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排序方式: 共有674条查询结果,搜索用时 15 毫秒
1.
Judyta Kruk Irena Baranowska Bogusaw Buszewski Sylwia Bajkacz Bartosz Kowalski Magdalena Ligor 《Chirality》2019,31(2):138-149
Plant material is a rich source of valuable compounds such as flavanones. Their different forms influence bioavailability and biological activity, causing problems with the selection of plant material for specific purposes. The purpose of this research was to determine selected flavanone (eriodictyol, naringenin, liquiritigenin, and hesperetin) enantiomer contents in free form and bonded to glycosides by an RP‐UHPLC‐ESI‐MS/MS method. Different parts (stems, leaves, and flowers) of goldenrod (Solidago virgaurea L.), lucerne (Medicago sativa L.), and phacelia (Phacelia tanacetifolia Benth.) were used. The highest content of eriodictyol was found in goldenrod flowers (13.1 μg/g), where it occurred mainly as the (S)‐enantiomer, and the greatest proportion of the total amount was bonded to glycosides. The richest source of naringenin was found to be lucerne leaves (4.7 μg/g), where it was mainly bonded to glycosides and with the (S)‐enantiomer as the dominant form. Liquiritigenin was determined only in lucerne, where the flowers contained the highest amount (1.2 μg/g), with the (R)‐enantiomer as dominant aglycone form and the (S)‐enantiomer as the dominant glycosylated form. The highest hesperetin content was determined in phacelia leaves (0.38 μg/g), where it was present in the form of a glycoside and only as the (S)‐enantiomer. A comparison of the different analyte forms occurring in different plant parts was performed for the first time. 相似文献
2.
A Dutour P Giraud C Kowalski L Ouafik P Salers V Strbak C Oliver 《Biochemical and biophysical research communications》1987,146(1):354-360
The rapid changes in TRH levels in the rat pancreas during the neonatal period make this organ an interesting model for the study of the regulation of TRH biosynthesis. Pancreatic RNAs were isolated by the guanidinium thiocyanate method and layered onto CsCl cushion. Northern blot preparations were hybridized with 32P labeled TRH cDNA probe. Pancreatic TRH mRNA was first detected in 19-day old fetuses and reached the highest level on day 0, then decreased, being barely detectable 14 days after birth. The neonatal injection of streptozotocin induced a dramatic drop of TRH mRNA levels 24 hours later. This result suggests that the peculiar evolution of TRH level in pancreas is partly due to the evolution of the expression of the TRH gene. 相似文献
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In studies on the effect of pH and temperature on cellulolytic and pectolytic activity of C. destructans, it was found that the isolates used produced only endoglucanases. The temperature and pH affected the synthesis of these enzymes. Fungi cultured at 26°C produced more of these enzymes than those grown at the two other temperatures. At 10°C, only one isolate produced minute amounts of endoglucanases. None of fungi studied exhibited cellulolytic activity in cultures grown at 20°C. Cellulolytic activity was found only in acidic media (pH 5.0). The fungi studied exhibited higher pectolytic than cellulolytic activity. In the post culture liquids of these organisms, both types of pectolytic enzymes (exo- and endo-PMG) were detected. Different temperature and pH values affected the production of these enzymes differently in various isolates. 相似文献
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J L Tilly H Billig K I Kowalski A J Hsueh 《Molecular endocrinology (Baltimore, Md.)》1992,6(11):1942-1950
Recent biochemical studies have suggested that apoptotic cell death is the molecular mechanism underlying the degeneration of ovarian follicles during atresia. Using a sensitive autoradiographic method for the detection of DNA fragmentation, we studied apoptosis in ovarian granulosa cells or intact follicles placed in serum-free culture as model systems to elucidate the hormonal regulation of atresia. Immature rats (25 days old) were primed for 2 days with 10 IU equine CG to induce a homogeneous population of mature preovulatory follicles. Granulosa cells isolated from these follicles contained predominantly intact high mol wt DNA. However, a time-dependent, spontaneous onset of internucleosomal DNA fragmentation characteristic of apoptotic cell death occurred in granulosa cells during culture. Treatment of granulosa cells with epidermal growth factor (EGF), transforming growth factor-alpha (TGF alpha), or basic fibroblast growth