Showing papers by "Ludwig Maximilian University of Munich published in 1970"

Das Carotinoidmuster und die Verbreitung des lichtinduzierten Xanthophyllcyclus in verschiedenen Algenklassen

Abstract: Die Pigmente wurden nach den bei Hager u. Stransky (1970) besprochenen Methoden identifiziert und ihre Mengen bestimmt.

Pathways of Hydrogen in Mitochondria of Saccharomyces carlsbergensis

Abstract: With mitochondria from Saccharomyces carlsbergensis the functional relationship of the exogenous and endogenous NAD system has been investigated with respect to the membrane barrier, the localisation of NADH dehydrogenase and other NAD-and flavine-linked dehydrogenases. 1 Added NAD and NADH do not permeate through the inner membrane into the matrix space of mitochondria from S. carlsbergensis despite the high rate of oxidation. There is no exchange between exogenous and endogenous NADH and NAD. 2 A transhydrogenation between external and internal NADH and NAD across the inner membrane is not observed. 3 By applying the “ferricyanide method” two separate dehydrogenases can be identified: one for the oxidation of exogenous NADH, located towards the outer surface of the inner mitochondrial membrane; and a second for the oxidation of endogenous NADH directed towards the inner surface. Both dehydrogenases are connected to the cytochrome chain through the ubiquinone pool. 4 About 50% of the total NADH dehydrogenase activity of yeast mitochondria is solubilized by sonication. The solubilized NADH dehydrogenase is tentatively identified with the external enzyme. This agrees with the finding that on opening the membrane by sonication the total activity of NADH-ferricyanide reduction increases by 65%. 5 Applying both [4B-3H]NADH and [4A-3H]NADH the oxidation of both exogenous and endogenous NADH by ferricyanide and by oxygen are found to be B-specific. 6 By application of the “ferricyanide method” to other substrates it is concluded that the dehydrogenases for glycerolphosphate and possibly lactate are localized before the barrier for ferricyanide while the dehydrogenases for ethanol, isocitrate and succinate are localized behind it. This barrier is identical with the inner mitochondrial membrane. 7 The existence of a mitochondrial alcohol dehydrogenase, accounting for about 6% of the total cellular activity and located in the matrix space, is established. The dual localization of alcohol dehydrogenase is considered to facilitate the equilibration between the intra- and extra-mitochondrial NAD systems via an ethanol-acetaldehyde shuttle.

Regulation of superficial nephron filtration rate by tubulo-glomerular feedback

Abstract: Possible regulation of glomerular filtration rate by tubulo-glomerular feedback from a late tubular site was studied in microperfusion experiments on rats. During perfusion of loops of Henle with varying flow rates and different perfusion solutions, filtration rate of the perfused nephrons was measured by total proximal fluid collection and inulin determination. During perfusion with isotonic Ringer's solution nephron filtration rate decreased significantly with increasing perfusion rates. Since proximal intratubular pressure was experimentally kept constant, this response must reflect decreased glomerular capillary pressure. Increasing the flow rate during perfusion with isotonic sodium sulfate or mannitol solutions was not associated with significant changes of filtration rate. Thus some correlate of the flow rate of normal loop of Henle fluid can affect filtrate formation. Such an effect may be mediated by the juxtaglomerular apparatus. Our results are consistent with the concept that the triggering signal is a function of the amount of distal sodium that is able to permeate the cell membrane at the receptor site rather than of distal intratubular sodium concentration.

