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  • Springer  (15)
  • American Chemical Society  (1)
  • The American Association for the Advancement of Science (AAAS)
  • Elsevier
  • 1985-1989  (16)
  • 1
    ISSN: 1573-7330
    Keywords: human in vitro fertilization ; implantation ; abortion ; follicular stimulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The incidence of pregnancy and abortion was analyzed in 1679 patients having embryos replaced after oocyte recovery and in vitro fertilization in order to alleviate their infertility. In these patients, 364 pregnancies were achieved and 108 abortions occurred. Patients were treated either on their natural cycle, having a spontaneous luteinizing hormone (LH) surge to induce ovalation, or after ovarian stimulation using clomiphene citrate alone or in combination with human menopausal gonadotropin (hMG). The data were assessed in relation to the numbers of embryos replaced, the follicular stimulation and ovulation induction regime used; the dose of gonadotropins and the dose of antiestrogens, and the age of the patient. The most successful treatment for the number of live births per laparoscopy was the use of clomiphene citrate in combination with human menopausal gonadotropin followed by human chorionic gonadotropin (hCG) to induce follicular maturation and ovulation. This treatment produced a significantly higher (P〈0.001) number of patients with multiple embryos (86.5%). There was no significant effect on pregnancy or abortion with alow (〈400-mg) or high (≥400-mg) dose of clomiphene. The total dose of gonadotropins used did not influence the incidence of pregnancy or abortion. The use of hCG with hMG induced a significant (P〈0.01) positive effect on the incidence of pregnancy. The incidence of pregnancy showed a progressive decline with increasing age but there was a highly significant (P〈0.01) increase in the incidence of abortion with increasing age. With increasing numbers of embryos replaced, up to three, the incidence of deliveries increased. The most successful follicular stimulation regime and the replacement of three embryos produced about 25% of the patients delivering normal healthy babies after embryo replacement.
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  • 2
    ISSN: 1573-7330
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-7330
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1520-5827
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-1424
    Keywords: K+ channel ; ATP ; ATP4− ; ADP3− ; RINm5F cell
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The31P-NMR technique has been used to assess the intracellular ratios and concentrations of mobile ATP and ADP and the intracellular pH in an insulin-secreting cell line, RINm5F. The single-channel current-recording technique has been used to investigate the effects of changes in the concentrations of ATP and ADP on the gating of nucleotide-dependent K+ channels. Adding ATP to the membrane inside closes these channels. However, in the continued presence of ATP adding ADP invariably leads to the reactivation of ATP-inhibited K+ channels, even at ATP4−/ADP3− concentration ratios greater than 7∶1. Interactions between ATP4− and ADP3− seem competitive. An increase in the concentration ratio ATP4−/ADP3− consistently evoked a decrease in the open-state probability of K+ channels; conversely a decrease in ATP4−/ADP3− increased the frequency of K+ channel opening events. Channel gating was also influenced by changes in the absolute concentrations of ATP4− and ADP3−, at constant free concentration ratios. ADP-evoked stimulation of ATP-inhibited channels did not result from phosphorylation of the channel, as ADP-β-S, a nonhydrolyzable analog of ADP, not only stimulated but enhanced ADP-induced activation of K+ channels, in the presence of ATP. Similarly, ADP was able to activate K+ channels in the presence of two nonhydrolyzable derivatives of ATP, AMP-PNP and βγmethylene ATP.
