Serological classification of spiroplasmas: current status

Data concerning serological classification of spiroplasmas are in good agreement, but slightly different numerical designations have been given to existing groups. It is proposed that a standardized system be adopted based on information developed mainly by the IRPCM working team on spiroplasmas. The type species (Spiroplasma citri) should be redefined to include only the agent of citrus stubborn disease (subgroup I-1). Six other subgroups, including three proposed by Bové et al. in this volume (I-5, I-6, and I-7), are members of the Group I complex. Because subgroups I-1, I-2, and I-3 (1) show significant reciprocal differences in DNA-DNA homology and two-dimensional electrophoretic protein profiles, (2) occupy exclusive habitats, (3) are each associated with important diseases, and (4) consist of clusters of very similar or identical strains, it is suggested that Latin binomials could be assigned to subgroups I-2 and I-3. It is proposed that those criteria could serve as general guidelines for consideration of subgroups for species status in the class Mollicutes. The I-4 subgroup is assigned an uncertain status, pending comparisons with the LB-12 (I-5), M55 (I-6), and N525 (I-7) subgroups. To previously described serogroups we add the CN-5 Cotinus beetle spiroplasma (IX), the AES-1 mosquito strain (X), and the MQ-4 Monobia strain (XI).     

Fine filaments in lymphatic endothelial cells

Several and various types of cells contain fine cytoplasmic filaments closely resembling the myofilaments of muscle cells (2, 18, 23, 24). In many of these cells and especially when cultured, it has been demonstrated that some of these filaments react with heavy meromyosin (HMM) in the same way as do the actin filaments of muscle cells (3, 6 7). This suggests that these filaments may be actinoid and form part of a contractile system. As fine intracytoplasmic filaments do occur in lymphatic endothelial cells (2, 14), we undertook an electron microscope investigation of their fine structure and their reaction on incubation with HMM and EDTA. We postulated that lymphatic endothelial cells possess a contractile filamentous system to which these filaments belong.     

Membrane lipids and ethanol tolerance in the mouse. The influence of dietary fatty acid composition

Mice of the TO Swiss strain received diets containing different amounts of saturated or unsaturated fat throughout life. These diets produced characteristic changes in cardiac phospholipid fatty acid composition, but produced no significant differences in fatty acid composition of phospholipids from a crude membrane fraction of brain. When littermates of these animals were exposed to ethanol vapour in an inhalation chamber it was observed that mice which had received a diet high in saturated fat lost the righting reflex at an estimated concentration of ethanol in blood higher than that required for mice receiving a control diet, or a diet rich in polyunsaturated fat. Analysis of the brain membrane fraction from those animals which had received ethanol revealed that mice receiving the highly saturated fat diet now had a significantly greater proportion of saturated fatty acids in brain membrane phospholipids. These results are discussed in relation to the hypothesis that brain membrane lipid composition may influence the behavioural response to ethanol.     

Intramembrane particles and the organization of lymphocyte membrane proteins

An experimental system was developed in which the majority of all lymphocyte cell-surface proteins, regardless of antigenic specificity, could be cross-linked and redistributed in the membrane to determine whether this would induce a corresponding redistribution of intramembrane particles (IMP). Mouse spleen cells were treated with P-diazoniumphenyl- β-D-lactoside (lac) to modify all exposed cell-surface proteins. Extensive azo- coupling was achieved without significantly reducing cell viability or compromising cellular function in mitogen- or antigen-stimulated cultures. When the lac-modified cell- surface proteins were capped with a sandwich of rabbit antilactoside antibody and fluorescein-goat anti-rabbit Ig, freeze-fracture preparations obtained from these cells revealed no obvious redistribution of IMP on the majority of fracture faces. However, detailed analysis showed a statistically significant 35 percent decrease (P less than 0.01) in average IMP density in the E face of the lac-capped spleen cells compared with control cells, whereas a few E-face micrographs showed intense IMP aggregation. In contrast, there was no significant alteration of P-face IMP densities or distribution. Apparently, the majority of E-face IMP and virtually all P-face IMP densities or distribution. Apparently, the majority of E-face IMP and virtually all P-face IMP do not present accessible antigenic sites on the lymphocyte surface and do not associate in a stable manner with surface protein antigens. This finding suggests that IMP, as observed in freeze-fracture analysis, may not comprise a representative reflection of lymphocyte transmembrane protein molecules and complexes because other evidence establishes: (a) that at least some common lymphocyte surface antigens are indeed exposed portions of transmembrane proteins and (b) that the aggregation of molecules of any surface antigen results in altered organization of contractile proteins at the cytoplasmic face of the membrane.     

