bluuebunny/crossref_metadata_2025_split huggingface dataset:
Immunodissection of sperm surface modifications during epididymal maturation
Authors: Eddy E. M. , Vernon R. B. , Muller C. H. , Hahnel A. C. , Fenderson B. A. 
Published: February 2005

AbstractMammalian spermatozoa undergo changes in morphology, composition, and function during transit through the epididymis. These changes correlate with acquisition by sperm of the ability to fertilize ova. It has been found that sperm from the cauda epididymidis, but not those from the caput epididymidis, are able to bind to the zona pellucida. This would imply a modification in sperm surface characteristics. Biochemical and immunological studies have demonstrated changes in sperm surface composition during epididymal maturation. These changes involve addition of epididymal maturation. These changes involve addition of epididymal secretory products to the sperm surface, loss or alteration of existing sperm surface molecules, and possibly the unmasking of preexisting molecules or epitopes. Several laboratories have studied the epididymal secretory proteins in the rat, but a consensus has not been reached on the identification, characterization, source, and sperm surface association of these proteins. Monoclonal antibodies are beginning to be used to characterize sperm surface components and sperm maturation antigens. They are proving to be valuable tools for the dissection of epididymal maturation when used in conjunction with biochemical and physiological approaches.
Sperm surface changes during the acrosome reaction as observed by freeze‐fracture
Authors: Fléchon Jacques‐E. 
Published: February 2005

AbstractThe mammalian acrosome reaction is an exocytotic process that can be analyzed by the technique of freeze‐fracture; only sperm cells capacitated in vitro or treated to elicit the acrosome reaction in vitro have been studied, and all pictures published are from material fixed before freezing. All the authors point out the appearance of particle‐free areas in the plasma membrane of the acrosomal region during capacitation and before any fusion. This is interpreted as an increase in membrane fluidity as suggested by studies on membrane lipid composition in guinea‐pig sperm. We have recently described the induced acrosome reaction in ram spermatozoa. Fusion starts at the limit of the anterior and equatorial segments and progresses forward in the anterior segment along ramified paths, resulting in a fenestration gradient of the acrosomal cap. Fusion propagation may be controlled by fluidity increase in the plasma membrane of the anterior segment, and it is probably inhibited in the equatorial segment by the ordered structure of the acrosomal membrane.
Inner acrosomal membrane of mammalian spermatozoa: Its properties and possible functions in fertilization
Authors: Huang T. T. F. , Yanagimachi R. 
Published: February 2005

AbstractThe inner acrosomal membrane (IAM) develops during the spermatid stage of differentiation as that portion of the Golgi‐derived acrosome granule that tightly associates with the condensing sperm nucleus. In some mammalian species, an electron‐dense proteinaceous material accumulates between the IAM and the nuclear envelope, collectively comprising the “perforatorium.” Evidence, including its partial purification and its structural resistance to detergents and sonlcation, suggests that the IAM is an unusually resiliant membrane. Dense paracrystalline arrays of intramembranous particles, a lack of lectin‐mediated receptor modulation, and its lack of participation in sperm‐egg fusion suggest that the IAM lacks the same degree of fluidity as the egg surface plasmalemma. Observations using monoclonal antibodies, however, suggest that some specific antigenic modulations may be possible within the IAM. Its structural rigidity is of obvious mechanical value during sperm penetration through the zone pellucida. An additional role as a scaffold for putative zona lysin material remains controversial. Biochemical evidence suggests that acrosin, for example, is not entirely soluble and that some remains sperm‐associated, depending on the conditions of acrosome disruption. Nevertheless, morphological studies do not agree on acrosin's specific localization to the IAM. Currently there is only very limited information concerning the localization of the other acrosomal enzymes to the IAM. Another possible role for the IAM in some species may be in recognizing the zona pellucida. Evidence for this derives from the observation that fucoidin, a fucose heteropolysaccharide, inhibits guinea pig sperm‐zona binding, and bound fucoidin can be localized to the IAM and equatorial regions of the living acrosomereacted spermatozoa. Finally, the IAM may have a role in early recognition/adhesion with the colemma.
Molecules that initiate or help stimulate the acrosome reaction by their interaction with the mammalian sperm surface
Authors: Meizel Stanley 
Published: February 2005

