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Biomedical subjects

R Walton

Publications and source records attributed to R Walton.

At least 37 records · Page 2Linked to original sources
PubMed1998

Coronal leakage: endotoxin penetration from mixed bacterial communities through obturated, post-prepared root canals.

Coronal leakage has been considered as one of the major causes of failure in root canal treatment. Bacteria have been shown to penetrate the root canal obturating materials and influence the periapical tissues. Endotoxin, a component of Gram-negative bacteria, is a potent inflammatory agent and may be able to penetrate obturating materials faster than bacteria. This in vitro study examined the possible penetration of post-prepared canals by endotoxin and bacterial cells derived from mixed bacterial communities. Results showed that both bacteria and endotoxin were able to penetrate the obturating materials in post-prepared canals; however, endotoxin penetration was faster than bacterial. If one speculates that a similar sequence of events occurs clinically, then such a rapid penetration of endotoxin could lead to an early periapical reaction, with subsequent treatment failure and need for retreatment or periapical surgery. The need for an immediate and proper coronal restoration after root canal treatment is therefore reinforced.

Analysis of Variance↗
PubMed1997

Intrapulpal injection: factors related to effectiveness.

UNLABELLED: The intrapulpal injection is commonly used when conventional anesthetic techniques fail during endodontic procedures. OBJECTIVES: This was a double-blind clinical study conducted to determine whether anesthetic solution was related to an effective intrapulpal injection. STUDY DESIGN: Thirty-five intrapulpal injections were given, all with back-pressure and either saline solution or anesthetic (2% lidocaine with 1:100,000 epinephrine). RESULTS: Thirty-three of the 35 injections were effective. Statistical analysis showed no significant difference between the two solutions. CONCLUSIONS: Data indicate that an effective intrapulpal injection depends on back-pressure and is independent of the solution used.

Anesthesia, Dental↗
PubMed1997

Enzymatic syntheses of GlcNAc beta 1-2Man and Gal beta 1-4GlcNAc beta 1-2Man as components of complex type sugar chains.

GlcNAc beta 1-2Man and GlcNAc beta 1-6Man were synthesized using the reverse hydrolysis activity of beta-N-acetylglucosaminidase from both jack beans and Bacillus circulans. In turn, Gal beta 1-4GlcNAc beta 1-2Man and Gal beta 1-4GlcNAc beta 1-6Man were synthesized regioselectively using the transglycosylation activity of beta-galactosidase from Diplococcus pneumoniae and B. circulans, respectively. These di- and trisaccharides are important components of complex type sugar chains and will be used as intermediates in our synthetic studies.

Acetylglucosaminidase↗
PubMed1995

Padded vs unpadded spine board for cervical spine immobilization.

OBJECTIVES: To determine whether padding the long spine board improves patient comfort, affects cervical spine (c-spine) immobilization, or increases sacral transcutaneous O2 tension. METHODS: A prospective randomized, controlled crossover study of healthy volunteers was conducted over a two-week period. Participants included 30 volunteers with no previous history of c-spine injury or disease. The subjects were randomized to either padded or unpadded long spine board immobilization with serial measurements of discomfort (using a visual analog scale) and transcutaneous tissue O2 tension obtained at zero and 30 minutes. Measurements of ability to flex, extend, rotate, and laterally bend the c-spine were made using a goniometer. The subjects then returned a minimum of three days later to complete the opposite half of the study (padded vs unpadded boards). RESULTS: Subject discomfort was significantly reduced in the padded group compared with the unpadded group (p = 0.024). There was no significant difference in flexion (p = 0.410), extension (p = 0.231), rotation (p = 0.891), or lateral bending (p = 0.230) for the two groups. There was no significant difference in the actual drop in sacral transcutaneous O2 tension from time zero to 30 minutes for the padded and the unpadded groups (mean drop = 14.8% +/- 17.5% vs 12.2% +/- 16.8%, respectively; p = 0.906). CONCLUSION: Adding closed-cell foam padding to a long spine board significantly improves comfort without compromising c-spine immobilization. Sacral tissue oxygenation does not appear affected by such padding for healthy volunteers.

Adult↗
PubMed1995

Comparison of peak oxygen consumption during cycle and treadmill exercise in severe chronic obstructive pulmonary disease.

