Electrophysiology of trichobothria in orb-weaving spiders (Agelenidae,Araneae)

Summary Trichobothria of the house spidersTegenaria atrica (C.L. Koch) andTegenaria derhami (Scopoli) were stimulated by linear deflection of the hair from its resting position to one side. The pulse response of the receptor cell was analyzed. At angular deflection velocities of 10^–21 deg/ms the receptor begins to discharge at an angle of 3 degrees. While the mean pulse rate remains constant during deflections of 10^–210^–1deg/ms the pulse train may be interrupted by repeated breaks. Discharge continues when the hair is bent proximally beyond the bothrium edge. When the hair is bent distally and touches the bothrium edge, however, discharge ceases. Responsible for this phenomenon seems to be an asymmetry of hair suspension. — Repeated deflection leads to logarithmically ascending latency curves and logarithmically falling curves of the pulse numbers. The function coefficients depend on velocities and repetition rates of the deflections. The adaptational effect is heightened by preceding stationary deflection in the direction of the dynamical stimulus. The mean pulse rate as a function of hair deflection velocity increases logarithmically. The mean pulse rate as a function of hair movement direction obeys a cosine law, provided that a given velocity and a definite deflection angle are used.Supported by grants of the Deutsche Forschungsgemeinschaft given to Prof. Dr. P. Görner in the field of the Schwerpunktprogramm RezeptorphysiologieThe present paper is part of a doctoral thesis. My thanks are due to Prof. Dr. P. G6rner for the theme, many valuable discussions and his constant readiness to help.     

Theoretical studies on the necessary number of components in mixtures

Summary Theoretical studies on the optimal numbers of components in mixtures (for example multiclonal varieties or mixtures of lines) have been performed according to phenotypic yield stability (measured by the parameter variance). For each component i, i = 1, 2,..., n, a parameter u_i with 0 u_i 1 has been introduced reflecting the different survival and yielding ability of the components. For the stochastic analysis the mean of each u_i is denoted by u ₁ and its variance by _i ² For the character total yield the phenotypic variance V can be explicitly expressed dependent on 1) the number n of components in the mixture, 2) the mean of the _i ² 3) the variance of the _i ² 4) the ratio and 5) the ratio _i ² /² where denotes the mean of the u _i and _u ² is the variance of the u _j. According to the dependence of the phenotypic stability on these factors some conclusions can be easily derived from this V-formula. Furthermore, two different approaches for a calculation of necessary or optimal numbers of components using the phenotypic variance V are discussed: A. Determination of optimal numbers in the sense that a continued increase of the number of components brings about no further significant effect according to stability. B. A reduction of b % of the number of components but nevertheless an unchanged stability can be realized by an increase of the mean of the u _i by 1% (with and _u ² assumed to be unchanged). Numerical results on n (from A) and 1 (from B) are given. Computing the coefficient of variation v for the character total yield and solving for the number n of components one obtains an explicit expression for n dependent on v and the factors 2.-5. mentioned above. In the special case of equal variances, _i ² = _o ² for each i, the number n depends on v, x = (₀/)² and y = (_u/)². Detailed numerical results for n = n (v, x, y) are given. For x 1 and y 1 one obtains n = 9, 20 and 79 for v = 0.30, 0.20 and 0.10, respectively while for x 1 and arbitrary y-values the results are n = 11, 24 and 95.This publication is an extended version of a lecture given at the 1984-EUCARPIA meeting (Section Biometrics in Plant Breeding) in Stuttgart-Hohenheim (Federal Republic of Germany)     

Soret spectroscopic and molecular graphic analysis of human semi-beta-hemoglobin formation

The interaction of heme-free (^o) and heme-containing (^h) chains of human hemoglobin has been monitored in 0.1 M potassium phosphate buffer, pH 7 or 8, at [5°C. Soret zero and first-derivative spectra were consistent with a uniform association reaction. Stopped-flow investigations demonstrated association rates on the order of 10⁷ M^–1 s^–1. This was 100-fold more rapid than the reported rate of combination of ^h and ^h proteins. This encounter-like rate of semi--hemoglobin (^oh) formation was increased by raising the pH from 7 to 8. pH change is known to affect the spatial arrangement of AB—GH helical entities. Molecular graphic analysis of modeled ^o protein superimposed over native ^h protein revealed an apo Mb-like structure with well-defined AB—GH segments. Repositioning of these core helical segments, resulting in increased conformational freedom of the ₁₁ interface, was apparently responsible for the enhanced association properties of the ^o protein.     

