Assimilation of 13NH 4 + by Anthoceros grown with and without symbiotic Nostoc

The pathways of assimilation of ammonium by pure cultures of symbiont-free Anthoceros punctatus L. and the reconstituted Anthoceros-Nostoc symbiotic association were determined from time-course (5–300 s) and inhibitor experiments using ¹³NH ₄ ⁺ . The major product of assimilation after all incubation times was glutamine, whether the tissues were cultured with excess ammonium or no combined nitrogen. The ¹³N in glutamine was predominantly in the amide-nitrogen position. Formation of glutamine and glutamate by Anthoceros-Nostoc was strongly inhibited by either 1mM methionine sulfoximine (MSX) or 1 mM exogenous ammonium. These data are consistent with the assimilation of ¹³NH ₄ ⁺ and formation of glutamate by the glutamine synthetase (EC 6.3.1.2)-glutamate synthase (EC 1.4.7.1) pathway in dinitrogen-grown Anthoceros-Nostoc. However, in symbiont-free Anthoceros, grown with 2.5 mM ammonium, formation of glutamine, but not glutamate, was decreased by either MSX or exogenous ammonium. These results indicate that during short incubation times ammonium is assimilated in nitrogenreplete Anthoceros by the activities of both glutamine synthetase and glutamate dehydrogenase (EC 1.4.1.2). In-vitro activities of glutamine synthetase were similar in nitrogen-replete Anthoceros and Anthoceros-Nostoc, indicating that the differences in the routes of glutamate formation were not based upon regulation of synthesis of the initial enzyme of the glutamine synthetase-glutamate synthase pathway. When symbiont-free Anthoceros was cultured for 2 d in the absence of combined nitrogen, total ¹³NH ₄ ⁺ assimilation, and glutamine and glutamate formation in the presence of inhibitors, were similar to dinitrogen-grown Anthoceros-Nostoc. The routes of immediate (within 2 min) glutamate formation and ammonium assimilation in Anthoceros were apparently determined by the intracellular levels of ammonium; at low levels the glutamine synthetase-glutamate synthase pathway was predominant, while at high levels independent activities of both glutamine synthetase and glutamate dehydrogenase were expressed.     

Unique acceptors for poly(ADP-ribose) in resting,proliferating and DNA-damaged human lymphocytes

Acceptor proteins for poly(adenosine diphosphoribosyl)ation were determined in resting human lymphocytes, in lymphocytes with N-methyl-N′-nitro-N-nitrosoguanidine-induced DNA damage and in lymphocytes stimulated to proliferate by phytohemagglutinin. Kinetic studies showed that the increase in ADP-ribosylation which occurred in response to N-methyl-N′-nitro-N-nitrosoguanidine (MNNG) treatment was greater in magnitude but more transient in duration than that which occurred in phytohemagglutinin-stimulated cells. Gel electrophoretic analyses revealed that MNNG treatment and phytohemagglutinin stimulation both caused an increase in ADP-ribosylation of poly(ADP-ribose) polymerase and core histones. In MNNG-treated cells, an increase in ADP-ribosylation of histone H1 was also observed. In contrast, phytohemagglutinin-stimulated cells showed no increase in ADP-ribosylation of histone H1. In MNNG-treated cells there was also ADP-ribosylation of a protein of molecular weight 62 000, while in phytohemagglutinin-stimulated cells there was a marked increase in ADP-ribosylation of a protein of molecular weight 96000. MNNG treatment of phytohemagglutinin-stimulated cells produced a pattern of ADP-ribosylation that appeared to be due to the combined effects of the individual treatments. 3-Aminobenzamide effectively inhibited ADP-ribosylation under all treatment conditions.     

Nomograms for Calculation of Heat Loss

Two nomograms are presented. The first enables the mean surface and body temperatures and the body heat content of a patient of given weight to be determined from measurements of skin temperature at three sites and of the core (rectal) temperature. The second enables the change in heat content of such a patient to be determined from the change in mean body temperature.     

Stimulation of Mycelial Growth of Endothia parasitica by Heavy Metals

Of 16 metal cations tested on agar medium, only copper and iron stimulated mycelial growth of Endothia parasitica in relatively high concentrations. Similarly enhanced growth was produced in high (32%) glucose concentrations and also when the fungus was grown on cellophane placed over the agar surface. E. parasitica secreted large amounts of oxalate that precipitated primarily as calcium oxalate at the periphery of the fungal colony, causing an opaque halo in the medium. Mycelial growth was retarded greatly when calcium oxalate accumulated, but retardation was reversed by copper and iron salts that prevented accumulation of the calcium oxalate crystals. E. parasitica grew well on media containing copper oxalate and copper-calcium oxalate but grew poorly with calcium oxalate as the carbon source and was inhibited by sodium oxalate in the medium. The specificity by which only copper and iron salts stimulated mycelial growth suggested that the metal and oxalate ions interact to form specific oxalate complexes that reverse the inhibition of simple oxalate salts. This probably accounts for enhanced growth in the presence of otherwise toxic levels of metals and oxalate. The stimulation did not occur in liquid cultures.     

