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101.
102.
The time course of the induction of callose in wounded pea roots 总被引:2,自引:0,他引:2
Summary Initial study indicated that much callose is produced in pea root tissues during the preparation of fresh hand-cut sections or during conventional fixation in formalin-acetic acid-alcohol, glutaraldehyde or acrolein. In contrast, there is little callose in freeze-substituted tissues and this is mostly in sieve tubes and considered endogenous. Freeze-substitution was subsequently used to monitor wound-induced callose development in the various tissues of pea roots. This development was fastest in the phloem, first detected 1 minute post-wounding and complete by 3 hours. In some parenchyma cells full development was delayed by 20 hours. By 100 hours, wound callose was no longer detectable in parenchyma cells but remained undiminished in the phloem. The implications of these results for all studies involving callose localization are discussed.Abbreviations C
callose
- FAA
formalin-acetic acid-alcohol
- GMA
glycol methacrylate
- P
phloem
- PAS
periodic acid-Schiffs
- PF
phloem fibres
- PP
pith parenchyma
- PW
post-wounding 相似文献
103.
Expression of biologically active human follitropin in Chinese hamster ovary cells 总被引:13,自引:0,他引:13
J L Keene M M Matzuk T Otani B C Fauser A B Galway A J Hsueh I Boime 《The Journal of biological chemistry》1989,264(9):4769-4775
To study the structure-function relationships of follitropin (FSH), we expressed the hormone in a heterologous cell system. A genomic clone bearing a 3.7-kilobase FSH beta insert containing the entire coding sequence was transfected alone or together with the alpha subunit gene into Chinese hamster ovary cells and stable lines expressing either FSH beta or FSH dimer were selected. Pulse-chase experiments revealed that, when transfected alone FSH beta was very slowly secreted similar to lutropin beta and thyrotropin beta but unlike choriogonadotropin beta which is efficiently secreted. However, cotransfection of the FSH beta and alpha subunit genes resulted in "rescue" of the beta subunit and rapid secretion of dimer. These data support the hypothesis that the glycoprotein hormones of pituitary origin have determinants for secretion that differ from those on the placental hormone, choriogonadotropin. Recombinant FSH stimulated steroidogenesis comparable to purified human FSH isolated from pituitaries in an in vitro rat granulosa cell assay and appears more homogeneous by chromatofocusing. Human FSH produced by this cell line provides a source of bioactive FSH for experimental and clinical use. 相似文献
104.
Ustilago maydis, the causal agent of corn smut disease, displays dimorphic growth in which it alternates between a unicellular, nonpathogenic yeast-like form and a dikaryotic, pathogenic filamentous form. Previously, a constitutively filamentous haploid mutant was obtained. Complementation of this mutant led to the isolation of the gene encoding adenylate cyclase, uac1. Secondary mutagenesis of a uac1 disruption strain allowed the isolation of a large number of suppressor mutants, termed ubc, for Ustilago bypass of cyclase, lacking the filamentous phenotype. Analysis of one of these suppressor mutants previously led to the identification of the ubc1 gene, encoding the regulatory subunit of cAMP-dependent protein kinase. In this report we describe the isolation of cosmids containing three new ubc genes, termed ubc2, ubc3, and ubc4. We also describe the morphology of the ubc2, ubc3, and ubc4 mutants in a uac1- background as well as in a background with a functional uac1 gene. In addition, we describe several mutant strains not complemented with any of the genes currently in hand and that are thus presumed to possess mutations in additional ubc genes. Copyright 1998 Academic Press. 相似文献
105.
The taste of polycose in hamsters 总被引:2,自引:2,他引:0
Hamsters show a preference for Polycose, a mixture of starch-derived
glucose polymers, that is as strong as their preference for sucrose.
