摘要:

AbstractMaking a durable joint requiresadaptingthe one present at birth to its subsequent mechanical usage and thenmaintainingit. Thetotalloads on a joint's momentarily loaded area plus the size of that area determine theunitloads on its articular cartilage and subchondral bone. Given those facts, this model suggests the following.For adaptaion: As is true for bone, a threshold range of unit loads that could turn cartilage modeling ON would lie below this tissue's microdamage threshold. When a joint's unit loads rose to that modeling threshold, chondral modeling would begin enlarging the momentarily loaded area to reduce and keep the unit loads on it below the microdamage thresholds of the bone and cartilage supporting that area.For maintenance: Maintenance activities would control the stiffness of cartilage and bone, which would also affect a joint's momentarily loaded area. These activities would usually repair whatever microdamage normally arises in those tissues, and could modify their microdamage thresholds too.In children, modeling and maintenance in bone and cartilage would function effectively.In adultschondral modeling becomes ineffective, but maintenance activities in bone and cartilage would remain effective, and likewise for modeling in the subchondral bone.This model assigns special importance in joint design to thestiffnessof bone, cartilage, and ligament (as distinguished from their strength), to thetypical largest unit: loads applied to them by a subject's usual weekly physical activities, and to theirmicrodamage. © 1994 Wiley‐Liss, I

ISSN:0003-276X    

DOI:10.1002/ar.1092400102

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

年代:1994

数据来源: WILEY

摘要:

AbstractThis model views the common, initiating cause of arthroses as excessive articular cartilage microdamage. If so, understanding it would become a central problem for understanding the pathogenesis of arthroses. The model proposes the microdamge can stem from: (1) Excessive total loads on normal joints; (2) underadaptations in a joint's size or shape that leave its momentarily loaded area too small for normal loads; (3) impaired microdamage repair in subchondral bone or articular cartilage; (4) abnormal composition or structure that makes a tissue develop excessive microdamage under normal loads. (5) (2)–(4) above could stem from changed set points or “lead times” for a joint's adaptations and maintenance, which in turn could stem from (6) genetic influences, some drugs, toxins, diseases, and “X,” and (7) from combinations of the above.In the pathogenesis of arthroses this model assigns special importance to the stiffness of joint tissues (as distinguished from their strength), to the typical largest unit loads they carry as a result of a subject's usual physical activities, and to microdamage in those tissues. © 1994 Wiley

ISSN:0003-276X    

DOI:10.1002/ar.1092400103

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

年代:1994

数据来源: WILEY

摘要:

AbstractBackground: The secretory protein transit between cisternae of endoplasmic reticulum (ER) and Golgi elements is blocked when the yeastSaccharomyces cerevisiae sec21mutant is shifted from the permissive (24°C) to a non‐permissive (37°C) temperature, but 30–50 nm vesicles accumulate in the cytoplasm. At the semi‐permissive temperature of 33°C there is no complete block but rather a slowdown of the protein transport between ER and Golgi. The purpose of the present investigation is to analyze the structural expression of these events.Methods: S. cerevisiae sec21mutants were maintained for 90 min at semi‐restrictive (33°C) or restrictive (37°C) temperatures and then progressively returned to 24°C. Following fixation in glutaraldehyde and a postfixation in potassium ferrocyanide reduced osmium, 0.08 to 0.2 μm thick sections were cut from Epon embedded yeasts. Using the thicker sections, stereopairs of electron microscope photographs were prepared and used to visualize the three‐dimensional configuration of the organelles.Results: At permissive temperature, the Golgi elements appeared as isolated networks of membranous tubules dispersed throughout the cytoplasm. The diameter of these membranous tubules varied considerably from one Golgi element to another. Larger tubules showed at their intersections distensions with size and staining intensity comparable with that of the secretory granules seen at proximity of the Golgi networks or at the cell periphery. Small vesicles in the 30–50 nm size range were rarely if ever observed in cells grown at permissive temperature. Golgi networks and secretion granules were less conspicuous in mutant cells maintained at 33°C and completely disappeared at 37°C. In both cases, the main structural feature was the presence in the cytoplam of numerous small vesicles and of short membranous tubules with a diameter identical to that of the small vesicles. As soon as 5 minutes after shifting mutants from 33°C to 24°C, the small vesciles disappeared from the cytoplasm, while secretory granules were actively produced in extensively developed Golgi network. When mutants were returned from 37°C to 24°C, the disappearance of small vesicles was more progressive and concomitant with the progressive reconstruction of Golgi networks.Conclusions: It is thus postulated that, in the above mentioned conditions, the small vesicles of thesec21mutant did not act as intermediate carriers between the endoplasmic reticulum and a pre‐existing Golgi apparatus, but rather fused together to produce newly formed Golgi networ

