Showing papers in "American Journal of Anatomy in 1974"

Origin, differentiation and renewal of the four main epithelial cell types in the mouse small intestine. V. Unitarian Theory of the origin of the four epithelial cell types.

Abstract: The previous articles of this series provided presumptive evidence that the four main differentiated cell types in the epithelium of the mouse small intestine: villus columnar, mucous, entero-endocrine, and Paneth cells, originate from the same precursor, the crypt-base columnar cell. In the present work, direct evidence was obtained in support of this view. It was first found that crypt-base columnar cells phagocytose non-viable cells in their vicinity, with the result that a large phagosome appears in the cytoplasm. Such phagosomes were then used as markers to follow the evolution of crypt-base columnar cells. In normal control animals, a rare crypt-base columnar cell includes a large phagosome containing Paneth cell remnants. By six hours after injection of two μCi 3H-thymidine per g body weight, a fair number of crypt-base columnar cells include a different type of phagosome containing labeled nucleus and granulefree cytoplasm, which is attributed to phagocytosis of a labeled crypt-base columnar cell killed by beta-radiation from the incorporated 3H-thymidine. By 12 hours after 3H-thymidine injection, phagosomes have appeared in partly differentiated mid-crypt columnar cells and oligomucous cells; by 18–24 hours, in fully differentiated columnar cells and in Paneth cells; and by 30 hours, in an entero-endocrine cell. Since phagosomes are first found in crypt-base columnar cells and only later in the four differentiated cell types, it is concluded that crypt-base columnar cells transform into cells of these four types and, therefore, behave as the stem cells of the epithelium. The finding of rare epithelial cells containing two different types of secretory material (either mucous globules and entero-endocrine granules, or mucous globules and Paneth cell granules) confirms that the stem cells are multipotential. These findings support the Unitarian Theory of epithelial cell formation in the small intestine.

Origin, differentiation and renewal of the four main epithelial cell types in the mouse small intestine. II. Mucous cells

Abstract: The mucous cell population of duodenum, jejunum and ileum was investigated in the light and electron microscopes with the help of radioautography in mice sacrificed at various times after single injection or continuous infusion of 3H-thymidine. Mucous cells are characterized by globules of mucus and by dilated cisternae of rough endoplasmic reticulum. Two subgroups of mucous cells, one called common and the other granular, may be identified. The granular mucous cells differ from the common ones by the presence of small dense granules embedded within the mucous globules. Each subgroup is further divided into immature oligomucous cells containing few mucous globules, and mature goblet cells with a large accumulation of mucous globules. Common and granular oligomucous cells are found exclusively in the crypt, mainly within the lower mid-crypt, whereas the corresponding two types of goblet cells are present in the upper part of the crypts and in the lower part of the villi. Only common mucous cells are observed in the upper part of the villi. The two types of oligomucous cells, but not goblet cells, have the ability to take up 3H-thymidine and divide. Electron microscopic radioautography demonstrates that, as oligomucous cells migrate upwards, they transform into goblet cells. The latter then migrate to the villus epithelium. In the case of granular mucous cells, this migration is associated with a gradual loss of the characteristic dense granules, so that the granular goblet cells reaching the upper part of the villi become common goblet cells. The goblet cells in the villus epithelium, regardless of their origin, ascend towards the villus tips where they are lost through the extrusion zones. The turnover time of common mucous cells is about three days, as for columnar cells; and that of granular mucous cells, somewhat shorter. In both cases, the divisions of oligomucous cells account only for the production of about half the mucous cells present. Hence, the other half must be derived from precursors other than oligomucous cells. Since a few crypt-base columnar cells contain the odd mucous globule, they are suspected of being the precursors of the two types of oligomucous cells and, through them, of the entire mucous cell population.

