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81.
A new single gene-recessive internode length mutant inPisum, lkc, is characterized. The internodes oflkc plants are 30–40% shorter than those of comparableLkc plants, and this is attributable to reductions in both cell length and the number of cells per internode. Dwarfism in the mutant is not due to modified gibberellin (GA) levels, as determined by gas chromatography-selected ion monitoring (GC-SIM) for GA1 and GA20, and bioassay (rice cv. Tan-ginbozu). Furthermore,lkc plants are not as responsive as the wild-type to applied GA1. The diminished stature oflkc plants appears to result from a direct or indirect interference with the transduction of the GA1 signal. 相似文献
82.
C Hertel M H Nunnally S K Wong E A Murphy E M Ross J P Perkins 《The Journal of biological chemistry》1990,265(29):17988-17994
Recombinant turkey erythrocyte beta-adrenergic receptors expressed in murine L cells exhibited characteristic avian subtype selectivity for agonists and antagonists. In 10 of the 11 clones studied, no agonist-induced internalization of receptor was observed, although agonist-induced uncoupling of receptor and adenylyl cyclase occurred rapidly. GTP caused little or no decrease in affinity for beta-adrenergic agonists. Such behavior is commonly observed in avian erythrocytes. In contrast, one clone was susceptible to agonist-induced receptor internalization and down-regulation even though it exhibited characteristic avian beta-adrenergic ligand-binding properties. The affinity of this variant receptor for agonists was also notably reduced by GTP. Electrophoresis of affinity-labeled receptor from this clone indicated an apparent size of about 33 kDa, about 12 kDa less than that of the native or recombinant turkey beta-adrenergic receptor. Genomic DNA from this cell line that encodes the receptor was cloned and partially sequenced. The coding region of the original receptor cDNA was interrupted after codon 412 (out of 483) and was followed by 36 base pairs of novel sequence prior to the first in-frame stop codon. These results suggest that the lack of both hormone-induced internalization and GTP-sensitive, high affinity binding of agonists that is characteristic of the beta-adrenergic receptor in avian erythrocytes is due to intrinsic properties of the receptor. The restoration of these phenomena in a C-terminally truncated mutant receptor suggests the importance of the C-terminal domain in determining these processes. 相似文献
83.
Replication of bacteriophage lambda DNA. Examination of variants containing double origins and observation of a bias in directionality 总被引:1,自引:0,他引:1
Maria Schnös Katherine J. Denniston Frederick R. Blattner Ross B. Inman 《Journal of molecular biology》1982,159(3):441-455
Bacteriophage λ variants have been constructed that possess two λ ori sites. Replicative intermediates resulting from infection with these phages have been investigated. We find that initiation of replication from the ori site on an EcoRI fragment (containing all the DNA sequences from within the red gene to the middle of gene O) cloned in the inverted orientation is predominantly bidirectional but occurs at a decreased frequency. Double initiations were observed at low frequency. However, a second cloned ori fragment (carrying two large deletions and a small insertion) cloned in the normal orientation demonstrated insignificant levels of replication from the cloned site unless the normal ori had already initiated.A bias in directionality of λ replication has been observed. Molecules that replicate unidirectionally propagate to the right more often than to the left. If the cloned ori-containing EcoRI fragment is inserted with reversed polarity, then the bias is towards the left. Bidirectional λ replicative intermediates also appear to show a similar bias but this is superimposed on a large, apparently random, effect that results in asymmetric growing-point propagation. 相似文献
84.
Phytochrome control of maize coleoptile section elongation: the role of cell wall extensibility 总被引:1,自引:0,他引:1 下载免费PDF全文
Maize (Zea mays) coleoptile section cell wall extensibility was found to be stimulated by red light. This stimulation was largely removed by simultaneous or immediately subsequent far-red treatment. Qualitatively similar patterns of response occurred at 0 C and 20 C. Plastic extensibility responded more than elastic extensibility after red light treatment. Red-induced extensibility increases were detectable by 20 minutes after irradiation, and extensibility continued to increase up to at least 1 hour after irradiation. The kinetics of escape from far-red reversibility indicate that the initial events leading to this phenomenon are among the fastest known phytochrome responses. 相似文献
85.
