Polychlorinated biphenyls are not substrates for the multidrug resistance transporter-1

The multidrug resistance (MDR) transporter is a phosphorylated glycoprotein (P-gp) that has been implicated in the efflux of a large variety of xenobiotics, thereby protecting vital organs. This study examines the hypothesis that the multidrug resistance transporter is involved in restricting the entry of polychlorinated biphenyls (PCBs) into the brain. Three test systems were used. First, the ATPase activity of the human P-gp was measured as an indicator of the interaction of PCBs with the MDR transporter. PCB congeners and metabolites included in the study were PCB 153, PCB 169, PCB 77, and the 4-hydroxy and 4,4'-dihydroxy metabolites of PCB 77. An increase in ATPase activity was observed for all the PCBs tested except the 4-hydroxy metabolite of PCB 77. Second, we studied the transport of (14)C-PCB 77 and (14)C-PCB153 in a cell-culture model using porcine kidney cells expressing the human MDR1 or the mouse mdr1a gene and compared it to the transport in control cells. No difference in directional transport due to P-gp was observed with either of the congeners in any of the cell lines. Finally, the distribution pattern of (14)C-PCB 77 in mdr1a knockout mice and genetically matched wild-type mice was measured. No significant differences in tissue distribution, especially in the brain tissue, were observed between wild-type and mdr1a knockout mice. These results suggest that some PCB congeners can bind to the MDR1 transporter; however, they may not be transported by it.     

Effects of Aroclor 1242 and different fish-based diets on vitamins A1 (retinol) and A2 (3,4-didehydroretinol), and their fatty acyl esters in mink plasma

The effects of a 21-week exposure to Aroclor 1242 (1mg per day in feed) on plasma concentrations of vitamins A(1) (retinol) and A(2) (3,4-didehydroretinol) and their principal fatty acyl esters (A(1)-16:0, A(2)-16:0 (palmitates), A(1)-18:1n-9; A(2)-18:1n-9 (oleates), and A(1)-18:0; A(2)-18:0 (stearates)) were studied in young female mink (Mustela vison) fed a diet based on freshwater smelt. These vitamin levels were also examined in mink fed diets containing Baltic herring or fatty marine fish. In the Aroclor-exposed smelt-fed mink, the plasma concentrations of A(1) and A(2) esters were significantly lower than the levels in controls fed the uncontaminated smelt diet. In addition, the A(2) esters reacted more sensitively to the polychlorinated biphenyls than did A(1) esters. In contrast, in the plasma of the exposed mink the level of alcoholic A(1) was normal, and transport of thyroxine (T(4)) and nonspecific lipoprotein transport of major lipids were not impaired. Despite the large dietary supply of vitamin A(2) and high levels of plasma A(2) esters, the mink fed freshwater smelt had only trace amounts of alcoholic vitamin A(2) in their plasma. The concentrations of A(1) and A(2) esters in the plasma of all the mink studied correlated with the hepatic total concentrations of the vitamins. Thus, in carnivores that have nonspecific lipoprotein transport of vitamin A esters, determination of plasma levels of the esterified vitamins may be a useful nondestructive way to estimate stores of the vitamin A analogs in the body and to assess the organochlorine-induced decrease in the vitamin stores.     

Expression of GADD153 in tumor cells and stromal cells from xenografted tumors in nude mice treated with cisplatin: correlations with cisplatin-DNA adducts

Purpose: Cisplatin is a commonly used antineoplastic agent that acts by forming adducts with DNA, and causing a response to the cellular injury. One of the components of this cellular injury response is the activation of the “growth arrest and DNA damage gene”GADD153. The level of GADD153 induction in tumor cells has been associated with the degree of cytotoxicity. The pupose of this study was to determine whether cisplatin activates GADD153 also in nontumor cells and how GADD153 protein levels correlate with cisplatin-DNA adducts in different cell types. Methods: Nude mice with xenografted squamous cell carcinoma were treated with cisplatin 10 mg/kg. Tumors were removed at 0 h (untreated controls), 24 h, and 48 h and immunohistochemically stained for GADD153 protein and cisplatin-DNA adducts. The staining reaction was quantitated in tumor cells and nonmalignant stromal cells separately, using computerized image analysis. Results: The GADD153 level was 4.5 times higher in tumor cells than in stromal cells in untreated mice. At 24 h after cisplatin treatment the GADD153 level had increased by 50% and 72% in tumor cells and stromal cells, respectively. Analysis of the cisplatin-DNA adducts showed a reversed pattern, with six-fold higher levels in stromal cells than in tumor cells at 24 h after treatment. By combining these data, we estimated that approximately 25-fold more GADD153 per cisplatin-DNA adduct was induced in tumor cells than in stromal cells. Conclusion: Our data suggest that different cell types may respond differently to DNA damage caused by cisplatin. Received: 5 March 1998 / Accepted: 21 July 1998     

Differential effects of microsomal enzyme inducers on in vitro thyroxine (T(4)) and triiodothyronine (T(3)) glucuronidation.

