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991.
Andrea Hoffmann Manfred Nimtz Ulrich Wurster † Harald S. Conradt 《Journal of neurochemistry》1994,63(6):2185-2196
Abstract: The carbohydrate structures of β-trace protein from human cerebrospinal fluid have been elucidated. This protein carries exclusively N-linked oligosaccharides at two sites (Asn29 and Asn56 ). Enzymatically released N -glycans were studied by compositional and methylation analyses, high-pH anion-exchange chromatography, and liquid secondary ion mass spectrometry. All glycans were found to be of the complex type, and most (90%) of them were biantennary with no (40%), one (40%), or two (20%) N -acetylneuraminic acid residues. The rest were triantennary chains or biantennary chains with intact or truncated lactosamine repeats. The innermost N -acetylglucosamine residues of nearly all structures were found to be α1,6-fucosylated. Peripheral fucose (about 20%α1,3-linked to N -acetylglucosamine) was also detected. Seventy percent of the oligosaccharides contained a bisecting N -acetylglucosamine. Especially in the neutral, but also in the monosialylated oligosaccharide fractions, many incomplete antennae consisting of N -acetylglucosamine only were present. At least 20 different N -glycans were identified. Analysis of the site-specific glycosylation patterns at Asn29 and Asn56 revealed only minor differences. According to the structural features (a high degree of fucosylation, high amounts of bisecting N -acetylglucosamine, as well as terminal N -acetylglucosamine and galactose residues, and significant amounts of N -acetylneuraminic acid in α2,3 linkage), this protein can be classified as "brain-type" glycosylated. 相似文献
992.
Telomeric repeat sequences 总被引:6,自引:0,他引:6
Chromosomes not only carry transcribed genes and their regulatory DNA sequences, but also contain regions that are required for the stability and maintenace of the chromosome as a unit. These include centromeres, telomeres and origins of replication. It is clear for replication origins and centromeres that the positions of these chromosomal organelles are determined by sites of the appropriate DNA sequences, but also that functional performance requires one or more contributing proteins. Telomeres are also structurally complex, with one or more DNA components, including simple telomeric repeats and more complex telomere-associated sequences, as well as one or more specific proteins that recognize these sequences. Accumulating evidence suggests that the simple telomeric repeats are required in most, but not all species, although they are not sufficient to determine the chromosomal position of a telomere. 相似文献
993.
Ådne M. Nafstad Bernt Rønning Kenneth Aase Thor Harald Ringsby Ingerid J. Hagen Peter S. Ranke Thomas Kvalnes Clare Stawski Katja Räsänen Bernt-Erik Sæther Stefanie Muff Henrik Jensen 《Journal of evolutionary biology》2023,36(4):650-662
An organism's energy budget is strongly related to resource consumption, performance, and fitness. Hence, understanding the evolution of key energetic traits, such as basal metabolic rate (BMR), in natural populations is central for understanding life-history evolution and ecological processes. Here we used quantitative genetic analyses to study evolutionary potential of BMR in two insular populations of the house sparrow (Passer domesticus). We obtained measurements of BMR and body mass (Mb) from 911 house sparrows on the islands of Leka and Vega along the coast of Norway. These two populations were the source populations for translocations to create an additional third, admixed ‘common garden’ population in 2012. With the use of a novel genetic group animal model concomitant with a genetically determined pedigree, we differentiate genetic and environmental sources of variation, thereby providing insight into the effects of spatial population structure on evolutionary potential. We found that the evolutionary potential of BMR was similar in the two source populations, whereas the Vega population had a somewhat higher evolutionary potential of Mb than the Leka population. BMR was genetically correlated with Mb in both populations, and the conditional evolutionary potential of BMR (independent of body mass) was 41% (Leka) and 53% (Vega) lower than unconditional estimates. Overall, our results show that there is potential for BMR to evolve independently of Mb, but that selection on BMR and/or Mb may have different evolutionary consequences in different populations of the same species. 相似文献
994.
Christina Uth Simon Englert Olga Avrutina Harald Kolmar Sascha Knauer 《Journal of peptide science》2023,29(12):e3527
We report the first application of a novel amino-Li resin to water-based solid-phase peptide synthesis (SPPS) applying the Smoc-protecting group approach. We demonstrated that it is a suitable support for the sustainable water-based alternative to a classical SPPS approach. The resin possesses good swelling properties in aqueous milieu, provides significant coupling sites, and may be applicable to the synthesis of difficult sequences and aggregation-prone peptides. 相似文献
995.
