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Biodiversity is essential to the viability of ecological systems. Species diversity in ecosystems is promoted by cyclic, non-hierarchical interactions among competing populations. Such non-transitive relations lead to an evolution with central features represented by the `rock-paper-scissors' game, where rock crushes scissors, scissors cut paper, and paper wraps rock. In combination with spatial dispersal of static populations, this type of competition results in the stable coexistence of all species and the long-term maintenance of biodiversity. However, population mobility is a central feature of real ecosystems: animals migrate, bacteria run and tumble. Here, we observe a critical influence of mobility on species diversity. When mobility exceeds a certain value, biodiversity is jeopardized and lost. In contrast, below this critical threshold all subpopulations coexist and an entanglement of travelling spiral waves forms in the course of temporal evolution. We establish that this phenomenon is robust, it does not depend on the details of cyclic competition or spatial environment. These findings have important implications for maintenance and evolution of ecological systems and are relevant for the formation and propagation of patterns in excitable media, such as chemical kinetics or epidemic outbreaks., Comment: Final submitted version; the printed version can be found at http://dx.doi.org/10.1038/nature06095 Supplementary movies are available at http://www.theorie.physik.uni-muenchen.de/lsfrey/images_content/movie1.AVI and http://www.theorie.physik.uni-muenchen.de/lsfrey/images_content/movie2.AVI

Colicins are narrow-spectrum antibiotics produced by and active against Escherichia coli and its close relatives. Colicin-producing strains cannot coexist with sensitive or resistant strains in a well-mixed culture, yet all three phenotypes are recovered in natural populations. Recent in vitro results conclude that strain diversity can be promoted by colicin production in a spatially structured, non-transitive interaction, as in the classic non-transitive model rock-paper-scissors (RPS). In the colicin version of the RPS model, strains that produce colicins (C) kill sensitive (S) strains, which outcompete resistant (R) strains, which outcompete C strains. Pairwise in vitro competitions between these three strains are resolved in a predictable order (C beats S, S beats R, and R beats C), but the complete system of three strains presents the opportunity for dynamic equilibrium. Here we provide conclusive evidence of an in vivo antagonistic role for colicins and show that colicins (and potentially other bacteriocins) may promote, rather than eliminate, microbial diversity in the environment.

IT has been shown by paper electrophoresis that xanthine dehydrogenase activity is bound to the globulin fractions of rat serum1. Using differential centrifugation, it was demonstrated that xanthine oxidase and xanthine dehydrogenase activities are present in the supernatant fluid corresponding to the ‘cell sap’ containing the soluble proteins of the rat liver2.

ELECTROPHORETIC fractionation of pancreatic juice components in a dog has been described in the literature1–4. Some of the authors2,3 isolated part of the fractions and studied their enzymatic activities. All authors used the free electrophoresis method with the exception of Delcourt and Delcourt4, who employed paper electrophoresis for the separation of the different fractions.

XANTHINE dehydrogenase from Drosophila melanogaster is of particular interest since mutants at two separate loci lack this enzyme1 while a mutant at a third locus produces about 25 per cent of normal activity2. In an effort to detect strains of flies with genetically altered forms of xanthine dehydrogenase we devised a technique involving paper-strip electrophoresis in which this enzyme is located after electrophoresis by spraying the strip with the enzyme's substrates, incubating it at 25° C, and then using paper chromatography to separate the fluorescent product from the substrate which also fluoresces. This technique is very simple, and has potential application to other enzymes. Paper electrophoresis of xanthine dehydrogenase in rat serum has previously been reported using the technique of elution and direct assay3,4.

WE have already described a fortuitous combination of events which led to the discovery that American newspapers and other paper products contain a potent analogue of the juvenile hormone of the European bug, Pyrrhocoris apterus L. (Heteroptera ; Pyrrhocoridae)1. When reared in contact with ‘active paper’ or when exposed to surfaces impregnated with extracts of the ‘paper factor’ (PF), fifth-stage Pyrrhocoris larvae undergo one or more supernumerary larval moults and finally die without completing metamorphosis or attaining sexual maturity. This same result is observed when 1 µg of partially purified PF is topically applied to young fifth instar larvae1,2.

