Effect of activin A on dehydroepiandrosterone and testosterone secretion by primary immature porcine Leydig cells.

In the present study, we evaluated the effect of the homodimer activin A on immature porcine Leydig cell functions in primary culture. Activin A (0.5-100 ng/ml) reduced hCG-stimulated dehydroepiandrosterone (DHEA) accumulation in a dose- and time-dependent manner, with a maximal inhibitory effect (58% decrease) at 20 ng/ml (8 x 10(-10) M). Activin A was found not to control steroidogenesis, either through a modulation of the gonadotropin LH/hCG binding or low-density lipoprotein cholesterol binding and internalization. However, activin A significantly decreased pregnenolone (p less than 0.002) and DHEA (p less than 0.001) formation (evaluated in the presence of 10(-5) M of WIN 24540, an inhibitor of 3 beta-hydroxysteroid dehydrogenase/isomerase [3 beta-HSDI]activity) in Leydig cells maximally stimulated with hCG (3 ng/ml, 3 h) or incubated in the presence of 22R-hydroxycholesterol (5 micrograms/ml, 2 h). These findings indicate that activin A probably exerts a partial inhibitory effect on cholesterol side-chain cleavage cytochrome P450 (P450scc) activity. On the other hand, activin A significantly (p less than 0.001) enhanced the conversion of exogenous pregnenolone and DHEA (500 ng/ml) but not of progesterone and androstenedione (500 ng/ml) into testosterone, suggesting that activin A potentially enhances 3 beta-HSDI activity in Leydig cells. Activin A action on 3 beta-HSDI activity was found to be closely related to that of transforming growth factor-beta 1 (TGF beta 1), since both activin A (20 ng/ml) and TGF beta 1 (2 ng/ml) induced a comparable and non-additive increase in 3 beta-HSDI activity.(ABSTRACT TRUNCATED AT 250 WORDS)     

Determination of insulin-like growth factor-I in normal subjects and in patients with growth hormone disorders by radioimmunoassay using biosynthetic homologous peptide

A highly sensitive and specific RIA for IGF-I has been developed using recombinant DNA-derived IGF-I of very high purity and specific antiserum to it. This assay system could detect IGF-I at as low concentrations as 20-30 ng/ml. The intra-assay and interassay coefficients of variation at various concentrations of IGF-I were 4.9 to 6.5% and 5.4 to 8.0%, respectively. The recovery rate of pure IGF-I added to plasma was 77.0 +/- 3.7%. The antiserum did not cross-react with porcine insulin, biosynthetic human insulin, hGH, hEGF, the synthetic C-domain of IGF-I or that of IGF-II, but reacted equally with an analog, Thr59-IGF-I. Plasma IGF-I was extracted by the acid-ethanol method before assay to separate IGF-I from its binding protein. When plasma IGF-I was assayed without extraction, the inhibition curves of serial dilution of plasma samples from several individuals were not parallel to the standard curve of IGF-I. The plasma concentration of IGF-I was 147 +/- 49 ng/ml (mean +/- SD) in 156 normal adults aged from 20-59 years. As reported by others, the IGF-I levels were low in cord plasma (41.8 +/- 23.5 ng/ml) and plasma of patients with GH deficiency (64.6 +/- 42.0 ng/ml), while its levels were high in normal children of pubertal ages (12-13 yr, 365 +/- 126 ng/ml) and in patients with active acromegaly (562 +/- 115 ng/ml). This RIA system is a simple and useful method for determining plasma IGF-I in normal and diseased states.     

Age-related changes in plasma leptin binding activity in rats: A comparison of a simple acid-ethanol precipitation technique with column chromatography

A novel assay for measuring the free leptin fraction was developed and validated against a chromatographic technique. The assay used acid-ethanol extraction (AEE) for separation of bound/free leptin moieties. The interassay coefficient of variation was 3.9%. The specificity for leptin binding was confirmed by incubation with 1 microg of unlabeled rat leptin that effectively competed with radiolabeled leptin whereas human growth hormone and interleukin-6 were ineffective in competing with radiolabeled leptin binding. Scatchard analysis of competitive binding experiments with rat plasma demonstrated a linear relationship with a binding affinity of 0.3-0.6 x 109 M-1. This novel assay was used to determine if age-related insensitivity to leptin action is secondary to altered serum leptin binding. Rats at various age groups were studied for changes in body adiposity and serum total and free leptin concentrations. Serum free leptin concentrations (ng/ml mean +/- SEM) were significantly increased in 24-month-old rats (5.56 +/- 0. 21) compared with 18-month-old rats (4.76 +/- 0.17) (P < 0.01) despite similar body weight and adiposity of the two age groups. The increase in plasma free leptin concentrations in 12-month-old rats (3.86 +/- 0.28) and 6-month-old rats (2.05 +/- 0.06) relative to 3-month-old rats (1.37 +/- 0.06) (P < 0.001) was out of proportion to the increase in body adiposity in aging rats. It is concluded that aging in rats is associated with relative insensitivity to leptin. This change cannot be attributed to increased plasma binding or to a reduction in the leptin free fraction.     

