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Biomedical subjects

J E Thomas

Publications and source records attributed to J E Thomas.

At least 91 records · Page 5Linked to original sources
PubMed1993

What to look for after you say 'open wide'. A guide to examination of the oral cavity.

Abnormal conditions of the oral cavity can have a significant impact on overall health, yet during many ostensibly complete physical examinations, the area is given only a perfunctory glance. Drs Thomas and Bender present guidelines for systematic, comprehensive evaluation of the oral cavity and provide case reports and figures to illustrate typical important findings.

Aged↗
PubMed1993

New non-invasive test of gastric acid secretion for use in children.

Loss of the gastric acid barrier may lead to recurrent enteric infections, small intestinal bacterial overgrowth, persistent diarrhoea, and thus malnutrition. To investigate this possibility, a new, non-invasive test of gastric acid secretion was developed ideal for field use in the developing world, where chronic diarrhoea and undernutrition are common. The test relies on the capacity of the kidney to retain H+ during gastric acid secretion, leading to a post-prandial urine 'alkaline tide'. Gastric intubation studies of seven healthy adult volunteers showed a direct relation between changes in gastric acid secretion and changes in urine acid output (measured as the H+/creatinine molar ratio in spot urine samples). Subjects who secreted gastric acid in response to stimulation with a sham feed showed a fall in urine acid output > 0.5 mmol H+/mmol creatinine (range -7.4 to -1.52 mean -1.12). The most reproducible decrease in urine acid output in response to normal food was observed around the time breakfast was usually eaten and was abolished by 36 hours of treatment with ranitidine. Breakfast time reductions in postprandial urine acid output in 22 healthy English children were comparable with those in healthy adults, and significantly different from values in achlorhydric adults. They were much more variable, however, in 106 Gambian children in whom values spanned both normochlorhydric and achlorhydric ranges (-12.7 to +1.8). Measuring changes in urine acid output at breakfast time provides a reliable indirect measure of gastric acid secretion that can be used in field conditions, enabling the relation between gastric acid output and the development of diarrhoeal diseases to be investigated.

Adult↗
PubMed1993

Tuberculosis: a growing concern for dentistry?

Dentists are increasingly treating patients who have significant medically compromising conditions, a number of which predispose individuals to tuberculosis. Three case reports describe patients with histories of tuberculosis exposure. The authors also discuss risk assessment and offer practical guidelines for dental management of these patients.

Aged↗
PubMed1993

Induction of tumor formation and cell transformation by polyoma middle T antigen in the absence of Src.

In polyomavirus-transformed cells, middle T antigen binds to and activates the protein tyrosine kinase, Src. To determine whether this interaction is critical for middle T transformation, we examined the ability of middle T to transform cells that lack endogenous Src (because of a targeted disruption of both Src alleles). Infection of newborn or 2-week-old Src-negative mice with a retrovirus encoding middle T led to the induction of visceral hemangiomas that were indistinguishable from tumors in wild-type mice with respect to their morphology, frequency or latency period. In addition, middle T was able to induce foci formation on cell monolayers and colony formation in soft agar in Src-negative immortalized fibroblasts. These results indicated that Src is not essential for middle T-induced transformation of the cells targeted in these assays. To examine the protein tyrosine kinases that interact with middle T in the absence of Src, we compared the level of middle T phosphorylation in immune complex kinase assays from Src-negative and Src-positive cell lysates, and identified the middle T-associated kinases in these cells. In Src-positive cell lysates, there was a similar level of middle T phosphorylation in Src and Yes immunoprecipitates, suggesting that middle T can bind to Src and Yes to a similar extent in this cell type. Fyn immunoprecipitates displayed fourfold lower levels of middle T phosphorylation than that detected in the Src and Yes immunoprecipitates. In Src-negative cells, the level of middle T phosphorylation in Yes and Fyn immunoprecipitates was not significantly different from that detected in the Src-positive cells, suggesting that the absence of Src does not lead to a compensating increase in the proportion of middle T associated with these kinases. The level of middle T-associated phosphatidylinositol 3'-kinase was also examined since this kinase is known to interact with middle T-kinase complexes. Phosphatidylinositol 3'-kinase activity associated with middle T was reduced 30-60% in Src-negative cells, suggesting that Src contributes at least one-third of the total middle T associated in wild-type cells. Taken together, these results indicate that Src is not required for middle T-induced hemangiomas in mice or for focus induction in immortalized fibroblasts, and that the residual level of Yes, Fyn and phosphatidylinositol kinase activity associated with middle T in Src-negative cells may compensate for the absence of Src.

