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At least 919 records · Page 51Linked to original sources
PubMed2006

Imposex in the golden apple snail Pomacea canaliculata in Taiwan.

The golden apple snail Pomacea canaliculata (Lamarck, 1822) was introduced into Taiwan intentionally in the early 1980s and has become a recurring pest that seriously threatens aquatic crops. In this study, a field description of imposex with a developed penis sheath and penis in female golden apple snails from crop/domestic wastewater drainage sites and a six-order river is presented for the first time. Based on the five field collections and the aquarium group, the vas deferens sequence (VDS) of P. canaliculata in imposex development was categorized into four stages, i.e., stage 0: without male genital system; stage 1: with rudimentary penis; stage 2: with rudimentary penis and penis sheath; and stage 3: the rudimentary penis developing into penis pouch and penis. The VDS indices varied between 1.07 and 2.82 and were lowest in the aquarium group and Yuanlin2. Regarding the severity of imposex, the aquarium group was less pronounced, as illustrated by the length of penis sheath and penis length, than the field collections (p<0.05). In respect of the penis length, males of the most imposex-affected site were up to 15% shorter than that of the aquarium group. Negative correlations between male penis length and female imposex characters (i.e., penis length and penis sheath length) were also observed.

Animals↗
PubMed2006

Mild and selective deprotection method of acetylated steroids and diterpenes by dibutyltin oxide.

Dibutyltin oxide (DBTO) was first utilized for the deacetylation of steroid and diterpene esters. The results showed the deprotection of acetylated steroids and diterpenes separately with moderate catalysis dibutyltin oxide in methanol selectively removed part acetyl groups of these substrates, whereas several functional groups of the steroids and diterpenes were retained and neither isomerization nor degradation of these substrates was observed. It seems that the acetyl groups with lower steric hindrance or near carbonyl, alkoxy, or hydroxyl groups can be cleaved by the reaction, whereas the acetyl groups with higher steric hindrance or without carbonyl, alkoxy, or hydroxyl groups neighboring were retained under the same conditions. One of the interesting results obtained was the selective hydrolysis of the 3beta-O-acetyl group in the presence of the 6beta group in 3beta,6beta-Di-O-acetyl-5alpha-hydroxypregn-16-en-20-one. This allows for subsequent introduction of one unit at C-3 and the other unit at C-6. This procedure is useful for the synthesis of a series of closely related isomers of 3beta,5alpha,6beta-trihydroxypregn-16-en-20-one and other widespread polyhydroxysteroids in marine organisms and some terrestrial species.

Acetylation↗
PubMed2006

Triphenyltin impairs a protein kinase A (PKA)-dependent increase of cytosolic Na+ and Ca2+ and PKA-independent increase of cytosolic Ca2+ associated with insulin secretion in hamster pancreatic beta-cells.

Oral administration of triphenyltin chloride (TPT) (60 mg/kg body weight) inhibits the insulin secretion by decreasing the cytoplasmic Ca2+ concentration ([Ca2+]i) induced by glucose-dependent insulinotropic polypeptide (GIP) in pancreatic beta-cells of the hamster. To test the possibility that the abnormal level of [Ca2+]i induced by TPT administration could be due to a defect in the cAMP-dependent cytoplasmic Na+ concentration ([Na+]i) in the beta-cells, we investigated the effects of TPT administration on the changes of [Na+]i induced by GIP, glucagon-like peptide-1 (GLP-1), or forskolin, an activator of adenylyl cyclase, and on the changes of [Na+]i or [Ca2+]i induced by 6-Bnz-cAMP, an activator of protein kinase A (PKA), and 8-pCPT-2'-O-Me-cAMP, an activator of Epac. The [Na+]i and [Ca2+]i were measured in islet cells loaded with sodium-binding benzofuran isophthalate (SBFI) and fura-2, respectively. In the presence of 135 mM Na+, TPT administration significantly reduced the rise in [Na+]i by 10 nM GLP-1, 10 microM forskolin, and 50 microM 6-Bnz-cAMP, but had not effect in a Na+-free medium. In the presence of 135 mM Na+, TPT administration also reduced the rise in [Ca2+]i by 8-pCPT-2'-O-Me-cAMP plus10 microM H-89, a inhibitor of PKA, and 6-Bnz-cAMP. Moreover, TPT administration significantly reduced the insulin secretion by 2 mM db-cAMP, GLP-1, GIP, and 8-pCPT-2'-O-Me-cAMP with and without H-89, and that by 6-Bnz-cAMP and forskolin. Our study suggested that TPT has inhibitory effects on the cellular Ca2+ response due to a reduced Na+ permeability through PKA-dependent mechanisms in hamster islet cells. Also TPT has the reduction of [Ca2+]i related to Na+-dependent insulin secretion after an activation of Epac.

