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排序方式: 共有1779条查询结果,搜索用时 30 毫秒
1.
THE TIMING OF DIVISION IN CHLAMYDOMONAS 总被引:3,自引:2,他引:1
2.
《Journal of molecular recognition : JMR》2017,30(5)
The HERV‐W family of human endogenous retroviruses represents a group of numerous sequences that show close similarity in genetic composition. It has been documented that some members of HERV‐W–derived expression products are supposed to play significant role in humans' pathology, such as multiple sclerosis or schizophrenia. Other members of the family are necessary to orchestrate physiological processes (eg, ERVWE1 coding syncytin‐1 that is engaged in syncytiotrophoblast formation). Therefore, an assay that would allow the recognition of particular form of HERV‐W members is highly desirable. A peptide nucleic acid (PNA)–mediated technique for the discrimination between multiple sclerosis‐associated retrovirus and ERVWE1 sequence has been developed. The assay uses a PNA probe that, being fully complementary to the ERVWE1 but not to multiple sclerosis‐associated retrovirus (MSRV) template, shows high selective potential. Single‐stranded DNA binding protein facilitates the PNA‐mediated, sequence‐specific formation of strand invasion complex and, consequently, local DNA unwinding. The target DNA may be then excluded from further analysis in any downstream process such as single‐stranded DNA‐specific exonuclease action. Finally, the reaction conditions have been optimized, and several PNA probes that are targeted toward distinct loci along whole HERV‐W env sequences have been evaluated. We believe that PNA/single‐stranded DNA binding protein–based application has the potential to selectively discriminate particular HERV‐W molecules as they are at least suspected to play pathogenic role in a broad range of medical conditions, from psycho‐neurologic disorders (multiple sclerosis and schizophrenia) and cancers (breast cancer) to that of an auto‐immunologic background (psoriasis and lupus erythematosus). 相似文献
3.
实夜蛾属二近缘种对寄主植物次生物质的反应:次生物质对幼虫生长和食物利用的影响 总被引:13,自引:3,他引:10
实夜蛾属(Heliothis)的棉铃虫(H. armigcra)和烟青虫(H. assulta)是近缘种,幼虫期取食多种相同的植物,其中含有不同的次生物质.本项工作是在人工饲料中分别加入0.5%的烟碱、番茄苷、棉子酚、丹宁酸等饲养早期六龄的幼虫,测定它们对生长和食物利用的影响.结果表明这些次生物质对两种幼虫有不同的作用:烟碱对棉铃虫没有明显影响,但对烟青虫的取食却有一定的刺激作用.丹宁酸、棉子酚、番茄苷可抑制两种幼虫的生长,而以番茄苷抑制烟青虫的生长最为显著.番茄苷主要通过抑制取食来影响幼虫的生长,而丹宁酸和棉子酚则具有降低消化率的作用.通过次生物质对这两种幼虫效应的比较可知,棉铃虫有较大的忍耐力. 相似文献
4.
V Pimpaneau P Midoux G Durand P De Baetselier M Monsigny A -C Roche 《Glycoconjugate journal》1989,6(4):561-574
Macrophages from various origins are known to express membrane lectins that mediate the endocytosis of mannose-bearing glycoconjugates. Most macrophage tumor cell-lines lack such receptors. In this paper we show by flow cytometry analysis that a newly generated macrophage hybridoma (2C11–12), which displays several macrophage characteristics, also expresses mannose membrane lectins, resulting in the internalization of fluoresceinylated neoglycoproteins into acidic compartments.Thioglycolate elicited mouse peritoneal macrophages and the 2C11–12 hybridomas were compared by flow cytometry with regard to the binding and endocytosis of 1-acid glycoprotein (AGP) variants separated by affinity chromatography on immobilized concanavalin A. AGP C eluted specifically with methyl -mannopyranoside, which contains two bi-antennary oligosaccharides, was endocytosed as mannosylated serum albumin (Man-BSA). In both types of macrophages, the fluoresceinylated ligands were internalized in acidic compartments as demonstrated by the fluorescence intensity increase upon monensin post-incubation. However the behaviour of the internalized ligands was found to be quite different. AGP C and Man-BSA were rapidly degraded by thioglycolate elicited peritoneal macrophages and excreted in the medium as small peptide fragments; conversely they remained a longer time in the 2C11–12 hybridoma. 相似文献
5.
