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Biomedical subjects

J Courtois

Publications and source records attributed to J Courtois.

16 recordsLinked to original sources
PubMed1991

Cloning and expression in Escherichia coli of dextranase genes from Bacteroides thetaiotaomicron.

A genomic bank was constructed in Escherichia coli HB101, consisting of DNA fragments from Bacteroides thetaiotaomicron strain 489 inserted within the vector pBR322. By screening on complex medium containing blue dextran, 10 stable dextranase-positive (Dex+) clones were isolated. Seven groups of Dex+ inserts were identified on the basis of their restriction maps and hybridization responses. Dextanase activity of the recombinant clones was weak, and was revealed on the selection medium after 15 days. Subcloning of a Sau3AI partially digested 3.2-kb insert in the expression vector pDR720 greatly enhanced dextranse activity on blue dextran plates in one clone, but the delay remained unaltered. This suggested that the enzyme was released by cell lysis. Expression of this 0.7-kb subcloned insert was dependent on the promoter region of tryptophan operon carried by pDR720.

Bacteroides↗
PubMed1988

High-frequency transformation of Rhizobium meliloti.

Transformation of R factor RP4 and its derivative pRK290 from Escherichia coli to Rhizobium meliloti is reported. The efficiency of transformation was in the range of 10(-5) per viable cell. In addition, chromosomal DNA prepared from one R. meliloti strain resistant to streptomycin was transferred to the isoleucine-valine-requiring mutant susceptible to streptomycin.

Chromosomes, Bacterial↗
PubMed1987

[Halitosis].

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Halitosis↗
PubMed1986

[Halitosis].

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Digestive System Diseases↗
PubMed1979

The occurrence of negative middle ear pressure in children: an analysis of supposed associated factors.

This study analyzed the occurrence of negative middle ear pressure in various groups of children by comparing them with control groups. A screening procedure recording middle ear pressure and screening audiogram was performed several times throughout the year in an unselected group of 352 seven-year-old children. From about 4000 measurements of middle ear pressure an average value for each child was calculated. By applying thresholds of pathology of -160 mm H2( and -240 mm H2O, the occurrence of pathology in the different groups was analyzed. A medical history of each child was obtained by questionnaires answered by parents, giving information concerning allergy, previous adenoidectomy, previous exposure to respiratory tract infections and the social group of the family. A score of dental caries was obtained in each child. Furthermore, the relationship to antibiotic treatment and the child's use of swimming pools was analyzed, based on single measurements. The use of swimming pools seems to be beneficial to children suffering from a negative middle ear pressure. However, the other variables showed no relationship to negative middle ear pressure. It is concluded that other unknown factors must be involved in the development of negative middle ear pressure and chronic OME in children.

Adenoidectomy↗
PubMed1979

The correlation between negative middle ear pressure and the corresponding conductive hearing loss in children. A 12-month study of 352 unselected 7-year-old children.

An epidemiological study of negative middle ear pressure in children made it possible to test its relationship to conductive hearing loss. About 350 children were subjected to a screening procedure recording audiogram and middle ear pressure five times during a 12-month period. Those children who failed to perceive just one tone or who had a middle ear pressure equal to or worse than -150 mmH2O in one or both ears were referred to the Hearing Clinic for conventional audiometry and middle ear pressure measurement each month. By computing the weighted average of the regressions for each child, a straight linear relationship was found between negative pressure and conductive hearing loss. In addition, a frequency dependence was found, the hearing loss being maximal at about 500 Hz. In general, the study shows that tympanometry is of limited value in predicting hearing loss in a child. The threshold for pathology of about -150 mmH2O, being a predisposing factor in secretory otitis media, corresponds to the upper confidence limit of the normal range of hearing loss found in this series. There is no distinct value of negative pressure that clearly distinguishes between normal and pathological condition, but it is concluded that a middle ear pressure worse than -150 mmH2O should be considered a probable hearing handicap.

Acoustic Impedance Tests↗
PubMedDate not supplied

[Halitosis].

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Halitosis↗