Early dynamics of the emission of solvated electrons from nanodiamonds in water

Solvated electrons are among the most reductive species in an aqueous environment. Diamond materials have been proposed as a promising source of solvated electrons, but the underlying emission process in water remains elusive so far. Here, we show spectroscopic evidence for the emission of solvated electrons from detonation nanodiamonds upon excitation with both deep ultraviolet (225 nm) and visible (400 nm) light using ultrafast transient absorption. The crucial role of surface termination in the emission process is evidenced by comparing hydrogenated, hydroxylated and carboxylated nanodiamonds. In particular, a transient response that we attribute to solvated electrons is observed on hydrogenated nanodiamonds upon visible light excitation, while it shows a sub-ps recombination due to trap states when excited with deep ultraviolet light. The essential role of surface reconstructions on the nanodiamonds in these processes is proposed based on density functional theory calculations. These results open new perspectives for solar-driven emission of solvated electrons in an aqueous phase using nanodiamonds.

Increasing the angular sensitivity of two-dimensional photonic crystal based sensors to arbitrary values

A new design of photonic crystal (PhC) for optical sensing using guided mode resonance (GMR) is presented. We theoretically show that angular sensitivity is inversely proportional to the group velocity of the probed mode and can be made arbitrarily high in a properly designed PhC. PhCs made in polycrystalline diamond on insulator are fabricated. The angular sensitivity dependence is validated. We measured modes with group velocity of c/80 at a wavelength of 800 nm. A sensitivity in the order of 500 ° per refractive index unit is inferred, a value much larger than the one usually encountered in PhCs.

Cellulose Fermentation by an Asporogenous Mutant and an Ethanol-Tolerant Mutant of Clostridium thermocellum

Two mutants of Clostridium thermocellum were isolated after UV light mutagenesis. Mutant A1, selected as asporogenous, exhibited a fermentation pattern similar to that of the wild type. However, at pH 6.5, the mutant degraded 12% more cellulose than did the wild type, leading to enhanced ethanol production. Mutant 647, selected as ethanol tolerant, was able to grow in medium containing 4% ethanol. During the early stage of the exponential growth phase, ethanol was produced as the main product, up to a concentration of about 9 g/liter. After 3 days of culture, 48.3 g (89% of the initial amount) of degraded cellulose per liter was fermented into 12.7 g of ethanol per liter.

Enhanced Cellulose Fermentation by an Asporogenous and Ethanol-Tolerant Mutant of Clostridium thermocellum

A mutant of Clostridium thermocellum isolated after UV mutagenesis and selection for resistance to fluoropyruvate was found to be asporogenous and ethanol tolerant. The mutant was also an ethanol hyperproducer, able to ferment 63 g of cellulose into 14.5 g of ethanol per liter of medium. The ratio of ethanol to total organic acids produced by the mutant was increased, and H(2) production was decreased. Culture conditions were optimized for ethanol production by the new strain.

Photoluminescent diamond nanoparticles for cell labeling: study of the uptake mechanism in mammalian cells

Diamond nanoparticles (nanodiamonds) have been recently proposed as new labels for cellular imaging. For small nanodiamonds (size <40 nm), resonant laser scattering and Raman scattering cross sections are too small to allow single nanoparticle observation. Nanodiamonds can, however, be rendered photoluminescent with a perfect photostability at room temperature. Such a remarkable property allows easier single-particle tracking over long time scales. In this work, we use photoluminescent nanodiamonds of size <50 nm for intracellular labeling and investigate the mechanism of their uptake by living cells. By blocking selectively different uptake processes, we show that nanodiamonds enter cells mainly by endocytosis, and converging data indicate that it is clathrin-mediated. We also examine nanodiamond intracellular localization in endocytic vesicles using immunofluorescence and transmission electron microscopy. We find a high degree of colocalization between vesicles and the biggest nanoparticles or aggregates, while the smallest particles appear free in the cytosol. Our results pave the way for the use of photoluminescent nanodiamonds in targeted intracellular labeling or biomolecule delivery.

