Osmolytes responsible for volume reduction under isosmotic or hypoosmotic conditions in Barnacle muscle cells.

In numerous animal cells, experimental manipulations that increase the intracellular free Ca2+ concentration induce cell volume reduction. This may occur under isosmotic conditions, e.g. when external Ca2+ (Ca(o)) is replaced by Mg2+ (42) or during exposure to hypoosmotic conditions (i.e. regulatory volume decrease, RVD) in the presence of Ca(o). We determined the osmolytes responsible for volume reduction under isosmotic and hypoosmotic conditions in barnacle muscle cells. Organic osmolytes (i.e. free amino acids and methylamines) and inorganic ions accounted for approximately 78% and 22% of the intracellular isosmotic activity, respectively. Isosmotic Ca(o) removal induced a net loss of KCI (with a ratio of 1K:1Cl) and free amino acids (FAA, mainly glycine and taurine). During RVD. the same ions (but in a proportion of 2K:1Cl) and FAA were lost. Since RVD was accompanied by extracellular alkalinization, the 2K:1Cl loss may be explained by the presence of a K+/H+ exchanger (or K+-OH- co-transporter) or Cl-/OH- exchanger. The lack of RVD in the absence of Ca(o) cannot be attributed to the loss of intracellular osmolytes during isosmotic Ca(o) removal because addition of Ca(o) during cell swelling promoted RVD.     

Elastin biosynthesis by smooth muscle cells cultured under scorbutic conditions

The proliferation of rat heart smooth muscle cells is unaffected by supplementation of the culture medium with ascorbic acid. The presence or absence of the vitamin has a pronounced effect, however, on the amount of alastin which is produced. Scorbutic cultures incorporate significantly more radioactive valine (an amino acid prevalent in elastin) into proteins present in the extracellular matrix than do supplemented controls, while there was no difference between the systems in the incorporation of labelled methionine (absent from elastin). Deficiency of ascorbic acid appears to result in an enhancement of the biosynthesis and extracellular processing of elastin in this culture system.     

Noncatalytic hydrolysis of guar gum under hydrothermal conditions

Guar gum, a naturally occurring heteropolysaccharide made of mannose and galactose, was hydrolytically degraded without a catalyst in a batch reactor to produce water-soluble (WS) saccharides including mono- and oligosaccharides. The degradation was carried out under hydrothermal conditions over ranges of temperature from 180 to 240 degrees C and of reaction time from 3 to 60min. Guar gum was readily dissolved and hydrolyzed, and the major products identified in the WS components were oligosaccharides with degrees of polymerization up to about 20, monosaccharides containing mannose and galactose, and 5-hydroxymethyl-2-furaldehyde (5-HMF). At 200 degrees C, the oligosaccharide yield, obtained from the difference between the yields of the total WS saccharides and monosaccharides, showed the highest value of 94.4% at 7min among all conditions studied, on the basis of the saccharide content in the initial sample. The oligosaccharide yield decreased with reaction time, and the yield of monosaccharides correspondingly increased, and reached the highest value of 34.5% (mannose 22.8%, galactose 11.7%) at 60min. The monosaccharides produced were further decomposed to secondary products such as 5-HMF. The maximum yield of 5-HMF obtained was 26.3% at 220 degrees C and 30min. The production and the decomposition of galactose somewhat preceded those of mannose.     

Agroclimatic conditions in Europe under climate change

To date, projections of European crop yields under climate change have been based almost entirely on the outputs of crop‐growth models. While this strategy can provide good estimates of the effects of climatic factors, soil conditions and management on crop yield, these models usually do not capture all of the important aspects related to crop management, or the relevant environmental factors. Moreover, crop‐simulation studies often have severe limitations with respect to the number of crops covered or the spatial extent. The present study, based on agroclimatic indices, provides a general picture of agroclimatic conditions in western and central Europe (study area lays between 8.5°W–27°E and 37–63.5°N), which allows for a more general assessment of climate‐change impacts. The results obtained from the analysis of data from 86 different sites were clustered according to an environmental stratification of Europe. The analysis was carried for the baseline (1971–2000) and future climate conditions (time horizons of 2030, 2050 and with a global temperature increase of 5 °C) based on outputs of three global circulation models. For many environmental zones, there were clear signs of deteriorating agroclimatic condition in terms of increased drought stress and shortening of the active growing season, which in some regions become increasingly squeezed between a cold winter and a hot summer. For most zones the projections show a marked need for adaptive measures to either increase soil water availability or drought resistance of crops. This study concludes that rainfed agriculture is likely to face more climate‐related risks, although the analyzed agroclimatic indicators will probably remain at a level that should permit rainfed production. However, results suggests that there is a risk of increasing number of extremely unfavorable years in many climate zones, which might result in higher interannual yield variability and constitute a challenge for proper crop management.     

