A mathematical model for nutrient-limited uniaxial growth of a compressible tissue.

We consider the uniaxial growth of a tissue or colony of cells, where a nutrient (or some other chemical) required for cell proliferation is supplied at one end, and is consumed by the cells. An example would be the growth of a cylindrical yeast colony in the experiments described by Vulin et al. (2014). We develop a reaction-diffusion model of this scenario which couples nutrient concentration and cell density on a growing domain. A novel element of our model is that the tissue is assumed to be compressible. We define replicative regions, where cells have sufficient nutrient to proliferate, and quiescent regions, where the nutrient level is insufficient for this to occur. We also define pathlines, which allow us to track individual cell paths within the tissue. We begin our investigation of the model by considering an incompressible tissue where cell density is constant before exploring the solution space of the full compressible model. In a large part of the parameter space, the incompressible and compressible models give qualitatively similar results for both the nutrient concentration and cell pathlines, with the key distinction being the variation in density in the compressible case. In particular, the replicative region is located at the base of the tissue, where nutrient is supplied, and nutrient concentration decreases monotonically with distance from the nutrient source. However, for a highly-compressible tissue with small nutrient consumption rate, we observe a counter-intuitive scenario where the nutrient concentration is not necessarily monotonically decreasing, and there can be two replicative regions. For parameter values given in the paper by Vulin et al. (2014), the incompressible model slightly overestimates the colony length compared to experimental observations; this suggests the colony may be somewhat compressible. Both incompressible and compressible models predict that, for these parameter values, cell proliferation is ultimately confined to a small region close to the colony base.

Understanding interactions between populations: Individual based modelling and quantification using pair correlation functions.

Understanding the underlying mechanisms that produce the huge variety of swarming and aggregation patterns in animals and cells is fundamental in ecology, developmental biology, and regenerative medicine, to name but a few examples. Depending upon the nature of the interactions between individuals (cells or animals), a variety of different large-scale spatial patterns can be observed in their distribution; examples include cell aggregates, stripes of different coloured skin cells, etc. For the case where all individuals are of the same type (i.e., all interactions are alike), a considerable literature already exists on how the collective organisation depends on the inter-individual interactions. Here, we focus on the less studied case where there are two different types of individuals present. Whilst a number of continuum models of this scenario exist, it can be difficult to compare these models to experimental data, since real cells and animals are discrete. In order to overcome this problem, we develop an agent-based model to simulate some archetypal mechanisms involving attraction and repulsion. However, with this approach (as with experiments), each realisation of the model is different, due to stochastic effects. In order to make useful comparisons between simulations and experimental data, we need to identify the robust features of the spatial distributions of the two species which persist over many realisations of the model (for example, the size of aggregates, degree of segregation or intermixing of the two species). In some cases, it is possible to do this by simple visual inspection. In others, the features of the pattern are not so clear to the unaided eye. In this paper, we introduce a pair correlation function (PCF), which allows us to analyse multi-species spatial distributions quantitatively. We show how the differing strengths of inter-individual attraction and repulsion between species give rise to different spatial patterns, and how the PCF can be used to quantify these differences, even when it might be impossible to recognise them visually.

Identifying the necrotic zone boundary in tumour spheroids with pair-correlation functions.

Automatic identification of the necrotic zone boundary is important in the assessment of treatments on in vitro tumour spheroids. This has been difficult especially when the difference in cell density between the necrotic and viable zones of a tumour spheroid is small. To help overcome this problem, we developed novel one-dimensional pair-correlation functions (PCFs) to provide quantitative estimates of the radial distance of the necrotic zone boundary from the centre of a tumour spheroid. We validate our approach on synthetic tumour spheroids in which the position of the necrotic zone boundary is known a priori It is then applied to nine real tumour spheroids imaged with light sheet-based fluorescence microscopy. PCF estimates of the necrotic zone boundary are compared with those of a human expert and an existing standard computational method.

On the derivation of approximations to cellular automata models and the assumption of independence.

