The concentration of morphine in serum of rats made dependent using a drug-admixed food method.

The present study reports on the induction of physical dependence in rats using morphine-admixed food and addresses the question of the resulting concentration of morphine in serum. The stability of morphine in food is good, since no decrease in concentration could be observed. The concentration of morphine in serum during the experiment was measured using a radioimmunoassay technique. A correlation was found between the food intake during a 7-hour period and the concentration of morphine in the serum at the end of that period, both for a 1 g/kg and a 2 g/kg batch of morphine-admixed food. The concentration of morphine in serum was also found to be dose-related during a period of 6-23 days when the rats were fed for a prolonged period. After long-term administration of 1 g/kg morphine in food a steady-state level of about 0.5 mg/l serum was obtained. Similarly with 2 g/kg morphine in food a steady-state level of 0.8-1.1 mg/l serum was reached. After withdrawal of morphine the serum concentration of morphine dropped to 0.1 mg/l within 24 hours and to below the detection limit within 48 hours. During the withdrawal period sharp drops were noted in body weight (20%) and food intake (50%) after one day.

The influence of sodium bromide in man: a study in human volunteers with special emphasis on the endocrine and the central nervous system.

Sodium bromide was administered orally in capsules to healthy volunteers in doses of 0, 4 or 9 mg Br-/kg/day using a double-blind design. Each treatment was given to seven males for 12 weeks and to seven non-pregnant females (not using oral contraceptives) over three full cycles. Special attention was paid to possible effects on the endocrine and central nervous systems. At the start and end of the study, a full medical history, the results of a physical examination, haematological studies and standard clinical chemistry and urine analyses were recorded for each subject. These showed no changes for individuals following treatment, except for some incidence of nausea associated with bromide-capsule ingestion. Mean plasma-bromide concentrations at the end of treatment were 0.08, 2.14 and 4.30 mmol/litre for males and 0.07, 3.05 and 4.93 mmol/litre for females of the 0-, 4- and 9-mg Br-/kg/day groups, respectively. Plasma half-life was about 10 days. In the females taking 9 mg Br-/kg/day (but in no other group) there was a significant (P less than 0.01) increase in serum thyroxine and triiodothyronine between the start and end of the study but all concentrations remained within normal limits. No changes were observed in serum concentrations of free thyroxine, thyroxine-binding globulin, cortisol, oestradiol, progesterone or testosterone, or of thyrotropin, prolactin, luteinizing hormone (LH) and follicle-stimulating hormone before or after the administration of thyrotropin-releasing hormone and LH-releasing hormone. Analysis of neurophysiological data (EEG and visual evoked response) showed a decrease in delta 1- and delta 2-activities and increases in beta-activities and in mean frequency (Mobility parameter) in the groups on 9 mg Br-/kg/day, but all the findings were within normal limits.

Some characteristics of a new multiple-channel photometer for through-the-plate reading of microplates to be used in enzyme-linked immunosorbent assay.

The performance of a prototype of a now commercially available multiple-channel photometer for high-speed reading of microplates to be used in the enzyme-linked immunosorbent assay was evaluated. For this purpose the extinction of a stable test liquid dispensed in flat-bottomed polystyrene microplates was measured, varying the test volume and the optical density. From the results obtained for dilutions of a single, biolgoically inactive material we concluded that the photometric inaccuracy is negligible when performing enzyme-linked immunosorbent assay with biologically active samples.

Report on results of a collaborative assay of BCG vaccines organized by the International Associaton of Biological Standardization.

In a collaborative assay initiated by the International Association of Biological Standardization 13 laboratories investigated the properties of 10 freeze-dried BCG vaccines made in different ways by different producers which met the requirements of the World Health Organization. The in vitro tests with respect to the dry weight of the bacteria, the number of culturable particles and the stability during storage at 37 degrees C gave results which showed statistically significant differences between vaccines as well as between laboratories. The use of a reference vaccine in the tests for the number of culturable particles did not improve the precision of the results. These tests are useful as in-process tests to assure the producer that his vaccine will consist of the required amount of bacteria of which a high percentage is living. It was found that all vaccines had a survival of more than 25% after 1 month at 37 degrees C with the exception of two vaccines in rubber-stoppered vials. The two in vivo tests, determining skin reactivity in guinea-pigs and multiplication of BCG in spleens of mice, resulted in nearly the same ranking of the vaccines with respect to their virulence, differing from that of the in vitro tests. In the skin reactivity test the simultaneous injection of both the reference vaccine and a test vaccine into the same animal achieved the elimination of the inter-laboratory variation of the results.

Potency testing of killed polio vaccine in rats.

Various laboratory animal species were considered for testing the potency of killed poliovaccine. The rat appeared most suitable for obtaining quantitative information by measuring the titre of the antibody response. There was, in general, a good correlation between antibody response in rats and D-antigen titre. This relationship appeared less clear for heat-degraded or long-stored vaccines.

Proficiency testing of water microbiology laboratories in The Netherlands.

In a 3-year period, four series of simulated water samples containing selected test strains were distributed to more than 50 laboratories in The Netherlands for bacteriological testing. Participating laboratories examined the samples by enrichment or membrane filtration methods, or both, for total coliform organisms, thermotolerant coliform organisms, faecal streptococci and standard plate counts (37 degrees and 22 degrees C) according to Dutch standard methods. The results were quantitatively satisfactory: the distribution of positive and negative results with subsamples conformed to stochastic variation; the standard deviation of membrane or plate counts was usually in the range which may be expected from a Poisson distribution, and there was good correspondence between average counts in participating laboratories and those expected from controls in the organizing laboratory. Problems of a qualitative nature were frequently encountered, however. Among them were a false positive response with a strain of Enterobacter cloacae in the thermotolerant coliform test; a false positive result with Clostridium perfringens in enrichment tests for total or thermotolerant coliform organisms and false positive results with Micrococcus varians in the faecal streptococcus test by membrane filtration. It is concluded that quality assessment should be a consistent activity in water microbiology laboratories. For this purpose, stable and well characterized reference materials are needed.

An investigation of a mouse model to estimate the potency of the diphtheria component in vaccines.

A mouse model to estimate the potency of the diphtheria toxoid components in vaccines using Vero cells to detect the neutralizing antibodies in the sera from immunized mice is described. The results obtained with this mouse model correlated significantly with those obtained in the lethal challenge test in guinea-pigs. For this reason it is suggested that the potency test in guinea-pigs be replaced by this mouse model because a considerable reduction in the number of animals used and costs can be achieved by the introduction of this mouse test for the routine control of the potency of the diphtheria component of vaccines.

A mouse model to estimate the potency of the diphtheria component in combined vaccines.

A mouse model is presented to estimate the potency of the diphtheria component in combined vaccines. In addition, a simplified mouse test is suggested for routine potency control of diphtheria. It will be important to discuss this approach to replace the lethal challenge test in guinea pigs.