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Biomedical subjects

A Powell

Publications and source records attributed to A Powell.

At least 37 records · Page 2Linked to original sources
PubMed2000

Constitutive nitric oxide release modulates neurally-evoked chloride secretion in guinea pig colon.

The role of constitutive nitric oxide (NO) release in enteric neural pathways regulating ion transport was examined in guinea pig distal colon, in vitro and ex vivo. In in vitro studies, 43% of colonic preparations exhibited oscillations in baseline short-circuit current (Isc), which were reduced by tetrodotoxin (TTX). The NO chelator, hemoglobin (Hb), and neuronal NO synthase inhibitor, 7-nitroindazole (7-NI), significantly increased the baseline Isc in these tissues, which was reduced by TTX. In tissues without oscillations in baseline Isc, Hb reduced the Isc, while 7-NI had little effect. In all tissues, electrical field stimulation (EFS; 15 V/10 Hz) caused a biphasic increase in the Isc which was enhanced by both Hb and 7-NI. In the ex vivo studies, basal release of nitric oxide was significantly lower in colonic segments isolated from guinea pigs administered N omega-nitro-L-arginine methyl ester (L-NAME) i.p. compared to control tissues. Moreover, carbachol, caused a 10-fold increase in NO release in control tissues, but had no effect in tissues isolated from the L-NAME group. L-NAME increased tissue conductance and EFS-induced changes in Isc, which were reversed by L-arginine. However, carbachol-induced ion secretion was unaltered in the L-NAME group compared to control animals. The results suggest that, in guinea pig colon, constitutive enteric NO release tonically suppresses submucous neural activity and it is involved in the maintenance of basal epithelial chloride secretion and mucosal permeability. Hence, constitutive NO promotes a delicate balance between pro-absorptive and pro-secretory processes in guinea pig colon.

Animals↗
PubMed2000

[Right bundle branch block and ST-segment elevation in right precordial leads: a marker for sudden cardiac death].

The authors present a patient with a specific ECG pattern and a history of syncope and malignant ventricular arrhythmias. Patients without demonstrable structural heart disease and an ECG pattern of RBBB and ST segment elevation in leads V1 through V3 are at risk for sudden cardiac death. They demonstrate the role of cardiac electrophysiology study including programmed ventricular stimulation and pharmacological testing in evaluation of patients with possible Brugada syndrome. The authors emphasize the role of implantable cardioverter defibrillator (ICD) therapy in treatment of patients with Brugada syndrome.

Biomarkers↗
PubMed2000

Problem drinking profiles of patients presenting to general practitioners: analysis of Alcohol Use Disorders Identification Test (AUDIT) scores for the Auckland area.

AIM: To quantify the prevalence and demography of at-risk and problematic drinkers in the population attending a random selection of general practices and to compare this with similar studies. METHOD: A study examining the uptake and utilisation of the "DRINKLESS" package to 369 New Zealand general practitioners was conducted during 1995/6. The "DRINKLESS" package was developed with the World Health Organisation collaborative study for brief intervention for at-risk alcohol consumption. The package uses the Alcohol Use Disorders Identification Test (AUDIT). There were 15,670 completed AUDIT questionnaires collected during the study. These were analysed to ascertain the prevalence and demography of at-risk and problematic drinkers attending general practitioners. RESULTS: There were 16% of patients identified as having either "risky drinking" or "problematic or dependent drinking". This pattern varied according to the occupation, age and gender of patients. CONCLUSIONS: The data confirm that large numbers of patients presenting to general practitioners experience alcohol problems of varying degrees. This study also suggests that the AUDIT will have satisfactory detection rates in a primary care setting.

Adolescent↗
PubMed2000

Initial results of reteplase in the treatment of acute lower extremity arterial occlusions.