Micropuncture evaluation of the importance of perivascular pH for the arteriolar diameter on the brain surface

Abstract: A micropipette technique was used to induce local changes of the bicarbonate concentration of the cerebro-spinal fluid surrounding arterioles on the exposed cerebral cortex of anaesthetized rats and cats. Injection volumes of a few nanoliters caused circumscribed and pronounced changes of the diameter of the arterioles under study: mock spinal fluid without bicarbonate dilated, while a solution containing 25 meq/l of bicarbonate constricted the vessels. In such experiments the localpCO2 of the arteriolar wall remains practically constant, since it is set by thepCO2 of the arterial blood and of the cerebral tissue. Hence the microinjections essentially consisted in a local change of the pH of the fluid surrounding a small segment of a cerebral arteriole. Since metabolic changes of the nervous tissue changes the periarteriolar pH, it is probable that local pH induced vasomotor changes of the type reported here participate in the so called metabolic regulation of the cerebral blood flow which underlies the local adaptation of the cerebral blood flow to changing functional demands.

Characterization of Neurospora crassa Mitochondria Prepared with a Grind-Mill

Abstract: Mitochondria can be isolated rapidly from Neurospora crassa with high yields by disrupting the hyphae suspension between the two grinding wheels of a simple mill. The isolated mitochondria respire with pyruvate + malate, succinate, and with NADH and NADPH in high rates and well coupled to oxidative phosphorylation. Three phosphorylation steps are involved in the oxidation of pyruvate and two in the oxidation of succinate, NADH and NADPH. Rotenone, antimycin and KCN inhibit the electron flow at the known steps. The cytochrome composition pattern is characterized by a particularly high content of cytochrome c. Evidence is given for the existence of two NADH-dehydrogenases for the oxidation of exogenous and endogenous NADH with different localizations on the inner mitochondrial membrane. On the basis of these properties, mitochondria from Neurospora crassa can be looked upon in analogy to mitochondria from yeast, particularly from Torulopsis utilis.

Quantitative Correlation between the Distribution of Anions and the pH Difference across the Mitochondrial Membrane

Abstract: The factors regulating the distribution of anions between the inner and outer mitochondrial phase have been investigated in the presence of respiratory inhibitors and oligomycin. 1 As the external pH is decreased, the ratio of the intra- to extramitochondrial concentration of added anions increases with acetate, malate and phosphate, and with citrate in the presence of malate. In contrast, the uptake of thiocyanate does not change significantly with the pH. 2 In the pH range used, the log of the anion distribution ratio is proportional to the pH difference across the mitochondrial membrane for acetate, malate and phosphate. 3 The anion distribution ratio is highly sensitive to pH at low external concentration and becomes largely independent of pH at high external concentration. 4 In double reciprocal plots of intra- against extramitochondrial concentration, it was found that the capacity (Am) for the uptake of phosphate, acetate, malate and succinate is independent of pH. The slopes (A1/2/Am) increase with pH due to the increase of the external concentration required for half maximal uptake. 5 The distribution ratio of phosphate and malate is proportional to the relative “free capacity” (α) at all the external pH tested. The dependence of the distribution ratio on the external pH is maximal for α= 1 and nil for α= 0. 6 The following relation holds for the dependence of the slope A1/2/Am on Δ pH: log Am/A1/2=a+bΔ pH. This relation was used to obtain the equation describing the dependence of the anion distribution on the Δ pH and on the capacity. 7 It is concluded that the distribution of anions, such as acetate, phosphate and Krebs cycle intermediates, at equilibrium can be explained essentially as a function of two parameters: (a) the pH difference across the mitochondrial membrane (b) the capacity of the mitochondria for anions.

1.3‐Dipolare Cycloadditionen, LVI. Eine bequeme Synthese von N‐substituierten Pyrrolen aus mesoionischen Oxazolonen und Alkinen

