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91.
92.
Michael P. Challen Timothy J. Elliott Ursula Kües Lorna A. Casselton 《Molecular genetics and genomics : MGG》1993,241(3-4):474-478
The A mating factor of Coprinus cinereus determines compatibility in mating by regulating part of a developmental sequence that leads to dikaryon formation. The A genes that trigger development encode two different classes of homeodomain proteins, and for a successful mating, a protein of one class, HD 1, must interact with a protein of the other class, HD 2. In this report we show that C. cinereus A genes that encode HD 2 proteins, a2-1 and b2-1, can elicit A-regulated development in the heterologous host C. bilanatus. Transformation rates were very low, suggesting that the genes were poorly transcribed. The fact that the HD 2 genes are functionally expressed implies successful heteromultimeric association of putative DNA-binding proteins coded by the two Coprinus species. This interaction was sufficient to satisfy the need for different A factors in the formation of a fertile C. bilanatus dikaryon, but fertile dikaryons were more readily produced in matings with the a2-1 gene transformants. The C. cinereus A genes, b1-1 and d1-1, which encode HD1 proteins, were either not expressed or their proteins were non-functional in C. bilanatus. These experiments raise some interesting questions regarding HD1–HD2 protein interactions. 相似文献
93.
Young Pardosa hortensis not only need their mother's help to leave their cocoon once developed (about 20 days), as they are unable to open it by themselves, but also during the period they are carried around in the cocoon. Using radioactive markers, indirect evidence revealed that the mother periodically opens the cocoon to feed her young and reseals it with fresh silk. Water is probably the main component in trophic exchange. 相似文献
94.
Aldo Ferretti Vincent P. Flanagan Joseph T. Judd Padmanabhan P. Nair Philip R. Taylor 《The Journal of nutritional biochemistry》1993,4(12)
Dietary supplementation with a fish oil concentrate (FOC) reduced the endogenous synthesis of prostacyclin (PGI2), as measured by the excretion of its major urinary catabolite, 2,3-dinor-6-oxo-PGF1α (PGI2-M). Thirty-four healthy men (24–57 years old) were given controlled diets and supplements that provided 40% of the energy from fat and a minimum of 22 mg/d of α-tocopherol for two consecutive experimental periods of 10 weeks each. During the experimental periods, the men received capsules containing 15 g/d of a placebo oil (PO) (period 1) or 15 g/d of the FOC (period 2). In addition to the PO or FOC, capsules contained 1 mg of α-tocopherol per g of fat as an antioxidant. The average daily excretion of PGI2-M during the last week of FOC supplementation (period 2) was 22% less (P = 0.0001) than at the end of the first period. These results are at variance with those reported in comparable human studies conducted by other investigators during the middle and late 1980s. A 20% reduction (P = 0.003) in the 11-dehydrothromboxane B2 to 2,3-dinor-6-oxo-PGF1α excretion ratio at the end of period 2 in this study demonstrates that a shift of the n-6 to n-3 polyunsaturated fatty acid ratio from 12.5 to 2.3 brings about a substantial modulation of the eicosanoid system. 相似文献
95.
Fenge Christel Klein Cornelia Heuer Carsten Siegel Ursula Fraune Elisabeth 《Cytotechnology》1993,11(3):233-244
For an optimized bioreactor design which is adapted to the cultivation of sensitive animal cells different modular bioreactor components for gentle agitation, sufficient aeration and long-term perfusion were developed and investigated with respect to their suitability from laboratory to production scale. Aeration systems have been designed for both shear sensitive cells and cells which tolerate bubbles. The systems are based on either membranes for bubble-free aeration or stainless steel sparger systems. They were characterized by determination of their oxygen transfer capacity and optimized in cultivation processes of different cell lines under process conditions such as batch and perfusion mode.Different impellers for suspension cells and cells grown on carriers were investigated for their suitability to ensure homogeneous gentle mixing. A large pitch blade impeller as well as a novel 3-blade segment impeller are appropriate for homogeneous mixing at low shear rates. Especially with the 3-blade segment impeller fluid mechanical stress can be reduced at a given stirrer speed which is advantageous for the cultivation of cells attached to microcarriers or extremely shear sensitive suspension cells. However, our results indicate that shear sensitivity of animal cells has been generally overestimated.Continuous perfusion of both suspension cell cultures and cells cultivated on microcarriers could be successfully performed over extended periods of time using stainless steel spinfilters with appropriate pore sizes and systems based on microporous hydrophilic membranes. Spinfilters are suitable cell retention systems for technical scale bioreactors allowing continuous perfusion cultures of suspension cells (pore size 10 to 20 m) as well as anchorage dependent cells grown on microcarriers (pore size 75 m) over six weeks to 3 months.Applying the developed modules for agitation, aeration and perfusion process adapted bioreactor set-ups can be realized which ensure optimum growth and product formation conditions in order to maximize cell and product yields. 相似文献
96.