PURPOSE: To assess the feasibility and efficacy of reteplase in transcatheter arterial thrombolysis for lower extremity occlusive disease. MATERIALS AND METHODS: Fifteen consecutive patients with acute lower extremity ischemia due to occlusive disease were treated by means of catheter-directed thrombolysis with reteplase. Following diagnostic angiography, thrombolysis was started either from an antegrade puncture site in cases of femoropopliteal occlusions, or from the contralateral groin in cases of thrombosis of the iliac artery, common femoral artery, or infrainguinal bypass grafts. Reteplase was infused at a rate of either 0.5 U/h (six patients) or 1.0 U/h (nine patients). RESULTS: Complete thrombolysis was achieved in all of the nine (100%) patients in the 1.0 U/h group and in four of six (66%) patients in the 0.5 U/h group for a combined success rate of 13 of 15 (87%). Clinical success was achieved in 11 of 15 patients overall (73%). Major bleeding complications occurred in none of the 9 patients in the 1.0 U/h group and in one (16%) of the six patients in the 0.5 U/h group for an overall rate of 6%. CONCLUSIONS: Reteplase shows promise as an alternative to urokinase in the treatment of lower extremity ischemia due to arterial occlusive disease.

Acute Disease↗
PubMed2000

Ultrastructural and karyotypic examination of in vitro produced bovine embryos developed in the sheep uterus.

This study examined whether development of bovine in vitro produced (IVP) blastocysts in the sheep uterus resulted in morphologically and karyotypically normal elongation stage bovine blastocysts. Seven day IVP bovine blastocysts, resulting from either in vitro maturation and fertilization, nuclear transfer (NT), or parthenogenic activation, were surgically transferred at the blastocyst stage into sheep uteri. Sheep were sacrificed after 7-9 days, and blastocysts were flushed from their uteri. One of each kind of IVP bovine blastocyst was recovered from sheep uteri for analysis by transmission electron microscopy, and nine NT blastocysts were used to establish cell cultures that were analysed for chromosome complement. TEM analysis of in vivo-derived elongation stage bovine and ovine blastocysts was done for comparative purposes. Most ultrastructural features of the 13-19 day blastocysts were similar to earlier stage blastocysts except that distinct alternative mitochondrial morphologies were found between epiblast and trophectoderm cells. Monociliated cells, presumably nodal cells, were observed in the bovine epiblast and hypoblast, and retrovirus-like particles were elaborated by cells in these same areas. Development in the sheep uterus of IVP bovine blastocysts resulted in the presence of crystalloid bodies in the trophectoderm cells, and apoptotic and necrotic cells were observed in the epiblast tissue. Thus, in vivo incubation in the sheep uterus allowed nearly normal development to the elongated blastocyst stage and may be useful for assessment of NT bovine blastocyst developmental competence. Cell cultures derived from the NT blastocysts had normal chromosome complements suggesting that activation by ionomycin and 6-dimethyl-aminopurine did not cause detrimental changes in ploidy in those blastocysts that developed.

Animals↗
PubMed2000

DNA preparation method can influence outcome of transgenic animal experiments.

In our continuing quest to improve the efficiency of producing transgenic animals, we have compared the influence of two transgene purification techniques on the efficiency of creating transgenic sheep and mice. Three hundred eighty-seven sheep zygotes and 2,737 mouse zygotes were microinjected with one of four transgenes. Transgenes were isolated from plasmid sequences either by agarose gel electrophoresis followed by gel extraction or by a single step sodium chloride gradient fractionation technique. Four transgenic sheep and 61 transgenic mice were produced. Both sheep and mice embryos responded similarly to transgene preparation methods. Overall, pregnancy rate was higher for recipients that received embryos injected with NaCl purified DNA (mean +/- SEM: 64 +/- 7% vs. 38 +/- 7%). Furthermore, offspring per zygote transferred (NaCl, 22 +/- 3% vs. Gel, 12 +/- 3%) and transgenics born per zygote transferred (NaCl, 3.9 +/- 0.6% vs. Gel, 1.5 +/- 0.6%) were higher when the NaCl purified DNA was used. However, the proportion of offspring born that were identified as transgenic did not differ between transgene purification methods. Transgenes responded differently to methods of preparation. One of the four genes yielded a significantly higher proportion of transgenics when the transgene was prepared by NaCl purification. These data suggest that on average the NaCl gradient purification technique results in a higher embryo survival rate to term for both sheep and mice, but the technique has no influence on rate of transgene integration.

Animals↗
PubMed1999

Controlled Formation of Low-Volume Liquid Pillars between Plates with a Lattice of Wetting Patches by Use of a Second Immiscible Fluid.

