Characterization of the inhibitory effect of glucocorticoids on the DNA replication of adult rat hepatocytes growing at various cell densities

Dexamethasone inhibited the basal and EGF-stimulated DNA synthesis of adult rat hepatocytes in primary culture. The inhibition was glucocorticoid-specific: It was shown by dexamethasone and hydrocortisone, but not by progesterone, testosterone, or estradiol; and was counteracted by the glucocorticoid antagonist RU-38486 in a concentration-dependent manner. Dexamethasone acted by decreasing the rate of entry into S-phase (kG1/S), while cell cycle parameters were unaffected. The steroid was able to decrease the kG1/S severalfold even when added more than 20 hr after EGF, half-maximal effect occurring 11 hr after the addition of dexamethasone. Densely populated areas were much more sensitive to the inhibition by dexamethasone than sparsely populated areas within the same culture dish: A moderate (10 nM) concentration of dexamethasone nearly abolished the DNA synthesis in densely populated areas of hepatocyte cultures with only marginal effect on sparsely populated cells.     

Effects of gravel size and peat material concentrations on embryo survival and alevin emergence of brown trout,Salmo trutta L.

Embryo survival and alevin emergence pattern of brown trout were studied in simulated redds with different homogeneous gravel sizes and different concentrations of peat material. Optimal survival (95%) occurred in 18 mm gravel and survival decreased with decreasing gravel size. High concentrations (40%) of peat material resulted in low survival (65%). The proportion of premature emerging alevins increased in finer gravels and at high peat concentrations. Premature alevins had a large yolk sac and are probably very vulnerable to predators.     

Effect of cholera toxin on rat intestinal permeability assessed with fluorescent dextran 3000

Abstract The effect of culture filtrate containing cholera toxin (CT) on rat intestinal permeability was studied using fluorescein isothiocyanate-labelled dextran 3000 (FITC-D3, M _r, 3000) as probe molecule. CT was given either perorally, via a gastric tube 90 min before, or locally in conjunction with the permeability measurement in the distal ileum. Compaired to the control animals, either mode of administration resulted in increased permeation of FITC-D3 from the intestine to portal blood. The effect of the local treatment was apparent after 5–10 min and prevailed during the 60-min measurement period. The results indicate that CT not only affects net water transport at the intestinal mucosa but also the passage of larger molecules across the intestinal wall.     

Observations on the cellular localization of dopamine in the caudate nucleus of the rat

Summary The cellular localization of dopamine in the caudate nucleus of the rat hat been studied with the highly sensitive and specific fluorescence method of Falck and Hillarp, and by electron microscopy. The histochemical studies provided strong support for the view that the dopamine is concentrated within very fine nerve fibres which have abundant varicosities with an intense fluorescence. The electron microscopical studies revealed the presence of a tightly packed plexus built up i.a. of abundant synaptic nerve terminals, many of which had a diameter below 0.4 . The terminals made synaptic contact mainly with processes that seemed to belong to an extensive dendrite net.The investigation was supported by research grants from the United States Public Health Service (02854-04), The Swedish Medical Research Council and the Knut and Alice Wallenberg Foundation.     

Expression of two heterologous promoters, Agrobacterium rhizogenes rolC and cauliflower mosaic virus 35S, in the stem of transgenic hybrid aspen plants during the annual cycle of growth and dormancy