During investigations on the synthesis of nucleotides in this laboratory, extensive use has been made of the paper chromatography of phosphorus-containing compounds. In the early experiments it was observed that in a descending pyridine – ethyl acetate – water system, disodium hydrogen phosphate gave two clear spots of approximately equal intensity with RF 0.17 and 0.55 on spraying with molybdate reagent1. Identical spots were obtained with sodium or potassium mono- or di-hydrogen phosphates, whereas ammonium phosphate and free orthophosphoric acid gave only the faster-running spot. Trisodium phosphate showed largely the slower spot with some trailing. (These RF values are quoted to give an indication of the positions of the spots. The temperature was not strictly controlled.) Other experiments showed the effect was not due to complexes with pyridine as the same double-spot phenomenon occurred in a butanol – water system. By buffering the phosphates with acid and alkali, it was found that the number of spots depended on the pH of the solution in which the phosphate was applied to the paper. Potassium dihydrogen phosphate below pH 3 gave only the faster running spot; between pH 3 and pH 9, both spots at RF 0.17 and 0.55 were in evidence, but by pH 10 (caustic soda added) only the slower spot appeared. Above pH 12 only a spot at RF 0.05 was obtained with a horseshoe appearance (compare Paterson and Reincke2).

THE quantitative determination of paper chromatographic spots is usually carried out by using a variety of photometric techniques. In many instances, however, the known methods lack specificity, reliability and sensitivity.

THE electrophoretic analysis by the ordinary Tiselius apparatus of the soluble proteins isolated from rat liver has already been described1–3; but the constituent components reported by these authors differed one from the other.

Biochemical Differences between Inbred and Outbred lines of Drosophila melanogaster studied by Paper Partition Chromatography

High-resolution genetic markers have revolutionized our understanding of vertebrate mating systems1, but have so far yielded few comparable surprises about kinship in social insects. Here we use microsatellite markers to reveal an unexpected and unique social system in what is probably the best-studied social wasp, Polistes dominulus. Social insect colonies are nearly always composed of close relatives2,3; therefore, non-reproductive helping behaviour can be favoured by kin selection, because the helpers aid reproductives who share their genes4. In P. dominulus, however, 35% of foundress nestmates are unrelated and gain no such advantage. The P. dominulus system is unlike all other cases of unrelated social insects, because one individual has nearly complete reproductive dominance over subordinates who could have chosen other reproductive options. The only significant advantage that subordinates obtain is a chance at later reproduction, particularly if the queen dies. Thus, P. dominulus societies are functionally unlike other social insects, but similar to certain vertebrate societies5,6, in which the unrelated helpers gain through inheritance of a territory or a mate.

An unpublished paper has recently come to light, which shows that even at an early age, Alfred Russel Wallace was bold enough to approach the scientific establishment with his ideas.

Mixing dried human sewage sludge with pulverized coal is being evaluated as a way to reduce carbon dioxide emissions from traditionally coal-fired power plants, as well as to overcome sewage-disposal problems. Here we investigate the effects of inhaling particles emitted from the combustion of this mixture and find that these cause significantly more lung damage in mice than do particles from coal alone, probably because of their zinc content. Our findings indicate that the use of dried municipal sewage sludge as a 'green' (CO2-neutral) replacement fuel should be considered with caution.

The costs — both in animal lives and euros — of the European REACH legislation on chemical testing are escalating. Thomas Hartung and Costanza Rovida argue for a suspension of certain toxicity tests.

PAPER electrophoresis became a suitable technique for embryological purposes when Kohn1 proposed the use of pure cellulose acetate as a supporting medium instead of filter paper. This method enables us to separate much smaller amounts of protein than hitherto : one single amphibian embryo yields enough protein to give a clear electrophoretic pattern.

IT has been reported previously1 that the short-day plant, Maryland Mammoth tobacco, will flower under long day-lengths (14½–15½ hr.) if exposed to varying dosages of γ-rays. Recently, we have been investigating the effect of γ-radiation on the endogenous level of the indole compounds occurring naturally in leaf, stem, root and apical tissues of γ-irradiated and normal Maryland Mammoth tobacco. Large quantities of these tissues (300–1,000 gm.) have been extracted with absolute ethanol, employing a technique for extraction and paper chromatography as described previously2. Microlitre quantities of the extracts, after acidification and extraction with ethyl ether, were spotted on Whatman No. 1 filter paper and chromatographed in seventeen different solvents. Colours were developed with p-dimethylaminobenzaldehyde. 3-Indoleacetic acid was not detected in any of more than thirty-five individual extractions of leaf, stem, root or apical tissues of normal or γ-irradiated Maryland Mammoth tobacco. However, an unidentified indole compound was found in the leaf and apical extracts with R F values as shown in Table 1.

