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121.
Gross structure and dimensions of the gills have been examined in a hill-stream sisorid catfish,Glyptothorax pectinopterus, which remains adhered to rocks by means of an adhesive organ developed on the ventral side of the thorax. The fish shows
a greater weight-specific gill area and greater length of the gill filaments by comparison with other hill-stream fishes.
Adaptation for life in a hill-stream habitat is shown by the presence of additional filaments on the gills and patches of
specialised cells on the filament epithelium. 相似文献
122.
D.V. SINGH. A.K. TRIPATHI AND H.D. KUMAR. 1991. Sodium chloride, up to 20 mmol/l concentration, had a positive effect on acetylene reducing activity and photosynthetic oxygen evolution of a paddy field cyanobacterium, Anabaena doliolum. Beyond 20 mmol/l level of salinity adverse effects appeared. A mutant resistant to 200 mmol/l NaCl was isolated by nitrosoguanidine mutagenesis. The mutant, NaCl-R200 , showed about 20–25% more nitrogenase activity and photosynthetic oxygen evolution than the parent. Better capacity of nitrogen fixation and photosynthesis possibly could help the mutant in synthesis of osmotic stabilizer to resist the salinity stress. 相似文献
123.
Y Tomiyama E Brojer Z M Ruggeri S J Shattil J Smiltneck J Gorski A Kumar T Kieber-Emmons T J Kunicki 《The Journal of biological chemistry》1992,267(25):18085-18092
Following an ill-defined activation event, the Arg-Gly-Asp (RGD) recognition site of the platelet integrin, glycoprotein IIb-IIIa (alpha IIb beta 3), can bind to fluid-phase, RGD-containing protein ligands, such as fibrinogen, or to the murine monoclonal IgM, PAC-1, which contains the sequence Arg-Tyr-Asp (RYD) within the third complementarity-determining region of its heavy chain (H3). PAC-1 has thus become a widely exploited marker of platelet alpha IIb beta 3 activation. In this report, we compare PAC-1 with two murine IgG, OP-G2 (IgG1 kappa) and LJ-CP3 (IgG1 kappa), that also contain the sequence RYD in H3 but bind to alpha IIb beta 3 without prior activation. Each antibody can inhibit the binding of the other two to intact platelets or to purified IIb-IIIa, the binding of each antibody is completely inhibited by peptides containing RGD, and H3 of each antibody uses the germline D-gene DSP 2.10 (CTATAGGTACGAC) which includes the sequence RYD. Two other murine IgG, HP20 and PCG1-1, cloned and sequenced by other laboratories, also utilize the DSP 2.10 sequence, but neither antibody binds to alpha IIb beta 3. From a comparison of the H3 sequences of these antibodies, we have developed a molecular model of the H3 loop region which can explain these differences in specificity. This model predicts that both the ability to bind to alpha IIb beta 3 and the activation dependence of that binding are a function of the orientation and, therefore, accessibility of the RYD sequence. This model and refinements thereof can be exploited to study the molecular basis for specificity and affinity of RGD-containing ligands for integrins. 相似文献
124.
125.
Donor-type activated natural killer cells promote marrow engraftment and B cell development during allogeneic bone marrow transplantation. 总被引:5,自引:0,他引:5
W J Murphy M Bennett V Kumar D L Longo 《Journal of immunology (Baltimore, Md. : 1950)》1992,148(9):2953-2960
Purified NK cells were obtained from mice with severe combined immune deficiency and were activated with human IL-2 (hrIL-2) in vitro to determine if, once activated, these cells could be transferred with compatible bone marrow cells (BMC) and promote marrow engraftment in irradiated allogeneic recipients. After culture with hrIL-2, these cells maintained a phenotypic and lytic spectrum consistent with a pure population of activated NK cells. These activated NK cells were then adoptively transferred with the donor BMC and rhIL-2 into lethally irradiated allogeneic hosts. The addition of NK cells with the BMC allowed for more rapid hematopoietic engraftment as determined through short term studies, and greater donor-derived chimerism with accelerated reconstitution of the B cell population as determined with long term analysis. No evidence of graft-vs-host disease was detected in the recipients receiving the activated NK cells with allogeneic T cell replete BMC and hrIL-2. The mechanism by which the transferred NK cells improved BMC engraftment was at least partly through the abrogation of the host effector cell's ability to mediate resistance to the marrow graft. Thus, the administration of donor-type activated NK cells with BMC and hrIL-2 may significantly augment hematopoietic engraftment and immune reconstitution in the clinical setting of allogeneic BMT without giving rise to graft-vs-host disease. 相似文献
126.
Extreme heterogeneity of Ty1-copia group retrotransposons in plants 总被引:18,自引:0,他引:18
Andrew J. Flavell Donald B. Smith Amar Kumar 《Molecular & general genetics : MGG》1992,231(2):233-242
127.
