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81.
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83.
Summary The elemental compositions of chloragosome granules in the earthworm Lumbricus rubellus living in non-polluted (Dinas Powys) and heavily Pb-polluted (Wemyss) soils were determined by fully quantitative electron probe X-ray microanalysis. P, Ca, S and Zn were the major elemental components of the chloragosomes. High Pb concentrations were found in chloragosomes of Wemyss animals; Pb was not detected in chloragosomes of Dinas Powys animals. Partial correlation and regression analysis indicated that the in vivo accumulation of Pb by chloragosomes was accompanied by diminished chloragosomal Ca concentrations. Pb is bound by P-containing ligand(s) in the chloragosome matrix. The sequestration of Pb by chloragosomes results in the detoxification of the metal by accumulative immobilization. 相似文献
84.
E L Morgan M V Hobbs M L Thoman J Janda D J Noonan J Kadar W O Weigle 《Journal of immunology (Baltimore, Md. : 1950)》1990,144(7):2499-2505
Fc region fragments derived from the enzymatic cleavage of human IgG have been shown to induce human peripheral blood-derived B cells to differentiate into Ig secreting cells (ISC). The synthetic peptide p23, corresponding to residues 335 to 357 in the Fc region of human IgG1, represents a region of the molecule responsible for stimulation of ISC formation. Fc region-induced ISC formation requires at least two signals; one supplied by Fc region activators and one supplied by a T cell-derived factor(s). In this report we show that the coculture of human PBMC with pFc' or p23, results in the release of factor(s) that resemble IL-6 in its pattern of biologic activity. This conclusion is based on the observations that supernatants from Fc region-stimulated PBMC cultures contained increased levels of elements that scored as positive in two assays for IL-6: the B9.9 hybridoma growth and the CESS cell differentiation assays. Moreover, RNA from Fc region-stimulation PBMC contained increased levels of IL-6 cDNA-hybridizable elements. Finally, it was observed that rabbit anti-IL-6 inhibited the ability of supernatants derived from Fc region-stimulated PBMC cultures to induce B9.9 cell proliferation as well as p23-induced ISC formation in intact PBMC cultures. Fc region fragments induce both monocytes and T cells to produce IL-6. Taken together, these results indicate that IL-6 is produced in Fc region-stimulated PBMC cultures and is involved in B cell activation by these activators. 相似文献
85.
CAP 37, a 37 kD human neutrophil granule cationic protein shares homology with inflammatory proteinases 总被引:6,自引:0,他引:6
H A Pereira J K Spitznagel J Pohl D E Wilson J Morgan I Palings J W Larrick 《Life sciences》1990,46(3):189-196
We have previously shown that a major granule-associated cationic protein CAP 37 (Mr = 37 kD) derived from human PMN is a monocyte-specific chemoattractant. The N-terminal amino acid sequence of this novel chemotactic protein shares significant homology with a number of inflammatory molecules with protease activity including elastase and cathepsin G. However, a critical substitution of a serine for a histidine at position 41, results in its lack of serine protease activity. 相似文献
86.
To study the effect of T-cell-derived BCGF-12kD on human B-cell autocrine growth-associated functions, we cultured Epstein Barr virus (EBV)-transformed normal B cells (LCL 72285) and Burkitt's lymphoma cells (Raji) in the presence or absence of BCGF-12kD. When cultured in media supplemented only with fetal calf serum, the LCL and Raji cell lines maintained relatively high levels of episomes. Although a similar level of proliferation could be maintained under defined culture conditions in media supplemented with BCGF-12kD, these conditions resulted in a time-dependent reduction of EBV sequences, as detected with EBV nuclear antigen (EBNA-1 and EBNA-2) gene probes. These results suggest that stimulation with T-cell-derived BCGF-12kD can alter a regulatory step which may be involved in the EBV transformation of B cells. 相似文献
87.
The convulsant properties of xanthine amine congener (XAC, 8-(4-(2-aminoethyl)-aminocarboxylmethyloxy)phenyl-1,3-dipropylxant hine) are compared to those of caffeine. Male Swiss albino mice were infused with convulsants through a lateral tail vein. Convulsion thresholds (i.e. the amount of convulsants required to elicit convulsions) of 39.8 +/- 2.0 mg/kg (n = 10) and 109.8 +/- 2.3 mg/kg (n = 10) were calculated for XAC and caffeine respectively. Pretreatment of animals with the adenosine receptor agonists 2-chloroadenosine, N6-cyclohexyladenosine or 5'-N-ethylcarboxamido-adenosine (1 mg/kg, i.p., 20 minutes prior to infusion) significantly decreased the seizure threshold of both XAC and caffeine. The adenosine uptake blockers, 6-nitrobenzylthioinosine or dipyridamole (0.25 mg/kg, i.p., 20 minutes prior to infusion) did not significantly affect the seizure threshold to either XAC or caffeine. The benzodiazepine agonist diazepam (5 mg/kg, i.p., 20 minutes prior to infusion) significantly increased the seizure threshold to both XAC (p less than 0.05) and caffeine (p less than 0.01), whereas the benzodiazepine antagonist Ro 15-1788 (10 mg/kg, i.p., 20 minutes prior to infusion) significantly increased the seizure threshold to caffeine (p less than 0.01), but not XAC. The results suggest that actions at benzodiazepine receptors may be a tenable hypothesis to explain the convulsant actions of caffeine, but not those of XAC. 相似文献
88.