THE antigenic properties of insulin are now well recognized, but no simple method has yet been described for the routine detection and assay of insulin antibodies. The method described here is based on the classical observation by Berson, Yalow, Bauman, Rothschild and Newerly1. They showed that during chromato-electrophoresis on filter paper, 131I-labelled insulin bound by insulin antibodies in human serum moves with the β-γ-globulins, while free insulin remains fixed at the point of application of the serum-insulin mixture on the filter paper. When an excess of unlabelled insulin mixed with a trace of labelled hormone is added to the anti-insulin serum, the excess insulin is adsorbed from solution by cellulose and the amount bound by the antibodies is measured in the supernatant solution. We have used this assay system for serum obtained from guinea-pigs treated with bovine insulin2 and capable of neutralizing insulin at rates ranging from 0.1 to 3.5 units per ml. serum. It can, however, be adapted for the detection and assay of antibody concentrations lower than this; it has not yet been used for anti-insulin sera of other animals or of man.

Detection by paper electrophoresis. Using starch gel electrophoresis, six cattle1, fourteen sheep2, three goat (see later) and three human3,4 β-globulin phenotypes have been recognized and indicated to be under the genetic control of three, five, two and three allelomorphs respectively. As one of us had noticed a variation in the number and position of the β-globulin zones in paper electrophoresis of animal sera, the two methods have been compared on sera from cattle, sheep and goats. Starch gel electrophoresis was carried out in phosphate buffer1 pH. 7.6, paper electrophoresis on a wide strip of horizontally suspended Whatman 3MM paper in barbiturate buffer pH 8.6, I 0.05. Typical examples of corresponding electropherograms of sheep and cattle sera are shown in Figs. 1 and 2. The electropherograms of goat sera shown in Fig. 3 are discussed below.

WHEN a solution of 7-hydroxypteridine1 was spotted on a sheet of Whatman No. 1 filter paper, irradiated with ultra-violet light (principally 254 mµ) for 5 min., and developed (by ascending chromatography) in various solvents, two spots appeared. One of these was identical with the starting material (unirradiated material was used as a control on the same piece of paper), and the other proved to be 5 : 6-dihydro-7-hydroxypteridine1. This reaction did not take place in aqueous solution (although 2 : 6-di-hydroxypteridine2 undergoes photochemical change in water), but it did if allyl-thiourea was present as a hydrogen donor (unirradiated controls were not reduced). 2- and 4-hydroxypteridine were found also to be photo-altered on paper; but the products have not yet been identified.

VARIOUS β-globulin types have been demonstrated, using starch-gel electrophoresis, in several species of mammals, namely, man1, cattle2, sheep3, goat4 and horse5. The present communication reports the discovery of similar variations in two species of monkey, Macaca mulatta and M. irus. Variations in the monkey β-globulins were initially detected by paper electrophoresis using barbital buffer at pH 8.6. However, the β-globulins were much better resolved when starch-gel was used instead of paper.

SOME well-known physico-chemical differences between human adult and fœtal haemoglobin prompted us to find if similar differences exist between haemoglobins from adult and new-born monkeys. The present communication describes the examination of the blood of 8 adult and 4 new-born monkeys (Macacus rhesus of North India) by the alkali resistance test and paper electrophoresis. Pregnant monkeys were obtained and were delivered in the cage to provide the new-born monkeys. Heart blood from the new-born and venous blood from the adult monkeys was collected in citrate solution. The alkali denaturation method of Singer et al. 1 was employed for determining the proportion of alkali-resistant haemoglobin. Electrophoresis was carried out in ‘Elphor’ apparatus using paper strip No. 2043 a Mg 1 at 250 V. for a period of 16 hr. in veronal buffer of pH 8.6 and ionic strength 0.05.

