The Soil Flagellate Heteromita globosa Accelerates Bacterial Degradation of Alkylbenzenes through Grazing and Acetate Excretion in Batch Culture

The impact of grazing by soil flagellates Heteromita globosa on aerobic biodegradation of benzene by Pseudomonas strain PS+ was examined in batch culture. Growth of H. globosa on these bacteria obeyed Monod kinetics (_max, 0.17 ± 0.03 h^–1; K_s, 1.1 ± 0.2 × 10⁷ bacteria mL^–1) and was optimal at a bacteria/ flagellate ratio of 2000. Carbon mass balance showed that 5.2% of total [ring-U-¹⁴C]benzene fed to bacteria was subsequently incorporated into flagellate biomass. Growth-inhibiting concentrations (IC₅₀) of alkylbenzenes (benzene, toluene, ethylbenzene) were inversely related with their octanol/ water partitioning coefficients, and benzene was least toxic for bacteria and flagellates with IC₅₀ values of 4392 (± 167) M and 2770 (± 653) M, respectively. The first-order rate constant for benzene degradation (k₁, 0.48 ± 0.12 day^–1) was unaffected by the presence or absence of flagellates in cultures. However, the rate of benzene degradation by individual bacteria averaged three times higher in the presence of flagellates (0.73 ± 0.13 fmol cell^–1 h^–1) than in their absence (0.26 ± 0.03 fmol cell^–1 h^–1). Benzene degradation also coincided with higher levels of dissolved oxygen and a higher rate of nitrate reduction in the presence of flagellates (p < 0.02). Grazing by flagellates may have increased the availability of dissolved oxygen to a smaller surviving population of bacteria engaged in the aerobic reactions initiating benzene degradation. In addition, flagellates may also have increased the rate of nitrate reduction through the excretion of acetate as an additional electron donor for these bacteria. Indeed, acetate was shown to progressively accumulate in cultures where flagellates grazed on heat-killed bacteria. This study provided evidence that grazing flagellates stimulate bacterial degradation of alkylbenzenes and provide a link for carbon cycling to consumers at higher trophic levels. This may have important implications for bioremediation processes.     

Biotreatment of groundwater contaminated with MTBE: interaction of common environmental co-contaminants

Contamination of groundwater with the gasoline additive methyl tert-butyl ether (MTBE) is often accompanied by many aromatic components such as benzene, toluene, ethylbenzene, o-xylene, m-xylene and p-xylene (BTEX). In this study, a laboratory-scale biotrickling filter for groundwater treatment inoculated with a microbial consortium degrading MTBE was studied. Individual or mixtures of BTEX compounds were transiently loaded in combination with MTBE. The results indicated that single BTEX compound or BTEX mixtures inhibited MTBE degradation to varying degrees, but none of them completely repressed the metabolic degradation in the biotrickling filter. Tert-butyl alcohol (TBA), a frequent co-contaminant of MTBE had no inhibitory effect on MTBE degradation. The bacterial consortium was stable and showed promising capabilities to remove TBA, ethylbenzene and toluene, and partially degraded benzene and xylenes without significant lag time. The study suggests that it is feasible to deploy a mixed bacterial consortia to degrade MTBE, BTEX and TBA at the same time.     

Simultaneous removal of benzene, toluene and xylenes mixture by a constructed microbial consortium during biofiltration

A bacterial consortium with complementary metabolic capabilities was formulated and specific removal rates were 0.14, 0.35, 0.04, and 0.39 h^–1 for benzene, toluene, o-xylene, and m,p-xylene, respectively. When immobilized on a porous peat moss biofilter, removal of all five (= BTX) components was observed with rates of 1.8–15.4 g m^–3 filter bed h^–1. Elimination capacities with respect to the inlet gas concentrations of BTX and airflow rates showed diffusive regimes in the tested concentration range of (0.1–5.3 g m^–3) and airflow (0.55–1.82 m³ m^–2 h^–1) except for o-xylene which reached its critical gas concentration at 0.3 g m^–3.     

