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131.
Mitogen- and isoproterenol-induced changes of [Ca2+]i in T cells attached to a glass substrate were examined. Murine (C57BL/6) splenic T cells were attached to coverslips or 35-mm dishes (MatTek) precoated with Cell Tak® (3.5 µg/cm2). The cells were then loaded with fluorescent dye (2 µg/ml of fura2-AM or fluo3-AM) and changes in [Ca2+]i in a population of cells (using a spectrofluorometer) or in single cells (using a confocal microscope) were measured during continuous superfusion. Population measurements of [Ca2+]i demonstrated that concanavalin A (Con A, 2 or 5 µg/ml) caused an increase in [Ca2+]i that rose to a peak and then declined to a steady state. The concentration-response relationship (0.05–5 µg/ml) had an EC50 of 0.3 µg/ml. Isoproterenol decreased the Con A-induced elevation of steady state [Ca2+]i. In single cell studies, the increase in [Ca2+]i in response to Con A typically occurred in about 50% of the cells in a microscope field, and the delay before activation varied among cells. Taken together, these data demonstrate that Cell Tak® can be used to attach T cells to glass coverslips and will be useful for the study of signaling mechanisms in T cells.  相似文献   
132.
BACKGROUND: We investigated the human immunodeficiency virus (HIV) proviral DNA sequence and copy number in alveolar macrophages (AM) and peripheral blood monocytes (PBM) from 10 HIV-positive patients without any active concurrent pulmonary disease to understand the nature of HIV-1 infection in vivo in the lung microenvironment. MATERIALS AND METHODS: The 10 seropositive patients without active pulmonary disease were selected based on chest roentegenography and pathological/cytological test of bronchoalveolar (BAL) fluid. In order to determine accurate proviral copy numbers, AM and PBM were isolated to 99 and 94% purity, respectively, and quantitative polymerase chain reaction (PCR), with a sensitivity to detect three copies of HIV proviral DNA per 10(5) cells, was applied. For analysis of genetic variation in HIV-1, PCR-amplified HIV-1 DNA from AM and PBM of five patients were subcloned and 2-12 clones from each sample underwent DNA sequence analysis of HIV-1 gp120 V3-V5. Heteroduplex mobility assays were performed to confirm the results of the sequence analysis. RESULTS: The proviral copy number in AM or PBM were less than 20 copies/10(5) cells in all patients, and five patients had less than the detection limit. There was no significant difference in HIV copy number between AM and PBM. No correlation was found between PBM/AM HIV copy number and CD4+ lymphocyte count in the peripheral blood. Sequence analysis revealed that the mean intrapatient genetic similarity in AM was 97.5 +/- 0.18% (n = 107), which was significantly higher than that in PBM (96.2 +/- 0.26% (n = 94), p < 0.001), suggesting that variability of HIV-1 DNA in AM was relatively limited. Divergence occurred when AM derived HIV-1 sequence was compared with PBM derived sequence from the same patient (95.8 +/- 0.17% (n = 223) p < 0.001). Phylogenetic analysis of DNA sequence demonstrated complete separation of HIV lineages from lung and blood in four of five patients. CONCLUSIONS: The results suggest the HIV-1 infection in AM is restricted in vivo with low viral burden and homogenous genotype. We propose that the pulmonary microenvironment may limit the extent of HIV-1 infection.  相似文献   
133.
BJ38 is a galactose/lactose-specific lectin (M r 38000) found at one pole ofBradyrhizobium japonicum. It has been implicated in mediating the adhesion of the bacteria to soybean roots, leading to the establishment of a nitrogen-fixing symbiosis. When the ligand lactose is added to cultures of the bacteria for at least 1 h prior to harvesting the cells for BJ38 isolation, the yield of the protein was found to be elevated in a dose-dependent fashion. Half maximal stimulation was observed at 50 µm; the effect was saturated at 1mm, where a 10-fold higher yield of BJ38 was obtained. Saccharides with a lower affinity for BJ38 than lactose yielded a correspondingly smaller induction effect when compared at a concentration of 1mm. The higher level of BJ38 induced by lactose is also manifested by an elevated amount of BJ38 detectable at the cell surface and by a higher number ofB. japonicum cells adsorbed onto soybean cells. Surprisingly, the induction of BJ38 expression seen with lactose was also observed with certain, but not all, flavonoids that induce thenod genes of the bacteria; genistein mimicked the induction observed with lactose, whereas luteolin failed to stimulate BJ38 production.  相似文献   
134.
A new species of poecilostomatoid copepod, Ostrincola humesi (Myicolidae), is described, based on specimens collected from the mantle cavity of the rock oyster, Saccostrea cucullata (Born), cultured in the Gulf of Thailand. A close comparison was made between the new species and Ostrincola koe Tanaka with which the new species was previously confused. A key to the nine species of Ostrincola is provided.  相似文献   
135.
