Transitions between blocked and zonal flows in a rotating annulus with topography

The mid-latitude atmosphere is dominated by westerly, nearly zonal flow. Occasionally, this flow is deflected poleward by blocking anticyclones that persist for 10 days or longer. Experiments in a rotating annulus used radial pumping to generate a zonal jet under the action of the Coriolis force. In the presence of two symmetric ridges at the bottom of the annulus, the resulting flows were nearly zonal at high forcing or blocked at low forcing. Intermittent switching between blocked and zonal patterns occurs because of the jet's interaction with the topography. These results shed further light on previous atmospheric observations and numerical simulations.     

Uracil DNA glycosylase activity is dispensable for immunoglobulin class switch

Activation-induced cytidine deaminase (AID) is required for the DNA cleavage step in immunoglobulin class switch recombination (CSR). AID is proposed to deaminate cytosine to generate uracil (U) in either mRNA or DNA. In the second instance, DNA cleavage depends on uracil DNA glycosylase (UNG) for removal of U. Using phosphorylated histone gamma-H2AX focus formation as a marker of DNA cleavage, we found that the UNG inhibitor Ugi did not inhibit DNA cleavage in immunoglobulin heavy chain (IgH) locus during CSR, even though Ugi blocked UNG binding to DNA and strongly inhibited CSR. Strikingly, UNG mutants that had lost the capability of removing U rescued CSR in UNG-/- B cells. These results indicate that UNG is involved in the repair step of CSR yet by an unknown mechanism. The dispensability of U removal in the DNA cleavage step of CSR requires a reconsideration of the model of DNA deamination by AID.     

Outcome following removal of canine spindle cell tumours in first opinion practice: 104 cases

O bjectives : To define the outcome of a cohort of canine patients with a histological diagnosis of spindle cell tumour of soft tissue managed solely by surgery in first opinion practice.
M ethods : Clinical details of 104 spindle cell sarcomas submitted to Finn Pathologists during the year 2000 were reviewed. Questionnaires were sent to the submitting veterinarians, requesting details about the tumour, surgery performed and ultimate outcome of the patient.
R esults : The method of surgical resection was described as marginal in 45 dogs (44·2 per cent). Excision margins of 3 cm or more were described in less than 10 per cent of cases. Tumours recurred locally in 29 dogs (27·9 per cent). Eighteen dogs (21·7 per cent) died of tumour-related causes. Most deaths were unrelated to sarcoma (50 dogs, 60·2 per cent) or unknown (15 dogs, 18 per cent). The median survival time was 1013 days. Tumour size, location or degree of surgical resection were not significantly related to survival or tumour recurrence. A palpable assessment of tumour invasion into underlying tissues was significantly associated with decreased disease-free interval (P<0·0001) and survival time (P = 0·0070).
C linical S ignificance : The results of this retrospective study indicate that many spindle cell tumours managed in first opinion practice exhibit a low-grade biological behaviour and may respond well to more conservative surgery than current recommendations advise.     

Evaluation of genetic diversity of eight grouper species <Emphasis Type="Italic">Epinephelus</Emphasis> spp. based on microsatellite variations

ABSTRACT:   Genetic diversity among eight species of grouper, Epinephelus bleekeri , E. coioides , E. malabaricus , E. ongus , E. akaara , E. maculatus , E. merra and E. fuscoguttatus , was studied using six microsatellite loci, Em-01 *, Em-03 *, Em-07 *, Em-08 *, Em-10 *, and CA-07 *, with the aim of exploring the feasibility of using microsatellite data for species identification. The results showed high levels of genetic differentiation among species ( F _ST  = 0.4403 and R _ST  = 0.4954). Species identification based on fixed allelic differences was possible between E. coioides , E. ongus , and E. fuscoguttatus at Em-01 * and between E. fuscoguttatus and E. ongus at Em-08 *. Private alleles were found in all species, except for E. ongus . Pairwise F _ST ranged 0.238–0.578 ( P  < 0.008 Bonferroni correction), and Nei's genetic distance ranged 0.433–2.710. Size homoplasy was observed at Em-03 * 157 allele, which was characterized by a T–C transition at the 119th nucleotide site of PCR products. The genetic assignment test unambiguously assigned each individual to the correct species. Thus, this test can be used for species identification of unknown individuals when the multilocus genotypes of the six microsatellite loci are available. The phylogenetic (neighbor-joining) tree, which was constructed based on the genetic distance matrix, separated the eight grouper species into two main groups.     

Onset of individual growth difference in larviculture of Pacific bluefin tuna <Emphasis Type="Italic">Thunnus orientalis</Emphasis> using fertilized eggs obtained from one female

We conducted a rearing experiment on Pacific bluefin tuna (PBT) larvae, which originated from one female broodstock, and determined the growth history of the larvae to clarify when the growth difference occurs. We investigated the otolith microstructure of the PBT larvae to examine the individual growth history and to predict the age and body size at the onset of individual growth difference. Since total length (TL) of fish can be back-calculated from otolith radius, we back-calculated TLs of 100 fish of 19 days post hatch (dph) divided into three size groups (small, intermediate, large). Growth difference was recognized from 3 dph (mouth opening), and the difference became larger thereafter. Growth of large-size fish was assumed to be promoted by the feeding conditions of PBT larvae.