Impact of intra- and interspecies variation of occludin on its function as coreceptor for authentic hepatitis C virus particles

Hepatitis C virus (HCV) is characterized by a narrow host range and high interindividual variability in the clinical course of infection. Both of these traits are thought to be largely due to genetic variation between species and between individual hosts. The tight junction component occludin (OCLN) is essential for HCV entry into host cells, and the differences between human and murine OCLN are thought to account in part for the inability of HCV to infect mice and hence preclude their use as a convenient small-animal model. This study assesses the impact of genetic variation in OCLN on cell culture-grown HCV (HCVcc) using a newly generated and characterized OCLN(low) subclone of the Huh-7.5 cell line (Huh-7.5 subclone in which endogenous OCLN expression has been downregulated by a short hairpin RNA). We report the frequency of coding nonsynonymous single nucleotide polymorphisms, i.e., polymorphisms resulting in amino acid exchanges, present in the human population and determine their ability to function as HCV (co)receptors. Moreover, we show that murine OCLN can sustain HCVcc entry, albeit with about 5-fold reduced efficiency compared to that of human OCLN. This reduction in efficiency is due solely to two amino acid residues previously identified by others using an HCV pseudoparticle approach. Finally, we use the Huh-7.5/OCLN(low) cell line to show that HCV spread between neighboring cells is strictly dependent on OCLN.     

Vertical Signalling Involves Transmission of Hox Information from Gastrula Mesoderm to Neurectoderm

Development and patterning of neural tissue in the vertebrate embryo involves a set of molecules and processes whose relationships are not fully understood. Classical embryology revealed a remarkable phenomenon known as vertical signalling, a gastrulation stage mechanism that copies anterior-posterior positional information from mesoderm to prospective neural tissue. Vertical signalling mediates unambiguous copying of complex information from one tissue layer to another. In this study, we report an investigation of this process in recombinates of mesoderm and ectoderm from gastrulae of Xenopus laevis. Our results show that copying of positional information involves non cell autonomous autoregulation of particular Hox genes whose expression is copied from mesoderm to neurectoderm in the gastrula. Furthermore, this information sharing mechanism involves unconventional translocation of the homeoproteins themselves. This conserved primitive mechanism has been known for three decades but has only recently been put into any developmental context. It provides a simple, robust way to pattern the neurectoderm using the Hox pattern already present in the mesoderm during gastrulation. We suggest that this mechanism was selected during evolution to enable unambiguous copying of rather complex information from cell to cell and that it is a key part of the original ancestral mechanism mediating axial patterning by the highly conserved Hox genes.     

Biochemical and Biophysical Response to Calcium Chloride Stress in Aspergillus niger and its Role in Malachite Green Degradation

Filamentous fungi show great promise in remediation of environmental contaminants such as industrial dyes. In the current study, Aspergillus niger (Genbank ID: JF437542) decolorized 82 % of the test dye malachite green (MG; 50 mg/l) during cultivation for 24 h. The organism decolorized only 6 % of the MG at higher concentration (250 mg MG/l) during the same time period and growth was inhibited at this higher MG concentration. Exposing A. niger to different types of stress resulted in variable impacts on ability to decolorize MG. CaCl₂ had the largest positive impact on decolorization. A. niger cultures treated with CaCl₂ (1 M) decolorized 46 % of the MG (250 mg/l) in 1 h compared to 6 % in untreated control cultures. CaCl₂ also increased catalase production in A. niger which strongly supported a direct relationship between stress response and decolorizing ability. Spectrophotometric measurement confirmed MG decolorization while Fourier transform infrared spectroscopy suggested that biodegradation of MG occurred. Cultures treated with CaCl₂ accumulated fewer toxic MG by-products than untreated cultures. CaCl₂-induced stress increased the permeability and conductivity of the fungal cell membrane. An observed increase in medium [H⁺] also suggested a change in Ca²⁺/H⁺ exchange capacity in the fungal cell. Calcium ions had a pronounced effect on membrane properties and this may have had an important impact on signal transduction. We conclude that A. niger decolorizes MG and that CaCl₂ enhances this process; the CaCl₂ effect appears to be associated with stress response.     

Impact of different levels of cinnamyl alcohol dehydrogenase down-regulation on lignins of transgenic tobacco plants

The effects of cinnamyl alcohol dehydrogenase (CAD, EC.1.1.1.195) down-regulation on lignin profiles of plants were analysed in four selected transgenic lines of tobacco (Nicotiana tabacum L. cv. Samsun) exhibiting different levels of CAD activity (8–56% of the control). A significant decrease in thioacidolysis yields (i.e. yield of β-O-4 linked monomers) and in the ratio of syringyl to guaiacyl monomers (S/G) was observed for three transgenic lines and the most drastic reduction (up to 50%) was correlated with the lowest level of CAD activity. Higher lignin extractability by mild alkali treatment was confirmed, and, in addition to a tenfold increase in C₆-C₁ aldehydes, coniferyl aldehyde was detected by high-performance liquid chromatography in the alkali extracts from the xylem of transgenic plants. In-situ polymerisation of cinnamyl aldehydes in stem sections of untransformed tobacco gave a xylem cell wall coloration strikingly similar to the reddish-brown coloration of the xylem of antisense CAD-down-regulated plants. Overall, these data provide new arguments for the involvement of polymerised cinnamyl aldehydes in the formation of the red-coloured xylem of CAD-down-regulated plants. Received: 24 January 1997 / Accepted: 14 May 1997     

The Silk Road Health Project: How Mobility and Migration Status Influence HIV Risks among Male Migrant Workers in Central Asia

Objectives

We examined whether mobility, migrant status, and risk environments are associated with sexually transmitted infections (STIs) and HIV risk behaviors (e.g. sex trading, multiple partners, and unprotected sex).

