SGK1 activity in Na+ absorbing airway epithelial cells monitored by assaying NDRG1-Thr346/356/366 phosphorylation.

Studies of HeLa cells and serum- and glucocorticoid-regulated kinase 1 (SGK1) knockout mice identified threonine residues in the n-myc downstream-regulated gene 1 protein (NDRG1-Thr(346/356/366)) that are phosphorylated by SGK1 but not by related kinases (Murray et al., Biochem J 385:1-12, 2005). We have, therefore, monitored the phosphorylation of NDRG1-Thr(346/356/366) in order to explore the changes in SGK1 activity associated with the induction and regulation of the glucocorticoid-dependent Na(+) conductance (G (Na)) in human airway epithelial cells. Transient expression of active (SGK1-S422D) and inactive (SGK1-K127A) SGK1 mutants confirmed that activating SGK1 stimulates NDRG1-Thr(346/356/366) phosphorylation. Although G (Na) is negligible in hormone-deprived cells, these cells displayed basal SGK1 activity that was sensitive to LY294002, an inhibitor of 3-phosphatidylinositol phosphate kinase (PI3K). Dexamethasone (0.2 muM) acutely activated SGK1 and the peak of this response (2-3 h) coincided with the induction of G (Na), and both responses were PI3K-dependent. While these data suggest that SGK1 might mediate the rise in G (Na), transient expression of the inactive SGK1-K127A mutant did not affect the hormonal induction of G (Na) but did suppress the activation of SGK1. Dexamethasone-treated cells grown on permeable supports formed confluent epithelial sheets that generated short circuit current due to electrogenic Na(+) absorption. Forskolin and insulin both stimulated this current and the response to insulin, but not forskolin, was LY294002-sensitive and associated with the activation of SGK1. While these data suggest that SGK1 is involved in the control of G (Na), its role may be minor, which could explain why sgk1 knockout has different effects upon different tissues.

Differences in mucosal appearances and in relapse rates in duodenal ulceration treated with sucralfate or cimetidine.

A total of 46 patients with duodenal ulcer were randomly assigned, without the knowledge of the investigators, to treatment with cimetidine 200 mg three times daily and 400 mg at night or sucralfate 1 g four times daily followed by one year of maintenance treatment with cimetidine 400 mg at night or sucralfate 1 g twice daily, respectively, in those patients with healed ulcers. The endoscopic healing rates and relapse rates during the maintenance period were similar, four relapses occurring in each group. All four relapses in the sucralfate group occurred at 12 months and only two were symptomatic. All the cimetidine relapses were symptomatic, two occurring at six months, one at nine months, and one at 12 months. Following the one year maintenance period, 13 cimetidine patients and 11 sucralfate patients were followed up for 36 months. During the first two years, nine of 13 (69 percent) cimetidine-treated and two of 11 (18 percent) sucralfate-treated patients had relapses. During the third year, three more sucralfate-treated patients and one more cimetidine-treated patient had relapses, making a total of 10 of 13 (77 percent) and five of 11 (45 percent) in the cimetidine and sucralfate groups, respectively. Duodenal biopsy specimens obtained before and after healing and after one year of maintenance were examined by light and electron microscopy. The sucralfate group showed greater improvement after one year of maintenance therapy than did the cimetidine group, although the appearances in either group were not predictive of subsequent relapse. The results show that relapses are less frequent and occur later after sucralfate therapy and also that the morphologic appearances are more normal after treatment with sucralfate than after treatment with cimetidine.

Ectopic hamartomatous thymoma. A distinctive benign lesion of lower neck.

Five cases of a distinctive tumor located in the soft tissues of the lower neck in adults are described. The lesion is characterized microscopically by the presence of four components: cellular areas made up of spindle elements; epithelial islands composed of solid nests, trabeculae and cysts; mature adipose tissue; and lymphocytes, sometimes arranged in a Hassall's corpuscle-like fashion. Electron microscopy and immunostaining for keratin showed that the spindle cell component was of epithelial nature. These tumors were supraclavicular or suprasternal in location, and no local recurrence has developed in any case following local resection. We interpret these lesions as benign tumors arising on the basis of a developmental defect. We think that they are derived from the third branchial arch and that they are composed of abnormal thymic tissue.

Chemodectoma of lung.

The histological and histochemical features of a primary chemodectoma of lung are described and compared with previously reported pulmonary chemodectomata. The tumour is of interest because, although there is physiological evidence that chemoreceptors are present in the lung, they have not yet been located anatomically.

Expression of intermediate-conductance, Ca2+-activated K+ channel (KCNN4) in H441 human distal airway epithelial cells.

