Genome-wide association study to identify genetic loci associated with gastrointestinal nematode resistance in Katahdin sheep

Resistance to gastrointestinal nematodes has previously been shown to be a moderately heritable trait in some breeds of sheep, but the mechanisms of resistance are not well understood. Selection for resistance currently relies upon faecal egg counts (FEC), blood packed cell volumes and FAMACHA visual indicator scores of anaemia. Identifying genomic markers associated with disease resistance would potentially improve the selection process and provide a more reliable means of classifying and understanding the biology behind resistant and susceptible sheep. A GWAS was conducted to identify possible genetic loci associated with resistance to Haemonchus contortus in Katahdin sheep. Forty animals were selected from the top and bottom 10% of estimated breeding values for FEC from a total pool of 641 sires and ram lambs. Samples were genotyped using Applied Biosystems™ Axiom™ Ovine Genotyping Array (50K) consisting of 51 572 SNPs. Following quality control, 46 268 SNPs were included in subsequent analyses. Analyses were conducted using a linear regression model in plink v1.90 and a single-locus mixed model in snp and variation suite . Genome-wide significance was determined by a Bonferroni correction for multiple testing. Using linear regression, loci on chromosomes 2, 3, 16, 23 and 24 were significantly associated at the genome level with FEC estimated breeding values, and we identified a region on chromosome 2 that was significant using both statistical analyses. We suggest a potential role for the gene DIS3L2 for gastrointestinal nematode resistance in Katahdin sheep, although further research is needed to validate these findings.     

Some Experiments with Salts of Heavy Metals as Fixatives

Heavy metal salts mostly in 0.5M concentration were used for tissue fixation and for albumin and gelatin precipitation. Tissues from dog, cat, and rabbit were stained in acid and basic stains. It was found that the atomic weight of the cation of the salt influenced its precipitating power. Penetration was either uniform or non-uniform and the resulting shrinkage generalized or cellular. Tissue hardening or high precipitating efficacy of a given salt did not always give good tissue preservation, but well preserved tissue was necessarily firm after fixation and fixed by a salt with a high precipitating efficacy. The mordanting effects of the fixatives were arbitrarily classified into three types: isomordants, basic mordants, and acid mordants.     

Block Staining of Nervous Tissue with Silver: II. Trichloracetic Acid, Sulfosalicylic Acid, Hofker's and Carnoy's Fluids as Fixatives

Alcoholic solutions of sulfosalicylic acid, trichloracetic acid and Hofker's solution fixed mammalian spinal cord with less shrinkage than ammoniated alcohol, but during the necessary alkalinization, washing, and silvering, the acid fixed specimens shrank more than those fixed in the alkaline alcohol. Specimens fixed in Carnoy's fluid shrank most. Successful silver stains were obtained after all the fixatives.     

Mussel dropping by Carrion and Hooded crows: biomechanical and energetic considerations

Dropping live mussels (Mytilus sp.) onto hard substrata by Carrion Crows (Corvus corone) and Hooded Crows (Corvus cornix) to access their flesh is a commonly observed behavior from late summer to spring in the United Kingdom and Ireland. Despite previous studies, several aspects of prey‐dropping behavior remained incompletely understood. From September 2008 to January 2010, we determined the heights of drops, likelihood of shell breakage from drops at different heights, effect of mussel size on breakability, energetic costs of flying to drop heights, and the energetic costs of transporting mussels from mussel beds to dropping sites. We studied Carrion Crows on the Isle of Cumbrae, Scotland, and Hooded Crows in Cork Harbor, Ireland. Initial experiments were carried out with mussels to determine breakability in relation to size and drop height, and to estimate mussel energy content. Sizes of mussel shells at Hooded Crow dropping sites were compared with those of live mussels from source mussel beds. Adult Carrion Crows (N = 10) dropped mussels from a mean height of 4.7 m, and adult Hooded Crows (N = 21) from 4.8 m. These heights were close to the minimum (4–4.8 m; determined experimentally) required to break all mussel shells on the first drop. Dropping mussels from the minimum height that guarantees breakage reduces handling time and, by minimizing the size of the resulting debris field, likely reduces the risk of kleptoparasitism. Juvenile Hooded Crows (N = 13) dropped mussels onto suboptimal substrates (gravelly mud) from variable heights (mean = 6.1 m) with a low success rate (0% on first drop). This inefficiency could reflect either inexperience or exclusion from prime hard‐substrate dropping sites by adults. Foraging Hooded Crows selected larger mussels, dropping no mussels <32‐mm shell length. Energetic calculations indicate that a Hooded Crow lifting a medium‐sized mussel (55‐mm shell length) to a height of 5 m incurs a cost of only 0.3% of energy assimilated from that mussel, whereas travel to and from a mussel bed 200 m away costs 5.8% of that energy. These results suggest that choice of mussel dropping height by crows is determined by shell breakability rather than the cost of flying up to the dropping height.     

