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991.
992.
In Vitro Propagation of the Protozoan Perkinsus Marinus, A Pathogen of the Eastern Oyster, Crassostrea Virginica 总被引:1,自引:1,他引:0
JEROME F. LA PEYRE MOHAMED FAISAL EUGENE M. BURRESON 《The Journal of eukaryotic microbiology》1993,40(3):304-310
ABSTRACT. Perkinsus marinus , a pathogen of eastern oysters ( Crassostrea virginica ), has been successfully propagated in vitro. Cultures of the parasite were initiated from heart fragments of an infected oyster. the cultured protozoan (designated Parkinsus -1) was similar in morphology at both the light and transmission electron microscopy levels to histozoic stages of P. marinus in naturally infected oysters. In addition, cultured cells incubated in fluid thioglycollate medium produced enlarged cells (prezoosporangia) that stained blue-black in Lugol's solution, a response characteristic to Perkinsus spp. and used in routine diagnosis. Polyclonal antibodies raised against P. marinus prezoosporangia reacted positively to Perkinsus -1. Finally, the cultured cells infected susceptible oysters and reisolation of Perkinsus -1 cells was possible from the hearts of experimentally infected oysters. the culture medium contained most of the known constituents of cell-free hemolymph of oysters. the success achieved in culturing P. marinus will allow further investigations aimed at reducing mortalities caused by this important oyster pathogen and at addressing many unanswered questions about its biology and pathobiology. 相似文献
993.
ELBA CUBERO TEREZA C. AVANCINI DE ALMEIDA MICHAEL O'MAHONY 《Journal of sensory studies》1995,10(3):307-324
There are many ways in which a laboratory difference test differs from 'real life' discrimination of foods. One of these is the interval of time between tasting the two stimuli to be discriminated. To investigate this, judges performed same-different discrimination tests using a citrus flavored beverage as a medium. The time interval between tasting the standard and comparison stimuli was varied. In this initial study, short intervals of zero, 30, 60 s were examined. For judges unfamiltar with the stimuli, performance deteriorated as the time interval increased. For judges familiar with the stimuli, the zero time interval elicited best performance but there was no decrease in performance when the interval was increased from 30 to 60 s. The results were explained by hypothesizing different types of memory trace for the standard stimulus being utilized for comparison with the comparison stimulus. 相似文献
994.
995.
Kuzoff RK; Sweere JA; Soltis DE; Soltis PS; Zimmer EA 《Molecular biology and evolution》1998,15(3):251-263
18S ribosomal RNA genes are the most widely used nuclear sequences for
phylogeny reconstruction at higher taxonomic levels in plants. However, due
to a conservative rate of evolution, 18S rDNA alone sometimes provides too
few phylogenetically informative characters to resolve relationships
adequately. Previous studies using partial sequences have suggested the
potential of 26S or large-subunit (LSU) rDNA for phylogeny retrieval at
taxonomic levels comparable to those investigated with 18S rDNA. Here we
explore the patterns of molecular evolution of entire 26S rDNA sequences
and their impact on phylogeny retrieval. We present a protocol for PCR
amplification and sequencing of entire (approximately 3.4 kb) 26S rDNA
sequences as single amplicons, as well as primers that can be used for
amplification and sequencing. These primers proved useful in angiosperms
and Gnetales and likely have broader applicability. With these protocols
and primers, entire 26S rDNA sequences were generated for a diverse array
of 15 seed plants, including basal eudicots, monocots, and higher eudicots,
plus two representatives of Gnetales. Comparisons of sequence dissimilarity
indicate that expansion segments (or divergence domains) evolve 6.4 to 10.2
times as fast as conserved core regions of 26S rDNA sequences in plants.
Additional comparisons indicate that 26S rDNA evolves 1.6 to 2.2 times as
fast as and provides 3.3 times as many phylogenetically informative
characters as 18S rDNA; compared to the chloroplast gene rbcL, 26S rDNA
evolves at 0.44 to 1.0 times its rate and provides 2.0 times as many
phylogenetically informative characters. Expansion segment sequences
analyzed here evolve 1.2 to 3.0 times faster than rbcL, providing 1.5 times
the number of informative characters. Plant expansion segments have a
pattern of evolution distinct from that found in animals, exhibiting less
cryptic sequence simplicity, a lower frequency of insertion and deletion,
and greater phylogenetic potential.
相似文献
996.
