Uptake and polar transport of indoleacetic acid in moss rhizoids

In the cucumber ( Cucumis sativus L. cv. Straight Eight) cotyledon expansion assay, cytokinin-stimulated ethylene production was separated from cytokinin-stimulated growth through the use of potassium and calcium salts. Low concentrations of KC1, which dramatically promoted growth induced by cytokinin, inhibited ethylene evolution, while CaCl₂ at a concentration that had no effect on growth, strongly promoted the cytokinin-induced ethylene evolution. In contrast to the growth response, stimulation of ethylene production was not directly related to the presence of potassium or calcium but to their relative concentrations. Concentrations of KCl and CaCl₂ which promoted ethylene evolution singly, strongly inhibited it when mixed together. Low rates of exogenous ethylene had no effect on the growth response. Both the growth and ethylene responses were found to be general cytokinin phenomena. Cotyledon respiration was promoted by KC1, CaCl₂ and cytokinin, but its stimulation was not correlated with either growth or ethylene production. In the presence of KClm cytokinin-induced respiration sharply lowered the content of certain sugars during the large growth response and followed KCl uptake. Analysis of KCl uptake showed that its growth promoting synergism with cytokinin was not due to osmotic effects.     

Biogenic Amine-Stimulated Cyclic Adenosine-3'',5''-Monophosphate Formation in the Rat Carotid Body

The subcutaneous injection of isoprenaline, salbutamol, histamine, and adrenaline to rats, which were subsequently killed by microwave irradiation, resulted in a rapid increase in the cyclic AMP content of the carotid body. On the other hand, noradrenaline, dopamine, adenosine, and 5-hydroxytryptamine, at doses at least 100 times greater than that of isoprenaline, did not significantly alter the cyclic nucleotide content in vivo. The response to isoprenaline was dose related, with an ED50 of 15 micrograms X kg-1, and reached a peak level 1-1.5 min after injection. Incubation of intact carotid bodies with isoprenaline (10(-5) M) in vitro also resulted in a 10-fold increase in cyclic AMP content. The in vivo response to isoprenaline could be blocked stereo-selectively by propranolol, and ICI 118.551, a beta 2-selective antagonist, blocks the isoprenaline-elicited increase in cyclic AMP completely at a dose of 30 micrograms X kg-1; whereas betaxolol, a beta 1-selective antagonist, was ineffective, even at a dose of 300 micrograms X kg-1. Hypoxia (5% oxygen in 95% N2) did not result in a significant increase in the cyclic AMP content, nor did it significantly alter the isoprenaline-stimulated increase in the cyclic AMP content of the rat carotid body. These results suggest that some catecholamines may stimulate cyclic AMP formation by interacting with a beta 2-adrenoceptor in the rat carotid body.     

A chemiluminescent method for measurement of activated oxygen forms in biological fluids and homogenates

A chemiluminescent method for measuring the concentration of activated oxygen species (O₂² and H₂O₂) is described. Its main features are: high sensitivity (10^?9 M H₂O₂), its applicability to systems with high optical absorbance in the visible spectral region, a wide linear dynamic range, and the possibility for recording the kinetics of the processes, in which activated oxygen species are involved.     

Vanadate-stimulated oxidation of NAD(P)H

Vanadate stimulates the oxidation of NAD(P)H by biological membranes because such membranes contain NAD(P)H oxidases which are capable of reducing dioxygen to O₂⁻ and because vanadate catalyzes the oxidation of NAD(P)H by O₂⁻, by a free radical chain mechanism. Dihydropyridines, such as reduced nicotinamide mononucleotide (NMNH), which are not substrates for membrane-associated NAD(P)H oxidases, are not oxidized by membranes plus vanadate unless NAD(P)H is present to serve as a source of O₂⁻. When [NMNH] greatly exceeds [NAD(P)H], in such reaction mixtures, one can observe the oxidation of many molecules of NMNH per NAD(P)H consumed. This reflects the chain length of the free radical chain mechanism. We have discussed the mechanism and significance of this process and have tried to clarify the pertinent but confusing literature.     

Behavioral adaptations for raiding in the slave-making ant,Polyergus breviceps

We studied recruitment behavior of the slavemaking ant Polyergus breviceps,which typically raids colonies of Formica gnava.The first test series demonstrated the importance of social context, by showing that recruitment was high during raiding, but virtually absent during preraid circling and during the return trip after a slave raid. The second test series showed that Formicapupae (alone or together with adults) must be present for workers of Polyegrusto recruit nestmates. The third test series demonstrated that panic alarm by raided Formicais caused by a pheromone, and we suggest that adults of Formicamay be the source of this secretion. Finally, the fourth test series showed that formic acid is lethal to adults of Formicabut has almost no adverse effect on Polyergus.This relative immunity by Polyergusmay enable them to remain organized while entering nests of Formicaduring slave raids.     

