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11.
Achim G. Rieth Stephan L. Baader Holger N. Lode Gernot Bruchelt Dietrich Niethammer 《Biometals》1992,5(4):223-227
Damage of CCC PM2 DNA by 6-hydroxydopamine (6-OHDA) and ascorbic acid (AA), compounds that are both able to release iron from ferritin, was significantly enhanced in the presence of ferritin. H2O2, a product of 6-OHDA autoxidation, did not induce DNA strand breaks in the absence of ferritin and only to a minor extent in the presence of ferritin. DNA damage by 6-OHDA and AA could be reduced by the hydroxyl radical scavenger mannitol, the iron chelator desferrioxamine, and, partly, by a combination of superoxide dismutase and catalase. These inhibitory effects were clearly less pronounced in the presence of ferritin. Ferritin obviously played an important role as a source of iron in the pro-oxidative processes of 6-OHDA and AA. These features might be of importance in cancer therapy since many tumor cells contain elevated ferritin levels. 相似文献
12.
Peter Heimann Stephan Laage Harald Jockusch 《Differentiation; research in biological diversity》1991,47(2):77-83
In the wobbler (WR) mouse, a neuromuscular mutant characterized by a motoneuron degeneration and male infertility, the cellular basis of the defect in spermiogenesis was studied by light and electron microscopy as well as by lectin binding. Spermatozoa of the wobbler mutant had rounded heads, and their motility was reduced. In histological sections of WR testes, spermatogenesis appeared normal up to the stage of round spermatids, but the elongation and flattening of the nucleus during late spermiogenesis did not occur. Numbers of spermatid nuclei in WR testes were reduced to 70%-80% of controls. The acrosomal marker glycoprotein, peanut agglutinin receptor, was synthesized, but the acrosomal membrane did not attach to the nucleus. The disturbance in spermiogenesis of the wobbler mouse is not due to impaired descent of the testis, nor to a lack of testosterone, and is distinct from that observed in other mouse mutants (quaking, QK; Purkinje cell degeneration, PCD) with combined neurological and spermiogenesis defects. 相似文献
13.
The Evolution of Restricted Recombination and the Accumulation of Repeated DNA Sequences 总被引:19,自引:6,他引:13
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We suggest hypotheses to account for two major features of chromosomal organization in higher eukaryotes. The first of these is the general restriction of crossing over in the neighborhood of centromeres and telomeres. We propose that this is a consequence of selection for reduced rates of unequal exchange between repeated DNA sequences for which the copy number is subject to stabilizing selection: microtubule binding sites, in the case of centromeres, and the short repeated sequences needed for terminal replication of a linear DNA molecule, in the case of telomeres. An association between proximal crossing over and nondisjunction would also favor the restriction of crossing over near the centromere. The second feature is the association between highly repeated DNA sequences of no obvious functional significance and regions of restricted crossing over. We show that highly repeated sequences are likely to persist longest (over evolutionary time) when crossing over is infrequent. This is because unequal exchange among repeated sequences generates single copy sequences, and a population that becomes fixed for a single copy sequence by drift remains in this state indefinitely (in the absence of gene amplification processes). Increased rates of exchange thus speed up the process of stochastic loss of repeated sequences. 相似文献
14.
Wolfgang Hagmann Claudio Denzlinger Stephan Rapp Gisbert Weckbecker Dietrich Keppler 《Prostaglandins & other lipid mediators》1986,31(2)
Mercapturic acid formation, an established pathway in the detoxication of xenobiotics, is demonstrated for cysteinyl leukotrienes generated in rats
after endotoxin treatment. The mercapturate N-acetyl-leukotriene E4 (N-acetyl-LTE4) represented a major metabolite eliminated into bile after injection of [3H]LTC4 as shown by cochromatography with synthetic N-acetyl-LTE4 in four different HPLC solvent systems. The identity of endogenoud N-acetyl-LTE4 elicited by endotoxin
was additionally verified by enzymatic deacetylation followed by chemical N-acetylation. The deacetylation was catalyzed by penicillin amidase. Endogenous cysteinyl leukotrienes were quantified by radioimmunoassay after HPLC separation. A N-acetyl-LTE4 concentration of 80 nmol/l was determined in bile collected between 30 and 60 min after endotoxin injection. Under this condition, other cysteinyl leukotrienes detected in bile by radioimmunoassay amounted to less than 5% of N-acetyl-LTE4. The mercapturic acid pathway, leading from the glutathione conjugate LTC4 to N-acetyl-LTE4, thus plays an important role in the deactivation and elimination of these potent endogenous mediators. 相似文献
15.
