Effects of the timing of initial feeding on growth and survival of spotted mandarin fish Siniperca scherzeri larvae

The effects of delayed first feeding on growth and survival of spotted mandarin fish Siniperca scherzeri larvae were examined under controlled conditions. Morphometric characters [yolk‐sac volume, oil globule volume, head depth (H_D), body depth (B_D), eye diameter (E_D), musculature height (M_H), mouth diameter (M_D) and total length (L_T)], body mass (M), specific growth rate (S_GR) and survival were evaluated under different first‐feeding time (2, 3, 4 and 5 days after hatching). Larvae began to feed exogenously at 2 days after hatching (DAH) and the point of no return (P_NR) occurred between 5 and 6 DAH at 23° C, range ±1·0° C. The yolk volume of larvae first‐fed at 2 days had a significant difference compared with that of larvae first‐fed at 3, 4 and 5 days on 3 and 4 DAH. The larvae first‐fed at 2 days achieved comparatively better growth performance than that of 3, 4 and 5 days. On 5 DAH, all morphometric characters had significant differences between 2 and 5 days and 2 and 4 days initial feeding, respectively. Total mortality was recorded on 9 DAH for the larvae first‐fed at 5 days. On 12 DAH, significant differences were observed between 2 and 4 days and 3 and 4 days initial feeding for all morphometric characters. From 16 DAH to the end of experiment, all growth variables of the larvae first‐fed at 2 days were significantly higher than those in other treatments. The S_GR (2–9 DAH) first‐fed at 2 and 3 days were significantly higher than 4 and 5 day treatments, and the S_GR (9–16 DAH) first‐fed at 2 days was significantly higher than 3 and 4 day treatments. There was no significant difference, however, of S_GR (16–28 DAH) among treatments. Survival rate was significantly higher at 2 days initial feeding (27·42%) when compared with 3 (15·96%) and 4 days (7·92%) initial feeding at the end of experiment. The present study suggests that the first feeding of S. scherzeri larvae should be initiated at 2 days after hatching for achieving good growth and survival.     

A cell permeable peptide analog as a potential-specific PET imaging probe for prostate cancer detection

Non-invasive detection of prostate cancer or metastases still remains a challenge in the field of molecular imaging. In our recent work of screening arginine- or lysine-rich peptides for intracellular delivery of a therapeutic agent into prostate cancer cells, an arginine-rich cell permeable peptide (NH₂GR₁₁) was found with an unexpectedly preferential uptake in prostate cancer cell lines. The goal of this work was to develop this peptide as a positron emission tomography (PET) imaging probe for specific detection of distant prostate cancer metastases. The optimal length of arginine-rich peptides was evaluated by the cell uptake efficiency of three fluorescein isothiocyanate (FITC)-tagged oligoarginines (NHGR₉, NHGR₁₁, and NHGR₁₃) in four human prostate cell lines (LNCaP, PZ-HPV-7, DU145, and PC3). Of the three oligoarginines, NH₂GR₁₁ showed the highest cell uptake and internalization efficiency with its subcellular localization in cytosol. The biodistribution of FITC-NHGR₉, FITC-NHGR₁₁, and FITC-NHGR₁₃ performed in control nude mice displayed the unique preferential accumulation of FITC-NHGR₁₁ in the prostate tissue. Further in vivo evaluation of FITC-NHGR₁₁ in PC3 tumor-bearing nude mice revealed elevated uptake of this peptide in tumors as compared to other organs. In vivo pharmacokinetics evaluated with ⁶⁴Cu-labeled NH₂GR₁₁ showed that the peptide was rapidly cleared from the blood (t _1/2 = 10.7 min) and its elimination half-life was 17.2 h. The PET imaging specificity of ⁶⁴Cu-labled NH₂GR₁₁ was demonstrated for the detection of prostate cancer in a comparative imaging experiment using two different human cancer xenograft models.     