Intramolecular electron redistribution in cytochrome c oxidase after photolysis of the partially reduced CO-bound enzyme was followed at a number of different wavelengths by absorption spectroscopy. Spectra were constructed for the first two phases of this process. The first phase (tau = 3 microseconds) has a spectrum essentially identical to the difference between the Fea and Fea3 reduced-minus-oxidized spectra, indicating a 1:1 stoichiometry between the amount of Fea3 oxidized and Fea reduced. It is not necessary to invoke reduction or oxidation of other redox carriers in this phase. The second phase (tau = 35 microseconds) spectrum appears to be a linear combination of the Fea3 and Fea reduced-minus-oxidized difference spectra, reflecting the oxidation of four parts of Fea3 for every part of Fea oxidized. This process can be described in terms of transfer to CuA of electrons from the Fea3<==>Fea equilibrium system established in the first phase. The relative contributions of Fea3 and Fea in the second phase allow us to calculate the equilibrium constant for Fea3<==>Fea electron exchange, which yields a delta Em of 36 mV for the two centers (Fea3 more positive). Together with the apparent rate constant for the fast phase, this equilibrium constant yields, in turn, the forward (kf) and reverse (kr) rates for electron transfer from Fea to Fea3 as follows: kf = 2.4 x 10(5) s-1 and kr = 6 x 10(4) s-1. kf is much faster than any observed step in the reaction of the reduced enzyme with O2. Thus, the catalytic mechanism of O2 reduction to water is not rate-limited by electron transfer from Fea to the binuclear Fea3/Cu(B) site. 相似文献
89.
Isolation and characterization of a membrane-attack-complex-inhibiting protein present in human serum and other biological fluids. 下载免费PDF全文
Cytosolic, detergent-solubilized and membrane-bound growth hormone (GH) receptors from rabbit adipose tissue and liver were tested for reactivity with a panel of monoclonal antibodies (MAbs). The cytosolic and detergent-solubilized forms of adipose tissue and liver GH receptors were identically reactive with four precipitating and two hormone-binding-site-directed MAbs. However, the membrane-bound form of the adipose receptor was 1000-fold less reactive with one binding-site-directed MAb (MAb 7) than the membrane-bound liver GH receptor. Reactivity with another inhibitory MAb (MAb 263) was identical for adipose tissue and liver membrane GH receptors. The relative potency of 22,000-Mr and 20,000-Mr forms of human GH was identical in assays with liver and adipose tissue membrane receptors. Thus, contrary to earlier suggestions, the discrepancy between the growth-promoting and insulin-like activities of 20,000-Mr human GH cannot be rationalized by a difference in the affinity of this hormone for 'somatogenic' and 'metabolic' receptors when the comparison is made in the same species. Cross-linking studies showed that the major GH-binding subunit of liver and adipose tissue GH receptors had the same Mr (54,000 +/- 5000, reduced). The ligand-binding subunits of liver and adipose tissue receptors are identical by several criteria, but one epitope on the adipose tissue receptor appears to be masked upon membrane insertion, possibly by close association with a tissue-specific component. Tissue specificity may be determined by association of a ubiquitous GH-binding subunit with tissue-specific membrane components, rather than by differences in amino acid sequence. 相似文献
90.
A recombinant adenovirus expressing an Epstein-Barr virus (EBV) target antigen can selectively reactivate rare components of EBV cytotoxic T-lymphocyte memory in vitro. 总被引:4,自引:1,他引:3 下载免费PDF全文
S M Morgan G W Wilkinson E Floettmann N Blake A B Rickinson 《Journal of virology》1996,70(4):2394-2402
While the bulk of a virus-induced cytotoxic T-lymphocyte (CTL) response may focus on a few immunodominant viral antigens, in certain tumor virus systems the detectability of clones recognizing other, subdominant antigens can assume particular importance. By using the human CTL response to Epstein-Barr virus (EBV) as a model system, here we show that even rare components of virus-specific memory can be selectively reactivated in vitro when the relevant target antigen is expressed in autologous stimulator cells from a recombinant adenovirus (RAd) vector. We generated a replication-deficient adenovirus, RAd-E3C, which in skin fibroblast cultures expressed the EBV nuclear antigen EBNA3C at a 10- to 100-fold-higher level than that naturally present in EBV-transformed lymphoblastoid cell lines (LCLs). Initial experiments with a donor whose polyclonal CTL response to LCL stimulation contained a strong EBNA3C-specific component showed that these CTLs could be efficiently reactivated by in vitro stimulation either with RAd-E3C-infected fibroblasts or with RAd-E3C-infected peripheral blood mononuclear cells. Then we studied donors whose responses to LCL stimulation contained little if any detectable EBNA3C reactivity but were dominated by clones recognizing other EBV target antigens; in vitro stimulation with RAd-E3C-infected peripheral blood mononuclear cells selectively reactivated EBNA3C-specific CTL clones from these individuals, with the epitope specificities of responses subsequently identified at the peptide level. This RAd-based approach could be applied more generally to screen for human CTL responses against any candidate target antigen expressed by tumor cells. 相似文献