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61.
P Q Barrett C M Isales W B Bollag R T McCarthy 《Canadian journal of physiology and pharmacology》1991,69(10):1553-1560
In the bovine adrenal glomerulosa cell, calcium influx through voltage-dependent calcium channels is critical to maintaining an aldosterone secretory response. In patch clamp, atrial natriuretic peptide (ANP) inhibits T-type calcium channel current yet stimulates L-type calcium channel current. In the present study the channel effects of ANP observed in the patch-clamp configuration were extended and related to populations of cells. We observed the following. (i) The effect of ANP on T-channel current resulted in the reduction in the open state probability. ANP decreased the mean open state duration from 14.2 to 1.8 ms/sweep. (ii) In the weakly depolarized cell stimulated by 8 mM K+, ANP reduced the level of aequorin luminescence (a measure of cytosolic calcium) and completely inhibited the stimulated rate of aldosterone secretion, returning it to prestimulation values. These effects are consistent with a decrease in net calcium channel influx and the reported inhibition of T-channel current. In contrast, the calcium channel blocker, nitrendipine, which at low dose selectively blocks L-type calcium channel flux, only slightly reduced luminescence, and partially inhibited the sustained secretory response. (iii) In the strongly depolarized cell, stimulated by 60 mM K+, ANP increased the level of aequorin luminescence consistent with an increase in net calcium channel influx and the reported stimulation of L-channel current. These results indicate that under physiological conditions the inhibition of T-type calcium channels may be involved in the inhibition of the aldosterone secretion induced by ANP. 相似文献
62.
Divergent conclusions exist as to whether inactive renin is present in nephrectomized rat plasma. A major factor contributing to this conflict may be related to significant changes in the "plasma blank" when trypsin-treated plasma is subjected to angiotensin I (AI) radioimmunoassay (RIA). In normal, but not nephrectomized rat plasma, AI-like substances are present in direct proportion to active renin. These substances are destroyed by trypsin. However, trypsin generates additional AI-like material, in both normal and nephrectomized rat plasma. This material, which is present in proportion to the renin substrate concentration, does not appear to be tetradecapeptide (TDP). In normal plasma, however, exogenous TDP is converted to AI in proportion to the active renin concentration and AI generation from TDP is increased by activation of inactive renin. However, in nephrectomized rat plasma, no AI generation from TDP was evident either before or after trypsin treatment. The coincident tryptic generation of a substance that quenches the levels of AI detected by RIA, combined with significant changes in the levels of endogenous and trypsin generated AI-like substances, may have significant bearing on the measured levels of inactive renin. 相似文献
63.
Amino acid compositions of the eggs of five lepidopteran hosts for Trichogramma minutum were compared with each other and with a non-host species, Rhodnius prolixus, in which T. minutum oviposits but does not develop. Host eggs are quite homogeneous, particularly when compared according to groupings of potentially interconvertible amino acids. Combined mole percent values for glycine, serine and alanine were higher in hosts (27.5–29.2 mole%) than in R. prolixus eggs (21.5 mole%), in bovine serum albumin (14.9%), which has been used as a protein source in artificial diets for T. minutum, or in many of the mixtures used in published diets for this species. Since these three amino acids make up 26.3 mole% of the adult amino acid content of T. minutum, their deficiency in diets could require metabolic compensation detrimental to development.Adult T. minutum arising from eggs of Manduca sexta, Choristoneura fumiferana, and Sitotroga cerealella are similar in amino acid composition to each other and, in general, to their hosts. Variability appears greater in hosts than in adult wasp composition, suggesting some interconversion of host amino acids to accommodate inflexible nutritional requirements of T. minutum.In the three host species tested, free amino acids constituted 15.8–19.3% by weight of the amino acid in egg contents. In M. sexta eggs, glycine, serine and alanine together make up 28.4% by weight of the total free amino acid, a much higher proportion than in many published diets. The four free amino acids (isoleucine, leucine, phenylalanine and histidine) reported to be oviposition stimulants in experiments on encapsulated diets are present in sufficient concentrations to induce oviposition in the host species tested and in R. prolixus.
