Showing papers by "University of Zurich published in 1969"

Gaussian elimination is not optimal

Abstract: t. Below we will give an algorithm which computes the coefficients of the product of two square matrices A and B of order n from the coefficients of A and B with tess than 4 . 7 n l°g7 arithmetical operations (all logarithms in this paper are for base 2, thus tog 7 ~ 2.8; the usual method requires approximately 2n 3 arithmetical operations). The algorithm induces algorithms for invert ing a matr ix of order n, solving a system of n linear equations in n unknowns, comput ing a determinant of order n etc. all requiring less than const n l°g 7 arithmetical operations. This fact should be compared with the result of KLYUYEV and KOKOVKINSHCHERBAK [1 ] tha t Gaussian elimination for solving a system of l inearequations is optimal if one restricts oneself to operations upon rows and columns as a whole. We also note tha t WlNOGRAD [21 modifies the usual algorithms for matr ix multiplication and inversion and for solving systems of linear equations, trading roughly half of the multiplications for additions and subtractions. I t is a pleasure to thank D. BRILLINGER for inspiring discussions about the present subject and ST. COOK and B. PARLETT for encouraging me to write this paper. 2. We define algorithms e~, ~ which mult iply matrices of order m2 ~, by induction on k: ~ , 0 is the usual algorithm, for matr ix multiplication (requiring m a multiplications and m 2 ( m t) additions), e~,k already being known, define ~ , ~ +t as follows: If A, B are matrices of order m 2 k ~ to be multiplied, write

Innervation Patterns in the Organ of Corti of the Cat

Abstract: The afferent and efferent nerve supply of the organ of Corti was studied after transsection of the olivo cochlear fibres in the vestibular nerve, the vestibular root, or at the floor of the fourth ventricle. After elimination of the efferent fibres by degeneration, the distribution patterns of the afferent fibres were evaluated with electron and light-microscopy. In the cat, all tunnel crossing radial fibres appeared to belong to the efferent innervation. The afferent fibres to the outer hair cells crossed the tunnel at the bottom as basilar fibres. The majority of afferent neurons ended at the inner hair cells and only a minority were associated with the outer hair cells. After selective transsection of the crossed olivo cochlear fibres, a great number of the efferent endings at the outer hair cells degenerated but also the number of internal spiral fibres seemed to be reduced.

Splitless Injection on Capillary Columns, Part I. The Basic Technique; Steroid Analysis as an Example

Abstract: A very simple procedure for splitless injection on capillary columns is discussed. In contrast to more sophisticated devices recently developed for the same purpose, the method described requires no additional equipment. The advantages of the method which broadens the use of capillary columns are discussed. Steroid analysis serves as an example of the applications

Sequence of the First 175 Nucleotides from the 5′ Terminus of Qβ RNA synthesized in vitro

Abstract: The nucleotide sequence of the 5′ end of bacteriophage Qβ RNA has been determined by a new method involving partial synthesis of the RNA in vitro. Neither of the codons commonly associated with the initiation of protein synthesis (AUG and GUG) was found before position 62. The sequence required for the initiation of synthesis of the coat protein (PuUGGCN) is not within the first 300 nucleotides from the 5′ end. A very stable hydrogen-bonded loop seems to exist close to the 5′ end of the molecule.

Defence, attack, and flight elicited by electrical stimulation of the hypothalamus of the cat.

