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Biomedical subjects

M J Stewart

Publications and source records attributed to M J Stewart.

At least 91 records · Page 5Linked to original sources
PubMed1994

The interaction of colloidal metals with erythrocytes.

The interactions of citrate reduced colloids (Ag, Au, and Bi) with intact erythrocytes and erythrocyte lysate have been studied by 1H spin echo NMR. Silver colloid is observed to induce cellular depletion of cytosolic glutathione and bismuth colloid induces cytosolic glutathione oxidation in the intact cell. In comparison, there is no detectable effect with gold colloid. With red cell lysate the three colloids all remove glutathione from the spectrum. The metal salts AgNO3 and NaAuCl4 both oxidize intracellular glutathione to diglutathione whereas BiO(NO3) has no effect. Thus colloidal preparations have a different reactivity to their parent metal salts. The differences observed between the three types of colloids (silver, gold, and bismuth) are unique to the colloids studied. None of the colloids studied were biologically inert in the erythrocyte model used.

Bismuth↗
PubMed1994

Measurement of blood pressure in the technological age.

Problems with conventional blood pressure measurement using the mercury sphygmomanometer, related to both equipment and technique, are discussed. The effect of observer bias on the measuring procedure is also considered. Blood pressure variability and the phenomenon of 'white coat' hypertension are then described and their impact on the interpretation of hypertensive cardiovascular risk is emphasized. The potential role of electronic sphygmomanometers, and the use of ambulatory BP monitoring equipment, to overcome some of these problems is analysed. Technical factors both in use and interpretation of ambulatory BP data are considered, emphasizing the lack of prospective data and the difficulties in defining a 'normal' range. The current role of such equipment in both research and clinical practice is defined.

Ambulatory Care↗
PubMed1994

Mothers of children with chronic conditions: supportive and stressful interactions with partners and professionals regarding caregiving burdens.

Ninety mothers appraised the specific sources and types of social support they received in relation to specific types of demands of caring for a child with a chronic condition. Qualitative data were collected during home interviews with the mothers of children with diabetes, spina bifida, or cystic fibrosis. Virtually all of the mothers described primary caregiver demands that were directly related to the child's condition, such as physical care, health care in illness situations, and the child's psychological and social development. Many mothers also reported secondary demands related to their own needs, family roles and relationships, and the mother's activities outside the home. Mothers experienced gaps in the support provided for specific caregiving burdens and encountered stressful interactions with their partners and health professionals in particular.

Adolescent↗
PubMed1994

Hope and social support as coping resources for adults waiting for cardiac transplantation.

Previous research has indicated that interpersonal support and hopefulness are important for people waiting for cardiac transplantation. However, little is known about their supportive networks, or whether support and hope are factors that enable coping during the waiting period. This study described the social networks of cardiac transplant candidates, and explored whether social support and hope contributed to effective coping. Thirty-one individuals in four Canadian transplant centres completed questionnaires regarding social support (Norbeck Social Support Questionnaire), hope (Miller Hope Scale), and coping (Jalowiec Coping Scale). Telephone interviews provided supplementary data about perceptions of helpful support behaviours. Study findings suggest that hope was the only variable that contributed to coping effectiveness (R2 = .41) and that respondents' social networks (primarily family, friends, and health professionals) were important sources of support. The data provide insight into the behaviours that transplant candidates find supportive and suggest strategies to maintain hopefulness during the waiting period.

Adaptation, Psychological↗
PubMed1994

HPLC and drug analysis.

Explore the source record for details and available documents.

Chromatography, High Pressure Liquid↗
PubMed1994

Cardiovascular effects of cigarette smoking: ambulatory blood pressure and BP variability.

Cigarette smoking and hypertension are independent risk factors for cardiovascular disease, but the relationship between them is complex. Smoking raises BP acutely, yet in epidemiological studies smokers have lower clinic BP than nonsmokers. To explore this apparent paradox we have compared 24h ambulatory BP profiles and BP variability of smokers, before and after a week's abstention from smoking, and nonsmoking controls. There was no evidence of a significant acute pressor effect from smoking. All three groups had similar ABP profiles but smokers had significantly more variable BP than nonsmokers and variability increased still further after a week's abstention. An increase in BP variability, possibly related to changes in baroreflex sensitivity, is a further mechanism by which smoking may increase cardiovascular risk.

Adult↗
PubMed1993

Can simultaneous ambulatory blood pressure and activity monitoring improve the definition of blood pressure?

