Inhibition of protein kinase C and anti-CD3-induced Ca2+ influx in Jurkat T cells by a synthetic peptide with sequence identity to HIV-1 gp41

We have previously shown that a synthetic peptide containing env residues 581-597 from HIV-1 inhibits lymphoproliferation of human PBMC. We have investigated the molecular mechanism(s) by which this HIV-1-derived peptide inhibits CD3-mediated signal transduction. We show that the peptide containing residues 581-597 from the HIV-1 transmembrane protein gp41 specifically inhibited the intracellular Ca2+ influx in Jurkat cells stimulated by the mAb OKT3 whereas it had no effect on the production of inositol triphosphate. In addition, the peptide inhibited protein kinase C (pkC)-mediated phosphorylation of the CD3 gamma-chain in intact cells and directly inhibited partially purified pkC. The inhibition was noncompetitive with respect to the substrates histone and ATP and independent of the regulatory domain of the enzyme. Furthermore, the peptide required internalization for inhibitory activity because no inhibition of lymphoproliferation was observed when cells were treated with peptide at 4 degrees C. Based on these results obtained with the peptide aa581-597, we postulate that the transmembrane protein gp41 of HIV-1 may inhibit pkC activity and thus block pkC-dependent immune function contributing to the immunosuppression of HIV-1-infected individuals.     

Genetic structure of the Painted Bunting and its implications for conservation of migratory populations

The Painted Bunting Passerina ciris is a Neotropical songbird which breeds primarily in the USA during the summer and migrates to Mexico, Central America, southern Florida and the Caribbean over the winter. Male Painted Buntings are brightly coloured, which makes them highly sought after as pets, particularly in Mexico, Central America and Europe. We used short sequence repeats (microsatellite DNA) to investigate the population genetic structure of the Painted Bunting and its implications in conservation management of migratory populations. We found a detectable level of population differentiation as revealed by pairwise F_ST and R_ST comparisons and Bayesian clustering analyses, with strong support for differentiation between eastern and western Painted Buntings (e.g. Oklahoma and Georgia F_ST = 0.1; P = 0.005; R_ST = 0.18; P = 0.04) in accordance with previous mitochondrial DNA analysis. We recovered additional support for two sub‐groups within the western clade. While linking migrant songbirds captured outside of the USA to their breeding populations remains a challenge, we show that natural levels of population genetic differentiation can be detected via microsatellite DNA markers and exploited in migratory connectivity studies. We also demonstrate the potential utility of our low‐cost markers for population identification of birds recovered from the pet trade by screening a small subset of samples (n = 5) collected as part of wildlife tracking. We discuss the implications of our results for future efforts to understand patterns of population decline in Painted Buntings more generally, as well as how we might expand this methodology to combat illegal pet‐trade activity in this and other songbird species.     

Influence of 4-hydroxynonenal on chemiluminescence production by unstimulated and opsonized zymosan-stimulated human neutrophils

The lipid peroxidation product 4-hydroxy-2, 3-trans-nonenal (HNE) has a spectrum of biological effects on different cell types depending on the concentrations tested. In particular micromolar HNE concentrations stimulate neutrophil migration and polarization whereas higher doses inhibit. In our experimental conditions, fMet-Leu-Phe (fMLP) increased CL production of both unstimulated and zymosan-stimulated neutrophils, whereas cell stimulation with low HNE concentrations as well as zymosan addition to HNE incubated cells did not enhance light emission. In contrast 10(-4) M HNE reduced CL emission by unstimulated cells nearly to background values, completely depressed CL production by zymosan-stimulated cells and reduced phagocytosis. Cysteine was found to be able to counteract the HNE effect by about 70 per cent. The possibility that this aldehyde could exert its inhibitory effect through the alkylation of NADPH-oxidase SH-groups is postulated. Moreover, our present data on differences observed between fMLP and HNE indicate a different chemotactic mechanism induced by these two classes of compounds and lead to the conclusion that the local functional features of the attracted cells may be different.     

