Metabolic activation of selected aromatic amines and polycyclic hydrocarbons by isolated subcellular fractions of Drosophila melanogaster

The applicability of microsomal preparations from Drosophilamelanogaster as the metabolic factor in the Salmonella mutagenicity assay with strains TA98 and TA100 was evaluated. Isolated cellular fractions (S27) from PB-pretreated flies activated N-acetyl-2-aminofluorene (2-AAF), N-hydroxy-N-aceyl-2-aminofluorene (N-OH-AAF), benzo[a]pyrene (BP), 9,10-dimethylanthracene (DA) and 2 -naphythylamine (NA)_into mutagenic metabolites, 7,-12-Dimethylbenz[a]-anthracene (DMBA) was ineffective under the conditions of the test.This study was performed in an effort to determine optimal conditions for activating, by Drosophila enzymes, aromatic amines and polycyclic hydrocarbons, with 2-AAF and BP as model mutagens. The following alterations improved the sensitivity of this combined Salmonella/Drosophila assay. (1) Incubation of the plates at 25°C for 1 night instead of permanent exposure at 37°C. (2) Isolation of S27 fractions instead of the conventional S9, because 9000 × g was not sufficient tio spin down Drosphila mitochondria.     

辐射对大鼠肺巨噬细胞Fc受体表达和特异吞噬功能的影响

以往的实验表明,巨噬细胞(Macrophages简称Mф)对一定辐射剂量内的照射表现出较强的辐射抗性。因此学者们转向研究照射后时间依赖性的Mф损伤变化。这主要是涉及照射后所致的迟发损伤效应。有关大剂量照射后,短时间观察Mф损伤效应的研究报道甚少。为此本文观察了大鼠肺巨噬细胞(AlveolarMacrophages简称AM)在体外受100—500 Gy     

Inhibition of an outwardly rectifying anion channel by HEPES and related buffers

Summary The effect of pH buffers and related compounds on the conductance of an outwardly rectifying anion channel has been studies using the patch-clamp technique. Single-channel current-voltage relationships were determined in solutions buffered by trace amounts of bicarbonate and in solutions containing N-substituted taurines (HEPES, MES, BES, TES) and glycines (glycylglycine, bicine and tricine), Tris andbis-Tris at millimolar concentrations. HEPES (pK_a=7.55) reduced the conductance of the channel when present on either side of the membrane. Significant inhibition was observed with 0.6mm HEPES on the cytoplasmic side (HEPES _i ) and this effect increased with [HEPES _i ] so that conductance at the reversal potential was diminished 25% with 10mm HEPES _i )and 70% at very high [HEPES _i ]. HEPES _i block was relieved by applying positive voltage but positive currents were not consistent with a Woodhulltype blocking scheme in that calculated dissociation constants and electrical distances depended on HEPES concentration. Results obtained by varying total HEPES _i concentration at constant [HEPES^–] and vice versa suggest both the anionic and zwitterionic (protonated) forms of HEPES inhibit. Structure-activity studies with related compounds indicate the sulfonate group and heterocyclic aliphatic groups are both required for inhibition from the cytoplasmic side. TES (pK_a=7.54), substituted glycine buffers (pK_a=8.1–8.4) andbis-Tris (pK_a=6.46) had no measurable effect on conductance and appear suitable for use with this channel.     

