Drug use is associated with lower plasma magnesium levels in geriatric outpatients; possible clinical relevance.

BACKGROUND: Hypomagnesemia has been associated with diabetes, cardiovascular disease, and other disorders. Drug use has been suggested as one of the risk factors for low magnesium (Mg) levels. In the elderly population, prone to polypharmacy and inadequate Mg intake, hypomagnesemia might be relevant. Therefore, we aimed to investigate associations between drug use and plasma Mg. METHODS: Cross-sectional data of 343 Dutch geriatric outpatients were analysed by Cox and linear regression, while adjusting for covariates. Drug groups were coded according to the Anatomical Therapeutic Chemical classification system; use was compared to non-use. Hypomagnesemia was defined as plasma Mg < 0.75 mmol/l and <0.70 mmol/l. RESULTS: Prevalence of hypomagnesemia was 22.2% (Mg < 0.75 mmol/l) or 12.2% (Mg < 0.70 mmol/l); 67.6% of the patients used ≥5 medications (polypharmacy). The number of different drugs used was inversely linearly associated with Mg level (beta -0.01; p < 0.01). Fully adjusted Cox regression showed significant associations of polypharmacy with hypomagnesemia (Mg < 0.75 mmol/l) (prevalence ratio (PR) 1.81; 95%CI 1.08-3.14), proton pump inhibitors (PR 1.80; 95%CI 1.20-2.72), and metformin (PR 2.34; 95%CI 1.56-3.50). Moreover, stratified analyses pointed towards associations with calcium supplements (PR 2.26; 95%CI 1.20-4.26), insulins (PR 3.88; 95%CI 2.19-6.86), vitamin K antagonists (PR 2.01; 95%CI 1.05-3.85), statins (PR 2.44; 95%CI 1.31-4.56), and bisphosphonates (PR 2.97; 95%CI 1.65-5.36) in patients <80 years; selective beta blockers (PR 2.01; 95%CI 1.19-3.40) if BMI <27.0 kg/m2; and adrenergic inhalants in male users (PR 3.62; 95%CI 1.73-7.56). Linear regression supported these associations. CONCLUSION: As polypharmacy and several medications are associated with hypomagnesemia, Mg merits more attention, particularly in diabetes, cardiovascular disease, and in side-effects of proton pump inhibitors and calcium supplements.

Assessment of interbreeding and introgression of farm genes into a small Scottish Atlantic salmon Salmo salar stock: ad hoc samples - ad hoc results?

An eclectic set of tissues and existing data, including purposely collected samples, spanning 1997-2006, was used in an ad hoc assessment of hybridization and introgression of farmed wild Atlantic salmon Salmo salar in the small Loch na Thull (LnT) catchment in north-west Scotland. The catchment is in an area of marine farm production and contains freshwater smolt rearing cages. The LnT S. salar stock was found to be genetically distinctive from stocks in neighbouring rivers and, despite regular reports of feral farm S. salar, there was no evidence of physical or genetic mixing. This cannot be completely ruled out, however, and low level mixing with other local wild stocks has been suggested. The LnT population appeared underpinned by relatively smaller effective number of breeders (Neb ) and showed relatively low levels of genetic diversity, consistent with a small effective population size. Small sample sizes, an incomplete farm baseline and the use of non-diagnostic molecular markers, constrain the power of the analysis but the findings strongly support the LnT catchment having a genetically distinct wild S. salar population little affected by interbreeding with feral farm escapes.

Microsatellite standardization and evaluation of genotyping error in a large multi-partner research programme for conservation of Atlantic salmon (Salmo salar L.).

