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Biomedical subjects

M Bennett

Publications and source records attributed to M Bennett.

At least 199 records · Page 11Linked to original sources
PubMed1995

Protection against Mycoplasma pulmonis infection by genetic vaccination.

The induction of an immune response against a foreign protein usually requires purification of that protein, which is injected into animals. The isolation of pure protein is time consuming and costly. Recently, a technique called biolistic transformation (biological ballistic system) microparticle injection, gene gun, or particle bombardment was developed. The basic idea is that DNA or biological material coated onto heavy tungsten or gold particles is shot into target cells or animals. We have vaccinated mice by introducing the gene (Mycoplasma pulmonis DNA or a specific fragment) encoding a protein recognized by a protective monoclonal antibody directly into the skin or muscle of mice by two methods: (i) using a hand-held form of the biolistic system that can propel DNA-coated gold microprojectiles (2 micrograms of DNA) directly into the skin; (ii) using a conventional intramuscular injection of the DNA (100 micrograms) into quadricep muscles of transfected mice. HeLa cells were transfected in vitro by the gene gun or by the liposomal delivery system. Indirect immuno-fluorescent antibody (IFA) assay of culture cells indicated that both methods could be successful. Production of antibody and cell-mediated immunity against M.pulmonis were monitored by assaying serum IFA and enzyme-linked immunosorbent assay (ELISA), and delayed type hypersensitivity. In addition, macrophage migration inhibition and lymphocyte transformation to antigen in spleen cells were also tested. Both delivery systems induced humoral and cellular immunity, and vaccinated the mice against infection. Genetic immunization by using the gene gun saves time, money, and labor; moreover, this general method is also applicable to gene therapy.

Animals↗
PubMed1995

2B4, a new member of the immunoglobulin gene superfamily, is expressed on murine dendritic epidermal T cells and plays a functional role in their killing of skin tumors.

Dendritic epidermal T cells (DETC), which are skin-specific members of the tissue-resident gamma delta T-cell family, are characterized by their potential to kill selected tumor targets by a non-major histocompatibility complex (MHC)-restricted mechanism. We have recently identified a new receptor molecule, 2B4, that appears to be associated with non-MHC-restricted recognition of tumor targets by natural killer cells. The purpose of this study was to determine whether DETC express 2B4 molecules, and, if so, to assess their functional roles in DETC-mediated killing of tumor targets. Short-term DETC lines as well as DETC freshly procured from skin expressed surface 2B4, as detected with a specific monoclonal antibody. Removal of interleukin (IL)-2 from DETC cultures caused substantial reduction in 2B4 expression levels as well as a reduction in cytotoxic capacity against YAC-1 targets in a standard 51Cr-release assay. Conversely, exposure to IL-2, but not to IL-7, elevated both 2B4 expression and cytotoxicity. To assess the functional roles played by surface 2B4, we pretreated DETC lines with anti-2B4 antibody and then tested for their killing potential. Anti-2B4, but not the control antibody, augmented their capacity to lyse YAC-1 targets (51Cr-release assays) and to disrupt the monolayers of Pam-212-transformed keratinocytes (visual assessment). Thus, we conclude that DETC express, in an IL-2-dependent manner, 2B4 molecules, which may play a unique role in the killing of skin-derived tumors.

Animals↗
PubMed1995

Immunotoxicity of polyunsaturated fatty acids in serum-free medium.

To test the effect of purified polyunsaturated fatty acids on immune cells in vitro, human peripheral blood mononuclear cells and murine spleen cells were incubated in Opti-MEM medium without serum or even albumin and with 2-mercapto-ethanol, insulin, transferrin and selenium as supplements. The human cells were stimulated with phytohemagglutinin and the murine cells were stimulated with Concanavalin A or lipopolysaccharide. Both human and murine cells were stimulated with recombinant human interleukin-2 to generate lymphokine activated killer cells. Linoleic and linolenic acids inhibited all of the immune responses tested, whereas docosahexaenoic and eicosapentaenoic acids did not. Similar effects were observed with cultured B16 F10 murine melanoma cells. Mixtures of linoleic and docosahexaenoic or eicosapentaenoic acids also inhibited the mitogenic response to phytohemagglutinin. Inhibition of lipid mediator production by indomethacin, quercetin, rutin, or nordihydroguariaretic acid, and addition of vitamins C and E with anti-oxidant activity failed to reverse the effects of linoleic acid. Thus, linoleic and linolenic acids appear to directly inhibit immune and tumor cells, at least under these conditions.

