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Biomedical subjects

G Thomas

Publications and source records attributed to G Thomas.

At least 847 records · Page 47Linked to original sources
PubMed1975

Kinetics of histone methylation in vivo and its relation to the cell cycle in Ehrlich ascites tumor cells.

The appearance of methylated lysines in newly synthesized histones from Ehrlich ascites tumor cells was measured during one generation time. Newly synthesized histones were pulse-labeled in vivo by L-[3H]lysine, and the time course of the uptake of label into monomethyl, dimethyl and trimethyllysine from gel-electrophoretically isolated histones F2a1 (H4) and F3 (H3) was followed. Methylation starts immediately after histone biosynthesis. It proceeds, however, more slowly than histone synthesis. Both the rate of methylation and the mechanism of methylation in F3 and F2a1 histones differ. F3 methylation can be described by a first-order reaction, i.e. the reaction rate depends only on the concentration of free methylation sites available. Rate constants of approximately 0.21 h-1 were found for all three methylation steps. Methylation in the F2a1 histone proceeds more slowly than in F3. The dimethylation step in this fraction can be described by a zero-order reaction with a rate constant which is the reciprocal of the duration of the DNA synthesis phase. Alternatively this step could be correlated with the transition of the cells from the S phase into the G2 phase. By the end of one generation time all methylation sites in all F2a1 and F3 molecules are occupied by methyl groups at a ratio of about 1:3:1 for monomethyl, dimethyl and trimethyllysine in the F3 histone. In the F2a1 molecule the methyllysines consist mainly of dimethyllysine.

Amino Acids↗
PubMed1975

Respiratory and humoral immune response to aerosol and intramuscular pertussis vaccine.

Animal experiments have shown that respiratory administration of pertussis antigen induces a protective immune response. In this study pertussis antibody in human respiratory secretions was measured and the response to aerosol and intramuscular pertussis immunization investigated. Substanial increases in this antibody occurred after aerosol immunization but no changes were found in serum antibody. The reverse was observed after intramuscular pertussis vaccine in adults but not with aerosol immunization. The latter method may be of value for paediatric medical and nursing personnel exposed to the risk of pertussis infection.

Aerosols↗
PubMed1975

Identification of a ribosomal protein essential for peptidyl transferase activity.

Extraction with 2 M lithium chloride removes a group of proteins (LiC1 SP) from 50S ribosomal subunits. Both the LiC1 SP and the resulting cores, which contain the remaining proteins as well as 5S and 23S RNA, lack peptidyl transferase activity, as measured by the "fragment reaction". Activity can be restored to the LiC1 cores by reconstitution with LiC1 SP under conditions of high temperature and high ionic strength. The LiC1 SP proteins were fractionated by carboxymethyl-cellulose and Sephadex G-100, and the individual fractions were tested by this reconstitution system. Of the 18 ribosomal proteins found in the LiC1 SP, only L16 is essential for reconstitution of peptidyl transferase activity.

Acyltransferases↗
PubMed1975

Blood platelet aggregation and personality traits.

Changes in blood platelet aggregation may precipitate episodes of arterial occlusive diseases. Little is known, however, regarding the influence of psychological traits, emotional states and other behavioral stressors on platelet aggregation phenomena. This study examined 46 healthy college men at rest and after submaximal treadmill exercise. Associations were found between the duration of platelet aggregation and a number of scores from the California Psychological Inventory and self-administered anxiety scales. The more socially adequate, poised and dominant persons--those with more mature ego development and less overt anxiety--had platelets with more prolonged aggregation reactions to the in vitro introduction of noradrenalin. Irreversible aggregation of platelets occurred more regularly to lower in vitro concentrations of noradrenalin in platelet samples drawn from subjects who were less anxious and tended to be more rigidly defensive. It is premature to attempt to derive clinical implications from this exploratory work, but some implications for the design of future research are discussed.

Adult↗
PubMed1975

tRNA tertiary structure in solution as probed by the photochemically induced 8-13 cross-link.

The conformation of ten purified tRNAs from Escherichia Coli has been investigated by means of the photo-induced cross-linking of 4Srd8 and Cyd13, which is sensitive to the juxtaposition of the two bases. Three tRNAs photo-react abnormally slowly; tRNAPhe, tRNAMet/m a and tRNAVal/2; a comparison with normally reacting species suggests that base 47 (Urd or modified Urd) is involved in a tertiary interaction in Class I tRNAs with the triplet 8, 14, 28. The UGA suppressor tRNATrp photoreacts significantly slower than the wild type. Thus the single base change Gua 24 to Ade induces a conformational change that alters the rate constant for the cross-linking reaction.

Base Sequence↗
PubMed1975

Progression in response patterns of fetal heart rate throughout labour.

