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Biomedical subjects

F J Rojas

Publications and source records attributed to F J Rojas.

16 recordsLinked to original sources
PubMed1992

Failed oocyte retrieval after lack of human chorionic gonadotropin administration in assisted reproductive technology.

OBJECTIVE: To document the absence of oocytes in follicular aspirates in women who, during controlled ovarian stimulation with gonadotropin-releasing hormone agonist (GnRH-a) and menotropins, fail to receive human chorionic gonadotropin (hCG) administration. DESIGN: Retrospective analysis of clinical laboratory data. SETTING: Multicentric. PATIENTS: Five women undergoing controlled ovarian hyperstimulation with GnRH-a and menotropins for programs of assisted reproductive technologies. RESULTS: The documented absence of an hCG injection produced "empty follicles" at transvaginal guided aspiration, despite numerous follicular lavages and aspiration of peritoneal fluid. The lack of oocytes and granulosa-cumulus complex in the follicular fluid was reverted in other cycles in the same patients when hCG was properly administered. CONCLUSIONS: (1) This study emphasizes the importance of proper patients' and nurses' instructions for preparation of hCG injections and proper mixture of vehicle and powder before follicular aspiration. (2) In the absence of cumulus-corona-oocyte complex at aspiration, measure serum beta-hCG to ascertain whether hCG injection was administered or not. (3) Routine preoperative beta-hCG levels may be helpful to avoid unnecessary surgeries.

Adult↗
PubMed1992

Penetration of zona-free hamster oocytes using human sperm aspirated from the epididymis of men with congenital absence of the vas deferens: comparison with human in vitro fertilization.

OBJECTIVES: To assess the ability of sperm aspirated from the epididymis of men with congenital absence of the vas deferens to penetrate zona-free hamster oocytes. To directly compare the performance of human epididymal sperm in the zona-free hamster oocyte sperm penetration assay (SPA) with the results of human in vitro fertilization (IVF). DESIGN: Sperm penetration assay was carried out with epididymal sperm retrieved microsurgically, and with ejaculated sperm obtained from fertile donors (internal controls). For direct comparison, SPA was performed with the same epididymal sperm sample used for IVF. PATIENTS, PARTICIPANTS: Men with congenital absence of the vas deferens undergoing sperm aspiration as part of their infertility treatment and control donors who provided ejaculated sperm. RESULTS: Epididymal sperm penetrated SPA with a score of 0% to 30%. The SPA scores for internal controls using ejaculated sperm was 30% to 71%. Linear regression analysis of the association between penetration scores in SPA and fertilization rate in IVF indicated a positive correlation that was highly significative. CONCLUSIONS: These findings using SPA confirm previous reports on the fertilizing potential of human epididymal sperm and its ability to produce normal pregnancies. The good correlation between SPA and human IVF using epididymal sperm suggest that SPA is an excellent bioassay to test laboratory experimental conditions for improving fertilizing capacity of human epididymal sperm.

Adult↗
PubMed1992

Regulation of cyclic adenosine monophosphate synthesis in human ejaculated spermatozoa. I. Experimental conditions to quantitate membrane-bound adenylyl cyclase activity.

Although cyclic adenosine monophosphate (cAMP) is an important regulator of motility and metabolism in human spermatozoa, little is known on the cellular system responsible for its synthesis. Here, we investigated the experimental conditions directly to quantitate adenylyl cyclase (AC) activity synthesizing cAMP in human ejaculated spermatozoa and analysed the general properties of the enzyme. A 10,000 g membrane fraction was prepared from washed sperm cells homogenized by sonication. AC activity was monitored by the direct conversion of [alpha-32P]adenosine triphosphate (ATP) into [32P]cAMP. Using a nucleoside triphosphate regenerating system to ensure availability of ATP substrate, the human sperm AC showed a steady production of cAMP for at least 1 h. The assay was optimized for pH, buffer concentration, membrane protein and substrate concentration. Activity was dependent upon the presence of Mn2+ as a divalent cation and showed a pH optimum between 7.0 and 8.5. Optimal activity required 5 mM ATP, 1 mM ethylenediamine tetraacetic acid (EDTA) and 20-40 mM total MnCl2. Dependence on Mn2+ was not mandatory; Mg2+ at 5-40 mM also supported significant activity, but the activity was 4-6 times lower than that with Mn2+. Regardless of the presence of Mn2+ or Mg2+ as divalent cation in the assay, human sperm AC was insensitive to the regulatory ligands NaF, guanine nucleotide or forskolin. Insensitivity to these ligands supports the proposal that this enzyme system does not contain a stimulatory guanine nucleotide-binding regulatory protein and that its catalytic component is unique and different from that of somatic cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗
PubMed1992

Regulation of cyclic adenosine monophosphate synthesis in human ejaculated spermatozoa. II. The role of calcium and bicarbonate ions on the activation of adenylyl cyclase.

