<Emphasis Type="Italic">Podospora anserina</Emphasis>: a model organism to study mechanisms of healthy ageing

The filamentous ascomycete Podospora anserina has been extensively studied as an experimental ageing model for more than 50 years. As a result, a huge body of data has been accumulated and various molecular pathways have been identified as part of a molecular network involved in the control of ageing and life span. The aim of this review is to summarize data on P. anserina ageing, including aspects like respiration, cellular copper homeostasis, mitochondrial DNA (mtDNA) stability/instability, mitochondrial dynamics, apoptosis, translation efficiency and pathways directed against oxidative stress. It becomes clear that manipulation of several of these pathways bears the potential to extend the healthy period of time, the health span, within the life time of the fungus. Here we put special attention on recent work aimed to identify and characterize this type of long-lived P. anserina mutants. The study of the molecular pathways which are modified in these mutants can be expected to provide important clues for the elucidation of the mechanistic basis of this type of 'healthy ageing' at the organism level.     

Isolation and characterization of cold-regulated transcriptional activator <Emphasis Type="Italic">LpCBF3</Emphasis> gene from perennial ryegrass (<Emphasis Type="Italic">Lolium perenne</Emphasis> L.)

In plants, low temperatures can activate the CBF cold response pathway playing a prominent role in cold acclimation by triggering a set of cold-related gene expressions. CBF homologous gene, designated as LpCBF3, from a cold-tolerant perennial ryegrass (Lolium perenne L.) accession was identified. It carries the sequences for nuclear localization signal (NLS), AP2 DNA-binding domains and an acidic activation present in most of the plant CBF proteins. Southern analysis indicated the presence of three homologs of LpCBF3 gene in perennial ryegrass genome, and only one amino acid variation in LpCBF3 protein between cold-tolerant and -sensitive perennial ryegrass accessions. In their putative promoter regions, some differential regions were found. Northern blotting and RT-PCR analysis found that LpCBF3 reached the highest expression after 1.5 h of cold treatment (4 degrees C). The COR homologous gene, a downstream gene of CBF, can be expressed in the plant stem of cold-tolerant perennial ryegrass accessions without cold treatment. Without cold treatment, the COR gene cannot be activated in cold-sensitive perennial ryegrass accessions. Cold treatment can prompt expression levels of COR homologous genes in both perennial ryegrass accessions. In transgenic Arabidopsis, the overexpression of LpCBF3 with the 35S promoter resulted in dwarf-like plants, later flowering and greater freezing tolerance.     

Interstitial fluid flow in the osteon with spatial gradients of mechanical properties: a finite element study

Bone remodelling is the process that maintains bone structure and strength through adaptation of bone tissue mechanical properties to applied loads. Bone can be modelled as a porous deformable material whose pores are filled with cells, organic material and interstitial fluid. Fluid flow is believed to play a role in the mechanotransduction of signals for bone remodelling. In this work, an osteon, the elementary unit of cortical bone, is idealized as a hollow cylinder made of a deformable porous matrix saturated with an interstitial fluid. We use Biot’s poroelasticity theory to model the mechanical behaviour of bone tissue taking into account transverse isotropic mechanical properties. A finite element poroelastic model is developed in the COMSOL Multiphysics software. Elasticity equations and Darcy’s law are implemented in this software; they are coupled through the introduction of an interaction term to obtain poroelasticity equations. Using numerical simulations, the investigation of the effect of spatial gradients of permeability or Poisson’s ratio is performed. Results are discussed for their implication on fluid flow in osteons: (i) a permeability gradient affects more the fluid pressure than the velocity profile; (ii) focusing on the fluid flow, the key element of loading is the strain rate; (iii) a Poisson’s ratio gradient affects both fluid pressure and fluid velocity. The influence of textural and mechanical properties of bone on mechanotransduction signals for bone remodelling is also discussed.     

How to measure image quality in tissue-based diagnosis (diagnostic surgical pathology)

Background

Automated image analysis, measurements of virtual slides, and open access electronic measurement user systems require standardized image quality assessment in tissue-based diagnosis.

Aims

To describe the theoretical background and the practical experiences in automated image quality estimation of colour images acquired from histological slides.

Theory, material and measurements

Digital images acquired from histological slides should present with textures and objects that permit automated image information analysis. The quality of digitized images can be estimated by spatial independent and local filter operations that investigate in homogenous brightness, low peak to noise ratio (full range of available grey values), maximum gradients, equalized grey value distribution, and existence of grey value thresholds. Transformation of the red-green-blue (RGB) space into the hue-saturation-intensity (HSI) space permits the detection of colour and intensity maxima/minima. The feature distance of the original image to its standardized counterpart is an appropriate measure to quantify the actual image quality. These measures have been applied to a series of H&;E stained, fluorescent (DAPI, Texas Red, FITC), and immunohistochemically stained (PAP, DAB) slides. More than 5,000 slides have been measured and partly analyzed in a time series.

Results

Analysis of H&;E stained slides revealed low shading corrections (10%) and moderate grey value standardization (10 – 20%) in the majority of cases. Immunohistochemically stained slides displayed greater shading and grey value correction. Fluorescent stained slides are often revealed to high brightness. Images requiring only low standardization corrections possess at least 5 different statistically significant thresholds, which are useful for object segmentation. Fluorescent images of good quality only posses one singular intensity maximum in contrast to good images obtained from H&;E stained slides that present with 2 – 3 intensity maxima.

