Reliability and validity of six-minute step test in patients with heart failure

Exercise intolerance is the hallmark consequence of advanced chronic heart failure (HF). The six-minute step test (6MST) has been considered an option for the six-minute walk test because it is safe, inexpensive, and can be applied in small places. However, its reliability and concurrent validity has still not been investigated in participants with HF with reduced ejection fraction (HFrEF). Clinically stable HFrEF participants were included. Reliability and error measurement were calculated by comparing the first with the second 6MST result. Forty-eight hours after participants underwent the 6MST, they were invited to perform a cardiopulmonary exercise test (CPET) on a cycle ergometer. Concurrent validity was assessed by correlation between number of steps and peak oxygen uptake (V̇O₂ peak) at CPET. Twenty-seven participants with HFrEF (60±8 years old and left ventricle ejection fraction of 41±6%) undertook a mean of 94±30 steps in the 6MST. Intra-rater reliability was excellent for 6MST (ICC=0.9), with mean error of 4.85 steps and superior and inferior limits of agreement of 30.6 and -20.9 steps, respectively. In addition, strong correlations between number of steps and CPET workload (r=0.76, P<0.01) and peak V̇O₂ (r=0.71, P<0.01) were observed. From simple linear regression the following predictive equations were obtained with 6MST results: V̇O₂ peak (mL/min) = 350.22 + (7.333 × number of steps), with R²=0.51, and peak workload (W) = 4.044 + (0.772 × number of steps), with R²=0.58. The 6MST was a reliable and valid tool to assess functional capacity in HFrEF participants and may moderately predict peak workload and oxygen uptake of a CPET.     

Free rotation dimensions of linear polymers and application to polyalkylene oxides and polyalkylene sulphides

A general expression has been derived for the mean square end-to-end distance 〈r²〉_0f of linear polymers in the unperturbed freely rotating state. For a chain having q bonds per segment, a degree of polymerisation p and a total of N (= pq) bonds in the chain, the expression may be written 〈r²〉_0f = N[A₀/q + AB/pq]. Here A₀ is the sum of scalar products of the bond vectors within a segment and A is the corresponding sum for pairs of bond vectors in adjacent segments. B denotes a series having a value dependent on p and the bond angles. The formula has been applied to the particular cases of [(CH₂)_m?X?]_p where X = oxygen, X = sulphur and m = 1, 2, 3, 4, 6, and 10. Calculations of [〈r²〉_0f/N]^1/2 have been made for values of p in the range 1 ? p ? ∞, and the variation of [〈r²〉_0f/N]^1/2 with both chain length and chain structure discussed.     

Structure of active species in the cationic polymerization of β-propiolactone and ε-caprolactone

The study of the structure of the end-groups of poly(β-propiolactone) and poly(ε-caprolactone) by ¹H, ³¹P{¹H} NMR, and IR spectroscopy revealed that the mode of ring scission in the monomer in the first propagation step depends on the initiator used. In the initiation of the β-propiolactone and ε-caprolactone polymerization with halonium salts ((CH₃)₂Br^⊕SbF₆^? or (CH₃)₂I^⊕SbF₆F₆^?) the exocyclic oxygen atoms in the monomer molecules are attacked and oxonium ions are formed. The propagation steps proceed with alkyl-oxygen bond scission in the active center and with attack at the exocyclic oxygen atom in the subsequent monomer molecule. Thus, the tertiary oxonium ions are the exclusive active species from the very beginning of the polymerization. Acylium cations (CH₃CO^⊕ SbF₆^? or CH₃CH₂CO^⊕SbF₆^?) as initiators attack both exo-and endocyclic oxygen atoms in the monomers and the initiation proceeds with almost equal proportions of alkyl-oxygen and acyl-oxygen bond scission. Thus, in the polymerization of β-propiolactone the concentration of the acylium growing species decreases with increasing number of propagation steps and finally the tertiary oxonium ions are becoming the exclusive growing species. In the polymerization of ε-caprolactone the active acylium centers apart from propagation participate also in side reactions leading to the cleavage of a proton.     

