摘要:

AbstractBackground: The Harderian glands of female Syrian hamsters contain very high concentrations of protoporphyrin (in the range of μg per mg of tissue) which accumulate in the tubulo‐alveoli of the gland. We have studied the process of synthesis, accumulation, and secretion of this cyclic compound by the secretory cells of the hamster Harderian glands.Methods: The animals used were female Syrian hamster of 15, 35, 75, 180, and 360 days of age. Items first examined were (1) percentage of the “clear cells,” (2) area occupied by intraluminal porphyrins, and (3) histological characteristics of “clear cells” by light and transmission electron microscopy (TEM). In a second study the total content of porphyrins was determined. Finally, the levels of mRNA for the enzyme aminolevulinate synthase (ALV‐S) were measured.Results: In the glands of female hamsters, both the tissue concentration and the intraluminal area occupied by protoporphyrin correlate with the appearance of a special type of cell (clear cells) which show signs of cell degeneration. In addition, the expression of the gene for ALV‐S, which is the limiting enzyme in porphyrin production, also parallels the relative number of clear cells. Analyzed under TEM, these clear cells display dilated mitochondria and short and swollen endoplasmic reticulum cisternae. In a late phase of necrosis, the nuclear envelope appears disorganized with scarce chromatin. The mitochondria undergo complete destruction, resulting in electron‐dense bacillar formations which progressively coalesce in large and dense areas of protoporphyrin. The cell dies after this accumulation, being secreted by a “cytogen” mechanism.Conclusions: In view of our results, the Harderian gland of female Syrian hamster may provide a useful model for the study of the mechanism by which the anomalous accumulation of protoporphyrin induces cell damage in human protoporphyria. ©

ISSN:0003-276X    

DOI:10.1002/ar.1092390402

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

年代:1994

数据来源: WILEY

摘要:

AbstractBackground: There is not universal agreement on the existence of the extracellular pathway from the pulp along the odontoblast layer to the predentin.Method: To confirm this pathway, the architecture of collagen fibrils in the rat incisor dentin and pulp, especially in the odontoblast layer of the lateral (periodontal ligament) sides of the tooth, was demonstrated in the present investigation using scanning electron microscopy of the maceration method for collagen networks.Results: Numerous collagen bundles were observed in the odontoblast layer in the mature odontoblast region which, except for the young odontoblast region, comprises the major portion of the incisor. The collagen bundles went from the pulp, through the odontoblast layer, and were woven into the collagen network of the predentin. The meshwork structure was composed of fine secondary fibrils among these collagen bundles. The surface of the predentin contained many oval‐shaped holes which were surrounded by collagen fibrils. Fracturing the dentin longitudinally relative to the dentinal tubules revealed that the arrangement of the collagen fibrils at the surface of the tubules was either circular or oblique. In the young odontoblast region, i.e., the thin portion from the apical end of the incisor where the mineralization of the dentin does not occur and where the height of the odontoblasts was less than 30 μm, many thick bundles composed of thick collagen fibrils ran straight from the pulp to the predentin through the odontoblast layer and fanned out into the collagen network of the predentin. These thick bundles might correspond to the so‐called “von Korff fibers.” The distribution of collagen fibrils in the pulp was random except on the surface of the blood vessels where the fibrils comprised two sheets of collagen: the inner sheet which coursed longitudinally to the long axis of the vessel, and the outer sheet which ran transversely.Conclusion: It was considered that the fluid in the pulp could flow to the predentin along the collagen fibrils through the tight junction between the odontoblasts. © 1994 Wiley

ISSN:0003-276X    

DOI:10.1002/ar.1092390403

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

年代:1994

数据来源: WILEY

摘要:

AbstractBackground: A substantial part of the endocrine pancreas has been previously described as being located either close to the excretory ducts as small clusters of endocrine cells and as Islets of Langerhans, or associated with the ducts as single endocrine cells scattered through the ductal epithelium.Methods: Four Wistar white adult rats were sacrificed and perfused via the thoracic aorta with 2.5% glutaraldehyde. After the usual treatment for the transmission electron microscopy, pieces of pancreas were sectioned consecutively for light microscopy. Consecutive ultrathin sections were performed in the most interesting cases.Results: The observations previously reported were confirmed. In addition, a new endocrine arrangement was detected and described as buds of endocrine cells (mainly B‐cells) protruding from the ductal epithelium into the surrounding tissue.Conclusions: The authors propose to explain the endocrine buds as components of the gastro‐entero‐pancreatic system or as a stage of an endocrine pancreatic “neo‐histogenesis” occurring in the adult rat pancreas. © 1994 Wil

ISSN:0003-276X    

DOI:10.1002/ar.1092390404

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

年代:1994

数据来源: WILEY

摘要:

