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Biomedical subjects

D Axelrod

Publications and source records attributed to D Axelrod.

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

Flexible fiberoptic rhinoscopy in the diagnosis of sinusitis.

Two-hundred forty-six patients with undiagnosed headache, after unrewarding neurologic evaluation, were referred to an allergy clinic and were evaluated both by routine sinus radiographs and flexible fiberoptic rhinoscopy. Ninety-eight patients had only rhinoscopic evidence of sinusitis (group I), 84 patients had both rhinoscopic and radiographic evidence of sinusitis (group II), and 64 patients had neither rhinoscopic nor radiographic evidence of sinusitis (group III). Antibiotic treatment resulted in relief of headaches in 94% of group I, 75% of group II, and 5% of group III patients. The distribution of sinus infections found by both rhinoscopy and radiography were similar; however, rhinoscopy may have found the disease earlier than radiography. Flexible fiberoptic rhinoscopy is an efficient method for the office diagnosis of sinusitis.

Adult↗
PubMed1988

Comparison of parenteral adrenocorticotropic hormone with oral indomethacin in the treatment of acute gout.

One hundred male patients who presented with acute gouty arthritis were alternately assigned to 2 treatment groups. Seventy-six patients completed the study protocol, in which each gout attack during a 1-year period was treated. For each gout episode, 36 patients received a single intramuscular injection of 40 IU of adrenocorticotropic hormone (ACTH), and 40 patients received oral indomethacin, 50 mg 4 times daily with meals, until the pain abated. The time interval until the pain was relieved, as well as any untoward effects, were recorded for each gout attack treated. Both groups were of similar age, and had similar values for intercritical serum uric acid, 24-hour urinary uric acid, and creatinine clearance (1 month after entry into the study). The mean interval (+/- SD) to relief of pain was significantly shorter for the ACTH group (3 +/- 1 hours) than for the indomethacin group (24 +/- 10 hours). No side effects were noted in the ACTH group. However, of the 40 patients receiving indomethacin, 22 had abdominal discomfort of dyspepsia, 15 had headaches, and 12 had difficulty with mentation. Single-dose parenteral ACTH appeared to be effective more rapidly and was associated with fewer side effects than oral indomethacin in the treatment of acute gout.

Acute Disease↗
PubMed1988

A fluorescence photobleaching study of the microsecond reorientational motions of DNA.

We have conducted a polarized fluorescence photobleaching recovery (FPR) study of the rotational dynamics of ethidium azide labeled DNA. Polarized photobleaching experiments provide data on microsecond and millisecond molecular reorientation that complement the information available from nanosecond fluorescence depolarization studies. In polarized FPR experiments an anisotropic angular concentration of fluorophore is created by bleaching dye molecules in a preferred orientation with a short, intense pulse of polarized light. The sample is then weakly illuminated, and the temporal variation in the emitted fluorescence is monitored. The fluorescence signal will systematically change as molecules undergo post-bleach reorientation and the angular distribution of dye tends toward isotropy. We have observed that the time dependence of our microsecond FPR curves is also determined in part by nonrotational phenomena. To isolate the reorientational recovery we conduct our FPR experiments in two modes (called parallel and perpendicular) that differ only in the polarization of the bleaching light. A quotient function, R(t), is constructed from the data obtained in these two modes; the variation with time of this new quantity is governed solely by processes that are sensitive to the polarization of the incident light (e.g., molecular rotation). It is found experimentally that R(t) remains constant, as expected, for rotationally restricted DNA systems despite a temporal recovery in the parallel and perpendicular FPR curves. We also follow the dynamics of solutions of phage lambda DNA as revealed in the temporal dependence of R(t). This DNA system rotationally relaxes after approximately 100 microseconds and the dye/DNA complex reorients substantially during the 10-microseconds bleach period. Our FPR data are interpreted in terms of dynamic models of DNA motion.

Azides↗
PubMed1988

Polarized fluorescence photobleaching recovery for measuring rotational diffusion in solutions and membranes.

A variation of fluorescence photobleaching recovery (FPR) suitable for measuring the rate of rotational molecular diffusion in solution and cell membranes is presented in theory and experimental practice for epi-illumination microscopy. In this technique, a brief flash of polarized laser light creates an anisotropic distribution of unbleached fluorophores which relaxes by rotational diffusion, leading to a time-dependent postbleach fluorescence. Polarized FPR (PFPR) is applicable to any time scales from seconds to microseconds. However, at fast (microsecond) time scales, a partial recovery independent of molecular orientation tends to obscure rotational effects. The theory here presents a method for overcoming this reversible photobleaching, and includes explicit results for practical geometries, fast wobble of fluorophores, and arbitrary bleaching depth. This variation of a polarized luminescence "pump-and-probe" technique is compared with prior ones and with "pump-only" time-resolved luminescence anisotropy decay methods. The technique is experimentally verified on small latex beads with a variety of diameters, common fluorophore labels, and solvent viscosities. Preliminary measurements on a protein (acetylcholine receptor) in the membrane of nondeoxygenated cells in live culture (rat myotubes) show a difference in rotational diffusion between clustered and nonclustered receptors. In most experiments, signal averaging, high laser power, and automated sample translation must be employed to achieve adequate statistical accuracy.