A method for the investigation of those transformations under which the visual recognition of a given object is invariant

An experiment is described which shows in operation the program set out in Foster (1972a) for the investigation of the invariance transformations of visual recognition. The concern in the present study is with the Lie group of rotations SO(2), and a certain centrally located foveal Landolt ring. By presenting to the visual system this Landolt ring and a rotated image in rapid succession, one attempted to induce a specified rotation-type phi-motion. Two subjects were employed. Both reported the existence of the required type of phi-motion for rotations ₀ of the Landolt ring about the visual axis with -2/72/7. By appealing to the basic Proposition 2 of Foster (1972 a), the conclusion is reached that the visual system appears capable of effecting upon a certain centrally located foveal annulus the local 1-parameter group of rotations about the visual axis ₀, [–2/7,2/7].     

Effects of UV-B on motility and photoorientation in the cyanobacterium,Phormidium uncinatum

UV-B irradiation has a detrimental effect on the survival of populations of the filamentous cyanobacterium, Phormidium uncinatum, at levels slightly higher than those currently measured at the surface of the earth. The organisms are not damaged or killed by UV-B radiation at 300 nm of 200 Wm^-2 for up to 20 h; but slightly increased levels of UV-B irradiation (2 h of 200 Wm^-2 at 300 nm) drastically impair motility, phototactic orientation and photophobic responses. These photosynthetic organisms require a narrow light intensity range for growth so that any decrease in their ability to actively search for and move into areas of favorable light conditions is bound to affect the survival of a population. The fluorescence yield of both phycobilins and chlorophyll is not altered even after 20 h of UV-B irradiation (200 Wm^-2 at 270 nm) indicating that UV-B at that dose does not affect the photosynthetic apparatus. The organisms are killed either by too bright intensities which bleach the photosynthetic pigments or by the lack of energy when they are unable to avoid moving into dark areas.     

The effect of monoterpenes on astaxanthin production by a mutant ofPhaffia rhodozyma

Summary The total pigment and astaxanthin content ofPhaffia rhodozyma increased with increasing concentrations -pinene up to 500 l -pinene/l. Above this concentration the total pigment and astaxanthin content as well as the biomass production decreased. The addition of 500 l -pinene/l increased the total pigment content from 1652 g/g to 2201 g/g and the astaxanthin content from 1554 g/g to 1883 g/g. A sharp decrease in maximum specific growth rate occurred above 150 l -pinene/l.     

Amplification of phleomycin induced death and DNA breakdown by caffeine in Escherichia coli

Summary Caffeine enhanced the degradation of DNA to acid soluble fragments in cultures of Escherichia coli exposed to Phleomycin (2 g/ml). Enhancement was particularly striking with stationary phase cultures, which normally exhibit negligible DNA breakdown when treated with 2 g/ml of Phleomycin. There is little DNA breakdown or death in UVR strains treated with phleomycin (2 g/ml) during exponential growth but when caffeine was present as well as Phleomycin, the kinetics of DNA breakdown and the amounts of DNA degraded were identical in all cultures tested including those of UVR, EXR, B/r type and B strains and equal to the maximum rate observed (with an EXR strain) in the absence of caffeine (ca. 1.7 % per min). High concentrations of Phleomycin (10 g/ml) had the same effect as the caffeine+Phleomycin (2 g/ml) combination and produced a uniform pattern of DNA breakdown in all strains tested. Caffeine did not seem to increase permeability of the bacterial coat. Given to the cells before exposure to Phleomycin it was ineffective in enhancing DNA breakdown. On the other hand, exposure of the bacteria to Phleomycin for a period of 40 min at 37° followed by caffeine was as effective as adding the two drugs together.Caffeine increased the efficiency of Phleomycin as an antibiotic for both growing and stationary phase cultures of e. coli B. It is suggested that caffeine aids the cooperative denaturation of DNA initiated by the attachment of Phleomycin molecules to thymine bases. This would allow single strand-specific endonucleases to attack the DNA and initiate DNA breakdown and cell death.This paper is dedicated to charlotte Auerbach on the occasion of her official retirement.     

