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121.
The synthesis, high affinity uptake and degradation of GABA were compared with GABA content measured simultaneously in the nigras of unoperated, hemitransected and kainate-treated rats. In intact animals nigral GABA concentration was linearly related to glutamate decarboxylase activity, but not to GABA aminotransferase (GABA-T) or GABA uptake. One week after hemitransection all three parameters showed a linear reduction with GABA content, suggesting striatonigral GABA neurones may account for as much as 90% of the GABA and GAD, 31% of the GABA-T and 58% of GABA uptake sites in whole nigra. Nigral kainate treatment unexpectedly reduced all four parameters in parallel by as much as 50%, consistent with the formation of an unselective lesion. 相似文献
122.
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
123.
124.
125.
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
126.
127.
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
128.
129.
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
130.
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