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281.
Summary Plant cell suspension cultures producing secondary metabolites have been permeabilized for product release by electroporation. The two cell cultures studied, i.e. Thalictrum rugosum and Chenopodium rubrum, require about 5 and 10 kV cm–1, respectively, for complete permeabilization (release of all the intracellularly stored product). The number of electrical pulses and capacitance used had a relatively limited effect on product release while the viability of the cells was strongly influenced by the latter. Conditions for complete product release resulted in total loss of viability of the cells after treatment. The release of product from immobilized cells was also achieved by electroporation. Cells entrapped in alginate required less voltage for permeabilization than free or agarose entrapped cells. 相似文献
282.
283.
Pancreatic islets of the Syrian golden hamster were maintained in culture for extended periods of time. Toxicity of streptozotocin in these cultures was evaluated by measurement of insulin secretion. Exposure of islets to 1 or 2 mM streptozotocin immediately following isolation resulted in a permanent and dose-related inhibition of insulin secretion. This was accompanied by islet disruption as observed by phase-contrast microscopy. Culture of islets for 24 hours before streptozotocin exposure afforded protection from toxicity. For example, exposure of freshly isolated islets to 2 mM streptozotocin resulted in complete destruction of beta cells, whereas islets similarly exposed after a 24 hr culture period continued to secrete insulin for many months. Islets maintained in culture for one week before exposure to 0.1–0.5 mM streptozotocin, however, became more sensitive than freshly isolated islets. Repeated weekly exposure of cultured islets to a non-toxic concentration (0.1 mM) resulted in sustained suppression of insulin secretion after 11 weeks. 相似文献
284.
Peter O''Connell G. Mark Lathrop Mark Leppert Yusuke Nakamura Ulrich Müller Jean-Marc Lalouel Ray White 《Genomics》1988,3(4):367-372
We have constructed a primary genetic map of human chromosome 18 consisting of 11 DNA markers and one serological marker (JK). Two of these loci define highly polymorphic VNTR systems. The markers define a continuous genetic linkage map of 97 cM in males and 205 cM in females; female genetic distances in a panel of 59 three-generation families were consistently about twice those observed in males. The high odds in support of the linear order of the markers on this recombination map, and the extent of coverage of chromosome 18, indicate that this map will permit efficient linkage studies of human genetic diseases that may be segregating on chromosome 18 and will provide anchor points for development of high-resolution maps for this chromosome. 相似文献
285.
The stem-galling sawfly Euura lasiolepisuses one or more plant wound compounds resulting from oviposition scars as cues in host discrimination (avoiding sites occupied by conspecifics). Four experiments were conducted to test hypotheses about how Euurapartitions resources. Experiment 1 demonstrated that Euuraavoids ovipositing on nodes with scars from previous ovipositions. Experiment 2 showed no evidence that the sawfly uses oviposition-deterring pheromones and indicated there is a time lag following oviposition before the oviposition scar becomes a deterrent. Experiment 3 showed that sawflies avoid artificially formed scars, demonstrating that a plant cue alone can lead to host discrimination. Experiment 4 showed that visual or tactile cues are not necessary for host discrimination and indicated that a plant wound compound functions as an oviposition deterrent. Both experimental results and field surveys showed that Euuraoviposition scars were more uniformly distributed than expected if sawflies were ignoring previous ovipositions. 相似文献
286.
The attack by the bud-galling sawfly, Euura mucronata , on its willow host was simulated by removing every other living bud from previous year's shoots in a natural stand of Salix cinerea . The impact of simulated attack on the growth of the willow and the subsequent attack by E. mucronata was estimated after one growing season. Experimental bud-killing resulted in a growth reaction in S. cinerea characterized by significant increase in the length of new shoots produced by the remaining buds Also the number of buds and E. mucronata galls per shoot were significantly higher on bud-removal branches as compared with control branches. The overall survival of E. mucronata larvae was better on long shoots than on short shoots. The result shows that sawfly attack increases the amount of high quality resources for the subsequent generation of the same sawfly as predicted by "resource regulation hypothesis". We conclude that these highly specialized insect herbivores have adapted to utilize and to maintain the willow's juvenile traits. Rapid regrowth of willows after damage may have originally arisen as an adaptation in response to other, less specific pressures such as mammal browsing or snow and ice damage. 相似文献
287.
