Intracellular distributian and substrate specificity of the 16 alpha-hydroxylase in the adrenal of human fetus

When [7α-³H] dehydroepiandrosterone was incubated with the adrenal homogenates of human fetus at 22 to 26 weeks gestational age, 16α-hydroxydehydroepiandrosterone and/or its sulfate was formed as the only detectable metabolite. The 16α-hydroxylase activity was concentrated in the microsomal fraction of the adrenal homogenate.[1,2-³H]Androstenedione, [4-¹⁴C] pregnenolone and [7α-³H] progesterone were also 16α-hydroxylated by incubation with the microsomal fraction. Amoung these substrates, progesterone gave the highest yield of 16α-hydroxylated products. By incubation with the microsomal fraction, formation of following steroids were also established: 6β-hydroxyandrostenedione from androstenedione; 17-hydroxypregnenolone, 17,21-dihydroxypregnenolone and dehydroepiandrosterone from pregnenolone; 17-hydroxy-progesterone, deoxycorticosterone, 11-deoxycortisol and androstenedione from progesterone.     

Steroid specificity of human placental 5-ene-3β-hydroxysteroid oxidoreductase

The properties of 5-ene-3β-hydroxysteroid oxidoreductase (3β-HSD) from human placental homogenates were studied invitro. The apparent Michaelis constants for 3β-HSD with the substrates pregnenolone (Δ⁵P) and dehydroepiandrosterone (DHA) were 170 nM and 40 nM respectively. The optimal pH for both these substrates was between 10 and 12. With NAD as the substrate, the Km for pregnenolone was 20 μM and for DHA, 17 μM. The activity of 3β-HSD was inhibited by various steroids. Competitive inhibitors (pregnenolone substrate) included: ethynylestradiol (inhibition constant Ki=7.3 nM), DHA (Ki=46 nM), estradiol-17β (Ki=46 nM), cholesterol (Ki=0.68 μM) and 16α-hydroxydehydroepiandrosterone (16αOHDHA) (Ki=2.2 μM). When the substrate was DHA, competitive inhibition occurred with the following steroids: ethynylestradiol (Ki=6.4 nM), estradiol-17β (Ki=69 nM), pregnenolone (Ki=91 μM), cholesterol (Ki=1.3 μM) and 16αOHDHA (Ki=1.9 μM). 4-Ene-3-ketosteroids such as androstenedione, progesterone (Δ⁴P), norethindrone and chlormadinone acetate acted as noncompetitive inhibitors towards both substrates.     

Determination of estriol, estriol sulfate, progesterone and neutral steroid mono- and disulfates in umbilical cord blood plasma

Fractions of unconjugated steroids, and steroid mono- and disulfates were isolated from cord plasma, and the concentrations of estriol, estriol sulfate, progesterone, 13 neutral steroid monosulfates (MoS) and 10 neutral steroid disulfates (DiS) were determined by gas-liquid chromatography. The mean concentrations in 30 cord plasma samples at term after normal pregnancy and delivery were as follows (μg/100 ml of free steroid ±standard deviation): estriol 16±5; estriol monosulfate 135±43; progesterone 59±19; dehydroepiandrosterone MoS 76±23; 5-androstene-3_β,17_α-diol DiS 279±77; 5-androstene-3_β,17_β-diol DiS 211±109; 16_α-hydroxydehydroepiandrosterone MoS 305±97; 16_β-hydroxy-dehydroepiandrosterone DiS 8±25; 33,17_β-dihydroxy-5-androsten-16-one MoS 37±16, DiS 29±15 5-androstene-3_β,16_α,17_β-triol MoS 25±9; 5-androstene-3_β,16_β,17_α-triol DiS 31±14; pregnenolone MoS 4±33; 5-pregnene-3_β,20_α-diol MoS 41±14, DiS 68±43; 16_α-hydroxypregnenolone MoS 101±42; 17-hydroxypregnenolone MoS 56±30; 21-hydroxypregnenolone DiS 26±15; 5-pregnene-3_β,20_α,21-triol MoS 37±18; 5_α-pregnane-3_α,20_α-diol MoS 21±10, DiS 54±21; 5_α-pregnane-3_β,20_α-diol MoS 18±9, DiS 7±39; 5_β-pregnane-3_α,20_α-diol MoS 17±7; 5_α-pregnane-3_α,20_α,21-triol MoS 110±56, DiS 22±19.The total amount of steroid monosulfates in the cord plasma pool was 1 mg/100 ml and that of steroid disulfates 0.5 mg/100 ml. 3_β-Hydroxy-Δ⁵-steroids predominated. Considerable amounts of saturated c₂₁ steroids were also detected. No statistically significant differences were found in the concentrations of any of the steroids studied, when a group of male and female fetuses were compared.     

