Symptoms and immunologic markers induced by exposure to methyltetrahydrophthalic anhydride

A study was performed in 43 workers exposed to methyltetrahydrophthalic anhydride (MTHPA) used as a hardener in an epoxy resin system. Ten workers sensitized to MTHPA (group SS; presence of serum IgE antibodies against a conjugate of MTHPA and human serum albumin (HSA) detected by RAST) had significantly higher levels of tryptase in nasal lavage fluid than 19 nonsensitized workers with work-related nasal symptoms (group NS) and 14 nonsensitized workers without nasal symptoms (group NN). This suggests an ongoing mast-cell-mediated reaction in the sensitized group. No statistically significant differences were found in the three groups concerning eosinophil cationic protein (ECP) and TAME-activity in lavage fluid. However, there was a significant increase in serum ECP in the SS group, as compared with a group of unexposed controls. Nasal challenge with MTHPA-HSA, performed in a subsequent study in seven workers from the SS group, six from the NS group, and seven from the NN, caused a larger increase of symptom score and a more pronounced decrease in nasal inspiratory peak flow in the SS group than in the other two groups. No significant rise was recorded for tryptase and ECP in lavage fluid in any of the three groups after challenge. The combined results of the two studies indicate that specific IgE antibodies play a pathogenetic role in at least some of the cases of work-related nasal symptoms associated with MTHPA exposure.     

Plant inhibitors of serine proteinases: Hageman factor fragment, kallikreins, plasmin, thrombin, factor Xa, trypsin, and chymotrypsin

Numerous plants were tested for inhibitors of human Hageman factor fragment (HF_f), plasma kallikrein, urinary kallikrein, plasmin, thrombin, porcine pancreatic kallikrein, and bovine Factor X_a, trypsin, and chymotrypsin. Pumpkin seeds and iris bulbs contain trypsin inhibitors which specifically inhibit HF_f. Flower bulbs—especially those of tulip, lily, hyacinth, and calla—are hitherto unrecognized rich sources of inhibitors with different inhibitory spectrums and physicochemical properties.     

Hydrolysis of arginine and tyrosine esters in mast cells exposed to epinephrine

Acting in a dose-dependent fashion in vitro, l-epinephrine caused rat peritoneal fluid cells to hydrolyze substituted arginine (BAEE, TAME) and tyrosine (BTEE) esters. Cell activation was complete within 5 min; repeated washing of activated cells did not result in loss of their BAEE-hydrolyzing capacity. BTEE-hydrolyzing capacity fell to pre-activation levels within 10 min, even in the absence of washing. This loss may be the result of an interaction of BTEE-esterase with cell-borne inhibitory factors. 8-Br-cGMP or noradrenaline acted like epinephrine. diBu-cAMP was inactive but inhibited cell activation by epinephrine or cGMP. Neither epinephrine, 8-Br-cGMP nor diBu-cAMP released histamine. Exposure of peritoneal cells to a hypotonie salt medium caused histamine release but not activation of esterase. However, hypotonically pretreated cells responded to epinephrine in the same way as normal cells. Diisopropyl-fluorophosphate prevented esterase activity on TAME and BTEE. Following differential centrifugation of peritoneal fluid cells, epinephrine-sensitive esterase was found only in mast cells; eosinophils, lymphocytes and monocytes were inactive. Compound $\text{48}\text{80}$, although less active than epinephrine, was also able to activate mast cells. The concentrations required were ten times higher than those needed to cause substantial release of histamine. The appearance of esterase activity in epinephrine-treated rat mast cells seems to be the outcome of cGMP-dependent changes, associated with reversible morphological alterations, but not with the release of histamine,     

Biotransformation and kinetics of excretion of tert-amyl-methyl ether in humans and rats after inhalation exposure.

tert-Amyl methyl ether (TAME) may be widely used as an additive to gasoline in the future. The presence of this ether in gasoline reduces the tail pipe emission of pollutants. Therefore, widespread human exposure to TAME may occur. To contribute to the characterization of potential adverse effects of TAME, its biotransformation was compared in humans and rats after inhalation exposure. Human volunteers (three males and three females) and rats (five males and five females) were exposed to 4 (3.8 +/- 0.2) and 40 (38.4 +/- 1.7) ppm TAME for 4 h in a dynamic exposure system. Urine samples were collected for 72 h in 6-h intervals and blood samples were taken at regular intervals for 48 h in humans. In urine, the TAME metabolites tert-amyl alcohol (t-amyl alcohol), 2-methyl-2, 3-butane diol, 2-hydroxy-2-methylbutyric acid, and 3-hydroxy-3-methylbutyric acid were quantified. TAME and t-amyl alcohol were determined in blood samples. After the end of the exposure period, blood concentrations of TAME were 4.4 +/- 1.7 microM in humans and 9.6 +/- 1.4 microM in rats after 40 ppm TAME, and 0.6 +/- 0.1 microM in humans and 1.4 +/- 0.8 microM in rats after 4 ppm. TAME was rapidly cleared from blood in both rats and humans. The blood concentrations of t-amyl alcohol were 9.2 +/- 1.8 microM in humans and 8.1 +/- 1.5 microM in rats after 40 ppm TAME, and 1.0 +/- 0.3 microM in humans and 1.8 +/- 0.2 microM in rats after 4 ppm TAME. t-Amyl alcohol was also rapidly cleared from blood. In urine of humans, 2-methyl-2,3-butane diol, 2-hydroxy-2-methylbutyric acid, and 3-hydroxy-3-methylbutyric acid were recovered as major excretory products in urine. In rats, 2-methyl-2,3-butane diol and its glucuronide were major TAME metabolites. t-Amyl alcohol and its glucuronide were minor TAME metabolites in both species. All metabolites of TAME excreted with urine in rats were rapidly eliminated, with elimination half-lives of less than 6 h. Metabolite excretion in humans was slower and elimination half-lives of the different metabolites were between 6 and 40 h in humans. The obtained data indicate differences in TAME biotransformation and excretion between rats and humans. In rats, TAME metabolites are rapidly excreted. In humans, metabolic pathways are different and metabolite excretion is slower. Recovery of TAME metabolites in urine was higher in humans as compared to rats, suggesting more intensive biotransformation of TAME in humans.     

