D-Fucose as a gratuitous inducer of the L-arabinose operon in strains of Escherichia coli B-r mutant in gene araC

d-Fucose, a nonmetabolizable analogue of l-arabinose, prevents growth of Escherichia coli B/r on a mineral salts medium plus l-arabinose by inhibiting induction of the l-arabinose operon. Mutations giving rise to d-fucose resistance map in gene araC and result in constitutive expression of the l-arabinose operon. Most of these mutations also permit d-fucose to serve as a gratuitous inducer. It is concluded that d-fucose-resistant mutants produce an araC gene product with an altered inducer specificity. Addition of l-arabinose to cells induced with the gratuitous inducer, d-fucose, resulted in severe transient repression of operon expression followed by permanent catabolite repression. Transient repression but no permanent catabolite repression was obtained when cells unable to metabolize l-arabinose were employed. It is concluded that transport of l-arabinose alone is sufficient to achieve transient repression of its own operon, but that metabolism of l-arabinose must occur to achieve permanent catabolite repression of the l-arabinose operon. This general effect has been termed "self-catabolite repression."

The Infection and Course of Tuberculosis in primary School Children

Since July 1953, tuberculin tests and x-ray examinations have been carried out periodically for 2341 children from 3 primary schools, which are located near the Inchon Red Cross T. B. Sanatorium. The purpose of this was to get some data on the course of tuberculosis in primary school children.All the 3 schools are located in small villages, lying some 4 to 10 Kms, away from the center of Inchon city, The parents were mostly farmers. In July 1956, tuberculin tests were made. and the children were classified into two groups(1) tuberculin positive and (3) tuberculin negative. Then microfilms we taken of all the children, including the tuberculin negative group. Periodic tuberculin tests were given to the tuberculin negative group at an interval of 4 to 5 months to find the convertors. These positive cases who were hem x-rayed with regular size film, blood sedimentation tests made and complete physic examine actions carried out. In all 1957, for the second time, Apriofilms were taken of the tuberculin positive group in order to carried out how many new cases of developed from this group. (For those cases which were found to need treatment or supervision at the first mass x-ray, follow-up x-ray examinations were given in April and Sept. 1957 respectively, to determine the course of the disease curing that period.) (Treatment had been discontinued for the most part due to leck of understanding of their parents).The following results were obtained from this Study:1)The percentage of tuberculin-positive reactors was 37%. 42% in the three school respectively The percentage of the positive reactors varied between 20% & 32% in the first grades; 45% & 56% in the 6th grades.2) Nearly 8% of negtive reactors were converted to positive during the period of the 14 months.The conversion rate seems to vary with the season.3) As a result of this survey, 103 cases (4.4% of all children) were found to need treatment or supervision , among them were 35 cases out of 65 new convertors discover during this study.4) of the 103 cases: above mentioned, more than 70% were simple primary t.b., about 20%, were chronic pulmonary t. b. (reinfection type) or suspected cases and the remaining 10% consisted of 3cases of pleurisy, 4 cases of segmental lesion, 1 case of hematogenous disseminated type.5) Of the 1027 negative reactors in the mass x-rays of July 1956, 18 cases had thrown abnormal x-ray shadows. Of these 8 cases, include 5 cases whose tuberculin react on became positive afters, and 3 cases needing treatment and for supervision. This would indicate that the tuberculin reaction is one of the most useful methods for sea eenining out F. B. , even though it is not absolutely dependable.6) Of those cases needing treatment or supervision, only 10% becames worse after 1 year, the rest of them improved or remained unchanged.7) Compared with the 3. 5% at which rate new cases are supposed to develop from positive reactors group, 54% of the new convertors showed roentgenological changes and 38% required treatment.8) Of the roentgenological changes discovered early following conversion, 68% the majority) was hilar node t. d., 23% (was primary complex, and the remaining 9% was pleurisy or segmental lesion. Most of these changes appeared at the same time when coversion was found , though we realize that segmental lesion may appear early or later following Development to chronic type from primary T. B. began to appear 5 to 10 months following conversion.9) Blood sedimentaion rate and degree of reactivity to tuberculin of new convertors seem to have some relationship to the development of tuberculosis.10) Of the new convertors, about 40% had subjective complaints ranging from several weeks to several months.11) Chronic type (reinfection type) seems to occur somewhat more frequently in the children, but maybe found even in the 1st grade. The extent of the lesions was minimal for most cases.12) In view of the fact the calcified lesions coexisted with the chronic type lesions in about 30% of the whole chronic type cases, the time relationship of development of chronic type to primary t. b.seems to be inconstant.ln summery, the general tendency of t.b. in primary school children seems to be as follows: About a half of the new convertors show roentgenological changes, and the simple primary pulmonary t. b. constitutes the main problem in primary school children. Thc Chronictype begins to appear on he one hand , but hematogenous spreadlso may occur rarely, and occasionally pleurisy or segmental lesion may develop.

A Small Epidemic of Tuberculosis in a Rural Village

1) As a result of mass-survey for the whole inhabitants of Yun-soo-dong, a small epidemic of tuberculosis was found in Poosoodi, a very small village of 239 inhabitants. The morbidity rated to 10 % and tuberculin sensitivity to 81 %.2) 7 adult cases of moderately or far advanced pulmonary tuberoulosis were found in such a smaIl community. 4 cases of them were cavitary form and supposed to have played an important role as potent sources of infection.3) 13 cases of primary type were found among the age groups less than 15 years, constituting the main part of victims of the epidemic caused by the potent sources of 10 infection. 10 of those 13 cases Were found among the 0-4 group. The morbidity and infection rate in the age group were extreme!y high, spiking up to 28 % and 44% respectively. ln the cases of 3 chronic pulmonary tuberculosis (adult type) among adolescence, the intimate and Iong-standing contacts with those open cases are supposed to have influenced on the development of disease.4) Frequent and intimate contacts with neighbors and the poor cOl1ditions of hygiene in rural area arc supposed to have played an important role in the spread of tuberculosis by providing an environment 5uitable for the spread of infection.