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排序方式: 共有2319条查询结果,搜索用时 15 毫秒
1.
Julie A. Harris Akihiko Koyama Sumihiro Maeda Kaitlyn Ho Nino Devidze Dena B. Dubal Gui-Qiu Yu Eliezer Masliah Lennart Mucke 《PloS one》2012,7(9)
Accumulation of hyperphosphorylated tau in the entorhinal cortex (EC) is one of the earliest pathological hallmarks in patients with Alzheimer’s disease (AD). It can occur before significant Aβ deposition and appears to “spread” into anatomically connected brain regions. To determine whether this early-stage pathology is sufficient to cause disease progression and cognitive decline in experimental models, we overexpressed mutant human tau (hTauP301L) predominantly in layer II/III neurons of the mouse EC. Cognitive functions remained normal in mice at 4, 8, 12 and 16 months of age, despite early and extensive tau accumulation in the EC. Perforant path (PP) axon terminals within the dentate gyrus (DG) contained abnormal conformations of tau even in young EC-hTau mice, and phosphorylated tau increased with age in both the EC and PP. In old mice, ultrastructural alterations in presynaptic terminals were observed at PP-to-granule cell synapses. Phosphorylated tau was more abundant in presynaptic than postsynaptic elements. Human and pathological tau was also detected within hippocampal neurons of this mouse model. Thus, hTauP301L accumulation predominantly in the EC and related presynaptic pathology in hippocampal circuits was not sufficient to cause robust cognitive deficits within the age range analyzed here. 相似文献
2.
James M. Mason Nita N. Scobie Akihiko H. Yamamoto 《Molecular & general genetics : MGG》1989,215(2):190-199
Summary The mutagen-sensitive mutant mus(1)104
D1
of Drosophila melanogaster maps to a position on the X chromosome very close to the meiotic mutant mei-41
D5
. Both mutants have been characterized as mutagen-sensitive and defective in post-replication repair. In the present report we show by complementation studies that mus(1)104 and mus(1)103 are allelic with mei-41. In addition, two reported alleles of mus(1)104 lie between the mei-41 alleles A10 and D5. The size of the mei-41 locus is estimated to be about 0.1 centimorgans (cM). Because several alleles of mei-41 have been shown to reduce recombination and increase meiotic chromosome loss and nondisjunction, mus(1)104
D1
females were examined for defects in meiosis. Although there was no evidence for reduced recombination on the second chromosome in homozygous mus(1)104
D1
females, heterozygous mus(1)104
D1
/mei-41
>D5
and mus(1)104
D1
/deficiency females showed reduced levels of recombination. However, there was no evidence of an increase in nondijunction in these females.We dedicate this article to the memory of Larry Sandler, who passed away suddenly on February 7, 1987 相似文献
3.
Summary Biosynthesis and processing of the protective protein for -galactosidase in normal and galactosialidosis fibroblasts were investigated using specific antiserum preparations. A 45-kd precursor was processed to a mature 30-kd protein in normal fibroblasts. The mature protective protein was not detected in any of the twelve galactosialidosis fibroblast strains examined in this study. The precursor was not detected in two cases and in the others was of heterogeneous molecular weight, i.e., normal, abnormally low, or abnormally high. These molecular abnormalities were not correlated with clinical manifestations of the patients. 相似文献
4.
5.
An enzyme hydrolyzing succinyl trialanine-4-nitroanilide was extracted from human kidney homogenate and purified by means of gel filtration on Sepharose CL-4B, anion-exchange chromatography on DEAE-Sepharose CL-6B and affinity chromatography on carbobenzoxy-L-Ala-L-Ala-D-Ala-polylysine-agarose. The purified enzyme consists of a single peptide, and its molecular weight was estimated to be about 125 000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The purified enzyme cleaved the substrate at the bond between succinyl dialanine and alanine-4-nitroanilide and showed a Km value of 2.1 mM at the optimal pH of 8.0. The activity was increased by Ca2+ and Mg2+, but was inhibited by phosphoramidon and ethylenediaminetetraacetic acid. The enzyme cleaved the oxydized insulin B chain, angiotensinogen tetradecapeptide, angiotensin I, angiotensin II, angiotensin III, [Sar1,Ala8]-angiotensin II, bradykinin, des-Pro2-bradykinin, Leu5-enkephalin, Met 5-enkephalin, [D-Ala2,Met5]-enkephalinamide and [D-Ala2-Met5]-enkephalin, but did not cleave [D-Ala2,D-Leu5]-enkephalin. The bonds on the amino side of the hydrophobic amino acids of the peptides were cleaved by the enzyme. 相似文献
6.
Immigration of the brown planthopper, Nilaparvata lugens, exhibiting various responses to density in relation to wing morphism 总被引:6,自引:0,他引:6
Considerable inherent variations in the relation between macropterous and brachypterous wing forms, and nymphal density were found in field populations of the brown planthopper, Nilaparvata lugens Stål (Homoptera: Delphacidae), collected from various locations in Japan. When compared under uniform laboratory rearing conditions, most of the female populations exhibited higher ratios of macropters with increasing nymphal density, but some showed extremely high proportion of brachypters and the others were highly macropterous, over broad ranges of density. These results indicate the possibility that the planthoppers in Japan, which are known not to persist in winter, are derived from different migration sources.About ten generations of successive selection for brachyptery from a population showing usual density-dependent wing morphism generated populations similar to highly brachypterous ones mentioned above. Genetic analysis of the inheritance of wing morphism revealed that brachyptery in the females was controlled by a single pair of dominant alleles. However, in the males wing forms did not segregate so clearly in the crossing experiments. This suggests that wing morphism in N. lugens in under sex-limited inheritance.
