Mutant mouse L-cells: a model for megaloblastic anaemia

Non-Hodgkin's lymphoma classification: ultrastructural morphometric studies for the quantification of nuclear compartments in situ

The condensed chromatin distribution in the nuclei of lymphocytes in non-Hodgkin's lymphoma (NHL) is a key element, along with nuclear size and shape, in the classification of this disease for therapeutic and prognostic purposes. This report describes the ultrastructural comparative quantification of the condensed chromatin and the interchromatinic (nuclear matrix or euchromatin) region in the nuclei of mitogen-stimulated human peripheral T lymphocytes and mouse spleen B lymphocytes, human germinal center lymphocytes, and lymphocytes in ten cases of NHL of a variety of subtypes. The sequential morphologic nuclear changes induced in lymphocytes by mitogens are reflected in human germinal center lymphocyte populations. The common features include the changes in the distribution and volume of condensed chromatin aggregates, as well as the fact that the major increments in nuclear volume during lymphocyte transformation result from increases in the volume of the interchromatinic region. In all subtypes of NHL analyzed morphometrically, subpopulations of lymphocytes were identified in which mean nuclear, condensed chromatin, and interchromatinic volumes were more or less equivalent to those of normal lymphocyte subsets in germinal centers in reactive hyperplasia. However, in NHL the abnormal cytologic characteristics of the nucleus result, at least in part, from a complex interplay of condensed chromatin distribution and amount, and the size of the interchromatinic region. Further complexity is introduced by the fact that in NHL these two nuclear compartments can independently be normal, increased, or reduced in size. Morphometric quantification of lymphocytes in NHL indicates that the interchromatinic (matrix) region of the nucleus is the key element in establishing the nuclear volume of neoplastic lymphocytes. The structural and functional, ribonucleoprotein interchromatinic region of the nucleus was visualized in normal and neoplastic lymphocytes by regressive uranyl-EDTA staining. Quantitative morphometric analysis indicates that the cytologic appearance of neoplastic lymphocytes, even within subtypes of NHL, is heterogeneous and that condensed chromatin quantity and distribution may be more critical than nuclear size in distinguishing between certain subtypes of NHL. Improvements in the classification of NHL will occur only with understanding of the alterations in the biologic mechanisms controlling gross nuclear organization and the morphologic events of the various differentiation pathways available to antigen-stimulated lymphocytes.

Effects of hyperthermia on the myelograms of adult and fetal guinea-pigs

The myelograms of adult guinea-pigs at various stages after brief exposure to hyperthermia were compared with those of control animals. The proportions of neutrophil and eosinophil metamyelocytes and of intermediate normoblasts were significantly reduced for at least 24 h after exposure and the proportions of neutrophil polymorphs and lobulated eosinophils were significantly increased over this period. The mitotic index was reduced for up to 5 h. Morphological changes in cells included hypersegmentation of nuclei, pyknosis, necrobiotic changes, development of pseudopodia, and abnormalities of mitosis. The myelograms of newborn guinea-pigs which had been heated on days 20-23 of pregnancy showed no significant changes.

Electron microscopic analysis of lymphocyte nuclei in non-Hodgkin's lymphoma

Ultrastructural studies of normal and neoplastic lymphocytes are presented that qualitatively and quantitatively assess the central cell organelle currently used by surgical pathologists in the classification of non-Hodgkin's lymphoma, the nucleus. Events occurring during normal lymphocyte transformation can be used to appreciate essential mechanisms involved in producing the appearance of the nucleus as seen by microscopy. Quantitation of nuclear subcompartments by morphometric image analysis reveals that determination of nuclear size is primarily due to the ribonucleoprotein materials distributed between condensed chromatin masses, the interchromatinic (euchromatin or nuclear matrix) region. Furthermore, such investigations show that amounts and distribution of condensed chromatin in lymphocyte nuclei cannot be adequately assessed from routine histologic sections. Ultrastructural morphometric analysis of representative cases of the principal subtypes of NHL indicates that the atypical morphologic appearance of neoplastic lymphocytes results from a complex interplay between total amounts of condensed chromatin in nuclei and the size of individual aggregates of condensed chromatin, one or both of which may be abnormal in NHL. Abnormalities of interchromatinic materials are also likely involved in ordering the gross appearance of the nucleus. Understanding of both the dynamic capabilities of the nucleus, and the organization of and interplay between the various subcompartments of this organelle will be helpful in improving the classification of NHL by surgical pathologists.

Nuclear morphologic and morphometric analyses of large noncleaved cell and immunoblastic non-Hodgkin's lymphomas

Both morphologically and immunologically, non-Hodgkin's lymphoma (NHL) of the large cell type has been shown to be a heterogeneous category. However, the homogeneity of the nuclear parameters, particularly size and condensed chromatin organization, used to classify this subtype of NHL has not been investigated. In fact, objective morphologic techniques have not been systematically applied to verify the segregation of NHL on the basis of nuclear parameters, a concept common to all current classification systems. In this study morphometric image analysis was used to compare the nuclei in 20 specimens from NHLs of the large cell type with those in mantle zone and germinal center lymphocytes from lymph nodes with reactive hyperplasia. Results of the assessment of mean nuclear area in large cell lymphomas revealed that this class is also heterogeneous, with some of the specimens having a nuclear size in the upper range of that for normal small lymphocytes. In addition, in only a few of these specimens was the mean nuclear area within the range of that for fully transformed germinal center lymphocytes. The majority of large cell lymphomas have a nuclear size more characteristic of partially transformed lymphocytes in germinal centers. In addition to indicating inconsistencies in the current diagnostic criteria used in NHL classifications, the results indicate reasons for interobserver variations in clinicopathologic trials; the validity of nuclear size as a prognostic indicator and the biologic basis for classifying NHL as a reflection of normal lymphocyte transformation are also questioned. In terms of patient management, the classifications of NHL currently used require objective reappraisal.