Search PubMed⌕ Search

Biomedical subjects

M J Dewey

Publications and source records attributed to M J Dewey.

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

Cell and tissue-specific expression of a heterologous gene under control of the myelin basic protein gene promoter in transgenic mice.

Myelin basic protein (MBP) is the second most abundant protein in CNS myelin. We have used transgenic mice to investigate the ability of the 5' flanking sequence of the mouse MBP gene to regulate the cell-type-specific- and temporal expression of a heterologous gene under its control. Transgenic mice were produced with a construct containing the bacterial chloramphenicol acetyltransferase (CAT) gene down-stream of the MBP 5' flanking sequence and CAT expression was monitored both enzymatically and histochemically. The results indicate that 1323 bp of 5' flanking sequence is sufficient to direct CAT expression specifically to the tissue and cell-type, in which MBP is normally synthesized. Additionally, this length of sequence also retains the ability to temporally regulate CAT levels in a manner analogous to endogenous MBP levels.

Animals↗
PubMed1991

Acute phase mediated change in glycosylation of rat alpha 1-acid glycoprotein in transgenic mice.

Transgenic mouse lines carrying the gene for rat alpha 1-acid glycoprotein (AGP) express the protein in the plasma at concentrations equal to or exceeding that of acute phase rats. Owing to the high basal level, these transgenic mice represent a unique experimental system for defining the largely unknown function of AGP. Since the carbohydrate moiety of AGP has been found to be changed during acute phase and the oligosaccharide structure to be important for immunomodulating activity of the protein, the rat AGP in transgenic mice was characterized by lectin-affinity immuno-electrophoresis. Unlike in the rat, the AGP in the transgenic mouse plasma consisted primarily of strongly concanavalin A-reactive forms. Acute phase mediated a several-fold increase in the total plasma concentration of AGP concomitant with a shift toward moderately concanavalin A-reactive forms. A similar change in concanavalin A-reactive forms was observed for the endogenous acute phase plasma protein haptoglobin. To define the role of inflammatory factors in AGP production, primary cultures of hepatocytes were prepared. In contrast to in vivo, the AGP recovered from tissue culture medium represented primarily the concanavalin A-non-reactive form. Treatment of the cells with recombinant human interleukin-1, interleukin-6 and dexamethasone stimulated the production of concanavalin A-reactive AGP forms. The data indicate that the glycosylation pattern of plasma-resident AGP is modulated by acute phase, but that the profile of AGP forms does not coincide with that secreted by hepatocytes in tissue culture. This finding demands an assessment of which of the possible glycosylated forms of AGP is functionally significant in vivo.

Animals↗
PubMed1990

Enhanced lung colonization and tumorigenicity of fused cells isolated from primary MCA tumors.

Cells derived from cell-cell fusion events were clonally isolated from primary methylcholanthrene (MCA)-induced tumors in allophenic mice. Compared with non-fused cells isolated from the same cultures, the fused cells had markedly greater experimental metastasizing (lung colonizing) activity, but only slightly greater tumorigenicity and the same cloning efficiency in soft agar. Cell-cell fusion may thus contribute to the generation of tumor heterogeneity that underlies the process of tumor progression.

Animals↗
PubMed1990

Inducible and tissue-specific expression of rat alpha-1-acid glycoprotein in transgenic mice.

alpha-1-Acid glycoprotein (AGP), which is produced in the mammalian liver and secreted into the blood-stream, is regulated by steroid hormones and by mediators of the acute phase response. In vitro transfection studies have shown that the response to glucocorticoids requires a cis-acting regulatory element, termed the glucocorticoid response element, that is located within 120 bp of the transcriptional start-site of the gene; induction by the acute phase mediators requires a different element, termed the distal regulatory element (DRE), that is located about 5 kb upstream of the start-site. To determine if these elements function in vivo, we have produced and characterized transgenic mice containing rat AGP gene constructs with and without the DRE. Five transgenic lines were produced from a 9.5-kb genomic AGP containing 4.7 kb of the 5' flanking region; this construct lacks the DRE. Another transgenic line was derived from a 10.7-kb clone that contains 5.3 kb of 5' flanking sequences including the DRE. All transgenic mice produced high levels of immunologically detectable rat AGP in the circulation, comparable to or in excess of that found in normal rats. There were correspondingly high concentrations of rat AGP transcripts in the liver. Transgene expression in all lines was induced in response to dexamethasone and during acute inflammation resulting from LPS treatment. The DRE-containing transgene underwent a greater induction in response to LPS than to dexamethasone; the transgene lacking the DRE responded similarly to both treatments. In cultured primary hepatocytes, the DRE-containing transgene was induced by the acute phase cytokines IL-1 and IL-6, and by dexamethasone, administered individually or in combination; the transgene lacking the DRE responded only to dexamethasone, and was not affected by the peptide hormones. Together, these results provide in vivo evidence supporting the notion that a minimum of two upstream sequences are responsible for the inflammatory induction of rat AGP. One element, which is located within the smaller 9.7-kb restriction fragment, is responsive to glucocorticoids and is likely to be the glucocorticoid response element located close to the transcriptional start site. The other element, the DRE, is located much further upstream and is responsible for imparting responsiveness to the acute phase cytokines.

