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21.
22.
Cloning and expression of cDNAs for the alpha subunit of the murine lymphocyte-Peyer''s patch adhesion molecule 总被引:5,自引:0,他引:5 下载免费PDF全文
H Neuhaus M C Hu M E Hemler Y Takada B Holzmann I L Weissman 《The Journal of cell biology》1991,115(4):1149-1158
cDNA clones encoding the alpha chain of the murine lymphocyte-Peyer's patch adhesion molecule (LPAM), which is associated with lymphocyte homing, have been isolated by screening with the human VLA-4 (alpha 4h) probe. Several alpha 4 antigenic determinants were identified on COS-7 cells after transfection. From overlapping clones, approximately 5 kb of contiguous nucleotide sequence have been determined, encoding a protein sequence of 1039 amino acids for the LPAM alpha chain (alpha 4m). LPAM is a member of the integrin family of cell-surface heterodimers, and alpha 4m is the murine homologue of the human alpha 4 h chain. The two proteins have a total sequence similarity of 84%, with an almost perfect conservation (31/32 amino acids) in the cytoplasmic domain. Like alpha 4h, alpha 4m is distinct from other integrin alpha chains because it has neither an I-domain nor a COOH-terminal cleavage site. The positions of the characteristic Cysteine residues are conserved, and a putative protease cleavage site is located near the middle of the protein sequence. The NH2-terminal part of the protein contains seven homologous repeats, and three of them include putative divalent cation-binding sites. These sites are among the most conserved between the alpha 4m sequence and other alpha chains, and may therefore be involved in the binding of integrin alpha and beta chains. An additional cDNA clone was isolated which shares a sequence of perfect homology with the alpha 4m encoding cDNAs, but has a unique 3' poly-A end. This observation correlates with the fact that three discrete murine RNA bands are observed in Northern blot experiments using alpha 4m as a probe, whereas only two human RNA species are described for alpha 4h, indicating a higher complexity for murine than for human sequences. 相似文献
23.
An improved approach for transformation of plant cells by microinjection: molecular and genetic analysis 总被引:4,自引:0,他引:4
Martin Schnorf Gabriele Neuhaus-Url Alessandro Galli Shigeru Iida Ingo Potrykus Gunther Neuhaus 《Transgenic research》1991,1(1):23-30
A new culture method for the injection of tobacco mesophyll protoplasts has been established. The protoplasts are embedded
in a thin layer of alginate and are nourished from the medium in the underlying basislayer. In the alginate layer the protoplasts
regenerate to calli at a frequency of up to 80%. Embedded protoplasts can be selected either with 50 mg l−1 kanamycin or 5 mg l−1 paromomycin. Single resistant cells can be recovered from about 10 000 sensitive cells in one alginate layer. Injection of
theneo gene (coding for neomycin phosphotransferase II) into protoplast derived single cells in the alginate layer results in kanamycin
resistant colonies that can be regenerated to mature plants. These plants express the neomycin phosphotransferase as shown
by enzyme activity assay. The integration of the transgene into the plant genome could be proved by Southern hybridization
to high molecular weight DNA. With this culture method 100 cells can be injected per hour. Transformation frequencies range
from 2 to 20%. In crossing experiments, it was shown that the foreign gene is transmitted to the next generation in a Mendelian
fashion. 相似文献
24.
Intact etioplasts with an intactness of 85% and with a cytosolic and a mitochondrial contamination of less than 10% were isolated from 8-d-old dark-grown barley (Hordeum vulgare) leaves. These plastids contained starch equivalent to 21.5 μmol of glucose per mg protein. From various likely precursors applied to isolated etioplasts, only dihydroxyacetone phosphate (DHAP) had significant effects on metabolite levels and on the internal ATP/ADP ratio. The concentration dependence of DHAP uptake exhibited saturation characteristics with half saturation at 0.36 mm DHAP and a maximal velocity of 6.6 μmol mg−1 of protein h−1. The transport was significantly inhibited by inorganic phosphate, pyridoxal-5′-phosphate, and 4,4′-diisothiocyano-2,2′-stilbenedisulfonate. The rate of glucose-6-phosphate uptake was much lower and not saturable up to a concentration of 10 mm. Exogenously applied [14C]DHAP was incorporated into starch at a rate of 0.14 μmol of DHAP mg−1 of protein h−1. Enzyme activities required to convert DHAP into starch were found to be present in etioplasts. Furthermore, enzymes generating ATP from DHAP for ADPglucose synthesis were also detected. Finally, a scheme is presented suggesting DHAP uptake to serve both as carbon skeleton and as energy source for starch synthesis, mediated by a translocator with properties similar to those of the triose phosphate translocator from chloroplasts. 相似文献
25.
