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Biomedical subjects

J Steketee

Publications and source records attributed to J Steketee.

12 recordsLinked to original sources
PubMed1989

Forskolin infusion in vivo increases ouabain binding in brain.

In order to investigate the possible regulation of brain Na,K-ATPase by cyclic AMP, we measured Na,K-ATPase activity and ouabain binding in cerebral cortex after intraventricular infusion of forskolin for 7 days. There was a dose-related increase in high-affinity ouabain binding, with a 75% increase at 12.5 micrograms/h forskolin. The effect on total enzyme activity was smaller but enzyme activity with high affinity for ouabain was increased by 65%, suggesting a selective effect on enzyme with high affinity for ouabain. Forskolin appeared not to interact directly with Na,K-ATPase in vitro.

Animals↗
PubMed1987

Quantification of patch test reactions by transcutaneous PO2 measurement.

The usefulness of transcutaneous oxygen tension (tc-PO2) measurement for quantification of positive patch test reactions was studied. A significant correlation was found between the visual grading and the quantitative tc-PO2 values. Tc-PO2 discriminated between visual grade 0 to 1+, 1+ to 2+, and 2+ to 3+ reactions. The results obtained by this method were compared with those obtained by other quantitative methods. Tc-PO2 measurement can be regarded as complementary to the laser Doppler technique, since it lacks the sensitivity of the laser Doppler technique in the range in negative to 1+ patch reactions, but it does discriminate between 2+ and stronger reactions.

Adult↗
PubMed1985

Erythromelalgia caused by platelet-mediated arteriolar inflammation and thrombosis in thrombocythemia.

Erythromelalgia was the presenting symptom in 26 of 40 patients with thrombocythemia in its primary form or when associated with polycythemia vera. The localized painful burning, redness, and warm congestion in the extremities could be accurately documented with thermography. Skin punch biopsy samples taken from the affected areas showed typical arteriolar inflammation, fibromuscular intima proliferation, and thrombotic occlusions. Erythromelalgia often progressed to ischemic acrocyanosis or necrosis in toes or fingers. Complete relief of pain and restoration of microvascular circulation disturbances was obtained with the cyclo-oxygenase inhibitors aspirin and indomethacin, but not with sodium-salicylate or the platelet inhibitors dipyridamole, sulfinpyrazone, ticlopidine, and dazoxiben. The erythromelalgia was alleviated during busulfan-induced remissions of thrombocythemia and its recurrence coincided with relapsing thrombocythemia. These observations suggest a causal relationship between erythromelalgia and thrombocythemia, in which platelet-mediated inflammatory and occlusive arteriolar changes play a part in the etiology of erythromelalgia.

Adult↗
PubMed1979

Thermal recovery of the skin after cooling.

A theoretical model of the skin is used to study the thermal recovery of the skin temperature after cooling. The analytical solution of the partial differential equation describing this model shows that recovery curves can be approximated by a two-exponential curve or even by a mono-exponential curve when the data from the first two minutes are omitted. With this model, it is possible to study the influence of the blood flow and the thermal conductivity lambda of the skin on the steady-state temperature and the decay constants mun. New experiments will be carried out to verify the relation between mu1, mu2 and the blood flow but now correcting for the influence of lambda, as predicted by the model.

Blood Circulation↗
PubMed1976

The influence of cosmetics and ointments on the spectral emissivity of skin.

Measurements of the spectral emmissivity, epsilon (lambda), of human skin described in a previous paper were performed with a modified monochromator by comparing the radiation from the skin with blackbody radiation in the wavelength range between 2 and 14 mum. Using the same equipment the spectral emissivity has been measured of skin which had been covered with different cosmetics and ointments. From these data it is possible to predict theoretically the apparent temperature difference as seen by an infrared scanner or radiometer with a detector of which the spectral detectivity, D (lambda), is known. These values are compared with the readings of a Bofors Thermograph with an InSb detector. When talcum venetum has been applied to the skin, a greater apparent temperature diffenence must be expected for thermographic cameras equipped with a HgCdTe detector than for cameras with InSb detectors.

Cosmetics↗
PubMed1975

Spatial resolution of thermographic cameras.

To obtain an impression of the spatial resolution of a number of thermographic cameras, a method similar to that of DODD et al. [1969] was followed: a test pattern with a series of line groups was scanned and the relative amplitude of the videosignal was plotted as a function of the spatial frequency (MTF). To make it possible to compare the various cameras directly, the spatial frequency was expressed in radians-1 and not in lines per millimeter, which makes the result less dependent on the distance. For one of the cameras, the MTF was also measured densitometrically, which yielded a lower value of spatial resolution. In practice this is of minor importance, because temperature differences are measured directly with the videosignal (isotherm mode) and not by density measurements. In contrast to Macey and Oliver [1972] who assumed that the resolution is determined by the time constant of the detector only, the resolution of the cameras investigated in our laboratory depended only on the dimensions of the detector.

Electronics↗