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Biomedical subjects

J M Ranz

Publications and source records attributed to J M Ranz.

7 recordsLinked to original sources
PubMed2001

How malleable is the eukaryotic genome? Extreme rate of chromosomal rearrangement in the genus Drosophila.

During the evolution of the genus Drosophila, the molecular organization of the major chromosomal elements has been repeatedly rearranged via the fixation of paracentric inversions. Little detailed information is available, however, on the extent and effect of these changes at the molecular level. In principle, a full description of the rate and pattern of change could reveal the limits, if any, to which the eukaryotic genome can accommodate reorganizations. We have constructed a high-density physical map of the largest chromosomal element in Drosophila repleta (chromosome 2) and compared the order and distances between the markers with those on the homologous chromosomal element (3R) in Drosophila melanogaster. The two species belong to different subgenera (Drosophila and Sophophora, respectively), which diverged 40-62 million years (Myr) ago and represent, thus, the farthest lineages within the Drosophila genus. The comparison reveals extensive reshuffling of gene order from centromere to telomere. Using a maximum likelihood method, we estimate that 114 +/- 14 paracentric inversions have been fixed in this chromosomal element since the divergence of the two species, that is, 0.9-1.4 inversions fixed per Myr. Comparison with available rates of chromosomal evolution, taking into account genome size, indicates that the Drosophila genome shows the highest rate found so far in any eukaryote. Twenty-one small segments (23-599 kb) comprising at least two independent (nonoverlapping) markers appear to be conserved between D. melanogaster and D. repleta. These results are consistent with the random breakage model and do not provide significant evidence of functional constraint of any kind. They support the notion that the Drosophila genome is extraordinarily malleable and has a modular organization. The high rate of chromosomal change also suggests a very limited transferability of the positional information from the Drosophila genome to other insects.

Animals↗
PubMed2000

The role of the psychiatrist as medical director: a survey of psychiatric administrators.

Previous surveys of public and community psychiatrists have demonstrated that medical directors perform a wider variety of tasks, and experience increased job satisfaction, compared to staff psychiatrists. Notwithstanding respondents' belief that clinical collaboration tasks contribute most to job satisfaction, the performance of administrative tasks is most highly correlated with overall job satisfaction. The current survey was undertaken to determine whether these findings could be replicated among hospital-based psychiatrists. Demographic and job characteristic profiles of hospital-based psychiatrists were clearly distinguished from those of community psychiatrists. Despite these differences, task profiles and job satisfaction parameters of hospital-based psychiatrists were comparable to those previously reported for community psychiatrists.

Adult↗
PubMed1999

Generation of a widespread Drosophila inversion by a transposable element.

Although polymorphic inversions in Drosophila are very common, the origin of these chromosomal rearrangements is unclear. The breakpoints of the cosmopolitan inversion 2j of D. buzzatii were cloned and sequenced. Both breakpoints contain large insertions corresponding to a transposable element. It appears that the two pairs of target site duplications generated upon insertion were exchanged during the inversion event, and that the inversion arose by ectopic recombination between two copies of the transposon that were in opposite orientations. This is apparently the mechanism by which transposable elements generate natural inversions in Drosophila.

Animals↗
PubMed1999

Comparative mapping of cosmids and gene clones from a 1.6 Mb chromosomal region of Drosophila melanogaster in three species of the distantly related subgenus Drosophila.

The successful hybridization of cosmid clones from Drosophila melanogaster (Sophophora subgenus) to the salivary gland chromosomes of other species as distantly related as those in the Drosophila subgenus attests their great potential for unravelling genome evolution. We have carried out, using 28 cosmids and 13 gene clones, a study of the organization of the D. melanogaster 95A-96A chromosomal region in three Drosophila subgenus species: D. repleta, D. buzzattii and D. virilis. These clones were first used to built an accurate map of this 1.6 Mb region of D. melanogaster chromosome 3R (Muller's element E). Then, they were hybridized and mapped to the homologous chromosome 2 of the other three distantly related species. The studied region is disseminated over 13 different sites of chromosome 2 in the Drosophila subgenus species, which implies a minimum of 12 inversion breakpoints fixed between the two subgenera. Extrapolation to the entire chromosome gives 90 fixed inversions. The D. melanogaster Pp1-96A-Acr96Aa segment conserved in D. repleta and D. buzzatii is longer than previously thought and is also conserved in D. virilis. In addition, three other D. melanogaster segments conserved in the three Drosophila subgenus species were found. Finally, our data indicate significant statistical differences in the evolution rate of Muller's element E among lineages, a result that agrees well with the previous cytogenetic data.

Animals↗
PubMed1997

Chromosomal homology and molecular organization of Muller's elements D and E in the Drosophila repleta species group.

Thirty-three DNA clones containing protein-coding genes have been used for in situ hybridization to the polytene chromosomes of two Drosophila repleta group species, D. repleta and D. buzzatii. Twenty-six clones gave positive results allowing the precise localization of 26 genes and the tentative identification of another nine. The results were fully consistent with the currently accepted chromosomal homologies and in no case was evidence for reciprocal translocations or pericentric inversions found. Most of the genes mapped to chromosomes 2 and 4 that are homologous, respectively, to chromosome arms 3R and 3L of D. melanogaster (Muller's elements E and D). The comparison of the molecular organization of-these two elements between D. melanogaster and D. repleta (two species that belong to different subgenera and diverged some 62 million years ago) showed an extensive reorganization via paracentric inversions. Using a maximum likelihood procedure, we estimated that 130 paracentric inversions have become fixed in element E after the divergence of the two lineages. Therefore, the evolution rate for element E is approximately one inversion per million years. This value is comparable to previous estimates of the rate of evolution of chromosome X and yields an estimate of 4.5 inversions per million years for the whole Drosophila genome.

Animals↗
PubMed1991

Creating a supportive environment using staff psychoeducation in a supervised residence.

The prevailing approach to rehabilitation in residential care emphasizes goal attainment. This approach often produces considerable stress for residents, most of whom have schizophrenia. Based on the view that low-demand environments, incorporating graduated expectations, may be more appropriate for this patient population, a three-component model for creating and maintaining a calm, supportive environment in a supervised residence was developed. The model utilizes staff psychoeducation, which is based on the principles of family psychoeducation, a highly effective intervention for patients with schizophrenia. The three components of the model are training in supportive interaction, a medication-monitoring program, and a behavioral approach to problem solving. Resident groups promote each of these components. The groups' goals are encouragement of positive, low-key interactions, compliance with medications, and slow, steady rehabilitation.

Adult↗