VITAMIN A deficiency seems to cause negative nitrogen balance in young rats1. In a preliminary report, Abdulnabi and Bieri2 indicated that in vitamin A-deficient as compared to pair-fed normal rats, the tyrosine- and phenylalanine-levels in the testes are increased and the threonine concentration of the liver shows a decrease. These results were obtained with microbiological assays, since paper chromatography failed to reveal any significant differences. We have compared the free amino-acid composition in blood, liver and kidneys of vitamin A-deficient and pair-fed normal rats by paper chromatography. Our results confirm the earlier observations of Abdulnabi and Bieri2 and show significant increase in the phenylalanine- and tyrosine-levels, and a simultaneous significant decrease in the threonine values in all the three tissues of the deficient rats.

IT has been shown by paper electrophoresis that genetically different types of β-lactoglobulin1,2 and α-lactalbumin3,4 occur in cow's milk. While genetic polymorphism of β-lactoglobulin is general among the cattle of different countries, that of α-lactalbumin has only been observed in two breeds of African zebus, the Nigerian White Fulani3 and the boran4 cattle of Kenya, but not in Icelandic, British3, Danish5 and North American6 (Holstein) cattle. Blumberg and Tombs noted the Nigerian White Fulani cattle to be similar in appearance to the ‘Brahmin’ cattle of the East, which were probably brought into Africa by the nomadic Fulani people, and suggested that α-lactalbumin-A might serve as a marker by which the affinities of the zebu cattle, and indirectly of the Fulani people associated with them, could be traced. We have now examined the α-lactalbumin and β-lactoglobulin polymorphism in Indian zebu cattle with the view of getting further information on this aspect. Moreover, from a comparison of electrophoretic patterns of non-casein proteins of African zebu3 and Indian buffalo milk7, the mobilities of zebu α-lactalbumin-A and of the single buffalo α-lactalbumin appeared to be approximately the same. This indicated that these two proteins might have closely similar physico-chemical properties as has been observed7–9 in the case of cow β-lactoglobulin-B and the single buffalo β-lactoglobulin.

INCREASING attention has been given recently to mercury pollution, especially in rivers and lakes, and to the movement of the element in aquatic food chains (reviewed in ref. 1). Most information has been obtained for situations where the environmental concentrations have been increased through local use of fungicides containing mercury, the presence of such compounds in wastes from the wood pulp and paper industries or the discharge of other industrial wastes.

Unmethylated reovirus and VSV mRNAs are specifically methylated to form 5'-terminal structures of the type, m-7-G(5')ppp(5')N by protein synthesising extracts prepared from wheat germ and mouse L cells. Reticulocyte mRNA also contains 5'-terminal m-7-G. MRNAs having 5'-terminal m-7-G stimulate protein synthesis in vitro. Removal of m-7-G by beta-elimination abolishes translation of the mRNAs.

LEUCOCIDIN is a product of Staphylococcus, consists of two proteins and is toxic to the polymorphonuclear leucocytes of rabbit and man. The study of the response of leucocytes to leucocidin has led to the unexpected finding that the changes that occur mimic those in excitable or secreting cells during membrane depolarization or stimulation by hormones1. Thus the permeability to cations but not other small molecules increases, protein in the cytoplasmic particles is secreted and calcium is accumulated in vesicles. It is probable that the primary response to leucocidin is the increased permeability to cations1. The changes in membrane structure that precede the altered cation permeability during membrane depolarization are unknown and the mode of action of leucocidin may be relevant. The study of the interaction of leucocidin with the isolated leucocyte membrane and with purified phospholipids led us to suggest that the primary action of leucocidin is to change the conformation of triphospho-inositide in the leucocyte surface membrane. This communication provides confirmatory evidence for this hypothesis.

RAT platelets contain a sulphated mucopolysaccharide1 which, when subjected to paper electrophoresis and to paper chromatography, showed a mobility similar to chondroitin sulphate-A but unlike that of heparin1,2. The acid mucopolysaccharide (AMPS) content of human serum increased during the early phase of the blood clotting process3; thrombocytes were suggested as a possible source of this additional serum mucopolysaccharide. When thrombin was added in vitro to a suspension of 35S-labelled pig platelets, up to 50 per cent of the radioactivity was lost from the platelets during clumping4. Electrophoretic identification of this released material has been attempted in the present investigation.

