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1.
Single cell observations of normal and of leukemic human bone marrow cells demonstrated cell-cell interactions of lymphocytes with hematopoietic progenitor cells. In all cases lymphocytes and target cells were from the same individual. Lymphocyte-target cell interactions occurred more frequently with normal committed progenitor cells and leukemic blast cells from acute myeloid leukemia than with precursor cells of the proliferative cell pool, including myeloblasts, promonocytes, erythroblasts and megakaryocytes. Both induction of mitosis and degeneration of the progenitor cells occurred after cell-cell interaction with almost the same frequency. Acute myeloid leukemic blast cells degenerated after contact with lymphocytes with the same frequency as normal progenitor cells (i. e. in 16% of cell contacts), but especially during mitosis. In contrast, normal and regenerating bone marrow progenitor cells from myeloproliferative diseases demonstrated no degeneration after cell-cell interaction with lymphocytes during mitosis. Otherwise the induction of mitoses by lymphocyte-target cell interactions was more frequently observed in normal progenitor cells than in leukemic blasts. 相似文献
2.
The mouse has an interferon-alpha (MuIFN-alpha) gene family containing at least four, and likely more than ten members. A segment of mouse chromosomal DNA and cDNAs encoding murine alpha IFNs have been cloned, and the sequence of two MuIFN-alpha DNAs determined. No intron was found in the chromosomal gene. The two coding sequences produced biologically active IFN when expressed in monkey cells under the control of an SV40 promoter, and in E.coli under the control of the ampicillinase promoter. MuIFN-alpha 1 had no detectable activity on human cells, while MuIFN-alpha 2 was 20% as active on human as on mouse cells. 相似文献
3.
4.
Summary Identification of argyrophilic cells, in pancreatic islets of normal rabbits, is accomplished by light and electron microscopy in osmium-fixed plastic-embedded tissues.Fixative, pretreatment and pH of silver nitrate solution were essential for the light microscopic study to reveal argyrophilic cells in osmium-fixed plastic-embedded pancreatic islet tissue. The best result was obtained with Dalton's osmium fixation and buffered silver nitrate methanamine solution at pH 9.O. The cytoplasmic granules of argyrophilic cells generally are densely packed but some of the cells show only sparse silver impregnated granules in the cytoplasm. Occasionally there are some non-argyrophilic granular cells in which, after silver impregnation, the cytoplasm appears clear. There are three kinds of cells in the pancreatic islets, i.e., argyrophilic granular cells, non-argyrophilic granular (clear) cells, and beta cells (situated centrally in the islet and stained light yellow in silver impregnated sections).The cells known as argyrophilic cells in light microscopy can be identified as alpha cells in electron micrographs by comparison of consecutive sections of the same cell.The author would like to express his appreciation to professor Roy C. Swan for his generous guidance. 相似文献
5.
Sequence requirements for the recognition of tyrosine-based endocytic signals by clathrin AP-2 complexes. 总被引:21,自引:4,他引:17
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W Boll H Ohno Z Songyang I Rapoport L C Cantley J S Bonifacino T Kirchhausen 《The EMBO journal》1996,15(21):5789-5795
We recently determined that fusion proteins containing tyrosine-based endocytic signals bind to the mu 2 subunit of AP-2, the complex that drives clathrin coat formation and mediates endocytosis from the plasma membrane. Here we analyze the selectivity of peptide recognition by mu 2 and by AP-2 using combinatorial selection methods and surface plasmon resonance. Both mu 2 and AP-2 are shown to interact with various sequences of the form tyrosine-polar-polar-hydrophobic (Yppø) found on receptors that follow the clathrin pathway. The optimal sequence for interaction with mu 2 and with AP-2 has tyrosine as an anchor and prefers arginine at position Y + 2 and leucine at position Y + 3. In contrast, no preferred sequence is detected surrounding the Yppø signal, indicating that recognition of the Yppø endocytic signal does not require a prefolded structure. We conclude that sorting into the endocytic pathway is governed by a surprisingly simple interaction between the mu 2 chain and a tyrosine-containing tetrapeptide sequence. 相似文献
6.
