CNS melanocortin and leptin effects on stearoyl-CoA desaturase-1 and resistin expression

The objective of this study was to determine whether centrally administered leptin decreased liver and adipose SCD1 expression or adipose resistin expression, and whether these effects were mediated by central melanocortin receptors. Male Sprague-Dawley rats were injected into the lateral cerebral ventricle (i.c.v.) once daily for 4 days with artificial cerebrospinal fluid (aCSF, 5 microl), leptin (10 microg) or MTII (0.1 nmol); two other groups were pretreated icv with the melanocortin antagonist, SHU9119 (1.0 nmol), followed by leptin or MTII. Epididymal and inguinal adipose tissue and liver were collected after rats were killed and mRNA expression of SCD1 and resistin was measured. Both leptin and MTII reduced SCD1 expression and pretreatment with SHU9119 reversed their effects. Neither leptin nor MTII affected resistin expression, but it was increased by SHU9119. These results show that CNS melanocortin receptors are likely mediators of leptin's effects on SCD1 expression in liver and adipose tissue, The findings were inconclusive concerning the effects of leptin and melanocortins on adipose resistin expression.     

Isolation and identification of gastrointestinal microbiota from the short-nosed fruit bat Cynopterus brachyotis brachyotis

Studies on the microbial ecology of gut microbiota in bats are limited and such information is necessary in determining the ecological significance of these hosts. Short-nosed fruit bats (Cynopterus brachyotis brachyotis) are good candidates for microbiota studies given their close association with humans in urban areas. Thus, this study explores the gut microbiota of this species from Peninsular Malaysia by means of biochemical tests and 16S rRNA gene sequences analysis. The estimation of viable bacteria present in the stomach and intestine of C. b. brachyotis ranged from 3.06 × 10¹⁰ to 1.36 × 10¹⁵ CFU/ml for stomach fluid and 1.92 × 10¹⁰ to 6.10 × 10¹⁵ CFU/ml for intestinal fluid. A total of 34 isolates from the stomach and intestine of seven C. b. brachyotis were retrieved. A total of 16 species of bacteria from eight genera (Bacillus, Enterobacter, Enterococcus, Escherichia, Klebsiella, Pantoea, Pseudomonas and Serratia) were identified, Enterobacteriaceae being the most prevalent, contributing 12 out of 16 species isolated. Most isolates from the Family Enterobacteriaceae have been reported as pathogens to humans and wildlife. With the possibility of human wildlife transmission, the findings of this study focus on the importance of bats as reservoirs of potential bacterial pathogens.     

Alpha3Na+/K+-ATPase is a neuronal receptor for agrin

Agrin, through its interaction with the receptor tyrosine kinase MuSK, mediates accumulation of acetylcholine receptors (AChR) at the developing neuromuscular junction. Agrin has also been implicated in several functions in brain. However, the mechanism by which agrin exerts its effects in neural tissue is unknown. Here we present biochemical evidence that agrin binds to the alpha3 subunit of the Na+/K+-ATPase (NKA) in CNS neurons. Colocalization with agrin binding sites at synapses supports the hypothesis that the alpha3NKA is a neuronal agrin receptor. Agrin inhibition of alpha3NKA activity results in membrane depolarization and increased action potential frequency in cortical neurons in culture and acute slice. An agrin fragment that acts as a competitive antagonist depresses action potential frequency, showing that endogenous agrin regulates native alpha3NKA function. These data demonstrate that, through its interaction with the alpha3NKA, agrin regulates activity-dependent processes in neurons, providing a molecular framework for agrin action in the CNS.     

Should symptomatic menopausal women be offered hormone therapy?

Many physicians remain uncertain about prescribing hormone therapy for symptomatic women at the onset of menopause. The American Society for Reproductive Medicine (ASRM) convened a multidisciplinary group of healthcare providers to discuss the efficacy and risks of hormone therapy for symptomatic women, and to determine whether it would be appropriate to treat women at the onset of menopause who were complaining of menopausal symptoms. MAJOR FINDINGS: Numerous controlled clinical trials consistently demonstrate that hormone therapy, administered via oral, transdermal, or vaginal routes, is the most effective treatment for vasomotor symptoms. Topical vaginal formulations of hormone therapy should be preferred when prescribing solely for the treatment of symptoms of vulvar and vaginal atrophy. Data from the Women's Health Initiative indicate that the overall attributable risk of invasive breast cancer in women receiving estrogen plus progestin was 8 more cases per 10,000 women-years. No increased risk for invasive breast cancer was detected for women who never used hormone therapy in the past or for those receiving estrogen only. Hormone therapy is not effective for the treatment of cardiovascular disease and that the risk of cardiovascular disease with hormone therapy is principally in older women who are considerably postmenopause. CONCLUSIONS: Healthy symptomatic women should be offered the option of hormone therapy for menopausal symptoms. Symptom relief with hormone therapy for many younger women (at the onset of menopause) with menopausal symptoms outweighs the risks and may provide an overall improvement in quality of life. Hormone therapy should be individualized for symptomatic women. This involves tailoring the regimen and dose to individual needs.     

