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L B Russell

Publications and source records attributed to L B Russell.

At least 73 records · Page 4Linked to original sources
PubMed1993

Molecular analysis of viable spontaneous and radiation-induced albino (c)-locus mutations in the mouse.

Thirty-one homozygous-viable, radiation-induced or spontaneous mutations at the albino (c) locus in mouse chromosome 7 were analyzed by Southern blot analysis with a tyrosine cDNA clone and with probes derived from the closely linked proviral integration sites Pmv-31 and Emv-23, which flank the tyrosinase gene on the proximal and distal sides, respectively. Thirteen of 27 radiation-induced and one of four spontaneous mutations manifested deletions or rearrangements for the tyrosinase gene. The sizes of four deletions found to break within the tyrosinase gene itself were estimated to be < or = 36 kb, < or = 40 kb, approximately 260 kb, and approximately 480 kb. Two homozygous-viable deletions were found to include flanking proviral loci, suggesting that they could be from 1500-2000 kb in length, if not longer. The existence of these very large, homozygous-viable deletions suggests that the one-to-two megabases including and surrounding the c locus harbor no genes essential for normal viability or fertility, although genes controlling more subtle (or "nonessential") phenotypes are likely to be present. These data thus provide some insight into the molecular structure of a number of viable c-locus mutations, whose nature could not be predicted solely on the basis of genetic analysis, as could be done for either lethal or reduced-pigment c mutations.

Albinism↗
PubMed1992

The mouse short ear skeletal morphogenesis locus is associated with defects in a bone morphogenetic member of the TGF beta superfamily.

The mouse short ear gene is required for normal growth and patterning of skeletal structures, and for repair of bone fractures in adults. We have carried out an extensive chromosome walk in the chromosome region that surrounds this locus. Here we show that the short ear region contains the gene for a TGF beta-related protein called bone morphogenetic protein 5 (Bmp-5). This gene is deleted or rearranged in several independent mutations at the short ear locus. Mice homozygous for large deletions of the Bmp-5 coding region are viable and fertile. Mutations at the short ear locus provide an important new tool for defining the normal functions of BMPs in mammals. The specific skeletal defects seen in short-eared animals, which occur against a background of otherwise normal skeletal structures, suggest that particular aspects of skeletal morphology may be determined by individual members of a family of signaling factors that can induce the formation of cartilage and bone in vivo.

Animals↗
PubMed1992

Genetic, cytogenetic, and molecular analyses of mutations induced by melphalan demonstrate high frequencies of heritable deletions and other rearrangements from exposure of postspermatogonial stages of the mouse.

Specific-locus experiments have previously shown melphalan to be mutagenic in all male germ-cell stages tested and particularly so in early spermatids. All but 2 of 24 specific-locus mutations recovered were tested genetically, cytogenetically, and/or molecularly. At least 12 of 15 tested mutations recovered from postspermatogonial stages but only 1 of 7 mutations recovered from stem-cell or differentiating spermatogonia gave evidence of being deletions or other rearrangements. Melphalan-induced mutations, thus, confirm the pattern of dependence of mutation structure on germ-cell stage that had been shown earlier for other chemicals. Results of the present investigation illustrate the capabilities of combined genetic, cytogenetic, and molecular analyses for characterizing the nature of specific-locus mutations. Fine-structure molecular mapping of long regions surrounding specific loci has been greatly facilitated by the availability of genetic reagents (particularly, deletion complexes) generated in specific-locus experiments over the course of decades. Reciprocally, this mapping permits increasingly detailed characterization of the nature of lesions induced by mutagenic exposures of germ cells, adding great powers for qualitative analysis of mutations to the specific-locus test. Cytogenetic and genetic investigations also provide evidence on lesion type, especially for loci at which mutations cannot yet be analyzed molecularly. Melphalan, like chlorambucil, can generate many mutations, a high proportion of which are deletions and other rearrangements, making this chemical valuable for generating mutations (at any locus) amenable to molecular access.

