Distribution of 2-naphthol sulphotransferase and its endogenous substrate adenosine 3′-phosphate 5′-phosphosulphate in human tissues

The activity of sulphotransferase towards 2-naphthol and the concentration of its endogenous substrate, adenosine 3'-phosphate 5'-phosphosulphate (PAPS), have been measured in five specimens of human liver, lung, and kidney, and the mucosa from the ileum and the ascending, descending and sigmoid colon. The activity of 2-naphthol sulphotransferase (mean nmol.min-1.mg-1 protein) was 1.82 (liver); 0.034 (kidney); 0.19 (lung); 0.64 (ileum); 0.47 (ascending colon); 0.50 (descending colon); 0.40 (sigmoid colon). The concentration of PAPS (mean nmol.g-1 wet tissue) was 22.6 (liver); 4.8 (kidney); 4.3 (lung); 12.8 (ileum); 8.1 (ascending colon); 7.5 (descending colon); 6.2 (sigmoid colon). The concentration of PAPS and the activity of 2-naphthol sulphotransferase were higher in the liver than in the extrahepatic tissues. There was significant difference between ileum and ascending colon, both the activity of sulphotransferase and the concentration of PAPS being higher in the former. 2-Naphthol sulphotransferase activity and the concentration of PAPS have consistent distribution patterns. Differences between the tissues studied were more marked for sulphotransferase than for its endogenous substrate.     

Evidence for monoaminergic involvement in triadimefon-induced hyperactivity

Triadimefon is a triazole fungicide that produces hyperactivity in both mice and rats similar to that seen following administration of compounds with catecholaminergic activity (e.g., d-amphetamine). To determine whether the triadimefon-induced hyperactivity is due to an action on CNS catecholaminergic systems, we evaluated the effects of combined treatment of triadimefon with either the tyrosine hydroxlase inhibitor d,l--methyl-p-tyrosine methyl ester HCl (MPT) or the amine depletor reserpine. Adult male Long-Evans hooded rats, approximately 70 days of age were used. Dosage-effect functions were determined for MPT (0–200 mg/kg IP), reserpine (0–2.5 mg/kg IP), d-amphetamine (0–3 mg/kg IP), and methylphenidate (0–40 mg/kg IP). Motor activity was measured as photocell interruptions in figure-eight mazes. The interaction between triadimefon and MPT was determined with the following groups: 1) vehicle control; 2) 200 mg/kg triadimefon PO; 3) 100 mg/kg MPT; and 4) both MPT and triadimefon. A similar design was used to determine the interaction between triadimefon and reserpine (0.62 mg/kg), MPT and d-amphetamine (1.5 mg/kg), and reserpine and methylphenidate (5.0 mg/kg). In the first experiment MPT did not block the increased motor activity produced by triadimefon (i.e., both triadimefon alone and MPT in combination with triadimefon produced significant increases in motor activity). MPT did, however, block d-amphetamine-induced hyperactivity. Since MPT did not antagonize the effect of triadimefon, these data suggest that increased motor activity produced by triadimefon is not mediated through release of newly synthesized catecholamines. In contrast, pretreatment with reserpine blocked the hyperactivity induced by both triadimefon and methylphenidate, which suggests that triadimefon-induced hyperactivity may be due to an interaction with CNS catecholamines stored in reserpine-sensitive pools.The research described in this article has been reviewed by the Health Effects Research Laboratory, US Environmental Protection Agency, and approved for publication. Approval does not signify that the contents necessarily reflect the views and policies of the Agency nor does mention of trade names or commercial products constitute endorsement or recommendation for use. Presented in part at the Annual Meeting of the Society for Neuroscience, New Orleans, LA, November, 1987     

The effects of clonidine and yohimbine on human information processing

The effects of clonidine and yohimbine on human information processing were tested in six normal volunteers ages 18–30 years. Subjects were tested in a pre-post design with sessions conducted at weekly intervals. Three drug conditions were: Placebo (lactose), 0.2 mg clonidine, and 30 mg yohimbine. Two choice reaction time (RT) tasks were used. One was a stimulus evaluation-response selection task (SERS) that has been shown to be sensitive tod-amphetamine, methylphenidate and scopolamine. The other task was to assess stimulus pre-processing and used spatial frequency as a discriminative stimulus. The principle finding was that clonidine slowed RT; this effect was significant for both tasks. In contrast, yohimbine tended to speed RT, but the effects were significant only for the spatial frequency task on some analyses while not for others. RTs to high spatial frequency stimuli were speeded more than for low spatial frequency. The effects of these two NE drugs were compared with findings withd-amphetamine and scopolamine and interpreted within the framework of a serial information processing model proposed by Callaway (1983). Specifically, it is suggested that yohimbine and clonidine affect an early pre-processing stage.     

