Chromosomal distribution of P and I transposable elements in a natural population of Drosophila melanogaster

The chromosomal distribution of P and I transposable elements was studied, by in situ hybridisation, in 25 isofemale lines of Drosophila melanogaster collected at Nasr'Allah in Tunisia. An important interline variability for the number of copies of both elements was revealed. The mean number of copies per line was 31.3 for P and 21.0 for I. Certain chromosome arms had a higher frequency of copies than others: arm 3R had the highest frequency of I elements; the X chromosome had the highest frequency of P elements and the lowest frequency of I elements. For both P and I elements the number of copies on the different chromosome arms is independent. Furthermore, there is no significant correlation between the number of copies of P and the number of copies of I for a given line. A study of the localisation of hybridisation sites on the X chromosome revealed the existence of preferred regions for each family. The population studied was of type M' in the P-M system of hybrid dysgenesis. There is no direct relationship between the M potential of an isofemale line and its number of copies of P elements. These results are compared with those of other investigators and the consequences for cytotype determination are discussed.     

A Raman spectroscopic study on the interaction of an ion-channel protein with a phospholipid in a model membrane system (gramicidin A/L-alpha-lysophosphatidylcholine)

The interaction of the ion channel polypeptide gramicidin A with the L-alpha-lysophosphatidylcholine micelles in a membrane state association (approximative molar ratio 1:9) was investigated by Raman spectroscopy. Studies were carried out over the spectral ranges of 700-1700 cm-1 and 2800-3100 cm-1 at 10 degrees C. The Raman spectrum of L-alpha-lysophosphatidylcholine micelles indicated a disordered structure of the lipid acyl chains by the high intensities of the gauche conformation vibrations. Changing from the micellar phase to the membrane state of association with gramicidin A, the intensities of all-trans stretching modes increased whereas the intensities of gauche conformation vibrations decreased, reflecting the emergence of ordered lipid chains. Hydrophobic interactions between the acyl chains and the polypeptide side chain residues were demonstrated. The absence of modifications in intensities of the very strong tryptophan vibrations in the complex spectrum indicated that, if the tryptophan-stacking interactions suggested by some authors exist, they are very weak ones.     

Specific inhibition of human granulocyte elastase with peptide aldehydes

The kinetic features of human granulocyte elastase, chymotrypsin, porcine pancreatic elastase and elastomucoproteinase were compared. Amino acyl ester substrates were assayed and Km and kcat values were defined. Aldehyde analogues of the p-nitroanilide substrates designed for granulocyte elastase as optimal for Km appeared to be potent inhibitors. Suc-D-Phe-Pro-valinal (Ki = 40 microM) was found to inhibit granulocyte elastase competitively and specifically when measured with synthetic substrates, and the Ki was 3 microM with the natural protein substrate, elastin.     

Binding inhibition by monoclonal antibodies of ovine placental lactogen to growth hormone receptors in human liver

In the radioreceptor assay for growth hormone (RRA-GH) using [125I]iodo-hGH, hGH and human liver membrane particulate fractions as tracer, hormone standard and receptors, respectively, ovine placental lactogen (oPL) is capable of inhibiting the binding of [125I]iodo-hGH in a parallel manner with hGH and in equipotency. Similarly, in the RRA-GH by employing [125I]iodo-oPL, oPL and human liver membrane particulate fractions as tracer, hormone standard and receptors, respectively, hGH is also equipotent as oPL in inhibiting the binding of [125I]iodo-oPL in a parallel fashion. The addition of monoclonal antibodies against oPL in the assay was effective in inhibiting the binding of [125I] iodo-oPL to human liver, but could not, however, inhibit the binding of [125I]iodo-hGH to human liver. Furthermore, the addition of the monoclonal antibodies in the RRA-GH did not affect the parallelism of the oPL standard but lowered the total binding of oPL. Our studies indicate that the structure of the binding sequence in oPL which binds to the GH receptor of human liver is not identical to the equivalent sequence of hGH and that the monoclonal antibodies compete with GH receptors in human liver for the binding of oPL.     

Comparative study of G- and C-banded chromosomes of five species of Microtidae

G-banded karyotypes were compared in the following species of Microtidae: Microtus nivalis; M. cabrerae; M. arvalis and Arvicola sapidus. Previous observations on A. sapidus and A. terrestris (Díaz de la Guardia & Pretel, Caryologia 32: 183–189, 1979) were also incorporated in this study. The results show that Robertsonian translocations and pericentric inversions are common mechanisms involved in the karyotypic evolution of this group. Interspecific differences in C-banding patterns were also analyzed. Using the karyograph method (Imai et al., Am. Nat. 121: 477–488, 1983), the evolutionary distances of the karyotypes were estimated, and an attempt was made to establish a presumptive phylogenetic tree.     

