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Background The current teaching in regard to the development of paranasal sinuses is that they are evaginations of the nasal cavity; this seems to totally ignore earlier observations. Methods Serial coronal sections of the heads of 23 human fetuses from 18-mm CR length to 282-mm CR length were stained by various methods and studied. Results The ethmoidal sinuses develop by the formation of ‘turbinal cushions’ at the 33-mm CR stage. By the 45-mm CR stage, the cushions have grown toward each other and made contact. The epithelium covering the cushions also proliferates to fill up the enclosed space, and it proliferates dorsoventrally as well. The cushions fuse at the 50-mm CR stage. The fusion part of the process should be described as a ‘constriction’ of the nasal cavity. Next, the epithelium disintegrates and results in the formation of the sinus. This part of the process only can be described as an ‘evagination’ of the nasal cavity. As the advancing epithelium of the sinus encounters cartilage, it causes disintegration of the developing nasal cartilage. This area of disintegration appears as a spot stained pink with H & E, black with mucicarmine, and yellow with van Gieson's stains, respectively. These spots are seen between the 89-mm and the 225-mm CR stages (both inclusive). Conclusions Two mechanisms operate in the development of ethmoidal sinuses: constriction of the nasal cavity by a pair of turbinal cushions, and evagination from the nasal cavity by proliferation and subsequent disintegration of the nasal epithelium. Anat. Rec. 249:96–102, 1997. © 1997 Wiley-Liss, Inc.

Mandibular condyles of fetal mice 19 to 20 days in utero were kept in an organ culture system for up to 10 days. After 2 days in culture the cartilage of the mandibular condyle appeared to have maintained all its inherent structural characteristics, including its various cell layers: chondroprogenitor, chondroblastic, and hypertrophic. After 5 days in culture no chondroblasts could be seen and, instead, the entire cartilage was occupied by hypertrophic chondrocytes. At the same time, the mesenchymal cells at the chondroprogenitor zone differentiated with osteoblasts which produced osteoid. Light microscopic examinations showed that the newly formed osteoid did not stain with acidic toluidine blue or with alcian blue, but stained intensively with the van Gieson stain and with Periodic acid-Schiff (PAS). The osteoid reacted with antibodies against type I collagen but not with antibodies against type II collagen. Electron microscopic examinations showed that the mineralization appeared to be associated with collagen fibers in bone rather than with matrix vesicles in the cartilage. The process of bone formation progressed with time and by the 10th day new bone replaced almost the entire cartilage, thus forming an expanded layer of membrane bone. This in vitro system represents an experimental model whereby undifferentiated precursor cells transform into osteoblasts with the subsequent formation of a typical membrane bone.

The distribution of 35S-sulfate-labeled macromolecules was examined within three regions of the transseptal ligament: the (1) mesial, (2) middle and (3) distal thirds. Swiss mice, 6 weeks of age, were injected with 35S-sulfate and killed after 1, 6, and 12 hours and 1, 2, 3, 4, 5, and 7 days. Silver grains and cell nuclei were counted on autoradiographs which had been counterstained by the Van Gieson method, and mean counts were analyzed statistically. Analysis of variance revealed no significant differences in mean number of cell nuclei between regions throughout the course of the experiment. 35S-sulfate was rapidly incorporated into the transseptal ligament macromolecules. Grain counts were highest 6 hours after injections: counts were highest over the middle and lowest over the mesial thirds of the ligament. The rate of grain removal was significantly higher in the middle third compared to the mesial or distal thirds (P less than 0.001) and was significantly lower in the mesial third compared to the middle or distal thirds (P less than 0.001). The half-life of labeled macromolecules was significantly greater in the mesial and distal thirds than in the middle third (P less than 0.005). The data demonstrate significantly higher rates of turnover more » of 35S-sulfate-labeled macromolecules in the middle region of the transseptal ligament. Since cellular density was similar throughout the transseptal ligament, higher turnover rates of 35S-sulfate-labeled macromolecules probably indicate higher rates of cellular activity in this region, possibly a result of tissue remodeling coincident to stresses generated by occlusal forces and physiologic drift of the adjacent teeth. « less

The anterior part of the mammalian nasal septum (NS) persists throughout the life span as hyaline cartilage, in contrast to cartilage in most parts of the body, which is gradually replaced by bone during development. In this study, we have cultured differentiating rat NS under various experimental conditions in an attempt to gain some insight into the osteogenic potential, if any, of the NS and its surrounding connective tissue. Differentiating NS from E15 and E19 rat embryos were dissected and grown under the following conditions: 1) organ cultured in Waymouth's medium or modified Eagle's medium, with or without serum; 2) cultured on chick chorioallantoic membrane (CAM); 3) implanted under rat kidney capsule (KC). Bone-like substance (BLS) never developed in organ cultures, but was observed in CAM cultures and KC implants after 7 days. The BLS was located external to the perichondrium of the NS and was stained red by the van Gieson's technique, indicating the presence of mature collagen. Further evidence of its bone-like characteristics was demonstrated by the presence of alkaline phosphatase and type I collagen. The CAM and KC represent two experimental conditions under which progenitor cells in the nasal septum area may be induced to synthesize BLS.

