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At least 937 records · Page 52Linked to original sources
PubMed1997

New Mutants of Phycomyces blakesleeanus for (beta)-Carotene Production.

The accumulation of (beta)-carotene by the zygomycete Phycomyces blakesleeanus is increased by mutations in the carS gene. The treatment of spores of carS mutants with N-methyl-N(prm1)-nitro-N-nitrosoguanidine led to the isolation, at very low frequencies, of mutants that produced higher levels of (beta)-carotene. Strain S556 produced about 9 mg of (beta)-carotene per g of dry mass when it was grown on minimal agar. Crosses involving strain S556 separated the original carS mutation from a new, unlinked mutation, carF. The carF segregants produced approximately as much carotene as did carS mutants, but they were unique in their ability to produce zygospores on mating and in their response to agents that increase carotenogenesis in the wild type. The carotene contents of carF segregants and carF carS double mutants were increased by sexual interaction and by dimethyl phthalate but were not increased by light or retinol. Mixed opposite-sex cultures of carF carS mutants contained up to 33 mg of (beta)-carotene per g of dry mass. Another strain, S444, produced more (beta)-carotene than did S556 but was marred by slow growth, defective morphology, and bizarre genetic behavior. In all the strains tested, the carotene concentration was minimal during the early growth phase and became higher and constant for several days in older mycelia.

Journal Article↗
PubMed1985

Physical and genetic map of a Rhizobium meliloti nodulation gene region and nucleotide sequence of nodC.

Infection of alfalfa by the soil bacterium Rhizobium meliloti proceeds by deformation of root hairs and bacterial invasion of host tissue by way of an infection thread. We studied an 8.7-kilobase (kb) segment of the R. meliloti megaplasmid, which contains genes required for infection. Site-directed Tn5 mutagenesis was used to examine this fragment for nodulation genes. A total of 81 R. meliloti strains with mapped Tn5 insertions in the 8.7-kb fragment were evaluated for nodulation phenotype on alfalfa plants; 39 of the insertions defined a 3.5-kb segment containing nodulation functions. Of these 39 mutants, 37 were completely nodulation deficient (Nod-), and 2 at the extreme nif-distal end were leaky Nod-. Complementation analysis was performed by inoculating plants with strains carrying a genomic Tn5 at one location and a plasmid-borne Tn5 at another location in the 3.5-kb nodulation segment. Mutations near the right border of the fragment behaved as two distinct complementation groups. The segment in which these mutations are located was analyzed by DNA sequencing. Several open reading frames were found in this region, but the one most likely to function is 1,206 bases long, reading from left to right (nif distal to proximal) and spanning both mutation groups. The genetic behavior of this segment may be due either to the gene product having two functional domains or to a recombinational hot spot between the apparent complementation groups.

Amino Acid Sequence↗
PubMed1987

Genomic organization of alpha satellite DNA on human chromosome 7: evidence for two distinct alphoid domains on a single chromosome.

A complete understanding of chromosomal disjunction during mitosis and meiosis in complex genomes such as the human genome awaits detailed characterization of both the molecular structure and genetic behavior of the centromeric regions of chromosomes. Such analyses in turn require knowledge of the organization and nature of DNA sequences associated with centromeres. The most prominent class of centromeric DNA sequences in the human genome is the alpha satellite family of tandemly repeated DNA, which is organized as distinct chromosomal subsets. Each subset is characterized by a particular multimeric higher-order repeat unit consisting of tandemly reiterated, diverged alpha satellite monomers of approximately 171 base pairs. The higher-order repeat units are themselves tandemly reiterated and represent the most recently amplified or fixed alphoid sequences. We present evidence that there are at least two independent domains of alpha satellite DNA on chromosome 7, each characterized by their own distinct higher-order repeat structure. We determined the complete nucleotide sequences of a 6-monomer higher-order repeat unit, which is present in approximately 500 copies per chromosome 7, as well as those of a less-abundant (approximately 10 copies) 16-monomer higher-order repeat unit. Sequence analysis indicated that these repeats are evolutionarily distinct. Genomic hybridization experiments established that each is maintained in relatively homogeneous tandem arrays with no detectable interspersion. We propose mechanisms by which multiple unrelated higher-order repeat domains may be formed and maintained within a single chromosomal subset.

Base Sequence↗
PubMedDate not supplied

Ionotropic glutamate receptors in Caenorhabditis elegans.

Ionotropic glutamate receptors (iGluRs) are an important class of heteromeric ligand-gated receptor complexes that mediate a large portion of the excitatory neurotransmission in the vertebrate CNS. Since the cloning of the first iGluR subunit in 1989, the study of this receptor family has rapidly developed in mammals and expanded to include the study of conserved glutamate receptors in simpler invertebrate systems, including the fruit fly Drosophila melanogaster and the soil nematode Caenorhabditis elegans. These model organisms have enabled the genetic analysis of glutamate receptors in the context of a simpler nervous system and provided new insights into receptor function and regulation. In this review we will focus on recent studies that have used genetic, behavioral, and electrophysiological techniques to study the function of iGluRs in C. elegans.

Amino Acids↗
PubMed2004

Examination of potential overlap in autism and language loci on chromosomes 2, 7, and 13 in two independent samples ascertained for specific language impairment.

