bluuebunny/crossref_metadata_2025 huggingface dataset:
Sex differences in Necturus urinary bladders
Authors: Lefevre M. E. , Norris J. , Hammer R.
Published: February 2005

We describe morphological sex differences in urinary bladders of the urodele amphibian Necturus maculosus. The mucosal epithelial cells of bladders from males were tall and contained considerable PAS‐positive material. In scanning electron micrographs of the mucosal surface, epithelial cells from male bladders were well demarcated and were capped with microplicae or with long cilia. The mucosal epithelial cells of bladders from females were low and contained only a small amount of PAS‐positive material; in scanning electron micrographs cell boundaries could not be distinguished and no cilia or microplicae were present. Bladders from males had higher transepithelial potential difference and lower water content than bladders from females. Urine analyses were not significantly different in the two sexes. It is suggested that response to androgens in the male accounts for the observed differences.
Quantitative analysis of cell turnover in the enamel organ of the rat incisor. Evidence for ameloblast death immediately after enamel matrix secretion
Authors: Smith C. E. , Warshawsky H.
Published: February 2005

During renewal of the enamel organ in the rat incisor cohorts of epithelial cells are transported sequentially through presecretory, secretory and maturation zones to the gingival margin where the life cycles of these cells terminate. This process was examined kinetically by determining the absolute flux of cells within each of these zones of amelogenesis. It was found that the efflux of ameloblasts, stratum intermedium and papillary layer cells from the presecretory zone was about equal to the efflux plus expected growth within the secretory zone. However, between the secretory and maturation zones about 50% more ameloblasts entered the maturation zone than were required to account for the egress at the gingival margin and the expected growth. Since there was no similar imbalance between these zones for papillary layer cells, it was concluded that this discrepancy must represent a 50% reduction in the size of the ameloblast population during the maturation stage of amelogenesis. It was calculated that a little over 25% of the loss occurred immediately at the start of maturation within the region of postsecretory transition and the remaining 25% of the loss occurred throughout the subsequent regions of the maturation zone. In addition to the kinetic analysis graphic reconstructions, or surface maps, of ameloblast nuclei were prepared. These maps illustrated the characteristics of ameloblast nuclear packing within the three zones of amelogenesis and they provided quantitative confirmation that as ameloblasts progress through the maturation zone, there is a loss of cells in an amount predicted by the kinetic analysis.
Fibers in monkey posterior articular nerves
Authors: Gardner Ernest , Lenn Nicholas J.
Published: February 2005

The distribution of axons in the posterior articular nerves in rhesus monkey has been studied in terms of ratio of myelinated to unmyelinated fibers, and size of myelinated fibers. Conduction velocity measurements were also made. The nerves contained 2,000 to 2,200 unmyelinated fibers of 0.2 to 1.2 μm. diameter. They contained 399 to 478 myelinated fibers, varying in size from 1.4 to 12.3 μm. Thus 80 to 85% of fibers in these nerves were unmyelinated. The maximum conduction velocity of 70 to 80 meters per second corresponded to an initial small deflection, with most fibers conducting at slower rates. These results are compared to previous reports which severely underestimated the number of unmyelinated fibers because electron microscope counts were not utilized.

It is suggested that pain fibers from the knee joint of monkey make up much of this large population of unmyelinated axons. An unknown number of post‐ganglionic sympathetic fibers is also included in the unmyelinated fiber group.
Spermatogenesis in the Chinese hamster
Authors: Oud J. L. , de Rooij D. G.
Published: February 2005

In this article a description of the process of spermatogenesis in the Chinese hamster is given.

Spermiogenesis could be divided into 16 steps. The cycle of the seminiferous epithelium was divided into 12 stages, coinciding with the first 12 steps of spermiogenesis. The relative and absolute duration of the stages was determined. The duration of the cycle of the seminiferous epithelium was found to be 17.0 days.

The morphology of the spermatogonia was studied in seminiferous tubules mounted “in toto.” Four classes of spermatogonia could be discerned: undifferentiated A spermatogonia (Ais, Apr, Aal), differentiated A spermatogonia (A1, A2, A3). In spermatogonia and B spermatogonia (B1, B2). It is interesting to note that the last generation of spermatogonia (B2) arises at the beginning of stage 7 and divides to give rise to primary spermatocytes in the second half of this stage; in most other species the last generation of spermatogonia arises in stage 4, giving rise to primary spermatocytes in stage 6.

The undifferentiated A spermatogonia were counted in six stages of the cycle, together with the differentiated A, In or B spermatogonia present in the same stages. The results of these cell counts are discussed in detail. One of the conclusions that could be drawn about the behaviour of the Ais and Apr spermatogonia during the cycle of the epithelium was that there is mitotic activity in these cells in several stages of the cycle. It is suggested that this mitotic activity serves to generate the Aal spermatogonia, which after one or more divisions transform into A1 spermatogonia between stages 2 and 8.
Proteolytic dechorionation of annual fish embryos
Authors: Lesseps Roland J. , Gast Elizabeth A.
Published: February 2005