Einwanderung von Nilaparvata lugens mit unterscheidlicher Reaktion auf Populationsdischte bei der Flügelausbildung
Zusammenfassung In Feldpopulationen von Nilaparvata lugens Stål., welche in verschiedenen Regionen Japans gesammelt wurden, bestand in der Beziehung zwischen makropteren bzw. brachypteren Flügelformen und der Larvendichte eine beträchtliche Variation. Unter einheitlichen Zuchtbedingungen im Laboratorium stieg der Makropterenanteil bei den meisten Weibchenpopulationen mit steigender Temperatur; bei einigen Populationen hingegen war entweder der Brachypterenanteil oder der Makropterenanteil extrem hoch und zwar über weite Dichtebereiche. Dies deutet auf die Möglichkeit hin, dass die Zikade in Japan, wo sie bekanntlich nicht überwintert, jeweils aus verschiedenen Quellen einwandert.Wenn eine Population mit der üblichen dichteabhängigen Flügelausbildung 10 Generationen lang auf Brachypterie selektioniert wurde, entstanden Populationen, die den erwähnten hochbrachypteren Populationen aus dem Feld glichen. Die genetische Analyse der Vererbung der Brachypterie ergab, dass bei Weibchen ein einzelnes dominantes Allel verantwortlich ist. Bei Männchen dagegen trennten sich bei Kreuzungsexperimenten die Flügelformen nicht so klar. Dies deuted auf Unterschiede zwischen den Geschlechtern bei der Vererbung der Flügelformen.相似文献
7.
“Bulk density” and “dry-matter content” are useful indices of dry-matter accumulation in plant organs. A theoretical equation
describing the relationship between these two indices was put forward. To examine the reliability of this equation, the seasonal
changes of these two indices were investigated in the leaves and stems of different ages ofAucuba japonica. In each organ both indices varied seasonally almost parallel to each other, but the seasonal changes of dry-matter content
were less obvious than those of bulk density. The observed bulk density was always larger than that calculated from the observed
dry-matter content by the theoretical equation. A drying experiment showed that this discrepancy was caused by the decrement
of the volume of the plant material by water loss during the period from the weight measurement to the volume measurement.
When the water loss was negligible, the equation described well the relationships between the two indices of the experimental
materials. It was also shown that this equation was useful for the estimation of the amount of air space in plant materials. 相似文献
8.
Satoshi Yoshida Masazumi Takeshita Akihiko Kawaguchi 《Biochemical and biophysical research communications》1984,124(2):322-328
The elongation of arachidoyl-CoA by swine cerebral microsomes resulted in the production of behenic acid (22:0) and lignoceric acid (24:0) concomitantly. When 4S-[4-2H1]NADPH was used for the elongation of arachidoyl-CoA, the incorporation of two deuterium atoms into 22:0 was observed by the technique of mass fragmentography. Furthermore, the incorporation of four deuterium atoms into 24:0 was also detected. On the other hand, when 4R-[4-2H1]NADPH was used, no deuterium was incorporated into the elongated products. 相似文献
9.
K Tojo Y Kato Y Kabayama H Ohta T Inoue H Imura 《Proceedings of the Society for Experimental Biology and Medicine. Society for Experimental Biology and Medicine (New York, N.Y.)》1986,181(4):517-522
Intracerebroventricular (icv) injection of neurotensin (NT) (2 micrograms/rat) suppressed prolactin (PRL) release induced by L-5-hydroxytryptophan (1 mg/100 g body wt, iv), prostaglandin E2(1 microgram/rat, icv), and FK33-824 (10 micrograms/100 g body wt, iv), a Met5-enkephalin analog, in urethane-anesthetized or conscious rats. In contrast, NT did not suppress elevated plasma PRL levels sustained by a large dose of domperidone (10 micrograms/100 g body wt, iv), a peripheral dopamine antagonist. In in vitro experiments, NT (10(-5) M) stimulated dopamine release from perifused rat hypothalamic fragments. These results suggest that central NT inhibits PRL secretion by stimulating dopamine release from the hypothalamus into hypophysical portal blood in the rat. 相似文献
10.
Tojo A 《Applied and environmental microbiology》1986,51(3):630-633
The mode of action of the toxic fragment (P-59) derived from bipyramidal-shaped delta-endotoxin of Bacillus thuringiensis subsp. kurstaki HD-1 on the silkworm Bombyx mori was investigated. An enzyme-linked immunosorbent assay showed that there was no translocation of P-59 from the gut lumen to the hemocoel. When membrane vesicles prepared from silkworm midgut were incubated with P-59, normally smooth surface of vesicles became rough, and patch formation was observed on the surface. Vesicles treated with P-59 tended to agglutinate. The vesicle-denaturing activity of a 130,000-dalton subunit protein of bipyramidal toxin was enhanced by treatment with a gut juice protease of the silkworm. P-59 did not cause any uncoupling effect on mitochondria of the silkworm midgut. These results suggest that the attacking site of this toxin is not the mitochondrion but the cell membrane of the susceptible cell. 相似文献