Convergence of marine megafauna movement patterns in coastal and open oceans.

The extent of increasing anthropogenic impacts on large marine vertebrates partly depends on the animals' movement patterns. Effective conservation requires identification of the key drivers of movement including intrinsic properties and extrinsic constraints associated with the dynamic nature of the environments the animals inhabit. However, the relative importance of intrinsic versus extrinsic factors remains elusive. We analyze a global dataset of ∼2.8 million locations from >2,600 tracked individuals across 50 marine vertebrates evolutionarily separated by millions of years and using different locomotion modes (fly, swim, walk/paddle). Strikingly, movement patterns show a remarkable convergence, being strongly conserved across species and independent of body length and mass, despite these traits ranging over 10 orders of magnitude among the species studied. This represents a fundamental difference between marine and terrestrial vertebrates not previously identified, likely linked to the reduced costs of locomotion in water. Movement patterns were primarily explained by the interaction between species-specific traits and the habitat(s) they move through, resulting in complex movement patterns when moving close to coasts compared with more predictable patterns when moving in open oceans. This distinct difference may be associated with greater complexity within coastal microhabitats, highlighting a critical role of preferred habitat in shaping marine vertebrate global movements. Efforts to develop understanding of the characteristics of vertebrate movement should consider the habitat(s) through which they move to identify how movement patterns will alter with forecasted severe ocean changes, such as reduced Arctic sea ice cover, sea level rise, and declining oxygen content.

Automated detection and enumeration of marine wildlife using unmanned aircraft systems (UAS) and thermal imagery.

Estimating animal populations is critical for wildlife management. Aerial surveys are used for generating population estimates, but can be hampered by cost, logistical complexity, and human risk. Additionally, human counts of organisms in aerial imagery can be tedious and subjective. Automated approaches show promise, but can be constrained by long setup times and difficulty discriminating animals in aggregations. We combine unmanned aircraft systems (UAS), thermal imagery and computer vision to improve traditional wildlife survey methods. During spring 2015, we flew fixed-wing UAS equipped with thermal sensors, imaging two grey seal (Halichoerus grypus) breeding colonies in eastern Canada. Human analysts counted and classified individual seals in imagery manually. Concurrently, an automated classification and detection algorithm discriminated seals based upon temperature, size, and shape of thermal signatures. Automated counts were within 95-98% of human estimates; at Saddle Island, the model estimated 894 seals compared to analyst counts of 913, and at Hay Island estimated 2188 seals compared to analysts' 2311. The algorithm improves upon shortcomings of computer vision by effectively recognizing seals in aggregations while keeping model setup time minimal. Our study illustrates how UAS, thermal imagery, and automated detection can be combined to efficiently collect population data critical to wildlife management.

Preparing Muscles for Diving: Age-Related Changes in Muscle Metabolic Profiles in Harp (Pagophilus groenlandicus) and Hooded (Cystophora cristata) Seals.

In adult marine mammals, muscles can sustain aerobic metabolism during dives in part because they contain large oxygen (O2) stores and metabolic rates are low. However, young pups have significantly lower tissue O2 stores and much higher mass-specific metabolic rates. To investigate how these differences may influence muscle function during dives, we measured the activities of enzymes involved in aerobic and anaerobic metabolic pathways (citrate synthase [CS], ß-hydroxyacyl-coenzyme A dehydrogenase [HOAD], lactate dehydrogenase [LDH]) and the LDH isoform profile in six muscles from 41 harp (Pagophilus groenlandicus) and 30 hooded (Cystophora cristata) seals ranging in age from fetal to adult. All neonatal muscles had significantly higher absolute but lower metabolically scaled CS and HOAD activities than adults (∼ 70% and ∼ 85% lower, respectively). Developmental increases in LDH activity lagged that of aerobic enzymes and were not accompanied by changes in isozyme profile, suggesting that changes in enzyme concentration rather than structure determine activity levels. Biochemical maturation proceeded faster in the major locomotory muscles. In combination, findings suggest that pup muscles are unable to support strenuous aerobic exercise or rely heavily on anaerobic metabolism during early diving activities and that pups' high mass-specific metabolic rates may play a key role in limiting the ability of their muscles to support underwater foraging.

