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1.
2.
The effect of phenylephrine, an alpha-1 adrenergic agonist, on development of body asymmetry was studied using a rat whole embryo culture system. Embryos were explanted at the presomite stage, cultured in 100% rat serum containing various concentrations of phenylephrine, and examined at the 20-25 somite stage for sidedness of asymmetric body structures, namely, bulboventricular loop, allantoic placenta, and tail. Phenylephrine treatment resulted in a dose-dependent increase of situs inversus with a maximum incidence of 52%. Coadministration of prazosin, an alpha-1 adrenergic antagonist, almost completely prevented this effect. Our results suggest that receptor-mediated stimulation of the alpha-1 adrenergic pathway is involved in the control of normal body asymmetry in developing rat embryos. 相似文献
3.
Halothane prevents nitrous oxide teratogenicity in Sprague-Dawley rats; folinic acid does not 总被引:1,自引:0,他引:1
The teratogenic effects of nitrous oxide (N2O) administered with halothane or folinic acid (FA) were studied in two separate experiments using a total of 206 timed-pregnant Sprague-Dawley rats. In each experiment, rats were exposed to either 1) air (n = 30-40); 2) N2O (50-75% for 24 h on day 8 of pregnancy, n = 20-30); 3) test agent (i.e., 0.27% halothane for 24 h on day 8 of pregnancy; or 5 mg/kg/day of FA on day 5-13 of pregnancy, subcutaneously by osmotic pump, n = 20-30); or 4) N2O + test agent (n = 20-30). Cesarean sections were performed on day 20, and fetuses were examined for visceral and skeletal abnormalities. There were no differences in pregnancy rate, number of implantations and live fetuses per rat, and fetal weight among any of the groups. Treatment with N2O resulted in significantly higher incidences of resorptions and of major visceral and minor skeletal abnormalities. Halothane administered with N2O protected against these effects; folinic acid did not. Using an additional 65 nonpregnant rats, hepatic methionine synthase activity was measured after treatment with 50% N2O, 50% N2O plus 0.27% halothane, or 50% N2O plus 5 mg/kg/day of folinic acid. Methionine synthase activity was equally depressed in all groups. These findings do not support the commonly held theory that inactivation of methionine synthase is the sole cause of N2O teratogenicity; rather, they suggest a multifactorial etiology, which may include changes in uterine blood flow. 相似文献
4.
Morphological and hybridization studies were carried out in H. pubiflorum s. 1. (2n= 14). Chromosome pairing observed at MI in the hybrids was high, but indications of weak sterility barriers were observed. It is concluded that (i) hybridization is fairly easy to perform, and the populations studied belong to the same species, (ii) no divergence in the ssp. halophilum genome was observed, except in (iii) a population with at least one reciprocal translocation, (iv) the halophilum × breviaristatum hybrids had lowered pairing with an increased frequency of univalents, (v) the pairing combined with morphology suggest recognition of H. pubiflorum ssp. breviaristatum (Parodi & Nicora) C. Baden (comb. nov.). 相似文献
5.
Summary We used in vitro growth inhibition assays to demonstrate that synthetic cecropin protein has potent activity against a range of plant pathogenic bacteria. We then prepared transgenic tobacco plants which express cecropin mRNA and protein. We have used Pseudomonas syringae pv tabaci infection of these transgenic tobacco as a model system to evaluate whether the plants which express cecropin protein also have increased tolerance to infection. We found no dramatic difference in disease response between plants which are expressing cecropin protein and control plants which were derived from the transformation with a binary vector which did not carry the gene encoding cecropin protein. 相似文献
6.
The ATP-binding-cassette transmembrane transporters (ABC transporters)
known from vertebrates belong to four major subfamilies: (1) the P-
glycoproteins (Pgp); (2) the cystic fibrosis transmembrane conductance
regulators (CFTR); (3) the Tap proteins encoded with the major
histocompatibility complex of mammals; and (4) the peroxisomal membrane
proteins. Both Pgp and CFTR have a structure suggesting a past internal
gene duplication; a phylogenetic analysis indicated that these duplications
occurred independently, while an independent tandem gene duplication
occurred in the case of the Tap family. Both the Pgp and Tap proteins show
evidence of relationship to bacterial ABC transporters lacking internal
duplication, and both are significantly more closely related to the HlyB
and MsbA families of transporters from purple bacteria than they are to ABC
transporters from nonpurple bacteria. The simplest hypothesis to explain
this observation is that eukaryotic Pgp and Tap genes are descended from a
mitochondrial gene or genes that were subsequently translocated to the
nuclear genome. The Pgp genes of eukaryotes are characterized by a
remarkable degree of convergent evolution between the ATP-binding cassettes
of their N- terminal and C-terminal halves, whereas no such convergence is
seen between the two halves of CFTR genes or between the duplicated Tap
genes. Exon 13 of the CFTR gene, which encodes a putative regulatory domain
not found in other ABC transporters apart from CFTR, showed high levels of
both synonymous and nonsynonymous difference in comparisons among different
mammalian species, suggesting that this region is a mutational hot spot.
相似文献
7.
8.
X Xiao G Hintermann AL Demanin J Piret 《Journal of industrial microbiology & biotechnology》1996,16(4):261-262
Streptomyces glaucescens is shown to possess -lactamase activity which is inhibitable by clavulanate. This is important in regard to its use as a cloning host for enzymes of \-lactam biosynthesis. 相似文献
9.
Presomite stage rat embryos were cultured for 45–49 hr with medium containing various adrenergic agonists and antagonists.
-Norepinephrine but not
-norepinephrine (several orders of magnitude less potent than the
-isomer at α-1 adrenergic receptors) resulted in a dose-dependent increase of situs inversus similar to that found for phenylephrine, an α-1 adrenergic agonist. Prazosin, an α-1 adrenergic antagonist, inhibited phenylephrine-induced situs inversus in a dose-dependent manner. Neither dexmedetomidine, an α-2 adrenergic agonist, nor isoproterenol, a β adrenergic agonist, caused situs inversus. These results provide pharmacological evidence that stimulation of α-1 but not of α-2 and β adrenergic receptors modulates the control of left/right sidedness in rat embryos. 相似文献
10.
Claus Baden 《Nordic Journal of Botany》1981,1(2):143-153
The genus Macrorungia C. B. Clarke is revised. 5 taxa have previously been proposed in the genus; the present revision recognises 3, viz. Macrorungia galpinii C. Baden sp. nov., M. longistrobus C. B. Clarke and M. pubinervia (T. Anders.) C. B. Clarke. The delimitation between Anisotes and Macrorungia is discussed. Phytogeographical and ecological aspects are discussed in relation to the phytogeog–raphical division of Africa. 相似文献