Genetic comparisons of New and Old World coregonid fishes*

The genetic relationships among New and Old World coregonid fishes were studied by electrophoresis. The genetic composition of 60 populations, representing perhaps nine commonly recognized species of Coregonus and Stenodus from Europe and North America was determined for 37 genetic loci. Six distinct genetic groups were evident. The first contained only populations of the inconnu, Stenodus leucichthys (Güldenstadt). The Nei genetic distance between Stenodus and Coregonus was 0.305, a relatively small value as compared to other salmonid inter-generic comparisons. The second genetic grouping contained the Arctic cisco, C. autumnalis (Pallas), the N. American lake cisco, C. artedii Lesueur, and the Irish pollan, C. autumnalis pollan Thompson. These three taxa appear to be conspecific on the basis of genetic distances. The third genetic grouping contained the European whitefish, C. lavaretus (L.), and the N. American lake whitefish, C. clupeaformis (Mitchill). European and lake whitefish may be conspecific. Lake whitefish from northwestern N. America were more closely related to European whitefish (genetic distance 0.038) than to lake whitefish from central N. America (genetic distance 0.098). The fourth group contained the broad whitefish, C. nasus (Pallas), which is perhaps more closely related to the European/lake whitefish groups than other coregonids. The fifth genetic grouping contained only the Asian endemic, C. peled (Gmelin), and the sixth contained the least cisco, C. sardinella Valenciennes, and vendace, C. albula (L.), which also appear to be conspecific. The widespread genetic groupings obtained for ciscoes indicate that they do not constitute a single closely related group within the genus Coregonus.     

Accumulation of scopoletin is associated with the high disease resistance of the hybrid Nicotiana glutinosa x Nicotiana debneyi

The high disease resistance of the amphidiploid hybrid of Nicotiana glutinosa x Nicotiana debneyi is associated with high constitutive levels of two phenolic compounds as analysed by high-performance liquid chromatography. The structures of these two compounds were elucidated by means of gas chromatography-tandem mass spectrometry, fluorescence- and light-spectrophotometry to be those of scopolin and scopoletin. They reached levels of 4 nmol·(g FW)^?1 and 35 nmol·(g FW)^?1, respectively, in leaf tissues of the hybrid, about 10–50 times the amount found in the parental species. Scopoletin showed a direct antimicrobial activity against Cercospora nicotianae, Phytophthora parasitica var. nicotianae, Pseudomonas syringae pvs. tabaci and syringae and tobacco mosaic virus when added to synthetic growth media, mixed with the inoculum or sprayed onto tobacco plants prior to inoculation. We postulate that the high amount of toxic phenolics in the leaves of the hybrid N. glutinosa x N. debneyi contributes to its high disease resistance.     

In vivo binding and clearance of circulating antigen by bispecific heteropolymer-mediated binding to primate erythrocyte complement receptor.

We have used the avidin/biotin system to construct soluble, cross-linked bispecific heteropolymers containing mAb to both the primate E C receptor and the DNP group. These heteropolymers facilitate in vitro binding of DNP-bovine gamma-globulin (DNP-BGG) to both human and squirrel monkey E. Intravenous injection in squirrel monkeys of DNP-BGG followed by heteropolymer leads to E binding and clearance from the circulation of a significant fraction of both heteropolymer and DNP-BGG, without lysis or clearance of the E. This methodology may potentially be used to treat a variety of infectious diseases and other syndromes associated with blood-borne pathogens.     

First ovulation and ketone body status in the early postpartum period of dairy cows

The effect of ketone body status on occurrence of first ovulation during early lactation was assessed in 84 multiparous dairy cows under field conditions. Animals were equally distributed across 8 farms and were controlled by the same herd fertility monitoring program. Cows were visited twice antepartum and 6 times postpartum at weekly intervals between 5:30 and 8:30 AM. On these occasions, body condition scores and milk yields were measured, blood and milk samples were taken, cows were gynecologically examined, and parameters of reproduction were determined. The onset of first ovulation was specified by milk progesterone determination and rectal palpation. Cows starting postpartum ovarian cyclicity within or after 30 d were classified as early and late responders (ER and LR, respectively). Resumption of the estrous cycle within 30 d postpartum is considered optimal under practical conditions, and classification based on this threshold value resulted in groups of equal size and equal distribution of ER + LR cows within farms. Ketone bodies measured were beta-hydroxybutyrate in serum and acetoacetate and acetone in serum and milk. Blood serum and milk ketone body concentrations during the first 6 wk of lactation were higher in LR than in ER, whereas plasma glucose and nonesterified fatty acid and milk fat, protein and urea concentrations did not differ between groups. Maximal concentrations of ketone bodies from parturition to first ovulation were better predictors of the onset of the estrous cycle than mean or minimal concentrations over the same period. Milk acetone and serum beta-hydroxybutyrate concentrations provided the most reliable information with regard to resumption of ovarian activity of all ketone bodies.     

Gene flow and effective population size in two life-history types of broad whitefish Coregonus nasus from the Canadian Arctic

In this study, the magnitude and direction of gene flow and estimates of effective population sizes (N(e) ) were quantified among two life-history types (lacustrine and anadromous) of broad whitefish Coregonus nasus in the lower Mackenzie River system. The data suggest that dispersal and subsequent gene flow occurs between these groups, with the former appearing to be asymmetrical. Gene flow may potentially be directionally biased as well, a result attributed to source-sink population dynamics and the ongoing process of post-glacial colonization and contemporary range expansion. Additionally, average N(e) estimates were consistently lower for lacustrine populations of C. nasus although confidence intervals for both contemporary and historical estimates broadly overlapped. The lower average estimates of N(e) for lacustrine populations was suggested to be the result of more recent founding events following post-glacial dispersal. This study provides one of the first assessments of gene flow and N(e) in an Arctic coregonine, results that may be relevant to other freshwater and anadromous Arctic species persisting in systems near the periphery of their range.     