A study of 70 fetal heart rate (FHR) traces throughout labour has allowed analysis of FHR responses associated with approximately 7000 individual uterine contractions. The significance of the less emphasized FHR patterns has been assessed and an attempt has been made to identify any trend or progression in the occurrence of these patterns. Transient acceleration was the most frequently occurring response in early labour and was the first observed response in the majority of cases. Decelerations became prevalent as labour progressed. A hypothesis is proposed to explain the observed overall progression in FHR responses and the possible physiological mechanisms underlying the cyclic changes in response patterns which occur throughout the course of labour.

Apgar Score↗
PubMed1975

The analysis of continuous fetal heart rate traces in the first and second stages of labour.

In the search for a simplified method of fetal heart rate trace assessment 50 traces recorded during the first stage of labour and those recorded in the last hour of each of a further 50 labours have been analysed intensively. The importance of baseline variability in predicting possible fetal distress in both the first stage and the last hour of labour is shown and the possible use of an objective measurement of baseline variability in the further screening for fetal acidosis is described. The importance of lag time measurement in the first stage of labour is demonstrated and the relationships between fetal scalp blood pH and other heart rate parameters is discussed. Significant inverse correlations between one-minute Apgar score and maximum amplitude of deceleration and total deceleration area in the last hour of labour are also shown. Temporal relationships between intrauterine pressure rises and transient changes of fetal heart rate failed to give significant correlations in the last hour. These findings in the last hour of labour are compared with those obtained in the first stage of labour and the differences are discussed.

Acidosis↗
PubMed1975

The aetiology, characteristics and diagnostic relevance of late deceleration patterns in routine obstetric practice.

A retrospective study is described in which all the late deceleration patterns seen in one obstetric unit over the course of 34 months have been reviewed with regard to their apparent aetiology, their characteristics and associated abnormal fetal heart rate patterns and the incidence of fetal distress. The results show that, regardless of the aetiology and the characteristics, the incidence of fetal distress (defined as a pH of less than 7-25 or an Apgar score of less than 7 at one minute) lies between 40 and 50 per cent. The implications of this degree of diagnostic inaccuracy are discussed and the importance of fetal blood sampling as the final arbiter in the diagnosis is emphasized. During the course of the study a significant relationship was demonstrated between the use of epidural analgesia and the incidence of late deceleration patterns. This finding is discussed.

Anesthesia, Epidural↗
PubMed1975

Pathological aspects of immunization of mice against influenza virus infection.

Groups of mice were immunized against influenza Ao/NWS virus by a single intranasal administration of inactivated homologous virus, by 2 intranasal doses of vaccine separated by an interval of 2 weeks, or by 2 intraperitoneal doses of the same vaccine. When subjected 2 weeks later to a standard challenge of 6 x 10(5) egg infecting units Ao/NWS virus instilled intranasally, mortality fell significantly from 64% in unimmunized mice to 39% in mice given a single intranasal dose of vaccine and to 29% in animals which received double intranasal vaccine. The best protection was conferred by double intraperitoneal immunization, after which mortality was 10%. Immunity waned with time, since the mortality of mice doubly immunized by the respiratory route and challenged 30 weeks later was 49%. Intrapulmonary lymphoid tissue developed in large amounts in a proportion of mice immunized by all methods and challenged after an interval of 2 weeks. Attention is drawn to this reaction as a possible unfavourable consequence of vaccination. There were no lesions in the lungs or central nervous system after immunization without subsequent challenge. The importance of histopathology in vaccine trials in experimental animals is emphasized by the consistently higher detection rate of lesions in lungs by histological examination than by visual inspection alone.

Animals↗
PubMed1974

Air sampling of smallpox virus.

Airborne smallpox virus has been recovered in an isolation hospital using an adhesive surface sampling technique in the presence of very low aerosol concentrations. Previous work in this field is reviewed. Successful recovery of airborne virus depends on sampling large volumes of air with a suitable sampler and thorough investigation of the whole sample taken for the presence of viable virus. More information on the characteristics and behaviour of airborne smallpox virus is needed in particular with regard to the future design and siting of smallpox isolation units.

Air Microbiology↗
PubMed1974

Synthesis of polyprenyltolouquinols from homogentisate and polyprenyl pyrophosphates in particulate fractions of Euglena and sugar beet.

Chloroplast-rich particles of sugar beet and Euglena gracilis are able to carry out the light-, H(2)O(2)- and O(2)-independent syntheses of a nonaprenyltoluquinol, an octaprenyltoluquinol and a phytyltoluquinol from homogentisate and nonaprenyl, octaprenyl and phytyl pyrophosphate. The formation of these compounds probably takes place by the concomitant polyprenylation (or phytylation) and non-oxidative decarboxylation of homogentisate.

Carbon Radioisotopes↗