Coordination polymers of Ln(III): Synthesis, characterization, catalytic and antimicrobial aspects

Coordination polymers of HEAP-ED with La(III), Pr(III), Nd(III), Sm(III), Gd(III), Tb(III) and Dy(III) metal ions have been synthesized and characterized by elemental analyses, electronic spectra, magnetic susceptibilities, FTIR, NMR, scanning electronic microscopy (SEM) and thermogravimetric analyses. Catalytic activity of selected coordination polymers was examined for pharmaceutical important organic synthesis. Antimicrobial activity of isolated Ln(III) coordination polymers against Escherichia coli, Bacillus subtilis, Staphylococcus aureus (bacteria) and Saccharomyces cerevisiae (yeast) were measured. It was observed from the study that the Ln(III) coordination polymers acted as an efficient and effective catalysts and antimicrobial agents.     

Expanded thermal niche for a diving vertebrate: A leatherback turtle diving into near-freezing water

The global distribution of extant reptiles is more limited than that of mammals or birds, with low reptilian species diversity at high latitudes. Central to this limited geographical distribution is the ectothermic nature of reptiles, which means that they generally become torpid at cold temperatures. However, here we report the first detailed telemetry from a leatherback turtle (Dermochelys coriacea) diving in cold water at high latitude. An individual equipped with a satellite tag that relayed temperature-depth profiles dived continuously for many weeks into sub-surface waters as cold as 0.4 °C. Global warming will likely increase the foraging range of leatherback turtles further into temperate and boreal waters.     

Metabolome and water status phenotyping of Arabidopsis under abiotic stress cues reveals new insight into ESK1 function

Metabolomic investigation of the freezing-tolerant Arabidopsis mutant esk1 revealed large alterations in polar metabolite content in roots and shoots. Stress metabolic markers were found to be among the most significant metabolic markers associated with the mutation, but also compounds related to growth regulation or nutrition. The metabolic phenotype of esk1 was also compared to that of wild type (WT) under various environmental constraints, namely cold, salinity and dehydration. The mutant was shown to express constitutively a subset of metabolic responses which fits with the core of stress metabolic responses in the WT. But remarkably, the most specific metabolic responses to cold acclimation were not phenocopied by esk1 mutation and remained fully inducible in the mutant at low temperature. Under salt stress, esk1 accumulated lower amounts of Na⁺ in leaves than the WT, and under dehydration stress its metabolic profile and osmotic potential were only slightly impacted. These phenotypes are consistent with the hypothesis of an altered water status in esk1 , which actually exhibited basic lower water content (WC) and transpiration rate (TR) than the WT. Taken together, the results suggest that ESK1 does not function as a specific cold acclimation gene, but could rather be involved in water homeostasis.     

Is there modal opponency in the thermal senses?

1. 1.The sensations evoked by pairs of distinct thermal stimuli applied to the back of the hand were studied in 17 volunteer subjects. Four stimulus combinations were used; neutral-cold (NC), neutral-neutral (NN), neutral-warm (NW), and cold-warm (CW).

2. 2.The subjects were first asked to estimate the magnitude of the thermal sensations evoked by the thermal stimuli. On average, the four pairs were reported as increasing magnitude in the following order: NC, CW, NN, and NW, seeming to suggest that the subjects experienced the cold-warm combination as a composite sensation of cold and warmth intermediate between pure cold and pure warmth.

3. 3.When asked only to detect the presence of a cold stimulus, the subjects performed as well for the CW combination as for the CN combination. This second result indicates that the reported composite magnitude of CW does not result from a true opponency of cold and warmth but from a cognitive combination of distinct sensations of cold and warmth.

The relationship between respiration and temperature in leaves of the arctic plant Saxifraga cernua

Abstract Saxifraga cernua, a perennial herb distributed throughout the arctic and subarctic regions, shows high levels of dark respiration. The amount of respiration exhibited by leaves and whole plants at any temperature is influenced by the pretreatment temperature. Plants grown at 10°C typically show higher dark respiration rates than plants grown at 20°C. The levels of alternative-pathway respiration (or cyanide-insensitive respiration) in leaves of S. cernua grown at high and low temperatures were assessed by treating leaf discs with 0.25 mol m^?3 salicylhydroxamic acid during measurements of oxygen consumption. Alternative pathway respiration accounted for up to 75% of the total respiration. Tissues from 20°C-grown plants yielded a Q₁₀ of 3.37 for normal respiration, and of 0.97 for alternative-pathway respiration. Tissues from 10°C-grown plants yielded a Q₁₀ of 2.55 for normal respiration, and of 0.79 for alternative-pathway respiration. The alternative pathway does not appear to be as temperature sensitive as the normal cytochrome pathway. A simple energy model was used to predict the temperature gain expected from these high rates of alternative-pathway respiration. The model shows that less than 0.02°C can be gained by leaves experiencing these high respiration rates.     