Subcellular fractionation of human eosinophils: Isolation of functional specific granules on isoosmotic density gradients

Subcellular fractionation has been an important tool in investigating human eosinophil structure and function, including localizing of cytokine/chemokines within granules, investigating granule protein translocation and intracellular transport during eosinophil secretion, and studying secretory mechanisms of granules. The resolution of organelles obtained by subcellular fractionation was improved considerably after the introduction of nonionic iodinated density-gradient metrizamide and Nycodenz media that, unlike sucrose, exhibit relatively low tonicity throughout the gradient. However, the structure and membrane preservation of isolated organelles were still compromised due to the lack of gradient isoosmolarity. This paper describes a detailed protocol of subcellular fractionation of nitrogen cavitated eosinophils on an isoosmotic iodinated density gradient (iodixanol - OptiPrep) and the isolation of well preserved and functional membrane-bound specific granules.     

The identification of serum ligand-binding proteins using immuno-precipitation techniques and autoradiography

The identification of ligand-binding proteins in serum is important for understanding many metabolic pathways and for interpreting clinical measurements. Most techniques presently available lack the facility to identify specific binding proteins. This problem has been overcome by combining the specificity of immunological methods with the sensitivity of radioisotope detection. The methods comprise an adaptation of 2-dimensional immuno-electrophoresis, and radial immunodiffusion, combined with radiolabelled ligands and autoradiography. They have been used to determine the serum binding of calcium, cadmium, thyroxine and the beta blocking drug propranolol. This technique has wide application to other ligand-binding interactions.     

Study on the thrombin-like enzyme preferentially releasing fibrinopeptide B from the snake venom of Agkistrodon halys Pallas

Three components with arginine esterase activities were found in the venom of the Chinese pit viper (Agkistrodon halys Pallas). They were identified as bradykinin releasing, thrombin-like and fibrinogenolytic enzymes respectively. The thrombin-like enzyme of A. halys Pallas was purified to a homogeneous state. It was a glycoprotein with molecular weight of about 43,000. Though this enzyme displayed a higher esterase activity on BAEE than trypsin and human thrombin, it showed very weak clotting ability on fibrinogen. The kinetic analysis of the release of fibrinopeptides A (FPA) and B (FPB) showed that the action mode of this enzyme on fibrinogen was just opposite to that of mammalian thrombin. FPB was first released, followed by FPA after a long lag period.     

Plasma kallikrein-generating activity evoked by rat peritoneal-fluid mast cells following treatment with epinephrine, 8-bromo-cyclic 3',5'-guanosine monophosphate or compound 48/80

Acting in a dose-dependent fashion, l-epinephrine caused rat peritoneal-fluid cells to rapidly deplete rat plasma kininogen in vitro; 8-bromo-cyclic 3′,5′-guanosine monophosphate (8-Br-cGMP) behaved similarly; N⁶-2¹-O-dibutyril-cyclic 3′,5′-adenosine monophosphate (di Bu-cAMP) inhibited this effect of epinephrine or 8-Br-cGMP. After fractionation of peritoneal-fluid cells by differential centrifugation, this kininogen-depleting activity was observed only in mast cells; eosinophils, lymphocytes, and monocytes were inactive. Epinephrine-treated mast cells were ablt to hydrolyze the trypsin substrates N-p-toluenesulfonyl-arginine-methyl-ester (TAME) or N-benzoyl-arginine-ethyl-ester and to generate the capacity to hydrolyze these substrates in rat plasma; because this activity accompanied kininogen depletion, it was attributed to plasma kininogenase (plasma kallikrein). Diisopropyl-fluorophosphate (DFP) inhibited the mast cell esterase activity toward TAME but did not prevent activated cells from depleting plasma kininogen. Thus, mast cell-bound argininase ester esterase may not have been necessary for the activation of plasma kininogenase. Mast cell heparin, exposed following epinephrine or 8-Br-cGMP treatment, may have been the activator of plasma kallikrein. Unlike DFP, Trasylol [polyvalent bovine proteinase inhibitor (BPTI)] inhibited both mast cell esterase and kininogen-depleting activity. This inhibitor may have acted on mast cells both as a heparin antagonist and and a non-specific esterase inhibitor. Compound $\text{48}\text{80}$, at concentrations causing 40 per cent release of mast cell histamine, failed to cause mast cells to exhibit the ability to active plasma kallikrein. At high concentrations it activated the kininogen depleting action of mast cells, but to a lesser degree than did epinephrine or 8-Br-cGMP. These compounds did not release histamine; it may be concluded, therefore, that the ability to activate plasma kininogenase was present in non-histamine releasing mast cells.     

叔戊烯合成甲基叔戊基醚的反应动力学

以催化裂化(FCC)汽油中分离出的C5馏分为原料,用修正的UNIFAC方法计算反应体系中的组分活度,并对活度模型和浓度模型进行比较.分别采用R-E机理和L-H机理对甲基叔戊基醚(TAME)的醚化过程进行研究,得出R-E机理模型较优.在模型建立的过程中用复合型法和非线性最小二乘法估算动力学参数.结果表明:对于非理想体系,用活度代替浓度进行动力学研究是正确的,所得R-E模型能够准确地验证平衡转化率及醚化反应结果.