We monitored, for the first time, the activity of two model heterologous promoters, the Agrobacterium rhizogenes rolC and the cauliflower mosaic virus (CaMV) 35S, throughout the annual cycle of growth and dormancy in a perennial species, hybrid aspen. Each promoter was fused to the uidA -glucuronidase (GUS) reporter gene and the constructs were introduced into the hybrid aspen genome by Agrobacterium-mediated transformation. Both wildtype and transgenic plants were cultivated under different regimes of photoperiod and temperature to induce passage through one growth-dormancy-reactivation cycle, and at intervals GUS staining was assessed in stem sections. In rolC::uidA transformants, GUS activity in rapidly growing current-year shoots was not only tissue-specific, being localized to the phloem, but also cell-specific at the shoot base, where it was present only in the companion cells. However, during the onset of dormancy induced by short photoperiod, GUS activity shifted laterally from the phloem to include the cortex and pith. After subsequent exposure to chilling temperatures to induce the transition between the dormancy stages of rest and quiescence, GUS activity almost disappeared from all stem tissues, but regained its original phloem specificity and intensity after the shoots were reactivated by exposing them to long photoperiod and high temperatures. In contrast, GUS activity in the stem of 35S::uidA transformants was strong in all tissues except for the vascular cambium and xylem, and did not vary in intensity during the growth-dormancy-reactivation cycle. The lateral shift and increased intensity of GUS activity in the stem of rolC::uidA transformants during dormancy induction was shown to be associated with the accumulation of starch, and to be mimicked by incubating stem sections in sucrose, as well as glucose and fructose, but not sorbitol, prior to the GUS assay. Our results demonstrate that the activities of the rolC and 35S promoters varied in very different, unpredictable ways during the annual cycle of growth and dormancy in a perennial species, and indicate that the spatial and temporal variation in rolC promoter activity that we observed in the stem of transgenic hybrid aspen plants is attributable to cellular and seasonal changes in sucrose content.     

Assignment of the dipeptidylpeptidase IV (DPP4) gene to pig Chromosome 15q21

A porcine 2-kb partial dipeptidylpeptidase IV (DPP4, EC 3.4.14.5) cDNA clone and a porcine 16-kb genomic fragment containing parts of the DPP4 gene were isolated, characterized, and used as probes to map the DPP4 gene to pig Chr (Chr) 15q21 by fluorescence in situ hybridization. A two-allele RFLP was revealed for the DPP4 gene. This polymorphism was utilized in a linkage test against the erythrocyte antigen G (EAG), previously assigned to Chr 15, and the microsatellite S0088, which is linked to EAG. The linkage analyses revealed significant evidence for linkage confirming the assignment of DPP4 to Chr 15.     

Crystallization and X-ray analysis of a single fab binding domain from protein L of Peptostreptococcus magnus

Protein L is a multi domain cell wall constituent of certain strains of Peptostreptococcus magnus which binds to the variable domain of immunoglobulin κ-light chains. A single immunoglobulin-binding domain of M_r = 9000 from this protein has been isolated and crystallized. The crystals are of space group P4₂2₁2, with cell dimensions a = b = 66.9 Å, c = 68.3 Å, and diffract to at least 2.2 Å resolution. The asymmetric unit of the crystal contains two molecules of the protein L domain, related by a noncrystallographic 2-fold axis, as revealed by a self-rotation function calculated with native diffraction data. © 1995 Wiley-Liss, Inc.     

Purification of thymidine kinase by affinity chromatography with an enzyme inhibitor as the ligand

An affinity column for the purification of thymidine kinase is described. The ligand in this column is a glycoprotein isolated from rat kidney. This glycoprotein inhibits phosphorylation of thymidine in cultured cells and in a cell-free assay system. With an affinity column containing the glycoprotein as a ligand, a 24-fold purification of thymidine kinase from an ammonium sulfate fraction of a crude tissue extract can be obtained. Thymidine kinase eluted from the affinity column migrates as one major band on polyacrylamide and as one diffuse major band on sodium dodecyl sulfate-polyacrylamide. The affinity column, with thymidine kinase bound to the inhibitor, can also be used as an assay system. When the glycoprotein is covalently attached to Sepharose, it retains its binding capacity for thymidine kinase but has apparently lost its ability to inhibit the enzyme. Thymidine kinase eluted from the affinity column is again sensitive to the glycoprotein. It seems to be a carbohydrate moiety of the glycoprotein that is responsible for the inhibition.