N2O O2 Research Articles

Endorphin and cortisol responses to surgical stress in newborns and infants

The beta-endorphin (BE) response to surgical stress in newborns and infants and its relation to pituitary-adrenal dynamics during stress is still unknown. Nine newborns 5 h to 5 days of age, and 5 infants 5 to 10 months old undergoing surgery were studied. All patients were anesthetized with N2O–O2 and halothane. Blood samples for BE and cortisol determinations were taken preoperatively and 30 min, 12 h, and 24 h after operation for radioimmunoassay. Both BE and cortisol levels in newborns were not significantly different from those in infants preoperatively (196±85.2 pg/ml vs. 138±47.8 pg/ml for BE and 23.7±17.5 μg/dl vs. 10.1±5.6 μg/dl for cortisol, P >0.05). At 30 min after operation, no significant increase in BE (220±106 pg/ml) and cortisol (36.1±21.2 μg/dl) was found in newborns, while significant increases (BE 493±281 pg/ml, cortisol 43.9±24.2 μg/dl) were found in infants compared to preoperative levels (both P <0.05). A significant difference between groups was seen in BE but not cortisol levels 30 min after operation. Both BE and cortisol declined to preoperative values within 24 h after surgery. Our study showed significant BE and cortisol responses to surgical stress in infants, but not in newborns. Factors such as age-related differential responses to the same anesthetic technique, duration of operation, and developmental differences in stress response are considered responsible for the differences.

Partial reversal of the cerebral effects of isoflurane in the dog by the benzodiazepine antagonist flumazenil.

Six dogs initially anaesthetized with isoflurane-N2O-O2 for surgery with cannulation of the sinus sagittalis for direct measurement of cerebral blood flow (CBF) and maintained with 1% isoflurane-N2-O2 anaesthesia, were given two 2-mg doses of the benzodiazepine antagonist flumazenil with an interval of 10 min. This was accompanied by a significant increase in the cerebral metabolic rate for oxygen (CMRO2) 10 min after the first 2-mg dose, and 5, 10 and 15 min after the second 2-mg dose, the increase varying in mean value from 9% to 14%. EEG was recorded in five of the six dogs and administration of flumazenil converted the EEG from a sleep pattern to an awake pattern in two of them. There were no significant changes in the CBF or mean arterial blood pressure (MABP) values. In the brain biopsies taken at the end of the study there were no significant changes in the adenylate energy charge (EC) and the lactate/pyruvate ratio (L/P) when compared to five other dogs not given flumazenil. It is concluded that flumazenil in this study demonstrated a partial antagonism of the cerebral effects of isoflurane.

Influence of the water regime on denitrification and aerobic respiration in soil

The influence of soil moisture on denitrification and aerobic respiration was studied in a mull rendzina soil. N2O formation did not occur below −30 kPa matric water potential (Ψm), above 0.28 air-filled porosity (a) and below 0.55 fractional water saturation (Θv/PV ≙ volumetric water content/total pore volume). Half maximum rates of N2O production and O2 consumption were obtained between Ψm = −1.2 and −12 kPa,a = 0.05 and 0.23, and Θv/PV = 0.63 and 0.92. No oxygen consumption was measured at Θv/PC ≧ 1.17. O2 uptake and denitrification occurred simultaneously arounda = 0.10 (at Ψm = −10 kPa and Θv/PV = 0.81) at mean rates of 3.5 µl O2 and 0.3 µl N2 h−1g−1 soil. Undisturbed, field-moist soil saturated with nitrate solution showed constant consumption and production rates, respectively, of 0.6 µl O and 0.22 µl N2O h−1g−1 soil, whereas the rates of air-dried remoistened soil were at least 10 times these values. The highest rates obtained in remoistened soil amended with glucose and nitrate were 130 µl O2 and 27 µl N2O h−1g−1 soil.

High‐pressure range of the recombination O + O2 → O3

AbstractThe recombination reaction O + O2 → O3 was studied by laser flash photolysis of pure O2 in the pressure range 3–20 atm, and of N2OO2 mixtures in the bath gases Ar, N2, (CO2, and SF6) in the pressure range 3–200 atm. Fall‐off curves of the reaction have been derived. Low‐pressure rate coefficients were found to agree well with literature data. A high‐pressure rate coefficient of k∞ = (2.8 ± 1.0) × 10−12 cm3 molecule−1 s−1 was obtained by extrapolation.

