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Biomedical subjects

B Alpert

Publications and source records attributed to B Alpert.

At least 55 records · Page 3Linked to original sources
PubMed1989

XANES spectroscopy sensitivity to small electronic changes. Case of carp azidomethemoglobin.

Spin states equilibrium of hemoglobin-iron varies with external conditions: pH, allosteric effectors, temperature. The small electronic reorganization of the iron caused by the spin state changes has been detected by X-ray absorption near edge structure (XANES) spectroscopy at room temperature. The iron K-edge region which is sensitive to spin state is located in 7110-7130 eV. Here are presented the 100% high spin and 100% low spin XANES spectra of carp azido ferric hemoglobin.

Animals↗
PubMed1989

The in vivo behavior of gentamicin-PMMA beads in the maxillofacial region.

Gentamicin-PMMA beads were placed in maxillofacial wounds of ten dogs, and gentamicin levels from wound drain sites, serum, and urine were measured by radioimmunoassay. The results indicate extremely high wound and modest urine levels (which decrease exponentially) concurrently with negligible serum levels of gentamicin. The results of this study of a highly vascularized area were similar to other studies in which beads were placed in avascular areas.

Animals↗
PubMed1988

Hospitalization stress in children: sensitizer and repressor coping styles.

To examine the effects of individual sensitizer/repressor coping styles on responses to hospital procedures, 56 children (mean age = 6.5 years) were observed during hospitalization for minor surgery. Although the sensitizer children, as classified by their mothers, did not differ from the repressor children on baseline measures including hospital preparation, they were more talkative, expressive, and active during hospital play observations. During blood tests and preoperative injections, the sensitizers, compared with the repressors, were reported by their mothers to observe the procedures, to seek additional information about the procedures, and to show more protest behaviors. Finally, the sensitizer children required fewer hours of intensive care.

Adaptation, Psychological↗
PubMed1988

Immediate skin grafting on microvascular free tissue transfers.

Clinical reports of pedicled muscle flaps and microvascular tissue transfers include two distinctly different strategies for skin grafting. Some authors describe immediate grafting, whereas others recommend a three- to 5-day interval between flap transfer and grafting. No systematic analysis of either strategy has been reported. We reviewed 51 consecutive successful free tissue transfers that involved immediate skin grafting. Ninety-six percent of the grafts survived without complication. Bot muscle and fascial flaps supported skin grafts. Skin grafts survived infected recipient sites, pedicle revisions, partial flap necrosis, and secondary operation. We conclude that immediate skin grafting on free tissue transfers is reliable.

Adult↗
PubMed1987

Fluctuation domains in myoglobin. Fluorescence quenching studies.

The dynamics of two domains in the myoglobin molecule, close to the heme and inside the protein medium including the surface, are investigated through the study of the fluorescence oxygen quenching of two probes imbedded in the heme pocket: zinc protoporphyrin IX (with a fluorescence lifetime of 2.1 ns) and metal-free protoporphyrin IX (with a fluorescence lifetime of 17.8 ns).

Heme↗
PubMed1986

Time-dependent response of fetal pulmonary blood flow to an increase in fetal oxygen tension.

We describe the temporal characteristics of the response of the fetal pulmonary circulation to the vasodilatory stimulus of a sustained increase in fetal PO2 (5.1 +/- 0.7 Torr) in 13 chronically prepared fetal sheep. Left pulmonary artery blood flow was measured by electromagnetic flow transducer. Fetal PO2 was increased by delivery of 100% oxygen to the ewe and did not significantly change during the 2 h period of oxygen administration. Fetal left pulmonary artery blood flow slowly increased to a peak approximately 2.7 times the control value 40-50 min after the onset of increased PO2. It then steadily declined toward baseline over the next hour of increased PO2. Maximal pulmonary blood flow in response to the increase in PO2 increased with gestational age. Pulmonary arterial, aortic, and left atrial blood pressures did not change significantly in the animals in which measurements were made. We conclude that the changes in fetal pulmonary blood flow with increased fetal PO2 depend upon the time after the PO2 is increased. The adaptation seen during the second hour suggests the existence of mechanisms that tend to keep the fetal pulmonary circulation chronically constricted at any PO2 likely to be encountered in fetal life.

