Nectar parasitism of Asclepias syriaca by ants: Effect on nectar levels,pollinia insertion,pollinaria removal and pod production

Summary Milkweed (Asclepias syriaca L.) umbels and stems attended by ants (Lasius neoniger Emery and Tapinoma sessile (Say)) initiated significantly fewer pods and showed a trend to produce fewer mature pods than did umbels and stems not attended by ants. Since similar numbers of pollinia were inserted in ant-attended flowers, we hypothesize that ant-excluded flowers obtain more pollinia from other clones than do ant-attended flowers of this normally non-selfing species. If pollinators from other clones first visited flowers not depleted of nectar by ants, they could provide this source of foreign pollinia. Our experiments suggest that nocturnal noctuid and geometrid moths can provide these pollinia.     

Interaction with lectins and differential wheat germ agglutinin binding of pyocin 103-sensitive and -resistant Neisseria gonorrhoeae

Strains of Neisseria gonorrhoeae were treated with pyocin 611 131 (pyocin 103) from Pseudomonas aeruginosa PA103, and isogenic resistant variants were isolated. The interaction of pyocin-sensitive and isogenic pyocin-resistant strains with wheat germ agglutinin (WGA) agglutinated all pyocin-sensitive, but not pyocin-resistant, strains. Binding of WGA to three pyocin-sensitive strains and their isogenic pyocin-resistant variants was examined quantitatively by using fluorescein-conjugated lectin. Pyocin-resistant strains maximally bound one-third to one-eighth the quantity of WGA bound by isogenic-sensitive strains. Linear Scatchard plots revealed homogeneous WGA-binding sites on three pyocin-sensitive and one pyocin-resistant strains. Biphasic Scatchard plots, obtained with two pyocin-resistant strains, show that WGA-binding sites in these strains are heterogeneous. The number of WGA-binding sites for pyocin-sensitive organisms ranged from 8 x 10(5) to 1 x 10(6) sites per coccus and from 1 x 10(5) to 3 x 10(5) sites per coccus for pyocin-resistant strains. The apparent association constant for WGA binding to pyocin-sensitive strains ranged from 3 x 10(6) to 6 x 10(6) liters/mol and from 6 x 10(6) to 1 x 10(7) liters/mol for pyocin-resistant strains. Gonococcal lipopolysaccharide was shown to serve as the pyocin 103 receptor by inhibition of pyocin activity. Lipopolysaccharide from a pyocin 103-resistant strain was not able to inhibit pyocin 103 activity. Pyocin 103 resistance was correlated with a structural alteration involving N-acetylglucosamine residues in gonococcal lipopolysaccharide. Based on interactions with wheat germ, soybean, and ricin lectins, a model of lipopolysaccharide structure in N. gonorrhoeae is presented.     

A comparison of the citrate synthases of Escherichia coli and Acinetobacter anitratum

Citrate synthase has been purified to homogeneity from a strain of the Gram-negative aerobic bacterium Acinetobacter anitratum in a form which retains its sensitivity to the allosteric inhibitor NADH. In subunit size, amino acid composition, and antigenic reactivity the enzyme shows a marked structural resemblance to the citrate synthase of the Gram-negative facultative anaerobe Escherichia coli. Whereas the E. coli enzyme is subject to a strong, hyperbolic inhibition by NADH (Hill's number n = 1.0, Ki = 2 microM), the A. anitratum enzyme shows a weak, sigmoid response (n = 1.6, I0.5 = 140 microM) to this nucleotide. With E. coli, NADH inhibition is competitive with acetyl-CoA, and noncompetitive with oxaloacetate; with A. anitratum, NADH is noncompetitive with both substrates. Acinetobacter anitratum citrate synthase shows hyperbolic saturation with acetyl-CoA (n = 1.8). The finding of Weitzman and Jones (Nature (London) 219, 270 (1968) that NADH inhibition of the enzyme from Acinetobacter spp. is reversible by AMP, while that from E. coli is not, is explained by the much greater affinity of the E. coli enzyme for NADH. Unlike E. coli citrate synthase, the A. anitratum enzyme does not react with the sulfhydryl reagent 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB) in the absence of denaturation. With a second sulfhydryl reagent, 4,4'-dithiodipyridine (4,4'-PDS), the A. anitratum enzyme reacts with 1 equiv. of subunit; this modification induces a partial activity loss (attributable to a arise in the Km for acetyl-CoA) and an increase in the sensitivity to NADH. With the E. coli enzyme, 4,4'-PDS causes complete inactivation. Acinetobacter anitratum citrate synthase is much more resistant to urea denaturation than the E. coli enzyme is; the resistance of both enzymes to urea is greatly improved in the presence of 1 M KCl. It is suggested that the amino acid sequences of the subunits of the citrate synthases of these two bacteria are about 90% homologous, and that the 10% differences are in key residues, perhaps largely in the subunit contact regions, which account for the differences in allosteric properties.     