Animals↗
PubMed1992

Chlorambucil-induced mutations in mice recovered in homozygotes.

Chlorambucil induced a number of recessive visible mutations in the mouse. Induction of these mutations was studied in two mating schemes, each designed to recover mutations after two intercrosses. In scheme 1, 10 mutations were detected in 82 mice; in scheme 2, 1 mutation was detected in 19 mice. We have estimated that the proportion of gametes carrying a recessive visible mutation may be as high as 25% after a dose of 10 mg of chlorambucil per kg to early spermatids. Seven of these mutations caused morphologically distinct abnormalities, including (i) a cerebellar abnormality similar to that expressed in homozygotes for the reeler (rl) mutation; (ii) open eyelids at birth; (iii) a rostral head hemangioma; (iv) abnormally small spleens, anemia, and umbilical hemorrhages; (v) immobility at birth; (vi) polycystic kidneys; and (vii) a circling behavior. Four additional mutations resulted in growth retardation and a runting syndrome. Because, in earlier studies, all molecularly characterized mutations induced by chlorambucil in poststem cells have proved to be deletions, these recessive visible mutations are probably deletions as well. These mutations may be useful in isolating and characterizing the genes responsible for the observed phenotypes.

Animals↗
PubMed1992

Murine fumarylacetoacetate hydrolase (Fah) gene is disrupted by a neonatally lethal albino deletion that defines the hepatocyte-specific developmental regulation 1 (hsdr-1) locus.

Homozygous deletion of the hepatocyte-specific developmental regulation 1 (hsdr-1) locus in mouse chromosome 7 results in perinatal death and a pleiotropic syndrome characterized by ultrastructural abnormalities of the liver and kidney, failure of induction of a number of specific transcription units in the liver and kidney during late gestation, and marked overexpression of an enzyme that defends against oxidative stress. Previously, the breakpoints of two albino (c) deletions (c14CoS and c1FAFyh) that genetically define hsdr-1 were localized, on a long-range map, in the vicinity of the distal breakpoint of a viable albino deletion (c24R75M) that breaks proximally within the c locus. Here we report the use of a probe derived from a deletion breakpoint fusion fragment cloned from c24R75M/c24R75M DNA to clone a breakpoint fusion fragment caused by the c14CoS deletion. The proximal breakpoint of the c14CoS deletion was discovered to disrupt a gene (Fah) encoding fumarylacetoacetate hydrolase, the last enzyme in the tyrosine degradation pathway. All of the extant c deletions eliciting the hsdr-1 phenotype prevent expression of the Fah gene in the liver, and all but one disrupt the coding segment of the gene. Therefore, the Fah gene maps within or proximal to the hsdr-1 locus, as defined by deletion breakpoints, and disruption of this gene may be partially or completely responsible for the phenotypes associated with the hsdr-1 deletion syndrome. These mouse mutants may also provide models for the human genetic disorder hereditary tyrosinemia, which is associated with fumarylacetoacetate hydrolase deficiency and liver and kidney dysfunction.

Amino Acid Sequence↗
PubMed1992

The risks of blood transfusion: the relative influence of acquired immunodeficiency syndrome and non-A, non-B hepatitis.

