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51.
52.
Judith Hesselbarth Christiane Werckenthin Babett Liebisch S. Schwarz 《Letters in applied microbiology》1995,20(3):180-183
Staphylococcus intermedius cultures from dogs, pigeons, horses and mink were investigated for the prevalence of the insertion elements IS 256 and IS 257 in relation to their antibiotic resistance. Copies of IS 256 could not be detected in any of the Staph. intermedius isolates tested whereas single copies of IS 257 occurred in the isolates from dogs and horses. The mink strains did not harbour IS 257 elements, whereas Staph. intermedius isolates from pigeons carried multiple copies of IS 257 as predicted from the hybridization patterns obtained with a gene probe derived from the internal part of the IS 257 -encoded transposase gene. Independently of the origin of the Staph. intermedius isolates, all IS 257 copies were found to be located in the chromosomal DNA. The large number of chromosomal IS 257 copies in the pigeon strains might help to explain chromosomal multiresistance in many of those strains. 相似文献
53.
Julia C. McNaughton Craig J. Marshall Judith E. Broom Gillian Hughes Wyn A. Jones Peter A. Stockwell George B. Petersen 《Journal of molecular evolution》1995,40(2):127-135
A THE-1 sequence in intron 7 of the human dystrophin gene has been found to represent a new subfamily of THE-1 elements. The sequence is closely related to the MstII family of repetitive sequences and is more like single-copy sequences found in the galago genome than any other THE-1 sequence previously reported. This new THE-1 sequence has been compared with two other complete THE-1 sequences and three related long-terminal repeat elements that we have previously found in intron 7 of the dystrophin gene, and with members of the same family from elsewhere in the primate genome. Parsimony and deletion analysis show that the cluster of THE-1 sequences in intron 7 of the dystrophin gene has arisen from at least three individual insertion events, rather than from the insertion and duplication of a single progenitor sequence.
Correspondence to: G.B. Petersen 相似文献
54.
Lesley Heseltine Judith M. Webster Roy Taylor 《Molecular and cellular biochemistry》1995,144(2):147-151
The dose response effect of a new adenosine analogue, GR 79236 (N-[1S trans-2-hydroxycyclopentyl] adenosine) upon insulin sensitivity was examined in human adipocytes. The influence of adenosine upon insulin sensitivity for suppression of lipolysis and stimulation of glucose transport was examined. Removal of adenosine by use of adenosine deaminase stimulated lipolysis to the same extent as did 10–9 M noradrenaline. GR79236 brought about dose dependent inhibition of lipolysis with half-maximal effect at 11.3±7.8×10–9 M. When lipolysis was stimulated by noradrenaline alone the subsequent inhibition of lipolysis brought about by GR79236 was significantly greater than that of insulin. To examine adenosine effects on the insulin signalling pathway separately from those on lipolysis, the insulin sensitivity of glucose transport was examined. Removal of adenosine brought about a small but significant increase in the concentration of insulin required for half-maximal stimulation of glucose transport. Adenosine agonists offer promise as new agents for the modulation of metabolism in diabetes and other states of insulin resistance. 相似文献
55.
Paul A. Hamblin Bruce A. Maguire Ruslan N. Grishanin & Judith P. Armitage 《Molecular microbiology》1997,26(5):1083-1096
In contrast to enteric bacteria, chemotaxis in Rhodobacter sphaeroides requires transport and partial metabolism of chemoattractants. Although a chemotaxis operon has been identified containing homologues of the enteric cheA, cheW, cheR genes and two homologues of the cheY gene, deletion of the entire chemotaxis operon had only minor effects on chemotactic behaviour under the conditions tested. Responses to sugars were enhanced in tethered cells but in all other chemotaxis assays behaviour of the operon deletion mutant was wild type. The mutant also showed wild-type responses to weak organic acids such as acetate and propionate, the dominant chemoattractants for this organism, under all conditions. This is in direct contrast to the enterics in which CheA, CheW and CheY are absolutely essential for taxis to PTS sugars, oxygen and MCP-dependent chemoeffectors. The operon deletion mutant was subjected to Tn5 transposon mutagenesis and new mutants selected using a chemotaxis and phototaxis screen. One mutant, JPA203, was non-chemotactic on swarm plates and showed inverted responses when tethered or subjected to changes in light intensity. Characterization of the Tn5 insertion in JPA203 identified a second chemotaxis operon in R. sphaeroides that contains homologues of cheY, cheA and cheR, the first homologue of cheB and two homologues of cheW. The new genes were labelled orf10, cheYIII, cheAII, cheWII, cheWIII, cheRII, cheB and tlpC. When introduced into a wild-type background, deletion of cheAII produced a chemotaxis minus phenotype in R. sphaeroides, suggesting that cheAII forms part of a dominant chemotactic pathway, whereas the earlier identified operon plays only a minor role under laboratory conditions. The data presented here support the existence of two chemosensory pathways in R. sphaeroides, a feature that so far is unique in bacterial chemotaxis. 相似文献
56.
