Structure of the C-terminal domain of the prokaryotic sodium channel orthologue NsvBa.

Crystallographic and electrophysiological studies have recently provided insight into the structure, function, and drug binding of prokaryotic sodium channels. These channels exhibit significant sequence identities, especially in their transmembrane regions, with human voltage-gated sodium channels. However, rather than being single polypeptides with four homologous domains, they are tetramers of single domain polypeptides, with a C-terminal domain (CTD) composed of an inter-subunit four helix coiled coil. The structures of the CTDs differ between orthologues. In NavBh and NavMs, the C-termini form a disordered region adjacent to the final transmembrane helix, followed by a coiled-coil region, as demonstrated by synchrotron radiation circular dichroism (SRCD) and double electron-electron resonance electron paramagnetic resonance spectroscopic measurements. In contrast, in the crystal structure of the NavAe orthologue, the entire C-terminus is comprised of a helical region followed by a coiled coil. In this study, we have examined the CTD of the NsvBa from Bacillus alcalophilus, which unlike other orthologues is predicted by different methods to have different types of structures: either a disordered region adjacent to the transmembrane region, followed by a helical coiled coil, or a fully helical CTD. To discriminate between the two possible structures, we have used SRCD spectroscopy to experimentally determine the secondary structure of the C-terminus of this orthologue and used the results as the basis for modeling the open and closed conformations of the channel.

The impact of stenting obstructing colorectal tumours in a district general hospital.

INTRODUCTION: The technique of stenting malignant obstructing colorectal lesions is established as an acceptable treatment with a low morbidity and mortality. This paper reviews our experience in stenting malignant colorectal obstruction and compares this group with those who underwent emergency surgery as their primary intervention. METHODS: A retrospectively kept database over four years was reviewed and patients who had undergone either stenting or emergency surgery for a malignant colorectal obstruction were identified. These patients' notes were retrieved and reviewed. RESULTS: During the duration of study, a total of 29 stents were placed in 28 patients, with a mean age of 78 y (range 59-96 years). Patients generally had significant co-existing morbidity, with a median ASA score of 2.5. The timing of stent placement was a mean of 3.4 days (1-9 days) after presentation, including time for relevant investigation and diagnosis. Mean length of hospital stay was 9.8 days (2-36 days). In the emergency operation category, during the period of study, a total of 38 patients had operations for large bowel obstruction, either because the lesion was not suitable for stenting, or the personnel for stenting were not available. These patients ranged in age from 45 to 96 years, with a mean age of 72.4 years. Patients in this group were generally a little fitter than the stented group, with a median ASA grade of 2, and 14/38 patients were ASA1 (the largest group). Despite this Post-operative recovery was slow with these patients, the average length of stay being 16 days (range 8-66 days). CONCLUSIONS: In this study, we report our data on the first four years of stenting malignant bowel obstruction. It is a feasible and acceptable means of treatment, and we have demonstrated comparable morbidity and mortality to that reported in medical literature. The technique may avoid the need for emergency operation with its concomitant risks, lengthy in-patient stay, and high likelihood for a stoma. We would advocate the use of self expanding metal stents where appropriate in the management of large bowel obstruction.

Light flux density threshold at which protein denaturation is induced by synchrotron radiation circular dichroism beamlines.

New high-flux synchrotron radiation circular dichroism (SRCD) beamlines are providing important information for structural biology, but can potentially cause denaturation of the protein samples under investigation. This effect has been studied at the new CD1 dedicated SRCD beamline at ISA in Denmark, where radiation-induced thermal damage effects were observed, depending not only on the radiation flux but also on the focal spot size of the light. Comparisons with similar studies at other SRCD facilities worldwide has lead to the estimation of a flux density threshold under which SRCD beamlines should be operated when samples are to be exposed to low-wavelength vacuum ultraviolet radiation for extended periods of time.

Day case haemorrhoidectomy.

