Two different sites of action for platelet activating factor and 1-O-alkyl-2-O-methyl-sn-glycero-3-phosphocholine on platelets and leukemic cells.

2-O-Methyl analogs of platelet activating factor (PAF) are potent anticancer agents. The sites of action and mechanisms of cell toxicity of these agents are as yet unknown. To better understand the mode of action of this class of anticancer agents, we examined the ability of 1-O-hexadecyl-2-acetylglycero-3-phosphocholine with the S or R configuration at C2 ((R)-PAF and (S)-PAF) and 1-O-hexadecyl-2-methoxyglycero-3-phosphocholine with the S or R configuration at C2 ((R)-ET-16-OCH3-GPC and (S)-ET-16-OCH3-GPC) to induce rabbit platelet aggregation and to inhibit [3H]thymidine uptake into WEHI-3B cells, HL-60 cells, and normal blood lymphocytes. The four chiral ether-linked lipids caused aggregation of rabbit platelets with the following order of potency: (R)-PAF greater than (S)-PAF greater than (R)-ET-16-OCH3-GPC greater than (S)-ET-16-OCH3-GPC; the EC50 values were 1 pM, 50 nM, 1 microM, and 50 microM, respectively. The cytotoxic effects of these ether lipids in leukemic cells was in reverse order to that observed for aggregation of platelets. The order of potency for inhibition of [3H]thymidine uptake by WEHI-3B and HL-60 cells was (R)-ET-16-OCH3-GPC = (S)-ET-16-OCH3-GPC greater than (S)-PAF greater than (R)-PAF; the EC50 values were 2, 2, 15, and greater than 40 microM, respectively. PAF antagonists (WEB 2086, CV 3988, triazolam, and SRI 63,441) blocked the action of the four ether lipids on platelets, while SRI 63,441 blocked the antineoplastic activity of the ether lipids on WEHI-3B and HL-60 cells. None of the four lipids was able to kill normal lymphocytes significantly. Scatchard analysis of PAF receptor binding revealed that HL-60 and WEHI-3B cells, which are sensitive to the cytotoxic action of ether-linked lipids, do not possess PAF receptors, whereas both normal lymphocytes and platelets do possess a PAF receptor. The present data indicate that the cytotoxic action of antineoplastic ether-linked lipids does not involve the PAF receptor. The protective role of SRI 63,441 in blocking the proaggregatory activity of the ether lipids in rabbit platelets involves PAF receptor, but cytotoxic activity against WEHI-3B and HL-60 cells does not result from its ability to act as a PAF antagonist.     

Genetic mapping of three human homologues of murine t-complex genes localizes TCP10 to 6q27, 15 cM distal to TCP1 and PLG

Human homologues of mouse t-complex genes have been cloned and localized physically to chromosome 6p or 6q. TCP1, TCP10, and PLG are human homologues of genes located in the proximal portion of the t-complex on mouse chromosome 17. We present here results of genetic mapping of these human t-complex homologues previously localized to 6q25-q27, 6q21-q27, and 6q26-q27, respectively, by physical techniques. TCP1 and PLG do not recombine with each other and are separated from TCP10 by about 15 cM, while the corresponding mouse genes are no more than 4 cM apart. Genetic mapping with markers well localized cytogenetically places TCP1 and PLG proximal to TCP10 and localizes the latter to the cytogenetic band 6q27. It is likely that the organization of human t-complex homologues on 6q is similar to that of t haplotypes rather than that of wildtype murine chromosome 17.     

The alpha- and beta-isoforms of the inhibitor protein of the 3',5'-cyclic adenosine monophosphate-dependent protein kinase: characteristics and tissue- and developmental-specific expression.

The inhibitor protein (PKI) of the cAMP-dependent protein kinase was first characterized from rabbit skeletal muscle. More recently a form of PKI was isolated and cloned from rat testis which shares relatively limited amino acid sequence with the rabbit skeletal muscle form. We have now isolated a cDNA from rat brain which encodes a protein corresponding to the rabbit skeletal muscle PKI. This establishes the presence of the "skeletal muscle" and "testis" proteins in the same species and therefore that they clearly represent distinct isoforms. We have also demonstrated that the isoform from testis, like the skeletal muscle isoform, is specific for the cAMP-dependent protein kinase and that it is able to inhibit this enzyme when expressed in cultured JEG-3 cells. Both forms contain the five specific amino acid recognition determinants which have been shown to be required for high affinity binding to the protein kinase catalytic site, although there is some noted lack of conservation of codons used for these residues. Overall, the two rat isoforms are only 41% identical at the amino acid level and 46% at the level of coding nucleotides. We propose that the rabbit skeletal muscle and rat testis forms be designated PKI alpha and PKI beta, respectively. Using Northern blot analysis, we have examined the tissue distribution of the two forms in the rat and their relative expression during development. In the adult rat, mRNA of the PKI alpha species is highest in muscle (both skeletal and cardiac) and brain (cortex and cerebellum).(ABSTRACT TRUNCATED AT 250 WORDS)     

Gene expression in nematode-infected plant roots

Summary A major pathogen of potato plants (Solanum tuberosum) is the potato cyst nematode (Globodera spp.), which induces localized redifferentiation of a limited number of host cells to form a specialized feeding-site termed the syncytium. A novel strategy utilizing the polymerase chain reaction (PCR) was employed to construct a cDNA library from dissected potato roots highly enriched in syncytial material. The library was differentially screened with cDNA probes derived from the infected root tissue from a compatible interaction and from healthy root tissue. Characterization of one gene identified by the library screen indicated an expression pattern that correlated with events in the immediate vicinity of the pathogen after syncytial establishment. The strategy for library construction and screening could be applicable to the study of gene expression in any plant-pathogen interaction in which the limited supply of cells at the interface of the two organisms precludes a more traditional approach.     