Regulation of TLR2 Expression and Function in Human Airway Epithelial Cells

Toll-like receptor (TLR1–6) mRNAs are expressed in normal human bronchial epithelial cells with higher basal levels of TLR3. TLR2 mRNA and plasma membrane protein expression was enhanced by pretreatment with Poly IC, a synthetic double-stranded RNA (dsRNA) known to activate TLR3. Poly IC also enhanced mRNA expression of adaptor molecules (MyD88 and TIRAP) and coreceptors (Dectin-1 and CD14) involved in TLR2 signaling. Additionally, mRNA expression of TLR3 and dsRNA-sensing proteins MDA5 and RIG-I increased following Poly IC treatment. In contrast, basal mRNA expression of TLR5 and TLR2 coreceptor CD36 was reduced by 77% and 62%, respectively. ELISA of apical and basolateral solutions from Poly IC-stimulated monolayers revealed significantly higher levels of IL-6 and GM-CSF compared with the TLR2 ligand PAM₃CSK₄. Pretreatment with anti-TLR2 blocking antibody inhibited the PAM₃CSK₄-induced increase in IL-6 secretion after Poly IC exposure. An increase in IL-6 secretion was also observed in cells stimulated with Alternaria extract after pretreatment with Poly IC. However, IL-6 secretion was not stimulated by zymosan or lipothechoic acid (LTA). These data demonstrated that upregulation of TLR2 following exposure to dsRNA enhances functional responses of the airway epithelium to certain (PAM₃CSK₄), but not all (zymosan, LTA) TLR2 ligands and that this is likely due to differences in coreceptor expression.     

A positive autoregulatory loop of LMP1 expression and STAT activation in epithelial cells latently infected with Epstein-Barr virus

STAT3 and STAT5 are constitutively activated and nuclear in nasopharyngeal carcinoma (NPC) cells. In normal signaling, STATs are only transiently activated. To investigate whether Epstein-Barr virus (EBV), and in particular the protein LMP1, contributes to sustained STAT phosphorylation and activation in epithelial cells, we examined STAT activity in two sets of paired cell lines, HeLa, an EBV-converted HeLa cell line, HeLa-Bx1, the NPC-derived cell line CNE2-LNSX, and an LMP1-expressing derivative, CNE2-LMP1. EBV infection was associated with a significant increase in the tyrosine-phosphorylated forms of STAT3 and STAT5 in HeLa-Bx1 cells. This effect correlated with LMP1 expression, since phosphorylated STAT3 and STAT5 levels were also increased in CNE2-LMP1 cells relative to the control CNE2-LNSX cells. No change was observed in STAT1 or STAT6 phosphorylation in these cell lines, nor was there a significant change in the levels of total STAT3, STAT5, STAT1, or STAT6 protein. Tyrosine phosphorylation allows the normally cytoplasmic STAT proteins to enter the nucleus and bind to their recognition sequences in responsive promoters. The ability of LMP1 to activate STAT3 was further established by immunofluorescence assays in which coexpression of LMP1 in transfected cells was sufficient to mediate nuclear relocalization of Flag-STAT3 and by an electrophoretic mobility shift assay which showed that LMP1 expression in CNE2-LNSX cells was associated with increased endogenous STAT3 DNA binding activity. In addition, the activity of a downstream target of STAT3, c-Myc, was upregulated in HeLa-Bx1 and CNE2-LMP1 cells. A linkage was established between interleukin-6 (IL-6)- and LMP1-mediated STAT3 activation. Treatment with IL-6 increased phosphorylated STAT3 levels in CNE2-LNSX cells, and conversely, treatment of CNE2-LMP1 cells with IL-6 neutralizing antibody ablated STAT3 activation and c-Myc upregulation. The previous observation that STAT3 activated the LMP1 terminal repeat promoter in reporter assays was extended to show upregulated expression of endogenous LMP1 mRNA and protein in HeLa-Bx1 cells transfected with a constitutively activated STAT3. A model is proposed in which EBV infection of an epithelial cell containing activated STATs would permit LMP1 expression. This in turn would establish a positive feedback loop of IL-6-induced STAT activation, LMP1 and Qp-EBNA1 expression, and viral genome persistence.     

The microbial plankton of Lake Fryxell,southern Victoria Land,Antarctica during the summers of 1992 and 1994

 Samples collected from Lake Fryxell, southern Victoria Land, Antarctica in January 1992 and 1994 were analysed for the abundance of bacterioplankton and the diversity and abundance of protistan plankton. At the times of sampling, 14 ciliate species and 10 species of autotrophic flagellate were recorded. The samples contained two species of rotifer (Philodina spp.), which formed the first record of planktonic metazoans in the Dry Valley lakes of this region of Antarctica. Bacterial concentrations ranged between 1.0 and 3.8×10⁸ l^-1 in the upper oxic waters increasing to 20×10⁸ l^-1 in the anoxic waters. Heterotrophic flagellates decreased in abundance down the oxygenated water column, disappearing completely at 9 m, and ranged between 0.28 and 7.39×10⁵ l^-1 in abundance. Autotrophic flagellates were much more abundant exhibiting a number of distinct peaks down the water column (1.89–25.3×10⁸ l^-1). The ciliated protozoa were very abundant (up to 7720 l^-1) in relation to flagellate and bacterial numbers, typical of oligotrophic lakes world-wide. The distribution of the protistan plankton showed marked zonation, probably in response to the differing salinity and temperature gradients in the water column. Possible trophic interactions are discussed and comparisons with other continental Antarctic lakes made. Received: 29 November 1995/Accepted: 18 February 1996     

Single-particle tracking of immunoglobulin E receptors (FcεRI) in micron-sized clusters and receptor patches

When mast cells contact a monovalent antigen-bearing fluid lipid bilayer, IgE-loaded FcεRI receptors aggregate at contact points and trigger degranulation and the release of immune activators. We used two-color total internal reflection fluorescence microscopy and single-particle tracking to show that most fluorescently labeled receptor complexes diffuse freely within these micron-size clusters, with a diffusion coefficient comparable to free receptors in resting cells. At later times, when the small clusters coalesce to form larger patches, receptors diffuse even more rapidly. In all cases, Monte Carlo diffusion simulations ensured that the tracking results were free of bias, and distinguished biological from statistical variation. These results show the diversity in receptor mobility in mast cells, demonstrating at least three distinct states of receptor diffusivity.