the ultrastructure of the accessory sex organs of the male rat

Z. Zellforsch. 137, 345--359 (1973) © by Springer-Verlag 1973

The Uhrastructure of the Accessory Sex Organs of the Male Rat

I. N o r m a l S t ruc tu re

Er ik DaM, Asmund Kjaerheim, and Kjell J. Tveter

Departments of Anatomy and Pathology, Dental Faculty, University of Oslo, and Department of Surgery, 0slo, University Hospital in Akershus, Norway

Received October 16, 1972

Summary. A systematic, comparative study of the accessory sex organs of the adult male rat was carried out after intra-aortic perfusion of the pelvic organs with glutaraldehyde. I t has been revealed that although the epithelial cells of the different lobes of the prostate have many features in common, it is also apparent that the cell type of the various lobes have specific ultrastructural characteristics of its own, which morphologically distinguish it from the cell type of the other lobes. I.e. : the different lobes may be identified by their specific ultrastructural feature. I t is also striking that the lobes, two-by-two, have so many morphological features in common that they may be divided in 3 subgroups. Based on the appearance of amount and localisation of the different organelles, the cells of the lateral lobe and the seminal vesicle are so alike that they morphologically may be classified as one group. Similarly, the coagulating gland and the dorsal lobe form another group, while the ventral lobe as a single form a third group. The few biochemical data from the different lobes which are accessible, seem suggestive to support this subgrouping.

Since the various prostate lobes and the seminal vesicles have their homologies in man, further investigation both morphologically and biochemically should be concentrated upon the different groups instead of the single lobe.

The study, which describes the different lobes and cell types in detail also show structures which have not been demonstrated within the prostatic epithelium before.

Key words: Accessory sex organs-- Male r a t - Prostate-- Seminal vesicles-- Ultrastruc- ture.

Introduction

There are several reports concerning the fine s t ructure of the mature ra t prostate, bu t they all deal with one or two lobes, or the seminal vesicles, only (Harkin, 1957 ; Brandes, 1966 ; Schrodt, 1961 ; t t e lminen and Ericsson, 1970, 1971 ; Szirmai and van der Linde, 1965). Ul t ras t ruc tura l changes dur ing fetal and postnata l de- ve lopment of the whole prostate has recently been published by Flickinger (1970, 1971).

A systematic, comparat ive s tudy of the fine s t ructure of all accessory sex glands in the adul t male ra t has never been carried out. The main purpose of this investi- gat ion was to adapt the perfusion f ixat ion method to the prostatic complex, pre- serving it in tote. This made subsequent dissection of the different lobes possible wi thout de t r iment to the fine structure.

The results of this invest igat ion have proven useful as a baseline for cytophys- iological studies now in progress.

346 E. Dahl st al. :

Materials and Methods

Five adult albino male rats (Charles River CDF strain), 4-6 months old and weighing 250-300 g, were used. Under nembutal and ether anaesthesia the iliae arteries on both sides were ligated to block the blood flow to the lower extremities. The aorta was cannulated with a plastic catheter of caliber no. 4 proximal to the renal arteries, and the tip of the catheter was then placed just above the aortic bifurcation. Rinsing and fixation of the pelvic organs were achieved by brief perfusion through the catheter with dextran followed by 1.7 per cent glutaraldehyde in 0.1 M phosphate buffer, pH 7.3, for 20 rain, using a per~usion pressure of about 150 mm Hg. Great care was taken to avoid manipulation of the prostate and the seminal vesicles during perfusion. The pelvic organs were then excised en bloc and fixed for an additional period of 2 hr by immersion in the perfusion fluid. For further details see Kjaerheim (1969).