AbstractBackground: Micro‐hardness investigations have shown that rat pups nursed by mothers on a low calcium diet and weaned with the maternal calcium‐deficient diet develop hypomineralized enamel. The inorganic and organic components of this enamel, their relationships, and their changes after return to normal diet have been studied by light and electron microscopy.Methods: The maturation zone of incisor enamel has been studied in: (1) rats nursed for 20 days by mothers on a low calcium diet and weaned for 30 days with the same diet (E1 enamel); (2) rats that after the calcium‐deficient diet were fed normal diet for 10 days (E2 enamel); and (3) rats nursed for 20 days by mothers on a normal diet and weaned for 30 days with a normal diet (controls).Results: The results showed that E1 enamel was hypomineralized, as noted by its Azure II‐Methylene blue stainability in undecalcified sections, its light staining with the von Kossa method, and its ultrastructure. E1 crystallites, although present throughout the whole enamel, were thinner than those of E2 enamel, which were similar to those of controls. E1 interrod crystallites were thicker in the intermediate than in the dentinal zone and were thicker than rod crystallites. Organic matrix was present throughout the whole E1 enamel. Its organic components (crystal ghosts) had the same shape, arrangement, and organization as those of inorganic crystallites. Crystal ghosts were greatly reduced in E2 enamel and in controls.Conclusions: The results lead to the conclusions that: (1) E1 enamel is hypomineralized, and its degree of calcification is restored by return to a normal calcium diet; (2) intra‐ and interprismatic calcification occurs in a different way; (3) crystallite thickness is initially greater in dentinal than in the superficial zone and is reversed as crystallite growth is completed; and (4) loss of enamel proteins is necessary for completion of crystallite growth and not for crystallite formation. © 1994 Wiley

ISSN:0003-276X    

DOI:10.1002/ar.1092390405

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

年代:1994

数据来源: WILEY

摘要:

AbstractBackground: Examination of a simple skeletal cantilevered beam‐like bone (artiodactyl calcaneus) suggests that regional differences in strain magnitude and mode (tension vs. compression) reflect regional adaptation in the structural/material organization of bone. The artiodactyl (e.g., sheep and deer) calcaneus has a predominant loading condition typified by the unambiguous presence of prevailing compressive and tensile strains on opposite cortices. Bone habitually loaded in bending may accommodate regional disparities in loading conditions through modifications of various aspects of its organization. These include overall bone build (gross size and shape), cross‐sectional shape, cortical thickness, and mineral content.Methods&Results: Cross‐sections taken along the calcaneal body exhibited cranial‐caudal elongation with the compression (cranial) cortex thicker than the tension cortex (P<0.01). Mineral content (ash fraction) was significantly greater in the compression cortex (P<0.01), averaging 6.6% greater than in the tension cortex. Strong positive correlations were found between mineral content and section location in both the tension (r2= 0.955) and compression (r2= 0.812) cortices. These correlations may reflect functional adaptations to the linear increases in stress that are known to occur in the distal‐to‐proximal direction in simple, unidirectionally loaded cantilevered beams. According to engineering principles, the roughly triangular transverse cross‐sectional geometries and thicker compression cortex are features consistent with a short cantilevered structure designed to resist unidirectional bending.Conclusions: Known differences in mechanical properties of bone in tension vs. compression suggest that these regional differences in cortical thickness and mineralization may be related to differences in strain mode. These structural/material dissimilarities, however, may be related to regional variations in strain magnitude, since bending and axially directed stresses in a simple cantilevered structure produce greater strain magnitudes in the compression domain. It is possible that the superimposed habitual strain magnitudes enhance strain‐mode‐specific adaptive responses. We hypothesize that these structural/material differences reflect the capacity of bone to process local information and produce a regionally heterogeneous organization that is appropriate for prevailing loading conditions. © 1994 Wiley‐Liss, Inc.This article is a US Government work and, as such, is in the public dotmain in the Unit

ISSN:0003-276X    

DOI:10.1002/ar.1092390406

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

年代:1994

数据来源: WILEY

摘要:

AbstractBackground: It has been hypothesized that bone has the capacity to accommodate regional differences in tension and compression strain mode and/or magnitude by altering its osteonal microstructure. We examined a simple cantilevered bone to determine whether regional differences in particular strain‐related features are reflected in the microstructural organization of compact bone.Methods&Results: The artiodactyl (e.g., sheep and deer) calcaneus has a predominant loading condition which is typified by prevailing compressive and tensile strains on opposite cortices, and variations in strain magnitudes across each of these cortices. Microscopic examination showed osteon density and cortical porosity differences between tension (caudal) and compression (cranial) cortices, averaging 11.4% more osteons in the compression cortex (P<0.01) and 80.2% greater porosity in the tension cortex (P<0.01). There is 43.5% more interstitial bone in the compression cortex (P<0.01). Osteons in the compression cortex also have smaller areas in contrast to the larger area per osteon in the tension cortex. Although no definite transcortical gradient in osteonal density or cortical porosity is found, fractional area of interstitial bone is largest and osteon population density is lowest in the endocortical regions of both tension and compression cortices. The endocortical regions also have greater porosity than their corresponding middle and pericortical regions (P<0.01).Conclusions: These osteonal microstructure and cortical porosity differences may be adaptations related to regional differences in strain mode and/or strain magnitude. This may be related to the disparity in mechanical properties of compact bone in tension vs. compression. These differences may reflect a capacity of bone to process local and regional strain‐related information. © 1994 Wiley‐Liss, Inc.This article is a US Government work and, as such, is in the public dotmain in the United states of A

ISSN:0003-276X    

DOI:10.1002/ar.1092390407

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

年代:1994

数据来源: WILEY

摘要:

AbstractBackground: The length‐force curve of mammalian skeletal muscle is often wider than expected on basis of the optimum length of the muscle fibers. Two important effects may explain this discrepancy: muscle pennation and distribution of fiber lengths in the muscle. In the present study of the effects of a Gaussian distribution of fiber lengths on muscle length‐force characteristics were investigated in rat gastrocnemius medialis.Methods: Fiber length‐force characteristics and parameter values of the Gaussian distribution were derived from literature data (Stephenson et al., 1989, J. Physiol.,410:351–366; Heslinga and Huijing, 1990, J. Morph.206:119–132; Zuurbier and Huijing, 1993, J. Morphol., 218:167–180). Three different constructions of the distribution model were compared with experimental data. Pennation effects were incorporated in the model.Results: Two constructions gave reasonably good results: (1) the model with a fiber optimum distribution, in which fibers acted at the same absolute length at a given muscle length; (2) the model in which fiber optimum length was uniform but absolute length at a given muscle length was distributed.Conclusions: In rat gastrocnemius medialis, the magnitude of the effects of these distributions is similar to pennation effects. The current results help to explain the relative wide working range of skeletal muscles in human movement and the differences in specific muscle tension as affected by muscle type, species, and age. © 1994 Wil

ISSN:0003-276X    

DOI:10.1002/ar.1092390408

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

年代:1994

数据来源: WILEY

摘要:

AbstractBackground: Glutathione S‐transferases (GSTs) are a family of isozymes that catalyze the conjugation of the tripeptide, glutathione, to various electrophilic compounds. The major GST in the pi class is GST‐P, a homodimer of the Yfsubunit, also known as Yp or rat subunit 7. This subunit is found in high concentrations in the epididymis and has recently been immunolocalized within epithelial principal and basal cells of the epididymis.Methods: In the present study we examine in groups of animals fixed in Bouin's fixative for light microscopy and in 4% paraformaldehyde and 0.5% glutaraldehyde in phosphate buffer for electron microscopy, the pattern of immunostaining for the Yfsubunit of GST‐P in the testis, efferent ducts and epididymis at various ages after birth.Results: In the epididymis, on postnatal days 7 and 15, an immunoperoxidase reaction was localized exclusively to the apical and supranuclear regions of the undifferentiated columnar epithelial cells of the entire epididymis. By day 21, a dramatic change had taken place. In the initial segment, intermediate zone and proximal caput epididymidis, the columnar cells showed a distinct checkerboard‐like staining pattern with cells ranging from being intensely reactive to unreactive. In contrast, principal cells of the distal caput, corpus, and proximal cauda epididymidis were weakly reactive. By day 28 the ratio of reactive to unreactive cells in the initial segment, intermediate zone, and proximal caput epididymidis was higher. By day 39, the differentiated columnar epithelial cells, referred to as principal cells, took on their adult staining pattern in the proximal and middle areas of the initial segment as well as the corpus and proximal cauda epididymidis where they were slightly reactive; in the distal initial segment they were strongly reactive. At day 49, principal cells in the intermediate zone and proximal caput became intensely reactive, while showing a distinct checkerboard‐like staining pattern in the distal caput; similar observations were made for tissues taken from 56 and 90‐day‐old animals. Basal cells also showed a variable staining pattern in the different epididymal regions as a function of age. At day 21, when they first appeared, they were unreactive except for an occasional reactive cell in the corpus region. At day 28, only in the corpus epididymidis were many basal cells seen to be reactive. By day 39 the more numerous basal cells of the corpus and proximal cauda epididymidis were intensely reactive and remained so into adulthood. In these regions, basal cells appeared as dome‐shaped cells (days 21, 28, 39), but then gradually flattened out and exhibited processes (days, 49, 56, adults) which collectively appeared to envelop the base of each tubule in a mesh‐like network. The change in basal cell shape in each region coincided with the arrival of fluid and spermatozoa into the lumen (corpus day 49, proximal cauda day 56). In other epididymal regions, basal cells at day 28 were mostly unreactive. However, there was a gradual increase in the number of reactive basal cells of these regions between day 39 and 56.Conculusions: The present results thus demonstrate a dramatic change in the immunostaining pattern for the yfsubunit of GAS‐p during postanatal development for both principal and basal cells along the epididymis. Such results suggest that different factors play a role in the regulation of the expression of the yfprotein, not only in different epididymal regions, but also in different cell types during postanatal development. ©