Animals↗
PubMed1989

Cell fusion in tumor development and progression: occurrence of cell fusion in primary methylcholanthrene-induced tumorigenesis.

Definitive evidence for the occurrence of cell fusion in tumorigenesis was sought in methylcholanthrene-induced sarcomas. This was approached by using allophenic mice generated from strains differing for electrophoretic variants of the ubiquitous, dimeric enzyme glucose phosphate isomerase, with fusion assessed by heterodimer formation. Eight-three carefully trimmed primary tumor samples (from 23 individual tumors in allophenic mice) were analyzed, as were 1,140 clones derived from them. In all primary tumor samples, zymograms exhibited one GPI homopolymeric band. Expression of a hybrid band (indicative of a fusion event) was not observed in these samples. However, 9 (0.8%) of the tumor clones demonstrated a distinct and reproducible hybrid band which was uniformly lost upon recloning. Our data suggest that cell fusion, although uncommon, occurs in the clonogenic cell fraction during primary MCA tumorigenesis and is followed rapidly by chromosome segregation.

Animals↗
PubMed1989

Variable evolutionary stability of Y chromosomal repeated sequences in the genus Mus.

The study reported here is an examination of the organization and evolution of three Y chromosomal repeated sequences, designated pBC10-0.6, pBC15-1.1, and pBA33-1.8, in five closely related species of the genus Mus. The species distributions of major restriction fragment length polymorphisms produced with a panel of restriction enzymes is used to develop the phylogenetic relationships between the five species studied. However, the apparent degree of relatedness among these species varied a great deal with each of the three probes and was also highly dependent on the particular restriction enzyme used. The usefulness for phylogenetic studies of closely associated sequences varying in evolutionary stability is discussed.

Animals↗
PubMed1989

Threat and loss in breast cancer.

The psychological well-being of forty-four breast cancer patients was assessed shortly before and after surgery, and at three and twelve months post-operatively. Regression analysis revealed type of treatment, control over treatment and concern for appearance as significant predictors of nature of subsequent mood state. Results are discussed with reference to the theoretical position that type of severe life event can predict the nature of ensuing psychological disorder.

Adaptation, Psychological↗
PubMed1989

Single locus (rol) control of extreme resistance to red cell osmotic lysis: intrinsic mode of gene action.

Previous work has indicated that inbred mouse strains C57BL/6 and DBA/2 produce red cells differing in their sensitivity to osmotic lysis and that the trait is under multigene control. A recombinant inbred strain (BXD-31), produced from C57BL/6 and DBA/2, has red cells manifesting resistance to osmotic lysis far greater than that of either progenitor. We demonstrate here that the fragility difference between BXD-31 and DBA/2 is the consequence of allelic variation at a single autosomal locus, termed rol. The resistance allele (rol') is almost completely recessive to the sensitive one (rols). Results of bone marrow chimera analyses indicate that (1) the mode of rol gene action is by a direct influence on the properties of the red cells rather than an indirect influence on their extracellular milieu, and (2) rol does not affect erythrocyte production and turnover. The fragility difference caused by rol variation is likely to involve the erythrocyte membrane or underlying cytoskeleton, since various red cell properties sensitive to ion metabolism differences are unaffected by the gene.

Animals↗
PubMed1989

Cellular site and mode of Fv-2 gene action. II. Conditional protection of Fv-2ss cells by admixture with Fv-2rr cells.

Fv-2ss marrow cells are protected in vivo from Friend virus-induced erythroleukemia by admixture with a preponderance of Fv-2rr marrow cells. This was demonstrated both in allophenic (mosaic) mice and in bone marrow chimeras constructed from C57BL/6 strains differing at Fv-2 and an enzyme marker (glucose phosphate isomerase). The bone marrow chimeras were constructed by injection of marrow cells from Fv-2ss mice into unirradiated Fv-2rr mice. Bone marrow chimeras derived from this procedure produced 1%-2% donor (Fv-2ss) erythrocytes; this level of chimerism was maintained indefinitely. All the bone marrow chimeras as well as allophenic mice with less than 20% Fv-2ss red cells failed to develop any of the symptoms of Friend disease after infection with the polycythemic strain of Friend virus. The Fv-2rr-mediated protection of Fv-2ss marrow cells could be reversed by pretreatment of the two types of chimeras with either monoclonal or polyclonal antithymocyte antisera. Chimeras treated with either reagent and infected with Friend virus developed symptoms of Friend disease and experienced a shift in their erythrocyte mosaic composition favoring cells of the susceptible genotype. These results are consistent with the notion that a functioning immune system plays a role in the Fv-2rr-mediated protection of Fv-2ss Friend virus target cells. Furthermore, these studies establish conditions whereby a small population of sensitive strain cells in an overwhelming background of resistant strain cells can be selectively expanded. Such conditions could be useful in efforts to clone the Fv-2 gene.

