Resource quality and stoichiometric constraints on stream ecosystem functioning

1. Resource quality and stoichiometric imbalances in carbon : nutrient ratios between consumers and resources can influence key ecosystem processes. In many streams, this has important implications for food webs that are based largely upon the utilization of terrestrial leaf‐litter, which varies widely among litter types in its value as a food source for detritivores and as a substrate for microbial decomposers. 2. We measured breakdown rates and macroinvertebrate colonization of leaf‐litter from a range of native and exotic plants of differing resource quality and palatability to consumers [e.g. carbon : nitrogen : phosphorus (C : N : P) ratios, lignin and cellulose content], in a field experiment. We also measured C : N : P ratios of the principal leaf‐shredding invertebrates, which revealed strong stoichiometric imbalances across trophic levels: C : N and C : P ratios typically differed by at least one order of magnitude between consumers and resources, whereas N : P imbalances were less marked. Application of the threshold elemental ratio approach, which integrates animal bioenergetics and body elemental composition in examining nutrient deficiency between consumers and resources, revealed less marked C : P imbalances than those based on the simpler arithmetic differences described above. 3. Litter breakdown rates declined as nutrient imbalances widened and resource quality fell, but they were independent of whether resources were exotic or native. The principal drivers of total, microbial and invertebrate‐mediated breakdown rates were lignin : N, lignin : P and fungal biomass, respectively. However, multiple regression using orthogonal predictors yielded even more efficient models of litter breakdown, as consumers responded to more than one aspect of resource quality. For example, fungal biomass and litter C : N both influenced invertebrate‐mediated breakdown. 4. Large stoichiometric imbalances and changes in resource quality are likely to have serious consequences for stream ecosystem functioning, especially when riparian zones have been invaded by exotic plant species whose chemical composition differs markedly from that of the native flora. Consequently, the magnitude and direction of change in breakdown rates and, thus, resource depletion, will be driven to a large extent by the biochemical traits (rather than taxonomic identity per se) of the resident and invading flora.     

Ethyl-EPA in Alzheimer's disease--a pilot study

This pilot study of ethyl-eicosapentaenoate (ethyl-EPA) in the treatment of Alzheimer's disease aimed to estimate the magnitude of any change in measures of cognition during a 12-week treatment period. A simple linear design was used in which each patient had a baseline period of 12 weeks without treatment, followed by 12 weeks' treatment with ethyl-EPA. Blood samples were taken both before and after the treatment period to measure erythrocyte membrane fatty acids. Assessments comprised cognitive measures and visual analogue ratings of overall assessment of functioning. There was little difference between treatment and baseline periods in the rate of decline of efficacy measures, except for a small improvement in carer's visual analogue rating (P=0.02). It was concluded that it is unlikely there were any clinically important treatment effects of ethyl-EPA on cognition during the 12-week treatment period. A longer treatment period may be necessary to demonstrate efficacy of ethyl-EPA in this disorder.     

Phylogenetic analyses identify 10 classes of the protein disulfide isomerase family in plants, including single-domain protein disulfide isomerase-related proteins

Protein disulfide isomerases (PDIs) are molecular chaperones that contain thioredoxin (TRX) domains and aid in the formation of proper disulfide bonds during protein folding. To identify plant PDI-like (PDIL) proteins, a genome-wide search of Arabidopsis (Arabidopsis thaliana) was carried out to produce a comprehensive list of 104 genes encoding proteins with TRX domains. Phylogenetic analysis was conducted for these sequences using Bayesian and maximum-likelihood methods. The resulting phylogenetic tree showed that evolutionary relationships of TRX domains alone were correlated with conserved enzymatic activities. From this tree, we identified a set of 22 PDIL proteins that constitute a well-supported clade containing orthologs of known PDIs. Using the Arabidopsis PDIL sequences in iterative BLAST searches of public and proprietary sequence databases, we further identified orthologous sets of 19 PDIL sequences in rice (Oryza sativa) and 22 PDIL sequences in maize (Zea mays), and resolved the PDIL phylogeny into 10 groups. Five groups (I-V) had two TRX domains and showed structural similarities to the PDIL proteins in other higher eukaryotes. The remaining five groups had a single TRX domain. Two of these (quiescin-sulfhydryl oxidase-like and adenosine 5'-phosphosulfate reductase-like) had putative nonisomerase enzymatic activities encoded by an additional domain. Two others (VI and VIII) resembled small single-domain PDIs from Giardia lamblia, a basal eukaryote, and from yeast. Mining of maize expressed sequence tag and RNA-profiling databases indicated that members of all of the single-domain PDIL groups were expressed throughout the plant. The group VI maize PDIL ZmPDIL5-1 accumulated during endoplasmic reticulum stress but was not found within the intracellular membrane fractions and may represent a new member of the molecular chaperone complement in the cell.     

