1,720,996 research outputs found
Effects of organochlorine xenobiotics on human spermatozoa
No full textThe organochlorine insecticide lindane is a widely distributed environmental pollutant belonging to the growing family of endocrine disrupting chemicals (EDCs). Lindane intercalates into the sperm membrane and alters the molecular dynamics of the bilayer. In the present paper, preliminary data are reported showing that doses of lindane as low as those found in the female genital tract secretions inhibit the sperm cytological responsiveness to progesterone, the physiological agonist which stimulates the onset of acrosome reactions at the site of fertilization. The hypothesis is put forth that even background levels of lindane may exert antifertility effects independently on the health status of either the male and female reproductive organs
Laurdan fluorescence spectroscopy reveals a single liquid-crystalline lipid phase and lack of thermotropic phase transitions in the plasma membrane of living human sperm
No full textMembrane lipid phase(s), phase coexistence, and thermotropic phase transitions have been investigated in viable human spermatozoa using Laurdan fluorescence spectroscopy. Generalized polarization (GP) values derived from Laurdan excitation and emission spectra confirm that the sperm plasma membrane is a low polar, highly rigid (liquid-ordered) structure, and give evidence that, in the range from 10 degrees C to 42 degrees C, membrane lipids are in a single liquid-crystalline phase. The absence of phase transitions in the same thermal range argues against the hypothesis that the lipid domains previously detected on the sperm sur-face are produced by lipid lateral phase separation. The above findings are likely accounted for by the high cholesterol to phospholipid molar ratio found in the human sperm membrane. This is the first time that membrane lipid phase and polarity have been detected and quantified in living mammalian spermatozoa
PARTITION OF THE ORGANOCHLORINE INSECTICIDE LINDANE INTO THE HUMAN SPERM SURFACE INDUCES MEMBRANE DEPOLARIZATION AND CALCIUM INFLUX
Full text linkThe effects of the insecticide lindane (the gamma-isomer of 1,2,3,4,5,6-hexachlorocyclohexane) on membrane potential, cytosolic free Ca2+ concentration ([Ca2+]i) and surface biophysical properties were studied in human spermatozoa. The insecticide induces rapid, transient and reproducible membrane depolarization and opening of voltage-dependent Ca2+ channels leading to an increase in [Ca2+]i. In contrast with the effect in somatic cells, lindane did not affect gamma-aminobutyric acid receptor-linked Cl- currents. Ca2+ and K+ currents were found to drive lindane-induced membrane depolarization and repolarization respectively, whereas Na+ and Cl- fluxes appear not to have a role in the phenomenon. The insecticide was still able to produce membrane depolarization both in the combined absence of extracellular Ca2+ and Na+ and in high-K+ buffer, suggesting that lindane alters the membrane dipole potential. In agreement with this, Laurodan and Prodan fluorescence spectroscopy revealed that lindane partition into the sperm plasma membrane lowers water molecular dynamics in the uppermost region of the membrane external leaflet, probably as the result of reordering of water dipoles. We propose that the first effect of lindane partitioning into the sperm plasma membrane is a change in the membrane dipole potential, which results in the activation of membrane-located Ca2+-influx pathways
3,3',4,4',5-Pentachlorobiphenyl (PCB 126) Induces Ca2+ Influx and Membrane Depolarization in Human Spermatozoa
No full textThe interaction of the organochlorine insecticide lindane with human spermatozoa: biochemical and biophysical aspects
No full textEffetti dell’insulina sulla dinamica molecolare della membrana plasmatica dello spermatozoo umano
No full textThe interaction of the xenobiotic organochlorine insecticide lindane with human spermatozoa: biochemical and biophysical findings
No full text
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
- …
