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The kinetics of protein-fluorescence change when rabbit skeletal myosin subfragment 1 is mixed with ATP or adenosine 5′-(3-thiotriphosphate) in the presence of Mg2+ are incompatible with a simple bimolecular association process. A substrate-induced conformation change with ΔG0<-24kJ·mol-1 (i.e. ΔG0 could be more negative) at pH8 and 21°C is proposed as the additional step in the binding of ATP. The postulated binding mechanism is M+ATP⇌M·ATP⇌M*·ATP, where the association constant for the first step, K1, is 4.5×103m-1 at I 0.14m and the rate of isomerization is 400s-1. In the presence of Mg2+, ADP binds in a similar fashion to ATP, the rate of the conformation change also being 400s-1, but with ΔG0 for that process being -14kJ·mol-1. The effect of increasing ionic strength is to decrease K1, the kinetics of the conformation change being essentially unaltered. Alternative schemes involving a two-step binding process for ATP to subfragment 1 are possible. These are not excluded by the experimental results, although they are perhaps less likely because they imply uncharacteristically slow bimolecular association rate constants.

Liquid paraffin-in-water emulsions stabilized by cationic (cetrimide) or non-ionic (cetomacrogol) surfactants and cetostearyl alcohol were examined at 25° in oscillatory mode, using the Weissenberg Rheogoniometer with parallel plates coupled to a digital transfer function analyser. Ternary systems, formed by dispersing the mixed emulsifiers in water, were similarly investigated. Each preparation was tested in the linear viscoelastic region, and fundamental rheological parameters, the storage modulus (G') and the real viscosity (ẽ') were derived as functions of frequency over the range 7.91 times 10−4to 25 Hz. All ternary systems behaved similarly with respect to frequency. As this increased, G' rose and ẽ' fell. These trends were related to the viscoelastic nature of the systems. Both mixed emulsifiers exhibited self-bodying mechanisms, so that emulsion consistency increased as the mixed emulsifier concentration rose. This was shown by increases in G' and ẽ' at each frequency. The shapes of the plots and other rheological properties were related to viscoelastic gel networks formed in the emulsion continuous phases. The ternary system parameters implied that emulsion networks were similar to ternary gels, that is, they formed by the interaction of long chain alcohol and aqueous surfactant solution. The oscillatory data were compared and correlated with creep data derived for similar ionic and non-ionic dispersed systems, previously described.

A Weissenberg Rheogoniometer with parallel plates coupled to a Solartron Digital Transfer Function Analyser was used at 25° in oscillatory mode to investigate liquid paraffin-in-water emulsions stabilized by alkyltrimethylammonium bromides (of C12-C18chain lengths) and cetostearyl alcohol. Ternary systems, formed by dispersing the quaternary surfactants and cetostearyl alcohol in water, were similarly examined. Each preparation was tested in the linear viscoelastic region and fundamental rheological parameters, the storage modulus (G') and the dynamic viscosity (η′), were derived as functions of frequency over the range 7.91 × 10−4to 25 Hz. The rheological properties of the emulsions were related to viscoelastic gel networks present in the continuous phases. The corresponding ternary system parameters implied that these networks were formed by the interaction of cetostearyl alcohol and aqueous surfactant solution. Ternary systems and emulsions behaved similarly with respect to frequency. As this increased, G' rose and η′ fell, the latter through several logarithmic decades. At low frequencies, G' and η′ rose as the quaternary alkyl chain length increased. Formulations containing quaternary surfactants of medium chain lengths (C14and C16) formed strong viscoelastic networks. The C12systems contained tenuous networks, and networks formed from the C18surfactant were not as rigid as predicted by the trend of the lower homologues. The oscillatory data were compared and correlated with creep data described previously.