Effects of ACTH and estradiol on steroid production by cultured adrenal cells from an anencephalic fetus and from normal adults

Dispersed adrenal cells from a 16 1/2 week anencephalic fetus, 7 fetuses with intact pituitaries and 3 adult subjects undergoing renal transplants were maintained in tissue culture and the steroidogenic responses to ACTH (0-10(3) pg/ml), with or without added estradiol (0-10(4) ng/ml) were evaluated. In the anencephalic preparation the response to ACTH was delayed, but by the fifth day production of cortisol, dehydroepiandrosterone (DHA) and DHA-sulfate was similar to that in the other cultured fetal adrenal cells. The addition of estradiol caused dose-related inhibition of cortisol production and concomitant increase in DHA and DHA-sulfate production. The adult adrenal cells in the presence of ACTH showed a much higher cortisol/DHA secretion ratio, but the addition of estradiol markedly reduced this ratio as in fetal cells. The data support the suggestion that the major factors which interact to impose the characteristic fetal pattern of adrenal steroidogenesis are ACTH and the synergistic effects of placental and intra-adrenal steroids (such as estradiol) which act to inhibit 3 beta-hydroxysteroid dehydrogenase activity.     

Corticotropin releasing hormone concentrations in umbilical cord blood of preterm fetuses.

Corticotrophin releasing hormone (CRH), dehydroepiandrosterone sulfate (DHEAS) and cortisol were measured in umbilical cord plasma obtained from 90 preterm and 98 term fetuses. Maternal plasma was obtained from 23 women who delivered preterm and from 23 women matched for gestational age who ultimately delivered term infants. Mean umbilical cord plasma CRH concentration was significantly higher in the preterm fetuses (n = 69, 538 +/- 63 pg/ml) compared to the term fetuses (n = 98, 280 +/- 22 pg/ml, P < 0.01). Mean DHEAS level in the preterm fetuses was 208 +/- 22 mg/dl (n = 56), cortisol level was 7 +/- 1 mg/dl (n = 58). Umbilical plasma CRH concentrations (808 +/- 170 pg/ml) were significantly higher at 24-27 weeks than at 28-31 or 31-34 weeks gestation. Cortisol levels (12 +/- 3 micrograms/dl) were highest at 24-27 weeks. Mode of delivery and the presence of labor did not affect fetal CRH levels. The highest fetal CRH levels were measured in the pregnancies complicated by hypertension as well as prematurity; however, fetal CRH levels remained higher in the preterm group compared to the term group when hypertensive pregnancies were excluded. Maternal plasma CRH levels were significantly higher in the group that delivered preterm compared to women who delivered at term matched for gestational age (1058 +/- 184 pg/ml compared to 456 +/- 71 pg/ml, P < 0.00).(ABSTRACT TRUNCATED AT 250 WORDS)     

Cortisol and cortisone levels in umbilical cord plasma and maternal plasma of normal pregnancies

A method for assaying cortisol and cortisone using chromatography on either paper or Sephadex LH-20 columns for isolation, followed by competitive protein binding, has been applied to umbilical cord and maternal plasma samples. In mixed cord plasma the mean cortisol concentration was 6.0 ± 0.8 μg/100 ml (n = 9) and the mean cortisone concentration was 13.5 ± 2.9 μg/100 ml (n = 9). In cord arterial plasma the mean cortisol concentration was 6.3 ± 2.9 μg/100 ml (n = 6) and the mean cortisone level was 10.1 ± 2.5 μg/100 ml (n = 6). For cord venous plasma, the mean level of cortisol was 5.6 ± 1.5 μg/100 ml (n = 6) and of cortisone was 13.5 ± 2.4 μg/100 ml (n = 6). Maternal plasma gave a mean value of cortisol of 42.3 ± 4.5 μg/100 ml (n = 6) and of cortisone of 6.2 ± 0.9 μg/100 ml. The results of this study suggest that the fetus at term-gestation produces cortisol. The significance of this production compared with placental transfer of maternal cortisol into the fetal circulation however is uncertain.     

Plasma levels of 16 alpha-hydroxypregnenolone, 16 alpha-hydroxyprogesterone and 16 alpha-hydroxydehydroepiandrosterone in the fetus and neonates.

