sirt1-null mice develop an autoimmune-like condition

The sirt1 gene encodes a protein deacetylase with a broad spectrum of reported substrates. Mice carrying null alleles for sirt1 are viable on outbred genetic backgrounds so we have examined them in detail to identify the biological processes that are dependent on SIRT1. Sera from adult sirt1-null mice contain antibodies that react with nuclear antigens and immune complexes become deposited in the livers and kidneys of these animals. Some of the sirt1-null animals develop a disease resembling diabetes insipidus when they approach 2 years of age although the relationship to the autoimmunity remains unclear. We interpret these observations as consistent with a role for SIRT1 in sustaining normal immune function and in this way delaying the onset of autoimmune disease.     

Lipid corrections in carbon and nitrogen stable isotope analyses: comparison of chemical extraction and modelling methods

1. Lipids have more negative delta(13)C values relative to other major biochemical compounds in plant and animal tissues. Although variable lipid content in biological tissues alters results and conclusions of delta(13)C analyses in aquatic food web and migration studies, no standard correction protocol exists. 2. We compared chemical extraction and mathematical correction methods for freshwater and marine fishes and aquatic invertebrates to better understand impacts of correction approaches on carbon (delta(13)C) and nitrogen (delta(15)N) stable isotope data. 3. Fish and aquatic invertebrate tissue delta(13)C values increased significantly following extraction for almost all species and tissue types relative to nonextracted samples. In contrast, delta(15)N was affected for muscle and whole body samples from only a few freshwater and marine species and had a limited effect for the entire data set. 4. Lipid normalization models, using C : N as a proxy for lipid content, predicted lipid-corrected delta(13)C for paired data sets more closely with parameters specific to the tissue type and species to which they were applied. 5. We present species- and tissue-specific models based on bulk C : N as a reliable alternative to chemical extraction corrections. By analysing a subset of samples before and after lipid extraction, models can be applied to the species and tissues of interest that will improve estimates of dietary sources using stable isotopes.     

Binding of phosphate and pyrophosphate ions at the active site of human angiogenin as revealed by X-ray crystallography

Human angiogenin (Ang) is an unusual homolog of bovine pancreatic RNase A that utilizes its ribonucleolytic activity to induce the formation of new blood vessels. The pyrimidine-binding site of Ang was shown previously to be blocked by glutamine 117, indicating that Ang must undergo a conformational change to bind and cleave RNA. The mechanism and nature of this change are not known, and no Ang-inhibitor complexes have been characterized structurally thus far. Here, we report crystal structures for the complexes of Ang with the inhibitors phosphate and pyrophosphate, and the structure of the complex of the superactive Ang variant Q117G with phosphate, all at 2.0 A resolution. Phosphate binds to the catalytic site of both Ang and Q117G in essentially the same manner observed in the RNase A-phosphate complex, forming hydrogen bonds with the side chains of His 13, His 114, and Gln 12, and the main chain of Leu 115; it makes an additional interaction with the Lys 40 ammonium group in the Ang complex. One of the phosphate groups of pyrophosphate occupies a similar position. The other phosphate extends toward Gln 117, and lies within hydrogen-bonding distance from the side-chain amide of this residue as well as the imidazole group of His 13 and the main-chain oxygen of Leu 115. The pyrimidine site remains obstructed in all three complex structures, that is, binding to the catalytic center is not sufficient to trigger the conformational change required for catalytic activity, even in the absence of the Gln 117 side chain. The Ang-pyrophosphate complex structure suggests how nucleoside pyrophosphate inhibitors might bind to Ang; this information may be useful for the design of Ang antagonists as potential anti-angiogenic drugs.     

Malignant mesenchymal tumors in two white-tailed jack rabbits (Lepus townsendii)

Two white-tailed jack rabbits (Lepus townsendii) with proliferative lesions in their internal organs were submitted to the Canadian Cooperative Wildlife Health Centre (Saskatoon, Saskatchewan, Canada) for necropsy because of concern that dogs that had contact with the hares might have been exposed to an infectious disease. In both hares, the primary diagnosis was neoplasia. One hare had metastatic leiomyosarcoma and uterine fibroma, the other had metastatic mesenchymal tumors involving the liver and mesentery. These cases represent the only reports of malignant mesenchymal tumors in white-tailed jack rabbits that we have found in the literature.     

