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91.
J. Seiler L. Brüel Walther G. Tischler und Lenz 《Molecular & general genetics : MGG》1920,24(3-4):290-300
Ohne Zusammenfassung 相似文献
92.
A Ballistreri M Giuffrida G Impallomeni R W Lenz R C Fuller 《International journal of biological macromolecules》1999,26(2-3):201-211
The sequence distributions of two microbial copolyesters obtained by fermentation of Rhodospirillum rubrum, grown with 3-hydroxyhexanoic or 3-hydroxyheptanoic acids, were determined by analyzing the oligomers prepared by partial pyrolysis or partial methanolysis of these copolyesters using fast atom bombardment mass spectrometry (FAB-MS). Oligomers up to pentamers were identified in the case of partial pyrolysis and up to tetradecamers in the case of partial methanolysis. The comparison between the experimental and calculated peak intensities of FAB mass spectra allows the calculation of compositions and sequence distributions, which in these copolyesters follow Bernoullian statistics, indicating that they are random terpolyesters. 相似文献
93.
94.
Andréa Baldasso-Zanon Andrew Oliveira Silva Nayara Franco Rafael V. Picon Guido Lenz Patrícia Luciana da Costa Lopez Eduardo C. Filippi-Chiela 《Journal of cellular biochemistry》2024,125(2):e30517
Colorectal cancer (CRC) is the third most common and deadliest cancer globally. Regimens using 5-fluorouracil (5FU) and Oxaliplatin (OXA) are the first-line treatment for CRC, but tumor recurrence is frequent. It is plausible to hypothesize that differential cellular responses are triggered after treatments depending on the genetic background of CRC cells and that the rational modulation of cell tolerance mechanisms like autophagy may reduce the regrowth of CRC cells. This study proposes investigating the cellular mechanisms triggered by CRC cells exposed to 5FU and OXA using a preclinical experimental design mimicking one cycle of the clinical regimen (i.e., 48 h of treatment repeated every 2 weeks). To test this, we treated CRC human cell lines HCT116 and HT29 with the 5FU and OXA, combined or not, for 48 h, followed by analysis for two additional weeks. Compared to single-drug treatments, the co-treatment reduced tumor cell regrowth, clonogenicity and stemness, phenotypes associated with tumor aggressiveness and poor prognosis in clinics. This effect was exerted by the induction of apoptosis and senescence only in the co-treatment. However, a week after treatment, cells that tolerated the treatment had high levels of autophagy features and restored the proliferative phenotype, resembling tumor recurrence. The pharmacologic suppression of early autophagy during its peak of occurrence, but not concomitant with chemotherapeutics, strongly reduced cell regrowth. Overall, our experimental model provides new insights into the cellular mechanisms that underlie the response and tolerance of CRC cells to 5FU and OXA, suggesting optimized, time-specific autophagy inhibition as a new avenue for improving the efficacy of current treatments. 相似文献
95.
Maike Lenz Niels Borlinghaus Leonie Weinmann Bettina M. Nestl 《World journal of microbiology & biotechnology》2017,33(11):199
Imine reductases are nicotinamide-dependent enzymes that catalyze the asymmetric reduction of various imines to the corresponding amine products. Owing to the increasing roles of chiral amines and heterocyclic compounds as intermediates for pharmaceuticals, the demand for novel selective synthesis strategies is vitally important. Recent studies have demonstrated the discovery and structural characterization of a number of stereoselective imine reductase enzymes. Here, we highlight recent progress in applying imine reductases for the formation of chiral amines and heterocycles. It particularly focuses on the utilization of imine reductases in reductive aminations of aldehydes and ketones with various amine nucleophiles, one of the most powerful reactions in the synthesis of chiral amines. Second, we report on the synthesis of saturated substituted N-heterocycles by combining them with further biocatalysts, such as carboxylic acid reductases, oxidases or transaminases. Finally, we summarize the latest applications of imine reductases in the promiscuous asymmetric hydrogenation of a highly reactive carbonyl compound and the engineering of the cofactor specificity from NADPH to NADH. 相似文献
96.
