Bacterial transposons and the mechanisms of their transposition

The published data on molecular mechanisms of transposons movement inside and between genomes are reviewed. The replicative mechanism of transposition of the family of Tn3-like elements is discussed, as well as the modes of bacteriophage Mu, Tn9, Tn10, Tn903 transposition. The factors affecting the choice of transposition pathways are analysed.     

A New Medium for the Detection and Enumeration of Clostridium perfringens in Foods

S ummary . This paper describes the development and use of a selective diagnostic medium for the detection and enumeration of Clostridium perfringens in foods. The medium gives higher counts of Cl. perfringens and fewer false positives than existing media.     

Staining Neuroglia with Silver Diammino-Hydroxide after Sensitizing with Sodium Sulfite and Embedding in Paraffin

Pieces of brain are fixed in formalin ammonium bromide for about 4 days at room temperature, and given the following treatment: After washing, dehydrating and clearing, embed in paraffin, section and mount. Deparaffinize sections and pass through graded alcohols to water. Sensitize in 5% sodium sulfite for 2 hours, wash in distilled water and impregnate with silver diamminohydroxide solution 2-5 minutes at room temperature. Reduce in 2% formalin, wash in distilled water and tone in gold chloride. Fix in 5% hypo, counterstain with 1% picric acid, dehydrate and cover in balsam. Equally good results are obtained by impregnating with Hortega's strong silver carbonate. The microglia, oligodendroglia, fibrous and protoplasmic astrocytes in the cat, rabbit, newborn and adult human are successfully stained by this method.     

Apomorphine-induced upregulation of serotonin 5-HT2A receptors in male rats is independent from development of aggressive behaviour.

The [3H]ketanserin binding characteristics in the apomorphine-induced aggressive and nonaggressive adult male Wistar rats were studied. Repeated apomorphine (0.5 mg/kg, once daily) treatment gradually induced aggressive behaviour in sixteen animals from twenty. Thereafter the animals were retrospectively divided into apomorphine-induced aggressive and nonaggressive group. The maximal number of the [3H]ketanserin binding sites was increased in the apomorphine-treated animals in the frontal (233.9+/-26.5, 364.6+/-31.7, and 367.0+/-34.8 fmol/mg protein for the vehicle, apomorphine-nonaggressive, and apomorphine-aggressive group, respectively) and cerebral cortex (164.2+/-6.7, 289.7+/-29.3, and 249.0+/-15.4 fmol/mg protein for the vehicle, apomorphine-nonaggressive, and apomorphine-aggressive group, respectively). In conclusion, our experiments demonstrate that repeated apomorphine treatment upregulates the maximal number of the 5-HT2A receptors in rat frontal and cerebral cortex as measured by [3H]ketanserin binding and this phenomenon is independent from the development of aggressive behaviour.     

Morphogenesis and Homology in Arthropod Limbs

Arthropods exhibit highly diverse limb morphologies rangingfrom unbranched walking legs to multibranched swimming paddles.Understanding morphogenesis in structurally diverse limbs canbe useful for ascertaining homologies between limbs. Structurallysimilar limbs have been produced by different evolutionary modificationsof morphogenesis in certain cases. Whereas it is easy to supportthe claim that whole arthropod limbs are homologous structures,I demonstrate that it is not always possible to draw well-foundedhomologies between parts of different limbs. This result isimportant with regard to general models of appendage developmentand evolution in arthropods because it clarifies contradictoryexplanations based exclusively on gene expression data.     

Transduction and Genetic Homology Between Pseudomonas Species putida and aeruginosa

Genetic crosses occur by transduction between the species Pseudomonas aeruginosa and P. putida. The frequency relative to intraspecific transfer is reduced and varies among markers, suggesting that these genomes contain discrete regions of homology and nonhomology.     

Assessment of Birmingham Medical Students

At Birmingham University since 1966 the major medical examinations began to be replaced by a process of continuous assessment. This is based on fairly frequent tests, usually at the end of each course, including short essay questions, multiple-choice questions, and tests of ability in wards and laboratory. At the end of the first final-year course 96 students underwent assessment. Of these 77 passed; 19 were referred for re-examination, of whom a further 12 passed subsequently. The scheme was found suitable by both teachers and external examiners.