The fine structure of secretory granules in submandibular glands of the rat during early postnatal development

The secretory end-pieces of the submandibular gland of rats during the first week of postnatal development are studied with regard to the fine structure of the secretion granules in these end-pieces. The terminal ends of the secretory ducts during this period consist of two types of cells; one cell is an acinar-type and the other is a duct-type found in the gland of adult rats. The secretion granules of the acinar-type cells are similar in appearance to those of the acinar cells in the gland of adult rats, and the structure of these granules remains the same throughout the week. However, granules widely different in appearance are present in the duct-type cells, and their structure varies in different cells as well as within a single cell at different stages of development. These granules contain unusual substructures which are not found in the secretion granules of adult rats, suggesting that the granules are transitory. Granules containing short tubular profiles are predominant in the gland of one day-old rats. A large number of granules in three day-old rats contain elongated tubules. More granules of widely different substructures are present in the gland of seven day-old rats than in the gland of younger rats. The matrix of the granules in seven day-old rats is of higher density than that of the granules in younger rats. In the dense matrix of these granules, less dense tubules form fingerprint-like or somewhat more irregular patterns.     

The influence of progestin and androgen on the fine structure of the male reproductive tract of the rat. II. Epididymis and sex accessory glands

Young adult male rats were administered medroxyprogesterone (Provera, Upjohn) alone and in combination with testosterone, as has been done to inhibit male fertility. The histology and fine structure of several segments of the epididymis, the ventral prostate, and the seminal vesicle were studied at intervals after treatment for up to 16 weeks. The epididymides of treated animals weighed less than those of control rats. Microscopic alterations in the epididymis were similar in rats treated with Provera alone and in those animals that received Provera and testosterone, but the changes varied with the segment of the epididymis. In the middle segment in the caput epididymidis, the normally abundant luminal sperm were absent but the epithelium retained its normal ultrastructural features. In the terminal segment in the cauda epididymidis, different changes were observed in the proximal and distal portions. In the proximal cauda epididymidis, the lumen was small, irregular in outline, and virtually devoid of sperm. The light cells of the epididymal epithelium in the proximal cauda contained extremely large numbers of dense bodies resembling lysosomes, which occupied most of the supranuclear and basal cytoplasm. In contrast, in the distal part of the cauda epididymidis, the epithelium had a normal appearance but the lumen was filled with debris, sperm, and spherical masses of cytoplasm that were apparently derived from germ cells. It is suggested that the clearing of the lumen of the proximal cauda epididymidis may reflect the greater activity of light cells of the epididymal epithelium in that region. Although alterations in spermatogenesis may be most important in the antifertility effect of progestin and androgen, these alterations in epididymal sperm and epithelium may also play a role. The weights of the prostate and seminal vesicles of rats treated with Provera (1 mg/100 g/day) were greatly reduced compared to those of control rats. Although there was considerable variation, in many specimens treated with Provera alone the epithelium of the prostate showed a change from a columnar to a cuboidal or squamous shape, and there was a reduction in the size and abundance of organelles involved in the formation of secretions. The microscopic structure of the seminal vesicle of rats treated with Provera was less severely affected than the prostate. Although the seminal vesicle epithelium of Provera-treated rats was generally not as tall as in control animals, the cells possessed parallel cisternae of rough endoplasmic reticulum, secretory vacuoles, and an active-appearing Golgi apparatus, suggesting that they continued to be able to form secretions in the presence of Provera. The weights of the sex accessory glands were maintained at control levels by the administration of testosterone, 100 μg/100 g/day, along with the Provera. A normal fine structure was present in the epithelium of both the prostate and seminal vesicle of rats administered this amount of testosterone in addition to Provera. Lower doses of testosterone (15 or 30 μg/100 g/day) were insufficient to maintain normal weight or ultrastructure of the sex accessory glands in the presence of Provera.     

Interpretation of respiratory tract histology in cot deaths.

The degree of inflammation in the trachea, bronchi, and lungs of 139 cot deaths has been analysed and each case allocated to one of four groups. In group I the changes were considered to be serious enough to have caused death, while group II cases showed similar abnormalities but of a less severe nature, and in this group there was some doubt as to whether they were a significant cause of death. Group III lesions were very minor in type and were not considered to be serious enough to have resulted in the death of the child. There was a good correlation between the degree of inflammation in the respiratory tract, and whether or not bacteria of any type were grown. The great majority of the bacterial pathogens were isolated from the first two groups. Respiratory viruses were isolated from three of the four cases of acute bronchiolitis included in group I, and also from a group II case which showed considerable bronchiolar inflammation. One-third of the cases with minor inflammation in the lung parenchyma (group III) showed some evidence of recent virus infection.     

