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1.
A spheroplast-like slime mutant of Neurospora crassa (lacking a rigid cell wall) was found to synthesize an identical spectrum of carotenoids as wild type strains except for -carotene. Furthermore strict photoregulation of the biosynthesis of these pigments as well as the characteristics of photoinduced carotenogenesis were also nearly identical in the mutant and in the wild type.  相似文献   

2.
Summary The BSG test was used in a comparative study of the linear chromosome differentiation and the idiograms of T. Macha ssp. tubalicum v. letschchumicum Dek. et Men., T. georgicum Dek., T. timopheevi. Zhuk., T. carthlicum Nevski, T. dicoccum Schrank, v. rufum, T. durum Desf. v. Arnautka were compiled.The karyotype of each polyploid wheat species consists of two groups of chromosomes. The first is formed by ten pairs of constant chromosomes occurring almost in all species and the second by all the rest of the variable chromosomes that are either fully specific for the species in question or occur only in a few species. T. timopheevi largely differs from other species of polyploid wheats in the high level and specific localization of structural heterochromatin on chromosomes. The rols of introgression in wheat evolution and the necessity of establishing a General Cytological Nomenclature of Cereal Chromosomes are discussed.  相似文献   

3.
The role of -tocopherol uptake system in human erythrocyte in the uptake of plasma -tocopherol has been suggested. However no information is available on -tocopherol uptake activity of human erythrocytes in the presence of high levels of D-glucose which is known to lead to pathological alterations in different cells including human erythrocytes. Therefore, in order to examine the effect of D-glucose on the binding of -tocopherol to human erythrocytes, the binding characteristics of -tocopherol to these cells were established first. Binding of [3H]-tocopherol to human erythrocytes was both saturable and specific. Scatchard analysis of -tocopherol binding to these cells showed the presence of two independent classes of binding sites with widely different affinities. The high affinity binding sites had a dissociation constant (Kd1) of 90 nM with a binding capacity (n1) of 900 sites per cell, whereas the low affinity binding sites had a dissociation constant (Kd2) of 5.2 M and a binding capacity (n2) of 105,400 sites per cell. Trypsin treatment abolished all the -tocopherol binding activity. Competition for the binding of -tocopherol to human erythrocytes was effective with other homologues of -tocopherol (-tocopherol, -tocopherol and -tocopherol) and their potency was almost equal to -tocopherol itself. The order of preference was -tocopherol > -tocopherol -tocopherol -tocopherol. Incubation of human erythrocytes with various concentrations of D-glucose did not affect -tocopherol uptake activity. Our data demonstrate the presence of an -tocopherol uptake system in human erythrocytes and that the -tocopherol uptake activity is not modulated by the presence of D-glucose.  相似文献   

4.
Summary Dissociated single cells from chicken retina or tectum kept in rotation-mediated cell culture aggregate, proliferate and establish a certain degree of histotypical cellto-cell relationships (sorting out), but these systems never form highly laminated aggregates (nonstratified R- and T-aggregates). In contrast, a mixture of retinal plus pigment epithelial cells forms highly stratified aggregates (RPE-aggregates, see Vollmer et al. 1984). The present comparative study of stratified and nonstratified aggregates enables us to investigate the process of cell proliferation uncoupled from that of tissue stratification. Here we try to relate these two basic neurogenetic processes with patterns of expression of cholinesterases (AChE, BChE) during formation of both types of aggregates.During early aggregate formation, in both stratified and nonstratified aggregates an increased butyrylcholinesterase activity is observed close to mitotically active cells. Quantitatively both phenomena show their maxima after 2–3 days in culture. In contrast, AChE-expression in all systems increases with incubation time. In nonproliferative areas, in the center of RPE-aggregates, the formation of plexiform layers is characterized initially by weak BChE and then strong AChE-activity. These areas correspond with the inner (IPL) and outer (OPL) plexiform layers of the retina in vivo. Although by sucrose gradient centrifugation we find that the 6S- and the fiber-associated 11S-molecules of AChE are present in all types of aggregates, during the culture period the ratio of 11S/6S-forms increases only in RPE-aggregates, which again indicates the advanced degree of differentiation within these aggregates.It is thus demonstrated that cholinesterases first correlate with neuronal cell proliferation and later with stratification, which indicates functions of both enzymes during both developmental periods.Abbreviations AChE acetylcholinesterase - BChE butyrylcholinesterase - iso-OMPA specific inhibitor of BChE - BW 284C51 specific inhibitor of AChE - IPL inner plexiform layer - OPL outer plexiform layer  相似文献   