S Matano G Baron H Stephan H D Frahm 《Folia primatologica; international journal of primatology》1985,44(3-4):182-203
Volumes of medial, interposed, and lateral cerebellar nuclei (MCN, ICN, and LCN) were measured in Insectivora, Scandentia, and Primates, including man. The relative size of the nuclei was expressed in size indices. Insectivora had by far the smallest cerebellar nuclei. The simians, in general, had larger cerebellar nuclei than the prosimians, but there was considerable overlap. From Insectivora to man, the MCN was the least progressive and the LCN the most progressive. The indices are expected to reflect the relative size of the three longitudinal zones of the cerebellum (vermis/MCN, pars intermedius/ICN, hemisphere/LCN). They, together with those of the ventral pons and cerebellum (part I), are discussed in relation to the predominant locomotor pattern of a species, and with reference to evolutionary trends in primate phylogeny. 相似文献
16.
By use of the pressure-clamp technique, the hydraulic conductivity of the brackish-water alga Lamprothamnium was found to be 5·10-6 cm s-1 bar-1. The dimensions of the internodes are so small that it is possible, for the first time, to measure a complete volume relaxation upon clamping the turgor pressure to a preset value by a feedback control of the pressure probe. As theoretically predicted, the values of the hydraulic conductivity obtained from the initial slope of the volume relaxation induced by the pressure clamp are in agreement (within experimental error) with those obtained from the half-time of the relaxation process. The cell volume also obtained from the analysis of the volume relaxation is the osmotically effective cell volume and is therefore slightly smaller than the value obtained by taking the dimensions of the cell including the cell wall.Abbreviations and symbols Lp
hydraulic conductivity
- P
turgor pressure
- Sv
initial slope of volume relaxion
- T1/2
half-time of volume relaxation
Dedicated to Professor Dr. H. Ziegler on the occasion of his 60th birthday 相似文献
17.
J F Blickle P Reville F Stephan P Meyer C Demangeat R Sapin 《Hormones et métabolisme》1984,16(7):336-340
It is well established that glucagon plays an important role in the regulation of fuel supplies as its plasma level increases during the first days of a complete fast. However, it is not certain that glucagon is involved in the adaptation to chronic starvation. In the present study, this problem was investigated by the determination of the changes in the plasma glucagon level elicited by an i.v. glucose tolerance test followed by an i.v. arginine perfusion in 26 self starved patients suffering from anorexia nervosa (AN) and 14 control patients having only minor neurotic disorders. The basal plasma glucagon level tended to be higher in the AN patients than in the controls; but the difference was not statistically significant. Glucagon responses to glucose and arginine observed in the AN patients were not significantly different from those seen in the control patients. In the AN patients, the insulin response to both loads was reduced and the plasma GH level increased paradoxically after the glucose load, whereas it rose normally after the arginine load. It may be concluded that in chronic starvation by AN the regulation of fuel supplies depends mainly on decreased insulin and increased growth hormone secretion. The role of glucagon seems to be of minor importance in this condition. 相似文献
18.
In this first of a series of papers concerning the theoretical analysis of rate theory models for ion transport through rigid pores, the case of vanishing interactions is investigated. "Rigidity" means that ions crossing membranes through pores see a fixed structure of the pores, not changing in time. A single pore is considered to be a sequence of (n + 1) activation barriers separated by n energy minima. The explicit analytical treatment is restricted to pores with regular internal barrier structure, including the nonequilibrium situation of an applied electric field. In this case the connection with continuum diffusion models is demonstrated by performing in the limit n leads to infinity (n = number of binding sites within the pores) the transition to continuum. Thus, from diffusion equations describing a discrete number of jumps, the corresponding diffusion-like partial differential equations and boundary conditions are generated. For regular pores, from the time dependent solutions of the discrete equations, the corresponding solutions of the continuum equations are explicitly generated. The time-dependent relaxation behaviour of the discrete model is in good agreement with the continuum model if one assumes more than two binding sites in the pores. 相似文献
19.
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