Exploration of the Production of Three Thiodiketopiperazines by an Endophytic Fungal Strain of Cophinforma mamane

Endophytic fungi possess a versatile metabolism which is related to their ability to live in diverse ecological niches. While culturing under laboratory conditions, their metabolism is mainly influenced by the culture media, time of incubation and other physicochemical factors. In this study, we focused on the production of 3 thiodiketopiperazines (TDKPs) botryosulfuranols A−C produced by an endophytic strain of Cophinforma mamane isolated from the leaves of Bixa orellana L collected in the Peruvian Amazon. We studied the time-course production of botryosulfuranols A−C during 28 days and evaluated the variations in the production of secondary metabolites, including the TDKPs, produced by C. mamane in response to different culture media, light versus dark conditions and different incubation times. We observed a short time-frame production of botryosulfuranol C while its production was significantly affected by the light conditions and nutrients of the culture media. Botryosulfuranols A and B showed a similar production pattern and a similar response to culturing conditions. Molecular networking allowed us to detect three compounds related to TDKPs that will be the focus of future experiments.     

A finite element model of myocardial infarction using a composite material approach

Computational models are effective tools to study cardiac mechanics under normal and pathological conditions. They can be used to gain insight into the physiology of the heart under these conditions while they are adaptable to computer assisted patient-specific clinical diagnosis and therapeutic procedures. Realistic cardiac mechanics models incorporate tissue active/passive response in conjunction with hyperelasticity and anisotropy. Conventional formulation of such models leads to mathematically-complex problems usually solved by custom-developed non-linear finite element (FE) codes. With a few exceptions, such codes are not available to the research community. This article describes a computational cardiac mechanics model developed such that it can be implemented using off-the-shelf FE solvers while tissue pathologies can be introduced in the model in a straight-forward manner. The model takes into account myocardial hyperelasticity, anisotropy, and active contraction forces. It follows a composite tissue modeling approach where the cardiac tissue is decomposed into two major parts: background and myofibers. The latter is modelled as rebars under initial stresses mimicking the contraction forces. The model was applied in silico to study the mechanics of infarcted left ventricle (LV) of a canine. End-systolic strain components, ejection fraction, and stress distribution attained using this LV model were compared quantitatively and qualitatively to corresponding data obtained from measurements as well as to other corresponding LV mechanics models. This comparison showed very good agreement.     

The submandibular musculature of phyllomedusinae (Anura: Hylidae): A reappraisal

The submandibular musculature of 37 species of the five currently recognized genera of the subfamily Phyllomedusinae (Anura: Hylidae) is described; observations are made on the variation and ontogeny of these muscles. Supplementary apical elements of the m. intermandibularis occur in all phyllomedusines studied, in addition to the supplementary posterolateral elements previously reported. Our observations are discussed in the context of 1) the proposed homology between supplementary apical and posterolateral elements; 2) the homology with the apical elements reported for Pelodryadinae (sister taxon of Phyllomedusinae); and 3) the implications for our understanding of the relationships between Phyllomedusinae and Pelodryadinae. Anatomical differences between the apical and posterolateral elements and their co‐occurrence in phyllomedusines indicate that these supplementary elements are not homologous. Despite differences between phyllomedusines and pelodryadines in the adhesion of supplementary fibers to the principal element of the m. intermandibularis and the occurrence of a broad aponeurosis or a medial raphe, the extensive morphological and developmental resemblances of the apical elements indicate that these structures are homologous, and that the presence of apical elements is a synapomorphy of Phyllomedusinae + Pelodryadinae. J. Morphol., 2011. © 2011 Wiley‐Liss, Inc.     

Long-term oscillations in grassland productivity induced by drought

Disturbances such as drought have immediate impacts on ecosystem functioning, but little is known about long-term dynamic consequences of disturbance. Here, we show that a major drought perturbed prairie grassland from nearly constant average annual production, and induced 9 years of oscillations with a 2-year period. This pattern occurred in unmanipulated plots in many widely separated fields that were part of two different long-term studies. Using direct and indirect tests, we could reject the hypothesis that the oscillations were externally imposed by climate or herbivores. Weak evidence supported the hypothesis that oscillations were internally generated, caused by a litter and nitrogen dependent feedback on productivity. This hypothesis was supported by the results of two other long-term studies, in which burning and, separately, nitrogen addition eliminated the 2-year oscillations in plant production. However, more direct evidence failed to support the litter hypothesis. A final, but untested hypothesis was suggested by the observation that production tended to be synchronized amongst dominant plants. Drought may have synchronized production dynamics amongst plants with biennially greater allocation to above-ground growth. Regardless of the specific mechanism, our results show that a single disturbance may have long-lasting effects on the dynamics of plant production.     

Autoradiographic demonstration of in vivo sialylation of endogenous acceptors at the microvillar surface of intestinal columnar cells after intraluminal administration of CMP-[3H]-sialic acid

To investigate the presence of glycosyltransferase activity at the apical surfaces of columnar cells in small intestine, CMP-[3H]-sialic acid was injected into the lumen of a ligated segment of rat jejunum; 5 min later the tissue was fixed and processed for light microscopic autoradiography. After a 3-6-month exposure, an autoradiographic reaction appeared over the microvillar surfaces of columnar cells, indicating the presence of surface sialyltransferase activity accompanied by endogenous acceptors. When CMP-[3H]-sialic acid was injected into the posterior chamber of rat eye or the lumen of mouse gallbladder, no autoradiographic reaction was observed at the surfaces of the cells facing these cavities. After injection of UDP-[3H]-galactose into the same three sites, an autoradiographic reaction was observed in the Golgi regions of the various epithelial cells, but not along their apical surfaces. Competition experiments using unlabeled galactose indicated that [3H]-galactose had been released from the nucleotide and had entered the cells to be incorporated into the Golgi apparatus.