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J Montenegro

Publications and source records attributed to J Montenegro.

11 recordsLinked to original sources
PubMed1992

Normothermic cardioplegia: is aortic cross-clamping still synonymous with myocardial ischemia?

The enthusiastic clinical reports on normothermic blood cardioplegia contrast with the paucity of data on the myocardial metabolic effects of this technique. The present study was therefore designed to assess whether normothermic blood cardioplegia really provides an aerobic environment during aortic cross-clamping. Thirty-one patients undergoing coronary (16 patients), valve (13 patients), and transplantation (2 patients) procedures were given continuous normothermic blood cardioplegia through the coronary sinus. Myocardial metabolism was assessed either immediately before aortic unclamping (16 patients) by collecting blood simultaneously from the cardioplegia infusion line and the aortic effluent or during reperfusion (15 patients) by collecting blood simultaneously from the radial artery and the coronary sinus. All samples were assayed for markers of anaerobiosis (blood gases, lactates), leukocyte activation (elastase), and lipid peroxidation (malondialdehyde, vitamin E). At the end of arrest, oxygen extraction was low, whereas the production of lactates was small, thereby suggesting the efficacy of normothermic blood cardioplegia in maintaining a predominantly aerobic metabolism. This was confirmed by postarrest data, as oxygen extraction measured immediately after cross-clamp removal was unchanged from prearrest values, whereas lactate metabolism yielded transient and limited production followed by prompt recovery of normal extraction patterns. There was no release of elastase from the myocardium, which suggests adequate protection of the coronary endothelium from ischemic injury and the related increase in leukocyte activation. Likewise, postarrest coronary sinus concentrations of malondialdehyde and vitamin E were identical to the respective arterial concentrations, thereby ruling out the occurrence of intramyocardial lipid peroxidation at the time of reperfusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Beta 2 microglobulin in CAPD.

The peritoneal clearance (Kp) and renal clearance (Kr) of beta 2 microglobulin (beta 2 m) were studied prospectively on 50 ESRD patients treated with CAPD, in order to determine the effect of the number of daily exchanges on Kp and to investigate the factors which influence the serum levels of beta 2m. Kr and Kp of beta 2m and creatinine (Cr) were calculated using standard formulae at the initiation of study and again at 6, 12, 18 and 24 months by collecting 24 hour urinary output and dialysate effluent. Kp of beta 2m of patients on 3 exchanges/day was .94 +/- .08 ml/min at the initiation of study and 1.1 +/- .08 at the end. For patients on 4 exchanges/day it was .99 +/- .14 ml/min and 1.1 +/- .12 respectively. There was no significant difference. Serum levels of beta 2m were lower on patients with significant residual renal function (RRF) (17 +/- .9 mg/L) than on patients without RRF (38 +/- 2 mg/L. p = .001). Serum levels of beta 2m correlated inversely with Kr of Cr and beta 2m at the initiation of study and at the end (r = .67 and .77 respectively, p = .0001). We conclude that serum levels of beta 2m correlate inversely with Kr of Cr and are expected to rise as RRF decreases. The combined peritoneal and renal excretion of beta 2m is less than its daily production. The number of dialysis exchanges does not influence Kp of beta 2m.

Adult↗
PubMed1991

Testing the safety of non-disconnect disposable Y sets for peritoneal dialysis.

In order to test the efficacy of the Del Clamp as a contamination barrier, the following protocol was carried out. Sixty bags of dialysate (1.5 L, 1.5% Dextrose) were connected to matching disposable Y sets and 100 mL of dialysate allowed to flow into each drain bag, after which the clamps were closed. The bags were arranged in groups of 10 and each group was inoculated with 1 mL of a standard suspension of S. aureus, S. epidermidis, E. coli, E. faecalis, P. aeruginosa and C. albicans, respectively. 3 bags were inoculated and left with the clamp open as controls. After 6 hr, incubation at 37 degrees C, 20 mL duplicate samples from each drain bag were centrifugated and processed for anaerobic and aerobic culture. None of the specimens taken from the sets grew bacteria or fungi. All the drain bags of the control sets grew the inoculated organism. We conclude that the Del Clamp makes CAPD safer by working as an effective contamination barrier and eliminating a potential for combination during the dialysis exchange.

