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  • 1
    Electronic Resource
    Electronic Resource
    Steric inhibition of cytoplasmic dynein and kinesin motility by MAP2 (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 24 (1993), S. 1-16 
    Details
    ISSN: 0886-1544
    Keywords: cytoplasmic dynein ; kinesin ; microtubules ; motility ; MAPs ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Using several in vitro motility assays, we found that motility driven by the microtubule (MT) motors, kinesin and cytoplasmic dynein, could be inhibited by MAP2 but not by tau protein or the MT-binding proteolytic fragment of MAP2.In MT gliding assays, even the presence of one MAP2 molecule per sixty-nine tubulin dimers caused an inhibition of about 75% of MT motility at low concentrations of both motors. The percent inhibition of motility decreased with increasing concentration of either motor, suggesting that the inhibition was the result of competition for access to the MT surface. The decrease in the number of moving MTs with MAP2 was correlated with an increase in the frequency of release of moving MTs from the motor-coated glass. In assays of in vitro vesicular organelle motility and formation of ER networks, the presence of MAP2 inhibited small vesicle movements and to a lesser extent ER network formation.To determine if competition for specific sites on the MT or coating of the MT surface inhibited motility, we used tau protein and the chymotryptic MT-binding fragments of MAP2 to coat MTs. No inhibition was observed and there was even an increase in the number of attached and moving MTs in the gliding assay with tau-coated MTs. Because MAP2, tau and the chymotryptic MT-binding fragments of MAP2 bind to the same domain on tubulin, masking of the MT surface sites does not appear responsible for the inhibition of motility by MAP2. Rather, we suggest that the sidearm of MAP2 interfered with the interaction of motors with MTs and caused a dramatic increase in the rate of MT release. In vivo, MAP2 could play a major role in the generation of cellular polarity even at substoichiometric levels by inhibiting transport on microtubules in specific domains of the cytoplasm. © 1993 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970240102
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  • 2
    Electronic Resource
    Electronic Resource
    Mechanical stimulation of skeletal muscle generates lipid-related second messengers by phospholipase activation (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 155 (1993), S. 63-71 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Repetitive mechanical stimulation of cultured avian skeletal muscle increases the synthesis of prostaglandins (PG) E2 and F2α which regulate protein turnover rates and muscle cell growth. These stretch-induced PG increases are reduced in low extracellular calcium medium and by specific phospholipase inhibitors. Mechanical stimulation increases the breakdown rate of 3H-arachidonic acid labelled phospholipids, releasing free 3H-arachidonic acid, the rate-limiting precursor of PG synthesis. Mechanical stimulation also increases 3H-arachidonic acid labelled diacylglycerol formation and intracellular levels of inositol phosphates from myo-[2-3H]inositol labelled phospholipids. Phospholipase A2 (PLA2), phosphatidylinositol-specific phospholipase C (PLC), and phospholipase D (PLD) are all activated by stretch. The stretch-induced increases in PG production, 3H-arachidonic acid labelled phospholipid breakdown, and 3H-arachidonic acid labelled diacylglycerol formation occur independently of cellular electrical activity (tetrodotoxin insensitve) whereas the formation of inositol phosphates from myo-[2-3H]inositol labelled phospholipids is dependent on cellular electrical activity. These results indicate that mechanical stimulation increases the lipid-related second messengers arachidonic acid, diacylglycerol, and PG through activation of specific phospholipases such as PLA2 and PLD, but not by activation of phosphatidylinositol-specific PLC. © 1993 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041550109
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  • 3
    Electronic Resource
    Electronic Resource
    The spermatogenesis of crustaceans. VI. The external morphology of the mature spermatozoa of mytilicola intestinalis, steuer (copepoda) (1979)
    New York, NY : Wiley-Blackwell
    Gamete Research 2 (1979), S. 235-245 
    Details
    ISSN: 0148-7280