In this study, we have applied our previous data describing the experimental conditions necessary for expression of cyclic adenosine monophosphate (cAMP)-synthesizing adenylyl cyclase in human ejaculated spermatozoa, to investigate the direct effects of calcium (Ca2+) and bicarbonate (HCO3-) upon activation of the enzyme in vitro. We report that the effects of Ca2+ and HCO3- were significantly dependent on the status of the enzyme activity. Thus, at a near saturating (10 mM) concentration of MnCl2 giving high enzyme activity, addition of less than 10 mM HCO3- did not affect adenylyl cyclase activity and higher concentrations inhibited the enzyme, with 50 mM HCO3- reducing the activity by 33%. Also, addition of less than 20 mM CaCl2 alone or in combination with 10 mM HCO3- did not significantly change the enzyme activity. In great contrast, enzyme activation was highly responsive to Ca2+ and HCO3- when MnCl2 was present at a concentration giving submaximal enzyme activity. Thus, at 2 mM MnCl2, adenylyl cyclase was markedly increased by CaCl2 concentrations between 10 and 100 mM. The activation was further enhanced by increasing concentrations of HCO3-, with 50 mM HCO3- giving the highest activity at 50-100 mM CaCl2. Activation by CaCl2 was also observed in the absence of added MnCl2, being significantly greater than basal activity at 10 mM CaCl2 and maximal at 100 mM CaCl2.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenylyl Cyclases↗
PubMed1991

The role of the adenylyl cyclase system in the regulation of corpus luteum function in the human and in nonhuman primates.

We have reviewed the properties of luteinizing hormone/human chorionic gonadotropic (LH/hCG)-sensitive adenylyl cyclase (AC) of human corpus luteum (CL) and its regulation by several hormones and nonhormonal activators. We have also described the changes in enzyme activity in membrane preparations of human and cynomolgus monkey CL obtained at various stages of the menstrual cycle and pregnancy. The data have been analyzed with respect to the functional status of the luteal tissue and to the species differences among primate CL. In the menstrual cycle, luteal AC responsiveness to LH/hCG was detectable during the midluteal phase, but not during the late luteal phase or in the follicular phase of the following cycle. In addition, nonhormonal stimulation was high in CL obtained during the midluteal and late luteal phases, but declined drastically by the follicular phase of the next cycle. In early pregnancy, the enzyme was unresponsive to LH/hCG stimulation, yet its sensitivity to nonhormonal stimulation was similar, if not identical, to that of midluteal phase CL. Functional activity was also evident at the end of pregnancy. These results demonstrate that expression of AC activity in primate luteal membrane changes significantly with varying hormonal status under physiologic conditions. It is concluded that the AC system in luteal membranes is an effective model to study the mechanisms that regulate function and life span of the human and nonhuman primate CL.

Adenylyl Cyclases↗
PubMed1991

Mycoflora and toxigenic Aspergillus flavus in Spanish dry-cured ham.

Sixty-five dry-salted hams were analysed. Aspergillus and Penicillium were the dominant genera. In general, the mould flora was dominated by Aspergillus spp. and primarily A. glaucus, A. fumigatus, A. niger and A. flavus. A flavus was found in 16 hams and 9 out of 16 strains examined produced aflatoxins 'in vitro'. Surface samples of dry-salted hams showed growth of inoculated A. parasiticus NRRL-2999 strains and production of aflatoxins in low levels at 25 and 30 degrees C. It is concluded that the presence of toxigenic strains in Spanish dry-salted ham does not constitute a health risk.

Aflatoxins↗
PubMed1991

The effect of bromocriptine on the motility of human spermatozoa and its capacity to penetrate the cervical mucus.

We investigated the direct effects of bromocriptine on the motility of the human ejaculated spermatozoa and its capacity to penetrate the cervical mucus (CM) in vitro. Washed sperm were incubated with a wide range of bromocriptine concentrations (0.005 to 5 mM). Progressive and total motility was evaluated after 15, 30, 60, and 180 minutes. No reduction of motility was observed at any concentration tested. Similar results were observed with semen samples. Failure to alter sperm motility was evident in samples with either good or reduced motility. Also, CM penetration as measured after 90 minutes by Penetrak assay (Serono Diagnostics, Randolph, MA) was not impaired by a concentration as high as 5 mM bromocriptine. We conclude that bromocriptine in a wide range of concentrations does not inhibit sperm motility nor does it impair the capability of the sperm to penetrate the CM. These data support the therapeutic use of daily vaginal bromocriptine for the treatment of infertility.

Animals↗
PubMed1990

Intrauterine inseminations with washed human spermatozoa does not induce formation of antisperm antibodies.

In this study we investigated the possible development of serum antisperm antibodies in women receiving repeated IUI. Patients acted as its own control and were evaluated before and after various (1 to 15) IUI cycles using three different assays for antisperm antibodies. It was found that only 2 out of 41 women developed antisperm antibodies. We concluded that exposure of the upper reproductive tract to washed spermatozoa during repeated IUI with partners' sperm does not significantly stimulate the appearance of serum antisperm antibodies.

Antibodies↗
PubMed1990

Insulin-like growth factors and thecal-granulosa-cell function.