Simultaneous determination of unconjugated 16 alpha-hydroxypregnenolone (16 alphaOH-Preg), 16 alpha-hydroxyprogesterone (16 alphaOH-Prog) and 16 alpha-hydroxydehydroepiandrosterone (16 alphaOH-DHEA) in fetal and neonatal plasma was performed utilizing a newly developed radioimmunoassay. In all neonates, the three 16 alpha-hydroxysteroid levels were consistently higher in umbilical cord plasma than in the maternal peripheral circulation. 16 alpha-OH-Preg in the umbilical arterial plasma increased from 11.2 +/- 3.1 at 24 weeks to 29.7 +/- 12.0 ng/ml at term, 16 alphaOH-Prog from 15.5 +/- 3.2 to 34.3 +/- 11.0 ng/ml and 16 alphaOH-DHEA from 5.1 +/- 1.2 to 5.9 +/- 1.0 ng/ml. In the anencephalic neonates, only 16 alphaOH-Preg showed an increase pattern under ACTH priming. 16 alpha-OH-Preg levels for normal full term neonates remain relatively constant at the first 24 hr and show a slight decrease at 3 days post partum. In small full term neonates, 16 alphaOH-Preg levels in umbilical arterial plasma are considerably higher than in normal neonates and remain at roughly equivalent levels for the first 5 days post partum. 16 alphaOH-Prog and 16 alphaOH-DHEA levels in umbilical arterial plasma in normal and small full term neonates are almost equal and both groups show a rapid decrease during the first 24 hr. Comparison with findings of the three 16 alpha-hydroxysteroids in fetal and neonatal plasma is discussed.     

Progestagen,androgen and oestrogen levels in plasma and ovarian follicular fluid during the oestrous cycle of the mare

The pattern of steroid hormone concentrations in the blood plasma of five mares was determined throughout eight oestrous cycles by radioimmunoassay. In three other mares the steroid hormone concentrations in the follicular fluid of 16 isolated follicles (⪖ 1 cm diameter) from both ovaries were analyzed on the first and third day of behavioural oestrus.The plasma levels of pregnenolone and progesterone as well as their 17α-hydroxylated metabolites showed similar ranges of concentration throughout the oestrous cycle. Luteolysis occurred 6 days prior to ovulation and was accompanied by a drop of all progestagens. Throughout the oestrous period (5 days prior to and including the day of ovulation) mean plasma concentrations of progestagens were <0.5 ng/ml and increased significantly one day after ovulation. Maximum plateau values were reached on day 6 after ovulation. A distinct (but not statistically significant) rise of androstenedione and testosterone plasma levels occurred during oestrus whereas dehydroepiandrosterone values increased significantly 6 days prior to ovulation and reached a maximum mean value of 1.14 ng/ml one day before ovulation. Levels then declined significantly on the day of ovulation. Oestrone and oestradiol-17β plasma concentrations increased significantly 4 and 3 days prior to the day of ovulation, respectively, and both remained elevated until one day before ovulation.A significant positive correlation could be detected between increasing follicle diameters and androstenedione as well as oestradiol-17β concentrations in the follicular fluid, whereas pregnenolone values showed a negative correlation with follicular diameter. Oestradiol-17β could be determined in 9 of the 16 follicular fluid samples. In 8 of these 9, oestradiol-17β predominated over all other steroid hormones.In view of the low concentrations of dehydroepiandrosterone detected in the follicular fluid, it is suggested that the increase in peripheral plasma values during oestrus is caused by an extra-follicular source(s).     

Insulin receptors in developing rat liver: Acquisition of down regulation in the immediate postnatal period

Alterations in the high and low affinity insulin receptor concentrations in developing rat liver were investigated. The number of high affinity receptors in partially purified plasma membranes from fetal rats increased from Days 19 through 22 of gestation, with no further increase in binding during the postnatal period. Fetuses of diabetic rats had approximately three times as many high affinity insulin receptors as age-matched fetuses of normal rats; however, by 1 day after birth the receptor number decreased to the normal level. Neither the number of low affinity receptors nor the affinity of insulin binding to high or low affinity receptors changed during development or between offspring of normal and diabetic rats. These changes in the number of high affinity hepatic insulin receptors from prenatal animals did not correlate with the concentration of plasma insulin. When suckling pups were rendered diabetic the changes in the number of high affinity insulin receptors correlated with alterations in plasma insulin concentrations. The number of high affinity sites/microgram DNA in hepatocytes from Day 18 fetal rats was not altered when cells were cultured for 48 h in medium containing 0, 250, or 5000 μU/ml of added insulin. When cultured hepatocytes derived from 1-day-old and adult rats were maintained in medium with added insulin concentrations of 250 or 5000 μU/ml the number of high affinity receptors/microgram DNA decreased as compared to the number of high affinity receptors in hepatocytes cultured in medium with no added insulin. This decrease in receptor number was accompanied by an increase in the affinity of insulin binding to its high affinity receptors. The data show that (i) only the high affinity insulin receptor number increases in rat liver during the prenatal period, (ii) fetuses of diabetic rats show a greater increase in high affinity receptors than do fetuses of normal animals, and (iii) the phenomenon of down regulation for high affinity insulin receptors is not observed in fetal rat liver, but is acquired in the immediate postnatal period.     

