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41.
42.
Developmental controls of morphological mutants of Phaseolus vulgaris L. conditioned by two independent loci, DL1 and DL2, were examined through grafting experiments and hydroponic studies. Phenotypes of mutant classes were duplicated by unions of scions and stocks derived from different genotypes. Results indicate that DL1 and DL2 regulate a root and shoot factor respectively, contributing to the mutant types. The allelic dosages of DL1 in the root and DL2 in the shoot rather than the genotype of the whole plant per se determine the severity of the mutant expression. Plants heterozygous for both loci with a temperature-sensitive expression of the mutant phenotype were used to determine physiological components involved. The primary abnormal developmental event associated with the appearance of mutant phenotypes, the restricted root growth at high temperature, could be overcome by the addition of cytokinin in hydroponic solution. These observations suggest that DL1 and DL2 may be related to the regulation of hormonal function or metabolism. 相似文献
43.
Cerebral Metabolic Effects of Monoamine Oxidase Inhibition in Normal and 1-Methyl-4-Phenyl-1,2,3,6-Tetrahydropyridine Acutely Treated Monkeys 总被引:2,自引:0,他引:2
Ernesta Palombo Linda J. Porrino† Alison M. Crane Krzysztof S. Bankiewicz‡ Irwin J. Kopin‡ Louis Sokoloff 《Journal of neurochemistry》1991,56(5):1639-1646
The neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) induces dopaminergic cell death in the substantia nigra pars compacta (SNpc) and clinical parkinsonism in humans and experimental animals. Pretreatment with monoamine oxidase inhibitors prevents this cell death and associated parkinsonism by blocking the oxidation of MPTP to a toxic intermediate. The 2-deoxyglucose method was used to study the acute effects of MPTP in the monkey brain and the effects of monoamine oxidase inhibition on local cerebral glucose utilization in both normal and MPTP-treated monkeys. MPTP administration alone caused a major increase in glucose utilization in the SNpc and smaller increases in some subnuclei within the ventral tegmental area in which eventual dopaminergic cell loss also occurs. Pretreatment with pargyline abolished these metabolic increases, a finding suggesting both that the oxidized product of MPTP generates the metabolic increases and that the increased glucose consumption may contribute to cell toxicity. On the other hand, in most cortical, thalamic, striatal, brainstem, and cerebellar areas MPTP alone caused reductions in glucose utilization, and pargyline failed to prevent these effects. Pargyline alone depressed metabolism in the locus coeruleus and a few other monoaminergic structures. 相似文献
44.
Non-green plastids (leucoplasts) isolated from pea roots are shown to be considerably active in forming aromatic amino acids by the shikimate pathway which, in contrast to the chloroplast pathway, is independent of light. Supply of phosphoenolpyruvate and 3-dehydroquinate, 3-dehydroshikimate, shikimate and quinate effectively enhances the formation of aromatic amino acids suggesting an intra- or/and intercellular intermediate transport. 相似文献
45.
Growth, expression of functional differentiation (as characterized by synthesis and secretion of milk proteins), and primary metabolism were studied for a mouse mammary epithelial cell line, COMMA-1D, in extended-batch and hollow-fiber reactor cultures. Batch cultures were performed on Costar polycarbonate membrane inserts, allowing basal and apical exposure to medium. Protein production was induced in both batch and hollow-fiber cultures in hormonesupplemented medium. In batch cultures, high levels of protein production and secretion were maintained for 18 days. Once differentiation was induced, the rate of deinduction was low, even in medium containing epidermal growth factor (EGF) and serum; cells continued to express and secrete proteins for at least 12 days after prolactin and hydrocortisone were removed. Cells in both batch and hollow-fiber cultures were highly glycolytic and exhibited low rates of glutaminolysis. In batch culture on membrane inserts, cells showed polarized metabolism between the apical and basal side, maintaining significant gradients of glucose and lactate. Medium hormonal composition and subsequent differentiation affected both glucose uptake and lactate yield for COMMA-1D in batch culture. (c) 1992 John Wiley & Sons, Inc. 相似文献
46.
Stomatal responses to light in the facultative Crassulacean acid metabolism species, Portulacaria afra 总被引:2,自引:0,他引:2
Guard cell responses to light are mediated by guard cell chlorophyll and by a specific blue light photoreceptor. Gas exchange and epidermal peel techniques were employed to investigate these responses in the facultative Crassulacean acid metabolism (CAM) species, Portulacaria afra (L.) Jacq. In P. afra individuals performing C3 metabolism, red light stimulated an increase in leaf conductance in intact leaves and stomatal opening in isolated epidermal peels, indicating the presence in guard cells of the chlorophyll-mediated response to light. Under a background of continuous red illumination, conductance exhibited transient increases following pulses of blue but not red light, indicating that the specific stomatal response to blue light was also operative. In contrast, in CAM individuals, conductance in gas exchange experiments and stomatal opening in epidermal peel experiments were not stimulated by red light. In CAM plants, conductance did not increase following blue light pulses administered over a range of temperatures, vapor pressure differences (VPD), ambient CO2 concentrations and background red light intensities. These results indicate that P. afra does possess typical guard cell responses to light when performing C3 metabolism. The metabolic pathways mediating these responses are either lost or inhibited when CAM is induced. 相似文献
47.
