Effects of glycerol on microtubule polymerization kinetics

Steady state and kinetic studies of polymerization of purified microtubule protein show little effect of glycerol on the steady state level of polymerization, as demonstrated by measurements of critical concentration. The rates of polymerization and depolymerization are slowed in the presence of glycerol. This data indicates that the stabilization of microtubules by high glycerol is largely a kinetic effect rather than a shift in equilibrium. However, the apparent critical concentration for microtubule polymerization from crude brain homogenate is substantially higher in the absence of glycerol, and glycerol appears to protect microtubule polymerization against the action of endogenous inhibitors.     

Traces of brain microtubule-associated proteins affect dynamic properties of microtubules

A method is described for measuring the quantities of stable and dynamic microtubules in a population in vitro. The method exploits the tendency of dynamic microtubules to depolymerize rapidly after being sheared. Stable microtubules, such as those protected by microtubule-associated proteins (MAPs), are broken to a smaller size by shearing, but do not depolymerize into subunits. The usual difficulty with this procedure is that the tubulin released from the dynamic microtubules rapidly repolymerizes before the end point of depolymerization can be measured. This has been overcome by including a small quantity of tubulin-colchicine complex in the mixture to block the repolymerization. For a total of 24 microM tubulin in a polymerization mixture, 10 microM of the sample polymerized originally under the conditions used. When 1.05 microM tubulin-colchicine complex was added at the time of shearing, the dynamic microtubules depolymerized, but the tubulin was released was unable to repolymerize and a small fraction of stable microtubules that resisted shear-induced depolymerization could then be detected. When traces of MAPs (0.23-2.8% by mass) were included in the tubulin mixture, the fraction of stable microtubules increased from 5% in the absence of added MAPs to 41% in the presence of 2.8% MAPs. All the MAPs in the mixture were found in the stable fraction and this stable fraction forms early during microtubule assembly. Calculations on the extent of enrichment of MAPs in the stable fraction indicated that as little as 4% MAPs in a microtubule protected it from shear-induced disassembly. The results suggest that low levels of MAPs may distribute nonrandomly in the microtubule population.     

Fascioloides magna (Bassi, 1875) in feral swine from southern Texas.

Between 1971 and 1975, Fascioloides magna was found in 46 of 67 (69%) feral swine (Sus scrofa) in southern Texas. Flukes were recovered from swine in areas where F. magna commonly has been recovered from white-tailed deer and cattle. One to 12 flukes were recovered from each infected animal. Their presence was indicated by black hematin pigment on the liver and various other internal organs. Eggs were not detected in the gallbladder or feces of infected animals although mature flukes and eggs were recovered in the livers suggesting that, like cattle, feral swine can be infected but are aberrant hosts for the parasite and do not disseminate eggs.     

cag+ Helicobacter pylori induce transactivation of the epidermal growth factor receptor in AGS gastric epithelial cells

The gastric pathogen Helicobacter pylori is known to activate epithelial cell signaling pathways that regulate numerous inflammatory response genes. The aim of this study was to elucidate the pathway leading to extracellular signal-regulated kinase (ERK) 1/2 phosphorylation in H. pylori-infected AGS gastric epithelial cells. We find that H. pylori, via activation of the epidermal growth factor (EGF) receptor activates the small GTP-binding protein Ras, which in turn, mediates ERK1/2 phosphorylation. cag+ strains of H. pylori are able to induce greater EGF receptor activation than cag- strains, and studies with isogenic mutants indicate that an intact type IV bacterial secretion system is required for this effect. Blockade of EGF receptor activation using tyrphostin AG1478 prevents H. pylori-mediated Ras activation, inhibits ERK1/2 phosphorylation, and substantially decreases interleukin-8 gene expression and protein production. Investigations into the mechanism of EGF receptor activation, using heparin, a metalloproteinase inhibitor and neutralizing antibodies reveal that H. pylori transactivates the EGF receptor via activation of the endogenous ligand heparin-binding EGF-like growth factor. Transactivation of gastric epithelial cell EGF receptors may be instrumental in regulating both proliferative and inflammatory responses induced by cag+ H. pylori infection.     

