The reproductive cycle of female Ballan wrasse Labrus bergylta in high latitude,temperate waters

This 2 year study examined the reproductive cycle of wild female Ballan wrasse Labrus bergylta in western Norway as a precursor to captive breeding trials. Light microscopy of ovarian histology was used to stage gonad maturity and enzyme‐linked immuno‐absorbent assay (ELISA) to measure plasma concentrations of the sex steroids testosterone (T) and 17β‐oestradiol (E₂). Ovarian recrudescence began in late autumn to early winter with the growth of previtellogenic oocytes and the formation of cortical alveoli. Vitellogenic oocytes developed from January to June and ovaries containing postovulatory follicles (POF) were present between May and June. These POF occurred simultaneously among other late maturity stage oocytes. Plasma steroid concentration and organo‐somatic indices increased over winter and spring. Maximal (mean ±s.e .) values of plasma T (0·95 ± 0·26 ng ml^?1), E₂ (1·75 ± 0·43 ng ml^?1) and gonado‐somatic index (I_G; 10·71 ± 0·81) occurred in April and May and decreased greatly in July when only postspawned fish with atretic ovaries occurred. Evidence indicates that L. bergylta are group‐synchronous multiple spawners with spawning occurring in spring and peaking in May. A short resting period may occur between late summer and autumn when previtellogenic oocytes predominate and steroid levels are minimal.     

Ovarian development and serum sex steroid and vitellogenin profiles in the female cultured sturgeon hybrid, the bester

Changes in serum levels of estradiol-17/J (E₂), testosterone (T), 17,20β-dihydroxy-4-pregnen-3-one (17,20β-P) and vitellogenin (VTG), in cultured adult female bester were examined in relation to ovarian development during a 1-year sampling period. Considerable variations in oocyte development were found among fish. Oocytes at previtellogenic stage (≥0–6mm in diameter) generally started to develop concomitantly with the degeneration of the first batch of oocytes. In vitellogenic individuals, ovaries were comprised of more advanced oocytes with diameter ranging from 0–6 to 2–6 mm and in the post-vitellogenic class, oocytes attained their largest size (>2–6mm) while the germinal vesicle was migrating towards the animal pole. Oocytes with a migrating nucleus were maintained during the winter period and massive degeneration started in April–May without germinal vesicle breakdown (GVBD) or ovulation occurring. Seasonal changes in E₂, T and VTG levels were well correlated with the advancement of oogenesis. Their levels increased during vitellogenesis, whereas in the post-vitellogenic (migratory nucleus) stage the levels of E₂ declined from 2–4 ng ml ^?1± to 1–2 ng ml ^?1 and VTG from 4–10 mg ml ^?1 to 0.–0.5 mg ml ^?1 while T levels remained high (50–60 ng ml ^?1). In contrast, serum levels of 17,20?-P were constantly low (less than 0.2 ng ml^?L) throughout the reproductive cycle. These results indicate that the time appropriate for induction of artificial reproduction would be from October–November to April–May when the oocytes are in the late Stages of the development.     

Synthesis and Antifungal Activities of Trichodermin Derivatives as Fungicides on Rice

Twenty new trichodermin derivatives, 2a – 5 , containing alkoxy, acyloxy, and Br groups in 4‐, 8‐, 9‐, 10‐ and 16‐positions were synthesized and characterized. The antifungal activities of the new compounds against rice false smut (Ustilaginoidea virens), rice sheath blight (Rhizoctonia solani), and rice blast (Magnaporthe grisea) were evaluated. The results of bioassays indicated that the antifungal activities were particularly susceptible to changes at 4‐, 8‐, and 16‐positions, but low to changes at 9‐ and 10‐positions. Most of these target compounds exhibited good antifungal activities at the concentration of 50 mg l^?1. Compound 4 (9‐formyltrichodermin; EC₅₀ 0.80 mg l^?1) with an CHO group at 9‐position displayed nearly the same level of antifungal activity against Ustilaginoidea virens as the commercial fungicide prochloraz (EC₅₀ 0.82 mg l^?1), while compound 3f ((8R)‐8‐{[(E)‐3‐phenylprop‐2‐enoyl]oxy}trichodermin; EC₅₀ 3.58 and 0.74 mg l^?1) with a cinnamyloxy group at C(8) exhibited much higher antifungal activities against Rhizoctonia solani and Magnaporthe grisea than the commercial fungicides prochloraz (EC₅₀ 0.96 mg l^?1) and propiconazole (EC₅₀ 5.92 mg l^?1), respectively. These data reveal that compounds 3f and 4 possess high antifungal activities and may serve as lead compounds for the development of fungicides in the future.     

