Above- and belowground carbon inputs affect seasonal variations of soil microbial biomass in a subtropical monsoon forest of southwest China

Soil microbial activity drives carbon and nutrient cycling in terrestrial ecosystems. Soil microbial biomass is commonly limited by environmental factors and soil carbon availability. We employed plant litter removal, root trenching and stem-girdling treatments to examine the effects of environmental factors, above- and belowground carbon inputs on soil microbial C in a subtropical monsoon forest in southwest China. During the experimental period from July 2006 through April 2007, 2 years after initiation of the treatments, microbial biomass C in the humus layer did not vary with seasonal changes in soil temperature or water content. Mineral soil microbial C decreased throughout the experimental period and varied with soil temperature and water content. Litter removal reduced mineral soil microbial C by 19.0% in the ungirdled plots, but only 4.0% in girdled plots. Root trenching, stem girdling and their interactions influenced microbial C in humus layer. Neither root trenching nor girdling significantly influenced mineral soil microbial C. Mineral soil microbial C correlated with following-month plant litterfall in control plots, but these correlations were not observed in root-trenching plots or girdling plots. Our results suggest that belowground carbon retranslocated from shoots and present in soil organic matter, rather than aboveground fresh plant litter inputs, determines seasonal fluctuation of mineral soil microbial biomass.     

Host surveys, ixodid tick biology and transmission scenarios as related to the tick-borne pathogen, Ehrlichia canis

The ehrlichioses have been subject to increasing interest from veterinary and public health perspectives, but experimental studies of these diseases and their etiologic agents can be challenging. Ehrlichia canis, the primary etiologic agent of canine monocytic ehrlichiosis, is relatively well characterized and offers unique advantages and opportunities to study interactions between a monocytotropic pathogen and both its vertebrate and invertebrate hosts. Historically, advances in tick-borne disease control strategies have typically followed explication of tick-pathogen-vertebrate interactions, thus it is reasonable to expect novel, more sustainable approaches to control of these diseases as the transmission of their associated infections are investigated at the molecular through ecological levels. Better understanding of the interactions between E. canis and its canine and tick hosts would also elucidate similar interactions for other Ehrlichia species as well as the potential roles of canine sentinels, reservoirs and models of tick-borne zoonoses. This article summarizes natural exposure studies and experimental investigations of E. canis in the context of what is understood about biological vectors of tick-borne Anaplasmataceae.     

Quantification of plasma DNA as a prognostic indicator in canine lymphoid neoplasia

Dogs have a similar incidence of spontaneous cancers as people, and a noninvasive test to monitor disease status in dogs would be of great value. Humans with cancer often have increased levels of cell‐free circulating DNA in their plasma, which has shown promise for diagnosis, prognosis and detection of residual disease. We hypothesized that dogs with cancer have increased circulating DNA compared with healthy dogs or dogs with non‐neoplastic diseases. Plasma DNA was measured in 40 healthy dogs, 20 dogs with non‐neoplastic diseases and 80 dogs with cancer. The reference interval for plasma DNA in healthy dogs was 1–15 ng mL^?1. Dogs with lymphoma and lymphoid leukaemia had significantly higher concentrations (range: 0–91 ng mL^?1, P < 0.0001). Antigen receptor rearrangement assays suggest that plasma DNA had the same clonality as the primary lymphoid tumours. Dogs with lymphoid neoplasia and plasma DNA >25 ng mL^?1 had shorter remission times than those with < 25 ng mL^?1 (P= 0.0116). In contrast to humans, where increased plasma DNA is seen in many diseases, dogs with nonlymphoid malignancies and non‐neoplastic diseases had plasma DNA concentrations similar to healthy dogs. This study shows that a portion of dogs with lymphoid neoplasia have increased tumour‐derived plasma DNA, which serves as a negative prognostic indicator.     

The effects of mutated skeletal ryanodine receptors on hypothalamic-pituitary-adrenal axis function in boars

