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Biomedical subjects

M J Dewey

Publications and source records attributed to M J Dewey.

At least 55 records · Page 3Linked to original sources
PubMed1984

The use and efficacy of child restraint devices. The Tennessee experience, 1982 and 1983.

The Tennessee Child Passenger Protection Act, mandating the use of child restraint devices for children younger than 4 years, took effect in 1978. In the years 1978 through 1983, eighty-one children younger than 4 years died in Tennessee traffic accidents; only two were in child restraint devices. During this period, as child restraint device use rose from 8% to more than 30%, the number of deaths among children younger than 4 years declined more than 50%. Analysis of supplemental accident reports filed in investigations of motor vehicle accidents involving children younger than 4 years during 1982 and 1983 showed that child restraint devices are highly effective in preventing death and in preventing or reducing injury. Children not in child restraint devices were 11 times more likely to die in an accident than children in child restraint devices. Children traveling in the arms of an adult were exposed to a risk of injury or death comparable to that of children left entirely unrestrained.

Accident Prevention↗
PubMed1984

Stable genotypic composition of blood cells in allophenic mice derived from congenic C57BL/6 strains.

Random shifts in blood cell genotypic composition are commonly observed in allophenic mice. This phenomenon was studied in 16 mosaic mice produced from very closely related strains, and no such changes were observed in the mosaic composition of erythrocytes, platelets, and lymphocytes over a period of 14 weeks. Furthermore, the mosaic distribution of a large group (66) of these mosaic mice was markedly biased in favor of those animals containing major contributions of both strains. This contrasts with what is normally found in collections of allophenic mice, in which the mosaic distribution curves are usually much flatter. While most allophenic mice have been produced from inbred strains with many genetic differences our results were obtained with congenic strains. This suggests that both properties, the unstable mosaic composition of blood cells and the flat mosaic distribution curves, are caused by specific genetic differences between cells of the two strains and are not inherent properties of allophenic mice. We propose that genetic differences cause these phenomena by inhibiting the mixing of cells of the two strains. Such might occur for example if, throughout development, cells of the same H-2 haplotype had greater affinity for each other than for ones of disparate H-2 haplotypes.

Animals↗
PubMed1983

Allophenic mice produced from embryos aggregated with antibody.

One difficulty in the production of allophenic mice by aggregation of preimplantation embryos is that they frequently roll apart before the bonds between the blastomeres have had time to form. One solution to the problem, described here, is to pretreat one of the embryos with rabbit anti-mouse serum just prior to pushing them together. Blastocyst formation is unhampered by antibody treatment, and numerous allophenic mice have already been produced with this new procedure.

Agglutination↗
PubMed1983

Isolation of recombinant bacteriophage containing male-specific mouse DNA.

The mammalian Y chromosome is an isolated piece of genetic material that directs sexual determination and gametogenesis. Very little is understood about the mechanism whereby the Y chromosome carries out these functions. Also, there is a severe lack of genetic markers on this chromosome. In order to understand the structure and function of the Y chromosome at the level of its DNA sequences and to provide genetic markers, we are isolating clones of DNA whose sequences are found primarily in DNA from male mice. To this end, we have developed a procedure for the identification of such clones. Application of this screening procedure to a lambda library derived from mouse sperm DNA has yielded 12 distinct clones, part of whose sequences are present predominantly in male DNA. Besides this DNA, they also contain other sequences that are shared with female DNA. These clones are either derived from the Y chromosome or they represent autosomal sequences specifically amplified during male development.

Animals↗
PubMed1983

Genetic control of hematopoietic kinetics revealed by analyses of allophenic mice and stem cell suicide.

The pluripotential hematopoietic stem cell is influenced by at least one gene that differs between DBA/2 and C3H/He, and C57BL/6 inbred mouse strains. This gene(s) manifests itself by its effect on susceptibility to killing of spleen colony forming cells (CFU-S) caused by hydroxyurea (HU). In strains DBA/2 and C3H/He 20% of the CFU-S population is normally in S phase whereas practically none from strain C57BL/6 are synthesizing DNA. On the other hand, in C57BL/6 in equilibrium DBA/2 allophenic mice we observed that the proportion of DBA/2 erythrocytes was higher than the proportion of DBA/2 lymphocytes; the fraction of platelets and neutrophils with the DBA/2 genotype fell between the values for erythrocytes and lymphocytes. Control experiments using mice congenic at the Fv-2 locus confirm that in both situations we are examining effects of a gene(s) other than Fv-2. For the effect on the S phase fraction of CFU-S, we refer to the gene(s) as Stk (stem cell kinetics). We suggest that the observed skewing in composition among the various mature blood cell types in C57BL/6 in equilibrium DBA/2 allophenic mice is caused by allelic variants of the Stk gene. Such variation would favor the formation of DBA/2 erythrocytes, platelets, and neutrophils over those of the C57BL/6 genotype.

