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Biomedical subjects

C M Epstein

Publications and source records attributed to C M Epstein.

61 records · Page 4Linked to original sources
PubMed1982

Voluntary alteration of visual evoked potentials.

Fifteen normal adults had pattern-shift visual evoked potentials (PSVEPs) using monocular checkerboard pattern reversal. Subjects were instructed to concentrate on the pattern in the first set of trials and then to avoid perceiving it in the second set. Direct, continuous visual observation ensured that the eye remained open and fixed on the pattern. Nonetheless, a third of the subjects could spontaneously alter or obliterate the PSVEP using several maneuvers, including meditation, daydreaming, and convergence. Several could produce shifts in apparent PSVEP latency. With explicit instruction, most subjects could learn to alter their PSVEP by maneuvers that are inapparent even to an observent technician.

Adult↗
PubMed1980

Decarboxylation of alpha-ketoisovaleric acid after oral administration in man.

The keto analogues of essential amino acids represent a promising therapeutic modality in hereditary and acquired disorders of nitrogen metabolism. The utilization of these substances in humans has been assayed primarily by nitrogen balance studies. A simple and accurate breath excretion test for 14CO2 enabled us to measure the decarboxylation of 1-14C-alpha-ketoisovaleric acid (KIV, the keto analogue of valine) in two normal and six diseased subjects. Normal volunteers as well as patients with gastrectomy, hepatic failure, renal failure, and myotonic dystrophy were tested in 5-g protein diets supplemented with essential amino acids and KIV (in place of valine). The normal volunteers and the gastrectomy patient were then restudied on 120 g protein/day. With low protein intake, 13 to 32% of ingeted KIV underwent rapid decarboxylation, and this proportion appeared to correlate inversely with damage to organ systems containing the branched-chain keto acid dehydrogenase. With high protein intake, the proportion decarboxylated rose to 44 to 53%. Thse results confirm that the decarboxylation of KIV in man varies under different conditions of dietary intake and metabolic disease. The 14CO2 brewth excretion test is applicable to other related analyses of carboxylic acid metabolism in human subjects.

Adult↗
PubMed1979

True checkerboard pattern reversal with light-emitting diodes.

The use of rectangular red light-emitting diodes permits construction of a true checkerboard pattern-reversal stimulator, which given evoked responses comparable in amplitude and wave form to those obtainable by a TV pattern generator. The device interfaces easily with commercial avergers and allows the incorporation of several features that may increase the sensitivity of visual evoked responses in screening for multiple sclerosis.

Brain↗