Masahiko Yamaguchi Scott Diamond Hiroyuki Watanabe Harald Gallati Wendy Baur John B. Sharefkin 《In vitro cellular & developmental biology. Animal》1993,29(11):867-872
Summary Increased expression of basic fibroblast growth factor (bFGF), platelet-derived growth factor (PDGF) A chain, and tissue plasminogen
activator (tPA) by smooth muscle cells (SMC) has been postulated to mediate the progression of intimal hyperplasia. We tested
whether heparin would suppress the expression of these genes in stimulated human saphenous vein SMC. Quiescent cultured human
saphenous vein SMC were stimulated for 4 h with heat-inactivated fetal bovine serum (10% by vol) in the presence or absence
of heparin (1 to 250μg/ml). Heparin (50μg/ml) attenuated the induction by serum of bFGF mRNA, tPA mRNA, and tPA secretion. Nonanticoagulant heparin also attenuated
serum induction of bFGF and tPA mRNA levels. To further study the role of second messenger signaling, a more specific mode
of SMC stimulation was used with thrombin (3 U/ml) in the presence or absence of dibutyryl cyclic AMP (Bu2-cAMP; 0.5 mM). In contrast to heparin, which had no effect on PDGF expression, Bu2-cAMP decreased the induction by thrombin of PDGF-A chain mRNA levels. In thrombin-stimulated SMC, Bu2-cAMP significantly decreased secretion of PDGF-AA protein. Thrombin, however, caused an increase in bFGF mRNA levels which
was potentiated by Bu2-cAMP with associated potentiation by Bu2-cAMP of intracellular bFGF protein levels. The induction of tPA mRNA and tPA secretion by thrombin was sharply blocked by
Bu2-cAMP. These results suggest that heparin reduces intimal hyperplasia at least partly via partial inhibition of SMC gene expression. 相似文献
996.
The pioneer tree Macaranga in SE Asia has developed manyfold associations with ants. The genus comprises all stages of interaction with ants, from facultative relationships to obligate myrmecophytes. Only myrmecophytic Macaranga offer nesting space for ants and are associated with a specific ant partner. The nonmyrmecophytic species are visited by a variety of different ant species which are attracted by extrafloral nectaries (EFN) and food bodies. Transitional Macaranga species like M. hosei are colonized later in their development due to their stem structure. Before the colonization by their specific Crematogaster partner the young plants are visited by different ant species attracted by EFN. These nectaries are reduced and food body production starts as soon as colonization becomes possible. We demonstrated earlier that obligate ant partners can protect their Macaranga plants against herbivore damage and vine cover. In this study we focused on nonspecific interactions and studied M. tanarius and M. hosei, representing a non-myrmecophyte and a transitional species respectively. In ant exclusion experiments both M. tanarius and M. hosei suffered significantly higher mean leaf damage than controls, 37% versus 6% in M. hosei, 16% versus 7% in M. tanarius. M. tanarius offers both EFN and food bodies so that tests for different effects of these two food rewards could be conducted. Plants with food bodies removed but with EFN remaining had the lowest mean increase of herbivore damage of all experimental groups. Main herbivores on M. hosei were mites and caterpillars. Many M. tanarius plants were infested by a shootborer. Both Macaranga species were visited by various ant species, Crematogaster spp. being the most abundant. We found no evidence for any specific relationships. The results of this study strongly support the hypothesis that non-specific, facultative associations with ants can be advantageous for Macaranga plants. Food bodies appear to have lower attractive value for opportunistic ants than EFN and may require a specific dietary adaptation. This is also indicated by the fact that food body production in the transitional M. hosei does not start before stem structure allows a colonization by the obligate Crematogaster species. M. hosei thus benefits from facultative association with a variety of ants until it produces its first domatia and can be colonized by its obligate mutualist. 相似文献
997.