In this study we measured activity and sleep time, using a wrist actigraph, in a population of 319 patients referred for ambulatory blood pressure monitoring (ABPM). Mean waking and sleeping blood pressure (BP) and the diurnal BP variation derived with this technique were compared to daytime (defined variously as 7 AM to 8 PM, 7 AM to 10 PM, or 7 AM to midnight) and nighttime pressure. To study the relationship of actigraph-derived activity data to BP variability in more detail, 30 patients underwent paired monitoring 1 to 18 (mean 8) days apart. Mean waking BP was then corrected for activity to determine whether this technique could improve reproducibility. Statistically but not clinically significant differences between waking and daytime BP were seen, with larger and potentially clinically relevant differences between sleeping and nighttime BP. The midnight to 7 AM time period gave the best estimate of observed sleeping time and the nocturnal dip of BP. The average correlation between activity and BP was 0.25 for systolic and 0.34 for diastolic BP, but with wide variation in the strength of the relationship both between and within individual patients. On average, activity accounts for 20% of systolic and 26% of diastolic BP variation. Correcting the mean waking BP to a standard activity level reduced within-patient variation by 6%/9%. This made no significant difference to overall reproducibility, perhaps because variability in this sample was low before adjustment, with the standard deviation of the difference equal to 8/4 mm Hg.(ABSTRACT TRUNCATED AT 250 WORDS)

Ambulatory Care↗
PubMed1993

The Drosophila ribosomal protein S6 gene includes a 3' triplication that arose by unequal crossing-over.

Ribosomal protein S6 (rpS6) is the major phosphoprotein of the small ribosomal subunit of eukaryotes and is phosphorylated in response to treatment with mitogens and other stimuli. We have examined the organization of the rpS6 gene of Drosophila melanogaster. Comparisons of a cDNA with genomic DNA identify a transcription unit including three exons. Two tandem repeats downstream of this transcription unit reiterate divergent copies of the third exon and flanking regions. Comparisons of these three repeats with respect to nucleotide base substitutions and deletions or insertions show clearly that they arose via a duplication and subsequent crossing-over between misaligned copies. Although no direct evidence exists that the downstream exons are transcribed, the maintenance of open reading frames in spite of extensive genetic changes is consistent with a protein-coding function.

Amino Acid Sequence↗
PubMed1993

Mutations in the Drosophila gene encoding ribosomal protein S6 cause tissue overgrowth.

We have characterized two P-element-induced, lethal mutations in Drosophila melanogaster which affect the larval hemocytes, mediators of the insect immune response. Each mutant displays larval melanotic tumors characteristic of mutations affecting the insect cellular immune system, and the moribund animals develop grossly hypertrophied hematopoietic organs because of increased cell proliferation and extra rounds of endoreduplication in some hematopoietic cells. Surprisingly, these mutations are due to P element insertions in the 5' regulatory region of the Drosophila gene encoding ribosomal protein S6 and cause a reduction of S6 transcript abundance in mutant larvae.

Animals↗
PubMed1993

Induction of hepatic inflammatory response by Plasmodium berghei sporozoites protects BALB/c mice against challenge with Plasmodium yoelii sporozoites.

BALB/c mice are about 2,000 times less susceptible to sporozoites of Plasmodium berghei than to Plasmodium yoelii. Associated with this is the innate cellular response mounted after injection with P. berghei. Host inflammatory cells do not normally attack P. yoelii during their development as exoerythrocytic forms (EEFs) in the liver. We used P. berghei sporozoites to induce host inflammation that might act against developing P. yoelii EEFs. Mice injected with P. berghei sporozoites followed 1 hr later with P. yoelii had a 58% reduction in P. yoelii EEFs. To establish whether this was due to events that occurred before vs. after invasion of hepatocytes by P. yoelii sporozoites, mice received P. yoelii sporozoites that were allowed to invade for 1 hr before subsequent injection with P. berghei; these mice showed minimal reduction in P. yoelii EEFs. Thus, most of the deleterious effects of P. berghei sporozoites appear to have been directed against P. yoelii sporozoites prior to their invasion of hepatocytes. Plasmodium yoelii that had already invaded were relatively unaffected. Further timing experiments showed that this effect was induced only by viable P. berghei sporozoites, which may thus induce rapid changes in sinusoid physiology leading to host resistance against P. yoelii sporozoites.

Animals↗
PubMed1992

Limitations of the triolein breath test.

Patients being investigated for intestinal absorptive capacity were classified as normals or malabsorbers on the basis of three fat absorption tests. Malabsorbers were further classified as mild, moderate, severe or gross according to severity of malabsorption. Using this classification system the triolein breath test was evaluated in 53 patients. Seventeen patients were excluded because their graph of percentage breath [14C]carbon dioxide versus time was exponential indicating that the peak [14C]-carbon dioxide may be occurring later than the six hour duration of the test. The sensitivity and specificity of the triolein breath test were found to be 100% and 96%, respectively and moderate correlations with the individual fat absorption tests were found. However, the breath test was limited in its capacity to predict the severity of malabsorption. Carbon dioxide output was also measured in order to determine the applicability of using an assumed value. The respiratory quotient and variability of results were high in nineteen patients indicating possible hyperventilation. In 32 patients with reproducible results and normal respiratory quotients the average carbon dioxide output was 8.66 mmol/kg per hour with a wide range of 5-12.4 mmol/kg per hour. Consequently the use of an assumed carbon dioxide output can introduce considerable errors in the triolein breath test. This study highlights drawbacks of the triolein breath test, particularly problems in using an assumed carbon dioxide output for its calculation, its inability to predict the severity of malabsorption and the nature of the dietary load used.

Adolescent↗