Pygidial Gland of Azteca NR. bicolor AND Azteca chartifex: Morphology and Chemical Identification of Volatile Components

The large paired reservoirs of the pygidial gland of Azteca nr. bicolor and A. chartifex represents the largest exocrine structure in the abdomen. The glands produce a secretion with a strong smell, which the ants release when they are disturbed. Analyses of the secretions by gas chromatography–mass spectrometry (GC-MS) revealed a mixture of iridoids and ketones. A. nr. bicolor contains 2-heptanone (8%) and a mixture of three iridodial isomers, with trans-trans-iridodial as the major component (32%). A. chartifex contains 6-methyl-5-hepten-2-one (13%) and the three isomeric iridodials with cis-trans-iridodial as the principal component (32%).     

A Proposal for Estimation of the Parameters of Multivariate Moving-average Models

A method is proposed for the preliminary estimation of the parameters of multivariate moving-average processes. Initially, m independent white-noise series are generated. Then the parameters are estimated through an iterative procedure. The algorithm is fast and simple since it does not require specialized software for time series but a least squares routine. The estimators are consistent and a simulation experiment shows good performance in finite samples. An applicati on to real data is also illustrated     

Acid-activated organoclays: preparation, characterisation and catalytic activity of polycation-treated bentonites

Samples of SWy-2 and SAz-1 loaded with increasing amounts of the polycation magnafloc 206, [(Me₂NCH₂CHOHCH₂)_n]ⁿ⁺Cl_n, were acid-treated using 6 M HCl at 95°C for 30, 90 and 180 min. The activity of these acid-activated polycation-exchanged clays for the conversion of α-pinene to camphene and limonene was determined and compared with that from clay samples (without polycation) acid-treated in the same manner. Acid treatment of polycation-exchanged bentonites produced hybrid catalysts which enhanced the activity of the clays for the isomerisation of α-pinene to camphene and limonene. The presence of the polycation had a more marked influence on the activity of samples derived from SAz-1 increasing the yield from 25% for acid-activated SAz-1 with no added polycation to 50% camphene for acid-activated polycation-exchanged SAz-1. The increase in yield for corresponding samples derived from SWy-2 was only from 42 to 52%. This enhancement in yield for samples derived from SAz-1 was attributed to the increased hydrophobicity of the polycation loaded clay whilst the comparable yields for SWy-2 in the absence and presence of polycation may suggest that SWy-2 disperses well in the non-polar α-pinene. The total yields (based on α-pinene) for the most active catalysts was between 80 and 90%. These yields are directly comparable with those obtained by others using zeolites and pillared clays although the acid-activated polycation-treated clays were marginally less selective towards camphene.     

Reduced adipose 18∶3ω3 with weight loss by very low calorie dieting

The human undergoing rapid and sustained weight loss by very low calorie dieting (VLCD) derives the majority of daily energy needs from adipose fatty acids. To evaluate the rates of metabolic utilization of individual fatty acids in humans, two groups of adult women outpatients were studied during major weight loss by VLCD. The diets used were either food or formula, providing the recommended dietary allowance for minerals and vitamins, with fat contents of 2–20 g/d. Group 1 consisted of 10 subjects [initial body mass index (BMI) 32.7, 157% of ideal body weight (IBW)] with a mean loss of 17.7 kg in 3–5 months. Group 2 consisted of 14 subjects (initial BMI 36.7, 167% of IBW) with a mean loss of 25.6 kg in 4–5 months. Adipose tissue biopsies were obtained by needle aspiration from Group 1 before and after weight loss and from Group 2 before, at the midpoint, and after weight loss. With weight loss in Group 1, the adipose tissue content of 18∶1ω9, 18∶2ω6, and 20∶4ω6 did not change, but 18∶3ω3 fell (0.67 to 0.56 wt%, p<0.0001) as did 20∶5ω3 (0.08 to 0.05, p<0.01). Adipose tissue 22∶6ω3 rose from 0.03 to 0.07 (p<0.01). In Group 2, only 18∶3ω3 showed a change, falling from 0.71 to 0.69 to 0.59 wt% across weight loss (p=0.03 by analysis of variance). We conclude that the major fatty acids are oxidized in proportion to their composition in adipose triglyceride. The significant reduction in the concentration of 18∶3ω3 during weight loss is unique among fatty acids. Its accelerated removal from adipose tissue indicates either a preferential step in β-oxidation or a defined need during supplemented fasting which exceeds its rate of provision from adipose stores. This work was presented in part at the Annual Meeting of the American Society for Clinical Nutrition, Washington, D.C., 1988.     