PURPOSE: The acquired immunodeficiency syndrome epidemic has greatly increased concern about the risk of blood transfusion. Many transfusions are now autologous, and when these are not available, both physicians and patients are more likely to question the advisability of transfusion. We evaluate the risk of preoperative blood transfusion and the contribution of human immunodeficiency virus (HIV) infection to that risk. METHODS: We used decision analysis to characterize the risk associated with HIV infection in days of life lost. The contributions to risk of acute transfusion reaction, hepatitis B, and non-A, non-B hepatitis are also estimated. Sensitivity analyses show the implications for transfusion risk of recent information about HIV infection in the blood supply and a new test for hepatitis C. RESULTS: The analysis shows that the contribution of HIV infection to the risk of death from transfusion, expressed in days of life expectancy lost, has become extremely small over the last several years. Currently, HIV infection accounts for less than 1% of the risk of death, while non-A, non-B hepatitis accounts for 97% to 98%. Further reductions in the risk of HIV infection, even to zero, will make relatively little difference in the safety of transfusion. The analysis also shows that the remaining risk from transfusion should decrease sharply, by more than two thirds, with the adoption of the test for hepatitis C. CONCLUSIONS: Efforts to improve the safety of blood should focus on reducing the risk of non-A, non-B hepatitis. The remaining risk of HIV infection is very small.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Frequency and nature of specific-locus mutations induced in female mice by radiations and chemicals: a review.

The inducibility of heritable mutations in female mammals has been measured in the mouse specific-locus test (SLT). For radiation-induced mutations, a large body of data has been accumulated that includes information about biological and physical factors that influence mutation yields. However, relatively few SLT studies in females have been conducted with chemicals to date. A single estimate of the spontaneous mutation rate in oocytes, 6/536,207, has been derived as the most appropriate one to subtract from experimental rates. This rate is highly significantly below the spontaneous mutation rate in males. Mutations recovered from females mutagenized at any time after about the 12th day post-conception are induced in non-dividing cells. In adult females, most oocytes are arrested in small follicles; maturation from this stage to ovulation takes several weeks. High-dose-rate radiations are more mutagenic in mature and maturing oocytes than in spermatogonia of the male; on the other hand, no clearly induced mutations have been recovered from irradiated arrested oocytes. Efficient repair processes have been invoked to explain the latter finding as well as the upward-curving dose-effect relation for acute irradiation, and the fact that dose protraction drastically reduces mutation yield from mature and maturing oocytes. The dose-protraction effect is much greater than that found in spermatogonia. Radiation-induced mutation rates in embryonic, fetal, and newborn females are overall lower than those in the mature and maturing oocytes of adults. A dose-protraction effect has also been demonstrated at an early developmental stage when the nuclear morphology of mouse oocytes most resembles that of the human. Of only 5 chemicals so far explored for their effect in oocytes, 2 (ethylnitrosourea, ENU, and triethylenemelamine, TEM), and possibly a third (procarbazine hydrochloride, PRC), are mutagenic--with at least one of these (ENU) mutagenic in arrested as well as maturing oocytes. However, the mutation rate is, in each case, lower than for treated male germ cells. By contrast, ENU-induced mutation yield for the maternal genome of the zygote is an order of magnitude higher than that for the zygote's paternal genome or for spermatogonia. A high proportion of mutants derived from chemical treatment of oocytes (including the oocyte genome in zygotes) are mosaics, probably owing to lesions affecting only 1 strand of the DNA. A characteristic of specific-locus mutations induced in oocytes is that they include a considerably higher percentage of large (multi-locus) lesions (LLs) than do mutations induced in spermatogonia.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Melphalan, a second chemical for which specific-locus mutation induction in the mouse is maximum in early spermatids.

Melphalan (MLP), a bifunctional alkylating agent structurally related to the highly mutagenic chemical chlorambucil (CHL), was found to induce high frequencies of specific-locus mutations in postspermatogonial germ cells of the mouse, and to be one of only a few chemicals that is also mutagenic in spermatogonial stem cells. Productivity patterns following MLP exposures resembled those that had been found for CHL. Mutation rates in successive male germ-cell stages were measured at three MLP-exposure levels in a total of 95,375 offspring. While the induced (experimental minus historical-control) mutation rate is relatively low in stem-cell spermatogonia (1.2 x 10(-5) per locus at a weighted-mean exposure of 7.3 mg/kg), it is about 5 times higher in poststem-cell stages overall, and peaks at 26.7 x 10(-5) per locus in early spermatids at a weighted-mean exposure of only 5.7 mg/kg. This "type-2 pattern" of mutation yield (Russell et al., 1990), i.e., peak sensitivity in early spermatids, has heretofore been found for only one other chemical, CHL. Mutation-rate data earlier reported for CHL (Russell et al., 1989) were augmented in the present study for comparison with MLP-induced rates. Because of the greater toxicity of MLP, average exposures used for this chemical were only about one-half of those for CHL. When MLP and CHL mutation rates are extrapolated to equimolar doses, they appear very similar for poststem-cell stages overall. However, in the case of CHL, a somewhat higher proportion of the mutations is induced in early spermatids than in the case of MLP.

