Bronchoconstrictor responses to sulfur dioxide or sulfur dioxide plus sodium chloride droplets in allergic,nonasthmatic adolescents

Eight atopic adolescent subjects without diagnosis of clinical asthma but with signs of hyperactive airways were studied. The subjects were exposed for 30 min at rest followed by 10 min during moderate exercise on a treadmill to the following: (1) filtered air, (2) 1 mg/m³ NaCl droplet aerosol, (3) 1 ppm SO₂ and NaCl droplet aerosol, or (4) 1 ppm SO₂. All exposures were at 75% relative humidity and 22 °C. Exposures to either SO₂ mode produced statistically significant changes in pulmonary function, whereas sham exposures to air on NaCl did not. These results are similar to those seen earlier in a group of extrinsic asthmatic adolescent subjects and are three to 22 times greater than changes we saw in a group of normal adolescent subjects. The changes seen after inhalation of SO₂ were not statistically different from those seen after inhalation of SO₂ and NaCl droplet aerosol. Our results indicate that inhalation of 1 ppm SO₂ by a group of atopic adolescents can produce exercise-induced bronchospasm at a level of exercise that has no effect by itself.     

Alternating copolymerization of cyclohexene oxide and sulfur dioxide

Copolymerization of cyclohexene oxide (CHO) and sulfur dioxide (SO₂) was conducted at 80°C by using a variety of catalysts both in the presence and absence of solvent. Aromatic tertiary amines such as pyridine gave an alternating copolymer of CHO and SO₂ in the presence of solvents such as 1,2-dimethoxyethane. The alternating copolymer obtained was a white thermoplastic which could readily be thermoformed. It was soluble in acetone and chloroform but insoluble in water and hexane. From the reaction of the equimolar mixture of CHO, SO₂ and pyridine at 20°C, an 1 : 1 : 1 adduct of CHO, SO₂ and pyridine (see formula 2 ) could be isolated. This adduct was confirmed to be the active species for the present copolymerization.     

Terpolymerization of sulfur dioxide with maleic anhydride and vinyl monomers

The free radical polymerization in ternary systems comprising sulfur dioxide, maleic anhydride and vinyl monomers, such as ethylene, propene, 2-methylpropene, 1-hexene, 1,3-butadiene, styrene, α-methylstyrene, vinyl chloride and methyl acrylate, was studied. In systems with α-methylstyrene only a copolymer of this monomer with maleic anhydride was obtained. In systems with methyl acrylate a terpolymer containing mainly methyl acrylate monomeric units was produced, whereas in all the other systems terpolymers containing ca. 50 mol-% of vinyl monomeric units were formed. In terpolymerizations carried out at low temperatures, SO₂ is a more reactive monomer than maleic anhydride. With increasing temperature the content of ? SO₂? monomeric units decreases in the products obtained. This is connected with an enhancement of the depropagation rate of this monomer. On the basis of the results obtained some aspects of the propagation and depropagation mechanisms in the systems studied are discussed.     

The cyclo-copolymerization of diallyl compounds and sulfur dioxide, 4. 4-(4-pyridyl)-1,6-heptadiene hydrochloride and sulfur dioxide

Copolymers of 4-(4-pyridyl)-1,6-heptadiene hydrochloride ( 1 ) and 4-(1-buten-4-yl)pyridine hydrochloride ( 2 ) with sulfur dioxide were prepared and their properties were investigated. The effects of the copolymerization conditions on the yields and viscosities of the obtained copolymers were studied. Their structures were studied by elemental analyses, IR, and ¹H- and ¹³C-NMR spectroscopy.     

Synthesis and characterization of some acrylic monomer/sulfur dioxide copolymers

The copolymerization of acrylic monomers (M) [acrolein (AL), methyl acrylate (MA), acrylamide (AM) and acrylonitrile (AN)] with liquid sulfur dioxide (S) at low temperature and high dilution in the presence of tert-butyl hydroperoxide gives high SO₂ incorporation into the resulting copolymers. Analysis of the composition of these polysulfones, by elemental analyses and ¹³C NMR, shows that they consist mostly of the MMM, SMM, MMS and MSM triad monomer sequences. Thermal (TG) analyses of selected samples demonstrate that their thermal stability, up to 30% weight loss, increases for different acrylic comonomers as follows: AL < AM < MA < AN. Preliminary flammability tests revealed that flame retardancy increases with increasing SO₂ content in the copolymer.     

