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Biomedical subjects

H L Mitchell

Publications and source records attributed to H L Mitchell.

At least 19 recordsLinked to original sources
PubMed2006

The management of knee pain in primary care: factors associated with consulting the GP and referrals to secondary care.

OBJECTIVES: To investigate the treatment of knee pain in primary care and the factors associated with consulting general practitioners (GPs) and referrals to specialist services. METHODS: Individuals with knee pain were identified through postal questionnaires sent to patients aged 50 and over from two GP practices in southeast London. Patients with knee pain were then invited to the department, where demographic, clinical and service use data were collected. Participants also completed measures of pain, function, handicap and illness beliefs. RESULTS: From the 2940 questionnaires that were sent out, the response rate was 34%. Of these, 49% reported experiencing knee pain in the previous 12 months. Two hundred and thirty-one patients with knee pain attended the department. One hundred and thirty-four (58%) had seen their GP about their knee pain, with 50 (37%) referred on to specialist services. Compared with non-consulters, consulters had more severe disease and higher levels of disability and handicap, and believed the condition was more severe and had major consequences on their lives. Those referred to specialist care had higher levels of handicap and also believed the condition was more severe, with major consequences on their lives, than those not referred. CONCLUSION: In this sample nearly half of those who reported knee pain had not seen their GP and were self-managing their condition. A mixture of physical, social and psychological factors predicted visits to GPs and rates of referral to secondary care. Patient perceptions about knee pain were important predictors of both consultations and referrals, highlighting the need to address both physical and psychosocial factors in relation to help-seeking.

Aged↗
PubMed2005

Maxillary incisor palatal erosion: no correlation with dietary variables?

The objectives of the study were to examine a relationship between tooth erosion affecting the palatal aspects of permanent maxillary central incisors with dietary, behavioral and medical variables. The methods included, 251 schoolchildren aged 11 to 13 years were recruited to participate. Each subject had dental impressions of the palatal aspects of both upper central incisors recorded at baseline, 9 and 18 months intervals. From these, electroconductive replicas were fabricated, mapped and compared using a surface matching technique. At the end of the study all participants underwent a structured interview that sought to assay the level of potential erosive dietary, behavioral and medical risk factors. Correlation analyses of the responses given in the final structured interview with the degrees of palatal tooth substance loss (both previous and measured) were under taken. The results showed: (1) The degree of previous erosion did not predict the level of measured ongoing erosion. (2) Brushing the teeth more frequently with fluoridated toothpaste correlated significantly with lower levels of ongoing erosion (P = 0 011). It was concluded that: (1) Evidence of previous palatal erosion did not predict future erosion. (2) The application of topical fluoride as a by-product of tooth brushing may provide an element of protection against palatal erosion. (3) In view of the lack of correlation between exposure to potential risk factors and the level of ongoing palatal tooth surface loss in this study, other factors (such as an individual's susceptibility and salivary buffering power) may well be more important predictors. The clinical relevance included: Preventive advice to patients with dental erosion should not only include the use of topical fluoride, in the form of toothpaste, but recognize individual susceptibility to this condition.

Adolescent↗
PubMed2004

Linear interpolation error in measured surfaces in a dental erosion study.

An extensive palatal erosion study, which is currently being undertaken at the University of Dundee, aims to detect erosion through the precise mapping of replicas of children's incisors. All perceived sources of error are being scrutinised closely. The error due to the interpolation of surface positions from discrete point measurements has been investigated so that its contribution to the erosion estimates can be gauged. The calculation of the error statistics made use of covariance functions to express the undulation of the tooth surfaces. It has been found that, for the measurement point spacing of 150 microm being used in the current project, the interpolation error for an incisor is typically about 25 microm, to be compared with the root-mean-square error due to tooth impression and replication procedures, assessed as being in the order of +/- 3 microm, and replica measurement, assessed as being in the order of +/- 5 microm. The interpolation error constitutes a surprisingly large proportion of the overall system error. The same error estimation technique can be applied usefully and without difficulty to other research studies concerning erosion or wear in natural or restorative dental surfaces.

Child↗
PubMed2004

Rationalization of quantitative tooth surface loss data for epidemiological research.