We describe a method for forming an array of microdroplets between two plates, at least one of which is patterned with a lattice of wetting patches, using a second immiscible fluid to control droplet formation. The method may be useful for performing multiple, small-volume biochemical reactions in parallel. We analyze the forces responsible for droplet formation, describe results of a computer simulation using Surface Evolver, and derive an analytic criterion for droplet formation in terms of the contact angles of the droplet:second fluid interface on the wetting patches and surrounding surface, the diameter of the wetting patches, the distance between wetting patches, and the distance between the plates. Copyright 1999 Academic Press.

Journal Article↗
PubMed1998

Soul consciousness and human suffering: psychotherapeutic approaches to healing.

A clinical approach to the understanding of disturbances of the psyche that otherwise would be regarded as pathological states of mind is described. A parallel is drawn between psychoanalytic object relations theory and "spiritual object relations," working from the premise that mind comes before matter. A number of clinical examples illustrate how both psychological and spiritual interpretations may be applied and that highlight the need for psychiatrists to be open to the transpersonal frame of reference.

Holistic Health↗
PubMed1998

Tomato fructokinases exhibit differential expression and substrate regulation

Two divergent genes encoding fructokinase, Frk1 and Frk2, have been previously shown to be expressed in tomato (Lycopersicon esculentum L.) and have now been further characterized with regard to their spatial expression and the enzymic properties of the encoded proteins. Frk1 and Frk2 mRNA levels were coordinately induced by exogenous sugar, indicating that both belong to the growing class of sugar-regulated genes. However, in situ hybridization indicated that Frk1 and Frk2 were expressed in a spatially distinct manner, with Frk2 mRNA primarily localized in cells of the fruit pericarp, which store starch, and Frk1 mRNA distributed ubiquitously in pericarp tissue. To evaluate the biochemical characteristics of the products of the Frk1 and Frk2 genes, each cDNA was expressed in a mutant yeast (Saccharomyces cerevisiae) line defective in hexose phosphorylation and unable to grow on glucose or fructose (Fru). Both Frk1 and Frk2 proteins expressed in yeast conferred the ability to grow on Fru and exhibited fructokinase activity in vitro. Although both Frk1 and Frk2 both utilized Fru as a substrate, only Frk2 activity was inhibited at high Fru concentrations. These results indicate that Frk2 can be distinguished from Frk1 by its sensitivity to substrate inhibition and by its temporal and spatial pattern of expression, which suggests that it plays a primary role in plant cells specialized for starch storage.

Journal Article↗
PubMed1998

Wooden foreign bodies in soft tissue: detection at US.

PURPOSE: To evaluate the use of ultrasound (US) for detection of wooden foreign bodies implanted in cadaveric specimens. MATERIALS AND METHODS: Wooden foreign bodies were randomly placed in the plantar soft tissues of three cadaver feet by using 5-mm-long incisions. Ten foreign bodies were 2.5 x 1.0 mm (length x diameter); 10 were 5.0 x 1.0 mm. Ten incisions were performed without implantation of foreign bodies. Three musculoskeletal radiologists independently performed US in blinded fashion and recorded the presence of a foreign body. Each used 7.5- and 10-MHz linear-array transducers and was informed of the possible presence of a foreign body. RESULTS: Sensitivity and specificity for detection of 2.5-mm-long foreign bodies were 86.7% and 96.7%, respectively. Sensitivity and specificity for detection of 5.0-mm-long foreign bodies were 93.3% and 96.7%, respectively. Overall sensitivity was 90.0%, with specificity of 96.7%, accuracy of 92.3%, positive predictive value of 98.0%, and negative predictive value of 83.0%. CONCLUSION: US can be used effectively to locate wooden foreign bodies as small as 2.5 mm in length. Given that many foreign bodies are radiographically undetectable, the accuracy and availability of US make it an excellent modality for evaluation of radiolucent foreign bodies.

Cadaver↗
PubMed1997

Incentives for general practitioners to provide brief interventions for alcohol problems.