HUMAN serum contains a thyroxine-binding protein which moves to a position between the α1 and α2 globulins on paper electrophoresis in a barbiturate buffer1. We have investigated the thyroxine-binding power of maternal and fœtal serum taken from pregnant rabbits at different stages of pregnancy. L-Thyroxine, labelled with iodine-131 and having a specific activity of 5 µc./µgm., was added to samples of the serum to give a concentration of about 0.05 µc./ml. of serum. Half to one hour later, 0.02 ml. of the serum was put on to a strip of Whatman No. 3 MM filter paper and electrophoresis carried out as described elsewhere2, using a barbiturate buffer at pH. 8.6 and ionic strength 0.1. After the current had been passed for 18 hr. the papers were dried and the position of the radioactivity determined by means of a continuously recording scanner. The bands of protein on the paper were then stained with lissamine green.

2-14C-Pteroyl-L-monoglutamic acid (0.5 mc. per millimole, 1 mgm.) was incorporated into banana food medium (100 gm.), and adult flies of Drosophila melanogaster (Oregon, wild-type) were allowed to feed and lay eggs on this medium. Larvae (six days old) were removed from this medium, transferred to moist filter paper and allowed to pupate. Pupae (100; 86 mgm.; not less than 48 hr., not more than 56 hr. pupation) were crushed with sand and 0.5 N aqueous ammonia solution (0.5 ml.) and heated on a steambath (10 min.). Solids were centrifuged off and supernatant liquid spotted on Whatman 3 MM paper. The solids were washed again with 0.5 N aqueous ammonia solution (0.4 ml.), centrifuged off and supernatant liquid added to the first spot. The paper area was cut out and radioactivity measured by immersion in a solution of 0.3 per cent diphenyloxazole in toluene (2 ml.) and counting with a ‘Panax’ scintillation counter (background, 1.096 counts/sec; background + sample, 1.357 counts/sec; sample, 0.26 count/sec; standard error, ± 0.035 count/sec). The radioactive area of the paper was chromatographed on 3 MM paper with propanol/5 per cent aqueous acetic acid (2 : 1 vol. by vol.) as developing solvent. To improve spot resolution, the paper was developed three times. On viewing in 365-mµ light, a bright purple fluorescent area was seen. This was cut out and chromatographed on 3 MM paper with butanol/acetic acid/water (4 : 1 : 5 vol. by vol.) (triple development). After air-drying, the paper was viewed in 365 mµ light and the fluorescent spots of isoxanthopterin (purple) and 2-amino-4-hydroxy-pteridine-6-carboxylic acid (bright blue) cut out. The acid spot was measured for radioactivity (background, 0.65 count/sec; background + sample, 1.10 counts/ sec; sample, 0.45 count/sec; standard error, 0.033 count/sec). The isoxanthopterin spot was further purified by chromatography on 3 MM paper with tert.-butanol/pyridine/water (50 : 15 : 35 vol. by vol.). The isoxanthopterin spot was measured for radioactivity (background, 0.65 count/sec; background + sample, 0.76 count/sec; sample, 0.11 count/sec.: standard error, 0.030 count/sec).

WE have previously suggested that immunologically reactive fragments of angiotensin II may arise in blood during the metabolism of the octapeptide by angiotensinases and that such an occurrence could compromise the measurement of blood angiotensin II by radioimmunoassay1. This proposal regarding the presence of angiotensin II fragments in blood has now been investigated by paper chromatography of ethanolic blood extracts and radio-immunoassay of eluates from serial sections along the chromatograms to detect immunoreactive angiotensin II fragments. The octapeptide angiotensin II was the predominant peptide detected in arterial blood samples from six human subjects and nine sheep, being 85 and 96 per cent of the total immunoreactivity respectively. In contrast to this finding in arterial blood, angiotensin II was a minor component in the chromatographic pattern of extracts of venous blood from six human subjects, comprising only 28 per cent of the total immunoreactivity. The major immunoreactive component present in venous blood possessed the mobility of the (3–8) hexapeptide of angiotensin II. These results indicate that radioimmunoassay of angiotensin II in ethanolic arterial blood extracts gives values which are close to the amount of the octapeptide actually present. The same radioimmunossay may, however, substantially over-estimate the true level of the octapeptide present in venous blood because of interference by the immunoreactive metabolites of angiotensin. The arterio-venous difference of the chromatographically isolated angiotensin II measured by the radioimmunoassay is consistent with bioassay observations that approximately two-thirds of the circulating angiotensin II is extracted and metabolized across tissue vascular beds. Measurement of the total immunoreactive angiotensin content of venous blood by radioimmunoassay of angiotensin II shows moderately good correlation with the arterial level of the octapeptide, and is probably adequate for clinical studies. Radioimmunoassay of blood angiotensin II during physiological studies on the role of angiotensin II in vascular and hormonal regulation should, however, be performed on arterial blood samples in order to obtain a true estimate of the concentration at which the octapeptide is presented to its target tissues.

