Maternal Obesity Induced by Diet in Rats Permanently Influences Central Processes Regulating Food Intake in Offspring

Hypothalamic systems which regulate appetite may be permanently modified during early development. We have previously reported hyperphagia and increased adiposity in the adult offspring of rodents fed an obesogenic diet prior to and throughout pregnancy and lactation. We now report that offspring of obese (OffOb) rats display an amplified and prolonged neonatal leptin surge, which is accompanied by elevated leptin mRNA expression in their abdominal white adipose tissue. At postnatal Day 30, before the onset of hyperphagia in these animals, serum leptin is normal, but leptin-induced appetite suppression and phosphorylation of STAT3 in the arcuate nucleus (ARC) are attenuated; the level of AgRP-immunoreactivity in the hypothalamic paraventricular nucleus (PVH), which derives from neurones in the ARC and is developmentally dependent on leptin, is also diminished. We hypothesise that prolonged release of abnormally high levels of leptin by neonatal OffOb rats leads to leptin resistance and permanently affects hypothalamic functions involving the ARC and PVH. Such effects may underlie the developmental programming of hyperphagia and obesity in these rats.     

Identification of chloroplast signal recognition particle RNA genes

The signal recognition particle (SRP) is a ribonucleoprotein complex responsible for targeting proteins to the ER membrane in eukaryotes, the plasma membrane in bacteria and the thylakoid membrane in chloroplasts. In higher plants two different SRP-dependent mechanisms have been identified: one post-translational for proteins imported to the chloroplast and one co-translational for proteins encoded by the plastid genome. The post-translational chloroplast SRP (cpSRP) consists of the protein subunits cpSRP54 and cpSRP43. An RNA component has not been identified and does not seem to be required for the post-translational cpSRP. The co-translational mechanism is known to involve cpSRP54, but an RNA component has not yet been identified. Several chloroplast genomes have been sequenced recently, making a phylogenetically broad computational search for cpSRP RNA possible. We have analysed chloroplast genomes from 27 organisms. In higher plant chloroplasts, no SRP RNA genes were identified. However, eight plastids from red algae and Chlorophyta were found to contain an SRP RNA gene. These results suggest that SRP RNA forms a complex in these plastids with cpSRP54, reminiscent of the eubacterial SRP.     

The effects of lipoxin A and lipoxin B on functional responses of human granulocytes

Lipoxin A and lipoxin B (LXA and LXB) are formed from arachidonic acid by leukocyte 5- and 15-lipoxygenases. We have assessed the effects of synthetic lipoxins on functional responses of human granulocytes. LXA stimulated migration at 1 nM. The effect was highly stereospecific, since e.g. 6S-LXA and LXB were less active than LXA. Neither synthetic LXA nor several of its stereoisomers provoked degranulation or aggregation. LXB and its isomers did not induce any of these functional responses. These results indicate that migratory granulocyte responses to LXA are highly stereospecific.     

Formation of lipoxin A by granulocytes from eosinophilic donors

The formation of arachidonic acid-derived lipoxygenase products was examined with human granulocytes obtained from eosinophilic donors. These eosinophil-enriched leukocyte populations, challenged in vitro with the ionophore of divalent cations A23187, transformed both exogenous and endogenous sources of arachidonic acid to several lipoxygenase-derived products, including 5(S), 6(R),15(S)-trihydroxy-7,9,13-trans-11-cis-eicosatetraenoic acid (lipoxin A). Lipoxin A was detected and characterized by high-pressure liquid chromatography (HPLC), ultraviolet absorbance, and gas-liquid chromatography-mass spectroscopy. Neither lipoxin B nor 6(S)-LXA was consistently detected in extracts from these incubations. The amounts of lipoxin A formed were proportional to the percentage of eosinophils present in the suspension. The results indicate that granulocytes from eosinophilic donors can generate lipoxin A.     

