摘要:

AbstractThe pathways of movement of dye‐markings on the tympanic membranes of 30 ears of 15 volunteers were investigated by photography with a Hopkin's rod. Two discrete pathways were identified. Movement on the pars tensa was centrifugal in all directions from the edge of the handle of malleus surface. This supported our previous suggestion that pars tensa epithelial migration is based on growth of the meatal plate. Movement on the more central part of the handle surface itself, however, was always upwards to the pars flaccida epithelium and then, with all dye on the latter, in a posterosuperior direction only.The covering epithelium of the pars flaccida/handle of malleus arises from the fundus of the early embryonic external canal. To explore the possibility that its migration may also commence early, the fundus was examined histologically in 12 embryo ears. It was shaped like an inverted pear to conform to the primordial head of the malleus above and its handle below. There was distinct flattening of the whole fundal epithelium in contrast to the side wall of the external canal, lending support to the concept of a primordial flux of epithelium in the main fundus and its inferior extension. The meatal plate grew from the rim of the fundus producing the pars tensa and deep external canal epithelia. This process, however, was not associated with significant cytologic alterations or increased expression of the human proliferation antigen, Ki‐67, at that rim. This suggests that the pars tensa epithelium grows and moves without the active involvement of the epithelium of the pars flaccida/handle of mall

ISSN:0002-9106    

DOI:10.1002/aja.1001890302

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

年代:1990

数据来源: WILEY

摘要:

AbstractIn three experiments of 30 weeks' duration, 93 adult female Wistar rats received controlled amounts of calcium with food and water, to produce a state of either hypercalcemia or hypocalcemia. A systematic sterological analysis of the thyroid glands and a radioimmunological analysis of thyroxine, triiodothyronine, and thyrotropine were performed. In the hypercalcemic rats, a reactive hyperplasia of the parafollicular cells was established; this was accompanied by morphological and biochemical signs of hyperfunction of the follicular cells, despite a reduced central stimulation by thyrotropin. In the hypocalcemic animals, no quantitative morphological changes in the parafollicular cells were observed; however, morphological and biochemical signs of hypofunction of the follicular cells were obvious, despite stronger central stimulation by thyrotropin. It is concluded that the extrinsic regulation of follicular cells by the blood calcium level is stronger than the intrinsic regulation by hypothalamo‐hypophyseal hormone

ISSN:0002-9106    

DOI:10.1002/aja.1001890303

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

年代:1990

数据来源: WILEY

摘要:

AbstractNuclei of pancreatic cells were isolated by trypsin‐detergent digestion of fresh tissue and stained with propidium iodide, and nuclear DNA was measured by flow cytometry. Samples were isolated from mice fed either chow or raw soya flour (RSF) for periods ranging from day to 48 weeks, beginning at 4 weeks of age. In chow‐fed mice, the pancreas contained about 80% diploid (2N) and 20% tetraploid (4N) cells at the start of the study, but tetraploidy gradually increased to about 40% 2 weeks later (6 weeks of age) and remained at this level from that time onwards. Low levels of octaploid nuclei (8N) were also present in some animals after 2 weeks. In RSF‐fed mice, about 20% tetraploid nuclei were also present for 1 and 2 days after starting RSF, but by 4 days tetraploidy had increased significantly to 40% and by 14 days had further increased to 50%. This level was significantly higher than that seen in chow‐fed animals and was maintained for up to 48 weeks. Significantly higher numbers of octaploid nuclei were also present in the RSF‐fed animals. In both chow‐ and RSF‐fed mice, most cells were mononuclear, averaging 70% in chow‐fed and 64% in RSF‐fed animals. This difference was significant. This study shows that the mouse pancreas differs from the rat pancreas in the absence of a large population of binucleate acinar cells and the presence of considerable nuclear tetraploidy. Raw soya flour feeding leads to significant changes in these features, but in this species these changes do not appear to predis

