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  • 1
    Electronic Resource
    Electronic Resource
    Atrial natriuretic peptide: A chemoattractant of human spermatozoa by a guanylate cyclase-dependent pathway (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 40 (1995), S. 371-378 
    Details
    ISSN: 1040-452X
    Keywords: Chemoattraction ; Chemokinesis ; Follicular fluid ; Gamete interaction ; Acrosome reaction ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Atrial natriuretic peptide (ANP), found in mammalian ovarian granulosa cells and oocytes (Kim et al., 1992, 1993), induces the human acrosome reaction (Anderson et al., 1994). The purpose of the present study was to determine whether ANP, as eggderived peptides from sea urchins, can act as a chemoattractant to human spermatozoa. Small lengths of capillary tubing that contained different concentrations of ANP were suspended over a suspension of washed spermatozoa. The number of spermatozoa that entered the tubing was determined. More than twice the number of spermatozoa moved into the tubing that contained a maximally effective concentration of ANP, as compared with tubing that contained only medium. The concentration of ANP that produced a half-maximal effect was 0.7 nM. The effect was blocked by LY83583, an inhibitor of guanylate cyclase. ANP produced more than a twofold increase in the rate of cGMP formation, an effect that was blocked by LY83583. Human ANP (5-27), a fragment of the intact peptide, had no chemoattractant activity. These findings suggest that a specific sperm receptor exists for the chemoattractant activity of ANP that is associated with guanylate cyclase. The chemoattractant activity of ANP is independent of the presence of extracellular calcium ions and is independent of the action of ANP as a stimulus of the acrosome reaction. There is no association between the chemoattractant activity of follicular fluid and the follicular fluid concentration of ANP. These data suggest that factors besides ANP are responsible for the chemoattractant activity of follicular fluid. The present study adds to evidence that human ANP is a potent modulator of human sperm function. © 1995 Wiley-Liss, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1080400314
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  • 2
    Electronic Resource
    Electronic Resource
    Proacrosin activation and acrosin release during the guinea pig acrosome reaction (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 25 (1990), S. 52-60 
    Details
    ISSN: 1040-452X
    Keywords: Spermatozoa ; Capacitation ; Acrosomal enzymes ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The kinetics of proacrosin activation and release from guine pig spermatozoa during the nonsynchronous acrosome reaction were studied. Epididymal spermatozoa were incubated at 37°C in a defined medium (pH 7.8) containing 1.7 mM Ca2+. After 195 min, 78% of the motile spermatozoa had undergone the acrosome reaction as determined by light microscopy. Acrosin and proacrosin levels in the spermatozoa and medium were measured at the beginning of the incubation period. Most of the total acrosin activity (78%) was associated with the spermatozoa, of which greater than 90% was in the form of proacrosin. Proacrosin represented a small, stable fraction (23%) of the total acrosin in the medium; it did not activate to acrosin while in the medium. After 195 min, a decrease in sperm-associated total acrosin (42%; p 〈 0.05) was accompanied by an increase in the total acrosin level in the medium (115%; P 〈 0.05). No change in the relative proacrosin content (percent of total acrosin) was evident in either medium or spermatozoa. Additional experiments quantified acrosin and proacrosin during the progression of the acrosome reaction. Both the loss of sperm-associated total acrosin and the increase in total acrosin levels in the medium were highly correlated with the fraction of acrosome-reacted spermatozoa (r = 0.954 and 0.922, respectively; P 〈 0.001). However, the rate of acrosin appearance in the medium was only 60% (P 〈 0.001) of the rate of acrosin loss from the spermatozoa. The fractional proacrosin content of spermatozoa (94%) and medium (31%) remained unchanged during the acrosome reaction (r = 0.15 and 0.30, respectively; P 〉 0.1). From these data, it was possible to estimate the total acrosin content of acrosome-intact spermatozoa (434 mlU/107 spermatozoa), and the fractions of the total sperm acrosin levels that are (1) released as active acrosin (37%), (2) released as proacrosin (17%), (3) inactivated (36%), and (4) associated with the spermatozoa (10%) during the acrosome reaction. The data suggest that proacrosin activation occurs within the spermatozoa, prior to distruption of the acrosome; this finding is consistent with the contention that acrosin is an active component of the mechanism underlying the acrosome reaction.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1080250110
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  • 3
    Electronic Resource
    Electronic Resource
    Characterization and inhibitor sensitivity of human sperm phospholipase A2: Evidence against pivotal involvement of phospholipase A2 in the acrosome reaction (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 27 (1990), S. 305-325 
    Details
    ISSN: 1040-452X