IL-11 and IL-11Rα immunolocalisation at primate implantation sites supports a role for IL-11 in placentation and fetal development

Embryo implantation, endometrial stromal cell decidualization and formation of a functional placenta are critical processes in the establishment and maintenance of pregnancy. Interleukin (IL)-11 signalling is essential for adequate decidualization in the mouse uterus and IL-11 promotes decidualization in the human. IL-11 action is mediated via binding to the specific IL-11 receptor α (IL-11Rα). The present study examined immunoreactive IL-11 and IL-11Rα in cycling rhesus monkey endometrium, at implantation sites in cynomolgus and rhesus monkeys and in human first trimester decidua and defined distinct spatial and temporal patterns. In cycling rhesus monkey endometrium, IL-11 and IL-11Rα increased in both basalis and functionalis regions during the secretory compared with the proliferative phase, with changing cellular locations in luminal and glandular epithelium and stroma. The patterns were similar overall to those previously described in human endometrium. Differences were seen in immunostaining during implantation in cynomologus and rhesus monkey. In the cynomolgus, very little staining for IL-11 or IL-11Rα was seen in syncytio- and cyto-trophoblast cells in the villi between days 12 and 150 of pregnancy although there was moderate staining in cytotrophoblast in the shell between days 12 and 17 and in subpopulations of cytotrophoblast cells invading the arteries at day 17. By contrast in the rhesus monkey between days 24 and 35 of pregnancy and in human first trimester placenta, cyto- and syncytio-trophoblast in the villi but not cytotrophoblast in the shell were positively stained. The most intense staining for both IL-11 and IL-11Rα was present within the decidua in the maternal component of implantation sites in all three primates but moderate staining was also present in maternal vascular smooth muscle and glands perivascular cells and epithelial plaques. These results are consistent with a role for IL-11 both during decidualization and placentation in primates.     

Accelerated hand bone mineral density loss is associated with progressive joint damage in hands and feet in recent-onset rheumatoid arthritis

Introduction

To investigate whether accelerated hand bone mineral density (BMD) loss is associated with progressive joint damage in hands and feet in the first year of rheumatoid arthritis (RA) and whether it is an independent predictor of subsequent progressive total joint damage after 4 years.

Methods

In 256 recent-onset RA patients, baseline and 1-year hand BMD was measured in metacarpals 2-4 by digital X-ray radiogrammetry. Joint damage in hands and feet were scored in random order according to the Sharp-van der Heijde method at baseline and yearly up to 4 years.

Results

68% of the patients had accelerated hand BMD loss (>-0.003 g/cm²) in the first year of RA. Hand BMD loss was associated with progressive joint damage after 1 year both in hands and feet with odds ratios (OR) (95% confidence intervals [CI]) of 5.3 (1.3-20.9) and 3.1 (1.0-9.7). In univariate analysis, hand BMD loss in the first year was a predictor of subsequent progressive total joint damage after 4 years with an OR (95% CI) of 3.1 (1.3-7.6). Multivariate analysis showed that only progressive joint damage in the first year and anti-citrullinated protein antibody positivity were independent predictors of long-term progressive joint damage.

Conclusions

In the first year of RA, accelerated hand BMD loss is associated with progressive joint damage in both hands and feet. Hand BMD loss in the first year of recent-onset RA predicts subsequent progressive total joint damage, however not independent of progressive joint damage in the first year.     

An overview of malaria transmission from the perspective of Amazon Anopheles vectors

In the Americas, areas with a high risk of malaria transmission are mainly located in the Amazon Forest, which extends across nine countries. One keystone step to understanding the Plasmodium life cycle in Anopheles species from the Amazon Region is to obtain experimentally infected mosquito vectors. Several attempts to colonise Ano- pheles species have been conducted, but with only short-lived success or no success at all. In this review, we review the literature on malaria transmission from the perspective of its Amazon vectors. Currently, it is possible to develop experimental Plasmodium vivax infection of the colonised and field-captured vectors in laboratories located close to Amazonian endemic areas. We are also reviewing studies related to the immune response to P. vivax infection of Anopheles aquasalis, a coastal mosquito species. Finally, we discuss the importance of the modulation of Plasmodium infection by the vector microbiota and also consider the anopheline genomes. The establishment of experimental mosquito infections with Plasmodium falciparum, Plasmodium yoelii and Plasmodium berghei parasites that could provide interesting models for studying malaria in the Amazonian scenario is important. Understanding the molecular mechanisms involved in the development of the parasites in New World vectors is crucial in order to better determine the interaction process and vectorial competence.     

Biocontrol evaluation of extracts and a major component,clusianone, from Clusia fluminensis Planch. & Triana against Aedes aegypti

Studies evaluated the effects of hexanic extracts from the fruits and flowers ofClusia fluminensis and the main component of the flower extract, a purified benzophenone (clusianone), against Aedes aegypti. The treatment of larvae with the crude fruit or flower extracts from C. fluminensis did not affect the survival ofAe. aegypti (50 mg/L), however, the flower extracts significantly delayed development of Ae. aegypti. In contrast, the clusianone (50 mg/L) isolate from the flower extract, representing 54.85% of this sample composition, showed a highly significant inhibition of survival, killing 93.3% of the larvae and completely blocking development of Ae. aegypti. The results showed, for the first time, high activity of clusianone against Ae. aegypti that both killed and inhibited mosquito development. Therefore, clusianone has potential for development as a biopesticide for controlling insect vectors of tropical diseases. Future work will elucidate the mode of action of clusianone isolated from C. fluminensis.