PubMed Health⌕ Search

Biomedical subjects

S J Segal

Publications and source records attributed to S J Segal.

At least 19 recordsLinked to original sources
PubMed1991

Norplant implants: the mechanism of contraceptive action.

OBJECTIVE: To determine if fertilization occurs unnoticed among Norplant users who are ovulatory. DESIGN: Serial blood samples were obtained during 1 month from sexually active Norplant users experiencing regular menstrual bleeding patterns and a control group of noncontracepting women trying to conceive. The sequential blood samples were assayed for the presence of human chorionic gonadotropin (hCG). SETTING: All samples were obtained from women receiving contraceptive service and health care at the Center for Research and Services in Human Reproduction and Contraception, Santo Domingo, The Dominican Republic. Assays for hCG were performed at the Department of Biomedical Sciences, University of Tampere, Finland. PATIENTS, PARTICIPANTS: A total of 32 women using Norplant implants were enrolled in the treatment group, and 20 women of proven fertility who were attempting to conceive served as a control group. INTERVENTIONS: Duration of Norplant use was as follows: 4 in the 2nd year of use, 13 in the 3rd year, 11 in the 4th year, 3 in the 5th year, and 1 in the 7th year. MAIN OUTCOME MEASURE: The determination of pregnancy was based on the presence of hCG in the luteal phase, using a sensitive and specific immunoenzymatic assay that can detect dimeric hCG as early as 7 days after ovulation. RESULTS: Nine pregnancies were detected. All were in the control group trying to conceive. Six of these advanced to clinical pregnancies, and three did not proceed beyond the next expected menses. None of the Norplant users had evidence of hCG production, whether the observed cycles were anovulatory or ovulatory. The probability of finding no pregnancies in the ovulatory months at risk among Norplant users is between 1 in 50 and 1 in 150,000. The null hypothesis that Norplant users conceive at a natural rate can be rejected at the 0.05 level. CONCLUSION: Interruption of early pregnancy (menstrual abortion) does not play a role in the mechanism of action of Norplant contraceptive implants.

Chorionic Gonadotropin↗
PubMed1989

Inactivation of human immunodeficiency virus in vitro by gossypol.

Gossypol, a polyphenolic aldehyde extracted from cottonseed, is a male anti-fertility agent which has been reported to have anti-viral activity. In this paper we report that gossypol inactivates human immunodeficiency virus (HIV) in an in vitro system. Following exposure of cell-free incubates of HIV to 100 uM gossypol, ultracentrifugation and inoculation of the washed pellet onto H9 cells, there is no evidence of elevated reverse transcriptase activity over 21 days. Treatment with lower concentrations of gossypol reduces the peak and lengthens the time to maximal reverse transcriptase activity compared with control cultures. These observations suggest that gossypol could be used as a vaginal spermicidal/virucidal agent. The mechanism of the in vitro anti-viral action as well as the effect of orally administered gossypol on the infectivity of semen of HIV-seropositive men warrant further study.

Cell Line↗
PubMed1989

Carbohydrate moieties of small placental hCG: requirement of mannose structure for biological activity.

The 43 kDa human chorionic gonadotropin (hCG) (SP-hCG) was purified from human placenta and analyzed for sugar moieties. The low hexosamine content suggests that SP-hCG probably lacks O-linked sugar chains in the beta-subunit and incompletely formed N-linked sugar chains in the alpha- and beta-subunits. In the present study SP-hCG was hydrolyzed with various glycosidases. Treatment of hCG or SP-hCG with O-glycan peptide hydrolase increased the mobility of asialo-hCG beta in reduced sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) while that of SP-hCG beta was unaffected, indicating that SP-hCG beta does not contain NeuNAc-Gal-GalNAc unit. Alpha-Mannosidase and endoglycosidase H hydrolyzed mannose and the high mannose-GlcNAc moieties, respectively, from alpha- and beta-subunits of SP-hCG, but not from the subunits of authentic hCG. Glycopeptidase F hydrolyzed completely the N-linked sugar chains from SP-hCG subunits, producing alpha- and beta-subunits with estimated Mr of 15,000 and 18,500, respectively. The biological activity of purified SP-hCG is about 50-80% of highly purified authentic hCG. In an in vitro system SP-hCG increased cAMP accumulation and testosterone production by rat Leydig cells to the same levels as that induced by hCG. However, the biological activity of SP-hCG was markedly reduced, following treatment with endoglycosidase H or alpha-mannosidase. To attain the level of testosterone production equivalent to that induced with untreated SP-hCG, 10-20 times higher dose of treated SP-hCG was required. On the other hand, cAMP accumulation induced with treated SP-hCG even at a very high concentration was substantially lower than that attained with untreated SP-hCG. In conclusion, the mannose moieties are essential structural components of the hormone in stimulating cAMP accumulation and steroidogenesis by rat Leydig cells.