After the glutaraldehyde fixation the different prostate lobes were gently dissected and cut into small cubes under the stereo microscope. Only the tip of the lateral prostate was used, since the intermediate region of the dorsolateral prostate contains a mixture of dorsal and lateral tissue (Gunn and Gould, 1957). For the same reason, tissue from the dorsal lobe was taken from an area or close to the midline as possible. Six blocks were processed from each lobe of the various animals, and all the specimens were rinsed for 10 rain in 0.15 M phosphate buffer (pH 7.3) and post-fixed in 1 per cent osmium tetroxide at 4 ° C for 2 hr (~¢Iillonig, 1961). After fixation the blocks were rapidly dehydrated in a graded series of acetone and embedded in Vestopal W (I~yter and Kellenberger, 1958).

Ultrathin sections were cut on an LKB Ultrotome III. The sections were examined in a Siemens Elmiskop I ~ electron microscope. From the same plastic blocks sections were prepa- red for light microscopy. These sections were stained on a heating stage with an aqueous solu- tion of 0.1 per cent toluidine blue adjusted to p g 8.9 with 0.067 M Na2HPO 4.

Observations

L i g h t M i c r o s c o p y . By light microscopy of 1 micron th ick p las t ic-embedded sec-

t ions i t was revealed t h a t the different lobes of the pros ta te have several histologi-

cal features in common. They are buil t up of acini (also called alveoli) of different

sizes, composed of co lumnar epi the l ium rest ing on a basement lamina. Each acinus

is surrounded by a sheath of connect ive tissue and smooth cells provided with nerve

fibers. F r o m experience gained by electron microscopy of the same tissue and

uti l izing the increased resolving power of l ight microscopy of such th in sections, i t

was possible to ident i fy the different lobes of the accessory sex glands in the l ight

microscope. The seminal vesicles were easily identif ied by its th ick muscular sheath, a large amoun t of secretory mater ia l and a papi l lary epithelium. The lateral pros-

t a te has a p rominen t brush border as its most typical feature. The epi thel ium of

the coagulat ing gland form branching papi l lary project ions and possesses an enormously di la ted endoplasmic ret iculum, which was seen l ight microscopical ly

as vacuoles in the basal cy toplasm of the epithelial cells. The dorsal lobe also con-

Figs. 1--5 demonstrate glandular epithelium from the ventral prostate

Fig. 1. Survey electron mierograph from the ventral prostate. The cells are characterized by enormous amount of rough endoplasmic retieulum ( R E R ) , a well developed Golgi apparatus (G) located in the apical part of the cell, a nucleus (iV) rich in ehromatin and located in the basal part of cell. Note the sparse amount of granules (arrows) and the few microvilli at the

luminal surface. L glandular lumen. Ca capillar. × 7500

Fig. 2. Higher magnification of the RER, which in this lobe, consists of narrow, mostly parallel cisternae filled with a homogeneous substance. × 15000

Accessory Sex Organs of the Male Rat 347

Fig. 3. Secretion granules of the dense type (SG). This granules are characterized by forming groups and typically located in the juxtaluminal position. × 20000

Fig. 4. Seeretion vacuoles (SV). These vacuoles which are recognized by their finely granular material may be encountered anywhere in the apical cytoplasm. × 20000

Fig. 5. Occasionally a third variety of secretion granules is seen. They consist of small, dense granules (arrow) eccentrically located within vacuoles. × 20000

348 E. Dahl et al. :

Figs. 6--11 illustrate prostatic epithelium from the lateral prostate lobe

Fig. 6. Survey electron micrograph of the lateral lobe. The cells are characterized by an extremely well developed brushborder, apical accumulation of large numbers of dense granules (SG), a large Golgi apparatus (G) and a basally located nucleus (N), moderately rich in chromatin. The rough endoplasmic reticulum ( R E R ) is mainly located in the basal cytoplasm, and well developed. ~qote the formation of secretion granules within the Golgi area (arrows) (cfr,

Fig. 8). ×9000

Accessory Sex Organs of the Male P~at 349

taines some branching papillae, but not to the same extent as in the seminal vesicle and the coagulating gland. I n the dorsal prostate apical blebs were often seen pro- jecting from the epithelial cells. The ventral prostate is the only gland which does not possess any specific light microscopic structure ; thus, identification of this lobe rests on exclusion of the other possibilities.

