The peptidoglycan recognition proteins LCa and LCx

Infection of bacteria triggers innate immune defense reactions in Drosophila. So far, the only bacterial component known to be recognized by the insect innate immune system is peptidoglycan, one of the most abundant constituents of the bacterial cell wall. Insects use peptidoglycan recognition proteins to detect peptidoglycan and to activate innate immune responses. Such specialized peptidoglycan receptors appear to have evolved from phage enzymes that hydrolyze bacterial cell walls. They are able to bind specific peptidoglycan molecules with distinct chemical moieties and activate innate immune pathways by interacting with other signaling proteins. Recent X-ray crystallographic studies of the peptidoglycan recognition proteins LCa, and LCx bound to peptidoglycan have provided structural insights into recognition of peptidoglycan and activation of innate immunity in insects. Received 28 December 2006; received after revision 2 February 2007; accepted 21 February 2007     

Therapeutic applications of bone marrow-derived stem cells in liver transplantation for end-stage liver diseases

Today, liver transplantation (LT) is the only established treatment for end-stage liver diseases. The de- velopment of LT, including OLT, cadaveric LT, split LT, living donor LT (LDLT), brings hopes to patients with these diseases. However, increasing donor shortage, rejection and life-long immunosuppression with its side effects are the major limitations of this therapy strategy. Bone marrow-derived stem cells (BMDSCs) are capable of differentiating into hepatocyte-like cells and contribute to liver injury repair. The microenvironment of liver injury caused by rejection, ischemia/reperfusion, loss of liver mass, recurrence of HCV and "small-for-size syndrome" after LT can attract a variety of bone marrow-derived stem cell population to the peripheral circulation and then migration to the injury liver to promote the hepatic function restoration. Additionally, BMDSCs can also take part in the functional regeneration of living donor liver after LDLT. This participation in liver regeneration may be associated to the interac- tion between SDF-1and its receptor CXCR4, involving HGF, IL-8, MMP9, and VEGF/VEGFR-2. BMDSC with its bio-characteristics could maintain the allograft tolerance from different angles and in different ways. In conclusion, BMDSCs transplantation, as a new assistant therapeutic method for LT, will ex- pand the space of LT, and provide more survival opportunities for the patients suffering liver diseases in the future.     

Receiving mixed signals: uncoupling oligodendrocyte differentiation and myelination

The development and maturation of an oligodendroglial cell is comprised of three intimately related processes that include proliferation, differentiation, and myelination. Here we review how proliferation and differentiation are controlled by distinct molecular mechanisms and discuss whether differentiation is merely a default of inhibited proliferation. We then address whether differentiation and myelination can be uncoupled in a similar manner. This task is particularly challenging because an oligodendrocyte cannot myelinate without first differentiating, and these processes are therefore not mutually exclusive. Is it solely the presence of the axon that distinguishes a differentiated oligodendrocyte from a myelinating one? Uncoupling these two processes requires identifying specific signals that regulate myelination without affecting the differentiation process. We will review current understanding of the relationship between differentiation and myelination and discuss whether these two processes can truly be uncoupled.     

Alternative exon usage selectively determines both tissue distribution and subcellular localization of the acyl-CoA thioesterase 7 gene products

Acyl-CoA thioesterases (ACOTs) catalyze the hydrolysis of acyl-CoAs to free fatty acids and coenzyme A. Recent studies have demonstrated that one gene named Acot7, reported to be mainly expressed in brain and testis, is transcribed in several different isoforms by alternative usage of first exons. Strongly decreased levels of ACOT7 activity and protein in both mitochondria and cytosol was reported in patients diagnosed with fatty acid oxidation defects, linking ACOT7 function to regulation of fatty acid oxidation in other tissues. In this study, we have identified five possible first exons in mouse Acot7 (Acot7a–e) and show that all five first exons are transcribed in a tissue-specific manner. Taken together, these data show that the Acot7 gene is expressed as multiple isoforms in a tissue-specific manner, and that expression in tissues other than brain and testis is likely to play important roles in fatty acid metabolism. Received 5 February 2007: received after revision 3 April 2007; accepted 19 April 2007     

Effects of vitamin B12 on plasma melatonin rhythm in humans: increased light sensitivity phase-advances the circadian clock?

Vitamin B12 (methylcobalamin) was administered orally (3 mg/day) to 9 healthy subjects for 4 weeks. Nocturnal melatonin levels after exposure to bright light (ca. 2500 lx) were determined, as well as the levels of plasma melatonin over 24 h. The timing of sleep was also recorded. Vitamin B12 was given blind to the subjects and crossed over with placebo. We found that the 24-h melatonin rhythm was significantly phase-advanced (1.1 h) in the vitamin B12 trial as compared with that in the placebo trial. In addition, the 24-h mean of plasma melatonin level was much lower in the vitamin B12 trial than with the placebo. Furthermore, the nocturnal melatonin levels during bright light exposure were significantly lower in the vitamin B12 trial than with the placebo. On the other hand, vitamin B12 did not affect the timing of sleep. These findings raise the possibility that vitamin B12 phase-advances the human circadian rhythm by increasing the light sensitivity of the circadian clock.     

Retrograde transport of endocytosed Shiga toxin to the endoplasmic reticulum.

Shiga toxin and some other protein toxins that act on targets in the cytosol have previously been shown to enter the trans-Golgi network. Transport by this route may be necessary for translocation of the toxin to the cytosol and for intoxication, but it is not known whether the enzymatically active part of the toxins actually enters the cytosol from the trans-Golgi network. It has been suggested that such toxins are transported in a retrograde manner to the endoplasmic reticulum and that translocation occurs in this organelle, but retrograde transport of endocytosed material beyond the trans-Golgi network has never been demonstrated. Here we show that in butyric acid-treated A431 cells endocytosed Shiga toxin is not only transported to the trans-Golgi network, but also to all Golgi stacks, to the endoplasmic reticulum and to the nuclear envelope. Furthermore, butyric acid sensitizes the cells to Shiga toxin, which is consistent with the possibility that retrograde transport is required for translocation of the toxin to the cytosol.     

The harmonic decomposition reconstruction for the exponential radon transform

The exponential Radon transform, a generalization of the Radon transform, is defined and studied as a mapping of function spaces. It is represented in terms of Fourier transform of its domain and range, and this leads to the harmonic decomposition reconstruction. The results are similar results of Tretiak and Metz. Foundation item: Supported by the National Natural Science Foundation of China (No. 19971064), Key Project of Science and Technology of Hubei Province Education Committee. Biography: Wang Jin-ping (1963-), male, Ph.D. candidate, research direction: numberical solution of singular integral equation and integral transformation etc.