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  • 1
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The positions of the centromeres of all 46 human chromosomes were analysed in three dimensional reconstructions of electron micrographs of 10 serially sectioned unpretreated human male fibroblast cells. The reconstructions show that the spatial positioning of the chromosomes during division is not random. The centromeres were arranged on a metaphase plate that was ellipsoidal and that tended to be flat. The distance of centromeres from the centre of the mitotic figure was correlated with chromosome size; small chromosomes tended to be central in all the metaphases. Large chromosomes were more peripheral, especially in cells that were more advanced in mitosis. Thus, there is a tendency for larger chromosomes to move outwards as metaphase advances. In many cells, the A group centromeres were overdispersed, whereas G group centromeres tended to be clustered. The acrocentric chromosomes (D and G groups) also tended to be clustered when analysed together, probably reflecting associations in nucleoli at the previous interphase. The results show that chromosome disposition is non-random and that it changes during division.
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  • 2
    ISSN: 1432-2242
    Keywords: Alfalfa ; Medicago sativa ; Mitochondrial RNA ; Organelle inheritance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Several large RNA molecules that migrated to electrophoretic positions ranging from 1.7–10 kb were observed in preparation of alfalfa (Medicago sativa) mitochondria. F1 progenies inherited the RNA's from both maternal and paternal parents (Fig. 1). Treatment of intact mitochondria with RNase A failed to remove the RNA's, indicating that they were contained within an RNase impermeable compartment. Further purification of mitochondria in linear sucrose gradients failed to separate the RNA's from mitochondria. Transmission electron microscopic examination of sucrose gradient purified mitochondria revealed that mitochondria were free of contamination by virus-like particles, indicating that the RNA's were contained within the mitochondrion. Biparental inheritance of large mitochondrial RNA's in alfalfa provides evidence that mitochondria are inherited biparentally in this species.
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  • 3
    ISSN: 1432-8798
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary.  Biological differences and molecular variability between six phenotypically distinct tobacco-infecting geminivirus isolates from southern Africa (Zimbabwe) and Mexico were investigated. Host range studies conducted with tobacco virus isolates ZIM H from Zimbabwe and MEX 15 and MEX 32 from Mexico indicated all had narrow host ranges restricted to the Solanaceae. Alignment of coat protein gene (CP) and common region (CR) sequences obtained by PCR, and phylogenetic analysis of the CP sequences indicated Zimbabwean isolates were distantly related to those from Mexico and that geographically proximal isolates shared their closest affinities with Old and New World geminiviruses, respectively. Zimbabwean isolates formed a distinct cluster of closely related variants (〉98% sequence identity) of the same species, while MEX 15 segregated independently from MEX 32, the former constituting a distinct species among New World geminiviruses, and the latter being a variant, Texas pepper virus-Chiapas isolate (TPV-CPS) with 95% sequence identity to TPV-TAM. Results collectively indicated a geographic basis for phylogenetic relationships rather than a specific affiliation with tobacco as a natural host. MEX 15 is provisionally described as a new begomovirus, tobacco apical stunt virus, TbASV, whose closest CP relative is cabbage leaf curl virus, and ZIM isolates are provisionally designated as tobacco leaf curl virus, TbLCV-ZIM, a new Eastern Hemisphere begomovirus, which has as its closest relative, chayote mosaic virus from Nigeria.
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  • 4
    ISSN: 1433-0350
    Keywords: Post-haemorrhagic hydrocephalus ; Intracranial pressure ; Ventriculo-peritoneal shunting ; Neurological outcome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The neuromotor outcome of 33 survivors of grade 3 or 4 neonatal post-haemorrhagic hydrocephalus born between 1975 and 1988 was assessed at a mean age of 4.7 years (9 months to 13 years). Two outcomes were determined: 12 patients were either normal (10) or had neurological signs without functional impairments (2), while 21/33 were moderately (16), severely (2), or profoundly impaired (3). Intracranial pressure (ICP) was measured in 26/33 patients (4–40 mm Hg): 2 had normal pressures (〈5.6 mm Hg) and were normal. Raised ICP was not significantly different between outcome groups. Twenty-seven children were shunted; 10/27 had five or more operations (up to 14) and all of these had abnormal neurological outcomes, whereas the number of children with 1–4 shunt procedures was equal in both outcome groups. The rise in morbidity after the fourth shunt procedure may be associated with the ventriculitis suffered by 9 of the 10 patients with more than four shunts (P〈0.01): this compares with 4/14 cases of ventriculitis in the children with 2–4 shunts and no cases of infection in the 3/27 who were shunted once. Outcome was independent of antenatal and perinatal factors including the age at or mode of presentation, and was unrelated to grade of intraventricular haemorrhage or parenchymal changes on ultrasound or CT scanning. Conclusion: for these small numbers, adverse outcome is statistically related to more than four shunt procedures and ventriculitis but independent of maximum ICP or other perinatal factors.
