Water hyacinth productivity and detritus accumulation

Water hyacinth [Eichhornia crassipes (Mart) Solms] productivity and detritus accumulation were evaluated in eutrophic lake water with and without added nutrients (fertilized and control reservoirs, respectively). Seasonal changes in plant productivity and detritus accumulation were determined at monthly intervals for one year. Significant differences were observed in plant productivity between seasons and nutrient additions. Seasonal plant productivity ranged from 1.9 to 23.1 mg (dry wt) ha⁻¹ for the fertilized reservoir and −0.2 to 10.2 mg ha⁻¹ for the control reservoir. Detritus accumulation was not significantly different between seasons or nutrient additions. Seasonal N assimilation by plants ranged from 34 to 242 kg N ha⁻¹ for plants in the fertilized reservoir and < 0 to 104 kg N ha⁻¹ for plants in the control reservoir. Annual net N recovered in detritus represented 21 and 28% of the total N removed by plants in the fertilized and control reservoirs, respectively. Net N loading to the reservoirs from detritus was 92 to 148 kg N ha⁻¹ yr⁻¹.     

Characterization of the glycosylation sites in yeast external invertase. I. N-linked oligosaccharide content of the individual sequons

External invertase is the product of the SUC2 gene of Saccharomyces cerevisiae. The deduced sequence of this enzyme (Taussig, R., and Carlson, M. (1983) Nucleic Acid Res. 11, 1943-1954) reveals it to contain 14 potential N-linked glycosylation sites, or sequons, although only 9-10 appear to be glycosylated (Trimble, R. B., and Maley, F. (1977) J. Biol. Chem. 252, 4409-4412). To determine the location of the glycosylated sequons, external invertase was deglycosylated with endo-beta-acetylglucosaminidase H and its component peptides analyzed by both fast atom bombardment mass spectrometry (FABMS) and classical peptide isolation procedures. By use of the former technique most of the glucosamine-containing sequons could be located and by the latter sufficient amounts of small glucosamine-containing peptides were isolated to enable their quantitation. From the combined FABMS and glucosamine analyses, it was established that eight of the sequons in a subunit of invertase are either completely or almost completely glycosylated, while five others are glycosylated to the extent of about 50% or less. In the case of two overlapping sequons (4 and 5), which include Asn92-Asn93-Thr-Ser, only the first Asn was glycosylated. Thus, all but one of the sequons of external invertase are glycosylated to some extent, giving an appearance of only 9-10 N-linked oligosaccharides/subunit. The sequence identity of both external and internal invertase was verified by FABMS and by peptide sequence analysis. In only one site was an amino acid found to differ from that deduced from the DNA sequence of the SUC2 gene. This occurred at position 390 where a proline was found in place of alanine, which could result from a single base change in the triplet specifying the latter amino acid.     

Diurnal rhythm in levels of haemolymph sugar and hyperglycaemic activity of eyestalk extract in the fresh water rice field crab (Oziotelphusa senex senex Fabricius)

The concentration of haemolymph sugar and the hyperglycaemic activity of eyestalk extract was measured six times (8, 12, 16, 20 and 4 h) over a 24-h period. The concentration of haemolymph sugar and hyperglycaemic activity of eyestalk extract was higher during the night (0 h through 8 h) than that noted in day time (12 h). The variations are closely related to the activity of the animal.     

Solid-phase syntheses of oligodeoxyribonucleoside methylphosphonates

Oligodeoxyribonucleoside methylphosphonates of defined sequence of the type d-Np(NP)nN, where n is 6-13, are readily prepared on insoluble polystyrene supports by use of protected 5'-(dimethoxytrityl)deoxyribonucleoside 3'-(methylphosphonic imidazolides) as synthetic intermediates. The imidazolides are prepared in situ by reaction of protected 5'-(dimethoxytrityl)deoxyribonucleoside with methylphosphonic bis(imidazolide) and can be stores in the reaction solution for up to 2 weeks at 4 degrees C with no loss in activity. The condensation reaction is accelerated by the presence of tetrazole, which appears to act as an acid catalyst. The half-life for dimer formation on the polystyrene support is 5 min, and the reaction is 95% complete after 60 min. Although similar kinetics are observed when controlled pore glass is used as the support, the extent of the reaction does not go beyond 78%, even after prolonged incubation. In order to simplify purification and sequence analysis of the oligomer, the 5'-terminal nucleoside unit is linked via a phosphodiester bond. This linkage may be introduced by either an o-chlorophenyl phosphotriester method or a cyanoethyl phosphoramidite method. The latter procedure simplifies the deprotection step, since the cyanoethyl group is readily cleaved by ethylenediamine, which also removes the base protecting groups and cleaves the oligomer from the support. The singly charged oligomers are easily purified by affinity chromatography on DEAE-cellulose. The chain lengths of the oligomers were confirmed after 5'-end labeling with polynucleotide kinase by partial hydrolysis of the methylphosphonate linkages with 1 M aqueous piperidine followed by polyacrylamide gel electrophoresis of the hydrolysate.(ABSTRACT TRUNCATED AT 250 WORDS)     

Stomatal Movement and Sucrose Uptake by Guard Cell Protoplasts of Commelina benghalensis L.