Recombinant human activin A stimulates development of bovine one-cell embryos matured and fertilized in vitro

The effects of recombinant human activin A on the development of bovine one-cell embryos matured and fertilized in vitro were investigated. In experiment 1, one-cell embryos were cultured in a chemically-defined medium, of modified synthetic oviduct fluid supplemented with 1 mg/ml polyvinyl alcohol (mSOF-PVA), containing different concentrations of activin (0, 0.1, 1, 10, and 100 ng/ml) until 240 hr after in vitro fertilization. The addition of -1 ng/m activin to mSOF-PVA improved development to the blastocyst stage (14.5–17.1%), compared with no addition of activin (5.6%). However, there was no significant difference in hatching rate of embryos among treatments. In experiments 2 and 3, the embryos were also cultured in MSOF-PVA at various periods of exposure to 10 ng/ml activin to evaluate (development to the morula and blastocyst stages, respectively. The proportion of morulae was significantly higher in culture with activin at 20–120 hr postinsemination (37.2%) than with control (25.7%). Total number of cells in morulae at 120 hr postinsemination significantly increased by the addition of activin at 20–72 hr (26.1 cells) and 20–120 hr (24.2 cells) postinsemination, compared with control (20.1 cells). When activin was added to the medium during 20–120 hr and 20–192 hr postinsemination, the percentages of blastocysts (18.0% and 18.7%, respectively) were significantly higher than in the control (9.6%). However, the total number of cells in blastocysts was not significantly different. These results demonstrate that activin stimulates the development of bovine one-cell embryos to the morula and blastocyst stages in vitro. © 1996 Wiley-Liss, Inc.     

Role of antidiuretic activity in the inhibition of renin secretion by vasopressin in anesthetized dogs

The nature of the activity of vasopressin which is responsible for the inhibition of renin secretion was studied by comparing the effects of vasopressin (AVP) and analogs of AVP in anesthetized water-loaded dogs. Infusion of AVP (1.0 ng/kg/min) increased mean arterial pressure (MAP) and decreased heart rate (HR) and free water clearance (CH2O). Plasma renin activity (PRA) decreased from 11.9 +/- 4.7 to 3.8 +/- 1.7 ng/ml/3 hr (p less than 0.05). A selective antidiuretic agonist, 1-deamino-8-D-arginine vasopressin (1.0 ng/kg/min), which had no effect on MAP or HR but was effective as AVP in decreasing CH2O, decreased PRA from 13.5 +/- 4.6 to 7.0 +/- 2.9 ng/ml/3 hr (p less than 0.05). Infusion of a selective vasoconstrictor agonist, 2-phenylalanine-8-ornithine oxytocin (1.0 ng/kg/min), increased MAP and decreased HR but did not decrease CH2O or PRA. A vasoconstrictor antagonist, d(CH2)5Tyr(Me)AVP (10 micrograms/kg), completely blocked the MAP and HR responses to AVP but did not block the decrease in CH2O or PRA (5.9 +/- 1.8 to 2.9 +/- 1.6 ng/ml/3 hr) (p less than 0.001). Infusion of the 0.45% saline vehicle had no significant effect on MAP, HR, CH2O or PRA. These results indicate that the inhibition of renin secretion by vasopressin in anesthetized water-loaded dogs is due to its antidiuretic activity.     

