Adoptions expérimentales de larves entre des fourmis de genres différents (II):Myrmica laevinodis Nylander etAnergates atratulus Schenck

Résumé Nous avons fait élever des larves d'Anergates atratulus par des ouvrières deMyrmica laevinodis à 22°C. Pour y parvenir, il n'est pas utile de faire hivernerensemble les larves d'Anergates et les ouvrières deMyrmica. La présence de larves autochtones n'empêche pas lesMyrmica d'élever des larves d'Anergates. Dans toutes les expériences lesMyrmica ont été soumises au fridavant de recevoir des larves d'Anergates. Aucune reine deMyrmica n'a été utilisée dans ces expériences.Sur les 64 larves d'Anergates que nous avons utilisées, 38 se sont transformées en imagos. C'est au début de l'adoption et au moment des métamorphoses que périrent la plupart des 26Anergates perdus. Les femelles vécurent en général 2 ou 3 jours et cherchèrent très tôt à quitter le nid natal. Les mâles vécurent 2 à 3 semaines.

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Summary Larvae ofAnergates atratulus were experimentally reared by workers ofMyrmica laevinodis, at 22°C. An overwintering of both larvae ofAnergates and workers ofMyrmica is not necessary for the success of that experiment. The presence of larvae ofMyrmica does not keep theMyrmica from rearing larvae ofAnergates. The workers ofMyrmica have been cooled, in all the experiments, before receiving larvae ofAnergates. No queen ofMyrmica have been used in that experiments.38 of the 64 larvae ofAnergates used became imagos. Most of the 26 lostAnergates died at the beginning of the adoption and during the metamorphosis. The females lived generally 2 or 3 days and tried, very early, to leave their native nest. The males lived 2 or 3 weeks.

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Anergates atratulus Myrmica laevinodis, 22 . bmecme Anergates Myrmica. Myrmica Anergates. Myrmica Anergates. Myrmica . 64 Anergates , 38 . 26 Anergates 2 3 . 2 3 .

     

Steady state changes in mitochondrial electrical potential and proton gradient in perfused liver from rats fed a high fat diet

In this work the protonmotive force (p), as well as the subcellular distribution of malate, ATP, and ADP were determined in perfused liver from rats fed a low fat or high fat diet, using density gradient fractionation in non acqueous solvents.Rats fed a high fat diet, despite an enhanced hepatic oxygen consumption, exhibit similar p to that found in rats fed a low fat diet, but when we consider the two components of p, we find a significant decrease in mitochondrial/cytosolic pH difference (pH_m) and a significant increase in mitochondrial membrane potential (_m) in rats fed a high fat diet compared to rats fed a low fat diet, which tend to compensate each other. In rats fed a high fat diet the concentration ratio of malate and ATP/ADP does not reflect the changes in pH_m and _m, which represent the respective driving force for their transport.The findings are in line with an increase in substrate supply to the respiratory chain which is, however, accompanied by a higher energy turnover in livers from HFD rats. By this way the liver could contribute to the lack of weight gain from the high caloric intake in HFD rats.     

Intracellular sites of the synthesis of sweet potato mitochondrial F1ATPase subunits

Summary Five subunits (-, -, -, - and -subunits) of the six -and -subunits) in the F₁ portion (F₁ATPase) of sweet potato (Ipomoea batatas) mitochondrial adenosine triphosphatase were isolated by an electrophoretic method. The - and -subunits were not distinguishable immunologically but showed completely different tryptic peptide maps, indicating that they were different molecular species. In vitro protein synthesis with isolated sweet potato root mitochondria produced only the -subunit when analyzed with anti-sweet potato F₁ATPase antibody reacting with all the subunits except the -subunit. Sweet potato root poly(A)⁺RNA directed the synthesis of six polypeptides which were immunoprecipitated by the antibody: two of them immunologically related to the -subunit and the others to the - and -subunits. We conclude that the -subunit of the F₁ATPase is synthesized only in the mitochondria and the -, - and -subunits are in the cytoplasm.     

