Biomedical subjects

J GULD

Publications and source records attributed to J GULD.

13 recordsLinked to original sources

PubMed1958

Stability of purified tuberculin in high dilution.

The authors have investigated the effect of storage on the potency of 5 TU dilutions (5 TU per 0.1 ml) of the purified tuberculin RT 19-21 (Statens Seruminstitut, Copenhagen).Dilutions stored at 2-4 degrees C, 20 degrees C and 37 degrees C for different periods up to 18 months were compared by intradermal testing. About 900 BCG-vaccinated schoolchildren were given duplicate tests and in addition 500 tests were made in BCG-vaccinated guinea-pigs.The results showed unexpected variability. It appeared that this variability was due to unsystematic variations in potency both between dilutions prepared at different times and between ampoules of the same dilution.Because of this variability only limited conclusions could be drawn. At 2-4 degrees C the effect of storage seemed to be very slight, the potency of the dilutions being reduced by less than 25% after 18 months. At the higher temperatures, the decrease in activity was more rapid. Nevertheless, the dilutions could be stored at room temperature (20 degrees C) for some months without any practically significant loss of potency.

Guinea Pigs↗

PubMed1958

Adsorption of tuberculin to glass.

Dilutions of the purified tuberculin RT 19-21 (Statens Seruminstitut, Copenhagen) have been found to be subject to unsystematic variations in potency. Preliminary investigations suggested that adsorption of tuberculin on to the container might be the cause. This possibility has been further explored in a series of experiments on guinea-pigs that is reported in the present paper.IT IS DEMONSTRATED THAT TUBERCULIN IS, IN FACT, ADSORBED TO THE GLASS SURFACE OF THE CONTAINER: tuberculin-active eluates are obtained from ampoules previously used for tuberculin, with a buffer eluant containing Tween 80.Estimates indicate that a 5 TU dilution of RT 19-21 (prepared to contain 5 TU or 0.0001 mg per 0.1 ml) loses on an average 60% of its active substance through adsorption. The amount adsorbed differs from one ampoule to another, and a negative correlation is observed between the potency of the original contents of the ampoule and the potency of the eluate obtained when the ampoule is refilled with Tween 80 eluant.The extent of adsorption depends on the strength of the dilution, the temperature, and the duration and extent of contact between dilution and container. Another observation is that shaking of the ampoule reduces adsorption.There are indications that the purified tuberculin RT 19-21 is composed of at least two fractions of different adsorbability.It is pointed out that the accuracy of tuberculin testing would be markedly increased if adsorption from the tuberculin dilutions could be prevented.

Adsorption↗

PubMed1958

Diluents for stabilization of tuberculin.

Tuberculin is known to be adsorbed to containers and syringes. In the present paper, the adsorption which takes place in the ampoules has been studied in relation to the diluent for the tuberculin.Adsorption was most evident in dilutions prepared with saline or with phosphate buffer containing dextran. The inclusion in phosphate buffer diluent of small amounts of proteins or synthetic surface-active agents decreased or prevented adsorption. A boric-acid sodium-borate diluent containing gum arabic, previously recommended for the preparation of stabilized tuberculin dilutions, was found to be ineffective.The most suitable diluent for the preparation of stable tuberculin dilutions was a 0.05 per thousand solution of Tween 80 in phosphate-buffered saline; this diluent appeared to prevent adsorption under a variety of experimental conditions.The inclusion of Tween 80 in the diluent had little or no effect on the general storage stability of purified tuberculin.Sensitization experiments in guinea-pigs, rabbits and humans showed that no sensitization against Tween 80 need be feared when a 0.05 per thousand solution of Tween 80 in phosphate buffered saline is used in the preparation of tuberculin dilutions.

Guinea Pigs↗

PubMed1958

Standardization of a new batch of purified tuberculin (PPD) intended for international use.

A new batch of PPD tuberculin, RT 23, prepared at the request of UNICEF by the Statens Seruminstitut, Copenhagen, has been compared with previous batches of tuberculin from the Statens Seruminstitut and with the International Standard for the Purified Protein Derivative of Mammalian Tuberculin. The comparisons were made by intradermal tuberculin testing. The majority of tests were carried out in human subjects with various types and levels of tuberculin sensitivity-namely, tuberculous patients in the Netherlands; BCG-vaccinated as well as spontaneously tuberculin-sensitive army recruits in the Netherlands; BCG-vaccinated schoolchildren in Denmark; population groups in the tropics (Mauritius and Nigeria) including a high proportion of persons with low-grade sensitivity. In addition, comparisons were made in guinea-pigs sensitized in different ways.For these comparisons, RT 23 was diluted both with phosphate-buffered saline alone (as were the other preparations) and with phosphate-buffered saline containing 0.05 per thousand Tween 80 as a stabilizing agent.The results were found to differe significantly with the type and level of sensitivity of the groups tested. Thus, while the potency ratio of RT 23 and the International Standard is about 2:1 in BCG-vaccinated persons, it is about 1:1 in persons with naturally acquired tuberculin sensitivity. RT 23 in diluent containing Tween 80 elicited larger reactions than did RT 23 in ordinary diluent; however, when reactions of the same size were compared, a difference in character was observed: the reactions to RT 23 diluted with Tween 80 were softer and less frequently bullous.On the basis of the results-in terms of reaction size-obtained in patients and in non-vaccinated recruits, it is suggested that one unit of RT 23 should be defined as 0.02 mug of the dry substance; for use as a first or single dose in routine testing, 0.02 mug of RT 23 in diluent stabilized with Tween 80, or 0.06 mug in diluent without Tween 80, is recommended.

Aged↗

PubMed1957

Interpretation of tuberculin reactions in populations with a high proportion of BCG-vaccinated persons.

In recent years there has been an apparent increase in the frequency with which inconsistent results are obtained in the routine tuberculin-testing carried out at the Central Tuberculosis Dispensary in Copenhagen. The author describes an investigation which was undertaken to find out the cause of these conflicting results. In this study, about a thousand non-tuberculous people, many of whom had previously been vaccinated with BCG, were tested by one of two different techniques. In another similar group of people, 300 tuberculin reactions were each read independently by three nurses.The pattern of tuberculin sensitivity observed among the nonvaccinated differed from that observed among the vaccinated. Whereas the reactions of the former could, with fair accuracy, be classified as "positive" or "negative" according to their size, those of the latter showed a unimodal distribution by size, so that any such classification was necessarily arbitrary. Moreover, it was found that many of the vaccinated individuals tended to give positive and negative reactions alternately to successive tests, owing to random variations in the testing techniques.The author concludes that it is impracticable to divide BCG-vaccinated people into "positives" and "negatives", and draws a parallel with populations in tropical countries, where the presence of "non-specific" sensitivity renders tuberculin-testing unreliable as a diagnostic tool.

BCG Vaccine↗

PubMed1956