首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   85篇
  免费   8篇
  93篇
  2023年   1篇
  2022年   3篇
  2021年   2篇
  2020年   1篇
  2019年   2篇
  2018年   2篇
  2017年   4篇
  2016年   4篇
  2015年   4篇
  2014年   5篇
  2013年   7篇
  2012年   4篇
  2011年   6篇
  2010年   7篇
  2009年   3篇
  2008年   4篇
  2007年   1篇
  2006年   2篇
  2005年   2篇
  2004年   2篇
  2002年   1篇
  2001年   1篇
  1999年   2篇
  1998年   4篇
  1996年   2篇
  1995年   3篇
  1994年   2篇
  1993年   2篇
  1989年   1篇
  1988年   1篇
  1987年   1篇
  1982年   1篇
  1978年   1篇
  1977年   3篇
  1974年   1篇
  1958年   1篇
排序方式: 共有93条查询结果,搜索用时 9 毫秒
1.
We compared male-reproductive-tract polypeptides of Drosophila melanogaster and D. simulans by using two-dimensional gel electrophoresis. Approximately 64% of male-reproductive-tract polypeptides were identical between two randomly chosen isofemale lines from these two species, compared with 83% identity for third-instar imaginal wing-disc polypeptides. Qualitatively similar differences were found between reproductive tracts and imaginal discs when D. sechellia was compared with D. melanogaster and with D. simulans. When genic polymorphism was taken into account, approximately 10% of male- reproductive-tract polypeptides were apparently fixed for different alleles between D. melanogaster and D. simulans; this proportion is the same as that found for soluble enzymes by one-dimensional gel electrophoresis. Strikingly, approximately 20% of male-reproductive- tract polypeptides of either D. melanogaster or D. simulans had no detectable homologue in the other species. We propose that proteins of the Drosophila male reproductive tract may have diverged more extensively between species than have other types of proteins and that much of this divergence may involve large changes in levels of polypeptide expression.   相似文献   
2.
When the outer surface of short-circuited frog skin was penetrated with microelectrodes, stable negative potentials that averaged near -100 mV were recorded consistently, confirming the results of Nagel (W. Nagel. 1975. Abstracts of the 5th International Biophysics Congress, Copenhagen. P-147.). The appearance of these stable potentials, V(O), concurrent with the observations that (a) a high resistance outer barrier R(O) accounting for approximately 75 percent or more of the transcellular resistance of control skins had been penetrated and that (b) 10(-5) M amiloride and reduced [Na] outside caused the values of V(O) to increase towards means value near -130 mV while the values of percent R(O) increased to more than 90 percent. It was of relationships were the same as the values of E(1) observed in studies of the current-voltage relationships were the same as the values of E’(1) defined as the values of voltage at the inner barrier when the V(O) of the outer barrier was reduced to zero by voltage clamping of the skins. Accordingly, these data are interpreted to mean that the values of E(1), approximately 130 mV, represent the E(Na) of the sodium pump at the inner barrier. 2,4-DNP was observed to decrease the values of transepithelial voltage less than E(1) the V(O) was negative. These data can be interpreted with a simple electrical equivalent circuit of the active sodium transport pathway of the frog skin that includes the idea that the outer membrane behaves as an electrical rectifier for ion transport.  相似文献   
3.

Background

In the absence of vaccines and limitations of currently available chemotherapy, development of safe and efficacious drugs is urgently needed for visceral leishmaniasis (VL) that is fatal, if left untreated. Earlier we reported in vitro apoptotic antileishmanial activity of n-hexane fractions of Artemisia annua leaves (AAL) and seeds (AAS) against Leishmania donovani. In the present study, we investigated the immunostimulatory and therapeutic efficacy of AAL and AAS.

Methodology/Principal Findings

Ten-weeks post infection, BALB/c mice were orally administered AAL and AAS for ten consecutive days. Significant reduction in hepatic (86.67% and 89.12%) and splenic (95.45% and 95.84%) parasite burden with decrease in spleen weight was observed. AAL and AAS treated mice induced the strongest DTH response, as well as three-fold decrease in IgG1 and two-fold increase in IgG2a levels, as compared to infected controls. Cytometric bead array further affirmed the elicitation of Th1 immune response as indicated by increased levels of IFN-γ, and low levels of Th2 cytokines (IL-4 and IL-10) in serum as well as in culture supernatant of lymphocytes from treated mice. Lymphoproliferative response, IFN-γ producing CD4+ and CD8+ T lymphocytes and nitrite levels were significantly enhanced upon antigen recall in vitro. The co-expression of CD80 and CD86 on macrophages was significantly augmented. CD8+ T cells exhibited CD62Llow and CD44hi phenotype, signifying induction of immunological memory in AAL and AAS treated groups. Serum enzyme markers were in the normal range indicating inertness against nephro- and hepato-toxicity.