Preparation of a series of sulfated tetrasaccharides from shark cartilage chondroitin sulfate D using testicular hyaluronidase and structure determination by 500 MHz1H NMR spectroscopy

Six tetrasaccharide fractions were isolated from shark cartilage chondroitin sulfate D by gel filtration chromatography followed by HPLC on an amine-bound silica column after exhaustive digestion with testicular hyaluronidase. Their structures were determined unambiguously by one- and two-dimensional 500 MHz¹H NMR spectroscopy in conjunction with HPLC analysis of chondroitinase AC-II digests of the tetrasaccharides. One fraction was found to contain two tetrasaccharide components. All the seven tetrasaccharides shared the common core structure GlcA1-3GalNAc1-4GlcA1-3GalNAc with various sulfation profiles. Four were disulfated comprising of two monosulfated disaccharide units GlcA1-3GalNAc(4-sulfate) and/or GlcA1-3GalNAc(6-sulfate), whereas the other three were hitherto unreported trisulfated tetrasaccharides containing a disulfated disaccharide unit GlcA(2-sulfate)1-3GalNAc(6-sulfate) and a monosulfated disaccharide unit GlcA1-3GalNAc(4-or 6-sulfate). These sulfated tetrasaccharides were demonstrated to serve as appropriate acceptor substrates for serum -N-acetylgalactosaminyltransferase, indicating their usefulness as authentic oligosaccharide substrates or probes for the glycobiology of sulfated glycosaminoglycans.Abbreviations NFU National formulary unit - COSY correlation spectroscopy - HOHAHA homonuclear Hartmann-Hahn - 1D or 2D one- or two-dimensional - IdoA l-iduronic acid - GlcA d-gluco-4-enepyranosyluronic acid - Di-0S GlcA1-3GalNAc - Di-4S GlcA1-3GalNAc(4-sulfate) - Di-4S GlcA1-3GalNAc(4-sulfate) - Di-6S GlcA1-3GalNAc(6-sulfate) - Di-6S GlcA1-3GalNAc(6-sulfate) - Di-diS _d GlcA(2-sulfate)1-3GalNAc(6-sulfate) - Di-diS_E GlcA1-3GalNAc(4, 6-disulfate) - U G, U, 2S, 4S, and 6S represent GlcA, GalNAc, GlcA, 2-O-sulfate, 4-O-sulfate, and 6-O-sulfate, respectively     

Hexahydroindanone derivatives of steroids formed by Rhodococcus equi

Summary A mutant strain of Rhodococcus equi accumulates three metabolites from the androst-4-ene-3,17-dione or from its degradation intermediate, 3a-H-4(3'-propionic acid)-7a-methylhexahydro-1,5-indanedione (MEPHIP). These three metabolites are: 3a-H-4a(3'-propionic acid)-5-hydroxy-7a-methylhexahydro-1-indanone--lactone (HIL); 3a-H-4(3'-trans acrylic acid)-5-hydroxy-7a-methylhexahydro-1-indanone (^2'-5-hydroxy-MEPHIP); and 3a-H-4(3'-hydroxy-3'-propionic acid)-5-hydroxy-7a-methylhexahydro-1-indanone (3'-hydroxy-HIL). The behaviour of this mutant allows us to propose a pathway for degradation of the intermediates, methylperhydroindanone propionates. However, during this degradation, the side-chain propionate was eliminated by a-oxidation mechanism. Offprint requests to: A. Miclo     

Contrasting leaf and ‘ecosystem’ CO2 and H2O exchange in Avena fatua monoculture: Growth at ambient and elevated CO2