Microsatellite genotyping is a common DNA characterization technique in population, ecological and evolutionary genetics research. Since different alleles are sized relative to internal size-standards, different laboratories must calibrate and standardize allelic designations when exchanging data. This interchange of microsatellite data can often prove problematic. Here, 16 microsatellite loci were calibrated and standardized for the Atlantic salmon, Salmo salar, across 12 laboratories. Although inconsistencies were observed, particularly due to differences between migration of DNA fragments and actual allelic size ('size shifts'), inter-laboratory calibration was successful. Standardization also allowed an assessment of the degree and partitioning of genotyping error. Notably, the global allelic error rate was reduced from 0.05 ± 0.01 prior to calibration to 0.01 ± 0.002 post-calibration. Most errors were found to occur during analysis (i.e. when size-calling alleles; the mean proportion of all errors that were analytical errors across loci was 0.58 after calibration). No evidence was found of an association between the degree of error and allelic size range of a locus, number of alleles, nor repeat type, nor was there evidence that genotyping errors were more prevalent when a laboratory analyzed samples outside of the usual geographic area they encounter. The microsatellite calibration between laboratories presented here will be especially important for genetic assignment of marine-caught Atlantic salmon, enabling analysis of marine mortality, a major factor in the observed declines of this highly valued species.

Size-dependent growth of individual Atlantic salmon Salmo salar alevins from hatch to first feeding.

Variation in egg size, hatch timing and size at hatch, and their influence on individual growth rates of Atlantic salmon Salmo salar alevins up to first feeding were examined in pure strain and hybrid crosses of fish from Scotland and Canada. At the intra-female, intra-cross type and inter-cross type levels, specific growth rates prior to first feed were strongly size dependent, with smaller and later hatching alevins growing significantly faster. The magnitude of this size-dependent growth was greatest in the hybrid crosses. This resulted in a 40% reduction in the coefficient of variation (c.v.) in alevin size from post-hatch to first feeding at the intra-female level, and a reduction of both intra- and inter-cross differences in alevin sizes in the same period.

A critical review of adaptive genetic variation in Atlantic salmon: implications for conservation.

Here we critically review the scale and extent of adaptive genetic variation in Atlantic salmon (Salmo salar L.), an important model system in evolutionary and conservation biology that provides fundamental insights into population persistence, adaptive response and the effects of anthropogenic change. We consider the process of adaptation as the end product of natural selection, one that can best be viewed as the degree of matching between phenotype and environment. We recognise three potential sources of adaptive variation: heritable variation in phenotypic traits related to fitness, variation at the molecular level in genes influenced by selection, and variation in the way genes interact with the environment to produce phenotypes of varying plasticity. Of all phenotypic traits examined, variation in body size (or in correlated characters such as growth rates, age of seaward migration or age at sexual maturity) generally shows the highest heritability, as well as a strong effect on fitness. Thus, body size in Atlantic salmon tends to be positively correlated with freshwater and marine survival, as well as with fecundity, egg size, reproductive success, and offspring survival. By contrast, the fitness implications of variation in behavioural traits such as aggression, sheltering behaviour, or timing of migration are largely unknown. The adaptive significance of molecular variation in salmonids is also scant and largely circumstantial, despite extensive molecular screening on these species. Adaptive variation can result in local adaptations (LA) when, among other necessary conditions, populations live in patchy environments, exchange few or no migrants, and are subjected to differential selective pressures. Evidence for LA in Atlantic salmon is indirect and comes mostly from ecological correlates in fitness-related traits, the failure of many translocations, the poor performance of domesticated stocks, results of a few common-garden experiments (where different populations were raised in a common environment in an attempt to dissociate heritable from environmentally induced phenotypic variation), and the pattern of inherited resistance to some parasites and diseases. Genotype x environment interactions occurr for many fitness traits, suggesting that LA might be important. However, the scale and extent of adaptive variation remains poorly understood and probably varies, depending on habitat heterogeneity, environmental stability and the relative roles of selection and drift. As maladaptation often results from phenotype-environment mismatch, we argue that acting as if populations are not locally adapted carries a much greater risk of mismanagement than acting under the assumption for local adaptations when there are none. As such, an evolutionary approach to salmon conservation is required, aimed at maintaining the conditions necessary for natural selection to operate most efficiently and unhindered. This may require minimising alterations to native genotypes and habitats to which populations have likely become adapted, but also allowing for population size to reach or extend beyond carrying capacity to encourage competition and other sources of natural mortality.

Unravelling first-generation pedigrees in wild endangered salmon populations using molecular genetic markers.

