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Biomedical subjects

A J Miles

Publications and source records attributed to A J Miles.

At least 19 recordsLinked to original sources
PubMed2005

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.

Circular Dichroism↗
PubMed2004

CDtool-an integrated software package for circular dichroism spectroscopic data processing, analysis, and archiving.

CDtool is a software package written to facilitate circular dichroism (CD) spectroscopic studies on both conventional lab-based instruments and synchrotron beamlines. It takes format-independent input data from any type of CD instrument, enables a wide range of standard and advanced processing methods, and, in a single user-friendly graphics-based package, takes raw data through the entire processing procedure and, importantly, uses data-mining techniques to retain in the final output all the information associated with the processing. It permits the facile comparison of data obtained from different instruments without the need for reformatting and displays it in graphical formats suitable for publication. It also includes the ability to automatically archive the processed data. This latter feature may be especially useful in light of recent funding institution directives with regard to data sharing and archiving and requirements for "good practice" and "traceability" within the pharmaceutical industry. In addition, CDtool includes a means of interfacing with protein data bank coordinate files and calculating secondary structures from them using alternate definitions and algorithms. This feature, along with a function that permits the facile production of new reference databases, enables the creation of specialized databases for secondary structural analyses of specific types of proteins. Thus the CDtool software not only enables rapid data processing and analyses but also includes many enhanced features not available in other CD data processing/analysis packages.

Archives↗
PubMed2000

Possible occupational asthma among adults presenting with acute asthma.

BACKGROUND: Little is known about the risk of occupational asthma or its causative agents in South Africa. The objective of this study was to determine the proportion of adult asthmatics whose asthma may be occupational, and the main agents or occupations involved. DESIGN AND SETTING: A descriptive surveillance study of adult patients presenting with acute asthma to the casualty units of two large public hospitals in Cape Town. METHODS: A brief questionnaire was completed by the casualty staff for a sample of 140 adult asthmatic patients. Respondents were classified as having possible occupational asthma on the basis of adult-onset asthma, exposure at time of onset to a known or suspected cause of occupational asthma, and symptoms that improved away from work. RESULTS: Eighteen patients (12.9%, 95% confidence interval (CI) 7.8-19.6%) met the criteria for occupational asthma. The main occupational categories in this group were spray painters (4 patients) and domestic workers (4 patients), with cleaning agents, dyes and paints being the most commonly reported exposures. A total of 36 patients (25.7%, 95% CI 18.7-33.7%) reported work aggravation of their asthma. CONCLUSIONS: A clinically significant proportion of adult-onset asthmatics, men and women, may have occupational causation, while an even larger proportion may have occupational aggravation. Since early intervention favourably influences prognosis in occupational asthma, all practitioners dealing with adult asthmatics should explore occupational factors.

Acute Disease↗
PubMed1998

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.

3T3 Cells↗
PubMed1996

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.

Amino Acid Sequence↗
PubMed1995

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.

Amino Acid Sequence↗
PubMed1995

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.

Adolescent↗
PubMed1994

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.

Amino Acid Sequence↗
PubMed1993

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.

Amino Acid Sequence↗
PubMed1993

A light- and developmentally-regulated DNA-binding interaction is common to the upstream sequences of the wheat Calvin cycle bisphosphatase genes.

We have characterised a DNA-binding interaction common to the upstream sequences of the wheat fructose-1,6-bisphosphatase (FBPase) and sedoheptulose-1,7-bisphosphatase (SBPase) genes. The recognition site for this sequence-specific binding activity, designated wheat FBPase factor (WF-1), is located within 125 bp of the transcription start site of each gene. Within these regions there are no sequence motifs similar to those shown to be important for light-regulated expression in other species. The binding activity was not detected in wheat root nuclear extracts, or in pea leaf extracts. There was a higher level of binding activity in light-grown than in dark-grown wheat leaves. The level was also found to decline when light-grown plants were given an extended dark treatment, but could be reinduced by light. Utilising the gradient of developmental maturity which exists within the wheat leaf it was found that WF-1 activity increases during leaf development.

Base Sequence↗
PubMed1993

Effect of anoreceptive intercourse on anorectal function.

This study is the first published assessment of the effect of anoreceptive intercourse (ARI) on anal sphincter tone and function. Forty anoreceptive (AR) male homosexuals were compared with 18 age matched non-anoreceptive (non-AR) heterosexual males. Subjects were questioned about ARI, defaecation and faecal incontinence. Anal resting pressure, maximum voluntary squeeze pressure, anal mucosal electrosensitivity, perineal descent and rectal sensation were measured in all subjects. Fourteen of the AR subjects but only one of the non-AR subjects had symptoms of frequent anal incontinence (P < 0.05). There was a significant reduction in both maximum anal resting pressure (P < 0.01) and anal mucosal electrosensitivity (P < 0.05) and a significant difference in the anal resting pressure profile (P = 0.02) in the AR subjects compared with the non-AR subjects. There was a significant reduction in maximum squeeze pressure in AR subjects with anal incontinence compared with either AR subjects without anal incontinence (P < 0.01) or non-AR subjects (P < 0.01). There were no significant differences in stoll consistency, frequency of defaecation, perineal descent or rectal sensation between the groups. ARI is associated with reduced resting pressure in the anal canal and an increased risk of anal incontinence. The risk of incontinence is greatest amongst AR subjects with reduced maximum squeeze pressure.

Adult↗
PubMed1991

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.

Acquired Immunodeficiency Syndrome↗
PubMed1991

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.

Acquired Immunodeficiency Syndrome↗
PubMed1990

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.

Abscess↗
PubMed1985

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.

Adenoviridae Infections↗