BACKGROUND: In normal subjects treadmill exercise usually produces the greatest maximal oxygen consumption (VO2max). This may not be true for patients with severe chronic obstructive pulmonary disease (COPD) in whom bicycle exercise, which offers support for the shoulder girdle, may produce a higher oxygen consumption than treadmill exercise. The aim of this study was to determine which mode of exercise produced the greatest oxygen consumption in patients with severe COPD. METHODS: Eight patients with severe COPD (forced expiratory volume in one second (FEV1) more than three standardised residuals below predicted) exercised to a symptom limited maximum on a bicycle and on a treadmill on separate days. The workload on the bicycle wa increased by 10 watts each minute, and the treadmill gradient was increased by 2.5% alternate minutes whilst the speed remained constant. Measurements of oxygen consumption (VO2), ventilation (VE), heart rate, and oxygen saturation were made, and capillary blood gases were measured before and immediately after exercise. Lactate concentration was measured before and four minutes after exercise. RESULTS: There were no differences at peak exercise between the two forms of exercise for VO2 (median 11.7 and 12.2 ml/min/kg for bicycle and treadmill, respectively), for VE (median 26.6 and 25.0 l/min, respectively), and for heart rate (median 119 and 115 beats/min, respectively). The median lactate levels after bicycle exercise were higher than those after the treadmill (2.42 v 0.94 mmol/l). CONCLUSIONS: Although only a small number of patients was studied and individual variability was large, there was no clear difference between the two forms of exercise. Regular bicycle exercise was unfamiliar to this group of patients and generated the greatest lactate response. The results do not support the hypothesis that bicycle exercise will produce a better performance in patients with severe COPD, but the two modes of exercise cannot be used interchangeably.

Aged↗
PubMed1995

Knowledge engineering for drug prescribing guidelines.

Prescribing drugs for the treatment of medical conditions is a very common activity for a doctor. Prescribing has enormous economic importance. Costs are rising quickly and there is an urgent need for doctors to have easy assess to advice about the cheapest, most effective therapy. On average 80% of GPs in the UK use a computer for their medical work and the figure is rising rapidly. Currently available systems provide only very simple checks and reminders. More sophisticated advice is provided by our prototype program. The program uses logic engineering to give advice, based on simple protocols for prescribing, tailored both to the condition being treated and the individual patient. The essential logical elements of the prescribing decision are discussed. These simple prescribing protocols may be the final common pathway for prescribing advice from many, more complex protocols for recommendations for drug treatment.

Cost Control↗
PubMed1994

MR imaging of benign fatty tumors in children: report of four cases and review of the literature.

This study correlates the magnetic resonance imaging characteristics with the pathologic findings in rare benign fatty soft tissue tumors in four children. A review of the literature is presented. Two cases of infiltrating lipoma displayed bright signal on both T1- and T2-weighted images, similar to that observed in subcutaneous fat. Histological study revealed extensive muscle infiltration by mature fat, with some areas of total fatty replacement. The case of facial lipomatosis revealed an extensive process of fatty invasion of adjacent soft tissue and osseous deformity by mass effect of the tumor. This lesion was bright on T1- and T2-weighted images. Histopathologic examination showed widespread invasion of squamous mucosa and skeletal muscle. The single case of lipoblastoma involved the presacral region and right buttock. This lesion, although bright on both T1 and T2 weighting, was relatively hypointense to subcutaneous fat on T1. Microscopic examination revealed a well-encapsulated fatty mass made up of cells ranging from lipoblasts to mature lipocytes. In childhood, when fatty lesions are almost always benign, a morphologic characterization by magnetic resonance may be sufficient basis on which to make critical therapeutic judgements.

Adolescent↗
PubMed1994

Effectiveness of apical clearing: histological and radiographical evaluation.

Preparation of the apical one-third in curved canals is difficult both in debridement and maintaining canal shape. A technique of final apical preparation, "apical clearing," attempted to debride and increase the apical size without transportation. Apical clearing is defined as: following cleaning and shaping, sequentially rotating files two to four sizes larger than the initial (master) apical file at working length, then rotating the largest apical file again after a final irrigation and drying. This study evaluated histologically and radiographically the quality of apical preparation with or without apical clearing. Examined were (a) extent of transportation and (b) debris accumulation in the apical third. Fifty-four extracted teeth with vital pulps and curved canals were divided into two groups. After step-back preparation, 29 had apical clearing and 25 did not. Pre- and postpreparation double-exposed radiographs evaluated canal deviation. The apical one-third of the canals was examined histologically and ranked, based on remaining tissue, predentin, dentin shavings, other debris, and canal walls planed. Radiographically, the apically cleared group showed slight deviation of the canal during preparation. Histologically, canals in the apically cleared group had significantly less remaining tissue, predentin and debris, as well as more canal walls planed. This experiment showed that apically the apical clearing technique resulted in better debridement, with minimal increase in apical transportation.

