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Biomedical subjects

G McDonald

Publications and source records attributed to G McDonald.

At least 73 records · Page 4Linked to original sources
PubMed1983

The relationship between global myocardial ischemia, left ventricular function, myocardial redox state, and high energy phosphate profile. A phosphorous-31 nuclear magnetic resonance study.

UNLABELLED: The onset of global myocardial ischemia was related to mechanical function (intraventricular pressure), cellular redox state (NADH fluorophotography), and high energy profile (phosphorous-31 nuclear magnetic resonance). Ten rabbit hearts were excised and perfused on a modified Langendorff apparatus (37 degrees C; pO2 480 Torr). Developed pressure and positive and negative dp/dt were determined at control, 1-10, 15, 30, 45, and 60 sec of acute global ischemia. NADH fluorophotographs were taken at control, 1-10, 15, 20, 30, 60 sec, and 5, 10, and 30 min. P-31 NMR spectra in 14 guinea pig hearts under identical conditions were obtained at control, 1, 5, 10, 20, 40, and 60 min of acute global ischemia. LV contractility diminished within 1 sec (P less than 0.01) of ischemia and dropped to less than 35% of control by 1 min. Reduction of mitochondria was detected by epicardial NADH fluorophotography at 2 sec of ischemia. Cellular pH diminished 0.3 pH units by 5 min. Adenosine triphosphate (ATP) concentration remained at control levels while phosphocreatine (PCr) dropped to 63 +/- 8.5% of control by 1 min of ischemia. CONCLUSIONS: After the onset of global ischemia (1) mitochondrial electron transport ceases by 2 sec; (2) acidosis develops immediately; (3) LV contractility diminishes by 1 sec; (4) ATP concentration appears to be buffered by PCr, and is dissociated from myocardial function.

Adenosine Triphosphate↗
PubMed1981

Misrepresentation, liberalism, and heterosexual bias in introductory psychology textbooks.

The present study investigated the content of 48 introductory psychology textbooks published over a five-year period (1975-1979) and recommended by publishing companies or psychology professors for use in Canadian universities. The findings indicated that for every one source of relevant information on homosexuality there were five sources of misrepresentative data that reflect a combination of misleading information, liberalism, and heterosexual bias. Textbook editors and authors have: (1) failed to address the rights and needs of gay people; (2) failed to document accurately the social changes associated with being gay; and (3) perpetuated societal stereotypes, thereby appearing to justify the prejudice and discrimination encountered by gay people in their daily lives. Guidelines for the discussion of lesbianism and male homosexuality in introductory psychology textbooks are proposed.

Adult↗
PubMed1978

Detection of 31P nuclear magnetic resonance signals in brain by in vivo and freeze-trapped assays.

The (31)P NMR spectrum of energy-related metabolites under strictly aerobic conditions in rapidly respiring tissues under physiological conditions has been approached by the study of the (31)P NMR signals in vivo and in freeze-trapped organs. Freezing the head of the anesthetized animal by liquid N(2), excision of the brain tissue (white and gray matter) at -196 degrees , and transfer to the NMR tube occurs without alteration of the metabolite concentrations. The sample is warmed to the region -15 degrees to -10 degrees , at which temperatures there is sufficient mobility for recording (31)P NMR at concentrations characteristic of brain tissues ( approximately 5 mM) with an adequate signal to noise ratio in 10 min but insufficient mobility for significant enzymatic activity. A approximately 0.4-sec acquisition time is adequate for nuclear relaxation and a 10-min scan gives an adequate signal to noise ratio. Metabolism of creatine phosphate, P(i), and sugar phosphates occurs by 1 hr at -10 degrees and 2 hr at -12 degrees . Extrapolation of the approximately zero order kinetics of disappearance of creatine phosphate and appearance of P(i) suggests that <10% of these two metabolites has been altered in the time of the first measurement.A comparison of the freeze-trapped state and the in vivo metabolite pattern is afforded in preliminary experiments on the head of the living mouse (brain and skeletal tissue) in aerobic and anaerobic states. Longer relaxation times and mild hypoxia due to the restricted diameter of the NMR tube gives significantly lower creatine phosphate/ATP values for this condition. Both direct in vivo and freeze-trapped assays of energy-related metabolites afford excellent approaches to the detection of anoxia and to the evaluation of metabolic control in hypoxic conditions.

