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Biomedical subjects

J Mackenzie

Publications and source records attributed to J Mackenzie.

At least 37 records · Page 2Linked to original sources
PubMed1995

Gynopia in nursing practice: the case of urethral catheterization.

A pilot study of catheterized women was designed to investigate their perceptions of pain and discomfort during the procedure. The study aimed to test the feasibility of conducting a larger randomized controlled trial. Problems were encountered during the execution of the study, due to the need to conform to established principles in clinical research. Restrictions on access to patients impinged upon the opportunity to 'cast the net wide' in order to generate meaningful data.

Attitude to Health↗
PubMed1994

A comparison study of the EF-18 agar/Hydrophobic Grid Membrane Filter (HGMF) method and the enzyme linked antibody (ELA)/HGMF method to the HPB standard method in the isolation of Salmonella.

As part of a comparative and collaborative study of rapid methods for the detection of Salmonella and the standard Health Protection Branch (HPB) method, six Federal and Provincial Laboratories compared the EF-18 agar/Hydrophobic Grid Membrane Filters (HGMF) method to the standard HPB method. Two Federal Laboratories also compared the enzyme linked antibody (ELA)/HGMF method (which is a further development of the EF-18 agar/HGMF method) to the standard method. During this study the false-negative rates ranged from 0% to 15% for the standard HPB method, from 5.88% to 43.5% for the EF-18 agar/HGMF method, and from 0% to 10.5% for the ELA/HGMF method. The EF-18 agar/HGMF method did not compare well with the standard HPB method due to the number of false-negatives. Problems with this method resulted from the inability to isolate colonies of Salmonella on the HGMF due to the small colony size, abnormal colony coloration, and overgrowth by competitors. The ELA/HGMF method, however, was shown to be comparable to the standard HPB method. The main advantages of this method are that the antibody-staining step is independent of colony coloration and carbohydrate utilization on the plating media; the ability to detect some unusual strains of Salmonella irrespective of their atypical reactions on the media; and the ELA staining can indicate the presence of Salmonella even when the HGMF is overgrown by competitors. Also, cultural confirmation can proceed simultaneously yet independently of the ELA staining procedure. The data presented here indicate that this method is worth further study.

Bacteriological Techniques↗
PubMed1994

Aortic valvuloplasty: an alternative for aortic insufficiency.

The authors describe a technique for aortic valve repair in patients with aortic regurgitation with excellent intermediate term results avoiding the complications of prosthetic valve replacement. Conservation of native valve tissue will obviate complications associated with prosthetic valves.

Aortic Valve↗
PubMed1993

Protein kinase C activity during the process of lung liquid clearance.

Although active transport of sodium plays an important role in the resolution of pulmonary edema, the biochemical regulation of this process is still under investigation. The purpose of this study was to evaluate the activity of protein kinase C during the process of lung liquid clearance. Alveolar flooding was induced by instilling 5% bovine serum albumin solution, saline, or heterologous serum in the air spaces of rats. The activity of protein kinase C was measured in both the instilled and control lungs at 10 min and 1 and 4 h after fluid instillation. Four hours after instillation of 5% bovine serum albumin, the ratio of protein kinase C activity in the instilled lung compared with the control lung was 2.2 +/- 0.3. Similar results were obtained following instillation with heterologous serum or saline. Since we measured a clearance rate of 0.8 ml/h in anesthetized rats, we can postulate that the activation of protein kinase C occurred when > 40% of the liquid had been cleared from the lung. This increased activity of protein kinase C was not due to an increase in kinase activity in the inflammatory cells or an increase in enzyme quantity but due to a decrease of protein kinase C inhibitory activity in the lung. These results suggest that protein kinase C second messenger system may play a regulatory role in lung liquid clearance.

Animals↗
PubMed1987

Sodium transport and the cellular sodium transport pool of colonic epithelium: effects of sodium loading, aldosterone and lithium.

The cellular sodium transport pool and sodium transepithelial fluxes were investigated in vivo in rat distal colon in relation to sodium loading by intravenous infusion (3.5 h), and to short (4 h) and prolonged (72 h) i.v. administration of aldosterone. Considerable natriuresis and increase in body sodium content were produced by the sodium load but there was no significant effect on the transcellular sodium flux (active absorption from lumen to plasma) or on the sodium transport pool. Both short and prolonged aldosteronism produced similar increases in the transport pool and in the transcellular sodium flux, but the transepithelial electrical potential difference (p.d.) was significantly greater in rats given the prolonged infusion. Addition of amiloride to the solution in the lumen of the colon almost completely abolished the p.d., the transport pool and the transcellular sodium flux of the rats receiving prolonged infusion, but had much less effect in those given the short infusion. The time-course of recovery of p.d. following prolonged aldosteronism was similar to that described for the turnover rate of rat colonic epithelial cells. Lithium within the lumen had no significant effect in untreated rats but after prolonged aldosterone infusion lithium reduced the p.d. and the transcellular sodium flux although the transport pool was not reduced. These findings are consistent with the hypothesis that aldosteronism renders the apical membranes of the epithelial cells permeable to lithium and that intracellular accumulation of lithium depresses active sodium transfer.(ABSTRACT TRUNCATED AT 250 WORDS)

Aldosterone↗
PubMed1985

Total body potassium and water, and exchangeable sodium, in muscular dystrophy.

