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Biomedical subjects

A Wallace

Publications and source records attributed to A Wallace.

At least 73 records · Page 4Linked to original sources
PubMed1994

Nucleotide sequence and expression of a ripening and water stress-related cDNA from tomato with homology to the MIP class of membrane channel proteins.

The nucleotide sequence and derived amino acid sequence were determined for a full-length version of the tomato cDNA clone, pTOM75, the mRNA for which has previously been shown to accumulate in roots, ripening fruit and senescing leaves. Computer analysis of the predicted protein product, which we have named tomato ripening-associated membrane protein (TRAMP) indicates strong homology to known transmembrane channel proteins from other organisms. Northern analysis showed that this gene was induced by waterstress and that this induction was unaffected in an ABA-deficient genetic background.

Amino Acid Sequence↗
PubMed1994

The utility of the Philips SRI-100 Real Time Portal Imaging Device in a case of postoperative irradiation for prevention of heterotopic bone formation following total hip replacement.

The new Radiation Oncology Department at the Heidelberg Repatriation Hospital in Melbourne, Australia commenced operation in June 1992. As part of quality control the Philips SL-15 linear accelerator was fitted with the Philips SRI-100 Real Time Portal Imaging Device (RTPID), the first such apparatus in Australia. One of its major advantages over older systems is its ability to provide a permanent hard copy of the image of the field treated. The computer image can be immediately manipulated and enhanced on the screen (with respect to such qualities as brightness and contrast) prior to the printing of the hard copy. This is a significant improvement over the more cumbersome older port films that required developing time, without any pre-assessment of the image quality. The utility of the Philips SRI-100 RTPID is demonstrated in the case of a patient irradiated soon after total hip replacement, as prophylaxis against heterotopic bone formation (HBF). The rapidity and quality of image production is a major advantage in these patients where post-operative pain may result in positional change between film exposure and image production. Extremely accurate shielding block position is essential to shield the prosthesis (and allow bone ingrowth for fixation) whilst avoiding inadvertent shielding of the areas at risk for HBF. A review of the literature is provided.

Adult↗
PubMed1994

Changes in systolic and diastolic ventricular function with cold cardioplegic arrest in man. The Multicenter Study of Perioperative Ischemia (McSPI) Research Group.

INTRODUCTION: Most of the cardiac surgery done today is performed with aortic cross-clamping and cardioplegic arrest. Despite improvements in cardioplegic techniques, ventricular dysfunction following cardioplegic arrest is a major cause of perioperative morbidity and mortality. This experiment will quantify the changes in left ventricular systolic function with cold cardioplegia. Four measures of cardiac function will be assessed with a volume conductance catheter. METHODS AND RESULTS: Thirty patients undergoing coronary artery bypass graft surgery had volume conductance and micromanometer catheters placed in their left ventricles. Preload reduction was used to measure Ees (the slope of the end-systolic pressure-volume relationship), EdP/dtMax-EDV (slope of dP/dtMax end-diastolic volume relationship), EPLRSW (slope of stroke work end-diastolic volume relationship), Eed (slope of the end-diastolic pressure-volume relationship), and ENegdP/dtMax-EDV (slope of the negative dP/dtMax end-diastolic volume relationship). Ees decreased from 4.32 +/- 2.94 prebypass to 2.52 +/- 1.06 mmHg/mL postbypass. CONCLUSION: Cold cardioplegic cardiac arrest is associated with postbypass systolic and diastolic ventricular dysfunction, which can be quantitated by volume conductance and micromanometer based measurements.

Diastole↗
PubMed1993

Cystic fibrosis carrier testing in early pregnancy by general practitioners.

OBJECTIVE: To assess the feasibility of genetic counselling in general practice by using cystic fibrosis carrier screening at the booking appointment as an integral part of routine antenatal care and as a paradigm for the wider participation of general practitioners in medical genetics. DESIGN: Maternal testing (male partner tested only if woman screens positive) and couple testing for cystic fibrosis carrier status in the antenatal population attending one general practice and, later, in a further six (outreach) practices also. SETTING: Two partner urban training practice (pilot practice) in south Manchester, and six north west practices (two inner city, three urban, one rural dispensing). SUBJECTS: Total practice population of 50,000 (pilot practice plus six outreach practices) with an estimated 500-800 pregnancies per year. MAIN OUTCOME MEASURES: (a) Proportion of carriers of cystic fibrosis identified, counselled, and appropriately managed within the first trimester of pregnancy; (b) questionnaire and interview measures of patient satisfaction and stress. RESULTS: Eleven carriers of cystic fibrosis were detected including one carrier couple. This carrier couple, after extensive counselling, elected to have prenatal diagnosis by chorionic villus biopsy. The fetus was homozygous normal. CONCLUSIONS: General practitioners can successfully integrate genetic counselling and cystic fibrosis carrier screening into the first antenatal booking appointment. When a carrier couple is identified clinical geneticists can help with the discussion of reproductive options, and prenatal diagnosis by chorionic villus biopsy can be completed within the first trimester. The results suggest that general practitioners will have an increasingly important role in medical genetics, subject to continuing evaluation of patient acceptability and stress.

