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排序方式: 共有132条查询结果,搜索用时 31 毫秒
1.
Ultrastructural analyses revealed the presence of six hemocyte types in the hemolymph of Panstrongylus megistus, partially confirming our previous results obtained through light microscopy. Prohemocytes: small, round hemocytes with a thin cytoplasm layer, especially rich in free ribosomes and poor in membranous systems. Plasmatocytes: polymorphic cells, whose cytoplasm contains many lysosomes and a well developed rough endoplasmic reticulum (RER). They are extremely phagocytic. Sometimes, they show a large vacuolation. Granulocytes: granular hemocytes whose granules show different degrees of electrodensity. Most of them, have an internal structuration. Coagulocytes: oval or elongated hemocytes, which show pronounced perinuclear cisternae as normally observed in coagulocytes. The cytoplasm is usually electrodense, poor in membranous systems and contains many labile granules. Oenocytoids: large and very stable hemocytes, whose homogeneous cytoplasm is rich in loose ribosomes and poor in membranous systems. Adipohemocytes: large cells, containing several characteristic lipid droplets. The cytoplasm is also rich in glycogen, RER and large mitochondria. The total and differential hemocyte count (THC and DHC) were also calculated for this reduviid. THC increases from 2,900 hemocytes/mm3 of hemolymph in the 4th instar to 4,350 in the 5th and then, decreases to 1,950 in the adults. Plasmatocytes and coagulocytes are the predominant hemocyte types. 相似文献
2.
J. Loch 《Plant and Soil》1985,83(1):77-83
Summary On the basis of pot experiments carried out on soils with different Mg contents using ryegrass, it could be established that Mg uptake by ryegrass is closely related to Mg in the EUF extracts. The Mg contents in the EUF extracts are therefore suitable indices of actually and potentially available Mg in soils.The ratio between Mg in the EUF extracts and Mg deposited on the electrode + filter varies. The absolute amount of Mg in the EUF extracts increases with increasing Mg content of the soils. The higher, however, the total desorbable Mg the lower are the Mg contents in the EUF extracts in comparison with the Mg contents deposited on electrode + filter. Besides total desorbable Mg the EUF-Mg fractions are influenced as well by the organic and inorganic CEC and by soil pH. The amount of EUF filtrate flowing through filter and electrode also has an influence on the amount of Mg in the EUF filtrate.Consequently for a proper evaluation of available soil Mg total EUF-Mg (Mg in the EUF filtrate + Mg deposited on electrode + filter) should be used. 相似文献
3.
A highly conserved nuclear gene for low-level phylogenetics: elongation factor-1 alpha recovers morphology-based tree for heliothine moths 总被引:8,自引:2,他引:6
Cho S; Mitchell A; Regier JC; Mitter C; Poole RW; Friedlander TP; Zhao S 《Molecular biology and evolution》1995,12(4):650-656
Molecular systematists need increased access to nuclear genes. Highly
conserved, low copy number protein-encoding nuclear genes have attractive
features for phylogenetic inference but have heretofore been applied mostly
to very ancient divergences. By virtue of their synonymous substitutions,
such genes should contain a wealth of information about lower-level
taxonomic relationships as well, with the advantage that amino acid
conservatism makes both alignment and primer definition straightforward. We
tested this postulate for the elongation factor-1 alpha (EF-1 alpha) gene
in the noctuid moth subfamily Heliothinae, which has probably diversified
since the middle Tertiary. We sequenced 1,240 bp in 18 taxa representing
heliothine groupings strongly supported by previous morphological and
allozyme studies. The single most parsimonious gene tree and the
neighbor-joining tree for all nucleotides show almost complete concordance
with the morphological tree. Homoplasy and pairwise divergence levels are
low, transition/transversion ratios are high, and phylogenetic information
is spread evenly across gene regions. The EF-1 alpha gene and presumably
other highly conserved genes hold much promise for phylogenetics of
Tertiary age eukaryote groups.
相似文献
4.
