numb, a gene required in determination of cell fate during sensory organ formation in Drosophila embryos

Neurons and support cells of each sensory organ in Drosophila embryos are most likely derived from a single precursor cell. This cell lineage is affected in numb mutants. Morphological alterations of sensory structures, as well as changes in the number of cells expressing cell type-specific markers, indicate that sensory neurons in numb mutant embryos are transformed into lineage-related nonneuronal support cells. Thus the numb gene controls the fate of progeny derived from sensory organ precursors. The numb gene has been isolated by the plasmid rescue method. The structure of its predicted product is discussed.     

A selective differential medium for the isolation of Listeria monocytogenes

A new medium has been developed for the isolation of Listeria monocytogenes from clinical specimens with a mixed flora. Almost complete inhibition of unwanted organisms was achieved and recognition of colonies of Listeria spp. was usually possible after 24 h using the aesculin-ferric ammonium citrate indicator system. Compared to McBride agar the new medium was more inhibitory to representative contaminating species in pure culture and more successful in isolating small numbers of L. monocytogenes from artificially seeded clinical specimens.     

Oxidant-mediated inhibition of ligand uptake by the macrophage mannose receptor

We have investigated the effect of oxidants on ligand recognition and internalization by the macrophage mannose receptor. Rat bone marrow macrophages were treated with increasing concentrations of H2O2 for 30 min at 37 degrees C. Fifty percent inhibition of ligand uptake was observed at 250 microM, with only 10% of control uptake remaining following exposure to 1 mM H2O2 for 30 min. Electron micrographic analysis of macrophages following H2O2 treatment showed no morphological alterations compared to untreated cells. Ligand uptake was also inhibited by the following H2O2 generating systems: menadione, xanthine/xanthine oxidase, glucose/glucose oxidase, and phorbol 12-myristate 13-acetate-stimulated polymorphonuclear leukocytes. Inhibition could be blocked by catalase plus or minus superoxide dismutase. Treatment of macrophages at 4 degrees C with H2O2 had no effect on ligand binding, whereas treatment with H2O2 at 37 degrees C reduced binding to 15% of control levels and decreased the number of surface receptors to one-third of control cells. H2O2 treatment inhibited ligand degradation by macrophages, but did not prevent ligand movement from the surface to the interior of the cell. In addition, ligand delivery to lysosomes was blocked by oxidant treatment. These results suggest that treatment of macrophages with reagent H2O2 or H2O2-generating systems inhibits the normal ligand delivery and receptor recycling process involving the mannose receptor. Potential mechanisms might include receptor oxidation, alterations in ATP levels, or membrane lipid peroxidation.     

Lipoprotein metabolism in hepatic lipase deficiency: studies on the turnover of apolipoprotein B and on the effect of hepatic lipase on high density lipoprotein

Hepatic lipase deficiency produces significant distortion in the plasma lipoprotein profile. Particles with reduced electrophoretic mobility appear in very low density lipoprotein (VLDL). Intermediate density lipoprotein (IDL) increases markedly in the circulation and plasma low density lipoprotein (LDL) levels fall. At the same time there is a mass redistribution within the high density lipoprotein (HDL) spectrum leading to dominance in the less dense HDL2 subfraction. The present study examines apolipoprotein B turnover in a patient with hepatic lipase deficiency. The metabolism of large and small very low density lipoproteins was determined in four control subjects and compared to the pattern seen in the patient. Absence of the enzyme did not affect the rate at which large very low density lipoproteins were converted to smaller particles within this density interval (i.e., of VLDL). However, subsequent transfer of small very low density lipoproteins to intermediate density particles was retarded by 50%, explaining the abnormal accumulation of VLDL in the patient's plasma. Despite this, intermediate density particles accumulated to a level 2.4-times normal because their subsequent conversion to low density lipoprotein has been almost totally inhibited. Consequently, the plasma concentration of low density lipoprotein was only 10% of normal. On the basis of these observations, hepatic lipase appears to be essential for the conversion of small very low density and intermediate density particles to low density lipoproteins. The pathways of direct plasma catabolism of these species were not affected by the enzyme defect. In vitro studies were performed by adding purified hepatic lipase to the patient's plasma.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

Comparative evaluation of fresh, fixed, and cryopreserved solid tumor cells for reliable flow cytometry of DNA and tumor associated antigen.

Five different protocols for the short-term preservation of cells used for multiparameter flow cytometric assay of tumour associated antigens (TAA) and DNA were assessed in cell suspensions prepared by mechanical disaggregation of 15 gynecological tumors. The protocols at 4 degrees C were 1) storage in buffer, 2) storage in 50% methanol, and 3) storage in buffer after formalin fixation. Tissues were also cryopreserved as cell suspensions and tissue blocks. When the TAA expression and DNA histograms of the preserved cells were compared with those in fresh cell suspensions, cryopreservation was found to be the best method: TAA expression was well preserved and there was a good correlation between TAA expression and the quality of the DNA histograms, respectively, in fresh and cryopreserved cells (RS: 0.82-0.91, P less than 0.001 for all TAAs). The cell suspensions preserved at 4 degrees C all showed a significant increase in background fluorescence (P less than 0.05) and a reduction in the TAA specific fluorescence (P less than 0.011). Methanol fixation was better than buffered formalin for the proteins studied, though both gave significantly worse results than cryopreservation. The quality of these cell suspensions and the correlation with TAA measurements in fresh cell suspensions deteriorated progressively with time, particularly if they were stored more than a week.     