OBJECTIVE: Day case haemorrhoidectomy in a District General Hospital. We have investigated the uptake and outcome of day case haemorrhoidectomy in a small district general hospital. METHOD: Case note review with completion of standard proforma for all patients undergoing haemorrhoidectomy as day case (same day admission and discharge) or inpatient over a 4-year period. RESULTS: Sixty patients underwent day case closed haemorrhoidectomy, 2 day case stapled haemorrhoidectomy and 1 day case open haemorrhoidectomy, whilst 18 patients were treated as in-patients. One patient required re-admission within 31 days for reactionary haemorrhage after day case surgery. None suffered acute urinary retention. Concomitant medical disease or emergency admission were the only reasons for exclusion from day case haemorrhoidectomy. Of the 18 patients treated as in-patients haemorrhoidectomy two had unplanned readmission. CONCLUSION: Closed haemorrhoidectomy with same day discharge should be offered to all patients that require surgical treatment of haemorrhoids and do not have other contra-indications to day case surgery.

VUV irradiation effects on proteins in high-flux synchrotron radiation circular dichroism spectroscopy.

Synchrotron radiation circular dichroism (SRCD) spectroscopy is emerging as an important new tool in structural molecular biology. Previously we had shown that in lower-flux SRCD instruments, such as UV1 at ISA and beamline 3.1 at the SRS, vacuum ultraviolet (VUV) radiation damage to proteins was not evident after exposure over a period of hours. No effects were detected in either the protein primary or the secondary structures. However, with the development of high-flux beamlines, such as CD12 at the SRS, this issue has been revisited because of changes observed in the SRCD spectra of consecutive scans of protein samples obtained on this high-flux beamline. Experiments have been designed to distinguish between two different possible mechanisms: (i) photoionization causing free radicals or secondary electrons producing degradation of the protein, and (ii) local heating of the sample resulting in protein denaturation. The latter appears to be the principal source of the signal deterioration.

Activity of the mitogenic Pasteurella multocida toxin requires an essential C-terminal residue.

Pasteurella multocida toxin (PMT) is a potent mitogen that also affects bone resorption. PMT acts intracellularly and is therefore postulated to have several domains involved in different aspects of its function. The toxin contains eight cysteine residues. Mutants with individual substitutions for each of these residues were constructed, and the effects of these on the biological activity of the toxin were determined by cultured-cell assays. Only the most C-terminal of the eight cysteines (C1165) was essential for full activity, although mutation of the cysteine residue at position 1159 caused a slight but reproducible loss of potency. In animal challenge experiments, mutant toxin (C1165S) was not toxic to piglets, even at doses exceeding a lethal dose of active PMT 1, 000-fold. The mutant and wild-type toxins displayed identical purification characteristics, similar susceptibility to proteolytic digestion, and circular dichroism profiles, which indicated that no gross structural changes had taken place. The function of the essential C1165 residue is not yet known, although its most likely role is an enzymatic one at or near the catalytic center of the toxin.

Promotion of fibroblast adhesion by triple-helical peptide models of type I collagen-derived sequences.

The dissection of the activities mediated by type I collagen requires an approach by which the influence of triple-helical conformation can be evaluated. The alpha 1 beta 1 and alpha 2 beta 1 integrin binding sites within type I collagen are dependent upon triple-helical conformation and contained within residues 14-822 from alpha 1(I). Seven alpha 1(I)-derived triple-helical peptides (THPs) were synthesized based on charge clustering (alpha 1(I)256-270, alpha 1(I)385-396, alpha 1(I)406-417, alpha 1(I)415-423, alpha 1(I)448-456, alpha 1(I)496-507, and alpha 1(I)526-537). Three additional THPs were synthesized (alpha 1(I)85-96, alpha 1(I)433-441, and alpha 1(I)772-786) based on previously described or proposed activities (Kleinman, H. K., McGoodwin, E.B., Martin, G. R., Klebe, R. J., Fietzek, P. P., and Wooley, D. E. (1978) J. Biol. Chem. 253, 5642-5646; Staatz, W. D., Foik, K. F., Zutter, M. M., Adams, S. P., Rodriquez, B. A., and Santoro, S. A. (1991) J. Biol. Chem. 266, 7363-7367; San Antonio, J. D., Lander, A. D., Karnovsky, M. J., and Slayter, H. S. (1994) J. Cell Biol. 125, 1179-1188). Of the ten THPs, alpha 1(I)772-786 THP had the greatest activity, with half-maximal normal dermal fibroblast adhesion occurring at a peptide concentration of 1.6 microM. Triple-helicity was essential for activity of this sequence, as the non-triple-helical peptide analog (alpha 1(I)772-786 SSP) exhibited considerably lower levels of cell adhesion promotion even at peptide concentrations as high as 100 microM. Within the sequence itself, residues 784-786 (Gly-Leu-Hyp) were important for cellular recognition, as the alpha 1(I)772-783 THP had greatly reduced cell adhesion activity compared with alpha 1(I)772-786 THP. Preliminary studies indicate that the beta 1 integrin subunit mediates fibroblast adhesion to alpha 1(I)772-786 THP. The identification of fibroblast integrin binding sites within type I collagen may have important implications for understanding collagen metabolism.