Conclusion

Evaluation of image quality and creation of formally standardized images should be performed prior to automatic analysis of digital images acquired from histological slides. Spatial dependent and local filter operations as well as analysis of the RGB and HSI spaces are appropriate methods to reproduce evaluated formal image quality.

     

Parasites of importance for human health in Nigerian dogs: high prevalence and limited knowledge of pet owners

Background

Dogs are the most common pet animals worldwide. They may harbour a wide range of parasites with zoonotic potential, thus causing a health risk to humans. In Nigeria, epidemiological knowledge on these parasites is limited.

Methods

In a community-based study, we examined 396 dogs in urban and rural areas of Ilorin (Kwara State, Central Nigeria) for ectoparasites and intestinal helminths. In addition, a questionnaire regarding knowledge and practices was applied to pet owners.

Results

Nine ectoparasite species belonging to four taxa and six intestinal helminth species were identified: fleas (Ctenocephalides canis, Pulex irritans, Tunga penetrans), mites (Demodex canis, Otodectes sp., Sarcoptes scabiei var. canis), ticks (Rhipicephalus sanguineus, Ixodes sp.), and lice (Trichodectes canis); and Toxocara canis, Ancylostoma sp., Trichuris vulpis, Dipylidium caninum, Taenidae and Strongyloides sp. Overall prevalence of ectoparasites was 60.4% and of intestinal helminths 68.4%. The occurrence of C. canis, R. sanguineus, T. canis, Ancylostoma sp. and T. vulpis was most common (prevalence 14.4% to 41.7%). Prevalence patterns in helminths were age-dependent, with T. canis showing a decreasing prevalence with age of host, and a reverse trend in other parasite species. Knowledge regarding zoonoses was very limited and the diseases not considered a major health problem. Treatment with antiparasitic drugs was more frequent in urban areas.

Conclusion

Parasites of importance for human health were highly prevalent in Nigerian dogs. Interventions should include health education provided to dog owners and the establishment of a program focusing on zoonotic diseases.

     

Discontinuous video recording of biopsies in the context of an integral third degree teaching program

Background

The application of Information and Communication Technologies (ICTs) in the field of university education can play an important role in order to fulfil the objectives of the European Space for Higher Education (ESHE). In the absence of an infrastructure that allows virtual preparations, the high definition video may become an alternative for many PC users and telepathology enthusiasts.

Methods

We have begun a video biopsy discontinuous recording pilot programme, also known as interval cinematography, in order to give our students pathological images to gather documentary evidence to follow their clinical cases. We have a working post available with a ZEISS Axioshop 2 microscope connected to a JVC digital camera with a double output for video, a PVM_14N1MDE Sony Triniton colour monitor and a LG RH199 HDD-DVD recorder.

Results

Pathologists can easily produce videos lasting between 45" and 5' according to the case. Later those videos are assessed all together and given to the student and/or the doctor who requested the case study.

Conclusion

Better follow-up studies of the cases can be achieved using Discontinuous video recording of biopsies. This approach has also clinical benefits since it contributes to the enrichment of integral patient care.

     

Synthesis and absolute configuration of hormone alpha1

An important biological event in phytopathogens of the genus Phytophthora is sexual reproduction, which is conducted by two mating types, A1 and A2. A factor known as hormone alpha1 is secreted by the A1 mating type and induces the formation of sexual spores (oospores) in the A2 mating type. Here we describe the asymmetric synthesis and assignment of the absolute configuration of hormone alpha1 by oospore-inducing assays of the synthesized isomers.     

Acetogenic anthraquinones: biosynthetic convergence and chemical evidence of enzymatic cooperation in nature

Phenylanthraquinones belong to the quite rare class of fully unsymmetric biaryls, consisting of two different molecular portions, an anthraquinone part, chrysophanol, and a phenyl part, 2,4-dihydroxy-6-methoxyacetophenone, linked together by phenol-oxidative coupling. The biosynthesis of these two moieties, from eight and four acetate units, respectively, bears some unique features: Chrysophanol is the first example of an acetogenic natural product that is, in an organism-specific manner, formed via more than one folding mode: In eukaryotes, like, e.g., in fungi, in higher plants, and in insects, it is formed via folding mode F, while in prokaryotes it originates through mode S. It has, more recently, even been found to be synthesized by a third pathway, which we have named mode S′. It is thus the first example of biosynthetic convergence in polyketide biosynthesis. The monocyclic “southern” portion of the molecule, which is much simpler (arising from only four acetate units and without decarboxylation), unexpectedly does not show the anticipated randomization of the C₂-labeling in the aromatic ring, but has clearly localized C₂ units, excluding any symmetric intermediate like, e.g., 2,4,6-trihydroxyacetophenone. This is confirmed by competitive feeding experiments with specifically ¹³C₂-labeled acetophenones, showing the O-methylation to be the decisive symmetry-preventing step, which hints at a close collaboration of the participating enzymes. The results make knipholone an instructive example of structure, function, and evolution of polyketide synthases and O-methyltransferases, and their cooperation.