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Biomedical subjects

P S Richardson

Publications and source records attributed to P S Richardson.

At least 19 recordsLinked to original sources
PubMed2001

Identification of a nonmucin glycoprotein (gp-340) from a purified respiratory mucin preparation: evidence for an association involving the MUC5B mucin.

Rate-zonal centrifugation of a reduced and alkylated respiratory mucin preparation identified a protein-rich fraction. This was subjected to trypsin treatment and one of the many liberated peptides was purified and its N-terminal sequence determined. The peptide was identical to a 14 amino acid sequence from the scavenger receptor cysteine-rich domain containing glycoprotein gp-340. A polyclonal antiserum, raised against the peptide, stained the serous cells in the submucosal glands of human tracheal tissue. The glycoprotein was purified from respiratory mucus by density-gradient centrifugation, gel chromatography, and anion exchange chromatography. The molecule exhibited a heterogeneous distribution of buoyant density (1.28-1.46 g/ml) that overlapped with the gel-forming mucins, was included on Sepharose CL-2B and was quite highly anionic. SDS-PAGE indicated a mass greater than 208 kDa and measurements performed across the molecular size distribution indicated an average M(r) of 5 x 10(5) with a range of M(r) from 2 x 10(5) to 1 x 10(6). Gel chromatography of respiratory mucus extracts ("associative" and "dissociative") indicated that this glycoprotein forms complexes that may involve the large gel-forming mucins MUC5AC and MUC5B. Rate zonal centrifugation suggested such complexes are more likely to involve MUC5B rather than MUC5AC mucins.

Amino Acid Sequence↗
PubMed2000

The initial dental health status of British Army Gurkha recruits.

AIM: To describe the initial dental health status of British Army Gurkhas who were recruited in 1999 and to compare the present caries data with previous unpublished data from before 1970 and 1983. DESIGN AND SETTING: A clinical examination was conducted on the 228 Gurkhas, the entire UK intake for 1999, during their second week of military training. The focus of the examinations was on caries experience. A questionnaire was employed to collect demographic data as well as information on the recruits' reported dental behaviour and beliefs. RESULTS: 1999 recruits who reported a dental problem within the past year were significantly more likely to have visited a dentist before compared to those recruits who reported no dental problems. The frequency distributions of D3MFT for the 1983 and 1999 recruits were very similar. CONCLUSIONS: Gurkha men are at relatively low risk of dental caries and predicted treatment time suggests a relatively small use of resources would be needed to make this group dentally fit. These recruits are an extremely homogeneous group who remain discernible from the general Nepalese population.

Adolescent↗
PubMed2000

Influence of pigment content, intracellular calcium and cyclic AMP on the ability of human retinal pigment epithelial cells to contract collagen gels.

PURPOSE: The aim of the study was to determine to what extent collagen gel contraction could be reduced by calcium and calmodulin antagonists and agents that elevate cyclic AMP in order to develop a pharmacological approach to prevent/arrest RPE contraction of epiretinal membranes in proliferative vitreoretinopathy. We also explored a possible role of pigment in collagen gel contraction. METHOD: We measured RPE mediated contraction of 3D collagen gels in the presence and absence of the calcium and calmodulin antagonists TMB8, Verapamil and Tamoxifen and the cAMP elevating agents IBMX and Forskolin. The effect of pigment on collagen gel contraction was assessed by comparing gel contraction mediated by RPE cells re-pigmented with melanin with that mediated by unpigmented RPE. The effect of IBMX on RPE proliferation was assessed using a BrdU ELISA and the effects of IBMX on RPE cytoskeleton and cell shape were assessed using Actin and Cytokeratin immunocytochemistry. RESULTS: We report that both cAMP elevating agents and calcium and calmodulin antagonists reduce RPE mediated collagen gel contraction. Cyclic AMP elevation was more effective than a reduction in calcium in reducing contraction. There were no significant advantages in combining both approaches. The presence of melanin had no effect on gel contraction. Calcium antagonists and particularly agents which elevate cAMP caused RPE cells in collagen gels to extend fewer and shorter processes. cAMP elevation in particular caused RPE cells to become more rounded and develop arborized cell processes. Immunostaining for actin and cytokeratin revealed changes in cytoskeletal organisation in response to IBMX in that cells contained less actin than untreated cells and concentrated cytokeratins more centrally. CONCLUSION: We have identified two possible pharmacological approaches which may provide a new direction for preventing or slowing down the development of PVR.