Voltage-gated chloride currents in cultured canine tracheal epithelial cells

Summary Chloride ions (Cl^–) are concentrated in airway epithelial cells and subsequently secreted into the tracheal lumen by downhill flux through apical Cl^– channels. We have studied Cl^– currents in cultured canine tracheal cells using the whole-cell voltage-clamp technique. Ultrastructural techniques demonstrated that the cells used in the electrophysiological experiments possessed apical membrane specializations known to be present in the intact, transporting cell type. Cultured cells 2–6 days old were characterized by an input resistance of 3.4±0.8 G (n=11) and a capacitance of 63.8±10.8 pF (n=26). A comparison of 3 and 4 day-old cells with 5 and 6 day-old cells showed that the input resistance decreased almost 50%, and the cell capacitance and the inward and outward currents increased concomitantly approximately 200%. Cultured cells 3–4 days old held at –40 mV produced currents of 196±22 pA at 50 mV and –246±27 pA at –90 mV (n=212) with pipette and bath solutions containing primarily 140 KCl and 140 NaCl, respectively. The chloride channel blocker diphenylamine-2-carboxylate (DPC, 100 m) suppressed whole-cell currents by 76.8% at 60 mV; however, currents were unaffected by the stilbenes SITS (1mm) and DNDS (1–30 m). Replacement of K⁺ with Cs⁺ in the pipette solution did not affect the outward current, the current reversal potential, or the input resistance of the cells, indicating that the current was not significantly K⁺ dependent when the intrapipette solution was buffered to a Ca²⁺ concentration of 20nm. The Cl^–/Na⁺ permeability ratio was estimated to be greater than 11 as calculated from reversal potential measurements in the presence of an internal to external NaCl concentration ratio of 12. Current equilibrium permeabilities, relative to Cl^– were: I^– (2.9)NO ₃ ^– (1.1)Br^– (1.1)Cl^– (1.0)F^– (0.93)MeSO ₄ ^– (0.19)gluconate (0.18)aspartate (0.14). Depolarizations to potentials greater than 20 mV elicited a time-dependent component in the outward current in 71% of the cells studied. Currents inactivated with a double exponential time course at the most depolarized voltages. Recovery from inactivation was fast, holding potential-dependent, and followed a double exponential time course. Current amplitude was increased via a cAMP-dependent pathway as has been demonstrated for single Cl-selective channels in cell-attached patches from cultured canine and human tracheal epithelial cells. Forskolin, an activator of adenylate cyclase, produced a 260% increase in the outward current at +50 mV. In summary, cultured canine tracheal cells have a single resting conductance that is Cl^– selective, voltage-dependent, and modulated by a cAMP-dependent mechanism. This preparation appears to be appropriate for analysis of cellular modulation of airway Cl^– channels and Cl^– secretion.     

慢性缺氧对肺动脉内皮依赖性和非内皮依赖性舒张反应的影响

本实验用生物测定法观察了模拟海拔5000m高度连续缺氧20d对大鼠肺动脉内皮依赖性和非内皮依赖性舒张反应的影响。结果显示慢性缺氧明显抑制了肺内和肺外动脉对乙酰胆碱、ATP、硝普钠和异丙肾上腺素舒张反应的敏感性和反应性。在浓度为10~(-6)mol/L时,缺氧组大鼠肺内动脉对乙酰胆碱、硝普钠和异丙肾上腺素的舒张反应分别只有对照组大鼠的61.3％、75.9％和61.7％,对浓度为1.8×10~(-5)mol/L的ATP的舒张反应只有对照组大鼠的64.9％。研究表明,ATP和乙酰胆碱主要是通过内皮舒张因子使肺动脉产生内皮依赖性舒张反应,硝普钠和异丙肾上腺素分别通过直接激活血管平滑肌细胞鸟苷酸环化酶和β受体使血管产生非内皮依赖性舒张反应。缺氧同时抑制了肺动脉内皮依赖性和非内皮依赖性舒张反应,提示慢性缺氧可能抑制了正常肺内舒血管活性物质的生理作用。     

吸烟对大鼠肺循环血流动力学及肺血管反应性的影响

本实验用大鼠29只,进行人工通气吸入烟气,初步探讨了吸烟对肺循环的影响。其中7只观察了吸烟对肺循环血流动力学的直接影响,结果表明,吸烟可致右心室收缩压、心输出量下降及心率减慢,肺循环阻力无明显改变。观察22只大鼠吸烟后缺氧所致肺循环血流动力学变化,结果表明,吸烟可使缺氧性肺血管反应降低,而且发生在肺循环血流动力学变化之前。     

Swelling and Ca2+-activated Anion Conductances in C127 Epithelial Cells Expressing WT and ΔF508-CFTR

