Uranium(III) coordination chemistry and oxidation in a flexible small-cavity macrocycle

U(III) complexes of the conformationally flexible, small-cavity macrocycle trans-calix[2]benzene[2]pyrrolide (L)2–, [U(L)X] (X = O-2,6-tBu2C6H3, N(SiMe3)2), have been synthesized from [U(L)BH4] and structurally characterized. These complexes show binding of the U(III) center in the bis(arene) pocket of the macrocycle, which flexes to accommodate the increase in the steric bulk of X, resulting in long U–X bonds to the ancillary ligands. Oxidation to the cationic U(IV) complex [U(L)X][B(C6F5)4] (X = BH4) results in ligand rearrangement to bind the smaller, harder cation in the bis(pyrrolide) pocket, in a conformation that has not been previously observed for (L)2–, with X located between the two ligand arene rings

Beta Blockers in Mental Retardation and Developmental Disorders

β-Adrenergic blockers appear to be effective in the management of verbal aggression, physical aggression, or self-injurious behavior associated with mental retardation and other developmental disorders. However, methodological limitations of the available studies make it difficult to judge the value of these treatments. Optimal doses for treating patients with mental retardation or developmental disorders appear lower than described in the general psychiatric literature, so low doses of β-blockers may be preferred in such patients with abnormal brain development. Children and adolescents with mental retardation or developmental disorders appear to respond to particularly low doses (e.g., below propranolol 150 mg daily). Propranolol is recommended for central blockade, and nadolol is recommended for peripheral blockade. Most β receptors in the brain (except cerebellum) seem to be β1 (cardiac type), but it is not clear that central blockade is required for psychotropic effects. Interim suggestions for empirical trials are offered, and rating scales and other measurement approaches are discussed. Since evidence supporting the efficacy of β-blockers in mental retardation or developmental disorders in children and adolescents is not definitive, the clinician is advised to consider designing an empirical trial for each patient, utilizing pre- and postmedication measures, when conventional treatments have been unsuccessful

On Invited Inferences

This work was supported in part by the 1970 MSSB Advanced Research Seminar in Mathematical Linguistics, sponsored by the National Science Foundation through a grant to the Center for Advanced Study in the Behavioral Sciences, Stanford, and held at the Ohio State University

Adaptation by introgression

Both selective and random processes can affect the outcome of natural hybridization. A recent analysis in BMC Evolutionary Biology of natural hybridization between an introduced and a native salamander reveals the mosaic nature of introgression, which is probably caused by a combination of selection and demography

Reticulate Evolution and Marine Organisms: The Final Frontier?

The role that reticulate evolution (i.e., via lateral transfer, viral recombination and/or introgressive hybridization) has played in the origin and adaptation of individual taxa and even entire clades continues to be tested for all domains of life. Though falsified for some groups, the hypothesis of divergence in the face of gene flow is becoming accepted as a major facilitator of evolutionary change for many microorganisms, plants and animals. Yet, the effect of reticulate evolutionary change in certain assemblages has been doubted, either due to an actual dearth of genetic exchange among the lineages belonging to these clades or because of a lack of appropriate data to test alternative hypotheses. Marine organisms represent such an assemblage. In the past half-century, some evolutionary biologists interested in the origin and trajectory of marine organisms, particularly animals, have posited that horizontal transfer, introgression and hybrid speciation have been rare. In this review, we provide examples of such genetic exchange that have come to light largely as a result of analyses of molecular markers. Comparisons among these markers and between these loci and morphological characters have provided numerous examples of marine microorganisms, plants and animals that possess the signature of mosaic genomes

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Criteria for strong and weak random attractors

The theory of random attractors has different notions of attraction, amongst them pullback attraction and weak attraction. We investigate necessary and sufficient conditions for the existence of pullback attractors as well as of weak attractors

Is the New Primate Genus Rungwecebus a Baboon?

BACKGROUND: In 2005, a new primate species from Tanzania, the kipunji, was described and recognized as a member of the mangabey genus Lophocebus. However, molecular investigations based upon a number of papionins, including a limited sample of baboons of mainly unknown geographic origin, identified the kipunji as a sister taxon to Papio and not as a member of Lophocebus. Accordingly, the kipunji was separated into its own monotypic genus, Rungwecebus. METHODOLOGY/PRINCIPAL FINDINGS: We compare available mitochondrial and nuclear sequence data from the voucher specimen of Rungwecebus to other papionin lineages, including a set of geographically proximal (parapatric) baboon samples. Based on mitochondrial sequence data the kipunji clusters with baboon lineages that lie nearest to it geographically, i.e. populations of yellow and chacma baboons from south-eastern Africa, and thus does not represent a sister taxon to Papio. Nuclear data support a Papio+Rungwecebus clade, but it remains questionable whether Rungwecebus represents a sister taxon to Papio, or whether it is nested within the genus as depicted by the mitochondrial phylogeny. CONCLUSIONS/SIGNIFICANCE: Our study clearly supports a close relationship between Rungwecebus and Papio and might indicate that the kipunji is congeneric with baboon species. However, due to its morphological and ecological uniqueness Rungwecebus more likely represents a sister lineage to Papio and experienced later introgressive hybridization. Presumably, male (proto-)kipunjis reproduced with sympatric female baboons. Subsequent backcrossing of the hybrids with kipunjis would have resulted in a population with a nuclear kipunji genome, but which retained the yellow/chacma baboon mitochondrial genome. Since only one kipunji specimen was studied, it remains unclear whether all members of the new genus have been impacted by intergeneric introgression or rather only some populations. Further studies with additional Rungwecebus samples are necessary to elucidate the complete evolutionary history of this newly-described primate genus