Sodium iodide symporter (NIS) gene expression in human placenta

The placenta must allow the passage of iodide from the maternal to the fetal circulation for synthesis of thyroxine by the fetal thyroid. The thyroid sodium iodide symporter (NIS) was cloned in 1996 and, although widely distributed among epithelial tissues, early studies failed to detect it in placenta. We demonstrated NIS mRNA in human placenta and in the human choriocarcinoma cell line, JAr. NIS protein was localized to trophoblasts, with a tendency to apical distribution, in sections of human placenta immunostained with a monoclonal antibody against hNIS. We conclude that NIS is expressed in placenta and may mediate placental iodide transport. (C) 2001 Harcourt Publishers Ltd.

Slowed conduction and ventricular tachycardia after targeted disruption of the cardiac sodium channel gene Scn5a

Voltage-gated sodium channels drive the initial depolarization phase of the cardiac action potential and therefore critically determine conduction of excitation through the heart. In patients, deletions or loss-of-function mutations of the cardiac sodium channel gene, SCN5A, have been associated with a wide range of arrhythmias including bradycardia (heart rate slowing), atrioventricular conduction delay, and ventricular fibrillation. The pathophysiological basis of these clinical conditions is unresolved. Here we show that disruption of the mouse cardiac sodium channel gene, Scn5a, causes intrauterine lethality in homozygotes with severe defects in ventricular morphogenesis whereas heterozygotes show normal survival. Whole-cell patch clamp analyses of isolated ventricular myocytes from adult Scn5a(+/-) mice demonstrate a approximate to50% reduction in sodium conductance. Scn5a(+/-) hearts have several defects including impaired atrioventricular conduction, delayed intramyocardial conduction, increased ventricular refractoriness, and ventricular tachycardia with characteristics of reentrant excitation. These findings reconcile reduced activity of the cardiac sodium channel leading to slowed conduction with several apparently diverse clinical phenotypes, providing a model for the detailed analysis of the pathophysiology of arrhythmias.

The effect of sodium chloride supplementation on the milk production of grazing Holstein Friesian cows during summer and autumn in a humid sub-tropical environment

Two studies were conducted to examine the effects of including NaCl at various rates in grain-based supplements for Friesian cows grazing established, dominant (>90%), rainfed kikuyu (Pennisetum clandestinum cv. Common) pastures during summer and autumn in a humid sub-tropical environment. In study 1 (19 January-27 March 1998), 48 cows (36 multiparous, 12 primiparous; 27-96 days postpartum) were allocated to one of four groups based on genetic merit, milk production, liveweight (LW) and days postpartum. They were fed (2.7 kg dry matter (DM) per cow, twice-a-day) one of four isoenergetic and isonitrogenous barley grain-based concentrates containing NaCl at concentrations (% as-fed) of either 0 (SC1), 1.1 (SC2), 2.2 (SC3) or 3.3 (SC4). Maximum temperature humidity index (THImax) was greater than or equal to78 during 50% of the experimental period. Concentrate NaCl content had no effect (P>0.05) on daily milk yield or LW change but daily yields of 4% fat corrected milk (FCM), fat and protein were higher (P0.05) among treatments at 7.6+/-1.24 kg DM per cow. In study 2 (18 January 1999-1 March 1999), 48 cows (32 pluriparous, 16 primiparous: 32-160 days postpartum) were fed (2.7 kg DM per cow twice-a-day) one of two isoenergetic and isonitrogenous barley grain-based concentrates containing NaCl at concentrations (% as-fed) of 0 (control) or 2.2 (HSC). THImax was greater than or equal to78 during 34% of days in the experimental period. Yields of milk, FCM, fat and protein were lower (P0.05) by concentrate NaCl content. These studies indicate that NaCl supplementation can be beneficial in terms of milk production during warm, humid conditions as opposed to milder conditions. (C) 2002 Elsevier Science B.V. All rights reserved.

Transcriptional regulation of the sodium-sulfate cotransporter NaSi-1 gene

Inorganic sulfate is one of the most abundant anions in mammalian plasma and is essential for proper cell growth and development, as well as detoxification and activation of many biological compounds. To date, little is understood how physiological levels of sulfate are maintained in the body. Our studies, and of others, have identified the NAS(i)-1 protein to be a functional sulfate transporter in the kidney and intestine, and due to this localization, constitutes a strong candidate gene for maintaining body sulfate homeostasis. Several factors, including hormones and metabolic conditions, have been shown to alter NAS(i)-1 mRNA and protein levels in vivo. In this study, we describe the transcriptional regulation of NaSi-1, with a focus on the mouse NaSi-1 gene (Nas1) that was recently cloned in our laboratory. Vitamin D (1,25-(OH)(2)D-3) and thyroid hormone (T-3) led to an increase in Nas1 promoter activity in OK cells. Mutational analysis of the Nas1 promoter resulted in identification of a direct repeat 6-type vitamin-D-responsive element (DR6 VDRE) at -525 to -508 and an imperfect inverted repeat 0-type T-3 responsive element (IRO T3RE) at -426 to -425 which conferred 1,25-(OH)(2)D-3 and T-3 responsiveness respectively. These findings suggest for vitamin D and thyroid hormone regulation of NaSi-1, may provide important clues to the physiological control of sulfate homeostasis.