5.
Here we investigated the neuroprotective effect of 17-estradiol in an in vitro model of ischemia. We used organotypic hippocampal slice cultures, acute or chronically treated with 17-estradiol (10 nM), and exposed to oxygen and glucose deprivation (OGD). Cellular death was quantified by measuring uptake of propidium iodide (PI), a marker of dead cells. In OGD exposed cultures, treated only with vehicle, about 70% of the CA1 area of hippocampus was labeled with PI, indicating a great percentage of cellular death. When cultures were treated with 17-estradiol (acute or chronically), this cellular death was reduced to 15%. This effect was prevented by LY294002 but was not by PD98059. Immunoblotting revealed that both, chronic and acute, treatments with 17-estradiol induced the phosphorylation/activation of Akt and the phosphorylation/inactivation of GSK-3. Our results show a clear neuroprotective effect of 17-estradiol and suggest that this effect could involve PI3-K pathway.  相似文献   

6.
Summary Microspores of soybean plants (Glycine max (L.) Meer.) of four cultivars were cytologically analysed. The pollen grains showed a clear dimorphism when stained with propionic-carmine from binucleate stage onwards. The majority of the grains are large, deeply stained and with asymmetric division (normal type) while the remainder grains are smaller, lightly stained, uninucleate or with two similar nuclei (P-pollen). The different frequencies of P-pollen on the four cultivars suggest a genotype effect of microspore dimorphism.  相似文献   

7.
Summary The bulk of the yolk proteins and lipoproteins constituting the yolks of mature oocytes in birds are synthesized by the liver and transported via the plasma to the oocytes where they are incorporated by micropinocytosis. Evidence is presented indicating that oocytes of hens possessing a mutation identified by Jones, Briles, and Schjeide as a restricted ovulator gene fail to incorporate normal amounts and proportions of low density lipoproteins, lipovitellin and possibly other proteins making up the bulk of the yolk material. Plasma albumin is taken into the yolks but the other proteins synthesized by the liver for deposition within the oocytes accumulate in the plasma, attaining very high levels. The possible nature of the lock preventing normal deposition of the excluded yolk proteins is discussed.  相似文献   

8.
Myristoylated Go was expressed in and highly purified from Escherichia coli strain JM109 cotransformed with pQE60 (Go) and pBB131 (N-myristoyltransferase, NMT). Non-denaturing gel electrophoresis and gel filtration analysis revealed that the Go, in its GDP-bound form, could form oligomers involving dimer, trimer, tetramer, pentamer, or hexamer and guanosine 5"-3-O-(thio)triphosphate (GTPS) activation induced disaggregation of the Go oligomers to monomers. The Go was crosslinked by a cross-linker, N,N"-1,4-phenylenedimaleimide (p-PDM), yielding multiple crosslinked products. In contrast, no obvious cross-linking occurred when Go was pretreated with GTPS. Immunoblot analysis also demonstrated oligomerization of the purified Go proteins and its disaggregation triggered by GTPS. These results provided direct evidence for the disaggregation–coupling theory and the disaggregation action of GTPS may further elucidate the regulatory role of GDP/GTP exchange in G protein-coupled signal transduction pathways.  相似文献   

