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Biomedical subjects

C J Thomas

Publications and source records attributed to C J Thomas.

At least 19 recordsLinked to original sources
PubMed1992

A combined PCR and selective enrichment method for rapid detection of Listeria monocytogenes.

Development of a routine detection assay for Listeria monocytogenes in foods that uses the polymerase chain reaction (PCR) and enrichment cultures was investigated. Oligonucleotide primers were chosen to amplify a 3' region of L. monocytogenes hlyA gene spanning a conserved HindIII site. PCR detection sensitivity for L. monocytogenes in dilutions of pure enrichment cultures was between 50 and 500 colony forming units. A short enrichment period before PCR amplification allowed detection of the organisms in a range of complex foods contaminated with 10(4) cfu/g. Detection sensitivity for the assay in the presence of chicken skin and soft cheese was determined at 10-100 cfu/g. Utilization of enrichment cultures and PCR allowed identification of the organism within 24 h or 2 days.

Bacteriological Techniques↗
PubMed1992

Complete mandibular denture stability when posterior teeth are placed over a basal tissue incline.

Six patients with previous denture experience were provided with new dentures. Metal indicators were placed on either side of the mandibular denture and a cobalt-chromium alloy marker was inserted in the left bucco-posterior area of the mandible in each case. In the new dentures posterior teeth were positioned up to the retro-molar pad, over the basal tissue slope of the posterior mandibular alveolar ridge. After habituation had taken place, a cineradiographic recording was made of chewing. Prior to the second recording the mandibular teeth were removed to a point where the remaining teeth were not over inclined residual alveolar ridges. Denture movement was observed by measuring the distances between the markers on an analytical projector. The results show a significant difference between the cranial values of the two chewing experiences. Values for all denture movements were less after removal of the teeth over an incline. These results support the clinical observation that teeth placed over a basal tissue incline have a destabilizing effect during complete mandibular denture function.

Adult↗
PubMed1992

Detection of Aeromonas salmonicida from fish by using polymerase chain reaction amplification of the virulence surface array protein gene.

A DNA-based assay was developed to detect Aeromonas salmonicida from infected fish by analyzing tissues, feces, and the tank water in which the infected fish were held. This analysis was done both by direct detection from samples and after a bacterial outgrowth step. Polymerase chain reaction (PCR) amplification of a 421-bp sequence from the 3' region of the surface array protein gene (vapA) of A. salmonicida provided a specific and sensitive method for the detection and identification of this important fish pathogen. The sensitivity of PCR detection of A. salmonicida directly from tissues was less than 10 CFU/mg. Furthermore, a detection level of 5 fg, equivalent to approximately 1 cell, was obtained by using purified chromosomal DNA as the template. This highly reproducible assay, which requires 45 min to complete, is therefore sensitive enough to be used as a noninvasive method for monitoring fish populations for the presence of carrier fish. Because the surface protein array (A-layer) is a virulence factor of A. salmonicida, PCR analysis with oligonucleotide primers directed at vapA can also be used to provide information on the potential virulence of a strain.

Aeromonas↗
PubMed1991

Tomato aspermy virus has an evolutionary relationship with other tripartite RNA plant viruses.

The entire RNA 3 (2214 nucleotides) of a chrysanthemum isolate of tomato aspermy virus (C-TAV) has been cloned and its sequence determined. C-TAV possesses two open reading frames which encode a 3a protein (277 amino acids) and a coat protein (229 amino acids). Computer-assisted comparisons were made between C-TAV RNA 3 and its predicted protein sequences and those of two other tripartite RNA viruses, cucumber mosaic virus (CMV) and brome mosaic virus (BMV). Results from this study suggest that a close evolutionary relationship exists between C-TAV, Q-CMV and BMV. Divergence of nucleotide and amino acid sequences between these viruses is not reflected at the level of the predicted secondary structure of the encoded proteins, where conservation is strong.

Amino Acid Sequence↗
PubMed1991

The influence of exercise-induced temperature elevations on the auditory brain-stem response (ABR).

The influence of exercise on the auditory brain-stem response (ABR) was examined in 16 healthy volunteers (8 female and 8 male). Ipsilateral ABR recordings were obtained before and after exercise on a bicycle ergonometer. The rise of body temperature so generated was 0.5-2.1 degrees C (mean, 1.3 degrees C) as measured in the contralateral external auditory meatus. Latencies of waves III and V (but not wave I) were found to be significantly lower immediately post-exercise (P less than 0.01). The temperature relations of the latency of wave V are described by the regression equation: Latency (ms) = 11.06-0.146 x temp. (degrees C). (The effects on amplitude were not significant, nor were male/female differences.) It is suggested that exercise hyperthermia could be an appropriate model for the evaluation of the ABR in fever.

Adult↗
PubMed1991

The early development of palatal rugae in the rat.

The palatal rugae in rats are contained in two of three zones of morpho-differentiation and develop around the time of palatal closure. Previous studies in humans and pigs have been based on crown-rump lengths but now controlled breeding in rats has allowed exact timing to be established. Twenty-nine female DB IX rats were fertilized and sacrificed in a controlled procedure and foetuses processed for light microscopy and SEM. Serial sagittal sections were made and stained with haematoxylin and eosin and Verhoef's stains. At day 13 the palate was open and no rugae were visible. At day 14 the palatal shelves had started to migrate medially and the ante-molar rugae appeared. At day 15 the palatal shelves were touching and the inter-molar rugae became visible, and at day 16 fusion was all but complete and the definitive rugal pattern established. The development and differentiation is more advanced than in humans and it is concluded that the rugae probably have a role to play in the oral function of animals whereas in humans they are becoming attenuated and the development timetable is retarded because of redundancy.

