An increase in intracellular cyclic AMP modulates nitric oxide production in IFN-gamma-treated macrophages

Macrophages treated with IFN-gamma alone are stimulated to produce nitric oxide. The level of nitric oxide production can be enhanced significantly when IFN-gamma treatment is combined with other agents (e.g., LPS, TNF-alpha, IL-2, etc.). We tested the hypothesis that cAMP plays a role in the IFN-gamma-induced activation of macrophages. Our experiments indicate that factors that increase the concentration of cAMP in the murine macrophage cell line ANA-1 can also enhance IFN-gamma-induced production of nitric oxide. PGE2 and cholera toxin increased the production of nitrite (an indicator of nitric oxide production) in IFN-gamma-treated ANA-1 macrophages by at least twofold. These factors produced no increase in nitric oxide production in the absence of IFN-gamma treatment. The increase in nitric oxide production corresponded to an increase in the accumulation of nitric oxide synthase mRNA without a change in stability of mRNA. Dibutyryl cAMP and Sp-cAMPs (a selective activator of cAMP-dependent protein kinase I and II) also increased nitric oxide production in IFN-gamma-treated macrophages. However, at very high concentrations (i.e., >100 microM), the stimulatory effect was decreased. These studies indicate that elevation of intracellular cAMP causes a dose-dependent, biphasic alteration of IFN-gamma-induced nitric oxide production in murine macrophages. Moreover, they suggest that agents that affect nitric oxide synthesis may do so via modulation of the cAMP second messenger system.     

Functional expression of three isoforms of human nitric oxide synthase in baculovirus-infected insect cells

Complementary DNAs encoding three human isoforms (neuronal, inducible, and endothelial) of nitric oxide synthase were cloned into the baculovirus expression vector pVL1392/1393. Transfection of Sf-9 insect cells with the recombinant baculovirus resulted in the expression of high levels of nitric oxide synthases. The expressed proteins of neuronal and inducible nitric oxide synthase were predominantly soluble, whereas the endothelial enzyme was for the most part, particulate. Recombinant enzymes were purified with 2',5'-ADP Sepharose affinity chromatography. The effects of reference enzymatic inhibitors (NG-methyl-L-arginine, NG-nitro-L-arginine and N-iminoethyl-L-ornithine) on recombinant expressed proteins were not significantly different from native nitric oxide synthase enzyme preparations. L-aminoguanidine was found to be much less potent in inhibiting recombinant or native human inducible nitric oxide synthase compared to the murine isoform. These findings indicate previously unappreciated interspecies differences in the action of nitric oxide synthase enzymatic inhibitors. The functional expression of human nitric oxide synthase isoforms in a heterologous expression system allowed screening of novel inhibitors. Studies indicated that S-ethylisothiourea and 2-amino-5,6-dihydro-6-methyl-4H-1,3-thiazine were potent novel inhibitors of human nitric oxide synthases.     

Topical progesterone as support for the luteal phase in induced cycles

e efficacy and tolerability of 2.5% natural vaginal progesterone as luteal phase support in pharmacologically induced cycles has been evaluated. MATERIALS AND METHODS: On the basis of the administered therapy, the population studied was subdivided at random into four different groups. Sixty patients came to the Sterility Autonomous Department of the Niguarda Ca' Granda Hospital in Milan from November 1994 to January 1996. Both ultrasonographic and plasmatic hormonal parameters have been evaluated on a monthly basis. RESULTS: The plasma progesterone levels and ultrasonographic endometrial thickness average values resulted more important in groups treated with topical progesterone; in these same groups a greater percentage of pregnancies was observed. CONCLUSIONS: The results obtained demonstrated that the drug studied can be recommended as a valid luteal phase support in pharmacologically induced cycles.     

An interactive activation approach to object processing: effects of structural similarity, name frequency, and task in normality and pathology

We present a computational model of the processes involved in retrieving stored semantic and name information from objects, using a simple interactive activation and competition architecture. We simulate evidence showing a cross-over in normal reaction times to make semantic classification and identification responses to objects from categories with either structurally similar or structurally dissimilar exemplars, and that identification times to objects from these two different classes correlate differentially with measures of the structural similarity of objects within the category and the frequency of the object's name. Structural similarity exerts a negative effect on object decision as well as naming, though this effect is larger on naming. Also, on naming, structural similarity interacts with the effects of name frequency, captured in the model by varying the weight on connections from semantic to name units; frequency effects are larger with structurally dissimilar items. In addition, (1) the range of potential errors for objects from these two classes, when responses are elicited before activation reached a stable state, differ--a wider range of errors occur to objects from categories with structurally similar exemplars; and (2) simulated lesions to different locations within the model produce selective impairments to identification but not to semantic classification responses to objects from categories with structurally similar exemplars. We discuss the results in relation to data on visual object processing in both normality and pathology.     

