Showing papers by "University of Freiburg published in 1976"

Coordinated induction and subsequent activity changes of two groups of metabolically interrelated enzymes. Light-induced synthesis of flavonoid glycosides in cell suspension cultures of Petroselinum hortense.

Abstract: The enzymes of the flavonoid glycoside pathway were specifically induced upon irradiation of a 10-day-old, dark-grown cell suspension culture of Petroselinum hortense Hoffm, with ultraviolet light. The curves for the activity changes of a first sequence of three enzymes (group I) revealed only small, but significant, differences. Sharp peaks in these enzyme activities were observed at about 17. 22, and 23 h after the onset of the irradiation. The apparent half-lives during the subsequent periods of decline ranged, in the same order, from about 10 to 15 and 17 h. No significant differences were found for the lag periods preceding the increases in the three enzyme activities. The possibility is discussed that the slight differences in the patterns of the light-induced activity changes are mainly due to different rates of degradation of the enzymes, suggesting an otherwise largely interpendent regulation. The patterns of the activity changes of four enzymes of the second sequence (group II) differed greatly from those observed for group I, but were again similar to one another. Thus, the two groups of enzymes appear to be regulated differently, despite their concomitant induction. A sigmoidal curve for the accumulation of the flavonoid glycosides was obtained upon the induction of the enzymes. This curve corresponded closely to that derived by integration of the curve for the activity changes of the first enzyme of group I. phenylalanine ammonia-lyase. It is concluded that this enzyme might be rate-limiting for the entire pathway.

IS-elements in microorganisms.

Abstract: The bacterial chromosome, while evolving by point mutations in its DNA, is thought to be rather stable with regard to its gross organization. For example, even though the DNAs of Salmonella and Escherichia cross-hybridize only weakly due to divergent sequence evolution (Demerec and New, 1965; Brenner et al., 1969), the genetic maps of the two bacteria are rather similar with respect to the order of functions (Sanderson and Demerec, 1965).

Red Light-enhanced Phytochrome Pelletability: Re-examination and Further Characterization.

Abstract: Red light-enhanced pelletability of phytochrome was observed in extracts of all 11 plants tested: Avena sativa L., Secale cereale L., Zea mays L., Cucurbita pepo L., Sinapis alba L., Pisum sativum L., Helianthus anuus L., Raphanus sativus L., Glycine max (L.) Merr., Phaseolus vulgaris L., and Lupinus albus L. This enhanced pelletability was observed in all 11 plants following in situ irradiation (in vivo binding) but only in Sinapis and Cucurbita after irradiation of crude extracts (in vitro binding). In vivo binding was not strongly dependent upon pH and, with few exceptions, was not markedly sensitive to high salt concentration, whereas in vitro binding was completely reversed by both high pH and high salt concentration. However, both binding phenomena were observed only with a divalent cation in the extract buffer. In vivo binding was further characterized using Avena which showed an increase in pelletability from less than 10% in dark control extracts to more than 60% in extracts of red light-irradiated shoots. The half-life for binding was 40 seconds at 0.5 C and was strongly temperature-dependent, binding being complete within 5 to 10 sec at 22 C. If pelletable phytochrome in the far red-absorbing form was photoconverted back to the red-absorbing form in situ, phytochrome was released from the pelletable condition with a half-life of 25 minutes at 25 C and 100 minutes at both 13 C and 3 C. No cooperativity in red light-enhanced pelletability with respect to phytochrome-far red-absorbing form was observed.

Studies on the regulation of myocardial blood flow in man. I.: Training effects on blood flow and metabolism of the healthy heart at rest and during standardized heavy exercise.

Abstract: In a comparative study 11 athletes and 11 untrained students were investigated at rest, of these 6 trained and 5 untrained individuals during exercise as well. Myocardial blood flow was measured by the argon method. Myocardial oxygen consumption, myocardial substrate uptake of glucose, lactate, and free fatty acids and cardiac output were determined by the direct Fick principle. Exercise was standardized according to 65% of an individual's maximal oxygen uptake (delta VO2 max). Coronary flow reserve was determined by dipyridamole injections. All measurements were made during hemodynamic and respiratory steady-state conditions with the subject in a supine position. At rest, myocardial blood flow and myocardial oxygen consumption were significantly lower in trained subjects compared to the untrained ones. These differences were more pronounced during heavy exercise. They cannot be explained completely by hemodynamic parameters. - During exercise, myocardial substrate uptake shifted to a predominant lactate uptake of almost 90% of total substrate uptake. Total substrate uptake as well as lactate uptake correlated significantly with myocardial oxygen. - Coronary flow reserve was lower in the trained group. It is concluded that the heart muscle of a trained individual requires less energy at a given work load than in the untrained state.

