摘要:

AbstractSerial sections of 105 human embryos (including 20 silver preparations) from stage 11 (24 days) to stage 22 (54 days) were studied, and 23 graphic reconstructions were prepared. The hypoglossal nucleus is evident at stage 12 and becomes isolated from other efferent nuclei at stage 14. The first hypoglossal nerve fibers appear at stage 12. The roots unite at stage 14 and the main trunk arrives in the tongue at stage 15. Four occipital somites can be identified during stage 13, and the sclerotomic material forms two bilateral masses. The fourth sclerotome separates in stage 14 and develops like a vertebra. This and the remaining sclerotomic material form the basioccipital and exoccipital parts of the chondrocranium, which are the first to appear. Four occipital myotomes develop and grow towards the tongue as the “hypoglossal cord”, which arrives prior to the hypoglossal nerve. The developmental similarity in the hypoglossal region between birds and mammals, combined with experimental studies in birds, renders it extremely likely that the hypoglossal musculature in mammals also is derived from occipital somites. The present study is the first in which this conclusion is adequately supported in the human. This investigation aids in the interpretation and timing of origin of variations (e.g., bipartite hypoglossal canal) and anomalies (e.g., persistent hypoglossal arte

ISSN:0002-9106    

DOI:10.1002/aja.1001690302

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

年代:1984

数据来源: WILEY

摘要:

AbstractThe bone‐marrowThe hyphenation of bone‐marrow preceeding sinusoids or endothelium in this paper is in accordance with the style required by The American Journal of Anatomy.R.M.Psinusoidal endothelium is a cellular bar‐rierthat separates developing blood cells in the extravascular space from the peripheral circulation. Mature blood elements enter the circulation via transendothelial migration pores. In the present study, monosaccharide constituents on the bone marrow endothelium were examined using lectin‐affinity cytochemistry. With lectin‐horseradish and lectin‐ferritin conjugates, mannosyl, N‐acetylglucosaminyl, galactosyl, N‐acetylgalactosaminyl, and sialic acid were localized to the luminal plasmalemma, bristle‐coated pits and diaphragmed fenestrae. These were conspicuously reduced on the abluminal plasmalemma. When the tissue was treated with biotinylated lectins followed by avidin‐ferritin, only a localization with wheat‐germ agglutinin (sialic acid; N‐acetylglucosaminyl) was observed. Pretreatment of the bone marrow with neuraminidase enabled the localization of the other monosaccharide components by the biotin‐avidin method. Accumulations of carbohydrate residues were identified near the endothelium subjacent to migrating cells. Fucosyl moieties marked byUlex europaeusagglutinin (UEA) reagents on the endothelium were not present. All binding was abolished by incubation of tissue and lectin conjugates with specific hapten sugars. Labeling was also not present after Pronase E treatment, indicating that the identified monosac‐charides are components of glycoproteins rather than glycolipids. The possible function of endothelial‐surface glycoproteins as receptors for the surfaces of mature blood cells and their role in trans

ISSN:0002-9106    

DOI:10.1002/aja.1001690303

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

年代:1984

数据来源: WILEY

摘要:

AbstractThe possibility has been investigated that nerves, which promote mitotic activity during the growth phase of limb regeneration, may also release factors upon injury to stimulate the cellular events during the initiation of regeneration. These events have been compared in control, innervated limb stumps and in limbs denervated for various periods before amputation. Wound closure occurred in an essentially normal manner in limbs denervated at the time of amputation but frequently occurred at reduced rates or not at all in limb stumps denervated 5 days before amputation. Tissue loss and various degrees of morphological regression were seen in many of the predenervated limb stumps, including all of those denervated for 6 days or more before amputation. Evidence is presented which suggests that regression may result from a combination of the denervated state and disturbance to the limb ' vascular system. Limbs predenervated 2‐10 days before amputation were fixed 7 days after amputation and examined histologically. All limb stumps, including those involved in regression, showed tissue dissociation and cellular dedifferentiation. Autoradiography revealed that the dedifferentiation involved DNA synthesis in both denervated and innervated limbs. Seven days after amputation, DNA‐labeling indices in limb stumps predenervated 2 or 4 days were similar to those of control limbs, but labeling indices were significantly reduced in limbs predenervated 6 or more days. The results are assessed in light of the state of nerve degeneration in the limbs at the time of amputation and are discussed in terms of what is known regarding nerve‐derived growth‐promoting sub

ISSN:0002-9106    

DOI:10.1002/aja.1001690304

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

年代:1984

数据来源: WILEY

摘要:

AbstractThe vascular architecture of the rat pampiniform plexus was studied by scanning electron microscopy of vascular corrosion casts. The plexus consists of a thick bundle of many anastomosing veins that entirely and closely surround the convoluted segments of the testicular artery. This specially developed close contact of the pampiniform plexus with the testicular artery may allow heat exchange between the plexus and the artery to maintain the cooled condition of the testis. The epididymal arteries are also closely surrounded by the networks of the epididymal veins. It is likely that heat exchange may operate even between these epididymal vessels. The ductus deferens is provided with no vascular channels for such heat exchange. A loose or coarse capillary network is always observed between the testicular artery and the pampiniform plexus. This network is supplied by the epididymal arteries and drains into the pampiniform plexus.

