Biomedical subjects

P C Sizonenko

Publications and source records attributed to P C Sizonenko.

At least 73 records · Page 4Linked to original sources

PubMed1985

Hydrophobic interaction chromatography (HIC) for the separation of protein-bound and free steroids. Application to binding protein and receptor assays.

Protein-bound steroids can be separated from free steroids using microcolumns of silica gel coated with an hydrophobic (octadecyl) solid phase. The bound fraction is eluted in the assay buffer, whereas the free fraction is retained quantitatively on the column in the first step and can be recovered in methanol. Both fractions can be quantitated directly (e.g. by liquid scintillation spectrometry when using radioactive ligands) or kept for further analysis (e.g. by TLC, HPLC etc.). Separation of the bound and free fractions is rapid, accurate and reproducible; intra- and inter-assay coefficients of variation are lower than 5 and 10%, respectively. Recovery of radioactive steroids is high (usually over 85%) and can be estimated separately for each sample. Since assay blanks are very low (typically less than 0.1% of input), this new method, which could be termed "hydrophobic interaction chromatography" (HIC), should prove especially useful for the development of sensitive binding assays, particularly in the field of steroid receptors. The HIC method compared well with three methods currently used for steroid binding assays, namely adsorption of unbound steroids on dextran-coated charcoal, gel filtration on Sephadex LH-20 and adsorption of steroid-protein complexes on DEAE-cellulose filters. Examples of application described here include studies on human plasma sex hormone binding globulin (SHBG) and SP2 placental protein (saturation analysis, binding specificity etc.), the separation of antibody-bound steroids in a radioimmunoassay and the estimation of androgen binding to rat epididymal androgen binding protein (rABP). Receptor assays are illustrated by saturation analysis of the mouse uterine oestrogen receptor and of the androgen receptor in the human genital skin.

Androgen-Binding Protein↗

PubMed1985

Inhibitory action of exogenous melatonin, 5-methoxytryptamine, and 6-hydroxymelatonin on sexual maturation of male rats: activity of 5-methoxytryptamine might be due to its conversion to melatonin.

The effect on sexual maturation of 6 different pineal indoles, including melatonin, and of the metabolite 6-hydroxymelatonin was studied in the male rat after daily injections from 20 to 40 days of age. Only 5-methoxytryptamine (5MT) and 6-hydroxymelatonin (6M), in addition to melatonin, inhibited the neuroendocrine-reproductive axis during sexual maturation. Their potencies when injected in the afternoon were in the range of one-twentieth to one-fifth that of melatonin. Like melatonin these two indoles had no effect when injected in the morning. N-acetylserotonin, serotonin, 5-hydroxytryptophol and 5-methoxytryptophol did not influence sexual maturation either when injected in the morning or in the afternoon. Chromatographic separation was performed on plasma extracts from rats injected daily with the biologically active indoles and killed 10-120 min after the last injection. This procedure confirmed that 6M injections did not increase plasma melatonin levels. In contrast, plasma melatonin levels in 5MT-treated rats were increased 1 h after the 5MT injection. These results suggest that 5MT or part of it might be acetylated to melatonin; thus inhibition of sexual maturation might be mainly due to melatonin. These results indirectly support the contention that melatonin is the principal pineal indoleamine playing a role during sexual maturation.

5-Methoxytryptamine↗

PubMed1985

Mating is random.

Human leukocyte antigen (HLA) typing was undertaken in 151 unrelated blood donors and in 35 normal couples having at least two living children. We compared observed and expected sharing of HLA antigens at four loci in normal couples. We also compared the observed sharing in couples with the expected sharing in unrelated blood donors if taken two by two and with the sharing observed after 1000 "synthetic matings" of normal couples. No statistically significant difference in HLA sharing appeared between these groups. Furthermore no differences were observed in the probabilities of sharing individual HLA antigens among the different groups. We thus conclude that the observed HLA sharing in normal couples is governed by chance alone and that mating is random in our population.

