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M Barac-Nieto

Publications and source records attributed to M Barac-Nieto.

63 records · Page 4Linked to original sources
PubMed1976

Effects of lactate and glutamine on palmitate metabolism in rat kindey cortex.

Rat renal cortical slices were incubated with [1-(14)C]palmitate bound to 2.5% albumin. The following effects were found: a)1 mM palmitate utilization or oxidation to CO(2) varied according to the concentration of lactate in the media, it increased at 0.8 and 3.2 mM, was unchanged at 8 mM, and decreased at 16 mM. Esterification was stimulated at 3.2 mM lactate. b) Addition of glutamine (0.1 mM) instead of lactate stimulated incomplete and complete oxidation of palmitate (1 mM), whereas high medium glutamine (10 mM) inhibited palmitate (1 mM) utilization, esterification, and oxidation to CO(2) but increased its incomplete oxidation. The low rate of exogenous palmitate oxidation observed in this study and the finding that exogenous palmitate oxidation is only partially inhibited at very high concentrations of exogenous lactate or glutamine are consistent with the view that these exogenous substrates contribute little to the oxidative metabolism of rat renal cortex in vitro, which probably depends on the supply of substrates endogenous to the tissue.

Animals↗
PubMedDate not supplied

Reported frequency of physical activity, fitness, and fatness in Kuwait.

We studied reported frequency of physical activity (PA), body composition, and fitness in Kuwaiti females (n = 84) and males (n = 72), urban office government employees, or students. A sedentary (SED) group reported no or occasional participation in self-directed PA of 30 minutes or more during the week for the last 6 months; group LOF (low frequency) participated in 1-2 sessions/week (walking, jogging, sports such as volleyball, soccer, or gym); group HIF (higher frequency) reported three or more sessions/week. Aerobic fitness was measured using Bruce's treadmill protocol. Body fat and fat-free mass (FFM) were estimated from seven skinfolds and body weight (BW). Grip strength and trunk flexibility were also measured. Maximal O(2) consumption (VO(2)max)/BW was proportional to reported frequency of PA in males and females, indicating reliability of the reported PA frequencies. SED males (%fat > 25), SED and LOF females (%fat > 30) were overweight. In males, LOF PA was associated with lower %fat and higher flexibility than SED, and in females with higher VO(2)max/FFM than SED. LOF females, in contrast to males, were resilient to or exercised at levels insufficient for fat loss but sufficient for aerobic conditioning of the FFM, likely related to the low VO(2)max of females in which PA would have the most effect. HIF PA (>/=3/week) was associated in females with significantly lower %fat and higher flexibility than SED females and no further aerobic conditioning of the FFM, and in males with no further differences in study variables compared with LOF males. Grip strength was higher in males than females but was unrelated to frequency of PA, likely reflecting lack of strength training in the activities of most participants. Thus, low-frequency PA was associated with health benefits both in males (lower %fat) and females (higher VO(2)max/FFM). Probably due to the generally low fitness level of females and, hence, the high aerobic effort (%VO(2)max) required for exercise sufficient to impinge on fat stores, this was only achieved in females participating in higher weekly frequency (>/=3) of PA.

Adult↗
PubMedDate not supplied

Use of proton MR spectroscopy and MR imaging to assess obesity.

We used 1H MR spectroscopy and MR imaging at 9.4-T to quantify and localize fat and water in the abdominal regions of 12 lean, normal, and obese mice. The D2O dilution method which measures also the equilibrium plasma D2O concentration by 2H MR spectroscopy was used to quantify body water and fat. In obese mice, the intensity of the fat 1H resonance was about 120% that of the water 1H resonance, about threefold higher than its value (about 45%) in normal mice. In lean mice, the fat/water intensity ratio was about 1:4, about half that in normal mice. Total body water was similar in obese and normal mice (19.9 +/- 1.5 and 18.7 +/- 1.3 mL) despite their very different body weights (50.1 +/- 3.1 g and 30.2 +/- 3.1 g, respectively), but slightly lower in lean mice (14.8 +/- 1.2 mL water; 22.1 g +/- 2.0 g weight). Selective methylene-proton images showed marked accumulation of fat in the abdomen and the retroperitoneal and subcutaneous spaces of obese mice. Selective water-proton images allowed clear resolution of the renal cortex, medulla, papilla, and urinary pelvis. The readily measurable resonance intensity ratio of abdominal fat to water is a sensitive index by which to characterize obesity.

Adipose Tissue↗
PubMedDate not supplied

31P nuclear magnetic resonance and saturation transfer studies of the isolated perfused rat kidney.

Previous studies using 31P nuclear magnetic resonance (NMR) saturation transfer techniques to quantitate the energy metabolism of the kidney have often resulted in estimates of adenosine triphosphate (ATP) turnover which are much lower than those predicted from the renal oxygen consumption and reasonable values of the P/O ratio. We measured the ATP turnover in isolated perfused kidneys of rats, using 31P NMR saturation transfer and a new procedure for quantitation of the intracellular Pi concentration. The estimated turnover rates of ATP were higher than previously reported. The P/O ratios calculated on the basis of these rates of ATP turnover and rates of renal oxygen consumption reported in the literature were within the range of theoretically possible values. Thus, 31P NMR saturation transfer can be used to quantitate the ATP turnover in the isolated perfused rat kidney.

Adenosine Triphosphate↗
PubMedDate not supplied

23Na, 19F, 35Cl and 31P multinuclear nuclear magnetic resonance studies of perfused rat kidney.

The concentration of intracellular sodium [Na+]i has been measured in the perfused rat kidney using 23Na nuclear magnetic resonance (NMR) in combination with the extracellular shift reagent Dy(PPPi)7-(2). The data show 100% visibility of Na+ in interstitial spaces. A measurement of the resonance intensities of intra- and extracellular 23Na ions along with a knowledge of the extracellular space as a fraction of the total kidney water space yielded an average [Na+]i of 27 +/- 2 mM for the kidney at 37 degrees C. After prolonged ischemia [Na+]i rose to approach that in the external medium. In the absence of 5% albumin in the perfusion medium, the linewidth of the 35Cl resonance of an adult kidney (45 Hz) was about twofold larger than that of the medium alone (25 Hz). In contrast, the linewidth of 35Cl resonance of an adult kidney perfused with an albumin-containing medium (82 Hz) was only about 27% of that from the medium alone (300 Hz). We interpret this effect to be due to compartmentation of albumin in the extracellular space such that the interstitial space is not freely accessible to albumin. However, for a developing, immature kidney from a growing animal, perfused with an albumin-containing medium, the linewidth of the 35Cl resonance (233 Hz) was only slightly less than that of the medium alone (300 Hz), indicating a much greater albumin permeability of the capillary walls. 19F NMR of a perfused adult kidney, loaded with the membrane-impermeant intracellular calcium indicator 5FBAPTA, yielded a value of 256 nM for [Ca2+]i. Induction of ischemia for 10 min caused the [Ca2+]i to rapidly rise to 660 nM, which could not be fully reversed by reperfusion, suggesting irreversible injury.

Adenosine Triphosphate↗