Studies on the metabolic role of peptidyl-tRNA hydrolase

Summary A mutant strain of Eschrichia coli that is temperature-sensitive for growth stopped protein biosynthesis at 43° C after a brief lag (Fig. 1). Cell-free extracts from the strain showed no specific defect in aminoacyl-tRNA synthetases, binding initiator tRNA to ribosomes (Table 1), protein chain elongation (Tables 2, 5) or protein chain termination (Tables 3, 4) at high temperature.The partially purified enzyme peptidyl-tRNA hydrolase, however, was temperature-sensitive (Table 6); the mutant hydrolase was inactivated rapidly at 43° C (Table 7). Mixing experiments ruled out the presence, in the mutant enzyme preparation, of an inhibitor and also demonstrated, on the mutant enzyme, a protective effect by wild type enzyme that was not shown by general coli proteins (Tables 8, 9).Interrupted mating allowed the temperature-sensitive growth phenotype to be mapped near to and before trp (Figs. 4, 5). Co-transsduction, mediated by bacteriophage P1, with trp ⁺ (frequency 7.5%) located the marker at 24 min on the coli map. All transductants for temperature-sensitive growth also had temperature-sensitive peptidyl-tRNA hydrolase activity in crude sonicates (Table 10). We provisionally conclude that the temperature-sensitive protein synthesis and growth are caused by a single genetic change in the structural gene (pth) for peptidyl-tRNA hydrolase.After shift to 43° C the polysomes of the mutant cells broke down into 70S particles (Figs. 2, 3). A defect in protein biosynthesis thus appeared to be located after termination and before reformation of new polysomes.The metabolic role of peptidyl-tRNA hydrolase is discussed in the light of these experiments.Journal paper No. J-7465 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa, project no. 1747.     

Dihydrofolate reductase and aminopterin resistance in Pneumococcus

Summary Wild-type pneumococci derived from Avery's strain R36A are sensitive to extracellular concentrations of the folate antimetabolite aminopterin exceeding 1.0x10^-6 M. Three classes of resistant strains are phenotypically distinguishable: amiB-r, amiA-r and amiD-r strains are resistant to low (1.5x10^-6 M), intermediate (0.5–4.0×10^-5 M) and high (4.5x10^-4 M) aminopterin levels respectively. The amiA and amiB regions are weakly linked, but linkage has not been established between either of these loci and the amiD region.Consistent with the maximum resistance conferred by mutations in the amiA locus, dihydrofolate (FH₂) reductase in cell-free extracts (CFE) of amiA-r strains has a two- to six-fold greater affinity for the substrate than dose the enzyme in wild-type CFE (Table 1); FH₂ reductase from amiA-r strains may also have reduced affinity for aminopterin. Specific activity of the enzyme is not affected by mutation in the amiA locus (Table 1) and its affinity for the cofactor (NADPH) is probably unaffected by mutation in this locus (Table 4). Dihydrofolate reductase activity in amiA5 CFE is considerably more thermolabile than that in wild-type CFE (Table 2).The enzyme in CFE of the high resistance strain amiD1 has the same affinity for the substrate, cofactor and antimetabolite as FH₂ reductase in wild-type CFE (Figs. 1–4, 8 and 9; Table 4). However, specific activity of the enzyme in amiD1 CFE is 11-fold higher than that in wild-type CFE (Table 1) and it is much more heat stable (Table 2).Some properties of FH₂ reductase in CFE of the high resistance recombinant strain amiA5amiD1 are intermediate between those in CFE of wild-type and amiD1.Preliminary results suggest that CFE of wild-type and amiA5 contain a factor, which is neither dialyzable nor heat sensitive, that has an inhibitory effect upon activity and stability of FH₂ reductase in amiD1 CFE (Tables 2 and 3).     

An automated paradigm for Drosophila visual psychophysics

Background

Mutations that cause learning and memory defects in Drosophila melanogaster have been found to also compromise visual responsiveness and attention. A better understanding of attention-like defects in such Drosophila mutants therefore requires a more detailed characterization of visual responsiveness across a range of visual parameters.