The psychrotrophic, dimorphic yeast Candida humicola, isolated from Antarctic soil, secretes an acidic protease into the medium. The secretion of this protease by C. humicola was found to be dependent on the composition of the medium. In YPD or yeast nitrogen base medium containing either amino acids or ammonium sulfate as the nitrogen source, the activity of the protease in the medium was low (basal level). However, when yeast nitrogen base medium was depleted of amino acids or ammonium sulfate and supplemented with proteins, the activity of the enzyme increased. The secretion of the enzyme was greater during exponential growth at low temperatures than during growth at higher temperatures. The purified protease had a molecular mass of 36,000 Da and was inhibited by pepstatin, iodoacetamide, and sodium dodecyl sulfate. Despite the prevalent cold temperatures in Antarctica, this extracellular protease of the psychrotrophic yeast C. humicola was active at temperatures ranging from 0 to 45 degrees C, with an optimum activity at 37 degrees C. 相似文献
128.
Glycine argyrea accession G1420 was evaluated for its response to inoculation with Agrobacterium rhizogenes strains LBA9402 and A4T, carrying wild type Ri plasmids, and by strains R1601 and A4TIII with engineered plasmids. Hypocotyls from young seedlings were the most responsive in producing roots at inoculation sites. Root production was also dependent on bacterial concentration. Excised, cultured roots produced green nodular callus which regenerated shoots on SC2 medium containing 1.1 mg l–1 6-benzylaminopurine and 0.005 mg l–1 indole-3-butyric acid. The transformed nature of the roots and of callus regenerating shoots was confirmed by the presence of opines and by dot blot analysis for Ri TL-DNA. Tissues regenerated from roots transformed by A. rhizogenes strains R1601 and A4TIII exhibited NPTII enzyme activity, confirming the stable integration and expression of the chimaeric kanamycin resistance gene in transgenic tissues.Abbreviations BAP
6-benzylaminopurine
- IBA
indole-3-butyric acid
- NPTII
neomycin phosphotransferase II
- SDS
sodium dodecyl sulphate 相似文献
129.
Summary An efficient algorithm for generating DNA structures from a given set of distance constraints has been developed. The present implementation is suited for single-stranded DNA. The performance of the program has been tested with constraint sets representative of most stringent theoretical cases and also with usually available experimental ones. The results indicate that use of NOE-derived constraints alone generates an extremely large family of conformers and suggest that the quality of structure determination may be enhanced by incorporating additional constraints obtained by other means. The speed of the program makes it ideal for interactive use in conjunction with other complementary algorithms such as those for spectral simulation, energy minimization and molecular dynamics calculations.Dedicated to the memory of Professor V.F. Bystrov 相似文献
130.
We synthesized and tested the biological properties of four fluorescent vasopressin analogs: [1-(2-mercapto)propionic acid]-8-lysine-N6-5-dimethylamino-naphthalene-1-sulfonyl vasopressin (D-MLVP), [1-(2-mercapto)propionic acid]-8-lysine-N6-carboxyfluorescein vasopressin (F-MLVP), [1-(2-mercapto)propionic acid]-8-lysine-N6-2-N-methylanthranilamide vasopressin (MA-MLVP), and [1-(2-mercapto)propionic acid]-8-lysine-N6-carboxytetramethylrhodamine vasopressin (R-MLVP). All fluorescent analogs were prepared by coupling the appropriate fluorochrome to the 6-amino group of the lysine residue in [1-(2-mercapto)propionic acid]-8-lysine vasopressin (MLVP) which was synthesized by the Merrifield solid-phase method. The structures of high performance liquid chromatography-purified MLVP and the fluorescent analogs were confirmed by fast atom bombardment mass spectrometry. F-MLVP, MA-MLVP, and R-MLVP effectively competed for 8-arginine vasopressin (AVP)-binding sites in canine renal plasma membranes and on the surface of porcine kidney cells (LLC-PK1, ATCC CL101). Dissociation constants for F-MLVP, MA-MLVP, and R-MLVP of 32, 8.8, and 26 nM, respectively, were calculated from the results of competition binding assays conducted with membranes. D-MLVP did not bind to plasma membranes. Dissociation constants for F-MLVP, MA-MLVP, and R-MLVP of 390, 38, and 160 nM, respectively, were calculated from the results of competition binding assays conducted with cells. F-MLVP, MA-MLVP, and R-MLVP at a concentration of 10(-6) M increased adenylate cyclase activity in canine renal plasma membranes to values 2.4, 2.9, and 2.6 times that of basal activity, respectively. A maximally active concentration of AVP (1 microM) increased adenylate cyclase activity in canine renal plasma membranes to a value 2.7 times that of basal activity. D-MLVP did not stimulate adenylate cyclase activity. F-MLVP, MA-MLVP, and R-MLVP at a concentration of 10(-6) M increased the cAMP content of porcine kidney cells from a basal level of 43 to 267, 160, and 469 pmol/mg of cell protein, respectively. Specific binding of these fluorescent analogs to receptors on the surface of LLC-PK1 cells was observed by fluorescence microscopy. These observations indicate that F-MLVP, MA-MLVP, and R-MLVP are biologically active fluorescent vasopressin analogs which are well-suited to the study of renal vasopressin receptors by fluorescence microscopy. 相似文献