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Biomedical subjects

A J Morgan

Publications and source records attributed to A J Morgan.

At least 109 records · Page 6Linked to original sources
PubMed1982

The accumulation and intracellular compartmentation of cadmium, lead, zinc and calcium in two earthworm species (Dendrobaena rubida and Lumbricus rubellus) living in highly contaminated soil.

The earthworm Lumbricus rubellus contained more Ca and Zn, and less Pb and Cd, than Dendrobaena rubida living in the same contaminated disused-mine soil. Differences in the kinetics of Ca turnover may account for some of the inter-specific differences in heavy metal burdens, although the calciferous glands do not seem to be directly involved in heavy metal excretion. A comparison of the present findings with published data indicated that the concentration of soil Ca and the bioavailability of heavy metals, both factors being allied to soil pH, are important exogenous determinants of heavy metal accumulation by different earthworm populations. Electron microprobe X-ray analysis of air-dried smears of chloragogenous tissue showed that the metals were fairly specifically compartmentalized into two distinct organelles in both worms: Ca, Pb and Zn were found (associated with P) in the chloragosomes; Cd was found (with S and probably in stoichiometric association) in a more electron-lucent vesicular component, designated the 'cadmosome', but which may be identical with the debris vesicles which are characteristic inclusions in conventionally-fixed chloragocytes. The in vivo incorporation of Pb by the chloragosomes of D. rubida was accompanied by the loss of Ca, Zn and P.

Animals↗
PubMed1982

Quantification of an Epstein-Barr virus-associated membrane antigen component.

A method is described for the preparation of a 125I-labelled membrane antigen (MA) component (gp340) from B95-8 cell membranes using sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). Good yields of antigenic material were obtained when renaturation of the [125I]gp340 was carried out by removal of SDS in the presence of urea and subsequent removal of the urea. The availability of purified, radiolabelled gp340 has provided the essential basis for the development of a radioimmunoassay which, for the first time, permits quantification of this antigen. The assay has been used to demonstrate that cell membrane MA is a better source of gp340 for large-scale work than is the Epstein-Barr virus envelope and to measure the increase in expression of gp340 following treatment of cells with 12-O-tetradecanoyl-phorbol-13-acetate (TPA).

Animals↗
PubMed1982

Purified Epstein-Barr virus Mr 340,000 glycoprotein induces potent virus-neutralizing antibodies when incorporated in liposomes.

The purified Mr 340,000 glycoprotein component of Epstein-Barr (EB) virus-induced membrane antigen complex incorporated into liposomes was shown to be a potent immunogen in mice. High-titer antisera were induced that (i) are specific for membrane antigen components without absorption, (ii) bind the antigens induced by three different EB virus isolates, and (iii) neutralize the ability of the virus to transform fetal cord blood lymphocytes in vitro. The development of this immunogenic form of purified antigen provides an important step towards a potential subunit vaccine against Epstein-Barr virus infection.

Antibodies, Viral↗
PubMed1981

A morphological and electron-microprobe study of the inorganic composition of the mineralized secretory products of the calciferous gland and chloragogenous.

The two pairs of lobes of the calciferous gland if the earthworm Lumbricus terrestris are specialized oesophageal diverticulae that secrete spherites ranging from 0.5 - 7.0 micrometers in diameter. Correlative transmission and scanning electron microscopy indicated that the spherites (which are predominantly CaCO3) are formed extracellularly in distinctive bays bounded by secretory-cell processes, and are mobilized anteriorly from the gland lumina to the lumen of a non-secretory pouch, where the majority coalesce and undergo phase transformation to concretions 0.5 - 1.0 mm in diameter consisting of a mass of cuboidal crystals with facets up to 40 micrometers. The distribution of Sr(0.1 ml 5% SrCl2 injected into the posterior coelomic cavity) was monitored in the mineralized secretory products of the calciferous glands by X-ray microanalysis of 10 micrometers - thick air-dried cryostat sections in a SEM. Strontium was not detected in chloragosomes at 2h and 24h post-injection. Strontium was transported anteriorly and specifically incorporated into gland spherites (detectable within 2h). This technique of Sr localization afforded sufficient structural and analytical resolutions to provide a confirmation of the sequence of extracellular changes in the gland/pouch system. In addition we were able to distinguish a population of growing spherites from the vast majority of mature spherites; size alone was a singularly poor indication of spherite growth. The major element constituents of the chloragosomes were P, Ca and Zn (Ca: P ranging from 0.4 to 1.0; Zn: P from about 0.05 to 0.45). Analysis of individual spherites showed that Ca was probably bound to P or P-containing matrix components, whilst Zn was probably linked to one or more different but unknown constituents.