Liver glucose-6-phosphatase proteins in suckling and weaned grey seal pups: structural similarities to other mammals and relationship to nutrition, insulin signalling and metabolite levels.

Phocid seals have been proposed as models for diabetes because they exhibit limited insulin response to glucose, high blood glucose and increasing insulin resistance when fasting. Liver glucose-6-phosphatase (G6Pase) catalyses the final step in glucose production and is central to glucose regulation in other animals. G6Pase comprises a translocase (SLC37A4) and a catalytic subunit (G6PC). G6PC and SLC37A4 expression and activity are normally regulated by nutritional state and glucostatic hormones, particularly insulin, and are elevated in diabetes. We tested the hypotheses that (1) grey seal G6PC and SLC37A4 cDNA and predicted protein sequences differ from other species' at functional sites, (2) relative G6Pase protein abundances are lower during feeding than fasting and (3) relative G6Pase protein abundances are related to insulin, insulin receptor phosphorylation and key metabolite levels. We show that G6PC and partial SLC37A4 cDNA sequences encode proteins sharing 82-95 % identity with other mammals. Seal G6PC contained no differences in sites responsible for activity, stability or subcellular location. Several substitutions in seal SLC37A4 were predicted to be tolerated with low probability, which could affect glucose production. Suckling pups had higher relative abundance of both subunits than healthy, postweaned fasting pups. Furthermore, relative G6PC abundance was negatively related to glucose levels. These findings contrast markedly with the response of relative hepatic G6Pase abundance to feeding, fasting, insulin, insulin sensitivity and key metabolites in other animals, and highlight the need to understand the regulation of enzymes involved in glucose control in phocids if these animals are to be informative models of diabetes.

Postnatal development of muscle biochemistry in nursing harbor seal (Phoca vitulina) pups: limitations to diving behavior?

Adult marine mammal muscles rely upon a suite of adaptations for sustained aerobic metabolism in the absence of freely available oxygen (O(2)). Although the importance of these adaptations for supporting aerobic diving patterns of adults is well understood, little is known about postnatal muscle development in young marine mammals. However, the typical pattern of vertebrate muscle development, and reduced tissue O(2) stores and diving ability of young marine mammals suggest that the physiological properties of harbor seal (Phoca vitulina) pup muscle will differ from those of adults. We examined myoglobin (Mb) concentration, and the activities of citrate synthase (CS), beta-hydroxyacyl coA dehydrogenase (HOAD), and lactate dehydrogenase (LDH) in muscle biopsies from harbor seal pups throughout the nursing period, and compared these biochemical parameters to those of adults. Pups had reduced O(2) carrying capacity ([Mb] 28-41% lower than adults) and reduced metabolically scaled catabolic enzyme activities (LDH/RMR 20-58% and CS/RMR 29-89% lower than adults), indicating that harbor seal pup muscles are biochemically immature at birth and weaning. This suggests that pup muscles do not have the ability to support either the aerobic or anaerobic performance of adult seals. This immaturity may contribute to the lower diving capacity and behavior in younger pups. In addition, the trends in myoglobin concentration and enzyme activity seen in this study appear to be developmental and/or exercise-driven responses that together work to produce the hypoxic endurance phenotype seen in adults, rather than allometric effects due to body size.

Development of aerobic and anaerobic metabolism in cardiac and skeletal muscles from harp and hooded seals.

In diving animals, skeletal muscle adaptations to extend underwater time despite selective vasoconstriction include elevated myoglobin (Mb) concentrations, high acid buffering ability (beta) and high aerobic and anaerobic enzyme activities. However, because cardiac muscle is perfused during dives, it may rely less heavily on Mb, beta and anaerobic pathways to support contractile activity. In addition, because cardiac tissue must sustain contractile activity even before birth, it may be more physiologically mature at birth and/or develop faster than skeletal muscles. To test these hypotheses, we measured Mb levels, beta and the activities of citrate synthase (CS), beta-hydroxyacyl-CoA dehydrogenase (HOAD) and lactate dehydrogenase (LDH) in cardiac and skeletal muscle samples from 72 harp and hooded seals, ranging in age from fetuses to adults. Results indicate that in adults cardiac muscle had lower Mb levels (14.7%), beta (55.5%) and LDH activity (36.2%) but higher CS (459.6%) and HOAD (371.3%) activities (all P<0.05) than skeletal muscle. In addition, while the cardiac muscle of young seals had significantly lower [Mb] (44.7%) beta (80.7%) and LDH activity (89.5%) than adults (all P<0.05), it was relatively more mature at birth and weaning than skeletal muscle. These patterns are similar to those in terrestrial species, suggesting that seal hearts do not exhibit unique adaptations to the challenges of an aquatic existence.