Abstract: 3-Methyl-2.4-diphenyl-oxazolium-5-oxid (2) vereinigt sich bei 0−130° mit Alkinen (Acetylen und Alkylderivate, phenylierte und acylierte Acetylene, Acetylen-carbonsaureester) unter Kohlendioxid-Abgabe zu den Pyrrolen 3, 5–13. Zahlreiche N-Acyl-sek.-aminosauren, bei denen die Isolierung des Oxazolium-5-oxids nicht gelingt, lassen sich in situ an Alkine zu den Pyrrol-Abkommlingen (20–28, 33–36, 38, 39) cycloaddieren, wenn man mit Acetanhydrid in Gegenwart des Dipolarophils behandelt. Die Additionsrichtung wird weniger von den Substituenten als von der Natur des Oxazolium-5-oxid-Rings bestimmt. 1,3-Dipolar Cycloadditions, LVI. A Convenient Synthesis of N-Substituted Pyrroles from Mesoionic Oxazolones and Alkynes 3-Methyl-2,4-diphenyl-oxazolium 5-oxide (2) combines at 0−130° with alkynes (acetylene and 1-alkynes, phenylated and acylated acetylenes, acetylenecarboxylic esters) to give initially adducts which then eliminate carbon dioxide to form the pyrroles 3, 5–13. Numerous N-acyl sec-amino acids which do not allow the isolation of oxazolium 5-oxides on anhydrization, can be utilized for cycloadditions if one treats them with acetic anhydride in the presence of suitable acetylenic dipolarophiles. The pyrroles 20–28, 33–36, 38, 39 have been prepared by this method. The direction of cycloaddition is determined mainly by the nature of the oxazolium 5-oxide ring rather than by the substituents in the 2- and 4-position.

Ein atlas der spaltsinnesorgane von Cupiennius salei keys. Chelicerata (Araneae)

Abstract: To facilitate further physiological investigation, a survey was undertaken of all the slit sense organs to be found on the body of the spider Cupiennius salei We counted and mapped more than 3 000 sensory slits in the cuticle about half of which are combined to small groups of up to 29 slits forming compound or lyriform organs

Influence of temperature on the population dynamics of the rotifer Brachionus calyciflorus pallas

Abstract: Experiments were designed to test the influence of temperature on the life table data of the rotifer Brachionus calyciflorus Pallas. It is examined how well the observed modifications agree with theoretical models, and how they influence the temporal changes of population densities in limited and unlimited laboratory populations. On the basis of the experimental results, the population dynamics of planktonic rotifers in several natural habitats were analysed and interpreted. Laboratory Studies at 15, 20, and 25° C. 1. In individual cultures, the duration of all developmental stages (eggs, juvenils, adults) decreased with increasing temperature (Table 1, Fig. 1). On the other hand, the rate of reproduction was positively correlated with temperature. As a result of this twofold influence of temperature, the mean number of offspring per female shows an optimum at 20° C. 2. Unlimited populations which grew exponentially were characterised by a stable age distribution. Within the temperature range under study, the intrinsic rate of natural increase of unlimited populations rose with increasing temperature. 3. In populations limited by food supply, the mean population densities as well as the type and the intensity of oscillations was determined (Table 4, Figs. 2-5). Egg ratios and proportions of immature animals were also determined. Highest mean population densities occured at low temperatures, highest maximum densities at high temperatures. The latter fact is the result of stronger oscillations at higher temperatures: at 15° C oscillations were damped, at 20° C permanent or just increasing (no extinction within 60 days), at 25° C clearly increasing (extinction within 30 days). Amplitude and frequence of the oscillations were positively correlated with temperature. 4. The optima for the population growth and abundance were apparently not at the same temperature (Table 4). 5. The mictic rate, measured as the proportion of sexual females in the population, was relatively small; in limited populations it was larger than in unlimited populations. Temperature had a positive influence at high population densities. Test of Population Models. 1. Using life table data of individuals, theoretical predictions about the growth rate and the age structure of populations during exponential growth have been made by several authors. It is shown that at all temperatures the predictive power of the well known demographic model of Lotka is about as good as that of a recent model by Edmondson (Table 2). It is suggested that both models give adequate causal descriptions of exponential growth inspite of their manifold and different simplifications. As a consequence it is concluded that the observed influences of temperature on exponential growth are the result of direct influences of temperature on the life table data. 2. When mean population densities were estimated by theoretical calculations of energy balance, a rather good agreement with the empirical data was found. 3. Determination of the animal's food efficiencies on the basis of the observed production of biomass suggest that the coefficient of efficiency is significantly larger at 15° C (37%) than at 20 and 25° C (27 and 28%, resp.). 4. According to Cook and to Ricker, the mean generation length T permits predictions about type and frequency of the oscillations. When T was calculated from the life table data, the predictions about the oscillations were in fairly good agreement with the results on limited populations. The meaning of the parameter T in species with overlapping generations is discussed. Field Observations. During 1967 measurements of temperature and population densities of Brachionus calyciflorus were carried out in 15 artificial basins (0.3-50 m3) and 7 ponds (Figs. 6-8). An analysis of these data gave the following results: 1. During sudden population explosions, the growth rates were, on the average, positively correlated with environmental temperature. The agreement with laboratory data is quite good (Fig. 9). It is concluded, that temperature co-determines this aspect of population dynamics in the field. 2. The largest maxima of population densities were found at 20-28° C. With about 105 individuals/liter they are in the same order of magnitude as the corresponding data of laboratory populations. Average population densities seem to be independent of temperature within the range of 12-28° C; outside this range they appear to decrease (Fig. 10). Average densities in the field were clearly lower (10-102 individuals/liter) than long-term means of population densities in experimental populations (about 104-105 individuals/liter). 3. Fluctuations were stronger at high than at low temperatures. The degree of temperature dependence is about the same in the laboratory and in the field. However, at all temperatures the absolute values were greater in the field than in laboratory populations of the same temperature (Fig. 11). Modifying influences of biotic factors (phytoplankton, competitors, predators) are discussed.