Birefringence of glycerinated crab muscle fiber under various conditions.

By using glycerinated single fibers of crab muscle (Sesarma haematocheir) which has long sarcomeres, the birefringence of the I band, H band and the overlapping region between thin and thick filaments was measured separately, under various environmental conditions. At the resting length, the birefringence of the fiber was decreased by the addition of Ca2+ in the absence of ATP, by about 0.35%. This birefringence decrease was found to take place in the overlapping region. The decrease corresponded to about 2% of the birefringence of thin filaments in this region. The birefringence of the fiber was increased by the addition of ATP in the absence of Ca2+, by about 6%. This birefringence increase also took place mostly in the overlapping region. The increase of birefringence by pyrophosphate was about half of that by ATP. The birefringence of the fiber was decreased by the increase of the ionic strength from 0.12 to 0.20. The origin of the observed changes of birefringence is discussed.     

On hydrolysis of cellulose and nitrocellulose under sulfate-reducing conditions

Hydrolysis of cellulose and nitrocellulose in the presence of sulfate-reducing bacterium Desulfovibrio vulgaris 1388 was studied. The cellulolytic activity was found in culture medium after D. vulgaris growth (1.45 ± 0.04 nmol/mg protein/min). In the presence of cellulose or nitrocellulose the activity accounted for 4.82 ± 0.23 and 2.35 ± 0.11 nmol/mg protein/min, respectively. The initial rates of cellulose decomposition were measured using toluene to inhibit the microbial uptake of hydrolysis product—glucose. It was established that 7.6% of initially added cellulose was hydrolyzed in 3 weeks. The highest rate of glucose accumulation was observed on day 10 (2.13 μmol glucose/g dry-wt cellulose/h). At the same time only 3.3% of nitrocellulose was hydrolyzed, since nitro-groups of polymer exerted negative influence on the hydrolysis process. It is supposed that nonspecific extracellular hydrolases participate in the polymers hydrolysis.     

Streptomyces flavogriseus cellulase: Evaluation under various hydrolysis conditions

Streptomyces flavogriseus CMCase and Avicelase were very stable at 30 degrees C but not at 40 degrees C or higher. beta-Glucosidase was less stable at all temperatures tested. Stabilities were similar at pH values between 5.5 and 7, the optimal range for enzyme activity. Cellulose solubilizing activity was reduced by 40% at a cellobiose concentration of 150mM but glucose inhibited activity by only 10% at this concentration. beta-Glucosidase was inhibited by 40% at a glucose concentration of 10mM (ten times the substrate concentration). Relatively dilute S. flavogriseus cellulase extensively hydrolysed acid-swollen cellulose at concentrations as high as 10%. More highly crystalline forms of cellulose were more resistant to attack.     

Glucocorticoid amplifies vasopressin-induced phosphoinositide hydrolysis in aortic smooth muscle cells

It has been reported that glucocorticoid modifies phosphoinositide (PI) hydrolysis stimulated by vasoactive agents in vascular smooth muscle cells. In the present study, we investigated the point at which glucocorticoid affects vasopressin-induced PI hydrolysis in primary cultured rat aortic smooth muscle cells. The pretreatment with dexamethasone significantly amplified the formation of inositol trisphosphate (IP₃) induced by vasopressin in a dose-dependent manner in a range of 1 pM to 10 nM. The effect of dexamethasone was dependent on the time of pretreatment up to 8 h. Dexamethasone had little effect on the number of vasopressin receptor and its affinity to vasopressin. The pretreatment with dexamethasone also amplified the formation of IP₃ induced by NaF, a GTP-binding protein activator, or angiotensin II. 12-O-Tetradecanoylphorbol-13-acetate, a protein kinase C (PKC)-activating phorbol ester, significantly reduced the dexamethasone-induced enhancement of IP₃ formation stimulated by vasopressin, angiotensin II or NaF. 4α-Phorbol-12, 13-didecanoate, a PKC-nonactivating phorbol ester, had little effect on the enhancement by dexamethasone. These results strongly suggest that glucocorticoid amplifies vasopressin-induced PI hydrolysis at a point downstream from GTP-binding protein in primary cultured rat aortic smooth muscle cells, and that the activation of PKC has a negative feedback effect on the amplification by glucocorticoid of vasopressin-induced PI hydrolysis.     

