Showing papers by "Free University of Berlin published in 1982"

Plants as transmission channels for insect vibrational songs

Abstract: The vibrational songs of several species of cydnid bugs and ‘small cicadas’ (leafhoppers and planthoppers) living on various types of plants are recorded by means of laser vibrometry. The recorded vibrational songs are analysed with respect to amplitude, frequency spectrum and structure in the time domain (Figs. 2–5). The emission of vibrational songs from singing insects on plants is simulated. A small magnet is glued to the surface of the plant and moved by means of an electromagnet about one cm away (Fig. 1). The vibrations are recorded by means of laser vibrometry. The propagation velocity of the vibrations increases with the square root of frequency, i.e. in the way expected for bending waves. The mechanical properties of plants ranging from soft bean plants to stiff reeds and maples are measured. The results are used for calculating the theoretical propagation velocities of bending waves. The measured and the calculated values are rather close (Table 1). Although the mechanical properties of the plants studied vary widely, the propagation velocities at a certain frequency are of the same order of magnitude (Table 1). In all the plants studied, only little vibrational energy is lost by friction at frequencies below some kHz. Communication by means of bending waves is possible over distances of some meters. The bending waves are reflected with little loss of energy both from the root and from the top of the plant. The vibration signals may therefore travel up and down the plant several times before decaying completely (Fig. 7). The vibration at a certain spot on the plant depends not only on the distance to and nature of the emitter, but also on the modes of vibration of the plant. The amplitude of vibration does not decrease monotonically with distance from the emitter (Fig. 6). These filtering properties of the plants mean that it is essentially impossible to predict which frequencies in the signals will be amplified or attenuated in the plant at the location of the receiving animal. The vibrational signals recorded from the animals cover wide frequency bandwidths. The signals are therefore well adapted to the filtering properties of the plants, but the signals of the species studied here do not appear to be particularly adapted to specific properties of the host plants. The muscular power needed for communication by means of various types of vibrational signals is calculated. The result of this calculation supports the conclusion that the signals recorded here are carried by means of bending waves. The communication strategies open to small insects are considered. Vibrational signals appear to be an efficient means of communication, but only certain types of signals are suited, because the plants cause a considerable distortion of the signals. One kind of distortion, the dispersive property, may — in theory — be used by the listening animals to obtain information about the direction and distance to the singing animals.

On the Interannual Variability of the Middle Stratosphere during the Northern Winters

Abstract: The variability of the stratospheric winters is investigated. Monthly mean 30-mbar temperatures over the North Pole which are available for a 26-year period, have been grouped according to the phase of the equatorial QBO at the 50-mbar level, following a suggestion of Holton and Tan (1980). It is shown that the winters are \"relatively undisturbed, cold\" with an enhanced tendency for the development of a pronounced \"normal wave 2 pattern\" when the equatorial winds at the 50-mbar level are from the west. Major midwinter warmings seem not to take place in this category, except near the sunspot maxima. In contrast, during the \"easterly\" phase of the equatorial QBO there is a tendency for an enhanced development of height-wave 1 already in early winter, which leads often to the development of a major warming during midwinter and hence to a generally warmer polar

Specific protein-nucleic acid recognition in ribonuclease T1-2'-guanylic acid complex: an X-ray study.

Abstract: RNase T1 is folded into an α-helix of 4.5 turns, covered by a four-strand antiparallel β-sheet. Specific recognition of 2′-guanylic acid arises from hydrogen bonding between main chain peptide groups and the O-6 and N-1–H of guanine, as well as from stacking of Tyr 45 on guanine. At the active site, Glu 58, His 92 and Arg 77 are involved in phosphodiester hydrolysis.

