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Biomedical subjects

C Stewart

Publications and source records attributed to C Stewart.

At least 199 records · Page 11Linked to original sources
PubMed1983

X chromosome-linked transmission and expression of retroviral genomes microinjected into mouse zygotes.

A genomic clone consisting of the Moloney leukemia proviral genome with moderately repetitive mouse sequences was microinjected into the pronucleus of a mouse zygote. An animal was derived that carried multiple copies of proviral DNA in a tandem array. No evidence for homologous recombination was obtained. The viral genome was expressed in this animal and was transmitted as a single unit to its offspring. Subsequent breeding studies revealed that the proviral DNA had integrated on an X chromosome.

Animals↗
PubMed1983

Septo-optic dysplasia and median cleft face syndrome in a patient with isolated growth hormone deficiency and hyperprolactinemia.

A pituitary evaluation was carried out in a 12-year-old girl who had early puberty, short stature, optic nerve hypoplasia, and agenesis of the corpus callosum. Her growth hormone (GH) response to insulin-induced hypoglycemia and arginine infusion was blunted. Basal and stimulated levels of prolactin were elevated. The association of GH deficiency and hyperprolactinemia suggests a disruption of the dopaminergic modulation of these hormones. The facial features seen in our patient, such as hypertelorism, V-shaped frontal hairline, and cleft nose and upper lip, are enough to justify the diagnosis of median cleft face (MCF) syndrome. However, the optic nerve hypoplasia and the GH deficiency are characteristics of septo-optic dysplasia, and, to our knowledge, they have never been described in patients with MCF syndrome. Our case fulfills the diagnostic criteria of both, representing a link between both ends of this spectrum.

Abnormalities, Multiple↗
PubMed1983

Growth hormone receptors in lymphocytes of growth hormone-deficient children.

Human growth hormone was injected intravenously into 18 growth hormone-deficient children and growth hormone binding sites in lymphocytes were investigated. Fresh circulating lymphocytes had a low initial value for the binding of growth hormone to solubilized receptors (3.45 +/- 1.46%) but after growth hormone injection, the binding rapidly increased to 14.8 +/- 4.2% at 2 1/2 h and 8.7 +/- 1.8% at 5 h. The sharp increase in binding is due to increase in the number of binding sites. Two control children who received chorionic gonadotropin had no change in lymphocyte growth hormone receptors. The methodological differences between the present study and previous attempts to identify human growth receptors in lymphocytes were (1) lymphocytes were separated and disrupted with Triton X-100 as quickly as possible (to avoid error from receptor leaking out of the cell) and (2) the receptors were assayed at 2 1/2 h after growth hormone administration (previous studies were 12-24 h later). One possible explanation for the data is that growth hormone receptor from liver is taken up by lymphocytes and rapidly released again, thus, contributing to the hormonal receptor economy in humans.

Adolescent↗
PubMed1983

Effect of oral zinc supplements on growth, hormonal levels, and zinc in healthy short children.

13 short children aged 7-13 years who had a retarded bone age and low hair zinc concentration (under 140 micrograms/g) were treated with oral zinc supplements for a year. There was a significant increase in the growth rate in the children whose hair zinc concentration increased. Growth hormone, testosterone and somatomedin C also increased after oral zinc supplementation. Data from 755 short healthy children who have attended our Growth Clinic are presented which describe their hair and serum zinc concentration at different ages. The data indicate a decline in hair zinc concentration after birth with a gradual increase at age 4-6 years, finally reaching adult normal levels after adolescence.

Administration, Oral↗
PubMed1982

DNA methylation, retroviruses, and embryogenesis.

By exposing preimplantation embryos to Moloney leukemia virus (M-MuLV), we have previously derived substrains of mice designated as Mov-1-Mov-13 which genetically transmit the virus from one generation to the next. In some of the substrains the inserted viral genome becomes activated at specific stages of embryogenesis and the available evidence suggests that these viral genomes are developmentally regulated. To investigate the effect of cellular differentiation on virus expression, M-MuLV was introduced either into preimplantation or post-implantation mouse embryos or into embryonal carcinoma (EC) cells. Whereas preimplantation embryos or EC cells are not permissive for virus expression, efficient replication occurred in postimplantation embryos or in differentiated cell lines. The viral genomes introduced into early embryonal cells were highly methylated and noninfectious when analyzed in the adult. In contrast, viral genomes introduced into postimplantation embryos or into differentiated cells remained unmethylated and were infectious in a transfection assay. These results demonstrate an efficient de novo methylation activity which appears to be involved in repression of genes introduced into pluripotent embryonal cells and which is not observed in cells of the postimplantation embryo or in differentiated cells in tissue culture.