Bacteriophage T7 genetics.

Abstract: It is generally taken for granted that the study of a subject under review has been sanctioned by the scientific community and therefore no further justification is needed. After 30 years of hectic phage genetics, it might, however, be appropriate to pause for a moment in order to evaluate the original motives and aims: why study the genetics of phage, and why, particularly, that of T7?

The aggregation pheromones of bark beetles: Progress and problems

Abstract: Bark beetles (Coleoptera: Scolytidae) are insect pests inhabiting the subcortical tissues of trees. They account for much of the timber losses in coniferous forests throughout the Northern Hemisphere. Destructive outbreaks have been recorded in the past and present alike as soon as windstorms, drought, flood, root competition, or defoliation impair tree health and provide suitable host material for exploding beetle populations. Attacking en masse, aggressive populations overcome their host trees regardless of health or vigor. What appears to be attack by brute force, however, is actually the outcome of an intriguing system of chemical communication which in many respects resembles that of social insects more closely than the sex pheromones of lepidoptera. The elements of scolytid communication are host-produced volatiles as well as insect-produced pheromones; the response is not truly sex-specific, with both male and female beetles aggregating [1]. This ensures the utilization of temporary habitats [2] such as broken limbs or lightning-struck trees, providing an obvious mechanism for survival of endemic populations. But the same mechanism may mark resistant trees for simultaneous mass attack when and where epidemic populations prevail. Consequently, the term \"population aggregating pheromones\" or briefly \"aggregation pheromones\" (Populationslockstoffe) was introduced to emphasize the pheromonal function in host colonization. This is not to overlook the fact that aggregation of both sexes leads to the encounter of a mate. Nevertheless, the target marked by bark-beetle pheromones is the host, in contrast to the sex pheromones, where it is the mate. The fact that bark beetles are attracted to, and aggregate on, suitable host material has been commonly known for centuries and was used empirically in Europe to combat the pest with \"trap trees\". Gmelin [3] described such procedures in his remarkable essay \"Abhandlung fiber die Wurmtrocknis\" as early as 1787. However, Anderson [4] was first to prove the existence of attractants experimentally in 1948 and another decade passed before research investigated this phenomenon systematically [5]. The experimental proof that beetle-produced volatiles are involved in bark-beetle attraction was followed by the first successful identification of three terpene alcohols [6] in 1966. Since then, considerable progress has been made in the identification of aggregation pheromones and related structures, as well as in the biosynthesis of such compounds and the insect's response behavior. Aggregation pheromones are thought to occur throughout the family of Scolytidae with a few possible exceptions [7]; but there are many bark-beetle species which respond most readily to resinous materials exuding from damaged or infested timber as, for example, Blastophagus piniperda [8]. In general, the beetles emerge from a brood tree or overwintering site and disperse in search of new breeding places. Random dispersal and close-range host recognition, which may include olfactory response to host odors (primary attraction), are considered instrumental. Invariably, the beetle initiating gallery construction selects the host. In monogamous bark-beetle species, this is the female; among polygamous beetles, the male. As they enter the bark, pheromones are released usually by defecation, and/or host volatiles are activated. Colonization starts in response to this strong and specific secondary attraction, which increases as more beetles enter the same host and generate more of the attractive principle (Fig. 1). During this stage of attack, the focus of attraction may extend from a part of a tree to the whole, and from several trees into an attractive area in which beetles aggregate for mutual attack of additional hosts. Many Dendroctonus and some Ips spp. are capable of marking new host trees in spite of copious resin flow which prevents the beetles from feeding. Such \"contact pheromones\" are appar-

