Hypothesis: can N-acetylcysteine be beneficial in Parkinson's disease?

Based on the finding of decreased mitochondrial complex I activity in the substantia nigra of patients with Parkinson's disease, we propose that the consequent reduction of ATP synthesis and increased generation of reactive oxygen species may be a possible cause of nigrostriatal cell death. Since sulfhydryl groups are essential in oxidative phosphorylation, thiolic antioxidants may contribute to the preservation of these proteins against oxidative damage. In the present paper, we hypothesize that treatment with a sulfur-containing antioxidant such as N-acetylcysteine may provide a new neuroprotective therapeutic strategy for Parkinson's disease.     

Can promotion of initiated cells be explained by excess replacement of radiation-inactivated neighbor cells?

Recently, the observed promotion in the clonal expansion of a two-stage cancer model was attributed to a small excess replacement probability for the initiated cells. The proposed mechanism of excess replacement was evaluated for single intermediate cells surrounded by normal cells. This paper investigates this mechanism further using the same biological parameters. If the formation of clones of intermediate cells is taken into account in a quantitative analysis of the proposed mechanism, it turns out that (1) for the initial strong increase of the promotional effect with exposure, a much larger and unlikely excess replacement probability is needed, and (2) the leveling of the promotional effect for high exposures cannot be explained by multiple normal neighbors of an intermediate cell being inactivated within one cell cycle, as it had been suggested. Perhaps these discrepancies could be partly resolved by a re-scaling of the original parameters, but this should be investigated further.     

Basal metabolic rate of endotherms can be modeled using heat-transfer principles and physiological concepts: reply to "can the basal metabolic rate of endotherms be explained by biophysical modeling?"

Our recent article (Roberts et al. 2010 ) proposes a mechanistic model for the relation between basal metabolic rate (BMR) and body mass (M) in mammals. The model is based on heat-transfer principles in the form of an equation for distributed heat generation within the body. The model can also be written in the form of the allometric equation BMR = aM(b), in which a is the coefficient of the mass term and b is the allometric exponent. The model generates two interesting results: it predicts that b takes the value 2/3, indicating that BMR is proportional to surface area in endotherms. It also provides an explanation of the physiological components that make up a, that is, respiratory heat loss, core-skin thermal conductance, and core-skin thermal gradient. Some of the ideas in our article have been questioned (Seymour and White 2011 ), and this is our response to those questions. We specifically address the following points: whether a heat-transfer model can explain the level of BMR in mammals, whether our test of the model is inadequate because it uses the same literature data that generated the values of the physiological variables, and whether geometry and empirical values combine to make a "coincidence" that makes the model only appear to conform to real processes.     

Spillover effects of retirement: Does health vulnerability matter?

The current literature investigating the impact of retirement and the associated spousal spillover effects overlooks the unintended effects of retirement on spouses in vulnerable health, namely spouses with long-term health conditions (LTHCs). In this paper, we fill this gap in the literature and investigate the impact of an individual’s retirement on their partner’s health outcomes when their partner has LTHCs. Given the inherent identification challenges associated with entry into retirement, we use the pension-qualifying age in Australia as an instrument. Based on data from the Household Income and Labour Dynamics in Australia survey, we find that the husband’s retirement has a positive impact on the wife’s quality-adjusted life years (QALY) and other physical and mental health outcomes. We also identify redistribution of domestic workload as a key transmission mechanism of the spousal spillover effects. Women with LTHCs will see their QALY and health improve only if their husband devotes more time to domestic tasks after retirement.     

Can the negative plant–soil feedback of Jacobaea vulgaris be explained by autotoxicity?

Field and bioassay studies with Jacobaea vulgaris (ragwort) have shown that plants grow poorly in soil originating from the rhizosphere of this species and that this can influence the dynamics of ragwort populations during secondary succession. In the present study we examined whether the negative effect of ragwort on conspecifics may be due to autotoxicity. First, we experimentally established that ragwort exerts negative plant–soil feedback. We subsequently examined the inhibitory effects on germination and seedling performance of different strengths of aqueous extracts made from shoot and root tissues of ragwort, and from soil in which ragwort had been growing. The effects of the extracts were tested for seedlings growing in sterilised soil or in glass beads with water. Finally, the inhibitory effect of entire root fragments on seedling performance was tested. We observed that performance of seedlings growing in glass beads was significantly reduced by the high and medium strength root and shoot extracts. Extracts made from soil did not differ significantly from the control, and seedlings growing in sterilised soil were also not affected by ragwort extracts. Seed germination was significantly reduced by the high strength shoot extract only. The root length of seedlings growing in water with root fragments was reduced significantly. We conclude that under laboratory conditions ragwort can be autotoxic and discuss the role that autotoxicity may play in influencing the dynamics of ragwort populations during secondary succession.     

Hot male: can sex in humans be modified by temperature?

Sex determination in many animals has an environmental component, particularly through temperature. In this article, it is argued that some evidence may by seen for this in humans, and it is proposed that the influence of temperature on sex determination may be a reason for the placing of testicles outside the body cavity in most male mammals.     

Plasma membrane: Can its structure and function be modulated by dietary fat?

