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831.
Humayun Khalid Keisuke Tsutsumi Hiromi Yamashita Masao Kishikawa Akio Yasunaga Shobu Shibata 《Cellular and molecular neurobiology》1995,15(2):257-268
Summary 1. Cellular expression and distribution of the stress response small heat shock protein 27 (hsp27) in 39 high-grade astrocytomas (27 glioblastoma multiformes, 12 anaplastic astrocytomas) and in 27 low-grade astrocytomas (grade I–II) were analyzed immunohistochemically.2. The correlation between hsp27 expression and tumor growth fractions of the astrocytomas was examined following Ki-67 immunostaining.3. The hsp27 staining was cell cytoplasmic. The hsp27 immunopositive rate was significantly higher in high-grade astrocytomas; the rates were 74% for glioblastomas, 58% for anaplastic astrocytomas, and 37% for low-grade astrocytomas. The small and large tumor cells, especially in glioblastomas, multinucleated tumor giant cells, tumor cells in the pseudopalisading and necrotic areas, cells of the microvascular endothelial proliferations, and tumor vascular smooth muscles were usually hsp27 positive. The mean percentage of hsp27-positive cells was significantly higher in the glioblastomas alone and in the combined high-grade astrocytomas, compared to the low-grade, and in recurrent rather than in primary high-grade astrocytomas.4. The high-grade astrocytomas had a highly statistical significant Ki-67 labeling index. The Ki-67 labeling indices were significantly higher in the hsp27-positive than the hsp27-negative astrocytomas, irrespective of the histological grade. In the high-grade astrocytomas with a Ki-67 labeling index of five and above, 81% of those tumors were hsp27 positive.5. Thus, a large number of human astrocytomas express hsp27, and hsp27 expression correlates with histological grades of astrocytoma and with tumor growth fractions. This being the case, hsp27 is likely to have a role in the growth of human astrocytomas. 相似文献
832.
Lectin cytochemistry was used to identify surface epitopes selectively expressed by chromaffin cell chemoreceptors (glomus cells) in the rat carotid body. Unexpectedly, these studies revealed that binding sites for peanut agglutinin (PNA; Arachis hypogea) were highly expressed by all neuroendocrine derivatives of the sympathoadrenal neural crest, including glomus cells, small, intensely fluorescent cells, and adrenal chromaffin cells in situ. In contrast, principal sympathetic neurons did not express PNA receptors. PNA binding was inhibited by 2% galactose. To determine whether expression of PNA receptors was selectively induced by neuroendocrine differentiation of sympathoadrenal precursors, we compared PNA labeling of embryonic sympathoblasts in the presence of either nerve growth factor (NGF) or the synthetic glucocorticoid dexamethasone (DEX). Dex-treated cells, which expressed several neuroendocrine traits, bound PNA, whereas NGF-treated neuronal derivatives did not. In addition, to examine whether expression of existing PNA receptors was down-regulated by neuronal differentiation of chromaffin cells, we compared labeling of PC12 cells, which normally bind PNA, in the presence and absence of NGF. Although PC12 cells acquired characteristic neuronal morphologies in the presence of NGF, they did not lose PNA labeling, even after 8 days of NGF treatment. These findings indicate that neuronal and neuroendocrine derivatives of the sympathoadrenal lineage can be distinguished by differential expression of carbohydrate epitopes and suggest that PNA receptors are induced by neuroendocrine differentiation. © 1995 John Wiley & Sons, Inc. 相似文献
833.
菠菜叶片提取液经PEG-6000沉淀、DE-52离子交换柱层析及分子筛SephectylS-300凝胶过滤得到两种分子量不同的依赖ATP的磷酸果糖激酶(PFK)。一为大分子酸型,分子量大于2000kD,其活力可被Pi、3-PGA、柠檬酸激活,被PEP强烈抑制,Pi能减缓此抑制作用,Mg2+为必需金属离子,但其浓度高于0.5mmol/L时酶活力降低;一为小分子酸型,分子量为300kD,其活性受Pi、3-PGA、柠檬酸和PEP抑制,Mg2+亦为必需金属离子,Hill系数为0.67,表现负协同效应。实验证明小分子酸型可能存在叶绿体中,大分子酸型属于胞质酶。 相似文献
834.
Sucrose-phosphate synthase activity and yield analysis of tomato plants transformed with maize sucrose-phosphate synthase 总被引:11,自引:0,他引:11
Marianne M. Laporte Julie A. Galagan Joseph A. Shapiro Michael R. Boersig Christine K. Shewmaker Thomas D. Sharkey 《Planta》1997,203(2):253-259
Sucrose synthesis is a major element of the interactions between photosynthesis and plant growth and development. Tomato (Lycopersicon esculentum Mill. cv. UC82B) plants transformed with maize sucrose-phosphate synthase (SPS; EC 2.3.1.14) expressed from either a ribulose-1,5-bisphosphate
carboxylase-oxygenase (Rubisco) small subunit promoter (SSU) or the cauliflower mosaic virus 35S promoter (35S) were used
to study effects of increased sucrose synthesis rates on plant growth. The plants were grown in growth chambers, field plots,
and open-top chambers. The 35S plants had a 2 to 3-fold increase in young-leaf SPS activity, a 10 to 20-fold increase in young-root
SPS activity and no increase in young-fruit SPS activity. The leaf SPS activity in one of the 35S lines fell to control levels
by two months of age. The SSU plants had a 4 to 5-fold increase in leaf SPS activity and no significant increase in root or
young-fruit SPS activity. One 35S line, which maintained high leaf SPS activity throughout development, yielded 70–80% more
than controls at both normal and elevated CO2 in open-top chambers in the field and 20–30% more than controls in two additional field trials. The other 35S line and the
two SSU lines either yielded less or did not differ from controls under several growth conditions. Since only one of four
transformed lines showed an increase in yield, we can not yet conclude that increased leaf SPS activity leads to increased
yield. However, increased leaf SPS activity appears to result in increased fruit sugar content since all three lines with
increased leaf SPS usually also had increased fruit sugars.
