Effects of high pressure on the catalytic and regulatory properties of UDP-glucuronosyltransferase in intact microsomes.

The effects of high pressure on the kinetic properties of microsomal UDP-glucuronosyltransferase (assayed with 1-naphthol as aglycon) were studied in the range of 0.001-2.2 kbar to clarify further the basis for regulating this enzyme in untreated microsomes. Activity changed in a discontinuous manner as a function of pressure. Activation occurred at pressure as low as 0.1 kbar, reaching one of two maxima at 0.2 kbar. As pressure was increased above 0.2 kbar, activity decreased, reaching a minimum at about 1.4 kbar followed by a second activation. The pathway for activation at pressure greater than 1.4 kbar was complex. The immediate effect of 2.2 kbar was nearly complete inhibition of activity. The inhibited state relaxed, however, over about 10 min (at 10 degrees C), to a state that was activated as compared with enzyme at 0.001 kbar or enzyme at pressures between 1.4 and 2.2 kbar, which was the highest pressure we could test. Examination of the detailed kinetic properties of UDP-glucuronosyltransferase indicated that the effects of pressure were due to selective stabilization of unique functional states of the enzyme at 0.2 and 2.2 kbar. Activation at 0.2 kbar was reversible when pressure was released. This was true as well as for activation at pressure greater than 1.4 kbar, but after prolonged treatment at 2.2 kbar, UDP-glucuronosyltransferase became activated irreversibly on release of pressure. The process by which prolonged treatment at 2.2 kbar led to permanent activation of UDP-glucuronosyltransferase after release of pressure was not reflected, however, by time-dependent changes in the functional state of UDP-glucuronosyltransferase at this pressure.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.      

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。     

Histochemical Demonstration of Enzyme Activities in Plastic and Paraffin Embedded Tissue Sections

Histochemical staining for enzymes is usually performed on frozen sections. This report lists the longer incubation times required to demonstrate esterase, acid phosphatase, β-galactosidase, and cytochrome oxidase in plastic embedded and routine paraffin embedded tissues. The sections embedded in plastic, i.e. water soluble methacrylate (Polyscience's JB-4) and cut at 2 μm, were far superior to frozen Sections and paraffin embedded sections both in tissue detail and in the localization of the histochemical reaction product.     

Characterization,Toxicity, and Optimization for the Growth and Production of Bacteriocin-like Substances by Lactobacillus curvatus

Probiotics and Antimicrobial Proteins - This study aimed to characterize, evaluate toxicity and optimize the conditions for the growth and production of bacteriocin-like substances by Lactobacillus...