A Three-Dimensional Skeletal Reconstruction of the Stem Amniote Orobates pabsti (Diadectidae): Analyses of Body Mass,Centre of Mass Position,and Joint Mobility

Orobates pabsti, a basal diadectid from the lower Permian, is a key fossil for the understanding of early amniote evolution. Quantitative analysis of anatomical information suffers from fragmentation of fossil bones, plastic deformation due to diagenetic processes and fragile preservation within surrounding rock matrix, preventing further biomechanical investigation. Here we describe the steps taken to digitally reconstruct MNG 10181, the holotype specimen of Orobates pabsti, and subsequently use the digital reconstruction to assess body mass, position of the centre of mass in individual segments as well as the whole animal, and study joint mobility in the shoulder and hip joints. The shape of most fossil bone fragments could be recovered from micro-focus computed tomography scans. This also revealed structures that were hitherto hidden within the rock matrix. However, parts of the axial skeleton had to be modelled using relevant isolated bones from the same locality as templates. Based on the digital fossil, mass of MNG 10181 was estimated using a model of body shape that was varied within a plausible range to account for uncertainties of the dimension. In the mean estimate model the specimen had an estimated mass of circa 4 kg. Varying of the mass distribution amongst body segments further revealed that Orobates carried most of its weight on the hind limbs. Mostly unrestricted joint morphology further suggested that MNG 10181 was able to effectively generate propulsion with the pelvic limbs. The digital reconstruction is made available for future biomechanical studies.     

Physiologically-induced changes in proopiomelanocortin mRNA levels in the pituitary gland of the amphibian Xenopus laevis

In the pars intermedia of the pituitary gland of the amphibian Xenopus laevis the level of mRNA encoding proopiomelanocortin (POMC), the precursor protein for alpha-melanophore-stimulating hormone (alpha-MSH), is shown to be dependent on physiological parameters. POMC mRNA levels in the pars intermedia of black-background-adapted Xenopus are much higher than those of white-adapted animals. These physiological changes in POMC mRNA levels are tissue-specific because they were not found in the pars distalis of the pituitary gland. Background transfer experiments revealed that modulation of POMC gene activity is much slower than changes in the secretion of alpha-MSH.     

Salinity tolerance of Mytilocypris henricae (Chapman) (Crustacea,Ostracoda)

Salinity tolerance, and the effects of temperature upon it, of the Australian ostracod Mytilocypris henricae (Chapman) was determined in direct transfer experiments using adults. Animals were subjected to a combination of 11 salinities (ranging between 0.0 g · 1^–1 and 45.0 g · 1^–1) and 4 temperatures (10, 15, 20 and 25 °C). Survival was analysed using two statistical techniques: the logit linear model and the proportional hazards model. Results show that both salinity and temperature have a significant effect on survival, but there is no significant interaction between temperature and salinity.     

Identification of in-vivo vibration modes of human tibiae by modal analysis

When attempting to evaluate the mechanical properties of human bones in vivo by mechanical vibration analysis, some essential requirements must be met. A quantitative relation between measured vibration parameters (e.g., natural frequency) and mechanical bone properties must be available, in-vivo vibration modes should correctly be identified and the associated natural frequencies reproducibly and accurately measured, the influence of joints and soft tissues must be known. These problems were addressed by modal analysis (i.e., experimental determination of natural frequencies, mode shapes and damping ratios) of human tibiae in the following situations: 1) dry excised tibiae, 2) fresh excised tibiae, 3) in-vivo tibiae, 4) tibiae in an amputated leg, in different steps of dissection. In the in-vivo measuring conditions used by the authors, the tibia vibration is practically free-free. Two single bending modes (at +/- 270 Hz and +/- 340 Hz, respectively), each of them corresponding with one principal direction for bending, were identified. The difference between the natural frequencies observed in vivo and those of fresh excised tibiae is almost completely caused by the effect of muscles (added mass and damping), whereas joints and skin play only a minor role. Frequency differences between fresh and dry excised tibiae are largely accounted for by the absence of bone marrow in the latter.     

Degradation of the fluoroquinolone enrofloxacin by wood-rotting fungi.

The veterinary fluoroquinolone enrofloxacin was degraded in vitro by four species of wood-rotting fungi growing on wetted wheat straw containing carbonyl-14C-labeled drug. A maximum 14CO2 production of 17% per week was observed with the brown rot fungus Gloeophyllum striatum, resulting in up to 53% after 8 weeks. However, rates reached at most 0.2 and 0.9% per week, if enrofloxacin was preadsorbed to native or gamma ray-sterilized soil, respectively.     

The ecological significance of nickel hyperaccumulation: a plant chemical defense

Nickel hyperaccumulating plants have more than 1000 mg Ni kg^–1 dry weight when grown on nickel-bearing soils. We hypothesized that Ni hyperaccumulation could serve as a chemical defense against herbivores In feeding experiments with potential insect herbivores and Ni hyperaccumulating plants, only those inseets fed leaves from plants grown on non-nickel-bearing soil survived or showed a weight gain. Among chemical parameters measured, only Ni content of plants was sufficient to explain this result. When subjected to herbivory by lepidopteran larvae, plants grown on Ni-amended soil showed greater survival and yield than plants on unamended soil. Ni hyperaccumulation may be an effective plant chemical defense against herbivores because of its high lethality, apparent low cost, and broad spectrum of toxicity.