Rubén C. Aguilar Lilia A. Retegui Marie-Catherine Postel-Vinay Leonor P. Roguin 《Molecular and cellular biochemistry》1994,136(1):35-42
We have previously shown that a monoclonal antibody (MAb) recognizing the human growth hormone (hGH) antigenic domain left exposed after binding to lactogenic receptors enhanced hGH binding probably through allosteric effects on the hormone binding site. Since receptors displaying different specificities would not recognize exactly the same hGH region, we explored whether some of our MAb could affect hGH binding to somatogenic receptors from rabbit liver and to human liver hGH-specific receptors.The effect of MAbAE5, AC8 and F11 on hGH binding was measured by determining the formation of125I-MAb:hGH:receptor complexes using two different experimental approaches. Results from procedure A, which involved the previous binding of the hormone to microsomes before adding125I-MAb, indicated that the hGH domain defined by epitopes AE5, AC8 and F11 is uncovered in the various hormone:receptor complexes.Procedure B was devised to reveal any alteration in the hGH molecule induced by the MAb. In this case preformed125I-MAb:hGH complexes were added to microsomes. Data showed that125I-MAb AE5:hGH complexes bound better to the various receptors than125I-MAb AE5 to hGH:receptor complexes. On the contrary, hGH previously bound to125I-MAb AC8 or125I-MAb F11 was less recognized by the receptors than the free hormone. Furthermore, binding of MAb AE5 or MAb F11 to hGH 20 K (a natural hGH variant lacking residues 32–46) also enhanced its affinity to the various receptors whereas MAb AC8 did not inhibit hGH 20 K binding.Results indicated that MAb recognizing the hGH antigenic area that remains unmasked after binding to different membrane-bound receptors are able to affect hormone binding site. MAb would induce either positive or negative allosteric changes in the hormone region involved in its binding to lactogenic, somatogenic and hGH-specific receptors. 相似文献
7.
F. Norbis M. Boll G. Stange D. Markovich F. Verrey J. Biber H. Murer 《The Journal of membrane biology》1997,156(1):19-24
In a previous report we documented an increased Na+-dependent transport of inorganic phosphate (P
i
) in Xenopus laevis oocytes injected with mRNA isolated from rabbit duodenum (Yagci et al., Pfluegers Arch.
422:211–216, 1992; ref 24). In the present study we have used expression cloning in oocytes to search for the cDNA/mRNA involved
in this effect. The identified cDNA (provisionally named PiUS; for P
i
-uptake stimulator) lead to a 3-4-fold stimulation of Na+-dependent P
i
-uptake (10ng cRNA injected, 3–5 days of expression). Na+-independent uptake of P
i
was also affected but transport of sulphate and l-arginine (in the presence or absence of sodium) remained unchanged. The apparent K
m
-values for the induced Na+-dependent uptake were 0.26 ± 0.04 mm for P
i
and 14.8 ± 3.0 mm for Na+. The 1796 bp cDNA codes for a protein of 425 amino acids. Hydropathy analysis suggests a lack of transmembrane segments.
In vitro translation resulted in a protein of 60 kDa and provided no evidence of glycosylation. In Northern blots a mRNA of
∼2 kb was recognized in various tissues including different intestinal segments, kidney cortex, kidney medulla, liver and
heart. Homology searches showed no similarity to proteins involved in membrane transport and its control. In conclusion, we
have cloned from a rabbit small intestinal cDNA library a novel cDNA encoding a protein stimulating P
i
-uptake into Xenopus laevis oocytes, but which is not a P
i
-transporter itself.
Received: 31 July 1996/Revised: 16 October 1996 相似文献
8.
The effect of somatostatin and its two tetrapeptide fragments was investigated on turning activity induced by unilateral substantia nigra lesion in rats. Somatostatin in a dose of 0.6 nM had no action on the turning behavior, while a dose of 6 nM increased slightly while a dose of 12 nM significantly the contralateral turning. Cys-Lys-Asn-Phe and Phe-Trp-Lys-Thr had no action in low or high doses on the turning activity of the animals. The results suggest that somatostatin has a direct postsynaptic dopamine receptor stimulating effect. It seems that for dopamine receptor stimulating action the complete somatostatin molecule is needed. 相似文献
9.
R. Taugner U. Boll P. Zahn Prof. Dr. W. G. Forssmann III 《Cell and tissue research》1976,172(4):431-446
Summary The intercellular connections between the epithelial cells of Bowman's capsule were investigated. It could be demonstrated that typical zonulae occludentes (tight junctions) are present in the species (rat, hamster, and Tupaia) studied. Freeze-fracturing shows a network of anastomizing strands; some species variations are described. In the rat two strands are common. In the golden hamster mostly two to four and occasionally five strands occur. In Tupaia regularly three tight junction strands are found and also gap junctions associated with the zonulae occludentes. In thin sections the goniometric analysis confirms the freeze-fracturing results and reveals attachment zones of macular shape, which are classified as intermediate junctions and desmosomes. The functional role of these cell junctions observed in the epithelium of Bowman's capsule is discussed. 相似文献
10.
The juxtaglomerular apparatus of the rat was studied after freeze-fracturing with special respect to intercellular junctions. It was found that juxtaglomerular granulated cells of the vas afferens are interconnected by gap junctions to adjacent cells (granulated cells, possibly also smooth muscle cells). Gap junctions have also been found on the surface of lacis cells and mesangial cells. It is therefore concluded that these cells of the juxtaglomerular apparatus and the glomerulus--granulated cells (possibly also smooth muscle cells) of the vas afferens, lacis cells and mesangium cells--form a functional system reacting in a coordinated manner to physiological stimuli. 相似文献