Laser kinetic spectroscopy studies of the bimolecular oxygenation of alpha- and beta-subunits within the R-state of human hemoglobin

Bimolecular oxygenation of tri-liganded R-state human hemoglobin (HbA) is described by bi-exponential kinetics with association rate constants k = 27.2 ± 1.3 (M·sec)^-1 and k = 62.9 ± 1.6 (M·sec)^-1. Both the observed processes have been assigned to the bimolecular oxygenation of - and -subunits of the native tetrameric protein by molecular oxygen. The quantum yields of photodissociation within the completely oxygenated R-state HbA are = 0.0120 ± 0.0017 and = 0.044 ± 0.005 for - and -subunits, respectively. The oxygenation reactions of isolated ^PCMB- and ^PCMB-hemoglobin chains are described by mono-exponential kinetics with the association rate constants k = 44 ± 2 (M·sec)^-1 and k = 51 ± 1 (M·sec)^-1, respectively. The quantum yields of photodissociation of isolated ^PCMB- and ^PCMB-chains (0.056 ± 0.006 and 0.065 ± 0.006, respectively) are greater than that observed for appropriate subunits within the R-state of oxygenated HbA.     

Ultrastruktur und Bildung von Poren im Endothel von porösen und geschlossenen Kapillaren

Zusammenfassung An einer Reihe von normalen und pathologisch veränderten Organen wird die Porenstruktur, Porenbildung und Porenrückbildung elektronenmikroskopisch untersucht. Die Endothelpore ist eine Diskontinuität in der Endothelwand mit einem sehr konstanten Durchmesser von 500 Å. Das Diaphragma ist nur mit der äußeren Membranlamelle am Porenrand verbunden. Diaphragmalose Poren sind etwas größer (Ø650 Å), zeigen einen glatten Porenrand und kommen besonders in verdichteten Endothelteilen vor. Frustrane Poren münden blind in Vakuolen oder liegen in porösen Endothelfalten im Gefäßlumen. Die eigentliche Bildung der Poren geschieht immer in abgeflachten ( 800 Å) Endothelteilen. Die vorbereitende Abflachung geht jedoch in den verschiedenen Endothelzonen (Periksryon, dicker Endothelwand, Cytoplasmainseln) unterschiedliche Wege. Alle diese Vorgänge stellen Vesikulation in besonderer Lage und mit besonderer Fusionsrichtung der Vesikel dar. Wegen dieser Unterschiede wird die Endothelwand in 4 Zonen eingeteilt: Perikaryon; dicke, porenlose Wandteile mit cytoplasmatischen Vesikeln; dünne, porenhaltige Teile ohne Zellorganellen; dicke Cytoplasmainseln, die die porösen Wandteile voneinander trennen. Der Vorgang der Porenrückbildung bleibt unklar. Vielleicht besteht er in der Faltung des Endothels, die zu porösen Vakuolen führt. Die Porenbildung verändert die Endotheloberfläche nicht, kann aber das Cytoplasmavolumen vermindern. Der Aufbau des Diaphragmas sowie der Mechanismus und die auslösenden Faktoren der Porenbildung werden diskutiert.

