Target antigens in malaria transmission blocking immunity

Malaria transmission blocking immunity has been found to operate against two distinct phases of development of malaria parasites in the mosquito midgut: (i) against the extracellular gametes and newly fertilized zygotes shortly after ingestion by a mosquito of parasitized blood and (ii) against the zygotes during their subsequent development into ookinetes. Immunity is antibody-mediated and stage-specific. A set of three proteins, synthesized in the gametocytes, expressed on the surface of the gametes and newly fertilized zygotes and subsequently shed during later transformation of the zygotes, has been identified as the target antigens of anti-gamete fertilization blocking antibodies. A single protein, synthesized and expressed on the zygote surface during its development to ookinetes, has been identified as the target of antibodies which block the development of the fertilized parasites in the mosquito. Immunization of human populations against gamete or zygote antigens, while not directly protecting an immunized individual from inflection, would reduce the transfer of malaria within the population. Such immunity, in addition to reducing the overall rate of malaria transmission, would, if combined with a vaccine against the asexual (disease-causing) stages, reduce the chance of selection of parasites that are resistant to the asexual vaccine by preventing their entry into the mosquito population.     

Axial ranking of residues in collagen in relation to edge association and fibril formation

In our earlier analysis of intermolecular interactions between collagen molecules, a major concern with the program employed is that it compared numbers of interactions between residues located on edges of defined, identical width and thus would not necessarily compare the same number of residues in each edge. This would be particularly true of some values of θ where well-defined vertical ranking of residues occurs. We have examined ranking of residues in relation to intermolecular edge association between bovine skin [α1(I)]₃ model collagen molecules by utilizing two different methods of counting intermolecular interactions between residues. The interaction peaks at θ = 27.69° and 36.00° are absent or relatively less intense in the plots obtained by utilizing radial distances between interacting residues instead of vertical bands of defined width. These studies suggest caution in accepting recently reported analyses of superhelix coiling of the collagen molecule which point to values of 27.69° or 36.00° for the twist of the superhelix. Although intramolecular interactions clearly point to interaction of collagen molecules at D intervals, they are insufficiently restricted in distribution to provide a reliable estimate of the superhelix angle by procedures so far employed.     

Proleptonchoides southindiae n. gen., n. sp., a New Leptonchoid from South India

Proleptonchoides southindiae n. gen., n. sp. (Dorylaimida: Leptonchidae), is described from soil around false tobacco (Lobelia excelsa) and cardamom (Elettaria cardamomurn) in South India. P. southindiae is prodelphic, has a short constricted esophageal bulb and flanged odontophore, and is phylogenetically close to Proleptonchus.     

Synergistic effect of heat-shock and UV-irradiation on mitosis and protein synthesis in G2-phase plasmodia of Physarum polycephalum Schw--reduction in UV-induced mitotic delay in a preheat-shocked system

The synergistic effect of UV irradiation and heat-shock during the last 3 hr of G2 phase of the cell cycle in the plasmodia of P. polycephalum, in terms of mitotic delay and inhibition of protein synthesis, has been evaluated. The mitotic delay due to both perturbers coordinately increased closer to mitosis. Maximum mitotic delay was obtained in plasmodia heat-shocked after UV irradiation, indicating the presence in this system of either a heat-labile mitogenic substance which is comparatively less susceptible to UV or a substance which is made more susceptible to hyperthermia by UV. A protective role for heat-shock applied before irradiation has been observed in that, radiation-induced mitotic delay is significantly reduced in this combination. There was severe inhibition of translation in all the perturbed classes. Organelle level effects which are independent of major protein synthetic activities or different levels of heat-shock protein production could be the reason for the lack of correlation between percentage inhibition of general protein synthesis and the extent of mitotic delay with respect to the two double-perturbed systems.     

Enantiospecific quantification of hexobarbital and its metabolites in biological fluids by gas chromatography/electron capture negative ion chemical ionization mass spectrometry.

A highly sensitive and specific assay based on gas chromatography/electron capture negative ion chemical ionization mass spectrometry has been developed for the analysis of the enantiomers of hexobarbital and its major metabolites in human urine and plasma. S-(+)-(5-2H3)hexobarbital and R-(-)-(5-2H3)hexobarbital were synthesized for clinical studies along with (+/-)-(1,5-2H6)hexobarbital and the deuterated major metabolites for use as internal and reference standards. Hexobarbital enantiomers and their metabolites were analyzed after pentafluorobenzyl and trimethylsilyl derivatization, following solid-phase extraction from plasma and urine. Intense negative ion spectra were observed for all of the derivatives. The base peak in the spectra corresponded to the M-pentafluorobenzyl anion [M-PFB]- except for 1,5-dimethylbarbituric acid, where M-. was the most abundant ion. The applicability of the method was demonstrated by following the plasma concentration-time profiles and urinary excretion in a male extensive metabolizer of mephenytoin who was given a pseudoracemic oral dose of hexobarbital containing equal 50 mg amounts of S-(+)-2(H0)hexobarbital and R-(-)-(2H3)hexobarbital. Marked stereoselective disposition was observed, with the R-(-)-enantiomer being more efficiently metabolized, primarily by alicyclic oxidation and ring cleavage.     

