A kinetic model for microbial growth on solid hydrocarbons

A kinetic model has been presented to explain the growth of microorganism on solid hydrocarbons. The model is based on the assumption that metabolite produced by the growing cells helps the dissolution of the solid substrate in the aqueous medium. The linear behavior of the growth curve predicted by the model is verified experimentally.     

Male indifference to female traits in an arctiid moth (Utetheisa ornatrix)

Abstract.  1. Female Utetheisa ornatrix (Lepidoptera: Arctiidae) mate selectively with large males able to transmit sizeable quantities of nutrient and defensive pyrrolizidine alkaloid with the spermatophore. The female gauges male size indirectly by assessment of the male's courtship pheromone.
2. Male Utetheisa invest upward of 10% of body mass in spermatophore production, and could therefore have been expected to be choosy; however, when offered females differing in alkaloid content, body mass, or mating status, males showed disregard of these parameters, both in their choice of partner and in their allocation of resources to the spermatophore.
3. It is concluded that Utetheisa males do not have the option to select females by comparison shopping . Females broadcast their attractant pheromone for less than an hour per day. Given this time constraint and the potentially high cost of mate localisation, males may have no choice but to mate on an opportunistic basis.     

Metrology in physics,chemistry, and biology

The association of physics and chemistry with metrology (the science of measurements) is well documented. For practical purposes, basic metrological measurements in physics are governed by two components, namely, the measure (i.e., the unit of measurement) and the measurand (i.e., the entity measured), which fully account for the integrity of a measurement process. In simple words, in the case of measuring the length of a room (the measurand), the SI unit meter (the measure) provides a direct answer sustained by metrological concepts. Metrology in chemistry, as observed through physical chemistry (measures used to express molar relationships, volume, pressure, temperature, surface tension, among others) follows the same principles of metrology as in physics. The same basis percolates to classical analytical chemistry (gravimetry for preparing high-purity standards, related definitive analytical techniques, among others). However, certain transition takes place in extending the metrological principles to chemical measurements in complex chemical matrices (e.g., food samples), as it adds a third component, namely, indirect measurements (e.g., AAS determination of Zn in foods). This is a practice frequently used in field assays, and calls for additional steps to account for traceability of such chemical measurements for safeguarding reliability concerns. Hence, the assessment that chemical metrology is still evolving.     

Modelling spatio-temporal interactions within the cell

Biological phenomena at the cellular level can be represented by various types of mathematical formulations. Such representations allow us to carry out numerical simulations that provide mechanistic insights into complex behaviours of biological systems and also generate hypotheses that can be experimentally tested. Currently, we are particularly interested in spatio-temporal representations of dynamic cellular phenomena and how such models can be used to understand biological specificity in functional responses. This review describes the capability and limitations of the approaches used to study spatio-temporal dynamics of cell signalling components.     

Duration of ERK1/2 phosphorylation induced by FGF or ocular media determines lens cell fate

The ocular environment is important for the establishment and maintenance of lens growth patterns and polarity. In the anterior chamber of the eye, the aqueous humour regulates lens epithelial cell proliferation whereas in the posterior, the vitreous humour regulates the differentiation of the lens cells into fiber cells. Members of the fibroblast growth factor (FGF) growth factor family have been shown to induce lens epithelial cells to undergo cell division and differentiate into fibers, with a low dose of FGF able to induce cell proliferation (but not fiber differentiation), and higher doses required to induce fiber differentiation. Both these cellular events have been shown to be regulated by the MAPK/ERK1/2 signalling pathway. In the present study, to better understand the contribution of ERK1/2 signalling in regulating lens cell proliferation and differentiation, we characterized the ERK1/2 signalling profiles induced by different doses of FGF, and compared these to those induced by the different ocular media. Here, we show that FGF induced a dose-dependent sustained activation of ERK1/2, with both a high (fiber differentiating) dose of FGF and vitreous, stimulating and maintaining a prolonged (up to 18 hr) ERK1/2 phosphorylation profile. In contrast, a lower (proliferating) dose of FGF, and aqueous, stimulated ERK1/2 phosphorylation for only up to 6 hr. If we selectively reduce the 18 hr ERK1/2 phosphorylation profile induced by vitreous to 6 hr, by specifically blocking FGF receptor signalling, the vitreous now fails to induce lens fiber differentiation but retains the ability to induce lens cell proliferation. These findings not only provide insights into the important role that FGF plays in the different ocular media that bathe the lens, but enlighten us on some of the putative molecular mechanisms by which one specific growth factor, in this case FGF, can elicit a different cellular response in the same cell type.     

