Effects of androgens on serum concentrations of gonadotropins and ovarian steroids in gilts

To examine how androgens affect endocrine events associated with increased ovulation rate, gilts were injected with androgen receptor agonists, an antagonist, or a combination of both. Blood samples were collected hourly from Day 13 to estrus (Day 0 = onset of estrus) coincident with gilts (n = 6 per treatment) receiving daily treatments of vehicle (corn oil), 10 mg of testosterone, 10 mg of 5 alpha-dihydrotestosterone (dihydrotestosterone), 1.5 g of flutamide (an androgen receptor antagonist), testosterone plus flutamide, or dihydrotestosterone plus flutamide. Treatment of gilts with testosterone or dihydrotestosterone alone increased (P < 0.05) concentrations of FSH in serum, and these effects were blocked by cotreatment with flutamide. Estradiol-17beta and androstenedione concentrations in serum were increased (P < 0.05) at 2 h after injection of testosterone or testosterone plus flutamide but not after dihydrotestosterone treatment, probably because of the role of testosterone as a substrate for estradiol-17beta and androstenedione synthesis. There were no effects of the six treatments on serum concentrations of progesterone during luteolysis, but treating gilts with testosterone shortened (P < 0.05) the proestrous period. Total embryonic loss by Day 11 in gilts treated with dihydrotestosterone was reversed when gilts were cotreated with dihydrotestosterone plus flutamide. Results of this experiment indicated that androgen actions both increased FSH secretion and reduced embryonic survival by a mechanism(s) dependent on the androgen receptor.     

Environmental setting of human migrations in the circum-Pacific region

Aim To assess the genetic and archaeological evidence for the migration of modern humans out of Africa to the circum‐Pacific region and compare the migration patterns with Late Pleistocene and Holocene changes in sea level and climate. Location Southern and eastern Asia, Australia, and Oceania. Methods Review of the literature and detailed compilations of data on early human settlements, sea level, and climate change. Results The expansion of modern humans out of Africa, following a coastal route into southern Asia, was initially thwarted by a series of large and abrupt environmental changes. A period of relatively stable climate and sea level from c. 45,000 yr bp to 40,000 yr bp supported a rapid coastal expansion of modern humans throughout much of Southeast Asia, enabling them to reach the coasts of northeast Russia and Japan by 38,000–37,000 yr bp . Further northwards, migrations were delayed by cold northern climates, which began to deteriorate rapidly after 33,000 yr bp . Human migrations along the coast of the Bering Sea into the New World appear to have occurred much later, c. 14,000 yr bp , probably by people from central Asia who were better adapted to cold northern climates. Cold, dry climates and rapidly changing sea levels leading into and out of the Last Glacial Maximum inhibited coastal settlement, and many of the sites occupied prior to 33,000 yr bp were abandoned. After 16,000 yr bp , the sea‐level rise slowed enough to permit coastal ecosystems to develop and coasts to be re‐colonized, but abrupt changes in climate and sea level inhibited this development until after 12,000 yr bp . Between 12,000 yr bp and 7000 yr bp there was a dramatic increase in reef and estuary/lagoon ecosystems, concurrent with a major expansion of coastal settlements. This early Holocene increase in coastal environments and the concomitant expansion of human coastal‐resource exploitation were followed by corresponding declines in both phenomena in the mid‐Holocene, c. 6000–4000 yr bp . This decline in coastal resources is linked to the drop in sea level throughout the Pacific, which may have caused the widespread population dislocations that ultimately led to the human expansion throughout Oceania. Main conclusions Climate and sea‐level changes played a central role in the peopling of the circum‐Pacific region.     

Protein Folding Failure Sets High-Temperature Limit on Growth of Phage P22 in Salmonella enterica Serovar Typhimurium

The high-temperature limit for growth of microorganisms differs greatly depending on their species and habitat. The importance of an organism's ability to manage thermal stress is reflected in the ubiquitous distribution of the heat shock chaperones. Although many chaperones function to reduce protein folding defects, it has been difficult to identify the specific protein folding pathways that set the high-temperature limit of growth for a given microorganism. We have investigated this for a simple system, phage P22 infection of Salmonella enterica serovar Typhimurium. Production of infectious particles exhibited a broad maximum of 150 phage per cell when host cells were grown at between 30 and 39°C in minimal medium. Production of infectious phage declined sharply in the range of 40 to 41°C, and at 42°C, production had fallen to less than 1% of the maximum rate. The host cells maintained optimal division rates at these temperatures. The decrease in phage infectivity was steeper than the loss of physical particles, suggesting that noninfectious particles were formed at higher temperatures. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed a decrease in the tailspike adhesins assembled on phage particles purified from cultures incubated at higher temperatures. The infectivity of these particles was restored by in vitro incubation with soluble tailspike trimers. Examination of tailspike folding and assembly in lysates of phage-infected cells confirmed that the fraction of polypeptide chains able to reach the native state in vivo decreased with increasing temperature, indicating a thermal folding defect rather than a particle assembly defect. Thus, we believe that the folding pathway of the tailspike adhesin sets the high-temperature limit for P22 formation in Salmonella serovar Typhimurium.     