Timothy G. Burland Anne M. Chainey Jennifer Dee Jennifer L. Foxon 《Developmental biology》1981,85(1):26-38
Cultures of amoebae of the mutant strain ATS23 isolated from strain CLd of Physarum polycephalum contain multinucleate cells and cells with increased nuclear DNA content. Plasmodia derived from ATS23 clones show abnormal morphology and defective sporulation. All abnormalities are enhanced by high incubation temperature (31 °C). Genetic analysis suggested that all the abnormalities were caused by a single mutation, denoted hts-23. The kinetics of plasmodium formation were followed in cultures of apogamic amoebae carrying hts-23 and hts+ (wild type) respectively. Results indicated that, relative to wild type, hts-23 did not increase the rate of plasmodium formation. There was evidence that, in both mutant and wild-type strains, commitment to plasmodium development occurred in uninucleate cells. Analysis of cell pedigrees by time-lapse cinematography indicated that the primary abnormal event in cultures of hts-23 amoebae was failure of cytokinesis; an apparently complete cleavage furrow was formed but cell separation failed, resulting in a binucleate cell. This event occurred randomly in pedigrees in which the majority of divisions were completed normally; its frequency increased during incubation at 31 °C. All other abnormalities in hts-23 amoebal cultures could be attributed to this primary event, assuming that DNA synthesis continued in the absence of cytokinesis and that the binucleate cells underwent the amoebal type of “open” mitosis, allowing the possibility of spindle fusion. This implies that the acquisition of “closed” mitosis is an essential early step in plasmodium development. 相似文献
86.
This paper describes a mathematical model for the enzymatic hydrolysis and fermentation of cellulose by Trichoderma reesei. The principal features of the model are the assumption of two forms of cellulose (crystalline and amorphous), two sugars (cellobiose and glucose), and two enzymes (cellulase and β-glucosidase). An inducer–repressor–messenger RNA mechanism is used to predict enzyme formation, and pH effects are included. The model consists of 12 ordinary differential equations for 12 state variables and contains 38 parameters. The parameters were estimated from four sets of experimental data by optimization. The results appear satisfactory, and the computer programs permit simulation of a variety of system changes. 相似文献
87.
Immunity was successfully transferred by ‘Transfer Factor’ prepared from leucocytes of two adult Scottish Blackface donor rams infected with O. circumcincta and T. colubriformis to 4-month-old susceptible Fin X Dorset lambs. The immunity was expressed by a significantly reduced faecal egg count and worm burden compared to challenged, untreated controls. The immunity was comparable to that produced in another group of lambs given an initial infection prior to challenge with both parasites. 相似文献
88.
89.
Ross H. Hall 《In vitro cellular & developmental biology. Plant》1976,12(3):216-224
Summary Cells possess extraordinary powers to organize their molecular processes not only to maintain a cell in a given steady state
but also to recognize that state during differentiation. Regulation of these organizational forces appears to be under the
control of chemical factors, and a hormonal concept of regulation has evolved. Hormones have been considered to act by reacting
with a specific target site. This may be part of their mode of action, but I would like to suggest that a hormone enters and
becomes part of a total molecular resonance system. In so doing, the entire molecular system of the cell is modified.
Of the known plant hormones, the cytokinins, because of their role in experimentally induced cell division and differentiation,
serve as a probe of hormonal involvement in differentiation. Cultured somatic cells of tobacco plants can be induced to undergo
differentiation by addition of cytokinin and auxin to the medium. Studies of the cytokinin hormones show a series of diverse
molecular involvements. The archetype cytokinin, N6-(Δ2-isopentenyl) adenosine (i6Ado), occurs in some molecular species of tRNA where it plays a vital role in the codon-anticodon interaction of tRNA and
m-RNA. i6Ado under-goes extensive metabolism in the tobacco tissue. It is either degraded to adenosine or converted to derivatives
that possess biological activity. It is perhaps, therefore, more correct to consider the hormone function as being derived
from this total metabolic web.
The normal somatic cells of tobacco cultures spontaneously change occasionally into an autonomous form that requires no external
growth factors. This line of cells synthesizes i6Ado. The metabolic web of the hormone-dependent strain can be perturbed by added auxin but such is not the case in the autonomous
strain. These data provide some insight into the altered state of cytokinin activity in which a cell line changes into an
autonomous form. Curiously, in become independent of the requirement for exogenous cytokinin, the autonomous tissue becomes
sensitive to added cytokinin. i6Ado also inhibits the growth of lines of mammalian cancer cells grown in culture.
Presented in the formal symposium on Information Transfer in Eukaryotic Cells, at the 26th Annual Meeting of the Tissue Culture
Association, Montreal, Quebec, June 2–5, 1975. 相似文献
90.
The arterio--alveolar nitrogen difference (aADN2) has been associated in 27 normal adult subjects aged 20--60 years. As it may be assumed that venous and arterial PN2 are identical, we have used a sample of venous blood. There is a significant positive correlation between aADN2 and age. As the increase of aADN2 with age resembles that found in the literature for AaDO2, we concluded that the latter may be explained by increasing VA/Qc inequality within the lung. 相似文献