María Teresa Boquete Zulema Varela José Angel Fernández Juan Antonio Calleja Cristina Branquinho Antonina Chilà Nils Cronberg Ricardo Cruz de Carvalho Cristiana Aleixo Belén Estébanez‐Pérez Verónica Fernández‐González rés Baselga Carola Gómez‐Rodríguez Juana María González‐Mancebo Sebastien Leblond Javier Martínez‐Abaigar Nagore G. Medina Encarnación Núñez‐Olivera Jairo Patiño Rubén Retuerto Antón Vázquez‐Arias Alain Vanderpoorten Harald G. Zechmeister Jesús Ramón Aboal 《植物分类学报:英文版》2023,61(1):213-226
Unisexual bryophytes provide excellent models to study the mechanisms that regulate the frequency of sexual versusasexual reproduction in plants, and their ecological and evolutionary implications. Here, we determined sex expression, phenotypic sex ratio, and individual shoot traits in 242 populations of the cosmopolitan moss Pseudoscleropodium purum spanning its whole distributional range. We tested whether niche differentiation, sex-specific differences in shoot size, and biogeographical history explained the spatial variation of reproductive traits. We observed high levels of sex expression and predominantly female-biased populations, although both traits showed high intraspecific variation among populations. Sex expression and sex ratio were partly explained by current macroscale environmental variation, with male shoots being less frequent at the higher end of the environmental gradients defined by the current distribution of the species. Female bias in population sex ratio was significantly lower in areas recolonized after the last glacial maximum (recent populations) than in glacial refugia (long-term persistent populations). We demonstrated that reproductive trait variation in perennial unisexual mosses is partially driven by macroscale and historical environmental variation. Based on our results, we hypothesize that sexual dimorphism in environmental tolerance and vegetative growth contribute to sex ratio bias over time, constraining the chances of sexual reproduction, especially in long-term persistent populations. Further studies combining genetic analyses and population monitoring should improve our understanding of the implications of the intraspecific variation in the frequency of sexual versusasexual reproduction in bryophyte population fitness and eco-evolutionary dynamics. 相似文献
998.
The fern family Polypodiaceae, with over 1600 species, is not only one of the most species-rich families of ferns, but also a major contributor to the vascular epiphytic diversity throughout the tropics. Although the vast majority of species belonging to this family prefer to grow as epiphytes, several species colonize successfully rheophytic, lithophytic, and even terrestrial habitats. Here, we explore the hypothesis that non-epiphytic habitat preferences, including terrestrial growth, evolved secondarily with epiphytes being the plesiomorphic habitat preference. The results of phylogenetic analyses, based on dense taxon sampling and four chloroplast DNA regions, were integrated with divergence time estimates and ancestral character state reconstructions to test these predictions. Both fossils and secondary calibration data were incorporated to obtain divergence time estimations. The results support the prediction of multiple transitions from epiphytic/lithophytic to terrestrial/rheophytic habitats occurring mainly in the Microsoreae lineage. The change in niche preferences coincides with niche colonization opportunities created by climatic fluctuations and geographical changes during the Oligocene and Miocene periods. 相似文献
999.
The cartilaginous fish Chimaera monstrosa swims slowly by means of pectoral fin movements, and fast by undulations of the tail. In order to compare the fibres in the corresponding muscles, they were studied by histochemistry and electron microscopy. Three fibre types were identified by microphotometry and morphometry. Most of the axial muscles are white fibres, containing little mitochondria and glycogen. Red fibres, with glycogen and about 5 % mitochondria constitute a thin sheet in the axial muscles, composed of one fibre layer only. Pink fibres, with intermediate amounts of glycogen and mitochondria are situated between these two types, but are often not covered by red fibres. Pectoral muscles contain numerous red and intermediate fibres, partially mixed, superficially, and white fibres deeper. Pectoral muscle red fibres contain about 25 % mitochondria, half of which are situated in subsarcolemmal accummulations. The sarcotubular system has T-tubules at the Z discs, and the terminal cisternae are partially divided by regularly spaced clefts. 相似文献
1000.
After injection of radioactively labelled Cortisol, the distribution of the radioactivity in the subcellular fractions of the rat uterus (nuclei, mitochondria, microsomes and 105 000 × g supernatant) was studied. In all fractions, radioactivity was observed and maxima were found 10, 20 and 50 min. after injection of the labelled hormone. Radioactivity was measured in all subcellular fractions even 180 min. after application of labelled cortisol. Additionally, radiolabelled progesterone and unlabelled cortisol in the ratio 1:1 or 1:2 (moles:moles) were injected into the animals. Studying the uptake of labelled progesterone in the subcellular fractions of the uterine tissue, revealed that no competition of unlabelled cortisol could be observed 10, 20 and 50 min. after application of the hormone mixture, compared with the control experiments. The results of this study give evidence that the progesterone uptake into rat uterus is specific and cannot be influenced by unlabelled cortisol. 相似文献