Delayed neurotoxicity of diisopropylfluorophosphate (DFP): autoradiographic localization of high-affinity [3H]DFP binding sites in the chicken spinal cord

The delayed neurotoxic organophosphate, diisopropylfluorophosphate (DFP) binds with high affinity to membrane-bound proteins from chicken nerve tissues. The autoradiographic distribution of [³H]DFP binding sites in spinal cord sections of chicken showed higher concentrations of binding sites in gray matter than in white matter. In the cervical region, fairly high densities of [³H]DFP binding sites were found in laminae X and to a lesser extent, in the ventral horn gray matter. To identify the membrane-associated DFP-binding proteins, detergent-solubilized membranes were labeled widi 5-10nM [³H]DFP (10pmol/mg protein) for 70 min at 37°C. Gel-exclusion chromatography of the [³H]DFP-radiolabeled membranes indicated at least two major radioactive proteins with apparent molecular weights of 150-670 kDa and 40-129 kDa. Although we could not identify the high affinity DFP binding proteins, the autoradiographic experiments clearly demonstrated that the DFP binding proteins localized on gray matter of chicken spinal cord.     

Heterogeneity of Na+/K+-ATPase from rectal gland of Squalus acanthias is not due to α isoform diversity

 Purified Na⁺/K⁺-ATPase (EC 3.6.1.37) isolated from the rectal gland of Squalus acanthias was characterized in ouabain-binding studies and with respect to isoform(s) of the α peptide. To avoid enzyme inactivation [³H]ouabain equilibrium binding was carried out at 20°C. The heterogeneity of Na⁺/K⁺-ATPase isolated from shark rectal gland was similar in [³H]ouabain binding as previously seen in hydrolytic studies. The binding isotherms were compatible with the existence of a high-affinity (K _dis 0.69 nM) and a low-affinity (K _dis 42 nM) component of 1.46 and 0.79 nmol^.(mg protein)^–1, respectively. In Western blots the α peptide of the enzyme hybridized with an isoform-specific polyclonal antibody raised to an α₃-specific region of the large intracellular domain of rat Na⁺/K⁺-ATPase, but not with the supposed α₃-specific monoclonal antibody MA3-915 with its epitope near the N-terminus. Semi-quantitative analysis of the reaction of the α₃-specific polyclonal antibody with the α peptide from the shark enzyme compared to the reaction with α peptide from rat brain enzyme indicated that this region is not exactly the same in the two species. The α peptide of shark enzyme was not recognized by α₁- or α₂-specific polyclonal antibodies, or by the α₁-specific monoclonal antibodies 3B and F6. The large intracellular domain of Na⁺/K⁺-ATPase from shark rectal gland thus seems to be α₃-like and no α isoform heterogeneity seems able to account for the heterogeneity seen in ouabain binding. Received: 7 August 1998 / Accepted: 6 November 1998     

重症肌无力重复神经电刺激检测的比较研究

目的比较肘肌、三角肌、小指展肌重复神经电刺激（RNS）对重症肌无力（MG）的诊断价值。方法应用低频RNS技术对18例MG患者的肘肌、三角肌、小指展肌进行疲劳前后的检测,用DANTECounterpoint肌电图仪记录。结果对照组肘肌、三角肌、小指展肌疲劳前RNS电压分别降低了1．54％±1．32％、1．64％±1．43％、0．62％±0．38％;疲劳后RNS电压分别降低了2．01％±1．75％、2．05％±1．98％、1．02％±0．75％。MG组肘肌、三角肌、小指展肌疲劳前测试阳性分别为9／18（50％）、10／18（55．6％）、3／18（16．7％）（P均＜0．05）;疲劳后RNS测试阳性分别为15／18（83．3％）、14／18（77．8％）、6／18（33．3％）（P均＜0．05）。经卡方检验,肘肌疲劳前后RNS测试阳性率有显著性差异（P＜0．05）。小指展肌、三角肌疲劳前后RNS测试阳性率对比无显著性差异。结论MG患者肘肌疲劳后RNS阳性率较疲劳前明显增高,而三角肌、小指展肌疲劳前后RNS阳性率无显著性差异;肘肌、三角肌RNS测试较小指展肌更敏感,但肘肌RNS方法简便,病人不适程度轻,有较大的临床实用价值。     