Methodology/Principal Findings

We designed an automated behavioral paradigm for efficiently dissecting visual responsiveness in Drosophila. Populations of flies walk through multiplexed serial choice mazes while being exposed to moving visuals displayed on computer monitors, and infra-red fly counters at the end of each maze automatically score the responsiveness of a strain. To test our new design, we performed a detailed comparison between wild-type flies and a learning and memory mutant, dunce ¹. We first confirmed that the learning mutant dunce ¹ displays increased responsiveness to a black/green moving grating compared to wild type in this new design. We then extended this result to explore responses to a wide range of psychophysical parameters for moving gratings (e.g., luminosity, contrast, spatial frequency, velocity) as well as to a different stimulus, moving dots. Finally, we combined these visuals (gratings versus dots) in competition to investigate how dunce ¹ and wild-type flies respond to more complex and conflicting motion effects.

Conclusions/Significance

We found that dunce ¹ responds more strongly than wild type to high contrast and highly structured motion. This effect was found for simple gratings, dots, and combinations of both stimuli presented in competition.     

A new paradigm for operant conditioning of Drosophila melanogaster

A freely walking single fly (Drosophila melanogaster) can be conditioned to avoid one side of a small test chamber if the chamber is heated whenever the fly enters this side. In a subsequent memory test without heat it keeps avoiding the heat-associated side. The memory mutants dunce ¹ and rutabaga ¹ successfully avoid the heated side but show no avoidance in the memory test. Wildtype flies can be trained to successively avoid alternating sides in a reversal conditioning experiment. Every single fly shows strong avoidance and a positive memory score. The new conditioning apparatus has several advantages: (1) Statistically significant learning scores can be obtained for individual flies. (2) Learning scores are obtained fully automatically without interference of the experimenter. (3) The procedure is fast, robust and requires little handling. Therefore the apparatus is suitable for largescale mutant screening. (4) Animals are not attached to a hook and thus can easily be used for breeding.Abbreviations dnc dunce gene - PI performance Index - rut rutabaga gene - S.E.M. standard error of mean     

Electrophysiological analysis of the temperature-sensitive paralyticDrosophila mutant,para ts

Summary Paralysis of flight in the temperature-sensitiveDrosophila mutantpara ^ts was found to be dependent on the rate of heating (Fig. 2). The gradual nature of the onset of paralysis during the temperature elevation was revealed by recording the electrical responses of the thoracic flight muscle fibers, evoked by cervical stimulation (Figs. 3,4). A neural focus of the mutation was indicated by intracellular current injections into identified flight muscle fibers during paralysis (Fig. 5) and by electrical activity recorded from gynandromorph flies, mosaic forpara ^ts (Table 1). Recording from picrotoxin-treated flies excluded a previous explanation of paralysis by a temperature-induced augmentation of GABAergic inhibition (Fig. 6). Under the same treatment, evidence was presented for a heterogeneous increase of excitation threshold for spike generation in certain neurons.Abbreviations DLM dorsolongitudinal muscle - DVM dorsoventral muscle - ts temperature sensitive - GABA Gamma aminobutyric acid We wish to thank Dr. E. Lifschytz for providing the facilities for culturing flies in his laboratory. This research was supported by Grant No. 625 from the U.S.-Israel Binational Science Foundation to D.D.     

Learning and discrimination of coloured papers in the walking blowfly,Lucilia cuprina

Summary A new training and testing paradigm for walking sheep blowflies, Lucilia cuprina, is described. A fly is trained by presenting it with a droplet of sugar solution on a patch of coloured paper. After having consumed the sugar droplet, the fly starts a systematic search. While searching, it is confronted with an array of colour marks consisting of four colours displayed on the test cardboard (Fig. 1). Colours used for training and test include blue, green, yellow, orange, red, white and black.Before training, naive flies are tested for their spontaneous colour preferences on the test array. Yellow is visited most frequently, green least frequently (Table 2). Spontaneous colour preferences do not simply depend on subjective brightness (Table 1).The flies trained to one of the colours prefer this colour significantly (Figs. 5 and 9–11). This behaviour reflects true learning rather than sensitisation (Figs. 6–7). The blue and yellow marks are learned easily and discriminated well (Figs. 5, 9, 11). White is also discriminated well, although the response frequencies are lower than to blue and yellow (Fig. 11). Green is discriminated from blue but weakly from yellow and orange (Figs. 5, 9, 10). Red is a stimulus as weak as black (Figs. 8, 9). These features of colour discrimination reflect the spectral loci of colours in the colour triangle (Fig. 14).The coloured papers seem to be discriminated mainly by the hue of colours (Fig. 12), but brightness may also be used to discriminate colour stimuli (Fig. 13).     