136.
Summary Plant hairy root cultures of Lithospermum erythrorhizon were carried out to produce shikonin derivatives by employing in situ extraction with n-hexadecane in a shake flask and a bubble column bioreactor. Over 95 % shikonin produced was recovered in the n-hexadecane layer. In flask cultures the maximum concentration of shikonin with n-hexadecane extraction was 3 times higher than that obtained without extraction. In the two phase bubble column reactor, 572.6 mg/L of shikonin and 15.6 g/L of dry cell mass were obtained after 54 days. Shikonin was produced at a constant level of 10.6 mg/L day during this period.  相似文献   
137.
We have successfully transferred and expressed a reporter gene driven by an -amylase promoter in a japonica type of rice (Oryza sativa L. cv. Tainung 62) using the Agrobacterium-mediated gene transfer system. Immature rice embryos (10–12 days after anthesis) were infected with an Agrobacterium strain carrying a plasmid containing chimeric genes of -glucuronidase (uidA) and neomycin phosphotransferase (nptII). Co-incubation of potato suspension culture (PSC) with the Agrobacterium inoculum significantly improved the transformation efficiency of rice. The uidA and nptII genes, which are under the control of promoters of a rice -amylase gene (Amy8) and Agrobacterium nopaline synthase gene (nos), respectively, were both expressed in G418-resistant calli and transgenic plants. Integration of foreign genes into the genomes of transgenic plants was confirmed by Southern blot analysis. Histochemical localization of GUS activity in one transgenic plant (R0) revealed that the rice -amylase promoter functions in all cell types of the mature leaves, stems, sheaths and roots, but not in the very young leaves. This transgenic plant grew more slowly and produced less seeds than the wild-type plant, but its R1 and R2 progenies grew normally and produced as much seeds as the wild-type plant. Inheritance of foreign genes to the progenies was also confirmed by Southern blot analysis. These data demonstrate successful gene transfer and sexual inheritance of the chimeric genes.  相似文献   
138.
Glucocorticoids regulate the expression of many liver-specific genes via glucocorticoid receptors. The presence of glucocorticoid receptors in liver has been reported in many mammalian species but not in nude mice. In the present study, we demonstrate the presence of specific glucocorticoid receptors in nude mouse liver. The binding of ligands to these receptors could be completely inhibited by RU486, and partially blocked by hydrocortisone and progesterone, whereas estrogen and testosterone had no effect. Hydrocortisone down-regulated the level of glucocorticoid receptors in livers of nude mice and correspondingly enhanced the activities of tyrosine aminotransferase and -glutamyltransferase. Our results indicate that glucocorticoid receptors in nude mouse liver are specific, fully functional, and present at levels 28.5-fold higher than in the liver of normal inbred mice. We suggest that the nude mouse is a valuable model for studies of hepatic glucocorticoid action and may provide a clue to a putative hepatic-thymic interaction.  相似文献   
139.
The contributions of the first and second variable regions of the human immunodeficiency virus type 1 gp120 glycoprotein to envelope glycoprotein structure, function, and recognition by a neutralizing antibody were studied. Several mutants with substitutions in the V2 loop demonstrated complete dissociation of the gp120 and gp41 glycoproteins, suggesting that inappropriate changes in V2 conformation can affect subunit assembly. Some glycoproteins with changes in V1 or V2 were efficiently expressed on the cell surface and were able to bind CD4 but were deficient in syncytium formation and/or virus entry. Recognition of gp120 by the neutralizing monoclonal antibody G3-4 was affected by particular substitutions affecting residues 176 to 184 in the V2 loop. These results suggest that the V1/V2 variable regions of the human immunodeficiency virus type 1 gp120 glycoprotein play a role in postreceptor binding events in the membrane fusion process and can act as a target for neutralizing antibodies.  相似文献   
140.
Interaction with the CD4 receptor enhances the exposure on the human immunodeficiency type 1 gp120 exterior envelope glycoprotein of conserved, conformation-dependent epitopes recognized by the 17b and 48d neutralizing monoclonal antibodies. The 17b and 48d antibodies compete with anti-CD4 binding antibodies such as 15e or 21h, which recognize discontinuous gp120 sequences near the CD4 binding region. To characterize the 17b and 48d epitopes, a panel of human immunodeficiency virus type 1 gp120 mutants was tested for recognition by these antibodies in the absence or presence of soluble CD4. Single amino acid changes in five discontinuous, conserved, and generally hydrophobic regions of the gp120 glycoprotein resulted in decreased recognition and neutralization by the 17b and 48d antibodies. Some of these regions overlap those previously shown to be important for binding of the 15e and 21h antibodies or for CD4 binding. These results suggest that discontinuous, conserved epitopes proximal to the binding sites for both CD4 and anti-CD4 binding antibodies become better exposed upon CD4 binding and can serve as targets for neutralizing antibodies.  相似文献   
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