大鼠胼胝体内神经肽Y免疫反应阳性纤维的发育

本实验用免疫组织化学ＡＢＣ法研究了大鼠胼胝体内神经肽Ｙ免疫反应阳性（ＮＰＹ－ＩＲ）纤维的生后发育。结果发现,许多ＮＰＹ－ＩＲ纤维在大鼠出生时便存在于胼胝体内。ＮＰＹ－ＩＲ胼胝体纤维的密度在生后１周内继续逐渐增高,在第２周内达到最高峰。之后,ＮＰＹ－ＩＲ胼胝体纤维的密度逐渐下降,至第３周末时接近成年时的水平,即仅有少量ＮＰＹ－ＩＲ纤维存在于胼胝体内。这些结果提示在大鼠早期生后发育过程中许多ＮＰＹ－ＩＲ胼胝体纤维是暂时性的,其作用可能与大脑皮质的机能发育有关。     

Effect of phenethyl alcohol and other organic substances on cellulase production

Cellulase can be produced from growth in noncellulosic substrate if the growth rate of the producing organism is restricted. Phenethyl alcohol (PEA) is a growth inhibitor and was used to control the growth of M. verrucaria in attempts to obtain increased cellulase production. Cellulase yield was found to be increased without a restriction in growth rate when PEA was present in low concentrations (0.03% v/v). The effect was observed for other organisms but notably L. trabea, which produced considerable enzyme from a small quantity of mycelium. Here increased cellulase synthesis was concomitant with restricted growth. Other chemicals with PEA-like structure (e.g. benzyl alcohol) resulted in similar or more extensive cellulase synthesis. Of the substances tried, propyl alcohol was most effective, followed by acetone. PEA causes a swelling of cell walls and inhibits spore formation. This and other data given suggest that PEA affects the cytoplasmic membrane or the cell wall or both. Cellulase synthesis is considered to take place in the membrane and wall region of the cell.     

Steroid UDP glucuronosyltransferases

The glucuronidation of steroids is a major process necessary for their elimination in the bile and urine. In general, steroid glucuronides are biologically less reactive than their parent steroids. However, in some cases often associated with disease and steroid therapy, more reactive or toxic glucuronides may be formed. The concentrations of specific steroid glucuronides in the blood may also indicate hormonal imbalances and may funnction as diagnostic markers of genetic defects in steroid synthesis and metabolism. In this review, the forms of UDP glucuronosyltransferase involved in steroid glucuronidation are described in terms of their specificities, functional domains and regulation. The available evidence suggests that steroid glucuronidation is mainly carried out by members of the UGT2B subfamily which are encoded by genes containing 6 exons. Members of this subfamily exhibit a regioselectively in their glucuronidation of steroids that is mediated by domains in the amino-terminal half on the protein encoded by exons 1 and 2. Although much of this review will describe studies in the rat, preliminary evidence indicates that a similar situation may exist in humans.     

BiP and calreticulin form an abundant complex that is independent of endoplasmic reticulum stress

BiP is found in association with calreticulin, both in the presence and absence of endoplasmic reticulum stress. Although the BiP-calreticulin complex can be disrupted by ATP, several properties suggest that the calreticulin associated with BiP is neither unfolded nor partially or improperly folded. (1) The complex is stable in vivo and does not dissociate during 8 hr of chase. (2) When present in the complex, calreticulin masks epitopes at the C terminus of BiP that are not masked when BiP is bound to an assembly-defective protein. And (3) overproduction of calreticulin does not lead to the recruitment of more BiP into complexes with calreticulin. The BiP-calreticulin complex can be disrupted by low pH but not by divalent cation chelators. When the endoplasmic reticulum retention signal of BiP is removed, complex formation with calreticulin still occurs, and this explains the poor secretion of the truncated molecule. Gel filtration experiments showed that BiP and calreticulin are present in distinct high molecular weight complexes in which both molecules interact with each other. The possible functions of this complex are discussed.     

Patterns of sequence variation in the mitochondrial D-loop region of shrews

Direct sequencing of the mitochondrial displacement loop (D-loop) of shrews (genus Sorex) for the region between the tRNA(Pro) and the conserved sequence block-F revealed variable numbers of 79-bp tandem repeats. These repeats were found in all 19 individuals sequenced, representing three subspecies and one closely related species of the masked shrew group (Sorex cinereus cinereus, S. c. miscix, S. c. acadicus, and S. haydeni) and an outgroup, the pygmy shrew (S. hoyi). Each specimen also possessed an adjacent 76-bp imperfect copy of the tandem repeats. One individual was heteroplasmic for length variants consisting of five and seven copies of the 79-bp tandem repeat. The sequence of the repeats is conducive to the formation of secondary structure. A termination-associated sequence is present in each of the repeats and in a unique sequence region 5' to the tandem array as well. Mean genetic distance between the masked shrew taxa and the pygmy shrew was calculated separately for the unique sequence region, one of the tandem repeats, the imperfect repeat, and these three regions combined. The unique sequence region evolved more rapidly than the tandem repeats or the imperfect repeat. The small genetic distance between pairs of tandem repeats within an individual is consistent with a model of concerted evolution. Repeats are apparently duplicated and lost at a high rate, which tends to homogenize the tandem array. The rate of D- loop sequence divergence between the masked and pygmy shrews is estimated to be 15%-20%/Myr, the highest rate observed in D-loops of mammals. Rapid sequence evolution in shrews may be due either to their high metabolic rate and short generation time or to the presence of variable numbers of tandem repeats.