The rubber tree (Hevea brasiliensis Muell. Arg.) homologue of the LEAFY/FLORICAULA gene is preferentially expressed in both male and female floral meristems

The rubber tree (Hevea brasiliensis Muell. Arg.) is an important source of natural rubber in tropical regions and, as with many woody species, shows a long juvenile phase. To understand the genetic and molecular mechanisms underlying the reproductive process in rubber trees, H. brasiliensis RRIM600 flower and inflorescence development have been characterized, the rubber tree FLORICAULA/LEAFY (FLO/LFY) orthologue, HbLFY, cloned, and its expression patterns were analysed during vegetative and reproductive development. The rubber tree, similar to other Euphorbiaceae species, produces lateral inflorescences containing male, female, and bisexual flowers. HbLFY is expressed in lateral meristems that give rise to inflorescences and in all flower meristems, consistent with a role in reproductive development. Complementation studies using Arabidopsis lfy mutants indicated that the biological function of LFY might be conserved among Brassicaceae and Euphorbiaceae species.     

Structural changes of the prion protein in lipid membranes leading to aggregation and fibrillization

Prion diseases are associated with a major refolding event of the normal cellular prion protein, PrP(C), where the predominantly alpha-helical and random coil structure of PrP(C) is converted into a beta-sheet-rich aggregated form, PrP(Sc). Under normal physiological conditions PrP(C) is attached to the outer leaflet of the plasma membrane via a GPI anchor, and it is plausible that an interaction between PrP and lipid membranes could be involved in the conversion of PrP(C) into PrP(Sc). Recombinant PrP can be refolded into an alpha-helical structure, designated alpha-PrP isoform, or into beta-sheet-rich states, designated beta-PrP isoform. The current study investigates the binding of beta-PrP to model lipid membranes and compares the structural changes in alpha- and beta-PrP induced upon membrane binding. beta-PrP binds to negatively charged POPG membranes and to raft membranes composed of DPPC, cholesterol, and sphingomyelin. Binding of beta-PrP to raft membranes results in substantial unfolding of beta-PrP. This membrane-associated largely unfolded state of PrP is slowly converted into fibrils. In contrast, beta-PrP and alpha-PrP gain structure with POPG membranes, which instead leads to amorphous aggregates. Furthermore, binding of beta-PrP to POPG has a disruptive effect on the integrity of the lipid bilayer, leading to total release of vesicle contents, whereas raft vesicles are not destabilized upon binding of beta-PrP.     

Pseudomonas aeruginosa: study of antibiotic resistance and molecular typing in hospital infection cases in a neonatal intensive care unit from Rio de Janeiro City,Brazil

This study had the objective of to analyze the demographic and bacteriologic data of 32 hospitalized newborns in an neonatal intensive care unit of a public maternity hospital in Rio de Janeiro city, Brazil, seized by Pseudomonas aeruginosa sepsis during a period ranged from July 1997 to July 1999, and to determine the antimicrobial resistance percentage, serotypes and pulsed field gel electrophoresis (PFGE) patterns of 32 strains isolated during this period. The study group presented mean age of 12.5 days, with higher prevalence of hospital infection in males (59.4%) and vaginal delivery (81.2%), than females (40.6%) and cesarean delivery (18.8%), respectively. In this group, 20 (62.5%) patients received antimicrobials before positive blood cultures presentation. A total of 87.5% of the patients were premature, 62.5% presented very low birth weight and 40.6% had asphyxia. We detected high antimicrobial resistance percentage to b-lactams, chloramphenicol, trimethoprim/sulfamethoxazole and tetracycline among the isolated strains. All isolated strains were classified as multi-drug resistant. Most strains presented serotype O11 while PFGE analysis revealed seven distinct clones with isolation predominance of a single clone (75%) isolated from July 1997 to June 1998.     

Binding of prion protein to lipid membranes and implications for prion conversion

The binding of the Syrian hamster prion protein, SHaPrP(90-231), to model lipid membranes was investigated by tryptophan fluorescence. Membranes composed of negatively charged or zwitterionic lipids, and raft-like membranes containing dipalmitoylphosphatidylcholine(1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), cholesterol and sphingomyelin, were investigated. It was found that SHaPrP(90-231) binds to negatively charged lipid membranes and raft-like membranes. Binding of PrP to negatively charged lipid membranes involves both electrostatic and hydrophobic lipid-protein interactions and results in partial insertion of PrP into the lipid bilayer. This membrane-inserted conformation of PrP is richer in beta-sheet structure and has a disruptive effect on the integrity of the lipid bilayer, leading to total release of vesicle contents. In contrast, the binding of PrP to raft-like membranes is driven by hydrophobic lipid-protein interactions and induces the formation of alpha-helical structure. This conformation of PrP with a high content of alpha-helix is formed only at pH 7 and does not destabilize the lipid bilayer. Our findings support the view that an interaction of PrP with lipid membranes could play a role in PrP conversion.     

Ecto-phosphatase activity on the cell surface of Crithidia deanei

In the present work we have partially characterized an ecto-phosphatase activity in Crithidia deanei, using viable parasites. This enzyme hydrolyzed p-nitrophenylphosphate at a rate of 3.55 +/- 0.47 nmol Pi/h x 10(8) cells. The dependence on p-NPP concentration shows a normal Michaelis-Menten kinetics for this phosphatase activity and the value of the apparent Km for p-NPP was 5.35 +/- 0.89 mM. This phosphatase activity was inhibited by the product of the reaction, the inorganic phosphate. Experiments using classical inhibitors of acid phosphatases, such as ZnCl2 and sodium fluoride, as well as inhibitors of phosphotyrosine phosphatase, such as sodium orthovanadate and ammonium molybdate, showed a decrease in this phosphatase activity, with different patterns of inhibition.     

