Investigations on the mode of action of sodium N-methyldithiocarbamate in Fusarium oxysporum f. sp. lycopersici

Summary A radiorespirometric technique was used to determine the effects of sodium N-methyldithiocarbamate (NaMDC) on uptake and oxidation of glucose by Fusarium oxysporum f. sp. lycopersici. The principal glucose oxidation pathway of the fungus was found to be the pentose cycle. Shifts to other oxidation pathways were not significant even when the fungus was treated with extremely high concentrations of NaMDC (5×10^-2 M). Only when zinc ions were added to NaMDC solutions were shifts in pathway (and a drastic increase in toxicity) noted. The main effect of NaMDC was to delay the complete oxidation of glucose to CO₂. In the concentration range between 0.5 to 10.0×10^-2 M NaMDC dose response curves were bimodal with respect to spore germination, colony development, and CO₂ production; with respect to glucose uptake the curves were unimodal. The bimodal dosage response curves could be divided into a first zone of inhibition, a zone of reversed toxicity, and a second zone of inhibition. Within the first zone of inhibition, colony development proved to be more sensitive to NaMDC than spore germination. In the zone of reversed toxicity the incorporation of carbon into the spores drops sharply, while in the second zone of inhibition a strong inhibition of glucose uptake is the dominating effect. It is indicated that NaMDC interfers with biosynthetic activities rather than enzymes of catabolic pathways.List of abbreviations NaMDC Sodium N-methyldithiocarbamate - NaDMDC Sodium dimethyldithiocarbamate - TMTD Tetramethylthiuram disulfide, [=Bis(dimethylthiocarbamyl)disulfid, Thiram^®] - DMTD N,N-dimethylthiuram disulfide [=Bis-(methylthiocarbamyl)disulfid] - MIT Methylisothiocyanate     

The morphology of an elevator and a depressor motoneuron of the hindwing of a locust

Summary Two metathoracic flight motoneurons of the locustChortoicetes terminifera have been stained by injection of cobalt. The motoneurons innervate the tergosternal (hindwing elevator) muscle 113 and the first basalar (hindwing depressor) muscle 127. The somata of both are on the ventral surface of the ganglion (Fig. 1), and their axons in the ipsilateral nerve 3A. The main neuropilar segment and large medial dendrites of each follow parallel courses through the ganglion even though the two motoneurons subserve antagonistic functions (Fig. 3). Differences in the smaller dendrites add characteristic detail to each. The dendritic trees are complex and cover virtually all of the ipsilateral dorsal neuropile. No branches cross the mid-line so that electrotonic coupling is eliminated as a possible means of co-ordination of motoneurons of the two sides (Fig. 4). The general shape of the motoneurons is similar in different animals but there is variation in the number and extent of the small dendrites (Fig. 6).Beit Memorial Research Fellow.     

Influence of copper and zinc ions on toxicity of sodium N-methyldithiocarbamate to Fusarium oxysporum f. sp. lycopersici

Summary It was found that dl-lactate, acetate, pyruvate, succinate, fumarate, malate, oxalacetate and L-aspartate stimulated considerably the production of the antitumor L-asparaginase EC-2 by a colicinogenic strain of E. coli in Tryptone medium. While in the absence of these stimulative substances enzyme production was about 0.01 IU/mg dry weight, it reached 0.57–1.18 IU/mg in the presence of the substances named above. Maximum effects were obtained at the concentrations 0.025–0.1 M; at higher concentrations enzyme production decreased. L-asparagine raised the enzyme production from 0.05 IU/mg to 0.70 IU/mg; in order to obtain this effect, however, it was necessary to lower the oxygen absorption rate. Citrate and -ketoglutarate had no stimulatory effect; the effect of L-glutamate was negligible. In the cases of dl-lactate, pyruvate and L-aspartate the dependence of stimulatory effects on the time of addition of the stimulants was studied. It was found that in the case of pyruvate and especially of dl-lactate enzyme production increased rapidly between the 4 and 6 h of cultivation, i.e. at the end of the exponential growth phase; it did not matter whether the stimulant had been added at zero, 2 or 4 h of cultivation. In the case of L-aspartate the situation was principally similar, though the enzyme production started later and increased more slowly.     

City-wide screening for urinary abnormalities in schoolgirls

Screening for urinary tract infection was carried out in 23,427 schoolgirls, aged 5 to 14 years, using Uricult and, for hematuria, glycosuria and proteinuria using Hema-combistix. Cultures of 10⁵ colonies per ml. or more on two occasions were obtained in 2.3% and a positive culture was confirmed by the family physician using standard culture techniques in 82.7% of cases, giving an overall incidence of infection of 1.9%. Fifty-eight percent of these children had no previous history of any urinary tract symptoms. Of the infected group 9.5% had pyelonephritic scarring, 58.7% chronic cystitis and 58.7% urethral stenosis. Two additional cases had unilateral ureteropelvic junction obstruction with hydronephrosis. Reflux occurred in 26.6% of those investigated by voiding cystogram. In 58% of cases the urinary tract infection was not accompanied by significant proteinuria, hematuria or pyuria.Proteinuria was detected on two occasions in 1.6% of the children and confirmed by the family physician in 33% of cases, giving an overall incidence of 0.5%. In this group 9.2% had evidence of pyelonephritic scarring without a positive urine culture.Hematuria was detected on two occasions in 0.6% of the children and was confirmed by the family physician in 53%, giving an overall incidence of 0.3%. Only one case with pyelonephritic scarring was seen in this group.Of the 25 cases with pyelonephritic changes only six had been previously diagnosed radiologically.Four previously unrecognized diabetics were also detected.     

