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21.
22.
V. L. Sevala J. E. Steele 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1991,161(4):349-355
Glycolytic intermediates and related metabolites were measured in the fat body of the American cockroach (Periplaneta americana) to locate the rate-limiting reactions that regulate glycolysis during the action of the corpus cardiacum (CC) in vitro.
相似文献
1. | The concentrations of glucose 1-phosphate, fructose 6-phosphate, and fructose 1,6-bisphosphate were approximately doubled after 30 min treatment with CC extract, whereas that of glucose 6-phosphate increased more than four-fold. Slightly lower increases occurred after 10 and 60 min treatment. |
2. | Triose phosphates, 2-phosphoglyceric acid, phosphoenolpyruvate and pyruvate were unaffected by CC extract. |
3. | Glycerol 3-phosphate, which is 20\2-200 times more concentrated than any of the other measured metabolites in the unstimulated tissue, is increased more than two-fold by CC extract. |
4. | NAD, NADP, and ATP were not significantly affected by CC extract. ADP was increased significantly by the gland extract. |
23.
Satoshi Takeo Reiko Tanonaka Kouichi Tanonaka Keiko Miyake Hideto Hisayama Norifumi Ueda Keiko Kawakami Hiromi Tsumura Shuichi Katsushika Yuzo Taniguchi 《Molecular and cellular biochemistry》1991,107(2):169-183
The present study was designed to induce massive accumulation of calcium in the myocardium and to evaluate the effect of calcium overload on myocardial contractile function and biochemical activity of cardiac subcellular membranes. Rats were treated with an oral administration of 500,000 units/kg of vitamin D3 for 3 consecutive days, and their hearts were sampled on the 5th day for biochemical analysis. On the 4th and 5th days, heart rate, mean aortic pressure, left ventricular systolic pressure and left ventricular dP/dt were significantly lowered in vitamin D3-treated rats, demonstrating the existence of appreciable myocardial contractile dysfunction. Marked increases in the myocardial calcium (67-fold increase) and mitochondrial calcium contents (24-fold increase) were observed by hypervitaminosis D3. Mitochondrial oxidative phosphorylation and ATPase activity were significantly reduced by this treatment. A decline in sarcolemmal Na+, K+-ATPase activity was also observed, while relatively minor or insignificant changes in calcium uptake and ATPase activities of sarcoplasmic reticulum were detectable. Electron microscopic examination revealed calcium deposits in the mitochondria after vitamin D3 treatment. The results suggest that hypervitaminosis D3 produces massive accumulation of calcium in the myocardium, particularly in the cardiac mitochondrial membrane, which may induce an impairment in the mitochondrial function and eventually may lead to a failure in the cardiac contractile function. 相似文献
24.
Ralph J. Larson 《Environmental Biology of Fishes》1991,30(1-2):57-70
Synopsis Seasonal cycles of reserve deposition and utilization in many fishes, amphibians and reptiles alleviate temporal mismatches
of energy supply and demand. Utilization of reserves can be related to maintenance during periods of reduced food supply,
to reproduction, particularly during periods of poor food availability, and to migration. Published data on the seasonal cycles
of reserves and reproduction inSebastes suggest that reserves are important for maintenance during wintertime periods of low food availability. Unlike many other
ectothermic vertebrates, some species ofSebastes deposit fat reserves at the same time as gametogenesis, a pattern consistent with the longevity and iteroparity evident in
the genus. Other species ofSebastes have similar seasonal timing of fat cycles, but since reproduction takes place later in the year, the decline in reserves
during winter coincides with the main period of reproductive activity. The significance of this is not clear. Interspecific
differences in amounts of reserves may be related to geographical differences in the seasonality or abundance of food. Intraspecific
variation in reserves, marked most strongly by allometry of reserves with regard to fish legth, bears further study, since
it may link the proces of sexual maturation and the responses of repeat spawners to variability in food supply and other environmental
factors. 相似文献
25.
