Mathematical modelling of drug transport in tumour multicell spheroids and monolayer cultures

In this paper we adapt an avascular tumour growth model to compare the effects of drug application on multicell spheroids and on monolayer cultures. The model for the tumour is based on nutrient driven growth of a continuum of live cells, whose birth and death generates volume changes described by a velocity field. The drug is modelled as an externally applied, diffusible material capable of killing cells, both linear and Michaelis-Menten kinetics for drug action on cells being studied. Numerical solutions of the resulting system of partial differential equations for the multicell spheroid case are compared with closed form solutions of the monolayer case, particularly with respect to the effects on the cell kill of the drug dosage and of the duration of its application. The results show an enhanced survival rate in multicell spheroids compared to monolayer cultures, consistent with experimental observations, and indicate that the key factor determining this is drug penetration. An analysis of the large time tumour spheroid response to a continuously applied drug at fixed concentration reveals up to three stable large time solutions, namely the trivial solution (i.e. a dead tumour), a travelling wave (continuously growing tumour) and a sublinear growth case in which cells reach a pseudo-steady-state in the core. Each of these possibilities is formulated and studied, with the bifurcations between them being discussed. Numerical solutions reveal that the pseudo-steady-state solutions persist to a significantly higher drug dose than travelling wave solutions.     

Biotransformations using plant cells, organ cultures and enzyme systems: current trends and future prospects

Plants are valuable sources of a variety of chemicals including drugs, flavours, pigments and agrochemicals. Some of the biochemical reactions occurring in plant cells are complex and cannot be achieved by synthetic routes. In vitro plant cell and organ cultures and plant enzymes act as suitable biocatalysts to perform these complex reactions. A wide variety of chemical compounds including aromatics, steroids, alkaloids, coumarins and terpenoids can undergo biotransformations using plant cells, organ cultures and enzymes. The biocatalyst-mediated reactions are regiospecific and stereospecific. Reaction types include oxidations, reductions, hydroxylations, methylations, acetylations, isomerizations, glycosylations and esterfications. Genetic manipulation approaches to biotransformation offer great potential to express heterologous genes and to clone and overexpress genes for key enzymes. Biotransformation efficiencies can further be improved using molecular techniques involving site-directed mutagenesis and gene manipulation for substrate specificity.     

Harmonised Australian Reference Intervals for Serum PINP and CTX in Adults

Bone turnover markers (BTMs) are classified as either formation or resorption markers. Their concentrations in blood or urine of adults are considered to reflect the rate of bone remodelling and may be of use in the management of patients with bone disease. Major inter-method differences exist for BTMs, and harmonisation of methods is currently being pursued at an international level. Based on published data, this article describes age- and sex-specific Australian consensus reference intervals for adults for serum procollagen type I amino-terminal propeptide (s-PINP) and serum β-isomerised carboxy-terminal cross-linking telopeptide of type I collagen (s-CTX).     

The Personality Behind Cheating: Behavioural Types and the Feeding Ecology of Cleaner Fish

The complex mutualistic relationship between the cleaner fish (Labroides dimidiatus) and their ‘clients’ in many reef systems throughout the world has been the subject of debate and research interest for decades. Game‐theory models have long struggled with explaining how the mixed strategies of cheating and honesty might have evolved in such a system and while significant efforts have been made theoretically, demonstrating the nature of this relationship empirically remains an important research challenge. Using the experimental framework of behavioural syndromes, we sought to quantitatively assess the relationship between personality and the feeding ecology of cleaner fish to provide novel insights into the underlying mechanistic basis of cheating in cleaner‐client interactions. First, we observed and filmed cleaner fish interactions with heterospecifics, movement patterns and general feeding ecology in the wild. We then captured and measured all focal individuals and tested them for individual consistency in measures of activity, exploration and risk taking (boldness) in the laboratory. Our results suggest a syndrome incorporating aspects of personality and foraging effort are central components of the behavioural ecology of L. dimidiatus on the Great Barrier Reef. We found that individuals that exhibited greater feeding effort tended to cheat proportionately less and move over smaller distances relative to bolder more active, exploratory individuals. Our study demonstrates for the first time that individual differences in personality might be mechanistically involved in explaining how the mixed strategies of cheating and honesty persist in cleaner fish mutualisms.     

Nest site preference and intrasexual competition in female sockeye salmon,Oncorhynchus nerka

Many ecological circumstances present individuals with a conflict between the inherent benefits of a particular habitat and the costs incurred in acquiring or retaining use of the habitat in the face of competition. For example, the reproductive biology of female Pacific salmon (Oncorhynchus spp.) led us to hypothesize that female nest site choice should reflect a compromise between the benefits of obtaining a high quality nest site and the cost of competing for and defending it. To test this hypothesis we studied female sockeye salmon (O. nerka) spawning on beaches in Iliamna Lake, Alaska using a combination of snorkel surveys, tagging, behavior observations, and models. Females showed spatial preferences in nest site selection (for shallower water, where water circulation was higher), aggressive competition in preferred areas was higher, and there was evidence for costs associated with this increased competition. Over the course of the season, spawning activity shifted from shallower to deeper water, consistent with a tradeoff between benefits for embryo survival associated with shallow sites and the costs of competing for them. However, it was also consistent with date-specific optimal sites related to the probability of embryo mortality for eggs spawned in shallow water late in the season, due to annual cycles in lake level and temperature.     

