摘要:

AbstractThis paper presents ultrastructural features of the contact region between particular tooth germs and Meckel's cartilage prior to, during, and after initial resorption of the perichondral bone and of the cartilage in the cichlidsHemichromis bimaculatusandAstatotilapia burtoni. Imminent resorption opposite such teeth is announced by the presence, in this region, of a particular cell type, considered to be a stage in the cytodifferentiation of osteoclasts. Slightly later, an osteoclast with typical ruffled border is seen to open a fenestra in the perichondral bone which surrounds Meckel's cartilage. Although the action of the osteoclast is directed primarily towards the bone, it may also affect, to a much lesser extent, the underlying uncalcified cartilage. Typically, fibroblast‐like cells invade the resorption cavity along with the osteoclast; the tooth germ soon follows. Capillaries are seen to invade the cartilage only at a later stage when a large cavity has been established. It is proposed that the fibroblast‐like cells may have a dual function: degradation of cartilage and deposition of new bone. Although these processes are normally limited to the area surrounding tooth germs at specific loci, tooth germs in other positions may sometimes be seen to invade the cartilage. They do so either passively, because of the existence of such a cavity, or as a result of their own resorption‐inducing activity. Whatever the mechanism, attachment bone is being deposited within the erosion cavity and on the surface of the exposed perichondral bone. The stimuli possibly eliciting resorption of Meckel's cartilage are discussed. It is hypothesized that pressure exerted by the growing tooth germ may stimulate the osteoblasts covering the bone surface and, in this way, provoke osteoclastic bone resorption. © 1992 Wiley‐L

ISSN:0003-276X    

DOI:10.1002/ar.1092340102

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe nuclear envelope of polytene nuclei of salivary glands ofDrosophila melanogasterdisplays modifications consisting of nuclear envelope invaginations (NEI) and evaginations (NEE). Ultrastructural analyses combined with three‐dimensional reconstruction and cytochemistry show that NEI are bounded by a single membrane and that they may arise as invaginations of the inner nuclear membrane. NEI extend deeply into the nucleus. The lumens of NEI may collapse resulting in membranous sheets which may combine with those arising from adjacent NEI to form intranuclear structures resembling annulate lamellae. All NEI are associated with NEE. In contrast to NEI, NEE are enclosed in a double membrane morphologically identical to the nuclear envelope. While NEI and NEE share wheat germ agglutinin binding properties with the nuclear envelope, they differ in their ability to localize lanthanum. Pore annuli of NEI display complete lack of lanthanum binding, while those of NEE exhibit minor deposition of this cation. In contrast, pore annuli of the nuclear envelope are specifically and significantly decorated by lanthanum. A conceptual model based on the results obtained suggests that NEI are formed by invaginations of the inner nuclear membrane, together with accompanying modifications of pore complexes. © 1992 Wiley‐Liss,

ISSN:0003-276X    

DOI:10.1002/ar.1092340103

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe characteristics of the lymphatic vessel endothelial wall have been investigated in human normal and inflamed dental pulps. In normal pulps the endothelial wall is characterized by the presence of micropinocytotic vesicles and intraparietal channels. In the inflamed pulpal tissue, where an increase in interstitial fluid pressure occurs, the distended endothelial wall presents open junctions between endothelial cells and the openings of the intraparietal channels. Moreover the micropinocytotic vesicles disappear. The cytoplasm of the endothelial cells is characterized by the presence of numerous Weibel‐Palade bodies, which increase in number in the dilated vessels. In the fibrillar apparatus surrounding the lymphatic vessel wall collagen fibrils are the prevalent component, while elastic fibers are not present.The different morphological properties of the lymphatic vessels are compared and discussed with regard to the variation of the functional conditions of the tissue. © 1992 Wiley‐Liss,

ISSN:0003-276X    

DOI:10.1002/ar.1092340104

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

年代:1992

数据来源: WILEY

摘要:

AbstractMost marsupials and some placental mammals possess enamel characterized by the presence of tubules, and the cellular origin of these structures has been the subject of a number of previous studies (See, for example, Lester, 1970; Azevedo and Goldberg, 1987). In the present report, tooth germs of the American opossum were examined to determine the structure and composition of enamel tubules during development and to analyze the enamel matrix relative to that of placental mammals with atubular enamel. For this purpose, tissues prepared by aqueous (decalcified and undecalcified) and anhydrous (undecalcified) methods were investigated by conventional transmission (TEM) and high voltage electron microscopy (HVEM), as well as by electron probe x‐ray microanalysis (EPMA), selected‐area electron diffraction (SAED), and electron spectroscopic imaging (ESI).Results indicate that most enamel tubules in the opossum begin as cytoplasmic remnants of Tomes' processes of ameloblasts. During development of the matrix, some of the tubules do not appear to be continuous throughout the prismatic layer. Sulfur is detectable around the lumen of the tubule in decalcified sections by EPMA and in and around the tubule by ESI. Calcium/phosphorus (Ca/P) molar ratios of the mineralizing matrix are generally higher than those found in enamel of other mammals and appear to decrease rather than increase with enamel maturation. The summary of data indicates the presence of sulfated glycoproteins or proteoglycans in this tissue, specifically around enamel tubules. Calcium and phosphorus are also present within the tubules, with the sulfated groups possibly binding calcium to prevent mineralization of the enamel tubules themselves. © 1992 Wiley‐Lis