THE technique of ‘fingerprinting’ developed by Ingram1 has proved to be of great value in the molecular analysis of haemoglobins. In principle, it is a combined paper electrophoresis and chromatography of the peptides released by enzymatic digestion, of haemoglobin. This enables the location of a probably occurring difference to a particular peptide. The method has proved its importance especially in the detection of amino-acid differences in normal and abnormal haemoglobins. This communication describes a modified system for fingerprinting haemoglobins.

THE amino-acid composition of bovine growth hormone has been determined1 by Levy's method2. This procedure, which involves paper chromatography of dinitrophenyl derivatives of amino-acids, is subject to certain limitations such as variable recoveries of tyrosine and lack of resolution of the leucine derivatives. The development of automated ion-exchange chromatography of amino-acids3 has prompted a re-investigation of the amino-acid composition of this protein.

IN connexion with metabolic disorders occurring in cows, such as parturient paresis and acetonaemia, an investigation concerning the keto-acids occurring in blood serum and urine was started. Several authors have carried out work in this field concerning man. Keto-acids are converted into 2,4-dinitrophenyl-hydrazones, after which they are separated by means of paper chromatography. The 2,4-dinitrophenyl hydrazones are reduced by hydrogen to amino-acids and identified as such. In this way Cavallini et al. 1, El Hawary and Thompson2, Markees3, Biserte and Dassonville4 and De Schepper et al. 5 showed that the following α-keto-acids occur in human blood: α-ketoglutaric acid, pyruvic acid, α-ketoisocaproic acid, α-ketoisovaleric acid and α-keto-β-methylvaleric acid. Moreover, it was shown that pyruvic acid predominates in human blood and α-ketoglutaric acid in human urine4.

SPERM cells of Paracentrotus lividus and Sphaerechinus granularis contain a quinone which shows the same chemical and physical properties as ubiquinone from the bovine heart. The method used for the extraction and purification of this invertebrate ubiquinone is quite similar to that used for the mammalian compound1. However, the presence in the extracts of a number of coloured substances, which have typical absorption spectra and which can undergo reversible oxidation-reduction, excluded the use of some common solvents, made column chromatography purification more difficult and restricted the use of the paper chromatography method and of the colorimetric test to the very purified material, that is, to its crystalline form only. It was impossible, therefore, to make any calculation of degree of purification during preparation and of the yield of the substance and of its original quantity. After several attempts the method was standardized as follows.

PREVIOUS investigators1 have shown the presence of glycogenic activity, presumably of adrenal steroidal origin, in the plasma of the salmon (Salmo salar). An appreciable part of the activity could be accounted for by steroids reacting as 17-hydroxycorticoids by the Nelson–Samuels analytical method2. Since this technique measures a variety of materials having a dihydroxyacetone side-chain on the 17 carbon, the specificity of the determination is questionable in species of which the pattern of adrenal steroid secretion has not been established. Moreover, although cortisol (which is measured by the Nelson–Samuels method) is the chief steroid in the plasma of some mammals, in others the chief steroid, corticosterone, is not detectable by this method. This is especially important because Hatey found the concentration of glycogen-depositing activity to be much higher than could be accounted for by the 17-hydroxycorticosteroids1. The nature of the steroid responsible for a large part of the biological activity of salmon plasma remains uncertain. An attempt has therefore been made to determine the nature of the circulating steroids in fish blood by application of paper chromatography.

