bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of puromycin on the ultrastructure of keratohyalin granules
Authors: Singh Baldev B. , McKinney Ralph V. , Brewer Phyllis
Published: February 2005

Keratohyalin granules (KHG) from control and puromycintreated hamster cheek pouch epithelium were studied by electron microscopy. The animals were killed 1–4 hours after injection with 75–100 microgram puromycin per gram body weight; controls were injected with saline. The KHG from control animals were round or oval and consisted of a finely granular background matrix containing many small, round, homogeneous electron‐dense deposits. The KHG from puromycin‐treated animals showed marked variation in morphology and size. They consisted of a coarse granular or speckled matrix and round, club‐shaped or comma‐shaped electrondense deposits. Since puromycin is known to inhibit protein synthesis, alterations in KHG structure support previous reports suggesting the protein nature of KHG.
Light and electron microscopic localization of ATPase in normal and degenerating testes of syrian hamsters
Authors: Gravis Curtis J. , Yates Robert D. , Chen I‐Li
Published: February 2005

The distribution of Mg++‐activated ATPase was determined with light and electron microscopy in normal and degenerating seminiferous tubules. In the normal animals ATPase was localized in the interface between spermatids and Sertoli cells, in association with the cytoplasmic filaments contained within Sertoli cell processes, and in the lymphatic endothelium. ATPase activity increased in degenerating tubules as observed by light microscopy. Electron microscopic investigations of the degenerating tubules which contained only spermatogonia and Sertoli cells revealed reaction product on the outer surface of the Sertoli cell processes and within the interface between adjacent Sertoli cells. Reaction product was also observed in the Sertoli cell processes between the cytoplasmic filaments and the cell membrane. Where filaments were absent in Sertoli cell processes, no reaction product was observed. These electron microscopic studies indicate that the increase in ATPase activity in testicular degeneration is probably a relative increase due to a loss of the germinal elements of the tubular epithelium and subsequent apposition of the Sertoli cell processes. We speculate that the ATPase activity localized within the Sertoli cell processes may be involved in providing an energy source for filament motility.
Polysaccharides in lung alveoli
Authors: Nir Izhak , Pease Daniel C.
Published: February 2005

Rat lung alveolar surfaces and contents were studied after using concanavalin A as a bifunctional agent to link exposed sugars to horseradish peroxidase, in accordance with a technique developed by Bernhard and Avrameas (1971). The Graham and Karnovsky (1969) diaminobenzidine procedure then was used to provide an electron‐dense reaction product so as to define the distribution of complex carbohydrates in alveoli.

A layer of very dense reaction product was intimately associated with the outer leaflets of the luminal plasma membranes of type I and II pneumocytes. Masses of generally less dense reaction product extended irregularly into the alveolar lumens. All pleomorphic membranous material free in the lumens also was coated by reaction product. When highly ordered tubular myelin bodies were seen, the reaction product filled all of the “gutters” created by the intersections of the membranes. Reasons are presented for believing that the intrinsic periodicity of the tubular myelin may be created and maintained by the domains of the complex carbohydrate units demonstrated by this cytochemical technique. The distribution of autologous albumin, demonstrated by antibody staining by Bignon et al. (1975), apparently coincides with the carbohydrate pattern, suggesting both may be associated as a glycoprotein. The ultimate relationships between carbohydrate moieties and phospholipid membrane systems proved to be of such complexity that we believe it justifiable to think that they also may be truly complexed together.
The features of sperm maturation in the epididymis of a marsupial, the brushtailed possum Trichosurus vulpecula
Authors: Temple‐Smith P. D. , Bedford J. M.
Published: February 2005

Possum spermatozoa undergo a distinctive process of maturation in the epididymis, as shown by change in the properties of the sperm surface, by modification of their morphology and by their increasing capacity for progressive motility.

Modification of the sperm surface over the head and tail is demonstrated by the different affinities of sperm from successive regions of the epididymis for FITC‐conjugated wheat germ agglutinin and concanavalin A, and for cationic ferric oxide colloidal particles. Changes in sperm head morphology are caused by (1) a dramatic reshaping and consolidation of the acrosome in which excess plasma membrane overlying it is sloughed as a cluster of vesicles, (2) a reorientation of the nucleus almost parallel to the axis of the tail and (3) distal movement of the droplet from its initial envelopment of the nucleus to an eccentric position on the anterior segment of the midpiece.

Spermatozoa released from the testis and caput epididymidis are essentially immotile or exhibit only lazy uncoordinated movements, whereas many from the corpus and most from the more distal regions of the epididymis display an energetic, progressive motility imparted by a rapid and stiff tail beat of narrow arc. This maturation of the capacity for motility is accompanied by an enhanced stability of the dense fibers and sheath, which become more resistant to the disruptive action of SDS and DTT, and by changes in the ultrastructure of the sperm tail. These include modification of the matrix of the mitochondria and also an unusual differentiation of the midpiece into two distinct segments. The anterior segment is defined by profuse peri‐mitochondrial stacks of membranes which develop as spermatozoa pass through the epididymis. These membranes, although prominent in mature spermatozoa fixed in situ, appear sparse and disorganised in spermatozoa fixed after 15 to 30 minutes of active motility in physiological medium, suggesting their possible utilisation in motile spermatozoa. The posterior segment is characterised by a thick peri‐mitochondrial cytoplasmic sleeve, by spirally arranged parallel fibrous bands immediately beneath the plasma membrane and, subsequently, as spermatozoa pass into the lower corpus epididymidis, by rows of flask‐shaped surface invaginations which develop between the spiral bands.

