Kinetic aspects of chain growth in Fischer-Tropsch synthesis.

Microkinetics simulations are used to investigate the elementary reaction steps that control chain growth in the Fischer-Tropsch reaction. Chain growth in the FT reaction on stepped Ru surfaces proceeds via coupling of CH and CR surface intermediates. Essential to the growth mechanism are C-H dehydrogenation and C hydrogenation steps, whose kinetic consequences have been examined by formulating two novel kinetic concepts, the degree of chain-growth probability control and the thermodynamic degree of chain-growth probability control. For Ru the CO conversion rate is controlled by the removal of O atoms from the catalytic surface. The temperature of maximum CO conversion rate is higher than the temperature to obtain maximum chain-growth probability. Both maxima are determined by Sabatier behavior, but the steps that control chain-growth probability are different from those that control the overall rate. Below the optimum for obtaining long hydrocarbon chains, the reaction is limited by the high total surface coverage: in the absence of sufficient vacancies the CHCHR → CCHR + H reaction is slowed down. Beyond the optimum in chain-growth probability, CHCR + H → CHCHR and OH + H → H2O limit the chain-growth process. The thermodynamic degree of chain-growth probability control emphasizes the critical role of the H and free-site coverage and shows that at high temperature, chain depolymerization contributes to the decreased chain-growth probability. That is to say, during the FT reaction chain growth is much faster than chain depolymerization, which ensures high chain-growth probability. The chain-growth rate is also fast compared to chain-growth termination and the steps that control the overall CO conversion rate, which are O removal steps for Ru.

Maternal telomere length inheritance in the king penguin.

Telomeres are emerging as a biomarker for ageing and survival, and are likely important in shaping life-history trade-offs. In particular, telomere length with which one starts in life has been linked to lifelong survival, suggesting that early telomere dynamics are somehow related to life-history trajectories. This result highlights the importance of determining the extent to which telomere length is inherited, as a crucial factor determining early life telomere length. Given the scarcity of species for which telomere length inheritance has been studied, it is pressing to assess the generality of telomere length inheritance patterns. Further, information on how this pattern changes over the course of growth in individuals living under natural conditions should provide some insight on the extent to which environmental constraints also shape telomere dynamics. To fill this gap partly, we followed telomere inheritance in a population of king penguins (Aptenodytes patagonicus). We tested for paternal and maternal influence on chick initial telomere length (10 days old after hatching), and how these relationships changed with chick age (at 70, 200 and 300 days old). Based on a correlative approach, offspring telomere length was positively associated with maternal telomere length early in life (at 10 days old). However, this relationship was not significant at older ages. These data suggest that telomere length in birds is maternally inherited. Nonetheless, the influence of environmental conditions during growth remained an important factor shaping telomere length, as the maternal link disappeared with chicks' age.

Digestive enzyme ratios are good indicators of hatchling yolk reserve and digestive gland maturation in early life stages of cuttlefish Sepia officinalis L.: application of these new tools in ecology and aquaculture.

In Sepia officinalis (Linnaeus, 1758), the digestive gland matures during the first month post-hatching, while a shift from intracellular acid to extracellular alkaline digestion occurs. The purpose of this study was to investigate the possibility of using enzymatic ratios for the description of digestive system maturation in early life stages of S. officinalis. Second, it is intended to apply these new tools as eco-physiological indicators for understanding the impact of cuttlefish eggs' life history from different spawning sites of the English Channel on digestive performance of juveniles. An experimental rearing was performed over 35 days after hatching (DAH) on juveniles from wild collected eggs in 2010 and 2011. Four digestive enzyme activities and their ratios [i.e., trypsin, cathepsin, acid (ACP), and alkaline (ALP) phosphatase, ALP/ACP, and trypsin/cathepsin] were studied along with histological features (e.g., internal yolk surface and digestive gland development). The two enzyme ratios were good indicators of digestive system maturation allowing the study of the digestive gland's development. They were highly correlated to juveniles' weight increase and histological features of the gland in early DAH. These ratios described more accurately the shift occurring between the intracellular acid and the extracellular alkaline modes of digestion in S. officinalis and were more specific than separated enzyme activities. Their application as eco-physiological tools revealed that enzyme ratios reflected yolk content and digestive gland development in new hatching juveniles. Finally, ALP/ACP ratio was shown to be a powerful tool to describe growth performance of S. officinalis which is useful for aquaculture optimization.

