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At concentrations of halothane achieved in skeletal muscle during clinical anaesthesia, NADH-dehydrogenase activity of isolated intact and sonicated beef heart mitochondria was inhibited approximately 50%. Inhibition was reversible but higher concentrations of halothane caused irreversible inactivation. Succinate oxidation was relatively unaffected. Solubilized, membrane-free preparations of NADH-dehydrogenase were insensitive to halothane. Effects of halothane on the kinetics of NADH oxidation and upon NADH-dehydrogenase activity linked to various electron acceptors suggest that the inhibitory effect occurred after halothane became bound to a component of the mitochondrial membrane, associated closely with NADH-linked flavoprotein and also with ubiquinone. Inhibitory properties of a series of halogenated compounds were related to their degree of halogenation. It is postulated that halothane reversibly inhibits oxidation of NADH-linked substrates by cardiac mitochondria, decreases mitochondrial electron transfer and consequently decreases ATP synthesis. This mechanism could explain the depressant effect of halothane on myocardial contractility.

Commercially available magnetostrictive composites employ the differential magnetostriction exhibited by materials of different composition and are therefore sensitive to temperature changes as well as to variations in magnetic field intensity. In order to overcome this problem a new approach has been adopted, using laminas of the same material which yet possess different magnetostrictive characteristics. It is shown how, by suitable choice of material, the laminas can be prepared from highly textured polycrystalline sheets so that one lamina contains a high proportion of 〈111〉 crystal directions along its length while the other contains mostly 〈100〉 crystal directions along its length. Such laminas are found to exhibit different magnetostrictive coefficients and may be bonded together to form an effective magnetostrictive composite which is inherently insensitive to temperature change.

Experimental evidence is adduced to suggest that electrodeposited iron‐nickel alloys may contain α‐phase regions in a γ‐phase matrix. This observation is taken as evidence of large variations in composition on a scale of 1000 A or less, and calculations are presented which show that it may be feasible to explain the observed uniaxial anisotropy in electrodeposited iron‐nickel alloys in terms of a magnetostrictive mechanism even though the average plating composition be that of a zerostrictive material.

Purification of tryptophan oxygenase (L-tryptophan oxidoreductase EC 1.13.1.12) from Pseudomonos acidovorans is described. When chromatographed on Sephadex G-200 or on DEAE Sephadex A-50, the enzyme was eluted in two distinct bands. Over the concentration range 10−6 – 10−4 M, cadmium stimulated the activity of the enzyme but inhibited it non-competitively at higher concentrations. A mechanism is suggested for the behaviour of the enzyme towards cadmium.

Experiments are reported which were carried out in order to study the effects of temperature cycling upon α-uranium polycrystals undergoing steady-state creep. The results of these experiments are discussed in terms of the internal stresses generated by anisotropic expansion of individual crystals in the aggregate; a theory which was developed earlier is extended to cover the case of large temperature cycles when the physical properties of uranium polycrystals vary during the cycle. An analogy between this theory and Parkes' theory of thermally-induced stresses in redundant engineering structures is pointed out, and it is shown that deformations caused by thermal transients may comprehensively be understood in terms of elastic cycling, shakedown and incremental collapse.

The results of subjecting dilute uranium alloy testspecimens to temperature cycling during steady-state creep are reported and discussed in terms of micro-structure. A previous analysis of the thermal cycling behaviour of CEGB uranium is shown to be applicable to dilute uranium-aluminium alloys consisting of a fine dispersion of intermetallic precipitates in a pure α-phase uranium matrix. Shakedown theory is inapplicable to dilute uranium-molybdenum alloys, in which two metallic phases coexist and an attempt is made to account for their behaviour in terms of a strain-energy distribution theory. This predicts that thermal cycling behaviour should be controlled by the continuous, or matrix, phase; specimens heat-treated to produce different matrix phases are shown to behave in a manner compatible with theory.

In order to characterize further the minialbumins (molecular weight 5,000 to 20,000) found in cadmium-poisoned men and animals, the tryptophan content of albumins found in the serum and urine of cadmium-poisoned monkeys was measured by two methods and compared with that of serum albumin (molecular weight 66,000) of normal animals. Normal serum albumin of the monkey was found to contain 2 residues of trytophan per molecule of the protein, whereas all albumins in the poisoned monkeys, whether of normal size or low-molecular weight, contained less tryptophan, this amino acid being absent entirely in the minialbumins of both serum and urine. Serum albumin of the usual molecular weight (66,000) in the cadmium-poisoned monkeys contained approximately 30% less tryptophan than its normal counterpart in untreated animals. Taken in conjunction with previous observations on the behaviour of minialbumins, which aggregate readily in low-salt media including isotonic saline, it is concluded that approximately 30% of the circulating serum albumin in the poisoned monkeys arose by aggregation of minialbumin molecules. On the basis of the close similarity in amino acid composition, in nearly all other respects, between the various albumins, it is suggested that minialbumin comprises a mixture of peptides derived by fission of the normal albumin molecule along its whole chain length, and that subsequently a peptide containing both tryptophan residues is either deleted metabolically or excluded in the preparation procedures.

