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Biomedical subjects

G Hewlett

Publications and source records attributed to G Hewlett.

At least 19 recordsLinked to original sources
PubMed2002

DNA from bovine papillomavirus type 2 induces warts in a xenograft model.

Bovine papillomavirus (BPV) type 2 DNA was inoculated into calf scrotal skin before grafting onto severe combined immunodeficient mice. Inoculation with viral DNA isolated from a bovine wart induced fibropapillomas that exhibited all the morphological features of a BPV infection in cattle. The production of capsid protein and infectious BPV2 particles was demonstrated by immunohistochemistry and a transformed cell focus assay. In contrast, the injection of molecularly cloned viral genomic DNA led to the induction of papilloma-like lesions in the epidermis, but a fibroma was not formed. In addition, only early genes were expressed and infectious virus particles could not be detected. A restriction enzyme accessibility assay suggested that the methylation status of the molecularly cloned BPV2 DNA was different from that of native viral DNA. A possible correlation between methylation status and tumour phenotype is discussed.

Animals↗
PubMed2001

Effectiveness of changes in the delivery of diabetes care in a rural community.

Diabetes has a significant impact upon health in rural Maori communities. A diabetes club was established to support self-care and improve diabetes management in a rural community in Northland, New Zealand. A structured approach to care and an associated audit were also introduced. Patient involvement and ownership of the condition were considered important issues. Monitoring of care processes increased by 79%. The first year of audit was associated with a reduction in mean fructosamine from 369 +/- 85 micromol L-1 to 321 +/- 65 micromol L-1 and this was sustained for a further 3 years. The number of people using insulin increased from 15 to 22%. The audit process facilitated the implementation of changes in the delivery of care. We conclude that the data indicate that the enthusiastic delivery of care in general practice, with a devolution of power to the patient, linked to an audit service can result in improved management among patients with Type 2 diabetes.

Community Participation↗
PubMed2001

Xenograft model for identifying chemotherapeutic agents against papillomaviruses.

The report describes the establishment and characterization of a mouse xenograft transplantation model for the study of papillomavirus infection of bovine skin. Calf scrotal skin was inoculated with bovine papillomavirus type 2 before grafting it to the dorsum of severe combined immunodeficient mice. The grafted skin contained epidermis, dermis, and a thin layer of fat. After 5 months the induced warts not only showed histological features of papillomavirus infections but also tested positive for viral DNA and papillomavirus capsid antigen. The formation of infectious virions was demonstrated by inoculation of new transplants with crude extract from the induced warts as well as in a cell culture focus assay. Topical application of bromovinyl-2'-deoxyuridine led to a reduction in viral DNA content in the developing wart. This small-animal xenograft model should be useful for characterizing antiviral compounds and providing an understanding of the regulation of papillomavirus infections.

Animals↗
PubMed1991

Ciprofloxacin enhances T cell function by modulating interleukin activities.

Ciprofloxacin (CIP) is a quinolone carboxylic acid derivative with a broad spectrum of antibacterial activity. CIP (0.1-30 micrograms/ml) enhanced DNA synthesis of mouse spleen cells and human peripheral blood lymphocytes (PBL) that had been activated with T cell mitogens or with alloantigens. In addition, CIP increased the amount of IL-2 found in the supernatants of phytohaemagglutinin (PHA)-stimulated human PBL. The presence of CIP in the medium (0.3-10 micrograms/ml) increased the levels of IL-1 found in the culture supernatants of adherence-enriched mouse macrophages, human monocyte/macrophages and a human monocytic cell line stimulated with lipopolysaccharide. In contrast there was no effect of CIP on the release of IL-1 by freshly isolated human monocytes or by cells of the keratinocyte line, A431. CIP alone had no influence on the basal release of IL-2 by NOB-1 cells, a T cell line that responds to IL-1 with an increase in IL-2 synthesis, but, in combination with recombinant IL-1, CIP significantly enhanced the release of IL-2 by these cells. The results of this study suggest that CIP modulates the immune response at two levels--the production of IL-2 by activated T cells and the production of IL-1 by activated monocyte/macrophages. However, CIP did not affect the primary antibody response in vitro or in vivo against sheep erythrocytes and ovalbumin respectively. Thus the enhancing action of ciprofloxacin on the immune system appears to be restricted to T cell function and macrophage/T cell interactions.

Animals↗
PubMed1989

A method for the quantitation of interleukin-2 activity.