Animals↗
PubMed1995

Identification of a recombinational breakpoint at the BAT5 locus in three intra-H-2 recombinant inbred mouse strains.

We have analyzed the S/D region in 14 inbred mouse strains by restriction fragment length polymorphism (RFLP) using human BAT2 and BAT5 genes as probes. In all recombinant strains, the recombinational breakpoint mapped centromeric to Bat-2 (D17H6S51E). In recombinant strains B6.R4, B6.AK1 and B10.BYR1, recombination occurred within or close to the Bat-5 (D17H6S82E) locus. The immunogenicity of B10.BYR1 and B6.R4 bone marrow cell (BMC) grafts differs from that of both sets of parents, as if genes at or just centromeric to Bat-5 are involved. The phenotype of B6.AK1 BMCs (Kb Dk) is similar to that of the H2k parent suggesting no changes occurred. However, RNA blot analysis has shown that the Bat-5 gene is expressed well in bone marrow cells of B10.BR mice but not in B6.AK1 marrow cells. Analysis of a limited number of tumor cells of hemopoietic origin identified a single transcript for Bat-5. Our present data identify a recombinational hot spot at the Bat-5 locus. The expression of Bat-5 or a nearby gene may influence the immunogenicity of BMCs.

Animals↗
PubMed1994

Expression of CD43 on murine and human pluripotent hematopoietic stem cells.

To understand regulation of hemopoiesis, it would be helpful to identify physiologically relevant function-associated molecules on stem cells. Here, we report the detailed examination of CD43 expression on murine and human pluripotent hemopoietic stem cells. Mouse stem cells were found within the Ly6+Lin-CD43high subpopulation of bone marrow. These cells, upon transfer into SCID mice, caused rapid repopulation of thymus, spleen, and bone marrow. Retransfer of bone marrow cells from primary SCID recipients of Ly6+Lin-CD43high cells into secondary recipients resulted in repopulation of lymphohemopoietic cells. All Ly6+Lin-CD43high cells were found to express high levels of c-kit. In contrast, Ly6+Lin-CD43-/low cells caused limited and variable thymic and splenic repopulation. These cells failed to repopulate the marrow cavity and did not contain retransplantable stem cells. These data indicate that murine pluripotent stem cells express high levels of CD43. Examination of human fetal bone marrow cells revealed a population of CD34+CD38-CD43+ cells. When single sorted cells with this phenotype were cultured in vitro, they were able to produce colonies with a dispersed growth pattern. Cells with this growth pattern have previously been shown to have myeloid and lymphoid growth potentials and extensive self-renewal capacity. Furthermore, CD34+CD38-HLA-DR+ cells, recently shown to be highly enriched in stem cell activity, expressed relatively high levels of CD43. Because CD43 has recently been shown to bind to intercellular adhesion molecule-1, these data suggest a possible role for CD43 in the regulation of hemopoiesis.

ADP-ribosyl Cyclase↗
PubMed1994

Integrated control of cell proliferation and cell death by the c-myc oncogene.

Regulation of multicellular architecture involves a dynamic equilibrium between cell proliferation, differentiation with consequent growth arrest, and cell death. Apoptosis is one particular form of active cell death that is extremely rapid and characterized by auto-destruction of chromatin, cellular blebbing and condensation, and vesicularization of internal components. The c-myc proto-oncogene encodes an essential component of the cell's proliferative machinery and its deregulated expression is implicated in most neoplasms. Intriguingly, c-myc can also act as a potent inducer of apoptosis. Myc-induced apoptosis occurs only in cells deprived of growth factors or forcibly arrested with cytostatic drugs. Myc-induced apoptosis is dependent upon the level at which it is expressed and deletion mapping shows that regions of c-Myc required for apoptosis overlap with regions necessary for co-transformation, autoregulation, inhibition of differentiation, transcriptional activation and sequence-specific DNA binding. Moreover, induction of apoptosis by c-Myc requires association with c-Myc's heterologous partner, Max. All of this strongly implies that c-Myc drives apoptosis through a transcriptional mechanism: presumably by modulation of target genes. Two simple models can be invoked to explain the induction of apoptosis by c-Myc. One holds that death arises from a conflict in growth signals which is generated by the inappropriate or unscheduled expression of c-Myc under conditions that would normally promote growth arrest. In this 'Conflict' model, induction of apoptosis is not a normal function of c-Myc but a pathological manifestation of its deregulation. It thus has significance only for models of carcinogenic progression in which myc genes are invariably disrupted.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Effect of 3'azido-2',3'-deoxythymidine (AZT) on experimental feline immunodeficiency virus infection in domestic cats.

