Survival,growth and sexual maturation in Atlantic salmon exposed to infectious pancreatic necrosis: a multi-variate mixture model approach

Background

Outbreaks of infectious pancreatic necrosis (IPN) in Atlantic salmon can result in reduced growth rates in a fraction of the surviving fish (runts). Genetic and environmental variation also affects growth rates within different categories of healthy animals and runts, which complicates identification of runts. Mixture models are commonly used to identify the underlying structures in such data, and the aim of this study was to develop Bayesian mixture models for the genetic analysis of health status (runt/healthy) of surviving fish from an IPN outbreak.

Methods

Five statistical models were tested on data consisting of 10 972 fish that died and 3959 survivors with recorded growth data. The most complex models (4 and 5) were multivariate normal-binary mixture models including growth, sexual maturity and field survival traits. Growth rate and liability of sexual maturation were treated as two-component normal mixtures, assuming phenotypes originated from two potentially overlapping distributions, (runt/normal). Runt status was an unobserved binary trait. These models were compared to mixture models with fewer traits (Models 2 and 3) and a classical linear animal model for growth (Model 1).

Results

Assuming growth as a mixture trait improved the predictive ability of the statistical model considerably (Model 2 vs. 1). The final models (4 and 5) yielded the following results: estimated (underlying) heritabilities were moderate for growth in healthy fish (0.32 ± 0.04 and 0.35 ± 0.05), runt status (0.39 ± 0.07 and 0.36 ± 0.08) and sexual maturation (0.33 ± 0.05), and high for field survival (0.47 ± 0.03 and 0.48 ± 0.03). Growth in healthy animals, runt status and survival showed consistent favourable genetic associations. Sexual maturation showed an unfavourable non-significant genetic correlation with runt status, but favourable genetic correlations with other traits. The estimated fraction of healthy fish was 81-85%. The estimated breeding values for runt status and (normal) growth were consistent for the most complex models (4 and 5), but showed imperfect correlations with estimated breeding values from the simpler models.

Conclusions

Modelling growth in IPN survivors as a mixture trait improved the predictive ability of the model compared with a classical linear model. The results indicated considerable genetic variation in health status among survivors. Mixture modelling may be useful for the genetic analysis of diseases detected mainly through indicator traits.     

A new genus and species of 'giant hutia' (Tainotherium valei) from the Quaternary of Puerto Rico: an extinct arboreal quadruped?

A large incomplete rodent femur from a Quaternary cave deposit near Barahona, Puerto Rico, is established as the holotype of Tainotherium valei , a new extinct genus and species. Although biogeographic and body size similarities suggest that it may be related to the Puerto Rican giant hutia Elasmodontomys , the Antillean large-bodied rodent family Heptaxodontidae is now interpreted as invalid, and it is impossible to assign Tainotherium to a particular caviomorph family in the absence of associated craniodental material. Tainotherium differs from other West Indian species in possessing a large femoral head, a proximally angled femoral neck, a short greater trochanter and a medially positioned lesser trochanter unconnected by an intertrochanteric crest, and a transversely flattened, anteroposteriorly bowed shaft lacking well-defined ridges. These characters are all associated with arboreal life habits in other mammal groups. The Puerto Rican land mammal fauna was dominated by a rodent radiation occupying a wide variety of niches before human arrival in the West Indies, but although arboreality is correlated with increased likelihood of survival in Quaternary mammalian extinction events, all of this fauna is now extinct. It is unlikely that decreasing aridity and the reduction of Puerto Rican savanna-type environments at the end of the Pleistocene contributed to the extinction of the arboreal Tainotherium , and habitat destruction by pre-Columbian Amerindians may instead have been responsible.     

