Cloning and expression of a functional rat liver D-beta-hydroxybutyrate dehydrogenase-beta-galactosidase fusion protein in Escherichia coli.

A rat liver bacteriophage lambda expression library was probed using polyclonal antibodies raised to purified rat liver D-beta-hydroxybutyrate dehydrogenase (BDH). A clone was selected that contained a 1.2-kb insert. The insert placed in an expression plasmid was utilized to transform Escherichia coli. These cells were shown to possess phosphatidylcholine-dependent BDH activity. Cells transformed with only the plasmid had no detectable BDH activity in the presence of phosphatidylcholine. The expressed activity in E. coli could be inhibited in a dose-dependent manner by BDH antiserum.     

Food provision to nestlings in the Hoopoe Upupa epops: implications for the conservation of a small endangered population in the Swiss Alps

In an attempt to recognize the possible ecological causes of the decline of a population of Hoopoes Upupa epops in the Swiss Alps, we collected data on resource exploitation. The prey provisioned to nestlings by parents was investigated at four breeding sites using photographs (n = 4353, 80% of which enabled prey identification). Molecrickets Gryllotalpa gryllotalpa and Lepidoptera (larvae and pupae) were dominant in nestling diet (93% frequency; 97% biomass). Although Molecrickets were provisioned less frequently (26%) than Lepidoptera (67%), they represented 68% of the total biomass (vs 29% for Lepidoptera). There was an overall negative relationship between the proportion of Molecricket biomass in the diet and the parents' feeding rate, whereas a comparison between broods showed that a higher provisioning activity did not lead to an increase in the biomass supplied to the chicks. A diet based on Molecrickets therefore appears to be energetically advantageous. As Molecrickets are a traditional prey of Hoopoes in central Europe, this might be relevant to other populations. In the study area, Molecrickets occur only on the intensively cultivated plain, whereas the majority of Hoopoe pairs nest at various altitudes on the foothills adjacent to the plain as the latter provides at present almost no suitable nesting sites. Hoopoes breeding higher up on the foothills seem to experience greater provisioning costs and have, on average, lower breeding success. Providing nest sites on the plain is the main conservation measure proposed for the local Hoopoe population. Further attention should also be paid to Molecrickets as these may be crucial for Hoopoes.     

FLUXNET and modelling the global carbon cycle

Measurements of the net CO₂ flux between terrestrial ecosystems and the atmosphere using the eddy covariance technique have the potential to underpin our interpretation of regional CO₂ source–sink patterns, CO₂ flux responses to forcings, and predictions of the future terrestrial C balance. Information contained in FLUXNET eddy covariance data has multiple uses for the development and application of global carbon models, including evaluation/validation, calibration, process parameterization, and data assimilation. This paper reviews examples of these uses, compares global estimates of the dynamics of the global carbon cycle, and suggests ways of improving the utility of such data for global carbon modelling. Net ecosystem exchange of CO₂ (NEE) predicted by different terrestrial biosphere models compares favourably with FLUXNET observations at diurnal and seasonal timescales. However, complete model validation, particularly over the full annual cycle, requires information on the balance between assimilation and decomposition processes, information not readily available for most FLUXNET sites. Site history, when known, can greatly help constrain the model‐data comparison. Flux measurements made over four vegetation types were used to calibrate the land‐surface scheme of the Goddard Institute for Space Studies global climate model, significantly improving simulated climate and demonstrating the utility of diurnal FLUXNET data for climate modelling. Land‐surface temperatures in many regions cool due to higher canopy conductances and latent heat fluxes, and the spatial distribution of CO₂ uptake provides a significant additional constraint on the realism of simulated surface fluxes. FLUXNET data are used to calibrate a global production efficiency model (PEM). This model is forced by satellite‐measured absorbed radiation and suggests that global net primary production (NPP) increased 6.2% over 1982–1999. Good agreement is found between global trends in NPP estimated by the PEM and a dynamic global vegetation model (DGVM), and between the DGVM and estimates of global NEE derived from a global inversion of atmospheric CO₂ measurements. Combining the PEM, DGVM, and inversion results suggests that CO₂ fertilization is playing a major role in current increases in NPP, with lesser impacts from increasing N deposition and growing season length. Both the PEM and the inversion identify the Amazon basin as a key region for the current net terrestrial CO₂ uptake (i.e. 33% of global NEE), as well as its interannual variability. The inversion's global NEE estimate of −1.2 Pg [C] yr⁻¹ for 1982–1995 is compatible with the PEM‐ and DGVM‐predicted trends in NPP. There is, thus, a convergence in understanding derived from process‐based models, remote‐sensing‐based observations, and inversion of atmospheric data. Future advances in field measurement techniques, including eddy covariance (particularly concerning the problem of night‐time fluxes in dense canopies and of advection or flow distortion over complex terrain), will result in improved constraints on land‐atmosphere CO₂ fluxes and the rigorous attribution of mechanisms to the current terrestrial net CO₂ uptake and its spatial and temporal heterogeneity. Global ecosystem models play a fundamental role in linking information derived from FLUXNET measurements to atmospheric CO₂ variability. A number of recommendations concerning FLUXNET data are made, including a request for more comprehensive site data (particularly historical information), more measurements in undisturbed ecosystems, and the systematic provision of error estimates. The greatest value of current FLUXNET data for global carbon cycle modelling is in evaluating process representations, rather than in providing an unbiased estimate of net CO₂ exchange.     