Some additional cytological details could be observed in the epithelial cells: the Golgi appara tus is encountered in all lobes as groups of light vacuoles in the apical region. Mitochondria and lysosome-like dark granules are seen in the major- i ty of ceils.

Electron Microscopy. To avoid a repetitive description of cell structures as they appear in each of the five glands, the most salient general features will be described here. Each acinus consists of columnar epithelial cells resting on a distinct basal lamina. All acini are surrounded by a coat of smooth muscle cells in 4-6 layers {Fig. 29). A thin coat, of connective tissue, usually a single layer of fibroblasts is inserted between the muscle layer. ~qerve fibers are regularly in close relation to the smooth muscle cells (Fig. 30). The epithelium generally consists of a single cell layer, with typical desmosomes, microvilli, a Golgi apparatus, lysosomes, a rough endoplasmie reticulum, secretion granules or secretion vacuoles and mitochondria of various sizes. Occasionally nuclear bodies (Fig. 25) filaments (Fig'. 26) and micro- tubules (Fig. 27) were found.

I n spite of such similarities a detailed analysis of the cell components revealed ul t ras t ructural differences between the different lobes and glands. The various lobes will therefore be described separately in the following.

So-called basal cells were observed in all lobes. They are inserted between the basal lamina and the surface epithelium in such a fashion tha t they do not abut on the lumen. The basal cells have irregular nuclei with their long axes parallel to the basement lamina. They show several similarities to the secretory cells, bu t lack secretion granules and mierovilli, and the REP~ and the Golgi are less prominent.

Ventral Prostate. The most characteristic feature of the epithelial cells is the enormous amount of I~EI~ in most areas of the cells (Fig. 1), mainly as parallel membranes bordering narrow cisternae (Fig. 2), but occasionally as whorl-like structures (parasomes). A well developed Golgi apparatus is located in the apical portion of the cell (Fig. 1). The secretion granules, which form three types, are no t parti- cularly numerous. The first type consists of dense spherical granules located in scattered groups near the apical cell surface (Fig. 3). The second type appears as vacuoles containing a finely granular material (Fig. 4). The third type is repre-

Fig. 7. Higher magnification of the RER, which also in this lobe consists of narrow, mostly parallel eisternae filled with a homogeneous substance. X 12000

Fig. 8. Part of the Golgi apparatus in cross section, demonstrating formation of secretion granules (arrows) and typical small dense granules eccentrically located within a somewhat large

vacuole, x 30000

Fig. 9. Dense, homogeneous secretion granules (SG) are regularly seen in one or two rows close to the cell surface. × 30000

Fig. 10. Secretion granules (SG) containing a less dense, fine granular material are encountered adjacent to the luminal surface, x 30000


Fig. 11. Some cells from the lateral prostate showed dorsolateral characteristics: i.e. they ex- hibit traits characteristic of lateral as well as dorsal cells. The dense secretion granules (SG) surrounded by an eccentric vacuole are typical of cells from the lateral lobe, whereas the dis-

tended cisternae of the R E R are typical of the dorsal lobe. x 6750

Accessory Sex Organs of the Male l~at 351

rented by small dense granules eccentrically located within vacuoles (Fig. 5). The nuclear membrane is wrinkled, sometimes forming deep indentations. The nucleus is rich in chromatin and occupies the basal portion of the cell (Fig. 1). A distinct nucleolus was often observed. At the luminal surface a small number of microvilli occurs regularly.