Abstract: 1. Affective behaviour patterns produced by electrical stimulation of the hypothalamus were studied in unanaesthetized, freely-moving cats. Bipolar stimulation with coaxial electrodes and small cathode was used to elicit defence, attack or flight. The development of these responses was studied by varying stimulation strength. In some experiments a stuffed animal was introduced in order to study the reactions of the cat to changes in the environment during stimulation. 2. The following responses were evoked at threshold intensity: (i) growling reaction; (ii) hissing reaction; (iii) two types of flight — type a preceded by hastily looking to and fro as if in search of an exit, type b preceded by inspection of surroundings, in most cases associated with sniffing. 3. Increasing stimulation 1.5 times threshold often yielded combined patterns. At points yielding the growling reaction a defence response in which growls alternated with hisses was obtained. The points yielding flight type a sometimes yielded hissing followed by flight. Increasing stimulation at hissing points yielded either a defence reaction or the combined effect hissing-flight. 4. The growling reactions were obtained from the tuber region. The hissing responses were obtained from points above the tuber. The flight reactions, type a, were produced from the intermediate zone extending from the level of the preoptic area to the mamillary bodies and type b from the caudo-lateral hypothalamus. 5. The reactions of the cats to a dummy during stimulation varied depending on the type of response which had been evoked in the absence of the dummy. The defence reaction was converted into threatening and striking of the dummy, the combined effects into threatening, striking or biting, culminating in sudden flight. The dummy was ignored during stimulation of points yielding flight type a, but examined by sniffing during stimulation of points yielding flight type b.

Chromosome studies on bone marrow from Chinese hamsters treated with benzodiazepine tranquillizers and cyclophosphamide.

Abstract: Chinese hamsters were treated for two weeks with high doses of chlordiazepoxide hydrochloride, diazepam, and medazepam. Chromosome preparations of bone marrow were made 5–8 h after the last drug application. Single chromatid breaks were found in 0.27% of the cells, an incidence not differing from control values. Cyclophosphamide was used as a known chromosome-breaking control substance in order to test the sensitivity and peculiarities of the bone marrow system. Doses of less than 16 mg/kg produced little chromosome damage whereas after doses of 32 mg/kg the incidence of chromosome aberrations was easily quantitated. The time interval between the last drug application and preparing the bone marrow proved to be of importance: after 10 applications of 64 mg/kg cyclophosphamide in a 14-day course of treatment, the percentage of metaphases with damaged chromosomes dropped from 96% at 6 h after the last medication to 16% at 24 h, 2–5% at 3 days, and to virtually zero after 6 days.

Electrophysiology of the intertectal commissures in the pigeon. II. Inhibitory interaction

Abstract: 1. In pigeons with one retina chronically removed, the tectal response to the stimulation of the contralateral eye was subjected to conditioning stimulation applied to the opposite tectum. The effect on evoked potentials and unitary responses was studied. 2. The response evoked by light flashes was depressed by the conditioning stimulation. In the response evoked by electrical stimulation of the optic nerve, the negative component of the slow wave was depressed by the conditioning stimulation. This depression was abolished by section of the tectal and posterior commissures. 3. Among 222 units activated by optic nerve stimulation, the conditioning tectal stimulation suppressed, delayed or reduced the discharge of 49 units (22%). The tectal stimulation did not evoke unitary discharge by itself nor had a facilitatory effect. The time course of the inhibition was from 5–70 msec with a maximal effect at 20–30 msec. The inhibited units had a latency longer than 4 msec and did not follow a stimulation frequency higher than I/sec. No unit could be inhibited in the superficial layers of the tectum, where the evoked response is negative, but 25% of the units were inhibited in the middle and deep layers, where the response is positive-negative or positive.

Homing in the ant Cataglyphis bicolor.

Abstract: Cataglyphis bicolor, an ant widely distributed in North Africa and the Near East, orient to the sun as well as to visual patterns of the environment. These two mechanisms can be separated. Foraging ants (hunters) orient to terrestrial cues as long as possible, and only after these have become ineffective do they switch over to the menotactical sun orientation. In the digging individuals, however, the visual knowledge of locality is significantly inferior to that of the hunters. Diggers vary considerably in size, but hunters belong to the largest size group. In addition, the largest and smallest individuals orient differently toward black and white areas and stripe patterns.

Melanin containing organelles in cells of the human gingiva.

