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71.
Summary Clinical dextran with desired molecular weight was produced continuously in the two-stage reactor. Cells ofLeuconostoc meseteroides B512F cultivated in the first reactor were transferred to the second reactor where sucrose and primer were added for clinical dextran production. By using this two-stage reactor, the fraction of desired clinical dextran increased significantly when observed with gel permeation chromatography. 相似文献
72.
To examine whether protein kinase C (PKC) plays a role in mediating growth inhibitory effects of hexamethylene bisacetamide (HMBA) we compared a control H29 colon cancer cell line to a derivative, HT29-PKC7, that overexpresses high levels of PKC beta 1. We found that although HMBA markedly inhibited the growth of the control cells, no inhibition was seen with the HT29-PKC7 cells. On the other hand the tumor promoter 12-0-tetradecanoyl-phorbol-13 acetate inhibited the growth of HT29-PKC7 cells, but no inhibition was seen with the control cells. Maximum inhibition of the growth of both cell lines was obtained by combined treatment with HMBA and TPA. These results may be relevant to the use of HMBA in combination with other agents in the therapy of specific cancers. 相似文献
73.
Y Nakano Y Sugita Y Ishikawa N H Choi T Tobe M Tomita 《Biochimica et biophysica acta》1991,1074(2):326-330
Decay-accelerating factor (DAF) was purified from human pooled urine by conventional techniques. The urine DAF was separated into two peaks, pool I and pool II, by gel chromatography. DAF-U1 was isolated from pool I by hydrophobic chromatography, and DAF-U2 from pool II by anti-DAF IgG column. The specific activities of DAF-U1 and DAF-U2 to decay membrane-phase C5 convertase were about 3% and 70% of membrane form DAF, respectively. However, both urine DAFs revealed a similar activity to each other and slightly higher activity than that of membrane form DAF in decay-accelerating fluid-phase C3 convertase of the alternative pathway. 相似文献
74.
Activation of p34cdc2 protein kinase activity in meiotic and mitotic cell cycles in mouse oocytes and embryos. 总被引:9,自引:0,他引:9
T Choi F Aoki M Mori M Yamashita Y Nagahama K Kohmoto 《Development (Cambridge, England)》1991,113(3):789-795
p34cdc2 protein kinase is a universal regulator of M-phase in eukaryotic cell cycle. To investigate the regulation of meiotic and mitotic cell cycle in mammals, we examined the changes in phosphorylation states of p34cdc2 and its histone H1 kinase activity in mouse oocytes and embryos. We showed that p34cdc2 has three different migrating bands (referred to as upper, middle and lower bands) on SDS-PAGE followed by immunoblotting with anti-PSTAIR antibody, and that the upper and middle bands are phosphorylated forms since these two bands shifted to the lower one by alkaline phosphatase treatment. In meiotic cell cycle, only germinal vesicle (GV) stage oocytes had the three forms. The phosphorylated forms decreased gradually in oocytes up to 2 h after isolation from follicles, and thereafter the phosphorylation states did not change significantly until metaphase II. However, the histone H1 kinase activity oscillated, being activated at the first and second metaphase in meiosis and inactivated at the time of the first polar body extrusion. These results suggest that changes in phosphorylation states of p34cdc2 triggered its activation at the first metaphase, but not inactivation and reactivation at the first and second metaphase, respectively. In mitotic cell cycle, phosphorylated forms appeared at 4 h after insemination, increased greatly just before metaphase, and were dephosphorylated in metaphase. Histone H1 kinase activity was high only at metaphase. This kinase activation is probably triggered by dephosphorylation of p34cdc2. 相似文献
75.
S Sagawa K Miki F Tajima H Tanaka J K Choi L C Keil K Shiraki J E Greenleaf 《Journal of applied physiology》1992,72(1):128-134
The mechanism for reduced voluntary water intake during water immersion was studied in eight men (19-25 yr of age) immersed to the neck while sitting for 3 h at 34.5 degrees C or in air at 28 degrees C when euhydrated (Eu-H2O and Eu-air, respectively) and hypohydrated (Hypo-H2O and Hypo-air) by 3.6% body weight loss. Thirst sensations (degree of thirst, mouth dryness and taste, drinking desirability, and stomach fullness) were similar at the beginning of Hypo-air and Hypo-H2O test periods. Initial drinking of tap water (15 degrees C) was 216 +/- 30 ml/7 min (P less than 0.05) with Hypo-air, decreased to 108 +/- 28 ml/7 min (P less than 0.05) with Hypo-H2O, and was 10-50 ml/10-30 min thereafter. Intake was less than 10 ml/10-30 min in Eu-air, and there was no drinking in Eu-H2O. Within the first 10 min of immersion, compared with Hypo-air findings, the significant reduction in drinking in the Hypo-H2O experiment was associated with unchanged plasma Na+, plasma osmolality, heart rates, and mean arterial pressures; the different responses were increased cardiac output, plasma volume, and atrial natriuretic peptides and decreased plasma renin activity and arginine vasopressin. Thus the extracellular pathway, as opposed to the osmotic pathway, appears to be the major mechanism for immersion-induced suppression of drinking. 相似文献
76.
Evidence for two independent pathways in the stimulation of steroidogenesis by luteinizing hormone involving chloride channels and cyclic AMP 总被引:1,自引:0,他引:1
The possible role of chloride channels in luteinizing hormone (LH) action on steroidogenesis in rat Leydig cells had been investigated. A chloride channel blocker, SITS (4-acetamido-4'-isothiocyanatostilbene-2,2'-disulphonic acid), inhibited LH-stimulated steroidogenesis at low (less than or equal to 1 ng/ml), but not at high (100 ng/ml) LH concentrations. In addition, dibutyryl cyclic AMP- and forskolin-stimulated steroidogenesis was unaffected by SITS. The removal of extracellular chloride potentiated steroidogenesis stimulated by submaximal but not maximal doses of LH. These results suggest that at low levels of LH, steroidogenesis depends on chloride channels whereas with high levels, cyclic AMP is the mediator of LH action. 相似文献
77.
Genes of the Escherichia coli pur regulon are negatively controlled by a repressor-operator interaction. 总被引:14,自引:11,他引:3 下载免费PDF全文
Fusions of lacZ were constructed to genes in each of the loci involved in de novo synthesis of IMP. The expression of each pur-lacZ fusion was determined in isogenic purR and purR+ strains. These measurements indicated 5- to 17-fold coregulation of genes purF, purHD, purC, purMN, purL, and purEK and thus confirm the existence of a pur regulon. Gene purB, which encodes an enzyme involved in synthesis of IMP and in the AMP branch of the pathway, was not regulated by purR. Each locus of the pur regulon contains a 16-base-pair conserved operator sequence that overlaps with the promoter. The purR product, purine repressor, was shown to bind specifically to each operator. Thus, binding of repressor to each operator of pur regulon genes negatively coregulates expression. 相似文献
78.
79.
The transposons Tn501(Hg) and Tn1721(Tc) are related 总被引:6,自引:0,他引:6
80.
Summary Cytochemical methods for the localization of glycoconjugates including concanavalin A-horseradish peroxidase (ConA-HRP) and dialysed iron were used to study the distribution of glycoconjugates in mast cell granules during degranulation. The ConA-HRP method revealed intense staining of discharged mast cell granules. Dialysed iron staining was seen at the granule periphery, with extruded granules exhibiting more intense staining than undischarged granules.Some of the work reported herein was performed in partial fulfillment of the requirements for a Ph.D. degree. 相似文献