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41.
Molecular Genetic Analysis of Myelin-Deficient Mice: Shiverer Mutant Mice Show Deletion in Gene(s) Coding for Myelin Basic Protein 总被引:17,自引:6,他引:11
42.
Summary Insight on the function of gangliosides. can emerge from knowledge of their cellular distribution. In this paper we review the structure of ganglioside GD3 and recent information on its cellular distribution. GD3 appears to be enriched in a variety of neural cell types including: reactive glia, gliomas, undifferentiated neurons, Muller glia, and oligodendroglia. Because each of these cell types share an enhanced permeability to ions and metabolites or possess properties associated with enhanced permeability, we suggest that GD3 is associated with enhanced membrane permeability. A possible function for GD3 in membrane permeability has implications for other cellular events such as metabolism, growth and interactions. 相似文献
43.
Thomas Hansen-Hagge Volker Lehmann Ulrich Seydel Buko Lindner Ulrich Zähringer 《Archives of microbiology》1985,141(4):353-358
The extraction, purification and structural characterization of two lipid A precursors (Ia and Ib) differing only in one hexadecanoic acid are described. Both precursors were synthesized at elevated temperatures by a new mutant of Salmonella typhimurium (mutant Ts5) which is conditionally defective in synthesis of the 3-deoxy-d-manno-octulosonic acid region of lipopolysaccharides.Both precursors were purified by repeated phenol/chloroform/petroleum ether (PCP) extractions followed by thin layer chromatography. Teh precursor preparation was free of lipopolysaccharides and phospholipids and contained less than 0.1% protein. Structural analysis which included chemical degradation procedures as well as positive ion laser desorption (LDMS) mass spectroscopy of dephosphorylated lipid A precursors showed together that precursor Ia represents a diphosphorylated glucosamine disaccharide containing two ester, two amide-linked residues of 3-hydroxytetradecanoic acid and lacks the ester-linked dodecanoic, tetradecanoic and hexadecanoic acid as well as 3-deoxy-d-manno-octulosonic acid. Precursor Ib has the same basic structure as precursor Ia, but contains in addition one mol of hexadecanoic acid per mol disaccharide which is linked to the 3-hydroxy group of the amide-bound 3-hydroxy-tetradecanoic acid of the reducing, terminal glucosamine residue.The structure of precursor Ib supports the conclusion that hexadecanoic acid incorporation occurs at an early stage in lipid A biosynthesis prior to the attachment of 3-deoxy-d-manno-octulosonic acid and/or other polar substituents.Abbreviations LDMS
laser desorption mass spectrometry
- KDO
3-Deoxy-d-manno-octulosonic acid
- Ts5
Salmonella typhimurium mutant Ts5
- PCP
phenol/chloroform/petroleum ether
- H2F2
hydrogen fluoride
This work is dedicated to Prof. Dr. Drews, Freiburg, on the occasion of his 60th birthday 相似文献
44.
Summary Stamenless-2 (sl2/sl2) is a temperature-sensitive mutant of tomato (Lycopersicon esculentum) which exhibits altered stamen development under different temperatures (Sawhney 1983). By using scanning electron microscopy, this study was conducted to investigate the differentiation of surface features of mutant and normal stamens grown under different temperatures, with the view to further determine the role of temperature in gene expression in stamen development. Mutant stamens grown under intermediate temperatures (23 °C day/18 °C night) differed from the normal in hair production, the shape of epidermal cells and in the pattern of cuticular thickenings. Under low temperatures (18 °C day/15 °C night), all surface features of mutant stamens closely resembled the normal, whereas under high temperatures (28 °C day/23 °C night), the patterns and types of hairs, epidermal cells, stomata, and cuticular thickenings on mutant stamens were similar to that of a gynoecium. The staminal features of normal stamens were not affected by different temperatures. This study shows that the expression of the sl2/sl2 allele is influenced by temperature conditions to the extent that the pattern of cellular differentiation characteristic of either the stamens or the carpels can be induced in mutant stamens. 相似文献
45.
