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1.
A low-pressure microwave-induced helium plasma serves as an excitation source for metal chlorides, nitrates, and sulfates vaporized from a filament, resulting in fractional vaporization and differential sensitivities of detection of the elements depending on the vapor pressures of their salts. The shapes of the single emission peaks, which are simple in the presence of potassium chloride, become complex and may double in number. 相似文献
2.
A. Verrips Gerry C. H. Steenbergen-Spanjers J. A. F. M. Luyten R. A. Wevers John H. J. Wokke Fons J. M. Gabreëls Bert G. Wolthers Lambert P. W. J. van den Heuvel 《Human genetics》1997,100(2):284-286
We report a new mutation in the sterol 27-hydroxylase (CYP 27) gene in a Dutch family with cerebrotendinous xanthomatosis:
a G→A transition in the splice donor site in intron 4. This mutation leads to skipping of exon 4, resulting in a loss of 66
amino acids in the CYP 27 enzyme molecule.
Received: 15 March 1997 / Accepted: 26 March 1997 相似文献
3.
Theresa M. Bert Kevin J. McCarthy Hector Cruz-Lopez Steven Bogdanowicz 《Evolution; international journal of organic evolution》1996,50(2):655-671
Many investigators categorize individuals from hybrid zones to facilitate comparisons among genotypic classes (e.g., parental, F1, backcross) for comparative studies in which components of fitness or geographic variation are being analyzed. Frequently, multiple character sets representing genetically independent traits are used to classify these individuals and various methodologies are employed to combine the classifications obtained from the different character sets. We adapted the principles of total evidence and taxonomic congruence (two formalized approaches used by systematists in formulating phylogenetic hypotheses) to address the problem of discriminating hybridizing species and classifying individuals from hybrid zones. As our model, we used two morphological (coloration and morphometric) and two molecular (allozyme and mitochondrial DNA restriction-fragment-length polymorphism) character sets that differentiate two stone crab species (Menippe adina and M. mercenaria). Using principal-components analysis, we determined that combining character sets and eliminating characters or character sets that did not have large eigenvector coefficients for the principal component that best separated the two species yielded the highest level of discrimination between species and allowed us to classify a broad range of morpho-genotypes as hybrids. For the stone crabs, three diagnostic allozyme loci and five diagnostic coloration characters best separated the species. The two character sets were not completely congruent, but they agreed in their classification of 50% of the individuals from the hybrid zone and rarely strongly disagreed in their classifications. Classification discrepancies between the two character sets probably represent variation between traits in interspecific gene flow rather than intraspecific, ecologically mediated variation. Our results support the assertions of previous investigators who espoused the benefits associated with using multiple character sets to classify individuals from hybrid zones and demonstrate that, if character sets are reasonably congruent and numerically balanced, combining diagnostic characters from multiple character sets (a total-evidence approach) can enhance discriminatory power between species and facilitate the assignment of hybrid-zone individuals to genotypic classes. On the contrary, classifying hybrid-zone individuals using character sets separately (a taxonomic-congruence approach) provides the opportunity to compare levels of introgression between species and to assess reasons for discordance among the data sets. 相似文献
4.
Evelien Wynendaele Frederick Verbeke Sofie Stalmans Bert Gevaert Yorick Janssens Christophe Van De Wiele Kathelijne Peremans Christian Burvenich Bart De Spiegeleer 《PloS one》2015,10(11)
Bacteria communicate with each other by the use of signaling molecules, a process called ‘quorum sensing’. One group of quorum sensing molecules includes the oligopeptides, which are mainly produced by Gram-positive bacteria. Recently, these quorum sensing peptides were found to biologically influence mammalian cells, promoting i.a. metastasis of cancer cells. Moreover, it was found that bacteria can influence different central nervous system related disorders as well, e.g. anxiety, depression and autism. Research currently focuses on the role of bacterial metabolites in this bacteria-brain interaction, with the role of the quorum sensing peptides not yet known. Here, three chemically diverse quorum sensing peptides were investigated for their brain influx (multiple time regression technique) and efflux properties in an in vivo mouse model (ICR-CD-1) to determine blood-brain transfer properties: PhrCACET1 demonstrated comparatively a very high initial influx into the mouse brain (Kin = 20.87 μl/(g×min)), while brain penetrabilities of BIP-2 and PhrANTH2 were found to be low (Kin = 2.68 μl/(g×min)) and very low (Kin = 0.18 μl/(g×min)), respectively. All three quorum sensing peptides were metabolically stable in plasma (in vitro) during the experimental time frame and no significant brain efflux was observed. Initial tissue distribution data showed remarkably high liver accumulation of BIP-2 as well. Our results thus support the potential role of some quorum sensing peptides in different neurological disorders, thereby enlarging our knowledge about the microbiome-brain axis. 相似文献
5.