Evolution of digestibility by Hind III: an analysis by light and electron microscopy

Digestion of Chinese hamster metaphase chromosomes from the Don cell line by Hind III restriction endonuclease followed by Giemsa staining were analysed by light and electron microscopy. The evolution of digestibility was studied and four digestion stages were characterized by different levels of chromosome structure. Three different condensation stages were established according to morphological criteria of length, width and separation among chromatids. It was observed that there are statistically significant differences in the digestion progress at the three condensation stages previously defined.     

Metabolic incorporation of 9-(2-anthryl)-nonanoic acid, a new fluorescent and photoactivable probe, into the membrane lipids of Chinese hamster ovary cells

9-(2-Anthryl)-nonanoic acid is a new fluorescent and photoactivable probe, which has been designed for studying the lateral diffusion rate and the lateral distribution of lipids in biological membranes by means of the anthracene photodimerization reaction. It is shown that this anthracene fatty acid is metabolically incorporated into the glycerophospholipids (phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol) of the eukaryotic Chinese hamster ovary cells in culture. Under our culture conditions (Eagle's minimal essential medium plus delipidized fetal calf serum) this incorporation proceeded with a very good rate (up to 45 mol/100 mol, after two days culture) and could be easily modulated depending on the way the cells were fed with the anthracene fatty acid. It occurred to a similar extent at the sn-1 (55 +/- 5%) or at the sn-2 (45 +/- 5%) position on the phospholipid glycerol backbone, without any degradation or elongation. No double labelling at the sn-1 and sn-2 positions was detected. Although incorporation of the anthracene fatty acid affected the cell growth rate (generation time of 48 h compared to a generation time of 21 h for control cells) it did not bring about cell mortality. This incorporation took place not only into the phospholipids but also into the triglycerides with, as a consequence, the appearance of strongly fluorescent lipid vesicles inside the cells. It affected the whole cell fatty acid composition by slightly increasing the amount of palmitic acid and markedly decreasing the amount of stearic and oleic acids.     

The species composition,occurrence and temporal stability of submerged aquatic macrophyte patches along the main channel border of pool 5A,Upper Mississippi River

Species composition, relative abundance, distribution and physical habitat associations of submerged aquatic macrophytes in the main channel border (MCB) habitat of Pool 5A, Upper Mississippi River (UMR) were investigated during the summers of 1980 and 1983. The submerged aquatic macrophytes in Pool .5A MCB were a small and stable component of the river ecosystem. Submerged plants occurred primarily in small, monospecific clumps. Clumps in close proximity to each other formed plant patches. Plant patches were stable in location and number between 1980 and 1983; 82.5% of the patches first observed in 1980 were present in 1983. Submerged macrophytes covered about 10–12 ha of the 201 ha MCB in Pool 5A. Submerged plants were most common in the lower two-thirds of the pool. Ten species of aquatic macrophytes occurred on rock channel-training structures and eleven occurred on non-rock substrates in the MCB. The most common submerged plants, in order of abundance, were Vallisneria americana Michx., Heteranthra dubia Jacq., Potamogeton pectinatus L., Ceratophyllum demersum L. and Potamogeton americanus C. & S.     

Cell types of the pars distalis of the hedgehog (Erinaceus europaeus L.) adenohypophysis: cytological, immunocytochemical and ultrastructural studies. 4. Thyrotropic cells

Staining and histochemical methods, immunofluorescence and electron microscopy were used to individualize the thyrotropic cells in the adenohypophysis of the non-hibernating hedgehog. One cell type was differentiated; its characteristics at the light and electron-microscopic levels were presented. Immunofluorescence has confirmed the functional significance of this cell type and the validity of the denomination of 'thyrotropic cells'.     

The Ultrastructure of the Gastrodermal Gland Cells in the Freshwater Planarian Dugesia gonocephala s.l.

Light and transmission electron microscopy have been used to study the gastrodermal gland cells of the triclad Dugesia gonocephala s.l. The events involved in the ultrastructural transformation and the secretion process in these cells were followed at four different stages in both fasted and fed animals. During the feeding stage their secretory granules are directly discharged into the intestinal lumen by means of a secretion process of the holocrine type that is described in this paper. It is suggested that such secretions contribute to extracellular digestion and that disintegration of the gland cells is accompanied by a differentiation of neoblasts into new gland cells, reflecting a turnover of gland cells during the triclad digestive stages.