PubMed · 2883582
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M Akam. Insect evolution. Molecules and morphology.. https://doi.org/10.1038/327184a0
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The Arrowhead gene encodes a LIM-homeodomain transcription factor required for establishment of a subset of imaginal tissues: the abdominal histoblasts and the salivary gland imaginal rings. Consistent with its role in development, during embryogenesis Arrowhead is expressed in each abdominal segment and in the labial segment. Late in embryonic development, expression is refined to the abdominal histoblasts and salivary gland imaginal ring cells themselves. When ectopically expressed in imaginal disc cells, Arrowhead causes programmed cell death and loss of corresponding adult structures. Therefore, Arrowhead expression is required for development of one set of imaginal cells and is incompatible with development of another, emphasizing the specificity of Arrowhead and the sensitivity of different target cells to its expression. Loss-of-function mutations in Arrowhead affect conserved or invariant amino acids in the LIM- and homeo-domains demonstrating the importance of these residues in LIM homeodomain protein activity.
In the studied mutant strain of Drosophila subobscura, 78% of the mitochondrial genomes lost >30% of the coding region by deletion. The mutations was genetically stable. Despite this massive loss of mitochondrial genes, the mutant did not seem to be affected. Distribution of the two genome types, cell levels of mitochondrial DNA, steady-state concentrations of the mitochondrial gene transcripts, mitochondrial enzymatic activities, and ATP synthesis capacities were measured in the head, thorax, and abdomen fractions of the mutant strain in comparison with a wild type strain. Results indicate that the deleted genomes are detected in all fractions but to a lesser extent in the male and female abdomen. In all fractions, there is a 50% increase in cellular mitochondrial DNA content. Although there is a decrease in steady-state concentrations of mitochondrial transcripts of genes affected by deletion, this is smaller than expected. The variations in mitochondrial biochemical activities in the different fractions of the wild strain are upheld in the mutant strain. Activity of complex I (involved in mutation) nevertheless shows a decrease in all fractions; activity of complex III (likewise involved) shows little or no change; finally, mitochondrial ATP synthesis capacity is identical to that observed in the wild strain. This latter finding possibly accounts for the lack of phenotype. This mutant is a good model for studying mitochondrial genome alterations and the role of the nuclear genome in these phenomena.
OBJECTIVE: To report clinical findings for New World comelids with uterine torsion and to compare results of 3 methods of correction. DESIGN: Retrospective case series. ANIMALS: 11 llamas and 3 alpacas with 20 uterine torsions. PROCEDURE: Information concerning history, clinical signs, management, and postpartum complications was retrieved from medical records. Information concerning subsequent reproductive performance was obtained by telephone interview of owners. RESULTS: Uterine torsion was corrected by celiotomy (n = 7); transvaginal manipulation (5), or rolling the dam (8). Direction of 19 of 20 torsions was clockwise when viewed from the rear. Retention of fetal membranes was reported for 5 camelids that underwent celiotomy, but was not reported in camelids after nonsurgical correction. The uterus prolapsed in 1 llama that underwent celiotomy and in another that underwent the rolling technique. Although 2 camelids that underwent celiotomy subsequently failed to conceive, all camelids treated by nonsurgical techniques conceived. CLINICAL IMPLICATIONS: Uterine torsion in camelids may be diagnosed by methods similar to those used in cattle. Surgical and nonsurgical methods can be used to correct torsion, and postpartum complications are rare when torsion is corrected by a nonsurgical method.