Concentrations of testosterone and androsterone in peripheral and umbilical venous plasma of fetal rats

Mean +/- s.d. testosterone concentrations in the peripheral plasma of 21- and 22-day-old male fetuses (1.32 +/- 0.43 ng/ml) were significantly (P less than 0.05) higher than those in the umbilical venous plasma (0.37 +/- 0.08 ng/ml). Testosterone concentrations in umbilical venous plasma of male and female (0.29 +/- 0.06 ng/ml) fetuses and in peripheral plasma of female fetuses (0.36 +/- 0.10 ng/ml) were not significantly different. Androsterone levels measured in umbilical venous plasma of male (11.5 +/- 2.5 ng/ml) and female (12.3 +/- 2.1 ng/ml) fetuses were nearly as high as those in peripheral plasma (males, 12.9 +/- 3.1; females, 13.3 +/- 3.5 ng/ml). There were high concentrations of androsterone in the placentas of male (33 +/- 4 ng/g) and female (33 +/- 5 ng/ml) fetuses, suggesting that this organ is the major source of fetal androsterone. We also conclude that a major part of the testosterone present in female fetuses is secreted by the placentas.     

The effects of pancreatectomy on the plasma concentrations of insulin-like growth factors 1 and 2 in the sheep fetus

The effects of hypoinsulinaemia and altered metabolite concentrations on the fetal plasma concentrations of insulin-like growth factors (IGF) have been investigated in chronically catheterized fetal sheep made insulin deficient by pancreatic ablation. Fetal pancreatectomy reduced significantly the plasma IGF-1 concentration and increased plasma IGF-2 activity in comparison with the values observed in sham operated fetuses. Mean plasma IGF-1 concentrations in the sham operated and pancreatectomized fetuses were 18.6 +/- 3.1 ng/ml (n = 7) and 13.4 +/- 1.4 ng/ml (n = 13) respectively. When all the data were combined, there was a significant positive correlation between the plasma concentrations of IGF-1 and insulin in utero. The mean IGF-2 activity was 2349 +/- 83 ng/ml (n = 7) in the sham operated fetuses and 3800 +/- 532 ng/ml in the pancreatectomized animals (n = 13). Plasma IGF-2 activity was correlated positively with plasma glucose, fructose and alpha-amino nitrogen levels and inversely related to the plasma insulin concentration in utero. These observations demonstrate that the fetal pancreas is essential for normal IGF production in the fetus and suggest that insulin, substrate availability and the IGFs may interact in the regulation of fetal growth.     

Testicular responsiveness to hCG of the ovine fetus in the last third of gestation

The in vivo and in vitro testicular responsiveness to hCG of hemicastrated lamb fetuses 95-99, 110-118 and 130-141 days of gestational age was studied. Basal plasma testosterone (T) levels were similar at all ages (less than 0.25 ng/ml), while the mean testicular concentrations of dehydroepiandrosterone sulfate (DHA-S), 17 alpha-hydroxyprogesterone (17-OHP) and T were higher in 95- to 99-day-fold fetuses. Plasma T levels and the concentration of T, DHA-S, 17-OHP, androstenedione (A) and cyclic adenosine 3'5'-monophosphate (cAMP) were increased by hCG in the hemicastrated animal at all ages. cAMP and T production by enriched preparations of dispersed interstitial cells from control testes was increased by hCG in all groups. In fetuses pretreated with hCG in vivo the addition of hCG in vitro failed to modify cAMP and T production. 100 micrograms of LHRH to a 130-day-old fetus increased plasma LH and T levels. From these experiments, it is suggested that the low plasma LH and T levels found throughout the last trimester of fetal life reflect a relative lack of endogenous LHRH synthesis and/or release, rather than reduced testicular steroidogenic capacity.     