A bioassay for the determination of interleukin-2 activity is described. We have compared the traditional method of data processing, which involves probit analysis and curve fitting, with a simpler method based on the so-called AUC (area under the curve). The latter method is readily applicable to spreadsheet software and can handle large amounts of data.

Animals↗
PubMed1988

Inhibition of HIV and virus replication by polysulphated polyxylan: HOE/BAY 946, a new antiviral compound.

Xylanpoly-(hydrogen sulphate) disodium salt with a molecular weight of about 6000 daltons (HOE/BAY 946) completely inhibited syncytium formation induced by the infection of T lymphocytes with HIV as well as viral replication at concentrations above 25 micrograms/ml. This dose was found to be inhibitory for several strains of HIV-1 and HIV-2. Low molecular weight fractions of the compound were less active against HIV, and high molecular derivatives were as active as HOE/BAY 946. A direct influence of the drug on the infectivity of the virus could not be demonstrated. The drug inhibited the reverse transcriptase of HIV. Treatment of permanently HIV-infected U937 cells resulted in a drastic reduction of virus particles released into the supernatant and points to an additional mode of action. A therapeutic effect of HOE/BAY 946 against retroviruses in vivo could be demonstrated in Friend leukaemia virus-infected mice. A clinical pilot study with the compound was started recently in Germany with AIDS patients who did not tolerate or refused to take zidovudine and with asymptomatic virus carriers.

Animals↗
PubMed1987

Cultivation of Bowes melanoma cells in the Opticell system: influence of the addition of protein supplements to the serum-free medium on the production of plasminogen activator.

The influence of a protein-free and a protein-rich, supplemented serum-free medium on the production of plasminogen activator (t-PA) from Bowes melanoma cells was investigated in the Opticell culture system and compared to tissue culture flask cultures. In the presence of medium supplements metabolic activity and t-PA production were favoured in both systems. The addition of supplements was apparently more effective in the Opticell than in flask cultures, because t-PA activity obtained in the Opticell was 2-3 times higher in protein-rich medium, but 2 times lower in unsupplemented medium than in flasks. These results indicate that the protein content in a serum-free medium is important for product formation in the Opticell, and serum-free media which work at small scale in tissue culture flasks are not always suited for technical culture systems such as the Opticell but have to be adapted to them.

Biotechnology↗
PubMed1987

Production of human monoclonal antibodies from immobilized cells in the Opticell culture system.

An EBV-transformed human B cell line, which produces monoclonal IgM antibodies, was cultured in an immobilized state on a ceramic matrix in the Opticell system. Cell growth, metabolic activity and product formation of these cells were optimized in a single semi-continuous culture of 10 inductions for 29 d. All in all, 19.5 g of IgM were harvested in 193 l of culture supernatant. The average production of IgM in the Opticell unit of 20 l was 0.7 g/d which was obtained even in serum-reduced medium (1%). Under optimal conditions IgM yields were enhanced to 1.5-2.0 g/d. These results indicate that the Opticell is a suitable system for the large scale production of monoclonal antibodies, particularly because the capacity for aeration and pumping of one Opticell unit is sufficient to control 3 growth chambers running in parallel.

Antibodies, Monoclonal↗
PubMed1985

A screening method to develop serum-free culture media for adherent cell lines.

A screening method was established to develop chemically defined, serum-free culture media for human adherent cell lines. It indicates within 2-6 months whether a certain cell line is suited for routine cultivation under serum-free conditions, and which medium supplements and surface coatings of the culture vessels the cells need for minimal demand. This method was tested with the human cell lines Bowes melanoma and prostate carcinoma 3 (PC 3).

Cell Adhesion↗
PubMed1982

A new model for investigations of T-cell functions in mice: differential immunosuppressive effects of two monoclonal anti-Thy-1.2 antibodies.