Effect of amiloride on sodium transport in frog skin. II. Sodium transport pool and unidirectional fluxes.

Abstract: The effect of Amiloride on several parameters of sodium transport was investigated on the isolated frog skin. Amiloride at a concentration of 10−4 M/l decreased the sodium concentration in the sodium transport pool from 8.9 meq/kg cell water to 3.7 meq/kg cell water. No effect was observed on the intracellular sodium which is exchangeable from the corium side. Short circuit current and unidirectional sodium influx were diminished to the same extent whilst the unidirectional sodium efflux was not affected. In contrast to the short circuit current, which reaches a new steady state value within seconds, the unidirectional sodium influx reaches its new steady state with a half-time of 3.3 min. From the difference in the time courses of the decreases of short circuit current and unidirectional sodium influx, an amount of sodium could be calculated which agreed well with the directly measured fall in the sodium transport pool.

The isolation and crystallization of yeast and rabbit liver triose phosphate isomerase and a comparative characterization with the rabbit muscle enzyme.

Abstract: Triose phosphate isomerase was isolated from brewer's yeast and rabbit liver and was obtained in crystalline form. Chemical, physical and kinetic properties were compared to rabbit muscle triose phosphate isomerase. 1 The molecular weight of all three enzymes is in the range of 56000 to 60000. In dodecyl sulfate or as modified maleylated protein, the enzymes dissociate into two polypeptide chains each having a molecular weight in the range of 24000 to 29000. 2 The rabbit muscle and liver enzymes appear to be indistinguishable in terms of their amino acid composition, electrophoretic mobility, kinetic properties, inhibition sensitivity, pH optimum, molecular weight and N-terminal amino acid (alanine). 3 The yeast enzyme, on the other hand, was found different in the following respects; it has a several fold lower content of sulfur amino acids, is highly resistant to inactivation through photooxidation as well as sulfhydryl and alkylating agents. Furthermore, it contains different N-terminal amino acids (valine and alanine) and has kinetic properties differing from those of the rabbit enzymes. 4 The crystalline liver and muscle enzymes could be resolved into three distinct electrophoretic forms in starch and polyacrylamide gels. The possible interpretation of the multiple forms in terms of hybrids or conformers is discussed.