Development of myoglobin concentration and acid buffering capacity in harp (Pagophilus groenlandicus) and hooded (Cystophora cristata) seals from birth to maturity.

Pinnipeds rely on muscle oxygen stores to help support aerobic diving, therefore muscle maturation may influence the behavioral ecology of young pinnipeds. To investigate the pattern of muscle development, myoglobin concentration ([Mb]) and acid buffering ability (beta) was measured in ten muscles from 23 harp and 40 hooded seals of various ages. Adult [Mb] ranged from 28-97 to 35-104 mg g tissue(-1) in harp and hooded seals, respectively, with values increasing from the cervical, non-swimming muscles to the main swimming muscles of the lumbar region. Neonatal and weaned pup muscles exhibited lower (approximately 30% adult values) and less variable [Mb] across the body than adults. In contrast, adult beta showed little regional variation (60-90 slykes), while high pup values (approximately 75% adult values) indicate significant in utero development. These findings suggest that intra-uterine conditions are sufficiently hypoxic to stimulate prenatal beta development, but that [Mb] development requires additional postnatal signal such as exercise, and/or growth factors. However, because of limited development in both beta and [Mb] during the nursing period, pups are weaned with muscles with lower aerobic and anaerobic capacities than those of adults.

Insulin resistance phenotypes and coronary artery disease in a native Pakistani cohort.

OBJECTIVE: To determine the relationship between insulin resistance (IR) and atheroma burden in Pakistanis. METHODS: A prospective case-control study of 400 patients selected for the presence/absence of angiographic disease. Coronary atheroma burden was quantified and IR and cardiovascular risk factors were measured. RESULTS: The patients were divided into two groups by QuickI score. Waist circumference (90 +/- 10 vs. 90 +/- 9 cm; p = 0.7) was similar but the groups differed in body mass index (26.5 +/- 3.7 vs. 24.2 +/- 3.5 kg/m(2); p < 0.001) and waist:hip ratio (0.94 +/- 0.09 vs. 0.90 +/- 0.06; p < 0.001). Lipid parameters showed similar high-density lipoprotein cholesterol (HDL-C) (0.77 +/- 0.23 vs. 0.82 +/- 0.22 mmol/l; p = 0.1) differences in triglycerides [1.32 (0.08-3.98) vs. 1.12 (0.37-3.61) mmol/l; p = 0.01], but no difference in low-density lipoprotein cholesterol (LDL-C) (2.75 +/- 1.00 vs. 2.90 +/- 0.94 mmol/l; p = 0.14). In insulin-resistant patients C-reactive protein (CRP) [6.8 (0.3-175.1) vs. 3.9 (0.2-57.9) mg/l: p < 0.001], sialic acid (82 +/- 14 vs. 77 +/- 15 mg/l; p < 0.001) aspartate transaminase [24 (7-171) vs. 21 (7-83) IU/l; p < 0.001] and gamma-glutamyl transferase [27 (8-482) vs. 21 (7-168) IU/l; p = 0.005] levels were increased. In insulin-resistant patients (n = 187), coronary artery disease (CAD) burden correlated (r = 0.55) with age (beta = 1.62; p < 0.001), HDL-C (beta = -53.2; p < 0.001), lipoprotein (a) (beta = 11.4; p = 0.007), smoking (beta = 7.98; p = 0.004), CRP (beta = 6.06; p = 0.03) and QuickI index (beta = -146; p = 0.04). In contrast in insulin-sensitive patients (n = 178) CAD burden (r = 0.46) correlated with LDL-C (beta = 10.0; p = 0.02), CRP (beta = 7.13; p = 0.03), HDL-C (beta = -38.1; p = 0.03), and weakly with age (beta = 0.73; p = 0.07) and smoking (beta = 5.52; p = 0.09). CONCLUSIONS: Indian Asians show a dichotomous insulin-resistance phenotype. Atheroma is associated with low HDL-C and inflammation associated in all but LDL-C is a factor in the insulin sensitive in contrast to age and extent of IR in the insulin resistant.

