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J Bustamante

Publications and source records attributed to J Bustamante.

11 recordsLinked to original sources
PubMed1992

Signal transduction and nonlinearities revealed by white noise inputs in the fast adapting crayfish stretch receptor.

Input-output relations were investigated in the fast adapting stretch receptor organ (RM2) of the crayfish by matching gaussian white noise (GWN) length inputs, with the resulting spike output. The analysis revealed the expected sensitivity to lengthening velocity, a behavior termed phasic. It also disclosed a sensitivity to sustained elongation, a performance termed tonic and previously not recognized in the RM2. Spectral analysis indicated the properties of a low-pass filter, confirming the tonic sensitivity. A variety of individual length trajectories could lead to a spike. The average trajectory consisted in a biphasic shortening-lengthening wave. The range of possible trajectories and their averages changed with stimulus prestretch and GWN amplitude, indicating that system properties depended on the input characteristics; i.e., a nonlinear operation. Length waveforms in the GWN were isolated by computing methods and the corresponding responses were calculated. Symmetric stimuli led to responses that reflected magnitudes and velocities asymmetrically. Nonlinear interactions between responses in the past and present were negligible. In conclusion, depending on the input, the RM2 modifies its operation to enhance the detectability of the functionally relevant signal in each natural situation.

Animals↗
PubMed1991

Melanin content and hydroperoxide metabolism in human melanoma cells.

Human melanoma cells were grown to exponential and stationary phases showing melanin contents of 4.2 +/- 0.3 and 11.3 +/- 0.6 micrograms/10(6) cells, respectively. The cells were separated in four subpopulations by a Percoll gradient; the subpopulation of density 1.07 (g/ml) was the most enriched in pigmented cells and produced 28 and 58% of the cells in exponential and stationary phases, respectively. Melanoma cells had similar superoxide dismutase and glutathione peroxidase activities in exponential and stationary phases. Moreover melanoma cells exhibited a higher catalase activity in the stationary phase: whole homogenate and cytosol activities were 7.0 +/- 0.3 and 10.8 +/- 0.6 U/mg protein, whereas in exponential phase the activities were 4.9 +/- 0.1 and 7.6 +/- 0.3 U/mg protein for whole homogenate and cytosol, respectively. The intracellular H2O2 steady-state concentration was 3.3 +/- 0.2 and 2.1 +/- 0.2 microM H2O2 for exponential and stationary phases, respectively. The spontaneous chemiluminescence of the two culture phases was 169 +/- 27 cps/10(6) cells (exponential) and 78 +/- 24 cps/10(6) cells (stationary). The cytotoxicity of H2O2 generated extracellularly by glucose oxidase was determined after 60 min of exposure. IC50 values for exponential and stationary cell cultures were 0.9 and 2.4 mU/ml of glucose oxidase, respectively. The increased catalase activities in the stationary phase as compared with the exponential phase are consistent with the decreased intracellular H2O2, with the decreased spontaneous chemiluminescence, and with the increased resistance to exogenous H2O2.

Catalase↗
PubMed1990

Adriamycin effects on hydroperoxide metabolism and growth of human breast tumor cells.

Human breast tumor cells MCF-7 were grown during 5 days in the presence of Adriamycin and the IC50 was 50 nM with the highest sublethal concentration 0.1 microM. At this latter concentration Adriamycin produced a complete inhibition of cell division and a partial reversion to a normal breast epithelial appearance. Similar effects of Adriamycin were observed in cells cultured in the presence of 10% FBS and in a chemically defined medium, with Se-glutathione peroxidase activities of 3.8 and 1.3 U/mg of protein, respectively. Cell size and cell oxygen uptake were increased by 41% and by 50%, respectively, in Adriamycin-treated cells. The spontaneous chemiluminescence of monolayers of intact MCF-7 cells (81 +/- 9 cps/mg protein) was increased by 48% in the Adriamycin-treated cultures (120 +/- 11 cps/mg of protein) in agreement with a 91% higher concentration of malondialdehyde in the same cultures. Adriamycin treatment produced a 71% increase in the steady state concentration of H2O2, which was estimated assuming diffusion equilibrium with the external medium, from 1.38 microM in the control cells to 2.38 microM in the treated cells. Cyanide-insensitive respiration was also higher in the cells exposed to the drug than in the control cells. Adriamycin did not affect the activity of the antioxidant enzymes, Cu-Zn and Mn-superoxide dismutase, Se and non-Se-glutathione peroxidase, and catalase. These results contribute to the current hypothesis that oxygen free radicals produced by Adriamycin redox cycling are responsible for at least part of the cytotoxic effects due to this drug.