Synthesis and characterization of dextran carboxylates for the specific chemical modification of human hemoglobin

The present study deals with the fixing of benzenehexacarboxylate (BHC) on dextran, with the aim of obtaining polyanionic polymers capable of decreasing the oxygen affinity of hemoglobin (Hb) by interacting with its phosphate binding site (allosteric site). The covalent coupling of these polymers onto oxyHb has been investigated for the synthesis of oxygen carriers with low oxygen affinity. This type of covalent conjugate could be of interest in intravascular use. Several steps were necessary to synthesize dextran with linked BHC (DEX-BHC). In each step, the structure of the modified dextran was determined by means of gel permeation chromatography, ¹H and ¹³C NMR spectroscopy, and low-angle laser light scattering. The aim was to determine the conditions of the reaction which lead to a minimization of cross-linking phenomena. The DEX-BHC obtained (0,27 mmol BHC/g polymer) decreased the oxygen affinity of Hb in the same way as the natural effector, 2,3-diphosphoglycerate (2,3-DPG) i.e., by reacting specifically with the amines of the protein allosteric site. This decrease in oxygen affinity was more accentuated after covalent coupling onto oxyHb, which means that the fixing point was probably localized in the 2,3-DPG binding site.     

Hexamethyldisiloxane-based nanoprobes for (1) H MRI oximetry

Quantitative in vivo oximetry has been reported using ¹⁹F MRI in conjunction with reporter molecules, such as perfluorocarbons, for tissue oxygenation (pO₂). Recently, hexamethyldisiloxane (HMDSO) has been proposed as a promising alternative reporter molecule for ¹H MRI‐based measurement of pO₂. To aid biocompatibility for potential systemic administration, we prepared various nanoemulsion formulations using a wide range of HMDSO volume fractions and HMDSO to surfactant ratios. Calibration curves (R₁ versus pO₂) for all emulsion formulations were found to be linear and similar to neat HMDSO for low surfactant concentrations (< 10% v/v). A small temperature dependence in the calibration curves was observed, similar to previous reports on neat HMDSO, and was characterized to be approximately 1 Torr/ °C under hypoxic conditions. To demonstrate application in vivo, 100 µL of this nanoemulsion was administered to healthy rat thigh muscle (Fisher 344, n = 6). Dynamic changes in mean thigh tissue pO₂ were measured using the PISTOL (proton imaging of siloxanes to map tissue oxygenation levels) technique in response to oxygen challenge. Changing the inhaled gas to oxygen for 30 min increased the mean pO₂ significantly (p < 0.001) from 39 ± 7 to 275 ± 27 Torr. When the breathing gas was switched back to air, the tissue pO₂ decreased to a mean value of 45 ± 6 Torr, not significantly different from baseline (p > 0.05), in 25 min. A first‐order exponential fit to this part of the pO₂ data (i.e. after oxygen challenge) yielded an oxygen consumption‐related kinetic parameter k = 0.21 ± 0.04 min^?1. These results demonstrate the feasibility of using HMDSO nanoemulsions as nanoprobes of pO₂ and their utility to assess oxygen dynamics in vivo, further developing quantitative ¹H MRI oximetry. Copyright © 2011 John Wiley & Sons, Ltd.     

Lowered microvascular vessel wall oxygen consumption augments tissue pO<Subscript>2</Subscript> during PgE1-induced vasodilation

Continuous infusion of intravenous prostaglandin E1 (PgE1, 2.5 μg/kg/min) was used to determine how vasodilation affects oxygen consumption of the microvascular wall and tissue pO₂ in the hamster window chamber model. While systemic measurements (mean arterial pressure and heart rate) and central blood gas measurements were not affected, PgE1 treatment caused arteriolar (64.6 ± 25.1 μm) and venular diameter (71.9 ± 29.5 μm) to rise to 1.15 ± 0.21 and 1.06 ± 0.19, respectively, relative to baseline. Arteriolar (3.2 × 10⁻² ± 4.3 × 10⁻² nl/s) and venular flow (7.8 × 10⁻³ ± 1.1 × 10⁻²/s) increased to 1.65 ± 0.93 and 1.32 ± 0.72 relative to baseline. Interstitial tissue pO₂ was increased significantly from baseline (21 ± 8 to 28 ± 7 mmHg; P < 0.001). The arteriolar vessel wall gradient, a measure of oxygen consumption by the microvascular wall decreased from 20 ± 6 to 16 ± 3 mmHg (P < 0.001). The arteriolar vessel wall gradient, a measure of oxygen consumption by the vascular wall, decreased from 20 ± 6 to 16 ± 3 mmHg (P < 0.001). This reduction reflects a 20% decrease in oxygen consumption by the vessel wall and up to 50% when cylindrical geometry is considered. The venular vessel wall gradient decreased from 12 ± 4 to 9 ± 4 mmHg (P < 0.001). Thus PgE1-mediated vasodilation has a positive microvascular effect: enhancement of tissue perfusion by increasing flow and then augmentation of tissue oxygenation by reducing oxygen consumption by the microvascular wall.     