Animals↗
PubMed2006

Response to alkyltins of two Na+-dependent ATPase activities in Tapes philippinarum and Mytilus galloprovincialis.

Organotin effects on the Na-dependent ATPases involved in ionic regulation of aquatic animals are poorly known, in spite of the largely documented contamination of seafood, especially bivalve molluscs. This study deals with the in vitro effect of TBT on the Na,K-ATPase and the ouabain-insensitive Na-ATPase in gill and mantle microsomes from the cultured bivalve molluscs Tapes philippinarum and Mytilus galloprovincialis. In the mussel also MBT, DBT and TeET were tested. While in both species the Na-ATPase showed an overall refractoriness to organotins, the Na,K-ATPase was progressively inhibited by increasing TBT concentrations (0-34 microM). In both species the Na,K-ATPase activity was more strongly inhibited in the gills than in the mantle. At the maximal TBT concentration tested (34.4 microM), while gill Na,K-ATPase activity was abolished, mantle enzyme activity was, respectively, reduced to 20% in T. philippinarum and to 50% in M. galloprovincialis. Mussel Na,K-ATPase was differently susceptive to the organotins tested and in both tissues showed an inhibition efficiency order TBT>DBT>>MBT=TeET (no effect), tentatively related to the different organotin polarity and to a possible interaction with membrane-bound enzyme complexes. The different response of the two ATPases to organotins is consistent with the known different susceptivity of the two enzyme activities to environmental contaminants, assay conditions and endogenous factors.

Animals↗
PubMed2004

Identification of principal cytochrome P-450 in triphenyltin metabolism in rats.

The in vivo and in vitro metabolism of triphenyltin using rat hepatic cytochrome P-450 (CYP) systems was investigated to confirm the specific CYP that is closely related to triphenyltin metabolism. No significant sex differences occurred between the in vivo and in vitro metabolic patterns of the chemical, indicating that the principal CYP for triphenyltin metabolism in rats is not a sex-specific form of CYP. In addition, seven types of complementary DNA (cDNA)-expressed rat CYPs, typical phenobarbital (PB)-inducible forms and the CYP2C subfamily were tested to determine the activity of triphenyltin metabolism. Among the CYP isoforms studied, although CYP2B1 had a small metabolic capacity, a marked dearylation of the chemical was induced by CYP2C6. Furthermore, anti-rat CYP2C6 antibodies and cimetidine, a selective CYP2C6 inhibitor, inhibited triphenyltin dearylation activity in the hepatic microsomes of rats. Taken together, these findings suggest that CYP2C6 is the principal CYP for the triphenyltin metabolism in rats.

Animals↗
PubMed2004

Tiered environmental risk assessment of methyltins from heat stabilizers in rigid PVC in Sweden.

The methyltins, methyltin 2-ethylhexyl mercaptoacetate and methyltin-2-mercaptoethyloleate sulfide, are used as heat stabilizers in rigid PVC. The degradation products monomethyltintrichloride (MMTTC) and dimethyltindichloride (DMTDC) may leach from the PVC, and enter the environment. A risk assessment was executed for the use of these products in Sweden, with the double aim to (a) assess the potential environmental risks, and (b) explore the possibilities of a tiered risk assessment. An initial assessment was executed with EUSES 1.0. The initial assessment showed no significant environmental risks on a regional scale. On a local scale however, emissions from a sewage treatment plant to the surface water pose a potential risk for the near proximity. In a second tier, this critical exposure route was studied in more detail; an improved exposure scenario was drawn up; and an additional sorption experiment was performed. This refinement resulted in much lower predicted environmental concentrations (<<PNEC). Measured methyltin concentrations in countries where methyltin heat stabilizers are registered, reveal concentrations ranging from < detection limit to intermediate values between concentrations predicted in the initial and refined assessment. The tiered assessment scheme proved valuable. Using this, the environmental risks due to the leaching of MMTTC and DMTDC from rigid PVC in Sweden are of no concern.