Optimization of the parameters of a CO chemical laser by increasing the length of the active medium

An experimental investigation was made of a CO chemical laser utilizing a CS2–N2O–O2 flame having an active medium up to 3 m long. Attention is drawn to the need to match the dimensions of the active medium to the mode structure of the resonator. A chemical efficiency of 15% was achieved for a cw laser radiation power of around 100 W.

Radiolysis of dihydrouracil and dihydrothymine in aqueous solutions containing oxygen; first- and second-order reactions of the organic peroxyl radicals; the role of isopyrimidines as intermediates

The nature and yields of the products of radiolysis of aqueous solutions of dihydrouracil containing both N2O and O2 strongly depend on pH and dose rate. At a dose rate of 0.3 Gy s–1 and at pH 3, the major products are barbituric acid (G 2.4), labile material (G 2.8), and uracil (G 0.1). The labile material is converted into uracil upon treatment with acid and is largely composed of 5,6-dihydro-6-hydroxyuracil. At pH 7 barbituric acid is absent and uracil becomes the major product (G 4.5); some labile material is also formed (G 0.7). At pH 5 the pattern of the product distribution changes as a function of dose rate. With increasing dose rate G(uracil) decreases whereas G(barbituric acid) increases. The predominant radical formed in the dihydrouracil system is the 6-peroxyl radical, and it has been found, using pulse radiolysis with both optical and conductometric detection, that this peroxyl radical can eliminate O2–˙ to give uracil via an unstable isomeric form of the pyrimidine (isouracil). The elimination is base-catalysed so that, under alkaline conditions, uracil is the major radiolysis product. At lower pH, and also at higher dose rates, bimolecular decay of the peroxyl radical competes with the O2–˙ elimination process, barbituric acid being a specific product of the bimolecular decay route. The mechanisms of these processes are discussed.Irradiation of dihydrothymine–N2O–O2 solutions gave similar results.

Radiolysis of di- and tri-methyl phosphates in oxygenated aqueous solution: a model system for DNA strand breakage

In the radiolysis of aqueous solutions of trimethyl phosphate saturated with N2O–O2 the major products (G values in parentheses) are dimethyl hydrogen phosphate (6.4), formic acid (3.1), formaldehyde (1.7), hydrogen peroxide (2.1), organic peroxide (0.5), and carbon monoxide (1.0). Oxygen is consumed (G 4.1). In the dimethyl phosphate (sodium salt) system the products and their G values are similar to those of the trimethyl phosphate system. Pulse radiolytic studies have shown that in the trimethyl phosphate system the first formed peroxyl radicals react with each other to give a short lived tetraoxide (2k= 9 × 108 dm3 mol–1 S–1). This intermediate decays either by concerted mechanisms or by fragmentation to form O2 and two oxyl radicals. Among other reactions these oxyl radicals undergo a 1,2-hydrogen shift, followed by a complex series of reactions. There are two processes that yield acids at longer reaction times. The faster process has been identified as the hydrolysis of formic dimethylphosphoric anhydride (k= 0.3 + 2.3 × 104[OH–]S–1). The slower process (k= 2600[OH–] S–1) is only observed in basic solutions and has not yet been identified with certainly. The present findings are used as a model to assist in the interpretation of some aspects of DNA radiolysis.

The radiolysis of uracil in oxygenated aqueous solutions. A study by product analysis and pulse radiolysis

Hydroxyl radicals are generated by the radiolysis of N2O–O2(4 : 1 v/v)-saturated aqueous solutions of uracil. They add to the 5,6-double bond of the substrate [80% at C(5), 20% at C(6)]. These radicals are converted by oxygen into the corresponding peroxyl radicals (I) and (II), respectively. Peroxyl radical (I) undergoes a base-induced O2–˙ elimination (kobs 8 × 103 s–1 at pH 10.5). As an intermediate 5-hydroxy-isopyrimidine is formed which rearranges into isobarbituric acid and adds water forming 5,6-dihydro-5,6-dihydroxyuracil. Competing with this base-induced reaction of radical (I) there is a bimolecular decay of radicals (I) and (II). These processes become predominat at low pH. For this reason a strong pH dependence of G(products) is observed. The major products are (G values at pH 3 and 10 in parentheses) 5,6-dihydroxy-5,6-dihydrouracil (1.1; 2.4), isobarbituric acid (0; 1.2), N-formyl-5-hydroxyhydantoin (1.6; 0.2), 5-hydroxybarbituric acid (0.9; 0.2). 5-Hydroxybarbituric acid is formed in its keto form. Its deprotonation (k 4.4 s–1) has been followed by pulse conductometry. Details of the reaction mechanism, e.g. the involvement of oxyl radicals in the bimolecular decay of (I) and (II), are discussed.