Effects of recombinant activin A on in vitro culture of mouse preantral follicles

Activins are part of the intragonadal factors that can modulate the actions of gonadotropins and regulate cellular functions during preantral or early antral stages of folliculogenesis in vivo. In a mouse early preantral follicle culture system, activin A production was measured and recombinant bovine activin A (r-ACT A) was added (10 or 50 ng/ml) to recombinant follicle-stimulating hormone (r-FSH)–supplemented (10 or 100 mIU/ml) medium for a 12-day culture period. Specificity of activin A action was ascertained by addition of recombinant human follistatin (r-FS; 20 or 100 ng/ml). Immunoreactive activin A concentrations in mouse follicle–conditioned medium increased by a factor of 20–50, reaching concentrations from 2 to 5 ng/ml at end of culture. In the initial days of culture, additions of r-ACT A to r-FSH-supplemented medium provoked a dramatic volumetric increase and earlier attachment of the follicle. A dose of 100 ng/ml r-FS was able to block the actions of 10 ng/ml but not those caused by 50 ng/ml r-ACT A. In follicle cultures supplemented with 10 mIU/ml r-FSH, additions of r-ACT induced a dose-dependent inhibin (INH) and estradiol (E₂) increase. Basal and human chorionic gonadotropin (HCG)–induced progesterone (P) production were not influenced by r-ACT A or r-FS additions. Addition of r-ACT A decreased (P = 0.017) the intact follicle survival rate and had no influence on final oocyte diameter. In cultures supplemented by 10 mIU/ml r-FSH, additions of r-ACT A did not influence progression and resumption of meiosis I. Use of a higher r-FSH supplementation dose (100 mIU/ml) tended to affect meiosis I adversely (P = 0.052), and r-ACT A addition amplified this effect significantly (P = 0.007). These in vitro experiments demonstrate pronounced effects from r-ACT on r-FSH-mediated follicle survival, growth, and estrogen biosynthesis. Mol. Reprod. Dev. 50:294–304, 1998. © 1998 Wiley-Liss, Inc.     

Total and free testosterone in plasma of hypo- and agonadal men.

Plasma total testosterone (T), apparently free T and testosterone binding globulin (TeBG) capacity determined in 14 normal men aged 30-40 years were 461 +/- 100 ng/100 ml, 9.4 +/- 3.0 ng/100 ml and 5.7 +/- 1.9 X 10(-8) M, respectively, whereas in 16 hypogonadal men the corresponding values were 38.6 +/- 27.2 ng/100 ml, 0.47 +/- 0.41 ng/100 ml and 10.4 +/- 3.4 X 10(-8) M showing the TeBG capacity significantly higher (p less than 0.001) in hypogonadal than in normal men. Treatment of 5 hypogonadal subjects with 250 mg testosterone enanthate plus 50 mg testosterone propionate decreased (p less than 0.001) the TeBG level from 14.7 +/- 2.5 X 10(-8YM to 8.3 +/- 1.4 X 10(-8) M on day 8 after a single injection. According to this difference in TeBG, the free T fraction in plasma rose from 0.94% to 1.9% of the total T concentration. These results suggest that alteration of total plasma T affected the TeBG capacity. Decreased T levels raised and increased T concentrations suppressed TeBG, but with a delayed response to the changed T concentrations. The initial mean values in 12 patients with prostatic cancer aged 60-74 years were 397 +/- 165 ng/100 ml, 4.05 +/- 1.8 ng/100 ml and 11.9 +/- 3.3 X 10(-8) M, respectively. The TeBG capacity in these patients was significantly higher and the free T concentration significantly lower (p less than 0.001) than those of the younger normal males. After treatment with 12 g diethylstilbestrol diphosphate and orchidectomy, the TeBG increased to 33.3 +/- 13.1 X 10(-8) M and the plasma free T concentration decreased to the minimal value of 0.053 +/- 0.04 ng/100 ml.     