AIMS: To assess current practices and attitudes of general practitioners towards prevention and intervention with problem drinkers. METHODS: GPs randomly selected in the Central and Southern Health Regions answered a 134 item questionnaire on their involvement with patients with alcohol related problems. RESULTS: In all, 136 general practitioners responded representing 85% of those approached. When asked how often they provided interventions with alcohol problems, 86% reported managing under 13 patients per year, indicating an intervention rate of less than 1% of the mean practice size. In terms of disease prevention, 86% rated 'drinking moderately' as important but this endorsement ranked fifth behind other lifestyle behaviours such as 'not smoking' at 99%. When asked about their perceived role, they indicated higher role legitimacy but lower work satisfaction with alcohol problems. In terms of training, three-quarters stated they had received less than eleven hours of postgraduate alcohol education. They also rated their current effectiveness with alcohol problems as substantially less than potential effectiveness. They indicated the main obstacles to be: government funding policies, lack of adequate training and a need for improved resources and support services. CONCLUSIONS: With research having established the effectiveness of interventions for harmful alcohol consumption, attention has shifted to ways of engaging general practitioners in providing interventions. This study highlighted how changes to government health policy and improved competency and skilled based training could lead to a greater acceptance by general practitioners of the role they could play in reducing alcohol related problems.

Alcoholic Intoxication↗
PubMed1996

Synthesis and secretion of the mouse whey acidic protein in transgenic sheep.

The synthesis of foreign proteins can be targeted to the mammary gland of transgenic animals, thus permitting commercial purification of otherwise unavailable proteins from milk. Genetic regulatory elements from the mouse whey acidic protein (WAP) gene have been used successfully to direct expression of transgenes to the mammary gland of mice, goats and pigs. To extend the practical usefulness of WAP promoter-driven fusion genes and further characterize WAP expression in heterologous species, we introduced a 6.8 kb DNA fragment containing the genomic form of the mouse WAP gene into sheep zygotes. Two lines of transgenic sheep were produced. The transgene was expressed in mammary tissue of both lines and intact WAP was secreted into milk at concentrations estimated to range from 100 to 500 mg/litre. Ectopic WAP gene expression was found in salivary gland, spleen, liver, lung, heart muscle, kidney and bone marrow of one founder ewe. WAP RNA was not detected in skeletal muscle and intestine. These data suggest that unlike pigs, sheep may possess nuclear factors in a variety of tissues that interact with WAP regulatory sequences. Though the data presented are based on only two lines, these findings suggest WAP regulatory sequences may not be suitable as control elements for transgenes in sheep bioreactors.

Animals↗
PubMed1995

Ankle and foot.

Explore the source record for details and available documents.

Achilles Tendon↗
PubMed1994

Development of transgenic sheep that express the visna virus envelope gene.

The ovine lentiviruses cause encephalitis, pneumonia, and arthritis in sheep worldwide. Visna virus is a prototype of this family and the pathogenesis and molecular biology of the virus has been well characterized. The envelope proteins of visna virus are responsible for binding of virus to host cells and for causing cell fusion. The surface glycoprotein also elicits cellular and humoral immune responses to the virus, the former being thought to be responsible for eliminating infected cells as well as causing inflammatory lesions. In this study, transgenic sheep were constructed that expressed the envelope genes of visna virus under the control of the visna LTR to investigate the role of the env gene in the pathogenesis of lentiviral disease in its natural host. Three transgenic lambs were identified that contain the env transgene and express the envelope glycoproteins. These transgenic animals have remained healthy and expression of the viral gene has had no obvious deleterious effect. Expression of the visna envelope protein was demonstrated by cell fusion mediated by the envelope gene as well as by immunoprecipitation of the envelope proteins with monoclonal antibodies and immunofluorescence analyses of Env protein in cells. The target cell for visna virus replication in infected animals is the monocyte/macrophage. In natural infection, the level of viral gene expression in these cells increases with cell maturation. In the transgenic sheep, monocytes did not express the envelope glycoproteins until they differentiated into macrophages in vitro. Expression of the env mRNA in macrophages was quantitated by an RNase protection assay. In addition to expression in macrophages, the transgene was expressed by fibroblasts isolated from skin of the transgenic sheep. Expression of both the Env and Rev proteins was detected by immunoprecipitation and immunofluorescence. Two of the three lambs responded immunologically to the expression of the transgene by producing binding antibodies to the envelope glycoproteins. Thus, these transgenic sheep provide a model to study whether a lentivirus glycoprotein will prevent infection or modulate disease in its natural host after virus challenge.

Animals↗