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Biomedical subjects

P McCormick

Publications and source records attributed to P McCormick.

18 recordsLinked to original sources
PubMed1997

Quality of life of candidates for and recipients of heart transplants.

OBJECTIVE: To describe the quality of life (QOL) of candidates for and recipients of heart transplants over a five-year period. DESIGN: Descriptive, longitudinal. SETTING: Canadian university-affiliated tertiary care medical centre. PATIENTS: Sixty-five candidates for heart transplantation; after one year, six candidates were still awaiting transplantation; 42 patients received transplants and were included in the study six months post-transplant. OUTCOME MEASURES: Three measures of QOL were used: the Index of Well-Being, Cantril's Self-Anchoring Striving Scale and the "time-trade-off technique'. INTERVENTION: Data were collected before transplantation, six months post-transplantation, one year post-transplantation and annually for the next four years; for individuals who did not receive transplants, data were collected six months and one year after the first interview. MAIN RESULTS: QOL scores were considerably higher after than before transplantation, and compared favourably with norms for the general population. For 11 individuals who did not receive transplants, QOL remained low. QOL for heart transplant recipients was remarkably stable over the five-year study period. The major predictors of QOL for candidates awaiting transplantation were health status, outlook and ability to work. After transplantation, the major predictors of QOL were outlook, health status and employment status. CONCLUSIONS: There is evidence to suggest that QOL improves after heart transplantation, and that improvement is relatively stable over time. Further work is needed to identify the factors that could result in improvements in QOL.

Adult↗
PubMed1996

Intraoperative monitoring of motor evoked potentials: a review of 116 cases.

We reviewed the results of motor evoked potential (MEP) and somatosensory evoked potential (SEP) monitoring during 116 operations on the spine or spinal cord. We monitored MEPs by electrically stimulating the spinal cord and recording compound muscle action potentials from lower extremity muscles and monitored SEPs by stimulating posterior tibial or peroneal nerves and recording both cortical and subcortical evoked potentials. We maintained anesthesia with an N2O/O2/opioid technique supplemented with a halogenated inhalational agent and maintained partial neuromuscular blockade using a vecuronium infusion. Both MEPs and SEPs could be recorded in 99 cases (85%). Neither MEPs nor SEPs were recorded in eight patients, all of whom had preexisting severe myelopathies. Only SEPs could be recorded in two patients, and only MEPs were obtained in seven cases. Deterioration of evoked potentials occurred during nine operations (8%). In eight cases, both SEPs and MEPs deteriorated; in one case, only MEPs deteriorated. In four cases, the changes in the monitored signals led to major alterations in the surgery. We believe that optimal monitoring during spinal surgery requires recording both SEPs and MEPs. This provides independent verification of spinal cord integrity using two parallel but independent systems, and also allows detection of the occasional insults that selectively affect either motor or sensory systems.

Evoked Potentials, Motor↗
PubMed1992

Parents' developmental perceptions and expectations for their high-risk infants.

This study examines the relationship between developmental outcomes of high-risk infants and parental perceptions and expectations. Parents of 209 consecutive high-risk infants were asked to provide their development interpretations and expectations before their infants received standard developmental assessments between April and October 1989. Moderate correlations between parents and professional assessments of motor and language skills were noted (p less than .05 to p less than .01). Most agreements occurred when infants were assessed as normal by professionals. Disagreements were common and occurred in all areas of development. These mismatches were not associated with gestational age at birth, neonatal complications, poverty, or estimates of parental experience. Professionals should take seriously any expressed developmental concerns by parents of high-risk infants. Expressed developmental concerns, however, cannot be relied on for developmental screening of high-risk infants.

Attitude↗
PubMed1989

Covert visual orienting: hemifield-activation can be mimicked by zoom lens and midlocation placement strategies.

How is attention distributed over visual space when an observer expects a target to occur at one of several possible locations? Two experiments sought to understand the source of the conflict between studies leading to the notions of hemifield activation (Hughes and Zimba 1985) and attentional gradients (Downing and Pinker 1985; Shulman et al. 1985, 1986). subjects were cued to attend one of the 4 corners of an imaginary square centered at fixation, allowing comparison of uncued locations in the cued and uncued hemifields. In one experiment marking of the 4 locations was varied to determine if providing a 'target' for attention is necessary to obtain within-hemifield gradients. RT was faster at the cued location than at the three uncued locations which had equivalent latencies, a pattern that was unaffected by marking of the potential target locations. This result, which is consistent with the notion of a gradient around the attended location is a strong disconfirmation of the hemifield activation hypothesis. The second experiment demonstrated that an unusual procedure for presenting the probe stimuli in Hughes and Zimba (1985) is at least partially responsible for their evidence for uniform hemifield activation. It is proposed that visual attention is directed to visuo-spatial channels with fixed structural properties, and that when attention to two locations is desired, the subject may attend a spatial channel located between them.

Adult↗
PubMed1984

Reduced fertility in women with X chromosome abnormality.

