Vertical seed dispersal by earthworms: a quantitative approach

Earthworms are supposed to play an important role in the dynamics of the soil seed bank, however, experimental evidence and quantitative data are scarce To evaluate the impact of the earthworm species Lumbricus terrains L on the vertical transport of seeds in the soil, laboratory experiments have been earned out Moreover, the worm casts produced and their seed content have been quantified in two chalk grassland sites during one year
The experiment on seed transport has been earned out in cylinders with controlled numbers of worms and seeds at different depths in stenlized soil Seeds used in this experiment proved to be eaten by the earthworms in preceding palatability tests A significant translocation of the seeds in the cylinders with earthworms was recorded after an eight-week period In spring earthworm activity was mainly found m the upper soil layers in the cylinders, whereas in summer the activity was spread over a larger vertical distance The amount of worm casts collected on permanently marked plots in two different chalk grasslands was very high a minimal quantity of c 750 g nr² of worm casts were produced yearly The number of germinative seeds brought to the soil surface by worm casts was at least 60-100 nr² each year This means that earthworm activity has a substantial impact on the soil seed bank dynamics and hence on the possibility of plant recruitment in this species-nch ecosystem     

The numbers of viable myxomycete cells in the alimentary tracts of earthworms and in earthworm casts

The numbers of 'plasmodium-forming units' (PFUs) of myxomycetes (mycetozoa or myxogastrids) in worm casts and soil were estimated by a most-probable-number method. Casts contained about five times more PFUs g dry wt˜' than did adjacent non-cast soil. Gut contents contained similar numbers to non-cast soil, but the proportion which was freezing resistant (and presumably in a resting stage) was greater. Numbers of PFUs in incubated worm casts increased rapidly, then fell. This transient increase probably accounts for the generally higher number observed in natural casts. Earthworms may serve as vectors of myxomycetes in soil.     

Effect of the Earthworms Lumbricus terrestris and Aporrectodea caliginosa on Bacterial Diversity in Soil

Earthworms ingest large amounts of soil and have the potential to radically alter the biomass, activity, and structure of the soil microbial community. In this study, the diversity of eight bacterial groups from fresh soil, gut, and casts of the earthworms Lumbricus terrestris and Aporrectodea caliginosa were studied by single-strand conformation polymorphism (SSCP) analysis using both newly designed 16S rRNA gene-specific primer sets targeting Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Deltaproteobacteria, Bacteroidetes, Verrucomicrobia, Planctomycetes, and Firmicutes and a conventional universal primer set for SSCP, with RNA and DNA as templates. In parallel, the study of the relative abundance of these taxonomic groups in the same samples was performed using fluorescence in situ hybridization. Bacteroidetes, Alphaproteobacteria, and Betaproteobacteria were predominant in communities from the soil and worm cast samples. Representatives of classes Flavobacteria and Sphingobacteria (Bacteroidetes) and Pseudomonas spp. (low-abundant Gammaproteobacteria) were detected in soil and worm cast samples with conventional and taxon-targeting SSCP and through the sequence analysis of 16S rRNA clone libraries. Physiologically active unclassified Sphingomonadaceae (Alphaproteobacteria) and Alcaligenes spp. (Betaproteobacteria) also maintained their diversities during transit through the earthworm intestine and were found on taxon-targeting SSCP profiles from the soil and worm cast samples. In conclusion, our results suggest that some specific bacterial taxonomic groups maintain their diversity and even increase their relative numbers during transit through the gastrointestinal tract of earthworms.     

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.     

