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Biomedical subjects

N J Alexander

Publications and source records attributed to N J Alexander.

At least 55 records · Page 3Linked to original sources
PubMed1991

Inhibition of human sperm-zona pellucida tight binding in the presence of antisperm antibody positive polyclonal patient sera.

Patient sera previously characterized as containing high levels of IgG and IgA antisperm antibodies that bound to the sperm surface, most specifically the head region, were evaluated for their effect on sperm-zona pellucida tight binding as assessed by the hemizona assay (HZA). Of the ten patient sera tested, 7 reduced zona binding by approximately half. Two of the most strongly inhibitory (greater than 70% inhibition) were examined for their effect on the prefertilization maturation of sperm. The patient sera did not affect sperm motion characteristics, or development of hyperactivated motility. However, in the presence of these sera some impedance was noted in calcium uptake after stimulation with human follicular fluid and in the acrosome reaction after calcium ionophore induction. Whether these two sera specifically affect sperm-zona pellucida binding or non-specifically affect the normal progression of capacitation remains to be eludicated.

Calcium↗
PubMed1991

Sites of antisperm antibody action.

Antisperm antibodies can affect sperm function in the cervical mucus, as they undergo capacitation, or during sperm-egg interaction. During capacitation, the sperm membrane destabilizes and antigens previously not available to antibodies may become exposed. Antibody attachment can reduce fertilization as measured by hamster egg preparation or the hemizona assay. A panel of monoclonal and polyclonal patient sera were tested for their ability to inhibit sperm-zona pellucida tight binding. We tested 25 monoclonals from a panel from the World Health Organization, but only nine were positive by indirect bead binding, indicating that the majority of the antibodies were not sperm surface antigens. The sera of 13 patients were used; three were negative and served as controls, nine had antibodies of the IgG isotype bound to 100% of the sperm heads examined, and seven also exhibited sperm specific IgA antibodies. Of the monoclonals tested, six inhibited zona binding by 60%. Sera of seven patients caused inhibition of greater than or equal to 50% zona binding; those from male patients caused the greatest inhibition. When further specific testing was conducted, one monoclonal caused the greatest inhibition of zona binding; sera of three patients inhibited zona binding by 70%. The antibodies, whether monoclonal or patient sera, were tested for their effect on capacitation. The ability to undergo hyperactivated motility after antibody exposure was assessed and no changes appeared due to antibody exposure. Serum from one of the patients appeared to affect sperm calcium influx to some extent. Sera from two patients appeared to reduce the number of spermatozoa capable of undergoing the acrosome reaction.(ABSTRACT TRUNCATED AT 250 WORDS)

Agglutination↗
PubMed1991

Male infertility: the focus shifts to sperm manipulation.

Few systemic approaches for treatment of the infertile male are available. Therefore, the focus has shifted to studies of sperm maturation in the female tract, tests of sperm function, and assisted reproduction. New methods of sperm evaluation allow a better determination of those samples that will and will not fertilize ova. These methods include the strict morphology examination, biochemical approaches such as evaluation of creatine kinase levels, and the hemizona assay. Computer assisted semen analysis has not yet proved important for diagnosis but has provided important research information. For example, the drug pentoxifylline significantly increases velocity and has also been shown to enhance in vitro fertilization. The term subfertile is extensively used in the literature but its clear definition and the prognosis for subfertile men have not been established. Approaches that may increase fertilization rates include reducing the gamete culture volume and removal of cumulus oophorus. Assisted reproductive technologies for patients with ejaculatory dysfunction have also been expanded. The use of improved semen processing techniques, advanced oocyte retrieval, and well-timed intrauterine insemination are enabling physicians to use decreasing numbers of viable sperm to achieve pregnancies.

Humans↗
PubMed1991

Studies on the in vitro spermicidal activity of synthetic magainins.

Two synthetic magainins A and G are shown to have spermicidal activity. Transmission electron microscopic micrographs show that both magainins alter the plasma membranes of sperm and that these actions are rapid. Further studies will better delineate the contraceptive potential of synthetic magainins.

Antimicrobial Cationic Peptides↗
PubMed1990

The prevalence of human immunodeficiency virus in patients and their spouses entering a large in vitro fertilization program.

