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Canine splenic lymphoid nodules are currently classified as indolent lymphomas (marginal zone lymphoma [MZL], mantle cell lymphoma [MCL]) or nodular hyperplasia (lymphoid [LNH] or complex [CNH] type). Their differentiation can be difficult on morphology, because of similar histologic appearance and poorly defined diagnostic criteria. Thirty-five surgical samples of splenic lymphoid nodules were reviewed in order to assess the diagnostic contribution of immunophenotyping, proliferative activity and clonality (PARR) in differentiating between hyperplastic and neoplastic lesions. Proliferative activity was evaluated by double immunolabeling for Ki-67 and CD79a, in order to separately assess the proliferative activity of B cells and non-B cells. Definitive diagnoses were MZL ( n = 11), MCL ( n = 4), LNH ( n = 10), and CNH ( n = 10). The overall concordance between histology and PARR was above 90%. Lymphomas had a significantly higher percentage of CD79a-positive areas (mean, 36.30%; P = .0004) and a higher B-cell proliferative activity (median Ki-67 index, 5.49%; P = .0012). The threshold value most accurately predicting a diagnosis of lymphoma was ≥28% of B-cell areas, with a Ki-67 index above 3%. Dogs were monitored for a median follow-up time of 870 days (IQR, 569-1225), and no relapses were documented. Overall median survival time was 1282 days. The combination of histology, immunohistochemistry and PARR can improve the diagnostic accuracy for canine splenic lymphoid nodules, although the long-term behavior of these lesions appears similar.

The possibility of a relation between the expression of root inducing (Ri) T‐DNA genes of Agrobacterium rhizogenes and changes in polyamine metabolism has been explored in fast‐growing tobacco hairy roots. Transformed root cultures have been established on hormone‐fee medium; they came from transgenic plants of Nicotiana tabacum L. cv. Xanthi with different altered phenotypes, designated transformed (T) and supertransformed (T'). T and especially T′ roots developed more rapidly both by elongation and lateral branching, and showed a higher growth rate than the untransformed control. After 3 weeks in culture, normal roots showed a very reduced meristematic zone, and flow cytometric analysis indicated that 2C nuclei were predominant in the apical parts in contrast to T and T′ roots, in which endopolyploidisation also appeared. Putrescine, spermidine and traces of spermine were present in all the samples, both in free and in conjugated forms. Putrescine was the major polyamine detected in controls and in transformed roots. At the time of excision, the polyamine levels were similar in normal, T and T′ roots. Significant differences were found during the progression of growth, particularly in the TCA‐insoluble fraction in which polyamines varied differently according to the type of roots, increasing considerably in T roots on day 8, then decreasing. The lower polyamine contents found in growing transformed roots were concomitant to low arginine (EC 4.1.1.19) and ornithine (EC 4.1.1.17) decarboxylase activities. It is suggested that polyamine levels and related enzyme activities are linked to growth kinetics rather than being a consequence of foreign gene expression.