1-Methyl-3-isobutylxanthine↗
PubMed1999

Physical characterization of a low-charge glycoform of the MUC5B mucin comprising the gel-phase of an asthmatic respiratory mucous plug.

We have previously noted that sequential extraction of an asthmatic mucous exudate with 6 M guanidinium chloride yielded a fraction of the mucins that were most resistant to solubilization and of high Mr [Sheehan, Richardson, Fung, Howard and Thornton (1995) Am. J. Respir. Cell Mol. Biol. 13, 748-756]. Here we show that this mucin fraction is dominated (at least 96% of the total) by the low-charge glycoform of the MUC5B gene product. Seen in the electron microscope the mucins appeared mainly as compact 'island' structures composed of linear threads often emanating from globular 'nodes' rather than the discrete linear threads more typical of mucins that we have previously described. The effect of reducing agents was as expected for other gel-forming mucins, i.e. reduced subunits or monomers of Mr 3x10(6)) were produced within 15 min of treatment. Kinetic experiments on the cleavage of the intact mucins with the proteinase trypsin indicated two clear regimes of fragmentation. An initial rapid cleavage generated mucins ranging from Mr=4x10(6) to 30x10(6) that in the electron microscope appeared as polydisperse threads (500-3000 nm in length), similar to normal and other respiratory mucins that we have previously characterized. A subsequent slower fragmentation over many hours yielded a major fragment of Mr 3x10(6) and length 200-600 nm, very similar in size and Mr to the subunits obtained by reduction. The results suggest that the MUC5B mucin is assembled, first into polydisperse linear threads, which are then linked together via a protein-mediated process. This might involve part of the mucin polypeptide or an as yet unidentified protein(s). The high proteinase susceptibility of the linkage suggests that it might be a point of control for mucin size and thus mucus rheology.

Asthma↗
PubMed1999

The posterior vitreous detachment clinic: do new retinal breaks develop in the six weeks following an isolated symptomatic posterior vitreous detachment?

PURPOSE: Symptomatic posterior vitreous detachment (PVD) is sometimes associated with sight-threatening retinal tears or retinal detachment. Patients are usually reviewed twice because it is believed that retinal breaks may develop within 6 weeks of a PVD and as such the management of a PVD consumes significant resources. The aim of this study was to find the frequency of retinal breaks developing within 6 weeks of an isolated PVD using the same experienced examiner at both visits. METHOD: Patients presenting to the eye casualty with symptomatic PVD were examined by the casualty staff. Those with a retinal break or retinal detachment were referred directly for treatment and those with only a PVD were seen within 8 days in the PVD clinic. They were examined by a vitreo-retinal Fellow using indirect ophthalmoscopy and a 20 D lens with scleral indentation. The position and nature of any retinal abnormalities were noted and compared with those described in the casualty notes. Those with sight-threatening breaks were referred for treatment and the remainder were reviewed 5 weeks later when the presence of any new breaks was noted. RESULTS: One hundred and seven patients were referred to the PVD clinic over a 6-month period, of whom 2 did not have a PVD. At the first visit to the PVD clinic 6 patients had round holes anterior to the equator, 2 had equatorial horseshoe tears and 1 had lattice with holes. At the second visit, 2 additional patients had round holes anterior to the equator but in both the retina had been obscured by vitreous haemorrhage at the first visit. No patient in whom a full examination was possible at the first visit developed further retinal pathology. CONCLUSION: These results demonstrate the need to perform a full examination of the peripheral retina with scleral indentation at the time of presentation and emphasise the importance of finding a vitreous haemorrhage following a symptomatic PVD. If no retinal breaks are detected by thorough examination at presentation, further reviews, in the absence of increasing symptoms, may not be necessary.

Adult↗
PubMed1998

Involvement of calcium in retinal pigment epithelial cell proliferation and pigmentation.

PURPOSE: The aim of this study is to explore the role of intracellular calcium in the mechanism of co-regulation of retinal pigment epithelial cells (RPE) by vitreous fluid and platelet mitogens, in order to evaluate the use of calcium modulating drugs in preventing RPE cell proliferation and contraction of fibrocellular membranes. METHODS: Monolayers of human RPE cells were loaded with Fura-2-AM and examined in a fluorimeter for changes in intracellular free calcium in response to platelet mitogens (PDGFAB or TGFbeta1) and vitreous fluid (containing vitreous substrate proteins), both alone or in combination. The effect of the calcium antagonists TMB8 and verapamil and the calmodulin antagonists J8 and tamoxifen were then examined on RPE cell proliferation and pigmentation, both in the presence and absence of vitreous substrate and platelet mitogens. RESULTS: We report that co-exposure of RPE cells to platelet mitogens and vitreous fluid produces an increase in intracellular free calcium of greater duration than that with either PDG-FAB, TGFbeta1 or vitreous fluid alone. Calcium and calmodulin antagonists significantly reduce RPE cell proliferation in both the presence and absence of vitreous substrate and platelet mitogens. Calcium antagonists also stimulate the accumulation of autofluorescent granules within RPE cells. CONCLUSIONS: Calcium signalling plays a role in the co-regulation of RPE cells by vitreous substrate and platelet mitogens. Drugs that lower intracellular calcium or inhibit calmodulin may offer an additional approach to preventing the hyperproliferation of RPE cells in PVR.