Between September 1987 and August 1989, all patients and their spouses entering our in vitro fertilization (IVF) program were screened for the human immunodeficiency virus (HIV) using the enzyme-linked immunosorbent assay (ELISA). Of 848 patients and 848 spouses tested, all but 4 patients and 1 husband tested negative. Of those who tested positive on repeat testing with ELISA, only one was positive on Western blotting (HIV prevalence, 0.59 per 1000). During this same time period 1187 samples of human cord blood were used to make tissue culture medium for the IVF embryology laboratory. One sample was discarded because of positive HIV on ELISA and Western blotting; two other samples were discarded because of positivity to the hepatitis B surface antigen. While we believe that routine HIV screening of IVF patients and their spouses is indicated, this population is of low risk for HIV positivity. Furthermore, continued screening of human sera used to make tissue culture media for IVF is mandatory.

Blotting, Western↗
PubMed1990

Sperm preparation affects reactivity of monoclonal antibodies.

The polyacrylamide gel electrophoresis (SDS-PAGE) patterns of extracts prepared from thrice-washed human sperm were compared with extracts of swim-up and non-rise sperm. For sperm extraction sodium deoxycholate (DOC), octylphenoxypolyethoxyethanol (NP-40), dithiothreitol (DTT), lithium 3,5-diiodosalicylate (LIS), or 3-[(3-cholamidopropyl) dimethylammonio]-1-propane sulfonate (CHAPS) were used. A pellet of pooled thrice-washed semen was divided and extracted with these detergents. Similar gel electrophoresis profiles, as revealed by silver staining, were observed with the LIS, DOC, NP-40 and CHAPS extracts, whereas DTT extracts lacked the 150 and 200 kDa bands. Different thrice-washed semen pools varied in their protein pattern, probably due to the presence of sloughed germinal cells, white blood cells and sloughed cells from the reproductive tract. Swim-up sperm extracts had a different protein profile from that of thrice-washed pools but pools of swim-up sperm had a more constant protein pattern than those of thrice-washed semen pellets. Monoclonal antisperm antibodies did not always recognize antigens of the same molecular weights in western blots when extracts of swim-up sperm versus thrice-washed sperm were compared. In immunoblot studies with monoclonals (produced against thrice-washed sperm, cloned five times, reactive by ELISA and sperm function tests), 4/12 reacted with 0.3% NP-40 extracts of thrice-washed sperm and 5/12 with 0.3% NP-40 extract of swim-up sperm. These findings suggest that definition of antigens by monoclonal antisperm antibodies will be influenced by the nature of sperm extract employed.

Antibodies, Monoclonal↗
PubMed1990

Effect of virus dose and nonoxynol-9 on the genital transmission of SIV in rhesus macaques.

One inoculation of cell-free SIVmac (50 TCID50) caused persistent viremia in nine of 13 female rhesus macaques inoculated intravaginally. Persistent viremia was produced in two of four male rhesus macaques by twice placing cell-free SIVMAC (50 TCID50) onto the skin and urethral os of the penis. Placing a spermicide containing nonoxynol-9 into the vaginal canal prior to repeated intravaginal inoculations of SIV prevented transmission of the virus in three of six female rhesus macaques.

Administration, Intravaginal↗
PubMed1990

Sperm bound to zona pellucida in hemizona assay demonstrate acrosome reaction when stained with T-6 antibody.

A monoclonal antibody, T-6, useful for detecting acrosome-reacted sperm based on an immunofluorescent assay, was employed to evaluate acrosomal status of human sperm that were tightly bound to hemisected human zonae pellucidae (hemizona assay). Over 90% of the bound sperm evaluated exhibited immunofluorescent patterns indicative of acrosome reaction. This staining method for evaluating the acrosomal status of sperm bound to the zona pellucida may enable definition of a group of male infertility patients heretofore not recognized.

Acrosome↗
PubMed1990

Human follicular fluid stimulates hyperactivated motility in human sperm.

Since human follicular fluid (FF) is known to enhance the acrosome reaction and capacitation, we investigated whether hyperactivated motility is stimulated by FF. Follicular fluid-treated sperm exhibited a threefold increase in hyperactivation compared with the controls. The use of fetal cord serum in the medium, instead of bovine serum albumin, supported the same high levels of hyperactivation, although the peak occurred at 3 hours rather than 5 hours of capacitation. When sperm were treated with a steroid-rich fraction of the FF, hyperactivation was stimulated to the same degree as with whole FF. In contrast, no stimulation occurred when sperm were treated with a FF fraction stripped of steroids. The FF enhancement of hyperactivation in vitro could augment the fertilizing capacity of subfertile sperm samples, providing also a glimpse of possible in vivo events as sperm traverse the FF-laden cumulus oophorus.