Induction of supernumerary ribs with sodium salicylate

Although many chemical agents induce supernumerary ribs (SNR), few efforts have been published examining the induction of SNR in the presence or absence of maternal toxicity and the effect of dose on SNR length. A single administration of sodium salicylate on Day 9 of pregnancy at different dose levels (120, 180, 240, and 300 mg/kg) was used to induce SNR in the thoracolumbar region. At 180, 240, and 300 mg/kg, body weight loss was observed for dams following the administration, associated with reduced food consumption. The mean litter incidence of SNR in the control groups ranged between 0 and 17.1% and in the treated groups (from 180 to 300 mg/kg) between 50.5 and 88.6%. At 120 mg/kg, no adverse effects were noted in dams and the incidence of SNR was in the range of the control groups. Furthermore, in the three highest dose groups, increased incidences of 27 presacral vertebrae (PSV) were noted. In most instances, fetuses with 27 PSV had extra ribs whereas fetuses with 26 PSV tended to have rudimentary ribs. The distinction of SNR between rudimentary and extra ribs is usually based on a ratio of the length of 14th to 13th rib of 0.50. However, this value does not reflect the separation of the apparent bimodal distribution of SNR induced by sodium salicylate. A ratio of 0.35, which corresponds to the superior limit of the SNR of control fetuses, seemed to better define the two populations of SNR.

Optimum incubation conditions of the domestic guinea fowl egg

1. During artificial incubation of 8000 guinea fowl eggs, the effects of temperature, relative humidity, rate of inflowing air and age of the laying flocks were determined. 2. Total duration of incubation was divided into setter (0 to 24 days) and hatcher (25 to 28 days) periods. Eggs transferred at the end of the setter period, (ET, % of fertile eggs) and hatching rate (HR, % of transferred eggs) were calculated, as well as the total hatching rate expressed as percentage of fertile eggs. 3. In the range 36 to 39 degrees C, temperature affected significantly (P < 0.001) ET and HR, with optima at 37.2 and 37.0 degrees C +/- 0.1 degrees C respectively. 4. During incubating period, relative humidity in the range 40 to 64% (water vapour partial pressure, PH2O = 17 to 34 Torr at 36 to 39 degrees C), significantly (P < 0.001) affected the total diffusive water loss and hatchling mass, both expressed as percentage of fresh egg mass. ET was significantly affected by water loss, the highest ET being for water loss of 13.3 +/- 0.5%. Optimal relative humidity was calculated to be 48 to 52% (PH2O = 23 to 25 Torr at 37.2 degrees C). 5. The rate of inflowing air significantly (P < 0.001) affected HR, with an optimum at 3.1 LSTPD/(h.egg). 6. The age of the laying flock significantly (P < 0.001) increased water loss; this was explained by a parallel increase of the mass specific shell conductance to water vapour. 7. Finally optimum incubation conditions were deduced, giving total hatching rates of 78 to 81% of fertile eggs, improving by 5 to 8% the best results obtained routinely in commercial practice.

Oxygen uptake and chorioallantoic blood flow changes during acute hypoxia and hyperoxia in the 16 day chicken embryo

Oxygen consumption rate (MO2) of hen eggs was measured on incubation day 16 (37.8 degrees C, 55% humidity) during acute exposure (90 min) to ambient hyperoxia (FI02 = 0.42) or hypoxia (FIO2 = 0.105). During the last part of these exposures, an H2 washout method was used to estimate relative changes in chorioallantoic membrane (CAM) blood flow, taking as an index the net change in the H2 washout rate constant between any experimental condition and the circulation arrested egg. Doubling normoxic FIO2 increased MO2 to an asymptotic value which was 4% above the normal (P less than 0.05; MO2 in normoxia = 890 mumols/h) even after correcting for the normoxic increase in MO2 with time during development (delta MO2/delta t = 21.5 mumols/h2; P less than 0.001). Halving FIO2 reduced MO2 calculated in the same way to 388 mumols/h. The estimate of the CAM blood flow, relative to normoxia, was 1.12 in hyperoxia (not significant, P = 0.05) and 0.68 in hypoxia (P less than 0.001). The limited changes in CAM blood flow and MO2 during hyperoxia indicate that they are both already close to their maximal values in normoxia. During acute hypoxia the 16 day embryo behaves as an oxygen-conformer; however, the small relative decrease in MO2 per unit of the flow index observed during hyperoxia suggests that the embryo can regulate its CAM blood flow to a small extent. The survival of the embryo and its recovery from hypoxia without a detectable O2 repayment suggest small if any anaerobic regulatory pathways and indicate a true metabolic depression.

