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Biomedical subjects

M Levitt

Publications and source records attributed to M Levitt.

At least 199 records · Page 11Linked to original sources
PubMed1980

Human platelet monoamine oxidase and the menstrual cycle.

Endocrine factors are known to affect platelet monoamine oxidase (MAO) activity. To assess the role of sex steroid hormones in regulating MAO, blood samples for platelet MAO assay were obtained twice weekly from 12 women. Peak MAO activity occurred during the ovulatory interval and a nadir occurred in the postovulatory phase, 5 to 6 days later. A 17% mean effect of menstrual variation from peak to nadir was noted. The implications for MAO studies in psychiatric research are discussed.

Adolescent↗
PubMed1980

Low platelet monoamine oxidase activity: a possible biochemical correlate of borderline schizophrenia.

Platelet monoamine oxidase (MAO) activity, psychiatric disorders, and family history of psychopathology were studied in 115 nonhospitalized, previously undiagnosed college student volunteers. Subjects were classified into two extreme groups: those with platelet MAO activity two standard deviations below the mean ("low-MAO" probands) and those with platelet MAO activity two standard deviations above the mean ("high"-MAO probands). Low-MAO probands were found to have a significant increase in the incidence of borderline schizophrenia and other psychiatric disorders compared to high-MAO probands. First-degree relatives of low-MAO probands were more often affected with psychiatric disorders and borderline schizophrenia than relatives of high-MAO probands. The data suggest that reduced platelet MAO activity is associated with psychiatric vulnerability and that the spectrum of schizophrenia may be more closely related to this vulnerability than other psychiatric disorders.

Adult↗
PubMed1979

Periodicity of deoxyribonuclease I digestion of chromatin.

Two methods have been used to measure the single-strand lengths of the DNA fragments produced by deoxyribonuclease I digestion of chromatin. The average lengths obtained are muliples of about 10.4 bases, significantly different from the value of 10 previously reported. This periodicity in fragment lengths is closely related to the periodicity of the DNA double helix in chromatin, but the two values need not be exactly the same.

Animals↗
PubMed1979

Normal metyrapone response after 1 month of high-dose methylprednisolone in cancer patients: a phase I study.

A dose of 125 mg of methylprednisolone was given iv each morning for 28 days to six patients with cancer. The posttreatment mean AM/PM serum cortisol (hydrocortisone) level of 19.55/11.27 microgram/dl showed a statistically significant (P less than 0.05) diurnal rhythm and did not differ from the pretreatment level (19.28/11.85 microgram/dl). The response to metyrapone (750 mg orally, every 4 hours X six doses) was assessed in five of the six patients before and after treatment. No abnormally low Compound S (11-deoxycortisol) levels were observed. The mean serum Compound S level (15.30 microgram/dl) achieved after treatment did not differ significantly from the pretreatment mean level (20.24 microgram/dl, P greater than 0.1). No adverse clinical effects were observed during or after this steroid treatment. Since significant hypothalamic-pituitary-adrenal suppression has not been demonstrated, this regimen appears to be safe for use in controlled studies of clinical efficacy.

Adenocarcinoma↗
PubMed1978

Conformational preferences of amino acids in globular proteins.

In a previous paper [Levitt, M., and Greer, J. (1977), J. Mol. Biol. 114, 181--239], an objective compilation of the secondary-structure regions in more than 50 different globular proteins was produced automatically. In the present paper, these assignments of secondary structure are analyzed to give the frequency of occurrence of the 20 naturally occurring amino acids in alpha helix, beta sheet, and reverse-turn secondary structure. Nineteen of these amino acids have a weak but statistically signficant preference for only on type of secondary structure. These preferences correlate well with the chemical structure of the particular amino acids giving a more objective classification of the conformational properties of amino acids than available before.

Amino Acids↗
PubMed1978

How many base-pairs per turn does DNA have in solution and in chromatin? Some theoretical calculations.

Calculations on a 20-base pair segment of DNA double helix using empirical energy functions show that DNA can be bent smoothly and uniformly into a superhelix with a small enough radius (45 A) to fit the dimensions of chromatin. The variation of energy with the twist of the base pairs about the helix axis shows the straight DNA free in solution is most stable with about 10 1/2 base pairs per turn rather than 10 as observed in the solid state, whereas superhelical DNA in chromatin is most stable with about 10 base pairs per turn. This result, which has a simple physical interpretation, explains the pattern of nuclease cuts and the linkage number changes observed for DNA arranged in chromatin.

Chromatin↗
PubMed1978

Experimental pancreatic carcinogenesis. II. Lifetime carcinogenesis studies in the outbred Syrian golden hamster with N-nitroso-bis(2-hydroxypropyl)amine.

A high incidence of pancreatic duct neoplasms was induced in outbred male Syrian golden hamsters following weekly sc injection of N-nitroso-bis(2-hydroxypropyl)amine for life. The first such tumors appeared as early as 16 experimental weeks; the maximum incidence reached 100% by the termination of the study. Tumors in the respiratory tracts and angiosarcomas of the livers of the hamsters were also observed in high frequency. Latency of the induced neoplasms was significantly decreased by the substitution of distilled water for olive oil as the vehicle for the carcinogen.

Animals↗
PubMed1978

Phase II study of adriamycin and bleomycin in patients with multiple myeloma.

Twenty-seven patients with far-advanced multiple myeloma, resistant to standard agents, were treated with either adriamycin (eight patients) or bleomycin (19 patients). Adriamycin was given iv at a dose of 60 mg/m2 every 3 weeks and bleomycin was administered im at a dose of 15 mg/m2 weekly. Drug toxicity was modest. One partial response was seen with each agent, both occurring in "good-risk" patients.

Aged↗
PubMed1977

Structure of nucleosome core particles of chromatin.

Cystals have been obtained on nucleosome cores and analysed by X-ray diffraction and electron microscopy. The core is a flat particle of dimensions about 110 X 110 X 57 A, somewhat wedge shaped, and strongly divided into two 'layers', consistent with the DNA being wound into about 1 3/4 turns of a flat superhelix of a pitch about 28 A. The organisation of the DNA can be correlated with the results to enzyme digestion studies. A change in the screw of the DNA double helix on nucleosome formation can be deduced.

Animals↗
PubMed1977

Diffuse histiocytic lymphoma. The need for aggressive restaging.

Fifteen patients with stage III and IV diffuse histiocytic lymphoma were treated with combination chemotherapy: cyclophosphamide, vincristine sulfate, prednisone, and procarbazine hydrochloride (COPP). Eight achieved a complete clinical remission. Of these, five relapsed, but remission was reinduced in three of these. Median survival of partial responders was 52 weeks compared to more than 129 weeks for complete responders. Complete clinical remission in diffuse histiocytic lymphomas did not presage a long disease-free interval as has been reported in biopsy proved remission series. Biopsy and staging by pathologic examination appear necessary to document remission in this disease.

Adult↗