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61.
Sarah L. Roberts-Oehlschlager James M. Dunwell 《Plant Cell, Tissue and Organ Culture》1990,20(3):235-240
A period of four days preincubation at 25 °C on a medium containing mannitol was found to be superior to those pretreatments requiring incubation at 4 °C. In addition, the yield of green plants was improved by orienting anthers flat on the medium during mannitol preincubation, and reducing the number of anthers cultured per dish. 相似文献
62.
Toshimitsu Okeda Yasushi Yokogawa Hiroaki Ueo Mary A. Bury Paul O. P. Ts'o Sarah A. Bruce 《In vitro cellular & developmental biology. Plant》1990,26(12):1157-1166
Summary Primary cultures of 9-d-gestation Syrian hamster embryo (E9) cells are distinct from primary cultures of later gestational
age in terms of their growth and differentiation. First, primary E9 cell cultures express multiple mesenchymal differentiation
lineages (e.g., adipocyte, myoblast) only rarely seen in cultures of 13-d-gestation fetal (F13) cells. Second, although most
primary E9 cultures have a limited in vitro proliferative life span and exhibit cellular senescence similar to primary cultures
of F13 cells, E9 cultures seem to have higher frequency of escape from senescence and conversion to continuous cell lines
compared to F13 cells. Moreover, this frequency can be further increased 4- to 5-fold by continuous exposure of the E9 cells
to tumor promoters or epidermal growth factor. Eleven continuous cell lines have been isolated from unreated, promoter-treated,
or epidermal growth factor-treated primary E9 cultures. Seven of these are neoplastic or preneoplastic. However, the remaining
four do not show any evidence of being in neoplastic progression and three of these continue to express the same differentiated
phenotype observed in ther parental primary cell cultures.
These studies were supported in part by grants from the National Institutes of Health (AG 01998), Bethesda, MD, and the U.S.
Department of Energy (DE-A-C02-76-EVO-3280), Washington, DC. 相似文献
63.
64.
Fungal spore populations in the outdoor and indoor atmosphere of Ismailia have been studied during the period from March 1992
to May 1993. A total of 23 350 cfu and 73 species were recorded,Cladosporium cladosporioides, Aureobasidium pullulans andAspergillus flavus were the most abundant. The indoor and outdoor mycoflora showed marked quantitative and qualitative differences. In view
of count, recorded species could be categorized into three groups as follows: (a) species showing higher counts in out- than
indoor, (b) species showing the opposite trend i.e. lower counts in out-door than indoor, (c) species showing approximately
equal counts in out- and indoor. Regarding seasonal periodicity, March and either September or October showed the highest
count for both normal fungal flora (NFF) and opportunistic fungal flora (OFF). While January and July showed the lowest count
of them both, May but not July was the lowest as for outdoor NFF. 相似文献
65.
J. Laybourn-Parry Mark R. James Diane M. McKnight John Priscu Sarah A. Spaulding Russell Shiel 《Polar Biology》1996,17(1):54-61
Samples collected from Lake Fryxell, southern Victoria Land, Antarctica in January 1992 and 1994 were analysed for the abundance
of bacterioplankton and the diversity and abundance of protistan plankton. At the times of sampling, 14 ciliate species and
10 species of autotrophic flagellate were recorded. The samples contained two species of rotifer (Philodina spp.), which formed the first record of planktonic metazoans in the Dry Valley lakes of this region of Antarctica. Bacterial
concentrations ranged between 1.0 and 3.8×108 l-1 in the upper oxic waters increasing to 20×108 l-1 in the anoxic waters. Heterotrophic flagellates decreased in abundance down the oxygenated water column, disappearing completely
at 9 m, and ranged between 0.28 and 7.39×105 l-1 in abundance. Autotrophic flagellates were much more abundant exhibiting a number of distinct peaks down the water column
(1.89–25.3×108 l-1). The ciliated protozoa were very abundant (up to 7720 l-1) in relation to flagellate and bacterial numbers, typical of oligotrophic lakes world-wide. The distribution of the protistan
plankton showed marked zonation, probably in response to the differing salinity and temperature gradients in the water column.
Possible trophic interactions are discussed and comparisons with other continental Antarctic lakes made.
Received: 29 November 1995/Accepted: 18 February 1996 相似文献
66.
Ravigadevi Sambanthamurthi Siti Hasnah Parman Mohd. Roslan Md. Noor 《Plant Cell, Tissue and Organ Culture》1996,46(1):35-41
Procedures are deseribed for the efficient isolation of protoplasts from a variety of oil palm (Elaeis guineensis Jacq.) tissues. Various factors including donor source, composition of enzyme mixture and culture medium affected the yield and viability of the protoplasts Polyembryogenic cultures of oil palm were the most suitable starting material in terms of yield, viability and metabolic competence. Pectolyase Y-23 in association with cellulase and hemicellulase was required for the efficient release of protoplasts from the oil palm tissues. Limited cell division to form microcallus was observed at very low frequency (<0.01%) when glutathione and catalase were incorporated in the culture medium.Abbreviations 2,4-d
dichlorophenoxyacetic acid
- DTT
dithiothreitol
- MES
2[N-morpholino] ethanesulphonic acid
- NAA
1-naphthalene acetic acid
- PVP
polyvinylpyrrolidone 相似文献
67.
Harold Gouzoules Sarah Gouzoules Kimran Miller 《International journal of primatology》1996,17(4):549-568
Signalers that misinform sufficiently open may become devalued as sources of information; however, “skepticism” and any comparison
involved in testing reliability entail a cost that involves delays and energy expenditure. Skepticism may be less costly though,
if, as a rule, animals are not equally skeptical of the signals of all conspecifics. Animals with the ability to recognize
individual conspecifics and to recall past encounters with them may have the capacity to restrict skepticism to subsets of
animals that are most likely to benefit from deception. We played tape-recorded alarm calls of high- and low-ranking rhesus
monkeys(Macaca mulatta) to their groups in a feeding context once daily over 8 consecutive days at the Yerkes Primate Center Field Station. Over
the sequence of playbacks, response was greater to the calls of high-ranking monkeys, adult response patterns were different
from those of juveniles, and for adults especially, decline in responsiveness was punctuated by partial resurgences of response.
These differences may be the consequence of the adults’ more extensive histories of interaction with group members that, though
generally reliable, vary with respect to the potential benefits of deceptive signaling. 相似文献
68.
69.
Among Trichophyton spp. examined for urease production, T. rubrum was negative, whereas T. mentagrophytes appeared to be the most active species. Urease was not detected in cell-free culture fluids of the tested fungi. The endocellular urease of the test fungi was essentially constitutive. Moreover, addition of urea to the growth medium of these organisms markedly inhibited their mycelial biomass and ureolytic yield. Environmental factors showed variable effects on the test fungi and there was no correlation between mycelial growth and urease activity of these fungi. 相似文献
70.