Origin, differentiation and renewal of the four main epithelial cell types in the mouse small intestine III. Entero‐endocrine cells

Abstract: The origin, differentiation and renewal of entero-endocrine cells was examined in the duodenum, jejunum and ileum of the mouse using light and electron microscopic radioautography after a single injection or continuous infusion of 3H-thymidine. When s-collidine buffered glutaraldehyde was used for fixation prior to electron microscopic study, all granules in all entero-endocrine cells were spheroidal and, therefore, their shape could not be used to classify the cells into subgroups, as done after fixation in phosphate buffered aldehyde. Thus, the cells were all considered as belonging in a single family. In the light microscope, mitosis is not observed in the entero-endocrine cells identified by iron hematoxylin staining. However, under the electron microscope, a few cells that contain a small number of characteristic granules, some filament bundles and many free ribosomes are in division or are labeled one hour after an injection of 3H-thymidine. These cells are interpreted as young entero-endocrine cells. They are located in the crypt base. They resemble crypt-base columnar cells and are, therefore, suspected of arising from them. Differentiation may be examined by following the fate of the young enteroendocrine cells which are labeled by 3H-thymidine. Within the crypts, these cells acquire a gradually increasing number of granules while losing the ability to divide. The few granules initially present usually have a particulate content and may include a small dense core; but, as differentiation proceeds and granules accumulate, their content is mostly dense and homogeneous. The differentiation of precursor cells into mature entero-endocrine cells takes about two days. Meanwhile, in the same manner as columnar and mucous cells, enteroendocrine cells migrate up the crypt, reach the villus and are lost at the extrusion zone. The turnover time of entero-endocrine cells is estimated to be 3.9 days in duodenum and 4.0 days in jejunum.

Monoamine-containing cell bodies in the squirrel monkey brain.

Abstract: Fifteen catecholamine-containing cell groups and eight indoleamine-containing cell groups are present in the brain of the squirrel monkey. Most of the catecholamine-containing cell groups (12) are similar to catecholamine-containing cell groups previously described in the rat. However, three catecholamine-containing cell groups not previously noted are found in the squirrel monkey brain. The indoleamine-containing cell groups are found within, or adjacent to, the raphe nuclei. Differences between the localization of indoleamine-containing cell bodies in the brain of the rat and the squirrel monkey are minor.

The postnatal development of the human temporomandibular joint.

Abstract: Fifty-one temporomandibular joints (24 male, 27 female) obtained at autopsy were used in the study. Forty-four specimens were younger than ten years while others ranged to 21 years. These joints were radiographed, sectioned sagittally or frontally, and slide-mounted as decalcified and undecalcified sections using conventional histologic techniques. The slides were examined microscopically in whole, polarized, and ultraviolet light. Two of the specimens surveyed exhibited fluorescent labeling as a consequence of therapeutic tetra cycline application. Throughout the postnatal developmental period the articular tissue and disc consist of fibrous connective tissue. Cartilage cells were not observed in these structures at any time during the twenty-one year age-span studied. At birth the disc is flat and develops an accentuated S-shaped profile as the articular tubercle develops. The articular tubercle is only a small elevation at birth and is formed by a combination of endochondral, immature, and ordinary intramembranous bone formation. The characteristic profile of the temporal portion of the joint is achieved during the first two or three years of life, after which gradual enlargement and compaction of bony structures occur. While the mandibular condyle grows in a constant posterior, superior, and lateral direction, it does not attain its mature contour until the late mixed dentition age. Condylar growth cartilage is approximately 1.5 mm thick at birth but it thins down in a short time to about 0.5 mm. During the first two years of life the growth cartilage is penetrated by vascularized connective tissue septa whose function appears to be nourishment of the cartilage. The growth cartilage does not show the columnar arrangement of chondrocytes seen in epiphyses, nor are isogenous groups observed. At 16 to 17 years, the growth cartilage becomes thinner and a closing plate of bone is beginning to coalesce below it.

Electron microscopic immunohistochemical localization of growth hormone-release inhibiting hormone (somatostatin) in the rat median eminence.

Abstract: Using an immunohistochemical technique at the electron microscopic level, we have observed that growth hormone-release inhibiting hormone (somatostatin), the hormone which inhibits the release of growth hormone, is contained in the secretory granules of many nerve endings mainly located in the external zone of the median eminence.

A scanning electron microscopic study of the nephron.

Abstract: Scanning electron microscopy was used to study the ultrastructural morphology of the nephron. Material for observation was taken from rat kidneys which were fixed by vascular perfusion. Different techniques for splitting open the kidney, combined with stereoscopic viewing, provided many instructive views of nephron morphology. In addition, scanning electron microscopy revealed a number of new features including (1) the complex organization and structure of kidney podocytes; (2) the distribution of endothelial pores and the presence of endothelial microprojections and branching endothelial thickenings; and (3) the presence, distribution and morphology of microprojections and cilia on the luminal surfaces of Bowman's capsule and the uriniferous tubules.