Animals↗
PubMed1992

The inequality of medical expenditures for several years in a healthy, nonelderly population.

Previous studies have shown that the distribution of annual medical expenditures for a population is very unequal and remains so for periods of more than 1 year. The authors use a better measure of inequality, the Gini coefficient, to test its persistence for longer periods. This measure is applied to data collected from the Rand Health Insurance Experiment. The experiment enrolled a nonelderly population typical of those covered by employer health plans for periods up to 5 years. The distributions of annual expenditures for this population are highly unequal, in line with previous studies. Inequality declines substantially when longer periods are considered.

Adolescent↗
PubMed1991

Molecular characterization of a region of DNA associated with mutations at the agouti locus in the mouse.

Molecular characterization of a radiation-induced agouti (a)-locus mutation has resulted in the isolation of a segment of DNA that maps at or near the a locus on chromosome 2 in the mouse. This region of DNA is deleted in several radiation- or chemical-induced homozygous-lethal a-locus mutations and is associated with specific DNA structural alterations in two viable a-locus mutations. We propose that DNA probes from this region of chromosome 2 will be useful for ultimately characterizing the individual gene or genes associated with a-locus function.

Animals↗
PubMed1991

Fatal lymphoreticular disease in the scurfy (sf) mouse requires T cells that mature in a sf thymic environment: potential model for thymic education.

Characteristic lesions in mice hemi- or homozygous for the X-linked mutation scurfy (sf) include lymphohistiocytic proliferation in the skin and lymphoid organs, Coombs' test-positive anemia, hypergammaglobulinemia, and death by 24 days of age. The role of the thymus in the development of fatal lymphoreticular disease in the scurfy mouse was investigated. Neonatal thymectomy doubles the life span of scurfy mice, moderates the histologic lesions, and prevents anemia, despite the continued presence of high levels of serum IgG. Animals bred to be nude and scurfy (nu/nu; sf/Y) are viable, fertile, and free of scurfy lesions. Bone marrow from scurfy mice can reconstitute lethally irradiated, H-2-compatible animals but does not transmit scurfy disease. We conclude, from these data, that scurfy lesions are mediated by T lymphocytes that mature in an abnormal (sf) thymic environment.

Animals↗
PubMed1991

Factors that affect the molecular nature of germ-line mutations recovered in the mouse specific-locus test.

The morphological specific locus test (SLT), which allows the scoring of 2,000 loci/hr/person, has been in use for four decades for measuring mammalian germ-line mutation rates under various conditions of exposure. More recently, the SLT's capabilities for the qualitative characterization of mutations have been exploited. The large sets of mutations centered on specific loci that have been accumulated over the years, including sets of nested deletions, have provided prime material for fine-structure genetic analyses. Subsequent molecular entry to these regions has led to intensive physical/functional mapping of megabase segments of the genome. In turn, these investigations have generated genetic and molecular tools for analyzing individual mutations as to extent and nature of the genomic lesion. Using the results of such analyses, it has been shown that germ-cell-stage at which mutagenic treatment is administered, rather than the nature of the mutagen used, may be the chief determinant of the nature of genomic lesions. These and related quantitative findings now make it possible to optimize conditions for the use of mutagens in providing desired types of mutations as tools (e.g., high incidences of deletions or other rearrangements vs. high incidences of point mutations).