Enzymic Synthesis of Lignin Precursors

Abstract: A cinnamoyl-coenzyme A reductase catalyzing the NADPH-dependent reduction of substituted cinnamoyl-CoA thiol esters to the corresponding cinnamaldehydes was isolated from cell suspension cultures of soybean (Glycine max L. var. Mandarin). A 1660-fold purification of the enzyme was achieved by (NH4)2SO4 fractionation, chromatography on DEAE-cellulose, hydroxyapatite and Sephadex G-100 and affinity chromatography on 5'-AMP-Sepharose. The apparent molecular weight of the reductase was found to be about 38 000 on the basis of the elution volume from a Sephadex G-100 column. Maximum rate of reaction was observed between pH 6.0 and 6.2 in 0.1-0.2 M citrate buffer at 30 degrees C. The enzyme was markedly inhibited by thiol reagents. The reductase showed a high degree of specificity for cinnamoyl-CoA esters. Feruloyl-CoA was the substrate with the lowest Km value (73 muM) and highest V (230 nkat/mg) followed by 5-hydroxy-feruloyl-CoA, sinapoyl-CoA, p-coumaroyl-CoA, caffeoyl-CoA and cinnamoyl-CoA. No reaction took place with acetyl-CoA. The Km value for NADPH varied with the type of substrate. Km values of 28, 120, and 290 muM were found with feruloyl-CoA, sinapoyl-CoA, and p-coumaroyl-CoA, respectively. The rate of reaction observed with NADH was only about 5% of that found with NADPH. The reaction products CoASH and NADP+ inhibited the reaction. The Ki values were in the range of 0.5-1 mM and the inhibition was of a noncompetitive (mixed) type. The role of the reductase in the biosynthesis of lignin precursors is discussed.

Measurements of fast light-induced light-scattering and -absorption changes in outer segments of vertebrate light sensitive rod cells

Abstract: Flash-induced changes of light-absorption and of light-scattering of vertebrate rod outer segments (ROS) from frog and cattle in suspension were measured at 380 and 800 nm The photometer used allows the observation of light intensity changes under well defined angles We studied the successive decrease of the signal amplitude in series of flashes One flash bleaches about 1% rhodopsin The following results are discussed: N: A small signal with time course and successive amplitude decrease comparable to the metarhodopsin II absorption change, probably arising from a structural change within the disc membrane Ni: A slow signal, disappearing with the first flash, which may be understood as an outer membrane effect P: A biphasic signal with a successive decrease rate, by a factor of 10 to 20 higher than that of the metarhodopsin II signal The two kinetically different components are separated by variation of the observation angle Two regions of different extension appear to change structurally with different time course “P” may reflect an influence of the light-induced transmitter release on disc shape and/or mass

Influence of low extracellular pH upon the Ca inward current and isometric contractile force in mammalian ventricular myocardium.

Abstract: In isolated papillary muscles of cats the changes in Ca inward current and isometric contractile force following a decrease of extracellular pH from 7.4 to 5.5 were studied. The Ca current was analyzed (a) by measuring the upstroke velocity of Ca-mediated action potentials and (b) in voltage clamp experiments using the double sucrose gap technique. 1. At a pH of 5.5 the upstroke velocity of the Ca-mediated action potential decreased to 65% of the control, while overshoot and action potential duration remained almost unchanged. Furthermore, the relative refractory period was prolonged and in some cases, a “Wenckebach-like” phenomenon occurred. In voltage clamp experiments, the slow inward current was found to be diminished to 50–60% of the initial control value and over a broad voltage range the current voltage relationship curve was shifted to weaker currents. Acidosis did not influence the steady state inactivation but altered the kinetics of inactivation of the slow inward current and induced an increase of τinactivation and τrecovery. This indicates that acidosis exerts a complex effect on the slow membrane channel. 2. The normal response of the Ca current towards variations of the extracellular Ca concentration (0.5–4 mM) or towards the addition of the β-stimulating compound isoproterenol (2 mg/l) was not altered by the lowered extracellular pH. 3. In the acid medium, isometric contractile force declined to 40% of the control value within 25 min and, thus, reacted stronger than the Ca current. This indicates that those forms of acidosis used in the present experiments caused their negative inotropic effect not exclusively via a depression of the Ca current. Rather an additional intracellular effect has to be assumed which finally leads to a reduced activity of the contractile system. 4. At pH 5.5 excess Ca (4mM) induced the same quantitative response of the contractile system as obtained at normal pH. In contrast, the positive-inotropic effect of 2 mg/l isoproterenol was more pronounced, whilst the sensitivity of the Ca inward current towards this β-stimulating compound remained unchanged.