内分泌疾病伴发焦虑抑郁症状特征及其治疗

目的初步探索内分泌疾病伴发焦虑抑郁症状的症状学及临床用药经验。方法对入选患者于治疗前、后进行焦虑抑郁自评量表、汉密顿抑郁焦虑量表、临床疗效总评定量表及Tess副反应量表评定,并以治疗后汉密顿焦虑、抑郁量表减分率作为疗效评定指标。结果内分泌不同疾病组之间的焦虑抑郁症状无显著性差异。赛乐特治疗能有效改善患者的焦虑抑郁症状,且毒副作用较轻。结论内分泌慢性病患者常伴发焦虑抑郁症状,作为代表药物之一,赛乐特安全有效,毒副作用轻,可用于改善内分泌疾病伴发的情绪障碍患者的生活质量。     

Detection of polycyclic aromatic hydrocarbon metabolites by high-pressure liquid chromatography after purification on immunoaffinity columns in urine from occupationally exposed workers

Objective: The objective in our study was to quantitate benzo[a]pyrene (B[a]P) metabolites by a combination of immunoaffinity chromatography and high-pressure liquid chromatography (HPLC) with fluorescence detection in urine from workers exposed to high levels of polycyclic aromatic hydrocarbons (PAH). Furthermore, by the simultaneous quantitation of 1-hydroxypyrene, the correlation between the B[a]P-tetrol and 1-hydroxypyrene would provide a means of evaluating the validity of 1-hydroxypyrene as a surrogate biomarker for occupational exposure to the potent carcinogen B[a]P in an electrode paste plant. Methods: The study was carried out at an electrode paste plant that produces electrode paste for Söderberg electrodes. A total of 34 pre- and post-shift urine samples and 17 personal air samples were collected from 17 workers during a normal work week. The concentration of 1-hydroxypyrene was measured in all urine samples. A recent method of quantitating B[a]P-r-7, t-8, t-9, c-10-tetrol in urine of humans exposed to low levels of PAH has been described. A modified version of this method involving purification of urine samples on immunoaffinity columns and HPLC analysis with fluorescence detection was used on urine samples from workers exposed to high levels of PAH. A monoclonal antibody (8E11) with binding affinity to B[a]P-tetrols was used. This antibody also binds several PAH-DNA adducts and metabolites, including 1-hydroxypyrene. Gas chromatography/mass spectroscopy (GC/MS) was also used for identification of metabolites isolated by HPLC fractionation. Results: From personal air sampling the mean exposure to particulate PAHs was 38?μg/m³. The mean concentration of urinary 1-hydroxypyrene was 3.9?μmol/mol creatinine in preshift samples and 10.2?μmol/mol creatinine in postshift samples. We could not identify detectable amounts of urinary B[a]P-tetrol by HPLC or fluorescence spectroscopy after purification on immunoaffinity columns. However, in the HPLC analysis we identified several hydroxyphenantrene metabolites that were detected at relatively high concentrations in all of the workers' urine samples. We could not separate 2- and 3-hydroxyphenanthrene (2?+?3-OH-Phe) in peak 1, and peak 2 contained both 1- and 9-hydroxyphenanthrene (1?+?9-OH-Phe). The phenanthrene metabolites were mainly conjugated to glucuronic acid and sulfate. There was a significant correlation between the 1-hydroxypyrene concentration and 2?+?3-OH-Phe (r?=?0.73) and 1?+?9-OH-Phe (r?=?0.64) in the urine samples. 1-Hydroxypyrene was measured in all post-shift urine samples but was not significantly correlated with workplace pyrene exposure, indicating that skin exposure is an important route of pyrene exposure in this factory. As with 1-hydroxypyrene, dermal PAH uptake may also account for the poor correlation between 2?+?3- and 1?+?9-OH-Phe and ambient phenanthrene. Discussion: Since dermal uptake is likely to be important in occupational PAH exposure in addition to inhalation, estimation of total PAH exposure is best achieved by quantitation of PAHs excreted into body fluids. However, it remains unclear whether there might be a difference in uptake and urinary excretion of 3-ring, 4-ring, or 5-ring PAHs and in the correlation between these metabolites and ambient-air PAH measurements. In summary, using immunaffinity chromatography, we did not find detectable amounts of B[a]P-tetrol in urine from workers occupationally exposed to PAH. However, by an HPLC/immunoaffinity method, relatively high amounts of 1-hydroxypyrene as well as 2?+?3- and 1?+?9-OH-Phe were quantitated in the urine samples, both of which are relevant as biomarkers of PAH exposure.     