Elevated CO₂ (ambient + 35 Pa) increased shoot dry mass production in Avena fatua by 68% at maturity. This increase in shoot biomass was paralleled by an 81% increase in average net CO₂ uptake (A) per unit of leaf area and a 65% increase in average A at the ecosystem level per unit of ground area. Elevated CO₂ also increased ecosystem A per unit of biomass. However, the products of total leaf area and light-saturated leaf A divided by the ground surface area over time appeared to lie on a single response curve for both CO₂ treatments. The approximate slope of the response suggests that the integrated light saturated capacity for leaf photosynthesis is 10-fold greater than the ecosystem rate. Ecosystem respiration (night) per unit of ground area, which includes soil and plant respiration, ranged from-20 (at day 19) to-18 (at day 40) mol m^-2 s^-1 for both elevated and ambient CO₂ Avena. Ecosystem below-ground respiration at the time of seedling emergence was -10 mol m^-2 s^-1, while that occuring after shoot removal at the termination of the experiment ranged from -5 to-6 mol m^-2 s^-1. Hence, no significant differences between elevated and ambient CO₂ treatments were found in any respiration measure on a ground area basis, though ecosystem respiration on a shoot biomass basis was clearly reduced by elevated CO₂. Significant differences existed between leaf and ecosystem water flux. In general, leaf transpiration (E) decreased over the course of the experiment, possibly in response to leaf aging, while ecosystem rates of evapotranspiration (ET) remained constant, probably because falling leaf rates were offset by an increasing total leaf biomass. Transpiration was lower in plants grown at elevated CO₂, though variation was high because of variability in leaf age and ambient light conditions and differences were not significant. In contrast, ecosystem evapotranspiration (ET) was significantly decreased by elevated CO₂ on 5 out of 8 measurement dates. Photosynthetic water use efficiencies (A/E at the leaf level, A/ET at the ecosystem level) were increased by elevated CO₂. Increases were due to both increased A at leaf and ecosystem level and decreased leaf E and ecosystem ET.     

Inverse relationship between poly (ADP-ribose) polymerase activity and 2′,5′-oligoadenylates core level in estrogen-treated immature rat

Summary The activity of poly (ADP-ribose) polymerase (ADPRP) and the content of 2,5-oligodenylates core (2,5A_n; n = 2,3 and 4) were measured in homogenates of the uterus and of the liver of immature rats immediately before (time 0) or at different times after injection of estradiol-valerate. ADPRP activity increased gradualy, starting 6 hours after estrogen injection, for about 4 days. Instead, the content of 2,5 A_n decreased by about 50% within 6 hours, and thereafter more slowly for 4 days to about 20% of starting values. Estrogen increased ADPRP activity and decreased 2,5A_n concentration also in the kidney and in the cardiac muscle of the same animals, but not in the skeletal muscle, where neither of the two parameters was affected. Injection of vehicle only (sesame oil) had no effect on ADPRP activity nor on 2,5A_n content of immature rat tissues.     

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].     

Holling's “hungry mantid” model for the invertebrate functional response considered as a Markov process. Part I: The full model and some of its limits

In this paper we give an analytical reformulation of Holling's (1966) simulation model for invertebrate predatory behaviour. To this end we represent a population of predators as a frequency distribution over a space of (physiological) states. The functional response of a predator is calculated from the (stable) equilibrium distribution of its state as a function of prey density.Starting from the general model various other models are obtained by limit processes, some of them new and some of them old. The more interesting of which will be studied in further papers in this series.List of Notation a rate constant of digestion - b maximum of rate constant of prey encounter in the mantid - b maximum pursuit duration in the mantid (_p(0)) - c satiation threshold for search - c satiation threshold for pursuit in the mantid: c=c(b-D_s/v)/b - D _m maximum sighting distance - D _p pursuit distance - D _s strike distance - expectation operator - f, f ₀ rate of change of satiation during search - f ₁ rate of change of satiation during prey handling - F functional response: number of prey eaten per unit of time by one predator - g rate constant of effective prey encounter in the gobbler and sucker - g₀ rate constant of prey encounter - g₁ probability of no prey loss from pursuit - g₂ probability of no prey escaping during pursuit - H Holling secretary correction factor in the sucker: fraction of the time spent searching - k _R density of R - k_T probability density of maximum prey handling time - K probability that maximum prey handling time is _e, i.e. pursuit duration is zero - K _R distribution function of R - N number of prey caught - p (marginal) density of S - p₀ density of S in search - p₁ simultaneous density of S and T - P probability - p ₁ marginal density of S in handling prey - q probability of strike success - R ratio of realized to maximum sighting distance - s, S satiation - satiation axis - t time - handling time axis - u eating speed - U homogeneous(0,1) random variable - v pursuit speed - V exponential(1) random variable - w prey weight - W exponential(_m) random variable - x prey density - ratio of maximum successful pursuit duration to meal duration (_pm/_e) - _pm - relative duration of successful pursuit (_p/_pm) - ratio of shortest to largest sighting distance - x_e - time already spent handling a prey item - rate of prey loss during prey handling - prey escape rate during pursuit - prey biomass density (xw) - , T maximum time still to be spent handling a prey item - _e meal duration - _m maximum handling time ( _e+ _p) - _p duration of successful pursuit - _pm maximum duration of successful pursuit (_p(0)) - hazard rate - _m maximum of hazard rate - scaled functional response (wF) - minimal i-state space     

