Decomposition Patterns of Foliar Litter and Deadwood in Managed and Unmanaged Stands: A 13-Year Experiment in Boreal Mixedwoods

Litter decomposition is a major driver of carbon (C) and nitrogen (N) cycles in forest ecosystems and has major implications for C sequestration and nutrient availability. However, empirical information regarding long-term decomposition rates of foliage and wood remains rare. In this study, we assessed long-term C and N dynamics (12–13 years) during decomposition of foliage and wood for three boreal tree species, under a range of harvesting intensities and slash treatments. We used model selection based on the second-order Akaike’s Information Criterion to determine which decomposition model had the most support. The double-exponential model provided a good fit to C mass loss for foliage of trembling aspen, white spruce, and balsam fir, as well as aspen wood. These litters underwent a rapid initial phase of leaching and mineralisation, followed by a slow decomposition. In contrast, for spruce and fir wood, the single-exponential model had the most support. The long-term average decay rate of wood was faster than that of foliage for aspen, but not of conifers. However, we found no evidence that fir and spruce wood decomposed at slower rates than the recalcitrant fraction of their foliage. The critical C:N ratios, at which net N mineralisation began, were higher for wood than for foliage. Long-term decay rates following clear-cutting were either similar or faster than those observed in control stands, depending on litter material, tree species, and slash treatment. The critical C:N ratios were reached later and decreased for all conifer litters following stem-only clear-cutting, indicating increased N retention in harvested sites with high slash loads. Partial harvesting had weak effects on C and N dynamics of decaying litters. A comprehensive understanding of the long-term patterns and controls of C and N dynamics following forest disturbance would improve our ability to forecast the implications of forest harvesting for C sequestration and nutrient availability.     

Interaction of ACTH, beta-endorphin and alpha-melanocyte stimulating hormone in relation to the corticosteroid production of isolated rat adrenocortical zona fasciculata and zona glomerulosa cells.

The combined effects of ACTH, beta-endorphin (beta-EP) and alpha-MSH were studied on the corticosteroidogenesis of isolated rat adrenocortical zona fasciculata and zona glomerulosa cells. beta-EP potentiated the effects of ACTH and alpha-MSH on the zona fasciculata corticosterone production but inhibited those on the zona glomerulosa aldosterone production. beta-EP did not affect the combined action of 4 x 10(-11) M ACTH and 5 x 10(-9) M alpha-MSH on the zona fasciculata or the zona glomerulosa cells, but it inhibited the stimulatory action of the combination of 1.6 x 10(-10) M ACTH and 10(-9) M alpha-MSH on the zona glomerulosa aldosterone production. An interaction of ACTH, beta-EP and alpha-MSH in relation to the zona fasciculata and zona glomerulosa corticosteroid production was found.     

Incomplete mitophagy in the mevalonate kinase-deficient Saccharomyces cerevisiae and its relation to the MKD-related autoinflammatory disease in humans

Mevalonate kinase deficiency (MKD) is an autosomal recessive disorder in humans that causes systemic autoinflammatory problems to children. Previously, we used a yeast model to show that MKD results in mitochondrial malfunctioning that may finally induce mitophagy. Here, we proved that MKD indeed induced general autophagy as well as mitophagy in yeast, but these mechanisms did not go to completion. Therefore, the limitation of mevalonate kinase activity produces dysfunctional mitochondria that might not be recycled, causing metabolic dysfunctions in the cells. Understanding this mechanism may provide a piece in solving the nonspecific autoinflammatory response puzzle observed in MKD patients.     

Role of Prostate Apoptosis Response 4 in Translocation of GRP78 from the Endoplasmic Reticulum to the Cell Surface of Trophoblastic Cells

