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61.
A new bacterial alcohol dehydrogenase active on degraded lignin and several low molecular weight aromatic compounds 总被引:1,自引:0,他引:1
Jean Pelmont Catherine Tournesac Ahmed Mliki Michel Barrelle Claude Beguin 《FEMS microbiology letters》1989,57(1):109-114
A new intracellular bacterial dehydrogenase has been purified. It was active in the reversible reduction by NADH of conjugated carbonyl groups in partially degraded lignin. It was also active on various aromatic aldehydes such as vanillin, syringaldehyde and cinnamaldehyde, but had no effect on acetovanillone and lignin models carrying a conjugated ketone. It is proposed that this enzyme functions as a broadly specific lignin dehydrogenase at the level of aldehydic groups that are present in the lignin preparations. 相似文献
62.
63.
Claude Penel Thomas Gaspar Michèle Crèvecoeur Claire Kevers Hubert Greppin 《Physiologia plantarum》1990,79(2):250-254
Ca2+ and Mn2+ activate the conversion of 1-aminocyclopropane-1-carboxylic acid (ACC) by root microsomes of Vicia lens as they do in other similar systems. The preparation of microsomes in the presence of Mn2+ greatly increases their ability to convert ACC into ethylene, without addition of Mn2+ in the reaction mixture. Ca2+ does not have this property. The effect could not be attributed to Mn2+ entrapping into membrane vesicles (sonication followed by repelleting had no effect) but, possibly, in part to Mn2+ -mediated binding to microsomes of a soluble factor favouring the conversion of ACC to C2 H4 . Although no direct correlation could be established in vitro between ethylene-forming-enzyme (EFE) and peroxidase activities, some soluble peroxidases might be this soluble factor. Mn2+ favoured attachment to membranes of some peroxidase activity from the soluble fraction and from commercial HRP and lipoxygenase. This binding effect of Mn2+ cannot be readily distinguished from its role in the generation of a chain of free radicals and in redox mechanisms. 相似文献
64.
65.
The response of pig Sertoli cell-enriched cultures to FSH was investigated by measuring plasminogen activator (PA) secretion in culture, throughout the nonpubertal and prepubertal periods. Sertoli cell-enriched populations could be isolated from birth until a testicular weight of 56 g. FSH elicited a dose-dependent increase in PA secretion by pig Sertoli cell-enriched cultures. The ED50 was minimal for cells coming from testes weighing 10-22 g, and increased more than 2-fold for cells from heavier testes. This suggests that, at the end of the non-pubertal period, an increased FSH sensitivity is important for initiation of spermatogenesis in this species, and that during the prepubertal period Sertoli cells become less sensitive to FSH. The FSH-stimulated PA secretion increased about 10-fold from a testicular weight of 25 g onwards, i.e. when primary spermatocytes appear in seminiferous tubules. 相似文献
66.
67.
Chromatographic and immunological evidence for mammalian GnRH and chicken GnRH II in eel (Anguilla anguilla) brain and pituitary 总被引:1,自引:0,他引:1
Gonadotropin-releasing hormone (GnRH) peptides in the brain and pituitary of the European eel (Anguilla anguilla) were investigated by reverse phase high performance liquid chromatography (HPLC) and radioimmunoassay with region-specific antisera. Two GnRH molecular forms were demonstrated in brain and pituitary extracts. One form eluted in the same position as synthetic mammalian GnRH on HPLC and was recognized by antibodies directed against the NH2 and COOH termini of mammalian GnRH as well as by antibodies to the middle region. The second form eluted in the same position as synthetic chicken GnRH II and was recognized by specific antibodies to this molecule. Salmon GnRH and chicken GnRH I were not detected. The occurrence of mammalian GnRH in teleost fish suggests that this molecular form is more ancient than was previously suspected and arose earlier than in primitive tetrapods, or that it has arisen in the eel through random mutation of salmon GnRH. The lack of salmon GnRH in the eel brain indicates that this molecular form is not common to all teleost species. The finding in eel brain of chicken GnRH II, which has previously been described in species of Mammalia, Aves, Reptilia, Amphibia, Osteichthyes, and Chondrichthyes, supports our hypothesis that this widespread structural variant may represent an early evolved and conserved form of GnRH. 相似文献
68.
