ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

feed icon rss

Your email was sent successfully. Check your inbox.

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

Proceed reservation?

Export
Filter
  • Clonal selection  (1)
  • Key words: Developing human femur — Ossification centers — Bone densitometry — DXA — Ultra-Hi-Resolution.  (1)
  • Springer  (2)
  • American Society of Hematology
  • Public Library of Science
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 66 (2000), S. 255-258 
    ISSN: 1432-0827
    Keywords: Key words: Developing human femur — Ossification centers — Bone densitometry — DXA — Ultra-Hi-Resolution.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. The purpose of the present work was to investigate the appearance of ossification centers in human femur by Dual-energy X-ray Absorptiometry (DXA), comparing densitometric data with morphogenetic events. Postero-anterior scans were performed on 31 dried femora (from 11.5 weeks of conceptual age to 1 year of postnatal life) by a Hologic QDR 1000 X-ray densitometer with Ultra-Hi-Resolution software. The results were expressed as bone mineral content (BMC, g) and bone mineral density (BMD, g/cm2). The analyses were performed on a rectangular area corresponding to the minimum width and total length of the shaft. The rectangular area was divided into five equal sections along its longitudinal axis, and BMC was calculated on each section. To distinguish the ossification area of the lesser trochanter with respect to the area of the greater trochanter, the proximal femoral end was divided into two portions, medial and lateral, respectively; BMC and BMD were calculated on each portion. Our data show that the ossification center of the femoral shaft extends prevalently in the proximal direction. A denser area was recognizable on the densitometric images at the level of the lesser trochanter from the 19th week of prenatal life and at the level of the greater trochanter at term. During development, the trends of BMC and BMD are similar in both trochanteric areas, but these parameters are fairly constantly higher at the level of the lesser trochanter. Our findings disagree with the data of the current literature on the postnatal appearance of the trochanteric ossification centers and suggest a different biomechanical interpretation of the secondary ossification of the femur.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Molecular genetics and genomics 263 (2000), S. 787-795 
    ISSN: 1617-4623
    Keywords: Key words Experimental neo-Darwinism ; Clonal selection ; Heterochromatin proteins ; Telomere sequence organization ; Y′ elements
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In Saccharomyces cerevisiae, imbalance of the genes coding for the heterochromatin components Sir3p and histone H4 (namely, overdosage of SIR3 and lack of one of the two genes coding for H4) causes modifications in telomere length and telomere sequence organization, favoring the insertion of Y′ elements into a stably shortened (C1–3A)n repeat tract. We report here that the newly inserted Y′ elements are unstable and are lost with high frequency, generating clonal subpopulations with short telomeres, as revealed by the analysis of a specific telomere (LIII) and of the overall population of telomeres. Moreover, the growth rates of the subpopulations with and without Y′ elements on LIII are different, the Y′-less individuals reproducing 20% more slowly than individuals bearing Y′ elements. When grown together with Y′-bearing individuals, the subpopulations with the normal LIII telomere (which are viable and genetically stable if grown alone) are rapidly competed out. Hence, genetic imbalance for the structural components of heterochromatin results in a complex and rapidly changing mixture of subpopulations in such cultures. Thus, in situations where subpopulations are allowed to compete, heterochromatin-based differential growth rates result in neo-Darwinian clonal selection.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...