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Biomedical subjects

K T Brown

Publications and source records attributed to K T Brown.

At least 37 records · Page 2Linked to original sources
PubMed1988

Percutaneous transluminal angioplasty of infrapopliteal vessels: preliminary results and technical considerations.

Infrapopliteal balloon angioplasty was performed in 11 patients facing reconstructive surgery for limb salvage. Twelve separate sessions of angioplasty were performed, during which 15 of 16 diseased tibial runoff vessels were successfully dilated. Three complications occurred during percutaneous transluminal angioplasty (PTA). One was related to the concomitant use of a thrombolytic agent to open a femoropopliteal bypass graft and not related to the angioplasty itself. No limbs were lost as a result of complications. The procedure was a technical success in nine of 12 cases (75%) and an initial clinical success in eight of the nine that were technically successful (89%). Follow-up ranged from 1 to 22 months. Six of the nine cases (67%) remained clinically successful during this period. Preliminary results suggest that infrapopliteal PTA is a safe and effective alternative to surgical reconstruction in selected patients.

Aged↗
PubMed1986

Computed tomography analysis of bone tumors: patterns of cortical destruction and soft tissue extension.

Computed tomography was used to identify three different ways in which primary bone tumors may transgress a bony cortex. Analysis of the pattern of cortical transgression was used in conjunction with the presence or absence of matrix mineralization to classify correctly the lesion into one of four different diagnostic categories in 84% of 72 cases. These data demonstrate that certain types of behavior characterize the lesions under discussion and that this information may be helpful in diagnosis.

Bone Neoplasms↗
PubMed1985

Pseudoprominent aorta: radiographic findings and CT correlation.

The presence of a persistent left-sided superior vena cava (LSVC) in the absence of a right-sided superior vena cava (RSVC) may be suspected on a posteroanterior (PA) chest radiograph because of a prominent-appearing ascending aorta, which results from the absence of the RSVC. In the absence of an RSVC, the right upper lobe abuts and outlines the course of the ascending aorta, allowing better demonstration of its profile. This report describes a patient with this finding on a PA chest radiograph. Computed tomographic correlation is presented.

Adult↗
PubMed1982

Micropipette puller design: form of the heating filament and effects of filament width on tip length and diameter.

Though the ultrafine short tips provided by our micropipette puller are helpful for many preparations, longer tips are still needed for some cases where target cells for intracellular work are deeply embedded in tissue. Because the original 'loop' type of heating filament proved unsuitable for widening to provide the longer tips, we studied simpler forms of heating filaments. By comparison with the common loop design, a rectangular trough filament proved to have many advantages without any significant disadvantage. In particular, this type of filament may be used at varying widths to provide long tips as well as short ones. Thus our micropipette puller can now provide tip lengths that extend upward by continuous gradations from about 6 to 27 mm, while maintaining tip diameter in the ultrafine range of 0.1 micrometer or less. These long tips have proved more reliable and free from bending than long tips traditionally provided by the Livingston puller. By using narrow filaments in conjunction with other parameters that influence tip size, tips have also formed with diameters up to 1.5 micrometers and lengths of only 2-3 mm.

Animals↗
PubMed1981

Indirect costs of federally supported research.

Indirect costs of federally supported research have increased steadily and dramatically since the current indirect cost policy became effective in 1966. The amount of research supported by any given level of federal funding has thus been markedly reduced, and this has become a critical factor limiting research support in the United States. The current policy has had multiple adverse effects that threaten the health of both the federal research program and the universities in which most of the research is conducted. This article examines the background and nature of the current policy, describes its consequences, and proposes simplifying modifications.

Budgets↗
PubMed1979

Technique for precision beveling of relatively large micropipettes.

