Band 29, Heft 9-10

The synthesis of the protected peptide Boc-His-Cys (M Bzl)-Val-Ala-Thr-Ala-N 2 H 3 (OH) is de­ scribed. This peptide is a fragment of an active center sequence of the streptococcal proteinase (EC 3.4.22.10) containing the essential SH-group of the enzyme

The synthesis of the protected peptides Boc-Val-Ala-Thr-Ala-Thr-Ala-Gln-Ile-OH and Thr-Ala-Gln-Ile-Met-Lys(Z)-NH 2 is described. These sequences are fragments of an active center peptide of the streptococcal proteinase (EC 3.4.22.10)

Acyl CoA derivatives of a number of cinnamic and benzoic acids have been synthesised via the appropriate acyl phenyl thiol esters. The reaction has potential application in the preparation of acyl CoA derivatives of radiolabelled aromatic carboxylic acids. UV absorption spectra have been determined for the CoA thiol esters following their purification by gel permeation chromato­ graphy. By comparison of the extinction in the the hydroxamate assay of Lipman and Tuttle, extinction coefficients for the series

The 13 C-Nuclear Magnetic Resonance spectra of xanthine, 1,3-dimethyl-xanthine (theophylline), 3,7-dimethyl xanthine (theobromine) and 1,3,7-trimethylxanthine (caffeine) were obtained and the lines assigned. Protonation-and N-Methylation parameters are derived by comparison of the 13C-chemical shifts of the protonated cations with those of the neutral molecules and also with those of the xanthine cation. The shifts are discussed in terms of variations in the shielding at the different C-atoms induced by N-methylation and protonation. Approximate correlations are found between the 13 C-chemical shifts and the π-electron densities at the C-atoms

New methods for the synthesis of the aminomethyldipyrrolylmethane and the aminomethyl-tripyrrane, which are resulting from formal head to tail condensation of porphobilinogen are de­ scribed. Porphobilinogen was used as base material in these procedures. The aminomethyl group of porphobilinogen reacts as an alkylating agent with several amines as well as with porpho-bilinogen-lactam. The condensation of porphobilinogen with its lactam gave the dipyrrolylmethane-lactam, which afforded after hydrolysis the desired aminomethyldipyrrolylmethane. The conden­ sation of the latter with porphobilinogen-lactam gave the lactam of the aminomethyltripyrrane, which was then hydrolysed to the free aminomethyltripyrrane

A study of the association of serotonine with 5'-AMP by PM R spectroscopy is described. The association constants obtained from the chemical shift of non-equivalent protons show considerable variation outside experimental error, a fact which wT as reported by several authors. To support the suppositon that small amounts of complexes of different stoichiometry, — which in general can hardly be detected — , are responsible for this phenomenon, computer simulation of various hypo­ thetical systems were investigated. The results clearly demonstrate that the neglect of minor fractions of complexes of different stoichiometries lead to significant variation in the association constants calculated for different protons, provided that these protons experience different magnetic enviro-ments in the different complexes.

The ultraviolet absorption spectra of uracil and its 5-halogenated derivatives have been in ­ vestigated in regard to the electron attracting properties of the substituents. It could be shown that the position of the two absorption bands is proportional to the inverse of the electronegativity; the extinction coefficients are a linear function of the electron affinities. In this way, the red shift obtained upon substitution with halogens can be explained. Also, the decrease in absorbance of the absorption bands at λ > 250 nm, occuring concomitant­ ly, is understandable. The increase in absorbance with increasing electron affinity, as observed in the case of the absorption bands at λ < 250 nm, might question the assumption that this band is due to a higher pi -pi* excitation