Animals↗
PubMed1981

Occupational cancer: experience in Ontario.

This paper reviews the experience of the Workmen's Compensation Board of Ontario in identifying cases of cancer that could be attributed to occupational hazards. Worker's claims for compensation are allowed if there is reasonable medical evidence that their cancer was caused by exposure to risk factors associated with their occupation. Details of the types of cancer associated with specific carcinogens or fields of employment are discussed. About 50% of the cases were related to exposure in particular industrial operations that functioned for relatively brief periods. The number of deaths from cancer identified as being caused by occupational factors is compared with the total for cancer from all causes in Ontario during the period 1971 through 1975. Although all workers eligible for compensation may not have been identified, the data suggest that less than 1% of cancer is presently caused by occupational factors.

Aniline Compounds↗
PubMed1981

Transient adrenogenital syndrome due to exposure to danazol in utero.

We describe a premature female infant exposed in utero to danazol during the first trimester of pregnancy. She was first observed in the newborn period with marked degree virilization and clinical findings suggestive of salt-losing congenital adrenal hyperplasia. This was supported by the high plasma levels of 17 alpha-hydroxyprogesterone and adrenocorticotropic hormone and low plasma cortisol level. Levels of testosterone, androstenedione, 11-deoxycortisol, and renin were also elevated. An excessive increase in the levels of 17 alpha-hydroxyprogesterone and 11-deoxycortisol to corticotropin administration associated with impaired increase in plasma cortisol level strongly suggests a partial block in the 21-hydroxylation of 17 alpha-hydroxyprogesterone. However, the high levels of 11-deoxycortisol also suggest a block of the steroid 11 beta-monooxygenase. A year later she was found to have normal basal levels of the adrenal steroids and normal response to corticotropin administration, pointing out the transitory nature of these abnormalities. It may be hypothesized that danazol produced a transitory block of the steroid 21- and 11 beta-monooxygenases in this child.

Adrenal Hyperplasia, Congenital↗
PubMed1981

Loss of organized fibronectin matrix from the surface of aging diploid fibroblasts (IMR-90).

Indirect immunofluorescence was used to investigate the production of a fibrillar fibronectin matrix by human diploid fibroblasts (IMR-90) as cells progress through their in vitro lifespan. Early and mid-passage cultures displayed a prominent fibrillar reticulum over the cell layer which formed within 24 hours of seeding. Even sparsely seeded early-passage cells exhibited fibrils of fibronectin on external surfaces. In contrast, fibrillar fibronectin was reduced or absent on surfaces of late-passage cells. However, the larger, non-proliferating, late-passage cells were producing fibronectin, 1h determined by radioimmunoassay of the medium.

Aging↗
PubMed1980

Exaggerated natriuresis in normotensive subjects with a previous history of pregnancy-associated hypertension.

The effect of an isotonic saline infusion on urinary sodium excretion and plasma renin activity (PRA) has been studied in 11 normotensive patients with a previous history of pregnancy-associated hypertension. The results have been compared with a group of controls matched for age, sex and parity. The results demonstrate an exaggerated natriuresis and a suppressed PRA response in the patients with a previous history or pregnancy-associated hypertension which is similar to those reported in patients with established 'essential' hypertension.

Adolescent↗
PubMed1980

Mycoplasma pneumonia: failure of erythromycin therapy.

Two cases of mycoplasma pneumonia are described which failed to respond to prolonged treatment with erythromycin. The substitution of oxytetracycline therapy resulted in rapid clinical and radiological resolution.

Adult↗
PubMed1980

Aggregation between teratocarcinoma cells and preimplantation mouse embryos.

The ability of two embryonal carcinoma (EC) cell lines, F9 and PC13, to aggregate with preimplantation 8-cell mouse embryos is described. Both adhere to the embryonic cells and subsequently compact with the embryos. The aggregates form blastocysts in culture. The blastocysts sometimes contain the EC cells, located almost always in their inner cell mass. Differentiated derivatives of EC cells, namely PYS-1 and PYS-2, as well as STO fibroblasts do not aggregate with embryos.

Animals↗