H. N. Krishnamurthy

Bio: H. N. Krishnamurthy is an academic researcher from Indian Institute of Science. The author has contributed to research in topics: Sperm & Spermatogenesis. The author has an hindex of 10, co-authored 14 publications receiving 557 citations.

Enhanced susceptibility of follicle-stimulating-hormone-deprived infertile bonnet monkey (Macaca radiata) spermatozoa to dithiothreitol-induced DNA decondensation in situ.

Abstract: Immunoneutralization of endogenous follicle-stimulating hormone (FSH) of adult male monkeys leads to oligospermia and infertility despite unchanged testosterone levels, The inability of these monkeys to impregnate despite repeated exposures to cycling females appeared to be due to abnormal alterations in the kinetics of germ cell transformations and deficient spermiogenesis. Here we investigated the stability of sperm chromatin in oFSH-immunized monkeys as a marker for spermiogenesis. The susceptibility of spermatozoa to in vitro decondensation induced by dithiothreitol (DTT, 0.05-50 mM) was studied by measuring the nuclear fluorescence of DTT-treated, ethidium bromide (EB)-stained sperm using flow cytometry. Changes in sperm morphology and binding of thiol-specific C-14-iodoacetamide (C-14-IA) were also monitored under the same conditions. Sperm from the immunized monkeys decondensed at a lower concentration of DTT, bound more EB, and decondensed more extensively than those from control animals. The difference was apparent in sperm from all regions of the epididymis. Immunized monkey sperm also bound significantly more C-14-IA at all concentrations of DTT. Overall, the effective concentration of DTT required to elicit 50% of maximal decondensation (ED50) of epididymal and ejaculated sperm was significantly lower for the immunized monkeys than even the caput sperm of controls. These results suggest that FSH deprivation in monkeys results in production of sperm with limited potential for disulfide formation and reduced chromatin stability.

Alterations in sperm characteristics of follicle-stimulating hormone (FSH)-immunized men are similar to those of FSH-deprived infertile male bonnet monkeys.

Abstract: The quality of sperm ejaculated by bonnet monkeys and normal, healthy proven fertile volunteer men, both actively immunized with ovine follicle-stimulating hormone (oFSH), was examined at different times of study for chromatin packaging and acrosomal glycoprotein concentration by flow cytometry. Susceptibility of sperm nuclear DNA to dithiothreitol (DTT)-induced decondensation, as measured by ethidium bromide binding, was markedly high compared with values at day 0 in men and monkeys during periods when FSH antibody titer was high. Sperm chromatin structure assay yields alphat values, which is another index of chromatin packaging. Higher alphat values, signifying poor packaging, occurred in both species following immunization with heterologous pituitary FSH. The binding of fluorosceinated pisum sativum agglutinin (PSA-FITC) to acrosome of sperm of monkeys and men was significantly low, compared with values at day 0 (control) during periods when cross-reactive FSH antibody titer was high and endogenous FSH was not detectable. Blockade of FSH function in monkeys by active immunization with a recombinant oFSH receptor protein corresponding to a naturally occurring messenger RNA (mRNA) also resulted in production of sperm with similar defects in chromatin packaging and reduced acrosomal glycoprotein concentration. Thus, it appears that in monkeys and men, lack of FSH signaling results in production of sperm that exhibit defective chromatin packaging and reduction in acrosomal glycoprotein content. These characteristics are similar to that exhibited by sperm of some class of infertile men. Interestingly, these alterations in sperm quality occur well ahead of decreased sperm counts in the ejaculate.

Growth and reproductive parameters of bonnet monkey (Macaca radiata)

Abstract: The present paper summarizes some of the important biological and physiological data recorded over a 30-year period on the biology of bonnet monkeys in captivity. Data on sexual maturity, menstrual cyclicity, general behaviour, endocrine profile, reproductive physiology, gestation, parturition, postpartum amenorrhoea in the female, and sexual maturity, hormone profile, and seasonal variation in sperm count of the male monkeys are presented. In addition to the biological values, weights of selected organs, vertebral and dental pattern are also presented. Menarche occurred at an age of 36±4 months and the first conception in the colony occurred at an age of 54±4 months. The average menstrual cycle length was 28±4.3 days. Majority of monkeys did not cycle regularly during March–June during which the temperature reached a peak. The pregnancy index of the colony was 80% with controlled breeding. The gestation period was 166±5 days with 6–7 months postpartum amenorrhoea. Males attained sexual maturity by the age of 6–7 years and exhibited the characteristic nocturnal surge of serum testosterone at this age and sperm concentration ranged from 116–799 millions/ejaculate.

Mechanisms of implantation: strategies for successful pregnancy

Abstract: Physiological and molecular processes initiated during implantation for pregnancy success are complex but highly organized. This review primarily highlights adverse ripple effects arising from defects during the peri-implantation period that perpetuate throughout pregnancy. These defects are reflected in aberrations in embryo spacing, decidualization, placentation and intrauterine embryonic growth, manifesting in preeclampsia, miscarriages and/or preterm birth. Understanding molecular signaling networks that coordinate strategies for successful implantation and decidualization may lead to approaches to improve the outcome of natural pregnancy and pregnancy conceived from in vitro fertilization.