Fate of radioactive gibberellin a(1) in maturing and germinating seeds of peas and Japanese morning glory

Radioactive gibberellin A₁ (³H-GA₁) was injected into excised fruits of peas and Japanese morning glory. These were then grown in sterile culture to maturity and the label was followed in the seeds during further development and subsequent germination. During development of both pea and morning-glory seeds a large part of the radioactivity became associated with the aqueous fraction, while another part of the ³H-GA₁ was converted into 2 new, acidic, biologically active compounds, designated X₁ and X₂. A relatively small part of the neutral compounds could be converted back to ³H-GA₁, X₁, and X₂ by means of mild acid hydrolysis. During germination of pea and morning-glory seeds, part of the bound compounds was released in the form of ³H-GA₁, X₁ and X₂ while, particularly during rapid seedling growth, a further conversion of ³H-GA₁, mainly to X₁, took place. In pea seedlings, growth during the first 2 to 3 days after imbibition was not affected by Amo-1618, an inhibitor of gibberellin biosynthesis. This, in conjunction with the findings on the interconversions between free and bound ³H-GA₁ suggests that, at least in peas, early seedling growth may at least partly be regulated by gibberellins released from a bound form which was formed during seed development.     

Dynamic affinity chromatography of heavy meromyosin subfragment-1

Heavy meromyosin subfragment-1 and its trinitrophenylated derivative 3ave been chromatographed on immobilized ATP, ADP and adenosine 5′-(β,γ-imino)triphosphate affinity chromatography columns, in the presence and in the absence of Mg²⁺ or Ca²⁺. Splitting of bound ATP was followed by using [γ-^{3 2}P]ATP columns. While the divalent cations had little effect on the chromatographic pattern in the case of the non-hydrolyzable ADP and adenosine 5′(β,γ-imino)triphosphate, they catalyzed splitting in the case of ATP and at the same time strongly increased the affinity of adsorption of the proteins. The protein-elution and the P_i-release patterns were different for the native and the modified proteins. These results have been interpreted in terms of protein binding to the various intermediates of the ATP hydrolysis reaction.     

Purification, characterization, and immunological properties for two isoforms of glutathione reductase from eastern white pine needles

Glutathione reductase (EC 1.6.4.2) was purified from Eastern white pine (Pinus strobus L.) needles. The purification steps included affinity chromatography using 2′, 5′-ADP-Sepharose, FPLC-anion-exchange, FPLC-hydrophobic interaction, and FPLC-gel filtration. Separation of proteins by FPLC-anion-exchange resulted in the recovery of two distinct isoforms of glutathione reductase (GR_A and GR_B). Purified GR_A had a specific activity of 1.81 microkatals per milligram of protein and GR_B had a specific activity of 6.08 microkatals per milligram of protein. GR_A accounted for 17% of the total units of glutathione reductase recovered after anion-exchange separation and GR_B accounted for 83%. The native molecular mass for GR_A was 103 to 104 kilodaltons and for GR_B was 88 to 95 kilodaltons. Both isoforms of glutathione reductase were dimers composed of identical subunit molecular masses which were 53 to 54 kilodaltons for GR_A and 57 kilodaltons for GR_B. The pH optimum for GR_A was 7.25 to 7.75 and for GR_B was 7.25. At 25°C the K_m for GSSG was 15.3 and 39.8 micromolar for GR_A and GR_B, respectively. For NADPH, the K_m was 3.7 and 8.8 micromolar for GR_A and GR_B, respectively. Antibody produced from purified GR_B was reactive with both native and denatured GR_B, but was cross-reactive with only native GR_A.     

Carbon use efficiency depends on growth respiration, maintenance respiration, and relative growth rate. A case study with lettuce

Carbon use efficiency (C_UE, the ratio between the amount of carbon incorporated into dry matter to the amount of carbon fixed in gross photosynthesis) is an important parameter in estimating growth rate from photosynthesis data or models. It previously has been found to be relatively constant among species and under different environmental conditions. Here it is shown that C_UE can be expressed as a function of the relative growth rate (r_GR) and the growth (g_r) and maintenance respiration coefficients (m_r): 1/C_UE = 1 + g_r + m_r/r_GR. Net daily carbon gain (C_dg), r_GR, and C_UE were estimated from whole‐plant gas exchange measurements on lettuce (Lactuca sativa L.) ranging from 24 to 66 d old. Carbon use efficiency decreased from 0.6 to 0.2 with increasing dry mass, but there was no correlation between C_UE and C_dg. The decrease in C_UE with increasing dry mass was correlated with a simultaneous decrease in r_GR. From the above equation, g_r and m_r were estimated to be 0.48 mol mol^?1 and 0.039 g glucose g^–1 dry matter d^?1, respectively. Based on the g_r estimate, the theoretical upper limit for C_UE of these plants was 0.68. The importance of maintenance respiration in the carbon balance of the plants increased with increasing plant size. Maintenance accounted for 25% of total respiration in small plants and 90% in large plants.     

