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Biomedical subjects

M McDonald

Publications and source records attributed to M McDonald.

At least 19 recordsLinked to original sources
PubMed1992

Effects of left ventricular dysfunction on the circadian variation of ventricular premature complexes in healed myocardial infarction.

Circadian variation in the onset of cardiovascular events including sudden cardiac death, myocardial infarction and ventricular arrhythmias has been described. The effect of left ventricular (LV) dysfunction on the circadian variation of ventricular premature complex (VPC) frequency was evaluated in 132 patients with frequent VPCs and reduced LV function after myocardial infarction. Patients were prospectively divided in 2 groups based on LV ejection fraction (EF) (those with LVEF less than or equal to 0.30, and those with LVEF between 0.30 and 0.45). Median hourly VPC frequencies and heart rates were compared between the 2 groups. Subgroup analyses based on treatment with beta-adrenoceptor blocking agents and on New York Heart Association functional class were also performed. In patients with LVEF greater than 0.30, a distinct circadian variation of VPCs, and the expected morning increase in VPC frequency were present. In contrast, a distinct circadian variation of VPCs was absent in patients with LVEF less than or equal to 0.30. A circadian variation of VPC frequency was also absent in patients with severe symptomatic congestive heart failure (New York Heart Association class III-IV). Treatment with beta-adrenoceptor blocking agents was associated with a loss of the circadian variation of VPC frequency. The circadian variation of heart rate was also blunted in the group treated with beta-adrenoceptor blocking agents. The proportion of subjects manifesting a positive correlation between heart rate and VPC frequency was lower in subjects with LVEF less than or equal to 0.30 (26%) than in those with LVEF greater than 0.30 (46%) (p less than 0.05). Thus, circadian variation of VPC frequency is absent in patients with severe LV dysfunction.

Adrenergic beta-Antagonists↗
PubMed1992

Blood cultures and antibiotic use in a neonatal intensive care unit.

A review of the duration of antibiotic courses in our Neonatal Intensive Care Unit (N.I.C.U.) has shown that in a significant number of cases there was non compliance with the antibiotic policy. An audit of neonatal sepsis and antibiotic usage over a six month period was performed in the N.I.C.U. at the Rotunda Hospital. Three hundred and forty-nine of the 3,163 infants born during this time were admitted to the N.I.C.U. One hundred and fifty-two infants had one or more episodes of suspected sepsis. In 168 instances this preceded a course of antibiotic therapy lasting longer than 48 hours. In 56 (33%) the infant was clinically septic and in 16 (9.5%) of those there was bacteriological proven sepsis. There were 112 episodes (60%) where there was no strong clinical evidence of sepsis and a negative investigation for sepsis where antibiotics were continued for more than 48 hours. The possible reasons why antibiotics were not stopped include the non specific nature of signs of sepsis in neonates, physicians' reluctance to discontinue antibiotics once started, and the logistic difficulty of obtaining routine culture results at weekends. The study emphasizes the need for regular surveillance of antibiotic usage in a N.I.C.U.

Anti-Bacterial Agents↗
PubMed1992

Providing shelter for street youth: are we reaching those in need?

A major longitudinal study of runaway and homeless youth resulted in the establishment of a safe house in Calgary. In order to further knowledge building and research in this field, users of the facility are routinely asked to fill out an intake form, and consent is obtained for the use of the information for research purposes. Data collected during the first fourteen months of its operation have now been analyzed. Results are compared to the original survey data to determine which youth are using the facility and which are being missed. Interesting similarities and differences are described and discussed.

Adolescent↗
PubMed1992

Maintenance of behavioral change in a cohort of homosexually active men.

OBJECTIVES: To assess associations of perceptions of sexual behavior change with actual risk behaviors and psychosocial variables, and to determine whether perceptions of behavior change predict subsequent behavior. DESIGN: Cohort study of homosexually active men. SETTING: Community health center in Boston, Massachusetts, USA. PATIENTS, PARTICIPANTS: Two hundred and sixty-two cohort members who participated in follow-up in 1989 and who had at least one subsequent visit. INTERVENTIONS: None. MAIN OUTCOME MEASURE: Composite risk behavior variable, based on unprotected anogenital contact and number of partners. RESULTS: Of the 96% who had effected behavior change, 47% perceived that they were able to maintain those changes consistently and 58% wanted to make more changes. Perceptions of consistent maintenance were associated with lower risk behavior, lower perceived riskiness of behaviors and susceptibility to AIDS, and fewer barriers to behavior change. Desire for more change was associated with increased behavioral effort, fewer barriers to condom use, and greater perceived riskiness of current behavior. Among those with lower risk behaviors, perceived inconsistent maintenance predicted relapse to more risky behavior at the following visit. CONCLUSIONS: Perceived maintenance of behavior change is potentially useful in identifying individuals at risk of relapse from safer sex.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Hemidiaphragmatic paresis during interscalene brachial plexus block: effects on pulmonary function and chest wall mechanics.