• 1.1. Compositional analysis of plasma membranes from rats fed nutritionally adequate diets different in fatty acid composition establishes that fundamentally different dietary fat intake results in alteration in structural lipid composition of plasma membranes in brain, liver and the intestinal mucosa.
• 2.2. Dietary differences in fatty acid intake altered the fatty acyl tail composition of plasma membrane phospholipids in brain, liver and intestinal mucosa.
• 3.3. Diet altered the phospholipid profile observed in brain synaptosomal and liver plasma membrane.
• 4.4. Feeding high vs low polyunsaturated to saturated fat diets for 7 days altered the fatty acid composition of phosphatidylcholine, phosphatidylethanolamine, sphingomyelin and mono-glucosylceramide isolated from plasma membrane of the intestinal mucosa

     

Use of fibrous diets by small herbivores: How far can the rules be 'bent'?

Allometric considerations suggest that small mammals should be unable to eat highly fibrous diets. A combination of the selective and more rapid passage of fibrous material through the gut, together with changes in gut capacity when energy requirements increase, may allow small mammals to escape these allometric constraints. Recent evidence that birds can absorb essential amino acids from the caecum (which has hitherto been considered insignificant in mammals) suggests that birds and mammals have evolved very different ways to be a herbivore.     

The prognosis of latent tuberculosis: can disease be predicted?

In humans, Mycobacterium tuberculosis persists for long periods in a clinically latent state, creating a huge reservoir of 'silent' tuberculosis (TB) (roughly one-third of the global population) from which new cases continually arise. A prognostic marker for active TB would enable targeted treatment of the small fraction of infected individuals who are most at risk of developing contagious TB, contributing greatly to TB control efforts. Here, we propose that TB-specific interferon-gamma release assays might be useful for identifying individuals with progressive infections who are likely to develop the disease. This might provide an unprecedented advantage for TB control, namely targeted preventive therapy for individuals who are most at risk of developing active contagious TB.     

Contrasting effects of hemiparasites on ecosystem processes: can positive litter effects offset the negative effects of parasitism?

Hemiparasites are known to influence community structure and ecosystem functioning, but the underlying mechanisms are not well studied. Variation in the impacts of hemiparasites on diversity and production could be due to the difference in the relative strength of two interacting pathways: direct negative effects of parasitism and positive effects on N availability via litter. Strong effects of parasitism should result in substantial changes in diversity and declines in productivity. Conversely, strong litter effects should result in minor changes in diversity and increased productivity. We conducted field-based surveys to determine the association of Castilleja occidentalis with diversity and productivity in the alpine tundra. To examine litter effects, we compared the decomposition of Castilleja litter with litter of four other abundant plant species, and examined the decomposition of those four species when mixed with Castilleja. Castilleja was associated with minor changes in diversity but almost a twofold increase in productivity and greater foliar N in co-occurring species. Our decomposition trials suggest litter effects are due to both the rapid N loss of Castilleja litter and the effects of mixing Castilleja litter with co-occurring species. Castilleja produces litter that accelerates decomposition in the alpine tundra, which could accelerate the slow N cycle and boost productivity. We speculate that these positive effects of litter outweigh the effects of parasitism in nutrient-poor systems with long-lived hemiparasites. Determining the relative importance of parasitism and litter effects of this functional group is crucial to understand the strong but variable roles hemiparasites play in affecting community structure and ecosystem processes.     

Can the extinction of Melitaea britomartis in NW Italy be explained by unfavourable weather? An analysis by Optimal Interpolation

We investigated possible correlations between climate-related factors and butterfly range restrictions by selecting a study case represented by four populations of Melitaea britomartis, which become ‘simultaneously’ extinct in NW Italy in 1976–1977 without any observable habitat change. To overcome difficulties related to the analysis of past extinctions and hypothesise causal factors, we applied the Optimal Interpolation method, a statistical method used to create a gridded climatological analysis of temperature and precipitation data, to a historical dataset containing all available information on the Italian butterfly fauna. We tested two different hypotheses: (1) the role of climate change, expressed as a general trend in temperature and precipitation data; (2) the role of extreme weather events, expressed as anomalous conditions during the years of extinctions. Our results show that long-term temperature and precipitation data do not present any clear trend at our study site, suggesting that they cannot be involved in the species’ extinction. On the opposite, 1976 and 1977 were climatologically critical for the study area. In particular, 1977 was characterized by the coldest summer in the entire historical dataset (1958–1977), with strong negative temperature anomalies. Moreover, both years experienced unusually many rainy days during spring and summer. The year 1977 in particular, was the wettest within the entire historical dataset. The years of M. britomartis populations’ extinction were characterised by many more cold and rainy days than usual during the species’ flight period. These results allow us to hypothesize a strong component of unfavourable weather in driving populations’ extinction.     

Could the improvements in the alcoholic fermentation of high glucose concentrations by yeast immobilization be explained by media supplementation?

Summary The maximal concentration of ethanol produced during the fermentation of 320 g/l glucose bySaccharomyces bayanus was higher when the yeast cells were immobilized either by adsorption on celite or by entrapment in k-carrageenan beads (from 10.5% with free cells up to 14.5% and 13.1% (v/v) respectively). This increase was due to medium supplementation with the compounds present in the immobilization supports.