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.     

Time and site of assembly of the peritrophic membrane of the mosquito Aedes aegypti

Summary We determined the time and site of secretion of the precursors of the peritrophic membrane (PM) in Aedes aegypti and when the structure is assembled. The fine structure of the developing membrane of blood-feed females was described, and the pattern of secretion of injected tritiated glucosamine analyzed autoradiographically. Immediately following blood feeding, ingested red cells rapidly become compressed, such that the surrounding plasma is extruded to the margin of the midgut contents. Thereby, ingested fluids form a narrow margin separating the blood mass from the midgut epithelium. By electron microscopy, the PM first becomes evident at about 4 to 8 h after blood is ingested, and the membrane attains mature texture by 12 h. The compacted mass of ingested erythrocytes seems to serve as a template for the forming structure. In contrast, tritiated glucosamine, injected into freshly engorged mosquitoes, begins to concentrate on the midgut microvilli by 2 h after feeding. By 8 h the label assumes the layered appearance that characterizes the fine structure of the mature membrane. In contrast to the prevailing concept that the PM of mosquitoes first assumes texture anteriorly immediately after blood is ingested, we find that this potential barrier to pathogen development forms no earlier than 4 h after feeding and that it is formed from precursors secreted along the entire length of the epithelium overlying the food mass.     

Antigen presentation in the rat. II. An Ia+ radiosensitive T cell can present antigen to primed Ia- T cells

We demonstrated previously the presence of an Ia+ (OX-6+) antigen-presenting cell within the rat T cell fraction that is capable of presenting antigen to antigen-primed OX-6-T cells. This antigen-presenting cell (T-APC) reacted with the monoclonal antibodies W3/25 and W3/13, which is known to react mainly with rat T cells. Further characterization of the T-APC indicated that the cell also reacted with the monoclonal antibody OX-19, which is highly specific for rat T cells. Moreover, the antigen-presenting function of the T-APC was sensitive to treatment with mitomycin C or gamma-irradiation (2000 rad). Under similar conditions, antigen presentation by partially purified dendritic cells or macrophages was totally resistant to these treatments. The antigen-presenting activity of gamma-irradiated T-APC was not reconstituted by the addition of the lymphokines IL 1, IL 2, or Con A supernatants. Although unirradiated T-APC were able to stimulate an MLR response, this function was also sensitive to gamma-irradiation, whereas the MLR-stimulating ability of macrophages and dendritic cells was resistant to gamma-irradiation. These data indicate that Ia+ T cells from the rat are capable of presenting antigen to antigen-primed T lymphocytes and that, in contrast to antigen presentation by macrophages and dendritic cells, the function of T-APC is gamma-radiation sensitive.     

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.     

Effect of parturition on serum glycerol and non-esterified fatty acids in obese and normal weight women

Serum glycerol and NEFA content variations are examined before and after labor in obese and normal weighing women (35 subjects). Blood glycerol and NEFA are shown to increase before delivery. Glycerol values are shown to drop to normal immediately after delivery, while NEFA values diminish to a lesser extent. Statistical analysis shown that blood glycerol increase could be pregnancy-dependent in both normal weighing and obese women, but that NEFA increase could be pregnancy-dependent in normal weighing women only. Obesity increases blood glycerol and NEFA concentration considerably, thus masking the effects of pregnancy.     

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).     

Characterization of two virulent Lactobacillus fermentum bacteriophages isolated from sour dough

Two different bacteriophages, FE5-B1 and Z63-B1, active against strains of Lactobacillus fermentum were isolated from a sample of sour dough of a regional wheat bread. They showed different host specificities when tested against 58 strains of obligately heterofermentative lactic acid bacteria, as well as differences in adsorption and one-step growth kinetics. The burst size of FE5-B1 was about 100 pfu cell⁻¹. This phage belonged to the A₁ morphotype of Myoviridae family, having an icosahedral head (83 nm diam.) and a sheathed contractile tail (170 nm in length). The phage consisted of five major structural proteins and had a genome of 86 kbp. Z63-B1 showed a burst size of 10 pfu cell⁻¹ and belonged to the B₁ morphotype or Siphoviridae family. Z63-B1 had an isometric head (60 nm diam.) and a non-contractile tail (160 nm in length), with eight major different structural proteins and a genome of 32 kbp.     

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     

Interaction of trace elements in a longitudinal study of human milk from full-term and preterm mothers

Concentrations of 8 trace elements (Fe, Cu, Zn, Se, Br, Pb, Rb, and Sr) at different lactation time were measured by the PIXE multi-elemental technique. Time dependence and interelement correlations were studied. A total of 200 milk samples from 32 lactating mothers were supplied from 2 to 120 d after delivery of 26 full-term and 6 preterm infants. All elements showed a lognormal frequency-distribution. The Fe, Cu, Zn, and Se contents in preterm milk were found to be somewhat different with respect to full-term milk. Cu, Zn, Se, Br, Pb, and Rb concentrations declined with lactation time, both in pre- and full-term samples. Sr and Fe contents did not show any change with time. Detailed analysis of data by partial correlation and multiple regression methods was performed. No substantial differences between preterm and full-term samples were found in the results of partial correlation analysis. Cu and Zn were found to be correlated with lactation time, whereas the measured time dependence for the other elements has to be attributed to the effect of the existing interelement correlation. All the measured elements appeared to be correlated with at least one other element. In particular, Se was inversely correlated with Zn and directly with Cu. The zinc and copper contents in milk can therefore depend on the variation in the mother selenium intake.     

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).