The effect of some macronutrients on adventitious root development on scion apple cultivars in vitro

The influence of some macronutrients, especially NH₄NO₃ and KNO₃, on root development of microcuttings from 3 apple scion cultivars is discussed. A reduction of the level of NH₄NO₃ in the medium from full strength to 1/4 strength significantly increased the percentage rooting of Gala and Royal Gala, but not Jonagold. Further reduction of NH₄NO₃ level from 1/4 strength to zero significantly reduced the percentage of rooting in Gala but not Royal Gala. Jonagold rooted best at zero concentration NH₄NO₃. Without NH₄NO₃, rooting percentages were as high as 100% for all 3 cultivars when KNO₃ was provided at full strength. The results show that adventitious roots can be induced on apple scion cultivars by media manipulation.     

Glucomannan-synthase activity in differentiating cells of Pinus sylvestris L.

Particulate membrane preparations have been isolated from cambial cells, and from differentiating and differentiated xylem cells of the main stem of pine trees. These preparations synthesise a 14 glucomannan from guanosine 5-diphosphate-mannose. The polysaccharide and the synthase have been characterized and the K_m and V_max for the synthase determined as 85 M and 52.9 M·min^-1, respectively. The enzymic activity was inhibited by the addition of guanosine 5-diphosphate-D-glucose so that the presence of an epimerase on the particulate fraction in conjunction with the synthase probably allowed the heteropolymer to be formed with the optimal ratio of the concentrations of the nucleoside-diphosphate sugar donors. No evidence for a polyprenyl-phosphate derivative as an intermediate during the polymer synthesis was obtained. Part of the control mechanism for the deposition of the large amounts of the glucomannan during the secondary thickening of the tracheids of the vascular system is by an increase in the amount of synthase activity at the endomembrane system of the cells. This probably occurs by an increase in the amount of enzyme which is modulated by gene regulation during differentiation.Abbreviations GDP guanosine 5-diphosphate - GLC gasliquid chromatography     

Action of rat liver Galβ1-4GlcNAc α(2-6)-sialyltransferase on Manβ1-4GlcNAcβ-OMe,GalNAcβ1-4GlcNAcβ-OMe,Glcβ1-4GlcNAcβ-OMe and GlcNAcβ1-4GlcNAcβ-OMe as synthetic substrates

Incubation of synthetic Man\1-4GlcNAc-OMe, GalNAc1-4GlcNAc-OMe, Glc1-4GlcNAc-OMe, and GlcNAc1-4GlcNac-OMe with CMP-Neu5Ac and rat liver Gal1-4GlcNAc (2-6)-sialyltransferase resulted in the formation of Neu5Ac2-6Man1-4GlcNAc-OMe, Neu5Ac2-6GalNAc1-4GlcNAc-OMe, Neu5Ac2-6Glc1-4GlcNAc-OMe and Neu5Ac2-6GlcNAc1-4GlcNAc-OMe, respectively. Under conditions which led to quantitative conversion of Gal1-4GlcNAc-OEt into Neu5Ac2-6Gal1-4GlcNAc-OEt, the aforementioned products were obtained in yields of 4%, 48%, 16% and 8%, respectively. HPLC on Partisil 10 SAX was used to isolate the various sialyltrisaccharides, and identification was carried out using 1- and 2-dimensional 500-MHz¹H-NMR spectroscopy.Abbreviations 2D 2-dimensional - CMP cytidine 5-monophosphate - CMP-Neu5Ac cytidine 5-monophospho--N-acetylneuraminic acid - COSY correlation spectroscopy - DQF double quantum filtered - HOHAHA homonuclear Hartmann-Hahn - MLEV composite pulse devised by M. Levitt - Neu5Ac N-acetylneuraminic acid - Neu5Ac2en 2-deoxy-2,3-didehydro-N-acetylneuraminic acid     