CHAPTER 2 – Humidity Relationships and Water Balance of Ticks∗

Abstract: Publisher Summary This chapter discusses the humidity relationships and water balance of ticks The life cycle of ticks is composed of relatively short parasitic phases during which engorgement takes place and of the extended nonparasitic phases without access to food and liquid This imposes great demands on their water balance mechanisms When a tick sucks blood from its host, it ingests large quantities of water and ions with the blood meal To concentrate the nutrient portion of the blood, and to maintain osmotic and ionic balance, excess water and ions have to be eliminated Various devices contribute to the maintenance of water balance in unfed ticks The distribution of different species of ticks, with regard to environmental humidities, is primarily determined by the degree of their integumental waterproofing Under equilibrium conditions, the amount of water in the body of a tick is related to the level of the environmental humidity; higher ambient humidities correspond with higher body water levels in the tick The vapor uptake systems, found among arthropods, are of independent evolutionary origin In some species, the specialized structures and essential components of the mechanism may have been evolved for the primary purpose of vapor absorption

Anticonvulsants during pregnancy and lactation. Transplacental, maternal and neonatal pharmacokinetics.

Abstract: Few data are available on placental transfer of anticonvulsants during early pregnancy. Nevertheless, it has been demonstrated that at this early stage of gestation, considerable amounts of phenytoin, primidone/phenobarbitone and carbamazepine as well as some of their metabolites are already present in fetal tissues. Potentially reactive metabolites of anticonvulsants can be formed by the fetal liver and accumulate in some organs. At term, most anticonvulsants are present in neonatal plasma in concentrations similar to those in maternal plasma. Valproic acid, on the other hand, can accumulate in fetal blood, for still unknown reasons. Elimination by the neonate is variable and is dependent on several factors, such as clinical state, pre- or perinatal enzyme induction, absorption of the drugs and their plasma protein binding. Neonatal acquisition of anticonvulsants via breast-feeding does not seem to be harmful for the neonate. In the case of phenobarbitone, however, the drug may accumulate in nursing neonates to levels approaching or even exceeding those of their mothers. Significant drug levels can also build up in neonates and infants nursed by carbamazepine- and ethosuximide-treated mothers. This review contains relevant pharmacokinetic data on anticonvulsant drugs widely used during pregnancy and the neonatal period. The differences between pregnant and non-pregnant adults as well as between neonates and older age groups are emphasized. Some pharmacokinetic data are correlated with clinical manifestations, such as seizure frequency, neonatal depression and withdrawal symptoms.

Quantum Mechanics of H‐Atom from Path Integrals

Abstract: The quantum mechanical Coulomb problem in two and three dimensions is solved completely in terms of path integrals. We derive the integral representations for the Green's functions in configuration space and recover the wave functions from factorized residues.

Resistance responses to Phoma lingam of plants regenerated from selected cell and embryogenic cultures of haploid Brassica napus.

Abstract: Resistant plants and plants with reduced susceptibility against the pathogen Phoma lingam could be regenerated from selected callus and embryogenic cultures of haploid rape (Brassica napus) previously treated with mutagens. In the two in vitro selection systems used — absence of fungus growth on the cultures after incubation with parasite spores and resistance to the toxic filtrate — the resistance to the toxin was effective. In addition, some regenerants with increased tolerance were obtained from unselected cultures. Resistance tests on regenerated plants were carried out by inoculation of whole plants in the greenhouse, reproducing as much as possible the infection mechanisms which take place under natural conditions. Preliminary results on resistance of the progeny of single susceptible and tolerant regenerants seem to indicate that the acquired resistances are of a genetic nature.

Temporal performance roles during vocal interactions in nightingales ( Luscinia megarhynchos B.)

Abstract: The temporal patterning of vocal interactions between territorial nightingales (Luscinia megarhynchos B). was investigated during nocturnal dyadic singing. We distinguished three forms of temporal performance roles (Table 1; Fig. 3): inserter (preferred song start 0.5–1.0 s after offset of a neighbour's song), overlapper (preferred song start 0.5–1.0 s after onset of a neighbour's song), and Autonomous bird (no evidence for temporal responses adjusted to the timing of a neighbour's singing; Fig. 4). With the beginning of the daily dawn chorus, mutual temporal adjustment of song performances could no longer be ascertained (Fig. 2). To test the flexibility of song onset timing, we presented subjects with three playback programs (I, II, III) simulating a non-flexible conspecific bird. Sequences of songs recorded from a stranger that shared no song types with the subjects were used; intersong pauses were unaltered in I, lengtened in II, and shortened in III. Results confirmed that the timing of song onset can be influenced by the temporal patterning of auditory stimuli (Table 1; Fig. 5): Inserters and overlappers sang at a slower rate during program II than during program I. During program III, which by accelerated stimulus succession caused frequent overlap of songs, inserters and overlappers interrupted their singing behaviour (Fig. 6). This suggests that overlapping, which results in signal interference, is of some functional significance in vocal interactions.

