Detection of bone marrow-derived cells in neointimal thickening in the rat carotid artery by nested polymerase chain reaction

The bone marrow origin of cells involved in neointimal formation after injury of the luminal surface of the vessel was confirmed by highly sensitive nested polymerase chain reaction on isolated vascular wall cells. The model of intimal hyperplasia after balloon angioplasty of the carotid artery in radiation bone marrow chimeras between male and female Wistar rats was used. The Y chromosomes of rat male donors of the bone marrow for irradiated females were used as a marker of bone marrow-derived cells. This approach demonstrated a bone marrow origin of a large fraction of α-actin-positive (smooth muscle) neointimal cells.     

Cortical alpha-2a adrenoreceptors involved in the inhibitory control of motor activity in neonatal rats

Involvement of alpha 2A-adrenoceptors in control of motor activity in neonatal rats was investigated using intrabrain injections of antisense deoxyoligonucleotide targeting mRNA of these receptors. Antisense-induced decrease in the receptor expression in the brain accompanied by an augmentation of animal's motor activity, which was evaluated as a number of paddling movements with the right forepaw. This antisense effect was stimulatory and was not related to somatic growth and maturation of reflexes in the animals. The antisensetreated pups differed from controls neither in body weight nor the latency of righting reflex. The data suggest that alpha 2A-adrenoceptors are involved in inhibitory control of motor activity of rat pups from the first day of life.     

A plant caspase-like protease activated during the hypersensitive response

To test the hypothesis that caspase-like proteases exist and are critically involved in the implementation of programmed cell death (PCD) in plants, a search was undertaken for plant caspases activated during the N gene-mediated hypersensitive response (HR; a form of pathogen-induced PCD in plants) in tobacco plants infected with Tobacco mosaic virus (TMV). For detection, characterization, and partial purification of a tobacco caspase, the Agrobacterium tumefaciens VirD2 protein, shown here to be cleaved specifically at two sites (TATD and GEQD) by human caspase-3, was used as a target. In tobacco leaves, specific proteolytic processing of the ectopically produced VirD2 derivatives at these sites was found to occur early in the course of the HR triggered by TMV. A proteolytic activity capable of specifically cleaving the model substrate at TATD was partially purified from these leaves. A tetrapeptide aldehyde designed and synthesized on the basis of the elucidated plant caspase cleavage site prevented fragmentation of the substrate protein by plant and human caspases in vitro and counteracted TMV-triggered HR in vivo. Therefore, our data provide a characterization of caspase-specific protein fragmentation in apoptotic plant cells, with implications for the importance of such activity in the implementation of plant PCD.     

Harry Potter and the structural biologist's (Key)stone

A report on the first European Keystone symposium 'Multi-protein complexes involved in cell regulation', Cambridge, UK, 18-23 August 2006.     

Thermal and hydric implications of diurnal activity by a small tropical frog during the dry season

Amphibians are typically intolerant of high temperatures and dehydrating conditions, and small species are particularly susceptible to desiccation. The rockhole frog, Litoria meiriana (Hylidae), is diurnal and is often observed on rocks in the sun near streams in tropical Australia. These hot, desiccating conditions are avoided by most frog species. We measured the microclimate in the areas used by frogs and the activity, body temperatures and hydric state of free‐ranging individuals of this small frog. We also used plaster models to further explore the dynamic nature of hydric state by combining estimates of water loss and water uptake with behavioural observations of activity and microhabitat selection. Both direct measures and estimates of dynamic hydric state indicated that free‐ranging frogs generally maintained a hydric state above 95% of full hydration, but occasionally, particularly during the afternoon, frogs allowed their hydric state to fall as low as 85%. Body temperatures of frogs remained below the critical thermal maximum (CT_max) even when the frogs were in the sun, because this species has no cutaneous resistance to evaporative water loss and so they cool by evaporation. However, during the hotter part of the day, on dry sunny substrates, the hydric state of the frogs could fall to near lethal hydration states (approximately 70% of full hydration) within a short period (approximately 20 min). Thus, the threat of desiccation appears to be more limiting than the threat of overheating. These diurnal frogs rely on frequent bouts of rehydration to support their ability to venture onto hot, dry rocks during the day.