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Biomedical subjects

R J Gilbert

Publications and source records attributed to R J Gilbert.

At least 19 recordsLinked to original sources
PubMed1992

Application of pyrolysis mass spectrometry to the investigation of outbreaks of food poisoning and non-gastrointestinal infection associated with Bacillus species and Clostridium perfringens.

Eighteen isolates of Bacillus species and 15 of Clostridium perfringens, all of which had been associated with outbreaks of either food poisoning or non-gastrointestinal infection (NGI), were examined for relatedness by pyrolysis mass spectrometry (PyMS). The PyMS-analysis correctly clustered all the groups of epidemiologically related isolates of both genera, and distinguished all the single, epidemiologically unrelated isolates of the same species. PyMS is a simple, rapid and inexpensive technique which can provide useful and accurate inter-strain comparisons within both the Bacillus and Clostridium genera in complete accord with conventional serological typing results.

Bacillaceae Infections↗
PubMed1992

Protein structure prediction from predicted residue properties utilizing a digital encoding algorithm.

Although many disparate methods have been applied to the problem, the accuracy of protein structural prediction still remains disappointingly low, averaging about 65% correct secondary structure assignment. A novel predictive method is presented here, which attempts to address some of the shortfalls inherent in representing a protein as a simple text-like sequence of amino acids, by deriving pattern-matching data from the predicted physical properties of a protein chain rather than from the sequence itself. A unique binary encoding algorithm is used to enable the property profiles to be correlated with known secondary structure, and hence to predict secondary structures for proteins with unknown structures. By treating the sequence in this manner, predictive accuracies averaging over 75% have been achieved.

Algorithms↗
PubMed1992

Two-dimensional coupling by gap junctions in cultured gastric smooth muscle monolayers.

We studied intercellular transfer in cultured rabbit gastric smooth muscle cell monolayers after microinjection of electrotonic current or the fluorescent probe Lucifer yellow CH. Because cultured gastric muscle cells proliferate in vitro and form regular arrays of parallel spindle-shaped cells, we sought to assess the role of cell shape and orientation in determining two-dimensional coupling properties. With the use of electron microscopy, gap junctions were identified between adjacent cells. Northern blot analyses using specific cDNA probes demonstrated expression of mRNA for the gap junction protein connexin43. Dye injection of Lucifer yellow resulted in 97% transfer to at least one adjacent cell, and 88% of adjacent cells received dye. Electrophysiological studies were performed using two intracellular microelectrodes to measure electrotonic current flow between cells at varying interelectrode distances. Current flow in the monolayers was modeled using a modified two-dimensional analysis. Initial assessment showed that the ratio of calculated space constants (longitudinal axis/perpendicular axis) was 4.4, indicating anisotropic conditions. However, when a geometric transform was used to normalize the spindle-shaped cells to regular hexagons, the space constants became statistically equivalent (200 microns longitudinal, 256 microns perpendicular). These results suggest that anisotropy of current flow in the monolayer of gastric smooth muscle cells was due primarily to the shape of the cells and not to intrinsic membrane properties or the distribution of gap junctions.

Animals↗
PubMed1992

The effect of study design on in situ treatment of carious enamel lesions.

The aim of this exploratory study was to investigate the influence of several factors on changes in the mineral content of carious enamel lesions treated in situ. The study involved 36 adult volunteers who used either a non-fluoride toothpaste or one of two fluoride toothpastes (1000 or 1500 ppm F). Human enamel specimens were prepared and attached to partial dentures as described previously (Schäfer, 1989) and treated in situ for between three and six weeks. The mineral content of lesions was determined by microradiography and computerized densitometry. The factors investigated in this study included study length, frequency of treatment, trial design, patient compliance, patient diet, and previous caries experience of the patient. The effects observed were small, relative to that of the treatment, and not statistically significant (p greater than 0.05). However, the trends in the data were all as would be intuitively predicted. Study duration correlated positively with observed lesion mineral content. Lesions worn by panelists using a fluoride toothpaste for six weeks contained greater levels of mineral with respect to placebo than did those in panelists on a three-week study. The residual variations in the three phases of the study were found to be similar, suggesting that there is no advantage in these studies having a cross-over design. Brushing frequency also correlated positively with observed lesion mineral content, with panelists brushing three times per day with a fluoridated dentifrice having lesions with greater levels of mineral, with respect to placebo, than those brushing twice per day. Overall, no clear relationship between reported diet and changes in lesion mineral levels was apparent.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Oral fluoride measurements for estimation of the anti-caries efficacy of fluoride treatments.