The nephronophthisis complex. A clinicopathologic study in children.

Abstract: The clinical and morphological findings are described in 27 children with nephronophthisis. Seventeen children were considered as sporadic cases. In 10 familial cases the presumed mode of inheritance was autosomal recessive. The clinical picture was rather uniform: polyuria-polydipsia, hyposthenuria, anemia, growth retardation, and azotemia with progressive renal failure. Six patients presented with tapeto-retinal degeneration. In a further seven children other ocular changes were detected. Two female siblings showed additional non-renal manifestations: mental retardation, pulmonary emphysema, skeletal anomalies, and congenital hepatic fibrosis.

Biological Significance of Sialic Acids

Abstract: Sialic acids are essential constituents of many glycoproteins, glycopeptides and glycolipids. This widespread occurrence in glycoconjugates of different origin indicates that a variety of biological functions should be associated with this sugar. There are vahd indications that siahc acids influence or even determine the recognition of low and high molecular-weight compounds, the action of certain hormones, physicochemical and catalytic properties of enzymes, hemostasis, cellular adhesiveness, antigenicity, transport processes and synaptic transmission. Despite this apparently heterogenous spectrum of biological actions, four main functions—according to the concept of Schauer (1982)—can be attributed to sialic acid: (1) Endowment of glycoconjugates and cellular membranes with a negative charge, (2) Influence on the macromolecular structure of certain glycoproteins, (3) Information transfer, (4) Protection of glycoconjugates and cells from recognition and degradation. This rather physicochemical classification could be of use when starting to elucidate the biological significance of sialoglycoconjugates. Reviews on siahc acids have recently been published by Rosenberg and Schengrund 1976, Neufeld and Ashwell 1980, and Schauer 1982. The aim of this contribution, however, is to emphazise the important role of sialic acids in the occurrence of pathobiochemical alterations found in animals and human beings.

Distributed expert problem treatment as a model for information system analysis and design

Abstract: We discuss the functional analysis and design of a general information provision mechanism. Our basic assumptions are that information provision mechanisms are best considered as a part of a problem management system which includes user, mechanism and knowledge resource, that such mechanisms must necessarily be multi-functional, and that they will include both human and machine components. By analyzing how such a mechanism must operate in order to help the user to treat her/his problem, we identify a number of discrete functions which interact in complex ways. This leads us to discuss a particular approach to the modelling and design of problem treatment situations, distributed problem treatment. This ap proach assumes that problem treatment can be broken down into a number of separate entitites, each of which makes hypotheses about its particular area of responsibility, and com municates these results to the other entities of the mechanism. We demonstrate, by partial example, that the information provisi...

Mass-yield distribution in proton and heavy ion induced target fragmentation processes

Abstract: It is shown that nuclear target fragmentation in proton and heavy ion induced reactions, in particular the following experimental facts concerning the mass-yield distribution can be understood in terms of a semiclassical model:(i) its independence on the mass of the projectile at approximately the same incident energies,(ii) its trend of approaching a limit at higher bombarding energies,(iii) its “U-formed” shape at sufficiently high bombarding energies. Standard methods in statistical theory of chemical equilibrium are used to calculate the mass-yield distribution for medium and heavy target nuclei in high-energy nuclear reactions where the Coulomb interaction between the fragments is taken into account selfconsistently. The result shows: The fact that the decaying rest target nucleus and its fragments are bounded objects of finite size and finite charge have significant influences, especially on the form of the mass-yield distributions.

