Concentration of Rift Valley Fever and Chikungunya Viruses by Precipitation

Simple and efficient methods for concentrating Rift Valley fever (RVF) virus and chikungunya (CHIK) virus are described. Ammonium sulfate, potassium sulfate, or alcohol was used as a precipitating agent and the precipitate was resuspended to volumes suitable for further processing and purification. The methods permitted concentration of live RVF virus and CHIK virus about 100-fold with negligible losses of virus. RVF virus retained a high level of infectivity with potassium aluminum sulfate and alcohol, but CHIK virus retained a higher infectivity level with ammonium sulfate than with potassium aluminum sulfate. The data indicate that serum plays an important role in the concentration of both viruses, at least when the sulfate methods are used.     

A quantitative description of the dynamics of excitation and inhibition in the eye of Limulus

By means of intracellular microelectrode techniques, we have measured the dynamics of the several processes which translate light stimulation into spike activity in the Limulus eye. The transductions from light to voltage and from voltage to spike rate, and the lateral inhibitory transduction from spike rate to voltage, we have characterized by transfer functions. We have checked the appropriateness of treating the eye as a system of linear transducers under our experimental conditions. The response of the eye to a large spot of light undergoing sine flicker has been correctly predicted.     

Phenolic metabolites of Ceratocystis ulmi

The C₁₀ acid 2,4-dihydroxy-6-(1-hydroxyacetonyl) benzoic acid, together with the 6-acetonyl- and 6-pyruvyl-analogues, has been identified as a metabolic product of Ceratocystis ulmi, the causative agent of Dutch elm disease. In a comparison of aggressive “fluffy” and non-aggressive “waxy” strains of C. ulmi, the C₁₀ acids were produced more rapidly and in greater yield by the former group.     

Enzymes related to lactate metabolism in green algae and lower land plants

Cell-free extracts of Chlorella pyrenoidosa contained two enzymes capable of oxidizing d-lactate; these were glycolate dehydrogenase and NAD(+)-dependent d-lactate dehydrogenase. The two enzymes could be distinguished by differential centrifugation, glycolate dehydrogenase being largely particulate and NAD(+)-d-lactate dehydrogenase being soluble. The reduction of pyruvate by NADH proceeded more rapidly than the reverse reaction, and the apparent Michaelis constants for pyruvate and NADH were lower than for d-lactate and NAD(+). These data indicated that under physiological conditions, the NAD(+)-linked d-lactate dehydrogenase probably functions to produce d-lactate from pyruvate.Lactate dehydrogenase activity dependent on NAD(+) was found in a number of other green algae and in the green tissues of a few lower land plants. When present in species which contain glycolate oxidase rather than glycolate dehydrogenase, the enzyme was specific for l-lactate rather than d-lactate. A cyclic system revolving around the production and utilization of d-lactate in some species and l-lactate in certain others is proposed.     

Ribosome Patterns in Escherichia coli Growing at Various Rates

The distribution of ribosomes, 30 and 50S subunits and polysomes, at three different growth rates of Escherichia coli strains B and K-12 has been studied. The usual percentage of subunits is about 20%. However, at the lowest growth rate (mu = generations/hour), mu = 0.45 at 30C, the proportion of subunits is about 30%. An exceptional situation exists in K-12 strains growing at maximum growth rate, mu = 1.35, where the percentage of subunits is 45%. Several points of control over ribosome production are thus indicated. It is suggested that "subunit pool" is essentially a reserve. Furthermore, the polysome content when related to deoxyribonucleic acid content varies directly with the growth rate, which indicates the average efficiency of polysomes in protein synthesis does not vary over the range of growth rates tested.     

Genetic basis for high limonene—cineole content of exceptional Mentha citrata hybrids