Despite broad similarities in the features of sperm maturation in this marsupial and in eutherian mammals, there are distinct differences in the structural organisation of their spermatozoa, particularly in the sperm head. Until more is known of the details of fertilisation in marsupials the significance of these differences will remain unclear.
Monoamine distribution in primate brain. III. Catecholamine‐containing varicosities in the hypothalamus of Macaca mulatta
Authors: Hoffman Gloria E. , Felten David L. , Sladek John R.
Published: February 2005

The histochemical fluorescence technique of Falck and Hillarp was used to examine the distribution of catecholamine‐containing varicosities within the hypothalamus of the rhesus monkey (Macaca mulatta). Varicosities were seen in heaviest concentrations within the periventricular area and the following nuclei: lateral and medial preoptic, supraoptic, paraventricular, arcuate and dorsomedial. Patterns observed presented striking similarities and dissimilarities to catecholamine distribution reported in the rat and cat. Catecholaminergic perikarya were not observed routinely.
Structural development of endocardial cushions
Authors: Markwald Roger R. , Fitzharris Timothy P. , Manasek Francis J.
Published: February 2005

Development of chick and rat endocardial cushions (cardiac mesenchyme) was studied histologically (using Nomarski differential interference optics on living and unfixed tissue), ultrastructurally (scanning and transmission electron microscopy), cytochemically (using acidified dialyzed iron as a visual probe for polyanionic material) and autoradiographically (using 35S) to elucidate the origin of the mesenchyme, the morphologic sequences leading to cushion formation and secretion of sulfated glycosaminoglycans, if any, by migrating mesenchymal cells. Cushion formation was similar for both species. Mesenchymal cells appeared initially, in 16‐ to 18‐somite embryos, beneath the endothelium (which lacked a basal lamina) of the future atrioventricular canal and outflow tract. The cytoplasm of cushion mesenchymal cells was structurally similar to the endothelium; probably these cells arose by proliferation of the endothelium. Mitotic figures among the “seeded” cells were also numerous. Cushion cells were initially attached to the endothelium by desmosomes but acquired motile apparatus (pseudopodia and filopodia containing microtubules and microfilamentous bundles). Serial sectioning of successively‐aged embryos (20–44 somites) indicated a centrifugal migratory direction. Interaction of the cell processes with extracellular matrix suggested that the latter was used as a migratory substrate. Contact of the advancing wedge of cushion cells with the myocardium produced no alteration in cell structure or mitotic activity. Localization of hyaluronidase‐sensitive, dialyzed iron (DI) precipitates in 250‐nm Golgi vacuoles and hyaluronidase‐sensitive 35S‐engendered silver grains over cushion cells indicated that this tissue contributed sulfated macromolecules to the matrix. Localization of hyaluronidase‐labile, DI material in coated, endocytic like vesicles and caveolae also suggested potential modification or conditioning of the matrix by migrating mesenchymal cells. Altogether the study established loci in developing cushions where disruption of the developmental sequence could engender valvular or septal defects.
Fixative tonicity for scannig electron microscopy of delicate chick embryos
Authors: Litke Larry L. , Low Frank N.
Published: February 2005

Fresh pullet eggs (White Leghorn strain) were incubated from 19–26 hours. Blastoderms were fixed in ovo by selected fixatives of various tonicities, postfixed in 2% OsO4, dehydrated in acetone, critical‐point‐dried in liquid CO2, coated with palladium‐gold and observed in a Cambridge S4 scanning electron microscope.

Shrunken cells with intracellular yolk granules embossed on the surface are produced by the strongly hypertonic Karnovsky's fixer (Final: 2010 mOsm). Embryos fixed with modified Karnovsky's fixer (Final: 373 mOsm) possess surfaces with irregular microappendages. Swollen cells with few microappendages are obsrved when embryos are fixed in a hypotonic environment (Final: 250 mOsm or less). Ideal fixatives preserve a relatively flat surface, with cells bordered by smooth surface microappendages. For adequate SEM fixation, fixative vehicle should be approximately isotanic for tissue, with aldehyde (2% or less) added to vehicle.
Immunohistochemical localization of gonadotropin‐releasing hormone (GnRH) in the fetal and early postnatal mouse brain
Authors: Gross Douglas S. , Baker Burton L.
Published: February 2005

The objectives were to (a) determine the age in development when GnRH is first detectable in the brain and (b) observe the distribution of GnRH throughout the fetal and early postnatal period. GnRH was localized immunohistochemically in fetal (15, 16, 17 and 19 days of gestation) and early postnatal (1‐ and 7‐day‐old) mice with the peroxidase‐antiperoxidase (PAP) method of Sternberger.