ISSN:0003-276X    

DOI:10.1002/ar.1092400104

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

年代:1994

数据来源: WILEY

摘要:

AbstractBackground: Osteoclasts and odontoclasts are multinucleated giant cells which resorb hard tissue by the ruffled borders. Recently, the authors reported the presence of a mononuclear osteoclast with a ruffled border in vitro. However, its presence in vivo has not been shown. To demonstrate the presence of a mononuclear odontoclast in humans, the present study used human deciduous teeth.Methods: After fixation and declacification, tartrate‐resistant acid phosphatase (TRACPase) activity was detected with the azo dye method, and then TRACPase‐positive cells were observed on resorbing areas of teeth. TRACPase‐positive cells could be distinguished from other cells by light microscopy, and the cells for investigation were serially sectioned by alternating semithin and ultrathin sections to observe their ultrastructure and three‐dimensional organization.Results: TRACPase activity was detected in both multinucleated odontoclasts and a mononuclear cell from serial sections. By electron microscopy, most of the multinucleated odontoclasts had ruffled borders and clear zones. A mononuclear TRACPase‐positive cell with a ruffled border and clear zone was reconstructed three‐dimensionally by NIKON COSMOZONE 2SA. The reconstruction showed that this cell had one irregularly shaped nucleus and a wide ring‐shaped clear zone and a small ruffled border. Under the ruffled border, this cell formed a small lacuna on the dentin surface. The results suggested that this cell was a mononuclear odontoclast.Conclusions: The present study concludes that cells with ruffled borders and clear zones observed by transmission electron microscopy can be identified as odontoclasts or osteoclasts irrespective of the number of nuclei. © 1994 W

ISSN:0003-276X    

DOI:10.1002/ar.1092400105

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

年代:1994

数据来源: WILEY

摘要:

AbstractBackground: The porphyrin concentrations of the Harderian glands of Syrian hamsters show marked sexual differences, with male levels being much lower than those of females. Porphyrinogenesis is inhibited by androgens, so orchidectomy leads to elevated male porphyrin concentrations; however, a number of other procedures (some of which also lower androgen levels) prevent this. We studied the effects of short‐day photoperiods and melatonin on Harderian porphyrin concentrations.Methods: Intact, castrated, or pinealectomized hamsters of both sexes were exposed to long‐day or short‐day photoperiods. Intact or castrated hamsters were given melatonin injections in the morning or the afternoon, or were given beeswax pellets containing melatonin. After a variable period, Harderian glands were dissected and porphyrins were measured.Results: Prolonged short‐day exposure (13 weeks) led to increased Harderian porphyrin concentrations and this rise was prevented by pinealectomy. The rise in Harderian porphyrins following short‐day exposure was small, compared with that following castration. Short‐day photoperiods also prevented the rise in porphyrin levels associated with castration and this effect was prevented by removal of the pineal. Melatonin injections, whether given in the morning or in the afternoon, had no effect on Harderian porphyrin concentration of castrated male hamsters. Continuous release melatonin pellets reduced the postcastrational rise in porphyrin levels in one experiment, while having no effect in another. In female hamster, neither short photoperiods nor melatonin pellets influenced Harderian porphyrin concentrations.Conclusions: These results suggested that a factor from the pineal gland helps maintain the low levels of porphyrin which are characteristic of male Harderian glands, despite the decrease in androgen levels which typically results from exposure to short days. Morning and afternoon injections of melatonin and continuous release melatonin pellets failed to resolve the question of whether this pineal factor is melatonin. Our results demonstrated that low male and high female porphyrin levels are maintained in Syrian hamsters, despite seasonal variations in the hormonal milieu, suggesting that these sexual differences are important for the (still unestablished) function of the Harderian glands in this species. © 1994 Wil

