Formation and regeneration of Frankia protoplasts

A technique for forming protoplasts from Frankia cells and regenerating them to the normal hyphal mode of growth is described. Electron microscopy proved that protoplasts were studied and not spores or small hyphae. Regenerated colonies were investigated for genetic markers. One ArI3 colony had been cured of its plasmids without being affected in its symbiotic properties.     

Reactions of 3-ethylcatechol and 3-(methylthio)catechol with catechol dioxygenases

The reactions of 3-ethylcatechol and 3-(methylthio)catechol with catechol 1,2-dioxygenase and catechol 2,3-dioxygenase from Pseudomonas putida were examined. Both 3-substituted catechols are oxidized by catechol 2,3-dioxygenase at approximately 30% of the rate observed for catechol oxidation by this enzyme. Analysis of the products of the reactions showed that ring cleavage occurs in a normal fashion between carbons 2 and 3 of the alternate substrates. 3-Ethylcatechol is oxidized by catechol 1,2-dioxygenase at about 6% of the rate of catechol oxidation; ring cleavage occurs between carbons 1 and 2 to give 2-ethyl-cis,cis-muconic acid. However, 3-(methylthio)catechol is a very poor substrate for catechol 1,2-dioxygenase (0.8% of the rate of catechol), but it is a potent competitive inhibitor (Ki = 0.6 microM). The effects of 3-(methylthio)catechol and 3-ethylcatechol on the visible and EPR spectra of catechol 1,2-dioxygenase are also reported.     

Dietary alpha-linolenic acid deficiency in adult rats for 7 months does not alter brain docosahexaenoic acid content, in contrast to liver, heart and testes.

In adult rats, 22:6(n - 3) dietary deficiency does not affect brain membranes, but has a significant effect on some other visceral organs. 60-day-old male rats fed a diet containing sufficient amounts of both linoleic and alpha-linolenic acid were divided into three groups. One group continued the same diet; the second was fed a diet containing 2% sunflower oil, the third was fed 10% sunflower oil (sunflower oil contains linoleic acid, but trace amount of alpha-linolenic acid). Animals were killed different times after receiving the new diets (1 to 31 weeks). For animals fed the diets containing only sunflower oil, deficiency in cervonic acid content (DHA, docosahexaenoic acid, 22:6(n - 3)) was not detected in whole brain, myelin or nerve endings within 31 weeks. In contrast, this acid progressively declined in liver, heart and testes up to 3 weeks and remained nearly stable thereafter. In parallel to the reduction of cervonic acid content, 22:5(n - 6) content increased in liver and heart, but not in testes. It also increased in brain, nerve endings and myelin from week 3, 6 and, 9 respectively. These results suggest that brain cervonic acid is highly preserved or is maintained at the expense of other organs.     

Comparative Study of 35 Bacteriophages of Lactobacillus helveticus: Morphology and Host Range

This survey included 23 phages isolated from cheese whey and 12 temperate phages induced with mitomycin from their lysogenic host strains. All of the phages had an isometric head and a tail with a contractile sheath. In addition, short-tailed (160-nm-long) and long-tailed (260-nm-long) phages were distinguished. Short-tailed phages were by far the most widespread in French cheese factories (32 of the 35 phages studied). The study of phage relationships enabled two large groups of strains to be distinguished: those not or slightly sensitive to phages and those very sensitive to phages. There was an obvious relationship in the first group between phage sensitivity (or resistance) and the geographic origin of the strains. The second group contained primarily strains from large international collections and those isolated from commercial starters. The relationships among short-tailed phages, either temperate or isolated as lytic, suggest that lysogenic strains could be the major source of phages in French cheese factories.     

A conformational rearrangement in gramicidin A: from a double-stranded left-handed to a single-stranded right-handed helix.

A conformational transition is described for the polypeptide, gramicidin A, in which a dimer that forms a left-handed intertwined antiparallel helix is converted to a single-stranded amino terminus to amino terminus right-handed helix. The starting structure is determined here by solution NMR methods while reference is made to the well-established folding motif of gramicidin in a lipid bilayer for the ultimate conformation of this transition. Furthermore, an organic solvent system of benzene and ethanol in which gramicidin has a unique conformation is identified. This conformation is shown to be very similar to that derived from X-ray diffraction of crystals prepared from a similar solvent system.     

