Biomedical subjects

K V R Reddy

Publications and source records attributed to K V R Reddy.

8 recordsLinked to original sources

PubMed2006

Inhibition of sperm-egg binding and fertilisation in mice by a monoclonal antibody reactive to 57-kDa human sperm surface antigen.

Monoclonal antibodies (mAbs) against spermatozoa are a popular approach to define sperm antigens involved in the process of fertilisation. The identification and characterisation of a 57-kDa fertility asssociated sperm antigen (FASA-57) from human spermatozoa was reported in an earlier paper by the authors. In the present report, studies to develop mAbs against partially purified FASA-57 are extended. From a panel of mAbs raised, one clone designated as 3H(4)B(9) was selected and characterised because it recognised native FASA-57. Indirect immunofluorescence studies revealed that FASA-57 localised on the acrosome of non-acrosome-reacted human spermatozoa and on the equatorial region after the acrosome reaction. Spermatozoa from several other mammalian species were also found to express this antigen, suggesting its evolutionary conservation across the species. The antigen localised specifically in spermatogonial cells and luminal spermatozoa of the testis and epididymis. Western blot studies showed the presence of a FASA-57-like protein in the mouse brain also, indicating that testis and brain share antigenic similarities. Further, the role of FASA-57 in sperm-egg interaction was investigated using a mouse model. The mAb 3H(4)B(9) inhibited sperm-egg binding and fusion in a dose-dependent manner with half-maximal inhibition at 2 microg mL(-1). In conclusion, FASA-57 appears to play an important role in sperm-egg recognition, fusion and fertilisation. Therefore, FASA-57 could be used as a diagnostic marker in the evaluation of male infertility.

Acrosome↗

PubMed2005

Characterization of cDNA encoding a human sperm membrane protein sharing homology with Huntington protein.

In our earlier study, we have reported the identification and characterization of a 57-kDa sperm membrane protein from human spermatozoa. The protein was found to be localized on the acrosome in acrosome intact spermatozoa and shifted to equatorial region after acrosomal induction. Further, we demonstrated that it plays a critical role in sperm--egg binding and fusion. Since the protein was found to be either absent or poorly expressed on the spermatozoa from infertile men, we designated it as Fertility Associated Sperm Antigen (FASA). A human epididymal cDNA library in Lambda-ZAP vector was screened with a polyclonal antibody raised against FASA. A clone was obtained with an insert of approximately 1.9 kb cDNA. The sequence showed 99% homology with a part of the human chromosome 11. EST database showed that a portion of 1.9 kb gene has 87% homology to gene encoding Huntington disease protein (HDP). The mutated form of this protein is responsible for Huntington's disease (HD) and is found in the brain cells of HD patients.

Amino Acid Sequence↗

PubMed2005

Antimicrobial peptides as microbicidal contraceptives: prophecies for prophylactics--a mini review.

The global increase in human immunodeficiency virus/acquired immune deficiency syndrome (HIV/AIDS) and sexually transmitted infections (STIs) has led to the introduction of barrier methods, such as condoms. However, drawbacks associated with condoms, such as men being reluctant to use them and women being unable to negotiate their use, have led to the search for better and acceptable alternatives, namely the microbicides. These are gel formulations that, when used prior to sexual intercourse, protect against the transmission of HIV and other STIs. However, after observing the side-effects of nonoxynol-9, a component of the microbicidal formulations available on the market, the focus has shifted to natural available compounds demonstrating the preferred protective effects. Antimicrobial peptides (AMPs) are one such group of compounds present in a wide range of organisms from bacteria to humans. The existing 750 or so, low-molecular-weight, cationic charged peptides are classified into five major groups based on their three-dimensional structure obtained by nuclear magnetic resonance studies. The hypothesized mode of action seems to be the interaction of the positively charged peptides with the negatively charged phospholipids present on the surface of the cell membrane. Various studies have demonstrated the effect of several AMPs, namely, defensins, protegrins, cathelicidins, cecropins, polyphemusins, magainins and melittins, against various STI-causing pathogens and HIV/herpes simplex virus, both in vitro and in vivo. The contraceptive efficacies of magainin and nisin in vitro and in vivo are worth mentioning. We believe these peptides are suitable candidates in the development of newer mechanism-based microbicides in future.