Animals↗
PubMed2003

Interference of methyl trachyloban-19-oate ester with CF(0) of spinach chloroplast H(+)-ATPase.

In isolated spinach chloroplasts, low concentrations (I(50)=14 microM) of methyl trachyloban-19-oate ester inhibited ATP synthesis and coupled electron transport as well as light-activated membrane-bound Mg(2+)-ATPase activity. Basal (-Pi) and uncoupled electron transport and heat-activated Ca(2+)-dependent ATPase activity of isolated coupling factor proteins were unaffected by methyl trachyloban-19-oate. Thylakoids partially stripped of coupled factor by EDTA were unable to accumulate protons in the light. However, increasing concentrations of methyl trachyloban-19-oate ester restored this ability. It is concluded that the methyl trachyloban-19-oate ester effects result from blocking proton transport through the CF(0) channel. Methyl trachyloban-19-oate ester exhibited non-competitive kinetics with DCCD and triphenyltin. These results suggest that the natural products, DCCD and triphenyltin, access inhibition sites in CF(0). The K(i) is 75 microM.

Chloroplast Proton-Translocating ATPases↗
PubMed2003

Triphenyltin enhances the neutrophilic differentiation of promyelocytic HL-60 cells.

Triphenyltin (TPT) is an environmental endocrine disruptor and toxic substance, but little information is available on its immunological effects. To assess the effect of TPT on leukocyte differentiation, we investigated its effect on the neutrophilic differentiation of HL-60 cells induced by dimethyl sulfoxide and granulocyte colony-stimulating factor (G-CSF) for 6 days. At a low concentration, 10(-7)M, TPT increased superoxide production by differentiated HL-60 cells stimulated with opsonized zymosan (OZ) by about 45% and increased expression of CD18, a component of the OZ-receptor, by about 90%. Real-time PCR analysis revealed that TPT augmented the expression not only of CD18 but also of components of superoxide-generating NADPH-oxidase, p47phox, 2.7-fold, and p67phox, 2.0-fold, and of granulocyte colony-stimulating factor receptor (G-CSFR), 3.0-fold, whereas various other endocrine disruptors, including parathion, vinclozolin, and bisphenol A, had no such enhancing effects. The results of a DNA macroarray analysis showed that TPT enhanced the expression of G-CSFR and certain other neutrophil functional proteins, including CD14 and myeloid leukemia cell differentiation protein (MCL-1), and that TPT induced a decrease in expression of LC-PTP, leukocyte protein-tyrosine phosphatase, to about half the control level. The TPT-dependent suppression of LC-PTP was confirmed by real-time PCR analysis, and the results of immunoblotting indicated that TPT enhances the expression of myeloid specific tyrosine kinase hck by about 30% at the protein level, and this together with the reduction of LC-PTP may enhance tyrosine phosphorylation, in turn resulting in enhancement of superoxide production. These findings suggest that TPT may have an enhancing effect on the neutrophilic maturation of leukocytes.

CD18 Antigens↗
PubMed1992

Modification of voltage-dependent Na+ current by triphenyltin, an environmental pollutant, in isolated mammalian brain neurons.

In order to reveal the profile of neurotoxicity of triphenyltin on the mammalian central nervous system (CNS) through the modification of a voltage-dependent Na+ channel, the effects of triphenyltin on the kinetics of voltage-dependent Na+ current (INa) were examined in acutely dissociated pyramidal neurons of rat hippocampus. Triphenyltin at the concentration of 1.10(-6) M decreased both the time to peak and the half-decay time of the INa without affecting the current-voltage relationship. Triphenyltin moved the steady-state inactivation curve to a depolarizing direction. In the presence of triphenyltin, the reactivation of Na+ channel inactivated during the depolarization occurred quicker than that of the control at the pulse intervals of less than 10 ms. It can be suggested that triphenyltin potentially increases the cell excitability in mammalian CNS through the modification of the INa.

