Hydroreactivity of stomata in kale leaves of different insertion level as determined by analysis of transpiration curves

Values of the water saturation deficit (WSD) for hydroactive stomatal movements of kale leaves were estimated using the method of transpiration curve analysis. Stomata of young leaves started closing at WSD values of 5 to 6 per cent and were completely closed at 18 to 20 per cent WSD. During maturation and ageing of leaves these WSD values increased to 12.5 and 18 to 23 per cent respectively. Thus the stomatal reaction is more sensitive to changes in WSD in adult leaves than in young ones. After maturation is attained both values decrease. In apparently withering leaves the individual phases of transpiration curves can barely be distinguished, probably for the reason that even under optimal conditions their stomata remain half-closed and at high WSD values an incomplete closing of the aperture occurs. The injured cuticle of withering leaves affects the shape of the transpiration curve as well.     

Biotic and abiotic factors driving the diversification dynamics of Crocodylia

Species diversity patterns are governed by complex interactions among biotic and abiotic factors over time and space, but are essentially the result of the diversification dynamics (differential speciation and extinction rates) over the long-term evolutionary history of a clade. Previous studies have suggested that temporal variation in global temperature drove long-term diversity changes in Crocodylia, a monophyletic group of large ectothermic organisms. We use a large database of crocodylian fossil occurrences (192 spp.) and body mass estimations, under a taxic approach, to characterize the global diversification dynamics of crocodylians since the Cretaceous, and their correlation with multiple biotic and abiotic factors in a Bayesian framework. The diversification dynamic of crocodylians, which appears to have originated in the Turonian (c. 92.5 Ma), is characterized by several phases with high extinction and speciation rates within a predominantly low long-term mean rate. Our results reveal long-term diversification dynamics of Crocodylia to be a highly complex process driven by a combination of biotic and abiotic factors which influenced the speciation and extinction rates in dissimilar ways. Higher crocodylian extinction rates are related to low body mass disparity, indicating selective extinctions of taxa at both ends of the body mass spectrum. Speciation rate slowdowns are noted when the diversity of the clade is high and the warm temperate climatic belt is reduced. Our finding supports the idea that temporal variations of body mass disparity, self-diversity, and the warm climate belt size provided more direct mechanistic explanations for crocodylian diversification than do proxies of global temperature.     

Lipid profile: causal relationship on cognitive performance in multiple sclerosis?

Molecular Biology Reports - Although cognitive impairment (CI) is classically associated with aging, it has been proposed that neurological pathologies may increase the risk to suffer CI. Despite...     

<Emphasis Type="Italic">Baraguatherium takumara</Emphasis>, <Emphasis Type="Bold">Gen. et Sp. Nov., the Earliest Mylodontoid Sloth (Early Miocene) from Northern South America</Emphasis>

We report a new genus and species of sloth, based on a partial mandible and associated femur, from the early Miocene of Venezuela. Baraguatherium takumara, gen. et sp. nov., represents the earliest member of the Mylodontoidea recognized from northern South America. Phylogenetically and morphologically, Baraguatherium possesses some plesiomorphic characters: a vasodentine layer in the core of the tooth similar to Octodontotherium, Paroctodontotherium, and Orophodon; molariforms parallel to the long axis of the toothrow; teeth with a very thin layer of cementum; mf1-mf3 series of similar size and bilobate; mf3 conspicuously piriform; and occlusal surface of tooth beveled, which places it at the base of the Mylodontidae clade. Baraguatherium was found in continental deposits that also preserve abundant wood and leaves associated with a near shore marine complex, indicating that Baraguatherium lived in a coastal tropical forest in the early Miocene in northern South America. The presence of a vasodentine layer in the core of the tooth is quite similar to Octodontotherium, Paroctodontotherium, and Orophodon and allows assignment of this new taxon to the Mylodontoidea.     