Acquired Immunodeficiency Syndrome↗

PubMed2004

Contraceptive efficacy of antimicrobial peptide Nisin: in vitro and in vivo studies.

Sexually transmitted infections and unplanned pregnancies present a great risk to the reproductive health of women. Therefore, female-controlled vaginal products directed toward disease prevention and contraception are needed urgently. In the present study, efforts were made to evaluate the contraceptive potential of Nisin. The effect of Nisin on sperm motility was assessed under in vitro and in vivo conditions. The results showed that sperm motility was completely inhibited with Nisin. The minimum effective concentration of Nisin required to immobilize sperm (80-100 x 10(6)) in vitro within 20 s was found to be 50 microg in rat, 200 microg in rabbit and 300-400 microg in monkey and human. The effect on sperm motility was observed to be dose- and time-dependent. Intravaginal administration of Nisin (200 microg) before mating during proestrus-estrous transition phase caused complete arrest of sperm motility and blockage of conception. Subacute toxicity studies in rats indicated that, repetitive intravaginal application of Nisin at the dose of 200 microg for 14 consecutive days induced no abnormalities either in the length of estrous cycle or in the morphology of vaginal epithelial cells. No histopathological abnormalities in vaginal tissue or any change in blood and serum biochemical profiles were observed. Furthermore, no adverse effects were observed on subsequent reproductive performance, neonate survival and development of pups. It is suggested that Nisin, with its antibacterial and spermicidal activities, could be developed as a potent vaginal contraceptive for future use in humans.

Administration, Intravaginal↗

PubMed2004

Antimicrobial peptides: premises and promises.

Antimicrobial peptides (AMPs) are an important component of the natural defences of most living organisms against invading pathogens. These are relatively small (< 10kDa), cationic and amphipathic peptides of variable length, sequence and structure. During the past two decades several AMPs have been isolated from a wide variety of animals, both vertebrates and invertebrates, and plants as well as from bacteria and fungi. Most of these peptides are obtained from different sources like macrophages, neutrophils, epithelial cells, haemocytes, fat body, reproductive tract, etc. These peptides exhibit broad-spectrum activity against a wide range of microorganisms including Gram-positive and Gram-negative bacteria, protozoa, yeast, fungi and viruses. A few peptides have also been found to be cytotoxic to sperm and tumour cells. AMPs are classified based on the three dimensional structural studies carried out with the help of NMR. The peptides are broadly classified into five major groups namely (a) peptides that form alpha-helical structures, (b) peptides rich in cysteine residues, (c) peptides that form beta-sheet, (d) peptides rich in regular amino acids namely histatin, arginine and proline and (e) peptides composed of rare and modified amino acids. Most of these peptides are believed to act by disrupting the plasma membrane leading to the lysis of the cell. AMPs have been found to be excellent candidates for developing novel antimicrobial agents and a few of these peptides show antimicrobial activity against pathogens causing sexually transmitted infection (STI), including HIV/HSV. Peptides, namely magainin and nisin have been shown to demonstrate contraceptive properties in vitro and in vivo. A few peptides have already entered clinical trials for the treatment of impetigo, diabetic foot ulcers and gastric helicobacter infections. In this review, we discuss the source, structures and mode of action with special reference to therapeutic considerations of various AMPs.

Animals↗

PubMed2004

Sperm membrane protein profiles of fertile and infertile men: identification and characterization of fertility-associated sperm antigen.

