Frequency of Escherichia coli O157:H7 isolation from stool specimens

During a 6-month period, 7252 faeces specimens were examined for Escherichia coli serotype O157:H7. Forty-nine specimens (0.7%) from 19 patients yielded this organism. Escherichia coli O157:H7 was the third most frequently isolated bacterial pathogen, following Campylobacter jejuni and (or) Salmonella sp. Although regional variation between laboratories determined whether Campylobacter jejuni or Salmonella was the primary bacterial pathogen isolated, E. coli O157:H7 was consistently isolated more frequently than either Shigella or Yersinia enterocolitica.     

Origin of abnormality in a human simelian foetus as elucidated by our knowledge of vertebrate development

In this paper we attempt to explain the abnormality of a simelian foetus with reference to our present knowledge of vertebrate development. The various developmental defects seem to have a single common origin: the speeding-up of the progression of cell differentiation in the notochord anlage--which is the organization centre of the embryo--during the regression of the Hensen's node. Cell activity involved in the morphogenetic movements in the chordamesoderm probably stopped before it should have. The elongation of the notochord anlage was not completed, resulting in the defective development of the posterior part of the foetus. A number of pairs of posterior trunk somites were not induced. Consequently (1) the pelvic limb buds, whose posterior parts were missing, fused, bringing in further developmental deviations in the limb skeleton and abdominal muscles; (2) there are no vertebrae between the first sacral vertebra and the misshaped coccyx formed by the tail bud. The derivatives of the posterior endoderm (hindgut, bladder and ureters) were not induced either. The cauda equina is deficient. The absence of functional kidneys and the presence of embryonic urinary tubules in the pelvic cysts which are wrapped up by gut epithelium suggest the induction of the metanephric mesenchyme by ectopic endoderm. The speeding-up of differentiation in the notochord anlage also probably resulted in the excessive extension of its anterior region which is the organizer of brain structures. This explains the overdevelopment of the nose and of the neurocranium, and the low position of the ear. A gene mutation as well as a mechanical stress are the possible causes of the abnormal behaviour of the notochord anlage.     

Differential Thermolability of Exonuclease and Endonuclease Activities of the recBC Nuclease Isolated from Thermosensitive recB and recC Mutants

The recBC nuclease (also called exonuclease V) has been partially purified from Escherichia coli K-12 strains carrying the thermosensitive recB270, recC271, and recB270 recC271 mutations. Of the multiple activities associated with the enzyme, only the adenosine 5'-triphosphate-dependent exonucleolytic hydrolysis of duplex deoxyribonucleic acid (DNA) is abnormally thermolabile. The exo- and endonucleolytic degradation of single-stranded DNA is no more thermosensitive than that catalyzed by the wild-type enzyme. These results suggest that the defects in genetic recombination, DNA repair, and the maintenance of cell viability observed in recBC mutants in vivo result primarily from the specific loss of adenosine 5'-triphosphate-dependent exonuclease active on duplex DNA.     

New Approach to Information Handling in General Practice

In this paper we describe the use of punched feature cards in a general practice for 18 months. Its advantages are the low cost, speed of information retrieval, visible statistics, computer compatibility, accuracy, confidentiality, flexibility, and simplicity of setting up and collection of information. The system encourages the doctor to ask questions about his practice, and could readily be adopted in other practices.     

Physical microhabitat requirements of freshwater pearl mussels,Margaritifera margaritifera (L.)

Surface sediment diatoms from the east coast of Lake Tanganyika were analysed using ordination and classification techniques, and compared with assemblages previously described from the northern part of the lake. Grain-size analyses were performed on subsamples. Four groups of diatom assemblages were recognised. The first group clusters samples taken in the north, far from the Rusizi river mouth. The second group comprises samples taken on silty sediment along the Tanzanian coast, including one sample taken near the mouth of the Malagarazi river and those from the northernmost part of the lake. The third group comprises surface sediments along the Burundian coast (near Ramba and Magara), and the fourth is characterised by epipsammic taxa. A sample taken near the central arm of the Malagarazi river is included in the latter group. The impact of small rivers on the diatom assemblages in the surface sediments is restricted to the mouth area.     

Chlamydia isopodii sp. n., an obligate intracellular parasite of Porcellio scaber

In an ultrastructural study of the hepatopancreas of Porcellio scaber, an obligate intracellular parasite, Chlamydia, was noted in the epithelial cells. Although the infection was found to extend the entire length of the hepatopancreas, it was most extensive in the glandular region. Indirect immunofluorescence testing revealed no cross-reactivity with either lymphogranuloma venereum or psittacosis antisera.