Incubation of early embryos of Nothobranchius korthausae in sterile Tris‐buffered pronase with added salts and EDTA results in complete dechorionation, after which development proceeds normally and at the same rate as in control embryos. The time required for dechorionation varies according to the age of the embryo and the concentration of pronase employed.
Granularity of cells in the juxtaglomerular apparatus in fetal rats after maternal nephrectomy or fetal unilateral nephrectomy
Authors: Eguchi Y. , Yamakawa Michiko , Arishima K. , Morikawa Y. , Hashimoto Y.
Published: February 2005

Granular cell indices (GCI: Dunihue and Robertson, 1957) in kidneys of fetal rats one day after maternal nephrectomy or fetal unilateral nephrectomy on day 21 of gestation were determined by examining sections stained with Bowie's technique. Maternal nephrectomy induced an extreme increase of GCI in fetal kidneys with increased granularity of cells in the juxtaglomerular apparatus. Fetal unilateral nephrectomy did not cause any significant change.
Ultrastructure of the cat sublingual gland
Authors: Tandler Bernard , Poulsen Jørgen Hedemark
Published: February 2005

The sublingual gland of the cat consists primarily of branched secretory tubules that open into an abbreviated duct system. The simple epithelium that composes the secretory tubules consists of an admixture of mucous and serous cells, with the former predominating. Some secretory tubules are capped by a serous demilune. Regardless of position, almost all serous cells have prominent basal folds and border on at least one intercellular canaliculus as well as on the tubule lumen. Serous cells possess an extensive array of irregular, distended cisternae of rough‐surfaced endoplasmic reticulum that frequently contain dense intracisternal granules. Serous granules are relatively few in number and rarely show evidence of substructure. Mucous cells, which lack basal folds, contain an apical mass of secretory material in the form of partially fused droplets. The duct system is somewhat less ordered than in most major salivary glands; secretory tubules empty into structures resembling intercalated ducts or may be in direct continuity with ducts intermediate in morphology between intercalated and excretory ducts. The absence of striated ducts noted in this study may be correlated with the high sodium content of cat sublingual saliva. The main excretory duct of the sublingual gland closely resembles that of the cat submandibular gland in terms of morphology, but exhibits little of the transport functions reported in the latter duct.
The localization of articular cartilage proteoglycan by electron microscopy
Authors: Shepard Nora , Mitchell Nelson
Published: February 2005

Rabbit articular cartilage was fixed with glutaraldehyde containing Ruthenium Red or Safranin O to localize proteoglycan. By light and electron microscopy, Safranin O proteoglycan localization is easily obtained. Ruthenium Red stained proteoglycan is easily visualized by electron microscopy. Previous digestion with papain prevented staining by either technique confirming that the material was indeed proteoglycan.

Using these methods of proteoglycan identification the sites of attachment to collagen are shown as well as the deposition of proteoglycan about cells of differing vitality and the relationship of proteoglycan to cell membranes.
The thyroid gland of the woodchuck, Marmota monax: A morphological study of seasonal variations in the follicular cells
Authors: Krupp P. P. , Young R. A. , Frink R.
Published: February 2005

The morphology of the thyroid gland of the woodchuck, Marmota monax, was studied during the four seasons of the year. In the spring the thyroid is extremely heterogeneous in appearance. Some follicular cells appear quite active. They contain a well defined Golgi apparatus, abundant large colloid droplets and pseudopodia but few, if any, apical vesicles. Other less active cells have poorly defined rough surfaced endoplasmic reticulum and lack a well developed Golgi apparatus. They do not contain apical vesicles or colloid droplets. Summer thyroids have uniformly small follicles which are lined by high cuboidal cells containing numerous mitochondria, apical vesicles, abundant rough surfaced endoplasmic reticulum, and lipid droplets but few colloid droplets. There is extensive lateral and basal infolding of the cytoplasmic membranes in these cells. In the fall and winter the follicles are larger than in the summer and contain more colloid. Numerous heterogeneous dense bodies appear in the cytoplasm of the follicular cells in the fall and increase in number in the winter when there is an obvious sparsity of such glycoprotein synthetic organelles as Golgi apparatus and rough surfaced endoplasmic reticulum. These morphologic changes are compared with previous studies of thyroid structure and function in other animals and are correlated with the seasonal physiologic activities of the woodchuck.
Ultrastructural alterations in neuroepithelial cells of mouse embryos exposed to cytotoxic doses of hydroxyurea
Authors: Sadler T. W. , Cardell R. R.
Published: February 2005

Developing neuroepithelial cells from the cranial region of neural folds were examined at various intervals from 15 minutes to four hours after administration of teratogenic (250 mg/kg) or embryolethal (500 mg/kg) doses of HU to ICR/DUB mice on ninth day of gestation. Thirty percent of surviving fetuses showed exencephaly after the teratogenic dose. The initial ultrastructural change in some neuroepithelial cells occurred within 15 minutes to one hour after treatment with the teratogenic dose and involved a breakdown of polyribosomes into monosomes which were dispersed evenly in the cytosome. At one to two hours, condensation of the cytoplasm and chromatin was observed along with distorted nuclear shape. At two to four hours, cells exhibited extremely condensed cytoplasm and fragmentation of the cells occurred. The affected cells showed pyknotic nuclei and segregation of fibrillar and granular components of the nucleolus. In some nuclei, particularly after treatment with the higher dose of HU, a condensation of the nucleolus was observed. At this stage images were obtained which indicated that neighboring cells phagocytosed the cellular fragments derived from the HU affected cells.
Myogenic cell formation in regenerating rat skeletal muscle injured by mincing I. A fine structural study
Authors: Snow Mikel H.
Published: February 2005