Quantum-Chemical DFT Study of Direct and H- and C-Assisted CO Dissociation on the χ-Fe5C2 Hägg Carbide.

The first step in the Fischer-Tropsch reaction is the production of C1 monomers by the dissociation of the C-O bond. Although Fe is the active metal, it is well known that under typical reaction conditions, it changes into various carbide phases. The Hägg carbide (χ-Fe5C2) phase is usually considered as the catalytically active phase. We carried out a comprehensive DFT study of CO dissociation on various surface terminations of the Hägg carbide, selected on their specific site topology and the presence of stepped sites. Based on the reaction energetics, we identified several feasible CO dissociation pathways over the Hägg carbide. In this study, we have compared the direct CO dissociation with H- and C-assisted CO dissociation mechanisms. We demonstrated that the reaction rate for CO dissociation critically depends on the presence and topology of interstitial C atoms close to the active site. Typically, the CO dissociation proceeds via a direct C-O bond scission mechanism on the stepped sites on the Fe carbide surface. We have shown a preference for the direct CO dissociation on the surfaces with a stepped character. The H-assisted CO dissociation, via a CHO intermediate, was preferred when the surface did not have a clear stepped character. We have also shown that activation barriers for dissociation are highly dependent on the surface termination. With a consistent data set and including migration corrections, we then compared the CO dissociation rates based on a simplified kinetic model. With this model, we showed that besides the activation energy, the adsorption energy of the CO, the C and the O species are important for the reaction rate as well. We found that the most active surface termination is a (111̅) surface cut in such a way that the surface exposes B5 sites that are not occupied by the C atoms. On these B5 sites, the direct CO dissociation presents the highest rate.

Acquired hemophilia due to factor VIII inhibitors in 34 patients.

BACKGROUND: Acquired hemophilia is a rare disease caused by the development of auto-antibodies against factor VIII. SUBJECTS AND METHODS: We studied the characteristics and outcomes of 34 patients (19 women and 15 men) with acquired hemophilia from 1980 to 1997. RESULTS: The mean age of the patients was 61 years (range, 22-93 years). An underlying disease was observed in 18 (53%) patients: 5 patients had cancer, 4 an autoimmune disorder, 2 a dermatologic disorder, 3 asthma, 3 were postpartum, and 1 had an adverse reaction to ampicillin. Factor VIII level was <5% in 30 (90%) patients; factor VIII antibodies were elevated (>10 Bethesda units) in 23 (69%) patients. Bleeding requiring transfusions was reported in 25 (75%) patients. Human factor VIII was given to 14 patients and porcine factor VIII to 5. Six patients received prothrombin complex concentrates and one desmopressin. Several immunosuppressive treatments were used, mainly corticosteroids, cyclophosphamide, and intravenous immunoglobulin. Bleeding stopped in all but one patient within 2 weeks. Most patients achieved complete remission, although two relapses were observed subsequently. CONCLUSION: This large study helps to clarify the presentation and clinical course of acquired hemophilia. Prospective studies are needed to determine the efficacy of treatment.

Structure--antitubulin activity relationship in steganacin congeners and analogues. Inhibition of tubulin polymerization in vitro by (+/-)-isodeoxypodophyllotoxin.

A new series of 23 synthetic analogues of the naturally occurring antitumor lignan steganacin was tested for the inhibition of microtubule assembly in vitro. Interestingly, (+/-)-isopicrostegane (I50 = 5 microM) was found to be almost as active as (+/-)-steganacin(I50 = 3.5 microM). On the other hand, racemic isodeoxypodophyllotoxin has an inhibiting activity of microtubule assembly comparable to that of (-)-podophyllotoxin, whereas (-)-isodeoxypodophyllotoxin is totally inactive.