Catalytic power of enzymes decreases with temperature: New insights for understanding soil C cycling and microbial ecology under warming

Most current models of soil C dynamics predict that climate warming will accelerate soil C mineralization, resulting in a long‐term CO₂ release and positive feedback to global warming. However, ecosystem warming experiments show that CO₂ loss from warmed soils declines to control levels within a few years. Here, we explore the temperature dependence of enzymatic conversion of polymerized soil organic C (SOC) into assimilable compounds, which is presumed the rate‐limiting step of SOC mineralization. Combining literature review, modelling and enzyme assays, we studied the effect of temperature on activity of enzymes considering their thermal inactivation and catalytic activity. We defined the catalytic power of enzymes (E_power) as the cumulative amount of degraded substrate by one unit of enzyme until its complete inactivation. We show a universal pattern of enzyme's thermodynamic properties: activation energy of catalytic activity (EA_cat) < activation energy of thermal inactivation (EA_inact). By investing in stable enzymes (high EA_inact) having high catalytic activity (low EA_cat), microorganisms may maximize the E_power of their enzymes. The counterpart of such EAs’ hierarchical pattern is the higher relative temperature sensitivity of enzyme inactivation than catalysis, resulting in a reduction in E_power under warming. Our findings could explain the decrease with temperature in soil enzyme pools, microbial biomass (MB) and carbon use efficiency (CUE) reported in some warming experiments and studies monitoring the seasonal variation in soil enzymes. They also suggest that a decrease in soil enzyme pools due to their faster inactivation under warming contributes to the observed attenuation of warming effect on soil C mineralization. This testable theory predicts that the ultimate response of SOC degradation to warming can be positive or negative depending on the relative temperature response of E_power and microbial production of enzymes.     

Chemical equilibrium and E value of Zn (ZnE) in inceptisols and entisols of tropical india

Summary The chemical equilibrium and E value for Zn was calculated in 9 soils of Haryana (India) which represented mainly entisol and inceptisols. The rate of isotopic exchange between⁶⁵Zn and native soil Zn was quite rapid and radioactivity reduced to about 0.2 per cent of initial activity after 3 days but total Zn concentration in soil solution did not decrease. In 5 out of 9 soils equilibrium was established in 2 to 3 days. In typic ustochrepts having high clay content (3,4) equilibrium was attained in two days. In typic udipsamments (2), typic camborthids (8) and aquic vertic ustichrepts (9) it took 3 days to set equilibrium. Typic ustochrepts (5) took 5 days for equilibrium whereas typic ustipssaments (6) and typic camborthids of high O.C. did not attain equilibrium even in 7 days. This indicated that the chemistry and availability of Zn in soil would depend on soil types. When Zn_E was estimated by applying activity after equilibrium with carrier Zn and by applying activity with carrier Zn before equilibrium was set, there was no agreement in Zn_E in two methods. Increasing Zn_E with increasing Zn dose was observed by both methods only in alkaline typic ustochrept (4). In some soils higher E values than added amounts were observed, whereas, in soil 8 negative E values were obtained. The E values become erratic and are over estimated where complex reactions take place due to high pH, high O.C. and high complex forming elements.     

Action of androgen and estrone implants on sexual behavior and reproductive organs of castrated male rabbits

Sexually mature but inexperienced male rabbits were castrated, immediately implanted with either testosterone (T), estrone (E₁), dihydrotestosterone (DHT), T + E₁, or DHT + E₁, and tested for male sexual behavior. Other castrates were not implanted, and testing was either begun immediately (Ca-I) or delayed for 4 weeks (Ca-D). Intact males served as controls (C). Latency to mount a teaser female and to ejaculate into an artificial vagina was tested twice in a morning three times per week for 8 weeks. Then, animals were sacrificed, and reproductive organs were measured. The Ca-I group responded slowly to sexual training and ceased nearly all sexual activity by 8 weeks, whereas the Ca-D males seldom displayed interest in the teaser female. Intact controls and the T and T + E₁, groups all responded to the teaser and mounted and ejaculated within a few seconds. DHT and E₁, individually maintained the sexual activity of castrates equivalent to that of C for 4–5 weeks, but the time required to mount and, particularly, to ejaculate increased thereafter. The results with DHT + E₁ were equivocal in that castrates with this hormone combination sustained sexual activity equivalent to that of the controls for 7 weeks, but one animal in particular became sexually inactive the last week of the experiment. Penis weight was at least partially maintained in all implanted castrates. Accessory sex gland weight was smallest in the DHT group and was significantly increased in the T + E₁ and DHT + E₁ groups. The largest ejaculates of fluid were obtained in the group receiving E₁ alone. These results may be interpreted to indicate a role of both androgen and estrogen centrally and peripherally in the rabbit.     