On the fine structure of horse sweat glands

Summary Sweat glands from different representative areas of the horse have been studied in 6 animals with light microscopy and the intermandibular and coccygeal regions from 2 animals with electron microscopy. The sweat glands were numerous and well developed in all areas examined. The columnar cells, dominated by secretory PAS-positive diastase resistant vesicles, were surrounded by myoepithelial cells resting on a well developed basal lamina. The cytoplasmic organelles characteristic for cells involved in secretion were present. The extensively folded basal plasma membrane, the numerous microvilli at the luminal border and the intraepithelial canaliculi lined with microvilli were morphological structures typical of cells involved in water and electrolyte transport. The observation of cytoplasmic protrusions were suggestive of apocrine secretion.On deputation from the Department of Anatomy, Bihar Veterinary College, Patna 14, Rajendra Agricultural University, Bihar, India. Supported by F.A.O. Veterinary Faculty for F.A.O.-Fellows and Scholars, Copenhagen, Denmark.     

The fine structural localization of acetylcholinesterase activity in the rat parotid and sublingual glands

The fine structural localization of acetylcholinesterase activity was studied in the rat parotid and sublingual glands. In both glands, reaction product was found in association with the axolemmae of stromal axons invested by Schwann cells and between the contact with effector cells. In the sublingual gland, reaction product was also found in association with surface vesicles and pits and the rough endoplasmic reticulum of myoepithelial cells.     

Carbohydrate histochemistry of rat respiratory glands

Cytochemical methods applied to examination of rat respiratory tract glands have revealed diversity of secretory complex carbohydrates. With the Alcian blue-periodic acid Schiff (AB-PAS) and the high iron diamine (HID) techniques at the light microscopic level, certain patterns of glycoprotein content were noted at various levels of the respiratory tract. Serous tubules and demilunes found in abundance in laryngeal and tracheal glands contained neutral glycoprotein. Mucous tubules found in abundance in epiglottal and laryngeal glands and in lesser number in tracheal glands most often produced sulfated glycoprotein. However, mucous tubules in epiglottal and tracheal glands contained a few cells with sialylated glycoprotein, and mucous tubules in some areas in laryngeal glands contained mainly cells producing sialylated glycoprotein. Mucous ducts found in abundance in lower laryngeal and tracheal glands formed mainly sialylated glycoprotein and contained infrequent cells with sulfated glycoprotein. The type of glycoprotein found in each cell type by light microscopy was confirmed at the ultrastructural level by the periodic acid-thiocarbohydrazide-silver proteinate (PA-TCH-SP), dialyzed iron (DI) and high iron diamine (HID) methods. Serous cell granules displayed light reactivity with the PA-TCH-SP method and no DI or HID affinity and were judged to contain sparse neutral glycoprotein. Serous granules disclosed negative central foci with the PA-TCH-SP method. Granules of most mucous tubule cells stained strongly with the PA-TCH-SP and HID procedures and contained abundant sulfated glycoprotein. Occasional mucous tubules stained with the PA-TCH-SP but not with the HID method and apparently corresponded with cells judged to form sialylated glycoprotein from their blue staining with the HID-AB sequence. Two zones within individual granules in some cells revealed different HID staining intensity and appeared to differ in the amount or kind of sulfated glycoprotein they contained. Some cells exhibited granule heterogeneity containing both HID-positive and unstained granules. Spherical cores present in granules of mucous tubules below the upper laryngeal level occasionally appeared bizonal and invariably lacked reactivity demonstrative of complex carbohydrate. Mucous duct cell granules stained heavily with the PA-TCH-SP and DI methods and reacted infrequently with the HID procedure and were considered generally to contain sialylated glycoprotein, and occasionally to form sulfated glycoprotein. The three carbohydrate stains distinguished a heavily and a moderately reactive zone in the cortex outside the monophasic or biphasic, carbohydrate-free cores in granules of some mucous duct cells.     

