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排序方式: 共有504条查询结果,搜索用时 31 毫秒
1.
神经生长因子对小鼠突触体内Ca^2+水平的调节作用 总被引:4,自引:1,他引:3
观察了多次海马内微注射NGF对小鼠突触体内游离钙水平的影响,并在离体情况下观察NGF对EGTA和CaCl2分别造成突触体内低钙和高钙状态的调节作用。结果如下:(1)在体实验表明,一定剂量的NGF可显著降低老年小鼠海马突触体内游离钙水平(P<005);(2)离体实验表明,当突触体游离钙水平降低时,适当剂量的NGF具有升高游离钙水平的作用;而突触体内游离钙水平升高时,则NGF有降低游离钙水平的作用。提示NGF对游离钙水平的双向调节作用可能是NGF改善老年性记忆衰退的作用机制。 相似文献
2.
MY Mancao LJ Sindel PH Richardson FM Silver 《Acta paediatrica (Oslo, Norway : 1992)》1996,85(1):118-120
Croup is an acute infectious illness usually occurring in children; it is characterized by brassy cough and stridor. The main pathogens include mainly parainfluenza and influenza viruses. Recently there have been reports of prolonged croup caused by the herpes simplex viruses. We report two cases of prolonged croup due to herpes simplex types 1 and 2. We also review and summarize the reported pediatric cases of herpetic croup. 相似文献
3.
Duncan WC; Illingworth PJ; Young FM; Fraser HM 《Human reproduction (Oxford, England)》1998,13(9):2532-2540
The molecular mechanisms involved in luteolysis are still unclear in the
primate. This study aimed to investigate the effect of induced luteolysis
on the ovarian luteinizing hormone (LH) receptor and the steroidogenic
enzyme, 3beta-hydroxysteroid dehydrogenase (3beta-HSD) in the marmoset
monkey. Luteolysis was induced in the mid-luteal phase either directly by
systemic prostaglandin F2alpha (PGF2alpha), or indirectly by LH withdrawal
using systemic gonadotrophin releasing hormone antagonist (GnRHant)
treatment. The LH receptor was studied by isotopic mRNA in-situ
hybridization and in-situ ligand binding and 3beta-HSD expression was
studied using isotopic mRNA in-situ hybridization and immunohistochemistry.
Induced luteolysis was associated with a reduction in the expression of LH
receptor (P < 0.0001) and 3beta-HSD mRNA, closely followed by a
reduction in the LH receptor (P < 0.05) and 3beta-HSD protein
concentrations within 24 h. There were no differences in the findings
whether luteolysis was induced with PGF2alpha or GnRHant. This study shows
that disparate mechanisms to induce luteolysis in the primate result in an
identical rapid loss of the LH receptor and 3beta-HSD. In conclusion,
induced luteolysis leads to rapid loss of the steroidogenic pathway in
luteal cells.
相似文献
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General primer polymerase chain reaction in combination with sequence analysis for identification of potentially novel human papillomavirus genotypes in cervical lesions.
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A J van den Brule P J Snijders P M Raaphorst H F Schrijnemakers H Delius L Gissmann C J Meijer J M Walboomers 《Journal of clinical microbiology》1992,30(7):1716-1721
We recently described the detection of potentially novel human papillomaviruses (HPV) genotypes (HPV types X [HPV X]) in cervical smears (A. J. C. van den Brule, C. J. L. M. Meijer, V. Bakels, P. Kenemans, and J. M. M. Walboomers, J. Clin. Microbiol. 28:2739-2743, 1990) by using the general primer-mediated polymerase chain reaction method (GP-PCR). In this study, the HPV specificities of GP-PCR products were determined by sequence analyses. M13 bacteriophage clones of PCR products derived from cloned unsequenced HPV genotypes 13, 32, 35, 43, 44, 45, 51, and 56 were subjected to dideoxy sequencing. Analyses of the putative amino acid sequences of these HPV types in addition to published HPV sequence data revealed stretches of highly conserved amino acid residues present in all HPV types, resulting in an HPV amino acid consensus sequence. Subsequently, HPV X-specific PCR products found in premalignant cervical lesions (n = 3), carcinomas in situ (n = 6), and invasive cancer (n = 6) were analyzed for their nucleotide sequences. Comparison of these sequences with published HPV nucleotide sequences and data obtained in this study revealed three HPV type 35, two HPV type 45, one HPV type 51, two HPV type 56, and six unique HPV X sequences, of which three types were present in four cases of carcinomas (in situ). The nucleotide sequences determined appeared to be unique after a data bank search. Furthermore, the sequences of all HPV X isolates matched the HPV amino acid consensus sequence, thus confirming HPV specificity. This study illustrates the power of GP-PCR in combination with sequence analysis to determine HPV specificity and genotyping of PCR products derived from sequenced as well as unsequenced HPVs, including novel, not yet identified HPV types. 相似文献
8.
