Structural and functional connectivity of marine fishes within a semi-enclosed Newfoundland fjord.

The interplay between structural connectivity (i.e. habitat continuity) and functional connectivity (i.e. dispersal probability) in marine fishes was examined in a coastal fjord (Holyrood Pond, Newfoundland, Canada) that is completely isolated from the North Atlantic Ocean for most of the year. Genetic differentiation was described in three species (rainbow smelt Osmerus mordax, white hake Urophycis tenuis and Atlantic cod Gadus morhua) with contrasting life histories using seven to 10 microsatellite loci and a protein-coding locus, PanI (G. morhua). Analysis of microsatellite differentiation indicated clear genetic differences between the fjord and coastal regions; however, the magnitude of difference was no more elevated than adjacent bays and was not enhanced by the fjord's isolation. Osmerus mordax was characterized by the highest structure overall with moderate differentiation between the fjord and St Mary's Bay (F(ST)c.0.047). In contrast, U. tenuis and G. morhua displayed weak differentiation (F(ST) < 0.01). Nonetheless, these populations did demonstrate high rates (< 75%) of Bayesian self-assignment. Furthermore, elevated differentiation was observed at the PanI locus in G. morhua between the fjord and other coastal locations. Interestingly, locus-specific genetic differentiation and expected heterozygosity were negatively associated in O. mordax, in contrast to the positive associations observed in U. tenuis and G. morhua. Gene flow in these species is apparently unencumbered by limited structural connectivity, yet the observed differentiation suggests that population structuring exists over small scales despite high dispersal potential.

Determination of anaesthetic agent concentration by refractometry.

Reference refractivity values have been derived for the anaesthetic agents halothane, isoflurane, enflurane, sevoflurane and desflurane which are traceable to national measurement standards. A simple method and equation have been derived for the application of these data to the measurement of agent concentration by refractometry. The main instrumental sources of uncertainty associated with this method are discussed and their respective contributions quantified. Agent concentration can be measured routinely at the +/- 1% level of uncertainty using this approach.

The cyclic hematopoietic dog: a model for spontaneous secondary amyloidosis. A morphologic study.

Spontaneous amyloidosis was found in dogs affected with hereditary cyclic hematopoiesis (CH dogs). Early perifollicular deposits of amyloid were observed in the spleens of 15-week-old CH dogs. By the 24th week, amyloid deposits were also found in the liver, kidneys, pancreas, adrenals, and small intestine; the incidence of the condition rose to more than 90%. The visceral involvement and the histologic characteristics of amyloid deposition closely resemble those of the secondary form in humans. A transient lymphoid hypoplasia was noted in the spleens of neonates and pups. This abnormality did not appear to be related to exogenous conditions. In young adult dogs, the initial hypoplastic characteristics were replaced by enlarged marginal zones in the follicles of the spleen, composed of pyroninophilic cells and, in a later stage, of PAS-positive cells. These cellular changes preceded the amyloid deposition. Due to the characteristic cyclic neutropenia of the hereditarily transmitted hematologic syndrome, most CH dogs experience episodes of infectious diseases, although the episodes of infection may be separated by long periods of relatively good health. This may provide the underlying antigenic stimulation which triggers the process of amyloid deposition. However, the lag period for the onset of amyloidosis is extremely short and the type of infections is not considered a predisposing factor for amyloid deposition. It is possible that a peculiar sensitivity of the lymphoid system in the CH dog would facilitate the development of widespread amyloidosis. Since the sequence of splenic lymphoid hypoplasia, follicular activation, and amyloid deposition associated with age are consistently repeated, the CH dog may be a suitable animal model for the study of the pathogenesis of secondary form of amyloidosis in humans.

Spontaneous fibrosarcoma in a thymus-transplanted nude mouse.

A fibrosarcoma was observed in a 6-month-old nude mouse that had a neonatal thymus transplant and had been kept since birth under nearly pathogen-free conditions. This was the first tumor found in more than 1,000 nude mice maintained in a colony in which mammary carcinomas were observed among the female heterozygous breeders. This finding confirmed the fact that malignant neoplasms are rare in an animal model that lacks T-cell-mediated immunologic capability and apparently contradicted the postulates of the immunosurveillance theory.