Elizabeth Knyihár-Csillik Pasko Rakic Prof. Dr. Bert Csillik 《Cell and tissue research》1989,258(3):515-525
Summary Transection of the sciatic nerve in Rhesus monkeys and the consequent transganglionic degenerative atrophy (TDA) of central terminals of primary afferents result in transneuronal degeneration of substantia gelatinosa (SG) cells. Severe degeneration is characterized by an increased electron density of the nucleus and by conspicuous shrinkage of the cytoplasm, mitochondrial swelling, dilation of cisterns of the rough-surfaced endoplasmic reticulum, accumulation of free ribosomes and an electron-dense material in the cytoplasm. In the mild form, dilation of cisternal elements of the endoplasmic reticulum, swollen mitochondria and accumulation of free ribosomes takes place. About 10% of SG cells in segment L5 undergo the severe form whereas the rest shows signs of the mild form. Cytoplasmic alterations that occur during transneuronal degeneration seem to start at the level of subsurface cisterns. Dendrites and axons of transneuronally degenerating SG cells also show a conspicuous electron density. By analyzing the synaptic relationships of such darkened dendrites, connections in the upper dorsal horn can be deciphered. Modular units of the primary nociceptive analyzer that evaluate noxious and innocuous inputs on the basis of thin versus thick (AC/A) afferent activity and subjecting them to descending control appear to be recruited from structurally dispersed elements of synaptic glomeruli. These are arranged alongside dendritic processes of large antenna cells which relay impulses to projection cells of the spinothalamic tract. 相似文献
6.
Citrobacter freundii, Paracoccus denitrificans and Pseudomonas stutzeri were grown either singly or in mixed culture in anaerobic nitrate or nitrite limited chemostats with formate and/or succinate as electron donors and carbon sources. C. freundii reduced nitrate or nitrite stoichiometrically to ammonia. Maximum molar growth yields for nitrate (nitrite) were 15.3 (9.9) g/mol for C. freundii on formate with succinate as carbon source, 15.3 (9.5) g/mol for Ps. stutzeri on succinate and 32.3 (20.4) g/mol for Pa. denitrificans on succinate. The almost identical growth yields indicate that the ATP output of the anaerobic processes in the nitrate (nitrite) ammonifying organism and Ps. stutzeri are nearly the same. In mixed cultures with either Ps. stutzeri or Pa. denitrificans, C. freundii was the best competitor for nitrate. These results show that in anaerobic environments C. freundii may compete successfully with denitrifying organisms. 相似文献
7.
The primary structure of angiogenin is 33% identical to that of bovine pancreatic ribonuclease (RNase), but the enzymatic activities of the two proteins differ markedly. Similarly, their susceptibilities to limited proteolysis differ as well. In contrast to RNase, angiogenin totally resists proteolysis by subtilisin. Indeed, among 16 proteases examined, only endoprotease Lys-C, trypsin, and pepsin are able to cleave angiogenin. Even with prolonged incubation, endoprotease Lys-C selectively cleaves the Lys-60-Asn-61 bond; the product retains full ribonucleolytic activity. Initially, trypsin also cleaves this same bond, but with time it causes extensive degradation. Pepsin, atpH 2, cleaves the Phe-9-Leu-10 bond, to give angiogenin (10–123), which displays 15% of the native activity toward ribosomal RNA (rRNA). The susceptibility to proteolysis and/or the sites of cleavage of angiogenin and bovine RNase differ markedly despite their structural homology. These differences are considered in terms of the amino acid sequences of the two proteins. 相似文献
8.