In the organum vasculosum of the lamina terminalis (OVLT) and in the median eminence of the fetus, GnRH was first detected at 17 days of gestation. In the OVLT, GnRH was found ventral to the preoptic recess of the third ventricle near the ventral surface of the brain. In addition, GnRH was located adjacent to the superficial portal capillaries near the surface of the median eminence. At 19 days of gestation, the distribution of GnRH was similar to that observed at 17 days and there was a marked increase in amount.

In the newborn mouse, GnRH was undetectable in the OVLT and its content in the median eminence was decreased as compared to that observed in the fetus. By the seventh postnatal day, a considerable accumulation of GnRH had occurred in the OVLT and median eminence. In the OVLT, it was associated with capillaries ventral to the preoptic recess, and its distribution in the median eminence was similar to that in the adult mouse.

In both the OVLT and median eminence of the fetal and early postnatal mouse GnRH appeared to be stored in axons and axon endings, but was not detectable in nerve cell bodies or ependymal cells. These observations suggest that the potential for neuroendocrine control of gonadotropin secretion exists in the fetal mouse as early as 17 days of gestation.
Desmosome‐like junctions between Sertoli and germ cells in the rat testis
Authors: Russell Lonnie
Published: February 2005

Desmosome‐like junctions between Sertoli cells and germ cells (spermatogonia, spermatocytes and non‐elongate spermatids) were observed in the adult rat testis. At all levels, certain features were characteristic of this relationship, the most prominent being a densification of the subsurface aspect of the plasma membranes of each cell. The Sertoli cell counterpart demonstrated an abundance of cytoplasmic fibrils which converged on the density, but no such feature was evident in the germ cell counterpart. The width of the intercellular space was variable, ranging in some regions from approximately 3–5 nm, to other regions of approximately 14–18 nm, the latter being representative of most areas of contact. A poorly represented, and often discontinous, intermediate dense line was observed in the intercellular space. Hypertonic fixative solutions containing dextrose were utilized to provoke tissue shrinkage and exaggeration of the intercellular space within the basal compartment of the testis. Cell separation was evident over most regions of the cells, except where desmosome‐like contacts were present. Forces transmitted from one cell to another at desmosome‐like contacts resulted in tearing of cellular fragments, while junctional regions of both cells remained intact. These observations indicate that desmosome‐like junctions are strong adhesive sites between germ cells and Sertoli cells.
Movement of spermatocytes from the basal to the adluminal compartment of the rat testis
Authors: Russell Lonnie
Published: February 2005

The progressive movement of primary spermatocytes from the basal to the adluminal compartment of the seminiferous tubule was studies after testes were fixed with standard and hypertonic solutions. In stages VI, VII and VIII of the cycle (classification of Leblond and Clermont, '52), preleptotene spermatocytes were observed within the basal compartment of the seminiferous tubule. Resting on the basal lamina, these cells were bound tightly to neighboring Sertoli cells by desmosome‐like junctions. In late stage VIII and early stage IX, basal processes of Sertoli cells were observed between the newly formed leptotene cells and the basal lamina, and in stage IX, the Sertoli processes met to form a junction of the zonula adherens type. This junction formed a permeability barrier which restricted the free access of fixative into the spaces around leptotene cells. Evidence for this was found in the absence of the shrinkage artifact produced with hypertonic solutions in earlier stages. In longitudinal sections, the permeability barrier was first observed in an area of the tubule in which sperm release was also taking place. In mid‐ stage IX and in stage X, Sertoli‐Sertoli junctional specializations formed de novo below the leptotene spermatocyte, while those from the preceding stages, present above the leptotene spermatocytes, remained intact. Thus, tight junctions were in evidence for a considerable period of the time, both above and below the leptotene spermatocytes. At no time in the process of germ cell movement toward the lumen did these cells exhibit evidence of amoeboid movement or lose desmosome‐like contacts with the surrounding Sertoli cells.

From this study it is concluded that the Sertoli cells play an active role in the transfer of spermatocytes to the adluminal compartment. A transient intermediate compartment of the seminiferous tubule is described, one which allows for the continual maintenance of the blood‐testis barrier during transit of spermatocytes from the basal to the adluminal compartment.
Morphological and histochemical organization of the flexor carpi radialis muscle in the cat
Authors: Gonyea W. J. , Ericson G. C.
Published: February 2005

Most studies concerning the structure and function of skeletal muscle have utilized the hind limb of the experimental animal. However, it has been shown that the number of behavioral tasks performed by the cat's forelimb is greater than that of the hind limb. In addition, the forelimb muscles exhibit a functional complexity not observed in hind‐limb musculature. The purpose of this study was to investigate the distribution of fast‐twitch and slow‐twitch muscle fibers and muscle spindles in the flexor carpi radialis muscle (FCR) and to correlate the distributional patterns in these structures with muscle tendon architecture and muscle function. It was found that the FCR, a wrist flexor, contains 37% slow‐twitch fibers and 63% fast‐twitch fibers. However, the slow‐twitch fibers were concentrated in the deep region located between the tendons of origin and insertion, while the fast‐twitch‐glycolytic fibers were concentrated more peripherally. Muscle spindles were associated with the slow‐twitch region and were never found in the region containing high concentrations of fast‐twitch‐glycolytic fibers. Fast‐twitch‐oxidative‐glycolytic fibers were uniformly distributed throughout the muscle. It is proposed that the association of muscle spindles with slow‐twitch fibers and the differential distribution of muscle fibers into slow‐twitch and fast‐twitch regions might allow these regions to function independently of one another when called upon to perform complex behavioral tasks.
Arrangement of connective tissue components in the walls of seminiferous tubules of man and monkey
Authors: Hermo L. , Lalli M. , Clermont Y.
Published: February 2005