"Caveolated cells" characterized by deep surface invaginations and abundant filaments in mouse gastro-intestinal epithelia.

Abstract: Light and electron microscope examination of gastro-intestinal epithelia in the adult mouse revealed the widespread presence of a cell type characterized by deep surface invaginations or “caveolae” and, accordingly, called “caveolated cell.” The caveolated cells are scattered within the epithelia of stomach, small and large intestine; they have a narrow apex bordering the lumen and a wide base in contact with the basement membrane. In the light microscope, they display microvilli longer than in nearby cells; the cytoplasm is usually pale and contains an apical group of parallel fibrils, next to which are minute light spaces which may correspond to the caveolae. In the electron microscope, each fibril is found to be composed of a bundle of straight filaments, extending from the core of a microvillus down into the deeper portion of the supranuclear region; microtubules are often associated with these filaments. Filaments of a different type are arranged in bundles which go from desmosome to desmosome around the apical region of the cell. The caveolae are long and tortuous channels opening at the cell surface between the microvilli and extending deep into the cytoplasm. From the walls of caveolae, polyp-like structures project into the lumen. The heads of the polyps are believed to be released into this lumen where they appear as small spheres. These in turn may come out of the caveolae to appear between and next to the microvilli. Caveolated cells are not numerous, e.g., they make up less than 1% of the epithelial cells in the crypts of descending colon. They may be found in the intestinal crypts among poorly differentiated cells, and at the surface of stomach and intestine among fully differentiated cells. They appear to undergo renewal, but since they have not been seen in mitosis, they probably arise from the differentiation of some other epithelial cells.

Three-dimensional structure of the osmium-impregnated Golgi apparatus as seen in the high voltage electron microscope.

Abstract: Osmication in an unbuffered aqueous solution of osmium tetroxide allows the forming face of the Golgi apparatus to be labeled in many cell types. This property was utilized to study the spatial configuration of this organelle by examining stereopairs of the same field taken at 1,000 KV after tilting a thick (1 to 7 μUm) section of − 7° or + 7° from the original (0°) position. When examined in 1 μm thick sections at magnifications ranging from 13,000 to 18,000 times, the osmic acid-impregnated element of the Golgi apparatus of ganglion nerve cells, Leydig cells or Sertoli cells takes the appearance of a single layered polygonal network of tubules. This network can only be seen at electron microscope magnifications and is referred to as the primary network or structure of the forming face of the Golgi apparatus. When 2 to 7 μm thick sections are examined under progressively lower magnifications, the details of the primary structure remain discernible but become less conspicuous. The osmiophilic portion of the Golgi apparatus now extends over large areas of the cytoplasm to form an extensive continuous structure. This structure which is in the range of visibility of the light microscope is referred to as the secondary network or structure of the forming face. In ganglion nerve cells, the secondary structure consists of a perinuclear network showing slender projections reaching the nucleus and wider expansions approaching the cell surface; in the Leydig cells it appears as an ovoid structure located at one pole of the nucleus whereas in Sertoli cells it forms a cylindrical structure located in the main shaft of the cytoplasm and extending from the nucleus towards the lumen of the seminiferous tubule. Thus the forming face of the Golgi apparatus displays a primary structure; the tubular roughly polygonal network, which is similar in the three cell types and a secondary structure which varies from cell to cell.

Postnatal growth of the extra- and intrafusal fibers in the soleus and medial gastrocnemius muscles of the cat.

Abstract: Development of intrafusal and extrafusal fibers in the soleus and medial gastrocnemius muscles in kittens was studied in sections stained by van Gieson or histochemical procedures. Cross-sectional areas of intrafusal and extrafusal fibers overlapped extensively in the two weeks following birth, with the means for intrafusal fibers in the medial gastrocnemius muscle being larger than those for the extrafusal fibers. A definite increase in extrafusal fiber size was seen at 20 days and in intrafusal fibers at 29 days. In the one mother cat studied, mean areas for soleus and medial gastrocnemius fibers were 12 and 59 times larger than those for a kitten sacrificed the day after birth, while the intrafusal fiber areas were 3.0 and 4.8 times greater. The equatorial region in nuclear bag fibers showed no significant growth in cross-sectional area, but almost doubled in length. In a newborn kitten, all extrafusal fibers in the soleus and medial gastrocnemius demonstrated a high level of nicotinamide adenine dinucleotide diaphorase activity, but with the adenosine triphosphatase reaction, fibers had either low or high activity. After one month, soleus fibers with high adenosine triphosphatase activity were scarce, whereas in the medial gastrocnemius fibers with both low and high levels of activity were present. The intrafusal fibers at birth were already morphologically and histochemically differentiated into nuclear chain and bag fibers, and two varieties of the latter could be recognized in slides treated for adenosine triphosphatase activity.