Reactivity of vinyl monomers in the copolymerization and terpolymerization with sulfur dioxide

The relative reactivities of vinyl monomers in low-temperature copolymerizations and terpolymerizations with SO₂ in the presence of tert-butyl hydroperoxide as initiator were compared. The highest copolymerization rates were found in systems containing an electron-donor monomer of low resonance stabilization, and the resulting products have an alternating structure. In reactions with monomers of high resonance stabilization and electron-acceptor properties, mainly homopropagation of the comonomer proceeds. In the terpolymerization of SO₂ with two electron-donor monomers, the relative reactivity of monomers depends mainly on their resonance stabilization. In the terpolymerization in systems SO₂/electron-donor monomer/electron-acceptor monomer the relative reactivity of acceptor monomers decreases with increasing inductive effect in the molecule.     

Terpolymerization of sulfur dioxide and methyl acrylate with electron donor monomers

The radical terpolymerization of sulfur dioxide and methyl acrylate with 1,3-butadiene, 2-methylpropene, propene, 1-hexene, 1-octene and vinyl chloride was studied by comparing the composition of terpolymers obtained under different reaction conditions and by analysis of ¹³C NMR spectra of selected terpolymers and copolymers. In the majority of systems studied, products are formed in which the ratio of SO₂ monomeric units to vinyl monomeric units is near to unity. The content of methyl acrylate monomeric units can change over a very wide range and depends mainly on the electron-donor properties of the vinyl monomer used, feed composition and conversion. An increase of the methyl acrylate content is also observed in many systems with a rise of the reaction temperature. The results obtained are interpreted in terms of a mechanisms involving the addition of individual monomers and reversibility of steps in which carbon-sulfur bonds are formed.     

The cyclo-copolymerization of diallyl compounds and sulfur dioxide, 5. Copolymerization of some 4-substituted 1,6-heptadiene derivatives with sulfur dioxide

Copolymers of sulfur dioxide with N-substituted 4-(1,6-heptadiene-4-yl)pyridinium chlorides and bromides ( 1 ) and N-substituted 4-(3-butenyl)pyridinium chlorides and bromides, and some other 1,6-heptadiene derivatives 3 substituted in 4-position were prepared. The effects of the copolymerization conditions on the conversions and viscosities of the copolymers were studied and their structures by elemental analyses, IR and ¹H NMR spectroscopy. The thermal stabilities of the copolymers were also examined.     

Synthesis and characterization of poly(propylene sulfite) from sulfur dioxide and propylene oxide using zinc derivatives as catalysts

The zinc glutarate catalyzed copolymerization of sulfur dioxide (SO₂) and propylene oxide (PO) was investigated in detail by varying temperature, time, monomer feed ratio, and PO feed per catalyst as well as by using solvents, such as PO and chloroform. An optimized copolymerization [PO]/[catalyst] = 300, and no solvent at 60°C, 40 h, [PO]/[SO₂] = 1, resulted in poly(propylene sulfite) (PPS) with high molecular weight I_n = 42 000 (I_w /I_n = 2.1) never achieved before. PPS was obtained in a yield of 66.9 g per g of catalyst (namely, 12.93 kg per mol of catalyst) and determined to consist of 90.4 mol‐% sulfite‐linkage and 9.6 mol‐% ether‐linkage. A polymer containing a large amount of ether‐linkages was additionally formed as a minor component. However, no formation of cyclic propylene sulfite as byproduct was detected. In addition, zinc hexacyanoferrate(III) was prepared and used in the copolymerization as a catalyst, but showed almost no catalytic activity.     

On the reaction of catenapoly(diphenoxy-λ5-phosphazene) with sulfur trioxide

The reaction of catenapoly(diphenoxy-λ⁵-phosphazene) ( 1 ) with SO₃ in 1,2-dichloroethane at 15°C, applying a mole ratio m = [SO₃]/[-–P(OC₆H₅)₂N—] ≤ 1,0 and subsequent quenching with water, leads to catenapoly(diphenoxy-λ⁵-phosphazene-co-diphenoxy-λ⁵-phosphazenium hydrogen sulfate) ( 2 ) containing up to 57% protonated nitrogen. At m > 1,0 C-sulfonation occurs, resulting in the formation of water-soluble catenapoly[diphenoxy-λ⁵-phosphazene-co-diphenoxy-λ⁵-phosphazenium hydrogen sulfate-co-bis(sulfophenoxy)-λ⁵-phosphazenium hydrogen sulfate] ( 3 ). The latter can be converted into catenapoly[diphenoxy-λ⁵-phosphazene-co-bis(sulfophenoxy)-λ⁵-phosphazene] ( 4b ) by treatment with alkali and subsequent percolating through a cation exchange resin. Analytical results show that C-sulfonation is preceded by the formation of a polymer-SO₃ donor-acceptor complex.     

