Role of oestradiol in the regulation of the seasonal antler cycle in female reindeer, Rangifer tarandus.
(1/123)
Reindeer (or caribou), Rangifer tarandus, is the only extant species of deer in which females as well as males normally develop antlers that are cast and regrown each year. This study investigated the role of ovarian oestradiol in the regulation of the seasonal antler cycle in female reindeer. Ovariectomized Norwegian reindeer living outdoors in northern Norway (69 degrees N) were treated with continuous-release subcutaneous Silastic implants containing oestradiol, which maintained the blood concentrations of oestradiol within the physiological range for the mating season from June to October-November. The treatment with oestradiol induced the synchronized maturation of the antlers and rapid cleaning of the velvet-like skin in August-September in the ovariectomized reindeer, a pattern very similar to that observed in ovary-intact controls living under the same conditions. The removal of the steroid implant in October-November caused the premature casting of the antlers in early winter in two of five animals, while the remainder cast at the normal time in spring; this response was seen whether the animals had received one or two oestradiol implants in autumn. The antlers developed by the ovariectomized, oestradiol-treated females were significantly heavier and carried more branches than the ovariectomized animals without oestradiol replacement, and were marginally heavier than the antlers of intact controls. These results support the view that oestradiol is the biologically active steroid secreted by the ovary in intact female reindeers that induces the normal development of the antlers. Oestradiol stimulates the growth and mineralization of the antler bone, the cleaning of the velvet, and suppresses the casting of the hard antlers. This endocrine control ensures that the hard antlers, which function as weapons, are retained throughout the autumn and winter when the females are normally pregnant and when competition between females over food in the snow is most intense; hence there is a reproductive advantage to explain the evolution of antlers in females. (+info)
Radionuclides in the lichen-caribou-human food chain near uranium mining operations in northern Saskatchewan, Canada.
(2/123)
The richest uranium ore bodies ever discovered (Cigar Lake and McArthur River) are presently under development in northeastern Saskatchewan. This subarctic region is also home to several operating uranium mines and aboriginal communities, partly dependent upon caribou for subsistence. Because of concerns over mining impacts and the efficient transfer of airborne radionuclides through the lichen-caribou-human food chain, radionuclides were analyzed in tissues from 18 barren-ground caribou (Rangifer tarandus groenlandicus). Radionuclides included uranium (U), radium (226Ra), lead (210Pb), and polonium (210Po) from the uranium decay series; the fission product (137Cs) from fallout; and naturally occurring potassium (40K). Natural background radiation doses average 2-4 mSv/year from cosmic rays, external gamma rays, radon inhalation, and ingestion of food items. The ingestion of 210Po and 137Cs when caribou are consumed adds to these background doses. The dose increment was 0.85 mSv/year for adults who consumed 100 g of caribou meat per day and up to 1.7 mSv/year if one liver and 10 kidneys per year were also consumed. We discuss the cancer risk from these doses. Concentration ratios (CRs), relating caribou tissues to lichens or rumen (stomach) contents, were calculated to estimate food chain transfer. The CRs for caribou muscle ranged from 1 to 16% for U, 6 to 25% for 226Ra, 1 to 2% for 210Pb, 6 to 26% for 210Po, 260 to 370% for 137Cs, and 76 to 130% for 40K, with 137Cs biomagnifying by a factor of 3-4. These CRs are useful in predicting caribou meat concentrations from the lichens, measured in monitoring programs, for the future evaluation of uranium mining impacts on this critical food chain. (+info)
Genetic diversity of pestiviruses: identification of novel groups and implications for classification.
(3/123)
The complete Npro coding sequences were determined for 16 pestiviruses isolated from cattle, pig, and several wild ruminant species including reindeer, bison, deer, and bongo. Phylogenetic analysis enabled the segregation of pestiviruses into the established species bovine viral diarrhea virus-1 (BVDV-1), BVDV-2, border disease virus (BDV), and classical swine fever virus (CSFV). For BVDV-1 five distinct subgroups were identified, while BVDV-2, BDV, and CSFV were each subdivided into two subgroups. The virus isolates from bongo and deer as well as one porcine virus isolate belong to BVDV-1. Interestingly, the isolates from reindeer and bison are distinct from the established pestivirus species. The Npro sequences from these two viruses are more similar to BDV than to the other pestivirus species. Calculation of the pairwise evolutionary distances allowed a clear separation of the categories species, subgroup, and isolate only when the reindeer/bison viruses were considered as members of an additional pestivirus species. Furthermore, the entire E2 coding sequences of a representative set of virus isolates covering all recognized species and subgroups were studied. Segregation of pestiviruses based on the E2 region was identical with that obtained with the N(pro) sequences. (+info)
Molecular characterization of Brucella strains isolated from marine mammals.
(4/123)
Recently, gram-negative bacteria isolated from a variety of marine mammals have been identified as Brucella species by conventional phenotypic analysis. This study found the 16S rRNA gene from one representative isolate was identical to the homologous sequences of Brucella abortus, B. melitensis, B. canis, and B. suis. IS711-based DNA fingerprinting of 23 isolates from marine mammals showed all the isolates differed from the classical Brucella species. In general, fingerprint patterns grouped by host species. The data suggest that the marine mammal isolates are distinct types of Brucella and not one of the classical species or biovars invading new host species. In keeping with historical precedent, the designation of several new Brucella species may be appropriate. (+info)
Genomic differentiation of Neanderthals and anatomically modern man allows a fossil-DNA-based classification of morphologically indistinguishable hominid bones.