Animals↗
PubMed1988

Interaction of gossypol with sperm macromolecules and enzymes.

The interaction of gossypol with sperm macromolecules is an important process for the gossypol action. It is of our interests to study the nature of this interaction in order to understand the mechanism of action of gossypol. Our experimental results support the thesis that gossypol inhibits sperm motility by blocking ATP production and utilization. The drug acts on the mitochondria, suppressing oxygen consumption, inhibiting pyruvate dehydrogenase and ATPase activities and probably on the motility apparatus by blocking dynein ATPase activity and preventing protein phosphorylation. The nature of the chemical bond in the interaction of gossypol and macromolecules is through the Schiff base formation and by the hydrophobic and nucleophilic attraction.

Adenosine Triphosphatases↗
PubMed1988

Purification and characterization of an incompletely glycosylated form of human chorionic gonadotropin from human placenta.

A small form of hCG (SP-hCG) was purified from an acetone powder preparation of human first trimester placenta by repeated gel filtration and ion exchange chromatography on a Q-Sepharose or FPLC Mono Q column. The estimated mol wt (Mr) of the small hCG by gel filtration is 43K compared to 58K for authentic hCG. The pI of SP-hCG is 10.0, suggesting deficiency of sialic acids. SP-hCG dissociates into subunits when treated with 6 M guanidine-HCl or analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Two beta-subunits of SP-hCG were found with estimated Mr of 23K and 20K. Both are distinctly smaller than authentic hCG beta. A single alpha-subunit was found, with an estimated Mr of 21 K. The immunoactivity (8,900-10,000 IU/mg) of highly purified SP-hCG was comparable to that of reference hCG (CR119) determined by a RIA method using anti-hCG antibodies. The hCG/LH receptor-binding activity of SP-hCG is equivalent to that of reference hCG (CR119). Its biological activity is lower than that of reference hCG (approximately 30% or more) assayed by the in vitro stimulation of rat Leydig cells to produce testosterone and cAMP. A high dose is required to attain the same level of stimulation as reference hCG. The amino acid composition of SP-hCG is similar to that of reference hCG, whereas its hexsamine content is significantly lower. Its glucosamine content is about half that in reference hCG, while it completely lacks galactosamine. These findings suggest that SP-hCG is deficient in O-linked oligosaccharide chain in the beta-subunit, and that the N-linked oligosaccharide chains of both subunits are shortened. SP-hCG is one of the principal forms of the hormone present in first trimester placenta and may be a key intermediate in the posttranslational biosynthesis of hCG. Although it lacks O-linked sugar chains and shortened N-linked sugar chains, it possesses substantial biological activity. To have full biological activity, the hCG molecule must contain the complete complement of sugar chains.

Amino Acids↗
PubMed1985

Absence of chorionic gonadotropin in sera of women who use intrauterine devices.

