Biological N2 fixation by heterotrophic and phototrophic bacteria in association with straw

Much of the crop residues, including cereal straw, that are produced worldwide are lost by burning. Plant residues, and in particular straw, contain large amounts of carbon (cellulose and hemicellulose) which can serve as substrates for the production of microbial biomass and for biological N₂ fixation by a range of free-living, diazotrophic bacteria. Microorganisms with the dual ability to utilise cellulose and fix N₂ are rate, but some strains that utilize hemicellulose and fix N₂ have been found. Generally, cellulolysis and diazotrophy are carried out by a mixed microbial community in which N₂-fixing bacteria utilise cellobiose and glucose produced from straw by cellulolytic microorganisms. N₂-fixing bacteria include heterotrophic and phototrophic organisms and the latter are apparently more prominent in flooded soils such as rice paddies than in dryland soils. The relative contributions of N₂ fixed by heterotrophic diazotrophic bacteria compared with cyanobacteria and other phototrophic bacteria depend on the availability of substrates from straw decomposition and on environmental pressures. Measurements of asymbiotic N₂ fixation are limited and variable but, in rice paddy systems, rates of 25 kg N ha^-1 over 30 days have been found, whereas in dryland systems with wheat straw, in situ measurements have indicated up to 12 kg N ha^-1 over 22 days. Straw-associated N₂ fixation is directly affected by environmental factors such as temperature, moisture, oxygen concentration, soil pH and clay content as well as farm management practices. Modification of managements and use of inoculants offer ways of improving asymbiotic N₂ fixation.In laboratory culture systems, inoculation of straws with cellulolytic and diazotrophic microorganisms has resulted in significant increases in N₂ fixation in comparison to uninoculated controls and gains of N of up to 72 mg N fixed g^-1 straw consumed have been obtained, indicating the potential of inoculation to improve N gains in composts that can then be used as biofertilisers. Soils, on the other hand, contain established, indigenous microbial populations which tend to exclude inoculant microorganisms by competition. As a consequence, improvements in straw-associated N₂ fixation in soils have been achieved mostly by specific straw-management practices which encourage microbial activity by straw-decomposing and N₂-fixing microorganisms.Further research is needed to quantify more accurately the contribution of asymbiotic N₂ fixation to cropping systems. New strains of inoculants, including those capable of both cellulolytic and N₂-fixing activity, are needed to improve the N content of biofertilisers produced from composts. Developments of management practices in farming systems may result in further improvements in N₂ fixation in the field.     

Theory of initial current density in membrane voltage-clamp experiments

Herein we show that the voltage-clamp current density at zero time calculated from electrodiffusion equations is linear in the clamping voltage for a simple membrane (no charge structure) and for a membrae with fixed charges. Such membranes are nonexcitable. Excitable membranes can be represented by a homogeneous membrane with dipole layers at the surface. In this case the initial current density will be linear in the clamping voltage if a critical field for a dipole layer reorientation is not passed through in changing from holding to clamping potential. Otherwise, deviation from nonlinearity may occur. This is in agreement with experimental data for the squid giant axon.     

Response of continuous cultures to stimuli in glucose feed rate and dilution rate

The response of continuous cultures of yeast was investigated following step disturbances in glucose feed rate and dilution rate. The responses of the culture to the stimuli were oscillatory. The oscillatory responses were explained in terms of cell synchrony which was induced by the step change. An understanding of continuous cultures to stimuli was made possible with an appreciation of the inherently oscillatory events occurring in the single cell cycle between one mitosis and the next. Step changes in glucose feed rate and dilution rate induced a partial synchrony, which enabled the inherently oscillatory behavior of the individual cells to be made observable in the culture as a whole.     

Drug Addiction,Psychotic Illness and Brain Self-Stimulation: Effective Treatment and Explanatory Hypothesis

Similarities between drug addiction and psychotic illness suggested that drug addicts could be treated with intensive ECT and phenothiazine drugs, a therapeutic approach effective in more serious psychotic illnesses.The use of this intensive treatment method is described in six drug addicts. Successful results were achieved in four patients who have been followed up for two to five years. The treatment program, the preliminary investigations and the follow-up procedures are described.Particular reference is made to the brain self-stimulation studies of Olds and others in animals, and those of Heath in man. A hypothesis is advanced to explain the various aspects of the clinical picture in both psychotic illness and drug addiction.The intensive method of treatment should be considered for drug addicts whose prognosis is otherwise poor. Further investigations along the lines of the proposed hypothesis might be profitable in other types of abnormal and maladaptive behaviour.     

The Use of Hypnosis in the Treatment of Exhibitionism

The use of hypnosis in the treatment of exhibitionism is described in three patients in whom the condition had been present for more than five years. In each patient there was no subsequent recurrence of the exhibitionism once therapeutic suggestions had been made in a deep hypnotic trance, the follow-up period being respectively five years, four and a half years, and one year.The method of treatment and the results are discussed in terms of the concepts of behaviour therapy.It is concluded that with certain patients suffering from exhibitionism the use of hypnosis may well be one of the best methods of treatment, but considerable care should be exercised to exclude those patients with an underlying psychosis, mental defect or psychopathic condition. It is also noted that the efficacy of the treatment would appear to depend on achieving a satisfactory depth of hypnotic trance. If this is not reached, the results are less likely to be successful.     

Distribution of ion channels on taste cells and its relationship to chemosensory transduction

Summary The presence and regional localization of voltagegated ion channels on taste cells inNecturus maculosus were studied. Lingual epithelium was dissected from the animal and placed in a modified Ussing chamber such that individual taste cells could be impaled with intracellular microelectrodes and the chemical environment of the apical and basolateral membranes of cells could be strictly controlled. That is, solutions bathing the the mucosal and serosal surfaces of the epithelium could be exchanged independently and the effects of pharmacological agents could be tested selectively on the apical or basolateral membranes of taste cells. In the presence of amphibian physiological saline, action potentials were elicited by passing brief depolarizing current pulses through the recording electrode. Action potentials provided a convenient assay of voltage-gated ion channels. As in other excitable tissues, blocking current through Na⁺, K⁺, or Ca²⁺ channels had predictable and consistent effects on the shape and magnitude of the action potential. A series of experiments was conducted in which the shape and duration of regenerative action potentials were monitored when the ionic composition was altered and/or pharmacological blocking agents were added to the mucosal or to the serosal chamber. We have found the following: (1) voltage-gated K⁺ channels (delayed rectifier) are found predominately, if not exclusively, on the chemoreceptive apical membrane; (ii) voltage-gated Na⁺ and Ca²⁺ channels are found on the apical (chemoreceptive) and basolateral (synaptic) membrane; (iii) there is a K⁺ leak channel on the basolateral membrane which appears to vary seasonally in its sensitivity to TEA. The nonuniform distribution of voltage-gated K⁺ channels and their predominance on the apical membrane may be important in taste transduction: alterations in apical K⁺ conductance may underlie receptor potentials ellicted by rapid stimuli.