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Summary Ultrastructure, formation and disappearance of endothelial pores was studied electron microscopically in several normal or experimentally changed organs. Pores being discontinuies in the endothelial wall have a very constant diameter of 500 Å. The diaphragm at the margin of the pore is in contact with only the outer lamella of the unit membrane. Pores without a diaphragm being somewhat larger (Ø 650 Å) show a smoother margin and are to be found in endothelia with dense cytoplasm. Frustrated pores form blind openings in vacuoles or are situated in porous endothelial folds within the vessel lumen. Pores alway are formed in flattened parts of endothelium ( 800 Å). In thick capillary walls the endothelium previously is flattened by vesiculation, which differs in different zones of the wall (Perikaryon, thick continuous endothelium, and cytoplasmic islands in porous capillaries) in location and direction of vesicle fusion. Because of these differences the endothelial wall is divided in 4 zones: Perikaryon; thick parts without pores containing cytoplasmic vesicles etc.; flattened, porous parts containing no cytoplasmic organelles; thick cytoplasmic islands which separate porous parts. The process removing pores is not clear. Perhaps they are removed by folding of the endothelial surface and formation porous vacuoles. Formation of pores dosn't enlarge or reduce the surface, but may reduce the cytoplasmic volume of endothelium. The nature of diaphragm as well as the mechanism and releasing factors of the formation of pores are discussed.

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Mit Unterstützung durch die Deutsche Forschungsgemeinschaft     

Transient state characteristics of adaptation to changes in light conditions for the cyanobacterium Oscillatoria agardhii

Transitions in growth irradiance level from 92 to 7 Em^-2 s^-1 and vice versa caused changes in the pigment contents and photosynthesis of Oscillatoria agardhii. The changes in chlorophyll a and C-phycocyanin contents during the transition from high to low irradiance (HL) were reflected in photosynthetic parameters. In the LH transition light utilization efficiencies of the cells changed faster than pigment contents. This appeared to be related to the lowering of light utilization efficiencies of photosynthesis. As a possible explanation it was hypothesized that excess photosynthate production led to feed back inhibition of photosynthesis. Time-scales of changes in the maximal rate of O₂ evolution were discussed as changes in the number of reaction centers of photosystem II in relation to photosynthetic electron transport. Parameters that were subject to change during irradiance transitions obeyed first order kinetics, but hysteresis occurred when comparing HL with LH transients. Interpretation of first order kinetic analysis was discussed in terms of adaptive response vs changes in growth rate.Non-standard abbreviations Chla chlorophyll a - CPC C-phycocyanin - PS II photosystem II - PS I photosystem I - RC II reaction center of photosystem II - P photosynthetic O₂-evolution - I irradiance, Em^-2 s^-1 - light utilization efficiency of cells, mmol O₂·mg dry wt^-1·h^-1/Em^-2 s^-1 - light utilization efficiency of photosynthetic apparatus, mol O₂·mol Chla ^-1·h^-1/Em^-2 s^-1 - P_max maximal rate of O₂ evolution by cells, mol O₂·mg dry wt^-1·h^-1 - P_max maximal rate of O₂ evolution by photosynthetic apparatus, mol O₂·mol·Chla ^-1·h^-1 - LL low light, E m^-2 s^-1 - HL high light, E m^-2 s^-1 - LH low to high light transition - HL high to low light transition - k specific rate of adaptation, h^-1 - specific growth rate, h^-1 - Q pool size of cell constituent, mol·mg dry wt^-1 - q net synthesis rate of cell constituent, mol·mg dry wt^-1·h^-1     

Cholinesterases and cell proliferation in “nonstratified” and “stratified” cell aggregates from chicken retina and tectum

