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Biomedical subjects

L Stern

Publications and source records attributed to L Stern.

At least 199 records · Page 11Linked to original sources
PubMed1967

The effect on serum ionic magnesium of exchange transfusion with citrated as opposed to heparinized blood.

Serum Mg++ levels before, during, and after replacement transfusion were determined in 20 newborn infants. In 10 infants exchanged with acid-citrate-dextrose (ACD) blood, the level fell from 1.75 +/- 0.16 mEq./l. to 0.99 +/- 0.16 mEq./l. By contrast, levels in 10 infants exchanged with two types of heparinized blood were unchanged: the pre-exchange values were 1.59 +/- 0.11, and the postexchange levels were 1.59 +/- 0.08 mEq./l. Mean values for donor bloods were 0.42 +/- 0.07 mEq./l. with ACD blood, and 1.45 +/- 0.03 mEq./l. with heparinized blood. In vitro studies involving the addition of known amounts of citrate to standard Mg++ solutions demonstrated that the citrate caused a reduction of ionic magnesium. It is proposed that the fall in serum Mg++ when ACD blood is used for exchange transfusion is the combined result of Mg++ binding by the citrate, and the dilution effect of the relatively large proportion of anticoagulant to blood (1:3) used with the ACD mixture.

Anticoagulants↗
PubMedDate not supplied

Motion direction signals in the primary visual cortex of cat and monkey.

When an image feature moves with sufficient speed it should become smeared across space, due to temporal integration in the visual system, effectively creating a spatial motion pattern that is oriented in the direction of the motion. Recent psychophysical evidence shows that such "motion streak signals" exist in the human visual system. In this study, we report neurophysiological evidence that these motion streak signals also exist in the primary visual cortex of cat and monkey. Single neuron responses were recorded for two kinds of moving stimuli: single spots presented at different velocities and drifting plaid patterns presented at different spatial and temporal frequencies. Measurements were made for motion perpendicular to the spatial orientation of the receptive field ("perpendicular motion") and for motion parallel to the spatial orientation of the receptive field ("parallel motion"). For moving spot stimuli, as the speed increases, the ratio of the responses to parallel versus perpendicular motion increases, and above some critical speed, the response to parallel motion exceeds the response to perpendicular motion. For moving plaid patterns, the average temporal tuning function is approximately the same for both parallel motion and perpendicular motion; in contrast, the spatial tuning function is quite different for parallel motion and perpendicular motion (band pass for the former and low pass for the latter). In general, the responses to spots and plaids are consistent with the conventional model of cortical neurons with one rather surprising exception: Many cortical neurons appear to be direction selective for parallel motion. We propose a simple explanation for "parallel motion direction selectivity" and discuss its implications for the motion streak hypothesis. Taken as a whole, we find that the measured response properties of cortical neurons to moving spot and plaid patterns agree with the recent psychophysics and support the hypothesis that motion streak signals are present in V1.

Animals↗
PubMedDate not supplied

Isolation and identification of "diazepam-like" compounds from bovine urine.

Attempts to isolate the putative endogenous ligand for the benzodiazepine receptor from bovine urine resulted in the identification of three isoflavans: equol (1), 3',7-dihydroxyisoflavan (2), and 4'-hydroxy-7-methoxyisoflavan (9), as "diazepam-like" compounds. 3-Chloro-9H-carbazole (17) was found to enhance the binding of diazepam in the benzodiazepine receptor binding assay. Pinosylvine monomethyl ether (18), indigo (20), and indirubin (21) were isolated as inactive compounds.

Animals↗