Pollination strategies in Cretan Arum lilies

Flowers of the genus Arum are known to attract dung‐breeding flies and beetles through olfactory deceit. In addition to this strategy, the genus has evolved several other pollination mechanisms. The present study aimed to characterize the pollination strategies of the Cretan Arum species by investigating the flowering phenology, thermogeny, inflorescence odours, and the pollinating fauna. The results obtained show that Arum cyrenaicum and Arum concinnatum emit a strong dung smell and exhibit the distinctive features associated with this pollination syndrome. Both species are highly thermogenic, have a similar odour profile and attract small‐bodied Diptera. Although sharing the same habitat, these two plant species are never found growing sympatrically as a result of the early blooming period of A. cyrenaicum. By contrast, Arum creticum and Arum idaeum have evolved a more traditional and mutually beneficial pollination mechanism. The stinking smell has been replaced by a more flower‐like odour that attracts bees (Lasioglossum sp.) and, occasionally, bugs (Dionconotus cruentatus). Although attracting the same pollinator, the main compound present in the odour of A. creticum is different from that of A. idaeum. Principal component analysis (PCA), based on physiologically active components of the flower odours determined by testing on the antenna of the Lasioglossum bee, revealed two different clusters, indicating that pollinators can potentially discriminate between the odours of the two species. A further PCA on the main floral odour volatiles as identified by gas chroatography‐mass spectroscopy from all the Arum species under investigation displayed odour‐based similarities and differences among the species. The PCA‐gas chomotography‐electroantennographic detection active peaks analysis showed that the two species, A. creticum and A. idaeum, form two groups and are clearly separated from A. cyrenaicum and A. concinnatum, which, conversely, cluster together. The evolutionary forces and selective pressures leading to diversification of pollination mechanisms in the Cretan Arum spp. are discussed. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101 , 991–1001.     

The multifunctional glycolytic protein glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a novel macrophage lactoferrin receptor

Several proteins with limited cell type distribution have been shown to bind lactoferrin. However, except in the case of hepatic and intestinal cells, these have not been definitively identified and characterized. Here we report that the multifunctional glycolytic protein glyceraldehyde-3-phosphate dehydrogenase (GAPDH) functions as a novel receptor for lactoferrin (Lf) in macrophages. GAPDH is a well-known moonlighting protein, and previous work from our laboratory has indicated its localization on macrophage cell surfaces, wherein it functions as a transferrin (Tf) receptor. The K(D) value for GAPDH-lactoferrin interaction was determined to be 43.8 nmol/L. Utilizing co-immunoprecipitation, immunoflorescence, and immunogold labelling electron microscopy we could demonstrate the trafficking of lactoferrin to the endosomal compartment along with GAPDH. We also found that upon iron depletion the binding of lactoferrin to macrophage cell surface is enhanced. This correlated with an increased expression of surface GAPDH, while other known lactoferrin receptors CD14 and lipoprotein receptor-related protein (LRP) were found to remain unaltered in expression levels. This suggests that upon iron depletion, cells prefer to use GAPDH to acquire lactoferrin. As GAPDH is an ubiquitously expressed molecule, its function as a receptor for lactoferrin may not be limited to macrophages.     

Phenotypic Plasticity in the Productions of Virulence Factors Within and Among Serotypes in the Cryptococcus neoformans Species Complex

Mycopathologia - The Cryptococcus neoformans species complex (CNSC) is a common opportunistic human fungal pathogen and the most frequent cause of fungal meningitis. There are three major serotypes...     

Inhibition of Nitric Oxide Synthase Blocks N-Methyl-D-Aspartate-, Quisqualate-, Kainate-, Harmaline-, and Pentylenetetrazole-Dependent Increases in Cerebellar Cyclic GMP In Vivo

The synthesis of nitric oxide by brain slices has been demonstrated in several laboratories. In addition, in vitro studies have demonstrated stimulation of nitric oxide synthesis by excitatory amino acid receptor agonists. These data have led to the hypothesis that this readily diffusible "intercellular messenger molecule" acts to generate a cascade effect by activating guanylate cyclase in several cell types and thereby augment levels of the second messenger cyclic GMP (cGMP). Therefore, we evaluated this hypothesis in vivo, by testing the actions of the nitric oxide synthase inhibitor N-mono-methyl-L-arginine (NMMA) on elevations in level of mouse cerebellar cGMP generated by excitatory amino acid receptor agonists. The stimulatory effects of D-serine, quisqualate, and kainate were all found to be antagonized by this enzyme inhibitor. In addition, NMMA antagonized the increases in cerebellar cGMP level elicited by harmaline and pentylenetetrazole, pharmacological agents that augment endogenous excitatory amino acid transmission. Our data are, therefore, the first in vivo demonstration that nitric oxide is an important "messenger molecule" in the cerebellum, mediating the actions of kainate, quisqualate, and N-methyl-D-aspartate receptor agonists on guanylate cyclase. These data are consistent with previous in vitro findings with kainate and N-methyl-D-aspartate.