Ultrastructural Pathology of the Cell and Matrix

A Text and Atlas of Physiological and Pathological Alterations in the Fine Structure of Cellular and Extracellular Components

Feroze N. Ghadially

• Publisher: Butterworth-Heinemann
• Year: 2013
• Print ISBN:
  9780407015715
• Edition: 3
• eBook ISBN:
  9781483192086
• Topic: Biological Sciences
• Subtopic: Biology
• Index: Biological Sciences

Ultrastructural Pathology of the Cell and Matrix: Third Edition Volume I present a comprehensive examination of the intracellular lesion. It discusses the analysis of pathological tissues using electron microscope. It addresses the experimental procedures made on the cellular level. Some of the topics covered in the book are the physiological analysis of the nucleus; nuclear matrix, interchromatin, and perichromatin granules; structure and function of centrioles; characteristics of mitochondria; Golgi complex in cell differentiation and neoplasia; and degranulation of rough endoplasmic reticulum. The intracytoplasmic and intranuclear annulate lamellae are fully covered. An in-depth account of the classification, history, and nomenclature of lysosomes are provided. The morphology and normal variations of melanosomes and anchoring fibrils are completely presented. A chapter is devoted to the endocytotic structures and cell processes. Another section focuses on the classification and nomenclature of fibrous components. The book can provide useful information to cytologists, scientists, students, and researchers.

1

Nucleus

Publisher Summary

This chapter discusses the microscopic structure of the nucleus. The nucleus shows a degree of irregularity when examined by an electron microscope. The significance of such irregularity of nuclear shape is obscure and the operative mechanisms poorly understood. Several hypotheses have been proposed to explain the folding of the nucleus in muscle cells. These include changes in the ionic concentration, mechanical compression, and structural connections extending between myofibrils and the nuclear envelope. An irregularity of the nuclear form provides an increased area of contact between the nucleus and the cytoplasm. In some cases, this seems to denote increased nucleocytoplasmic exchanges and heightened metabolic activity. The neoplastic nucleus, although irregular and altered, continues to bear some resemblance to its normal counterpart. This is best demonstrated by the fact that crenated, folded, or concertina-like nuclei of contractile cells—like smooth muscle cells, striated muscle cells and myofibroblasts—are also often seen in tumors of these cells. The nuclei of some leukemic cells tend to be more irregular in form than their normal counterparts; at times, cells may be found where the nucleus are segmented, lobulated, or beset by numerous invaginations so that the nuclear form is quite irregular. Electron microscopic studies have focused attention on a much more common and consistent pattern of nuclear change in the necrotic cell, which is spoken of as chromatin margination. The phenomenon of nucleolar margination has led many observers to speculate that such an arrangement facilitates nucleocytoplasmic exchanges.

Introduction

Early ultrastructural studies were concentrated mainly on the new and intriguing structures revealed by the electron microscope in the cytoplasm and not the nucleus, which revealed only an assortment of granules intermingled with some filamentous and amorphous material. The sentiments of that era are recorded by Moses (1956), who stated ‘Most electron microscopists acknowledge that the nucleus appears to be as remarkable for its lack of obvious ordered detail as the cytoplasm is for the richness in it’. Dissatisfaction with the state of affairs was expressed by many workers and is epitomized by Bernhard and Granboulan (1963), who stated ‘In electron microscopical cytology the interphase nucleus of the normal somatic cell has been the neglected orphan compared with cytoplasmic organelles’. Such sentiments have been reiterated by others, for example by Kaye (1969), who states ‘Research on the nucleus seems remarkably unfruitful compared with that on cytoplasmic organelles when results achieved by similar efforts are considered’.

However, disenchantment with electron microscopic studies on the nucleus is no longer warranted, because later studies have revealed much that is new and interesting, as evidenced by the fact that this chapter on the nucleus is the largest in this book.