Nutrient availability and maize growth in a soil amended with earthworm casts from a South African indigenous species

The study was undertaken to assess the availability to maize of nutrients from earthworm casts (wormcasts) collected from a grazing paddock in the Eastern Cape province of South Africa. Maize (cv PAN 473) was grown in pots filled with ground wormcasts, non-casted surrounding soil and a mixture of the two media. Fertiliser application increased growth and uptake of nutrients by maize grown on both wormcast and non-casted soil. Maize grown on wormcasts had significantly (p < 0.05) higher plant height, stem diameter, dry weight and showed higher nutrient uptake and lower fertiliser response than that grown on corresponding non-casted surface soil. The uptakes of plant nutrients, growth and dry matter yields were in the order fertiliser>wormcasts>non-casted soil. Mixing worm casts with non-casted soil improved maize growth and nutrient uptake over non-casted soil. It is concluded that wormcasts could be used as a soil amendment for crop production, especially in small-scale production systems.     

Interactions of prostaglandins with subpopulations of ovine luteal cells. I. Stimulatory effects of prostaglandins E1, E2 and I21

Preparations of small and large steroidogenic cells from enzymatically dispersed ovine corpora lutea were utilized to study the $\text{in}$$\text{vitro}$ effects of luteinizing hormone (LH) and prostaglandins (PG) E₁, E₂ and I₂. Cells were allowed to attach to culture dishes overnight and were incubated with either LH (100 ng/ml), PGE₂, PGE₂, or PGI₂ (250 ng/ml each). The secretion of progesterone by large cells was stimulated by all prostaglandins tested (P < 0.05) while the moderate stimulation observed after LH treatment was attributable to contamination of the large cell population with small cells. Prostaglandins E₁ and E₂ had no effect on progesterone secretion by small cells, while LH was stimulatory at all times (0.5 to 4 hr) and PGI₂ was stimulatory by 4 hr. Additional studies were conducted to determine if the effects of PGE₂ upon steroidogenesis in large cells were correlated with stimulated activity of adenylate cyclase. In both plated and suspended cells PGE₂ caused an increase (P < 0.05) in the rate of progesterone secretion but had no effect upon the activity of adenylate cyclase or cAMP concentrations within cells or in the incubation media. Exposure of luteal cells to forskolin, a nonhormonal stimulator of adenylate cyclase, resulted in marked increases in all parameters of cyclase activity but had no effect on progesterone secretion. These data suggest that the actions of prostaglandins E₁, E₂ and I₂ are directed primarily toward the large cells of the ovine corpus luteum and cast doubt upon the role of adenylate cyclase as the sole intermediary in regulation of progesterone secretion in this cell type.     

Effects of plant species on phosphorus availability in a range of grassland soils

Vegetative conversion from grass to forest may influence soil nutrient dynamics and availability. A short-term (40 weeks) glasshouse experiment was carried out to investigate the impacts of ryegrass (Lolium perenne) and radiata pine (Pinus radiata) on soil phosphorus (P) availability in 15 grassland soils collected across New Zealand using ³³P isotopic exchange kinetics (IEK) and chemical extraction methods. Results from this study showed that radiata pine took up more P (4.5–33.5 mg P pot^–1) than ryegrass (1.1–15.6 mg pot^–1) from the soil except in the Temuka soil in which the level of available P (e.g., E _1min P_i, bicarbonate extractable P_i) was very high. Radiata pine tended to be better able to access different forms of soil P, compared with ryegrass. There were no significant differences in the level of water soluble P (Cp, intensity factor) between soils under ryegrass and radiata pine, but the levels of Cp were generally lower compared with original soils due to plant uptake. The growth of both ryegrass and radiata pine resulted in the redistribution of soil P from the slowly exchangeable P_i pool (E _{> 10m} P_i, reduced by 31.8% on the average) to the rapidly exchangeable P_i (E _1min-1d P_i, E _1d-10m P_i) pools in most soils. The values of R/r ₁ (the capacity factor) were also generally greater in most soils under radiata pine compared with ryegrass. Specific P mineralisation rates were significantly greater for soils under radiata pine (8.4–21.9%) compared with ryegrass (0.5–10.8%), indicating that the growth of radiata pine enhanced mineralisation of soil organic P. This may partly be ascribed to greater root phosphatase activity for radiata pine than for ryegrass. Plant species × soil type interactions for most soil variables measured indicate that the impacts of plant species on soil P dynamics was strongly influenced by soil properties.     