The degenerative and early regenerative events following mincing and autotransplantation of rat skeletal muscle were examined at the ultrastructural level. During the first eight hours after injury, myonuclei undergo pyknosis, mitochondria become enlarged and vesiculated, myofilaments appear less distinct than normal and the sarcolemmata either disappear or become extensively fragmented. Further degeneration of the myofibers progresses slowly until macrophages and polymorphonuclear neutrophils invade the degenerating sarcoplasm between one to four days after mincing. Scattered throughout the minced muscle implant during the first 24 hours after injury are small, viable‐appearing, undifferentiated cells located between the external lamina and degenerating sarcoplasm. Such cells, which are structurally similar to satellite cells seen in uninjured muscle, are believed to be regenerating presumptive myoblasts due to their mesenchymal‐like morphology and sublaminar position. External laminae of the injured muscle fibers do not undergo immediate degenerative changes, but rather persist during the first three to six days as laminar tubes within which spindle‐shaped myoblasts and newly formed myotubes are frequently observed. Examples of regenerating myoblasts in the process of budding‐off from damaged muscle fibers were not observed in this study. Therefore, the evidence suggests that satellite cells are the major source of regenerating myoblasts in skeletal muscle of the rat.
An improved perfusion fixation method for the testis
Authors: Forssmann W. G. , Ito S. , Weihe E. , Aoki A. , Dym M. , Fawcett D. W.
Published: February 2005

A reliable and uniform vascular perfusion fixation method for the testis has been developed by using an initial washout solution containing a vasodilator and an anticoagulant. This is followed by a brief fixation with a sodium phosphate buffered formaldehyde‐glutaraldehyde solution of conventional strength, and then a second more concentrated aldehyde fixative solution containing picric acid. The method takes into account some of the unique features of the vascular supply of the male genital tract for its favorable perfusion and fixation. The advantages of this method are: (1) consistently favorable preservation of the testis; (2) simple and inexpensive apparatus; and (3) stable and relatively innocuous stock solutions.
Leukocyte emigration and migration in the vagina following mating in the rabbit
Authors: Phillips David M. , Mahler Susan
Published: February 2005

Within 45 minutes after mating in the rabbit, numerous heterophil leukocytes adhere to the endothelium of venules in the vagina. Initial association appears to occur via small protuberances from the leukocyte which fit into small indentions in the endothelial cell. Following adherence, leukocytes flatten and pass between endothelial cells. A regular intercellular space separates the leukocyte from the endothelial cells. Leukocytes subsequently migrate through the connective tissue to the epithelium. By three hours postcoitus, the region beneath the basement lamina of the vaginal epithelium is crowded with numerous juxtaposed leukocytes. Leukocytes subsequently migrate between epithelial cells into the vaginal lumen where they actively engulf spermatozoa. Spermatozoa appear to be ingested head first. Numerous small filaments are observed in the leukocyte cytoplasm in the region adjacent to the sperm head. Degranulation of azurophyl granules follows sperm uptake. The leu kocyte response can be elicited either by spermatozoa (from the epididymis) or by semen (from vasectomized bucks), but is not elicited by ovulation (with human chorionic gonadotropin). It is suggested that the response may be initiated because the vagina does not distinguish between semen, spermatozoa and bacterial infection.
Hemopoietic repopulating potential of subcutaneous exudate cells
Authors: Scuderi Philip , Rosse Cornelius , Everett Newton B.
Published: February 2005

Inflammatory exudate (SE) cells were collected from subcutaneous coverslips in mice and transferred into lethally irradiated (1,000 r) recipients. Eight days after transplantation 59Fe incorporation in the spleen and bone marrow was significantly greater than in controls treated with the suspending medium only. One hundred percent of mitoses were of the T6T6 karyotype in the marrow and spleen when SE cells were obtained from CBA/T6T6 donors. The repopulating potential of SE cells, however, lagged significantly, behind that of bone marrow cells and the failure to observe consistently macroscopic spleen colonies calls into question whether the observed regeneration was due to pluripo‐tent stem cells. Radioautographic studies with 3H‐TdR showed that the majority of SE cells had recently been generated, but long‐lived, noncycling cells of lymphoid and monocytoid morphology were also present in the exudate.
A technique for the dry preservation of functioning orthopaedic specimens
Authors: Hamilton James J.
Published: February 2005

A method is presented by which fresh anatomical material may be preserved in a dry state while maintaining joint function and motion. This method could be likened to the tanning of the tendons and ligaments directly on the bones. Mastery of this technique has allowed the preservation of not only the tendinoskeletal system, but also the nervous, vascular, and endotracheal systems as well. While some skill in dissection is necessary, a large amount of the dissection can be done by chemical methods. The actual processing of the specimen is easily done with materials that are readily available. When finished, the specimen is dry, flexible, essentially odorless, and extremely durable. This method can be utilized for material ranging from simple osseous specimens to highly sophisticated dissections. These specimens have been found to be of exceptional advantage in teaching by demonstrating function as well as spatial relationships.
Intercellular junctional complexes of the rat seminiferous tubules: A freeze‐fracture study
Authors: McGinley Dennis , Posalaky Zoltan , Porvaznik Martin
Published: February 2005

