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Biomedical subjects

B Alpert

Publications and source records attributed to B Alpert.

At least 19 recordsLinked to original sources
PubMed1992

An infrared study of 2H-bond variation in myoglobin revealed by high pressure.

A high-pressure Fourier-transform infrared technique was used to probe the evolution of 2H bonds inside the helical segments of myoglobin in relation to p2H, Tris concentration in the medium and iron-ligand nature. The analysis was focused on changes in the conformation-sensitive amide-I' band, reflecting the peptide C = O group stretching vibrations coupled to the in-plane N-2H bending and C = N stretching modes. From data obtained under high pressure, the strength of 2H bonds, inside the alpha-helical segments of the protein at atmospheric pressure, is not simply a function of p2H and salt concentration. At low Tris concentration (50 mM), the strength of these 2H bonds increases with p2H, whereas for a higher Tris concentration (100 mM) this strength is lower at p2H 7 than at p2H 6.0 or 8.5. It is also observed that the azidometmyoglobin molecule exhibits tighter intrahelical interactions and lower sensitivity to pressure than aquametmyoglobin. Information is also presented regarding interhelical interactions in relation to the solvent.

Animals↗
PubMed1992

Experience with rigid fixation of mandibular fractures and immediate function.

The results of using rigid fixation for 75 mandibular fractures in 52 patients and allowing immediate function were retrospectively analyzed. Sixteen percent of fractures developed postoperative infection. All infections were in fractures associated with teeth; none occurred in fractures fixed within 24 hours of injury. Angle and posterior body fractures were most likely to become infected. Fractures with improperly applied rigid fixation also were subject to a high infection rate. It was unusual for infection involving this type of treatment to prolong the course of therapy or affect the final outcome.

Adolescent↗
PubMed1992

Cementless total hip arthroplasty in renal transplant patients.

Twenty-seven cementless total hip arthroplasties were performed in 17 steroid-dependent renal transplant patients. The average age at operation was 39 years, and the average daily dose of prednisone was 10.9 mg. At a mean of 48 months post-surgery, all patients had good to excellent hip ratings on clinical examination and the results compared favorably with 235 non-steroid-dependent age-matched patients using the identical prosthetic hip system. The results of this study suggest that long-term immunosuppression does not prevent bone ingrowth. Noncemented total hip arthroplasty appears to be a reasonable therapeutic option for end-stage osteonecrosis in steroid-dependent renal transplant patients.

Adult↗
PubMed1992

Incidence and prevalence of Lyme disease in a suburban Westchester County community.

This study was designed to determine the incidence and prevalence of Lyme disease in a section of Chappaqua, NY, a residential community in which Lyme disease is epidemic, and to identify risk factors for this disease. On the basis of clinical history and baseline serologic testing, the overall prevalence of Lyme disease for 114 persons entering the study was 8.8%. The incidence during the 5-month study period of May through September 1989 was 2.6%; all three incident cases had erythema migrans (EM). Hours outdoors per week in play or exercise correlated with the occurrence of Lyme disease.

Adolescent↗
PubMed1991

Variations of electrostatic interactions in myoglobin probed by UVRR spectroscopy. Effect of iron ligand and pH on tryptophan and tyrosine vibrations.

The present work investigates the variations of electrostatic interactions within the myoglobin molecule associated with azide heme binding and pH variations. Far ultraviolet (223 nm) resonance Raman spectroscopy of the tryptophan and tyrosine residues, along with acid-base titration measurements, have been used to monitor variations in the protein matrix. With previously determined mode assignments, it is shown that the Trp and Tyr residues of the globin moiety are influenced by the charge spatial distribution. Upon ligand binding or under various pH conditions, the polar interactions inside the protein appear to be modulated by the electric field generated by the charge array. It is concluded that the binding site properties of myoglobin can be modulated by the charge spatial distribution within the protein, even in the absence of measurable conformational changes of the bulk.

Animals↗
PubMed1991

Alteration of heme axial ligands in hemoglobin by organic solvents analyzed by CD, FTIR, and XANES techniques.