Differential regulation by phytochrome of the appearance of plastidic and cytoplasmatic isoforms of glutathione reductase in mustard (Sinapis alba L.) cotyledons

An increase of glutathione reductase (GR; EC 1.6.4.2) activity during the transformation of mustard (Sinapis alba L.) cotyledons from storage organs to photosynthetically competent leaves was previously found to be controlled by light acting via phytochrome (Drumm, H., Mohr, H., Z. Naturforsch. 28c 559–563, 1973). Two isoforms of GR could be separated by disc electrophoresis. In the present study we have applied ionexchange chromatography to separate isoforms of GR during the development of the cotyledons. Furthermore, the technique of in situ photooxidation of plastids was used to distinguish between plastidic and cytoplasmatic isoforms. The isoform GR₂ is the plastidic enzyme, as shown by its sensitivity to photooxidative treatment, while GR₁ is a cytoplasmatic protein not affected by photooxidative treatment of plastids. Both isoforms are promoted by phytochrome but with different time courses. The appearance of GR₁ is independent of the integrity of the plastids, as one might expect. However, unexpectedly, the phytochrome-mediated re-appearance of GR₂ after a photooxidative treatment is much less affected by photooxidative destruction of the plastids, i.e. by the lack of a particular plastidic factor, than was to be expected from previous experience with typical plastidic proteins. An interpretation of this finding must await measurements at the level of GR₂ mRNA.Abbreviations c continuous - D darkness - FR far-red light (3.5 W·m^-2) - FPLC fast protein liquid chromatography - GR glutathione reductase (EC 1.6.4.2) - NF Norflurazon - R fed light (6.8 W·m^-2) - = Pfr/Ptot wavelength-dependent photoequilibrium of the phytochrome system     

Physiological activity and receptor binding of 9α fluorohydrocortisone

Hepatic gluconeogenic stimulation by 9αfluorocortisol was associated with saturation of GR₁ and GR₃ entities of the glucocorticoid specific receptor (GR), even in presence of spironolactone; renal glycogen levels were not altered. Binding to MR₁ and MR₂ components of the mineralocorticoid specific receptor (MR) in the kidney persisted even in presence of 100 fold excess of nonradioactive corticosterone although this was totally abolished by cold equimolar spironolactone. These data suggest that this fluorinated derivative may be particularly appropriate in studying organ specific responses.     

Production of N2O in soil during decomposition of dead yeast cells with different spatial distributions

Production and sources of N₂O were determined in soil columns amended with autoclaved yeast cells either mixed into or added as 0.5 cm³ lumps to the soil in combination with no or 200 g NO₃ ^--N g^-1. At four occasions over a two-week study period, subsets of cores were measured for N₂O production during 4-hour incubations under atmospheres of ambient air, 10 Pa of C₂H₂, and N₂, respectively. Denitrification enzyme activity (DEA) was assessed in subsamples of cores that had been incubated continuously under air.Autoclaved yeast provided a C-source readily available for denitrifying bacteria in the soil. Nitrous oxide production was negligible in unamended columns whereas accumulated N₂O losses in the presence of yeast material were substantial, varying between 15 to 49 ng N₂O-N g^-1 h^-1. Mixing yeast into the soil caused the highest production of N₂O followed by the yeast lump and no yeast treatments. Incubation in the presence of 10 Pa C₂H₂ indicated that denitrification was the sole source of N₂O, in accordance with an increase in DEA. Nitrous oxide production and DEA peaked after 4–7 days of incubation, and both were unaffected by additional NO₃ ^-. Two-to four-fold responses to anaerobiosis and accumulation of NO₃ ^- and NH₄ ⁺ in proximity of the lumps indicated that N₂O production here was limited by relatively low C-availability. In contrast, 10- to 12-fold responses to anaerobiosis and no accumulation of inorganic N suggested a higher C-availability where yeast was mixed into the soil.     

