Fibrillar bundles in canine lymphomas: an ultrastructural study

Nucleic acid distribution pattern as a possible biomarker for metabolic activities of neoplastic cells: a digitally-aided fluorescence microscopy study on normal and neoplastic lymphocytes of acute and chronic canine lymphocytic leukemia

Background

Metabolic states of neoplastic cells are increasingly being relied upon for diagnostic and prognostic assessment of neoplastic conditions. The nucleic acid distribution pattern of cells in general, in terms of degree of condensation of the nuclear chromatin and overall spread of the nucleic acid within the nuclear and cytoplasmic compartments, can reflect the metabolic state of the cell. This simple but logical concept appears not be put into consideration to date as numerous attempts are being made towards formulating reliable biomarkers for rapid diagnosis, prognosis and subsequent therapeutic interventions for neoplastic conditions. We comparatively evaluated nucleic acid distribution patterns of normal lymphocytes and neoplastic cells of lymphocytic lineage, employing light and fluorescence microscopy procedures, as well as digital imaging analytical methods.

Results

The results demonstrate distinctiveness in the pattern of nucleic acid distribution for the normal lymphocytes and three lymphocytic neoplastic cell-types of canine lymphocytic leukemia that are categorized as small, intermediate and large neoplastic lymphocytes. Variably-shaped cytoplasmic processes laden with single-stranded nucleic acids (SSNA) were observed for the small and intermediate-sized neoplastic lymphocytes, compared with large neoplastic lymphocytes and the normal lymphocytes; the latter two categories of cells being virtually devoid of similar processes. Prominent cytoplasmic and nuclear clumps of SSNA, indicative of a higher rate of metabolic activity, were also observed within the neoplastic cells compared with fewer and narrower SSNA of the normal cells.

Conclusion

The comparative relative increases of SSNA in cytoplasmic processes and other cellular areas of small and intermediate-sized neoplastic lymphocytes is reflective of greater metabolic activity in neoplastic cells in general compared with their normal cellular counterparts.

Malignant lymphoma in nasal cavity and paranasal sinuses of a dog

A case of a canine large cell type T-cell lymphoma, with features of high-grade malignancy is described. The tumour was found confined in the nasal cavity and the paranasal sinuses of a crossbred German Shepherd dog. Histological examination revealed the features of a highly malignant large cell lymphoma. Ultrastructurally, the lymphoid tumour cells bore cytoplasmic protrusions that interdigitated tightly. From a panel of tumour markers used, the neoplastic cells were stained only for vimentin. Immunophenotyping of the tumour cells by means of CD3, CD79, kappa-light chains and lambda-light chains detection was undertaken. The tumour stained only for CD3 and was classified as T-cell lymphoma.

Retrovirus-like activity in an immunosuppressed dog: pathological and immunological findings

A putative retrovirus was isolated from a dog with a severe, acquired immunodeficiency-like syndrome. The haematological abnormalities and immunological deficiencies included anaemia, leucopenia (lymphopenia and neutropenia), thrombocytopenia, decreased humoral immunity, and ineffective T-cell responses in-vitro. The necropsy findings included generalized lymphoid depletion, severe bone marrow hypoplasia, plasmacytic infiltrates in lymphoid and non-lymphoid organs, and severe secondary infections. Supernates of peripheral blood mononuclear cell cultures from the affected dog contained an agent with manganese-dependent reverse transcriptase (RT) activity that sedimented at a density of 1.122 g/ml. RT activity was also found post-mortem in extracts prepared from the bone marrow, lymph nodes, and small intestine. The lymph nodes and small intestine expressed a 3.8 kb mRNA that was recognized by a bovine leukaemia virus (BLV) pol DNA probe by Northern blotting. DNA isolated from the lymph nodes and small intestine from the affected dog showed distinct band patterns by Southern analysis, suggesting an exogenous retrovirus. The retrovirus could be propagated in normal canine peripheral blood mononuclear cells or short-term canine lymphocyte cell lines in-vitro, and was cytopathogenic for cells of canine, but not human, origin. These results suggest the existence of a pathogenic canine retrovirus capable of producing disease of the type associated with retroviruses in other species.

Clustering in canine malignant lymphoma

A clustering of generalized malignant lymphoma is reported in a single household of Rottweiler dogs (both parents and three of the four sibling in one litter) and in a breeding pair of unrelated Scottish terriers. In addition, malignant lymphoma of the myocardium was found in three directly related otterhounds (the sire and two sibling offspring). Possible genetic and viral factors in the aetiology of canine malignant lymphoma are discussed.