The objectives of the current experiment were to determine whether boars heterozygous for the mutation in skeletal ryanodine receptors (sRyR), known to cause porcine stress syndrome, differed from wild-type boars in hypothalamic-pituitary-adrenal axis (HPA) function. We have examined basal plasma ACTH, cortisol, and corticosteroid-binding globulin (CBG) concentrations; plasma ACTH and cortisol responses to a nose-snare stressor and at slaughter; dexamethasone suppression of plasma ACTH and cortisol concentrations; and glucocorticoid receptor (GR) density in the pituitary gland, hippocampus, hypothalamus, and frontal cortex. We have also examined carcass yields, composition, and meat quality to determine whether differences in HPA activity were accompanied by an increased incidence of meat quality characteristics associated with pale, soft, exudative (PSE) meat. Thirty boars either heterozygous or wild-type (n = 15 per genotype) for mutated sRyR were tested for HPA function at 7 mo of age. Heterozygous boars had lower basal plasma ACTH (P < .05) and cortisol (P < .04) concentrations. Integrated basal plasma ACTH and cortisol levels were also lower (P < .05 and P < .005, respectively). Genotype had no significant effect on basal CBG, stressor-induced (nose snare or slaughter) or dexamethasone suppression of plasma ACTH or cortisol concentrations. No differences in immunoreactive GR levels were found in the pituitary gland or any brain region examined. We did find a significant, negative correlation (r = -.62, P < .02) between peak (0800) basal plasma ACTH concentrations and hippocampal GR levels. The alterations in basal HPA function in heterozygous boars were accompanied by lighter body weights (P < .03), decreased carcass fat depth (P < .04), and increased carcass lean yields (P < .02). There was a higher incidence of meat quality characteristics associated with PSE meat in heterozygous boars indicated by higher carcass temperatures (P < .04) and meat brightness (P < .0001) with lower carcass pH at slaughter (P < .03) and after chilling (P < .003). In conclusion, we have found differences in basal and not stressor-induced HPA function between boars heterozygous and wild-type for mutated sRyR. This altered basal HPA activity was accompanied by an increased incidence of meat quality aspects associated with PSE meat in heterozygous boars.     

Physicochemical Properties of Rice Endosperm Proteins Extracted by Chemical and Enzymatic Methods

Rice proteins are nutritional, hypoallergenic, and healthy for human consumption. Efficient extraction with approved food‐grade enzymes and chemicals are essential for commercial production and application of rice protein as a functional ingredient. Rice endosperm proteins were isolated by alkali, salt, and enzymatic methods and evaluated for extractability and physicochemical properties. Alkali (RP_A) and salt (RP_S) methods extracted 86.9 and 87.3% of proteins with 65.9 and 58.9% yield, respectively. The enzymatic methods with Termamyl (RP_ET) and amylase S (RP_EA) extracted 85.8 and 81.0% proteins with 85.2 and 86.2% yield, respectively. Enthalpy values of RP_A (1.79 J/g), RP_S (1.22 J/g), RP_ET (nondetectable), and RP_EA (0.17 J/g), determined by differential scanning calorimetry, demonstrated that the varying level of denaturation of proteins depends on the method of extraction. Surface hydrophobicity data supported this observation. Alkali‐ and salt‐extracted proteins had higher solubility and emulsifying properties than those of enzyme‐extracted proteins. Comparatively, more favorable protein composition, lower surface hydrophobicity, higher solubility, and a lower degree of thermal denaturation of alkali‐ and salt‐extracted proteins contributed to higher emulsifying and foaming properties than those of enzyme‐extracted proteins; therefore, alkali‐ and salt‐extracted proteins can have enhanced functional use and a potential starting material for preparing tailored rice protein isolates.     

Volatiles from the 1994 Eruptions of Rabaul: Understanding Large Caldera Systems

The 1994 eruption of Rabaul, in Papua New Guinea, involved a small plinian eruption at Vulcan and a vulcanian eruption on the opposite side of the caldera at Tavurvur. Vulcan's ash leachates indicate seawater interaction that is consistent with earlier observations of low sulfur dioxide emissions and the presence of ice crystals in the initial plinian eruption cloud. In contrast, Tavurvur ash leachates indicate no seawater interaction, and later sulfur dioxide emissions remained high despite low-level eruptive activity. Silicic melt inclusions indicate that the andesitic melt contained about 2 weight percent water and negligible carbon dioxide. Mafic melt inclusions in Tavurvur ash have water and carbon dioxide contents that vary systematically over the course of the eruption. The mafic melt inclusions suggest that a mafic dike intruded from below the silicic chamber and provide further evidence that mafic intrusions drive caldera unrest.     

A stable silicon(0) compound with a Si=Si double bond

Dative, or nonoxidative, ligand coordination is common in transition metal complexes; however, this bonding motif is rare in compounds of main group elements in the formal oxidation state of zero. Here, we report that the potassium graphite reduction of the neutral hypervalent silicon-carbene complex L:SiCl4 {where L: is:C[N(2,6-Pri2-C6H3)CH]2 and Pri is isopropyl} produces L:(Cl)Si-Si(Cl):L, a carbene-stabilized bis-silylene, and L:Si=Si:L, a carbene-stabilized diatomic silicon molecule with the Si atoms in the formal oxidation state of zero. The Si-Si bond distance of 2.2294 +/- 0.0011 (standard deviation) angstroms in L:Si=Si:L is consistent with a Si=Si double bond. Complementary computational studies confirm the nature of the bonding in L:(Cl)Si-Si(Cl):L and L:Si=Si:L.