Summary Dissociated single cells from chicken retina or tectum kept in rotation-mediated cell culture aggregate, proliferate and establish a certain degree of histotypical cellto-cell relationships (sorting out), but these systems never form highly laminated aggregates (nonstratified R- and T-aggregates). In contrast, a mixture of retinal plus pigment epithelial cells forms highly stratified aggregates (RPE-aggregates, see Vollmer et al. 1984). The present comparative study of stratified and nonstratified aggregates enables us to investigate the process of cell proliferation uncoupled from that of tissue stratification. Here we try to relate these two basic neurogenetic processes with patterns of expression of cholinesterases (AChE, BChE) during formation of both types of aggregates.During early aggregate formation, in both stratified and nonstratified aggregates an increased butyrylcholinesterase activity is observed close to mitotically active cells. Quantitatively both phenomena show their maxima after 2–3 days in culture. In contrast, AChE-expression in all systems increases with incubation time. In nonproliferative areas, in the center of RPE-aggregates, the formation of plexiform layers is characterized initially by weak BChE and then strong AChE-activity. These areas correspond with the inner (IPL) and outer (OPL) plexiform layers of the retina in vivo. Although by sucrose gradient centrifugation we find that the 6S- and the fiber-associated 11S-molecules of AChE are present in all types of aggregates, during the culture period the ratio of 11S/6S-forms increases only in RPE-aggregates, which again indicates the advanced degree of differentiation within these aggregates.It is thus demonstrated that cholinesterases first correlate with neuronal cell proliferation and later with stratification, which indicates functions of both enzymes during both developmental periods.Abbreviations AChE acetylcholinesterase - BChE butyrylcholinesterase - iso-OMPA specific inhibitor of BChE - BW 284C51 specific inhibitor of AChE - IPL inner plexiform layer - OPL outer plexiform layer     

Growth,acetylene reduction activity and localization of nitrogenase in relation to vesicle formation in Frankia strains Cc1.17 and Cp1.2

A comparative study was conducted on the effect of NH₄Cl on growth, vesicle formation and formation of nitrogenase of Frankia strains Cc1.17 and Cp1.2, derived from root nodules of Colletia cruciata and Comptonia peregrina, respectively. On a medium without combined nitrogen (P-N), both strains formed spherical cells, called vesicles, like many other Frankia strains. Data are presented on the number of vesicles per mg protein, after cultivation in media with sodium propionate as C-source without combined nitrogen (P-N) or with 0.2 g NH₄Cl/l (P+N). Strain Cp1.2 as may other Frankia strains, showed on P+N medium a very strong reduction of vesicle formation of 99% relative to the number of vesicles formed on P-N medium, after 11 days growth. However, in strain Cc11.17 this reduction was only 70%. The occurence of relatively large numbers of vesicles in P+N media has not yet been reported for other Frankia strains. No acetylene reduction activity was found in NH ₄ ⁺ -grown cells. The regulation of induction of nitrogenase in Frankia by NH₄Cl was tested by immuno-gelectrophoresis using antisera against nitrogenase of Rhizobium leguminosarum PRE. The component I of the enzyme showed crossreactivity while the component II had only a weak crossreaction. The experiments indicated that no nitrogenase was detectable in the NH ₄ ⁺ -grown cells. For the localization of nitrogenase, relative amounts of the enzyme were compared in whole cells and vesicle-enriched fractions. Western blots showed a significant enrichment of nitrogenase in the vesicle fractions, which indicated that most of the nitrogenase was localized in the vesicle.     

Comparative residual toxicities of pesticides to the predator Agistemus industani (Acari: Stigmaeidae) on citrus in Florida