Dipeptidyl peptidase IV (DPP IV) is a serine exopeptidase expressed at high levels in rat kidney, liver and lung. We established eight monoclonal antibodies against partially purified DPP IV from rat liver plasma membranes. By means of a competitive dot blot assay with purified DPP IV, these antibodies were shown to recognize four different epitopes of the glycoprotein, designated A - D. The epitopes are located on the extracellular domain of DPP IV, as shown by papain digestion of liver plasma membranes. Treatment of DPP IV with neuraminidase and glycopeptide N-glycosidase F, as well as incubation of hepatocytes with the alpha-mannosidase I inhibitor deoxymannojirimycin, revealed that epitope A may be formed by a mannose-rich sugar chain and epitope D might represent a complex carbohydrate structure in the mature glycoprotein, while the epitopes B and C are formed by the protein moiety. Concanavalin A reduced the binding of monoclonal antibody to epitope A by 78%. Binding to epitope D was blocked by 73% with wheat germ lectin, and by more than 99% with sialic acid; epitopes B and C were unaffected by any of the lectins or sugars tested. The immunological cross-reactivity with DPP IV from Morris hepatoma 7777 was demonstrated with monoclonal antibodies against epitopes A-C. Epitope D was not recognized on hepatoma DPP IV. However, in addition to DPP IV, four hepatoma plasma membrane glycoproteins were precipitated by the monoclonal antibody against the epitope D, indicating that this epitope is not uniquely restricted to DPP IV. 相似文献
5.
Stich S Loch A Leinhase I Neumann K Kaps C Sittinger M Ringe J 《European journal of cell biology》2008,87(6):365-376
For bone repair, transplantation of periosteal progenitor cells (PCs), which had been amplified within supportive scaffolds, is applied clinically. More innovative bone tissue engineering approaches focus on the in situ recruitment of stem and progenitor cells to defective sites and their subsequent use for guided tissue repair. Chemokines are known to induce the directed migration of bone marrow CD34(-) mesenchymal stem cells (MSCs). The aim of our study was to determine the chemokine receptor expression profile of human CD34(-) PCs and to demonstrate that these cells migrate upon stimulation with selected chemokines. PCs were isolated from periosteum of the mastoid bone and displayed a homogenous cell population presenting an MSC-related cell-surface antigen profile (ALCAM(+), SH2(+), SH3(+), CD14(-), CD34(-), CD44(+), CD45(-), CD90(+)). The expression profile of chemokine receptors was determined by real-time PCR and immunohistochemistry. Both methods consistently demonstrated that PCs express receptors of all four chemokine subfamilies CC, CXC, CX(3)C, and C. Migration of PCs and a dose-dependent migratory effect of the chemokines CCL2 (MCP1), CCL25 (TECK), CXCL8 (IL8), CXCL12 (SDF1alpha), and CXCL13 (BCA1), but not CCL22 (MDC) were demonstrated using a 96-multiwell chemotaxis assay. In conclusion, for the first time, here we report that human PCs express chemokine receptors, present their profile, and demonstrate a dose-dependent migratory effect of distinct chemokines on these cells. These results are promising towards in situ bone repair therapies based on guiding PCs to bone defects, and encourage further in vivo studies. 相似文献
6.
7.
AV Shevchenko IG Budzanivska TP Shevchenko VP Polischuk D Spaar 《Archives Of Phytopathology And Plant Protection》2013,46(2):139-146
The work was focused on the investigation of possible dependencies between the development of viral infection in plants and the presence of high heavy metal concentrations in soil. Field experiments have been conducted in order to study the development of systemic tobacco mosaic virus (TMV) infection in Lycopersicon esculentum L. cv. Miliana plants under effect of separate salts of heavy metals Cu, Zn and Pb deposited in soil. As it is shown, simultaneous effect of viral infection and heavy metals in tenfold maximum permissible concentration leads to decrease of total chlorophyll content in experiment plants mainly due to the degradation of chlorophyll a. The reduction of chlorophyll concentration under the combined influence of both stress factors was more serious comparing to the separate effect of every single factor. Plants' treatment with toxic concentrations of lead and zinc leaded to slight delay in the development of systemic TMV infection together with more than twofold increase of virus content in plants that may be an evidence of synergism between these heavy metal's and virus' effects. Contrary, copper although decreased total chlorophyll content but showed protective properties and significantly reduced amount of virus in plants. 相似文献
8.
