ULTRASTRUCTURE AND PIGMENTS OF TWO STRAINS OF THE PICOPLANKTONIC ALGA PELAGOCOCCUS SUBVIRIDIS (CHRYSOPHYCEAE)1

The organelle ultrastructure and photosynthetic pigments of a new isolate of the picoplanktonic alga Pelagococcus subviridis Norris from the East Australian Current was compared with the North Pacific Ocean type species. No differences in the ultrastructure of the two isolates were observed. Mitosis was studied in detail in the Australian strain, and showed two unusual features: the de novo appearance of centrioles prior to mitosis, and the formation of a small, extra-nuclear spindle. The major carotenoids in both strains were fucoxanthin and a 19′-butanoyloxyfucoxanthin-like pigment, with diadinoxanthin and diatoxanthin as secondary pigments. Several minor carotenoids have not yet been identified. In addition to chlorophylls a and c₂, a new chlorophyll c derivative (chlorophyll c₃), present in both strains, was separated by high-performance thin-layer chromatography (HPTLC). The Australian isolate, unlike the type material, showed no evidence of chlorophyllase activity during cell harvest and extraction. While the pigment composition suggests affinities with certain newly examined prymnesiophytes, organelle ultrastructure indicates Pelagococcus to be a member of the Chrysophyceae. Mitosis is, however, atypical of both Prymnesiophyceae and Chrysophyceae, and if this picoplanktonic alga is to be retained in the Chrysophyceae it must be seen as a most unusual member.     

ULTRASTRUCTURE OF TETRASPOROGENESIS IN THE CORALLINE ALGA HALIPTILON CUVIERI(RHODOPHYTA)1

Tetrasporogenesis begins with the formation of the tetra-sporocyte, an elongate, apparently wall-less, cell containing few organelles. The tetrasporocyte rapidly elongates and a distinctive cell wall forms before the onset of meiosis. During this elongation phase there is also an increase in the number of plastids and mitochondria. The meiotic tetrasporocyte is characterized by extensive development of perinuclear endoplasmic reticulum (PNER) and peripheral endoplasmic reticulum (PER) and during the latter stages of sporogenesis by internuclear endoplasmic reticulum. Immediately next to the nuclear envelope the inter-cisternal spaces of the PNER are filled with very electron dense material and the PNER cisternae are quite narrow, while further away from the nucleus the PNER cisternae dilate. Throughout meiosis there is continued replication of plastids and mitochondria as well as synthesis of starch and the formation of Golgi-derived vesicles with very osmiophilic contents. Cytokinesis begins with the formation of striated thickenings on the inside of the tetrasporocyte wall, at the sites where the cleavage furrow, produced by infurrowing of the plasmalemma, will be formed. Early in cytokinesis the PER disappears and is replaced by osmiophilic vesicles and mitochondria. Tubular plasmalemma invaginations of 27–30 nm width also appear during the early stages of tetraspore wall formation. The ultra-structure of the early stages of tetraspore germination is also described.     

Effects of vasopressin-mastoparan chimeric peptides on insulin release and G-protein activity.

Two chimeric peptides, consisting of the linear vasopressin receptor V1 antagonist PhAc-D-Tyr(Me)-Phe-Gln-Asn-Arg-Pro-Arg-Tyr, in the N-terminus and mastoparan in the C-terminus connected directly (M375) or via 6-aminohexanoic acid (M391), have been synthesised. At 10 microM concentration, these novel peptides increased insulin secretion from isolated rat pancreatic islet cells 18-26-fold at 3.3 mM glucose and 3.5-5-fold at 16.7 mM glucose. PTX pretreatment of the islets decreased the peptide-induced insulin release. M375 and M391 bind to V1a vasopressin receptors with affinities lower than the unmodified vasopressin antagonist, but with K(D) values of 3.76 nM and 9.02 nM, respectively, both chimeras are high affinity ligands. The GTPase activity and GTPgammaS binding in the presence of these peptides has been characterised in Rin m5F cells. Comparison of the influence of the peptides M375 and M391 on GTPase activity in native and pertussis toxin-treated cells suggests a selective activation of G alpha(i)/G alpha(o) subunits, combined with a suppression of other GTPases, primarily G alpha(s). However, the GTPgammaS binding data show that the peptides retain some of the activating property even in PTX-treated cell membranes. In conclusion, the conjugation of mastoparan with the V1a receptor antagonists produce peptides with properties different from the parent peptides that could be used to elucidate the role of different G proteins in insulin release.     