We studied the effects of unilateral hemidiaphragmatic paresis caused by interscalene brachial plexus block on routine pulmonary function in eight patients. In an additional four patients, we studied changes in chest wall motion during interscalene block anesthesia by chest wall magnetometry. Ipsilateral hemidiaphragmatic paresis, as diagnosed by ultrasonography, developed in all patients within 5 min of interscalene injection of 45 mL of 1.5% mepivacaine with added epinephrine and bicarbonate. Large decreases in all pulmonary function variables were measured in every patient. Forced vital capacity and forced expiratory volume at 1 s decreased 27% +/- 4.3% and 26.4% +/- 6.8%, respectively (P = 0.0001). Peak expiratory and maximum midexpiratory flow rates were also significantly reduced. Interscalene block caused changes in pulmonary function and chest wall mechanical motion that were similar to those published in previous studies on patients with hemidiaphragmatic paresis of pathological or surgical etiology. Interscalene block probably should not be performed in patients who are dependent on intact diaphragmatic function and in those patients unable to tolerate a 25% reduction in pulmonary function.

Adult↗
PubMed1992

Revision of the acetabular component with an uncemented Harris-Galante porous-coated prosthesis.

One hundred and forty revisions for loosening of the acetabular component were performed in 124 patients, with the use of an uncemented Harris-Galante acetabular prosthesis. A component was considered loose if there was a change in its position or vertical or horizontal migration, or both, of four millimeters or more, as demonstrated on serial radiographs. All patients were followed prospectively for a mean of forty-one months (range, twenty-four to seventy-six months). Bone-grafting was performed at the time of the revision in 127 of the hips. Identifiable failure of fixation of the acetabular component occurred in only two hips (1 per cent), which had both severe acetabular bone loss and pelvic discontinuity. In one of these hips, fixation of the component could not be achieved during the revision, and the component subsequently migrated. No other components migrated. Only one patient had a revision of the index acetabular operation. A continuous radiolucency developed at the bone-mesh interface of five acetabular components, and in one other hip a small portion of the mesh separated. This hip was reoperated on for a problem with the femur, and the socket was found to be rigidly fixed. No other evidence of loosening was identified. All of the bone grafts united, but partial resorption of the graft occurred in thirty-nine hips. Although there were substantial osseous defects that necessitated major bone-grafting, revision with the uncemented Harris-Galante porous-coated acetabular component provided superior fixation compared with that reported in other series in which cemented acetabular components were used for revision. Of the 140 hips, eighty-nine (64 per cent) had a postoperative score of good or excellent, according to the Harris hip-rating system. Twenty-eight (70 per cent) of the forty hips that had revision of the acetabular component alone were rated as good or excellent.

Acetabulum↗
PubMed1992

Septic discitis resulting from Escherichia coli urosepsis.

Septic discitis refers to a primary suppurative process involving the intervertebral disc space and occurs as a result of hematogenous invasion or contamination by pyogenic organisms. A case of septic discitis is described in a 77-year-old woman following an episode of Escherichia coli urosepsis. Despite bed rest, an orthosis, and appropriate antibiotics, the patient ultimately had to undergo surgical disc removal. The diagnosis of septic discitis is often made in the context of other diseases that share common clinical and laboratory findings. Magnetic resonance imaging appears well suited for diagnostic confirmation of septic discitis. Needle biopsy and aspiration results should be used to determine the appropriate choice of antibiotic for this disease process.

Aged↗
PubMed1991

Immunodiagnosis of feline immunodeficiency virus infection using recombinant viral p17 and p24.