Outstanding among these achievements are the studies on the nuclear envelope, and the nucleolus. There is much here of interest for both the student of normal structure and the pathologist. Similarly, our knowledge of viral and non-viral inclusions has been enhanced, and many an old controversy regarding the nature of these inclusions has been settled. This subject, of course, is of great interest to pathologists; hence I have dealt with it in some detail in this chapter. It is amazing how much more one can discern in these inclusions with the light microscope once their ultrastructural features are recognized.

On the other hand, light microscopic studies of the mitotic nucleus have proved more rewarding than studies of ultrathin sections through these structures. Hence, only the interphase nucleus is dealt with in this chapter; the mitotic nucleus receives only passing mention in this and later chapters.

Nuclear shape

In ultrathin sections examined with the electron microscope, many nuclei show a degree of irregularity of form quite beyond that expected from their light microscopic appearance. It need hardly be pointed out that this is no shrinkage artefact, since other organelles such as mitochondria are not crenated or shrunken. This phenomenon, although at first perplexing, can be readily explained when one considers that the thinness of the sections employed in electron microscopy gives a virtually two-dimensional view of the state of affairs at the plane of section, while the much thicker sections employed for light microscopy may be regarded as several superimposed thin sections where projections and indentations which overlie each other cancel out and give a smooth appearance to the nuclear margin. No doubt the higher magnification employed in electron microscopy also contributes to this phenomenon by revealing small irregularities which would appear insignificant or be beyond the resolving power of the light microscope.

Thus the electron microscope shows that many nuclei which one had come to regard as smooth and round or oval, can in fact be quite irregular and at times beset by an unsuspected slender deep invagination*. The significance of such irregularity of nuclear shape is obscure and the operative mechanisms poorly understood. However, a few interesting studies and speculations regarding this point are worth recording.

Perhaps the best known example here is the nucleus of smooth and striated muscle which in ultrathin sections often shows a markedly folded or convoluted appearance. This has now been correlated with the state of the cell, the nucleus being unfolded and elongated in the relaxed phase and ovoid and invaginated after contraction of the muscle cell (Lane, 1965; Panner and Honig, 1967; Franke and Schinko, 1969; Bloom and Cancilla, 1969; Crissman et al., 1978). Similar changes also occur in the nuclei of endothelial cells of blood vessels (Plate 1), and it is reasonable to assume that this, too, may be correlated with the state of the vessel wall (Majno et al., 1970). Several hypotheses have been proposed to explain the folding of the nucleus in muscle cells. These include: (1) changes in the ionic concentration (Franke and Schinko, 1969); (2) mechanical compression (Bloom and Cancilla, 1969) and structural connections extending between myofibrils and the nuclear envelope (Franke, 1970a; Crissman et al., 1978).

Plate 1 Folded and invaginated nuclei (E) are seen in the endothelial cells of this collapsed blood vessel from the subsynovial tissue of man. × 14000 (Ghadially and Roy, unpublished electron micrograph)

Instances may be cited where complexity of nuclear form is related to maturation and ageing of the cell. The classic example here is the neutrophil leucocyte where the nucleus becomes segmented and lobed as the cell increases in age. In mature normal articular cartilage there is a population of cells which very rarely divide, but suffer in situ necrosis with the passage of time. Barnett et al. (1963) have observed an increased complexity of nuclear form in this population of cells as animals (rabbits) grow older. There is also evidence that human hepatic and adrenal cell nuclei (Kleinfeld and Koulish, 1957; Sobel et al., 1969a) show invaginations of the nuclear envelope and complexity of ...

Table of contents

• Cover image
• Title page
• Table of Contents
• Dedication
• Copyright
• Preface to the third edition
• Preface to the second edition
• Preface to the first edition
• Acknowledgements
• Chapter 1: Nucleus
• Chapter 2: Centrioles
• Chapter 3: Mitochondria
• Chapter 4: Golgi complex and secretory granules
• Chapter 5: Endoplasmic reticulum
• Chapter 6: Annulate lamellae