    Keywords: speramtozoon-copepoda (My tilicola intestinalis) ; external morphology ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The external structure of the male gamete of Mytilicola intestinalis is studied under a scanning electron microscope and compared with transmission electron micrographs of thin sections corresponding to the different parts of same. The cell in question is long and filiform, showing, along a significant part of its length, two ridges or expansions helicoidally arranged and diametrically opposed. Four different parts or segments can be identified in this spermatozoon: segment A, characterized by its screw-like aspect; segment B, the longest, provided with well-developed helicoidal expansions; segment C, showing an uneven surface and lacking expansions; and segment D, with a smooth surface and decreasing diameter. The significance of this original structure in a spermatozoon, considered immobile until now, is discussed, stating different hypotheses with regard to the possible mobility of the cell just before fertilization takes place.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1120020307
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  • 4
    Electronic Resource
    Electronic Resource
    Nuclear morphogenesis during spermiogenesis in the nudibranch molluscHypselodoris tricolor (Gastropoda, opisthobranchia) (1986)
    New York, NY : Wiley-Blackwell
    Gamete Research 13 (1986), S. 159-171 
    Details
    ISSN: 0148-7280
    Keywords: nudibranch ; spermiogenesis ; nuclear morphogenesis ; chromatin condensation ; manchette ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: An electron microscope study was carried out on Hypselodoris tricolor spermatids to describe the development of the nuclear morphogenesis and investigate the possible cause(s) of the change in the shape of the spermatid nucleus during spermiogenesis. Three different stages may be distinguished in the course of the nuclear morphogenesis on the basis of the morphology and inner organization of the nucleus. Stage 1 spermatid nuclei are spherical or ovoid in shape and the nucleoplasm finely granular in appearance. Stage 2 nuclei exhibit a disc- or cup-shaped morphology, and the chromatin forms short, thin filaments. During stage 3, a progressive nuclear elongation takes place, accompanied by chromatin rearrangement, first into fibers and then into lamellae, both formations helically oriented. A row of microtubules attached to the nuclear envelope completely surrounds the nucleus. Interestingly, the microtubules always lie parallel to the chromatin fibers adjacent to them. Late stage 3 spermatids show the highest degree of chromatin condensation and lack the manchette at the end of spermiogenesis. Our findings indicate the existence of a clear influence exerted on the chromatin by the manchette microtubules, which appear to be involved in determining the specific pattern of chromatin condensation in Hypselodoris tricolor.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1120130209
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  • 5
    Electronic Resource
    Electronic Resource
    The spermatogenesis of crustaceans: The external morphology of the spermatozoa of heterocypris incongruens, ramdohr (Ostracoda) (1979)
    New York, NY : Wiley-Blackwell
    Gamete Research 2 (1979), S. 89-97 
    Details
    ISSN: 0148-7280
    Keywords: spermatozoon-ostracoda (Heterocypris incongruens) ; external morphology ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: In various papers on the original spermatozoon of the Ostracoda, its helicoidal disposition has been indicated as the principle characteristic of this gamete, at cell structure level as well as in its external morphology. Through a combined study with scanning electron microscope (SEM) and transmission electron microscope (TEM), we have been able to establish the corresponding relationship between the cell architecture and the spermatozoon's external morphology. In the case of Heterocypris incongruens, the helicoidal relief of the gamete's external surface along the greatest part of its length, is the result of the twisting and undulating of a structure derived from the nucleus' external membrane, endoplasmic reticulum, and Golgi apparatus, called “feather-like organelle.” In keeping with the shape of this surface relief, the spermatozoon can be divided into three regions: An anterior one with a corkscrew form, a middle one showing a relief in the form of a screw with four threads, and a posterior or tail one without helicoidal relief. Finally, we discuss the different criteria existing on the possible orientation of this spermatozoon when it moves, as well as the functional advantages that the possession of a filiform, helicoidal, and mobile gamete represents.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1120020110
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  • 6
    Electronic Resource
    Electronic Resource