Residual toxicities of registered and selected experimental pesticides used on citrus against Agistemus industani Gonzalez (Acari: Stigmaeidae) were compared. Pesticides considered highly toxic to A. industani were: abamectin 0.15 EC at 731ml/ha+FC 435-66 petroleum oil at 46.8l/ha, pyridaben 75WP at 469g/ha, ethion 4EC at 7.01l/ha+FC 435-66 petroleum oil at 46.8l/ha, propargite 6.55 EC at 3.51l/ha, chlorfenapyr 2SC at 1.46l/ha applied alone or in combination with FC 435-66 petroleum oil at 46.8l/ha, sulphur 80DF at 16.81kg/ha, dicofol 4EC at 7.01l/ha, fenbutatin oxide 50WP at 2.24kg/ha, benomyl 50WP at 2.24kg/ha, benomyl 50WP at 1.68kg/ha+ferbam 76 GF at 5.60kg/ha, ferbam 76GF at 11.21kg/ha, neem oil 90EC at 46.8l/ha, and copper hydroxide DF (40% metallic copper) at 4.48kg metallic copper/ha+FC 435-66 petroleum oil at 46.8l/ha. Pesticides that were moderately to slightly toxic included: copper sulphate 98% at 4.48kg metallic copper/ha+FC 435-66 petroleum oil at 46.8l/ha, fenbuconazole 2F at 280ml/ha+FC 435-66 petroleum oil at 46.8l/ha, FC 435-66 petroleum oil applied alone at 46.8l/ha or 23.4l/ha, and diflubenzuron 25WP at 1.40kg/ha. Pesticides that were non-toxic included: fenbuconazole 2F at 585ml/ha, malathion 57EC at 5.85l/ha, FC 435-66 petroleum oil at 46.8l/ha, carbaryl 80S at 3.36kg/ha, chlorpyrifos 4EC at 4.68l/ha, and formetanate 92SP at 1.12kg/ha. Understanding the toxic effects of field weathered pesticides against key predacious mite species is important for effective IPM. The results of this study provide a comparison of direct and indirect toxic effects of various pesticides to A. industani under field conditions.     

Male swarms at landmarks and scramble competition polygyny inPolistes gallicus (Hymenoptera: Vespidae)

At the end of summer, males of Polistes gallicusfly in swarms around vertical landmarks and land in clusters on their favorite perches, where they drag their legs and abdomen. Here males occasionally crowd around a perched female; they make no effort to defend an exclusive mating territory but instead attempt to copulate by displacing rivals from the female. In this work we describe this spatial-nuptial system, which entails site fidelity without territoriality, unisexual swarms, common patrol routes, collective sexual approaches, and scramble competition polygyny. Mating success is evaluated in relation to the familiarity with flight paths (routine patrollers versus newcomers), to the type of sexual approach (single males versus in- group males), and, in the laboratory, to the individual activity level.     

Unique sequences for two HLA-DRB1 genes expressed on distinct DRw6 haplotypes

We have used restriction fragment length polymorphism (RFLP) analysis and DNA sequencing to characterize two distinct DRB1 alleles expressed on DRw52 and DQw7-associated haplotypes but not readily defined by conventional DR serology. These two haplotypes, designated HLA-D HAG and PEV, react variably with DRw13(w6), DRw14(w6), and the more broad DR 3+6 antisera. Analysis of RFLP revealed that HLA-D HAG and PEV are associated with different DRw52 variants, and that HAG is indistinguishable from DRw18(3) haplotypes. Sequencing of the HAG and PEV DRB1 genes showed each to represent novel alleles. Nevertheless, these sequences show similarities with the other alleles of the DR5, w6, and w8 family. HAG (DRB1*1303) appears to have arisen either from two recombinational events involving at least three DRB1 sequences (DRB1*1101, DRB1*0803, DRB1*0401) or from a single recombinational event together with multiple point mutational events. PEV appears to represent a DRB1*1301-1302/DRB1*1101 recombinant allele, with recombination having occured in the region of bases 175 – 198. The results of this study suggest that the DRw52 family haplotypes is derived from a relatively restricted number of ancestral sequences, with diversity among DRB1 alleles within this family arising through gene conversion or recombination events.     

Monoclonal antibody specific for α2→8-linked oligo deaminated neuraminic acid (KDN) sequences in glycoproteins. Preparation and characterization of a monoclonal antibody and its application in immunohistochemistry