Conclusions/Significance

Our results establish the two-prong antileishmanial efficacy of AAL and AAS for cure against L. donovani that is dependent on both the direct leishmanicidal action as well as switching-on of Th1-biased protective cell-mediated immunity with generation of memory. AAL and AAS could represent adjunct therapies for the treatment of leishmaniasis, either alone or in combination with other antileishmanial agents.  相似文献   
4.
Aims Our study was conducted in the Nokrek Biosphere Reserve (NBR) in the Garo hills districts of Meghalaya, Northeast India. Our aim was to assess the effects of human activities on plant diversity,population structure and regeneration.Methods We selected a representative 1.2 hm2 stand in both the core and buffer zones of NBR. Structure and composition were determined by randomly sampling square quadrats, population structure was assessed by determining age structure, and regeneration was assessed by measuring densities of seedling, sapling and adult trees.Important findings More woody species were recorded from the core zone than the buffer zone (87 vs. 81 species), and there were a large number of tropical, temperate, and Sino-Himalayan, Burma-Malaysian and Malayan elements, primitive families and primitive genera. The trees were distributed in three distinct strata,canopy, subcanopy and sapling. Subcanopy and sapling layers had the highest species richness (81% -88% ). Lauraceae and Euphorbiaceae were the dominant families in terms of the number of species, and a large number of families were represented by single species. Most woody species (57 % - 79 % ) were contagiously distributed and had low frequency ( < 20% ). Although stand density was high in the buffer zone, its basal area was low compared to the stand in the core zone. Low similarity and high β-diversity indicate marked differences in species composition of the stands. Shannon diversity index was high in both the stands, while Simpson dominance index was low. The diameter-class distribution for dominant species revealed that the most had a large number of young individuals in their populations. Preponderance of tree seedlings, followed by a steep decline in population density of saplings and adult trees, indicated that the seedling to sapling stage was the most critical in the life cycle of the tree populations. Most species (42 % - 48 % ) had no regeneration,25 % - 35 % had good/fair regeneration, and the rest had poor regeneration or reoccurred as immigrants.  相似文献   
5.
Diclofenac sodium is known to interfere with renal physiology by inhibiting prostaglandins. Previous studies indicate that various nephrotoxins damage proximal renal tubules by altering alkaline phosphatase (APase) activity. APase has been reported to be a function related marker in renal proximal tubular epithelia where it is highly expressed. Present investigation deals with toxicity caused in mice kidney at histological and biochemical levels after diclofenac administration. Diclofenac toxicity was assessed by localizing APase in kidney histochemically and biochemically. Intramuscular diclofenac administration (10 mg/kg/body wt) for 30 days exhibited substantial degeneration in kidney. A marked change in APase activity was observed in histochemical and biochemical studies. A change was noticed in specific activity of APase at different periods of diclofenac treatment. Decrease in specific activity of APase after 10 days (18.41 %) and 30 days (55.3 %) of diclofenac exposure was observed. However, an insignificant hike in APase was observed after 20 days of drug therapy. Similar trends in APase activity were evidenced by the electrophoretic analysis. Histological and ultrastructural observations also corroborated above mentioned findings. Present investigation gives an insight into probable mechanism of renal pathology caused by diclofenac administration in mice.  相似文献   
6.
Several options for treating Herpes Simplex Virus type 1 and type 2 are available. However, non-specific inhibition and drug resistance warrants the discovery of new anti-herpetic compounds with better therapeutic profile or different mode of action. The non-nucleoside inhibitors of HSV DNA polymerase target the site that is less important for the binding of a natural nucleoside or nucleoside inhibitors. In the present study, we have explored the possibility to find a new lead molecule based on α-pyrone analogs as non-nucleoside inhibitors using structure based modeling approach. The designed molecules were synthesized and evaluated for anti-HSV activity using MTT assay. The compound 5h with EC(50) 7.4μg/ml and CC(50) 52.5μg/ml was moderately active against HSV when compared to acyclovir. A plaque reduction assay was also carried out and results reveal that 5h is more effective against HSV-1 with better selective index of 12.8 than against HSV-2 (SI=3.6). The synthesized compounds were also evaluated for anti-HIV activity, but none were active.  相似文献   