Accumulated body burden and endogenous release of lead in employees of a lead smelter.

Bone lead levels for 367 active and 14 retired lead smelter workers were measured in vivo by X-ray fluorescence in May-June 1994. The bone sites of study were the tibia and calcaneus; magnitudes of concentration were used to gauge lead body burden. Whole blood lead readings from the workers generated a cumulative blood lead index (CBLI) that approximated the level of lead exposure over time. Blood lead values for 204 of the 381 workers were gathered from workers returning from a 10-month work interruption that ended in 1991; their blood level values were compared to their tibia and calcaneus lead levels. The resulting relations allowed constraints to be placed on the endogenous release of lead from bone in smelter works. Calcaneus lead levels were found to correlate strongly with those for tibia lead, and in a manner consistent with observations from other lead industry workers. Relations between bone lead concentration and CBLI demonstrated a distinctly nonlinear appearance. When the active population was divided by date of hire, a significant difference in the bone lead-CBLI slope emerged. After a correction to include the component of CBLI existing before the workers' employment at the smelter was made, this difference persisted. This implies that the transfer of lead from blood to bone in the workers has changed over time, possibly as a consequence of varying exposure conditions.

Cytotoxic properties of a new synthetic demethylpodophyllotoxin derivative, BN 58705, against human tumor cell lines.

The in vitro cytotoxic properties of a newly synthesized demethylpodophyllotoxin derivative, 4-o-butanoyl-4'-demethylpodophyllotoxin (BN 58705), were determined by using several human tumor cell lines of different histological origin and of different sensitivity to conventional chemotherapeutic drugs (Adriamycin and cis-diammine-dichloride platinum). BN 58705 is shown to be cytotoxic against various human tumor cell lines as assessed by the MTT assay. Furthermore, BN 58705 is shown to be cytotoxic against several drug-resistant tumor cell lines. BN 58705 is cytotoxic at concentrations 100- to 1000-fold lower than those of Adriamycin or cis-diammine-dichloride platinum required to achieve similar cytotoxicity. BN 58705 did not mediate DNA fragmentation of target cells, whereas the epipodophyllotoxin-like etoposide induced DNA cleavage by stabilizing the DNA-enzyme intermediate. Like vinca alkaloids, BN 58705 induced a block in the mitotic phase of the cell cycle. By comparison, BN 58705 exerted a stronger cytotoxic activity in vitro than did either etoposide, an epipodophyllotoxin, or vincristine, a vinca alkaloid. When BN 58705 was applied in vivo in mice, it resulted in low toxicity (50% lethal dose, 150 mg/kg). These results demonstrate than BN 58705 is cytotoxic to drug-resistant human tumor cell lines and is manyfold more potent than conventional drugs. The cytotoxic potency and low toxicity of BN 58705 are important criteria to establish its potential chemotherapeutic efficacy in vivo.

Fasting-induced rise in locomotor activity in rats coincides with increased protein utilization.

The aim of this study was to investigate the possible relation between the modifications in locomotor activity (on running wheel) which occur during prolonged fasting and changes in the utilization of energy reserves. In 18-week-old rats, we found that the rate of body mass loss reflects the changes in nitrogen excretion that occur over three phases of fasting: (I) initially decreasing, (II) maintained at a low level and (III) increasing. Locomotor activity started to increase during phase II without a change in its nycthemeral pattern. By contrast, the 10-fold higher daily locomotor activity that occurred in phase III was marked by a higher proportion of diurnal activity. Using 9-, 18-, and 33-week-old rats, in order to obtain a different timing in the metabolic changes during fasting, we could confirm the coincidence between the later rise in locomotor activity and the occurrence of phase III. Refeeding of rats of either age in phase III rapidly suppressed fasting-induced changes in locomotor activity. These data accord with the idea that behavioral changes reflecting the search for food are triggered by a later and reversible change in the utilization of body protein vs. lipid stores during prolonged fasting.