Adenosine Triphosphate↗
PubMed1978

Mental subnormality in Northern Ireland.

A prevalence survey of mental subnormality in Northern Ireland was carried out on lines similar to an earlier investigation by MacKay (1971). In a general population of one and a half million there were 6,854 ascertained subnormal individuals. The male : female ratio was 1. 14 :1. Approximately one in three subnormal people was under residential care. The prevalence of severe subnormality (IQ less than 50) in the 15-19 year old group was 4.81. The findings do not support the "steady rate" theory of severe subnormality.

Adolescent↗
PubMed1977

Pattern detection by mongol and non-mongol subnormals.

Ten mongols and ten clinically heterogeneous subnormals matched on chronological age, mental age and digit span took part in an experiment in which tape-recorded supra-span digit sequences with different patterns were presented. There were six patterns: random, mirror (e.g. 583385); same-digit pairs (e.g. 558833), same-digit throughout (e.g. 333333), couplet repetition (e.g. 585858) and triplet repetition (583583). The numbers of digits correctly recalled in any order by the mongols in the various conditions ranked from least to most were: random, mirror, same-digit pairs, same-digit messages, triplet repetition and couplet repetition. The rank order for the non-mongols was the same except that the positions of couplet and triplet repetition were reversed. Mongols had significantly poorer recall for random, mirror and same-digit pair messages than non-mongols but were their equals in other conditions. The mongols' performance was more sensitive to pattern than the performance of the other subjects. There was some evidence that, in the messages with same-digit pairs and the same digit throughout, all subjects (but mongols in particular) tended to insert new digits into the response sequence and that the digit introduced was the next one in simple arithmetic progression. It would appear that the hypothesis about poor auditory-vocal channelling capacities of mongols needs qualification.

Adult↗
PubMed1977

Real-time cross-sectional echocardiographic diagnosis of coarctation of the aorta: a prospective study of echocardiographic-angiographic correlations.

Real-time cross-sectional echocardiographic sector scan examinations were performed from a suprasternal notch location to image aortic anatomy in 15 children (ages 1 day to 21 years) who were subsequently shown at cardiac catheterization to have coarctation of the descending thoracic aorta. The resulting echocardiographic images of the ascending, transverse and descending aorta imaged juxtaductal coarctation in all 15 patients. Echocardiography predicted discrete coarctation of the aorta in eight, isthmic hypoplasia in two, hourglass type coarctation deformities in three and longer segment coarctation in four patients. Catheterization and angiography confirmed all of these anatomic observations. The control group, 100 patients with congenital heart disease but without angiographic coarctations, included four patients with right-sided aortic arch and six patients with dextrocardia. The ascending, transverse and descending aorta were adequately imaged in 94 of these and no descending aortic abnormalities were noted. This study shows the potential utility of cross-sectional echocardiography for the noninvasive precatheterization or preoperative assessment of coarctation of the aorta in children and critically ill newborns.

Adolescent↗
PubMed1975

Un-united fracture of the scaphoid.

The anterior approach as described by Matte and Russe for treatment of ununited fractures of the scaphoid was employed in 48 patients using autologous cortical cancellous pegs and chips. Operative intervention occurred in an average period of 14 months after fracture. The average time to radiological union was 3.5 months; the average follow-up was 2 years. Union occurred in 43 patients. The anterior approach is recommended because of its simplicity. Neither avascular necrosis nor a small proximal pole fragment are contraindications to the procedure.

Carpal Bones↗