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The effect of small additions of scandium and zirconium on microstructure, thermodynamic and mechanical properties during the non-isothermal annealing of the mould-cast and cold-rolled aluminium was studied. Electrical resistometry together with the microhardness (HV0.3) measurements and transmission electron microscopy compared to differential scanning calorimetry results were used to characterize the effect. The Al–Sc–Zr-based alloy with a small addition of Ti in both states reaches the peak hardness by annealing to 330 °C due to precipitation of the Al 3 Sc particles. Relative resistivity changes (above 240 °C) of both alloys exhibit similar dependence on annealing temperature. Precipitation of particles (L1 2 structure) at 390 °C and 450 °C was observed by TEM. The apparent activation energy for precipitation of Al 3 Sc particles was calculated. The decomposition sequence of oversaturated solid solution of the studied Al–Sc–Zr-based alloy is compatible with the recently published decomposition sequence of Al–Sc–Zr system and the formation of layer rich in Ti, namely: Sc-rich clusters → Al 3 Sc phase → layer rich in Zr → layer rich in Ti → Al 3 (Sc,Zr,Ti) phase.

The protective effect of pig immune colostrum, serum and immunoglobulins IgG, IgM and IgA against the enterotoxic strain ofEscherichia coli O55, was studied in newborn germfree piglets. This strain produced accumulation of fluid and dilatation of intestine when injected into the ligated ileal segment of germfree piglets, which is considered to be the typical effect of enterotoxins. Erosion of the intestinal epithelium and penetration of bacteria into the submucosa were also observed. Immune serum, colostrum and all the immunoglobulin classes used produced a local protective effect, IgA being most effective. The mechanism of protection conferred by these immunoglobulins is discussed with respect to the possible pathogenic action of enterotoxicEscherichia coli O55 in the intestinal tract of immunologically virgin germfree piglets.

Composite systems of the crosslinked and soluble poly(2-hydroxyethyl methacrylate) (PHEMA) matrix with various contents of crosslinked PHEMA particles containing 0.4, 1.0 and 20.0 wt. percent ethylenedimethacrylate as the crosslinking agent were prepared. Stress relaxations at the elongation λ = 1.1, stress-strain curves, Poisson's ratios, the degree of swelling and ultimate characteristics of samples swollen in water at 25°C were measured. With increasing filler content the time effects in the systems and the stress-at-break σb, and strain-at-break, σ b , also increase; these results corroborate the viscoelastic concept of the ultimate behaviour. An agreement was found between the experimentally determined course of the initial modulus G 0 and that predicted by Van der Poel as a function of the volume fraction of filler νf only for those systems in which the content of the crosslinking agent in the filler is smaller than in the matrix; systems with a higher content of the crosslinking agent in t...

Vitamin B12 was determined in biological materials by three basically different methods: microbiological assay with Lactobacillus leichmannii, microbiological assay with Escherichia coli and radioassay. The method with E. coli has a relatively low sensitivity to vitamin B12 and in some cases of vitamin B12 determination in microbial materials it can be used only after a separation of the interfering substances by gel chromatography. The procedure is suitable for orientational determinations of vitamin B12 because it is very little affected by external factors. The assay with L. leichmannii is universal owing to its high specifity and sensitivity to vitamin B12. The main disadvantage of the latter procedure depends on the high requirements for a clean atmosphere which can be mained in laboratories in industrial areas only with difficulties. These limitations do not apply to the quick and sensitive radioassay. The radioassay can be used after a suitable adjustment of the working procedure for large series of analyzes of biological materials without any preliminary separational techniques. The test can be carried out in normal laboratories providing that the principles of work with radionuclides are obeyed.

Palladium(II) halide complex anions can be titrated with different quaternary salt solutions. Titrations can be monitored potentiometrically with a simple PVC membrane-coated aluminium wire electrode. A comparative study with different cationic titrants showed the dependence of the titration stoichiometry on the structure of the cationic reagent used. The procedures can be utilized for monitoring the Pd(II) concentration in galvanic contact baths.