Enhanced biodegradation of phenol by a microbial consortium in a solid–liquid two phase partitioning bioreactor

Two phase partitioning bioreactors (TPPBs) operate by partitioning toxic substrates to or from an aqueous, cell-containing phase by means of second immiscible phase. Uptake of toxic substrates by the second phase effectively reduces their concentration within the aqueous phase to sub-inhibitory levels, and transfer of molecules between the phases to maintain equilibrium results in the continual feeding of substrate based on the metabolic demand of the microorganisms. Conventionally, a single pure species of microorganism, and a pure organic solvent, have been used in TPPBs. The present work has demonstrated the benefits of using a mixed microbial population for the degradation of phenol in a TPPB that uses solid polymer beads (comprised of ethylene vinyl acetate, or EVA) as the second phase. Polymer modification via an increase in vinyl acetate concentration was also shown to increase phenol uptake. Microbial consortia were isolated from three biological sources and, based on an evaluation of their kinetic performance, a superior consortium was chosen that offered improved degradation when compared to a pure strain of Pseudomonas putida ATCC 11172. The new microbial consortium used within a TPPB was capable of degrading high concentrations of phenol (2000mgl^–1), with decreased lag time (10h) and increased specific rate of phenol degradation (0.71g phenolg^–1cellh). Investigation of the four-member consortium showed that it consisted of two Pseudomonas sp., and two Acinetobacter sp., and tests conducted upon the individual isolates, as well as paired organisms, confirmed the synergistic benefit of their existence within the consortium. The enhanced effects of the use of a microbial consortium now offer improved degradation of phenol, and open the possibility of the degradation of multiple toxic substrates via a polymer-mediated TPPB system.     

Continuous monitoring of cellulase action on microcrystalline cellulose

Summary Cellobiose oxidase from Phanerochaete chrysosporium was used for continuous monitoring of cellulase action on microcrystalline cellulose (Avicel). Two protocols are described, the parameter monitored being either the decline in electrode potential as ferricyanide is reduced or consumption of dioxygen. Most experiments used a commercial cellulase preparation from Trichoderma reesei and ferricyanide as acceptor. Within 1 min of an addition of cellulase, ferricyanide reduction reached a steady rate. This was converted into a rate of production of substrate for celobiose oxidase, in mol·min^–1. Experiments were conducted either with a constant concentration of cellulase and increasing Avicel, or with constant Avicel and increasing cellulase. Kinetic analysis of the experiments with constant cellulase indicated a K _mof 4.8 ± 1.0 (g cellulose)·1^–1, which was close to the value predicted from binding studies. The specific activity of the cellulase was measured as 375±25 mol·(g cellulase)^–1·min^–1 in experiments with a high cellulose concentration, but was less than half this value when the cellulose was saturated with cellulase. The maximal rate of cellulose degradation was 9.6±1.3 mol·(g cellulose)^–1·min^–1.     

Momordica charantia fruit juice stimulates glucose and amino acid uptakes in L6 myotubes