Animals↗
PubMed2000

The intermolecular migration of polyol stannylenes as a reaction contributing to the regioselectivity of substitution.

Pairs of the partially protected glycosides benzyl 4,6-O-benzylidene-beta-D-galactopyranoside, benzyl 2,3-di-O-benzyl-beta-D-galactopyranoside, benzyl 2,6-di-O-benzyl-alpha-D-galactopyranoside, and benzyl 2,3-di-O-benzyl-alpha-D-glucopyranoside were treated with equimolar proportions of Bu2SnO in benzene in the conditions of stannylene formation, and the resulting mixture was benzoylated in situ with benzoyl chloride. Estimation of the product of benzoylation led to the following order of reactivity in the stannylenation reaction: 2,3-diol > 4,6-diol, and 2,3-diol > 3,4-diol. An intermolecular migration of dibutyltin between sugars was demonstrated. It is considered that these migrations contribute efficiently to the regiospecificity of the stannylene reaction.

Benzoates↗
PubMed2001

The anomalous reactivity of the bis(dibutylstannylene) acetal of pentaerythritol: a case of triple activation.

The only dibutyltin derivative of pentaerythritol which is observed by refluxing with dibutyltin oxide in methanol is a bis(dibutylstannylene) acetal. This is converted to the expected dibenzyl ether with benzyl bromide, in the presence of tetraethylammonium bromide in boiling toluene, but benzoylation at room temperature gives a tribenzoate. A mechanism is suggested to account for this triple activation.

Acetals↗
PubMed2002

Regioselective sulfonylation of 6,1',6'-tri-O-tritylsucrose through dibutylstannylation: synthesis of 4'-O-sulfonyl derivatives of sucrose.

3-O-Mesyl-1,6-di-O-trityl-beta-D-fructofuranosyl-(2-->1)-6-O-trityl-alpha-D-glucopyranoside (3) was synthesized via stannylation of 6,1',6'-tri-O-tritylsucrose with dibutyltin oxide in benzene, followed by treatment of the crude product with methanesulfonyl chloride in the presence of triethylamine in dichloromethane at 0 degrees C. A similar treatment of the tri-tritylsucrose in toluene, instead of benzene, yielded 4-O-mesyl-1,6-di-O-trityl-beta-D-fructofuranosyl-(2-->1)-6-O-trityl-alpha-D-glucopyranoside (4) as the major product. The X-ray crystal structure of the corresponding acetyl derivative, 3-O-acetyl-4-O-mesyl-1,6-di-O-trityl-beta-D-fructofuranosyl-(2-->1)-2,3,4-tri-O-acetyl-6-O-trityl-alpha-D-glucopyranoside (5), confirms the position and stereochemistry of the methanesulfonyl group at C-4 of the fructofuranosyl ring.

Crystallography, X-Ray↗
PubMed1997

Reductive cleavage of permethylated polysaccharides with borane-methyl sulfide complex and butyltin trichloride.

Several per-O-methylated monosaccharides and polysaccharides were used as models in an attempt to identify more convenient reagents for accomplishing reductive cleavage of glycosidic linkages. Included in the model studies were methyl alpha- and beta-D-glucopyranoside, methyl alpha- and beta-D-mannopyranoside, and methyl alpha- and beta-D-ribofuranoside. These studies led to the identification of a new promoter, butyltin trichloride, for carrying out reductive cleavage when borane-methyl sulfide complex was used as the reducing agent. These reagents were found to accomplish the reductive cleavage of per-O-methylated amylose, cellulose, and pullulan to give only the expected derivatives of 1,5-anhydro-D-glucitol. These reagents also accomplished reductive cleavage of per-O-methylated insulin to give only the expected derivatives of 2,5-anhydro-D-mannitol and 2,5-anhydro-D-glucitol. Reductive cleavage using these reagents is easy to perform, and subsequent acetylation of the products is readily accomplished in situ.

