摘要:

AbstractThe distribution and migration of the cardiac neural crest was studied in chick embryos from stages 11 to 17 that were immunochemically stained in whole‐mount and sectioned specimens with a monoclonal antibody, HNK‐1. The following results were obtained: (1) The first phase of the migration in the cardiac crest follows the dorsolateral pathway beneath the ectoderm. (2) In the first site of arrest, the cardiac crest forms a longitudinal mass of neural‐crest cells, called in the present study, the circumpharyngeal crest; this mass is located dorsolateral to the dorsal edge of the pericardium (pericardial dorsal horn) where splanchic and somatic lateral mesoderm meet. (3) A distinctive strand of neural‐crest cells, called the anterior tract, arises from the mid‐otic level and ends in the circumpharyngeal crest. (4) By stage 16, after the degeneration of the first somite, another strand of neural‐crest cells, called the posterior tract, appears dorsal to the circumpharyngeal crest. It forms an arch‐like pathway along the anterior border of the second somite. (5) The seeding of the pharyngeal ectomesenchyme takes place before the formation of pharyngeal arches in the postotic area, i.e., the crest cells are seeded into the lateral body wall ventrally from the circumpharyngeal crest; and, by the ventralward regression of the pericardial dorsal horn, lateral expansion of pharyngeal pouch, and caudal regression of the pericardium, the crest cell population is pushed away by the pharyngeal pouch. Thus the pharyngeal arch ectomesenchyme is segregated. (6) By stage 14, at the occipital somite level, ventrolateral migration of the neural crest is observed within the anterior half of each somite. Some of these crest cells are continuos with the caudal portion of the circumpharyngeal crest. An early contribution to the enteric neuroblasts is apparent

ISSN:0002-9106    

DOI:10.1002/aja.1001910302

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

年代:1991

数据来源: WILEY

摘要:

AbstractTartrate‐resistant acid adenosine triphosphatase activity at pH 6.5, using a lead‐salt method, was localized at light and electron microscopic levels in cartilage and bone matrices, osteocalsts, and chondrocalsts. Cartilage matrix staining occurred after vascular invasion of the growth plate. In osteoclasts, activity was present in lysosomes, extracellular ruffled border channels, and the underlying cartilage and bone matrices. Staining artifacts occurred at lower pH levels (pH 5.4, 5.0).Adenosine diphosphate, p‐nitrophenylphosphate, thiamine pyrophosphate, and α‐naphthylphosphate also acted as substrates; but no activity was observed when adenosine monophosphate, adenylate‐(β,γ‐methylene) diphosphate, and β‐glycerophosphate were used. The activity was inhibited by NaF, dithionite, and a high concentration of p‐chloromercuribenzoic acid, and activated by simultaneous addition of FeCl2and ascorbic acid, as has been shown in biochemical studies. These histochemical results support the view that the adenosine triphosphate hydrolyzing activity at pH 6.5 is due to tartrate‐resistant acid phosphatase (TRAP).There were some differences in ultrastructural localization between TRAP and tartrate‐sensitive acid phosphatase (TSAP) activities in osteoclasts: TSAP activity was more intense in lysosomes and Golgi complexes and TRAP was stronger in the cartilage and bone matrices. It is suggested, therefore, that most of TRAP is in an inactive form in cells and is