The aims of this work were (a) to assess the oral bioavailability of fluoride delivered from dentifrices and (b) to test for a possible link between the results and clinical data obtained with the same dentifrices. Oral fluoride concentrations were measured in samples of saliva and plaque taken from seven subjects, after use of dentifrices which contained 0, 1000, 1500, and 2500 micrograms F/g as sodium monofluorophosphate. Salivary fluoride in samples obtained within the first few hours after a single dentifrice application, or up to 20 h after four weeks' daily use, increased with increasing F content of the dentifrice. For example, the mean zero-time intercepts of the second phase of salivary fluoride clearance curves for the above dentifrices were 0.46, 1.48, 1.88, and 3.03 mumol F/L, respectively. Plaque fluoride measured after four weeks' daily use of the dentifrices exhibited similar dose-response behavior. Linear regression analysis showed these trends to be statistically significant for both saliva (p less than 0.001) and plaque (p less than 0.025). Mean saliva and plaque fluoride concentrations were inversely associated with mean three-year caries increments for the three fluoride-containing dentifrices obtained in a recent clinical trial: DMFS scores 6.80, 6.33, and 5.71, respectively (Stephen et al., 1988). This suggests that oral fluoride measurements are a valuable in vivo method for the evaluation of the potential anti-caries efficacy of fluoride-containing dental products.

Adult↗
PubMed1992

Intra-oral models to assess cariogenicity: evaluation of oral fluoride and pH.

The main purpose of this paper is to review the various methods used for evaluation of fluoride retention in saliva, plaque, and enamel following application of topical anti-caries treatments such as F dentifrices and F mouthwashes. Such methods monitor delivery of fluoride to the site of action, the mouth, and so can be regarded as assessing potential for treatment action. It is concluded that intra-oral fluoride measurements are appropriate to support bioequivalence claims for anti-caries treatments, provided that particular chosen methods have been calibrated against clinical data. Studies purporting to show superiority are of interest mechanistically, but links to caries are not sufficiently understood to define superiority claims. A wide variety of methods has been used for determination of the fluoride content of enamel. Of these, well-established methods such as the micro-drill and acid-etch procedures are appropriate for routine comparative testing, whereas sophisticated instrumental techniques such as SIMS are more appropriate for detailed mechanistic studies. Intra-oral pH measurements are also relevant to many topical treatments. Single-site determinations in plaque are preferred, but for comparative studies non-specific determinations may be adequate.

Dental Caries↗
PubMed1991

Human listeriosis and paté: a possible association.

OBJECTIVES: To study trends in human listeriosis and determine possible sources of infection. DESIGN: Descriptive analysis of laboratory reports of human listeriosis together with a survey of subtypes of Listeria monocytogenes isolated from patients and foodstuffs and an interview survey of patients to obtain food histories. SETTING: United Kingdom and Republic of Ireland 1985 to 1990. RESULTS: There was a near doubling in the incidence of human listeriosis in England, Wales, and Northern Ireland between 1985 and mid-1989 followed by a sharp decline. The upsurge in cases was caused largely by two strains of L monocytogenes, which accounted for 30-54% of the annual totals. These strains were less common before 1987 and after July 1989. A survey of paté in England and Wales in July 1989 showed that it frequently contained L monocytogenes. A similar survey in July 1990 showed a reduction in the proportions of samples contaminated. In 1989 patés from a single plant (manufacturer Y) were more likely to be contaminated by L monocytogenes and at higher levels than those from other producers. Most strains of L monocytogenes recovered from manufacturer Y's paté in 1989 were indistinguishable from those responsible for the 1987-9 upsurge in human listeriosis and were uncommon among isolates from patés from other manufacturers and from a wide range of other foodstuffs. Patients infected with the types of L monocytogenes found in paté were significantly more likely to have recently eaten paté than those affected by other strains. The start of the decline in numbers of cases of listeriosis coincided with government health warnings on paté consumption and the suspension of supplies from manufacturer Y. CONCLUSIONS: Contamination of paté was a likely contributory cause of the increase in the incidence of listeriosis between 1987 and 1989.

England↗
PubMed1991

Anticalculus effect of a dentifrice containing 0.5% zinc citrate trihydrate.

A doubleblind 3-month anticalculus clinical study was conducted to determine the magnitude of the antitartar effect to be derived from use of a 0.5% zinc citrate dentifrice. From a population of 1600 subjects exhibiting calculus, 1210 subjects (age 18 and over) were selected and received a dental prophylaxis. The subjects were initially stratified on the basis of calculus score, age, and sex, then allocated randomly to a 3-month usage period of one of two treatment groups. These were a dentifrice containing 0.5% zinc citrate or a control dentifrice without zinc citrate. Calculus was assessed using the Volpe-Manhold Index. Oral soft tissue status was assessed throughout the course of the study. At the conclusion of the study 964 subjects had completed the trial: 486 using the zinc citrate dentifrice and 478 using the control. The results showed that the mean calculus scores in the group using the dentifrice containing zinc citrate were 13.7% lower than those of the group using the control dentifrice. This finding was statistically significant (P less than 0.05). No adverse effects related to the use of either dentifrice were observed.