Animals↗
PubMed1981

Antigenic differences between the membrane antigen polypeptides determined by different EB virus isolates.

The antigenic specificities of the membrane antigen (MA) complex of three Epstein-Barr (EB) virus-producing cell lines have been compared by complete absorption of an anti-MA antiserum with P3HR-1 cells, followed by testing for residual anti-MA antibody activity against B95-8 and QIMR-WIL cells. Indirect membrane immunofluorescence showed that the absorbed serum, which had lost the capacity to bind P3HR-1 cells, nevertheless gave bright staining on a small proportion of B95-8 cells. SDS-polyacrylamide gel electrophoretic analysis of 125I-labelled MA polypeptides showed that the absorbed serum was able to isolate MA polypeptides from both B95-7 and QIMR-WIL cells, but not from P3HR-2 cells. The results demonstrate that there is substantial sharing of antigenic specificities between the MA determined by three isolates of EB virus, and some antigenic divergence.

Animals↗
PubMed1980

Observations on the EB virus envelope and virus-determined membrane antigen (MA) polypeptides.

Experiments have been carried out to identify the polypeptide components of the Epstein-Barr (EB) virus-determined membrane antigen (MA) complex. Cells were radioiodinated using lactoperoxidase and the 125I-labelled surface antigens, released by Triton X100, were analysed by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) after complexing either with human sera having anti-MA activity or with a rabbit antiserum to EB virus. Using cells carrying EB virus isolated from four different conditions, including for the first time nasopharyngeal carcinoma (NPC), we have demonstrated four major polypeptides. One, with a molecular weight of 85,000, was remarkedly constant irrespective of the cell line from which it came; two, with molecular weights varying from 240,000 to 270,000 and from 320,000 to 340,000, showed minor differences in mobility apparently depending on the species of origin of the cells (human or marmoset), rather than disparity between strains of virus. A fourth component, of 160,000 daltons, was found on only two of the cell lines studied. In addition, it has been shown for the first time that the same polypeptides composing the MA complex are present on the viral envelope itself. The fact that the rabbit antiserum to EV virus recognized only the two highest molecular weight MA components, yet showed virus-neutralizing activity, indicates the importance of these two polypeptides for use in a vaccine designed to induce virus-neutralizing antibodies.

Animals↗
PubMed1979

Non-freezing techniques of preparing biological specimens for electron microprobe X-ray microanalysis.

In this paper a review is presented of the many ways the fluids involved in conventional wet chemical E.M. preparative techniques (including precipitation procedures) disturb the in vivo chemical integrity of biological tissues. The artifacts discussed are: (i) bulk element loss, (ii) phase transformations in mineralized tissues, (iii) redistribution of endogenous tissue elements; (iv) introduction of extraneous elements. Finally, the range of biological applications to which wet chemical methods have been successfully applied by various authors is briefly discussed to provide a realistic working perspective. It is stressed that in most of these applications the authors restrict themselves to a comparison of the chemistry of cells or their constituent organelle systems and do not attempt to define the in vivo chemical composition of cells. The author concludes that since all preparative procedures available to the microprobe analyst suffer from some form of restrictive compromise, it may not be advisable to think of a general microprobe preparative technique but, alternatively to apply different preparative techniques according to the specific biological answers sought.