Cellular automata are discrete agent-based models, generally used in cell-based applications. There is much interest in obtaining continuum models that describe the mean behaviour of the agents in these models. Previously, continuum models have been derived for agents undergoing motility and proliferation processes, however, these models only hold under restricted conditions. In order to narrow down the reason for these restrictions, we explore three possible sources of error in deriving the model. These sources are the choice of limiting arguments, the use of a discrete-time model as opposed to a continuous-time model and the assumption of independence between the state of sites. We present a rigorous analysis in order to gain a greater understanding of the significance of these three issues. By finding a limiting regime that accurately approximates the conservation equation for the cellular automata, we are able to conclude that the inaccuracy between our approximation and the cellular automata is completely based on the assumption of independence.

Distinguishing between mechanisms of cell aggregation using pair-correlation functions.

Many cell types form clumps or aggregates when cultured in vitro through a variety of mechanisms including rapid cell proliferation, chemotaxis, or direct cell-to-cell contact. In this paper we develop an agent-based model to explore the formation of aggregates in cultures where cells are initially distributed uniformly, at random, on a two-dimensional substrate. Our model includes unbiased random cell motion, together with two mechanisms which can produce cell aggregates: (i) rapid cell proliferation and (ii) a biased cell motility mechanism where cells can sense other cells within a finite range, and will tend to move towards areas with higher numbers of cells. We then introduce a pair-correlation function which allows us to quantify aspects of the spatial patterns produced by our agent-based model. In particular, these pair-correlation functions are able to detect differences between domains populated uniformly at random (i.e. at the exclusion complete spatial randomness (ECSR) state) and those where the proliferation and biased motion rules have been employed - even when such differences are not obvious to the naked eye. The pair-correlation function can also detect the emergence of a characteristic inter-aggregate distance which occurs when the biased motion mechanism is dominant, and is not observed when cell proliferation is the main mechanism of aggregate formation. This suggests that applying the pair-correlation function to experimental images of cell aggregates may provide information about the mechanism associated with observed aggregates. As a proof of concept, we perform such analysis for images of cancer cell aggregates, which are known to be associated with rapid proliferation. The results of our analysis are consistent with the predictions of the proliferation-based simulations, which supports the potential usefulness of pair correlation functions for providing insight into the mechanisms of aggregate formation.

ISG12 is a critical modulator of innate immune responses in murine models of sepsis.

Sepsis is still a major burden for our society with high incidence of morbidity and mortality each year. Molecular mechanisms underlying the systemic inflammatory response syndrome (SIRS) associated with sepsis are still ill defined and most therapies developed to target the acute inflammatory component of the disease are insufficient. Recently the role of nuclear receptors (NRs) became a major topic of interest in transcriptional regulation of inflammatory processes. Nuclear receptors, such as the peroxisome proliferators-activated receptors (PPARs), have been demonstrated to exert anti-inflammatory properties by interfering with the NFκB pathway. We identified the nuclear envelope protein, interferon stimulated gene 12 (ISG12), which directly interacts with NRs. ISG12 is a co-factor stimulating nuclear export of NRs, thereby reducing the anti-inflammatory potential of NRs such as NR4A1. To examine the role of ISG12 in acute inflammatory processes we used recently generated ISG12 deficient mice. We can clearly demonstrate that lack of ISG12 prolongs survival in experimental sepsis and endotoxemia. Furthermore we can show that several acute inflammatory parameters, such as systemic IL6 cytokine levels, are downregulated in septic ISG12-/- animals. Consistently, similar results were obtained in in vitro experiments in peritoneal macrophages derived from ISG12 deficient mice. In contrast, mice deficient for the nuclear receptor NR4A1 exhibited an exacerbated innate immune response, and showed a significantly higher mortality after lethal endotoxemic challenge. This dramatic phenotype could be restored in ISG12/NR4A1 double deficient mice. We conclude from our data in vitro and in vivo that ISG12 is a novel modulator of innate immune responses regulating anti-inflammatory nuclear receptors such as NR4A1.

Analysis of myeloperoxidase activity in wound fluids as a marker of infection.