Assessing patterns of species distribution and abundance is important to understand the driving processes of, and predict
future changes in, biodiversity. To this date, ecological studies have been mainly designed to investigate the effects of
the mean magnitude of predictor variables, although ecological factors naturally vary in space and time. In a nine month long
field experiment, we tested the effects of different temporal patterns (regular, lowly and highly irregular) in biomass removal
(=disturbance event) on the diversity, species composition, and biomass accrual of macrobenthic assemblages grown on 15 × 15 cm2 PVC-panels. For each pattern of disturbance, disturbance events were timed at three sequences to control for possible confounding
effects with recruitment patterns. Disturbance intensity was kept identical among treatments. Assemblages developed in the
absence of disturbance for 3 months prior to a 150-day manipulation period, during which the biomass from 20% of the panel
area was removed at each of ten disturbance events. Additional undisturbed settlement panels were deployed in the field to
assess monthly recruitment rates and species succession over a one year period. Disturbance (i) reduced biomass and total
species cover, (ii) changed species composition during the first half of the manipulation period significantly, and (iii)
was without effect on species richness and evenness. Irregular disturbance regimes enhanced the abundance of the ascidian
Ciona intestinalis, biomass accrual, and total species cover of assemblages relative to the regular disturbance regime, but had either no or
only transient effects on diversity and species composition, respectively. Neither the degree of irregularity in disturbance
nor the sequence of disturbance events affected any of the response variables significantly. Recruitment of species was strongly
seasonal with almost only diatoms recruiting during winter, while recruitment was most intense during summer. Our results
suggest that the temporal patterns of predictor variables might be of low explanatory power for the variance of responses
in communities with seasonal recruitment patterns that are exposed to a high level of disturbance. Thus the need to include
temporal patterns of predictor variables in experimental designs may depend on community dynamics and the characteristics
of the process under investigation.
S. Wollgast and M. Molis contributed equally to this work. 相似文献
97.
98.
1. Several theoretical models predict under what conditions maximum species diversity can be maintained, and they are often used to develop effective ecosystem management plans. 2. Two models that are currently used to predict patterns of species diversity were empirically tested in marine subtidal benthic communities of different successional stages. 3. The two models were: the interactive effects of nutrient availability and disturbance frequency proposed by Kondoh (2001; Proceedings of the Royal Society London B, 268, 269-271), and the intermediate disturbance hypothesis (IDH) proposed by Connell (1978; Science, 199, 1302-1310). 4. Interactive effects were found to be transient and only occurred in the older communities, while the unimodal pattern suggested by the IDH was not supported in either successional stage. 5. It is concluded that these models are very general and thus lack sufficient explanatory power. Both models require a number of specific prerequisites for maximum diversity to be found, and though applicable in many different ecosystems they need to be refined as tools in order that they can be effectively used in habitat management plans. 相似文献
99.
Elizandra Braganhol Daiane Huppes Andressa Bernardi Márcia Rosângela Wink Guido Lenz Ana Maria Oliveira Battastini 《Cell and tissue research》2009,335(2):331-340
Glioblastoma multiforme is the most common type of primary brain tumour and has the worst clinical outcome. Nucleotides represent
an important class of extracellular molecules involved in cell proliferation, differentiation and apoptosis. Alterations in
purinergic signalling have been implicated in pathological processes, such as cancer, and glioma cell lines are widely employed
as a model to study the biology of brain tumours. Increasing evidence, however, suggests that glioma cell lines may not present
all the phenotypic and genetic characteristics of the primary tumours. We have compared the biological characteristics of
C6 rat glioma cells in culture and the same cells after their implantation in the rat brain and growth in culture (denominated
as the C6 ex vivo culture model). Parameters evaluated included cell morphology, differentiation, angiogenic markers, purinergic receptors
and ecto-nucleotidase mRNA profile/enzymatic activity. Analysis of the C6 glioma cell line and C6 ex vivo glioma cultures revealed distinct cell morphologies, although cell differentiation and angiogenic marker expressions were
similar. Both glioma models co-expressed multiple P2X and P2Y receptor subtypes with some differences. In addition, the C6
glioma cell line and C6 ex vivo glioma cultures exhibited similar extracellular ATP metabolism and cell proliferation behaviour when exposed to cytotoxic
ATP concentrations. Thus, the disruption of purinergic signalling is a feature shown not only by glioma cell lineages, but
also by primary glioma cultures. Our results therefore suggest the participation of the purinergic system in glioma malignancy.
This study was supported by grants from the Brazilian agencies CNPq, FAPERGS and Fundo de Incentivo à Pesquisa e Eventos (HCPA).
E. Braganhol and D. Huppes were recipients of Brazilian CNPq fellowships; A. Bernardi was the recipient of a CAPES fellowship. 相似文献
100.
Membrane fission is the last step of membrane carrier formation. As fusion, it is a very common process in eukaryotic cells, and participates in the integrity and specificity of organelles. Although many proteins have been isolated to participate in the various membrane fission reactions, we are far from understanding how membrane fission is mechanically triggered. Here we aim at reviewing the well-described examples of dynamin and lipid phase separation, and try to extract the essential requirements for fission. Then, we survey the recent knowledge obtained on other fission reactions, analyzing the similarities and differences with previous examples. 相似文献