Summary Most Mentha species have 1–25% 1-limonene and 0.5–8% 1,8-cineole, but 19 individuals having more than 50% limonene-cineole were found in a progeny of 10,000 Strain 2 M. citrata — M. crispa F ₁ hybrids. When the same strain of M. citrata (2 n = 96) having the genotype I₁I₁ i ₂ i ₂, a lavender herbage odor with oil assaying 30% linalool and 58.5% linalyl acetate, is hybridized with the closely related octoploid species M. aquatica (2 _n = 96) having the genotype i ₁ i ₁ i ₂ i ₂, a menthofuran herbage odor with oil assaying 65–80% menthofuran, the fertile F ₁ hybrids should have the genotype I ₁ i ₁ i ₂ i ₂ and a lavender odor with oil assaying 84–90% linalool — linalyl acetate. In addition to 111 normal lavender-odored hybrids, this cross gave one individual (Strain 38) having 20.4% limonene and 36.4% cineole and one individual (Strain 625) having 67.5% limonene and 23.6% cineole. Since M. aquatica is homozygous for menthofuran production, and since Strain 38 — M. aquatica backcross progenies had the disomic ratio of 1 limonene and cineole-odored: 1 methofuran-odored, it is evident that the 57% limonene — cineole content of Strain 38 is due to a single dominant gene Lm. Strains 38 and 625 were hybridized with other tester species having known genotypes for other oil constituents to demonstrate that the gene Lm prevents the conversion of limonene to more advanced compounds, namely: carvone, pulegone, methofuran, menthone, menthol, and menthyl acetate which are normally developed in the oil of other species having the recessive gene lm. Strain 38 hybrids with M. citrata show that the dominant I gene interrupts oil biogenesis at an earlier stage than the Lm gene and largely prevents the synthesis of limonene and cineole. Nine of 21 strains having 57– 94% limonene — cineole were investigated. Strains 38 and 62 had the genotype i ₁ i ₁ i _{2 i 2} Lm ₁ lm ₁ lm ₂ lm ₂ or i ₁ i ₁ i ₂ i ₂ lm ₁ lm ₁ Lm ₂ lm ₂, whereas Strain 625 and six others had the genotype i ₁ i ₁ i ₂ i ₂ Lm ₁ lm ₁ Lm ₂ 1m ₂. These segregants from the segmental allopolyploids may be explained by assuming that M. aquatica has the genotype and Strain 2 of M. citrata the genotype with A and a designating the non-homologous centromere regions of the two chromosome pairs carrying the linked genes on different chromosome arms. Crossing over between the genes would not be detectible when there is normal autosyndetic bivalent pairing, whereas occasional quadrivalent pairing of the four chromosomes of Strain 2 of M. citrata could lead to gene interchanges between chromosomes non-homologous for the centromere region.Research Assistant, Research Assistant, Senior Chemist, and Director of Plant Research respectively.     

Pediococci Residing on Plants

The pediococci residing on plants resemble the lactobacilli, but they differ from the streptococci in their limited distribution and low population level on plants. They are a subgroup within the genus Pediococcus which grow freely in neutral media and require neither NaCl nor CO(2). They are most readily recognized by the ability to initiate growth in liquid media, acidified to pH 5.0, which contain 1.5% sodium acetate. In stained preparations the cells occur singly and in pairs, short chains, and clusters. The occurrence of two-dimensional tetrads may be rare; this varies with the individual culture and with the culture medium. The terminal pH in 2% glucose broth varies from 3.6 to 4.3. Ability to initiate growth at 45 C, production of ammonia from arginine, dissimilation of malate, and fermentation of arabinose are confirmatory characteristics. The subgroup contains only two quite similar, but differentiable, species. P. acidilactici initiates growth at 50 C and produces catalase on heated blood medium but does not produce acid-sensitive catalase; a majority of the strains fail to initiate growth at 10 C and many fail to ferment maltose and lactose. P. pentosaceus initiates growth at 10 C but not at 50 C and produces acid-sensitive catalase; catalase production on heated blood medium is transient; a majority of the cultures ferment maltose, salicin, and trehalose. No carbohydrate serves reliably to differentiate between the species. The guanine plus cytosine ratio of P. pentosaceus deoxyribonucleic acid (DNA) was determined to be 35.1 +/- 1.2 and that of P. acidilactici DNA is 38.5 +/- 0.8.     

Aromatase activity in human ovarian cancer

Eighty-four tumor samples from 70 women with primary ovarian cancer were assayed for cytosol estrogen (ERc) and progestin (PRc) receptor concentrations and aromatase activity. In addition, 22 of the tumors were studied for their response to the aromatase inhibitor, 4-OH-androstenedione, in a soft agar clonogenic cell assay system. Although aromatase activity was detected in almost all of the primary tumors, this enzyme was barely detectable in the majority of metastatic tumor samples. There was no significant correlation between aromatase activity and either the ERc or PRc content of the tumors, or tumor grade. Of 12 tumors grown successfully in the soft agar culture system, only 1 showed a substantial (>50%) reduction in colony-forming efficiency after exposure to the aromatase inhibitor. These results suggest that local estrogen biosynthesis probably does not play an important role in the majority of epithelial ovarian tumors. However, there may be a small subset of estrogen receptor-positive tumors in which aromatase could provide a local growth stimulus.