The generally accepted microbiological assay for „total folacin” (with Lactobacillus casei), based on the sample treatment with sole conjugase, has been found to be completely unsatisfactory, when starch or glycogen-containing samples were assayed. The so called „total folacin” content, determined in this way, is much lower than the actual one, because a part of folacin remains bound to polysaccharides, and is not transferred into the extract and thus not detected by the microbiological assay. The authors showed that the additional sample treatment with amylolytic enzymes is entirely necessary when actual „total folacin” content is to be determined in starch or glycogen containing samples. The presented analytical results of a series of food samples bring evidence for this idea. The actual total folacin content in such types of samples is up to 80 % higher than that determined by procedures used up till now. The ability of polysaccharides to bind folacin was studied in model systems. Pteroyl-glutamic acid (PGA) was adsorbed onto glycogen, 4 types of starch, amylose and amylopectin. The complete desorption of PGA., was achieved with α-amylase, in case of maize starch the addition of glucoamylase was necessary. PGA is bound to starch by physical sorption which has been proved by its desorption with increasing salt concentration.

Aminoacyl (Phe, Gly) derivatives of nucleoside aliphatic analogues bearing a hydroxyalkyl chain have been prepared by the condensation of the alcohols with N-benzyloxycarbonyl-amino acid in the presence of DCC followed by hydrogenolysis in methanol. These compounds inhibit peptidyl transferase activity and binding of acceptor substrate to E. coli ribosomes. The inhibitory activity is not much affected by the nature of either the aminoacyl or the heterocyclic base residue. In the transfer reaction, no peptide bond formation occurs with the above compounds as acceptors.

Precolostral germfree piglets were perorally immunized with sheep erythrocytes daily, beginning on the 5th day of life. At different intervals the numbers of IgM, IgG and IgA antibody-forming cells were estimated in the spleens, lymph nodes and intestinal mucosa by the haemolytic plaque method. In the beginning of the response IgM antibody-forming cells were detected in intestinal mucosa and mesenteric lymph nodes. IgA plaque-forming cells appeared later and were predominant during the whole period in all organs tested. In all lymphatic organs tested the appearance of IgG antibody-producing cells followed that of IgA plaque-forming cells. The development of immunoglobulins and antibody of different isotypes in intestinal contents and sera was compared with the cellular kinetics found in these young animals after local stimulation.

Transfer of the acetyl- l -leucine (AcLeu) residue from AcLeu-pentanucleotide to synthetic substrates under conditions of the fragment reaction was used to study the specificity of the acceptor site of ribosomal peptidyl transferase. 2′(3′)-O-Aminoacyl nucleosides are the simplest acceptor substrates. Their acceptor activity is dependent on the nature of the nucleoside to which the amino acid residue is bound. The acceptor activity decreased in the sequence 2′(3′)-O- l -phenylalanyladenosine (A-(Phe)) > I-(Phe) > C-(Phe); U-(Phe) was inactive. The presence of a free 2′-hydroxyl group in the ribose moiety of the aminoacyl adenosines was important for the acceptor activity, as shown by the low activity of dA-(Phe) in comparison with A-(Phe). Acceptor activity was influenced by the nature of the side chain of the amino acid residue bound to adenosine: A-(Phe) was a more active acceptor than puromycin, while the acceptor activity of 2′(3′)-O-glycyladenosine A-(Gly) was very low. Free phenylalanine, phenylalanine methyl ester, and adenosine did not act as acceptors. As terminal products of the reactions of AcLeu-pentanucleotide with puromycin, A-(Phe), I-(Phe) and C-(Phe), we isolated AcLeu-puromycin, 2′(3′)-O- acetyl- l -leucyl- l -phenylalanyladenosine (A-(AcLeu-Phe)), I-(AcLeu-Phe) and C-(AcLeu-Phe), respectively.

Es wird uber 2 Ringanalysen von Riboflavinbestimmungen berichtet, an denen 13 Institute der RGW-Lander beteiligt waren. Zur Anwendung gelangten eine Fluoreszenzmethode, 2 Varianten der Lumiflavinmethode sowie eine mikrobiologische Methode mit L. casei ϵ bei zwei verschiedenen Nahrmedien. Die Ergebnisse wurden statistisch ausgewertet. Das mikrobiologische Verfahren zeigte die beste Ubereinstimmung und wird fur eine offizielle Standardisierung innerhalb der RGW-Lander vorbereitet.

