Stability Assessment of p-i-n Perovskite Photovoltaic Mini-Modules Utilizing Different Top Metal Electrodes

Long-term stability is one of the major challenges for p-i-n type perovskite solar modules (PSMs). Here, we demonstrate the fabrication of fully laser-patterned series interconnected p-i-n perovskite mini-modules, in which either single Cu or Ag layers are compared with Cu/Au metal-bilayer top electrodes. According to the scanning electron microscopy measurements, we found that Cu or Ag top electrodes often exhibit flaking of the metal upon P3 (top contact removal) laser patterning. For Cu/Au bilayer top electrodes, metal flaking may cause intermittent short-circuits between interconnected sub-cells during operation, resulting in fluctuations in the maximum power point (MPP). Here, we demonstrate Cu/Au metal-bilayer-based PSMs with an efficiency of 18.9% on an active area of 2.2 cm² under continuous 1-sun illumination. This work highlights the importance of optimizing the top-contact composition to tackle the operational stability of mini-modules, and could help to improve the feasibility of large-area module deployment for the commercialization of perovskite photovoltaics.

Compositional and Interfacial Engineering Yield High-Performance and Stable p-i-n Perovskite Solar Cells and Mini-Modules

Through the optimization of the perovskite precursor composition and interfaces to selective contacts, we achieved a p-i-n-type perovskite solar cell (PSC) with a 22.3% power conversion efficiency (PCE). This is a new performance record for a PSC with an absorber bandgap of 1.63 eV. We demonstrate that the high device performance originates from a synergy between (1) an improved perovskite absorber quality when introducing formamidinium chloride (FACl) as an additive in the "triple cation" Cs_0.05FA_0.79MA_0.16PbBr_0.51I_2.49 (Cs-MAFA) perovskite precursor ink, (2) an increased open-circuit voltage, V_OC, due to reduced recombination losses when using a lithium fluoride (LiF) interfacial buffer layer, and (3) high-quality hole-selective contacts with a self-assembled monolayer (SAM) of [2-(9H-carbazol-9-yl)ethyl]phosphonic acid (2PACz) on ITO electrodes. While all devices exhibit a high performance after fabrication, as determined from current-density voltage, J-V, measurements, substantial differences in device performance become apparent when considering longer-term stability data. A reduced long-term stability of devices with the introduction of a LiF interlayer is compensated for by using FACl as an additive in the metal-halide perovskite thin-film deposition. Optimized devices maintained about 80% of the initial average PCE during maximum power point (MPP) tracking for >700 h. We scaled the optimized device architecture to larger areas and achieved fully laser patterned series-interconnected mini-modules with a PCE of 19.4% for a 2.2 cm² active area. A robust device architecture and reproducible deposition methods are fundamental for high performance and stable large-area single junction and tandem modules based on PSCs.

Concentration- and time-dependent effects of the synthetic estrogen, 17alpha-ethinylestradiol, on reproductive capabilities of the zebrafish, Danio rerio

Partial or full life-cycle tests are needed to assess the potential of endocrine-disrupting compounds (EDCs) to adversely affect development and reproduction of fish. Small fish species such as zebrafish, Danio rerio, are under consideration as model organisms for appropriate test protocols. The present study examines how reproductive effects resulting from exposure of zebrafish to the synthetic estrogen 17alpha-ethinylestradiol (EE2) vary with concentration (0.05 to 10 ng EE2 L(-1), nominal), and with timing/duration of exposure (partial life-cycle, full life-cycle, and two-generation exposure). Partial life-cycle exposure of the parental (F1) generation until completion of gonad differentiation (0-75 d postfertilization, dpf) impaired juvenile growth, time to sexual maturity, adult fecundity (egg production/female/day), and adult fertilization success at 1.1 ng EE2 L(-1) and higher. Lifelong exposure of the F1 generation until 177 dpf resulted in lowest observed effect concentrations (LOECs) for time to sexual maturity, fecundity, and fertilization success identical to those of the developmental test (0-75 dpf), but the slope of the concentration-response curve was steeper. Reproduction of zebrafish was completely inhibited at 9.3 ng EE2 L(-1), and this was essentially irreversible as a 3-mo depuration restored fertilization success to only a very low rate. Accordingly, elevated endogenous vitellogenin (VTG) synthesis and degenerative changes in gonad morphology persisted in depurated zebrafish. Full life-cycle exposure of the filial (F2) generation until 162 dpf impaired growth, delayed onset of spawning and reduced fecundity and fertilization success at 2.0 ng EE2 L(-1). In conclusion, results show that the impact of estrogenic agents on zebrafish sexual development and reproductive functions as well as the reversibility of effects, varies with exposure concentration (reversibility at < or = 1.1 ng EE2 L(-1) and irreversibility at 9.3 ng EE2 L(-1)), and between partial and full life-cycle exposure (exposure to 10 ng EE2 L(-1) during critical period exerted no permanent effect on sexual differentiation, but life-cycle exposure did).

