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921.
Summary It is reported that concanavalin A (conA) and wheat germ agglutinin (WGA) have a differential binding pattern on normal mouse spleen lymphocytes and the surface of Dalton's lymphoma cells. It is suggested that sialic acid on the cell surface controls the expression of lectin binding sites. Further, it has been observed that the increased release of sialic acid from cell surfaces aftercis-dichlorodiammine platinum (II) (cis-Platin) treatment is due to the increased activity of sialidase.To whom reprint requests should be addressed. 相似文献
922.
Presynaptic neurones may contribute a unique glycoprotein to the extracellular matrix at the synapse 总被引:4,自引:0,他引:4
As the extracellular matrix at the original site of a neuromuscular junction seems to play a major part in the specificity of synaptic regeneration, considerable attention has been paid to unique molecules localized to this region. Here we describe an extracellular matrix glycoprotein of the elasmobranch electric organ that is localized near the nerve endings. By immunological criteria, it is synthesized in the cell bodies, transported down the axons and is related to a glycoprotein in the synaptic vesicles of the neurones that innervate the electric organ. It is apparently specific for these neurones, as it cannot be detected elsewhere in the nervous system of the fish. Therefore, neurones seem to contribute unique extracellular matrix glycoproteins to the synaptic region. Synaptic vesicles could be involved in transporting these glycoproteins to or from the nerve terminal surface. 相似文献
923.
Cell-surface adherence reactions are fundamental to the biology of lymphocytes, monocytes and granulocytes. The lymphocyte function-associated 1 (LFA-1) and macrophage 1 (Mac-1) glycoproteins mediate differing types of adhesion reactions on these cells. LFA-1 participates in T-lymphocyte and natural killer-cell adhesion to target cells, whereas the Mac-1 antigen is identical to the complement receptor type 3, which mediates adhesion of monocytes and granulocytes to C3bi-sensitized particles. Deficiency of these proteins, in a heritable disease, results in multiple adhesion-related leukocyte defects. LFA-1 and Mac-1 resemble one another in overall structure, having alpha-subunits of relative molecular mass (Mr) 180,000 and 170,000, respectively, which are non-covalently associated with beta-subunits of Mr 95,000 in alpha 1 beta 1 complexes. Peptide mapping and immunological cross-reactivity have shown that the beta-subunits are highly related if not identical, but have revealed no similarities between the alpha-subunits. Nonetheless, the shared beta-subunit suggested that LFA-1 and Mac-1 might be members of a protein family containing diversified but evolutionarily related alpha-subunits. Therefore, we examine here the structure of the alpha-subunits by N-terminal amino-acid sequencing. Sequence homology shows that the alpha-subunits are members of a novel leukocyte adhesion protein family, and suggests that their evolution occurred by gene duplication. A search for similarities to previously sequenced proteins reveals a further unexpected homology between LFA-1 and leukocyte (alpha) interferons. 相似文献
924.
Immunocytochemical localization of GnRH (gonadotropin releasing hormone) systems in the brain of a marine teleost fish,the sole 总被引:2,自引:0,他引:2
J. Nunez Rodriguez O. Kah B. Breton F. Le Menn 《Cellular and molecular life sciences : CMLS》1985,41(12):1574-1576
Summary The GnRH system was studied in the brain of the sole by immunocytochemistry (peroxidase-antiperoxidase method) (PAP) using antibodies to synthetic salmon GnRH (s-GnRH). Two centers containing immunoreactive cell bodies were observed in the forebrain, one located at the junction between the olfactory bulbs and the telencephalon and the other in the preoptic area. Numerous immunoreactive fibers were found, especially in the telencephalon, hypothalamus, pituitary, optic tectum and retina. 相似文献
925.
926.
The human pan-leukocyte antigen Leu-8 has attracted wide interest because its presence or absence identifies suppressor-inducer and helper-inducer CD4+ T-lymphocyte subsets respectively. We report here that Leu-8 is the human homologue of the mouse Mel-14 homing receptor, a molecule that promotes the initial adhesion of blood-borne lymphocytes to the specialized post-capillary endothelium of peripheral lymph nodes. We also show that Leu-8 can adopt both conventional and phospholipid anchored forms, a finding that may have relevance in the context of antigen shedding following activation or homing. The assignment of lymphocytes to different functional classes based on lymph node homing potential may represent a more general association between lymphocyte function and tissue distribution. 相似文献
927.
Summary In the presence of verapamil (0.1 mM) rat soleus muscle fibers failed to generate action potentials with overshoots. In fibers with their Vm set to a local level of –90 mV, verapamil produces a gradual reduction in the amplitude of the repetitive action potentials; this effect is more pronounced at high rates of stimulation (100 Hz). Our results suggest a local anesthetic action of this drug that could contribute with its calcium channel blocking effect to the diminished mechanical tension observed in the presence of the drug.Acknowledgments. We thank A. Losavio and M. Stefanolo for technical assistance. This work was supported by grants from CONICET and SUBCYT, Buenos Aires, Argentina and Muscular Dystrophy Association, USA. 相似文献
928.
Mitochondrial class II introns encode proteins related to the reverse transcriptases of retroviruses 总被引:6,自引:0,他引:6
Organelle introns share several distinctive features that set them apart from their counterparts in nuclear-encoded pre-messenger RNAs (reviewed in ref. 1): their termini do not obey the GU...AG rule; the introns are 'structured' (members of the same family or 'class' can theoretically adopt very similar RNA secondary conformations and several of the postulated pairings have been confirmed by studies of splicing mutants and their revertants (see, for example, ref. 4); many introns from both classes contain long open reading frames. We report here that the proteins potentially encoded by four class II introns are related to several RNA-dependent polymerases of viral and transposable element origins. 相似文献
929.
Insulin-like growth factor-II gene expression in Wilms' tumour and embryonic tissues 总被引:4,自引:0,他引:4
J Scott J Cowell M E Robertson L M Priestley R Wadey B Hopkins J Pritchard G I Bell L B Rall C F Graham 《Nature》1985,317(6034):260-262
Wilms' tumour (nephroblastoma) is an embryonal neoplasm occurring in hereditary and spontaneous forms. Both types show rearrangements of the short arm of chromosome 11. The germ line of children with the rare inherited triad of aniridia, genito-urinary abnormality and mental retardation carry a chromosome 11 that has a deletion in its short arm (band 11p13) and these children are at increased risk of developing Wilms' tumour. Neonates with the Beckwith-Wiedemann syndrome, in which there may be duplication of the 11p13-11p15 region, are similarly predisposed. In the spontaneous form of the tumour a deletion of the 11p14 band in tumour cells, but not in normal cells, has been reported, and the development of homozygosity for recessive mutations in the 11p region is implicated in the aetiology of Wilms' tumour. In view of these chromosomal rearrangements and because Wilms' tumour is histologically indistinguishable from the early stages of kidney development, we have now examined the expression of genes localized to 11p in Wilms' tumour and human embryonic tissue. In 12 sporadic tumours examined, the expression of the gene coding for insulin-like growth factor-II (IGF-II), localized to the 11p15 region, was markedly increased relative to adult tissues, but was comparable to the level of expression in several fetal tissues including kidney, liver, adrenals and striated muscle. This may reflect the stage of tumour differentiation, but could also contribute to the malignant process, as IGF-II is an embryonal mitogen. 相似文献
930.