The effect of tin and lead on levels of essential metals (Zn, Cu, Ca, Fe) in rabbit tissues was compared in relation to the route of administration. Animals received intraperitoneally, or per os, SnCl2 (2 mg Sn/kg) or Pb(CH3COO)2 (3.5 mg Pb/kg) every day for 5 d or for 1 mo. Copper, zinc, iron, and calcium were determined by AAS in the liver, kidneys, spleen, brain, bone marrow, and blood; lead and tin concentration were measured in the blood of animals. Tin and lead administered per os caused either no changes or the decreased concentration of endogenous metals in several tissues. The other route of administration (ip) of both metals generally contributed to the increased storage of essential elements. Blood tin levels of tin treated animals were only about less than or equal to 1/10 of blood lead concentrations of rabbits exposed to lead. 相似文献
6.
Stephen P. Arnerić Jong-Inn Woo Mary P. Meeley Donald J. Reis 《Neurochemical research》1988,13(5):423-428
We sought to determine in rat striatum whether the release of neurotransmitter amino acids aspartate (Asp), glutamate (Glu) and gamma-aminobutyric acid (GABA) were affected by local neurons. To do so, unilateral microinjections of ibotenic acid, an excitotoxin that destroys local neurons without affecting fibers of passage, were made into the striatum. Release of endogenous amino acids from lesioned and intact striatal slices were measured by HPLC one week later. The effectiveness and specificity of the lesion were confirmed by measuring the enzyme activity associated with extrinsic dopamine neurons (tyrosine hydroxylase; 111±14%), intrinsic GABA neurons (glutamic acid decarboxylase; 19±7%) and intrinsic acetylcholine neurons (choline acetyltransferase; 37±10%). Destruction of local striatal neurons markedly attenuated the release of GABA (41±12% of control) elicited by depolarization with K+ (35 mM), but did not significantly reduce the K+-evoked release of Asp (80±17%) and Glu (92±8%). However, spontaneous release of Asp and Glu was significantly greater than that observed in unlesioned tissue (159±18% and 209±27%, respectively), while the spontaneous release of GABA was not significantly reduced (75±43%). Although release of the neurotransmitter amino acids Asp, Glu and GABA were affected by the lesion, the release of the non-neurotransmitter amino acid tyrosine was unaffected. These data are consistent with the hypotheses that: 1) the predominant source of releasable stores of endogenous Asp and Glu in the striatum arises from extinsic neurons, and 2) that the spontaneous release of Asp and Glu from axon terminals in the striatum may be regulated, at least in part, by local inhibitory neurons. 相似文献
7.
Päivi Heikkilä Arvi I. Kahri Christian Ehnholm Petri T. Kovanen 《In vitro cellular & developmental biology. Plant》1988,24(9):936-942
Summary To define the role of endogenously synthesized cholesterol in the differentiation of adrenocortical cells in primary culture,
fetal rat adrenal cells were cultured in the presence of exogenous cholesterol (serum-supplemented medium) or in the absence
of it (serum-free medium or lipoprotein-free medium). Ultrastructurally the cells had features of glomerulosa cells: mitochondria
were oval or rod shaped with lamellar inner membranes. The amount of smooth endoplasmic reticulum was small, and lipid droplets
were few. When the cells were cultured in serum-free medium some intracytoplasmic vacuoles were seen. The undifferentiated
zona glomerulosa-like cells secreted low amounts of corticosterone and 18-OH-deoxycorticosterone (18-OH-DOC) in all three
media (serum-supplemented medium, serum-free medium, and lipoprotein-free medium). Stimulation of the adrenocortical cells
with ACTH induced the ultrastructural features of differentiated zona fasciculata-like cells. Mitochondrial inner membranes
were well developed in lipoprotein-free medium, but not in serum-free medium. The amount of intracellular lipids was increased
in both media devoid of cholesterol. In the ACTH stimulated cultures the presence of exogenous cholesterol resulted in increased
secretions of corticosterone and 18-OH-DOC. In the absence of an exogenous source of cholesterol, the amounts of steroids
secreted were only half of that secreted in the presence of serum-supplemented medium. Endogenously synthesized cholesterol
is sufficient for the morphologic differentiation of fetal rat adrenocortical cells under ACTH stimulation. However, without
exogenously provided cholesterol, the steroid production accounts only for half of the maximal output achieved using serum-supplemented
medium.
This work was supported by Finnish Culture Foundation. 相似文献
8.