GABA induces behavioral and developmental metamorphosis in planktonic molluscan larvae

Swimming planktonic larvae of the marine gastropod mollusc Haliotis rufescens require exogenous GABA or its homologs for induction of their genetically programed behavioral and developmental metamorphosis to the adult form. This requirement is stereochemically specific and absolute; GABA at 10(-6) M is fully effective in the induction of cellular differentiation, proliferation and organogenesis. The kinetics of the development of larval competence for GABA induction, and of the early metamorphic processes induced by GABA, are described. Biochemical, histological and electron micrographic analyses suggest that cyclic AMP, calcium, and a glycopeptide secretion from the cephalic sensory complex may mediate transduction of the GABA signal in the control of behavioral and morphogenetic changes induced by this environmentally deployed transmitter substance. This first observation and characterization of a major role for GABA in the control of differentiation and development, and the experimentally tractable system in which these are demonstrated, are of significance for further biomedical research.     

Capacity for biosynthesis of prostaglandin-related compounds: distribution and properties of the rate-limiting enzyme in hydrocorals, gorgoniants, and other coelenterates of the Caribbean and Pacific.

A convenient and reliable assay is described for PGEP synthetase, the rate-limiting enzyme determining the total capacity for biosynthesis of prostaglandin-related compounds. Results of such assays, performed withe fresh specimens under both field and laboratory conditions, newly identify several marine coelenterate species as potentially important resources of PGRCs for research and possible development. Properties of the typical marine coelenterate PGEP synthetase, and the reaction which this enzyme catalyzes, have been further characterized.     

A unique course in anthropology

The course in forensic anthropology presented at Florida State University is designed to train criminal investigators in the application of physical anthropological and archaeological techniques to the investigation of buried bodies. Modification of archaeological field techniques by experimentation using artificial graves allows the recovery of fragile and easy to overlook evidence and ensures the recovery of all possible material for analysis by the physical anthropologist. An introduction to physical anthropology enables the criminal investigator to effectively communicate his needs and understand the type of information required for adequate identification of remains by a physical anthropologist.     

Neonatal infection with mouse thymic virus. Differential effects on T cells mediating the graft-versus-host reaction.

Neonatal infection with mouse thymic virus (TA), a murine herpes virus, produced extensive but temporary necrosis of the thymus which was maximal at 10 to 14 days of age. Studies of precursor and amplifier cells mediating graft-vs-host (GVH) reactivity of thymocytes, spleen cells (SC), and lymph node cells (LNC) of normal and TA-infected mice were made at 4 and 8 weeks of age. Infection with TA resulting in a profound reduction (70 to 80%) in the direct GVH reactivity of thymocytes at both ages; by comparison, the capacity of thymocytes to produce synergy when combined with normal LNC was normal at 8 weeks. Direct GVH reactivity of SC was depressed 90% 4 weeks after infection with TA but returned to near normal at 8 weeks. Direct GVH reactivity of LNC from TA-infected mice was normal at 4 and 8 weeks of age, but amplifier T cell activity in LNC was markedly depressed at 8 wekks. These results demonstrate that TA has highly selective effects upon subpopulations of T cells in thymus and lymph node.     

The effect of Bordetella pertussis on the antibody response in mice to type III pneumococcal polysaccharide.

The effect of an i.p. injection of Bordetella pertussis on the primary humoral immune response in mice to the thymus-independent antigen SIII has been studied. Suppression of the antibody response occurred when pertussis cells were injected at the same time as an optimal immunizing dose of SIII. In contrast, the antibody response to high doses of SIII was enhanced by B. pertussis. When SIII alone was injected, only 19S antibody was detected. However, when B. pertussis was administered with either optimal or high doses of SIII, 7S as well as 19S antibody against SIII was produced.