Fluorometric assay of histamine in tissues and body fluids: Choice of the purification procedure and identification in the nanogram range

Abstract: Several procedures for the isolation of histamine from tissues and body fluids were examined For the fluorometric assay of histamine concentrations higher than 1 μg/g tissue or ml blood the extraction into n-butanol as well as the cation-exchange chromatography on Dowex 50W-X8 proved suitable The determination of histamine in whole blood of dogs gave valid results only after chromatography on Dowex 50, in human plasma and gastric juice only after the combined application of both purification methods Histamine was identified by thin-layer chromatography on cellulose, by inactivation in the presence of purified diamine oxidase from pig kidney and purified histamine methyltransferase from guinea-pig brain, by the biological activities and by the fluorescence spectra of the condensation product between histamine and o-phthaldialdehyde Histamine concentrations in tissues and body fluids of man and some laboratory animals are reported

Postsynaptic potentials from a single monopolar neuron of the ganglion opticum I of the blowfly Calliphora

Abstract: Hyperpolarizing potentials were recorded from second order monopolar neurons of the ganglion opticum I of Calliphora by means of glass microcapillaries. The eye was stimulated with a spotlike light source. Potentials were recorded in relation to the intensity of the light stimulus. The recording site was identified by marking the cell with a dye and by localizing the tip of the electrode.

Untersuchungen über die lichtabhängige Carotinoidsynthese

Abstract: The purpose of these studies was to find which steps in the biosynthetic pathway of carotenoids in Fusarium are under photoregulation. After separation by column chromatography ζ-carotene, neurosporene, γ-carotene, torulene, neurosporaxanthin and lycopene were identified from their absorption spectra in visible light and by co-chromatography tests with carotenoids from other organisms. No other carotenoids were detected. These components were each present in trace amounts (0.5–2 μg/g dry weight) in stricly dark grown cultures. During incubation of the mycelium in buffered glucose solutions in darkness these carotenoids accumulated slowly but linearly with time.

Die Lokalisation endogener Peroxydase in der Glandula parotis der Ratte

Abstract: Die Lokalisation endogener Peroxydase wurde in der Glandula parotis der Ratte mit der Methode von Graham und Karnovsky (1966) untersucht Lichtmikroskopisch ist das Reaktionsprodukt im basalen Cytoplasma, in den Sekretgranula und, nach Pilocarpinreizung, in den Lumina der interzellularen Sekretkapillaren, der Drusenendstucke und der Schaltstucke nachweisbar Der Speichel enthalt eine Peroxydase, die durch Hitze (100°) und durch KCN und 3-Amino-1,2,4-Triazol hemmbar ist Der Speichel zeigt bei 415 mμ eine Schulter im Absorptionsspectrum, die nach Komplexbildung mit H2O2 um 15 mμ nach rechts verschoben wird Elektronenmikroskopisoh last sich das Reaktionsprodukt der Peroxydase in allen Cisternen des rauhen endoplasmatischen Reticulums, einschlieslich der perinuclearen Cisterne, in glattwandigen Blaschen zwischen rauhem endoplasmatischen Reticulum und Golgi-Membranstapeln, in den kondensierenden Vacuolen und in allen Sekretgranula nachweisen Die Cisternen des Golgi-Apparates enthalten selten Reaktionsprodukt In der Glandula parotis der Ratte sind vorwiegend die kondensierenden Vacuolen, in geringerem Mase auch die Cisternen des Golgi-Apparates, an der Segregierung und Kondensierung von Peroxydase beteiligt

[Formation of maxima in the absorption spectrum of carotenoids in the region around 370 nm; consequences for the interpretation of certain action spectra].