BACKGROUND: Neutrophilic polymorphonuclear leukocytes play a crucial role in the host defence against bacterial and fungal infections. They participate in the inflammatory response through the liberation of peptides and enzymes like myeloperoxidase (MPO). Therefore, MPO has a potential as a marker enzyme for the diagnosis of wound infection. METHODS: Substrate specificities and reaction pathways of MPO were investigated for new MPO substrates: crystal violet, leuco crystal violet, fast blue RR (4-benzoylamino-2,5-dimethoxybenzenediazonium chloride hemi(zinc chloride) salt) and various systematically substituted model substrates based on 2,7-dihydroxy-1-(4-hydroxyphenylazo)naphtalene-3,6-disulphonic acid. In addition, fast blue RR was covalently bound to siloxanes allowing immobilization of the substrate, while cellobiosedehydrogenase was integrated for generation of hydrogen peroxide required by MPO. RESULTS: Elevated concentrations of MPO were found in infected wounds compared with non-infected wounds (92.2 ± 45.0 versus 1.9 ± 1.8 U/mL). Various soluble and immobilized substrates were oxidized by MPO in wound samples and the influence of substrate structure and reaction pathways were elucidated for selected compounds. CONCLUSIONS: Incubation of different MPO substrates with infected wound fluid samples resulted in a clear colour change in the case of elevated MPO concentrations, thus allowing early diagnosis of wound infection.

Efficient phagocytosis of periodontopathogens by neutrophils requires plasma factors, platelets and TLR2.

BACKGROUND: Periodontitis represents a chronic infection of supportive dental tissues by distinct gram-negative bacteria. It is characterized by chronic and local inflammation as well as transient bacteremia with frequently occurring infections at distant sites. OBJECTIVES: The present work aimed to clarify the role of platelets and plasma factors in neutrophil interactions with the periodontopathogens A. actinomycetemcomitans and P. gingivalis. METHODS: Phagocytosis, cell-cell interactions and activation of platelets and neutrophils in response to periodontopathogens were analyzed by flow cytometry, confocal microscopy and bacteria survival assay. Plasma factors, platelet signaling pathways and receptors involved in platelet-neutrophil-bacteria interactions were determined. The role of platelet and neutrophil TLR2 in phagocytosis was further evaluated in a murine TLR2 knockout model. RESULTS: In the presence of plasma neutrophil-mediated clearance of periodontopathogens is doubled due to opsonisation of bacteria. Platelets, which become activated by periodontopathogens, further enhance clearance of bacteria by 20%, via direct interaction with neutrophils. Plasma factors (e.g. CD14) are required for platelet activation, which is mainly TLR2 dependent and results in PI3K/Akt activation. In a murine TLR2 knockout model we prove that platelet TLR2 is important for formation of platelet-neutrophil aggregates and enhanced phagocytosis of periodontopathogens. In contrast, neutrophil TLR2 is not involved in platelet-neutrophil aggregate formation but is required for efficient phagocytosis. CONCLUSIONS: These data indicate that efficient elimination of periodontopathogens by neutrophils involves a complex interplay of plasma factors as well as platelets and requires functional TLR2. By enhancing neutrophil activation platelets contribute to immune defense but may also foster inflammation.

Tinea capitis in early infancy treated with itraconazole: a pilot study.

BACKGROUND: Tinea capitis is the most common fungal infection of the scalp in childhood, but a very rare disorder in the first year of life. OBJECTIVE: To evaluate the efficacy, tolerability and safety of itraconazole in 7 children aged between 3 and 46 weeks (median: 36 weeks) suffering from tinea capitis caused by Microsporum canis. METHODS: Prospective case note study. In all patients KOH testing and fungal cultivation on Sabouraud dextrose agar were performed. RESULTS: 7 patients (5 girls and 2 boys) were included in the period between 2001 and 2008. The causative etiologic agent was Microsporum canis in all children. The patients received itraconazole 5mg/kg bodyweight daily for 3 to 6 weeks with no clinically side effects being noted. In all patients clinical and mycological cure could be achieved. CONCLUSION: Itraconazole proved to be a safe and effective treatment option for Microsporum canis induced tinea capitis in children in their first year of life.

Highly homologous HERC proteins localize to endosomes and exhibit specific interactions with hPLIC and Nm23B.

Small HERC proteins are defined by the presence of one RCC1-like domain and a HECT domain. Having evolved out of one common ancestor, the four members of the family exhibit a high degree of homology in genomic organization and amino acid sequence, thus it seems possible that they might accomplish similar functions. Here we show that small HERC proteins interact with each other and localize to the same cellular structures, which we identify as late endosomes and lysosomes. We demonstrate interaction of HERC3 with the ubiquitin-like proteins hPLIC-1 and hPLIC-2 and we establish interaction of HERC5 with the metastasis suppressor Nm23B. While hPLIC proteins are not ubiquitinated by HERC3, HERC5 plays an important role in ubiquitination of Nm23B. In summary, although small HERC proteins are highly homologous showing the same subcellular distribution, they undergo different molecular interactions.