Lateral Prostate. A typical feature of the epithelium of this lobe is the large number of microvilli constituting an extremely well developed brush border (Fig. 6). Another characteristic feature is the apical accumulation of large numbers of small, dense granules, each being eccentrically located within a somewhat larger vacuole (Fig. 6). Other types are spherical, dense, homogeneous secretion granules (Fig. 9) and finely granular granules (Fig. 10). The Golgi apparatus is well developed and sometimes container small, elongated condensations of secretory material within some of the Golgi cisternae (Fig. 8). The major part of the well developed REI~ is situated inthe basal cytoplasm (Figs. 6, 7). I t usually consists of parallel, flattened cisternae, but in a few instances a concentric pattern as in parasomes was encountered. Lysosomes were occasionally seen. The basally located nucleus has a regular shape and is moderately rich in chromatin. Some cells from the lateral prostate show dorsalateral characteristics, i.e. they possess a well developed brush border apically located eccentric secretion granules typical of lateral cells as well as wide R E R cisternae typical of dorsal cells (Fig. 11). In addition some acini of the lateral prostate contain cells with characteristic features of the dorsal prostate.

Dorsal Prostate. The most conspicuous trait of the epithelial cells of the dorsal prostate is the configuration of the REP~, which consists of widely dilated cisternae with interlacing thin strands of cytoplasm (Figs. 12, 14). The size of the R E R cisternae however, is not so large as in the coagulating gland. I t should be mentioned that in this lobe cytoplasmic apical blebs were seen in the majori ty of the glandular lumina, a finding which was never made within the other lobes. A well developed Go]gi apparatus is located apically (Fig. 12). Lysosomes and residual bodies of various types are relatively common (Figs. 15--17). Secretion granules are absent, but vacuoles, presumably containing secretory products and having a finely granular interior, were regularly seen in the apical part of the cell (Fig. 13). A single crystal- loid body, about 0.8 micron long and 0.3 micron broad, was observed within the basal cytoplasm (Fig. 18). A pale spherical or somewhat indentated nucleus, is located in the basal par t of the cell. A distinct nucleolus was often seen. A small number of microvilli covers the surface of this cell.

Figs. 12--18 illustrate epithelium from the dorsal prostate

Fig. 12. Survey electron micrograph of the dorsal prostate. The cells are characterized by widely dilated cisternae of the rough endoplasmic reticulum (RER) and well developed Goigi apparatus (G). Dense bodies (Db) are rather numerous. Note the absence of dense secretion

granules. N nucleus, x 6000

Fig. 13. While secretion granules are absent, secretory vacuoles (SV) are present in the Golgi area (G) and in the juxta-luminal cytoplasm. Numerous coated vesicles (CV) arc observed in

the Goigi area. x 24000


Fig. 14. Detail electron micrograph which illustrates the widely dilated cisternae of the rough endoplasmic reticulum (RER) in the basal par t of the lateral lobe cell. N nucleus. × 12000

Fig. 15. Dense bodies (Db) often of the residual body type are relatively common in tile lateral lobe. N nucleus. × 7500

Fig. 16. In the basal par t of the cytoplasm, dense bodies of different morphology are often encountered. × 40000


Coagulating Gland. The most characteristic finding in the epithelium of this lobe is the RER, which consists of enormously dilated cisternae filled with a homogeneous substance (Fig. 19). The basal area of many cells is almost entirely occupied by such cister:tae, which are traversed by interlacing strands of cytoplasm. Some- times the cytoplasm is reduced to papillary projections within a sea of cisternae (Fig. 20). A prominent Golgi apparatus was seen apically. Vacuoles containing a granular material are present in the Golgi area (Figs. 19, 21). Lysosome-like bodies are relatively frequent throughout the cytoplasm (Fig. 19). The cells are provided with a few microvilli on their luminal surface. The nucleus is placed centrally. I t has a spherical form with some indentations of the nuclear membrane and is sparse in chromatin.

Seminal Vesicles. The most prominent finding within the epithelial cells of this gland was a great number of membrane bounded vacuoles, each containing an eccentrically located small secretion granule (Figs. 22, 23). A well developed Golgi apparatus was seen in the middle portion of the cell containing several secretion granules. The R E R is rather extensive (Fig. 24). I t generally forms parallel cisternae in longitudinal section, but sometimes small parasomes are present. Several dense bodies are located in the basal cytoplasm (Fig. 22). The basally located nucleus is rich in chromatin and has an elongated shape. The number of microvilli on the luminal surface is small. Scattered lipid droplets are found within the basal cytoplasm of the cells (Fig. 28).

