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Biomedical subjects

D Romero

Publications and source records attributed to D Romero.

81 records · Page 5Linked to original sources
PubMed1987

Reiterated DNA sequences in Rhizobium and Agrobacterium spp.

Repeated DNA sequences are a general characteristic of eucaryotic genomes. Although several examples of DNA reiteration have been found in procaryotic organisms, only in the case of the archaebacteria Halobacterium halobium and Halobacterium volcanii [C. Sapienza and W. F. Doolittle, Nature (London) 295:384-389, 1982], has DNA reiteration been reported as a common genomic feature. The genomes of two Rhizobium phaseoli strains, one Rhizobium meliloti strain, and one Agrobacterium tumefaciens strain were analyzed for the presence of repetitive DNA. Rhizobium and Agrobacterium spp. are closely related soil bacteria that interact with plants and that belong to the taxonomical family Rhizobiaceae. Rhizobium species establish a nitrogen-fixing symbiosis in the roots of legumes, whereas Agrobacterium species is a pathogen in different plants. The four strains revealed a large number of repeated DNA sequences. The family size was usually small, from 2 to 5 elements, but some presented more than 10 elements. Rhizobium and Agrobacterium spp. contain large plasmids in addition to the chromosomes. Analysis of the two Rhizobium strains indicated that DNA reiteration is not confined to the chromosome or to some plasmids but is a property of the whole genome.

Cloning, Molecular↗
PubMed1986

Genetic and biochemical identification of the glutamate synthase structural gene in Neurospora crassa.

Neurospora crassa cells require glutamate synthase activity for growth under ammonium-limiting conditions. Despite the physiological importance of glutamate synthase, little is known about the genetics of its expression. To identify the glutamate synthase structural gene, we isolated three new mutants lacking this activity. All mutations are recessive to the wild-type allele and belong to the same complementation group as the previously described en(am)-2 (C24) mutation. Two lines of evidence indicate that en(am)-2 is the structural gene for glutamate synthase in N. crassa. The en(am)-2+ gene shows a gene dosage effect on enzyme activity, and some mutants lacking glutamate synthase activity have cross-reacting material. These data suggest that the mutations are located in the structural gene for N. crassa glutamate synthase.

Alleles↗
PubMed1985

Glutamine synthetase-constitutive mutation affecting the glnALG upstream promoter of Escherichia coli.

The spontaneous gln-76 mutation of Escherichia coli (Osorio et al., Mol. Gen. Genet. 194:114-123, 1984) was previously shown to be responsible for the cis-dominant constitutive expression of the glnA gene in the absence of a glnG-glnF activator system. Nucleotide sequence analysis has now revealed that gln-76 is a single transversion T.A to A.T, an up-promoter mutation affecting the -10 region of glnAp1, the upstream promoter of the glnALG control region. Both, wild-type and gln-76 DNA control regions were cloned into the promoter-probe plasmid pKO1. Galactokinase activity determinations of cells carrying the fused plasmids showed 10-fold more effective expression mediated by gln-76 than by the glnA wild-type control region. Primer extension experiments with RNA from strains carrying the gln-76 control region indicated that the transcription initiation sites were the same in both the gln-76 mutant and the wild type.

Base Sequence↗
PubMed1985

The U.S. Transuranium Registry report of the 241Am content of a whole body. Part IV: Preparation and analysis of the tissues and bones.

Los Alamos National Laboratory has analyzed autopsy tissue for the USTR, as a part of its study of the uptake, distribution and retention of Pu and other transuranic elements in occupationally exposed workers since 1978. In April 1979, Los Alamos received the internal organs and bone samples from the first whole-body donation to the USTR. The donor was known to have an internal deposition of 241Am. All soft tissue, the bones from the right half of the skeleton, and the odd-numbered vertebrae were received at Los Alamos in February 1980. The bones were subdivided along anatomical areas of interest. All soft tissues and bone specimens were analyzed for their 241Am content. A total deposition of 147.4 nCi 241Am was measured. Approximately 18% of the 241Am remaining in the body (disregarding that in the left hand), was found in the soft tissues, and 82% was in the bones and teeth. The soft tissues and organs containing the largest amounts of 241Am were the combined soft tissue (striated muscle, connective tissue and skin) 8.8%; liver, 6.4% and respiratory tract, 1.5%. The remaining organs accounted for 0.9% of the systemic burden.

