Charles J. Flickinger

Ultrastructural observations on the postnatal development of the rat prostate

SummaryThe postnatal development of the rat prostate has been studied with the electron microscope. Major developmental changes begin during the second week after birth and involve organelles associated with the formation of secretions. The amount of granular endoplasmic reticulum and the size of the Golgi complex increase greatly. Large vacuoles that probably contain secretory material are formed, and the lumen of the prostatic acini appears to contain secreted material. Large lysosomes with polymorphic interiors are present as early as 10 days after birth, and they become numerous by the end of the third week. Differences in fine structure between the different lobes of the prostate are detectable in 10–14 day old rats. The subsequent differentiation of the granular endoplasmic reticulum into the forms characteristic of the different prostatic lobes is described. The initial changes in the prostate occur in advance of sexual maturity of the animal, and the adult appearance of the gland is attained by 4–5 weeks after birth.

Fine structure of the wolffian duct and cytodifferentiation of the epididymis in fetal rats.

SummaryThe fine structure of the Wolffian duct and alterations that occur with the differentiation of the epididymis have been studied in fetal rats ranging in length from 5 to 22 mm (12 to 19 days gestation). Contents of the columnar Wolffian duct cells include basal and perinuclear granular endoplasmic reticulum, sparse apical agranular endoplasmic reticulum, elongate mitochondria, and a small Golgi complex. Large membrane-bounded dense bodies contain cellular organelles and may represent parts of degenerating cells ingested by phagocytosis. During the development of the epididymis from the Wolffian duct in older fetuses, “intracytoplasmic confronting cisternae” of the granular endoplasmic reticulum become numerous, and the agranular reticulum in the apical part of the cell increases moderately in abundance. Concomitantly, the apical cell surface is modified. Many microvilli are formed, indentations of the plasma membrane appear between the microvilli, and the number of coated vesicles in the apical cytoplasm increases. These changes closely follow the onset of androgen secretion by the fetal testis, and it is suggested that they may occur in response to androgen. The relation of these differentiations to known adult functions of the epididymis is discussed.

The fine structure and development of the seminal vesicles and prostate in the fetal rat

SummaryThe development of the seminal vesicle from the Wolffian duct and of the prostate from the urogenital sinus has been studied in rat fetuses from day 14 of gestation to birth with the use of the electron microscope. Prior to the onset of androgen secretion, the cells of the urogenital sinus and the caudal part of the Wolffian duct have a simple undifferentiated appearance. After the onset of androgen secretion by the fetal testes at day 15, “intracytoplasmic confronting cisternae” of the granular reticulum appear in both urogenital sinus and Wolffian duct. Portions of the granular endoplasmic reticulum of the urogenital sinus become distended with a finely granular, moderately dense material. In the urogenital sinus, many hemidesmosomes are formed at the basal surface of the epithelium. Specializations of the extracellular materials are present opposite the hemidesmosomes. The formation of the seminal vesicles and the prostate begins at day 18–19 of gestation. The cells of the seminal vesicle are taller than the Wolffian duct cells from which they arise, the granular endoplasmic reticulum increases moderately in amount, and a patent lumen is formed. The cells of the fetal prostate do not differ greatly from those of the urogenital sinus from which they arise except that the prostatic cells initially lack hemidesmosomes. The fine structural changes are discussed in relation to the onset of fetal androgen secretion, the formation of the organs, and the functions of the cells in adult life.

The pattern of growth of the golgi complex during the fetal and postnatal development of the rat epididymis

The growth of the Golgi complex was studied during the fetal and postnatal development of the rat epididymis. Prenatal and newborn animals had small Golgi complexes composed of a linear arrangement of 1–3 stacks of 4–6 highly flattened cisternae and several types of smooth vesicles. The most rapid growth of the Golgi apparatus occurred during the first 3 weeks after birth. Increases were observed in the number of stacks of cisternae, the number of cisternae per stack, and the size of individual cisternae, but the relative importance of these different modes of growth varied with the developmental stage. Initial changes observed in animals 10 days old were increased distention and fenestration of cisternae, accompanied by increase in the number of stacks of cisternae and their arrangement in a circular pattern. Growth between 10 and 21 days occurred mainly by increases in the lateral extent of the cisternae and in the number of cisternae per stack. Golgi vacuoles also appeared at this stage. After the first 3 weeks, growth was less rapid, but continued until the animals were 6 weeks old. Examples of close apposition between the endoplasmic reticulum and the Golgi apparatus were observed at all stages. Possible mechanisms of growth of the Golgi complex and the source of the new membrane are discussed.

The fine structure of the nucleoli of normal and actinomycin D-treated Amoeba proteus

The fine structure of the nucleoli of normal and actinomycin D-treated Amoeba proteus was studied utilizing fixation in Karnovskys glutaraldehyde—formaldehyde mixture. The multiple nucleoli of normal cells had a predominately granular substructure. Although some regions appeared to possess a fibrillar component as well, discrete areas of differentiated substructure were not identified. Nucleoli of actinomycin-treated cells first became more dense and regularly spherical and then exhibited segregation of nucleolar components. The center of the nucleoli was composed of ∼ 50 fibrils and was surrounded by a rim of 100–150 dense granules. Peripheral regions contained low density material mainly of an amorphous character. In cells treated with actinomycin for 3–4 days, nucleolar vacuoles became common. The similarity in the response of the presumed nucleoli of amoebae to that reported for many higher cells is discussed in terms of possible structural and functional analogies between the nucleoli of amoebae and other cells. It is suggested that normal amoeba nucleoli possess fine fibrils and granules characteristic of other nucleoli, and that the unusually uniform fine structure commonly observed is due to the close packing and intermixing of these components.

Mitochondrial Polymorphism inAmoeba proteus

SummaryThe fine structure of the mitochondria ofAmoeba proteus was studied utilizing several methods of fixation. Different forms of mitochondria were detected within the same ameba following aldehyde fixation. Morphological differences between them were most evident in cells fixed withKarnovskys glutaraldehyde-formaldehyde mixture. Mitochondria with a dense matrix appeared to be rod-shaped and had tubular cristae of variable width. In comparison, other mitochondria had a lighter matrix, an irregular spherical shape, and narrower more uniform tubular cristae. A small percentage of mitochondria with intermediate characteristics was noted. The results obtained with the various preparative procedures are compared and the possible significance of the morphological types is discussed.

Chapter 11 Methods for Handling Small Numbers of Cells for Electron Microscopy

Publisher Summary This chapter presents several methods for handling a limited amount of material for electron microscopy. The techniques of preliminary embedding in agar, of microcentrifugation, and of embedding in a capillary tube are most useful for free cells, such as protozoa; the various modifications of the flat, in situ embedding technique have been most widely used with cultured cells, grown and embedded on a flat surface. Most investigations with the electron microscope have dealt with tissues or suspensions of large numbers of free cells or cell organelles. If free cells or their parts are available in sufficient quantity, they may be centrifuged into a pellet and subsequently processed just as a piece of tissue. When, however, experiments have to deal with visually selected and/or manually manipulated cells, the electron microscopist is confronted with the task of keeping track of a microscopic amount of material through the prolonged processes of selection, fixation, dehydration, embedding, and sectioning. Single free cells, such as protozoa, may be embedded in a capillary tube. If more material is available, the use of a microcentrifuge is quick and efficient.