Cellular localization of cytochrome c 553 in the N2-fixing cyanobacterium Anabaena variabilis

The in situ location of the electron carrier protein cytochrome C ₅₅₃ (cyt c ₅₅₃) has been investigated in both vegetative cells and heterocysts of the cyanobacterium Anabaena variabilis ATCC 29413 using the antibody-gold technique, carried out as a post-ernbedding immunoelectron microscopy procedure. When using a rabbit polyclonal anti-cyt c ₅₅₃ specific antiserum an intense labelling, associated mainly with the cell periphery (cytoplasmic membrane and periplasmic area), was seen in both heterocysts and vegetative cells. The selective release of most of the cellular cyt c ₅₅₃ during a Tris-EDTA treatment confirms a periplasmic localization of this protein in A. variabilis. The results indicate that most of cyt c ₅₅₃ is located in the periplasmic space. The roles ascribed to this protein in both respiration and photosynthesis in cyanobacteria are discussed.Abbreviations Cyt c ₅₅₃ cytochrome c ₅₅₃ - PBS phosphate buffered saline (20 mM sodium phosphate, 0.9% NaCl, pH 7.4) - PMSF phenylmethylsulfonyl fluoride Recipient of a Research Fellowship of the Alexander von Humboldt Foundation (Bonn, FRG) for a leave to the University of Konstanz.     

Effect of parasympathetic denervation on acetylcholine levels in the rat parotid gland. Is there an extraneuronal pool of acetylcholine?

Parasympathetic denervation of the rat parotid gland by avulsion of the auriculotemporal nerve caused a marked and lasting decrease in gland weight. Parasympathectomy did not change the levels of choline in the gland but decreased by 60% the levels of acetylcholine (ACh) ten days after surgery and 65% at 28 days. It is puzzling that relatively high levels of ACh remained after parasympathetic denervation. The presence of additional cholinergic nerves that innervate the gland, or pass through it en route to other structures may account for some of the remaining ACh. Also, Schwann cells from denervated nerves might have contributed to some of the ACh. The existence of an extraneuronal source of ACh is considered.     

Struttura ed ultrastruttura dell'apparato genitale maschile di Drosophila melanogaster Meig.

Summary The structure of the testes of Drosophila melanogaster Meig. was re-examined by means of phase contrast and polarized light microscopy; the ultrastructure was investigated by electron microscopy. Testes from adult virgins of wild strain Varese were studied, but some observations were made also on the testes of different aged insects, of some insects examined at different times during and after mating, and on testes from sterile mutant strains.The results are summarized in the following points: 1) The testis is made up of an external wall and of an internal germinal tissue. The wall appears to be composed of two overlapping layers of very flattened cells: pigmented cells and muscle cells. 2) The ultrastructure of the muscle cells gives rise to some interesting considerations arising out of the fact that there are two kinds of filaments, but without any evident transverse band organization. 3) The testis falls into three different portions according to the organisation of the germinal tissue: the apical portion (spermatogonial zone), the middle portion (spermagenetic zone) and the terminal portion (spermatic zone). 4) The germinal tissue is made up of germinal cells and interstitial cells. The germinal cells occur in groups consisting of a fixed number of elements in a syncytial state: these groups are enveloped by interstitial cells forming the cyst. The cysts can be considered as the supracellular unit of germinal tissue.The results are discussed in relation to numerous problems, such as: the existence and meaning of the syncytial state of the germinal cells; the existence of a functional cycle of the interstitial cells associated with the maturation of germinal elements; the phagocytic and mechanical functions of terminal epithelium; the existence of various movements of germinal tissue elements along the length of the testis from the apical zone to the terminal one.The paper ends with a discussion on functional aspects of the male reproductive organs.

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Ricerche eseguite col sussidio del C.N.R. (Roma).     

Identification of two different glyceraldehyde-3-phosphate dehydrogenases (phosphorylating) in the photosynthetic protist Cyanophora paradoxa

Two different glyceraldehyde-3-phosphate (G3P) dehydrogenase (phosphorylating) activities, namely NAD- and NADP-dependent, have been found in cell extracts of the cyanelle-bearing photosynthetic protist Cyanophora paradoxa. Whereas the two G3P dehydrogenase activities were detected with similar specific activity levels (0.1 to 0.2 U/mg of protein) in extracts of the photosynthetic organelles (cyanelles), only the NAD-dependent activity was found in the cytosol. Thus, a differential intracellular localization occurred. The perfect overlapping of the two G3P dehydrogenase activity peaks of the cyanelle in both hydrophobic interaction chromatography and subsequent FPLC (fast protein liquid chromatography) gel filtration indicated that the two activities were due in fact to a single NAD(P)-dependent G3P dehydrogenase (EC 1.2.1.-) with a molecular mass of 148,000. SDS-PAGE of active fractions from FPLC gel filtration showed that the intensity of the major protein band (molecular mass, 38,000) of the enzyme preparation clearly paralleled the activity elution profile, thus suggesting a tetrameric structure for the cyanelle dehydrogenase. On the other hand, FPLC gel filtration analysis of the cytoplasmic fraction revealed a NAD-dependent G3P dehydrogenase with a native molecular mass of 142,000, being equivalent to the classical glycolytic enzyme (EC 1.2.1.12) present in the cytosol of all the organisms so far studied. The significance of these results is discussed taking into account that the cyanobacteria, photosynthetic prokaryotes which share many structural and biochemical features with cyanelles and are considered as their ancestors, have a similar NAD(P)-dependent G3P dehydrogenase.Abbreviation FPLC Fast protein liquid chromatography     

Diversity of Xiphinema americanum-group Species and Hierarchical Cluster Analysis of Morphometrics

Of the 39 species composing the Xiphinema americanum group, 14 were described originally from North America and two others have been reported from this region. Many species are very similar morphologically and can be distinguished only by a difficult comparison of various combinations of some morphometric characters. Study of morphometrics of 49 populations, including the type populations of the 39 species attributed to this group, by principal component analysis and hierarchical cluster analysis placed the populations into five subgroups, proposed here as the X. brevicolle subgroup (seven species), the X. americanum subgroup (17 species), the X. taylori subgroup (two species), the X. pachtaicum subgroup (eight species), and the X. lambertii subgroup (five species).     

