Successive phase-transition phenomena and phase diagram of the phosphatidylcholine-water system as revealed by differential scanning calorimetry

A completely dehydrated dipalmitoylphosphatidylcholine (DPPC) was prepared with dehydration under high vacuum and at a temperature above its main transition temperature. Thermal analyses on about forty different samples of the DPPC-water system indicated that the main transition temperature decreased stepwise with an increase in the water content to the limiting temperature at 42.6°C, reflecting the thermal behaviors of a total of five endothermic peaks. The pretransition appeared at a water content above 17 g%, and the predominant role of ‘newly incorporated water’ between the bilayers of DPPC molecules at the pretransition was made evident.     

Anti-Allergic Role of Cholinergic Neuronal Pathway via α7 Nicotinic ACh Receptors on Mucosal Mast Cells in a Murine Food Allergy Model

The prevalence of food allergy (FA) has increased in developed countries over the past few decades. However, no effective drug therapies are currently available. Therefore, we investigated cholinergic anti-inflammatory pathway as a regulatory system to ameliorate disrupted mucosal immune homeostasis in the gut based on the pathophysiological elucidation of mucosal mast cells (MMCs) in a murine FA model. BALB/c mice sensitized with ovalbumin received repeated oral ovalbumin for the development of FA. FA mice developed severe allergic diarrhea and exhibited enhanced type 2 helper T (Th2) cell immune responses in both systemic immunity and mucosal immunity, along with MMCs hyperplasia in the colon. MMCs were localized primarily in the strategic position of the mucosal epithelium. Furthermore, the allergic symptoms did not develop in p85α disrupted phosphoinositide-3 kinase-deficient mice that lacked mast cells in the gut. Vagal stimulation by 2-deoxy-D-glucose and drug treatment with nicotinic ACh receptor (nAChR) agonists (nicotine and α7 nAChR agonist GTS-21) alleviated the allergic symptoms in the FA mice. Nicotine treatment suppressed MMCs hyperplasia, enhanced MPO and upregulated mRNA expression of Th1 and Th2 cytokines in the FA mice colon. MMCs, which are negatively regulated by α7 nAChRs, were often located in close proximity to cholinergic CGRP-immunoreactive nerve fibers in the FA mice colon. The present results reveal that the cholinergic neuroimmune interaction via α7 nAChRs on MMCs is largely involved in maintaining intestinal immune homeostasis and can be a target for a new therapy against mucosal immune diseases with homeostatic disturbances such as FA.     

Desulfurization of dibenzothiophene by Corynebacterium sp. strain SY1.

Strain SY1, identified as a Corynebacterium sp., was isolated on the basis of the ability to utilize dibenzothiophene (DBT) as a sole source of sulfur. Strain SY1 could utilize a wide range of organic and inorganic sulfur compounds, such as DBT sulfone, dimethyl sulfide, dimethyl sulfoxide, dimethyl sulfone, CS2, FeS2, and even elemental sulfur. Strain SY1 metabolized DBT to dibenzothiophene-5-oxide, DBT sulfone, and 2-hydroxybiphenyl, which was subsequently nitrated to produce at least two different hydroxynitrobiphenyls during cultivation. These metabolites were separated by silica gel column chromatography and identified by nuclear magnetic resonance, UV, and mass spectral techniques. Resting cells of SY1 desulfurized toluenesulfonic acid and released sulfite anion. On the basis of these results, a new DBT degradation pathway is proposed.     

Tissue and plasma globotriaosylsphingosine could be a biomarker for assessing enzyme replacement therapy for Fabry disease

Fabry disease is a genetic disease caused by a deficiency of α-galactosidase A (GLA), which leads to systemic accumulation of glycolipids, predominantly globotriaosylceramide (Gb3). With the introduction and spread of enzyme replacement therapy (ERT) with recombinant GLAs for this disease, a useful biomarker for assessing the response to ERT is strongly required. We measured the tissue level of lyso-globotriaosylsphingosine (lyso-Gb3) in Fabry mice by means of high performance liquid chromatography, and compared it with the Gb3 level. The results revealed a marked increase in the lyso-Gb3 level in most tissues of Fabry mice, and which decreased after the administration of a recombinant GLA as in the case of Gb3, which is usually used as a biomarker of Fabry disease. The response was more impressive for lyso-Gb3 compared with for Gb3, especially in kidney tissues, in which a defect significantly influences the morbidity and mortality in patients with this disease. The plasma level of lyso-Gb3 also decreased after the injection of the enzyme, and it was well related to the degradation of tissue lyso-Gb3. Thus, lyso-Gb3 is expected to be a useful new biomarker for assessing the response to ERT for Fabry disease.     

