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Atomic force microscopy (AFM) has been used to measure the strength of bonds between biological receptor molecules and their ligands. But for weak noncovalent bonds, a dynamic spectrum of bond strengths is predicted as the loading rate is altered, with the measured strength being governed by the prominent barriers traversed in the energy landscape along the(More)
Carbohydrate--protein bonds interrupt the rapid flow of leukocytes in the circulation by initiation of rolling and tethering at vessel walls. The cell surface carbohydrate ligands are glycosylated proteins like the mucin P-selectin glycoprotein ligand-1 (PSGL-1), which bind ubiquitously to the family of E-, P-, and L-selectin proteins in membranes of(More)
A simple micromechanical method has been developed to measure the rupture strength of a molecular-point attachment (focal bond) between two macroscopically smooth membrane capsules. In the procedure, one capsule is prepared with a low density coverage of adhesion molecules, formed as a stiff sphere, and held at fixed position by a micropipette. The second(More)
Testicular size, semen characteristics and serum reproductive hormone levels were studied in 1239 normal Chinese men. The mean testicular size of 17 ml in this group of subjects was similar to other reports in Orientals but was smaller than that reported in Caucasians. Semen volume, and the sperm count, motility and morphology were comparable to those(More)
BACKGROUND As reference laboratory methods for measuring free testosterone (FT) by equilibrium dialysis (ED) are laborious, costly and nonautomatable, FT levels are often calculated (cFT) rather than measured. However, the predictive accuracy of such estimates in routine use relative to laboratory measurements is not well defined. We provide a large-scale(More)
Short term exposure of the testis to heat causes degeneration of germ cells. However, the mechanisms underlying this process are poorly understood. The major objectives of this study were to determine whether the heat-induced loss of germ cells in the adult rat occurs via apoptosis, to document its stage-specific and cell-specific distribution, and to(More)
The major objectives of the present study were to document the temporal and stage-specific acceleration of germ cell apoptosis in adult rats after selective suppression of pituitary gonadotropins by GnRH antagonist (GnRH-A) treatment, and to examine the possibility that apoptosis is the sole mechanism of germ cell death in response to hormonal deprivation.(More)
Previous studies in the Sprague-Dawley rat have demonstrated that male reproductive aging is primarily a neuroendocrine dysfunction characterized by decreased pulsatile LH secretion leading to low serum testosterone (T) levels, whereas sperm production is relatively well maintained. In contrast to the Sprague-Dawley rat, the Brown-Norway (BN) rat has a(More)
The objectives of the study were to determine stage-specific changes in the kinetics of germ cell apoptosis induced by administration of exogenous testosterone (T) alone and to examine whether addition of a single testicular heat exposure would enhance the induction of germ cell apoptosis and the suppression of spermatogenesis by T. Adult male rats were(More)
We have used a biomembrane force probe decorated with P-selectin to form point attachments with PSGL-1 receptors on a human neutrophil (PMN) in a calcium-containing medium and then to quantify the forces experienced by the attachment during retraction of the PMN at fixed speed. From first touch to final detachment, the typical force history exhibited the(More)