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Biomedical subjects

C McCarthy

Publications and source records attributed to C McCarthy.

At least 109 records · Page 6Linked to original sources
PubMed1982

A total population study of diagnosed chromosome abnormalities in Queensland, Australia.

Aneuploidy and structural chromosome rearrangements comprise a significant group of abnormalities in the general population. The true incidence of such abnormalities can be obtained by large research studies of consecutive newborns. In practice, the observed incidence of such chromosome abnormalities is obtained by karyotyping subjects who present for clinical reasons. The difference between the observed clinically indicated rates and the assumed rate (by comparison with data from consecutive newborn studies) would allow the estimation of the unrecognised chromosome abnormality load in the general population. The difference between these two rates would provide valuable data concerning the appropriateness of selection techniques for routine chromosome analysis. This paper reports such a study, from Queensland, Australia. A total population 5-year survey (1976-1980) of the diagnosed chromosome abnormalities in this unselected primary population of 2.2 million people is reported. Five hundred and eighty-nine chromosome abnormalities were detected in a consecutive series of 6092 karyotypes performed (9.7%). This figure is significantly lower than that found in most other reported series where case selection for karyotyping is determined by clinical criteria. In this current study the annual diagnostic rate for chromosome abnormalities was 5.41 per 100,000 of the general population. Cumulative frequency histograms for all types of chromosome abnormality, by age, are presented. In current practice, 32% of chromosome abnormalities are not diagnosed until adult life. Fifty percent of cases of chromosome abnormality (of all types) remain undiagnosed by the age of 1 year, in spite of a relatively liberal acceptance rate on the part of laboratories offering routine karyotyping services. It is concluded that a positive diagnostic rate greater than 10%, in routine chromosome laboratories, probably indicates that more than half the true cases of chromosome abnormality in a population are being missed.

Adolescent↗
PubMed1980

Isolation of deoxyribonucleic acid from Mycobacterium avium by rapid nitrogen decompression.

Deoxyribonucleic acid (DNA) of high molecular weight could be isolated from cells of Mycobacterium avium if the cells were exposed to nitrogen gas at 1,500 lb/in2 for 30 min and then brought to atmospheric pressure by rapid decompression. DNA isolated from the cells had a molecular weight of 4.8 x 10(6) to 17.4 x 10(6). DNA was also released into the fluid in which the cells were suspended during nitrogen decompression. One-half of this DNA, representing 3% of the total DNA phosphorus in the cells had a uniform molecular weight of 4.2 x 10(6). This DNA was linear in conformation, and removal of associated carbohydrates did not change its sedimentation rate. The biological function or significance of the 4-megadalton DNA was not determined.

Bacteriological Techniques↗
PubMed1978

Ammonium ion requirement for the cell cycle of Mycobacterium avium.

Mycobacterium avium has a defined cell cycle in which small cells elongate to about five times their original length and then divide by fragmentation. The nitrogen requirement for production of maximal number of colony-forming units was assessed by varying concentrations and kinds of nitrogen source in the medium. Ferric ammonium citrate at a concentration in 7H10 medium of 0.17 mumol/ml or ammonium chloride at 0.25 mumol/ml as the nitrogen source permitted the cells to elongate and to undergo limited division, with the final culture at 4 x 10(7) colony-forming units per ml. Ammonium chloride at 2.5 mumol/ml or glutamine at 1.37 mumol/ml supported completion of the cell cycle with final colony-forming units at about 5 x 10(8)/ml. Other amino acids, including glutamic acid, at 2.5 mumol/ml did not support completion of the cell cycle, although in most cases an intermediate number of colony-forming units per milliliter were formed. Limited uptake of [(14)C]glutamic acid and uptake of [(14)C]glutamine were not detectable until cell fission began. Cells not limited for nitrogen took up five times as much (35)S during fission as limited cells did during the same time. The nonlimited cells contained 10 times as much sulfolipid as the nitrogen-limited cells at the end of the cell cycle. These results demonstrate that rapidly dividing cells of M. avium utilize amino acids and sulfur and also synthesize sulfolipids in events that are apparently separable from metabolic functions of elongating cells. The results are contrasted with those found for other mycobacteria in which no cell cycle has been demonstrated.

Amino Acids↗
PubMed1976

Synthesis and release of sulfolipid by Mycobacterium avium during growth andcell division.

Mycobacterium avium exhibits a life cycle wherein small cells elongate to form filaments. The life cycle is unique in that elongated cells will undergo rapid division by fragmentation only if fatty acid is present. The utilization of [14C]palmitic acid and [3H]oleic acid by M. avium during the life cycle was assessed. Four glycolipids, identifiable by elution patterns from hydroxylapatite columns, were associated with postfission cells and contained isotope from the precursor fatty acid. The incorporation of 3H from oleic acid into the cellular glycolipids was maximal during cell division, but as much as 73% of the radioactivity was lost to the lipids from cells in the postfission status. Three of the glycolipids were sulfatides into which 36S was incorporated by M. avium. The [35]sulfatides were synthesized by cells undergoing fragmentation and were recovered from the medium at the termination of cell fission. These results demonstrated that the isotope was not lost to the cells because of turnover, but rather that the labeled compounds were released, intact, from the cells after fission. Because of the facile release of the sulfolipids, it was suggested that they were part of the cell envelope of M. avium cells during the division process.

Cell Division↗
PubMed1975

Mechanical syringe drive for vitreous surgery.

A mechanical syringe drive permits one-handed, precise control of the suction force at the time of vitrectomy, is autoclavable, utilizes disposable syringes, and can be operated by surgeon or assistant.

Humans↗
PubMed1975

A chin-operated switch for motorized three-axis microscopic movement.

A chin-operated switch was developed to permit control of motorized operating microscope movement simultaneously along three axes. It permits use of both feet to operate surgical modalities, decreases microscope positioning time, and decreases needless hand movements.

Microscopy↗
PubMed1974

Effect of palmitic acid utilization on cell division in Mycobacterium avium.

Mycobacterium avium, a facultative pathogen for humans, undergoes a life cycle in which selected small cells elongate and then fragment to form coccobacilli. M. avium cells of uniform size were selected by membrane filtration and tested for growth and division in the presence or absence of palmitic acid. Growth was measured by increased cellular protein, and cell division was determined by increased colony-forming units on agar or, electronically, by increased numbers of particles. Both growth and division rates of M. avium were found to be dependent upon the initial concentration of palmitic acid presented to the cells. The division constant varied from 0.05 to 0.13 when the concentration of palmitic acid ranged from 0 to 175 nmol/ml of medium. With [(14)C]palmitic acid as a tracer, it was found that rapid cell division began upon cessation of fatty acid uptake. During division, new lipid materials were released which contained (14)C derived from [(14)C]palmitic acid. Limited cell division and no fragmentation occurred in fatty acid-starved cultures. During fatty acid starvation, the transparent colony form, considered a pathogen, underwent a transition to the colony form considered a nonpathogen. The possible relationships between the organism's dependence on fatty acid and its ability to infect humans are discussed.

Carbon Radioisotopes↗