The diffusion of carbon dioxide in erythrocytes and hemoglobin solutions

Summary The CO₂ diffusion constant (Krogh's diffusion constant) has been estimated from the CO₂ flux across layers with defined thickness under steady state conditions.At 22°C and in hemoglobin solutions with a concentration of 33 g% the diffusion constant for CO₂ was found to be 3.3×10^–4 cm² min^–1 atm^–1. This value is about 40% of the diffusion constant for CO₂ in water. The relationship between the diffusion constant and the hemoglobin concentration was approximately linear in a concentration range of 10–40 g%. The temperature coefficient of the diffusion constant was –0.5%/°C both in water and hemoglobin solutions. At 38°C and in a hemoglobin solution with a concentration of 33 g%, the diffusion constant for CO₂ was therefore 3.0×10^–4 cm² min^–1 atm^–1, the diffusion coefficient 11×10^–6 cm² s^–1.A general theory for the diffusion of CO₂ in hemoglobin solutions has been derived. According to this theory the diminution of the CO₂ diffusion in hemoglobin solutions in comparison to water can be explained quantitatively by a reduction of the water space by the hemoglobin molecules.The diffusion constant for CO₂ in layers of erythrocytes was insignificantly (0–3%) smaller than in hemoglobin solutions with the same hemoglobin concentration. It is concluded that the erythrocyte membrane does not offer a considerable resistance for the CO₂ diffusion.     

Carbon dioxide storage and nonbicarbonate buffering in the human body before and after an Himalayan expedition

Before and 7–12 days after an Himalayan expedition CO₂ equilibration curves were determined in the blood plasma of 12 mountaineers by in vitro and in vivo CO₂ titration; in vivo osmolality changes (ΔOsm?·?ΔPCO₂ ^?1, ΔOsm?·?ΔpH^?1, where PCO₂ is the partial pressure of CO₂) during the latter experiments yielded estimates of whole body CO₂ storage. In vitro ?Δ[HCO₃ ^?]?·?ΔpH^?1 [nonbicarbonate buffer capacity (β) of blood] was increased 7 days after descent [before 31.3 (SEM 0.4) mmol?·?kgH₂O^?1, after?38.3?(SEM 3.9)?mmol?·?kgH₂O^?1; P<0.05] resulting from an increased proportion of young erythrocytes; in additional experiments an augmented β was found in young (low density cells) compared to old cells [<1.097 g?·?ml^?1: 0.216 (SEM 0.028) mmol?·?gHb^?1, >1.100?g?·?ml^?1: 0.145?(SEM 0.013)?mmol?·?gHb^?1, where Hb is haemoglobin; P<0.02]. In spite of increased Hb mass in vivo Δ[CO_2total]?·?ΔPCO₂ ^?1 [0.192?(SEM 0.010)?mmol?·?kgH₂O^?1?·?mmHg^?1] and ?Δ[HCO₃ ^?]?·?ΔpH^?1 [17.9?(SEM 1.0)?mmol?·?kgH₂O^?1] as indicators of extracellular β rose only slightly after altitude (7 days +16%, P<0.02; +7%, NS) because of haemodilution. The ΔOsm?·?ΔPCO₂ ^?1 [0.230?(SEM 0.015) mosmol?·?kgH₂O^?1?·?mmHg^?1] remained unchanged. Prealtitude differences in ΔOsm?·?ΔpH^?1 between hypercapnia [?41?(SEM 5)?mosmol?·?kgH₂O^?1] and hypo-capnia [?20?(SEM 3)?mosmol?·?kgH₂O^?1; P<0.01] disappeared temporarily after return since the former slope was reduced. The high value during hypercapnia before ascent probably resulted from mechanisms stabilizing intracellular pH during moderate hypercapnia which were attenuated after descent.     

