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Biomedical subjects

F M Johnson

Publications and source records attributed to F M Johnson.

At least 37 records · Page 2Linked to original sources
PubMed1985

A mutation in the beta-globin gene detected in the progeny of a female mouse treated with ethylnitrosourea.

A mouse with a variant hemoglobin was discovered during electrophoretic screening of (C57BL/6J X DBA/2J)F1 progeny of females treated with ethylnitrosourea. The variant trait was transmitted as a simple Mendelian alternate at the Hbb locus in all crosses except those involving the original carrier of the mutation. The proband mouse which received the mutation directly from the mutagen-treated parent was a germinal mosaic for the mutant and normal Hbbs alleles. The mutant allele was designated Hbbs2. The mutant haplotype specifies both an electrophoretically fast hemoglobin band and a hemoglobin band in the normal beta single hemoglobin position. Thus, the mutation has altered one of the tandemly duplicated genes at the Hbbs locus. A comparison of the relative concentrations of the two hemoglobins in Hbbs2 mice demonstrates preferential expression of the mutant gene, possibly analogous to the enhanced expression of Hbbdmaj in the Hbbd haplotype. Analysis of the amino acid sequence of the variant beta-globin revealed that the valine at position 60 was changed to glutamic acid. The simplest mutation mechanism for such an alteration is an A X T----T X A transversion.

Animals↗
PubMed1985

Lack of evidence for skeletal abnormalities in offspring of mice exposed to ethylnitrosourea.

Using morphometrical methods, we investigated variation in the skeletons of more than 400 offspring of C57BL/6J and DBA/2J male mice that had received either a 250 mg/kg dose of the mutagen ethylnitrosourea or a solvent control. Sperm involved in the matings developed from cells in the spermatogonial stage at the time the animals were injected. Although variants were detected, differences in frequencies of gross abnormalities and minor variations in shape between treated and control groups were almost all nonsignificant. There were also no major differences in measures of variability within the groups of offspring from either the treated males or the control group. Additional examination of the skeleton for changes in the frequency of a series of nonmetrical variants also provided no evidence of differences between the treated and control groups that could be attributed to induced mutations. These results conflict with previous findings that ethylnitrosourea is a potent inducer of dominant skeletal mutations.

Abnormalities, Drug-Induced↗
PubMed1985

Hematology of a murine beta-thalassemia: a longitudinal study.

Mice homozygous for a spontaneous mutation, in which the beta-major globin gene is deleted, have clinical symptoms of beta-thalassemia. These mice have a hypocellular, hypochromic, microcytic anemia that becomes more severe with increasing age. The defective red cell morphology, decreased osmotic fragility of erythrocytes and shortened red cell life span found in beta-thalassemic mice are similar to those observed in human beta-thalassemia. Synthesis of beta-globin is depressed but not as much as might be expected because the expression of the beta-minor globin gene is enhanced to encode two to three times more globin than in normal mice. Splenomegaly, an enlarged pool of stem cells for erythropoiesis, and iron overloading occur in older mice. The fact that these mice remain moderately healthy makes them a very suitable animal model in which to develop and test alternative techniques of gene therapy that could be successfully applied to the treatment of human thalassemia. Homozygous beta-thalassemic mice have large deposits of iron in their tissues, which might make these mice also useful for in vivo tests of the effectiveness and possible long-term side effects of newly developed iron chelators.

Animals↗
PubMed1983

A mouse model for beta-thalassemia.

A mutation that produces an absolute deficiency of normal beta-major globin polypeptides has been recovered from a DBA/2J male mouse. Most mice homozygous for the deficiency survived to adulthood and reproduced but were smaller at birth than their littermates and demonstrated a hypochromic, microcytic anemia with severe anisocytosis, poikilocytosis, and reticulocytosis and the presence of inclusion bodies in a high proportion of circulating erythrocytes. Mice heterozygous for the deficiency demonstrated a mild reticulocytosis but were not clinically anemic. Analysis of globin chain synthesis in vitro by 3H-leucine incorporation revealed that beta-globin synthesis was nearly normal (95%) in heterozygotes and about 75% of normal in deficiency homozygotes. Molecular characterization of the mutation by restriction analysis revealed a deletion of about 3.3 kb of DNA, including regulatory sequences and all coding blocks for beta-major globin. Based on genetic and hematological criteria, mice homozygous for the mutant allele, designated Hbbth-1, represent the first animal model of beta-thalassemia (Cooley's anemia), a severe genetic disease of humans.