The fruit of Momordica charantia (family: Cucurbitacea) is used widely as a hypoglycaemic agent to treat diabetes mellitus (DM). The mechanism of the hypoglycaemic action of M. charantia in vitro is not fully understood. This study investigated the effect of M. charantia juice on either ³H-2-deoxyglucose or N-methyl-amino-a-isobutyric acid (¹⁴C-Me-AIB) uptake in L6 rat muscle cells cultured to the myotube stage. The fresh juice was centrifuged at 5000 rpm and the supernatant lyophilised. L6 myotubes were incubated with either insulin (100 nM), different concentrations (1–10 g ml^–1) of the juice or its chloroform extract or wortmannin (100 nM) over a period of 1–6 h. The results were expressed as pmol min^–1 (mg cell protein)^–1, n= 6–8 for each value. Basal ³H-deoxyglucose and ¹⁴C-Me-AIB uptakes by L6 myotubes after 1 h of incubation were (means ± S.E.M.) 32.14 ± 1.34 and 13.48 ± 1.86 pmol min^–1 (mg cell protein)^–1, respectively. Incubation of L6 myotubes with 100 nM insulin for 1 h resulted in significant (ANOVA, p < 0.05) increases in ³H-deoxyglucose and ¹⁴C-Me-AIB uptakes. Typically, ³H-deoxyglucose and ¹⁴C-Me-AIB uptakes in the presence of insulin were 58.57 ± 4.49 and 29.52 ± 3.41 pmol min^–1 (mg cell protein^–1), respectively. Incubation of L6 myotubes with three different concentrations (1, 5 and 10 g ml^–1) of either the lyophilised juice or its chloroform extract resulted in time-dependent increases in ³H-deoxy-D-glucose and ¹⁴C-Me-AIB uptakes, with maximal uptakes occurring at a concentration of 5 g ml^–1. Incubation of either insulin or the juice in the presence of wortmannin (a phosphatidylinositol 3-kinase inhibitor) resulted in a marked inhibition of ³H-deoxyglucose by L6 myotubes compared to the uptake obtained with either insulin or the juice alone. The results indicate that M. charantia fruit juice acts like insulin to exert its hypoglycaemic effect and moreover, it can stimulate amino acid uptake into skeletal muscle cells just like insulin. (Mol Cell Biochem 261: 99–104, 2004)     

Significance of the Leaf Area Ratio in Hevea brasiliensis Under High Irradiance and Low Temperature Stress

Adjustment in leaf area : mass ratio called leaf area ratio (LAR) is one of the strategies to optimize photon harvesting. LAR was recorded for 10 genotypes of Hevea brasiliensis under high irradiance and low temperature and the genotypes were categorized into two groups, i.e. high LAR and low LAR types. Simultaneously, the growth during summer as well as winter periods, photosynthetic characteristics, and in-vitro oxidative damage were studied. Low LAR (19.86±0.52 m² kg^–1) types, recorded an average of 18.0 % chlorophyll (Chl) degradation under high irradiance and 7.1 % Chl degradation under low temperature. These genotypes maintained significantly higher net photosynthetic rate (P _N) of 10.4 mol(CO₂) m^–2 s^–1 during winter season. On the contrary, the high LAR (24.33±0.27 m² kg^–1) types recorded significantly lower P _N of 4 mol(CO₂) m^–2 s^–1 and greater Chl degradation of 37.7 and 13.9 % under high irradiance and low temperature stress, respectively. Thus LAR may be one of the physiological traits, which are possibly involved in plant acclimation process under both stresses studied.     

Biodegradation of methyl <Emphasis Type="Italic">tert</Emphasis>-butyl ether using bacterial strains

Prospective methyl tert-butyl ether (MTBE) degrading bacterial strains and/or consortia were identified. The potential for aerobic degradation of MTBE was examined using bacterial isolates from contaminated soils and groundwater. Using the 16S rDNA protocol, two isolates capable of degrading MTBE (Rhodococcus pyridinivorans 4A and Achromobacter xylosoxidans 6A) were identified. The most efficient consortium of microorganisms was acquired from contaminated groundwater. The growth of both strains and the consortium on MTBE was supported by various organic substrates, and monitored using Bioscreen®. The biochemical oxygen demand of the cultures was measured using OxiTop®, and their MTBE concentrations were estimated by gas chromatography. After 3 weeks of aerobic cultivation using n-alkanes as cosubstrate, the concentration of MTBE in R. pyridinivorans 4A was reduced to 62.4 % of its initial amount (50 ppm).     

