摘要:

AbstractThe rat incisor is a continuously erupting, so‐called “rootless,” tooth. It differs from human or similar “rooted” teeth in that its generative cells persist at the base of the tooth. These cells are derived from the invagination of oral epithelium which forms the dental lamina and the developing dental organ. This epithelium becomes a vase‐shaped structure surrounding a condensation of connective tissue elements called the dental papilla. The cells on the labial aspect of the epithelial dental organ specialize to form enamel. The cells on the lateral and lingual aspects remain undifferentiated and are called Hertwig's epithelial sheath. The odontoblasts are derived from the dental papilla. The hard tissues of the tooth form continuously at the base, and the tooth erupts into the oral cavity where the incisal edge is worn by abrasive action during gnawing (v. Brunn, 1887; Addison and Appleton, '15; Schour and Massler, '42).Hertwig's sheath extends from the base of the tooth to a short distance beyond the point where dentin formation commences. At this level the epithelial cells separate and the sheath disintegrates. As these cells separate, cementoblasts and collagen fibers appear adjacent to the newly forming dentinal surface. Apatite crystals are deposited in the matrix of collagen fibers and a thin layer of cementum results (Selvig, '63). Since Hertwig's sheath is persistent at the base of the tooth, this initial phase of cementogenesis is continuous.In rooted teeth, on the other hand, initial cementogenesis is completed when the root becomes fully formed, and Hertwig's sheath has been expended. There may be subsequent progressing depositions of cementum to form one or several strata. This initial stratum is called “primary cementum” and the successive layers are called “secondary cementum.” Primary cementum contains fine fibrils arranged radially (fiber cementum). Secondary cementum generally contains cells (osteocementum) but it may be acellular. Regardless of category, cementum contains matrix (intrinsic) fibers, and also, in most cases, Sharpey's (extrinsic) fibers (Lehner and Plenk, '36; Egli, '46; Held, '51; Schmid, '51; Sicher, '62).During the course of eruption of the rat incisor, the periodontal fibers which are attached to the cementum move with the tooth until they somehow undergo dissolution prior to the entry of the tooth into the oral cavity. A similar picture is obtained during the more limited period of eruption of rooted teeth. The mechanisms of formation, reorganization and dissolution of the periodontal fibers are all matters of biologic importance. Moreover, investigations of these phenomena may have some bearing upon understanding those pathologic processes which involve the detachment of the gingiva from teeth and the exfoliation of teeth

ISSN:0002-9106    

DOI:10.1002/aja.1001150302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1964

数据来源: WILEY

摘要:

AbstractHuman salivary and lacrimal glands have been studied with a variety of methods to demonstrate polysaccharides in tissue section. On the basis of these studies, an attempt has been made to clarify the classification of exocrine cells. Serous cells secrete proteinaceous material without significant polysaccharide in the secretory granules such as the pancreatic acinar cell and gastric chief cell. Seromucous cells secrete a watery product, but the secretory granules contain variable amounts of mucopolysaccharide in the secretory granule. Typical seromucous cells are found in the parotid gland, lacrimal gland, submaxillary gland and eccrine sweat glands. Mucous cells liberate a viscous product rich in mucopolysaccharide. The typical mucous cell is the intestinal goblet cell. Other examples are the mucous portion of the submaxillary gland, the entire sublingual gland, bronchial gland, and Brunner's gland. Human pancreatic acinar and gastric chief cells are unique as compared to other species since the secretory granules of these cells, usually considered to be serous, contain a small amount of neutral mucopolysaccharide.

ISSN:0002-9106    

DOI:10.1002/aja.1001150303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1964

数据来源: WILEY

摘要:

AbstractIn an early stage of metamorphosis of atypical spermatids of a pond snail,Cipangopaludina malleataReeve, numerous vesicles of a circular form appear in the juxtanuclear region. These vesicles represent the rough‐surfaced endoplasmic reticulum of the atypical spermatids. As amorphous contents within the vesicles increase in density an amount, Palade granules, 130 to 150 A in diameter, attached to the external surface of the vesicles, disappear gradually and at the same time an apparently single layered limiting membrane is transformed to a double layered structure.It has been revealed that a Feulgen‐positive material appearing in the vesicles transforms into a PAS‐positive material in the atypical maturing spermatids, and such material is transported as D bodies through intercellular spaces into the nutritive cell. In the nutritive cell, G bodies make their appearance as a transitional form of mitochondria. Structural changes from a homogeneous appearance to concentric and parallel lamellar structures have been traced in both bodies. It is a noticeable fact that a lamellar structure is often found surrounding an electron‐lucent space of both bodies. An occurrence of the electron‐lucent space within both bodies suggests that the contents of the bodies may be transported via the tubular system of the endoplasmic reticulum in the mantle to the typical maturing spermatids.Turnbull's blue tests have shown that the dense particles, 50 to 70 A in diameter, appearing in the D and G bodies are organic iron compounds. It is interesting that lipid is found in a helical appearance along the typical maturing spermatid head part, suggesting that lipid is located in the cytoplasm surrounding th