9.
On the basis of symposium contributions onChlorella, Hibbertia, Eucalyptus, Ambrosia and on numerical approaches some fundamental problems of (bio)systematics, evolution, and taxonomic categories are discussed: Methods available for analysing affinities; conflicting evidence from phenetic, biochemical, cytogenetic and other analyses; further classification problems in cases of intermediacy, etc. While sibs of various levels and their natural hierarchy often can be objectively defined, this appears impossible for particular taxonomic levels itself (e. g. species). A single objective taxonomic system of organisms is unrealistic. Certain guiding lines for relative and practicable concepts of species and genus are proposed.Presented at the symposium Speciation and the Species Concept during the XIIth International Botanical Congress, Leningrad, July 8, 1975.  相似文献   

10.
A catalytic fragment, 1-298, derived from limited chymotryptic digestion of phosphorylaseb kinase (Harris, W.R.et al., J. Biol. Chem., 265: 11740–11745, 1990), is reported to have about six-fold greater specific activity than does the subunit-calmodulin complex. To test whether there is an inhibitory domain located outside the catalytic core of the subunit, full-length wild-type and seven truncated forms of were expressed inE. coli. Recombinant proteins accumulate in the inclusion bodies and can be isolated, solubilized, renatured, and purified further by ammonium sulfate precipitation and Q-Sepharose column. Four out of seven truncated mutants show similar ( 1-353 and 1-341) or less ( 1-331 and 1-276) specific activity than does the full-length wild-type , 1-386. Three truncated forms, 1-316, 1-300, and 1-290 have molar specific activities approximately twice as great as those of the full-length wild-type and the nonactivated holoenzyme. All recombinant s exhibit similarK m values for both substrates, i.e., about 18M for phosphorylaseb and about 75 M for MgATP. Three truncated s, 1-316, 1-300, and 1-290, have a 1.9- to 2.5-fold greater catalytic efficiency (V max/K m) than that of the full-length wild-type and a 3.5- to 4.5-fold greater efficiency than that of the truncated 1-331. This evidence suggests that there is at least one inhibitory domain in the C-terminal region of , which is located at 301-331· 1-290, but not 1-276, which contains the highly conserved kinase domain, is the minimum sequence required for the subunit to exhibit phosphotransferase activity. Both 1-290 and 1-300 have several properties similar to full-length wild-type , including metal ion responses (activation by free Mg2+ and inhibition by free Mn2+) pH dependency, and substrate specificities.  相似文献   

11.
We studied the effect of nestmate separation on trophallaxis in the polydomous ant Cataglyphis iberica. After dividing three colonies into two equivalent subgroups, one queenright and one queenless, we quantified the frequency of trophallaxis within each subgroup, between the workers from the two subgroups (mixed trophallaxis), and trophallaxis involving the queen. Observations of trophallaxis were conducted over four periods of time: for 2 weeks before the separation of the two subgroups, 8 weeks during separation, immediately after reunification, and 3 weeks following reunification. Subgroups were identically fed on the eve of each day of observation. Group separation induced an increase in mixed frequencies of trophallaxis just after reunification, after which trophallaxis returned to the initial level observed before separation. Previous results showed that group separation in C. iberica induces hydrocarbon profile divergence and that reunification restores this chemical modification. The current results seem to indicate that increased trophallaxis permits a uniform odor to be reestablished among previously separated ants. Trophallaxis involving the queen is infrequent and does not seem to be crucial in the process of odor exchange. Our data confirm that trophallaxis plays a key role in establishing the Gestalt colony odor, particularly among naturally separated satellite nests in a polydomous species like C. iberica.  相似文献   

