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Wingfield BD; Grant WS; Wolfaardt JF; Wingfield MJ 《Molecular biology and evolution》1994,11(3):376-383
The genus Ceratocystis sensu stricto includes important fungal pathogens of
woody and herbaceous plants. This genus is distinguished from species in
Ceratocystis sensu lato by the presence of Chalara anamorphs. Ascospore
shape has been used extensively in delineating Ceratocystis taxa, which
show a large variety of ascospore shapes. Sequence analysis of one region
of he 18S ribosomal RNA subunit and two regions of the 28S ribosomal RNA
subunit showed that there was a majority of multiple substitutions at
nucleotide sites and that there was a low transition/transversion ratio, T
= 0.72. Both of these results suggest that these are well established, old
species. Ascospore morphology, for the most part, was not congruent with
the molecular phylogeny, and the use of morphological characters may be
misleading in the taxonomy of these species.
相似文献
35.
MJ Doughty 《Biotechnic & histochemistry》2016,91(8):501-509
Goblet cells were visualized in impression cytology specimens from bulbar conjunctiva of the rabbit eye using Giemsa staining. Highly magnified images were used to generate outlines of the goblet cells and their characteristic eccentric nuclei. Using sets of 10 cells from 15 cytology specimens, I found that the longest dimension of the goblet cells averaged 16.7 ± 2.3 μm, the shortest dimension averaged 14.4 ± 1.8 μm and the nucleus averaged 6.3 ± 0.8 μm. The goblet cells were ellipsoid in shape and the longest:shortest cell dimension ratio averaged 1.169 ± 0.091. The goblet cell areas ranged from 108 to 338 μm2 (average 193 ± 50 μm2). The area could be predicted reliably from the longest and shortest dimensions (r2 = 0.903). The areas of goblet cell nuclei were 15–58 μm2 (average 33 ± μm2) and the nucleus:cytoplasm area fraction was predictably greater in smaller goblet cells and less in the larger goblet cells (Spearman correlation = 0.817). The nuclei were estimated to occupy an average of 9.5% of the cell volume. The differences in size, shape and nucleus:cytoplasm ratio may reflect differences in goblet cell maturation. 相似文献
36.
Winterer G Smolka M Samochowiec J Mulert C Ziller M Mahlberg R Wuebben Y Gallinat J Rommelspacher H Herrman WM Sander T 《Human genetics》2000,107(5):513-518
Gamma-aminobutyric acid (GABA)A-receptors play a crucial role in the generation of electroencephalogram (EEG) oscillations and evoked potentials (ERPs). The present association study was designed to test whether EEG and ERPs are modulated by genetic variations of the human GABAA beta2 (GABRB2) and gamma2 (GABRG2) genes on chromosome 5q33. The genotypes of two nucleotide substitution polymorphisms of the GABRB2 and GABRG2 genes were assessed in 95 psychiatrically healthy subjects of German descent. Neurophysiological phenotyping was performed with four factorized EEG/ERP parameters: EEG activation, anterior and posterior EEG synchronization, and event-related activity (N100/ P200-complex). No genotypic association was found for the GABRB2 nucleotide exchange polymorphism with any electrophysiological parameter. A significant association was found between the genotype of the intronic GABRG2 G-->A nucleotide exchange and the event-related N100/P200 (ANOVA: F=3.81; df=2; P=0.026). A comparison of homozygous subjects carrying either the G/G or A/A genotype of the GABRG2 polymorphism consistently revealed an even stronger difference in the effect-size (ANOVA: F=11.13; df=1; P=0.002). Post hoc analysis of this association with current density analysis in three-dimensional neuroanatomic Talairach space-time showed a reduction in the event-related signal power after 120 ms in the right dorsolateral prefrontal cortex. Taking into account the risk of false-positive association findings attributable to multiple testing, our results encourage further replication studies to examine the phenotype-genotype relationship of GABRG2 gene variants and event-related prefrontal activity. 相似文献
37.
The avian spinal cord is characterized by an absence of motor nerves and sensory nerves and ganglia at its caudalmost part. Since peripheral sensory neurons derive from neural crest cells, three basic mechanisms could account for this feature: (i) the caudalmost neural tube does not generate any neural crest cells; (ii) neural crest cells originating from the caudal part of the neural tube cannot give rise to dorsal root ganglia or (iii) the caudal environment is not permissive for the formation of dorsal root ganglia. To solve this problem, we have first studied the pattern of expression of ventral (HNF3beta) and dorsal (slug) marker genes in the caudal region of the neural tube; in a second approach, we have recorded the emergence of neural crest cells using the HNK1 monoclonal antibody; and finally, we have analyzed the developmental potentials of neural crest cells arising from the caudalmost part of the neural tube in avian embryo in in vitro culture and by means of heterotopic transplantations in vivo. We show here that neural crest cells arising from the neural tube located at the level of somites 47-53 can differentiate both in vitro and in vivo into melanocytes and Schwann cells but not into neurons. Furthermore, the neural tube located caudally to the last pair of somites (i.e. the 53rd pair) does not give rise to neural crest cells in any of the situations tested. The specific anatomical aspect of the avian spinal cord can thus be accounted for by limited developmental potentials of neural crest cells arising from the most caudal part of the neural tube. 相似文献
38.
Nikolausz M Kappelmeyer U Nijenhuis I Ziller K Kästner M 《Systematic and applied microbiology》2005,28(7):582-587
A phylogenetic analysis of 6 strains of dichloromethane (DCM) utilizing bacteria was performed. Based on the almost complete 16S rDNA sequence determination, all strains clustered together and showed high sequence similarity to Hyphomicrobium denitrificans, except for the strain MC8b, which is only moderately related to them and probably represents a distinct species. The 16S rDNA-based phylogenetic tree was compared to the one obtained from the DNA sequence data of the dcmA gene coding DCM dehalogenase, the key enzyme of DCM utilization. The topology of the two trees is in good agreement and may suggest an ancient origin of DCM dehalogenase, but also raises questions about the original role of the enzyme. 相似文献
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What's in a name; Genetic structure in Solanum section Petota studied using population-genetic tools
Mirjam MJ Jacobs Marinus JM Smulders Ronald G van den Berg Ben Vosman 《BMC evolutionary biology》2011,11(1):42