Animals↗
PubMed1991

The paternal genome in mouse zygotes is less sensitive to ENU mutagenesis than the maternal genome.

The two parental genomes lie separate within the zygote and may be differentially affected by environmental influences. We have shown earlier (Russell et al., 1988) that the maternal genome within the mouse zygote is exquisitely sensitive to the induction of point mutations by N-ethyl-N-nitrosourea (ENU), and that the initial lesion probably occurs in one strand of the DNA. The present experiment measured specific-locus mutation induction in the paternal genome. Zygotes containing a multiple-recessive maternal genome (a; b; p cch; d se; s) and the corresponding wild-type alleles in the paternal one were exposed to 50 mg ENU/kg in vivo at one of two stages: the presumed times of sperm entry and early pronuclear stage. At weaning age, the resulting mice were examined for mutations at the marked loci as well as for other mutations producing externally visible phenotypes. At the marked loci, one possible mosaic (for b) was observed among 2113 classified offspring that had been treated with ENU as zygotes; this animal failed to transmit a mutation. By contrast, in the reciprocal cross (which tests the maternal genome) we had observed 8 specific-locus mutations (6 of them mosaics) among 1555 offspring that had received the same dose of ENU during sperm entry (and completion of oocyte meiosis II). In the present experiment, we also found one mutation at other loci (two at other loci in the reciprocal cross). The frequency of offspring with small white belly spots was significantly greater in the treated groups (3.5 and 1.9% at the earlier and later stage, respectively) than in the control (1.0%), the excess being almost entirely due to daughters. Genetic tests of a large number of such offspring failed to find a genetic cause. Instead, it appears that this phenotype may be influenced by factors in the intrauterine environment. It is concluded that shortly after sperm entry, the paternal genome of the zygote is less sensitive than the maternal one to the induction of mutations by ENU.

Animals↗
PubMed1991

Induction of specific-locus mutations in male germ cells of the mouse by acrylamide monomer.

Acrylamide monomer (AA), injected into male mice at the maximum tolerated dose of 5 x 50 mg/kg (24-h intervals), significantly increased the specific-locus mutation rate in certain poststem-cell stages of spermatogenesis, but not in spermatogonial stem cells. Germ-cell stages in which the treatment induced dominant lethals--namely, exposed spermatozoa and late spermatids (number of surviving offspring only 3% and 27%, respectively, of those in concurrent controls)--jointly yielded the highest frequency of specific-locus mutations. AA thus conforms to Pattern 1 in our earlier classification of chemicals according to the spermatogenic stage at which they elicit maximum response (Russell et al., 1990). No specific-locus mutations were observed among 17,112 offspring derived from exposed spermatogonial stem cells, a result which rules out (at the 5% significance level) an induced mutation rate greater than 2.3 times the historical control rate. A sustained high productivity in matings made for several months following week 3 indicates that there is no significant spermatogonial killing and that cell selection is presumably not the explanation for the negative result. On the basis of genetic and/or cytogenetic evidence, the mutations induced postmeiotically by AA were 'large lesions' (multi-locus), while one of 2 recovered from exposure of differentiating spermatogonia is probably a small lesion. An earlier survey of mammalian mutagenesis results led us to conclude that, regardless of the classification of a chemical according to the stage at which it elicits its maximum response, the nature of mutations is determined by the germ-cell stage in which they are induced (Russell et al., 1990). The AA results on lesion size and on distribution of mutations among the loci fit the general pattern.

Acrylamide↗
PubMed1991

Reverse genetics in the mouse and its application to the study of deafness.

