Evidence for rapid limitation of the I element copy number in a genome submitted to several generations of I-R hybrid dysgenesis in Drosophila melanogaster

Summary When Drosophila melanogaster males coming from a class of strains known as inducer are crossed with females from the complementary class (reactive), a quite specific kind of sterility is observed in the F₁ female progeny (denoted SF). The inducer chromosomes differ from the reactive chromosomes by the presence of a transposable element (called the I factor) that is responsible for the induction of this dysgenic symptom. In the germ line of dysgenic females, up to 100% of the reactive chromosomes may be contaminated, i.e. they acquire I factor(s) owing to very frequent replicative transpositions. A contaminated reactive stock was obtained by reconstructing the reactive genotype in the offspring of SF females and its kinetics of invasion by I elements was followed in the successive inbred dysgenic generations. The results show that the mean copy number of I elements increased very quickly up to the level of inducer strains and then stayed in equilibrium even though the dysgenic state was perpetuated by selection for SF sterility at every generation. The possible mechanisms of this copy number limitation are discussed.     

Temperature Dependence of Drug Interaction with the Platelet 5-Hydroxytryptamine Transporter: A Clue to the Imipramine Selectivity Paradox

Although [3H]imipramine is a selective radioligand for the 5-hydroxytryptamine (5-HT) transporter in human platelets, its affinity for binding to the 5-HT transporter complex at 0 degrees C (0.6 nM) is significantly higher than its potency for inhibition of [3H]5-HT uptake at the physiological temperature of 37 degrees C (Ki = 29 nM). As this apparent discrepancy could be related to the assay temperature, we studied the thermodynamics of drug interaction with the 5-HT transporter at assay temperatures between 0 degrees C and 37 degrees C, using as radioligands [3H]imipramine (0 degrees C and 20 degrees C) and [3H]paroxetine (20 degrees C and 37 degrees C), a newly available probe for the 5-HT transporter. At 20 degrees C, Ki values of 14 tricyclic and nontricyclic drugs for inhibition of [3H]imipramine and [3H]paroxetine binding to human platelet membranes were highly significantly correlated (r = 0.98, p less than 0.001), validating the use of these two radioligands to study the 5-HT transporter over a temperature range larger than was previously possible with [3H]imipramine alone. The affinity of imipramine for the 5-HT transporter is progressively enhanced with decreasing incubation temperature, thus favoring the selectivity of [3H]imipramine for the 5-HT transporter at 0 degrees C. At 37 degrees C, the Ki of imipramine for inhibition of [3H]paroxetine binding is 32 nM, and equals its Ki value for inhibition of 5-HT uptake into human platelets. With the exception of chlorimipramine, other tricyclic 5-HT uptake inhibitors showed a temperature sensitivity in their interaction with the 5-HT transporter similar to that of imipramine.(ABSTRACT TRUNCATED AT 250 WORDS)     

Axonal Transport Characteristics of Gangliosides in Sensory Axons of Rat Sciatic Nerve

The distribution of axonally transported gangliosides and glycoproteins along the sciatic nerve was examined from 3 h to 4 weeks following injection of[3H]glucosamine into the fifth lumbar dorsal root ganglion of adult rats. Incorporation of labeled precursor into these glycoconjugates reached a maximal level in the ganglion within 6 h. Outflow patterns of radioactivity for glycoproteins showed a well-defined crest with a transport rate of approximately 330 mm/day. In contrast, the crest of transported gangliosides was continuously attenuated, implying a significant deposition along the axon, and an alternative method of calculating velocity was required. Analysis of accumulation of labeled material at double ligatures demonstrated both anterograde and retrograde transport of glycoproteins and gangliosides and allowed for the calculation of an anterograde transport rate of about 270 mm/day for each. Additional evidence of ganglioside transport is provided in that the TLC pattern of transported radioactive gangliosides accumulating at a ligature is significantly different from the pattern seen in the dorsal root ganglion or following intraneural administration of the labeled precursor. These data indicate that gangliosides are transported at the same rapid rate as glycoproteins but are subject to a more extensive exchange with stationary material than are glycoproteins.     

Life history adaptations of Gasterosteus aculeatus in a Mediterranean wetland

Synopsis The life cycle of leiurus-type Gasterosteus aculeatus occurring in a Mediterranean coastal wetland is described. Fish have a low number of lateral plates, short spines and marked sexual dimorphism in size. The life cycle is strictly annual, adults dying shortly after breeding. Adult fish migrate into seasonally-flooded freshwater marshes to breed, and the young migrate back to brackish water to pass the summer and autumn. Breeding occurs in March at water temperatures of about 10°C, the season lasting about 50 days. Growth of fish occurs throughout the year, but differs from year to year, resulting in variable adult size. Maximum gonadal investment of male fish is in autumn, whereas that of females is in spring. Gonadal investment of female fish, as measured by gonado-somatic index and fecundity, is higher than in other studied leiurus populations, but the number of clutches produced in a season is probably low. These differences in life history from other studied populations of sticklebacks are seen as adaptations to a mediterranean-type climate (high summer temperatures, seasonality of water bodies) and to heavy predation by fish-eating birds.     