In primates the membrane separating the seminiferous epithelium from the interstitial space is composed of one to three (monkey) or two to six layers (man) of myoid cells associated with one to two layers of fibrocyte‐like adventitial cells. All these cells are separated from each other by irregular spaces filled with various connective tissue intercellular components. Subjacent to the elements of the seminiferous epithelium is a continuous, often redundant, basement membrane. A similar basement membrane‐like material forms a layer next to and over small areas of the plasma membrane of myoid cells. Collagen fibrils grouped in bundles of various sizes are seen in all connective tissue layers but are particularly abundant in the space between the seminiferous epithelium and the innermost layer of myoid cells. Elastic fibrils demonstrated by the Verhoeff iron hematoxylin technique are also present. Composed of a homogeneous material, the elastic fibrils are short, irregular, branching entities with a diameter comparable to or smaller than that of collagen fibrils. In addition, an abundance of microfibrils with a diameter of 12–15 nm is present in the various connective tissue layers. These microfibrils have a densely stained cortex and a lightly stained core. When seen close to the myoid cells, bundles of microfibrils appear to insert on well defined areas next to the plasma membrane. These areas commonly face the patches of electron‐dense material observed on the inner aspect of the plasma membrane of the myoid cells and in which the actin filaments are inserted. Bundles of microfibrils often span the gap between myoid cells of the same layer as well as those of adjacent layers. Microfibrils are also closely related to the surface of elastic fibrils and are seen intertwining with collagen fibrils. Thus microfibrils appear to bridge and bind together adjacent myoid cells and anchor the surface of these cells to the bundles of elastic and collagen fibrils present in the intercellular spaces of the limiting membrane.
An electron microscopic study of absorption of peroxidase conjugated immunoglobulin G by guinea pig visceral yolk sac in vitro,
Authors: King Barry F.
Published: February 2005

In the guinea pig and some other animals, passive immunity is conferred on the developing fetus by passage of immunoglobulin from mother to fetus across the yolk sac. In order to examine the cytological pathway involved in immunoglobulin transport, guinea pig visceral yolk sacs from late in gestation were exposed in vitro to peroxidase‐conjugated guinea pig immunoglobulin G (IgG‐HRP). Tissue was then fixed, incubated to show the site of localization of peroxidase reaction product and prepared for electron microscopy. The results suggested that the first step in the uptake of IgG‐HRP by yolk sac is attachment of the protein to the surface coats of endocytic invaginations at the apical surfaces of the endodermal cells. The endocytic vesicles then appear to pinch off from the surface and move deeper into the cytoplasm. Some of the small endocytic vesicles fuse with large apical vacuoles, which often contain large amounts of reaction product. Other small endocytic vesicles pinch off from the surface, move deeper into the cytoplasm and fuse with the lateral plasmalemma; their protein content is emptied into the intercellular space by exocytosis. From the intercellular spaces the protein presumably diffuses across the basement membrane and connective tissue spaces and enters the vitelline capillary bed. It is postulated that the latter cellular pathway, involving small vesicles and the intercellular spaces, is utilized by those immunoglobulins which are transferred intact across the yolk sac endoderm.
The effect of large unilateral cortical lesions on rubrospinal tract sprouting in newborn rats
Authors: Castro Anthony J. , Clegg Denis A. , McClung J. Ross
Published: February 2005

Many previous reports have demonstrated the development of aberrant neural connections in response to neonatal brain lesions. This investigation was undertaken to study possible alterations, particularly axonal sprouting, in rodent rubrospinal projections after neonatal destruction of the corticospinal tract through frontal cortical ablation. The neonatal ablations were made by aspiration in 1 to 2‐day‐old rats under hypothermic anesthesia. At three to six months after neonatal surgery, the rubrospinal tracts were ablated bilaterally in these same animals as well as in controls, by stereotaxically transecting the ventral tegmental decussation. Animals were killed two to six days after adult surgery, and rubrospinal projections were demonstrated using the Fink‐Heimer degeneration stain. No differences in the pattern of rubrospinal projections were observed between animals with neonatal cortical lesions and controls. In all animals rubrospinal projections were located primarily in Rexed's lamina VI with a slight distribution into lamina V and the dorsal portion of lamina VII. Various hypotheses explaining the lack of rubrospinal sprouting after neonatal cortical lesions are presented, along with possible experiments to test these hypotheses.
The comparative fine structure of the interhemal membrane of chorioallantoic placentas from six genera of myomorph rodents
Authors: King Barry F. , Hastings Richard A.
Published: February 2005