Response of protozoans to detergent-enzymes

Summary These studies were divided into two parts: (1) time until death curves in which Paramecium caudatum Ehrenberg was exposed to selected concentrations of the detergent-enzyme Axion, and (2) exposure of fresh-water protozoan communities to selected concentrations of Axion. The former were carried out in test tubes, the latter in plastic troughs with a constantly flowing fluid. Both types of bioassays were carried out with filtered water from Douglas Lake, Michigan, U.S.A. at a temperature of about 25° C. One hundred percent of an exposed population of Paramecium caudatum was killed in 20 to 30 minutes at a concentration of 100 ppm of Axion. No appreciable change in the controls was noted during these tests. The bioassays with fresh-water protozoan communities were carried out in plastic troughs with a constant flow of Douglas Lake water. During the exposure period the lake water flow was stopped and a flow of Axion solution was substituted for approximately three hours. After this exposure period lake water flow were restored. The number of species was determined before and at intervals following exposure. Appropriate controls were maintained. A three hour exposure to 56 ppm (introduced concentration) of Axion caused a 35 percent reduction in the number of species in less than five hours with recovery to the original number in approximately 145 hours; a three hour exposure to 75 ppm caused a 54% reduction in number of species in less than five hours with recovery to the original number in approximately 240 hours; 100 ppm produced a 55 percent reduction with recovery in approximately 200 hours; 125 ppm produced a 48% reduction with recovery in approximately 148 hours; 200 ppm caused a 78% reduction with recovery in about 140 hours. Response patterns vary as do those of bioassays with single species. However, it is important to note that each test community had different types of species present, and it is quite likely that some communities had a higher percentage of sensitive species than others. Since this variation also occurs in nature the tests are probably representative of the differences that exist when natural communities are exposed to wastes. Variation in control troughs was less than ± 10 percent in the number of species.     

Cyclic Expression of A Nuclear Protein In A Dinoflagellate

Nuclei of the dinoflagellate Crypthecodinium cohnii strain Whd were isolated and nuclear proteins were extracted in three fractions, corresponding to the increasing affinity of these proteins to genomic DNA. One fraction contained two major bands (48- and 46-kDa) and antibodies specific to this fraction revealed two major bands by Western blot on nuclear extracts, corresponding to the 46- and 48-kDa bands. The 48-kDa protein was detected in G1 phase but not in M phase cells. An expression cDNA library of C. cohnii was screened with these antibodies, and two different open reading frames were isolated. Dinoflagellate nuclear associated protein (Dinap1), one of these coding sequences, was produced in E. coli and appeared to correspond to the 48-kDa nuclear protein. No homologue of this sequence was found in the data bases, but two regions were identified, one including two putative zinc finger repeats, and one coding for two potential W/W domains. The second coding sequence showed a low similarity to non-specific sterol carrier proteins. Immunocytolocalization with specific polyclonal antibodies to recombinant Dinap1 showed that the nucleus was immunoreactive only during the G1 phase: the nucleoplasm was immunostained, while chromosome cores and nuclear envelopes were negative.     

Repeated Cocaine Alters Glutamate Receptor Subunit Levels in the Nucleus Accumbens and Ventral Tegmental Area of Rats that Develop Behavioral Sensitization

Increased glutamate transmission in the nucleus accumbens and ventral tegmental area has been proposed as a mechanism underlying sensitized behavioral responses to repeated cocaine administration. GluR1, GluR2/3, and NMDAR1 subunits of glutamate receptors were quantified from immunoblots in these brain nuclei in rats at 24 h and 3 weeks after discontinuing 1 week of daily cocaine injections. Motor behavior was monitored after the first and last injections of daily cocaine, and those rats that showed >20% increase in motor activity after the last compared with the first injection were considered to have developed behavioral sensitization. The subjects that developed behavioral sensitization showed a significant increase in GluR1 levels in the nucleus accumbens at 3 weeks but not at 24 h of withdrawal. Conversely, sensitized animals showed a significant increase in NMDAR1 and GluR1 levels in the ventral tegmental area at 1 day but not at 3 weeks of withdrawal. None of these increases occurred in the rats exposed to daily cocaine that did not develop behavioral sensitization (<20% increase in motor activity), and no changes were measured in the level of GluR2/3 in any treatment group. The functional importance of the increases in glutamate receptor subunit levels is suggested by the fact that the changes were present only in rats that developed behavioral sensitization to repeated cocaine administration.