The effects of mixed solvents on the ligand binding site in hemoglobin have been investigated though three spectroscopic techniques. Two classes of organic solvents (amides and alcohols) known to increase or decrease the hemoglobin affinity have been chosen for this study. The analysis of the iron CO stretching band shows that the ligand binding sites of alpha CO and beta CO subunits inside the alpha 2 beta 2 hemoglobin tetramer exhibit multiple conformations. From the circular dichroism and X-ray absorption near-edge structure data, it appears that no core deformation or heme reorientation occur with the affinity changes. The iron-ligand average bond angle is the sole parameter that depends on the external solvent. Since cosolvents seem to affect the dynamics rather than the hindrance of the heme cavity, we suggest that the protein affinity could be associated with a hierarchy of subtle dynamic states.

Alcohols↗
PubMed1991

Subchondral bone in osteoarthritis.

To determine whether subchondral bone in osteoarthritis differs from that seen in normal human aging, osteoarthritic femoral heads removed for total hip arthroplasty were compared with normal age-matched and young autopsy controls. Standardized, 1-cm deep, weight-bearing and nonweight-bearing subchondral bone blocks, as well as cancellous core bone, 2-4 cm deep on the articular surface, were examined in each femoral head. Mineralization was assessed using density fractionation and chemical analysis, and compared to histomorphometry. In osteoarthritis, both weight-bearing and nonweight-bearing surface subchondral bone showed a lower degree of mineralization than age-matched and young controls. Histomorphometric analysis showed that subchondral bone thickness, as well as all osteoid parameters and eroded surfaces, were increased in osteoarthritic samples versus controls. Mineralization in the deep cancellous core bone increased with normal aging but underwent less change with osteoarthritis. Histomorphometry of the cancellous core showed that osteoid parameters, but not bone volume, were increased in osteoarthritis versus controls. In conclusion, osteoarthritis is associated with a thickening of the subchondral bone with an abnormally low mineralization pattern.

Aged↗
PubMed1990

Subunit interactions in hemoglobin probed by fluorescence and high-pressure techniques.

The dissociation of the subunits of human adult oxyhemoglobin has been investigated by using steady-state fluorescence anisotropy, multifrequency phase fluorometry, and high hydrostatic pressure. Human hemoglobin obtained by using two purification procedures (bulk preparation by centrifugation or further fractionation using anion-exchange chromatography) was labeled with an extrinsic fluorescent probe, 5-(dimethylamino)naphthalene-1-sulfonyl chloride (DNS-Cl). The long fluorescence lifetime of this probe allows for the observation of the macromolecular tumbling, and thus provides a method for observing changes in the size of the complex upon subunit dissociation under differing solution conditions of proton and organic phosphate concentration. At pH 7, the dansylated preparations of bulk and fractionated hemoglobin showed a concentration-dependent decrease in the anisotropy which though not identical can only arise from the tetramer to dimer dissociation. We observed primarily the dimer at pH 9 and a small destabilization of the tetramer in the presence of saturating inositol hexaphosphate (IHP). High-pressure experiments allowed for the observation of the dissociation of the hemoglobin dimer into monomers. From these measurements, we estimate the dimer dissociation constant to be between 0.1 and 1 nM. We compare the present results on the subunit affinities in hemoglobin obtained from steady-state and time-resolved fluorescence data with those obtained previously by using gel filtration, sedimentation, and kinetic techniques. These comparisons are indicative of a certain degree of conformational heterogeneity in the hemoglobin preparations.

Chromatography, Gel↗
PubMed1990

Relationship between protein/solvent proton exchange and progressive conformation and fluctuation changes in hemoglobin.

The pH dependence of the tertiary structural changes and the quaternary reorganization of the alpha beta interface of oxyhemoglobin in solution has been previously observed in our laboratory. The present work aims to establish whether or not these progressive structural changes with pH result from proton exchange between the protein and the solvent. We therefore have used infrared spectroscopy, acid/base titration and 1H/2H exchange to assess the effect of external proton concentration on the structural and dynamic properties of the hemoglobin molecule in solution. This study is also performed on the carbonmonoxy form since the affinity of hemoglobin for CO is much higher than for oxygen. The present findings demonstrate that affinity changes are closely related to protein fluctuations, as well as structural modifications. An increased affinity, induced either by ligand replacement or pH variation, is associated with the constrained chains exhibiting a lower degree of fluctuation, together with a looser alpha beta interface association.