Analysis of Variance↗
PubMed1979

Rate-dependent action potential changes in rat atrium.

Experiments in isolated left atria from rat hearts were performed in order to study the effects of stimulation rate on the transmembrane action potential. 1. Two components (fast and slow) of the action potential upstroke could be differentiated by adding MnCl2 to the perfusion solution. 2. With the increase in rate of stimulation over the control cycle length (500 msec), amplitude, Vmax and action potential duration at 80% of repolarization (D80) diminished in normal Krebs. In Mn-containing Krebs, only a slight reduction in amplitude was recorded. Resting potential and action potential duration at 20% (D20) and 50% (D50) of repolarization were only slightly affected in normal Krebs and not at all in Mn-Krebs. 3. Low rates of stimulation in normal Krebs increased D50 only slightly; however, D80 increased significantly while other parameters remained constant. No effects were seen in Mn-Krebs. 4. The results with Mn-Krebs indicate the importance of slow inward current on changes induced by stimulation rates. A possible mechanism relating intracellular calcium concentration and the outward K current, depending on the rate of stimulation, is discussed.

Animals↗
PubMed1978

Changes in copper and ceruloplasmin in chronic renal insufficiency treated by hemodialysis and peritoneal dialysis.

Serum copper and ceruloplasmin as well as other parameters in 68 patients with chronic renal insufficiency were studied. It was found that chronic renal insufficiency increases neither the serum copper nor the serum ceruloplasmin. In the group on hemodialysis, there is a progressive increase of copper and ceruloplasmin in serum due to a liberation of 44.44% of the copper content of the membranes. In the group on periodic peritoneal dialysis, there is also an increase of serum copper during the dialysis. We do not have an explanation for this finding.

Adolescent↗
PubMedDate not supplied

[Study, using non-invasive methods, of prostheses manufactured at the Instituto Nacional de Cardiología Ignacio Chávez].

We study the phonocardiogram, M mode, two-dimensional and Doppler pulsed echocardiogram of 30 patients, who underwent implantation of a bovine pericardial bioprosthesis manufactured at the Instituto Nacional de Cardiología Ignacio Chávez. We describe 26 patients with prosthesis in mitral position, 22 females and 4 males, with age between 19 to 60 years. After surgery, 22 were in functional I and 2 in class II of the New York Heart Association Criteria. Two patients (6.6%) died of extracardiac complications. Phonocardiogram: Mitral prosthesis closing click (MPCC) were recorded at all, the interval Q wave-MPCC was of 0.09 +/- 0.02 sec. The interval second sound-mitral prosthesis opening click (S2-MPOC) measured 0.10 +/- 0.01 sec. Mid-diastolic murmur were recorded in 8 patients (30.7%). The O-F slope of the apexcardiogram was of 82 +/- 40 mm/sec. Ten patients had tricuspid insufficiency. Echocardiogram: The D-E velocity of mitral prosthesis opening was of 318 +/- 99 mm/sec and the E-F slope velocity of 15 +/- 6.2 mm/sec. All patients except one showed paradoxical motion of the intraventricular septum. The prosthesis stents distance was of 14.1 +/- 2 mm, the internal diameter of 17.8 +/- 2.9 mm and the valvular area was calculated in 2.5 +/- 0.08 cm2. The flow velocity/diameter was 62.6 +/- 26.8 cm/sec/mm and the flow velocity/opening area of 52.5 +/- 26.1 cm/sec/cm2.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