This paper provides a description of the intercellular junctions in the rat testis, as observed using the freeze fracture technique. These intercellular junctions were categorized into four general types: Sertoli cell tight junctions, myoid cell tight junctions, gap junctions, and “heterogeneous junctions.” The Sertoli cell tight junctions had a mean depth of 3.1 μm in the basal to apical direction, and contained 25 to 50 (average: 36) parallel rows of particulate sealing elements. The myoid cell tight junction was neither continuous nor extensive, but focal in nature. Interestingly the sealing elements of this junction, like those of the Sertoli cell tight junction, were quite particulate in nature. Typical gap junctions were observed between Sertoli cells, where they were intercalated between the parallel rows of the Sertoli cell tight junction. The most interesting observation was the identification of gap junction‐like structures, in various stages of formation, on germ cell membrane fracture faces, both in the basal and adluminal compartments. Lastly, the unusual “heterogeneous junction” was observed on large membrane fracture faces in close proximity to cells in the adluminal compartment, presumably between Sertoli cells. These junctions appeared to consist of both tight and gap junction elements.
Seasonal variation in the morphology of thyroid parafollicular (C) cells in the woodchuck, Marmota monax: A light and electron microscopic study
Authors: Frink R. , Krupp P. P. , Young R. A.
Published: February 2005

The morphology of parafollicular (C) cells in the thyroid gland of the woodchuck, Marmota monax, was studied during the four seasons of the year. The spring C cells are characterized by a large Golgi zone, rough‐surfaced endoplasmic reticulum, free ribosomes and relatively few dense granules. In the summer these cells appear to be larger and many are packed with dense granules. Fall cells exhibit morphological characteristics suggestive of intense synthetic activity, having rough‐surfaced endoplasmic reticulum in whorls or parallel arrangement, a large Golgi apparatus and few, to many granules, some of which are larger than those seen in the spring and summer C cells. In the winter, most of the C cells are packed with granules. The Golgi zone, when observed, is small and the rough‐surfaced endoplasmic reticulum is sparse. Many cell profiles exhibit apparent granule dissolution. These cyclic morphological findings are discussed along with previous studies of other hibernators and are correlated with the seasonal activities of the woodchuck.
Postnatal development of mitral cell perikaryon in the olfactory bulb of the rat. A light and ultrastructural study
Authors: Singh Dyal N. P. , Nathaniel Edward J. H.
Published: February 2005

The differentiation of the mitral cell perikaryon in postnatal rat olfactory bulb was studied with the light and electron microscope. At birth the mitral cell was distinguishable and occupied a definitive position in the mitral cell layer. The cell contained a large oval nucleus surrounded by a thin rim of cytoplasm. Ribosomes, free and clustered, were scattered in the cell cytoplasm. Rough endoplasmic reticulum was relatively scarce. The Golgi complexes were made up of stacks of smooth‐surfaced cisternae and associated vesicles. In certain cases the Golgi complexes projected into cellular processes. Mitochondria were present in all regions of the cytoplasm and contained well developed cristae. At the end of the first week, the mitral cell had developed significantly in size, and the cytoplasm contained well‐developed rough endoplasmic reticulum. The Golgi complexes were made up of several stacks of smooth‐surfaced cisternae with the association of vesicles and electron dense bodies. The apical dendrites o mitral cells at this periiod had increased significantly in length. Subsequently, during the second and third week, the rough endoplasmic reticulum and Golgi complexes became well developed. Associated with the Golgi complexes were electron dense lysosomal bodies. At three weeks and in older cells it was observed that dense lysosomal bodies. At three weeks and in older cells it was observed that dense lipofuschin granules increased significantly. It is suggested that the mitral cell matures and differentiates earlier than cells in the cerebral cortex.
Scanning electron microscopy of palatal mucosa maintained in organ culture: A method for three‐dimensional visualization of cell morphology
Authors: Bergenholtz Axel , Hallmans GöRan , Hanstrom Lennart
Published: February 2005

A scanning electron microscopic (SEM) study of palatal mucosa maintained in organ culture (50% O2‐Eagle's MEM w/o serum) from 12 to 360 hours is presented. The morphological changes occurring in the explants during culture are illustrated and the findings are compared with those observed using transmission electron microscopy and light microscopy. The results confirm that cellular fine structure in epithelium and connective tissue is more easily visualized when SEM is employed following in vitro maintenance of explants as opposed to examination of fresh uncultured biopsies. The in vitro system used would appear to be applicable to studies designed to investigate the effect of various substances on cell proliferation and cell interactions.
Functional anatomy of lymph nodes. II. Peripheral lymph‐borne mononuclear cells
Authors: Kelly R. H. , Balfour Brigid M. , Armstrong J. A. , Griffith S.
Published: February 2005

In the rabbit a number of large mononuclear cells with ruffled surface membranes travel from the skin and superficial tissues of the leg, via the lymphatics, to the popliteal lymph node: they constitute 40‐50% of the total cell population in the afferent lymph. About 10% of these cells are actively phagocytic when tested in vitro and about 3% are found to contain Langerhans granules.