The possibility of living or long-lived cationic polymerization in the butyl vinyl ether/iodine/liquid sulfur dioxide system

The polymerization of butyl vinyl ether (nBuVE) initiated by iodine in the presence of liquid sulfur dioxide has been investigated. The number-average molecular weight increased with monomer concentration and after the addition of a fresh feed of the monomer at the end of the first polymerization step. This behavior has been observed in media of different polarity, that is, SO₂/toluene = 80 : 10 or 50 : 40 v/v and SO₂/CH₂Cl₂ = 20 : 70 v/v ¹H NMR spectroscopy revealed the presence of aldehyde terminal group derived from acetal end group, indicating the presence of living or long-lived propagating species. The average number of polymer chains carrying aldehyde end groups is higher than the initial iodine concentration, suggesting that an additional initiation process by hydrogen iodide is taking place.     

Reactivity of the Dicationic Ruthenium–Alkylidene Complex [Ru(DMF)3(IMesH2)(=CH—2—(2—PrO)—C6H4)],2+(BF4−)2] in Ring‐Opening Metathesis and Cyclopolymerization

The reactivity of the dicationic Ru–alkylidene complex [Ru(DMF)₃(IMesH₂)(—CH—2—(2—PrO)—C₆H₄)]²⁺(BF₄^?)₂] ( 1 , IMesH₂ = 1,3‐dimesitylimidazolin‐2‐ylidene) in the ring‐opening metathesis polymerization (ROMP) of various functional norborn‐2‐enes as well as in the cyclopolymerization of different 1,6‐heptadiynes is reported. Due to its dicationic character, complex 1 is highly electrophilic and possesses high reactivity towards alkenes and 1,6‐heptadiynes. Generally, a pronounced difference in reactivity between monomers bearing coordinating groups and those that lack such moieties is observed. In the presence of ionic monomers containing coordinating anions such as Br^? and I^?, a rapid change in the nature of the propagating alkylidene from a dicationic to a neutral one is observed.     

Molecular size and gel formation in branched poly(methyl methacrylate) copolymers

Branched copolymers of methyl methacrylate with ethylene dimethacrylate or pentaerythritol tetramethacrylate with high weight average molecular weights M_w were prepared by free radical polymerization. The double bond conversion of these polymers (β) was measured dilatometrically and the gel point (β_c) was located by extrapolation of bulk viscosity measurements. The polymers were studied by light-scattering, ¹H NMR and viscometry. Hence it was possible to investigate the relationship between the molecular weight M_w and the reduced conversion quantity (1 ? β/β_c)^?1 and also the molecular weight dependence of the z-average mean square radius of gyration 〈S²〉_z. Considerable deviations from the classical Stockmayer theory but also from percolation theory were observed. ¹H NMR showed a relative small extent of ring formation (10 to 24%) and a reduced apparent reactivity of the pendant double bonds, while the delay in the gel formation appeared to be caused by a much higher ring formation (80 to 90%). This apparent inconsistency is explained by a size-dependent ring formation, where the extent of ring formation is increased with the molecular dimensions; simultaneously, the pendant double bonds become progressively less accessible to cross-linking by growing radicals. The molecular weight dependence of 〈S²〉_z is found to be in agreement with this heterogeneous reaction model.     

Ventilatory responses to exercise and carbon dioxide in elderly and younger humans

Summary The present investigation examined the relationship between CO₂ sensitivity [at rest (S _R) and during exercise (S _E)] and the ventilatory response to exercise in ten elderly (61–79 years) and ten younger (17–26 years) subjects. The gradient of the relationship between minute ventilation and CO₂ production ( _E/ CO₂) of the elderly subjects was greater than that of the younger subjects [mean (SEM); 32.8 (1.6) vs 27.3 (0.4); P<0.01]. At rest, S _R was lower for the elderly than for the younger group [10.77 (1.72) vs 16.95 (2.13) 1 · min^–1 · kPa^–1; 1.44 (0.23) vs 2.26 (0.28) 1 · min^–1 · mmHg^–1; P<0.05], but S _E was not significantly different between the two groups [17.85 (2.49) vs 19.17 (1.62) l · min^–1 · kPa^–1; 2.38 (0.33) vs 2.56 (0.21) 1 · min^–1 · mmHg^–1]. There were significant correlations between both S _R and S _E, and _E/ CO₂ (P<0.05; P<0.001) for the younger group, bot none for the elderly. The absence of a correlation for the elderly supports the suggestion that _E/ CO₂ is not an appropriate index of the ventilatory response to exercise for elderly humans.     