Americium↗
PubMedDate not supplied

Repeated sequences in bacterial chromosomes and plasmids: a glimpse from sequenced genomes.

To gain insight into the extent of exact DNA repeats in sequenced bacterial genomes and their plasmids, we analyzed the collection of completely sequenced bacterial genomes available at GenBank using the program Miropeats. This program draws graphical representations of exact DNA repeats in whole genomes. In this work, we present maps showing the extent and type (inverted or direct) of exact DNA repeats longer than 300 bp for the whole collection. These repeats may participate in a variety of events relevant for bacterial genome plasticity, such as amplifications, deletions, inversions, and translocations (via homologous recombination), as well as transposition. Additionally, we review recent data showing that high-frequency architectural variations in genomic structure occur at both the interspecies and interstrain levels.

Bacteria↗
PubMedDate not supplied

Effects of retinoic acid and amifostine on in vitro growth of normal hemopoietic progenitor cells.

Association of all-trans retinoic acid (ATRA) and amifostine (AMF) might be an alternative in treatment of myelodisplatic syndromes. In this study we undertook a preliminary in vitro research on the effects of a combination of ATRA and AMF on normal hemopoietic progenitors. Mononuclear, non-adherent cells from peripheral blood of normal volunteers, were incubated with AMF, at a the concentration of 500 microM and then cultured for CFU-GM and BFU-E growth adding to culture dishes before gelling ATRA at the concentration 10(-6) and 10(-12)M. Controls were cultures not pre-incubated with AMF, cultures incubated with AMF without addition of ATRA and cultures without addition of any drug. ATRA addition did not have significant effects on hemopoietic progenitors growth. Association of ATRA and AMF do not appear to synergize to stimulate in vitro growth of hemopoietic progenitors.

Amifostine↗
PubMedDate not supplied

[Emergence and brain development of executive functions].

Development of executive functions (EF) during childhood and adolescence is closely related to frontal lobe maturation and its connections with other cortical and subcortical structures. The main maturative processes are myelination and synaptic pruning, both of which work on the brain following a hierarchical model. Different studies agree with the fact that EF emerge at the age of 6 years. However, these studies have used complex neuropsychological tests, which require appropriate functioning of several cognitive functions. This is why differential development of different EF components cannot be observed. To do so, other studies have designed simpler tasks, which only need active maintenance of information and inhibition, both basic functions for the appropriate execution of more complex EF tasks. When these simple tasks are used, an early appearance of EF can already be noticed at the age of 12 months, and there are important advances between the third and fifth year. Consequently, the idea of the frontal lobe being "functionally silent" until adolescence seems definitively discarded.

Brain↗
PubMedDate not supplied

Condom use among women choosing long-term hormonal contraception.

CONTEXT: Women who rely on long-term hormonal contraception may neglect to use condoms, and thus increase their risk of contracting sexually transmitted diseases, including AIDS. METHODS: Data from a prospective, multisite study were collected to examine the probability of condom use among 1,073 new users of either the contraceptive implant or injectable; users were interviewed when they accepted their method and again six months to one year later. Multivariate logistic regression analyses identified factors that significantly predicted the likelihood of dual method use. RESULTS: Condom use dropped markedly among women who adopted long-term hormonal contraception. The proportion who always used condoms in the previous three months fell from 21% at the time of adoption to 11% at follow-up. Among women with one sexual partner, this decrease was from 20% to 10%; however, among those with more than one partner, use increased from 25% to 31%. The factors significantly predicting dual method use included previous condom use (odds ratio of 2.5), receipt of AIDS-specific counseling (odds ratio of 1.6), the perception of being at some risk of AIDS at baseline (odds ratio of 1.4) and having had more than one sexual partner over the study period (odds ratio of 5.4). In addition, injectable users, teenagers and black women were more likely than other women to use condoms with their hormonal method. CONCLUSIONS: Although condom use among all women declined markedly once they initiated long-term hormonal contraception, frequency of condom use varied by subgroup and was associated with several factors. Most importantly, women with more than one sexual partner and those who received a message during counseling on the need to continue using condoms were more likely than others to use condoms in conjunction with the implant or injectable.

Adolescent↗