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81.
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
82.
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
83.
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
84.
85.
Addi R. Fadel Dan Q. Jin Gaetano T. Montelione Ronald M. Levy 《Journal of biomolecular NMR》1995,6(2):221-226
Summary Order parameters for the backbone N–H and C–H bond vectors have been calculated from a 150 ps molecular dynamics (MD) simulation of human type- transforming growth factor in H2O solvent. Two kinds of crankshaft motions of the polypeptide backbone are observed in this MD trajectory. The first involves small-amplitude rocking of the rigid peptide bond due to correlated changes in the backbone dihedral angles i–1 and i. These high-frequency librational crankshaft motions are correlated with systematically smaller values of motional order parameters for backbone N–H bond vectors compared to C–H bond vectors. In addition, infrequent crankshaft flips of the peptide bond from one local minimum to another are observed for several amino acid residues. These MD simulations demonstrate that comparisons of N–H and C–H order parameters provide a useful approach for identifying crank-shaft librational motions in proteins. 相似文献
86.
本文报道了采自贵州沿河土地坳下奥陶统的牙形石,计有25属39种,根据牙形石组合特片分析,认为其与黔北其它地区下奥陶统牙形石组合面貌基本一致,属北大西洋牙形石动物地理区。 相似文献
87.
鱼腥藻HB1017株化能异养生长的研究 总被引:5,自引:1,他引:4
以葡萄糖和蔗糖为碳源,检测了六株(种)鱼腥藻的化能异养生产能力。其中鱼腥藻HB1017株化能异养生长较快,鱼腥藻HB0株化能异养生长缓慢,其余四种鱼腥藻不能进行化能异养生长。鱼腥藻HB1017株能利用果糖、葡萄糖、蔗糖为底物进行化能异养生长,但生长速率依次递减,差别显著。8磅湿热灭菌的果糖和蔗糖,与过滤灭菌的相比,只能维持低得多的化能异养生长速率。然而,8磅湿热灭菌的葡萄糖能维持比过滤法灭菌的高得 相似文献
88.
生态环境对白芷产量质量的影响 总被引:1,自引:0,他引:1
生态环境对白芷产量质量的影响陈兴福,丁德蓉,刘岁荣,卢进,黄文秀(四川省中医药研究院药物种植研究所,南川648408)EffectofEco-EnvironmentonDahurianAngelicaYieldandItsQuality¥ChenXi... 相似文献
89.
90.
本文根据武家村发现的第四纪哺乳类,海、陆相软体类化石,以及地层中所含的植物孢粉和岩性特征,把该地区第四纪地层初步划分为全新统、晚更新统、中更新统(陆相沉积)和早更新统(海相沉积)。 相似文献