Cell wall anionic polymers and peptidoglycan of Actinoplanes philippinensis VKM Ac-647

The cell wall of Actinoplanes philippinesis VKM Ac-647 harbours several carbohydrate-containing anionic polymers. (1) The main polymer of the wall is of a poly(glycosylglycerol phosphate) nature. Its monomeric units — O--d-mannopyranosyl-(14)--d-galactopyranosyl-(11)-glycerol monophosphates — are connected by phosphodiester bonds involving the hydroxyl groups at glycerol C3 and galactose C6. There also are chains without mannosyl substitutents. The teichoic acid structure has been established by chemical analysis and with ¹H and ¹³C NMR spectroscopy. This is the first finding of a teichoic acid with mannosyl residues in a bacterial cell wall. (2) The phosphorylated mannan contains mannose and 2-O-methylmannose. Its core chain has -1,2; -1,3; and -1,6 substitutions as revealed by ¹³C NMR spectroscopy.The peptide unit of the peptidoglycan contains no l-alanine, instead of which position 1 is occupied by glycine; and diaminopimelic acid is represented, besides its meso- (or DD) form, by small amounts of its LL isomer.Abbreviations Gro glycerol - Gro2P glycerol-2 phosphate - APT attached-proton-test - P_tot total content of phosphorus - P_lab phosphorus mineralized in 7 min at 100°C - P_NA phosphorus of nucleic acids - P_stab stable phosphorus - T trace amounts     

Restriction in the conformational flexibility of apoproteins in the presence of organic cosolvents: a consequence of the formation of "native-like conformation".

The influence of n-propanol on the overall -helical conformation of -globin, apocytochrome C, and the functional domain of streptococcal M49 protein (pepM49) and its consequence on the proteolysis of the respective proteins has been investigated. A significant amount of -helical conformation is induced into these proteins atpH 6.0 and 4°C in the presence of relatively low concentrations of n-propanol. The induction of -helical conformation into the proteins increased as a function of the propanol concentration, the maximum induction occurring around 30% n-propanol. In the case of -globin, the fluorescence of its tryptophyl residues also increased as a function of n-propanol concentration, the midpoint of this transition being around 20% n-propanol. Furthermore, concomitant with the induction of helical conformation into these proteins, the proteolysis of their polypeptide chain by V8 protease also gets restricted. The -helical conformation induced into - and -globin by n-propanol decreased as the temperature is raised from 4 to 24°C. In contrast, the -helical conformation of both - and -chain (i.e., globin with noncovalently bound heme) did not exhibit such a sensitivity to this change in temperature. However, distinct differences exist between the n-propanol induced -helical conformation of globins and the -helical conformation of - and -chains. A cross-correlation of the n-propanol induced increase in the fluorescence of -globin with the corresponding increase in the -helical conformation of the polypeptide chain suggested that the fluorescence increase represents a structural change of the protein that is secondary to the induction of the -helical conformation into the protein (i.e., an integration of the helical conformation induced to the segments of the polypeptide chain to influence the microenvironment of the tryptophyl residues). Presumably, the fluorescence increase is a consequence of the packing of the helical segments of globin to generate a native-like structure. The induction of -helical conformation into these proteins in the presence of n-propanol and the consequent generation of native-like conformation is not unique to n-propanol. Trifluoroethanol, another helix-inducing organic solvent, also behaves in the same fashion as n-propanol. However, in contrast to the proteins described above, n-propanol could neither induce an -helical conformation into performic acid oxidized RNAse-A nor restrict its proteolysis by proteases. Thus, the high sensitivity of apoproteins and the protein domains to assume -helical conformation in the presence of low concentration of n-propanol with a concomitant restriction of the proteolytic susceptibility of their polypeptide chain appears to be unique to those proteins that exhibit high -helical propensities. Apparently, this phenomenon of helix induction and the restriction of proteolysis reflects the formation of rudimentary tertiary interaction of the native protein and is unique to apoproteins or structural domains of -helical proteins. Consistent with this concept, the induction of -helical conformation into shorter polypeptide fragments of 30 residues, (e.g., _1-30, which exists in an -helical conformation in hemoglobin) is very low. Besides, this peptide exhibited neither the high sensitivity to the low concentrations of n-propanol seen with the apoproteins/protein domains nor the resistance toward proteolysis. The results suggest that the organic cosolvent induced decrease in the conformational flexibility of the apoprotein, and the consequent restriction of their proteolytic cleavage provides an opportunity to develop new strategies for protease catalyzed segment condensation reactions.     