Effects of different proportions of nutrients on insects

Digestibility and nutrient composition of foodstuffs, be they plant or not, and the nutritional requirements of insects vary. The qualitative nutritional requirements among insects are quite similar. Therefore, qualities of foodstuff as measured by its ability to promote or support growth, etc. depend on how well the nutrient composition of foodstuff made available by digestion fits the nutritional requirements of the insect. This is better seen using synthetic diets rather than plants. From such investigations it is found that, provided all essential nutrients are present, the proportions of essential nutrients in a foodstuff contribute more to nutritional quality than do the absolute amounts of nutrients. Thus, nutrient balance per se can affect: rate of food consumption and efficient utilization; parasites with respect to host food; rate of growth and development as such, and with respect to temperature; and food selection in an insect.

---

Schlussfolgerung Ich bin der Überzeugung, daß die Kenntnis der Ernährung unser Verständnis der Insekt-Nahrungspflanzen-Beziehung vergrößern und möglicherweise Wege weisen kann, um Insekten zu manipulieren und Pflanzen zu schützen. Dabei brauchen keine geheimnisvollen Dinge betrachtet zu werden, denn die Prinzipien der tierischen Ernährung und Nahrungsaufnahme lassen sich auch auf Insekten anwenden. Bei Insekten wie bei Säugern variieren Verdaulichkeit und Nährwert der Nahrungsstoffe und unterscheiden sich so von einem Tier oder Insekt zum anderen. Auch die Nahrungsansprüche der Insekten sind unterschiedlich. So müssen sowohl die Nahrungsansprüche der Insekten wie der Nährwert der betreffenden Nahrungsstoffe in diesen Beziehungen als Veränderliche angesehen werden. Da jedoch alle Insekten ganz ähnliche Nahrungsansprüche zu haben scheinen, und sehr wahrscheinlich alle Pflanzen ungefähr die 25 Nährstoffe enthalten, welche die Insekten benötigen, erscheint es zweifelhaft, daß qualitative Faktoren eine sehr entscheidende Rolle in den Beziehungen zwischen Insekten und Pflanzen zu spielen vermögen. Höchstwahrscheinlich sind quantitative Faktoren am wichtigsten. Diese hängen davon ab, wieviel von jedem Nährstoff die Verdauung eines Nahrungsmittels für die Ernährung des Insekts verfügbar machen kann; und wie gut sich die Beträge und Anteile der verfügbar gemachten Nährstoffe in die quantitativen Ernährungsansprüche des Insekts, einschließlich besonders der proportionalen Beziehungen, einfügen. Offensichtlich hängt die wirksame Ausnutzung des Nahrungsmittels für die Ernährung von dieser Einpassung ab, wie an gewissen Kriterien der Leistung der Insekten abzulesen ist. Deshalb sind unzweifelhaft die Quantitäten und vorzugsweise die Proportionen der betreffenden essentiellen Nährstoffe das wichtige Forschungsgebiet für Nahrungsuntersuchungen in den Insekt-Pflanzen-Beziehungen.

     

Activity of phenol oxidases at the puparium formation stage in development of nineteen lozenge mutants of Drosophila melanogaster

Phenol oxidase activity of activated A₁ and A₂ (A₃) electrophoretic components from 19 lozenge mutant and three lozenge double mutant strains was compared to that of wild type flies. Melanin production by the activated A components with tyrosine as substrate was compared to activity in the same acrylamide gels with dopa as substrate. Melanin production decreased, first in the A₁ band and then in the A₂ (A₃) band, with increased morphological expression of the mutant genes. No melanin bands were obtained with either substrate in five of the more severely affected mutants. A possible correlation between phenol oxidase activity and quinone production necessary for normal development of eyes, female accessory sex organs, and claws is discussed.Supported by PHS grant AM-08331-05.     

CHROMOSOME MICROMANIPULATION : III. Spindle Fiber Tension and the Reorientation of Mal-Oriented Chromosomes

Kinetochore reorientation is the critical process ensuring normal chromosome distribution. Reorientation has been studied in living grasshopper spermatocytes, in which bivalents with both chromosomes oriented to the same pole (unipolar orientation) occur but are unstable: sooner or later one chromosome reorients, the stable, bipolar orientation results, and normal anaphase segregation to opposite poles follows. One possible source of stability in bipolar orientations is the normal spindle forces toward opposite poles, which slightly stretch the bivalent. This tension is lacking in unipolar orientations because all the chromosomal spindle fibers and spindle forces are directed toward one pole. The possible role of tension has been tested directly by micromanipulation of bivalents in unipolar orientation to artificially create the missing tension. Without exception, such bivalents never reorient before the tension is released; a total time "under tension" of over 5 hr has been accumulated in experiments on eight bivalents in eight cells. In control experiments these same bivalents reoriented from a unipolar orientation within 16 min, on the average, in the absence of tension. Controlled reorientation and chromosome segregation can be explained from the results of these and related experiments.     

Deoxyribonucleic Acid Base Compositions of Selected Mycoplasmas and L-Phase Variants

Deoxyribonucleic acid base compositions were determined for 25 Mycoplasma strains and 6 L-phase variant strains. Values obtained correlated well with the results of other investigators.     

Regulation of the meta Cleavage Pathway for Benzoate Oxidation by Pseudomonas putida

Catechol or 2-hydroxymuconic semialdehyde cannot participate as functional inducers of the meta pathway for benzoate metabolism in Pseudomonas putida. Induction of the first two enzymes of the pathway must be mediated by benzoate, or its analogues, as primary substrate.