Stereospecific production of the herbicide phosphinothricin (glufosinate) by transamination: cloning, characterization, and overexpression of the gene encoding a phosphinothricin-specific transaminase from Escherichia coli

We have cloned the gene encoding a 43-kilodalton transaminase from Escherichia coli K-12 with a specificity for L-phosphinothricin [L-homoalanine-4-yl-(methyl)phosphinic acid], the active ingredient of the herbicide Basta (Hoechst AG). The structural gene was isolated, together with its own promoter, and shown to be localized on a 1.6-kilobase DraI-BamHI fragment. The gene is subject to catabolite repression by glucose; however, repression could be relieved completely when 4-aminobutyrate (GABA) served as the sole nitrogen source. The regulation pattern obtained and a comparison of the restriction map of the initially cloned 15-kilobase SalI fragment with the physical map of the E. coli K-12 genome suggest that the cloned gene is identical with gabT, a locus on the gab gene cluster of E. coli K-12 which codes for the GABA:2-ketoglutartate transaminase (EC 2.6.1.19). A number of expression plasmids carrying the isolated transaminase gene were constructed. With these constructs, the transaminase expression in transformants of E. coli could be increased up to 80-fold compared with that in a wild-type control, and the transaminase constituted up to 20% of the total soluble protein of the bacteria. Thus, the protein crude extracts of the transformants could be used, after a simple heat precipitation step, for the biotechnological production of L-phosphinothricin in an enzyme reactor.     

Dual Effects of K+ Depoiarisation on Inositol Polyphosphate Production in Rat Cerebral Cortex

Depolarisation of [3H]inositol-prelabelled slices of rat cerebral cortex with elevated extracellular K+ induced a rapid and marked increase in inositol polyphosphate accumulation. Addition of the muscarinic antagonist atropine (10 microM) markedly inhibited the K+-induced accumulation of inositol tetrakisphosphate (InsP4), with only a slight reduction in stimulated inositol bis- and trisphosphate levels. Inhibitory effects on InsP4 were noted at the earliest time period measured (30 s) and suggested the involvement of released endogenous acetylcholine in part of the response. The atropine-insensitive component of depolarisation did not appear to be secondary to release of noradrenaline, histamine, or 5-hydroxytryptamine, because addition of prazosin, mepyramine, or ketanserin was without effect on the K+ response. Furthermore, secretion of a neuropeptide that could stimulate phosphoinositide hydrolysis was unlikely, because the peptidase inhibitor bacitracin was also without effect. The results suggest that endogenous acetylcholine can stimulate phosphoinositide metabolism by interacting with muscarinic receptors and that this is particularly evident on InsP4 accumulation. Atropine-insensitive responses may be secondary to Ca2+ entry via voltage-sensitive channels.     

Expression of bovine adrenodoxin in E. coli and site-directed mutagenesis of /2 Fe-2S/ cluster ligands.

Expression systems for adrenodoxin into the periplasm and the cytoplasm of E. coli have been developed as a prerequisite for site-directed mutagenesis studies. In both systems the /2Fe-2S/ cluster of the protein was correctly assembled, the cytoplasmic one gives, however, a tenfold higher expression level. To determine which of the five cysteines at positions 46, 52, 55, 92, and 95 coordinate the /2Fe-2S/ center, they have been individually mutated into serines. From these mutants, only C95S forms a functionally active holoprotein. Thus, residues 46, 52, 55, and 92 are the cysteines that coordinate the /2Fe-2S/ cluster in adrenodoxin.     

Conversion of fat into yeast biomass in protein-containing waste-water

Summary Candida tropicalis S001 was grown on the lipid fraction of a protein-containing waste-water in order to (i) remove fat from the water, and (ii) produre yeast biomass for feed. The yeast cells were separated from the waste-water by sedimentation. Defatted waste-water was used for methane production and gave a yield of a 0.3 m³ methane/kg reduced chemical oxygen demand. The maximum specific growth rate (µ_max) of C. tropicalis growing on waste-water fat at pH 4.0 was 0.35 h^–1; the fat content was decreased from 8 g/l to about 0.1 g/l within 24 h. In continous culture a corresponding reduction was maintained at dilution rates up to 0.36 h^–1. The effect on growth of pH, temperature and CO₂ concentration was studied with triolein as the major carbon source. The µ_max was nearly constant (0.16 h^–1) in the pH and temperature range of 3.2–4.0 and 30°–38° C, respectively; 10% CO₂ was optimal for growth. Growth on triolein resulted in a biomass yield of 0.70 g dry weight/g fat. Offprint requests to: S. Rydin     

Formalin fixation strongly influences biomechanical properties of the spine

As fresh human cadaveric spine specimens for in vitro testing are hard to obtain and carry a potential risk of infection, the possibility of using embalmed spine specimens has been considered. The cross-linking effect of formalin fixation, however, raises uncertainties regarding the biomechanical likeness of preserved specimens. They have been reported to be stiffer, but no quantitative data exist.

The purpose of this study was to determine the biomechanical differences between fresh and formalin-fixed spine specimens, using L1–2 motion segments from six 16-week-old calf spines. The range of motion and neutral zone were determined in flexion-/extension, left/right axial rotation, and right/left lateral bending.

The range of motion decreased in the formalin fixed specimens by as much as 80%, and the neutral zone by as much as 96%. The results of this study therefore imply that, for biomechanical testing, formalin-fixed specimens are not representative of the in vivo conditions.