Adult↗
PubMed1997

Natural killer and lymphokine-activated cytotoxicity following anaesthesia in patients with uveal malignant melanoma.

The role of enucleation in the treatment of ocular melanoma has been questioned by those who believe that it may increase circulating melanoma cells, increasing the incidence of metastases. Some aspects of the immune system are depressed by general anaesthesia, therefore this study was initiated to assess the effect of general anaesthesia on natural killer (NK) cell and interleukin-2 (IL-2)-activated cytotoxicity in 19 patients using 51Cr-labelled target cells (K 562 and SW 742). NK cytotoxicity was increased at induction and during the operation which was due to significant increases in female, but not male patients. At 1 week post-surgery, female patients had decreased NK cytotoxicity compared with males at this interval. NK cytotoxicity compared with males at this interval. NK cytotoxicity was increased intra-operatively when alfentanyl was used, and if the mean tumour diameter was > 15.0 mm the NK cytotoxicity was increased intra-operatively compared with that in patients with smaller tumours. IL-2-stimulated cytotoxicity was reduced at 1 day post-surgery in females only. There was an increased IL-2-stimulated cytotoxicity at induction when propofol was used and IL-2-stimulated cytotoxicity was reduced at 1 week post-operatively if the patient's mean tumour diameter was > 15.0 mm. If NK cell and lymphokine-stimulated cell cytotoxicity are involved in limiting metastatic disease, the patient' sex and tumour size and the anaesthetic agent used may influence the survival rates following surgery.

Adult↗
PubMed1997

Panoramic radiographic screening: a risk-benefit analysis.

PURPOSE OF STUDY: To determine the amount of clinically relevant pathology found by panoramic radiographic screening in a young adult population and to assess whether such screening is justified. POPULATION STUDIED: The records of 1101 RAF recruits enlisted in 1988-89, average age 19 years (range 16-26). METHOD: The routine dental panoramic tomograph screening films of the sample population were inspected by the author on a masked-out screen under 2X magnification. Where instances of dubious pathology were found these films were shown to a consultant oral surgeon for a second opinion. The literature on the risks associated with radiographic screening and the prevalence of intra-osseous pathology was reviewed. FINDINGS: There was a considerable number of findings reported, including three large isolated radiolucent areas, 75 periradicular radiolucent areas, four probable cysts and 1187 unerupted mandibular third molars. However, when the clinical significance of these 'lesions' was assessed only those related to dental causes appeared to have significant clinical implications and the literature indicated that these could have been detected by selective radiology. CONCLUSION: The quantity of clinically relevant pathology did not justify routine panoramic radiographic screening in young adults.

Adolescent↗
PubMed1997

Selective periapical radiology compared to panoramic screening.

PURPOSE OF STUDY: To assess whether selected periapical radiographs, taken according to High Yield Criteria, can reveal as much intra-osseous pathology as universal panoramic screening. POPULATION STUDIED: The records of 1101 RAF recruits enlisted in 1988-89, average age 19 years (range 16-26). METHODS: The clinical records and bitewing radiographs of the recruits were examined and the requirement for periapical radiographs determined according to high yield criteria. A template, cut out to simulate the area covered by a periapical bitewing radiograph, was placed over the suspect region on the panoramic film and any findings found within the template recorded. The entire dental panoramic tomograph was then examined on a masked screen under 2X magnification and any further findings recorded. FINDINGS: There was a considerable number of findings reported, including three large isolated radiolucent areas, 75 periradicular radiolucent areas, four probable cysts and 1187 unerupted mandibular third molars. However, when the clinical significance of these 'lesions' was assessed only those related to dental causes appeared to have significant clinical implications and the results indicated that these could have been detected by selective radiology. CONCLUSION: This study showed that the only pathology which occurs frequently enough to justify radiographic screening of the jaws in young adults is related to teeth. It seems probable that this type of pathology can be at least as well detected by selective periapical screening, using high yield criteria, as is possible by universal panoramic screening.