The contribution of size-fractionated plankton to biomass and primary production of phytoplankton in saline–alkaline ponds

Primary productivity, biomass and chlorophyll-a of size fractionated phytoplankton (<0.22 m, <3 m, <8 m, <10 m, <40 m, <64 m, <112 m and <200 m) were estimated in 6 ponds and 5 experimental enclosures. The results showed that the planktonic algae less than 10 m are important in the biomass and production of phytoplankton in saline–alkaline ponds. The production of size fractionated phytoplankton corresponding to <112 m, <10 m and <3 m in saline–alkaline ponds were 10.5 ± 6.6 , 8.6 ± 5.4 and 0.33 ± 0.1 mgC l^–1 d^–1, respectively. Mean community respiration rate was 1.80 ± 0.73, 1.69 ± 0.90 and 1.38 ± 1.12 mgC l^–1 d^–1, respectively. The average production of phytoplankton corresponding to micro- (10–112 m), nano- (3–10 m) and pico- (<3 m) were 1.61, 8.30 and 0.33 mgC l^–1 d^–1, respectively. The ratio of those to the total phytoplankton production was 15%, 79% and 3%, respectively. The mean respiration rate of the different size groups was 0.11, 0.31 and 1.38 mgC l^–1 d^–1; the ratio of those to total respiration of phytoplankton was 6%, 17% and 77%, respectively. The production of size-fractionated phytoplankton corresponding to <200 m, <10 m and <3 m in enclosures was 2.19 ± 1.63, 2.08 ± 1.75 and 0.22 ± 0.08 mgC l^–1 d^-1, respectively. Mean community respiration rates were 1.25 ± 1.55, 1.17 ± 1.42 and 0.47 ± 0.32 mgC l^–1 d^–1, respectively. The average production of phytoplankton corresponding to micro- (10–200 m), nano- (3–10 m) and pico- (<3 m) plankton was 0.11, 1.86 and 0.22 mgC l^–1 d^–1, respectively. The ratio of those to the total production of phytoplankton was 5%, 85% and 10%, respectively. The mean respiration rate of different size groups were 0.08, 0.72 and 0.46 mgC l^–1 d^–1, the ratio of those to total respiration of phytoplankton was 6%, 57% and 37%, respectively. The concentrations of chlorophyll-a of the phytoplankton in the corresponding size of micro- (10–112 m), nano- (3–10 m) and pico- (<3 m) plankton in the experimental ponds were 19.3, 98.2 and 11. 9 g l^–1, respectively. The ratio of those to the total chlorophyll-a was 15%, 76% and 9%, respectively. The concentrations of chlorophyll-a of phytoplankton micro- (10–200 m), nano- (3–10 m) and pico- (<3 m) plankton in enclosures were 1.7, 34.3 and 3.0 g l^–1, respectively. The ratio of those to the total chlorophyll-a was 4%, 88% and 8%, respectively.     

Binding of chloride and a disulfonic stilbene transport inhibitor to red cell band 3

Summary The effect of chloride on 4,4-dibenzamido-2,2-disulfonic stilbene (DBDS) binding to band 3 in unsealed red cell ghost membranes was studied in buffer [NaCl (0 to 500mm) + Na citrate] at constant ionic strength (160 or 600mm). pH 7.4, 25°C. In the presence of chloride, DBDS binds to a single class of sites on band 3. At 160mm ionic strength, the dissociation constant of DBDS increases linearly with chloride concentration in the range [Cl]=450mm. The observed rate of DBDS binding to ghost membranes, as measured by fluorescence stopped-flow kinetic experiments, increases with chloride concentration at both 160 and 600mm ionic strength. The equilibrium and kinetic results have been incorporated into the following model of the DBDS-band 3 interaction: The equilibrium and rate constants of the model at 600mm ionic strength areK ₁=0.67±0.16 m,k ₂=1.6±0.7 sec^–1,k _–2=0.17±0.09 sec^–1,K ₁=6.3±1.7 m,k ₂=9±4 sec^–1 andk _–2=7±3 sec^–1. The apparent dissociation constants of chloride from band 3,K _Cl, are 40±4mm (160mm ionic strength) and 11±3mm (600mm ionic strength). Our results indicate that chloride and DBDS have distinct, interacting binding sites on band 3.     