Anxiety↗
PubMed1993

Do deficiencies of endothelial derived relaxing factor contribute to myocardial stunning?

Myocardial stunning is a phenomenon in which ventricular function is depressed by prior ischemia and remains suboptimal when blood flow is resumed. It is also characterized by coronary vascular endothelial dysfunction that is related to the duration of ischemia and can result in protein leakage, myocardial hemorrhage, or increased coronary vascular resistance. It is thought that local vascular tone is regulated by endothelium derived relaxing factor (EDRF), a compound commonly believed to be identical to nitric oxide (NO). EDRF increases the effects of other vasodilators through the formation of cyclic guanosine monophosphate (cGMP) by guanylate cyclase. Patients with various cardiovascular disorders have been found to have dysfunction in the EDRF system, and EDRF paradoxically produces vasoconstriction in atherosclerotic arteries. Similarly, EDRF stimulation of vasodilation due to acetylcholine, calcium ionophores, or platelets appears to be reduced in coronary arteries that have been damaged by ischemia and reperfusion. By increasing EDRF production or inhibiting its breakdown, EDRF precursors such as L-arginine, the superoxide radical scavenger superoxide dismutase, nitroglycerin, and nitroprusside all cause vasodilation by increasing NO levels in the setting of myocardial ischemia. These therapies may also improve local "microvascular" function, thereby improving ventricular function.

Animals↗
PubMed1993

Characterization of Trypanosoma cruzi populations by several molecular markers supports a clonal mode of reproduction.

Chilean T. cruzi populations from different endemic areas and transmission cycles were characterized at several biochemical levels, to mention: hybridization with kinetoplast DNA probes, molecular karyotype, isoenzyme studies and kinetoplast DNA restriction fragment length polymorphism. Furthermore, an immunological approach with immune sera from Balb/c infected mice with different T. cruzi populations was used to differentiate among parasite types by the in vitro complement-mediated lysis assay. Parasite grouping by the above described methods allows to classify T. cruzi populations on a very defined number, suggesting that they have a clonal structure.

Animals↗
PubMed1992

Beyond silver staining.

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Electrophoresis, Polyacrylamide Gel↗
PubMed1992

Ultramicrodetection of proteins in polyacrylamide gels.

Here we report the development of a highly sensitive procedure to detect proteins within separation matrices which should facilitate the characterization of rare proteins. The procedure is based on photochemical reactions where very low amounts of silver are deposited around proteins and in a series of steps are converted to silver sulfide. When this conversion is carried out in the presence of [35S]thiourea the resulting radioactive silver sulfide allows detection down to femtogram quantities of protein. In this work we applied the above principle to proteins separated on sodium dodecyl sulfate-polyacrylamide gels, thus not influencing physical and chemical parameters which are important for separation. This procedure should find application in any technique where detection of very low or limited amounts of proteins are required.

Electrophoresis, Polyacrylamide Gel↗
PubMed1992

Characterization of Chilean, Bolivian, and Argentinian Trypanosoma cruzi populations by restriction endonuclease and isoenzyme analysis.