Involvement of corticosterone in the fasting-induced rise in protein utilization and locomotor activity.

During fasting, most of the energy is derived from lipids whereas proteins are efficiently spared. However, there is a late rise in net protein utilization. Fasting is also associated with an increase in locomotor activity. Because the plasma corticosterone level increases concomitantly with these metabolic and behavioral changes, the involvement of corticosterone has been hypothesized. To test this, the net protein utilization and locomotor activity were investigated in fasted adrenalectomized (Adx) rats, with or without replacement with corticosterone, and in fasted intact rats treated with RU486, an antagonist of type II glucocorticoid receptors. During the phase of fasting characterized by protein sparing, urine nitrogen loss was further reduced in Adx rats and in RU486-treated controls compared with intact rats and with Adx rats with corticosterone replacement: this indicates a catabolic effect of corticosterone through type II receptors. In the last phase of fasting, the rise in net protein breakdown was suppressed in Adx rats and restored by corticosterone replacement. The increase in locomotor activity induced by fasting in controls was suppressed in Adx and restored by corticosterone replacement. This rise in running activity was still present in RU486-treated rats. In conclusion, this study shows that corticosterone plays a critical role in the changes of both protein catabolism and locomotor activity during prolonged fasting.

Milking strategy in subantarctic fur seals Arctocephalus tropicalis breeding on Amsterdam Island: evidence from changes in milk composition.

Milk composition was investigated throughout the 10-mo pup-rearing period in subantarctic fur seals (Arctocephalus tropicalis) breeding on Amsterdam Island. The mean milk composition was 42.8% +/- 5.7% lipid, 12.1% +/- 1.5% protein, and 42.6% +/- 7.3% water. Subantarctic fur seals breeding on Amsterdam Island produced one of the richest milks ever reported in otariids (20.4 +/- 2.9 kJ/g), with lipid content contributing 85% of total gross energy. The high lipid levels measured in the milk of subantarctic fur seals breeding on Amsterdam Island is consistent (i) with the relatively long time lactating females spend at sea, due to the relatively poor local trophic conditions near the colony that necessitate that they travel long distances to reach the foraging grounds, and (ii) with the consequently short time mothers spend with their pups ashore. Milk composition changed according to the time mothers were fasting ashore: milk produced during the first 2 d spent ashore, when more than 80% of milk transfer occurred, had higher levels of lipids, proteins, and gross energy than milk produced later during the visit ashore, suggesting that the pups were fed with two types of milk during a suckling period. Throughout the year, mothers in good condition produced milk of higher lipid content than others, suggesting that individual foraging skills contribute to enhance milk quality. Milk lipid and gross energy content varied with pup age, according to quadratic relationships, increasing during the earlier stages of lactation before reaching asymptotic values when pups were 180 d old. The stage of lactation appears to be a better predictor of milk lipid content than the duration of the preceding foraging trip, suggesting that either changes in the nutritional requirements of the pup and/or seasonal changes in trophic conditions act on milk composition. These changes in milk quality may also be related to changes in maternal care; lactating subantarctic fur seals apparently reallocate their body reserves toward gestation rather than lactation at the end of the pup-rearing period.

[Malacoplakia. Apropos of a case of retroperitoneal site]. / Malacoplasie. A propos d'une observation avec localisation rétropéritonéale.

Malacoplakia is a granulomatous inflammatory disease caused by a disorder of macrophage bactericidal function. The disease, histologically characterized by the presence of Michaelis-Gutmann bodies, has a preference for the urogenital tract and less frequently affects the gastrointestinal tract and the retroperitoneal region. We report the unusual case of a male patient who presented with retroperitoneal pseudotumoral malacoplakia associated with vesical malacoplakia. The main pathophysiological, diagnostic and therapeutic aspects of this rare disease are described.