Syntheses,Receptor Bindings,in vitro and in vivo Stabilities and Biodistributions of DOTA‐Neurotensin(8–13) Derivatives Containing β‐Amino Acid Residues – A Lesson about the Importance of Animal Experiments

Neurotensin(8–13) (NTS(8–13)) analogs with C‐ and/or N‐terminal β‐amino acid residues and three DOTA derivatives thereof have been synthesized (i.e., 1 – 6 ). A virtual docking experiment showed almost perfect fit of one of the 1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetraacetic acid (DOTA) derivatives, 6a , into a crystallographically identified receptor NTSR1 (Fig. 1). The affinities for the receptors of the NTS analogs and derivatives are low, when determined with cell‐membrane homogenates, while, with NTSR1‐exhibiting cancer tissues, affinities in the single‐digit nanomolar range can be observed (Table 2). Most of the β‐amino acid‐containing NTS(8–13) analogs (Table 1 and Fig. 2), including the ⁶⁸Ga complexes of the DOTA‐substituted ones ( 6 ; Figs. 2 and 5), are stable for ca. 1 h in human serum and plasma, and in murine plasma. The biodistributions of two ⁶⁸Ga complexes (of 6a and 6b ) in HT29 tumor‐bearing nude mice, in the absence and in the presence of a blocking compound, after 10, 30, and 60 min (Figs. 3 and 4) lead to the conclusion that the amount of specifically bound radioligand is rather low. This was confirmed by PET‐imaging experiments with the tumor‐bearing mice (Fig. 6). Comparison of the in vitro plasma stability (after 1 h) with the ex vivo blood content (after 10–15 min) of the two ⁶⁸Ga complexes shows that they are rapidly cleaved in the animals (Fig. 5).     

Tunicatimonas pelagia gen. nov., sp. nov., a novel representative of the family Flammeovirgaceae isolated from a sea anemone by the differential growth screening method

A Gram-negative, strictly aerobic, reddish-pink pigmented, non-motile, rod-shaped strain designated N5DB8-4^T, was isolated from an orange-striped sea anemone Diadumene lineata by a differential growth screening method. Phylogenetic analyses based on the 16S rRNA gene sequence revealed that the novel isolate was affiliated with the family Flammeovirgaceae of the phylum Bacteroidetes and that it showed highest sequence similarity (89.1%) to Porifericola rhodea N5EA6-3A2B^T. The strain could be differentiated phenotypically from recognized members of the family Flammeovirgaceae. The G+C content of the DNA is 52.6 mol%, the major respiratory quinone is menaquinone 7 (MK-7) and iso-C15:0, C16:1ω5c and iso-C15:1 G (the double-bond position indicated by capital letter is unknown) were the major fatty acids. From the distinct phylogenetic position and combination of genotypic and phenotypic characteristics, the strain represents a novel taxon for which the name Tunicatimonas pelagia gen. nov., sp. nov. is proposed. The type strain of Tunicatimonas pelagia is N5DB8-4^T (=KCTC 23473^T = NBRC 107804^T).     

Properties of learning and memory inDrosophila melanogaster

Summary Drosophila melanogaster can be conditioned to avoid an odorant selectively after being shocked in its presence (Quinn et al., 1974). In the following study learning and memory properties of the flies are reported. The major part of the conditioned behavior is acquired after a single training trial (Fig. 2). Similar degrees of learning are obtained by using various odorants in various combinations (Table 1). The flies can learn to avoid selectively several odorants at a time, can learn to discriminate between different concentrations of the same odorant (Fig. 4), and can also learn to distinguish a mixture of odorants from its components. If not extinguished, the selective avoidance decays slowly and can be detected for hours, its magnitude depending upon the intensity of training (Fig. 6). Memory can be disrupted by narcosis during the first 20 min after training, but not afterwards (Fig. 7). A study of learning properties of wild-type strains and various morphological and behavioral mutants reveals differences in performance (Table 2). However, the differences cannot be attributed with certainty to differences in learning and memory, per se, because the mutants differ in other aspects of behavior, e.g., locomotor activity and phototaxis. Of the wild-type strains tested, Canton-S performed the best.I thank Dr. S. Benzer for the hospitality of his laboratory, and S. Benzer, D. Byers, W. Harris, L. Jan, Y.-N. Jan, W. Quinn, D. Ready and M. Shankland for valuable discussions. This work was supported by an EMBO long-term fellowship and by a grant from the National Science Foundation to Dr. S. Benzer.     