Simultaneous determination of pregnenolone and 17α-hydroxypregnenolone by semi-micro high-performance liquid chromatography with an immobilized cholesterol oxidase as a pre-column reactor: application to bovine adrenal fasciculata cells

A method for the simultaneous determination of pregnenolone and 17α-hydroxypregnenolone by high-performance liquid chromatography with an immobilized cholesterol oxidation enzyme reactor was developed. Pregnenolone and 17α-hydroxypregnenolone were converted to progesterone and 17α-hydroxyprogesterone, respectively, by the immobilized enzyme packed into the reactor column, and could thus be monitored by UV absorption at 240 nm. The calibration curves for pregnenolone and 17α-hydroxypregnenolone were linear in the range of 0.4-10 and 0.3-10 μg/ml with a correlation coefficient of 0.9993 and 0.9998, respectively. The detection limit at a signal-to-noise ratio of 3 was 0.12 and 0.08 μg/ml for pregnenolone and 17α-hydroxypregnenolone, respectively. The conversion rate of pregnenolone to progesterone and 17α-hydroxypregnenolone to 17α-hydroxyprogesterone was 90.6% and 99.3%, respectively. Intra-day and inter-day precision (in terms of percentage coefficient of variation) were less than 9.3%, with accuracy greater than 94.8%. This method was successfully applied to the simultaneous determination of pregnenolone and 17α-hydroxypregnenolone secreted into the culture medium of bovine adrenal fasciculata cells and of both analytes produced within the cells.     

The determination of allopurinol and oxipurinol in human plasma and urine

A method is described for allopurinol and oxipurinol assay within human plasma and urine in the range expected during therapy. The method is based on high-performance ion-exchange chromatography following an efficient sample purification step using Chelex-100 resin in the Cu²⁺ form. Linear calibration curves are produced for allopurinol over the range 0.05–10 μmole/1 (0.068–1.36 μg/ml) in plasma and 0.005–1 mmole/1 (0.68–136 μg/ml) in urine and for oxipurinol 0.5–100 μmole/1 (0.076–15.2μg/ml) in plasma and 0.1–2 mmole/1 (15.2–304 μg/ml) in urine.     

槲皮素对人脑胶质瘤干细胞生物学行为及miR-29s家族的影响分析

目的探讨分析槲皮素对人脑胶质瘤干细胞（BGSCs）生物学行为及miR-29s家族的影响。 方法使用干细胞培养液对U87人脑胶质瘤细胞进行培养,采用CCK-8法检测槲皮素对BGSCs细胞增殖抑制率,采用流式细胞技术检测槲皮素对BGSCs细胞凋亡影响,并采用real-time PCR鉴定槲皮素对BGSCs细胞中miR-29a、miR-29b以及miR- 29c表达的影响。采用t检验以及方差分析进行统计学分析。 结果随着槲皮素浓度的增加,BGSCs细胞增殖抑制率增加24 h 0 μg/ml（0.00±0.12）%、10 μg/ml（1.36±0.38）%、20 μg/ml（15.33±3.01）%、40 μg/ ml（29.50±4.57）%、80 μg/ml（40.21±6.42）%、160 μg/ml（61.21±7.48）,F = 76.273,P < 0.05;48 h 0 μg/ml （0.09±0.05）%、10 μg/ml（9.84±2.17）%、20 μg/ml（28.57±3.84）%、40 μg/ ml（43.59±5.21）%、80 μg/ml（59.50±3.28）%、160 μg/ ml（70.21±9.48）%,F = 85.392,P < 0.05,且同浓度槲皮素作用48 h对BGSCs细胞增殖抑制率高于作用24 h（P < 0.05）。随着槲皮素浓度的升高,BGSCs细胞凋亡率升高[0 μg/ml（13.42±1.21）%、20 μg/ml（38.47±9.28）%、40 μg/ml（59.34±7.20）%、80 μg/ml（71.42±9.47）%,F = 57.493,P < 0.05]。不同浓度槲皮素处理BGSCs细胞后,可促进BGSCs细胞miR-29s家族miR- 29a/ b/ c相对表达量,且随着槲皮素浓度的增加,BGSCs细胞miR-29s家族相对表达量增加[miR-29a 0 μg/ml（1.04±0.08）、20 μg/ml（1.16±0.05）、40 μg/ml（1.30±0.10）、80 μg/ ml（1.41±0.09）,F = 19.281,P < 0.05;miR-29b 0 μg/ml（1.06±0.09）、20 μg/ml（1.13±0.05）、40 μg/ml（1.25±0.07）、80 μg/ml（1.30±0.09）,F = 13.427,P < 0.05;miR-29c 0 μg/ml（1.03±0.07）、20 μg/ml（1.15±0.03）、40 μg/ml（1.22±0.06）、80 μg/ml（1.31±0.08）,F = 14.502,P < 0.05]。 结论槲皮素可有效抑制人脑BGSCs增殖,促进人脑BGSCs凋亡,并促进人脑BGSCs中miR- 29s家族表达。     