Rho-dependent agonist-induced spatio-temporal change in myosin phosphorylation in smooth muscle cells.

Agonist-induced translocation of RhoA and the spatio-temporal change in myosin regulatory light chain (MLC20) phosphorylation in smooth muscle was clarified at the single cell level. We expressed green fluorescent protein-tagged RhoA in the differentiated tracheal smooth muscle cells and visualized the translocation of RhoA in a living cell with three-dimensional digital imaging analysis. The stimulation of the cells by carbachol initiated the translocation of green fluorescent protein-tagged wild type RhoA to the plasma membrane within a minute. The change in MLC20 phosphorylation level after carbachol stimulation was monitored by using phospho-Ser-19-specific antibody recognizing the phosphorylated MLC20 in single cells. Cells expressing the dominant negative form (T19N) of RhoA significantly suppressed sustained MLC20 phosphorylation during the prolonged phase (>300 s), whereas the maximum phosphorylation level (reached at 10 s after stimulation) of these cells was not significantly different from the control cells. The kinetics of RhoA translocation was consistent with that of sustained myosin phosphorylation, suggesting the involvement of a RhoA pathway. Carbachol stimulation increased myosin phosphorylation within a minute both at the cortical and the central region. On the other hand, during prolonged phase, myosin phosphorylation was sustained at the cortical region of the cells but not at the central fibers. A myosin light chain kinase-specific inhibitor, ML-9, diminished myosin phosphorylation at the central region of the cells after the stimulation but not at the cortical area. On the other hand, Y-27632, a Rho kinase-specific inhibitor, diminished myosin phosphorylation at the cortical region but not the central region. The results clearly show that the myosin light chain kinase pathway and the Rho pathway distinctly change myosin phosphorylation in smooth muscle cells in both a temporal and spatial manner.     

Molar microwear in Praeanthropus afarensis: evidence for dietary stasis through time and under diverse paleoecological conditions

Molar microwear fabrics in extant mammals vary with diet and, more particularly, the physical properties of the items that are consumed. Praeanthropus afarensis is well represented in the fossil record over a prolonged and radiometrically controlled temporal span, and reasonably robust paleoecological reconstructions are available for the various localities from which it is known. We therefore examined molar microwear in this species to determine whether diet varied in relation to time or in response to different ecological conditions. Of more than 70 specimens of Pr. afarensis that contain one or more worn permanent molars, only 19 were found to be suitable for microwear analysis. These derive from eight temporal horizons in the Laetolil Beds and Hadar Formation spanning approximately 400kyr (3.6-3.2Ma). Six paleoecological categories have been reconstructed for these horizons, and these were ranked on the basis of floral cover. None of the microwear variables observed for Pr. afarensis is significantly associated with either temporal or paleoecological rank. Thus, microwear and, by extension, diet does not appear to have altered significantly in Pr. afarensis through time or in response to different paleoecological circumstances. The wear pattern that appears to have characterized Pr. afarensis overlaps extensively that of Gorilla gorilla beringei and differs notably from the fabrics of extant primates (e.g., Cebus apella and Cercocebus albigena) that consume hard objects. The high proportion of scratches on Pr. afarensis molars suggests the inclusion of fine abrasives in or on the food items consumed by those individuals sampled in this study. Although Pr. afarensis may have been morphologically equipped to process hard, brittle items, the microwear data suggest that it did not necessarily do so, even in the face of varying environmental circumstances. Explanatory scenarios that describe Pr. afarensis as part of an evolutionary trajectory involving a more heavily masticated diet with an increased reliance on hard, brittle items need to be reconsidered. However, fallback foods that were consumed during relatively short, albeit critical periods may have exerted sufficient selective pressure to explain the evolution of the comparatively robust Pr. afarensis trophic apparatus. Because it is unlikely that many individuals from such restricted temporal intervals would be sampled in the paleontological record, we suggest that the most productive approach to the elucidation of paleodiet is the integration of genetic (morphological) and epigenetic (microwear and isotopic) lines of evidence.