The capability of the algaeChlorella vulgaris andScenedesmus obliquus of utilizing amino acids as the sole nitrogen source

The capability of utilizing 20 amino acids and 2 amides as the sole nitrogen source for growth was studied in two green algae (Chlorophyceae). A comparison was made of the growth rate of algae in a mineral nutrient solution containing nitrate as the nitrogen source, with that in the same solution in which nitrogen in the form of nitrate was substituted by an equivalent nitrogen amount in the form of various amino acids. In addition to this, another series of experiments was carried out in whioh both culture media were supplied with glucose. The results show that both algae utilize a series of amino acids in dependence of their structure (mostly 3-carbon amino acids). The growth rate ofChlorella in the presence of these sources is the same as in nitrate, that ofScenedesmus even much higher. In the cultures containing glucose both algal species exhibit a higher growth rate in the media with the nitrate nitrogen source than in those with amino acids (with the exception of glycine inScenedesmus).     

Influence of antilymphocyte and antipolymorphonuclear sera on the pyrogenic effect of scarlet fever toxin

The role played by lymphocytes in the pyretic response to scarlet fever toxin (ET) was studied in vivo using antilymphocyte serum (ALS). Two i.v. injections of ALS inhibited the pyretic response to a subsequent ET injection in rabbits. The course of endotoxin fever remained uninfluenced by ALS. Antipolymorphonuclear serum had no effect on the pyretic response to either of the toxins. Pretreatment with ALS also inhibited the skin reaction after i.d. injection of ET. These findings are further evidence a mediating role of lymphocytes in the biological effects of ET, among other things in the release of endogenous pyrogen.     

Microorganisms in the rhizosphere of wheat colonized by the fungusGaeumannomyces graminis var.tritici

The population of microorganisms in wheat rhizosphere changed in the presence of the fungus Gaeumannomyces graminis var. tritici causing the take-all of wheat. In the majority of cases when the soil was artificially contaminated by the fungus, both the number of bacteria in the rhizosphere and the bacteria/fungi ratio temporarily increased. At the beginning bacteria growing in the presence of NH4+ predominated, later bacteria utilizing organic N-substances prevailed. Pseudomonas fluorescens and the related species colonized the rhizosphere and the soil to a greater extent in the presence of G. graminis. The wheat rhizosphere with G. graminis was found to contain a higher level of the slime-producing bacterium Agrobacterium spp.; this microorganism occurred on hyphal surfaces (in hyphosphere) of both G. graminis growing in soil and Mucor spp. Changes in microbial populations in the wheat rhizosphere during the first stage of colonization by G. graminis can be partly explained by a simultaneous rhizosphere colonization by microorganisms which accompany this fungus in soil. In the period of increase in the number of bacteria in rhizosphere a temporary stimulation of wheat growth was observed.     

Evaluation of three E-rosette assays in melanoma patients

Summary The percentage of E-rosette-forming cells (E-RFC) was determined repeatedly in the peripheral blood of 43 patients with malignant melanoma. Three methods of E-rosette assaying were used: total E-rosette test, active E-rosette test, and 29° C E-rosette assay.Depressed E-RFC values were found in fewer assays than normal values. The mean values of E-RFC and the proportion of depressed E-RFC in patients in stage I did not differ from the values in healthy control persons whatever method of assay was used.The frequency of depressed E-RFC values was higher in advanced stages. Significant differences were demonstrated between stage I and stages II and III combined in the values for total and for active E-rosettes (P<0.01).The active E-rosette test and the 29° C E-rosette assay gave no more positive results (i.e., depressed E-RFC values) than the total E-rosette test in melanoma patients.     

Electron-microscopic localization of acetyl coenzyme A carboxylase in cells of Claviceps purpurea

Summary The ultrastructural localization of acetyl-CoA carboxylase activity was studied in two strains of the ascomycetous fungus Claviceps purpurea differing in the ergot alkaloid synthesis. Mycelia were harvested by centrifugation of saprophytic submerged cultures, fixed in cold 3% glutaraldehyde in 0.05 M cacodylate buffer pH 7.2 and washed repeatedly in the same buffer. The incubation medium of Yates et al. (1969) had to be modified in the molarity of ATP. The best results were obtained with a medium of the following composition: 50 mM cacodylate buffer pH 7.2, 4 mM ATP, 3.5 mM lead nitrate, 13.5 mM sodium citrate, 3.75 mM sodium bicarbonate, 1.25 mM manganese chloride, 0.4 mM acetyl-CoA and 2 mM biotin. The fixation is a prerequisite for a distinct localization. The enzyme activity was detected only in cells producing high amount of clavine alkaloids. It was confined to the membranes of endoplasmic reticulum and their derivatives: tonoplast of vacuoles, tiny vesicles and amorphous material inside vacuoles. The reaction product was very fine and localized in both leaflets of the membranes. The specificity of the reaction was confirmed by negative results in control preparations: boiled cells incubated in the complete medium, cells incubated in the medium supplemented with avidin or in the media from which either ATP, or acetyl CoA, or sodium bicarbonate, or biotin were omitted. It is suggested that the activity of acetyl-CoA carboxylase is linked to the synthesis of clavine alkaloid precursors which occurs in the endoplasmic reticulum and its derivatives.With technical assistance of J. Martínková     

Induction of chromosomal disturbances other than tetraploidy in barley root tips by colchicine treatment

Barley embryos were treated by 0.1% colchicine for 30 min. Samples of root tips were fixed after 4 h, 8 h and 12 h. In the first sample,c-metaphases, normal metaphases and anaphases were present jointly. Inc-metaphases, chromosomes sometimes tended to make two groups with 7 chromosomes in each. In anaphases, lagging chromosomes, tripolar and multipolar anaphasos were found. No chromosomal aberrations were detected in anaphases and metaphases. No chromosome disturbances were found in root tips sampled 8 h and 12 h after colchicine treatment.