ISSN:0002-9106    

DOI:10.1002/aja.1001890304

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe innervation of the guinea pig spleen was investigated by electron microscopy. Unmyelinated nerve fibers in the capsulotrabecular and arterial systems were found to contain large and small granular and small agranular synaptic vesicles in their terminals and are thought to be sympathetic adrenergic in nature. They influence the contraction of the smooth muscle cells by diffusion innervation in these systems. These nerve terminals were also scattered in both the red and the white pulp. Pulp nerves wrapped by Schwann cells were further enclosed by myofibroblastic reticular cells. This condition revealed that the pulp nerves pass through the connective‐tissue spaces of the reticular fibers, which contain elastic fibers, collagenous fibrils, and lamina densa‐like materials of the usual basement laminae. One of the target cells for the pulp nerves is considered to be the myofibroblastic reticular cell in the reticular meshwork. Neurotransmitter substances released from the naked adrenergic nerve terminals travel through the reticular fibers and may play a role, by both close association innervation and diffusion innervation, in the contraction of reticular cells to expose the reticular fibers. At the exposed sides, connective‐tissue elements of the reticular fibers are bathed with blood plasma, and the included naked nerve terminals, devoid of Schwann cells but with basement laminae of these cells, face free cells at some distance or are in close association with free cells, especially lymphocytes, macrophages, and plasma cells. The close ultrastructural relationship between the naked adrenergic nerve terminals and immunocytes strongly suggests that there is an intimate relationship between the immune system and the sympathetic nervous system through both close association innervation and diffusion innervation. Thus splenic adrenergic nerves of the guinea pig may play a triple role in (1) contraction of smooth muscle cells to regulate blood flow in the organ, (2) induction of the exposure of reticular fibers by contraction of the reticular cells in order to form a close relationship of the nerve terminals with the immunocytes, and (3) subsequent neuroimmunomodulation of the immuno

ISSN:0002-9106    

DOI:10.1002/aja.1001890305

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe human trapezius muscle has an origin that is more extensive than that of any other body muscle; it has a complex macroscopic structure with fibers running in different directions. Histochemical analysis of multiple samples, obtained from different parts of the trapezius muscle from five males, showed marked differences in the distribution and the cross‐sectional fiber area of the fiber types among different parts of the muscle as well as among individuals. As revealed by the mATPase activity, after different levels of alkaline and acidic preincubations, the lower third of the descending portion, the transverse, and the ascending portions of the muscle had a predominance of type I fibers (low mATPase activity at pH 9.4), whereas the most superior parts of pars descendens had a higher frequency of type II fibers (high mATPase activity at pH 9.4). The fibers of the most superior parts of the muscle were considerably smaller compared with those in all the other parts. In sections stained for NADH‐TR, motheaten fibers were observed within parts of the descending portion. Their location and their larger fiber area, compared with that of ordinary type I fibers, may be related to frequent and/or continuous use of these fibers. In conclusion, the differences in fiber type composition between the different parts of the muscle probably reflect different functional demands on the trapezius muscle in various head, neck, and shoulder movements. We suggest that the interindividual differences in muscle fiber composition are due, at least in part, to genetic fact

ISSN:0002-9106    

DOI:10.1002/aja.1001890306

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

年代:1990

数据来源: WILEY

摘要:

AbstractWe undertook a light and scanning electron microscopic study of the eye in the Magellanic penguin (Spheniscus magellanicus). The anatomical peculiarities of the eyeball shape in Sphenisciformes have been previously described by others; here, we show that they are accompanied by several modifications in the organization of the anterior segment of the eye. The main change was found in the portion of opaque sclera extending from the cornea to the anterior border of the scleral ossicles, which was much broader than in other avian eyes. This scleral region was made of a very dense fibrous tissue and was as difficult to cut as the ossicles. The corneoscleral boundary was also different from that of other birds, since the aqueous humor channel and the pectinate ligament were located 1.0–1.5 mm posterior to the cornea. The osseous ring was formed by 13 bones, including three pairs of over‐and underplates. There was a single ciliary muscle, with meridionally oriented striated fibers. They were inserted on a circumference along the boundary between the fibrous sclera and the ossicles, far away from the wall of the aqueous humor channel. On their posterior end, the muscle fibers formed a tendinous structure attached to the inner surface of the sclera and to the outer surface of the ciliary body. Only short zonular fibrils were observed. These anatomical features are probably relevant for the adaptation of penguin eyes to vision on land and in the aquatic environm

ISSN:0002-9106    

DOI:10.1002/aja.1001890307

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

年代:1990

数据来源: WILEY

摘要:

AbstractArteriovenous anastomoses in the rabbit ear were examined with scanning electron microscopy to elucidate the structural differentiation of the media of the shunt. Arterial, intermediate, and venous segments in the shunt and two layers of the media in the intermediate segment were differentiated based on cell shape and cell organization. In the arterial segment, smooth muscle cells were spindle‐shaped, either elongated or short, with a few branches, and were arranged circularly or diagonally with respect to the vessel's long axis. There were also stellate muscle cells with radiating processes. In the intermediate segment, the smooth muscle cells of the outer layer of the media were also arranged circularly and resembled the elongated cells in the arterial segments, but they were more irregular in shape and had more processes than those of the arterial segment. The epithelioid cells of the inner layer of the media were oval or polygonal and oriented irregularly with respect to the vessel's long axis, clustering to form longitudinal plicae. The smooth muscle cells of the venous segment were flat with many lateral processes and formed a thin, discontinuous layer. The smooth muscle cells in the arterial segment and those of the outer layer of the intermediate segment exhibited a highly rugged surface texture, indicating their strong contractility; the epithelioid cells and the smooth muscle cells in the venous segment exhibited a generally smooth surface, indicating less contractility. The intermediate segments were supplied with a dense nerve plexus. The intermediate segments, therefore, may be actively involved in the regulation of blood flow under neuronal influenc

ISSN:0002-9106    

DOI:10.1002/aja.1001890308

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

年代:1990

数据来源: WILEY

摘要:

AbstractOsteoclast‐mediated bone resorption is increased in response to 1,25 dihydroxyvitamin D (1,25[OH]2D or calcitriol). Osteopetrosis is a metabolic bone disease characterized by defective, osteoclast‐mediated bone resorption, which co‐exists with elevated serum 1,25‐(OH)2D levels in some osteopetrotic children and animals. We examined the effects of high doses of calcitriol on osteoclast number and cytochemistry in both normal and osteopetrotic(os)rabbits. Calcitriol was continuously infused at doses of 0.5, 2.5, or 25 μg/kg/day via subcutaneously implanted osmotic minipumps for a period of 7 days. Following treatment, the proximal tibial metaphyses were processed for histomorphometric and cytochemical analyses. Sections were stained for tartrate‐resistant acid phosphatase (TrAP) or acid ATPase (TraATPase). Osteoclasts were significantly reduced in untreatedosrabbits compared with age‐matched normal littermates between birth and 3 weeks of age (41–46% of normal). Whereas most normal osteoclasts (85%) stained heavily for TrAP or TraATPase, less than half ofososteoclasts were heavily stained for these acid hydrolases. Infusions of 1,25(OH)2D resulted in elevations of osteoclast numbers in both normal andosrabbits, but the number of osteoclasts remained significantly lower in mutants than in normal littermates at any given dose. Calcitriol infusions also resulted in a significant increase in the percentage ofososteoclasts staining heavily for TrAP and TraATPase. These results suggest that in response to 1,25(OH)2D normal osteoclasts increase their production of acid hydrolases before increasing cell numbers and that, in spite of high levels of endogenous calcitriol,osrabbits can respond to exogenous 1,25(OH)2D as evidenced by increased osteoclast number and cytochemical staining, even though these osteoclasts fail to resorb the excess skeletal matrix. Thus the defect in the mutant skeleton appears to be in the initial cytodifferentiation of osteoclasts, not in their responsiveness to endogenous regulators of b

ISSN:0002-9106    

DOI:10.1002/aja.1001890309

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe ontogenetic development of the nucleus ambiguus was studied in a series of human embryos and fetuses ranging from 3 to 12.5 weeks of menstrual age (4 to 66 mm crown‐rump length). They were prepared by Nissl and silver methods. Nucleus ambiguus neuroblasts, whose neurites extend towards and into the IXth and rostral Xth nerve roots, appear in the medial motor column of 4–6‐week‐old embryos (4.25–11 mm). These cells then migrate laterally (6.5 weeks, 14 mm) to a position near the dorsal motor nucleus of X. At 7 weeks (15 mm), nucleus ambiguus cells begin their migration, which progresses rostrocaudally, into their definitive ventrolateral position. The basic pattern of organization of the nucleus is established in its rostral region at 8 weeks (22.2–24 mm) and extends into its caudal region by 9 weeks (32 mm), when its nearly adult organization is evident. Cells having the characteristics of mature neurons first appear rostrally in the nucleus during the 8.5–9‐week period (24.5–32 mm), gradually increase in number, and constitute the entire nucleus at 12.5 weeks (65.5 mm). Definitive neuronal subgroups first appear at 10 weeks (37.5 mm) in the large rostral nuclear region. These features suggest that the human nucleus ambiguus develops along a rostrocaudal temporospatial gradient. Evidence indicates that function of nucleus ambiguus neurons, manifested by fetal reflex swallowing, occurs after the cells migrate into their definitive position, establish the definitive nuclear pattern, and exhibit matur

ISSN:0002-9106    

DOI:10.1002/aja.1001890310

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

年代:1990

数据来源: WILEY

ISSN:0002-9106    

DOI:10.1002/aja.1001890301

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

年代:1990

数据来源: WILEY