Effect of photoperiod and temperature on the development of frost hardiness in three Alnus species

The influence of short day and low temperature on cold acclimation of A. crispa (Ait.) Pursh, A. glutinosa (L.) Gaertn. and A. rubra Bong, was investigated. Two clones of each species originating from in vitro propagation were exposed to three daylength/temperature treatments. Periodically plantlets were exposed to controlled freezing temperature in order to evaluate their level of frost hardiness.
Short day (SD) and cold temperature (CT) and long day (LD) and cold temperature (CT) were the most effective treatments for the development of frost hardiness in shoots and roots of the three species tested. Short day (SD) and warm temperature (WT) induced a significant increase in hardiness in shoots of all three species. However, this treatment did not trigger root hardening. A. crispa was found to be the hardiest species followed by A. glutinosa and A. rubra . Intraspecific variation was observed between the two A. glutinosa clones. A glutinosa clone AG8, a Russian provenance, showed a greater freezing resistance than A. glutinosa clone AG2, a German provenance.     

Inhibition of carbonic anhydrases in type I muscle fibers influences contractility

We tested the effects of inhibiting the carbonic anhydrase activity of rat soleus and extensor digitorum longus muscles on the isometric contractile properties and the resistance to fatigue. SOL and EDL muscles from female rats were incubated in vitro in the presence of methazolamide, a specific inhibitor of carbonic anhydrase, before determining their contractile properties. Methazolamide had no effects on the contractile properties of the soleus muscle (10(-5) or 10(-3) M) and extensor digitorum longus (10(-3) M), except for the half-relaxation time of the soleus muscle which increased significantly. Values for half-relaxation time were significantly increased with both concentrations of the inhibitor. Muscles were then submitted to a fatigue protocol lasting 30 min. During the fatigue test, no significant difference was observed between control and 10(-5) M methazolamide soleus muscles. In presence of 10(-3) M methazolamide however, the soleus muscle showed a significantly increased resistance to fatigue compared with control preparations. No significant effect was observed with the extensor digitorum longus muscle exposed to 10(-3) M methazolamide. Results are discussed in terms of the presence of two different isoforms of carbonic anhydrase that may be associated with calcium uptake and energy metabolic processes, respectively.     

In vitro propagation of mature trees of Alnus incana (L.) Moench.

Mature trees of European grey alder (Alnus incana) were micropropagated on a modified MS medium containing 2.5 M BA, 6.2 mM (500 mg l^-1) NH₄NO₃ and 1.5% glucose. Prior to in vitro culture, mature scions were multiplied through grafting and cutting techniques. Shoot tips from cuttings were established in vitro. After six months of culture, shoots were rooted either in vitro or in vivo and plantlets were transferred to greenhouse conditions.     

Major contribution of epididymis to alpha-glucosidase content of ram seminal plasma

Acid alpha-glucosidase and L-carnitine (a well-known epididymal marker) were measured in rete testis and epididymal fluids of adult male rams. These fluids were collected by selective catheterization or by a micropuncture technique, respectively. Both parameters remained at a low and constant level in rete testis and all along caput and corpus epididymidis. Then they increased at equivalent rates in cauda epididymidis to much higher levels than those in seminal plasma (5 mU/mg protein and 10 mM, respectively). An optimum pH study of alpha-glucosidase activity in these fluids showed two well-separated peaks in rete testis and caput epididymal fluids around pH 4 and 7, respectively, but only a single peak at pH 4 in cauda epididymidis that was comparable to the one in seminal plasma. Sucrose density gradient fractions analyzed for their enzyme content in the absence or presence of sodium dodecyl sulfate (1% w/v), a selective inhibitor of acid alpha-glucosidase activity, allowed the demonstration of two enzyme forms at pH 6.8 in rete testis fluid sedimenting in the 7S and 4S regions of the gradient, while a unique 4S form was encountered in cauda epididymidis and in seminal plasma. Although the fate of the minor 7S component of the rete testis fluid in its epididymal transit is presently unknown, similarities between the enzyme in cauda epididymidis and seminal plasma are strong enough to support the hypothesis that epididymis contributes primarily to the acid alpha-glucosidase content of ram seminal plasma.     

Nature of the residual alpha-1,4-glucosidase activity in the seminal plasma of vasectomized men

Vasectomy leads to a drastic decrease of neutral alpha-1,4-glucosidase from human seminal plasma. The nature of this residual enzyme activity has been ascertained according to optimum pH and sucrose density gradient analysis with or without inhibitors of neutral (maltotriose) or acid (sodium dodecyl sulfate) alpha-1,4-glucosidase. Data from the present study provide strong evidence that the enzyme content of the seminal plasma is of mixed nature after exclusion of the epididymis.     

Heredity and overfeeding-induced changes in submaximal exercise VO2

The present study investigated the role of heredity in determining changes in the energy cost of submaximal exercise in response to short-term overfeeding. Six pairs of monozygotic twins were subjected to a 1,000 kcal/day surplus for 22 days with careful experimental controls over food intake and physical activities. O2 consumption (VO2) was measured during a submaximal treadmill exercise test 165 min postprandially before and the morning after the overfeeding protocol. As expected, overfeeding induced significant increases in body weight and fat mass. No significant increase in mean exercise VO2 was observed after overfeeding. However, the interindividual variation in overfeeding-induced changes in exercise VO2 was large and not randomly distributed. When comparing intrapair variance for changes in exercise VO2 to interpair variance, a moderate to high within-pair resemblance in response, i.e., a genotype-overfeeding interaction, was observed. Changes in exercise VO2 were positively correlated with those in postexercise levels of blood catecholamines, particularly epinephrine. A negative correlation was found between changes in exercise VO2 and body fat gain. These results are consistent with the concept of a role for the sympathoadrenal system in the regulation of adaptive thermogenesis and the predisposition to store fat. Moreover, these data suggest that the sensitivity to adapt in exercise energy expenditure after overfeeding is inherited to a significant extent.     

In vitro cleavage specificity of the adenovirus type 2 proteinase

Two in vitro proteinase assay systems were developed and used to study the peptide bond specificity and substrate specificity of the adenovirus endoproteinase. Five adenovirus precursor proteins (PVI, PVII, PVIII, 87K, 11K), all found in the virion of the ts1 mutant grown at the nonpermissive temperature, were digested by the proteinase. All, except 11K, were cleaved to their mature counterparts. Some of the proteins, particularly the 87K terminal protein, were processed via cleavage intermediates similar to those found in vivo. The data suggest that the proteinase specifically hydrolyses Gly-Ala bonds. The high specificity for the natural substrates and the failure to cleave foreign proteins suggest that cleavage activity is determined not only by primary sequence but also by other physical features of the substrate. Enzyme activity was inhibited by diisopropylfluorophosphate, showing that it is a serine proteinase.