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391.
Charles A. Owen 《Biological trace element research》1981,3(3):217-224
The subcutaneous injection of Walker 256 carcinosarcoma cells into a rat was followed by a pronounced increase in plasma ceruloplasmin activity. This lasted only about 3 weeks even though the tumors were still enlarging rapidly. Based upon studies with67Cu, the increase in plasma ceruloplasmin seemed to reflect increased production of the enzyme by the livers of rats bearing the tumors. Injections of turpentine also raised plasma ceruloplasmin, but to a significantly lesser extent and normal values were reached within 2 weeks. 相似文献
392.
393.
Margareta Glanser Siniša N. Ban Charles L. Cooney 《Applied microbiology and biotechnology》1981,13(1):54-59
Summary In this work we discuss the aerobic biodegradation of sodium sulfite liquor of (NaSSL) and sodium lignosulfonate (NaLS) in
a firwood sulfite waste liquor by a mixed culture of microorganisms consisting of two Trichosporon yeasts and bacteria in the Arthrobacter (two species), Pseudomonas and Chromabacterium genera. Under established process parameters, the NaSSL was biodegradated in one or two stages by mixed cultures. The kinetics
in each stage was studied. The optimal ratio of NaLS and sugars in the substrate for the growth of mixed culture was determined.
The growth of the monocultures of the bacteria on the NaLS and the growth of the yeasts as monocultures on the NaSSL substrate
were examined. UV absorption and IR spectra were employed as analytical methods to follow the microbial degradation of NaLS.
The aim of this research was to study the biodegradation process and kinetics and to remove by means of mixed culture the
maximum amount of organic matter from NaSSL. 相似文献
394.
Margaret S.Y. Chai Charles A. Reavill Cecelio J. Vidal David T. Plummer 《Neurochemistry international》1981,3(5):311-321
Extraction of the white matter of pig brain with EDTA, lysolecithin or Triton X-100 gave poor yields of soluble acetylcholinesterase although these agents had proved effective at solubilizing the enzyme in the grey matter. This finding, together with the observation that the strong detergent sodium deoxycholate, was needed to solubilize the enzyme, shows that it is more difficult to remove acetylcholinesterase from the white matter of brain than from the grey. This could mean that the enzyme in the white matter is more firmly bound to the membrane than the enzyme in the grey matter.The difference in binding of the enzyme from the two regions of the brain is also reflected in the affinity chromatography experiments which showed a lower recovery for the acetylcholinesterase of white matter compared with the enzyme from grey matter.Starch-block electrophoresis of acetylcholinesterase showed a single negatively charged peak of activity for both the naturally soluble and the deoxycholate solubilized preparations. The presence of only one form on electrophoresis suggests that the molecular species of acetylcholinesterase do not arise from differences in charge.Sucrose density gradient centrifugation of the two preparations from white matter gave a single peak of activity with a sedimentation constant of about 10 S. This corresponds closely to the major species of molecular weight 260,000 detected by gradient gel electrophoresis. Other forms detected in both enzyme preparations by gradient gel electrophoresis were species with molecular weights of 660,000, 180,000, 130,000 and 115,000. The significance of these species in terms of the formation of oligomers is discussed.A comparison was made with the corresponding preparations of acetylcholinesterase from the grey matter and the results showed that acetylcholinesterase from the white and grey matter of pig brain were very similar. The exception to this was the species with a molecular weight of 68,000 which was present in the grey but not the white matter of pig brain. 相似文献
395.
396.
A deterministic predator-prey model is presented for describing the dynamics of a solid tumor in the presence of a specifically
reactive lymphocyte population which is stimulated by, and antagonistic to, the tumor. The qualitative behavior of the solutions
is developed and briefly compared to the results of transplantation experiments. Although the model is primitive, it leads
to predictions that are in general agreement with observation and intuitive expectations. In particular, it is found that:
(1) very low levels of transplanted tumor will not survive in the recipient. (2) At somewhat higher levels, tumor growth will
be uncontrolled in the syngeneic recipient. However, immune intervention if early enough, can lead to control and elimination
of the tumor. (3) At still higher levels of transplanted tumor, no amount of immune intervention will be effective in controlling
the tumor. (4) If the recipients immune system is suppressed prior to transplantation, or is debilitated for any reason, the
chance that the tumor will grow increases. (5) If the recipients immune system is stimulated prior to transplantation, the
chance of tumor survival decreases. (6) The survival of the tumor is much more sensitive to changes in tumor parameters (for
example, antigenicity) than in lymphocyte parameters. In addition it makes the unintuitive prediction that (7) There areisolated instances under which anincrease in the number of lymphocytes canincrease the chance of tumor survival. 相似文献
397.