Cysteine↗
PubMed1990

Fluorescence decay kinetics of the tryptophyl residues of myoglobin: effect of heme ligation and evidence for discrete lifetime components.

The fluorescence decay kinetics of the tryptophyl residues of sperm whale and yellowfin tuna myoglobin have been determined by using time-correlated single photon counting, with picosecond resolution. Purification by HPLC techniques resulted in the isolation of samples that exclusively displayed picosecond decay kinetics. Lifetimes of 24.4 ps for Trp14 and 122.0 ps for Trp7 were found for oxy sperm whale myoglobin (pH 7), which agree with theoretical predictions [Hochstrasser, R. M., & Negus, D. K. (1984) Proc. Natl. Acad. Sci. U.S.A. 81, 4399-4403]. The effects of ligand binding and pH on the decay kinetics were investigated, and the results were shown to be consistent with the known crystal structures. Data for the met form of sperm whale myoglobin were analyzed both in terms of a sum of discrete exponential components and as a continuous gamma distribution of exponential decays. The results were not found to support the existence of multiple, structurally distinct conformation states in myoglobin.

Animals↗
PubMed1990

Aerobics enhances cardiovascular fitness and agility in preschoolers.

Investigated effects of aerobic exercise on a sample of 24 preschoolers. Thirty minutes of aerobic exercises were provided daily for a period of 8 weeks for a group of 12 children while the remaining 12 children engaged in freeplay on the school playground. The children were given pretests and posttests on the following measures: a submaximal exercise test on a pediatric bicycle (baseline and three workloads), an agility test, a health knowledge test, a self-esteem scale, and an observational measure of their gross-motor activity. Despite comparability on pretests, significant group X repeated measures effects suggested that the aerobic exercise group showed decreases in heart rate at all three workloads as well as increases in agility and self-esteem following the exercise program. These findings suggest that cardiovascular fitness, agility, and self-esteem can be facilitated in preschoolers by an aerobic exercise program.

Arousal↗
PubMed1989

Parameters controlling the kinetics of ferric and ferrous hemeproteins reduction by hydrated electrons.

To clarify the processes of hemeproteins reduction, three classes of these proteins (ferric, ferrous and desFe) were reduced by hydrated electrons generated by pulse radiolysis. Spectral and kinetic investigations were made on alpha hemoglobin chain and myoglobin. Human alpha chain has been chosen to avoid all ferric contaminations and horse ferric myoglobin to eliminate all ferrous protein fractions. We have successively studied the influences of: the iron presence, its oxidation state (II and III), the protein charge and the iron-ligand nature (H2O, OH-, N3- and CN-). For alpha human hemoglobin chain without metallic ion or with ferrous iron, the reduction rates are the same: 1.1 +/- 0.2.10(10) M-1.s-1. In the case of horse ferric myoglobin, the reduction rates depend principally on the protein charge (from pH 6.3 to pH 9.5, the reduction rate of Mb(FeIII)N3- decreases from 2.5 +/- 0.5.10(10) M-1.s-1 to 1.2 +/- 0.2.10(10) M-1.s-1) and are also modulated by the equilibrium constant of the hemeprotein-ligand association (1.2 +/- 0.2.10(10) M-1.s-1 for Mb(FeIII)N3- and 0.8 +/- 0.2.10(10) M-1.s-1 for Mb(FeIII)CN-, at pH 9.8).

Chemical Phenomena↗
PubMed1989

Implication of the alpha 1 beta 1 interface in the hemoglobin affinity changes. A comparative study between normal and San Diego fully ligated hemoglobins.

The alpha 1 beta 1 interface of normal and mutated San Diego hemoglobins in their fully liganded form was investigated, through the SH vibrational absorption of beta-112 cysteine, by Fourier-transform infrared spectroscopy. The center frequency of this thiol group was significantly shifted in San Diego hemoglobin compared with normal human hemoglobin. Different dimer organization between the two proteins was also revealed by circular dichroism of the heme. These findings agree well with assessment that the alpha 1 beta 1 interface, far from being inert, is involved in the affinity changes of the hemoglobin molecule.

Binding Sites↗
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↗