A controlled study was undertaken to determine whether unnoticed pregnancies routinely occur in users of the intrauterine contraceptive device (IUD). Starting on day 10 of the menstrual cycle and continuing through the onset of menstruation or until the diagnosis of pregnancy, we collected daily blood samples from three groups of normally menstruating young women. The study groups were (A) IUD users (n = 30), (B) women with tubal ligation (n = 30), and (C) women trying to become pregnant (n = 15). The sequential serum samples were analyzed by radioimmunoassay for progesterone (P), human luteinizing hormone (hLH), and human chorionic gonadotropin (hCG). No positive hCG assays in luteal phase blood sera of IUD users were observed. The only positive hCG determinations of IUD users coincided with the preovulatory surge of hLH. Two subjects who became pregnant, as judged by progressive increases in hCG and P levels in the luteal phase, belonged to the group planning pregnancy. The finding of two pregnancies in 15 months of exposure is consistent with the assumption of natural fertility. The probability of no pregnancies in 30 months at risk, as observed among the IUD users, is between 1 in 200 and 1 in 100,000, depending on the assumption made for natural fertility. The study demonstrates that IUD users do not retain their natural fertility, and that IUDs do not exert their antifertility effect as abortifacient agents. If a confirmed pregnancy is detected in an IUD user, it may be assumed to represent an isolated case of contraceptive failure.

Adult↗
PubMed1984

Apparent chorionic gonadotropin immunoreactivity in human non-placental tissues: reduction by protease inhibitors or heat treatment.

Thirty-three of forty-one non-placental human tissue samples analysed by radioimmunoassay (RIA) appeared to contain immunoreactive hCG-like material. Tissues with apparent hCG in appreciable quantity were exposed to heat or protease inhibitors to ascertain the contribution of proteolytic enzyme activity to the observed immunoreactivity. Following incubation with protease inhibitor N-alpha-p-tosyl-L-lysine chloromethyl ketone-HCl (TLCK) at a dose that has no effect on the hCG standard curve and reduces the assayable hCG in term placenta by less than 20%, the hCG-like immunoreactivity of testicular and colon tissues was reduced by 39 to 90%. Similarly, heat treatment virtually eliminated hCG-like immunoreactivity of non-placental normal tissues, but had little effect on purified hCG or hCG present in term placenta. The factor present in normal non-placental human tissue giving positive results in the RIA for hCG is not identical to native hCG; it may be proteolytic in nature thus influencing the radioligand assay. The residual immunoreactivity measured following heat treatment of purified hCG increases when anti hCG-beta antiserum is used, but decreases when either anti hCG-alpha or anti-hCG is used.

Chorionic Gonadotropin↗
PubMed1984

Serum prolactin profiles of normal human conceptual cycles.

Commencing on day 10 of the menstrual cycle through onset of subsequent menses, or confirmation of pregnancy, daily sera collected from 15 women planning pregnancy were analyzed by radioimmunoassays (RIA) for prolactin (hPRL), estradiol-17 beta and luteinizing hormone (hLH). Two of the observed subjects became pregnant in the single cycles studied. The profiles of these hormones during the early gestation following spontaneous ovulation were established. No distinct midcycle peaks of hPRL were observed in either subject. Enormous spikes were observed in daily prolactin values, with wide variations between subjects.

Adolescent↗
PubMed1984

Daily serum choriogonadotropin concentrations in early human gestation.

Fifteen regularly menstruating, healthy women were studied from day 10 of the menstrual cycle to either confirmation of pregnancy or spontaneous menses. Daily blood samples were obtained and serum luteinizing hormone (LH), human chorionic gonadotropin hormone (hCG), 17 beta-estradiol and progesterone were determined by means of specific radioimmunoassay (RIA). Two of the women experienced spontaneous conception with a rise in hCG on 12 and 13 days after LH peak.

Adolescent↗
PubMed1984

Antispermatogenic action of gossypol in men.

Twelve Brazilian men were treated with gossypol for 1 year. The treatment schedule consisted of oral administration of 20 mg gossypol daily for 4 months, followed by a maintenance dose of 20 mg on alternate days (3 days a week), totaling 60 mg weekly for 8 months. Ten men became azoospermic at the end of the fourth month of treatment, and the two others developed marked oligospermia with necrospermia. Except for one man who complained of transient listlessness and fatigue, the subjects reported no side effects during treatment. No changes in libido or potency were reported, and plasma testosterone remained unchanged. Blood chemistry values, which included complete blood cell count, cholesterol, glucose, triglycerides, acid phosphatase, urea, transaminases, sodium, and potassium, were not changed significantly during treatment. The response of the pituitary to gonadotropin-releasing hormone stimulation and the response of the testis to gonadotropin stimulation appeared normal in men treated with gossypol. After treatment, the sperm counts reverted to essentially normal levels in 8 of 12 men. In four men, azoospermia continued 1 year after discontinuation of gossypol treatment. Retrograde phlebography carried out in three of the four men who remained azoospermic after discontinuation of therapy revealed subclinical varicocele.