An activin-A/C chimera exhibits activin and myostatin antagonistic properties

Activins are involved in many physiological and pathological processes and, like other members of the transforming growth factor-beta superfamily, signal via type II and I receptor serine kinases. Ligand residues involved in type II receptor binding are located in the two anti-parallel beta strands of the TGF-beta proteins, also known as the fingers. Activin-A mutants able to bind ActRII but unable to bind the activin type I receptor ALK4 define ligand residues involved in ALK4 binding and could potentially act as antagonists. Therefore, a series of FLAG-tagged activin-A/C chimeras were constructed, in each of which eight residues in the wrist loop and helix region (A/C 46-53, 54-61, 62-69, and 70-78) were replaced. Additionally, a chimera was generated in which the entire wrist region (A/C 46-78) was changed from activin-A to activin-C. The chimeras were assessed for ActRII binding, activin bioactivity, as well as antagonistic properties. All five chimeras retained high affinity for mouse ActRII. Of these, only A/C 46-78 was devoid of significant activin bioactivity in an A3 Lux reporter assay in 293T cells at concentrations up to 40 nM. A/C 46-53, 54-61, 62-69, and 70-78 showed activity comparable with wild type activin-A. When tested for the ability to antagonize ligands that signal via activin type II receptors, such as activin-A and myostatin, only the A/C 46-78 chimera showed antagonism (IC(50), 1-10 nM). Additionally, A/C 46-78 decreased follicle-stimulating hormone release from the LbetaT2 cell line and rat anterior pituitary cells in primary culture in a concentration-dependent manner. These data indicate that activin residues in the wrist are involved in ALK4-mediated signaling. The activin antagonist A/C 46-78 may be useful for the study and modulation of activin-dependent processes.     

High-performance liquid chromatographic assay for xanomeline, a specific M-1 agonist, and its metabolite in human plasma

A reversed-phase high-performance liquid chromatographic assay (HPLC) was utilized for monitoring xanomeline (LY246708/NNC 11–0232) and a metabolite, desmethylxanomeline, in human plasma. Xanomeline, desmethylxanomeline and internal standard were extracted from plasma with hexane at basic pH. The organic solvent extract was evaporated to dryness with nitrogen and the dried residue was reconstituted with 0.2 M HCl-methanol (50:50, v/v). A Zorbax CN 150 × 4.6 mm I.D., 5-μm column and mobile phase consisting of 0.5% (5 ml/l) triethylamine (TEA) adjusted to pH 3.0 with concentrated orthophosphoric acid-tetrahydrofuran (THF) (70:30, v/v) produced consistent resolution of analytes from endogenous co-extracted plasma components. Column effluent was monitored at 296 nm/0.008 a.u.f.s. and the assay limit of quantification was 1.5 ng/ml. A linear response of 1.5 to 20 ng/ml was sufficient to monitor plasma drug/metabolite concentrations during clinical trials. HPLC assay validation as well as routine assay quality control (QC) samples indicated assay precision/accuracy was better than ±15%.     

The existence of activin A/erythroid differentiation factor and its inhibitor in human serum: comparison of normal and chronic renal failure sera.

Activin A/EDF, initially found as a differentiation inducer of murine Friend erythroleukemia, also has a stimulatory effect on erythropoiesis in vitro and in vivo. Here we proved activin A/EDF activity in human serum. The activin A/EDF level in 18 normal human serum samples was measured by a specific bioassay and was found to be 8.3 +/- 4.6 ng/ml, indicating that there exists sufficient activity to affect erythropoiesis in normal serum. In contrast, activin A/EDF activity was reduced in the chronic renal failure patients and 23/26 serum samples examined showed levels below 1.2 ng/ml. Further analysis using HPLC revealed that chronic renal failure serum actually contained as much activin A/EDF as normal serum, and that the difference between normal and patient serum existed in the content of a specific inhibitor of activin A/EDF. This observation suggests the possibility that the inhibitor is participating in the regulation of activin A/EDF activity in vivo in chronic renal failure patients and also the possibility of activin A/EDF could be utilized in the therapy of the anemia of such patients.     

Determination of vitamin D and its metabolites in plasma from normal and anephric man

A multiple assay capable of reliably determining vitamins D(2) and D(3) (ergocalciferol and cholecalciferol), 25(OH)D(2) (25-hydroxyvitamin D(2)) and 25(OH)D(3) (25-hydroxyvitamin D(3)), 24,25(OH)(2)D (24,25-dihydroxyvitamin D), 25,26(OH)(2)D (25,26-dihydroxyvitamin D) and 1,25(OH)(2)D (1,25-dihydroxyvitamin D) in a single 3-5ml sample of human plasma was developed. The procedure involves methanol/methylene chloride extraction of plasma lipids followed by separation of the metabolites and purification from interfering contaminants by batch elution chromatography on Sephadex LH-20 and Lipidex 5000 and by h.p.l.c. (high-pressure liquid chromatography). Vitamins D(2) and D(3) and 25(OH)D(2) and 25(OH)D(3) are quantified by h.p.l.c. by using u.v. detection, comparing their peak heights with those of standards. 24,25(OH)(2)D and 25,26(OH)(2)D are measured by competitive protein-binding assay with diluted plasma from vitamin D-deficient rats. 1,25(OH)(2)D is measured by competitive protein-binding assay with diluted cytosol from vitamin D-deficient chick intestine. Values in normal human plasma samples taken in February are: vitamin D 3.5+/-2.5ng/ml; 25(OH)D 31.6+/-9.3ng/ml; 24,25(OH)(2)D 3.5+/-1.4ng/ml; 25,26(OH)(2)D 0.7+/-0.5ng/ml; 1,25(OH)(2)D 31+/-9pg/ml (means+/-s.d.). Values in two normal human plasma samples taken in February after 1 week of high sun exposure are: vitamin D 27.1+/-7.9ng/ml; 25(OH)D 56.8+/-4.2ng/ml; 24,25(OH)(2)D 4.3+/-1.6ng/ml; 25,26(OH)(2)D 0.5+/-0.2ng/ml. Values in anephric-human plasma are: vitamin D 2.7+/-0.8ng/ml; 25(OH)D 36.4+/-16.5ng/ml; 24,25(OH)(2)D 1.9+/-1.3ng/ml; 25,26(OH)(2)D 0.6+/-0.3ng/ml; 1,25(OH)(2)D was undetectable.     