1. Introduction Gougerotin (I), a dipeptidyl pyrimidine nucleoside antibiotic, has been found to specifically inhibit the step of protein biosynthesis which is catalyzed by ribosomal peptidyl transferase [l-S] . Since three gougerotin analogues have been synthesized recently [6] , 1-[3(sarcosyl-D-seryl-)amino3-deoxy$-D-gluco- pyranosyl-)uracil (II, cf. fig. l), I-[3-(sarcosyl-D- seryl-)amino-3-deoxy-P-D-glucopyranosyl-)cytosine (III) and l-[4-(sarcosyl-D-seryl-)amino-4-deoxy-O-D- glucopyranosyl-)cytosine (IV), we made an attempt to characterize the mechanism of action of gougerotin (I) and its analogues (II-IV) on the activity of ribo- somal peptidyl transferase. The results are presented below, together with a discussion of relationships be- tween structures I-IV and their inhibitory activity. 2. Materials and methods Ribosomes were prepared from

Digestion of ribosomes by ribonuclease T1 results in the inactivation of peptidyl transferase and of the binding ability of the donor site. However, the binding activity of the acceptor site is not affected by ribonuclease digestion. The binding sites of ribonuclease-treated ribosomes retain their original sensitivity to chloramphenicol, spiramycin, erythromycin and lincomycin. Digestion of 50-S ribosomal subunits by ribonuclease T1 results in the loss of peptidyl transferase activity and of the binding ability of the donor site in the same way as digestion of 70-S ribosomes either intact or recombined from 30-S and 50-S subunits. The acceptor activity of the acceptor binding site of 50-S ribosomal subunits does not change after T1ribonuclease digestion. Erythromycin, bound to the ribosomes before digestion by ribonuclease T1, decreases the rate of inactivation of peptidyl transferase, whereas spiramycin does not change the effect of ribonuclease on transfer activity.

The effect of antibiotics on the coded binding of peptidyl-tRNA to the ribosome and the transfer of the peptidyl residue from peptidyl-tRNA to puromycin has been studied. The coded binding of polylysyl-tRNA was inhibited only by tetracyclines, the binding of acetylphenyl-alanyl-tRNA was inhibited by tetracyclines and streptomycin and stimulated by spiramycin and carbomycin. The most potent inhibitors of the puromycin reaction with polylysyl-tRNA were the macrolides erythromycin, spiramycin, carbomycin and oleandomycin, inhibiting by 50% at a concentration of 0.1 μM; neomycin (1 μM), chloramphenicol (100 μM), tetracyclines (100 μM), streptomycin (50 μM) and streptovitacin A (1 mM) were somewhat less effective. The puromycin reaction with acetylphenylalanyl-tRNA was inhibited by antibiotics in a similar way, only erythromycin stimulated this reaction at concentrations between 0.1 and 500 μM.

The oxidation-reduction activity of the basidiomyceteOudemansiella mucida was studied in relation to its growth in a laboratory fermentor. Cytochromes were detected in the mycelium destroyed by sonication, flavin diaphorase, polyphenoloxidase, peroxidase and catalase were found to be present in the mycelial homogenate from Waring-blendor. The obtained values of the enzymatic activity were dependent on the method of preparation of the mycelium. Homogenization in a Waring-blendor was the most appropriate. Certain interrelationships between the appearance and activity of the enzymes followed and the phase of submerged growth of the fungus were shown. The results document the succession of cytochromes, flavins and polyphenoloxidase and the specific time differences of the activity of catalase and that of peroxidase.