Size and distribution of oxygen stores in harp and hooded seals from birth to maturity.

Pinnipeds rely primarily on oxygen stores in blood and muscles to support aerobic diving; therefore rapid development of body oxygen stores (TBO(2)) is crucial for pups to transition from nursing to independent foraging. Here, we investigate TBO(2) development in 45 harp (Pagophilus groenlandicus) and 46 hooded (Cystophora cristata) seals ranging in age from neonates to adult females. We found that hooded seal adults have the largest TBO(2) stores yet reported (89.5 ml kg(-1)), while harp seal adults have values more similar to other phocids (71.6 ml kg(-1)). In adults, large TBO(2) stores resulted from large blood volume (harp169, hood 194 ml kg(-1)) and high muscle Mb content (harp 86.0, hood 94.8 mg g(-1)). In contrast, pups of both species had significantly lower mass-specific TBO(2 )stores than adults, and stores declined rather than increased during the nursing period. This decline was due to a reduction in mass-specific blood volume and the absence of an increase in the low Mb levels (harp 21.0, hood 31.5 mg g(-1)). Comparisons with other phocid species suggests that the pattern of blood and muscle development in the pre- and post-natal periods varies with terrestrial period, and that muscle maturation rates may influence the length of the postweaning fast. However, final maturation of TBO(2) stores does not take place until after foraging begins.

Panmictic population structure in the hooded seal (Cystophora cristata).

Two putative populations of hooded seals (Cystophora cristata) occur in the North Atlantic. The Greenland Sea population pup and breed on the pack ice near Jan Mayen ('West Ice') while the Northwest Atlantic population is thought to pup in the Davis Strait, in the Gulf of St. Lawrence (the 'Gulf'), and off southern Labrador or northeast Newfoundland (the 'Front'). We used microsatellite profiling of 300 individuals at 13 loci and mitochondrial DNA sequencing of the control region of 123 individuals to test for genetic differentiation between these four breeding herds. We found no significant genetic differences between breeding areas, nor evidence for cryptic nor higher level genetic structure in this species. The Greenland Sea breeding herd was genetically most distant from the Northwest Atlantic breeding areas; however, the differences were statistically nonsignificant. Our data therefore suggest that the world's hooded seals comprise a single panmictic genetic population.

Metabolic syndrome and risk of coronary heart disease in a Pakistani cohort.

OBJECTIVE: To assess the relation of the metabolic insulin resistance syndrome (M-IRS) with coronary heart disease (CHD) in Pakistani patients. SUBJECTS: 200 patients with angiographic disease (CHD(+)) matched with 200 patients with chest pain without occlusive disease (CHD(-)). DESIGN: Prospective case-control study. SETTING: Tertiary referral cardiology unit in Pakistan. RESULTS: M-IRS was present in 37% of CHD(+) versus 27% of CHD(-) patients by criteria for white patients or 47% versus 42%, respectively, by Asian criteria (p < 0.001). After adjustment for other risk factors, M-IRS was not a significant predictor for CHD or angiographic disease. Age (p = 0.03), smoking (p < 0.001), diabetes-years (p = 0.003), sialic acid (p = 0.01), and creatinine (p = 0.008) accounted for the excess risk of CHD. Similarly, age (p = 0.005), creatinine (p < 0.001), cigarette pack-years (p = 0.02), diabetes-years (p = 0.003), and sialic acid (p = 0.08) were predictors of greater angiographic disease. M-IRS differed between Pakistani and white patients, as waist circumference correlated weakly (r = -0.03-0.08, p = 0.45-0.52) with triglycerides, high density lipoprotein cholesterol, systolic blood pressure, or glucose. Sialic acid was the only inflammatory marker associated with M-IRS. CONCLUSIONS: Despite strong associations between individual risk factors associated with M-IRS and a univariate association between M-IRS and CHD in native Pakistanis, the principal discriminant risk factors in this group are age, smoking, inflammation, diabetes-years, and impaired renal function. The poor sensitivity of M-IRS for CHD reflects the high underlying prevalence of M-IRS, thus reducing sensitivity, confounding by other urban lifestyle traits, or a lack of association of waist circumference with M-IRS risk factors. The definition of M-IRS may have to be revised to increase its power as a discriminant risk factor for CHD in Pakistani populations.