The cycle of the seminiferous epithelium and spermatogenesis in the bovine testis

Abstract: Morphological changes in the acrosomic system and nuclei of developing spermatids were evaluated as a basis for classifying the stages of the cycle of the seminiferous epithelium in the bovine testis Light microscopic examination of periodic acid-Schiff-stained testicular tissue permitted identification of 14 steps of spermatid development (spermiogenesis) The first 12 steps in this sequence were utilized as the major criterion to divide the cycle of the seminiferous epithelium into 12 distinct stages Following this, the pattern of germ cell differentiation was investigated by counting the number of germ cells at each stage of the cycle Based on cell counts, type A spermatogonia divided primarily during stages VII–VIII and IX–X of the cycle Some type A cells divided again at the end of stage XII to produce intermediate spermatogonia, while others apparently remained “dormant” until the following cycle At the end of stage IV, intermediate spermatogonia divided to produce type B1 spermatogonia which in turn divided at the end of stage V to produce type B2 spermatogonia Primary spermatocytes appeared during stage VIII and divided late in stage XI of the following cycle to form secondary spermatocytes These divided to form young spermatids at the end of stage XII It was concluded that changes in the acrosomic system and nuclear morphology of developing spermatids provide useful criteria for dividing the cycle of the seminiferous epithelium into stages as well as investigating the pattern of germ cell development during spermatogenesis in the bovine testis

Changes in the mucosa of the small intestine following methotrexate administration or abdominal x-irradiation.

Abstract: Adult male rats received 5 mg methotrexate daily and were sacrificed 1, 1.5, 2, 2.5 and 3 days after the beginning of the treatment. Other groups received 9,000 rads of abdominal x-radiation and were sacrificed 1, 2 and 3 days later. Histological samples were taken from five regions of the small intestine and processed for light microscopic examination. Average area occupied by the crypts and the villi respectively, was measured per unit length of histological section. A few animals received 3H-thymidine an hour before the methotrexate treatment or irradiation; the histological samples were processed for radioautography. Significant mitotic activity was absent throughout the experiments. During the first 1.5 days, mainly the crypts diminished. Radioautography revealed that migration of crypt cells to the villi continued during this time. During the second and third days, the villi also showed marked diminution, and cell migration became irregular. In general, the histometric data were similar after methotrexate and irradiation. Epithelial denudation started in terminal ileum on the third day after methotrexate. The epithelium was much reduced but not yet denuding at this time in the irradiated animals. Methotrexate inhibition of DNA and RNA synthesis was assumed to be associated, respectively, with mitotic inhibition and with a decline of protein synthesis which manifested itself in villus diminution. Survival of epithelial cells varied presumably according to the amount of RNA pool and was longest in cells being in the S-phase at the onset of the treatment. The similarity of the data after irradiation implied a similar sequence of events.

A scanning electron microscopic study of the extrapulmonary respiratory tract

Abstract: Scanning electron microscopy, sometimes supplemented with transmission electron microscopy, was used to study the ultrastructural morphology of the extrapulmonary respiratory tract. Material for observation was taken from male rat respiratory tracts which were fixed in situ and critical point-dried. Goblet cells, brush cells, potential ciliated cells, ciliated cells, cornified vestibule cells and the olfactory mucosa could be distinguished by their characteristic surface morphologies. The distribution of these various cell types throughout the extrapulmonary respiratory tract is described. Transmission electron microscopy of material treated with ruthenium red reveals that a polyanionic surface layer coats all cilia, microvilli and the intervening cell surfaces on all cell types found in the nasal cavities, trachea and extrapulmonary bronchi.