Adolescent↗
PubMed1996

Mucins in airway secretions from healthy and chronic bronchitic subjects.

Little is known about whether the properties of respiratory mucins are altered as a result of airway irritation, but histochemical studies of respiratory tract secretory cells show a more 'acidic' staining pattern after exposure to tobacco smoke. Furthermore it has been suggested that proteoglycans are the major glycoconjugates in 'normal' respiratory secretions, whereas mucins predominate in sputum. To investigate these observations further, mucins from secretions collected from the tracheal surface of healthy non-smoking 'normal' subjects and sputum from patients with chronic bronchitis were compared. All samples contained one major mucin population after density-gradient centrifugation, and a small amount of 'denser' mucin was present in some chronic bronchitic and one of the 'normal' samples. Proteoglycans were not a major component of 'normal' secretions. The major mucin population from chronic bronchitic samples had molecular masses between 10 and 30 MDa and behaved as random coils in solution. Whole mucins from 'normal' individuals and chronic bronchitic patients were excluded from Sepharose CL-2B, whereas reduced subunits were included. Proteolysis of subunits yielded two populations of high-molecular-mass glycopeptides differing in size, suggesting the presence of two different tandem repeat regions in the mucins. Finally, mucins from patients with chronic bronchitis are less, rather than more, acidic than those from 'normal' individuals. Mucins from bronchitic sputum and 'normal' secretions are thus similar in their macromolecular properties, but differ slightly in charge density.

Adolescent↗
PubMed1996

Dental treatment needs of a cohort of Royal Air Force recruits over 5 years.

The paper reports the dental status of a cohort of Royal Air Force (RAF) recruits in 1988 and details the work required to render and maintain them dentally fit for their first 5 years in the service. The mean DMFT (7.3) at inspection in 1988 increased by 0.8 whilst the mean number of restorations placed was 4.0. Endodontic therapy was required by 13.4 percent of the recruits and crowns were provided for 9.6 percent. The recruits required twice as many restorations in their first year in the service to render them dentally fit as were required in any subsequent year to maintain fitness, this work needed 58 minutes of dental officers' time in their first year and 43 minutes per year thereafter. The number of dentists seen or courses of treatment undertaken did not have a significant effect on the number of restorations provided. The prevalence and incidence of caries in this group appeared to justify the RAF's policy of annual inspections but the number of carious lesions which did not progress far enough to require restoration after 5 years indicated that a preventive approach to treatment planning is important to avoid overtreatment.

Adolescent↗
PubMed1996

The difference between clinical and bitewing detection of approximal and occlusal caries in Royal Air Force recruits.

This paper reports on differences between the clinical and radiographic detection of caries, on both occlusal and approximal surfaces, in a cohort of Royal Air Force (RAF) recruits (mean age 18.9 years). It was found that the clinical examination detected only 30 per cent of the total lesions found by both methods combined. The radiographic examination found 201 per cent extra occlusal dentinal lesions and 192 per cent extra approximal dentinal lesions. In those recruits where caries was evident, the mean number of dentinal lesions found after the clinical examination was 1.0 compared to 2.7 lesions after the radiographic data were added. It was concluded from these results that radiographs are essential for assessment of the prevalence of both approximal and occlusal caries in service recruits. The epidemiological effect, in this age group, of the lower sensitivity of the clinical examination was to underestimate the overall DMFT by 7.8 per cent, although nearly three times as many dentinal lesions were diagnosed from radiographs as were detected clinically.

Adolescent↗
PubMed1996

Susceptibility of tooth surfaces to carious attack in young adults.

This paper reports on the pattern of carious attack, prior to and after enlistment, experienced by a cohort of 291 Royal Air Force recruits first inspected in 1988 and observed again in 1992. On enlistment the recruits had suffered more occlusal than approximal caries. Over the next five years approximal caries occurred more often than occlusal caries in premolars, its incidence was the same as that of occlusal caries in first molars but less than for occlusal caries in second molars. On enlistment, 88 per cent of the occlusal surfaces of first molars and 56 per cent of second molars were already missing, filled or carious. One in 10 sound molars succumbed to occlusal caries during the study although only 1 in 120 premolars did likewise. It was concluded that the incidence of occlusal caries in this age group justifies placing or repairing fissure sealants in molar teeth.

Adolescent↗
PubMed1995

Effect of TNF, IL-1, and IL-6 on the proliferation of human Tenon's capsule fibroblasts in tissue culture.

