Expandable metal stent placement for benign colorectal obstruction: outcomes for 23 cases

BACKGROUND

Self-expanding metal stents (SEMS) are an established treatment for palliation of malignant colorectal strictures and as a bridge to surgery for acute malignant colonic obstruction. Patients with benign colonic strictures may benefit from stent placement, but little data exist for this indication.

METHODS

All cases of colonic stent placement identified from a prospectively collected gastrointestinal database from April 1999 to August 2006 were reviewed. During the study period, 23 patients with benign obstructive disease underwent endoscopic SEMS placement. The etiologies of the stricture were diverticular/inflammatory (n = 16), postsurgical anastomotic (n = 3), radiation-induced (n = 3), and Crohn's (n = 1) disease. All strictures were located in the left colon. Five patients had an associated colonic fistula. Uncovered Enteral Wallstents or Ultraflex Precision Colonic stents (Boston Scientific) were endoscopically placed in all but one patient.

RESULTS

Stent placement was technically successful for all 23 patients, and obstruction was relieved for 22 patients (95%). Major complications occurred in 38% of the patients including migration (n = 2), reobstruction (n = 4), and perforation (n = 2). Of these major complications, 87% occurred after 7 days. Four patients did not undergo an operation. Of the 19 patients who underwent planned surgical resection, 16 were successfully decompressed and converted from an emergent operation to an elective one with a median time to surgical resection of 12 days (range, 2 days to 18 months). Surgery was delayed more than 30 days after stent placement for six of these patients. Of the 19 patients who underwent a colectomy, 8 (42%) did not need a stoma after stent insertion.

CONCLUSIONS

SEMS can effectively decompress high-grade, benign colonic obstruction, thereby allowing elective surgery. The use of SEMS can offer medium-term symptom relief for benign colorectal strictures, but this approach is associated with a high rate of delayed complications. Thus, if elective surgery is planned, data from this small study suggest that it should be performed within 7 days of stent placement.

Role of glutamine synthetase in nitrogen metabolite repression in Aspergillus nidulans

Glutamine synthetase (GS), EC 6.3.1.2, is a central enzyme in the assimilation of nitrogen and the biosynthesis of glutamine. We have isolated the Aspergillus nidulans glnA gene encoding GS and have shown that glnA encodes a highly expressed but not highly regulated mRNA. Inactivation of glnA results in an absolute glutamine requirement, indicating that GS is responsible for the synthesis of this essential amino acid. Even when supplemented with high levels of glutamine, strains lacking a functional glnA gene have an inhibited morphology, and a wide range of compounds have been shown to interfere with repair of the glutamine auxotrophy. Heterologous expression of the prokaryotic Anabaena glnA gene from the A. nidulans alcA promoter allowed full complementation of the A. nidulans glnADelta mutation. However, the A. nidulans fluG gene, which encodes a protein with similarity to prokaryotic GS, did not replace A. nidulans glnA function when similarly expressed. Our studies with the glnADelta mutant confirm that glutamine, and not GS, is the key effector of nitrogen metabolite repression. Additionally, ammonium and its immediate product glutamate may also act directly to signal nitrogen sufficiency.

Functional analysis of TamA, a coactivator of nitrogen-regulated gene expression in Aspergillus nidulans

The tam A gene of Aspergillus nidulans encodes a 739-amino acid protein with similarity to Uga35p/Dal81p/DurLp of Saccharomyces cerevisiae. It has been proposed that TamA functions as a co-activator of AreA, the major nitrogen regulatory protein in A. nidulans. Because AreA functions as a transcriptional activator under nitrogen-limiting conditions, we investigated whether TamA was also present in the nucleus. We found that a GFP-TamA fusion protein was predominantly localised to the nucleus in the presence and absence of ammonium, and that AreA was not required for this distribution. As the predicted DNA-binding domain of TamA is not essential for function, we have used a number of approaches to further define functionally important regions. We have cloned the tamA gene of A. oryzae and compared its functional and sequence characteristics with those of A. nidulans tamA and S. cerevisiae UGA35/DAL81/DURL. The Aspergillus homologues are highly conserved and functionally interchangeable, whereas the S. cerevisiae gene does not complement a tamA mutant when expressed in A. nidulans. Uga35p/Dal81p/DurLp was also found to be unable to recruit AreA. The sequence changes in a number of tamA mutant alleles were determined, and altered versions of TamA were tested for tamA complementation and interaction with AreA. Changes in most regions of TamA appeared to destroy its function, suggesting that the overall conformation of the protein may be critical for its activity.

