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Biomedical subjects

J M England

Publications and source records attributed to J M England.

At least 19 recordsLinked to original sources
PubMed1992

Major histocompatibility (B) complex control of the growth pattern of v-src DNA-induced primary tumors.

Observations that the major histocompatibility (B) complex is a determinant of the growth pattern of Rous sarcoma virus (RSV)-induced tumors raised the question as to whether control is exerted at the level of a v-src-determined, i.e., transformation-specific, function. To investigate this point, the tumor size scores and tumor profile indices of v-src-induced tumors were compared in two lines of chickens congenic for B complex genotypes. The finding that the growth patterns of tumors, induced by v-src DNA inoculation at 6 weeks posthatch, differ in these two lines establishes that the B complex exerts control over tumor growth at the level of a v-src-determined function. The potential importance of this control, in terms of the naturally occurring case of an avian sarcoma virus infection, is suggested by the observation that the patterns of tumor growth in a given congenic line are similar whether the tumors are induced by v-src DNA or by RSV.

Animals↗
PubMed1992

A comparison of differential white cell counting on the Coulter VCS and the Technicon H1 using simple and multiple regression analysis.

This study uses the statistical methods of simple and multiple regression to compare the differential white blood count on the Coulter VCS and Technicon H1 analysers. The results demonstrate that both are good at distinguishing lymphocytes, neutrophils and eosinophils. Monocyte differential counts show disappointing correlation, both by simple and multiple regression techniques. Basophils, though less frequently a clinical problem, also correlated poorly in this study.

Basophils↗
PubMed1992

The selection of laboratory equipment.

The last few years have seen dramatic changes in laboratory haematology. Technological developments with increasing levels of automation have resulted in a plethora of new instruments. The choice of which to buy, often confused by conflicting advice and persuasive salesmanship, must be balanced by the need for cost containment. This calls for an understanding of the principles of selection to ensure that the system that is chosen will provide reliable results in the most efficient manner at the lowest possible cost. Most of the instruments which are currently available perform their intended tasks reasonably well albeit with some inter-instrument differences, usually due to different operating procedures and different methods of calibration. The task is to find a system that performs the required tests correctly and reliably, fits into the work requirements of the laboratory and is accepted by the staff who will operate it, whilst its cost both capital and recurrent, should be within the department's financial constraints. The selection of laboratory equipment is thus a complex and time consuming task.

Cost-Benefit Analysis↗
PubMed1992

Rapid resolution of duck hepatitis B virus infections occurs after massive hepatocellular involvement.

A study was carried out to determine some of the factors that might distinguish transient from chronic hepadnavirus infection. First, to better characterize chronic infection, Pekin ducks, congenitally infected with the duck hepatitis B virus (DHBV), were used to assess age-dependent variations in viremia, percentage of DHBV-infected hepatocytes, and average levels of DNA replication intermediates in the cytoplasm and of covalently closed circular DNA in the nuclei of infected hepatocytes. Levels of viremia and viral DNA were found to peak at about the time of hatching but persisted at relatively constant levels in chronically infected birds up to 2 years of age. The percentage of infected hepatocytes was also constant, with DHBV replication in virtually 100% of hepatocytes in all birds. Next, we found that adolescent ducks inoculated intravenously with a large dose of DHBV also developed massive infection of hepatocytes with an early but low-level viremia, followed by rapid development of a neutralizing antibody response. No obvious quantitative or qualitative differences between transiently and chronically infected liver tissue were detected in the intracellular markers of viral replication examined. However, in the adolescent duck experiment, DHBV infection was rapidly cleared from the liver even when up to 80% of hepatocytes were initially infected. In all of these ducks, clearance of infection was accompanied by only a mild hepatitis, with no evidence that massive cell death contributed to the clearance. This finding suggested that mechanisms in addition to immune-mediated destruction of hepatocytes might make major contributions to clearance of infections, including physiological turnover of hepatocytes in the presence of a neutralizing antibody response and/or spontaneous loss of the capacity of hepatocytes to support virus replication.

Age Factors↗
PubMed1992

Etoposide treatment suppresses atherosclerotic plaque development in cholesterol-fed rabbits.