A peptide model of basement membrane collagen alpha 1 (IV) 531-543 binds the alpha 3 beta 1 integrin.

Tumor cell adhesion to the triple-helical domain of basement membrane (type IV) collagen occurs at several different regions. Cellular recognition of the sequence spanning alpha 1(IV)531-543 has been proposed to be independent of triple-helical conformation (Miles, A. J., Skubitz, A. P. N., Furcht, L. T., and Fields, G. B. (1994) J. Biol. Chem. 269, 30939-30945). In the present study, integrin interactions with a peptide analog of the alpha 1(IV)-531-543 sequence have been analyzed. Tumor cell adhesion (melanoma, ovarian carcinoma) to the alpha 1(IV)531-543 chemically synthesized peptide was inhibited by a monoclonal antibody against the alpha 3 integrin subunit, and to a lesser extent by monoclonal antibodies against the beta 1 and alpha 2 integrin subunits. An anti-alpha 5 monoclonal antibody and normal mouse IgG were ineffective as inhibitors of tumor cell adhesion to the peptide. Two cell surface proteins of 120 and 150 kDa bound to an alpha 1(IV)531-543 peptide affinity column and were eluted with 20 mM EDTA. When the eluted proteins were incubated with monoclonal antibodies against either the alpha 3 or beta 1 integrin subunit, proteins corresponding in molecular weight to alpha 3 and beta 1 integrin subunits were precipitated. No proteins were immunoprecipated with monoclonal antibodies against the alpha 2 or alpha 5 integrin subunits. Thus, the alpha 3 beta 1 integrin from two tumor cell types has been shown to bind directly to the alpha 1 (IV)531-543 peptide. The alpha 1(IV)531-543 peptide is the first collagen-like sequence that has been shown to bind the alpha 3 beta 1 integrin.

Randomized trial of laparoscopic cholecystectomy and mini-cholecystectomy.

Three hundred and ten patients having elective cholecystectomy were randomized to either laparoscopic cholecystectomy or mini-cholecystectomy. There were 155 patients in each group. Conversion to open cholecystectomy was significantly more common with laparoscopic cholecystectomy (13 versus 4 per cent) and complications were significantly more frequent with laparoscopic cholecystectomy (9 versus 3 per cent). If laparoscopic cholecystectomy was successful, hospital stay was significantly shorter than for mini-cholecystectomy (2 versus 3 days respectively), but overall the hospital stay was not significantly different. Postoperative analgesia requirements were reduced and return to normal activities and to work were faster after laparoscopic cholecystectomy. There was no significant cost difference between the two procedures.

Promotion of cell adhesion by single-stranded and triple-helical peptide models of basement membrane collagen alpha 1(IV)531-543. Evidence for conformationally dependent and conformationally independent type IV collagen cell adhesion sites.