Plasma estrogens,progesterone and chorionic gonadotropin in pregnant rhesus monkeys (Macaca mulatta) after ovariectomy

Maternal peripheral plasma concentrations of estrone (E₁), estradiol-17β (E₂), and progesterone (P) were determined in 4 rhesus monkey ovariectomized in early pregnancy (22–24 days). After ovariectomy, plasma concentrations of E₁ and E₂ were basal for 1 to 2 weeks. In contrast, slightly higher estrogen levels, which may be attributed to the ovaries, were found in intact pregnant monkeys. E₂ levels increased rapidly after this and exceeded those of E₁ until the 5th month of gestation. From that time until parturition, E₁ levels equaled or exceed those of E₂ in most instances. The pattern of P concentrations was similar to that observed in intact monkeys. Urinary chorionic gonadotropin (MCG) levels in ovariectomized monkeys were not significantly differen from those found in normal pregnancies. Thus, the patterns for circulating E_l, E₂ and P, as well as for the excretion of MCG,. after ovari-ectomy were remarkably similar to those found in intact, pregnant rhesus monkeys, indicating minimal ovarian influence.     

The effect of different kinds of electrolyte and non‐electrolyte solutions on the survival rate and morphology of zebrafish Danio rerio embryos

The effect of electrolyte and non‐electrolyte solutions on the survival and on the morphology of zebrafish Danio rerio embryos was investigated. Embryos in different ontogenetic stages were incubated in electrolyte (NaCl, KCl, MgCl₂ and CaCl₂) and non‐electrolyte solutions [sucrose and polyvinylalcohol (PVA)] of different concentrations for 5 – 15 min. The embryos were hatched to the long‐pec stage and the effective concentrations which caused a 50% decrease in embryo development (EC₅₀) were determined. The morphometric changes, which were caused by the test solutions, were measured. Ion channel blockers were used to see if active ion transport played a role for embryo survival. Finally, dechorionated embryos were exposed to the test solutions to get indications about the importance of chorion and perivitelline space. For 12 hours post fertilization (hpf) embryos and a 15 min exposure period, EC₅₀ was highest for MgCl₂ (1·60 mol l^?1), followed by sucrose (0·73 mol l^?1), NaCl (0·49 mol l^?1), KCl (0·44 mol l^?1), CaCl₂ (0·43 mol l^?1) and PVA [0·0005 mol l^?1 (2·2%)]. EC₅₀ were lower for early embryonic stages than for advanced stages for all solutions with exception of MgCl₂ and sucrose. At the EC₅₀, MgCl₂ and CaCl₂ solutions did not induce morphometric changes. NaCl and sucrose solutions induced reversible morphometric changes, which were compensated within 10 min. Only the EC₅₀ of KCl and PVA solutions induced permanent morphometric changes, which could not be compensated. Incubation of embryos in electrolyte and non‐electrolyte solutions together with ouabain (blocker of Na⁺– K⁺ ATPase), HgCl₃ (dose‐dependent inhibition of aquaporine channels), verapamil (inhibition of calcium and magnesium uptake) and amiloride (inhibition of sodium uptake) significantly decreased the per cent of embryos developing to the long‐pec stage in comparison to the same solutions without blockers. Ouabain and HgCl₃ also induced morphometric changes. For dechorionated embryos the survival rates in water and in the different test solutions were similar to untreated embryos.     

