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Biomedical subjects

D W Morris

Publications and source records attributed to D W Morris.

At least 37 records · Page 2Linked to original sources
PubMed1992

Genetic analysis of the effects of Mtv-2 on the T cell repertoire in the WXG-2 mouse strain.

In this report, the T cell repertoire was studied in a natural genetic model system using a novel mouse strain (WXG-2) carrying a single pathogenic mouse mammary tumor virus (MMTV) provirus (Mtv-2) on an otherwise MMTV-free genetic background. The Mtv-2 provirus has complete biological activity, produces infectious milk-transmitted virus, and contributes to mammary carcinogenesis by an insertion mutation mechanism. In mice carrying the Mtv-2 provirus, T cells expressing V beta 14 were specifically deleted in mice with a functional MHC class II I-E gene but not in I-E- controls. The deletion of V beta 14+ T cells was more rapid in mice with the Mtv-2 provirus than in Mtv-2-free control mice infected with exogenous MMTV. In addition, the Mtv-2 deletion phenotype was age dependent. A slow depletion of V beta 14+ T cells was observed, and greater than 95% of the V beta 14+ T cells were eliminated by 6 months of age. These experiments indicate that (i) the Mtv-2 provirus encodes or regulates expression of a V beta 14-specific superantigen, (ii) interactions between Mtv-2 and other MMTV proviruses are not necessary for the V beta 14 deletion phenotype, (iii) the presence of a retroviral superantigen in all cells is not sufficient for T cell depletion during neonatal development in the thymus, and (iv) the Mtv-2 provirus and its associated exogenous provirus have the same V beta specificity.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Intracellular amplification of proviral DNA in tissue sections using the polymerase chain reaction.

We developed a new method to amplify cell DNA in situ using the polymerase chain reaction (PCR). Proviral sequences of mouse mammary tumor virus (MMTV) contained in cultured cells and tissue sections were amplified intracellularly using a thermal cycler. Two techniques were employed to maintain the localization of the amplified DNA. First, complementary tails at the 5' ends of the oligonucleotide primers resulted in the synthesis of high molecular weight concatamers containing the target sequences. Second, the PCR was carried out in a thin film of agarose solidified over the tissue sections. The specifically amplified and localized DNA was then detected by in situ hybridization (ISH). Our results demonstrate that (a) DNA in tissue sections can serve as the target for the polymerase chain reaction in situ, (b) cell morphology is maintained, and (c) a target of 167 BP can be specifically detected in individual cells. This technique should be generally applicable to amplifying cellular DNA targets in tissue sections for detection in situ.

Animals↗
PubMed1990

Insertion mutation of the int-1 and int-2 loci by mouse mammary tumor virus in premalignant and malignant neoplasms from the GR mouse strain.

Mouse mammary tumor virus (MMTV)-induced mammary adenocarcinomas can develop from several different premalignant precursors common in GR mice. Insertion mutagenesis of the mammary protooncogenes int-1 and int-2 was studied in this multistep system by analyzing samples from various stages of neoplastic development for novel int-1 and int-2 restriction fragments generated by MMTV provirus integration. int-1 and int-2 insertion mutations were observed in both premalignant lesions and malignant tumors. Some of the tumors with insertion mutations were experimentally derived from insertion mutation-free premalignant precursors. Each class of neoplasm examined had a characteristic frequency of int-1 and int-2 insertion mutations; however, no correspondence was observed between neoplasm morphology and mutation of either gene. These results indicate that insertion mutation of the int-1 and int-2 loci by MMTV provirus can be involved in the earliest identifiable stages of neoplastic development as well as during progression of premalignant lesions to tumors. Insertion mutation of int-1 and int-2 is therefore not stage specific in this system.

Animals↗
PubMed1989

Isolation of a pathogenic clone of mouse mammary tumor virus.