Vagotonicity of Violence: Biochemical and Cardiac Responses to Violent Films and Television Programmes

In a search for a reproducible means of evoking different types of emotional stress it was found that in spite of increased adrenaline secretion slowing of the heart occurred when watching violent television programmes. Further evidence of increased vagal tone was provided by the “sinus arrhythmia” effect, a widening of the gap between the maximum and minimum heart rates during the respiratory cycle in parts of the humour, violence, and suspense sections of the television programme.Groups of people taken to see two particularly violent films showed similar evidence suggesting vagal overactivity, together with increases in plasma free fatty acids and decreases in triglycerides. As these changes occurred even with β-blockade it is suggested that they might be caused by non-sympathetically mediated changes in the levels of hormones, such as growth hormone, producing lipolysis.The ability to assess objectively an individual''s reaction to viewing violence might make it possible to judge the likely social impact of violent films and television programmes.     

Thymus cell maturation: II. Differentiation of three “mature” subclasses in Vivo

Several thymus cell subclasses may be defined on the basis of their sedimentation velocity, their light-scattering properties (a measure of cell volume), or binding of a fluoresceinated anti-Thy 1.2 antiserum. Using a multiparameter fluorescence-activated cell sorter (FACS), cells with distinguishable light-scattering or fluorescence intensity (after staining with fluorescein anti-Thy 1.2) were separable for analysis of intrathymic maturation pathways. Outer thymic cortical large and medium lymphocytes were the only cells labeled within 1 hr after transcapsular diffusion of administered [³H]thymidine. These labeled cells were also entirely contained in the brightest fluorescence intensity (with fluorescein anti-Thy 1.2) subclass. Under conditions of [¹H] thymidine “chase” in vivo, label shifted proportionately and apparently in parallel to three “mature” subclasses: (1) small thymocytes with high surface concentrations of Thy 1.2, representing ~ 80% of all thymus cells; (2) slightly larger cells, with very low surface Thy 1.2, which are indistinguishable from cortisone-resistant thymocytes, and which make up less than 10% of all thymus cells; (3) dead or fragile cells.     

The effect of Trypan Blue, suramin and aurothiomalate on the breakdown of 125I-labelled albumin within rat liver lysosomes

1. A fraction enriched in lysosomes was prepared by centrifugation from the livers of rats that had been injected 0.5h before death with (125)I-labelled albumin. When suspended in sucrose-protected buffer, pH7.4, and incubated at 22 degrees C for 2h, the particles progressively released iodotyrosine into the medium. Albumin digestion did not occur if the particles were subjected to treatments known to break lysosomes or if particles from uninjected rats were incubated in medium containing (125)I-labelled albumin. It is concluded that the observed production of iodotyrosine results from protein hydrolysis within intact heterolysosomes. 2. Particles from rats pre-treated with Trypan Blue, suramin or aurothiomalate released iodotyrosine more slowly than controls. Since these compounds are enzyme inhibitors that concentrate in liver lysosomes after administration in vivo, their effect is ascribed to intralysosomal inhibition of proteolysis. The doses used did not decrease endocytosis of albumin into liver or cause increased lysosome breakage during incubation, thus allowing some alternative explanations of the decreased proteolysis to be eliminated. Particulate carbon, a non-inhibitor that also concentrates in lysosomes, did not affect albumin hydrolysis.     

Intrinsic optical and passive electrical properties of cut frog twitch fibers

This article describes a new apparatus for making simultaneous optical measurements on single muscle fibers at three different wavelengths and two planes of linear polarization. There are two modes of operation: mode 1 measures the individual absorbances of light linearly polarized along and perpendicular to the fiber axis, and mode 2 measures retardation (or birefringence) and the average of the two absorbance components. Although some intact frog twitch fibers were studied, most experiments used cut fibers (Hille, B., and D. T. Campbell. 1976. Journal of General Physiology. 67:265-293) mounted in a double-Vaseline-gap chamber (Kovacs, L., E. Rios, and M. F. Schneider. 1983. Journal of Physiology. 343:161-196). The end-pool segments were usually exposed for 2 min to 0.01% saponin. This procedure, used in subsequent experiments to make the external membranes in the end pools permeable to Ca indicators (Maylie, J., M. Irving, N. L. Sizto, G. Boyarsky, and W. K. Chandler. 1987. Journal of General Physiology. 89:145-176; Maylie, J., M. Irving, N. L. Sizto, and W. K. Chandler. 1987. Journal of General Physiology. 89:41-143), was routinely employed so that all our cut fiber results would be comparable. A simple method, which does not require microelectrodes, allowed continual estimation of a fiber's membrane (rm) and internal longitudinal (ri) resistances as well as the external resistance (re) under the Vaseline seals. The values of rm and ri obtained from cut fibers with this method agree reasonably well with values obtained from intact fibers using microelectrode techniques. Optical measurements were made on resting and action potential-stimulated fibers. The intrinsic fiber absorbance, defined operationally as log10 of the ratio of incident light to transmitted light intensity, was similar in intact and cut preparations, as were the changes that accompanied stimulation. On the other hand, the resting birefringence and the peak of the active change in cut fibers were, respectively, only 0.8 and 0.7 times the corresponding values in intact fibers. Both the amplitude and the half-width of the active retardation signal increased considerably during the time course of cut fiber experiments; a twofold increase in 2 h was not unusual. Such changes are probably due to a progressive alteration in the internal state of the cut fibers.