Toshiyuki Itaya Eric Fearon Troy Fiesinger Barbara Hunt Bert Vogelstein Philip Frost 《Cancer immunology, immunotherapy : CII》1991,33(4):267-273
Summary The transfection of murine SP1 tumor cells with the hemagglutinin (HA) gene of influenza virus results, after fluorescent-activated cell sorting (FACS), in the selection of high-HA-expressing cell lines called H4A and H4B. Both lines fail to grow in syngeneic animals at doses that result in 100% tumor take of non-transfected tumor cells. Both grow in immunosuppressed mice. SP1 and H4A or H4B cells express few class I major histocompatibility complex (MHC) antigens but do express class II IAk antigens. H4A or H4B cells engender a cytotoxic T lymphocyte (CTL) response but cannot protect against a challenge with SP1 cells. This CTL response is inhibited by anti-CD4 but not anti-CD8 antibodies. Using FACS, we were able to select a population (called H5AK5) with high class-I MHC antigen expression. Like H4A and H4B, H5AK5 cells fail to grow in syngeneic animals but do grow in immunosuppressed mice. However, unlike H4A or H4B, H5AK5 can induce protection against a challenge with 1 × 105 SP1 cells. These studies indicate that the immunogenicity ofHA-transfected SP1 cells may correlate with the cell-surface expression of class II MHC antigens. However, HA-expressing SP1 cells seem able to induce a protective response against a parent SP1 cell challenge only if they also express class I MHC antigens. This view is supported by the observations that SP1 cells expressing murine interleukin-2 do not express class I MHC antigens, fail to grow in syngeneic animals, do grow in immunosuppressed mice but do not protect against a challenge with parental SP1 cells.This work was supported by The Clayton Fund, The Sid W. Richardson Foundation and PHS grants CA 39853 and 41525. Toshiyuki Itaya is a visiting scientist supported by the Smith Education Fund of the Department of Cell Biology. Troy Fiesinger is a summer research investigator sponsored by The University of Texas M. D. Anderson Cancer Center Summer Program for College Students 相似文献
9.
The nitrogen of an allylic amine can serve as the fulcrum for stereocontrolled delivery of oxygen to an adjacent trigonal site, and cis-hydroxyamino sugars can thus be prepared. Methods for achieving the complementary procedure, namely, control of the delivery of nitrogen to an adjacent site by an allylic oxygen, are described. For example, treatment of methyl 2,3,6-trideoxy--
-erythro-hex-2-enopyranoside with trichloroacetonitrile gave an imidate ester which reacted with iodonium dicollidine perchlorate to give 2-trichloromethyl-(methyl 2,3,4,6-tetradeoxy-2-iodo--
-altropyranoside)-[3,4-d]-2-oxazoline. Exhaustive reductive dehalogenation of this product followed by hydrolysis led to methyl N-acetyl--
-ristosaminide. An analogous series of reactions was used to prepare the corresponding daunosaminide. 相似文献
10.
Differential Adhesion and Infection of Nematodes by the Endoparasitic Fungus Meria coniospora (Deuteromycetes) 下载免费PDF全文
The conidia of the endoparasitic fungus Meria coniospora (Deuteromycetes) had different patterns of adhesion to the cuticles of the several nematode species tested; adhesion in some species was only to the head and tail regions, on others over the entire cuticle, whereas on others there was a complete lack of adhesion. After adhesion, the fungus usually infected the nematode. However, adhesion to third-stage larvae of five animal parasitic nematodes, all of which carry the cast cuticle from the previous molt, did not result in infection. M. coniospora infected animal parasitic nematodes when this protective sheath was removed. Seven preparations of sialic acid (N-acetylneuraminic acid) gave three types of response in adhesion-infection of nematodes: (i) a significant reduction in conidial adhesions; (ii) no interference with adhesion, but a 10-day delay in infection; and (iii) a delay in infection by 2 to 3 days. The current results support previous findings indicating involvement of sialic acids localized on nematode cuticles in recognition of prey by M. coniospora. 相似文献