AbstractThis review deals with exogenous molecules that stimulate the acrosome reaction (AR) of mammalian sperm in vitro, presumably by acting at the sperm surface. Such molecules may exert their effect(s) by stimulating capacitation and/or by stimulation or initiation of the AR, and they are probably present at one of three putative in vivo sites (also discussed here) for the AR of a fertilizing sperm: the oviductal fluid, the cumulus oophorus matrix, and the zona pellucida. The molecules discussed include serum albumin, hydrolytic enzymes (particularly proteases); hormones including biogenic amines, estradiol, and arachiodonic acid metabolites; sulfur‐containing β‐amino acids; glycosaminoglycans such as hyaluronic acid; and a zona pellucida glycoprotein. Possible mechanisms to explain the effects of these molecules are also discussed. Several conclusions and suggestions are offered in this review: (1) There is more than one site for the AR of a fertilizing sperm in vitro, depending on experimental conditions and species, but the site(s) at which the AR of a fertilizing sperm occur(s) in vivo is/are still a matter of disagreement; (2) there are a number of molecules that can stimulate or initiate the AR in vitro, and such molecular duplication may also exist in vivo to ensure fertility; and (3) synergistic interaction between some of those exogenous molecules may occur in the stimulation of capacitation and the stimulation or initiation of the AR.
Fine structure of the mammalian egg cortex
Authors: Longo Frank J. 
Published: February 2005

AbstractThe cortices of a number of mammalian eggs are not strucurally homogeneous but are polarized. In mouse ova the plasma membrane is a mosaic; the cytoplasm overlying the meiotic spindle is devoid of cortical granules and consists of a filamentous layer containing actin. Functionally, this cortical polarity may be related to the restriction of sperm‐egg interaction and fusion to a specific region of the ovum cortex and to dynamic changes of the egg cortex during fertilization, including cortical granule exocytosis, polar body formation, and fertilization cone development. The origin of cortical polarity in mammalian oocytes and its possible relation to components of the cytoskeletal system and meiotic apparatus are discussed and compared with cortical features of eggs of other vertebrates and invertebrates.
Freeze‐fracture observations on mammalian oocytes
Authors: Koehler James K. , Clark Judy M. , Smith Dianne 
Published: February 2005

AbstractFreeze‐fracture studies on mammalian oocytes have been hampered by the relatively small numbers of cells available at a given time as well as by difficulties encountered in effectively freezing these large, watery cells. We have nevertheless pursued this area because of the benefits of visualizing membrane faces involved in various fusion reaction by the freezefracture method. Our observations indicate no overall change in intramembranous particle (IMP) distribution before and after sperm penetration, although the question of possible alterations of these structures at the precise locus of sperm attachment remains open. Preliminary statistical analysis indicates that there is a much higher IMP density on the P face than on the E face of the plasma membrane and that the microvillar membranes bear more IMPs than those of the intermicrovillus regions. Probes of lipid subclasses were used to determine the distribution of cholesterol and anionic lipid in the egg plasma membrane. Filipin and tomatin showed extensive complex formation in microvillus as well as nonmicrovillus regions, whereas anionic lipids (using polymyxin B) have been difficult to detect on the oocyte surface. These results are discussed relative to current views of membrane fusion mechanisms.
Sperm penetration through oocyte investments in mammals
Authors: Talbot P. 
Published: February 2005

AbstractLiterature on the interactions between eutherian gametes is reviewed. The oocyte cumulus complex of the female is surrounded by a zona pellucida, corona radiata, and cumulus layer. Sperm undergo an acrosome reaction before penetrating the zona pellucida. The morphological consequences of this reaction and its possible role(s) in penetration of the oocyte cumulus complex are considered. The acrosomal enzyme, hyaluronidase, has been thought to aid sperm in penetrating the cumulus layer and corona radiata. Several recent investigations, including one that shows that motile cells lacking hyaluronidase can penetrate to the zona surface, do not support this idea. Other possible roles of this enzyme in fertilization are discussed. The development of in vitro fertilization systems that employ physiological numbers (1–100) of sperm will be valuable in studying the mechanisms used by sperm to penetrate the oocyte cumulus complex.
The basement‐membrane‐like matrix of the mouse EHS tumor: I. Ultrastructure
Authors: Inoue S. , Leblond C. P. 
Published: February 2005

