Mononuclear Cell Leukemia in Aged Sprague-Dawley Rats

A mononuclear cell leukemia in Sprague-Dawley rats is described in which liver, spleen, and lung involvement was a constant feature. The cell was 16 to 25 μm in diameter with round, oval or indented nucleus, and the cytoplasm contained bright red granules. This is the first report of such a leukemia in Sprague-Dawley rats and a comparison with mononuclear cell leukemia in other strains of laboratory rats is made.

Immature Megakaryocytes in the Mouse: Morphology and quantitation by acetylcholinesterase staining

Three types of immature megakaryocytes, detected by their morphological properties, have been characterized in bone marrow of normal C57BL/6 mice. Morphological classification of these cells was carried out by determining (1) presence and relative amount of acetylcholinesterase, (2) cell size, (3) nuclear/cytoplasm ratio, and (4) nuclear shape. The immature megakaryocytes were classified as: (A) cells distinguished by a round nucleus (10.6 +/- 1.1 mu diameter; mean +/- SEM), which had the highest nucleus / cytoplasm ratio and lowest content of acetylcholinesterase; (B) cells with an indented nucleus (13.0 +/- 1.9 mu diameter), which had increased acetylcholinesterase content and reduced nucleus/cytoplasm ratio compared to the round-nucleus cell type; and (C) lobed-nucleus cells (14.5 +/- 2.9 mu diameter), which showed further increase in acetylcholinesterase content and reduction in nucleus/cytoplasm ratio. Increased numbers of immature megakaryocytes were detected, indicating that a proportion of these cells are undetected using conventional staining techniques. Based on the observed alterations in size, acetylcholinesterase content, and nuclear complexity, it was concluded that these cells constitute part of a progressive maturation sequence intermediate between the progenitor cell (CFU-Mk) and mature easily recognizable megakaryocytes.

Immature Megakaryocytes in the Mouse: Morphology and quantitation by acetylcholinesterase staining

Three types of immature megakaryocytes, detected by their morphological properties, have been characterized in bone marrow of normal C57BL/6 mice. Morphological classification of these cells was carried out by determining (1) presence and relative amount of acetylcholinesterase, (2) cell size, (3) nuclear/cytoplasm ratio, and (4) nuclear shape. The immature megakaryocytes were classified as: (A) cells distinguished by a round nucleus (10.6 +/- 1.1 mu diameter; mean +/- SEM), which had the highest nucleus / cytoplasm ratio and lowest content of acetylcholinesterase; (B) cells with an indented nucleus (13.0 +/- 1.9 mu diameter), which had increased acetylcholinesterase content and reduced nucleus/cytoplasm ratio compared to the round-nucleus cell type; and (C) lobed-nucleus cells (14.5 +/- 2.9 mu diameter), which showed further increase in acetylcholinesterase content and reduction in nucleus/cytoplasm ratio. Increased numbers of immature megakaryocytes were detected, indicating that a proportion of these cells are undetected using conventional staining techniques. Based on the observed alterations in size, acetylcholinesterase content, and nuclear complexity, it was concluded that these cells constitute part of a progressive maturation sequence intermediate between the progenitor cell (CFU-Mk) and mature easily recognizable megakaryocytes.

Herpestype Virus and Type C Particles in Spontaneous Equine Lymphoma

Herpestype and type C virus particles are known to produce tumors in animals of certain species, and to be present in a variety of human tissues. Similar particles were found in a horse lymphoma.Electron microscope study was carried out on a tumorous prescapular lymph node from an adult female horse with spontaneous lymphoma. Lymph node cells grown in vitro for a total of 105 days (6th passage) were also studied. The lymph node was infiltrated by blastic cells of reticulum cell type and of lymphoblast type. No virus particles were found in the original lymph node. The cultured cells have a large cytoplasm with well developed rough endoplasmic reticulum and Golgi's apparatus, and an indented nucleus with marginated chromatin. Occasionally, intranuclear fibrous structures were observed. Elongated nuclear protrusion were frequently seen.