bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fusion of nasal swellings in the mouse embryo: Regression of the nasal fin
Authors: Gaare John D. , Langman Jan 
Published: February 2005

AbstractThe nasal fin is an epithelial seam that develops by fusion between the epithelial linings of the medial and lateral nasal swellings. Shortly after its formation the nasal fin regresses and is replaced by mesenchyme, with exception of its most posterior portion which remains as the bucconasal membrane. Since the regression of the nasal fin plays an important role in the formation of the upper lip and primary palate, the breakdown of the fin was examined with the electron microscope in 12‐day‐old mouse embryos.Shortly before the epithelial linings of the opposing nasal swellings make contact, cell degeneration characterized by condensation and fragmentation occurs in the epithelial linings of the prospective fusion areas. Apparently direct contact between the nasal swellings is not necessary to cause cell death.After fusion has established the nasal fin, epithelial cells continue to degenerate by condensation and fragmentation. Cell degeneration, however, can not account for complete regression of the fin, since many morphologically healthy epithelial cells are always present. Since no indication was found that the surviving epithelial cells transform into mesenchymal cells, it is suggested that they are incorporated into the adjacent epithelial linings of the expanding primitive nasal and oral cavities.The extracellular dense bodies that result from degenerating cells are engulfed by neighboring epithelial cells, in which they form phagocytic vacuoles. Some of these epithelial cells containing numerous cytoplasmic vacuoles appear to transform into large round macrophages.When the acid phosphatase procedure was applied, many heterophagic vacuoles contained a black precipitate, indicating that, after being phagocytosed, the dense fragments are digested by lysosomal enzymes. A similar black precipitate appeared over autophagic vacuoles.
A freeze‐fracture study of the topographic relationship between inner enamel‐secretory ameloblasts in the rat incisor
Authors: Warshawsky H. 
Published: February 2005

AbstractA correlated study using freeze‐fracture replicas and routine thin sectioning was done on the ameloblasts which secrete inner enamel in the rat incisor. These ameloblasts are columnar cells aligned in rows parallel to the cross‐sectional plane of the incisor. Each cell has a Tomes' process at its distal end which is contained within a cavity of interrod enamel. Tomes' processes of a particular row of cells are inclined towards the mesial side of the tooth, while those of the next row are inclined towards the lateral side, so that the processes cross each other at 90°. Freeze‐fracture replicas were used to examine the surfaces of ameloblasts between adjacent rows and the surfaces of the cells within the row. Replicas of the surfaces between rows showed that ameloblasts are curved so that their proximal and distal ends (Tomes' processes) are both directed towards the same side of the tooth. The surface of each row bears the impression left upon it by the cells in the adjacent row which have been fractured away. This cell‐impression is also curved, but in the opposite direction to the cells which it crosses. It was thus shown that not only the Tomes' processes of adjacent rows but the entire cell bodies cross one another. This crossing is slight at the proximal ends of the cells, but marked at the level of the distal junctional complex. At this level a cell from a particular row curves across several cells of the neighbouring row and forms large tight junctions with at least two cells in that row. The proximal and distal junctional complexes form zones of tight junctions around the cell. The distal complex is more extensive than the proximal and the tight junctions are better developed between adjacent rows. Gap junctions are, however, larger between cells within the rows. The study demonstrated the effectiveness of freeze‐fracture replicas in obtaining 3‐dimensional details about ameloblast shape, and this information was used to evaluate the supposed movement of ameloblasts during inner enamel formation.
Myology of the shoulder of Pontoporia blainvillei, including a review of the literature on shoulder morphology in the cetacea
Authors: Strickler Timothy L. 
Published: February 2005