At millimolar concentrations of ATP the ATPase activity of regulated actomyosin (which consisted of myosin and of actin containing the regulatory proteins tropomyosin and troponin) was lower than that of unregulated actomyosin (containing actin devoid of the regulatory proteins) when the ionic strength was high (> 0 .0 3 ᴍ KCl). At low ionic strength (0.03 ᴍ KCl) the ATPase activity of regulated actomyosin was similar to or even higher than that of unregulated acto­ myosin. Besides increasing ionic strength an increasing actin-myosin ratio tended to depress the ATPase activity of regulated actomyosin below that of unregulated one. At lower ATP concen­ trations (0.1 mᴍ or lower) the ATPase activity of regulated actomyosin was higher than that of unregulated actomyosin at any ionic strength and at any actin-myosin ratio. EGTA inhibited the ATPase of regulated actomyosin under any conditions at high ATP concentrations. At lower ATP concentrations EGTA inhibited either at higher ionic strength or at a higher actin-myosin ratio. The inhibition of the ATPase activity of acto-HMM by increasing ionic strength was not in­ fluenced by the regulatory proteins. - For the interpretation of these results it has been assumed that in actomyosin regulated actin can adopt three states: A low-affinity state which activates the ATPase of myosin only slightly (occurring at high ATP concentrations and in the absence of Ca 2+ ), a high affinity state which activates the ATPase of myosin better than does unregulated actin (occurring at low concentrations of ATP and in the presence of Ca 2+ ), and an intermediate state. This latter state (occurring at high concentrations of ATP and in the presence of Ca 2+ or at low concentrations of ATP and in the absence of Ca 2+ ) activates the ATPase of myosin less than does unregulated actin when the actin-myosin ratio is high (wide spacing of myosin on the actin filaments) but activates more (or at least not less) when the actin-myosin ratio is low (dense spacing of myosin on the actin filaments)

The surface pressure was measured as a function of area/molecule for chlorophyll a (Chl) and cytochrome c (Cyt) at a heptane-water interface. At a surface pressure of 6 dyn/cm the area per molecule of Chl(A 6 ) = 113 ± 6 Å 2 , for reduced Cyt c (red. Cyt) the A 6 = 5000 ± 300 Å 2 and for oxidized Cyt c (ox. Cyt) A 6 = 4100 ± 250 Å 2 . Cyt appears to denature at the interface. Irradiation results in a decrease of the A 6 for Chl to A 6 = 100 ± 5 Å 2 . There appears to be interaction between Chi and red. Cyt in a mixed film no interaction is observed between Chi and ox. Cyt

The role of lipid exchange in the curvature elasticity of bilayers is studied theoretically. Blocking of exchange between the monolayers may give rise to a nonequilibrium lipid distribution going hand in hand with a spontaneous curvature. Some possible consequences for vesicular deformations are discussed. Lipid nonequilibrium is tentatively suggest as one possible cause for certain shape transformations of red blood cells

From X-ray photographs informations are derived in the region between small angle and wide angle scattering about the quaiternary structure of the biopolymere collagen. A splitting of the equatorial and meridional reflections implies a unit cell with lattice parameters α = 38.2 Å and b - 34.9 Å tilted around the b-axis by 3.5°. However, there exists no crystallographic lattice, but the single protofibrils build up this lattice only as a statistical average. Thisu causes a slight dis­ placement of the reflections of the third order against their ideal positions. Introducing moreover paracrystallinie distortions a comparison of the Fraunhofer-pattern of this model with the experi­ mental results shows a good agreement

A biospecific adsorbent for the separation of different nucleic acids was prepared by covalent attachment of a chromophore analog of actinomycin C 1 (D) to Sepharose 4 B. The immobilized chromophor-derivative was obtained by condensation of 2-nitro-3-hydroxy-4-methylbenzoic acid with N 6 -(6-aminohexyl)-Sepharose 4 B, reduction of the nitro group and oxidative coupling with 2-amino-3-hydroxy-4-methylbenzoyl-β-(N,N-diethylamino) -ethylamide. Since the chromophore of actinomycin has a high affinity to DNA. DNA/RNA-mixtures were separated by retardation of DNA on this resin

Leaf-extract of Rhus salicifolia is shown to contain, besides myricetin, quercetin and kaempferol, the rare myricetinmethylethers syringetin and europetin and the quercetin-methylethers ombuin and rhamnetin. The structures are proved by spectral analysis (UV, MS, NMR) and by cochromato­ graphy with authentic substances

The study of the triterpenoids and their related substances of Euphorbia paralias resulted in isolation of ursolic acid, cycloartenol, 24-methylenecycloartenol, uvaol, a hydrocarbon fraction (n-C 29 n-C 35 ), alcohol fraction (hexacosanol and octacosanol) and a sterol fraction (β-sitosterol, stigmasterol, campesterol and cholesterol)