Phenological advancement in arctic bird species: relative importance of snow melt and ecological factors

Previous studies have documented advancement in clutch initiation dates (CIDs) in response to climate change, most notably for temperate-breeding passerines. Despite accelerated climate change in the Arctic, few studies have examined nest phenology shifts in arctic breeding species. We investigated whether CIDs have advanced for the most abundant breeding shorebird and passerine species at a long-term monitoring site in arctic Alaska. We pooled data from three additional nearby sites to determine the explanatory power of snow melt and ecological variables (predator abundance, green-up) on changes in breeding phenology. As predicted, all species (semipalmated sandpiper, Calidris pusilla, pectoral sandpiper, Calidris melanotos, red-necked phalarope, Phalaropus lobatus, red phalarope, Phalaropus fulicarius, Lapland longspur, Calcarius lapponicus) exhibited advanced CIDs ranging from 0.40 to 0.80 days/year over 9 years. Timing of snow melt was the most important variable in explaining clutch initiation advancement (“climate/snow hypothesis”) for four of the five species, while green-up was a much less important explanatory factor. We found no evidence that high predator abundances led to earlier laying dates (“predator/re-nest hypothesis”). Our results support previous arctic studies in that climate change in the cryosphere will have a strong impact on nesting phenology although factors explaining changes in nest phenology are not necessarily uniform across the entire Arctic. Our results suggest some arctic-breeding shorebird and passerine species are altering their breeding phenology to initiate nesting earlier enabling them to, at least temporarily, avoid the negative consequences of a trophic mismatch.     

Ly6Chigh Monocytes Become Alternatively Activated Macrophages in Schistosome Granulomas with Help from CD4+ Cells

Alternatively activated macrophages (AAM) that accumulate during chronic T helper 2 inflammatory conditions may arise through proliferation of resident macrophages or recruitment of monocyte-derived cells. Liver granulomas that form around eggs of the helminth parasite Schistosoma mansoni require AAM to limit tissue damage. Here, we characterized monocyte and macrophage dynamics in the livers of infected CX3CR1^GFP/+ mice. CX₃CR1-GFP⁺ monocytes and macrophages accumulated around eggs and in granulomas during infection and upregulated PD-L2 expression, indicating differentiation into AAM. Intravital imaging of CX₃CR1-GFP⁺ Ly6C^low monocytes revealed alterations in patrolling behavior including arrest around eggs that were not encased in granulomas. Differential labeling of CX₃CR1-GFP⁺ cells in the blood and the tissue showed CD4⁺ T cell dependent accumulation of PD-L2⁺ CX₃CR1-GFP⁺ AAM in the tissues as granulomas form. By adoptive transfer of Ly6C^high and Ly6C^low monocytes into infected mice, we found that AAM originate primarily from transferred Ly6C^high monocytes, but that these cells may transition through a Ly6C^low state and adopt patrolling behavior in the vasculature. Thus, during chronic helminth infection AAM can arise from recruited Ly6C^high monocytes via help from CD4⁺ T cells.     

The evidence for functional non-CpG methylation in mammalian cells

In mammalian genomes, the methylation of cytosine residues within CpG dinucleotides is crucial to normal development and cell differentiation. However, methylation of cytosines in the contexts of CpA, CpT, and CpC (non-CpG methylation) has been reported for decades, yet remains poorly understood. In recent years, whole genome bisulphite sequencing (WGBS) has confirmed significant levels of non-CpG methylation in specific tissues and cell types. Non-CpG methylation has several properties that distinguish it from CpG methylation. Here we review the literature describing non-CpG methylation in mammalian cells, describe the important characteristics that distinguish it from CpG methylation, and discuss its functional importance.     

Proteomic profiling of N‐linked glycoproteins identifies ConA‐binding procathepsin D as a novel serum biomarker for hepatocellular carcinoma

The aim of this study was to identify novel biomarkers for the diagnosis of, and potential therapeutic targets for, hepatocellular carcinoma (HCC). Multilectin affinity chromatography was used to enrich N‐linked glycoproteins from nontumorous liver and HCC tissues followed by 2DE and protein identification by MS. Twenty‐eight differentially expressed proteins were identified. Western blotting validated consistently lower concentrations of human liver carboxylesterase 1 and haptoglobin, and higher concentration of procathepsin D (pCD) in HCC tissues. Knockdown of cathepsin D (CD) expression mediated by siRNA significantly inhibited the in vitro invasion of two HCC cell lines, SNU449 and SNU473, which normally secrete high‐levels of CD. Prefractionation using individual lectins demonstrated an elevation in ConA‐binding glycoforms of proCD and CD in HCC tissues. In the serum of HCC patients, “ConA‐binding proCD” (ConA‐pCD) is significantly increased in concentration and this increase is comprised of several distinct upregulated acidic isoforms (pI 4.5–5.5). Receiver operating characteristic analysis showed that the sensitivity and specificity of serum ConA‐pCD for HCC diagnosis were 85% and 80%, respectively. This is the first report that serum ConA‐pCD is increased significantly in HCC and is potentially useful as a serological biomarker for diagnosis of HCC.