Animals↗
PubMed1990

A new fimbrial type (PCFO9) on enterotoxigenic Escherichia coli 09:H- LT+ isolated from a case of infant diarrhea in central Australia.

The genes determining the biosynthesis of a new putative colonization factor, designated PCF09 have been cloned from an LT+ enterotoxigenic Escherichia coli 09:H- isolated during an outbreak of infant diarrhea in Central Australia. Electron microscopy has shown it to be of the fibrillar type. Purification of the major pilin subunit showed it to have a size of approximately 27 kDa. NH2-terminal analysis of the major subunit has shown the PCFO9 determinant to be distinct from other fimbriae although there is some conservation of certain residues. A synthetic oligodeoxynucleotide probe based on the NH2-terminal amino acid sequence of the purified protein has been used in Southern hybridization analyses to define the region on pPM1320 encoding the structural gene for the major pilin subunit.

Amino Acid Sequence↗
PubMed1990

Impression material consistency and peripheral tissues.

The behaviour of three alginate impression materials was tested in vivo by sectioning the peripheries of a series of impressions in a standard manner and measuring the extension in three directions: buccal, lingual and into the depth of the sulcus. The three materials used reacted in accordance with their various consistencies. There were statistically significant differences between all the materials in the inferior measurement, but very few differences in the buccal dimension. Lingually however, one extended significantly further than the other two. It is concluded that the facial tissues, probably muscles, play a restraining role in buccal impression material extension but that the inferior and lingual extensions are more susceptible to the consistency of the material rather than the tissues. This should be carefully considered before selecting a suitable material for impressions.

Adult↗
PubMed1990

Role of the P plasmid in attenuation of Vibrio cholerae O1.

The conjugative plasmid P of Vibrio cholerae has been shown to have a suppressive effect on the virulence of hypertoxigenic strains like 569B. In this study, we have sought to analyze this phenomenon. Utilizing the infant mouse cholera model, we have demonstrated that the presence of P increases the 50% lethal dose of V. cholerae classical Inaba 569B by more than 300-fold. No effect of P on cholera toxin (CT) production, whether measured by GM1 enzyme-linked immunosorbent assay, by CT activity in ligated rabbit ileal loops, or by transcription from the CT promoter, could be discerned. Colonization of the intestine by P+ derivatives was dramatically reduced although only a minor effect could also be demonstrated on in vitro attachment to intestinal strips. Electron microscopic examination suggested that the P plasmid was affecting the production of the TCP pilus. Another conjugative plasmid, V, has also been examined, but it had no effect on virulence.

Animals↗
PubMed1990

Clinical study of the modified Equipoise clasp.

The modified Equipoise clasp has been developed to overcome the negative aesthetics of anterior clasping. Fifteen patients involving twenty-two Equipoise clasps were followed up for retention, aesthetics and oral health. Examiners found that 36.4% of the clasps gave poor retention, 18.1% were reasonable and 45.5% were good. Aesthetics were 23.6% poor, 36.4% reasonable and 50% good. Oral health was 9.1% poor, 50% reasonable and 40.9% good. The patients reported that retention was 13.3% reasonable and 86.7% good. Twenty percent of the patients felt aesthetics were reasonable and 80% felt it was good. The clasps were reasonably comfortable in 13.3% and most comfortable in 86.7%. The Equipoise clasp can be used with success for, among others, the Kennedy Class IV case if the correct clinical and laboratory procedures are followed. However, it is unsuitable in, for example, a Class I dentition where posterior stability is poor. Its lingual window can adversely affect oral hygiene and careful patient selection is necessary.

Consumer Behavior↗
PubMed1979

Spoilage association of chicken skin.

The bacterial succession on the skin of broiler chicken carcasses stored at 2 degrees C was traced, and the ability of representative isolates to produce off-odors was determined by using sterile leg and breast muscle sections. Off-odors were identified by olfactory and chemical means. The inability of peptone-iron agar to detect sulfide-producing strains was noted.

Animals↗
PubMed1979

The use of screening investigations in psychiatry.

This is a study of the results of screening tests on all new psychiatric in-patients over a period of one year. Although none of the results indicated definite physical causes for the psychiatric illness, 10 per cent of the tests revealed abnormalities resulting from or co-incidental with the psychiatric illness. Of these abnormal results 61 per cent led to no further investigation or treatment, and the significance of this is discussed.

Aged↗
PubMed1979

Continuing medical education: linking the community hospital and the medical school.

Community hospitals and medical schools have different but complementary resources to carry out continuing medical education. To strengthen the educational capabilities of both, a group of community hospitals has been linked to a medical school in a continuing medical education network. A peripatetic educational development team based at the medical school completes the link by helping community hospital physicians identify educational needs and develop educational responses, using both local and medical school experts as faculty. The educational development team provides skills and staffing which no small or moderate-sized community hospital could afford alone. The program is financially feasible for community hospitals and the medical school, does not consume the resources of either, and conserves the time of the community physician and medical school faculty.

California↗