The effect of a prolonged darkness (48 h) with a following re-illumination on the prenyllipid metabolism of chloroplasts is tested in green Hordeum seedlings. Continuous darkness induces thylakoid and prenyllipid breakdown and changes the remaining lipoquinone and carotenoid metabolism of chloroplasts to that of etioplasts. Re-illumination, in turn, reverses the effects of darkness and regenerates the photosynthetic apparatus within 24 hours by a continuous and spe­cific synthesis of certain thylakoid prenyllipids. 1. The level of chlorophylls, vitamin K 1 and that of the oxidized benzoquinone forms, plasto-quinone-9 and α-tocoquinone, decreases continuously in darkness. All these prenyllipids are re­ synthesized upon re-illumination, whereby a faster destruction rate in the dark (α-tocoquinone + plastoquinone-9 > vitamin K 1 > chlorophylls) corresponds to a faster re-accumulation rate in the light. 2. The concentration of the reduced benzoquinones plastohvdroquinone-9 and α-tocopherol. which are preferentially deposited in the osmiophilic plastoglobuli, increases until 24 hours of dark­ness and decreases thereafter either continuously (plastohydroquinone-9) or exhibits another strong increase (α-tocopherol). Re-illumination results only in the accumulation of the oxidized quinone forms (mainly plastoquinone-9 and little α-tocoquinone) ; the level of plastohydroquinone remains, however, almost constant with a concomitant and steady decrease in the concentration of α-tocopherol. Darkness changes the main metabolite flow in benzoquinone synthesis via the formation of α-tocopherol (a trimethyl-, phythyl-(1,4-benzoquinone derivative) and light (re-illumination) via the production of plastoquinone-9 (a trimethyl, solanesyl-1.4-benzoquinone). 3. Carotenoids are enriched throughout the dark phase (mainly xanthophylls, little β-carotene) with a higher accumulation rate than after re-illumination, which yields again a higher portion of β-carotene. The correlation of prenyl chain synthesis (phytyl chain for chlorophylls and vitamin K 1 , solanesyl chain for plastoquinone-9) in the light with a reduced rate of carotenoid formation is discussed with respect to prenyl biosynthesis. 4. It is concluded that breakdown and re-synthesis of thylakoids and their prenyllipds, which are described here in a prolonged dark phase with following re-illumination, also occur during natural day-night growth of plants. The turnover of the thylakoid membranes and their lipids does, however, not get visible, since the decomposition in the night is recompensated by new synthesis during day. From the destruction rate one can calculate in a first approximation the biological half life time (τ 1 / 2 ) which gives values in the range of 7 to 2,5 days for all thylakoid prenyllipids

Flower chromoplasts of Narcissus pseudonarcissus have been isolated in high purity and inte­ grity by a new procedure. From these chromoplasts circular DNA molecules in supercoiled form have been isolated and demonstrated by electron microscopy to have a contour length of about 44 μm (molecular weight about 92 x 10 6 daltons)

Various mono-and diazaphenanthrenes were prepared and assayed for their activity as inhibi­tors of photosynthetic electron flow in isolated chloroplasts in order to get more insight into the mechanism of action of the well known inhibitor o-phenanthroline = 1,10-diazaphenanthrene. The results show that 1-, 4-and 5-azaphenanthrene are only slightly less active than 1,10-diazaphen-anthrene. In the case of the different diazaphenanthrenes, 1,4-, 1,7-and 5,6-diazaphenanthrene exhibited somewhat lower activity than 1,10-diaphenanthrene, whereas 2,9-and 4,7-diazaphen-anthrene were completely inactive. Substitution at C-atoms of 1,10-diazaphenanthrene leads to an increase in activity in the case of the 4-and 7-position, regardless of electropositive or electro­ negative substituents, whereas substitution at the 2-, 3-, 5-, 6-, 8-and 9-position leads to a de­ creased activity. The ability of 1,10-diazaphenanthrene to form iron complexes seems to be of little relevance to the inhibitory activity on photosynthetic electron transport. This follows also from the fact that other strong iron complexing agens, like 2.2'-bipyridine or 8-hydroxyquinoline, are not inhibitory

The influence of different concentrations of PbCl 2 on the activity of several enzymes of the chlorophyll biosynthesis in isolated spinach chloroplasts was analyzed. The succinyl-CoA-synthetase was weakly inhibited; a concentration of 2 mᴍ PbCl 2 reduced the enzyme activity for 30% only. The concentration of δ-aminoevulinic acid (ALA) after incubation of the chloroplast homogenate with the substrates for the succinyl-CoA-synthetase + ALA-synthetase (cf. Fig. 9) was increased by lower concentrations of PbCl 2 (0 - 50 μm) and decreased by higher (>50 μm). This can be explained by a correspondent influence of PbCl 2 on the activity of ALA-synthetase or (more probably) by a relative stronger inhibitory effect of PbCl 2 on the ALA-metabolizing than on ALA-producing enzymes. δ-Aminoevulinic acid dehydratase is strongly inhibited at low concentrations of PbCl 2 , as it is in animals. The same is true for porphobilinogenase