S. cerealella egg contents having approximately 1.8 g amino acid, yield one or rarely two adult T. minutum (1g amino acid/insect). In contrast, M. sexta eggs with 94 g amino acid each yield an average of 10–12 adults (8.2g amino acid/insect). This suggests that small hosts are allocated few eggs which can only develop into small adults because of nutrient supply (parasitoid size in metabolically restricted), whereas much larger hosts are allocated proportionately fewer eggs than the former resulting in larger, and presumably more viable and fecund, adults (parasitoid size is established behaviourally). 相似文献
64.
Interaction of leukocyte integrins with ligand is necessary but not sufficient for function 总被引:9,自引:0,他引:9 下载免费PDF全文
The leukocyte integrins (CD11/CD18 or beta 2-type integrins) are expressed exclusively on leukocytes and participate in many adhesion- dependent functions (Arnaout, M.A. 1990. Blood. 75:1037-1050; Springer, T. A. 1990. Nature. (Lond.) 346:425-434; Dustin, M. L., and T. S. Springer. 1991. Annu. Rev. Immunol. 9:27-66). The avidity of leukocyte integrin binding to their ligands or counter-receptors is dependent upon response to intracellular signals (Wright, S. D., and B. C. Meyer. 1986. J. Immunol. 136:1759-1764; Dustin, M. A., and T. S. Springer. 1989. Nature (Lond.). 341:619-624). We have investigated the effects of a novel mAb (mAb 24) which defines a leukocyte integrin alpha subunit epitope that is Mg(2+)-dependent and may be used as a "reporter" of the activation state of these receptors (Dransfield, I., and N. Hogg. 1989. EMBO (Eur. Mol. Biol. Organ) J. 8:3759-3765; Dransfield, I., A.-M. Buckle, and N. Hogg. 1990. Immunol. Rev. 114:29-44; Dransfield, I., C. Cabanas, A. Craig, and N. Hogg. 1992. J. Cell Biol.) Data is presented to show that this mAb inhibits monocyte-dependent, antigen-specific T cell proliferation and IL-2-activated natural killer cell assays which are both dependent on lymphocyte function-associated antigen-1 (LFA-1), and complement receptor type 3 (CR3)-mediated neutrophil chemotaxis to f-Met-Leu-Phe. This inhibitory effect is not caused by the prevention of receptor/ligand binding because LFA-1/ICAM-1, LFA-1/ICAM-2,3 and CR3/iC3b interactions are, under activating conditions, promoted rather than blocked by mAb 24. As it does not interfere with mitogen- stimulated T cell proliferation, it is unlikely that mAb 24 transduces a "negative" or antiproliferative signal to the T cells to which it is bound. Using a model system of transient activation of LFA-1, we have found that mAb 24 prevents "deadhesion" of receptor/ligand pairs, possibly locking leukocyte integrins in an "active" conformation. It is speculated that inhibition of leukocyte integrin function by this mAb reflects the necessity for dynamic leukocyte integrin/ligand interactions. 相似文献
65.
Identification of envelope protein epitopes that are important in the attenuation process of wild-type yellow fever virus. 下载免费PDF全文
B K Sil L M Dunster T N Ledger M R Wills P D Minor A D Barrett 《Journal of virology》1992,66(7):4265-4270
Monoclonal antibodies (MAbs) have been prepared against vaccine and wild-type strains of yellow fever (YF) virus, and envelope protein epitopes specific for vaccine (MAbs H5 and H6) and wild-type (MAbs S17, S18, S24, and S56) strains of YF virus have been identified. Wild-type YF virus FVV, Dakar 1279, and B4.1 were each given six passages in HeLa cells. FVV and B4.1 were attenuated for newborn mice following passage in HeLa cells, whereas Dakar 1279 was not. Examination of the envelope proteins of the viruses with 87 MAbs showed that attenuated viruses gained only the vaccine epitope recognized by MAb H5 and lost wild-type epitopes recognized by MAbs S17, S18, and S24 whereas the nonattenuated Dakar 1279 HeLa p6 virus did not gain the vaccine epitope, retained the wild-type epitopes, and showed no other physical epitope alterations. MAb neutralization-resistant (MAbr) escape variants generated by using wild-type-specific MAbs S18 and S24 were found to lose the epitopes recognized by MAbs S18 and S24 and to acquire the epitope recognized by vaccine-specific MAb H5. In addition, the MAbr variants became attenuated for mice. Thus, the data presented in this paper indicate that acquisition of vaccine epitopes and loss of wild-type epitopes on the envelope protein are directly involved in the attenuation process of YF virus and suggest that the envelope protein is one of the genes encoding determinants of YF virus pathogenicity. 相似文献
66.