Selenocysteine lyase activity was detected in crude extracts from a cysteine-requiring mutant ofEscherichia coli K-12. The level of activity was the same whether cells had been grown aerobically or anaerobically, with or without selenocysteine.
Selenocysteine lyase catalyzes the conversion of selenocysteine to alanine and elemental Se, a reaction that is followed by
a nonenzymatic reduction of the Se to hydrogen selenide. Both of these end products were identified in this study. With cysteine
as the substrate, alanine and H2S were formed, but only at levels 50% less than the products formed from selenocysteine. Selenocysteine lyase has been identified
in a number of mammals and bacteria; its presence in a cysK mutant ofE. coli K-12 suggests a common route whereby hydrogen selenide, derived from selenocysteine, can then be assimilated into selenoproteins. 相似文献
46.
A chlorophyll b-less mutant of Chlamydomonas reinhardtii (Pg
27) was isolated after UV irradiation of the wild type cells. This photosynthetically competent mutant totally lacks chlorophyll b and the CP2 chlorophyll-protein complex. However, SDS-PAGE, proteolytic digestions and immunodetections demonstrated that the 24–25 Kd apoproteins of the lacking CP2 complex are still present in thylakoids of the Pg27 mutant. It is concluded that this CP2-less mutant is affected in the biosynthesis pathway of chlorophyll b.This CP2-less mutant was crossed with a CP1-less mutant (Fl5) Fluorescence emission spectra and fluorescence inductions in the presence of DCMU were analysed in the resulting (cp
2
–
, cp
1
+
), (cp
2
+
, cp
1
–
), (cp
2
+
, cp
1
+
), cp
2
–
, cp
1
–
)tetratype. Differences in PS 2 optical cross section and in the relative amplitude or localisation of fluorescence emission peaks fit well with a quadripartite model where PS1 and PS2 would each correspond to a reaction centre core complex (CP1 and CP2 respectively) associated to a light harvesting antenna (LHC1 and LHC2 respectively). The occurrence of energy transfers from PS1 peripheral antenna to PS2 in the Fl
5 mutant shows that, in absence of CP1, at least a part of its associated PS1 light harvesting antenna migrates in the PS2 containing appressed thylakoids.Abbreviations Chl
Chlorophyll
- LHC
Light harvesting chl a/b complex
- CP2
Predominant form of LHC or SDS polyacrylamide gels
- WT
Wild type
- DM
Double mutant (cp
1
–
, cp
2
–
)
- SDS-PAGE
sodium dodecyl sulfate polyacrylamide gel electrophoresis
- DOC-PAGE
Deoxycholate polyacrylamide gel electrophoresis 相似文献
47.
P. C. Banerjee 《Archives of microbiology》1986,144(4):405-407
Phosphoglucose isomerase negative mutant of mucoid Pseudomonas aeruginosa accumulated relatively higher concentration of fructose 1,6-bisphosphate (Fru-1,6-P2) when mannitol induced cells were incubated with this sugar alcohol. Also the toluene-treated cells of fructose 1,6-bisphosphate aldolase negative mutant of this organism produced Fru-1,6-P2 from fructose 6-phosphate in presence of ATP, but not from 6-phosphogluconate. The results together suggested the presence of an ATP-dependent fructose 6-phosphate kinase (EC 2.7.1.11) in mucoid P. aeruginosa.Abbreviations ALD
Fru-1,6-P2 aldolse
- DHAP
dihydroxyacetone phosphate
- F6P
fructose 6-phosphate
- G6P
glucose 6-phosphate
- Gly3P
glyceraldehyde 3-phosphate
- KDPG
2-keto 3-deoxy 6-phosphogluconate
- PFK
fructose 6-phosphate kinase
- PGI
phosphoglucose isomerase
- 6PG
6-phosphogluconate 相似文献
48.
