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31.
Schubert Hendrik; Schiewer Ulrich; Tschirner Erhard 《Journal of plankton research》1989,11(2):353-359
The fluorescence characteristics of the cyanobacteria Synechocystisaquatilis Sauv., Microcystis firma (Breb. et Lenorm.) Schmidleand Synechococcus leopoliensis (Racib.) Kom. and the green algaScenedesmus quadricauda (Turp.) Breb. were examined. In thethree cyanobacteria, phycocyanin is the main accessory pigment.Phycoerythrin is not present in our investigated strains ofcyanobacteria. The highest excitation of the chlorophyll a (Chla) fluorescence of cyanobacteria resulted from light with wavelengthsof 620630 nm. A definite Kautsky effectis also evident at this wavelength. However, excitation withblue light (420520 nm) produced only very slight fluorescence.The Kautsky effect is not evident at these wavelengths, evenat high photon flux densities. For Scenedesmus, fluorescencecharacteristics typical of green algae were found. The fluorescenceexcitation of cyanobacteria at 620 nm corresponds to a photosynthesispeak in the action spectrum measured in terms of O2 production.The results underline the necessity of fluorescence measurementsat several wavelengths whenever mixed populations are involved.Such measurements also present possibilities for more accurateestimation of biomass and potential photosynthetic productionin mixed populations. 相似文献
32.
Ectopic head and foot formation in Hydra: Diacylglycerol-induced increase in positional value and assistance of the head in foot formation 总被引:1,自引:0,他引:1
Werner A. Müller 《Differentiation; research in biological diversity》1990,42(3):131-143
In wild type Hydra magnipapillata, daily application of the protein kinase C activator diacylglycerol (DAG) evokes sprouting of periodically spaced ectopic heads along the body column and leads to loss of the ability to regenerate proximal structures including the foot. The present transplantation studies show that the appearance of ectopic heads is preceded by an early increase in the 'positional value' (P-value) or 'head activation potential' of the gastric column. Long before ectopic head structures emerge, pieces of DAG-treated tissue transplanted into the corresponding positional level of untreated hosts induce head formation instead of being integrated, whereas pieces implanted from untreated donors into DAG-treated hosts form feet. Foot formation implies a decrease in the P-value. This down-regulation is promoted through long-range assistance by the head. Thus, after termination of the DAG treatment ectopic feet are intercalated midway between the periodically spaced heads; moreover, untreated polyps onto which additional distal heads have been grafted regenerate feet faster than do one-headed polyps and may form supernumerary feet. Multiheaded animals can also be produced using two substances (K-252a and xanthate D609) that interfere with signal transduction, but the mode by which secondary heads arise is different from DAG-induced ectopic head formation. Presumably because the assistance by the parental head is impaired, buds fail to form a foot and detach and instead give rise to stable secondary body axes. It is assumed that the P-value along the body varies according to the number of cellular receptors for factors serving as intercellular signals.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
33.
A native high molecular complex (Mr 850000) containing about 50% of the allphycocyanin of the phycobilisome but lacking allophycocyanin B was separated from isolated phycobilisomes by gel electrophoresis. It was designated APCM since the large linker polypeptide LCM was exclusively localized in this complex. The complex exhibited a ?196°C fluorescence emission maximum at 673 nm (671 nm at 25°C). In addition, a core complex (designated APC, Mr≥1000000) consisting of both APCM and AP 680 was isolated by combined gel filtration and linear gradient centrifugation. At 25°C this complex showed dual emission peaks at 670 and 680 nm demonstrating functional independence of the terminal emitters. A complex similar to APCM can be isolated from phycobilisomes of Anabaena variabilis. This is evidence that APCM is the constitutive center of the tricylindrical core of hemidiscoidal cyanobacterial phycobilisomes. Two models summarizing the structural and functional consequences of the results are presented in the discussion. 相似文献
34.
Influence of interferon-gamma and extracellular tryptophan on indoleamine 2,3-dioxygenase activity in T24 cells as determined by a non-radiometric assay. 总被引:1,自引:1,他引:0 下载免费PDF全文
E R Werner G Werner-Felmayer D Fuchs A Hausen G Reibnegger H Wachter 《The Biochemical journal》1988,256(2):537-541
The indoleamine 2,3-dioxygenase (EC 1.13.11.17) activity in human T24 cells has been investigated in cell extracts by using a non-radioactive assay. It is enhanced in a dose-dependent manner up to 25-fold by interferon-gamma. The maximum reaction velocity is increased rather than the Km, which remains at 4 mumol/l. Induction of activity starts 3 h after stimulation and reaches a plateau at 21-48 h. Decreased stimulation was observed in the presence of high L-tryptophan concentrations. 相似文献
35.
A new recombinant procoagulant protein derived from the cDNA encoding human factor VIII 总被引:1,自引:0,他引:1
P Meulien T Faure F Mischler H Harrer P Ulrich B Bouderbala K Dott M Sainte Marie C Mazurier M L Wiesel 《Protein engineering》1988,2(4):301-306
We have constructed new B domain deletion derivatives of human factor VIII (FVIII) by manipulating the cDNA using recombinant DNA techniques. One of these new derivatives, FVIII delta II, in which amino acids 771(pro)-1666(asp) have been deleted, no longer contains the protease cleavage site at amino acid position 1648(arg)-1649(glu) known to be involved in the initial step of FVIII processing. We have expressed this molecule in both baby hamster kidney (BHK) 21 cells using the vaccinia virus (VV) expression system and have established Chinese hamster ovary (CHO) derived permanent cell lines expressing either recombinant (r)FVIII or FVIII delta II. The characteristics of FVIII delta II have been compared to those of rFVIII and/or plasma derived (pd) FVIII. FVIII delta II has the following properties: (i) it exhibits FVIII procoagulant activity; (ii) it is expressed at 5-fold higher levels than is the complete molecule in comparable systems; (iii) it migrates for the most part as a single major band on SDS-PAGE, in contrast to the complete molecule; (iv) it is activated to a greater extent by thrombin than is either rFVIII or pdFVIII; and (v) it retains the ability to bind von Willebrand factor (vWf). 相似文献
36.