A simple brassinolide analogue 2α, 3α-dihydroxy-17β-(3-methyl-butyryloxy)-7-oxa-B-homo-5α-androstan-6-one which induces bean second internode splitting

A new synthetic brassinolide analogue, 2,3-dihydroxy-17-(3-methylbutyryloxy)-7-oxa-B-homo-5-androstan-6-one (11), has been shown to exhibit typical brassinolide activity characterised by elongation, swelling, twisting and splitting of the bean second internode. It was prepared from the known lactone 2,3,17-trihydroxy-7-oxa-B-homo-5-androstan-6-one (4) which was transformed to an isopropylidenedioxy derivative. After protection of the 2- and 3-hydroxy groups it yielded the 2,3-isopropylidenedioxy-17-(3-methyl-butyryloxy)-7-oxa-B-homo-5-androstan-6-one (7) on treating with 3-methylbutyryl chloride in pyridine. The analogue with a 2-methylbutyric moiety (10, 2,3-dihydroxy-17-(2-methyl-butyryloxy)-7-oxa-B-homo-5-androstan-6-one) in position 17 stimulated only elongation and swelling of the bean second internode. However, in this bioassay 100 times more 10 or 11 compared to 24-epibrassinolide is required to obtain the same effects. Analogues with -oriented hydroxyl groups at C-2 and C-3 (14,15), a 6-ketone (17,18) or 6-oxa-7-oxo-lactone system (12,13) in ring B lack the typical brassinolide activity. In addition, the active brassinosteroids applied to the second internode stimulated a similar, but 30% lower elongation of the first internode. From data presented here we conclude that the presence of two hydroxy groups in the positions 22 and 23 of the brassinolide side chain, which are considered as a key structural requirement, is not absolutely necessary for a compound to exhibit typical brassinosteroid activity. Nevertheless, these compounds have generally 2–10 times lower activity than that having 22,23-vicinal diol in the side chain.     

Determination of the transmembrane proton gradient in the anaerobic bacterium Desulfovibrio desulfuricans by 31P nuclear magnetic resonance

The transmembrane proton gradient of the sulfate-reducing bacterium Desulfovibrio desulfuricans strain CSN has been determined by in vivo³¹P nuclear magnetic resonance (NMR) spectroscopy in the absence of dioxygen. At pH 7.0 in the medium (pH_ex) the intracellular pH (pH_in) was 7.5. By lowering pH_ex to 5.9 pH_in decreased to 7.1. At pH_ex greater than 7.7 the transmembrane proton gradient (pH) was zero. The uncouplers 3,3,4,5-tetrachlorosalicylanilide (TCS) and carbonylcyanide-m-chlorophenylhydrazone (CCCP), or the permeant anion thiocyanate caused complete dissipation of pH.Abbreviations CCCP carbonylcyanide-m-chlorophenylhydrazone - TCS 3,3,4,5-tetrachlorosalicylanilide - MOPS 3-(N-morpholino)-propanesulfonic acid - P _i inorganic phosphate - pH _in (pH_ex) intracellular (extracellular) pH - pH transmembrane proton gradient (pH_in-pH_ex) - electrochemical membrane potential - chemical shift in parts per million - NMR nuclear magnetic resonance     

Erratum: Cloning and sequencing of the phycocyanin gene from Spirulina maxima and its evolutionary analysis

The genes were cloned for the two apoprotein subunits, and ,of phycocyanin from the cyanobacterium Spirulina maxima = Arthrospiramaxima) strain F3. The - and -subunit gene-coding regionscontain 489 bp and 519 bp, respectively. The -subunit gene is upstreamfrom the -subunit gene, with a 111-bp segment separating them.Similarities between the -subunits of S. maxima and nine othercyanobacteria were between 58% and 99%, as were those between the -subunits. The maximum similarity between the - and -subunits from S. maxima was 27%.     