Received: 18 November 1996 / Accepted: 22 January 1997 相似文献
835.
同步辐射小角X射线散射(SAXS)实验站所用的探测器由原来的NaI闪烁计数器改为位置灵敏探测器,其位置分辨好于100 μm,有效探测面积为50 mm×10 mm,得到了较以往更高质量的SAXS谱,并成功地对液体样品的SAXS谱进行了测试. 相似文献
836.
Seven unique substitutions have been introduced by site-directed mutagenesis into the first conserved region of the small subunit of ribulose bisphosphate carboxylase/oxygenase from Anacystis nidulans 6301. After expression of each large, altered-small subunit gene tandem in Escherichia coli, two substitutions in the small subunit tyr17asp17 (Y17D) and arg10gly10 (R10G) result in little or no carboxylase activity. For the latter substitution, no L8S8enzyme complex could be detected suggesting that this mutation prevents assembly. Mutant enzymes containing the following substitutions R11G, T14A, S16A, Y17D and P19A have CO2/O2specificity factors ( values) of 40, 35, 18, 39 and 44, respectively, compared with that of 44 for wild-type recombinant enzyme whereas P20A has full carboxylase activity and a value of 55. 相似文献
837.
The structure of the keratan sulphate chains attached to fibromodulin from human articular cartilage
The small keratan sulphate proteoglycan, fibromodulin, has been isolated from pooled human articular cartilage. The main chain
repeat region and the chain caps from the attached N-linked keratan sulphate chains have been fragmented by keratanase II
digestion, and the oligosaccharides generated have been reduced and isolated. Their structures and abundance have been determined
by high pH anion-exchange chromatography.
These regions of the keratan sulphate from human articular cartilage fibromodulin have been found to have the following general
structure:
Significantly, both α(2-6)- and α(2-3)-linked N-acetyl-neuraminic acid have been found in the capping oligosaccharides. Fucose,
which is α(1-3)-linked as a branch to N-acetylglucosamine, has also been found along the length of the repeat region and in
the capping region. The chains, which have been found to be very highly sulphated, are short; the length of the repeat region
and chain caps is ca. nine disaccharides.
These data demonstrate that the structure of the N-linked keratan sulphate chains of human articular cartilage fibromodulin
is similar, in general, to articular cartilage derived O-linked keratan sulphate chains. Further, the general structure of
the keratan sulphate chains attached to human articular cartilage fibromodulin has been found to be generally similar to that
of both bovine and equine articular cartilage fibromodulin.
Abbreviations: KS, keratan sulphate; IEC, ion-exchange chromatography; ELISA, enzyme linked immunosorbent assay; Gal, β-D-galactose;
Fuc, α-L-Fucose; GlcNAc, N-acetylglucosamine (2-acetamido-β-D-glucose); GlcNAc-ol, N-acetylglucosaminitol (2-acetamido-D-glucitol);
NeuAc, N-acetyl-neuraminic acid; 6S/(6S), O-ester sulphate group on C6 present/sometimes present; NMR -nuclear magnetic resonance;
HPAE, high pH anion-exchange; PED, pulsed electrochemical detection; HPLC, high performance liquid chromatography
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
838.
To evaluate the rate at which the four main aflatoxins (aflatoxins B1, B2, G1 and G2) are able to cross the luminal membrane of the rat small intestine, a study about intestinal absorption kinetics of these mycotoxins has been made. In situ results obtained showed that the absorption of aflatoxins in rat small intestine is a very fast process that follows first-order kinetics, with an absorption rate constant (k
a
) of 5.84±0.05 (aflatoxin B1), 4.06±0.09 (aflatoxin B2), 2.09±0.03 (aflatoxin G1) and 1.58±0.04 (aflatoxin G2) h–1, respectively. 相似文献
839.
Jan Decher 《Biodiversity and Conservation》1997,6(7):1007-1026
This article considers the conservation of relict natural habitat in West Africa, especially habitat preserved in traditional
sacred groves. Government-sanctioned conservation is contrasted with local grassroots efforts of conservation. Evidence for
the ecological value of sacred groves is based on results of a field study of small mammal communities conducted on the Accra
Plains of Ghana and on published sources on the conservation and use of sacred groves from various countries. The study employed
standard mark-and-recapture techniques for the sampling for terrestrial small mammals, and mist netting for the sampling of
bat communities. Pragmatic approaches combining conservation and sustainable use are considered, as are traditional values
that have preserved the sacred groves in the past for up to several hundred years in some cases. In part because these groves
shelter unique small mammal and plant communities, traditional values and protection mechanisms should be integrated into
the newly emerging cultural and religious contexts. The issues encountered during this study reveal that effective conservation
involving local peoples requires a concerted interdisciplinary effort.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
840.