Animals↗
PubMed1985

A fluorescence decay time study of tryptophan in isolated hemoglobin subunits.

The time-resolved fluorescence behavior of tryptophan residues in isolated human hemoglobin subunits was determined using a sync-pumped dye laser system and time-correlated single photon counting detection. Two decay components having values near 80 ps and 2 ns were found in the fluorescence decay of the alpha-subunit. The data for the beta-chains were best fitted with 3 decay components of 90 ps, 2.5 ns and 6.4 ns. We propose that the decay times correspond to conformations of the proteins in which the disposition of the tryptophan to the heme residue differs.

Hemoglobin A↗
PubMed1985

Ligand binding processes in hemoglobin. Chemical reactivity of iron studied by XANES spectroscopy.

K-absorption edge of coordinated ions exhibits a fine structure (through the use of XANES, or x-ray absorption near edge structures) that reflects the electronic repartition and the chemical reactivity of these ions. Comparative analysis of iron K-absorption-edge shape for hemoglobin derivatives with different ligand affinity suggests strongly that in hemoglobin, iron-forms with high and low affinity are highly improbable.

Adult↗
PubMed1984

A model of dynamic quenching of fluorescence in globular proteins.

A model is presented for the quenching of a fluorophore in a protein interior. At low quencher concentration the quenching process is determined by the acquisition rate of quencher by the protein, the migration rate of quencher in the protein interior, and the exit rate of quencher from the protein. In cases where the fluorescence emission observed in the absence of quencher could be described by a single exponential decay, the presence of quencher led to doubly exponential decay times, and the aforementioned exit rates of the quencher could be determined from experimental data. At high quencher concentration, the processes became more complex, and the deterministic rate equations used at low quencher concentration had to be modified to take into account the Poisson distribution of quencher molecules throughout the protein ensemble and also by using a migration rate for quencher in the protein interior that is a function of the quencher concentration. Simulations performed for typical fluorescent probes in proteins showed good agreement with experiments.

Kinetics↗
PubMed1984

Oxygen distribution and migration within Mbdes Fe and Hbdes Fe. Multifrequency phase and modulation fluorometry study.

Quenching of the intensity and lifetime of porphyrin fluorescence from Mbdes Fe and Hbdes Fe (iron-free myoglobin and hemoglobin) by oxygen was investigated using a multifrequency cross-correlation phase fluorometer. The single exponential decay characteristic of porphyrin emission of Mbdes Fe and Hbdes Fe became doubly exponential upon application of oxygen pressure. The results were interpreted in terms of a general model of dynamic quenching of fluorescence in globular proteins. The model accounted for the rate k+ of acquisition of quencher by the protein, the exit rate k- of quencher from the protein, and the migration rate chi of quencher in the protein interior. The values of k+, k-, and chi were different for Mbdes Fe and Hbdes Fe. The addition of 40% sucrose, which increased the bulk viscosity sixfold, modified these rates. These results are discussed and compared with previous quenching studies on proteins. The significance of these results and the model for the interpretation of protein quenching studies is emphasized.

Animals↗
PubMed1984

Clinical and chemical assessment of thyroid function during therapy with amiodarone.

Clinical and chemical variables of thyroid function were studied in 26 patients with symptomatic ventricular tachyarrhythmias before and during long-term oral treatment with amiodarone. The mean (+/-SEM) pretreatment thyroxine (T4) level in the 26 patients was 7.32 +/- 0.33 micrograms/dL, and increased notably to 10.15 +/- 0.47 micrograms/dL by 30 to 120 days after treatment. The free thyroxine index (FT4I) was also notably elevated. Clinical hyperthyroidism or goiter did not develop, but clinical hypothyroidism occurred in four patients during and in one patient after discontinuation of amiodarone treatment. Notable titers of antithyroid antibodies were found in the serum of two of the five and a family history of thyroid disease was present in three of the five hypothyroid patients. An elevation of both the T4 level and the FT4I above the normal range is an expected finding in patients receiving amiodarone and does not by itself indicate hyperthyroidism. Patients with positive antithyroid antibodies or a family history of thyroid disease prior to treatment with amiodarone may be at an increased risk of hypothyroidism developing when treated with this drug.

Adult↗