The Selective Staining of Mitochondria

A critical analysis of extant selective mitochondrial stains has elucidated certain empirical criteria for the adoption of dyes for trial. These criteria include a specific triphenylmethane structure for the dye, with sulfonation and the use of aniline and heat as adjuvants. By the application of these characteristics the dyes fast green FGF and light green SF yellowish were chosen for study and proved to be highly selective mitochondrial stains. They are applicable to both tissue slices and homogenate studies and permit examination of the internal structure of mitochondria.     

Intraspecific competition and aggression for shells in the hermit crab Pagurus samuel1s

Many studies have investigated shell‐related behaviour in hermit crabs. Few studies, however, have focused specifically on the intraspecies aggression associated with shell competition. We examined intraspecies aggression in hermit crab (Pagurus samuelis) pairs as it relates to competition for a limiting resource, gastropod shells. Pairs of hermit crabs were observed in the laboratory in four different treatments that varied the presence or absence of shells for one or both of the crabs. Measurements of the latency to respond, the number of bouts, and the fight durations were recorded. There was a significant difference among treatments for all three measurements, and naked hermit crabs were much more aggressive than housed hermit crabs. There was no significant difference in aggression between males and females in any of the three treatments. The heightened aggression observed in naked P. samuelis is likely in service of acquiring a protective shell.     

A design criterion for symmetric model discrimination based on flexible nominal sets

Experimental design applications for discriminating between models have been hampered by the assumption to know beforehand which model is the true one, which is counter to the very aim of the experiment. Previous approaches to alleviate this requirement were either symmetrizations of asymmetric techniques, or Bayesian, minimax, and sequential approaches. Here we present a genuinely symmetric criterion based on a linearized distance between mean-value surfaces and the newly introduced tool of flexible nominal sets. We demonstrate the computational efficiency of the approach using the proposed criterion and provide a Monte-Carlo evaluation of its discrimination performance on the basis of the likelihood ratio. An application for a pair of competing models in enzyme kinetics is given.     

Hibernation patterns of Turkish hamsters: influence of sex and ambient temperature

Turkish hamsters (Mesocricetus brandti) are a model organism for studies of hibernation, yet a detailed account of their torpor characteristics has not been undertaken. This study employed continuous telemetric monitoring of body temperature (T _b) in hibernating male and female Turkish hamsters at ambient temperatures (T _as) of 5 and 13 °C to precisely characterize torpor bout depth, duration, and frequency, as well as rates of entry into and arousal from torpor. Hamsters generated brief intervals of short (<12 h), shallow test bouts (T _b > 20 °C), followed by deep torpor bouts lasting 4–6 days at T _a = 5 °C and 2–3 days at T _a = 13 °C. Females at T _a = 5 °C had longer bouts than males, but maintained higher torpor T _b; there were no sex differences at T _a = 13 °C. Neither body mass loss nor food intake differed between the two T _as. Hamsters entered torpor primarily during the scotophase (subjective night), but timing of arousals was highly variable. Hamsters at both T _as generated short, shallow torpor bouts between deep bouts, suggesting that this species may be capable of both hibernation and daily torpor.     

Atmospheric Production of Glycolaldehyde Under Hazy Prebiotic Conditions

The early Earth’s atmosphere, with extremely low levels of molecular oxygen and an appreciable abiotic flux of methane, could have been a source of organic compounds necessary for prebiotic chemistry. Here, we investigate the formation of a key RNA precursor, glycolaldehyde (2-hydroxyacetaldehyde, or GA) using a 1-dimensional photochemical model. Maximum atmospheric production of GA occurs when the CH₄:CO₂ ratio is close to 0.02. The total atmospheric production rate of GA remains small, only 1×10⁷ mol yr^???1. Somewhat greater amounts of GA production, up to 2 × 10⁸ mol yr^???1, could have been provided by the formose reaction or by direct delivery from space. Even with these additional production mechanisms, open ocean GA concentrations would have remained at or below ~1 μM, much smaller than the 1–2 M concentrations required for prebiotic synthesis routes like those proposed by Powner et al. (Nature 459:239–242, 2009). Additional production or concentration mechanisms for GA, or alternative formation mechanisms for RNA, are needed, if this was indeed how life originated on the early Earth.