Identification of endocrine-disrupting effects in aquatic vertebrates and invertebrates: report from the European IDEA project

The EU-funded project IDEA aimed to evaluate (a) what parameters and endpoints allow the detection of endocrine-mediated developmental and reproductive effects of (xeno)estrogens in life cycle- and life stage-specific toxicity tests with the zebrafish Danio rerio, a small laboratory fish used in many ecotoxicity test guidelines, and (b) whether substances that act as estrogens in vertebrates may also adversely affect the development, differentiation, and reproduction of aquatic invertebrates. The invertebrate species investigated included Hydra vulgaris, Gammarus pulex, Chironomus riparius, Hyalella azteca, and Lymnaea stagnalis. The animals were exposed to the model estrogenic chemicals ethynylestradiol (EE2), bisphenol A (BPA), and octylphenol (OP), which exert their endocrine activity in vertebrates through the estrogen receptor. As endpoints, developmental and reproductive parameters at the organism level as well as molecular and cellular parameters were measured. Life cycle exposure of zebrafish to (xeno)estrogens induced a specific, partly irreversible response pattern, consisting mainly of (a) induction of vitellogenin (VTG), (b) alterations of gonad differentiation, (c) delay of first spawning, and (d) reduced fertilization success. The effects of EE2 on zebrafish were expressed at environmentally realistic concentrations, while BPA and OP became effective at concentrations higher than those usually found in the environment. The vitellogenic response was equally sensitive as the reproductive parameters in the case of EE2, but VTG was more sensitive in the case of BPA. Partial life cycle exposure of zebrafish had lasting effects on fish development and reproduction only when the fish were exposed during the stage of juvenile bisexual gonad differentiation. In (partial) life cycle and multigeneration studies with invertebrates, (xeno)estrogenic impact was assessed by a range of developmental and reproductive parameters including hatching, growth, moulting, mating behavior, and egg number. Several parameters were found to be responsive to (xeno)estrogens; however, most effects were induced only at higher, probably nonphysiological concentrations. Low-dose effects were observed in full life cycle experiments, particularly in the second generation. It remains to be established whether the estrogen-induced alterations in the invertebrate species indeed do result from disturbances of the endocrine system. The findings of the present research project support the development of appropriate testing methodologies for substances with estrogenic activity.

Development and validation of a homologous zebrafish (Danio rerio Hamilton-Buchanan) vitellogenin enzyme-linked immunosorbent assay (ELISA) and its application for studies on estrogenic chemicals

Vitellogenin (VTG) was isolated by anion exchange chromatography from plasma of female zebrafish (Danio rerio) induced with 17alpha-ethinylestradiol (EE2). The purity of the VTG isolate was confirmed by polyacrylamide gel electrophoresis (SDS-PAGE). Purified VTG was used to raise polyclonal antibodies in rabbits and the specificity of the antisera for VTG confirmed by Western blot analysis of plasma proteins separated by SDS-PAGE. The antibodies cross-reacted with two proteins in the plasma of female zebrafish, with molecular masses of approximately 142 and 171 kDa. No cross-reactivity was observed with any other plasma proteins. A competitive enzyme-linked immunosorbent assay (ELISA) was developed using the polyclonal zebrafish VTG (z-VTG) antibodies and purified z-VTG as ligand and standard, respectively. The z-VTG ELISA was sensitive with a detection limit of between 2.0 and 3.0 ng purified VTG/ml, and a working range between 3 and 500 ng/ml (30-85% binding). The ELISA demonstrated precision, with inter- and intra-assay variations of 7.5+/-2.7 and 4.9+/-1.4%, respectively. Plasma from adult zebrafish and whole body homogenates from juvenile zebrafish diluted parallel with the z-VTG standard in the ELISA, validating the assay for quantifying z-VTG in both of these tissues. Exposure of adult male zebrafish to EE2 via water induced a concentration-dependent induction of VTG with a lowest observed effect concentration (LOEC) < or =1.67 ng EE2/l (for a 21-day exposure). The homologous z-VTG ELISA provides a valuable tool for the study of environmental estrogens in zebrafish.

The influence of fasting on blood and plasma composition of herring gulls (Larus argentatus)

Populations of scavenging seabird species in the North Sea may fluctuate with an artificial food source: the availability of fishery waste. To document this impact, it is necessary to assess the birds' nutritional status during periods with decreased fishing activity. Reference data for this purpose was collected from 22 herring gulls investigated during laboratory fasting. After 6 d of food deprivation and body mass losses exceeding 15%, the first birds entered starvation phase 3. Comparatively, this is a rather weak fasting capacity. Plasma levels of total protein and thyroid hormones decreased and beta-hydroxybutyrate increased with fasting duration. The leucocyte proportions were shifted from lymphocytes to heterophils. After 3 d of refeeding, most of the fasting changes were reversed. Plasma enzyme activities increased and hematocrit, hemoglobin, and erythrocyte numbers decreased in both fasting and control birds, most likely as a result of experimental stress and repeated blood sampling. Glucose, cholesterol, monocytes, basophils, and glycosylated hemoglobin remained fairly constant. Triglycerides, free fatty acids, uric acid, and urea varied significantly, but changes were not as clearly a result of fasting. Therefore, total protein, beta-hydroxybutyrate, triiodothyronine, thyroxine, and lymphocyte and heterophil percentages may be the most reliable indicators of the nutritional status and the condition of free-living herring gulls.

Extramedullary facial plasmacytomas with anaplastic features: a diagnostic dilemma with implications for treatment

Extramedullary plasmacytomas (EMPs) are rare plasma-cell tumors of the soft tissue that occur predominantly in the nasal sinuses and oropharynx. Subcutaneous and cutaneous plasmacytomas of the face are distinctly unusual. The authors report a case of rapidly expanding EMP involving the lip and contralateral nasolabial fold of a native Alaskan man with a 25-year history of recurring solitary bone plasmacytomas (SBP). An incisional biopsy revealed sheets of monotypic plasmablasts with anaplastic features. The pathologic and clinical findings were most consistent with a Richter transformation from a low-grade to a high-grade malignancy, or anaplastic myeloma (AM). With combined chemotherapy and radiation therapy, he achieved a complete response. The clinical and laboratory features of this most unusual plasma-cell dyscrasia are reviewed with an emphasis placed on diagnosis and treatment.