Animals↗
PubMed1982

Audiogenic seizure susceptibility of C57BL/6 in equilibrium DBA/2 allophenic mice.

Allophenic mice composed of cells from a strain (DBA/2) susceptible to sound-induced seizures and cells from a strain (C57BL/6) resistant to them were produced by embryo aggregation techniques. Twenty-eight allophenic mice were tested for audiogenic seizure susceptibility. The results were compared with the genotypic composition of the coat melanocytes. For those animals with a predominance of one genotype or the other in the coat, their seizure phenotype was the same as that of the strain most represented in the coat. In contrast, those animals with major contributions of both genotypes in the coat demonstrated the entire spectrum of susceptibility phenotypes. Such results are likely to be a manifestation of a relatively small target tissue for the genes influencing the development of audiogenic seizure susceptibility.

Acoustic Stimulation↗
PubMed1982

Genetic differences in red cell osmotic fragility: analysis in allophenic mice.

Mice of strain DBA/2J were found to produce red cells considerably more resistant to osmotic lysis than cells from C57BL/6J or the F1 hybrid between the two strains. Such strain-specific differences in osmotic fragility could be the result of genetically determined humoral or other systemic differences that indirectly influence red cell properties. Alternatively, this phenotypic variation might be an inherent property of the erythrocyte themselves and be directly controlled by their genotype. Analysis of red cells from allophenic (mosaic) mice of the strain composition C57BL/6J in equilibrium DBA/2J demonstrated that the latter possibility is the case. In such mice, erythrocytes of the DBA/2J genotype are relatively more resistant to osmotic lysis than are those of the C57BL/6J genotype; partial lysis of allophenic blood at intermediate salt concentrations results in marked enrichment for DBA/2J cells among the survivors. Future experiments designed to determine the mechanism underlying this difference can now focus on the properties of the red blood cells per se with the certainty that this property is inherent to the genotype of each cell.

Animals↗
PubMed1982

Friend viral pathogenesis in C57BL/6 reversible DBA/2 allophenic mice.

Infection of mice with Friend erythroleukemia virus initially causes massive proliferation of erythroid precursors accompanied by splenomegaly and reticulocytosis. Strains of mice differ among themselves in susceptibility to Friend virus and one of the major genes affecting the early response to viral infection is Fv-2. Allophenic mice compounded from a resistant strain C57BL/6 (Fv-2rr) and a susceptible one DBA/2 (Fv-2ss) were infected with the polycythemic strain of Friend virus to determine whether susceptibility/resistance was limited to cells of the respective genotypes or if there was an influence across the genotypic barriers. The manifestations of viral pathogenesis monitored were splenomegaly, reticulocytosis and leukocytosis. In addition, the proportion of red cells of the two genotypes in each animal was monitored before and after viral infection by analyses for strain specific electrophoretic variants of hemoglobin and glucose phosphate isomerase. The group of allophenic mice with 25% or more susceptible-strain red blood cells all developed symptoms of virus-induced disease and also revealed dramatic increases in the number of red cells of the susceptible-strain genotype. Thus, no evidence for protection of susceptible-strain cells by ones of the resistant strain could be observed and the disease developed primarily in susceptible strain cells. On the other hand infected animals with 15% or less DBA/2 red cells were severely retarded in the development of Friend disease. Under these circumstances susceptible strain target cells might fail to undergo viral induced replication as a result of direct protection by resistant strain cells. Alternatively, other more complex mechanisms might be involved such as protective anti-viral immune reactions.

Animals↗
PubMed1980

Introduction of a viral thymidine kinase gene and the human beta-globin gene into developmentally multipotential mouse teratocarcinoma cells.