The tectorial membrane of the rat

Abstract: Histochemical, x-ray analytical and scanning and transmission electron microscopical procedures have been utilized to determine the chemical nature, physical appearance and attachments of the tectorial membrane in normal rats and to correlate these results with biochemical data on protein-carbohydrate complexes. Additionally, pertinent histochemical and ultrastructural findings in chemically sympathectomized rats are considered. The results indicate that the tectorial membrane is a viscous, complex, colloid of glycoprotein(s) possessing some oriented molecules and an ionic composition different from either endolymph or perilymph. It is attached to the reticular laminar surface of the organ of Corti and to the tips of the outer hair cells; it is attached to and enclose the hairs of the inner hair cells. A fluid compartment may exist within the limbs of the “W” formed by the hairs on each outer hair cell surface. Present biochemical concepts of viscous glycoproteins suggest that they are polyelectrolytes interacting physically to form complex networks. They possess characteristics making them important in fluid and ion transport. Furthermore, the macromolecular configuration assumed by such polyelectrolytes is unstable and subject to change from stress or shifts in pH or ions. Thus, the attachments of the tectorial membrane to the hair cells may play an important role in the transduction process at the molecular level.

The fine structure of monkey Sertoli cells in the transitional zone at the junction of the seminiferous tubules with the tubuli recti.

Abstract: The monkey testis contains an axial rete in a highly vascular central core of loose connective tissue. Seminiferous tubules join the rete along its entire length. The short terminal segments of the tubules are lined mainly by Sertoli cells. There is then a transition from Sertoli cell epithelium to the simple cuboidal epithelium of tubuli recti, which connect the seminiferous tubules to the rete testis. Electron microscopic observations of the Sertoli cell in the terminal regions of the seminiferous tubules reveal a highly lobulated nucleus, a unique nucleolus and a columnar cell body with an irregular free surface bearing processes of varied form projecting into the tubule lumen. The cytoplasm is characterized by a well developed rough endoplasmic reticulum, large numbers of lipid droplets, and an extraordinary abundance of 70 A filaments. Occasionally these latter are so densely packed that other organelles are excluded from large areas of the cytoplasm. Profiles of smooth endoplasmic reticulum are few in marked contrast to the usual condition of Sertoli cells elsewhere in the seminiferous tubules. Many of the Sertoli cells in the terminal regions of the seminiferous tubules contain spermatozoa in various stages of degradation. Small lymphocytes, never observed in normal seminiferous tubules, are distributed in small numbers among the Sertoli cells of the transitional zone. No desmosomes or other junctional specializations are observed at the interface of lymphocytes with the surrounding Sertoli cells. The cytology of the terminal region of the seminiferous tubules is discussed in relationship to exit of sperm from the tubules, the blood-testis barrier, and the pathogenesis of immune orchitis.

Localization of luteinizing hormone‐releasing hormone in the mammalian hypothalamus

Abstract: Utilizing immunohistochemistry with rabbit antiserum to synthetic luteinizing hormone-releasing hormone (LRH), LRH was localized in the peripheral region of the median eminence in the mouse and rat, and more generally in the median eminence of the guinea pig.

Development of the zona pellucida in the rat oocyte

Abstract: Ovaries of weanling and juvenile rats were studied by electron microscopic and cytochemical techniques, with particular reference to the role of the Golgi complex in the formation of the zona pellucida. The zona pellucida type of material first appears in the perivitelline space at the stage when the oocyte acquires a single layer of flattened and cuboidal granulosa cells, and is completely formed when the granulosa cells attain a cuboidal shape. The intimate association of the Golgi complex with the oocyte plasmalemma and the presence of mucopolysaccharide in its saccules and vesicles suggests that the Golgi complex of the oocyte plays an important role in the synthesis of the zona pellucida. The zona pellucida of the rat egg consists of a single layer of acid mucopolysaccharide which is structurally distinguishable from the liquor folliculi. Formation of the primary liquor folliculi is attributed to the Golgi complexes in granulosa cells.

In vivo and electron microscopic observations on Schwann cells in developing tadpole nerve fibers.