Abstract: Biopsies of the marginal gingiva obtained from 21 caucasoid subjects (average age of 25 years) served for the electron microscopic examination of epithelial melanocytes and their organelles. In 60 to 70 per cent of the subjects, melanin producing dendritic melanocytes could be observed within the stratum basale and the suprabasal stratum spinosum. Electron microscopically, 2 types of structurally different melanocytes could be distinguished: inactive, and actively premelanosomes producing and melanin synthesizing cells. The number of premelanosomes and melanosomes per cytoplasmic unit area of melanocyte projections increased towards their peripheral termination. The developmental stages of possibly two structurally different premelanosomes are described to be comparable to those of the human skin. Fully melanized ovoid melanosomes were measured to be 0.27±0.06 micron long and 0.10±0.04 micron wide. Striated bars inside premelanosomes are suggested to represent a tightly coiled spiral possibly reflecting the molecular arrangement of tyrosinase. The findings are discussed with reference to the knowledge of melanocytes, premelanosomes and melanosomes in human skin, hair bulbs and melanomatous tissues.

Study of Luminal Coronary Collateral Circulation in the Beating Canine Heart

Abstract: The action of halothane on sinoatrial, ventricular, and Purkinje fibers was studied by means of intracellular microelectrodes. Rabbit atrial fibers were not very sensitive to even high (2%) concentrations of halothane. Sheep Purkinje fibers showed a significant hyperpolarization from 82 mv to 87 mv, a marked shortening of the duration of the action potential from 370 msec to 233 msec, and a diminution of the overshoot from 30 mv to 21 mv under the influence of 1% halothane. The rate of rise was now significantly rchanged with this concentration. In the presence of 2% halothane the resting potential did not differ significantly from the value obtained with 1% halothane. The duration of the action potential and of the refractory period were further diminished to 165 msec and to 109 msec, respectively. The rate of rise was now significantly reduced to 245 v/sec and the overshoot further decreased to 17 mv. Conduction time was increased by about 20% with 1% halothane and more than twofold with 2% halothane. Ventricular fibers of sheep did not show significant changes of the resting potnetial under the influence of 2% halothane. However, the duration of the action potential was markedly shortened from 338 msec to 231 msec, the effective refractory period was significantly reduced from 295 msec to 208 msec, and the overshoot decreased from 21 mv to 11 mv. Possible mechanisms underlying these changes and which may cause arrhythmias are discussed.

Detection of heterozygotes for phenylketonuria by column chromatography and discriminatory analysis.

Abstract: Extract: Phenylalanine (100 mg/kg) was administered orally to 19 parents of patients with phenylketonuria and to 26 control subjects. Concentrations of phenylalanine and tyrosine in plasma were determined by column chromatography before phenylalanine administration and at 1, 2, 3, and 4 hours after loading. The values of two control subjects (C 21 and C 25) and of two parents (P 4 and P 6) were unusually low or high. Excluding subjects C21, C25, P4, and P6, the following calculations of the values after loading were made: Mean and SD of mean of phenylalanine levels at each time: in spite of a significant difference, there was a slight overlap. Sum of the phenylalanine values: significant difference, no overlap. Sum of the phenylalanine/tyrosine ratios: significant difference, no overlap. Using these criteria, control subjects C21 and C25 were considered to be heterozygotes. The values of subject P 4 (father of a known patient) were within the range of the control group; paternity was excluded by blood group analysis. The values of subject P 6 were unusually high and could not be explained satisfactorily. The concentrations of phenylalanine and tyrosine after loading were evaluated by discriminatory analysis. Thus, subjects C 21, C 25, and P 4 were excluded, but values were calculated both including and excluding subject P 6. To compare the different criteria of evaluation, the index of Penrose (discriminatory power = D/s) was calculated. A better separation was obtained with discriminatory analysis than with the sum of the phenylalanine values or of the phenylalanine/tyrosine ratios. The use of column chromatography and evaluation by discriminatory analysis seems to improve the possibilities of detection of heterozygotes for phenylketonuria. Speculation: With discriminatory analysis, the separation of heterozygotes for phenylketonuria from normal subjects was better than with other criteria of evaluation. We believe that this method could be used successfully for determination of heterozygosity in other inborn errors of metabolism with recessive inheritance when several variables are available for each subject examined.