Some endocrine traits of transgenic rabbits. I. Changes in plasma and milk hormones.

The aim of these studies was to compare some endocrine and non-endocrine characteristics of transgenic (carrying mammary gland-specific mWAP-hFVIII gene construct) and non-transgenic rabbits. The concentrations of corticosterone, progesterone, testosterone, estradiol, insulin-like growth factor I (IGF-I) and human factor VIII (hFVIII) in the blood plasma of adult females (9 months of age, third generation transgenic animals), adult males, and young females (1-2 months of age, fourth generation of transgenic animals), as well as in the milk of lactating adult females, were analyzed by using RIA. In addition, litter size and body mass of pups born by transgenic and non-transgenic females from the third generation were compared. Transgenic animals were compared with their non-transgenic siblings (the same genetic and epigenetic background). Transgenesis did not influence plasma hFVIII, but significantly increased corticosterone (in all animals), reduced IGF-I (in adult males and females), testosterone and estradiol, (in young females) and altered progesterone (increase in adult males and decrease in adult females) concentrations in blood plasma. In addition, transgenic females had higher milk concentrations of testosterone, but not progesterone or IGF-I than their non-transgenic sisters. These endocrine changes were not associated with changes in litter size. Transgenic male (but not female) pups have smaller body mass than control animals. These observations demonstrate the influence of transgenesis per se on the animal growth and endocrine system (secretion of reproductive and stress steroid hormones as well as growth factors) over four generations.

Alpha-catulin, a Rho signalling component, can regulate NF-kappaB through binding to IKK-beta, and confers resistance to apoptosis.

Rho GTPases regulate diverse cellular functions including adhesion, cytokinesis and motility, as well as the activity of the transcription factors NF-kappaB, serum response factor and C/EBP. alpha-Catulin, an alpha-catenin-related protein that shares structural similarities with cytoskeletal linker proteins, facilitates Rho signalling by serving as a scaffold for the Rho-specific guanine nucleotide exchange factor Lbc. We report here that alpha-catulin also interacts with a key component of the NF-kappaB signalling pathway, namely the IkappaB kinase (IKK)-beta. In co-immunoprecipitations, alpha-catulin can bind IKK-beta and Lbc. Ectopic expression of alpha-catulin augmented NF-kappaB activity, promoted cell migration and increased resistance to apoptosis, whereas knockdown experiments showed the opposite effects. Together, these features suggest that alpha-catulin has tumorigenic potential.

Ecological genomics of marine Roseobacters.

Bacterioplankton of the marine Roseobacter clade have genomes that reflect a dynamic environment and diverse interactions with marine plankton. Comparative genome sequence analysis of three cultured representatives suggests that cellular requirements for nitrogen are largely provided by regenerated ammonium and organic compounds (polyamines, allophanate, and urea), while typical sources of carbon include amino acids, glyoxylate, and aromatic metabolites. An unexpectedly large number of genes are predicted to encode proteins involved in the production, degradation, and efflux of toxins and metabolites. A mechanism likely involved in cell-to-cell DNA or protein transfer was also discovered: vir-related genes encoding a type IV secretion system typical of bacterial pathogens. These suggest a potential for interacting with neighboring cells and impacting the routing of organic matter into the microbial loop. Genes shared among the three roseobacters and also common in nine draft Roseobacter genomes include those for carbon monoxide oxidation, dimethylsulfoniopropionate demethylation, and aromatic compound degradation. Genes shared with other cultured marine bacteria include those for utilizing sodium gradients, transport and metabolism of sulfate, and osmoregulation.

The additive value of second opinion teleconsulting in the management of patients with challenging inflammatory, neoplastic skin diseases: a best practice model in dermatology?

