摘要:

AbstractThyroid glands from female rats kept vitamin A deficient for one, two, and three months were examined by electron microscopy. After one month on the diet, no consistent alterations were noted. After two months, the colloid in some follicles displayed a peripheral zone of decreased density. In addition, ultimobranchial follicles within the gland had become keratinized. After two to three months on the diet, cells were seen entering the colloid. Many of these cells were identified as follicular cells since they often occurred in groups and occasionally exhibited remnants of desmosomes. Often the cells within the colloid appeared vacuolated, and by light microscopy were thought to contain lipid. However, electron microscopy revealed that these cells contained many digestive vacuoles rather than lipid droplets.Quantitative and autoradiographic studies indicated that thyroids of vitamin A deficient rats took up less radioiodide than thyroids of control rats. The keratinization of ultimorbranchial follicles in vitamin‐A deficiency has been suggested as preliminary in the histogenesis of squamous cell carcinoma. However, an effect of vitamin A deficiency on thyroid follicular cells has not heretofore been reported. It's possible that the presence of follicular cells in the colloid reflects an accelerated turnover of these cells and could indicate an early pathological sig

ISSN:0002-9106    

DOI:10.1002/aja.1001560202

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

年代:1979

数据来源: WILEY

摘要:

AbstractInjection of viable BCG into the subarachnoid space of immunized and non‐immunized dogs produced a 10‐fold increase in the populations of pial free cells. In immunized animals injected three days previously with BCG, stereoscopic SEM revealed that many pial cells had rounded up and were protruding into the subarachnoid space. With continued rounding these cells took on amoeboid characteristics, with shapes that suggested a capacity for cell movement. Internally, these pial cells possessed an increased volume of perinuclear cytoplasm and organelles. Reactive pial cells could be distinguished from macrophages of presumed hematogenous origin on the basis of their surface morphology. These findings suggested that pial cells had the ability to alter their normal structural and behavioral characteristics and to become macrophage‐like under these conditions of secondary challenge b

ISSN:0002-9106    

DOI:10.1002/aja.1001560203

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

年代:1979

数据来源: WILEY

摘要:

AbstractIn exploring the evolution and adaptive significance of epididymal function, we have studied the male excurrent duct and spermatozoa of a monotreme mammal ‐ the echidna. Sperm maturation in the echidna excurrent duct appears simpler than that in most therians examined. Furthermore, neither the duct nor the spermatozoa of the echidna display specific therian characteristics; they bear a much closer resemblance to those of non‐passerine birds.The echidna spermatozoon is filiform, the sperm tail has no distinctive features, and the anterior seventh of the undulating nucleus is covered by a modest acrosome. Immediately behind this a restricted apposition between plasma membrane and nuclear envelope constitutes a post‐acrosomal ring. This is evident also in some reptiles and marsupials, whereas in Eutheria such a membrane association appears as the posterior ring at the base of the sperm nucleus.Maturation of spermatozoa in the Wolffian duct of the echidna appears to be expressed only in a changing capacity for motility and in loss of the cytoplasmic droplet. Neither surface, structural nor acrosomal changes that characterize sperm maturation in therian mammals have been detected in maturing echidna spermatozoa. The echidna duct displays little of the regional complexity of the epithelium that typifies this duct in the Theria. Of five regions distinguishable on the basis of epithelial morphology, the first two appear to be counterparts of efferent ducts by virtue of a low columnar, partially ciliated epithelium. The tall pseudo‐stratified Golgi‐rich epithelium of the major portion of the duct broadly resembles that of the therian epididymis, but it displays only two structurally distinguishable regions, the more distal being the site of a dense luminal secretion. The foamy epithelial cells of the fifth and terminal region, characterized by a mass of supra‐nuclear vesicles and rough ER, suggest a secretory function that may in some way contribute significantly to the ejaculate, for accessory glands are poorly developed in monotremes.Maturation of spermatozoa in the Wolffian duct of the echidna appears to be expressed only in a changing capacity for motility and in loss of the cytoplasmic droplet. Neither surface, structural nor acrosomal changes that characterize sperm maturation in therian mammals have been detected in maturing echidna spermatozoa. The echidna duct displays little of the regional complexity of the epithelium that typifies this duct in the Theria. Of five regions distinguishable on the basis of epithelial morphology, the first two appear to be counterparts of efferent ducts by virtue of a low columnar, partially ciliated epithelium. The tall pseudo‐stratified Golgi‐rich epithelium of the major portion of the duct broadly resembles that of the therian epididymis, but it displays only two structurally distinguishable regions, the more distal being the site of a dense luminal secretion. The foamy epithelial cells of the fifth and terminal region, characterized by a mass of supra‐nuclear vesicles and rough ER, suggest a secretory function that may in some way contribute significantly to the ejaculate, for accessory glands are poorly developed in monotremes.The possibility is considered that the relative complexity of epididymal function and sperm structure in therian mammals could have been determined by evolutionary change in the milieu of the female tract, and/or in the character of the egg vestments that the fertilizing spermatozo

ISSN:0002-9106    

DOI:10.1002/aja.1001560204

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

年代:1979

数据来源: WILEY

摘要:

AbstractThe ultrastructure of hepatocytes, bile canaliculi, and hepatic sinusoids of the larval lamprey,Petromyzon marinus, was examined using thinsectioned and freeze‐fractured tissues. The liver is a “tubular gland” with hepatocytes arranged in a tubular fashion around large bile canaliculi. Hepatocytes are roughly conical in shape, with their tapered apices facing a bile canalicular lumen. They possess extensive rough and smooth endoplasmic reticulum, a well‐developed Golgi complex, abundant mitochondria, and varying numbers of large secondary lysosomes. Both secondary lysosomes and the Golgi complex are concentrated in the apical or peribiliary cytoplasm, indicating a possible role in bile secretion. The apical surfaces of the hepatocytes bear numerous elongate microvilli and occasional cilia, which project into the bile canaliculi. The hepatocytes are joined, apically, by junctional complexes composed of zonulae occludentes and adhaerentes. In freeze‐fracture, the zonulae occludentes are of variable apicobasal depth and consist of honeycomb‐like meshworks of fibrils. Spaces of variable width frequently appear in the P‐face grooves, indicating that the zonulae occludentes are “leaky.” Numerous communicating (gap) junctions join the hepatocytes laterally. Varying numbers of lateral microvilli project into the intercellular spaces and, basally, the plasma membrane is deeply infolded, resulting in the formation of apparently interdigitating basal processes resting upon a thin basal lamina. Sinusoids are composed of both a heavily‐fenestrated, continuous endothelium, and phagocytic reticulo‐endothelial (Kupffer) cells. Despite the difference in arrangement of their hepatocytes, the mammalian and lamprey livers show similar ult

ISSN:0002-9106    

DOI:10.1002/aja.1001560205

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

年代:1979

数据来源: WILEY

摘要:

AbstractSeptation of the truncus arteriosus of the normal chick embryo heart was surveyed systematically with the light microscope. Tissue from replicate samples at successive periods of development was sectioned within an arbitrary coordinate system based on positional reference points along the external surface of the heart. Correlation of several aspects of tissue morphology within this spatial and temporal reference‐frame yielded a new description of tissue associations and kinetics during septation.A stable complex of tissue structures appeared in the downstream, distal truncus at Stage 25 and persisted throughout the septation process. This complex consisted of (1) the cephalic margin of the myocardial sheath, and (2) the adjacent bifurcation of the vascular lumen, linked together by (3) the newly condensed Y‐shaped strap of cells forming the aorticopulmonary septum. The apparent motion of this septation‐complex toward the ventricle(s), the appearance within the thoracic cavity of the adjacent segments of the aortic arches, and measures of tissue length and width suggested that septation was accompanied, and perhaps initiated, by increased tension along the truncus.The truncal ridges remained upstream from the complex, with mesenchymal condensations beneath the endocardium differentiating into the definitive semilunar valves. Downstream from the bifurcation, mesenchyme in the aortic arch region condensed around the separate lumens to form the smooth muscular tunica media of the great arteries. The epicardium developed in a caudocephalic direction along the heart tube. Vagal innervation approached the heart cephalocaudally. Capillaries formed along the dividing truncus in both directions. Autoradiography following3H‐thymidine labelling demonstrated reduced DNA synthetic activity in the cephalic margin of the myocardium and aorticopulmonary septum, compared with the associated loose mes

ISSN:0002-9106    

DOI:10.1002/aja.1001560206

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

年代:1979

数据来源: WILEY

摘要:

AbstractThe study of Mullerian Inhibiting Substance (MIS) has been made possible because of the organ‐culture bioassay devised by Picon ('69) for detecting MIS in vitro. We have studied the degeneration of the female Mullerian duct of the rat fetus, the target tissue of the assay, with electron microscopy. We have observed that the involution of the female Mullerian duct in the organ‐culture assay follows a pattern of degeneration similar to the normal involution of the male Mullerian duct under the influence of MIS from the fetal testis (Price et al., '77). This involution involves alterations in the duct epithelium subsequent to a response of the mesenchyme surrounding the duct. The degeneration of a specific organ system under the direct influence of a specific factor, Mullerian Inhibiting Substance, represents an example of “programmed cell d

ISSN:0002-9106    

DOI:10.1002/aja.1001560207

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

年代:1979

数据来源: WILEY

摘要:

AbstractLuteinizing hormone and follicle‐stimulating hormone were identified by immunocytochemistry in the same cells of the pituitary pars tuberalis, following hypophysectomy in the rat. A marked hyperplasia and hypertrophy of these cells occurred in response to hypophysectomy. These findings are discussed in light of the potential for hormone production by pars tuberalis gonadotropes following hypophysectomy performed as part of an experimental protocol, as well as that performed for palliation of human metastatic breast cance

ISSN:0002-9106    

DOI:10.1002/aja.1001560208

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

年代:1979

数据来源: WILEY

摘要:

AbstractBy means of silicone rubber injections, we confirmed the existence of several types of aglomerular arterial pathways within kidneys of aged rats. In superficial cortex some interlobular arteries divide to form aglomerular branches (Ludwig's arterioles) towards cortex corticis. In juxtamedullary cortex these pathways are relatively more numerous, they comprise: (a) Vasa Recta Vera, (b) glomeruli in which afferent and efferent arterioles form a continuous vessel and (c) glomeruli with two efferent vessels, one by‐passing glomerular tuft. In addition, results obtained in the rat by the microsphere technique are in agreement with our morphological observation

ISSN:0002-9106    

DOI:10.1002/aja.1001560209

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

年代:1979

数据来源: WILEY

ISSN:0002-9106    

DOI:10.1002/aja.1001560201

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

年代:1979

数据来源: WILEY