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61.
The rooting ability of 2 cm long shoots ofPisum sativum L., derived from differentin vitro shoot-tip cultures in two pea cultivars Bohatýr and Kleine Rheinländerin was evaluated. In three mutually independent experiments the full and half-strength Murashige-Skoog medium (containing full or half concentration of macro and microelements), with sucrose concentrations 10–30 g l-1, and with various NAA and IAA combinations, was tested. The variant with half concentration of macro- and microelements, supplemented with 30 g l1 sucrose, and with growth regulators in the quantity of 1 μM proved optimum. 相似文献
62.
63.
Rajendra G. Mehta Leonard J. Schiff Steven J. Moore Ann Marie Buckley Marcia I. Dawson 《In vitro cellular & developmental biology. Plant》1986,22(3):164-168
Summary The mechanism of action of retinoid in reversing keratinization in hamster trachea is yet unknown. The purpose of this study
was to determine if cellular retinoic acid binding protein (CRABP) is present in tracheal epithelium following incubation
in serum-free, vitamin A-deficient culture medium for 10 days, and if the effectiveness of a retinoid in reversing keratinization
in organ culture is correlated with its ability to compete for CRABP sites. The cytosol prepared from tracheal cultures contained
CRABP at a concentration of 2.61 pmoles per mg protein. Of the four retinoids with carboxyl end group selected for the study,
two of the biological active retinoids competed for the CRABP sites. However, no correlation was observed between the biological
activity of the inactive retinoids and their ability to associate with the CRABP sites. These results indicate that even though
the action of retinoid may be mediated by retinoid binding protein, it cannot be used as a sole predicator of retinoid response
in hamster trachea.
This investigation was supported by Contract N01-CP-31012 and U. S. P. H. Grants CA30512 and CA32428, which were awarded by
the Division of Cancer Etiology, National Cancer Institute, DHHS.
Editor's Statement Tracheal organ cultures provide a useful model for the study of epithelial differentiation and carcinogenesis.
Much attention has been given to the action of retinoids in this process. Mehta et al. demonstrate a lack of correlation between
biological activity and specific cytosolic binding of members of this class of compounds, pointing out the need for a more
complete biochemical understanding of the mechanism of action and active forms of retinoids in this and other systems in vivo
and in vitro. David W. Barnes 相似文献
64.
Patricia A. James F. Louise Lavender Gillian M. Lawrence Deryck G. Walker 《Biochemical genetics》1985,23(7-8):525-538
Partially purified preparations of the hepatic glucokinase from C3H/He and C58 inbred mice have been used to explore the molecular basis for the observed twofold difference in activity between the strains. The single codominant gene that appears to regulate activity, the alleles of which are designated Gka and Gkb, respectively, for the two strains, could represent a structural gene change. This now seems unlikely because the mouse enzyme, although showing small differences from rat glucokinase, appeared to be identical in the two strains with respect to thermal stability, electrophoretic mobility in agarose gels, and kinetic properties such as the apparent K
m values for MgATP2– and glucose and the unique cooperative interaction with the latter substrate. The enzymes also reacted identically in a range of immunological tests (double-diffusion, immunoelectrophoresis, immune precipitation and immune inhibition assays) and ELISA immune inhibition assays indicated that the twofold difference in activity was due to a similar difference in antigenically active enzyme. Genetic control over the physiologically significant regulation of enzyme amount is therefore probable.This work has been supported in part by a grant from the British Diabetic Association and a Training Studentship to PAJ from the Medical Research Council (U.K.). 相似文献
65.