Animals↗
PubMed1983

Analysis of a mouse alpha-globin gene mutation induced by ethylnitrosourea.

A DBA/2 mouse treated with ethylnitrosourea sired an offspring whose hemoglobin showed an extra band following starch gel electrophoresis. The variant hemoglobin migrated to a more cathodal position in starch gel. Isoelectric focusing indicated that chain 5 of the mutant hemoglobin migrated to a more cathodal position than the normal chain 5 from DBA/2 mice and that the other alpha-globin, chain 1, was not affected. On focusing gels the phenotype of the mutant allele, Hbay9, was expressed without dominance to normal chain 5, and Hbay9/Hbay9 homozygotes were fully viable in the laboratory. The molecular basis for the germinal mutation was investigated by analyzing the amino acid sequence of chain 5y9, the mutant form of alpha-chain 5. A single amino acid substitution (His leads to Leu) at position 89 was found in chain 5y9. We propose that ethylnitrosourea induced an A leads to T transversion in the histidine codon at position 89 (CAC leads to CTC). This mutation has apparently not been observed previously in humans, mice or other mammals, and its novel occurrence may be indicative of other unusual mutational events that do not ordinarily occur in the absence of specific mutagen exposure.

Amino Acid Sequence↗
PubMed1983

Laser photoradiation therapy of cancer.

We conducted a trial of photoradiation therapy of cancer at the University of California at Irvine. The basis of this technique is a photochemical reaction between an i.v.-injected material, hematoporphyrin derivative, and red light (wavelength, 630 nm). Hematoporphyrin derivative localized in malignant tissue, resulting in selective destruction of cancer cells upon illumination with red light. One hundred twenty-eight sites of recurrent cancer or premalignant lesions were treated in 37 patients. Of this group, 35 patients had recurrent cancer refractory to conventional therapy, and two had premalignant lesions. Favorable responses were achieved in 67% of the sites treated. The dose of hematoporphyrin derivative used in this study ranged from 2 to 5 mg/kg with the majority of patients receiving 3 mg/kg. Total light dose administered appeared to be the most critical parameter evaluated. Light doses in excess of 20 J/sq cm generally resulted in blistering and necrosis of intact skin, while no appreciable increase in response was observed. Photoradiation therapy has demonstrable efficacy in cancer therapy and avoids much of the morbidity of current conventional techniques.

Hematoporphyrins↗
PubMed1982

In vitro cellular effects of hematoporphyrin derivative.

Several in vitro cell systems were exposed to hematoporphyrin derivative (HPD): established lines of rat kangaroo epithelial kidney; normal mouse embryonic fibroblasts; and differentiated neonatal rat myocardial cells. The uptake of HPD (25 to 100 micrograms/ml) by individual cells occurred rapidly over a 2-hr period and leveled off by 24 hr. HPD was excreted from cells by 48 hr after exposure. However, a low level of HPD (above background) was maintained in cells for up to 4 days following cessation of exposure. Intracellular binding of HPD was to mitochondria as demonstrated by fluorescence microscopy. HPD was also shown to have a growth-inhibiting effect on rat kangaroo cells without added light. The growth effects on mouse cells were less marked.

Animals↗
PubMed1981

A null mutation at the mouse Phosphoglucomutase-1 locus and a new locus Pgm-3.

A null mutation at the phosphoglucomutase locus (Pgm-1) was discovered by electrophoretic analysis of the inbred mouse strain C57BL/6J. The null allele (Pgm-1n) was shown to segregate as a Mendelian unit alternative to the Pgm-1a and Pgm-1b alleles. Mice expressing the Pgm-1n allele, either in the heterozygous or homozygous state, are viable, healthy, and fertile. The occurrence of the Pgm-1n mutant revealed a previously unreported genetic locus (Pgm-3) that controls the expression of a third phosphoglucomutase. Two electrophoretically expressed alleles of Pgm-3 (inherited without dominance) are found in the inbred mouse strains C57BL/6J and DBA/2J. Linkage observed between the Pgm-3 locus, the dilute locus (d) and the cytoplasmic malic enzyme locus (Mod-1) has allowed assignment of the Pgm-3 locus to chromosome 9. A striking tissue specific expression of Pgm-1 and Pgm-3 was observed. Products of the Pgm-3 locus were detected in kidney, testes, brain, and heart. In contrast, Pgm-1 controlled isozymes were present in kidney, spleen, ovaries, and erythrocytes.