After isotopic labelling the majority of lymph‐borne mononuclear cells can be detected within the regional node for at least 24 hours; most being located in the paracortex and a few in the interfollicular cortex. It is proposed that these cells, including those containing Langerhans granules, belong to the “mononuclear phagocyte system.”

Possible functions of these lymph‐borne cells are discussed with particular reference to antigen transport.
Light and scanning electron microscopic observations of the effects of sublethal doses of methotrexate on the rat small intestine
Authors: Jeynes B. J. , Altmann G. G.
Published: February 2005

The small intestines of adult rats were examined by light and scanning‐electron microscopy after sublethal doses of methotrexate were injected at 5, 3 and 1 mg, respectively, per rat per day, for three days. Methotrexate inhibited mitosis and thereby disrupted the steady state system of the epithelium. Villi and crypts progressively diminished up to about four and one‐half days after the initial injection. Thereafter, recovery began and, by day 7, relatively normal morphology was restored. In the degenerative phase, the loss of crypt‐villus continuum was frequently observed, the former crypts forming cyst‐like structures. The columnar cells became flat and pleomorphic but epithelial continuity was maintained. Goblet cells apparently decreased in number. Paneth cells, especially in the ileum, appreciably increased in size and number. During the recovery phase, the cystic crypts apparently re‐established continuity with the villus epithelium. Size and proportion of all epithelial cell types returned to normal. Scanning electron microscopy showed villus fusion and the cellular pleo‐morphism and loss of microvilli during the degenerative phase. During recovery of the villi some alteration in orientation and shape remained as shown by scanning electron microscopy.
Fluoride‐induced mineralization within vacuoles in maturative ameloblasts of the rat
Authors: Kuhar Kenneth J. , Eisenmann Dale R.
Published: February 2005

Dense crystalline deposits appeared within vacuoles in rat maturative ameloblasts as a result of repeated injections of sodium fluoride. The crystals assumed varied arrangements but were always observed within intracellular vacuoles. The crystals resemble those of normal enamel and resist microincineration. They are readily dissolved by decalcification and leave behind an organic framework which matches the outline of the crystals. An experimental model is presented which may be useful in further studies of calcium transport, enamel matrix absorption or digestion of cellular debris.
The effect of marcaine on muscle and non‐muscle cells in vitro
Authors: Schultz E. , Lipton B. H.
Published: February 2005

The effect of the local anaesthetic Marcaine on muscle and non‐muscle cell types was examined using an in vitro assay. Each of the cell types examined (myotubes, myoblasts, fibroblasts and liver parenchyma) expressed morphological alterations when incubated in Marcaine‐medium. Myotubes were the most sensitive of the cells studied and exhibited several pronounced membrane structural changes after short incubation periods in Marcaine‐medium. The toxic effects of Marcaine were irreversible and the myotubes continued to degenerate despite being placed in fresh medium. Myo‐blasts and non‐muscle cells, however, demonstrated a rapid recovery when removed from the Marcaine‐medium. Since Marcaine is thought to compete with Ca++ for specific sites on cell membranes, it is proposed that the differential effects which were observed are dependent upon the level of calcium related activities being carried out by the cells.
Morphological studies on the adrenergic innervation of white adipose tissue
Authors: Slavin Bernard G. , Ballard Kathryn W.
Published: February 2005

White adipose tissue was obtained from the mesentery, epididymis, omentum and subcutis of rats which were fed, fasted or fasted and then refed. Tissue samples were prepared using the glyoxylic acid method to detect adrenergic nerves by fluorescence histochemistry. Other tissue samples were fixed with an aldehyde solution containing sodium molybdate which is specific forcatecholamine granules in nerve terminals. Thin and serial thick sections (0.25–0.5μm) were viewed with a conventional electron microscope and with the high voltage electron microscope. With fluorescence microscopy it was found that most of the blood vessels except veins and venules were richly innervated. The most extensive branching of nerves down to the capillary level was found in the mesentery and epididymal fat of fasted‐refed rats. Relatively few adipocytes appeared to be innervated. With electron microscopy, nerve terminals were found distributed with most blood vessels including capillaries, and with some adipocytes. Only 2‐3% of all adipocytes were innervated by adrenergic nerves. It is suggested that in the adipose tissue sites studied the major adrenergic innervation is mainly for the supply of blood vessels.
Unusual features of the nuclear envelope in human spermatogenic cells
Authors: Chemes H. E. , Fawcett D. W. , Dym M.
Published: February 2005