Chi-Square Distribution↗
PubMed1993

Further evidence for the importance of free carboxylate in epoxysuccinate inhibitors of thiol proteases.

Analogs of Ep-475 (2a), designed to explore the role played by the carboxylate in epoxysuccinate thiol protease inhibitors, have been synthesized and tested as inhibitors of papain and cathepsin B. Papain and cathepsin B are rapidly inactivated by carboxylates 2a and 6a, but are inactivated much more slowly by 2b-2f, 6c, and 6f, in which the carboxylate is absent or replaced by an amide, ester, or ketone. This order of reactivity contrasts with the inherent reactivity of substituted epoxides toward a non-enzymatic thiolate, previously shown to decrease in the order: COCH3 > CO2CH3 > CONH2 > H > CO2H. The results suggest that electrostatic attraction between the carboxylate of the inhibitor and protonated His159 of papain facilitates docking of the inhibitor in the active site of the enzyme, a conclusion reached previously from X-ray crystallographic structures of epoxysuccinates bound to papain. The most reactive isoleucine analog, 6a, was significantly less reactive than leucine-containing Ep-475 (2a), while the less reactive isoleucine derivatives, 6c and 6f, were similar in reactivity to the corresponding leucine derivatives, 2c and 2f, respectively.

Carboxylic Acids↗
PubMed1993

[MNSs system mother-newborn segregation distortions].

We present segregation distortions for the MNSs system and for the sex ratio found among 400 mother-newborn pairs, from the northern Area of Santiago and the middle-low and low socioeconomic strata. Three subsamples were taken: from the non private patients of the Clinical Hospital of the University of Chile; from the Hospital San José, a public hospital of this Area; controls of malformed newborns belonging to an international study from the Clinical Hospital of the University of Chile. In spite of the almost homogeneity of socioeconomic strata and area, the differences among these subsamples did not allow us to take them as only one sample. We found excess of heterozygous individuals for the MN locus, specially among mothers. Ss heterozygotes had a higher sex ratio than ss homozygotes. Several distortions could not be dealt with as having a regular pattern in the three subsamples. A possible technical error is discussed.

Chile↗
PubMed1992

Endodontic interappointment flare-ups: a prospective study of incidence and related factors.

Severe pain and/or swelling following a root canal treatment appointment are serious sequelae. Information varies or is incomplete as to the incidence of these conditions and related factors. In this study, data were collected at root canal treatment appointments on demographics, pulp/periapical diagnoses, presenting symptoms, treatment procedures, and number of appointments. Patients that then experienced a flare-up (a severe problem requiring an unscheduled visit and treatment) had the correlating factors examined. Statistical determinations were by chi-square analysis with significance at 0.05 or less. Nine hundred forty-six visits resulted in an incidence of 3.17% flare-ups. Flare-ups were positively correlated with more severe presenting symptoms, pulp necrosis with painful apical pathosis, and patients on analgesics. Fewer flare-ups occurred in undergraduate patients and following obturation procedures. There was no correlation between patient demographics or systemic conditions, number of appointments, treatment procedures, or taking antibiotics.

Acute Disease↗
PubMed1992

Epidemiology of canine leishmaniasis: prevalence, incidence and basic reproduction number calculated from a cross-sectional serological survey on the island of Gozo, Malta.

Assessment of the resilience of canine leishmaniasis to control or, more ambitiously, the effort needed to eradicate infection, requires an estimate of the basic case reproduction number (R0). This paper applies the theoretical results of Hasibeder, Dye & Carpenter (1992) to data from a cross-sectional survey on the Maltese island of Gozo in which dogs of known age, sex and occupation (pet, guard etc) were subjected to three different serological tests for the presence of specific antibody (IFAT, DAT and ELISA). Difficulties in interpreting these test results, and hence of determining the proportion of dogs infected, present the main obstacle to estimating R0: estimates are critically dependent on the choice of threshold separating seropositives from seronegatives. The data do, however, allow a robust comparative analysis of risk which shows that the force of infection experienced by working dogs is about three times higher than that of pet dogs, a degree of non-homogeneous contact which actually has little effect on estimates of R0. We suggest a cautious point estimate of R0 congruent to 11, and comment briefly on its significance for leishmaniasis control.

Age Factors↗