ISSN:0002-9106    

DOI:10.1002/aja.1001150304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1964

数据来源: WILEY

摘要:

AbstractCritical inocula of Enders strain of mumps virus were injected over the blastoderm at 36, 48, 60, 72 and 96 hours of incubation (37°C). Surviving embryos were harvested at daily intervals up to 14 days postinoculation.Gross and microscopic observations revealed the lens to be the only organ consistently exhibiting abnormal development following inoculation with mumps virus. By comparison, maldevelopment in other structures was occasionally observed up to the third day postinoculation, but rarely in embryos surviving three or more days. Characteristic lens cataracts were observed, but only in embryos which had been inoculated prior to Hamburger‐Hamilton stage 18, i.e., prior to separation of the lens vesicle from surface ectoderm.An analysis of the histopathogenesis of lens cataracts in embryos inoculated at stages 8–17 indicates that the differentiating lens fibers became progressively more extensively damaged as development proceeded. However, it is evident that the differentiation of new lens fibers proceeded peripherally as the more mature fibers continued to be destroyed centrally. It can be concluded that differentiating lens fibers are highly susceptible to damage by mumps virus, but the initiation of the characteristic defect occurred in our experiments only during the early formative phases of lens develop

ISSN:0002-9106    

DOI:10.1002/aja.1001150305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1964

数据来源: WILEY

摘要:

AbstractThe telencephalon was removed with iridectomy scissors in stages from 1 to 20 somites, with the vast majority of operated chicks being at 5 to 10 somites. The most chance of successfully producing cyclopia appears to be at 6 to 7 somites. Twelve cyclopean embryos, with operated stages ranging from 5 to 10 somites, were produced among the first 271 operations. Subsequently, 398 operations, concentrated on 9‐ to 10‐somite embryos, proved that cyclopia is very much less apt to follow this sort of operation at these stages than at the very slightly younger stages.Serial sections of the cyclopean embryos were stained with a modification of the Bodian protargol stain. An oral hypophysis is usually present in these embryos, making them in this respect similar to the majority of cyclopean embryos for which this point is reported in the literature, but making them different from experimentally produced cyclopean amphibian embryos reported in the literature. The sequence of fusion of extrinsic ocular muscle components and the patterns of their nerves, as the cyclopean defect becomes more severe, indicates that the reversal of bilateralization is a ventralization.Coupled with biochemical work on the chick and the more recent of the biochemical work of others on amphibia, the results allow one to suggest that experimental stimuli resulting in the cyclopean mode of development may act either on prechordal substrate or on neural tissue of telencephalon and diencephalon, or on both substrate and neural tissue, and that they may be effective over a considerable period of time, up to and including the period of actual bilateralization of the optic primor

ISSN:0002-9106    

DOI:10.1002/aja.1001150306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1964

数据来源: WILEY

摘要:

AbstractA quantitative study of changes in the germinal epithelium of rat testes exposed to 43°C for 15 minutes was performed. Testicular tissue was studied at intervals of 2, 4, 6, 8 and 26 days after exposure to heat. The frequency distribution of the various stages of spermatogenesis, the resting spermatocytes, spermatogonia and Sertoli cells were not affected by the exposure to heat. On the other hand, primary spermatocytes in stage IX (leptotene), to and including dividing spermatocytes in stage XIV, were injured, excepting for pachytene spermatocytes in stages V and VI of spermatogenesis. The spermatids were affected by heat only in step 1 and the early part of step 2 of spermiogenesis. Those beyond step 2 continued to mature and form adult spermatozoa. The data indicate that heat produces selective damage to the germinal epithelium affecting only specific types of germinal epithelium cells

ISSN:0002-9106    

DOI:10.1002/aja.1001150307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1964

数据来源: WILEY

摘要:

AbstractRabbit anti‐rat‐kidney antiserum, when injected into rats seven, eight, nine and ten days pregnant, results in embryonic death, growth retardation and malformations. The spectrum of malformations is different for each day of gestation studied. The kidney malformations produced are related to its qualities as a potent general teratogenic agent and not to any specific effect on the developing urinary system. The utilization of low doses of kidney antiserum can result in a significant increase in the incidence of malformations without interfering with either the survival or growth of the exposed fetuses. It is not known whether the teratogenicity of this antiserum is due to (a) induced maternal biochemical or physiological pathology, (b) direct toxicity to the embryo or (c) interference with the deciduo‐trophoblast. Although some other antisera have not been found to be teratogenic, rabbit anti‐rat‐placental serum has also been found to be a potent teratogenic agent having similar properties to kidney antiserum.The relevance of potent teratogenic proteins to the problem of human malformations is purely hypothetical and further investigation may reveal that no relationship exists between teratogenic proteins and human malformations. In spite of this, the findings reported herein should prove to be both stimulating and pr

ISSN:0002-9106    

DOI:10.1002/aja.1001150308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1964

数据来源: WILEY

摘要:

AbstractIn the squirrel monkey, nerve cells in certain areas of the brain are characterized by abundant granules which stain intensely with aldehyde‐fuchsin but not with chromium hematoxylin.These cells fall into three main types: Type A, with a polar clumping of the granules, characterize the region surrounding the stria terminalis in the amygdala and the supratrochlear nucleus of the mid‐brain. Type B, which have a heavy diffuse granulation, are found in the lateral and caudal hypothalamus and in nucleus raphes ventralis. Less heavily granulated cells classified as Type C distinguish the entire nucleus subthalamicus, and are prominent in nucleus septalis triangularis, rostral midline thalamus, and area CA2 of the rostral hippocampus. Cells of these corresponding types and distribution are not seen in the brains of cat, rat and mouse.The cerebellum and pineal body contain extracellular material which stains with aldehyde‐fuchsin but not chromium hematoxylin.The granules of the nerve cells stain with PAS, Sudan black B, and oil red O, suggesting that they have carbohydrate and lipid components.As in other species, the neurosecretory substance of the paraventricular and supraoptic nuclei is stained both by aldehyde‐fuchsin and chromium hematoxylin. Material showing a positive reaction to both these stains is also found in the glia of the nucleus septalis triangularis, subfornical organ, lateral hypothalamus, and locus caeruleus. All these regions, except the lateral hypothalamus, show similarly staining material in the extracellular spaces.Of anatomical interest is the close association of the aldehyde‐fuchsin positive neurons with phylogenetically ancient cellular structures and fiber systems of the brain. In the squirrel monkey they would seem to provide a basis for further characterization of certain nuclei and a new division of the

ISSN:0002-9106    

DOI:10.1002/aja.1001150309

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1964

数据来源: WILEY

摘要:

AbstractInterest in the possibility of a fluid medium for the transport of oxygen in the respiration of terrestrial vertebrates was aroused by the author's discovery of a watery fluid in the bronchioles of human cadavers and of domestic animals. In the literature of respiration the tolerance of water injected into the lungs of living animals had been demonstrated by Claude Bernard in 1869. Water as the vehicle for oxygen in the respiration of terrestrial invertebrates has been recorded many times. The life of fishes and of invertebrates inhabiting the waters of the world is dependent upon oxygen dissolved in this medium. The present paper records: (a) The author's experience in seeking and recording evidence of the presence of a watery medium in the respiratory organs of a series of vertebrates, and (b) presents evidence in explanation of the method of oxygen transport from the termination of the bronchial system into the capillary blood‐stream of the lung. The investigation called for special techniques, apparatus and instruments; these are described. The period of investigation extended, with many interruptions, from '10 to '60; during which period reports of progress have been publishe

ISSN:0002-9106    

DOI:10.1002/aja.1001150310

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1964

数据来源: WILEY

摘要:

AbstractThe pathways by which intestinal lymph enters the blood were studied with radiologic and radioactive tracer techniques in normal sheep and in sheep after thoracic duct occlusion. It was concluded that direct connections between the intestinal lymphatics and blood vessels in the abdomen and caudal thorax in normal sheep are very uncommon if they occur at all.During the first few days after the thoracic duct of sheep was occluded in the thorax, transfer of protein from intestinal lymph to blood was slow. At this time, the abdominal lymphatics were grossly dilated and lymphatic valves incompetent. After about 1–2 weeks, the abdominal lymphatics were of more normal size and drainage of lymph protein to the blood occurred more rapidly. At least some of this protein entered the blood within lymph nodes. After 4–7 weeks, direct vascular connections between the thoracic duct and hemiazygos vein had develo

ISSN:0002-9106    

DOI:10.1002/aja.1001150311

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1964

数据来源: WILEY