Animals↗
PubMed1988

Refractive index within the lens of a goldfish eye determined from the paths of thin laser beams.

The paths of 15 micron diameter laser beams traversing goldfish eye lenses were photographed. Measurements of these photographs gave experimental data for the distance of the exit point of each ray from the lens axis as a function of the corresponding entrance distance. A number of mathematical models with distinct distributions of refractive index within the lens were analysed by tracing rays to simulate the experimental data. The only distributions for which the simulated and experimental data were in agreement have a refractive index N which varies continuously with distance r from the lens center in a manner consistent with that originally proposed by Matthiessen: N2 = a - br2. Estimates for the central (1.55-1.57) and surface (1.35-1.38) refractive indices of the goldfish eye lens are derived from the preferred model, but these differ from those previously given by Matthiessen for other species. The optical performance of the lens models is also compared by third-order analyses.

Animals↗
PubMed1984

Mobility of extrajunctional acetylcholine receptors on denervated adult muscle fibers.

We report the lateral mobility of extrajunctional acetylcholine receptors (AChR), marked with fluorescently labeled alpha-bungarotoxin, on rat flexor digitorum brevis single muscle fibers maintained in cell culture. Mobility is measured by a modification of the fluorescence photobleaching recovery technique. The denervated rat flexor digitorum brevis muscle fibers exhibit a nonuniform distribution of AChR on their sarcolemmas. Diffusely distributed AChR have an average diffusion coefficient of about 2.5 X 10(-11) cm2/sec, somewhat lower than that of diffusely distributed AChR on embryonic rat myotubes in culture. Extrajunctional AChR aggregated into small clusters (less than 20 microns) have an average diffusion coefficient of about 5 X 10(-12) cm2/sec. Both the clustered and nonclustered extrajunctional AChR have lateral mobilities several orders of magnitude greater than that of junctional AChR.

Animals↗
PubMed1983

Total internal reflection fluorescence study of energy transfer in surface-adsorbed and dissolved bovine serum albumin.

A simple adaptation of a commercial spectrofluorometer allows selective excitation of fluorescent biomolecules adsorbed to a solid surface while they are in equilibrium with a bulk solution. As a demonstration of this technique, we have detected a change in the effective singlet-singlet energy transfer in fluorescence-labeled bovine serum albumin (BSA) upon adsorption to a fused silica surface. The technique combines total internal reflection fluorescence excitation of surface-adsorbed BSA with a fluorescence spectroscopic examination of energy transfer between two different fluorophores that are covalently bound to amino groups in each BSA molecule. Two donor--acceptor pairs were used, 4-chloro-7-nitro-2,1,3-benzoxadiazole-rhodamine and dansyl-eosin. For studies of surface-adsorbed BSA, we constructed a device in which the excitation light of a standard fluorescence spectrometer totally internally reflects from a surface at which adsorbed BSA is in equilibrium with the bulk solution. A shallow evanescent wave is created, which excites fluorescence from only those BSA molecules in close proximity to the surface. Spectral examination shows significantly less effective singlet-singlet energy transfer from the donor to the acceptor in surface-adsorbed BSA relative to that in native bulk-dissolved BSA. Under appropriate and reasonable assumptions, the energy transfer change between native and adsorbed states of fluorescent BSA can be interpreted as a conformational change of BSA upon adsorption.

Adsorption↗
PubMed1983

Immunoglobulin surface-binding kinetics studied by total internal reflection with fluorescence correlation spectroscopy.

An experimental application of total internal reflection with fluorescence correlation spectroscopy (TIR/FCS) is presented. TIR/FCS is a new technique for measuring the binding and unbinding rates and surface diffusion coefficient of fluorescent-labeled solute molecules in equilibrium at a surface. A laser beam totally internally reflects at the solid-liquid interface, selectively exciting surface-adsorbed molecules. Fluorescence collected by a microscope from a small, well-defined surface area approximately 5 micron2 spontaneously fluctuates as solute molecules randomly bind to, unbind from, and/or diffuse along the surface in chemical equilibrium. The fluorescence is detected by a photomultiplier and autocorrelated on-line by a minicomputer. The shape of the autocorrelation function depends on the bulk and surface diffusion coefficients, the binding rate constants, and the shape of the illuminated and observed region. The normalized amplitude of the autocorrelation function depends on the average number of molecules bound within the observed area. TIR/FCS requires no spectroscopic or thermodynamic change between dissociated and complexed states and no extrinsic perturbation from equilibrium. Using TIR/FCS, we determine that rhodamine-labeled immunoglobulin and insulin each nonspecifically adsorb to serum albumin-coated fused silica with both reversible and irreversible components. The characteristic time of the most rapidly reversible component measured is approximately 5 ms and is limited by the rate of bulk diffusion. Rhodamine-labeled bivalent antibodies to dinitrophenyl (DNP) bind to DNP-coated fused silica virtually irreversibly. Univalent Fab fragments of these same antibodies appear to specifically bind to DNP-coated fused silica, accompanied by a large amount of nonspecific binding. TIR/FCS is shown to be a feasible technique for measuring absorption/desorption kinetic rates at equilibrium. In suitable systems where nonspecific binding is low, TIR/FCS should prove useful for measuring specific solute-surface kinetic rates.

Animals↗