Gonadal development and sex steroids in a female Arctic charr broodstock

Gonadal development and plasma levels of sex steroids were investigated in female Arctic charr at 3-week intervals over a 12-month period. Circulating levels of oestradiol-17β (E₂), testosterone (T) and 17,20β-dihydroxy-4-pregnen-3-one (17,20β-P) were measured by radioimmunoassay, and gonadal status assessed through histological examination and measurement of gonadosomatic index (GSI) and frequency distribution of oocyte size-classes. Gonadal recrudescence during March-July was characterized by modest but insignificant increases in plasma levels of E₂ (2–4 ng ml^?1) and T (2–5 ng ml^?1) and recruitment of oocytes into yolk accumulation. Only a small and insignificant rise in GSI and no apparent increase in oocyte diameter occurred during this period, indicating that the rate of yolk formation and oocyte growth was low. Following transformation from stage V (peripheral yolk granule stage) to stage VI (yolk granule migration stage) in late July, the vitellogenic oocytes entered a phase of rapid growth which resulted in a marked rise in GSI until ovulation commenced in late September. Gonadal growth during this period was accompanied by increases in plasma levels of E₂ and T which peaked at 11 ± 1 (mid-August) and 71 ± 5ng ml^?1 (late September), respectively. The levels of both steroids dropped rapidly during final maturation and ovulation, followed by a surge in plasma levels of 17,20β-P which peaked at an average of 74 ± 17 ng ml^?1 in early October. All three steroids returned to basal levels within a month after ovulation, and all steroids, except E₂, remained low until March of the following year. A slight increase in E₂ detected in February and March during the second season may have been associated with recruitment into vitellogenesis of a new generation of oocytes. It is suggested that the abrupt increase in vitellogenesis in late July may reflect a condition-dependent decision to proceed with maturation, once the energy reserves have been repleted during spring-early summer.     

The gills as an important uptake route for the essential nutrient iron in freshwater rainbow trout Oncorhynchus mykiss

Short-term (3h) acquisition of iron (16 nmol ⁵⁹FeCl₃ l⁻¹) from oxic, alkaline fresh water was assessed in rainbow trout Oncorhynchus mykiss in the presence or absence of a range of iron chelators, all of which had differing binding affinities for ferric iron [100 μmol l⁻¹ of desferrioxamine (DFO), Log₁₀K₁ 32·5; citric acid Log₁₀K₁ 11·9; nitrilotriacetic acid (NTA) Log₁₀K₁ 15·9, CP20 and CP94 (Log₁₀K₁ > 30), as well as humic acid (HA), Log₁₀K₁ 5·04, 5 mg l⁻¹]. In the absence of chelators (control conditions) O. mykiss acquired iron from the water under laboratory lights (wavelength range of the lights 440–650 nm, peak intensity 548–626 nm) via the gill. In these conditions iron uptake onto the gill had a maximum transport capacity (J_max) of 11·2 pmol Fe g⁻¹ h⁻¹ (gill organ mass) and a K_m of 21·3 nmol Fe l⁻¹ h⁻¹. Furthermore, there were two components to iron accumulation into the carcass of these fish, a slow rate of aqueous iron uptake at low concentrations (6–24 nmol Fe l⁻¹), followed by a faster rate of uptake at higher iron concentrations (48–96 nmol Fe l⁻¹), suggesting that the rate-limiting step of iron uptake at low iron concentrations is the apical entry step. O. mykiss also acquired iron in the presence of HA, although the majority of the other chelators prevented iron uptake. Ultraviolet light (354 nm) treatment of Fe-DFO increased iron bioavailability. Results suggest that rainbow trout are able to access either the predicted very low concentrations (picomolar) of ferrous iron present in fresh water or the ferric oxide complexes present in oxic environments. The iron uptake rate measured (0·75 pmol g⁻¹ h⁻¹) would be sufficient to provide a substantial proportion (c. 85%) of the daily iron requirements of growing salmonid fry.     

