Enzymatic synthesis of 6′-deoxychalcone in cultured Glycyrrhiza echinata cells

5-Deoxy-(iso)flavonoids are biosynthesized from 6-deoxychalcone (isoliquiritigenin). The coaction of a reductase with chalcone synthase (CHS) has been established in soybean cells to be responsible for the synthesis of 6-deoxychalcone. Western blot analysis of crude extracts from cultured cells of Glycyrrhiza echinata, another member of the Leguminosae, revealed proteins which cross-react with an antiserum raised against the soybean reductase. DEAE-Cellulose chromatography of the extract yielded fractions which showed CHS activity but not deoxychalcone synthase activity, and these fractions were also negative in Western blot analysis. In contrast, fractions displaying positive signals with the antiserum were also able to synthesize 6-deoxychalcone/5-deoxyflavanone. These results indicate that in G. echinata, too, synthesis of 6-deoxychalcone is likely to be performed by the coaction of the reductase and CHS. Induction of the reductase and CHS by yeast extract treatment of the cells was demonstrated.Abbreviations CHS chalcone synthase - DOCS 6-deoxychalcone synthase - YE yeast extract.     

The value of spatial experience and group size for ant colonies in direct competition

Animals often search for food more efficiently with experience. However, the contribution of experience to foraging success under direct competition has rarely been examined. Here we used colonies of an individually foraging desert ant to investigate the value of spatial experience. First, we trained worker groups of equal numbers to solve either a complex or a simple maze. We then tested pairs of both groups against one another in reaching a food reward. This task required solving the same complex maze that one of the groups had been trained in, to determine which group would exploit better the food reward. The worker groups previously trained in the complex mazes reached the food reward faster and more of these workers fed on the food than those trained in simple mazes, but only in the intermediate size group. To determine the relative importance of group size versus spatial experience in exploiting food patches, we then tested smaller trained worker groups against larger untrained ones. The larger groups outcompeted the smaller ones, despite the latter's advantage of spatial experience. The contribution of spatial experience, as found here, appears to be small, and depends on group size: an advantage of a few workers of the untrained group over the trained group negates its benefits.     

Alteration of T cell subsets and induction of suppressor T cell activity in normal subjects after exposure to sunlight

The effects of exposure to natural sunlight on the immune system were studied in 15 normal human subjects. Exposure was for 1 hr each day for 12 days over 2 wk and tests were carried out before, on completion, and 2 wk after completion. In comparison to concurrent studies on 13 age- and sex-matched controls, sun-exposed subjects had a significant increase in their circulation of T cells recognized by OKT8 monoclonal antibodies and a decrease in OKT4 positive T cells. Suppressor T cell activity measured in pokeweed mitogen-stimulated cultures of T and B cells was significantly increased against IgG and IgM production. These changes were still evident in many of the subjects 2 weeks after completion of the sun exposure. A trend for depression of natural killer cell activity against a melanoma target cell was noted in the present study, but this did not appear as marked as that noted previously in subjects exposed to radiation in solariums. The differences between the effect of radiation from solariums and natural sunlight on the immune system may result from the higher dosage of UV-A in radiation from solariums. The results suggest that exposure to sunlight may favor the induction of suppressor pathways in response to antigenic stimuli and that this may limit immune responses against tumor cells such as melanoma. They support the idea from animal studies that systemic changes in the immune system may be an important factor in the association of UV radiation with malignancy.     

Use of monoclonal antibodies to pregnanediol-3α-glucuronide for the development of a solid phase chemiluminescence immunoassay

Monoclonal antibodies to pregnanediol-3α-glucuronide were produced by hybridomas between P3-X63-Ag8 variants and spleen cell of mice immunized with a bovine serum albumin conjugate of the homologous hapten. The ascites fluid collected from mice inoculated with the cloned hybridoma cells contained antibodies with high specifity and affinity to pregnanediol-3α-glucuronide. A sensitive solid-phase chemiluminescence immunoassay for urinary pregnanediol-3α-glucuronide was established utilizing these antibodies. The assay was validated in terms of specificity, accuracy, sensitivity and precision. When urine samples were assayed for pregnanediol-3α-glucuronide, the results obtained by the solid-phase chemiluminescence immunoassay method and the conventional gas liquid chromatographic method agreed well (n = 30, r=0.96). The method may be of value for monitoring luteal function since it is fast, sensitive and does not require the use of radioisotopes or purification of the biological sample. Monoclonal antibody preparations facilitate rigorous standardization of the assay.     

Transglutaminase Activity in Rat Brain: Characterization, Distribution, and Changes with Age

The activity of transglutaminase was characterized in the rat brain. In adults, comparable levels of transglutaminase activity are present in all brain regions examined. The activity is present in all subcellular fractions, as studied by differential centrifugation, but the soluble fraction contains the highest specific activity. The endogenous activity (enzyme activity assayed in the absence of the exogenous substrate casein) is very low in all subcellular fractions, except in the synaptosomal fraction where its highest levels are about 40-60% of the activity assayed in the presence of casein. Furthermore, enzyme activity is present on the external surface of synaptosomes. In the soluble fraction, maximal activity can be detected between pH values of 9 and 10 when assayed in the presence of 5 mM CaCl2 (with half-maximal activity requiring 0.75 mM CaCl2) and 0.4 mM putrescine (with an apparent Km for putrescine of 0.1 mM). The activity can be partially inhibited by ZnCl2 (with an IC50 of 4.5 mM) and by AlCl3 (with an IC50 of 5.1 mM). In the cerebellum, where the full span of neuronal development can be studied after birth, the highest specific activity is observed just after birth, thereafter the activity starts to decline and by 14 days, after a reduction of about 65%, it reaches levels observed throughout life.     

The crystal structure of d(CCCCGGGG): a new A-form variant with an extended backbone conformation

The crystal structure of d(CCCCGGGG) has been determined at a resolution of 2.25 A. The oligomers crystallize as A-DNA duplexes occupying crystallographic two-fold axes. The backbone conformation is, in general, similar to that observed in previously reported crystal structures of A-DNA fragments, except for the central linkage, where it adopts an extended structure resulting from all trans conformation at the P-O5'-C5'-C4' bonds. This type of conformation facilitates interstrand stacking between the guanines at the C-G site. The local helix twist at this step is very small (25 degrees) compared to an overall average of 33.5 degrees. The unique structure of the C-G base-pair step, namely the extended backbone and the distinct stacking geometry, may be an important feature in the recognition mechanism between double-stranded DNA molecules and restriction endonucleases such as Msp I, which cuts the sequence CCGG very specifically with a rate unaffected by neighboring base pairs.     

Nuclear magnetic resonance study of the interaction of zinc with thymulin

Interaction of Zn2+ with thymulin was investigated by 1H NMR spectroscopy. In DMSO-d6 solution, Zn2+ forms a complex with a nonapeptide involving the C-terminal carboxylate and the hydroxyl groups of the two serine residues in position 4 and 8, in a tetrahedral structure.     

New sesquiterpene lactones from Artemisia herba alba

The structures of herbolides A, B and C, new sesquiterpene lactones isolated from Artermisia herba alba, were determined by chemical and spectroscopic methods.