ISSN:0003-276X    

DOI:10.1002/ar.1092390409

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

年代:1994

数据来源: WILEY

摘要:

AbstractBackground: A significant part of the liver volume consists of regions in which hepatocytes are in close contact with large branches of the afferent (portal vein) or efferent (hepatic vein) vessels. As most studies have addressed zonation of gene expression around the parenchymal branches of the portal and hepatic vein only, the patterns of gene expression in hepatocytes surrounding larger vessels are largely unknown.Methods: For that reason, we studied the patterns of expression of the mRNAs and proteins of the pericentral marker enzymes glutamine synthase, ornithine aminotransferase, and glutamate dehydrogenase and the periportal marker enzymes phosphoenolpyruvate carboxykinase and carbamoylphosphate synthase in the rat liver, in relation to the branching pattern of the afferent and efferent hepatic veins with immuno and hybridocytochemical techniques. These patterns of expression were compared with those seen in mouse, monkey, and pig liver.Results: The distribution patterns of the genes studied appear to reflect the “intensity” of the pericentral and periportal environment, glutamine synthase and phosphoenolpyruvate carboxykinase requiring the most pronounced environment, respectively. The patterns of gene expression around the large branches of the portal and hepatic vein were found to be related to the parenchymal branches in the neighbourhood of these large blood vessels. Only the cells of the limiting plate retain their periportal and pericentral phenotype for those marker enzymes that do not require a pronounced periportal or pericentral environment to be expressed. GS‐negative areas in the pericentral limiting plate appear to correlate with a local absence of draining central veins, and become more frequent and extensive around the larger branches of the hepatic vein.Conclusions: The similarity of the observed patterns of gene expression of the genes studied in mouse, rat, monkey, pig, and man suggests that they reflect a general feature of gene expression in the mammalian liver. A comparison of mouse, rat, pig, and human liver suggests that the presence of glutamine synthase‐negative areas reflects the branching order of the efferent hepatic blood vessel. © 1994 Wiley

ISSN:0003-276X    

DOI:10.1002/ar.1092390410

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

年代:1994

数据来源: WILEY

摘要:

AbstractBackground: The respiratory submucosal glands are a major source of secretions in the airway. Human submucosal laryngeal glands have been scarcely studied, with no works existing about their ultrastructure and histochemistry.Methods: Samples of epiglottis, ventricle, false vocal folds and true vocal folds were fixed in 10% buffered formalin for histochemical study with conventional and carbohydrate lectin histochemistry. Other samples were fixed in 2.5% glutaraldehyde and conventionally processed for transmission electron microscopy.Results: The human submucosal laryngeal glands are composed of serous tubules; mucous tubules; collector duct; and final portion of this duct. The serous cells showed sialosulphomucins and affinity for WGA and Con‐A lectins. With a previous treatment with neuraminidase, they also labelled with PNA. The mucous cells contained sialosulphomucins and showed affinity for WGA and DBA lectins in the samples proceeding from blood group A, and for WGA, UEA‐I and LTA with those from blood group O. Ultrastructurally, the serous cells presented a wide variety of granules, cells in which seromucous granules predominated. The mucous cells presented larger‐sized granules which were very electron‐lucent. The collector duct was composed of mitochondria‐rich cells and basal cells. A cell which we have termed “intermediate” was identified in the transition zone between the mucous tubules and the collector duct, and in the final portion of the collector duct. It had morphological characteristics as if it were a transition between a goblet cell and collector duct cell. Some nerve endings with cholinergic and peptidergic vesicles were found among the myoepithelial cells.Conclusions: These glands presented some histological differences from the bronchial glands, the mucous secretion was related to the blood group antigens, and the serous cells showed a wide variability in their secretory granules, many of them being of a seromucous type. © 1994 W

ISSN:0003-276X    

DOI:10.1002/ar.1092390411

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

年代:1994

数据来源: WILEY