beta-thymosin is required for axonal tract formation in developing zebrafish brain

beta-Thymosins are polypeptides that bind monomeric actin and thereby function as actin buffers in many cells. We show that during zebrafish development, &bgr;-thymosin expression is tightly correlated with neuronal growth and differentiation. It is transiently expressed in a subset of axon-extending neurons, essentially primary neurons that extend long axons, glia and muscle. Non-neuronal expression in the brain is restricted to a subset of glia surrounding newly forming axonal tracts. Skeletal muscle cells in somites, jaw and fin express beta-thymosin during differentiation, coinciding with the time of innervation. Injection of beta-thymosin antisense RNA into zebrafish embryos results in brain defects and impairment of the development of beta-thymosin-associated axon tracts. Furthermore, irregularities in somite formation can be seen in a subset of embryos. Compared to wild-type, antisense-injected embryos show slightly weaker and more diffuse engrailed staining at the midbrain-hindbrain boundary and a strong reduction of Isl-1 labeling in Rohon Beard and trigeminal neurons. The decreased expression is not based on a loss of neurons indicating that beta-thymosin may be involved in the maintenance of the expression of molecules necessary for neuronal differentiation. Taken together, our results strongly indicate that beta-thymosin is an important regulator of development.     

Enantioselective correlation between retention factor and lipophilicity index in chiral separation on cellulose and amylose tris(3,5-dimethylphenylcarbamate) CSPs in reversed mode: A case study

For a series of alkyl substituted N-arylthiazoline-2-(thi)one atropisomers 1-14, lipophilicity indexes log kw obtained by polycratic RP-HPLC were compared to ln k(+)-S and ln k(-)-R obtained on CHIRALCEL OD-R(R) (reversed mode) and CHIRALPAK AD-RH(R) (reversed mode). Linear correlations were obtained in most cases. It appears that the correlation lines for R and S enantiomers may be parallel, convergent, or divergent, accounting for the observed alpha variation in going from methyl to tert-butyl series. Some tentative hypothesis are given as future investigation routes. Copyright 2000 Wiley-Liss, Inc.     

A 4-AP-sensitive current is enhanced by chronic carbon monoxide exposure in coronary artery myocytes

A physiological role of carbon monoxide has been suggested for coronary myocytes; however, direct evidence is lacking. The objective of this study was to test the effect of chronic carbon monoxide exposure on the K(+) currents of the coronary myocytes. The effect of 3-wk chronic exposure to carbon monoxide was assessed on K(+) currents in isolated rat left coronary myocytes by the use of the patch-clamp technique in the whole cell configuration. Moreover, membrane potential studies were performed on coronary artery rings using intracellular microelectrodes, and coronary blood flow in isolated heart preparation was recorded. Carbon monoxide did not change the amplitude of global whole cell K(+) current, but it did increase the component sensitive to 1 mM 4-aminopyridine. Carbon monoxide exposure hyperpolarized coronary artery segments by approximately 10 mV and, therefore, increased their sensitivity to 4-aminopyridine. This effect was associated with an enhancement of coronary blood flow. We conclude that chronic carbon monoxide increases a 4-aminopyridine-sensitive current in isolated coronary myocytes. This mechanism could, in part, contribute to hyperpolarization and to increased coronary blood flow observed with carbon monoxide.     

Mammary leptin synthesis,milk leptin and their putative physiological roles

This paper reviews data on mammary leptin and leptin receptor gene expression as well as on blood and milk leptin levels during the pregnancy-lactation cycle in humans, rodents and ruminants, with the aim of better understanding milk leptin origin and functions. The few published papers report that leptin may be produced by different cell types in the mammary tissue, and may act as a paracrine factor on mammary epithelial cell proliferation, differentiation and/or apoptosis via adipose-epithelial and/or myoepithelial-epithelial cellular interactions. In addition to leptin synthesis, epithelial cells may transfer leptin from the blood, and these two mechanisms may account for the presence of leptin in the milk. The respective parts of these two processes remain to be determined, as well as the true milk leptin levels. Indeed, reported concentrations for milk leptin vary strongly according to species and mainly according to the milk fractions and the assay methods used. If leptin levels in milk (and specially colostrum) are found to be significant, this hormone could be involved in neonate physiology.     

Chronic carbon monoxide enhanced IbTx-sensitive currents in rat resistance pulmonary artery smooth muscle cells

Exogenous carbon monoxide (CO) can induce pulmonary vasodilation by acting directly on pulmonary artery (PA) smooth muscle cells. We investigated the contribution of K+ channels to the regulation of resistance PA resting membrane potential on control (PAC) rats and rats exposed to CO for 3 wk at 530 parts/million, labeled as PACO rats. Whole cell patch-clamp experiments revealed that the resting membrane potential of PACO cells was more negative than that of PAC cells. This was associated with a decrease of membrane resistance in PACO cells. Additional analysis showed that outward current density in PACO cells was higher (50% at +60 mV) than in PAC cells. This was linked to an increase of iberiotoxin (IbTx)-sensitive current. Chronic CO hyperpolarized membrane of pressurized PA from -46.9 +/- 1.2 to -56.4 +/- 2.6 mV. Additionally, IbTx significantly depolarized membrane of smooth muscle cells from PACO arteries but not from PAC arteries. The present study provides initial evidence of an increase of Ca2+-activated K+ current in smooth muscle cells from PA of rats exposed to chronic CO.     