Microbial processes of the carbon and sulfur cycles in the Chukchi Sea

The research performed in August 2004 within the framework of the Russian-American Long-term Census of the Arctic (RUSALCA) resulted in the first data concerning the rates of the key microbial processes in the water column and bottom sediments of the Bering strait and the Chukchi Sea. The total bacterial counts in the water column varied from 30 × 10³ cells ml^?1 in the northern and eastern parts to 245 × 10³ cells ml^?1 in the southern part. The methane content in the water column of the Chukchi sea varied from 8 nmol CH₄l^?1 in the eastern part of the sea to 31 nmol CH₄l^?1 in the northern part of the Herald Canyon. Microbial activity occurred in the upper 0–3 cm of the bottom sediments; the methane formation rate varied from 0.25 to 16 nmol CH₄dm^?3 day^?1. The rates of methane oxidation varied from 1.61 to 14.7 nmol CH₄dm^?3 day^?1. The rates of sulfate reduction varied from 1.35 to 16.2 μmol SO ₄ ^2? dm^?1 day^?1. The rate of methane formation in the sediments increased with depth, while sulfate reduction rates decreased (less than 1 μmol SO ₄ ^2? dm^?3 day^?1). These high concentrations of biogenic elements and high rates of microbial processes in the upper sediment layers suggest a specific type of trophic chain in the Chukchi Sea. The approximate calculated balance of methane emission from the water column into the atmosphere is from 5.4 to 57.3 μmol CH₄m^?2 day^?1.     

Increased synthesis of α‐tocopherol,paramylon and tyrosine by Euglena gracilis under conditions of high biomass production

Aims: To analyse the production of different metabolites by dark‐grown Euglena gracilis under conditions found to render high cell growth. Methods and Results: The combination of glutamate (5 g l^?1), malate (2 g l^?1) and ethanol (10 ml l^?1) (GM + EtOH); glutamate (7·15 g l^?1) and ethanol (10 ml l^?1); or malate (8·16 g l^?1), glucose (10·6 g l^?1) and NH₄Cl (1·8 g l^?1) as carbon and nitrogen sources, promoted an increase of 5·6, 3·7 and 2·6‐fold, respectively, in biomass concentration in comparison with glutamate and malate (GM). In turn, the production of α‐tocopherol after 120 h identified by LC‐MS was 3·7 ± 0·2, 2·4 ± 0·1 and 2 ± 0·1 mg [g dry weight (DW)]^?1, respectively, while in the control medium (GM) it was 0·72 ± 0·1 mg (g DW)^?1. For paramylon synthesis, the addition of EtOH or glucose induced a higher production. Amino acids were assayed by RP‐HPLC; Tyr a tocopherol precursor and Ala an amino acid with antioxidant activity were the amino acids synthesized at higher concentration. Conclusions: Dark‐grown E. gracilis Z is a suitable source for the generation of the biotechnologically relevant metabolites tyrosine, α‐tocopherol and paramylon. Significance and Impact of the Study: By combining different carbon and nitrogen sources and inducing a tolerable stress to the cell by adding ethanol, it was possible to increase the production of biomass, paramylon, α‐tocopherol and some amino acids. The concentrations of α‐tocopherol achieved in this study are higher than others reported previously for Euglena, plant and algal systems. This work helps to understand the effect of different carbon sources on the synthesis of bio‐molecules by E. gracilis and can be used as a basis for future works to improve the production of different metabolites of biotechnological importance by this organism.     

Radionuclides content in grape molasses soil samples from Central Black Sea region of Turkey

The activity concentrations of radionuclides in grape molasses soil samples collected from Zile (Tokat) plain in the Central Black Sea region of Turkey were measured by using gamma spectrometer with a NaI(Tl) detector. Also, the concentrations of ²²²Rn in soil samples and air were estimated essentially taking the activity concentrations of ²²⁶Ra measured in soil samples. Grape molasses soil samples with calcium carbonate content are used for sedimentation for making molasses in this region. The average activity concentrations of ²³²Th, ²²⁶Ra, ⁴⁰K, and ¹³⁷Cs were found as 62 ± 2, 68 ± 3, 479 ± 35, and 8.0 ± 0.3 Bq kg^?1, respectively. The average concentrations of ²²²Rn in soil samples and air were estimated to be 50 kBq m^?3 and 144 Bq m^?3. From the activity concentrations, absorbed gamma dose rate in outdoor air (D), annual effective dose from external exposure (E_E), annual effective dose from inhalation of radon (E_I), and excess lifetime cancer risk (ELCR) were estimated in order to assess radiological risks. The average values of D, E_E, E_I, and ELCR were found to be 90 nGy h^?1, 110 μSv y^?1, 1360 μSv y^?1, and 4 × 10^?4, respectively.     