Modeling seed germination in Melisa officinalis L. in response to temperature and water potential

Seed germination is greatly influenced by both temperature (T) and water potential (ψ) and these factors largely determine germination rate (GR) in the field. Quantitative information about T and ψ effects on seed germination in lemon balm (Melisa officinalis L.) is scarce. The main objective of this study was to quantify seed germination responses of lemon balm to T and ψ, and to determine cardinal temperatures in a laboratory experiment. A segmented model was used to describe the effects of ψ (i.e., T) on GR and other germination parameters. The segmented model estimates were 7.2 °C for base (T _b), 28.9 °C for optimum (T _o), 40.1 °C for ceiling temperature (T _c) and 1.64 physiological days (f _o) (equivalent to a GR_max of 0.610 d^?1 and a thermal time of 35.6 °C days) to reach 50 % maximum germination in the control (0 MPa) treatment (R ² = 0.99, RMSE = 0.005 day^?1). The inherent maximum rate of germination (days) was calculated by the [GR_max = 1/f _o] model. ψ affected cardinal temperatures. From 0 to ?0.76 MPa, when ψ increased, T _b was a constant 7.2 °C to ?0.38 MPa and increased linearly to 20.1 °C as ψ decreased. T _o and f _o increased linearly from 28.9 to 30 °C, and from 1.64 to 5.4 day^?1, respectively as ψ decreased. However, there was no signification difference in T _o as ψ decreased nor did T _c decrease from 40.1 to 35 °C as ψ decreased. T _b, T _c and GR_max were the sole parameters affected by ψ and could be used to characterize differences between ψ treatments with respect to GR at various Ts. Therefore, the segmented model and its parameters can be used in lemon balm germination simulation models.     

Effects of Cadmium,Copper, Lead,and Zinc Contamination on Metal Accumulation by Safflower and Wheat

Accumulation of heavy metals (HMs) in cultivated soils is a continuing environmental problem in many parts of the world. An increase in HM concentration can enhance uptake of toxic metals by crops and enter the human food chain. In this study, the uptake behavior of wheat and safflower was evaluated in a calcareous soil by using 12 undisturbed columns in which half were artificially contaminated. Heavy metals in the form of CdCl₂ (15 mg Cd kg^{? 1}), CuSO₄ (585 mg Cu kg^{? 1}), Pb(NO₃)₂ (117 mg Pb kg^{? 1}), and ZnCl₂ (1094 mg Zn kg^{? 1}) were sprayed on the soil surface and completely mixed in the top 10 cm. The background total concentrations of Cd, Cu, Pb and Zn were 1.6, 29.5, 17.5 and 61.2 mg kg^{? 1}, respectively. After metal application, half of the columns (3 contaminated and 3 uncontaminated) were sown with wheat (Triticum aestivum) and the other half with safflower (Carthamus tinctorious) and grown for 74 days until maturity. After harvesting, soil columns were cut into 10-cm sections and analyzed for HNO₃- and DTPA-extractable metal concentrations. Metal concentrations were also measured in different plant tissues. The results showed that artificial contamination of topsoil decreased the transpiration rate of wheat by 12% and that of safflower by 6%. In contaminated columns, Cd, Cu, Pb, and Zn accumulation in wheat shoot was greater by 8.0-, 1.9-, 3.0-, and 2.1-fold than the control, respectively. Accordingly, these numbers were 46.0-, 1.3-, 1.7-, and 1.6-fold in safflower shoot. Soil contamination with HMs resulted in a 55% decrease in shoot dry matter yield of wheat while it had no significant effect on shoot dry matter of safflower. The normalized water consumption for safflower was therefore not affected by metal contamination (≈ 13 mm H₂O g^{? 1} of dry weight for all safflower and uncontaminated wheat treatments), while contaminated wheat was much less water efficient at about 27 mm H₂O g^{? 1} dry weight. It was concluded that although artificial contamination had a negative effect on wheat growth, it did not affect safflower's normal growth and water efficiency.     

Regulation of formation of covalently bound flavins in liver and cerebrum by thyroid hormones.

