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Biomedical subjects

M Brennan

Publications and source records attributed to M Brennan.

At least 145 records · Page 8Linked to original sources
PubMed1979

Erythrocyte membrane lipids in Friedreich's ataxia.

In a study of the lipid composition of erythrocyte membranes in Friedreich's ataxia, the concentration of the major membrane components (phospholipids, cholesterol and protein) in ataxic patients, family members, and control subjects were found to be the same. The total fatty acid distribution was also normal. However, an altered distribution of phospholipid classes in erythrocytes was noted (an increase of PI + PS and a decrease of PE in Friedreich's ataxia patients).

Adult↗
PubMed1979

Discrimination of infants' cry-signals.

A technique for clustering infants' cry-signals on the basis of perceptually discriminable acoustic characteristics is reported. A cry-sequence containing all pairwise combinations of 24 signals was constructed. These signals have been used previously in cry-recognition studies (e.g., Wasz-Hockert, et al., 1968) and consist of six each of pain, hunger, pleasure, and birth. 20 musically competent subjects were tested individually and instructed to compare each cry with the one immediately preceding it in the sequence. Forced-choice "similarity" scores were summed for every pair of cries. These "similarity scores" were data for both a manual and a computerized clustering method. There was absolute agreement between these two methods, and the clusters of cry-signals correspond very closely to the four original cry groups. This seems a valid technique for examining the acoustic similarity of infants' cry-signals.

Adolescent↗
PubMed1979

A study of hysterectomy in a family practice.

This paper reports on a study of women in a family practice who have undergone hysterectomy as compared with a group of matched controls. Significant differences were found in the greater number of major surgical procedures (other than hysterectomy) and the reporting of chronic and recurrent symptoms for the study group. Study group women were also found to have a greater number of identified intrapersonal and family problems. There was no significant difference, however, in the number of identified chronic organic problems. Differences which did not reach statistical significance suggest that women in the study group may be more likely to be living without a male partner, to be using long-term medication, and to be smokers. A most important finding was that the group of women who had undergone hysterectomy had also had 2.6 times the number of major surgical operations than the controls, excluding the hysterectomy. There were no differences between the two groups with respect to a number of other factors studied, eg, education, religion, history of psychiatric admission, obesity.

Adult↗
PubMed1979

The role of religious institutions in evangelization.

Religious institutions are called to make an exodus out of their own holy land into the true holy land of humankind. By reflecting on the Beatitudes and Jesus' humanity, Catholic-sponsored health care institutions can better understand the meaning of evangelization.

Bible↗
PubMed1978

Attitudes and patterns of practice: a comparison of graduates of a residency program in family medicine and controls.

Two groups of graduates of the University of Western Ontario Faculty of Medicine were compared. The study group had satisfactorily completed a two-year residency program in family medicine at the University, commencing at graduation from medical school; the controls had completed a one-year internship after graduation, but had not pursued specific residency training in family medicine. Both groups were engaged in family practice in Ontario at the time of the study. As predicted, the groups differed in their attitudes; the graduates were more satisfied with practice than the controls and placed more importance on emotional factors in illness. Anticipated differences in patterns of care provided were also found. Family medicine graduates of conducted proportionately more noninstitutional care. The findings were not generalized beyond the one program. The advantages and limitations of program evaluation through studies of graduates are discussed.

Attitude of Health Personnel↗
PubMed1977

Pigment binding of copper in human bile.

The copper profile of human bile was studied using a Cu-free preparative polyacrylamide gel system. 85 percent and 91 percent of the Cu in the bile of two subjects was found in a leading pigmented band with no additional detectable copper in the remainder of the gel in either subject. The content of the pigmented band was recovered from the gel by an intermediate electrophoretic technique. Subsequent n-butanol extraction removed contaminating bile salts with the formation of a Cu containing pigmented precipitate. Using thin-layer cellulose chromatography this precipitate was separated into two pigments which on the basis of color and diazotization reaction were believed to be conjugated bilirubins. Addition of Cu transformed the pigments into biochemically different species. 64Cu verified copper binding by the altered pigments.

Bile↗
PubMed1977

Unfolding and refolding occur much faster for a proline-free proteins than for most proline-containing proteins.

The kinetics for unfolding and refolding of a parvalbumin (band 5) have been examined as a function of pH near the transition region, using stopped-flow techniques. This protein is rather unusual in that it has no proline residues, and therefore serves as a good example to test the hypothesis that the rate-limiting step seen in denaturation reactions is due to the cis-trans isomerization of proline peptide bonds in the denatured state. The kinetics for parvalbumin unfolding and refolding are complex, with the data being resolvable into two fast phases at 25 degrees. The slower of the two phases seen for the parvalbumin is about 100 to 500 times faster than the slow phase seen for proline-containing proteins under the same conditions! These results argue strongly in support of the proline isomerization hypothesis. It is also suggested that the slower phase seen for parvalbumin and the second-slowest phase seen for proline-containing proteins might be due to the cis-trans isomerization of peptide bonds of non-proline residues.

Animals↗
PubMed1977

Prognostic value of infranodal conduction time in patients with chronic bundle branch block.

