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  • 1
    ISSN: 1546-1718
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Medicine
    Notes: [Auszug] Birds diverged from mammals 300–350 million years ago (Mya). In mammals, the male is the heterogametic sex (XY male and XX female) and 'maleness' is under the control of a testis-determining factor, SRY, located on the Y chromosome. In contrast, sex determination in birds operates through a ...
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1546-1718
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Medicine
    Notes: [Auszug] Townes-Brocks syndrome (IBS, OMIM #107480) is a rare autosomal-dominant malformation syndrome with a combination of anal, renal, limb and ear anomalies1. Cytogenetic findings2 suggested that the gene mutated in IBS maps to chromosome 16q12.1, where SALL1 (previously known as HSAL1), a human ...
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  • 3
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 266 (1977), S. 532-533 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Comparative isozyme studies have proved a powerful tool in substantiating ancestral diploid-tetraploid relationships, for example in teleostean fish14 and various examples of gene duplication in mammals including man have been taken as support of the idea of ancestral polyploidy in this taxonomic ...
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  • 4
    ISSN: 1438-2385
    Keywords: Key words High vacuum transfer ; Solvent assisted flavour evaporation ; Stable isotope dilution analysis ; Flavour isolation ; 4-Hydroxy-2 ; 5-dimethyl-3(2H)-furanone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  A compact and versatile distillation unit was developed for the fast and careful isolation of volatiles from complex food matrices. In connection with a high vacuum pump (5×10–3 Pa), the new technique, designated solvent assisted flavour evaporation (SAFE), allows the isolation of volatiles from either solvent extracts, aqueous foods, such as milk or beer, aqueous food suspensions, such as fruit pulps, or even matrices with a high oil content. Application of SAFE to model solutions of selected aroma compounds resulted in higher yields from both solvent extracts or fatty matrices (50% fat) compared to previously used techniques, such as high vacuum transfer. Direct distillation of aqueous fruit pulps in combination with a stable isotope dilution analysis enabled the fast quantification (60 min including MS analysis) of compounds such as the very polar and unstable 4-hydroxy-2,5-dimethyl-3(2H)-furanone in strawberries (3.2 mg/kg) and tomatoes (340 μg/kg). Furthermore, the direct distillation of aqueous foods, such as beer or orange juice, gave flavourful aqueous distillates free from non-volatile matrix compounds.
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  • 5
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 251 (1974), S. 146-148 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] It seems obvious that the apparent loss of hCG sensitivity of the Leydig cell after birth must be causally connected with the separation of the foetus from the mother. It seems likely that the cells are deprived of a stimulus for growth and activity. This stimulus might be another hormone which is ...
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  • 6
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 249 (1974), S. 377-379 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Testicular androgens are synthesised by stimulus of the gonadotrophic hormones, luteinising hormone (LH) or human chorionic gonadotrophin (HCG). Recent studies have shown that the gonadotrophic effect is mediated by a specific HCG-receptor in the testicular Leydig cells; the stimulation of ...
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  • 7
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Embryonic germ cells as well as germline stem cells from neonatal mouse testis are pluripotent and have differentiation potential similar to embryonic stem cells, suggesting that the germline lineage may retain the ability to generate pluripotent cells. However, until now there has been no ...
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  • 8
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Non-repetitive DNA of anciently tetraploid teleostean species was analysed for the presence of duplicated sequences. Closely related diploid species were investigated in comparison. From the reassociation kinetics of total nuclear DNA, rate constants and fraction sizes of classes of repetitive and non-repetitive sequences were determined. DNA fractions enriched in the slowest renaturing sequence class were prepared and subjected to reassociation. The rate constants of these reactions were compared with the values expected for single-copy DNA from analytical genome size determinations. From reassociated DNA enriched in non-repetitive sequences also the melting temperatures were determined as a measure of internal base sequence heterogeneity. It has been shown that the two ancient tetraploids Cyprinus carpio and Thymallus thymallus are, with regard to the thermal stability of reassociated non-repetitive DNA, and with regard to the correspondence of reaction rates with the values expected for single copy DNA, indistinguishable from diploid controls (Rutilus rutilus, Clupea harengus and Sprattus sprattus). The tetraploid species Salmo irideus, Salvelinus fontinalis and Coregonus lavaretus appear as very recent tetraploids with regard to these criteria. The significance of the results for estimating the time of occurence of polyploidisation events in these taxa is discussed.
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  • 9
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Zusammenfassung Bei Maus, Ratte, Meerschwein und Goldhamster wurde das LDH-Isoenzymmuster während der preimplantativen und frühen postimplantativen Entwicklung mit Hilfe der Mikro-Disk-Elektrophorese untersucht. Dabei fand sich vor der Implantation nur LDH1 (β-Untereinheiten), nach der Implantation zunächst nur LDH5 (α-Untereinheiten); weitere Isoenzyme kamen in Abhängigkeit vom Alter der Embryonen später hinzu. Daraus kann geschlossen werden, daß bei Rodentiern allgemein während der preimplantativen Entwicklung ausschließlich der aus β-Ketten bestehende mütterlich übertragen LDH-Vorrat vorhanden ist und die Aktivierung der embryonalen LDH-Gene erst nach der Implantation erfolgt. Dabei wird zuerst das Gen für α-Ketten und später das Gen für β-Ketten der LDH aktiviert. Im Gegensatz dazu werden beim Kaninchen offensichtlich die embryonalen LDH-Gene bereits längere Zeit vor der Implantation aktiviert: während in Oocyten aus dem Ovar wie bei Rodentiern ebenfalls nur β-Ketten nachweisbar sind, können bei 86 Std alten Embryonen (mittlere Blastocyste) mehrere LDH-Isoenzyme nachgewiesen werden, an deren Bildung α- und β-Untereinheiten beteiligt sind.
    Notes: Summary The LDH-isoenzyme pattern was studied by microdisc electrophoresis in pre-implantation and early post-implantation embryos of the mouse, rat, guinea-pig and Syrian hamster. Prior to implantation only LDH1 (β subunits) is present. After implantation only LDH5 (α subunits) is demonstrable; additional isoenzymes appear subsequently. This indicates that in rodent species in general the total pre-implantation LDH activity is based on the maternally transmitted β subunits while the activation of the embryonal LDH genes starts only with implantation. Moreover, the gene for α-subunits is activated first and the gene for β subunits follows later on. As in rodents, LDH1 is also the only LDH isoenzyme present in the ovarian oocyte in the rabbit. However, in contrast to rodents, the embryonal LDH genes start functioning long before implantation in the rabbit: in the 86-hour-old rabbit embryo (middle blastocyst) isoenzymes formed of α and β subunits are already present.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Human genetics 〈Berlin〉 15 (1972), S. 355-356 
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Zusammenfassung In Oocyten oder unbefruchteten Eizellen verschiedener Säuger finden sich verschiedene LDH-Isoenzymmuster. Während bei Species der Ordnungen Rodentia und Lagomorpha stets nur LDH1 (β-Untereinheiten) gefunden wurden, zeigten Arten der Ordnungen Carnivora und Artiodactyla weitere LDH-Isoenzyme, die auf Beteiligung von α-Untereinheiten schließen lassen.
    Notes: Summary Different LDH isoenzyme patterns are present in oocytes or unfertilized egg cells of different mammals. While in species of the orders Rodentia and Lagomorpha only LDH1 (β-subunits) has been found, species of the order Carnivora and Artiodactyla show further LDH isoenzymes, indicating the participation of α-subunits.
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