Isolation and characterization of rabbit anti-m32,2,7G antibodies

Abstract: Antibodies specific for intact 2,2,7-trimethylguanosine (m3 2,2,7G) were induced by immunization of rabbits with a nucleoside-human serum albumen (HSA) conjugate. Competition radioimmunoassay showed that the antibody distinguishes well between intact m3 2,2,7G and its alkali-hydrolysed form (m3 2,2,7G*). Antibody specificity is largely dependent on the presence of all three methyl groups in m3 2,2,7G: none of the less extensively methylated nucleosides m7G, m2G and m2 2,2G is able to compete efficiently with the homologous hapten. Little or no competition was observed with m1G, m1A, m6A, m5U and each of the four unmodified ribonucleosides. Binding studies with nucleoplasmic RNAs from Ehrlich ascites cells suggest that the antibody reacts specifically with the m3 2,2,7G-containing cap structure of the small nuclear U-RNAs (U-snRNAs). Thus the antibody should be a valuable tool for studying the role of the 5'-terminal regions of the U-snRNAs of eucaryotic cells.

Flip-flop hydrogen bonding in a partially disordered system

Abstract: Cyclodextrins have proved useful as model systems for the study of hydrogen bonding1, α-Cyclodextrin (α-CD) crystal-lizes from water as a hexahydrate having well defined hydrogen bonds (O—H…O) in linear and circular arrangements favouring ‘endless’ …O—H…O—H…O—H… chains1–3. The larger β-cyclodextrin (β-CD) forms a crystalline dodecahydrate, β-CD·12H2O in which X-ray localization of the hydroxyl hydrogen atoms is made difficult because 25 of the 45 hydroxyl groups are statistically disordered and water molecules enclosed within the β-CD cavity are distributed over several sites that are not fully occupied4. We have therefore carried out a neutron diffraction study of β-CD at the Oak Ridge high flux isotope reactor to determine whether there is any well defined hydrogen bonding in disordered systems. In β-CD there are 19 hydrogen bonds of the type O—H…H—O. In these bonds, oxygen atoms are in the normal O—H…O distance range5, but two statistically half-occupied H atoms are arranged between them. The fact that the H…H separation of ∼1 A is so short that the two H atoms positions are mutually exclusive suggests an equilibrium between two states: O—H…O⇌O…H—O. Of the two H atoms only one is in hydrogen-bonding contact at a given time; the other one is flipped out to form a hydrogen bond with an adjacent acceptor group and vice versa. Because long hydrogen-bonding chains are involved in a cooperative, concerted motion (domino effect), we have coined the term ‘flip-flop hydrogen bond’. This study demonstrates that hydrogen bonds are opera-tive in disordered systems and display dynamics even in solid state.

Disorder version of the Abelian Higgs model and the order of the superconductive phase transition

Abstract: We transform the Abelian Higgs model in three dimensions (i.e. the Grinzburg-Landau theory) to a disorder field theory. The new fields describe the grand canonical ensemble of vortex lines in the superconductor and take a nonzero expectation in the normal state (signalizing their proliferation). The disorder theory allows for a simple determination of the tricritical point where the second-order phase transition changes to first. This happens for a Grinzburg-Landau parameter (= ratio of penetration depth to coherence length)K 0.8/√2.

Double-blind study on the effect of cigarette smoking on the chromosomes of human peripheral blood lymphocytes in vivo

Abstract: A double-blind study with 170 smokers and 124 non-smokers revealed a doubling of the frequencies of exchange-type aberrations in the peripheral blood lymphocytes of smokers as compared with non-smokers. Smokers (N = 24) had 1 SCE more per metaphase than non-smokers (N = 20), an effect that is significant but low when compared with the effect on structural chromosomal aberrations. These results show that structural chromosomal aberrations are better indicators of the genetical effects of low chronic exposures to mutagens in man than SCEs. The frequencies of micronuclei in 3-day lymphocyte cultures showed no differences in smokers (N = 95) and non-smokers (N = 39). Non-smokers (N = 99) had significantly higher frequencies of 2nd metaphases in 48-h cultures in vitro than smokers (N = 141), indicating an effect of smoking on the stimulation of lymphocytes by PHA in vitro.