Animals↗
PubMed1976

Effect of a lathyrogen (aminoacetonitrile hydrochloride) on aortic physiosclerosis and skeletal mineralization in growing rats of different age.

In one experiment, four groups of six-week-old-male PVG rats were, respectively, given tap water ('control group'), 0.00125M, 0.0025M, and 0.005M lathyrogen (aminoacetonitrile hydrochloride: AAN) solutions ad libitum for a period of 20 weeks. In a second experiment, 12-week-old male rats were similarly treated. It was found that the younger rats were far more susceptible to lathyrogenic influences than the older rats. For example, the rate of aortic physiosclerosis was significantly retarded in the six-week-old rats at dosages of 0.00125M and 0.0025M (the six-week-old rats exposed to 0.005M AAN were eliminated from the experiment before its completion), whilst physiosclerosis was unaffected even in those 12-week-old rats exposed to 0.005M AAN. The degree of mineralization of the femur (as reflected by its ash, Ca, Mg, Na, and K content) was retarded in approximately dose-dependent fashion in the rats of both ages, the effect being somewhat more pronounced in the younger animals. These results were discussed in the context of the known effects of lathyrogenic compounds on the biochemical maturation of connective tissue components, and also in the context of previous attempts to modify the lifespan of laboratory animals by lathyrogen administration.

Acetonitriles↗
PubMed1976

The application of x-ray analysis in the transmission electron analytical microscope (T.E.A.M.) to the quantitative bulk analysis of biological microsamples.

This paper describes: (a)methods for the high and low temperature ashing of biological tissue samples about 10(-4)-10(-5) g in weight; (b)a method of spraying the solubilized ash on to specimen grids which produces droplets of a size convenient for their quantitative analysis in a transmission electron analytical microscope (T.E.A.M.), but without the need to know the actual volume of individual droplets; (c)the construction of standard curves for determining the absolute concentration of Na, Mg, P, S, K, and Ca simultaneously in a given sample. For most of the elements the error in analysis was about 5% or less. It was proposed that the technique is useful for detecting local element-compartments in complex tissues, and thus may be an important aid in the interpretation of the results of point analyses performed on sections taken from adjacent micro-volumes.

Calcium↗
PubMed1975

Influence of age and sex on the calcification of rat aorta in relation to bone mineralization.

Thoracic aortas of pvg rats accumulated Ca (analysed by flame spectrophotometry) throughout mature life, with females having slightly higher levels than males at each age interval studied. Femur Ca concentration was similarly elevated in female rats, and was maintained fairly constant in both sexes after 19 weeks of age. Femur Mg and K levels showed an over-all decrease with age; whilst the Na concentration fell up to 19 weeks, and then decreased steadily. It was concluded that a simple shift of Ca from the ageing skeleton into soft tissues cannot adequately account for aortic physiosclerosis.

Age Factors↗
PubMed1975

Age changes in some inorganic constituents of bone and aorta: a comparative study in wild-trapped and laboratory mice (Mus).

Age changes in tibia Ca, Mg, Na and K concentrations in wild populations of house mice trapped on the islands of Skokholm and May were compared with the changes monitored in a laboratory-bred strain of Skokholm mice, and in Tuck albino mice. Strain differences were recorded in the temporal changes of Ca, Mg and Na--the wild-trapped Skokholm population having a particularly characteristic alteration in tibial chemistry. Strain differences in bone-electrolytes were attributed predominantly to fundamental genetic differences between populations. Tibia Na and K levels were far more variable than the Ca and Mg levels in all four strains. Electrolyte variability was greater in the wild populations than in laboratory populations. Some thoracic aortas taken from female mice trapped on Skokholm were highly calcified, due possibly to gross arteriosclerosis produced by the endocrine events of reproduction. Elevated calcium levels were not detected in male aortas taken from the wild; neither were the aortas of male and female laboratory-bred Skokholm mice subject to gross calcification.

Aging↗