BACKGROUND: Telemedicine is the practice of healthcare using interactive processes of communication to facilitate healthcare delivery, including diagnosis, consultation and treatment, as well as education and transfer of medical data. The aim of teledermatology, just as telemedicine, is to promote best practice procedures and to improve the consistency and competence of health care. AIM: To investigate the diagnostic additive value of second opinion teleconsulting in patients with challenging dermatoses, among dermatologists working in two different dermatology departments. SETTING: Thirty-three cases of patients with challenging inflammatory and neoplastic skin diseases at the University of L'Aquila Department of Dermatology were sent for teleconsultation to the Department of Dermatology, Medical University of Graz, Austria. METHODS: All cases were selected in the outpatient service in L'Aquila. After face-to-face consultation with a local colleague had been completed, images were sent using a store-and-forward (SAF)-based system (http://www.telederm.org) to Graz. Histopathological examination together with follow-up of the patient represents the diagnostic gold standard for this study. RESULTS: Telediagnosis was correct in 26 of 33 (78.8%) cases. Sixteen of 33 cases (48.5%) had already been diagnosed face-to-face by at least one of the two dermatologists in L'Aquila. In 10 of 33 cases (30.3%), the correct diagnosis was made in teleconsultation only. CONCLUSIONS: Second opinion teleconsulting may represent an additive value in the diagnosis of numerous challenging inflammatory and neoplastic skin diseases. It may be particularly useful as a best practice model for smaller departments in order to discuss and/or to confirm diagnoses and also for the management of patients with unusual difficult dermatoses.

Expansion of signal transduction networks.

Signal transduction networks of different cell types show a large variety in their structural design. In this paper, basic structural properties of signal transduction networks are investigated. For this, such networks with the recently developed method of network expansion are analysed. This method allows for a structural analysis of networks by calculating signal expansion profiles when provided with certain compounds, for example growth factors, inactive kinases and so on (seed compounds), to initiate such an expansion. The presented results may put forth valuable hints on the evolution of signalling networks.

Feasibility and acceptance of telemedicine for wound care in patients with chronic leg ulcers.

We examined the feasibility and acceptance of teledermatology for wound management of patients with chronic leg ulcers by home-care nurses. Forty-one chronic leg ulcers of different origin in 14 patients were included. After an initial in-person visit in which leg ulcers were assessed and classified, and underlying diseases noted, follow-up visits were done by home-care nurses. Once a week 1-4 digital images of the wound and surrounding skin and relevant clinical information were transmitted via a secure Website to an expert at the wound care centre. The experts provided an assessment of wound status and therapeutic recommendations. In 89% of the 492 teleconsultations, the quality of images was sufficient or excellent and the experts were confident giving therapeutic recommendations. Treatment modalities were changed or adapted in one-third of the consultations. There was a significant decrease in visits to a general physician or the wound care centre. The acceptance of teledermatology was high in patients, home-care nurses and wound experts. Teledermatology offers great potential for chronic wound care and seems to be accepted both by patients and health-care persons.

Comparison of a two- or three-week regimen and a review of treatment of erythema migrans with phenoxymethylpenicillin.

BACKGROUND: A longer duration treatment is preferred in erythema migrans (EM) to prevent late complaints. OBJECTIVES: To determine whether 20 (20d-pt) or 14 days (14d-pt) of phenoxymethylpenicillin (PenV) have similar efficacy in treating EM and preventing further sequelae. PATIENTS AND METHODS: In a prospective double-centre study, 102 patients with EM were treated with PenV 1.5 million IU thrice daily for either 20 or 14 days and followed up for 12 months. RESULTS: The primary cure rate after treatment with PenV was 91.5% (79.6-97.6) for 20d-pt vs. 91.7% (77.5-98.2) for 14d-pt; p > 0.99). In 7 patients (4/20d-pt and 3/14d-pt), persistent or newly arising symptoms required retreatment. After 1 year, all patients were cured. The immune response showed no statistical difference between the treatment groups in the follow-up period. CONCLUSION: A 2-week treatment regimen of PenV seems to be as effective as a 3-week course with no statistical differences for clinical and serological findings after treatment.

Forced solitary waves and fronts past submerged obstacles.

Herein, an efficient numerical method is presented to describe the flow of a liquid in an open channel with various types of bottom configurations. The method is developed for steady two-dimensional potential free surface flows. The resulting nonlinear problem is solved numerically by boundary integral equation methods. In addition weakly nonlinear solutions are derived. New solutions which complement those of Dias and Vanden-Broeck [J. Fluid Mech. 59, 93-102 (2004)] are presented. Furthermore some solutions for channel flows past dips in the bottom are discussed.