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Biomedical subjects

D Ricketts

Publications and source records attributed to D Ricketts.

At least 19 recordsLinked to original sources
PubMed2001

Management of the deep carious lesion and the vital pulp dentine complex.

This article describes the relationship between the carious process and pulp-dentine complex reactions. Where the balance between the two is in favour of the carious process and where conventional cavity preparation leads to a direct pulp exposure, the direct pulp cap technique is described. The success of the technique is addressed and more importantly an alternative technique for caries removal, namely stepwise excavation, is described which may lead to a reduced risk of carious exposure and the need for the direct pulp cap technique.

Dental Caries↗
PubMed2000

Approaches towards the quantitative analysis of peptides and proteins by reversed-phase high-performance liquid chromatography in the absence of a pure reference sample.

A reversed-phase HPLC protocol for the quantitative analysis of peptides and proteins is presented. It is applicable to purified samples and potentially to crude biological extracts. The key feature is that an analytically pure reference sample of the analyte is not required because the extinction coefficient for the UV absorbance at 280 nm can be accurately estimated from the amino acid sequence. The concentration of a protein can therefore be calculated from the peak area relative to an internal standard. Sources of error and limitations of the method are systematically considered. Tryptophan containing peptides gave closer agreement to expected values than those with only tyrosine. It was found that analogous, previously used methods could not be directly applied to lower wavelengths.

Chromatography, High Pressure Liquid↗
PubMed1997

Hidden caries: what is it? Does it exist? Does it matter?

Hidden caries is a term used to describe occlusal dentine caries that is missed on a visual examination, but is large enough and demineralised enough to be detected radiographically. The detection rate of such lesions will depend upon the prevalence of caries in the population and the frequency with which bitewing radiographic examinations are performed. Whether 'hidden caries' is a distinct clinical entity, reflecting a particular anatomical fissure topography or a different bacterial aetiology, is unknown. It is possible that an improved visual examination, with careful cleaning and drying of teeth, may improve occlusal caries detection to the point where 'hidden caries' no longer exists. However, this possibility has yet to be tested clinically and until it is, practising dentists would be wise to examine bitewing radiographs carefully for occlusal demineralisation. The authors would treat such hidden lesions by removing soft caries and placing sealant restorations.

Dental Caries↗
PubMed1995

Model sclerotization studies. 3. Cuticular enzyme catalyzed oxidation of peptidyl model tyrosine and dopa derivatives.

Incubation of N-acetyltyrosine methyl ester with cuticular enzymes, isolated from the wandering stages of Calliphora sp larvae, resulted in the generation of N-acetyldopa methyl ester when the reaction was carried out in the presence of ascorbate which prevented further oxidation of the o-diphenolic product. Enzymatic oxidation of N-acetyldopa methyl ester ultimately generated dehydro N-acetyldopa methyl ester. The identity of enzymatically produced N-acetyldopa methyl ester and dehydro N-acetyldopa methyl ester has been confirmed by comparison of the ultraviolet and infrared spectral and chromatographic properties with those of authentic samples as well as by nuclear magnetic resonance studies. Since N-acetyldopaquinone methyl ester was also converted to dehydro N-acetyldopa methyl ester and tyrosinase was responsible for the oxidation of N-acetyldopa methyl ester, a scheme for the cuticular phenoloxidase catalyzed conversion of N-acetyltyrosine methyl ester to dehydro N-acetyldopa methyl ester involving the intermediary formation of the quinone and the quinone methide is proposed to account for the observed results. The conversion of N-acetyldopa methyl ester to dehydro derivative remarkably resembles the conversion of the sclerotizing precursor, N-acetyldopamine, to dehydro-N-acetyldopamine observed in the insect cuticle. Based on these comparative studies, it is proposed that peptidyl dopa derivatives could also serve as the sclerotizing precursors for the sclerotization of the insect cuticle.

Animals↗
PubMed1994

1,2-dehydro-N-beta-alanyldopamine as a new intermediate in insect cuticular sclerotization.

Sclerotization of insect cuticle is an extremely important biochemical process for the successful survival of most insects. N-Acetyldopamine and N-beta-alanyldopamine are two widely used sclerotizing precursors. N-Acetyldopamine is converted by phenoloxidase, quinone isomerase, and quinone methide isomerase to generate the reactive intermediates quinone, quinone methide, and quinone methide imine amide for use in quinone tanning, quinone methide sclerotization, and alpha,beta-sclerotization, respectively. N-beta-Alanyldopamine has been claimed to be used only by phenoloxidase and quinone isomerase for quinone tanning and quinone methide sclerotization thereby attributing biochemical diversity to the coloration and strength of different cuticles. However, we demonstrate here that cuticular enzymes isolated from the larvae of Calliphora possess the capacity to generate 1,2-dehydro-N-beta-alanyldopamine from N-beta-alanyldopamine. Chemical synthesis of 1,2-dehydro-N-beta-alanyldopamine and its further oxidation are reported for the first time. Comparative biochemical studies confirm that both the sclerotizing precursors, N-acetyldopamine and N-beta-alanyldopamine, are used by all three different mechanisms of the unified theory of sclerotization.