Two particular types of sialoglycoproteins have been detected in fish: polysialoglycoproteins containing 28-linked polysialic acid (8Neu5Gc2) _n present in unfertilized Salmonidae fish eggs, and glycoproteins bearing oligo/polymers of deaminated neuraminic acids (KDN) found in the vitelline envelope of the eggs and ovarian fluid. We report the preparation and characterization of a monoclonal antibody specifically recognizing oligo/polymers of KDN sequences in glycoproteins and its application in immunohistochemistry. Fusion of spleen cells from a BALB/c mouse immunized with a KDN-rich glycoprotein (KDN-gp) containing (8KDN2) _n 6(KDN23Gal13GlNAc13) GalNAc1 residues, with mouse myeloma cells yielded a hybrid cell line producing a monoclonal antibody that bound to KDN-gp, but not to KDN-gp depleted of KDN residues. The specificity of the monoclonal antibody, designated mAb.kdn8kdn, was determined by an enzyme-linked immunosorbent assay using KDN-gp samples that varied in KDN content. These antigens were prepared by the selective removal of KDN residues from the native KDN-gp. The mAb.kdn8kdn reacted most strongly with the intact KDN-gp and less strongly with KDN-gp samples containing decreased numbers of KDN residues. The mAb.kdn8kdn was shown specifically to recognize the 28-linked oligo/polyKDN sequences, (8KDN2) _n , and to be able to distinguish specifically (8KDN2) _n chains from (8Neu5Ac2) _n and (8Neu5Gc2) _n chains. The antibody was used successfully for the immunohistochemical detection of reactive KDN epitopes in sections of paraffin embedded rat pancreas. Several controls verified the specificity of the immunohistochemical staining, thus providing the first demonstration of (8KDN2) _n sequences in a mammalian tissue. The mAb.kdn8kdn can now be used to search further for glycoconjugates containing (8KDN2) _n chains and will facilitate studies on their biosynthesis, intracellular localization and function.     

Synthetic substrate analogues for UDP-GlcNAc: Manα1-6R β(1-2)-N-acetylglucosaminyltransferase II. Substrate specificity and inhibitors for the enzyme

UDP-GlcNAc: Man1-6R (1-2)-N-acetylglucosaminyltransferase II (GlcNAc-T II; EC 2.4.1.143) is a key enzyme in the synthesis of complexN-glycans. We have tested a series of synthetic analogues of the substrate Man1-6(GlcNAc1-2Man1-3)Man-O-octyl as substrates and inhibitors for rat liver GlcNAc-T II. The enzyme attachesN-acetylglucosamine in 1-2 linkage to the 2-OH of the Man1-6 residue. The 2-deoxy analogue is a competitive inhibitor (K _i=0.13mm). The 2-O-methyl compound does not bind to the enzyme presumably due to steric hindrance. The 3-, 4- and 6-OH groups are not essential for binding or catalysis since the 3-, 4- and 6-deoxy and -O-methyl derivatives are all good substrates. Increasing the size of the substituent at the 3-position to pentyl and substituted pentyl groups causes competitive inhibition (K _i=1.0–2.5mm). We have taken advantage of this effect to synthesize two potentially irreversible GlcNAc-T II inhibitors containing a photolabile 3-O-(4,4-azo)pentyl group and a 3-O-(5-iodoacetamido)pentyl group respectively. The data indicate that none of the hydroxyls of the Man1-6 residue are essential for binding although the 2- and 3-OH face the catalytic site of the enzyme. The 4-OH group of the Man-O-octyl residue is not essential for binding or catalysis since the 4-deoxy derivative is a good substrate; the 4-O-methyl derivative does not bind. This contrasts with GlcNAc-T I which cannot bind to the 4-deoxy-Man- substrate analogue. The data are compatible with our previous observations that a bisectingN-acetylglucosamine at the 4-OH position prevents both GlcNAc-T I and GlcNAc-T II catalysis. However, in the case of GlcNAc-T II, the bisectingN-acetylglucosamine prevents binding due to steric hindrance rather than to removal of an essential OH group. The 3-OH of the Man1-3 is an essential group for GlcNAc-T II since the 3-deoxy derivative does not bind to the enzyme. The trisaccharide GlcNAc1-2Man1-3Man-O-octyl is a good inhibitor (K _i=0.9mm). The above data together with previous studies indicate that binding of the GlcNAc1-2Man1-3Man- arm of the branched substrate to the enzyme is essential for catalysis. Abbreviations: GlcNAc-T I, UDP-GlcNAc:Man1-3R (1-2)-N-acetylglucosaminyltransferase I (EC 2.4.1.101); GlcNAc-T II, UDP-GlcNAc:Man1-6R (1-2)-N-acetylglucosaminyltransferase II (EC 2.4.1.143); MES, 2-(N-morpholino)ethane sulfonic acid monohydrate.     