12.
The influence of n-propanol on the overall -helical conformation of -globin, apocytochrome C, and the functional domain of streptococcal M49 protein (pepM49) and its consequence on the proteolysis of the respective proteins has been investigated. A significant amount of -helical conformation is induced into these proteins atpH 6.0 and 4°C in the presence of relatively low concentrations of n-propanol. The induction of -helical conformation into the proteins increased as a function of the propanol concentration, the maximum induction occurring around 30% n-propanol. In the case of -globin, the fluorescence of its tryptophyl residues also increased as a function of n-propanol concentration, the midpoint of this transition being around 20% n-propanol. Furthermore, concomitant with the induction of helical conformation into these proteins, the proteolysis of their polypeptide chain by V8 protease also gets restricted. The -helical conformation induced into - and -globin by n-propanol decreased as the temperature is raised from 4 to 24°C. In contrast, the -helical conformation of both - and -chain (i.e., globin with noncovalently bound heme) did not exhibit such a sensitivity to this change in temperature. However, distinct differences exist between the n-propanol induced -helical conformation of globins and the -helical conformation of - and -chains. A cross-correlation of the n-propanol induced increase in the fluorescence of -globin with the corresponding increase in the -helical conformation of the polypeptide chain suggested that the fluorescence increase represents a structural change of the protein that is secondary to the induction of the -helical conformation into the protein (i.e., an integration of the helical conformation induced to the segments of the polypeptide chain to influence the microenvironment of the tryptophyl residues). Presumably, the fluorescence increase is a consequence of the packing of the helical segments of globin to generate a native-like structure. The induction of -helical conformation into these proteins in the presence of n-propanol and the consequent generation of native-like conformation is not unique to n-propanol. Trifluoroethanol, another helix-inducing organic solvent, also behaves in the same fashion as n-propanol. However, in contrast to the proteins described above, n-propanol could neither induce an -helical conformation into performic acid oxidized RNAse-A nor restrict its proteolysis by proteases. Thus, the high sensitivity of apoproteins and the protein domains to assume -helical conformation in the presence of low concentration of n-propanol with a concomitant restriction of the proteolytic susceptibility of their polypeptide chain appears to be unique to those proteins that exhibit high -helical propensities. Apparently, this phenomenon of helix induction and the restriction of proteolysis reflects the formation of rudimentary tertiary interaction of the native protein and is unique to apoproteins or structural domains of -helical proteins. Consistent with this concept, the induction of -helical conformation into shorter polypeptide fragments of 30 residues, (e.g., 1-30, which exists in an -helical conformation in hemoglobin) is very low. Besides, this peptide exhibited neither the high sensitivity to the low concentrations of n-propanol seen with the apoproteins/protein domains nor the resistance toward proteolysis. The results suggest that the organic cosolvent induced decrease in the conformational flexibility of the apoprotein, and the consequent restriction of their proteolytic cleavage provides an opportunity to develop new strategies for protease catalyzed segment condensation reactions.  相似文献   

13.
Summary We have determined the sequence of a rat A3/A1-crystallin complementary DNA (cDNA) clone and the (partial) sequence of the human B3-crystallin gene. Calculation of the ratio of silent to nonsynonymous substitution between orthologous A3/A1-, B3-, and other - and -crystallin sequences revealed that the region encoding the two globular domains of the A3/A1-crystallin sequence is the best conserved during evolution, much better than the corresponding region of the B1-, B3-, or the -crystallin sequences, and even better (at least in the rodent/frog comparison) that the well-conserved A-crystallin sequence. Remarkably, the rate of change of the A3/A1-crystallin coding sequence does not differ in the rodent and primate lineages, in contrast with previous findings concerning the evolution rates of the A- or -crystallin sequences in these two lineages. Comparison of the regions that encode the four motifs of the -crystallin between orthologous mammalian sequences showed that the extent of nonsynonymous substitution in each of these four homologous motif regions is the same. However, when the orthologous -crystallin genes of more distantly related species (mammals vs chicken or frog) are compared, the extent of nonsynonymous substitution is higher in the regions encoding the external motifs I and III than in the regions encoding the internal motifs II and IV. This phenomenon is also observed when paralogous members of the /-crystallin supergene family are compared.  相似文献   

