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Biomedical subjects

A J Morgan

Publications and source records attributed to A J Morgan.

114 records · Page 7Linked to original sources
PubMedDate not supplied

Subcellular distribution of cadmium and its cellular ligands in mussel digestive gland cells as revealed by combined autometallography and X-ray microprobe analysis.

Autometallography (AMG) and electron probe X-ray microanalysis (EPXMA) were applied in combination to determine the subcellular distribution of Cd and its subcellular ligands in the digestive gland cells of Cd-exposed mussels Mytilus galloprovincialis. Black silver deposits (BSD), which reveal the presence of metals when AMG is applied, were only localized in digestive cell lysosomes. Digestive cell cytoplasm and basophilic cells were devoid of BSD. EPXMA (static probe and X-ray mapping) indicated that Cd, S (possibly associated with metallothioneins or metallothionein-like proteins) and autometallographical Ag ions are co-localized within digestive cell lysosomes. In addition, Cd and S co-occur in the absence of Ag in the cytosol of digestive cells. AMG does not reveal the presence of the Cd 'pool' strongly bound to cytosolic Cd-metallothionein complexes; only 'free' Cd or Cd supposedly loosely bound to (semi)digested metallothionein within lysosomes was revealed. The levels of lysosomal Cd were indirectly quantified by stereology as the volume density of BSD (V(v)BSD). Significantly higher values were recorded in Cd-exposed mussels compared with controls at all exposure times. However, V(v)BSD values were lower at days 7 and 21 than at day 1. This relative decrease in V(v)BSD reflected another (and confounding) response elicited by Cd-exposure in the digestive epithelium: the volume density of basophilic cells (V(v)BAS) increased significantly as exposure progressed. Due to this cell-type replacement, the net accumulative capacity of the digestive epithelium decreases at long exposure times.

Animals↗
PubMedDate not supplied

Protection of cottontop tamarins against Epstein-Barr virus-induced malignant lymphoma by a prototype subunit vaccine.

Epstein-Barr (EB) virus is one of the five herpesviruses of man. Strong links between this agent and the chain of events causing two human cancers, endemic Burkitt's lymphoma and undifferentiated nasopharyngeal carcinoma, have long been evident (reviewed in ref. 1). Because of this, and because of the very high incidence of nasopharyngeal carcinoma in certain large populations, it was suggested in 1976 that a vaccine should be developed against EB virus to prevent infection and thereby reduce tumour incidence amongst those at risk. The virus-determined membrane antigen (MA) was proposed as immunogen because it was known to elicit naturally occurring virus-neutralizing antibodies in man and because analogous antigens had been shown to act as effective experimental vaccines for preventing the herpesvirus-induced lymphomas of Marek's disease in chickens. Progress has been achieved in defining, quantifying and preparing MA molecules, and in enhancing their immunogenicity; a sensitive assay for antibodies to MA has been elaborated. Here we report that isolated cell membranes expressing MA, or purified MA glycoprotein of relative molecular mass (Mr) 340,000 (gp340), have been used to vaccinate cottontop tamarins (Saguinus oedipus oedipus), and that animals receiving either preparation were protected against the effects of a 100% tumour-inducing challenge dose of EB virus.

Animals↗
PubMedDate not supplied

Developing a new method for soil pollution monitoring using molecular genetic biomarkers.

Physiological responses to environmental stressors may induce changes in gene expression as part of an organism's homeostatic mechanisms. Thus molecular genetic biomarkers have the potential to be used for monitoring sublethal chemical exposure in ecosystems. This paper describes a methodological assessment of the suitability of a protocol to monitor selected biomarkers. The TaqMan real-time quantitative polymerase chain reaction was used to measure gene transcription in earthworms (Lumbricus rubellus) maintained on control or cadmium- or copper-spiked soil. Changes in the expression of two target genes, that encoding metallothionein isoform 2 (MT-2) and that encoding the mitochondrial large ribosomal subunit (MLRS), were quantified against the internal control gene beta-actin. The protocol used produced reliable and reproducible results. Transcript levels displayed qualitative and quantitative differences in the responses to the two metal ions. MLRS gene levels were unaffected by exposure to cadmium but displayed a response to high levels of copper. Conversely, cadmium greatly induced MT-2 gene expression, but copper only altered transcription of this gene at high exposure concentrations. This study demonstrates that it is now technically feasible to use gene expression as an index of pollution exposure in environmentally relevant organisms.

Adaptation, Physiological↗