Carolina Loch Warwick Duncan Paulo C. Simões-Lopes Jules A. Kieser R. Ewan Fordyce 《Zoomorphology》2013,132(2):215-225
Longitudinal and cross sections of teeth from 17 species of the Recent dolphins (Delphinoidea and Inioidea) were examined under scanning electron microscope to study the arrangement and ultrastructure of dental tissues with reference to phylogenetic and functional constraints. For most species, enamel had a simple bi-layered structure of radial enamel and an outer layer of prismless enamel. The outer prismless layer varied from 5 to 30 % of enamel thickness. The enamel of Burmeister’s porpoise (Phocoena spinipinnis) was entirely prismless. The prisms had an open sheath; tubules and tuft-like structures were common at the enamel-dentine junction. Cetacean dentine was characterized by irregularly distributed dentinal tubules in a relatively homogenous dentinal matrix. Radial enamel was observed in all Delphinoidea and in the franciscana (Pontoporia blainvillei), whereas the Amazon river dolphin (Inia geoffrensis) had prisms organized in Hunter–Schreger bands. HSB in enamel are regarded as a device for resisting propagation of cracks. These may occur due to increased functional demands, possibly related to the hardness of the species diet. Simplification in tooth shape and reduced biomechanical demands plausibly explain the primitive radial organization among delphinoids and Pontoporia. The HSB structure in the Amazon river dolphin, similar to those of extinct archaeocetes, seems to have secondary functional implications. However, the distribution of HSB in more-basal odontocetes is too poorly known to judge whether the HSB of Inia are a retained plesiomorphic feature or convergence. 相似文献
9.
The consensus concept for thermostability engineering of proteins: further proof of concept 总被引:13,自引:0,他引:13
Lehmann M Loch C Middendorf A Studer D Lassen SF Pasamontes L van Loon AP Wyss M 《Protein engineering》2002,15(5):403-411
Previously, we calculated a consensus amino acid sequence from 13 homologous fungal phytases. A synthetic gene was constructed and recombinantly expressed. Surprisingly, consensus phytase-1 was 15-26 degrees C more thermostable than all parent phytases used in its design [Lehmann et al. (2000)Protein Eng., 13, 49-57]. In the present study, inclusion of six further phytase sequences in the amino acid sequence alignment resulted in the replacement of 38 amino acid residues in either one or both of the new consensus phytases-10 and -11. Since consensus phytase-10, again, was 7.4 degrees C more thermostable than consensus phytase-1, the thermostability effects of most of the 38 amino acid substitutions were tested by site-directed mutagenesis. Both stabilizing and destabilizing mutations were identified, but all affected the stability of the enzyme by <3 degrees C. The combination of all stabilizing amino acid exchanges in a multiple mutant of consensus phytase-1 increased the unfolding temperature from 78.0 to 88.5 degrees C. Likewise, back-mutation of four destabilizing amino acids and introduction of an additional stabilizing amino acid in consensus phytase-10 further increased the unfolding temperature from 85.4 to 90.4 degrees C. The thermostabilization achieved is the result of a combination of slight improvements from multiple amino acid exchanges rather than being the effect of a single or of just a few dominating mutations that have been introduced by chance. The present findings support the general validity of the consensus concept for thermostability engineering of proteins. 相似文献
10.
Michalski B Mazurek U Olejek A Graniczka M Loch T Poreba R Wilczok T 《Folia histochemica et cytobiologica / Polish Academy of Sciences, Polish Histochemical and Cytochemical Society》2001,39(Z2):108-109
Proliferative and angiogenic activity of tissue specimens taken from women with various vulvar pathologies were evaluated by determining the number of mRNA VEGF molecules and H4 histone mRNA molecules, by means of the QRT-PCR (TaqMan) technique. Following a cluster analysis the results, where normalised. Euclidean distances were used, all the cases were classified into three groups of pathologies. Group I included low degree vulvar pathologies, group II included high degree vulvar pathologies and group III included vulvar pathologies with high proliferative and angiogenic activity. Significant differences were found in the proliferative and angiogenic activity between groups I and III, and between groups II and III, while no statistically significant differences were found between groups I and II. 相似文献