AbstractThe fine structure of the extracellular matrix was examined in the Engelbreth‐Holm‐Swarm (EHS) tumor of the mouse. The matrix is composed of layers parallel to the surface of the associated cells; the layers are poorly defined close to the cells (proximal region) but quite distinct at a distance from the cells (distal region). In the proximal region of the matrix, the indistinct layers are composed of three types of structures: (1) a network of 3‐to 8‐nm‐thick „cords”︁ makes up the bulk of the tissue. (2) Within the network are scattered few 7‐ to 10‐nm‐wide, hollow rods of indefinite length, referred to as „basotubules”︁; their cross section has a dense, more‐or‐less‐circular or pentagonal wall and a light lumen containing a spherule. In addition, many plae profiles similar to these cross sections are present; they are interpreted as small, independent structures. (3) Minute structures composed of two parallel, 3.5‐nm rodlets are referred to as „double pegs.”︁ In the distal region of the matrix, the distinct layers include the same three types of structures, but basotubules are numerous and prominent; in each layer, they are arranged in picket‐fence fashion along two parallel planes. Cords are packed between them. Double pegs are scattered throughout the clear interlayer spaces.Inasmuch as cord network, basotubules, and double pegs are present in the two regions of the tumor matrix, both regions resemble basement membrane. To explain the contrast between the paucity of basotubules in the proximal region and their abundance in the distal region, it is proposed that, as the production of newer matrix by the cells causes the older matrix to be displaced distally, the independent structures seen as pale profiles in the proximal region gradually assemble into basotubules.
Binding of lectin‐fluorescein conjugates to intracellular compartments of growth‐plate chondrocytes in situ
Authors: Farnum Cornelia E. 
Published: February 2005

AbstractIn this study, lectin‐binding techniques are applied to growthplate cartilage to analyze the intracellular localization of lectin‐binding glycoconjugates of chondrocytes in situ. The binding of ten fluorescein‐conjugated lectins is analyzed on 1‐μm‐thick Epon‐embedded, nondecalcified sections of growth plates from Yucatan swine. Comparisons are made to intracellular binding in chondrocytes of tracheal, articular, and auricular cartilage. Ear epithelium, tracheal epithelium, and kidney are used as positive control tissues for the specificity of lectin binding. Only the mannose‐binding lectins had affinity for the RER and nuclear envelope. Eight lectins reacted within the Golgi complex with characteristic patterns which ranged from localized fine linear strands to extensive vesicular accumulations. When cartilage slabs were exposed before embedment to the ionophore monensin to disrupt intracellular transport through the Golgi, it was possible to define differential subcompartments of the Golgi complex, based upon sites of sugar addition. Also, it was possible to characterize the cytoplasmic deposits of reserve‐zone chondrocytes which were positive with concanavalin A as glycogen, based upon their sensitivity to amylase. This method allows resolution at the light‐microscopic level of lectin‐binding glycoconjugates with localization to specific organelles. Patterns of intracellular binding were consistent with biochemical data relating to the subcellular localization of processing steps of complex carbohydrates prior to secretion.
Distribution of intramembranous particles and filipin‐sterol complexes in mouse sperm membranes: Polyene antibiotic filipin treatment
Authors: Toshimori Kiyotaka , Higashi Ruiko , Ōura Chikayoshi 
Published: February 2005