Exogenous mouse mammary tumor virus (MMTV) was cloned from a GR mammary tumor. Clone lambda GRT39 contained a full-length integrated MMTV(GR) provirus and both 5' and 3' host flanking DNA. The lambda GRT39 provirus had no apparent structural changes associated with cloning and retained the exogenous MMTV gag gene poison sequence. When introduced into rat mammary adenocarcinoma LA7 cells, the lambda GRT39 provirus was fully expressed. lambda GRT39-transfected LA7 cells made MMTV RNA, had gp52 SU protein on the cell surface, and produced B-type retrovirus particles characteristic of MMTV. Mammary tumors developed in hormone-stimulated BALB/c females injected with MMTV from lambda GRT39-transfected LA7 cells [MMTV (lambda GRT39)]. The tumors had new, clonally integrated copies of the MMTV(lambda GRT39) provirus and were expressing MMTV antigen. These data indicate that the lambda GRT39 provirus is biologically active and pathogenic.

Adenocarcinoma↗
PubMed1989

Automation of protein crystallization trials: use of a robot to deliver reagents to a novel multi-chamber vapor diffusion plate.

We report here the automation of search procedures to rapidly screen a large number of reagents and incubation conditions that lead to the formation of protein crystals. The system consists of a Biomek 1000 Automated Laboratory Workstation from Beckman Instruments under the control of a custom user-interface program developed by Cryschem. A plate composed of twenty-four vapor diffusion chambers, each with its own reservoir well and protein drop holder was designed by Cryschem to fit the Biomek table. The Cryschem software manages a large data base of incubation conditions and generates instructions for the workstation to dispense the protein, buffers, detergents, cofactors and other reagents used to promote the formation of protein crystals. The plate is manually positioned on the Biomek table and then under program control additions are automatically made to each chamber as follows: Precipitating solution is added to each reservoir well and the protein solution along with the precipitating solution and various other reagents are added to each drop holder. The plate is removed from the table and a mylar tape is applied to simultaneously seal all the chambers. The plates are placed at a controlled temperature and periodically examined for crystal formation.

Biotechnology↗
PubMed1987

Survey of int region DNA rearrangements in C3H and BALB/cfC3H mouse mammary tumor system.

Rearrangement of the int-1 and int-2 regions of mouse chromosomes was compared in the C3H and BALB/cfC3H hyperplastic alveolar nodule and its hyperplastic outgrowth (HPO) model systems by examining the DNA of the different stages of the neoplastic progression, with use of the Southern blot technique. Rearrangement of int region DNAs associated with proviral amplification occurred more frequently in spontaneous tumors (19 of 27) than in tumors from HPOs (7 of 37) and rarely occurred in HPOs (1 of 29). However, the int-1 rearrangement maintained in 1 BALB/cfC3H HPO line through 11 transplant generations suggests that the int-1 rearrangement is neither sufficient nor necessary for progression to mouse mammary carcinoma.

Animals↗
PubMed1986

Transfer, by selective breeding, of the pathogenic Mtv-2 endogenous provirus from the GR strain to a wild mouse line free of endogenous and exogenous mouse mammary tumor virus.

The GR laboratory mouse strain has five endogenous proviral copies of the mouse mammary tumor virus (MMTV). One of these, Mtv-2, is unique because it causes mammary carcinomas in virtually 100% of breeding GR females prior to 1 year of age. To facilitate studies of this locus in particular, and mammary tumorigenesis in general, we genetically tailored a new mouse line, WXG-2, which bears Mtv-2 as its only endogenous MMTV provirus. The WXG-2 line was constructed by making hybrids between the GR strain and a wild mouse line free of both endogenous and exogenous MMTV, backcrossing to the MMTV-free line, and fixing the Mtv-2 locus in a population with the desired genotype. Mammary tumors were observed in 5 of the 20 hybrid females carrying the endogenous Mtv-2 provirus. The WXG-2 line represents a new model system for studying MMTV-induced mammary tumorigenesis in the absence of multiple endogenous proviruses.

Animals↗
PubMed1985

Characterization of an endogenous retrovirus-repetitive DNA chimera in the mouse genome.