Interactions of prostaglandins with subpopulations of ovine luteal cells. I. Stimulatory effects of prostaglandins E1, E2 and I2

Preparations of small and large steroidogenic cells from enzymatically dispersed ovine corpora lutea were utilized to study the effects of luteinizing hormone (LH) and prostaglandins (PG) E₁, E₂ and I₂. Cells were allowed to attach to culture dishes overnight and were incubated with either LH (100 ng/ml), PGE₂, PGE₂, or PGI₂ (250 ng/ml each). The secretion of progesterone by large cells was stimulated by all prostaglandins tested (P < 0.05) while the moderate stimulation observed after LH treatment was attributable to contamination of the large cell population with small cells. Prostaglandins E₁ and E₂ had no effect on progesterone secretion by small cells, while LH was stimulatory at all times (0.5 to 4 hr) and PGI₂ was stimulatory by 4 hr. Additional studies were conducted to determine if the effects of PGE₂ upon steroidogenesis in large cells were correlated with stimulated activity of adenylate cyclase. In both plated and suspended cells PGE₂ caused an increase (P < 0.05) in the rate of progesterone secretion but had no effect upon the activity of adenylate cyclase or cAMP concentrations within cells or in the incubation media. Exposure of luteal cells to forskolin, a nonhormonal stimulator of adenylate cyclase, resulted in marked increases in all parameters of cyclase activity but had no effect on progesterone secretion. These data suggest that the actions of prostaglandins E₁, E₂ and I₂ are directed primarily toward the large cells of the ovine corpus luteum and cast doubt upon the role of adenylate cyclase as the sole intermediary in regulation of progesterone secretion in this cell type.     

Changes in Morphology of J774.1 Macrophage-like Cells and Release of Prostaglandin E2 Induced by Bacterial Acidic Polysaccharides

In an attempt to finding polysaccharides with immunostimulating activity, we isolated 14 bacteria that produced polysaccharides from soil. The polysaccharides produced by these bacteria and by strains kept in this laboratory and commercial polysaccharides were tested for ability to activate J774.1 macrophage-like mouse cells. Acidic polysaccharides, especially those from the newly isolated bacteria, induced spreading of the cells and release of prostaglandin E₂ from the cells, which are manifestations of a state of activation. The prostaglandin E₂-releasing activity of the polysaccharides was 1/10 to 1/20 on a weight basis of that of Escherichia coli lipopolysaccharide, a potent immunostimulant.     

Response of transpiration to rain pulses for two tree species in a semiarid plantation