A defective conditioned behavior and a defective adenylate cyclase in theDrosophila mutantrutabaga

Summary TheDrosophila X-linked mutantrutabaga (Duerr and Quinn 1982) fails to perform normally in olfactory conditioning paradigms, in spite of being able to sense odorants and shock (Figs. 1–3).rut is capable of forming an association between shock and odorant, but memory decays rapidly; the memory of the mutant following intensive training resembles that of normal flies following very brief training (Fig. 4).rut flies also display in vitro a defective adenylate cyclase activity (Fig. 6). The enzyme in the mutant is responsive to stimulation by a putative neurotransmitter and by a guanyl nucleotide (Fig. 8) but the activity is lower than normal even in the presence of forskolin (Fig. 8) and MnATP (Fig. 9), suggesting that the lesion is closely associated with the function of the catalytic subunit.rut/ + heterozygotes are semi-recessive with regard to both the behavioral defect and the biochemical defect (Figs. 5, 7). The behavioral and the biochemical lesions detected inrut flies are discussed in light of current molecular models of learning.     

Organization of inputs to motoneurons during fictive respiration in the isolated lamprey brain

Summary The intracellular activity of motoneurons during fictive respiration in the isolated lamprey brain was investigated. In association with each respiratory cycle three distinct PSP phases were observed: an early, low amplitude EPSP phase; a large, brief EPSP phase that drove action potentials; and a subsequent IPSP phase (Fig. 1). Selective midline and trigeminal lesions, and trigeminal stimulation, demonstrated that the large excitatory and inhibitory phases were generated by a previously described pair of central pattern generators located in the trigeminal region of the medulla (V) (Figs. 3, 4). Lesion studies further showed that the low amplitude excitatory input could be produced independently of the trigeminal pacemakers (Figs. 3, 5), near the region of the medulla that contains the respiratory motoneurons (VII, IX, and X).In addition to normal fictive respiration, the isolated brain was found to produce several variations of the respiratory pattern. These motor programs, coughs, arousal breathing, and weak breathing, were distinguished from the normal respiratory pattern by their much longer burst durations, distinctive underlying synaptic input, and separate coordinating mechanism (Figs. 6–8). Activity similar to these motor programs could be independently produced by the caudal medulla after both trigeminal central pattern generators had been removed (Figs. 5, 6). Lesion studies, and the observation that respiratory-related neural activity ceased in the trigeminal region during the production of these long-duration programs, suggest that the caudal medulla also contains paired central pattern generators involved in lamprey respiration (Figs. 5, 9, 10).Abbreviations CPG central pattern generator - HRP horseradish peroxidase     

Double-strand breaks of DNA of C57BL and mdx mouse cardiomyocytes after dynamic stress

One of the approaches to analysis of survival of cardiomyocytes during oxidative stress can be the use of animals with genetic defects—mdx mice. In mdx mice, disturbance of dystrophine synthesis is known to be accompanied by development of oxydative stress in contractile cells that in turn produces cell death. Earlier we established that dynamic stress leads to the formation of low molecular DNA fragments in the mdx mouse myocardium. It is beyond any doubt that the DNA fragmentation develops via formation of double-strand DNA breaks (DB). To record the dynamics of the appearance and disappearance of DB in the mdx mouse cardiomyocytes after dynamic stress, we used an antibody to the phosphorylated form of the γ-H2Ax histone. In the absence of stress, DB in myocardial cell nuclei are revealed both in C57Bl and in mdx mice. The percentage of cardiomyocyte nuclei with DB in C57Bl and in mdx mice was 0.05 ± 0.07% and 6.7 ± 0.2%, respectively (Table 1). In the C57Bl mice 1 h after dynamic stress the fraction of labeled cardiomyocyte nuclei rose to 1.0 ± 0.02%, while in the mdx mice—to 41.7 ± 11.4% (Table 1). At 24 h after the dynamic stress 5.7 ± 0.2% cardiomyocyte nuclei remained labeled in the mdx mouse myocardium (Table 1), whereas in C57Bl mice no labeled cardiomyocyte nuclei were revealed. One hour after the dynamic stress, 0.3 ± 0.2% of cardiomyocyte nuclei of the C57Bl mice incorporated ³H-thymidine. In the mdx mice, 2.9 ± 0.5% of cardiomyocyte nuclei incorporated ³H-thymidine. At 24 h after the stress and ³H-thymidine administration the percentage of cardiomyocyte nuclei in the mdx mice fell to 0.4 ± 0.2%. In the C57Bl mice primarily labeled nuclei were not revealed. The ³H-thymidine incorporation is not associated with entrance of cardiomyocytes into the mitotic cycle; we consider it as a manifestation of reparative DNA synthesis. We conclude is that the disappearance of DB in DNA from the mdx mouse myocardium 24 h after the dynamic stress is associated both with DNA reparation and the loss of cardiomyocytes.     