Discussion

Studies of different lobes (Schrodt, 1961 ; Helminen and Ericsson, 1970) and of the postnatal development (Flickinger, 1971) have defined the general ultrastructural features of the rat prostatic epithelium. From the information available, the cells are primarely characterized by extensive granular endoplasmic reticulum, a large Go]gi apparatus, and numerous secretory granules.

In the present investigation, which continues these observations, the whole prostatic complex has been examined after vascular perfusion under identical ex- perimental conditions. I t has been revealed that although the epithelial cells of the different lobes have many features in common, it is also apparent that the cell type of the various lobes has specific ultrastruetural characteristics of its own, which morphologically distinguish it from the cell type of the other lobes. I.e., the different lobes may be identified by their specific ultrastructurM feature. In the following, the subgrouping of the accessory sex glands will be discussed in further detal.

The lateral lobe is characterized by a eonspicious brush border, numerous dense secretory granules within the Golgi area as well as in the apical par t of the cell, and generally flattened RER. Since the cells of this lobe are the only ones with brushborder, they can easily be identified by this criterion alone.

Fig. 17. Circular membranes (arrow) suggesting segregation are sometimes observed in normal epithelial cells of the dorsal prostate. × 15000

Fig. 18. Within the basal cytoplasm a single cytoplasmic inclusion with complex structure suggested to be a crystalline structure was encountered. × 50000


Figs. 19--21 illustrate epithelium from the coagulating gland

Fig. 19. Survey electron micrograph of the coagulating gland. The cells are characterized by enormously dil~ted eisternae of the rough endoplasmic reticulum (RER) filled with a homogeneous substance. Secretion granules are ~bsent, bu t vacuoles (SV) containing a granular material, presumably the secretory product, are observed in the apical cytoplasm. Lysosome-like bodies (Db) are regularly encountered. The nucleus (N) is located in the middle par t of the cell.

× 8 000

Accessory Sex Organs of the Male l%at 355

The coagulating gland is characterized by the extensive cisternae of the RER, a rather pale, centrally located nucleus, and moderately dense secretion granules within the apical part of the cell.

The dorsal lobe, which may have several features in common with the coagulating gland, is also characterized by dilated RER, but not to the same degree as in the coagulating gland. In addition, the secretory material in these cells is seen as a flocculent substance whitin vacuoles. The nucleus is generally located towards the basal part of the cell.

The ventral lobe is characterized by a well developed, flat RER, appearing as parallel rows of narrow cisternae. Dilated cisternae are absent. The nucleus is rather elongated, rich in chromatin and located in the basal part of the cell, often adjacent to the basal membrane.

The seminal vesicles, which has many features in common with the lateral lobe, are characterized by dense secretory granules within the Golgi area as well as the apical part of the cell, and flattened RER. Contrary to the lateral lobe, only scattered microvi]li are seen at the surface of the cell (cfr. the lateral lobe).

Even if it has been revealed that the different lobes separately have almost specific characteristics of their own, it is also striking that the lobes, two-by-two, have so many morphological features in common that they may be divided into subgroups. Based on the appearance, the amount and the localisation of the different organelles, the cells of the lateral lobe and the seminal vesicles are so alike that they morphologically may be classified as one group. Similarly, the coagulating gland and the dorsal lobe form another group, while the ventral lobe as a single forms a third group. When these groups are compared, their morphologic differences are obvious and undoubtfuI. Group one (lateral prostate-~-vesic]e) is recognized by its secretion granules, group two (coagulating gland and dorsal prostate) by the dilated cisternae and group three (ventral lobe of the prostate) by the flattened RER. As pointed out by Schrodt (1961) and Flickinger (1971), there are variations in the morphology whithin the same acinus of the lateral prostate. At the interface between the dorsal and lateral prostate, intermingling of individual cells may occur. In this area, some acini may contain both cell types (cell types of the lobes). In the present study the existence of a dorso-]ateral transitional cell-type has even been demonstrated, containing a mixture of morphological features of both the dorsal and lateral prostate lobes.