Role of cortisol in the ACTH-induced suppression of testicular steroidogenesis in guinea pigs

In order to investigate the role of cortisol in the regulation of testicular function, adult male guinea pigs were challenged with ACTH (20 IU), cortisol (8 or 16 mumol), or with ACTH plus dexamethasone (DEX, 2 mumol). The amounts of cortisol, testosterone, progesterone, and androstenedione present in the plasma or secreted by incubated adrenals or testes were determined by radioimmunoassay. The plasma concentrations of LH were determined using a radioimmunoassay for rat LH. ACTH treatment elevated cortisol plasma concentrations to 999% of control values, whereas it reduced testosterone plasma levels to 43% of control values. ACTH treatment did not affect LH plasma levels. A significant negative correlation was found in ACTH-treated animals, when the cortisol and testosterone plasma concentrations in serially taken blood samples (30-240 min after treatment) were compared (rs = -0.90 and rs = -0.99, P < 0.05). In addition to cortisol, ACTH raised progesterone and androstenedione plasma concentrations. If animals were treated with 2 mumol DEX + ACTH, the plasma levels of cortisol and androstenedione but not of progesterone, testosterone or LH were changed. ACTH stimulated the in vitro secretion of cortisol, progesterone and androstenedione by the adrenals but reduced the in vitro release of androstenedione and testosterone by the testes. In summary, treatment of guinea pigs resulted in elevated cortisol and in reduced testosterone plasma concentrations. The mechanism of the cortisol-induced inhibition of testicular function was independent of the LH plasma concentrations. The in vitro experiments indicate that cortisol directly interacts with the Leydig cells, presumably by inhibiting the activity of the testicular 17 alpha-hydroxylase and/or C17,20-lyase. Taking into account the results of comparable investigations in the rat, the inhibition of the testicular 17 alpha-hydroxylase and/or C17,20-lyase takes place if the intracellular cortisol exceeds the capacity of the 11 beta-hydroxysteroid dehydrogenase to inactivate it.

Clean-up and re-use of kieselguhr (Extrelut) for liquid-liquid extraction of urinary cortisol

Cortisol was isolated from human urine using kieselguhr (Extrelut)-filled columns. After use, Extrelut was cleaned-up once with distilled water and twice with ethanol. Before re-use, the cleaned-up kieselguhr was dried for 24 h by a warm air stream. The comparison of cortisol recovery from human urine and HPLC chromatograms of urinary extracts show that Extrelut can be repeatedly used for liquid-liquid extraction of urinary cortisol.

The use of salivary cortisol measurements for the non-invasive assessment of adrenal cortical function in guinea pigs

For collection of saliva, cotton buds (Q-tips) were inserted into the guinea pig's cheek pouch, parallel with the cheek teeth. The recovery of saliva from the buds increased with the volume applied: whereas the recovery was 63% when 20 microliters were applied, it increased to 85% when 120 microliters were applied. The recovery of cortisol was closely related to the volume of saliva obtained by centrifugation (r = 0.99, p < 0.001). The mean value of salivary cortisol concentrations in untreated animals was 6.6 ng/ml, with relatively large variations across minutes and days within and between animals. Salivary cortisol was significantly increased if animals were singly caged, either in their familiar housing room or in an unfamiliar empty test room. In comparison to these changes, a much more pronounced increase of salivary cortisol occurred after the intramuscular (i.m.) administration of 20 IU ACTH: while the pretreatment value was 2.2 ng/ml, cortisol concentrations increased to 47 ng/ml (1 h), 72 ng/ml (2 h), 137 ng/ml (3 h) and 170 ng/ml (4 h), respectively. Similarly, i.m. administration of 2 IU insulin resulted in a significant increase of salivary cortisol (2 h: 37 ng/ml, 3 h: 24 ng/ml, 4 h: 25 ng/ml). The present study shows that the cortisol concentrations in the saliva of guinea pigs can be used as an index of adrenal cortical function in preference to the more commonly measured concentrations in the plasma. The advantages of the saliva method are: Firstly, cortisol values reflect the biologically active, unbound fraction in the plasma and are thus less affected by concentration changes of the corticosteroid-binding globulin. Secondly, saliva is easy to collect and the collection method is non-invasive; thus, no handling- or stress-induced changes of the adrenal gland occur. Thirdly, the ease of collection facilitates investigations which require frequent sampling.

Saliva cortisol and testosterone in the guinea pig: measures for the endocrine function of adrenals and testes?

For collection of saliva, cotton buds (Q-tips) were inserted into the guinea pig's cheek pouch, parallel with the cheek teeth. Within 5 min, sufficient fluid was collected for cortisol and testosterone measurements. In saline-treated animals, saliva cortisol and testosterone were about 15 ng/mL and 1.5 ng/mL, corresponding to plasma levels of 52 ng/mL and 5.9 ng/mL. Within 2-4 h after administration of 20 IU ACTH, saliva and plasma cortisol concentrations were strikingly elevated: saliva: 125 ng/mL (2 h), 157 ng/mL (4 h); plasma: 458 ng/mL (2 h), 736 ng/mL (4 h). This treatment did not influence testosterone in saliva, but reduced it in plasma (2.4 ng/mL (4 h)). In animals receiving 100 IU HCG, saliva testosterone remained unchanged, whereas its plasma levels were markedly raised (9.6 ng/mL (2 h), 12.5 ng/mL (4 h)). These results show that saliva cortisol offers promise as a noninvasive method of monitoring changes in guinea pig adrenocortical function. Saliva testosterone, on the other hand, does not correlate with plasma values; hence it cannot be used to assess testicular function in the guinea pig.