Protein degradation and proteinases during yeast sporulation.

Abstract: During ascospore formation in Saccharomyces cerevisiae, at least 60–70% of the pre-existing vegetative protein was broken down at a rather constant rate until the time mature asci appeared. Under the same conditions in a non-sporulating haploid derived from the same strain the rate of protein degradation, although initially comparable to that of sporulating cells, decreased much more rapidly. Proteins synthesized at different times during sporulation had approximately the same degradation rates as the vegetative proteins. Similar rates of degradation were observed for the vegetative proteins in all fractions obtained from cell homogenates by differential centrifugation. Protein breakdown after transfer to sporulation medium was blocked by uncouplers and inhibitors of energy metabolism, and was partially inhibited by cycloheximide. Polyacrylamide gel electrophoresis, in the presence of sodium dodecylsulfate, of the proteins extracted from vegetative cells and from isolated asci and ascospores revealed that ascus formation was accompanied by a shift of the cellular proteins to a lower molecular weight. From several proteinase inhibitors tested, only tosyl-p-lysine chloromethylketone slightly reduced the rate of ascus formation. During sporulation the total activity of proteinase A increased more than twofold with a maximum at 18 h after transfer to sporulation medium. Total proteinase B activity showed a striking increase in the first hours after transfer to sporulation medium and after that remained constant throughout sporulation. The levels of carboxypeptidase Y and of the proteinase B inhibitor were not significantly altered during sporulation. The proteinases and the proteinase B inhibitor were present within the mature ascospore. The proteinases, from both vegetative and sporulating cells were eluted with the same ionic strength from DEAE-Sephadex, and they were undistinguishable in their sensitivity to different proteinase inhibitors. No additional proteolytic activities could be detected in sporulating cells using 3H-labelled denatured yeast protein as a substrate.

Chirality of insect pheromones: Response interruption by inactive antipodes

Abstract: (-)-disparlure, or both enantiomers [1] resulted in distinctly different response patterns by the nun moth and the gypsy moth (Fig. 1). With the nun moth, response to the traps increased with the concentration of(+)-disparlure regardless of the addition of(-)-disparlure (Table 1) which is known to drastically suppress gypsy-moth response at r~/cemic or higher concentrations [1]. Tests using traps baited with (-)-disparlure only ted to conflicting results. No moths were caught in two areas but large numbers in another [4]. Our findings are well in accordance with observations which indicate that nun moths respond to increasing concentrations of racemic disparlure while gypsy moths do so to a lesser degree [5]. One possible explanation of this phenomenon rests, indeed, with chiral differences in pheromone production between the two species [6]. Hypothetically, P. dispar would be expected to produce the (+)-enantiomer only, while P. monacha might produce both optical antipodes of the disparlure.

Characterization of nuclear membranes and endoplasmic reticulum isolated from plant tissue.

Abstract: Nuclei, nuclear membranes and rough endoplasmic reticulum (rER) were isolated from onion root tips and stems. Structural preservation and purity of the fractions was determined by electron microscopic and biochemical methods. Gross compositional data (protein, phospholipid, nonpolar lipids, sterols, RNA, DNA), phospholipid and fatty acid patterns, enzyme activities (ATPases, ADPase, IDPase, glucose-6-phosphatase, 5'-nucleotidase, acid phosphatase, and NADH- and NADPH-cytochrome C reductases), and cytochrome contents were determined. A stable, high salt-resistant attachment of some DNA with the nuclear membrane was observed as well as the association of some RNA with high salt-treated nuclear and rER membranes. The phospholipid pattern was identical for both nuclear and rER membranes and showed a predominance of lecithin (about 60%) and phosphatidyl ethanolamine (20-24%). Special care was necessary to minimize lipid degradation by phospholipases during isolations. Nonpolar lipids, mostly sterols and triglycerides, accounted for 35-45% of the membrane lipids. Sterol contents were relatively high in both membrane fractions (molar ratios of sterols to phospholipids ranged from 0.12 to 0.43). Sitosterol accounted for about 80% of the total sterols. Palmitic, oleic, and linoleic acids were the most prevalent acids in membrane-bound lipids as well as in storage lipids and occurred in similar proportions in phospholipids, triglycerides and free fatty acids of the membrane. About 80% of the fatty acids in membrane phospholipids and triglycerides were unsaturated. A cytochrome of the b5 type was characterized in these membranes, but P-450-like cytochromes could not be detected. Both NADH and NADPH-cytochrome c reductases were found in nuclear and rER membranes and appeared to be enriched in rER membranes. Among the phosphatases, Mg2+-ATPase and, to lesser extents, ADPase, IDPase and acid phosphatase activities occurred in the fractions, but significant amounts of monovalent ion-stimulated ATPase, 5'-nucleotidase and glucose-6-phosphatase activities did not. The results obtained emphasize that the close biochemical similarities noted between rER and nuclear membranes of animal cells extend to these fractions from plant cells.