In order to extend the cytological information available on the structure of the interhemal membrane in cricetid rodents, in particular, and myomorph rodents, in general, we have examined the fine structure of the placental labyrinth in five genera of cricetid rodents (Lemmus, Dicrostonyx, Clethrionomys, Microtus and Peromyscus) and one genus of murid rodent (Acomys). Small pieces of labyrinth from near‐term placentas were fixed in glutaraldehyde and osmium tetroxide and processed for electron microscopy. The interhemal membranes of all the species examined were hemotrichorial. The outermost layer of trophoblast, bordering the maternal blood spaces, was celular and often contained some patent fenestrae, whereas the middle and inner trophoblastic layers were apparently syncytial. The outermost trophoblastic layer of all the species contained abundant granular endoplasmic reticulum. The intercellular space between the outer and middle layers was variable in width, primarily due to the complex folding of the surface of the middle layer. The surfaces of the middle and inner layers were closely apposed. The middle trophoblastic layer in several species contained filamentous “glomerular bodies” and the innermost layer, particularly of Peromyscus, contained smooth membranous whorls. A basal lamina separated the innermost trophoblastic layer from the fetal capillary endothelium. The endothelial cells in most of the species contained fenestrated regions. These observations are compared to those on other hemochorial placentas, and common features of cricetid (and myomorph) rodent placental fine structure are emphasized.
Regeneration of tooth development in vitro following sodium fluoride treatment
Authors: Kerley Michael A. , Kollar Edward J.
Published: February 2005

Mandibular incisors were dissected from the jaws of 15‐ and 16‐ days C57BL/10 mouse embryos and cultured on agar‐solidified Eagle's basal medium supplemented with fetal calf serum, an antibiotic, and glutamine. The experimental medium was the same as the control except that fluoride was added such that the final concentrations ranged from 2.0‐8.0 mM NaF. Control and experimental explants were recovered after two, four and six days of incubation and studied histologically. After two days of fluoride treatment (3.0 mM NaF), cellular degeneration was observed in the dental papilla mesenchyme while the enamel organ epithelium appeared more resistant. Prolonged treatment or treatment at higher concentrations resulted in destruction of the dental papilla. The enamel organ was still present but was abnormal and reduced. Older tooth germs were less affected overall when incubated at the same fluoride dosage and time of treatment. When explants subjected to limited exposure (2 days) to fluoride were placed on control medium, the suppressed tooth germs recovered. The recovery was enhanced by grafting untreated mesenchyme to the treated explants followed by incubation on control medium. The observations indicate that NaF can suppress the development of tooth germs in vitro and that recovery from the suppresion does occur. The more severe inhibition observed in the mesenchymal component when compared to the response of the epithelial component of the treated explants suggests that fluoride may alter the ultimate morphology of the tooth crown by disrupting the normal epithelial‐mesenchymal interaction which occurs during early tooth development.
Pathogenesis of osteopetrosis in the microphthalmic mouse: Reduced bone resorption
Authors: Marks Sandy C.
Published: February 2005

Bone resorption, stimulated by injection of parathyroid extract, was measured in vivo in microphthalmic mice as the rate of release of 3H from bone after incorporation of 3H‐proline. Bone resorption in these mice, which inherit osteopetrosis, was less than 10% of that in normal littermates. Autoradiography confirmed the reduction in removal of radioactive bone matrix and in bone growth in microphthalmic mice. The ability of these mice to raise the serum calcium concentration in response to PTE was also reduce. These results, that bone resorption is reduced in microphthalmic mice, are discussed in relation to the pathogenesis and cure of the disease.
Three‐dimensional studies of resorption spaces and developing osteons
Authors: Tappen N. C.
Published: February 2005

Resorption spaces and their continuations as developing osteons were traced in serial cross sections from decalcified long bones of dogs, baboons and a man, and from a human rib. Processes of formation of osteons and transverse (Volkmann's) canals can be inferred from these three‐dimensional studies. Deposits of new osseous tissue begin to line the walls of the spaces soon after termination of resorption. The first deposits are osteoid, usually stained very darkly by the silver nitrate procedure utilized, but a lighter osteoid zone adjacent to the canals occurs frequently. Osteoid linings continue to be produced as lamellar bone forms around them; the large canals of immature osteons usually narrow very gradually. Frequently they terminate both proximally and distally as resorption spaces, indicating that osteons often advance in opposite directions as they develop. Osteoclasts of resorption spaces tunnel preferentially into highly mineralized bone, and usually do not use previously existing canals as templates for their advance. Osteons evidently originate by localized resorption of one side of the wall of an existing vascular channel in bone, with subsequent orientation of the resorption front along the axis of the shaft. Advancing resorption spaces also apparently stimulate the formation of numerous additional transverse canal connections to neighboring longitudinal canals. Serial tracing and silver nitrate differential staining combine to reveal many of the processes of bone remodeling at work, and facilitate quantitative treatment of the data. Further uses in studies of bone tissue and associated cells are recommended.
Programmed cell death in the Müllerian duct induced by Müllerian inhibiting substance
Authors: Price J. Michael , Donahoe Patricia K. , Ito Yasuo , Hendren W. Hardy
Published: February 2005

The importance of a secretory product of the fetal testis, Müllerian Inhibiting Substance, in determining the fate of the Müllerian duct in the developing male fetus has been well documented. The present investigation has examined the mechanism of action of Müllerian Inhibiting Substance in the male rat fetus during the course of Müllerian duct degeneration.

