Function of the extensor mechanism of the knee after using the 'patellar-loop technique' to reconstruct the patellar tendon when replacing the proximal tibia for tumour.

The aim of this study was to analyse the gait pattern, muscle force and functional outcome of patients who had undergone replacement of the proximal tibia for tumour and alloplastic reconstruction of the extensor mechanism using the patellar-loop technique. Between February 1998 and December 2009, we carried out wide local excision of a primary sarcoma of the proximal tibia, proximal tibial replacement and reconstruction of the extensor mechanism using the patellar-loop technique in 18 patients. Of these, nine were available for evaluation after a mean of 11.6 years (0.5 to 21.6). The strength of the knee extensors was measured using an Isobex machine and gait analysis was undertaken in our gait assessment laboratory. Functional outcome was assessed using the American Knee Society (AKS) and Musculoskeletal Tumor Society (MSTS) scores. The gait pattern of the patients differed in ground contact time, flexion heel strike, maximal flexion loading response and total sagittal plane excursion. The mean maximum active flexion was 91° (30° to 110°). The overall mean extensor lag was 1° (0° to 5°). The mean extensor muscle strength was 25.8% (8.3% to 90.3%) of that in the non-operated leg (p < 0.001). The mean functional scores were 68.7% (43.4% to 83.3%) (MSTS) and 71.1 (30 to 90) (AKS functional score). In summary, the results show that reconstruction of the extensor mechanism using this technique gives good biomechanical and functional results. The patients' gait pattern is close to normal, except for a somewhat stiff knee gait pattern. The strength of the extensor mechanism is reduced, but sufficient for walking.

Cell-cycle dependent transformation competence in Dictyostelium discoideum.

We describe a modification of the transformation procedure for Dictyostelium which allows for a more exact estimate of transformation efficiency and the isolation of primary transformants. Investigations of transformation competence revealed a negative correlation to cell density and a distinct distribution during the cell-cycle. In synchronized cells, transformation efficiency is 2-3 fold higher during mitosis when compared to unsynchronized cells.

Structure, expression, and inactivation by gene disruption of the Dictyostelium discoideum prespore gene EB4.

We present the nucleotide sequence of the cell type specific prespore gene EB4 which encodes a protein containing a hydrophobic leader sequence and two distinct domains of amino acid repeats. By RNase protection experiments we have determined the genomic organization of the gene which differs substantially from the previously published data. An antibody directed against one of the repeat structures (hexamer repeat) specifically reacts with a developmentally regulated antigen of 58 kd. Gene disruption transformants were obtained by transformation with a genomic DNA fragment. The transformants express a 3' truncated mRNA and do not react with the anti-hexamer antibody. So far, we could not detect any phenotypic aberrations in the transformed cell line.

A colony-blot technique for the detection of specific transcripts in eukaryotes.

We present a simple and rapid technique for the detection of specific transcripts in eukaryotic cells. The method allows the screening of large numbers of clones for the expression of a gene of interest, similar to the colony blotting techniques described for prokaryotes. We have used this method to monitor developmentally regulated transcription of endogenous genes and the expression of foreign genes in transformed Dictyostelium discoideum cells. The same procedure can be applied to detect specific transcripts in yeast and should thus provide a useful molecular tool for most biological systems.

Regulatory sequences in the promoter of the Dictyostelium Actin 6 gene.

The promoter region of the developmentally regulated Actin 6 gene of Dictyostelium has been dissected by a series of deletions. Functional analysis of the deletions in Dictyostelium transformants revealed two short regulatory sequences: a positive upstream element (PUE) between -599 and -572 which increases transcription by a factor of 10 but does not affect the developmental pattern of expression and an upstream activator sequence (UAS) between -249 and -215 which is essential for transcription and proper developmental regulation. The UAS partially coincides with a conserved sequence with dyad symmetry found upstream of several Dictyostelium actin genes (Romans and Firtel, 1985a).