Female↗

PubMed1985

Long-term results of GnRH analogue (Buserelin) treatment in girls with central precocious puberty.

The GnRH analogue Buserelin was given for one year to six girls with central precocious puberty in a daily subcutaneous dose of 20 micrograms/kg/day. A decrease of plasma estradiol and vaginal maturation index to prepubertal values was obtained in 5 out of 6 cases. Bone maturation decreased and final predicted adult height improved significantly. This analogue of GnRH appears to be an effective medication for gonadotropin dependent precocious puberty in girls.

Buserelin↗

PubMed1985

Daily administration of melatonin delays rat vaginal opening and disrupts the first estrous cycles: evidence that these effects are synchronized by the onset of light.

The effect of daily melatonin administration was investigated in the immature female rat. Starting on day 15 of age, 100 micrograms melatonin were injected sc at different times of the day in animals housed in 12 h of light, 12 h of darkness or 16 h of light, 8 h of darkness. Melatonin given 9-11 h after the onset of light in both lighting regimens resulted in a 10-day delay of vaginal opening, a dissociation of the relation between vaginal opening and first proestrus, and a disruption of the initial estrous cycles. The same dose of melatonin given at other times during the photoperiod had no effect on sexual maturation. GnRH secretion in melatonin-treated animals was decreased, as judged by 30% lower pituitary GnRH receptor number in animals killed after opening of the vagina. During the diestrous phases, plasma levels of LH, FSH, and 17 beta-estradiol were similar to those in control rats, but during proestrus, the surge of FSH was higher, and the peak of estradiol was higher and of a longer duration. This hormonal pattern suggests a build-up of hormones in secreting cells, which follows the lower incidence of proestrous phases in melatonin-treated rats. This build-up of FSH was indeed present, with higher concentrations in the pituitary during diestrus after melatonin treatment, while pituitaries removed during proestrus had lower contents of FSH. These results confirm that chronic melatonin administration delays sexual maturation of female rat, probably by retarding maturation of hypothalamic GnRH-producing cells. Thus, melatonin could modify basal GnRH secretion or pulsatile release. Pituitary and ovarian responsiveness do not seem to be affected, since proestrous surges of 17 beta-estradiol, LH, and FSH occur, albeit at a reduced frequency. The results also show that there is a window of maximum sensitivity to administration of melatonin 9-11 h after the onset of light, and that this window of sensitivity is synchronized by the onset of light. This raises the possibility that the abnormal presence of endogenous melatonin during this period of the day could induce abnormal sexual development.

Animals↗

PubMed1985

Ontogeny of hypothalamic luteinizing hormone-releasing hormone (GnRH) and pituitary GnRH receptors in fetal and neonatal rats.

Although it is known that LH secretion starts at 17 days of gestation in the fetal rat and that this first LH release is most likely driven by hypothalamic GnRH, an earlier role for GnRH during fetal life has been postulated with the observation that presence of GnRH is important before day 13 of gestation for the differentiation of the pituitary anlage. In order to clarify the different roles of GnRH during fetal life, we have studied the first appearance of GnRH in the fetal brain, the expression of GnRH receptors in the fetal pituitary gland, and the presence of GnRH immunoreactivity within the fetal gonadotrophs. GnRH was present in the earliest brain tissue examined (12 days of gestation). From 12-17 days, GnRH content of fetal brain remained low and then increased markedly by the end of gestation. No immunoreactive GnRH-like material could be detected in rat placental tissue throughout gestation. Binding sites for GnRH were detected as early as 12 days of gestation in fetal pituitary glands. However, binding was very low until 16 days. At 17 days, Scatchard analysis indicated the presence of high affinity, low capacity binding sites [affinity constant (Ka) = 10(10) M-1]. Intracellular presence of GnRH as seen by immunocytochemistry using ultrathin sections prepared by cryoultramicrotomy was first visible at 14 days and started to increase at 16 days. LH was first detectable in the fetal pituitary by RIA at 17 days; FSH was first detectable at 21 days, and PRL at 1 day of postnatal life. Thereafter, neonatal pituitary contents of LH, FSH, and PRL increased linearly with-time, as did the number of pituitary GnRH receptors. At 10 days of postnatal life, pituitary contents of LH and FSH were significantly higher in females than in males. In summary, hypothalamic GnRH appears early in fetal life and potentially can induce differentiation of the pituitary anlage. Conversely, the presence at 15 days of gestation of specific binding sites for GnRH and of intracellular GnRH immunoreactivity in gonadotrophs indicates that the hypophysiotropic action of GnRH clearly precedes the start of LH biosynthesis.