Specific language impairment is a neurodevelopmental disorder characterized by impairments essentially restricted to the domain of language and language learning skills. This contrasts with autism, which is a pervasive developmental disorder defined by multiple impairments in language, social reciprocity, narrow interests and/or repetitive behaviors. Genetic linkage studies and family data suggest that the two disorders may have genetic components in common. Two samples, from Canada and the US, selected for specific language impairment were genotyped at loci where such common genes are likely to reside. Significant evidence for linkage was previously observed at chromosome 13q21 in our Canadian sample (HLOD 3.56) and was confirmed in our US sample (HLOD 2.61). Using the posterior probability of linkage (PPL) to combine evidence for linkage across the two samples yielded a PPL over 92%. Two additional loci on chromosome 2 and 7 showed weak evidence for linkage. However, a marker in the cystic fibrosis transmembrane conductance regulator (7q31) showed evidence for association to SLI, confirming results from another group (O'Brien et al. 2003). Our results indicate that using samples selected for components of the autism phenotype may be a useful adjunct to autism genetics.

Autistic Disorder↗
PubMed2006

Evaluation of epidemiologic evidence for primary adult brain tumor risk factors using evidence-based medicine.

We evaluate genetic, behavioral, developmental and experiential risk factors for primary adult brain tumors (primarily, astrocytoma and meningioma) using a systematic set of principles adapted from evidence-based medicine standards. In addition to ionizing radiation, rare mutations in highly penetrant genes associated with certain diseases/syndromes, and epilepsy and seizures (which probably result from, rather than cause, adult brain tumors), only the unexplained observation of familial aggregation of astrocytoma has been consistently shown. There is promising renewed interest in associations between infections, allergic conditions and adult brain tumor risk. Our knowledge of the causes of adult brain tumors is limited and should be expanded by results from large, well-designed studies of novel potential risk factors and potential interactions between known and suspected risk factors.

Astrocytoma↗
PubMed2026

Sex-specific disruptions in PKCγ signaling in a mouse model of spinocerebellar ataxia type 14.

Spinocerebellar ataxia type 14 (SCA14) is an autosomal dominant neurodegenerative disease caused by mutations in the gene encoding protein kinase C γ (PKCγ), a Ca2+- and diacylglycerol-dependent Ser/Thr kinase dominantly expressed in cerebellar Purkinje cells. These mutations impair autoinhibitory constraints to increase the basal activity of the kinase, resulting in deficits in the cerebellum that are not observed upon simple deletion of the gene, and severe ataxia. To better understand the impact of aberrant PKCγ signaling in disease pathology, we developed a knockin murine model of the SCA14 mutation ΔF48 in PKCγ. This fully penetrant mutation is severe in humans and is mechanistically informative, as it has high basal activity but is unresponsive to agonist stimulation. Genetic, behavioral, and molecular testing revealed that ΔF48 PKCγ mice have ataxia-related phenotypes and an altered cerebellar phosphoproteome driven primarily by enhanced Ca2+/calmodulin-dependent kinase 2 signaling, effects that were more severe in male mice. Analysis of existing human data revealed that SCA14 has a significantly earlier age of onset for males compared with females. Data from this clinically relevant mutation suggested that enhanced basal activity of PKCγ is sufficient to cause ataxia and that treatment strategies to modulate aberrant PKCγ may be particularly beneficial in males.

Animals↗
PubMed2004

Pater familias.

Explore the source record for details and available documents.

Adaptation, Psychological↗
PubMedDate not supplied

Genotype-environment correlations for language-related abilities: implications for typical and atypical learners.

Recent behavioral genetic research has shown that genetic propensities are associated with individual differences in experiences, and thus, what may appear to be environmental effects can reflect genetic influence. This study examines passive genotype-environment correlations (GECs) for language-related abilities by comparing environment-child language associations in adoptive and nonadoptive families. The results provide evidence for the genetic mediation of the association between home environmental variables, such as the provision of toys and games, maternal involvement, and degree of intellectual/cultural orientation with children's language-related abilities. Developmental changes in passive GECs are considered, and the implications for typical and atypical learners are discussed.

Adoption↗
PubMed2006

Race-specific geography of prostate cancer incidence.

BACKGROUND: This study evaluated geographic distribution of race-specific prostate cancer incidence in Connecticut and Massachusetts. This cross-sectional analysis of census and cancer registry data included records of 29,040 Whites and 1,647 African Americans diagnosed with incident prostate cancer between 1994 and 1998. A spatial scan statistic was used to detect and test significance of the geographic variation in race-specific incidence rates within the two-state area. RESULTS: Significant geographic variation in age-adjusted incidence rates among both White and African American men was observed, with little overlap noted between distributions. Identified locations reflected patterns of residential segregation and socio-economic conditions. Among Whites, places with higher than expected incidence had higher socioeconomic status than places with lower than expected incidence. No discernable relationship between social indicators and rate variation among African Americans was evident. CONCLUSION: Differences in race-specific geographic distribution of prostate cancer incidence do not suggest a shared environmental etiology. Further study of genetic, behavioral and health care factors affecting the occurrence and/or reporting of the disease is warranted. This study highlights the need for race- and geographic-specific interventions to better control disease within at-risk communities and for on-going analysis into social and contextual factors that contribute to observed disparities between African Americans and Whites in the occurrence of cancer.

Black or African American↗