Gardening for Homonyms: Integrating Science and Language Arts to Support Children's Creative Use of Multiple Meaning Words

Curriculum integration can increase the presence of science at the elementary level. The purpose of this article is to share how two second-grade teachers have integrated language arts content as a part of science-language arts instruction in a garden-based learning context. One application was a teacher-designed Gardening for Homonyms lesson, which supported new ways of thinking about words and wordplay while developing science vocabulary related to structure and function, diversity of life, and interdependent relationships in ecosystems. This article provides the lesson and discusses its implementation in two second-grade classrooms. Examples of student work illustrate children's creative thought around and application of multiple meaning words. Pre-, post-, and extended posttest measures of students' ability to generate and to use homonyms demonstrate that this science-language arts integrated lesson can result in both short- and long-term learning. Applications and follow-up from the lesson over two subsequent years have engaged second and third grade students in study/inquiry about plant growth and life cycles while utilizing many facets of language arts, which have ranged from labeling an experimental design and writing predictions and results to conversing about digital “GigaPan” images on growing strawberries.     

Evidence of the existence of a high-density lipoprotein transformation factor in pig and rabbit plasma

Experiments have been conducted to elucidate the incubation conditions necessary for the transformation of pig high-density lipoproteins (HDL) from particles resembling the HDL3 subfraction of human plasma into particles resembling human HDL2. All incubations were performed at 37 degrees C for 24 h in the presence of 0.002 M p-chloromercuriphenylsulphonic acid, a chemical inhibitor of lecithin-cholesterol acyltransferase. There was no transformation when pig HDL (1.09 less than d less than 1.21 g/ml) was incubated either in isolation or in the presence of bovine serum albumin. In addition, there was no transformation when the 1.25 g/ml infranatant of pig plasma was added to the incubation. In the presence of the 1.25 g/ml infranatant of rabbit plasma, by contrast, a significant proportion of the pig HDL was transformed into HDL2. The possibility that this result may have been the consequence of the lipid-transfer activity in rabbit plasma was excluded by the observation that a partially purified preparation of rabbit lipid-transfer protein was ineffective in promoting the HDL transformation. Experiments were also performed with the 1.09 g/ml infranatant of pig plasma. This fraction contained HDL and the plasma proteins but no other lipoprotein. In contrast to the absence of change in incubations of a mixture containing isolated pig HDL (1.09 less than d less than 1.21 g/ml) and the 1.25 g/ml infranatant of pig plasma, during incubation of the 1.09 g/ml infranatant there was an obvious formation of HDL2. It has been concluded that there exists in plasma an HDL-transformation factor which is distinct from both lecithin-cholesterol acyltransferase and the lipid-transfer protein. This factor was detectable in the 1.25 g/ml infranatant of rabbit plasma and in the 1.09 g/ml infranatant of pig plasma. As the factor was not detected in isolated pig HDL or in the 1.25 g/ml infranatant of pig plasma, the 1.21-1.25 g/ml fraction of plasma may be a useful starting point for further investigation of this factor.     

Regional and Subcellular Localization of Li+ and Other Cations in the Rat Brain Following Long-Term Lithium Administration

Abstract: Rats were given LiCl in their diet (40 mmol/kg dry weight) for at least 3 months to elucidate the regional and subcellular localization of Li⁺ in the brain as well as the effect of chronic lithium administration on the distribution of other cations. At steady-state the mean concentrations of Li⁺ were 0.66 mmol/kg wet weight in the whole brain and 0.52 mM in plasma. The tissue/plasma concentration ratio exceeded unity in all anatomical regions. No region showed excessive accumulation of Li⁺. Whole brain or regional contents of Na⁺ or K⁺ were unaffected by lithium treatment. Subcellular Li⁺ localization was demonstrated in nuclear, crude mitochondrial, and microsomal fractions of whole brain homogenate. Subfractionation of the crude mitochondrial fraction revealed energy-independent intrasynaptosomal and intramitochondrial Li⁺ and K⁺ localization at 0–4°C. Li⁺ administered in vivo disappeared within 10 min from synaptosomes incubated at 37°C. Li⁺ added in vitro at 1 mM attained a synaptosomal steady-state concentration within 30 min at 37°C. In control rats, synaptosomal concentrations and synaptosomal/medium concentration gradients of cations paralleled their respective in vivo concentrations and gradients. Lithium treatment caused synaptosomal depletion of K⁺ and Mg²⁺ and hence probably partial membrane depolarization. Addition of 1 mM Li⁺ in vitro also caused synaptosomal Mg²⁺ depletion. The results indicate that Li⁺ is “accumulated” in brain sediments and synaptosomes following its long-term treatment. The estimated intracellular and intrasynaptosomal Li⁺ concentrations are lower than predicted by passive distribution according to the Nernst equation, evidencing active extrusion of Li⁺.     