Animals↗

PubMed1985

[Value of the assay of plasma steroids in the control of congenital adrenal hyperplasia].

Twenty patients with congenital adrenal hyperplasia due to 21-hydroxylase deficiency have been followed during a mean period of 68.4 months (from 19 to 120 months). Plasma 17 alpha-hydroxyprogesterone, delta 4-androstenedione and testosterone have been measured at regular intervals and correlated to growth and bone maturation. Satisfactory growth was obtained through repeated changes in the daily dose of oral hydrocortisone which varied from 58.7 +/- 37 mg/m2/day in infants to respectively 19.3 +/- 7.0 and 25.3 +/- 7.2 mg/m2/day in prepuberty and puberty. Fludrocortisone was added in 15 cases because of evidence of salt loss. delta 4-androstenedione and 17 alpha-hydroxyprogesterone are the best markers of adequate suppression of the pituitary-adrenal axis in both sexes. Testosterone can be used in girls and prepubertal boys. In some cases with low levels of androgens suggesting oversuppression, a reduced velocity of bone maturation was observed, particularly in young subjects.

17-alpha-Hydroxyprogesterone↗

PubMed1984

In vitro production of pregnancy-associated plasma protein A by human decidua and trophoblast.

Immunohistochemical techniques and direct measurements of pregnancy-associated plasma protein A (PAPP-A) have demonstrated the presence of PAPP-A in trophoblast and decidua. The purpose of the present study was to investigate the possibility that these tissues are capable of producing PAPP-A in vitro. Trophoblast and decidua were obtained from term deliveries and from legal surgical terminations of pregnancy (7 to 12 weeks). In addition to trophoblast and decidua, myometrium was also obtained during two hysterectomies in the first trimester of pregnancy. Tissues were incubated in medium 199 at 37 degrees C under an oxygen/carbon dioxide atmosphere. Media containing either pregnancy-associated serum or non-pregnancy-associated serum were changed after 8 hours of incubation in medium 199 alone. In addition to PAPP-A, human placental lactogen (hPL) and prolactin (Prl) were measured in homogenates and media by radioimmunoassays in order to confirm the viability of the cultured tissues. Addition of pregnancy-associated serum to the media induced a significant release of PAPP-A from trophoblast and decidua when compared to that in control cultures. Non-pregnancy-associated serum had no effect. Myometrium did not release any measurable PAPP-A into the medium even in the presence of pregnancy-associated serum. Cycloheximide added to pregnancy-associated serum significantly inhibited the release of PAPP-A from trophoblast and decidua. These last tissues, irrespective of the culture condition, released significantly more PAPP-A as well as hPL and Prl than was initially present in the tissue. These data demonstrate that PAPP-A is released in vitro by trophoblast and decidua (but not by myometrium) and that this release can be magnified by a factor present only in pregnancy-associated serum. The release of PAPP-A, hPL, and Prl is considered as a de novo production since concentration of these proteins are higher in media and tissues after incubation compared to concentrations initially present in the tissue before culture and since cycloheximide significantly inhibits the release of PAPP-A, Prl, and hPL from the cultured tissues.