Ventilatory and behavioural responses of the marbled sole Pseudopleuronectes yokohamae to progressive hypoxia

This study identified ventilatory and behavioural responses in the marbled sole Pseudopleuronectes yokohamae under experimentally induced progressive decreases in dissolved oxygen (DO) levels. Ventilation frequency showed an increase with decreasing DO levels from normoxia to 2·75 mg O₂ l^?1, followed by a decrease in ventilation frequency at decreased DO levels from 2·00 to 0·75 mg O₂ l^?1. At DO levels below 2·00 mg l^?1, behaviours at the bottom were suppressed, whereas avoidance behaviours increased. A decrease in avoidance behaviours was observed from 1·00 to 0·75 mg O₂ l^?1. Upside‐down reversal and incapacitation at DO levels of 1·00–0·75 mg O₂ l^?1 suggested that sublethal effects on P. yokohamae were induced. The responses observed before the sublethal DO level could be interpreted as an effort to maintain oxygen uptake, reduce routine activities and facilitate avoidance. The observed DO level thresholds that induce behavioural responses, in addition to sublethal effects, indicate hypoxia‐tolerance that is important for understanding the effects of hypoxia on coastal ecosystems.     

Impact of altering the water table height of an acidic fen on N2O and NO fluxes and soil concentrations

The impact of experimentally intensified summer drought and precipitation on N₂O and NO turnover and fluxes was investigated in a minerotrophic fen over a 2‐year period. On three treatment plots, drought was induced for 6 and 10 weeks by means of roofs and drainage and decreased water table levels by 0.1–0.3 m compared with three nonmanipulated control plots. When averaged over the three treatment plots, both N₂O and NO emission showed only little response to the drought. On the single plot scale, however, a clear impact of the treatment on N₂O and NO fluxes could be identified. On the plot with the weakest water table reduction hardly any response could be observed, while on the plot with the greatest drainage effect, N₂O and NO fluxes increased by 530% and 270%, respectively. Rewetting reduced NO emissions to background levels (0.05–0.15 μmol m^?2 h^?1), but heavily enhanced N₂O emission (18–36 μmol m^?2 h^?1) for several days in the plots with largest water table reduction. These peaks contributed up to 40% to the cumulative N₂O fluxes and were caused by rapid N₂O production according to isotope abundance data. According to N₂O concentrations and isotope abundance analysis N₂O was mostly produced at depths between 0.3 and 0.5 m. During water table reduction net N₂O production in 0.1 m depth steadily increased in the most effectively dried plot from 2 up to 44 pmol cm^?3 day^?1. Rewetting immediately increased net N₂O production in the topsoil of the drought plots, showing rates of 18–174 pmol cm^?3 day^?1. This study demonstrates that drought and rewetting can temporarily increase N₂O emission to levels that have to date only been reported from nutrient rich and degraded fens that have been drained for agricultural purposes.     

Gonadogenesis in early developmental stages of Acipenser naccarii and influence of estrogen immersion on feminization