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  • 5
    ISSN: 1432-2242
    Keywords: Diversity ; Molecular-markers ; Pea (Pisum) ; Relatedness-trees ; Mantel's test
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract DNA-based molecular-marker techniques have been proven powerful in genetic diversity estimations. Among them, RFLP was the first and is still the most commonly used in the estimation of genetic diversity of eukaryotic species. The recently developed PCR-based multiple-loci marker techniques, which include RAPD, AFLP, Microsatellite-AFLP and inter-SSR PCR, are playing increasingly important roles in this type of research. Despite the wide application of these techniques, no direct comparison of these methods in the estimation of genetic diversity has been carried out. Here we report a direct comparison of DNA-based RFLP with various PCR-based techniques regarding their informativeness and applicability for genetic diversity analysis. Among ten pea genotypes studied, all the PCR-based methods were much more informative than cDNA-RFLP. Genetic diversity trees were derived from each marker technique, and compared using Mantel's test. By this criterion, all trees derived from the various molecular marker techniques, except for the tree derived from inter-SSR PCR, were significantly correlated, suggesting that these PCR-based techniques could replace RFLP in the estimation of genetic diversity. On the basis of this result, AFLP analysis was applied to assess the genetic diversity of a sample of accessions representing the various species and subspecies within the genus Pisum.
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  • 6
    ISSN: 1432-2242
    Keywords: Key words Diversity ; Molecular-markers ; Pea (Pisum) ; Relatedness-trees ; Mantel's test
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract DNA-based molecular-marker techniques have been proven powerful in genetic diversity estimations. Among them, RFLP was the first and is still the most commonly used in the estimation of genetic diversity of eukaryotic species. The recently developed PCR-based multiple-loci marker techniques, which include RAPD, AFLP, Microsatellite-AFLP and inter-SSR PCR, are playing increasingly important roles in this type of research. Despite the wide application of these techniques, no direct comparison of these methods in the estimation of genetic diversity has been carried out. Here we report a direct comparison of DNA-based RFLP with various PCR-based techniques regarding their informativeness and applicability for genetic diversity analysis. Among ten pea genotypes studied, all the PCR-based methods were much more informative than cDNA-RFLP. Genetic diversity trees were derived from each marker technique, and compared using Mantel's test. By this criterion, all trees derived from the various molecular marker techniques, except for the tree derived from inter-SSR PCR, were significantly correlated, suggesting that these PCR-based techniques could replace RFLP in the estimation of genetic diversity. On the basis of this result, AFLP analysis was applied to assess the genetic diversity of a sample of accessions representing the various species and subspecies within the genus Pisum.
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Child 9 (1983), S. 0 
    ISSN: 1365-2214
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine , Psychology
    Notes: Summary Polarized light goniometry recordings were obtained from 46 neurologically normal children aged 4–15 years. Asymmetry in terms of thigh and knee angle differences between right and left legs was common in children aged less than 10 years but uncommon in children aged more than 10 years. This asymmetry was predominantly in the direction of more flexion on the right side. The tendency for goniometric asymmetry to mirror asymmetry on clinical examination was slight and did not reach statistical significance. It is suggested that angular asymmetry during gait which occurs in some children under 10 years of age may be related to unequal rates of maturation of the two hemispheres. Other minor neurological asymmetries, neuro-anatomical asymmetries and postural asymmetries which may be found in normal children are discussed.
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Child 13 (1987), S. 0 
    ISSN: 1365-2214
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine , Psychology
    Notes: Summary Summary Twenty-five normal newborns aged between 3 and 6 days had their movements recorded by (a) clinical observation in a controlled environment, (b) chart recording from an automatic movement mattress over 4 hours, and (c) cine photography triggered by the movement mattress. Over 80 different individual types of movement were grouped into six categories: (a) progression movements (obligatory reciprocal movements), (b) symmetrical movements (slower flexion or extension movements), (c) startle movements, (d) asymmetrical tonic neck reflex and ‘Moro’, (e) facial movements and (f) athetoid movements. The normal newborn's motor activity is significantly related to the level of arousal, gestational age, and environmental variables sueh as position, temperature, light and noise.
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  • 9
    ISSN: 1615-6102
    Keywords: Bacteria ; Bemisia tabaci ; Bemisia argentifolii ; Endosymbionts ; Microorganism ; Symbiosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The ultrastructure of the endosymbionts of several populations of whitefly (Homoptera: Aleyrodidae) was examined using transmission electron microscopy. Consistent differences in morphology and relative number of endosymbionts were observed between species and biotypes of whitefly within the Bemisia taxon.Bemisia argentifolii (=B. tabaci B biotype) individuals from Hawaii, Florida, and Arizona contained two morphological types of microorganisms housed within the mycetocyte cells of immature whiteflies. In contrast, individuals from populations ofB. tabaci A biotype from Arizona and Mexico, andB. tabaci Jatropha biotype from Puerto Rico, consistently contained three distinct morphological types of microorganisms within their mycetocytes. Organisms fromB. tabaci A and Jatropha biotypes differed from each other in the relative frequency of each type of microorganism. These observations suggest that different whitefly biotypes may have variable combinations of micro-fauna, with some possibly unique to each group, and furthers the hypothesis that variation in whitefly endosymbionts may be associated with the development of biotypes.
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  • 10
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 175 (1955), S. 229-233 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Introduction THE purpose of this article is to describe the results of recent infra-red and X-ray measurements on coals, to summarize briefly the joint conclusions, and to compare them with those of other investigators. More detailed accounts of the infra-red and X-ray work are being published ...
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