Dominance and effects of strange conspecifics on aggressive interactions in the hermit crab Pagurus longicarpus (say)

Dominance orders in the hermit crab Pagurus longicarpus were observed in the laboratory. Groups of four crabs formed loose dominance hierarchies as determined by repeated display and retreat behaviour. Stronger dominance orders were inversely correlated with the frequency of aggressive interactions. Recognition of individuals, as measured by frequency and intensity of aggressive encounters between familiar crabs and introduced strangers, was not important in maintaining dominance orders. Rather, P. longicarpus recognized the aggressive state of conspecifics, as shown by frequencies of aggressive encounters after individuals of different dominance rankings were exchanged between established hierarchies.     

The site of active uptake of atmospheric water in larvae of Tenebrio molitor

Larvae starved and desiccated for 8 days will then take up water from 93% r.h., the gain ceasing by 7 days. The rate and amount of uptake were the same in those starved at 0% r.h. as in those starved at 53% r.h. Tying off the last abdominal segment prevents uptake while tying off the first abdominal segment allowed one-third as much gain as controls. This supports the theory that active uptake of atmospheric water is by way of the rectum and not the body cuticle. Because of the time taken to reach equilibrium, of the same uptake after exposure at 53% as after 0% r.h., and of a large overshoot in uptake, it is suggested that the phenomenon in this species is a by-product of drying the faeces and not a vital aspect of the physiology of water balance.     

Locomotor performance and cost of transport in the northern flying squirrelGlaucomys sabrinus

We assess locomotor performance by northern flying squirrelsGlaucomys sabrinus Shaw, 1801 and test the hypothesis that gliding locomotion is energetically cheaper than quadrupedal locomotion. We measured 168 glides by 82 northern flying squirrels in Alaska. Mean glide distances varied from 12.46 m to 14.39 m, with a maximum observed glide distance of 65 m. Mean glide angles varied from 41.31° to 36.31°, and mean air speed ranged from 6.26 m/s to 8.11 m/s. There were no differences in the performance of male and female flying squirrels. We used models of transport cost to provide an initial assessment of the hypothesis that gliding locomotion is energetically less expensive than quadrupedal locomotion. For glides of average length, cost of gliding was less than cost of quadrupedal locomotion except when the animals climbed to the launch point very slowly or ran quickly. Thus the hypothesis that gliding is less expensive than quadrupedal locomotion is supported.     

DNA single-strand breakage in mammalian cells induced by redox cycling quinones in the absence of oxidative stress

Quinone-induced cell death is often attributed to oxidative stress during which the formation of DNA strand breaks is thought to play an important role. In this study, extensive DNA damage was observed in human chronic myelogenous leukemic cells (K562) exposed for 15 minutes to low concentrations (15–100 μM) of the redox cycling quinones 2,3-dimethoxy-1,4-naphthoquinone (2,3-diOMe-1,4-NQ) and menadione. However, DNA strand breakage and cell death could not be attributed to oxidative stress as the intracellular level and redox status of the reducing equivalents NADP(H) and GSH were unaffected. The intracellular level of NAD⁺ was found to correlate well with the extent of DNA repair (r = 0.93, P < 0.02) and cell proliferation (r = 0.96, P < 0.01) in cells exposed to the quinones. In contrast, a significant decrease in the level of intracellular ATP was only observed in cells exposed to menadione (50–100 μM). These results suggest that redox cycling quinones are capable of inducing DNA damage in mammalian cells by a mechanism that does not involve oxidative stress. Following DNA damage, cell death is dependent on the availability of NAD⁺, which may be key to the rapid repair of strand breaks. © 1995 John Wiley & Sons, Inc.     

Radical production in liver mitochondria by peroxidic tumor promoters

Eleven peroxides have been tested to determine if there is a correlation between tumor-promoting activity and the ability to stimulate radical production in mitochondria. When non-respiring rat liver mitochondria are treated with these peroxidic compounds in the presence of DMPO, ESR signals are observed from the spin trapping of carbon- and oxygen-centered radicals in the case of 4 of the 7 peroxides that are known to be tumor promoters. Enhancement of carbon-centered radical production is observed in the presence of respiratory substrate. Thus there does not appear to be a correlation between tumor-promoting activity of peroxidic compounds and radical production in mitochondria. Oxidants can act as promoters either by 1- or 2-electron oxidation pathways; both types of mechanisms may be inhibited by antioxidants, which can scavenge either radicals or electrophiles.