Efficient determination of angles subtended by Cα-Hα and N-HN vectors in proteins via dipole-dipole cross-correlation§

The angle CH,NHN subtended by the internuclear vectors 13C-H and 15N-HN in doubly-labeled proteins can be determined by observing the effect of cross-correlation between the dipolar interactions on zero- and double-quantum coherences involving 13C and 15N. Two complementary 2D experiments with the appearance of 15N-HN correlation spectra yield signal intensities that depend on the rate of interconversion through cross-correlated relaxation of in-phase and doubly antiphase zero- and double-quantum coherences. The ratio of the signal intensities in the two experiments bears a simple relationship to the cross-correlation rate, and hence to the angle CH,NHN. Assuming planarity of the peptide bond, the dihedral angle (between C and C) can be determined from the knowledge of CH,NHN. The experiments are very time-effective and provide good sensitivity and excellent spectral resolution.     

Potential induced in a spherical cell by an intracellular point source and an extracellular point sink

Summary The potential is calculated for all time, inside and outside a spherical cell for a point source of current inside the cell and a point sink located a finite distance outside the cell. The source and sink are step functions in time. An eigenfunction expansion is obtained, valid for arbitrary =_m a/_i , where _i and _m are the conductivities inside the cell and in the membrane, respectively, a is the cell radius and the membrane thickness. For small , the eigenfunction expansion is expanded in powers of . The time dependence of the potential contains transients with two widely differing time constants =C_m a/_i, where C_m is the membrane surface capacitance, and _m=/. Closed-form expressions are obtained for the two leading terms, for small , after the rapid transient is over. The remaining time dependence is only in the potential inside the cell, and is a simple exponential increase, independent of position within the cell. It is found that the transmembrane potential is insensitive to the location of the extracellular sink at long times, but not at short times. The dependence of the potential on location of source, sink, and observer is studied for long times after the quick transients are over. A uniqueness theorem is derived for the solution to Laplace's equation for the membrane boundary condition.This work was supported in part by NSF Grant No. GB-24965. Dr. Peskoff is the recipient of NIH Special Research Fellowship No. 1F03 GM 55849-01. Mr. Ramirez is a Ford Foundation Pre-doctoral Fellow.     

Expression of a chimeric stilbene synthase gene in transgenic wheat lines

A chimeric stilbene synthase (sts)gene was transferred into wheat. Stilbene synthases play a role in the defence against fungal diseases in some plant species (e.g. groundnut or grapevine) by producing stilbenetype phytoalexins like resveratrol. Resveratrol is also claimed to have positive effects to human health. Embryogenic scutellar calli derived from immature embryos of the two commercial German spring wheat cultivars Combi and Hanno were used as target tissue for cotransformation by microprojectile delivery. The selectable marker/reporter gene constructs contained the bargene either driven by the ubiquitinpromoter from maize (pAHC 25, also containing the uidAgene driven by the ubiquitinpromoter), or by the actinpromoter (pDM 302) from rice. The cotransferred plasmid pStil 2 consisted of a grapevine stscoding region driven by the ubiquitin promoter. Eight transgenic Combi and one Hanno T_Oplant were obtained and, except one Combi T_Oplant, found to be cotransformants due to the integration of both the stsgene and the selectable marker or reporter genes. Expression of the stsgene was proven by RTPCR, and, for the first time, by detection of the stilbene synthase product resveratrol by HPLC and mass spectrometry. The stsgene was expressed in four of the seven transgenic Combi T_{_o}plants. Two of the respective T₁progenies segregated in a Mendelian manner were still expressing the gene. Investigations into methylation of the stsgene showed that in three nonexpressing progenies inactivation was paralleled by methylation.