Analysis of the occurrence and distribution of tobacco rattle virus in field soil and disease in a subsequent tulip crop 总被引:2,自引:0,他引:2
ANTOON T PLOEG FRANS C ZOON JOOP DE BREE CEES J ASJES 《The Annals of applied biology》1996,129(3):461-469
The occurrence and distribution of tobacco rattle virus (TRV) in field plots was determined by soil bait-testing and disease incidence in tulips subsequently grown on these plots was studied. The virus occurred in patches, calculated as 1.5 m × 3.6 m. The presence of virus was not correlated with numbers of potential vector trichodorid nematodes. Of three trichodorid nematode species present, only Paratrichodorus teres transmitted TRV which, as with virus isolates obtained in bait-tests and from infected tulips, reacted in serological tests with an antiserum prepared against a Dutch isolate of pea-early browning virus (PEBV). Virus prevalence in a subsequent tulip crop was 0.8% and in a sample of tulip plants, virus was recovered only from plants showing virus symptoms. Plots from which TRV was recovered in bait-tests yielded significantly more virus diseased tulips than plots which tested negative for virus. Growing bait-plants in field-plots, as compared with greenhouse tests using soil collected as a series of sub-samples, resulted in an underestimate of the occurrence of TRV. 相似文献
997.
998.
Induction and Growth of 'Microspore-Derived' Embryos of Brassica napus ssp. oleifera 总被引:2,自引:0,他引:2
DUNWELL J. M.; CORNISH M.; DE COURCEL A. G. L.; MIDDLEFELL-WILLIAMS J. E. 《Journal of experimental botany》1983,34(12):1768-1778
Three cultivars of spring rape (Brassica napus ssp. oleifera),Tower, Willi and Duplo, were used for a study of induction andgrowth of microspore-derived embryos, Buds, 2.0mm in length, containing uninucleate microspores were harvestedand stored for 14 d at 4 ?C in darkness. Anthers were then removedand cultured on a liquid medium based upon that of Murashigeand Skoog and containing 8% sucrose, 0.5 mg l1 naphthylaceticacid and 0.05 mg l1 benzylaminopurine. Cultures werepre-incubated at 35 ?C for 03 d and then incubated at30 ?C. After a total of 42 d incubation, cultures were scoredfor the presence of macroscopic embryos (12 mm in length)and for the presence of anthers containing abortive embryoidswhich had not developed further. The cultivars differed greatly in terms both of the frequencyof anthers showing induced embryoids and of the final yieldof embryos. Tower showed the highest frequency of induction(maximum 38% of cultured anthers with induced embryoids) whereasthe highest yield (equivalent to 1.1 embryo per cultured anther)was obtained from anthers of the cv. Duplo after a 3 d treatmentat 35 ?C. Yields from the other cultivars were much lower andwere relatively unaffected by the 35 ?C treatment. Key words: Brassica napus, Rape, Anther culture, Pollen, Haploid 相似文献
999.
MORENO M. L.; LEYTON C.; SANS J.; DE LA TORRE C. 《Journal of experimental botany》1983,34(12):1748-1755
The aim of the present work is to detect possible differencesin the chromatin of plants replicated in the absence of proteinsynthesis. The kinetics of nuclease digestion in Allium cepa L., evaluatedafter making the cells permeable, was faster for the chromatinof meristem cells replicated in the presence of 1.0 µgml1 cycloheximide than in control cells. In order to have a synchronous population in the meristems,cells were labelled as binucleate by a short treatment with5.0 mM caffeine. Treated cells failed to increase both theircontent in dense chromatin and intranuclear histones. Thesefacts suggest that chromatin replicated in the presence of cycloheximidedid not incorporate histones and was unable to be integratedinto dense chromatin patches. Key words: Allium cepa L., Chromatin replication, Protein synthesis 相似文献
1000.
JOHAN F. DE JONCKHEERE PIERRE PERNIN MASSIMO SCAGLIA ROLF MICHEL 《The Journal of eukaryotic microbiology》1984,31(2):324-331
Fourteen strains of Naegleria australiensis, including the type strain, were compared for virulence for mice, maximum growth temperature, lectin agglutination, isoenzyme pattern, and total protein banding pattern. Their relation to other species of Naegleria also was compared by immunoelectrophoretic analysis. Strains with high virulence, comparable to that of N. fowleri, were found to be different in concanavalin A agglutination as well as with regard to zymograms and total protein patterns. Although serologically different from N. fowleri and reacting with N. australiensis antiserum in the fluorescent antibody test, these high-virulence strains differed in number of immunoelectrophoretic precipitin bands. Because of these results, the high-virulence strains are considered to be a subspecies of N. australiensis. The low-virulence strains showed minor differences from the type strain. Thus, N. australiensis does not appear to be as homogenous a species as N. fowleri. Pathogenic N. australiensis also seems to be more widespread than previously thought. 相似文献