Polyesters containing sulfur. I. Products of melt polycondensation of diphenylmethane-4,4′-di(methylthioacetic acid) with some diols

Several new polyesters containing sulfur in the main chain were obtained by melt polycondensation of diphenylmethane-4,4′-di(methylthioacetic acid) with ethanediol, 1,3-propane diol, 1,4-butanediol, 1,5-pentenediol, 1,6-hexanediol, 1,2-propanediol, and 2,2′-oxydiethanol. The structure of all polyesters was determined from elemental analysis and infrared (IR) spectra. Yield, reduced viscosity, molecular weight, and softening temperature for reaction products have been found. Initial decomposition and initial intensive decomposition temperature were defined from the curves of thermogravimetric analysis.     

Diffusion with simultaneous immobilization in polymer–dye systems. I. Diffusion of the cationic dye anilana red BL in the anionically modified polyester fiber dilana

The diffusion coefficient of the cationic dye Anilana Red BL in the anionically modified polyester fiber Dilana has been calculated regarding a general diffusion-immobilization model. In the model the mobile species are distinguished from the immobilized ones. In computations of Sand's equation and experimentally determined sorption isotherm of the dye in the fiber, the rate-of-dyeing curve and the concentration profiles of the dye in the same fiber were employed. The diffusion coefficient of the mobile species of Anilana Red BL in the fiber is two orders of magnitude higher than the average diffusion coefficient obtained from Hill's equation and the apparent diffusion coefficient calculated by the Boltzmann–Matano method.     

Lipid characteristics of RSV-transformed Balb/c 3T3 cell lines with different spontaneous metastatic potentials

To determine whether a metastatic phenotype may be corelated with a characteristic lipid pattern, we compared the lipid composition of low metastasizing Balb/c 3T3 cells transformed by the B77 strain of Rous sarcoma virus (B77-3T3 cells) with that of a subclone isolated by growth in 0.6% agar, the B77-AA6 cells, which exhibit a high capacity for spontaneous metastasis. B77-3T3 cells revealed characteristics in their lipid composition common to other systems of transformed cells, i.e., an accumulation of ether-linked lipids, a reduction of the more complex gangliosides, an increase of oleic acid (18∶1) and a decrease of arachidonic (20∶4) and C22 polyunsaturated fatty acids in phospholipids. High metastatic B77-AA6 cells showed: a) an even more marked decrease of complex gangliosides; b) a more pronounced increase of 18∶1 and decrease of 20∶4 and 22 polyunsaturated fatty acids in certain phospholipid classes; and c) a higher percentage of alkyl-acyl subfractions in both phosphatidylcholine and phosphatidylethanolamine than B77-3T3 cells. Comparing the data for other systems of metastatic cells with those of lipid studies of spontaneously metastasizing B77-AA6 cell system leads us to conclude that the metastatic phenotype is characterized by a change in ether-linked lipids, rather than in fatty acids.     

Initial Molecular Recognition Steps of McjA Precursor during Microcin J25 Lasso Peptide Maturation

Microcin J25 (MccJ25) has emerged as an excellent model to understand the maturation of ribosomal precursor peptides into the entangled lasso fold. MccJ25 biosynthesis relies on the post‐translational modification of the precursor McjA by the ATP‐dependent protease McjB and the lactam synthetase McjC. Here, using NMR spectroscopy, we showed that McjA is an intrinsically disordered protein without detectable conformational preference, which emphasizes the active role of the maturation machinery on the three‐dimensional folding of MccJ25. We further showed that the N‐terminal region of the leader peptide is involved in interaction with both maturation enzymes and identified a predominant interaction of V43–S55 in the core McjA sequence with McjC. Moreover, we demonstrated that residues K23–Q34 in the N‐terminal McjA leader peptide tend to adopt a helical conformation in the presence of membrane mimics, implying a role in directing McjA to the membrane in the vicinity of the lasso synthetase/export machinery. These data provide valuable insights into the initial molecular recognition steps in the MccJ25 maturation process.     

Tracking Protein S‐Fatty Acylation with Proteomics

Recently, Hang and co‐workers developed “acyl‐PEG exchange” (APE), which allows the investigation of protein S‐fatty acylation with mass‐tag labelling and gel electrophoresis, methods that are accessible to any biochemistry laboratory.