Experiments were undertaken to define the role of two calcium-associated enzyme systems in modulating transmitter-stimulated production of cyclic nucleotides in rat brain. Cyclic AMP (cAMP) accumulation was examined in cerebral cortical slices using a prelabeling technique. The enhancement of isoproterenol-stimulated cAMP production by alpha-adrenergic and gamma-aminobutyric acid-B (GABAB) agonists was reduced by exposing the tissue to EGTA, a chelator of divalent cations, or quinacrine, a nonselective inhibitor of phospholipase A2. Likewise, chronic (2 weeks) administration of corticosterone decreased the alpha-adrenergic and GABAB receptor modulation of second messenger production. Neither cyclooxygenase nor lipoxygenase inhibitors selectively influenced the facilitating response of alpha-adrenergic and GABAB agonists. Other experiments revealed that although norepinephrine and 6-fluoronorepinephrine stimulated inositol phosphate (IP) production in cerebral cortical slices with potencies equal to those displayed in the cyclic nucleotide assay, selective alpha 1-adrenergic agonists were less efficacious on IP formation and were without effect in the cAMP assay. Conversely, a selective alpha 2-adrenergic receptor agonist facilitated the cAMP response to a beta-adrenergic agonist without affecting IP formation. The rank orders of potency of a series of alpha-adrenergic antagonists suggest that IP accumulation is mediated solely by alpha 1-adrenergic receptors, whereas the augmentation of cAMP accumulation is regulated by a mixed population of alpha-adrenergic sites. The results suggest that the alpha-adrenergic and GABAB receptor-mediated enhancement of isoproterenol-stimulated cAMP formation appears to be more closely associated with phospholipase A2 than phospholipase C and may be mediated by arachidonate or some other fatty acid. 相似文献
26.
Koji Yamada Masafuni Sasaki Genki Kimura 《In vitro cellular & developmental biology. Plant》1986,22(4):212-216
Summary We examined cellular protein content in four temperature-sensitive (ts) mutants of rat 3Y1 fibroblasts (3Y1tsD123, 3Y1tsF121,
3Y1tsG125, and 3Y1tsH203) under various conditions of culture that affect cell proliferation. When proliferation of the ts
mutants was inhibited at a nonpermissive temperature (39.8°C) in the G1 phase, prominent accumulation of cellular protein occurred in three mutants (3Y1tsF121, 3Y1tsG125, and 3Y1tsH203) but not
in 3Y1tsD123. The over-accumulation of protein at 39.8°C in the former three mutants was inhibited at high cell densities.
At low cell densities there was an upper limit in the protein accumulation at 39.8°C. When the three mutants, proliferation-arrested
at high cell densities at 33.8°C, were replated sparsely in fresh medium and shifted to 39.8°C, proliferation was completely
inhibited whereas over-accumulation of protein occurred. These results indicating dissociation of protein accumulation and
cell proliferation suggest that the two events are regulated by different mechanisms.
This work was supported in part by a Grant-in-Aid for Encouragement of Young Scientists (1984) to K. Y. from the Ministry
of Education, Science, and Culture, Japan. 相似文献
27.
The composition of coloured carotenoids in the milo shoot was investigated quantitatively (high performance liquid chromatography) during light-mediated plastidogenesis, including the time span of photodelay as caused by medium and high light fluxes. It was found that as long as only the far-red-absorbing form of phytochrome operates, the carotenoid pattern remains virtually the same as in complete darkness (violaxanthin and lutein as major constituents, traces of -carotene). On the other hand, the pattern changes dramatically in white or red light with increasing amounts of chlorophyll (lutein and -carotene dominate, -carotene showing the strongest relative increase). Photodelay during the early phase of plastidogenesis affects the carotenoid composition strongly. Increase of neoxanthin, violaxanthin and -carotene contents are diminished while lutein accumulation proves resistant towards chlorophyll-mediated photoinhibition. The photodelay can be diminished by an appropriate light pretreatment. The data indicate that light-mediated control over carotenoid accumulation is exerted at three levels: i) a coarse control through phytochrome, ii) fine tuning in connection with chlorophyll accumulation, iii) stabilization of holocomplexes against photodecomposition.Abbreviations GG14
high fluence rate green-yellow light
- HPLC
high-performance liquid chromatography
- Chl
chlorophyll
- WLw
weak white light (1200 lx)
- WLm
medium flux white light (12000 lx) 相似文献
28.