The effects of thyroxine (T₄) and triiodothyronine (T₃) treatment upon the formation of [2-¹⁴C]flavins bound covalently to tissue proteins in liver and cerebrum were measured 1 h after a subcutaneous injection of [2-¹⁴C]riboflavin in male rats of different ages. In livers of rats of ages 2, 3, and 12 months, T₄ (100 μg/100 g body wt) and T₃ (25 μg/100 g body wt) in daily intraperitoneal doses for 7 days each increased incorporation into covalently bound flavins 50% above that in saline-treated controls. In newborn rats, T₄ in doses of 10 μg/rat for 7 days increased incorporation similarly to that in adults. In adult rats doses of T₃ from 2.5 to 25 μg/100 g body wt were nearly as effective as larger doses of T₃ and T₄ in increasing the formation of covalently bound flavins in liver. In cerebra of newborn rats, T₄ was ineffective in increasing the formation of covalently bound flavins. However, in cerebra of rats of ages 2, 3, and 12 months, both T₃ and T₄ consistently increased the formation of covalently bound flavins. Doses of T₃ from 2.5 to 25 μg/100 g body wt produced significant increases. These findings are of interest in view of our previous demonstration that the formation of flavin adenine dinucleotide, the major tissue flavin, is not increased in rat brain even by massive doses of thyroid hormones. The present results indicate that the formation of the fraction of flavins bound covalently to tissue proteins differs from the usual pattern of brain metabolism of adult rats in being subject to control by thyroid hormones.     

Cytoplasmic DNA-binding phosphoproteins of Physarum polycephalum.

The cytoplasmic DNA-binding proteins of Physarum polycephalum were recovered by chromatography of cytosol extracts on sequential columns of native and denatured calf thymus DNA-cellulose. 5.4% of the total cytosol protein was bound to native DNA-cellulose, while 4.4% was bound to denatured DNA-cellulose. Stepwise salt gradient elution of the columns separated the DNA-binding proteins into 9 fractions which were analysed by acrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. Several hundred discrete polypeptide bands were identified, with many more high molecular weight polypeptides (greater than 100 000 D) binding to native than to denatured DNA. Continuous in vivo labelling of microplasmodia in KH₂[³²P]O₄ and [³H]leucine was used to determine which of the DNA-binding proteins were phosphorylated, and to approximate their phosphorus content. About 30–40 phosphoproteins were resolved among the DNA-binding proteins. Most phosphoproteins contained less than 3 phosphates per polypeptide, but a small number of low molecular weight phosphoproteins (less than 50 000 D) contained from 5 to 10 phosphates per polypeptide. The majority of high molecular weight DNA-binding phosphoproteins bound to native DNA and were eluted with 0.25 M NaCl. As a group, the DNA-binding proteins were enriched in protein-bound phosphorus when compared with the cytosol proteins which did not bind to DNA. The phosphorus content of the cytoplasmic DNA-binding proteins was similar to that of the acidic nuclear proteins.     

Tight nucleotide binding sites and ATPase activities of theRhodospirillum rubrum RrF1-ATPase as compared to spinach chloroplast CF1-ATPase

SolubilizedRhodospirillum rubrum RrF₁-ATPase, depleted of loosely bound nucleotides, retains 2.6 mol of tightly bound ATP and ADP/mol of enzyme. Incubation of the depleted RrF₁ with Mg²⁺-ATP or Mg²⁺-AMP-PNP, followed by passage through two successive Sephadex centrifuge columns, results in retention of a maximal number of 4 mol of tightly bound nucleotides/mol of RrF₁. They include 1.5 mol of nonexchangeable ATP, whereas all tightly bound ADP is fully exchangeable. A similar retention of only four out of the six nucleotide binding sites present on CF₁ has been observed after its passage through one or two centrifuge columns. These results indicate that the photosynthetic, unlike the respiratory, F₁-ATPases have fasterk _off constants for two of the Mg-dependent nucleotide binding sites. This could be the reason for the tenfold lower Mg²⁺ than Ca²⁺-ATPase activity observed with native RrF₁, as with -depleted, activated CF₁. An almost complete conversion of both RrF₁ and CF₁ from Ca²⁺- to Mg²⁺-dependent ATPases is obtained upon addition of octylglucoside, at concentrations below its CMC, to the ATPase assay medium. Thus, octylglucoside seems to affect directly the RrF₁ and CF₁ divalent cation binding site(s), in addition to its proposed role in relieving their inhibition by free Mg²⁺ ions. The RrF₁-ATPase activity is 30-fold more sensitive than CF₁ to efrapeptin, and completely resistant to either inhibition or stimulation by the CF₁ effector, tentoxin. Octylglucoside decreases the inhibition by efrapeptin and tentoxin, but exposes on CF₁ a low-affinity, stimulatory site for tentoxin.Abbreviations: CF₁, EcF₁, MF₁, and TF₁, the soluble F₁-ATPase from chloroplasts, PE. coli, mitochondria,R. rubrum, and the thermophilic bacterium PS3, respectively: AMP-PNP, adenylyl-, -imidodiphosphate; CMC, critical micellar concentration; DTT, dithiothreitol, LDAO, lauryl dimethylamine oxide.Dedicated to Professor Achim Trebst in honor of this 65th birthday.     