ISSN:0003-276X    

DOI:10.1002/ar.1092400106

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

年代:1994

数据来源: WILEY

摘要:

AbstractBackground: In marsupials implantation occurs about two‐thirds the way through the short gestation before which time the embryo is surrounded by the permeable shell membrane which prevents physical contact between the trophoblast and uterine epithelium. Although the trophoblast has been shown to be invasive to varying degrees in several species of marsupials, the ultrastructure of the embryonic‐uterine cell interactions at the time of implantation has not been described in this group.Methods: Thick plastic sections and transmission electron microscopy were employed to investigate the cellular interactions at implantation in the fat‐tailed dunnart (Sminthopsis crassicaudata), a dasyurid Australian marsupial.Results: Our results show that epithelial penetration begins when the embryo is at the late presomite/early somite stage. In the trilaminar region of the yolk sac (TYS), trophoblast cells adjacent to the embryo form desmosomes with uterine epithelial cells and also appear to fuse with them to form hybrid cells, the cytoplasm of which resembles that of trophoblast. Later in the TYS, as the placenta develops, trophoblast microvilli and larger cell processes invaginate, and interdigitate with, the highly folded maternal epithelium but do not invade it. At this time in the bilaminar, or avascular, yolk sac (BYS), multinucleate trophoblast giant cells (TGCs) from an annular region adjacent to the sinus terminalis intrude between, and possibly fuse with, the maternal epithelium. The invading TGCs spread laterally above the residual basal lamina before migrating into the stroma.Conclusions: In this species of marsupial at least, the cell interactions at the time of implantation are similar to those seen in some eutherian species despite the fact that the fetal chorion is of yolk sac rather than allantoic origin. © 1994 Wiley‐L

ISSN:0003-276X    

DOI:10.1002/ar.1092400107

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

年代:1994

数据来源: WILEY

摘要:

AbstractBackground: In mammals, the oviductal secretory cells and their secretions play important roles in reproductive and developmental events. Therefore, many electron microscopic studies of mammalian oviductal epithelial cells have been performed.Methods: The secretory cells in various regions of the rat oviduct during the estrous cycle were examined by transmission electron microscopy.Results: In the fimbriae, the secretory cells contained small secretory granules with moderately electron‐dense matrices and many large bodies that resembled lipid droplets. In the ampullar cells, small secretory granules with moderately electron‐dense matrices were observed in the apical cytoplasm. In the isthmus, the secretory cells contained numerous secretory granules with moderately electron‐dense matrices. Electron‐dense areas were frequently observed in many of the granules of the isthmic cells. Vesicles, partially filled with a dense substance, frequently were observed in the isthmic cells and occasionally in the ampullar cells. Very long stereocilia projected from the surfaces of the isthmic secretory cells into the lumen. Exocytosis of the secretory granules was observed. In addition, there was evidence to suggest the release of the bodies that resembled lipid droplet occurred. Cysts and ciliated vacuoles that appeared to be intraepithelial were frequently observed in the fimbrial and ampullar epithelia. No dramatic changes in the relative numbers of ciliated and secretory cells in any oviductal segment were observed during the estrous cycle.Conclusions: Our ultrastructural observations of the rat oviduct revealed marked regional variations in the morphological features of secretory cells. These results may provide insight into regional and cellular differences in the function of the rat oviduct. © 1994 Wiley

ISSN:0003-276X    

DOI:10.1002/ar.1092400108

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

年代:1994

数据来源: WILEY

摘要:

AbstractBackground: Immobilin is a protein secreted by principal cells of the distal initial segment, intermediate zone and caput epididymidis of adult rats, which serves to immobilize spermatozoa. In the distal cauda, epithelial clear cells are involved in its endocytosis. The objective of this study was to correlate the developmental events in the maturation of the epdidymis with the timing of immobilin secretion and endocytosis in order to evaluate the testicular or epididymal factors which may influence or regulate immobilin expression.Methods: Our approach was to follow and compare the developmental expression of immobilin by light microscope immunocytochemistry in control and efferent duct ligated rats of different postnatal ages.Results: Coincident with the morphological maturation of the principal cells by postnatal day 39, immobilin displayed the characteristic secretory immunostaining pattern found in adults. This adult‐like expression occurred despite the absence of spermatozoa in the lumen but was coincident with high levels of circulating and luminal androgens. In contrast, immobilin secretion in rats whose efferent ducts were ligated at day 15 was weak to non‐existent in the principal cells of the caput epididymidis at day 28 and remained so into adulthood, indicating that principal cells of this region of the epididymis are dependent either directly or indirectly upon testicular factors present in the lumen for immobilin expression. However, secretion of immobilin in the principal cells of the distal initial segment was unaffected by ligation and unlike the case in control rats high levels of immobilin also continued to be secreted into adulthood by the principal cells of the proximal initial segment. Thus in the distal initial segment immobilin secretion is not regulated by luminal factors originating from the testis, while in the proximal initial segment the normal suppression of immobilin that occurs by postnatal day 39 is. Despite ligation, endocytosis of immobilin by clear cells of the distal cauda epididymidis occurred by day 49, indicating that luminal testicular factors are not essential for stimulating the uptake of immobilin by these cells.Conclusions: The results taken together suggest that there are stimulatory and inhibitory luminal testicular factors involved in the regional development of immobilin secretion in the epididymis. There are also immobilin secreting regions in the epididymis, whose secretory development is independent of luminal testicular factors. © 1994 Wiley‐Lis

ISSN:0003-276X    

DOI:10.1002/ar.1092400109

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

年代:1994

数据来源: WILEY

摘要:

AbstractBackground: The leading cause of death and disability in patients suffering from aneurysmal subarachnoid hemorrhage (SAH) is cerebral vasospasm, a persistent, progressive, and often irreversible constriction of cerebral arteries. A wide array of pathological changes occur in cerebral arteries following SAH, with endothelial injury being the earliest and most consistent one. Since intact endothelium modulates many reflexes that influence vascular tone, damage to them may represent a significant contributor to cerebral vasospasm.Methods: Changes in local cerebellar blood flow (LCBF) and pathological alterations in major cerebral arteries were studied and compared in rats at various time intervals following SAH. SAH induced by the subarachnoid injection of 0.3 ml of whole blood. Sham rats received a subarachnoid injection of 0.3 ml of isotonic saline.Results: Except for an immediate but transient decrease, LCBF remained unchanged over a 3 day period following saline injection. Likewise, there were no pathological alterations in cerebral arteries of saline‐injected rats. In contrast, the subarachnoid injection of whole blood produced significant changes in both LCBF and cerebral arteries. Within 30 minutes postblood injection, LCBF became significantly decreased and remained so for 4 hours. However, within 24 hours, LCBF had returned to control levels where it remained for 3 days. Endothelial injury was observed in the basilar and middle cerebral arteries from 30 minutes through 4 hours, the same periods in which LCBF was significantly reduced. Within 24 hours, the time period in which LCBF had rebounded to control ranges, cerebral arteries showed no evidence of endothelial damage and resembled control cells.Conclusion: The results indicate a direct correlation between changes in LCBF and the structural integrity of endothelial cells in the early stages following SAH. The lack of chronically depressed LCBF (after 1 day) may be related to the quick structural repair of endothelium. © 1994 Wiley‐Liss,

ISSN:0003-276X    

DOI:10.1002/ar.1092400110

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

年代:1994

数据来源: WILEY

摘要:

AbstractBackground: Acid cysteine proteinase inhibitor (ACPI, also called cystatin A) is a protein that is present in the epithelial cells of the skin and in the dendritic reticulum cells of lymphoid tissues. In this study the presence and cellular localization of ACPI in the thymus was investigated.Methods: The cellular and topographical location of ACPI was immunohistochemically demonstrated in the normal thymus of man.Results: ACPI was found in the cells of the‐Hassall's corpuscles and in many medullary cells. Most of these cells were epithelial cells, as shown by the results of immunohistochemical cytokeratin and epithelial membrane antigen stainings. Also, some individual cytokeratin negative but S‐100 positive medullary reticular dendritic cells were stained with ACPI.Conclusions: The finding that ACPI is constantly present in the thymus at restricted and specific cellular locations leads to the suggestion that protease inhibitors may play a role in specific thymic functions. © 1994 Wiley‐Lis

ISSN:0003-276X    

DOI:10.1002/ar.1092400111

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

年代:1994

数据来源: WILEY