Identification of a 175 kDa protein as the ligand-binding subunit of the rat liver sinusoidal endothelial cell hyaluronan receptor 总被引:2,自引:1,他引:1
The rat liver sinusoidal endothelial cell (LEC) hyaluronan (HA)receptor was previously identified using a photoaffinity HAderivative (J. BioL Chem., 267, 2045120456, 1992). Twopolypeptides with Mr = 175,000 and 166,000, were consistentlycrosslinked, suggesting that the LEC HA receptor is an oligomer.Whether one or both subunits participate in HA binding, wasnot determined. Here we investigate the HA-subunit interactionsand the potential oligomeric nature of the LEC HA receptor.When Sephacryl-400 gel filtration chromatography was used toenrich the HA receptor, the 175 kDa polypeptide was the majorband seen by SDS-PAGE analysis. Little staining was seen at166 kDa, suggesting that the 175 kDa protein could be separatedfrom the 166 kDa protein and still retain HA-binding activity.A ligand blot assay was used to determine if each individualsubunit could bind HA. LEC proteins were separated by nonreducingSDS-PAGE, and then immobilized onto nitrocellulose. 125I-HAbound to a 175 kDa polypeptide but not to the 166 kDa protein.A high molecular weight band of 相似文献
57.
Gerhard Schenk Roy Layfield Judith M. Candy Ronald G. Duggleby Peter F. Nixon 《Journal of molecular evolution》1997,44(5):552-572
Members of the transketolase group of thiamine-diphosphate-dependent enzymes from 17 different organisms including mammals,
yeast, bacteria, and plants have been used for phylogenetic reconstruction. Alignment of the amino acid and DNA sequences
for 21 transketolase enzymes and one putative transketolase reveals a number of highly conserved regions and invariant residues
that are of predicted importance for enzyme activity, based on the crystal structure of yeast transketolase. One particular
sequence of 36 residues has some similarities to the nucleotide-binding motif and we designate it as the transketolase motif.
We report further evidence that the recP protein from Streptococcus pneumoniae might be a transketolase and we list a number of invariant residues which might be involved in substrate binding. Phylogenies
derived from the nucleotide and the amino acid sequences by various methods show a conventional clustering for mammalian,
plant, and gram-negative bacterial transketolases. The branching order of the gram-positive bacteria could not be inferred
reliably. The formaldehyde transketolase (sometimes known as dihydroxyacetone synthase) of the yeast Hansenula polymorpha appears to be orthologous to the mammalian enzymes but paralogous to the other yeast transketolases. The occurrence of more
than one transketolase gene in some organisms is consistent with several gene duplications. The high degree of similarity
in functionally important residues and the fact that the same kinetic mechanism is applicable to all characterized transketolase
enzymes is consistent with the proposition that they are all derived from one common ancestral gene. Transketolase appears
to be an ancient enzyme that has evolved slowly and might serve as a model for a molecular clock, at least within the mammalian
clade.
Received: 13 September 1995 / Accepted: 14 November 1996 相似文献
58.
A. H. Macpherson suggested that much of the current geographic diversity in Canadian Arctic mammals resulted from isolation in refugia during the Wisconsin glacial stage. This study evaluates the refugium hypothesis, insofar as it applies to Nearctic Dicrostonyx , by means of a statistical analysis of geographic variation in 13 skull characters. Overall, geographic variation among samples is not significant, although D. hudsonius and D. unalascensis are geographically and morphologically distinct. Some variation in skull shape is correlated with winter temperature. Partitioning tests on other measures of shape variation indicate some discontinuities consistent with the refugial hypothesis. Discrete samples reflect possible refugial populations in northern North America, Eastern Beringia and two southern periglacial refugia, one in eastern North America and at least one in western North America. 相似文献
59.
The renal vasculature of the toad, Bufo marinus, was studied mainly by means of scanning electron microscopy of vascular corrosion casts. All arterial branches terminated in a glomerulus. Each glomerulus was supplied by only one afferent arteriole. No shunts between afferent and efferent arterioles were observed. The glomerular channels appeared to be permanent capillaries. No evidence supporting the theory of freely shifting glomerular blood channels was found. Efferent arterioles radiated out towards the dorsal surface of the kidney where they connected with peritubular vessels. The renal portal veins produced an anastomosing plexus on the dorsal surface of the kidney, giving rise to the peritubular vessels. Peritubular vessels ran radially toward the ventral surface of the kidney, where they formed the roots of the renal veins. Attention is drawn to the possibility of hairpin countercurrent exchange between the capillary-like efferent arterioles and the peritubular vessels in the dorsal kidney. 相似文献
60.
Peter H. Byers Karen A. Holbrook Judith G. Hall Paul Bornstein John W. Chandler 《Human genetics》1978,40(2):157-169
Summary Several individuals from one family are described with a unique form of spondyloepiphyseal dysplasia. Characteristic features include shorttrunked short stature, punctate corneal dystrophy and marked disorganization of dermal collagen fibrils when examined by transmission electron microscopy. Inheritance is compatible with either dominance and a variable expression or X-linkage. Although the basic defect has not been determined, the tissue distribution is consistent with a defect in a non-collagenous component that affects collagen fibril formation or stability. 相似文献