Bestimmung der Chiralität der enantiomeren α-Cyclogeraniumsäuren, α-Cyclogeraniale, α-Jonone, γ-Jonone, α-Carotine, ε-Carotine und verwandter Verbindungen durch chemische Verknüpfungsreaktionen. Vorläufige Mitteilung†

Abstract: Die im Titel genannten enantiomeren Verbindungen sind durch chemische Reaktionen mit Ambrein und Manool verknupft worden, so dass ihre Chiralitat festgelegt ist. Damit ist zum erstenmal die Konfiguration eines chiralen Carotinoidkohlenwasserstoffes bestimmt. Das naturlich vorkommende (+)-α-Jonon hat R-Konfiguration, ebenso das naturliche (+)-α-Carotin.

Rifampicin inhibits focus formation in chick fibroblasts infected with Rous sarcoma virus.

Abstract: The transformation—as manifested by focus formation—of chick fibroblasts infected with Rous sarcoma virus is ten times more strongly suppressed by rifampicin than replication of the virus itself.

Zur Stereochemie der aromatischen CLAISEN‐Umlagerung

Abstract: The possible transition state conformations (chair (S), boat (W), and twist (T), respectively cross (K) forms) and methods for their determination in the thermal ortho-CLAISEN rearrangement of allyl aryl ethers are discussed. Crotyl 3,5-dimethylphenyl ether (11) gives a mixture of 2-(α-methylallyl)-3,5-dimethyl-phenol (12) and 4-crotyl-3,5-dimethyl-phenol (13) on heating in N, N-diethylaniline. Values of 3 and 31 were obtained for the ratio of 12/13 for trans-11 and cis-11, respectively. It therefore follows that both ethers rearrange steroselectively ( > 90%) by the S or W forms of the activated complex. αMethylallyl 6-alkylphenyl ethers rearrange on heating in various solvents to a mixture of trans-and cis-2-crotyl-6-alkyl-phenols. The amount of the cis-phenols in the rearrangement products decreases with the increasing bulk of the 6-alkyl substituent. This result is only obvious if the chair form of the transition state during the rearrangement of these ethers is highly favoured. trans-Crotyl 2,6-dimethylphenyl ether (trans-33) rearranges highly steroselectively (94%) on heating to trans-4-crotyl-2,6-dimethyl-phenol (trans-34). In the case of the corresponding cis ether 33, the rapid cis trans isomerisation of this ether and the cis/trans ratio of the phenol 34 indicate that the reverse rearrangement of the intermediate ortho-dienone to the ether 33 and the further rearrangement to 4-crotyl-2,6-dimethyl-phenol (34) has little stereoselective character.

Fine structure of synapses in central nervous system of insects

Abstract: Die Feinstruktur der Synapsen im Insekten-Neuropil (Formica lugubris Zett.) wurde genauer untersucht. Dabei gelang der Nachweis von axo-axonischen Synapsen sowohl in „Simplex-Form“ als auch in „Dyaden“-Stellung (wie in der Retina der Wirbeltiere). Diese Dyaden sind durch eine T-formige prasynaptische „dense projection“ gekennzeichnet. Die hellen synaptischen Blaschen reagieren positiv auf die Zinkjodid-Osmium-Farbung. Die PTA-Blockfarbung macht die Synapsen im Insekten-Neuropil besonders augenfallig. Zwei extreme Architekturtypen des Neuropils konnten nachgewiesen werden: eine mit vorherrschenden prasynaptischen Endigungen und die andere mit einer Vielzahl postsynaptischer Elemente, welche vereinzelte prasynaptische Endkolben umgeben.

