Biomedical subjects

K A Hobson

Publications and source records attributed to K A Hobson.

21 records · Page 2Linked to original sources

PubMed1997

Isolation of microsatellite DNA markers from a passerine bird, Dendroica petechia (the yellow warbler), and their use in population studies.

We describe the isolation and genetic characterization of five microsatellite loci in a passerine bird, the yellow warbler Dendroica petechia, and assess their use for various types of population-level analysis using data from two breeding populations. All five loci show levels of variability comparable to those observed in other vertebrates (Hexp = 0.388-0.989). One locus, Dp mu 05, is highly variable with 46 alleles detected in 41 individuals. All loci appeared to segregate in a Mendelian fashion as judged by patterns of inheritance in known families. However, one locus showed a significant heterozygote deficiency in one population suggesting the possible presence of null alleles at this locus. These markers provide a highly accurate system for determination of parentage in this species: the probability of detecting extrapair fertilization by males given known maternity was 0.999 in each of two separate populations. Comparison of allele frequencies and genetic distances between the two populations showed no evidence for significant differences in allele frequencies at individual loci, whereas the overall genetic distance and FST-value are significantly different from zero suggesting weak differentiation. Finally, cross-species amplification experiments showed that at least one locus appears to amplify products in a wide range of birds including nonpasserine species. Thus, our results demonstrate that these loci will provide a useful set of genetic information for addressing a wide range of population-level analyses in this and other bird species.

Animals↗

PubMed1995

Can seal eating explain elevated levels of PCBs and organochlorine pesticides in walrus blubber from eastern Hudson Bay (Canada)?

Walrus (Odobenus rosmarus) blubber samples from Inukjuak and Akulivik (East Hudson Bay), Foxe Basin (Igloolik and Hall Beach) and Loks Land (East Baffin Island) were analysed for PCB congeners (ortho and non-ortho substituted) and other persistent organochlorines (DDT, toxaphene, chlordanes, dieldrin, mirex), as well as chlorinated dioxins/furans, to document spatial trends in contaminants in Canadian Arctic marine biota. Samples from 19 of 53 individuals had concentrations of SigmaPCBs greater than 1000 ng g(-1) (wet wt); the remaining individuals had much lower concentrations (50-600 ng g(-1)). Highest concentrations were found in samples from Inukjuak where average concentrations in blubber of females (N = 9) were 1450 +/- 954 ng g(-1) toxaphene, 2750 +/- 1780 ng g(-1) SigmaCHLOR, 2160 +/- 925 ng g(-1) SigmaDDT and 4790 +/- 2380 ng g(-1) SigmaPCB. SigmaPCB and SigmaDDT concentrations greater than 1000 ng g(-1) were unexpected based on previous studies of walrus from Greenland and Alaska. Local contamination was ruled out because levels of all organochlorines were elevated in each animal from Inukjuak, and elevated levels were also found in animals from Akulivik and Loks Land. Walrus from Inukjuak had sigma13C and sigma15N values in muscle intermediate between those of ringed seals (Phoca hispida) and those of walrus from Akulivik with low organochlorine levels. There was a weak but significant correlation between and sigma15N and (log)SigmaPCB. The Inukjuak walrus also had higher proportions of highly chlorinated PCB congeners, and higher DDE/SigmaDDT ratios than walrus from Igloolik or Akulivik. The results suggest that the walrus with elevated organochlorines are feeding at a higher trophic level than those with low levels and are probably utilizing ringed seals for a portion of their diet.

Journal Article↗

PubMedDate not supplied

Persistent organic pollutants (POPs) in a small, herbivorous, arctic marine zooplankton (Calanus hyperboreus): trends from April to July and the influence of lipids and trophic transfer.

Samples of Calanus hyperboreus, a herbivorous copepod, were collected (n = 20) between April and July 1998, and water samples (n = 6) were collected in May 1998, in the Northwater Polynya (NOW) to examine persistent organic pollutants (POPs) in a high Arctic marine zooplankton. Lipid content (dry weight) doubled, water content (r2 = 0.88) and delta15N (r2 = 0.54) significantly decreased, and delta13C significantly increased (r2 = 0.30) in the C. hyperboreus over the collection period allowing an examination of the role of these variables in POP dynamics in this small pelagic zooplankton. The rank and concentrations of POP groups in C. hyperboreus over the entire sampling was sum of PCB (30.1 +/- 4.03 ng/g, dry weight) > sum of HCH (11.8 +/- 3.23) > sum of DDT (4.74 +/- 0.74), sum of CHLOR (4.44 +/- 1.0) > sum of CIBz (2.42 +/- 0.18), although these rankings varied considerably over the summer. The alpha- and gamma-HCH and lower chlorinated PCB congeners were the most common POPs in C. hyperboreus. The relationship between bioconcentration factor (BCF) and octanol-water partition coefficient (Kow) observed for the C. hyperboreus was linear and near 1:1 (slope = 0.72) for POPs with a log Kow between 3 and 6 but curvilinear when hydrophobic POPs (log Kow > 6) were included. Concentrations of sum of HCH. Sum of CHLOR and sum of CIBz increased over the sampling period, but no change in sum of PCB or sum of DDT was observed. After removing the effects of time, the variables lipid content, water content, delta15N and delta13C did not describe POP concentrations in C. hyperboreus. These results suggest that hydrophobic POP (log Kow = 3.86.0) concentrations in zooplankton are likely to reflect water concentrations and that POPs do not biomagnify in C. hyperboreus or likely in other small, herbivorous zooplankton.

Adipose Tissue↗