Different types of human germ cells show unusual features of the nuclear envelope. Spermatogonial nuclei demonstrate two kinds of modifications. The first one is a series of intranuclear flattened cisterns, parallel to each other and to the inner aspect of the nuclear envelope. The second one is a nuclear envelope protrusion into the cytoplasm occupied by a double membrane‐limited vesicle. Pores are found on the membrane of the vesicle facing the interior of the nucleus. In spermatocytes the nuclear pores are concentrated over certain areas and completely absent from others. In the regions where they are absent a single cytoplasmic cistern of rough endoplasmic reticulum is closely apposed to the outer membrane of the nuclear envelope. Early modifications of the nuclear surface appear in spermatids before the attachment of the acrosomic vesicle and may indicate an active role of the nuclear envelope in the morphogenesis of the acrosome. In round spermatids nuclear pores are absent from the area which is first related to the Golgi and later covered by the acrosomal cap. Single or multiple layers of cytoplasmic annulate lamellae are closely associated with the nuclear envelope over the pore rich areas. Frequently there are intranuclear accumulations of dense material adjacent to the annulate lamellae‐nuclear pore complex. The chromatoid body is usually present on the cytoplasmic side of this complex. In the elongating spermatids most annulate lamellae are free in the cytoplasm, often in relation with Golgi and chromatoid body remnants near the axial filament. Few stacks of annulate la‐mellae are noted adjacent to the pore rich nuclear regions. It is suggested that the described modifications are related to an active nuclear‐cytoplasmic interaction.
Testosterone and UVL‐B stimulation of epidermal melanocytes in rat scrotal skin
Authors: Glimcher Mark Edward , Wilson Michael J. , Szabo George
Published: February 2005

The effects of UVL‐B and/or testosterone replacement therapy are compared in normal and castrated rats in order to determine whether testosterone is required for UVL‐B (280‐315 nm) stimulation of melanogenesis in the testosterone‐dependent epidermal melanocyte system of the scrotal skin of black Long Evans rats. Testosterone is not a prerequisite for UVL‐B stimulation of melanocytes as in both castrates and normal animals the melanocytes respond to UVL‐B by increases in size, length and number of dendrites (dendriticness), and tyrosinase activity (intensity of Dopa reaction). Addition of testosterone to castrates does enhance the effects of UVL‐B. However, UVL‐B with or without testosterone cannot maintain normal melanogenesis in rats irradiated immediately after castration nor can it restore normal melanogenesis following long term castration. Both the amount of UVL energy/exposure and the number of exposures are important variables in stimulation of the epidermal melanocytes. Administration of a dose of UVL‐B to castrates in a single exposure is ineffective, while the same overall dose spread over several exposures increases the size and dendriticness of melanocytes. Testosterone and UVL‐B act synergistically in affecting melanogenesis although neither singly nor in combination are they able to fully restore normal melanogenesis.
Ultracytochemical localization of Na+,K+‐activated ATPase in chloride cells from the gills of a euryhaline teleost
Authors: Hootman Seth R. , Philpott Charles W.
Published: February 2005

The activity of the electrolyte transport enzyme, sodium, potassium‐activated adenosine triphosphatase (Na+,K+‐ATPase), in the gills of the pinfish, Lagodon rhomboides, increased markedly following transfer of fish from brackish water to seawater. Cytochemical localization of Na+,K+‐ATPase via its potassium‐dependent phosphatase (K+‐NPPase) activity in the branchial epithelium of pinfish adapted to seawater demonstrated that chloride cells are the major sites for the enzyme. Subcellularly, the heaviest depositions of reaction product were observed lining the cytoplasmic membrane surfaces of the labyrinth of anastomosing plasma membrane tubules that ramifies throughout the chloride cell cytoplasm. Enzyme activity was demonstrated also on the cytoplasmic surface of the apical crypt membrane and on the cytoplasmic surfaces of vesicles in the cytoplasm subjacent to the crypt. Deletion of potassium from the cytochemical incubation medium or inclusion of 10 mM ouabain abolished the reaction products associated with these membranes. The significance of these cytochemical results is discussed with reference to current hypotheses of chloride cell function.
Differences in mouse ovarian cells as distinguished by horseradish peroxidase labelling
Authors: Carron Christopher P. , Longo Frank J.
Published: February 2005

The extracellular space of mouse ovarian follicles and stroma contained horseradish peroxidase (HRP) reaction product one minute after intravenous injection of the tracer. In addition to pinocytotic uptake of the tracer, non‐vesicular staining with HRP reaction product, heretofore unrecognized, was noted in a variety of ovarian cell‐types. This diffuse staining was correlated with changes in cellular morphology suggestive of degeneration. These findings are discussed in relation to the composition of cell populations comprising follicles and ovarian stroma and alterations in cell function.
Further observations on tubulobulbar complexes formed by late spermatids and sertoli cells in the rat testis
Authors: Russell Lonnie D.
Published: February 2005

The present study extends earlier findings (Russell and Cler‐mont, '76) by describing additional details of the structure, relationships, distribution, origin, and fate of tubulobulbar complexes. Freeze‐fracture and thin section observations reveal few membrane associated particles and no appreciable cell coat in the membranes forming the tubulobulbar complex. The opposing plasma membranes of the complex do not appear to form a junction, although junctional formation might be expected by the close proximity (4.0 nm apart) of the Sertoli and spermatid plasma membranes. Sertoli filaments of the network which encircle the tubular portion of the complex measure 5.0‐7.0 nm across and appear to insert into the Sertoli plasma membrane. Tubulobulbar complexes initially form in association with a cell surface modification (bristle‐coated pit) of the Sertoli plasma membrane. The first tubulobulbar complexes develop large bulbous components (up to 2.5μm across), which soon lose connection with the spermatid and become incorporated into large phagocytic vacuoles (secondary lysosomes). As bulbs undergo dissolution, newly formed tubulobulbar complexes are observed to replace these structures. Thus, the data indicate that more than one generation of tubulobulbar complexes develop. Moreover, the tubular and bulbous portions of most dissociating complexes (as well as neighboring Sertoli lysosomes) show acid phosphatase activity. Near the time of sperm release, all complexes at the concave aspect of the spermatid head are resorbed. New tubulobulbar complexes, many lacking terminal bulbous dilations, form at the dorsal and lateral aspects of the spermatid head. These persist even after all ectoplasmic specializations and most Sertoli cytoplasm have been withdrawn from a position facing the spermatid head. The presence of tubulobulbar complexes just prior to the time of sperm release is in support of previous findings indicating that tubulobulbar complexes participate in anchoring the head of the late spermatid prior to sperm release. Past the zone of sperm release a few abnormally shaped cells, which had not been released with other spermatids of the same generation, display intact tubulo‐bulbar complexes. The persistence of these and other structures may be the means by which abnormally shaped spermatids are retained and prevented from traversing the male duct system.
Impregnation of soft biological specimens with thermosetting resins and elastomers
Authors: Hagens Gunther Von
Published: February 2005

