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61.
62.
The teleost Fundulus heteroclitus (L.) possesses two loci, Gpi-A and Gpi-B,
for the glycolytic enzyme, glucose-phosphate isomerase (GPI; D-
glucose-6-phosphate ketol-isomerase; E.C. 5.3.1.9). The Gpi-B locus is
polymorphic in Fundulus, with two common alleles, Gpi-Bb and Gpi-Bc,
distributed in a clinal manner in populations along the east coast of North
America. Since this clinal distribution is strongly correlated with a
temperature gradient, we asked whether the GPI-B2 allozymes were
functionally adapted to the thermal environment in which a given phenotype
predominated. The two major GPI-B2 allozymes were purified to homogeneity
and were characterized as to molecular weight, isoelectric pH, thermal
denaturation, and kinetic parameters. Both GPI-Bb2 and GPI- Bc2 allozymes
have molecular masses of 110 kD, and they have isoelectric pHs of 6.4 and
6.6, respectively. The GPI-Bb2 allozyme was more stable to thermal
denaturation than was the GPI-Bc2 enzyme. Kinetic properties of the allelic
isozymes were investigated both as a function of pH and as a function of
temperature. At 25 degrees C, over the pH range considered, there were no
significant differences between allozymes, either in Km for
fructose-6-phosphate or in Ki for 6- phosphogluconate, but apparent Vmax
values differed between pH 7.5 and pH 8.5. All steady-state kinetic
parameters showed strong temperature dependence, but the allozymes differed
only in the Ki for 6- phosphogluconate at temperatures greater than 30
degrees C. On the basis of the observed structural and functional
differences alluded to above, the hypothesis that the major allelic
isozymes of the Gpi-B locus were functionally equivalent was rejected.
However, it is not yet known whether these structural and functional
differences have any significance at higher levels of biological
organization.
相似文献
63.
Effect of castanospermine on the structure and secretion of glycoprotein enzymes in Aspergillus fumigatus. 总被引:1,自引:1,他引:0
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Aspergillus fumigatus secretes a number of glycosidases into the culture medium when the cells are grown in a mineral salts medium containing guar flour (a galactomannan) as the carbon source. At least some of these glycosidases have been reported to be glycoproteins having N-linked oligosaccharides. In this study, we examined the effect of the glycoprotein processing inhibitor, castanospermine, on the structures of the N-linked oligosaccharides and on the secretion of various glycosidases. Cells were grown in the presence of various amounts of castanospermine; at different times of growth, samples of the media were removed for the measurement of enzymatic activity. Of the three glycosidases assayed, beta-hexosaminidase was most sensitive to castanospermine; and its activity was depressed 30 to 40% at 100 micrograms of alkaloid per ml and even more at higher alkaloid concentrations. On the other hand, beta-galactosidase activity was hardly diminished at castanospermine levels of up to 1 mg/ml, but significant inhibition was observed at 2 mg/ml. beta-Galactosidase was intermediate in sensitivity. Cells were grown in the presence or absence of castanospermine and labeled with [2-3H]mannose, [6-3H]glucosamine, or [1-3H]galactose to label the sugar portion of the glycoproteins. The secreted glycoproteins were digested with pronase to obtain glycopeptides, and these were identified on Bio-Gel P-4 (Bio-Rad Laboratories). The glycopeptides were then digested with endoglucosaminidase H to release the peptide portion of susceptible structures, and the released oligosaccharides were reisolated and identified on Bio-Gel P-4. The oligosaccharides from control and castanospermine-grown cells were identified by a combination of enzymatic and chemical studies. In control cells, the oligosaccharide appeared to be mostly Man8GlcNAc and Man9GlcNAc, whereas in the presence of alkaloid, the major structures were Glc3Man7GlcNAc and Glc3Man8GlcNAc. These data fit previous observations that castanospermine inhibits glucosidase I. 相似文献
64.
Andrew RJ Mitchell Philip Roberts Jonas Eichhöfer Jonathan Timperley Oliver JM Ormerod 《Cardiovascular ultrasound》2004,2(1):1-4
Percutaneous coronary intervention can be associated with distal embolization of thrombotic material causing myocardial necrosis and infarction. We discuss the role of intravascular imaging to guide the use of a distal protection device by describing the outcome of a young woman presenting with non-ST elevation myocardial infarction. Coronary angiography demonstrated an isolated minor stenosis in the proximal left anterior descending coronary artery with slight haziness beyond the lesion. Intravascular ultrasound confirmed an extensive thrombus overlying a bulky atherosclerotic plaque. A distal filter wire was therefore successfully used to reduce the risk of distal embolization. The use of intravascular ultrasound in patients presenting with acute coronary syndrome may reveal large thrombi that are difficult to image using conventional angiographic techniques. Intravascular ultrasound can therefore be used as a tool to select lesions requiring distal protection. 相似文献
65.
