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141.
A suitable medium was developed from modified Richard's medium plus V8 juice (RM8) to produce high levels of desiccation-tolerant conidia ofTrichoderma harzianumstrain 1295-22. The addition of 9% (v/v) glycerol to RM8 improved both biomass production and desiccation tolerance of the conidia ofT. harzianum.This medium was then used in a laboratory scale fermenter (1.5 liter) to determine optimal operating conditions. The optimal temperature for conidial production and desiccation tolerance improvement in the fermenter was 32°C when dissolved oxygen was maintained at 50% saturation of air, and the stirring rate was 1000 revolutions per minute. The initial water potential of the medium (with 9% glycerol) was −3.7 MPa, the pH was 6, and neither was controlled during fermentation. Changes in medium pH and dissolved oxygen were associated with the stages of morphological development and conidiation. The pH of the medium decreased concurrently with germ-tube elongation and mycelium development and then increased to 6.0–6.2 at phialide formation. Intensive conidiation occurred at pH 6.3–6.5 and reached its maximal level at 6.9–7.1. Changes in pH values could be used as indicators to monitor the morphological development and conidiation ofT. harzianumduring fermentation. The use of a 48-h-old culture inoculum, rather than conidial inoculum, to start fermentation reduced the time required to complete the shift from vegetative growth to phialide formation. Intensive conidiation occurred immediately after the addition of culture inoculum and reached maximum levels within 68 h of fermentation. Dry weight of biomass increased with the duration of fermentation and was greatest at 96 h. However, no improvements in conidia/gram and CFU/gram were achieved after 72 h of fermentation. The desiccation tolerance of conidia harvested at 72 or 96 h was significantly (P = 0.05) greater than that of conidia harvested at 48 h of fermentation. Results obtained from this study could be used for further scale-up of the fermentation process. 相似文献
142.
Hyun Koo Kim Moon Sun Ham Jong Soo Hong Jin Ha Lee Kyung Yu Park Hyeon Yong Lee 《Biotechnology and Bioprocess Engineering》1996,1(1):32-35
A moving aeration-membrane (MAM) bioreactor was employed for the production of 2 μg/mL of tissue type Plasminogen Activator (tPA) in serum free medium from normal human fibroblast cells. This system could maintain high cell density for long periods of steady state conditions in perfusion cultivation. Under normal operating conditions, shear stress was as low as 0.65 dynes/cm2 at the agitation speed of 80 rpm. Even though cell density gradually decreased with increasing agitation speed, tPA production increased linearly with increasing shear stress within a moderate range. This culture system allowed production of 2 μg tPA/mL while maintaining a high cell density of 1.0×107 viable cells/mL. 相似文献
143.
Richard J. Bold Jin Ishizuka Srinivasan Rajaraman †J. Regino Perez-Polo Courtney M. Townsend Jr. James C. Thompson 《Journal of neurochemistry》1995,64(6):2622-2628
Abstract: Carcinoid tumors are a group of neuroendocrine neoplasms distributed widely throughout the body but most commonly occurring in the gut. These tumors retain many characteristics of their neural crest origin, including secretion of neuroactive peptides and responsiveness to neurotrophic substances. Nerve growth factor (NGF), a neurotrophic protein involved in maintenance and differentiation of peripheral sympathetic and sensory neurons, regulates growth of several neural tumor cells by inducing a differentiated phenotype and subsequent inhibition of cell growth rate. We examined the actions of NGF in a functioning human pancreatic carcinoid cell line (termed BON). NGF has no effect on the cytoarchitecture or constitutive secretion of bioamines in this carcinoid cell line. NGF, however, stimulates the in vitro cellular proliferation of BON cells. BON cells possess mRNA for the NGF receptors (p75LNGFR and p140trkA ) and membrane-associated tyrosine kinase activity is increased in response to NGF. Both the mitogenic activity of NGF, as well as the receptor-linked tyrosine kinase activity, can be abrogated in BON cells by the trkA inhibitor K-252a and specific anti-NGF antibody. Our studies demonstrate that NGF is a mitogen for this carcinoid cell line without effect on cellular phenotype or cytoarchitecture. NGF may play a role in the development and progression of human carcinoid tumors. 相似文献
144.