Seasonal characteristics of surface water fulvic acids from Lake Biwa and Lake Tankai in Japan

Seasonal characteristics of surface water fulvic acids (FAs) isolated from Japanese clear-water lakes were investigated. Qualitative changes in Lake Biwa and Lake Tankai FAs were determined and compared. Although the relative molecular weights determined by high-performance size-exclusion chromatography did not change remarkably, the elemental compositions, E₆₀₀^1% E_{600}^{1\% } values and ¹H- and ¹³C-NMR spectral properties varied with the season. Both the H/C and N/C ratios for Lake Biwa FAs tended to be higher than those for Lake Tankai FAs, but O/C ratios were lower and decreased from spring to winter. The E₆₀₀^1% E_{600}^{1\% } values suggested that Lake Biwa FAs contained lower levels of unsaturated structures than Lake Tankai FAs, and the amounts of these structures increased in winter. The ¹H and ¹³C NMR spectra indicated that Lake Biwa FAs are richer in saturated aliphatic chains, especially in spring. Overall, Lake Biwa FAs exhibited clearer seasonal changes in these characteristics than Lake Tankai FAs, suggesting that the seasonal variation may depend on changes in aquatic microbial activities.     

Effect of D,L-propargylglycine on cystathionine metabolism in rats

Hepatic gamma-cystathionase activity at 12 h after the intraperitoneal injection decreased in proportion to the amount of D,L-propargylglycine administered, but hepatic cystathionine beta-synthase activity did not change. Contents of cystathionine in the liver increased gradually from 0.25 mg to 30 mg/200 g body weight in proportion to the amounts of D,L-propargylglycine injected; in the kidney, 0.5 mg to 10 mg; in the brain, 5 mg to 20 mg; in the serum, 0.25 mg to 30 mg. Contents of N-acetylcystathionine in the liver and kidney also increased in parallel with the accumulation of cystathionine.     

Accumulation of Betacyanin in Phytolacca americana Cells and of Anthocyanin in Vitis sp. Cells in Relation to Cell Division in Suspension Cultures

In suspension cultures of Vitis sp., maximal accumulation ofanthocyanin was observed during the stationary phase. Accumulationof anthocyanin occurred in parallel with the cessation of celldivision under conditions such as a reduction of the concentrationof phosphate in the medium, or the presence of aphidicolin,an inhibitor of DNA synthesis. By contrast, in suspension culturesof Phytolacca americana, aphidicolin inhibited the accumulationof betacyanin and cell division. When aphidicolin was removedfrom cells by washing, partially synchronized division of cellswas induced and the accumulation of betacyanin also occurred,in conjunction with cell division. In the absence of phosphatefrom the medium, cell division did not occur and accumulationof betacyanin also ceased. Readdition of phosphate to cellsstarved for phosphate induced both cell division and the accumulationof betacyanin. These results indicate a positive correlationbetween the accumulation of betacyanin and cell division inPhytolacca which contrasts with a negative correlation betweenthe accumulation of anthocyanin and cell division in Vitis. (Received April 17, 1989; Accepted December 23, 1989)     

Investigating the reaction and substrate preference of indole-3-acetaldehyde dehydrogenase from the plant pathogen Pseudomonas syringae PtoDC3000

Aldehyde dehydrogenases (ALDHs) catalyze the conversion of various aliphatic and aromatic aldehydes into corresponding carboxylic acids. Traditionally considered as housekeeping enzymes, new biochemical roles are being identified for members of ALDH family. Recent work showed that AldA from the plant pathogen Pseudomonas syringae strain PtoDC3000 (PtoDC3000) functions as an indole-3-acetaldehyde dehydrogenase for the synthesis of indole-3-acetic acid (IAA). IAA produced by AldA allows the pathogen to suppress salicylic acid-mediated defenses in the model plant Arabidopsis thaliana. Here we present a biochemical and structural analysis of the AldA indole-3-acetaldehyde dehydrogenase from PtoDC3000. Site-directed mutants targeting the catalytic residues Cys³⁰² and Glu²⁶⁷ resulted in a loss of enzymatic activity. The X-ray crystal structure of the catalytically inactive AldA C302A mutant in complex with IAA and NAD⁺ showed the cofactor adopting a conformation that differs from the previously reported structure of AldA. These structures suggest that NAD⁺ undergoes a conformational change during the AldA reaction mechanism similar to that reported for human ALDH. Site-directed mutagenesis of the IAA binding site indicates that changes in the active site surface reduces AldA activity; however, substitution of Phe¹⁶⁹ with a tryptophan altered the substrate selectivity of the mutant to prefer octanal. The present study highlights the inherent biochemical versatility of members of the ALDH enzyme superfamily in P. syringae.