The action of Müllerian Inhibiting Substance mimics the general morphogenetic phenomenon of “programmed cell death,” although important differences were found compared to the majority of other studies of cell death. The initial morphological event in the degenerating Müllerian duct is an increase in lysosomes within the duct cells. Following loss of polarity and orientation, the duct cells are subsequently removed by invading macrophages from the surrounding mesenchyme. Concommitant with the differentiation of these macrophages, the adjacent mesenchyme assumes a characteristic whorled pattern around the degenerating Müllerian duct. Cytochemical localization of acid phosphatase confirmed the presence of newly formed lysosomes within the Müllerian duct cells and subsequently within the cytoplasm of the invading macrophages.
Complicated colobomatous microphthalmos in the BW rat: A new form of inherited retinal degeneration
Authors: Wyse J. P. H. , Hollenberg M. J.
Published: February 2005

A new model of inherited retinal degeneration has been found in the rat. It is inherited in association with a number of other ocular defects, including microphthalmos, coloboma, retinal dysplasia, optic nerve hypoplasia and/or aplasia, as well as medullation of the nerve fiber layer of the retina. Together, these abnormalities constitute a condition referred to as complicated colobomatous microphthalmos. This condition was originally discovered in the Bmn strain of rats but subsequently transferred to a new genetic background in the Bmn‐wys strain of rats (BW). This facilitated the histological evaluation of both the developmental and degenerative ocular defects in the adult animals. A well defined pattern emerged relating eye size, optic nerve size and retinal histology. Normal‐sized eyes had normal‐sized optic nerves and normal retinal histology while intermediate‐sized eyes with no optic nerves had uniformly thin retinas. In contrast, intermediate‐sized eyes with small optic nerves had areas of both normal thickness and thin retina. All of these eyes developed retinal degeneration characterized by a late onset and slow progression associated with normal phagocytic activity in the pigment epithelium and a tendency for the rod outer segments to fragment into very thin structures rather than accumulate as lamellar debris. This indicates that the retinal degeneration in the BW model differs in many respects from the well studied RCS model.
Proteolytic activity of guinea pig spermatozoa after induction of the acrosomal reaction in vitro
Authors: Gaddum‐Rosse P. , Blandau R. J.
Published: February 2005

After inducing the acrosomal reaction in guinea pig spermatozoa in vitro, the sperm were tested for proteolytic activity by applying them to membranes of fixed gelatin. One to 5% of them showed slight evidence of proteolytic activity, while the rest were completely negative. Sperm that had retained their acrosomes throughout the incubation period displayed intense proteolytic activity. These results suggest that proteinases may be lost from spermatozoa as a result of the acrosomal reaction.
Morphological changes induced by cyclophosphamide in crypt epithelium of the small intestine in mice: Light and electron microscopic studies
Authors: Sobhon Prasert , Wanichanon Chaitip , Sretarugsa Prapee
Published: February 2005

When a single sublethal dose (300 mg/kg body weight) of cyclophosphamide was injected intraperitoneally into experimental mice, several morphological alterations were detected in the crypt epithelium within a few hours. These were (a) mitotic activity of epithelial cells decreased, reaching the lowest level at 16 hours; (b) an abnormally high number of lymphocytes and cells with eosinophilic granules appeared in the epithelium; later these cells degenerated and the maximum number of dead cells was observed at six hours after the drug injection. At four days post‐injection the morphology of crypt epithelium had returned to normal.

Electron microscopic examination revealed that although the mitotic activity of crypt epithelial cells was depressed, there was little change in their morphology following the drug administration. However, many intermediate stages of degeneration of lymphocytes and eosinophilic cells were observed in the intercellular spaces as well as apparently inside the cytoplasm of crypt epithelial cells. The eosinophilic cells are characterized by the presence of large crystal‐containing granules in the cytoplasm, and are believed to be equivalent to “globular leucocytes” described by many investigators. Evidence from this study suggests that lymphocytes and globular leucocytes are more sensitive to cyclophosphamide than crypt epithelial cells, and that they degenerate in crypt epithelium.
Mode of locomotion of Schwann cells migrating in vivo
Authors: Billings‐Gagliardi Susan
Published: February 2005

