摘要:

AbstractExtreme variants of anecephaly in two human embryos of the same stage, namely 22 (54 days), shed new light on problems such as craniocerebral interrelationships and the timing of developmental events. Embryo X had a chondrocranium that possessed features typical of a holoacranial anencephalic skull and an extremely well‐preserved brain, in which some of the neural tracts were comparable to those in a normal control. On the other hand, embryo Y of the same stage had a completely degenerated brain, although the chondrocranium was more nearly normal and represented the precursor of a meroacranial skull. A comparison of the two cases seems to indicate a certain independence between skull and brain. Moreover, it appears possible that the disturbances are related primarily to the skeletal, and only secondarily to the nervous, component. Comparisions with experimental data allow the conclusion that the maldevelopment involves mostly paraxial mesenchyme and little or no disturbance of neural crest. The timing of the mesenchymal defect is probably as early as stages 8 and 9 (18–20 days). This is also the time at which mesenchymal defects can result in failure of the neural tube to cl

ISSN:0002-9106    

DOI:10.1002/aja.1001900302

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

年代:1991

数据来源: WILEY

摘要:

AbstractIn the present study, the morphological, histochemical, biochemical, and cellular aspects of the pathogenesis of bromodeoxyuridine (BrdU)‐induced cleft palate in hamster fetuses were analyzed. Morphological observations indicated that BrdU interferes with the growth of the vertical shelves and thus induces cleft palate. At an ultrastructural level, BrdU‐induced changes were first seen in the mesenchymal cells. Eighteen hours after drug administration, the initial alterations were characterized by swelling of the nuclear membrane and the appearance of lysosomes in the mesenchymal cells of the roof of the oronasal cavity. During the next 6 hr, as the palatal primordia developed, lysosomes were also seen in the overlying epithelial cells. The appearance of lysosomal activity, which was verified by acid phosphatase histochemistry, was temporally abnormal and was interpreted as a sublethal response to BrdU treatment. Later the cellular alterations subsided; 48 hr after BrdU treatment, they were absent in both the epithelial and mesenchymal cells of the vertically developing palatal shelves. Subsequently, unlike controls (in which the palatal shelves undergo reorientation and fusion), the BrdU‐treated shelves remained vertical until term. Biochemical determination of DNA synthesis indicated that although there was an inhibition of DNA synthesis at the time of appearance of palatal primordia, a catch‐up growth during the ensuing 12 hr may have restored the number of cells available for the formation of a vertical palatal shelf. It was suggested that BrdU affected cytodifferentiation in the palatal tissues during the critical phase of early vertical development to induce a cleft

ISSN:0002-9106    

DOI:10.1002/aja.1001900303

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

年代:1991

数据来源: WILEY

摘要:

AbstractA method for the differentiation of sutural patterns of the human cranial vault is introduced. Three criteria of differentiation are considered, one for size and two for shape: (1)maximal shape extension;(2) basic configuration; (3)secondary protrusion.The method is illustrated here for the coronal and lambdoid sutures of 70 recent Italian skulls (35 adult males and 35 adult females). Differences between coronal and lambdoid sutural size and shape can be detected analytically; for example, the coronal suture commonly shows lesser degrees ofshape extension, a simplerbasic configuration, and an absence ofsecondary protrusion.Heterogeneity within each suture, as well as a relationship among corresponding sections and between the three criteria adopted, have been also observed; symmetry predominates for both the sutures, and sexual differences are slight.

ISSN:0002-9106    

DOI:10.1002/aja.1001900304

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe kidney ofDiceros bicornishas about 60 lobes, all appearing peripherally. These are separated by interlobar septa, except for small septal defects through which tubules pass. Renal capsule and interlobar septa are fibromuscular and contain small blood vessels. The kidney is about 65% cortex. It contains about 12.5 × 106glomeruli, which form about 7% of the cortical mass and 4.6% of the renal mass. Diameter of a glomerular capsule is about 244 μm, there being no difference in size across the cortex in these adults. The ureter bifurcates into a cephalic and a caudal, fibromuscular, urothelial‐lined conduit, into which open about 23 urothelial‐lined infundibula. The common large collecting duct, or tubus maximus, of every lobe opens at the apex of its infundibulum. Two tubi may join into one infundibulum. The tubi and their terminal collecting ducts (of Bellini) are part of the inner medulla. Musculature of conduits and infundibula is largely longitudinal. The calyx may be represented by a circular muscle bundle near the apex of every infundibulum. The large intralobar veins are partly adherent to their infundibulum and calyx and receive arcuate veins via valved orifices. Most branches of the renal artery enter via the interlobar septa. Within a septum they branch again and also supply numerous perforators, which thence enter the cortex. Remaining branches of the renal artery enter cortex directly from without. A fibromuscular scaffolding lies deep to arcuate veins where they contact medulla. Where these veins contact cortical tubules; however, their walls become merely endothelium, like the walls of the interlobular