Odor, drug and toxin analysis with neuronal networks in vitro: extracellular array recording of network responses

Neurons, by virtue of intrinsic electrophysiological mechanisms, represent transducers that report the dynamics of cell death, receptor-ligand interactions, alterations in metabolism, and generic membrane perforation processes. In cell culture, mammalian neurons form fault-tolerant, spontaneously active systems with great sensitivity to their chemical environment and generate response profiles that are often concentration- and substance-specific. Changes in action potential patterns are usually detected before morphological changes and cell damage occur, which provides sensitivity and reversibility. Such biological systems can be used to screen rapidly for novel pharmacological substances, toxic agents, and for the detection of certain odorants. Existing simple culture preparations can already be employed effectively for the detection of chemical compounds. So far, three strategies have been investigated in pilot experiments: (1) Substance-dependent major changes in spontaneous native activity patterns. All synaptically active agents (e.g. glutamate, strychnine, N-methyl D-aspartic acid) as well as metabolic poisons generate such changes. (2) Substance-dependent changes in network oscillations via disinhibition. The regularized, oscillatory activity is altered by synaptically and metabolically active substances, ion channel blockers, and toxins. (3) Detection of paroxysmal responses indicating major, pathological membrane currents in large subpopulation of cells. We have explored these three strategies via 64 channel array recordings using spontaneously active murine spinal cord cultures. The glycine receptor blocker strychnine reliably generated increased multichannel bursting at 5-20 nM and regular, coordinated bursting above 5 microM. During biculline-induced network oscillations many compounds alter oscillation frequencies or terminate activity in a substance-specific manner. Finally, the gp120 protein of the AIDS virus (at 1 microgram/ml) produces massive, unique paroxysmal discharges that may last as long as 2 min. These results indicate that cultured neuronal networks are practical systems that can be used for the detection and identification of a great variety of chemical substances. The concept of dynamic fingerprinting to identify specific compounds is discussed.     

The tryptase, mouse mast cell protease 7, exhibits anticoagulant activity in vivo and in vitro due to its ability to degrade fibrinogen in the presence of the diverse array of protease inhibitors in plasma

Mouse mast cell protease (mMCP) 7 is a tryptase of unknown function expressed by a subpopulation of mast cells that reside in numerous connective tissue sites. Because enzymatically active mMCP-7 is selectively released into the plasma of V3 mastocytosis mice undergoing passive systemic anaphylaxis, we used this in vivo model system to identify a physiologic substrate of the tryptase. Plasma samples taken from V3 mastocytosis mice that had been sensitized with immunoglobulin (Ig) E and challenged with antigen were found to contain substantial amounts of four 34-55-kDa peptides, all of which were derived from fibrinogen. To confirm the substrate specificity of mMCP-7, a pseudozymogen form of the recombinant tryptase was generated that could be activated after its purification. The resulting recombinant mMCP-7 exhibited potent anticoagulant activity in the presence of normal plasma and selectively cleaved the alpha-chain of fibrinogen to fragments of similar size as that seen in the plasma of the IgE/antigen-treated V3 mastocytosis mouse. Subsequent analysis of a tryptase-specific, phage display peptide library revealed that recombinant mMCP-7 preferentially cleaves an amino acid sequence that is nearly identical to that in the middle of the alpha-chain of rat fibrinogen. Because fibrinogen is a physiologic substrate of mMCP-7, this tryptase can regulate clot formation and fibrinogen/integrin-dependent cellular responses during mast cell-mediated inflammatory reactions.     

Systematic screening of the LDL-PLA2 gene for polymorphic variants and case-control analysis in schizophrenia

Systematic scans of the genome using microsatellite markers have identified chromosome 6p21.1 as a putative locus for schizophrenia in multiply affected families. There is also evidence from a series of studies for a role of abnormal phospholipid metabolism in schizophrenia. In light of these findings, and the role of platelet activating factor in neurotransmission and neurodevelopment, we have examined the LDL-PLA2 (plasma PAF acetylhydrolase, PAF-AH) gene, a serine dependent phospholipase that has been mapped by hybrid mapping to chromosome 6p21.1, as a positional candidate gene for schizophrenia. The gene was systematically screened using SSCP/HD analysis for polymorphisms associated with the disease. Four polymorphic variants were found within the gene and studied in a group of 200 schizophrenic patients and 100 controls. The variant in exon 7 (Iso195Thr) was found to be weakly associated with schizophrenia (p = 0.04) and the variant in exon 11 (Val379Ala) almost reached significance (p = 0.057). After correcting for multiple testing no significant associations were detected. Haplotype analysis combining pairs of polymorphisms also provided no evidence for association of this gene with schizophrenia in our sample of patients.     

Salmonella arizonae sepsis in a lynx

A 4.5-wk-old lynx (Felis lynx) was presented for necropsy with a history of poor growth, mild diarrhea, anemia, and lethargy. The liver was enlarged and had a 7 mm long fracture that resulted in severe intraabdominal hemorrhage and death. Microscopic lesions were indicative of severe ulcerative cystitis and septicemia. Pure cultures of Salmonella arizonae were isolated from the liver, kidney, and spleen. Based on differences in the chronicity of inflammation in the urinary bladder versus other organs, we speculate that chronic cystitis caused by S arizonae lead to septicemic infection.