Total body potassium (40K method) and total body water and exchangeable sodium (both by isotope dilution) were determined in 26 boys, aged 5-17 years, with muscular dystrophy. Total body potassium values were compared with measurements in a large series of normal boys on the basis of height. Total body potassium was reduced even in the youngest patients and was only slightly higher in the older boys, despite their considerably greater height. Exchangeable sodium increased with increasing height in a way similar to that of normal boys. Total body water was also reduced but increased with growth, although to a lesser extent than expected for normal boys. The total body water measurements indicated that many of the affected boys were very obese, despite an apparently normal body weight. An intravenous bolus of 22Na distributed at a similar rate in boys with muscular dystrophy to that in normal males. In relation to the predicted values, total body potassium and 24 h urinary creatinine excretion of the affected boys both declined at a rate of 4% per year.

Adipose Tissue↗
PubMed1984

The effects of ionic concentration and light on the binding of enzymes to rod outer segment membranes.

The binding of cyclic GMP phosphodiesterase (PDE) to bovine rod outer segment membranes has been measured under various conditions of ionic strength, light and darkness and with and without added GTP. Comparison of the effects of magnesium, calcium and sodium ions shows that it is ionic strength rather than the nature of the ion that determines the binding, and that Ca2+ has no special properties in this respect. The level of light-induced activity of the bound PDE has been measured under the different conditions, and this shows that a relatively constant proportion (1-5%) of the bound PDE is in an active site irrespective of how the membranes have been washed. This means that sufficient GTP-binding protein (GBP) is also bound to the membranes to maintain a constant proportion of active PDE. The washed membranes are capable of activating more PDE molecules than those already bound, and even bleached membranes washed twice with GTP-containing, low-ionic strength buffers could activate considerable numbers of added PDE molecules. These experiments suggest that under the ionic strength conditions of the intact cell effectively all of the PDE is membrane bound, and that exposure to light or changes in the Ca2+ concentration are unlikely to cause significant changes in the amount of PDE bound, or to the level of its activity.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1984

Amiloride sensitive and insensitive sodium pathways and the cellular sodium transport pool of colonic epithelium in rats.

Methods for measurement of the epithelial Na transport pool (Nat) using epithelial scrapings and for analysing the transepithelial ionic fluxes of rat distal colon in vivo into transcellular and paracellular components have been used to study the amiloride sensitive (a.s.) and amiloride insensitive (a.i.) transcellular pathways in relation to variations of Nat. In the Na-replete normal rats, substitution of SO4 for Cl in the lumen approximately halved the Na transported by a.i. pathways and reduced Nat by about 60%, but in the Na-depleted rats, substitution of SO4 did not affect either the Na transported by a.s. pathways or Nat. The value of Nat for normal rats, with 150 mM-NaCl in the lumen, was 6-7 nmol Na mg-1 dry weight (corresponding to about 2-3 mmol kg-1 cell water) and fell by about 60% when lumen Na concentration was reduced to 50 mM. Its turnover half-time was 0.6 min. Nat was about threefold greater in the Na-depleted than in the normal rats but became undetectable when amiloride was in the lumen. Amiloride did not affect Nat in normal rats. We conclude that the increased Na absorption in Na depletion depended on substitution of a.s. for a.i. apical membrane pathways allowing increased Na entry into the epithelial cells so expanding Nat and stimulating the basolateral Na pumps.

Amiloride↗
PubMed1982

Studies on the uptake of exogenous phosphoglycerides by Escherichia coli B cells.

The uptake of exogenous lipids by Escherichia coli B was studied under various conditions. Lysophosphoglycerides were absorbed more readily than diacyl analogues when sonicated dispersions of a single lipid were used. When these same lipids were admixed with coliform lipids and dispersed as vesicles, the uptake of lysophosphoglyceride diminished and was approximately equal to that of diacyl analogues. Neutral lipids such as diglyceride, fatty acid, and cholesterol were also absorbed when admixed and dispersed as vesicles with coliform lipids. The uptake of lysophosphoglyceride was stimulated slightly by all divalent cations tested except Mg2+; monovalent cations were ineffective. Uptake was accompanied by conversion of lysophosphoglyceride to diacyl analogues. In the presence of Ca2+, lysophosphatidylethanolamine also formed a more polar lipid product yet unidentified. The uptake of lipid did not cause release of 3H label into the medium from cells that had been grown in [3H]acetate-containing medium. Also, the [3H]phosphoglyceride content of such labelled cells remained constant. Thus the uptake process did not involve exchange of membrane lipid with the medium or an enhanced hydrolysis of endogenous lipids, but it represented a net gain of lipid by the cell. The uptake did not seem to involve a stable adsorption of lipid at the surface of the cell as could be judged from electron microscopic examination of the cells after incubation; the cell surfaces were devoid of adsorbed vesicle or liposomal types of structures and did not display evidence of expansion. [3H]Cholesterol-[32P]phospholipid mixtures were taken up without a change in isotopic ratio. This result together with the other evidence presented indicate a net uptake of exogenous lipid by a process likely involving fusion.

Acetates↗