The manner of locomotion of Schwann cells during normal development was studied by means of repeated observations and photomicrographs of individual cells at closely spaced time intervals and focal levels. In developing tadpole peripheral nerves, Schwann cells move sporadically with brief periods of rapid translation of the whole cell interspersed with longer intervals when the cell shows little or no overall movement. Highest rates of locomotion averaged 5 μm/minute with a duration of no greater than four to six minutes. Net rates of speed measured over at least 20 minutes were always considerably lower, with the average being 1.9 μm/minute. Rapid locomotion involves protrusion and growth of several pseudopodia, while the cell body remains in place, followed by attachment of these processes to an axonal surface, and finally detachment of the trailing portions of the cell as the entire cell hitches forward, “inchworm‐style.”
Preimplantation development, fate of the zona pellucida, and observations on the glycogen‐rich oviduct of the little bulldog bat, Noctilio albiventris
Authors: Rasweiler John J.
Published: February 2005

The reproductive biology of Noctilio albiventris was investigated histologically in 112 females collected at the start of their synchronized breeding season during two different sampling years in the Cauca Valley of Colombia. Both ovaries were functional, but the animals were generally observed to be monovular. Embryonic development in the oviduct was found to proceed to blastocyst formation and loss of the zona pellucida. In 22 animals the discarded zona had been left behind in the oviduct upon passage of the embryo into the uterus and was still undissolved at the time of amniogenesis, the latest stage examined. The zonae which had passed into the uterus with the embryos often exhibited signs of dissolution. Most of the early blastocysts were morphologically distinctive, lacking a typical inner cell mass and being instead largely bilaminar. Degenerating ova from previous ovulations were found in the oviducts of two pregnant bats, suggesting that Noctilio may be another species in which the embryo stimulates its own escape from the oviduct. During tubal passage of the embryo the secretory cells of the oviductal ampulla and isthmus exhibited a transient engorgement with glycogen, particularly on the side ipsilateral to the new corpus luteum.
Development of the metatarsophalangeal joint of the chick embryo: Morphological, ultrastructural and histochemical studies
Authors: Mitrovic Dragoslav R.
Published: February 2005

The histogenesis and mechanism of joint clefting of the developing chick embryo up to the fifteenth day of incubation have been studied morphologally, ultrastructurally, and by histochemical methods. Cell degenration was consistently noted 24 hours after differentiation of the joint tissue, and it is postulated that this early cell necrosis might account for the loosening of the medial part of articular mesenchyme (interzone) leading to differentiation of a three‐layered embryonic joint. At the time of joint clefting degenerative cells were also seen in the peripheral parts of the developing articular cavity. In somes cases clefting was immediately preceded and/or accompanied by the appearance of elongated, basophilic and electron‐opaque cells closely arranged along the zone of tissue cleavage. These cells were thought to be implicated in some way in the clefting process and later to constitute a surface cell layer of articular cartilage. In addition to these observations clear morphological and histo‐autoradiographic evidence was found for the presence of an organic component, presumably mucopolysaccharide, in the primitive synovial fluid. Fluid secretion might also account for tissue cleavage at the sites of its accumulation.

The data reported here suggest that joint cavity formation results from a combination of both intrinsic, genetically expressed and extrinsic mechanical factors acting synchronously.
The role of movement in the development of a digital flexor tendon
Authors: Beckham Cassandra , Dimond Richard , Greenlee Theodore K.
Published: February 2005

D‐tubocurarine was injected into the air sac of 8‐day chick embryos to prevent movement of the digits of the hind limb. The embryos were paralyzed from the tenth to the eighteenth day, when the experiment was terminated. The immobilization of the flexor digitorum profundus tendons in the tarsus resulted in a loss of specialized structures around and on this tendon, as determined by light and electron microscopy. Specialized areas observed in the normal chick (synovial cavity, fibrocartilaginous area, and elastic vinculum) failed to form, as a result of the paralysis of the digit.

Several authors have shown previously that movement is a requirement for the molding and maintenance of joint cavities in vivo, in ovo and in vitro (see text for references). We have shown that movement of the tendon is required to produce a functional tendon apparatus in the embryo and predict that movement is also required for regeneration after injury.
Endothelial cell membrane: Differences in the density of intramembranous particles between tissue‐ and blood‐fronts revealed by freeze‐fracture
Authors: Shaklai Matityahu , Tavassoli Mehdi
Published: February 2005

Significantly higher density of intramembranous particles (IMP) was noted in the endothelial plasma membrane facing the blood‐front compared to the tissue‐front. The difference may be related to the function of the vascular endothelium as an active barrier between the blood and the tissue.
An ultrastructural study of developing extracellular matrix in vitelline blood vessels of the early chick embryo
Authors: Murphy Mark E. , Carlson Edward C.
Published: February 2005

This investigation was designed to describe the morphological events in embryonic development of peripheral blood vessels (vasculogenesis) and to relate this process to the appearance of extracellular matrix (ECM) during growth and maturation of these tissues. Extraembryonic vitelline vessels of the early chick embryo were chosen for this study and light, transmission, and scanning electron microscopy were carried out on vessels excised from chick embryos (Hamburger‐Hamilton stages 8 through 23). Our data show that early (stage 10) vessels are composed of two distinct epithelial layers, an inner layer of presumptive endothelium surrounded by a layer of splanchnopleuric mesoderm. During development, the inner layer gives rise to mature vascular endothelium while splanchnopleuric mesoderm differentiates to form primitive vascular smooth muscle. Ultrastructural studies show the presence of collagen and basal lamina in the extracellular space between these two layers during initiation of endothelial and smooth muscle cytodifferentiation. Furthermore, ruthenium red‐positive material is present on basal surfaces of developing vascular endothelium at this time, indicating possible glycosaminoglycans (GAG) or other polyanionic components of the ECM. These data suggest that the sequential production of basal lamina, collagen(s), and/or GAG's by developing peripheral vessel wall epithelia may be critical to their final differentiation.
The effect of cytochalasin B on the neuroepithelial cells of the mouse embryo
Authors: Webster William , Langman Jan
Published: February 2005