Responses of transpiration (E _c) to rain pulses are presented for two semiarid tree species in a stand of Pinus tabulaeformis and Robinia pseudoacacia. Our objectives are to investigate (1) the environmental control over the stand transpiration after rainfall by analyzing the effect of vapor pressure deficit (VPD), soil water condition, and rainfall on the post-rainfall E _c development and recovery rate, and (2) the species responses to rain pulses and implications on vegetation coverage under a changing rainfall regime. Results showed that the sensitivity of canopy conductance (G _c) to VPD varied under different incident radiation and soil water conditions, and the two species exhibited the same hydraulic control (?dG _c/dlnVPD to G _cref ratio) over transpiration. Strengthened physiological control and low sapwood area of the stand contributed to low E _c. VPD after rainfall significantly influenced the magnitude and time series of post-rainfall stand E _c. The fluctuation of post-rainfall VPD in comparison with the pre-rainfall influenced the E _c recovery. Further, the stand E _c was significantly related to monthly rainfall, but the recovery was independent of the rainfall event size. E _c enhanced with cumulative soil moisture change (ΔVWC) within each dry–wet cycle, yet still was limited in large rainfall months. The two species had different response patterns of post-rainfall E _c recovery. E _c recovery of P. tabulaeformis was influenced by the pre- and post-rainfall VPD differences and the duration of rainless interval. R. pseudoacacia showed a larger immediate post-rainfall E _c increase than P. tabulaeformis did. We, therefore, concluded that concentrated rainfall events do not trigger significant increase of transpiration unless large events penetrate the deep soil and the species differences of E _c in response to pulses of rain may shape the composition of semiarid woodlands under future rainfall regimes.     

Quantitative observations on the population ecology of Branchiura sowerbyi (Oligochaeta,Tubificidae)

Cohorts of Branchiura sowerbyi were reared at different temperatures and initial population densities in order to obtain data suitable for the interpretation of population dynamics in field populations. Percent hatching from cocoons reaches its maximum at 25 °C and decreases towards lower and higher temperatures. Embryonic development time, T_E, was measured and the relative threshold temperature, 10 °C, calculated by extrapolation. The degree day requirement for embryo development is 195 °C d. The time of first cocoon laying (T_gm) was observed and the ratio T_E/T_gm was seen to fit with that of other tubificid species cultured so far. Embryo mortality is rather high, while worm mortality is low or very low. Fecundity increases from 15 to 20 °C but decreases at 25 °C. A mathematical model for the simulation of population densities with four size-stage compartments is suggested. It could be used for the optimization of worm uptake (simulated as stage specific mortality) in mass cultures reared for the production of Branchiura, to be used as food for fish fingerlings.     

Sensitivity of canopy transpiration to altered precipitation in an upland oak forest: evidence from a long-term field manipulation study

Climate‐induced changes in regional precipitation could have important implications for the carbon, water, and nutrient cycles of forest ecosystems. However, few studies have examined the response of deciduous forests to increases or decreases in precipitation. Therefore, the throughfall displacement experiment (TDE) was established in 1993 near Oak Ridge, Tennessee to examine the sensitivity of an upland oak (Quercus spp.) forest to ambient, wet (+33%), and dry (?33%) precipitation regimes. Sap flux measurements on co‐occurring tree species were scaled using species‐specific estimates of stand sapwood area to derive daily and seasonal rates of canopy transpiration (E_C) from 2000 to 2003. With the exception of 2003, which was an extremely wet year, daily E_C in the dry plot, and occasionally during extended droughts in the ambient and wet plots, declined as water potential in the upper 0.35 m soil profile approached ‐3.0 MPa. Seasonal patterns of soil water potential and treatment‐specific differences in E_C were dependent on precipitation frequency and intensity. Supplemental precipitation added to the wet plot increased seasonal E_C on average by 9% (range ?1% to 19%), whereas extended periods of drought on the dry plot in 2000, 2001, and 2002 were sufficient to reduce seasonal E_C by 26–30% compared with the ambient plot. There was a strong correlation between seasonal E_C and the water stress integral, a cumulative index of drought severity and duration. A polynomial fitted to these data indicated that reductions in seasonal E_C on the order of 40% were possible given TDE‐imposed reductions in soil water potential. Application of this equation to all years of the TDE (1994–2003) revealed considerable interannual and treatment‐specific variation in canopy transpiration. In general, a 33% removal of throughfall on the dry plot during 1995, 1998, and 2002 resulted in a 23–32% reduction in seasonal E_C compared with the ambient plot. While droughts in deciduous forests are often limited in duration and tend to occur late in the growing season, soil water deficits of the magnitude observed in this study have the potential to impact local and regional forest water budgets.     

