Browsing by Author "GUTIERREZ, G"

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    ANTIFERROMAGNETIC INTERACTION BETWEEN 2 EASY-PLANE FERROMAGNETIC HEISENBERG-CHAINS
    (1994) DIAZ, V; GUTIERREZ, G; FERRER, R
    Nonlinear magnetic excitations in the Heisenberg magnetic system CsNiF3, when an antiferromagnetic interchain interaction is present between two neighboring easy-plane ferromagnetic chains, are studied. Using a two-lattice model and defining coherent states on each site for the two chains the discrete coupled equation for the averages of the spin components are given. In the easy-plane limit it is found that three kinds of static magnetic excitations can exist, depending on the value of the antiferromagnetic interchain exchange interaction J2. The inclusion of this antiferromagnetic interchain interaction makes the problem of the nonlinear magnetic excitations appear in a new light.
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    THE ACROSOME REACTION-INDUCING ACTIVITY OF INDIVIDUAL HUMAN FOLLICULAR-FLUID SAMPLES IS HIGHLY VARIABLE AND IS RELATED TO THE STEROID CONTENT
    (1992) MORALES, P; LLANOS, M; GUTIERREZ, G; KOHEN, P; VIGIL, P; VANTMAN, D
    In this study, we have evaluated the relationship between the acrosome reaction-inducing activity of individual human follicular fluid samples and their steroid content. Eighteen samples of follicular fluid were obtained during egg retrieval in six patients undergoing assisted fertilization. Motile spermatozoa were incubated in modified Tyrode's medium (26 mg/ml bovine serum albumin) for 20 h at 1 X 10(7) cells/ml. In a single experiment, aliquots of a semen specimen were simultaneously treated with an aliquot of each follicular fluid sample. The percentage of acrosome reacted spermatozoa was determined using fluorescein isothiocyanate-conjugated Pisum sativum agglutinin (FITC - PSA) lectin. The fluids were also analysed by radioinimunoassay to determine the levels of progesterone, 17-alpha-hydroxy-progesterone, testosterone and oestradiol. The results showed that there was a positive, highly significant correlation between the acrosome reaction-inducing activity and the progesterone level of each follicular fluid sample (r = 0.72, P < 0.005). Additionally, treatment of the follicular fluid samples with charcoal-dextran caused both a decrease in progesterone concentration and the total loss of the acrosome reaction-inducing activity. The addition of progesterone restored the acrosome reaction-inducing ability in 88% of samples. These data support the idea that progesterone in follicular fluid is the molecule responsible for inducing the acrosome reaction in human spermatozoa.