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Biomedical subjects

J M England

Publications and source records attributed to J M England.

At least 37 records · Page 2Linked to original sources
PubMed1990

Recommended methods for the assignment of assay values to stabilized cell suspensions.

Stabilized blood suspensions are required for the transfer of data from accurately calibrated reference instruments to service laboratory instruments. However, the more the cells are stabilized to increase shelf life, the less like fresh blood they become. Fixation is quite satisfactory for producing red count standards but it affects the flexibility, shape factor and the assigned MCV of the erythrocytes. Because of these problems values must be assigned indirectly by assigning values to fresh blood by reference methods and subsequently comparing fresh bloods with stabilized suspensions on a range of user instruments. The details for these methods are given and the reasons for these requirements are discussed.

Blood Cell Count↗
PubMed1990

Surrogate materials for calibration and control: the use of latex particles as calibrants for red cell volume measurements.

Latex particles, including BCR Certified Reference Material CRM 166a, have important applications for checking linearity and for calibrating aperture-impedance instruments used to determine red-cell volumes. Studies performed on Coulter Counters, e.g. the ZBi/C1000, ZM/C256 and Model S Plus IV, using a series of three different mono-sized latex particles have shown linearity but non-zero intercepts. This emphasizes the importance of calibrating instruments at more than one point. Latex particles also have an important role in calibration of red-cell volume measurements provided that a relative latex: red-cell shape factor has been assigned when the instrument is calibrated with fresh blood. Such relative shape factors are independent of latex particle size but need to be specific for instrument type and probably also for the orifice and diluent to be used. Nevertheless latex calibrants can serve an important role in standardizing red-cell volume measurements.

Calibration↗
PubMed1989

Coincidence correction in red blood cell counting.

A method has been developed for accurate correction of red blood cell count for coincidence in aperture-impedance electronic blood cell counters. It is based on extrapolation of the slope of regression of the counts which are obtained with sequential dilutions of the samples.

Erythrocyte Count↗
PubMed1989

Discriminant functions.

Discriminant Functions (DFs), first described by Fisher in 1936, have been applied to the classification of microcytic disorders such as iron deficiency and heterozygous thalassemia. Mathematically DFs are weighted linear combinations of variables. If the underlying assumption of multivariate normality is valid DFs provide the best possible classification. Variables may need to be transformed before the DF is derived. When two groups have to be classified it is easy to visualise the DF. With one variable the DF is represented by the point which provides the best separation. In the bivariate situation the two groups form ellipses and the DF is the best line of separation whilst in the trivariate case the two groups are ellipsoids and a plane forms the best separation. Ratios and power functions are equivalent to DFs but they are less efficient and less rigorously derived. To apply DFs in hematological practice it is necessary to carefully select the measurements to be included and to define the case selection criteria. Once the DF has been derived it should be tested on a new data set and its transferability assessed. Like any single test the DF will have sensitivity and specificity which may need to be adjusted by changing the "cut-off" if the DF is used for screening rather than for differential diagnosis.

Diagnosis↗
PubMed1988

The capacity of avian retrovirus-induced sarcomas to expand by infectious virus production.

Sarcomas arising in FP chickens infected with subgroup B avian sarcoma virus at increasing times posthatch were compared for their capacity to mediate recruitment of new sarcoma cells by infectious virus production. This comparison was premised on the observation that primary sarcoma growth is much slower when older chickens are infected with avian sarcoma virus. As measured in a transplantation assay, no age-related diminution in the recruitment capacity of sarcoma tissue from virus-infected transplant donors was observed, despite the marked age-related differences in their patterns of primary sarcoma growth. These observations establish that a diminished recruitment capacity is not required for slow primary sarcoma growth. The capacity to induce the formation of sarcomas at sites distal to the primary sarcoma was correlated with a strong recruitment capacity.

Animals↗
PubMed1988

The arginine-stimulated insulin response is impaired in congenital duck hepatitis B virus infection.

Duck hepatitis B virus (DHBV) infects both A (glucagon-containing) and B (insulin-containing) islet cells. To examine the effect of this infection on islet cell function, baseline and secretagogue-augmented plasma insulin and glucagon levels as well as the pancreatic content of insulin and glucagon were compared in congenitally DHBV- and noninfected ducks. No difference in baseline plasma levels or the pancreatic content of insulin or glucagon was detected. However, the magnitude of the second phase of the biphasic arginine-stimulated insulin response was markedly diminished in infected ducks.

Animals↗
PubMed1987

Humoral immune responsiveness in duck hepatitis B virus-infected ducks.

Immunofluorescence assays with fixed tissue sections were used to characterize antibody reactivity in sera obtained from duck hepatitis B virus-infected ducks. Under conditions of experimental infection, antibody to core antigen but not to surface antigen was detectable. A majority of the ducks infected at 8 days after hatching and a minority of those infected at 1 day after hatching showed a transient anti-core antigen humoral response; this response was stronger in the antibody-positive ducks infected on day 8 than in those infected on day 1. Antiviral antibody was not detected in the sera of ducks congenitally infected with duck hepatitis B virus. Several of the infected ducks, but none of the uninfected ducks, exhibited autoantibody reactivity for alpha-islet-cell-associated antigen.