Insulin-like growth factors (IGFs) belong to a family of low mol. wt, single chain polypeptides inducing growth promotion and insulin-like metabolism effects and regulating both cell replication and differentiation. Recent studies in laboratory animals suggest that IGFs play an important role as intraovarian regulators in several mammalian species. The purpose of this article was to review current concepts of interactions between the IGFs and the thecal-granulosa-cell function. To provide a basic understanding of these interactions, we have first analysed data concerning biosynthesis, biochemical structure, pharmacokinetics, degradation, binding proteins and receptors for IGFs. Then we have discussed the specific interactions between IGFs and theca-granulosa-cell regulation, and analysed the significance of the relationship to the pathophysiology of some endocrine and reproductive disorders, including hyperandrogenism and female infertility.

Androgens↗
PubMed1989

Delayed occurrence of an LH surge after HCG administration during ovarian stimulation with gonadotrophins: effect of LHRH treatment.

Previous studies have shown the appearance of a spontaneous luteinizing hormone (LH) surge after human chorionic gonadotrophin (HCG) administration in human menopausal gonadotrophin (HMG)/HCG-stimulated menstrual cycles. In this report we investigated the effect of leuprolide acetate, a long-acting luteinizing hormone releasing hormone (LHRH) agonist, on the occurrence of these post-HCG rises in serum LH. Two groups of patients were included. Group 1: 10 patients receiving HCG as a part of an HMG/HCG protocol for induction of follicular development in an IVF/GIFT program and Group II: 10 patients treated as Group I, but receiving the LHRH agonist leuprolide acetate to inhibit gonadotrophin secretion prior to and during ovarian stimulation. In Group I, none of the patients showed a surge prior to HCG administration. However, an LH surge following HCG treatment was apparent in four patients (40%). Pregnant patients (2/10) had low mean levels (less than or equal to 2.5 mIU/ml LH) in the follicular phase and showed no LH surge after HCG. In Group II, baseline levels of serum LH were reduced significantly (mean, 1.4 +/- 0.1 mIU/ml; P less than 0.001) compared to Group I. No patient showed an LH surge either before or after HCG administration and the occurrence of pregnancy was higher (6/9 transfers) than in Group I. In spite of the differences in pregnancy rates, the combined therapy versus HMG therapy showed no significant difference in number of oocytes collected or serum oestradiol levels. This suggests that high levels of serum LH, whether prior to or after HCG administration, may have a detrimental effect on the establishment of pregnancy despite adequate follicular growth.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1979

Gonadal receptors. II. Effects of time and reaction volume upon the binding of human chorionic gonadotropin and human luteinizing hormone to particulate receptors.

The effect of reaction volume upon the binding of gonadotropins by particulate receptors was studied. Two experimental approaches were used: one involved increasing the reaction volume of the binding assay (i.e. diluting the hormone and receptor concentrations and will be referred to as buffer coincubation studies) and the other involved incubating the testicular homogenate in various buffer volumes prior to the binding assay (buffer preincubation stidies). The results showed that the number of hormone binding sites inferred from Scatchard analysis was inversely related to the reaction volume in the coincubation as well as in the preincubation studies. Time-dependent dissociation of receptors from the intact testis was demonstrated by perifusion studies and the loss of receptors from intact testis correlated with the appearance of soluble factors (Bhalla, V.K., Haskell, J., Grier, H. and Mahesh, V.B. (1976) J. Biol. Chem. 251, 4947--4957) in the eluate obtained. The results obtained along with those presented in the preceding manuscript (Chen, C.J.H., Lindeman, J.G., Trowbridge, C.G. and Bhalla, V.K. (1979) Biochim. Biophys. Acta 284, 407--435) question the validity of the rapid equilibrium model which assumes reversible hormone occupancy of a fixed number of receptor sites. An alternate binding model is proposed herein and its implications are discussed.

Animals↗
PubMedDate not supplied

Performance and sensitivity of modern home pregnancy tests.

We have studied the performance of three currently available home pregnancy tests. The Advance is a test based on monoclonal antibodies in an enzyme immunoassay format that specifically detects hCG in urine. The positive results are determined by the presence of a blue color in a color stick (30 minutes). The Daisy 2 and FACT are tests based on monoclonal antibodies that specifically detect hCG in urine in a hemagglutination inhibition assay; positive results are demonstrated by the deposition of a dot ring at the bottom of the test tube (45 minutes). Thirty-five patients who eventually became pregnant in that cycle collected the first morning urine specimens from day of ovulation (determined by ultrasound) in artificial insemination donor (AID) cycles, or from the date of gamete intrafallopian transfer (GIFT) for 16 consecutive days. In each specimen, the Advance, Daisy 2, and FACT tests were performed; in addition, beta-hCG levels were determined by radioimmunoassay. All the home pregnancy tests studied can detect pregnancy as early as 9 or 10 days post-conception, and they give positive results at the time of the expected onset of menses in 70%, 95%, and 88% of cases for Daisy 2, Advance, and FACT, respectively. The sensitivity of the these home pregnancy tests was determined to be about 200 mIU/mL of urine after correlating their positive or negative results with the concentrations of urinary beta-hCG determined by radioimmunoassay.

Antibodies, Monoclonal↗