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。     

Characterization of lysosomal hydrolases that are elevated in Gaucher's disease.

Although Gaucher's disease occurs in three distinct forms with greatly varying degrees of severity, there is no correlation between the clinical course of the disease and levels of residual glucocerebrosidase, the fundamental enzymatic deficiency. In an effort to study secondary changes which might contribute to the pathology of Gaucher's disease, homogenates of spleen, liver, and brain tissue, as well as serum from patients with Gaucher's disease were analyzed for their content of a number of lysosomal enzymes. Extracts of 8 Gaucher spleens contained 3- to 4-fold increases in acid phosphatase activity as well as 5-to 10-fold increases in galactocerebrosidase⁵ activity. The marked elevation in galactocerebrosidase activity in Gaucher spleen was documented using various [³H]galactose labeled galactocerebrosides as substrates and with [³H]galactose labeled lactocerebroside under the “lactosylceramidase I”⁵ assay conditions established by Suzuki (Tanaka, H., and Suzuki, K., 1975, J. Biol. Chem., 250, 2324–2332) that measure galactocerebrosidase activity specifically in the presence of G_mi-ganglioside β-galactosidase. Acid phosphatase determinations using extracts of liver from a case of infantile, neuropathic Gaucher's disease revealed a 2-fold elevation in this activity, whereas brain acid phosphatase activity in this case was similar to that of control tissue. Separation of hexosaminidase A and B activities on DEAE-Sephadex columns indicated increases in both forms of the enzyme in Gaucher tissue with the major increase occurring in the hexosaminidase B component. Glucuronidase and nonspecific esterase were observed to be elevated approximately 2-fold. However, not all lysosomal enzyme activities were increased. Levels of splenic arylsulfatase A and B, α-arabinosidase, sphingomyelinase, α-mannosidase, and G_mi-ganglioside β-galactosidase activities in Gaucher spleen were unremarkable. G_mi-ganglioside β-galactosidase was measured using 4-methylumbelliferyl-β-d-galactopyranoside and [³H]galactose labeled lactocerebroside under the specific assay conditions described by Suzuki for the determination of “lactosylceramidase II” activity. Although levels of arylsulfatase A and B in Gaucher spleen were similar to those of control tissue, arylsulfatase A activity was markedly reduced (20% of control) in homogenates of brain from the case of infantile (type 2) Gaucher's disease. The metabolic and pathologic consequences of these changes in lysosomal enzymes in Gaucher's disease are discussed.