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Biomedical subjects

J Alvarado

Publications and source records attributed to J Alvarado.

15 recordsLinked to original sources
PubMed1991

Determination of Cd, Cr, Cu, Pb and Zn in human semen by graphite furnace atomic absorption spectrometry after microwave sample dissolution.

Human semen samples were analyzed by graphite furnace atomic absorption spectrometry, using L'vov platforms and the method of standard additions, to determine their Cd, Cr, Cu, Pb and Zn content. The samples were analyzed directly and after conventional and microwave wet acid dissolution. Matrix modification, using magnesium and palladium nitrates and ammonium biphosphate solutions, was evaluated for the analysis of the microwave-digested samples. The best results were obtained for Cr, Cu and Zn using Pd(NO3)2, and a mixture of Mg(NO3)2 and Pd(NO3)2 solutions. The direct analysis of water-diluted semen produced inaccurate results with unacceptably high standard deviations. The results obtained for the microwave-dissolved samples showed relative standard deviation values within the range 0.63-8.4%. The analysis of spiked semen solutions showed recoveries of the added analytes ranging from 96 to 104%. The accuracy of the measurements was checked against the NIST 1,577a, bovine liver, standard reference material. Sample dissolution time was drastically reduced from 3-4 hours, using the conventional method, to approximately 8 minutes using the microwave-assisted wet acid digestion procedure.

Cadmium↗
PubMed1979

Transplantation of cultured bovine corneal endothelial cells to species with nonregenerative endothelium. The cat as an experimental model.

The in vivo transplantation of cultured bovine corneal endothelial cells has been attempted in the cat. Cat corneas denuded of their endothelium were coated with bovine corneal endothelial cells previously maintained in tissue culture. When grafted back into cat recipients, the corneal buttons remained clear with no edema. Alizarin red staining of the endothelial side of the corneal transplant demonstrated that the coated bovine corneal endothelial cells reorganized themselves into a highly organized cell monolayer within eight days in vivo. In contrast, corneas denuded of their endothelium became opaque and edematous within seven days and remained so thereafter. These results demonstrate that cultured corneal endothelial cells remain functional in vitro and can replace a damaged or nonfunctional endothelium i

Animals↗
PubMed1979

A method for the dynamic continuous estimation of excitability changes of single fiber terminals in the central nervous system.

A method is presented allowing direct and continuous estimation of the excitability changes of single fiber terminal arborizations within the central nervous system. In essence, the method measures the current required to maintain a preset antidromic firing probability of the unit under study. This implies operation in a closed loop system controlled by a computer. With this technique one can accurately determine input-output curves of single units requiring relatively small current variations (0.15-2.1 microA) to change from zero to maximal probability of response. The method also allows measurement of the excitability changes produced by conditioning volleys to sensory nerves.

Animals↗
PubMed1979

Transplantation of cultured bovine corneal endothelial cells to rabbit cornea: clinical implications for human studies.

Rabbit corneas denuded of their endothelium were coated with bovine corneal endothelial cells (from steers) previously maintained in tissue culture for short (20 generations) or prolonged (200 generations) periods. When grafted back into female rabbits, the corneal buttons remained clear and showed no edema. In contrast, denuded corneas coated with bovine keratocytes and grafted into rabbits became opaque and edematous within 7 days and remained so thereafter. Bovine corneal endothelial cells of the grafted corneas, which had remained clear for over 100 days, proliferated actively when put back into tissue culture. The corneal endothelial cells of the graft were characteristic of the male (XY). The chromosome number of the endothelium of the recipient rabbit was 2n = 44 with sex chromosomes characteristic of the female (XX). Results of the karyotype analysis show that there was no invasion of the corneal button by the recipient endothelium and, conversely, no invasion of the recipient endothelium by the endothelium on the corneal button. These results demonstrate that cultured corneal endothelial cells remain functional in vitro and can replace a damaged or nonfunctional endothelium in vivo.

Animals↗
PubMed1979

Human trabecular cells. I. Establishment in tissue culture and growth characteristics.

After a careful dissection of trabecular tissue from recent postmortem specimens, human trabecular cells were established in tissue culture with 250 ng/ml fibroblast growth factor (FGF), Dulbecco's modified Eagle's medium (DME), and 10% human serum. These conditions have allowed propagation of human trabecular cells for a number of passages at high density without apparent cellular degeneration. FGF increased the rate of cell division and the plating efficiency for trabecular cells but was not needed after cells had achieved confluency. Human trabecular cells had a pattern of growth which differed from human corneal keratocytes and human corneal endothelial cells compared at a similar passage. Propagation of human trabecular cells in vitro may provide a valuable source of experimental material to study the functional aspects of these cells which line the trabecular meshwork.

Adolescent↗
PubMed1978

Magnesium supplementation in protein-calorie malnutrition.

The widespread observation of magnesium depletion in edematous malnutrition has been confirmed in Guatemalan children. The magnesium requirement during initial stages of therapy has been estimated as 2.7 mEq/kg per day. This may be achieved by adding 0.5% MgSO4.7H2O to a solution containing 15% dextromaltase and 1.5% KCl which is used to dilute whole milk; two parts milk and one part dilution mixture. The replacement of magnesium deficits was not essential for recovery from edematous malnutrition, however, the present evidence suggested that the rate of recovery was accelerated by approximately 2 weeks in those children who received the supplement.

Child↗
PubMed1977

Sequential changes in body composition during infection: electron probe study IV.

Alterations occur in human muscle electrolyte and water composition in response to infection. There appear to be at least two basic mechanisms; the first is an exchange of sodium for potassium without alteration in water content of muscle. The second is an increase in cellular Na and water without a loss of K on a dry weight basis. In a series of studies in monkeys, Salmonella typhimurium sepsis was induced as an experimental model. Both patterns of muscle response to infection were detected. Electron probe microanalysis revealed that the loss of K concentration was due to an accumulation of intracellular saline which dilute the K content. The mechanism of this is unclear; however, a concomitant increase in undertermined osmoles in the serum suggests that there may be an increase in organic osmoles within the cell which leads to the dilution of intracellular K concentration.

Animals↗
PubMed1977

Extraocular muscle fibers: ultrastructural identification of iontophoretically labeled fibers contracting in response to succinylcholine.

Cat extraocular muscle fibers (from the superior rectus or inferior oblique) were penetrated in vivo with Procion red-filled glass microelectrodes. When stable penetrations were obtained, succinylcholine (Sch), 8 to 20 microng, was injected into the femoral vein. In some fibers, a depolarization-repolarization response was obtained with the same time course (2 min.) as the total muscle contraction. The depolarizing fibers were labeled iontophoretically. The ultrastructural characteristics of five depolarizing fibers and three control (nondepolarizing) fibers were then studied. The fibers that did not depolarize to Sch had the characteristics of singly innervated cells, whereas those sensitive to Sch had morphological characteristics of multi-innervated fibers.

Animals↗