Sulfur dynamics in mineral horizons of two northern hardwood soils. A column study with 35S

Sulfur dynamics of two Spodosols were ascertained using soil columns constructed from homogenized mineral soil from nothern hardwood ecosystems at the Huntington Forest (HF) in the Adirondack Mountains of New York and Bear Brook Watershed in Maine (BBWM). Columns were leached for 20 weeks with a simulated throughfall solution with³⁵SO₄ ^2-. Sulfur constituents were similar to those of other Spodosols, with the organic S fractions (C-bonded S and ester sulfate) constituting over 90% of total S. HF soil columns had higher total S (14.9 mol S g^-1) than that for the BBWM soil columns (7.4 mol g^-1) primarily due to higher C-bonded S in the former.Initially, adsorbed SO₄ ^- accounted for 5 and 4% of total S for the BBWM and HF soil columns, respectively. After 20 weeks, adsorbed SO₄ ^2- decreased (81%) in BBWM and increased (33%) in HF soil columns. For both HF and BBWM soil columns, C-bonded S increased and ester sulfate decreased, but only for HF columns was there a net mineralization of organic S (5.6% of total S). The greatest decrease in ester sulfate occurred at the top of the columns.Leaching of³⁵S was less than 0.5% of the³⁵S added due to its retention in various S constituents. There was an exponential decrease in³⁵S with column depth and most of the radioisotope was found in C-bonded S (70–88 and 70–91% for BBWM and HF, respectively). The rapid turnover of adsorbed SO^2- ₄ was reflected in its high specific activity (834 and 26 kBq mol^-1 S for BBWM and HF, respectively). The lower specific activity of adsorbed SO₄ ^2- in HF was attributable to greater isotopic dilution by non-radioactive SO^2- ₄ derived from greater organic S mineralization in the HF versus the BBWM columns.Both soil columns initially had high levels of NO^- ₃ which resulted in the generation of H⁺ and net retention of SO₄ ^2- in the early phase of the experiment due to pH dependent sulfate adsorption; later NO₃ ^- decreased and SO₄ ^2- was desorbed. Leaching of NIO₃ ^- and SO₄ ^2- was correlated with losses of Mg²⁺ and Ca²⁺ of which the latter was the dominant cation.Analyses using both S mass balances and radioisotopes corroborate that for BBWM soil columns, SO^2- ₄ adsorption-desorption dominated the S biogeochemistry while in HF soil columns, organic S mineralization-immobilization processes were more important. It is suggested that similar techniques can be applied to soils in the field to ascertain the relative importances of SO₄ ^2- adsorption processes and organic S dynamics.     

Hydrological and biogeochemical controls on the timing and magnitude of nitrous oxide flux across an agricultural landscape

Anticipated increases in precipitation intensity due to climate change may affect hydrological controls on soil N₂O fluxes, resulting in a feedback between climate change and soil greenhouse gas emissions. We evaluated soil hydrologic controls on N₂O emissions during experimental water table fluctuations in large, intact soil columns amended with 100 kg ha^?1 KNO₃‐N. Soil columns were collected from three landscape positions that vary in hydrological and biogeochemical properties (N= 12 columns). We flooded columns from bottom to surface to simulate water table fluctuations that are typical for this site, and expected to increase given future climate change scenarios. After the soil was saturated to the surface, we allowed the columns to drain freely while monitoring volumetric soil water content, matric potential and N₂O emissions over 96 h. Across all landscape positions and replicate soil columns, there was a positive linear relationship between total soil N and the log of cumulative N₂O emissions (r²= 0.47; P= 0.013). Within individual soil columns, N₂O flux was a Gaussian function of water‐filled pore space (WFPS) during drainage (mean r²= 0.90). However, instantaneous maximum N₂O flux rates did not occur at a consistent WFPS, ranging from 63% to 98% WFPS across landscape positions and replicate soil columns. In contrast, instantaneous maximum N₂O flux rates occurred within a narrow range (?1.88 to ?4.48 kPa) of soil matric potential that approximated field capacity. The relatively consistent relationship between maximum N₂O flux rates and matric potential indicates that water filled pore size is an important factor affecting soil N₂O fluxes. These data demonstrate that matric potential is the strongest predictor of the timing of N₂O fluxes across soils that differ in texture, structure and bulk density.     