    Keywords: Human spermatozoa ; Phospholipase A2 inhibitors ; Human acrosome reaction ; Acrosin inhibitors ; Calmodulin antagonist ; Enzyme kinetics ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The kinetic properties and inhibitor sensitivity of human sperm phospholipase A2 (PLA2; EC 3.1.1.4) were studied. Phospholipase activity was isolated from human spermatozoa by acid extraction. Hydrolysis of dipalmitoyl phosphatidylcholine was specific to the sn-2 position. Activity was sensitive to product inhibition (60% inhibition by 0.1 mM lysophosphatidylcholine). The effects of Ca2+ and sodium deoxycholate on enzyme activity were biphasic; maximal activities were observed at 0.5 mM concentration of each agent. PLA2 was stimulated (135%) by 3% dimethylsulfoxide and was inhibited by elevated ionic strength (approximately 70% inhibition with either 0.2 M NaCl or 0.2 M KCl). Two molecular forms of PLA2 were kinetically distinguishable, one with an apparent Michaelis constant and maximal reaction velocity of 3.0 μM and 0.64 mlU/mg protein and the other with respective constants of 630 μM and 32.0 mlU/mg protein. Both forms of the enzyme were Ca2+ dependent and heat stable; however, the low-Km activity was less resistant to 60°C preincubation at pH 7.5 (28% inactivation of low-Km activity after 45 min, as compared to no effect on high-Km activity). Quinacrine was a noncompetitive PLA2 inhibitor with Kis for low- and high-Km activities of 0.42 mM and 0.49 mM, respectively. Trifluoperazine (calmodulin antagonist) inhibited the high-Km activity noncompetitively (Ki = 87 μM) and the low-Km activity by a mechanism consistent with the removal of a nonessential activator. Dissociation and rate constants for inactivation of low- and high-Km activities by p-bromophenacyl bromide were 0.28 mM and 0.032 min-1, and 0.73 mM and 0.066 min-1, respectively. PLA2 was inhibited by p-nitrophenyl-p′-guanidinobenzoate, at higher concentrations (10-4-10-3 M) than required to inhibit trypsinlike proteinases; p-aminobenzamidine, another potent trypsin/acrosin inhibitor, stimulated (approximately 40%) PLA2 at concentrations from 2-5 mM but inhibited PLA2 (40-50%) at a concentration of 10 mM. MnCl2 (5mM) inhibited low- and high-Km PLA2 activities by 77% and 76%, respectively. Quinacrine (0.4 mM), trifluoperazine (20 μM), p-bromophenacyl bromide (20 μM), and MnCl2 (5 mM) were tested as inhibitors of the ionophore A23187-induced human acrosome reaction. Inhibition was noted only with quinacrine (32%) and MnCl2 (93%). The effect of MnCl2 was restricted to an interaction with A23187, rather than with PLA2; p-Bromophenacyl bromide inhibited (P 〈 0.05) PLA2 (29%) when added to intact spermatozoa but had no effect on the acrosome reaction. PLA2 inhibition was poorly correlated with the acrosome reaction. Results from this study suggest that (1) human sperm contain at least two kinetically distinguishable forms of PLA2, with properties similar to those of PLA2 in other species and tissues; (2) PLA2 inhibition is not a likely mechanism for inhibition of acrosome reactions by acrosin inhibitors; (3) sperm PLA2 may be modulated by an endogenous activator; (4) the low-Km PLA2 is similar to the group I (pancreatic) enzyme; and (5) PLA2 is not a pivotal or rate-limiting step in the human acrosome reaction.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1080270405
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  • 4
    Electronic Resource
    Electronic Resource
    Retention of differentiated characteristics by cultures of defined rabbit kidney epithelia (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 130 (1987), S. 245-254 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Rabbit nephron segments of proximal convoluted tubules (PCT); proximal straight tubules (PST); cortical and medullary thick ascending limbs of Henle's loop (CAL, MAL); and cortical, outer medullary, and inner medullary collecting tubules (CCT, OMCT, IMCT) were individually microdissected and grown in monolayer culture in hormone supplemented, defined media. Factors favoring a rapid onset of proliferation included young donor age, distal tubule origin, and the addition of 3% fetal calf serum to the medium. All primary cultures had polarized morphology with apical microvilli facing the medium and basement membrane-like material adjacent to the dish. Differentiated properties characteristics of the tubular epithelium of origin retained in cultures included ultrastructural characteristics and cytochemically demonstrable marker enzyme proportions. PCT and PST were rich in alkaline phosphatase; CAL stained strongly for NaK-ATPase; CCT contained two cell populations with regard to cytochrome oxidase reaction. A CCT-specific antikeratin antibody (aLEA) was immunolocalized in CCT cultures, and a PST cytokeratin antibody stained PST cultures. The biochemical response of adenylate cyclase to putative stimulating agents was the same in primary cultures as in freshly isolated tubules. In PCT and PST adenylate cyclase activity was stimulated by parathyroid hormone (PTH) but not by arginine vasopressin (AVP); CAL and MAL adenylate cyclase was stimulated by neither PTH nor AVP; CCT, OMCT, and IMCT adenylate cyclase was stimulated by AVP but not by PTH. NaF stimulated adenylate cyclase activity in every cultured segment. It is concluded that primary cultures of individually microdissected rabbit PCT, PST, CAL, MAL, CCT, OMCT, and IMCT retain differentiated characteristics with regard to ultrastructure, marker enzymes, cytoskeletal proteins, and hormone response of adenylate cyclase and provide a new system for studying normal and abnormal functions of the heterogeneous tubular epithelia in the kidney.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041300210
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