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N J Alexander

Publications and source records attributed to N J Alexander.

154 records · Page 9Linked to original sources
PubMedDate not supplied

Surface structure of spermatozoa frozen for artificial insemination.

Samples of human semen frozen in liquid nitrogen ( - 196 degrees C) with no glycerol, 5 and 10% glycerol were compared with samples that were untreated, with 10% glycerol but not frozen, and spermatozoa frozen at -20 degrees C. SEM and TEM of the samples indicates that 10% glycerol caused fewer surface changes of the spermatozoa than other treatments. Motility counts after the various freezing treatments were also highest when 10% glycerol was used as the cryoprotectant. Nonetheless, cryopreservation is detrimental to spermatozoa and often causes considerable damage to the acrosome with a leakage of the acrosomal contents.

Cell Count↗
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Hemizona assay (HZA) demonstrates effects of characterized mouse antihuman sperm antibodies on sperm zona binding.

Characterized antihuman sperm monoclonal antibodies from mice were evaluated using the hemizona assay (HZA) to determine whether sperm:zona binding was effected. The seven monoclonal antibodies were characterized using human sperm in agglutination, immobilization, and penetration assays. Semen was provided by four fertile men and used in the HZA to determine if the presence of a monoclonal antibody would affect tight binding of the sperm to the zona pellucida. Pre-incubation of MA-14 for 1 h with the sperm induced a 33-54% reduction of the number of tightly bound sperm. This antibody reacts to an antigen located on the acrosome and midpiece. Experiments in which there was no pre-incubation of the antibody with sperm, resulted in no significant reduction in the number of sperm bound in the HZA. These findings suggest that an anti-human sperm antibody produced in mice can modulate sperm:zona binding. Reduction in zona binding could indicate a cause of immune-related infertility and this test may be useful in selecting an antigen for contraceptive vaccine development.

Acrosome↗
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Sperm antigens and reactivity of antisperm monoclonal antibodies in ELISA.

Several types of sperm antigenic suspensions as well as the whole sperm, either methanol-fixed or air-dried, were checked for intensity of binding to monoclonal antisperm antibodies with known characteristics of reactivity to sperm. The activity of sperm antigen--antibody binding was measured by ELISA (enzyme-linked immunosorbent assay) and compared in several variations (parallely run) of the assay where different types of sperm antigen preparations were applied. The obtained results were then evaluated for statistical significance in Wilcox test. It was shown that antibody reactivity was markedly higher in experiments where the whole sperm was coated in a solid-phase in comparison to results obtained with adhered different sperm antigenic suspensions. However, one exception was noted, where the results from ELISA, run with sperm organic extract, were (statistically) insignificantly lower than those obtained with the whole sperm. Therefore, organic sperm extracts (containing mostly glycolipids) can be a valuable alternative to screening for antisperm antibody activity and/or infertility background.

Antibodies, Monoclonal↗
PubMedDate not supplied

Complement-inhibiting activity of seminal plasma.

Human seminal plasma has an anticomplement effect that can be measured by a standard immune hemolytic assay. We found that about 20% of samples lack complement-inhibiting activity. To determine the anatomical origin of a complement inhibitor, inhibition of hemolysis was measured in seminal plasma samples that were primarily of prostatic, vesicular, or epididymal/testicular origin, as well as in seminal plasma from vasectomized men. All samples contained complement-inhibiting activity, although epididymal fluid showed nearly twice the amount. Therefore, the factor (or factors) is ubiquitous in secretions of the male reproductive tract. Complement-inhibiting activity is eluted in two high-molecular-weight peaks upon gel filtration. We found evidence that the inhibitory factor is not lactoferrin, a proteinase, or one of the proteinase inhibitors known to be present in human seminal plasma. It seems likely that the complement inhibitor in seminal plasma protects gametes and reproductive tissues from complement-mediated damage.

Chromatography, Gel↗
PubMedDate not supplied

Vasectomy-induced autoimmunity: antisperm and antinuclear autoimmune monoclonal antibodies.

Antibodies to sperm and testicular autoantigens are a hallmark of vasectomy-induced murine autoimmunity. We generated five autoimmune monoclonal antibodies with spleen cells from nonimmunized but vasectomized BDF1 male mice as fusion partners in two experiments. Four of the antibodies, designated Vx 4, Vx 8, Vx 10, and Vx 23, recognize, as determined by fluorescence microscopy, topographically restricted sperm-specific antigenic determinants that appear in the germinal epithelium as spermatogenesis progresses. Antibodies Vx 8 and Vx 10 identified 60,000- and 97,000- dalton, mouse-specific sperm antigens restricted to the anterior acrosome and posterior acrosome, respectively. Antibody Vx 23 identified a 35,000- to 40,000- dalton antigen on the midpiece and postacrosomal regions of epididymal mouse sperm. The antigenic target of antibody Vx 4 on the midpiece region could not be identified with the Western blot technique. Both Vx 4 and Vx 23 cross-reacted with human, rabbit, and monkey sperm; immunofluorescence revealed that they were bound onto the midpiece region. By immunofluorescence, a single clone (Vx 24) distinctly reacted with the nuclei of somatic and testicular germ cells but not the nuclei of sperm. The isolation of this antinuclear autoantibody raises questions about the development of nonsperm-specific autoantibodies after vasectomy in the mouse.

Animals↗
PubMedDate not supplied

Atherosclerosis of cynomolgus monkeys hyper- and hyporesponsive to dietary cholesterol. Lack of effect of vasectomy.

A moderately atherogenic diet was fed to young adult cynomolgus macaque males that were observed to be either hypo- or hyperresponsive to dietary cholesterol and who were randomized into groups to be either vasectomized or sham-vasectomized. The extent of atherosclerosis was found to be considerably greater at all arterial sites studied for the monkeys that were hyperresponsive to dietary cholesterol. The differences in atherosclerosis development among the hyperresponder monkeys occurred primarily in the proximal portions of the coronary arteries, the proximal and distal portions of the common carotid arteries, and only in the most proximal portions of the femoral arteries. There were no significant effects of vasectomy or sham vasectomy on atherosclerosis extent in either the hyper- or the hyporesponding groups, although there was a suggestion of somewhat larger lesions in the left circumflex coronary artery of hyperresponder monkeys that were vasectomized and somewhat smaller atherosclerotic lesions in the left common carotid arteries of vasectomized monkeys. The data presented here do not support our first report of worsened atherosclerosis among cynomolgus monkeys fed diets high in cholesterol. The findings of the current study are consistent with recent epidemiological studies of vasectomized and nonvasectomized human males.

Animals↗
PubMedDate not supplied

Mechanism of genital transmission of SIV: a hypothesis based on transmission studies and the location of SIV in the genital tract of chronically infected female rhesus macaques.

To understand the biologic processes involved in transmission of HIV, we examined the genital tracts of chronically infected female macaques and localized SIV-infected cells. SIV was found in the genital tract of 12 of 16 animals and SIV-infected cells were located in the cervix and vagina. Inoculation of cell-free SIV into the blind vaginal pouch of hysterectomized macaques resulted in systemic infection. We propose a hypothesis to explain the early events in the genital transmission of SIV.

Animals↗