Thomas Botz Dr. Peter Mattusch Prof. Dr. Willy Hilgenberg 《Journal of Phytopathology》1988,122(2):135-142
Populations of pathogenic Pseudomonas syringae pv. syringae were monitored on apparently healthy leaves, blossoms, and fruit from two apple orchards with known histories of blister bark and a pear orchard with a known history of blossom blast. Populations on blossoms and fruits were higher on pears than on apples. Yellow-pigmented, non-pathogenic bacteria might have suppressed or masked the presence of P. syringae pv. syringae on apple trees. Populations of P. syringae pv. syringae on apple and pear leaves fluctuated sharply but higher levels generally occurred during the 1984/85 growing season than during the drier 1983/84 season. This investigation indicates that the resident phase of P. syringae pv. syringae is probably a major source of inoculum for apple blister bark and pear blossom blast in South Africa. 相似文献
288.
A serum free medium was developed, that could be used for the large scale propagation of various cell lines in bioreactors. The medium is based on a 1:1 mixture of Iscove's Modified Dulbecco's Medium and Ham's Medium F12, supplemented with transferrin, insulin and a BSA/oleic acid complex. Several myelomas, hybridomas derived from different myelomas and spleen cells, and other lymphoid and non-lymphoid cell lines were cultivated at growth rates comparable to those observed using serum-supplemented media. There was furthermore no reduction in the formation of products such as monoclonal antibodies or recombinant human interleukin-2.Abbreviations Ag8
Mouse myeloma cell line P3-X63-Ag8.653
- BME
Basal Medium Eagle
- BSA
Bovine Serum Albumin
- DMEM
Dulbecco's Modified Eagle's Medium
- EDTA
Ethylenediaminete-traacetic Acid
- e-PC
Phosphatidyl choline from egg yolk
- FCS
Fetal Calf Serum
- FGF
Fibroblast Growth Factor
- GHL
Glycyl-histidyl-lysine
- HDL
High Density Lipoprotein
- HPL
Human Plasma Lipid
- IF
1:1 mixture of IMDM and Ham's F12
- IMDM
Iscove's Modified Dulbecco's medium
- LDL
Low Density Lipoprotein
- NS1
Mouse myeloma cell line NSI-1-Ag4-1
- PBS
Phosphate Buffered Saline
- s-PC
Phosphatidylcholine from soy beans
- s-PE
Phosphatidylethanolamine from soy beans
- s-lecithin
lecithin from soy beans 相似文献
289.
Peter Aaby Jette Bukh Ida Maria Lisse Maria Clotilde da Silva 《BMJ (Clinical research ed.)》1988,296(6631):1225-1228
The mortality from measles was studied in an urban area of Guinea-Bissau one year before and five years after the introduction of a vaccination programme. The years after the introduction of immunisation saw a decline in mortality among unvaccinated children with measles. This decline occurred despite a lower age at infection and an increasing prevalence of malnourished children. State of nutrition (weight for age) did not affect the outcome of measles infection. The incidence of isolated cases, however, increased in the period after the introduction of measles vaccination. As mortality was lower among these cases, diminished clustering explained some of the reduction in mortality. Comparison between the urban district and a rural area inhabited by the same ethnic group showed a lower age at infection, less clustering of cases, and lower case fatality ratios in the urban area.Endemic transmission of measles in urban districts leads to less clustering of cases, which may help explain the usually lower case fatality ratios in these areas. As measles vaccination increases herd immunity and diminishes clustering of cases, it may reduce mortality even among unvaccinated children who contract the disease. 相似文献
290.