Gustav Kramer und Ursula von St. Paul 《Journal of Ornithology》1956,97(4):353-370
Zusammenfassung Schon veröffentlichte Feststellungen über verringertes Heimfindevermögen von Brieftauben im Winter werden bestätigt.Durch wiederholte Auflassungen über die gleiche Kurzstrecke (von NNW 22 km nach SSO) wird gezeigt, daß die Einzeltaube regelmäßig wesentlich schlechter abschneidet, wenn sie die gleiche, im Sommer durchflogene Strecke im Winter wiederholt. Durch Verwendung einer hinreichenden Anzahl von Erstfliegern in beiden Jahreszeiten wird der Wintereffekt auch durch Vergleich von Heimkehrschnelligkeiten verschiedener Individuen sichergestellt.Es wird gezeigt, daß die Verwandlung des Landschaftsbildes nicht die Ursache des winterlichen Versagens sein kann. Es ist auch unwahrscheinlich, daß die im Winter geringere Höhe des Sonnenstandes schuld ist. Entgegen einer früher vonKramer geäußerten Meinung können auch weder niedrige Temperaturen als solche noch direkt mit ihnen streng gekoppelte Faktoren verantwortlich gemacht werden.Der Einwand, daß es sich beim Wintereffekt nicht um eine Orientierungsbehinderung, sondern um eine jahreszeitlich, vielleicht mit der Taglänge korrelierte Schwächung des Heimkehrimpulses handeln möge, wird kritisch besprochen. Gegen diesen Einwand wird geltend gemacht, daß nach den bisherigen Erfahrungen der März noch zu den Winter-Monaten zählt; sogar ein Aprilflug trug intermediäre Züge. Dagegen funktioniert das Heimkehrvermögen im September noch gut. — Eine Korrelation mit der Intensität des Fortpflanzungsverhaltens kann deswegen nicht vorliegen, weil die Fortpflanzungsaktivität schon im Februar erheblich gesteigert ist. Es wird der Nachweis geführt, daß bei gleichen Temperaturen im Winter signifikant verschiedene Heimkehrerfolge an nahe beisammenliegenden Daten (3. 1. und 26. 1. 1956) erzielt werden können.Auch für andere Strecken (36 km S — N, 41 km O — W, 94 km S — N) werden Vergleiche von Heimflügen im Sommer mit solchen im Winter angestellt. Die Winterergebnisse sind durchweg erheblich schlechter.Das Bestehen des Wintereffekts zeigt, daß die Orientierung bei der Heimkehr auch über kurze Strecken nicht auf dem visuellen Erkennen von Landschaftsstrukturen beruht. Der Orientierungsmechanismus ist vielmehr unbekannt. Es ist vorläufig zu vermuten, daß er identisch ist mit dem, der über weitere Distanzen wirksam ist.Mit Unterstützung der Deutschen Forschungsgemeinschaft, welche das Fahrzeug zur Verfügung stellte und die Betriebsmittel dafür trug. 相似文献
97.
Kayser Bengt; Favier Roland; Ferretti Guido; Desplanches Dominique; Spielvogel Hilde; Koubi Harry; Sempore Brigitte; Hoppeler Hans 《Journal of applied physiology》1996,81(6):2488-2494
Kayser, Bengt, Roland Favier, Guido Ferretti, DominiqueDesplanches, Hilde Spielvogel, Harry Koubi, Brigitte Sempore, and HansHoppeler. Lactate and epinephrine during exercise in altitudenatives. J. Appl. Physiol. 81(6):2488-2494, 1996.We tested the hypothesis that the reported lowblood lactate accumulation ([La]) during exercise inaltitude-native humans is refractory to hypoxia-normoxia transitions byinvestigating whether acute changes in inspiredO2 fraction(FIO2) affect the[La] vs. power output ()relationship or, alternatively, as reported for lowlanders, whetherchanges in [La] vs. on changes inFIO2 are related tochanges in blood epinephrine concentration ([Epi]). Altitude natives [n = 8, age 24 ± 1 (SE) yr, body mass 62 ± 3 kg, height 167 ± 2 cm]in La Paz, Bolivia (3,600 m) performed incremental exercise with twolegs and one leg in chronic hypoxia and acute normoxia (AN). Submaximalone- and two-leg O2 uptake (O2) vs. relationships were not altered byFIO2. AN increased two-legpeak O2 by 10% and peak by 7%. AN paradoxically decreasedone-leg peak O2 by 7%,whereas peak remained the same. The[La] vs. relationships were similar tothose reported in unacclimatized lowlanders. There was a shift to theright on AN, and maximum [La] was reduced by 7 and 8% forone- and two-leg exercises, respectively. [Epi] and[La] were tightly related (mean r = 0.81) independently ofFIO2. Thus normoxiaattenuated the increment in both [La] and [Epi]as a function of , whereas the correlation between[La] and [Epi] was unaffected. These data suggest loose linkage of glycolysis to oxidative phosphorylation under influence from [Epi]. In conclusion, high-altitudenatives appear to be not fundamentally different from lowlanders with regard to the effect of acute changes inFIO2 on [La] during exercise. 相似文献
98.