factor (bFGF) inhibited the spontaneous onset of apoptotic DNA cleavage found during culture by 40-60%. In contrast, insulin-like growth factor I, insulin, TGF beta and tumor necrosis factor-alpha were ineffective. Likewise, activation of the protein kinase A or C pathways with forskolin or phorbol 12-myristate 13-acetate, respectively, did not prevent the onset of DNA fragmentation, although inclusion of a tyrosine kinase inhibitor (genistein) completely blocked the ability of EGF, TGF alpha, and bFGF to suppress apoptosis in granulosa cells. Similar to cultured granulosa cells, a spontaneous onset of apoptosis was also observed to occur in isolated preovulatory follicles during culture. Furthermore, treatment of follicles with EGF or bFGF inhibited the spontaneous initiation of apoptosis, and the suppressive effects of these growth factors were also attenuated by co-treatment with genistein.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
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A comparative description of mitochondrial DNA differentiation in selected avian and other vertebrate genera 总被引:14,自引:1,他引:13
Levels of mitochondrial DNA (mtDNA) sequence divergence between species
within each of several avian (Anas, Aythya, Dendroica, Melospiza, and
Zonotrichia) and nonavian (Lepomis and Hyla) vertebrate genera were
compared. An analysis of digestion profiles generated by 13-18 restriction
endonucleases indicates little overlap in magnitude of mtDNA divergence for
the avian versus nonavian taxa examined. In 55 interspecific comparisons
among the avian congeners, the fraction of identical fragment lengths (F)
ranged from 0.26 to 0.96 (F = 0.46), and, given certain assumptions, these
translate into estimates of nucleotide sequence divergence (p) ranging from
0.007 to 0.088; in 46 comparisons among the fish and amphibian congeners, F
values ranged from 0.00 to 0.36 (F = 0.09), yielding estimates of P greater
than 0.070. The small mtDNA distances among avian congeners are associated
with protein-electrophoretic distances (D values) less than approximately
0.2, while the mtDNA distances among assayed fish and amphibian congeners
are associated with D values usually greater than 0.4. Since the
conservative pattern of protein differentiation previously reported for
many avian versus nonavian taxa now appears to be paralleled by a
conservative pattern of mtDNA divergence, it seems increasingly likely that
many avian species have shared more recent common ancestors than have their
nonavian taxonomic counterparts. However, estimates of avian divergence
times derived from mtDNA- and protein-calibrated clocks cannot readily be
reconciled with some published dates based on limited fossil remains. If
the earlier paleontological interpretations are valid, then protein and
mtDNA evolution must be somewhat decelerated in birds. The empirical and
conceptual issues raised by these findings are highly analogous to those in
the long-standing debate about rates of molecular evolution and times of
separation of ancestral hominids from African apes.
相似文献
10.
Methods for computing the standard errors of branching points in an evolutionary tree and their application to molecular data from humans and apes 总被引:23,自引:2,他引:21
Statistical methods for computing the standard errors of the branching
points of an evolutionary tree are developed. These methods are for the
unweighted pair-group method-determined (UPGMA) trees reconstructed from
molecular data such as amino acid sequences, nucleotide sequences,
restriction-sites data, and electrophoretic distances. They were applied to
data for the human, chimpanzee, gorilla, orangutan, and gibbon species.
Among the four different sets of data used, DNA sequences for an
895-nucleotide segment of mitochondrial DNA (Brown et al. 1982) gave the
most reliable tree, whereas electrophoretic data (Bruce and Ayala 1979)
gave the least reliable one. The DNA sequence data suggested that the
chimpanzee is the closest and that the gorilla is the next closest to the
human species. The orangutan and gibbon are more distantly related to man
than is the gorilla. This topology of the tree is in agreement with that
for the tree obtained from chromosomal studies and DNA-hybridization
experiments. However, the difference between the branching point for the
human and the chimpanzee species and that for the gorilla species and the
human-chimpanzee group is not statistically significant. In addition to
this analysis, various factors that affect the accuracy of an estimated
tree are discussed.
相似文献