PubMed Health⌕ Search

Biomedical subjects

M A Atkinson

Publications and source records attributed to M A Atkinson.

100 records · Page 6Linked to original sources
PubMed1983

Intranuclear distribution of herpes simplex virus type 2 DNA synthesis: examination by light and electron microscopy.

Uptake of [3H]thymidine by serum-starved baby hamster kidney cells infected with herpes simplex virus type 2 was investigated by light microscopic and electron microscopic autoradiography. The distribution of incorporated label altered throughout the period of viral DNA synthesis. It was restricted initially to a few well-defined sites within the nucleus which increased in size and spread as infection proceeded until the entire nucleus was involved. The label was not associated with any identifiable subnuclear structure although there was a high degree of association with the nuclear membrane at early times post-infection.

Animals↗
PubMed1982

The polymeric state of actin in the human erythrocyte cytoskeleton.

Reports on the polymeric state of actin in the red cell have been diverse. We have used phalloidin to stabilize the actin in erythrocyte ghosts prior to extraction in low ionic strength media. A mild proteolytic digestion and Sepharose 4B gel filtration enable an F-actin polymer to be isolated in pure form [1]. Detailed size analysis of this polymer in a range of experiments suggests that actin exists in the erythrocyte principally as a polymer of 100 nm length composed of 30 monomers in a double helical chain 15 monomers long with an estimated molecular weight of 1.3 X 10(6) daltons.

Actins↗
PubMed1982

The apparent inducibility of tumour marker glycoproteins in a melanoma cell line selected for growth in low levels of glucose.

It has been reported previously that malignancy in hybrid cells is associated with changes in two glycoproteins of molecular mass 90,000 and 100,000. In the current paper the characteristics of a clonal derivation of a murine melanoma cell line (PG19G-), selected for growth in low levels of glucose, are described. The cells had considerably reduced amounts of the 90 K and 100 K glycoproteins as judged by lectin affinity-labelling. When the level of glucose in the medium is raised the two glycoproteins become detectable after a few hours. This inducibility is specific for D-glucose and D-mannose at concentrations in excess of 300 mg/l and is inhibited by cytochalasin B but not by cytochalasin A. The 90 K glycoprotein differs from the 100 K in that its level varies with the glucose concentration even in the parent cell line PG19 and in other tumour lines. This is not the case for the 100 K glycoprotein, the synthesis and/or glycosylation of these two glycoproteins are, therefore, governed by separate control mechanisms. The relationship of the glucose-sensitive proteins to the glucose transporter is discussed.

Animals↗
PubMed1981

Studies on the surface properties of hybrid cells. III. A membrane glycoprotein found on the surface of a wide range of malignant cells.

We report here the presence of a glycoprotein of apparent molecular mass 90000 daltons on the surface of membranes of malignant cells, which is absent or very much reduced on the surface of non-malignant cells. This glycoprotein is rich in sialic acid and appears to be sensitive to the concentration of cAMP under certain conditions. Analysis of the labelled sugars present in the glycoproteins of cells metabolically labelled with [14C]glucosamine suggests that all the enzymes necessary for the conversion of the tracer precursor into the sugars normally found to be labelled are present in both the malignant and the non-malignant cells.

Animals↗
PubMed1980

Studies on the surface properties of hybrid cells. I. Sialyl-transferase activity in homogenates of malignant and non-malignant cells.

We report here a method for the assay of the sialyl-transferase activity in crude homogenates of a wide range of cell lines growing in tissue culture. Our results indicate that particulate preparations from both malignant and non-malignant cells show a Km of 0.25 mM towards CMP-sialic acid in the presence of an excess of glycoprotein acceptor. There appear to be increased amounts of the enzyme associated with the preparations from malignant sources which are reflected in an increase in the apparent Vmax of these. The elevated level of sialyl-transferase activity seen in the malignant cell populations is, paradoxically, associated with a decrease in the amount of bound sialic acid associated with both the whole cell homogenate preparations and the surface of these cells.

Animals↗
PubMed1980

Studies on the surface properties of hybrid cells. II. Sialyl-transferase activity on the surface of malignant and non-malignant cells.

A measurable surface activity of sialyl-transferase is demonstrated by a number of different methods to exist on the plasma membranes of both malignant and non-malignant cells. The amount of enzyme present on the surface of malignant cells is found to be higher than that on the non-malignant ones in a wide range of malignant and non-malignant cell lines. It is proposed that the difference in apparent activity results in part from the presence of incomplete glycoproteins in the surface membranes of the malignant cells and in part from an increased rate of membrane synthesis in these cells.

Animals↗
PubMed1978

The fine structure of cells infected with temperature-sensitive mutants of herpes simplex virus type 2.

The fine structure of cells infected with the HG 52 strain of herpes simplex virus type 2 and 13 temperature-sensitive mutants derived from it was investigated. In cells infected with the wild-type virus, development of virions appeared to be similar to that described in previous reports. However there were two exceptions to this: (1) capsid envelopment apparently occurred de novo in the nucleus; (2) densely staining vacuolar accumulations were seen, frequently surrounding virus capsids. The 13 temperature-sensitive mutants of the virus were divided into three classes according to the type of capsid, if any, produced in cells infected and maintained at the non-permissive temperature. Class I mutants produced no capsids, Class II mutants produced empty and partial-cored capsids and Class III mutants produced empty, partial- and dense-cored capsids. Cellular alterations were also determined. Membranous tubular structures, previously unreported for herpes simplex virus, were observed in cells infected with Class III mutants and very occasionally with wild-type virus at the non-permissive temperature. Cytoplasmic particles were also found, but could not be correlated with any particular class of mutant.

Capsid↗
PubMed1975

Frog virus 3 replication: electron microscope observations on the terminal stages of infection in chronically infected cell cultures.

An examination of BHK, CEF, and FHM cells chronically infected with frog virus 3 has been made by scanning and transmission (thin section, freeze fracture, and surface replica) electron microscopy. With minor differences the pattern of virus development is similar in all three cell line. Virus particles were detected in cell nuclei which subsequently became degenerate very late in infection. Three inclusions were associated with frog virus 3 cytoplasmic foci of infection; lamella structures, extensive microtubule formation (in BHK and FHM cells), and linear crystalline structures. The last two structures may play a role in creating or maintaining the cell rounding c.p.e. revealed by scanning electron microscopy. Very late in infection most BHK and FHM, but not CEF, cells are stripped of the plasma membrane. Replicas of frozen fractured BHK cells featured cytoplasmic foci of infection, budding at the plasma membrane, and showed that at early times when virus is detected in the nucleus, the nuclear membranes are intact and morphologically unaltered. Budding at the plasma membrane was better resolved by scanning and as surface replicas. This demonstrated that sparse to profuse localized budding occurred. Frequently virus particles were located singly, or as multiples, at the end of, or along, cytoplasmic protrusions which occur both on the body of the cells and at the cytoplasmic/coverslip 'interface'.

Animals↗