PVF1, a PDGF/VEGF homolog,is sufficient to guide border cells and interacts genetically with Taiman

The border cells of the Drosophila ovary undergo a well-defined and developmentally regulated cell migration. Two signals have previously been shown to control where and when the cells migrate. The steroid hormone ecdysone, acting through its receptor and a coactivator known as Taiman, contributes to regulating the timing of border cell migration. PVF1, a growth factor related to platelet-derived growth factor and vascular-endothelial growth factor, contributes to guiding the border cells to the oocyte. To probe the mechanisms controlling border cell migration further, we performed a screen for genes that exhibit dominant genetic interactions with taiman. We identified 14 genomic regions that interact with taiman. Within one region, we identified Pvf1 as the gene responsible for the interaction. Signaling by PVF1 has been proposed to guide the border cells to their proper target, but ectopic PVF1 has not been tested for its ability to redirect the border cells. We tested the ability of PVF1, as well as other factors such as Gurken, to guide the border cells to new targets. Our results demonstrate that ectopic expression of PVF1 is sufficient to redirect border cells in some egg chambers but that the other factors tested are not. These data suggest that the guidance of border cell migration is robust and that there are likely to be additional factors that contribute to long-range guidance of these cells. In addition, we find that taiman and Pvf1 regulate the dynamic localization of E-cadherin in the border cells, possibly accounting for the interaction between these two pathways.     

Ethnic differences in allelic distribution of IFN-g in South African women but no link with cervical cancer

BACKGROUND: The failure of specific types of human papillomaviruses (HPV) to raise effective immune responses may be important in the pathogenesis of cervical cancer, the second most common cancer in South African women. Polymorphisms of a number of cytokine genes have been implicated in inducing susceptibility or resistance to cancers caused by infectious agents owing to their role in determining host immune response. Polymorphisms of IL-10 and IFN-gamma genes are believed to influence the expression and/or secretion levels of their respective cytokines. METHODS AND RESULTS: In this study, women with histologically proven cancer of the cervix (n = 458) and hospital-based controls (n = 587) were investigated for bi-allelic -1082 (A/G) polymorphisms of IL-10 and the bi-allelic +874(A/T) polymorphisms of IFN-gamma. In addition, the distributions of the allelic frequencies were stratified in both the African and mixed race population groups of South Africa. We found striking differences in the allele distribution of IFN-gamma (X2 = 0.02) among the two ethnic groups. A significant increase in the allele distribution of the IFN-gamma AA genotype was found in the African group compared to the mixed population group (OR, 0.5; 95% CI, 0.2-1.0). For IL-10 there were no significant allelic differences between the two South African ethnic groups. Furthermore, when the ethnic groups were combined the IL-10 allelic frequencies in the combined South African data were similar to those observed in an Oriental population from Southern China and in an Italian population. However, the allele frequencies of the IFN-gamma genotype among the two South African ethnic groups were different when compared to an Italian Caucasoid group. While crude analysis of these data showed both statistically significantly increased and diminished risks of cervical cancer among high producers of INF-gamma and low producers of IL-10 respectively, these associations were no longer significant when the data were adjusted for confounding factors. CONCLUSION: These findings demonstrate a clear correlation between ethnicity and IFN-gamma polymorphism across different population groups. However, these differences in ethnicity and gene polymorphisms in the aforementioned cytokines are suggested not to influence the development of invasive cervical cancer but may represent an important susceptibility biomarker for other diseases and should be explored further.     

Mechanisms of bradykinin-mediated dilation in newborn piglet pulmonary conducting and resistance vessels

Bradykinin (BK) is a potent dilator of the perinatal pulmonary circulation. We investigated segmental differences in BK-induced dilation in newborn pig large conducting pulmonary artery and vein rings and in pressurized pulmonary resistance arteries (PRA). In conducting pulmonary arteries and veins, BK-induced relaxation is abolished by endothelial disruption and by inhibition of nitric oxide (NO) synthase with nitro-L-arginine (L-NA). In PRA, two-thirds of the dilation response is L-NA insensitive. Charybdotoxin plus apamin and depolarization with KCl abolish the L-NA-insensitive dilations, findings that implicate the release of endothelium-derived hyperpolarizing factor (EDHF). However, endothelium-disrupted PRA retain the ability to dilate to BK but not to ACh or A-23187. In endothelium-disrupted PRA, dilation was inhibited by charybdotoxin. Thus in PRA, BK elicits dilation by multiple and duplicative signaling pathways. Release of NO and EDHF contributes to the response in endothelium-intact PRA; in endothelium-disrupted PRA, dilation occurs by direct activation of vascular smooth muscle calcium-dependent potassium channels. Redundant signaling pathways mediating pulmonary dilation to BK may be required to assure a smooth transition to extrauterine life.     

Statistical aspects in physical mapping application to the genome of O. oeni strain GM

This work addresses issues around physical maps, in particular, for circular genomes. The overlapping relationship between two fragments obtained by applying two different restriction enzymes, separately, is classified as nonoverlapping, partial overlapping, and total overlapping. A double partial overlapping can also appear in a particular situation. Taking into account DNA fragment lengths and under the assumption that the left-hand endpoints of the two restriction fragments are independent random variables, each of which with a uniform distribution along a circular genome, we present expressions for prior probabilities of those events. This information is combined with hybridization data via Bayes' theorem, in order to evaluate corresponding posterior probabilities. Additionally, we explore a sensitivity analysis to quantify the effect of length variation in the results.