Regulation of alcoholic fermentation in batch and chemostat cultures of Kluyveromyces lactis CBS 2359

Kluyveromyces lactis is an important industrial yeast, as well as a popular laboratory model. There is currently no consensus in the literature on the physiology of this yeast, in particular with respect to aerobic alcoholic fermentation (‘Crabtree effect’). This study deals with regulation of alcoholic fermentation in K. lactis CBS 2359, a proposed reference strain for molecular studies. In aerobic, glucose-limited chemostat cultures (D=0·05–0·40 h⁻¹) growth was entirely respiratory, without significant accumulation of ethanol or other metabolites. Alcoholic fermentation occurred in glucose-grown shake-flask cultures, but was absent during batch cultivation on glucose in fermenters under strictly aerobic conditions. This indicated that ethanol formation in the shake-flask cultures resulted from oxygen limitation. Indeed, when the oxygen feed to steady-state chemostat cultures (D=0·10 h⁻¹) was lowered, a mixed respirofermentative metabolism only occurred at very low dissolved oxygen concentrations (less than 1% of air saturation). The onset of respirofermentative metabolism as a result of oxygen limitation was accompanied by an increase of the levels of pyruvate decarboxylase and alcohol dehydrogenase. When aerobic, glucose-limited chemostat cultures (D=0·10 h⁻¹) were pulsed with excess glucose, ethanol production did not occur during the first 40 min after the pulse. However, a slow aerobic ethanol formation was invariably observed after this period. Since alcoholic fermentation did not occur in aerobic batch cultures this is probably a transient response, caused by an imbalanced adjustment of enzyme levels during the transition from steady-state growth at μ=0·10 h⁻¹ to growth at μ_max. It is concluded that in K. lactis, as in other Crabtree-negative yeasts, the primary environmental trigger for occurrence of alcoholic fermentation is oxygen limitation. © 1998 John Wiley & Sons, Ltd.     

Temporal Roles of Platelet and Coagulation Pathways in Collagen- and Tissue Factor-Induced Thrombus Formation

In hemostasis and thrombosis, the complex process of thrombus formation involves different molecular pathways of platelet and coagulation activation. These pathways are considered as operating together at the same time, but this has not been investigated. The objective of our study was to elucidate the time-dependency of key pathways of thrombus and clot formation, initiated by collagen and tissue factor surfaces, where coagulation is triggered via the extrinsic route. Therefore, we adapted a microfluidics whole-blood assay with the Maastricht flow chamber to acutely block molecular pathways by pharmacological intervention at desired time points. Application of the technique revealed crucial roles of glycoprotein VI (GPVI)-induced platelet signaling via Syk kinase as well as factor VIIa-induced thrombin generation, which were confined to the first minutes of thrombus buildup. A novel anti-GPVI Fab EMF-1 was used for this purpose. In addition, platelet activation with the protease-activating receptors 1/4 (PAR1/4) and integrin αIIbβ3 appeared to be prolongedly active and extended to later stages of thrombus and clot formation. This work thereby revealed a more persistent contribution of thrombin receptor-induced platelet activation than of collagen receptor-induced platelet activation to the thrombotic process.     

Density-based topology optimization for 3D-printable building structures

Structural and Multidisciplinary Optimization - This paper presents the study of a new penalty method for density-based topology optimization. The focus is on 3D-printable building structures with...     

Glutathione is a key player in metal-induced oxidative stress defenses

Since the industrial revolution, the production, and consequently the emission of metals, has increased exponentially, overwhelming the natural cycles of metals in many ecosystems. Metals display a diverse array of physico-chemical properties such as essential versus non-essential and redox-active versus non-redox-active. In general, all metals can lead to toxicity and oxidative stress when taken up in excessive amounts, imposing a serious threat to the environment and human health. In order to cope with different kinds of metals, plants possess defense strategies in which glutathione (GSH; γ-glu-cys-gly) plays a central role as chelating agent, antioxidant and signaling component. Therefore, this review highlights the role of GSH in: (1) metal homeostasis; (2) antioxidative defense; and (3) signal transduction under metal stress. The diverse functions of GSH originate from the sulfhydryl group in cysteine, enabling GSH to chelate metals and participate in redox cycling.     