Discrimination of insect wingbeat-frequencies by the batRhinolophus ferrumequinum

Summary Five Greater Horseshoe bats,Rhinolophus ferrumequinum, were trained in a two-alternative forced-choice procedure to discriminate between artificial echoes of insects fluttering at different wingbeat rates. The stimuli were electronically produced phantom targets simulating fluttering insects with various wingbeat frequencies (Figs. 3, 4). Difference thresholds for wingbeat rates of 50 Hz and 100 Hz were determined. For an S+ of 50 Hz the difference threshold values lay between 2.8 and 4.6 Hz for individual bats; with an S+ of 100 Hz they increased to between 9.8 and 12.0 Hz (Figs. 5, 6, Table 1).Three bats, previously trained to discriminate between a S+ of 50 Hz and a S– with a lower wingbeat rate, were tested with higher frequency stimuli. When they had to decide between their old S+ of 50 Hz and either a 60 or 70 Hz echo two bats continued to select the 50 Hz stimulus while the third bat now preferred the faster fluttering insects (Table 2).During the discrimination task the echolocation behavior of the bats was monitored. When the phantom targets were presented all bats increased their duty-cycle of sound emission from about 40% to sometimes near 70%. They did so by either emitting longer echolocation calls or by increasing the sound repetition rate (Figs. 7, 8).The results show that Greater Horseshoe bats can determine the wingbeat rate of flying insects with an accuracy between 6 and 12%. Possible cues for flutter rate determination by cf-fm bats from natural and artificial insect echoes are discussed.Abbreviations DC duty-cycle - PD pulse duration - PI pulse interval - cf constantfrequency - fm frequency modulation     

Mutagenic action of hydroxylamine and methoxyamine on yeast

Summary Hydroxylamine (HA) in 0.1-2M concentration induces in yeast mutation and recombination. Cell survival, and reversion induction show a striking variation from one experiment to another (Figs. 1, 3). There is no clear-cut dose-dependence (Fig. 2). HA inhibits respiration, alcohol dehydrogenase and catalase activities (Tables 1, 2, 4). However, these effects are at least partly reversed when the HA-treated cells are incubated for 1 h in phosphate buffer (Fig. 4, Tables 3 and 6). Catalase inhibition by 10-²M HA does not induce recombination (Table 5). Acetoxime, pyruvoxime and glucosoxime do not seem to be mutagenic (Table 7).The level of free HA in a homogenate of cells treated for 3 h with 1 M HA, without postincubation in buffer is ca. 10-²M.It is suggested that within the yeast cells HA undergoes decomposition into free radicals and peroxide, which directly or through chain reactions induce DNA damages. The direct reaction of HA with cytosine, if it occurs at all, does not seem to play an important role in HA mutagenesis in yeast.     

Centrally-mediated synaptic input: Effects on an identified crayfish mechanosensory interneuron