Fibroblast stimulation in schistosomiasis. XII. Identification of CD4+ lymphocytes within schistosomal egg granulomas as a source of an apparently novel fibroblast growth factor (FsF-1).

Granulomas that form around Schistosoma mansoni eggs deposited in the liver secrete a variety of fibrogenic factors that may provide a molecular link between chronic inflammation and hepatic fibrogenesis in schistosomiasis. We recently isolated from conditioned medium of egg granuloma cultures a approximately equal to 60-kDa heparin-binding growth factor for fibroblasts. Because this protein is distinct from other defined heparin-binding growth factors, we designated it "fibroblast stimulating factor-1" (FsF-1). We now report that FsF-1 is a lymphokine. We prepared IgG antibody against purified FsF-1 and determined that it did not cross-react with a variety of growth factors or recombinant interleukins. Using two-color flow cytometry of dissociated granuloma cell suspensions, we observed that approximately 20% to 25% of granuloma CD4+ lymphocytes express surface FsF-1. We isolated CD4+ granuloma lymphocytes by FACS and observed that these cells spontaneously secrete into culture supernatant a fibroblast mitogen that is neutralized by anti-FsF-1 antibody. Furthermore, anti-FsF-1 can specifically immunoprecipitate a metabolically labeled protein produced by the granuloma CD4+ lymphocytes. The labeled protein has the same apparent molecular mass (approximately equal to 60 kDa) as FsF-1 purified from granuloma culture supernatants. These findings define CD4+ lymphocytes as a source of FsF-1. Because FsF-1 has biologic and chemical features distinct from most other defined lymphokines and from other heparin-binding growth factors, FsF-1 appears to be a novel lymphokine.     

DNA-directed alkylating ligands as potential antitumor agents: sequence specificity of alkylation by intercalating aniline mustards

The sequence preferences for alkylation of a series of novel parasubstituted aniline mustards linked to the DNA-intercalating chromophore 9-aminoacridine by an alkyl chain of variable length were studied by using procedures analogous to Maxam-Gilbert reactions. The compounds alkylate DNA at both guanine and adenine sites. For mustards linked to the acridine by a short alkyl chain through a para O- or S-link group, 5'-GT sequences are the most preferred sites at which N7-guanine alkylation occurs. For analogues with longer chain lengths, the preference of 5'-GT sequences diminishes in favor of N7-adenine alkylation at the complementary 5'-AC sequence. Magnesium ions are shown to selectively inhibit alkylation at the N7 of adenine (in the major groove) by these compounds but not the alkylation at the N3 of adenine (in the minor groove) by the antitumor antibiotic CC-1065. Effects of chromophore variation were also studied by using aniline mustards linked to quinazoline and sterically hindered tert-butyl-9-aminoacridine chromophores. The results demonstrate that in this series of DNA-directed mustards the noncovalent interactions of the carrier chromophores with DNA significantly modify the sequence selectivity of alkylation by the mustard. Relationships between the DNA alkylation patterns of these compounds and their biological activities are discussed.     

Chemical cross-linking study of complex formation between methylamine dehydrogenase and amicyanin from Paracoccus denitrificans

Two soluble periplasmic redox proteins from Paracoccus denitrificans, the quinoprotein methylamine dehydrogenase and the copper protein amicyanin, form a weakly associated complex that is critical to their physiological function in electron transport [Gray, K. A., Davidson, V. L., & Knaff, D. B. (1988) J. Biol. Chem. 263, 13987-13990]. The specific interactions between methylamine dehydrogenase and amicyanin have been studied by using the water-soluble cross-linking agent 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide (EDC). Treatment of methylamine dehydrogenase alone with EDC caused no intermolecular cross-linking but did cause intramolecular cross-linking of this alpha 2 beta 2 oligomeric enzyme. The primary product that was formed contained one large and one small subunit. Methylamine dehydrogenase and amicyanin were covalently cross-linked in the presence of EDC to form at least two distinct species, which were identified by nondenaturing polyacrylamide gel electrophoresis (PAGE). The formation of these cross-linked species was dependent on ionic strength, and the ionic strength dependence was much greater at pH 6.5 than at pH 7.5. The effects of pH and ionic strength were different for the different cross-linked products. SDS-PAGE and Western blot analysis of these cross-linked species indicated that the primary site of interaction for amicyanin was the large subunit of methylamine dehydrogenase and that this association could be stabilized by hydrophobic interactions. In light of these results a scheme is proposed for the interaction of amicyanin with methylamine dehydrogenase that is consistent with previous data on the physical, kinetic, and redox properties of this complex.