The TamA protein fused to a DNA-binding domain can recruit AreA, the major nitrogen regulatory protein, to activate gene expression in Aspergillus nidulans

The areA gene of Aspergillus nidulans encodes a GATA zinc finger transcription factor that activates the expression of a large number of genes subject to nitrogen metabolite repression. The amount and activity of the AreA protein under different nitrogen conditions is modulated by transcriptional, post-transcriptional, and post-translational controls. One of these controls of AreA activity has been proposed to involve the NmrA protein interacting with the DNA-binding domain and the extreme C terminus of AreA to inhibit DNA binding under nitrogen sufficient conditions. In contrast, mutational evidence suggests that the tamA gene has a positive role together with areA in regulating the expression of genes subject to nitrogen metabolite repression. This gene was identified by the selection of mutants resistant to toxic nitrogen source analogues, and a number of nitrogen metabolic activities have been shown to be reduced in these mutants. To investigate the role of this gene we have used constructs encoding the TamA protein fused to the DNA-binding domain of either the FacB or the AmdR regulatory proteins. These hybrid proteins have been shown to activate expression of the genes of acetate or GABA utilization, respectively, as well as the amdS gene. Strong activation was shown to require the AreA protein but was not dependent on AreA binding to DNA. The homologous areA gene of A. oryzae and nit-2 gene of Neurospora crassa can substitute for A. nidulans areA in this interaction. We have shown that the same C-terminal region of AreA and NIT-2 that is involved in the interaction with NmrA is required for the TamA-AreA interaction. However, it is unlikely that TamA requires the same residues as NmrA within the GATA DNA-binding domain of AreA.

The tamA gene of Aspergillus nidulans contains a putative zinc cluster motif which is not required for gene function

Expression of many nitrogen catabolic enzymes is controlled by nitrogen metabolite repression in Aspergillus nidulans. Although the phenotypes of tamA mutants have implicated this gene in nitrogen regulation, its function is unknown. We have cloned the tamA gene by complementation of a new tamA allele. The tamA sequence shares significant homology with the UGA35/DAL81/DURL gene of Saccharomyces cerevisiae. In vitro mutagenesis of sequences encoding a putative zinc cluster DNA binding domain indicated that this motif is not required for in vivo TamA function.

Detection of anthelmintic resistance by culture in vitro of parasitic stages of ovine nematodes

Exsheathed L3 larvae of Haemonchus contortus were cultured at 38.5 degrees C in a complex medium supporting growth to adult worms. Although there was a clear difference in response between susceptible and benzimidazole/ivermectin/closantel resistant H. contortus using thiabendazole, the test failed to differentiate satisfactorily between the strains using ivermectin or closantel.

The distribution of the infective larvae of sheep gastro-intestinal nematodes in soil and on herbage and the vertical migration of Trichostrongylus vitrinus larvae through the soil

From May 1982 until September 1983 samples of soil and herbage were collected from a paddock grazed from May to October 1982, and for two short periods between May and July 1983, by sheep infected with gastro-intestinal nematodes. Few infective larvae were recovered from the soil although appreciable numbers of larvae were recovered from the herbage. Infective larvae of Trichostrongylus vitrinus in faeces buried in the soil of grass plots, at a depth of 10 cm, each month from April 1982 until March 1983, migrated on to the herbage at all times of the year, few remaining in the soil. The significance of the soil as a reservoir of infective larvae is discussed.

Observations on the bionomics of the free-living stages of Trichostrongylus vitrinus

Eggs of Trichostrongylus vitrinus in faecal pellets deposited on grass plots each month from April 1981 to March 1982 developed into infective larvae. From October to March development was slow and mortality of the pre-infective stages was very high. From April to September development was more rapid. The weather was generally dry and mortality of the pre-infective stages was high on plots with short herbage but was lower on most of the plots with long herbage, especially in July and August. In the laboratory, development of eggs into infective larvae was completed at temperatures ranging from 4 degrees C to 27 degrees C in faecal pellets which were either kept moist or dried out slowly, but not in faecal pellets which dried out rapidly. The rate of development increased as the temperature rose. Infective larvae survived for up to 16 months on the herbage of grass plots; some survived during very cold weather in the winter of 1981/82. In the laboratory, infective larvae suspended in tap water survived even longer at 4 degrees C and 10 degrees C but not at higher temperatures. They were rapidly killed by continuous freezing. They survived for up to 8 weeks when subjected to desiccation. The relationship between climatic conditions and the development and survival of the free-living stages is discussed.