A new method for impregnation of biological specimens with thermosetting resins and elastomers is described. The method has the advantage that the original relief of the surface is retained.

The impregnation is carried out by utilizing the difference between the high vapor tension of the intermedium (e.g., methylene chloride) and the low vapor tension of the solution to be polymerized. After impregnation, the specimen is subject to polymerization conditions without surrounding embedding material.

The optical and mechanical properties can be selected by proper choice from various kinds of resins and different procedures, for example, by complete or incomplete impregnation. Acrylic resins, polyester resins, epoxy resins, poly‐urethanes and silicone rubber have been found suitable for the method.

Excellent results have been obtained using transparent silicone rubber since after treatment the specimens are still flexible and resilient, and have retained their natural appearance.
Ultrastructure of the fetal rat anterior pituitary gland at term and during prolonged gestation
Authors: Anderson Judy E. , Thliveris James A.
Published: February 2005

The ultrastructure of the fetal rat anterior pituitary gland is described at term (day 22) and during experimentally prolonged gestation (days 23, 24, 25). The latter was achieved by daily subcutaneous injections of five mg progesterone to gravid females from the twentieth through the twenty‐fourth day. Using morphological criteria for classifying pituitary cells (Moriarty, '73), six different types were observed: thyrotrophs, gonadotrophs, corticotrophs, mammotrophs, somatotrophs and non‐granulated cells.

During prolonged gestation (days 24 and 25 only), cells designated as cor‐ticotrophs revealed changes suggesting increased activity, i.e., proliferation and dilation of the endoplasmic reticulum, dilated Golgi membranes and a reduction of secretory granules. In addition, meconium staining, which is indicative of fetal distress, was also observed on days 24 and 25. The ultrastructural changes noted suggest an increase in corticotroph activity due to fetal hypoglycemia and hypoxia which are known to occur as a result of placental insufficiency during prolonged gestation (Roux et al., '64; Vorherr, '75; Thliveris, '76).
Response of periodontal ligament cells to orthodontic force: Ultrastructural identification of proliferating fibroblasts
Authors: Yee John A.
Published: February 2005

The morphologic response of periodontal ligament (PDL) cells in an area of tension created by orthodontic force has been assessed by transmission electron microscopy. Young adult male rats were sacrificed at 24, 48, 72, 96 and 120 hours following orthodontic stimulation. The earliest detectable response was the appearance of increased numbers of mitotic cells in the PDL at 24 hours post‐stimulation. The most significant ultrastructural feature of these cells was the presence of intracellular vesicles containing collagen microfibrils. These vesicles were identical to profiles present in interphase PDL fibroblasts involved in collagen phagocytosis associated with turnover of the ligament. Between 48 and 120 hours the alveolar bone surface in the region examined was characterized by the presence of newly generated osteoblasts and active bone formation. Intracellular collagen was never observed in osteoblasts. These observations suggest that at least a portion of the population of PDL cells which proliferate in response to orthodontic force represent functional ligament fibroblasts.
A novel technique for high resolution analysis of the cytoskeleton
Authors: Trotter John A. , Kelley Robert O.
Published: February 2005

A new technique is described for producing and examining carbon‐platinum replicas of the cytoskeleton of cultured cells. This technique allows the individual components of the cytoskeleton to be visualized and positively identified in the transmission electron microscope, and also permits an analysis of the 3‐dimensional disposition of these components.
Fine structural studies on white adipocyte differentiation
Authors: Slavin Bernard G.
Published: February 2005

The differentiation of mammalian white adipocytes from prenatal through early postnatal periods was studied by light and electron microscopy in C57BL mice. Anatomical regions chosen for this study were the epididymal, mesometrial, mesenteric and inguinal fat pads. In each of these regions, adipocytes differentiated from fibroblast‐like cells (preadipocytes) characterized by an ovoid nucleus, profiles of rough endoplasmic reticulum, microtubules, microfilaments, spherical mitochondria, and small multiple lipid inclusions. Preadipocytes of the inguinal fat pad were first observed prior to birth (17–19 days), whereas, in the other anatomical sites, these cells were not observed until one to three days postnatally. As differentiation proceeded, and as the adipocytes assumed a spherical shape, there was a progressive decrease in the amount of rough endoplasmic reticulum and microfilaments concomitant with transient glycogen storage and an increase in the size of lipid droplets. Mature unilocular adipocytes were observed in the inguinal fat pads at three days of age. On the other hand, these cells did not appear until seven days after birth in the epididymal fat pad, mesometrium and mesentery. Regardless of the anatomical region studied, the differentiation of preadipocytes to adipocytes proceeded similarly. Preadipocytes could not be distinguished from fibroblasts morphologically within the fat depots studied. Adipocytes at the mid‐stages of differentiation and in all regions studied occasionally exhibited close intercellular contacts of varying morphology.
Ultrastructural localization of histones in epiphyseal chondrocytes
Authors: Wezeman Frederick H.
Published: February 2005