Walter K. F. Seelentag Ursula Günthert Parvin Saremaslani Eva Futo Madeleine Pfaltz Philipp U. Heitz Jürgen Roth 《Histochemistry and cell biology》1996,106(3):283-289
CD44 isoforms have been implicated in tumor progression and metastasis formation. This study presents a thorough immunohistochemical
analysis of CD44 standard and isoform expression in normal human skin appendages and epidermis applying monoclonal antibodies
against CD44s, CD44v3, -v4, -v5, -v6, and -v9. An improved immunohistochemical protocol with microwave-based antigen retrieval
in paraffin sections and heavy metal amplification of the diaminobenzidine reaction product provided enhanced resolution and
sensitivity as compared to studies on frozen sections. The hair follicle, the seborrheic and eccrine sweat glands were strongly
positive for all CD44 isoforms studied. In the latter, the clear cells but not the dark (intercalated) cells were positive.
The sudoriferous ducts adjacent to the glands were weakly positive for all CD44 isoforms and strongly positive near the skin
surface. In the apocrine glands, the basal cells showed only a moderate positivity. The myoepithelial cells expressed only
CD44s. In the epidermis, all CD44 isoforms were detectable, with strongest CD44 immunostaining in the lower third of the stratum
spinosum and weaker staining in the stratum basale and the upper two-thirds of the stratum granulosum. The stratum granulosum
and corneum were unreactive. Thus, a regional and cell type-specific CD44 expression was revealed.
Accepted: 10 May 1996 相似文献
99.
Ursula A. Germann Timothy C. Chambers Suresh V. Ambudkar Ira Pastan Michael M. Gottesman 《Journal of bioenergetics and biomembranes》1995,27(1):53-61
Cells expressing elevated levels of the membrane phosphoprotein P-glycoprotein exhibit a multidrug resistance phenotype. Studies involving protein kinase activators and inhibitors have implied that covalent modification of P-glycoprotein by phosphorylation may modulate its biological activity as a multidrug transporter. Most of these reagents, however, have additional mechanisms of action and may alter drug accumulation within multidrug resistant cells independent of, or in addition to their effects on the state of phosphorylation of P-glycoprotein. The protein kinase(s) responsible for P-glycoprotein phosphorylation has(ve) not been unambiguously identified, although several possible candidates have been suggested. Recent biochemical analyses demonstrate that the major sites of phosphorylation are clustered within the linker region that connects the two homologous halves of P-glycoprotein. Mutational analyses have been initiated to confirm this finding. Preliminary data obtained from phosphorylation- and dephosphorylation-defective mutants suggest that phosphorylation of P-glycoprotein is not essential to confer multidrug resistance. 相似文献
100.
Selective Inhibition of the Tricarboxylic Acid Cycle of GABAergic Neurons with 3-Nitropropionic Acid In Vivo 总被引:2,自引:1,他引:1
Abstract: The effects of 3-nitropropionic acid (3-NPA), an inhibitor of succinate dehydrogenase, on cerebral metabolism were investigated in mice by NMR spectroscopy. 3-NPA, 180 mg/kg, caused a dramatic buildup of succinate. Succinate was labeled 5.5 times better from [1-13 C]glucose than from [2-13 C]acetate, showing a predominantly neuronal accumulation. [1-13 C]Glucose labeled GABA in the C-2 position only, compatible with inhibition of the tricarboxylic acid (TCA) cycle associated with GABA formation, at the level of succinate dehydrogenase. Aspartate was not labeled by [1-13 C]glucose in 3-NPA-intoxicated animals. In contrast, [1-13 C]glucose labeled glutamate in the C-2, C-3, and C-4 positions showing uninhibited cycling of label in the TCA cycle associated with the large, neuronal pool of glutamate. The labeling of glutamine, and hence GABA, from [2-13 C]acetate showed that the TCA cycle of glial cells was unaffected by 3-NPA and that transfer of glutamine from glia to neurons took place during 3-NPA intoxication. The high 13 C enrichment of the C-2 position of glutamine from [1-13 C]glucose showed that pyruvate carboxylation was active in glia during 3-NPA intoxication. These findings suggest that 3-NPA in the initial phase of intoxication fairly selectively inhibited the TCA cycle of GABAergic neurons; whereas the TCA cycle of glia remained uninhibited as did the TCA cycle associated with the large neuronal pool of glutamate, which includes glutamatergic neurons. This may help explain why the caudoputamen, which is especially rich in GABAergic neurons, selectively undergoes degeneration both in humans and animals intoxicated with 3-NPA. Further, the present results may be of relevance for the study of basal ganglia disorders such as Huntington's disease. 相似文献