Photosynthetic oxygen reduction by isolated chloroplast lamellar systems has been studied with the aid of superoxide dismutase. Two mechanisms of oxygen reduction by illuminated chloroplast lamellar systems can be differentiated: 1. In the presence of low potential electron acceptors like AQ or MV the superoxide free radical ion is the product of autooxidation of the reduced acceptor. Addition of superoxide dismutase has no influence on the initial rates of oxygen reduction. 2. Stimulation of photosynthetic oxygen reduction by o-diphenols is only observed in the absence of superoxide dismutase and ascorbate; apparently the superoxide free radical ions is involved in both initiation and propagation of a chain reaction. If the ferredoxin-stimulated photosynthetic oxygen reduction is measured, both ascorbate and superoxide dismutase are active as inhibitors. By heating suspensions of chloroplast lamellar systems, a substance is released into the supernatant which exhibits the activity of an oxygen reducing factor (ORF) with properties similar to o-diphenols: The stimulation of photosynthetic oxygen reduction is reversed by addition of either SDM or ascorbate. A reaction sequence for photosynthetic oxygen reduction in the presence of ferredoxin is considered, which is initiated by the superoxide free radical ion produced by autooxidation of reduced ferredoxin; the superoxide free radical ion "activates" an endogenous oxygen reducing factor, which in this "active" state can reduce oxygen to O 2 · - . The presence of either superoxide dismutase or ascorbate yields in chain termination by scavenging the superoxide free radical ion

Ferredoxin-stimulated photosynthetic oxygen reduction and concommitant decarboxylation of glyoxylate by chloroplast lamellar systems is inhibited by ascorbate but ferredoxin dependent NADP + -reduction is not. In the presence of low potential electron acceptors (AQ or MV) this influence of ascorbate on glyoxylate decarboxylation by chloroplast lamellar systems is no longer observed. Using the diaphorase activity of NADP-ferredoxin reductase either bound to the chloroplast lamellar system or as an isolated enzyme fraction glyoxylate decarboxylation in the dark can be observed in the presence of NADPH + H + and autooxidizable electron acceptors (AQ, MY, fer­ redoxin). The influence of ascorbate on this dark reaction, depends on whether the activity of the isolated or the lamellae-bound enzyme is measured: 1. With the isolated enzyme no influence of ascorbate on AQ-, MV-or ferredoxin-stimulated glyoxylate decarboxylation is observed. 2. The dark-reaction with NADPH + H + as electron donor, catalyzed by the bound enzyme however is inhibited by ascorbate both in the presence of either ferredoxin or AQ. This and other observations support the view that the site of inhibition by ascorbate of oxygen reduction by chloroplast lamellar systems in the presence of ferredoxin is not identical with either the reducing side of photosystem I, ferredoxin or NADP-ferredoxin reductase. The site of inhibition by ascor­ bate is more likely connected with an additional pathway involved in photosynthetic oxygen re­ duction by chloroplast lamellar systems, which is located at the reducing side of photosystem I, i. e. in the vicinity of the NADP-ferredoxin reductase. By heat treatment of isolated chloroplast lamellar systems a factor is released showing the activity of an ascorbate-sensitive oxygen reductant upon illumination in the presence of chloroplast lamellar systems. A model for photosynthetic oxygen reduction is proposed which includes ferredoxin and a membrane-bound oxygen reductant in series. Oxygen reduction by this pathway is only operating when the available NADP is fully reduced

If Agrobacterium tumefaciens is treated with 8-methoxypsoralen (8-MP) and irradiated with long wave UV the subsequent growth of the bacteria is stopped whereas respiration continues for at least 7 hours. Treatment with 8-MP or UV alone has no effect. Also the wound healing processes in Kalanchoe leaves are inhibited by simultaneous applications of 8-MP and UV. Tumor induction on Kalanchoe leaves is reduced by simultaneous treatment with 8-MP and UV of a. the inducing bacteria before infection; b. the wounded leaves before infec­ tion : c. the infected leaves at least up to 24 hours after infection. These results are discussed in relation to a participation of bacterial or host DNA in the infec­ tion process

