Studies on the metabolism of steroid hormones. Part II. Reversible steroid-protein interactions via enol intermediates

[6β- ²H]Testosterone is metabolized by rat liver microsomes to 6β,17β-dihydroxy-4-androsten-3-one with toss of the deuterium label. Some of the deuterium label was lost from the residual substrate through reversible interactions with the microsomal enzymes. These facts suggest that the enolic form of Δ⁴-3-oxo steroids is involved in the enzyme-substrate complex.     

Gas exchange of Agropyron desertorum: diurnal patterns and responses to water vapor gradient and temperature

Summary The response of leaf gas exchange to environmental variables were measured at different levels of drought stress for Agropyron desertorum, a naturalized perennial bunchgrass of the semiarid shrub steppes of western North America. Leaf conductance (stomatal plus boundary layer) was more sensitive to changes in water vapor gradient than to changes in leaf temperature. Assimilation was sensitive to both temperature and vapor gradient, and also appeared to be affected by conductance and high transpiration rates. The magnitudes of both assimilation and conductance decreased with increased drought conditions. Diurnal patterns of gas exchange were measured during 3 growing seasons. For a typical spring day with moderate leaf temperature and vapor gradient, diurnal patterns were similar for plants at different levels of soil water availability. Assimilation was relatively constant during most of the day, but conductance decreased during the afternoon. Total daily carbon gain was decreased to a lesser extent than daily water loss as soil water was depleted. Consequently, the ratio of daily carbon gain to daily water loss, i.e. daily water use efficiency, increased with decreased soil water content for diurnals under spring conditions. Diurnal patterns of assimilation for a typical summer day with high leaf temperature and vapor gradient differend from those for a spring day. An afternoon decrease in assimilation was typical during a summer day. Daily carbon gain, water use, and water use efficiency for summer diurnals decreased only under severe drought conditions. Almost complete recovery of assimilation and conductance occurred if leaf microclimate was ameliorated during the afternoon of either spring or summer diurnals. Thus, conditions responsible for a midday depression in assimilation during a single day did not have persistent effects on leaf gas exchange. Daily carbon gain of a typical summer day was restricted by leaf microclimate during the afternoon, but daily water use efficiency was not relatively increased by the amelioration of leaf microclimate.     

Impact of multiple stressors on juvenile fish in estuaries of the northeast Pacific

A key step in identifying global change impacts on species and ecosystems is to quantify effects of multiple stressors. To date, the science of global change has been dominated by regional field studies, experimental manipulation, meta‐analyses, conceptual models, reviews, and studies focusing on a single stressor or species over broad spatial and temporal scales. Here, we provide one of the first studies for coastal systems examining multiple stressor effects across broad scales, focused on the nursery function of 20 estuaries spanning 1,600 km of coastline, 25 years of monitoring, and seven fish and invertebrate species along the northeast Pacific coast. We hypothesized those species most estuarine dependent and negatively impacted by human activities would have lower presence and abundances in estuaries with greater anthropogenic land cover, pollution, and water flow stress. We found significant negative relationships between juveniles of two of seven species (Chinook salmon and English sole) and estuarine stressors. Chinook salmon were less likely to occur and were less abundant in estuaries with greater pollution stress. They were also less abundant in estuaries with greater flow stress, although this relationship was marginally insignificant. English sole were less abundant in estuaries with greater land cover stress. Together, we provide new empirical evidence that effects of stressors on two fish species culminate in detectable trends along the northeast Pacific coast, elevating the need for protection from pollution, land cover, and flow stressors to their habitats. Lack of response among the other five species could be related to differing resistance to specific stressors, type and precision of the stressor metrics, and limitations in catch data across estuaries and habitats. Acquiring improved measurements of impacts to species will guide future management actions, and help predict how estuarine nursery functions can be optimized given anthropogenic stressors and climate change scenarios.     

