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Biomedical subjects

D Barnes

Publications and source records attributed to D Barnes.

At least 127 records · Page 7Linked to original sources
PubMed1992

Visible light-activated glass ionomer cement: use as liners/bases and restoratives.

Traditional glass ionomer cements were sensitive to moisture during the initial state and were subject to dehydration as the material began to harden. Preliminary findings from in vitro studies and clinical trials indicate that a new light activated glass ionomer cement exhibits high shear bond values, reduced microleakage and improved aesthetics.

Dental Cavity Lining↗
PubMed1991

Human and mouse S-protein mRNA detected in northern blot experiments and evidence for the gene encoding S-protein in mammals by Southern blot analysis.

Human S-protein is a serum glycoprotein that binds and inhibits the activated complement complex, mediates coagulation through interaction with antithrombin III and plasminogen activator inhibitor I, and also functions as a cell adhesion protein through interactions with extracellular matrix and cell plasma membranes. A full length cDNA clone for human S-protein was isolated from a lambda gt11 cDNA library of mRNA from the HepG2 hepatocellular carcinoma cell line using mixed oligonucleotide sequences predicted from the amino-terminal amino acid sequence of human S-protein. The cDNA clone in lambda was subcloned into pUC18 for Southern and Northern blot experiments. Hybridization with radiolabeled human S-protein cDNA revealed a single copy gene encoding S-protein in human and mouse genomic DNA. In addition, the S-protein gene was detected in monkey, rat, dog, cow and rabbit genomic DNA. A 1.7 Kb mRNA for S-protein was detected in RNA from human liver and from the PLC/PRF5 human hepatoma cell line. No S-protein mRNA was detected in mRNA from human lung, placenta, or leukocytes or in total RNA from cultured human embryonal rhabdomyosarcoma (RD cell line) or cultured human fibroblasts from embryonic lung (IMR90 cell line) and neonatal foreskin. A 1.6 Kb mRNA for S-protein was detected in mRNA from mouse liver and brain. No S-protein mRNA was detected in mRNA from mouse skeletal muscle, kidney, heart or testis.

Amino Acid Sequence↗
PubMed1991

The effect of chlorpromazine and methylprednisolone on NMR relaxation times in the normal cat brain.

This small experimental study describes the effects on the NMR relaxation times in normal cat brain of a 5-day course of high dose methylprednisolone and, separately, a 1-month course of standard dose daily chlorpromazine. Methylprednisolone had no influence on T1 or T2 in these tissues, but chlorpromazine produced a transient fall of T1 of thalamus, and rise in T2 of white matter: both normalize after 4 weeks. The mechanism of these changes is unknown. It is concluded that these drugs should not interfere with the quantitative MRI monitoring of brain abnormalities in patients receiving them, although the unlikely occurrence of longer term effects of chlorpromazine has not been excluded.

Animals↗
PubMed1991

Karyotypic stability of serum-free mouse embryo (SFME) cells.

Mouse embryo cultures derived in serum-containing medium undergo growth crisis or senescence after fewer than 20 population doublings, followed by the emergence of genetically altered, polyploid 'immortalized' cells capable of growing indefinitely. Serum-free mouse embryo (SFME) cells, derived in medium in which serum is replaced with growth factors and other supplements, do not exhibit growth crisis or gross chromosomal aberrations when cultured for well over 100 population doublings and display other unique properties. We examined culture conditions and physiological factors affecting karyotypic stability in long term cultures of SFME cells derived from several mouse strains. Cloning SFME cells consistently isolated colonies with altered karyotype, even when the clones were derived from parent cultures with no karyotypic alterations. After 140-200 population doublings in vitro, the percentage of SFME cells showing hyperdiploidy or structural chromosomal abnormalities increased, although the modal chromosome number remained diploid. SFME cells transformed with molecularly cloned oncogenes did not show alterations in karyotype beyond that expected from the clonal origins of these cells, indicating that malignant transformation of SFME cells does not result in general karyotypic instability.

Animals↗
PubMed1991

Serum inhibition of proliferation of serum-free mouse embryo cells.

Serum-free mouse embryo (SFME) cells, derived in medium supplemented with insulin, transferrin, high density lipoprotein, epidermal growth factor, and fibronectin, do not undergo crisis, maintain a predominantly diploid karyotype with no detectable chromosomal abnormalities for well over 100 population doublings in vitro, and are growth inhibited by concentrations of serum that are growth-stimulatory for most cell lines in culture. Serum inhibition of SFME cell proliferation was reversible and was not prevented by addition of the supplements of the serum-free medium, even when added repeatedly during the culture period. The serum effect on SFME cell proliferation could be detected after incubation in serum-containing medium for as little as 8 h. SFME cells in serum-containing medium were arrested in the G1 phase of the cell cycle with a greatly reduced rate of incorporation of precursors into DNA and thymidine kinase activity, while a reduction in rate of incorporation of amino acids into protein was not observed. SFME cultures maintained for extended periods in serum-containing medium underwent a crisis-like period followed by the appearance of variant cells capable of growing in serum-supplemented medium. These cells exhibited abnormal karyotype and were resistant to several inhibitors of proliferation active on the parent SFME cell type.

Amino Acids↗
PubMed1991

The longstanding MS lesion. A quantitative MRI and electron microscopic study.