In isolated bovine rod outer segments metarhodopsin I -II absorption-changes are measured using rapid flash-photometry. The rapid H + -uptake accompanying this transition is measured using phthaleine pH-indicators. 1. The meta I -II equilibrium is pH-dependent in the same manner as the proton uptake (Figs 1 ,1 4). This can be explained by the assumption that the meta II conformation is stabilized by the protonization of an amino-group, which in its protonized state cannot be re-enfolded into the hydrophobic core of the molecule, since it is too polar (Fig. 15). In the proposed model the con­ formation-regulating proton binding group is not in the chromophoric region of rhodopsin. This resolves the well known contradiction between the expected bathochromic and observed hypso-chromic shift of meta II H + . The model furthermore involves that the dissociation-constant of the protonized group differs from the measured apparent pK = 6.3. 2. The meta I -II transition is H + (and OH - )-catalysed (Figs 4, 5). The kinetics show usually a characteristic deviation from a first-order process (Fig. 2). This can be explained by some in­ homogeneity of the rhodopsin-molecules e. g. some differences in the shieldings of the catalytic centers from H + (and OH - ). 3. The activation energy decreases with increasing proton-concentration (Fig. 6). The protons seem to open a new reaction pathway with a smaller activation energy. 4. Triton X 100 and ethanol increase, sodium-desoxycholate slows down the velocity of the M-I-II-transition, whereas digitonin has only a small effect (Fig. 7). 5. The relaxation-velocity of the optical pH-signal depends on the structural state of the rhodopsin-containing substrate (Figs 10. 11). The outer membrane of the outer segment and the disc-membrane are regarded as possible H + -diffusion-barriers (Fig. 12), because the time lag between M II -signal and pH-signal is nearly eliminated, when the membranes are destroyed by digitonin. 6. In some experiments, using successive non-saturating flashes, an initial H + -uptake of 2 - 3 H + /M II was observed (Fig. 17). After full-bleaching, however, the ΣH + /ΣM II -ratio is one. The hypothesis of a conformative coupling of 2 - 3 rhodopsin-molecules is presented (Fig. 18). The possible existence of an "unfolded" state of rhodopsin is discussed on the basis of a photo-regeneration-experiment, in which no H + -release was observed (Figs 19, 20)

The numbers of light quanta available to photoreceptors of lens-and different types of com­ pound eyes are calculated on the basis of photometric considerations. It is shown that the results depend upon the situation in the optical environment: For point-like lightsources such as stars receptors in compound eyes generally receive considerably less numbers of light quanta compared n. g. with the human eye. This is due to the small sizes of the ommatidial facets. For extended optical surroundings, however, the numbers of quanta reaching the receptors in typical insect compound eyes of the apposition type are comparable to those in the human eye. In this respect the optical superposition eye of nocturnal insects like E ph estia is an exceptional case, where there is an improvement in the numbers of quanta reaching the receptors by a factor 100 to 1000 com­ pared to the eyes of bee or man

Rat liver chromatin was titrated by poly-ᴅ-lysine of mol.wt. 140,000. Approximately 32% of the phosphate groups of the chromatin were found to react with the polycation. By submitting the chromatin-poly-ᴅ-lysine complex to pronase and DNase I digestion and by further submitting the obtained DNA-lysine complex to hydroxy-apatite-chromatography, "free" DNA was isolated. The mean S-value of this DNA was found to be 10 ± 0 .8 , corresponding to approximately 2100 nucleo­ tide pairs, its renaturation kinetics similar to total DNA. On the basis of these results and on the findings that histone-saturated DNA-histone recombinates are digested with DNase I up to 65% a model of chromatin structure was proposed, taking into account protein covered-and free DNA regions