Polymer of Controlled Chain Length Carrying Hydrophilic Galactose Moieties for Immobilization of DNA Probes

The synthesis and the “living” cationic polymerization of a new saccharidic monomer namely the 1,2 : 3,4‐di‐O‐isopropylidene‐6‐O‐(2‐vinyloxy ethyl)‐D ‐galactopyranose have been investigated. The monomer structure has been characterized by ¹H and ¹³C NMR, elemental analysis and mass spectrometry. It has been polymerized with acetaldehyde diethyl acetal/trimethylsilyl iodide as initiating system in presence of ZnCl₂ as co‐initiator. Macromolecules of controlled chain length (from 2 500 g·mol^–1 to 7 500 g·mol^–1) were obtained, bearing protected saccharidic moieties as side‐groups, and aldehyde as ω‐end‐groups which could be turned into amine ω‐end‐groups. Finally, the saccharidic residues were deprotected in order to perform the binding of DNA probes (oligonucleotides) onto the hydrophilic polymer chains through the anomeric site of the galactose moieties.     

The facilitating effect of gangliosides on the electrogenic (Na+/K+) pump and on the resistance of the membrane potential to hypoxia in neuromuscular preparation

The effects have been investigated of a mixture of gangliosides from beef brain cortex (GM₁, GD_1a, GD_1b and GT₁) either added to the bathing medium or injected intraperitoneally on muscle fibres and nerve terminals in mouse diaphragm. The electrogenic (Na⁺/K⁺) pump activity of muscle fibres enriched with sodium was increased by 38% after 2-h pretreatment with gangliosides (5×10^–8 mol ·l^–1). Muscles from animals treated with gangliosides did not show the substantial depolarization of the resting membrane potential (RMP) in K⁺-free solution (6 h) shown by control muscles. Further, treatment with gangliosides slowed the changes in muscle fibre RMP and frequency of the miniature end-plate potentials in oxygen deprived muscles.     

Urokinase Plasminogen Activator Receptor-Deficient Mice Demonstrate Reduced Hyperoxia-Induced Lung Injury

Patients with respiratory failure often require supplemental oxygen therapy and mechanical ventilation. Although both supportive measures are necessary to guarantee adequate oxygen uptake, they can also cause or worsen lung inflammation and injury. Hyperoxia-induced lung injury is characterized by neutrophil infiltration into the lungs. The urokinase plasminogen activator receptor (uPAR) has been deemed important for leukocyte trafficking. To determine the expression and function of neutrophil uPAR during hyperoxia-induced lung injury, uPAR expression was determined on pulmonary neutrophils of mice exposed to hyperoxia. Hyperoxia exposure (O₂>80%) for 4 days elicited a pulmonary inflammatory response as reflected by a profound rise in the number of neutrophils that were recovered from bronchoalveolar lavage fluid and lung cell suspensions, as well as increased bronchoalveolar keratinocyte-derived chemokine, interleukin-6, total protein, and alkaline phosphatase levels. In addition, hyperoxia induced the migration of uPAR-positive granulocytes into lungs from wild-type mice compared with healthy control mice (exposed to room air). uPAR deficiency was associated with diminished neutrophil influx into both lung tissues and bronchoalveolar spaces, which was accompanied by a strong reduction in lung injury. Furthermore, in uPAR^−/− mice, activation of coagulation was diminished. These data suggest that uPAR plays a detrimental role in hyperoxia-induced lung injury and that uPAR deficiency is associated with diminished neutrophil influx into both lung tissues and bronchoalveolar spaces, accompanied by decreased pulmonary injury.Patients with acute lung injury or the acute respiratory distress syndrome commonly receive supportive care consisting of low tidal volume protective ventilation and the administration of high concentrations of inspired oxygen.^1,2 Prolonged exposure to high oxygen concentrations, however, can worsen or induce lung damage in already injured or previously healthy lungs.³ The mechanisms underlying hyperoxia-induced lung injury are beginning to be understood, despite difficulties in distinguishing the effects of exposure to hyperoxia from those of the inciting disease for which oxygen therapy was started. Insight into factors involved in hyperoxia-induced lung injury could help identify possible new targets for improving the management of patients who require supplemental oxygen.The inflammatory response to hyperoxia is dominated by neutrophils and likely mediated by the generation of reactive oxygen species.^1,3 The recruitment of neutrophils to the lungs on exposure to hyperoxia has been linked to the local production of CXC chemokines and the expression of CXCR2, the predominant neutrophil receptor for CXC chemokines in rodents.^4,5,6 In addition, increased expression of adhesion molecules on the pulmonary endothelial cell surface has been found to contribute to neutrophil trafficking into the bronchoalveolar compartment during hyperoxia.⁷ We and others recently identified a pivotal role for the urokinase plasminogen activator receptor (uPAR, CD87) in neutrophil migration to the lungs during bacterial pneumonia.^8,9 uPAR is a glycosylphosphatidylinositol-linked receptor expressed by a variety of cell types, including hemopoietic cells, endothelial cells and many different neoplastic cells, that has been implicated as an important player in leukocyte trafficking.^10,11 At present it is unknown whether uPAR is involved in hyperoxia-induced neutrophil migration and lung injury. Therefore, in the present study we sought to investigate the expression and function of neutrophil uPAR during hyperoxia-induced lung inflammation.     

