygen uptake did not increase significantly. No metabolic or thermal evidence was found to support cold adaptation in the obese women. Ergometer exercise in water as well-tolerated, as evidenced by no exercise-related injuries and an adherence rate of 93 per cent. It was concluded that, while cold exposure does not increase caloric expenditure significantly in obese individuals, exercising regularly in cool water may be beneficial as it may motivate obese people to exercise at higher intensity for thermal comfort and the water environment may help prevent injuries.

Adipose Tissue↗
PubMed1981

A comparison of methods of assessment of body composition including neutron activation analysis of total body nitrogen.

Fourteen healthy men underwent determinations of total body nitrogen (TBN) by prompt gamma neutron activation analysis and total body potassium (TBK) by whole body counting to estimate the muscle and nonmuscle components of the fat-free body mass (FFBM) and their protein contents. Comparison of FFBM estimated from TBN and TBK (60.6 +/- 6.9 kg, mean +/- SD), densitometry (62.3 +/- 7.1 kg), TBK alone (62.2 +/- 8.0 kg) and TBW (63.9 +/- 7.8 kg) showed no differences among the techniques. Similarly, there were neither differences in fat mass nor percent body fat among the methods. Analysis of the chemical composition of FFBM of this group showed TBK/FFBM = 62.6 +/- 2.3 mEq/kg, TBW/FFBM = 74.6 +/- 0.2%, TBN/FFBM = 32.74 +/- 1.09 g/kg, protein/FFBM = 20.5+/- 0.7%. The calculated mineral content of the FFBM was 6.4%. These values are strikingly similar to the values calculated by direct chemical analysis. It was concluded that the combined TBN-TBK method is a valid technique for estimating body composition in man.

Adipose Tissue↗
PubMed1981

A practical and reliable method for determination of urinary 3-methylhistidine.

A practical and reliable semiautomated method for analysis of urinary 3-methylhistidine (3-MH) was designed combining the isolation of 3-MH by ion-exchange chromatography with the color reaction given by ninhydrin-orthopthalaldehyde (ninhydrin-OPT) reagent after alkalinization. 2 ml of urine were passed through disposable columns packed with an ion-exchange resin (Dowex 50-X8, 200-400 mesh) and the acidic and neutral amino acids were eluted with 10 ml of 0.2 M pyridine solution. Then, the 3-MH was quantitatively eluted and separated from histidine with a volume of 9 ml of a 1.5 M pyridine solution. Standard Autoanalyzer equipment was used for the automation of spectrophotometry. The method permits the analysis of 40 samples in duplicate per day. The 3-MH color reaction was linear for concentrations from 0.015 to 0.24 mu mol/ml. The mean recoveries of 3-MH from standards and urine were 98.6 +/- 1.3 and 99.0 +/- 1.3%, respectively. Duplicate determinations of urine samples showed a variation coefficient of 1.8%. An excellent agreement was obtained between urine samples analyzed by the present method and by an amino acid analyzer. The need for the elimination of the interfering amino acids was clearly demonstrated.

Amino Acids↗
PubMed1981

Karyotyping chromosomes by electron microscopy. Condensation-inhibition of G bands in human and Chinese hamster chromosomes by a BrdU-Hoechst 33258 treatment.

A BrdU-Hoechst 33258 treatment of living cells, which selectively induced condensation-inhibition of G-band chromatin in human and Chinese hamster chromosomes, is presented. As a consequence mitotic chromosomes showed high resolution R-banding patterns when examined by light and electron microscopy. Besides each whole chromosome identification, this procedure also permitted the electron microscopic study of specific structures, such as satellites, secondary constrictions, telomeres, centromeres, as well as G and R bands, some of them no visible by light microscopy. We have also observed that the chromatin of G and R bands behave as blocks of chromatin condensation and that G-band chromatin develops condensation along G2. Under the BrdU-Hoechst 33258 treatment, chromatin fibers seem to invert their spontaneous pattern of condensation within the chromosomes.

Animals↗
PubMed1981

Variability of body density in ambulatory subjects measured at different days.

The variability of weight in air and underwater, residual lung volume and body density was studied in ambulatory men who were advised to maintain a constant diet and level of physical activity for four days (group I) and 60 days (group II). It was assumed that data obtained from group I which included volunteers familiar with the densitometric procedure would yield more reliable information than from group II which consisted of inexperienced subjects. Weight underwater and residual lung volume were the most variable measurements. The precision in body density varied from 0.0008 to 0.0018 g.ml-1, equivalent to 0.32 and 0.73% body fat in groups I and II, respectively. The data suggest that familiarity with the technique did not influence the reliability of body density measurement. Body composition as indicated by body density appears to remain constant over relatively long periods during which diet and levels of physical activity are controlled.

Adult↗
PubMed1981

Relationship between endogenous 3-methylhistidine excretion and body composition.

Fourteen healthy men (aged 20-30 yr) consumed two isocaloric, isonitrogenous diets in the sequence of a 4-day meat diet (MD) followed by a 7-day meal-free diet (MFD). Urinary 3-methylhistidine (3MH) excretion during the MD (513 +/- 21 mumol . day-1, mean +/- SE) was significantly higher (P less than 0.01) than day 3 of the MFD (230 +/- 10 mumol . day-1), after which the mean daily 3MH output was constant with a mean coefficient of variation of 4.5%. There was no change in fat-free body mass (FFBM) determined by densitometry at the start (62.3 +/- 1.8 kg) and the end (62.2 +/- 1.9 kg) of the 11-day dietary period. Mean muscle mass (MM) calculated from measurements of total-body potassium and nitrogen was 23.4 +/- 1.3 kg. Endogenous 3MH excretion was related more closely to MM (r = 0.91, P less than 0.001) than to FFBM measured by densitometry (r = 0.81, P less than 0.001). Only a low correlation coefficient (r = 0.33, P less than 0.05) was observed between 3MH and the nonmuscle component of FFBM. Urinary creatinine output also was correlated significantly with 3MH (r = 0.87; P less than 0.001) and MM (r = 0.79; P less than 0.01). It is concluded that because endogenous 3MH is significantly related to MM in man, it can be used as a marker to study in vivo total-body muscle protein degradation provided that the necessary dietary restrictions are observed.

Adult↗