Isolation of an organic anion binding protein from rat liver plasma membrane fractions by affinity chromatography

As part of a study of hepatic organic anion transport, solubilized liver plasma membrane proteins were subjected to affinity chromatography on bilirubin- and sulfobromophthalein-labeled agarose columns. Both columns retained a Sudan Black and PAS negative protein of molecular weight 60,000 daltons, which cochromatographed with [³⁵S]sulfobromophthalein on Sephadex G-75, and reversibly bound [³⁵S]sulfobromophthalein in vitro with high affinity (K_a ? 10⁷ M^?1) and a valence of 2. Erythrocyte ghost membranes did not contain this protein. Sulfobromophthalein-agarose retained two additional smaller proteins which did not cochromatograph with [³⁵S]sulfobromophthalein. Their significance is unclear. This study supports the hypothesis that liver cell plasma membranes participate in the hepatic transport of organic anions.     

Nutrient uptake by intact and disturbed roots of loblolly pine seedlings

Most measurements of nutrient uptake use either hydroponic systems or soil-grown roots that have been disturbed by excavation. The first objective of this study was to test how root excavation affects nitrate uptake. Rates of NO₃^? uptake by mycorrhizal loblolly pine (Pinus taeda L.) seedlings were measured in intact sand-filled columns, hydroponics, and disturbed sand-filled columns. Total nitrate uptake in intact sand-filled columns was higher than in disturbed columns, indicating that disturbance lowers uptake. Transferring plants from the sand-filled columns to hydroponics had little effect on NO₃^? uptake beyond delaying uptake for an hour. The second objective of this study was to determine whether NH₄⁺, Ca²⁺, Mg²⁺ and K⁺ uptake could be studied using sand-filled columns, since previous studies had tested this method only for nitrate uptake. Uptake rates of NH₄⁺ and K⁺ were positive, while Ca²⁺ and Mg²⁺ uptake rates were negative in intact sand-filled columns, indicating that net efflux may occur even without physical disturbance to the root system. The sand-filled column approach has some limitations, but holds promise for conducting nutrient uptake studies with minimal disturbance to the root system.     

Formation of bound gibberellins inPharbitis nil

Summary Developing seeds ofPharbitis nil accumulate free as well as bound gibberellins until a maximum level is reached at approximately 25 days after anthesis. Seeds from CCC-treated parent plants have a strongly reduced level of free as well as bound gibberellins. When different spray reagents were used it was found that trichloroacetic acid in particular was suitable to locate non-hydrolysed bound GA fractions on thin-layer plates. Chromatography showed two major bound GA fractions, determined with spray reagents as well as by means of hydrolysis.³H-GA₁ applied to youngPharbitis plants was converted to two water-soluble compounds present in the aqueous phase. The rate of conversion was significantly enhanced when³H-GA₁ and¹⁴C-glucose were applied to the same plants. Chromatography indicated that one of the conversion products of³H-GA₁ became at least partly associated with the applied¹⁴C-glucose (or its products). This suggestion was also supported by the fact that mild acid hydrolysis of the aqueous fraction resulted in the reappearance of³H-GA₁ and a conversion product of³H-GA₁, including a¹⁴C-radioactivity peak cochromatographing with¹⁴C-glucose. However, the conversion products obtained with³H-GA₁ applied to plants appeared to be chromatographycally different from any of the bound-GA fraction established by means of hydrolysis or spray reagents in developing seeds.Abbreviation GA(s) gibberellin(s).     

Paradoxical nature of estrogen agonist and antagonist binding in rat liver

Whereas Tamoxifen exerts potent antiestrogenic action in ER dependent breast cancer, it was largely without effect on rat liver gluconeogenesis which could be dramatically diminished by estrogens and androgens. Although estradiol was preferentially bound to an ER₄ component that coeluted with CBG from DE-52 columns, ³H-tamoxifen labelled the ER₃ moiety that was clearly distinct from transcortin. Similarly, testosterone was bound to the AR₄ entity but R-1881 was eluted in the AR₃ region. All these ER and AR populations were furthermore distinct from liver GR. These, for the first time, demonstrate polymorphic nature of AR and ER and suggest that agonist and antagonist actions may be expressed via separate populations of the receptor, contrary to the established, classical view that dictates competitive antagonism between them for the one and the same site.