Genetic variants of the laboratory mouse can serve as useful models for hereditary deafness syndromes in humans. Recessive mutations at the shaker-1 (sh-1) and whirler (wi) loci, in chromosomes 7 and 4, respectively, both result in circling behavior and a deafness syndrome. In sh-1 homozygotes this deafness is associated with neurophysiological abnormalities that may be accompanied by structural abnormalities of the inner ear. Radiation-induced deletion mutations are being used in a strategy of reverse genetics to identify the genes defined by these mutations. Genetic analyses have refined the position of sh-1 to a chromosomal interval between break points of deletions involving the closely linked albino (c) locus. A cDNA encoding olfactory marker protein (OMP) and the anonymous locus D7OR1 have also been mapped to this interval. These clones contribute to the physical map of the sh-1 region and could be important for accessing the sh-1 gene itself. Similarly, we have identified a radiation-induced deletion of the brown (b) locus that covers the wi locus and two that do not. Thus, the wi locus has been located within a chromosome 4 interval defined by structural rearrangements, which should likewise aid in identifying closely linked molecular clones.

Animals↗
PubMed1991

X-linked lymphoreticular disease in the scurfy (sf) mutant mouse.

Scurfy (sf) is a spontaneous, sex-linked, recessive mutation that maps to the extreme proximal portion of the X chromosome, about 2 centimorgans from sparse fur (spf). Hemizygotes for sf manifest several clinical disorders, evident at 14 days of age, including scaliness and crusting of the eyelids, ears, and tail, runting, reddening and swelling of the genital papilla, anemia, cachexia, and early death (average, 24 days). Our studies indicate that the phenotype of hemizygous scurfy is not, as has been suggested, a model for human X-linked ichthyosis, but appears to be a disease primarily affecting the lymphoreticular, and possibly the hematopoietic, systems. Gross lesions include marked splenomegaly, hepatomegaly, enlarged lymph nodes, and variable thickening of the ears. The characteristic histologic lesion is a lymphohistiocytic proliferation and infiltration of peripheral lymph nodes, spleen, liver, and skin. In routine hematoxylin and eosin-stained sections, these lesions efface lymph node architecture, thicken the dermis, and form nodular portal infiltrates in the liver. Scurfy lesions characteristically contain a population of large blastlike cells with round to oval nuclei, a vesicular chromatin pattern, and prominent single nucleoli. Mixed perivascular infiltrates of lymphocytes, macrophages, and granulocytes sometimes are found in kidney, heart, pancreas, lung, and mesenteries. There is excessive hematopoiesis in the liver and spleen. Cells expressing B220 or Thy-1 antigens localize to appropriate areas in the lymph nodes and spleen, but are rare in the portal infiltrates and are absent from the skin. There is a marked, polyclonal increase in serum IgG, severe Coombs'-positive anemia, and leukocytosis with atypical mononuclear cells. Scurfy mice are negative for antinuclear antibodies. Despite their morphologically aberrant lymphoreticular system, scurfy mice can exist in a conventional environment without evidence of opportunistic infection. Raising scurfy mice in a specific-pathogen-free environment does not alter disease expression. Thus, while our findings indicate that scurfy disease may be the result of immune dysfunction, it is not a classic immunodeficiency.

Animals↗
PubMed1990

Genetic ablation of a mouse gene expressed specifically in brain.

The 1B1075 gene was initially identified from a cDNA clone of a rat brain messenger RNA expressed in particular subsets of CNS neurons and pituitary cells. Although the protein encoded by this gene is of unknown function, its sequence suggests that it may be related to secretogranin proteins, which are found in association with secretory granules in a variety of peptidergic endocrine and neuronal cells. Here we show that the mouse 1B1075 gene is located between the dilute (d) and short ear (se) genes on chromosome 9. Many different deletion mutations have previously been isolated in the genetic region that includes these genes. By producing mice carrying two deletions that overlap at the 1B1075 locus, the gene for this brain-specific message can be completely eliminated from otherwise viable animals. The animals missing the 1B1075 gene provide an important new tool for determining the function of this gene in the brain. In addition, these results provide a new molecular entry point for detailed characterization of other genes in the d-se region.

Animals↗