Pulsed laser deposition of hydroxyapatite thin films on Ti–6Al–4V: Effect of heat treatment on structure and properties

Hydroxyapatite (HA) is an attractive biomaterial that has been widely used as a coating for dental and orthopedic metal implants. In this work, HA coatings were deposited on Ti–6Al–4V substrates by laser ablation of HA targets with a KrF excimer laser. Deposition was performed at ambient temperature under different working pressures that varied from 10^?4 to 10^?1 torr of oxygen. The as-deposited films were amorphous. They were annealed at 290–310 °C in ambient air in order to restore the crystalline structure of HA. The coatings morphology, composition and structure were investigated by scanning electron microscopy, atomic force microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction techniques. Mechanical and adhesive properties were examined using nanoindentation and scratch tests, respectively. The stability of the HA coatings was tested under simulated physiological conditions. This study reveals that the combination of pulsed laser deposition and post-deposition annealing at 300 °C have the potential to produce pure, adherent, crystalline HA coatings, which show no dissolution in a simulated body fluid.     

Aqueous polymerization of methacrylamide initiated by the redox system K2S2O8/ascorbic acid

The polymerization of methacrylamide initiated by the redox system K₂S₂O₈/ascorbic acid has been studied at 35 ± 0,2°C under the influence of atmospheric oxygen. The molecular oxygen autocatalyses the polymerization rate. The rate of polymerization is independent of the activator (ascorbic acid) concentration within the range 2,83 · 10^?3 to 11,3 · 10^?3 mol · l^?1, this does not hold below or above the given concentration range. The rate varies linearly at low monomer concentration (up to 17,76 · 10^?2 mol · l^?1). The catalyst exponent decreases from nearly unity (0,94) to 0,57 with increasing concentration of the catalyst probably due to participation of primary radicals in the termination of growing chain. The initial rate is not changed by the addition of a strong acid (H₂SO₄) within the range 15 · 10^?5 to 30 · 10^?5 mol · l^?1. With the activator (ascorbic acid) alone, an optimum is observed within the pH range 2,9–3,5. The initial rate and the limiting conversion increases with increasing polymerization temperature. The overall energy of activation as calculated from the ARRHENIUS plot has been found to be 16,0 kcal.mol^?1 within the temperature range 30–45°C. Organic solvents (water miscible only) and small amounts of neutral salts, (KCl, Na₂SO₄) depress the initial rate and the maximum conversion. The addition of small amounts of catalysts like Cu^2⊕, Mn^2⊕, Ag^oplus; increases the initial rate but no appreciable increase in the limiting conversion is observed.     

Fluorinated methacrylamide chitosan hydrogel systems as adaptable oxygen carriers for wound healing