The cyanobacterium Oscillatoria agardhii was grown in continuous culture under various light conditions in order to study the interactions of light on phosphorus-limited growth. Under severe P-limiting (light-saturating) conditions, a low chlorophyll a and C-phycocyanin content was found. In addition, the light-harvesting capacity, reflected in the values of P
max (maximum light-saturated oxygen production rate) and (photosynthetic affinity), were low compared to light-limited cultures.Reduction of the light climate, either by reduction of the length of the photoperiod or light-intensity, resulted in an increase in light-harvesting capacity (higher pigment content, P
m and ) during growth under P-limiting conditions. Light-induced changes in P
max and could be related to the relative growth rate, being the actual growth rate as a fraction of the growth rate which would be observed under light-limiting conditions.Under P-limiting conditions, reduction of the light-climate caused a reduction in dry weight of the culture. This decrease was mainly due to a decrease in carbohydrate content of the cells. Under all conditions tested, carbohydrates were found to accumulate during the light-period and to be consumed during the dark-period.Evaluation of carbohydrate consumption in the dark yielded a specific maintenance rate constant of 0.001 h-1. This observation leads to the conclusion that the specific maintenance rate constant is independent on the character of the growth rate limiting nutrient for O. agardhii. 相似文献
29.
Effects of weak acids on proline accumulation in barley leaves: a comparison between abscisic acid and isobutyric acid 总被引:1,自引:1,他引:0
Abstract. When isobutyric acid (IBA) or abscisic acid (ABA) are supplied to leaf sections a similar rapid and marked decrease in the intracellular pH is observed. This acidification is accompanied by an increase in proline level which is about the same for both 3 mol m−3 IBA and 1 mol m−3 ABA treatments.
Fusicoccin (FC), known to act at the proton pump level, almost completely suppresses the ABA-induced acidification of the cell sap, whereas it only partially counteracts the acidifying effect of IBA, in particular during short periods of treatment. This effect of FC is paralleled by a similar inhibition of the induced proline accumulation: in fact, FC completely suppresses the ABA-induced increase in proline during short treatment periods, whereas it is only effective in inhibiting the IBA-induced proline accumulation after long treatment periods.
These data seem to suggest that the ABA- and IBA-induced changes in proline level might be mediated by changes in the intracellular pH. 相似文献
Fusicoccin (FC), known to act at the proton pump level, almost completely suppresses the ABA-induced acidification of the cell sap, whereas it only partially counteracts the acidifying effect of IBA, in particular during short periods of treatment. This effect of FC is paralleled by a similar inhibition of the induced proline accumulation: in fact, FC completely suppresses the ABA-induced increase in proline during short treatment periods, whereas it is only effective in inhibiting the IBA-induced proline accumulation after long treatment periods.
These data seem to suggest that the ABA- and IBA-induced changes in proline level might be mediated by changes in the intracellular pH. 相似文献
30.
The nitrogen balance of Raphanus sativus X raphanistrum plants. I. Daily nitrogen use under high nitrate supply 总被引:1,自引:1,他引:0
E.-D. SCHULZE † G. KOCH F. PERCIVAL H. A. MOONEY C. CHU 《Plant, cell & environment》1985,8(9):713-720
Abstract Growth-chamber cultivated Raphanus plants accumulate nitrate during their vegetative growth. After 25 days of growth at a constant supply to the roots of 1 mol m?3 (NO?3) in a balanced nutrient solution, the oldest leaves (eight-leaf stage) accumulated 2.5% NO?3-nitrogen (NO3-N) in their lamina, and almost 5% NO3-N in their petioles on a dry weight basis. This is equivalent to approximately 190 and 400 mol?3 m?3 concentration of NO?3 in the lamina and the petiole, respectively, as calculated on a total tissue water content basis. Measurements were made of root NO?3 uptake, NO?3 fluxes in the xylem, nitrate uptake by the mesophyll cells, and nitrate reduction as measured by an in vivo test. NO?3 uptake by roots and mesophyll cells was greater in the light than in the dark. The NO?3 concentration in the xylem fluid was constant with leaf age, but showed a distinct daily variation as a result of the independent fluxes of root uptake, transpiration and mesophyll uptake. NO?3 was reduced in the leaf at a higher rate in the light than in the dark. The reduction was inhibited at the high concentrations calculated to exist in the mesophyll vacuoles, but reduction continued at a low rate, even when there was no supply from the incubation medium. Sixty-four per cent of the NO?3 influx was turned into organic nitrogen, with the remaining NO?3 accumulating in both the light and the dark. 相似文献