摘要:

AbstractThe intermediate zone (IZ) of nonperfused and perfused spleens in three species of primitive mammals (shrew, mole, platypus) was studied morphologically. The IZ is a tissue zone consisting of plexiform vessels, probably venous capillaries, and is located transitionally between the white and red pulp. The IZ is separated from the white pulp by the arterial net (AN), in which the white pulp arteries terminate. Development of the IZ differs between the three species examined being distinctive in the platypus and shrew. The IZ is thin in the mole spleen. A closed type of arteriovenous (A‐V) anastomosis was demonstrated in or around the IZ in the two Insectivora species examined. In the shrew spleen, peripheral arterial branches running within the IZ anastomose with the AN around the follicle. The AN anastomoses eventually with venous plexi‐form vessels of the IZ around the nonfollicular area of the white pulp to form a closed system. In the mole spleen, A‐V anastomoses were noted between white pulp arteries (follicular and AN) and veins of the red pulp, either by direct communication or through fenestrated IZ vessels compatible with the plexiform vessels of the shrew spleen. A‐V anastomosis in the IZ is probable, but not confirmed, in the platypus spleen, as analysis was limited to a nonperfused specimen. Well‐developed ellipsoids were noted around arterial terminals of the IZ in the shrew spleen. Ellipsoids were also noted around all arterial terminals of the mole spleen directed to the red pulp. Most ellipsoids of the mole spleen appeared located within the IZ. No ellipsoids were present around arterial terminals of the IZ in the platypus spleen.Closed circulation was noted in terminals of the pulp artery in spleens of all three species. All pulp arteries of the mole spleen are postellipsoid segments of white pulp (AN and follicle) arteries. No ellipsoids were found around terminals of the pulp artery (penicillar artery) in shrew and platypus spleens.The IZ is probably homologous to the perilymphatic sinusoid (vein) of the lungfish spleen and may be regarded as part of the red pulp. The IZ may be representative of primitive mammalian spleens that have closed circulation. The marginal zone (MZ) of common mammalian spllens is probably a modified IZ by differentiation (remodelling) of the intrasplenic vein. In this process, with drawal of venous vessels from the IZ occurrred, leaving a lymphoreticular zone with open circulation (MZ). The marginal sinus reported in some mammalian spleens is probably a modified AN formed durig this process. Possible morphological alterations of the spleen in vertebrate phylogeny are

ISSN:0002-9106    

DOI:10.1002/aja.1001870402

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

年代:1990

数据来源: WILEY

摘要:

AbstractCross and longitudinal sections from the encapsulated portions of chicken tibialis anterior and extensor digitorum longus muscle spindles were examined to determine whether their intrafusal fibers were a structurally homogeneous or heterogeneous population. The techniques used were the histochemical actomyosin (mATPase) reaction, and fluorescence immunohistochemistry employing two monoclonal antibodies, CA‐83 and CCM‐52, that are specific for myosin heavy chains. After incubation with antibody CCM‐52, intrafusal fibers fluoresced either strongly or weakly to moderately. Antibody CA‐83 was even more selective. In addition to identifying the strongly reactive category, it clearly separated the remaining fibers into unreactive and moderately reactive groups. As a whole, after incubation for mATPase, pH 9.6 preincubation, unreactive fibers stained darker than strongly reactive fibers. Moreover, the cross‐sectional area of the unreactive fibers was significantly larger than that of the strongly reactive fibers. In the average‐size muscle spindle with six intrafusal fibers, there were four unreactive fibers and two strongly reactive fibers. In about one‐third of the receptors examined, one moderately reactive fiber was present. Taken together, the data indicate that intrafusal fibers of chicken tibialis anterior and extensor digitorum longus muscles are not structurally homogeneous. The oberserved variations can be better explained in terms of different fiber types than of continuous gradients within one

ISSN:0002-9106    

DOI:10.1002/aja.1001870403

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

年代:1990

数据来源: WILEY

摘要:

AbstractA study of pathways of lymphocyte migration through mouse spleen revealed lymphatic channels closely following arteries in trabeculae and white pulp. Because there is no detailed record of the layout of deep splenic lymphatics in the mouse, or other species, we present our observations in this paper, relating our findings to normal migratory pathways of lymphocytes through the spleen. Lymphatics draining the spleen are so inconspicuous that they often are not mentioned in anatomical discussions. The data presented clearly demonstrate (1) the existence and layout of deep lymphatic vessels in the mouse spleen, and (2) that migrating lymphocytes exit white pulp via these lymphatic vessels.CD4+and CD8+T cell subsets migrated proximally along the central artery from distal (dPALS) to proximal periarterial lymphatic sheaths (pPALS) and exited via deep lymphatic vessels that originate there. B cells migrated from dPALS to enter lymphatic nodules (NOD), thus segregated from T cells. B cells then migrated toward and exited via deep lymphatics. The appearance of labelled lymphocytes in lymph coincided with their disappearance from white pulp compart‐ments. Labelled T cells were observed in splenic lymphatics as early as 1 hr after intravenous infusion but took, on average, about 6 hr. B cells took somewhat longer. Thus T and B cells entered and left white pulp through shared pathways, but took divergent intermediate routes through dedicated zones, pPALS for T cells, NOD for B cell