ISSN:0003-276X    

DOI:10.1002/ar.1092340105

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

年代:1992

数据来源: WILEY

摘要:

AbstractWe have measured capillary distribution in costal and crural canine diaphragm using two methods: histochemical processing and perfusion fixation. Each of 18 dogs was deeply anesthetized, the abdomen opened, and the left inferior phrenic artery cannulated. The animal was heparinized and overdosed with pentobarbital. The right hemidiaphragm was frozen, either postexcision (Protocol 1) or intact with no preload (Protocol 2), for histochemical processing. The left hemidiaphragm was fixed by perfusion in situ using 2% glutaraldehyde, either with preload (Protocol 1) or without (Protocol 2). Costal and crural regions of each hemidiaphragm were sampled for analysis. Frozen samples were sectioned and processed for acid‐stable (pH 4.0) ATpase activity; perfusion‐fixed samples were postifixed, stained, embedded in Epon, and sectioned. Measurements were made using a digital imaging system. We found that muscle fibers had smaller cross‐sectional areas in costal than in crural diaphragm; capillary‐to‐fiber ratio (C:F) did not differ by region and regional differences in capillary density could be attributed to differences in fiber size. Results depended critically on methodology. In perfusion‐fixed muscle, fiber area was less, C:F was greater, and capillary density was greater than in histochemically‐processed tissue. We conclude that capillary distribution is similar in costal vs. crural diaphragm and that perfusion fixation identifies capillaries more effectively than histochemistry. © 1992 W

ISSN:0003-276X    

DOI:10.1002/ar.1092340106

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

年代:1992

数据来源: WILEY

摘要:

AbstractIn clinical practice, repaired tendocalcaneus (Achilles tendon) ruptures are often protected in immobilization casts for 4 weeks in the fully plantar flexed position and for up to another 4 weeks after returining the ankle to joint neutral. Moderate to severe muscle atrophy occurs within 4 weeks of immobilization in plantar flexion, but it is not known if this atrophy is minimized or reversed following restoration of joint neutral position. We tested the hypothesis that the extent of atrophy could be reduced by returning the ankle to joint neutral after 4 weeks of immobilization. Eighteen rabbits were anesthetized, and their right hindlimbs were casted with the knee flexed 90° and the ankle fully planter flexed. Three animals each were studied after 3, 4, 6, or 8 weeks of immobilization. After 4 weeks of immobilization, the immobilization casts of the remaining six rabbits were modified to reture the ankle to joint neutral for another 2 or 4 weeks. For muscle studies, the animals were anesthetized, and the soleus (SOL), plantaris (PLN), and gastrocnemius (GST) muscles were removed and weighed; the SOL and PLN were quick frozen and processed for histochemical fiber typing and fiber cross‐sectional area measurement. All three muscles showed significantly reduced muscle weight to body weight ratios after 3 weeks of immobilization. SOL was the most affected, and GST was least affected. There was no significant further atrophy through 8 weeks of immobilization. The atrophy corrolated with a significant reduction of mean fiber area (MFA) for Types I, IIo, and IIc fibers in SOL and PLN. In PLN, Type IIg fiber area was not significantly reduced. MFAs of fibers of SOL and PLN muscles that were lengthened by returning to ankle joint neutral for 2 or 4 weeks were not different from those from those of limbs kept at planter flexion for 6 or 8 weeks. These data indicate that atrophy had reached a near‐maximal extent within 4 weeks and that subsequent lengthening of the muscles did not reverse the atrophy. © 1992 Wiley‐Li

ISSN:0003-276X    

DOI:10.1002/ar.1092340107

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

年代:1992

数据来源: WILEY

摘要:

AbstractA low dose of Cyproterone acetate (CPA; 1 mg/kg body weight/day for 70 days) was administered to adult male rhesus monkeys to assess its effects on testicular and epididymal structure and function in a nonhuman primate species. CPA caused extensive degenerative changes in morphology of seminiferous, efferent duct, and epididymal epithelia, including decrease in diameter of seminiferous and epididymal tubules and their lumen, height of epididymal epithelium, and an increase in intertubular connective tissue. The protein profile of spermatozoa showed alterations during their epididymal transit in control and CPA‐treated monkeys. In CPA‐treated animals, 19 polypeptides were acquired and nine were eliminated during epididymal transit in contrast to acquisition of 12 and loss of 14 polypeptides in control animals. Treatment with CPA also resulted in the appearance of 14 new polypeptides in epididymal cytosol and luminal fluid, probably of lysosomal origin. The protein pattern of caput and cauda epididymal tubule cytosol, maintained in organ culture and exposed to 100 μM CPA for 3 days, showed absence of eight polypeptides.These results indicate that even at the low dose used in this study, CPA has caused spermatogenic arrest, degenerative changes in the epididymal structure, and alterations in epididymal and sperm protein profile. Suppression of serum testosterone levels indicates the need for androgen supplementation if CPA is to be used for male contraception. © 1992 Wiley‐Li

ISSN:0003-276X    

DOI:10.1002/ar.1092340108

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

年代:1992

数据来源: WILEY

摘要:

AbstractApproximately 700Abrothrix longipiliswere trapped in Argentina, and their reproductive organs were studied. Some were kept briefly in captivity. Males have the same body length as females but are 8% heavier. Sexually immature males are shorter and lighter than breeding males of the same age. Few individuals in the wild live as long as two years. All overwintering males come into breeding condition in the spring and become infertile in the autumn. All overwintering females have open vaginas in the spring, and most undergo several infertile ovulatory cyles, probably without copulating, before they become pregnant. Corpora lutea of the sterile cycles accumulate; there may be as many as 28 in a pair of ovaries. The average number of ova shed per cycle is 4.66; average litter size is 3.85. Ovulation is spontaneous. There is postpartum ovulation and fertilization without intervening sterile cycles but with maintenance of old corpora lutea.Unusual architecture of the penis and vagina may result from unusual timing of hormone production during development, and the disjunction of ovulation and fertilization may similarly result from hormonal heterochrony at the beginning of the breeding season. The apparently nonadaptive wastage of ova in sterile cycles may be a novel example of kin selection. © 1992 Wiley‐Liss, I

ISSN:0003-276X    

DOI:10.1002/ar.1092340109

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe lungs of the polar fox and dog have the typical form and lobular structure characteristic of beasts of prey. Both display secondary fusion of the cranial and middle lobes in the left lung, but this is more extensive in the fox. A consistent relationship between the beast body mass and the mass and volume of the lungs is present. The relative weight of dog lungs independent of body size (weight index) is 1.7 times that of the polar fox. In the latter the parenchyma is much more subdivided than in the dog. There are 23 segments per lung pair in the polar fox, compared to 19 in the dog. Although these are of unequal size throughout the lungs of both species, corresponding segments in the fox are about half as large as those in the dog. The greater segmentation of polar fox lungs may be of assistance in restricting the spread of inflammatory processes. © 1992 Wiley‐Liss, I

ISSN:0003-276X    

DOI:10.1002/ar.1092340110

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

年代:1992

数据来源: WILEY

摘要:

AbstractTo evaluate further the role of type II alveolar epithelial cells in primate lung development, lungs of fetal (46 to 155 days gestational age [DGA]), postnatal, and adult rhesus monkeys were investigated with antibodies against surfactant protein A (SP‐A), Alcian blue (AB) staining, and periodic acid‐Schiff (PAS) staining with/without alpha‐amylase pre‐treatment.In adult and postnatal lungs, type II cells (cuboid shape; large, roundish nucleus) displayed a unique cytoplasmic staining for SP‐A. In prenatal lungs, a low‐columnar to cuboid type of cell with a large, roundish nucleus was first detectable by 62 DGA. It was the only cell type to line the distalmost tubules or buds of the prospective respiratory tract. It exhibited (initially partial) cytoplasmic staining for SP‐A. AB and PAS stainings showed the presence of acid glycoconjugates and large apical and/or basal glycogen fields. After 95 DGA, the lining of the distal respiratory tract additionally displayed flatter cells with immunoreactivity for SP‐A and non‐reactive zones. Columnar epithelium (pseudostratified or simple) never stained for SP‐A.We conclude that morphologically identifiable type II cells first appear in fetal rhesus monkey lungs by 62 DGA (pseudoglandular period). The cells may already synthesize surfactant and extracellular matrix components. They generate type I cells, and thus the entire pulmonary acinus lining. These conclusions for the rhesus monkey fully agree with our earlier conclusions for another primate, the human, and for rodents. However, as presently shown, primates differ greatly from rodents with respect to the timing of type II cell differentiation (at 29–38% versus 73–75% of gestation or at 22–25% versus 48–49% of prenatal lung developme

ISSN:0003-276X    

DOI:10.1002/ar.1092340111

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

年代:1992

数据来源: WILEY