ISSN:0002-9106    

DOI:10.1002/aja.1001910303

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe ontogeny of reticular cells in the ileal Peyer's patch of sheep from 70 days gestational age was studied by light and electron microscopy and by enzyme histochemistry. Small to medium‐sized lymphocytes were seen in the lamina propria at 97 days, when the stroma was essentially still mesenchymal. By 110 days, the stromal cells in the dome/follicle primordia had differentiated into reticular fibroblasts, whose processes and fibers were seen to surround groups of lymphocytes. With advancing age the number and size of primordia increased, and proliferation was obvious among the lymphocytes. Processes of reticular cells increased in number and penetrated between individual lymphocytes of the groups. Coarser desmosome‐like contacts were seen between the reticular cells from 115 days onwards. A central light area in the follicle was apparent from 130 days onwards. The fine structure of the stromal cells in this light follicle center developed towards but never became similar to that of follicular dendritic cells in a typical germinal center. The fine interdigitating end branches of the stromal cells were less numerous, and the dense homogeneous material present in between the end branches was not observed in the ileal Peyer's patch follicle. Instead, small particles and vesicles were seen between the various cell types of the light center and were not restricted to the intercellular spaces between the stromal cells. In the dark peripheral zone of the follicle, the stromal cells retained more immature features. The follicle became bordered by a capsule at an early stage. This capsule was formed by multiple layers of flattened fibroblasts separated by small amounts of intercellular material only. The alkaline phosphatase, Mg2+‐dependent adenosine triphosphatase and 5′nucleotidase reactivities of the follicular dendritic cells in the ileal Peyer's patch were similar to those of early prenatal primary follicles of sheep lymph nodes. This study indicates that the stromal cells of the ileal Peyer's patch are mesenchymal in nature and different from those of germinal centers and the epithelial stromal cells of bursa Fabricii of birds. © 1991 Wiley

ISSN:0002-9106    

DOI:10.1002/aja.1001910304

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe sinoatrial ring bundle (SARB). was originally described as a “whitish bundle of tissue which describes an almost complete loop around the two venae cavae and the coronary sinus” in the adult rabbit heart (Paes de Carvalho et al., 1959). The histologically and electrophysiologically differentiated structure, derived from the embryonic venous valves, was suitably placed for rapid conduction from sinoatrial (SA) to atrioventricular (AV) node, but no evidence was found for this role. Today, the function of the SARB remains obscure. Cholinesterase/silver staining reveals the neural pattern associated with the SARB and suggests a function. Throughout its extent, the SARB contains a bundle of parallel muscle fibers and accompanying long nerves. The nerves distribute to structures at either side of the loop: superolaterally to pectinate muscle and inferomedially to the region of the AV node. Along the curve of the right SARB, the nerves contribute to a dense neural plexus with nerves coiled around muscle. The plexus communicates with the nearby SA node and with the ganglia inferior to the node near the inferior vena cava. The morphological pattern of neural elements is suitably organized to suggest tension monitoring and internodal, neural communicat

ISSN:0002-9106    

DOI:10.1002/aja.1001910305

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe structure of the human caput epididymidis was examined by gross morphological and light and electron microscopic techniques. There were at least seven types of tubules, each characterized by a different epithelium. These tubules were connected with one another by at least eight types of junctions to form a network. Most of the caput epididymidis was composed of efferent ducts. Within these, five types of tubules, each with a different ciliated epithelium, were found in different regions; and four types of junctions between the efferent ducts and the epididymal tubule were observed. The efferent ducts left the testis, initially as parallel straight tubules containing both ciliated and non‐ciliated cells in an epithelium of irregular height. Each efferent duct then coiled tortuously into lobules that folded over one another. These efferent ducts then branched out as thin tubules to join a network of dark tubules which were lined by a regular epithelium containing prominently vacuolated, nonciliated cells. These tubules anastomosed via common cavities characterized by a ciliated cuboidal epithelium and sometimes joined tubules exhibiting a non‐vacuolated ciliated epithelium. The latter, as well as typical efferent ducts, made connection with the epididymis proper in both end‐to‐end and end‐to‐side junctions. In the more distal junctions with the epididymis, the efferent ducts joined to a transitional epididymal ductule before joining to the side of the epididymis proper. Post‐junctional epithelia in the beginning of the epididymis occasionally contained patches of cells characteristic of efferent ducts. Tall cells with long stereocilia constituted a discontinuous “initial segment”‐like region of the epididymis. This is the most detailed study so far of the epithelia and the tubule organization in the caput epididymidis of any species, and most of the results are reported for the first time for the human. Although the pattern of the tubule network resembles that of some domestic species, the rich variety of epithelia has not been