Sucrose concentration in guard cells of epidermal strips ofCommelina benghalensis increased with stomatal opening. Sucroseuptake patterns were investigated using guard cell protoplastsof C. benghalensis. Sucrose (0.5 mM) uptake into these protoplastswas sensitive to pH, with an optimum at pH 6. Uptake of sucroseinto guard cell protoplasts was inhibited by 2,4-dinitrophenol(DNP), diethylstilbestrol (DES) and (ptrifluoromethoxy)carbonylcyanide phenylhydrozone (FCCP), while DCMU and o-phenanthrolinehad no effect on the uptake of sucrose. Fusicoccin (FC) stimulatedsucrose influx. The influence of pH and the effect of the metabolicinhibitors on the sucrose uptake into the guard cell protoplastsare consistent with an energy dependent membrane-function. (Received July 7, 1986; Accepted September 26, 1986)     

Stimulation of Escherichia coli adenylate cyclase activity by elongation factor Tu, a GTP-binding protein essential for protein synthesis

A unique feature of eucaryotic adenylate cyclases is their interaction with GTP-binding proteins that mediate hormonal responses. Until now, there has been no evidence for regulation of Escherichia coli adenylate cyclase by a GTP-binding protein. We describe here that the most abundant protein in E. coli, the GTP-binding protein EF-Tu, which is important as an elongation factor in protein synthesis, also serves as a stimulator of adenylate cyclase activity. Homogeneous EF-Tu specifically increased the activity of purified adenylate cyclase as much as 70%; other E. coli GTP-binding proteins had no effect on enzyme activity. A study of the guanine nucleotide specificity for EF-Tu-mediated stimulation of adenylate cyclase activity suggested that the preferred activator is EF-Tu X GDP. To account for the GTP-specific stimulation of adenylate cyclase activity observed in intact cells, we propose that the nucleotide specificity for EF-Tu-dependent activation of adenylate cyclase is governed by other factors in the cell.     

Effect of Light and Benzyladenine on Dark-Treated Growing Rice (Oryza sativa) Leaves II. Changes in Peroxidase Activity

Changes in peroxidase activity were studied in the attachedfirst leaf of dark-treated Oryza sativa L. cv. Bala seedlingsin response to benzyladenine and light treatments during laterperiods of leaf growth, prior to maturation. Darkness causeda mild decrease in peroxidase activity; but in illuminated leaves,the enzyme activity was stable at all times. There was a sharprise in peroxidase activity in dark-treated leaves upon lightor benzyladenine application, irrespective of the time of treatment.Benzyladenine treatment to illuminated leaves also caused arise in peroxidase activity. Exogenous hydrogen peroxide, glycolateand amizol resulted in a rise in peroxidase activity, whichwas further enhanced by benzyladenine treatment in both lightand dark incubated leaves. Proline maintained chlorophyll levels,whereas hydroxyproline caused chlorophyll degradation. Benzyladenineenhanced the proline effect and counteracted the hydroxyprolineeffect on chlorophyll. Both proline and hydroxyproline increasedperoxidase activity in the leaves of light and dark incubatedseedlings, and the enzyme activity further increased after benzyladeninetreatment. (Received December 7, 1984; Accepted May 8, 1985)     

HTLV-III env gene products synthesized in E. coli are recognized by antibodies present in the sera of AIDS patients

The envelope gene of HTLV-III, the retrovirus directly linked to AIDS, encodes a protein of 856 amino acids. Our sequence analysis of the cloned HTLV-III (HXB-3) env gene and its comparison with other isolates reveal significant divergence, especially in the external portion of this protein. A large segment of the env gene (1800 bp) was inserted into the expression vector pEV-vrf3, and a corresponding 68 kd protein, which encompasses both the extracellular and the membrane-associated regions of the native protein, was produced in E. coli. Several smaller polypeptides, which appear to be internal initiation products, were also produced. All 50 AIDS patient sera obtained from different locations in the United States specifically recognized the bacterially synthesized envelope proteins, as judged by Western blots. This suggests that these proteins will be useful for the diagnosis of HTLV-III infection and possibly as a vaccine against AIDS.     

Phosphoethanolamine and phosphocholine transferases in gray matter and white matter from developing rat brain

We have studied the activities of 2′,3′-cyclic nucleotide 3′-phosphohydrolase, 1,2-diacylglycerol: CDPethanolamine phosphoethanolamine transferase (EC 2.7.8.1), and 1,2-diacylglycerol: CDPcholine phosphocholine transferase (EC 2.7.8.2) in developing rat brain gray matter and white matter. The specific activity of cyclic nucleotide phosphohydrolase was 5–8 fold higher in white matter than in gray matter at all ages. No significant changes were observed during development. The specific activity of phosphocholine transferase was 2 to 3 fold higher than phosphoethanolamine transferase at all ages both in gray and white matter. Both phosphocholine transferase and phosphoethanolamine transferase increased more than 2 fold in specific activity between 14 and 90 days of age. The total activity of phosphocholine transferase also showed an increase during development. The apparentK _m values for nucleotides and dicaprin were similar in gray matter and white matter. Except for lowK _m values for nucleotides at 14 days of age, no significant changes were observed during development. Changes in rates of glycerophospholipid synthesis may be partly due to the specific activities of these enzymes but are also determined by the quantities of substrates and inhibitors and by affinities for the substrates. Special Issue dedicated to Dr. Eugene Kreps.