Partitioning of persistent organic pollutants in grey seal (Halichoerus grypus) mother-pup pairs.

Phocid seals have lipid rich milk, which is known to serve as a transfer medium through which persistent organic pollutants (POPs) move from mother to offspring during lactation. However, knowledge on this generational transfer of different POPs and the partitioning of these compounds in maternal and offspring tissues over the course of the lactation are limited. In this study we examined the qualitative and quantitative partitioning of a range of chlorinated POPs in maternal blubber, blood and milk as well as in pup blubber, collected early in the lactation period and late in the lactation period. In the lactating female, the high-chlorinated and hydrophobic compounds were passed less efficiently into the milk than the low-chlorinated compounds and more water-soluble compounds. Significantly, lower maternal blood concentrations than in maternal blubber biopsies suggest a stratification of POP concentrations in the blubber column of lactating female and lower concentrations in the metabolic active inner layers. Over the course of lactation, there was a significant increase in maternal blood and milk concentrations of POPs as opposed to no change in maternal blubber biopsy concentrations. This was most apparent for the hydrophobic and high-chlorinated compounds. The most likely explanation for this is that the metabolic active inner blubber layer, from which the milk lipids are derived from, is in steady state with the circulatory system, while the outer layers are more static and only slowly respond to changes in concentrations elsewhere in the body. The concentrations of the high-chlorinated and hydrophobic compounds were substantially lower in pup blubber than in maternal blubber. This probably relates the combined effect of these compounds stratification in maternal blubber and their slow transfer into the milk. The present study shows that the more hydrophobic and high-chlorinated compounds come to steady state less quickly in the different tissues than the more water-soluble and low-chlorinated compounds in the lactating female and her offspring. This has implications for which matrices to choose when sampling for assessing the toxicological risk of POPs in seals.

Tris (4-chlorophenyl) methane and tris (4-chlorophenyl) methanol in marine mammals from the Estuary and Gulf of St. Lawrence.

Levels of tris (4-chlorophenyl) methanol (TCPM) and its presumed precursor tris (4-chlorophenyl) methane (TCPMe) are reported in marine mammals from the Estuary and Gulf of St. Lawrence, Canada. These compounds were measured in blubber samples of seals and whales using ion trap mass spectrometry (MS/MS) detection. Detectable concentrations of both TCPM and TCPMe were observed in all of the samples analysed. Concentrations of these compounds varied with species ranging from 1.7 to 153 and from 1.3 to 50.6 ng/g lipid wt. for TCPM and TCPMe, respectively. TCPM was from 1.3 to 10 times more concentrated than TCPMe. The highest levels of both TCPM and TCPMe were observed in adult male beluga whales (Delphinapterus leucas) from the St. Lawrence Estuary, while adult female beluga whales from the same area showed levels similar to those in the seals examined. Among the four seal species investigated, TCPM and TCPMe levels were the highest in grey (Halichoerus grypus) and hooded (Cystophora cristata) seals, and lowest in harp seals (Phoca groenlandica). Intermediate levels were found in harbour seals (Phoca vitulina); however, their concentrations might be underestimated considering the younger mean age of these animals. Ratios of both 4,4'-DDE/sigma DDT and TCPM/sigma TCP were very similar between animals from the same species. Strong correlations between sigma TCP and sigma DDT were also observed for each species of mammals, most likely indicating that both sigma TCP and sigma DDT are bioaccumulated in marine mammals. The relationships between sigma DDT and sigma TCP also demonstrate that sigma TCP are less bioaccumulated than sigma DDT by the marine mammal species examined.

Renin-angiotensin system polymorphisms and coronary events in familial hypercholesterolemia.

