NO2-/NO3- levels in blood and principal organs in rats treated with lipopolysaccharide

It is well revealed that activation of macrophages stimulated by endotoxin resulted in induction of nitric oxide synthase which catalyze nitric oxide (NO) formation from L-arginine. Consequently, blood concentrations of NO2-/NO3- (NOx-) are shown to increase. We studied on pharmaco/toxicokinetics of NOx- in serum and principal organs in Wistar male rats after i.p. administrations of LPS and NaNO3. The serum levels of NOx- at 1 h and 6 h after nitrate administration (10 mg/kg, i.p.) were 240 and 120 microM, respectively. Tissue levels of NOx- in lung, liver and kidneys were ca.1/2 of the serum level. Those levels in spleen and brain were ca.1/4 and 1/10 of the serum level, respectively. The correlation of NOx- levels in serum and these 5 organ tissues between 1 h and 6 h after administration of nitrate was r = 0.992 suggesting no specific accumulation of NOx- in these organs. The serum level of NOx- at 18 h after LPS treatment (1 mg/kg, i.p.) was 430 microM. The correlation of NOx- levels in serum and 5 organ tissues between LPS and nitrate administrations was shown to be r = 0.851. NOx- levels of serum, lung, kidneys and brain showed good correlation but liver and spleen showed out of the correlation. The liver tissue level of NOx- after LPS treatment was low compared with the expected value from the serum level. The reason may be explained partially by the liver weight increase and the liver toxicity with increased GPT and gamma-GT levels due to LPS. Contrary to this, NOx- level of spleen tissue after LPS treatment was more than 2-fold compared with the expected value from the serum level suggesting NO formation in the spleen. This was supported by the markedly high concentration (73.2 nmol/g tissue) of NO2- in the spleen tissue. NO2- levels in lung (34.5 nmol/g tissue) and brain (14.3) were also found to be significantly high after stimulation with LPS suggesting NO formation in these organs. Increased formation of NO2- in these organs by LPS stimulation suggests the formation of active nitrogen oxides such as N2O3 which is an effective nitrosating agent in non-acidic conditions in vivo.     

Degradation patterns of different adhesives and bonding procedures

Various types of resin adhesives and procedures are available in the clinical field, so comprehensive understanding of degradation is required for each material and bonding procedure. The objective of this study was to investigate the bond durability for different adhesives and bonding procedures. Resin-dentin bonded beams were prepared with the use of two adhesives (One-Up Bond F/self-etching primer system and One Bond/total-etch adhesive) and two experimental groups for the bonding procedure (wet and dry bonding of the total-etch adhesive). Those samples were soaked in water for 24 h(control), 6 and 12 months. After the water immersion, the bond strengths were measured by the microtensile bond test, and subsequently fractography was performed with the use of SEM. Statistically significant reduction of the bond strength (p < 0.05) was apparent after 12 months of water exposure in the range 22-48% of the control. The bonding resin was eluted from the hybrid layer of the self-etching and the total-etch adhesives for the wet bonding. Micromorphological alterations were found due to the hydrolysis of collagen fibrils with the total-etch adhesive for the dry bonding mode. These pathologic alterations were in accord with the bond strength.     

Solute composition and heat shock proteins in rat renal medulla

 The high content of heat shock proteins (HSPs) 25 and 72 in the hyperosmotic inner medulla of the concentrating kidney has been ascribed to the high NaCl and urea concentrations in this kidney zone. To assess the effects of variations in the composition of solutes in the renal medulla on the intrarenal distribution of HSPs, rats were fed either a high- or low-Na diet for 3 weeks. These diets result in greatly differing urine and inner medullary solute composition. Sodium dodecyl sulphate polyacrylamide gel electrophoresis and Western blot techniques were used to analyse HSP25 and HSP72 in the cortex, outer medulla and inner medulla. In addition, the amounts of organic osmolytes (sorbitol, myo-inositol, betaine and glycerophosphorylcholine) and urea in the tissue were determined by high-performance liquid chromatography. Intra- and extracellular electrolyte concentrations at the papillary tip were measured by electron microprobe analysis. In the high-Na group, urine osmolality was about 1000 mosmol/kg lower than in rats fed a low-Na diet, due to lower urea concentrations. The sum of urine sodium and potassium concentrations, however, did not differ between the two groups. Neither in the outer nor in the inner medulla was the sum of the concentrations of organic osmolytes affected by the dietary treatment. The sum of sodium, potassium and chloride concentrations did not differ between the two experimental groups, neither in the interstitial nor in the intracellular compartments. However, the urea content and the amounts of HSP25 and HSP72 were significantly lower in the inner medulla of the group of rats fed a high-Na diet. Our results suggest that urea participates in the regulation of the medullary levels of the HSPs and that both HSP25 and HSP72 are components of mechanisms protecting medullary cells against the deleterious effects of high urea concentrations. Received: 30 September 1996 / Received after revision: 30 December 1997 / Accepted: 21 January 1997