Photoreactions of Small Organic Molecules V. Absorption‐, Photoion‐ and Resonancephotoelectron‐Spectra of CF3Cl2, CF2Cl2, CFCl3 in the Energy Range 1025 eV

Abstract: The absorption spectra, photoion spectra, and resonance photoelectron spectra of CF3Cl, CF2Cl2, and CFCl3 have been measured in the energy range from 9 eV to 25 eV, - Absolute cross sections of absorption are given. The stability of the parent ions decreases with increasing symmetry of the parent molecules. The fragment ions have been analyzed. Besides photocations, atomic chlorine and fluorine, fluoride and chloride are formed. The decay mechanisms are discussed, spectra are influenced by autoionization. The resonance photoelectron spectra reveal some new ionization potentials at high excitation energies. Es wurden die Absorptions-, Photoionen- und Resonanzphotoelektronenspektren von CF3Cl, CF2Cl2 und CFCl3 im Energiebereich von 925 eV gemessen.—Fur die Absorptionsspektren werden absolute Wirkungsquerschnitte angegeben. Die Stabilitat der Molekulionen nimmt mit steigender Symmetrie der neutralen Molekule ab. Die Fragmentionen wurden analysiert; neben verschiedenen Photokationen, atomarem Chlor und Fluor werden Fluorid und Chlorid gebildet. Die Zerfallsmechanismen werden diskutiert, der Einflus von Autoionisation auf die Spektren kann nachgewiesen werden. Die Resonanzphotoelektronenspektren zeigen einige bisher nicht beobachtete lonisierungs-potentiale bei hohen Anregungsenergien.

Packing analysis of carbohydrates and polysaccharides. IV. A new method for detailed crystal structure refinement of polysaccharides and its application to V‐amylose

Abstract: A method is described for predicting and solving crystal structures of linear homopolysaccharides. The method is based on the refinement of the structure with respect to either stereochemical constraints or x-ray diffraction intensities. In the refinement process, all conformational and packing features of the molecule, such as bond lengths, bond angles, conformational angles, nonbonded contacts, hydrogen bonds, etc., can be allowed to vary until the structure reaches both a conformation and crystalline packing that are in minimum disagreement with the stereochemical restraints and the diffraction data. In this fashion, both packing and conformational features of the structure can be simultaneously refined, and not separately as has been the custom in the past. The refinement procedure is based on a method of constrained optimization which possesses improved characteristics of reaching a solution and avoiding false minima, in comparison with least squares methods. The procedure is, in addition, capable of easily finding molecules of solvent of crystallization. The method was applied to further refining the previously solved crystal structure of V-amylose. The results indicated that contrary to the previously found six-fold molecular symmetry in the P212121 space group, the V-amylose molecule exhibits only two-fold symmetry with the asymmetric unit consisting of three glucose residues in one-half turn of the helix. The three residues are nonequivalent principally due to unequal rotational positions of the hydroxymethyl groups. The crystal structure of V-amylose predicted from stereochemical refinement was identical in all details with that obtained from refining against X-ray data. The excellent agreement with the diffraction data was indicated by the crystallographic disagreement index R = 0.25.