Phylogeny of five Prosopium species with comparisons with other Coregonine fishes based on isozyme electrophoresis*

Phylogenetic relationships of Prosopium gemmifer, P. spilonotus, P. williamsoni, P. cylindraceum and P. coulteri species were determined based on variation at 37 allozyme loci, and compared with Stenodus and nine species of Coregonus. Of the three genera, Prosopium was the most distinct with Nei genetic distances to Coregonus of D=0·55—1·05 and to Stenodus of D=0·58—0·92. Stenodus and Coregonus were closely related but grouped as sister taxa with a mean genetic distance of 0·31 (range 0·22—0·40). These results agree with the degree of morphological differentiation among the genera as well as with observations concerning hybridization, e.g. many Coregonus species hybridize with Stenodus, but no natural hybrids are known between Prosopium and other coregonines. Within Prosopium, P. coulteri was the most divergent species branching out at D=0·51 from the others and followed by P. cylindraceum at D=0·28. The three remaining species are closely related. Among them P. williamsoni joins P. gemmifer and P. spilonotus at 0·04, and the distance between the two Bear Lake endemics is only 0·004. The distance between P. cylindraceum and the remaining Prosopium species is similar to distances between Stenodus and Coregonus. The small genetic distance between P. spilonotus and P. gemmifer suggests their recent divergence. Even though no fixed differences were found between them, diVerent alleles were present at two loci at large enough frequencies to indicate reproductive isolation. This confirms that P. gemmifer and P. spilonotus are good biological species as indicated by their distinct morphology and ecology.     

DNA Methylation Mediates Persistent Epileptiform Activity In Vitro and In Vivo

Epilepsy is a chronic brain disorder involving recurring seizures often precipitated by an earlier neuronal insult. The mechanisms that link the transient neuronal insult to the lasting state of epilepsy are unknown. Here we tested the possible role of DNA methylation in mediating long-term induction of epileptiform activity by transient kainic acid exposure using in vitro and in vivo rodent models. We analyzed changes in the gria2 gene, which encodes for the GluA2 subunit of the ionotropic glutamate, alpha-amino-3-hydroxy-5-methyl-4-isoxazole proprionic acid receptor and is well documented to play a role in epilepsy. We show that kainic acid exposure for two hours to mouse hippocampal slices triggers methylation of a 5’ regulatory region of the gria2 gene. Increase in methylation persists one week after removal of the drug, with concurrent suppression of gria2 mRNA expression levels. The degree of kainic acid-induced hypermethylation of gria2 5’ region varies between individual slices and correlates with the changes in excitability induced by kainic acid. In a rat in vivo model of post kainic acid-induced epilepsy, we show similar hypermethylation of the 5’ region of gria2. Inter-individual variations in gria2 methylation, correlate with the frequency and intensity of seizures among epileptic rats. Luciferase reporter assays support a regulatory role for methylation of gria2 5’ region. Inhibition of DNA methylation by RG108 blocked kainic acid-induced hypermethylation of gria2 5’ region in hippocampal slice cultures and bursting activity. Our results suggest that DNA methylation of such genes as gria2 mediates persistent epileptiform activity and inter-individual differences in the epileptic response to neuronal insult and that pharmacological agents that block DNA methylation inhibit epileptiform activity raising the prospect of DNA methylation inhibitors in epilepsy therapeutics.     

Dietary characteristics of co-occurring polar cod (<Emphasis Type="Italic">Boreogadus saida</Emphasis>) and capelin (<Emphasis Type="Italic">Mallotus villosus</Emphasis>) in the Canadian Arctic,Darnley Bay

Reduction in sea ice due to climate change is expected to have a negative impact on habitat availability for Arctic marine fishes and induce range expansion of species from southern environments. Such an effect will likely be observed in the abundance of polar cod, Boreogadus saida (Lepechin, 1774), as well as interspecific interactions of this intermediate-level trophic taxon, particularly in more southerly fringing seas in the Arctic. Polar cod and capelin, Mallotus villosus (Müller, 1776), are pelagic, planktivorous forage fishes, which occupy similar dietary niches and are the primary prey of marine predators. Co-occurring polar cod and capelin were collected at seven stations in Darnley Bay, NT, during August 2013. Standard length (SL), used as a proxy for age, suggested that polar cod (mean ± 1 SD: 71.1 ± 10.3 mm) were predominantly age 1+ and capelin (96.2 ± 13.4 mm) were mostly age 2+. Stomach content analyses indicated that both species feed extensively on calanoid copepods (Calanus hyperboreus, C. glacialis, Metridia longa) and amphipods (Themisto libellula). There was high dietary overlap between capelin and polar cod, evidenced by Schoener’s index (0.80). Additionally the quantity of dietary items, biomass and energetic content consumed differed among size classes in both capelin (SL, 70.5–132.0 mm) and polar cod (SL, 42.1–114.4 mm). This study illustrates that the diets of these sympatric forage fishes in an Arctic ecosystem are very similar, indicating a high potential for interspecific competition as the sub-Arctic capelin expands its range into Arctic regions with climate change.