[Acquired angioneurotic edema caused by acquired deficiency of C1 esterase inhibitor disclosing lymphoproliferative syndrome. Apropos of a case, review of the literature]. / Oedème angio-neurotique (acquis) par déficit acquis en inhibiteur de Ci-estérase révélateur d'un syndrome lympho-prolifératif. A propos d'un cas, revue de la littérature.

One case of acquired angio-neurotic oedema is described and discussed with the other cases recorded in literature since Caldwell's one in 1972. This entity is characterized by: --the late onset of angio-oedema but its presence only in about half cases, --a complement deficiency resulting from the lack of C1-esterase inhibitor, --the absence of familial identical cases, --the great frequency of associated illnesses overall lympho-proliferative diseases, --the therapeutic response to either etiologic treatment of the associated disease or to the symptomatic effect of drugs used in hereditary angio-neurotic oedema.

Endogenous lignans--a potential endogenous digitalis.

Lignans are natural products formed by oxidative dimerization of monomeric phenols. A few were recently discovered in human and animal urine, semen and blood plasma but their role has never been assessed. We investigated the actions of mammalian lignans obtained by total synthesis or extracted from the urine of pregnant women, on the Na+K+-pump in human red cells. Some of the tested lignans (enterolactone, prestegane B and 3-O-methylenterolactone) inhibited the Na+K+-pump activity with IC50 ranging from 5 to 9 X 10(-4) mol/l. The IC50 for ouabain (7 X 10(-7) mol/l) was not modified by addition of lignans suggesting a non-competitive inhibition.

Microfabricated planar glass gas chromatography with photoionization detection.

We report the development of a microfabricated gas chromatography system suitable for the separation of volatile organic compounds (VOCs) and compatible with use as a portable measurement device. Hydrofluoric acid etching of 95x95mm Schott B270 wafers has been used to give symmetrical hemi-spherical channels within a glass substrate. Two matching glass plates were subsequently cold bonded with the channels aligned; the flatness of the glass surfaces resulted in strong bonding through van der Waals forces. The device comprised gas fluidic interconnections, injection zone and 7.5 and 1.4m long, 320microm internal diameter capillaries. Optical microscopy confirmed the capillaries to have fully circular channel profiles. Direct column heating and cooling could be achieved using a combination of resistive heaters and Peltier devices. The low thermal conductivity of glass allowed for multiple uniform temperature zones to be achieved within a single glass chip. Temperature control over the range 10-200 degrees C was achieved with peak power demand of approximately 25W. The 7.5m capillary column was static coated with a 2microm film of non-polar dimethylpolysiloxane stationary phase. A standard FID and a modified lightweight 100mW photoionization detector (PID) were coupled to the column and performance tested with gas mixtures of monoaromatic and monoterpene species at the parts per million concentration level. The low power GC-PID device showed good performance for a small set of VOCs and sub ng detection sensitivity to monoaromatics.

Two-dimensional electrophoresis of the total polypeptides in ripe red grape berries.

The total polypeptide composition of mature grape berries was analyzed by one-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis and two-dimensional electrophoresis (isoelectric focusing in the first dimension followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis in the second dimension), followed by Coomassie Blue and nitrate silver staining, respectively. Adapted methods for total protein preparation of grapes and for two-dimensional gel electrophoretic separation of polypeptides are presented. The grape patterns presented up to 52 fractions with Mrs ranging from 15,000 to 110,000. The polypeptides displayed pIs from 4.6 to 7.3. A group of spots from Mr 28,000 to 83,000 and with a pI from 4.6 to 5.4 was strongly silver stained. The Mr 28,000 spot, pI 4.6, was revealed to be a complex of four fractions. Reproducible separations were obtained with the different carrier ampholyte mixtures tested.

Long-term fasting and re-feeding in penguins.

