Total en bloc lumbar spondylectomy. Case report.

The authors describe a technique for total en bloc spondylectomy that can be used for lesions involving the lumbar spine. The technique involves a combined anterior-posterior approach and takes into account the unique anatomy of the lumbar spine. This technique allows for the en bloc resection of lumbar vertebral tumors, thus optimizing outcome while minimizing the risk of neurological injury. The technique is described in detail with the aid of neuroimaging studies, photographs of gross pathological specimens, and illustrations, and a discussion of other authors' experiences is provided for comparison.

Structure and developmental expression of troponin I isoforms. cDNA clone analysis of avian cardiac troponin I mRNA.

We isolated avian (chicken and quail) cardiac troponin I (TnIcardiac) cDNA clones for studies of Tn-Icardiac protein structure/evolution and developmental gene regulation. Comparison of the cDNA-predicted avian TnIcardiac amino acid sequences with known TnI sequences indicated 1) that the presence of an N-terminal extension sequence carrying a dual protein kinase A phosphorylation target site and an adjacent proline-rich segment is an ancient cardiac-specific feature of TnI which has been conserved since the bird/mammal divergence, 2) that features of the near-N-terminal troponin C (TnC)-binding site sequence suggest isoform-specific adaptation of TnI and TnC, and 3) that the avian TnIcardiac internal actin/TnC-binding, actomyosin-inhibitory, domain shows significant sequence divergence from mammalian TnIcardiac sequences, including the absence of a protein kinase C target site which is a cardiac-specific feature of TnI in mammals. Use of the cDNA clones to probe TnIcardiac mRNA expression during striated muscle development showed active expression in cardiac muscle from early developmental times (day 4 in ovo), but not in embryonic or adult skeletal muscle or in embryonic skeletal muscle cell cultures. Transcriptional run-on analysis showed that the heart-specific expression of TnIcardiac mRNA in embryonic striated muscle reflects transcriptional control of TnIcardiac gene expression. In many other contractile protein gene families, genes encoding cardiac isoforms are expressed early in skeletal muscle development and are later repressed. Thus, the restriction of active TnIcardiac gene expression to the cardiac muscle cell lineage is an unusual expression pattern for cardiac contractile protein genes and indicates that diverse gene regulatory mechanisms direct the differential expression of cardiac and skeletal muscle isoforms in different muscle gene families.