Estrogen and spermatogenesis.

Abstract: Although it has been known for many years that estrogen administration has deleterious effects on male fertility, data from transgenic mice deficient in estrogen receptors or aromatase point to an essential physiological role for estrogen in male fertility. This review summarizes the current knowledge on the localization of estrogen receptors and aromatase in the testis in an effort to understand the likely sites of estrogen action. The review also discusses the many studies that have used models employing the administration of estrogenic substances to show that male fertility is responsive to estrogen, thus providing a mechanism by which inappropriate exposure to estrogenic substances may cause adverse effects on spermatogenesis and male fertility. The reproductive phenotypes of mice deficient in estrogen receptors alpha and/or beta and aromatase are also compared to evaluate the physiological role of estrogen in male fertility. The review focuses on the effects of estrogen administration or deprivation, primarily in rodents, on the hypothalamo-pituitary-testis axis, testicular function (including Leydig cell, Sertoli cell, and germ cell development and function), and in the development and function of the efferent ductules and epididymis. The requirement for estrogen in normal male sexual behavior is also reviewed, along with the somewhat limited data on the fertility of men who lack either the capacity to produce or respond to estrogen. This review highlights the ability of exogenous estrogen exposure to perturb spermatogenesis and male fertility, as well as the emerging physiological role of estrogens in male fertility, suggesting that, in this local context, estrogenic substances should also be considered "male hormones."

Impairment of spermatogenesis in mice lacking a functional aromatase (cyp 19) gene

Abstract: It is well established that spermatogenesis is controlled by gonadotrophins and testosterone. However, a role for estrogens in male reproduction recently was suggested in adult mice deficient in estrogen receptor α. These mice became infertile primarily because of an interruption of fluid reabsorption by the efferent ductules of the epididymis, thus leading to a disruption of the seminiferous epithelium [Hess, R. A., Bunick, D., Lee, K. H., Bahr, J., Taylor, J. A., Korach, K. S., and Lubahn, D. B. (1997) Nature (London) 390, 509–512]. Despite the demonstration of the aromatase enzyme, which converts androgens to estrogens, and estrogen receptors within the rodent seminiferous epithelium, the role of aromatase and estrogen in germ cell development is unknown. We have investigated spermatogenesis in mice that lack aromatase because of the targeted disruption of the cyp19 gene (ArKO). Male mice deficient in aromatase were initially fertile but developed progressive infertility, until their ability to sire pups was severely impaired. The mice deficient in aromatase developed disruptions to spermatogenesis between 4.5 months and 1 year, despite no decreases in gonadotrophins or androgens. Spermatogenesis primarily was arrested at early spermiogenic stages, as characterized by an increase in apoptosis and the appearance of multinucleated cells, and there was a significant reduction in round and elongated spermatids, but no changes in Sertoli cells and earlier germ cells. In addition, Leydig cell hyperplasia/hypertrophy was evident, presumably as a consequence of increased circulating luteinizing hormone. Our findings indicate that local expression of aromatase is essential for spermatogenesis and provide evidence for a direct action of estrogen on male germ cell development and thus fertility.

Fertility Preservation in Breast Cancer Patients: A Prospective Controlled Comparison of Ovarian Stimulation With Tamoxifen and Letrozole for Embryo Cryopreservation

Abstract: Purpose To develop safe ovarian stimulation methods to perform in vitro fertilization (IVF) in breast cancer patients who wish to preserve their fertility via embryo cryopreservation before chemotherapy. Patients and Methods Sixty women (age range, 24 to 43 years) with breast cancer were prospectively studied. Twenty-nine patients underwent 33 ovarian stimulation cycles with either tamoxifen 60 mg/d alone (Tam-IVF) or in combination with low-dose follicle-stimulating hormone (TamFSH-IVF) or letrozole 5 mg in combination with FSH (Letrozole-IVF). After IVF, all resultant embryos were cryopreserved to preserve fertility. Recurrence rates were compared with controls (n 31) who elected not to undergo IVF. Results Compared with Tam-IVF, both TamFSH-IVF and Letrozole-IVF patients had greater numbers of follicles (2 0.3 v 6 1 and 7.8 0.9, respectively; P .0001), mature oocytes (1.5 0.3 v 5.1 1.1 and 8.5 1.6, respectively; P .001), and embryos (1.3 0.2 v 3.8 0.8 and 5.3 0.8, respectively; P .001). Peak estradiol (E2) levels were lower with Letrozole-IVF and Tam-IVF compared with TamFSH-IVF. After 554 31 days (range, 153 to 1,441 days) of follow-up, cancer recurrence rate was similar between IVF and control patients (three of 29 v three of 31 patients, respectively; hazard ratio, 1.5; 95% CI, 0.29 to 7.4), and this estimate was not affected by cancer stage. Conclusion The combination of low-dose FSH with tamoxifen (TamFSH-IVF) or letrozole (Letrozole-IVF) results in higher embryo yield compared with Tam-IVF. Recurrence rates do not seem to be increased, but the letrozole protocol may be preferred because it results in lower peak E2 levels.