Microsatellite markers for the native Texas perennial grass, Panicum hallii (Poaceae)

? Premise of the study: We developed microsatellites for Panicum hallii for studies of gene flow, population structure, breeding experiments, and genetic mapping. ? Methods and Results: Next-generation (454) genomic sequence data were used to design markers. Eighteen robust markers were discovered, 15 of which were polymorphic across six accessions of P. hallii var. hallii. Fourteen of the markers cross-amplified in a P. capillare accession. For the 15 polymorphic markers, the total number of alleles per locus ranged from two to 26 (mean: 11.0) across six populations (11-19 individuals per population). Observed heterozygosity (mean: 0.031) was 13.7 times lower than the expected heterozygosity (mean: 0.426). ? Conclusions: The deficit of heterozygous individuals is consistent with P. hallii having a high rate of self-fertilization. These markers will be useful for studies in P. hallii and related species.     

Mapping of ionomic traits in Mimulus guttatus reveals Mo and Cd QTLs that colocalize with MOT1 homologues

Natural variation in the regulation of the accumulation of mineral nutrients and trace elements in plant tissues is crucial to plant metabolism, development, and survival across different habitats. Studies of the genetic basis of natural variation in nutrient metabolism have been facilitated by the development of ionomics. Ionomics is a functional genomic approach for the identification of the genes and gene networks that regulate the elemental composition, or ionome, of an organism. In this study, we evaluated the genetic basis of divergence in elemental composition between an inland annual and a coastal perennial accession of Mimulus guttatus using a recombinant inbred line (RIL) mapping population. Out of 20 elements evaluated, Mo and Cd were the most divergent in accumulation between the two accessions and were highly genetically correlated in the RILs across two replicated experiments. We discovered two major quantitative trait loci (QTL) for Mo accumulation, the largest of which consistently colocalized with a QTL for Cd accumulation. Interestingly, both Mo QTLs also colocalized with the two M. guttatus homologues of MOT1, the only known plant transporter to be involved in natural variation in molybdate uptake.     

Morphological Changes in the Midgut of Aedes aegypti L. (Diptera: Culicidae) Larvae Following Exposure to an Annona coriacea (Magnoliales: Annonaceae) Extract

Bioinsecticides are important in the control of disease vectors, but data regarding their physiological effects on target insects are incomplete. This study describes morphological changes that occur in the midgut of third instar Aedes aegypti L. (Diptera: Culicidae) following treatment with a methanolic extract of Annona coriacea (Magnoliales: Annonaceae). Dissected midguts were subdivided into anterior and posterior regions and analyzed by light and scanning electron microscopy. Insects exposed to the extract displayed intense, destructive cytoplasmic vacuolization in columnar and regenerative midgut cells. The apical surfaces of columnar cells exhibited cytoplasmic protrusions oriented toward the lumen, suggesting that these cells could be involved in apocrine secretory processes and/or apoptosis. We report that A. coriacea extracts induced morphological alterations in the midgut of A. aegypti midgut larvae, supporting the use of plant extracts for control of the dengue vector.     

How to build a mammalian super-predator

Questions surrounding the biology of large fossil predators that differ markedly from living forms have long intrigued palaeobiologists. Among such taxa few have excited more interest than sabertooth cats, whose distinctive hypertrophied canines are suggestive of killing behaviors and feeding ecologies that may have departed widely from those of extant carnivores. Moreover, considerable variation among sabertooth species is further suggestive of intriguing differences within the group. Behavior and ecology in another large, extinct mammalian carnivore, the Australian marsupial lion (Thylacoleo carnifex), has also proven contentious. In this study, we assemble a wide range of cranio-dental and postcranial indices in a dataset including machairodont sabertooths, T. carnifex and an extensive sample of extant taxa in order to examine the palaeobiology of these charismatic fossil carnivores. Results of multivariate analyses point to significant relationships between behavior and overall body proportions in extant mammalian carnivores. Postcranial morphologies of two American dirk-tooth species of sabertooth (Smilodon) depart greatly from those of living felids and group most closely with bears among living placentals. Scimitar-tooth species of Homotherium and Machairodus cluster with modern pantherine cats. The marsupial lion groups with Smilodon. If these latter two phylogenetically disparate clades do represent a specialized, robust ecomorph adapted to predation on large prey, then it is a body plan that might be effectively identified on the basis of a handful of ‘bear-like’ postcranial features in combination with a more typically ‘felid-like’ carnassialization of the cheektooth row.     