Measurement of salivary cortisol in guinea pigs

For collection of saliva, cotton buds (Q-tips) were inserted into the guinea pig's cheek pouch, parallel with the cheek teeth. Within 5 minutes, sufficient fluid was collected for salivary cortisol measurements. Salivary cortisol was about 7 ng/ml after intramuscular (i.m.) injection of 0.2 ml saline. Compared with saline treatment, it was drastically increased after i.m. injection of ACTH or cortisol. Taking into account the close relationship between the amounts of cortisol in saliva and plasma in cortisol- or ACTH-treated animals, we conclude that measuring saliva cortisol offers promise as a noninvasive method to monitor the changes of adrenocortical function in guinea pigs.

Dissociation of plasma and urinary steroid values after application of stressors, insulin, vasopressin, ACTH, or dexamethasone in the Mongolian gerbil

The amounts of cortisol and testosterone in the plasma or urine of Mongolian gerbils exposed to stress factors or treated subcutaneously with insulin (2 IU), vasopressin (1 IU), ACTH (6 IU) or dexamethasone (50 micrograms) were determined. Increased plasma cortisol was observed in animals stressed by ether anesthesia or immobilisation (1-4 hours), or treated with insulin, vasopressin or ACTH. Cortisol levels were reduced after dexamethasone administration. Plasma testosterone was elevated in animals stressed by ether anesthesia or handling plus seizure; no other treatment altered testosterone levels. An augmented cortisol excretion, which lasted one day, occurred in gerbils immobilised for one as well as for four hours. A much more prolonged stimulation of cortisol excretion, lasting three days, was seen in animals receiving ACTH or dexamethasone plus ACTH. Testosterone excretion was stimulated by ACTH and dexamethasone plus ACTH; it was not influenced by any other treatment. The present study shows that analysis of circulating steroid levels is the only reliable approach to assess the secretory activity of Mongolian gerbil adrenals or testes. In some experimental conditions (e.g. after stressor application or ACTH treatment) cortisol excretion may be used as an index of adrenal secretory function. In contrast, the striking differences between cortisol values present in plasma and urine of peptide-or dexamethasone-treated gerbils indicate that urinary cortisol does not reflect short-term changes of adrenal function. Similarly, the striking differences of testosterone values in plasma and urine indicate that urinary testosterone monitoring cannot be used to determine the secretory activity of gerbil testes.

Rapid and efficient method for extraction and separation of glucocorticosteroids and sex steroids from urines

The influence of different pH values on the recoveries of glucocorticosteroids and sex steroids from Kieselguhr-filled minicolumns has been investigated. While the recoveries of all steroids tested were similar if samples had acidic or neutral pH values, sex steroids could effectively be separated from glucocorticosteroids by increasing the pH value to 13.7: recoveries were 1.7% for glucocorticosteroids and 56-76% for sex steroids. For the determination of sex steroids in biological samples it is recommended to adjust samples to a strong alkaline pH before extraction; this holds especially true for samples with very high glucocorticosteroid levels.

Body weight and water intake of guinea pigs: influence of single caging and an unfamiliar new room

No changes in body weight are observed if adult male guinea pigs are removed from their groups and kept singly in their home enclosure. In contrast, subjects markedly lose weight and show a marked reduction of water intake if isolated from their groups and caged singly in an unfamiliar test room. It is recommended that if guinea pigs have to be caged singly, they should remain in their home room, for enabling them to express their need for oldfactory/auditory contact with conspecifics.

Protein binding of cortisol by means of competitive adsorption: application to cortisol binding by serum of sixteen eutherian mammals

1. Binding of 3H-cortisol by serum proteins by means of competitive adsorption was relatively high by serum of the gerbil, human, rabbit, sheep, tree shrew, hamster, rhesus monkey and horse. 2. A somewhat lower binding was observed by serum proteins of the baboon, cattle, dog, rat and cat. 3. Serum taken from either the mouse, guinea pig or pig gave very flat binding curves, specific binding not exceeding 5% of added 3H-cortisol. 4. It is concluded that the measurement of protein-binding of 3H-cortisol by means of competitive adsorption is a reliable method for serum of most eutherian species but is unsuited if serum of the mouse, guinea pig or pig is used.

Effects of fungal metabolites on testosterone secretion in vitro

To study the direct effect of mycotoxins belonging to different chemical classes on testicular function, dispersed interstitial cells from testes of adult gerbils were short-term cultured either in the absence or presence of mycotoxins, and testosterone secretion was measured. When interstitial cells were incubated with T-2 toxin (0.0076-38.3 nM) there was a dose-dependent decrease of testosterone production (r = -0.72, ID50 = 0.042 nM). Since neither progesteronenor DHEA-stimulated testosterone production was affected by T-2 toxin, the observed inhibition of basal secretion was apparently due to a decrease of pregnenolone production and/or conversion of pregnenolone to progesterone. Much higher concentrations of zearalenone or of ochratoxin A were necessary to induce a similar inhibition of steroidogenesis (369 microM and 1838 microM, respectively) when compared to T-2 toxin. In contrast, citrinin or cyclopiazonic acid affected testosterone secretion only slightly, values reaching significant levels at doses of 1.74 nM (citrinin) and 149 nM (cyclopiazonic acid). In the presence of kojic acid (2.63-2633 nM) a significant, though not dose-dependent inhibition of testosterone secretion was observed. From these experiments it is concluded that mycotoxins of distinct chemical structure act directly on testicular tissue, presumably by inhibiting early steps of the steroidogenic pathway.