Dominance hierarchy in a herd of female eland antelope (Taurotragus oryx) in captivity

The dominance hierarchy of a group of adult female elands (n=10) kept in captivity was followed for 34 months. Outcomes of dominance relationships at the beginning and end of the study were compared. A clear dominance hierarchy existed in the herd. The dominance pattern was complex, but triads were predominantly (95%) transitive or linear. Reversal of dominance occurred in 12 dyads (27%), of which eight (67%) involved a single female. Two females shared the most dominant rank at the beginning of the study. One of these two females and another female later assumed the highest dominance rank on different occasions. A single female remained most subordinate throughout the study period. The correlation between body weight and dominance rank was not significant (r=0.46; P=0.21). Similarly, dominance rank was not associated with the taming potential of the females. However, the median dominance value increased in females with good taming potential, while it decreased in those with poor taming potential. In conclusion, captive eland antelope have a dynamic and complex dominance hierarchy that is predominantly linear. Zoo Biol 23:323–333, 2004. © 2004 Wiley‐Liss, Inc.     

Discriminating small molecule DNA binding modes by single molecule force spectroscopy

Drugs may interact with double stranded DNA via a variety of binding modes, each mode giving rise to a specific pharmacological function. Here we demonstrate the ability of single molecule force spectroscopy to discriminate between different interaction modes by measuring the mechanical properties of DNA and their modulation upon the binding of small molecules. Due to the unique topology of double stranded DNA and due to its base pair stacking pattern, DNA undergoes several well-characterised structural transitions upon stretching. We show that small molecule binding markedly affects these transitions in ways characteristic to the binding mode and that these effects can be detected at the level of an individual molecule. The minor groove binder berenil, the crosslinker cisplatin and the intercalator ethidium bromide are compared.     

Isolation of twelve microsatellite loci,using an enrichment protocol,in the phytopathogenic fungus Puccinia striiformis f.sp. tritici

We report the characterization of 12 microsatellite markers in the biotrophic fungus Puccinia striiformis f.sp. tritici, responsible for yellow rust on wheat. An enrichment protocol was used to isolate microsatellite loci, and polymorphism was explored with 96 isolates from natural populations collected from several French and Chinese locations. Eight primers (67%) showed cross‐amplification when tested with eight isolates of P. triticina.     

Lethal osteogenesis imperfecta congenita and a 300 base pair gene deletion for an alpha 1(I)-like collagen.

Broad boned lethal osteogenesis imperfecta is a severely crippling disease of unknown cause. By means of recombinant DNA technology a 300 base pair deletion in an alpha 1(I)-like collagen gene was detected in six patients and four complete parent-child groups including patients with this disease. One from each set of the patients'' clinically unaffected parents also carried the deletion, implying that affected patients were genetic compounds. The study suggests that prenatal diagnosis should be possible with 100% accuracy in subjects without the deletion and with 50% accuracy in those who possess it (who would be either heterozygous--normal, or affected with the disease).     

Prehistoric sunflower (Helianthus Annuus L.) domestication in Mexico

Early remains of Helianthus annuus L. unearthed at the San Andrés site in the Gulf Coast region of Tabasco, Mexico, constitute the earliest record of domesticated sunflower. Accelerator mass spectrometry (AMS) age determinations of a large domesticated seed and achene produced dates of 4130 ± 40 years before the present (B.P.) and 4085 ± 50 B.P., respectively. These discoveries challenge the longstanding hypothesis that sunflower was domesticated in eastern North America. Moreover, when considered with other recent discoveries on plant domestication, these data suggest a reconsideration of the idea that the eastern United States was an independent hearth for domestication.     

Embryogenesis recapitulates oogenesis in swine.

Events during oogenesis can affect embryogenesis so dramatically that oocytes can be identified that are progenitors of embryos which would probably die if they remained in the host pig, but would live if appropriately transferred to another female. This review goes backward from embryonic to oocyte development, first discussing how subtle differences between littermate embryos can result in the death of some embryos and then relating the causes of those differences to events during follicular maturation. Embryonic development is not uniform in swine. The larger blastocysts within a litter synthesize estradiol sooner than their less developed contemporaries. Estradiol advances uterine secretions to the benefit of the more developed blastocysts, but results in an asynchronous and hostile environment for the less developed blastocysts. Through a series of experiments, the pattern of oocyte and follicular development was found to be one of the sources of subsequent disparity among blastocysts. In pigs mated before ovulation, the first oocytes released at ovulation were the first fertilized and became the more developed blastocysts 12 days later. Inversely, the later ovulated oocytes were the last to be fertilized and became the smaller blastocysts. These smaller blastocysts can develop normally, but because of estrogenic advancement of uterine secretions, they will preferentially die.