Adult↗
PubMed1991

ATP-dependent control of steady-state cytosolic calcium in cultured gastric smooth muscle.

The regulation of intracellular calcium uptake and release in cultured gastric smooth muscle cells was studied in saponin-permeabilized cells derived from the rabbit antrum. Cells were studied in an ATP-regenerating medium in which the value of the ATP-to-ADP ratio was fixed by variation of the relative concentrations of creatine and creatine phosphate in the presence of a constant concentration of adenine nucleotides and creatine kinase. Free calcium in the medium was measured through the use of the fluorescent probe fura-2. As the ratio of ATP/ADP was increased (8.5, 55.0, and 155.0), the rate of calcium sequestration was increased, resulting in a decrease of steady-state free calcium (275.2, 178.4, and 98.1 nM, respectively). The addition of glucose (5 mM) and hexokinase (15 U/ml), which results in an increase of ADP due to the phosphorylation of glucose in the medium, caused an increase of free calcium concentration to a new set point of approximately 400 nM. Mitochondrial blockade with antimycin A before permeabilization had no effect on calcium sequestration or the resultant free calcium concentration, indicating that under physiological conditions calcium is sequestered predominantly into nonmitochondrial storage sites. Specific variation of ATP/ADP had no effect on the concentration dependence of inositol trisphosphate-induced calcium efflux, suggesting the functional independence of intracellular calcium influx and efflux pathways. These results indicate a significant role for cytoplasmic ATP/ADP in the control of intracellular calcium sequestration and the regulation of steady-state calcium concentration in cultured gastrointestinal smooth muscle cells.

Adenosine Diphosphate↗
PubMed1991

Comparison between evaluation methods for the anti-caries efficacy of monofluorophosphate-containing dentifrices.

A comparison is described of three methods of preclinical assessment of potential anti-caries efficacy for topical fluoride treatments. Methods are compared using dentifrices containing 1,000, 1,500 and 2,500 ppm F as sodium monofluorophosphate (SMFP). These formulations have been shown elsewhere to give a statistically significant dose response of increasing anti-caries efficacy [Stephen et al., 1988]. An in situ enamel insert model, oral fluoride pharmacokinetics and F uptake to demineralised enamel are all shown to correlate with clinical efficacy for the test dentifrices studied.

Adult↗
PubMed1990

An outbreak of foodborne botulism associated with contaminated hazelnut yoghurt.

The largest recorded outbreak of foodborne botulism in the United Kingdom occurred in June 1989. A total of 27 patients was affected; one patient died. Twenty-five of the patients had eaten one brand of hazelnut yoghurt in the week before the onset of symptoms. This yoghurt contained hazelnut conserve sweetened with aspartame rather than sugar. Clostridium botulinum type B toxin was detected in a blown can of hazelnut conserve, opened and unopened cartons of hazelnut yoghurt, and one faecal specimen. Cl. botulinum type B was subsequently cultured from both opened and unopened cartons of the hazelnut yoghurt and from one faecal specimen. Investigations indicated that the processing of the conserve was inadequate to destroy Cl. botulinum spores. Control measures included the cessation of all yoghurt production by the implicated producer, the withdrawal of the firm's yoghurts from sale, the recall of cans of the hazelnut conserve, and advice to the general public to avoid the consumption of all hazelnut yoghurts.

Adolescent↗
PubMed1990

Red kidney bean poisoning in the UK: an analysis of 50 suspected incidents between 1976 and 1989.

Between July 1976 and February 1989, 50 incidents of suspected red kidney bean poisoning were reported in the UK. Nine incidents in which nausea, vomiting and diarrhoea developed within 1-7 h of ingestion, were confirmed by the detection of haemagglutinin in the beans. The diagnosis was made on a further 23 incidents on the basis of symptoms, incubation time and the description of preparation of beans prior to consumption. The haemagglutinin (lectin), which occurs naturally in the red kidney bean, is inactivated by thorough cooking of well soaked beans. In many of the outbreaks reported the implicated beans were consumed raw or following an inadequate heat process.

Cooking↗
PubMed1990

Synthetic DNA probes for detection of enterotoxigenic Clostridium perfringens strains isolated from outbreaks of food poisoning.

Four synthetic oligonucleotides encoding different parts of the Clostridium perfringens enterotoxin gene were used to test the enterotoxigenicity of C. perfringens strains isolated from confirmed outbreaks of food poisoning. Of the 245 strains isolated from food and feces originating from 186 separate outbreaks, 145 (59%) gave hybridization reactions with each of the four DNA probes used, while 104 strains did not hybridize with any of the probes. There was no correlation between serotype and the presence of the enterotoxin gene, although the C. perfringens enterotoxin gene was rarely detected among nontypable strains (17%). Results show that DNA hybridization is a suitable method for the identification of C. perfringens strains which have the potential to produce enterotoxin.

Base Sequence↗