Interactions of Carbon Dioxide and Food Odours in Drosophila: Olfactory Hedonics and Sensory Neuron Properties

Behavioural responses of animals to volatiles in their environment are generally dependent on context. Most natural odours are mixtures of components that can each induce different behaviours when presented on their own. We have investigated how a complex of two olfactory stimuli is evaluated by Drosophila flies in a free-flying two-trap choice assay and how these stimuli are encoded in olfactory receptor neurons. We first observed that volatiles from apple cider vinegar attracted flies while carbon dioxide (CO₂) was avoided, confirming their inherent positive and negative values. In contradiction with previous results obtained from walking flies in a four-field olfactometer, in the present assay the addition of CO₂ to vinegar increased rather than decreased the attractiveness of vinegar. This effect was female-specific even though males and females responded similarly to CO₂ and vinegar on their own. To test whether the female-specific behavioural response to the mixture correlated with a sexual dimorphism at the peripheral level we recorded from olfactory receptor neurons stimulated with vinegar, CO₂ and their combination. Responses to vinegar were obtained from three neuron classes, two of them housed with the CO₂-responsive neuron in ab1 sensilla. Sensitivity of these neurons to both CO₂ and vinegar per se did not differ between males and females and responses from female neurons did not change when CO₂ and vinegar were presented simultaneously. We also found that CO₂-sensitive neurons are particularly well adapted to respond rapidly to small concentration changes irrespective of background CO₂ levels. The ability to encode temporal properties of stimulations differs considerably between CO₂- and vinegar-sensitive neurons. These properties may have important implications for in-flight navigation when rapid responses to fragmented odour plumes are crucial to locate odour sources. However, the flies’ sex-specific response to the CO₂-vinegar combination and the context-dependent hedonics most likely originate from central rather than peripheral processing.     

Blood lipid concentrations and other cardiovascular risk factors: distribution,prevalence, and detection in Britain

To establish the distribution of blood lipid concentrations and the prevalences of other risk factors for cardiovascular disease in Britain 12 092 men and women aged 25-59 in Glasgow, Leicester, London, and Oxford were studied. Subjects were selected by opportunistic case finding, in which patients consulting their general practitioner for any reason were offered a health check by appointment, or random selection from age-sex registers, in which an invitation for a health check was posted. The overall rate of response was 73%, being 91-94% by opportunistic case finding and 36-63% by random selection. At the health check subjects answered a brief questionnaire about risk factors for cardiovascular disease, and their height, weight, and blood pressure were recorded; a blood sample was taken for measuring plasma concentrations of cholesterol, triglyceride, high density lipoprotein cholesterol, and glucose.The mean cholesterol concentrations were 5·9 (SD 1·2) and 5·8 (1·2) mmol/l in men and women, respectively. In London the mean value was 5·5 (1·2) mmol/l for both men and women and was significantly lower than mean values in the three other centres, among which there were no significant differences. In men and women aged 25-29 concentrations were similar but they increased in men until the age of 45-49, after which they showed no further increase; in women concentrations did not increase until the age of 40-44 and by the age of 50-59 values were higher than in men. Mean triglyceride concentrations were significantly higher in men than in women (1·8 (1·4) v 1·3 (0·9) mmol/l, respectively), and trends with age were similar to those for cholesterol concentrations, except that at no age were values higher in women than in men. Mean triglyceride values overall were higher in Glasgow and London than in Oxford and Leicester. Body mass index was higher in Glasgow and London than in the other two centres and correlated with systolic and diastolic blood pressures and triglyceride concentration. In addition, subjects in Glasgow smoked significantly more than those in the other centres. These observations could contribute to the higher rate of coronary heart disease in Glasgow. Plasma lipid concentrations and the prevalences of other risk factors for cardiovascular disease were similar in subjects selected by opportunistic case finding and by random selection.In Britain cholesterol values have changed little during the past 12 years despite dietary recommendations and health education. Identifying subjects at particularly high risk of coronary heart disease is required to supplement advice to the general population to reduce the prevalence of this disease. Opportunistic case finding would be an appropriate method of identifying such subjects in general practice, although none of the potential markers for hyperlipidaemia was particularly useful in identifying all subjects at high risk.     