AbstractThe purpose of this paper is to describe in detail the shoulder myology of the La Plata River Dolphin, Pontoporia blainvillei, and to review the literature on cetacean shoulder myology. Three fetal and one adult animal were used for the collection of morphological information. Pontoporia is less specialized in its shoulder anatomy that most delphinid cetaceans, and shares several characteristics with some mysticetes. The omohyoid and anterior serratus anterior muscles are found in both Pontoporia and the mysticete Balaenoptera, but are absent in most delphinids. The pectoralis abdominalis and three rhomboideus divisions are found in Pontoporia and Kogia, but in only a few delphinid species described in the literature. It is suggested that these characteristics are associated with a generalized use of the forelimb in Pontoporia.
Ultrastructural differences in efferent ducts and several regions of the epididymis of the hamster
Authors: Flickinger Charles J. , Howards Stuart S. , English H. F. 
Published: February 2005

AbstractThe ultrastructure of the hamster efferent ducts and epididymis was studied and the results were correlated with previously published data on the composition of luminal fluid obtained by micropuncture. Samples of the efferent ducts and parts of the epididymis designated initial segment, caput, corpus, proximal cauda, distal cauda, and “epididymal vas” were prepared. The efferent ducts contained principal cells characterized by a profusion of apical vesicles and numerous very large vacuoles that were distributed throughout the cytoplasm. Ciliated cells had few vesicles and vacuoles. Occasional cells contained many particles resembling glycogen. In the epididymis, the following trends were observed. The height of the epithelium and the size of the principal cells declined from initial segment to distal cauda. Apical vesicles and vacuoles with a light content were extremely numerous in principal cells of the initial segment and decreased progressively in the more distal regions. In the initial segment, basal and perinuclear rough endoplasmic reticulum was abundant and was distended with a material that resembled newly synthesized protein. Further distally in the epididymis cisternae of the rough endoplasmic reticulum were narrow and contained little intracisternal material. Light cells containing many vesicles, vacuoles, and lysosome‐like structures were very prominent in the caudal segments. The epithelium of the epididymal vas had features intermediate between cauda epididymidis and ductus deferens. The cytoplasmic droplet in luminal sperm began to migrate caudally between the caput and corpus epididymidis and reached the posterior extremity of the middle piece in the distal cauda. Some degenerating sperm were observed in the lumen of the distal segments of the epididymis.The abundance of cytoplasmic vesicles and vacuoles in principal cells of the efferent ducts and initial segment of the epididymis correlated with the site of greatest fluid absorption as determined by micropuncture studies, suggesting that these structures are involved in absorption of fluid from the lumen. Between the caput and distal cauda epididymal segments, where absorption of sodium and potassium but not of fluid occurred, there were few vesicles and vacuoles in principal cells, but the “light” cells were large and numerous and contained many vacuoles. The principal cells of the initial segment were best equipped with rough endoplasmic reticulum to synthesize a protein.
Effects of estrogen on human seminiferous tubules: Light and electron microscopic analysis
Authors: Lu Cheryle C. , Steinberger Anna 
Published: February 2005

AbstractMorphological features of testes from four subjects after longterm treatment with ethinyl‐estradiol (1–2 mg daily) and from five non‐treated patients with prostatic carcinoma were studied by means of light and electron microscopy. The non‐treated seminiferous tubules contained spermatogonia, spermatocytes, spermatids, spermatozoa, and Sertoli cells and showed no apparent morphologic abnormalities. On the other hand, the estrogen‐treated testicular tissue contained only Sertoli cells and very few spermatogonia within the seminiferous tubules. The nuclei of Sertoli cells occasionally contained two nucleoli. The nucleolar complex was composed of a fine granular spherical body surrounded by a large granular, reticular network. The cytoplasm of the Sertoli cell contained osmiophilic lipid‐like bodies. These lipid‐like bodies appeared more pronounced in patients treated with higher doses of estrogen, suggesting a diminution of secretion of Sertoli cell hormone. Blebbing from the outer nuclear membrane appeared to have formed numerous vesicles in the cytoplasm. These vesicles usually contained several membrane‐bound granular bodies. In the estrogen‐treated testes, there was a marked increase in thickness and infolding of the basement membrane. Two unusual patterns of the basement membrane were observed: one appeared to be a reticular anastomosis, the other, an electron‐dense trilayer. The morphological picture of seminiferous tubules from the estrogen‐treated subjects appeared to correlate well with the suppressed plasma and testicular levels of testosterone, the undetectable circulating gonadotrophins, and the elevated plasma and testicular levels of estradiol‐17β reported by Rodriguez‐Rigau et al. (1977).
Induced ovulation, development of the corpus luteum, and tubal transport in the striped skunk (Mephitis mephitis)
Authors: Wade‐Smith Julia , Richmond Milo E. 
Published: February 2005