Methods

We used Respondent Driven Sampling (RDS) to recruit external male migrant market vendors from Kyrgyzstan, Uzbekistan, and Tajikistan as well internal migrant and non-migrant market vendors from Kazakhstan. We conducted multivariate logistic regressions to examine the effects of mobility combined with the interaction between mobility and migration status on STIs and sexual risk behaviors, when controlling for risk environment characteristics.

Results

Mobility was associated with increased risk for biologically-confirmed STIs, sex trading, and unprotected sex among non-migrants, but not among internal or external migrants. Condom use rates were low among all three groups, particularly external migrants. Risk environment factors of low-income status, debt, homelessness, and limited access to medical care were associated with unprotected sex among external migrants.

Conclusion

Study findings underscore the role mobility and risk environments play in shaping HIV/STI risks. They highlight the need to consider mobility in the context of migration status and other risk environment factors in developing effective prevention strategies for this population.     

Synthesis and evaluation of cholecystokinin trimers: A multivalent approach to pancreatic cancer detection and treatment

In the quest for novel tools for early detection and treatment of cancer, we propose the use of multimers targeting overexpressed receptors at the cancer cell surface. Indeed, multimers are prone to create multivalent interactions, more potent and specific than their corresponding monovalent versions, thus enabling the potential for early detection. There is a lack of tools for early detection of pancreatic cancer, one of the deadliest forms of cancer, but CCK2-R overexpression on pancreatic cancer cells makes CCK based multimers potential markers for these cells. In this Letter, we describe the synthesis and evaluation of CCK trimers targeting overexpressed CCK2-R.     

Nitrate modulation of Bacillus sp. biofilm components: a proposed model for sustainable bioremediation

Biotechnology Letters - The presence of different pollutants in wastewater hinder microbial growth, compromise enzymatic activity or compete for electrons required for bioremediation pathway....     

Effects of guanosine on insulin secretion and adenylyl and guanylyl cyclase activities of isolated rat islets of Langerhans

The effect of guanosine on insulin secretion adenylyl and guanylyl cyclase activities of isolated rat islets of Langerhans was investigated. Guanosine (1–100 μM) inhibited glucose, tolbutamide, theophylline and prostaglandin E₂-stimulated insulin secretion although it failed to affect glucagon stimulated secretion. Prostaglandin E₂-stimulated adenylyl cyclase of islets was inhibited by guanosine although guanosine had no effect on basal, fluoride, glucagon or GTP-stimulated activity. Guanosine markedly decreased basal guanylyl cyclase activity of islets.These results suggest that guanosine may affect insulin release by inhibiting adenylyl and guanylyl cyclase activities in the ß-cell thereby decreasing the intracellular concentrations of cyclic nucleotides.This effect may be important in modulating the secretory response of the islets to a variety of hormonal agents.     

Micropropagation and production of arbutin in oriental strawberry tree (<Emphasis Type="Italic">Arbutus andrachne</Emphasis> L.)

A protocol for micropropagation of Arbutus andrachne from seeds was developed. Results indicated that none of the seeds cultured on Murashige and Skoog (MS) medium, with or without plant growth regulators (PGRs), germinated. Seeds soaked in 250 mg l⁻¹ gibberellic acid (GA₃) at 4°C for 3 days, then cultured on water-agar medium containing 2.0 mg l⁻¹ GA₃ exhibited 80–100% germination and developed into usable seedlings. Shoot proliferation was tested on MS or B5 medium containing different concentrations of cytokinin. No shoot proliferation was observed on PGR-free medium. Proliferation was more successful on MS than on B5 medium. On both media, the most successful proliferation was obtained using zeatin as a cytokinin type. Rooting was tested on MS medium containing different concentrations of auxin. Rooting failed on PGR-free medium and on medium containing indole-3-acetic acid (IAA), 0.25 or 0.5 mg l⁻¹ indole-3-butyric acid (IBA), or 0.25, 0.5 or 2.0 mg l⁻¹ α-naphthaleneacetic acid (NAA). Rooting (40%) was most successful with 1.0 mg l⁻¹ NAA. Rooted plantlets exhibited 80% survival in all mixtures of peatmoss and perlite, and acclimatized plants were successfully grown in the greenhouse. Quantitative analysis of arbutin performed on in vivo and in vitro leaves using high-performance liquid chromatography (HPLC) revealed that in vivo leaves contained higher arbutin content (0.3–0.81% w/w) than in vitro leaves (0.09% w/w). The highest yield of arbutin in vivo was detected in leaves collected in August, and the lowest yield in leaves collected in December.