A novel approach to flexor hallucis longus tenography.

OBJECTIVE: This article presents a technically simple and more accurate approach to flexor hallucis longus (FHL) tenography than any we found reported in the literature. CONCLUSION: Tenography is used to evaluate and treat tenosynovitis. Standard FHL tenography protocol involves either direct percutaneous access of the FHL synovial sheath posterior to the medial malleolus or indirect filling of the FHL sheath from an injection of the flexor digitorum longus (FDL) tendon sheath, which often communicates with the FHL tendon sheath. However, with these methods, difficulty entering the FHL sheath may be encountered. We adapted our technique to access the FHL sheath as it courses below the sustentaculum talus. Our early experience with five cases using this technique reflects a 100% success rate with accurate needle placement within the FHL tendon sheath, thereby improving procedural efficiency.

The role of human alkyladenine glycosylase in cellular resistance to the chloroethylnitrosoureas.

To investigate the possible role of glycosylase action in causing tumor resistance, a full-length, histidine-tagged human alkyladenine glycosylase has been purified from the cloned human gene contained in a pTrc99A vector propagated in a tag alkA mutant Escherichia coli. This human enzyme releases both 3-methyladenine and 7-methylguanine from methylated DNA but in contrast to previous studies of the bacterial AlkA glycosylase, it does not release any adducts from [(3)H]chloroethylnitrosourea-modified DNA. This finding suggests that the alkyladenine DNA glycosylase-dependent resistance to the toxic effects of the chloroethylnitrosoureas reported previously in the literature may occur by a mechanism other than through direct glycosylase action.

Alkylation resistance of E. coli cells expressing different isoforms of human alkyladenine DNA glycosylase (hAAG).

The alkyladenine DNA glycosylase (AAG) has been cloned from mouse and humans. AAG knock out mouse cells are sensitized to a variety of alkylating and cross-linking agents suggesting AAG is active on a variety of substrates. In humans, two isoforms have been characterized that are generated by alternative splicing and contain either exon 1a or 1b (hAAG1 or hAAG2). In this study, we examine the ability of the both known isoforms of human AAG (hAAG) to contribute to survival of Escherichia coli from treatments with simple alkylating agents and cross-linking alkylating agents. Our results show that hAAG is effective at repairing methyl lesions when expressed in E. coli, but is unable to afford increased resistance to alkylating agents producing larger alkyl lesions such as ethyl lesions or lesions produced by the cross-linking alkylating agents N,N'-bis-chloroethyl-N-nitrosourea (BCNU), N-(2-chloroethyl)-N-nitrosourea (CNU) or mitomycin C. In the case of CNU, expression of hAAG causes increased sensitivity rather than resistance, suggesting deleterious effects of hAAG activity. We also demonstrate that there are no apparent differences between the two isoforms of hAAG when recovery from damage produced by all alkylating agents is tested.