Animals↗
PubMed1988

Failure of hospitals to promote the use of child restraint devices.

Motor vehicle accidents are the leading cause of death in children. In 1977, Tennessee adopted the nation's first law requiring the use of child restraint devices (CRDs), but despite extensive promotional efforts, a majority of young children still travel unrestrained. We surveyed all acute-care hospitals in Tennessee to determine their policies regarding CRDs. Of 109 hospitals with obstetric services, 28 (26%) had a policy calling for discharged newborns to be transported in CRDs; only seven (5%) of 128 pediatric services had such a policy. It is time for hospitals and professional organizations to adopt policies to ensure that the parents of every child discharged from an obstetric or pediatric unit are educated concerning CRD use laws and are able to comply with them. Pediatricians should consider incorporating "discharge in child restraint device" into their routine discharge orders.

Accidents, Traffic↗
PubMed1988

Effect of laboratory error on the identification of persons with hypercholesterolemia in an employee health service.

Cholesterol is a major risk factor for coronary heart disease. Of 117 employees seen consecutively in the Tennessee State Employee Health Service voluntary screening program, 86 (74%) had cholesterol levels above the reference range reported by a commercial clinical laboratory. This was three times greater than the calculated expected number of 29 (25%, 17 at moderate risk, 12 at high risk for coronary disease). Age and sex adjustment using Lipid Research Clinic guidelines reduced the number with elevated cholesterol to 55 (47%, 24 at moderate risk, 31 at high risk). Split sample cholesterol assays run independently by the commercial laboratory and a university laboratory showed excellent correlation (r = 0.99, commercial laboratory = 1.0 (university laboratory) + 10.8), but a systematic difference of 12.4 mg/dL (SD = 6.4 mg/dL, paired-t = 9.63, p less than 0.00001) between the two laboratories. Further adjustment for this difference reduced the number with elevated cholesterol to 41 (36%, 26 at moderate risk, 15 at high risk). This experience illustrates how small systematic laboratory errors in cholesterol determination can greatly exaggerate the number of persons reported to have clinically important cholesterol elevations. Clinical laboratories should report age and sex adjusted cholesterol reference ranges and provide clients periodic quality assurance reports that their measurements of cholesterol levels are accurate.

Adult↗
PubMed1987

Multiple forms of male-specific simple repetitive sequences in the genus Mus.

Previous reports indicate that in laboratory strains of mice, males are distinct from females in possession of repetitive DNA, notably devoid of Eco RI and Hae III sites and rich in the simple tetranucleotides GATA/GACA. We report here that such sequences originated in an ancestor common to laboratory mice, Mus hortulanus, M. spretus, and possibly also M. cookii. Interestingly, other male-specific satellite sequences were detected in M. caroli, M. cookii, M. saxicola, and M. minutoides. This novel satellite is also likely to be composed of simple repetitious sequences, but does not contain GATA and GACA. Thus, the Y chromosome appears to contain a disproportionately large amount of simple repetitious DNA. An attractive explanation for these results is that long tandem arrays of simple repeated sequences are generated at high frequency throughout the genome and that they are retained for a longer time on the Y chromosome due to the absence of homologous pairing at meiosis.

Animals↗
PubMed1987

Cellular competition in the development of ocular tissues in allophenic mice.

C57BL/6 mice exhibit impaired lens development as evidenced by competition studies with allophenic (chimeric) mice. Strain-specific differences in electrophoretic forms of glucose phosphate isomerase were exploited to determine the strain composition of various ocular and nonocular tissues in allophenic mice constructed from C57BL/6 and DBA/2 strains. As expected, there was variation from one animal to the next in overall mosaic composition, as well as variation among most ocular and nonocular tissues within individual animals. In contrast, when individual lenses from the same animals were assayed there was a marked and consistent deficiency of the C57BL/6 component. Control experiments indicated that these results are not the consequence of peculiarities of marker enzyme expression in the lens. Since lens formation occurs early in embryogenesis any anomaly at this stage could influence the normal induction of later ocular structures. We believe that the impaired lens-forming capacity of C57BL/6 mice may be the underlying cause of the 5-10% frequency of overt ocular defects in this strain.