AbstractOvulatory pattern, development of the corpus luteum (CL), and early tubal transport are described for 6 unmated and 19 mated striped skunks (Mephitis mephitis) killed after known copulation times. Ovulation is induced by copulation and occurs around 42 hours (range = 40–50 hours) after first insemination. Seventeen of 19 females killed between 36 hours and 19 days postcoitus had ovulated. Two females killed at 36 hours had not ovulated; however, their follicles showed preovulatory changes and were significantly larger (p < 0.01) than those of unmated females. Six unmated females, killed during and three weeks after the normal breeding season, had not ovulated. Ovarian events, such as preovulatory changes, ovulation, and development of the corpus luteum (CL), are described for animals killed 36 hours to 19 days post‐coitus. Maximum CL size occurred at 11 days post‐coitus and coincided with the onset of embryonic migration and enlargement. Embryonic development reflected individual variation in ovulation times. The first polar body was extruded at ovulation and the second at fertilization. Pronuclear stages were predominant at 42 to 48 hours and 3 to 8‐cell stages at 72 to 96 hours; morulae (containing up to 95 cells) entered the uterus at seven days. Blastocysts were observed first at 11 days when embryonic spacing and enlargement began. Implantation occurred by 19 days.
The role of lymphoid cells in bone resorption: Cellular immunological competence in ia rats
Authors: Schneider Gary B. 
Published: February 2005

AbstractThe ia (incisors absent) rat is a naturally occurring mutant that has osteopetrosis resulting from reduced bone resorption. A number of in vestigators have reported that other osteopetrotic mutant rats (op) and mice (mi and op), in addition to demonstrating the skeletal manifestations of the disease, have cellular immunological defects. In light of the fact that bone resorption has been demonstrated to be controlled by hematopoietic tissues and more specifically by mononuclear cells isolated from lymphoid organs, it seemed appropriate to investigate immunological competence in the ia rat, to determine whether or not it had this defect in common with the op rat.Contrary to the results presented for other osteopetrotic mutants, we found that the thymuses in our ia mutants had a normal cellular composition and the T‐cell‐dependent zones in the lymph nodes were not deficient in lymphocytes. Therefore, this study was undertaken to investigate the response of ia rats to oxazolone, which produces one type of T‐cell‐dependent immune response, delayed hypersensitivity.The results of these studies indicate that ia rats at 18 days of age have the ability to develop delayed hypersensitivity, as shown by both a blastogenic response in the lymph node draining the site of sensitization and a positive skintest. The magnitudes of these responses were similar in ia and normal littermates, both histologically and quantitatively. Therefore, the ia mutant does not appear to have a defect of the thymus‐dependent immune system, and further studies should be carried out to investigate other parameters of immunological competence in these animals.
Quantitative analyses of the fiber population in rat chorda tympani nerves and fungiform papillae
Authors: Farbman Albert I. , Hellekant Goran 
Published: February 2005