Several regions within the triple-helical domain of type IV collagen function as cellular recognition sites. We have demonstrated previously that melanoma cell activities promoted by the alpha 1(IV)1263-1277 sequence are enhanced by triple helicity (Fields, C. G., Mickelson, D. J., Drake, S.L., McCarthy, J.B., and Fields, G.B. (1993) J. Biol. Chem. 268, 14153-14160), whereas Eble et al. reached similar conclusions for alpha 1 beta 1 integrin-mediated fibrosarcoma cell adhesion to [alpha 1(IV)]2 alpha 2(IV)434-472 (Eble, J. A., Golbik, R., Mann, K., and Kühn, K. (1993) EMBO J. 12, 4795-4802). In the present study, we have examined the cell adhesion activities of a third region in type IV collagen. A single-stranded peptide (SSP) incorporating the alpha 1(IV)531-543 sequence promoted the adhesion of melanoma, ovarian carcinoma, and Jurkat cells in a dose-dependent manner, with 40% cell adhesion observed at [SSP] = 1.8, 11.5, and 42.2 microM, respectively. Nearly identical results were obtained for cell adhesion to an all-D-enantiomer of the SSP, suggesting that the cell surface receptor(s) for this site do not discriminate based on chirality. The alpha 1(IV)531-543 sequence maintained its cell adhesion promoting activity when incorporated into a homotrimeric triple-helical polypeptide, although relative levels of adhesion were either slightly enhanced or slightly diminished compared with the SSP. Triple-helical conformation was thus not critical for cellular recognition of the alpha 1(IV)531-543 sequence. Single-site substitution experiments of the SSP showed no overall correlation between the biological effects of substitutions and SSP conformation. The SSP, D-SSP, triple-helical polypeptide, and SSP substitution results suggest that cell recognition of the alpha 1(IV)531-543 sequence is generally independent of substrate conformation. The present and prior studies indicate that "conformationally dependent" and "conformationally independent" cellular recognition sites exist within the triple-helical domain of type IV collagen.

Solid-phase synthesis and stability of triple-helical peptides incorporating native collagen sequences.

A generally applicable solid-phase methodology has been developed for the synthesis of triple-helical polypeptides incorporating native collagen sequences. Three nascent peptide chains are C-terminal linked through one N alpha-amino and two N epsilon-amino groups of Lys, while repeating Gly-Pro-Hyp triplets induce triple helicity. Different protecting group strategies, including several three-dimensionally orthogonal schemes, have been utilized for the synthesis of four homotrimeric triple-helical polypeptides (THPs) of 79-124 residues, three of which incorporate native type IV collagen sequences. Highly efficient assemblies were achieved by 9-fluorenylmethoxycarbonyl (Fmoc) N alpha-amino group protection, in situ 2-(1H-benzotriazole-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate mediated couplings, and 1,8-diazabicyclo [5.4.0] undec-7-ene mediated Fmoc group removal. THPs were characterized by Edman degradation sequencing, size-exclusion chromatography, mass spectrometry, reversed-phase high performance liquid chromatography, and CD spectroscopy. THP thermal stabilities ranged from 35 to 59 degrees C, with chain length and Hyp content being the influential factors. Melting temperatures and van't Hoff enthalpies for peptide triple-helical denaturation could be correlated well to Hyp content. The THP synthetic protocol developed here will allow for the study of both structure and biological activity of specific collagen sequences in homotrimeric and heterotrimeric forms.

Emergency laparotomy in patients with AIDS.

The presentation, operative management and final diagnosis were reviewed in 28 patients with AIDS (27 men and one woman) who underwent emergency laparotomy. On clinical and radiological examination, six patients showed features of toxic megacolon, five patients had small bowel obstruction, six patients had localized peritonitis and three had perforated viscus with generalized peritonitis. The most common disease processes were acute colitis in seven patients (associated with cytomegalovirus (CMV) infection in six), intra-abdominal lymphoma in five patients, acute appendicitis in five patients (associated with CMV infection in two), and atypical mycobacterial (MAI) infection in four patients. Two perioperative deaths occurred; one in a patient with acute pancreatitis and a second with generalized peritonitis. Later deaths were due to progression of AIDS, and patient survival at 1 month, 3 months and 6 months was 89 per cent, 64 per cent and 48 per cent, respectively. Lower operative mortality than in previously reported series may be due to earlier intervention in CMV toxic megacolon. Surgery, however, conferred less benefit in patients with acute abdominal pain from MAI infection or lymphoma. With careful patient selection, emergency laparotomy may achieve worthwhile palliation in patients with AIDS.

Persistent ulceration of the anal margin in homosexuals with HIV infection.