ISSN:0002-9106    

DOI:10.1002/aja.1001900305

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

年代:1991

数据来源: WILEY

摘要:

AbstractTestes from rabbits aged 1–9 weeks were examined by light microscopy. Changes in seminiferous tubule dimensions, testicular volume, and volume fraction of tubules were assessed. Germ cells and Sertoli cells were counted in round tubular cross sections and total germ cell number in each testis was estimated. Mitotic, meiotic, and degenerative activities of germ cells as well as their basal or central positions within tubules were quantified. A marked, steady increase in testis volume and in tubular length and volume occurred over the prepubertal period; but diameter underwent no significant increase and in fact decreased until week 4. Overall, tubules lengthened 40‐fold and testis volume increased 25‐fold; the percentage volume of the testis occupied by tubules rose from one‐third neonatally to three‐fifths at the onset of spermatogenesis. The ratio of germ cells to total tubular (germ and Sertoli) cells was lowest at 3 weeks. However, the total number of germ cells increased little until 3 weeks, after which it rose at a sharp rate commensurate with testis volume. Percentage of germ cells in mitosis peaked sharply at 3 weeks, dropped in subsequent weeks, and then rose at 7 weeks at the initiation of spermatogenesis. Importantly, the surge in mitosis at 3 weeks was followed by a redistribution of germ cells to a predominantly basal location from 3 to 7 weeks. Meiotic activity was sparse at 7 weeks and became abundant by 9 weeks. Germ cell degeneration remained relatively constant during weeks 1 through 6, with an increase a

ISSN:0002-9106    

DOI:10.1002/aja.1001900306

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe present study was carried out to determine whether the major steroidogenic organelles of luteal cells quantitatively reflect variations in ovarian steroid secretion rates during pregnancy in the rat. Assessments were made on day 16 and in the morning (AM) and afternoon (PM) of day 22 (term is day 23). Ovarian steroidogenesis differs both quantitatively and qualitatively between these stages of pregnancy, so together they provide an ideal physiological model to study structural‐functional relationships in the ovary. Corpora lutea of five rats were examined at each stage after progesterone and 20α‐hydroxypregn‐4‐en‐3‐one (20α‐OHP) secretion rates had been determined by a venous outflow technique. Total progestin secretion (progesterone plus 20α‐OHP) fell from 32.5 ± 5.2 to 9.8 ± 1.2 μg/hr per ovary (mean ± SEM) between day 16 and day 22 AM but then increased to 22.6 ± 1.4 μg/hr per ovary by day 22 PM. The total volume of luteal cell cytoplasm was slightly greater at day 22 AM and PM than at day 16. Similarly, the volumes of smooth endoplasmic reticulum (SER), lipid droplets, and membrane‐bound granules all increased, but the volume of mitochondria decreased slightly. In contrast, the surface areas of SER and the inner and outer mitochondrial membranes did not change between day 16 and day 22 AM but then increased substantially by day 22 PM. Therefore, steroid secretion rates per unit area of steroidogenic membrane showed no consistent pattern over the stages examined. Thus these data do not support the existence of a consistent structural‐functional relationship over the normal range of secretory activity in the rat corpus luteum. It is likely that a number of factors, including a variable reserve capacity for steroidogenesis and secretion of nonsteroid hormones, cont

ISSN:0002-9106    

DOI:10.1002/aja.1001900307

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

年代:1991

数据来源: WILEY

摘要:

AbstractTrimetaphosphatase (TMPase) and cytidine‐5′‐monophosphatase (CMPase) were used as lysosomal markers in the transitional ameloblasts (TA) to investigate the distribution of lysosomal structures and to correlate the cytochemical findings with the ultrastructural features of these cells. Of particular interest were the cytochemical and morphological changes which occur as the ameloblasts approach the maturation stage of enamel formation. The sequence of changes observed provides a basis for designation of three regions of the transitional zone (early and late TA and modulating ameloblasts). In the early TA region, the cells decreased in height and contained phagic vacuoles as well as numerous TMPase and CMPase reactive structures. Late transitional ameloblasts had invaginations at their distal ends as well as membrane‐bound structures, both filled with fine granular material. Dense bodies, phagic vacuoles, and other elements of the lysosomal system were enzyme reactive. Modulating ameloblasts lacked the phagic vacuoles but exhibited large numbers of multivesicular bodies, vesicles, and secretory granules. Their distal ends were morphologically altered indicating a change towards ruffle‐ or smooth‐ended varieties of maturation ameloblast. In the former, increased granular material was observed within cell membrane invaginations and associated membrane‐bound structures. In the latter, intercellular spaces widened and were filled with granular material. The present cytochemical findings of an extensive lysosomal system in transitional ameloblasts confirm the function of those cells in reducing the secretory ameloblast population and in the selective elimination of their protein‐synthesizing organelles. Furthermore, this extensive lysosomal system and the present morphological findings are consistent with a potential role for transitional ameloblasts in contributing to the marked loss of enamel protein known to occur du

ISSN:0002-9106    

DOI:10.1002/aja.1001900308

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

年代:1991

数据来源: WILEY

摘要:

AbstractDeposition of inhaled particulates onto the respiratory mucosa is relatively great in that portion of the nasal cavity unprotected by ciliated, goblet, or keratinized superficial cells. The cytochrome P‐450 system is an important enzyme system involved in the biotransformation of xenobiotics into metabolites that are more readily absorbed. To examine the transitional region caudal to the nasal vestibule, nasal tissues of hamster and rat were prepared for immunocytochemistry. Blocks of tissue representing four levels along the axis of the nasal cavity were examined. Paraffin sections were processed through the avidin‐biotin peroxidase procedure, with diaminobenzidine tetrahydrochloride as the chromagen. Enzyme localization was accomplished through the use of antibodies for three rabbit cytochrome P‐450 isozymes; 2, 5, and 6 (subfamilies IIB, IVB, and IA, respectively); and for rabbit NADPH‐cytochrome P‐450 reductase. Enzyme distribution was similar in both hamster and rat nasal tissues except in cells of striated and intercalated ducts of nasal glands and in cells of the nasolacrimal duct where immunoreactivity for reductase and isozyme 2 was intense in nonciliated cells lining the nonolfactory epithelium, in sustentacular cells of the olfactory epithelium, and acinar cells of olfactory glands. Distribution of reaction products to isozyme 5 and 6 were similar to but not so intense as those of reductase an isozyme 2. Reaction products for reductase and isozyme 2 occurred generally in the same cellular and intracellular regions with the following exceptions: isozyme 2 was more concentrated in cells of striated ducts and of the nasolacrimal duct, and reductase was more abundant in intercalated ducts of nasal glands. Ciliated and goblet cells in epithelia lining much of the nasal cavity evidenced little reactivity; those ciliated cells adjacent to olfactory mucosa contained reaction product. It is concluded that the nonciliated epithelium adjacent to the internal ostium of the nose contains enzymes essential for biotransforming extrinsic particles that impinge on it from inhaled air

ISSN:0002-9106    

DOI:10.1002/aja.1001900309

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

年代:1991

数据来源: WILEY

摘要:

AbstractThis study reports the ultrastructure of subpopulations of epithelial cells of the thymic parenchyma during the post‐hatching development of the rainbow trout,Salmo gairdneri, kept at 14°C. At hatching, the thymus contained a small number of medium and large thymocytes interspersed among three different types of epithelial cells: (1) epthelial cells adjacent to the connective tissue capsule; (2) ramified dark epithelial cells with electron‐dense cytoplasm; and (3) pale electron‐lucent epithelial cells displaying secretory‐like features. All these cell types were anchored to one another by desmosomes and had apparently differentiated from the pharyngeal epithelium. At 4 days after hatching, the thymus enlarged, and numerous gaps occurred between the cell processes of contiguous epithelial cell processes of contiguous epithelial cells adjacent to the capsular connective tissue. In 21‐day‐old trout, thymic trabeculae developed carrying blood vessels, and a subcapsular zone became evident containing lymphoblasts and large subcapsular epithelial cells. In 30‐day‐old trout, an outer thymic zone developed consisting of spindle‐shaped epithelial cells which formed a dense network. At this stage, scattered cystic cells, which apparently differentiated from the pale epithelial c

ISSN:0002-9106    

DOI:10.1002/aja.1001900310

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

年代:1991

数据来源: WILEY

ISSN:0002-9106    

DOI:10.1002/aja.1001900301

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

年代:1991

数据来源: WILEY