14.
The obstruction of the bladder outlet induces a marked increase in bladder mass, and this is accompanied by reduced contractility of bladder smooth muscle and alteration in the cellular architecture. In this study, we show that the composition of various isoforms of actin, a major component of the contractile apparatus and the cytoskeletal structure of smooth muscle, is altered in response to the obstruction-induced bladder hypertrophy. Northern blot analysis of the total RNA isolated from hypertrophied urinary bladder muscle, using a cDNA probe specific for smooth muscle -actin, shows over 200% increase in the -actin mRNA. However, the estimate of the amount of actin from the 2D gel reveals only a 16% increase in -actin, since the 2D gel electrophoresis does not distinguish -smooth muscle actin from -cytoplasmic actin. The bladder smooth muscle -actin and the smooth muscle -actin mRNA are not altered in response to the hypertrophy. The obstructed bladder also reveals a decrease in the -cytoplasmic actin (37%) and a concomitant diminution in the -cytoplasmic actin mRNA (29%). Hence, the composition of the actin isoforms in bladder smooth muscle is altered in response to the obstruction-induced hypertrophy. This alteration of the actin isoforms is observed at both the protein and mRNA levels.  相似文献   

15.
Members of the (13)--glucan glucanohydrolase (EC 3.2.1.39) gene family have been mapped on the barley genome using three doubled haploid populations and seven wheat-barley addition lines. Specific probes or polymerase chain reaction (PCR) primers were generated for the seven barley (13)--glucanase genes for which cDNA or genomic clones are currently available. The seven genes are all located on the long arm of chromosome 3 (3HL), and genes encoding isoenzymes GI, GII, GIII, GIV, GV and GVII (ABG2) are clustered in a region less than 20 cM in length. The region is flanked by the RFLP marker MWG2099 on the proximal side and the Barley Yellow Mosaic Virus (BYMV) resistance gene ym4 at the distal end. The gene encoding isoenzyme GVI lies approximately 50 cM outside this cluster, towards the centromere. With the exception of the gene encoding isoenzyme GIV, all of the (13)--glucanase genes are represented by single copies on the barley genome. The probe for the isoenzyme GIV gene hybridized with four DNA bands during Southern blot analysis, only one of which could be incorporated into the consensus linkage map.  相似文献   

16.
The white rot basidiomycete Phanerochaete chrysosporium metabolized 1-(3,4-diethoxyphenyl)-1,3(dihydroxy)-2-(4'-methoxyphenyl)-propane (XII) in low nitrogen stationary cultures, conditions under which the ligninolytic enzyme system is expressed. 3,4-Diethoxybenzyl alcohol (IV), 1,2(dihydroxy)-1-(4-methoxyphenyl)ethane (XX) and anisyl alcohol were isolated as metabolic products indicating an initial , bond cleavage of this dimer. Exogenously added XX was rapidly converted to anisyl alcohol, indicating that XX is an intermediate in the metabolism of XII. Fungal cleavage of the , bond of 1-(3-4-diethoxyphenyl)-1-(hydroxy)-2-(4'-methoxyphenyl)ethane (XI) also occurred, indicating that a hydroxymethyl group is not a prerequisite for this reaction. P. chrysosporium also metabolized 1-(4-ethoxy-3-methoxyphenyl)-2,2(dihydroxy)-2-(4'-methoxyphenyl)propane-1-ol (XIII). The major products of the degradation of this triol included 4-ethoxy-3-methoxybenzyl alcohol (III) and 2-hydroxy-1-(4-methoxyphenyl)-1-oxoethane (XXI). The nature of the products formed indicates that this triol is also cleaved directly at the , bond. The significant difference in the nature of the products formed from the diaryl propane (XII) and the triol (XIII), however, suggests that XIII is not an intermediate in the major pathway for the degradation of XII. Metabolites were identified after comparison with chemically synthesized standards by GLC-mass spectrometry.Abbreviations GLC Gas liquid chromatography - TMSi trimethylsilyl - TLC thin layer chromatography - MS mass spectrometry  相似文献   