Liquid paraffin-in-water emulsions stabilized by mixed emulsifiers of a surfactant (cetrimide or cetomacrogol) and a long-chain alcohol were used as model systems to represent pharmaceutical semisolids. They were examined in their linear viscoelastic regions using creep and oscillatory (Weissenberg rheogoniometer) techniques. Storage and loss compliances (J′and J″)over the frequency range 2.5 × 10−8to 1.5 × 10−1Hz. were calculated from creep data using numerical formulas. The transformed compliances were used to derive the other oscillatory functions, the storage and loss moduli (G′and G″), the storage and loss viscosities (η′and η″), and the loss tangent (tan a) at the same frequencies. The agreement between transformed functions and those obtained directly from oscillatory measurements at frequencies ranging from 7.91 × 10−4to 1.5 × 10−1Hz. was generally good. Discrepancies at the extremities of this range were a result of the practical difficulties involved when creep measurements are made at very short times (representing high frequencies) and evaporation of water from the parallel plates of the rheogoniometer during low frequency dynamic experiments. Neither small strain technique alone covered the entire frequency or time range necessary for an exhaustive study of semisolids. Creep data were unavoidably inaccurate at high frequencies, and the limitations of the rheogoniometer gear box prevented oscillatory measurements from being made at extremely low frequencies. The unification of data from oscillatory and creep measurements so as to provide a dynamic description over an extended frequency range (10−8–25 Hz.) is discussed. The variations of each function with frequency are considered with reference to linear viscoelastic theory; the limiting values and the shapes of the plots at low frequencies agreed well with the theoretical values for viscoelastic liquids. It was concluded that such interconversion techniques are applicable and valuable for interpreting the rheological behavior of a pharmaceutical system.

Transient kinetic studies of Mg2+-dependent heavy-meromyosin ATPase (adenosine triphosphatase) were done by monitoring the release of both ADP and Pi into the reaction medium by using linked assay systems. The release of Pi was monitored by its quantitative transfer to ADP, with concomitant reduction of NAD+in the presence of d-glyceraldehyde 3-phosphate, d-glyceraldehyde 3-phosphate dehydrogenase and phosphoglycerate kinase. The dissociation rates of the products, ADP and Pi, from heavy meromyosin were shown to be faster than the rate-controlling process, which occurs after the initial bond cleavage of ATP. The chromophoric ATP analogue, 6-mercapto-9-β-d-ribofuranosylpurine 5′-triphosphate (thioATP) was used as a substrate and spectral changes associated with a single turnover of heavy meromyosin could be assigned to elementary processes of the mechanism. It was shown that the dissociation rate of thioADP was not the rate-controlling process of the thioATPase, whose catalytic-centre activity was 7.6 times that of the ATPase at pH8. The dissociation rate of ADP from heavy meromyosin was measured by using thioATP as displacing agent and was found to be 2.3s-1, which is about 50 times the catalytic-centre activity of the ATPase at pH8. Transient kinetic studies with chromophoric adenosine phosphate analogues have general application for kinases and ATPases both in characterizing the chemical states of the intermediates and in delineating the elementary processes of the enzyme mechanism.

A staining sequence for the simultaneous demonstration of thyrotrophs, gonadotrophs, and acidophils in the anterior hypophysis is described. It consists of permanganate oxidation, aldehyde-thionin, luxol fast blue, periodate oxidation and leuco fuchsin. By this technique rat and dog pituitaries fixed in mercuric chloride-formalin show blue-black thyrotrophs, red gonadotrophs, green acidophils and unstained or faintly stained chromophobes.

A mixture containing thionin, 0.5 gm; paraldehyde, 7.5 ml; concentrated HCl, 1 ml; and 70% ethanol, 91.5 ml, when allowed to ripen for several days, produces a stain which, when applied to sections of tissue fixed in a Zenker-based fixative, resembles in its effects the aldehyde-fuchsin stain of Gomori, but presents certain advantages.

1. Acid extracts of muscle-fibre preparations from human biopsies incubated with [U-14C]glucose were chromatographically analysed. 2. Radioactivity of fructose was significantly greater in muscle from childhood dystrophy patients and also in female carriers of the disease compared with normal, foetal, neurogenic muscle disease and polymyositis control groups. 3. Measurements of the activity of polyol-NADP oxidoreductase (EC 1.1.1.21) and L-iditol-NAD oxidoreductase (EC 1.1.1.14) in muscle extracts compared with the ability of extracts to dephosphorylate fructose 6-phosphate, indicated that the probable route of fructose formation from glucose is via glucitol. The mean activities of the two specified enzymes in dystrophic muscle showed 13- and 3–5-fold increases respectively compared with normal muscle, and smaller increases compared with other controls. 4. Direct comparison of labelling patterns following incubation of muscle-fibre preparations with d-[U-14C]glucose, d-[U-14C]fructose and d-[U-14C]glucitol showed that these three substances are rapidly interconvertible mutual major metabolic products, confirming the glucitol pathway as a major route of fructose formation. 5. [U-14C]fructose is readily metabolized by dystrophic muscle, excluding the possibility of its accumulation being the result of poor utilization. 6. Inhibition of polyol oxidoreductase in dystrophic muscle preparations by 3,3'-tetramethyleneglutarate drastically reduces the ability of the fibres to utilize [U-14C]-glucose, and prevents the formation of [14C]fructose. 7. Some implications of these results are discussed in relation to the pathogenesis of childhood muscular dystrophy.

