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  • 1990-1994  (2)
  • Amino acid substitution  (1)
  • Colonoscopy  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular evolution 39 (1994), S. 569-578 
    ISSN: 1432-1432
    Keywords: Sex ratio of mutation rate ; Silent substitution ; Amino acid substitution ; Selective constraints ; Loss of Y-linked genes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have sequenced the entire exon (∼1,180 bp) encoding the zinc finger domain of the X-linked and Y-linked zinc finger genes (ZFX and ZFY, respectively) in the orangutan, the baboon, the squirrel monkey, and the rat; a total of 9,442 by were sequenced. The ratio of the rates of synonymous substitution in the ZFY and ZFX genes is estimated to be 2.1 in primates. This is close to the ratio of 2.3 estimated from primate ZFY and ZFX intron sequences and supports the view that the male-to-female ratio of mutation rate in humans is considerably higher than 1 but not extremely large. The ratio of synonymous substitution rates in ZFY and ZFX is estimated to be 1.3 in the rat lineage but 4.2 in the mouse lineage. The former is close to the estimate (1.4) from introns. The much higher ratio in the mouse lineage (not statistically significant) might have arisen from relaxation of selective constraints. The synonymous divergence between mouse and rat ZFX is considerably lower than that between mouse and rat autosomal genes, agreeing with previous observations and providing some evidence for stronger selective constraints on synonymous changes in X-linked genes than in autosomal genes. At the protein level ZFX has been highly conserved in all placental mammals studied while ZFY has been well conserved in primates and foxes but has evolved rapidly in mice and rats, possibly due to relaxation of functional constraints as a result of the development of X-inactivation of ZFX in rodents. The long persistence of the ZFY-ZFX gene pair in mammals provides some insight into the process of degeneration of Y-linked genes.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Surgical endoscopy and other interventional techniques 7 (1993), S. 33-36 
    ISSN: 1432-2218
    Keywords: Colonoscopy ; Fluoroscopy ; Cecum ; Ileocecal sphincter ; Appendiceal orifice ; Transillumination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Confirming colonoscopic intubation of the cecum can be a laborious, time-consuming, and often frustrating endeavor. Anatomic landmarks may offer visual clues of cecal intubation, but the predictability of this evidence is unclear. The presence of three cecal landmarks, alone and in combination, were evaluated to precisely define their reliability. Between February and October of 1991, 601 of 708 (85%) consecutive colonoscopic examinations were able to be completed to the cecum as confirmed by fluoroscopy. All three cecal landmarks studied were present in 64% (386/601), two cecal landmarks in 32% (189/601), and one cecal landmark in 4% (26/601) of the patients. Therefore, at least two cecal landmarks were identified in 96% (575/601) of the patients. The ileocecal sphincter was identified in 98% (591/601) of patients overall, in 98% (185/189) of patients with 2 cecal landmarks, and in 77% (20/26) of patients with 1 cecal landmark. The appendiceal orifice was seen in 87% (524/601) of patients overall and in 72% (137/189) of patients with 2 cecal landmarks. Transillumination through the abdominal wall was possible in 74% (447/601) of patients overall and in 30% (56/189) of patients with 2 cecal landmarks. In summary, the ileocecal sphincter is the most reliable cecal landmark and is invariably visualized, even when all other landmarks are obscure. While other cecal landmarks, such as the appendiceal orifice and transillumination, are consistently identified, they are most valuable when found in association with the ileocecal sphincter.
    Type of Medium: Electronic Resource
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