Genotoxicity of streptozotocin

Streptozotocin (Streptozocin, STZ, CAS No. 18883-66-4) is a monofunctional nitrosourea derivative isolated from Streptomyces achromogenes. It has broad spectrum antibiotic activity and antineoplastic properties and is often used to induce diabetes mellitus in experimental animals through its toxic effects on pancreatic beta cells. STZ is a potent alkylating agent known to directly methylate DNA and is highly genotoxic, producing DNA strand breaks, alkali-labile sites, unscheduled DNA synthesis, DNA adducts, chromosomal aberrations, micronuclei, sister chromatid exchanges, and cell death. This antibiotic was found to be mutagenic in bacterial assays and eukaryotic cells. STZ is also carcinogenic; a single administration induces tumors in rat kidney, liver, and pancreas. Several lines of evidence indicate that free radicals are involved in the production of DNA and chromosome damage by this compound. Because of the use of STZ as an antineoplastic agent, the study of its genotoxicity has considerable practical significance. The purpose of this review is to present our current knowledge regarding the genotoxicity of STZ.     

Frequency and distribution patterns of zoosporic fungi from moss-covered and exposed forest soils

Uniflagellate zoosporic "fungi" (=Chytridiomycota and the zoosporic protista Hyphochytriomycota) are common inhabitants of soil. However, at what scale differences in their spatial distribution can be detected is poorly known. The first objective of this study was to assess the association of organismal distribution and frequency with two microhabitats: moss-covered and exposed forest soils, at four macroscopically similar but spatially separate sites in the Blue Ridge and Allegheny Mountains of Virginia. The second objective was to provide statistically either acceptance or denial of inferences derived from sampling regimes involving a more limited number of samples. To evaluate the scale where distributional differences may occur within a site, protocols involved four collection regimes and random point and linear transect sampling. Chytrid frequency on thalli of two moss genera was greatest in the soil surrounding and under the moss rhizoids. Random point sampling methods suggested differences in zoosporic fungal frequency between moss-covered soil and the exposed soil adjacent to mosses, as well as between two moss taxa. Linear transect sampling methods also suggested differences in zoosporic fungal frequencies between moss-covered soil and soil proximal to mosses. However, statistical analysis of random point samples using a goodness-of-fit test demonstrated that there was no significant difference in frequency of zoosporic fungi from moss-covered soil and exposed soil proximal to mosses. More importantly, there was a significant difference in the frequency of ubiquitous and common zoosporic fungal species between different moss/soil complexes. This study demonstrates that differences in chytrid distribution can be detected at a microscale while at a larger scale, similarity in frequency and distribution was found.     

Phosphatidylinositol 3-kinase activity negatively regulates stability of cyclooxygenase 2 mRNA

Human alveolar macrophages have both lipopolysaccharide (LPS)-induced and constitutive phosphatidylinositol 3-kinase (PI3K) activity. We observed that blocking PI3K activity increased release of prostaglandin E2 after LPS exposure, and increasing PI3K activity (interleukin-13) decreased release of prostaglandin E2 after LPS exposure. This was not because of an effect of PI3K on phospholipase 2 activity. PI3K inhibition resulted in an increase in cyclooxygenase 2 (COX2) protein, mRNA, and mRNA stability. PI3K negatively regulated activation of the p38 pathway (p38, MKK3/6, and MAPKAP2), and an active p38 was necessary for COX2 production. The data suggest that PI3K inhibition of p38 modulates COX2 expression via destabilization of LPS-induced COX2 mRNA.     

Nonselective currents and channels in plasma membranes of protoplasts from coats of developing seeds of bean

In developing bean (Phaseolus vulgaris) seeds, phloem-imported nutrients move in the symplast from sieve elements to the ground parenchyma cells where they are transported across the plasma membrane into the seed apoplast. To study the mechanisms underlying this transport, channel currents in ground parenchyma protoplasts were characterized using patch clamp. A fast-activating outward current was found in all protoplasts, whereas a slowly activating outward current was observed in approximately 25% of protoplasts. The two currents had low selectivity for univalent cations, but the slow current was more selective for K(+) over Cl(-) (P(K):P(Cl) = 3.6-4.2) than the fast current (P(K):P(Cl) = 1.8-2.5) and also displayed Ca(2+) selectivity. The slow current was blocked by Ba(2+), whereas both currents were blocked by Gd(3+) and La(3+). Efflux of K(+) from seed coat halves was inhibited 25% by Gd(3+) and La(3+) but was stimulated by Ba(2+) and Cs(+), suggesting that only the fast current may be a component in the pathway for K(+) release. An "instantaneous" inward current observed in all protoplasts exhibited similar pharmacology and permeability for univalent cations to the fast outward current. In outside-out patches, two classes of depolarization-activated cation-selective channels were observed: one slowly activating of low conductance (determined from nonstationary noise to be 2.4 pS) and another with conductances 10-fold higher. Both channels occurred at high density. The higher conductance channel in 10 mM KCl had P(K):P(Cl) = 2.8. Such nonselective channels in the seed coat ground parenchyma cell could function to allow some of the efflux of phloem-imported univalent ions into the seed apoplast.     