Estimating genetic parameters of architectural and reproductive traits in young macadamia cultivars

Macadamia in the orchard environment is relatively unaltered from its natural form, and there is considerable scope to alter vegetative and reproductive architecture with the aim of improving yield efficiency through breeding. An understanding of the genetic and environmental control of architecture and the dynamics between vegetative and reproductive characteristics are fundamental to identifying traits for yield improvement. This experiment calculated the broad-sense heritability (H) of architectural traits and genetic correlations between vegetative and reproductive traits over 2 years. Cutting-grown clones (n?=?3) of 15 macadamia genotypes were subsampled from a randomised high-density plot planted in 2011 in South East Queensland, Australia, and observed for two seasons between 2015 and 2017. Clonal values from independent linear mixed models for multiple traits were combined in principal component analysis (PCA) to provide an insight to potential genetic relationships between traits, and genetic correlations were calculated from multivariate linear mixed model analysis. At the tree scale, canopy volume and yield had low H (0.07 and 0.14, respectively), implying a strong environmental influence on these complex traits. Architectural components of canopy volume and yield were considered at multiple scales, for which H ranged from 0.06 to 0.68, suggesting architectural traits at lower scales may be manipulated by breeding. Specific traits displayed strong genetic relationships with yield and canopy volume, suggesting that indirect selection for yield efficiency may be possible via selection for architectural and floral traits, to improve future macadamia cultivars.     

A 10-year demographic study of rabbitbrush (Chrysothamnus nauseosus): growth,survival and water limitation

A population of 126 adult rabbitbrush (Chrysothamnus nauseosus var. consimilis) was followed for 10 consecutive years from 1983 through 1992 in a sanddune ecosytem on the north shore of Mono Lake, California. The study area received an average (1981–1992) of 160 mm total annual precipitation of which 55 mm fell from April through October, making this site drier than other known sites in the Great Basin desert where C. nauseosus occurs. Cover of all shrubs was 18.0%, and that of C. nauseosus 7.5%, in the 3077 m² study plot. Water was limiting for this population of C. nauseosus, exerting large effects on new canopy growth and reproductive effort in a given year, on survival, and on establishment of juveniles into the adult population. Growth and survivorship of the adult shrubs were significantly correlated with the depth to ground water, which varied from 3.6 to 6.0 m below the surface during the study, and not with any measure of precipitation in a given year or adjacent years. Shrubs in this population exhibited a net decrease in size between 1983 and 1992. The region experienced a significant drought from 1987 onwards, with some increase in precipitation after 1990. Mortality of shrubs began in 1987 and reached 22% by 1992. Individuals that died were smaller on average initially than individuals surviving throughout the study: 50% or more of the individuals having 4000 cm² of canopy or less at the start of the study died by 1992. Elevation (m msl) of each shrub in the study area, presumably correlated with depth to ground water, had no effect on growth but a weak effect on survival during the study period. Specific microsite had significant effects, with shrubs on steep slopes being smaller, having more negative growth slopes, and being more likely to die during the drought compared to individuals occurring on flatter gradients. Recruiment of juveniles into the population did not occur after 1985. Competition between shrubs could not be definitively demonstrated during the study, but only indirect tests for competition were used. Adult C. nauseosus and adults of all species combined (Sarcobatus vermiculatus with 9.6% cover, Tetradymia tetrameres with 0.8% cover and Chrysothamnus viscidiflorus with 0.02% cover) were randomly distributed, failing to support the hypothesis of competition if competition for water results in a uniform distribution of shrubs. Moreover, comparison of the spatial dispersion of C. nauseosus individuals before (1985) and after (1992) mortality did not reveal competitive thinning toward uniformity. On the other hand, larger individuals were farther from their nearest neighbor than were smaller individuals, an effect postulated to result from competitive thinning.     

Consumption by carabid beetles of three cereal aphid species relative to other prey types

The cereal aphidRhopalosiphum padi has previously been found to be a low quality prey for a range of generalist arthropod predators. The aim of this study was to reveal, using food consumption experiments whether this applies to other cereal aphids. The question of whether predator feeding capacity increased when several aphid species were offered relative to a single aphid species was also addressed by measuring food consumption on a mixed aphid diet relative to single aphid diets. Food consumption by five carabid beetles of the three cereal aphid speciesRhopalosiphum padi, Sitobion avenae andMetopolophium dirhodum was determined relative to fruit fliesDrosophila melanogaster and the collembolanIsotoma anglicana. Feeding rate was measured as food consumption over 24 hour both for previously satiated and beetles starved for 7 days. Generally the largest aphid consumption was ofM. dirhodum and the lowest ofR. padi, withS. avenae in between. The mixed aphid consumption experiments did not reveal a higher feeding rate on mixed aphid diets relative to single aphid diets. The results indicate low preference forR. padi andS. avenae.     