Biotransformation of chlorpyrifos and bioremediation of contaminated soil

Five aerobic consortia capable of degrading chlorpyrifos as a sole carbon source in aqueous medium showed degradation in the range of 46–72% after 20 days. Pseudomonas fluorescence, Brucella melitensis, Bacillus subtilis, Bacillus cereus, Klebsiella species, Serratia marcescens and Pseudomonas aeroginosa, isolated from these consortium, showed 75–87% degradation of chlorpyrifos as compared to 18% in control after 20 days of incubation. Bioremediation of chlorpyrifos-contaminated soil with P. fluorescence, B. melitensis, B. subtilis and P. aeroginosa individually showed 89%, 87%, 85% and 92% degradation, respectively, as compared to 34% in control after 30 days. Population dynamics of the introduced isolates based on antibiotic resistance survival and REP-PCR indicated 60–70% survival based on antibiotic resistance, but only 35–45% of the inoculated population based on REP-PCR. During bioremediation studies, 3,5,6-trichloro-2-pyridinol (TCP) was detected as metabolite of chlorpyrifos degradation by P. aeroginosa after 20 days, which was utilized and disappeared after 30 days. Whole-cell studies also showed that P. aeroginosa gave TCP as the product of chlorpyrifos degradation, which was further metabolized to unknown polar metabolites.

Scientific relevance

Potential application in sites for effective in situ bioremediation of chlorpyrifos, a neurotoxic insecticide widely used in India.     

Effect of osmotic gradient on ADH-induced intramembranous particle aggregates in toad bladder

Summary Paired toad urinary bladders were prepared without or with an osmotic gradient (175 mosm) across them, stimulated for 2.5 (n=6), 5 (n=6), 30 (n=6) or 60 (n=6) min with ADH (20 mU/ml), and studied by freeze-fracture electron microscopy. Water permeability at these times was assessed in additional bladders (n=6 for each case) after tissue fixation according to the technique of Eggena. After both 60 and 30 min of ADH stimulation, the presence of a gradient compared with the absence of one was associated with fewer aggregates (242±35vs. 382±14 ×235 m^–2 at 60 min,P<0.01; 279±36vs. 470±51 ×235 m^–2 at 30 min,P<0.01) and lower water permeability (8.4±1.1vs. 18.8±1.8g×min^–1×cm^–1 ×mosm ^–1 at60min,P<0.005; 9.2±1.0vs. 22.0±2.1 g ×min^–1×cm^–2×mosm ^–1 at 30 min,P<0.001). In addition, with a gradient both maximum water permeability and maximum aggregate frequency were reached nearly together; a similar correspondence occurred without a gradient. We conclude that in the presence of an osmotic gradient both the ADH-associated aggregates and the water permeability response to ADH are prevented from reaching the higher levels observed in bladders not exposed to a gradient.     

A cone disk atomizer for production of biocompatible magnetic microcapsules for culture of anchorage-dependent mammalian cells

A cone disk atomizer has been designed for preparation of gelatin/polystyrene magnetic microcapsules for use as microcarriers in anchorage-dependent mammalian cell culture. This apparatus facilitates continuous production of microcapsules and ignores surfactants or organic solvents in traditional emulsion. Compared with the flat-disk atomizer, the feeding flow is subjected to a normal pressure provided by the special cone-shaped disk and liquid slide is dramatically decreased in the cone-disk atomizer. A flow-rate-limitation is observed in both flat-disk atomization and cone-disk atomization. A 36% increase in flow-rate limitation was observed in cone-disk atomization than in flat-disk atomization indicating the potential of this method for large-scale preparations. Nomenclature d _p average diameter of solid cores (m)D disk diameter (m)g gravity acceleration (9.8 m s^–2) Ga Galileo number defined by Equation (3) Q flow rate of feeding slurry (m³ s^–1) Re Q flow rate Reynolds number defined by Equation (2)Re rotating speed Reynolds number defined by Equation (1) angular speed of rotating disk (rad s^–1) _l density of liquid (kg m^–3) _s density of the mixing slurry (kg m^–3) density difference between solid cores and liquid (kg m^–3) viscosity of the mixing slurry (Pa s)     

