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11.
The vascular anatomy ofHelminthostachys zeylanica was examined with special reference to anomalous secondary tissue. Primary xylem development gradually takes place centrifugally. In branched rhizomes with destroyed apices, the vascular cylinder apical to the insertion of branch traces is generally composed of primary xylem, accessory xylem, inner parenchyma of radially arranged cells, outer parenchyma of irregularly arranged cells, and partly crushed phloem, listed in order going outwards. The accessory xylem as well as the inner parenchyma ofHelminthostachys zeylanica is probably secondarily produced, partly to contribute to the branch traces, in a position corresponding to that of secondary vascular tissue developed from a normal cambium inBotrychium sensu lato. It is suggested that although a cambium is lacking inHelminthostachys zeylanica, the secondary vascular tissues are comparable between the genera. The phylogenetic implication of this tissue is discussed. 相似文献
12.
We reported previously that the haploid genome of standard strains of laboratory mice contains approximately 70 copies of an amplified long genomic sequence, designated ALGS, that includes a retroposon of the gene for elongation factor 2 (MER). The length of each repeating unit is more than 60 kb, and the sequence of the unit is highly conserved among the repeats. In the present study, Southern blot analysis of the genomes of wild rodents demonstrated that the ALGS is present in all subspecies of Mus musculus and is abundant in M. spicilegus, whereas it is absent in M. spretus as well as in Rattus and other closely related genera. This result indicates that the amplification occurred after the species differentiation with the genus Mus and at least prior to the differentiation of subspecies of M. musculus. To locate chromosomal positions of the ALGS, in situ hybridization was carried out with laboratory strains and wild mice. It appears that the ALGS is located in the centromeric regions of most chromosomes in laboratory mice, M. musculus and M. spicilegus, whereas no positive signals were observed with M. spretus, in accordance with the results from the Southern blotting analysis. 相似文献
13.
Comparative development of the narrow pinnules of rheophyticOsmunda lancea and of the broad pinnules of a related dryland species,O. japonica, was examined and the origin of rheophytic stenophylly was discussed. The mature leaves and their various parts ofO. lancea are smaller and narrower than those ofO. japonica. The young pinnules ofO. lancea at the initiation of cell expansion are smaller than those ofO. japonica. The growth pattern of the pinnules is fundamentally the same in the two species, but pinnule growth period is shorter inO. lancea than inO. japonica. While the largest growth rate in pinnule length is quite similar, inO. lancea the pinnules are less elongated and much less broadened during ontogeny. Cell expansion in the mesophyll and epidermis proceeds
acropetally and toward the margin along the axes of costules and veins. Although the numbers of mesophyll and epidermal cells
between two adjacent veinlets are almost the same inO. lancea andO. japonica, during the subsequent growth period inO. lancea, the cells expand to a smaller extent and the veinlets become more narrowly oblique to the costule. This oblique distortion
of laminar segments framed by veins causes stenophylly, an allometric modification. The stenophylly ofO. lancea is believed to have arisen by heterochronic evolution, in particular, progenesis. 相似文献
14.
A cytological and reproductive study of the diploid and triploid agamosporousDryopteris pacifica was made to elucidate the origin of its infraspecific cytotypes. Some triploids produced 16 spore mother cells (SMCs) sometimes with n=41II+41I chromosomes, in addition to eight SMCs with n=123II, in each sporangium. In the former case the 16 SMCs usually underwent abnormal meiosis to give rise to some 50 spores, some of which were regular-shaped; in the latter the eight SMCs multiplied into 32 spores by normal meiosis. We found that spores from one of the triploid plants developed into either diploid or triploid gametophytes, which further apogamously produced diploid or triploid sporophytes, respectively. This novel mechanism of ploidy reduction is discussed in relation to the origin of diploid agamosporous ferns, the taxonomic complexity of the species, and the correlation of agamospory with polyploidy. The mechanism is also compared to that operating in agamospermous angiosperms. 相似文献
15.