Radioimmunoassay of testosterone in late fetal and newborn rabbit plasma, gonads and adrenal glands]

A radioimmunoassay was used for measuring testosterone in the plasma, gonads and adrenals of 28, 29, 30 and 31-day-old rabbit fetuses of both sexes and newborns. A marked sex difference was shown in the concentrations of testosterone in plasma and in gonads whereas in adrenals the levels of testosterone were low in both sexes (34 to 147 pg/10 mg). In male fetuses, plasma testosterone levels increased from the 28th (133 +/- 20 pg/ml) to the 31st day (361 +/- 119 pg/ml) of intrauterine life, reaching then the values observed in the newborns (387 +/- 73 pg/ml). Plasma from males, on the other hand contained, at all stages studied, significantly more testosterone than plasma from female fetuses (21 +/- 6 to 41 +/- 11 pg/ml) and female newborns (42 +/- 6 pg/ml). In the same way, fetal testicular testosterone concentrations varying from 1 382 +/- 218 to 2 317 +/- 333 pg/10 mg were similar to those measured in the newborns (1 940 +/- 304 pg/10 mg) and significantly higher than fetal (13 to 34 pg/10 mg) or neonatal (44 pg/10 mg) ovarian concentrations. These results showed at evidence the endocrine activity of the fetal testis during this period.     

A precursor role for DHA in a feto-placental unit for oestrogen formation in the mare.

Plasma levels of total oestrogens and dehydroepiandrosterone (DHA) were measured by radioimmunossay in samples taken from various blood vessels in both maternal and fetal compartments in 11 Pony mates. High concentrations of oestrogens (greater than 100 ng/ml of plasma), expressed as oestrone equivalents, were found in the fetal circulation. On both the fetal and maternal sides, oestrogen concentrations were lower in blood going to than from the placenta. DHA concentrations, on the other hand, were higher in blood flowing to the placenta from the fetus. The fetal gonads were seen as the source of DHA, which was present in remarkably high concentrations (greater than 800 ng/ml of plasma) in venous samples from fetal ovaries and fetal testes. A precursor role in placental oestrogen formation is suggested for DHA secretion by the fetal gonads.     

Protective effects of grape seed extract against oxidative and nitrative damage of plasma proteins

Oxidative stress, vascular inflammation, endothelial dysfunction plays a crucial role in the pathogenesis of cardiovascular diseases. The aim of our in vitro study was to examine the antioxidative properties of grape seed extract, and its potential protective effect on the haemostatic function of human fibrinogen under oxidative stress conditions, induced by peroxynitrite (100 μM). The preincubation of plasma with the tested extract (0.5-50 μg/ml or 0.5-300 μg/ml) reduced the formation of 3-nitrotyrosine and diminished oxidation of thiol groups in plasma proteins. The low concentrations (0.5-50 μg/ml) of grape seed extract also decreased the level of carbonyl groups, however at higher concentrations (100-300 μg/ml) this effect was not observed. Furthermore, grape seed extract counteracted the inhibitory effect of peroxynitrite on human plasma clotting. The results obtained in this study indicate that components of the grape seed extract posses antioxidative properties and may be promising substances for the creation of new dietary supplements.     

Plasma corticosteroid dynamics in channel catfish, Ictalurus punctatus (Rafinesque), during and after oxygen depletion

Plasma corticosteroid concentrations in channel catfish, Ictalurus punctatus , (normally 1.0 ± 0.3 μg/100 ml) increased significantly (to 5.9 ± 1.2μg/100 ml) in response to acute oxygen depletion and then returned to control levels within 30 min after the dissolved oxygen concentration was increased; however, a secondary increase in plasma corticosteroid levels was observed 6 h after exposure. Corticosteroid levels also increased in fish exposed to dissolved oxygen concentration of <0.2 mg/1 for three days. Methylene blue was not effective in preventing interrenal response to low dissolved oxygen. No diurnal plasma corticosteroid rhythm was observed in fish exposed to diurnal chemical rhythms of culture ponds.