In this study a series of novel, biocompatible hydrogels able to repeatedly takeup and deliver oxygen at beneficial levels have been developed by conjugating various perfluorocarbon (PFC) chains to methacrylamide chitosan via Schiff base nucleophilic substitution, followed by photopolymerization to form hydrogels. The synthesized fluorinated methacrylamide chitosan (MACF) hydrogels were confirmed by high resolution ¹⁹F NMR. Synthesized MACF hydrogels were tested for their ability to takeup and then release oxygen for future use in dermal wound healing. Depending on the PFC substitution type maximum O₂ uptake was observed within 2–6 h, followed by complete release to the surrounding environment (5% CO₂) within 12–120 h at oxygen partial pressures of 1–25 mm Hg h^?1, providing outstanding system tuning for wound healing and regenerative medicine. MACFs with the most fluorines per substitution showed the greatest uptake and release of oxygen. Interestingly, adding PFC chains with a fluorinated aromatic group considerably enhanced oxygen uptake and extended release compared with a linear PFC chain with the same number of fluorine molecules. MACF hydrogels proved to be readily reloaded with oxygen once release was complete, and regeneration could be performed as long as the hydrogel was intact. Fibroblasts were cultured on MACFs and assays confirmed that materials containing more fluorines per substitution supported the most cells with the greatest metabolic activity. This result was true, even without oxygenation, suggesting PFC-facilitated oxygen diffusion from the culture medium. Finally, MACF gradient hydrogels were created, demonstrating that these materials can control oxygen levels on a spatial scale of millimeters and greatly enhance cellular proliferative and metabolic responses.     

Phosphate and cyclic AMP excretion decreases during less than 12 hours of hypoxia in conscious rats

Hypocapnia is known to have an antiphosphaturic effect that overcomes the phosphaturic effect of hypoxia. The objective of this study was to examine whether conscious rats exposed to acute hypoxia show a decrease in phosphate excretion due to the concomitant hypocapnia. Wistar rats weighing 200 g were exposed to hypoxia (inspired oxygen fraction=0.10) or normoxia (inspired oxygen fraction=0.21) for 6 h; and rats were alternately exposed to hypoxia or normoxia every 12 h for a total 36 h. Renal clearance and hormone studies were performed. Rats exposed to 6 h of hypoxia (n = 11) showed significant hypophosphaturia and decreases in absolute and fractional excretion of phosphate (0.38±0.10 μg min^-1, mean ±SE, P<0.0001 and 0.59±0.15%, P<0.0001) as compared with normoxic rats (n = 11, 3.91±0.68 μg min-¹ and 5.62±0.85%). In addition, nephrogenous adenosine 3′,5′-cyclic monophosphate level per glomerular filtrate was significantly decreased (-0.87±0.64 nmol dL GF^-1, P<0.05) and plasma parathyroid hormone level was unchanged (45.2±9.5 pg mL-¹) after 6 h of hypoxia as compared with normoxic rats (4.03±1.83 nmol dL GF-¹ and 54.3±10.4 pg mL-¹). A parallel increase in urinary noradrenaline and a decrease in dopamine excretion was observed in rats after 6 h of hypoxia. The decreased phosphate and adenosine 3′,5′-cyclic monophosphate excretion during acute hypoxia were restored to normoxic levels by reoxygenation with 21% oxygen in the study of 12-h intermittent hypoxia. In summary, (1) hypoxia produced by inhalation of 10% oxygen for 12 h or less causes reduced phosphate and adenosine 3′,5′-cyclic monophosphate (cAMP) excretion by spontaneously breathing rats; (2) these effects are reversed by reoxygenation and (3) hypoxia elicits a parallel increase in noradrenaline excretion and a decrease in dopamine excretion. These data suggest that renal adrenergic and dopaminergic systems play important roles in hypophosphaturia during acute hypoxia in conscious rats.     

Spatial variation of aortic wall oxygen diffusion coefficient from transient polarographic measurements

Polarographic current transients following a voltage step (turn-on transient) were measured with bare cathodes (25 μm diameter) and shallowly recessed oxygen microelectrodes (<5μm diameter). Except for the initial part of the current transient, the experimental measurements were in excellent agreement with simple models in the literature, which predict an inverse relationship with . Turn-on transients were measured in aqueous solutions with known physical properties, and in aortic wall tissue from three different species (n=6 rabbits, n=3 dogs, and n=1 miniature pig). Oxygen diffusion coefficients (D) were determinedin vitro by comparing time constants measured by the same microelectrode in saline and in strips of aortic wall tissue at 37°C. On the inner side (endothelium and intima) of the aorta, D averaged (±S.E.) 7.0 (±0.8)×10⁻⁶ cm²/s in 6 rabbits, 6.4 (±1.0)×10⁻⁶ cm²/s in 3 dogs, and was 4.6×10⁻⁶ cm²/s in the pig. On the adventitial side, D was 9.5×10⁻⁶ cm²/s in 1 rabbit, 11.4 (±1.2)×10⁻⁶ cm²/s in 3 dogs, and 8.1×10⁻⁶ cm²/s in the pig. For every aortic strip on which D was measured from both sides, D for the inner wall was always lower, overall by a little more than one third (p<0.001). The lower D on the endothelial side may limit oxygen transport to the vascular wall and play a role in atherogenesis.     