Abstract: 1. Most carotenoids show a 3-peak-absorption curve in the visible spectral region in polar solutions. The addition of a definite quantity of H2O to such solutions (ethanol, methanol, aceton, isopropanol) changes the absorption curve of these pigments in a characteristic manner. A new peak appears in the uv region of the spectrum (e.g.in the case of lutein at 370 nm); simultaneously the 3-peak fine structure of the visible spectrum diminishes and completely disappears after further addition of H2O. Such changes are observed especially in the case of lutein and zeaxanthin, but also in the case of neoxanthin, violaxanthin and lycopene (of the carotenoids analyzed). During thermic excitation (45° C) the uv-peak in the carotenoid spectrum disappears and the normal 3-peak curve is restored; upon cooling the uv-peak appears again. The variation of the carotenoid spectrum and the formation of a maximum in the uv-region are possibly caused by an aggregation of the pigment molecules with participation of H2O molecules. This formation of polymers obviously leads to an alteration in the distribution of electrons in the chromophore system of the carotenoid molecule and thereby to a change of the light absorption. 2. Water-soluble carotenoid complexes isolated from spinach chloroplasts show a strong light absorption in the uv-region and a one-peak absorption curve in the visible blue. After transfer of the complex to polar solutions a characteristic 3-peak carotenoid curve appears in the blue region of the spectrum; concomitantly the maximum in the uv disappears. That means that carotenoids which are bound to membranes or particles in the intact cell may have a 4-peak absorption curve similar to that of pigments which are dissolved in the water-containing alcohols mentioned above. It is conceivable that those carotenoids which do not form uv peaks in the dissolved state are able to do so under conditions under which carotenoids are bound to membranes or particles. 3. The similarity of some action spectra to certain 4-peak, carotenoid spectra is striking. This is true particularly for the action spectrum of the first positive curvature of Avena coleoptile (Fig. 10).

Darstellung und Eigenschaften mesoionischer Oxazolone

Abstract: Die Synthese und die spektralen Eigenschaften sydnon-analoger 3-Methyl-2.4-diaryl-oxazolium-5-oxide (2, 16–21) werden beschrieben. Die Thermolyse von 2 fuhrt zu einem tetra-substituierten Allen, das vielleicht durch Dimerisation eines mit 2 valenztautomeren Ketens (28) und Kohlendioxid-Abspaltung gebildet wird. Bei der Offnung des Oxazolium-oxid-Ringes mit Verbindungen HX greift das Nucleophil an der Carbonylgruppe an. Auch uber den Verlauf der Autoxydation von 2 werden Aufschlusse erzielt. Preparation and Properties of Mesoionic Oxazolones Synthesis and spectral properties of 3-methyl-2,4-diaryloxazolium 5-oxides (2, 16–21) are described. The thermolysis of 2 affords a tetrasubstituted allene; possibly this is the result of a dimerization of the ketene 28 which is a valence tautomer of 2, and elimination of carbon dioxide. In the ring opening of oxazolium 5-oxides with compounds HX the nucleophile attacks the carbonyl group. Also the course of autoxidation of 2 was investigated.

The factors determining temporal variation in Brachionus calyciflorus pallas (rotatoria)