We found that an endogenous mouse mammary tumor provirus, GR-MTV-8, is embedded within a member of the BAM HI family of long interspersed repetitive mouse DNAs. GR-MTV-8 appears to be transcriptionally silent at its normal chromosomal position in the mouse genome. The provirus is transcriptionally active, however, when cloned and transfected into mouse cells (Kennedy et al., Nature (London) 295:622-624, 1982). We propose that the transcriptional inactivity of GR-MTV-8 in situ is due to an inhibitory effect, possibly involving DNA methylation, attributable to the flanking BAM HI element.

Animals↗
PubMed1985

Mammary tumors in feral mice lacking MuMTV DNA.

Two mammary tumors developed in feral mice treated with dimethylbenzanthracene. The tumors, livers, and spleens of these animals contained no MuMTV proviral DNA. Neither tumor had amplified or rearranged int-1 or int-2 loci. This demonstrates that mammary tumorigenesis can occur in mice in the absence of endogenous and exogenous MuMTV.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1984

Hyperplastic and neoplastic changes in the mammary glands of feral mice free of endogenous mouse mammary tumor virus provirus.

Laboratory colonies of feral mice (Mus musculus domesticus) have been established with specific mouse mammary tumor virus (MuMTV) genotype, including colonies lacking any proviral DNA (ev-) or carrying only a single copy of MuMTV DNA (ev+). No evidence of a decline in reproductive capacity has been observed in the first 8 generations. Both the ev- and ev+ mice showed normal mammary gland development and the development of hyperplastic lesions in the older females. The mice were very resistant to spontaneous or chemically induced mammary tumors. However, the occurrence of 1 mammary tumor in an ev- mouse indicates that mammary neoplasias can occur in the absence of MuMTV DNA. The few tumors that do occur in the ev- mice provide a unique opportunity to study the neoplastic process in the absence of proviral DNA.

Animals↗
PubMed1983

Alterations of acquired mouse mammary tumor virus DNA during mammary tumorigenesis in BALB/cfC3H mice.

The patterns of the milk-transmitted (exogenous) mouse mammary tumor virus (MuMTV) DNA restriction endonuclease fragments in the nodule and tumor stages of BALB/cfC3H mouse mammary neoplasia were compared with the use of the Southern blot analysis. Acquired MuMTV restriction fragments were detected in DNA from hyperplastic alveolar nodules (HAN), from primary hyperplastic outgrowths (HPO), from families of transplanted HPO, from tumors from HPO, and from serially transplanted tumors. The restriction fragment patterns suggested that the HAN were composed of clonal dominant populations. Transplantation of subdivisions of individual HAN resulted in HPO with DNA restriction patterns suggesting that HAN also contained two or more subpopulations. In all cases, HAN subpopulations shared MuMTV restriction fragments suggesting a common origin. Forty-seven tumors arising from HPO shared MuMTV restriction fragments with the HPO. Most but not all tumors had additional acquired MuMTV restriction fragments not detected in the progenitor HPO, indicating that they were composed of a distinct subpopulation that originated from the HPO. The restriction fragment pattern in some tumor lines was remarkably stable through many transplant generations. Some tumors had no major additional restriction fragments, suggesting that major rearrangements of MuMTV DNA are not required for tumorigenesis.

Animals↗
PubMed1981

Plasmid vectors capable of transferring large DNA fragments to yeast.

We have constructed several cloning vectors which can be used in vitro packaging and yeast transformation. These plasmids have been designed for the convenient cloning of large segments of DNA and their transfer to yeast. They contain bacterial plasmid DNA sequences for replication and selection in Escherichia coli, yeast 2-microns plasmid DNA sequences or chromosomal replicators and yeast markers necessary for replication and selection in yeast, and the cohesive ends of bacteriophage lambda which allow packaging of recombinant molecules into lambda phage heads. Large fragments (22-38 kb) of Klebsiella pneumoniae and Zea mays DNA were ligated into plasmid vector pBTI-1 to make complete genome libraries. One clone from the K. pneumoniae library was amplified in E. coli and the purified DNA used to transform yeast cells. Transformation of yeast by large DNA fragments occurred at high frequencies. The recombinant plasmid was stably maintained in yeast, provided selective pressure for Leu+ transformants was maintained. The structurally complete recombinant plasmid can be recovered from yeast by transforming E. coli to ampicillin resistance. Fewer than 5% of the recovered plasmids had undergone recombination with endogenous yeast 2-microns plasmid.