ISSN:0002-9106    

DOI:10.1002/aja.1001910306

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe development of the stratified squamous epithelium of the tympanic membrane and external auditory canal was studied in serial sections of 124 mouse ears aged from 11 gestational days to 100 days. A fold developed from the edge of the fundus of the primary canal. It possessed two regions: firstly the meatal plate, which produced the pars tensa‐covering epithelium (zone 2) and most of the deep ear canal epithelium (zone 3), and secondly the fundal extension plate, which grew from that part of the fundus not forming the meatal plate. The fundal extension plate gave rise to the pars flaccida‐covering epithelium (zone 1) and also to the adjacent deep canal epithelium (zone 3). A difference from human development was that zone 3 in the mouse, in both the meatal plate‐and the fundal extension plate‐derived areas, formed adnexal structures. In the early development of the meatal plate, zone 3, at its tip, was swollen and actively mitotic and extended always for a short distance on to the zone 2 side. Zone 2, first perceived two days after zone 3, became progressively attenuated, and by the fourth day after its formation was a single thin layer. It is suggested that the proximal part of zone 3, situated in the mature ear around the periphery of the tympanic membrane, is a generation center for unidirectional outward flux of epithelium which terminates in the mouse at the first adnexal structure. It may cause the whole of zone 2 to move in the same direction by negative contact inh

ISSN:0002-9106    

DOI:10.1002/aja.1001910307

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe morphology and distribution of immunoreactive (GnRH) neural elements in the hypothalamus of the adult nulliparous female rabbit were examined. Approximately 1,000 GnRH cells (range 890‐1136) were counted in the right half of the hypothalamus. Two distinct GnRH cell types were observed: GnRH cells with rough or spiny contours accounted for 64% of the total immunoreactive cells, and smooth‐contoured cells represented 34% of the total. The majority of immunoreactive neural elements were found in the anterior hypothalamus. GnRH cells and processes were located primarily in the ventral and medial anterior hypothalamus forming an inverted V pattern. Processes were followed from the medial preoptic area and suprachiasmatic nucleus to the infundibular stem. Extrahypothalamic projections of GnRH cells were observed. Immunoreactive fibers were also found to contact the ependymal lining of the third ventricle. It is concluded that two morphologically distinct GnRH cell types exist and have a broad distribution in the rabbit hypothalamus. The functinal significance of these cell types requires further st

ISSN:0002-9106    

DOI:10.1002/aja.1001910308

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.1001910309

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

年代:1991

数据来源: WILEY

摘要:

AbstractMutations at more than 30 loci in mice have been shown to cause deleterious effects on the immune system. Immunologic defects caused by certain of these mutations are determined at the level of hematopoietic progenitor cells or at the level of hematopoietic cell‐stromal cell interactions. The immunological mutants described in this paper serve as experimental tools with which to increase our understanding of the development and regulation of the mammalian immune syste

ISSN:0002-9106    

DOI:10.1002/aja.1001910310

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

年代:1991

数据来源: WILEY

摘要:

AbstractHL‐60 cells, a human promyelocytic leukemia cell line, contain amplified c‐mycDNA sequences and mRNA transcripts. These cells can be induced to undergo macrophage differentiation by phorbol esters, which results in suppression of c‐mycexpression and cessation of cell proliferation. The nuclear matrix (NM), a nuclear skeleton resistant to DNase I digestion and high salt extraction, is proposed to be involved in DNA replication, gene regulation, and the correct distribution of DNA at mitosis. We have previously identified a nuclear‐matrix‐associated region (MAR) of the c‐mycprotooncogene to reside in a 1.4‐kb region between Cla I and Eco RI restriction sites at the 3′‐end of the gene. A 172‐bp Dra I/Dra I subfragment of the 1.4‐kb region was shown to be a major component of the MAR (myc‐MAE), and this subfragment was demonstrated to be recognized by a nuclear protein (p25). In this report we demonstrate that ϕX174 DNA, or the synthetic copolymers poly[d(G·C)] and poly[d(A·T)], are not effective suppressors of the binding of themyc‐MAR to isolated NM, indicating that the binding sequence(s) are unique. We find that the addition of partially purified protein p25 increases the relative affinity of themyc‐MAR for HL‐60 NM in an in vitro assay system. NM isolated from HL‐60 macrophages induced by phorbol esters retains significantly moremyc‐MAR DNA fragment in the presence of an excess amount of competitor DNA than does NM from untreated HL‐60 cells. These data suggest that a change of themyc‐MAR association with the NM occurs after

ISSN:0002-9106    

DOI:10.1002/aja.1001910311

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

年代:1991

数据来源: WILEY