Mitochondrial DNA differentiation during the speciation process in Peromyscus

We address the problem of the possible significance of biological speciation to the magnitude and pattern of divergence of asexually transmitted characters in bisexual species. The empirical data for this report consist of restriction endonuclease site variability in maternally transmitted mitochondrial DNA (mtDNA) isolated from 82 samples of Peromyscus polionotus and P. leucopus collected from major portions of the respective species' ranges. Data are analyzed together with previously published information on P. maniculatus, a sibling species to polionotus. Maps of restriction sites indicate that all of the variation observed can be reasonably attributed to base substitutions leading to loss or gain of particular recognition sites. Magnitude of mtDNA sequence divergence within polionotus (maximum approximately equal to 2%) is roughly comparable to that observed within any of five previously identified mtDNA assemblages in maniculatus. Sequence divergence within leucopus (maximum approximately equal to 4%) is somewhat greater than that within polionotus. Consideration of probable evolutionary links among mtDNA restriction site maps allowed estimation of matriarchal phylogenies within polionotus and leucopus. Clustering algorithms and qualitative Wagner procedures were used to generate phenograms and parsimony networks, respectively, for the between-species comparisons. Three simple graphical models are presented to illustrate some conceivable relationships of mtDNA differentiation to speciation. In theoretical case I, each of two reproductively defined species (A and B) is monophyletic in matriarchal genealogy; the common female ancestor of either species can either predate or postdate the speciation. In case II, neither species is monophyletic in matriarchal genotype. In case III, species B is monophyletic but forms a subclade within A which is thus paraphyletic with respect to B. The empirical results for mtDNA in maniculatus and polionotus appear to conform closely to case III. These theoretical and empirical considerations raise a number of questions about the general relationship of the speciation process to the evolution of uniparentally transmitted traits. Some of these considerations are presented, and it is suggested that the distribution patterns of mtDNA sequence variation within and among extant species should be of considerable relevance to the particular demographies of speciation.      

Structure--activity relationship of inhibitors of hydroxyapatite formation.

The relative abilities of some compounds to inhibit the transformation of amorphous calcium phosphate into hydroxyapatite were determined. Organic diphosphates, fructose 1,6-bisphosphate, pyrophosphate, imidodiphosphate and 3-phospholycerate all inhibited to various degrees. Strong inhibition was observed with phosphonoformate, and phosphocitrate proved to be the most powerful of the inhibitors examined. On the basis of these new findings an improved concept of the structure--activity relationship of inhibitors is proposed and mechanisms for inhibitor action are discussed.     

Active cation transport and Na+K+Mg ATPase of the monotreme erythrocytes

The erythrocytes of the echidna (Tachyglossus aculeatus) and platypus (Ornithorhynchus anatinus), which are practically devoid of intracellular ATP content (1), were examined for active Rb⁸⁶ influx and for the presence of Na+K+Mg ATPase. We found that intact erythrocytes of both species possess the ability to actively transport cations. Ouabain sensitive Rb⁸⁶ influx in the echidna was approximately 0.17 μmoles/ml cells × hr, whereas the platypus exhibited a higher value of 0.43 μmoles/ml cells × hr. Surprisingly, ouabain sensitive Na+K+Mg ATPase activity of isolated membranes was high amounting to some 15 to 25 fold higher than the human erythrocyte counterpart determined under identical conditions. These findings suggest that a trace amount of ATP is sufficient to maintain active cation transport across the monotreme cell membranes.     

Behavioral Weight Control for Overweight Adolescents Initiated in Primary Care

Objective: This study evaluates the post-treatment and short-term follow-up efficacy of, as well as participant satisfaction for, a 4-month behavioral weight control program for overweight adolescents initiated in a primary care setting and extended through telephone and mail contact. Research Methods and Procedures: 44 overweight adolescents were randomly assigned to either a multiple component behavioral weight control intervention (Healthy Habits [HH]; n = 23) or a single session of physician weight counseling (typical care [TC]; n = 21). Weight, height, dietary intake, physical activity, sedentary behavior, and problematic weight-related and eating behaviors and beliefs were assessed before treatment, after the 4-month treatment, and at 3-month follow-up. Participant satisfaction and behavioral skills use were measured. Results: HH adolescents evidenced better change in body mass index z scores to post-treatment than TC adolescents. Body mass index z scores changed similarly in the conditions from post-treatment through follow-up. Behavioral skills use was higher among HH than TC adolescents, and higher behavioral skills use was related to better weight outcome. Energy intake, percentage of calories from fat, physical activity, sedentary behavior, and problematic weight-related or eating behaviors/beliefs did not differ by condition or significantly change over time independent of condition. The behavioral intervention evidenced good feasibility and participant satisfaction. Discussion: A telephone- and mail-based behavioral intervention initiated in primary care resulted in better weight control efficacy relative to care typically provided to overweight adolescents. Innovative and efficacious weight control intervention delivery approaches could decrease provider and participant burden and improve dissemination to the increasing population of overweight youth.