Isolated rat livers were perfused with 3,4-dimethoxybenzaldehyde and 3,4-dimethoxybenzoic acid, which were 14 C-labelled in the m eta-and/or para-configurated methoxy group. Because the aldehyde group was completely oxydized to the carboxylic acid, the perfusions with 3,4-dimethoxybenzalde­ hyde and those with 3,4-dimethoxybenzoic acid exhibited principally the same results. After per­ fusion with a 1:1 mixture of (4 -O -[ 14 C]methyl)-and (3 -O -[ 14 C]methyl)-3,4-dimethoxybenzalde­ hyde, each of which had the same specific activity, thin layer chromatography of an extract of the perfusate revealed both radioactive 4-hydroxy-3-methoxybenzoic acid and radioactive 3-hydroxy-4-methoxybenzoic acid as demethylation products. The distribution of radioactivity between these two metabolites was determined as 20:1. Thus, demethylation of the 3,4-dimethoxyphenyl com­pound occurs preferentially at the para-configurated methoxy group. After perfusion with a mixture of (4-O-[ 14 C] methyl) -and (3 -O -[ 14 C] methyl) -3,4-dimethoxybenzoic acid under identical conditions the distribution of radioactivity of the named demethylation products was determined as 15:1. After perfusion with (4 -O -[ 14 C] methyl) -3,4-dimethoxybenzaldehyde or (4-O -[ 14 C] methyl)-3,4-di-methoxybenzoic acid alone, extracts of the perfusates revealed the expected radioactive 3-hydroxy-4-methoxybenzoic acid. In addition it was found, that the 4-hydroxy-3-methoxybenzoic acid pro­ duced contained small quantities of radioactivity. From these results it may be infered that an interconversion between 3-hydroxy-4-methoxy-and 4-hydroxy-3-methoxybenzoic acid has occured. The identification of the metabolites, separated by thin-layer chromatography, was performed by the reversed isotope dilution technique

1. [ 131 I] ʟ-thyroxine (T 4 ) or [ 131 I] ʟ-triiodothyronine (T 3 ) was added in 50 pᴍ - 25 nᴍ and 26 pᴍ -132 nᴍ concentrations to suspensions of rat liver mitochondria. In distribution equilibria between soluble proteins and mitochondria the adsorption of the thyroid hormones to the mito­ chondria followed an approximately linear function when the radioactive hormones were added within the range of physiological concentrations. At identical protein concentrations T 3 was ad­sorbed to the mitochondria one tenth more strongly than T 4 when neither serum proteins nor cell sap had been added. The adsorption of both T 3 and T 4 to mitochondria and soluble proteins is reversible. The distribution of the thyroid hormones between organelles and soluble proteins depends on the ratio of the protein concentration in the sedimented mitochondria to the protein concentration in the supernate after centrifugation. The desorption of T 3 and T 4 from the mito­ chondria by soluble proteins, however, represents no linear function. 2. The distribution equilibria of simultaneously added 131 I -T 4 and 125 I -T 3 can be shifted by certain drugs. Chlorpromazin and dinitrophenol displaced the thyroid hormones from their binding to soluble proteins onto the mitochondria. Vice versa, phenylbutazone, phenytoin, brom-sulfalein and silymarin displaced the hormones from the mitochondria more strongly than from soluble proteins. Sodium oleate displaced the hormones in both directions. Minor shifting effects or none at all could be detected when several other drugs were used. The described procedure apparently yields new information on some effects of drug action

The growth inhibition of human lymphoblastoid cells by human interferon preparations (HIF) and a mock-interferon preparation (Mock-IF) was studied. HIF was induced in suspensions of primary human leukocytes by Newcastle Disease Virus. Mock-IF was prepared from uninduced cell suspension of a comparable batch. The highest degree of inhibition of cell propagation was ob­ tained on the EBV producer line P3HR1, the inhibition of the cell lines Raji and SKL 1 was significantly lower, no effect was observed on the cell line RPMI 1788 originating from a healthy donor. Mock-IF also caused a growth inhibition but to a lower degree as HIF. HIF and Mock-IF are similar in the following properties: 1. Stability at pH 2 at 4 °C for four days, 2. sensitivity to tryptic digestion, and 3. molecular weights in the range between 5,000 and 40,000 daltons

Total protein synthesis in mouse cells but not in confluent chick embryo fibroblasts (CEF) is inhibited shortly after infection with vaccinia virus. This inhibition by the infecting virus is enhanced drastically if the mouse cells have been pretreated with homologous interferon pre­parations. The enhanced reduction of protein synthesis also occurs if the cells are treated with actinomycin D and is therefore to a large extent caused by an enhanced inhibition of amino acid incorporation into host cell proteins. Enhanced inhibition of total protein synthesis during the early stages of infection may be a prerequisite for the complete degeneration of the cells (lysis) which occurs later. Various alterations of mouse cells and chick embryo fibroblasts due to exposure to homologous interferon preparations are discussed with respect to the antiviral state induced in these cells

