摘要:

AbstractThe observed fit of bone mass to a healthy animal's typical mechanical usage indicates some mechanism or mechanisms monitor that usage and control the three longitudinal growth, bone modeling, and BMU‐based remodeling activities that directly determine bone mass. That mechanism could be named a mechanostat. Accumulated evidence suggests it includes the bone itself, plus mechanisms that transform its mechanical usage into appropriate signals, plus other mechanisms that detect those signals and then direct the above three biologic activities.In vivostudies have shown that bone strains in or above the 1500–3000 microstrain range cause bone modelling to increase cortical bone mass, while strains below the 100–300 microstrain range release BMU‐based remodeling which then removes existing cortical‐endosteal and trabecular bone. That arrangement provides a dual system in which bone modeling would adapt bone mass to gross overloading, while BMU‐based remodeling would adapt bone mass to gross underloading, and the above strain ranges would be the approximate “setpoints” of those responses.The anatomical distribution of those mechanical usage effects are well known. If circulating agents or disease changed the effective setpoints of those responses their bone mass effects should copy the anatomical distribution of the mechanical usage effects. That seems to be the case for many agents and diseases, and several examples are discussed, including postmenopausal osteoporosis, fluoride effects, bone loss in orbit, and osteogenesis imperfecta.The mechanostat proposal is a seminal idea which fits diverse evidence but it requires critique and exp

ISSN:0003-276X    

DOI:10.1002/ar.1092190104

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

年代:1987

数据来源: WILEY

摘要:

AbstractThere is little information available concerning the effects of functional and therapeutic forces on Sharpey fibers and adjacent bone matrix. In the present study, springs were placed between the left first and second maxillary molar teeth of rats and retained for 1, 2, 3, 4, or 5 days. The right side served as a control. Tissues from sham‐operated, untreated animals were also studied. Maxillae were removed, fractured, rendered anorganic with sodium hypochlorite, and then examined by scanning electron microscopy (SEM). Some tissues were demineralized and examined by high‐voltage electron microscopy (HVEM). Sharpey fibers were studied at the alveolar wall and at the midline of the interdental septum (intra‐septal Sharpey fibers). In 5‐day experimental tissues, SEM showed intra‐septal Sharpey fibers had either a reduced number of, or lacked, unmineralized cores. Unit collagen fibrils in 5‐day tissues viewed by HVEM were densely packed into Sharpey fibers which had no afibrillar areas. Sharpey fibers at the alveolar wall demonstrated no observable changes in morphology or in pattern of mineralization. After 5 days of spring placement, the mean diameters of intra‐septal fibers were significantly less than those at the alveolar wall (p<0.001). The disparity in Sharpey fiber diameters of treated and untreated control animals suggests that untreated controls are essential to the design of studies of rodent tooth movement. This study suggests that orthodontic tooth movement produces changes in the morphology and mineralization patterns of Sharpey fibers which might affect the mechanical strength of the

ISSN:0003-276X    

DOI:10.1002/ar.1092190105

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe patterns of fluorescence associated with maturation ameloblasts of mandibular incisors labeled with 7‐nitrobenz‐2‐oxa‐1,3‐diazole‐phallacidin (NBD‐phallacidin) for the detection of F‐actin were investigated in normal and fluoride‐treated rats. In normal rats, bands of smooth‐ended ameloblasts (SA) exhibited intense fluorescence at their proximal ends only. Bands of ruffle‐ended ameloblasts (RA) exhibited strong fluorescence at their distal ends as well as at their proximal ends. Regional differences in degree of intensity within the bands and between bands were displayed. In the apical part of the RA bands the proximal fluorescence was intense; it then decreased in an incisal direction; and it finally was absent close to the adjacent SA band. The incisal extension of strong proximal fluorescence in RA bands was short in early maturation and long in late maturation. The fluorescence pattern at both ends of the ameloblasts was cyclically repeated throughout the region of ameloblast modulation corresponding to the numbers of SA bands. In rats receiving 113 ppm fluoride in their drinking water for 2 months the number of fluorescence and ameloblast modulation cycles was reduced equally indicating that the cyclic F‐actin localization is a phenomenon related to ameloblast modulation. Electron microscopy revealed that areas of strong fluorescence contained filament bundles, presumably actin filaments, in relation to continuous junctions occluding the interameloblast spaces. Areas of weak or no fluorescence were related to discontinuous macular junctions. The results suggest that the changes in F‐actin distribution correlate well with junctional complex development, and therefore, possible functions related to the interameloblast spaces within the RA bands may be redistributed as the ameloblasts are carried incisall

ISSN:0003-276X    

DOI:10.1002/ar.1092190106

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

年代:1987

数据来源: WILEY

摘要:

AbstractSympathectomy was carried out in 4‐week‐old Sprague‐Dawley rats by unilateral surgical removal of the superior cervical ganglion. Sham‐treated rats served as controls. All rats were injected with tetracycline hydrochloride at surgery as well as 36 hr prior to sacrifice. Rats were killed at 7, 14, or 21 days following sympathectomy. Mandibular periosteal and endosteal surfaces were analyzed by fluorochrome morphometry. Osteoclasts were identified by acid phosphatase staining, and incisor and molar root sockets were analyzed morphometrically. Following sympathectomy, periosteal and endosteal apposition as well as the rate of mineralization were significantly lower. At the same time, a significant increase in the number of osteoclasts per socket as well as in active and inactive bone resorption surfaces was also seen. All parameters, however, returned to normal values 2–3 weeks after sympathectomy. The data provide the first direct quantitative evidence that sympathetic neurons modulate bone resorption and bone remodelin

ISSN:0003-276X    

DOI:10.1002/ar.1092190107

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

年代:1987

数据来源: WILEY

摘要:

AbstractCytochemical and biochemical glucose 6‐phosphatase (G6Pase) activity was examined in brown adipose tissues of normal, cold‐exposed, or starved mice. In addition, G6Pase activity in white adipose tissue and hexokinase activity in brown and white adipose tissues were biochemically measured. In normal animals, the reaction product for G6Pase activity was localized in the endoplasmic reticulum and nuclear envelope of brown adipose cells. The amount of the reaction product increased in cold‐exposed or starved animals. Biochemical G6Pase activity (259.7 ± 48.5 ng Pi/min/mg protein) in brown adipose tissues of normal animals was higher when the value was compared with values of other organs. Biochemical G6Pase and hexokinase activities increased rapidly in brown adipose tissues of cold‐exposed animals, and a close relation was found between activities of the two enzymes. In brown adipose tissues of animals starved for 3 days, biochemical G6Pase activity increased, but hexokinase activity did not change. In white adipose tissues of normal, cold‐exposed, or starved animals, G6Pase activity was very low, although the enzyme activity increased slightly in animals starved for 3 days. The results show that the high G6Pase activity in brown adipose cells probably relates to thermogenesis in cold‐exposed animals and may be concerned with glucose release into the blood in sta

ISSN:0003-276X    

DOI:10.1002/ar.1092190108

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe effects of physical exercise (running) and immobilization by splinting on the number and size of proteoglycan (PG) granules and the diameter of collagen fibers of the articular cartilage were studied with the transmission electron microscope with a stereological method. The lateral tibial condyles of 24 young rabbits were examined. The analysis was carried out in the superficial, middle, and deep zones of uncalcified articular cartilage and also in the pericellular, territorial, and interterritorial regions of each zone. PGs were demonstrated in situ by using en bloc staining with the cationic dye ruthenium red, which binds to negative groups of glycosaminoglycans. Results of the control group showed that there was a large pericellular number of PG granules, and the number of granules tended to increase through cartilage depth. The mean diameter of PG granules was highest in the superficial zone and decreased through cartilago depth. The collagen fibers were thicker in the interterritorial than in the territorial region and their diameters increased from superficial toward the deep zone of uncalcified cartilage. Results of the experimental groups showed that the number of ruthenium‐red‐positive PG granules decreased by 3–46% in all zones and regions after both physical exercise and joint immobilization. On the other hand, the diameter of PG granules increased by 4–42% in all zones and regions in all groups. Collagen fibers in the territorial region of the middle zone were thinner in the exercised and in the splinted knee, while thicker in the contralateral knee to the splinted limb, as compared with the controls. Depending on its degree, mechanical stress or loading of the joint is suggested to have either anabolic or catabolic effects on articular ca

ISSN:0003-276X    

DOI:10.1002/ar.1092190109

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

年代:1987

数据来源: WILEY

摘要:

AbstractIsolated myocytes were prepared from Sprague Dawley rats, golden Syrian hamsters, and Hartley guinea pigs to investigate regional variations in myocyte size. Cell volume (V) was measured with a Coulter Channelyzer, cell length (L) was measured directly, and cross‐sectional area (CSA) was calculated from V/L. Compared to values from the left ventricle (LV), right ventricular L was shorter in the rat (P<.01) and hamster (P<.05) and longer in the guinea pig (P<.01). Guinea pig atrial L was shorter (P<.01) than L in the right ventricle (RV) but did not differ from L in the LV. No significant differences in L existed between endomyocardium, middle myocardium, and epimyocardium of the LV in all three species. In rats and hamsters, myocytes from the RV had smaller V and CSA values (P<.01) compared to any region of the LV. A transmural gradient of cellular dimensions existed in the LV of the rat, but not in hamster, with V and CSA of endomyocardium being largest and epimyocardium smallest (P<.01). Endomyocardial V and CSA were larger (P<.01) than all other regions in the hamster, but the difference was not significant compared to epimyocardial V. In the guinea pig, no significant differences in V existed between RV and LV or between the three LV regions. No pattern of regional differences was seen between ventricular CSA values in the guinea pig. Guinea pig atrial V and CSA values were smaller (P<.01) than those for ventricular myocytes. Therefore, regional differences in cardiac myocyte size vary among different rodent specie