The membrane effects of 17β-estradiol on chondrocyte phenotypic expression are mediated by activation of protein kinase C through phospholipase C and G-proteins

Growth plate chondrocytes from both male and female rats have nuclear receptors for 17β-estradiol (E₂); however, recent studies indicate that an alternative pathway involving a membrane receptor may also be involved in the female cell response. E₂ directly affects the fluidity of chondrocyte membranes derived from female, but not male, rats. In addition, E₂ activates PKC in a nongenomic manner in female cells, and chelerythrine, a specific inhibitor of PKC, inhibits E₂-dependent alkaline phosphatase activity in these cells, indicating PKC is involved in the signal transduction mechanism. The aims of this study were: (1) to examine if PKC mediates the effect of E₂ on chondrocyte proliferation, differentiation, and matrix synthesis; and (2) to determine the pathway that mediates the membrane effect of E₂ on PKC. Confluent, fourth passage resting zone (RC) and growth zone (GC) chondrocytes from female rat costochondral cartilage were treated with 10⁻¹⁰ to 10⁻⁷ M E₂ in the presence or absence of the PKC inhibitor chelerythrine, and changes in alkaline phosphatase specific activity, proteoglycan sulfation, and [³H]thymidine incorporation were measured. To examine the pathway of PKC activation, chondrocyte cultures were treated with E₂ in the presence or absence of genistein (an inhibitor of tyrosine kinases), U73122 or D609 (inhibitors of phospholipase C [PLC]), quinacrine (an inhibitor of phospholipase A₂ [PLA₂]), and melittin (an activator of PLA₂). Alkaline phosphatase specific activity and proteoglycan sulfation were increased and [³H]thymidine incorporation was decreased by E₂. The effects of E₂ on all parameters were blocked by chelerythrine. Treatment of the cultures with E₂ produced a significant dose-dependent increase in PKC. U73122 dose-dependently inhibited the activation of PKC in E₂-stimulated female chondrocyte cultures. However, the classical receptor antagonist ICI 182780 was unable to block the stimulatory effect of E₂ on PKC. Moreover, the classical receptor agonist diethylstilbestrol (DES) had no effect on PKC, nor did it alter the stimulatory effect of E₂. Inhibition of tyrosine kinase and PLA₂ had no effect on the activation of PKC by E₂. The PLA₂ activator also had no effect on PKC activation by E₂. E₂ stimulated PKC activity in membranes isolated from the chondrocytes, demonstrating a direct membrane effect for this steroid hormone. These data indicate that the rapid nongenomic effect of E₂ on PKC activity in chondrocytes from female rats is sex-specific and dependent upon a G-protein-coupled phospholipase C.     

Prostaglandin stimulation of ovarian ornithine decarboxylase in vitro.

Prostaglandins E₁ and E₂ caused a 5–10 fold stimulation of ornithine decarboxylase activity in granulosa cells isolated from porcine ovarian follicles. The minimally effective concentration of prostaglandin E₂ was 10 ng/ml and the plateau of activity was reached at 500 ng/ml. Prostaglandin F_2α was ineffective. 1-Methyl,3-isobutyl-xanthine, a phosphodiesterase inhibitor, potentiated the effect of both submaximal and maximal effective doses of prostaglandin E₂, suggesting that the effect of prostaglandin E₂ is mediated by cAMP. The effect of prostaglandin E₂ was similar to that of luteinizing hormone and a cAMP analogue, 8-Bromo-cAMP.     

Mechanism of increased renal prostaglandin E2 in uranyl nitrate-induced acute renal failure

