Diploid (2n = 58) and triploid (3n = 87) cfiannel catfish Ictalurus punctatus were reared indoors in circular fiberglass tanks equipped with rotating disc biofilters. Triploids were significantly heavier than diploids at 8 months of age and older. Triploid male and fbmale channel catfish also had smaller gonads with altered histology. Triploids converted feed more efficiently, and may provide greater profits in commercial catfish culture than diploids.

Abstract. To determine the diagnostic and/or prognostic importance of chromosomal aberrations identified in dogs with malignant (non-Hodgkin's) lymphoma, clinical stages for 6 1 dogs with lymphosarcoma were determined, the lymph node(s) were histopathologically graded, and the malignant tissue lymphocytes were karyotyped. The results from life table survival curve analysis demonstrated that first remission length and survival time were significantly longer in 15 of 6 1 (25%) dogs that had a trisomy of chromosome 13 as the primary chromosomal aberration than in those dogs (46/61, 75%) with other primary chromosomal aberrations ( P < 0.05). Sex, age, weight, histopathologic subtype and grade, World Health Organization (WHO) clinical stage, WHO and modified Karnofsky performance status, chromosomal modal number, and treatment protocol were of no prognostic importance in predicting first remission length or survival time ( P > 0.05). Multivariate analysis did not identify a significant correlation between the prognostic groups or within the various prognostic subsets (P > 0.05). The pathogenesis of canine and human non-Hodgkin's lymphoma, as observed cytogenetically, differs.

Minor axis, major axis, and volume measurements of erythrocyte nuclei were compared by discriminant analysis to determine which variable best predicted ploidy levels. Predicted correct classification percentages for minor axis, volume, major axis, and all variables combined were 8 1.33, 86.2 1, 92.36 and 92.65%, respectively. Minor axis and volume measurements were not as accurate in predicting ploidy levels because nuclear shape changed as the ploidy level changed from the diploid to triploid state. Mean major axis measurements alone classified 92.36% of the fish correctly with a discriminant level of 4.726 pm.

Aphidicolin (APC)-sensitive fragile sites were identified in chromosome preparations from peripheral lymphocyte cultures of 12 four-way crossbred pigs. A χ² analysis demonstrated that aphidicolin-induced breakage events and previously reported in vivochromosome rearrangement events were not independent. Comparison of expected Poisson and negative binomial distributions to observed breakage patterns indicated that the negative binomial distribution provided a better fit to experimental data. The negative binomial distribution is consistent with a distribution of breakage rates, i.e., non-constant rates of breakage at chromosomal loci across the genome.

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