A survey of sodium hypochlorite use by general dental practitioners and endodontists in Australia

Background: Sodium hypochlorite is used commonly as an endodontic irrigant, but there are no published reports that provide details of its use. This survey sought to determine the percentage of Australian dentists who practiced endodontics, whether they used sodium hypochlorite for irrigation, and the manner of dilution, storage and dispensing sodium hypochlorite used by both dentists and endodontists. Methods: All Australian endodontists and a stratified random sample of 200 general dentists in Australia were surveyed to address the issues identified above. Results: Almost 98 per cent of dentists surveyed performed endodontic treatment. Among endodontists, nearly 94 per cent used sodium hypochlorite for irrigation compared with just under 75 per cent of general dentists: Sodium hypochlorite use by general dentists was more common in Victoria and South Australia than in other States. An infant sanitizer (Milton or Johnson's Antibacterial Solution) was used by just over 92 per cent of general practitioners and by more than 67 per cent of endodontists. All other respondents used domestic bleach. One hundred and sixty four of the respondents (80 per cent of endodontists and over 90 per cent of general dentists) used a 1 per cent w/v solution. Ten practitioners used a 4 per cent w/v solution, five used a 2 per cent w/v solution and four used a 1.5 per cent w/v solution. Eighty per cent of the practitioners who diluted their sodium hypochlorite before use, used demineralized water for this purpose. The remainder used tap water. Only four practitioners stored sodium hypochlorite in a manner which risked light exposure and loss of available chlorine content. Conclusions: Sodium hypochlorite is commonly used as an endodontic irrigant and Australian dentists generally stored the material correctly.

Synthesis and complexation properties of some novel lariat-crown ethers

Several new lariat-crown ethers bearing either bridged bisdioxine or tetraoxaadamantane units as chiral substituents are prepared by reacting the corresponding amino-crown ether derivatives with the dimeric alpha-oxoketene, the latter obtained by flash vacuum pyrolysis of a furan-2,3-dione precursor. Complexation properties towards differently charged metal ions are investigated by H-1 NMR titration to obtain complexation constants (K-c-values for potassium/ sodium rhodanides: 480-1100 mol dm(-3)), as well as extraction experiments to explore the metal ion transportation abilities of the new lariat crown derivatives. In particular, a significantly increased ability to transport metal ions from water into chloroform was found with spherical tetraoxaadamantyl derivatives when compared with the free amino-benzocrown ethers.

Functionalized macrocyclic compounds: potential sensors of small molecules and ions

The potential applications of macrocycles in chemistry and at its interfaces with biology and physics continue to emerge, one of which is as receptors for small molecules and ions. This review illustrates these applications with examples from the last ten years employing complexation as the binding mechanism; some of the systems presented have already found real-world sensor applications. In any case, the challenges remain to design more selective and sensitive receptors for guests.

Sensitivity of Helicoverpa armigera nucleopolyhedrovirus polyhedra to sodium dodecyl sulfate

Sodium dodecyl sulfate (SDS) is commonly used to extract polyhedra from infected cells and diseased dead larval tissues. It was found, however, that 80% of Helicoverpa armigera nucleopolyhedrovirus (HaSNPV) polyhedra produced via cell culture were damaged after 30 min of 0.5% SDS treatment whereas only 20% of in vivo produced polyhedra were damaged by the same treatment. Transmission and scanning electron microscopy revealed that the damaged polyhedra had lost their polyhedron envelopes and virions were dislodged from the polyhedrin matrix, leaving empty spaces that were previously occupied by the occluded virions. Up to 20% in vitro produced polyhedra were resistant to SDS and remained intact, even after a 24 h exposure to SDS. This sensitivity to SDS was observed across a range of cell culture media, including serum supplemented media. Electron microscopy also revealed that the inferior polyhedron envelope of in vitro produced polyhedra is likely due to poor interaction between the polyhedron envelope, polyhedron envelope protein (PEP), and polyhedrin matrix. The PEP gene was cloned and sequenced and mutations in this gene were ruled out as an explanation. In vitro produced polyhedra that were passed through insect larva once were resistant to SDS, indicating that a critical component is lacking in insect cell culture medium used for producing HaSNPV or the cells growing in culture are inefficient in some ways in relation to production of polyhedra. (C) 2002 Elsevier Science (USA). All rights reserved.