Abstract: 1. Die Temporalvariation von Brachionus calyciflorus betrifft vor allem ein Paar Posterolateraldornen (PL), die in ihrer Ausbildung von vollst\:andigem Fehlen bis zu K\:orperl\:ange variieren k\:onnen. Die Bildung dieser Dornen wird durch Hunger, tiefe Temperatur und einen Stoff hervorgerufen, den das r\:auberische R\:adertier Asplanchna ins Medium abgibt. Diese drei Faktoren wurden quantitativ vergleichend auf Unterschiede in der Art ihrer Wirksamkeit und auf ihre Bedeutung f\:ur die Variation im Freiland untersucht. 2. Es besteht eine positive Korrelation zwischen der L\:ange der PL und derjenigen der anderen Dornen, die stets vorhanden sind (Abb. 1). Diese anderen Dornen variieren auch noch bei Fehlen der PL, und zwar in gleichem Sinne (Tabelle 2). 3. Hunger und tiefe Temperatur k\:onnen nur kurze PL induzieren, zur Ausbildung langer PL ist der Asplanchna-Stoff notwendig (Abb. 2). Die Effekte der drei Faktoren k\:onnen sich \:uberlagern. Hohe Temperatur scheint dabei hemmend auf die Dornenbildung einzuwirken. Die Art der Inkubation hat keinen erkennbaren Einflu\sB auf die Variation der Reaktion (Abb. 3 und 4); auch bei maximaler Reaktion ist die Streubreite nicht verringert. 4. Es gibt keine deutliche Tradierung des Variationstyps: bei allen drei Faktoren manifestiert sich die nahezu volle Reaktion auf einen induzierenden Reiz in der n\:achsten Generation (Abb. 5). 5. Die Temperatur hat einen Einflu\sB auf die K\:orpergr\:o\sBe: je tiefer die Temperatur ist, desto gr\:o\sBer sind die Tiere. Dieser Temperatureinflu\sB besteht aus einer pr\:a- und einer postnatalen Komponente (Abb. 6 und 7). 6. Die Determination der Dornenl\:ange erfolgt in allen F\:allen vor der Geburt (vgl. Abb. 5). Die dorneninduzierenden Faktoren bestimmen die Proportionen der Neonaten, nach der Geburt erfolgt das Dornenwachstum negativ allometrisch mit einer konstanten Allometrierate k=0,54, die von der Art der Dorneninduktion, der Gr\:o\sBe der Dornenanlage und den Aufzuchtbedingungen unabh\:angig ist (Tabelle 4 und Abb. 9). 7. Mit Hilfe der Allometriebeziehung wird ein Dornenindex ID definiert, der von der K\:orpergr\:o\sBe der Tiere unabh\:angig ist. Mit ihm k\:onnen die Dornenausbildungen von Populationen verglichen werden, auch wenn diese unterschiedliche Altersstruktur besitzen. Ebenso sind auf diese Weise die verschiedenen Alters- (bzw. Gr\:o\sBen-) Klassen einer Stichprobe bez\:uglich ihrer Dornenausbildung miteinander vergleichbar. Unterschiede in den Dornenindices verschiedener Altersklassen einer Stichprobe weisen darauf hin, da\sB ein dorneninduzierender Faktor (wie etwa der Asplanchna-Stoff) Schwankungen unterworfen war (Abb. 10). Auf diese Weise kann man aufgrund einer einzigen Planktonprobe Aussagen \:uber die Vorgeschichte der dorneninduzierenden Faktoren in den letzten Tagen und Wochen machen (Abb. 11 und 12). 8. Es wurde ein reproduzierbarer Test auf die dorneninduzierende Aktivit\:at eines Mediums ausgearbeitet. Mit Hilfe deses Testes lie\sB sich eine relative Einheit der Asplanchna-Stoffmenge (as) definieren. Die pro Volumen-und Zeiteinheit gebildete Stoffmenge ist der Asplanchnen-Dichte proportional und h\:angt von der Temperatur ab (im Bereich von 10\2-25\dg C: Q10=4). Ein Asplanchna produziert z.B. bei 20\dg C in 25 sec die Stoffmenge, die in 1 ml gerade erkennbare Dornenbildung bewirkt. Entsprechende Werte werden f\:ur 10, 15 und 25\dg C angegeben (Tabelle 6). Der Stoff zerf\:allt jedoch exponentiell (Abb. 14a). Diese nat\:urliche Stoffzersetzung ist ebenfalls temperaturabh\:angig (Halbwertszeit je nach Temperatur 1\2-3 Tage, Abb. 14b). Jeder Asplanchnen-Dichte kann theoretisch eine Gleichgewichtskonzentration an Stoff zugeordnet werden, die sich aus Daten der Produktion und des Zerfalls berechnen l\:a\sBt (Tabelle 6). In Populationsversuchen wie im Freiland stellten sich jedoch die theoretisch errechneten Stoffkonzentrationen nicht ein, m\:oglicherweise weil die Brachionus den Stoff inkorporieren. Eine pragmatische Korrektur der theoretischen Asplanchnastoff-Bilanz (keine Akkumulation \:uber 24 Std hinaus) ergab gute \:Ubereinstimmung zwischen den erwarteten und den beobachteten Dornenindices (in Experimental-und Freilandpopulationen). 9. Ein quantitativer Vergleich der Effektivit\:at der drei dorneninduzierenden Faktoren (Abb. 17) ergab, da\sB lange Dornen (mittl. ID>0,3) weder durch tiefe Temperatur noch durch Hunger induziert werden k\:onnen, sondern allein durch die Asplanchna-Substanz hervorgerufen werden. 10. Auch im Freiland ist der Asplanchna-Stoff das wichtigste induzierende Agens. Labortests zeigen, da\sB Wasser aus Teichen, in denen Asplanchnen vorkommen, dorneninduzierende Aktivit\:at besitzen (Tabelle 7). Dies gilt f\:ur Asplanchna sieboldi (s. 1.) und f\:ur A. priodonta. Die Dornenindices der Neonaten zeigen in ihrem zeitlichen Verlauf eine gute Korrelation mit der Asplanchnen-Dichte (Abb. 20\2-22), die der Adulten zeigen eine Phasenverschiebung, die dem Alter der Tiere entspricht. Verschwinden die Asplanchnen aus dem Biotop, so gehen die Dornenindices mit einer zeitlichen Verz\:ogerung von einigen Tagen ebenfalls zur\:uck. Der Einflus der Temperatur ist im Freiland schwacher als im Labor (Abb. 23). Die mogliche Wirksamkeit unbekannter Faktoren im Freiland wird diskutiert. 11. Mittels Labortests lie\sBen sich Unterschiede in der Reaktionsnorm zweier St\:amme von verschiedenen Fundorten nachweisen (Abb. 2). Diese betreffen (unabh\:angig von der Art des Induktionsfaktors) die mittleren Dornenindices, mit denen die Tiere auf bestimmte Induktionsreize reagieren. 12. Es werden denkbare Mechanismen der Dornenbildung besprochen und m\:ogliche Unterschiede in der physiologischen Wirkungsweise der drei dorneninduzierenden Faktoren diskutiert. Einige Aspekte, die die Funktion der zyklomorphen Dornenbildung betreffen, werden angedeutet.