Uric acid and urea in relation to protein catabolism in long-term fasting geese

Five ganders were subjected to an experimental fast comparable to that which spontaneously occurs during breeding in domestic geese, and during migration and breeding in various wild birds. Plasma uric acid and urea concentrations, and their excretion as a proportion of total nitrogen excretion, were studied in relation to daily change in body mass per unit body mass, mg/mdt. This variable has previously been found to reflect changes in protein catabolism over the three phases of fast: I, dm/mdt and protein utilization both decrease; II, they are maintained at a low value; and III, they increase. In the fed state, daily total nitrogen excretion was 5 gN X 24 h-1; uric acid, ammonia and urea accounted for 51, 15 and 5% respectively. The high remaining proportion of excreted nitrogen (29%), after subtraction of uric acid-N, ammonia-N and urea-N to total nitrogen, accords with the literature. During fasting, the changes in daily excretion of uric acid, urea, ammonia and total nitrogen followed a pattern essentially similar to that for dm/mdt. Uric acid accounted for a progressively increasing fraction of total nitrogen, up to 76% at the end of phase III, while urea remained at a constant 5%. Plasma concentrations of both uric acid and urea followed similar trends during the fast, in particular both increasing during phase III, i.e. when there was a rise in nitrogen excretion. This suggests they could be used as an index in field investigations, to determine whether birds which naturally fast in connection with specific activities have entered into the situation where proteins are no longer spared.

Oxygen consumption of the chick embryo's respiratory organ, the chorioallantoic membrane

A new technique based on stopping the chick embryo's blood circulation in the intact egg was used to measure in situ the chorioallantoic (CA) oxygen consumption, MCAO2, from incubation day 12 to 20. Total egg MO2, MTOTO2, and wet and dry masses of embryo and CA were also measured daily. Embryo MO2, MEMBO2, was calculated. Mean MCAO2 decreased from 71 mumol X h-1 (17% of MTOTO2, 24% of MEMBO2) at 12 days to 62 mumol X h-1 (5% of MTOTO2) at 20 days. Dry mass of CA did not change significantly. Water remained at a high level in CA (88-94%), but embryo water decreased from 93% to 82% between days 12 and 20. The fairly high level of MCAO2, more marked at young stages, calls for corrections in respiratory and circulatory embryonic variables derived from MTOTO2, such as CA blood flow, CA diffusive capacity for O2, and CA arterio-venous shunt. Mass specific values and intra-specific allometric relations in bird embryos should be recalculated on the basis of MEMBO2 instead of MTOTO2.

Ambient temperature and ketone body plasma concentration in fasting geese

The effect on ketonemia of alternate exposure to ambient temperatures (Ta) of 25 and 5 degrees C was investigated in fasting geese. Three experimental birds were compared to three controls continuously exposed to 25 degrees C Ta while fasting. During the first 9 days of fasting, when both groups were exposed to 25 degrees C, plasma concentration of beta-hydroxybutyrate (beta-OHB) increased similarly in both, from 0.10 +/- 0.02 to 6.62 +/- 0.71 mmol X L-1. It later plateaued at 8-9 mmol X L-1 in the control birds. When the experimental birds were exposed to 5 degrees C Ta between the 9th and 15th day of the fast, it increased further during the first 24 h but thereafter decreased of 57%, from 8.62 +/- 1.56 to 3.73 +/- 1.24 mmol X L-1. This decrease was reversed within the 6 days of return to 25 degrees C Ta. In both groups, plasma acetoacetate (AcAc) concentration remained very low during the fast: 51 +/- 1 mumol X L-1. This reversible cold-induced effect on ketonemia may be used for investigating the possible role of ketone bodies in protein sparing during fasting.

Purification and properties of the endoglucanase C of Clostridium thermocellum produced in Escherichia coli

The celC gene, which codes for a new endoglucanase of Clostridium thermocellum, termed endoglucanase C, was found to be expressed when cloned in Escherichia coli. The enzyme was purified to electrophoretic homogeneneity from E. coli and its biochemical properties were studied. It differs from the previously studied endoglucanases A and B. In particular, endoglucanase C displays features common to endo- and exoglucanases, since it had a high activity on carboxymethylcellulose and on p-nitrophenyl-beta-D-cellobioside where only the agluconic bond was split. In addition, the enzyme was able to release cellobiose units from G3, G4 and G5 cellodextrins. Endoglucanase C was characterized by Western blot in a culture supernatant from C. thermocellum grown on cellulose, using an antiserum raised against the enzyme produced by E. coli.

