The mutation rate and the distribution of mutational effects of viability and fitness in Drosophila melanogaster

The empirical distributions of the average viability and fitness of mutation accumulation lines of Drosophila melanogaster were analyzed using minimum distance estimation. Data come from two different experimental designs where mutations were allowed to accumulate: 1) in copies of chromosome II protected from natural selection and recombination (viability: Mukai et al., 1972; Ohnishi, 1977; fitness: Houle et al., 1992), 2) in inbred lines derived from the same isogenic stock (viability: Fernández & López-Fanjul, 1996; fitness: this paper). Information from all data sets converged, indicating that the mutational rates were small, about 1% for viability and 3% for fitness. For both traits, the rate of mutational decline appears to be smaller than suggested by previous studies (about one-fifth of the latter), the average mutational effect was neither severe nor very slight, ranging from -0.1 to -0.3, and the distribution of mutant effects was, at most, slightly leptokurtic. Therefore, the mutational load in natural populations is one to two orders of magnitude smaller than previously thought (as based upon analyses conditional to estimates of the mutational decline of viability or fitness that appear to be biased upward). Over 95% of the mutational variance of each trait was contributed by non-slightly deleterious mutations (absolute homozygous effect larger than 0.03 or 0.1, depending on the data set considered) occurring at a rate not higher than 0.025 per haploid genome and generation. Our data suggest that most deleterious mutations affecting fitness act mainly through a single component-trait.     

Spatial organization of microtubules and microfilaments in larval and adult salivary glands of Drosophila melanogaster

We examined the distribution of microtubules and microfilaments by conventional fluorescence microscopy and laser scanning confocal microscopy in larval and adult salivary glands of Drosophila melanogaster. The cells of the larval salivary gland epithelium were characterized by the same spatial distribution of microfilaments, whereas microfilament localization was more complex in adult salivary glands, showing some regional differentiation. Microtubules distributed throughout the cell cytoplasm of the larval salivary glands, whereas in adult glands they were mostly observed in the basal or apical cytoplasm of the cells. These observations were related to the secretory process and the mechanism of saliva discharge.     

Innate metabolic differences and mutagen sensitivity of Drosophila melanogaster. I. Radiosensitivity of hyperkinetic mutant

The sensitivity to gamma-rays of a hyperkinetic mutant (HK1), characterized by high metabolic activity, has been studied and compared with gamma-ray sensitivity of the wild-type Oregon-K. Radiation damage, as measured by the frequency of induced dominant lethals (DL) and sex-linked recessive lethals (SLRL), was more in HK1 as compared with Or-K. The maximal sensitivity differences for these parameters were observed in the first brood. Translocations, on the contrary, were in general fewer in the HK1 compared with Or-K. These results have been interpreted in terms of reduced repair of mutational lesions in the energy-stressed cells of KH1.     

New mutants of Drosophila melanogaster

Characteristics are given of 57 Drosophila melanogaster mutants catched in the South and Soeth-West Iran.     

Influence of the temperature and strain rate on the deformability of low-alloy carbon steel

The influence of the temperature, strain, and strain rate on the deformability of low-alloy carbon steel is studied experimentally. Samples are tested on the STD 812 torsional plastometer at Czestochowa Technological University. The hardening of low-alloy carbon steel at different strain rates and temperatures is plotted on the basis of the results for its resistance to deformation. For all the curves, the rate of hardening is high in the initial section, with no relaxation processes. The influence of the strain rate and temperature on the maximum resistance to deformation is quantitatively determined; this is important for practical purposes. The resistance to deformation declines on account of relaxation. The influence of the strain rate and temperature on the mean hardening rate in the range 0 < ε_u < ε_u*is also studied.     

Resistance to starvation in insects: importance of the amount of lipid reserves in adult Drosophila melanogaster

At 25 degrees C, mean survival duration of adults starved after emergence varied from 58 to 112 hours, according to genotype and larval growth conditions. This duration was highly correlated with the amount of lipids. The great variability in the amount of lipids (from 15 to 35% of initial dry weight) seems to have an adaptative significance for adult survival in natural conditions.     

Glycosidases are present on the surface of Drosophila melanogaster spermatozoa

We investigated the presence of enzymes on the surface of Drosophila melanogaster spermatozoa that might bind the carbohydrate residues of the egg shell. Spectrophotometric and fluorimetric studies were used on whole spermatozoa to assay galactosyltransferase and glycosidase activities. No galactosyltransferase is present on the sperm surface, whereas two glycosidases, beta-N-acetylglucosaminidase (GlcNAc'ase) and alpha-mannosidase (Man'ase), have been evidenced. They have an optimal pH of 6-6.5 and 4, respectively. The same glycosidases were detected as soluble forms probably secreted by the seminal vesicle epithelium. We suggest that these enzymes might be involved in the recognition of alpha-mannose and beta-N-acetylglucosamine residues present on the egg shell at the site of sperm entry.     