Copolymers of acrylates with sulfur dioxide: Synthesis and structural studies by 13C NMR spectroscopy

The copolymerization of sulfur dioxide with methyl, ethyl, butyl or 2-ethylhexyl acrylate was studied. The influence of the composition of monomer feed and reaction temperature on the composition of the copolymers was investigated. The maximum content of sulfonyl units in the copolymers, obtained at ?78°C, was found to be ca. 30 mol-% and to decrease with increasing temperature. The sequence distribution in the copolymers was determined by ¹³C NMR spectroscopy. It was proved that acrylates do not undergo alternating propagation with SO₂, and the minimum number of acrylate monomeric units in a homosequence is 2. The results obtained were compared with those obtained from studies on the copolymerization of SO₂, with other monomers, and are discussed in terms of the alternating copolymerization theory and the penultimate model.     

Cationic Monomer‐Isomerization Polymerization of Oxetanes Having an Ester Substituent,to Give Poly(orthoester) or Polyether

This study shows the cationic monomer‐isomerization polymerization of 3‐R¹‐oxetanes ( 1 ) having a 3‐ester substituent (—CH₂OCOR²) through two ring‐opening routes (R¹ = CH₃, Ph; R² = Pr, Ph). The polymerization of 1 with Lewis acids usually gave poly(orthoester) ( 3 ) or polyether ( 4 ), together with bicyclic orthoester ( 2 ) as the isomerization product. The isomerization took place prior to polymerization, because of the preferable nucleophilic attack of the intermolecular carbonyl oxygen. Subsequently, 2 polymerized in either a single‐ or double‐ring‐opening manner depending on temperature. The single‐ring‐opening polymerization of 2 below room temperature was an equilibrium polymerization through bicyclic oxonium ends leading to 3 , and the thermodynamic parameters were estimated according to Dainton's equation. Thus, Corey's orthoester synthesis from ester‐substituted oxetanes is regarded as a phenomenon in the equilibrium polymerization only around the ceiling temperature (T_c). Above T_c, 2 brought about the double‐ring‐opening polymerization through monocyclic diaoxacarbenium ends to afford 4 . Relatively bulky R¹ and R² such as the Ph group exerted a large steric effect on both polymerization routes. As a special case arising from this effect, the CF₃SO₃H‐catalyzed reaction of 1 c (R¹, R² = Ph) resulted in an unusual cyclodimerization accompanied by the elimination of benzoic acid, owing to the susceptibility of the neophyl skeleton to cation transfer.     

Ventilatory response of prepubertal boys and adults to carbon dioxide at rest and during exercise

Summary The aim of this study was to determine whether the greater ventilation in children at rest and during exercise is related to a greater CO₂ ventilatory response. The CO₂ ventilatory response was measured in nine prepubertal boys [10.3 years (SD 0.1)] and in 10 adults [24.9 years (SD 0.8)] at rest and during moderate exercise ( CO₂ = 20 ml·kg^–1·min^–1) using the CO₂-rebreathing method. Three criteria were measured in all subjects to assess the ventilatory response to CO₂: the CO₂ sensitivity threshold (Th), which was defined as the value of end titalPCO₂ (P _ETCO₂) where the ventilation increased above its steady-state level; the reactivity slope expressed per unit of body mass (SBM), which was the slope of the linear relation between minute ventilation ( _E) andP _ETCO₂ above Th; and the slope of the relationship between the quotient of tidal volume (V _T) and inspiration time (t _I) andP _ETCO₂ (V _T ·t _I ^–1 ·P _ETCO₂ ^–1) values above Th. The _E,V _T, breathing frequency (f _R), oxygen uptake ( O₂), and CO₂ production ( CO₂) were also measured before the CO₂-rebreathing test. The following results were obtained. First, children had greater ventilation per unit body weight than adults at rest (P<0.001) and during exercise (P<0.01). Second, at rest, onlyV _T ·t _I ^–1 ·P _ETCO₂ ^–1 was greater in children than in adults (P<0.001). Third, during exercise, children had a higher S_BM (P < 0.02) andV _T ·t _I ^–1 ·P _ETCO₂ ^–1 (P<0.001) while Th was lower (P<0.02). Finally, no correlation was found between _E/ CO₂ and Th while a significant correlation existed between _E/ CO₂ and S_BM (adults,r=0.79,P<0.01; children,r=0.73,P<0.05). We conclude that children have, mainly during exercise, a greater sensitivity of the respiratory centres than adult. This greater CO₂ sensitivity could partly explain their higher ventilation during exercise, though greater CO₂ production probably plays a role at rest.