Worth emphasizing is the fact that each acinus is surrounded by a distinct coat of smooth muscle cells provided with nerve fibers of autonomic origin. Some nerve fibers were also seen adjacent to the epithelial cells, but they were never seen pene- trating the basement membrane.

Correlation o] Structure and Function. Unfortunately, biochemical data on the different lobes are relatively sparse, and correlation of structure and function must

Fig. 20. High magnification of the RER. The cytoplasm extends into the cisternae of the RER, forming papillary projections (Pp) appearing as cytoplasmic islands in cross section. × 24000

Fig. 21. Within the well developed Golgi area (G), vacuoles (arrows) containing a granular, secretory material are encountered. × 15000


Figs. 22--24 il lustrate epithelium from the seminal vesicle

Fig. 22. Survey electron micrograph of the seminal vesicle. The cells are characterized by apical accumulation of large numbers of dense granules (SG), eccentrically located within vacuoles, and basally located rough endoplasmic reticulum ( B E R ) which consists of narrow, mostly parallel cisternae. Within the glandular lumen, the secreted material is very dense. The nucleus

(N) is relatively rich in chromatin. Note the different sizes within the Golgi area. × 4350

Accessory Sex Organs of the Male Ra t 357

:Figs. 25--30 show structures which have not been demonstrated within the prostatic epithelium before

Fig. 25. Nuclear body (Nb) with a dense, finely granular matrix. × 20000

:Fig. 26. Bundle of cytoplasmic fi laments (arrow) from the seminal vesicle. × 30000

Fig. 27. Cytoplasmic mierotubule (arrow) from the coagulating gland. × 60000

Fig. 28. Lipid droplets (L) within the basal cytoplasm of the seminal vesicle gland. N nucleus × 9 000

:Fig. 29. Each acinus is surrounded by three or four layers of smooth muscle cells (SM), which are invested in connective tissue (CT). CY cytoplasm. N nucleus. ×8000

Fig. 30. Bundle of nerve fibers (NF) invested by Sehwann cell cytoplasm (SW) close to a smooth muscle cell (SM). ×40000

Fig. 23. Pa r t of the Golgi apparatus demonstrat ing formation of secretion granules (arrow) and typical dense granules of different sizes, eccentrically located within a somewhat large

vacuole. × 30000

:Fig. 24. The rough endoplasmie reticulum consists of narrow, mostly parallel cisternae filled with a homogeneous substance. × 24000

24 z. Zellforsch., Bd. 137

358 E. Dahl et al . :

be t en ta t ive . The u l t r a s t ruc tu re of the cells in the presen t s t u d y is all cons is tent wi th the charac ter i s t ics of p ro te in synthes iz ing cells. The large a m o u n t of secret ion granules, especial ly in the la te ra l lobe and the seminal vesicles, suppor t the general view of m a r k e d synthes iz ing product ion . I t is in teres t ing to note, t h a t the dorsa l p ros t a t e and the coagula t ing g land (group 2) are r ich in f ructose (Mann, 1964) a subs tance which is no t encounte red in the o ther lobes. Fu r the rmore , the dorsa l lobe and coagula t ing g land (group 2) bo th lack citric acid. On the o ther hand, ci tr ic acid is p resen t in the l a te ra l lobe and seminal vesicle (group 1) as well as in the ven t ra l lobe (group 3). Espec ia l ly since t he var ious p ros ta t i c lobes and the seminal vesicles, excep t the ven t ra l p ros ta te , have the i r homologies in the m a n (Price, 1963), fu r ther s tudies should be concen t r a t ed upon the d i f ferent groups ins tead of single lobes.