Excretion of electrolytes, free cortisol and aldosterone-18-oxo-glucuronide in 24-hr urines of the Mongolian gerbil (Meriones unguiculatus): effect of lysine-vasopressin and adrenocorticotrophin administration, and of changes in sodium balance

1. Administration of lysine-vasopressin (LVP, 1 IU/animal) strongly reduced electrolyte excretion in 24 hr urines of adult male Mongolian gerbils, but had no effect on free cortisol (C) or aldosterone-18-oxo-glucuronide (Aldo-gluc.) excretion. 2. (1-24) ACTH, given at a dosage of 20 IU/animal, increased C and Aldo-gluc. excretion but did not influence electrolyte excretion. 3. Fluid intake and potassium excretion were decreased in animals offered a control or a sodium-deficient diet; contrasting, excretion of C was stimulated. 4. In contrast to other rodents, Aldo-gluc. excretion showed no changes in Mongolian gerbils offered a sodium-deficient diet, but was diminished in animals either fed a control diet or given saline (154 mmol/l) as drinking water.

Changes of basal and steroidal precursor-stimulated testosterone secretion in isolated Mongolian gerbil and guinea pig testes after a single episode of heating

1. In the absence of steroidal precursors, testosterone secretion by Mongolian gerbil testes incubated at 37 degrees C was 340 ng/g tissue/4 hr. Addition of 1 microgram progesterone or DHEA drastically stimulated testosterone secretion by testes incubated at 37 degrees C (progesterone: 3281 ng/g tissue/4 hr, DHEA: 4654 ng/g tissue/4 hr). 2. While neither basal nor DHEA-stimulated production of testosterone was significantly affected by a single episode of heating (43-44 C for 30 min), progesterone-stimulated testosterone secretion markedly decreased during the 4-hr incubation period. 3. In contrast, in isolated testes of adult guinea pigs, a single episode of heating (44 degrees C for 30 min) resulted in a drastic reduction of basal and precursor-stimulated testosterone production during the 4-hr incubation period. 4. From these data it appears that enzymatic activities in the testes of the two species do not have their maxima at the same temperature, but rather in each case at, or close to, the temperature prevailing in the scrotal testis.

Urinary excretion of free progestins, androgens, and estradiol after injection of (1-24)ACTH in the Mongolian gerbil

Injection of a "long-acting" synthetic adrenocorticotrophin [(1-24)ACTH, 20 IU/animal] into Mongolian gerbils resulted in a 3.1 fold increase of urinary free testosterone excretion over 2 days. It was accompanied by an elevation of urinary free progesterone (2.1 fold), 17-hydroxyprogesterone (2.5 fold), DHEA (2.8 fold) and androstenedione (3.0 fold) excretion. Similarly, administration of human chorionic gonadotrophin (HCG, 100 IU/animal) increased urinary excretion of free testosterone (2.3 fold), progesterone (4.1 fold), 17-hydroxyprogesterone (2.9 fold), DHEA (4.6 fold), androstenedione (5.4 fold) and of estradiol (2.9 fold). Data presented in this work show that the measurement of urinary free steroid excretion represents a reliable index for the secretory activity of the adrenal-gonadal-axis, and that it may in some aspects be more practicable than the measurement of steroid plasma levels, especially in small laboratory animals, enabling us to monitor the excretion of various steroids over longer time periods without stressing the animals by handling/or blood sampling.

Gonadotrophin- and androgen precursor-stimulated testosterone secretion by interstitial cells from Mongolian gerbil testes: influence of plasma proteins and elevated temperature

Interstitial cells isolated from Mongolian gerbil testes have been used to investigate the effects of plasma proteins and incubation temperature on HCG- and androgen precursor-stimulated testosterone secretion. Short term (15 min) incubation of interstitial cells with various precursors resulted in a significant increase of testosterone release. On the other hand, no stimulatory effect of HCG (10 mIU) could be observed. Precursor (e.g. progesterone)-stimulated testosterone secretion linearly increased with cell concentrations (0.5 x 10(5) to 4.0 x 10(5) cells/0.7 ml medium, r = less than 0.99, p less than 0.001). In the presence of 50% horse plasma, progesterone-stimulated testosterone secretion was even more pronounced. Similarly, also gerbil, rat, calf or human plasma significantly increased progesterone-stimulated testosterone output. Interestingly, this effect was markedly reduced in the presence of cortisol. While incubation of interstitial cells for 15 min at either 40 degrees C or 42 degrees C had no significant effect on androgen precursor- or HCG-stimulated testosterone secretion, incubation of cells at 44 degrees C resulted in a drastic reduction of HCG-stimulated testosterone release, without affecting progesterone- or DHEA-stimulated testosterone secretion. Taken the simplicity to make interstitial cells unresponsive to HCG into account, heat-treated cells might prove to be a versatile tool to distinguish between HCG- and protein-/androgen precursor-stimulated testosterone secretion in vitro.

