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Biomedical subjects

B Grab

Publications and source records attributed to B Grab.

At least 55 records · Page 3Linked to original sources
PubMed1974

A simple epidemiological model for evaluating the malaria inoculation rate and the risk of infection in infants.

A simple epidemiological model for evaluating the malaria inoculation rate and the risk of infection in infants was applied to describe the disease picture in an area of East Africa. Fairly good agreement was noted between the actual and expected curves of disease acquisition; this model could therefore be used for simulating epidemiological processes. Entomological and parasitological inoculation rates were compared by means of different approaches. As a result, it was possible to calculate the factor of proportionality defined as the proportion of anophelines having in their glands sporozoites that are actually infective.

Animals↗
PubMed1973

The second international standard for polymyxin B.

Since supplies of the first International Standard for Polymyxin B were exhausted, it was replaced by a second international standard the potency of which was estimated from the results of a collaborative assay carried out by 5 laboratories in 4 countries. The wide variations in the results probably resulted from difficulties experienced in handling the first international standard. The potency finally agreed upon by the collaborating laboratories, on the basis of the overall mean values obtained after rejection of the most discrepant assays, was 8 403 IU/mg. That value was accepted by the WHO Expert Committee on Biological Standardization (1970), which consequently defined the International Unit of polymyxin B as the activity contained in 0.000119 mg of the second international standard.

International Cooperation↗
PubMed1973

The international standard for colistin.

An International Standard for Colistin has been established and the International Unit defined as the activity contained in 0.00004878 mg of this preparation. The unit was defined on the basis of a collaborative assay in which nine laboratories from six different countries participated. The material used to prepare the international standard had been manufactured in Japan; it was shown to have a composition similar to that of material produced in Europe and to be suitable for the assay of colistin from the existing sources of manufacture.

Colistin↗
PubMed1973

The international reference preparation of colistin methane sulfonate.

The international unit of colistin methane sulfonate has been defined by collaborative assay as the activity contained in 0.00007874 mg of the international reference preparation. The definition was based on results from 7 laboratories in 5 countries which carried out assays against their existing national standards. Because of the complex heterogeneity in composition of this antibiotic the international reference preparation was not designated as an international standard.

Colistin↗
PubMed1972

Methods for the surveillance of endemic treponematoses and sero-immunological investigations of "disappearing" disease.

Although the treatment of whole communities with long-acting penicillin for the control of endemic treponematoses of childhood during the past twenty years has led to a remarkable initial regression of disease, early clinical yaws has not yet been eliminated in large endemic areas and the elimination of early childhood syphilis has been observed in favourable environmental conditions in a single instance only. In most areas, transmission of infection continues at varying levels and recrudescence or periodic focal outbreaks continue to occur.Mass penicillin campaigns have been undertaken in 46 countries and up to the end of 1970 some 160 million people had been examined and some 50 million clinical cases, latent cases, and contacts had been treated. In the past few years, sero-epidemiological studies of the changing pattern of disease and infection have become possible and methods for long-term surveillance of endemic treponematoses have been developed. The application of these methods to the study of "disappearing" disease is described, particularly with regard to yaws but also to childhood syphilis and pinta.

Adolescent↗
PubMed1972

An international reference preparation for human serum immunoglobulins G, A and M: content of immunoglobulins by weight.

An International Reference Preparation for Human Serum Immunoglobulins G, A, and M has been established by the World Health Organization and international units have been assigned to it. This paper describes international collaborative assays carried out by 10 specialized laboratories, which attempted to define the immunoglobulin contents of the International Reference Preparation by weight. For all immunoglobulins the estimates of contents by weight were imprecise, largely owing to heterogeneity of estimates between laboratories. Mean estimates of immunoglobulin contents by weight are given, but it is considered that the results of assays of immunoglobulin against the International Reference Preparation or related preparations are more precisely expressed in terms of international units.

Europe↗
PubMed1971

Epidemiological model of typhoid fever and its use in the planning and evaluation of antityphoid immunization and sanitation programmes.

An epidemiological model has been constructed for typhoid fever in a stable population in order to study the transmission of infection at different levels of endemicity. It involves a number of parameters representing the proportions of epidemiological subgroups in the population-such as the susceptible, the infected, and the immune-and rates of transition between the groups. Numerical values based on available evidence were assigned to the parameters, to provide a realistic simulation of stable endemicity.Changes were then introduced in the values of some of the parameters in order to study the consequences of mass vaccination and improvements in general health conditions and sanitation, in particular on the incidence of disease.The model shows that a single mass vaccination reduces the incidence of disease considerably, but the gain is largely lost after a few years. Repeated vaccinations at 5-year intervals will produce further decreases in incidence, though the additional gain becomes smaller at each consecutive vaccination.The model was also used to estimate the possible effect of improvements in sanitation. The incidence decreases to a new level of stability when the transmission of the infection is reduced because of improved sanitation. The effect of sanitation is long-lasting and in this respect gives better results than vaccination.The simultaneous application of mass vaccination and sanitation gives a cumulative effect, which in some cases tends to be close to the effect of sanitation alone.The model was used to forecast the probable effect of preventive measures against typhoid fever, such as mass immunization and sanitation programmes, on a selected population in terms of prevention of disease, as well as in terms of relative costs and benefits. It provides a useful guide for the rational use of funds and the facilities to be set aside for typhoid fever control purposes.Other possible uses of the model are briefly discussed.The need to adjust the model in relation to specific conditions in the community is stressed, as is the need to readjust it to take into account changes in the pattern of life and the natural history of typhoid fever.

