Operon dynamics with state dependent transcription and/or translation delays

This paper is focused on SIS (Susceptible-Infected-Susceptible) epidemic dynamics (also known as the contact process) on populations modelled by homogeneous Poisson point processes of the Euclidean plane, where the infection rate of a susceptible individual is proportional to the number of infected individuals in a disc around it. The main focus of the paper is a model where points are also subject to some random motion. Conservation equations for moment measures are leveraged to analyze the stationary regime of the point processes of infected and susceptible individuals. A heuristic factorization of the third moment measure is then proposed to obtain simple polynomial equations allowing one to derive closed form approximations for the fraction of infected individuals in the steady state. These polynomial equations also lead to a phase diagram which tentatively delineates the regions of the space of parameters (population density, infection radius, infection and recovery rate, and motion rate) where the epidemic survives and those where there is extinction. A key take-away from this phase diagram is that the extinction of the epidemic is not always aided by a decrease in the motion rate. These results are substantiated by simulations on large two dimensional tori. These simulations show that the polynomial equations accurately predict the fraction of infected individuals when the epidemic survives. The simulations also show that the proposed phase diagram accurately predicts the parameter regions where the mean survival time of the epidemic increases (resp. decreases) with motion rate.

     

New species and records of orbiliaceous fungi from Georgia,USA

Orbilia georgiana and O. renispora are described as new species to science, in addition, O. eucalypti, O. occulta, and O. xanthoguttulata are reported based on collections taken from the state of Georgia, USA. Orbilia xanthoguttulata is a new record for North America. The morphology of all species is described based on both sexual and asexual morphs. Asexual morphs were obtained from ascospore isolates, from which also DNA was extracted and used to amplify rDNA genes (ITS and LSU) for phylogenetic comparison.     

Orbilia tianmushanensis sp. nov., a new member of the O. luteorubella group with an unusual asexual morph

A new species of Orbilia related to O. luteorubella is described mainly based on morphological characters of its asexual morph and molecular data. The sexual morph does not significantly differ from O. luteorubella, whereas the asexual morph obtained from its ascospore isolate resembles members of the non-predacious genus Dactylella, because it has fusiform phragmoconidia borne singly at the apex of conidiophores. Phylogenetic analysis showed that this strain clustered with a clade that included available strains of the O. luteorubella aggregate and was distant from all analysed Dactylella species. Within this clade, the new strain fell between species with filiform conidia and those of a Pseudotripoconidium anamorph. By combining morphological and phylogenetic analyses, we conclude that our isolate belongs to a new taxon. Pleomorphism of the new taxon is described and discussed.     

Perfusion Imaging in Pusher Syndrome to Investigate the Neural Substrates Involved in Controlling Upright Body Position

Brain damage may induce a dysfunction of upright body position termed “pusher syndrome”. Patients with such disorder suffer from an alteration of their sense of body verticality. They experience their body as oriented upright when actually tilted nearly 20 degrees to the ipsilesional side. Pusher syndrome typically is associated with posterior thalamic stroke; less frequently with extra-thalamic lesions. This argued for a fundamental role of these structures in our control of upright body posture. Here we investigated whether such patients may show additional functional or metabolic abnormalities outside the areas of brain lesion. We investigated 19 stroke patients with thalamic or with extra-thalamic lesions showing versus not showing misperception of body orientation. We measured fluid-attenuated inversion-recovery (FLAIR) imaging, diffusion-weighted imaging (DWI), and perfusion-weighted imaging (PWI). This allowed us to determine the structural damage as well as to identify the malperfused but structural intact tissue. Pusher patients with thalamic lesions did not show dysfunctional brain areas in addition to the ones found to be structurally damaged. In the pusher patients with extra-thalamic lesions, the thalamus was neither structurally damaged nor malperfused. Rather, these patients showed small regions of abnormal perfusion in the structurally intact inferior frontal gyrus, middle temporal gyrus, inferior parietal lobule, and parietal white matter. The results indicate that these extra-thalamic brain areas contribute to the network controlling upright body posture. The data also suggest that damage of the neural tissue in the posterior thalamus itself rather than additional malperfusion in distant cortical areas is associated with pusher syndrome. Hence, it seems as if the normal functioning of both extra-thalamic as well as posterior thalamic structures is integral to perceiving gravity and controlling upright body orientation in humans.     

Leg orientation as a clinical sign for pusher syndrome

Background  

Effective control of (upright) body posture requires a proper representation of body orientation. Stroke patients with pusher syndrome were shown to suffer from severely disturbed perception of own body orientation. They experience their body as oriented 'upright' when actually tilted by nearly 20° to the ipsilesional side. Thus, it can be expected that postural control mechanisms are impaired accordingly in these patients. Our aim was to investigate pusher patients' spontaneous postural responses of the non-paretic leg and of the head during passive body tilt.     

Regional alterations in brain amino acids during the estrous cycle of the rat

Concentrations of 11 amino acids, including the neurotransmitters GABA, glutamate, aspartate, glycine and taurine, were determined in 12 brain regions of female rats during different stages of the estrous cycle. In addition, amino acids and sex hormone levels were determined in plasma. All sample collections were done in the forenoon between 9 and 11 a.m. Most regional amino acid levels measured did not change signficantly during estrous cycle, but significant alterations were found for GABA and glutamate in hypothalamus. Both amino acids were slightly decreased in hypothalamus during proestrus, which might reflect an alteration of GABA turnover in response to the high estrogen levels during this stage. A decreased glutamate level during proestrus was also found in thalamus, while both glutamate and GABA did not vary throughout estrous cycle in any of the other examined regions, including substantia nigra, amygdala, striatum, cortex and hippocampus. When diestrus was subdivided according to progesterone levels, high levels of this hormone seemed to be associated with effects on metabolism of certain amino acids, including glycine in substantia nigra, alanine in thalamus and threonine in pons/medulla. However, the few changes in regional amino acid concentrations found during the estrous cycle were so small that the functional significance of these changes cannot be ascertained without further determination of the cellular or subcellular compartments of brain tissue involved.     

Colipila, a new genus in the Helotiales

Colipila, a new member of the Helotiales, is erected for two previously undescribed lignicolous species resembling Dasyscyphella and Lachnum by macroscopy. Species of Colipila are characterized by their long, entirely smooth, hyaline, thin-walled, multiseptate, subulate to basally fusoid hairs that tend to be curved on the stipe and lower flanks, and dimorphic, partly strongly protruding paraphyses which closely resemble the hairs. The type species, C. masduguana, is recorded repeatedly in southern France on rotten decorticated branches and trunks of Castanea sativa on the moist forest floor in sub-Mediterranean regions with siliceous soils, but also once on Quercus robur in a temperate forest with calcareous soil. The second species, C. pilatensis, was found on wood of an unidentified member of Rosaceae in a calcareous region of the Northern Alps and is known only from the holotype. The phylogenetic position of C. masduguana within the Helotiales was not resolved based on the analysis of nuclear LSU ribosomal DNA sequences. A key to the species of Colipila is provided.