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Biomedical subjects

P Powers

Publications and source records attributed to P Powers.

At least 37 records · Page 2Linked to original sources
PubMed1991

Feminist nursing research without gender.

This theoretic article examines the potential for different types of nursing research to reinforce or undermine gender categories that historically have served to limit some women and marginalize others. Feminist research that gathers or analyzes information in the form of a male/female or man/woman dichotomy risks reproducing social relations damaging to women. Other approaches to dispersing or deconstructing gender dichotomies are discussed, and a series of questions about feminist nursing research is raised.

Female↗
PubMed1991

Glucose flux from dietary disaccharides: all sugars are not absorbed at equal rates.

Considerable discrepancies exist in the literature regarding the rates of glucose absorption from the common dietary disaccharides, lactose, maltose, and sucrose. This study compared the unidirectional flux of glucose derived from dietary disaccharides with that of their constituent monosaccharides in vitro. Lactose-stimulated short-circuit current (Isc) and mucosal-to-serosal flux (Jm----s) were lower than that of an equimolar glucose-galactose mixture and were phlorizin inhibitable. Maltose- and glucose-stimulated Isc were similar, but Jm----s of glucose derived from the hydrolysis of maltose was lower than that of free glucose. Sucrose-stimulated Isc and Jm----s were similar to that of an equimolar glucose-fructose mixture. Isc and Jm----s of glucose from both maltose and sucrose were phlorizin and acarbose inhibitable. We conclude that the rate of glucose uptake from disaccharides is less than or equal to that of free glucose and is dependent on the glucose source. We speculate that regulation of glucose uptake from disaccharides can occur at three sites: the hydrolytic enzyme, the glucose transporter, and the tight junctions.

Absorption↗
PubMed1990

Beta-globin locus activation regions: conservation of organization, structure, and function.

The human beta-globin locus activation region (LAR) comprises four erythroid-specific DNase I hypersensitive sites (I-IV) thought to be largely responsible for activating the beta-globin domain and facilitating high-level erythroid-specific globin gene expression. We identified the goat beta-globin LAR, determined 10.2 kilobases of its sequence, and demonstrated its function in transgenic mice. The human and goat LARs share 6.5 kilobases of homologous sequences that are as highly conserved as the epsilon-globin gene promoters. Furthermore, the overall spatial organization of the two LARs has been conserved. These results suggest that the functionally relevant regions of the LAR are large and that in addition to their primary structure, the spatial relationship of the conserved elements is important for LAR function.

Animals↗
PubMed1990

Early changes in the permeability of the blood-brain barrier produced by toxins associated with liver failure.

Our study was designed to determine whether substances that appear in the serum during the course of liver failure have a detrimental effect on the passive permeability of the blood-brain [blood-cerebrospinal fluid (CSF)] barrier. Lactic acid, octanoic acid, and ammonia were infused into rabbits for 4 h. The permeability changes of the blood-brain barrier were quantified by infusing polyethylene glycol 400 (PEG 400) and measuring the quantity and average mol wt of the PEG 400 that entered the CSF. The lipid solubility and effective diffusional radius of the PEG molecules were also quantified to provide greater precision for measurements using this probe. None of the animals receiving toxic infusions became seriously ill during the infusions. Low dose infusions of lactic acid, octanoic acid, and ammonia increased the effective pore diameter of the blood-brain barrier from 7.3 A to an average of 8.5 A. The amount of PEG entering the CSF increased from 1.7 to 4.0 (p less than 0.025), 4.7 (p less than 0.025), and 6.7 (p less than 0.001) mmol/L, respectively. Rabbits with galactosamine-induced liver failure had 10.1 mmol/L PEG 400 in the CSF (P less than 0.001) before any evidence of cerebral edema. These changes occur soon after these toxins accumulate in the plasma and may alone or together with other toxins account for the permeability changes that allow neurotoxic substances to enter the brain during hepatic disease and encephalopathies such as Reye's syndrome.