The soluble alpha-mannosidases of Drosophila melanogaster

The alpha-mannosidases are implicated in both the catabolism of carbohydrates and the N-linked glycosylation pathway in insects, but little is known of the biochemistry of these glycosidases. In order to study the soluble alpha-mannosidases of Drosophila melanogaster we have used artificial fluorogenic substrates for detection of activity in situ following non-denaturing gel electrophoresis. This approach also permitted examination of the mannosidases present in different tissues and the sensitivity of the enzymes to known mannosidase inhibitors. Fluorogenic substrates were also used to determine the pH optima of partly purified mannosidases. We report that D. melanogaster contains several soluble alpha-mannosidase activities. Acidic mannosidases were detected in the gut, fat body and haemolymph of third-instar larvae. The major activity detected in larval guts was a neutral mannosidase presumed to be involved in digestion.     

Sympathetic nervous system activity and resting metabolic rate in vegetarians

We examined the resting metabolic rate (RMR) and sympathetic nervous system activity of young male vegetarians (n = 17) and nonvegetarians (n = 40). Subjects were characterized for RMR by indirect calorimetry, norepinephrine kinetics from infusions of tritiated norepinephrine, energy and macronutrient intake from a 3-day food diary, and body composition by underwater weighing. Vegetarians reported a greater relative intake of carbohydrates (62% +/- 5% v 51% +/- 6%, P < .01) and a lower relative intake of fat (25% +/- 5% v 33% +/- 6%, P < .01) than nonvegetarians, whereas no differences were observed in daily energy intake, body composition, or maximal aerobic capacity (VO2max) between groups. Vegetarians exhibited an 11% higher absolute RMR (1.29 +/- 0.15 v 1.16 +/- 0.13 kcal/min, P < .01), a higher plasma concentration of norepinephrine (216 +/- 33 v 165 +/- 18 pg/mL, P < .01), and a greater norepinephrine appearance rate (0.50 +/- 0.08 v 0.36 +/- 0.09 micrograms/min, P < .01) than nonvegetarians. After statistically controlling for differences in relative amounts of carbohydrate and fat in the diet and for norepinephrine concentrations, no significant differences in adjusted RMR between vegetarians and nonvegetarians were noted. These results suggest that the higher RMR observed in young male vegetarians is partially mediated by differences in dietary macronutrient composition and increased sympathetic nervous system activity.     

温度对浸矿微生物活性及铜浸出率的影响

研究了从紫金山铜矿生物堆浸矿堆中分离出来的浸矿菌群在不同温度下的氧化活性和对紫金山硫化铜矿石的浸出规律,并利用变性梯度凝胶电泳法研究了15℃和30℃的菌群组成情况.结果表明:所分离的细菌的最佳生长温度为30℃,浸出10d,铜浸出率为87.62%,在最佳生长温度以外铜浸出率都会降低;15℃和30℃的优势菌分别为Leptospirillum fer-riphilum和Acidithiobacillus thiooxidans,两个温度下均有同一种劣势菌Acidithiobacillus caldus;优势菌种随温度的变化是与菌种的性质相关的.     

Influence of temperature and strain rate on slip and twinning behavior of zr

The stress-strain behavior of pure Zr was studied systematically at various temperatures and strain rates. At 76 K, Zr deforms predominantly by twinning, whereas above room temperature (RT), slip is the controlling deformation mode. A transition in the rate-controlling deformation mode from slip to twinning has been observed to occur at intermediate temperatures during the course of plastic deformation. Above 373 K, slip dominates the entire course of deformation. The transition from slip to twinning in the stress-strain behavior is linked to differing strain-hardening rates and temperature sensitivities of the two deformation modes.     

Mutation and evolution of microsatellites in Drosophila melanogaster

Levels of nucleotide polymorphism in the Drosophila melanogaster genome are correlated with rates of recombination. This relationship may be due to hitchhiking of advantageous mutations (selective sweeps) or to continual removal of deleterious mutations from the genome (background selection). One test of the relative contributions of selective sweeps and background selection to the observed levels of variation in the genome of D. melanogaster is to compare levels of nucleotide variability (with a mutation rate on the order of 10(-9) per nucleotide per generation) with more rapidly evolving DNA loci such as microsatellites. This test depends critically on details of the mutational process of microsatellites. In this paper, we summarize our studies of microsatellite characteristics and mutation rates in D. melanogaster. We find that D. melanogaster microsatellites are short and have a mutation rate (6.5 x 10(-6) per locus per generation) several orders of magnitude lower than mammals studied to date. We further show that genetic variation at 18 dinucleotide repeat microsatellites in a population of D. melanogaster from Maryland is correlated with regional rates of recombination. These and other microsatellite data suggest that both background selection and selective sweeps may contribute to the correlation between DNA sequence variation and recombination in Drosophila.     

Development of the giant fiber neuron of Drosophila melanogaster

The origins and vicissitudes of envy are discussed from the viewpoints of Boris and the Kleinians. Their ideas, coupled with a relational perspective of the therapeutic process, enrich our understanding and inform our work concerning the emergence, processing, and working through of envy in the therapy group. A variable in the negative therapeutic reaction, envy can be destructive to the therapy process. It is proposed that envy, accompanied by shame and guilt, is likely to enter the group via enactments. They are fueled by projective identification, which, if ignored, impede the continuation of the group process. Four clinical vignettes illustrate how envy enters the group and how the group functions as a container and transformational object as it processes the projective identifications and works through the enactments.