Genetic and blood coagulation characterization of “Swedish” families with von Willebrand's disease types I and III: New aspects of heredity

Summary Twenty-five patients with von Willebrand's disease (vWD) type III were analysed with regard to blood coagulation variables and possible deletions. Nine of the probands and their families were further investigated with DNA linkage analyses. Different patterns of heredity can be suggested in our families with vWD type III, on the basis of blood coagulation analyses. The findings suggest homozygosity in five families and the possibility of compound heterozygosity or a new mutation in the proband in three families. The linkage analyses confirm the results of the coagulation analyses. The segregation of the von Willebrand factor (vWF) gene can be followed in the families, and carrier diagnosis can be made in several of the probands' relatives. The possibility of large deletions in the vWF gene of the probands and their parents was investigated with probes representing the whole vWF cDNA. No deletions were found.This study was approved by the Ethics Committee of the Karolinska Hospital (No. 84:1)     

Reconstitution of the tonoplast amino-acid carrier into liposomes

The tonoplast amino-acid transporter of barley (Hordeum vulgare L.) mesophyll cells was functionally reconstituted by incorporating solubilized tonoplast membranes, vacuoplast membranes or tonoplast-enriched microsomal vesicles into phosphatidylcholine liposomes. (i) Time-, concentration- and ATP-dependence of amino-acid uptake were similar to results with isolated vacuoles. Although the orientation of incorporation could not be controlled, the results indicate that the transporter functions as a uniport system which allows regulated equilibration by diffusion between the cytosolic and vacuolar amino-acid pools. (ii) The ATP-modulated amino-acid carrier was also successfully reconstituted from barley epidermal protoplasts and Valerianella or Tulipa vacuoplasts, indicating its general occurrence. (iii) Fractionation of solubilized tonoplasts by size-exclusion chromatography followed by reconstitution of the fractions for glutamine transport gave two activity peaks: the first eluted in the region of high-molecular-mass vesicles and the second at a size of 300 kDa for the Triton-protein micelle.Abbreviation SDS-PAGE sodium dodecyl sulfate-polyacryl-amide gel electrophoresis This work was part of our research efforts within the Sonderforschungsbereich 176 of the University. We gratefully acknowledge experimental support by Marion Betz and valuable discussions with Professors U. Heber and U.-I. Flügge and Dr. Armin Gross (University of Würzburg) and Dr. E. Martinoia (ETH, Zürich, Switzerland).     

Malonyl-CoA in skeletal muscle and liver of streptozotocin-diabetic rats.

Malonyl-CoA, the inhibitor of carnitine palmitoyl transferase I, has been examined in this study in the muscle and liver of diabetic rats. Male Sprague-Dawley rats were rendered diabetic with streptozotocin (6 mg/100 g body wt). The gastrocnemius/plantaris muscles and liver samples were frozen at liquid nitrogen temperature. Muscle malonyl-CoA was 1.8 +/- 0.2 pmol/mg in control rats and 1.5 +/- 0.2 pmol/mg in the diabetic rats. This difference was not statistically significant. Liver malonyl-CoA of control rats was 8.6 +/- 0.8 pmol/mg, in comparison to 4.3 +/- 0.6 pmol/mg in diabetic rats. In the liver, high concentrations of malonyl-CoA inhibit fatty acid oxidation and ketogenesis. Failure of malonyl-CoA to decline in muscle in the diabetic may be responsible in part for the diversion of fatty acids to the liver, thereby enhancing hepatic fatty acid oxidation and ketogenesis.     

Morphological evidence for a close interaction of chromaffin cells with cortical cells within the adrenal gland

Summary The adrenal medulla appears to exert a regulatory influence on adrenocortical steroidogenesis. We have therefore studied the morphology of rat, porcine and bovine adrenals in order to characterize the contact zones of adrenomedullary and adrenocortical tissues. The distribution of chromaffin cells located within the adrenal cortex and of cortical cells located within the adrenal medulla was investigated. Chromaffin cells were characterized by immunostaining for synaptophysin and chromogranin A, both being considered specific for neuroendocrine cells. Cortical cells were characterized by immunostaining for 17-hydroxylase, an enzyme of the steroid pathway. Cellular contacts of chromaffin cells and cortical cells were examined at the electron microscopical level. In rat and porcine adrenals, rays of chromaffin cells, small cell clusters and single chromaffin cells or small invaginations from the medulla could be detected in all three zones of the cortex. Chromaffin cells often spread in the subcapsular space of the zona glomerulosa. In porcine and bovine adrenals, 17-hydroxylase immunoreactive cells were localized within the medulla. Single cortical cells and small accumulations of cells were spread throughout this region. At the ultrastructural level, the chromaffin cells located within the cortex in pig and rat adrenals formed close cellular contacts with cortical cells in all three zones. Our morphological data provide evidence for a possible paracrine role of chromaffin cells; this may be important for the neuroregulation of the adrenal cortex.