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R D Thomas

Publications and source records attributed to R D Thomas.

At least 73 records · Page 4Linked to original sources
PubMed1993

Reactive mediastinal lymphadenopathy in bronchiectasis assessed by CT.

Mediastinal lymphadenopathy is commonly detected on CT. It is a non-specific finding, but because of its significance in the treatment in lung carcinoma it is important to know with which other disease states it is associated. We present a series of 42 patients in whom CT of the chest was used to confirm a clinical diagnosis of bronchiectasis. The size, number and distribution of mediastinal lymph nodes is documented. Lymph nodes were visible in 81% of patients. Nodes larger than 10 mm, the recognised maximum size for normal nodes in the U. K., were detected in 29%. In the absence of other recognised causes of lymphadenopathy in these patients, these findings confirm "reactive" mediastinal lymph node enlargement in bronchiectasis.

Adolescent↗
PubMed1993

DNR policy.

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Heart Arrest↗
PubMed1992

Metastatic malignant struma ovarii. Two case reports.

Struma ovarii is an ovarian germ cell tumor consisting mainly of thyroid tissue. Five percent of struma ovarii are malignant, and of these only five percent metastasize. The rarity of this disease has resulted in difficulty in agreeing on treatment regimes and in limited imaging experience. The authors report two cases and highlight the imaging and monitoring difficulties encountered in their management. The authors conclude that I-131 has a role to play both therapeutically and in monitoring these patients, but that biochemical testing is a more reliable indicator of disease status.

Adolescent↗
PubMed1992

Carcinogenic mixtures.

Human populations are generally exposed simultaneously to a number of toxicants present in the environment, including complex mixtures of unknown and variable origin. While scientific methods for evaluating the potential carcinogenic risks of pure compounds are relatively well established, methods for assessing the risks of complex mixtures are somewhat less developed. This article provides a report of a recent workshop on carcinogenic mixtures sponsored by the Committee on Toxicology of the U.S. National Research Council, in which toxicological, epidemiological, and statistical approaches to carcinogenic risk assessment for mixtures were discussed. Complex mixtures, such as diesel emissions and tobacco smoke, have been shown to have carcinogenic potential. Bioassay-directed fractionation based on short-term screening test for genotoxicity has also been used in identifying carcinogenic components of mixtures. Both toxicological and epidemiological studies have identified clear interactions between chemical carcinogens, including synergistic effects at moderate to high doses. To date, laboratory studies have demonstrated over 900 interactions involving nearly 200 chemical carcinogens. At lower doses, theoretical arguments suggest that risks may be near additive. Thus, additivity at low doses has been invoked as as a working hypothesis by regulatory authorities in the absence of evidence to the contrary. Future studies of the joint effects of carcinogenic agents may serve to elucidate the mechanisms by which interactions occur at higher doses.

Animals↗
PubMed1992

Helping those in need.

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Dental Care for Persons with Disabilities↗
PubMed1992

Echocardiography and genetic counselling in tuberous sclerosis.

OBJECTIVE: To assess echocardiography as an investigation for the detection of occult gene carriers in tuberous sclerosis. PATIENTS: Sixty parents of children with tuberous sclerosis who had been extensively investigated for signs of the disease and 60 age and sex matched controls. PROCEDURE: Blind study by two experienced echocardiographers and blind interpretation of video recordings by an adult cardiologist. SETTING: Cardiology department of a district general hospital. RESULTS: Two parents and three controls had bright echodense areas interpreted as possible rhabdomyomas. CONCLUSIONS: In our hands echocardiography of adults is not an investigation with a high specificity for gene detection in tuberous sclerosis.

Adult↗
PubMed1991

Stereoselective formation of bis(alpha-aminoacyl) esters of 5'-AMP suggests a primitive peptide synthesizing system with a preference for L-amino acids.

In the biosynthesis of proteins, each amino acid passes from the aminoacyl adenylate to become an amino acid ester and finally a 2' (3') peptidyl ester of the AMP residue at the end of a tRNA. Consequently, the chemistry of protein synthesis is the chemistry of aminoacyl and peptidyl AMP. Our data has revealed properties of 5'-AMP and its esters which should allow the preferential catalytic synthesis of L-amino acid peptides via a bis(2', 3'-aminoacyl) ester intermediate. Results in this paper concern one step in the proposed process and show that preexisting Ac-L-Phe monoester reacts about 2.5-times faster to form diester than preexisting Ac-D-Phe monoester.

Adenosine Monophosphate↗
PubMed1991

Double duty.

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Career Choice↗
PubMed1990

Chemical esterification of 5'-AMP occurs predominantly at the 2' position.

We describe experiments here which show that chemical esterification of 5'-adenylic acid (5'-AMP) with N-acetyl D- or L-phenylalanine (Ac-D- or Ac-L-Phe) imidazolide occurs principally, if not exclusively, at the 2' position. Furthermore, in experiments with the formation of the 2'-3' diester with butyric acid and N-acetyl glycine (Ac-Gly), we found the second esterification was also predominantly at the 2' position. This means that mixed diesters can be predictably prepared with the positions of the substituents known. The results are consistent with a model for the preferential catalytic synthesis of L-based peptides via a 2'-3' diester intermediate of purine monoribonucleotides.

Adenosine Monophosphate↗