Animals↗
PubMed1986

A case of macrocytosis and megaloblastic erythropoiesis of unknown aetiology.

The clinical and laboratory features in a non-anaemic 23-year-old female with marked macrocytosis and florid megaloblastic erythropoiesis of unknown aetiology are described. The bone marrow cells gave a normal deoxyuridine-suppressed value indicating that the megaloblastic erythropoiesis was not caused by vitamin B12 or folate deficiency or an impairment of the methylation of deoxyuridylate due to any other cause. The megaloblastic changes were associated with a marked degree of dyserythropoiesis, the most frequent ultrastructural abnormality being the presence of single or multiple intranuclear clefts. The characteristic light and electron microscope features of type I and type III congenital dyserythropoietic anaemia, in which mild megaloblastic changes may be seen, were absent. The distribution of the erythroblasts in the cell cycle was grossly abnormal and similar to that in severe pernicious anaemia; a high proportion of the cells were in the G2 phase and a substantial proportion seemed to have become arrested after progressing through part of the S phase. The bone marrow macrophages contained phagocytosed erythroblasts indicating that erythropoiesis was ineffective. It seems likely that the primary biochemical defect in the erythroblasts was some congenital disorder of DNA or nucleoprotein synthesis.

Adult↗
PubMed1985

Differential white cell counting on the Coulter Counter Model S Plus IV (three population) and the Technicon H6000; a comparison by simple and multiple regression.

Simple and multiple regression analyses have been used to see which of the differential white count measurements on the Technicon H6000 could be used to predict the differential white count measurements on the Coulter Counter Model S Plus IV (three population). The S Plus IV lymphocytes are predicted by the Technicon H6000 lymphocytes plus 39% of monocytes. The S Plus IV granulocytes are predicted by the Technicon H6000 neutrophils plus most of eosinophils, plus 43% of large unstained cells. The S Plus IV mononuclear cells are predicted by 5% of the Technicon H6000 lymphocytes plus 41% of monocytes, plus basophils, plus most of the large unstained cells plus 31% of eosinophils.

Evaluation Studies as Topic↗
PubMed1985

Future needs and expected trends in peripheral blood cell analysis: erythrocyte histograms.

Erythrocyte histograms should be analysed in accordance with the ICSH recommended protocol to determine: How many red cell populations are present and the proportion of the total red cells which are included in each population. The central tendency (mode, median & mean) and dispersion (size ratio, geometric standard deviation & coefficient of variation) for each population. The proportion of microcytic or macrocytic cells in each population. Examples are given to show how the patient's diagnosis is assisted by careful analysis of the histograms and the effect of treatment monitored by sequential testing. Histograms can be generated from blood films or from aperture-impedance and light-scatter volume measurements. Volume measurements on these systems are influenced by the red cell shape and internal refractive index. Mean cell hemoglobin concentration affects both shape in the aperture-impedance orifice and internal refractive index in light-scatter systems. There is poor agreement between volume histograms obtained on the two measuring systems and the histograms available on current automated instruments provide no more useful information than can be obtained from the blood film. Automated instruments need to produce histograms with fewer artefacts and the histograms should then be examined in accordance with the ICSH protocol. This approach should maximise the diagnostic value of the complete blood count.

Automation↗
PubMed1984

Individual cells in tissues of DHBV-infected ducks express antigens crossreactive with those on virus surface antigen particles and immature viral cores.

Double immunofluorescence assays of fixed sections of tissues from Pekin ducks congenitally infected with duck hepatitis B virus were carried out to score cells reactive to antiserum elicited either to viral DNA synthesis complexes (immature cores) purified from liver of infected ducks or to viral surface antigen particles and virions purified from sera of viremic ducks. Subpopulations of doubly fluorescent cells were detectable in liver (hepatocytes and bile duct epithelia), in kidney (proximal tubular epithelia), and in pancreas (acinar-associated cells and endocrine alpha and beta cells); all cells reactive with one antiserum were reactive with the second antiserum. Competition assays established that the cell-associated antigens recognized by the two antisera were mutually non-crossreactive. The cell-associated antigen recognized by the antiserum elicited to the purified immature cores appears to be crossreactive with a 35,000-Da polypeptide fraction associated with immature cores.

Animals↗
PubMed1984

Viral antigen in endocrine cells of the pancreatic islets and adrenal cortex of Pekin ducks infected with duck hepatitis B virus.