Functional mapping of NPY/PYY receptors in rat and human gastro-intestinal tract

Peptide YY (PYY) is involved in the regulation of several gastro-intestinal functions, including motility. The aims of the present study were (i) to characterize the effects of PYY on smooth muscle strips obtained from the different gastro-intestinal segments in rats and in humans and (ii) to realize a map of the Y receptors expression. Contractions of strips were recorded under isometric conditions, using PYY and acetylcholine as control. We observed that PYY induced a contraction of muscle strips from rat proximal colon, but displayed no effect on other gut segments. Using RT-PCR, mRNA encoding the Y1 and Y4 receptors were detected in muscle strips depending on the segment. In humans, the muscle preparations responded to ACh but not to PYY. Moreover, only Y2 receptor mRNA was found in the ileum and the left colon, but not in other segments. Our study shows the heterogeneity in the expression of Y receptors along the gastro-intestinal tract, and reveals great discrepancies between rats and humans both concerning the expression of Y receptor, and the response of smooth muscle strips to PYY.     

Karyotype identity of two subspecies of Eld's deer [Cervus eldi (Cervinae, Artiodactyla)] and its consequences for conservation

Among the three subspecies generally recognized within the Eld's deer (Cervus eldi)--C. e. eldi, C. e. thamin, and C. e. siamensis--C. e. siamensis is considered to be particularly endangered following its disappearance from a major portion of its original range. The only captive breeding population of this subspecies is in the zoological parks at the Paris Museum of Natural History. Taking into account its low effective population size (Ne = 7) and the increasing levels of inbreeding, the continued breeding of this "micropopulation" in isolation from closely related subspecies and in particular from C. e. thamin, which is much more common in zoos as well as in the nature, is questioned. As an initial step in determining if crosses between these subspecies could be performed without risk of outbreeding depression due, in part, to gross differences in their karyotypes, a comparative chromosome banding analysis (RBG-bands) of C. e. siamensis and C. e. thamin was undertaken. No chromosomal differences were identified between the taxa at the level of resolution obtained. The study suggests that, at least from a karyotypic perspective, no obvious differences delimit the two subspecies, and hybridization between endangered C. e. siamensis and C. e. thamin is not likely to lead to impaired fertility in hybrid animals.     

The conformation of apolipoprotein A-I in high-density lipoproteins is influenced by core lipid composition and particle size: a surface plasmon resonance study

Plasma high-density lipoproteins (HDL) are a heterogeneous group of particles that vary in size as well as lipid and apoprotein composition. The effect of HDL core lipid composition and particle size on apolipoprotein (apo) A-I structure was studied using surface plasmon resonance (SPR) analysis of the binding of epitope-defined monoclonal antibodies. The association and dissociation rate constants of 12 unique apo A-I-specific monoclonal antibodies for isolated plasma HDL were calculated. In addition, the association rate constants of the antibodies were determined for homogeneous preparations of spherical reconstituted HDL (rHDL) that contained apo A-I as the sole apolipoprotein and differed either in their size or in their core lipid composition. This analysis showed that lipoprotein size affected the conformation of domains dispersed throughout the apo A-I molecule, but the conformation of the central domain between residues 121 and 165 was most consistently modified. In contrast, replacement of core cholesteryl esters with triglyceride in small HDL modified almost the entire molecule, with only two key N-terminal domains of apo A-I being unaffected. This finding suggested that the central and C-terminal domains of apo A-I are in direct contact with rHDL core lipids. This immunochemical analysis has provided valuable insight into how core lipid composition and particle size affect the structure of specific domains of apo A-I on HDL.     

Motogenic effect of recombinant HGF on airway epithelial cells during the in vitro wound repair of the respiratory epithelium

Cell migration is the earliest mechanism involved in the wound repair process of the respiratory epithelium and could be potentially enhanced by growth factors. In the present work, we investigated the localisation of the hepatocyte growth factor (HGF) receptor (c-Met) during wound repair and evaluated the effect of recombinant HGF (rHGF) on cell migration by using an in vitro model of airway epithelial wound repair. By using immunohistochemical methods, we observed that the immunoreactivity of the c-Met proto-oncogene was increased in epithelial cells engaged in the process of tissue repair. The incubation of wounded cultures with increasing concentrations of rHGF (0.2, 2, 20, and 200 ng/ml) induced a significant (P < 0.02) dose-dependent effect on the wound repair index, with a maximum effect produced at 20 ng/ml (+31.3%). The cell migration speed reached 50.2 micrometer/h at this concentration, compared to 20.4 micrometer/h in the absence of rHGF. No significant effect on cell proliferation was observed in the repairing area in the presence of rHGF. These results suggest that rHGF is able to improve the wound repair process of the airway epithelium by increasing cell migration.