Determination of copper in different chloroplast preparations

The determination of total Cu is not often correlated with states of deficiency in plant material. This fact makes it necessary to look for biologically active Cu. Suspensions of thylakoid membranes and photosystem II particles, properly diluted with 13 mM nitric acid, were used for this purpose. The presence of a minute quantity of an antifoaming agent, such as 1-octanol, is essential when an aliquot of the slurry is injected into the graphite furnace of the atomic absorption spectrophotometer. Good agreement was obtained between our results and those obtained by a classical dry combustion method. Reproducibility was better than 5% when expressed as relative standard deviation.     

Testing the phylogeny of swordtail fishes using split decomposition and spectral analysis

We examine ways of testing for the reliability of inference from biological sequence data using sequences from Xiphophorus fishes and newly implemented methodology for sequence analysis. The approach we take provides one means to examine the fit between model and data for different sequences and hence to evaluate heterogeneity between data sets. In the case of the present study we show D-loop sequences to be a better molecule for studying the phylogeny of Xiphophorus fishes than cytochrome b sequences. The results of the split decomposition and spectral analysis confirm an earlier phylogenetic hypothesis which had been based on maximum parsimony, neighbor-joining, maximum likelihood analyses. Correspondence to: A. Meyer     

Conservation of Salmonella typhimurium Deoxyribonucleic Acid in Partially Diploid Hybrids of Escherichia coli

Partially diploid Escherichia coli K-12 hybrids recovered from mating with a Salmonella typhimurium Hfr strain were found to differ with respect to the manner in which they conserved the added Salmonella deoxyribonucleic acid (DNA). Five of the diploid hybrids examined appeared to maintain the Salmonella DNA as part of a functional F-merogenote; these hybrids were sensitive to the male-specific phage, R-17, responded as males to the female-specific phage, phiII, and transferred their inherited Salmonella genetic markers at high frequency in conjugation experiments. Six diploid hybrids were observed which were not sensitive to R-17, and from which the added Salmonella DNA was not transmissible in conjugation tests; nevertheless, these hybrids responded as males to phiII, and the Salmonella chromosomal fragments were conserved in them as parts of supercoiled, circular DNA elements. It was concluded that these circular DNA elements were defective F-merogenotes, unable to direct the synthesis of F-pili. Three diploid hybrids were found which were not sensitive to R-17, and which responded as females to phiII; no circular DNA was found in them, and it was concluded that their conservation of the Salmonella genetic fragments was accomplished in some manner which did not involve association with F or assumption of the supercoiled circular configuration. Other partially diploid hybrids were observed which appeared similar to these latter three hybrids with regard to their conservation of the Salmonella DNA, but which also contained an infecting F-factor; in these hybrids, both genetic and molecular experiments indicated that the unstably conserved Salmonella DNA was not associated physically with the F-factor.     

Passive Avoidance Learning Results in Region-Specific Changes in Concentration of and Incorporation into Colchicine-Binding Proteins in the Chick Forebrain

Abstract: Incorporation of [¹⁴T]leucine into trichloracetic acid-precipitable material and tubulin-enriched fractions, and total tubulin levels as determined by colchicine-binding activity and retention on DE81 filter discs, were measured in various regions of the chick brain following training on a one-trial passive avoidance task, suppression of pecking at a chromed bead as a consequence of the aversive taste of methylanthranilate. Radioactive pulse time was 0.5 h. The only brain region in which changes were found was the anterior forebrain roof, the same area in which biochemical changes in response to exposure of the birds to an imprinting stimulus have been observed previously. In the anterior forebrain roof the changes observed as a consequence of training were detectable at 0.5 and 24 h after the 10-s training experience but not 48 h subsequently. One-half hour after training, there were increases of the order of 20 or 30% in [¹⁴T]leucine incorporation into particulate and postmitochondrial TCA-precipitable material and a tubulin-enriched fraction purified as above. There were comparable increases in the total amount of colchicine-binding activity. By 48 h, none of these increases were detectable. Subcellular fractionation of the particulate fraction showed that most of the increase of incorporation into the tubulin-enriched fraction and in colchicine-binding activity was present in the soluble content of the synaptosomes; there were no increases in either measure in the synaptic membrane fraction. The possible role of changed levels and turnover of tubulin in the plastic responses of the brain to learning experiences is discussed.     

Echinococcus multilocularis in the mouse: The in vitro protoscolicidal activity of peritoneal macrophages

Baron R. W. and Tanner C. E. 1977. Echinococcus multilocularis in the mouse: the in vitro protoscolicidal activity of peritoneal macrophages. International Journal for Parasitology7: 489–495. The larvae of Echinococcus multilocularis are susceptible to the protoscolicidal activity of infected A/J mouse peritoneal cells. It is shown that the effector cell in this response is an activated macrophage. Preincubation of protoscolices in ‘immune’ serum increases their susceptibility to the protoscolicidal activity of infected mouse peritoneal cells. Macrophages activated nonspecifically by BCG or Taenia crassiceps infections also exhibit protoscolicidal activity in vitro. The identity of the effector cell was confirmed by scanning electron microscopy. It is shown that ‘immune’ macrophages adhere to and form close cellular contacts with the protoscolex surface. It is concluded that resistance to hydatid infections is mediated by activated macrophages.