Effects of D2 dopamine receptor blockade with raclopride on intracranial self-stimulation and food-reinforced operant behaviour

To examine the involvement of D2 dopamine receptors in the neural mechanism of reinforcement, raclopride tartrate, a D2 specific dopamine antagonist with a relatively fast central action, was injected into 32 rats. The D2 antagonist reduced bar-pressing responses reinforced with electrical stimulation of the ventral tegmental area (ED₅₀=0.079 mol/kg) and those reinforced with food (ED₅₀=0.58 mol/kg) in 18–30 min after IP injection. The reduction in response rates could not be attributed to an interference with motor functions. An increase in the frequency of brain-stimulation pulses and a change in the schedule of food reinforcement, which respectively increased the baseline rate of responding, did not alter the effectiveness of raclopride. SCH 23390, a D1-specific dopamine antagonist, was sensitive to similar manipulation of reinforcement. These results seem to suggest that D1 and D2 antagonists may be acting at different locations in the neural mechanism underlying the reinforcement of operant behaviour.     

Drug Binding to α1-Acid Glycoprotein Studied by Circular Dichroism

The interactions of acidic and basic drugs with ₁-acid glycoprotein (₁-AGP) were investigated using circular dichroism (CD) measurements. Extrinsic Cotton effects were generated by the binding of drugs to ₁-AGP. The CD data suggested the presence of a single binding site on the ₁-AGP molecule. The induced ellipticities of the acidic drug–₁-AGP system decreased with increasing pH, while the ellipticities for the basic drugs increased with pH. The ellipticities for all drugs were reduced by the addition of fatty acids. Furthermore, the induced ellipticities decreased in the presence of cesium chloride for basic drugs bound to ₁-AGP. The extrinsic Cotton effects therefore appear to result from hydrophobic interaction with ₁-AGP for the acidic drugs and from hydrophobic and electrostatic interactions for the basic drugs.     

Prodrugs of 5-Iodo-2′-Deoxyuridine for Enhanced Ocular Transport

Problems associated with the use of 5-iodo-2-deoxyundine (IDU) in the treatment of herpes simplex keratitis can be attributed largely to the polar nature of IDU resulting in its poor permeability across the lipoidal epithelial layer of the corneal membrane. Five aliphatic 5-esters of IDU were synthesized and evaluated as prodrugs for potential use in the treatment of deep ocular infections such as stromal keratitis, iritis, and even retinitis. A parabolic relationship between in vitro corneal membrane permeability and carbon chain length of prodrugs is evident. For a given prodrug, enzymatic hydrolysis proceeded most readily in iris–ciliary body, followed by cornea and aqueous humor. An increase in carbon chain length made the prodrugs more enzymatically labile but more resistant to chemical hydrolysis at pH 7.4 and 34°C. The 5-butyryl ester of IDU exhibited an approximately fourfold increase in aqueous humor IDU concentration relative to IDU at 25 min following instillation of 25-µl 5 mM solutions.     

Immunoglobulin mimicry by Hepatitis C Virus envelope protein E2

Hepatitis C virus (HCV) establishes persistent infection in the majority of infected individuals. The currently accepted hypothesis of immune evasion by antigenic variation in hypervariable region 1 (HVR1) of glycoprotein E2 does not however, explain the lack of subsequent immune recognition. Here, we show that the N-terminal region of E2 is antigenically and structurally similar to human immunoglobulin (Ig) variable domains. E2 is recognized by anti-human IgG antibodies and also possesses common amino acid (aa) sequence features of the conserved v-gene framework regions of human Ig light chains in particular but also heavy chains and T cell receptors. Using a position specific scoring system, the degree of similarity of HVR1 to Ig types correlated with immune escape and persistence in humans and experimentally infected chimpanzees. We propose a unique role for threshold levels of Ig molecular mimicry in HCV biology that not only advances our concept of viral immune escape and persistent infection but also provides insight into host-dependent disease patterns.     