Gonad development processes and the effects of a single 8‐hour immersion treatment with 17β‐estradiol (E2, 400 μg L⁻¹) on sex differentation in the Adriatic sturgeon, Acipenser naccarii, were investigated. After migration of germ cells, gonadal ridges appeared in 16‐ to 18‐day old larvae and undifferentiated gonads in 55‐ to 60‐day old larvae. Putative ovaries with notches in the germinal epithelium and presumed testes with smooth germinal epithelium appeared in 180–185‐day old juveniles. Ovaries with proliferating oogonia and early meiotic oocytes clusters were observed in 292‐day old juveniles. Testes did not exhibit germ cell mitosis until 430 days of age. Developmental stages in E₂‐treated animals closely followed those of controls up to 430 days. The treatment significantly increased the percentage of ovaries when administered to embryos about 1.5 day before hatching, while did not significantly altered the normal 1/1 sex ratio when administered to 1.5‐day old pre‐larvae and 10‐day old larvae. It is likely that in A. naccarii exogenous E₂ administration may act through a feedback mechanism of self‐supporting steroid production and that steroids are the physiological inducers of sex differentiation, as in most teleosts. The E₂‐immersion treatment, easier than time‐consuming administration through food, could be a good approach to control sex differentiation and caviar production.     

Excessive ovarian follicular development in pregnant pigtailed macaques (Macaca nemestrina)

To evaluate the status and possible control of ovarian follicular development during pregnancy, circulating levels of estrone (E₁), estradiol-17β (E₂), and follicle-stimulating hormone (FSH) were measured throughout gestation in both intact and ovariectomized pregnant pigtailed monkeys (Macaca nemestrina). From an additional group of pregnant monkeys, ovaries were obtained at late gestation (on day 150 or 159 of pregnancy) for histological studies. Circulating concentrations of E₁ and E₂ increased on day 13 and remained elevated for about 10 days; they then declined and reached low levels on day 32 of gestation. After day 60, there were gradual but smaller increases in estrogen levels to day 140, after which both E₁ and E₂ levels increased significantly, reaching maximum levels (E₁ = 832.2 ± 210.8 pg/ ml; E₂ = 1.66 ± 0.32 ng/ml) at the end of pregnancy. Removal of ovaries on day 35 of gestation did not affect pregnancy or the pattern of estrogen secretion. Serum concentrations of FSH demonstrated only minor fluctuations during pregnancy but were similar to those found during the early follicular phase of cycling pigtailed monkeys investigated in this study. Ovarian histology revealed extensive follicular growth; in addition to the corpus luteum of pregnancy, ovaries were packed with pre-antral, small antral, and medium-sized Graafian follicles. Some of these follicles appeared to be cystic and showed various degree of atresia; their general appearance was similar to the follicles of human females with polycystic ovary syndrome. Our data suggest that FSH may initiate ovarian follicular growth during gestation. High levels of estrogens were incapable of suppressing FSH secretion but may be responsible for the induction of atresia in a large number of follicles in pregnant pigtailed monkeys.     

Characterizing the escape response of juvenile summer flounder Paralichthys dentatus to diel‐cycling hypoxia

Swimming speed, angular correlation and expected displacement were measured in juvenile summer flounder Paralichthys dentatus acclimated to either oxygen saturation (c. 7·8 mg O₂ l^?1; saturation‐acclimated fish) or diel‐cycling hypoxia (cycling between 11·0 and 2·0 mg O₂ l^?1) for 10 days and subsequently exposed to more severe diel‐cycling hypoxia (cycling between 7·0 and 0·4 mg O₂ l^?1). Saturation‐acclimated P. dentatus exhibited an active response to declining dissolved oxygen (DO) by increasing swimming speed, angular correlation and expected displacement to peak levels at 1·4 mg O₂ l^?1 that were 3·5, 5·5 and 4·2 fold, respectively, greater than those at DO saturation. Diel‐cycling hypoxia‐acclimated P. dentatus also exhibited an active response to declining DO, although it was relatively less pronounced. Diel‐cycling hypoxia‐acclimated P. dentatus swimming speed, however, still doubled as DO decreased from 7·0 to 2·8 mg O₂ l^?1. Diel‐cycling hypoxia‐acclimated P. dentatus did not recover as well from low DO exposure as did saturation‐acclimated fish. This was reflected in their relatively more random swimming (low angular correlation between successive moves) and poor maintenance of rank order between individuals during the recovery phase. Even saturation‐acclimated P. dentatus did not resume swimming at speeds observed at saturation until DO was 4·2 mg O₂ l^?1. Paralichthys dentatus were very sensitive to decreasing DO, even at DO levels that were not lethal or growth limiting. This sensitivity and their poor recovery may preclude juvenile P. dentatus from using highly productive nursery habitats affected by diel‐cycling hypoxia.     