Cortical propagation tracks functional recovery after stroke

Stroke is a debilitating condition affecting millions of people worldwide. The development of improved rehabilitation therapies rests on finding biomarkers suitable for tracking functional damage and recovery. To achieve this goal, we perform a spatiotemporal analysis of cortical activity obtained by wide-field calcium images in mice before and after stroke. We compare spontaneous recovery with three different post-stroke rehabilitation paradigms, motor training alone, pharmacological contralesional inactivation and both combined. We identify three novel indicators that are able to track how movement-evoked global activation patterns are impaired by stroke and evolve during rehabilitation: the duration, the smoothness, and the angle of individual propagation events. Results show that, compared to pre-stroke conditions, propagation of cortical activity in the subacute phase right after stroke is slowed down and more irregular. When comparing rehabilitation paradigms, we find that mice treated with both motor training and pharmacological intervention, the only group associated with generalized recovery, manifest new propagation patterns, that are even faster and smoother than before the stroke. In conclusion, our new spatiotemporal propagation indicators could represent promising biomarkers that are able to uncover neural correlates not only of motor deficits caused by stroke but also of functional recovery during rehabilitation. In turn, these insights could pave the way towards more targeted post-stroke therapies.     

Dietary xenosterols lead to infertility and loss of abdominal adipose tissue in sterolin-deficient mice

The investigation of the human disease sitosterolemia (MIM 210250) has shed light not only on the pathways by which dietary sterols may traffic but also on how the mammalian body rids itself of cholesterol and defends against xenosterols. Two genes, ABCG5 and ABCG8, located at the sitosterolemia locus, each encodes a membrane-bound ABC half-transporter and constitutes a functional unit whose activity has now been shown to account for biliary and intestinal sterol excretion. Knockout mice deficient in Abcg5 or Abcg8 recapitulate many of the phenotypic features of sitosterolemia. During the course of our studies to characterize these knockout mice, we noted that these mice, raised on normal rodent chow, exhibited infertility as well as loss of abdominal fat. We show that, although sitosterolemia does not lead to any structural defects or to any overt endocrine defects, fertility could be restored if xenosterols are specifically blocked from entry and that the loss of fat is also reversed by a variety of maneuvers that limit xenosterol accumulation. These studies show that xenosterols may have a significant biological impact on normal mammalian physiology and that the Abcg5 or Abcg8 knockout mouse model may prove useful in investigating the role of xenosterols on mammalian physiology.     

Binding of the lipid peroxidation product 4-hydroxynonenal to human polymorphonuclear leukocytes

4-Hydroxynonenal (HNE) is produced during peroxidation of polyunsaturated fatty acids. It exerts a chemokinetic effect on human polymorphonuclear leukocytes (PMN). Investigations of this mechanism were performed. The results indicate that [³H]-HNE binding to PMN results both in non-specific bonds to the numerous SH groups of the cells and in binding to a saturable, reversible and specific HNE site. Scatchard analysis revealed that this is a single site with an apparent affinity constant of 319 nM and a density of 1·57 pmol (10⁶)^?1 cells. This specific binding site may be involved in the chemokinetic effect of HNE.     

Identification of the endocrine cells detected by the monoclonal antibody HISL-19 in human tissues.

The human endocrine cells reacting with the monoclonal antibody HISL-19 were identified with hormone antisera of proven specificity using a double immunostaining procedure. The epitope for HISL-19 was found in all types of pituitary cells except ACTH cells, in thyroid C cells, in all types of adrenal medullary and pancreatic islet cells and in somatostatin and pancreatic polypeptide cells of the gastrointestinal mucosa. No staining was found in parathyroid cells and in most gastrointestinal endocrine cells. Either paranuclear focal accumulation or diffuse cytoplasmic distribution of immunoreactive material were found. The spectrum of HISL-19 immunoreactive cells was found to be only in part complementary to that of cells immunoreactive for chromogranin A. Thus, it is concluded that the monoclonal antibody HISL-19 is a useful addition to other immunohistochemical markers for the detection of cells showing neuroendocrine features.