The hymen at different stages of life from birth to menopause was examined under the microscope. Each section was stained with hematoxylin and eosin, Van Gieson, Best's carmine, Orcein, PAS, Mallory's and modified Wilder technique. The modified Bodian's technique was used to stain the nerve fibers and the nerve cells. The main bulk of the hymen is formed of fibrous connective tissue, partly elastic and partly collagenous fibers. Both surfaces are covered by stratified squamous epithelium which lacks any evidence of cornification. The epithelium is thicker at the attached edge. Glycogen granules are equally present on the vaginal and on the vulvar surface. The connective tissue papillae are more numerous and more branching at the free edge and on the vaginal surface. There is no trace of glandular or muscle element. The hymen is not richly supplied with nerve fibers. No nerve cells and fibers are present at the free edge of the hymen. Nerve cells are bipolar, small in size, oval, spindle or kidney shaped. The terminal nerve fibers penetrate the epithelium in between the connective tissue papillae. In the newborn the hymen is vascular and the epithelium is thick. During pregnancy the epithelium is very thick and very rich in glycogen. At menopause the epithelium is thin and certain areas are cornified.

Substitution of flavianic acid (50 mM) or of a stoichiometric mixture of naphthol yellow S and hydrochloric acid, in place of picric acid in Van Gieson type mixtures gives deeper yellow colors to cytoplasm, muscle and erythrocytes. Higher concentrations of acid fuchsin can be used with consequent greater density of collagen fiber staining and improved contrast. The familiar weakening of hematoxylin nuclear stains by exposure to Van Gieson mixtures can be largely avoided by inclusion of 0.1 M ferric chloride in the Van Gieson mixture. Alum hematoxylin can then be used in place of the unstable iron hematoxylin solutions, and the iron hematoxylin effect is attained by the iron postmordanting in the Van Gieson bath. A ten minute prestain in an alum hematoxylin containing 0.5% hematoxylin is adequate but density can be enhanced by longer staining or by staining at higher temperature; 5–10 min at 60°C is suggested. The iron containing flavianic or picric acid Van Gieson staining baths should be restricted to three minutes; longer exposures gradually weaken nuclear staining. Substitution of 0.1 M copper sulfate for the iron in the Van Gieson bath also yields dark gray to black nuclei. Aluminum chloride (0.1 M) has an effect similar to the control hydrochloric acid, while the chromium ion seems quite inferior, even to the control HCl mixture. A ferrous sulfate hematoxylin ripened overnight with a small amount of ferric chloride gives excellent progressive nuclear staining, adequate in 2–5 minutes, and not excessive in 30 minutes. The solution gradually deteriorates in 6–8 weeks.

The mesonephric duct was studied in female camel fetuses (Gartner's duct). All fetuses were well developed, aged from two to three months. The female internal genital organs were sectioned at 10 μ and stained with hematoxylin-eosin or Van Gieson's stain. In camel fetuses, the duct is usually lined with one layer of cuboidal or columnar epithelium which may be ciliated. Degeneration and cavitation occur in the lower vaginal part, which finally obliterates the previous structure, or changes it to many layers. These two processes occur in succession at different levels of the vaginal portion and are not uniform stages along the whole duct. The appearance of the duct is variable at different levels and at the same level in different ducts. The two ducts may leave the submucosa superiorly and enter the musculature of the vagina at different levels. No glands opening into the mesonephric duct were observed. The upper (mesosalpingeal) part is smaller in caliber than the lower and seems to be immune to the obliteration and cavitation mentioned.

The present work is concerned with the extreme controversy of views over the problem of the dependency of embryonic muscular development on neural factors. A chemopharmacological method was adopted to selectively block the motor nerve endings. One hundred and seventy-seven chick embryos, 6–7 days old, were injected in ovo with marginal doses of oily tubocurarine. The control embryos were injected with arachis oil. Eleven days after injection, the majority of the embryos injected with curare were macroscopically stunted, especially the limbs. Specimens from experimental and control embryos were fixed simultaneously in isotonic 10% formalin made in Howard's solution. Sections were stained with hematoxylin and eosin, Mallory's phosphotungstic acid hematoxylin and Van Gieson. Dawson's technique was used to demonstrate the whole of the embryo skeletons. Microscopic examination of the limb musculature revealed inhibition of development and differentiation. The muscle fibers were reduced in size and number, poorly striated and contained many centrally situated nuclei. In the chick, it is suggested that at a critical time of development the final differentiation and maturation of skeletal muscles begin to become dependent on the anatomical and physiological intactness of the motor nerves. This time is found to be approximately between the sixth and seventh days of incubation. The significance of these observations is discussed.