Animals↗
PubMed1990

A rural outbreak of Legionnaires' disease linked to visiting a retail store.

Between May 7 and June 7, 1986, 27 residents of a rural county in Maryland developed legionellosis, and two died. Legionella pneumophila serogroup 1 was cultured from the sputum of two patients and identified in lung tissue of a third patient by direct fluorescent antibody staining. An additional 11 patients had four-fold rises in antibody titer to L. pneumophila, and 13 had single titers greater than or equal to 1:256. To determine risk factors for disease, we performed a case-control study. Twelve of 16 case-patients reported visiting store A in the two weeks before onset of illness compared with four of 28 control-patients. A serologic survey of employees showed that employees of store A were 3.63 times more likely than control employees to have titers of antibody to L. pneumophila greater than or equal to 1:256 (95% confidence intervals 0.8, 16.7). Cultures of soil specimens, samples of water from the hot water system of store A and from stagnant ponds near store A collected five weeks after the end of the outbreak were negative for Legionella species. Store A was adjacent to a site of excavation and construction during May 1986, when the community was experiencing an extended drought. This investigation suggests that exposure to excavation and construction activity may be a risk factor for legionellosis.

Adult↗
PubMed1989

An evaluation of impedance plethysmography and 125I-fibrinogen leg scanning in patients following hip surgery.

Venous thromboembolism is a common post-operative complication in patients following hip surgery. 125I-fibrinogen leg scanning and impedance plethysmography (IPG), are often used in the detection of venous thrombi in such patients. Information on the sensitivity and specificity of these non-invasive tests for the diagnosis of venous thrombosis following hip surgery is relevant for both patient management and for choosing the appropriate outcome measure for clinical trials evaluating new prophylactic regimens. We determined the sensitivity and specificity of the IPG alone, the 125I-fibrinogen leg scan alone, as well as the combined use of the two tests from a retrospective analysis of 685 hip surgery patients who participated in clinical trials of anti-thrombotic prophylaxis. These patients were followed prospectively with non-invasive tests. Bilateral venography was attempted either when one or both screening tests became positive or on day 10-14 post-operatively if both screening tests remained negative. Adequate venography was obtained in 1,010 (73.7%) legs and thrombi were identified in 198 (19.6%) legs. The sensitivities of the IPG and leg scanning were 12.9% and 44.6% respectively; the corresponding specificities were 98.1% and 95.0%. The sensitivity of a positive result on one or both screening tests was 49.6% with a specificity of 93.9%. Therefore, leg scanning and IPG, even in combination, are not sufficiently accurate to be recommended as the only strategy for the diagnosis of venous thrombosis following hip surgery. Venography should be considered in all patients undergoing surveillance testing either when one or both of the screening tests become positive or on day 10-14 if the screening tests remain negative.

Fibrinogen↗
PubMed1989

Monitoring of intestinal transplant rejection.

Our results show that maltase, sucrase, and lactase activity are present at a normal level in nonrejecting small bowel transplants after an initial postoperative decline. This confirms that the disaccharide absorbing capacity of these grafts is intact. In allogeneic bowel, however, the levels of maltase and sucrase decline as histologic rejection occurs. These results suggest that serial maltase, sucrase, and possibly lactase levels in allogeneic intestinal transplants may serve as a useful adjunct in the monitoring of small bowel transplant rejection.

Animals↗
PubMed1989

Comparative evaluation of urographic contrast media, inulin, and 99mTc-DTPA clearance methods for determination of glomerular filtration rate in clinical transplantation.

