Carotenoid dynamics in Atlantic salmon

Background  

Carotenoids are pigment molecules produced mainly in plants and heavily exploited by a wide range of organisms higher up in the food-chain. The fundamental processes regulating how carotenoids are absorbed and metabolized in vertebrates are still not fully understood. We try to further this understanding here by presenting a dynamic ODE (ordinary differential equation) model to describe and analyse the uptake, deposition, and utilization of a carotenoid at the whole-organism level. The model focuses on the pigment astaxanthin in Atlantic salmon because of the commercial importance of understanding carotenoid dynamics in this species, and because deposition of carotenoids in the flesh is likely to play an important life history role in anadromous salmonids.     

Biodegradation of oily sludge in Norwegian soils

Summary The degradation rate of oily sludge in soil under Norwegian conditions has been studied in field experiments during a 32 months' period. The experimental plots were added 0, 200, 400, and 600 kg N per ha. In uncultivated soil the oil content was reduced by respectively 4, 9, 22, and 26% during the first 9 months. In the same period the corresponding biodegradation in cultivated soil were 10, 15, 39, and 45%. At the end of the experiment only minor differences between the two different soil types were found. The mean degradation in percent was now 35, 50, 74, and 83, respectively. The optimum temperature for oil degradation in soil was found to be about 18°C. About 2/3 of the optimum activity was retained at 12°C. No leaching of oil or lead through soil columns infiltrated with oily sludge could be observed. A close relationship between oil content of the soil and the rate of water infiltration was found. Due to the extremely high content of lead in this oily sludge, a second application of sludge could not be recommended.     

Cannibalism and fratricide: mechanisms and raisons d'être

Cannibalism and fratricide refer to the killing of genetically identical cells (siblings) that was recently documented in two Gram-positive species, Bacillus subtilis and Streptococcus pneumoniae, respectively. Cannibalism occurs during the early stages of sporulation in B. subtilis, whereas fratricide occurs in S. pneumoniae during natural genetic transformation. Here, we compare and contrast these two phenomena and discuss whether these processes are fundamentally different from the more traditional 'chemical warfare' among bacteria.     

Targeted reduction of complex models with time scale hierarchy--a case study

With the increasing flow of biological data there is a growing demand for mathematical tools whereby essential aspects of complex causal dynamic models can be captured and detected by simpler mathematical models without sacrificing too much of the realism provided by the original ones. Given the presence of a time scale hierarchy, singular perturbation techniques represent an elegant method for making such minimised mathematical representations. Any reduction of a complex model by singular perturbation methods is a targeted reduction by the fact that one has to pick certain mechanisms, processes or aspects thought to be essential in a given explanatory context. Here we illustrate how such a targeted reduction of a complex model of melanogenesis in mammals recently developed by the authors provides a way to improve the understanding of how the melanogenic system may behave in a switch-like manner between production of the two major types of melanins. The reduced model is shown by numerical means to be in good quantitative agreement with the original model. Furthermore, it is shown how the reduced model discloses hidden robustness features of the full model, and how the making of a reduced model represents an efficient analytical sensitivity analysis. In addition to yielding new insights concerning the melanogenic system, the paper provides an illustration of a protocol that could be followed to make validated simplifications of complex biological models possessing time scale hierarchies.     

A biofilm growth protocol and the design of a magnetic field exposure setup to be used in the study of magnetic fields as a means of controlling bacterial biofilms

The use of prosthetic implants is increasing both in the United States and around the world and there is a concomitant rise in cases of biofilm‐based, persistent infections that are quite serious and virtually impervious to antibiotic treatment. The development of alternate therapies that do not involve long term use of high levels of antibiotics or surgical intervention is needed. Based on the success of using electric or magnetic fields to alter certain physiological processes, it is hypothesized that relatively low level magnetic fields, in conjunction with the appropriate antibiotic, may be able to help control and eventually clear bacterial biofilms on a prosthetic. In order to test this hypothesis, it is necessary to first develop a means of growing laboratory grade biofilms on specific materials in a way that is repeatable between experiments and that can be reproduced by other laboratories. Secondly, a means of applying controlled magnetic fields to the surfaces supporting the biofilms at a defined temperature must be developed. This article addresses both of these points. Bioelectromagnetics 31:56–63, 2010. © 2009 Wiley‐Liss, Inc.     

DNA sequence profiles of the colorectal cancer critical gene set KRAS-BRAF-PIK3CA-PTEN-TP53 related to age at disease onset

The incidence of colorectal cancer (CRC) increases with age and early onset indicates an increased likelihood for genetic predisposition for this disease. The somatic genetics of tumor development in relation to patient age remains mostly unknown. We have examined the mutation status of five known cancer critical genes in relation to age at diagnosis, and compared the genomic complexity of tumors from young patients without known CRC syndromes with those from elderly patients. Among 181 CRC patients, stratified by microsatellite instability status, DNA sequence changes were identified in KRAS (32%), BRAF (16%), PIK3CA (4%), PTEN (14%) and TP53 (51%). In patients younger than 50 years (n = 45), PIK3CA mutations were not observed and TP53 mutations were more frequent than in the older age groups. The total gene mutation index was lowest in tumors from the youngest patients. In contrast, the genome complexity, assessed as copy number aberrations, was highest in tumors from the youngest patients. A comparable number of tumors from young (<50 years) and old patients (>70 years) was quadruple negative for the four predictive gene markers (KRAS-BRAF-PIK3CA-PTEN); however, 16% of young versus only 1% of the old patients had tumor mutations in PTEN/PIK3CA exclusively. This implies that mutation testing for prediction of EGFR treatment response may be restricted to KRAS and BRAF in elderly (>70 years) patients. Distinct genetic differences found in tumors from young and elderly patients, whom are comparable for known clinical and pathological variables, indicate that young patients have a different genetic risk profile for CRC development than older patients.     

Capacity and Adaptations of General Practice during an Influenza Pandemic

Background

GPs play a major role in influenza epidemics, and most patients with influenza-like-illness (ILI) are treated in general practice or by primary care doctors on duty in out-of-hours services (OOH). Little is known about the surge capacity in primary care services during an influenza pandemic, and how the relationship between them changes.

Aim

To investigate how general practice and OOH services were used by patients during the 2009 pandemic in Norway and the impact of the pandemic on primary care services in comparison to a normal influenza season.

Materials

Data from electronic remuneration claims from all OOH doctors and regular GPs for 2009.

Methods

We conducted a registry-based study of all ILI consultations in the 2009 pandemic with the 2008/09 influenza season (normal season) as baseline for comparison.

Results

The majority (82.2%) of ILI consultations during the 2009 pandemic took place in general practice. The corresponding number in the 2008/09 season was 89.3%. Compared with general practice, the adjusted odds ratio for ILI with all other diagnoses as reference in OOH services was 1.23 (95% CI, 1.18, 1.27) for the 2008/2009 season and 1.87 (95% CI, 1.84, 1.91) for the pandemic influenza season. In total there was a 3.3-fold increase in ILI consultations during the pandemic compared to the 2008/09 season. A 5.5-fold increase of ILI consultations were observed in OOH services in comparison to the 2008/09 season. Children and young adults with ILI were the most frequent users of OOH services during influenza periods.

Conclusions

The autumn pandemic wave resulted in a significantly increased demand on primary care services. However, GPs in primary care services in Norway showed the ability to increase capacity in a situation with increased patient demand.