Microsomal enzyme inducers that increase UDP-glucuronosyltransferase (UDP-GT) activity are suspected to affect the thyroid gland by increasing the glucuronidation of T(4), which reduces serum thyroxine (T(4)). In response to reduced serum T(4), serum thyroid-stimulating hormone (TSH) increases. However, not all microsomal enzyme inducers that reduce serum T(4) produce an increase in serum TSH. We have shown that serum TSH is increased the most in rats treated with the microsomal enzyme inducers phenobarbital (PB) or pregnenolone-16alpha-carbonitrile (PCN), whereas TSH is affected less in rats treated with 3-methylcholanthrene (3MC) and Aroclor 1254 (PCB). It is unclear why serum TSH is differentially affected by various microsomal enzyme inducers. We propose that the glucuronidation of T(3) might be the reason serum TSH is increased by some microsomal enzyme inducers but not by others. Male Sprague-Dawley rats were fed either a basal diet or a diet containing PB (at 300, 600, 1200, or 2400 ppm), PCN (at 200, 400, 800, or 1600 ppm), 3MC (at 50, 100, 200, or 400 ppm), or PCB (at 25, 50, 100, or 200 ppm) for 7 days; and T(4) and T(3) UDP-GT activities were then determined. T(4) UDP-GT activity was increased in rats treated with PB (120%), PCN (250 to 400%), 3MC (400 to 600%), or PCB (300 to 430%). In contrast, T(3) UDP-GT activity was increased in rats treated with PB (90%) or PCN (120 to 200%), whereas 3MC and PCB treatments did not have an appreciable effect. In conclusion, differential effects on T(3) glucuronosyltransferase activity were found in rats treated with microsomal enzyme inducers.     

PCB-153 exposure coordinates cell cycle progression and cellular metabolism in human mammary epithelial cells

2,2′,4,4′,5,5′-Hexachlorobiphenyl (PCB-153) is a non-metabolizable environmental chemical contaminant commonly found in breast milk of PCB exposed individuals, suggesting that chronic exposure to PCB-153 could have adverse health effects. We have shown previously that PCB-153 increased reactive oxygen species levels in non-tumorigenic MCF-10A human mammary epithelial cells, which were associated with DNA damage, growth inhibition, and cytotoxicity. This study investigates the hypothesis that PCB-153 exposure coordinates cell cycle progression and cellular metabolism by inhibiting cyclin D1 accumulation. PCB-153 treated MCF-10A cells exhibited a dose and time dependent decrease in cyclin D1 protein levels. The decrease in cyclin D1 protein levels was associated with an inhibition in AKT and GSK-3β phosphorylation, which correlated with an increase in cyclin D1-T286 phosphorylation. Fibroblasts carrying a mutant form of cyclin D1 (T286A) were resistant to PCB-153 induced degradation of cyclin D1. Pre-treatment of cells with a proteasome inhibitor (MG132) suppressed PCB-153 induced decrease in cyclin D1 protein levels. Interestingly, suppression in cyclin D1 accumulation was associated with an increase in cellular glucose consumption, and hexokinase II and pyruvate kinase protein levels. These results suggest that cyclin D1 coordinates cell cycle progression and cellular metabolism in PCB-153 treated non-tumorigenic human mammary epithelial cells.     

四种不同方法检测CA153的观察

目的:研究电化学免疫分析(ECLIA)、化学发光免疫分析法(CLIA)、间接酶联免疫吸附试验(ELISA)和放射免疫法(RIA)四种方法检测的可靠性及在方法学上哪一种更具有优势。方法:用四种方法分别检测血清CA153,进行准确度、阴、阳性预测值、灵敏度和特异性方面的比较。结果:四种方法检测结果差异无显著性(P>0.05),并且相关良好(r=0.9973),但ECLIA和CLIA在分析灵敏度、特异性、精密度及抗干扰能力方面均优于放射免疫法。结论:ECLIA和CLIA完全能够替代RIA和ELISA法,实现分析程序自动化,并具有试剂稳定,标志物有效期长,对人体没有危害和适宜临床肿瘤标志物大批量样品检测等优点。     