Plasma clearance of inulin (Cin), 99mTc-DTPA (CDTPA), and urographic contrast media (CCM) were determined simultaneously in 31 patients with varying levels of renal function evaluated in the setting of affiliated cardiac and renal transplantation programs. Cin and CDTPA were calculated from the ratio of simultaneously measured plasma concentration and urine excretion rate of these test agents (UxV/P). CCM was derived from x-ray fluorescence measurement of plasma iodine (PI) content following intravenous injection of 50 ml of nonionic, low-osmolar contrast media (180 mg I/ml). Urine collections were not required for CCM determinations. No adverse reactions attributable to CM occurred in any patient, and follow-up serum-creatinine values did not differ significantly from prestudy levels. CCM determined from the rate of decline in PI between 3 hr and 4 hr following administration of contrast media ("slope-intercept" technique) [Ccm-SI] correlated closely with corresponding levels of Cin (r = .86, P less than 0.0001). and CDTPA (r = 0.89, P less than 0.0001). Mean CCM-SI/Cin and CCM-SI/CDTPA ratios for the entire study cohort were 1.09 +/- 0.06 and 1.08 +/- 0.06, respectively. CCM-SI determinations also correlated well with CCM levels derived from a single measurement of PI ("single sample" technique) made at 3 hr following injection of contrast media (r = 0.94, P less than 0.0001). Both CCM-SI and CCM determined by the "single sample" method (CCM-3 degrees SS) tended to overestimate Cin and CDTPA, however, when the latter were less than 20 ml/min/1.73 m2 (mean CCM-SI/Cin and Ccm-3 degrees SS/Cin ratios 1.36 +/- 0.14 and 1.95 +/- 1.0, respectively. Reproducibility was evaluated by paired comparison of 3-hr vs. 4-hr "single sample" CCM determinations (r = 0.99, P less than 0.0001). In addition, analysis of the variation in iodine content between duplicate specimens obtained at each of these time intervals revealed a mean ratio of 1.0 +/- 0.01 (P = NS vs. identity). Contrast clearance determination utilizing the slope-intercept method is accurate, safe, pragmatic, and more precise than serum-creatinine and endogenous-creatinine clearance for measurement of renal function in clinical transplantation.

Contrast Media↗
PubMed1989

A prospective comparison of four techniques for measuring platelet-associated IgG.

We describe a prospective study comparing four different assays for PAIgG. Platelets from patients with a variety of thrombocytopenic disorders were collected into ACD, washed, and the PAIgG then measured using three assays for surface PAIgG. These included: (a) a direct binding assay using 125I-monoclonal anti-IgG (MoAb); (b) a direct binding assay using 125I-staphylococcal protein A (SPA); and (c) a two-stage assay. PAIgG also was measured using an assay for 'total' PAIgG following platelet lysis. The mean +/- SD number of molecules of IgG per platelet on washed platelets from 29 healthy, non-thrombocytopenic controls was: 86 +/- 80 (125I-MoAb); 94 +/- 96 (125I-SPA); 3520 +/- 1890 (two-stage surface assay); and 10,850 +/- 3720 (total PAIgG). A total of 62 different patients with idiopathic thrombocytopenic purpura or thrombocytopenia complicating systematic lupus erythematosus, and 73 different patients with 'non-immune' thrombocytopenia, were tested using each of the four assays. These 'non-immune' thrombocytopenic patients included patients with carcinoma, septicaemia, pre-eclampsia, chronic leukaemia, thrombotic thrombocytopenic purpura, haemolytic uraemic syndrome, acute leukaemia and myelodysplasia. All four assays gave similar results for both the immune and non-immune thrombocytopenic patients. The sensitivity of the assays for the most severely thrombocytopenic patients with immune thrombocytopenia was: MoAb 60%; SPA 88%; two-stage 82%; and 'total' PAIgG 88%. The specificity of the four assays in the non-immune thrombocytopenic patients was 57% 'total' PAIgG; 63% two-stage surface; 25% SPA; 38% MoAb.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies, Monoclonal↗
PubMed1989

Clostridium perfringens food poisoning: use of serotyping in an outbreak setting.

