Home visiting by general practitioners in England and Wales.

OBJECTIVE--To use data from the fourth national survey of morbidity in general practice to investigate the association between home visiting rates and patients'' characteristics. DESIGN--Survey of diagnostic data on all home visits by general practitioners. SETTING--60 general practices in England and Wales. SUBJECTS--502 493 patients visited at home between September 1991 and August 1992. MAIN OUTCOME MEASURES--Home visiting rates per 1000 patient years and home visiting ratios standardised for age and sex. RESULTS--10.1% (139 801/1 378 510) of contacts with general practitioners took place in patients'' homes. The average annual home visiting rate was 299/1000 patient years. Rates showed a J shaped relation with age and were lowest in people aged 16-24 years (103/1000) and highest in people aged > or = 85 years (3009/1000). 1.3% of patients were visited five or more times and received 39% of visits. Age and sex standardised home visiting ratios increased from 69 (95% confidence interval 68 to 70) in social class I to 129 (128 to 130) in social class V. The commonest diagnostic group was diseases of the respiratory system. In older age groups, diseases of the circulatory system was also a common diagnostic group. Standardised home visiting ratios for the 60 practices in the study varied nearly eightfold, from 28 to 218 (interquartile range 67 to 126). CONCLUSIONS--Home visits remain an important component of general practitioners'' workload. As well as the strong associations between home visiting rates and patient characteristics, there were also large differences between practices in home visiting rates. A small number of patients received a disproportionately high number of home visits. Further investigation of patients with high home visiting rates may help to explain the large differences in workload between general practices and help in allocation of resources to practices.     

Molecular evolution of cytochrome c oxidase: rate variation among subunit VIa isoforms

Cytochrome c oxidase (COX) consists of 13 subunits, 3 encoded in the mitochondrial genome and 10 in the nucleus. Little is known of the role of the nuclear-encoded subunits, some of which exhibit tissue-specific isoforms. Subunit VIa is unique in having tissue-specific isoforms in all mammalian species examined. We examined relative evolutionary rates for the COX6A heart (H) and liver (L) isoform genes along the length of the molecule, specifically in relation to the tissue-specific function(s) of the two isoforms. Nonsynonymous (amino acid replacement) substitutions in the COX6AH gene occurred more frequently than in the ubiquitously expressed COX6AL gene. Maximum-parsimony analysis and sequence divergences from reconstructed ancestral sequences revealed that after the ancestral COX6A gene duplicated to yield the genes for the H and L isoforms, the sequences encoding the mitochondrial matrix region of the COX VIa protein experienced an elevated rate of nonsynonymous substitutions relative to synonymous substitutions. This is expected for relaxed selective constraints after gene duplication followed by purifying selection to preserve the replacements with tissue-specific functions.      

Neurospora Mutant Deficient in Tryptophanyl-Transfer Ribonucleic Acid Synthetase Activity

A tryptophan auxotroph of Neurospora crassa, trp-5, has been characterized as a mutant with a deficient tryptophanyl-transfer ribonucleic acid (tRNA) synthetase (EC 6.1.1.2) activity. When assayed by tryptophanyl-tRNA formation, extracts of the mutant have less than 5% of the wild-type specific activity. The adenosine triphosphate-pyrophosphate exchange activity is at about half the normal level. In the mutant derepressed levels of anthranilate synthetase and tryptophan synthetase were associated with free tryptophan pools equal to or higher than those found in the wild type. We conclude that a product of the normal tryptophanyl-tRNA synthetase, probably tryptophanyl-tRNA, rather than free tryptophan, participates in the repression of the tryptophan biosynthetic enzymes.     

Studies on an interesting Saccharomyces carlsbergensis mutant

The genetics of a spontaneous double mutant Hla, belonging toSaccharomyces carlsbergensis, has been studied. The two mutated loci, controlling the biosyntheses of lysine and uracil are either loosely linked or they are located on separate chromosomes. Spontaneous mutations in the two genes are therefore likely to have followed from two independent mutagenic events. The mating-type locus, the methionine, the lysine and the uracil synthesising loci are not linked. Segregations for mating-type locus are Mendelian where as segregations for lysine, uracil and methionine synthesising loci are both Mendelian and Non-Mendelian. The 4:0 class of Non-Mendelian segregation is not found. The apparently Non-Mendelian segregations for mehtionine synthesis can be explained on the basis of the presence of two complementary methionine synthesising genes in Hla.

---

Zusammenfassung Die Genetik eines spontanen Doppelmutanten Hla, der zuSaccharomyces carlsbergensis gehört, wurde untersucht. Die zwei Loci, die die Biosynthese von Lysin und Uracil kontrollieren, sind entweder locker gebunden oder sind an verschiedene Chromosomen gebunden. Spontane Mutationen in beiden Genen sind deshalb wahrscheinlich das Ergebnis von zwei unabhängigen mutagenen Faktoren. Der Locus der Geschlechtstype, die Loci der Synthese von Methionine, Lysine und Uracil sind nicht gebunden. Die Absonderung des Locus für die Geschlechtstype ist gemäß Mendel, während die Absonderung für Lysine, Uracil und Methionine teils gemäß, teils nicht gemäß Mendel erfolgt. Die Klasse 4 : 0 der Absonderung nicht gemäß Mendel ist nicht gefunden worden. Die scheinbare Absonderung nicht gemäß Mendel für die Synthese von Methionine kann auf Grund der Gegenwart von zwei komplementären Genen in Hla für die Synthese von Methionine erklärt werden.

     

Production of exotoxins by Aeromonas spp. at 5°C

The ability of 60 strains of Aeromonas to produce enterotoxin and haemolysin after cultivation at 5°C for 7–10 d was investigated. The strains were isolated from lamb meat, offal, carcasses and faeces, and had previously been tested for their ability to produce these exotoxins at 37°C. The results showed that some strains of Aeromonas hydrophila and A. sobria were capable of producing enterotoxin and haemolysin at 5°C, but none of the A. caviae strains tested produced these two factors. Of the 30 A. hydrophila strains investigated 25 and 27 were enterotoxigenic and haemolytic respectively. Likewise, of the 24 A. sobria strains investigated 16 and 18 were enterotoxigenic and haemolytic respectively. The results indicate that certain strains of Aeromonas species, in particular A. hydrophila and A. sobria , are of potential public health significance in meats stored at refrigeration temperature.