Amylose↗
PubMed1986

Influence of organotins on rat platelet aggregation mechanisms.

The effects of ten organotins on rat platelet aggregation mechanisms were examined. Bis(tri-n-butyltin)oxide was the most potent inhibitor of both ADP- and collagen-induced aggregation, and it was the only organotin that directly induced aggregation. It also increased the latent period for induction of aggregation by collagen. Triphenyltin hydroxide was a weak inhibitor of both ADP- and collagen-induced aggregation. However, in contrast to bis(tri-n-butyltin)oxide, it decreased the latent period for collagen-induced aggregation. A similar effect also was observed with diphenyltin dichloride, phenyltin trichloride, and cyhexatin. Tri-n-butyltin chloride and tetra-n-butyltin demonstrated specificity in their action since aggregation induced by ADP but not collagen was inhibited. Tri-n-propyltin chloride, trimethyltin chloride, and fenbutatin oxide were without discernible effect on rat platelet aggregation.

Adenosine Diphosphate↗
PubMed1986

Effect of orally administered dioctyltin dichloride on murine immunocompetence.

The immunotoxicological effects of di(n-octyl)tin dichloride (DOTC) in the mouse were measured using a well-defined system to monitor alterations in immune responsiveness towards both self and heterologous cell membrane components. Oral weekly administration of DOTC caused a suppression of the anti-self erythrocyte antibody response. The humoral response against rat erythrocytes was also diminished. Although humoral responsiveness was affected only at a dose level which caused thymic atrophy (500 mg/kg body wt) the delayed type hypersensitivity reaction to oxazolone, a measure of cell-mediated immunity, was not affected. These data indicate that DOTC can suppress specific aspects of murine immunocompetence and may be relevant in designing studies for assessing possible hazards associated with environmental chemicals.

Administration, Oral↗
PubMed1997

Pancreatic fibrosis in experimental pancreatitis induced by dibutyltin dichloride.

BACKGROUND & AIMS: Regulatory mechanisms in chronic pancreatitis finally resulting in pancreatic fibrosis cannot be studied sufficiently in human pancreas. Results of a new pancreatitis model in rats suitable for investigation of the processes leading to pancreatic fibrosis are presented. METHODS: Experimental pancreatitis was induced by intravenous application of 8 mg/kg body wt dibutyltin dichloride. Pancreatitis was characterized by histology, serum parameters, and immunohistochemistry, detecting inflammatory cells. Gene expression of collagen type I and transforming growth factor beta1 was shown by Northern blot analysis. RESULTS: Dibutyltin dichloride induced an acute edematous pancreatitis within 24 hours. Extensive infiltration with mononuclear cells could be observed after day 7 followed by the development of fibrosis. Parallel to the cell infiltration, an upregulation of messenger RNA-encoding collagen type I and transforming growth factor beta1 could be shown. An active inflammatory process could be shown until the end of the observation period, i.e., 2 months. CONCLUSIONS: The findings suggest that dibutyltin dichloride-induced pancreatitis in rats is suitable to study cellular interactions and mediators involved in the development of pancreatic fibrosis.

Animals↗
PubMed2000

Determination of butyltin and phenyltin species by reversed-phase liquid chromatography and fluorimetric detection.

Chromatographic separation of monobutyltin (MBT), monophenyltin (MPhT), dibutyltin (DBT), diphenyltin (DPhT), tributyltin (TBT) and triphenyltin (TPhT) was studied using end-capped reversed-phases (RP) and methanol-acetic acid-water or acetronitrile-acetic acid-water mixtures as mobile phases. Several RP columns were evaluated, and the effect of acetic acid, oxalic acid, triethylamine, and organic modifier on peak shape and retention was examined. A method based on gradient elution RPLC and fluorimetric detection is proposed for the determination of DBT, DPhT, TBT and TPhT. The sensitivity of the method makes it suitable for environmental analysis.

Chromatography, Liquid↗