An outbreak of Clostridium perfringens food poisoning occurred among attendees of a firehouse luncheon. The predominant symptoms of diarrhea (100%) and abdominal pain (81%) among case-patients, the mean incubation period (13.4 h), and the mean duration of illness (21.2 h) were all characteristic of C. perfringens enteritis. Roast beef, although not epidemiologically implicated, was the most likely vehicle of transmission. Fecal specimens from case-patients contained a median C. perfringens spore count of greater than 10(6) and yielded isolates that were heat sensitive and predominantly nonhemolytic, produced C. perfringens enterotoxin A, and, in the majority of specimens (four of five), were identical in serotype. Food samples were negative. This outbreak demonstrates that following enumeration of C. perfringens from a suitable number of fecal specimens from case-patients, serotyping of the isolates may be helpful in implicating C. perfringens as the cause of foodborne illness. This is especially true when implicated food items test negative or are no longer available for testing.

Adolescent↗
PubMed1988

Development of the human coagulation system in the healthy premature infant.

This study was designed to determine the postnatal development of the human coagulation system in the healthy premature infant. Consecutive mothers of healthy premature infants born at either St Joseph's Hospital or McMaster University Medical Centre in Hamilton were asked for consent. One hundred thirty-seven premature infants (30 to 36 weeks of gestational age) entered the study. The premature infants did not have any major health problems and did not require ventilation or supplemental oxygen. Demographic information and a 20-mL blood sample were obtained in the postnatal period on days 1, 5, 30, 90, and 180. Between 40 and 96 premature infants were studied on each day for each of the following tests: prothrombin time, activated partial thromboplastin time, thrombin clotting time, plasminogen; 13 factor assays [fibrinogen, II, V, VII, VIII, IX, X, XI, XII, XIII, high-mol-wt kininogen (HMWK), prekallikrein (PK), von Willebrand factor (vWF)] and eight inhibitors [antithrombin III (AT-III), heparin cofactor II, alpha 2-antiplasmin, alpha 2-macroglobulin, alpha 1-antitrypsin, C1 esterase inhibitor, protein C (PC), and protein S (PS)]. A combination of biologic and immunologic assays were used. Between 30 to 36 weeks there was a minimal effect of gestational age for levels of AT-III, PC, and factors II and X only; therefore, the entire data set was used to generate reference ranges for these components of the coagulation system for premature infants. Next, the results for the premature infants were compared with those of a previously published study in 118 fullterm infants and with those for adults. An effect of gestational age was shown for plasminogen, fibrinogen, factors II, V, VIII, IX, XI, XII, HMWK, and all eight inhibitors. In general, the postnatal maturation towards adult levels was accelerated in premature infants as compared with the fullterm infants. By 6 months of age, most components of the coagulation system in premature infants had achieved near adult values.

Age Factors↗
PubMed1987

Outbreak of neonatal Citrobacter diversus meningitis in a suburban hospital.

Between February and June, 1983, four cases of Citrobacter diversus neonatal meningitis were identified at a suburban Baltimore hospital. One of the 4 infants died at age 13 months, 2 (both of whom had brain abscesses) have evidence of developmental delay and 1 appears to be normal after 33 months of follow-up. A review of microbiology records revealed that C. diversus had been present in the hospital nursery prior to identification of the first infant with meningitis, with isolation from infants born 7 months, 4 months and 4 days, respectively, before the first meningitis case. C. diversus was isolated from 21 infants born during the outbreak period and from hand or rectal cultures of 5 nursing personnel. All isolates were biotype E, with two distinct clusters of cases identified on the basis of plasmid profile and serotype. In a case-control study isolation of C. diversus was significantly associated with male sex, low birth weight and care by house pediatricians. The outbreak was controlled by stringent infection control measures and exclusion of personnel carriers. During the 24 months following the outbreak 3431 babies discharged from the nursery were cultured for C. diversus; 3 were colonized with the organism.