Summary High-level mechanosensory interneurons integrate a substantial amount of polysynaptic input. We have used an identified interneuron, the crayfish (Procambarus clarki) caudal photoreceptor (CPR), to examine the extent and specificity of interneuronal input as received by a physiologically complex, smalldiameter sensory unit. Presynaptic central neurons were identified by antidromic stimulation of connective fibers and characterized physiologically relative to the bilateral responses observed in the paired CPR's. Eleven inhibitory interneurons have been identified, including cells with ipsilateral (Fig. 4), contralateral (Fig. 5) and bilateral effects (Fig. 6). Seven excitatory interneurons have been identified, including examples from each of the respective categories above (Figs. 7–9). The results of this survey are summarized in Table 1; axon locations are presented in Fig. 10.It has also been demonstrated that several of these fibers are themselves ascending mechanoreceptive interneurons (e.g., fiber 122, Fig. 1). Thus, for the encoding of environmental stimuli, these results indicate that central integration involves a lateral exchange of tactile information among a set of interrelated sensory interneurons. However, the possibility still exists that some of these fibers represent descending pathways for central influence of local (segmental) integrative processes.Abbreviations CPR caudal photoreceptor - EPSP excitatory postsynaptic potential - IPSP inhibitory postsynaptic potential This work has been supported in part by a Research Fellowship from Bryn Mawr College (to G.A.M.) and by Research Grants from NIH (NS-12971-03) and the Whitehall Foundation. This paper is a contribution of the Tallahassee, Sopchoppy and Gulf Coast Marine Biological Association (No. 123).     

Respiratory adaptations in carp blood influences of hypoxia, red cell organic phosphates, divalent cations and CO2 on hemoglobin-oxygen affinity

Summary This study concerns the adaptation of oxygen transporting function of carp blood to environment hypoxia, tracing the roles played by erythrocytic cofactors, inorganic cations, carbon dioxide and hemoglobin multiplicity.Carp acclimated to hypoxia ( 30 mmHg) display striking increases in blood oxygen affinity compared to normoxic ( =120–150 mm) specimens (P ₅₀'s are 3.0 and 7.0 mm, respectively, at pH 7.9 and 20°C). This correlates with a marked decrease in erythrocytic concentrations of NTP (nucleoside triphosphates) (Figs. 1, 2, Table 1), permitting investigation of the time-course of the response (Fig. 3). That GTP (guanosine triphosphate) plays a greater role than ATP in the allosteric regulation of blood oxygen affinity, follows from greater decreases in its concentration during hypoxia, and its greater effect on oxygen affinity of the hemoglobin (Figs. 1, 5). It is furthermore shown that divalent cations (which complex with NTP) inhibit the regulatory role of GTP on O₂ affinity to a lesser extent than that of ATP (Fig. 7). However, the divalent cation, Mg²⁺, occurs in similarly high concentrations in the erythrocytes of hypoxic and normoxic fish (Table 1). CO₂ specifically depresses the O₂ affinity of carp hemoglobin, but below pH 8.3, its effect is obliterated by ATP and GTP suggesting that the chains are the main sites for CO ₂ ^– binding. Four carp hemoglobin components are isolated and their oxygen-binding properties compared with those of the cofactor-free hemolysate (Figs. 4, 8, 9). The results are discussed comparatively with special reference to hemoglobin function in fish and mammals.     

Glucosephosphate isomerase (GPI) of the teleostFundulus heteroclitus (linnaeus): Isozymes, allozymes and their physiological roles

Summary In order to evaluate the role of glucose-phosphate isomerase (GPI) inFundulus heteroclitus, the isozymes and allozymes were purified and some of their physical and kinetic properties determined.Isozymes were purified from both liver (GPI-B) and muscle (GPI-A) tissue (Tables 1, 2). Gel filtration of the native enzyme and SDS-polyacrylamide gel electrophoresis indicated that all forms are dimers of approximately 110,000 Daltons (Figs. 4, 5). Although thermal stability studies revealed no differences between the allozymes, the isozymes were clearly different (Figs. 6, 7). Kinetic analysis showed further differences between isozymes inK _m for substrate andK _I for 6-phosphogluconate (Figs. 8, 9; Table 3). No significant differences were found between the allozymes of the B-locus under the conditions employed in this study.Based on the tissue specificities and the functional differences between isozymes, we propose a possible regulatory role for GPI-B inF. heteroclitus. The sensitivity of this isozyme to 6-phosphogluconate inhibition may allow GPI-B to act as a regulatory enzyme in the partitioning of carbon flow between glycolysis and the hexose monophosphate shunt.Abbreviations me -mercaptoethanol - F6P fructose-6-phosphate - G1P glucose-1-phosphate - G6P glucose-6-phosphate - G6Pase glucose-6-phosphatase - G6PDH glucose-6-phosphate dehydrogenase - GPI glucosephosphate isomerase - HK hexokinase - HMP hexose monophosphate shunt - 6PG 6-phosphogluconate - PGM phosphoglucomutase Supported in part by: NSF grants DEB-76-19877 to D.A.P. and PCM 77-16838 to B.D.S., NIH Biomedical grant 5-50-7RR07-041 and a grant from the National Geographic Society. G.D.S. and R.V.B. are NIH trainees supported by a training grant (No. HD00139) to the Department of Biology, The Johns Hopkins University. This is contribution No. 1052 from the Department of Biology     