To study the mechanisms by which monocytes/macrophages and smooth muscle cells contribute to atherosclerotic lesions, we studied atherosclerotic plaque formation in cholesterol-fed rabbits treated with etoposide, a drug that has been shown to have several effects that could interfere with the proposed interactions between these two cell types (M.W. Aarnoudes et al, Virchows Arch B 1984;47:211-216 and M. Rozencweig et al, Cancer 1977;40:334-342). Our results show that long-term etoposide treatment of New Zealand White rabbits maintained on a high-cholesterol diet decreases the extent of fatty streak formation in the aortic intima. Moreover, the plaques formed in the presence of etoposide are thinner and at least focally have less fibrous tissue and fewer smooth muscle cell-derived foam cells than do plaques in control rabbits. These effects are independent of the extent of the diet-induced hyperlipemia or an effect of etoposide on blood cell count and may be related to the inhibition of intimal cell proliferation by etoposide.

Animals↗
PubMed1991

Regression of v-src DNA-induced sarcomas is under host genetic control.

Previous results have established that subcutaneous inoculation of chickens (line SC) with a v-src(+) subviral DNA fragment induces the formation of progressor sarcomas at the wing web site of inoculation. Because the sarcoma cells are incompetent for production of exogenous progeny virus, this system is a useful model of tumor expansion by sarcoma cell division, in the absence of infection-mediated recruitment of new tumor cells. The present study was undertaken to define conditions that modulate the pattern of growth (regression vs progression) of v-src DNA-induced sarcomas. These conditions were found to include the line of chicken or the presence on the subviral v-src(+) DNA fragment of a viral replication-specific sequence that includes env.

Animals↗
PubMed1991

Induction of a diffuse mesothelioma in chickens by intraperitoneal inoculation of v-src DNA.

The presence of peritoneum-based, cytokeratin-positive tumor cells, as detected under conditions of intravenous inoculation of chickens with a v-src-positive DNA fragment, raised the possibility that such DNA may be inductive for diffuse mesothelioma. To investigate this possibility, chickens were inoculated intraperitoneally with v-src DNA, and the resultant peritoneum-based tumor tissue was subjected to histopathological analysis. On the basis of (i) morphology, (ii) immunohistochemistry/histochemistry, and (iii) ultrastructure, we concluded that this tissue represents a diffuse mesothelioma.

Animals↗
PubMed1991

Tumor immunity generated in the course of regression of v-src-induced sarcomas.

Previous studies have indicated that the regression versus progression of v-src-DNA-induced sarcomas is dependent on chicken line. As a first step in analyzing the role of tumor immunity as a determinant of this line dependence, experiments were undertaken to ascertain whether an antisarcoma immune response is generated in the course of sarcoma growth in TK chickens, a regressor line. To assay for this response, test TK chickens in which v-src-induced wing web sarcomas had regressed, as well as control TK chickens that had not been exposed to v-src, were challenged in protocols known to yield v-src-dependent sarcoma formation and monitored for challenge sarcoma growth. Compared with the control chickens, the test chickens showed a significant resistance to the sarcomagenic challenge. These results raise the possibility that the antisarcoma response that is inducible in regressor lines, as demonstrated here in terms of a protective effect against a subsequent sarcomagenic challenge, may also underlie the regression of v-src-induced primary sarcomas.

Animals↗
PubMed1990

Wing web or intravenous inoculation of chickens with v-src DNA induces visceral sarcomas.

We have previously found that sarcomas localized to visceral organs frequently arise following wing web inoculation of Rous sarcoma virus. This observation prompted an investigation of whether visceral sarcomas are also inducible by wing web inoculation of a subgenomic viral DNA fragment (v-src DNA) that includes v-src but lacks genes encoding viral structural protein. For this analysis, line SC chickens were inoculated with v-src DNA at 1-2 days posthatch and monitored for 9 weeks. Ninety percent of the chickens developed wing web (primary) tumors at the site of inoculation and, of these, about 30% exhibited visceral tumors. All tumors were histologically identifiable as sarcomas, and both the primary and visceral sarcoma cells were specifically reactive with two monoclonal antibodies elicited to different peptide fragments of pp60v-src. In a separate set of experiments, visceral sarcomas were also observed in about half of the line SC chickens that had been inoculated intravenously with v-src DNA. These results indicate that exogenous progeny virus production is not required for v-src-induced, visceral sarcoma formation. In addition, they demonstrate that intravenous inoculation of v-src DNA is a means to achieve rapid and widespread, disseminated sarcoma growth.

Animals↗
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↗