WE have examined the incorporation of radiocarbon from [14C] glucose, [2-14C] acetate and [1 : 4-14C2] succinate into the soluble metabolic intermediates of bull semen. Samples (50 µl.) of the semen, used within 6 h of collection, were mixed with 50 µl. of a solution containing 0.1 mM adenosine triphosphate, 2 mM magnesium sulphate, 10 mM potassium chloride and 1µc. of the labelled substrate dissolved in 0.1 M potassium phosphate buffer, pH. 7.4. The mixtures were incubated aerobically at 37° C for 30 min. At the end of the incubation period the enzyme systems were inactivated by the addition of 400 µl. of boiling ethanol and the mixtures centrifuged at 500g. The radioactive substances present in the supernatants were separated by two-dimensional paper chromatography, visualized by autoradiography and the carbon-14 measured by the techniques described by Smith and Moses1.

IT has been previously reported that incubation of egg lecithin with human plasma produces on the guinea-pig ileum a slow contraction which is, in many respects, indistinguishable from the slow contraction produced by the original plasma1. The slow contracting substance, which is formed in the plasma on incubation with lecithin, can be extracted with alcohol, can be adsorbed on kaolin, and can be precipitated by calcium. It is interesting to note that the amount of egg lecithin which doubles the slow muscle-contracting effect of dialysed plasma is about 250 mg per cent of the plasma, a concentration which roughly corresponds to the concentration of the naturally occurring choline-containing phospholipids in human plasma. This observation suggested an attempt to separate the lipid-soluble slow muscle-contracting substances from human plasma and from the lecithin-plasma incubate which contains 0.25 per cent egg lecithin.

IN an earlier communication1, a technique was described for obtaining consistent separations of the cytoplasmic proteins of rat liver using electrophoresis on filter paper. A notable improvement in resolution has been observed following the treatment of the protein mixtures with n-butanol. The use of this reagent was suggested by the experiments of Morton2 on the extraction of various enzymes from the particulate fractions of the cell structure.

IT is now known that α-casein from cow milk, which appears electrophoretically homogeneous under many different conditions, consists of at least two compounds which have been designated α- and k-casein1. α-Casein from goat milk, which has similar properties to that from cow milk2 and the same phosphorus content3, showed signs of inhomogeneity during electrophoresis by the moving-boundary method2. Using zone electrophoresis on filter paper it has now been found that the α-component of freshly prepared goat casein does consist of at least two electrophoretically distinct fractions which, until further characterization, will be called α1- and α2-casein in order of decreasing electrophoretic mobility.

Irvine1 and Hoffer and Mahon2 reported on the occurrence of a compound giving a characteristic mauve colour with Ehrlich's reagent on paper. The significance of this metabolite is that it occurs with greater frequency in psychotic individuals. This finding has been confirmed by several investigators3–5. Ellman et al.6, however, reported that a metabolite apparently identical to the one in question may be derived from phenothiazines and occurs in the urine of patients on phenothiazine therapy. Recently, Irvine7 has identified the mauve factor as 2,4-dimethyl-3-ethylpyrrole on the basis of chromatographic and mass spectral studies. This report is concerned with the identity of the mauve factor, a critique of various isolation procedures used by different investigators and its pharmacological action on the central nervous system (CNS). The possible CNS effect is important because several laboratories have postulated a metabolic product in the schizophrenic which may be stimulant and hallucinogenic.

PAPER chromatography has been used for obtaining a qualitative picture of the distribution of carnosine and ‘carnosinase’ in the albino rat.

CONTACT insecticides are often formulated as solutions in oil and presented as deposits sprayed on to surfaces. The spread of oil on to insects walking over superficial films is an essential process in the action of such a deposit, though the quantities of oil involved are extremely small. Using a radioactive tracer technique, measurements have been made of the rate of uptake of oil by active flies of the species Phormia terraenovae R–D from deposits of 3 (µl./cm.2 of a refined mineral oil (‘Risella 17’) on Whatman No. 1 filter paper. Traces of a radioiodine preparation (131I) di-iodo-octadecane were added to the oil and the specific activity adjusted to 2 mc./ml. of oil. The flies were exposed to the oiled substrate by the method of Lewis and Hughes1. After exposure the insects were washed three times in ether to remove the superficial oil from the cuticle, and the tissues later extracted with ether followed by 10 per cent sodium hydroxide.