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981.
Thirty-two barley cultivars grown in Spain, 18 of the two-row type and 14 of the six-row type, were screened for plant regeneration
from cultured immature embryos. Although there was much variation in regeneration capacity among the cultivars, plants were
obtained from all cultivars except Almunia. No statistical differences were found in the percentage of regeneration between
two- and six-row types. The influence of the auxins 2,4-dichlorophenoxyacetic acid, dicamba, and picloram on the induction
and maintenance of embryogenesis and regeneration capacity after 3–4 months in culture, were evaluated for cultivars Cobra,
Hop and Reinette. Hop had the highest rates of maintenance of embryogenic capacity and plant regeneration. The medium containing
dicamba gave the best embryogenic callus induction, maintenance and regeneration. Five regeneration media, differing in growth
regulators and micronutrient composition, as well as partial desiccation of the calli before regeneration, were tested. The
regeneration medium containing 10 μm copper sulfate gave the best results. Regeneration frequencies after 3–4 months in culture of cultivar Hop were raised from
59.5 to 93.7% in this medium. Silver nitrate and partial desiccation of the calli also enhanced plant regeneration, but the
medium containing 10 μm of silver nitrate reduced root formation.
Received: 30 October 1997 / Revision received: 3 April 1998 / Accepted: 17 April 1998 相似文献
982.
Phylogenetic utility of the nuclear gene arginine decarboxylase: an example from Brassicaceae 总被引:10,自引:2,他引:8
Arginine decarboxylase (ADC) is an important enzyme in the production of
putrescine and polyamines in plants. It is encoded by a single or low-copy
nuclear gene that lacks introns in sequences studied to date. The rate of
Adc amino acid sequence evolution is similar to that of ndhF for the
angiosperm family studied. Highly conserved regions provide several target
sites for PCR priming and sequencing and aid in nucleotide and amino acid
sequence alignment across a range of taxonomic levels, while a variable
region provides an increased number of potentially informative characters
relative to ndhF for the taxa surveyed. The utility of the Adc gene in
plant molecular systematic studies is demonstrated by analysis of its
partial nucleotide sequences obtained from 13 representatives of
Brassicaceae and 3 outgroup taxa, 2 from the mustard oil clade (order
Capparales) and 1 from the related order Malvales. Two copies of the Adc
gene, Adc1 and Adc2, are found in all members of the Brassicaceae studied
to data except the basal genus Aethionema. The resulting Adc gene tree
provides robust phylogenetic data regarding relationships within the
complex mustard family, as well as independent support for proposed tribal
realignments based on other molecular data sets such as those from
chloroplast DNA.
相似文献
983.
John A. White Carson C. Chow Jason Rit Cristina Soto-Treviño Nancy Kopell 《Journal of computational neuroscience》1998,5(1):5-16
We study some mechanisms responsible for synchronous oscillations and loss of synchrony at physiologically relevant frequencies (10–200 Hz) in a network of heterogeneous inhibitory neurons. We focus on the factors that determine the level of synchrony and frequency of the network response, as well as the effects of mild heterogeneity on network dynamics. With mild heterogeneity, synchrony is never perfect and is relatively fragile. In addition, the effects of inhibition are more complex in mildly heterogeneous networks than in homogeneous ones. In the former, synchrony is broken in two distinct ways, depending on the ratio of the synaptic decay time to the period of repetitive action potentials (s/T), where T can be determined either from the network or from a single, self-inhibiting neuron. With s/T > 2, corresponding to large applied current, small synaptic strength or large synaptic decay time, the effects of inhibition are largely tonic and heterogeneous neurons spike relatively independently. With s/T < 1, synchrony breaks when faster cells begin to suppress their less excitable neighbors; cells that fire remain nearly synchronous. We show numerically that the behavior of mildly heterogeneous networks can be related to the behavior of single, self-inhibiting cells, which can be studied analytically. 相似文献
984.
Fanjul-Moles ML Bosques-Tistler T Prieto-Sagredo J Castañón-Cervantes O Fernández-Rivera-Río L 《Comparative biochemistry and physiology. Part A, Molecular & integrative physiology》1998,119(1):263-269
The effects of light intensity and duration on metabolic and behavioral parameters of two species of crayfish, Procambarus clarkii and Procambarus digueti, were studied. Sixty animals of each species were submitted to high irradiance conditions of two different photoperiod lengths, one normal light/dark (LD) 12:12 and one extreme LD 20:4 for 2 weeks. Hemolymph, lactate and oxygen consumption were determined throughout the experimental period. Simultaneously in 18 additional animals of each species, motor activity was individually recorded under the same control and experimental conditions. Both species showed a decrease in oxygen uptake and an increase in hemolymph lactate concentration. The statistical significance of this finding was higher for LD 20:4. This extreme condition evoked a significant decrease of motor activity in P. clarkii and a high mortality rate in P. digueti. P. digueti did not survive after the experiment, whereas P. clarkii survived and adapted to the laboratory conditions. Changes in metabolic and behavioral parameters could indicate different adaptation abilities in these species. 相似文献
985.