Conformation and mobility of the arabinan and galactan side-chains of pectin

The function of the arabinan and galactan side-chains of pectin remains unknown. We describe 13C NMR experiments designed to yield spectra from the most mobile polymer components of hydrated cell walls isolated from a range of plant species. In pectin-rich cell walls, these corresponded to the pectic side-chains. The arabinan side-chains were in general more mobile than the galactans, but the long galactan side-chains of potato pectin showed high mobility. Due to motional line-narrowing effects these arabinan and galactan chains gave 13C NMR spectra of higher resolution than has previously been observed from 'solid' biopolymers. These spectra were similar to those reported for the arabinan and galactan polymers in the solution state, implying time-averaged conformations resembling those found in solution. The mobility of the highly esterified galacturonan in citrus cell walls overlapped with the lower end of the mobility range characteristic of the pectic side-chains. The cellulose-rich cell walls of flax phloem fibres gave spectra of low intensity corresponding to mobile type II arabinogalactans. Cell walls from oat coleoptiles appeared to contain no polymers as mobile as the pectic arabinans and galactans in primary cell walls of the other species examined. These properties of the pectic side-chains suggest a role in interacting with water.     

Unique perspectives on the influence of size and age on consumer δ15N from a rainbow smelt complex

Analysis of covariance indicated size had a greater influence than age on δ¹⁵N in three rainbow smelt Osmerus mordax morphotypes of Lake Utopia, New Brunswick, Canada. The distinction in size between the three forms allowed a unique analysis and separation of size and age effects, which is not commonly possible because of the strong correlation between size and age. These results provide support for the continued use of δ¹⁵N as a trophic level indicator in food web studies. While a slight increase in δ¹⁵N with age ( P ≤ 0·05) in intermediate-sized smelt raises questions about a potential accumulation of ¹⁵N with age, the effect of size was far stronger in governing δ¹⁵N values. The possible confounding influence of age when interpreting trophodynamics of short-lived consumers appears to be small.     

Current status of long term ventilation of children in the United Kingdom: questionnaire survey

ObjectivesTo identify the number and current location of children, aged 0 to 16 years, requiring long term ventilation in the United Kingdom, and to establish their underlying diagnoses and ventilatory needs.DesignPostal questionnaires sent to consultant respiratory paediatricians and all lead clinicians of intensive care and special care baby units in the United Kingdom.SubjectsAll children in the United Kingdom who, when medically stable, continue to need a mechanical aid for breathing.Results141 children requiring long term ventilation were identified from the initial questionnaire. Detailed information was then obtained on 136 children from 30 units. Thirty three children (24%) required continuous positive pressure ventilation by tracheostomy over 24 hours, and 103 received ventilation when asleep by a non-invasive mask (n=62; 46%), tracheostomy (n=32; 24%), or negative pressure ventilation (n=9; 7%). Underlying conditions included neuromuscular disease (n=62; 46%), congenital central hypoventilation syndrome (n=18; 13%), spinal injury (n=16; 12%), craniofacial syndromes (n=9; 7%), bronchopulmonary dysplasia (n=6; 4%), and others (n=25; 18%). 93 children were cared for at home. 43 children remained in hospital because of home circumstances, inadequate funding, or lack of provision of home carers. 96 children were of school age and 43 were attending mainstream school.ConclusionsA significant increase in the number of children requiring long term ventilation in the United Kingdom has occurred over the past decade. Contributing factors include improved technology, developments in paediatric non-invasive ventilatory support, and a change in attitude towards home care. Successful discharge home and return to school is occurring even for severely disabled patients. Funding and home carers are common obstacles to discharge.

Key messages

• The number of children requiring long term ventilatory support has increased substantially in the past 8 years
• Ventilatory support at home is the best option for meeting the child’s psychological needs and enhancing quality of life
• The majority of children dependent on long term ventilation live at home and attend mainstream schools
• A shift of care has occurred from intensive care units to less acute areas

     

Lineage-specific transformation after differentiation of multipotential murine stem cells containing a human oncogene.