Body Fluids↗
PubMed1990

Reproductive immunology: relevance to infertility practice.

Both, men and women can develop antisperm antibodies as the response to numerous factors, however immune-mediated infertility is a relative condition, i.e. may reduce but not totally prevent fertility. Different techniques can detect antisperm antibodies and show how these antibodies may interfere with fertilization process. To overcome immune-mediated infertility, the immunosuppressive therapy and in vitro treatment of antibody-coated sperm cells including in vitro fertilization have been proposed.

Antibodies↗
PubMed1990

Serum hormone levels affect sperm function.

If hormone levels affect sperm motility during capacitation, then the serum added to samples prepared for artificial insemination could affect sperm fertilizability. We investigated various sperm functional movement characteristics (percent motile, progressive velocity, linearity, beat cross frequency, lateral head displacement, longevity, and hyperactivation) in specimens incubated with women's sera, as well as exogenous hormone preparations of estradiol (E2) and progesterone (P). Early follicular phase serum (low E2 and low P) maintained motility and longevity. Sperm in E2-treated medium exhibited higher progressive velocity, linear motility, and longevity. In contrast, the percent motility decreased as sperm exhibited hyperactivated motility with P.

Estradiol↗
PubMed1990

Characteristics of monoclonal antibodies reactive with human sperm and seminal plasma.

The characteristics of monoclonal antibodies developed against human spermatozoa are described. Out of 10 monoclonal antibodies 9 did not react in ELISA with human RBC, WBC, platelets, Raji cells nor mouse sperm. Four monoclonal antibodies reacted with monkey sperm and all 10 reacted with human seminal plasma. Monoclonal antibodies showed differential reactivity with pre- and post-capacitated sperm. Four monoclonal antibodies were able to agglutinate sperm whereas none of these were positive in sperm-immobilization assay. Interestingly, two monoclonal antibodies (MA-46 and MA-50) were able to block the attachment of pre-capacitated sperm to zona denuded hamster oocytes. MA-46 and MA-50 recognized in immunoblot spermatozoa antigens having apparent molecular weights of 14 and 20 K Da and greater than 200 K Da respectively. The monoclonal antibodies reported in this study will be useful in further delineating the spermatozoa antigens involved in regulation of fertility.

Animals↗
PubMed1989

Genital mucosal transmission of simian immunodeficiency virus: animal model for heterosexual transmission of human immunodeficiency virus.

An animal model for the heterosexual transmission of human immunodeficiency virus (HIV) was developed by the application of simian immunodeficiency virus (SIV) onto the genital mucosas of both mature and immature, male and female rhesus macaques. Virus preparations were infused into the vaginal vaults or the urethras (males) of the animals through a soft plastic pediatric nasogastric feeding tube. The macaques that were infected by this route (six males and nine females) developed SIV-specific antibodies, and SIV was isolated from peripheral mononuclear cells of all seropositive animals. One male and one female infected by this route developed severe acquired immunodeficiency syndrome-like disease with retroviral giant-cell pneumonia. As few as two inoculations of cell-free SIV containing 50 50% tissue culture infective doses induced persistent viremia. Cell-free virus preparations were capable of producing infection by the genital route. Much higher doses of virus were required to transmit SIV by this route than are required for transmission by intravenous inoculation. Thus, it appears that the mucous membranes of the genital tract act as a barrier to SIV infection. Spermatozoa and seminal plasma were not required for the genital transmission of SIV. Rarely, SIV was recovered from mononuclear cells in semen and vaginal secretions. The SIV-rhesus macaque model is suitable for assessing the role of cofactors in heterosexual transmission of HIV and will be useful for testing the effectiveness of spermicides, pharmacologic agents, and vaccines in preventing the heterosexual transmission of HIV.

Acquired Immunodeficiency Syndrome↗
PubMed1989

Mouse monoclonal antibodies against human sperm: evidence for immunodominant glycosylated antigenic sites.

Thirty mouse monoclonal antibodies (MoAbs) raised against human sperm detect common antigenic determinants on human lymphocytes, erythrocytes, bacteria and endotoxin. Specific chemical, enzymatic and lectin blocking studies indicate that the sperm-associated antigens defined by these MoAbs are glycoconjugates. Further studies including reactivity of these MoAbs with organic sperm extracts indicate that the predominant carriers of these carbohydrate antigens are glycolipids and that the terminal immunodominant monosaccharide may be N-acetyl-glucosamine or N-acetylgalactosamine.

Animals↗