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81.
Determination of the respiration kinetics for mycelial pellets of Phanerochaete chrysosporium. 总被引:2,自引:2,他引:0 下载免费PDF全文
In mycelial pellet cultures of the white rot basidiomycete Phanerochaete chrysosporium, low oxygen concentration negatively affects the production of the extracellular lignin peroxidases and manganese peroxidases which are key components of the lignin-degrading system of this organism. To test the hypothesis that oxygen limitation in the pellets is responsible for this effect, oxygen microelectrodes were used to determine oxygen concentration gradients within the mycelial pellets of P. chrysosporium. Pellets were removed from oxygenated cultures, allowed to equilibrate with air, and probed with oxygen microelectrodes. The oxygen profiles were modelled assuming that O2 uptake follows a Michaelis-Menten relationship. The Vmax and Km values for oxygen uptake were 0.76 +/- 0.10 g/m3 of pellet per s and 0.5 +/- 0.3 g/m3, respectively. These kinetic values were used to predict respiration rates in air-flushed cultures, oxygen-flushed cultures, and cultures with large pellets (diameter greater than 6 mm). The predicted respiration rates were independently validated by experimentally measuring the evolution of carbon dioxide from whole cultures. 相似文献
82.
We report the use of a sensitive and specific enyzme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR) to study the expression of protein D, a major androgen-regulated sperm-binding glycoprotein at the protein and mRNA level in different anatomical regions of the rat epididymis. The concentration of protein D in the caput, corpus and cauda region of the epididymis was 10.2 +/- 0.67, 7.3 +/- 0.61 and 22.8 +/- 1.34 ng/micrograms total protein, respectively. The total RNA extracted from the caput, corpus and cauda regions of the rat epididymis was amplified by PCR with oligonucleotide primers specific for the 5' and 3' portion of protein D cDNA. Compared to the caput and cauda region, a significant reduction (greater than 82 +/- 3%) in the expression of protein D mRNA levels was observed for corpus epididymal RNA. This data demonstrates regional differences in the concentration of protein D and suggests that protein D expression may be regulated at the level of mRNA within the corpus epididymidis. 相似文献
83.
84.
Analysis of human chromosome 21: correlation of physical and cytogenetic maps; gene and CpG island distributions. 总被引:40,自引:3,他引:37 下载免费PDF全文
K Gardiner M Horisberger J Kraus U Tantravahi J Korenberg V Rao S Reddy D Patterson 《The EMBO journal》1990,9(1):25-34
Human chromosome 21 has been analyzed by pulsed-field gel electrophoresis using somatic cell hybrids containing limited regions of the chromosome and greater than 60 unique sequence probes. Thirty-three independent NotI fragments have been identified, totalling 43 million bp. This must account for essentially the entire long arm, and therefore gaps remaining in the map must be small. The extent of the pulsed-field map has allowed the direct correlation of the physical map with the cytogenetic map: translocation breakpoints can be unambiguously positioned along the long arm and the distances between them measured in base pairs. Three breakpoints have been identified, providing physical confirmation of cytogenetic landmarks. Information on sequence organization has been obtained: (i) 60% of the unique sequence probes are located within 11 physical linkage groups which can be contained in only 20% of the long arm; (ii) 9/21 genes are clustered within 4%; (iii) translocation breakpoints appear to occur within CpG island regions, making their identification difficult by pulsed-field techniques. This analysis contributes to the human genome mapping effort, and provides information to guide the rapid investigation of the biology of chromosome 21. 相似文献
85.
Characterization of differentiated syrian golden hamster pancreatic duct cells maintained in extended monolayer culture 总被引:4,自引:0,他引:4
S. Hubchak M. M. Mangino M. K. Reddy D. G. Scarpelli 《In vitro cellular & developmental biology. Plant》1990,26(9):889-897
Summary Epithelial cells isolated from fragments of hamster pancreas interlobular ducts were freed of fibroblast contamination by
plating them on air-dried collagen, maintaining them in serum-free Dulbecco's modified Eagle's (DME):F12 medium suppleneted
with growth factors, and selecting fibroblast-free aggregates of duct cells with cloning cylinders. Duct epithelial cells
plated on rat type I collagen gel and maintained in DME:F12 supplemented with Nu Serum IV, bovine pituitary extract, epidermal
growth factor, 3,3′, 5-triodothyronine, dexamethasone, and insulin, transferrin, selenium, and linoleic acid conjugated to
bovine serum albumin (ITS+), showed optimal growth as monolayers with a doubling time of about 20 h and were propagated for as long as 26 wk. Early
passage cells consisted of cuboidal cells with microvilli on their apical surface, complex basolateral membranes, numerous
elongated mitochondria, and both free and membrane-bound ribosomes. Cell grown as monolayers for 3 mo. were more flattened
and contained fewer apical microvilli, mitochondria, and profiles of rough surfaced endoplasmic reticulum; in addition, there
were numerous autophagic vacuoles. Functional characteristics of differentiated pancreatic duct cells which were maintained
during extended monolayer culture included intracellular levels of carbonic anhydrase and their capacity to generate cyclic
AMP (cAMP) after stimulation by 1×10−6
M secretin. From 5 to 7 wk in culture, levels of carbonic anhydrase remained stable but after 25 to 26 wk decreased by 1.9-fold.