Dynamics of circulating osteocalcin in rats during growth and under experimental conditions.

Osteocalcin is the most abundant non-collagenous protein produced in the process of bone formation. A specific radioimmunoassay has been developed using a rabbit antiserum raised against osteocalcin extracted from rat bone. The sensitivity of the assay was tested in male and female rats under different experimental conditions: ovariectomy led to a mild increase in circulating osteocalcin (70.6 +/- 6.9 vs 51.6 +/- 6.3 ng/ml; p < 0.05) and deprivation of dietary calcium elevated plasma levels further (119 +/- 6.3 ng/ml; p < 0.01). As expected, pharmacological enhancement of bone turnover with calcitriol produced a significant increase in plasma osteocalcin (296 +/- 24.1 vs 89.5 +/- 5.1 ng/ml; p < 0.01), whereas prednisolone, a steroidal compound known to inhibit osteoid mineralization, significantly reduced circulating concentrations of this protein (70 +/- 7.4 vs 100 +/- 6.3 ng/ml; p < 0.05). Plasma kinetics recorded in female rats between birth and the 100th week revealed a highly significant (p < 0.001) elevation peaking at the third week (231 +/- 70.6 ng/ml) and slowly declining to reach values measured at birth (41.3 +/- 9.2 ng/ml) at the 16th week (47 +/- 4.6 ng/ml). Subsequently, a small but significant (p < 0.05) decline towards senescence was recorded. The osteocalcin surge preceded the period of rapid growth (weeks 3 to 11) estimated by vertebral length progression, showing a tendency to stabilize as growth spurt slowed down. A moderate but significant (p < 0.01) increment was observed after mating (87.8 +/- 5.1 vs 69.5 +/- 4.0 ng/ml). Although plasma osteocalcin remained stable during lactation, average levels were elevated in comparison with age-matched non-pregnant controls.(ABSTRACT TRUNCATED AT 250 WORDS)     

Determination of UDP-N-acetylglucosamine:β-D-mannoside-1,4-N-acetylglucosaminyltransferase-III in patients sera with chronic hepatitis and liver cirrhosis using a monoclonal antibody

The glycoprotein UDP-N-acetylglucosamine: beta-D-mannoside-1,4-N-acetylglucosaminyltransferase-III (GnT-III) catalyzes the addition of N-acetylglucosamine via a beta-1, 4-linkage to the beta-linked mannose of the trimannosyl core of N-linked glycans. It has been reported that the expression of GnT-III increases in many oncogenically transformed cells and human hepatocellular carcinoma (HCC) tissues, and GnT-III enzyme activity in serum can be used for the detection and monitoring of primary hepatomas and hepatocellular carcinomas. A solid-phase enzyme-linked immunosorbent sandwich assay in which a polyclonal antibody (PAb) to aglycosylrecombinant GnT-III (AGR-GnT-III) and a monoclonal antibody (mAb) are employed as a capture protein and probe protein, respectively, is described. The sensitivity of the PAb-mAb sandwich assay, as determined by the dose-response effect for AGR-GnT-III, was 10 ng/ml. This assay was specific for GnT-III and did not detect beta-1, 6-N-acetylglucosaminyltrasferase-V (GnT-V). AGR-GnT-III concentrations in 377 serum specimens were determined by the PAb-mAb sandwich assay and the results were analyzed based on the disease category, using 1.99 microg/mL (AGR-GnT-III) as a cut-off value. The AGR-GnT-III level of 61 normal serum samples was 0.57 +/- 0.71 microg/ml (mean +/- SD). The results revealed an elevation in serum AGR-GnT-III levels in 60 of 86 patients (3.03 +/- 2.04 microg/ml) with liver cirrhosis (LC) and 86 of 91 patients (2.73 +/- 0.59 microg/ml) with chronic hepatitis (CH). By contrast, 3 of 61 normal subjects, 9 of 34 patients (1.02 +/- 1.03 microg/ml) with acute hepatitis and 8 of 38 patients (1.79 +/- 0.56 microg/ml) with a variety of non-hepatic diseases exhibited a slight increase above the cut-off value. These results indicate that serum AGR-GnT-III levels are elevated predominantly in LC or CH cases. Serum AGR-GnT-III concentration, as measured by the developed PAb-mAb sandwich assay, may be a useful differential marker as a diagnostic aid for CH and/or LC and warrants further investigations with expanded serum panels.     

