Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Springer  (15)
  • The American Association for the Advancement of Science (AAAS)
  • Elsevier
  • 1985-1989  (15)
  • 1
    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.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 2
    Electronic Resource
    Electronic Resource
    Springer
    ISSN: 1573-2665
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Studies of the basic biochemical mechanisms underlying muscle damage aimed at finding agents which might reduce the amount of damage occurring in muscular dystrophy and other severe myopathies have been performed. These have suggested three types of agent which might be useful for this purpose, namely calcium antagonists, phospholipase inhibitors, and antioxidants or scavengers of reactive-free radicals. Vitamin E falls into the latter of these three categories and has been shown to reduce the amount of damage which occurs in isolated skeletal muscles following a given stress. It is suggested that, in the absence of calcium antagonists having relatively specific and effective actions on skeletal muscle or suitable inhibitors of muscle phospholipases in man, therapy with vitamin E or other antioxidants may reduce the amount of muscle damage occurring in patients with severe myopathies.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 1573-5117
    Keywords: pH ; aluminium ; drift ; macroinvertebrates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 24 h experimental episodes were created in a soft-water stream in upland Wales, by the simultaneous addition at separate points of sulphuric acid, aluminium sulphate and citric acid. In an upstream reference zone (A) the pH remained above 7, while in the treatment zones, B, C and D successively downstream, it was reduced to c. pH 4.9. Concentrations of filterable aluminium were 0.05 mg l-1 in Zone B, 0.27 mg l-1 (0.11 mg l-1 ‘labile’) in Zone C, and 0.23 mg l-1 (0.00 mg l-1 ‘labile’) in Zone D. Chemical manipulation coincided with a spate, during which flow increased from 0.02 m3s -1 to a maximum of 0.07 m3s-1. Only the ephemeropteran B. rhodani showed a drift response: drift density was not affected by flow (Zone A) or by organically bound aluminium (Zone D), but increased approximately 6-fold in both the acid (B) and ‘labile’ aluminium (C) zones; its benthic density declined significantly in Zones C and D, by 78% and 89% respectively. We relate these results to the biological importance of aluminium chemistry during natural acidic episodes.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 4
    ISSN: 1573-2665
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Magnetic resonance (MR) is rapidly entering many fields of clinical medicine following a long history as a powerful tool in physics and chemistry. The non-invasive and non-destructive property of this technique has enabled the chemical shift in higher magnetic fields to be exploited to identify and quantitate metabolites in bothin vitro andin vivo analysis. High resolution proton spectroscopy of body fluids has been shown to be complementary with established analytical techniques, while the development of whole body large bore magnets is enabling both the study of structure and metabolism in humansin vivo. Phosphorus MR spectroscopy has provided a method of monitoring ATP production and utilisationin situ in both perfused preparation and intact tissue. In human muscle it has been possible to test established theories of tissue energy metabolism. It provides a unique method with which to evaluate the state of tissue oxidative metabolism. The opportunities afforded by other nuclei are being studied, but the low sensitivity of the MR technique forces limitations. Recent technical advances in tissue localization have as yet only been applied in a limited way. The use of MR in metabolic disease will be considered with specific reference to disorders of skeletal muscle metabolism.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 5
    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.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 6
    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.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 7
    ISSN: 1573-7330
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 8
    ISSN: 1573-7330
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 9
    ISSN: 1439-6327
    Keywords: Muscle weakness ; Muscle fatigue
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Fatiguing contractions of the adductor pollicis muscle were produced by intermittent supramaximal stimulation of the ulnar nerve in a set frequency pattern, in six normal subjects. At the end of an initial fatiguing contraction series, low frequency fatigue (LFF) had been induced and persisted at 15 min of recovery. Stimulated fatiguing activity was then repeated in an identical fashion to the initial series. At high frequencies, declines in force were similar for both series. At low frequencies, declines in force were greater during the second series despite similar changes in compound muscle action potential amplitude. This confirmation that LFF persists during subsequent stimulated activity, and reduces low but not high frequency fatigue resistance, suggests that the impaired endurance of fatigued muscle during voluntary activity primarily results from peripheral changes at low frequency. These findings also have implications for therapeutic electrical stimulation of muscle.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 10
    ISSN: 1439-6327
    Keywords: Eccentric contractions ; Muscle damage ; Muscle pain ; Radioisotope uptake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We have studied the occurrence of skeletal muscle uptake of 99mtechnetium pyrophosphate (Tc-PYP), creatine kinase (CK) release and muscle pain in normal subjects after exercise. Five subjects stepped on and off a high bench in such a way that one leg stepped up and the other down. Pain only developed in the muscles used for descending: quadriceps, adductors and gluteal muscles of one leg and the calf muscle of the other. A large rise in plasma CK occurred in four subjects but no increased Tc-PYP muscle uptake was seen in the quadriceps. In the four subjects with high CK effluxes, increased isotope uptake was seen in the thigh adductors used when stepping down; in the two subjects with the largest CK effluxes there was extensive uptake into the gluteal muscles. Muscle pain preceded and was not well correlated with either the magnitude of the enzyme release or the amount and distribution of increased muscle isotope uptake. We conclude that delayed onset muscle pain, the cause of which remains unknown, is a poor indicator of muscle damage as indicated by circulating muscle enzymes and muscle isotope uptake. Tc-PYP uptake by skeletal muscle can provide useful information about the localisation and time course of muscle damage.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...