One patient with the karyotype 46,X,del(X)(p11.23) and three patients with 45,X/46,XX mosaicism were fertile or showed normal ovarian function. The patient with the Xp deletion has two daughters with the same chromosomal abnormality. A study of these patients and of others reported in the literature indicated that fertility of patients with X chromosomal abnormality has a markedly shorter duration than fertility of the normal female. Menopause commonly occurred during the second and third decade of age. We suggest that such fertility is related to the rate of germ cell attrition and hypothesize that germ cell attrition in the human female is influenced by genes of multiple effect which are carried on the X chromosome. The more of these genes which are present the slower the rate of germ cell attrition.

Adolescent↗
PubMed1983

A class of large polysaccharides contains the antigenic determinants for the cytotoxic antibodies in a conventional syngeneic anti-F9 serum as well as a monoclonal antibody prepared against F9 cells.

The molecular natures of the antigenic targets detected by cytotoxic antibodies in both a monoclonal antibody (ECMA-3) made against F9 cells and a conventional mouse anti-F9 serum were investigated. Both of the antibodies precipitated a class of high molecular weight polysaccharides from Nonidet P40 lysates of F9 cells. These molecules were labeled by radioactive galactose and fucose but only poorly by amino acids; in addition, they were fairly resistant to pronase and the digest still had a molecular weight of 70 K or more. Even after extensive pronase digestion the polysaccharides inhibited the cytotoxic activities of the antibodies, suggesting that the antigenic targets reside on the carbohydrate portion. This class of polysaccharides was shown to be a minor component of the characteristic large polysaccharides of F9 cells.

Animals↗
PubMed1983

Cis-trans test shows a functional relationship between non-allelic lethal mutations in the T/t-complex.

Recessive lethal mutations in the T/t-complex of the mouse characteristically show defective genetic complementation, even when they affect very different stages of embryogenesis and are known to be nonallelic. To address the question of their genetic or functional relationship, we have applied the cis-trans test, using several well defined recombinant t-chromosomes that carry two or more lethal mutations, and others that are devoid of specific lethals. We show here that the defective complementation that occurs between different t-lethals is a specific result of the trans configuration; thus these genes, which may map as much as 15 cM apart, constitute a functional unit. Some speculations are presented to interpret this enigma in terms of DNA plasticity.

Alleles↗
PubMed1982

Gene mapping within the T/t complex of the mouse. I. t-Lethal genes are nonallelic.

The t haplotypes of mouse chromosome 17 are natural polymorphisms in wild populations that contain mutations that affect or control such diverse functions as tail length, embryonic lethality and maturation and function of male germ cells. The major impediment to dissecting the genetics of this complex region has been its unusual property of recombination suppression in heterozygotes with wild-type chromosomes. Recently it was shown that recombination suppression does not occur in heterozygotes containing two different t haplotypes, which suggested that t chromosomes may be mismatched with respect to wild-type but share sequences that permit crossing-over between them. Thus for the first time questions of allelism and map positions of the t-lethal mutations can be addressed. We report here the results of three experiments that analyzed the tw12 haplotype trans to either tw5, tw32 or tw18. In all cases these lethal mutations were nonallelic to tw12. These results, together with evidence for functional relatedness, suggest the t-lethals may be a gene family spread out over more than 15 centiMorgans of chromosome 17.

Alleles↗
PubMed1981

Human intestinal potential difference: recording method and biophysical implications.

1. The transmural electrical potential difference (PD) of the intact human small intestine was recorded with close attention to electrical symmetry, shielding from electro-magnetic waves and correction for junction potentials. 2. The PD is -12 mV (mucosa-negative) in the fasting jejunum and ileum and does not change during perfusion with isotonic NaCl. 3. Absorption of Na and Cl appears to be non-electrogenic and the 'resting' PD is probably generated by active anion secretion of fasting intestinal contents. 4. Diffusion potentials during isotonic D-mannitol perfusion indicated higher cation selectivity in the ileum than in the jejunum. 5. The calculated contribution of a free-solution path to total paracellular permeability is 55% in the jejunum but only 15% in the ileum. 6. No 'streaming' potential was detected during osmotic water flow, suggesting that the cation-selectivity of the channels is temporarily inactivated during dilatation of the lateral intercellular space.

Adult↗
PubMed1981

The incidence of contrast medium induced acute tubular necrosis following arteriography.

Twenty-one patients slated for high-dose arteriography were studied to investigate the impact of predisposing medical conditions upon contrast medium induced acute renal failure. The study suggests that predisposing medical conditions are the most important factor determining the incidence of acute renal failure and the probability, speed, and degree of recovery of renal function. Patients with diabetes mellitus incur the highest risk of contrast medium induced acute renal failure. A dose relationship is also suggested. Contrast medium doses containing more than 100 g of iodine uniformly produced acute tubular necrosis in patients with predisposing medical conditions. Conversely, contrast medium doses containing less than 80 g of iodine produced clinically manifest acute renal failure in only one of 14 patients with predisposing medical conditions. Subclinical levels of acute renal failure were recognized in a large number of patients by routine measurement of radionuclide filtration fractions, serum creatinine levels, and urine osmolality and sodium concentration.

Acute Kidney Injury↗