(5/123)
Southern blot hybridizations of genomic DNA were introduced as a relatively simple fossil-DNA-based approach to classify remains of Neanderthals. When hybridized with genomic DNA of either human or Neanderthal origin, DNA extracted from two Neanderthal finds-the Os parietale, from Warendorf-Neuwarendorf, Germany, and a clavicula, from Krapina, Croatia-was shown to yield hybridization signals that differ by at least a factor of two compared to the signals obtained with the use of fossil DNA of an early Homo sapiens from the Vogelherd cave (Stetten I), Germany. When labeled chimpanzee DNA was used as a probe, Neanderthal and human DNA, however, revealed hybridization signals of similar intensity. Thus, the genome of Neanderthals is expected to differ significantly from the genome of anatomically modern man, because of the contrasting composition of repetitive DNA. These data support the hypothesis that Neanderthals were not ancestors of anatomically modern man. (+info)
Evidence for the presence of two novel pestivirus species.
(6/123)
The genus Pestivirus of the family Flaviviridae comprises four species, namely Bovine viral diarrhea virus-1 (BVDV-1), BVDV-2, Border disease virus (BDV), and Classical swine fever virus (CSFV). Comparative analyses of partial sequences have suggested that pestivirus isolates from giraffe (Giraffe-1) and reindeer (Reindeer-1) are distinct from the established species (Becher et al., Virology 262, 64--71, 1999). In this study, we report the complete genomic sequences of pestivirus strains Giraffe-1 and Reindeer-1. Comparative sequence analyses revealed considerable differences among Giraffe-1, Reindeer-1, and the currently recognized pestivirus species. Phylogenetic analysis of the complete coding sequences of these two strains, along with 13 other sequences representing the four established species, indicated that CSFV, BDV, and Reindeer-1 have bifurcated from one common branch and BVDV-1 and BVDV-2 from another. In the former branch BDV and the pestivirus from reindeer are more similar to each other than to CSFV. The giraffe pestivirus is equally distinct from both major branches. In addition, the antigenic relatedness of pestivirus isolates covering the observed major genetic groups was studied by cross-neutralization assays. A clustering procedure on the basis of antigenic differences indicated the presence of six major groups corresponding to the genetically defined groups. Taken together, the results of our analyses addressing both nucleotide sequence relatedness and serological relatedness argue for the inclusion of Giraffe-1 and Reindeer-1 as the first members of two separate novel species within the genus Pestivirus. (+info)
Wet belly in reindeer (Rangifer tarandus tarandus) in relation to body condition, body temperature and blood constituents.
(7/123)
Wet belly, when the reindeer becomes wet over the lower parts of the thorax and abdomen, sometimes occurs in reindeer during feeding. In a feeding experiment, 11 out of 69 reindeer were affected by wet belly. The problem was first observed in 7 animals during a period of restricted feed intake. When the animals were then fed standard rations, 3 additional animals fed only silage, and 1 fed pellets and silage, became wet. Four animals died and 1 had to be euthanized. To investigate why reindeer developed wet belly, we compared data from healthy reindeer and reindeer affected by wet belly. Urea, plasma protein, glucose, insulin and cortisol were affected by restricted feed intake or by diet but did not generally differ between healthy reindeer and those with wet belly. The wet animals had low body temperature and the deaths occurred during a period of especially cold weather. Animals that died were emaciated and showed different signs of infections and stress. In a second experiment, with 20 reindeer, the feeding procedure of the most affected group in the first experiment was repeated, but none of the reindeer showed any signs of wet belly. The study shows that wet belly is not induced by any specific diet and may affect also lichen-fed reindeer. The fluid making the fur wet was proven to be of internal origin. Mortality was caused by emaciation, probably secondary to reduced energy intake caused by diseases and/or unsuitable feed. (+info)
The role of parasites in the dynamics of a reindeer population.
(8/123)
Even though theoretical models show that parasites may regulate host population densities, few empirical studies have given support to this hypothesis. We present experimental and observational evidence for a host-parasite interaction where the parasite has sufficient impact on host population dynamics for regulation to occur. During a six year study of the Svalbard reindeer and its parasitic gastrointestinal nematode Ostertagia gruehneri we found that anthelminthic treatment in April-May increased the probability of a reindeer having a calf in the next year, compared with untreated controls. However, treatment did not influence the over-winter survival of the reindeer. The annual variation in the degree to which parasites depressed fecundity was positively related to the abundance of O. gruehneri infection the previous October, which in turn was related to host density two years earlier. In addition to the treatment effect, there was a strong negative effect of winter precipitation on the probability of female reindeer having a calf. A simple matrix model was parameterized using estimates from our experimental and observational data. This model shows that the parasite-mediated effect on fecundity was sufficient to regulate reindeer densities around observed host densities. (+info)