Toluene inhibits hippocampal neurogenesis in adult mice

Toluene, a representative industrial solvent and abused inhalant, decreases neuronal activity in vitro and causes mental depression and cognitive impairment in humans. However, the effects of toluene on brain function and the sites of its action are poorly understood. This study investigated the temporal changes of neurogenesis in the hippocampus of adult C57BL/6 mice after acute administration of toluene using two immunohistochemical markers for neurogenesis, Ki-67 and doublecortin (DCX). In addition, after toluene treatment, depression-like behaviors and learning and memory tasks were examined to assess hippocampal neurogenesis-related behavioral dysfunction. The number of Ki-67- and DCX-positive cells in the dentate gyrus of adult hippocampi declined acutely between 0 h and 24 h after toluene treatment (500 mg/kg, i.p.) and increased gradually from 2 to 8 days post-administration. The level of Ki-67 and DCX immunoreactivity decreased in a dose-dependent manner within the range of toluene administered (0-1000 mg/kg). In tail suspension and forced-swim tests performed at 1 and 4 days after toluene treatment (500 mg/kg), mice showed significant depression-like behaviors compared to the vehicle-treated controls. In the contextual fear conditioning and object recognition memory test, the mice trained at 1 and 4 days after toluene treatment showed significant memory defects compared to the vehicle-treated controls. This study suggests that acute exposure to toluene reduces the rate of adult hippocampal neurogenesis and can cause hippocampal dysfunction such as depression and cognitive impairment.     

静态顶空气相色谱法测定盐酸西那卡塞中的残留溶剂

目的 采用静态顶空气相色谱分析方法测定盐酸西那卡塞原料药中残留的四氢呋喃、乙酸乙酯、二氯甲烷、乙醇和甲苯.方法 采用DB-WAX色谱柱(30 m×0.32 mm,0.25 μm),FID检测器,内标法定量.分别考察了溶剂、顶空平衡温度、顶空平衡时间、相比、色谱柱对残留溶剂测定的影响.结果 5种残留溶剂的线性范围分别为36 ～ 108、250 ～ 750、30 ～ 90、250 ～750、44.5 ～133.5μg·mL-1,平均回收率分别为98.2％、98.3％、98.4％、98.8％、98.1％,RSD分别为3.37％、3.36％、4.65％、2.97％、3.13％.结论 所用方法简便、准确、灵敏度高、重复性好,适用于盐酸西那卡塞中残留溶剂的测定.     

Effect of troglitazone on cytochrome P450 enzymes in primary cultures of human and rat hepatocytes

1. Troglitazonewas the first thiazolidinedione approved for clinical use in the treatment of non-insulin-dependent diabetes mellitus. During clinical investigations of drug-drug interactions with therapeutics (terfenadine and cyclosporine) known to be metabolized by CYP3A4, pharmacokinetic interactions were noted upon troglitazone multiple-dose treatments. The nature of the interactions suggested induction of CYP3A enzymes. 2. Primary cultures of human hepatocytes were used to investigate the induction potential of troglitazone with respect to CYP3A4, CYP2B6 and CYP1A1/2. In human hepatocytes, troglitazone induced both immunoreactive CYP3A4 protein and testosterone 6beta-hydroxylase activity in a dose-dependent fashion (EC₅₀ = 5-10 muM), accompanied by an increase in CYP3A4 mRNA. The capacity of troglitazone to induce CYP3A4 was between that of rifampin (EC₅₀ = ~0.8 muM) and dexamethasone (40-50 muM). Troglitazone increased CYP2B6 immunoreactive protein but did not significantly effect CYP1A1/2 activity, immunoreactive protein or mRNA. 3. Troglitazone produced significant increases in CYP3A message, protein and activity in primary rat hepatocytes, a slight increase in CYP2B1/2 activity and no change in CYP1A1/2 message or activity. 4. These results provide evidence that troglitazone can induce CYP3A and CYP2B enzymes while apparently not altering CYP1A. This provides a rationale for the clinically observed interactions of troglitazone with selected CYP3A4 substrates.     