A technique is described for embedding various sizes of diamond dust in a film of Varathane laid upon an optically flat glass surface. This forms a precise and very durable abrasive surface. When such abrasive surfaces are used with previously described equipment, micropipettes may be beveled rapidly and reliably to tip diameters extending from 0.5 micron to indefinitely large sizes. Beveled tips formed in this manner are extremely sharp, as shown by high resolution SEM photographs. Plugging of the micropipette tip during beveling is prevented by applying pressure to the contained electrolyte. This procedure allows the micropipette's electrical resistance to be monitored accurately and continuously, so that beveling may be stopped at the electrical resistance associated with any predetermined tip diameter. The beveling of such relatively large micropipettes appears to have a variety of applications in neurophysiology, plus additional applications in kidney and capillary micropuncture work.

Microelectrodes↗
PubMed1979

Effects of the rod receptor potential upon retinal extracellular potassium concentration.

It has been hypothesized that the light-evoked rod hyperpolarization (the receptor potential) initiates the light-evoked decrease in extracellular potassium ion concentration, [K+]o, in the distal retina. The hypothesis was tested using the isolated, superfused retina of the toad, Bufo marinus; the receptor potential was recorded intracellularly from red rods, and [K+]o was measured in the photoreceptor layer with K+-specific microelectrodes. In support of the hypothesis, variations in stimulus irradiance or duration, or in retinal temperature, produced qualitatively similar effects on both the receptor potential and the decrease in [K+]o. A mechanism for the relationship between the receptor potential and the decrease in [K+]o was suggested by Matsuura et al. (1978. Vision Res. 18:767-775). In the dark, the passive efflux of K+ out of the rod is balanced by an equal influx of K+ fromthe Na+/K+ pump. The light-evoked rod hyperpolarization is assumed to reduce the passive efflux, with little effect on the pump. Thus, the influx will exceed the efflux, and [K+]o will decrease. Consistent with this mechanism, the largest and most rapid decrease in [K+]o was measured adjacent to the rod inner segments, where the Na+/K+ pump is most likely located; in addition, inhibition of the pump with ouabain abolished the decrease in [K]o more rapidly than the rod hyperpolarization. Based upon this mechanism, Matsuura et al. (1978) developed a mathematical model: over a wide range of stimulus irradiance, this model successfully predicts the time-course of the decrease in [K+]o, given only the time-course of the rod hyperpolarization.

Animals↗
PubMed1978

Opposing effects of calcium and barium in vertebrate rod photoreceptors.

Intracellular recording in outer segments of red rods of the toad retina showed that increasing Ca(2+) concentration in the perfusate mimicked certain aspects of light adaptation. Light sensitivity was reduced, the amplitude of light responses was reduced, the time course of light responses was altered by shortening the delay to the peak and increasing the decay rate, and the resting membrane potential was generally increased. These results provide further support for the hypothesis that Ca(2+) acts as an internal transmitter that is subject to light-induced release from the rod saccules. The addition of Ba(2+) to the perfusate mimicked dark adaptation by having effects opposite to all those described for Ca(2+). The Ba(2+) effects were specific, Mg(2+) and Sr(2+) being ineffective in similar or greater concentration. Also, Ba (2+) gave clear effects at concentrations as low as 0.1 mM. It is proposed that Ba(2+) enters the cell and reduces the uptake of Ca(2+) into the rod saccules, because the various effects of Ba(2+) upon light responses all seem explicable from this hypothesis. Ba(2+) also reduced the resting membrane potential, probably by reducing the membrane conductance for K(+). The demonstrated effects of Ba(2+) indicate an important role for Ba(2+) in analyzing the ionic aspects of transduction in vertebrate photoreceptors. They also suggest a critical physiological role for Ba(2+) in controlling both the resting properties and light-induced responses of vertebrate rods, because barium has been reported to be concentrated in outer and inner segments of cat photoreceptors.

Animals↗
PubMed1974

Beveling of fine micropipette electrodes by a rapid precision method.

A technique has been developed for embedding alumina particles 0.05 micrometer in size in the surface of a polyurethane film laid on glass. This abrasive surface is used for rapid, precise, and reliable beveling of Pyrex micropipettes with tip diameters at least as small as 0.1 micrometer. In the snapping turtle retina the beveled electrodes give much better cell penetration and intracellular response stability than unbeveled electrodes of considerably higher proach to this problem.

Aluminum↗