Adult↗
PubMed1982

Comparative prolactin profiles in IUD users and non-IUD users.

Starting from the 10th day of the menstrual cycle through onset of the subsequent menstrual bleeding, daily blood samples were collected from 14 women using Copper T IUDs and 10 normal control women. The serum samples were analysed by radioimmunoassay (RIA) for human prolactin (hPRL) and human luteinizing hormone (hLH). hPRL values were subjected to statistics. Episodic patterns of hPRL were observed for all subjects. IUD users show generally lower daily levels of hPRL than non-IUD users, but the apparent differences were statistically insignificant.

Female↗
PubMed1981

A synthetic peptide capable of eliciting antibodies that neutralize human chorionic gonadotropin.

Antisera generated to the human chorionic gonadotropin beta-subunit (hCGbeta) have been shown not only to neutralize the biologic activity of hCG but also to cross-react with human luteinizing hormone (hLH). In an attempt to reduce such cross-reactivity, a peptide fragment analogous to the amino acid sequence of the carboxylterminal 45 residues (101-145) of the hCGbeta-subunit with alpha-aminobutyric acid substituting for cysteine at position 110 was synthesized and tested for ability to produce antibodies interacting with hCG. Antisera were generated in rabbits to a conjugate of this peptide with tetanus toxoid emulsified with Freund's complete adjuvant. Antibody titers and specificity were assessed by the double-antibody technique. The results show that the antisera to the synthetic hCGbeta fragment bound 125I-labeled hCG and did not cross-react with hLH in the radioimmunoassay system. Most importantly, the antisera effectively neutralized the biologic activity of hCG as determined by the rat uterine weight assay.

Amino Acid Sequence↗
PubMed1980

Perinatal study in Tientsin: 1978.

Clinical records of a total of 3320 singleton births, representing the year 1978, at the two Tientsin Medical College Hospitals, Tientsin, People's Republic of China, were studied to ascertain (a) reproductive parameters such as the average age of the mothers at first and successive births and (b) the relationships between perinatal deaths, prematurity and birth weight and the mothers's age, number of previous pregnancies, parity, maternal conditions in the prenatal and delivery period and operative procedures of delivery.

Adult↗
PubMed1979

Production of choriogonadotropin-like factor by a microorganism.

Extracts from an acetone powder preparation of a culture of a microorganism tentatively named Progenitor cryptocides contain choriogonadotropin (CG)-like factor as determined by radioimmunoassay with antiserum to human (h)CG beta subunit COOH-terminal peptide and radioreceptor assay with bovine corpus luteum membranes. Possible interference by proteases in the extracts was excluded. Immunoreactive materials reacting with antisera to hCG beta subunit and hCG beta subunit COOH-terminal peptide were also found in the extracts. No free alpha subunit was detected. The CG-like factor was purified by chromatography on Sephadex G-100, concanavalin A-Sepharose, and DEAE-Sephadex A-50. The factor was adsorbed by concanavalin A-Sepharose, suggesting that it contains mannose and glucose moieties. The factor was eluted at the same position as standard hCG on Sephadex G-100. It dissociated into two bands when subjected to sodium dodecyl sulfate/polyacrylamide gel electrophoresis; the bands corresponded to the respective standard hCG subunits. The biological activity of the purified factor as determined by the rat uterine weight assay and the ovarian weight assay was equivalent to 380 (95% confidence limits: 320-490) and 880 (780-1020) international units/mg, respectively. It can be concluded from the present results that a microorganism produces a glycoprotein that is biologically active and has physicochemical properties similar to those of hCG.

Bacteria↗