Ultrastructural morphology of leukemic cells from 14 dogs

Transmission and/or scanning electron microscopic features of leukemic cells from seven dogs with myelomonocytic leukemia, four dogs with monocytic leukemia, and three dogs with lymphocytic leukemia were studied. Few ultrastructural features distinguished normal cells from leukemic cells. Nuclear to cytoplasmic asynchrony, abnormal cytoplasmic granules, nuclear pockets, and cytoplasmic fibrillar bundles were seen more frequently in leukemic cells. Small ridges or ruffles and a few microvilli were surface characteristics of cells from dogs with myelomonocytic leukemia. An occasional cell had large undulating ruffles. Cells from dogs with monocytic leukemia and lymphocytic leukemia usually had smoother surfaces.

Reverse transcriptase activity and particles of retroviral density in cultured canine lymphosarcoma supernatants

Lymphoid tissue from 43 cases of canine lymphosarcoma and from 40 clinically normal dogs have been examined for markers of retrovirus infection. From 69-76% of culture supernatants from lymphosarcomas were shown to contain particles of retroviral density and to possess poly rC-oligo dG templated polymerase (reverse transcriptase) activity compared with 17-24% of culture supernatants from normal canine lymphoid cells. In 6 culture supernatants from cases of lymphosarcoma, high molecular weight 60-70S RNA was detected and shown to be found in association with this particulate reverse transcriptase activity. No such RNA was detected in 6 culture supernatants from normal canine lymphoid cells.

Intermediate-sized filaments in leukemia cells

Electron microscopic studies on human acute leukemias have shown that leukemic populations contain spherical and polarized cells in various proportions. As recorded by time-lapse cinematography, the two cell configurations represent different functional states: resting cells are completely spherical, locomotive cells are polarized with a conspicuous extension posteriorly. In 9 out of 12 cases of acute myeloid leukemia the two cell configurations were found to coincide with a different pattern of intermediate-sized filaments (ISF). Most spherical myeloblasts possessed large bundles of ISF (a minority had small bundles), whereas polarized myeloblasts showed small groups or single filaments. A similar correlation between cell shape and arrangement of ISF was observed in a transplantable undifferentiated rat leukemia. Two concepts can be distinguished with regard to the role of fibrillar structures in leukemic myeloblasts: thick bundles of ISF either represent a pathological state or have a functional significance. A tentative interpretation of our own results provides some arguments in favor of a disaggregation-reaggregation cycle of thick ISF bundles, whereas a pathological ("end stage") nature of these structures appears less likely.

The pathology of spontaneously occurring malignant lymphoma in sheep

The most common locations of tumours in 22 sheep with malignant lymphoma were the lymph nodes (19 sheep), spleen (14), liver (13), kidney (10), small intestine (9) and heart (9). The distribution of the lesions could be classified as multicentric (14 sheep, alimentary (6), skin (1) and thymic (1). Histological examination of malignant lymphomas from 40 sheep showed there were three reticulum cell sarcomas, and 37 lymphosarcomas. The lymphosarcomas were further classified on the basis of cytological features as lymphoblastoid, lymphocytic/prolymphocytic, prolymphocytic and lymphocytic in 14, 6, 11 and six cases, respectively. Viruses were not detected by electron microscopy in tumourous tissue from 10 sheep with malignant lymphoma.

Atypical glycogen deposits in a plasmacytoma: an ultrastructural study

A solitary, benign plasmacytoma, arising from the gum of the lower jaw of a dog, was studied by light and electron microscopy. Some of the tumour cell nuclei showed the characteristic clockface or cartwheel pattern of heterochromatin distribution similar to that found in normal plasma cells. Like normal plasma cells the tumour cells were endowed with rough endoplasmic reticulum but this was invariably dilated or visiculated. Glycogen deposits were found within mitochondria and within the dilated and vesiculated rough endoplasmic reticulum. The idea that these deposits were derived secondarily from glycogen deposits in the cytoplasm seems untenable because no glycogen particles were found in the cytoplasmic matrix. It would therefore appear that most, perhaps all, stages of glycogen synthesis occurred within the mitochondria and rough endoplasmic reticulum of some of these tumour cells.