Two monoclonal anti-Thy-1.2 antibodies were investigated for their activity in eliminating T cells in vitro and in vivo. Both antibodies exert a complement-dependent cell cytotoxicity in vitro. Antibody B that belongs to the IgM class shows a 100-fold higher complement-dependent cytotoxic activity than antibody C, which is of IgG2a class. However, administration of antibody C into Balb/c mice results in the elimination of T cells as determined by the failure of different T-cell functions. Within 24 hours after administration of antibody C, the reactivity of spleen of lymph-node cells to T-cell mitogens, the antibody response to the T-cell-dependent antigen SRBC and the SRBC-induced delayed-type hypersensitivity are completely abolished. These effects are dose-dependent in a dose range of 0.1-1.0 mg Ig protein per animal and affects only T cells in the peripheral lymphoid organs. The Thy-1.2-bearing cells residing in the thymus are not impaired by the treatment of the animals with this monoclonal antibody and are able to repopulate the peripheral lymphoid organs within 30 to 60 days. Investigations into the mode of action of the removal of peripheral T cells revealed that antibody-C-coated Thy-1.2-bearing cells are rapidly phagocytosed by macrophages, while antibody-B-coated Thy-1.2-bearing cells are not. This might be the reason for the differential in-vivo activities of the two monoclonal antibodies. A model with new qualities for the study of functions and the regeneration of T cells in vivo has been established.

Animals↗
PubMed1979

Stress management.

Explore the source record for details and available documents.

Group Processes↗
PubMed1979

Macrophages/monocytes require cell-to-cell contact in order to regulate the growth of a murine lymphoma cell line.

The mechanism of the macrophage-regulated proliferation of the murine lymphoma cell line FIO 30 has been further investigated. It appears that the macrophage is alone in its ability to support FIO 30 growth; a macrophage-like cell line, however, is unable to provide the stimulus required by the FIO 30 cells for their proliferation. Investigations into the nature of this stimulus indicate that the serum factor pro-MaSF and a macrophage cell surface component act synergistically to support the growth of the FIO 30 cell, but only when the two cell types are in close promixity. MaSF has also been further characterized and is shown to be closely associated with serum albumin.

Animals↗
PubMed1977

The role of fetal calf serum in the primary immune response in vitro.

The mode of action of 2-mercaptoethanol (2-ME) on the primary immune response in vitro was investigated. Fetal calf serum (FCS) was preincubated with 2-ME and lyophilized to remove free 2-ME. This 2-ME-treated FCS was able to substitute the function of adherent cells in the primary immune response against sheep red blood cells (SRBC) in vitro; Fractionation of 2-tme-treated FCS on a Sephadex G-100 column showed that 2-ME acted on a high molecular serum component which after activation, could substitute for macrophages. In order to obtain a humoral immune response against SRBC in vitro, spleen cells require selected FCS. These "good" sera could be distinguished from "deficient" sera by their higher content of this 2-ME-activated factor. The height of the in vitro immune response to SRBC was dependent on the amount of activated factor added to the culture medium. FCS normally required in the culture medium could be completely replaced by the factor-containing fraction without deleterious effect on the culture medium. The factor should be added to the spleen cells during the first 24 h of culture and remain there for 72 h in order to obtain an optimal immune response. The factor could be partially absorbed by spleen cells but not by SRBC. The relationship between macrophage, 2-ME, and FCS in eliciting an in vitro primary immune response is discussed.

Antibody Formation↗
PubMed1977

Growth regulation of a murine lymphoma cell line by a 2-mercaptoethanol or macrophage-activated serum factor.

A mouse lymphoma cell line has been established that is dependent for growth on the presence of an activated serum component. This growth factor is found in an inactive form in fetal bovine serum (FBS) and can be activated by 2-mercaptoethanol and by macrophages. A factor-containing fraction can be separated from FBS by Sephadex G-100 chromatography and once activated, can be used as a substitute for whole serum in the culture medium without adverse effect on the cell growth. The significance of these findings with respect to the study of the immune response and cancer research is discussed.

Animals↗
PubMed1977

Humoral primary immune response in vitro in a homologous mouse system: replacement of fetal calf serum by a 2-mercaptoethanol or macrophage-activated fraction of mouse serum.

The primary immune response in mouse spleen cell cultures against heterologous red cell antigens is dependent on the medium being supplemented with selected batches of fetal calf serum. Mouse serum itself is not able to support this response. The active immune response-supporting component in fetal calf serum seems to be a distinct factor (s), which has been partially purified by Sephadex G-100 filtration and termed MaSF-2-mercaptoethanol-activated serum factor. In this report it is demonstrated that MaSF is also present in mouse serum. For functional detection, mouse MaSF has to be separated from higher m.w. inhibitors, and has to be activated by 2-ME. After separation and activation mouse MaSF can support the primary immune response in a completely homologous in vitro culture system. Evidence is presented that MaSF can also be activated by macrophages. It is concluded that macrophages and 2-ME have the same mode of action in the primary immune response in vitro, i.e., induction of lymphocyte competence by activation of a serum factor.

Animals↗