The coding sequences of p17 and p24 of the Glasgow-8 strain of feline immunodeficiency virus (FIV) were amplified using the polymerase chain reaction and cloned into plasmid vectors. The predicted amino-acid sequences of FIV/Glasgow-8 p17 and p24 were compared with those of the Petaluma and PPR isolates of FIV. As seen with other retroviruses, these gag gene products are highly conserved, indicating that the protein products would be suitable antigens to detect anti-FIV antibodies in an immunoassay. Both p17 and p24 were stably expressed in Escherichia coli as fusion proteins with glutathione S transferase. A pure preparation of each fusion protein was obtained from induced bacterial lysates by affinity chromatography using glutathione-agarose beads. These recombinant proteins were used in an enzyme-linked immunosorbent assay to detect antibodies directed against FIV p17 and p24 in cat sera. This assay allows the identification of seropositive cats following infection with FIV and has greater sensitivity and specificity than a currently available immunodiagnostic test.

Amino Acid Sequence↗
PubMed1979

Phenotypic intersex (female pseudohermaphroditism) in a dachshund dog.

A male miniature rough-haired dachshund, presented with episodic haematuria, was found to be a female pseudohermaphrodite. A littermate also had an abnormality of the urogenital tract and their dam had received a progesterone implant during pregnancy. Chromosome analysis of the intersex revealed XX/XY mosaicism in certain tissues.

Animals↗
PubMed1979

Lactate dehydrogenase levels and isozyme patterns. Measurements in the aqueous humor and serum of retinoblastoma patients.

Lactate dehydrogenase (LDH) activity was determined in 24 cases of histologically proved retinoblastoma. The mean level was 1,825 IU/L, with a range of 10 to 15,920 IU/L. Twenty-two patients had elevated aqueous humor LDH levels. In two, the aqueous humor level was within the normal range. Student's t testing showed a highly significant difference between cataract and retinoblastoma aqueous humor. The retinoblastoma aqueous humor to blood ratio ranged from 0.045 to 58,529--not a good index of retinoblastoma. Isozyme patterns of retinoblastoma aqueous humor were statistically similar to those of normal cataract aqueous humor. The serum LDH level of cataract patients was not statistically different from that of retinoblastoma patients. The LDH 5/LDH 1 ratio of retinoblastoma aqueous humor ranged from 0.042 to 27.05--not a good index of retinoblastoma, as 28 of 34 aqueous samples of cataract patients had LDH 5 greater than LDH 1. Ten of 13 retinoblastoma patients had aqueous humor LDH 5 greater than LDH 1. The best index of the presence or absence of retinoblastoma is the total aqueous humor LDH level.

Aqueous Humor↗
PubMed1979

Testicular tumor in male pseudohermaphrodite with X/XY chromosomal mosaicism.

A case of testicular tumor in an intersex patient is presented. Knowledge of the potential of gonadal malignancy is important in the management of disorders of sexual differentiation. These patients, in whom the fields of oncology, embryology, endocrinology, and genetics intersect, provide a fruitful ground for clinical investigation.

Adult↗
PubMed1979

Biosynthesis of glycosylated hemoglobins in the monkey.

We have investigated the in vivo biosynthesis of the minor hemoglobin components in the rhesus monkey. The elution profile of rhesus hemolysate on BioRex 70 cation exchange resin was analogous to that of human hemolysate. The rhesus Hb Alc peak was identified with the TBA test, which revealed a carbohydrate content identical to that of human Hb A1c. A rhesus monkey was injected with autologous 55Fe-bound transferrin, and the specific activity of each of the minor and major components was followed for over 70 days. As previously shown in man, rhesus Hb alc accumulated specific activity almost linearly over the erythrocyte life-span, indicative of slow and continuous conversion of Hb A0 to Hb Alc. This study revealed two new findings. (1) The specific activity of rhesus Hb Alb was always significantly less than that of Hb Alc. This result suggested that HB Alb is made by further posttranslational modification of Hb Alc. (2) The first portion of rhesus Hb A0 to be eluted on BioRex 70 contained a significant amount of carbohydrate and lower initial specific radioactivity than did the latter portion. This unexpected heterogeneity in the major hemoglobin component reflects slow, nonenzymatic glycosylation at sites other than at the N-terminus of the beta-chain.

Animals↗
PubMed1978

Epidemiology of cancers: I. Cancerous diseases of the large bowel.

A pilot study of cancerous diseases of the large bowel in Canterbury is described. The experience of 346 patients derived from the Cancer Registry for 1970-72 is presented. The feasibility of the method is demonstrated with the identification of guidelines for future work. The preliminary results suggest some special features in New Zealand. While demographic characteristics do not appear to help in defining persons at high risk from cancerous diseases of the large bowel, nevertheless other features of the natural history of this disorder indicate that it might be feasible to define high risk profiles.

Adult↗