AbstractThe numbers of nerve fibers in 44 intact chorda tympani nerves (CT) from 34 rats were counted on electron micrographic montages of cross‐sections of the nerves. The mean number of fibers was 1,096, consisting of 641 myelinated and 455 unmyelinated fibers. There was no significant difference in the mean number of fibers between CT's from right and left sides, nor was there any significant difference in counts between CT segments taken from the middle ear and those taken from just proximal to the region where the CT joins the lingual nerve. The relative contribution of efferent and afferent fibers in the CT was assessed in 13 animals as follows. Intracranial surgery was performed to cut the root of the facial nerve just proximal to its entrance into the internal auditory meatus on the right side. After 19 to 21 days, to allow Wallerian degeneration of the efferent fibers, counts were made as above. The mean number of afferent fibers in the rat CT was 484 myelinated and 122 unmyelinated (606 total); the intact left CT's from the same animals contained a mean of 616 myelinated and 402 unmyelinated (1,018 total) fibers. The afferent limb of the CT, therefore, contains 79% of the total number of myelinated fibers and only 30% of the total number of unmyelinated fibers. Removal of the superior cervical sympathetic ganglion did not significantly affect the numbers of fibers. In order to determine whether the efferent limb of the CT contributes fibers to the fungiform papillae on the tongue, we compared the number of (CT) fibers in fungiform papillae from “de‐efferented” rat tongues with that from papillae of controls. In order to make this comparison, it was necessary to section the lingual nerve, which contributes about 75% of the total number of fibers to the fungiform papillae. This was done in both the control and de‐efferented animals. There was no significant difference in mean number of fibers in fungiform papillae innervated by a de‐efferented CT when compared with those innervated by an intact CT. There is, then, no evidence from these studies to suggest the presence of an efferent CT component within the fungiform papilla.
Immunoreactive β‐endorphin and acth in the same neurons of the hypothalamic arcuate nucleus in the rat
Authors: Sofroniew Michael V. 
Published: February 2005

AbstractImmunoreactive ACTH and β‐endorphin (β‐End) were localized in the brain and pituitaries of normal and colchicine‐treated rats, using the immunoperoxidase method at the light microscopic level. On adjacent serial 5‐μm paraffin sections of anterior pituitaries, both ACTH and β‐End could be found in the same cells. On adjacent 5‐μm paraffin sections of brains of colchicine‐treated rats, both ACTH and β‐End could be found in the same perikarya of hypothalamic arcuate nucleus neurons. It appeared that all perikarya containing β‐End contained ACTH as well, suggesting that neurons producing β‐End also produce ACTH. Pathways of ACTH fibers corresponded to pathways of β‐End fibers. These findings suggest that the synthesis, and transport, of ACTH and β‐End are linked in the brain as well as in the pituitary, possibly through a common precursor.
A scanning electron microscope study of aberrations in the prism pattern of rat incisor inner enamel
Authors: Risnes Steinar 
Published: February 2005

AbstractThe prism pattern in the inner enamel of adult rat incisors was studied with the SEM in unfixed tissues that had been sectioned, ground, polished, and etched. Six different types of aberrations in the prism pattern were encountered: 1. Prism lamellae may be shorter than the mesio‐lateral width of enamel. 2. Prism lamellae may deviate from a transverse orientation. 3. Prism lamellae may “fuse” or “bifurcate.” 4. Prisms of two adjacent lamellae may pursue a common course. 5. Prisms may change direction. 6. Variations exist in the outline of transversely cut prism profiles. Aberrations were observed at any distance from the dentino‐enamel junction.These observations were used as a basis for an analysis of the movement of ameloblasts during rat incisor amelogenesis. It was concluded that it is physically possible for the ameloblasts to create the observed aberrations as they move along the path of the prisms. However, the aberrations seem to make it more difficult to understand the factors controlling ameloblast movement. Occasionally crystallite bridges connecting adjacent prisms were observed. A configuration resembling a bifurcating prism is presented.
Lack of association between avian cartilages of different embryological origins when maintained in vitro
Authors: Fyfe David MacG , Hall Brian K. 
Published: February 2005

AbstractThe possibility that cartilages of differing embryological origins behave as separate types with respect to cell‐to‐cell associations was tested by placing the cut ends of transversely sectioned embryonic chick tibial cartilages (of mesodermal origin) in apposition to transversely sectioned Meckel's cartilages (a neural crest (ectodermal) cartilage) on the surface of a semi‐solid organ culture medium and maintaining the combinations in vitro for five to ten days. Tibia‐tibia and Meckel's cartilage‐Meckel's cartilage (homotypic) combinations, which served as controls, became united by a common extracellular matrix and by the proliferation of chondroblasts. Analysis of combinations where one partner had been prelabelled with 3H‐thymidine indicated that chondroblasts intermingled at the contact zone. In contrast, tibia‐Meckel's cartilage (heterotypic) combinations became separated by a layer of fibrous tissue. The chondroblasts at the contact zone failed to intermingle. We conclude that avian embryonic chondrocytes are not all equivalent and that part of their non‐equivalence could be related to their embryological origin either from the mesoderm or from the ectodermal neural crest.
Evidence that sclerotomal cells do not migrate medially during normal embryonic development of the rat
Authors: Gasser Raymond F. 
Published: February 2005