His bundle recordings were obtained in 121 patients with chronic bundle branch block and the patients were followed for a mean period of 18 months. Seventy-nine patients had an infranodal conduction time (H-Q) less than 70 msec while 42 had H-Q greater than or equal to 70 msec. There was no significant difference in mean age, smoking history, diabetes, syncope, dizziness, blood pressure, and serum cholesterol or triglyceride levels between the two groups. There was a significantly greater incidence of progresssion to second degree or third degree atrioventricular block (9/42, 21%), and of severe congestive heart failure (16/42, 38%) in patients with H-Q greater than or equal to 70 compared with those with H-Q less than 70 (1/79, 1.3%; and 13/79, 16%, respectively). The risk of sudden death was significantly greater only in the group with H-Q greater than or equal to 70 and severe congestive heart failure. There was no correlation between the presence of first degree atrioventricular block and/or any particular type of bundle branch block pattern with sudden death and/or progression to second degree or third degree atrioventricular block. Analysis of the surface electrocardiogram is only of limited value in predicting high risk patients with chronic bundle branch block. Electrophysiologic studies are of greatest value in patients with bundle branch block with transient neurologic symptoms in whom no cause for the symptoms is evident.

Bundle-Branch Block↗
PubMed1977

X-radiation actions on the neuromuscular transmission.

The effects of high doses of X-radiation (100 kilorads) on the neuromuscular transmission of isolated sciatic nerve-sartorius muscle preparations of the frog, as evaluated by bioelectrical characteristics, were explored. Intracellular microelectrode recordings after X-irradiation showed that the resting, excitation and action potentials of nerve fibers approaching the synaptic terminal region of the motor end-plate became lessened, and also presented a slower velocity of impulse propagation, earlier than that observed in muscle cells. After forty minutes following the irradiation period, the neuromuscular transmission became blocked, although muscle fibers still responded to direct electrical stimulation. Records taken at the motor end-plate region of muscle cells, demonstrated the presence of postsynaptic miniature end-plate potentials (m.e.p.p.'s), the sequence of which fits closely into a random Poisson distribution. X-irradiation elicited an increase of the rate of m.e.p.p.'s and induced membrane changes over fine terminal nerve branches, leading into a failure to initiate and propagate action potentials. Only as time progressed, this nerve bioelectrical impairment was accompanied by a similar one in muscle cells, associated to the inability to develop contractile tension. The increase of m.e.p.p.'s frequency due to depolarization by a high K+ concentration, of presynaptic nerve membranes of control and irradiated preparations, was reversed by a high Mg+--Ca2+--free media. However, a concentration of Mg2+, which normally reduced quantal release of acetylcholine (ACh), without altering presynaptic nerve membrane potentials, failed to modify the spontaneous basal frequency of m.e.p.p.'s, both in irradiated and control preparations. The findings of the present study suggest that the presynaptic ACh synthesis, storage, and availability for ACh liberation are not early affected by X-rays, i.e. at a time when transmission from nerve to muscle had already failed. On the contrary, the most precocius membrane changes following X-irradiation, seem related to the mechanisms underlying nerve resting, excitation, and action potentials. The smallest presynaptic nerve terminal fibers close to the motor end-plate, are the most radiosensitive portion of the myoneural junction. Indeed, their bioelectric characteristics are early affected by X-rays, resulting in a failure to generate and propagate nerve impulses which lead to a blockade of neuromuscular transmission.

Action Potentials↗
PubMed1975

Consideration of the Possibility that the slow step in protein denaturation reactions is due to cis-trans isomerism of proline residues.

A model is proposed to account for the observation that the denaturation of small proteins apparently occurs in two kinetic phases. It is suggested that only one of these phases--the fast one--is actually an unfolding process. The slow phase is assumed to arise from the cis-trans isomerism of proline residues in the denaturated protein. From model compound data, it is shown that the expected rate for isomerism is in satisfactory agreement with the rates actually observed for protein folding. It is also shown that a simple model of protein unfolding based on the isomerism concept is very successful in accounting for many known experimental characteristics of the kinetics and thermodynamic of protein denaturation. Thus, the model is able to predict that two kinetic phases will be seen in the transition region while none are seen in the base-line regions, that both the fast and slow refolding phases lead to the native protein as the product, that the fast phase becomes the only observable phase for jumps ending far in the denatured base-line region, that most or all small proteins show a limiting low-temperature activation energy of ca. 20,000 cal, and that the relaxtion time for the slow phase seen in cytochrome c denaturation is much shorter than for all other small proteins. By utilizing "double-jump" experiments, it is shown directly that the slow phase is not part of the unfolding process but that it corresponds to a transition among two or more denatured forms which have identical spectroscopic (286.5 nm) properties. Thus, the slow relaxation is "invisible" except in the transition region where it couples to the fast unfolding equilibrium. Finally, since the present model assumes that only one of the major kinetic phases seen in denaturation reactions is concerned with the denaturation process per se, it is in agreement with numerous thermodynamic studies which show consistency with the two-state model for unfolding.

Calorimetry↗