The improbability of irradiated spermatozoa as gene transfer vectors in chickens

Summary It is concluded that chromatin fragments derived from irradiated chicken spermatozoa are not viable vectors for gene transfer. In three experiments conducted at sequential intervals over a period of 1 1/2 years, no marker traits were found in 1,065 G₀ progeny from irradiated spermatozoa of Minnesota Dominant Marker males inseminated into recessive Rhode Island Red and White Leghorn females. The inability to secure transformants is ascribed to the following factors: a maximum of five and probably fewer potential vector fragments for each G₀ progeny because of irradiation effect on spermatozoan ability to enter the germinal disc; uncertainty of DNA integrity from highly irradiated chromatin; no known mechanism for release of chromatin fragments from irradiated spermatozoa supernumerary pronuclei; and the uncertainty of selective integration into the zygotic nucleus.Paper No. 17153, Scientific Journal Series of the Minesota Agricultural Experiment Station     

Temperature acquisition as a function of the computer-based biofeedback system utilized: An exploratory analysis

Thermal biofeedback is widely used to treat various clinical disorders. Given its widespread utility, and the variability among the biofeedback systems currently on the market, it is important to investigate which systems are most effective for training various skills. This study compared the performance of normal subjects on two different computer-biofeedback systems. Results indicated a significant difference in subject performance between the two systems. Limitations and implications of these findings are discussed.     

Territory re‐establishment in Cyprinodon variegatus lacepede

Cyprinodon variegatus males were allowed to establish territories in small aquaria. The ability of a male to maintain a territory was examined under conditions that varied group composition and sequentially varied space availability. Three cohorts of males were identified: non‐territorial individuals, rarely territorial individuals, and frequently territorial individuals. The results indicate that group social structure is not affected by changes in available space. Although no single male was always territorial in trials that varied group composition, a small number of males were frequently territorial. Often these successful males were temporarily displaced, but they typically regained a territory in subsequent trials.     

The complete mitochondrial DNA sequence of the green alga Pseudendoclonium akinetum (Ulvophyceae) highlights distinctive evolutionary trends in the chlorophyta and suggests a sister-group relationship between the Ulvophyceae and Chlorophyceae

The mitochondrial genome has undergone radical changes in both the Chlorophyta and Streptophyta, yet little is known about the dynamics of mtDNA evolution in either of these lineages. In the Chlorophyta, which comprises four of the five recognized classes of green algae (Prasinophyceae, Trebouxiophyceae, Ulvophyceae, and Chlorophyceae), the mitochondrial genome varies from 16 to 55 kb. This genome has retained a compact gene organization and a relatively complex gene repertoire ("ancestral" pattern) in the basal lineages represented by the Trebouxiophyceae and Prasinophyceae, whereas it has been reduced in size and gene complement and tends to evolve much more rapidly at the sequence level ("reduced-derived" pattern of evolution) in the Chlorophyceae and the lineage leading to the enigmatic chlorophyte Pedinomonas. To gain information about the evolutionary trends of mtDNA in the Ulvophyceae and also to gain insights into the phylogenetic relationships between ulvophytes and other chlorophytes, we have determined the mtDNA sequence of Pseudendoclonium akinetum. At 95,880 bp, Pseudendoclonium mtDNA is the largest green-algal mitochondrial genome sequenced to date and has the lowest gene density. These derived features are reminiscent of the "expanded" pattern exhibited by embryophyte mtDNAs, indicating that convergent evolution towards genome expansion has occurred independently in the Chlorophyta and Streptophyta. With 57 conserved genes, the gene repertoire of Pseudendoclonium mtDNA is slightly smaller than those of the prasinophyte Nephroselmis olivacea and the trebouxiophyte Prototheca wickerhamii. This ulvophyte mtDNA contains seven group I introns, four of which have homologs in green-algal mtDNAs displaying an "ancestral" or a "reduced-derived" pattern of evolution. Like its counterpart in the chlorophycean green alga Scenedesmus obliquus, it features numerous small, dispersed repeats in intergenic regions and introns. Its overall rate of sequence evolution appears to be accelerated to an intermediary level as compared with the rates observed in "ancestral" and "reduced-derived" mtDNAs. In agreement with the finding that Pseudendoclonium mtDNA exhibits features typical of both the "ancestral" and "reduced-derived" patterns of evolution, phylogenetic analyses of seven mtDNA-encoded proteins revealed a sister-group relationship between this ulvophyte and chlorophytes displaying "reduced-derived" mtDNAs.     

Design, synthesis, and characterization of peptide nanostructures having ion channel activity

We report the synthesis and the functional studies of multiple crown alpha-helical peptides designed to form artificial ion channels. The approach combines the versatility of solid phase peptide synthesis, the conformational predictability of peptidic molecules, and the solution synthesis of crown ethers with engineerable ion-binding abilities. Several biophysical methods were employed to characterize the activity and the mode of action of these crown peptide nanostructures. The 21 residue peptides bearing six 21-EC-7 turned out to facilitate the translocation of ions in a similar fashion to natural ion channels.     

Calcineurin activation influences muscle phenotype in a muscle-specific fashion

Background  

The calcium activated protein phosphatase 2B, also known as calcineurin, has been implicated as a cell signaling molecule involved with transduction of physiological signals (free cytosolic Ca²⁺) into molecular signals that influence the expression of phenotype-specific genes in skeletal muscle. In the present study we address the role of calcineurin in mediating adaptations in myosin heavy chain (MHC) isoform expression and muscle mass using 3-month old wild-type (WT) and transgenic mice displaying high-level expression of a constitutively active form of calcineurin (MCK-CN* mice).     

Helping thy neighbors: spillover at the mossy fiber glomerulus

Neurotransmitter "spillover" between neighboring synapses challenges the principle of synapse specificity. In this issue of Neuron, show that release from neighboring presynaptic sites contributes significantly to AMPA receptor-mediated postsynaptic currents at cerebellar mossy fiber synapses. Unexpectedly, spillover is predicted to improve the reliability and reduce the variability of transmission at this glomerular synapse.