ISSN:0003-276X    

DOI:10.1002/ar.1092190110

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

年代:1987

数据来源: WILEY

摘要:

AbstractPrenatal development of ciliated cells in the human fallopian tube was studied by light and electron microscopy in specimens obtained from 12 fetuses, aged 12–40 weeks. On light microscopy, transverse sections of the ampullary portion of the tube revealed a slit‐like lumen at 12 weeks. The lumen began to fold by 15 weeks, and formed the typical villous structures by 31 weeks. On electron microscopy, the epithelial cells contained a large number of sub‐ and supranuclear glycogen particles until 18 weeks and an occasional solitary cilium. At 20–22 weeks, instead of glycogen particles, cytoplasmic organelles such as mitochondria, rough endoplasmic reticula and Golgi apparatus were well developed, and some cells possessed cilia with a 9 + 2 microtubular structure. Between 22 and 31 weeks, ciliated cells were sporadically observed. At 31 weeks, the epithelial cells accumulated a large number of sub‐ and supranuclear glycogen particles. Afterwards, numerous ciliated cells with well‐developed cytoplasmic organelles were observed

ISSN:0003-276X    

DOI:10.1002/ar.1092190111

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

年代:1987

数据来源: WILEY

摘要:

AbstractTuft cells are present in most columnar epithelia derived from endoderm including the small intestine. They are characterized by long, wide apical microvilli and an extensively developed cytoplasmic tubulovesicular system. We examined in detail the structural features of the apical plasma membrane of small intestinal tuft cells from adult guinea pigs, rats, and adult and suckling mice with freeze‐fracture and conventional transmission electron microscopy methods and utilized cationized ferritin and horseradish peroxidase as tracers to determine whether tuft cells endocytose macromolecules. The microvillus membrane of intestinal tuft cells has few P‐face intramembrane particles, displays little alkaline phosphatase activity, and is highly enriched in cholesterol. Tuft cell tight junctions resemble those of absorptive cells in strand count and strand‐to‐strand crosslinks but, unlike those of absorptive cells, they display many abluminal free‐ending strands. Tuft cells of adult and suckling mouse intestine show no evidence of internalization of cationized ferritin or, in suckling mice, uptake of horseradish peroxidase. We conclude that the microvillus membrane of small intestinal tuft cells is protein poor but cholesterol‐rich and that small intestinal tuft cells do not endocytose macromolecules in bulk from the intes

ISSN:0003-276X    

DOI:10.1002/ar.1092190112

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

年代:1987

数据来源: WILEY

摘要:

AbstractGlobule leukocytes, dispersed throughout the respiratory epithelium as single cells, were isolated from rat trachea and were enriched by centrifugation on a discontinuous Percoll gradient. The isolation and enrichment procedure yields a cell fraction containing 75% globule leukocytes. The cell viability, as assessed by trypan blue exclusion, was at least 98%. Cells were maintained in short‐term culture without apparent loss of viability and enzyme activity. The isolated globule leukocytes seem not to express significant levels of cytotoxicity against51Cr‐labeled YAC‐1 target cells. In fixed cytocentrifuge smears, globule leukocytes appear as more or less rounded to oval cells with a low nucleo‐cytoplasmic ratio and with a mostly eccentrically located nucleus. Characteristic intracytoplasmic granules are stained with toluidine blue, alcian blue, and May‐Grünwald‐Giemsa stains. The applied cytochemical methods demonstrate that tracheal globule leukocytes are stained for alpha naphthyl acetate esterase and naphthol‐AS‐D‐chloroacetate esterase, but not for alpha naphthyl butyrate esterase, N‐acetyl‐DL‐phenylalanine‐B‐naphthyl esterase, and endogenous peroxidase. Isolated rat peritoneal cells were used as positive control cells for the cytochemical reactions. The obtained cytochemical profile of tracheal globule leukocytes is compared to the known cytochemical profile of intestinal globule leukocytes and large granular lymphocytes. The cytochemical dissimilarities between tracheal and intestinal globule leukocytes may suggst that both kinds of globule leukocytes represent a different form of the same cell type or even different cell types.The cytochemical pattern of tracheal globule leukocytes is closely related to that of large granular lymphocytes, which have been postulated as a possible s

ISSN:0003-276X    

DOI:10.1002/ar.1092190113

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

年代:1987

数据来源: WILEY