Endocrine cells in the pancreas and adrenal glands of duck hepatitis B virus-infected ducks were examined for the presence of viral antigen. Analysis of pancreas tissue was based on double immunofluorescence assays in which anti-duck hepatitis B virus serum was used to detect viral antigen, and anti-glucagon and anti-insulin serum were used, respectively, to identify endocrine alpha and beta cells. Assays of pancreas from infected ducks ranging in age from 3 to 20 weeks indicated that subpopulations of both alpha and beta cells expressed viral antigen. A higher percentage of viral antigen-positive cells was observed in alpha-islets than in beta-islets. As assayed by immunofluorescence and immunoperoxidase staining with anti-viral serum, small clusters of viral antigen-positive cells were detected in the adrenal glands of young infected ducks. These cells were identified as cortical cells on the basis of histologic criteria.

Adrenal Cortex↗
PubMed1984

Protocol for evaluation of automated blood cell counters. International Committee for Standardization in Haematology (ICSH).

This protocol is proposed for the evaluation of automated blood cell counters to assess the performance, advantages and limitations of such instruments. It is based on the International Committee for Standardization in Haematology (ICSH) 'Protocol for type testing equipment and apparatus used for haematological analysis' (1978a) and the British Committee for Standardization in Haematology 'Guidelines for the evaluation of instruments used in haematology' (Shinton, England & Kennedy, 1982). The document has been prepared by the ICSH Panel on Cytometry after discussion with colleagues. This tentative protocol will be reviewed 1 year after publication, in accordance with the ICSH rules, before it is adopted as a definitive standard.

Blood Cell Count↗
PubMed1983

Experimental transmission of duck hepatitis B virus.

Susceptibility to experimental infection with duck hepatitis B virus (DHBV) was explored, with the objective of defining procedures that were both rapid and reproducible. For the purpose of these experiments, a small flock of DHBV-free breeders was established as a source of susceptible eggs and ducklings, since ca. 10% of the ducks (all ages) from commercial flocks were DHBV infected. Intravenous inoculation of DHBV into 15-day duck embryos from the DHBV-free flock produced a persistent infection, with a high-titer viremia, in at least 80% of the injected animals. The tissue tropism of DHBV in these experimentally infected animals was similar to that associated with natural, congenital infections from viremic ducks to their progeny. Virus antigen was found not only in hepatocytes and bile duct epithelium of liver, but also in cells associated with exocrine and endocrine pancreas, and in proximal convoluted tubular epithelium of kidney. Infection of embryonic liver was rapid, as evidenced by active synthesis of DHBV-DNA by reverse-transcription of RNA by 24 hr postinjection. During this latter analysis, formation of supercoiled viral DNA appeared to precede the reverse-transcription phase of viral DNA synthesis, suggesting that this species may be important in initiation of infection.

Animals↗
PubMed1983

Viral nucleic acid synthesis and antigen accumulation in pancreas and kidney of Pekin ducks infected with duck hepatitis B virus.

Liver, pancreas, and kidney from Pekin ducks infected with duck hepatitis B virus (DHBV) were assayed for the presence of both viral antigen and replication-specific forms of viral nucleic acid. In young congenitally infected ducks, antigen was detectable in hepatocytes and bile duct epithelia, in kidney glomeruli and tubular epithelia, and in cells localized to pancreatic acini. In older experimentally infected ducks, antigen was detectable in hepatocytes, in glomeruli and tubular epithelia, and in cells localized to presumptive pancreatic alpha-islets. All but the glomeruli-associated viral antigen appeared to be localized to the cytoplasm of antigen-positive cells. Much of the glomeruli-associated antigen appeared to be extracellular and was detected in glomeruli that were positive for the accumulation of immunoglobulin, observations suggestive of the deposition of viral antigen-antibody complexes. As analyzed with bulk tissue, replication-specific forms of viral nucleic acid were detectable in liver and pancreas from the young congenitally infected ducks and in liver and kidney from the older experimentally infected ducks.

Animals↗
PubMed1983

An assessment of the Coulter Counter Models S Plus II and III.

The Coulter Counter Models S Plus II and III have been evaluated. No serious safety hazards were identified. Scientific assessment showed some non-linearity in the Hb which caused the MCH and MCHC to vary as samples were diluted. Precision and carry-over were satisfactory. The results obtained compared well with those of the Coulter Counter Model S, except for WBC; reference methods showed better accuracy on the Models S Plus II and III. Platelet counts agreed with those by phase-contrast microscopy and the lymphocyte percentage was similar to that from the blood film except in the lymphoproliferative disorders. The whole blood and pre-dilute modes gave similar results though the platelet count was slightly higher in the whole blood mode. In the National External Quality Assessment Scheme results were in accordance with those from other Model S Plus Users. Time did not allow a detailed evaluation of the cell volume distribution curves but it was noted that the white cell profile was useful for detecting platelet aggregation. Efficiency assessment showed throughputs of 66 and 93 samples per hour on the Models S Plus II and III respectively. The platelet count was clinically useful as was the lymphocyte percentage measurement which rendered some differentials unnecessary. Rejection of the white cell profile was a helpful index of abnormality on the Model S Plus II but occurred non-specifically on the Model III tested.

Adult↗