1,721,049 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
CD4-mediated Anchoring of the Seminal Antigen gp17 onto the Spermatozoon Surface.
No full textA soluble 17 kDa glycoprotein, namely gp17, was previously isolated from human semen and used to obtain mouse monoclonal or chicken polyclonal antibodies. This protein was shown to bind CD4+ T-cells and to soluble recombinant CD4 in vitro. Here, we report that the anti-gp17 monoclonal antibodies are captured by ejaculated spermatozoa and that gp17-like antigens are released by cell acid extraction. Immunoblotting experiments with monoclonal antibodies indicated that SDS-lysates from spermatozoa contain proteins with the same electrophoretic and antigenic properties of CD4 and gp17. Anti-CD4 mouse monoclonal antibodies were used to coprecipitate from NP40-lysate proteins reacting with chicken anti-gp17 antibodies. Analytical chromatography demonstrated that a number of gp17-like forms are present in the seminal plasma, put that only the 1 kDa species can be detected in the spermatozoa lysate. This protein was localised by immunofluorescence on the post-acrosomal region of the spermatozoon. The same surface domain was also reactive with anti-CD4 antibodies. After treatment to induce in vitro capacitation, gp17 was detected all over the spermatozoon head. Conversely, only a minor part of the treated spermatozoa exhibited CD4 immunostaining, which remained localised on the post-acrosomal region. The possible function of CD4 and gp17 on male germ cells is discussed
Two rat middle-piece coating antigens are lost upon in vitro capacitation.
No full textThe rat sperm-binding antigen, CFS, contains two subunits, RSV IV and RSV V. Sperm-bound RSV IV was previously detected using anti-RSV IV antibodies, while the presence of RSV V on the cell surface was doubtful. The RSV V subunit was purified from rat seminal vesicle secretion by gel filtration and ionic exchange chromatography. Rabbit polyclonal mono-specific antibodies against either RSV IV or RSV V were used to monitor the binding of the CFS complex onto the rat spermatozoa in indirect immunofluorescence experiments with FITC-conjugated goat anti-rabbit antibodies. Caudal epididymal spermatozoa were incubated in vitro with CFS and evidence of the presence of both subunits on the cell surface was obtained as the heterodimeric sperm-coating antigen was detected on the whole tail. Restriction of the CFS binding sites to the middle-piece surface domain of ejaculated spermatozoa was observed. In addition, release of CFS from this plasma membrane region was observed after in vitro capacitation. The localization of CFS before capacitation and its absence from the sperm surface after capacitation are compatible with a role of this factor as an inhibitor of motility in rat decapacitation
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Purification of a 240 kDa protein from serum and follicular fluid of water buffalo and its identification as Haptoglobin.
No full textThe fluids from healthy growing follicles of water buffalo were previously found free of the polypeptides H (M(r) 36,000) and L (M(r) 21,000) which were instead detected in fluids from atretic follicles and blood. Here we report evidence that these two polypeptides, as selected from serum by specific anti-L antibodies, are the subunits of an oligomeric protein. The protein was purified from serum or follicular fluid, and its molecular weight (240 kDa), isoelectric point (6.5), and amino acid composition were determined. The NH2-terminal sequences of the subunits L and H were analyzed: 100% and 90% homology with alpha and beta chains of bovine haptoglobin, respectively, was found. Thus, haptoglobin can be used as a novel molecular marker to assess the physiological state of the blood-follicle barrier or discriminate between atretic and healthy follicles
Localization and capacitation-dependent loss of Buffalo sperm-coating antigens shared with rat sperm.