Potentially Active Iron,Sulfur, and Sulfate Reducing Bacteria in Skagerrak and Bothnian Bay Sediments

In many marine surface sediments, the reduction of manganese (Mn) and iron (Fe) oxides is obscured by sulfate reduction, which is regarded as the predominant anaerobic microbial respiration process. However, many dissimilatory sulfate and sulfur reducing microorganisms are known to utilize alternative electron acceptors such as metal oxides. In this study, we tested whether sulfate and sulfur reducing bacteria are linked to metal oxide reduction based on biogeochemical modeling of porewater concentration profiles of Mn²⁺ and Fe²⁺ in Bothnian Bay (BB) and Skagerrak (SK) sediments. Steady-state modeling of Fe²⁺ and Mn²⁺ porewater profiles revealed zones of net Fe (0–9 cm BB; ～10 and 20 cm SK) and Mn (0–5 cm BB; 2–8 cm SK) species transformations. 16S rRNA pyrosequencing analysis of the in-situ community showed that Desulfobacteraceae, Desulfuromonadaceae and Desulfobulbaceae were present in the zone of Fe-reduction of both sediments. Rhodobacteraceae were also detected at high relative abundance in both sediments. BB sediments appeared to harbor a greater diversity of potential Fe-reducers compared to SK. Additionally, when the upper 10 cm of sediment from the SK was incubated with lepidocrocite and acetate, Desulfuromonas was the dominant bacteria. Real-time quantitative polymerase chain reaction (qPCR) results showed decreasing dsrA gene copy numbers with depth coincided with decreased Fe-reduction activity. Our results support the idea that sulfur and sulfate reducing bacteria contribute to Fe-reduction in the upper centimeters of both sediments.     

Computer-assisted determination of left ventricular endocardial borders reduces variability in the echocardiographic assessment of ejection fraction

Background

Left ventricular size and function are important prognostic factors in heart disease. Their measurement is the most frequent reason for sending patients to the echo lab. These measurements have important implications for therapy but are sensitive to the skill of the operator. Earlier automated echo-based methods have not become widely used. The aim of our study was to evaluate an automatic echocardiographic method (with manual correction if needed) for determining left ventricular ejection fraction (LVEF) based on an active appearance model of the left ventricle (syngo^®AutoEF, Siemens Medical Solutions). Comparisons were made with manual planimetry (manual Simpson), visual assessment and automatically determined LVEF from quantitative myocardial gated single photon emission computed tomography (SPECT).

Methods

60 consecutive patients referred for myocardial perfusion imaging (MPI) were included in the study. Two-dimensional echocardiography was performed within one hour of MPI at rest. Image quality did not constitute an exclusion criterion. Analysis was performed by five experienced observers and by two novices.

Results

LVEF (%), end-diastolic and end-systolic volume/BSA (ml/m²) were for uncorrected AutoEF 54 ± 10, 51 ± 16, 24 ± 13, for corrected AutoEF 53 ± 10, 53 ± 18, 26 ± 14, for manual Simpson 51 ± 11, 56 ± 20, 28 ± 15, and for MPI 52 ± 12, 67 ± 26, 35 ± 23. The required time for analysis was significantly different for all four echocardiographic methods and was for uncorrected AutoEF 79 ± 5 s, for corrected AutoEF 159 ± 46 s, for manual Simpson 177 ± 66 s, and for visual assessment 33 ± 14 s. Compared with the expert manual Simpson, limits of agreement for novice corrected AutoEF was lower than for novice manual Simpson (0.8 ± 10.5 vs. -3.2 ± 11.4 LVEF percentage points). Calculated for experts and with LVEF (%) categorized into < 30, 30–44, 45–54 and ≥ 55, kappa measure of agreement was moderate (0.44–0.53) for all method comparisons (uncorrected AutoEF not evaluated).

Conclusion

Corrected AutoEF reduces the variation in measurements compared with manual planimetry, without increasing the time required. The method seems especially suited for unexperienced readers.     

gamma-Tocopherol nebulization by a lipid aerosolization device improves pulmonary function in sheep with burn and smoke inhalation injury

Fire accident victims who sustain both thermal injury to skin and smoke inhalation have gross evidence of systemic and pulmonary oxidant damage and acute lung injury. We hypothesized that gamma-tocopherol (gT), a reactive O(2) and N(2) scavenger, when delivered into the airway, would attenuate lung injury induced by burn and smoke inhalation. Acute lung injury was induced in chronically prepared, anesthetized sheep by 40% total burn surface area, third-degree skin burn and smoke insufflation (48 breaths of cotton smoke, <40 degrees C). The study groups were: (1) Sham (not injured, flaxseed oil (FO)-nebulized, n=6); (2) SA-neb (injured, saline-nebulized, n=6); (3) FO-neb (injured, FO-nebulized, n=6); and (4) gT+FO-neb (injured, gT and FO-nebulized, n=6). Nebulization was started 1 h postinjury, and 24 ml of FO with or without gT (51 mg/ml) was delivered into airways over 47 h using our newly developed lipid aerosolization device (droplet size: 2.5-5 microm). The burn- and smoke inhalation-induced pathological changes seen in the saline group were attenuated by FO nebulization; gT addition further improved pulmonary function. Pulmonary gT delivery along with a FO source may be a novel effective treatment strategy in management of patients with acute lung injury.     