Transmission and ecology of trypanosomatid flagellates of water striders (Hemiptera: Gerridae) 总被引:1,自引:0,他引:1
An investigation of transmission and ecology of the monogenetic trypanosomatids, Blastocrithidia gerridis and Crithidia flexonema, in Gerris is described. Motile free-living flagellates of both species were found in the faeces of Gerris and in the water on which the bugs inhabited. Transmission of both trypanosomatid species occurred from naturally infected wild-caught bugs to flagellate-free laboratory-bred bugs via water. Crithidia flexonema was also transmitted to laboratory-bred bugs after being isolated in culture. Observations of experimentally infected bugs indicate that C. flexonema flagellates are imbibed and pass through the fore- and midgut to the hindgut where they become attached and multiply. There was no evidence to suggest transovarial transmission. In a 3-yr investigation into the prevalence of trypanosomatids in a natural population of adult Gerris odontogaster, it was found that the infection rate varied between 19% and 100%. There was no significant difference in infection rates between females and males. The infection rate peaked for each year in late spring or early summer. The significance of these results is discussed in relation to the ecology and behaviour of Gerris. The results indicate that the infections are maintained in hibernating bugs over winter. 相似文献
66.
Perera M Whitehead M Molyneux D Weerasooriya M Gunatilleke G 《PLoS neglected tropical diseases》2007,1(2):e128
Background
Lymphatic filariasis (LF) is a so-called neglected tropical disease, currently overshadowed by higher-profile efforts to address malaria, tuberculosis, and HIV/AIDS. Despite recent successes in arresting transmission, some 40 million people who already have the disease have been largely neglected. This study aims to increase understanding of how this vulnerable, neglected group can be helped.Methods
We used purposive sampling to select 60 men and women with filarial lymphoedema (45 with filarial elephantiasis and 15 men with filarial hydrocoele) from the south of Sri Lanka in 2004–2005. Participants were selected to give a balance of men and women and poor and nonpoor, and a range of stages of the disease. Participants'' experiences and the consequences of their disease for the household were explored with in-depth qualitative, semistructured interviews.Findings
LF was extremely debilitating to participants over long periods of time. The stigma attached to the condition caused social isolation and emotional distress, and delayed diagnosis and treatment, resulting in undue advancement of the disease. Free treatment services at government clinics were avoided because the participants'' condition would be identifiable in public. Loss of income due to the condition was reported by all households in the sample, not just the poorest. Households that were already on low incomes were pushed into near destitution, from which it was almost impossible to escape. Affected members of low-income households also had less opportunity to obtain appropriate treatment from distant clinics, and had living and working conditions that made hygiene and compliance difficult.Significance
This highly vulnerable category of patients has low visibility, thus becoming marginalized and forgotten. With an estimated 300,000 total cases of elephantiasis and/or oedema in Sri Lanka, and around 300,000 men with filarial hydrocoele, the affected households will need help and support for many years to come. These individuals should be specially targeted for identification, outreach, and care. The global strategy for elimination is aimed at the cessation of transmission, but there will remain some 40 million individuals with clinical manifestations whose needs and problems are illustrated in this study. 相似文献67.
68.
Bell DJ Nyirongo SK Molyneux ME Winstanley PA Ward SA 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2007,847(2):231-236
This article describes high-performance liquid chromatographic assays for the quantification of sulfadoxine (SDX), pyrimethamine (PYM), chloroquine (CQ), amodiaquine (AQ) and desethylamodiaquine (AQM) from whole blood. All four assays were set up and validated in Malawi using a common high-performance liquid chromatography platform and column and involved the use of simple mobile phase and extraction reagents. Calibration curves were linear (r(2)>0.95) in the ranges 5-100microg/ml, 50-1000, 150-1500, 100-1000 and 100-1000ng/ml for SDX, PYM, CQ, AQ and AQM, respectively. Intra-assay and inter-assay coefficients of variation were <15% at 3 points spanning the concentration range and <20% at the lower limit of quantification. The assays were specific with no interference from the other antimalarials described in this report. All four assays use liquid-liquid extraction, reversed-phase chromatography and UV detection and require between 50 and 200microl of blood. Because the assays share common instruments and reagents, they are cost-efficient and could be used to optimise antimalarial drug therapies in other resource poor settings. 相似文献
69.
70.