Issues in Diisocyanate Antibody Testing

Diisocyanates are used to produce a wide variety of polyurethane products; they are also recognized as an important cause of occupational asthma. Their chemical reactivity presents challenges to toxicologists and clinicians alike seeking to understand the mechanisms underlying diisocyanate asthma. In this article, we review the literature on immunoassay detection of IgE and IgG binding to diisocyanate–protein conjugates and assess the utility of such testing as a diagnostic tool and exposure indicator. Data from 29 studies of occupational exposure to diisocyanates revealed considerable variability in assay methodology and heterogeneity in the prevalence of positive antibody responses across laboratories. In studies that included both confirmed diisocyanate asthma subjects and exposed nonasthmatics, positive IgE responses identified cases with low sensitivity (18–27%), but high specificity (96–98%). Detection of IgG binding to diisocyanate conjugates is an indirect, qualitative indicator of disease status and past diisocyanate exposure. The utility of these assays is limited, however, due to a lack of (1) method standardization, (2) population norms to guide interpretation of results, and (3) demonstration that the assays improve either on disease prediction or on exposure confirmation beyond that of other indicators. Sources of assay heterogeneity are discussed and suggestions are offered for improving test performance and interpretability.     

LDI-glycerol polyurethane implants exhibit controlled release of DB-67 and anti-tumor activity in vitro against malignant gliomas

The purpose of the present study was to develop a biodegradable and biocompatible polyurethane drug delivery system based on lysine diisocyanate (LDI) and glycerol for the controlled release of 7-tert-butyldimethylsilyl-10-hydroxy-camptothecin (DB-67). DB-67 has yet to be implemented in any clinical therapies due to the inability to delivered it in sufficient quantities to impact tumor growth and disease progression. To remedy this, DB-67 was covalently incorporated into our delivery system by way of an organometallic urethane catalyst and was found to be dispersed evenly throughout the LDI-glycerol polyurethane discs. Scanning electron micrographs indicate that the LDI-glycerol discs are uniform and possess a pore distribution typical of the non-solvent casting technique used to prepare them. The release rates of DB-67 from the LDI-glycerol discs were found to vary with both time and temperature and were shown capable of delivering therapeutic concentrations of DB-67 in vitro. Cellular proliferation assays demonstrate that empty LDI-glycerol discs alone do not significantly alter the growth of malignant human glioma cell lines (U87, T98G, LN229 and SG388). DB-67-loaded LDI-glycerol polyurethane discs were found to inhibit cellular proliferation by 50% on average in all the malignant glioma cell lines tested. These results clearly demonstrate the long-term, slow release of DB-67 from LDI-glycerol polyurethane discs and their potential for postoperative intracranial chemotherapy of cancers.     

气相色谱法测定3-氯-7-氨基去乙酰氧基头孢烷酸中残留溶剂

目的:建立3-氯-7-氨基去乙酰氧基头孢烷酸(7-ACCA)中丙酮、甲醇、二氯甲烷、乙酸乙酯、异丁醇、吡啶、甲苯残留量的测定方法。方法:采用气相色谱法,载气为氮气,FID检测器,色谱柱为Agilent INNOWAX毛细管柱,柱温为程序升温:起始温度70℃,保持6 min,以10℃/min升温至160℃,保持1 min;进样量1.0μl,分流进样,分流比10∶1,外标法检测7-ACCA中丙酮、甲醇、二氯甲烷、乙酸乙酯、异丁醇、吡啶、甲苯的含量。结果:在本研究建立的色谱条件下,丙酮、甲醇、二氯甲烷、乙酸乙酯、异丁醇、吡啶、甲苯的最低检出质量浓度分别为2.5μg/ml、1.5μg/ml、15μg/ml、2.5μg/ml、2.5μg/ml、2.5μg/ml、11μg/ml。样品中仅检测到丙酮,且其残留量远在药典规定的限量以下。结论:建立的方法能有效控制7-ACCA中丙酮、甲醇、二氯甲烷、乙酸乙酯、异丁醇、吡啶、甲苯的残留量。     

Nasal response in subjects undergoing challenges by inhaling occupational agents causing asthma through the nose and mouth

