Pteridine reductase mechanism correlates pterin metabolism with drug resistance in trypanosomatid parasites

Pteridine reductase (PTR1) is a short-chain reductase (SDR) responsible for the salvage of pterins in parasitic trypanosomatids. PTR1 catalyzes the NADPH-dependent two-step reduction of oxidized pterins to the active tetrahydro-forms and reduces susceptibility to antifolates by alleviating dihydrofolate reductase (DHFR) inhibition. Crystal structures of PTR1 complexed with cofactor and 7,8-dihydrobiopterin (DHB) or methotrexate (MTX) delineate the enzyme mechanism, broad spectrum of activity and inhibition by substrate or an antifolate. PTR1 applies two distinct reductive mechanisms to substrates bound in one orientation. The first reduction uses the generic SDR mechanism, whereas the second shares similarities with the mechanism proposed for DHFR. Both DHB and MTX form extensive hydrogen bonding networks with NADP(H) but differ in the orientation of the pteridine.     

Biocavity lasers for biomedicine

Laser technology has advanced dramatically and is an integral part of the healthcare delivery systems of today. Lasers are used in laboratory analyses of human blood samples and serve as surgical tools that kill, burn or cut tissue. Recent semiconductor microtechnology has reduced the laser size to the size of a biological cell or even a virus particle. The integration of these ultra-small lasers with biological systems makes it possible to create microelectrical mechanical systems that might revolutionize healthcare delivery.     

Influence of yeast immobilization on fermentation and aldehyde reduction during the production of alcohol-free beer

Production of alcohol-free beer by limited fermentation is optimally performed in a packed-bed reactor. This highly controllable system combines short contact times between yeast and wort with the reduction of off-flavors to concentrations below threshold values. In the present study, the influence of immobilization of yeast to DEAE-cellulose on sugar fermentation and aldehyde reduction was monitored. Immobilized cells showed higher activities of hexokinase and pyruvate decarboxylase compared to cells grown in batch culture. In addition, a higher glucose flux was observed, with enhanced excretion of main fermentation products, indicating a reduction in the flux of sugar used for biomass production. ADH activity was higher in immobilized cells compared to that in suspended cells. However, during prolonged production a decrease was observed in NAD-specific ADH activity, whereas NADP-specific activity increased in the immobilized cells. The shifts in enzyme activities and glucose flux correlate with a higher in vivo reduction capacity of the immobilized cells.     

Comparing protocols for preparation of DNA-free total yeast RNA suitable for RT-PCR

Background  

Preparation of RNA free from DNA is a critical step before performing RT-PCR assay. Total RNA isolated from several sources, including those obtained from Saccharomyces cerevisiae, using routine methodologies are frequently contaminated with DNA, which can give rise to amplification products that mimic the amplicons expected from the RNA target.     

Application of Direct Agglutination Test (DAT) and Fast Agglutination Screening Test (FAST) for sero-diagnosis of visceral leishmaniasis in endemic area of Minas Gerais,Brazil

Background  

The direct agglutination test (DAT) has proved to be a very important sero-diagnostic tool combining high levels of intrinsic validity and ease of performance. Otherwise, fast agglutination screening test (FAST) utilises only one serum dilution making the test very suitable for the screening of large populations.     

Allergic fungal sinusitis. A report of two cases with diagnosis by intraoperative aspiration cytology

BACKGROUND: Allergic fungal sinusitis (AFS) is a newly recognized form of sinusitis characterized by opacification of the paranasal sinuses by "allergic mucin" (AM) admixed with scattered fungal organisms. AM consists of necrotic, or partially necrotic, eosinophils and Charcot-Leyden crystals suspended in lakes of laminated, mucinous material. AFS is characterized by the absence of bone or soft tissue invasion, purulent exudate or granulomatous inflammation. Clinically, it is important to differentiate AFS from both acute invasive fungal sinusitis and noninvasive mycetoma because the three diseases are treated with different modalities and have different prognoses. Although the radiologic features of AFS are often characteristic, occasionally it may be difficult to exclude neoplasia. CASES: Two cases of AFS, in which intraoperative diagnosis was made on the basis of the presence of both AM and fungal organisms, are reported. CONCLUSION: Cytologic diagnosis of AFS can be made from intraoperative sinus aspirates from the presence of AM and fungal elements. AM and fungi provide presumptive evidence for a noninvasive, allergic fungal disease and can help reassure clinicians intraoperatively and guide clinical management.     

Growth and yield traits of sorghum grown on acid soil at varied aluminum saturations

Genetic manipulation of crops to tolerate mineral stresses is a practical approach to improve productivity of tropical acid soils. Both acid soil tolerant (AS-T) and susceptible (AS-S) sorghum [Sorghum bicolor (L.) Moench] genotypes were grown in the field on an acid ultisol at Quilichao, Colombia, South America at 60% (60-Al) and 40% (40-Al) Al saturation to evaluate plants for growth and yield traits. Except for days to flowering and root mass scores, AS-T genotypes showed no differences in growth (plant height, head length and width, second internode length and diameter, and acid soil toxicity rating) and yield (total and stover dry matter yields, grain yield, head yield, seeds per head, and 100-seed weight) traits when plants were grown at 60-Al or 40-Al. Plants grown at 60-Al were delayed in flowering and had lower root mass scores. The AS-S genotypes showed improvement for the growth and yield traits when grown at 40-Al compared to 60-Al. The growth and yield traits of the AS-S genotypes were usually less favorable for plants grown at 40-Al than the same traits were for the AS-T genotypes grown at 60-Al. Harvest indices (ratio of grain to total plant yield) were no different for the genotypes grown at 40-Al, and only slightly higher for the AS-T genotypes grown at 60-Al. Sorghum genotypes more tolerant to acid soil conditions showed favorable growth and yield traits when grown under relatively severe acid soil (60-Al, pH 4.1) conditions. Certain sorghum genotypes were able to adapt and effectively produce grain when grown on acid soils with few inputs to reduce acid soil toxicity problems. Published as Paper No. 6690, Journal Series, Mississippi Agricultural and Forestry Experiment Station. Funding received in part from the International Sorghum/Millet Collaborative Research Support Program (INTSORMIL CRSP) through US Agency for International Development (USAID) grant AID/DAN-1254-G-SS-5065-00 and project Nos. MS-111 (MSU) and NE-114 (UNL).