    The spermatogenesis of crustaceans. VII. Review of spermatozoon of the crayfish Astacus astacus (Malacostraca, Decapoda, Macrura, Reptantia) (1981)
    New York, NY : Wiley-Blackwell
    Gamete Research 4 (1981), S. 65-82 
    Details
    ISSN: 0148-7280
    Keywords: spermatozoon-crayfish (Astacus astacus) ; ultrastructure ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The star-like spermatozoon of Astacus astacus consists of a spheroidal central body around which various prolongations of same, denominated spines, are arranged. In the interior of the gamete the following parts may be distinguished: (1) The acrosomic region, formed by a complex vesicle, or thick-walled, helmetshaped body, whose opening is orientated towards the nuclear region. In the interior of the vesicle different structures can be appreciated. (2) The nuclear region, which is formed by a large cupuliform nucleus limited by a double membrane. In the nucleoplasm numerous bundles of microtubules, mixed with noncondensated chromatin fibers, are found. (3) The laminar region, present in other Decapoda, is practically nonexistent. Within the spines of these spermatozoa, only microtubules can be observed. The morphology of this crayfish is similar to that presented by Brachiura, another group of Reptantia.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1120040110
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  • 7
    Electronic Resource
    Electronic Resource
    Cytochemical analysis of the anionic sites on the membrane of the stallion spermatozoa during the epididymal transit (1987)
    New York, NY : Wiley-Blackwell
    Gamete Research 18 (1987), S. 319-332 
    Details
    ISSN: 0148-7280
    Keywords: sperm membrane ; stallion spermatozoa ; spermatic maturation ; ultrastructural cytochemistry ; cellular microelectrophoresis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The structure, relative density, and distribution of anionic sites on the surface of epididymal and ejaculated spermatozoa were studied using polycationic ferritin (CF), colloidal iron hydroxide (CIH), various enzymatic treatments, methylation, and de-acetylation. Macro-molecules containing sugar residues, probably sialic acid, are part of the sperm membrane and show a characteristic distribution and density that is dependent of the sperm region and of its origin. Unlike the spermatozoa of other eutheria examined, the exposure of the stallion spermatozoa to neuraminidase treatment did not produce significant changes in the density of the negative charge of the sperm surface. The ability of purified neuraminidase to act only after saponification suggests that sialic acid may be present in the acetylated form. When CIH was used it is seen that the density of the negative charge is rather uniform within a particular segment of the spermatozoa and abruptly changes at the junction of morphologically distinct segments (Between the acrosomal and post acrosomal region of the sperm head and between the post acrosomal region and middle piece of the flagellum). The acrosome presented more negative groups dissociated at pH 1.8 than the postacrosomal region. A greater concentration of anionic sites over the flagellum was also observed when CIH and CF were used. This assymetry probably represents different domains that may be related to specific functions.The cytochemical observations and the cellular electrophoretic mobility measurements did not show striking differences on the negative charge of sperm obtained from different regions of epididymis and ejaculates in contrast to previous results in other species. The spermatozoa collected from caput epididymidis bind CIH but not all population present equal response. In corpus and cauda region of epididymis the population displaying the capacity to bind CIH or CF significantly over the head and tail surface was the majority.This study corroborates that the distribution and density of terminal oligosaccharide residues on the sperm plasma membrane has species specific characteristics. The surface charge of the spermatozoa obtained either during the breeding or nonbreeding season, determined by measurements of cellular electrophoretic mobility and by the binding pattern of CIH and CF, does not show significant differences.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1120180406
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  • 8
    Electronic Resource
    Electronic Resource
    IGF-I and the IGF-I receptor in development of nonmammalian vertebrates (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 35 (1993), S. 427-433 
    Details
    ISSN: 1040-452X