A new peroxinectin-like gene preferentially expressed during oogenesis and early embryogenesis in Drosophila melanogaster

Several peroxidase isozymes have been described in Drosophila melanogaster. We describe a peroxinectin-like gene (Dpxt) in D. melanogaster. Peroxinectin is a cell-adhesive hemoperoxidase which binds superoxide dismutase and mediates blood cells attachment and spreading in the crayfish Pacifastacus leniusculus. The Dpxt predicted protein has a putative RGD-integrin binding tripeptide. The Dpxt mRNA is present in high amounts in late oogenesis and in early embryogenesis until the cellular blastoderm stage. It is virtually absent at other stages of the Drosophila life cycle, suggesting that Dpxt function is restricted to the early stages of fly development.     

Gene expression markers for Caenorhabditis elegans vulval cells

The analysis of cell fate patterning during the vulval development of Caenorhabditis elegans has relied mostly on the direct observation of cell divisions and cell movements (cell lineage analysis). However, reconstruction of the developing vulva from EM serial sections has suggested seven different cell types (vulA, vulB1, vulB2, vulC, vulD, vulE, and vulF), many of which cannot be distinguished based on such observations. Here we report the vulval expression of seven genes, egl-17, cdh-3, ceh-2, zmp-1, B0034.1, T04B2.6 and F47B8.6 based on gfp, cfp and yfp (green fluorescent protein and color variants) reporter fusions. Each gene expresses in a specific subset of vulval cells, and is therefore useful as a marker for vulval cell fates. Together, expressions of markers distinguish six cell types, and reveal a strict temporal control of gene expression in the developing vulva.     

Evidence for local inflammation in complex regional pain syndrome type 1

BACKGROUND: The pathophysiology of complex regional pain syndrome type 1 (CRPS 1) is still a matter of debate. Peripheral afferent, efferent and central mechanisms are supposed. Based on clinical signs and symptoms (e.g. oedema, local temperature changes and chronic pain) local inflammation is suspected. AIM: To determine the involvement of neuropetides, cytokines and eicosanoids as locally formed mediators of inflammation. METHODS: In this study, nine patients with proven CRPS 1 were included. Disease activity and impairment was determined by means of a Visual Analogue Scale, the McGill Pain Questionnaire, the difference in volume and temperature between involved and uninvolved extremities, and the reduction in active range of motion of the involved extremity. Venous blood was sampled from and suction blisters made on the involved and uninvolved extremities for measurement of cytokines interleukin (IL)-6, II-1beta and tumour necrosis factor-alpha (TNF-alpha), the neuropetides NPY and CRGP, and prostaglandin E2RESULTS: The patients included in this study did have a moderate to serious disease activity and impairment. In plasma, no changes of mediators of inflammation were observed. In blister fluid, however, significantly higher levels of IL-6 and TNF-alpha in the involved extremity were observed in comparison with the uninvolved extremity. CONCLUSIONS: This is the first time that involvement of mediators of inflammation in CRPS 1 has been so clearly and directly demonstrated. This observation opens new approaches for the succesful use and development of immunosuppressives in CRPS 1.     

Na transport proteins are expressed by rat alveolar epithelial type I cells

Despite a presumptive role for type I (AT1) cells in alveolar epithelial transport, specific Na transporters have not previously been localized to these cells. To evaluate expression of Na transporters in AT1 cells, double labeling immunofluorescence microscopy was utilized in whole lung and in cytocentrifuged preparations of partially purified alveolar epithelial cells (AEC). Expression of Na pump subunit isoforms and the alpha-subunit of the rat (r) epithelial Na channel (alpha-ENaC) was evaluated in isolated AT1 cells identified by their immunoreactivity with AT1 cell-specific antibody markers (VIIIB2 and/or anti-aquaporin-5) and lack of reactivity with antibodies specific for AT2 cells (anti-surfactant protein A) or leukocytes (anti-leukocyte common antigen). Expression of the Na pump alpha(1)-subunit in AEC was assessed in situ. Na pump subunit isoform and alpha-rENaC expression was also evaluated by RT-PCR in highly purified (approximately 95%) AT1 cell preparations. Labeling of isolated AT1 cells with anti-alpha(1) and anti-beta(1) Na pump subunit and anti-alpha-rENaC antibodies was detected, while reactivity with anti-alpha(2) Na pump subunit antibody was absent. AT1 cells in situ were reactive with anti-alpha(1) Na pump subunit antibody. Na pump alpha(1)- and beta(1)- (but not alpha(2)-) subunits and alpha-rENaC were detected in highly purified AT1 cells by RT-PCR. These data demonstrate that AT1 cells express Na pump and Na channel proteins, supporting a role for AT1 cells in active transalveolar epithelial Na transport.