Abstract: The migration of Schwann cells and their early association with axons were studied in transparent tadpole tail fins. Nomarksi optics revealed that in vivo these cells are pleomorphic, changing their shape by extending and withdrawing long, blunt pseudopods. Daily observations of the same fiber fascicles for a month or more combined with intensive short-term studies of other tadpoles showed that migrating Schwann cells move sporadically at rates of up to 114 μm/day. They are usually, although not always, in contact with one or more axons. In the electron microscope, these migrating cells are similar in cytoplasmic structure to others that have settled down and begun to spread along axons; however, they possess no basal lamina. Later, Schwann cells become more spindle-shaped and acquire a basal lamina. Schwann cell surface characteristics and the changes imposed by the presence of the basal lamina may be important in the establishment of permanent axon-Schwann cell relationships. In our living material we were unable to visualize the intricate, rapidly changing associations between Schwann cells and small axonal fascicles that precede myelination. However, they are probably more complex than Speidel's studies would indicate.

Hepatic glycogen patterns in fasted and fed rats.

Abstract: Hepatic glycogen patterns are described for rats adapted to a precisely controlled feeding schedule and ad libitum fed rats. Liver samples were processed for biochemical and histochemical glycogen analysis at precise intervals following a 22 hour fast and a 2 hour meal. Histochemical determination of glycogen (PAS) after freeze substitution showed lobular patterns of hepatic glycogen which correlate with chemically determined glycogen levels and nutritional states of the rats. After 22 hour fasting, hepatocytes from rats with low glycogen levels ( 5%). Glycogen depletion reduced glycogen staining in cells throughout the lobule, but centrilobular patterns prevailed until late in depletion when periportal patterns appeared. Ad libitum-fed rats showed similar glycogen patterns except maximum deposition was characterized by centrilobular or even lobular distribution of glycogen, and periportal patterns of glycogen were seen only rarely in extreme fasted rats. Differences in lobular patterns between ad libitum and control fed rats is apparently related to lower maximum hepatic glycogen levels reached by ad libitum-fed animals.

Adrenergic innervation of the mammalian choroid plexus

Abstract: Choroid plexuses from the four cerebral ventricles of mice, rats, guinea-pigs, rabbits, cats, cows, and monkeys were either sectioned after freeze-drying or stretched on microscope slides for subsequent exposure to formaldehyde gas to demonstrate fluorescent adrenergic nerves. All plexuses received a substantial amount of noradrenaline-containing axons which originated in the superior cervical sympathetic ganglia. The nerve terminals enclosed both arterial and venous vessels. Some of the terminals in the tufts of the choroid plexus ran between the base of the epithelial cells and the underlying vascular wall. Thus, there are structural possibilities for a sympathetic innervation of the plexus epithelium, the plexus blood vessels, or both.

Effect of hypophysectomy and gonadotropin treatment on follicular development and ovulation in the hamster

Abstract: In hamsters hypophysectomized on day 1 of the cycle (morning of ovulation) on days 1–28 post-hypophysectomy 99% of follicular development is limited to small and medium sized follicles with no more than five layers of granulosal cells. Since the largest preantral follicles on day 1 of the cycle have 10–12 layers of granulosal cells, it is evident that follicles become dependent on gonadotropins at an early stage of their maturation. The daily injection of 200 μg ovine follicle stimulating hormone (FSH) on days 8–11 post-hypophysectomy results in large antral follicles; when 10 μg ovine luteinizing hormone (LH) is then injected the animals ovulate 32 eggs. When 200 μg FSH on day 8 post-hypophysectomy is followed by 50 μg FSH on days 9–11, injecting LH results in the ovulation of nine eggs — comparable to the ovulation rate of intact hamsters. These experiments indicate that superovulation depends on sustained high levels of FSH whereas the ovulation of a normal number of eggs requires an initially high level of FSH and then much lower maintenance levels. When replacement therapy with 200 μg FSH for four days is started on the day of hypophysectomy (day 1) or day 2, follicles fail to develop past the six-seven granulosal layer stage. However, deferring the initial injection of FSH until day 3 results in antral follicles that are ovulated by LH (ovulation = 36 eggs). This suggests that functional corpora lutea inhibit the effects of FSH on follicular growth. Progesterone administered to hypophysectomized hamsters (days 8–11 post-hypophysectomy) increases the percentage of medium follicles at the expense of smaller stages. Progesterone injected daily along with FSH also prevents follicular development past the six-seven granulosal layer stage in 14 of 24 hypophysectomized animals.

Morphology of the nasal cavities and associated structures in Artibeus jamaicensis and Myotis lucifugus.

