Long-term dissolution of mercury from a non-mercury-releasing amalgam.

The hazards of mercury from dental amalgams have long been recognized. This study examined the mercury release from a "non-mercury-releasing" dental amalgam, Composil, over a 104-week period. Four cylindrical specimens were incubated in 10 ml of purified water at 37 degrees C. The incubate was changed at the end of each 24-hour period and assayed for its mercury content at biweekly intervals. Mercury estimation was carried out using cold-vapor, atomic absorption spectrophotometry over a 104-week period. Results showed that the overall mean release of mercury was 43.5 +/- 3.2 micrograms/cm2/24 hr, and the amount of mercury released remained fairly constant during the duration of the experiment. This study showed that Composil releases mercury in quantities that far exceed those detected in other amalgam systems.

Significance of hydrogen ion concentration on the dissolution of mercury from dental amalgam.

The potential risks of mercury dissolution from dental amalgam have long been recognized. This study examined the effect of hydrogen ion concentration on the release of mercury from two dental amalgams: an admixed high-copper amalgam and a new tin- and copper-free amalgam. Specimens of each type of amalgam were incubated citric acid buffer of pH 2.5 or pH 7.0. Results showed that, for both types of amalgam, specimens incubated at pH 2.5 released statistically significantly greater (P less than .0001) quantities of mercury than did specimens incubated at pH 7.0. Release of mercury from the tin- and copper-free amalgam was also statistically significantly greater (P less than .0001) than that of the higher-copper amalgam at both pH levels.

Thermal effect on the dissolution of mercury from two dental amalgams.

Various factors affect dissolution of mercury from dental amalgams. In this study we examined the effect of temperature on the release of mercury from two dental amalgams, namely an admixed high-copper amalgam (Contour) and a new tin- and copper-free amalgam (Composil). Ten cylindrically-shaped specimens of each type of amalgam were used in this investigation, and were divided into two equal groups. The five specimens in each group were each incubated in 10 ml purified water at either 37 degrees C or 60 degrees C, with a change of water every 24 h over an 8-day period. The quantity of mercury released from each amalgam specimen during each incubation period was expressed as micrograms cm-2 24 h-1. The amount of mercury released was estimated by cold-vapour atomic spectrometry. The results demonstrate that specimens incubated at 60 degrees C released significantly larger amounts of mercury than specimens incubated at 37 degrees C for both types of amalgam. The release of mercury by Composil was significantly greater than that by Contour (P less than or equal to 0.0001) for both temperatures studied. Raising the incubation temperature caused a disproportionate increase in mercury release from Composil compared to Contour.

Comparison of release of mercury from three dental amalgams.

Mercury release from dental amalgams has generated considerable concern in recent years and is the subject of this study. Specimens of one admixed high-copper amalgam (Contour), one lathe-cut low-copper amalgam (SDI), and a new tin- and copper-free amalgam claimed to be non-mercury-releasing (Composil) were evaluated for release of mercury when incubated in purified water at 37 degrees C. Measurement of mercury was done by cold-vapor atomic absorption spectrophotometry, and the amount released was expressed as micrograms/cm2/24 hr. Study was conducted over a four-week period. Results show that Contour and SDI released similar insignificant amounts (mean release of less than 0.1 microgram/cm2/24 hr) compared with Composil (mean release of 41.0 micrograms/cm2/24 hr). The difference in release by Composil compared with that by Contour and SDI is highly significant (P less than 0.001). The implications of chronic release of mercury from dental amalgams are discussed. Long-term release studies are in progress.

Absorption of mercuric sulphide following oral administration in mice.

Mercuric sulphide or its counterpart cinnabar occurring in nature has long been associated with Chinese traditional medicine. Because of the reputed insolubility of this compound it has been assumed that it would not be significantly absorbed from the gastrointestinal tract after oral administration. In this study groups of mice were fed a diet containing either mercuric sulphide or cinnabar. Their urine was collected on alternate days for a 1-week period at the end of which they were killed and their livers and kidneys assayed for mercury by atomic absorption spectrophotometry. The mercury contents in their urine and organs were found to be significantly higher compared to control mice (P less than 0.001) indicating that significant absorption of mercury from the gut has occurred.