The compound 3'azido-2',3'-deoxythymidine (AZT) inhibits the replication of feline immunodeficiency virus (FIV) in cell culture, and treatment with the compound has been reported to induce some clinical improvement in some cases of feline FIV infection. In order to determine the effect of prophylactic treatment with AZT on experimental FIV infection, cats were treated with the compound at 0.2, 1.0, 5, 25 or 50 mg kg-1 day-1 for 29 days. One day after the treatment was started, they were inoculated with 150 cat infectious doses of FIV. All the cats became viraemic, seroconverted and developed lymphadenopathy, although the onset of each was delayed in the cats given higher doses of AZT. Anaemia developed in the cats given high doses of AZT. Virus re-isolated from the cats given 50 mg kg-1 day-1 was as susceptible to AZT in cell culture as the inoculated virus. Thus AZT is much less effective in cats than might have been expected from the results of in vitro studies.

Animals↗
PubMed1994

Acute arthritis of cats associated with feline calicivirus infection.

Twelve specific pathogen-free cats were infected either by intra-articular inoculation or by contact exposure to one of two strains of feline calicivirus (FCV), either F65, a field strain originating from an outbreak of lameness in a group of cats, or a vaccine strain. Following either route of exposure, both strains induced signs typical of FCV infection including oral and nasal ulceration, conjunctivitis and ocular discharge. These signs were of equal severity for both virus strains, but overall, following either route of infection, F65 induced more severe disease than the vaccine strain, with marked pyrexia, lethargy and lameness. Vaccine virus only induced a relatively mild lameness following intra-articular inoculation. Gross pathological and histopathological lesions were seen in some of the joints, but again changes were more severe in the F65-exposed cats. Virus was isolated from both normal and affected joints from both groups of F65-exposed cats, and from a joint from each cat inoculated intra-articularly with vaccine virus. Mild transient lameness was also seen in one of two control cats inoculated intra-articularly, but no pathological changes were seen or virus isolated from joints. A cDNA probe used in RNA dot blot hybridisation experiments was found to be specific and more sensitive than virus isolation in detecting FCV in selected tissues. This may be useful in future studies on the pathogenesis of FCV disease and in studies on viral persistence in FCV carriers.

Acute Disease↗
PubMed1994

Protection of mice against experimental murine mycoplasmosis by a Mycoplasma pulmonis immunogen in lysogenized Escherichia coli.

A construct of the Mycoplasma pulmonis (MP) genomic library, using randomly sheared DNA, was cloned in lambda gt11 and transfected into C600 Escherichia coli organisms. Clones of E. coli expressing a fusion protein reactive with anti-MP and monospecific serum were transferred orally or intravenously into Balb/c mice. Expression of the fusion protein was induced by adding isopropyl-beta-D-thiogalactopyranoside to the drinking water. This vaccination protocol led to local and systemic antibody formation, to generation of immune lymphocytes and to protection against large numbers of virulent MP organisms. This approach might be generally successful in preventing infectious disease.

Administration, Oral↗
PubMed1994

Apramycin-resistant Escherichia coli isolated from pigs and a stockman.

Escherichia coli serotype O147:K89:K88a,c was found to be associated with outbreaks of diarrhoea in preweaner pigs of up to 4 weeks of age on a pig unit. Resistance to apramycin, gentamicin, netilmicin, tobramycin and other antibiotics was associated with conjugative plasmids of approximately 62 kb. The presence of a gene which encoded for the aminoglycoside acetyltransferase enzyme AAC(3)IV was confirmed by DNA hybridization. Samples collected during the following 12 months revealed widespread dissemination of these resistance plasmids in non-serotypable, non-haemolytic E. coli throughout the farm. Apramycin-resistant E. coli were also isolated from a stockman and it appeared from plasmid profile analysis and antibiotic sensitivity testing that the human isolates carried the same plasmid as that carried by the porcine E. coli. Klebsiella pneumoniae, with a slightly smaller conjugative plasmid and similar resistance pattern, was isolated from the stockman's wife.

Agricultural Workers' Diseases↗
PubMed1994

Evaluation of social problem solving in schizophrenia.