Valérie Maxime Marguerite Peyraud-Waitzenergger Guy Claireaux Claude Peyraud 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1990,160(1):31-39
Summary Oxygen consumption, gill ventilation, blood acid-base/ionic status and haemoglobin oxygen affinity were studied in seawater-adapted adult salmon (Salmo salar) during five weeks after transfer into fresh water. Freshwater exposure induced the following changes: Standard oxygen consumption (
) and ventilatory flow (
) decreased markedly during the first days after transfer, then decreased more gradually until a new steady-state was achieved at which
and
were about 80% and 56% of the control values, respectively. The marked increase in oxygen extraction coefficient (Ew
O
2) and the marked decrease in the oxygen convection requirement (
) were associated with a reduction in the partial pressure of carbon dioxide in arterial blood (Pa
CO
2), in spite of a decrease of both ventilatory flow and water CO2 capacitance. These results suggested that transfer into fresh water induced an increase in branchial diffusive conductance. A biphasic pattern was observed in the time-course of the changes in both plasma ion concentration and acid-base status. During the first 10 days, plasma Na+, K+, and Cl– concentrations fell abruptly, then more gradually. [Cl–] decreased more than [Na+] resulting in a progressive increase in the [Na+]/[Cl–] ratio. During the second phase of acclimation to fresh water plasma Na+, K+, and Cl– concentrations progressively increased. [Cl–] increased more than [Na+], so that [Na+]/[Cl–] ratio decreased. Transfer into fresh water did not significantly change plasma lactate concentration. Upon exposure to fresh water, blood pH increased from 7.94±0.04 to 8.43±0.06 at day 10 and then decreased to 8.08±0.03 at day 34. The increase in blood pH induced by transfer to fresh water initially represented a mixed metabolic/respiratory alkalosis. However, after 15 days Pa
CO
2 had returned to pretransfer values and the alkalosis was purely metabolic. The metabolic component of the alkalosis was associated with appropriate changes in the plasma strong ion difference (S.I.D.). Blood alkalosis moved the oxygen dissociation curve to the left, so that P50 was decreased by 30% below the value in seawater for the maximal increase in blood pH. This rise in haemoglobin affinity for O2, associated with a marked increase in blood buffer capacity, are regarded as adaptative processes allowing the salmon to cope with the markedly increased energy expenditure required for upstream migration. 相似文献
69.
70.
Amina El Jamali Nadia Rachdaoui Claude Jacquemin Claude Corrèze 《Journal of neurochemistry》1996,67(6):2532-2539
Abstract: Long-term (48-h) forskolin treatment of rat astroglial cells led to a slight decrease (30–40%) in the response to isoproterenol, vasoactive-intestinal peptide, guanyl 5'-(βγ-imido)diphosphate, guanosine 5'- O -(3-thiotriphosphate) [GTP(S)], and AIF4 − in crude membrane fractions. In contrast, the acute stimulatory effect of forskolin was increased by 1.25–1.5-fold. These two opposite effects of forskolin were mediated by a cyclic AMP-dependent mechanism. No changes in Gs α, Gi α, or Gβ protein levels could be determined by immunoblotting using specific antisera. No significant differences were observed in the ability of G proteins extracted from control and forskolin-treated cells to reconstitute a full adenylyl cyclase activity in membranes from S49 cyc− cells, lacking Gs α protein. Gs α proteins were detected in two pools of membranes, one in the heavy sucrose fractions and the other in light sucrose fractions. Forskolin treatment of the cells shifted Gs α protein toward the light-density membranes. We did not find any significant change in the distribution of adenylyl cyclase. In contrast to the decreased stimulation of adenylyl cyclase activity by agonists acting via Gs α, observed in the crude membrane fraction, the responses of adenylyl cyclase to forskolin as well as to GTP(S) were increased in the purified plasma membrane fractions. These results may indicate that sensitization of the catalyst appears to be the dominant component in the astroglial cell response to long-term treatment by forskolin. 相似文献