The role of air temperature in determining dormancy release and flowering ofCorylus avellana L.

Summary 7 years of airborne pollen monitoring in Perugia (central Italy) were used to determine the temperature requirements to break dormancy and to resume growth and bloom ofCorylus avellana L.,Corylus needs 1000 chill-units to complete its dormancy and this value, in the Perugian area, is met by the end of December or the first days of January. MoreoverCorylus trees require 220 growth degree hours before they are able to flower. If air temperature is high, this value can be achieved in only 10 days, but if the temperature remains too low, the heat accumulation can require up to 35 days. With these parameters it is possible to build a model to predict the date of the beginning ofCorylus avellana pollen season.     

Geminiviruses: Genome structure and gene function

The plant pathogenic single‐strand DNA‐containing geminiviruses have been the recent focus of intense investigation, owing both to their agronomic importance and to their potential as vectors for the expression of foreign genes in plants. Molecular genetic studies have provided detailed information on the genomic organization of many of these viruses. A greater genetic complexity has been demonstrated among the members of this viral family than had previously been suspected, as well as an apparently rapid rate of evolution of genetic diversity. We now recognize fundamental differences in the genome structure and organization of the whitefly‐ and leafhopper‐transmitted viruses, as well as among those geminiviruses infecting dicotyledonous or monocotyledonous hosts. This knowledge has provided new insights into the evolution of these viruses. The viral genes involved in replication and in systemic movement in the plant have been defined, and viral origins for single‐strand (ss) and double‐strand (ds) DNA replication have been mapped to small nucleotide regions. With the structural features of the viral genomes now well defined, current efforts are focused on elucidating the molecular aspects of viral gene regulation and interactions with host‐cell components that lead to the production of disease. Recent progress in determining the mechanism of replication and systemic movement and the contributions of these to symptom and disease development are discussed in the context of the potential for genetically engineering disease‐resistant plants.     

Effect of calcium ion uptake on Candida albicans morphology

In liquid culture using a synthetic medium, added magnesium but not calcium was required for exponential growth of Candida albicans yeast cells. However, medium without added divalent cations supported 2-3 generations of yeast growth or germ tube induction. The addition of calcium ions (1.0 mM) at any stage during the induction of germ tube formation caused reversion to a yeast mode of growth, in contrast to the effect of zinc and cobalt ions which were toxic to all growth. Inhibition of germ tube formation by calcium was not observed in the presence of either magnesium (10 microM) or manganese (100 microM). The presence of either of these ions caused inhibition of 45Ca uptake in yeast cultures. We conclude that unrestricted calcium uptake resulted in the specific inhibition of C. albicans mycelial growth, indicating a critical role for calcium in the regulation of C. albicans morphogenesis.     

Enhanced lipolysis is not evident in adipocytes from exercise-trained SHR

Adipocytes from spontaneously hypertensive rats (SHR) are not as responsive to isoproterenol or dibutyryl adenosine 3',5'-cyclic monophosphate (cAMP) stimulation compared with Sprague-Dawley or Wistar-Kyoto rats. Lipolytic activity in adipocytes from trained normotensive rats was enhanced in response to 1 microM isoproterenol and 0.5 mM dibutyryl cAMP but not in adipocytes from trained SHR. Decreases in isoproterenol-stimulated (1 microM) cAMP accumulation were evident in adipocytes from trained normotensive rats but not in adipocytes from trained SHR. Basal and agonist-induced lipolysis in fat cells isolated from both normotensive rats and SHR immediately following a 60-min run was increased in both sedentary and trained rats. Adenylate cyclase activity in fat cell membranes was blunted in sedentary and trained SHR both in the absence and presence of 100 microM 5'-guanylyl imidophosphate. No apparent differences existed in antagonist affinity of binding sites for the antagonist dihydroalprenolol in normal rats or SHR. Evidence for a change in affinity of agonist isoproterenol might be indicated based on the enhanced potency of isoproterenol to stimulate lipolysis in trained normal rats. beta-Adrenergic receptor density and antagonist affinity were not different in normotensive rats and SHR in response to training. However, displacement of [3H]dihydroalprenolol in adipocytes from SHR required greater concentrations of isoproterenol compared with adipocytes from normotensive rats, further suggestive of increased agonist affinity of binding sites in normal rats. These data suggest a postreceptor lesion of the lipolytic pathway in adipocytes from spontaneously hypertensive rats, possibly at the guanine nucleotide regulatory protein level.(ABSTRACT TRUNCATED AT 250 WORDS)