Ross H. Hall

Cytokinins in the Soluble RNA of Plant Tissues

The cytokinin, N6-(Δ2-isopentenyl) adenosine occurs in the soluble RNA of yeast and mammalian tissue and has now been detected in plant soluble RNA. A hydroxylated derivative of this cytokinin 6-(cis-4-hydroxy-3-methylbut-2-enylamino)-9-,β-D-ribofuranosylpurine has also been identified as a constituent of plant soluble RNA.

Sulfur-Containing Nucleoside from Yeast Transfer Ribonucleic Acid: 2-Thio-5(or 6)-uridine Acetic Acid Methyl Ester

A nucleoside, isolated from yeast transfer RNA, has been assigned the structure 2-thio-5-uridine acetic acid methyl ester on the basis of high-esolution mass spectrometry, chemical properties, and ultraviolet spectra. The alternate 6-substituted isomeric structure cannot yet be completely ruled out.

Biosynthesis of N6-(Δ2-isopentenyl)adenosine in the transfer ribonucleic acid of cultured tobacco pith tissue

Abstract When mevalonic acid-[2- 14 C] is added to the culture media of tobacco pith tissue (Wisconsin strain 38), a significant amount of radioactive label is incorporated into the transfer ribonucleic acid (tRNA). All of this radioactivity is located in the N 6 -(Δ 2 -isopentenyl)adenosine component of the tRNA. The addition of N 6 -(Δ 2 -isopentenyl)adenosine to the media does not appear to depress the degree of incorporation of the radioactive label into the tRNA. A crude enzyme system was extracted from the pith tissue that catalyzes the attachment in vitro of the Δ 2 -isopentenyl side-chain to preformed tobacco tRNA. This in vitro system is analogous to the in vitro system for the biosynthesis of N 6 -(Δ 2 -isopentenyl)adenosine in yeast and rat liver tRNA (Fittler et al., Biochem. Biophys. Acta 31 , 517, 1968). The addition of d,l -mevalonic acid (12 μmoles/l) to the culture media containing indoleacetic acid (2 mg/l) appears to partially replace the requirement of the tobacco tissue for a cytokinin. Under these conditions a two- to five-fold increase in yield over control cultures is obtained.

Concerning the presence of the cytokinin, N 6-(?2-isopentnyl) adenine, in cultures of Corynebacterium fascians

SummaryCorynebacterium fascians causes a fasciation disease in a number of dicotyledons and this disease appears to be caused by compounds with cytokinin activity elaborated by the infecting bacteria. Extractions of C. fascians in late logarithmic phase under conditions where the pH never falls below 7.0 yield about 2 μg/l of N6-(Δ2, a potent cytokinin. If a mild acidification step is included in the extraction procedure the yield increases to about 12 μg/l. This is due to release of N6-(Δ2-isopentenyl)adenine from C. fascians tRNA during the extraction procedure. In terms of total cytokinin activity present in C. fascians cultures, N6-(Δ2-isopentenyl)adenine appears to be a minor component.

Cytokinin Activity of Ureidopurine Derivatives Related to a Modified Nucleoside Found in Transfer RNA

By use of a radioactive labeling technique N-(nebularin-6-ylcarbamoyl)threonine has been detected in plant transfer RNA. Derivatives of this nucleoside promote cell division of a cytokinin-requiring soya bean tissue.

Preparation of chromatin from tissue culture cells—A convenient method

A detailed procedure is described for isolating chromatin from small amounts of tissue culture cells. The method utilizes the observation that it is possible to obtain a purified, concentrated, chromatin fraction by isopycnic gradient centrifugation in a low ionic strength solution containing 39% (wv) metrizamide. Such chromatin preparations appear to give good yields of DNA and have their normal complement of protein and RNA when compared with other chromatin isolation procedures. The procedure is simple to use, except for the isopycnic gradient centrifugation step, the only major equipment required is a clinical centrifuge and a light microscope. The method should be of value when a number of chromatin preparations are being assayed simultaneously.

Fractionation of L-cell chromatin into DNA, RNA, and protein fractions on Cs2SO4 equilibruim density gradients

Abstract A new procedure is described for fractionation of chromatin into DNA, RNA, and total chromatin protein. By isopycnic gradient centrifugation of chromatin preparations in Cs 2 SO 4 solutions containing dimethylsulfoxide and sodium sarcosyl it is possible to obtain highly purified fractions of these components. The method gives a very high yield of these chromatin fractions unlike some other methods, where irreversible binding to columns occurs. Also with this method it is possible to obtain highly concentrated fractions, which after a simple dialysis step, can be conveniently analyzed by polyacrylamide gel electrophoresis. Nuclei from L-929 cells were isolated by a method involving citric acid or by a method using a nonionic detergent. The yields of DNA obtained by both methods was compared. Chromatin was isolated from purified nuclei (prepared in either of the above ways) in two different ways also. In one method, chromatin was extracted from nuclei with 1 m NaCl. A second method involving fractionation of lysed nuclei in sucrose and metrizamide solutions was also used. The yields of DNA obtained by both methods was compared. There appears to be little nuclear membrane contamination of any of these chromatin preparations. A preliminary analysis of L-929 cell chromatin total RNA and protein fractions on polyacrylamide and agarose gels has been made. Both fractions appear to be quite complex with a wide spectrum of subcomponents of differing S values.

Resolution of mixtures of sugars by means of partition chromatography on columns: resolution of a mixture of the four aldopentoses and 2-deoxyribose and of certain hexoses.

Abstract A preparative partition column technique has been developed which will resolve mixtures of monosaccharides of the pentose and hexose series. the sugars are quantitatively eluted from the columns and the use of volatile salt-free solvents simplifies final recovery.

University education and the natural environment: are they compatible?

The ability to construct a society that can function effectively within the limitations of a finite planet is rapidly becoming the preeminent problem of mankind. The decision‐makers of the next few decades are now being educated in our universities. Are the students receiving an education compatible with the realities of a finite environment? In the present university environment the student is exposed to a specialized didactic education that, in terms of mode of perception, is anti‐ecological. Universities should be seeking new approaches to education that eliminate arbitrary subject barriers and teach in an in‐depth all‐at‐once manner.

Is modern food ecologically sound

An ecological definition of human nourishment would consider nourishment as consumption of one life form by another. The quality of nourishment, therefore, depends on the quality of ecological processes. How does modern food processing stand when judged in this context? A growing percentage of national diets consists of food products fabricated from highly refined and synthetic ingredients. In the processing a degree of wholeness inherent in natural foods is lost. With the marked shift in dietary patterns in the last 30 years, one would expect nutrition scientists to have assessed these new foods. Such is not the case because the science has not progressed sufficiently to the point where it could assess the nutritional quality of this type of food. The result is that food technology is rapidly evolving essentially unmonitored. The prudent policy would be to recognize this inability to ascertain the effects and slow or stop the trend towards unproven synthetic foods.