Hyung-Joo Jin Jeong–Ha Kim Chul Hyun Sohn R.E. DeWreede Tae–Joo Choi G.H.N. Towers J.B. Hudson Yong–Ki Hong 《Journal of applied phycology》1997,9(4):383-388
Fifty-nine species of marine macrophytes from the coasts of British Columbia, Canada and Korea have been screened for the
presence of PCR inhibitors, namely inhibitors of Taq DNA polymerase. Eleven of the species displayed some inhibitor activity.
At the concentration of 5 μg of methanol extract in 25μL reaction mixture of PCR containing 1.5 unit of Taq DNA polymerase,
one (Ulva sp.) of 8 Chlorophyta, eight (Colpomenia bullosa, Ecklonia cava, Endarachne binghamiae, Fucus distichus, Hizikia
fusiformis, Sargassum confusum, Sargassum sagamianum, and Sargassum thunbergii) of 28 Phaeophyta, and one (Symphyocladia latiuscula)
of 34 Rhodophyta showed inhibition in PCR amplification. In the case of the water extract, two (Cladophora columbiana, Ulva
sp.) Chlorophyta, seven (Endarachne binghamiae, Fucus distichus, Hizikia fusiformis, Sargassum confusum, Sargassum sagamianum,
Sargassum horneri, Scytosiphon dotyi) Phaeophyta, no Rhodophyta and one (Phyllospadix scouleri) seagrass showed inhibition
in PCR amplification. the methanol fraction of Sargassum confusum and the water fraction of Fucus gardneri (mid–intertidal)
have been found to inhibit PCR at level as low as 0.5 μg in 25μL of PCR reaction mixture.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
145.
Genetic and cytological studies were conducted with a new male-sterile, female-fertile soybean [Glycine max (L.) Merr.] mutant. This mutant was completely male sterile and was inherited as a single-recessive gene. No differences in
female or male gamete transmission of the recessive allele were observed between reciprocal cross-pollinations in the F1 or F2 generations. This mutant was not allelic to any previously identified soybean genic male-sterile mutants: ms1, ms2, ms3, ms4, ms5, or ms6. No linkage was detected between sterility and flower color (W1 locus), or between sterility and pubescence color (T1 locus). Light microscopic and cytological observations of microsporogenesis in fertile and sterile anthers were conducted.
The structure of microspore mother cells (MMC) in male-sterile plants was identical to the MMCs in male-fertile plants. Enzyme
extraction analyses showed that there was no callase activity in male-sterile anthers, and this suggests that sterility was
caused by retention of the callose walls, which normally are degraded around tetrads at the late tetrad stage. The tapetum
from male-sterile anthers also showed abnormalities at the tetrad stage and later stages, which were expressed by an unusual
formation of vacuoles, and by accumulation of densely staining material. At maturity, anthers from sterile plants were devoid
of pollen grains.
Received: 13 May 1996 / Revision accepted: 19 August 1996 相似文献
146.
147.
148.
Two cloning vectors designed for use in Escherichia coli and the thiobacilli were constructed by combining a Thiobacillus intermedius plasmid replicon with a multicloning site, lacZ(prm1), and either a kanamycin or a streptomycin resistance gene. Conditions necessary for the introduction of DNA into T. intermedius and T. neapolitanus via electroporation were examined and optimized. By using optimal electroporation conditions, the gene encoding a carboxysome shell protein, csoS1A, was insertionally inactivated in T. neapolitanus. The mutant showed a reduced number of carboxysomes and an increased level of CO(inf2) necessary for growth. 相似文献
149.
150.
高必需氨基酸转基因马铃薯的研究 总被引:8,自引:0,他引:8
80年代以来,马铃薯遗传转化系统日趋成熟,转基因工程植株已被广泛应用于基础科学研究[1]。作为食物蛋白和能量主要来源的马铃薯,提高其蛋白质含量及质量的遗传工程研究正受到人们的普遍关注[2]。Yang等[2]将旨在改善氨基酸平衡的CAT-HEAAE(氯酶素乙酰转移酶-高含量人体必需氨基酸)融合基因导入马铃薯,获得了Southernblot、Northernblot、Westernblot的证据,但尚缺少氨基酸分析的资料。玉米醇溶蛋白(zein)[3]是一个富含甲硫氨酸的贮存蛋白,它和人工合成的HE… 相似文献