Comparative study of microbiological and histopathological techniques used for the detection of Helicobacter pylori 总被引:3,自引:0,他引:3
Muñoz E Corcuera MT Roldán M Gómez F Picazo A Baquero M Alonso MJ 《European journal of histochemistry : EJH》1998,42(4):297-302
This study evaluates the sensitivity, specificity and predictive values of several techniques commonly used for the detection of Helicobacter pylori in an analysis of 105 biopsy specimens (gastric and duodenal). For comparative purposes, the techniques investigated were divided into 2 groups: histopathological and microbiological. The former included hematoxylin-eosin and Giemsa stains, a Gram stain modified for use in tissue, and immunohistochemical techniques. Microbiological analysis was performed using culture, the urease test and the conventional Gram stain. The immunohistochemical techniques proved to be the most sensitive (93%). The modified Gram stain was sufficiently sensitive (92%) and specific (97%) for the detection of the bacterium. When combined with a microbiological technique such as the urease test, this stain showed increased sensitivity (96%) but its specificity was reduced to 94%. This combination of tests is recommended for the detection of H. pylori in biopsy specimens since it is easily performed at low cost and gives excellent results. For economical reasons, it is suggested that the use of immunohistochemical techniques should be restricted to specific cases. 相似文献
986.
Ceballos Salobreña A Gaitán Cepeda LA Ruesga MT Ceballos García L Quindós G 《Revista iberoamericana de micología》1998,15(3):141-145
The aim of this study has been to determine the prevalence of oral candidiasis and oral Candida carriers in an AIDS population under highly active antiretroviral therapy. Eighty-six AIDS patients treated with an antiretroviral combination (indinavir o ritonavir o saquinavir + zidovudine [AZT] + lamivudine [3TC]). Patients were grouped attending the predisposing factors for HIV infection in: intravenous drug users (IDU), heterosexuals, homosexuals, patients using hematological products or having unknown factors. Oral cavity was examined and an oral specimen was inoculated in a chromogenic culture medium (Albicans ID, bioMérieux, France). The prevalence of oral Candida lesions was 30.2% and Candida was isolated from 54.7% of patients. The predominant species was C. albicans serotype A in all the groups with the exception of homosexual patients, were C. albicans serotype B was the predominant. The IDU group showed the higher prevalence of Candida lesions and oral yeasts colonization, followed by the group of heterosexuals and homosexuals. An association was found between the presence of lesions and/or Candida spp. and the clinical stage or the viral concentration. The species Candida dubliniensis was isolated in the oral samples of two patients with candidosis and in two individuals without oral candidosis. The finding of this species in Spanish patients can be added to the data obtained in epidemiological studies in other countries. 相似文献
987.
Trichophyton simii in a "Caí" monkey (Cebus apella) colony in the province of Corrientes, Argentina.
Boehringer SI Cicuta ME Santa Cruz A Gómez L Patiño EM Borda JT 《Revista iberoamericana de micología》1998,15(4):300-301
The objective is to describe an outbreak of Trichophyton simii in a Cebus apella monkey colony in Argentine. During summer, alopecic zones appeared on dorsal regions from head to base of the tail of the animals. The hair and skin of nine animals were streaked onto Sabouraud dextrose with cloramphenicol and incubated at 25 degrees C. By the 10th day, white, filamentous colonies, which turned pale pink, developed from simples of four animals. Microscopical examinations were carried out and, because of colony and macroconidia morphology, were classified as Trichopyton simii. Although infection with T. simii is considered a zoonosis, we did not find human cases. 相似文献
988.
989.
F E Muñiz-Lozano G Domιnguez-Sánchez Y Dιaz-Viveros D M Barradas-Dermitz 《Journal of industrial microbiology & biotechnology》1998,21(6):296-299
A novel bacterial strain producing D-aminoacylase was isolated from organic waste and identified as Stenotrophomonas maltophilia ITV-0595. The isolation was performed using N-acetyl-D-phenylglycine (NAcDPG) as the sole source of C and N. The optimum pH for enzyme expression was 8 at 37°C. Using N-Ac-DPG
concentrations from 0.5 up to 3% w/v, it was observed that at the 1% level, the microorganism showed acceptable responses
in both enzyme activities and cell growth. From the different tested compounds N-acetyl-D-methionine (1%) was the best enzyme inducer (Sp. act. = 4.14 U mg−1 protein, Vol. act. = 0.17 U ml−1) and the only one that increased cell growth.
Received 13 June 1997/ Accepted in revised form 29 October 1998 相似文献
990.
Veena Prasad Asish Ray Chaudhuri Matthew Curcio Isao Tomita Fukutaro Mizuhashi Kyoji Murata Richard F. Ludueña 《The protein journal》1998,17(7):663-668
Tubulin, the subunit protein of microtubules, undergoes a time-dependent loss of functional properties known as decay. We
have previously shown that the drug 2-(4-fluorophenyl)-1-(2-chloro-3,5-dimethoxyphenyl)-3-methyl-6-phenyl-4(1H)-pyridinone (IKP104) accelerates decay, but that in the presence of colchicine, IKP104 becomes a stabilizer of tubulin. To
see if this is due to conformational effects specific to colchicine or simply to occupancy at the colchicine site, we examined
the effects of nocodazole and podophyllotoxin, two well-known competitive inhibitors of colchicine for binding to tubulin,
on IKP104’s acceleration of decay. We found that podophyllotoxin abolished IKP104’s accelerating effect and, like colchicine,
turned it into a stabilizer of tubulin. Nocodazole’s effects were similar to those of podophyllotoxin and colchicine, in that
it abolished IKP104-induced enhancement of decay; however, in the presence of nocodazole, IKP104 caused little or no stabilization
of tubulin. Since colchicine, nocodazole, and podophyllotoxin have very different interactions with tubulin, but all inhibit
the IKP104-induced enhancement of decay, our findings suggest that this inhibition arises from occupancy of the colchicine
site rather than from a direct conformational effect of these two drugs. 相似文献