Experimental Pyelonephritis in Dogs

Both E. coli and S. aureus were simultaneously injected into the left renal arteries of 55 female dogs. The arteries were occluded for 10 minutes prior to the injection and 10 minutes after. The renal veins were occluded during the injection and for 10 minutes after.

Ten animals did not survive longer than 24 hours. Ten of 45 developed neither renal lesions nor bacteriuria; of the remaining 35 which did, five were killed on each of the second, seventh and fourteenth days, and their renal lesions were assessed. Eighteen of the remaining 2 which developed bacteriuria were killed 3 to 12 weeks following surgery when bacteria could no longer be recovered from the urine. Only two dogs had persistent bacteriuria 12 weeks after surgery. All animals which developed bacteriuria had gross lesions in the left kidney but not the right.

Naturally occurring renal lesions were found in 17 of 78 random-source dogs at laparotomy. E. coli was cultured from the urine of five of these dogs but not from the kidneys. These lesions were morphologically similar to experimental ones.

It is concluded that with this method renal lesions similar to spontaneous ones can be produced, but care must be taken to exclude the relatively large percentage of random-source dogs with naturally occurring lesions from any study.

Various forms of infectious nephritis have been reported to be among the commonest diseases of dogs (1, 2). The successful production of chronic pyelonephritis in dogs depends on a variety of factors in addition to injecting bacteria into either the renal artery or ureter. Thus, ureteral obstruction, renal anoxia and reduced pulse pressure increased the susceptibility to renal infection (3, 4, 6, 7, 8).

Our laboratory has been concerned with the production of experimental pyelonephritis in dogs so that the efficacy of various treatments could be studied. The present work was undertaken to standardize methods of producing the disease and to compare experimental renal lesions with naturally occurring ones.

     

Apollo 12 seismic signal: indication of a deep layer of powder

The seismic signal caused by the Apollo 12 lunar module is interpreted in terms of propagation between source and receiver through a layer of powder in which sound velocity increases with depth. This increase, which is due to compaction, extends over several kilometers and leads to a concentration of seismic waves toward the surface. Computer simulations with the use of ray acoustics and on the assumption of a randomly undulating lunar surface approximate well the observed signal. Seismic amplitudes are greatly enhanced in such a medium compared to solid rock, so that the observed signal requires less power to be transmitted than previously estimated.     

Mercury's magnetosphere after MESSENGER's first flyby

Observations by MESSENGER show that Mercury's magnetosphere is immersed in a comet-like cloud of planetary ions. The most abundant, Na+, is broadly distributed but exhibits flux maxima in the magnetosheath, where the local plasma flow speed is high, and near the spacecraft's closest approach, where atmospheric density should peak. The magnetic field showed reconnection signatures in the form of flux transfer events, azimuthal rotations consistent with Kelvin-Helmholtz waves along the magnetopause, and extensive ultralow-frequency wave activity. Two outbound current sheet boundaries were observed, across which the magnetic field decreased in a manner suggestive of a double magnetopause. The separation of these current layers, comparable to the gyro-radius of a Na+ pickup ion entering the magnetosphere after being accelerated in the magnetosheath, may indicate a planetary ion boundary layer.     

Radio method for the precise measurement of the rotation period of the Earth

Radio interferometry with independent high-precision clocks, without a high-frequency communication channel between the stations, is now a possibility. It allows the stations to be as far apart as the earth can accommodate. This then makes the radio band from 10- to 60-centimeters wavelength the best frequency range for high-precision angular measurements, since the variability of the atmosphere is less disturbing there than in the optical band.     

Quantitative genetics and heritability of growth-related traits in hybrid striped bass (Morone chrysops ♀ × Morone saxatilis ♂)

Commercially farmed, hybrid striped bass - female white bass (Morone chrysops) crossed with male striped bass (Morone saxatilis) - represent a rapidly growing industry in the United States. Expanded production of hybrid striped bass, however, is limited because of uncontrolled variation in performance of fish derived from undomesticated broodstock. A 10 × 10 factorial mating design was employed to examine genetic effects and heritability of growth-related traits based on dam half-sib and sire half-sib families. A total of 881 offspring were raised in a common environment and body weight and length were recorded at three different times post-fertilization; parentage of each fish was inferred from genotypes at 10 nuclear-encoded microsatellites. Dam and sire effects on juvenile growth (weight and length) and growth rate were significant, whereas dam by sire interaction effect was not. The dam and sire components of variance for weight and length (at age) and growth rate were estimated using a Restricted Maximum Likelihood algorithm. Estimates of broad-sense heritability of weight, using a family-mean basis, ranged from 0.67 ± 0.17 to 0.85 ± 0.07 for dams; estimates for sires ranged from 0.43 ± 0.20 to 0.77 ± 0.10. Estimates of broad-sense heritability of growth rate (based on weight), using a family-mean basis, ranged from 0.69 ± 0.12 to 0.82 ± 0.09 for dams and from 0.69 ± 0.13 to 0.81 ± 0.08 for sires. Similar results were obtained with length data. Both genetic and phenotypic correlations between weight and length were close to unity. High genetic (0.98-0.99) and phenotypic (0.79) correlations between growth rates measured at two time intervals suggested that selection for growth rate at an early life stage could affect growth rate at a later life stage. Estimates of general combining ability (GCA) for growth rates differed significantly among dams and among sires, whereas estimates of specific combining ability (SCA) for each dam × sire combination did not differ significantly from zero. These results suggest that additive-effect genes contributed to the differences in juvenile growth.