We examined social problem solving in schizophrenia. Twenty-seven schizophrenic patients in an acute hospital, 19 patients with bipolar disease, and 17 demographically matched nonpatient controls were tested on an empirically developed problem-solving battery that assessed the ability to generate solutions to problems, the ability to evaluate the effectiveness of solutions, and the ability to implement solutions in a role-playing format. Schizophrenic Ss were impaired on all 3 problem-solving domains compared with the nonpatient controls, but bipolar Ss were equally impaired. Several alternative explanations for these findings were considered. The most compelling hypothesis is that the deficits resulted from different factors: cognitive impairment for schizophrenic Ss and acute illness for bipolar Ss. However, longitudinal studies are required to determine whether problem-solving deficits in schizophrenic patients persist during periods of remission. Implications for rehabilitation strategies are discussed.

Adult↗
PubMed1994

Hantavirus: an increasing problem?

Hantaviruses are enveloped RNA viruses and members of the Bunyaviridae family. They are transmitted from various rodent hosts by inhalation of infected urine, saliva or faeces. Infection in rodent hosts is inapparent but persists for life. Person-to-person spread of hantavirus has not been described. Two main presentations of the disease occur. Haemorrhagic fever with renal syndrome (HFRS) is due to Hantaan, Seoul, Puumala, Porogia and Belgrade viruses. In general HFRS due to Hantaan, Porogia and Belgrade viruses is more severe and has higher mortality than that due to Puumala (nephropathia epidemica) or Seoul viruses. Hantaan is predominant in the Far East (Korea, Japan, China), Porogia and Belgrade in the Balkans, and Puumala in Western Europe; Seoul has a world-wide distribution. Hantavirus pulmonary syndrome (HPS) is a recently described infection with high mortality (60%) due to adult respiratory distress syndrome. The virus (Muerto Canyon Virus) is a hantavirus but different genotypically from previous strains. Management of hantavirus infections may require bed-rest, sedation, circulatory and ventilatory support and renal dialysis. Ribavirin if administered early in the illness may be of benefit.

Animals↗
PubMed1994

Natural killer cells recognize common antigenic motifs shared by H-2Dd, H-2Ld and possibly H-2Dr molecules expressed on bone marrow cells.

Murine natural killer (NK) cells can mediate specific rejection of bone marrow cell (BMC) allografts. Whereas positive recognition of allogeneic MHC antigens forms the basis for T cell alloreactivity, it has been postulated that NK cells are reactive against targets that do not express certain self-encoded MHC class I antigens. Here, we study the immunogenicity of BMC grafts from two class I transgenic mice, D8 (B6 mice with an H-2Dd transgene) and C3H.Ld (C3H mice with an H-2Ld transgene). D8 BMC grafts are acutely rejected by B6 but not D8 recipients. This suggests that antigenic motifs associated with the H-2Dd molecule are recognized. B6 mice depleted of their CD3+ but not NK1.1+ cells can still reject D8 BMC grafts. These data suggest that NK1.1+/CD3- cells recognize the H-2Dd derived antigenic motifs. Similarly, C3H.Ld BMC grafts are rejected by B6 x C3H F1 but not B6 x C3H.Ld F1 recipients. Thus, antigenic motifs associated with the H-2Ld molecule can also be recognized. Furthermore, expression of either H-2Dd or H-2Ld by the recipients renders them unable to reject D8 or C3H.Ld BMC grafts. Therefore, H-2Dd and H-2Ld molecules appear to express common antigenic motifs recognized by NK cells. Additional studies with B6.R4 (KbIbSbDr), an intra-H-2 recombinant mouse, indicated that a third class I molecule, possibly H-2Dr, also shared the common antigenic motifs with both H-2Dd and H-2Ld molecules. Thus, positive recognition of class I antigens by NK cells can occur. However, expression of some of these antigenic motifs appear to be negatively controlled by certain H-2r genes as suggested by rejection of D8 and B6.R4 BMC grafts by D8 x B10.RIII F1 and B6.R4 x B10.RIII F1 hybrids respectively.

Animals↗
PubMed1994

Susceptibility in cell culture of feline immunodeficiency virus to eighteen antiviral agents.

The in-vitro susceptibilities of two strains of feline immunodeficiency virus to 18 antiviral agents were determined in two cell lines. In terms of inhibiting p24 antigen production, the nucleoside-analogue reverse transcriptase inhibitors were the most effective compounds. Inhibition was also observed with aurintricarboxylic acid, phosphonoformate and butyldeoxynorjirimycin, but not with the other agents tested.

Animals↗