The irradiation at 365 nm in the presence of the skin-photosensitizing furocoumarins of Graffi leukaemia cells, producers of an oncogenic RNA virus, determines the arrest of cell duplication and of the synthesis of the nucleic acids; the virus, on the other hand, remains equally oncogenic for newborn mice and still capable of reproduction

14 C-labeling by means of neutron irradiation of nitrogen containing heterocyclic compounds such as benzimidazoles and purines has been studied. The isolation of radiochemical pure compounds was realised by a microbiological method using P . sherm anii. This microorganism utilizes benzimida­ zoles and purines for the base moiety of vitamin B 12 ana­ logues, which were isolated and degradated. Microbiological methods seem to provide and excellent tool not only for checking specific radioactivity but also for the isolation of radiochemical pure compounds

Correlation between cross-linkages formation in native DNA and skin photosensitizing activity of furocoumarins

Sporophores of Hygrocybe species (Agaricales) contain muscaflavin, a pigment recently isolated from Amanita muscaria. Spectroscopic and chemical evidence for its dihydroazepine structure 5a is presented, indicating a close biogenetic relationship to betalamic acid 6a. The chemical nature of the water soluble pigments of Hygrocybe is dis­ cussed

A simple chromatographic procedure for the separation of betalaine pigments is described. The betalaines of Amanita muscaria, A . caesarea and A . flavoconia are compared and the composition of several musca-aurins is given

The major product of uridine gamma irradiation in aerated aqueous solution (10 -3 ᴍ, pH ~6) has been identified: N-(β-ᴅ-ribofuranosyl) -formamide. Thin-layer silica gel chromatography and spectroscopic methods (mass spectrometry. NMR, IR, optical rotation) enabled us to isolate and characterize this product. It may be assumed that this substance resulted from the hydrolytic degradation of unstable hydroxy-hydroperoxides. It was also prepared by uridine oxydation with pertrifluoracetic acid. A similar major compound in the radiolysis of uridylic acid has been found

The attack of OH radical on pyrimidic ring preferential­ ly took place at position 5 at neutral pH and at position 6 at low acidic pH. The trans isomers were always the major products. These conclusions arose from studies involving comparison with synthetic peroxides: c£s-6-hydroperoxy-5-hydroxy-5,6-dihydrothymine (1), as-5-hydroperoxy-6-hydro-xy-5,6-dihydrothymine (2) , frans-6-hydroperoxy-5-hydroxy-5.6-dhydrothymine (3) and ?rans-5-hydroperoxy-6-hydroxy-5.6-dihydrothymine (4) . The NMR coupling constants of the OH-6 proton with H-6 allowed us to assign unambiguously the structures of these peroxides in agreement with 18 O mass spectrometry results. G radiolytic values and NMR data are given

This paper deals with a study of some tests in rats in vivo after gamma irradiation in the presence and in the ab­ sence of selenourea. The factors considered were the total protein content, the protein pattern, and some serum enzymes, like GOT, GPT and AP. The result shows that the preadministration of selenourea modifies fovourably the changes induced by ionizing radiation

Metaphase chromosomes of group A isolated from the imipramine-treated lymphocyte cultures did bind more tritiated poly-ʟ-lysine ( 3 H-PL) than the control chromosomes. The increase in binding was dependent on the length of treatment and on contraction of chromosomes. The effect of contraction was more pronounced for the treated chromosomes than for controls and was larger when the treatment was done 4 hours before termination of culture. The observed differences in the 3 H-PL binding probably reflect differences in the chromosomal surface morphology

Rats exposed to [ 14 C-methyl]-dichlorvos excrete labelled 7-methylguanine, 3-methyladenine, and 1-methylnicotinamide in the urine

The functional role of the large trachea which runs from a spiracle in the thorax down the leg (tympanal trachea) was analysed in relation to the tympanal organ. The tympanal trachea not only tunes the tympanal organ to a certain frequency (Fig. 1) but is important for the directional sense of hearing in the whole animal. The directional sensitivity of the ear depends only on the relative positions of the spiracle of the tympanal trachea and the direction of sound (Fig. 2), irrespective of the foreleg walking position

Brittle stars exhibit a very remarkable taxis in electric field. All the arms become oriented to the cathode and the animal physically approaches to this electrode