Communicable Disease Control↗
PubMed1970

A research standard for human serum immunoglobulins IgG, IgA and IgM.

A pooled human serum, partly diluted, has been distributed into ampoules and freeze-dried in several batches. The freeze-dried material has been examined in an international collaborative assay and certain properties have also been estimated in individual laboratories.On the basis of these tests this material was considered to be suitable for use as a standard for the estimation of IgG, IgA and IgM for clinical purposes using the single-radial-diffusion or similar techniques. Greater uniformity of results than is obtained at present should be achieved if this material were in general use.Estimates of immunoglobulins from different laboratories using this material as a standard showed small but significant variability. This variability was probably related to the heterogeneity of immunoglobulins and of antisera, and it limits the precision of immunoglobulin estimations by techniques at present in use.Batches of this material have been distributed to various centres. 67/68 has been established as the British research standard for human serum immunoglobulins IgG, IgA and IgM for which the unit of potency is defined as the activity present in 0.8147 mg of dry powder. The average activity per ampoule of 67/86 is 100 units of IgG, IgA and IgM. The average activities of other related preparations have been estimated.

Animals↗
PubMed1967

Dispersion studies of Culex pipiens fatigans tagged with 32P in the Kemmendine area of Rangoon, Burma.

The flight range and the dispersion of a vector are important factors when control or eradication measures are being considered and when general biological information is desired. The present work on Culex pipiens fatigans was carried out under conditions where breeding is intensive and housing congested. The radioactive tagging method adopted seemed to be harmless to the mosquito and gave excellent results.Radioactive adults emerging under normal conditions from larvae collected in the centre of the Kemmendine Experimental Area did not appear to differ in flight behaviour from radioactive adults released at one time in the centre. Mosquitos of both sexes dispersed fairly evenly in all directions from the release point; this fact is likely to be of practical value in control and biological experiments. Some mosquitos even crossed a river over one-third of a mile (500 m) wide and specimens were collected by hand more than (1/2) mile (800 m) from the release point without the use of lures or traps.The method also yielded valuable data on the daily mortality of adults and on the total mosquito population in the area. There seems little doubt that the radioisotope tagging technique can be a most valuable weapon in the hands of the biologist or epidemiologist.

Animals↗
PubMed1967

Evaluation of Wuchereria bancrofti infection in Culex pipiens fatigans in Rangoon, Burma.

In the past, several indices have been proposed to evaluate the threat of vectors to the community. Such indices, if accurately determined, could serve to assess the effectiveness of vector control campaigns. In this paper, a "risk of infection" index is introduced for the case of urban filariasis transmitted by Culex pipiens fatigans in Rangoon, Burma. This index is directly proportional to the three principal parameters that determine the extent of transmission-namely, the biting density of the vector, the proportion parous to total biting, and the proportion infective to total parous; all these parameters are easily determined from biting catches. Examples of the use of the index are given and it is noted that, in areas where conditions are not favourable to the vector throughout the year, or where the speed of development of the parasite in the vector may not be constant, these variables must be taken into account in calculating the index.

Animals↗
PubMed1967

The second International Standard for Oxytetracycline.

The National Institute for Medical Research, London, was requested by the WHO Expert Committee on Biological Standardization to establish a second International Standard for Oxytetracycline, since stocks of the first International Standard were depleted. A batch of 500 g of oxytetracycline dihydrate obtained in 1963 was distributed into ampoules in 125-mg amounts; the ampoules were filled with dried nitrogen and sealed. The usual procedure of exhaustively drying the material was omitted since removal of water of hydration adversely affects stability of oxytetracycline dihydrate. The proposed replacement material has been assayed biologically in terms of the first International Standard in 9 laboratories in 7 countries by means of plate-diffusion and turbidimetric assays.Significant heterogeneity of the potencies obtained by the different laboratories and within 3 laboratories was not attributable to any known differences in assay technique; the weighted mean potencies obtained by all laboratories were within a range of +/-2% of the over-all mean potency.The potency of the second International Standard is approximately 3% less than that of the first International Standard but no significant difference in composition or purity could be detected by a variety of chemical and physical analytical methods. The material has been established as the second International Standard for Oxytetracycline with a defined potency of 880 IU/mg. The International Unit of Oxytetracycline is defined as the activity of 0.0011364 mg of the second International Standard of Oxytetracycline.

Oxytetracycline↗