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Biomedical subjects

R Cohn

Publications and source records attributed to R Cohn.

At least 37 records · Page 2Linked to original sources
PubMed1985

Differential visual evoked cortical responses to direct and peripheral stimulation in man.

Clearly defined differential summated cortical evoked responses are demonstrated for central and peripherally applied visual stimuli. Central vision is associated with a low amplitude positive peak at 75 msec and a prominent high voltage positive peak at around 100 msec; later relatively low amplitude positive peaks are generally also observed. With peripheral stimulation at 15 degrees and greater the 75 msec positive peak is accentuated; the 100 msec positive peak becomes inconspicuous, and the later positive peaks at 165 msec and greater are strongly enhanced. These data support the hypothesis that the positive peaks are the cortical responses to the differential actions of the rod and cone cell components of the retina.

Evoked Potentials, Visual↗
PubMed1984

"Leukemic" pattern of in vitro growth in a patient with Down syndrome and transient myeloproliferative disorder.

Peripheral blood cells from a female infant with Down syndrome and over 60% circulating myeloblasts were cultured in soft agar. Growth was virtually restricted to cluster formation, and cluster-forming cells resided almost exclusively in the very light density fraction (SG less than 1.062). Morphological assessment of clusters revealed no evidence of cellular differentiation beyond the blast cell stage. Despite receiving no specific chemotherapy, the peripheral blood normalized within 2 months, and there was no evidence of leukemia when the patient died aged 1 year from cardiac pathology. The findings indicate that caution should be exercised when assessing prognosis on the basis of in vitro growth characteristics in such patients.

Agar↗
PubMed1983

Correlation of initial thiothixene serum levels and clinical response. Comparison of fluorometric, gas chromatographic, and RBC assays.

A series of three experiments addressed major problems concerning the use of serum levels as predictors of clinical response to thiothixene (Navane) hydrochloride in schizophrenia: correlation of initial test doses with clinical response; comparison of fluorescence spectrophotometry with gas chromatography in relation to clinical response; and comparison of serum levels with RBC levels in relation to clinical response. All assays correlated (near r = .5) with Brief Psychiatric Rating Scale improvement during hospitalization, except RBC levels seemed to have superior correlations (.64) in patients with lower serum levels. These correlations are similar to those obtained with steady state levels. The different methods of determining thiothixene concentrations were highly intercorrelated as well. Thus, single-dose serum levels give important clinical correlations regardless of which assay is used for thiothixene determination.

Adult↗
PubMed1982

Serum level monitoring of thiothixene in schizophrenia: acute single-dose levels at fixed doses.

After establishing a strong correlation between steady-state thiothixene levels and levels drawn 2.5 hours after a 20-mg test dose, the authors examined the correlation between clinical improvement and serum levels drawn 2.5 hours after a single 20-mg test dose of thiothixene. For 30 male schizophrenic inpatients, improvement on the Brief Psychiatric Rating Scale was significantly correlated with the single test-dose levels. Serum levels were also positively correlated with age, which may explain the tendency of elderly patients to require lower neuroleptic doses and to exhibit a higher incidence of side effects. The results suggest that acute single-dose levels may be useful in predicting clinical response to thiothixene.

Administration, Oral↗
PubMed1981

Correlation of thiothixene serum levels and age.

Two experiments are reported in which acute single test dose levels of thiothixene (Navane) were correlated with age. In the first study 20 mg oral doses were given to 28 male subjects and serum levels were drawn 2 h later. Mean age was 30 and correlation of serum level with age was 0.43, P less than 0.02. In a second older group with a mean age of 41, 10 mg oral doses were given to 25 subjects. A correlation with age of 0.41, P less than 0.05 was obtained with age. In prior work such acute levels have been found to correlate with steady-state serum levels and with clinical response to the medication. Few side-effects were seen in these populations and no correlations were obtained between serum levels and any side-effects.

Adult↗
PubMed1979

On the clinical significance of the plasma alpha-amino-n-butyric acid:leucine ratio.

The ratio of plasma alpha-aminobutyric acid to plasma leucine that has been proposed as a specific biochemical marker of alcoholic liver injury, was measured in normal children an children with a variety of metablic disorders. The ratio was found to be lower in children that in adults. It was elevated in children with Reye's syndrome, tyrosinemia, homocystinuria, nonketotic hyperglycinemia, and ornithine transcarbamylase deficiency. The results indicate that an elevated ratio is not specific for adults with alcoholic liver injury and that the ratio may be high even without the presence of clinically apparent hepatic disease. An altered ratio may reflect the presence of an inherent metabolic defect.

Adult↗
PubMed1979

Biotin-response organicaciduria. Multiple carboxylase defects and complementation studies with propionicacidemia in cultured fibroblasts.

Fibroblast cultures from two individuals with biotin-responsive organicacidemia were found to have a pleiotropic deficiency of propionyl-CoA carboxylase, beta-methylcrotonyl-CoA carboxylase, and pyruvate carboxylase activities after growth in biotin limited culture medium, conditions which do not affect the carboxylase activities of normal cells. All three enzyme activities were restored to normal levels after transferring the mutant strains to biotin-rich medium. Both patients excreted abnormal levels of an array of metabolic intermediates, including beta-methylcrotonate, beta-hydroxyisovalerate, beta-hydroxypropionate, and lactate, which reflect metabolic blocks at all three carboxylase sites.14 mutants deficient in only propionyl-CoA carboxylase activity from patients with propionicacidemia and the two biotin-responsive strains were examined for complementation with seven previously mapped pcc mutants. No new pcc complementation groups were identified. Nine of the mutants were mapped to group pccA. The remaining 12 mutants mapped to pccBC or its B or C subgroups, confirming the complex nature of this group. The biotin-responsive mutants failed to complement each other but did complement mutants from all the pcc groups. Thus biotin-responsive organicacidemia is defined by a new complementation group, bio. The results obtained in this study suggest that the bio mutants have a defect of either biotin transport or a common holocarboxylase synthetase required for the biotin activation of all three mitochondrial carboxylases.

Acidosis↗