Transport of Ca2+ into amoebae of Dictyostelium discoideum was studied using 45Ca and a lanthanum stopping technique. Ca2 uptake was found to be rapid and showed saturation kinetics. No difference was found in Ca2+ uptake between vegetative and aggregation competent cells, the V(max) for unstimulated amoebae being approx. 10 nmol/10(7) cells per min. Ca2+ uptake had the characteristics of passive facilitated diffusion using a saturatable carrier and NaN3 and ouabain were not inhibitory. The chemoattractants cAMP and folate, previously reported to stimulate the uptake of Ca2+ into amoebae, did not stimulate the rate of Ca2+ uptake by this carrier but increased the extent of Ca2+ taken up over the period 10-30 s after chemotactic stimulation. The significance of these findings for the function of Ca2+ in chemotactic signalling is discussed. 相似文献
66.
Addition of a mixture of EGF + insulin to quiescent cell cultures synergistically stimulates the cells to reinitiate DNA synthesis and cell division. We have previously demonstrated that this mixture rapidly increases ATP turnover in quiescent cells. The present work shows that each of the two growth factors, EGF and insulin, when added separately to quiescent cells was able to stimulate the phosphorylation of the organic acid-soluble compounds (Po) pool and ATP turnover. The stimulation of ATP turnover was closely correlated with the increase in phosphorylation of the Po pool which suggests that Po labelling reflects the ATP turnover. In many experiments, the synergy between the two growth factors on the early increase in phosphorylation of the Po pool was clearly shown. Doubling the concentration of EGF (12-24 ng/ml) or insulin (50-100 ng/ml) did not increase early stimulation of phosphorylation of the Po pool, whereas simultaneous addition of the two growth factors induced a greater stimulation than that of each growth factor separately added. The augmentation in Po labelling after addition of EGF or insulin alone was transient. The synergistic effect of the two growth factors was more significant when determined 150 or 300 min after growth-factor addition. In our experimental conditions, each of the two growth factors, EGF and insulin, was able to induce a stimulation of DNA synthesis. However, the best stimulatory effect was observed with the mixture of the two which synergistically increased DNA synthesis determined between 6 and 24 h after growth-factor addition. The comparison between DNA replication and Po labelling suggests a correlation between the increase in DNA replication and in the total ATP synthesized in the first 5 h after cell stimulation by growth factors added separately or in combination. 相似文献
67.
Control of replication of FII plasmids: comparison of the basic replicons and of the copB systems of plasmids R100 and R1 总被引:7,自引:0,他引:7
The copy numbers of the FII plasmids R1 and R100 were determined in four different ways and found to be identical. Deletion of one of the copy number control genes, copB, together with its promoter gives rise to plasmid copy mutants with an increased copy number. The increase was found to be 8- and 3.5-fold for plasmids R1 and R100, respectively. These deletion derivatives were found to be extremely sensitive to the presence of CopB activity from their own parent plasmid but not to that of the other plasmid. Hence, the CopB protein and its target are plasmid-specific and not FII-group-specific. These results are consistent with the high degree of nonhomology between plasmids R1 and R100 in a 250-bp region covering the distal part of the copB gene and the repA promoter region, which contains the target for the CopB protein. 相似文献
68.
Three major forms of monoiodinated VIP (M125I-VIP) were isolated after chloramine-T iodination and HPLC purification. The iodinated tyrosine residue was located in each form of M125I-VIP using arginase C and trypsin digestion for obtaining defined fragments containing only one tyrosine residue. The HPLC isolated iodinated fragments thus obtained were used for HPLC comigration studies with iodinated synthetic C and N terminal VIP fragments and for amino acid analysis. The first two eluting peaks 1 and 2 are (M125I-Tyr10-VIP); peak 1 has an oxidized methionine; peak 3 is a (M125I-Tyr22-VIP) which also has an oxidized methionine. A reduced counterpart of peak 3 named peak 4 was isolated by further HPLC analysis. The ability of the different species of M125I-VIP to stimulate adenosine cyclic 3',5'-phosphate (cAMP) production in transformed colonic cells in culture (HT-29) was compared to that of native VIP. The mean potencies of the M125I-VIP species expressed as a percentage relative to the potency of native VIP were, peak (1): 0.98; (2): 0.84; (3): 1.38; (4): 1.48, in the range of concentrations tested (2-60 pM). The M125I-Tyr22-VIP are significantly more active than native VIP (P less than 0.01). Oxidation of methionine or iodination of tyrosine 10 does not significantly modify the biological activity of VIP. We conclude that iodination of Tyr-22 located in the apolar helical COOH-terminal of VIP increases the effectiveness of VIP interaction with its receptors. Thus the tyrosyl residue and the localized hydrophobic features of VIP are critically involved in the function of this neurotransmitter. 相似文献
69.