Recessive Nonsense Suppressors in SACCHAROMYCES CEREVISIAE : Action Spectra, Complementation Groups and Map Positions 总被引:4,自引:3,他引:1
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Bun-Ichiro Ono Yumiko Ishino-Arao Masahiro Tanaka Ikuko Awano Sumio Shinoda 《Genetics》1986,114(2):363-374
Three genes SUP111, SUP112 and SUP113 of Saccharomyces cerevisiae have been identified that can mutate to give recessive omnipotent nonsense suppressors. Alleles of these loci can also act as allosuppressors; that is, different phenotypes, due apparently to different efficiencies of suppression, can result from different alleles at a given locus. The SUP111, SUP112 and SUP113 loci map to the right arms of chromosomes VIII, VII and XIII, respectively. 相似文献
16.
17.
A high-molecular-mass protease, ingensin, was purified to homogeneity from rabbit reticulocytes by DEAE-cellulose, HPLC gel filtration, and hydroxyapatite chromatographies. By these procedures, ingensin activity was separated from the activities of two other unique aminopeptidases, one of which is activated by ATP. Ingensin had the following properties: the optimum activity was seen around pH 9.0 and at 50 degrees C; addition of 0.04% SDS and 1 mg/ml linoleic acid resulted in 8- and 4-fold increases in peptide-hydrolyzing activity, respectively. The molecular mass was found to be 700,000 +/- 100,000 daltons on gel filtration, but SDS electrophoresis revealed that the enzyme is composed of several subunits with molecular weights of less than 35,000. The N-terminal-blocked tyrosine- and arginine-MCA derivatives, but not Arg-MCA, were hydrolyzed rapidly by ingensin. The approximate Km values for the reaction of ingensin with Suc-Leu-Leu-Val-Tyr-MCA and Z-Ala-Arg-Arg-MCA were 0.32 and 0.12 mM, respectively. The degradation of several proteins in the reticulocyte extract was stimulated by the addition of SDS and linoleic acid. The activator concentrations necessary for stimulation of the protein hydrolysis are similar to those of the purified reticulocyte ingensin for synthetic substrates. Ingensin did not associate with either right-side-out or inside-out red cell membranes. These results suggest that ingensin is a cytosolic fatty acid-stimulated protease, which is involved in the protein turnover in reticulocyte extracts. 相似文献
18.
We have defined one type of acid alpha-glucosidase and two types of neutral alpha-glucosidases from quail skeletal muscle on the basis of differences in the elution patterns on a DEAE-cellulose column. The appearance of the two neutral alpha-glucosidase isoenzymes was age-dependent. A decrease in acid alpha-glucosidase activity was demonstrated in Japanese quails with glycogenosis type II. The characteristics of these three alpha-glucosidase isoenzymes are described. 相似文献
19.
Morphine-Induced Changes in Histamine Dynamics in Mouse Brain 总被引:5,自引:5,他引:0
Masahiro Nishibori Ryozo Oishi Yoshinori Itoh Kiyomi Saeki 《Journal of neurochemistry》1985,45(3):719-724
The effect of the acute morphine treatment on histamine (HA) pools in the brain and the spinal cord was examined in mice. Morphine (1-50 mg/kg, s.c.) administered alone caused no significant change in the steady-state levels of HA and its major metabolite, tele-methylhistamine (t-MH), in the brain. However, depending on the doses tested, morphine significantly enhanced the pargyline (65 mg/kg, i.p.)-induced accumulation of t-MH and this effect was antagonized by naloxone. A specific inhibitor of histidine decarboxylase, alpha-fluoromethylhistidine (alpha-FMH) (50 mg/kg, i.p.), decreased the brain HA level in consequence of the almost complete depletion of the HA pool with a rapid turnover. Morphine further decreased the brain HA level in alpha-FMH-pretreated mice. Morphine administered alone significantly reduced the HA level in the spinal cord, an area where the turnover of HA is very slow. These results suggest that the acute morphine treatment increases the turnover of neuronal HA via opioid receptors, and this opiate also releases HA from a slowly turning over pool(s). 相似文献
20.