Crystal structure of human thymidine phosphorylase in complex with a small molecule inhibitor

Human thymidine phosphorylase (HTP), also known as platelet-derived endothelial cell growth factor (PD-ECGF), is overexpressed in certain solid tumors where it is linked to poor prognosis. HTP expression is utilized for certain chemotherapeutic strategies and is also thought to play a role in tumor angiogenesis. We determined the structure of HTP bound to the small molecule inhibitor 5-chloro-6-[1-(2-iminopyrrolidinyl) methyl] uracil hydrochloride (TPI). The inhibitor appears to mimic the substrate transition state, which may help explain the potency of this inhibitor and the catalytic mechanism of pyrimidine nucleotide phosphorylases (PYNPs). Further, we have confirmed the validity of the HTP structure as a template for structure-based drug design by predicting binding affinities for TPI and other known HTP inhibitors using in silico docking techniques. This work provides the first structural insight into the binding mode of any inhibitor to this important drug target and forms the basis for designing novel inhibitors for use in anticancer therapy.     

Assessing the Relationship between Vector Indices and Dengue Transmission: A Systematic Review of the Evidence

Background

Despite doubts about methods used and the association between vector density and dengue transmission, routine sampling of mosquito vector populations is common in dengue-endemic countries worldwide. This study examined the evidence from published studies for the existence of any quantitative relationship between vector indices and dengue cases.

Methodology/Principal Findings

From a total of 1205 papers identified in database searches following Cochrane and PRISMA Group guidelines, 18 were included for review. Eligibility criteria included 3-month study duration and dengue case confirmation by WHO case definition and/or serology.A range of designs were seen, particularly in spatial sampling and analyses, and all but 3 were classed as weak study designs. Eleven of eighteen studies generated Stegomyia indices from combined larval and pupal data. Adult vector data were reported in only three studies. Of thirteen studies that investigated associations between vector indices and dengue cases, 4 reported positive correlations, 4 found no correlation and 5 reported ambiguous or inconclusive associations. Six out of 7 studies that measured Breteau Indices reported dengue transmission at levels below the currently accepted threshold of 5.

Conclusions/Significance

There was little evidence of quantifiable associations between vector indices and dengue transmission that could reliably be used for outbreak prediction. This review highlighted the need for standardized sampling protocols that adequately consider dengue spatial heterogeneity. Recommendations for more appropriately designed studies include: standardized study design to elucidate the relationship between vector abundance and dengue transmission; adult mosquito sampling should be routine; single values of Breteau or other indices are not reliable universal dengue transmission thresholds; better knowledge of vector ecology is required.     

Extensive DNA polymorphism at the factor XIIIa (F13A) locus and linkage to HLA.

A 1,161-bp EcoRI fragment from the 5' end of the cDNA coding for human factor XIIIa (gene symbol F13A) was used to identify RFLPs in human DNAs. Several different RFLPs were identified with 15 different restriction enzymes. Two RFLPs detected with the restriction enzyme BamHI and one multiallelic RFLP detected with BclI were used for further studies. Linkage relationships between these three polymorphisms and the HLA complex were studied in DNA samples from the 40 Centre d'Etude du Polymorphisme Humain families. Combining all of the data to form highly informative haplotypes, we found linkage to HLA with a maximum lod score of 11.44 at a recombination fraction of .25 for males and .35 for females. These three RFLPs at the FXIIIa locus provide a highly informative marker for the short arm of chromosome 6 with an observed heterozygosity of 91%. Using this marker and the HLA locus, one can confirm or exclude the assignment of gene loci to most of chromosome 6p.     

High pressure neurologic syndrome type 2 seizure in mice

Progressive compression in helium/oxygen (heliox) atmospheres elicits in mice and many other vertebrates tested a complex series of effects known as the high pressure neurologic syndrome (HPNS). The most dramatic behavioral manifestations of the syndrome are two successive and distinct convulsive seizures. HPNS type 1 and type 2. In the present study, a maximum likelihood estimation procedure was applied to 11 models of inheritance of the difference in the time elapsed until manifestation of the type 2 seizure in heliox-compressed C57BL/6 and BALB/c mouse strains, their F1 hybrid, and the backcross generations. The "preferred" model specifying interaction between two major unlinked autosomal loci was confirmed indirectly by further breeding tests. The tests also showed that type 1 and type 2 seizure thresholds are uncorrelated but type 1 always preceded type 2. A challenge to the latter result involving mating backcross mice with high type 1 and type 2 seizure thresholds to mice with low type 1 and type 2 seizure thresholds produced no instance of alteration of the seizure order.     

Effects of pollen and nitrogen availability on reproduction in a woodland herb,Lysimachia quadrifolia

Summary Relationships between pollen loads, resource availability, and fruit and seed production were determined for Lysimachia quadrifolia ramets in two adjacent sites (the scrub site and the open site) in 1982, 1983, and 1984. Pollen loads limited % fruit set and seed production in the open site in 1982 and 1983. Reproduction in the scrub site was resource limited in 1982, as shown by an increase in % fruit set when one-half of the flowers on a ramet were removed prior to fruit initiation. In the scrub site in 1983, pollination of one-half of the flowers on a ramet decreased the % fruit set of the remaining, unpollinated flowers. Fruit production in the same site was limited by pollen in 1984. Addition of nitrogen fertilizer to the scrub site in 1984 had no effect on fruit and seed production. There was more variation in fruit set between sites than between years. There was no trend to greater fruit set or number of seeds/fruit on early flowers compared to late flowers on the same ramet. Correlations between measures of reproduction were positive or insignificant. These results demonstrate year-and site-specific variation in the factors that limit plant reproduction.     