Recent UK National Surveys have revealed a high prevalence of tooth surface loss (TSL) because of erosion in Children and Adolescents. Although digital surface mapping and surface matching techniques may be used to quantify its progression with time, reporting TSL of individuals as a function of either mean depth loss or volume loss, this can be inadequate when transferred for epidemiological analysis. For example, a tooth displaying multiple regions of depth loss may deserve to be distinguished from a tooth with a single localised area of erosion, although the total volume change may be the same. A potential solution, explored here, is to use both the quantitative wear data and colour coded surface representation plots generated by such methods to arrive at a single categorical wear score [1 (< or = 5% of surface exhibits TSL) to 5 (> or = 51% of surface exhibits TSL)]. Two examiners independently categorized, on two separate occasions, the TSL of 53 maxillary incisors (26 subjects observed at baseline and 9 months). Their performance was assessed for intra- and inter-examiner agreement by; (i) calculating the percentage of agreement, (ii) a Wilcoxon matched-pairs signed rank test. Thereafter, in cases of disagreement a consensus score was allocated and a regression analysis of this versus the numerically derived percentage of the surface that had undergone change was carried out. Intra- and inter-examiner agreement was 100 and 88.7% respectively and for the inter-examiner comparison P = 0.0456. The categorical scores and the quantitative wear data correlated linearly (R = 0.82). It is concluded that the method used to rationalize the quantitative TSL data is both reproducible and reflects the quantitative data. Its use should be helpful in epidemiological TSL studies but continued vigilance is required in cases of examiner disagreement.

Adolescent↗
PubMed2004

A novel approach to evaluating the reproducibility of a replication technique for the manufacture of electroconductive replicas for use in quantitative clinical dental wear studies.

The assessment of the progression of tooth surface loss has until recently been limited to either the application of subjective ranking scales or visual comparison of sequential study casts. The development of quantitative measuring techniques offers the potential of greater accuracy and sensitivity. As direct intra-oral measurement is problematical such approaches often utilize impressions of the teeth, recorded at different epochs, to construct replicas for mapping and comparison. This in vitro investigation sought to determine the reproducibility of such an approach taking into account the total process chain. Two inlay cavities (one large, one small) were prepared in the palatal aspect of a plastic maxillary central incisor and restored with two flush fitting inlays. A series of impressions of this tooth were recorded, using a special tray and an addition cured light bodied silicone impression material (President, Coltene, Switzerland), with (a) both inlays in (b) both inlays out (c) large inlay out and small inlay in (d) large inlay in and small inlay out - a total of 16 impressions. Electroconductive replicas were fabricated from these and mapped using a computer controlled probe. Each series simulated wear of the tooth. A surface matching and difference detection algorithm was then used to compare each series of replicas and calculate the proportion of the surface undergoing simulated wear by a direct comparison of (a) matched to (b) or, indirectly as the summation of the results of matches of (a) with (c) and (a) with (d). The mean proportion of the surface with wear calculated directly was 26.6% (s.d.=0.6) and indirectly 26.1% (s.d. = 0.5). A one-way anova revealed no significant difference (P > 0.05). It is concluded that determining wear by this method is highly reproducible.

Algorithms↗
PubMed2003

Assessment of a procedure for detecting minute levels of tooth erosion.

Over a period of some years, the components of a system for discerning erosion on children's teeth have been progressively developed, for use in an extensive project seeking correlations between erosion and various perceived risk factors. The aim was the detection of minute levels of erosion, based on mappings of the palatal surfaces of the maxillary central incisors in children. Significant challenges were encountered, the primary problem being the impracticality of placing control marks that would aid the realignment of successive measurements. The paper describes the erosion detection system and initial experiences based on the results of the first 100 subjects measured after 9 months. The procedures detected the occurrence of erosion of 50 microm magnitude on about one-quarter of the teeth over the 9 month period, at a precision estimated to be +/- 15 microm. The occurrence of some anomalous incidents prevented the procedure from being fully automatic, and it necessitated human examination of a graphical diagram derived from the surface matching program, but it was nevertheless superior to current practices of examining impressions or replicas entirely by eye.

Child↗
PubMed2002

Evaluation of the accuracy and reproducibility of a replication technique for the manufacture of electroconductive replicas for use in quantitative clinical dental wear studies.