7.
8.
Cathepsins have been found to have important physiological roles. The implication of cathepsin L in various types of cancers is well established. In a search for selective cathepsin L inhibitors as anticancer agents, a series of 2-cyanoprrolidine peptidomimetics, carrying a nitrile group as warhead, were designed. Two series of compounds, one with a benzyl moiety and a second with an isobutyl moiety at P(2) position of the enzyme were synthesized. The synthesized compounds were evaluated for inhibitory activity against human cathepsin L and cathepsin B. Although, none of the compounds showed promising inhibitory activity, (E)N-{(S)1-[(S)2-cyano-1-pyrrolidinecarbonyl]-3-methylbutyl}-2,3-diphenylacrylamide (24) with an isobutyl moiety at P(2) was found to show selectivity as a cathepsin L inhibitor (Ki 5.3 microM for cathepsin L and Ki > 100 microM for cathepsin B). This compound could act as a new lead for the further development of improved inhibitors within this inhibitor type.  相似文献   
9.
Gold nanoparticles (GNPs) based dipstick competitive immunoassay was developed to detect organochlorine pesticide such as DDT at nanogram level (ppb). GNPs of definite size were synthesized and conjugated to anti-DDT antibodies (IgY), which served as the detecting reagent. DDA-BSA conjugate (antigen) was immobilized on to nitro cellulose (NC) membrane containing strip. GNPs conjugated anti-DDT antibodies were treated with different concentrations of free DDT ranging from 0.7 ng mL−1 to 1000 ng mL−1 to form an immunocomplex. This immunocomplex solution was further reacted with DDA-BSA conjugate immobilized NC membrane containing strips by dipping the strip in the immunocomplex solution. The free GNPs conjugated anti-DDT antibodies present in the immunocomplex solution were targeted for competitive binding with immobilized DDA-BSA on NC membrane containing strip. Depending on the concentration of free DDT in the sample the binding of GNPs conjugated anti-DDT antibodies to the immobilized DDA-BSA varied and was detected by the development of red color (due to gold nanoparticles) in the detection zone of NC membrane containing strips. The intensity of color development was inversely proportional to the DDT concentration with maximum intensity at zero DDT concentration. The lowest detection limit of DDT was determined to be 27 ng mL−1 with the optimized conditions. The dipstick technique based on GNPs is suitable for the detection of several toxins in food and environmental samples and can be applied for rapid on-site testing of pesticides.  相似文献   
10.
Recent experiments using expression, immunolocalization, and cell culture approaches have provided leading insights into regulation of luteal angiogenesis by different growth factor systems and its role in the function of corpus luteum (CL) in buffalo. On the contrary, lymphangiogenesis and its regulation in the CL are still poorly understood. The aim of this study was to evaluate the expression and localization of lymphangiogenic factors (vascular endothelial growth factor [VEGF]-C and VEGFD), their receptor (VEGFR3), and lymphatic endothelial marker (LYVE1) in bubaline CL during different stages of the estrous cycle and to investigate functional role of VEGFC and VEGFD in luteal lymphangeogenesis. The mRNA and protein expression of VEGFC, VEGFD, and VEGFR3 was significantly greater in mid and late luteal phases, which correlated well with the expression of LYVE1. The lymphangiogenic factors were localized in luteal cells, exclusively in the cytoplasm. Immunoreactivity of VEGFC was greater during midluteal phase and that of VEGFD was greater during the mid and late luteal phases. Luteal cells were cultured in vitro and treated for different time duration (24, 48, and 72 hours) with VEGFC and VEGFD each at 50, 100, and 150 ng/mL concentration and VEGFC with VEGFD at 100 ng/mL concentration. The temporal increase in LYVE1 mRNA expression was significant (P < 0.05) in VEGFC and VEGFC with VEGFD treatment and no significant change was seen in VEGFD treatment. Thus, it seems likely that VEGFD itself has little role in lymphangiogenesis but along with VEGFC it might have a synergistic effect on VEGFR3 receptors for inducing lymphangiogenesis. In summary, the present study provided evidence that VEGFC and VEGFD, and their receptor VEGFR3, are expressed in bubaline CL and are localized exclusively in the cell cytoplasm, suggesting that these factors have a functional role in lymphangiogenesis of CL in buffalo.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号