Observations on the ultrastructure of nucleated erythrocytes and thrombocytes,with particular reference to the structural basis of their discoidal shape

Summary The marginal band of nucleated erythrocytes in the toadfish is found, in electron micrographs, to be composed of about twenty-five microtubules approximately 200 Å in diameter. These form a bundle that encircles the erythrocyte just beneath the plasma membrane. These observations support the interpretation of Meves 1904, that this relatively stiff equatorial band may contribute to the maintenance of the discoid shape of nucleated erythrocytes in fish, amphibians, reptiles and birds.Similar microtubules form an annular bundle encircling the nucleus in fish thrombocytes. The number of tubular elements involved here is in excess of one hundred and they are located deep to the ectoplasmic layer instead of immediately beneath the plasmalemma. The term endoplasmic ring is therefore proposed for this structure.Comparative observations on nucleated erythrocytes of various species are presented showing that the density and fine structure of the material occupying the interchromosomal areas of the nucleus, always matches the cytoplasm and is related to the hemoglobin concentration of the species. These ultrastructural observations are consistent with the optical absorption and biochemical findings of other investigators indicating the presence of intranuclear hemoglobin in nucleated erythrocytes. Crystalline order is occasionally found in electron micrographs of the hemoglobin rich areas of the nucleus in toadfish erythrocytes but is not found in the cytoplasm.This research was supported by grant G-12916 of the National Science Foundation.     

Isolation and characterization of 18 microsatellite loci in the Egyptian vulture (Neophron percnopterus)

We developed 18 new microsatellite loci for the endangered Egyptian vulture (Neophron percnopterus). Microsatellite loci were screened for variation in two different populations belonging to separate subspecies: the nominal N. p. percnopterus and the Canarian N. p. majorensis. Mean expected heterosygosities were respectively 0.51 and 0.46, while the mean number of alleles per locus was 4.7 and 3.9. These new markers allow further genetic studies for the endangered Canarian Egyptian Vulture.     

Hematopoietic chimerism monitoring based on STRs: quantitative platform performance on sequential samples.

Hematopoietic stem cell transplantation (HSCT) creates a donor-recipient cellular chimerism in the patient, which is quantitatively assayed from peripheral blood based on STR-DNA. Since chimerism values often vary across a patient's samples, it is important to determine to what extent this variability reflects technical aspects of platform performance. This issue is systematically assessed in the current study for the first time. Using the SGM Plus multiplex PCR kit and ABI platform, the longitudinal performance of STR markers was quantitatively evaluated in two chimeric models with true values, and in patient samples (n >500 marker loci). Computation of percent chimerism for each marker, and mean (sample) percent chimerism, standard deviation, and coefficient of variance was performed by our ChimerTrack utility. In chimeric models with known values, individual markers exhibited an accuracy (observed/true) of 88-98%; replication precision was 92-100% true, with a mean error of 2%. Fragment size calling was greater than 99% accurate and precise. Patient results were comparable for markers, relaive to sample means. One source of technical variability in chimerism estimation was allelic differential amplification efficiency. The latter was influenced by signal amplitude, dye label, marker size, and allelic size interval. It can be concluded that long-term chimeric tracking is routinely feasible using this platform in conjunction with ChimerTrack software. Importantly, mean percent chimerism, for any sample, should closely approximate the true chimeric status, with a technical accuracy of 98%. Guidelines are presented for selecting an optimized marker profile.     

Feeding preferences in 2 disjunct populations of tiger snakes, Notechis scutatus (Elapidae)

Variations at both the genetic and phenotypic levels play animportant role in responses to food and food-related stimuli.Knowledge of such variations is crucial to understanding howpopulations adapt to changing environments. We investigatedthe dietary preferences of 2 tiger snake populations and comparedthe responses of diet-naive animals (laboratory-born neonates),diet-controlled animals (laboratory-reared juveniles), and naturaldiet–experienced animals (wild-caught adults) to visualand chemical cues from 6 prey types (mouse, skink, silver gull,chicken, shearwater, and frog). The mainland population inhabitsa swamp, feeds mostly on frogs, and suffers heavy predation.The second population inhabits a small nearby offshore islandwith no standing water (no frogs); feeds mostly on skinks, mice,and, as adults, silver gull chicks; and suffers no known predation.Although different prey are eaten in the 2 populations, adultwild-caught snakes from both populations showed a significantpreference for 3 types of prey (frog, mouse, and chick), irrespectiveof their natural diet. Neonates responded to all prey cues morethan they did to control stimuli in both populations. However,the island neonates showed significantly higher interest insilver gull chick stimuli (the main prey of the island adultsnakes) than did their mainland conspecifics. Laboratory-bredjuveniles displayed behavioral plasticity by significantly increasingtheir response to mice after being fed baby mice for 7 months.We conclude that genetic-based differences in food-related cuesare important in tiger snakes but that they are also capableof behavioral plasticity. Island adult and neonate snakes exhibitedresponses to prey types no longer consumed naturally (frog),suggesting that behavioral characters may have been retainedfor long periods under relaxed selection. Island neonates showeda strong interest in a novel prey item (silver gull). This resultcomplements previous work describing how island snakes havedeveloped the ability to swallow larger prey than usual, aswell as seemingly developing a taste for them.