The role of renin-angiotensin system polymorphisms as risk factors for coronary heart disease (CHD) is controversial. This study investigated their role in patients with heterozygous familial hypercholesterolemia (FH). Polymorphism frequencies for angiotensin-I-converting enzyme insertion/deletion (ACE I/D), angiotensinogen M235T, and angiotensin-II type I receptor (AG2R) A1166C were determined in 112 patients with FH and 72 patients with polygenic hypercholesterolemia, of whom 26.7% and 41.6%, respectively, had established CHD. None of the polymorphisms were associated with risk of CHD in patients with polygenic hypercholesterolemia in this study. Logistic regression analysis of risk factors for CHD in patients with FH identified male sex (odds ratio [OR]=3.03; 95% CI, 3.07 to 3.72; P=0.05), smoking (OR=2.91; 95% CI, 2.16 to 4.24; P=0.05), diastolic blood pressure (OR=3.70; 95% CI, 3.43 to 3.97; P=0.02), plasma glucose (OR=3.31; 95% CI, 3. 10 to 3.52; P=0.04), and the AG2R A1166C polymorphism as risk factors. The OR for the AG2R A1166C polymorphism was 2.26 (95% CI, 1.26 to 3.72; P=0.06) and increased to 3.10 (95% CI, 1.20 to 7.52; P=0.04) after adjustment for other risk factors. The AG2R A1166C polymorphism may interact with severe hypercholesterolemia and other risk factors to increase risk of CHD in FH patients.

Effects of lipids in patients with familial hypercholesterolaemia on the kinetics of the sodium-lithium countertransporter.

Sodium-lithium countertransport kinetics were measured in 87 patients (50 male; 37 female) with heterozygous familial hypercholesterolaemia (FH) and a group of 38 age range and sex-distribution matched controls. Basic clinical data including basic anthropometry, blood pressure were obtained and blood was taken for detailed lipid biochemistry, glucose and insulin measurement. Patients with FH had elevated total cholesterol, low-density lipoprotein (LDL)-cholesterol and apolipoprotein B concentrations compared to controls. The activity and log transformed maximal velocity (Vmax) of the sodium-lithium countertransporter unlike the affinity (Km) were reduced in patients with FH compared to controls (geometric means 0.172 vs 0.217 mmol Li+/L.RBC.hr; P = 0.02; 0.237 vs. 0.317 mmol Li+/L.RBC.hr; P = 0.009 respectively). In multiple regression analysis, log normalised SLC activity correlated weakly with log triglyceride (beta = 0.225; P = 0.06) and cholesterol (beta = -0.112 P = 0.06). Log Vmax correlated with log triglyceride (beta = 0.307; P = 0.02), and high-density lipoprotein (HDL) (beta = 0.74; P = 0.03) whilst Km correlated with HDL (beta = 1.73; P<0.001) and apoAI (beta = -1.76; P = 0.0048), LDL (beta = -0.14; P = 0.05), and creatine kinase (beta = 0.003; P = 0.01). Cholesterol and triglyceride concentrations rather than insulin resistance seem to be the key features affecting the environmental alteration of sodium lithium countertransporter Vmax in patients with familial hypercholesterolaemia.

Transfer of fatty acids from female seal blubber via milk to pup bladder.

Fatty acids were determined by gas chromatography followed by principal component analysis (PCA) and soft independent modelling of class analogy (SIMCA) in the blubber of 18 female grey seals, Halichoerus grypus, in their milk and in the blubber of their 1-week-old nursing pups. Large individual differences were observed in both blubber and milk content of fatty acids. The fatty acid composition of the milk was systematically different from the composition in maternal blubber, with higher relative amounts of the saturated acids, the monounsaturated with 20 carbon atoms and the n3 polyunsaturated, except 18:3n3. The composition of the fatty acids in the blubber of the pups was different from that of the milk. The same fatty acids that were enriched in the milk were depleted in the blubber of the pups. Therefore the fatty acid composition in the blubber of the pups was similar to that in the adults, although not identical. The results from this investigation imply that the composition of the fatty acids in the blubber of female seals and in the blubber of their pups cannot be determined directly by analysis of fatty acid composition of milk.

Identification of genetic heterogeneity in Refsum's disease.