AbstractThe distribution of intramembranous particles (IMPs) and membrane filipin‐sterol complexes (FSC) was examined ultrastructurally in mouse spermatozoa from the male reproductive tract and ejaculates. IMPs were qualitatively analyzed on freeze‐fracture replicas of glutaraldehyde‐fixed tissue, while membrane FSC were quantitatively analyzed on replicas of filipin‐treated cells. The distribution pattern of IMPs of mouse spermatozoa was fundamentally similar to that of other mammalian spermatozoa. (1) In the head, the plasma membrane had a heterogeneous population density, e.g., few IMPs on the acrosomal region, particularly few on the marginal segment, and somewhat regularly arranged IMPs on the postacrosomal region. The acrosomal membrane had many IMPs in hexagonal arrays. The nuclear membrane had many IMPs on the P‐face, few IMPs on the variegated E‐face, and an intense population density on the P‐face of the basal plate. (2) In the neck, the plasma membrane had many IMPs with square arrangements of small IMPs in some areas on the P‐face; the redundant nuclear membrane had a few IMPs on both P‐ and E‐faces. (3) In the tail, the plasma membrane had diagonal rows of IMPs in some areas amongst larger IMPs on the middle piece, while it had „zippers”︁ composed of IMPs running parallel to the axis on the principal piece. The distribution of sperm membrane FSC may be summarized as follows: (1) In the head, the acrosomal plasma membrane, which was heavily labeled with filipin, had much more FSC in the equatorial segment than in the marginal segment throughout the study. The postacrosomal plasma membrane generally had no FSC, but some sperm in ejaculates were slightly positive to filipin. The acrosomal membranes (both outer and inner) had no FSC. The nuclear membrane in the main part of the head had less FSC in vas deferens and ejaculated sperm than in the epididymal sperm. The nuclear membrane on the basal plate had no FSC. (2) In the neck, the plasma membrane had little FSC. The redundant nuclear envelope had scattered FSC with a higher incidence in the epididymal sperm than in those from the vas deferens and ejaculates. The membrane scroll, which was elongated from the extreme caudal end of the redundant nuclear envelope, had abundant FSC in the vas deferens and ejaculated sperem. (3) The tail plasma membrane (both middle and principal piece), which was weakly labeled with filipin, had less FSC in sperm from the vas deferens and ejaculates than in those from the epididymis. The limiting membrane covering the mitochondria had no FSC.
The early development of the sheep trophoblast and the involvement of cell death
Authors: Carnegie J. A. , McCully M. E. , Robertson H. A. 
Published: February 2005

AbstractDuring the period of rapid elongation prior to the initiation of placental attachment (days 12–16 of gestation), the ovine blastocyst consists of a single layer (primarily) of roughly cuboidal trophoblastic cells with an inner lining of flattened endodermal cells. Well‐developed spot desmosomes link the adjacent cell borders in both the trophoblastic and endodermal layers. The trophoblastic cells contain acid phosphatase‐positive, lysosomelike organelles, the mean diameter of which increases greatly between days 12 and 16 and whose contents vary during development. Also during the developmental period studied, trophoblast cells accumulate lipid; and periodic acid‐Schiff‐positive binucleate cells appear within the trophoblast layer. A consistent observation throughout the 5 days of rapid growth and differentiation of the blastocyst was the death and disintegration of some trophoblast cells. These disintegrating cells are usually singly dispersed within the trophoblast, although occasionally groups of four or five are observed. The cell death may indicate overall remodelling of the blastocyst, or the cells may represent genetically deficient cells which are unable to respond to the appropriate signal to differentiate.
An excursion through the ultrastructural world of quick‐frozen pancreatic islets
Authors: Dudek R. W. , Boyne A. F. 
Published: February 2005

AbstractIn this article we have presented a philosophical and historical perspective on quick freezing, freeze‐drying, freeze‐substitution, and immunocytochemical localization of pancreatic islet hormones. A compilation of our findings indicates that (1) quick‐freezing does not produce any gross distortion of islet tissue; (2) the amount of usable islet tissue for ultrastructural analysis is approximately 13 μm deep from the frozen edge; (3) three different cell types can be identified in quick‐frozen tissue based on general morphological characteristics; (4) freeze‐substitution with tetrahydrofuran produces a unique ultrastructural appearance in which ribosomes are particularly striking; (5) with the use of protein A‐gold, insulin and glucagon can be localized immunocytochemically on silver‐gray (50‐nm‐thick) sections treated with 1% ovalbumin at room temperature overnight; (6) secretory granules of quick‐frozen alpha and beta cells may exist in either a swollen or condensed state; (7) swollen beta cell secretory granules contain a filamentous material that demonstrates immunogold labeling for insulin; (8) insulin and glucagon can be localized within the cisternae of endoplasmic reticulum; (9) our methods provide not only discrete immunocytochemical localization of hormone, but also well‐preserved cellular compartments; (10) energy electron loss spectroscopy (EELS) has shown that quantifiable nitrogen maps can be used as an index of hormone packaging in secretory granules; and (11) the sectioning properties of secretory granules at the ultramicrotome change when islet tissue is unosmicated and sectioned on glycerol.
Scanning electron microscopy of cell surface antigens labeled with colloidal gold
Authors: de Harven E. , Soligo D. 
Published: February 2005

