The effect of leptin on Lep expression is tissue-specific and nutritionally regulated.

Leptin, the product of the Obese (Lep) gene, orchestrates behavioral and metabolic responses to nutrient intake. Here, we demonstrate tissue-specific autoregulation of Lep. Moderate increases in circulating leptin considerably decreased Lep expression in adipose tissue and induced lep expression in skeletal muscle, a tissue that normally does not express this gene. Changes in nutrient availability resulted in rapid alterations in Lep autoregulation. These findings demonstrate negative feedback regulation of Lep in fat, and indicate that leptin secretion can function as a vehicle of 'cross-talk' between adipose tissue and skeletal muscle, leading to tissue-specific modulation of the 'leptin signal'.     

Conversion of bovine pancreatic DNase I to a repair endonuclease with a high selectivity for abasic sites.

Bovine pancreatic deoxyribonuclease I (DNase I) is a nuclease of relatively low specificity which interacts with DNA in the minor groove. No contacts are made between the protein and the major groove of the nucleic acid. DNase I is structurally homologous to exonuclease III, a DNA-repair enzyme with multiple activities. One of the main differences between the two enzymes is the presence of an additional alpha-helix in exonuclease III, in a position suggestive of interaction with the major groove of DNA. Recombinant DNA techniques have been used to add 14 amino acids, comprising the 10 amino acids of the exonuclease III alpha-helix flanked by a glycine rich region, to DNase I. The polypeptide has been inserted after serine 174, an amino acid on the surface of DNase I corresponding to the location of the extra alpha-helix in exonuclease III. The recombinant protein, DNase-exohelix, has been purified and its catalytic activities towards DNA investigated. The recombinant protein demonstrated a high selectivity for endonucleolytic cleavage at abasic sites in DNA, a property of exonuclease III but not native DNase I. Thus the insertion of 14 amino acids at Ser174, converts DNase I to an exonuclease III-like enzyme with DNA-repair properties.     

Derivation and characterization of human embryonic stem cell lines from the Chinese population

Human embryonic stem cells(hESCs) can self-renew indefinitely and differentiate into all cell types in the human body.Therefore,they are valuable in regenerative medicine,human developmental biology and drug discovery.A number of hESC lines have been derived from the Chinese population, but limited of them are available for research purposes.Here we report the derivation and characterization of two hESC lines derived from human blastocysts of Chinese origin.These hESCs express alkaline phosphatase and hE...     

Chimeras of the integrin beta subunit mid-region reveal regions required for heterodimer formation and for activation.

A central region of the beta2 integrin subunit, RN (residues D300 to C459), was replaced by the equivalent sequences from beta1 and beta7 to give the chimeras beta2RN1 and beta2RN7. Whilst the former construct failed to form heterodimer at the cell surface with alphaL, the later of these could be expressed together with the alphaL subunit to form a variant LFA-1. Based on recent modelling work, the RN region consists of two parts, one is the C-terminal end of the putative A-domain (RB, residues D300 to A359), and the other the mid-region (BN, residues Y360 to C459). Chimeras exchanging the two component regions were made. Of the four resultant chimeras, only the beta2RB1 chimera failed to support LFA-1 expression. Thus the beta1 specific residues of this region affect the interaction with the alphaL subunit. Whereas the alphaL/beta2RB7 LFA-1 variant is wildtype like with respect to ICAM-1 adhesion, the alphaLbeta2BN1 and alphaLbeta2BN7, as well as the alphaLbeta2RN7, variants are more adhesive than the wildtype. These results suggest that an authentic beta2 mid-region is, in part, required for maintaining the LFA-1 in a resting state.     

Chicken IL-6 is a heat-shock gene

The febrile response is elicited by pyrogenic cytokines including IL-6 in response to microorganism infections and diseases in vertebrates. Mammalian HSF1, which senses elevations in temperature, negatively regulates the response by suppressing pyrogenic cytokine expression. We here showed that HSF3, an avian ortholog of mammalian HSF1, directly binds to and activates IL-6 during heat shock in chicken cells. Other components of the febrile response mechanism, such as IL-1β and ATF3, were also differently regulated in mammalian and chicken cells. These results suggest that the febrile response is exacerbated by a feed-forward circuit composed of the HSF3-IL-6 pathway in birds.     

Taurine transporter is expressed in vascular smooth muscle cells

Summary. The regulation of vascular smooth muscle cells (VSMCs) function by taurine has been a subject of increasing interest and investigation, and taurine is taken up into cells through a specific transporter system, the taurine transporter (TAUT). In the present study, we examined the expression of TAUT in VSMCs and the kinetic parameters of the uptake process of TAUT in VSMCs. RT-PCR and western blot demonstrated that the mRNA and protein of TAUT was expressed in VSMCs in vitro. Immunohistochemistry using antibody for TAUT revealed the expression of this protein in rat thoracic aorta. The maximal [³H]taurine uptake rate in VSMCs was 37.75 ± 3.13 pmol/min per mg of protein, with a K _m value of 5.42 ± 0.81 μM. Thus, VSMCs are able to express a functional taurine transporter. The regulation and detailed function of taurine and TAUT in VSMCs remain unclear, but our findings suggest a functional role for them in VSMCs metabolism.     

A direct observation of bacterial coverage and biofilm formation by Acidithiobacillus ferrooxidans on chalcopyrite and pyrite surfaces

To obtain a fundamental understanding of the population behaviour of Acidithiobacillus ferrooxidans at chalcopyrite and pyrite surfaces, the early stage attachment behaviour and biofilm formation by this bacterium on chalcopyrite (CuFeS₂) and pyrite (FeS₂) were studied by optical microscopy, Raman spectroscopy, time-of-flight secondary ion mass spectrometry (ToF-SIMS) and electron backscatter diffraction (EBSD). The results indicate there was no significant difference in selectivity of bacterial attachment between chalcopyrite and pyrite. However, the result of ToF-SIMS analysis suggests that the surface of the pyrite was covered more extensively by biofilm than that of the chalcopyrite, which may indicate more extracellular polymeric substances (EPS) formation by bacterial cells growing on pyrite. EBSD and optical image analysis indicated that selectivity of bacterial attachment to chalcopyrite was not significantly affected by crystal orientation. The results also suggest that the bacterial population in defective areas of chalcopyrite was significantly higher than on the polished surfaces.