Wie richtet eine Flußseeschwalbenkolonie (Sterna hirundo) ihr Abwehrverhalten auf den Feinddruck durch Silbermöwen (Larus argentatus) ein?

How a Common Tern (Sterna hirundo) Colony Defends itself against Herring Gulls (Larus argentatus) The subject of this study is the anti-predator behaviour of a small common tern colony near a large herring gull colony on the island of Mellum, West Germany (Fig. 1). In 1980 the number of gulls crossing this tern colony increased during the terns' chick-stage (Fig. 4). Observed predation of tern chicks was independent of tide and time of day (3., Fig. 5). The frequency of tern reactions corresponded to the number of herring gull crossings (Fig. 5, Table 1). The terns' responses increased between morning and evening (Fig. 8). Tern up-flights and attacks increased absolutely and as a percentage, with the advance of the breeding season (Fig. 3, 4). They were positively correlated with the observed chick predation and the number of pairs with chicks, most markedly with chicks older than 5 days (Figs. 3, 4; Table 1). This increased defence was maintained by fewer pairs as, by then, many had lost their own broods (Fig. 4). As the breeding season progressed, herring gulls increasingly became the main cause of tern up-flights and the object of the attacks (Figs. 9–11). The up-flights of the whole colony, which occurred frequently and spontaneously during incubation, were observed only rarely after hatching and were almost exclusively a response to herring gulls (Figs. 10, 12). The lower herring gulls flew over the colony, the more frequently common terns flew up or attacked and the more individuals were involved in these responses (Figs. 6, 13, 14). During the breeding period, communal up-flights and attacks by terns increased as a percentage (Figs. 12, 13, 15–17). Group-attacks effected changes in the gulls' flying-routes more often than did individual attacks (Fig. 18). Despite the defence behaviour and its adaptation to the predation pressure, herring gulls often succeeded in robbing chicks. This is why the breeding success of the common tern was poor (< 0.4 chicks/nest). Possible reasons for this are discussed.     

Diverse modes of 5′‐[4‐(aminoiminomethyl)phenyl]‐[2,2′‐bifuran]‐5‐carboximidamide (DB832) interaction with multi‐stranded DNA structures

The modes of binding of 5′‐[4‐(aminoiminomethyl)phenyl]‐[2,2′‐Bifuran]‐5‐carboximidamide (DB832) to multi‐stranded DNAs: human telomere quadruplex, monomolecular R‐triplex, pyr/pur/pyr triplex consisting of 12 T*(T·A) triplets, and DNA double helical hairpin were studied. The optical adsorption of the ligand was used for monitoring the binding and for determination of the association constants and the numbers of binding sites. CD spectra of DB832 complexes with the oligonucleotides and the data on the energy transfer from DNA bases to the bound DB832 assisted in elucidating the binding modes. The affinity of DB832 to the studied multi‐stranded DNAs was found to be greater (K_ass ≈ 10⁷M^?1) than to the duplex DNA (K_ass ≈ 2 × 10⁵M^?1). A considerable stabilizing effect of DB832 binding on R‐triplex conformation was detected. The nature of the ligand tight binding differed for the studied multi‐stranded DNA depending on their specific conformational features: recombination‐type R‐triplex demonstrated the highest affinity for DB832 groove binding, while pyr/pur/pyr TTA triplex favored DB832 intercalation at the end stacking contacts and the human telomere quadruplex d[AG₃(T₂AG₃)₃] accommodated the ligand in a capping mode. Additionally, the pyr/pur/pyr TTA triplex and d[AG₃(T₂AG₃)₃] quadruplex bound DB832 into their grooves, though with a markedly lesser affinity. DB832 may be useful for discrimination of the multi‐sranded DNA conformations and for R‐triplex stabilization. © 2009 Wiley Periodicals, Inc. Biopolymers 93: 8–20, 2010. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com