Urinary excretion of free glucocorticosteroids and testosterone in the Mongolian gerbil (Meriones unguiculatus): effects of long-acting corticotrophin and human gonadotrophin

1. Methods for the quantitative collection of 24-hr urines of small laboratory animals and for the measurement of urinary free glucocorticosteroids and testosterone are described. 2. Urinary glucocorticosteroids and testosterone were determined in 0.1-0.5 ml-aliquots of 1/100 diluted urines after kieselgur mini-column extraction. 3. Excretion of glucocorticosteroids and testosterone in undisturbed Mongolian gerbils was 329 and 13 ng/day, respectively. 4. Administration of long-acting (1-24)ACTH (20 IU/animal) increased glucocorticosteroid and testosterone excretion to about 2000 ng/day (glucocorticosteroids) and to about 30 ng/day (testosterone) over 3 days. 5. In animals injected with 100 IU/animal HCG, testosterone excretion was elevated to about 35-50 ng/day over 3 days. 6. As the results show, the measurement of urinary excretion of free glucocorticosteroids and testosterone is a reliable index of adrenal-gonadal function in the Mongolian gerbil. 7. Furthermore, in small laboratory animals, steroid measurements in 24-hr urines may be superior to determinations in plasma, since amounts of urinary steroid are relatively high and 24-hr urines can be collected over longer time periods without stressing the animals.

The responsiveness to (1-24) ACTH of Mongolian gerbil adrenals superfused in vitro as a function of basal secretion

Wide variations have been found in the responsiveness to (1-24)ACTH of Mongolian gerbil adrenal glands superfused in vitro. These variations were not correlated to corticosteroid plasma levels or to adrenal weights. In contrast, (1-24)ACTH-stimulated secretion greatly depended on basal in vitro secretion (quarters: r = 0.97, p less than 0.01; slices: r = 0.90, p less than 0.001) indicating that the fine adjustment of basal corticosteroidogenesis forms an important part of the regulatory mechanisms modulating (1-24)ACTH-stimulated corticosteroid secretion in vitro.

Rapid and fine adjustment of corticosteroidogenesis operating in the adrenal gland of the Mongolian gerbil (Meriones unguiculatus) superfused in-vitro

Corticosteroid release from adrenals of male adult Mongolian gerbils (Meriones unguiculatus) has been studied during continuous and discontinuous in-vitro superfusion. Corticosteroid output from glands of untreated animals with plasma corticosteroid levels below 300 ng/ml was 3.3 +/- 0.3 ng/adrenal pair/min and decreased only slightly with the length of superfusion (60 min: 3.1 +2- 0.3 ng/adrenal pair/min). In-vitro secretion was significantly higher from adrenals of animals which had corticosteroid plasma levels of over 300 ng/ml, underwent clonic-tonic seizures, or were injected with 6 IU/animal (1-24) ACTH. On the other hand, injection of 2 X 50 micrograms dexamethasone markedly decreased corticosteroid plasma levels but had no significant effect on in-vitro secretion of corticosteroids. In contrast to the slow and small, but long-lasting stimulation of corticosteroid secretion elicited by (1-24) ACTH, secretion could be changed within much shorter time periods, either by the addition of plasma proteins to superfusion medium or by stops of superfusion flow. While a significant stimulation of corticosteroid output occurred after the addition of 1% or 10% BSA or rat plasma, stops of superfusion flow for 1.5 or 10 min resulted in a strong inhibition of steroidogenesis, as is evident from corticosteroid amounts found in the first 1-min samples after re-start of superfusion. Within 4-5 min after re-start of superfusion, secretion returned to basal values. Corticosteroid amounts secreted from adrenals superfused in-vitro were significantly higher than those secreted from adrenals incubated in-vitro. In addition, prolonged incubation suppressed corticosteroidogenesis (30 min: 100%, 60 min: 64%, 90 min: 56%, 120 min: 59%). The results demonstrate that superfusion of sliced adrenal tissue gives insights into aspects of adrenal function, including the rapid changes in synthesis and secretion after flow stops which cannot be investigated by incubation of either tissue slices or isolated cells. The possibility that the observed decline in corticosteroidogenesis during flow stops may be due to a feedback inhibition resulting from corticosteroids accumulating within slices is discussed.

Testosterone secretion by Mongolian gerbil interstitial cells during short-term incubation depends on androgen precursors and serum proteins but not on gonadotrophins

Interstitial cells from the testes of the Mongolian gerbil have been used to investigate the effects of serum proteins on testosterone production stimulated by hCG and steroidal precursors. Short-term incubation of interstitial cells with progesterone or DHEA resulted in a rapid increase of testosterone secretion; this effect was even more pronounced in the presence of calf serum. On the other hand, addition of hCG (10 mIU) had no significant effect on testosterone release during the 30-min incubation. These results demonstrate that the magnitude of the steroidogenic response of short-term incubated interstitial cells is a complex function, mainly of precursor concentrations and binding capacities of serum proteins but not of gonadotrophins.