One important contributory factor in producing anaemia in lead poisoning in human subjects is undoubtedly the inhibition of the biosynthesis of haem in erythroid bone marrow cells (Eriksen, 1955). To what extent a haemolytic action of lead participates has been the subject of much experi mental study. McFadzean and Davis (1949) demonstrated more abundant stippled cells in the bone marrow of lead poisoned guinea-pigs than in the peripheral circula tion, such cells being rapidly and preferentially taken up by the spleen. The interpretation of the data was that punctate basophilic erythrocytes were abnormal both in haemoglobin content and physical structure as a consequence of damage by lead before the corpuscles were released from the haemopoietic site. The peripheral action of lead has not been evaluated with certainty. Aub, Fairhall, Minot, and Reznikoff (1926) made extensive studies in vitro, mainly on washed red blood cells in phosphate-free Ringer solutions. The addition of small quantities of lead chloride caused increased mechanical fragility of the corpuscles which, however, became more resistant to hypotonie haemolysis. An in creased mechanical fragility of the circulating cor puscles through contact with plasma lead was re garded as the essential feature of the anaemia of lead poisoning. Indirect evidence which supported this view has been reported more recently, namely, raised urobilinogen excretion in lead-poisoned guinea-pigs (Baikie, 1954) and coproporphyrinuria I in severely poisoned workmen (Kench, Lane, and Varley, 1952). The data in a recent investigation (Holecek and Penickov?, 1957) are unfortunately qualitative only.

An analysis of the creep behaviour of α-uranium polycrystals at low applied stresses indicates that internal stresses of the order of 600 psi (0.42 kg/nun2) may be present in the specimens. Experiments are reported which demonstrate that the cause of the internal stress is surface oxidation; a simple model is used to predict that the compressive yield stress of a coherent oxide film is of the order of 280 000 psi (197 kg/mm2), and it is suggested that this high value may be related to elastic fracture during formation. Differences in behaviour between y-quenched, and β-quenched samples are traced to inherent differences in precipitate distribution and grain size.

The phase diagram of Cu 3 SbSe 4 indicates that this material is not a congruently melting compound, but that it forms via a peritectic reaction at about 390°C. The material grown either by a Bridgman or quenching process is p-type, with carrier concentrations of about 2 × 10 19 /cm 3 and 3 × 10 18 /cm 3 , respectively. The addition of Zn produces n-type crystals with a carrier concentration of 3 × 10 17 /cm 3 . The room temperature energy gap of Cu 3 SbSe 4 is 0.25 ± .05 eV as determined by optical absorption. Cu 3 AsSe 4 was also prepared but was not congruently melting, while Cu 3 AsTe 4 and Cu 3 SbTe 4 apparently do not form.

Results of investigations using X-ray diffraction and electron-beam microprobe techniques have shown that copper and Permalloy platings interdiffuse at low temperatures (in the range 180-230°C) when plated-wire memory elements are annealed for times as short as 50 h. Measurable interdiffusion between Permalloy platings and gold substrates does not occur in similar conditions. Both magnetic and compositional changes during aging are found to occur by a thermally activated process with activation energies around 38 kcal/mol. It is shown, however, that copper-diffusion and magnetic-dispersion changes during aging are merely concurrent processes, neither being the other's cause.

Urinary protein from five cadmium workers has been examined, two men exposed to cadmium dust and three to cadmium fume. No difference was discernible between the two groups in regard to the quantity of protein excreted (10 to 36 times the average normal) or to the chemical composition and molecular weight of the protein. Cadmium urinary protein exhibits a complex electrophoretic pattern on paper, with five components. These have mobilities similar to the five main fractions of serum. All their molecular weights, however, are in the range 20 to 30,000. Filter paper electrophoresis showed a preponderance of globulins, especially α2, over albumin. On column electrophoresis, however, a relatively higher proportion of albumin appeared, due probably to a change of mobility of a heat incoagulable protein, which constituted 20 to 25% of the whole. The heat incoagulable protein had a high content of glycine, serine, hexose, methylpentose, and sialic acid. Electrophoretic fractions 1 and 2 of the urinary protein were similarly rich in glycine, serine, hexose, methylpentose, and sialic acid, possibly due to presence of heat incoagulate protein. The presence of two components in fraction 1 became evident from ultracentrifugal studies. Plasma proteins could be demonstrated immunologically in the urine, but the relative proportion present could not be assessed. Urinary proteins associated with cadmium absorption include components of low molecular weight and high carbohydrate content similar to those which have been observed in normal urine. The distinctive feature of the proteinuria appears to be the presence of a low molecular urinary albumin, the origin of which is the subject of further study.

Results of grain-size measurements in Permalloy platings suggest that recrystallization is possible at temperatures as low as 200°C, but that it is an extremely heterogeneous process. No worthwhile correlation was found to exist between observed grain size and magnetic dispersion in samples aged in the temperature range 180 and 230°C, and it is suggested that the magnetic aging which occurs under these conditions may be due to some other diffusion-controlled process than recrystallization; a process such as chemical homogenization is tentatively preferred.

MALIGNANT hyperpyrexia is a rare but often fatal complication of inhalation anaesthesia in man1. The fluorinated hydrocarbon halothane, CF3CHBrCl, is among the many anaesthetic agents which have been implicated2. A similar syndrome has been described in a pure Landrace strain of pig3. The onset of this phenomenon is rapid (10–15 min after administration of halothane) and there is extreme rigidity of skeletal muscles, a rapid rise in body temperature to 42°–45° C, severe acidosis and a fatal outcome in spite of cooling, muscle relaxants and intravenous alkalis. Once initiated, the process seems independent of the tissue concentration of halothane, which appears to act as a trigger. A few animals have recovered after brief exposure to halothane.