Background Subjects with occupational asthma (OA) often report nasal symptoms, but nasal reactions to inhalation challenges with occupational agents have not been well characterized. Methods Fifteen subjects with OA (eight due to high-molecular-weight agents - flour and guar gum - and seven due to isocyanates) underwent inhalational challenges using closed-circuit devices (dry particles for high-molecular-weight agents and gas generator for isocyanates) on two occasions, 2-4 weeks apart in a random fashion. On one occasion, they inhaled through the nose and, on another, through the mouth. The FEV, was monitored for up to 8 h afterward, and symptoms were documented with a standardized questionnaire on nasal symptomatology, assessment of nasal resistance by rhinomanometry, and nasal lavage for the examination of cells and mediators. Results Inhaling through the mouth and through the nose:

• 1) yielded similar asthmatic responses (25 ± 8% and 22 ± 10% maximum changes in FEV₁)
• 2) more than doubled the peak nasal symptoms and nasal resistance when the maximum daily response was compared with prechallenge results.

This increase occurred on the days of inhalational challenges through the mouth and through the nose. There were some significant responses assessed by nasal lavage in terms of cells and mediators, again with no differences between the days of challenges through the mouth and through the nose. Conclusions Inhaling occupational agents of high or low molecular weight, including isocyanates, whether through the mouth or nose:

• 1) results in a similar asthmatic response
• 2) causes a significant nasal response in terms of symptoms and an increase n i nasal resistance
• 3) causes some significant changes in inflammatory cells and mediators.

     

Combined alveolitis and asthma due to hexamethylene diisocyanate (HDI), with demonstration of crossed respiratory and immunologic reactivities to diphenylmethane diisocyanate (MDI)

A worker exposed intermittently to hexamethylene diisocyanate (HDI) developed episodes of dyspnea, wheezing, and fever on working days. Complete lung function tests performed when the subject was asymptomatic were normal except for increased airway responsiveness to histamine, which significantly improved after a 3 wk period off work. At that time, specific inhalation challenges with HDI were carried out. After being exposed for 5 min, the subject developed general malaise, cough, fever, and leukocytosis, together with a mixed restrictive and obstructive breathing defect. We demonstrated a subsequent increase in airway hyperexcitability, which lasted for 2 mo. The subject was also challenged with diphenylmethane diisocyanate (MDI) for 15 min. A late obstructive reaction was documented. Increased levels of specific IgG antibodies against HDI-human serum albumin (HSA) and MDI-HSA were demonstrated.     

The guinea pig model of diisocyanate sensitization. I. Immunologic studies

Two strains of guinea pigs were parenterally immunized with well-characterized diisocyanate-protein conjugates. Hapten-specific IgE antibodies were detected in the sera of English short-hair strain guinea pigs immunized with either toluene diisocyanate-human serum albumin (TDI-HSA) or hexamethylene diisocyanate-HSA (HDI-HSA) when these sera were analyzed by the 168 hr passive cutaneous anaphylaxis (PCA) technique followed by intravenous challenges with conjugates of respective ligands coupled to an unrelated carrier protein, transferrin. IgG1 antibodies and precipitating antibodies were demonstrated in Hartley strain guinea pigs immunized with TDI/HDI-HSA conjugates. The hapten specificity of these antibodies was proved by PCA inhibition experiments and antibody absorption experiments. In the precipitating antibody system, this was further confirmed by immunoelectrophoretic analysis. Cross-reactivity between HDI and TDI was not observed in the PCA experiments. However, apparent cross-reactivity in the double gel diffusion experiments was due to new antigenic determinants formed by isocyanates after conjugation with proteins. It was therefore apparent that immune responses of guinea pigs immunized with protein conjugates of bifunctional isocyanates were heterogeneous and involved multiple specificities for hapten, carrier protein, and new antigenic determinants. It was postulated that the complex nature of the immune response generated by diisocyanate compounds in the guinea pig may also serve as a more appropriate model of isocyanate-induced human sensitivity reactions, which are known to involve diverse immunologic and nonimmunologic mechanisms.