Synthetic substrates were used to investigate the specificity of the acceptor site of ribosomal peptidyl transferase. The results may be summarized as follows: 1. (i) Simple synthetic compounds, namely 2′(3′)- O -aminoacyl-adenosines representing the ultimate terminal residue of aminoacyl-tRNA, can replace aminoacyl-tRNA in the transfer reaction and serve as acceptors of the nascent peptide residue, both with AcPhe-tRNA ‡ and with (Lys) n -tRNA as the peptide donor. 2. (ii) The acceptor activity of the substrates is influenced by the nature of the side chain of the amino acid residue bound to adenosine; A-Phe was nearly as active as puromycin while A-Gly and A > (CH 2 NH 2 ). (OEt) were inactive. 3. (iii) For an association between ribosomal peptidyl-transferase and the acceptor substrates the presence of free 2′-OH group in the ribose moiety of aminoacyl-adenosines is required as is shown by the low activity of dA-Phe in comparison with A-Phe. 4. (iv) The acceptor activity of the substrates tested is specific with respect to the nucleoside to which the amino acid residue is bound. Activity decreased in the sequence puromycin, A-Phe, I-Phe, C-Phe; G-Phe and U-Phe did not serve as acceptors of the peptide chain. Using AcPhe-tRNA as the donor of the AcPhe residue and A-Phe, C-Phe and I-Phe as acceptors, we isolated A-PhePheAc, C-PhePheAc and I-PhePheAc as terminal products of the reaction. The individual building blocks of aminoacylribonucleosides tested as such did not act as acceptors. Negative results were obtained with ammonium ions, tyramine, free amino acids, their amides and esters, adenosine, inosine and the puromycin aminonucleoside.

In mycelial acetone powder of the basidiomyceteOudemansiella mucida, the presence of enzymatic systems of NADH2-oxidase and-dehydrogenase type and of NAD+-dependent alcoholdehydrogenase (using ethanol as substrate) has been detected. NADH2-oxidase has its optimal pH value in the region of 6,0 and is not too active. NADH2-dehydrogenase which reduces 2,6-dichlorophenolindophenol is very active, may be eluted from the mycelial preparation with water and its adequate pH is in the region of 6,2. On the other hand, NADH2-dehydrogenase reducing triphenyltetrazolium chloride is non-eluable with water, its activity depends on the presence of menadione and its adequate pH lies in the region of 7,4.

The transfer reaction with pA-fMet as a donor substrate is strongly stimulated by CMP, whereas the transfer reaction with CpApCpCpA-acLeu as a donor substrate is inhibited by CMP. These results indicate that the donor site of peptidyl transferase contains specific binding sites for the terminal adenosine and for the cytidylic acid residue in the terminal sequence CpCpA of tRNA and that an attachment of proper nucleotides to the donor site induces a conformational change in peptidyl transferase.

The ribosomal 50 S subunit may assume two conformations differing in biological activity [ 1, 21 . In one conformation of the 50 S subunit peptidyl transferase (which is a component of this subunit) catalyzes the transfer of the peptide chain from peptidyl-tRNA to puromycin. In the second conformation the enzyme is inactive. The enzymically active conformation is converted to the inactive conformation by removal of NH: ions from the medium. The biologically inactive conformation can be converted back to the active one upon incubation with ammonium ions at a higher temperature (40’) [ 1,2] . The reactivation is markedly temperature-dependent so that practically no reactivation takes place at 0” even in the presence of ammonium ions. A similar temperature dependence was observed by Nomura and Erdmann for the reconstitution of the 50 S subunit from its components ]31 . The inactivation of peptidyl transferase which takes place during the change of ribosome conformation may be caused by a decrease of affinity for the corresponding substrate at the donor site, the acceptor site or at both simultaneously. In addition the change in conformation of the 50 S subunit may result in a distortion of the spatial arrangement of the binding sites so that no peptide transfer can take place even if both binding sites are occupied by the proper substrates. In this paper the inactivation mechanisms were studied. 2. Methods

Physiological and morphological properties ofPropionibacterium shermanii were estimated in a liquid semisynthetic medium of initial pH between 7 – 10. Prolongation of the lag phase and a shift of the stationary phase occurred at higher initial pH values of the medium, The growth response of the strain depended on the way of glucose addition (either sterilized in the medium or added aseptically after sterilization). At pH 8.5 and higher the cells begin to form slime and capsules. The strain exhibited growth activity even at initial pH values of the medium 11.5.

Germfree piglets were fed a diet supplemented with cell walls and a protein isolate from Candida utilis for 54 days. Besides morphological signs of activation of the lymphoid tissue which occurred primarily in the intestine of piglets which had been fed yeast cell walls, even an increased serum immunoglobulin level could be detected. In sera and intestinal content of piglets fed both with cell walls and isolated protein, specific antibodies capable of agglutinating yeasts were present. Even though a limited number of experimental animals was employed it can be concluded that the yeast material added to the diet elicited an immune response.