Summary The cell-body layer of the lamina ganglionaris of the housefly, Musca domestica, contains the perikarya of five types of monopolar interneuron (L1–L5) along with their enveloping neuroglia (Strausfeld 1971). We confirm previous reports (Trujillo-Cenóz 1965; Boschek 1971) that monopolar cell bodies in the lamina form three structural classes: Class I, Class II, and midget monopolar cells. Class-I cells (L1 and L2) have large (8–15 m) often crescentshaped cell bodies, much perinuclear cytoplasm and deep glial invaginations. Class-II cells (L3 and L4) have smaller perikarya (4–8 m) with little perinuclear cytoplasm and no glial invaginations. The midget monopolar cell (L5) resides at the base of the cell-body layer and has a cubshaped cell body. Though embedded within a reticulum of satellite glia, the L1–L4 monopolar perikarya and their immediately proximal neurites frequently appose each other directly. Typical arthropod (-type) gap junctions are routinely observed at these interfaces. These junctions can span up to 0.8 m with an intercellular space of 2–4 nm. The surrounding nonspecialized interspace is 12–20 nm. Freezefracture replicas of monopolar appositions confirm the presence of -type gap junctions, i.e., circular plaques (0.15–0.7 m diam.) of large (10–15 nm) E-face particles. Gap junctions are present between Class I somata and their proximal neurites, between Class I and Class II somata and proximal neurites, and between Class II somata. Intercartridge coupling may exist between such monopolar somata. The cell body and proximal neurite of L5 were not examined. We also find that Class I and Class II somata are extensively linked to their satellite glia via gap junctions. The gap width and nonjunctional interspace between neuron and glia are the same as those found between neurons. The particular arrangement and morphology of lamina monopolar neurons suggest that coupling or low resistance pathways between functionally distinct neurons and between neuron and glia are probably related to the metabolic requirements of the nuclear layer and may play a role in wide field signal averaging and light adaptation. 相似文献
70.
Ewa Nizankowska Angelita Q. Sheridan Marie H. Maile Carol J. Cross Rafal Nizankowski Krystyna Prochowska Andrew Szczeklik 《Prostaglandins & other lipid mediators》1985,29(3):349-362
We evaluated in a double-blind study the bronchodilatory properties of 2-decarboxy-2-hydroxymethyl prostaglandin E1 (PGE1-carbinol), described recently as a nonirritant bronchodilator in animals. Fifteen asthmatic patients received by inhalation single doses of 1, 10, and 30 μg PGE1-carbinol, 55 μg PGE2, and placebo (10% ethanol in normal saline, which was also used as diluent for the PGs). Such pulmonary function tests as forced expiratory volume in 1 second, forced vital capacity, and maximal expiratory flow were monitored during 2 hours following inhalation of each compound. 10 and 30 μg PGE1-carbinol produced significant but short-acting bronchodilation, similar to that caused by 55 μg PGE2. One-third of the patients reported mild cough and throat irritation during and shortly after inhalation of 30 μg PGE1-carbinol or 55 μg PGE2. Placebo and 1 μg PGE1-carbinol produced minimal side effects, but neither agent caused bronchodilation. In an adjunctive, unblinded trial, the same patients received 400 μg fenoterol. Fenoterol caused greater bronchodilation 15 and 30 minutes after inhalation than did the PGs in the double-blind study. 相似文献