J. L. Smith M. M. Bencivengo R. L. Buchanan C. A. Kunsch 《Archives of microbiology》1986,144(2):131-136
In this study, we investigated the relationship between carbohydrate metabolism and repression of staphylococcus enterotoxin A (SEA) in Staphylococcus aureus 196E and a pleiotrophic mutant derived from strain 196E. The mutant, designated at strain 196E-MA, lacked a functional phosphoenolpyruvate phosphotransferase system (PTS). The mutant produced acid, under aerobic conditions, from only glucose and glycerol. The parent strain contained an active PTS, and aerobically produced acid from a large number of carbohydrates. Prior growth in glucose led to repression of SEA synthesis in the parent strain; addition to the casamino acids enterotoxin production medium (CAS) led to more severe repression of toxin synthesis. The repression was not related to pH decreases produced by glucose metabolism. When S. aureus 196E was grown in the absence of glucose, there was inhibition of toxin production as glucose level was increased in CAS. The inhibition was related to pH decrease and was unlike the repression observed with glucose-grown strain 196E. The inhibition of SEA synthesis in mutant strain 196E-MA was approximately the same in cells grown with or without glucose and was pH related. Repression of SEA synthesis similar to that seen with glucose-grown S. aureus 196E could not be demonstrated in the mutant. In addition, glucose-grown S. aureus 196E neither synthesized -galactosidase nor showed respiratory activity with certain tricarboxylic acid (TCA) cycle compounds. Glucose-grown strain 196E-MA, however, did not show supressed respiration of TCA cycle compounds; -galactosidase was not synthesized because the mutant lacked a functional PTS. Cyclic adenosine-3, 5-monophosphate did not reverse the repression by glucose of SEA or -galactosidase synthesis in glucose-grown S. aureus 196E. An active PTS appears to be necessary to demonstrate glucose (catabolite) repression in S. aureus.Abbreviations SEA
staphylococcal enterotoxin A
- SEB
staphylococcal enterotoxin B
- SEC
staphylococcal enterotoxin C
- PTS
phosphoenolpyruvate phosphotransferase system
- CAS
casamino acids salts medium
- TCA
tricarboxylic acid cycle 相似文献
49.
本文报道大肠杆菌的ColE1类似质粒的一个低拷贝数突变型。从载体质粒pUC4衍生的重组质粒pPGVT3在大肠杆菌宿主DF2145中是不稳定的,以pPGVT3转化DF2145时在4o℃培养得不到转化子。用诱发点突变的羟胺体外处理pPGVF3质粒DNA,得到一个稳定性提高了的突变质粒pPGVT3HA,突变的位置被确定在质粒的pUC部分,突变降低了pUC及其衍生质粒的拷贝数。文中对质粒的稳定性与拷贝数的关系作了讨论。 相似文献
50.
Interleukin-1 Hyperproduction by In Vitro Activated Peripheral Macrophages from Cerebellar Mutant Mice 总被引:3,自引:1,他引:2
B. Kopmels E. E. Wollman J. M. Guastavino N. Delhaye-Bouchaud† D. Fradelizi J. Mariani† 《Journal of neurochemistry》1990,55(6):1980-1985
Several mutations in mice produce complex patterns of neuronal degeneration of the cerebellum and of its afferent pathways. In the staggerer (sg/sg) mutant, atrophy of the lymphoid organs and immunological abnormalities have been described. To search for a possible link between the neurological and the immune disorders in this mutant, we studied the production by its peripheral macrophages of interleukin-1 (IL-1), which roles in both immune and nervous systems are well established. Suspensions of peritoneal and/or spleen macrophages from mutants and their appropriate controls were stimulated in vitro by lipopolysaccharide. Northern and dot blots, performed with murine IL-1 cDNA probes, revealed a clear-cut hyperexpression of IL-1 mRNA in staggerer macrophages. An IL-1 bioassay using the IL-1-responsive D10.G4 cell line also revealed a sixfold increase of IL-1 activity in the macrophage supernatants of staggerer mutant mice. The hyperproduction was found in 3-week to 1-year-old staggerer and also in heterozygous (+/sg) mice. A similar phenomenon existed in cerebellar mutants lurcher, Purkinje cell degeneration (pcd), and to a lesser extent reeler and wobbler, but was absent in the neurological mutants weaver, jimpy, and motor end plate disease (medH). These observations establish that in several point mutations in mice, central nervous degeneration is associated with dysregulation of IL-1 production by peripheral macrophages. 相似文献