Population growth of a gorgonian coral: equilibrium and non-equilibrium sensitivity to changes in life history variables

Summary A size dependent model of population growth of the Caribbean gorgonian Plexaura A is developed based on observed rates of survival, growth and colony fragmentation at a site in the San Blas Islands, Panama. Sensitivity and elasticity analyses indicate that the fate of large colonies has the greatest effect on population growth. Variables which directly affect the generation of large colonies have the next greatest effect on population growth. These variables include the recruitment of large fragments, and the survivorship of colonies in the next smaller size class. Sexual reproduction has an extremely limited ability to affect population growth. Vegetative reproduction has a greater potential effect on growth rates. Environmental conditions regularly change the matrix of transition probabilities which predicts population growth. This keeps the population from approaching its stable size class distribution. Deviations from the stable size class distribution alter sensitivity and elasticity and in this case have the effect of increasing the importance of survivorship of the smallest colonies. Nonequilibrium conditions alter sensitivity analyses and it is important to assess whether populations are at equilibrium and to determine the effects of such deviations on the sensitivity analysis.     

Effects of experience on palatability hierarchies of novel plants in the polyphagous grasshopperSchistocerca americana

Summary We studied the influence of diet composition and breadth on the subsequent acceptability of three novel plants to sixth instarSchistocerca americana. Rearing diets of equal breadth differing in composition, and diets differing in breadth, significantly altered first meal length on some but not all of the test plants. These effects on palatability altered and at times reversed the palatability hierarchy of insects reared on different diets. The effects of rearing insects on broad diets were not produced by exposure to the plant odors alone, but apparently required contact with a diversity of plants while feeding. Switching diets for 24 h prior to testing did not alter preferences induced by rearing diets. The relationship of these patterns to induced preferences in other insects, and some possible mechanisms for generating induced preferences, are discussed.     

Ultrastructural immunolocalization of actin in a fungus

Summary We have successfully localized fungal actin for the first time using immuno-electron microscopy and hyphal tips of the rice blast pathogenMagnaporthe grisea. Following ultrarapid freezing, samples were processed in a novel substitution fluid of 10% acrolein in anhydrous ethanol and embedded in LR White resin. A monoclonal anti-actin antibody, previously shown to recognizeM. grisea actin, bound specifically to filasomes concentrated in the peripheral cytoplasm of subapical regions, and to the core-region of the Spitzenkörper.Abbreviations IEM immuno-electron microscopy - TEM transmission electron microscopy     

Restoration of normal stamen development and pollen formation by fusion of different cytoplasmic male-sterile cultivars of Nicotiana tabacum

Summary Fusion of two cytoplasmic male-sterile cultivars of Nicotiana tabacum, one with N. bigelovii cytoplasm and one with N. undulata cytoplasm, resulted in the restoration of male fertility in cybrid plants. All male-fertile cybrids exhibited fused corollas, which is characteristic for the cultivar with N. undulata cytoplasm, while their stamen structures varied from cybrid to cybrid, some producing stamens with anthers fused to petal-like appendages and one producing stamens of a normal appearance for N. tabacum. Restriction enzyme digestion and agarose gel electrophoresis of mitochondrial DNA showed that mitochondrial DNA of the fertile cybrids was more similar to the male-sterile cultivar with the cytoplasm of N. undulata than to the cultivar with N. bigelovii cytoplasm. Some restriction fragments were unique to the male-fertile cybrids. Comparisons between stamen structure and mitochondrial DNA for eight fertile progeny from one cybrid plant led to the identification of several restriction fragments that appeared at enhanced levels in connection with normal stamen development.     

Localization of growth arrest-specific genes on mouse Chromosomes 1, 7, 8, 11, 13, and 16

Growth arrest in NIH3T3 cells is associated with increased expression of a variety of mRNAs, several of which have been isolated as cDNA clones. Six of these growth arrest-specific (Gas) genes were mapped by following the inheritance of DNA restriction fragment length variants (RFLVs) associated with them in panels of recombinant inbred (RI) strains of mice and in the progeny of backcrosses both between laboratory mouse strains and between a laboratory strain and Mus spretus. The six genes are unlinked. Gas-1 maps to Chromosome (Chr) 13, Gas-2 to Chr 7, Gas-3 to Chr 11, Gas-4 to Chr 16, Gas-6 to Chr 8, and Gas-10 to Chr 1.