Kinetic Evidence for Reactive Intermediates

Abstract: Spectroscopic methods have recently been developed that allow the direct detection of reactive intermediates under favorable circumstances. The most general and reliable method, however, is still the indirect one, which makes use of the priciple of kinetic competition; this method is based on the freedom of the intermediate to choose between several reaction possibilities. The following discussion is addressed less to the specialist in reaction mechanisms than to the outsider who wishes to obtain some idea of the value and limitations of the kinetic method.

The ultrastructure of cellulose from wood. Part 2. Problems of the isolation of cellulose.

Abstract: During the delignification of wood several processes overlap one another. One of these is the penetration of the wood samples by the delignifying solution. Penetration tests under different conditions show that there is almost no difference in the penetration depth of wood samples penetrated by diffusion only and of wood samples treated with pressure. In both cases the pits are closed during the flow of fluids. Vacuum treated samples show better penetration and most of the pits in these samples remain open. The distribution of fluids within the cell walls takes place in the intercellular spaces, in small openings in the compound middle lamella and in the secondary wall 1 as well as in very fine pores in the secondary wall 2. The penetration of a wood sample is greatly facilitated if the sample is mechanically injured. A slowly proceeding delignification with ethylene sulphite shows that the delignification obviously starts in the S 1 layer and proceeds from there towards the compound middle lamella and the S 2 layer. In the first stages of lignin removal the compound middle lamella is also attacked, the attack beginning at the border of the pit chambers.