Dinucleoside tetraphosphate variations in cultured tumor cells during their cell cycle and growth

Asynchronous and synchronized cultures of A549 and HTC cells were used to detect possible, cell cycle or cell density specific variations in the intracellular pools of dinucleoside tetraphosphates (Ap4X). No important variations of the nucleotide pools were observed during cell growth. When HTC cells were released from mitotic arrest, a decrease by a factor of N3 Ap4X and ATP levels was observed when the cells entered the G1 phase. This decrease is essentially due to cell doubling. When A549 cells were released from an arrest at the G1/S boundary, the nucleotide pool size increased slightly during the G2 phase just before mitosis. This result is in agreement with both earlier data from our laboratory and the observed decrease in Ap4X pool after release from mitotic-arrested HTC cells. These results suggest that the Ap4X and ATP pools are only subjected to very small variations during the cell cycle, essentially in the G2 phase and after mitosis.     

Chromatographic and immunological evidence that chloroplastic and cytosolic pea (Pisum sativum L.) NADP-isocitrate dehydrogenases are distinct isoenzymes

Two NADP-isocitrate dehydrogenase isoenzymes designated as NADP-IDH₁ and NADP-IDH₂ (EC 1.1.1.42) were identified in pea (Pisum sativum) leaf extracts by diethylaminoethylcellulose chromatography. The predominant form was found to be NADP-IDH₁ while NADP-IDH₂ represented only about 4% of the total leaf enzyme activity. These enzymes share few common epitopes as NADP-IDH₂ was poorly recognized by the specific polyclonal antibodies raised against NADP-IDH₁, and as a consequence NADP-IDH₂ does not result from a post-translational modification of NADP-IDH₁. Subcellular fractionation and isolation of chloroplasts through a Percoll gradient, followed by the identification of the associated enzymes, showed that NADP-IDH₁ is restricted to the cytosol and NADP-IDH₂ to the chloroplasts. Compared with the cytosolic isoenzyme, NADP-IDH₂ was more thermolabile and exhibited a lower optimum pH. The data reported in this paper constitute the first report that the chloroplastic NADP-IDH and the cytosolic NADP-IDH are two distinct isoenzymes. The possible functions of the two isoenzymes are discussed.Abbreviations BSA bovine serum albumin - DEAE diethylaminoethyl - NADP-IDH NADP-isocitrate dehydrogenase - NADP-IDH₁ cytosolic NADP-IDH - NADP-IDH₂ chloroplastic NADP-IDH     

Effects of etretinate on the distribution of elements in rats

We studied in the rat the effects of the drug etretinate (Tigason), given at three doses 3, 10, and 30 mg/kg body wt for 1 mo, on the concentrations of Na, K, Ca, Mg, Fe, S, P, Cu, and Zn in the plasma, brain, thymus, heart, liver, lung, kidney, testicle, muscle, and bone. The elements were simultaneously determined in tissues after nitric acid dissolution by inductively coupled plasma emission spectrometry using a JY 48 instrument. At the dose of 3 mg/kg, etretinate did not induce any statistically significant modifications of the element distribution. At the dose of 10 mg/kg, the main observed modifications were in plasma an increase of copper (+38%) and a decrease of zinc (-25%). At the highest dose of 30 mg/kg, some variations of the concentrations of elements in tissues were observed. But, on no account did retinoids induce an alteration of the mineral composition of bone, despite obvious macroscopic bone alterations.     

The Opecoelidae (Digenea) of sparid fishes of the western Mediterranean. III. Macvicaria Gibson & Bray, 1982

Macvicaria obovata (Molin) n. comb. is redescribed from Sparus aurata off the Mediterranean coast of France and a neotype is designated. Specimens from Oblada melanura off Israel may belong to the same species. It is mainly characterized by the uterine extension between the ovary and the anterior testis and the lack of a vitelline confluence in the forebody. M. maillardi n. sp. is also described from Sparus aurata off the southern coast of France. Its uterus does not pass between ovary and testes and the vitelline fields are confluent in the forebody. M. crassigula (Linton) n. comb. is redescribed from Diplodus annularis, D. sargus, D. vulgaris, Pagellus erythrinus and Sparus pagrus off Corsica, Calamus bajonado off Bermuda, Spicara smaris, D. annularis off Yugoslavia, D. sargus off Israel, and D. cervinus, Sparodon durbanensis and Cheilodactylus fasciatus in the SW Indian Ocean. It is similar to M. maillardi, but differs in being smaller, having a greater sucker ratio and a larger pharynx. It may well be a species-complex. M. dubia (Stossich) n. comb. is redescribed from Oblada melanura off Corsica and Yugoslavia. It is similar to M. maillardi and M. crassigula, but has a more anteriorly situated genital pore.