Cis-dominant regulatory mutations affecting the formation of glucose-repressible alcohol dehydrogenase (ADHII) in Saccharomyces cerevisiae

Abstract: The formation of ADHII in Saccharomyces cerevisiae is regulated by carbon catabolite repression. There are two genes involved in the formation of ADHII: ADR2, the structural gene as identified by electrophoretic variants and ADR1, possibly a regulatory gene. A new genetic element involved in the regulation of ADHII was identified by three allelic mutants insensitive to strong glucose repression. They were called ADR3 c (wild type designation ADR3) and found to be tightly linked to the structural gene, ADR2. The alcohol dehydrogenase found in ADR3 c mutants could not be distinguished electrophoretically from the ADHII of the glucose-sensitive wild type, ADR3. Dominance relations between ADR3 c and ADR3 were established in diploids heterozygous for ADR3 and the two alleles of ADR2 (ADR2-S: slow ADHII, ADR2-F: fast ADHII). During growth on 10% glucose, an ADR3 c ADR2-F/ADR3 ADR2-S heterozygous diploid formed only the fast ADHII variant whereas an ADR3 c ADR2-S/ADR3 ADR2-F heterozygote produced only the slow form. This was taken as evidence of the cis-dominance of all ADR3 c alleles. The cis-effect of ADR3 c was also demonstrated in glucose-derepressed diploids. The ADR3 c mutations do not only cause glucose-insensitive ADHII formation, but also reduce the activity of the adjacent structural gene during derepression. Thus ADR3 c alleles were considered to be controlling site mutations. No pleiotropic effects were observed on the formation of enzymes related to the function of ADHII. An adr1 ADR2 ADR3 single mutant did not form ADHII. In contrast to this, an adr1 ADR2 ADR3 c double mutant formed ADHII at a similar level as an ADR1 ADR2 ADR3 c mutant. This showed that ADR3 c was epistatic over adr1 (previously suggested as a positive regulatory gene). From this it was concluded that ADR1 is in fact a positive regulatory gene the function of which is required for the expression of the structural gene for ADHII, ADR2. ADR3 is the controlling site for the structural gene ADR2. Mutations at this site, ADR3 c , alleviate the requirement for the ADR2 gene product. ADR3 c is discussed as a promotor or operator site.

Centrally symmetric convex bodies and distributions

Abstract: To each centrally symmetric convex body is assigned a distribution on the sphere. As applications, geometric formulas and a characterization of zonoids are obtained.

The slow membrane channel as the predominant mediator of the excitation process of the sinoatrial pacemaker cell.

Abstract: The slow upstroke velocity of the action potential of primary pacemaker cells of the sinoatrial node suggests the slow membrane channel to be involved in the excitation process of these cells. In order to prove this the effect of promotors and inhibitors of the slow membrane channel upon the excitation process of the isolated sinoatrial node of rabbits was studied. 1. The action potentials of primary pacemaker cells had an upstroke velocity of 1.7 +/- 1.1 V/sec and an overshoot of 8.1 +/- 4.6 mV with a threshold potential of -40.1 +/- 4.5 mV. A decrease of the extracellular Ca concentration from 2 mM to 0.2 mM led to reduction of upstroke velocity and overshoot whereas an increase from 2 mM to 4 mM augmented both parameters. But the inward current is not only carried by Ca ions but by Na ions as well, since Na withdrawal diminished upstroke velocity and overshoot. 2. The promotors of the slow inward current, isoproterenol and caffeine, produced a significant increase of upstroke velocity and overshoot. On the other hand, verapamil (1 mg/1) and D 600 (0.4 MG/1) completely blocked the excitation process within 20-25 min. The same effect could be produced by the bivalent cations Ni (1 mM), Co (1 mM), and Mn (1 mM). These organic and inorganic inhibitors exerted their blocking effect without significant changes of the maximal diastolic potential and the threshold potential. 3. In the continued presence of Ni, Co and Mn ions their inhibitory effect could be neutralized nearly completely by isoproterenol (2.5 mg/1). But excess Ca (6 mM) increased the upstroke velocity only to a small degree. In contrast to the findings in the ventricular myocardium the blocking effect of verapamil and D 600 could be overcome neither by isoproterenol nor by excess Ca. The excitation process in the sinotrial node is mediated solely by the slow membrane channel. It allows the influx of both Ca and Na ions which act as charge carrier of the slow inward current. The fact, that the inhibitory effect of verapamil and D 600 cannot be neutralized by catecholamines or excess Ca seems to indicate that some properties of the slow membrane channel are not exactly identical in sinotrial pacemaker cells and in the ventricular myocardium.

Esterases in histochemistry and ultrahistochemistry.

Abstract: The histochemical identification of individual esterases is a problem that has not yet been overcome. Inhibitors and different substrates reveal different patterns of distribution. 8-hydroxyquinoline acetate is a useful substrate in ultrahistochemistry. There is evidence of a relationship between esterase distribution and function.