However, in the hamster, taste aversions to Polycose may be less easily
acquired than taste aversions to sucrose and the qualitative aspects of
Polycose are unknown in this species. In order to examine the taste of
Polycose in the hamster, we utilized a taste-aversion protocol with two
conditioning trials. Animals were trained to avoid one of three different
conditioning stimuli: 50 mM sucrose, 100 mM Polycose and a mixture of 50 mM
sucrose with 100 mM Polycose. Control animals were conditioned with
deionized water. After the second conditioning trial, generalization
testing began for the three conditioning stimuli plus 3 mM citric acid, 300
mM KCI and 30 mM NaCl. The results showed that aversions to Polycose,
sucrose or the Polycose/sucrose mixture cross- generalized, demonstrating
that Polycose and sucrose share a common taste percept in the hamster. None
of the aversions generalized to NaCl, citric acid or KCI. In addition,
comparisons among the patterns of taste generalizations indicated that the
tastes of Polycose and sucrose also had distinct qualitative components.
Finally, although the taste of 100 mM Polycose was more salient than the
taste of 50 mM sucrose, the taste of sucrose could still be detected in a
mixture with Polycose.
相似文献
106.
S. Gedik ME Erdemli M Gul B Yigitcan H Gozukara Bag Z Aksungur 《Biotechnic & histochemistry》2018,93(4):267-276
We investigated repair of acrylamide (AA) induced damage in intestines by administration of crocin. We used 40 male Wistar rats in four groups of 10 animals: control, AA, crocin, and AA + crocin groups. We investigated biochemical and histological changes to small and large intestine. AA ingestion decreased glutathione (GSH) levels and total antioxidant status (TAS) in the intestine compared to the control group, while superoxide dismutase (SOD) and catalase (CAT) activities, and total oxidant status (TOS) and malondialdehyde (MDA) levels were increased. Villi were shortened and villus degeneration was observed in ileum of the AA group. Degeneration of surface epithelium and Liberkühn crypts were observed in colon sections. GSH and TAS levels increased after administration of AA together with crocin, while SOD and CAT levels and TOS and MDA levels decreased; significant recovery of histological damage also was observed. We found that crocin exhibits protective effects on AA induced small and large intestine damage by inhibiting oxidative stress. 相似文献
107.
The growth of the freshwater microalga Scenedesmus obliquus was studied at 30°C in a mineral culture medium with phosphorus concentrations of between 0 and 372 μ
. The values for the specific growth rates, between
and
, fitted a semistructured substrate-limitation model with μm1 = 0·0466 h−1, μm2 = 0·0256 h−1 and
. The specific uptake rate of phosphorus reached a maximum value of qSm1 = 658·01 × 10−4 μmol P mg−1 biomass h−1. 相似文献
108.
109.
The endangered Uluguru Bush Shrike Malaconotus alius is a large, black-headed bush shrike, strictly endemic to the Uluguru Mountains in Tanzania. It has recently been suggested that this species has been misplaced within the genus Malaconotus and might instead be related to Malagasy Vangidae. To assess its systematic affinities, we analysed 1518 bp of sequence data obtained from a nuclear intron (myoglobin intron-2) and a mitochondrial protein-coding gene (ND2) using parsimony, maximum likelihood and Bayesian inference. Both genes strongly support the traditional placement within the genus Malaconotus , suggesting that similarities between the Uluguru Bush Shrike and the Vangidae are due to convergence. These results caution that taxonomic changes should not be made without a proper character analysis (i.e. assignment of character homology). 相似文献
110.
JÉRÔME SUEUR DAN VANDERPOOL CHRIS SIMON DAVID OUVRARD THIERRY BOURGOIN 《Biological journal of the Linnean Society. Linnean Society of London》2007,91(4):611-626
To estimate the potential contribution of ethological and ecological parameters to the mechanisms of species formation and species isolation in the Palearctic cicada genus Tibicina , we constructed a molecular phylogenetic hypothesis of extant Tibicina species. Seven mitochondrial genes and a fragment of a nuclear gene were sequenced (3046 bp). Mitochondrial genes included 547 informative sites but the nuclear gene was too conserved to be included in the analysis. The tree was characterized by a basal polytomy indicating that Tibicina species arose rapidly. Such rapid radiation might explain the low divergence in the acoustic communication observed between species. Parameters describing habitat selection and acoustic communication were mapped onto the tree. A shift in habitat selection accompanied by acoustic changes might have contributed to one speciation event. The stochastic distribution of the same acoustic characters on the other branches of the tree implies, however, that the subtle acoustic differences between species could be the result of previous speciation events and independent evolutionary histories, rather than having contributed themselves in the speciation and isolation processes. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 91 , 611–626. 相似文献