The fine structure of the pia mater of the rat

Tissue from the central nervous system of 11 adult Sprague-Dawley rats fixed by vascular perfusion with buffered aldehydes was used in a study of the fine structure of the pia mater. Surface tissue from the cerebral and cerebellar cortices, ventral pons, olfactory bulb, tuber cinereum, spinal cord, superior colliculus, optic chiasm, and median longitudinal fissure was examined. Variations in pial composition occurred within each of these selected areas although a basic pattern prevailed throughout. The components of the pia mater are described under three categories: pial cells, extracellular elements, and macrophages. The pial cells are the more numerous cell type, possessing long, flattened cytoplasmic processes which contain few inclusions. These cells vary in thickness in any one area and there may be from one to six distinct cytoplasmic layers. Fenestrations between pial cell processes or total absence of pial cells are occasionally encountered. Unit collagen fibrils make up most of the extracellular material of the pia. These have a major period of about 550 Å and are about 400 Å wide. Macrophages are rounded up and contain various cytoplasmic inclusions. In normal animals evidence of active phagocytosis is rare.     

The fine structure of vascular sympathetic neuromuscular contacts in the rat

The fine structure of the neuromuscular contacts of arterioles and small arteries from the jejunum and mesentery of the rat has been studied. There is a rich innervation of these vessels, consisting of bundles of axons in the adventitia around the vessels. In the typical sympathetic neuromuscular contact on a small blood vessel, the axon bundle is loose, the Schwann cell cover is deficient, the neuromuscular distance is less than 1,500 Å, the basement membranes of axon and smooth muscle cell are fused together, and the axon tends to follow the contour of the smooth muscle cell. However, it is not possible to be certain that these criteria are essential for a true functional neuromuscular contact. In particular, it appears from the structural findings that a neuromuscular distance of 2,000–3,000 Å or more could well be compatible with effective neuromuscular transmission. Smooth muscle cells in arterioles often have multiple innervation, and an axon probably innervates more than one smooth muscle cell. Occasional axons contain mainly or solely vesicles of the “large granular” type.     

The fine structure of the interstitial tissue of the rat prostate

The structure of the interstitial tissue of the rat prostate has been studied using the light and electron microscopes in an attempt to determine the role of the fibromuscular stroma in the normal functioning of the gland. Smooth muscle cells and fibroblasts are the most numerous cell types. They are accompanied by macrophages, mast cells, and undifferentiated cells of low electron density. Smooth muscle cells have cytoplasmic protrusions that extend into corresponding depressions in adjacent muscle cells, and, at these points, the intercellular space is narrowed to 150–2000 Å. Smooth muscle cells and fibroblasts are arranged in parallel in septa between adjacent epithelial alveoli and form a sheath around each alveolus. Proceeding peripherally from the epithelium into the interstitial tissue, this sheath is composed of a layer of one or two highly flattened fibroblasts and a parallel layer of smooth muscle cells, followed subsequently by additional layers of fibroblasts and smooth muscle that merge into the remainder of the interstitial tissue. Most of the capillaries have an uninterrupted endothelium, but in some regions endothelial fenestrations are present. Unmyelinated axons contain aggregations of small granular and agranular vesicles. Vesicles are found in axons at distances up to several thousand angstroms from muscle cells and in axons that approach to within 150–200 Å of smooth muscle cells. In some cases an axon lies in a deep depression in the surface of a muscle cell. The type of innervation and variety of intercellular contact between muscle cells is discussed in relation to probable physiological characteristics of the tissue.     

The fine structure of the epithelium of prostate glands in adult female mastomys erythroleucus Temm.

The prostate glands in adult female Mastomys were studied with the light and the electron microscope. In the light microscopy, each prostatic acinus is lined by a single layer of tall cuboidal secretory epithelial cells which are surrounded by a capsule composed of a few layers of elongated and flattened cells. The acinar secretory epithelial cells show no presence of the supranuclear light areas in their cytoplasm and tend to be more readily stained with toluidine blue in the perinuclear and the upper basal cytoplasm than in the rest cytoplasm. In the electron microscopy, sharply localized pittings are occasionally found on the luminal surface and further the secretory granules which are closely situated to the apical cell surface are recognized. In the supranuclear cytoplasm, several well-developed Golgi apparatuses appear individually and early developing secretory granules are also observed. In the perinuclear and the upper basal cytoplasm the rough endoplasmic reticulum is well developed while in the lower basal cytoplasm the smooth endoplasmic reticulum is conspicuously developed and predominates.