Calcium-supported calpain degradation rates for cardiac myofibrils in diabetes

Objective The purpose was to investigate the calcium required for calpain-mediated degradation of selected cardiac myofibril proteins modified by diabetes, sulfhydryl (SH) and hydrophobic reagents.Methods: After 20 weeks of streptozotocin-induced (55 mg·kg^–1) diabetes, calcium sensitive calpain (1.5 U·ml^–1) degradation rates of purified cardiac myofibrillar proteins (1 mg·ml^–1) were measured,in vitro, and compared to degradation rates for N-ethylmaleimide (NEM) and 2-ptoluidinylnapthalene-6-sulfonate (TNS) treated samples.Results: Diabetes (blood glucose of 550±32 mg·dl^–1) reduced the yield of purified myofibrillar protein with minimal change in fibril protein composition. Total SH group reactivities (nmol·mg^–130min) were 220±21, 163±17 and 156±24 for control, diabetic and NEM-treated (0.5mM) myofibrils (p0.05). Calpain degradation rates were faster for all diabetic and SH modified myofibrillar proteins (p0.05), with a 45 and 35% reduction in the pCa₅₀ for a 37 kDa protein of diabetic and NEM-treated fibril complexes. For control myofibrils, both 100 and 200 uM TNS, reduced calpain degradation rates to a similar extent for all substrate proteins. In contrast, diabetic and NEM-treated samples showed a further reduction in calpain degradation rates with increasing TNS from 100 to 200 divi.Conclusion Our results support the hypothesis that in diabetes the calcium requirements for calpain degradation rates are reduced and dependent upon sulfhydryl group status and Ca²⁺-induced hydrophobic interactions, implicating a 37 kDa myofbillar-complexed protein.     

Seasonality of red and green macroalgae from Antarctica—a long-term culture study under fluctuating Antarctic daylengths

Summary The seasonal development of the endemic Antarctic alga Palmaria decipiens (Palmariales, Rhodophyta) and of the Antarctic-cold temperate algae Iridaea cordata, Gigartina skottsbergii (Gigartinales, Rhodophyta), Enteromorpha bulbosa (Ulvales, Chlorophyta) and Acrosiphonia arcta (Acrosiphoniales, Chlorophyta) was monitored during two years in a culture study under fluctuating daylengths mimicking the conditions on King George Island (Antarctica). Temperature was kept constant at 0°C and nutrient levels were maintained at 0.6 moles m^–3 nitrate and 0.025 moles m^–3 phosphate. In P. decipiens, blades on germlings and on thalli from the previous season are initiated under Antarctic winter conditions and show maximum growth in October. Formation of blades on old thalli of I. cordata and G. skottsbergii started between June and August, maximum growth occurred in December. Sporangia started to form in G. skottsbergii in September and March and spore release was observed 9 months later at 27 mol photons m^–2s^–1. E. bulbosa and A. arcta grew optimally in November and December conditions. Spore or gamete release was observed in December and January in plants kept at 46 mol m ^–2 s^–1 and in January to March in plants kept at lower photon fluence rates, respectively. The minimum light requirements for completion of the life cycle were 31.4 mol m^–2 year^–1 in A. arcta, 47.1 mol m^–2 year^–1 in E. bulbosa and P. decipiens and 141.3 molm^–2 year^–1 in I. cordata and G. skottsbergii. These values suggest lower distribution limits of either 53±23 m, 49 ±22 m and 38±17 m in clear offshore waters or of 28 ±5 m, 26±5 m and 20±4 m in small inshore fjords of the Antarctic Peninsula region.Contribution No. 282 of the Alfred-Wegener-Institute für Polar-u. Meeresforschung     

Decrease of polypeptides in the PS I antenna complex with increasing growth irradiance in the red alga Porphyridium cruentum