Electrophysiological studies of H441 human distal airway epithelial cells showed that thapsigargin caused a Ca(2+)-dependent increase in membrane conductance (G(Tot)) and hyperpolarization of membrane potential (V(m)). These effects reflected a rapid rise in cellular K(+) conductance (G(K)) and a slow fall in amiloride-sensitive Na(+) conductance (G(Na)). The increase in G(Tot) was antagonized by Ba(2+), a nonselective K(+) channel blocker, and abolished by clotrimazole, a KCNN4 inhibitor, but unaffected by other selective K(+) channel blockers. Moreover, 1-ethyl-2-benzimidazolinone (1-EBIO), which is known to activate KCNN4, increased G(K) with no effect on G(Na). RT-PCR-based analyses confirmed expression of mRNA encoding KCNN4 and suggested that two related K(+) channels (KCNN1 and KCNMA1) were absent. Subsequent studies showed that 1-EBIO stimulates Na(+) transport in polarized monolayers without affecting intracellular Ca(2+) concentration ([Ca(2+)](i)), suggesting that the activity of KCNN4 might influence the rate of Na(+) absorption by contributing to G(K). Transient expression of KCNN4 cloned from H441 cells conferred a Ca(2+)- and 1-EBIO-sensitive K(+) conductance on Chinese hamster ovary cells, but this channel was inactive when [Ca(2+)](i) was <0.2 microM. Subsequent studies of amiloride-treated H441 cells showed that clotrimazole had no effect on V(m) despite clear depolarizations in response to increased extracellular K(+) concentration ([K(+)](o)). These findings thus indicate that KCNN4 does not contribute to V(m) in unstimulated cells. The present data thus establish that H441 cells express KCNN4 and highlight the importance of G(K) to the control of Na(+) absorption, but, because KCNN4 is quiescent in resting cells, this channel cannot contribute to resting G(K) or influence basal Na(+) absorption.

The mesorectum in rectal cancer surgery--the clue to pelvic recurrence?

Five cases are described where minute foci of adenocarcinoma have been demonstrated in the mesorectum several centimetres distal to the apparent lower edge of a rectal cancer. In 2 of these there was no other evidence of lymphatic spread of the tumour. In orthodox anterior resection much of this tissue remains in the pelvis, and its is suggested that these foci might lead to suture-line or pelvic recurrence. Total excision of the mesorectum has, therefore, been carried out as a part of over 100 consecutive anterior resections. Fifty of these, which were classified as 'curative' or 'conceivably curative' operations, have now been followed for over 2 years with no pelvic or staple-line recurrence.

Lymph node metastases in early rectal cancer.

Local excision of early rectal tumours is an attractive proposition, avoiding the morbidity and mortality of major resection and possible permanent stoma. This study was designed to investigate the incidence of lymph node metastases associated with tumours that are locally confined to the bowel wall. A total of 454 rectal excision specimens were reviewed. Twenty-two (20 per cent) of 109 patients with tumours locally confined to the bowel wall had metastases in local lymph nodes, although 14 of these had only one or two involved nodes. Three of 27 patients with tumours that did not penetrate through the submucosa had lymph node metastases. Less well differentiated tumours were more likely to have metastasized but there was no significant difference in the height or size of tumours or in the depth of invasion between patients with or without lymph node metastases.

Comparison of relapse rates and of mucosal abnormalities after healing of duodenal ulceration and after one year's maintenance with cimetidine or sucralfate: a light and electron microscopy study.

Forty six patients with endoscopically diagnosed duodenal ulceration were randomly allocated to treatment with either sucralfate 1 g qds (n = 24) or cimetidine 200 mg tds and 400 mg nocte (n = 22). When the ulcers healed, a maintenance dose of sucralfate 1 g bd or cimetidine 400 mg nocte was given for one year (or until relapse if earlier). Biopsies of duodenal mucosa adjacent to ulcer sites for light and electron microscopy were obtained before and after healing and again after one year's maintenance if the ulcer remained healed. Duodenal biopsies were also taken from 20 age and sex matched controls. Rates of healing and relapse during maintenance did not differ between the two treatments, although relapses occurred earlier with cimetidine. In the three year post-maintenance follow up period 10/13 cimetidine patients relapsed compared with four of 11 sucralfate patients (p less than 0.05), the relapses occurring significantly earlier in the cimetidine treated patients (p less than 0.05). Mucosal biopsies from both treatment groups still showed considerable abnormalities after healing. During maintenance, however, the sucralfate scores fell significantly (p less than 0.02) to near control levels unlike the cimetidine scores which remained raised at pretreatment values. The histological and ultrastructural changes were not predictive of later relapse. These findings favour the use of sucralfate in preference to cimetidine for maintenance treatment in the prevention of relapse of healed duodenal ulcers.