Expression of selectin ligands on murine effector and IL-10-producing CD4+ T cells from non-infected and infected tissues

Endothelial selectins are crucial for the recruitment of leukocytes into sites of inflammation. On T cells, ligands for selectins become induced upon differentiation into the effector/memory stage. Initial in vitro studies suggested a correlation between the Th1 phenotype and ligand expression, but whether this also holds true in vivo remained uncertain. We here analyzed selectin ligands on CD4+ T cells producing IFN-gamma, IL-4 or IL-10, prototypic cytokines of the Th1, Th2 and Tr1 subset, respectively. We analyzed mice infected with influenza virus, the bacterium Listeria, and the parasites Toxoplasma (all Th1 models) or Nippostrongylus (Th2 model). A link between the Th1 phenotype and ligand expression was not found in vivo. Surprisingly, the potentially regulatory IL-10-producing T cells displayed the highest frequency of ligand-positive cells in general. Within the inflamed tissues, the frequencies of P-selectin-binding cells increased in the dominant subset, either Th1 or Th2. Up-regulation was also found for E-selectin ligands during influenza, but not Nippostrongylus infection. In conclusion, conditions driving T cell polarization into either Th1 or Th2 in vivo do not affect the expression of selectin ligands, but acquisition of P-selectin binding and hence migration into inflamed tissues is boosted by an inflammatory milieu.     

Increased Hepatic Cholesterol Accumulation in Transgenic Mice Overexpressing Human Secretory Phospholipase A2 Group IIA

It has been demonstrated in transgenic mice that the overexpression of human phospholipase A2 group IIA (sPLA2), an acute-phase reactant, is associated with depressed plasma cholesterol levels, altered lipoprotein compositions, and increased lipid depositions in aortic walls. It was the aim of the present study to investigate whether the reduced plasma cholesterol levels in sPLA2-transgenic mice may be due to an increased transfer of lipids from sPLA2-modified lipoproteins to the liver and/or other nonvascular tissues. Ten sPLA2-transgenic mice and an equal number of nontransgenic littermates were fed a cholesterol-enriched (1%) diet for 13 weeks. After autopsy, cholesterol and triglyceride concentrations were measured in homogenates of liver, spleen, kidney, and myocardial tissues. Compared to the nontransgenic controls, the sPLA2-transgenic mice exhibited significantly lower plasma cholesterol levels, which was due to a reduction in both HDL and beta-lipoprotein (LDL + beta-VLDL) cholesterol. Liver tissues from the transgenic mice were found to contain significantly increased concentrations of free and esterified cholesterol, which was not associated with increased triglyceride concentrations. Spleen, kidney, and heart tissues of the two animal groups showed no significant differences in cholesterol or triglyceride concentrations. The findings suggest that the overexpression of human secretory phospholipase A2 group IIA leads to an enhanced delivery of cholesterol from phospholipolysed lipoproteins to the liver. This mechanism is likely to contribute to the development of hypocholesterolemia observed in patients with inflammatory diseases.     

Immunologic immaturity, but high IL-4 productivity, of murine neonatal thymic CD4 single-positive T cells in the last stage of maturation

To determine the levels of maturation and differentiation ofmurine CD4 single-positive (SP) T cells, we compared the secondaryresponses of staphylococcal enterotoxin A (SEA)-induced neonatalthymic, adult thymic and adult splenic CD4 SP T cell blastsprepared from whole or heat-stable antigen^low CD4 SP T cells.Proliferative responses upon re-stimulation with SEA were strongin adult splenic CD4 SP T cell blasts, but quite weak in neonatalthymic and adult thymic CD4 SP T cell blasts. SEA-induced IL-2production was weaker in neonatal thymic blasts than in theadult splenic CD4 SP T cell blasts. In contrast, SEA-inducedIL-4 production was high in neonatal thymic CD4 SP T cell blasts,and low in adult splenic and thymic CD4 SP T cell blasts. Expressionof GATA-3, that directs production of IL-4 in T cells, examinedat protein and mRNA levels, was higher in neonatal thymic cellsthan in adult thymic and splenic cells. These results suggestthat neonatal and adult thymic CD4 SP T cells in the final stageof maturation are relatively immature compared with adult splenicCD4 SP T cells. The cytokine production profile of neonatalthymic CD4 SP T cells suggests that they are inclined towardsa T_h2 response.