J. H. Medina C. Peña M. Piva C. Wolfman M. L. de Stein C. Wasowski C. Da Cunha I. Izquierdo A. C. Paladini 《Molecular neurobiology》1992,6(4):377-386
Great progress has been made in the last 5 yr in demonstrating the presence of benzodiazepines (BDZs) in mammalian tissues,
in beginning studies on the origin of these natural compounds, and in elucidating their possible biological roles. Many unanswered
questions remain regarding the sources and biosynthetic pathways responsible for the presence of BDZs in brain and their different
physiological and/or biochemical actions. This essay will focus on recent findings supporting that: (1) BDZs are of natural
origin; (2) mammalian brain contains BDZs in concentrations ranging between 5.10−10–10−8
M; (3) dietary source of BDZs might be a plausible explanation for their occurrence in animal tissues, including man; (4) the
formation of BDZ-like molecules in brain is a possibility, experimentally supported; (5) BDZ-like molecules including diazepam
andN-desmethyldiazepam are elevated in hepatic encephalopathy; and (6) natural BDZs in the brain are involved in the modulation
of memory processes. Future studies using the full range of biochemical, physiological, behavioral, and molecular biological
techniques available to the neuroscientist will hopefully continue to yield exciting and new information concerning the biological
roles that BDZs might play in the normal and pathological functioning of the brain. 相似文献
9.
Effect of applied and internal hormones on vitrification and apical necrosis of different plants cultured in vitro 总被引:2,自引:0,他引:2
Natalia V. Kataeva Irena G. Alexandrova Raisa G. Butenko Elena V. Dragavtceva 《Plant Cell, Tissue and Organ Culture》1991,27(2):149-154
Development of vitrification and apical necrosis was followed in Camellia sinensis, Gerbera jamesonii, Malus domestica and hybrid Populus tremula x P. alba shoots cultured in vitro on Murashige & Skoog (MS) medium with different concentrations of growth regulators. High humidity in the culture vessels and excess of BA in the medium were found to be the major factors influencing vitrification. Lack of exogenous cytokinin in the medium during successive subcultures induced apical necrosis in poor-rooting species (Malus domestica, Camellia sinensis). The level of internal phytohormones (ABA, IAA, IPA, 2iP, Z, ZR) was determined in the apple shoots by means of ELISA. The content of internal cytokinins in the vitrified apple shoots was several times greater than in normal ones, which supports the hypothesis that excess of cytokinins, inducing rapid divisions of cells in meristems in the atmosphere with high humidity, is responsible for vitrification. Apical necrosis of the plantlets that appeared after cultivation on cytokinin-free medium is the result of deficiency in endogenous hormones in apple shoots and this being confirmed by analysis of endogenous hormones in apple shoots.Abbreviations BA
benzyladenine
- BHT
butylated hydroxy-toluene
- ABA
abscisic acid
- IAA
indole-3-acetic acid
- ELISA
enzyme-linked immunosorbent assay
- IPA
isopentenyladenosine
- 2iP
isopentenyladenine
- NAA
naphthyl-3-acetic acid
- TBS
trishydroxymethylaminomethane buffered saline
- TLC
thin layer chromatography
- Z
zeatin
- ZR
zeatin riboside 相似文献
10.
Yoshihiro Toh Akiko Mizutani Fuminori Tokunaga Tatsushi Muta Sadaaki Iwanaga 《Cell and tissue research》1991,266(1):137-147
Summary The structure of hemocytes in the normal state and during blood coagulation, and the intracellular localization of three clotting factors and two antimicrobial factors were examined in the Japanese horseshoe crabTachypleus tridentatus. Two types of hemocytes were found in the circulating blood: non-granular and granular hemocytes. The latter contained numerous dense granules classed into two major types: L- and D-granules. The L-granules were larger (up to 1.5 m in diameter) and less electron-dense than the D-granules (less than 0.6 m in diameter). The L-granules contained three clotting factors and one antimicrobial factor, whereas the D-granules exclusively contained the other antimicrobial factor. After treatment with endotoxin, the L-granules were released more rapidly than the D-granules, although almost all granules were finally exocytosed. The granular hemocyte possessed a single Golgi complex; possible precursor granules of L-granules and D-granules contained tubular and condensed dense material, respectively. These data are discussed in relation to the self-defense mechanisms of the horseshoe crab. 相似文献