Teratocarcinoma (TCC) stem cells provide unique prospects for the introduction of specific genes into mice, by virtue of their dual capacity for propagation in vitro and for normal differentiation in embryos. In this study, we have demonstrated that foreign genes amenable to selection in culture can be transferred into the stem cells and expressed. These cells maintain expression of the gene for long periods during differentiation in tumors in vivo in the absence of selective pressure. The cells also integrate an unlinked nonselectable gene at high frequency. Addition of the cloned herpes simplex virus (HSV) thymidine kinase (tk; ATP:thymidine 5'-phosphotransferase, EC 2.7.1.21) gene to cultures of tk(-)TCC cells yielded tk(+) colonies at a frequency of one colony per 4 mug of plasmid DNA. This transformation efficiency, although appreciably lower than for mouse L tk(-) cells, permits the isolation of many transformants. The HSV provenance of the transformed phenotype was verified by the characteristic electrophoretic mobility of the tk protein and by neutralization of the tk activity with specific antiserum. Moreover, blot hybridization tests revealed at least one intact copy of the viral tk gene integrated into the DNA of transformed cells. When injected into syngeneic mice, the cells formed solid tumors with various differentiating tissues. From blot hybridization comparisons with their cell lines of origin, seven of nine tumors examined had maintained the HSV tk gene without significant loss or rearrangement. Viral tk enzyme activity could also be demonstrated in at least some of the tumors. Cotransfer of the cloned human beta-globin gene along with the unlinked HSV tk gene was successful in 2 of 10 tk(+) transformants. Thus, defined genes can be stably introduced into TCC cells in culture and maintained in vivo in a form in which they are transcribed and translated to produce a functional protein.

Animals↗
PubMed1978

Teratocarcinoma cells as vehicles for introducing specific mutant mitochondrial genes into mice.

The immediate purpose of the experiment was to establish a means of introducing specific mitochondrially encoded mutant genes into mice. Mouse teratocarcinoma stem cells were used as vehicles for the cytoplasmic markers because of their known capacity for normal somatic and germinal differentiation after injection into blastocysts. The mutation of choice, chloramphenicol resistance (CAP(R)), was first produced in a melanoma cell line by mutagenesis and selection. The CAP(R) trait was then transferred from a resistant melanoma cell to a sensitive (CAP(S)) teratocarcinoma cell by fusing to the latter only the cytoplasmic portion of the CAP(R) donor. This indirect route demonstrated the cytoplasmic provenance of the mutation. Protein synthesis in mitochondria isolated from the cybrid, or cytoplasmic hybrid, cells was barely affected by chloramphenicol, in contrast to the inhibitory influence of the drug on mitochondria of the parent teratocarcinoma line. Cells of the cybrid clone resembled teratocarcinoma cells and retained their ability to form diverse tissues in solid tumors produced from subcutaneous grafts. Cells from the tumors were retransplanted and were tested periodically by culture in chloramphenicol; they were found to be stably CAP(R) even after 16 weeks in vivo in the absence of the selective agent. The CAP(R) cybrids were microinjected into blastocysts of another inbred strain and, after transfer to foster mothers, mosaic mice were obtained. They comprised both cybrid- and blastocyst-derived cells in various tissues, as indicated by strain-specific nuclear markers. These results demonstrate successful normal differentiation of the CAP(R) lineage in vivo. Teratocarcinoma cybrids thus offer a practical portal of entry of preselected mitochondrial genes into mice. This will ultimately permit in vivo investigation of maternally transmitted traits, of mitochondrial genetic influences in specialized cells, and of possible roles of cytoplasmic genes in clinical and disease states.

Animals↗
PubMed1977

Mosaic mice with teratocarcinoma-derived mutant cells deficient in hypoxanthine phosphoribosyltransferase.

Mutagenized stem cells of a cultured mouse teratocarcinoma cell line were selected for resistance to the purine base analog 6-thioguanine. Cells of a resistant clone were completely deficient in activity of the enzyme hypoxanthine phosphoribosyltransferase (HPRT, IMP:pyrophosphate phosphoribosyltransferase, EC 2.4.2.8), the same X-linked lesion as occurs in human Lesch-Nyhan disease. After microinjection into blastocysts of another genetic strain, the previously malignant cells successfully participated in normal embryogenesis and tumor-free, viable mosaic mice were obtained. Cells of tumor lineage were identified by strain markers in virtually all tissues of some individuals. Mature function of those cells was evident from their tissue-specific products (e.g., melanins, liver proteins). These mutagenized teratocarcinoma cells are therefore developmentally totipotent. Retention of the severe HPRT deficiency in the differentiated state was documented in extracts of mosaic tissues by depressed specific activity of the enzyme, and also by presence of unlabeled clones in autoradiographs of explanted cells incubated in [(3)H]hypoxanthine. Some mosaic individuals had mutant-strain cells in only one or a few tissues. Such animals may provide unique opportunities to identify the tissue sources of particular aspects of the complex disease syndrome. The tissue distribution of HPRT-deficient cells suggests that selection against them is particularly strong in blood of the mosaic mice, as is already known to be the case in human heterozygotes. This phenotypic parallelism supports the expectation that afflicted F(1) male mice that might be obtained from mutant germ cells can serve as a model of the human disease.

Animals↗