    Keywords: Chick embryos ; Organogenesis ; δ-crystallin gene ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Extracellular signals are likely to be involved in the control of growth and differentiation during embyrogenesis of vertebrates. These signals include, among others, several members of the insulin family: insulin-like growth factor (IGF)-I, IGF-II, and insulin. In the chick embryo, maternal IGF-I is stored in the yolk. In addition, the embryonic IGF-I gene is expressed very early and in late development in multiple tissues. We have used reverse-transcribed (RT) RNA and amplification by the polymerase chain reaction (PCR) to detect IGF-I gene expression. IGF-I was preferentially expressed in cephalic regions during late neurulation and early organogenesis. During late organogenesis, in some tissues, such as the eye lens, IGF-I gene expression is compartmentalized to a subset of cells, the epithelial cells. In these lens cells, IGF-I stimulates transcription of the δ-crystallin gene. Competence to respond to IGF-I exists in multiple cell types, since, based on binding studies, receptors for IGF-I are widespread in the gastrulating and neurulating embryo. Target tissues in which an autocrine/paracrine role for IGF-I appears more likely are the developing eye lens and retina, which are avascular organs rich in IGF-I receptors. In late development, IGF-I may have an additional endocrine role, with an impact on the general growth of the chick embryo. In embryos developed ex ovo, that show growth retardation after day 10 of embyrogenesis, IGF-I serum levels are very low. By day 8, expression of IGF-I mRNA in these embryos is markedly reduced in multiple tissues. Future studies in which IGF-I and its receptor are overexpressed or abolished should clarify the function of this growth factor in development. © 1993 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1080350418
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  • 9
    Electronic Resource
    Electronic Resource
    Preservation of antigenic reactivity after cryofixation, cryosubstitution, and cryoembedding in Lowicryl HM23: Application to alcohol dehydrogenase in Drosophila fat body (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 24 (1993), S. 453-454 
    Details
    ISSN: 1059-910X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jemt.1070240511
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  • 10
    Electronic Resource
    Electronic Resource
    Surface expression and distribution of Fc receptor III (CD 16 molecule) on human natural killer cells and polymorphonuclear neutrophils (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 28 (1994), S. 277-285 
    Details
    ISSN: 1059-910X
    Keywords: NK cells ; Neutrophils ; Fcγ receptor ; Immunogold ; SEM ; Backscattered electron imaging ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Human natural killer cells and polymorphonuclear neutrophils constitutively express the low-affinity IgG Fc receptor (FcγRIII, CD16 molecule). To investigate cell surface morphology, antigenic receptor density, and topographical distribution of FcγRIII on the plasma membrane of natural killer cells and polymorphonuclear neutrophils, conventional scanning electron microscopy (SEM), flow cytometry, and immunoscanning electron microscopy were used. FcγRIII was detected with an indirect immunogold labeling procedure, and receptors were visualized in the backscattered and secondary electron imaging mode of SEM. Natural killer cells showed a cell surface morphology compatible with lymphocytic differentiation characterized by microvilli and microridges. Polymorphonuclear neutrophils showed surface features characterized by ridges with folds and scattered short microvilli. Natural killer cells displayed a lower cell labeling density, whereas polymorphonuclear neutrophils showed a high level of expression of FcγRIII on the plasma membrane by quantitative analysis with SEM in the backscattered electron imaging mode. Flow cytometry analysis confirmed these findings. Analysis of the topographical distribution of FcγRIII antigenic receptor sites by SEM in the backscattered and secondary electron imaging modes showed that FcγRIII on natural killer cells are randomly distributed, whereas FcγRIII are located on ridges and folds of the plasma membrane of polymorphonuclear neutrophils. These observations suggest that natural killer cells and polymorphonuclear neutrophils differ in their levels of expression and topographic distribution of FcγRIII on the plasma membrane. This different spatial distribution of FcγRIII would provide morphological evidence of certain cellular functions mediated by natural killer cells and polymorphonuclear neutrophils. © 1994 Wiley-Liss, Inc.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jemt.1070280404
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