Citrobacter↗
PubMed1987

von Willebrand factor is present on the surface of platelets stimulated in plasma by ADP.

von Willebrand factor (vWf) can bind to glycoprotein (GP) IIb/IIIa on activated platelets. The significance of this interaction is unclear, however, because it has not been possible to detect vWf binding to GPIIb/IIIa on platelets stimulated in plasma. We have developed an indirect, flow cytometry assay that uses fluorescein-labeled antibodies to detect vWf and fibrinogen on platelets. Using this assay, we found vWf on the surface of platelets stimulated in plasma by ADP. The number of platelets that bound vWf increased in proportion to ADP concentration and incubation time. Washed platelets in a protein-free buffer activated by 1 mumol/L calcium ionophore A23187 or 10 mumol/L ADP also bound vWf, suggesting that we were detecting surface binding of alpha-granule-derived vWf. Monoclonal antibodies against the vWf binding site on GPIb (6D1) and the vWf and fibrinogen binding sites on GPIIb/IIIa (LJP5 and LJ-CP8, respectively) were used to characterize the mechanism of vWf binding to stimulated platelets. Ristocetin-induced binding of vWf was inhibited by 6D1, and ADP-induced binding of fibrinogen was inhibited by LJ-CP8. None of these antibodies inhibited ADP-induced vWf binding. Aspirin and prostaglandin E1 also inhibited ADP-induced binding of vWf in platelet-rich plasma. During platelet activation in plasma, vWf derived from alpha-granules becomes bound to the platelet surface possibly being transferred already associated with a binding site.

Adenosine Diphosphate↗
PubMed1987

Development of the human coagulation system in the full-term infant.

The investigation of many hemostatic defects in the newborn is limited by the lack of normal reference values. This study was designed to determine the postnatal development of the human coagulation system in the healthy full-term infant. Consecutive mothers of healthy full-term infants born at St Joseph's Hospital in the city of Hamilton were approached for consent. One hundred eighteen full-term infants (37 to 42 weeks' gestational age) were entered into the study. Demographic information and a 2-mL blood sample were obtained in the postnatal period on days 1, 5, 30, 90, and 180. Between 40 and 79 full-term infants were studied on each day for each of the coagulation tests. Plasma was fractionated and stored at -70 degrees C for batch assaying of the following tests: prothrombin time, activated partial thromboplastin time, thrombin clotting time, and factor assays (biologic): fibrinogen, II, V, VII, VIII, IX, X, XI, XII, and high-molecular weight kininogen. Factor XIII subunits A and S, von Willebrand factor, and the inhibitors antithrombin III, alpha 2-antiplasmin, alpha 2-macroglobulin, alpha 1-antitrypsin, C1 esterase inhibitor, protein C, and protein S were measured immunologically. Plasminogen, prekallikrein, and heparin cofactor II were measured by using chromogenic substrates. The large number of infants studied at each time point allowed us to determine the following: the range of normal for each test at five time points in the postnatal period; that coagulation tests vary with the postnatal age of the infant; that different coagulation factors show different postnatal patterns of maturation; and that near-adult values are achieved for most components by 6 months of life. In summary, this large cohort of infants studied consecutively in the postnatal period allowed us to determine the normal development of the human coagulation system in the full-term infant.

Aging↗
PubMed1987

Analysis of the clinical findings used to diagnose coliform mastitis in dairy cows, and comparison to a prediction model.

Logistic regression was used to analyze the clinical findings (attributes) which predicted coliform mastitis in 113 dairy cattle, 36 of which had coliforms cultured from milk. Weakness of the cow, swelling of the udder, decreased body temperature and watery consistency of the milk were selected for the model. An analysis was then done to find the attributes which clinicians used when predicting that a cow would have a coliform cultured. Clinicians appeared to use water consistency of the milk, shivering, firmness of the udder, pulse rate, elevated body temperature, and respiratory rate. In a final analysis the clinicians' predictions were forced into the model to determine which attributes might be used by clinicians to increase diagnostic accuracy. Inclusion of weakness of the cow, swelling of the udder, decreased temperature of the cow, and duration of mastitis of less than 24 hours increased accuracy over clinical prediction alone. Accuracy of cowside diagnosis might be increased if more attention were paid to these attributes when making a diagnosis of coliform mastitis.

Animals↗