Bacteriophage lambda↗
PubMed1981

Measuring effectiveness of service aides in infant immunization surveillance program in North Central Texas.

The Immunization Division of Texas Public Health Region 5 sought to measure the per cent of referrals taking immunization action as a result of service aide contact. From data collected on newborn-nonresponders during a 12-month period, results show that aides may be credited with influencing 44 percent of the referrals reporting subsequent immunization.

Community Health Workers↗
PubMed1981

Restriction endonuclease studies of hyperplastic outgrowth lines from BALB/cfC3H mouse hyperplastic mammary nodules.

The DNA's isolated from five mouse hyperplastic mammary gland outgrowth lines from BALB/cfC3H mice were digested with the restriction endonucleases PsTI, BamHI, or EcoRI; electrophoresed; and analyzed by Southern blotting and autoradiography. Proviral DNA sequences from the acquired C3H mouse mammary tumor virus were detected in the DNA of all five lines, indicating that they were infected. The DNA of the five hyperplastic lines contained more EcoRI and BamHI mouse mammary tumor virus proviral DNA fragments than did DNA from normal organs, suggesting that the hyperplastic tissues were composed of more homogeneous cell populations than was lactating mammary gland. Each hyperplastic line had unique and reproducible BamHI and EcoRI restriction (integration) patterns which were stable over as many as seven transplant generations. Three sublines, which originated from the same hyperplastic alveolar nodule, had unique integration patterns but also shared several fragments. On the basis of these observations, we propose that mouse mammary "hyperplasias" are clonal dominant premalignant neoplasms.

Animals↗
PubMed1980

Bacteriophage K7, a double stranded DNA phage that infects strains of Escherichia coli harbouring drug resistance factors of incompatability group W.

Bacteriophage K7 is specific for Escherichia coli strains harbouring R factors of incompatability group W, including hybrid coliphage P1-Myxococcus virescens plasmids. The phage has an unusual morphology with an isometric head and long tail of variable length. The tail lengths appear to fall into classes corresoonsing to simple multimers of a unit length. Partially purified lysates of the phage include material that may represent phage particles in the process of biogenesis and other material demonstrating attachment of phage to cell envelope. Newly released phage DNA contains single standed ends. In the course of work. E. coli strains that harbour R factor Sa were found to be apparently restrictive.

Coliphages↗
PubMed1978

Transduction of Myxococcus virescens by coliphage P1CM: generation of plasmids containing both phage and Myxococcus genes.

Chloramphenicol-resistant Myxococcus virescens were obtained by infecting myxococci with Escherichia coli specialized transducing phage P1CM. The drug-resistant myxococci were phenotypically unstable. They contained more than one type of plasmid; these plasmids were not found in the parent strain. Chloramphenicol-resistant E. coli were obtained by transformation with either a fraction of myxococcal DNA containing the plasmids or with P1CM prophage DNA. These transformants contained plasmids. Escherichia coli transformed by DNA from the myxococci contained both P1CM and myxococcal genes. Individual transformant clones differed in the genetic make-up of their plasmids. Among the myxococcal genes expressed in these plasmid-harbouring E. coli strains were a capacity for self-transmissibility and a pattern of phage sensitivity characteristic of R factor incompatibility group W. Escherichia coli transformed with P1CM prophage contained incomplete P1CM genomes; none of the chloramphenicol-resistant transformants produced P1CM phage particles. The significance of these findings for an understanding of mechanisms for the generation of R factors is discussed.

Chloramphenicol↗