Gas diffusive conductance of sea-level hen eggs incubated at 2900 m altitude

Sea level hen eggs, selected for their shell conductance (water vapor conductance, HH2O), were incubated at a simulated high altitude, PB = 529 Torr, ca. 2900 m, at 72% relative humidity (rh) to prevent excessive water loss due to hypobaric condition; they were transferred to 150 m 18-24 h before measurements. Control eggs were incubated at 150 m, PB = 750 Torr, rh = 60%. In 8- to 18-day embryos, total CO diffusive conductance, GCO; embyronic body mass, BM; oxygen consumption, MO2; blood hematocrit, Hct; hemoglobin concentration, [Hb]; and heart mass, HM, were measured. Total water loss was the same in both groups, 12% initial egg mass. However, the severe effects of high altitude: 72% mortality and 9% malformation, and reduced increases of BM and MO2, can be related partially to the strong hypocapnia, which resulted from the high shell conductance (GH2O = 18.1 mg X (d X Torr)-1, and was superimposed on the hypoxia. GCO was reduced, while Hct, [Hb] and HM were not significantly affected. When measurements were normalized to BM, MO2 and GCO were identical in the two groups, whereas [Hb] and HM were higher at 2900 m (differential growth). Thus, during incubation, gas diffusive conductance appeared to depend on embryo development and did not adapt to altitude hypoxia. Compared with controls, GCO in high-altitude eggs actually decreased in proportion to BM growth.

Blood circulation and oxygen transport in the fetal guinea pig

Anaesthetized fetal guinea pigs near term were studied under conditions, where maternal placental flow of haemoglobin was maintained within the normal range. The rate of maternal fetal equilibration of intravenously injected 3H2O was found to be similar as in unanaesthetized animals (half time 4 min) indicating that fetal circulation was undisturbed under the present experimental conditions. Umbilical blood flow as determined by a modified 3H2O method was 0.13 ml . min-1 . g-1 of fetal body mass. Radioactive microspheres, injected into the fetal saphenous (jugular) vein, were distributed to the placenta, the lower body, the upper body and the lungs at a ratio of 31(47):27(39):30(6):12(8). From these data, cardiac output was calculated (0.38 ml . min-1 . g-1) and found to be almost equally distributed between the placenta, the lower body and the upper body. There was preferential streaming of the inferior vena caval blood to the upper body. There was no evidence for flow through a ductus venosus. The O2-saturation in the fetal carotid arterial blood was 59 +/- 4%. The O2-supply to the fetal tissues was estimated to be 3 times the oxygen consumption.

Blood oxygen consumption and erythrocyte types in embryonic and postnatal chicken

In an extension of previous work showing that oxygen consumption (MO2) of chick blood cells declines from 5 to 14-15 days incubation age, declines more steeply to hatching, rises abruptly up to 4-6 posthatch days, and declines thereafter, we investigated the succession of embryonic and posthatch erythrocytic types by performing differential erythrocyte (RBC) counts. MO2 of RBC groups separated by density gradients and fractionation into younger and older RBC populations were measured in 1- to 22-day-old posthatch chicks. The embryonic MO2 decline can be attributed to the appearance of erythrocytic types with successively lower metabolism. The MO2 slope change at 14-15 days incubation coincides with the predominance of definitive erythrocytes with oval nuclei over other cell types. The posthatch MO2 rise is due to a temporary invasion of immature RBC, especially postnatal polychromatic erythroblasts. MO2 then decreases as these cells mature.

Facilitated diffusion of lactic acid in the guinea-pig placenta

In the guinea-pig placenta which was artificially perfused on the fetal side while maternal placental blood flow was controlled, the placental transfer per mean transplacental concentration difference (the transfer coefficient TC) was determined for lactate. TC for L-lactate (TCLL) was compared to that for D-lactate (TCDL) and measured for various concentrations of L-lactate, bicarbonate, pyruvate and CO2. Applying a "closed circuit" perfusion technique, L-lactate and proton concentrations on both sides of the placenta were followed during infusion of HCl and sodium L-lactate into the fetal circulation. It was found that TCLL is 3 times TCDL. TCLL is depressed by increasing concentrations of L-lactate while TC for Cl-36 is not. TCLL is also depressed by 50 mmol.1-1 pyruvate. Concentration changes of glucose do not affect TCLL. TCLL rises with the proton concentration, independently of the concomitant changes of the bicarbonate concentration. Transplacental proton concentration gradients produce L-lactate concentration gradients and vice versa. It is concluded that (1) facilitated diffusion of L-lactate occurs in the placenta and that (2) L-lactate transfer is coupled with proton transfer. Beside the well-known placental transport system for glucose this is the second passive transport system found in a placenta.