Culture Media↗

PubMed1984

Plasma prolactin and cortisol concentrations in epileptic patients during the night.

Plasma cortisol and prolactin concentrations were determined every four hours, from 8 PM to 8 AM, in 19 epileptic patients during EEG recording of sleep. Data were compared with those obtained from 12 healthy young male volunteers studied under similar conditions. Patients had normal cortisol rhythm, with peak levels at 4 AM or 8 AM and trough at midnight. A sleep-related increase in prolactin concentration was observed in all patients. The range of prolactin concentrations in the patients was also normal. Treatment with valproic acid (ten patients) and frequent abnormal EEG discharges (five patients) did not affect cortisol and prolactin secretion.

Adolescent↗

PubMed1984

The disappearance rate of pregnancy-associated plasma protein-A (PAPP-A) after the end of normal and abnormal pregnancies.

PAPP-A is a macromolecular glycoprotein associated with human pregnancy. In vitro, PAPP-A is produced by explant cultures of trophoblast and decidua. The present work was undertaken to see if the presence of decidua had any effect on the disappearance rate of PAPP-A after removal of the placenta either by surgery or by spontaneous delivery. PAPP-A was measured before and at different times after a normal delivery (n = 6), after a termination of early pregnancy (n = 11) and after surgery for ectopic pregnancy (n = 8). The half life of PAPP-A after normal delivery (52.9 +/- 25.8 h, SD) was significantly (p less than 0.03) less than after a first trimester termination (93.9 +/- 41.6 h). After surgery for ectopic pregnancy in patients with curetted decidua, PAPP-A disappeared significantly faster (p less than 0.005) then in patients with intact decidua (84.1 +/- 17.8 vs 241.2 +/- 81.5 h). These results indicate that PAPP-A continues to be produced by the decidua after removal of the trophoblast in early pregnancy.

Abortion, Legal↗

PubMed1984

Prolactin and the gut: a controversy.

Previous reports suggest that prolactin could be one of the factors controlling intestinal mucosal growth. Therefore plasma levels of prolactin have been measured at the time of jejunal biopsy performed for suspicion of celiac disease. One hundred eighty-seven biopsies from 166 children have been reviewed according to histology, age, diagnosis, and plasma prolactin. No difference in the plasma prolactin could be detected among a group of 117 normal biopsies (9.4 +/- 0.4 ng/ml, mean +/- SEM), 31 biopsies with partial atrophy of various degree (9.0 +/- 0.9 ng/ml), and 39 biopsies with flat mucosa (9.1 +/- 0.7 ng/ml), nor could we demonstrate an increase in prolactin according to age and diagnosis (celiac disease before and after treatment, cow's milk protein intolerance, isolated postenteritic syndrome, selective sugar intolerance, and functional gut problems). Prolactinlike material has been detected by immunoperoxidase in the jejunal mucosa. The intracellular granules are located in the infranuclear portion of isolated epithelial cells mainly in the crypts. This material could not be correlated with the corresponding prolactinemias, whatever the histological appearance of the mucosa. These results would suggest that plasma prolactin is not a marker of jejunal regeneration in children. The nature and function(s) of this prolactinlike material remain to be established.

Adolescent↗

PubMed1984

Pregnancy-associated plasma protein-A (PAPP-A): concentration in uterine fluid and immunohistochemical localization in the endometrium.

Pregnancy-associated plasma protein-A (PAPP-A) was localized immunohistochemically in the endometrium and measured in uterine fluid of non-pregnant women. The variations of PAPP-A concentrations in uterine fluid during the menstrual cycle paralleled those found in the endometrium. In patients receiving hormone therapy there was a significant correlation between the uterine fluid PAPP-A concentration and the progestogen to oestrogen potency ratio of the hormonal treatment. The presence of PAPP-A in the uterine fluid cannot simply be explained by blood contamination or cell damage. These results are interpreted as indirect evidence for an exocrine as well as an endocrine secretion of PAPP-A by the endometrium which might be influenced by hormones.