Novel integrated microdialysis-amperometric system for in vitro detection of dopamine secreted from PC12 cells: design, construction, and validation

A novel dual channel in vitro apparatus, derived from a previously described design, has been coupled with dopamine (DA) microsensors for the flow-through detection of DA secreted from PC12 cells. The device, including two independent microdialysis capillaries, was loaded with a solution containing PC12 cells while a constant phosphate-buffered saline (PBS) medium perfusion was carried out using a dual channel miniaturized peristaltic pump. One capillary was perfused with normal PBS, whereas extracellular calcium was removed from extracellular fluid of the second capillary. After a first period of stabilization and DA baseline recording, KCl (75 mM) was added to the perfusion fluid of both capillaries. In this manner, a simultaneous “treatment–control” experimental design was performed to detect K⁺-evoked calcium-dependent DA secretion. For this purpose, self-referencing DA microsensors were developed, and procedures for making, testing, and calibrating them are described in detail. The electronic circuitry was derived from previously published schematics and optimized for dual sensor constant potential amperometry applications. The microdialysis system was tested and validated in vitro under different experimental conditions, and DA secretion was confirmed by high-performance liquid chromatography with electrochemical detection (HPLC–EC). PC12 cell viability was quantified before and after each experiment. The proposed apparatus serves as a reliable model for studying the effects of different drugs on DA secretion through the direct comparison of extracellular DA increase in treatment–control experiments performed on the same initial PC12 cell population.     

G Protein beta gamma subunits act on the catalytic domain to stimulate Bruton's agammaglobulinemia tyrosine kinase.

G proteins are critical cellular signal transducers for a variety of cell surface receptors. Both alpha and betagamma subunits of G proteins are able to transduce receptor signals. Several direct effect molecules for Gbetagamma subunits have been reported; yet the biochemical mechanism by which Gbetagamma executes its modulatory role is not well understood. We have shown that Gbetagamma could directly increase the kinase activity of Bruton's tyrosine kinase (Btk) whose defects are responsible for X chromosome-linked agammaglobulinemia in patients. The well characterized interaction of Gbetagamma with the PH (pleckstrin homology)/TH (Tec-homology) module of Btk was proposed to be the underlying activation mechanism. Here we show that Gbetagamma also interacts with the catalytic domain of Btk leading to increased kinase activity. Furthermore, we showed that the PH/TH module is required for Gbetagamma-induced membrane translocation of Btk. The membrane anchorage is also dependent on the interaction of Btk with phosphatidylinositol 3,4,5-trisphosphate, the product of phosphoinositide 3-kinase. These data support a dual role for Gbetagamma in the activation of Btk signaling function, namely membrane translocation and direct regulation of Btk catalytic activity.     

DIVING BEHAVIOR OF SUBADULT AND ADULT HARBOR SEALS IN PRINCE WILLIAM SOUND, ALASKA

Satellite-linked depth recorders (SDRs) were attached to 47 harbor seals in Prince William Sound, Alaska, during 1992–1996. Parameters describing diving effort, diving focus, and focal depth (depth bin to which diving was focused) were calculated from binned data on maximum dive depth and time spent at depth, and analyzed using repeated-measures mixed models. This analysis method accounted for individual variability, temporal autocorrelation, and the binned nature of SDR data, which are often ignored using standard statistical techniques. Results indicated that diving effort remained steady from September to April, when seals spent 68%-75% of their overall time in the water. Time spent in the water declined to 60% in May and to about 40% in July. Seals spent the most time in the water at night and the least in the morning. The diving of all seals in all months was highly focused. Overall, diving was focused to one depth bin approximately 75% of the time. Diving was more focused for females than for males and subadults. Focal dive depth was deepest in winter and shallowest during May-July. Focal depth and diving focus varied by region. Collinearity between month and region in the focal depth model suggests that seals move in winter to regions where prey are found deeper in the water column. Variations in diving behavior presumably result from combinations of regional bathymetry, seasonal cycles in type or depth distribution of prey, and seal life-cycle events such as reproduction and molting.