Mechanism of interfacial polycondensation and the direct synthesis of stable polyamide membranes

Abstract: The mechanism of membrane formation by interfacial polycondensation was studied. For the time-conversion curves the equation was derived (x′ = reduced membrane thickness). The membrane morphology was investigated by x-ray scattering and electron microscopy. It was found that the polymer chains are mainly oriented perpendicularly to the interface in the direction of membrane growth. The order of chain packing decreases with increasing thickness. Stable polyamide membranes consisting of two layers can be obtained by formation of a supporting layer of crosslinked copolyamide on a thin layer of Nylon-6,10. The swelling properties of these membranes were studied.

Light-induced enzyme synthesis in cell suspension cultures of Petroselinum hortense. Demonstration in a heterologous cell-free system of rapid changes in the rate of phenylalanine ammonia-lyase synthesis.

Abstract: The conditions for protein synthesis in vitro with polyribosomes from cell suspension cultures of parsley (Petroselinum hortense) and a wheat-germ extract were investigated. Two different criteria were used as estimates of the translational activity: (a) the total rate of incorporation of [35S]methionine into acid-insoluble material, (b) the ratio of large (molecular weight > 25000) to small (molecular weight < 25000) peptide products. Depending on which of the two criteria was employed, the pH optimum and the optimal concentrations for Tris-acetate, magnesium acetate, KCl, methionine and the wheat-germ extract differed considerably. The translational activity of the polyribosomes (both criteria) was efficiently protected by 0.1 M Mg2+ against degradation during the isolation procedure. The rate of synthesis of phenylalanine ammonia-lyase in vitro with the polyribosomes was determined by measuring the incorporation rate of l-[35S]methionine into protein which was precipitable by a rabbit antiserum preparaed for the purified enzyme. The immunoprecipitate was analyzed by disc;gel electrophoresis in the presence of dodecylsulfate and was shown to contain small amounts of the complete enzyme subunits and relatively large amounts of shorter peptides which were also characteristic for the enzyme. The time courses of light-induced changes in the rate of phenylalanine ammonia-lyase synthesis in vitro were investigated during a period of 15 h under two different conditions of induction: the cell cultures were irradiated with ultraviolet light either (A) continuously or (B) for 2.5 h and then returned to darkness. Although the highest rate of enzyme synthesis was observed somewhat later in experiment A than in experiment B, the periods of time during which the rate of synthesis increased rapidly were limited in both cases to only a few hours. The results obtained in vitro were identical within the limits of the experimental error with theoretical calculations of the changes in the rate constant of phenylalanine ammonia-lyase synthesis in vivo. These changes were calculated from the corresponding curves for the changes in the enzyme activity under the two conditions of induction. The results are in agreement with previous observations suggesting that the induction of phenylalanine ammonia-lyase by light in the parsley cells was a short-term effect whose efficiency was greatly reduced within the 15 h of experimentation, even under continuous irradiation.

Double ionization of rare gases. I. Ion formation by electron impact

Abstract: We have determined the ratio of doubly to singly charged ions for He, Ne, and Ar caused by the impact of electrons with 2 keV energy. Special attention was given to the examination of the reliability of the apparatus with respect to its handling of differently charged ions. The results do not confirm the data of Van der Wiel et al., but they are in good agreement with those of Schram et al.

Laser UV Microirradiation of Interphase Nuclei and Post-Treatment with Caffeine A New Approach to Establish the Arrangement of Interphase Chromosomes

Abstract: Laser UV microirradiation of Chinese hamster interphase cells combined with caffeine post-treatment produced different patterns of chromosome damage in mitosis following irradiation of a small area of the nucleus that may be classified in three categories: I) intact metaphase figures, II) chromosome damage confined to a small area of the metaphase spread, III) mitotic figures with damage on all chromosomes. Category III might be the consequence of a non-localized distortion of nuclear metabolism. By contrast, category II may reflect localized DNA damage induced by microirradiation, which could not be efficiently repaired due to the effect of caffeine. If this interpretation is right, in metaphase figures of category II chromosome damage should occur only at the irradiation site. The effect might then be used to investigate neighbourhood relationships of individual chromosomes in the interphase nucleus.