Determination of ajulemic acid and its glucuronide in human plasma by gas chromatography-mass spectrometry

A method using gas chromatography-mass spectrometry (GC-MS) and solid-phase extraction (SPE) was developed for the determination of ajulemic acid (AJA), a non-psychoactive synthetic cannabinoid with interesting therapeutic potential, in human plasma. When using two calibration graphs, the assay linearity ranged from 10 to 750 ng/ml, and 750 to 3000 ng/ml AJA. The intra- and inter-day precision (R.S.D., %), assessed across the linear ranges of the assay, was between 1.5 and 7.0, and 3.6 and 7.9, respectively. The limit of quantitation (LOQ) was 10 ng/ml. The amount of AJA glucuronide was determined by calculating the difference in the AJA concentration before ("free AJA") and after enzymatic hydrolysis ("total AJA"). The present method was used within a clinical study on 21 patients suffering from neuropathic pain with hyperalgesia and allodynia. For example, plasma levels of 599.4+/-37.2 ng/ml (mean+/-R.S.D., n=9) AJA were obtained for samples taken 2 h after the administration of an oral dose of 20 mg AJA. The mean AJA glucuronide concentration at 2h was 63.8+/-127.9 ng/ml.     

A novel IL-18BP ELISA shows elevated serum IL-18BP in sepsis and extensive decrease of free IL-18

IL-18 binding protein (IL-18BP) is a circulating antagonist of the proinflammatory Th1 cytokine IL-18. It effectively blocks IL-18 by forming a 1:1 high affinity (Kd=400 pM) complex, exhibiting a very low dissociation rate. We have developed a sandwich ELISA for IL-18BPa and determined its limit of detection (62 pg/ml). Interference by IL-18 and related cytokines, as well as cross reactivity with other IL-18BP isoforms (b, c, and d) were determined. Using this ELISA, we measured serum IL-18BPa in large cohorts of healthy individuals and in septic patients. Serum IL-18BPa in healthy individuals was 2.15+/-0.15 ng/ml (range 0.5-7 ng/ml). In sepsis, the level rose to 21.9+/-1.44 ng/ml (range 4-132 ng/ml). Total IL-18 was measured in the same sera by an electrochemiluminescence assay and free IL-18 was calculated based on the mass action law. Total IL-18 was low in healthy individuals (64+/-17 pg/ml) and most of it ( approximately 85%) was in its free form. Total IL-18 and IL-18BPa were both elevated in sepsis patients upon admission (1.5+/-0.4 ng/ml and 28.6+/-4.5 ng/ml, respectively). At these levels, most of the IL-18 is bound to IL-18BPa, however the remaining free IL-18 is still higher than in healthy individuals. We conclude that IL-18BPa considerably inhibits circulating IL-18 in sepsis. Yet, exogenous administration of IL-18BPa may further reduce circulating IL-18 activity.     