BACKGROUND: Male infertility is the major cause of conception failure in about 25% of all infertile couples. Understanding the causes of male infertility depends to a certain extent on the proteins present on the spermatozoa. The study aim was to investigate first, whether there is any difference in the expression of sperm membrane proteins between fertile and infertile males; and second, whether there is any functional significance of these proteins in the spermatozoa. METHODS: Six different protocols were employed to extract sperm membrane proteins. A 57 kDa protein was identified and purified using different chromatographic techniques. The homogeneity and isoelectric point of the protein was confirmed by 2D-electrophoresis. The protein was characterized by immunofluorescence, ELISA, flow cytometry, SDS-PAGE and Western blot analysis. The role of 57 kDa protein in sperm-oocyte binding was studied in vitro. RESULTS: All six sperm extracts of normozoospermic and infertile subjects showed 16-18 major and 12-15 minor protein bands. However, in one of the methods, the lysis buffer containing N-octyl-beta-D-glycopyranoside (NOG) resulted in an additional protein band at the 57 kDa region in 95% of normozoospermic samples. The protein was either absent (approximately 80%) or negligible (approximately 20%) in infertile subjects. The protein was localized to the head of non-acrosome-reacted spermatozoa (NAR), and shifted to the equatorial segment in acrosome-reacted (AR) spermatozoa. The antibody directed against purified 57 kDa protein inhibited binding of human sperm to zona-free hamster oocytes in a dose-dependent manner. CONCLUSIONS: The results suggest that lack and/or low expression of 57 kDa protein may be one of the reasons for infertility in men. Therefore, the protein could be used as a marker for sperm quality in men.

Animals↗

PubMed2004

Evaluation of antimicrobial peptide nisin as a safe vaginal contraceptive agent in rabbits: in vitro and in vivo studies.

In the midst of the global epidemics of both unwanted pregnancies and sexually transmitted infections (STIs), options that provide protection are ideal. In the present study, nisin, a known antimicrobial peptide, was evaluated for safety and contraceptive potential in vitro and in vivo in the rabbit. A concentration of 400 microg nisin per ml was found to be spermicidal in vitro, and the effect was dose and time dependent. In vivo studies indicated that intravaginal application of 1 mg nisin blocked conception in rabbits. Repeated application of nisin (50 mg/animal per day) in rabbits for 14 consecutive days did not cause local inflammation or damage to the vaginal epithelium. In addition, the rate of diffusion of nisin into the blood via the vaginal mucosal epithelium, and its clearance from the circulation was found to be rapid. No treatment-related changes were observed in the reproductive performance of rabbits after cessation of treatment. Furthermore, no changes were observed in the gestation period, subsequent growth and survival of neonates in these animals. When male rats were given nisin orally for 13 consecutive weeks, no effect was observed on reproductive performance. The number of pups born, survival and growth of pups were unaltered. The affinity studies of nisin revealed that spermatozoa are more susceptible to nisin than red blood cells and vaginal epithelial cells. We suggest that nisin with spermicidal and antimicrobial properties could serve as a safe vaginal contraceptive for future therapeutic interventions in STIs.

Absorption↗

PubMed2003

Integrin receptors: the dynamic modulators of endometrial function.

Cell-cell and cell-extracellular matrix (ECM) interactions play a critical role in various developmental processes, including differentiation, proliferation and migration of cells. ECM proteins can influence cellular function thus creating a complex feedback mechanism. The adhesion of cells to each other, their ECM proteins and endothelial surfaces is mediated by a variety of membrane proteins collectively known as adhesion molecules. Adhesion molecules have been further divided into five subfamilies, the integrins, the selectins, the cadherins, the mucins and the immunoglobulin superfamily. Members of the integrin family of cell surface adhesion receptors are important mediators of cell-ECM contact. Integrin receptors are alpha beta heterodimers with a transmembrane segment, a short cytoplasmic domain and a large extracellular domain. The role of integrins in reproduction has been established. Several reasons make these molecules very attractive due to their constant involvement from egg to birth. They participate in sperm-egg interaction, fertilization, implantation and placentation in many species including humans. Integrins provide signals to individual cells essential for growth and development of different tissues. In the present review, we describe (1) the regulatory pathways for controlling expression of integrins in the endometrium, (2) various biomarkers and their role in endometrial function, (3) reproductive disorders in women related to aberrant integrin expression in the endometrium and (4) the functional significance of integrins available from gene knockout studies.

Animals↗