Animals↗
PubMed1992

Isolation of Helicobacter pylori from human faeces.

Helicobacter pylori is arguably the commonest chronic infection in man. However, its route of transmission is unknown. We have isolated viable H pylori from the faeces of an infected individual from The Gambia. The organism was cultured on selective media after concentration of faecal bacteria by centrifugation in a buffer equilibrated with a microaerophilic gas mixture. Growth characteristics, microscopic appearances, and enzyme activities were the same as those of a typical gastric isolate of H pylori. Protein preparations derived from the new isolate and the typical strain were antigenically similar, and had very similar electrophoretic profiles (including two major protein bands of 62 and 26 kDa, corresponding to the urease enzyme subunits). With the same technique, organisms with the colony morphology, growth requirements, enzyme activities, and microscopic appearances of H pylori were isolated from the faeces of 9 of 23 randomly selected children aged 3-27 months from a Gambian village with a high prevalence of H pylori infection in early life. Faecal-oral transmission is probably important in the spread of infection in such communities.

Adult↗
PubMed1992

The nucleotide sequence of the infectious cloned DNA component of tobacco yellow dwarf virus reveals features of geminiviruses infecting monocotyledonous plants.

An infectious clone of the Australian geminivirus tobacco yellow dwarf virus (TobYDV) was constructed from virus-specific double-stranded DNA isolated from infected tobacco and used to demonstrate a single-component genome. The nucleotide sequence of TobYDV DNA comprises 2580 nucleotides. TobYDV DNA has three coding regions, two in the virion sense and one in the complementary sense, homologous to those identified for other geminiviruses, particularly those infecting monocotyledonous (monocot) plants. The complementary sense coding region is comprised of two overlapping reading frames, with an intron of 86 nucleotides. Efficient splicing of the mRNA for this coding region was observed in the infected dicotyledonous (dicot) hosts bean and tobacco despite the intron having an A + U content (57%) more typical of geminiviruses of monocot plants. TobYDV encapsidates a small oligonucleotide able to prime synthesis of the complementary DNA strand in vitro. The TobYDV genome organization, low A + U intron, and encapsidated oligonucleotide primer resemble those of the monocot-infecting geminiviruses. These results strongly suggest that TobYDV is a monocot geminivirus which has become adapted to dicot hosts.

Base Sequence↗
PubMed1992

Oncogenes in X-ray-transformed C3H 10T1/2 mouse cells and in X-ray-induced mouse fibrosarcoma (RIF-1) cells.

In order to better understand the molecular basis of X-ray induced carcinogenesis we have investigated RNA levels of oncogenes in an X-ray transformed C3H 10T1/2 fibroblast line (XTD) and RIF-1 cells isolated from an X-ray-induced fibrosarcoma in a C3H mouse. Steady-state levels of K-ras, H-ras, N-ras, abl, sis, src, and fos were unchanged in the X-ray-transformed cells compared with non-transformed C3H 10T1/2 cells. However, myc and raf mRNA levels were increased dramatically in the transformed cells. Data further suggests a possible alteration in processing of raf RNA in the XTD cells. Southern blot analysis of secondary transfectants induced with XTD DNA indicated that the oncogenic phenotype did not segregate with the myc or raf loci; nor with nine other oncogenes analysed.

