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Biomedical subjects

M Bennett

Publications and source records attributed to M Bennett.

At least 109 records · Page 6Linked to original sources

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

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

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

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

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

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

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

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

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

Human cowpox 1969-93: a review based on 54 cases.

This survey of the clinical and epidemiological features of human cowpox, a rare but relatively severe zoonotic infection, is based on 54 cases, many unpublished, which we have studied since 1969. Patients present with painful, haemorrhagic pustules or black eschars, usually on the hand or face, accompanied by oedema, erythema, lymphadenopathy, and systemic involvement. Severe, occasionally fatal, cases occur in eczematous and immunosuppressed individuals, although cowpox has not yet been reported in anyone infected with the human immunodeficiency virus. Variations in the clinical features are described, and the differential clinical diagnosis of cowpox, parapox, herpes virus, and anthrax infections is discussed. The role of the laboratory in diagnosis is described, and the value of electron microscopy in providing rapid confirmation is emphasized. Care in taking a detailed history will assist in the initial clinical diagnosis, and a history of contact with domestic cats, particularly during July-October, is important. The possible influence of smallpox vaccination on the incidence and severity is discussed and discounted.

Adolescent

Expression of CZ-1: a CD45RB epitope on progenitors of natural killer and other haematopoietic cells.

CZ-1 is a novel sialic acid-dependent epitope of the murine CD45RB molecule which is expressed on cells that proliferate when cultured in IL-2. Because IL-2 appears to be important in the differentiation of NK cells, the authors examined the expression of CZ-1 on immature NK-lineage cells within the bone marrow. All mature NK1.1+ cells as well as their NK1.1- IL-2 responsive precursors were CZ-1+. Furthermore, IL-2 unresponsive transplantable NK progenitor cells expressed CZ-1 also. To examine expression of CZ-1 on other immature lymphoid progenitor cells, CZ-1+ and CZ-1- marrow cells were transplanted into lightly irradiated scid mice. Transfer of CZ-1+ cells resulted in rapid and sustained generation of thymocytes and splenic B cells, whereas CZ-1- cells caused delayed repopulation. This suggested that the slowly repopulating pluripotent stem cells lacked CZ-1. Therefore, expression of CZ-1 on Ly6+ Lin- c-kit+ cells, highly enriched for pluripotent stem cells, was examined. This population appeared to be homogeneously CZ-1dull. Thus, it appears that expression of CZ-1 is developmentally regulated, with differentiation associated with increased expression. Since CZ-1 is expressed on a protein tyrosine phosphatase, it is likely that this molecule regulates differentiation of NK and other lymphoid cells.

Animals

The impact on community palliative care services of a hospital palliative care team.

This retrospective study examined the influence of a hospital palliative care team on the activity of a local hospice home care team over a four-year period from May 1989 to April 1993 in East Leeds. The increasing referral to death interval observed in home care patients over this period appears to be due to the presence of the hospital team. The increasing work-load of the home care team generated by the hospital team is discussed with reference to solutions to meet this increasing demand. A district or regional planning strategy is recommended to co-ordinate existing and potential palliative care services.

England

dishevelled is required during wingless signaling to establish both cell polarity and cell identity.

The dishevelled gene of Drosophila is required to establish coherent arrays of polarized cells and is also required to establish segments in the embryo. Here, we show that loss of dishevelled function in clones, in double heterozygotes with wingless mutants and in flies bearing a weak dishevelled transgene leads to patterning defects which phenocopy defects observed in wingless mutants alone. Further, polarized cells in all body segments require dishevelled function to establish planar cell polarity, and some wingless alleles and dishevelled; wingless double heterozygotes exhibit bristle polarity defects identical to those seen in dishevelled alone. The requirement for dishevelled in establishing polarity in cell autonomous. The dishevelled gene encodes a novel intracellular protein that shares an amino acid motif with several other proteins that are found associated with cell junctions. Clonal analysis of dishevelled in leg discs provides a unique opportunity to test the hypothesis that the wingless dishevelled interaction species at least one of the circumferential positional values predicted by the polar coordinate model. We propose that dishevelled encodes an intracellular protein required to respond to a wingless signal and that this interaction is essential for establishing both cell polarity and cell identity.

Amino Acid Sequence

Cloning and characterization of the 2B4 gene encoding a molecule associated with non-MHC-restricted killing mediated by activated natural killer cells and T cells.

We have recently described a signal transducing molecule, 2B4, expressed on all NK and T cells that mediate non-MHC-restricted killing. The gene encoding this molecule was cloned and its nucleotide sequence determined. The encoded protein of 398 amino acids has a leader peptide of 18 amino acids and a transmembrane region of 24 amino acids. The predicted protein has eight N-linked glycosylation sites, suggesting that it is highly glycosylated. Comparison of 2B4 with sequences in the databanks indicates that 2B4 is a member of Ig supergene family, and it shows homology to murine and rat CD48 and human LFA-3. Northern blot analysis has shown at least three transcripts for 2B4 in adherent lymphokine-activated killer cells of several mouse strains and TCR-gamma/delta dendritic epidermal T cell lines but not in allospecific T cell clones. These three mRNA are the products of differential splicing of heterogeneous nuclear RNA. Southern blot analysis of genomic DNA from several mouse strains revealed that 2B4 belongs to a family of closely related genes. The 2B4 gene has been mapped to mouse chromosome 1 by analysis of 2B4 expression in recombinant inbred mouse strains.

Amino Acid Sequence

Correspondence between a mammalian spliceosome component and an essential yeast splicing factor.

None of the mammalian splicing factors that have been cloned corresponds to the yeast pre-messenger RNA splicing factors, the PRP proteins. Here, a generalizable strategy was used to isolate a complementary DNA encoding the mammalian spliceosome-associated protein (SAP) SAP 62. It is demonstrated that SAP 62 is the likely functional homolog of the yeast PRP11 protein. Both PRP11 and SAP 62 associate stably with the spliceosome, contain a single zinc finger, and display significant amino acid sequence similarity. Unlike PRP11, SAP 62 contains 22 proline-rich heptapeptide repeats at the carboxyl-terminus.

Amino Acid Sequence