Fluoride alters type I collagen expression in the early stages of odontogenesis.

Fluoride alters the expression and post-translational modifications of extracellular matrix proteins in dentin. The aim of our study was to determine the effects of fluoride on type I collagen expression during the early stages of tooth germ development in rats. Pregnant dams were divided into three groups and fed a standard diet. From the fifth day of pregnancy the three groups received tap water with, respectively, trace amounts of fluoride (C), a low fluoride concentration (FL) or and a high fluoride concentration (FH). Changes in type I collagen expression and distribution were evaluated. The expression of type I collagen was restricted to the extracellular spaces of cells of mesenchymal origin. In the youngest animals the most intense immunoreactivity for type I collagen was detected in predentin of the FL group. Although the intensity of immunostaining increased in proportion to the age of the animals, the largest increase in the groups investigated was detected in the FL group. We concluded that a low concentration of fluoride can act as a stimulator of type I collagen deposition in the extracellular matrix of dentin, while high concentrations of fluoride have an opposite effect, acting as an inhibitor of type I collagen formation in dentin.

Methacrylate uptake by isolated hepatocytes and perfused rat liver.

I showed recently (Int. J. Biochem. Cell Biol. 27, 1311-1316, 1995) that methacrylate formed in vivo from methyl methacrylate (a basic component of polymer used in medicine and industry) is very efficiently removed from the blood. To resolve whether the liver is responsible for methacrylate elimination from the blood, methacrylate uptake by isolated hepatocytes and by perfused liver was investigated. For comparative purposes methacrylate uptake by perfused heart was also examined. It has been found that methacrylate is eliminated efficiently both by isolated hepatocytes and by perfused liver. The whole liver eliminated more than 100-fold of this compound compared to the whole heart. If the rate of methacrylate uptake was calculated per gram of tissue, the liver was 10 times more effective than the heart. KCN (2 mM) addition inhibited methacrylate uptake both by the liver and the heart by approximately 40% at 20 min of perfusion. Pretreatment of rats with galactosamine, which causes liver damage, resulted in a significant inhibition of methacrylate uptake. The data presented in this paper suggest that the liver plays a central role in the methacrylate elimination from the blood. From the results published recently and presented in this paper one can conclude that the relatively low toxicity of orally administered methyl methacrylate is the consequence of a rapid ester hydrolysis with the subsequent elimination of methacrylate by the liver. The toxicity of methacrylate (especially towards organs other than the liver) could be increased under conditions leading to liver damage.

Effect of methyl methacrylate on mitochondrial function and structure.

1. Treatment of isolated rat liver mitochondria with methyl methacrylate (MM) produced membrane disruption as evidenced by the release of citrate synthase, and changes in the ultrastructure of mitochondria. 2. At concentration 0.1%, MM uncoupled oxidative phosphorylation as evidenced by stimulation of state 4 respiration supported either by pyruvate plus malate or succinate (+rotenone) and ATP-ase activity in intact mitochondria. 3. At concentration 1% MM stimulated ATP-ase activity in intact mitochondria and succinate (+ rotenone) oxidation at state 4 and was without effect on this substrate oxidation at state 3. 4. MM inhibited pyruvate plus malate oxidation either at state 3 or in the presence of uncoupling agents. 5. MM inhibited the NADH oxidase of electron transport particles at a concentration which failed to inhibit either succinic oxidase or the NADH-ferricyanide reductase activity. 6. The data presented suggest that in the isolated mitochondria MM inhibits NADH oxidation in the vicinity of the rotenone sensitive site of complex I. 7. The general conclusion is that MM may block an electron transport and to uncouple oxidative phosphorylation in rat liver mitochondria. The overall in vitro effect would be to prevent ATP synthesis which could result in cell death under in vivo conditions.

High performance liquid chromatographic determination of methacrylate in blood serum.

Methacrylic acid is a hydrolytic breakdown product of methylmethacrylate which is widely used in orthopaedic surgery, dentistry and in the chemical industry for fabrication of acrylic resins. Information on the toxicity of methacrylic acid and its metabolism is limited. To facilitate studies in this field we developed a liquid chromatographic procedure allowing determination of methacrylate in blood serum. The procedure was based on reversed-phase HPLC using a gradient elution with UV detection at 210 or 240 nm. The method was linear up to 5 mM concentration with a detection limit of 0.5 microM. The procedure was applied to determination of methacrylate in rat blood serum after administration of sodium methacrylate solution into the stomach. A peak of this compound was demonstrated in the chromatogram 10 min after administration which disappeared after 60 min, confirming suitability of the method for biological applications.

Phosphate-dependent glutaminase of rat skeletal muscle. Some properties and possible role in glutamine metabolism.

A relatively high activity (26.7 nmol/min per mg mitochondrial protein) of phosphate-dependent glutaminase (EC 3.5.1.2; L-glutamine amidohydrolase) was found in rat skeletal muscle (mixed type from hindlegs) mitochondria incubated in 200 mM potassium phosphate (pH 8.2); the activity was lower in rat heart and diaphragm mitochondria. Phosphate-dependent glutaminase was also found in human skeletal muscle mitochondria, but the activity was about 3-5 times lower than in rat skeletal muscle. Multiplying the specific activity of mitochondrial glutaminase by the amount of mitochondrial protein present in 1 g of rat skeletal muscle the maximum glutaminase activity was found to be 0.352 mumol/min per g wet tissue. The rat skeletal muscle enzyme appears to be similar in many respects to phosphate-dependent glutaminase of the kidney (e.g., S0.5 for glutamine, K0.5 for phosphate, the pH activity profile, inhibition by glutamate). These properties make the skeletal muscle enzyme very similar to the 'kidney type' glutaminase isoenzyme of rat tissues. A significant difference between rat kidney and skeletal muscle enzymes is their adaptive response during acidosis. While the kidney enzyme increases during acidosis, the skeletal muscle glutaminase activity does not. A possible role of glutaminase in the glutamine metabolism in rat skeletal muscle is discussed.

[Selected cases of prosthetic treatment in patients with lowered height of the occlusion]. / Wybrane przypadki leczenia protetycznego pacjentów z obnizona wysokoscia zwarcia.

In the paper three selected cases that illustrate comprehensive prosthetic treatment in which modern methods and prosthetic materials have been used non-conventional composed bridges with partial crowns on abutment teeth sealed with composites in patients with deep bite are reported. For facing the crowns and bridges such materials as Izosit, porcelain, acryl-derived material--Colorstat which is superior to acrylate considering its physicochemical properties have been used. For the reconstruction of the patients, own teeth Izofil adhesive material has been used for capping the teeth partly or totally establishing a new occlusal situation in anterior and lateral segments.

Deamination of adenosine 5'-phosphate and adenosine as a possible source of ammonia in human and bovine parotid glands.

1. The liberation of ammonia from adenosine 5'-phosphate (AMP) and adenosine and the release of inorganic phosphate from AMP were investigated in homogenates of bovine and human parotid glands. 2. Adenosine phosphate deaminase (AMP deaminase) was purified from bovine and human parotid glands. The enzyme preparations obtained were free from adenosine deaminase and 5'-nucleotidase activities. 3. AMP incubated with human parotid gland homogenate produced inosine 5'-phosphate, adenosine, inosine and ammonia. The amount of ammonia accumulating in the incubation mixture was equal to the sum of inosine 5'-phosphate plus inosine. 4. These results demonstrate the presence in human parotid of AMP deaminase and adenosine deaminase.