Animals↗
PubMed1994

The effect of endocrine therapy on the levels of oestrogen and progesterone receptor and transforming growth factor-beta 1 in metastatic human breast cancer: an immunocytochemical study.

The levels of oestrogen receptor (ER), progesterone receptor (PR) and transforming growth factor-beta 1 (TGF-beta 1) were measured by immunocytochemistry in 19 patients prior to and 1 month after the start of endocrine therapy (tamoxifen 10 patients; aromatase inhibition 9 patients). A complete or partial response was observed in 10 patients. The proportion of cells showing ER staining was higher in responding patients, but there was no change observed with endocrine therapy in either responding or non-responding patients. In contrast, cells staining for PR in responding patients were significantly reduced following therapy (59 +/- 9% to 24 +/- 9%: P < 0.05). There was no reduction in immunocytochemical PR in non-responding patients, although the numbers of these patients with initially positive PR levels was small. Stromal tissue adjacent to tumour cells stained with the antibody to TGF-beta 1, with particularly intense staining at the periphery of tumour cell aggregates. There was no correlation between the degree of TGF-beta 1 staining and ER or PR status, and no evidence of a change with endocrine therapy. It is concluded that neither tamoxifen nor aromatase inhibitors produce a change in the ER content or TGF-beta 1 content of breast tumours as detected immunocytochemically, but PR levels are significantly reduced after therapy in responding patients.

Adult↗
PubMed1994

An orthopaedic theatre timings survey.

The efficient use of operating lists is important to clear waiting lists and because they are expensive to run (at 1988 prices, 151 pounds per hour). Of general surgical theatre session time, 49% is used for performing operations, but no survey of orthopaedic theatre sessions has been published. In light of this we surveyed 151 elective orthopaedic lists at three hospitals. Our aims were to determine the use of operating rooms and the reasons for inefficient use of time. We found 60% of elective list time was used for operating and 21% for turnover. No useful activity occurred during the remaining 19% of theatre time. An average start delay of 26.5 min and average early finish of 14.5 min contributed to this. Only 9/151 (6%) of lists started within 5 min of the scheduled time. Of unnecessary delays contributing to this, 63% involved anaesthetic staff and 24% theatre staff. Surgeons were implicated in 10% of start delays. There were less start delays if senior anaesthetic staff were present. During lists, turnover times were quicker if a consultant surgeon was present (P = 0.0022). We conclude that more efficient use of elective orthopaedic theatre sessions is possible and could be achieved if more detailed preparation was undertaken by the anaesthetic, theatre and surgical staff concerned. If a consultant surgeon is present the list is likely to proceed with fewer delays.

Anesthesiology↗
PubMed1994

Radiographic detection of occlusal caries: effect of X-ray beam factors on diagnosis.

The aim of this laboratory study was to determine whether the diagnostic potential of bite-wing radiographs in the diagnosis of occlusal caries could be improved by alteration of X-ray beam properties. Bite-wing radiographs of molar teeth with 16 sound and 32 carious occlusal surfaces were taken at conventional settings of 65 kVp, 15 mA and 0.3 s (4.5 mAs) and at 70 kVp, 10 mA and 1.0 s (10 mAs), to produce a darker overexposed film. Results showed that, although the overexposed radiograph resulted in more correct diagnosis of dentine caries, its use increased the number of false-positive diagnoses. More importantly, the experimental exposure factors would have led to an unacceptably high radiation dose to the patient with arguable diagnostic benefit. As such it cannot be recommended in any way for patient examination.

Bicuspid↗
PubMed1993

Prediction of response to endocrine therapy in breast cancer using immunocytochemical assays for pS2, oestrogen receptor and progesterone receptor.