Ancylostoma caninum: the finger cell neurons mediate thermotactic behavior by infective larvae of the dog hookworm

Bhopale, V. M., Kupprion, E. K., Ashton, F. T., Boston, R., and Schad, G. A. 2001. Ancylostoma caninum: The finger cell neurons mediate thermotactic behavior by infective larvae of the dog hookworm. Experimental Parasitology 97, 70-76. In the amphids (anteriorly positioned, paired sensilla) of the free-living nematode Caenorhabditis elegans, the so-called finger cells (AFD), a pair of neurons, each of which ends in a cluster of microvilli-like projections, are known to be the primary thermoreceptors. A similar neuron pair in the amphids of the parasitic nematode Haemonchus contortus is also known to be thermoreceptive. The hookworm of dogs, Ancylostoma caninum, has apparent structural homologs of finger cells in its amphids. The neuroanatomy of the amphids of A. caninum and H. contortus is strikingly similar, and the amphidial cell bodies in the lateral ganglia of the latter nematode have been identified and mapped. When the lateral ganglia of first-stage larvae (L1) of A. caninum are examined with differential interference contrast microscopy, positional homologs of the recognized amphidial cell bodies in the lateral ganglia of H. contortus L1 are readily identified in A. caninum. The amphidial neurons in A. caninum were consequently given the same names as those of their apparent homologs in H. contortus. It was hypothesized that the finger cell neurons (AFD) might mediate thermotaxis by the skin-penetrating infective larvae (L3) of A. caninum. Laser microbeam ablation experiments with A. caninum were conducted, using the H. contortus L1 neuronal map as a guide. A. caninum L1 were anesthetized and the paired AFD class neurons were ablated. The larvae were then cultured to L3 and assayed for thermotaxis on a thermal gradient. L3 with ablated AFD-class neuron pairs showed significantly reduced thermotaxis compared to control groups. The thermoreceptive function of the AFD-class neurons associates this neuron pair with the host-finding process of the A. caninum infective larva and shows functional homology with the neurons of class AFD in C. elegans and in H. contortus.     

Parakaketio longiprostatus gen. et sp.n., a Marine Tubificid (Oligochaeta) from Florida, U.S.A.

Parakaketio longiprostatus sp.n. is described from shallow marine water in S.E. Florida. The male ducts of the new genus Parakaketio resemble those of Kaketio Righi & Kanner, 1979, but do not end as voluminous, eversible pseudopenes, rather as simple tubes opening directly to the exterior through simple pores.     

Predicting Outcome on Admission and Post-Admission for Acetaminophen-Induced Acute Liver Failure Using Classification and Regression Tree Models

Background/Aim

Assessing prognosis for acetaminophen-induced acute liver failure (APAP-ALF) patients often presents significant challenges. King’s College (KCC) has been validated on hospital admission, but little has been published on later phases of illness. We aimed to improve determinations of prognosis both at the time of and following admission for APAP-ALF using Classification and Regression Tree (CART) models.

Methods

CART models were applied to US ALFSG registry data to predict 21-day death or liver transplant early (on admission) and post-admission (days 3-7) for 803 APAP-ALF patients enrolled 01/1998–09/2013. Accuracy in prediction of outcome (AC), sensitivity (SN), specificity (SP), and area under receiver-operating curve (AUROC) were compared between 3 models: KCC (INR, creatinine, coma grade, pH), CART analysis using only KCC variables (KCC-CART) and a CART model using new variables (NEW-CART).