Adult↗

PubMed1984

Diurnal rhythm of melatonin action on sexual maturation of male rats.

Immature male Wistar rats with a 12:12 h light-dark cycle received daily s.c. melatonin injections of 100 micrograms from 20 to 40 days of age. Melatonin administration during the late photophase (9 h after the onset of light) or during the late scotophase (9 h after the onset of darkness) caused reduced weights of testes and seminal vesicles, lowered plasma levels of testosterone, LH and FSH, and decreased number of pituitary GnRH receptors, a series of observations which reflects delayed sexual maturation at 40 days. In contrast, no effect was observed when melatonin was injected during the early photophase of scotophase (5 h after the onset of light or darkness, respectively). In order to better investigate the night hours, melatonin action was studied in rats that were born and raised with a shifted 12:12 h light-dark cycle. When the light phase was shifted by 5 and 17 h 1 week before the animals were born, sensitivity to melatonin action was unchanged. The responsiveness of the neuroendocrine-reproductive axis to exogenous melatonin was then studied throughout the day-night cycle. The inhibitory influence of melatonin increased gradually during the late photophase and reached a peak just before the onset of darkness. No effect was observed during the first 7 h of the dark phase; however, melatonin injected 9 h after the onset of darkness again had an inhibitory influence equivalent to about 50% of that observed in the late photophase , whereas administration 2 h later remained without effect. These results demonstrate that the time of administration of melatonin within the day-night cycle is critical for melatonin action.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1984

Daily afternoon administration of melatonin does not irreversibly inhibit sexual maturation in the male rat.

Previous studies from our laboratory demonstrated that daily afternoon melatonin injections from 20-40 days of age inhibited sexual development of young male rats, whereas in adult animals, similar injections had no effect. The present study was designed to determine more precisely the critical age period during which melatonin exerts its inhibiting effect and to see whether spontaneous sexual maturation resumes after discontinuation of melatonin administration at 45 days of age or even during continuous administration of melatonin until 115 days of age. Sexual maturation was evaluated using weights of seminal vesicles and testes; plasma levels of testosterone, FSH, and LH; pituitary contents and concentrations of FSH and LH; and, finally, pituitary content of GnRH receptors. Administration of melatonin to young male rats from 20-30 days of life had the same inhibitory effect on sexual maturation at 40 days as melatonin injections from 20-40 days. In contrast, administration of melatonin from 30-40 days only slightly decreased plasma testosterone concentration, weight of seminal vesicles, and pituitary GnRH receptor content. Melatonin administration from 38-40 days had no effect. Daily melatonin administration from 20-45 days of age was followed by resumption of sexual maturation, as observed at 70 days. The recovery was complete by 80 days of age when all of the parameters studied reflected complete sexual maturation. Finally, in rats treated continuously with melatonin from days 20 until 115, sexual maturation occurred but was delayed by about 20-30 days. Beginning of sexual development was observed at 60 days of life, and full development was attained only at 100 days. These data confirm that melatonin delays sexual maturation in the young male rat when administered daily in the afternoon. They demonstrate that this inhibitory action of melatonin is most critical between 20 and 30 days of life and is reversible regardless of whether melatonin administration is discontinued after 45 days of life. The suppression of the pubertal peaks of pituitary GnRH receptor number and pituitary and plasma FSH concentrations in treated rats suggests that melatonin interferes with the pubertal increase in GnRH secretion. In conclusion, these reversible effects of melatonin suggest that this pineal indolamine represents an important factor for the timing of sexual maturation.

Aging↗

PubMed1984

Hormonal changes during puberty: V. Transient pubertal gynecomastia: abnormal androgen-estrogen ratios.

