Gene regulation during anaerobiosis in soya roots

The proteins of soybean roots undergoing anaerobiosis can be grouped into three classes. Class 1 proteins are induced severalfold and at least 28 of these were identified by in vivo labeling. These proteins include the enzymes alcohol dehydrogenase (ADH), fructose aldolase, pyruvate decarboxylase, phosphoglucomutase, and lactate dehydrogenase. Class 2 proteins include such enzymes as glucose phosphate isomerase, sucrase, and malate dehydrogenase; their specific activity remains constant in aerobiosis or anaerobiosis. The third class of proteins includes those enzymes such as peroxidase whose activity decreases more than 90% after just 1 day in anaerobiosis. Immunoblotting coupled with two-dimensional chromatography of in vitro translated plant extracts demonstrated that ADH level during anaerobiosis is controlled by its mRNA concentration. Little or no mRNA for ADH was detected in aerobically grown roots. This suggests that the increased level of ADH activity is due to de novo synthesis of the mRNA rather than activation of a sequestered mRNA or superactivation of the protein.     

Purification and properties of two distinct groups of ADH isozymes from Chinese hamster liver

Two major classes of alcohol dehydrogenase isozymes have been purified from Chinese hamster liver. The two isozyme classes have the same subunit molecular weights but different electrophoretic mobilities. They have a similar range of substrates but different KROM values and sensitivities to the inhibitor pyrazole. The ADHs are immunologically related as determined by Ouchterlony double diffusion experiments. These results suggest that the isozymes are encoded by different structural gene loci derived from a common ancestral gene.Financial support was provided by the National Cancer Institute of Canada and the Medical Research Council of Canada, Grant MT4860. J.-P. Thirion is a Research Scholar of the Science Research Council of Quebec.     

Rabbit burrows or artificial refuges are a critical habitat component for the threatened lizard, <Emphasis Type="Italic">Timon lepidus</Emphasis> (Sauria,Lacertidae)

Refuges are crucial for most animal species as they offer essential protection against predators and provide buffered environmental conditions to their occupants. Our data show that northern populations of the threatened ocellated lizard (Timon lepidus) depend on the availability of the burrows excavated by the European rabbit (Oryctolagus cuniculus). In the last decade, a severe decline in rabbit populations has had a disastrous effect on lizard numbers. To compensate for the lack of refuges, artificial shelters were constructed in autumn 2005 and 2007 and were monitored the following years (2006–2009). Most of the artificial refuges were rapidly occupied by lizards, notably juveniles, suggesting that this technique was successful to improve lizard habitat. Because other factors such as food resources might be also crucial, further assessments are required to determine if artificial refuges are sufficient to stem population decline. These results nonetheless provide an encouraging option to maintain and/or to restore threatened populations, for instance through a buffering of rabbit burrow fluctuations. More generally, the availability of suitable refuges (e.g. natural or artificial) is likely to be a central component for the conservation of many reptile species. The combination of empirical and experimental data further demonstrates that great attention must be paid to the structure and distribution of the refuges and that simple practical actions can effectively improve habitat quality for threatened species.     

Selection of chinese hamster somatic cell mutants after irradiation of BUdR-labelled cells.

The selection of somatic cell mutants after irradiation of BUdR-labelled cells is improved with the use of a mercury lamp combined with a plastic sheet which filters the unwanted wave lengths below 303 nm. New somatic cell mutants defective for galactose metabolism or auxotrophe for fetal calf serum were thus isolated.     

Circular dichroism studies of freeze-drying-induced conformational changes in human hemoglobin

Freeze-drying of hemoglobin leads to the formation of a significant amount of methemoglobin. It is possible to decrease this transformation in the presence of protective compounds. The mechanism of action of these protectors is presently unknown. Spectroscopic absorption and CD spectra between 190 and 700 nm are presented for samples of hemoglobin freeze-dried with or without protection and for control solutions of oxyhemoglobin and methemoglobin. The interpretation of the dichroic spectra allows us to observe the secondary, tertiary, and quaternary structure changes that hemoglobin undergoes with freeze-drying. The results indicate that the absence of a protector weakly influences the conformation in the vicinity of the heme and increases the helicity of protein chains from 75 to 81%. Furthermore, experimental data, in agreement with electron-spin resonance measurements, suggest that the protective effect is not the result of a direct bond between the iron and the compound added.