Results

Traditional KCC yielded 69% AC, 90% SP, 27% SN, and 0.58 AUROC on admission, with similar performance post-admission. KCC-CART at admission offered predictive 66% AC, 65% SP, 67% SN, and 0.74 AUROC. Post-admission, KCC-CART had predictive 82% AC, 86% SP, 46% SN and 0.81 AUROC. NEW-CART models using MELD (Model for end stage liver disease), lactate and mechanical ventilation on admission yielded predictive 72% AC, 71% SP, 77% SN and AUROC 0.79. For later stages, NEW-CART (MELD, lactate, coma grade) offered predictive AC 86%, SP 91%, SN 46%, AUROC 0.73.

Conclusion

CARTs offer simple prognostic models for APAP-ALF patients, which have higher AUROC and SN than KCC, with similar AC and negligibly worse SP. Admission and post-admission predictions were developed.

Key Points

• Prognostication in acetaminophen-induced acute liver failure (APAP-ALF) is challenging beyond admission• Little has been published regarding the use of King’s College Criteria (KCC) beyond admission and KCC has shown limited sensitivity in subsequent studies• Classification and Regression Tree (CART) methodology allows the development of predictive models using binary splits and offers an intuitive method for predicting outcome, using processes familiar to clinicians• Data from the ALFSG registry suggested that CART prognosis models for the APAP population offer improved sensitivity and model performance over traditional regression-based KCC, while maintaining similar accuracy and negligibly worse specificity• KCC-CART models offered modest improvement over traditional KCC, with NEW-CART models performing better than KCC-CART particularly at late time points     

The spatial ecology of the whiskered bat (Myotis mystacinus) at the western extreme of its range provides evidence of regional adaptation

Although widespread, the ecology of the whiskered bat, Myotis mystacinus in Europe remains poorly understood. Ireland is positioned at the most western extreme of this species’ range. To ascertain the ecology of M. mystacinus at its geographic range extreme, the roosting behaviour, home range and habitat use of females in a maternity roost in Ireland was investigated by radio-tracking. M. mystacinus were active in a diversity of habitats: namely, mixed woodland, riparian vegetation, arable land and rough grassland. However, only mixed woodland and riparian habitats were selected as core foraging areas. This is in contrast to a previous study from Britain where only pasture was utilised but is in agreement with data from Slovakia, where woodland was also selected, whilst riparian areas were also utilised by this species in Germany. A high degree of overlap in the foraging areas of individuals was observed. A total of seven roosts were utilised by tracked bats and roost switching behaviour was observed. We discuss our contrasting results in respect to range limitations, regional variability in landscape structure and the composition of bat communities. The present results have implications for the conservation of M. mystacinus within Ireland and other parts of its range, highlighting the need for range wide ecological studies. Regional variability in the ecology of bats related to landscape factors is an important consideration for bat conservation and therefore must be incorporated into future management plans.     

Comparison of ticarcillin and piperacillin in Kenney's semen extender

Ticarcillin and piperacillin were compared to determine their effect on sperm motility and bacterial growth of equine semen samples diluted in Kenney's glucose skim milk semen extender. Each ejaculate (n=11) was divided into three portions and glucose skim milk semen extender solution was added. The control semen extender solution contained extended semen and no antibiotic, whereas ticarcillin and piperacillin solutions contained extended semen plus 1.0mg/mL of ticarcillin or piperacillin, respectively. An aliquot was removed (1h after collection) to evaluate sperm motility and microbial concentration. All three solutions were stored at 4 degrees C and aliquots were obtained at 24 and 48 h to determine sperm motility and microbial concentration. Mean percentages of motile and progressively motile sperm did not differ significantly among control and antibiotic-containing solutions after storage. Control-extended semen samples from ejaculates of stallions (n=11) were contaminated with aerobic gram-positive and gram-negative bacteria. In solutions that contained either antibiotic, growth of these microbes was inhibited after 1, 24, and 48 h at 4 degrees C. Semen samples from stallions (n=5) were extended with Kenney's glucose skim milk extender containing no antibiotic, ticarcillin or piperacillin and then inoculated with approximately 5 x 10(2)CFU/mL Klebsiella pneumoniae or Pseudomonas aeruginosa; there was no significant difference between antibiotics in the inhibition of microbial growth. In conclusion, piperacillin was an appropriate alternative to ticarcillin in extenders for equine semen.