Histological sections obtained from 70 patients with breast cancer, all of whom had received endocrine therapy for metastatic or locally advanced disease, were assessed for specific immunocytochemical staining of oestrogen receptor and the oestrogen-induced protein pS2. There was also sufficient material from 25 patients for an assessment of progesterone receptor by immunocytochemistry. We found that, when using a "cut-off" point of 50% for ER and PR, and of 25% for pS2, ER was positive in 22/29 responders and in 12/41 non-responders, and thus was significantly associated with response to endocrine therapy. Similarly, in those subjects in whom PR was measured, PR was positive in 5/14 responders and negative in all 11 non-responders, again being significantly correlated with response. However, pS2 did not relate to response, being only positive in 10/29 responders and negative in 26/41 non-responders. The different response categories varied in their "percentage of positivity" as determined by the 2 tests. Thus, for ER and pS2 we observed: complete response--71% for ER compared with 14% for pS2; partial response--77% compared with 41%; stable disease--36% compared with 64%; and progressive disease--27% compared with 27%. We conclude that at the present time ER appears to be the most reliable indicator for predicting response to endocrine therapy in patients with breast cancer.

Adult↗
PubMed1993

The AO classification of long bone fractures: an early study of its use in clinical practice.

Over a period of 6 months, 543 long bone fractures were classified using the AO classification system. Factors important in determining the management of fractures occurring in three regions; hip, forearm and tibia, were identified. In hip fractures, we found that the anatomical configuration of the fracture, and therefore its classification, generally determined management. However, there were other factors that influenced the more specific form of surgical treatment used. In forearm fractures, the age of the patient was the most important factor determining treatment, while many factors, including consultant preference, determined the treatment of tibial fractures. While we found the system useful for audit purposes, we also found that it was unnecessarily complicated and often fell short of playing a useful role in the planning of management.

Adolescent↗
PubMed1993

Who should code orthopaedic inpatients? A comparison of junior hospital doctors and coding clerks.

Our principal aim was to determine whether coding for billing purposes is adequately completed by hospital doctors. We also wanted to determine whether events during the inpatient stay prompted coding. We investigated the completeness and accuracy of ICD9 and OPCS4 coding at two departments of orthopaedics. Coding was for billing purposes only; retrieval of clinical data was limited to individual cases. Junior Hospital Doctors (JHDs) undertook coding at one department, coding clerks at the other. At each side 100 sets of notes concerning inpatient admissions were reviewed. Coding clerks returned coding data of higher completeness and quality (completeness x accuracy) than JHDs, but of lower accuracy. Completeness of data from JHDs reflected motivation to code and this was influenced by events during the course of admission. JHDs coded best for patients undergoing elective surgery, and worst for patients managed non-operatively. Coding clerks coded for all groups equally well. In the current study coding data returned by JHDs was of lower completeness and accuracy than has been described for other coding systems. We attribute the lower completeness to the low motivation of JHDs when coding for billing purposes and the lower accuracy to difficulty in using the system. Motivation could be increased by incorporating coding into departmental audit, the generation of discharge summaries and record collection for personal logbooks.

Abstracting and Indexing↗
PubMed1993

Markers of data quality in computer audit: the Manchester Orthopaedic Database.

This study investigates the efficiency of the Manchester Orthopaedic Database (MOD), a computer software package for record collection and audit. Data is entered into the system in the form of diagnostic, operative and complication keywords. We have calculated the completeness, accuracy and quality (completeness x accuracy) of keyword data in the MOD in two departments of orthopaedics (Departments A and B). In each department, 100 sets of inpatient notes were reviewed. Department B obtained results which were significantly better than those in A at the 5% level. We attribute this to the presence of a systems coordinator to motivate and organise the team for audit. Senior and junior staff did not differ significantly with respect to completeness, accuracy and quality measures, but locum junior staff recorded data with a quality of 0%. Statistically, the biggest difference between the departments was the quality of operation keywords. Sample sizes were too small to permit effective statistical comparisons between the quality of complication keywords. In both departments, however, the poorest quality data was seen in complication keywords. The low complication keyword completeness contributed to this; on average, the true complication rate (39%) was twice the recorded complication rate (17%). In the recent Royal College of Surgeons of England Confidential Comparative Audit, the recorded complication rate was 4.7%. In the light of the above findings, we suggest that the true complication rate of the RCS CCA should approach 9%.

Data Collection↗
PubMed1992

Streptococcal gangrene presenting as hip pain: two case reports and review of the literature.

Two cases of streptococcal gangrene are reported. Both patients, with hip pain and no obvious source of infection, presented to the same orthopaedic team within a few days. After initial treatment with NSAIDs the outcome was fatal in the cases described. A review of the literature revealed that the administration of NSAIDs may accelerate the course of the disease. The authors conclude that this very rare cause of arthralgia and malaise should be excluded before the administration of NSAIDs for such complaints.

Adult↗