This work sought to evaluate the accuracy and reproducibility of a replication process that formed electroconductive replicas from addition cured silicone impressions for the purposes of monitoring tooth surface loss. Replicas were constructed by painting the surface of impressions with one of three high silver content electroconductive paints [Electrocure (EC), RS Silver Paint (SP) and Electrolube (EB)] and, once dry, backing this up with a cyanoacrylate based gel material (Zapit) and die stone. For each paint an impression was recorded of a gauge block of known step height (1270 microm) and five impressions of the palatal surface of a laboratory standard maxillary central incisor were also recorded. All impressions were taken using an addition cured silicone impression material (President). The resultant electroconductive replicas were mapped using a computer controlled probe. This data was analysed to determine both the replica's step height and, using surface matching techniques, the reproducibility of the replication process. The mean step heights recorded were; EC=1268.43 (s.d.=12.09), SP=1267.09 (s.d. 1.77) and EB 1299.58 (s.d. 14.47). Both EC and SP recorded the step height to within 3 microm. In the repeat replication of the palatal surface of an upper central incisor SP maintained a greater constancy of surface topography (99.6%) that was statistically superior to both EC (P < 0.05) and EB (P < 0.01). The SP was therefore the preferred paint for this technique. Bearing this in mind the replication technique was both accurate and reproducible but vigilance, as to the selection of paint for the process, should be exercised so as not to affect the good accuracy and reproducibility of the technique.

Algorithms↗
PubMed2001

Selection of a Bifidobacterium strain to complement resistant starch in a synbiotic yoghurt.

AIMS: To employ an in vitro screening regime to select a probiotic Bifidobacterium strain to complement resistant starch (Hi-maizetrade mark) in a synbiotic yoghurt. METHODS AND RESULTS: Of 40 Bifidobacterium isolates examined, only B. lactis Laftitrade mark B94 possessed all of the required characteristics. This isolate hydrolysed Hi-maizetrade mark, survived well in conditions simulating passage through the gastrointestinal tract and possessed technological properties suitable for yoghurt manufacture. It grew well at temperatures up to 45 degrees C, and grew to a high cell yield in an industrial growth medium. In addition to resistant starch, the organism was able to utilize a range of prebiotics including inulin, and fructo-, galacto-, soybean- and xylo-oligosaccharides. Pulse field gel electrophoresis of restriction enzyme cut chromosomal DNA revealed that B. lactis Laftitrade mark B94 was very closely related to the B. lactis Type Strain (DSM 10140), and to the commercial strains B. lactis Bb-12 and B. lactis DS 920. However, B. lactis Laftitrade mark B94 was the only one of these isolates that could hydrolyse Hi-maizetrade mark. This phenotypic difference did not appear to be due to the presence of plasmid encoded amylase. Bifidobacterium lactis Laftitrade mark B94 survived without substantial loss of viability in synbiotic yoghurt containing Hi-maizetrade mark during storage at 4 degrees C for six weeks. CONCLUSION: Bifidobacterium lactis Laftitrade mark B94 is a promising new yoghurt culture that warrants further investigation to assess its probiotic potential. SIGNIFICANCE AND IMPACT OF THE STUDY: In vitro screening procedures can be used to integrate complementary probiotic and prebiotic ingredients for new synbiotic functional food products.

Bifidobacterium↗
PubMed2001

Conduct of an algorithm in quantifying simulated palatal surface tooth erosion.

In order to test the ability of an algorithm to quantify simulated palatal erosion, a total of 10 extracted permanent upper central incisors were mounted in brass blocks. Baseline impressions were recorded using an addition cured silicone impression material in a metal impression tray. Once set and removed from the teeth, the impressions were coated twice with a high silver content electroconductive paint, applied using a brush, before being backed up with die stone to form an electroconductive replica. Each tooth was then subject to three treatments: application of phosphoric acid etchant gel for 60 s, application of etchant gel for 120 s and immersion for 3 h in Diet Coca-Cola*. After each one the replication process was repeated. Thereafter all replicas were mapped using a computer controlled electrical probe and the resultant digital terrain models (DTMS) compared using a surface matching and difference detection algorithm (SMADDA). Surface matching was unsuccessful only in one instance. As the duration of the insult increased, so did the proportion of the surface that underwent change to a maximum of 33.3%. Anatomical site was significantly (P < 0.05) associated with the susceptibility to erosion. The cingulum periphery appeared most resistant to this. The algorithmic approach offers much scope for monitoring dental erosion as acid dissolution of the tooth's surface appears to occur gradually. The cingulum region appears relatively more resistant to this process than other tooth sites and thus facilitates the process of surface matching. Further testing is however, required to determine precisely the algorithm's upper tolerance level.

Algorithms↗
PubMed1999

Presentation of quantitative tooth wear data to clinicians.