van Galen JC Dukers DF Giroth C Sewalt RG Otte AP Meijer CJ Raaphorst FM 《European journal of immunology》2004,34(7):1870-1881
Polycomb group (PcG) genes encode two chromatin-binding protein complexes, the PRC1 and the PRC2 PcG complexes, which are essential for the maintenance of cell identity and play a role in oncogenesis. PcG complexes were recently identified as novel regulators of hematopoiesis, and appear to be expressed in a non-overlapping pattern in resting and mature follicular B cells. Using highly specific antisera in combination with immunohistochemistry and triple immunofluorescence, we investigated the expression pattern of nine human PcG genes in germinal center (GC) B cells and highly purified germinal center B cell subpopulations. PcG proteins were detected in characteristic binding patterns that were not necessarily related to mutually exclusive expression of the two PcG complexes. We conclude that the two PcG complexes are expressed throughout GC development, and that the fine composition of each complex is determined by the differentiation status of the cell. In addition, a subset of dividing cells with a centrocyte CD marker profile was identified that co-expresses core components of the PRC1 and PRC2 complex. We propose that these cells reflect a transitional stage between resting and dividing follicular B lymphocytes, and that they possibly represent the healthy precursors of nodal large B cell lymphomas. 相似文献
9.
Transition metal complexes containing vanadium IV have been shown to
modulate the cellular redox potential and catalyse the generation of
reactive oxygen intermediates (ROI). Since sperm function is exquisitely
susceptible to ROI, we examined the effects of stable chelate complexes of
vanadocenes on human sperm motility. We synthesized seven structurally
distinct chelate complexes of bis(cyclopentadienyl)vanadium(IV) with
bidentate ligands [i.e. vanadocene acetylacetonato monotriflate (VDacac),
vanadocene hexafluoro acetylacetonato monotriflate (VDHfacac), vanadocene
N-phenyl benzohydroxamato monotriflate (VDPH), vanadocene acethydroxamato
monotriflate (VDH), vanadocene catecholate (VDCAT), vanadocene bipyridino
ditriflate (VDBPY), and vanadocene dithiocarbamate monotriflate (VDDTC)],
and evaluated their spermicidal activity using computer-assisted sperm
analysis (CASA; Hamilton-Thorne). All seven chelate complexes of vanadocene
elicited potent spermicidal activity at micromolar concentrations (EC50
values: 3.9-106 microM) without affecting the sperm acrosome integrity. The
catecholate and acetylacetonate complexes of vanadocene were the most
active and the bipyridyl complex the least active with an order of efficacy
VDCAT > VDacac > VDDTC > VDPH > VDH > VDHfacac > VDBPY.
The spermicidal activity of chelate complexes of vanadocenes was rapid and
irreversible since the treated spermatozoa underwent apoptosis, as
determined by the flow cytometric analysis of mitochondrial membrane
potential, surface annexin V binding assay, in-situ nick-end labelling of
sperm nuclei, and confocal laser scanning microscopy. These results provide
unprecedented evidence that chelate complexes of vanadocene with bidentate
ligands have spermicidal and apoptosis inducing properties. These
vanadocene complexes, especially VDacac, may be useful as contraceptive
agents.
相似文献
10.
We determined if we could transfer X-radiation resistance from CHO AA8 cells to their radiosensitive, mutant V3 cells by several methods. These methods include co-incubating the two cell lines for three days before irradiation, adding heavily-irradiated AA8 to V3 cells following irradiation of the latter and then co-incubating these cells for at least eight days during the colony-forming assay and lastly, adding conditioned medium from unirradiated, subconfluent AA8 cells to V3 cultures and incubating for two days before irradiation. None of these procedures enhanced the clonogenic survival of the V3 cells to a single dose of 4 Gy X-radiation. Adding heavily-irradiated V3, instead of AA8, cells did not increase the clonogenic survival of the 4 Gy-irradiated V3 cells either, indicating that there was no autocrine mode of action. Moreover, adding conditioned medium from a related CHO cell line, K1, to its own radiosensitive, mutant 5-11 and incubating for two days before irradiation did not enhance clonogenic survival of the latter to a single dose of 3 Gy X-radiation. We therefore conclude that it is unlikely that CHO cells have the X-radiation resistance factor that has been reported in some mouse melanoma cell lines by other investigators. 相似文献