Animals↗
PubMed1987

Erythroid cell fusion in the early phase of Friend virus leukemogenesis.

Infection of susceptible strain mice with the oncogenic Friend erythroleukemia virus initially results in fulminant erythroid hyperplasia. Several weeks later a frank erythroid leukemia develops. At the earliest stages of Friend disease there is extensive cell fusion involving erythroid cells but not platelets and granulocytes. Fusion was detected in experiments with allophenic (chimeric) mice whose component strains express electrophoretically distinct forms of the dimeric enzyme glucose phosphate isomerase (GPI). Infection of such animals with the polycythemic strain of Friend virus resulted in the rapid development of Friend disease. Concomitant with the appearance of early disease symptoms was the appearance in the red cells of the heterodimeric form of GPI, an unequivocal consequence of cell fusion. Platelet and granulocyte samples from the same infected animals failed to exhibit the hybrid GPI form. Furthermore, no hybrid dimer was evident in red cells from chimeric mice in which blood formation had been stimulated by phenylhydrazine treatment. These observations suggest that the occurrence of cell fusion early after infection by Friend virus is a significant aspect in the rapid development of neoplastic disease.

Animals↗
PubMed1986

Moderately repeated mouse Y chromosomal sequence families present distinct types of organization and evolutionary change.

Male specific repeated sequences compose approximately 10% of the mouse Y chromosome. This was deduced from studies of genomic phage clones that contain male specific DNA, and three subcloned EcoRI fragments pBC10-0.6, pBC15-1.1, and pBA33-1.8. Southern analyses and in situ hybridization of metaphase chromosomes show these three sequences to be present in 100-200 copies on the Y chromosome and in female DNA as single copies. One of these, pBC10-0.6, was directly demonstrated to be on the X chromosome. All three exhibited male specific transcription. These sequences are found in two distinct organizations. Subclone pBC10-0.6 is uniformly found in a long HpaI repeat unit of 9.7 Kbp. Subclones pBC15-1.1 and pBA33-1.8 are distributed throughout several EcoR1 repeat families in which the male specific fragments are interspersed. These male specific fragments also differ among themselves with regard to the types and frequency of evolutionary changes.

Animals↗
PubMed1986

Genotype-limited changes in platelet and erythroid kinetics in Friend-virus-infected allophenic mice.

We report here results suggesting that cells of the megakaryocytic lineage or uncommitted precursor cells may be targets for Friend-virus-induced proliferation, and that genetic differences (other than Fv-2) between strains C57BL/6 and DBA/2 affect the susceptibility of these cells to Friend virus. The evidence suggesting this was derived from experiments with C57BL/6 in equilibrium DBA/2 allophenic mice. Within the first few weeks following infection of these mice with the polycythemic NB-tropic strain of Friend virus (FV-P), we observed a rapid shift in the genotypic composition of both red cells and platelets in favor of those of the DBA/2 genotype. Infection with the anemia-inducing strain of Friend virus (FV-A) also resulted in preferential production of DBA/2 strain erythrocytes, but its effect on platelet kinetics was nil. The FV-P- and FV-A-induced change in red cell composition is consistent with the view that erythroid precursors are target cells for Friend virus and that viral infection preferentially stimulates proliferation of susceptible strain (DBA/2) erythroid precursors. As for the platelet shifts induced by FV-P (and not FV-A), we believe the changes in platelet mosaicism also could be caused by viral-induced proliferation of DBA/2 platelet precursors, or more primitive progenitors, over the C57BL/6 ones. Thus, these results implicate the existence of nonerythroid target cells for FV-P-induced proliferation, as well as the existence of genetic differences between strains C57BL/6 and DBA/2 that modulate the responsiveness of such cells to infection.

Animals↗
PubMed1985

Cellular site and mode of Fv-2 gene action.

The Fv-2 genotype of erythroid progenitors directly determines whether they will undergo viral-induced transformation. This conclusion was reached from studies of allophenic mice compounded from congenic C57BL/6 strains differing at Fv-2 and an enzyme marker (GPI). Infection of these Fv-2ss in equilibrium Fv-2rr mosaic animals with the polycythemic strain of Friend virus results in the development of Friend disease. Concomitant with disease symptoms is a shift in the mosaic composition of the erythrocytes in favor of those of the susceptible strain. The observed viral-induced shift in the erythrocyte composition is paralleled by a similar change in the mosaic composition of the CFU-E pool but not the primitive (d8) BFU-E pool. Thus, with regard to this particular Fv-2 phenotype (susceptibility to FV-P-induced cellular hyperplasia), Fv-2 manifests itself specifically in the erythroid lineage, either in mature (d3) BFU-E or CFU-E.

Animals↗