Glucose-regulated protein 78 (GRP78) is an endoplasmic reticulum (ER) molecular chaperone that belongs to the heat shock protein 70 family. GRP78 is also present on the cell surface membrane of trophoblastic cells, where it is associated with invasive or fusion properties of these cells. Impaired mechanism of GRP78 relocation from ER to the cell surface was observed in preeclamptic cytotrophoblastic cells (CTB) and could take part in the pathogenesis of preeclampsia. In this study, we have investigated whether prostate apoptosis response 4 (Par-4), a protein identified as a partner of GRP78 relocation to the cell surface in prostate cancer cells, is present in trophoblastic cells and is involved in the translocation of GRP78 to the cell surface of CTB. Par-4 is indeed present in trophoblastic cells and its expression correlates with expression of membrane GRP78. Moreover, overexpression of Par-4 led to an increase of cell surface expression of GRP78 and decreased Par-4 gene expression reduced cell surface localization of GRP78 confirming a role of Par-4 in relocation of GRP78 from ER to the cell surface. Accordingly, invasive property was modified in these cells. In conclusion, we show that Par-4 is expressed in trophoblastic cells and is involved in transport of GRP78 to the cell surface and thus regulates invasive property of extravillous CTB.     

Exposure to nectar-realistic sugar concentrations negatively impacts the ability of the trypanosome parasite (Crithidia bombi) to infect its bumblebee host

1. The ideal conditions for a parasite are typically found with its preferred host. However, prior to transmission to a naïve host and successful infection, a parasite may have to withstand extrinsic environmental conditions. Some parasites have adapted to time away from hosts, for example, by co-opting vectors or by having drought-resistant growth stages. However, other parasites may have no obvious adaptations to persist during prolonged transmission cycles. Consequently, the environment may detrimentally impact parasite fitness and ultimately epidemiology. 2. Here, we investigate the impact of nectar-realistic sugar concentrations on the ability of the trypanosome parasite Crithidia bombi, which may be transmitted between conspecifics at flowers, to infect its bumblebee host Bombus terrestris and to reproduce during the infection (parasitaemia). Our results show, following 30 min exposure to our experimental nectars that as sugar concentration increases, infection prevalence and parasitaemia decrease. This is likely due to the increased osmotic stress C. bombi experiences in high sugar, aqueous environments. 3. Consequently, if C. bombi transmission is facilitated by nectar or a high-sugar environment, it may have a negative impact on parasite fitness.     

Etiology and Epidemiology of Diarrhea in Hospitalized Children from Low Income Country: A Matched Case-Control Study in Central African Republic

Background

In Sub-Saharan Africa, infectious diarrhea is a major cause of morbidity and mortality. A case-control study was conducted to identify the etiology of diarrhea and to describe its main epidemiologic risk factors among hospitalized children under five years old in Bangui, Central African Republic.

Methods

All consecutive children under five years old hospitalized for diarrhea in the Pediatric Complex of Bangui for whom a parent’s written consent was provided were included. Controls matched by age, sex and neighborhood of residence of each case were included. For both cases and controls, demographic, socio-economic and anthropometric data were recorded. Stool samples were collected to identify enteropathogens at enrollment. Clinical examination data and blood samples were collected only for cases.

Results

A total of 333 cases and 333 controls was recruited between December 2011 and November 2013. The mean age of cases was 12.9 months, and 56% were male. The mean delay between the onset of first symptoms and hospital admission was 3.7 days. Blood was detected in 5% of stool samples from cases. Cases were significantly more severely or moderately malnourished than controls. One of the sought-for pathogens was identified in 78% and 40% of cases and controls, respectively. Most attributable cases of hospitalized diarrhea were due to rotavirus, with an attributable fraction of 39%. Four other pathogens were associated with hospitalized diarrhea: Shigella/EIEC, Cryptosporidium parvum/hominis, astrovirus and norovirus with attributable fraction of 9%, 10%, 7% and 7% respectively. Giardia intestinalis was found in more controls than cases, with a protective fraction of 6%.

Conclusions

Rotavirus, norovirus, astrovirus, Shigella/EIEC, Cryptosporidium parvum/hominis were found to be positively associated with severe diarrhea: while Giardia intestinalis was found negatively associated. Most attributable episodes of severe diarrhea were associated with rotavirus, highlighting the urgent need to introduce the rotavirus vaccine within the CAR’s Expanded Program on Immunization. The development of new medicines, vaccines and rapid diagnostic tests that can be conducted at the bedside should be high priority for low-resource countries.     

Impact of genetic variations in ADORA2A gene on depression and symptoms: a cross-sectional population-based study

Purinergic Signalling - Genetic variants involved in adenosine metabolism and its receptors were associated with increased risk for psychiatric disorders, including anxiety, depression, and...