Animals↗
PubMed1992

Assay of urease-inhibiting activity in serum from children infected with Helicobacter pylori.

In order to provide a basis for obtaining further information concerning the host response to Helicobacter pylori urease, four assay methods for detecting urease-inhibiting activity in serum were examined. A quantitative assay, established in a COBAS BIO centrifugal fast analyzer and based on detection of the consumption of NADH by glutamate dehydrogenase stimulated by ammonia production, was considered most suitable for large-scale serological work. Serum samples from 63 children (aged 5 to 16 years), 28 of whom had seropositive H. pylori gastritis, were assayed. One of the serum samples in this latter group showed significant inhibitory activity. This serum sample was one of 13 in the seropositive group known to bind to urease antigen. It showed no inhibitory activity against Bacillus pasteurii or jack bean urease. Protein A binding and heat treatment indicated that the inhibitory activity was immunoglobulin G mediated. The patient from whom this sample was collected showed no distinctive features in his illness. The COBAS BIO analyzer-based urease inhibition assay provides a new tool for studying one aspect of the host response to H. pylori infection.

Child↗
PubMed1992

Amino acid pools in developing Chlamydomonas reinhardtii: vegetative cells, gametes, and mature zygotes.

Free amino acid pools were examined for cultures of vegetative cells, gametes, and mature zygotes of the unicellular green alga Chlamydomonas reinhardtii (Dangeard). The total pool of amino acids found in premature gametes of strains 137c+ (10.0 pmol-micrograms protein-1) and 137c- (10.8 pmol.micrograms protein-1) decreased to levels about half that seen in vegetative 137c- cells (19.8 pmol.micrograms protein-1). Following light activation, amino acid pools in these gametes increased to 18.7 pmol.micrograms protein-1 in 137c+ cells and 20.0 pmol.micrograms protein-1 in 137c- cells. With the exception of cystine, individual amino acid pools in these cells had increased once more to levels similar to those seen in vegetative cells grown in liquid medium. Levels of cystine remained one to two orders of magnitude lower than that seen in vegetative cells. Mature 137c+ and 137c- gametes mixed in solutions of either 2 mM cystine or 2 mM cysteine (half-cystine) suffered a 52-64% reduction, respectively, in the number of vis-à-vis conjugative pairs formed. This suggests that pools of endogenous cystine may play a role in the onset of mating. In zygotes levels of all amino acid pools, except histidine, were depressed; levels of cystine, valine, and phenylalanine were nondetectable in these cells.

Amino Acids↗
PubMed1992

A physician's guide to early detection of oral cancer.

Oral cancer is a disease of the elderly that is more prevalent in patients who drink alcohol, smoke, or are chronically exposed to the sun. An oral examination is recommended annually for all elderly patients and more often for patients with these risk factors. The key to diagnosis and long-term patient survival is recognition of early lesions, which are often asymptomatic. Cancerous lesions occur more frequently at specific oral sites and may be difficult to differentiate from lesions caused by such benign conditions as denture irritation and herpetic ulcers.

Aged↗
PubMed1991

Phosphorylation of c-Src on tyrosine 527 by another protein tyrosine kinase.

The protein tyrosine kinase activity of the cellular Src protein is negatively regulated by phosphorylation at tyrosine residue 527 (Tyr527). It has not been established whether this regulatory modification of Src is mediated by autophosphorylation or by another cellular protein kinase. The phosphorylation of a modified form of c-Src that lacks kinase activity was examined in mouse cells that do not express endogenous Src (because of the targeted disruption of both src alleles). Phosphorylation of the inactive form of Src on Tyr527 occurred to a similar extent in cells lacking endogenous Src as it did in cells expressing Src. Therefore, Tyr527 phosphorylation, and thus negative control of Src kinase activity, is mediated by another cellular protein tyrosine kinase.

Amino Acid Sequence↗