摘要:

AbstractDuring early development of the mammalian eye, invagination and differential growth result in the formation of a cleft, the optic fissure, through which the hyaloid artery reaches the interior of the optic cup. Closure of this fissure was studied by electron microscopy in hamster embryos from days 10 through 12 of gestation. Closure occurred only when and where the basal lamina, which invests the entire wall of the optic cup, had disappeared. No morphological evidence was found that indicated a mechanism for the breakdown of the basal lamina lining the fissure, the fusion of surface cells of opposing sides and restoration of the basal lamina along inner and outer margins of the wall after closure. While in previous light microscopic investigations of the developing human eye eversion of the inner layer into the fissure has been reported, an inversion of the outer layer was found in this study. During inversion cells of the outer layer temporarily changed their orientation. While most of these cells remained within the layer when it returned to its normal position, some cells became separated and degenerated. Inversion of the outer layer, breakdown of the basal lamina and degeneration of superfluous cells appear to be necessary events for a normal closure to occur.

ISSN:0002-9106    

DOI:10.1002/aja.1001450402

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

年代:1976

数据来源: WILEY

摘要:

AbstractIn the present study rats were unilaterally ovariectomized (ULO) and the surgically removed ovary was frozen for 13 days. After allowing the remaining ovary to compensate with respect to number of ova shed, the frozen graft was thawed and transplanted subcutaneously to determine the effect on ovulation number, cycle length, uterine weight, ovarian weight and plasma levels of estradiol‐17 β (E2) and progesterone.Rats ULO at 45 days of age, which received an autograft 13 days later, had a decrease in the number of eggs shed as compared to control ULO rats (6.4 ± 0.8 vs. 11.1 ± 0.9 eggs, respectively) and a decrease in plasma E2(14.5 ± 1.7 vs. 21.0 ± 1.5 pg/ml, respectively). No differences were observed in progesterone concentration, uterine weight, ovarian weight or cycle length. In contrast, rats ULO at 31 days of age, which received an autograft 13 days later, showed no differences in comparison to control ULO rats. Castrates which received ovarian autografts developed cycling vaginal smears and had increased E2(31.9 ± 4.3 pg/ml) and decreased progesterone (18.3 ± 1.9 ng/ml) levels.Since ULO animals with autografts shed fewer ova, the present study demonstrates that the amount of ovarian tissue influences ovulation number either by utilization of gonadotropins or by an, as yet, undefined m

ISSN:0002-9106    

DOI:10.1002/aja.1001450403

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

年代:1976

数据来源: WILEY

摘要:

AbstractIn order to gain additional information regarding renal circulatory patterns, we have used both ink and resin injections to study the arterial supply to the mesonephric kidney of trout. Arterial injections through the dorsal aorta with ink were made for histological preparations in which the length, termination and relationship of glomerular vessels were examined. Similar injections with methyl methacrylate were made in preparation of corrosion casts to provide us with gross replicas of the aortic branches to the kidney as well as casts of glomerular structure for scanning electron microscopy.The sequence of vessels through which arterial blood passed to the renal corpuscle and ultimately to the uriniferous tubules was traced. Each afferent arteriole was found to terminate in three to six brancehs which formed anastomosing circuits of capillaries; these vessels reunited at the hilum to form a single efferent arteriole. The efferent arterioles in turn traveled a short distance to peritubular capillary beds and sinusoids.Morphological evidence was found for preglomerular sphincter‐like action only. The glomerular vessels were found to be similar to, although less complex than, those of the outer and mid‐cortical regions of the dog kid

ISSN:0002-9106    

DOI:10.1002/aja.1001450404

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe cytological characteristics of two modes of muscle hypertrophy were studied in the extensor digitorum longus muscle of the rat. Compensatory hypertrophy (CH) was produced by tenotomy of the tibialis anterior muscle and work‐induced hypertrophy (WIH) was produced by forced swimming of the animal. While both methods produced an increase in muscle weight and cell size, these two parameters did not correlate. Morphometric analyses of the hypertrophied muscle cells demonstrated that in CH‐muscle there was an increase in mitochondrial volume density, a decrease in myofibrillar volume density and no change in sarcotubular or nuclear volume density. WIH‐muscle demonstrated an increase in sarcotubular volume density but no change in mitochondrial, myofibrillar or nuclear volume density. It is concluded that in CH‐muscle, the cell volume increase is attributable to mitochondrial volume increase and that there is no increase in the contractile myofibrillar component of the cell. WIH‐muscle, on the other hand, has a cell volume increase which is attributable to a proportional increase in these o

ISSN:0002-9106    

DOI:10.1002/aja.1001450405

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

年代:1976

数据来源: WILEY

摘要:

AbstractLight‐staining cells, distinct from myoid cells, were identified in electron micrographs of the limiting membrane of rat seminiferous tubules. While these cells were also found free in the interstitial space, they were observed mostly in the myoid cell layer of the limiting membrane but were never seen within the seminiferous epithelium itself. The light cells were characterized by a pale‐stained cytoplasm containing a spheroidal Golgi apparatus next to a polymorphous often kidney‐shaped nucleus, a few cisternae of rough endoplasmic reticulum and some granules of various types including multivesicular bodies.In hematoxylin‐stained whole mounts of dissected tubules, these light cells were readily identified under the light microscope by nuclear morphology and light‐staining juxtanuclear Golgi apparatus. The incidence of these cells, per unit surface area of tubular wall, was calculated, taking into consideration the stages of the cycle of the seminiferous epithelium with which they were associated. Distributed along the entire length of seminiferous tubules, their number varied significantly during the cycle. Low numbers were found in stages II–IV and XIII of the cycle, while high numbers were found in stages IX to XII and XIV–I of the cycle. These observations indicate that the seminiferous epithelium may exert an influence on the population of light cells present in the tubular limi

ISSN:0002-9106    

DOI:10.1002/aja.1001450406

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

年代:1976

数据来源: WILEY

摘要:

AbstractArchitecture of the bone marrow vasculature, particularly that of the femur, was analyzed in three amphibian species in relation to the early phylogeny of marrow hematopoiesis. A dye‐injection method and histological techniques, including both serial sectioning and reconstruction methods, were used for this purpose. From these observations the following conclusions may be drawn. (1) Marrow hematopoiesis is absent from the femur of the urodelan (Triturus pyrrhogaster) and appears first in the femur of the primitive anuran (Xenopus laevis). (2) The site of primitive hematopoiesis (granulopoiesis) is the subendosteal region where the venous vascular net develops. (3) The primitive vascular architecture observed in the femur ofXenopusis characterized by the absence of a central vein. Subendosteal veins drain the blood from the bone marrow. A vein collateral to the primary artery appears in the femur ofRana catesbeiana, an advanced anuran, in which further development of both the subendosteal venous plexus and hematopoietic activity are noted. In both anura examined, the primitive blood sinuses form near the mid‐shaft of the femur. The proliferation of mesenchymal elements containing dark pigment, presumably melanin, was also noted in this area. (4) The architecture of marrow vessels in Rana approaches the structure noted in mammalian bone marrow. (5) Fat tissue is observed in the urodelan bone marrow prior to the appearance of hematopoietic activity. This indicates that the formation of marrow fat is phylogenetically unrelated to the development of hematopoiesis.The present investigation on primitive hematopoiesis suggests that the development of hematopoietic activity is intimately related to the development of the marrow vasculature, particularly that of the subendosteal venous plexus. A favorable vascular arrangement may be necessary to allow active hematopoie

ISSN:0002-9106    

DOI:10.1002/aja.1001450407

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe ultrastructure of the fetal guinea pig neural lobe was studied from day 40 to day 60 of gestation. Pituitaries were taken every five days and at least four glands from each gestational period were examined.Bundles of nerve fibers had invaded the periphery of the gland on day 40. By day 50 axon profiles were distributed throughout the entire posterior pituitary though pituicyte processes continued to act as a barrier between axons and the perivascular space of capillaries. Neural processes established contact with the capillaries between days 55 and 60.Neurosecretory granules (NSG) were present within a few axons on day 40. The number of axons with NSG and the total quantity of granules increased gradually throughout fetal development. Electron‐lucent granules (microvesicles) were observed infrequently until the day of birth. A population of dense‐cored vesicles, 70–80 mμ in diameter, was present from day 50 onward; a second population with larger diameters was also present throughout the developmental sequence and these increased from 90–130 mμ in diameter to 170–220 mμ in diameter between days 40 and 60.The presence of neurosecretory granules is discussed in relation to the onset of synthesis and storage of neurohypophys

ISSN:0002-9106    

DOI:10.1002/aja.1001450408

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe effects of thyroxine and ACTH on the ultrastructure of cells of the adrenal zona fasciculata were studied by morphometric analysis and compared by two‐way analysis of variance. The results indicate that the effects of thyroxine and ACTH are different and independent. The statistically significant differences in effect of thyroxine and ACTH are: thyroxine causes an increase in the volume fraction of mitochondria and a decrease in the volume fraction of endoplasmic reticulum independent of ACTH; thyroxine causes a decrease in surface density of mitochondria and endoplasmic reticulum in the absence of ACTH, but in the presence of ACTH this effect is moderated by an interaction of thyroxine and ACTH. There were no statistically significant effects of either thyroxine or ACTH on volume fraction or surface density of liposome

ISSN:0002-9106    

DOI:10.1002/aja.1001450409

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

年代:1976

数据来源: WILEY

ISSN:0002-9106    

DOI:10.1002/aja.1001450401

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

年代:1976

数据来源: WILEY