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Biomedical subjects

M A Clark

Publications and source records attributed to M A Clark.

At least 253 records · Page 14Linked to original sources
PubMed1982

Studies on putrefactive ethanol production. I: Lack of spontaneous ethanol production in intact human bodies.

The possibility of the production of ethanol by bacterial metabolism of blood glucose was investigated by studying a series of 26 hospital autopsies. The patients died from a wide variety of nontraumatic causes and the bodies were transported within 4 h of death to the morgue, where they were refrigerated for 0 to 28 h before samples of vitreous humor were collected for ethanol analysis. In addition, right heart blood was obtained using sterile technique for cultures as well as ethanol and glucose determinations. Ethanol was measured using gas-liquid chromatography, and glucose values were determined with a glucose oxidase method. In 13 cases, one to three species of microorganisms were isolated, but in no case was a blood or vitreous ethanol value greater than 10 mg/dL recorded. Ethanol values were also less than 10 mg/dL in the 13 cases with negative culture results. These data strongly suggest that de-novo production of ethanol by microbial metabolism does not occur in intact bodies which are refrigerated within 4 h of death. The detection of ethanol under such conditions is therefore probably indicative of antemortem consumption.

Adolescent↗
PubMed1981

Suppression of tumorigenicity in cybrids.

We investigated cytoplasmic control of tumorigenicity in cybrids. Cytoplasts derived from nontumorigenic cells were fused to the highly tumorigenic 984 C1 10-15 cell line derived from a murine teratoma. The resultant cybrids did not retain the tumorigenicity of the original cell line. In addition, the majority demonstrated the ability to differentiate into skeletal muscle. The results of these experiments indicate a heritable suppression of the tumorigenic phenotype by nontumorigenic cytoplasm. These findings are in contrast to our previous experiments in which we used a different experimental system and demonstrated a nuclear control of tumorigenicity in cybrids.

Animals↗
PubMed1981

The role of tubulin in the steroidogenic response of murine adrenal and rat Leydig cells.

The Y-1 murine adrenal and CCL43 rat Leydig tumor cell lines were used as model systems for studying the role of tubulin in steroidogenesis. Prior to the stimulation of steroidogenesis it was observed that most of the tubulin present in these cells, as determined by indirect immunofluorescence, was in a 0.2-0.6 micrometers dia. granular form. When these cells were treated with ACTH and cAMP, respectively, it was observed that the granular form of tubulin was replaced by many organized microtubules. These granules were identified in the electron microscope using tubulin antibody/ferritin localization and appeared to be membrane-bound and identical to structures previously described as containing cholesterol. We have isolated these structures using cell homogenization and sucrose gradient centrifugation and analyzed the steroid composition by thin layer chromatography (94% cholesterol, 6% cholesterol ester). These granules also contained tubulin as determined by gel electrophoresis. In addition, they contained acid phosphatase as determined by their ability to hydrolize beta-glycerolphosphate. We suggest that tubulin may be involved in the sequestering of cholesterol by preventing its transport to the mitochondria where conversion to pregnenolone takes place, and that steroidogenesis is increased when tubulin is dissociated from the cholesterol granules.

Adrenal Gland Neoplasms↗
PubMed1981

Pseudoleukemia. Ineffective regulation of granulopoiesis.

A neonate with Down's syndrome confirmed by chromosomal analysis had leukocytosis, with a WBC count of 48,000/cu mm, at age 13 days. Differential counts showed 70% to 90% blast forms by light microscopy. The blast-cell granules stained negatively with Sudan black B and alpha-napthyl butyrate esterase. Myeloperoxidase activity evaluated light and electron microscopy was negative. The granules stained positively with PAS, beta-glucuronidase, and tartrate-sensitive acid phosphatase. Indirect immunofluorescence for terminal-deoxynucleotidyl-transferase was negative. Our results show that the blast cells of pseudoleukemia may be of lymphoid origin.

Bone Marrow Cells↗
PubMed1980

Immunisation in the first year of life.