Abstract: Anatomical differences in olfactory structures point to a more highly developed olfactory sense in the frugivorous bat Artibeus jamaicensis than in the insectivorous bat Myotis lucifugus. Artibeus' nostrils show greater potential for differential control of nasal airstreams. Its nasal cavities, in contrast to Myotis, are clearly demarcated into olfactory and respiratory portions. Both species have seven turbinals, but of the five ethmoturbinals, Artibeus has four endoturbinals and one ectoturbinal whereas Myotis has three and two, respectively. The configuration and histology of the more complex turbinals of Artibeus indicates a greater surface area of olfactory epithelium. The nasal epithelia are thicker in Artibeus. Olfactory receptors appear similar in both species but the thickness and composition of the olfactory epithelium in Artibeus suggests the presence of about twice as many receptors per unit area. This is also reflected in the relative prominence of olfactory nerve bundles. From these and other bulbar relationships we conclude that the proportion of fila olfactoria to large mitral cells, as reflected by the olfactory bulb glomeruli, is some function of a fundamental 2:1 relationship. Nasal glands, with flaps covering two of their more prominent ducts, and blood vessels are more pronounced in Artibeus. This presumably correlates with the nasal type of phonation exhibited by this bat as well as a greater ability to condition air per se. Nasopalatine ducts exist in both species but only Artibeus has a vomeronasal organ. A diffuse ganglion accompanies the organ; some of its neurons are associated with the unmyelinated vomeronasal nerve, whereas others are intraepithelial. The vomeronasal nerve terminates in a prominent accessory olfactory bulb.

Scanning and transmission electron microscopy of the rat kidney

Abstract: This study utilized scanning and transmission electron microscopy of renal tissue to provide new information on the gross and microscopic structure of the kidney. The luminal surface of the proximal convoluted tubule was characterized not only by the border of microvilli, but also by crater-like depressions, and circumferential folds. In tissue processed for scanning electron microscopy the proximal tubular cells separated along their lateral surfaces clearly exposing the topography of the lateral cell projections of cytoplasm which have been generally unavailable for viewing because of their interdigitation with adjacent cells. The various segments of the nephron were identified on the basis of position in the kidney, general morphology, and the distribution and form of apical microvilli, cilia, or flaps. The external surface of the papillary tip had several parallel furrows into which the collecting ducts opened. Large plaquelike depressions lined the papillary surface. The opposed surface of the renal pelvis had small plaque-like depressions separated by narrow ridges. Transmission electron microscopy of plastic-embedded tissue specimens which had been previously dehydrated by the critical point drying method demonstrated that little damage occurred from this procedure.

Electron microscope immunohistochemical localization of vasopressin in the hypothalamus and neurohypophysis of the normal and brattleboro rat

Abstract: Using an immunoperoxidase technique at the ultrastructural level, vasopressin was localized in the axons of both the supraoptic and paraventricular nuclei, in the internal zone of the median eminence and the posterior pituitary but not in the perikarya of the neurosecretory neurons. A complete absence of histochemical reaction was found in the hypothalamo-neurohypophyseal tract of the rat with hereditary hypothalamic diabetes insipidus (Brattleboro strain).

Distribution of calcitonin-containing cells in the human thyroid.

Abstract: Human thyroid glands obtained within 2.5 hours of death were examined for the presence and distribution of calcitonin-containing cells using horseradish peroxidase as an indicator in an indirect immunohistochemical procedure. The glands were cut into 10 to 20 transverse slices per lobe and fixed in glutaraldehyde. A representative section of each paraffin-embedded slice was processed and systematically scanned for calcitonin-containing cells. Of 13 glands examined, ten contained calcitonin cells. The cells were found mostly in the follicular epithelium both singly and in groups. They were most numerous in the central region of each lobe of the gland. The isthmus and poles were devoid of calcitonin cells and only occasionally were these cells found at the surface. Parathyroid glands were examined by the same procedure for the presence of calcitonin cells but none were observed. These results demonstrate that calcitonin-containing cells are found regularly in human thyroid glands and that the distribution of these cells is centered in the central region of each lobe of the gland.

Freeze-fracture appearance of the capillary endothelium in the cerebral cortex of mouse brain†

Abstract: Extensive tight junctions are located between overlaps of plasma membranes of capillary endothelial cells. Micropinocytotic vesicles are few in number and are seen as invaginations on the A face and as protrusions on the B face. The freeze-fracture appearance of these cells is consistent with their thin section appearance and their role as the site of the blood-brain barrier.

