Distribution of the Shoshone scuplin ( Cottus greenei: Cottidae) in the Hagerman Valley of south central Idaho

Cottus greenei, a potentially threatened species endemic to Idaho, was collected from 49 localities in 25 springs/streams in south central Idaho. Most localities were along the north bank of the Snake River in waters of the Thousand Springs formation, Gooding County. One population was found in a spring in the main Snake River. Another sculpin, Cottus bairdi, was collected with C. greenei at 23 locations in 16 springs/streams. Confusion concerning the type locality of Cottus greenei is discussed.        

Conversion of testosterone to androstenedione by liver homogenates of testicular feminized mice

Summary Liver homogenates of testicular feminized (Tfm) mice carrying the protective (o^hv) gene were found to be less capable of converting testosterone to androstenedione than Tfm without the protective gene.This work was supported by the Medical Research Council of Canada, No. MT 4192 and Ortho Pharmaceutical Company.     

cdx4 mutants fail to specify blood progenitors and can be rescued by multiple hox genes

Organogenesis is dependent on the formation of distinct cell types within the embryo. Important to this process are the hox genes, which are believed to confer positional identities to cells along the anteroposterior axis. Here, we have identified the caudal-related gene cdx4 as the locus mutated in kugelig (kgg), a zebrafish mutant with an early defect in haematopoiesis that is associated with abnormal anteroposterior patterning and aberrant hox gene expression. The blood deficiency in kgg embryos can be rescued by overexpressing hoxb7a or hoxa9a but not hoxb8a, indicating that the haematopoietic defect results from perturbations in specific hox genes. Furthermore, the haematopoietic defect in kgg mutants is not rescued by scl overexpression, suggesting that cdx4 and hox genes act to make the posterior mesoderm competent for blood development. Overexpression of cdx4 during zebrafish development or in mouse embryonic stem cells induces blood formation and alters hox gene expression. Taken together, these findings demonstrate that cdx4 regulates hox genes and is necessary for the specification of haematopoietic cell fate during vertebrate embryogenesis.     

Central aromatization of testosterone in testicular feminized mice

Summary Aromatization of testosterone was examined in hypothalamic and cerebral cortex tissues from 32 mice-10 normal males, 10 normal females, 2 carrying the testicular feminized gene (Tfm) and 10 Tfm with the modifying (o^hv) gene. Total aromatization was 1.5 times greater in normal males than females. In both forms of Tfm, conversions were equal and similar to normal females.This work was supported by the Medical Research Council of Canada.     

Preseismic velocity changes observed from active source monitoring at the Parkfield SAFOD drill site

Measuring stress changes within seismically active fault zones has been a long-sought goal of seismology. One approach is to exploit the stress dependence of seismic wave velocity, and we have investigated this in an active source cross-well experiment at the San Andreas Fault Observatory at Depth (SAFOD) drill site. Here we show that stress changes are indeed measurable using this technique. Over a two-month period, we observed an excellent anti-correlation between changes in the time required for a shear wave to travel through the rock along a fixed pathway (a few microseconds) and variations in barometric pressure. We also observed two large excursions in the travel-time data that are coincident with two earthquakes that are among those predicted to produce the largest coseismic stress changes at SAFOD. The two excursions started approximately 10 and 2 hours before the events, respectively, suggesting that they may be related to pre-rupture stress induced changes in crack properties, as observed in early laboratory studies.