Calcium‐dependent behavioural responses to acute copper exposure in Oncorhynchus mykiss

Using rainbow trout Oncorhynchus mykiss, the present study demonstrated that: (1) calcium (Ca) increased the range of copper (Cu) concentrations that O. mykiss avoided; (2) Ca conserved the maintenance of pre‐exposure swimming activity during inescapable acute (10 min) Cu exposure. Data showed that when presented with a choice of Cu‐contaminated water (ranging from 0 to 454 µg Cu l^?1) and uncontaminated water in a choice tank, O. mykiss acclimated and tested at low Ca concentration (3 mg Ca l^?1) avoided the 10 µg Cu l^?1 only. By contrast, O. mykiss acclimated and tested at high Ca concentration (158 mg Ca l^?1) avoided all the Cu concentrations ≥37 µg l^?1. The Cu avoidance was connected with increased spontaneous swimming speed in the Cu‐contaminated water. When subjected to inescapable Cu exposure (35 µg Cu l^?1), O. mykiss acclimated and tested at low Ca concentration reduced their spontaneous swimming speed, whereas no response was observed in O. mykiss acclimated and tested at high Ca concentration. Collectively, the data support the conclusion that in O. mykiss the behavioural responses to acute Cu exposure are Ca‐dependent.     

Prostaglandins inhibit testosterone secretion by mouse testes in vitro

Production of testosterone (T) by decapsulated mouse testes in vitro was significantly inhibited by adding prostaglanain (PG) A₁, PGA₂ or PGE₁ to the incubation medium. Prostaglandin A₁ at a concentration of 10^?6M inhibited T production in this system both in the presence of moderate amounts of hCG (12.5 or 25.0 mIU/ml), and in the absence of gonadotropins. However, in the presence of very high levels of hCG (125.0 mIU/ml), all PGs tested appeared to have had a slight potentiating effect on T production when added in concentrations ranging from 10^?7 to 10^?5M, and the inhibition of T accumulation in the medium was consistently observed only when the concentration of PGs was increased to 10^?3M. These results suggest that a direct effect of PGs on testicular steroidogenesis may account for, or contributes to, the decrease in peripheral T levels observed after administration of PGs in vivo.     

Decomposition of soybean grown under elevated concentrations of CO2 and O3

A critical global climate change issue is how increasing concentrations of atmospheric CO₂ and ground‐level O₃ will affect agricultural productivity. This includes effects on decomposition of residues left in the field and availability of mineral nutrients to subsequent crops. To address questions about decomposition processes, a 2‐year experiment was conducted to determine the chemistry and decomposition rate of aboveground residues of soybean (Glycine max (L.) Merr.) grown under reciprocal combinations of low and high concentrations of CO₂ and O₃ in open‐top field chambers. The CO₂ treatments were ambient (370 μmol mol^?1) and elevated (714 μmol mol^?1) levels (daytime 12 h averages). Ozone treatments were charcoal‐filtered air (21 nmol mol^?1) and nonfiltered air plus 1.5 times ambient O₃ (74 nmol mol^?1) 12 h day^?1. Elevated CO₂ increased aboveground postharvest residue production by 28–56% while elevated O₃ suppressed it by 15–46%. In combination, inhibitory effects of added O₃ on biomass production were largely negated by elevated CO₂. Plant residue chemistry was generally unaffected by elevated CO₂, except for an increase in leaf residue lignin concentration. Leaf residues from the elevated O₃ treatments had lower concentrations of nonstructural carbohydrates, but higher N, fiber, and lignin levels. Chemical composition of petiole, stem, and pod husk residues was only marginally affected by the elevated gas treatments. Treatment effects on plant biomass production, however, influenced the content of chemical constituents on an areal basis. Elevated CO₂ increased the mass per square meter of nonstructural carbohydrates, phenolics, N, cellulose, and lignin by 24–46%. Elevated O₃ decreased the mass per square meter of these constituents by 30–48%, while elevated CO₂ largely ameliorated the added O₃ effect. Carbon mineralization rates of component residues from the elevated gas treatments were not significantly different from the control. However, N immobilization increased in soils containing petiole and stem residues from the elevated CO₂, O₃, and combined gas treatments. Mass loss of decomposing leaf residue from the added O₃ and combined gas treatments was 48% less than the control treatment after 20 weeks, while differences in decomposition of petiole, stem, and husk residues among treatments were minor. Decreased decomposition of leaf residues was correlated with lower starch and higher lignin levels. However, leaf residues only comprised about 20% of the total residue biomass assayed so treatment effects on mass loss of total aboveground residues were relatively small. The primary influence of elevated atmospheric CO₂ and O₃ concentrations on decomposition processes is apt to arise from effects on residue mass input, which is increased by elevated CO₂ and suppressed by O₃.     