Bronchiolar neuro-epithelial bodies in the neonatal mouse lungs

Abstract: Bronchiolar neuro-epithelial bodies in neonatal mice were studied by light and electron microscopy. These bodies occurred in thickened areas of the epithelium, and consisted of groups of specialized, non-ciliated columnar epithelial cells with many cytoplasmic granules. These cells were usually closely parallel to one another and had elongated nuclei containing conspicuous peripheral chromatin condensations. These cells were associated with intra-epithelial axons. With electron microscopy, the non-myelinated axon under the neuro-epithelial body was observed to penetrate the basal lamina and enter the epithelial layer. After penetration, the intra-epithelial axon containing numerous mitochondria lost its Schwann cell sheath, became enlarged, and ramified among the epithelial cells. These innervated neuro-epithelial bodies probably function as sensory receptors in the bronchioles.

The permeability to carbon of the sinusoidal lining cells of the embryonic rat liver and rat bone marrow.

Abstract: This study is concerned with the passage of carbon particles through the sinusoidal lining cells of bone marrow and embryonic liver of the rat. A carbon suspension (Pelikan C11/1431A, Gunther Wagner, Hanover) diluted 1:1 with double strength Tyrode solution, was administered through the aorta for the bone marrow studies and through the umbilical vein for observations on the embryonic liver. The carbon particles have a diameter ranging from 220 to 380 A with a mean diameter of 280 A. Within three minutes after the injection, the particulate was present in the extravascular spaces. Neither the sinusoidal walls of the bone marrow nor of the embryonic rat liver prior to 16 days gestation have preformed apertures. In both cases, the carbon particles enter the extravascular space through fenestrae with diaphragms. No carbon particles occur in the junctional spaces between the lining cells. The temporary pores caused by diapedetic blood cells maintain a tight seal and no particulate was observed leaving the vascular space at these sites. At 17 days of gestation, open gaps develop in the endothelial lining of the embryonic rat liver and particulate material leaves the vascular lumen through these openings. The presence of bristle-coated vesicles containing particulate material at the abluminal side of the lining cells is interpreted as a retrograde uptake by these phagocytic cells rather than as evidence for vesicular transmural transport.

Cell types in cutaneous type I mechanoreceptors (Haarscheiben) and their alterations with injury

Abstract: Type I mechanoreceptors (also called Haarscheiben or “domes”) are small elevations on the cat's skin, each being supplied by a myelinated sensory fiber. The fiber terminates in apposition to specialized receptor cells (Merkel cells) lying at the base of the epithelium investing the structure. When a group of domes was injured some of the neighboring domes became structurally altered as determined by light and electron microscopy. The changes observed resembled those which accompany denervation and involved the loss of Merkel cells and their apposed sensory nerve terminals from the dome. Since this trauma was produced indirectly it has been called secondary injury. Cells showing some of the morphological features of both keratin-producing epithelial cells and Merkel cells were observed in secondarily injured domes and in non-injured domes. The presence of such transitional cells suggests that Merkel cells may be derived from keratinocytes.

Quantitative electron microscopic autoradiography of in vivo incorporation of 3H-choline, 3H-leucine, 3H-acetate and 3H-galactose in non-ciliated bronchiolar (Clara) cells of mice.

Abstract: The participation of Clara cells in the formation of alveolar surfactant and their general metabolism were studied in mice by quantitative autoradiography under electron microscopy after in vivo incorporation of four precursors: 3H-choline, 3H-leucine, 3H-acetate and 3H-galactose. Tritiated choline, a specific precursor of the dipalmitoyl-phosphatidylcholine-active fraction of the surfactant, is not incorporated into Clara cells. In contrast, 3H-acetate is first incorporated actively into the endoplasmic reticulum and Golgi apparatus of these cells and, subsequently, in its secretory granules. It is suggested that acetate follows the general metabolism of the cell and/or is transformed into cholesterol. Tritiated leucine is incorporated into the secretory granules, although part of it remains more permanently in the cells. Tritiated galactose is actively incorporated, passes through the Golgi apparatus and eventually appears in the secretory granules. These results suggest that the Clara cell does not synthetize the tensio-active fraction of the lining layer, as does pneumocyte II, but participates in the synthesis and secretion of proteins, glucides and possibly the cholesterol belonging to the hypophase.