On the mechanism of biosynthesis of leukotrienes and related compounds

[10D-³H; 3-¹⁴C]- and [10L-³H; 3-¹⁴C]arachidonic acids were incubated with human polymorphonuclear leukocytes and with human platelets. Leukotriene B₄ and 5(S),12(S)-dihydroxy-6trans,8cis,10trans,14-cis-eicosatetraenoic acid (5,12-DHETE) were isolated and the ³H/¹⁴C ratios determined. It could be concluded that the 10D (pro-R)-hydrogen is eliminated in the conversion of 5(S)-hydroperoxy-6trans,8cis,11cis,14cis-eicosatetraenoic acid into leukotriene A₄ whereas in the conversion of arachidonic acid into 5,12-DHETE the 10L (pro-S)-hydrogen is lost. Incubation of the doubly labeled arachidonic acids with human platelets confirmed and extended previous data on the stereochemistry of the hydrogen removal from C-10 during the conversion into 12(S)-hydroperoxy-5cis,8cis,10trans,14cis-eicosatetraenoic acid, i.e., the 10L (pro-S)-hydrogen is eliminated and the 10D (pro-R)-hydrogen retained.     

Dissimilatory nitrate reduction to nitrate, nitrous oxide, and ammonium by Pseudomonas putrefaciens.

The influence of redox potential on dissimilatory nitrate reduction to ammonium was investigated on a marine bacterium, Pseudomonas putrefaciens. Nitrate was consumed (3.1 mmol liter-1), and ammonium was produced in cultures with glucose and without sodium thioglycolate. When sodium thioglycolate was added, nitrate was consumed at a lower rate (1.1 mmol liter-1), and no significant amounts of nitrite or ammonium were produced. No growth was detected in glucose media either with or without sodium thioglycolate. When grown on tryptic soy broth, the production of nitrous oxide paralleled growth. In the same medium, but with sodium thioglycolate, nitrous oxide was first produced during growth and then consumed. Acetylene caused the nitrous oxide to accumulate. These results and the mass balance calculations for different nitrogen components indicate that P. putrefaciens has the capacity to dissimilate nitrate to ammonium as well as to dinitrogen gas and nitrous oxide (denitrification). The dissimilatory pathway to ammonium dominates except when sodium thioglycolate is added to the medium.     

Structural characterization of non-acid glycosphingolipids in kidneys of single blood group O and A pigs

Total non-acid glycosphingolipids were isolated from the kidneys of single pigs serologically typed on their red blood cells as blood groups O and A. Glycolipid species were purified by HPLC and structurally characterized by thin-layer chromatography, mass spectrometry, proton NMR spectroscopy, degradation analysis, and reactivity with various monoclonal antibodies, Gal alpha 1-4Gal-specific E. coli bacteria, and lectins. Glucosyl-, globotriaosyl-, and globotetraosylceramides were the predominant molecular species with lactosyl- and globopentaosylceramides (IV3GalGb4Cer) as abundant constituents too. Small amounts of galactosyl- and digalactosylceramides were also present. In the blood group O pig kidneys, blood group H antigens based on four different core saccharides (types 1, 2, 4, and lactosyl core) were identified and the major blood group structure was V2FucIV3Gal-Gb4Cer. In the kidneys from the blood group A pig the corresponding blood group A antigens were found and in addition, a type 3 chain blood group A antigen was indicated by mass spectrometry and by its reactivity with a monoclonal antibody. Trace amounts of the type 2 chain-based X and Y antigens were found while blood group B antigens and the type 1 chain based Lewis antigens could not be detected. The ceramide part of the glycolipids was mainly composed of dihydroxy 18:0 long chain bases and non-hydroxy 16:0-24:0 fatty cids.     