Release ofTelenomus remus [Hym. scelionidae] againstSpodoptera frugiperda [Lep.: Noctuidae] in Florida,U.S.A.

Telenomus remus Nixon, a scelionid egg parasite of Lepidoptera, was released against fall armyworm,Spodoptera frugiperda (J. E. Smith), near Homestead, Florida U.S.A. from May 1975 — May 1977. A small percentage (4.5) of the egg masses collected were parasitized byT. remus, however no recoveries were made in the months following the final release. An egglarval parasite,Chelonus insularis (=texanus) (Cresson), was reared from 50% of the larvae from eggs collected.T. remus apparently was not established in Florida.

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Résumé Telenomus remus Nixon, scelionide parasite des œufs de lépidoptères, a été laché contreSpodoptera frugiperda (J. E. Smith) près de Homestead en Floride, de mai 1975 à mai 1977. Un faible pourcentage des pontes récoltées (4,5%) se révélèrent parasitée parT. remus, cependant aucun parasite ne fut retrouvé dans les mois qui suivirent le dernier lacher. Un parasite ovo-larvaire,Chelonus insularis (=texanus) (Cresson) a été obtenu à partir de 50% des larves issues des œufs récoltés. ApparemmentT. remus n'a pas été établi en Floride.

     

DNA base sequence changes induced by diethyl sulfate in postmeiotic male germ cells of Drosophila melanogaster

Summary The DNA base sequence changes induced by diethyl sulfate (DES) were analyzed in postmeiotic male germ cells of Drosophila melanogaster. 31 transmissible vermilion mutants were recovered in F₁ and F₂ generations, with a frequency of 2.6 × 10^–4 for the F₁, and of 1.8–13 × 10^–4 for the F₂. The results show that DES induces both base pair substitutions (93%) and deletions (7%). In accord with its relatively high ability to alkylate oxygens in DNA, the most frequent type of sequence alteration among the basepair changes are GC-AT transitions, accounting for 73% of mutations, followed by transversions AT-TA (10%). DES also induced AT-GC transitions and AT-CG transversions. Both induced deletions were intralocus deletions, not occurring between basepair repeats. No influence of neighboring bases on the mutation position was found.     

Phylogenetic analysis of slippage-like sequence variation in the V4 rRNA expansion segment in tiger beetles (Cicindelidae)

Sequence variation in the middle part of the small-subunit rRNA was studied for representatives of the major groups in the family Cicindelidae (Coleoptera). All taxa exhibited a much expanded segment in variable region V4 compared to D. melanogaster. This expanded segment was not found in other groups of beetles, including three taxa in the closely related Carabidae. Secondary structure predictions indicate that the expanded segment folds into a single stem-loop structure in all taxa. Despite its structural conservation, the fragment differs strongly in primary sequence, even between closely related sister taxa. Several features of these sequences are consistent with slippage replication as the mechanism that has generated this sequence variation: the level of internal sequence repetition as measured by the relative simplicity factor (RSF), its variation in length between close relatives, and the strong nucleotide bias compared to the remainder of the gene. With few exceptions, there was also a correlation between sequence length and the level of sequence repetition, frequently interpreted as the result of slippage. Phylogenies inferred from the expansion segment were not consistent with existing hypotheses from other molecular data for the group. This indicates that DNA sequences in this region are not homologous throughout the entire Cicindelidae, but it leaves open the possibility that this expansion segment can be used for phylogeny reconstruction within subgroups. The implications of a phylogenetic approach to the understanding of slippage-like evolution are discussed.