PubMed Health⌕ Search

Biomedical subjects

R C Warren

Publications and source records attributed to R C Warren.

At least 37 records · Page 2Linked to original sources
PubMed1986

Increased concentration of circulating calcitonin gene related peptide during normal human pregnancy.

Calcitonin gene related peptide is an extremely potent vasoactive peptide that causes profound vasodilatation in man. Its distribution in perivascular nerves suggests that one of its functions may be the regulation of peripheral vascular tone. Pregnancy is a physiological condition in which there are major haemodynamic changes. An increase in plasma volume of about 40% necessitates changes in peripheral vascular tone. In a cross sectional study plasma concentrations of immunoreactive calcitonin gene related peptide were measured throughout normal pregnancy and at five to seven days post partum. Calcitonin gene related peptide concentrations were significantly increased throughout pregnancy but fell after delivery. Calcitonin gene related peptide may participate in the physiological regulation of vasomotor tone in man.

Adolescent↗
PubMed1986

First trimester prenatal diagnosis of congenital rubella: a laboratory investigation.

Acute primary maternal infection with rubella virus during pregnancy often, but not invariably, leads to the congenital rubella syndrome. Diagnosis by detection of virus specific IgM in the mother is not always possible, and in those cases in which IgM is detected the fetus has not necessarily also been infected. A method for direct, prenatal detection of fetal infection would allow more accurate early diagnosis of congenital rubella syndrome. In this study a case of suspected preconception rubella infection that was not referred until 14 weeks after the appearance of a rash was studied to determine whether a retrospective serological diagnosis of primary rubella could be made, and whether direct evidence of fetal infection could be obtained from a chorionic villus biopsy specimen by detecting virus specific antigens or ribonucleic acid (RNA) sequences. Monoclonal antibodies and a cloned complementary deoxyribonucleic acid probe were used successfully to detect antigens to rubella virus antigens and RNA sequences in the chorionic villus biopsy specimen, which was taken at 15 weeks' gestation. This method should serve as a new approach to the diagnosis of congenital rubella syndrome in utero.

Adult↗
PubMed1986

The arylsulphatases of chorionic villi: potential problems in the first-trimester diagnosis of metachromatic leucodystrophy and Maroteaux-Lamy disease.

Three pregnancies at risk for late infantile metachromatic leucodystrophy have been monitored using chorionic villus biopsies. In the first of these a false negative diagnosis was made following assay of arylsulphatase A in villi. Subsequent studies have shown that this error was probably due to interference from another sulphatase in the villi, although the possibility that maternal contamination was also partly responsible could not be excluded. For reliable prenatal diagnosis of metachromatic leucodystrophy using chorionic villi it is advisable that studies with the nitrocatechol substrate are carried out on fractionated homogenates, or that the natural substrate is used. Problems may also occur when chorionic villi are used for assay of arylsulphatase B for first trimester diagnosis of Maroteaux-Lamy disease.

Arylsulfatases↗
PubMed1985

First trimester diagnosis of hypophosphatasia with a monoclonal antibody to the liver/bone/kidney isoenzyme of alkaline phosphatase.

Prenatal diagnosis of hypophosphatasia was made by alkaline phosphatase (ALP) assay on a chorionic villus sample taken in the first trimester. Monoclonal antibodies against the liver/bone/kidney (LBK) and placental isoenzymes of ALP were used, and the bound isoenzymes were quantified by an amplification system. Very low activities of the LBK isoenzyme indicated an affected fetus. Diagnosis was confirmed by ultrasound scan at 15 weeks' gestation, and by ALP measurement in amniotic fluid supernatant and fetal serum.

Adult↗
PubMed1985

First trimester prenatal diagnosis and detection of carriers of haemophilia A using the linked DNA probe DX13.

Although the use of a gene specific deoxyribonucleic acid (DNA) probe is the method of choice for detecting carriers of genes for rare genetic disorders, there will always be families in which such probes cannot be used because key subjects are not informative for restriction fragment length polymorphisms in or around the gene. In these cases closely linked DNA markers have to be used. An X chromosome specific DNA probe, DX13, which is closely linked to the haemophilia A locus on the X chromosome, was used for early prenatal diagnosis in two cases and to detect carriers in a series of nine possible heterozygote women. The first reported crossover between DX13 and the factor VIII:C locus was observed in this study. There are complexities inherent in using any linked DNA probe for assignment of genes, but such techniques are clinically important.

Female↗
PubMed1984

Detectability of low-contrast features in computed tomography.

Factors affecting low-contrast feature detectability in computed tomography have been investigated using signal detection experiments. Detectability of a circular object in a uniform noise field was found to increase with decreasing window width. With increasing viewing distance, detectability increased to a maximum before decreasing; the optimal viewing distance was found to increase with decreasing window width. Detectability was independent of window level and image luminance, over the range of values studied. A mathematical model of the CT display system and the human visual system was constructed, using empirical transfer characteristics as system descriptors and an optimal matched filter model of pattern recognition. Theoretical signal-to-noise ratios were in qualitative agreement with the experimental data when account was taken of the visual contrast sensitivity function and the effect of noise internal to the observer. Quantitative discrepancies suggest either that visual matched filter processing is sub-optimal, or that use of the contrast sensitivity function as a spatial filter is only approximately valid. Compared with the visual system characteristics, those of the display system were insignificant. Modifications to CT display configurations are suggested in order to maximise information transfer between the display system and the visual system of the radiologist.

Data Display↗
PubMed1981

Contrast and latitude of CT hard copy: an ROC study.

A decision between film and paper for CT hard copy must be based on the different latitudes of the two media. The author conducted a receiver operating characteristic (ROC) analysis in which image information was matched to the characteristics of the recording media by adjusting both the window width of the display and the monitor contrast. Under these conditions, film images were found to be superior to print images for detection of noise-limited features. It is proposed that if the same optimization procedure were applied to clinical CT scans, the information content of the images could be increased.

Humans↗
PubMed1980

Sero-diagnosis of invasive aspergillosis: attempts to determine antigen and antibody relevance to infection.

Attempt was made to define antigens and antisera which might prove useful in diagnosis of invasive aspergillosis in man. A convalescent antiserum (serum from rabbits after liver infection with Aspergillus fumigatus conidia) which might be more representative of immunological reaction to fungal growth in vivo, did not react in enzyme-linked immunosorbent assay with commerical antigens which are used at present in attempts to detect antibody response in systemic infections in man. However, this convalescent antiserum reacted with antigens from a range of fungal extracts. Antigens from young culture filtrates in particular the 24th culture filtrate are advocated as the standard antigens for antibody detection using conventional immunoprecipitation techniques. For the detection of circulating antigens, the use of convalescent antiserum in enzyme-linked immunosorbent assay might be promising in the early diagnosis of invasive aspergillosis.

Antibodies, Fungal↗