The flow of jelly within a honeybee colony 总被引:8,自引:0,他引:8
Karl Crailsheim 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1992,162(8):681-689
Summary The flow of jelly from 100 nurse bees to the members of two normal-sized colonies was measured during one night. To follow the flow, nurses were injected with 14C-phenylalanine. They incorporated this label into the protein of their hypopharyngeal (brood food) glands and their own body protein. When they were allowed trophallactic contacts during the investigation period a loss of label and a shift away from the abdomen was observed, indicating protein synthesis in the hypopharyngeal glands from previously stored protein. Very young larvae were fed less frequently than older ones. Younger workers received larger amounts of jelly than older ones, but considerable amounts were given to foragers. Drones behaved similarly. Between one-third and one-half of the distributed jelly was given to imagines; 10% and 16% of all workers received radioactive jelly from 100 nurses in the two colonies during one night. Thus, jelly is a very important food for adult honey bees. There was a remarkable exchange of label within the class of nurses themselves that is interpreted as communication within the social system.Abbreviation dpm
decays per minute 相似文献
48.
Summary The use of an Ussing chamber with well-defined mixing characteristics coupled to a mass spectrometer permits the concurrent evaluation of transepithelial current and oxidative metabolism with improved temporal resolution. The time-course of the amiloride-sensitive currentI
a and the rate of suprabasal CO2 productionJ
CO2
sb
were observed in 10 toad urinary bladders at short-circuit and after clamping at 100 mV, serosa positive. Following perturbation of (0100mV),I
a declined sharply within 1/2 min, remained near constant 15 min, and then increased slightly.J
CO2
sb
declined more gradually, remained near constant at 4–7 min, and then declined further. Detailed analysis revealed an early quasi-steady state with near constancy ofJ
CO2
sb
starting at 2.9±1.1 (sd) min and lasting 4.7 ±1.8 (sd) min, followed by relaxation to a later steady state at about 15 min. During the early quasi-steady state,I
a was also nearly constant. Considering that in steady statesI
a/FJ
Na
a
, the rate of transepithelial active Na transport, during the early quasi-steady state mean values ±se ofJ
Na
a
,J
CO2
sb
and (J
Na
a
/J
CO2
sb
) were, respectively, 29.9±1.7%, 59.4 ±3.2%, and 56.4±5.7% of values at short-circuit. Corresponding values during the late steady state were 41.4±6.0%, 38.2±6.1%, and 111.3±8.6%. Thus the flow ratioJ
Na
a
/J
CO2
sb
was depressed significantly during the early quasi-steady state, but returned later to the original value. The results of measurements ofI
a andJ
CO2
sb
in three hemibladders were qualitatively similar. In terms of a phenomenological black-box treatment the findings are consistent with earlier studies indicating incomplete coupling between transport and metabolism. Further studies will be required to clarify the molecular basis for these observations. 相似文献
49.
John S. Hothersall Salmata Zubairu Patricia McLean A. Leslie Greenbaum 《Journal of neurochemistry》1981,37(6):1484-1496
The effect of 6-aminonicotinamide (6AN) treatment on the activities of alternative pathways of glucose metabolism in 20-day-old rat brain was evaluated by measurements of yields of 14CO2 from glucose labeled with 14C on carbons 1, 2, 3 + 4, or 6 and uniformly labeled glucose, and from the incorporation of 14C from specifically labeled glucose into lipids by brain slices from cerebral hemispheres and cerebellum. At the highest dose of 6AN used (35 mg/kg body weight) there was a significant decrease in the 14CO2 yields via the pentose phosphate pathway, the glycolytic route, tricarboxylic acid (TCA) cycle, and via the glutamate-gamma-aminobutyric acid pathway. Giving a graded series of doses (20-35 mg 6AN/kg body weight) revealed a hierarchy of responses in which the pentose phosphate pathway, lactate, glyceride-glycerol, and fatty acid formation were most sensitive, followed, in sequence, by the pyruvate dehydrogenase reaction, the glutamate-gamma-aminobutyrate route and, finally, the TCA cycle. The nature of the blocks in the various pathways was examined by the use of metabolite profiles. 相似文献
50.
Alterations of Phospholipid Metabolism in Rat Cerebral Cortex Mince Induced by Cationic Amphiphilic Drugs 总被引:3,自引:3,他引:0
Abstract Cationic amphiphilic drugs (CADs) of varied clinical use were screened to determine their capacity to alter the pattern of labeling with 32 Pj of cerebral cortex mince phospholipids. The altered phospholipid labeling patterns were qualitatively similar, the prominent features being reduced incorporation into phosphatidylcholine and increased incorporation into phosphatidic acid. Relative potencies were: (±)-propranolol > chlorpromazine = 4,4'-bis(diethylaminoethoxy) α,β -diethyldiphenylethane > desipramine > di-bucaine > pimozide > oxymetazoline = fenfluramine = haloperidol = chloroquine > amphetamine = no drug added. Propranolol was used to study the action of CADs further. Its effect was time- and dose-dependent, but in contrast with pineal gland, no label appeared in phosphatidyl-CMP (CDP-diacylglycerol), nor did dialysis of the mince to reduce diffusible substrates or exogenous addition of substrates cause appearance of liponucleotide. Thus lack of diffusible precursors is not responsible for CAD effects in vitro. Pulse-chase experiments with 32 P1 and [2-3 H]glycerol suggested that inhibition of phosphatidate phosphohydrolase may be partly responsible for the observed alterations in phospholipid labeling in the presence of CADs. 相似文献