Optimization of l‐DOPA production by Brevundimonas sp. SGJ using response surface methodology

l ‐DOPA (3,4‐dihydroxyphenyl‐l ‐alanine) is an extensively used drug for the treatment of Parkinson's disease. In the present study, optimization of nutritional parameters influencing l ‐DOPA production was attempted using the response surface methodology (RSM) from Brevundimonas sp. SGJ. A Plackett–Burman design was used for screening of critical components, while further optimization was carried out using the Box–Behnken design. The optimized levels of factors predicted by the model were pH 5.02, 1.549 g l^?1 tryptone, 4.207 g l^?1 l ‐tyrosine and 0.0369 g l^?1 CuSO₄, which resulted in highest l ‐DOPA yield of 3.359 g l^?1. The optimization of medium using RSM resulted in a 8.355‐fold increase in the yield of l ‐DOPA. The anova showed a significant R² value (0.9667), model F‐value (29.068) and probability (0.001), with insignificant lack of fit. The highest tyrosinase activity observed was 2471 U mg^?1 at the 18th hour of the incubation period with dry cell weight of 0.711 g l^?1. l ‐DOPA production was confirmed by HPTLC, HPLC and GC‐MS analysis. Thus, Brevundimonas sp. SGJ has the potential to be a new source for the production of l ‐DOPA.     

A highly active phosphoglucomutase from Clostridium thermocellum: cloning, purification, characterization and enhanced thermostability

Aims: Discovery and utilization of highly active and thermostable phosphoglucomutase (PGM) would be vital for biocatalysis mediated by multiple enzymes, for example, high‐yield production of enzymatic hydrogen. Methods and Results: The thermophilic cellulolytic bacterium Clostridium thermocellum was hypothesized to have a very active PGM because of its key role in microbial cellulose utilization. The Cl. thermocellum ORF Cthe1265 encoding a putative PGM was cloned and expressed in Escherichia coli. The purified enzyme appeared to be a monomer with an estimated molecular weight of 64·9 kDa. This enzyme was found to be a dual‐specificity enzyme – PGM/phosphomannomutase (PMM). Mg²⁺ and Mn²⁺ were activators. Ser144 was identified as an essential catalytic residue through site‐directed mutagenesis. The k_cat and K_m of PGM were 190 s^?1 and 0·41 mmol l^?1 on glucose‐1‐phosphate and 59 s^?1 and 0·44 mmol l^?1 on mannose‐1‐phosphate, respectively, at 60°C. Thermostability of PGM at a low concentration (2 nmol l^?1, 100 U l^?1) was enhanced by 12‐fold (i.e. t_1/2 = 72 h) at 60°C with addition of bovine serum albumin, Triton X‐100, Mg²⁺and Mn²⁺. Conclusions: The ORF Cthe1265 was confirmed to encode a PGM with PMM activity. This enzyme was the most active PGM reported. Significance and Impact of the Study: This highly active PGM with enhanced thermostability would be an important building block for in vitro synthetic biology projects (complicated biotransformation mediated by multiple enzymes in one pot).