Alleles↗
PubMed1981

Mouse spermatogonia exposed to a high, multiply fractionated dose of a cancer chemotherapeutic drug: mutation analysis by electrophoresis.

Male mice of the DBA/2J strain were injected with procarbazine at a dose of 200 mg/kg body weight twice weekly until an accumulated dose of 2400 mg/kg was reached. A concurrent control group, injected only with the vehicle (saline) was also established. Most of the treated animals died as a result of exposure and all survivors became temporarily sterile. After regaining fertility the few survivors were repeatedly mated with C57BL/6J females over several weeks time to generate a population of F1 animals. The parental animals and the F1 were subsequently analyzed by electrophoresis for the occurrence of newly arisen mutations of spermatogonial origin. A mutation in the gene Pep-3 was found.

Animals↗
PubMed1981

Mutation-rate determinations based on electrophoretic analysis of laboratory mice.

Rate calculations are described for germinal mutations detected by an electrophoretic system as applied to mice in a series of recent experiments. The utility of the electrophoretic system is examined from several comparative viewpoints. The electrophoretic approach has a number of features to recommend it for future applications concerned with genetic hazard assessment. Its advantages include sensitivity, versatility, cost effectiveness and relevance to humans.

Alleles↗
PubMed1981

Electrophoretically detected germinal mutations induced in the mouse by ethylnitrosourea.

Male DBA/2J and C57BL/6J mice were treated with ethylnitrosourea (EtNU) at a dose of 250 mg/kg of body weight. After a sterile period of 11 weeks, the treated animals were mated with untreated females; treated DBA with C57 and treated C57 with DBA. A small control group of untreated males was established, and a larger control group from earlier experiments was also used for comparison. Tissue samples removed surgically from the parents and F1 offspring were examined by electrophoresis. Nine newly arisen mutants attributable to induction by EtNU were found in 22,512 loci tested for mutation. No mutations were encountered in 290,252 control locus tests. A preliminary study conducted concomitantly with the electrophoretic analyses for dominant lethal effects and physical malformation showed no increase over background due to EtNU treatment of spermatogonia, which suggests that mutations induced by EtNU tend not to be expressed in this way. The nature of the mutants identified by electrophoresis facilitates follow-up analyses leading to increased understanding of the molecular basis and the physiological effects of induced mutations in mammalian organisms.

Alleles↗
PubMed1980

Identification and biochemical analysis of mouse mutants deficient in cytoplasmic malic enzyme.

During the biochemical screening of mutant enzymes in mice, individuals with an apparent nonfunctional allele at the locus (Mod-l) responsible for cytoplasmic malic enzyme were identified by starch gel electrophoresis and by enzyme activity measurements. A series of matings and genetic analyses were made, and mice homozygous for the nonfunctional or null allele (Mod-ln) were produced. The mutation appeared to occur spontaneously in the C57BL/6J strain. By double-immunodiffusion and enzyme immunoinactivation assays, the null mutants were shown to express no proteins that cross-react with the antiserum to cytoplasmic malic enzyme (CRM-negative). In liver homogenates of homozygous null mutants, lack of protein components that form complexes with IgG from the cytoplasmic malic enzyme specific antiserum was further demonstrated by passage of the original serum through a mutant liver homogenate--Sepharose column, where the postadsorbed serum retained its titer and specificity. The residual malic enzyme activity (< 10% of the normal) observed in various tissue homogenates of the homozygous null mutants was attributed to that of mitochondrial isozyme of malic enzyme. Assays of enzymes from tissues of different genotypes revealed no significant differences in activities of six other enzymes in the related metabolic pathways. However, in liver from mutant mice, a lower NADPH/NADP+ ratio was consistently observed in comparison to that from control mice. Both the mutant and the control mice of the same age were found to have comparable body weight and lipid content.

Alleles↗