ISSN:0002-9106    

DOI:10.1002/aja.1001690305

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

年代:1984

数据来源: WILEY

摘要:

AbstractExtensive morphometric measurements were made on the vestibular system of the rabbit (Oryctulagus cuniculus), the gerbil (Meriones unguiculatus), the chinchilla (Chinchilla laniger), and the squirrel monkey (Saimiri sciureus) from serial sections of temporal bones. Additionally, a more limited set of measurements were also completed on the owl monkey (Aotus trivirgatus), the Capuchin monkey (Cebussp.), the harp seal (Pagophilus groenlandicusErxleben, 1777), and the two‐toed sloth (Choloepussp.). The following measurements were made: (1) radius of curvature (R) of each membranous semicircular canal (herein called semicircular duct—see nomenclature inNomina Anatomica(1968)) (2) cross‐sectional diameter of the ducts and the osseous semicircular canals, and (3) some pertinent morphometrics of the cristae ampullares and the utricle. In all species studied (1) the radii of curvature of the three semicircular ducts are dissimilar, with that of the lateral duct being as small as, or smaller than, those of the anterior and posterior ducts; (2) R for the anterior duct is largest in the harp seal and the rabbit; (3) the canal and duct dimensions are largest in the Capuchin and squirrel monkeys, the two‐toed sloth, and the harp seal, and smallest in the gerbil; (4) the proportion of otic fluid “space” that is occupied by endolymph shows a ranking of gerbil>rabbit>two‐toed sloth>chinchilla = owl monkey>squirrel monkey>Capuchin monkey>harp seal; and (5) the gross ampullary and utricular dimensions are largest in the harp seal and smallest in the gerbil. These measurements were used for determining the time constants describing semicircular‐canal dynamics in the Steinhausen (1931, 1933) and Oman‐Marcus

ISSN:0002-9106    

DOI:10.1002/aja.1001690306

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

年代:1984

数据来源: WILEY

摘要:

AbstractSubcutaneous adipose tissues from fetal and young rats were studied with enzyme histochemical techniques. Lipid staining and histological evaluation were also utilized to compare the development of a wide variety of enzyme activities to cytoplasmic lipid deposition and morphological differentiation of adipocytes. Three distinct stages of adipose‐tissue differentiation were postulated. In stage III, adipocytes were morphologically differentiated (rounded, basal‐lamina positive) and enzyme reactive for many enzymes. In stage II, however, adipocytes were reactive for some enzymes but were not morphologically differentiated. Stage I adipose tissue was histologically distinct from connective tissue but did not contain lipid‐laden cells or enzyme‐reactive cells. Stages I and II (95%) were predominant in fetuses, whereas stage III (90%) was predominant in young animals. Histochemical analysis of adipocytes in newborn rats established the metabolic competence of these cells despite their small size. These studies indicate that enzymatic differentiation of adipocytesclearly precedes morphological differen

ISSN:0002-9106    

DOI:10.1002/aja.1001690307

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

年代:1984

数据来源: WILEY

摘要:

AbstractThis study was designed to study the time course of the incorporation of55Fe into the ameloblasts of maturation in rat incisors. Male Sherman rats (100 ± 5 gm) were injected intravenously with 0.9 mCi of55Fe and sacrificed in pairs by perfusion at various time intervals from 5 min to 7 days after injection. The incisors were demineralized in 4.13% disodium EDTA, postfixed in 1% osmium tetroxide in veronal acetate buffer, and embedded in Epon. Incisors from control rats injected with only physiological saline were treated in the same way. Sections from blocks of tissue in the zone of maturation were prepared for light microscope radioautographic observations. The greatest incorporation of iron occurred at 9 mm within the zone, at this site the ameloblasts contained few pigment granules. About 5 mm deeper into the zone the activity fell off to zero, as observed at 2.5 hr after injection of55Fe. Between 1 day and 7 days after injection the55Fe labeling was found over the cells containing many pigment granules, while the initial labeling over the cells within 9 mm of the zone had diminished. These data have shown that at any given time, from 30 min to 4 hr, the iron enters the maturation ameloblasts over a wide extent of the zone, reaching a maximum at about 9 mm from the onset of maturation. However, at longer times (1 day to 7 days) the labeling curve shifts and shows the greatest activity beyond 9 mm within the zone

ISSN:0002-9106    

DOI:10.1002/aja.1001690308

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

年代:1984

数据来源: WILEY

摘要:

AbstractThe spleen ofNeoceratodus forsteriKrefft grows in the shape of a “boomerang” on the left lateral‐dorsal‐right lateral part of the borderline between the foregut and the yolkgut. Development of the spleen follows the following stages: (1) appearance of the splenic primordium as a mesenchymal condensation in a limited portion of the region supplied by the third and fourth vitelline arteries on both sides, (2) development of the splenic sinuses within the primordium, (3) formation of the “gastric” and enteric splenic portal systems and (4) growth of the spleen along the anterior extremity of the spiral valve. The blood vascular dynamics of the foregut and the yolkgut are intimately involved with the formation of the spleen in this species. These processes were, therefore, compared with similar processes in other animals, and the characteristics of this organ common to vertebrates were i

ISSN:0002-9106    

DOI:10.1002/aja.1001690309

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

年代:1984

数据来源: WILEY

ISSN:0002-9106    

DOI:10.1002/aja.1001690301

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

年代:1984

数据来源: WILEY