We have previously demonstrated that decreased cortical prostaglandin metabolism can contribute significantly to an increase in renal tissue levels and activity of prostaglandin E₂ in bilateral ureteral obstruction, a model of acute renal failure. In the present study, we have further investigated whether alterations in prostaglandin metabolism can occur in a nephrotoxic model of acute renal failure. Prostaglandin synthesis, prostaglandin E₂ metabolism (measured as both prostaglandin E₂-9-ketoreductase and prostaglandin E₂-15-hydroxydehydrogenase activity), and tissue concentration of prostaglandin E₂ were determined in rabbit kidneys following an intravenous administration of uranyl nitrate (5 mg/kg). No changes in the rates of cortical microsomal prostaglandin E₂ and prostaglandin F_2α synthesis were noted at the end of 1 and 3 days, while medullary synthesis of prostaglandin E₂ fell by 47% after 1 day and 43% after 3 days. Cortical cytosolic prostaglandin E₂-9-ketoreductase activity was found to be decreased by 36% and 76% after 1 and 3 days respectively. No significant changes were noted in cortical cytosolic prostaglandin E₂-15-hydroxydehydrogenase activity after 3 days. Cortical tissue levels of prostaglandin E₂ increased by 500% at the end of 3 days. These data demonstrate that in nephrotoxic acute renal failure, decreased prostaglandin metabolism (i.e., prostaglandin E₂-9-ketoreductase activity) can result in increased tissue levels of prostaglandin E₂ in the absence of increased prostaglandin synthesis and suggest that alterations in prostaglandin metabolism may be an important regulator of prostaglandin activity in acute renal failure.     

17β-Estradiol regulation of protein kinase C activity in chondrocytes is sex-dependent and involves nongenomic mechanisms

17β-Estradiol (E₂) regulates growth plate chondrocyte differentiation in both a sex- and cell maturation–dependent manner, and the sex-specific effects of E₂ appear to be mediated in part by membrane events. In this study, we examined whether E₂ regulates protein kinase C (PKC) in a cell-maturation and sex-specific manner and whether E₂ uses a nongenomic mechanism in regulating this enzyme. In addition, we determined if PKC mediates the E₂-dependent stimulation of alkaline phosphatase activity seen in chondrocytes. Confluent, fourth passage resting zone (RC) and growth zone (GC) chondrocytes from male and female rat costochondral cartilage were treated with 10⁻¹⁰ to 10⁻⁷ M E₂. E₂ caused a dose-dependent increase in PKC in RC and GC cells from female rats. Peak stimulation was at 90 min. Increased PKC was evident by 3 min in both RC and GC and was still evident in RC cells at 720 min, but in GC cells activity returned to baseline by 270 min. Actinomycin D had no effect at 9, 90, 270, or 720 min, but there was a small decrease in E₂-stimulated PKC in RC treated with cycloheximide at 90 and 270 min and in GC treated for 90 min. E₂ increased cytosolic and membrane PKC at 9 min and by 90 min promoted translocation of PKC activity from the cytosol to the membranous compartment of female RC cells. Antibodies specific for the α, β, δ, ε, and ζ isoforms of PKC revealed that PKCα in female GC and RC cells is activated by E₂. There was a small, but statistically significant, increase in PKC in male RC cells in response to E₂, but it was not dose-dependent, and no effect of E₂ was noted in male GC cells. 17α-estradiol, an inactive isomer of E₂, did not affect PKC specific activity in RC or GC cells from either female or male rats. Chelerythrine, a specific inhibitor of PKC, inhibited E₂-dependent alkaline phosphatase activity, indicating that E₂ mediates its rapid effects on alkaline phosphatase via PKC. J. Cell. Physiol. 176:435–444, 1998. © 1998 Wiley-Liss, Inc.     

Study of the PG E2 synthetase activity of different regions of dog and rabbit hearts

Prostaglandin E₂ synthetase activity of the microsomal fraction from different parts of dog and rabbit heart was tested with 3H-arachidonic acid as substrate. PG E₂ synthesized was separated and purified by TLC and determined by the radiometric method or by bioassay. In the experimental conditions adopted, it was shown that the heart tissue is endowed with an enzyme system capable of synthesizing PG E₂ but this PG E₂ synthetase activity is not uniformly distributed in the different parts of the heart. It is highest in the right atrium and the activity of the atria is higher than that of the ventricles. It is species-dependent. The closely similar repartition of PG E₂ synthetase activity and sympathetic nerve endings strongly suggests that PG E₂ modulates adrenergic neurotransmission in the heart.