There is increasing interest in the use of molecular genetic data to infer genealogical relationships among individuals in the absence of parental information. Such analyses can provide insight into mating systems and estimations of heritability in the wild. In addition, accurate pedigree reconstruction among the founders of endangered populations being reared in captivity would be invaluable. Many breeding programs for endangered species attempt to minimize loss of genetic variation and inbreeding through strategies designed to minimize global co-ancestry, but they assume a lack of relatedness among the founders. Yet populations that are the target of such programs are generally in serious demographic decline, and many of the available founders may be closely related. Here we demonstrate determination of full and half-sib relationships among the wild founders of a captive breeding program involving two endangered Atlantic salmon populations using two different approaches and associated software, pedigree and colony. A large portion of the juveniles collected in these two rivers appear to be derived from surprisingly few females mating with a large number of males, probably small precocious parr. Another group of potential founders, obtained from a local hatchery, clearly originated from a small number of full-sib crosses. These results allowed us to prioritize individuals on the basis of conservation value, and are expected to help minimize loss of genetic variation through time. In addition, insight is provided into the number of contributing parents and the mating systems that produced this last generation of endangered wild Atlantic salmon.

A microsatellite linkage map for Atlantic salmon (Salmo salar).

A linkage map of the Atlantic salmon is described here consisting of 15 linkage groups containing 50 microsatellite loci with a 14 additional unlinked markers (including three allozymes). The map shows the largest sex-specific recombination rate differences so far found in any vertebrate species (3.92:1 female:male). Homologies with previous linkage mapping studies of Atlantic salmon and rainbow trout are described. An in silico search of the Genbank database carried out using the microsatellites used in the mapping process identified significant matches between the flanking regions of the microsatellite SS11 and the calcium-binding mitochondrial carrier protein, 'Aralar1'.

Restricted matrilineal gene flow and regional differentiation among Atlantic salmon (Salmo salar L.) populations within the Bay of Fundy, eastern Canada.

Matrilineal phylogenetic divergence among Atlantic salmon stocks of the Bay of Fundy in south eastern Canada is investigated. Sequence variation in two regions of the mitochondrial ND1 gene, encompassing 710 base pairs, is described for 168 salmon from 11 rivers. Mean overall haplotype and nucleotide diversity (h and pi) observed are 0.5014 and 0.00095, respectively. Nested clade analysis (NCA) and molecular analysis of variance (AMOVA) both point to highly restricted gene flow among rivers and show the haplotype distribution to be geographically structured. Variation among predefined regions of the Bay (16%) is greater than among populations within these regions (14%) The main regional differentiation occurs between rivers of the geographically isolated inner Minas Basin and those elsewhere in the Bay. Differentiation most probably reflects the pattern and nature of the historical processes associated with post-glacial colonisation of the area by salmon following the last Pleistocene glacial maximum c. 180,00 yrs BP.

Mitochondrial DNA variation in Pleistocene and modern Atlantic salmon from the Iberian glacial refugium.

Current understanding of the postglacial colonization of Nearctic and Palearctic species relies heavily on inferences drawn from the phylogeographic analysis of contemporary generic variants. Modern postglacial populations are supposed to be representative of their Pleistocene ancestors, and their current distribution is assumed to reflect the different colonization success and dispersal patterns of refugial lineages. Yet, testing of phylogeographic models against ancestral genomes from glacial refugia has rarely been possible. Here we compare ND1 mitochondrial DNA variation in late Pleistocene (16,000-40,000 years before present), historical and contemporary Atlantic salmon (Salmo salar) populations from northern Spain and other regions of western Europe. Our study demonstrates the presence of Atlantic salmon in the Iberian glacial refugium during the last 40,000 years and points to the Iberian Peninsula as the likely source of the most common haplotype within the Atlantic lineage in Europe. However, our findings also suggest that there may have been significant changes in the genetic structure of the Iberian refugial stock since the last ice age, and question whether modern populations in refugial areas are representative of ice age populations. A common haplotype that persisted in the Iberian Peninsula during the Pleistocene last glacial maximum is now extremely rare or absent from European rivers, highlighting the need for caution when making phylogeographic inferences about the origin and distribution of modern genetic types.

Parental assignment in fish using microsatellite genetic markers with finite numbers of parents and offspring.