OBJECTIVE: The purpose of this study was to ascertain the ease of interpretation and usefulness of different modes of presenting quantitative tooth wear data to clinicians. METHOD AND MATERIALS: A questionnaire that sought to ascertain both the ease of interpretation and usefulness of different modes of presentation for monitoring tooth wear was distributed to 67 clinicians. These modes (contour maps, surface topography and difference plots, and color-coded surface difference plots) were a product of ongoing development that used a mathematic algorithm to detect and quantify wear of teeth with time. A follow-up questionnaire, based on a fusion of the desirable features of surface topography and color-coded surface difference plots, was distributed to 40 of the original respondents to ascertain any improvement in clarity. RESULTS: In all respects, contour maps were rated significantly more difficult to interpret and less useful than the other techniques evaluated. No significant difference was detected between the other modalities. The follow-up questionnaire demonstrated a significantly enhanced utility of the revised plot in informing the clinician as to the worn sites and quantity of wear. CONCLUSION: The combined mode of presentation seems an excellent way of presenting wear results to clinicians for clinical application.

Computer Graphics↗
PubMed1998

DNA repair in higher plants.

Numerous studies have demonstrated a requirement in plants for repair of DNA damage arising from either intrinsic or extrinsic sources. Investigations also have revealed a capacity for repair of certain types of DNA damage, and conversely, identified mutants apparently defective in such repair. This article provides a concise overview of nuclear DNA repair mechanisms in higher plants, particularly those processes concerned with the repair of UV-induced lesions, and includes surveys of UV-sensitive mutants and genes implicated in DNA repair.

Arabidopsis↗
PubMed1998

Mathematical shape matching as a tool in tooth wear assessment--development and conduct.

The quantitative assessment of restoration and tooth wear usually requires fixed reference points from which measurements are made. In longitudinal patient follow-up the loss or erosion of such points may preclude measurement and an alternative approach is to seek regions of coincidence and conflict in digital models of before and after wear surfaces, with a continuous refinement of the parameters of the coordinate transformations, until the closest correspondence between them is found. A computer program has been written to implement the algorithm and assess the technique's capacity to find the match between surfaces both artificially generated and from tooth replicas recorded from patients at different epochs. The program was able to achieve the desired ends, demonstrating the utility of the technique in tooth wear assessment but identifying the need to refine the program further to enhance both its difference detection capabilities and level of automation. Examination of the theory and practical experience highlighted certain situations when user understanding is invaluable to ensure a satisfactory solution. This strengthened the investigators' resolve against reliance upon commercially based surface fitting programs whose basis may not be fully understood. Notwithstanding this surface matching is a powerful tool in the investigation of dental wear.

Algorithms↗
PubMed1997

Development of a novel system for assessing tooth and restoration wear.

OBJECTIVES: This investigation sought to develop a mapping apparatus for use in the assessment of both tooth and restoration wear. METHODS: A computer controlled mapping device, capable of scanning a suitably prepared electroconductive tooth replica by means of an electrical feedback mechanism, was constructed and its accuracy assessed by measuring the thicknesses of four engineers' slip gauges 12 times each. The reproducibility of three potential methods of rendering a die stone replica electroconductive was also investigated. Finally, tooth replicas were surface profiled and compared empirically with the originals using a commercial surface mapping program. RESULTS: The overall mean accuracy of the mean thicknesses of the slip gauges was 4.4 (2.8) microns. Surface deposition of either nickel spray or gold leaf, upon a ready formed replica, did not give a reproducible thickness. Precoating silicone impressions with nickel spray prior to replica production overcame this problem. On an empirical basis the instrument yielded accurate digital terrain models of tooth replicas. CONCLUSIONS: A surface mapping device has been developed which is both accurate and reproducible. A satisfactory electroconductive surface may be produced upon a tooth replica by precoating a silicone impression with nickel spray before casting the replica. The technique should prove invaluable for monitoring both tooth and restoration wear but further work is necessary to examine how such an approach will perform clinically.

Dental Impression Materials↗
PubMed1997

Conversion disorder presenting in a patient with an implantable morphine pump and an epidural abscess resulting in paraplegia.

Conversion disorders are symptoms or deficits affecting voluntary motor or sensory function that suggest a neurological or medical condition. The psychological symptoms associated with the medical condition must be preceded by conflict or other stressors. We present an individual who developed conversion disorder and paraplegia secondary to a sterile epidural abscess near the tip of her surgically implanted, epidural morphine infusion pump. She manifested at varying times both transient bilateral blindness and pseudoseizures consistent with a diagnosis of conversion disorder. Neurological evaluation for seizure activity and meningitis were negative. The etiology of the sterile epidural abscess remained unknown. The essential features of conversion disorder, according to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, are discussed. Treatment of patients diagnosed with conversion disorder remains primarily supportive, with the focus on consistency and behavioral management. Extreme caution is suggested in regards to further investigations.

Abscess↗
PubMed1997

Skeletal muscle sarcoplasmic reticulum Ca(2+)-ATPase gene expression in congestive heart failure.

