Successful Non-Surgical Transfer of Horse Embryos to Mule Recipients

Mules, hybrids resulting from the mating of a horse mare (Equus caballus, 2n = 64) to a Jack donkey (E. asinus, 2n = 62), are generally infertile. Five horse embryos were transferred non‐surgically to two cyclic and one acyclic recipient mules. In the mares and cycling mules, oestrus and ovulation were induced with, respectively, d ‐cloprostenol and human chorionic gonadotrophin (hCG). The acyclic mule, on the other hand, received oestradiol benzoate when the embryo donor was showing oestrus and progesterone after the donor had ovulated and until pregnancy diagnosis. Non‐surgical embryo collections were attempted on day 7 after ovulation and recovered embryos were transferred transcervically into the mules’ uteri. Mules that became pregnant were blood sampled serially for equine chorion gonadotrophin (eCG), progestagen and total conjugated oestrogen concentrations until around 6 months of gestation. The three embryos transferred to the acyclic mule did not produce any pregnancies whereas both embryos transferred to the cycling mules resulted in the birth of live foals. The peak concentration and duration of secretion of eCG differed markedly between the two pregnant mules, although both animals appeared to develop secondary corpora lutea beyond day 40 of gestation, as in normal intraspecies horse pregnancy. Moreover, the rise in serum oestrogen concentrations from around day 90 was also similar to that seen in normal pregnant mares. Parturition occurred spontaneously on day 348 of gestation in both mules and the resulting colt foals developed normally to weaning. Thus, cycling mules can carry a horse conceptus after non‐surgical embryo transfer and give birth to a normal mature foal.     

Cosmic-ray tracks in plastics: the apollo helmet dosimetry experiment

Counts of tracks from heavy cosmic-ray nuclei in helmets from Apollo missions 8 and 12 show variations caused by solar modulation of the galactic cosmic-ray flux. Specific estimates of the biological damage to certain nonreplaceable cells by track-forming particles during these space missions indicate that the fraction of deactivated cells could range from a lower limit of 3 x 10(-7) to an upper limit of 1.4 x 10(-4).     

From trees to fleas: masting indirectly affects flea abundance on a rodent host

Mast seeding causes strong fluctuations in populations of forest animals. Thus, this phenomenon can be used as a natural experiment to examine how variation in host abundance affects parasite loads. We investigated fleas infesting yellow-necked mice in beech forest after 2 mast and 2 non-mast years. We tested 2 mutually exclusive scenarios: (1) as predicted by classical models of density-dependent transmission, an increase in host density will cause an increase in ectoparasite abundance (defined as the number of parasites per host), versus (2) an increase in host density will cause a decline in flea abundance (“dilution,” which is thought to occur when parasite population growth is slower than that of the host). In addition, we assessed whether masting alters the relationship between host traits (sex and body mass) and flea abundance. We found a hump-shaped relationship between host and flea abundance. Thus, the most basic predictions are too simple to describe ectoparasite dynamics in this system. In addition, masting modified seasonal dynamics of flea abundance, but did not affect the relationship between host traits and flea abundance (individuals with the highest body mass hosted the most fleas; after controlling for body mass, parasite abundance did not vary between sexes). Our results demonstrate that pulses of tree reproduction can indirectly, through changes in host densities, drive patterns of ectoparasite infestation.     

Paraoxonase (PON) 1, 2 and 3 Expression in Granulosa Cells and PON1 Activity in Follicular Fluid of Dairy Cows

Normal metabolic activity in ovarian follicles may result in oxidative stress and damage to oocytes. The aim of this study was to evaluate expression of the natural anti‐oxidants paraoxonase (PON) 1, 2 and 3 in granulosa cells and PON1 activity in follicular fluid (FF) and plasma of dairy cows. For the first experiment, ovaries were collected from cows at slaughter, after which follicles were dissected and classified as oestrogen active (EAF) or atretic (ATF). Expression of PON1, PON2 and PON3 mRNA was evaluated in granulosa cells, and activity of PON1 was measured in FF. PON1 mRNA was undetectable in granulosa cells, PON2 mRNA expression was not different between follicle types, and PON3 mRNA tended to be higher in EAF (p = 0.11). The activity of PON1 in FF was higher (p = 0.01) for EAF (82.6 ± 8.0 kU/L) than ATF (53.9 ± 6.8 kU/L), as were high‐density lipoproteins (HDL), low‐density lipoproteins (LDL) and total cholesterol concentrations. In the second experiment, we aimed to compare plasma and FF PON1 activity in early lactation Holstein cows (n = 15) with pre‐ovulatory EAF. Activity of PON1 was twofold higher (p < 0.0001) in plasma (122.5 ± 11.1 kU/L) than in FF (61.4 ± 5.2 kU/L). Plasma concentrations were also higher (p < 0.0001) for HDL, LDL and total cholesterol when compared to FF. In conclusion, FF concentrations of PON1, HDL, LDL and total cholesterol were higher in healthy oestrogen active bovine follicles than in atretic follicles. PON1 was not expressed by granulosa cells indicating that high PON1 activity in bovine FF is apparently derived by transfer from blood in association with HDL.     

Efficacy of zeta-cypermethrin as pour-on or spray formulations for the control of buffalo fly (Haematobia irritans exigua) in cattle

Objective To determine the efficacy of zeta-cypermethrin in controlling buffalo fly ( Haematobia irritans exigua ).
Design Five field trials in northern and central Queensland.
Procedure Zeta-cypermethrin pour-on at 2.5 mg/kg, spray at 62.5 ppm, deltamethrin pour-on and pour-on vehicle were applied to groups of 20 cattle. Buffalo fly counts were conducted three times before treatment and 3, 7, 14, 21, 28 and 35 days after treatment.
Results In central Queensland where synthetic pyrethroid resistance in buffalo fly populations was rare, 2.5 mg/kg of zeta-cypermethrin pour-on gave good control of buffalo fly for 4 weeks and was better than a deltamethrin product. A zeta-cypermethrin spray used at 62.5 ppm gave 14 days control. In far-north Queensland where resistance to synthetic pyrethroids and heavy rain was common, the maximum period of efficacy of zeta-cypermethrin pour-on was reduced to 2 weeks.
Conclusion In areas where there is low resistance to synthetic pyrethroids among buffalo flies, zeta-cypermethrin pour-on can be expected to give good control for 4 weeks.     

Detrital Zircon Link Between Headwaters and Terminus of the Upper Triassic Chinle-Dockum Paleoriver System

New detrital-zircon geochronologic data reveal that a through-going paleoriver connected Texas with Nevada in Late Triassic time. Sandstone from the Upper Triassic Santa Rosa Sandstone (Dockum Group) from northwestern Texas contains a detrital zircon suite nearly identical to that found in western Nevada in the Upper Triassic Osobb Formation (Auld Lang Syne Group, correlative with the Chinle Formation). The Santa Rosa Sandstone was derived in large part from the eroded Cambrian core of the Amarillo-Wichita uplift, as evidenced by abundant zircons with ages of 515 to 525 million years. Other zircon grains in the sandstone are Permian, Devonian, Proterozoic, and Archean in age and, with the exception of the Archean grain, are also matched by the population in the Nevada strata.