No full textThe heterodimeric sperm-coating protein CFS was previously localised on the middle-piece region of rat spermatozoa by anti-CFS rabbit antibodies. CFS-immunorelated antigens were detected in the secretion of the water buffalo seminal vesicle by protein electrophoresis and Western blotting. Spermatozoa from buffalo epididymal cauda were incubated with the rat antigen and, upon immunostaining with anti-CFS antibodies and goat anti-rabbit fluorescein isothiocyanate (FITC)-conjugated IgGs, CFS was found attached on both the post-acrosomal region and the tail. Indirect immunofluorescence analysis permitted the localisation of CFS-related antigens on the same domains of buffalo ejaculated spermatozoa. These results suggest that the buffalo antigens not only share some epitopes with the homologous rat antigen but may also have some of its functional properties. Ejaculated spermatozoa were capacitated in vitro and then assayed for their content of CFS-like antigens. An inverse relationship was found between the levels of capacitation and the amounts of antigens detected, thus suggesting that the in vitro treatment was effective at removing CFS-related proteins from the cell surface. Titration of these proteins to monitor plasma membrane changes during sperm manipulation or to evaluate sperm quality is proposed
Security of Public Key Cryptosystems based on Chebyshev Polynomials.
Get PDFChebyshev polynomials have been recently proposed for designing public-key systems. Indeed, they enjoy some nice chaotic properties, which seem to be suitable for use in Cryptography. Moreover, they satisfy a semi-group property, which makes possible implementing a trapdoor mechanism. In this paper we study a public key cryptosystem based on such polynomials, which provides both encryption and digital signature. The cryptosystem works on real numbers and is quite efficient. Unfortunately, from our analysis it comes up that it is not secure. We describe an attack which permits to recover the corresponding plaintext from a given ciphertext. The same attack can be applied to produce forgeries if the cryptosystem is used for signing messages. Then, we point out that also other primitives, a Diffie-Hellman like key agreement scheme and an authentication scheme, designed along the same lines of the cryptosystem, are not secure due to the aforementioned attack. We close the paper by discussing the issues and the possibilities of constructing public key cryptosystems on real numbers
Detection of a sperm-coating antigen in the semen of Bubalus bubalis
No full text1. Surface antigens of B. bubalis spermatozoa were solunilized by Triton X-100 and EDTA; 2. Two major polypeptides, immunoprecipitated from the seminal plasma by the antibodies against the sperm extract, exhibited the same electrophoretic mobilities of two immunorelated sperm surface antigens; 3. The two polypeptides were isolated from the seminal plasma, by a multi-step chromatographic procedure, and found subunits of a single protein (MW 30,000, called SP 30; 4. The SP 30 protein bound in vitro to the postacrosomal region of homologous spermatozoa from cauda epididymis; 5. The localization of the sperm-coating antigen on the cell surface is compatible with a role in the fertilization process
CD4-mediated Anchoring of the Seminal Antigen gp17 onto the Spermatozoon Surface.
No full textA soluble 17 kDa glycoprotein, namely gp17, was previously isolated from human semen and used to obtain mouse monoclonal or chicken polyclonal antibodies. This protein was shown to bind CD4+ T-cells and to soluble recombinant CD4 in vitro. Here, we report that the anti-gp17 monoclonal antibodies are captured by ejaculated spermatozoa and that gp17-like antigens are released by cell acid extraction. Immunoblotting experiments with monoclonal antibodies indicated that SDS-lysates from spermatozoa contain proteins with the same electrophoretic and antigenic properties of CD4 and gp17. Anti-CD4 mouse monoclonal antibodies were used to coprecipitate from NP40-lysate proteins reacting with chicken anti-gp17 antibodies. Analytical chromatography demonstrated that a number of gp17-like forms are present in the seminal plasma, put that only the 1 kDa species can be detected in the spermatozoa lysate. This protein was localised by immunofluorescence on the post-acrosomal region of the spermatozoon. The same surface domain was also reactive with anti-CD4 antibodies. After treatment to induce in vitro capacitation, gp17 was detected all over the spermatozoon head. Conversely, only a minor part of the treated spermatozoa exhibited CD4 immunostaining, which remained localised on the post-acrosomal region. The possible function of CD4 and gp17 on male germ cells is discussed
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