THE antitumour properties of certain inorganic platinum compounds in mice were first reported by Rosenberg et al.1. Of thirty-four compounds tested the cis-platinum (ii) diamminodichloride and the cis-platinum (iv) diamminotetrachloride had the highest activity, producing marked regression of large solid sarcoma 180 tumours in 63–100% of mice.

It is found that the drain current of m.o.s.t. devices depends exponentially on gate voltage over a wide range of current when the surface of the device is depleted. An explanation of this effect is given. The results show that low-current measurements of this type for a variety of substrate bias conditions can provide information on the density of midgap states and the amount of impurity segregation in practical structures.

In the investigation of certain types of conformational equilibria, the ultrasonic absorption technique can be used to supplement information derived from more conventional spectroscopic techniques, and thereby lead to a more detailed analysis of molecular configuration.Nuclear magnetic resonance, infrared spectra, and ultrasonic absorption measurements indicate that both 4-methyl trimethylene sulfite and 4-methyl trimethylene sulfate exist as equilibrium mixtures of two chair isomers. In each case one isomer is strongly predominant.

INTERFERON inducers seem to be the most practical way of making use of interferons in clinical practice. Helenine1obtained from a fungus Penicillium funiculosum is a powerful interferon inducer and Lampson et al.2found that the activity was present in a fraction consisting of double stranded RNA. Other double stranded RNA inducers have been discovered, for example, that from Escherichia coli infected with RNA bacteria virus MS2 (ref. 3) and also certain copolymers of synthetic polyribonucleotides.

PATIENTS with the carcinoid syndrome typically show high blood levels of 5-hydroxytryptamine and increased urinary excretion of 5-hydroxyindolyl-3-acetic acid. Variants of the tumour have, however, been described in which the major secretion is 5-hydroxytryptophan1.

Measurements have been performed on the source-leakage currents associated with short-channel m.o.s.t. devices. Both space-charge-limited and non-space-charge-limited punchthrough currents have been observed as a function of gate and drain voltages, and physical mechanisms describing these currents are briefly discussed.

THE association between brain monoamines and nerve terminals has been interpreted as evidence of a neuro-transmitter function. It has been shown that serotonin (5-hydroxytryptamine, 5HT) is localized in fine neurones which project to the forebrain. and whose cell bodies lie in the raphé nuclei of the midbrain1,2. The transmitter hypothesis has been further substantiated by the finding that stimulation of these nuclei increases forebrain levels of 5-hydroxyindol-3-ylacetic acid (5HIAA), the metabolite of 5HT3, and increases the release of 5HT from brain into cortical cups4. Using the rate of formation of 5-hydroxy-indoles after tryptophan administration in vivo as an index of the rate of hydroxylation of tryptophan5, the limiting step in the synthesis of 5HT, stimulation has been shown not only to increase release of 5HT but also to accelerate the rate of production of the amine (unpublished observations of D. Eccleston, M. Randic and A. Padjen). This could arise from immediate electrical effects on membrane permeability with changes in transport of substrate to existing enzyme. We have examined whether the increased rate of amine production continues after stimulation has ceased, which would suggest that the stimulation caused enzyme induction.

AFTER an injection of 14C-5-hydroxytryptophan, autoradiographic grains were found to accumulate in the sympathetic neurones of the pineal gland and vas deferens1. These observations suggested that the sympathetic nerves of these organs might take up or retain 5-hydroxytryptamine. Subsequent work has shown that 5-hydroxytryptamine can accumulate in the guinea-pig vas deferens in vitro by an active transport process2. Subcellular distribution studies also indicated that the site of accumulation of the 5-hydroxytryptamine is the storage vesicle present in the sympathetic neurone2. Certain drugs such as imipramine3and cocaine4are potent inhibitors of the uptake of noradrenaline into sympathetic neurones, and these drugs also block the uptake of 5-hydroxytryptamine in platelets5and some tissues in the rat6. Subsequent work has shown that the site of blockade of noradrenaline uptake is the neuronal membrane7. These observations prompted us to investigate the ability of these drugs to block the uptake in the vas deferens of 5-hydroxytryptamine labelled with carbon-14.