AbstractA method is described and discussed that permits the specific labeling of the surface of prefixed cells with the colloidal gold marker viewed with the scanning electron microscope. Its value depends exclusively on the use of backscattered electron imaging. Its advantages include (1) the possibility of preserving the surface features of the labeled cells, (2) the ease with which specificity can be established, (3) the possibility of making total counts of the labeled surface antigenic sites, and (4) the possibility of achieving distinct labeling for two different antigens expressed on the surface of the same cell.
Immunocytochemical studies of pituitary hormones with PAP, ABC, and immunogold techniques: Evolution of technology to best fit the antigen
Authors: Childs Gwen V. , Unabia Geda , Ellison Dayle 
Published: February 2005

AbstractThe immunocytochemical technology in our laboratory has evolved in response to specific needs for more efficient, refined stains for each antigen. The rationale for the application of each of the immunocytochemical techniques used today is described, and detailed methods are given. In the early 1970s, it was determined that the peroxidase‐antiperoxidase complex (PAP) stain provided the most sensitive means of detection of adrenocorticotropin (ACTH) at the electron microscope level even in tissues prepared with conventional fixation and embedding techniques that are considered rather harsh for the maintenance of antigenicity. Application of the same PAP complex technique to the larger glycoprotein antigens, like follicle‐stimulating hormone (FSH), however, proved far more difficult; and the problem was resolved partially when more gentle fixation‐embedding protocols were applied. The production of an efficient, reliable stain for FSH was achieved only with the avidin‐biotin peroxidase complex (ABC) stains were applied in the early 1980s. This technique also allowed more efficient reactions for all the antigens, and morphometric data could thereby be collected more rapidly. Thus, we concluded that the light microscope immunoperoxidase techniques were excellent for the morphometric analysis of pituitary cell types in both pre‐embedding and postembedding stains. However, the need for a more refined stain for its quantification at the electron microscope level on individual organelles led to the development of the colloidal gold stain in 1983–1984. This technique, which is new to our laboratory, is also described and illustrated in this report. Also included is a description of our studies of the effect of fixation and embedding processes on hormone antigenicity and techniques used to control background and nonspecific reactions. It is hoped that the novice will find the description of the rationale for the evolution of technology in our laboratory useful in making choices for his or her own immunocytochemical stains.
Dual immunostaining procedure demonstrating neurotransmitter and neuropeptide codistribution in the same brain section
Authors: Joseph Shirley A. , Piekut Diane T. 
Published: February 2005

AbstractA method for sequential immunostaining of two antigens in the same section and the application to neuronal elements in the CNS is described. This method employs the peroxidase‐antiperoxidase (PAP) technique as a first sequence, followed by glucose oxidase‐antiglucose oxidase (GAG) complex as the second sequence, yielding rich brown and vibrant blue reaction products, respectively. Application of the PAP/GAG immunoreagents as dual markers for various neuropeptide and neurotransmitter systems is described in detail and the procedure is outlined. Comparisons with other dual staining methods are discussed and the application to other systems is presented.
Two‐color immunoperoxidase staining: Visualization of anatomic relationships between immunoreactive neural elements
Authors: Hancock M. B. 
Published: February 2005

AbstractA method for differentially staining for two antigens in single sections is described. Paraffin‐embedded or Vibratome sections are incubated in two sequences of immunoperoxidase (PAP) reagents using a diaminobenzidine (DAB)‐nickel ammonium sulfate solution to localize the first antigen, and DAB alone to localize the second antigen. With these chromagens, black and amber‐colored reaction products are generated at the locations of the first and second antigens, respectively. The reaction products are stable and provide excellent color contrast. With this technique, the anatomical relationships between two sets of immunoreactive elements can be studied in individual sections. Intimate spatial associations that would probably not be detected by an examination of adjacent sections stained for each antigen can be visualized with this two‐color immunoperoxidase method.