Comparisons of endocrinological and testis parameters in 18-month-old Ile de France and Romanov rams

Endocrinological and testis parameters of adult 18-month-old Ile de France (IF) and Romanov (Ro) rams were compared during sexual season. Testis weights, total volumes of intertubular tissue, and of blood and lymph vessels, total seminiferous tubule length, rete testis flow rate and daily production of germ cells were significantly higher in IF than in Ro rams. These variations originated from differences in Sertoli cell numbers, which were established before puberty. When daily productions of germ cells, of ABP or of RTF were expressed per Sertoli cell, they were higher in Ro than in IF rams. Quality of spermatids, as measured by their cellular size prior to elongation, was lower in Ro than in IF. The number of FSH-binding sites per Sertoli did not differ between the two breeds but FSH plasma levels were higher in Ro than in IF rams. Total numbers of Leydig cells per testis, their individual size or their LH-binding capacity did not differ significantly between the two breeds. However, the ratio of mean testosterone upon mean LH plasma levels were greater in Ro than in IF rams while both breeds had identical LH mean plasma levels.     

Systemic lupus erythematosus in a colony of dogs

A colony of dogs was obtained by the mating of a female German Shepherd Dog crossbred and a male Belgian Shepherd Dog crossbred, both with systemic lupus erythematosus (SLE). The colony also contained 16 dogs representing F1, F2, and F3 generations. Ten colony dogs had circulating antinuclear antibodies, and 5 of the 10 had clinical signs of SLE. Two F3-generation females had signs of severe SLE. Two dogs had antibodies to extractable nuclear antigen, notably 1 dog had antibodies to Smith (Sm) antigen and 1 had antibodies to Sjogren syndrome A (SSA) antigen. Thymulin (serum thymic factor associated with zinc) titers were generally low in the descendants, but fluctuations were detected within the same dog. In vitro response of lymphocytes from these colony dogs to concanavalin A was maximal for lower mitogenic concentrations, compared with response of lymphocytes from 10 healthy dogs. The suppressive lymphocyte activity in 6 autoimmune colony dogs was diminished in comparison with the activity in 5 nonautoimmune colony dogs and 6 healthy dogs.     

Fast variability of tera-electron volt gamma rays from the radio galaxy M87

The detection of fast variations of the tera-electron volt (TeV) (10(12) eV) gamma-ray flux, on time scales of days, from the nearby radio galaxy M87 is reported. These variations are about 10 times as fast as those observed in any other wave band and imply a very compact emission region with a dimension similar to the Schwarzschild radius of the central black hole. We thus can exclude several other sites and processes of the gamma-ray production. The observations confirm that TeV gamma rays are emitted by extragalactic sources other than blazars, where jets are not relativistically beamed toward the observer.     

Predicting species-habitat relationships: does body size matter?

Context

Allometric scaling laws are foundational to structuring processes from cellular to ecosystem levels. The idea that allometric relationships underlie species characteristic selection scales, the spatial scales at which species respond to landscape features, has recently been investigated, however, supporting empirical evidence is scarce.

Objectives

Lack of pattern can be explained by inaccurate estimation, low power, confounding factors, or absence of a relationship. In this paper, we evaluate the relationship between body size and species characteristic selection scales after overcoming limitations of previous study designs.

Methods

We conducted 1328 avian point counts across the state of Nebraska using the robust sampling design to account for imperfect detection. We used Bayesian latent indicator scale selection with N-mixture models to estimate species’ characteristic selection scales of six habitat features for 86 species. We propagated the uncertainty associated with assigning characteristic scales to a model of the relationship between body size and characteristic spatial scales.

Results

Species characteristic scales varied across habitat predictors, and varied in the uncertainty associated with selecting single characteristic scales. After propagating uncertainty our results do not support a relationship between species’ body size and the spatial scales at which they respond to landscape features.

Conclusions

As species abundance integrates birth, death, immigration, and emigration processes, each of which are influenced by ecological processes manifesting at various scales, we question whether a general allometric relationship should be expected. Our results suggest that selection may act on responses to specific environmental features, rather than responses to spatial scale per se.