Thylakoids isolated from cells of the red alga Porphyridium cruentum exhibit an increased PS I activity on a chlorophyll basis with increasing growth irradiance, even though the stoichiometry of Photosystems I and II in such cells shows little change (Cunningham et al. (1989) Plant Physiol 91: 1179–1187). PS I activity was 26% greater in thylakoids of cells acclimated at 280 mol photons · m^–2 · s^–1 (VHL) than in cells acclimated at 10 mol photons · m^–2 · s^–1 (LL), indicating a change in the light absorbance capacity of PS I. Upon isolating PS I holocomplexes from VHL cells it was found that they contained 132±9 Chl/P700 while those obtained from LL cells had 165±4 Chl/P700. Examination of the polypeptide composition of PS I holocomplexes on SDS-PAGE showed a notable decrease of three polypeptides (19.5, 21.0 and 22 kDa) in VHL-complexes relative to LL-complexes. These polypeptides belong to a novel LHC I complex, recently discovered in red algae (Wolfe et al. (1994a) Nature 367: 566–568), that lacks Chl b and includes at least six different polypeptides. We suggest that the decrease in PS I Chl antenna size observed with increasing irradiance is attributable to changes occurring in the LHC I-antenna complex. Evidence for a Chl-binding antenna complex associated with PS II core complexes is lacking at this point. LHC II-type polypeptides were not observed in functionally active PS II preparations (Wolfe et al. (1994b) Biochimica Biophysica Acta 1188: 357–366), nor did we detect polypeptides that showed immunocross-reactivity with LHC II specific antisera (made to Chlamydomonas and Euglena LHC II).Abbreviations Bis-Tris bis(2-hydroxyethyl)imino-tris(hydroxymethyl)methane - DCPIP 2,6-dichlorophenol indophenol - -dm dodecyl--d-maltoside - HL high light of 150 mol photons · m^–2 · s^–1 - LGB lower green band - LHC I light-harvesting complex of PS I - LHC II light-harvesting complex of PS II - LL low light of 10 mol photons · m^–2 · s^–1 - ML medium light of 50 mol photons · m^–2 · s^–1 - MES 2-(N-morpholino) ethanesulfonic acid - P700 reaction center of PS I - PFD photon flux density - Trizma tris(hydroxymethyl)aminomethane - UGB upper green band - VHL very high light of 280 mol photons · m^–2 · s^–1     

β-Adrenoreceptors of multiple affinities in a clonal capillary endothelial cell line and its functional implication

-Adrenoreceptor has been studied in a clonal capillary endothelial cell line established from the vascular bed of the bovine adrenal medulla. [³H]Dihydroalprenolol ([³H]DHA) binding to the isolated plasma membranes from these cells has demonstrated the presence of -adrenoreceptors with two different affinities. the dissociation constants (K_d) have been found to be 0.27±0.09×10^–9 M and 2.96±0.31×10^–9 M, respectively with the corresponding B_max of 5.1±0.05 and 70.0±0.2 pmol/mg protein, respectively. Inhibition of [³H]DHA binding to the -receptor by atenolol (a ₁-antagonist) and ICI 118,551 (a ₁-antagonist) has suggested that the IC_50cor (=K_i) for atenolol and ICI 118,551 for high affinity site are 0.08±0.03×10^–12 M and 0.25±0.08×10^–12 M, respectively. This, therefore, indicates that both atenolol and ICI 118,551 are able to displace the bound ligand effectively but the ₁-selective antagonist atenolol is 3 times more potent than its ₂ counterpart, ICI 118,551. Displacement of [³H]DHA binding to the endothelial cell plasma membrane by the agonists isoproterenol, epinephrine and norephinephrine has established a relative order of K_i for these agents as isoproterenol (0.56±0.19×10^–9 M)–9 M)>-norepinephrine (0.71±0.24×10^–9 M) for the high affinity site. The corresponding values for the low affinity site, however, are 4.62±0.64×10^–9 M, 6.21±0.86×10^–9 M and 5.90±0.82×10^–9 M, respectively for the same agonists. Increased intracellular cAMP accompanied with cellular proliferation in the presence of isoproterenol has suggested not only the coupling of -adrenoreceptors to the adenylate cyclase system but also its involvement in endothelial cell proliferation.Abbreviations DHA Dihydroalprenolol - cAMP 3:5 cyclic adenosine monophosphate - DTT dithiothreitol - MEM minimal essential medium - 8Br-cAMP 8-bromo-adenosine 3:5 cyclic monophosphate     