ISSN:0002-9106    

DOI:10.1002/aja.1001870404

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

年代:1990

数据来源: WILEY

摘要:

AbstractMigration pathways of B cell and CD4+and CD8+T cell subsets of murine thoracic duct lymphocytes (TDL) were mapped. Per weight, the spleen accumulated more TDL than any other organ, regardless of lymphocyte subset. Spleen autoradiographs showed early accumulations of TDL in marginal zone and red pulp. Many TDL exited the red pulp within 1 hr via splenic veins. The remaining TDL entered the white pulp, not directly from the adjacent marginal zone but via distal periarterial lymphatic sheaths (dPALS). From dPALS, T cells migrated proximally along the central artery into proximal sheaths (pPALS) and exited the white pulp via deep lymphatic vessels. B cells left dPALS to enter lymphatic nodules (NOD), then also exited via deep lymphatics.T cells homed to lymph nodes more efficiently than B cells. Lymphocytes entered nodes via high‐endothelial venules (HEV). CD4+TDL reached higher absolute concentrations in diffuse cortex than did CD8+T cells. However, CD8+TDL moved more quickly through diffuse cortex than did CD4+TDL. B cells migrated from HEV into NOD. Both T and B TDL exited via cortical and medullary sinuses and efferent lymphatics. A migration pathway across medullary cords is described.All TDL subsets homed equally well to Peyer's patches. T TDL migrated from HEV into paranodular zones while B cells moved from HEV into NOD. All TDL exited via lymphatics. Few TDL entered zones beneath dome epithelium. All subsets were observed within indentations in presumptive M cells of the dome epitheliu

ISSN:0002-9106    

DOI:10.1002/aja.1001870405

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe morphogenesis and innervation of the ventral abdominal musculature inXenopusembryos was examined using microscopic techniques. Muscle development begins at Nieuwkoop and Faber Stage 31, when aggregates of undifferentiated cells form on the ventrolateral margins of rostral trunk myotomes. During subsequent stages, aggregates form and detach from progressively more caudal myotomes to form a series of seven discrete cell clusters (anlagen). The anlagen migrate ventrally in a cell‐free space between the epidermis and a subepidermal layer of pigment cells. Extracellular aggregates of 30‐nm granules are evident transiently between the migrating anlagen and the epidermis. During stages 39 and 40, each anlage transforms into a sheet of myotubes which attaches rostrally and caudally to adjacent sheets to form a seven‐segmented muscle. The series of broad segments, approximately one fiber thick, extends from the pericardium to the level of the proctodeum. The embryonic muscle is innervated by the ventral rami of spinal nerves 2 to 9. The major nerve trunks to the muscle develop between stages 35/36 and 40. Axons initially grow ventrally along the paths taken by the muscle anlagen. When the anlagan become muscle segments, the nerves are deep to the narrow boundaries between the segments. Spinal nerve 2 ramifies in the first muscle segment and sends fibers rostrally to the geniohyoid muscle. The findings represent the first description of the development of this muscle inXenopusand the first account of the development of the abdominal motor nerves in an amphibian e

ISSN:0002-9106    

DOI:10.1002/aja.1001870406

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

年代:1990

数据来源: WILEY

摘要:

AbstractDevelopment of the upper dentition inAlligator mississippiensisas investigated using a close series of accurately staged and aged embryos, hatchlings, and young juveniles up to 11 days posthatching, as well as some young and old adult specimens. Studies from scanning electron miscroscopy, light microscopy, acetate and computer reconstructions, radiography and macroscopy were combined to elucidate the details of embryonic dental development, tooth initiation pattern, dentitional growth, and erupted functional dentition. The results were compared with those from the lower jaw and related to the development of other craniofacial structures.Approximately 17 early teeth in each jaw half develop as surface teeth, of which 13 project for 1 to 12 days before sinking into the mesenchyme. The first three teeth initiate directly from the oral epithelium at Ferguson stages 14–15 (days 15–19 after egg laying), before there is any local trace of dental lamina formation. All other teeth develop from a dental prolamina or lamina; and with progressive lamina development, submerged teeth initiate from the aboral end leading to the formation of replacement teeth. All teeth form dentin matrix, but 12 early teeth do not form enamel. Approximately 20 embryonic teeth are resorbed, 6 are transitional, and 42 function for longer periods after hatching.The embryonic tooth initiation pattern (illustrated by defining a tooth position formula) does not support the previous models of Odontostichi, Zahnreihen, and Tooth Families, each of which postulates perfect regularity. Up to three interstitial tooth positions develop between sites of primary tooth initiation, and families with up to five generations at hatching are at first arbitrarily defi

ISSN:0002-9106    

DOI:10.1002/aja.1001870407

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

年代:1990

数据来源: WILEY

ISSN:0002-9106    

DOI:10.1002/aja.1001870401

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

年代:1990

数据来源: WILEY