A Chronobiological Approach to Circulating Levels of Renin, Angiotensin-Converting Enzyme, Aldosterone, ACTH, and Cortisol in Addison's Disease

This study deals with a chronobiological approach to the circadian rhythm of the renin-angiotensin-aldosterone system (RAAS) and the ACTH-cor-tisol axis (ACA) in patients with Addison's disease (PAD). The aim is to explore the mechanism(s) for which the circadian rhythmicity of the RAAS and ACA takes place. The study has shown that both the RAAS and ACA are devoid of a circadian rhythm in PAD. The lack of rhythmicity for renin and ACTH provides indirect evidence that their rhythmic secretion is in some way related to the circadian oscillation of aldosterone and cortisol. This implies a new concept: a positive feedback may be included among the mechanisms which chronoregulate the RAAS and ACA.     

Serum angiotensin-converting enzyme activity in pre-eclamptic pregnancy: evidence for a relative hypermesorACEemia

The circadian rhythm of serum angiotensin-converting enzyme (ACE) activity was investigated in pregnant women with normal and pre-eclamptic gestation. The chronobiological approach was able to document the occurrence of a circadian rhythm for serum ACE activity in normal pregnancy. Such a rhythm is characterized by a decreased mesor and amplitude and a shifted crest. The circadian rhythm for serum ACE activity was not detectable in pre-eclamptic pregnancy. Such an abrogation is accompanied by a negligible decrease of mesor suggesting the occurrence of a relative hyperACEemia. This disorder could play a role in pregnancy-induced hypertension.     

Phylogeny and morphology of Hirsutella tunicata sp. nov. (Ophiocordycipitaceae), a novel mite parasite from Peru

A new species of Hirsutella was isolated from unidentified mites on Petri plates inoculated with soil and root fragments collected from asparagus rhizosphere at Virú, Northern Peru. The fungus differs from other Hirsutella species by an envelope surrounding the conidium, conidia dimension and DNA sequences. In PDA cultures, the mycelium produced aerial hyphae with conidiogenous cells mainly at right angles, occasionally showing a secondary conidiophore. The solitary conidia are cymbiform, slightly apiculate, 5.0–6.0 × 3.0–4.0 μm. Phylogenetic analyses with partial rRNA and β-tubulin gene sequences confirmed the fungus as an Hirsutella (Ophiocordycipitaceae). Closest species shown by maximum likelihood and neighbor-joining trees were H. nodulosa and H. aphidis, from which the new species differs for conidium or conidiogenous cells dimensions, lack of synnemata and host type. A recombination event was also detected in the rRNA of the holotype strain, involving Ophiocordyceps sinensis as major parent and O. cochlidiicola as minor parent. A complement, inverted insertion was also found in its rRNA, involving part of the ITS2 and 5.8S regions, flanked by two short nucleotide arrays. Due to conidia dimension and phylogenetic position, the fungus is described as Hirsutella tunicata sp. nov. A review of mononematous Hirsutella species is provided.     

Habitat use of coexisting introduced eastern cottontail and native European hare

The niche of introduced species and that of native ones may overlap, thus causing detrimental effects on the latter through competitive interactions. We used radio telemetry to investigate habitat partitioning during the active period by the introduced American eastern cottontail (Sylvilagus floridanus) and the native European hare (Lepus europaeus) in sympatric conditions. Home ranges of cottontails varied from 1.1–2.2 ha in autumn to 3.0–3.6 ha in summer. In hares, home ranges were 30.5–33.8 ha in summer and increased to 49.5–85.9 ha in winter. Both species used an overall area composed of about 27% of natural habitats (i.e., meadows, woodlands, shrubby habitats, shores, and uncultivated land) and over 70% of field crops. The coexistence of the two species appeared to be facilitated by habitat partitioning. Habitat use of cottontails was characterized by a preference for natural habitats at the study area level as well as within the home ranges, while hares showed a preference for crop fields at both spatial scales and a seasonal selection of meadows within home ranges. Habitat overlap measured with the Pianka index was 0.57–0.64 in autumn and winter, and increased in summer and spring to 0.73–0.78. Our results provide evidence of different resource selection strategies adopted by these two sympatric lagomorph species. Hare populations are often found in agricultural landscapes at low-densities, while cottontails are currently spreading throughout Northern Italy to such an extent that an eradication programme appears unfeasible. In this situation, conservation measures for hares and other species should also take into consideration the presence or possible arrival of cottontails. Habitat restoration measures that would increase the amount of fallow lands and shrublands may favour cottontails more than hares. In areas where introduced lagomorphs are present, the necessity of natural open landscapes for hares may be better faced by increasing the presence of meadows, that are seasonally used by hares and not by cottontails.