Spontaneous fasting during reproduction (sometimes with a full stomach) and moult is a major characteristic of the annual cycle of penguins. Long-term fasting (up to four months in male emperor penguins) is anticipated by the accumulation of fat (incubation fast) and of fat and protein (moult fast). During most of the incubation fast, birds rely almost entirely on lipids as an energy source, body proteins being spared. However, below a critical (but non-total) fat store depletion, marked behavioural, metabolic, and endocrine changes occur. Spontaneous locomotor activity increases and the egg is transitorily left unincubated for increasingly long periods, until its definitive abandon and the bird departs to re-feed at sea. These changes are thought to be activated by an endogenous re-feeding signal triggered before lethal energy depletion. An increase in body protein catabolism in the face of a reduction in lipid availability and utilisation, and an increase in circulating corticosterone vs. a decrease in plasma prolactin, are likely to be major metabolic and hormonal components of this signal. The survival and rapid restoration of energy stores in birds having departed to re-feed at a stage of near total lipid depletion demonstrates the effectiveness of the re-feeding signal. Penguins, and possibly other seabirds, are therefore appropriate animal models for understanding the long-term interactions between body energy reserves and fasting, breeding and feeding physiology and behaviour.

Carbamoyl phosphate biosynthesis and partition in pyrimidine and arginine pathways of Escherichia coli. In situ properties of carbamoyl-phosphate synthase, ornithine transcarbamylase and aspartate transcarbamylase in permeabilized cells.

A procedure for the permeabilization of Escherichia coli cells was adapted to the in situ determination of the catalytic and regulatory properties of the enzymes responsible for the biosynthesis of carbamoyl phosphate and its utilization in the pyrimidine and arginine pathways. Differences in enzyme sensitivity to effectors and changes in pH dependence were observed. Partition of carbamoyl phosphate in the two metabolic pathways could be measured under conditions of substrate saturation. The results obtained will allow to test experimentally the theoretical predictions made by A. Goldbeter (1973) PhD thesis, Université Libre de Bruxelles, on the distribution of carbamoyl phosphate and the oscillation of its intracellular concentration.

Behavioral changes in fasting emperor penguins: evidence for a "refeeding signal" linked to a metabolic shift.

This study examines the relationships between metabolic status and behavior in spontaneously fasting birds in the context of long-term regulation of body mass and feeding. Locomotor activity, escape behavior, display songs, body mass, and metabolic and endocrine status of captive male emperor penguins were recorded during a breeding fast. We also examined whether body mass at the end of the fast affected further survival. The major part of the fast (phase II) was characterized by the maintenance of a very low level of locomotor activity, with almost no attempt to escape, by an almost constant rate of body mass loss, and by steady plasma levels of uric acid, beta-hydroxybutyrate, and corticosterone. This indicates behavioral and metabolic adjustments directed toward sparing energy and body protein. Below a body mass of approximately 24 kg (phase III), spontaneous locomotor activity and attempts to escape increased by up to 8- and 15-fold, respectively, and display songs were resumed. This probably reflected an increase in the drive to refeed. Simultaneously, daily body mass loss and plasma levels of uric acid and corticosterone increased, whereas plasma levels of beta-hydroxybutyrate decreased. Some experimental birds were seen again in following years. These findings suggest that at a threshold of body mass, a metabolic and endocrine shift, possibly related to a limited availability of fat stores, acts as a "refeeding signal" that improves the survival of penguins to fasting.

[Augmentation of nitrogen efficiency and hyperphagia associated with refeeding after prolonged fast in the domestic goose]. / Augmentation du rendement azoté et hyperphagie associées à la réalimentation après un jeûne prolongé chez l'oie domestique.

The domestic goose is hyperphagic after a fast resulting in a 40% decrease in body mass (a decrease similar to that during breeding anorexia). Food intake is maximum on the 8th day of refeeding. As it is then an average of 2.5 times higher than before the fast, food intake may thus reach the value during forced-feeding for "foie gras". Since nitrogen assimilation rate also increases 2.5 times, nitrogen fixation is increased 6.8 times, suggesting a high level of protein synthesis.