Trabeculectomy is a commonly performed procedure for primary open angle glaucoma and is successful in the majority of cases. However, certain factors including aphakia, previous surgery, secondary glaucomas, ethnic origin, and the long term use of topical antiglaucoma medications may be associated with a reduced success rate. The mechanism (or mechanisms) which influence clinical outcome following trabeculectomy remain elusive. Alterations in the composition of the conjunctiva or aqueous humour may be partly responsible for this effect, and this could be mediated by cytokines. In this study we found that tumour necrosis factor (TNF), and interleukin 1 (IL-1) were capable of stimulating the proliferation of Tenon's capsule fibroblasts in tissue culture. Interleukin 6 (IL-6) did not appear to have any effect. The relevance of this to wound healing following trabeculectomy is discussed.

Aged↗
PubMed1995

Mucus glycoconjugate complexes released from feline trachea by a bacterial toxin.

This paper describes low-density mucus glycoconjugates released from feline trachea by dirhamnolipid (DRL), a toxin from Pseudomonas aeruginosa. Mucus glycoconjugates in feline tracheas were radiolabeled in vivo with 3H-proline and 14C-glucose. Control mucus and that released by 200 micrograms/ml DRL were dissolved in guanidine hydrochloride buffer (GuHCl) and chromatographed on Sepharose CL-2B. Molecules eluting in the void volume (V0) of the column were isolated by isopycnic density gradient centrifugation in CsCl/GuHCl. All samples gave peaks of radiolabeled and periodic acid/Schiff (PAS)-reactive material at rho = approximately 1.50 and approximately 1.60 g/ml, but DRL-stimulated samples contained low-density material (rho < 1.32 g/ml), also PAS-reactive and radiolabeled. Control secretions incubated with DRL in vitro did not form low-density material. In Triton X-100 (1% vol/vol), a nonionic detergent, low-density material behaved as smaller molecules, running in the partially included volume (Vi) of the column of Sepharose CL-2B, but still in the V0 of Sephacryl S-300. Incubation with chondroitinase ABC, heparinase II and III, and keratanase failed to change its elution profile on S-300, evidence against glycosaminoglycans; but proteolysis with trypsin or proteinase K gave two peaks, peptide fragments near the totally included volume of the column and glycopeptides in V0. The V0 glycopeptides banded between 1.50 and 1.55 g/ml in a CsCl gradient and eluted as a single peak in the Vi of Sephacryl S-400, suggesting a distinct homogeneous glycopeptide, smaller than those from normal mucins. The main 14C-labeled sugars in this glycopeptide were fucose, glucosamine, galactosamine, and galactose, consistent with a mucin. Thus, DRL releases stable but noncovalent complexes containing one or more distinct mucinlike glycoconjugates, probably combined with lipids and peptides. We discuss their possible relevance to airway diseases, including cystic fibrosis.

Animals↗
PubMed1995

Analysis of respiratory mucus glycoproteins in asthma: a detailed study from a patient who died in status asthmaticus.

Airway mucus from asthmatics is often unusually solid. The death of a patient in status asthmaticus allowed the collection of 28 g of abnormal airway mucus at autopsy. Its chemical and physical properties were studied to reveal differences from more normal airway mucus. The gel plug taken from the airways could be dispersed in 6 M guanidinium chloride, but it took > 1 wk and 700 ml of extractant to disperse 3 g of exudate completely. In contrast, treatment with 10 mM dithiothreitol, which reduces disulfide bonds, dispersed the gel within seconds. Mucins accounted for 25% of the non-dialyzable material in the gel, while DNA constituted < 1% and proteoglycans could not be detected. The mucins were similar in architecture and general composition to other respiratory mucins and were present at a high concentration (approximately 40 mg/ml). The majority of mucins were of extreme size (mean M(r) 30-40 x 10(6)) and slow to dissolve, but sequential extraction experiments on the gel exudate demonstrated a proportion of mucins (15%), the most readily extracted, which had a higher density, 1.45-1.55 g/ml, a lower M(r) (11.5 x 10(6)) and were markedly more acidic than the bulk of the mucins. Both major and minor mucin populations were extremely heterogeneous in mass distribution. Electron microscopy of the major mucin species demonstrated extensive networks of molecules many microns in length. The major mucin species was distinctly less acidic than mucins previously described from either normal or diseased airways. Amino acid analysis of fractions across the charge distribution suggested the presence of at least two different mucin proteins occurring as distinct glycoforms.

Gels↗