AbstractDuring embryonic development the medial part of the somite disorganizes or breaks up into sclerotomal cells which, according to many published reports, migrate medially to surround the notochord. The purpose of the study was to determine whether these cells actually migrate medially toward the notochord. Distances were measured between the notochord and the adjacent neural tube and the somite or its remnant during the period of somite disorganization. Serially sectioned, normal 10.5‐ to 13.5‐day (d) rat embryos were used. Only transverse sections through the middle of the fourth cervical (C‐4) body segment were measured, corresponding to the level of somite No. 8 (10.5 d) or its dermatomyotome remnant (10.5–11.5 d) or spinal nerve C‐4 (12.5–13.5 d). Measurements were taken at six stages from photographic montages, all of which were made at precisely the same magnification. The notochord was the central axial structure from which the measurements were determined. The changes in distance show that during the period of somite breakup the neural tube grows dorsally, away from the notochord which lies adjacent to its ventral surface. Simultaneously the somite remnant moves laterally and dorsally, all the while maintaining its position relative to the overlying ectoderm and leaving behind a trail of sclerotomal cells.Also at each stage cell counts were made on the medial sclerotomal region of the C‐4 segment. The average counts reveal that not only does the total number of cells increase substantially over the three‐day period (42–7,546), but also the total number of mitoses (3.5–200), while the mitotic index decreases (9.0–2.7). High proliferative activity is apparent in the medial sclerotomal cells throughout the 3‐day period. The evidence supports the conclusion that local proliferation of the trailing cells, which were left by the somite remnant as it moved dorsolaterally, causes the subsequent increase in density of the perichordal tissue, rather than an influx of migrating cells. Instead of sclerotomal cells migrating medially toward the notochord, the present study suggests that these cells retain their position relative to the notochord or central axis and that the medial sclerotomal region forms as a result of the growth movements of the surrounding structures.
Subdivision of mouse vibrissae on an embryological basis, with descriptions of variations in the number and arrangement of sinus hairs and cortical barrels in BALB/c (nu/+; nude, nu/nu) and hairless (hr/hr) strains
Authors: Yamakado Makoto , Yohro Takeshi 
Published: February 2005

AbstractDevelopment of vibrissae was studied in dd/y mouse embryos by scanning electron microscopy. Arrangement of vibrissae and cortical barrels were also studied by light microscopy in adult dd/y, BALB/c(nu/+), nude (BALB/c,nu/nu) and hairless (hr/hr) mice to find genetic or epigenetic variations. Rudiments of vibrissae first appear on Day 12 of pregnancy as longitudinal ridges on the developing muzzle, and each hair rudiment is represented by a dome on the ridges. The dorsal two rows (A and B; Woolsey and Van der Loos, 1970) of mystacial vibrissae are on the lateral nasal prominence, while the ventral three (C, D and E) are on the maxillary prominence. Smaller hairs of mystacial vibrissae appear at the labial part of the maxillary prominence on Day 13. The rudiments of rhinal hairs also appear at this stage on the part of the muzzle derived from the medial nasal prominence. Thus the so‐called mystacial vibrissae should be subdivided into three (or 4, including the rhinal) groups on an embryological basis. They are the lateral nasal, the maxillary and the labial.A supernumerary sinus hair and a corresponding barrel was observed between B and C rows uni‐ or bilaterally in one third of individuals of BALB/c, nude and hairless mice. It is suggested that supernumerary hairs tend to occur between the groups of hairs as defined above. In nude and hairless mice small barrels representing labial hairs are diminished in number. The number of hair follicles, however, is normal.