Observations on the effect of anthelmintic treatment on the transmission of Hyostrongylus rubidus and Oesophagostomum spp. among sows at pasture

The transmission of Hyostrongylus rubidus and Oesophagostomum spp. following anthelmintic treatment was studied over a period of two years in a herd of sows kept out-of-doors on a commercial farm in south-eastern England. The sows were moved on to a clean pasture each autumn and at the same time were treated with an anthelmintic. The treatment was repeated six months later when the faecal worm egg count was rising. Contamination of the pasture with worm eggs was both light and intermittent. The pasture herbage remained free of infective larvae until the early summer; subsequently the herbage became lightly infected with larvae so that transmission of the parasites was possible, but limited. The level of infection on the herbage was much lower than was seen in earlier observations when the more commonly used system of treating groups of sows at different times of the year, in between farrowings, was used.

Observations on the development and survival of the free-living stages of Hyostrongylus rubidus both in their natural environments out-of-doors and under controlled conditions in the laboratory

Faces containing eggs of Hyostrongylus rubidus were deposited on grass plots each month throughout 1980. Eggs in faeces deposited on plots from May to October developed into infective larvae but in May development was completed only in artificially moistened faeces, the weather was warm and dry and natural faeces dried out rapidly resulting in the death of eggs and pre-infective larvae. For the remainder of this period the weather was sufficiently warm and wet for development to be completed. More eggs developed into infective larvae on plots with well-grown herbage than on plots with short herbage. In April a few eggs survived and developed into 1st-stage larvae but no further development took place. In the laboratory development was completed at temperatures ranging from 10 to 27 degrees C but no development took place at 4 degrees C. Out-of-doors infective larvae survived on herbage for up to 10 months while in the laboratory, infective larvae suspended in tap water survived even longer to 10 and 22 degrees C, but the larvae were rapidly killed by continuous freezing and by desiccation when the relative humidity was less than 95%. The relationship between climatic conditions and the development and survival of the free-living stages is discussed and a comparison made with the free-living stages of Oesophagostomum dentatum.

Observations on the development and survival of the free-living stages of Oesophagostomum dentatum both in their natural environments out-of-doors and under controlled conditions in the laboratory

Eggs of Oesophagostomum dentatum in faeces deposited on grass plots from May to October developed into infective larvae. Warm wet weather facilitated development but weather conditions which caused the faeces to dry out rapidly resulted in a heavy mortality of eggs and pre-infective larvae. During the winter no development took place and the eggs died. In the early spring and late autumn a few eggs survived and developed into 1st-stage larvae but they died without developing further. In the laboratory no development took place at 4 degree C but at temperatures ranging from 10 to 25 degree C development into infective larvae was completed, the rate increasing as the temperature rose. Out-of-doors infective larvae survived in faeces and on herbage for 1 year under a wide range of climate conditions including the exceptionally cold winter of 1978--79. In the laboratory, infective larvae suspended in water survived even longer at temperatures ranging from 4 to 27 degree C. They were rapidly killed by continuous freezing and by desiccation when the relative humidity was less than 90%. The relationship between climatic conditions and the development and survival of the free-living stages is discussed.

Transmission of Oesophagostomum spp among sows at pasture

The transmission of Oesophagostomum species in sows kept on pastureland on a commercial farm was studied over a period of almost two years. Worm eggs were excreted on to the pasture continuously but they gave rise to infective larvae during the summer and autumn only when climatic conditions were conducive to development. The output of worm eggs was maintained at a moderate level and the numbers of adult worms in culled sows rarely exceeded more than a few thousand but some sows carried heavy infestations of immature worms. No direct relationship between the level of the herbage infestation and the numbers of adult worms and the output of worm eggs was apparent. The use of anthelmintics had only a transitory effect on the level of infection and an alternative system of anthelmintic treatment is suggested.