A systematic approach to the assessment of erythropoiesis.

The pathogenesis of anaemia may be simple or complex and the differential diagnosis can be difficult. An appreciation of the erythropoietic processes is required, together with regular review of investigations, to ensure that appropriate protocols are adopted. The application of tests, which define different facets of erythropoiesis, should be appropriate to the clinical circumstances. In some situations, such as the anaemia of chronic disorders, pregnancy and chronic renal failure, a detailed analysis of erythropoiesis is often required. Guidelines for investigating anaemia due to megaloblastosis or haemoglobinopathy are well established, whereas disturbances of iron metabolism are often difficult to classify. These require a clear distinction between storage and functional iron to differentiate whether the defect is due to readily treatable simple iron deficiency or more complex mechanisms, which do not respond to iron supplementation. Determination of red cell haemoglobin content, reticulocyte analysis and the assay of serum transferrin receptors are new generation parameters developed to address this. Practice pressures and new treatment options have contributed to investigations becoming more complex, especially those of the secondary anaemias, as new tests have become more readily available and often automated. This has resulted in reduced turnaround times and clinical demand has driven request patterns. Initiatives to develop evidence-based anaemia management protocols are welcomed but, wherever possible, should be developed through collaboration between the haematology department and the user unit, and based on available guidelines.

Laboratory control of oral anticoagulant therapy: preservation of prothrombin time specimens using a polypropylene collection system.

Previous studies have shown a marked time and temperature dependent shortening of the prothrombin time (PT) when blood is exposed to borosilicate (glass) or siliconized borosilicate tubes. Current recommendations are that samples for PT estimation should be tested within 2 h of collection. In this study using polypropylene collection tubes, blood obtained from 30 patients on oral anticoagulant therapy showed no significant change in International Normalized Ratio (INR) value after 24 h storage--either at 4 degrees C or room temperature. After 48 h. changes in INR values from refrigerated samples were still clinically insignificant. After 48 h storage at room temperature, however, a minority of samples showed an increase in INR value which may be of clinical importance. The range of INRs studied was 1.0-9.1. In a second evaluation, replicate specimens from 22 orally anticoagulated patients with INRs ranging from 1.0 to 9.6 showed no significant change after 24 h at either temperature--even when samples had been subjected to 30 min of gentle agitation prior to storage and analysis. Overall, the results indicate that when polypropylene collection tubes are used, prothrombin time specimens can be successfully preserved for up to 24 h at room temperature or up to 48 h when refrigerated.

Transmitter mediated regulation of energy metabolism in nervous tissue at the cellular level.

The Monoamines 5-hydroxytryptamine (5-HT), noradrenaline (NA) and histamine, and the peptide Vasoactive Intestinal Polypeptide (VIP), regulate energy metabolism in nervous tissue, in addition to producing excitation and/or inhibition. These transmitters induce glycogen hydrolysis in a concentration dependent manner. The glycogen breakdown is brought about by increased cyclic AMP formation, or translocation of calcium ions to activate phosphorylase, and is partially localized in glial cells. Data from a diversity of nervous systems, including leech and snail ganglia, and rodent cortex, point towards important roles for neurons containing these transmitters in the regulation of the glycogen turnover. It is proposed that energy metabolism may be controlled within domains defined by the geometric arrangements of the neurons releasing these transmitters. The different domains may overlap temporally and spatially to coordinate energy metabolism in relation to increases in neuronal activity. The non-myelin forming glial cells, which contain glycogen whose turnover rate is altered by the transmitters, appear to be important in the local supply of energy substrate to neurons.

Modulation of glial glycogen metabolism by 5-hydroxytryptamine in leech segmental ganglia.

Leech segmental ganglia (16 out of 23 per animal) were divided into experimental and control groups (4 ganglia per group). The amounts of glycogen in the ganglia were assayed by a specific extraction procedure and fluorimetry, or by liquid scintillation counting following labelling of the glycogen by [(3)H]glucose. Within any individual animal the amounts of glycogen in the ganglia were relatively constant (max. variation 16%). 5-HT (10(?6)-10(?4) M) reduced in a dose-dependent manner the endogenous glycogen (max. 20% reduction), and the [(3)H]glycogen (max. 60% reduction). The glycogenolytic effect was studied by light-microscope autoradiography in serial sections of segmental ganglia previously exposed to [(3)H]glucose. The 5-HT-mediated glycogenolysis was localized principally in the glial cells surrounding the neuron perikarya. 5-HT, in addition to its conventional transmitter role, may regulate the supply of energy substrate from glial cells to neurons within domains defined by the projections of the neurons from which it is released.

Incorporation of [3H]2-deoxyglucose into glycogen in nervous tissues.

Mice were injected with [3H]2-deoxyglucose and after 1 h high molecular weight glycogen was extracted from brain, liver and muscle tissues. 1-2% of the total radioactivity in each tissue was recovered in the glycogen fraction. Isolated buccal ganglia of the pond snail, Planorbis, and isolated abdominal ganglia of the horse leech Haemopis, were exposed in vitro to [3H]2-deoxyglucose for 1 h. 1-10% of the total radioactivity in these tissues was located in the high molecular weight glycogen fraction. Treatment of the extracted labelled glycogen fractions with amyloglucosidase caused release of the label in a manner consistent with the breakdown of labelled glycogen. Ganglia of snail and leech were exposed to [3H]2-deoxyglucose, fixed in glutaraldehyde and osmium tetroxide solutions, and prepared for autoradiography using aqueous histological processing. Light and electron microscope autoradiography showed that over 90% of the label was positively associated with glycogen particles (alpha- and beta-particles). Certain previously published reports on the incorporation of 2-deoxyglucose into glycogen are discussed in relation to these findings. It is concluded that [3H]2-deoxyglucose is partially incorporated into glycogen in nervous tissue; the labelled 2-deoxyglycogen withstands aqueous histological processing and can be visualized directly by autoradiography.