At 5 to 7 wk of culture, cyclic AMP increased 8.7-fold over basal levels after secretin stimulation. Although pancreatic duct
cells cultured for 25 to 26 wk showed lower basal levels of cAMP, they were still capable of generating significant levels
of cAMP after exposure to serretin with a 7.0-fold increase, indicating that secretin receptors and the adenyl cyclase system
were both present and functional. These experiments document that pancreatic duct monolayer cultures can be maintained in
a differentiated state for up to 6 mo. and suggest that this culture system may be useful for in vitro physiologic and pathologic
studies.
This research was supported by grant CA34051 from the National Cancer Institute, Bethesda, MD. 相似文献
86.
87.
Summary A mixed culture of Endomycopsis fibuligera NRRL 76 and Zymomonas mobilis ZM4 could directly and more efficiently ferment cassava starch (22.5% w/v) to ethanol (10.5% v/v) than the monocultures. The combination of culture filtrate of E.fibuligera containing amylases and Z.mobilis simultaneously saccharified and fermented the cassava starch to ethanol equally well. Glucoamylase (0.01%) added to the fermenting medium improved ethanol (13.2% v/v) production by the above mixed culture to almost the theoretical level (98%) indicating that this enzyme is a rate-limiting factor in E.fibuligera. Z. mobilis alone converted the enzymehydrolyzed starch only to almost theoretical level (98%). 相似文献
88.
Mepiquat chloride (N, N-dimethylpiperidinium chloride), well known as PIX, is a potential systemic plant growth regulator. The effects of PIX on plant height, stem elongation, leaf area, net photosynthetic rates, chlorophyll content, sucrose and starch levels, and RuBP carboxylase activity in cotton (Gossypium hirsutum L. cv. DES 119) plants were measured. PIX was sprayed (0, 7.65, 15.3, 30.6 or 61.2 g active ingredient ha–1) on the plants at first square (25 days after emergence) and measurements were made at frequent intervals. Plant height was clearly reduced by PIX. The total length of vegetative branches and fruiting branches was 40% and 50% less than the control. Total leaf area in PIX treated plants was 16% less than the control. Net photosynthetic rates were 25% less in PIX-treated leaves. PIX treated leaves had more chlorophyll content. The activity of RuBP carboxylase was decreased in PIX treated plants. Starch accumulation was noticed in PIX treated leaves while sucrose content was not changed. The data reported here suggest that reduced growth responses induced by PIX results in partial loss of photosynthetic capacity in cotton at least up to 20 days after application of the growth regulator. 相似文献
89.
K. B. Singh M. V. Reddy 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1996,92(5):509-515
Ascochyta blight [Ascochyta rabiei (Pass.) Lab.] is the most destructive disease of chickpea (Cicer arietinum L.), but it can be managed effectively by the use of resistant cultivars. Therefore, a breeding programme was initiated during 1977–78 at ICARDA, Syria, to breed blight-resistant, high-yielding chickpeas with other desirable agronomic traits. Crosses were made in main season at Tel Hadya, Syria, and the F1s were grown in the off season at Terbol, Lebanon. The F2, F4 and F5 generations were grown in a blight nursery in the main season where blight epidemic was artificially created. The plants and progenies were scored for blight resistance and other traits. The F3 and F6 generations were grown in the off season under normal day length to eliminate late-maturing plants. The pedigree method of breeding was followed initially, but was later replaced by the F4-derived family method. The yield assessment began with F7 lines, first at ICARDA sites and later internationally. A total of 1584 ascochyta blight-resistant chickpea lines were developed with a range of maturity, plant height, and seed size not previously available to growers in the blight-endemic areas in the Mediterranean region. These included 92 lines resistant to six races of the ascochyta pathogen, and 15 large-seeded and 28 early maturity lines. New cultivars produced 33% more seed yield than the original resistant sources. The yield of chickpea declined by 340 kg ha-1, with an increase in blight severity by one class on a 1–9 scale, reaching zero yield with the 8 and 9 classes. Development of blight-resistant lines made the introduction of winter sowing possible in the Mediterranean region with the prospect of doubling chickpea production. Twenty three cultivars have been released so far in 11 countries.Joint contribution from ICARDA and ICRISAT. ICRISAT Journal Article no. JA 1886. 相似文献
90.
Lauffenburger DA Chu L French A Oehrtman G Reddy C Wells A Niyogi S Wiley HS 《Biotechnology and bioengineering》1996,52(1):61-80
Peptide growth factors and other receptor-binding cytokine ligands are of interest in contemporary molecular health care approaches in applications such as wound healing, tissue regeneration, and gene therapy. Development of effective technologies based on operation of these regulatory molecules requires an ability to deliver the ligands to target cells in a reliable and well-characterizable manner. Quantitative information concerning the fate of peptide ligands within tissues is necessary for adequate interpretation of experimental observations at the tissue level and for truly rational engineering design of ligand-based therapies. To address this need, we are undertaking efforts to elucidate effects of key molecular and cellular parameters on temporal and spatial distribution of cytokines in cell population and cell/matrix systems. In this article we summarize some of our recent findings on dynamics of growth factor depletion by cellular endocytic trafficking, growth factor transport through cellular matrices, and growth factor production and release by autocrine cell systems. (c) 1996 John Wiley & Sons, Inc. 相似文献