Frost resistance of winter rape leaves as related to the changes in water potential and growth capability

Differential thermal analysis indicated that the frost resistance of winter rape leaves ( Brassica napus L. var. oleifera L. cv. Gòrczanski), collected from plants grown in the cold (5/2°C), relies mainly on their ability to supercool to −9 to −11°C, i.e. consists in freezing avoidance. Initiation of ice formation in the cold-acclimated leaves resulted in the death of more than 50% of the cells as determined with a conductivity method. The development of freezing tolerance appeared to be an attribute of the second stage of plant hardening and was induced by the exposure of plants to a slightly subzero temperature (−5°C) for 18 h. Such a treatment brought about a sudden and persistent water potential decrease in the leaves, despite the fact that they had reabsorbed water from the medium prior to water potential measurements. Water potential changes were associated with a higher growth capability of the leaves as checked by determinations of disk area increments. It is suggested that the increased frost tolerance of the cold-grown winter rape leaves, subjected to subfreezing temperature, is related to the decreased water potential of the tissue caused by changes in turgor and/or in osmotic pressures of the cells.     

Genetic variability for heat shock proteins in common wheat

Summary The response of the common wheat line Chinese Spring to heat shocks of different time lengths was studied by the two-dimensional (2D) electrophoresis of denatured proteins. After a heat shock of 5 h, 33 heat shock proteins (HSPs) accumulated in an amount sufficient to be revealed by silver stain. Two other wheat lines (Moisson and Selkirk) were then submitted to a heat shock of 5 h, and the responses of the 3 lines were compared: of a total of 35 HSPs, 13 (37.1%) were quantitatively or qualitatively variable. This variability concerns low-molecular-weight and high-molecular-weight HSPs. The three genotypes showed thermal tolerance but Chinese Spring's response to heat treatments was slightly different from those of the other two lines The possibility of a relationship between HSP patterns and thermal sensitivity is discussed.     

Ecological aspects of thermoregulation at high altitudes: the case of andean Liolaemus lizards in northern Chile

Summary We document activity field temperatures, daily activity patterns, and extent of thermoregulation in four species of Liolaemus lizards inhabiting at high altitude (above 3500 m) in the Andes of northern Chile. These four species have similar activity field temperature (Tb near 29°C) despite their being distributed at different altitudinal belts. However, conspicuous differences exist between higher-altitude (L. alticolor and L. jamesi) and lower-altitude (L. islugensis and L. ornatus) lizards regarding extent of thermoregulation and activity period. Some differences in morphology, behavior, and patterns of microhabitat occupancy are also apparent among these four species and are seemingly related to the thermal environment to which they are subjected. In comparison to eight low-altitude Liolaemus species in central Chile (Tb near 35°C) the four high-altitude species in northern Chile have lower activity field temperature. The latter is apparently due to the constraints imposed by the harsh Andean thermal environment, a hypothesis supported by the fact that high-altitude Liolaemus lizards under laboratory conditions demonstrate body temperatures that exceed by 5°C or more, those recorded in the field.     

Low temperature delays development of photosystem II activity in winter rye leaves

The ability of leaves to acclimate photosynthetically to low temperature was examined during leaf development in winter rye plants ( Secale cereale L. cv. Puma) grown at 20°C or at 6°C. All leaves grown at 6°C exhibit increased chlorophyll (Chl) levels per leaf area, higher rates of uncoupled, light-saturated photosystem I (PSI) electron transport, and slower increases in photosystem II (PSII) electron transport capacity, when compared with 20°C leaves. The stoiehiometry of PSI and PSII was estimated for each leaf age class by quantifying Chl in elcctrophorctic separations of Chl-protein complexes. The ratio of PSII/PSI electron transport in 20°C leaves is highly correlated with the ratio of core Chl a -proteins associated with PSII (CPa) to those associated with PSI (CP1). In contrast, PSII/PSI electron transport in 6°C leaves is not as well correlated with CPa/CP1 and is related, in part, to the amount and organization of light-harvesting Chl a/b -proteins associated with PSII. CPa/CP1 increases slowly in 6°C leaves, although the ratio of CPa/CP1 in mature 20°C and 6°C leaves is not different. The results suggest that increased PSI activity at low temperature is not related to an increase in the relative proportion of PSI and may reflect, instead, a regulatory change. Photosynthetic acclimation to low environmental temperature involves increased PSI activity in mature leaves shifted to 6°C. In leaves grown entirely at 6°C, however, acclimation includes both increased PSI activity and modifications in the rate of accumlation of PSII and in the organization of LHCII.