Over 10 percent of a group of 1180 Christchurch infants received either no immunisation, incomplete immunisation or late immunisation during the first year of life. Failure to provide the child with the recommended course of immunisation was most common amongst families of non-European ethnic origin, single parent families and families with depressed living standards.

Ethnicity↗
PubMed1980

Techniques for purifying L-cell karyoplasts with minimal amounts of cytoplasm.

Mouse L-929 cells centrifuged in the presence of cytochalasin B (CB) separate into cytoplasmic (cytoplasts) and nuclear (karyoplasts) fractions, but both of these fractions contain some whole-cell contaminants. We describe here two techniques for eliminating most of these whole cells from the karyoplast population. The first involves incubating cells in the presence of tantalum (Ta) particles, followed by enucleation and separation, on a Ficoll gradient. The small karyoplasts separate from the whole cells which contain a greater number of Ta particles. The second procedure uses a cell sorter that allows purification of karyoplasts from whole cells on the basis of light scatter. Both methods remove the whole-cell contaminants and the larger, and possibly viable, karyoplasts from the smaller karyoplast population. These purified karyoplasts are unable to regenerate but may be rescued by fusion with cytoplasts.

Animals↗
PubMed1980

Alternative method for identifying reconstituted cells.

Enucleation techniques combining mild centrifugation in the presence of cytochalasin B permit cells to be separated into nuclear fragments (karyoplasts) and cytoplasmic fragments (cytoplasts). These fragments, though stable for a short time, will ultimately degenerate by the procedures described in this report. One can, however, fuse cytoplasts to karyoplasts by using polyethylene glycol and obtain viable reconstituted cells whose properties may be useful for understanding some aspects of the nuclear-cytoplasmic interactions associated with tumorigenicity and steroidogenesis. However, the presence of cybrids, hybrids, and parental whole cell contaminants along with the reconstituted cell population make it necessary to have genetic markers that reside in both the nucleus and cytoplasm in order to preferentially identify reconstituted cells derived from a karyoplast fused to a cytoplast. By utilizing the Y-1 cell line, which is tumorigenic and responds to corticotropin by secreting steroids, and the AMT-BU-A1 (AMT) cell line, which is nontumorigenic and does not respond to corticotropin but has a nuclear marker, BrdUrd(r), and a cytoplasmic marker, CAP(r), we have reconstituted cells containing Y-1 karyoplasts and AMT cytoplasts. In this report we extend our previous techniques by describing an identification procedure that allowed us to isolate cells reconstituted from AMT karyoplasts fused to Y-1 cytoplasts. The results of these experiments support the concept that with these cell lines the nucleus (karyoplast) is ultimately sufficient to control the phenotypic expression or suppression of tumorigenicity and steroidogenesis.

Adrenocorticotropic Hormone↗
PubMed1979

Independent production of CO2 sensitivity by nuclear gene Dly and a transmissible agent from delayed-recovery Drosophila melanogaster.

Flies of stocks designated delayed-recovery by McCrady and Sulerud (1964) remain temporarily paralyzed after exposure to carbon dioxide. This condition is similar to CO2-sensitivity, which occurs in flies infected with the maternally transmitted sigma viruus, but is due, at least in part, to the third chromosome mutant gene Dly. Because earlier work indicated that extracts of delayed-recovery flies could occasionally transmit CO2 sensitivity when injected into resistant recipients, we have tested the possibility that some delayed-recovery stocks contain a sigma-like transmissible virus, in addition to the Dly gene. We found that TDR-orange, a stock derived from the original delayed-recovery line, and temperature-cured populations of the same stock, both contain some agent that is transmissible by injection. TDR-BC3f, a stock derived by backcrossing through the male line to eliminate maternally transmitted factors, does not appear to contain such an infectious agent, but remains sensitive to CO2. These observations lead us to the conclusion that the originally described delayed-recovery stocks harbor an infectious extrachromosomal agent, in addition to possessing the Dly gene, and each is capable of producing a sensitivity to carbon dioxide.

Animals↗