Economical modification of a radioimmunoassay of digoxin with negligible interference from cord and neonatal sera.

The Amerlex digoxin radioimmunoassay was modified to reduce the running cost by five times. The modified method compared well with the original method (y = 1.0138x + 0.00916, r = 0.9936). Using the modified method, the performance with the American Association for Clinical Chemistry quality control program was consistently satisfactory for 1 year. When normal cord and neonatal sera were tested with the modified method, 41% of the 22 samples of cord serum and 68% of the 19 samples of neonatal serum produced digoxin levels less than or equal to 0.05 ng/ml. The highest digoxin level produced by cord and neonatal sera was 0.3 ng/ml.

Adverse drug reaction reporting in the Singapore General Hospital.

Adverse Drug Reaction reporting was made mandatory in the Singapore General Hospital in January 1978. Reports on a total of 59 patients were received on 34 drugs ranging from antibiotics to Chinese medicine. Antimicrobial drugs topped the list of adverse reactions. The most frequently reported drugs in decreasing order of reports were ampicillin, allopurinol, aspirin compound preparations, cloxacillin, digoxin, streptomycin, penicillins and insulins. Allergies were the most common reactions seen.

Effect of propranolol on the release of choline from guinea-pig small intestine in vitro.

1. Choline was released into the fluid bathing the serosal surface of segments of guinea-pig small intestine. The mean rate of release (nmol choline per cm of intestine per h) in the first hour was 10-2 and in the second hour 8-0. 2. Propranolol 1 mM in the mucosal fluid caused a significant (P less than 0-01) increase in the rate at which choline was released into the serosal fluid. The mean rates were 15-4 and 19-2 for the first and second hour, respectively. 3. It is suggested that the effect of propranolol observed in the present study is likely to be due to a non-specific direct action on biological membranes.

Drug inhibition of anaphylactic histamine release from peritoneal cells of rats infected with Toxocara canis.

An experimental model for studying anaphylactic histamine release from rat peritoneal cells in vitro is described. Rats were sensitized by feeding the infective eggs of ttoxocara canis, the antigen being prepared from the infective eggs. The characteristics of histamine release are comparable with those found for other anaphylactic systems. Addition of 0.2% inactivated normal rat serum to the incubation media reduced the spontaneous histamine release from 11.5 +/- 1.9% to 3.1 +/- 1.6% (mean +/- SD) of total histamine, whereas the corresponding figure for anaphylactic histamine release was 41.3 +/- 19.7%. Both disodium cromoglycate (DSCG) and levamisole produced a dose-related inhibition of histamine release, with DSCG being the more potent drug.

The release of 5-hydroxytryptamine from rabbit small intestine in vitro.

1. A method is described by which the lumen of intestinal segments may be perfused separately and simultaneously under identical conditions of perfusion pressure and temperature, and the rate of appearance of 5-hydroxytryptamine (5-HT) into the serosal fluid measured.2. 5-HT appeared in the serosal fluid from quiescent segments of rabbit intestine at a rate of about 4.0 ng/cm intestine/hr and about 14.0 ng/cm intestine/hr from segments performing active peristaltic movements.3. For both quiescent and active segments, when the perfusion fluid contained a monoamine oxidase inhibitor, nialamide (Niamid), the rate of appearance of 5-HT was increased and if, in addition, 5-HT was present in the perfusion fluid the rate of appearance of 5-HT in the serosal fluid was even greater.4. The rate of appearance of 5-HT from the intestine of rabbits pretreated with reserpine was about 0.8 ng/cm intestine/hr and Niamid only slightly increased this rate. However, if 5-HT as well as Niamid were present the rate of appearance of 5-HT was about 6.0 ng/cm intestine/hr.5. Possible explanations for these findings are discussed.