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Biomedical subjects

C McCarthy

Publications and source records attributed to C McCarthy.

At least 127 records · Page 7Linked to original sources
PubMed1971

Electronic counting in growth studies of Mycobacterium avium.

Metabolically uniform cells of Mycobacterium avium were obtained by selective filtration. The life cycle of these cells was followed by photomicrographs, electronic enumeration, and sizing and by viability and protein determinations. The cells elongate to form filaments several times their initial length; the increase in mass is reflected by a five- to sixfold increase of total protein in the culture. The filaments then fragment causing the production of viable coccobacilli. The techniques employed to obtain this form of growth are described and comparisons with nocardial growth are noted.

Bacterial Proteins↗
PubMed1971

Utilization of palmitic acid by Mycobacterium avium.

Mycobacterium avium accumulates (14)C-palmitic acid with saturation kinetics; the process is both temperature dependent and pH sensitive. The fatty acid is incorporated into triglyceride in vivo and the conversion is detectable within 5 min after exposure of the cells to (14)C-palmitic acid. The triglyceride is rapidly utilized because (14)CO(2) evolution from it begins within 30 min after (14)C-palmitic acid accumulation. Data from silicic acid column chromatography of extracts of cultures that have divided many times in medium containing (14)C-palmitic acid indicate that a large proportion of the cell lipid is triglyceride, but the radioactivity is widely dispersed among the other lipids. It is estimated that about 5% of the cell dry weight is triglyceride in a postexponential culture.

Carbohydrates↗
PubMed1970

Spontaneous and Induced Mutation in Mycobacterium avium.

Mycobacterium avium exhibits two colonial forms, transparent and opaque, on 7H10 agar. The transparent variant of M. avium B2900 undergoes a spontaneous transition to the opaque form at the rate of 4.7 x 10(-5) to 3.5 x 10(-4) per cell per generation. The two variants differ in cell morphology and mass; the opaque cells are two to three times as large as the transparent in terms of dry weight, total protein, deoxyribonucleic acid, or carbohydrate. A search for auxotrophic mutants resulted in the induction, by nitrosoguanidine or ultraviolet irradiation, of conditional, salt-sensitive mutants. One such mutant requires methionine and tryptophan supplementation for growth in a medium containing a buffer at high molarity. The clinical and physiological significance of these findings is discussed.

Journal Article↗
PubMed1969

Heat-sensitive step in deoxyribonucleic acid-mediated transformation of Bacillus subtilis.

Over 90% of the competent cells in a population of Bacillus subtilis lost their competence after being heated to 50 C for 5 min. There was only a slight loss in the number of transformants if the culture was heated for 5 min after the termination of transformation, but 90% of the transformants were lost after 1 hr at 50 C. The population as a whole grew at a slightly faster rate at 50 C than at 32 C. We postulate that a heat-labile factor is required for the uptake or retention (or both) of deoxyribonucleic acid (DNA) in the cell, since uptake of (32)P-DNA into a deoxyribonuclease-resistant form was inversely proportional to the time of exposure to heat. Cells that had lost competence after being heated did not regain their competence for at least several hours, although other cells in the population became competent. These data suggest that the heat-labile factor required for competence is synthesized only once during the period that a cell remains competent.

Bacillus subtilis↗
PubMed1969

Heat-activated endonuclease in Bacillus subtilis.

A heat-stable, heat-activated endonuclease was found in sonic extracts of the transformable strain Bacillus subtilis 168 when the organism was grown to logarithmic phase in minimal medium. The enzyme was not present in the poorly transformable strain 23. The endonuclease was stable to 100 C for 30 min and, in a crude extract, was activated by heating at 80, 90, or 100 C. The activation caused a 5- to 10-fold increase in total units of enzyme activity. Sucrose gradient centrifugation indicated that the enzyme in a crude preparation has a major form (molecular weight, 66,000) which remains unchanged after heat activation. Under the assay conditions employed, the endonuclease did not release acid-soluble material from the substrate, high molecular weight tritiated deoxyribonucleic acid. The product, in double-stranded form, had a molecular weight of approximately 10(5), but it appeared to have undergone single-strand breaks.

Bacillus subtilis↗
PubMed1967

Macromolecular synthesis in newly transformed cells of Bacillus subtilis.

The capacity of newly transformed cells of Bacillus subtilis to synthesize deoxyribonucleic acid (DNA), ribonucleic acid (RNA), and protein has been determined by following the kinetics of suicide after their exposure to tritiated precursors of each of these macromolecules. Competent cells, whether transformed or not, are heterogeneous with respect to DNA synthesis. About 40 to 50% are latent in DNA synthesis. This latency may persist for 2.5 to 3 hr since transformants are resistant to thymineless death for this period after DNA addition. The remainder of the transformants synthesize DNA at one-half the rate of the cells of the total population. Synthesis of stable RNA does not occur at an appreciable rate in newly transformed cells. Newly transformed cells, however, do synthesize protein extensively, as demonstrated by the lethality of incorporated tritiated amino acids. Either chloramphenicol or actinomycin D treatment during the time of exposure to the tritiated amino acid prevented the suicide of transformants.

Amino Acids↗
PubMedDate not supplied

Thoracic aortic dissection or aneurysm: clinical presentation, diagnostic imaging and initial management in a tertiary referral centre.