Actions of roxindole at recombinant human dopamine D2, D3 and D4 and serotonin 5-HT1A, 5-HT1B and 5-HT1D receptors

Roxindole is a potential antidepressant agent. The present study determined its affinity and agonist efficacy at recombinant human (h) dopamine hD₂, hD₃ and hD₄ and serotonin (5-HT) h5-HT_1A, h5-HT_1B and h5-HT_1D receptors. Roxindole exhibited high affinity at hD₃ as well as at hD₂ (short isoform) and hD₄ (4-repeat isoform) receptors (pK _i values 8.93, 8.55 and 8.23, respectively). Further, it displayed high affinity at h5-HT_1A receptors (pK _i = 9.42) but modest affinity at 5-HT_1B and 5-HT_1D receptors (pK _i values 6.00 and 7.05, respectively). In [³⁵S]GTPγS binding experiments, roxindole was >20-fold more potent in stimulating [³⁵S]GTPγS binding at hD₃ than at hD₂ or hD₄ receptors (pEC₅₀ = 9.23 vs. 7.88 and 7.69). However, whereas roxindole exhibited partial agonist activity at hD₃ and hD₄ sites (E _max = 30.0% and 35.1%, respectively, relative to dopamine = 100%), it only weakly activated hD₂ receptors (E _max = 10.5%). Roxindole potently blocked dopamine-stimulated [³⁵S]GTPγS binding at hD₂ receptors (pK _B = 9.05). In comparison, the dopamine receptor agonist, (-)quinpirole, acted as a partial agonist at hD₃ and hD₄ sites (E _max = 67.4% and 66.3%, respectively) but surpassed the efficacy of dopamine at hD₂ receptors (E _max = 132%). At h5-HT_1A receptors, roxindole behaved as a high affinity (pK _i = 9.42) partial agonist (E _max = 59.6%, relative to 5-HT = 100%), whereas (-)quinpirole had negligible activity. The selective 5-HT_1A antagonist, WAY 100,635, blocked roxindole (100 nM)-stimulated [³⁵S]GTPγS binding at h5-HT_1A receptors in a concentration-dependent manner (pK _B = 9.28). Roxindole only weakly stimulated [³⁵S]GTPγS binding at 5-HT_1B and 5-HT_1D receptors (E _max = 27.1% and 13.7%). The present data suggest that roxindole activates mainly D₃ vs. D₂ or D₄ receptors and 5-HT_1A vs. 5-HT_1B or 5-HT_1D receptors. Activation of D₃ and/or 5-HT_1A receptors may thus contribute to its potential antidepressant properties. Received: 4 February 1999 / Accepted: 29 March 1999     

Pindolol binding to 5-HT1A receptors in the human brain confirmed with positron emission tomography

The augmentation effect of (–)pindolol as used in combination with SSRI to treat major depression has been ascribed to blocking of dorsal raphe nucleus cell body 5-HT autoreceptors. In this study, the radioligand [carbonyl-¹¹C]WAY-100635 and positron emission tomography were used to establish whether pindolol at a clinical dose level (10 mg s.o.d.) occupies 5-HT_1A receptors in the human brain in vivo. Three healthy males were recruited and each subject was used as his own control. The 5-HT_1A receptor occupancy was calculated for the frontal and temporal cortex and the raphe nuclei, using and a ratio analysis with the cerebellar cortex as the reference region. Maximal pindolol plasma concentration was reached within 3 h after drug administration. Two hours after pindolol administration, the regional 5-HT_1A receptor occupancy was within the range 7–21% in the three subjects. The study confirms that the 5-HT_1A-receptor may be a clinically significant target for pindolol. Received: 8 March 1999 / Final version: 15 March 1999     

Dopamine transporter and D2-receptor density in late-onset alcoholism

Rationale: Late onset type 1 alcoholism has been suggested to be associated with an underlying dopaminergic defect. Therefore, it is relevant to study both postsynaptic D₂-receptor and presynaptic dopamine transporter (DAT) densities among alcoholics. Objective: We investigated DAT densities, along with striatal and extrastriatal dopamine D₂-receptor densities, in nine non-violent late-onset male alcoholics, who had no major mental disorder nor antisocial personality disorder (ASPD), and nine healthy controls. Methods: [¹²³I]PE2I and [¹²³I]epidepride were used in SPECT imaging. Results: DAT occupancy ratios (striatum/cerebellum) were significantly lower among alcoholics than in controls. Extrastriatal D₂-receptor occupancy ratios (temporal pole/cerebellum) were not significantly different between the groups. Conclusions: Striatal presynaptic DAT densities are decreased among type 1 alcoholics, and this finding is not associated with recent alcohol abuse. Received: 22 March 1999 / Final version: 25 June 1999     