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  • 6
    ISSN: 1432-2048
    Keywords: Glutathione S-transferase ; Herbieide detoxification ; Suspension culture ; Zea (herbicide detoxification)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The metabolism of the s-triazine herbicide atrazine has been compared in Zea mays seedlings and cell suspension cultures. The rapid detoxification observed in the shoots of whole plants was not seen in the cultured cells. This difference in metabolism could be accounted for by the varying substrate specificities of the isoenzymes of glutathione S-transferase (EC 2.5.1.18) present in the plant and the cells. A single form of the enzyme isolated from leaf tissue conjugated both atrazine and the chloracetanilide herbicide metolachlor. However, the two isoenzymes present in suspension-cultured cells although active against metolachlor, showed no activity toward atrazine. Following purification, the major form of transferase present in the cells was physically similar to the enzyme isolated from leaf (Mr=55000). Both proteins were dimers of subunit Mr=26300, and with isoelectric points in the range pH 4.3-4.9. The minor form of the enzyme present in culture showed a greater specificity for metolachlor than the major species. In addition the overall activity and ratio of the two isoenzymes varied over the culture growth cycle. These findings illustrate the need for characterizing enzymes involved in herbicide detoxification in plant cell cultures.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Planta 171 (1987), S. 144-144 
    ISSN: 1432-2048
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Planta 175 (1988), S. 99-106 
    ISSN: 1432-2048
    Keywords: Detoxification (herbicide) ; Enzyme induction ; Glutathione S-transferase ; Herbicide antidote ; Zea (herbicide detoxification)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An antiserum to glutathione S-transferase (EC 2.5.1.18) from maize (Zea mays L.) responsible for herbicide detoxification has been raised in rabbit. The antiserum was specific to the Mr 26000 subunit of the enzyme from maize seedlings and suspension-cultured cells, and recognized the isoenzymes active toward both atrazine and metolachlor. When plants were treated for 24 h with the herbicide antidote N,N-diallyl-2-2-dich-loroacetamide (DDCA), enzyme activities toward metolachlor were doubled in the roots and this was associated with a 70% increase in immunodetectable protein. Translation of polysomal RNA in vitro showed that the increase in the transferase in root tissue was brought about by a ninefold increase in mRNA activity encoding the enzyme. Treatment of suspension-cultured cells with cinnamic acid, metolachlor and DDCA raised enzyme activities but did not increase synthesis of glutathione S-transferase. In cultured maize cells, enzyme synthesis was maximal in mid-logarithmic phase, coinciding with the highest levels of enzyme activity. When callus cultures were established from the shoots of a maize line known to conjugate chloro-s-triazines, enzyme activity towards atrazine was lost during primary dedifferentiation. However, levels of total immunodetectable enzyme and activity toward metolachlor were increased in cultured cells compared with the parent shoot tissue.
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  • 9
    ISSN: 1573-4927
    Keywords: Trisomy ; chromatin ; average nucleosome size ; mouse
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The chromatin of a mouse that is trisomic for part of chromosome 7 was investigated. Chromatin from trisomic tissue has a smaller average nucleosome DNA repeat length than chromatin from tissue taken from normal diploid littermates. DNA of the nucleosome cores is the same size in both normal and trisomic tissues. Not all of the nucleosome monomers have different repeat lengths. Normal and trisomic mouse kidney cells in tissue culture maintained their nucleosome repeat-length differences.
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  • 10
    ISSN: 1573-0581
    Keywords: electromagnetics ; permafrost ; offshore exploration ; electrical anisotropy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A novel variation of the geophysical technique known as MOSES, for Magnetometric Off-Shore Electrical Sounding, has been developed to map the electrical properties of the sea floor in Aretic regions. The particular target is the permafrost layer under the Beaufort Sea, a layer containing frozen or partially frozen sediment from 100 to 600 m thick underlying shallow sea water, typically 10 to 100 m deep, and several tens of metres of soft sediment. A detailed knowledge of the location and physical properties of the permafrost layer is essential for accurate interpretation of reflection seismic data. The permafrost can contain pockets, regions or layers of gas hydrate. The latter is both a possible resource and a hazard to drilling operations or hydrocarbon production. A local map of the permafrost zone is essential geotechnical information required prior to the construction of an offshore structure or pipeline. The MOSES method is particularly suitable for offshore electrical mapping as it can be made relatively insensitive to the shielding effects of the highly conductive sea water, in sharp contrast to many other electrical techniques. The transmitter is a vertical, long-wire bipole, extending from the sea surface to the sea floor. A commutated current is fed to two large electrodes: one near the sea surface and the other on the sea floor. The return current is through the sea water and the subjacent sediment. The receiver consists of two horizontal orthogonal coils located on the sea floor, and the data are measurements of two components of the magnetic field as a function of frequency and transmitter-receiver horizontal separation. The electrical conductivity of a sample of frozen material is much smaller than that of unfrozen or partially frozen sediment of the same type. Frozen and unfrozen thin layers are often observed sequentially throughout the geological section. The resistivity measured as a function of depth by an electrical logging tool is consequently highly variable. The resulting depth-averaged resistivity, the resistivity resolved by a surface electrical method, is macro-an-isotropic. An experimental design study reveals that both the vertical and horizontal averaged resistivities could be determined in a MOSES sounding without vertical scale distortion. A test of the methodology in very shallow water was conducted in the spring of 1986 at a site, approximate coordinates (70° N, 134.5° W), 85 km north-west of the town of Tuktoyaktuk. The instrumentation was lowered and subsequently recovered through holes in the ice which covers the Beaufort Sea at that time of the year. The transmitter power was obtained from a single lead-acid battery. Transmitter-receiver separations ranged from 10 to 300 m. A rapid increase in sediment resistivity with depth was observed. The higher resistivity values are consistent with those expected for a partially frozen zone.
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