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Annemarie MM Vlaar Tjerk de Nijs Marinus JPG van Kroonenburgh Werner H Mess Ania Winogrodzka Selma C Tromp Wim EJ Weber 《BMC neurology》2008,8(1):42
Background
Transcranial duplex sonography (TCD) of the substantia nigra has emerged as a promising, non-invasive tool to diagnose idiopathic Parkinson's disease (IPD). However, its diagnostic accuracy in patients with undefined parkinsonism remains to be determined. 相似文献66.
Sterigmatocystin (STG) is a toxic metabolite produced by severalAspergillus species. Because of its toxic and carcinogenic properties the occurrence of STG in food is considered to represent a potential
hazard to man. The present study was designed to investigate following points:
相似文献
1 | A survey of STG incidence in Ras cheese on local markets. Ras cheese samples were collected from Cairo, Giza and Kalubia governorates. Thirty five percent of the samples contained the toxin with a mean value of 22.23 μg /kg |
2 | Fate of STG contaminating milk during Ras cheese processing. Milk was artificially contaminated with 125 μg/kg and processed into Ras cheese. Eighty percent of the toxin was distributed into the curd and 20% into the whey. Cheese ripening effected toxin content and the effect was temperature dependent. At 6°C: toxin concentration was slightly affected; at 20°C the toxin was reduced by 16% after 90 days when low toxin concentration was used. |
3 | Formation of STG byA versicolor mold on Ras cheese. Ras cheese blocks were contaminated with spores of the mold. Toxin production started after 45 days of ripening and reached a maximum at 90 days and then declined. Cow’s milk favoured toxin production over buffaloe’s. Aged cheese inhibited toxin production. |
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Howe GT; Bucciaglia PA; Hackett WP; Furnier GR; Cordonnier-Pratt MM; Gardner G 《Molecular biology and evolution》1998,15(2):160-175
The phytochrome photoreceptors play important roles in the photoperiodic
control of vegetative bud set, growth cessation, dormancy induction, and
cold-hardiness in trees. Interestingly, ecotypic differences in
photoperiodic responses are observed in many temperate- zone tree species.
Northern and southern ecotypes of black cottonwood (Populus trichocarpa
Torr. & Gray), for example, exhibit marked differences in the timing of
short-day-induced bud set and growth cessation, and these responses are
controlled by phytochrome. Therefore, as a first step toward determining
the molecular genetic basis of photoperiodic ecotypes in trees, we
characterized the phytochrome gene (PHY) family in black cottonwood. We
recovered fragments of one PHYA and two PHYB using PCR-based cloning and by
screening a genomic library. Results from Southern analyses confirmed that
black cottonwood has one PHYA locus and two PHYB loci, which we arbitrarily
designated PHYB1 and PHYB2. Phylogenetic analyses which included PHY from
black cottonwood, Arabidopsis thaliana and tomato (Solanum lycopersicum)
suggest that the PHYB/D duplications in these species occurred
independently. When Southern blots were probed with PHYC, PHYE, and PHYE
heterologous probes, the strongest bands that we detected were those of
black cottonwood PHYA and/or PHYB. These results suggest that black
cottonwood lacks members of the PHYC/F and PHYE subfamilies. Although black
cottonwood could contain additional PHY that are distantly related to known
angiosperm PHY, our results imply that the PHY family of black cottonwood
is less complex than that of other well-characterized dicot species such as
Arabidopsis and tomato. Based on Southern analyses of five black cottonwood
genotypes representing three photoperiodic ecotypes, substantial
polymorphism was detected for at least one of the PHYB loci but not for the
PHYA locus. The novel character of the PHY family in black cottonwood, as
well as the differences in polymorphism we observed between the PHYA and
PHYB subfamilies, indicates that a number of fundamental macro- and
microevolutionary questions remain to be answered about the PHY family in
dicots.
相似文献
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Testing the covarion hypothesis of molecular evolution 总被引:14,自引:8,他引:6
The covarion hypothesis of molecular evolution states that the fixation of
mutations may alter the probability that any given position will fix the
next change. Tests of this hypothesis using the divergence of real
sequences are compromised because models of rate variation among sites
(e.g., the gamma version of the one-parameter equation) predict sequence
divergence values similar to those for the covarion process. This study
therefore focuses on the extent to which the varied and unvaried codons of
two well-diverged taxa are the same, because fewer are expected by the
covarion hypothesis than by the gamma model. The data for these tests are
the protein sequences of Cu, Zn superoxide dismutase (SOD) for mammals and
plants. Simulation analyses show that the covarion hypothesis makes better
predictions about the frequencies of varied and unhit positions in common
between these two taxa than does the gamma version of the one-parameter
model. Furthermore, the analysis of SOD tertiary structure demonstrates
that mammal and plant variabilities are distributed differently on the
protein. These results support the conclusions that the variable and
invariable codons of mammal and plant SODs are different and that the
covarion model explains the evolution of this protein better than the gamma
version of the one-parameter process. Unlike other models, the covarion
hypothesis accounts for rate fluctuations among positions over time, which
is an important parameter of molecular evolution.
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