Azotobacter vinelandii strains of disparate origin produce azotobactin siderophores with identical structures

Summary The yellow green fluorescent siderophore, azotobactin, was purified from cultures of twoAzotobacter vinelandii strains. Structural analysis of azotobactin from the North AmericanA. vinelandii strains O and its capsule negative variant UW (also called OP) revealed that both strains produced azotobactins with identical structures. Moreover, azotobactin produced by these two strains was structurally identical to azotobactin D, the fluorescent siderophore previously isolated from the EuropeanA. vinelandii strain D (CCM 289). Unlike strains of fluorescentPseudomonas which produce structurally diverse pyoverdins, strains ofA. vinelandii of disparate origin produced azotobactins of identical structure. Lactonization of azotobactin did not interfere with the ability of this compound to function as a siderophore.     

Feeder cells enhance oncolytic and proliferative activity of long-term human bone marrow interleukin-2 cultures and induce different lymphocyte subsets

Summary The effect of feeder cells on oncolytic activity of lymphocyte subsets and their growth was evaluated in long-term human bone marrow interleukin-2 (IL-2) cultures. Two B-lymphoblastoid cell lines (Daudi and Epstein-Barr-virus-transformed BSM) and two human leukemias, AML-M5, were used as feeder cells. The most prominent effects were seen in cultures stimulated with Daudi cells. In these cultures, cytotoxic activity was 100–1000 times increased against a broad range of target cells and the total cellular expansion was more than 40 times higher than in control cultures. This Daudi-related effect appeared to be mediated by natural killer (NK) cells, since cellular expansion occurred mostly in the CD16⁺ and CD56⁺ CD3^– NK cell subset. In cultures stimulated with BSM and acute myelogenous leukemia (AML) feeder cells, the increase in proliferation was similar, but the enhancement of cytotoxicity, even though significant, was less prominent. Although all feeder cells were effective in stimulation of bone marrow reactivity, the highest cytotoxicity was always observed with feeder cells autologous to the targets, indicating some degree of specificity. This was especially evident in cultures stimulated with autologous versus allogeneic AML feeder cells. In contrast to Daudistimulated IL-2 cultures, in which the highest expansion of CD3^– CD56⁺ NK cells was observed, in BSM and AML cultures, the CD3⁺ CD56^+/- T cell subsets were more prolific. This indicates that the response and phenotypic heterogeneity of bone marrow cultures depends on the type of feeder cells used. This observation indicates that the preferential stimulation of a pertinent lymphocyte subset for therapeutic purposes may be possible.Recipient of Florence Maude Thomas Cancer Research Professorship     

Regulation of the trimethylamine N-oxide (TMAO) reductase in Escherichia coli: analysis of tor::Mud1 operon fusion

Summary Mud1 insertion mutants of Escherichia coli were obtained in which the lac structural genes were fused to the promoter of torA, a gene encoding the trimethylamine N-oxide (TMAO) reductase. Expression of the fusion is induced by TMAO and repressed by oxygen. However, in contrast to the nar operon which codes for the nitrate reductase structural genes, the tor::Mud1 fusion was found to be independent of the positive control exerted by the nirR gene product and not repressed by the molybdenum cofactor. The torA gene which is strongly linked to pyrF (28.3 U) is different from any tor gene already described in E. coli or in Salmonella typhimurium.     

THE CLASSIFICATION OF PROBOSCIDEA: HOW MANY CLADISTIC CLASSIFICATIONS?

Abstract— Hennig conceived a method to build a "phylogenetic system", with the stipulation that a "properly drawn phylogenetic tree must be directly translatable into the language of phylogenetic systematics". Consequently, this system could be the general reference system of biology. A review of the classificatory technical improvements, conventions and rules which have been proposed for the past twenty years together with their application to the classification of the Proboscidea, leads to the conclusion that more than one formal system can be built upon one given cladogram. As words are used more frequently for communication than diagrams, schemes or graphs, the "general reference system of biology1' remains somewhere in Utopia. The "phylogenetic system" is rather more synonymous with a cladogram than with a written classification.     

Optimization of the bare platinum electrode as an oxygen measurement system in photosynthesis

This paper is concerned with the definition of the standard conditions required for optimum operation of the bare platinum electrode with photosynthetic samples. Experimental evidence shows the following: 1) Polarization circuits should have zero resistance; 2) The electrolyte layer between the electrodes should have a conductance higher than 54×10^{–6 –1} per mm² of platinum electrode area; 3) The electrodes should be polarized just before taking the measurements. All these facts can be interpreted in terms of phenomena occurring on the electrode: The adsorption of hydrogen on the electrode imposes the need for low resistances in the system, and oxygen consumption by the electrode is minimized by polarizing the electrodes as late as possible. This investigation increases the reliability of the bare platinum electrode and gives a basis for a comparison of the results from different experiments. Demonstrations of the pertinence of these conditions are made in our lab with the algae Dunaliella Tertiolecta.