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  • 1
    ISSN: 1432-2307
    Keywords: Mouse teratoma ; Centrifugal elutriation ; Melanotic neuroepithelium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Dissociation and elutriation procedures were applied to the OTT-6050 mouse teratoma line carried in subcutaneous implants in 129/J mice in order to enrich the differentiating neuroepithelial cells. Subsequent renal subcapsular implantation of one of the resultant cell fractions (IB-9) in syngeneic mice led to the constant production of macroscopically pigmented tumors which, in addition to undifferentiated stem cells, contained primitive neuroepithelial populations composed of medullary epithelium, neuroblasts, and numerous ependymoblastic rosettes. Melanin pigment, confirmed by the presence of melanosomes and premelanosomes, was found in medullary epithelium and other primitive neural cells. The tumors preserved their characteristics through 65 sequential transplants over a period of 5 1/3 years. The pigment was maintained in vitro for up to 3 months in an organ culture system. Subcutaneous or intracerebral transplantation of the renal tumors of the IB-9 fraction accentuated the capacity of these primitive cells towards further neuroepithelial differentiation into mature synapse-forming neurons, and was associated with a decrease in primitive neuroepithelium and an absence or a marked decrease of melanin. Return of the tumor to the kidney resulted in the reappearance of melanin after one to three passages, again associated with the presence of primitive neuroepithelium. The recognition of melanin pigment in the OTT-6050 mouse teratoma transplants could be a useful marker for the successful selection of primitive neuroepithelial cell populations in this experimental tumor system. These populations may help to study the relationship between melanin production and certain types of primitive neuroectodermal tumors in man.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0533
    Keywords: Glioblastomas ; Organ culture method ; Autoradiography ; Kinetics ; Growth fraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Five human glioblastomas maintained in an organ culture system were studied by autoradiography to determine, after 8 days in vitro, the growth fraction (GF) of the explants, their total cell cycle time (T C) and cell cycle phase durations (T S,T G1,T G2 andT M), and their potential doubling time (T pot) after pulse-labeling with [3H] TdR for 1 h. These parameters were derived from computer analysis of fraction of labeled mitoses (FLM) curves. The results fell into two groups. In two tumors, the cultures had a GF of 0.25 and 0.23. From the FLM curves were derived aT C of 89 and 83 h, aT S of 16.5 and 9.5 h, and aT G1 of 60 and 61 h.T M was estimated at 0.9 and 0.6 h, andT G2 12h. TheT pot was 12 days. These values approximate those reported for glioblastomas and other human malignancies in vivo. The explants of three other glioblastomas gave different FLM curves: the derivedT S were increased to 36 and 55 h, estimatedT M ranged from 2.4 to 4.5 h, andT G2 ranged from 11 to 20 h.T C andT G1 could not be estimated. In two tumors the GF was reduced to 0.12 and 0.11, with aT pot of respectively 52 and 39 days. These values are comparable to those reported for astrocytomas of intermediate malignancy. In the third tumor, the GF was only 0.014. The reduction in GF and the lengthening of cell cycle components in this group of explants are similar to the kinetic changes reported in some in vivo tumors and three-dimensional in vitro systems that have reached a plateau stage of growth. They are probably related to the greater opportunities for cell-to-cell contacts and the resulting increased differentiation favored by the organ culture technique.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We report here the complete nucleotide sequence of the E. coli triose phosphate isomerase gene. The gene encodes a polypeptide of 255 amino acids which is approximately 46% homologous to eukaryotic triose phosphate isomerases, and approximately 38% homologous to the enzyme from a thermophilic bacterium, Bacillus stearothermophilus. The nucleotide sequence is 55% homologous to that of the corresponding gene in the yeast Saccharomyces cerevisiae. To our knowledge, this is the first report of the sequence of a gene coding a glycolytic enzyme from a prokaryotic organism.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The microorganism Candida utilis was grown on both filtered and unfiltered substrate obtained from enzymatic hydrolysis of starch in corn dust. For growth on filtered substrate, the average integrated biomass energetic yield value based on biomass-substrate data was η = 0.55 and for growth on unfiltered substrate an average yield value of η = 0.59 was obtained. Material and energy balances showed that the presence of unfiltered corn residue in the media had no significant effect on the yields. Statistical methods were developed and used to obtain best estimates of the growth parameters. Values of the biomass energetic yield corrected for maintenance (ηmax = 0.619) and the maintenance coefficient (me = 0.043) were obtained for growth on filtered substrate. Values of ηmax = 0.741 and me = 0.142 were obtained for the growth on unfiltered substrate. The consistency of data and parameter estimates was relatively good for filtered substrate; however, parameter estimates for unfiltered substrate were not consistent. Growth experiments without filtration of the products of starch hydrolysis resulted in protein-enriched products with about 39.73% protein.
    Additional Material: 14 Tab.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 24 (1982), S. 633-649 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This work is concerned with statistical methods to estimate yield and maintenance parameters associated with microbial growth. For a given dilution rate, an experimenter typically measures substrate concentration, oxygen utilization rate, the rate of carbon dioxide evolution, and biomass concentration. These correlated response variables each contain information about the maintenance and yield parameters of interest. A maximum likelihood estimator which combines this correlated information for the yield and maintenance parameters is proposed, evaluated, and tested on literature data. Both point and interval estimators are considered.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-2878
    Keywords: Command ; control ; and communications ; military cybernetics ; optimal decision functions ; minimum expected cost
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract A new generation ofC 3 (command, control, and communication) models for military cybernetics is developed. Recursive equations for the solution of theC 3 problem are derived for an amphibious campaign with linear, time-varying dynamics. Air and ground commanders are assumed to have perfect intelligence and perfect communications. Numerical results are given for the optimal decision rules.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1573-2878
    Keywords: Command, control, and communication ; integral equations ; optimal decision functions ; minimum expected cost
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract A formidable problem in the mathematical studies of C3 (command, control, and communication) is the determination of the optimal decision rules for force commitments to be employed by headquarters. Recursive equations are derived for an amphibious campaign with time-invariant linear dynamics and quadratic costs. Air and ground commanders are assumed to have perfect intelligence with degraded communication between them.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1572-9699
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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