A study of the outcome of surgical treatment of ulceration of the anal margin occurring in male homosexuals with HIV infection was undertaken. Ten patients with acquired immunodeficiency syndrome and three patients with symptomatic HIV infection were referred to the Department of Surgery with painful anal ulceration which had not responded to medical treatment. The medical treatments given prior to surgical referral included high dose oral acyclovir, intravenous foscarnet and broad spectrum antibiotics. Excision biopsy was performed in 12 patients and in 11 cases was followed by healing of the ulcers within 10 weeks. One patient died 2 weeks postoperatively from Pneumocystis carinii pneumonia without healing. The response to excision biopsy was unexpected but suggests that surgical excision may be beneficial for lesions which have failed to respond to aggressive medical treatment.

Surgical management of anorectal disease in HIV-positive homosexuals.

One thousand and ninety human immunodeficiency virus (HIV)-positive homosexual or bisexual males were seen in one hospital for management of HIV disease over a 9-year period. One hundred and fifty-five patients were referred by acquired immunodeficiency syndrome (AIDS) physicians for general surgical management. The most frequent reason for surgical referral (64 patients) was anorectal disease which occurred in 5.9 per cent of all HIV-positive patients. One or more diagnoses were reached in 61 of the 64 patients referred with anorectal disease: warts (38 per cent of diagnoses), anorectal ulceration (26 per cent), perianal sepsis (15 per cent), neoplasia (14 per cent) and haemorrhoidal disease (8 per cent). Anorectal symptoms were relieved in 68 per cent of patients and the median survival of those treated was 17.5 months from the time of surgical referral. Both warts and perianal sepsis were associated with in situ neoplasia, but no case of progression from in situ to invasive anal squamous carcinoma was detected. The aetiology of anorectal ulcers was not clear, but surgical excision of anal ulcers and skin tags can produce healing. Palliation of anorectal symptoms in HIV-positive homosexual patients is possible but some conditions are unusual and surgeons should be familiar with their presentation and management.

Adenoviruses and pediatric gastroenteritis.

Adenoviruses were found in 8.6% of 900 pediatric inpatients with diarrhea who were tested by electron microscopy of a fecal specimen and cell culture inoculation of a throat swab and an anal swab specimen. In 5.1% of these patients, including 13.5% of patients who were four through five months of age, adenovirus particles were visualized in the fecal specimen. Controlled study demonstrated that visualized adenoviruses, especially those that did not grow readily in conventional Hep-2 cell cultures, were significantly associated with diarrhea. About 80% of the visualized adenoviruses from patients with diarrhea or vomiting or both, including 94% of the viruses that grew in the 293 cell line but that did not grow readily in Hep-2 cultures, proved to be enteral adenoviruses--adenoviruses from either group F (type 40) or group G (type 41). Inpatients with gastroenteritis and confirmed enteral adenoviruses ranged in age from one through 16 months, with a median age of seven months. Enteral adenoviruses apparently are endemic in this locale, as one or more of these viruses have been found in every calendar month for nine successive years.

Pediatric viral gastroenteritis during eight years of study.

During the period January 1974 through July 1982, fecal samples from 1,537 pediatric inpatients with gastroenteritis were tested for enteric viruses by electron microscopic and rotavirus enzyme-linked immunosorbent assay techniques. Rotaviruses were detected in 34.5% of these patients, enteric adenoviruses were detected in 4.7%, approximately 27-nm viruses were detected in 1.6%, and at least one of these agents was found in 40.1% of the study subjects. Three infections were by an apparently new agent which morphologically is a rotavirus, but which failed to react in the rotavirus enzyme-linked immunosorbent assay. During the first 8 calendar years of study, rotaviruses were detected in 39.0% of 577 patients in the even-numbered years and 30.3% of 702 patients in the odd-numbered years. Adenoviruses were found in all calendar months. Rotaviruses were found in inpatients in November through July, whereas approximately 27-nm viruses were found in October through June. The percentage of patients who had a demonstrated viral infection rose steadily from 7.4% in September to 72.0% in January and then steadily declined to 2.9% in August. Viral infection was especially common in study subjects who were 7 through 24 months of age; 61% of such children had one or more enteric viruses. Rotavirus-infected patients tended to be younger during the months of greatest rotavirus activity than at the beginning and end of the rotavirus season, presumably because of a greater exposure to virus at the height of the rotavirus outbreak.