Ninety-one Chilean, 15 Bolivian, and 9 Argentinian Trypanosoma cruzi stocks, isolated from various hosts and vectors, were characterized by schizodeme analysis with EcoRI and MspI endonucleases. The three major similar pattern groups that emerged from this sample correlated with results of isoenzyme analysis. This result confirms previous work and supports the hypothesis of the clonal structure of natural populations of T. cruzi, fully defined at the level of isoenzyme analysis, quantitative kinetoplast DNA restriction fragment length polymorphism, and kinetoplast DNA hybridization analysis. In Chile, sylvatic and domestic cycles of T. cruzi transmission appear to be mainly independent: genetically different families of natural clones are specific to these cycles. Nevertheless, the possibility of overlap remains unclear. Results described here indicate that natural clones inhabiting Chilean regions appear genetically related to the natural clones identified in neighboring countries. In Chile the more frequently sampled parasite types are natural clone 39 and a genetically closely related clone NP13. In this work an evaluation of T. cruzi natural clone mixtures in T. cruzi stocks from Chile was performed for the first time by schizodeme analysis before and after serial transfer in mouse maintenance. The results indicate that six of nine stocks are composed of two or more natural clones. This observation raises the relevant question of whether specific T. cruzi natural clones generate different clinical features of Chagas' disease.

Animals↗
PubMed1992

Haemagglutinins and fimbriae of soft rot Erwinias.

Strains of phytopathogenic soft rot Erwinia spp. were examined for haemagglutinin (HA) production. Mannose-sensitive HA was found only in five of 15 strains of E. carotovora subsp. carotovora. Mannose-resistant HA (MRHA) was found in 12 of 15 strains of E.c. carotovora, ten of 13 strains of E.c. subsp. atroseptica and the single strain of E.c. subsp. betavasculorum, as well as all seven strains of E. chrysanthemi. MRHA, detectable only in a microtitre tray HA assay was of either broad- or narrow-spectrum activity when examined against blood of seven different animal species and could be inhibited by the beta-galactoside asialofetuin. Fimbriae of ca 10 nm diameter were found on MRHA(+) bacteria E.c. carotovora and E.c. atroseptica.

Animals↗
PubMed1992

Generation and characterization of a monoclonal antibody specific for the major thiol-activated cysteine proteinase of Porphyromonas gingivalis W83.

An IgM monoclonal antibody specified for the thiol-activated proteinase of the oral pathogen Porphyromonas gingivalis W83 was generated. The antibody reacted with a single protein of approximate molecular mass 43 kDa in outer membrane preparations of P. gingivalis. Immuno-electron microscopy using the monoclonal antibody and immunogold labelling confirmed the cell surface location of the thiol-activated proteinase. The monoclonal antibody failed to detect any proteins in Western blot analysis of other closely related oral bacteria. The specificity of this monoclonal antibody to the thiol-activated proteinase of P. gingivalis should allow its use as a diagnostic tool for the rapid enumeration of P. gingivalis in clinical samples.

Antibodies, Bacterial↗
PubMed1992

Down-regulation of scatter factor in MRC 5 fibroblasts by epithelial-derived cells. A model for scatter factor modulation.

Scatter factor/hepatocyte growth factor (SF/HGF) is a multifunctional cytokine produced by embryonic fibroblasts and other mesenchymal cells that affects the growth and/or the movement of certain epithelia. Here we report that expression of scatter factor activity by MRC 5 cells, a strain of normal human embryonic lung fibroblasts, is greatly reduced as a result of co-culture of these cells with SVK14, an SV40-transformed human keratinocyte cell line. Using a cDNA probe to the beta chain of human HGF, we have found that the fall in SF activity in MRC 5/SVK14 co-cultures is accompanied by the loss of SF/HGF transcripts. As the inhibition of SF activity coincides with the disappearance of SF/HGF transcript, we conclude that inhibition of the SF activity expressed by MRC 5 cells by co-culture with SVK14 involves transcriptional regulation.

Animals↗
PubMed1991

Racial differences in drug response: isoproterenol effects before and after propranolol.

The aim of this study was to determine in young, healthy men the relative contribution of pharmacodynamic factors inherent between two groups known to respond differently to hypertensive therapy. Black (n = 10) and white (n = 10) men received an isoproterenol sensitivity test before and after propranolol (0.1 mg/kg, then 50 micrograms/min). There were greater increases (twofold) in systolic BP following the 1.0- and 1.5-microgram isoproterenol dose (P less than 0.05) in the black group. During propranolol there were no differences in free (1)-propranolol concentrations between the groups; however, propranolol decreased resting heart rate in the white group more than in the black group (P less than 0.05). Cardiac index decreased less in the black group compared to the white group (P less than 0.05). Following the second isoproterenol challenge, there again were greater increases in systolic BP in the black group at both the 10- and the 20-micrograms isoproterenol dose (P less than 0.05). Our study has highlighted the importance of cross-racial studies in evaluating drug effects.

Adult↗