Amino-acid absorption by developing herring eggs

¹⁴C-glycine absorption by eggs of the herringClupea harengus from a 2 µM solution at 15°C depends on the stage of embryonic development. Unidirectional¹⁴C-glycine influx rates are small at early stages: 0.6 ± 0.1 and 0.5 ± 0.1 pmoles egg^–1 h^–1 in embryos 5 h and 28 h after fertilization, respectively. They increase drastically about 51 h after fertilization (prior to blastopore closure) to 3.7 ± 0.9 pmoles egg^–1 h^–1. Glycine uptake steadily continues to increase almost until hatching (maximum values = 18.8 ± 2.7 pmoles egg^–1 h^–1), decreasing slightly prior to hatching. Distribution ratios (radioactivity µl^–1 of egg volume: radioactivity µl^–1 ambient medium) exceed the equilibrium ratio of 1 between 51 h and 78 h after fertilization, reaching values of 4.7 two days prior to hatching, thus suggesting the presence of a transport mechanism capable of transferring the amino acid against the concentration gradient. Curves for concentration-dependent¹⁴C-glycine and¹⁴C--aminoisobutyric acid absorption are very similar; they consist of a linear portion at higher concentrations and a saturable component, indicating a mediated uptake process. Calculations performed by means of aminoacid absorption rates and O₂ uptake data suggest that herring eggs scarcely obtain nutritional benefits from absorption of dissolved amino acids in natural spawning areas.     

Temporal variability and production of Euterpina acutifrons (Copepoda: Harpacticoida) in the Cananéia Lagoon estuarine system,São Paulo,Brazil

Diel and seasonal variations in abundance, population structure, biomass and production rate of the harpacticoid copepod Euterpina acutifrons were studied in the Cananéia Lagoon estuarine system, São Paulo, Brazil. Zooplankton samples were collected at 4-h intervals during multiple 24-h periods, from February 1995 to January 1996. Copepodites and adults of E. acutifrons were present in the plankton throughout the year (temperature, 18.6–29.4 °C; salinity, 4.5–33.0 psu; chlorophyll-a concentration, 1.32–20.42 g l^–1). Abundance of E. acutifrons showed considerable diel variations. On most sampling dates, higher abundances were recorded at times when salinity was higher. Biomass varied from 0.044 ± 0.046 (daily mean ± SD) to 5.264±3.425 mg C m^–3. The estimated production rates (minimum ± SD–maximum ± SD) were 0.034±0.035–4.95±3.25 (Ikeda-Motoda model), 0.035±0.036–5.123±3.347 (Huntley-Lopez model), and 0.016±0.017–2.101±1.372 mg C m^–3 d^–1 (Hirst-Sheader model).     

Microbiological degradation of the herbicide dicamba

Summary Pseudomonas paucimobilis was isolated from a consortium which was capable of degrading dicamba (3,6-dichloro-2-methoxybenzoic acid) as the sole source of carbon. The degradation of dicamba byP. paucimobilis and the consortium was examined over a range of substrate concentration, temperature, and pH. In the concentration range of 100–2000 mg dicamba L^–1 (0.5–9.0 mM), the degradation was accompanied by a stoichiometric release of 2 mol of Cl^– per mol of dicamba degraded. The cultures had an optimum pH 6.5–7.0 for dicamba degradation. Growth studies at 10°C, 20°C, and 30°C yielded activation energy values in the range of 19–36 kcal mol^–1 and an average Q₁₀ value of 4.0. Compared with the pure cultureP. paucimobilis, the consortium was more active at the lower temperature.