The effects of photoinhibition on the photosynthetic light-response curve of green plant cells (Chlamydomonas reinhardtii)

The photosynthetic response to light can be accurately defined in terms of (1) the initial slope (quantum yield); (2) the asymptote (light-saturated rate); (3) the convexity (rate of bending); and (4) the intercept (dark respiration). The effects of photoinhibition [which damages the reaction centre of photosystem II (PSII)] on these four parameters were measured in optically thin cultures of green plant cells (Chlamydomonas reinhardtii). The convexity of the light-response curve decreased steadily from a value of 0.98 (indicating a sharply bending response) to zero (indicating Michaelis-Menten kinetics) in response to increasing photoinhibition. Photoinhibition was quantified from the quantum yield of inhibited cells relative to that of control cells. The quantum yield was estimated by applying linear regression to low-light data or by fitting a non-rectangular hyperbola. Assuming the initial slope is linear allowed comparison with earlier work. However, as the convexity was lowered this assumption resulted in a significant underestimate of the true quantum yield. Thus, the apparent level of photoinhibition required for a zero convexity and the initial decrease in light-saturated photosynthesis depended upon how the quantum yield was estimated. If the initial slope of the light response was assumed to be linear the critical level of inhibition was 60%. If the linear assumption was not made, the critical level was 40%. At the level of inhibition where the convexity reached zero, the light-saturated rate of photosynthesis also began to decrease, indicating that this level of inhibition caused photosynthesis to be limited at all light intensities by the rate of PSII electron transport. At this level of inhibition the F_m-F_i signal (where F_m is maximal chlorophyll fluorescence and F_i is intermediate chlorophyll fluorescence of dark adapted cells; Briantais et al. 1988) from the fluorescence induction curve was zero and the F_i-F_o signal (where F_o is initial chlorophyll fluorescence of dark adapted cells) was 30% of the control, indicating dramatic reduction or complete elimination of one type of PSII. These data do not contradict published mathematical models showing that the ratio of the maximum speed of electron transport in PSII relative to the maximum speed of plastoquinone electron transport can determine the convexity of the photosynthetic response to light.Abbreviations and Symbols Chl chlorophyll content - DCMU 3-(3,4-dichlorophenyl)-1,1-dimethylurea - F_o, F_i, F_m initial, intermediate, and maximal Chl fluorescence of dark adapted cells - P rate of net photosynthesis per unit chlorophyll (mol-(mg Chl)^–1 · s^–1) - PSII photosystem II - PQ plastoquinone - initial slope to the light-response curve - convexity (rate of bending) of the light-response curve of photosynthesis - Q photosynthetically active photon flux density (400–700 nm, mol · m^–2 · ^–1) The present investigation was supported by the Swedish Council for Forestry and Agricultural Research, the Swedish Environmental Protection Board, and the Swedish Natural Science Research Council. We thank Dr. Deborah D. Kaska (Department of Biological Sciences, University of California, Santa Barbara, Calif., USA) for giving us Chlamydomonas algae. We thank Professor G. Öquist (Department of Plant Physiology, University of Umea, Umea, Sweden) for his encouragement, valuable comments and discussion.     

Induction of Inorganic Carbon Accumulation in the Unicellular Green Algae Scenedesmus obliquus and Chlamydomonas reinhardtii

The induction of a dissolved inorganic carbon (DIC) accumulating mechanism in the two algal species Scenedesmus obliquus (WT) and Chlamydomonas reinhardtii (137 c+) was physiologically characterized by monitoring DIC uptake kinetics at a low and constant DIC concentration (120-140 micromolar), after transfer from high-DIC culturing conditions. A potentiometric titration method was used to measure and calculate algal DIC uptake. Full acclimation to low-DIC conditions was obtained within a period of 90 min, after which time the DIC uptake had been increased 7 to 10 times. Experiments were also conducted in the presence of inhibitors against DIC accumulation. The inhibitor of extracellular carbonic anhydrase (CA), acetazolamide (50 micromolar), inhibited the adaptation partly, while the inhibitor of both extra- and intracellular CA, ethoxyzolamide (50 micromolar) totally inhibited the acclimation. Cycloheximide (10 micrograms per milliliter), which inhibits protein synthesis on cytoplasmic ribosomes, and vanadate (180 micromolar), which inhibits the plasmamembrane bound ATPase, also inhibited the acclimation totally. These results taken together suggest that the algae are dependent on intracellular CA, plasmamembrane bound ATPase, and de novo protein synthesis for DIC accumulation. Also, these components are more important than extracellular CA for the overall function of the DIC-accumulating mechanism.