Charles J. Mode 《Bulletin of mathematical biology》1977,39(6):693-704
Stochastic models of human reproduction are beginning to play significant roles in the evaluation of family planning programs.
A class of stochastic processes called absorbing, agedependent, semi-Markov processes frequently arises in the construction
of such models. The paper begins with a discussion of some technicalities regarding absorbing, age-dependent, semi-Markov
processes. Then, an algorithm due to Littman, which makes possible the computerization of this class of stochastic processes,
is presented. Briefly, Littman’s algorithm provides an efficient method for numerically solving systems of renewal type integral
equations, provided the system does not contain a large number of equations. After setting down a concrete model for a large
clinical trial of intrauterine devices conducted in Taiwan, the paper concludes with a discussion of a method for validating
the model based on the data collected in the clinical trial.
Presented at the Society for Mathematical Biology Meeting, University of Pennsylvania, Philadelphia, August 19–21, 1976. 相似文献
398.
Two diastereoisomers, 5R,6R-5-hydroxy-6(9α)-oxido-11α,15S-dihydroxyprost-13-enoic acid (7) and 5S,6S-5-hydroxy-6(9α)-oxido-11α,15S-dihydroxyprost-13-enoic acid (10) were synthesized for evaluation as possible biosynthetic intermediates in the enzymatic transformation of PGH2 or PGG2 into PGI2. The synthetic sequence entails the stereospecific reduction of the 9-keto function in PGE2 methyl ester after protecting the C-11 and C-15 hydroxyls as tbutyldimethylsilyl ethers. The resulting PGF2α derivative was epoxidized exclusively at the C-5 (6) double bond to yield a mixture of epoxides, which underwent facile rearrangement with SiO2 to yield the 5S,6S and 5R,6R-5-hydroxy-6(9α)-oxido cyclic ethers. It was found that dog aortic microsomes were unable to transform radioactive 9β-5S,6S[3H] or 9β-5R,6R[3H]-5-hydroxy-6(9α)-oxido cyclic ethers into PGI2. Also, when either diastereoisomer was included in the incubation mixture, neither isomer diluted the conversion of [1-14C]arachidonic acid into [1-14C]PGI2. 相似文献
399.
Michael Fernandes Gaddo Onesti Roberto Fiorentini Giuseppe Bellini Anne B. Gould Kwan Eun Kim Charles Swartz 《Life sciences》1977,20(4):623-626
Renal hypertension was induced by ligation of the aorta between renal arteries in rats sympathectomized with 6-hydroxydopamine. In the early phase, equally severe hypertension developed in the denervated group as compared to innervated controls. Later, blood pressure was lower in the denervated rats. Initially, increases in plasma renin were seen in both groups; the levels, however, were markedly lower in the denervated rats. Later, the renin levels were similar and not different from baseline. It is concluded that adrenergic neural activity is not essential in the development of renal hypertension; the maintenance of the chronic state, however, depends in part on adrenergic innervation. 相似文献
400.
Frank A. Smith Dwight E. Gardner Charles L. Yuile Ofelia H. de Lopez Larry L. Hall 《Life sciences》1977,20(7):1131-1138
Rats given 5 ppm F as FAc (equivalent to 26 ppm of NaFac) in the drinking water for approximately four months deposited as much fluoride in the skeletal system as did rats receiving 5 ppm F as NaF in the water. Little evidence could be found for the presence of organically bound fluoride in bone after ingesting FAc, though an appreciable proportion of skeletal fluoride deposited when NaF was ingested was shown not to respond to the fluoride ion electrode. The daily urinary excretion of total fluoride after FAc was somewhat greater than after NaF; about two thirds of this fluoride responded to the electrode, whereas more than 90 percent of the total fluoride after NaF was ionic in nature. The data are interpreted as showing that the rat is capable of splitting the C-F bond in FAc and/or in its fluoride-containing metabolites, with subsequent skeletal storage and renal excretion of the released fluoride ion. The chronic administration of this low level of FAc caused an early but temporary retardation of growth. The Krebs cycle was interfered with, as evidenced by increased concentrations of citrate in the kidney and urine. At termination of the experiment, histological examination of the testes showed that the FAc had induced severe damage characterized by massive disorganization of the tubules, nearly total loss of functional cells, absence of sperm, and damage to the Sertoli cells. 相似文献