Eleven‐day mouse embryos were cultured in a medium containing cytochalasin B (10 μg/ml) to examine the effect of the drug on the developing CNS. The embryos were exposed to the drug for two hours. After culturing, the embryos were prepared for light and electron microscopy and the neuroepithelium of the cerebral vesicles was examined. The following abnormalities were noted in the cytochalasin B‐treated embryos: (1) mitotic figures were situated in the middle of the neuroepithelial layer instead of on the lumen, indicating that premitotic nuclear migration had been prevented; (2) binucleate cells were found in the neuroepithelial layer, indicating that cytochalasin B does not interfere with mitosis but prevents cytokinesis; (3) the microfilaments usually seen in the apex of the neuroepithelial cells were disrupted and formed an amorphous mass of filamentous material; (4) some neuroepithelial cells were free in the lumen, whereas others protruded into the ventricle but appeared to remain attached to the internal limiting border by their junctional complexes; and (5) in some regions the neuroepithelial cells had broken away from their end‐feet at the basal lamina. These morphological changes were associated with a change in the internal limiting boundary from concave to convex and vacuolation of the external processes of the cells. The relationship between cytochalasin B, microfilaments and these morphological changes is discussed.
Influence of abdominal temperature on epididymal function in the rat and rabbit
Authors: Bedford J. Michael
Published: February 2005

The effects of body temperature on sperm maturation and sperm storage in the epididymis have been studied in rats and rabbits by surgical reflection of the epididymis into the abdomen without disturbing its continuity with a functional scrotal testis. Rats so treated remained fertile during a period of 13 months, as judged by a sequence of normal litters born to their female cage mates, and cryptepididymal rabbits remained fertile for four months or more according to the individual, as evidenced by eggs fertilized and litters born after artificial insemination or natural mating. By contrast, spermatozoa confined by ligatures within an abdominal cauda epididymidis never retain their potential for motility for more than a brief period (5 days in rat; 8–10 days in rabbit), as compared with several weeks in contra‐lateral scrotal controls. It is uncertain whether their early death at abdominal temperatures resulted primarily from a suppressive effect of the temperature on the spermatozoa themselves, or on the caudal epithelium.

Because of an increasing presence of apparently immature spermatozoa in the ejaculate of the first cryptepididymal rabbit between 7 and 11 months postoperatively, the rate of sperm transport through the epididymis of seven cryptepididymal rabbits was estimated by labelling with tritiated thymidine. As judged by the time of appearance of labelled spermatozoa in the ejaculate, transposition of the rabbit epididymis to the abdomen ultimately causes a progressive increase in the rate of sperm transport through it from a normal of nine days to two to five days in the cryptepididymal state.

Thus, although maturation may eventually be compromised to some degree because of an increased rate of sperm passage, and sperm storage is inhibited, abdominal temperature apparently does not alter the essential biochemical nature of the epididymal milieu required for maturation. These results are reviewed in light of the suggestion (Bedford, '78) that the cauda epididymidis has been the prime mover in scrotal evolution.
Cytodifferentiation of secretory cells in the sublingual gland of the prenatal rat: A histological, histochemical and ultrastructura study
Authors: Redman Robert S. , Ball William D.
Published: February 2005

Sublingual and submandibular glands were prepared for light and electron microscopy, and for histochemical staining with periodic acid‐Schiff (PAS), Alcian Blue (AB) or both (AB‐PAS). Between 15 and 17 days post‐conception, the sublingual gland undergoes active morphogenesis from a single, solid bud into a branched glandular tree. At 18 days the first overt signs of secretory differentiation appear in the formation of cells with three kinds of secretion granules; that is, electron‐dense serous granules, empty‐looking mucous granules with fine thread‐like substructures, and granules which have the general appearance of mucous granules but also contain an internal, electron‐dense core (“mixed” granules). During the period from 18 to 20 days, all three types of granulated cells increase in number, with mucous cells predominating, and they all border directly on the acinar lumina, in seemingly random combinations in different acini. This diversity is reflected in the histochemical staining, since most acini and cells are both PAS‐ and AB‐positive, but a substantial minority stain only with PAS, indicating that they contain serous granules. By comparison, all secretory cells in the submandibular gland stain with PAS but not with AB after the initial appearance of secretory granules at 18 days. From 20 days to birth (at 22 days), the cells with mixed granules disappear, while the cells with serous granules become fewer in number and displaced to the peripheral outpocketings of the acini. As a result of these changes, the general organization in the newborn is similar to that in the adult, i.e., purely mucous acini with serous demilunes.