Nutritional status and physical fitness of elderly sportsmen

The nutritional status of elderly sportsmen has not been reported on, neither has the nutritional balance nor the precise relationship between nutritional status and physical fitness been detailed for this population. Thus, group of 18 sportsmen [age 63 (SD 4.5) years] was monitored by weighing their food during a 6-day period. Macro nutrient, mineral and vitamin content was derived from tables. Daily energy expenditure (DEE) and sport activity (DSA) were quantified over a 7-day period using a questionnaire. Physical fitness was assessed by maximal oxygen uptake (V˙O_2max) measurements. The DEE was 11 429 (SD 1890) kJ · day⁻¹. The DSA corresponded to 38% of DEE and V˙O_2max to 35.9 (SD 6.1) ml · min⁻¹ · kg⁻¹. When compared with French recommended dietary allowances (RDA) intakes were higher for energy (+24%), macro nutrients, and most minerals and vitamins. Despite high energy intakes, some subjects had mineral and vitamin deficits. Energy intakes were significantly related to intakes of magnesium, phosphorus, iron, vitamins B2, B6, C and to V˙O_2max, but not to age. Stepwise regressions indicated that vitamin C intake was the only determinant to have a relationship with V˙O_2max. Thus, most elderly sportsmen had higher nutritional status than RDA, although some had mineral and vitamin deficits. It is therefore suggested that elderly sportsmen should be encouraged to consume food with higher mineral and vitamin contents. Accepted: 17 June 1997     

Hypoxemia During Hemodialysis

Decrease in arterial oxygen tension has been reported during hemodialysis.^1-3 The etiology of the hypoxemia has not been clearly demonstrated. Intravascular leukostasis,¹ pulmonary arterial microembolization,³ and loss of CO₂ through the dialyzer are some of the explanations given for this abnormality.^2,4 Why a small percentage of hemodialysis patients develop profound, symptomatic hypoxemia has not been satisfactorily explained.     

Effects of hyaluronic acid on macrophage phagocytosis and active oxygen release

The effects of hyaluronic acid (HA) on macrophage function, in terms of the phagocytosis of latex beads and superoxide anion and hydrogen peroxide release stimulated by phorbol myristate acetate (PMA), were studied in guinea-pig peritoneal macrophages. Phagocytosis was inhibited in a dose- and molecularweight-dependent manner by HA. The addition of PMA to the culture, at a dose of more than 10 ng ml^?1, caused an increase in the release of active oxygens. The release of active oxygens was inhibited by high molecular weight HA (MW 2.02×10⁶, HA-202) in a dose-dependent manner. In cell-free systems, HA-20-2 had a negligible effect in scavenging these active oxygens. Of the three molecular sizes of HA (MW: 0.28×10⁶, 0.98×10⁶ and 2.02×10⁶), HA-202 most strongly inhibited the active oxygen release. These results indicate that high-molecular-weight HA acts directly on macrophages to inhibit phagocytosis and active oxygen formation, which, in turn, ameliorates the progression of chronic inflammation.     

Zur stabilität der komplexen anionen bei der kationischen polymerisation

The counterions appearing in the mechanism of the cationic polymerization are able to decay according to and so give rise to termination reactions. For the model systems (C₆H₅)₃C^⊕MtX^?_n+1(Mt = B, Al, Sn, P, As, Sb, In, Ti, Fe; X = F, Cl, Br) the decay has been investigated by spectroscopic and conductometric methods. The overall decay rate constant k_z is hardly influenced by traces of water (c_H2O<10^?3mol.l^?1) and by structure variations of the cation. On the other hand, k_z increases by decreasing the concentration of the salt. When the structure is varied k_z increases with decreasing donor strength of the ligands X; the sensitivity of the anion to changes in the ligand sphere increases corresponding to the ionization potential of the central atom Mt. Addition of tetracyanoethylene raises the stability of the anions. The results can be explained by the HSAB principle and fit well in a scheme of stabilization of anions by acceptors.     

Physiological studies on trematodes — Fasciola gigantica rate of oxygen consumption

Summary 1. The Q _O ² of adult F. gigantica has been compared with F. hepatica.2. The oxygen consumption of the experimental parasite has been found to be very low.3. There is a marked difference in Q _O ² values of the whole and minced parasite.