Three-Dimensional Structure of the Intercalated Disc Reveals Plicate Domain and Gap Junction Remodeling in Heart Failure

The intercalated disc (ICD) orchestrates electrochemical and mechanical communication between neighboring cardiac myocytes, properties that are perturbed in heart failure (HF). Although structural data from transmission electron microscopy two-dimensional images have provided valuable insights into the domains forming the ICD, there are currently no three-dimensional (3D) reconstructions for an entire ICD in healthy or diseased hearts. Here, we aimed to understand the link between changes in protein expression in an ovine tachypacing-induced HF model and ultrastructural remodeling of the ICD by determining the 3D intercalated disc architecture using serial block face scanning electron microscopy. In the failing myocardium there is no change to the number of ICDs within the left ventricle, but there is an almost doubling of the number of discs with a surface area of <1.0 × 10⁸μm² in comparison to control. The 3D reconstructions further revealed that there is remodeling of the plicate domains and gap junctions with vacuole formation around and between the contributing membranes that form the ICDs in HF. Biochemical analysis revealed upregulation of proteins involved in stabilizing the adhesive and mechanical properties consistent with the morphological changes. Our studies here have shown that in tachypacing-induced HF mechanical stresses are associated with both structural and molecular alterations. To our knowledge, these data together provide novel, to our knowledge, insights as to how remodeling at the molecular and structural levels leads to impaired intercellular communication.     

A new method of monitoring ventilatory activity in mussels and its use in a study of the ventilatory patterns of Mytilus edulis L.

An apparatus for measuring pumping rates in mussels, based on the delivery of exhaled sea water into a constant flow of fresh water, is described. When food is available, pumping is continuous for several days although there are signs of satiation after ≈ 1 wk. When food is withdrawn pumping does not cease for several hours especially in animals which have been food-deprived for some time before feeding. Food-deprived mussels often fail to pump for periods of > 24 h and ventilatory bursts are carried out at flow rates well below maximum. Shell valve movements and diffusion of oxygen through the gape between open valves can supplement ciliary ventilation.     

The Bielschowsky Staining Technic a Study of the Factors Influencing Its Specificity for Nerve FIBERS

By comparing results obtained with adult mammalian tissue from introducing variables into each separate step in block-staining by the Bielschowsky silver method, the following conclusions were reached:

1. No specific means for inhibiting the staining of connective tissue and still permitting complete staining of nerve fibers was found, but the avoidance of overstaining was very helpful toward such differentiation.
2. Overstaining could be corrected by reducing the concentration of the silver nitrate bath or by adding an excess of ammonia to the ammoniated silver bath.
3. Staining of fine fibers was favored by adding acetic acid to the formaldehyde used for fixation or by adding pyridin to the silver nitrate bath.
4. Addition of protein-precipitating organic acids (trichloracetic or sulfosalicylic) to the fixative was disadvantageous.
5. Prolonged fixation favored an increase in intensity of the stain. Four days' time was sufficient.
6. Extraction of lipids with ammoniated alcohol gave results similar to those obtained after extraction with pyridin, but the stain was lighter.
7. Ammoniated silver carbonate without excess ammonia had an action similar to ammoniated silver hydroxide with excess ammonia.
8. An excess of ammonia in the ammoniated silver solution (Ag 0.1 N) was tolerated, without apparent impairment of nerve-fiber staining, up to 6 M NH₃, altho the use of more than 3 M excess (2 cc. concentrated ammonia water added to 100 cc. of balanced ammoniated silver hydroxide solution) seemed unnecessary.
9. Impregnation with 1.7% (0.1 N) silver nitrate solution was quite satisfactory and variations in the concentrations of this bath suggested that the practical limits of concentrations that would be generally satisfactory lay between 0.3 and 3.0%.
10. The writers' experiences agreed with Agduhr's relative to the advantage of washing in 2.5% acetic acid between the ammoniated silver bath and formaldehyde reduction.

     

The Strip Method for Counting Nerve Fibers or other Microscopic Units

A comparison of complete counts of nerve fibers by the strip method with the photographic method showed a minimum difference of 0.3% and a maximum of 2.9%. The preparations counted were selected for clarity and discreteness of fibers to avoid introducing an error (ambiguity of fibers) which is not pertinent to any particular method of counting. Agreement of counts with estimates radicated the feasibility of estimates when the greatest accuracy is not required.