The authors examined 40 patients with Hodgkin's lymphoma suspected from the localization of the process in mediastinum. They used X-ray investigation, radioisotope lung perfusion, radiogold-colloid lymphography and 67Ga-citrate scintigraphy. They found that, when the disease was diagnosed, X-ray examinations including tomography and lung perfusion gave reliable information in only half the cases whereas the other two nuclear medical methods showed positive results in 88% and 82%, respectively. In the diagnosis of relapse, the yield of these former methods was substantially higher, between 82--90%.

Specificity of the method of indirect hemolysis in agarose using specific anti-immunoglobulin antisera was verified by testing the antibody activity of IgM, IgG and IgA isotypes isolated from the immune colostrum and serum of adult pigs. The cellular and humoral kinetics of antibody response was studied in colostrum-deprived germfree piglets after a long-term daily peroral immunization with sheep erythrocytes. At different intervals the numbers of IgM, IgG, and IgA antibody-forming cells were determined in the spleens, mesenteric nodes, and intestinal mucosa by the hemolytic plaque method. In the beginning of the response the formation of IgM antibodies (direct plaques) was detected in intestinal mucosa and in mesenteric nodes. This response was followed by a considerably more marked IgA response which was detected also in the spleen. Beginning on the 40th day of feeding with antigen an inhibition of the antibody response was detectable. The level of immunoglobulins and antibodies in intestinal contents and sera was compared with cellular kinetics.

A special strain of Propionibacterium shermanii (P.sh.) was shortly activated (2 × 6 h at 30 °C) in a semisynthetic medium and used either alone or in symbiosis with c lactose fermenting yeast, e.g. Kluyveromyces fragilis (K.f.). The contents of vitamin B12 folacin, thiamine, niacin and vitamin B6 were thus significantly enhanced in several milk products. The two microorganisms were first cultivated separately in sterile milk to prepare a “milk inoculum”. In the case of P.sh., 5% of the activated inoculum, and in that of K. f. only 1% of a yeast… ilk culture (24 h at 30 °C) were used. Depending on the milk product required, either 1% of this P.sh. inoculum alone, or together with 1.0 or 0.5% of K. f. milk inoculum was used simultaneously with the cream starter.

Mittels Papierchromatographie und Hochspannungselektrophorese konnten in Trichloressigsaureextrakten vonE. coli 3–8 Aminosauren enthaltende Peptide isoliert werden, in denen am haufigsten Glutaminsaure, Glycin, Cystein, Lysin, Asparagin und Alanin vorkommt.

Antibiotics inhibiting peptidyltransferase have been classified into three groups according to their action on the substrate binding to the acceptor and donor site of ribosomal peptidyltransferase. 1. Group 1: erythromycin and oleandomycin stimulate the binding of both the acceptor and donor substrate. These antibiotics have a weaker stimulating effect on the binding to the donor site and stronger one on the binding to the acceptor site of ribosomes from an erythromycin-resistant mutant than from a sensitive strain. 2. Group 2: spiramycin, carbomycin and lincomycin inhibit the binding of both the acceptor and donor substrate. The binding of both substrates to the ribosomes from the erythromycin-resistant strain is less inhibited than the binding to the ribosomes from the parent strain. 3. Group 3: gougerotin and chloramphenicol stimulate the binding of the donor substrate and inhibit the binding of the acceptor substrate. The binding of the acceptor substrate to erythromycin-resistant ribosomes is inhibited by chloramphenicol to the same extent, whereas the inhibition by gougerotin is weaker; on the other hand, the binding of the donor substrate is less stimulated by chloramphenicol and more so by gougerotin. The antagonistic effect of erythromycin on the inhibition of the binding to the acceptor and donor sites by other antibiotics has been examined with sensitive and erythromycin-resistant ribosomes. Erythromycin completely abolishes the inhibition of the binding of both acceptor and donor substrates to sensitive ribosomes caused by spiramycin, carbomycin and lincomycin, and reverses about 50 % of the inhibition of the binding to the acceptor site caused by chloramphenicol, gougerotin and puromycin. In resistant ribosomes, erythromycin affects the inhibition of the binding caused by the aforesaid antibiotics in the same manner as in sensitive ribosomes, except for the inhibition of the binding to the acceptor site by gougerotin, which is not affected by erythromycin at all.