Radiation chemistry of carbohydrates. Part 14. Hydroxyl radical induced oxidation of D-glucose in oxygenated aqueous solution

D-Glucose (5 × 10–3M) has been γ-irradiated in N2O–O2(80 : 20 v/v) saturated aqueous solutions (dose rate 1.1 × 1015 eV g–1 s–1), and the G values of 22 products determined. Major products (G values in parentheses) are : D-gluconic acid (1)(0.9). D-arabino-hexosulose (2)(0.9). D-ribo-hexos-3-ulose (3)(0.57), D-xylo-hexos-4-ulose (4)(0.50), D-xylo-hexos-5-ulose (5)(0.60). D-gluco-hexodialdose (6)(1.55), and L-threo-tetrodialdose (12)(0.20). Products (1)–(6) are thought to be formed by OH attack at C-1–C-6, followed by oxygen addition and and HO2 elimination. In competition, reactions between the glucose peroxyl radicals and HO2·(O2–·) give rise to fragmentation of C–C bonds. The major product from these fragmentation reactions is (12)(precursor. radical at C-5). From a dose rate study using electron pulses from a van de Graaff generator it has been shown that the rates of HO2· elimination are in the order: C-1 C-2, C-3, C-4 > C-6 C-5. Furthermore, it has been calculated that OH radicals abstract a hydrogen atom from C-1 and C-2 with a probability of ca. 20%. from C-3 and C-4 of ca. 10% from C-5 of ca. 15%, and from C-6 ca. 30%.

Primary Yields and Mechanisms in the Radiolysis of N2O from High Intensity Electron Pulse Irradiations of N2O–O2 Mixtures

The yields of N2, O2, NO, and O3 have been measured from the Febetron radiolysis of N2O–O2 mixtures with and without SF6. A mechanism consistent with the yields from 0–100% O2 and with known ionic abundances and reaction rate data has been derived. The major features of this mechanism are both dissociative neutralization of N2O+ and excitation of N2O to give N2(X1Σ) and O(1D) and smaller amounts of N2(B3Π) and O(3P). The large yields of NO and N2 observed are mainly due to reaction of O(1D) with N2O to give both N2 and O2 and NO.

Collision Broadening of Rotational Absorption Lines. VI. Pressure Broadening of Microwave Absorption Spectra Involving Oxygen

The pressure broadening of microwave absorption lines by collisions involving O2 has been investigated using a method presented earlier for analyzing and evaluating microwave linewidth parameters under conditions where impact-theory assumptions are valid. A value of (1.16 ± 0.12) D· Å was obtained for the molecular quadrupole moment of O2 from linewidth data for broadening of NH3 inversion lines by O2. This value is in reasonably good agreement with values determined by other methods, and should constitute an upper limit to the true value since only dipole–quadrupole interaction was considered in the linewidth calculations, This value of the molecular quadrupole moment of O2 was used to calculate linewidth parameters for H2O–O2 broadening, OCS–O2 broadening, N2O–O2 broadening, O2–O2 self-broadening, and the broadening of the 9– line of O2 by various foreign gases. These results are in general smaller than the experimental values, suggesting that the effects of higher-order interactions are important in collisions with O2.

Heat Conductivities of Polyatomic Gases and Their Binary Mixtures

A hot-wire apparatus of the ``potential leads'' type has been used to determine the thermal conductivities of nitrogen, oxygen, nitric oxide and nitrous oxide, and the binary mixtures: N2O–N2, N2O–O2, N2O–NO and NO–N2, over the temperature range 30° to 200°C. Corrections were made for the various possible sources of error, and the final results are accurate to within 2%. The results for single gases are discussed in terms of the original Eucken formula, the diffusion-mechanism theory and the Mason-Monchick theory. The mixtures are treated in terms of the general Hirschfelder equation, and also by use of the Wassiljewa-type relation. In the latter case, the experimental Wassiljewa coefficients are compared with those calculated by the Mason-Saxena and Lindsay-Bromley approximate relations.