Antiepileptic drugs and pregnancy: altered utilization patterns and teratogenesis.

Abstract: Although we have long known that the course of epilepsy can change for the better or worse during pregnancy, the reasons for such changes are not known. Pregnancy does not in itself cause either epileptic seizures or the occurrence of a status epilepticus. Studies have shown that in about one-quarter of women who have had seizures prior to becoming pregnant, seizure frequency increases during pregnancy (Fig. 1). In another quarter of this population seizure frequency decreases during pregnancy, and in about half of the group there is no change (1). More recent prospective studies show somewhat greater variability-ranging from 8 to 46%-although the average is the same for increase in seizure frequency (2-5). A variety of physiological mechanisms and psychological factors have been put forth as possible causes for this increase (Table 1). Experimental findings and clinical evidence have yet to establish a correlation between hormonal or metabolic changes during pregnancy and the number of seizures. There have been no controlled studies on the influence of pregnancy-related psychological problems in women with epilepsy. It has been suggested that ambivalence toward the child or husband and tension and anxiety can lead to loss of sleep or hyperventilation, which can in turn precipitate seizures. Also, psychological problems may result in irregular medication during pregnancy, and the resultant fall in the plasma concentration of antiepileptic drugs may contribute to an increase in seizure frequency. Recent observations have shown that the plasma concentration of antiepileptic drugs tends to fall during pregnancy and to increase during the puerperium (6). No large-scale investigations of ethosuximide and valproate disposition during pregnancy have been made. A decrease in the plasma concentration of the frequently prescribed drugs phenytoin, phenobarbital, and carbamazepine has often been observed (Figs. 2 and 3). However, the extent and the time course of the decrease vary considerably among drugs and individuals, and during different pregnancies in the same individual ( 7 3 ) . Mean values of the plasma concen-

Observed adiabatic corrections to the born-oppenheimer approximation for diatomic molecules with ten valence electrons

Abstract: Using millimeter-wave (mw) spectroscopy pure rotational transitions were measured with very high precision in several vibrational states for many compounds of the group III/VII and IV/VI diatomic molecules. The spectra were fitted to the usual Dunham expansion adopting the normal mass relations for the Ylk except for Y01 in order to combine all data of different isotopes for the same compound. For Y01 the atomic mass relation given by Watson is used which introduces phenomenological parameters Δ01A, Δ01B for molecule AB taking the adiabatic and nonadiabatic corrections to the Born-Oppenheimer approximation into account. All observed spectra are well described by such a procedure. From these calculations the correction parameters Δ01A, Δ01B were obtained with an accuracy of ≈ 10% or better. Using known values of the rotational gJ factor and of the electric dipole moment the nonadiabatic part was calculated and with this result the adiabatic part was evaluated from Δ01 for each atom. The adiabatic correction does not change very much for one specific atom by varying the chemical counterpart and in general it is less than 30% of the total correction for this class of molecules. The only exceptions are InI and the Tl and Pb compounds for which the adiabatic corrections are obtained ten to hundred times larger than those of the other compounds. No explanation is known for this behavior in the published literature.

Energy Balance of Mixed-Valent Eu Ions

Abstract: The interconfigurational mixing and excitation energies, $\ensuremath{\Gamma}$ and ${E}_{x}$, of the Eu ions in ${\mathrm{EuCu}}_{2}$${\mathrm{Si}}_{2}$ are determined experimentally as functions of pressure and temperature. $\ensuremath{\Gamma}$ seems to depend only on ${E}_{x}$, and the strongly nonlinear $\ensuremath{\Gamma}({E}_{x})$ reflects the intra-ionic multiplet splittings and degeneracies of $4{f}^{6}$. The observed pressure and temperature dependence of ${E}_{x}$ is analyzed self-consistently in terms of contributions from mixing, elastic, and conduction-electron energies, which arise from the temperature and pressure dependence of the valence.