Epiphyseal growth plate chondrocyte nuclei of growing rats were studied for histone content using the ammoniacal silver technique. This stain, which is specific for the demonstration of the arginine‐rich fractions of histones, revealed that growth plate nuclei vary in their histone content. Nuclei of cells of the proliferating zone revealed a significantly greater amount of postformalin ammoniacal silver deposit consistent with the presence of arginine‐rich histones.
Structure and function of the intestinal epithelial cells in the perch (perca fluviatilis l.)
Authors: Noaillac‐Depeyre J. , Gas N.
Published: February 2005

An ultrastructural study of the intestinal absorptive epithelium in perch (Perca fluviatilis) has shown that the perch intestine can be divided into three segments: the proximal segment, the middle segment and the distal segment. The enterocytes of the proximal segment are found to be concerned with lipid absorption. The absorbed fat gives rise to the presence of two forms of inclusions: lipid particles and lipid droplets. Enterocytes of the middle segment exhibit the typical ultrastructural features of pinocytosis; these consist of extensive invaginations of the luminal surface membrane and accumulation of vacuoles in the apical cytoplasm. Exogenous proteins are ingested by absorptive cells from the intestinal lumen by a process similar to that described in neonatal mammals. In the distal segment the absorptive cells have few, short microvilli.

Besides the absorptive epithelial cells, goblet cells, endocrine cells, pearshaped cells, and plasma cells are occasionally found.
Scanning electron microscopic examination of human pulonary capillaries using a latex replication method
Authors: Kendall Michael W. , Eissmann Edward
Published: February 2005

The human pulmonary microvasculature from the apical bronchopulomanary segment was studied by scanning electron microscopy using latex relpicas. The latex replica was composed of a blend of vinyl chloride latexes using a plasticized vinyl chloride copolymer with a vinyl chloride copolymer. The polymerized latex produced a cast of the pulmonary arterial vascular tree, including the capillary patterns, which freely anastomose, thereby draining blood into pulmonary veinules and veins. The latex was injected via a gravity flow system modified from its earlier application in Guinea pig lungs. The apparently normal lungs from two recently deceased humans (dead for 5‐6 hours and held in refrigeration) were perfused with heparinized Ringer's solution and subsequently injected with latex. The resulting latex casts of the capillaries revealed a three‐dimensional network arranged in irregular vascular rings or ovals. This patterns was most conspicuous in deep and intermediate bronchopulmonary segmental areas. However, the subpleural capillaries produced casts that often terminated blindly, as observed with stereo SEM, suggesting that these vessels may tend to form thrombi more easily as compared with capillaries from other regions of the lung alveoli. The pulmonary arteriolar replicas contained indentations representing endothelial cell nuclei, and the capillary replicas projected oval evaginations that may represent discrete loci or capillary mural attenuations.
Surface area ratios. III. A stereological method for estimating relative changes in average hepatocytes
Authors: Bolender Robert P.
Published: February 2005

Stereological information seems to be most interpretable, with respect to experimental changes, when related to an average cell. Current methods for obtaining an average cell volume essentially consist of dividing an aggregate volume of cells by the number of nuclei therein, assuming one nucleus per cell (Loud, ′68). Hepatocytes represent a somewhat special case, however, in that some are binucleated. Since the number of hepatocytes in one cm3 of tissue is less than the number of hepatocyte nuclei in the same cm3, dividing the hepatocytic volume by the number of nuclei gives only an average “mononuclear” hepatocyte. Such an estimate creates two interpretation difficulties: (1) the volume of an average mononuclear hepatocyte is less than that of an average hepatocyte; and (2) changes in the proportion of binucleated cells may compromise the “relative comparisons” for which the method was originally intended. The purpose of this study is to describe a new approach that can avoid these difficulties altogether, and then to assess the errors associated with the average mononuclear hepatocyte estimates. This was accomplished by combining a surface area ratio method, which can detect average cell changes without being influenced by binucleated cells, with the method of Loud (′68), which is affected as described above. The experimental model was the rat liver (n = 20) recovering for 3 days from 5 daily injections of sodium phenobarbital (100 mg/kg). The results indicate that changes in the average cell volumes for the two methods have similar slopes, but by not accounting for binucleated cells, the average mononuclear hepatocyte reference overestimates average hepatocytic volume changes by 63.1%. Similarly, the mononuclear hepatocyte reference overestimates changes in the surface areas of the ER by 32.1% (range = 26.1% to 39.1%), the SER by 21.6% (range = 14.3 to 30.1%), and the RER by 65.1% (range = 54.6% to 76.4%).