Dysphagia and hemispheric stroke: A transcranial magnetic study

INTRODUCTION: Dysphagia is a common and distressing consequence of hemispheric stroke. STUDY AIM: To verify the usefulness of transcranial magnetic stimulation (TMS) studies of swallowing in healthy subjects and in stroke patients. MATERIAL AND METHODS: TMS studies of the motor cortical projections to the upper esophageal sphincter were performed in 45 patients with acute mono-hemispheric stroke (26 patients with dysphagia) and 20 healthy adult volunteers. RESULTS: TMS of either hemisphere in normal volunteers evoked motor evoked potentials (MEP) in the esophagus. The average point of optimal excitability was slightly more anterior in the right hemisphere; otherwise, MEP amplitudes and latencies were similar from both hemispheres as were the areas of the cortical map. The cortical map area and amplitude of MEPs were significantly smaller and the latencies longer after stimulation of the affected hemisphere compared with the unaffected hemisphere and pooled control data. Twenty-four dysphagic patients (92.3%) had abnormalities of MEP of the affected hemisphere, while only five non-dysphagic patients (26%) had these abnormalities. Dysphagic patients were older and had more disability compared with non-dysphagic patients. MEPs of the affected hemisphere of patients with dysphagia were later and smaller in amplitude than MEPs of non-dysphagic patients. The cortical map area was also smaller. CONCLUSION: The esophagus is represented bilaterally in motor cortex, but the hot spot lies more anterior to Cz in right hemisphere compared to left hemisphere. Both the severity of stroke and neuroplasticity of the unaffected hemisphere have implications in the development of dysphagia.     

Direct inhibition of ERK1/2 phosphorylation as a possible mechanism for the antiproliferative action of 3,4-diOH-PCB3 in the MCF-7 cell line

Our previously published data showed that 260 h of exposure to 3,4-diOH-PCB3 decreased proliferation in the MCF-7 cell line. In the present study, we sought to determine whether this is due to action on the SHBG/cAMP/PKA system, activation of which can inhibit cell proliferation, or to direct inhibition of ERK1/2 phosphorylation. MCF-7 human breast cancer cells were treated for 72 h with 4-monochlorobiphenyl (PCB3), 4′-hydroxy-4-monochlorobiphenyl (4-OH-PCB3) or 3′4′-dihydroxy-4-monochlorobiphenyl (3,4-diOH-PCB3) (300 nM). After the completion of the treatment, cell proliferation was measured with a BrdU incorporation assay. SHBG, cAMP, PKA and ERK1/2 levels in the cells were determined via ELISA.PCB3 and 4-OH-PCB3 had no effect on extra- or intracellular SHBG levels, while a stimulation of SHBG intra- but not extracellular levels was noted in cells exposed to 3,4-diOH-PCB3. Both, pre- and co-incubation with SHBG decreased the proliferation of 3,4-diOH-PCB3-treated cells. Neither PCB3 nor its metabolite had an effect on the cAMP/PKA pathway. A decrease of both ERK1/2 forms was noted under the influence of 3,4-diOH-PCB3. In conclusion, the data presented clearly showed that the antiproliferative action of 3,4-diOH-PCB3 is not mediated by activation of the SHBG/AMP/PKA pathway, but many other plasma membrane receptors seem to be involved in the non-genomic action of 3,4-diOH-PCB3, and instead is due to direct inhibition of the ERK1/2 system.     

颈椎前路融合器-钢板一体化系统植入治疗颈椎病护理要点

目的：介绍颈椎前路融合器—钢板一体化系统(PCB)植入术围手术期护理。方法：对2l例颈椎前路PCB植入术患实施术前、术后及康复一体化护理，并进行了初期随访。结果：本组患平均下床时间为术后8h，6个月以上15例随访观察，颈椎融合率96．5％，未见PCB术后并发症。结论：PCB装置能提供即刻的颈椎稳定，术后不用带颈托制动，护士在围手术期给予正确的指导和护理，能减少并发症的发生，提高患的生活质量。     

Decreased survival in pancreatic cancer patients with high concentrations of organochlorines in adipose tissue

We analysed adipose tissue concentrations of persistent organic pollutants (POPs) in 21 cases with exocrine pancreatic cancer. The comparison group consisted of 59 subjects. Significantly increased concentrations of polychlorinated biphenyls (PCBs), hexachlorobenzene (HCB), sum of chlordanes and polybrominated diphenylethers (PBDEs) were found in the cases. For 1,1,-dichloro-2,2-bis(p-chlorophenyl)-ethylene (p,p'-DDE) no significant difference was seen. For PCBs no odds ratio (OR) could be calculated since all cases had concentration>median in controls used as a cut-off. HCB yielded OR=53.0, 95% confidence interval (CI)=4.64-605 and sum of chlordanes OR=18.4, 95% CI=2.71-124 whereas OR was not significantly increased for p,p'-DDE or PBDEs. Body mass index (BMI) at the time of tissue sampling was significantly lower for the cases. This might have influenced the results. Using BMI one year previously or decreasing the concentrations of POPs with the same percentage as weight loss among the cases did not change the results. Survival of the cases was shorter in the group with the concentration of POPs>median among cases, significantly so for the sum of PCBs (147 vs. 294 days), p,p'-DDE (134 vs. 302 days), and sum of chlordanes (142 vs. 294 days) in the high and low group, respectively. The results were based on a low number of cases and should be interpreted with caution.