CFTR is a chloride channel that is required for fluid secretion and salt absorption in many exocrine epithelia. Mutations in CFTR cause cystic fibrosis. CFTR expression influences some ion channels, but the range of channels influenced, the mechanism of the interaction and the significance for cystic fibrosis are not known. Possible interactions between CFTR and other ion channels were studied in C127 mouse mammary epithelial cell lines stably transfected with CFTR, ΔF508-CFTR, or vector. Cell lines were compared quantitatively using an ¹²⁵I efflux assay and qualitatively using whole-cell patch-clamp recording. As expected, ¹²⁵I efflux was significantly increased by forskolin only in the CFTR line, and forskolin-stimulated whole-cell currents were time- and voltage independent. All three lines responded to hypotonic challenge with large ¹²⁵I efflux responses of equivalent magnitude, and whole-cell currents were outwardly rectified and inactivated at positive voltages. Unexpectedly, basal ¹²⁵I efflux was significantly smaller in the ΔF508-CFTR cell line than in either the CFTR or control cell lines (P < 0.0001), and the magnitude of the efflux response to ionomycin was largest in the vector cell line and smallest in the cell line expressing ΔF508-CFTR (P < 0.01). Whole-cell responses to ionomycin had a linear instantaneous I-V relation and activated at depolarizing voltages. Forskolin responses showed simple summation with responses to ionomycin or hypotonic challenge. Thus, we found no evidence for interactions between CFTR and the channels responsible for swelling-mediated responses. Differences were found in basal and ionomycin-stimulated efflux, but these may arise from variations in the clonally selected cell lines that are unrelated to CFTR expression. Received: 15 November 1995/Revised: 16 February 1996     

Complement-dependent induction of DNA synthesis and cell proliferation in human liver connective tissue cells in vitro

Summary Liver connective tissue cells (LCTC) isolated from patients with fibrotic livers have morphological and biochemical characteristics of myofibroblasts. We have examined the proliferation of LCTC derived from normal livers and from livers with fibrosis of different etiologies, as well as proliferation of skin fibroblasts. We have compared proliferation rates in the presence of fresh human serum and heat-inactivated serum. While skin fibroblast and LCTC from normal liver showed no difference, proliferation of LCTC from fibrotic livers was markedly decreased in the presence of heat-inactivated serum. We demonstrate that the native complement component C1 is a factor involved in the induction of DNA synthesis and proliferation of LCTC isolated from fibrotic livers. We propose that native C1, acting probably in cooperation with other growth factors, is involved in the expansion of connective tissue cells during the development of liver fibrosis.     

Chronic Pseudomonas aeruginosa endobronchitis in rhesus monkeys: II. A histopathologic analysis

We have recently established a rhesus monkey model of chronic Pseudomonas aeruginosa (PA) endobronchitis by bronchoscopic instillation of PA-embedded agar beads. All experimental animals developed chronic neutrophilic endobronchitis similar to chronic PA endobronchitis in cystic fibrosis (CF). Histopathologic studies further confirmed similarities to chronic PA endobronchitis in CF, including marked peribronchial inflammation, epithelial damage, presence of degraded cilia and ciliary abnormalities, appearance of PA bacterial clusters, mucosal hyperplasia, goblet cell hypertrophy/hypersecretion, airway obstruction, alveolar abnormalities, bronchiectasis, and fibrosis.     

人肝刺激因子对大鼠实验性慢性肝损伤的保护作用

从健康孕妇水囊引产４─６个月龄的胎儿取肝,采用ＬａＢｒｅｃｑｕｅ方法提取人肝刺激因子（ｈＨＳＳ）。经３Ｈ－胸腺嘧啶核苷参入肝ＤＮＡ法测定其生物活性。表明此ｈＨＳＳ可刺激肝细胞ＤＮＡ合成。采用皮下注射ＣＣｌ４和饮用１０％乙醇来制备慢性肝损伤动物模型,观察了ｈＨＳＳ的保护肝脏作用。结果表明：ｈＨＳＳ可使ＣＣｌ４－乙醇所致慢性肝损伤大鼠的死亡率、血清谷丙转氨酶水平、肝组织中羟脯氨酸含量的升高以及肝组织中丙二醛的含量降低。肝组织切片表明：ｈＨＳＳ能减轻肝组织的损伤程度,促进肝细胞再生,并能明显防止肝纤维化的形成和发展。可见,ｈＨＳＳ对ＣＣｌ４－乙醇所致的慢性肝损伤大鼠有明显的保护作用,其机制可能与促进肝细胞再生及抑制肝细胞膜的脂质过氧化有关。