We have examined a serum-deprived culture system in order to verify that it is suitable for the study of burst forming unit erythroid (BFU-E) progenitor cells from premature neonates. Optimum growth of BFU-E from premature neonates was observed with each media constituent using the same concentration as that previously described for adult subjects. Growth of immature BFU-E from premature neonates were highly dependant upon a source of Burst Promoting Activity and mature BFU-E derived colonies emerged at day 12 compared to day 14 in adults. Our preliminary results with the validated medium suggest that premature infants have increased peripheral blood concentrations of BFU-E compared to healthy adult controls.Abbreviations Ad
Adherent cells
- BPA
Burst promoting activity
- BFU-E
Burst forming unit erythroid
- Epo
Erythropoietin
- IL3
Interleukin-3
- LDC
Low density (<1.077 g ml1) peripheral blood mononuclear cells 相似文献
67.
68.
Jane Barrett 《BMJ (Clinical research ed.)》1991,302(6791):1535-1536
69.
Cloning and sequencing of the V regions of the anti-DNA monoclonal antibodies (mAbs), H438 and H130, indicate that H438 is encoded by a J558 VH gene, a single D region nucleotide, and unmutated JH1, V kappa-1C and J kappa 1 genes, and the H130 L chain is encoded by a V kappa-21 subgroup gene J kappa 1 gene. Identification of VH438, which shared VH hybridization pattern with 6% of a panel of 352 MRL/lpr hybridomas, suggests that the frequency of J558 use among spontaneously activated B cells in MRL/lpr mice is greater than previously reported. The VHH438 J558 family gene is identical to VHPAR, which encodes the independently derived MRL/lpr autoantibody, MRP-2, and is highly homologous to the previously reported VHH130, which is identical to a BALB/c germ-line VH gene. Comparison of consensus sequences of homologous autoantibodies and previously reported restriction mapping suggest that a minimum of three highly related J558 germ-line genes encode lupus autoantibodies. 相似文献
70.
Charles D. Hébert Sumiyo Endo Kenneth S. Korach Jeff Boyd J. Carl Barrett John A. Mclachlan Retha R. Newbold 《In vitro cellular & developmental biology. Animal》1992,28(5):327-336
Neonatal treatment with estrogens is associated with development of uterine adenocarcinomas in CD-1 mice. Treatment with the
synthetic estrogen diethylstilbestrol (DES) on Days 1 to 5 after birth results in 90% incidence of these hormonedependent
lesions in 18-mo.-old mice. Three cell lines were established from these DES-associated tumors. Each of these cell lines exhibited
morphologic and ultrastructural characteristics of transformed epithelial cells, including an increased nuclear:ytoplasmic
ratio, enlarged and irregular nuclei with multiple nucleoli and areas of chromatin condensation, positive staining for cytokeratin,
desmosomes, and microvilli. After subcutaneous injection into nude mice, all three cell lines formed solid tumors within 4
wk. Although the primary uterine tumors and tumor transplants in nude mice had been shown to be estrogen-dependent and estrogen-receptor
positive, neither the monolayer growth nor the tumorigenicity of any of the three cell lines in this study was enhanced by
or dependent on estrogen. Estrogen receptor levels were low in early and intermediate passage cells. Allele-specific oligonucleotide
hybridization analysis of PCR-amplified cell line DNA revealed no point mutations in the 12th, 13th, or 61st codons of the
K-ras or H-ras protooncogenes. Southern analysis revealed no changes in genomic organization of the putative tumor suppressor
gene DCC, but demonstrated a three-to four-fold amplification of the c-myc gene in one cell line. Expression of c-myc RNA
was concomitantly increased in the same cell line. These three transformed cell lines represent the end point in the process
of hormone-associated tumorigenesis and as such should prove useful in investigating the molecular changes and the mechanisms
involved in hormonal carcinogenesis. 相似文献