Changes in the size of reconstituted high density lipoproteins during incubation with cholesteryl ester transfer protein: the role of apolipoproteins.

It has been reported previously that the particle size distribution of discoidal, reconstituted HDL (r-HDL) changes dramatically during incubation in vitro with cholesteryl ester transfer protein (CETP). The present study was undertaken in order to determine whether these changes are influenced by the apolipoprotein composition of the r-HDL. Two preparations of r-HDL that contained egg phosphatidylcholine (egg PC) and unesterified cholesterol (UC) but differed in their apolipoprotein composition were used for the study. One preparation contained apolipoprotein (apo) A-I only (A-I w/o A-II r-HDL) while the other contained apoA-I and apoA-II (A-I w A-II r-HDL). The Stokes' radius of the major population of particles in the (A-I w/o A-II) and (A-I w A-II) r-HDL was, respectively, 4.8 and 4.9 nm. When the (A-I w/o A-II) r-HDL were incubated with CETP, most of the particles of radius 4.8 nm were converted to populations of smaller and larger particles. The smaller particles had Stokes' radii of 4.3 and 3.9 nm. The radii of the larger particles ranged from 8.2 to 13.7 nm. When the (A-I w A-II) r-HDL were incubated with CETP larger particles (Stokes' radii = 8.4-11.0 nm) appeared but there was minimal conversion to smaller particles. In addition, a significant proportion of the original (A-I w A-II) r-HDL of radius 4.9 nm was still present at the end of the incubation. These results are consistent with apoA-II inhibiting the conversion of r-HDL to small particles. It is concluded that the apolipoprotein content of r-HDL is an important determinant of the sizes of the particles that are formed during incubation with CETP.     

Selection of carbohydrate-binding cell phenotypes using oligosaccharide-coated magnetic particles

Neoglycoconjugate coated magnetic beads were assessed for theirability to selectively isolate human cells with known anti-carbohydratereactivity. Four lung cancer cell lines, NCI-H146, NCI-N417D,SKMES-1, EKVX; two acute lymphoblastic leukemia lines, MOLT-4and CCRF-CEM; and the anti- Le^c (isolactosamine) hybridoma,LU-BCRU-G7, were tested. The neoglycoconjugates (biotinylatedpseudopolysaccharides) bound uniformly to streptavidin coatedmagnetic beads as demonstrated by FTTC labeled lectin. Streptavidinbeads alone did not bind to any of the cell types. The anti-Le^c hybridoma cell line, LU BCRU-G7, demonstrated binding onlyto Le^c pseudopolysaccharide coated magnetic beads. Subsequentincubation in the presence of unlabeled pseudopolysaccharideresulted in the release of the beads from the cell surface.Although there was some heterogeneity within the individuallung and leukemic cell lines, positive cells showed strong rosetteformation with the coated beads. The A_dl disaccharide coatedbeads showed binding in all four lung cancer cell lines, withthe Le^c and the H (type1) pseudopolysaccharide-bead conjugatesonly reactive in the N417 and H146 SCLC lines. The range ofL-selectin ligand-coated beads were all successful in bindingto the acute lymphoblastic leukemia cell lines MOLT4 and CCRF-CEM.This approach provides a versatile model for the study of cell-surfacecarbohydrate interactions that should find application in manyareas of cell biology. carbohydrate-coated magnetic beads cell selec-tion lectins neoglycoconjugates pseudopolysaccharides