The plasma profiles of 8 hormones were followed over the course of prepuberty and puberty in 30 adolescent males who developed gynecomastia and 24 who did not. Throughout puberty, ratios of delta 4-androstenedione to estrone (E1) and estradiol (E2) were significantly lower in the gynecomastia group than in the control group. Similarly, ratios of dehydroepiandrosterone-sulfate to E1 and E2 were significantly lower in the gynecomastia group. In contrast, ratios of plasma testosterone to E1 and E2 as well as plasma progesterone and PRL concentrations, were similar in both groups. Because of the adrenal origin of dehydroepiandrosterone and its sulfate, and of peripheral conversion of adrenal androgens to E1 and to E2, it appears that either decreased adrenal production of androgens and/or increased conversion of dehydroepiandrosterone-sulfate and delta 4-androstenedione to estrogens cause transient gynecomastia in adolescent boys.

Adolescent↗

PubMed1984

Circulating beta-2-microglobulin levels during pregnancy and their possible relationship with feto-maternal histocompatibility.

Plasma beta 2 microglobulin (beta 2m) levels have been measured by radioimmunoassay in normal pregnant women, in two successive pregnancies of a woman who shares HLA antigens with her husband, in normal twin pregnancies, in toxemic pregnancies and in hydatidiform moles. During normal pregnancy, plasma beta 2m levels decrease reaching a minimum at week 14 and increase thereafter to a maximum at week 34. In the two successive pregnancies of the one patient with HLA compatibility, beta 2m concentrations were significantly lower than in normal pregnancies. Women with monozygotic twins had significantly less beta 2m than women with heterozygotic twins. Toxemic patients bearing female fetuses had also statistically lower beta 2m levels than toxemic women with male fetuses. Patients suffering from hydatidiform moles had beta 2m levels in the range of normal pregnant patients. Since circulating beta 2m is produced by lymphocytes one might assume that low beta 2m levels reflect a reduced activity of lymphocytes. The results presented here allow to propose a hypothesis which will have to be verified that reduced beta 2m levels are associated with an increased feto-maternal histocompatibility.

Adult↗

PubMed1984

Primary hyperparathyroidism and rickets. A case report and review of the literature.

A case of primary hyperparathyroidism with clinical signs of rickets in a 15-year-old boy of South Morocco is presented. X-ray findings include a diffusely osteoporotic skeleton with areas of subperiostal resorption, cysts and metaphyseal rachitic changes. Hypercalcaemia, hypophosphataemia, increased alkaline phosphatase are found together with low calcidiol and high calcitriol plasma levels. The surgical removal of a chief-cell adenoma of a parathyroid gland leads to very rapid bone healing as well as normalization of blood chemistry. Reviewing the literature shows that 10 similar cases have been described. However, no correlation can be established between the occurrence of rachitic lesions and the Ca X P product. When limited calcium is available from the gut, elevated calcitriol then contributes to mobilize more mineral from bone, in conjunction with parathormone. In addition, the interaction of these 2 hormones on the renal tubule maintains a phosphate leak, creating proper conditions for the development of rachitic lesions.

Adenoma↗

PubMed1983

Pregnancy-associated plasma protein-A (PAPP-A) inhibits thrombin-induced coagulation of plasma.

Concentrations of immunoreactive PAPP-A have been found significantly lower in the serum as compared to heparin or EDTA plasma from the same patients. After coagulation significant amounts of PAPP-A remain associated with the clot. Purified PAPP-A inhibits thrombin induced coagulation of plasma. This inhibition cannot be attributed to a direct effect of PAPP-A on thrombin. It is exerted via an activation of endogenous antithrombin III since the inhibitory effect of PAPP-A on thrombin induced coagulation in a euglobulin system can be observed only if antithrombin III is added. The fact that protamine sulphate is capable of neutralizing the inhibitory effects of PAPP-A made us postulate that PAPP-A, like heparin, possesses strongly acidic residues which bind to protamine.

Animals↗