O W Neuhaus 《Proceedings of the Society for Experimental Biology and Medicine. Society for Experimental Biology and Medicine (New York, N.Y.)》1992,200(1):85-89
Adult male rats were maintained on 0, 5, 10, 15, and 20% casein diets to produce a series of animals having serum alpha 2u-globulin levels varying linearly from a normal of 31 micrograms/ml to a minimum of 13 micrograms/ml. In this way, it was possible to titrate endogenously the renal reabsorption and urinary excretion of this low molecular weight protein. The average maximal reabsorption rate (Tm) was established to be 9.7 micrograms/min and was reached at a renal filtered load (F alpha 2u) of 13.6 micrograms/min. These data were expressed in terms of a Tm:F alpha 2u ratio of 0.71. Below this value, the reabsorption declined from 70% to 50% of the F alpha 2u. Above 0.71, where F alpha 2u is less than the Tm, the reabsorption increased to 80-90%. It was observed that the fractional renal uptake of the alpha 2u-globulin varied linearly with the filtered load. 相似文献
26.
Membrane-wall interrelationship in Gaffkya homari: sulfhydryl sensitivity and heat lability of nascent peptidoglycan incorporation into walls. 总被引:4,自引:3,他引:1 下载免费PDF全文
Membrane-walls from Gaffkya homari require a specific interrelationship between membrane and wall that functions in the incorporation of nascent peptidoglycan into the preexisting peptidoglycan of the wall. Two different methods were used to inhibit selectively this incorporation process: (i) sensitivity to sulfhydryl reagents and (ii) heat inactivation. Of the sulfhydryl reagents tested, 2.2 mM iodoacetamide inhibited the synthesis of wall peptidoglycan 50%, whereas greater than 100 mM was required to inhibit the synthesis of sodium dodecyl sulfate (SDS)-soluble peptidoglycan. Heat treatment at 37 degrees C (t 1/2 = 5.7 min) inhibited wall peptidoglycan synthesis without affecting SDS-soluble peptidoglycan synthesis. Inhibition of LD-carboxypeptidase by iodoacetamide and heat gave 50% inhibition and t 1/2 values similar to those observed for the incorporation process. Thus, it is suggested that the LD-carboxypeptidase may be one of the enzymes responsible for the sulfhydryl sensitivity and heat lability and that this enzyme may play a role in the relationship between membrane and wall in G. homari. 相似文献
27.
In Chortoicetes terminifera 45 independently-occurring B-chromosomes were tested and 23 distinct banding variants were detected with either G- or C-banding; six types were found more than once. In particular the Type I banding morph was detected 12 times indicating that individuals carrying this type may be under a different regime of selection compared with individuals bearing other types of banding morph; or the Type I may be subjected to a higher rate of meiotic drive in either or both sexes than other types. Also the Type I appeared to be obviously related to four other banding morphs whereas most types were not obviously related to any other banding morphs, but a few were similar in banding pattern to one or two other types. Three types of B-chromosomes were found in three or more different populations. A relatively high frequency of the Type I banding morph was found in one population, which was probably mainly composed of non-migratory individuals, and also in a laboratory-raised population. The most likely mechanisms for small changes in the banding sequence of the B-chromosomes are three-break insertions which are often indistinguishable from inversions. Rearrangements which add or delete bands, or sequences of bands, to or from B-chromosomes are probably the result of exchanges which are now known to take place in rare individuals with two B-chromosomes. The most distal region of all the banding morphs of the B-chromosome in C. terminifera, plus a short interstitial region in some types, is not late-replicating and has the banding characteristics of euchromatin. The rest of the chromatin of the B-chromosomes is heterochromatic and is the latest replicating heterochromatin in the whole genome. It consists of G-bands, which are also deeply stained with C-banding, and alternating G-interbands, which in turn are stained grey with C-banding. Both of these staining combinations are seen in heterochromatin of the normal complement. The heterochromatin of the B-chromosomes is condensed throughout 1st meiotic prophase in the male and in all somatic interphase nuclei where it can be quickly detected using the G-banding technique. The B-chromosome has a relatively constant, acrocentric morphology with a tendency to increase of length of the long arm as band numbers increase. Isochromosomes of the long arm have been seen only in laboratoryraised embryos. From egg pods with significantly fewer than expected B-chromosomes it is strongly suggested that more than one male may fertilize the eggs in a single pod. 相似文献
28.
C Neuhaus W Kerner V Maier E F Pfeiffer 《Hormone and metabolic research. Supplement series》1979,(8):115-118
In 8 insulin-dependent diabetics, the effect of D-Trp8-D-Cys14-somatostatin on blood glucose, growth hormone, and glucagon levels as well as on insulin requirements from an artificial endocrine pancreas was studied during a balanced meal. The somatostatin analogue was infused at a rate of 25 microgram/h preceeded by a bolus injection of 25 microgram 30 minutes before ingestion of the meal. At this dose the analogue had no effect on glucagon levels and insulin requirements from the artificial pancreas. On the other hand, there was a significant lowering effect on fasting blood glucose levels, possibly indicating a direct inhibition of hepatic glucose production. Furthermore, there might be a slight effect on growth hormone levels, as was demonstrated by a rebound increase after termination of analogue infusion. 相似文献
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