Thermodynamics and kinetics of t-butylbicyclophosphorothionate binding differentiate convulsant and depressant barbiturate stereoisomers acting via GABAA ionophores

The temperature dependence of [³⁵S]-t- butylbicyclophosphorothionate (TBPS) binding to the convulsant sites of the GABA_A receptor complex was studied in membrane preparations of rat forebrain. Although specific [³⁵S]TBPS binding was maximal around 20° C, the rate constants of dissociation decreased monotonously between 37°C and 2° C. The displacing potencies of the convulsant S(+) enantiomer of 1-methyl-5-phenyl-5-propyl-barbituric acid (MPPB) (IC₅₀ = 1250 ± 30 M) and the depressant R(–) MPPB (IC_5O = 310 ± 5 M) did not show significant changes between 19° C and 37° C. Therefore barbiturate binding seems to be driven by entropic, rather than enthalpic changes. An excess of MPPB enantiomers elicited accelerated and polyphasic dissociations of [³⁵S]TBPS as compared to the monophasic dissociation by TBPS. Arrhenius analysis was applied to the measurable initial rate constants of dissociation. Arrhenius plots were linear between 2° C and 37° C. Activation parameters were similar when [³⁵S] TBPS dissociation was triggered by the convulsants TBPS and S(+) MPPB. It can be attributed to similar conformations of the closed ionophore complex. In contrast, the depressant R(–) MPPB strongly decreased the activation energy of TBPS dissociation from the open ionophore ternary complex.In whole-cell patch-clamp experiments R(–) MPPB, but not S(+) MPPB, elicited chloride currents in rat primary cortical cultures with an EC₅₀ value of 560 ± 30 M and a Hill coefficient of 2.9 ± 0.2. These currents were similar to those elicited by GABA and blocked by TBPS. A kinetic scheme is proposed for the dissociation of TBPS and to explain the different effects of MPPB enantiomers. Submillimolar R(–) MPPB is supposed to bind to (about three) barbiturate sites on GABA_A-ionophores and to open them in a cooperative manner to result in a decreased activation energy for accelerated displacement of convulsant binding.     

Pharmacological and molecular discrimination of brain I2-imidazoline receptor subtypes

I₂-imidazoline receptors labelled with [³H]-idazoxan in the rabbit and rat brains displayed high and low affinity, respectively, for the guanidide amiloride; reinforcing the previous definition of I_2A-imidazoline receptors expressed in the rabbit brain and Its-imidazoline receptors expressed in the rat brain. Other drugs tested displayed biphasic curves in competition experiments, indicating the existence of high and low affinity sites for both subtypes of I₂-imidazoline receptors. Among the drugs studied, bromoxidine, moxonidine, (+)- and (-)-medetomidine and clorgyline were more potent on the high and/or low affinity sites of 1_2B- than on their corresponding of I_2A-imida-zoline receptors (K _iH ratios 20 to 65). No correlation was found for the potencies of the drugs tested at the low affinity sites of both I₂-imidazoline receptor subtypes. Preincubation (30 min at 25°°C) with 10^-6 M clorgyline reduced by 60% the B _max of [³H]-idazoxan binding to I₂ B-imidazoline receptors in the rat brain, but it did not affect the binding parameters of the radioligand saturation curves to I_2A-imidazoline receptors in the rabbit brain. These results indicated that I_2A- and I_2B-imidazoline receptor subtypes differ in the pharmacological profiles of their high and low affinity sites and in the ability to irreversibly bind clorgyline. In rat cortical membranes western blot detection of immunoreactive imidazoline receptor proteins revealed a double band of 29/30 kDa and two less intense bands of 45 and 66 kDa. In rabbit cortical membranes the antibody used detected proteins of 30, 57 and 66 kDa. It is suggested that different imidazoline receptor proteins (45 vs 57 kDa) may account for the different pharmacological profiles of I2-imidazoline receptor subtypes.