Radioreceptor assay for atrial natriuretic factor

Interest in accurate measurement of atrial natriuretic factor (ANF) in biological fluids and various tissues has been stimulated by recent data indicating the possible role of ANF in the homeostasis of salt and water. The presence of high-affinity binding sites for ANF in rat glomeruli has allowed us to develop a rapid, sensitive, and simple radioreceptor assay (RRA). A saturable high-affinity binding site on the membranes of rat glomeruli has been characterized by a dissociation constant of 33 pM and binding capacity of 396 fmol/mg protein. Rat plasma extracts or atrial homogenates or standards were incubated with radioiodinated ANF and a preparation of rat glomerular membranes. The receptor-bound and free radioactivity were separated by filtration on Whatman GF/C paper after 1 h incubation at room temperature. The sensitivity of the RRA was 2.08 fmol. The effective concentration of standard ANF that displaced 50% of labeled receptor-bound ANF (EC50) was 43.3 +/- 2.6 fmol/ml (n = 7). Both intra- and interassay coefficients of variation were smaller than 11%. This RRA assay has been compared with radioimmunoassay (RIA). High correlations for 19 plasma extracts and 34 atrial homogenates (r = 0.973 and r = 0.954, respectively) tested by RRA and RIA were obtained. This good correlation between the two methods suggests that the immunoreactive material found in rat plasma and atrial homogenates also displays biological activity.     

Determination of testosterone in saliva and blow of bottlenose dolphins (Tursiops truncatus) using liquid chromatography-mass spectrometry

A rapid, accurate and reproducible assay utilising high performance liquid chromatography-mass spectrometry (LC-MS) has been developed and validated for determining testosterone concentrations in saliva and blow of bottlenose dolphins. Sample preparation used solid phase extraction with specific preconditioning of cartridges. Analytes were eluted with 100% acetonitrile, dried under nitrogen and stored at -80 degrees C. Samples were reconstituted in 60% acetonitrile for LC-MS analysis. Chromatographic separation was achieved with an Alltech Macrosphere C8 stainless steel analytical column (2.1 mm x 150 mm i.d., 5 microm particle size, 300 angstroms pore size) using a 55% mobile phase B isocratic method (mobile phase A = 0.5% acetic acid; mobile phase B = 0.5% acetic acid, 90% acetonitrile). Samples were analysed in SIM at m/z 289.20 (testosterone mw 288.40) and a positive ion ESI. The limit of quantification was 0.5 ng/ml with a limit of detection of 0.2 ng/ml. The concentration curve was linear from 0.5 to 50 ng/ml (y = 0.01x + 0.0045, r(2) = 0.959, r = 0.979, p < 0.001). The R.S.D.s of intra- and inter-batch precision were less than 15% for saliva and 11% blow. Recovery of the assay for saliva was 93.0 +/- 7.9% (50 ng/ml) and 91.5 +/- 3.72% (1 ng/ml), and for blow was 83.3 +/- 6.8% (50 ng/ml) and 85.8 +/- 4.6% (1 ng/ml). Recovery of the internal standard in saliva was 73.0 +/- 14.2% and in blow was 78.63 +/- 4.29. The described assay was used to determine the presence of endogenous testosterone in saliva (9.73-23 ng/ml, n = 10) and blow (14.71-86.20 ng/ml, n = 11) samples of captive bottlenose dolphins.     

Localization of an activin/activin receptor system in the porcine ovary.

The aim of this study was to locate a possible activin/activin receptor system within porcine ovaries containing functional corpora lutea. In situ hybridization was used to assess the gene expression of beta(A)- and beta(B)-activin subunits, and immunohistochemical studies were done to detect activin-A protein and activin receptor type II. mRNA expression of the beta(A)- and beta(B)-activin subunits was found in the granulosa from the unilaminar follicle stage onward, in the developing thecal layer of multilaminar and small antral follicles, in the theca interna of mid-sized antral follicles, in corpora lutea, and in the ovarian surface epithelium. Immunoreactive activin A protein could be detected at the same ovarian sites, but in thecal tissue of small antral follicles only. This protein was also demonstrated at the peripheral zone of oocytes from multilaminar and antral follicles. A positive immunoreaction for activin receptor was found in granulosa cells from multilaminar and older follicles and in oocytes from the earliest stages of follicular development onward. In late multilaminar follicles and in antral follicles, the oolemma was stained. Except for small antral follicles, a positive activin receptor immunoreaction was absent in the follicular theca. Activin receptor immunoreaction was furthermore present in corpora lutea and in the ovarian surface epithelium. It is concluded that, within porcine ovaries containing functional corpora lutea, an activin/activin receptor system is present in all intact follicles, the corpora lutea and the surface epithelium. Within follicles, granulosa and theca cells are the main sites of activin synthesis, while oocytes and granulosa cells are the main activin binding sites.