Deterministic predictions for the proportion of offspring assigned to different numbers of parent-pairs are developed in order to investigate the power of microsatellite loci for parental assignment in fish species. Comparisons with stochastic simulation results show that predictions based on exclusion probabilities are accurate, provided that the number of parents involved in the crosses is large. Accounting for sampling of parents gave very accurate predictions for a small number of parents and a single biallelic locus. For large numbers of loci or large numbers of alleles per locus stochastic simulations are, however, the only available method to predict the power of assignment of a particular set of loci when the number of parents is small. Nine 5-allele loci or six 10-allele loci with equifrequent alleles, are sufficient for assigning, with certainty, parents to 99% of the fish resulting from either 100 or 400 crosses. Results simulating a set of highly polymorphic microsatellites developed for Atlantic salmon show that the four most informative loci are sufficient to assign at least 99% of the offspring to the correct pair with 100 crosses involving 100 males and 100 females. An additional locus is required for correctly assigning 99% of the offspring when the 100 crosses are produced with 10 males and 10 females.

Genetic divergence at the NAD+-dependent malic enzyme locus in Atlantic salmon from Europe and North America

The distribution of genetic variation for NAD+ malic enzyme (ME*) polymorphism in the Atlantic salmon was assessed in both anadromous and resident populations. The analysis revealed a major allelic divergence between North America and Europe. The *80 variant occurred in 39 of 40 North American samples, ranging in frequency from 0 to 0·515. In contrast, it was detected in only three fish from two of the 35 European locations analysed. Eleven fish from two rivers in north-west France had the *110 variant. While heterogeneity among North American populations was significant, no regional differentiation was apparent and anadromous and resident salmon were not found to differ.

Egg survival and timing of hatch in two Scottish Atlantic salmon stocks

Atlantic salmon eggs from the Rivers Oykel and Shin were monitored in three rivers and in culture. Significant mortality, attributable to low pH, was found for both stocks in the River Oykel though it was eightfold higher for the non-native Shin eggs. Shin eggs hatched earlier at all three wild sites but hatched later in culture. The observations are consistent with genotype-environment interactions for pH sensitivity and developmental rate.

Stocking success of Scottish Atlantic salmon in two Spanish rivers.

A previous analysis of proportions of stocked and wild Atlantic salmon among angled fish in the Rivers Asón and Nansa in northern Spain based on the analysis of MEP-2* genotypes is extended. The results reinforce the initial conclusion that returns of stocked Scottish salmon are significantly lower than returns for wild fish.

Detection of an NAD(+)-dependent malic enzyme locus in the Atlantic salmon Salmo salar and other salmonid fish.

Electrophoretic studies of malate oxidoreductases routinely assess variation in two enzymes, malate dehydrogenase (EC 1.1.1.37) and malic enzyme (NADP+) (EC 1.1.1.40). By modification of the standard isozyme staining conditions for these enzymes, we have resolved a new NAD(+)-preferring, MgCl2-requiring malic enzyme which is indicated to be EC 1.1.1.39. The enzyme was detected in 10 salmonid fish species of the genera Salmo, Salvelinus, and Onchorynchus. Phenotypic variation indicates that the novel enzyme is tetrameric and coded by a single locus. Inheritance in S. salar follows a single-locus model and the phenotypes are unlinked to polymorphisms for sMDH-3,4* and mMEP-2*, two malate oxidoreductase loci previously shown to be variable in this species.

Description and genetics of glucose phosphate isomerase (GPI) and phosphoglucomutase (PGM) polymorphisms in Asellus aquaticus (L.).

Analysis of Western European populations of Asellus aquaticus uncovered 10 electrophoretic phenotypes of glucose phosphate isomerase (GPI) and 7 of phosphoglucomutase (PGM). Breeding studies indicate that the variation is controlled by codominant alleles at two autosomal loci. Genotype frequencies in the two sexes do not differ significantly, mating between genotypes is random, and no structural linkage is detectable between the two loci. PGM shows nongenetic, "secondary" banding, particularly in animals stored at -20 degrees C prior to electrophoresis. This secondary banding confounds the identification of the genetic variation but can be controlled by the reducing agent 2-mercaptoethanol.