HIV-particles in spermatozoa of patients with AIDS and their transfer into the oocyte

By immunocytochemistry and in situ hybridization at the electron microscopy level, and by the PCR technique, we have shown that HIV-1 binds and enters normal sperm; that viral particles, their antigens, and nucleic acid are present in sperm from HIV-1 infected men; and that such sperm can transfer HIV-1 like particles to normal human oocytes. We also present evidence that a galactosylceramide-like compound is present on the sperm membrane and could function as an alternative receptor for HIV.     

Unusual pattern of bacterial ice nucleation gene evolution

Bacterial ice nucleation activity (INA+ phenotype) can be traced to the product of a single gene, ina. A remarkably sparse distribution of this phenotype within three bacterial genera indicates that the ina gene may have followed an unusual evolutionary path. Southern blot analyses, coupled with assays for ice-nucleating ability, revealed that within four bacterial species an ina gene is present in some strains but absent from others. Results of hybridization experiments using DNA fragments that flank the ina gene suggested that the genotypic dimorphism of ina may be anomalous. A phylogenetic analysis of 16S ribosomal RNA gene sequences from a total of 14 ina+ and ina- bacterial strains indicated that the ina+ bacteria are not monophyletic but instead phylogenetically interspersed among ina- bacteria. The relationships of ina+ bacteria inferred from ina sequence did not coincide with those inferred from the 16S data. These results suggest the possibility of horizontal transfer in the evolution of bacterial ina genes.      

Retinitis pigmentosa: rapid neurodegeneration is governed by slow cell death mechanisms

For most neurodegenerative diseases the precise duration of an individual cell''s death is unknown, which is an obstacle when counteractive measures are being considered. To address this, we used the rd1 mouse model for retinal neurodegeneration, characterized by phosphodiesterase-6 (PDE6) dysfunction and photoreceptor death triggered by high cyclic guanosine-mono-phosphate (cGMP) levels. Using cellular data on cGMP accumulation, cell death, and survival, we created mathematical models to simulate the temporal development of the degeneration. We validated model predictions using organotypic retinal explant cultures derived from wild-type animals and exposed to the selective PDE6 inhibitor zaprinast. Together, photoreceptor data and modeling for the first time delineated three major cell death phases in a complex neuronal tissue: (1) initiation, taking up to 36 h, (2) execution, lasting another 40 h, and finally (3) clearance, lasting about 7 h. Surprisingly, photoreceptor neurodegeneration was noticeably slower than necrosis or apoptosis, suggesting a different mechanism of death for these neurons.     

Visceral adipose inflammation in obesity is associated with critical alterations in tregulatory cell numbers

Background

The development of insulin resistance (IR) in mouse models of obesity and type 2 diabetes mellitus (DM) is characterized by progressive accumulation of inflammatory macrophages and subpopulations of T cells in the visceral adipose. Regulatory T cells (Tregs) may play a critical role in modulating tissue inflammation via their interactions with both adaptive and innate immune mechanisms. We hypothesized that an imbalance in Tregs is a critical determinant of adipose inflammation and investigated the role of Tregs in IR/obesity through coordinated studies in mice and humans.

Methods and Findings

Foxp3-green fluorescent protein (GFP) “knock-in” mice were randomized to a high-fat diet intervention for a duration of 12 weeks to induce DIO/IR. Morbidly obese humans without overt type 2 DM (n = 13) and lean controls (n = 7) were recruited prospectively for assessment of visceral adipose inflammation. DIO resulted in increased CD3⁺CD4⁺, and CD3⁺CD8⁺ cells in visceral adipose with a striking decrease in visceral adipose Tregs. Treg numbers in visceral adipose inversely correlated with CD11b⁺CD11c⁺ adipose tissue macrophages (ATMs). Splenic Treg numbers were increased with up-regulation of homing receptors CXCR3 and CCR7 and marker of activation CD44. In-vitro differentiation assays showed an inhibition of Treg differentiation in response to conditioned media from inflammatory macrophages. Human visceral adipose in morbid obesity was characterized by an increase in CD11c⁺ ATMs and a decrease in foxp3 expression.

Conclusions

Our experiments indicate that obesity in mice and humans results in adipose Treg depletion. These changes appear to occur via reduced local differentiation rather than impaired homing. Our findings implicate a role for Tregs as determinants of adipose inflammation.     