Alpha-tocopherol modulates genes involved in hepatic xenobiotic pathways in mice

Hepatic proteins involved in xenobiotic pathways (Phases I, II and III) are responsible for the metabolism and disposition of endogenous and exogenous compounds including dietary phytochemicals. To test the hypothesis that elevated alpha-tocopherol intakes alter gene expression of hepatic xenobiotic pathways, mice were fed diets supplemented with either 1000 IU (+E) or 35 IU (E) all-rac-alpha-tocopheryl acetate for 4 months; liver RNA was isolated, and gene expression was determined using both whole genome microarray and real-time quantitative polymerase chain reaction analyses. Hepatic alpha-tocopherol (173+/-18 vs. 21+/-1 nmol/g, mean+/-S.E.) and its metabolite (2,5,7,8-tetramethyl-2-(2'-carboxyethyl)-6-hydroxychroman, 0.232+/-0.046 vs. 0.031+/-0.019 nmol/g) concentrations were approximately eightfold higher following the +E dietary treatment. In +E relative to E mice, gene expression of Phase I enzymes, P450 oxidoreductase and cytochrome P450 3a11 increased 1.6- and 4.0-fold, respectively; two Phase II genes, sulfotransferase 2a and glutathione S-transferase mu 3, increased 10.8- and 1.9-fold respectively, and a Phase III biliary transporter, Abcb1a, doubled. Thus, consumption of high-level dietary alpha-tocopherol simultaneously coordinated Phase I, II and III gene expression. These data demonstrate that increased hepatic alpha-tocopherol modulates its own concentrations through increasing xenobiotic metabolism, a process that may alter metabolism of other foreign compounds, such as therapeutic drugs and phytochemicals, in humans.     

High resolution scanning electron microscopy of plasmodesmata

Symplastic transport occurs between neighbouring plant cells through functionally and structurally dynamic channels called plasmodesmata (PD). Relatively little is known about the composition of PD or the mechanisms that facilitate molecular transport into neighbouring cells. While transmission electron microscopy (TEM) provides 2-dimensional information about the structural components of PD, 3-dimensional information is difficult to extract from ultrathin sections. This study has exploited high-resolution scanning electron microscopy (HRSEM) to reveal the 3-dimensional morphology of PD in the cell walls of algae, ferns and higher plants. Varied patterns of PD were observed in the walls, ranging from uniformly distributed individual PD to discrete clusters. Occasionally the thick walls of the giant alga Chara were fractured, revealing the surface morphology of PD within. External structures such as spokes, spirals and mesh were observed surrounding the PD. Enzymatic digestions of cell wall components indicate that cellulose or pectin either compose or stabilise the extracellular spokes. Occasionally, the PD were fractured open and desmotubule-like structures and other particles were observed in their central regions. Our observations add weight to the argument that Chara PD contain desmotubules and are morphologically similar to higher plant PD.     

Novel galanin receptor subtype specific ligands in feeding regulation

Galanin a 29/30-residue neuropeptide has been implicated in several functions in the central nervous system, including the regulation of food consumption. Galanin and its analogues administered intraventricularly or into the hypothalamic region of brain have been shown to reliably and robustly stimulate the consumption of food in sated rodents. Three galanin receptor subtypes have been isolated, all present in the hypothalamus, but little is known about their specific role in mediating this acute feeding response. Presently, we introduce several novel GalR2 selective agonists and then compare the most selective of these novel GalR2 subtype selective agonists to known GalR1 selective agonist M617 for their ability to stimulate acute consumption of several foods shown to be stimulated by central administration of galanin. GalR1 selective agonist M617 markedly stimulated acute consumption of high-fat milk, but neither GalR2 selective agonist affected either high-fat milk or cookie mash intake. The present results are consistent with the involvement of GalR1 in mediating the acute feeding consumption by galanin and suggest an approach applicable to exploring galanin receptor specificity in normal and abnormal behavior and physiology.