Cu based zeolites: A UV–vis study of the active site in the selective methane oxidation at low temperatures

An extensive series of 30 Cu exchanged zeolites and Cu impregnated silicas and aluminas have been tested in their capacities to stabilize the bis(μ-oxo)dicopper core. This core shows a remarkably activity towards methane, as it selectively hydroxylates methane into methanol at the low temperature of 125 °C. UV–vis spectroscopy is an easy approach to detect the presence of this bis(μ-oxo)dicopper core since it is characterized by an intense charge transfer band at 22 700 cm⁻¹. In this way it was found that after calcination, only the Cu exchanged zeolites ZSM-5 and MOR are capable of stabilizing this core. In addition, an optimum in the Si/Al ratio and in the calcination temperature were observed, indicating that this core requires a rather specific coordination environment. For ZSM-5, the optimal Si/Al ratio for bis(μ-oxo) dicopper core formation is between 12 and 30 and the amount of this core increases with increasing copper loading above Cu/Al = 0.2. Calcination in O₂ should be done at temperatures higher than 280 °C and lower than 700 °C. After reaction with methane at low temperature (150 °C), it was found that only Cu-ZSM-5 and Cu-MOR yielded methanol, whereas all the other Cu based materials yielded almost no methanol. At higher temperatures (200 °C) however, Cu-FER and Cu-BEA showed comparable methanol yields as Cu-ZSM-5 and also the methanol yield of Cu-MOR increased at this higher reaction temperature, indicating that a second not yet identified Cu-oxygen species is activated in the FER, BEA and MOR zeolites at higher temperatures.     

Chronic renal failure in infants: effect of strict conservative treatment on growth

Two female sibs of first cousin Iranian parents were found to have the syndrome of spastic paraplegia, optic atrophy with poor vision, microcephaly, and normal cognitive development. Karyotype analysis showed a normal female constitution in one and a male constitution (46,XY) in the other. The XY female showed normal female external genitalia, normal uterus and tubes, and streak gonads. SRY gene sequencing was normal. We conclude that the present family probably represents a new autosomal recessive trait of pleiotropic effects including XY sex reversal and adds further evidence for the heterogeneity of spastic paraplegia syndromes as well as sex reversal syndromes.     

Nanoporous Hydrogen Bonded Polymeric Microparticles: Facile and Economic Production of Cross Presentation Promoting Vaccine Carriers

Nanoporous microparticles are produced in a single step based on hydrogen bonding between a neutral polymer and tannic acid. These particles are stable in physiological medium, are non‐toxic to in vitro cultured cells, and can efficiently encapsulate proteins. In vitro and in vivo experiments show that these porous hydrogen bonded microparticles are able to induce antigen‐specific cellular and humoral immune responses against encapsulated vaccine antigens. Considering the easy and low cost manufacturing of this dry powder formulation from approved readily available components, it is anticipated that this technology holds great promise for the formulation of vaccines for developing countries or for pandemic vaccines where long term storage under refrigerated conditions is a major issue. Additionally, due to the versatility of the approach facilitates straightforward co‐encapsulation of a wide variety of additional components to further modulate the immune response.     

The alarm call system of two species of black-and-white colobus monkeys (Colobus polykomos and Colobus guereza).

Vervet monkey alarm calling has long been the paradigmatic example of how primates use vocalizations in response to predators. In vervets, there is a close and direct relationship between the production of distinct alarm vocalizations and the presence of distinct predator types. Recent fieldwork has however revealed the use of several additional alarm calling systems in primates. Here, the authors describe playback studies on the alarm call system of two colobine species, the King colobus (Colobus polykomos) of Ta? Forest, Ivory Coast, and the Guereza colobus (C. guereza) of Budongo Forest, Uganda. Both species produce two basic alarm call types, snorts and acoustically variable roaring phrases, when confronted with leopards or crowned eagles. Neither call type is given exclusively to one predator, but the authors found strong regularities in call sequencing. Leopards typically elicited sequences consisting of a snort followed by few phrases, while eagles typically elicited sequences with no snorts and many phrases. The authors discuss how these call sequences have the potential to encode information at different levels, such as predator type, response-urgency, or the caller’s imminent behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Undecylenic acid: A valuable renewable building block on route to Tyromycin A derivatives

A key intermediate for the synthesis of Tyromycin A, a C‐20 tetrachlorodicarboxylic acid, was produced in six steps starting with the dimerization of methyl 10‐undecenoate which was obtained from a renewable resource, e.g. castor oil. The acyloin condensation product was then oxidized, transformed to the diene, followed by ozonization, chlorination and finally oxidation to the corresponding tetrachlorodicarboxylic acid.