Glucose-6-phosphate dehydrogenase deficiency in northern Mexico and description of a novel mutation

Glucose-6-phosphate dehydrogenase deficiency (G6PD) is the most common enzyme pathology in humans; it is X-linked inherited and causes neonatal hyperbilirubinaemia, chronic nonspherocytic haemolytic anaemia and drug-induced acute haemolytic anaemia. G6PD deficiency has scarcely been studied in the northern region of Mexico, which is important because of the genetic heterogeneity described in Mexican population. Therefore, samples from the northern Mexico were biochemically screened for G6PD-deficiency, and PCR-RFLPs, and DNA sequencing used to identify mutations in positive samples. The frequency of G6PD deficiency in the population was 0.95% (n = 1993); the mutations in 86% of these samples were G6PD A^?202A/376G , G6PD A^?376G/968C and G6PD Santamaria^376G/542T . Contrary to previous reports, we demonstrated that G6PD deficiency distribution is relatively homogenous throughout the country (P = 0.48336), and the unique exception with high frequency of G6PD deficiency does not involve a coastal population (Chihuahua: 2.4%). Analysis of eight polymorphic sites showed only 10 haplotypes. In one individual we identified a new G6PD mutation named Mexico DF^193A>G (rs199474830), which probably results in a damaging functional effect, according to PolyPhen analysis. Proteomic impact of the mutation is also described.     

Macrophage migration inhibitory factor plays a role in the regulation of microfold (M) cell-mediated transport in the gut

It has been shown previously that certain bacteria rapidly (3 h) up-regulated in vivo microfold cell (M cell)-mediated transport of Ag across the follicle-associated epithelium of intestinal Peyer's patch. Our aim was to determine whether soluble mediators secreted following host-bacteria interaction were involved in this event. A combination of proteomics and immunohistochemical analyses was used to identify molecules produced in the gut in response to bacterial challenge in vivo; their effects were then tested on human intestinal epithelial cells in vitro. Macrophage migration inhibitory factor (MIF) was the only cytokine produced rapidly after in vivo bacterial challenge by CD11c(+) cells located beneath the M cell-rich area of the follicle-associated epithelium of the Peyer's patch. Subsequently, in vitro experiments conducted using human Caco-2 cells showed that, within hours, MIF induced the appearance of cells that showed temperature-dependent transport of microparticles and M cell-specific bacterium Vibrio cholerae, and acquired biochemical features of M cells. Furthermore, using an established in vitro human M cell model, we showed that anti-MIF Ab blocked Raji B cell-mediated conversion of Caco-2 cells into Ag-sampling cells. Finally, we report that MIF(-/-) mice, in contrast to wild-type mice, failed to show increased M cell-mediated transport following in vivo bacterial challenge. These data show that MIF plays a role in M cell-mediated transport, and cross-talk between bacteria, gut epithelium, and immune system is instrumental in regulating key functions of the gut, including M cell-mediated Ag sampling.     

Structural basis of GC-1 selectivity for thyroid hormone receptor isoforms

Background

Multiple protein templates are commonly used in manual protein structure prediction. However, few automated algorithms of selecting and combining multiple templates are available.

Results

Here we develop an effective multi-template combination algorithm for protein comparative modeling. The algorithm selects templates according to the similarity significance of the alignments between template and target proteins. It combines the whole template-target alignments whose similarity significance score is close to that of the top template-target alignment within a threshold, whereas it only takes alignment fragments from a less similar template-target alignment that align with a sizable uncovered region of the target. We compare the algorithm with the traditional method of using a single top template on the 45 comparative modeling targets (i.e. easy template-based modeling targets) used in the seventh edition of Critical Assessment of Techniques for Protein Structure Prediction (CASP7). The multi-template combination algorithm improves the GDT-TS scores of predicted models by 6.8% on average. The statistical analysis shows that the improvement is significant (p-value < 10^-4). Compared with the ideal approach that always uses the best template, the multi-template approach yields only slightly better performance. During the CASP7 experiment, the preliminary implementation of the multi-template combination algorithm (FOLDpro) was ranked second among 67 servers in the category of high-accuracy structure prediction in terms of GDT-TS measure.

Conclusion

We have developed a novel multi-template algorithm to improve protein comparative modeling.