Electrophysiology of the intertectal commissures in the pigeon I. Analysis of the pathways

Abstract: 1. In pigeons with one retina chronically ablated, the intertectal relationship was studied before and after section of the tectal and posterior commissures. Photic stimulation of the eye or electrical stimulation of the optic nerve or tectum and microelectrode recording in the optic tectum were used. 2. The electrical stimulation of one tectum evoked a potential in the contralateral tectum with a latency of 1.2 msec. The tectal and/or posterior commissures were responsible for its transmission. 3. The photic stimulation of one eye or the electrical stimulation of one optic nerve evoked a biphasic potential in the ipsilateral tectum. It appeared first in the middle layers and persisted without reversal through the deep layers of the tectum. Its peak was delayed by 10–16 msec, over the first contralateral response. It diminished or disappeared after section of the tectal and posterior commissures. 4. The results show that a visual input reaching one optic tectum is led to the contralateral tectum through the tectal and/or posterior commissures.

Plasma Renin Activity in Patients with Coarctation of the Aorta

Abstract: In 10 patients with coarctation of the aorta, plasma renin activity was measured after recumbency and orthostatism in peripheral venous blood and, in some cases, in renal venous blood also. In nine of these patients, basic plasma renin values and those obtained under stimulatory conditions lay within normal range, and only in one patient were the values elevated. However, since this patient displayed the lowest gradient of mean arterial blood pressure proximal and distal to the stenosis, it can be regarded as improbable that the elevation in plasma renin activity was caused by the coarctation. Plasma renin activity in the renal venous blood of both kidneys, which was measured in three patients, showed no elevation. On the basis of observations of other authors and of our own studies it can be concluded that the kidneys can contribute to the development of prestenotic hypertension in acute constriction of the aorta in experiments with animals, but in chronic coarctation in animals or in man the humoral or ...

Interaction of defence and flight reactions produced by simultaneous stimulation at two points in the hypothalamus of the cat.

Abstract: 1. The results presented in the present paper are an extension of preceding work devoted to exploration of the hypothalamic defence and flight fields using coaxial electrodes with small cathode. In 33 cats simultaneous stimulation was applied to two points which upon single stimulation had yielded defence, flight, or defence and flight respectively. Results were compared with those produced at either point alone. In 2 cats combined stimulation of a defence and a flight point was carried out with a stuffed cat present. 2. The latencies and rates of the vocal effects associated with defence (growling and hissing), and the latencies of flight (jump from the table) were measured. 3. Simultaneous stimulation of two points which had yielded defence, or of two points which had yielded flight resulted in facilitation (spatial summation) of the effects evoked: a more complete defence response associated with decrease of the latencies and increase in the rates of the vocal effects; decrease of flight latencies and increase of flight impetuosity. 4. Simultaneous stimulation of a defence point which had yielded growling at lower threshold than hissing, and of a point which had yielded flight resulted in facilitation of hissing. Growling and flight were often suppressed; when they occurred, latencies were lengthened and growling rates were increased somewhat. 5. Stimulation of a defence point with a dummy present produces striking (fending off). Simultaneous stimulation of a flight point resulted in facilitation of both hissing and striking. 6. It is concluded that the complex patterns obtained when defence is combined with flight are the result of facilitatory and inhibitory interaction between the elements of the individual patterns.

Thermische Reaktionen im Massenspektrometer Modellreaktionen zur Untersuchung thermischer Umalkylierungen. 11. Mitteilung über das massenspektrometrische Verhalten von Stickstoffverbindungen

Abstract: During the introduction of an organic compound into the mass spectrometer thermal reactions can take place before the ionisation process, thus changing the structure of the compound. On the basis of known experimental results the following reactions, which are independent of electron bombardment are discussed: decarboxylation, dehydration, loss of alcohols, decarbonylation, decomposition of carboxylic esters, retro aldol reaction and similar processes, retro DIELS-ALDER reaction, isomerisation, disproportionation, hydrogenolysis-dehydrogenolysis, transalkylation, dimerisation, and pyrolysis of quaternary nitrogen containing compounds. Finally, the results of novel model reactions concerning thermal transalkylation are discussed.