Spontaneous thoracic aortic dissection carries a high mortality despite progress in diagnosis and treatment. Early and accurate diagnosis is paramount and dependent on clinical and diagnostic imaging skills. A retrospective review of 55 consecutive patients referred with suspected thoracic aortic dissection to a medical cardiology department was performed. Clinical follow up was complete to November 1995. Median age was 68 years (range 30-93), with 37 males, 18 females. Presenting complaints included interscapular chest pain in 23 (42 per cent), neurological deficit in 2 (4 per cent), and limb ischaemia in 8 (15 per cent). On examination 34 (62 per cent) patients had hypertension, 5 (9 per cent) a pulse deficit and 10 (18 per cent) aortic incompetence. Electrocardiography confirmed myocardial infarction in 1. Chest X-ray showed a widened mediastinum in 37 (67 per cent) patients. Dissection was confirmed in 35 (64 per cent) patients (13-DeBakey Type I, 6-Type II, 14-Type III); 10 had nondissecting aneurysm. Contrast aortography was equally sensitive (84 per cent) and more specific (100 per cent vs 80 per cent) than computed tomography for detection of dissection. Surgical repair was performed on 24 patients with concomitant coronary artery bypass grafting in 6. At follow up 33 patients were alive. Clinical diagnosis of thoracic aortic dissection or aneurysm may be difficult. Frequently more than one imaging modality may be required in order to provide all of the necessary information for optimal patient management.

Adult↗
PubMedDate not supplied

Depression and anxiety in rheumatoid arthritis: the role of perceived social support.

BACKGROUND: Rheumatoid arthritis is a common, disabling, autoimmune disease with significant psychiatric sequelae. AIMS: We aimed to identify the prevalence of depression and anxiety in patients with rheumatoid arthritis attending hospitals, and to elucidate the role played by illness variables, disability variables and psychosocial variables in predicting levels of depression and anxiety. METHODS: We assessed depression, anxiety, arthritis-related pain, arthritis-related disability and perceived social support in 68 adults with rheumatoid arthritis. RESULTS: Sixty-five per cent of patients had evidence of depression (37.5% moderate or severe) and 44.4% had evidence of anxiety (17.8% moderate or severe). Both depression and anxiety were highly correlated with several measures of arthritis-related pain and functional impairment. After controlling for age, gender, marital status and duration of arthritis, perceived social support was a highly significant independent predictor of both depression and anxiety. CONCLUSIONS: These findings suggest that increasing social support may be particularly important in the management of depression and anxiety in rheumatoid arthritis.

Anxiety Disorders↗
PubMedDate not supplied

Asymptomatic sacroiliitis in inflammatory bowel disease. Assessment by computed tomography.

Plain film radiographs and computed tomography scans of sacroiliac joints in 65 asymptomatic patients with known inflammatory bowel disease were performed and evaluated by two radiologists. Computed tomography revealed the presence of asymptomatic sacroiliitis in 21 (32%) of the 65 patients (New York grades 2 to 4); asymptomatic sacroiliitis was identified by plain film radiography in only 10 (18%) of 57 patients (p < 0.001). No correlation was observed between the presence or absence of sacroiliitis, and the age and sex of patients, disease type, or duration of disease. The prevalence and diagnostic value of computed tomography in the detection of asymptomatic sacroiliitis in patients with inflammatory bowel disease are discussed.

Adult↗
PubMedDate not supplied

Factors that affect the cell cycle of Mycobacterium avium.

Mycobacterium avium, a pathogen of both animals and humans, is an acid-fast bacterium that is very drug-resistant and pleomorphic in colony and cellular morphology. By selective filtration, cells 1 micrometer long could be obtained. When placed in fresh medium, these small cells elongated to form filaments that aggregated during about a 40-hr incubation period. The filamentous cells divided rapidly for an additional 40 hr, with a doubling time of approximately 6 hr. Fission ceased, and the resulting culture consisted of coccobacilli. The cell cycle would not proceed if the cells were starved for either fatty acid or ammonium ion. During elongation (the growth phase), protein, DNA, and triglycerides were synthesized exponentially. During the fission stage, the triglycerides were utilized and redistributed among other cellular constituents. It is proposed that the cell cycle offers a unique system by which to test drugs that may inhibit growth of, or be bactericidal for, M. avium.

Cell Cycle↗
PubMedDate not supplied

Evaluation of patients with diabetes mellitus for coronary artery disease using dobutamine stress echocardiography.

BACKGROUND: There is a high prevalence of coronary artery disease (CAD) in patients with diabetes mellitus. Detection of inducible ischaemia using treadmill exercise testing may be limited by the relatively poor inherent predictive accuracy of the test. The purpose of this study was to determine the value of dobutamine stress echocardiography (DSE) for the detection of CAD in patients with diabetes mellitus. METHODS: Patients with diabetes mellitus referred for cardiac assessment were considered eligible for study. DSE was performed in a standard fashion. Significant CAD was defined as a > 50% luminal diameter stenosis on coronary angiography. RESULTS: A total of 52 patients (mean age 59 years) with diabetes mellitus were studied prospectively using DSE. Risk factors for CAD included hypertension in 19, family history in 21, hypercholesterolaemia in 14, history of smoking in 38. The sensitivity, specificity, positive and negative predictive values of DSE for detection of CAD were 82, 54, 84 and 50% respectively. CONCLUSION: The specificity of DSE for CAD in patients with diabetes mellitus is low. Whether this reflects an underdetection of small vessel disease by contrast coronary angiography or whether it relates to test performance is unclear.

Cardiotonic Agents↗