Localization of immunoreactive epidermal growth factor receptors in human nervous system 总被引:6,自引:0,他引:6
M H Werner L B Nanney C M Stoscheck L E King 《The journal of histochemistry and cytochemistry》1988,36(1):81-86
Epidermal growth factor is a well-defined peptide which stimulates cell growth and elicits cell responses in a variety of tissues by binding to specific receptors, EGF-R. A specific antiserum against the EGF receptor, which has previously been used to characterize EGF-R in human skin, fibroblasts, and smooth muscle, was used to survey the distribution of EGF-R in human nervous system. Portions of formalin-fixed, paraffin-embedded autopsy specimens were examined by use of immunohistochemical staining (PAP technique) with EGF-R antiserum. Many types of nerve cells, e.g., cerebral cortical pyramidal cells, hippocampal pyramidal cells, Purkinje cells, anterior horn cells, and dorsal root ganglion neurons, contained immunoreactive EGF-R. However, immunoreactive EGF-R were not detected in astrocytes, oligodendrogliocytes, and other small neurons such as granule cells. Intense immunostaining for EGF-R was also detected in ependymal cells from choroidal and extrachoroidal locations. Although immunoreactive EGF-R is widely distributed in human nervous system, the functional role of EGF and its receptor in the nervous system remains unknown. 相似文献
37.
Peter O''Connell G. Mark Lathrop Mark Leppert Yusuke Nakamura Ulrich Müller Jean-Marc Lalouel Ray White 《Genomics》1988,3(4):367-372
We have constructed a primary genetic map of human chromosome 18 consisting of 11 DNA markers and one serological marker (JK). Two of these loci define highly polymorphic VNTR systems. The markers define a continuous genetic linkage map of 97 cM in males and 205 cM in females; female genetic distances in a panel of 59 three-generation families were consistently about twice those observed in males. The high odds in support of the linear order of the markers on this recombination map, and the extent of coverage of chromosome 18, indicate that this map will permit efficient linkage studies of human genetic diseases that may be segregating on chromosome 18 and will provide anchor points for development of high-resolution maps for this chromosome. 相似文献
38.
Effect of mutations in a zinc-binding domain of yeast RNA polymerase C (III) on enzyme function and subunit association. 总被引:11,自引:7,他引:4 下载免费PDF全文
M Werner S Hermann-Le Denmat I Treich A Sentenac P Thuriaux 《Molecular and cellular biology》1992,12(3):1087-1095
The conserved amino-terminal region of the largest subunit of yeast RNA polymerase C is capable of binding zinc ions in vitro. By oligonucleotide-directed mutagenesis, we show that the putative zinc-binding motif CX2CX6-12CXGHXGX24-37CX2C, present in the largest subunit of all eukaryotic and archaebacterial RNA polymerases, is essential for the function of RNA polymerase C. All mutations in the invariant cysteine and histidine residues conferred a lethal phenotype. We also obtained two conditional thermosensitive mutants affecting this region. One of these produced a form of RNA polymerase C which was thermosensitive and unstable in vitro. This instability was correlated with the loss of three of the subunits which are specific to RNA polymerase C: C82, C34, and C31. 相似文献
39.
A 46,XY female patient with streak gonads and a large deletion of Yp is described. The deletion included the Y chromosomal genes SRY, ZFY, and RPS4Y. The patient did not display any Turner stigmata, such as webbing of the neck, cardiac or other abnormalities. The findings argue against an important role of RPS4Y in the prevention of Turner stigmata in males and are consistent with a role of SRY in testis differentiation in humans. 相似文献
40.
haemolysin of Escherichia coli: Comparison of pore-forming properties between chromosome and plasmid-encoded haemolysins 总被引:3,自引:0,他引:3
Roland Benz reas Döbereiner Albrecht Ludwig Werner Goebel 《FEMS microbiology letters》1992,105(1-3):55-62
Abstract Lipid bilayer experiments were performed with chromosome-encoded haemolysin of Escherichia coli . The addition of the toxin to the aqueous phase bathing lipid bilayer membranes of asolectin resulted in the formation of transient ion-permeable channels with two states at small transmembrane voltages. One is prestate (single-channel conductance 40 pS in 0.15 M KCl) of the open state, which had a single-channel conductance of 420 pS in 0.15 M KCl and a mean lifetime of 30 s. Membranes formed of pure lipids were rather inactive targets for this haemolysin. Experiments with different salts suggested that the haemolysin channel was highly cation-selective at neutral pH. The mobility sequence of the cations in the channel was similar if not identical to their mobility sequence in the aqueous phase. The single-channel data were consistent with a wide, water-filled channel with an estimated minimal diameter of about 1 nm. The pore-forming properties of chromosome-encoded haemolysin were compared with those of plasmid-encoded haemolysin. Both toxins share common features, oligomerize probably to form pores in lipid bilayer membranes. Both types of haemolysin channels have similar properties but different lifetimes. 相似文献