Congestive heart failure leads to skeletal muscle abnormalities, one of which is a prolongation of sarcoplasmic reticulum Ca2+ flux. The purpose of this study was to determine whether skeletal muscle of spontaneous hypertensive and heart failure rats have alterations in the expression of the sarcoplasmic (or endoplasmic) reticulum Ca(2+)-ATPase (SERCA) gene. Northern analysis revealed that SERCA1, the predominant skeletal muscle isoform, was decreased by 45%, 43%, and 58% in the tibialis anterior, plantaris, and diaphragm muscles, respectively. Ribonuclease protection assay showed that the decrease was due to the adult isoform, SERCA1a, with minor changes in the alternatively spliced neonatal isoform, SERCA1b. There was no change in SERCA1 mRNA levels in gastrocnemius muscles. No change was found in SERCA2a (cardiac/slow skeletal isoform) mRNA or protein levels or in SERCA2b (smooth muscle isoform), dihydropyridine receptor, or alpha-actin mRNA levels in diaphragm muscle. Northern blot and ribonuclease protection assays showed that SERCA2a decreased 61% in the heart while the alternatively spliced isoform, SERCA2b, decreased 27%. Western analysis of the tibialis anterior, diaphragm, and gastrocnemius muscles showed a decrease in SERCA1 protein levels by 46%, 64%, and 42%, respectively, whereas sarcoplasmic reticulum Ca(2+)-ATPase activity, a functional correlate of SERCA expression, was decreased by 38%, 38%, and 40% in the same muscles, SERCA2 protein expression decreased by 36% in the failing heart. Decreases in both mRNA and protein suggest pretranslational control of SERCA1 expression, whereas the lack of decreased SERCA1 mRNA in gastrocnemius muscle suggests translational regulation. The decreased SERCA1 protein expression in all muscles studied probably contributes to contractile abnormalities related to excitation-contraction coupling function in heart failure.

Animals↗
PubMed1996

Cognitive-linguistic demands and speech breathing.

This investigation examined the influence of cognitive-linguistic processing demands on speech breathing. Twenty women were studied during performance of two speaking tasks that were designed to differ in cognitive-linguistic planning requirements. Speech breathing was monitored with respiratory magnetometers from which recordings were made of the anteroposterior diameter changes of the rib cage and abdomen. Results indicated that speech breathing was similar across speaking conditions with respect to nearly all measures of lung volume, rib cage volume, and abdomen volume. Task-related differences were found for certain fluency-related measures. Specifically, the number of syllables produced per breath group was smaller, average speaking rate was slower, and average lung volume expended per syllable was greater under a higher cognitive-linguistic demand condition than under a lower-demand condition. These differences were explained by the fact that silent pauses, particularly those associated with expiration, were more prevalent and longer in duration under the higher-demand condition. It appears that the mechanical behavior of the breathing apparatus during speaking generally is unaffected by variations in cognitive-linguistic demands of the type investigated; however, fluency-related breathing behavior appears to be highly sensitive to such demands.

Affect↗
PubMed1996

Trauma-induced neurotoxicity in rat hippocampal neurons.

BACKGROUND AND PURPOSE: We have previously shown that traumatic injury of hippocampal cells triggers release of a soluble neurotoxin that can be transferred to an uninjured culture. The mechanism of this trauma-induced neurotoxicity is independent of glutamate receptor activation. We extended this observation to study the mechanism of this neurotoxicity. METHODS: Dissociated rat hippocampal neurons were traumatized by disrupting the culture by scratching the plate. The toxicity expressed by the injured culture was studied by transferring the medium to an uninjured culture and assessing the death rate by trypan blue exclusion. RESULTS: This neurotoxin is stable in the medium at room temperature for several hours and withstands boiling. The molecular weight is between 100 and 500. The release and the effect of this toxin seem to be independent of glutamate receptor activation. The toxicity is unaffected by removal of extracellular calcium. However, dantrolene dose-dependently blocked the toxicity in the recipient culture, suggesting that the release of intracellular stores of calcium is involved in the toxic effect. This release of calcium is likely to be followed by an activation of nitric oxide synthase because competitive nitric oxide synthase inhibitors attenuated this toxicity. Consistent with this result, cholecystokinin octapeptide significantly reduced cell death when combined with this toxic medium. CONCLUSIONS: Traumatic injury of dissociated cells can propagate neurotoxicity in uninjured cells by a soluble toxin released into the extracellular space. This toxin causes a rise in cytosolic calcium that activates nitric oxide synthase that can be blocked by cholecystokinin.

Animals↗