17.
Aeromonas salmonicida variants were characterized for alterations in their cell surface structure and used to examine reconstitution of the surface protein layer (A-layer). Variants lacking outer membrane O-polysaccharide were devoid of A-layer and excreted stainable floret-like material of the surface protein (A-protein). One variant, showing partial loss of O-polysaccharide, was associated with a disrupted A-layer and excretion of some A-protein. Variants lacking A-protein but possessing O-polysaccharide rapidly absorbed and concentrated sufficient excreted A-protein at the cell surface to coat the cells with a single confluent layer. Although differences in electrophoretic mobilities of A-proteins and O-polysaccharides from typical and atypical strains were evident, the different A-proteins and A-protein-deficient variants were interchangeable for reconstitution of a surface protein layer. No association of A-protein with cell surfaces of unrelated gram-negative bacteria was observed.Abbreviations A-layer additional surface protein layer - A-protein surface protein - Ast Aeromonas salmonicida typical - Asa Aeromonas salmonicida atypical - A- phenotypically A-protein-negative variant - O- phenotypically O-polysaccharide-negative variant - Owk phenotypically O-polysaccharide weak variant - BHI brain heart infusion - SDS-PAGE sodium dodecylsulfate-polyacrylamide gel electrophoresis - TEM transmission electron microscopy  相似文献   

18.
Comparative computer-assisted analysis was used to study putative GlpR regulons responsible for metabolism of glycerol and glycerol-3-phosphate in genomes of -, -, and -proteobacteria. New palindromic GlpR-binding signals were identified in -proteobacteria, consensus sequences being TGTTCGATAACGAACA for Enterobacteriaceae, wTTTTCGTATACGAAAAw for Pseudomonadaceae, and AATGCTCGATCGAGCATT for Vibrionaceae. The signals in - and -proteobacteria were also identified: they contained 3–4 direct TTTCGTT repeats separated by 3–4 nucleotide pairs.  相似文献   

19.
Gal1-3GlcNAc (1) and Gal1-3GlcNAc-SEt (2) were synthesized on a 100 mg scale by the transgalactosylation reaction of bovine testes -galactosidase with lactose as donor andN-acetylglucosamine and GlcNAc-SEt as acceptors. In both cases the product mixtures contained unwanted isomers and were treated with -galactosidase fromEscherichia coli which has a different specificity, under conditions favouring hydrolysis, yielding besides the desired products, monosaccharides and traces of trisaccharides. The products were purified to >95% by gel filtration, with a final yield of 12% of 1 and 17% of 2, based on added acceptor. In a separate experiment Gal1-6GlcNAc-SEt (3) was synthesized by the transglycosylation reaction using -galactosidase fromEscherichia coli. No other isomers were detected. Compound 3 was purified by HPLC.  相似文献   

20.
1,3-Fucosyltransferase solubilized from human liver has been purified 40 000-fold to apparent homogeneity by a multistage process involving cation exchange chromatography on CM-Sephadex, hydrophobic interaction chromatography on Phenyl Sepharose, affinity chromatography on GDP-hexanolamine Sepharose and HPLC gel exclusion chromatography. The final step gave a major protein peak that co-chromatographed with 1,3-fucosyltransferase activity and had a specific activity of 5–6 µmol min–1 mg–1 and anM r 44 000 deduced from SDS-PAGE and HPLC analysis. The purified enzyme readily utilized Gal1-4GlcNAc, NeuAc2-3Gal1-4GlcNAc and Fuc1-2Gal1-4GlcNAc, with a preference for sialylated and fucosylated Type 2 acceptors. Fuc1-2Gal1-4Glc and the Type 1 compound Gal1-3GlcNAc were very poor acceptors and no incorporation was observed with NeuAc2-6Gal1-4GlcNAc. A polyclonal antibody raised against the liver preparation reacted with the homologous enzyme and also with the blood group Lewis gene-associated 1,3/1,4-fucosyltransferase purified from the human A431 epidermoid carcinoma cell line. No cross reactivity was found with 1,3-fucosyltransferase(s) isolated from myeloid cells. Examination by Northern blot analysis of mRNA from normal liver and from the HepG2 cell line, together with a comparison of the specificity pattern of the purified enzyme with that reported for the enzyme expressed in mammalian cells transfected with theFuc-TVI cDNA, suggests a provisional identification ofFuc-TVI as the major 1,3-fucosyltransferase gene expressed in human liver.Died June, 1991  相似文献   

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