Long Range Force between Pre-Replication Complexes (Pre-RC) in DNA Controls Replication and Cell Cycle Progression

A nonstationary interaction, that controls DNA replication and the cell cycle, is derived from a manybody physics model in a chemically open T cell. The model predicts a long range force F()=-(/2) (1-)(2-) between the pre-replication complexes (pre-RCs) bound by DNA, =/N being the relative displacement of preRCs, the number of pre-RCs, N the threshold for initiation, and the compressibility modulus in thelattice of pre-RCs which behaves like an elastically braced string. Initiation of DNA replication is induced by a switch of sign of F(), from attraction (-)and assembly in the G ₁ phase (0 < < N), to repulsion (+) and partialdisassembly in the S phase (N < < 2N), with release of licensing factors from the pre-RCs, thus explaining prevention of re-replication. Replication is terminated by a switch of sign of F at = 2N, when all primed replicons are duplicated once, and F(0)=0 corresponds to a resting cell in absence of driving force at = 0. The switch of sign of force at = N also explains the dynamic instability in growing microtubules (MTs), as well as switch in the interleukin-2 (IL2) interaction with its receptor in late G ₁, at the restriction point. Shape, slope and scale of the response curves derived agree well with experimental data from dividing T cells and polymerizing MTs, the variable length of which is due to anonlinear dependence of the growth amplitude on the initial concentrations of tubulin dimers and guanosine-tri-phosphate (GTP).     

Contextualizing Images in Dreams and Daydreams

A contextualizing image (CI) is a powerful central image of a dream which appears to contextualize (provide a picture-context for) the dreamer's emotion. For instance, dreamers who have experienced any serious traumatic event sometimes dream, I was overwhelmed by a tidal wave. This appears to picture their feeling of terror and/or vulnerability.A scoring system for CIs is examined here and is applied to dreams and daydreams supplied by 40 students. Two raters scoring dreams on a blind basis showed good inter-rater reliability. Recent dreams were shown to have more as well as more intense CIs than recent daydreams; likewise, dreams that stand out had more intense CIs than daydreams that stand out. Students with thin boundaries had more and more intense CIs than students with thick boundaries in their recent dreams and nightmare, but not so clearly in dreams and nightmares that stand out. The emotions judged as contextualized by the powerful images tended towards fear/terror and helplessness/vulnerability in dreams (especially in dreams that stand out) whereas emotions contextualized by images in daydreams showed a wide range with no clusters.     

Inhibitory ca2+-control of movement of beads coated withphysarum myosin along actin-cables inChara internodal cells

Summary The actin-activated ATPase activityPhysarum myosin was shown to be inhibited of M levels of Ca²⁺. To determine if Ca²⁺ regulates ATP-dependent movement ofPhysarum myosin on actin, latex beads coated withPhysarum myosin were introduced intoChara cells by intracellular perfusion. In perfusion solution containing EGTA, the beads moved along the parallel arrays ofChara actin filaments at a rate of 1.0–1.8 m/sec; however, in perfusion solution containing Ca²⁺, the rate reduced to 0.0–0.7 m/sec. The movement of beads coated with scallop myosin, whose actin-activated ATPase activity is activated by Ca²⁺, was observed only in the perfusion solution containing Ca²⁺, indicating that myosin is responsible for the inhibitory effect of Ca²⁺ onPhysarum myosin movement. The involvement of this myosin-linked regulation in the inhibitory effect of Ca²⁺ on the cytoplasmic streaming observed inChara internodal cell andPhysarum plasmodium was discussed.Abbreviations ATP adenosine 5-triphosphate - DTT dithiothreitol - EDTA ethylenediaminetetraacetic acid - EGTA ethyleneglycolbis(-aminoethylether) N,N,N,N-tetraacetic acid - PIPES piperazine-N,N-bis(2-ethanesulfonic acid)