Corticosteroidogenesis in the isolated Mongolian gerbil adrenal gland during continuous and discontinuous superfusion

Corticosteroid (C) release by adrenals of male Mongolian gerbils (Meriones unguiculatus) has been studied during continuous and discontinuous (flow stop) superfusion. Flow stops of superfusion for 1, 5, 10 or 20 min resulted in a significant accumulation of C within adrenal tissue and superfusion flask. Amounts of C in the first 2-min samples after re-start of superfusion were positively correlated with the amounts secreted during continuous superfusion (5 min: r = 0.97, 10 min: r = 0.97, 15 min: r = 0.74, 20 min: r = 0.84, all p less than 0.001) and with the length of flow stops (1-20 min: r = 0.92, p less than 0.001). However, C concentrations in superfusates were significantly lower than values calculated from secretion during continuous superfusion and the length of flow stops (0 min = 100%, 1 min: 92%, 5 min: 65%, 10 min: 49%, 15 min: 39%, 20 min: 35%). As is evident from the very similar C amounts secreted by adrenals incubated for 15 min without or with 95%O2/5%CO2 (234 vs 256% of basal secretion), flow stop-induced inhibition of corticosteroidogenesis was not due to a lack of oxygen during flow stops. The results demonstrate that superfusion of sliced adrenal tissue gives insights into regulatory mechanisms, including the rapid changes of corticosteroidogenesis during short-lasting flow stops, which cannot be studied in static incubation of either tissue slices or isolated cells. The possibility that the observed decline in steroidogenesis during flow stops may be due to a local feedback inhibition resulting from C accumulating in the microenvironment of adrenal cells is discussed.

The influence of dehydroepiandrosterone on basal and gonadotrophin-stimulated testosterone secretion by Mongolian gerbil interstitial cells incubated or superfused in vitro

1. Testosterone secretion by Mongolian gerbil interstitial cells incubated in the absence of HCG linearly increased with cell concentration (1 x 10(5) cells: 0.6 ng/4 hr, 10 x 10(5) cells: 8.0 ng/4 hr). Addition of 100 mIU HCG resulted in a drastic increase of testosterone secretion which was linear between concentrations of 1 x 10(5) and 4 x 10(5) cells. 2. Compared to HCG-stimulated testosterone release, secretion was significantly higher by cells incubated with 60-100 ng DHEA. 3. During the 4-hr incubation period, 53-69% of added progesterone and 72-88% of added dehydroepiandrosterone (DHEA) were converted to testosterone by cells freshly prepared or stored for 1-3 days at 4 degrees C. On the other hand, prolonged storage at 4 degrees C resulted in a marked decrease of HCG-stimulated testosterone secretion. 4. Testosterone secretion by interstitial cells superfused in vitro increased with the length of HCG (100 mIU/ml) application from 0.08 to 0.22 ng/10(6) cells/min (10 and 60 min, respectively). A much faster and pronounced elevation was found when cells were stimulated with DHEA (200 ng/ml: 0.06-0.80 ng/10(6) cells/min, 0 and 20 min, respectively). 5. After interstitial cells have been stimulated with a DHEA (200 ng/ml) pulse for 30 min and then superfused with medium only for an additional 30 min, testosterone secretion remained significantly elevated and could not be further stimulated by superfusing medium which contained as much as 100 mIU/ml HCG.

Inhibition of aldosterone synthesis induced by flow-stop in the Mongolian gerbil adrenal gland superfused in vitro

Stopping of superfusion flow for short periods resulted in a significant accumulation of aldosterone within the Mongolian gerbil adrenal gland superfused in vitro. Aldosterone amounts in the first 2-min samples after the re-starting of superfusion were positively correlated with the length of flow-stop; however, they were significantly lower than calculated amounts: 5-min stop: 37 +/- 1% inhibition, 10-min stop: 51 +/- 1% inhibition. In addition, aldosterone secretion was significantly suppressed during prolonged incubation. The results suggest that aldosterone and glucocorticosteroid amounts in adrenal tissue may modulate basal corticosteroidogenesis and that self-suppression forms an important part of the control mechanisms involved in corticosteroidogenesis.

Adrenal function in the Mongolian gerbil (Meriones unguiculatus): influence of confinement stress upon glucocorticosteroid, progesterone, dehydroepiandrosterone, testosterone and androstenedione plasma levels, adrenal content and in-vitro secretion

The pattern of adrenal steroid secretion and the response to confinement stress were investigated in male Mongolian gerbils (Meriones unguiculatus). Steroid levels of glucocorticosteroids (GC), progesterone (P), dehydroepiandrosterone (DHEA), testosterone (T) and androstenedione (A) in plasma, adrenal tissue and superfusates of adrenals superfused in-vitro were measured by radioimmunoassay. The sensitivity of the assay systems and the low cross-reactivity of the antisera used allowed the determination of steroid levels in small samples (5-200 microliters), without prior chromatography. GC plasma levels were much higher than values of P, DHEA, T or A (176.7, 2.4, 3.3, 2.6 and 2.8 ng/ml, respectively). Confinement stress resulted in a significant increase of GC and DHEA plasma levels; similarly, adrenal content of GC, DHEA and P was markedly increased. In contrast, the applied stress factor had no significant effects on either plasma levels of P, T or A or on adrenal T or A content. Compared to plasma levels or adrenal content, amounts of steroids secreted from adrenals superfused in-vitro were very low (GC: 57.1, P: 2.1, DHEA: 23.0, T: 1.8, A: 3.0 pg/mg/min, respectively). Confinement stress significantly stimulated GC, P and DHEA secretion in-vitro but had no effects on T or A release. The secretion of GC, P, DHEA and T, but not of A was significantly increased by in-vitro stimulation with 0.01-10.0 mIU (1-24) ACTH. Interestingly, the amounts of GC and P, and of GC and DHEA secreted from incubated adrenal slices stimulated with (1-24) ACTH and from adrenals of controls and stressed gerbils superfused in-vitro were significantly correlated. By measuring steroid plasma levels and profiles of steroids secreted from adrenocortical and testicular tissue it now seems possible to characterize in more detail the effects of chronic intermittent stress upon the adrenalgonadal axis and the possible interrelationship between glucocorticosteroid and androgen secretion, especially in small laboratory animals from which only limited amounts of blood can be obtained repeatedly.