Expression of human apolipoprotein A-II and its effect on high density lipoproteins in transgenic mice.

Apolipoproteins A-I and A-II comprise approximately 70 and 20%, respectively, of the total protein content of HDL. Evidence suggests that apoA-I plays a central role in determining the structure and plasma concentration of HDL, while the role of apoA-II is uncertain. To help define the function of apoA-II and determine what effect increasing its plasma concentration has on HDL, transgenic mice expressing human apoA-II and both human apoA-I and human apoA-II were produced. Human apoA-II mRNA is expressed exclusively in the livers of transgenic animals, and the protein exists as a dimer as it does in humans. High level expression of human apoA-II did not increase HDL concentrations or decrease plasma concentrations of murine apoA-I and apoA-II in contrast to what was observed in mice overexpressing human apoA-I. The primary effect of overexpressing human apoA-II was the appearance of small HDL particles composed exclusively of human apoA-II. HDL from mice transgenic for both human apoA-I and human apoA-II displayed a unique size distribution when compared with either apoA-I or apoA-II transgenic mice and contain particles with both these human apolipoproteins. These results in mice, indicating that human apoA-II participates in determining HDL size, parallel results from human studies.     

Muscle fiber hypertrophy, hyperplasia, and capillary density in college men after resistance training

McCall, G. E., W. C. Byrnes, A. Dickinson, P. M. Pattany,and S. J. Fleck. Muscle fiber hypertrophy, hyperplasia, and capillary density in college men after resistance training.J. Appl. Physiol. 81(5):2004-2012, 1996.Twelve male subjects with recreationalresistance training backgrounds completed 12 wk of intensifiedresistance training (3 sessions/wk; 8 exercises/session; 3 sets/exercise; 10 repetitions maximum/set). All major muscle groupswere trained, with four exercises emphasizing the forearm flexors.After training, strength (1-repetition maximum preacher curl) increasedby 25% (P < 0.05). Magneticresonance imaging scans revealed an increase in the biceps brachiimuscle cross-sectional area (CSA) (from 11.8 ± 2.7 to 13.3 ± 2.6 cm²;n = 8;P < 0.05). Muscle biopsies of thebiceps brachii revealed increases(P < 0.05) in fiber areas for type I(from 4,196 ± 859 to 4,617 ± 1,116 µm²;n = 11) and II fibers (from 6,378 ± 1,552 to 7,474 ± 2,017 µm²;n = 11). Fiber number estimated fromthe above measurements did not change after training (293.2 ± 61.5 × 10³ pretraining; 297.5 ± 69.5 × 10³ posttraining;n = 8). However, the magnitude ofmuscle fiber hypertrophy may influence this response because thosesubjects with less relative muscle fiber hypertrophy, but similarincreases in muscle CSA, showed evidence of an increase in fibernumber. Capillaries per fiber increased significantly(P < 0.05) for both type I(from 4.9 ± 0.6 to 5.5 ± 0.7;n = 10) and II fibers (from 5.1 ± 0.8 to 6.2 ± 0.7; n = 10). Nochanges occurred in capillaries per fiber area or muscle area. Inconclusion, resistance training resulted in hypertrophy of the totalmuscle CSA and fiber areas with no change in estimated fiber number,whereas capillary changes were proportional to muscle fiber growth.

     

Immobilization of Burkholderia cepacia in polyurethane-based foams: embedding efficiency and effect on bacterial activity

Immobilization of the trichloroethylene-degrading bacterium Burkholderia cepacia was evaluated using hydrophilic polyurethane foam. The influence of several foam formulation parameters upon cell retention was examined. Surfactant type was a major determinant of retention; a lecithin-based compound retained more cells than pluronic- or silicone-based surfactants. Excessive amounts of surfactant led to increased washout of bacteria. Increasing the biomass concentration in the foam from 4.8 to 10.5% dry weight per wet weight of foam resulted in fewer cells being washed out. Embedding at reduced temperature did not significantly affect retention, while the use of a silane binding agent gave inconsistent results. The optimal formulation retained all but 0.2% of total embedded cells during passage of 2 L of water through columns containing 2 g of foam. All foam formulations tested reduced the culturability of embedded cells by several orders of magnitude, but O₂ consumption and CO₂ evolution rates of embedded cells were never less than 50% of those of free cells. Nutrient amendments stimulated an increase in cell volume and ribosomal activity in immobilized cells as indicated by hybridization studies using fluorescently labeled ribosomal probes. These results indicate that, although immobilized cells were mostly nonculturable, they were metabolically active and thus could be used for biodegradation of toxic compounds. Received 23 December 1996/ Accepted in revised form 13 March 1997