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Biomedical subjects

P N John

Publications and source records attributed to P N John.

13 recordsLinked to original sources
PubMed1989

Glycated fibrinogen: a new index of short-term diabetic control.

Fibrinogen is a plasma protein with a short half-life of four days and, therefore, glycated fibrinogen may be valuable as an index of short-term diabetic control. We have developed a simple, rapid method for determining glycated fibrinogen using affinity chromatography. The differences in the percentage of glycated fibrinogen between normal subjects, well-controlled diabetics and poorly-controlled diabetics were highly significant. There was a significant correlation between glycated fibrinogen and glycated haemoglobin for all these subjects. However, in selected subjects with rapidly improving diabetic control the difference between the fall over three days in glycated fibrinogen and glycated haemoglobin was highly significant. In subjects with deteriorating control over an average of four weeks there was a significant difference between the increase in glycated fibrinogen and glycated haemoglobin. We suggest that glycated fibrinogen may be a valuable adjunct to glucose measurements in the assessment of short-term diabetic control due to its rapid change following alterations in control.

Adult↗
PubMed1983

A collaborative study of the measurement of glycosylated haemoglobin by several methods in seven laboratories in the United Kingdom.

A collaborative study compared methods for measuring glycosylated haemoglobin in seven laboratories in the United Kingdom. No satisfactory standard for general use was found. Satisfactory internal quality control systems were in use for each assay which allowed the maintenance of a normal range in each participating laboratory. No satisfactory quality control system suitable for general use could be identified. Costs and convenience of the assays are reported. The technical problems with each type of assay and precautions for their use were identified, such as the need for standardization in incubation times, the practicability of automation of colorimetric assays, and the precision of pH needed for buffers in column separation methods. The relevance of the technical problems to interpretation of measurements is also considered. It is concluded that laboratories measuring glycosylated haemoglobin should maintain a normal range, use 'in-house' quality controls to monitor assay performance and keep clinical colleagues informed of the findings and of any changes in methodology that might affect the interpretation of results.

Autoanalysis↗
PubMed1982

Antenatal diagnosis of haemoglobinopathies by Biorex chromatography of haemoglobin.

Biorex chromatograhpy of haemoglobin has been compared to the standard chromatographic separation of radioactive globin chains in 60 fetal blood samples obtained for the antenatal diagnosis of haemoglobinopathies. Biorex chromatography of haemoglobin permitted two measurements, the optical density at 418 nm and the radioactivity incorporated into fetal and adult haemoglobin. The two measurements were highly correlated (r2=0.96) and enabled a distinction between homozygous from heterozygous states of the diseases to be made, particularly in beta thalassaemia. A single column was used for 50 analyses. This fast and very sensitive method is proposed for the antenatal diagnosis of haemoglobinopathies using fetal blood.

Anemia, Sickle Cell↗
PubMed1970

Autoradiographic demonstration of inhomogeneous distribution of sodium in single oocytes of Bufo bufo.

1. Autoradiography of frozen cells labelled with (22)Na has been used to locate a sequestered fraction of internal Na in the oocyte which exchanges very slowly or not at all with external Li.2. Relative grain density in nucleus and cytoplasm, measured photometrically, was used as an indication of (22)Na distribution within the oocyte. In test experiments grain density fell to 50% within 19 mum of the edge of the section. Owing to the large diameter of the oocyte (> 600 mum) and its nucleus (> 200 mum), this resolution was adequate to determine cytoplasmic/nuclear (C/N) ratios of grain density.3. In oocytes fully loaded with (22)Na, the mean C/N ratio was 0.92 +/- 0.03 (n = 11). After 5 hr exchange in Li-substituted Na-free Ringer solution, the mean C/N ratio was 2.18 +/- 0.04 (n = 11). After 5 hr exchange in Ringer solution as a control, the mean C/N ratio was 1.39 +/- 0.18 (n = 7). The cytoplasm thus contained a fraction of (22)Na inexchangeable with Li, and more slowly exchangeable with Na than that in the nucleus.4. The non-Li-exchangeable fraction of internal Na thus revealed appeared to be quantitatively similar to that already demonstrated by studies of (22)Na fluxes and of internal Na activity by means of Na-sensitive micro-electrodes.

Animals↗
PubMedDate not supplied

Haemoglobin A1 and congenital malformation.

Two hundred and thirty pregnancies were studied in 196 diabetic women. Seven women with babies found to have major malformations had a higher median first trimester haemoglobin A1 (12.9%) than the median HbA1 (10.8%) in those with normal babies (p = 0.06). No relationship was found between the occurrence of minor malformations and first trimester maternal haemoglobin A1. Two of the seven congenital malformations were diagnosed antenatally at a time when therapeutic abortion could be offered. Expert antenatal ultrasound scanning should be offered to all pregnant diabetic women as poor glycaemic control at the time of conception and organogenesis, as evidenced by raised first trimester HbA1, predisposes to congenital malformation.

Adult↗