Dif ferent mechanisms of secret ion have been proposed for the pros ta te . A holocrine mode of secret ion was suggested for the dorsa l lobe (Gunn and Gould, 1957) an apocr ine mode for the l a te ra l p ros t a t e (Price and Wi l l i ams-Ashman, 1961) and a merocr ine in the ven t ra l lobe (Helminen and Ericsson, 1970). I n the presen t s tudy , we were unab le to suppor t the idea of apoer ine or holocrine secretion. Our f indings s t rong ly indicate t ha t , general ly, the mode of secret ion is a merocr ine one in the whole accessory geni ta l complex. However , for t he dorsa l lobe, we could not exclude the poss ib i l i ty t h a t an apocr ine form of secret ion m a y opera te in add i t i on to a merocr ine form. Blebb ing of the lumina l surface was f requen t ly seen in the dorsa l lobe in our exper iments , even though g rea t care had been t a k e n to ensure satisfac- t o r y p rese rva t ion . Such apical b lebbing was reduced af ter cas t ra t ion , and af ter t r e a t m e n t wi th estrogen, b u t was a sal ient fea ture in cas t r a t ed ra ts t r e a t ed with t e s tos te rone (unpubl i shed observat ion) . I t m igh t be possible t h a t the dorsa l pros- t a t e is more prone to f ixa t ion a r t i fac t s t h a n the o the r lobes, so t h a t apical b lebbing m a y stil l be an a r t i f ac t r a the r t h a n express ion of apocr ine form of secretion.

References

Brandes, D. : The fine structure and histochemistry of prostatic glands in relation to sex hor- mones. Int. Rev. Cytol. 20, 207-276 (1966).

Flickinger, C. J. : The fine structure and development of the seminal vesicles and prostate in the fetal rat. Z. Zellforseh. 109, 1-14 (1970).

Flickinger, C. J. : Ultrastructural observations on the postnatal developmentof the rat prostate. Z. Zellforsch. 113, 157-173 (1971).

Gunn, S. A., Gould, T. C. : A correlative anatomical and functional study of the dorsolateral prostate of the rat. Anat. Rec. 128, 41-53 (1957).

ttarkin, J. C." An electron microscopic study of the castration changes in the rat prostate. Endocrinology 69, 185-199 (1957).

Helminen, H. J., Ericsson, J. L. E. : On the mechanism of lysosomal enzyme secretion. Elec- tron microscopic and histochemieal studies on the epithelial cell of the rats ventral prostate. J. Ultrastruet. Res. 33, 528-549 (1970).

Helminen, H. J., Ericsson, J. L. E. : Ultrastructur~l studies on prostatic involution in the rat. Mechanism of autophagy in epithelial cells, with special reference to the rough-surfaced endoplasmic reticulum. J. Ultrastruct. Res. 86, 708-724 (1971).

Kjaerheim, A. : Studies of adrenocortical ultrastructure. 1. Aldehyde perfusion fixation of the domestic fowl. Acta anat. (Basel) 74, 424-453 (1969).

Mann, T. : The biochemistry of semen and of the male reproductive tract. London : Methuen & Co., Ltd. 1964.

1Y[illonig, G. : The advantages of a phosphate buffer for OsO 4 solutions in fixation. J. appl. Phys. 32, 1637 (1961).


Price, D., Williams-Ashman, H. Gj.: The accessory reproductive glands of mammals. In: Young, W. C. (ed.). Sex and internal secretions, p. 366-448. Baltimore: Williams & Wilkins Comp. ].961.

Ryter, A., Kellenberger, E. : L'inclusion au polyester pour l 'ultramicrotomie. J. Ultrastruct. ]~es. 2, 200-214 (1958).

Schrodt, G. 1~. : The fine structure of the lateral lobe of the rat prostate gland. Comparison with the dorsal and other lobes, ft. Ultrastruct. Res. 5, 485-496 (1961).

Szirmai, J. A., Linde, P. C. van der: Effect of castration on endoplasmic reticulum of the seminal vesicle and other target epithelia in the rat. J. Ultrastruct. Res. 12, 380-395 (1965).

Dr. Erik Dahl Department of Anatomy Dental Faculty University of Oslo P.O. Box 1052 Blindern, Norway

24*

the ultrastructure of the accessory sex organs of the male rat

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