Refsum's disease (MIM 266500) is a recessive disorder characterised by defective peroxisomal alpha-oxidation of phytanic acid. A Refsum's disease gene, phytanoyl-CoA hydroxylase (PAHX), has been localised to chromosome 10p13 between the markers D10S226-D10S223. This study investigated whether all cases of Refsum's disease were linked with chromosome 10p13. Eight genetically informative families comprising 92 individuals including 17 living patients with a Refsum's disease phenotype and initial plasma phytanic acid > 200 micromol/L were recruited. Linkage to the 10pter-10p11.2 region was investigated using a panel of eight dinucleotide repeat markers. Linkage analysis of this phenotypically identical cohort suggested that Refsum's disease was genetically heterogeneous (Zmax = 5.28, alpha = 0.45). Two subgroups were identified. One group of four families with eight affected individuals had a maximum multipoint lod score for linkage of 3.89 in the region D10S547 to D10S191, whilst in another three families with nine affected individuals linkage to this region was definitely excluded. Our results show that Refsum's disease is genetically heterogeneous, with up to 55% of cases not being linked to the PAHX gene locus at D10S547 to D10S223. This suggests that Refsum's disease, in common with other peroxisomal 'diseases', may be more accurately described as a heterogeneous syndrome.

Differing relationships of methylene tetrahydrofolate reductase genotypes with cardiovascular risk in familial and polygenic hypercholesterolaemia.

BACKGROUND: Plasma homocysteine and the methylene tetrahydrofolate reductase C677T polymorphism have been suggested as being risk factors for cardiovascular disease. OBJECTIVE: To determine whether plasma homocysteine and the methylene tetrahydrofolate reductase C677T polymorphism are risk factors for coronary heart disease in patients with heterozygous familial hypercholesterolaemia as compared with those with polygenic hyperlipidaemia. METHODS: Plasma homocysteine and the methylene tetrahydrofolate reductase polymorphism were assessed with other risk factors in 112 patients with familial hypercholesterolaemia and 72 patients with polygenic hyperlipidaemia, of whom 29 (25.8%) and 30 (41%) respectively had established cardiovascular disease and in 100 healthy normal subjects. RESULTS: Plasma homocysteine was not significantly elevated in patients with and without coronary heart disease with familial hypercholesterolaemia or polygenic hyperlipidaemia compared with controls. The allele frequencies for C677T were significantly different in patients with coronary heart disease and with polygenic hyperlipidaemia (0.35 versus 0.29) (P = 0.02) as opposed to those with coronary heart disease and familial hypercholesterolaemia (0.25 versus 0.30) (P = 0.63). Methylene tetrahydrofolate reductase genotype but not homocysteine had a weak association with coronary heart disease in logistic regression analysis in patients with polygenic hyperlipidaemia (P = 0.05) but neither methylene tetrahydrofolate reductase genotype or plasma homocysteine was a risk factor in patients with familial hypercholesterolaemia. CONCLUSION: Whilst methylene tetrahydrofolate reductase genotype may be a weak risk factor for coronary heart disease in polygenic hyperlipidaemia as opposed to familial hypercholesterolaemia, homocysteine does not seem to be an important risk factor for coronary heart disease in patients in southern UK.

Fat transfer and energetics during lactation in the hooded seal: the roles of tissue lipoprotein lipase in milk fat secretion and pup blubber deposition.

Hooded seals (Cystophora cristata) lactate for 3.6 days during which females simultaneously fast and transfer large amounts of energy to their pups through fat-rich milk. Pups grow rapidly, principally due to blubber deposition. Lipoprotein lipase (LPL), the primary enzyme responsible for tissue uptake of triglyceride fatty acids, may strongly influence both maternal milk fat secretion and pup blubber deposition. We measured the energetic costs of lactation (using hydrogen isotope dilution, 3H2O), milk composition, prolactin, and LPL activity (post-heparin plasma LPL [PH LPL], blubber, mammary gland and milk; U) in six females. PH LPL and blubber LPL were measured in their pups. Females depleted 216.3 MJ.day-1 of body energy and fat accounted for 59% of maternal mass loss and 90% of postpartum body energy loss, but maternal body composition changed little. Maternal blubber LPL was negligible (0.0-0.2 U), while mammary LPL was elevated (1.8-2.5 U) and was paralleled by changes in prolactin. Estimated total mammary LPL activity was high (up to 20,000 U.animal-1) effectively favoring the mammary gland for lipid uptake. Levels of total blubber LPL in pups increased seven-fold over lactation. Pups with higher PH LPL at birth had greater relative growth rates (P = 0.025). Pups with greater blubber stores and total blubber LPL activity had elevated rates of fat deposition (P = 0.035).