We transfected the human EJ bladder carcinoma oncogene (Ha-rasEJ-1) into multipotential embryonal carcinoma cell line P19. The transgenic P19(ras+) cells expressed high levels of both the mRNA and the p21EJ protein derived from the oncogene. When cultured in the presence of retinoic acid, P19(ras+) cells differentiated and developed into the same spectrum of differentiated cell types as the parental P19 cells (namely, neurons, astrocytes, and fibroblast-like cells). Thus, it seems unlikely that the Ha-ras-1 proto-oncogene product plays a role in initiation of differentiation or in the choice of differentiated cell lineage. Most of the P19(ras+)-derived differentiated cells contained relatively low levels of p21EJ and were nontransformed, whereas certain cells with fibroblast-like morphology continued to express the Ha-rasEJ-1 gene at high levels and were transformed (i.e., immortal and anchorage independent). Fibroblasts derived from P19 cells did not become transformed following transfection of the Ha-rasEJ-1 oncogene, suggesting that transformation of the fibroblast cells only occurred if the oncogene was present and expressed during the early stages of the developmental lineage.     

Phylogenetic analysis using insertion sequence fingerprinting in Escherichia coli

Chromosomal DNA from 23 closely related, pathogenic strains of Escherichia coli was digested and probed for the insertion sequences IS1, IS2, IS4, IS5, and IS30. Under the assumption that elements residing in DNA restriction fragments of the same apparent length are identical by descent, parsimony analysis of these characters yielded a unique phylogenetic tree. This analysis not only distinguished among bacterial strains that were otherwise identical in their biochemical characteristics and enzyme electrophoretic mobilities, but certain aspects of the topology of the tree were consistent across several unrelated insertion elements. The distribution of IS elements was then reexamined in light of the inferred phylogenetic relationships to investigate the biological properties of the elements, such as rates of insertion and deletion, and to discover apparent recombinational events. The analysis shows that the pattern of distribution of insertion elements in the bacterial genome is sufficiently stable for epidemiological studies. Although the rate of recombination by conjugation has been postulated to be low, at least two such events appear to have taken place.      

Epidemiology of Antimicrobial Resistance in Escherichia coli Isolates from Raccoons (Procyon lotor) and the Environment on Swine Farms and Conservation Areas in Southern Ontario

Antimicrobial resistance is a global threat to livestock, human and environmental health. Although resistant bacteria have been detected in wildlife, their role in the epidemiology of antimicrobial resistance is not clear. Our objective was to investigate demographic, temporal and climatic factors associated with carriage of antimicrobial resistant Escherichia coli in raccoons and the environment. We collected samples from raccoon paws and feces and from soil, manure pit and dumpsters on five swine farms and five conservation areas in Ontario, Canada once every five weeks from May to November, 2011–2013 and tested them for E. coli and susceptibility to 15 antimicrobials. Of samples testing positive for E. coli, resistance to ≥ 1 antimicrobials was detected in 7.4% (77/1044; 95% CI, 5.9–9.1) of raccoon fecal samples, 6.3% (23/365; 95% CI, 4.0–9.3) of paw samples, 9.6% (121/1260; 8.0–11.4) of soil samples, 57.4% (31/54; 95% CI, 43.2–70.8) of manure pit samples, and 13.8% (4/29; 95% CI, 3.9–31.7) of dumpster samples. Using univariable logistic regression, there was no significant difference in the occurrence of resistant E. coli in raccoon feces on conservation areas versus farms; however, E. coli isolates resistant to ≥ 1 antimicrobials were significantly less likely to be detected from raccoon paw samples on swine farms than conservation areas and significantly more likely to be detected in soil samples from swine farms than conservation areas. Resistant phenotypes and genotypes that were absent from the swine farm environment were detected in raccoons from conservation areas, suggesting that conservation areas and swine farms may have different exposures to resistant bacteria. However, the similar resistance patterns and genes in E. coli from raccoon fecal and environmental samples from the same location types suggest that resistant bacteria may be exchanged between raccoons and their environment.