摘要:

AbstractTissue obtained from young dogs was fixed in buffered aldehydes by vascular perfusion or direct immersion. Selected hearts were maintained in modified mammalian Ringer's solution for three to five minutes prior to fixation. The chambers of the heart and related valves were exposed by dissection and prepared by routine techniques for observation by scanning electron microscopy (SEM). Subsequent to SEM studies, selected specimens were embedded in Epon 812 and sectioned for transmission electron microscopy (TEM).The cardiac endothelium, when fixed immediately in buffered aldehydes, presents an essentially invariable surface throughout the interior of the heart. The predominant nuclear bulges and attenuated peripheral plasmalemma are consistently smooth, with occasional marginal ruffles, scattered microvilli and small blebs. Apart from the higher population of nuclear bulges on valvular surfaces, local variations in SEM of endocardium occur in response to the various stages of systole and diastole encountered. These physiological changes do not produce microappendages.Immersion for three to five minutes in (Chenoweth's) Ringer's solution, prior to fixation, produces a substantial population of microappendages. The cellular surface acquires a swirled appearance erupting in microvilli, blebs and ruffles. These exhibit considerable pleomorphism.There is great lability of the endocardial surface in response to a classic “holding solution” widely used in preparatory techniques. In preparing soft tissues for SEM caution must be used if physiological “holding solutions” are used prior to f

ISSN:0002-9106    

DOI:10.1002/aja.1001420202

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

年代:1975

数据来源: WILEY

摘要:

AbstractThe existence of two classes of spermatogonial stem cells in the rat testis, i.e., reserve type A0spermatogonia and renewing, types A1‐A4spermatogonia, postulated by Clermont and Bustos‐Obregon (′68), was reexamined in a quantitative analysis of type A spermatogonia in both whole mounts of tubules and in radioautographed sections of testes from animals killed at various times, up to 26 days, after one or multiple injections of3H‐thymidine.The cell counts obtained from whole mounts of tubules revealed that the number of isolated type A0cells per unit area of limiting membrane remained constant throughout the cycle of the seminiferous epithelium. Paired type A0spermatogonia also remained unchanged in number per unit area of basement membrane from stage I to stage VIII of the cycle. The low mitotic index of type A0spermatogonia (0.1%) indicated that these cells were not actively involved in the production of spermatogonia or spermatocytes during each cycle of the seminiferous epithelium and thus were considered as reserve stem cells.The type A1spermatogonia, which are formed during stage I of the cycle, remained resting until stage IX, when they undertook a series of four successive divisions resulting in the production of new type A1and Intermediate‐type spermatogonia. An analysis of the labeling indices of type A spermatogonia obtained from cell counts in radioautographed testicular sections after a single or multiple3H‐thymidine injections indicated that the percentages of labeled type A cells corresponded to the percentages of type A1‐A4at each stage, whereas the percentages of unlabeled type A cells corresponded to the percentages of type A0spermatogonia obtained from counts of cells in whole mounts. This confirmed that type A0cells were generally non‐proliferative throughout the cycle of the seminiferous epithelium while the type A1‐A4spermatogonia underwent complete renewal during each cycle. The present results thus support the concept of the existence of two classes of spermatogonial s

ISSN:0002-9106    

DOI:10.1002/aja.1001420203

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

年代:1975

数据来源: WILEY

摘要:

AbstractLenses of CFl mice were studied with the transmission electron microscope at frequent intervals through 13 months following a transcorneal needle injury to the lens. While this kind of injury causes a high incidence of traumatic cataract in the human and frog, it elicits a repair process in the mouse lens whereby the damaged capsule, epithelium and lens fibers are rapidly renewed and permanent lens opacity seldom occurs. Ultrastructural changes in lens epithelial cells adjacent to the wound, which precede and accompany localized cellular proliferation and production of new capsule, involve a rapid increase or enlargement of organelles associated with protein synthesis and assembly. The capsule and epithelium are repaired within a couple of months. Cortical lens fibers in the wound area undergo conformational changes into smaller, ordered arrays of “membranous sacs.” These are replaced within a week by normal appearing lens fibers. There is minimal degeneration or hyperplasia noted, and except for a few fibroblastic cells on the lens surface, little evidence remains of the injury by two months. Ultrastructural differences between mouse and human lens, such as presence or absence of dense bundles of microfilaments and desmosomes are considered in relation to lens shape and tension, and susceptibility to injury‐induced cat

ISSN:0002-9106    

DOI:10.1002/aja.1001420204

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

年代:1975

数据来源: WILEY

摘要:

AbstractDirect morphometric estimation of the number of intestinal crypts per 10 mm length of jejunum, the total number of cells per crypt, and the number of Paneth cells per crypt was performed using Zenker‐fixed, serially sectioned small intestines from adult BALB/c mice. The mean volume of a crypt cell was estimated to be in the order of 6.6 ± 0.1 × 10−4mm3, while the total volume of all cells in a single crypt was 1.833 ± 0.02 × 10−1mm3. The cell population per crypt was 278 ± 7 cells, of which 44 ± 10 were Paneth cells. It was estimated further that 265 ± 30 crypts per 10 mm length of jejunum contained 7.4 ± 0.1 × 104cells, including 1.2 ± 0.24 × 103Paneth cells. The volume of all crypt and Paneth cells per 10 mm length of jejunum was in the order of 49 ± 1.2 and 8 ± 1.8 mm3, respectively. The volume of the tunica muscularis and the surface area of the crypt's lumina were estimated to be 33.5 ± 2.2 mm3and 118 ±

ISSN:0002-9106    

DOI:10.1002/aja.1001420205

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

年代:1975

数据来源: WILEY

摘要:

AbstractThis study was undertaken to identify an ubiquitous granular leukocyte found inCatostomus commersonniiLacépède. The cell contains large, numerous, strongly PAS‐positive cytoplasmic granules, an eccentric nucleus and prominent, persistent juxtanuclear space. It develops in the hemopoietic tissue of the kidney, and mature cells are found not only in kidney and peripheral blood but also in areas of connective tissue where mast cells are usually located. Electron microscopy confirms the presence of a large Golgi apparatus, unlamellated cytoplasmic granules and extensive rough‐surfaced endoplasmic reticulum.Histochemical studies show that the cytoplasmic granules are alcianophobic, non‐metachromatic and unstained by acridine orange. Histamine is detectable spectrophotometrically in kidney tissue, but the PAS‐positive granular leukocyte does not consistently degranulate after treatment with histamine liberator 48/80.The authors suggest that while the PAS‐positive granular leukocyte is not identical with classical basophils/mast cells, which are absent inC. commersonnii, it may represent an evolutionary precursor of

ISSN:0002-9106    

DOI:10.1002/aja.1001420206

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

年代:1975

数据来源: WILEY

摘要:

AbstractThe ultrastructure of normal human mammary cells cultured from post‐weaning breast fluids is described. Cells from confluent monolayers in two week old cultures were studied. The epithelial nature of these cells was established by the demonstration of a well developed system of cell‐to‐cell interdigitation and numerous desmosomes. These cells also share with breast epithelial cells in vivo, polarity, with blunt short microvilli on the apical surface and an oriented arrangement of organelles in the basal and apical portions of the cells. The Golgi apparatus, which is the most highly developed organelle, is localized in the apical pole and contains substantial quantities of secretory material in the cisternae and vesicles. A variegated palisade of finely granular material mixed with tonofilaments is seen in the basal portion of the cells; many of these tonofilaments end in the terminal web of the desmosomes.The regular occurrence of these cells in breast fluids during the terminal phases of lactation suggests that their separation is a part of normal breast invol

ISSN:0002-9106    

DOI:10.1002/aja.1001420207

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

年代:1975

数据来源: WILEY

摘要:

AbstractThis report illustrates some of the errors that may occur during in vivo and in vitro maturation and fertilization of mammalian ova, considers the possible mechanisms accounting for their occurrence, and discusses their functional consequences. Included in the description are anomalies of oocyte and follicular development, i.e., multinucleated oocytes, polyovular follicles, and aberrations of zona pellucida formation. Also considered are deviations from the normal process of oocyte maturation such as chromosomal anomalies, development of abnormal nuclear structures (subnuclei), inhibition of polar body formation and aberrations of polar body structure. Anomalies of the process of fertilization such as polyspermia, sperm penetration into polar bodies, and development of multinucleated blastomeres in two‐cell embryos are also describe

ISSN:0002-9106    

DOI:10.1002/aja.1001420208

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

年代:1975

数据来源: WILEY

摘要:

AbstractUsing an immunohistochemical technique at the electron microscopic level, we have observed that within the axon terminals of the guinea pig neurohypophysis neurophysin is present in the large neurosecretory granules, as well as in the axoplasm. A description of a freeze‐substitution technique for neural lobe is also presen

ISSN:0002-9106    

DOI:10.1002/aja.1001420209

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

年代:1975

数据来源: WILEY

ISSN:0002-9106    

DOI:10.1002/aja.1001420201

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

年代:1975

数据来源: WILEY