Bacteria↗
PubMed1989

A volume-dependent, chloride-sensitive component of taurine release stimulated by potassium from retina.

Chick retinas exposed to 56 mM KCl showed marked swelling of cells and synaptic structures, detected by morphological examination as well as by measurements of cell water content. Retinal cell swelling is prevented by omission of chloride. Potassium chloride, 56 mM, elicited the efflux of [3H]taurine by a process that is partly calcium-dependent, highly chloride-dependent (80%), and sensitive to furosemide. The release of [3H]dopamine under the same conditions is completely calcium-dependent and increases in the absence of chloride. The chloride-dependent component of [3H]taurine efflux seems related to increases in volume changes since it is markedly reduced when cell swelling is prevented either by maintaining constant the K X Cl product (Donnan equilibrium) or by making the solution hypertonic with mannitol. Omission of calcium and of chloride showed additive effects, practically suppressing the potassium-stimulated release of taurine. These results suggest that the potassium-stimulated efflux of [3H]taurine consists of a large component associated to changes in cell volume and a small component probably related to the depolarizing effects of potassium.

Animals↗
PubMed1988

A chloride-dependent component of the release of labeled GABA and taurine from the chick retina.

The characteristics and ionic dependence of the release of [3H]gamma-aminobutyric acid ([3H]GABA) and [3H]taurine from the chick retina, stimulated by kainic acid (KA) and by depolarizing concentrations of potassium was examined and compared to those of [3H]dopamine. KA (100 microM) highly stimulated the release of [3H]GABA (25-fold over resting efflux), induced a moderate increase in [3H]taurine and did not increase the efflux of [3H]dopamine. The efflux of [3H]GABA stimulated by KA was totally calcium-independent but it was markedly sodium and chloride dependent. Chloride dependence was assessed by replacing chloride with the impermeant anion gluconate, or by addition of the anion transport blocker 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS). Depolarizing concentrations of KCl (56 mM) stimulated the release of [3H]GABA, [3H]taurine and [3H]dopamine to about the same extent. The release of [3H]GABA and [3H]taurine was only partially calcium dependent, in contrast to the highly calcium-dependent efflux of [3H]dopamine. A sodium-free medium increased the resting efflux and decreased the potassium-stimulated release of [3H]GABA and [3H]taurine; the resting efflux of [3H]dopamine was unaffected and the potassium-induced efflux was somewhat increased. The potassium-stimulated efflux of [3H]GABA and [3H]taurine showed a chloride-dependent component which was higher for taurine whereas the resting efflux was not modified. The stimulated release of [3H]dopamine was increased in a chloride-free medium. The ionic dependence of KA and potassium stimulated efflux of [3H]GABA and [3H]taurine showed properties similar to those of the homoexchange-activated efflux of amino acids which was also found sodium and chloride dependent and clearly different from the calcium-coupled neurotransmitter release process. Exposure of retinas to KA and potassium produced retinal cell swelling which is prevented in a chloride-free medium. Results are discussed in terms of a particular efflux mechanism for [3H]GABA and [3H]taurine in the retina in response to stimulation associated with changes in ionic gradients and retinal cell swelling.

Animals↗
PubMed1978

Clinical and histological kidney involvement in human kala-azar.

A 19-year-old women developed prolonged fever, weight loss, hepatosplenomegaly, anemia, leukopenia, and hyperglobulinemia. Appropriate tests indicated that she had visceral leishmaniasis (kala-azar). Urinalysis demonstrated significant proteinuria and microhematuria with the presence of red cell casts. A kidney biopsy was performed. Light microscopy showed a slight mesangial thickening and segmental mesangial proliferation. Immunofluorescence demonstrated deposits of immunoglobulins A and M, complement, and fibrinogen. Electron microscopy showed subendothelial and intramembranous deposits. After treatment with N-methylglucamine antimonate the proteinuria and microhematuria disappeared and the patient recovered uneventfully.

Adult↗