Hofmeister effects in protein unfolding kinetics: estimation of changes in surface area upon formation of the transition state

We studied the effect of three electrolytes (LiCl, Na(2)SO(4), GuHCl) on the unfolding reaction of chymopapain, a two-domain protein belonging in the papain family of cysteine proteinases. Due to methodological reasons, these studies were carried out at pH 1.5 where the protein unfolds following biphasic kinetics. We have observed the presence of two different effects of electrolyte concentration on the unfolding reactions. At low ionic strength, the ionic atmosphere brought about an increase in reaction rates, regardless of the type of ions being present; this effect is attributed to a general "electrostatic screening" of charge-charge interactions in the macromolecule. At high ionic strength, each electrolyte exerted a distinctively different effect: both rate constants were largely increased by GuHCl (a well-known protein denaturant), but only slightly by LiCl; in contrast, Na(2)SO(4) (a good precipitant) decreased the value of both unfolding rates. These ion-specific (Hofmeister) effects were further used to estimate changes in accessible surface area (DeltaASA) upon formation of the transition states (TS) for unfolding. Results obtained with LiCl and Na(2)SO(4), which we analyzed by means of a parameterization derived from published solubility data of amino acid derivatives, are consistent with DeltaASA increments (for each phase) of about 8.0% of the total theoretical DeltaASA for complete unfolding of the chymopapain molecule. Results in the presence of GuHCl, which were analyzed by using a previous parameterization of protein unfolding data, gave larger DeltaASAs of activation, equivalent to 13 and 16% of the total unfolding DeltaASA.     

A non-synonymous nucleotide substitution can account for one evolutionary route to sesquiterpene synthase activity in the TPS-b subgroup

Plant sesquiterpene and hemiterpene synthases in the monoterpene synthase dominated TPS-b subgroup are thought to have evolved independently from a monoterpene synthase ancestor. A TPS-b sesquiterpene synthase from apple (MdAFS1), which predominantly produces α-farnesene, can also synthesize the monoterpene (E)-β-ocimene. The dual activity offered a functional link to an ancestral MdAFS1 enzyme and a rational basis for investigation of the evolution of TPS-b sesquiterpene enzymes. Protein modelling and mutagenesis analysis of the MdAFS1 active site identified a non-synonymous nucleotide substitution that could account for the requisite shift in substrate specificity necessary for the emergence of its sesquiterpene activity during the evolution of the TPS-b enzymes.     

THERPA: A small molecule database related to prion protein regulation and prion diseases progression

Prion diseases are fatal neurodegenerative disorders that affect humans and animals. Although various small molecules have been evaluated for application in the treatment of prion diseases, none have been shown to be efficacious. Expanding our knowledge of these molecules is important for understanding of the complex mechanisms of prion diseases. To improve access to the scattered information on small molecules related to prion diseases, we built a database of therapeutic molecules associated with prion diseases (THERPA, therpa.pythonanywhere.com). THERPA includes 119 small molecules and their 283 relationships with prion diseases. THERPA is an interactive visual database and useful for improving search efficiency which can help researchers identify intrinsic small molecules that can be used for developing therapeutics for prion diseases.     

Potentiometric redox measurements in the environment: a novel perspective on method powers and limitations

Biogeochemistry - The South China Sea (SCS) is one of the largest marginal seas in the world, but the processes that control the silicon cycle are not well understood. Here, we analyse the factors...     

Female reproductive behaviour,ovarian hormones and vaginal cytology of the induced ovulator, <Emphasis Type="Italic">Ctenomys talarum</Emphasis>

In the present study, we evaluated whether reproductive condition affects female reproductive behaviour in the induced ovulator Ctenomys talarum. We also explored the effect of the interaction with a male on the reproductive condition of females. To evaluate this, we arranged mating trials and evaluated female reproductive behaviour. Reproductive status of females was evaluated using a combined approach of vaginal smears, urinary progesterone and oestradiol, and ovarian histology. Behaviours denoting attraction (‘male sniff’ and ‘mount attempts’) and mutual courtship behaviours (‘spin’ and copula) were correlated with vaginal cytology before and oestradiol and progesterone levels in urine 12 h after male–female encounter. After 24 h of the interaction, oestradiol levels and vaginal epithelization increased while progesterone levels decreased in soliciting females. C. talarum females’ reproductive behaviour was related to its physiological reproductive state and vaginal cytology. The kind of male interaction, whether couples copulated or remained indifferent affected the later status of females. Females are induced ovulators by mating but male presence and interaction also affected other components of their reproductive physiology such as ovarian hormones and vaginal cytology.