Population structure and survival in a solitary wasp (Microbembex cubana: Hymenoptera,Sphecidae, Nyssoninae)

Summary This paper documents population structure in a solitary wasp, Microbembex cubana (Hymenoptera, Sphecidae, Nyssoninae), on a small (15 km²) Bahamian island. A relatively isolated portion of this population was studied April–June 1985. The population comprised small aggregations of territorial males and nesting females. Individuals of both sexes were with rare exceptions faithful to a home aggregation during their one- to two-month adult lifespans, conducting all reproductive activities there. Individuals from different aggregations, however, mixed daily during these activities: feeding on nectar, hunting for provisions and retiring to clustered sleeping burrows. Significant variation occurred among the nine breeding aggregations in size, density, sex-ratio (which was on average 2:1 in favor of males) and survival (which was 0.93–0.99 per individual/per day and which was not higher for females than for males). Aggregations retained the same characteristics for longer than the life expectancies of individuals in them.Factors affecting reproductive success and survivorship in M. cubana are complex: they are apparently only partially overlapping between males and females and subject to spatial variation. Patterns in the data suggest several hypotheses about how behavior, morphology and habitat interact to shape population processes. I propose that aggregations arise and are characterized by considerable behavioral inertia because individual M. cubana use conspecifics as sources of information on resource quality. Because M. cubana occurs in secondary habitats, individuals retain flexibility in responding to better opportunities for reproduction, but this population exhibits more viscosity than reported for other ground-nesting solitary Hymenoptera.     

Function of calmodulin in postsynaptic densities. II. Presence of a calmodulin- activatable protein kinase activity

Because the calmodulin in postsynaptic densities (PSDs) activates a cyclic nucleotide phosphodiesterase, we decided to explore the possibility that the PSD also contains a calmodulin-activatable protein kinase activity. As seen by autoradiographic analysis of coomassie blue-stained SDS polyacrylamide gels, many proteins in a native PSD preparation were phosphorylated in the presence of [γ-(32)P]ATP and Mg(2+) alone. Addition of Ca(2+) alone to the native PSD preparation had little or no effect on phosphorylation. However, upon addition of exogenous calmodulin there was a general increase in background phosphorylation with a statistically significant increase in the phosphorylation of two protein regions: 51,000 and 62,000 M(r). Similar results were also obtained in sonicated or freeze thawed native PSD preparations by addition of Ca(2+) alone without exogenous calmodulin, indicating that the calmodulin in the PSD can activate the kinase present under certain conditions. The calmodulin dependency of the reaction was further strengthened by the observed inhibition of the calmodulin-activatable phosphorylation, but not of the Mg(2+)-dependent activity, by the Ca(2+) chelator, EGTA, which also removes the calmodulin from the structure (26), and by the binding to calmodulin of the antipsychotic drug chlorpromazine in the presence of Ca(2+). In addition, when a calmodulin-deficient PSD preparation was prepared (26), sonicated, and incubated with [γ-(32)P]ATP, Mg(2+) and Ca(2+), one could not induce a Ca(2+)-stimulation of protein kinase activity unless exogenous calmodulin was added back to the system, indicating a reconstitution of calmodulin into the PSD. We have also attempted to identify the two major phosphorylated proteins. Based on SDS polyacrylamide gel electrophoresis, it appears that the major 51,000 M(r) PSD protein is the one that is phosphorylated and not the 51,000 M(r) component of brain intermediate filaments, which is a known PSD contaminant. In addition, papain digestion of the 51,000 M(r) protein revealed multiple phosphorylation sites different from those phosphorylated by the Mg(2+)-dependent kinase(s). Finally, although the calmodulin-activatable protein kinase may phosphorylate proteins I(a) and I(b), the cyclic AMP-dependent protein kinase, which definitely does phosphorylate protein I(a) and I(b) and is present in the PSD, does not phosphorylate the 51,000 and 62,000 M(r) proteins, because specific inhibition of this kinase has no effect on the levels of the phosphorylation of these latter two proteins.     

Testosterone binding in the chick oviduct

A novel androgen receptor was observed in estrogen-stimulated chick oviducts but not in unstimulated oviducts. This binding component showed a preference for androgens and could therefore be distinguished from oviduct receptors for estadiol and progesterone. Testosterone was tightly bound having a dissociation constant (Kd) of 2.7 × 10^?10 M. Sucrose gradient centrifugation, under low ionic strength conditions, showed testosterone to be bound as an 85 complex. These binding properties, plus the estrogen dependency of this component, suggest its role as a biological receptor for androgens.