Basal and HCG-stimulated testosterone production by interstitial cells of the Mongolian gerbil (Meriones unguiculatus)--II. Influence of glucocorticosteroids and steroidal precursors

Compared to testosterone production by Mongolian gerbil interstitial cells in the absence of HCG or precursors, testosterone formation was significantly elevated by the addition of 100 ng pregnenolone, progesterone, 17-hydroxyprogesterone or DHEA. Production increased linearly with the amounts of precursors added (pregnenolone: r = 0.99; progesterone: r = 0.98; 17-OH-progesterone: r = 0.96; DHEA: r = 0.92, N = 40, all P less than 0.001). Approximately 50% of DHEA were converted to testosterone during the 6-hr incubation period. Neither the addition of 100 ng 11-deoxycortisol, 11-deoxycorticosterone, cortisol, corticosterone, cortisone, 18-OH-corticosterone, 21-deoxycortisone or 11-dehydrocorticosterone, nor of 100 ng estradiol had a significant effect on testosterone production by isolated interstitial cells incubated without or with 1 mIU HCG. Testosterone production by isolated interstitial cells was significantly increased within 2 min after the addition of 100 ng DHEA; production then linearly increased with the length of incubation (r = 0.98, N = 40, P less than 0.001). After addition of as little as 2 ng DHEA, testosterone formation was higher than by cells incubated without DHEA. While testosterone production could not be stimulated by the addition of 1-500 microIU HCG during a 30-min incubation period, it was drastically elevated by the addition of 10, 20 or 100 ng DHEA. Steroidal precursor concentrations secreted by the Mongolian gerbil adrenal gland incubated in vitro for 120 min were too low to stimulate testosterone production by interstitial cells. On the other hand, testosterone synthesis could be increased by the addition of 10-100-microliter aliquots of adrenal extracts.

Basal and HCG-stimulated testosterone production by interstitial cells of the Mongolian gerbil (Meriones unguiculatus)--I. Influence of preincubation length, medium composition and temperature

In the absence of HCG, production of testosterone by whole testes superfused in vitro was quite constant during the 5-hr superfusion period. Addition of 23-184 mIU/ml HCG caused a significant increase of testosterone production which was apparent from 30 min after start of superfusion. Basal and HCG-stimulated testosterone production by whole testes was significantly higher (400, 1950 ng/testis/5 hr, without and with 100 mIU HCG) than by isolated cells (200, 1350 ng/testis/5 hr). Incubation of isolated interstitial cells in medium 199 supplemented with fetal calf serum (FCS), (N-2-hydroxyethylpiperazine-N-2-ethanesulphonic acid, HEPES) and 3-isobutyl-methylxanthine (MIX), and in medium 199 without FCS, HEPES or MIX, gave similar testosterone responses. While centrifugation at 8000 g for 2 min drastically diminished testosterone formation by isolated interstitial cells, production was similar by cells incubated in either 0.5, 1.0 or 1.5 ml medium. A significant decrease of testosterone synthesis by isolated interstitial cells was found when cells were stored at 4 degrees C for 2 days and then were incubated at 35 degrees C for 6 hr without or with 1-1000 microIU HCG. While isolated interstitial cells incubated at 5 degrees C did not produce testosterone at all, testosterone production increased to 49.5 +/- 3.9 ng/10(5) cells (30 degrees C) and 24.1 +/- 1.1 ng/10(5) cells (40 degrees C), respectively. HCG-stimulated testosterone production was maximal when interstitial cells were incubated at 34 degrees C.

Effects of acute stress, (1-24)ACTH administration and changes in superfusion temperature and flow rate on the in vitro secretion of glucocorticosteroids and aldosterone from the Mongolian gerbil (Meriones unguiculatus) adrenal gland

The release of glucocorticosteroids and aldosterone rapidly decreased after start of superfusion and reached a steady base-line within 60-90 min of superfusion. While secretion markedly varied between experiments, it was very constant in the same experiment (coefficient of variation: 7.4-2.2% for glucocorticosteroids and 5.8-3.9% for aldosterone). After repeated exposure of adrenal tissue to 1 IU/ml (1-24)ACTH, glucocorticosteroid release progressively increased; under the same conditions aldosterone secretion was not changed. Glucocorticosteroid secretion from glands of animals stressed by 1-hr confinement or of animals injected with 6 IU (1-24)ACTH was significantly higher than that of controls over the 60-min superfusion period. Aldosterone secretion was not affected significantly by these pretreatments. After reduction of temperature from 35 to 1 degrees C, steroid release ceased. Elevation of temperature from 12 to 32 degrees C resulted in a linear increase of glucocorticosteroid and aldosterone secretion. A highly significant positive correlation was found between glucocorticosteroid and aldosterone amounts secreted from adrenals superfused at temperatures between 1 and 35 degrees C (r = 0.91, n = 116, P less than 0.0001). Changes of flow rate from 0.5 to 1.5 ml/min for 5 min induced a short term (1 min) stimulation of glucocorticosteroid and aldosterone release; reduction of flow rate to 0.5 ml/min for 5 min drastically diminished secretion of steroids below control levels for 1 min.