Important questions remain unanswered about the sequence of events leading to progressive and ultimately irreversible tissue damage in MS. This study was designed to investigate the pathological characteristics of, and function of, the blood-brain barrier within longstanding MS lesions using quantitative and Gd-DTPA enhanced MRI techniques. The ultrastructural appearances of postmortem lesions from a single, separate case of MS have been correlated with the MRI findings. Both MRI and ultrastructural analysis revealed considerable heterogeneity in the chronic lesions: some are 'closed' with no detectable extracellular water, but most are 'open' and show expansion of the extracellular space to as much as 87% of tissue area. This variable expansion probably results from differing degrees of axonal loss. Evidence of blood-brain barrier damage was found in only 17% of lesions, was less severe than that seen in acute lesions, and may result from repeated previous inflammatory insults. The findings imply progressive axonal loss in lesions as they age. It is possible that this loss is related to clinical progression of the disease.

Adult↗
PubMed1991

An adult onset hexosaminidase A deficiency syndrome with sensory neuropathy and internuclear ophthalmoplegia.

A 42 year old man presented with a slowly progressive gait disturbance, generalised weakness, dysarthria, clumsiness and tremor of his hands, and involuntary jerks. Hexosaminidase A activity in plasma, leucocytes and fibroblasts was considerably reduced, establishing the diagnosis of GM2 gangliosidosis. Clinical examination showed two previously unreported features, a clinically evident sensory neuropathy and internuclear ophthalmoplegia.

Adult↗
PubMed1991

Toxicity equivalency factors for PCBs?

In December 1990 the U.S. Environmental Protection Agency sponsored a workshop to discuss the applicability of an interim "toxicity equivalency factor" (TEF) approach to assessing risks posed by exposures to complex mixtures of polychlorinated biphenyls (PCBs). The group concluded that application of the TEF approach to PCBs would be less straightforward than it was in the case of chlorinated dibenzo-p-dioxins and dibenzofurans (CDDs/CDFs). It appears that "dioxin"-like properties of some PCB congeners are amenable to a TEF treatment that is compatible with that used for CDDs/CDFs. Such a scheme also seems to have utility in assessing risks to wildlife. Other non-"dioxin"-like toxic endpoints (e.g., neurotoxicity) appear to have a different structure-activity-related mechanism-of-action that requires a separate TEF scheme. The workshop identified data gaps in toxicology and analytical chemistry that hinder adoption of proposed TEF schemes for PCBs at this time.

Benzofurans↗
PubMed1991

Gallium-SPECT in the detection of prosthetic valve endocarditis and aortic ring abscess.

A 52-yr-old man who had a bioprosthetic aortic valve developed Staphylococcus aureus bacteremia. Despite antibiotic therapy he had persistent pyrexia and developed new conduction system disturbances. Echocardiography did not demonstrate vegetations on the valve or an abscess, but gallium scintigraphy using SPECT clearly identified a focus of intense activity in the region of the aortic valve. The presence of valvular vegetations and a septal abscess was confirmed at autopsy. Gallium scintigraphy, using SPECT, provided a useful noninvasive method for the demonstration of endocarditis and the associated valve ring abscess.

Abscess↗
PubMed1991

Oncogene transformation frequency of nonsenescent SFME cells is increased by c-myc.

Immortalized, postcrisis mouse embryo cell cultures derived in serum-containing medium display genomic abnormalities and an altered, preneoplastic phenotype. These lines can be transformed with single oncogenes, such as Ha-ras, while efficient transformation of precrisis, genomically unaltered rodent embryo cultures require cooperating oncogenes, such as Ha-ras and the mouse c-myc gene constitutively expressed. Serum-free mouse embryo (SFME) cells, cultured under conditions in which serum is replaced by growth factors and other supplements, are 'immortalized' in the genomically unaltered state. SFME cells do not exhibit growth crisis or gross chromosomal aberration, and are dependent on epidermal growth factor for survival, growth inhibited by serum, and are nontumorigenic. Transformation of SFME cells can be achieved with ras alone, but the introduction of c-myc increased the transfection frequency upon subsequent transfection with ras by as much as twenty fold. Similar results were obtained with mutationally activated neu oncogene and with genomic human tumor DNA. Constitutive expression of c-myc alone did not alter the properties of the SFME cells. These results demonstrate that c-myc alters cellular responses to oncogenes in a culture system in which oncogene-induced immortalization is not a factor, indicating that the effects of myc may extend beyond an 'immortalization' function in these cells.

Animals↗
PubMed1991

Comparison of epidermal growth factor receptor expression in lung cancer by immunohistochemical staining of both frozen and formalin fixed specimens.

Two monoclonal antibodies used to investigate the expression of the epidermal growth factor receptor (EGF-R) in 45 lung cancers were compared. The R1 antibody recognises the extracellular domain portion of the receptor and the F4 is directed against the cytoplasmic portion. The reactivities of the two antibodies have been compared in fresh frozen tumour specimens. In addition the staining activity of the F4 antibody (the first to EGF-R which can be used in archival material) was compared using frozen and paraffin sections from the same series of tumours. Comparisons of the numbers of cells staining with the R1 and F4 antibody showed only slight discrepancy when fresh material was examined. The discrepancy that existed could be explained by the heterogeneity of the tumours. Very similar results were obtained using the F4 antibody on paraffin embedded and fresh non-small cell lung cancer material. We conclude that the expression EGF-R can be detected reliably by the F4 antibody in both the fresh frozen and formalin fixed, paraffin embedded material and could be useful in assessing the clinical importance of EGF-R in archival tumour material.

Cytological Techniques↗