Interaktionen von Auxin und Äthylen bei der thigmotropen Bewegung der Ranken von Cucumis sativus

Summary Coiling of intact or excised cucumber (Cucumis sativus) tendrils can be induced by IAA or ethylene. The velocity of coiling in different regions of the tendrils correlates with the capacity for auxin-stimulated ethylene synthesis. Ethylene (Ethephon) induces an increase in membrane permeability of tendrils, and as a result the efflux of substances previously taken up (glucose) is stimulated. It is assumed that this may contribute to the contraction of the ventral side of the tendril. The excretion of glucose after ethylene treatment can be reduced by Ca²⁺, and calcium also inhibits coiling of tendrils following incubation in ethephon solution. Auxin stimulated ethylene synthesis in the ventral half of the tendril is several times higher than in the dorsal half and it is hypothesized that this may be a cause for the different reactions of the two sides of a tendril following a mechanical stimulus.

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Abkürzungen: IAA=Indol-3-essigsäure; ABA=Abscisinsäure     

Physiological studies on pea tendrils. V. Membrane changes and water movement associated with contact coiling

The coiling of excised pea tendrils in response to mechanical stimulation is accompanied by an increased efflux from their cut bases of electrolytes and label from previously absorbed ¹⁴C-acetate and ¹⁴C-sucrose. The major excreted cation is H⁺; H⁺ loss is potentiated by pretreatment with benzoic acid, which also leaves the tendrils during coiling.

Label from previously absorbed tritiated water is excreted during coiling, mainly from the ventral side of the tendril, which contracts in the initial phase of coiling. Such label does not pass from the ventral to the dorsal side. Similarities between this and other rapidly moving systems in plants are surveyed and a hypothesis to explain turgor movements is advanced.

     

Touch- and Methyl Jasmonate-induced Lignification in Tendrils of Bryonia dioica Jacq.

The touch-induced free coiling response of Bryonia dioica tendrils is accompanied by the differentiation of supporting tissue at the ventral side of the organ, becoming the inner (concave) side of the coiled tendril. As part of this process, the Bianconi plate, a continuous sclerenchyma sheath stretching along the ventral face of the five bicollateral vascular bundles, becomes strongly lignified. During this reaction, the extractable activity of phenylalanine ammonia-lyase in the tendrils increases four- to five-fold, while the amount of PAL, as demonstrated by immunoblotting, remains unchanged. This touch-induced process can also be elicited by airborne application of methyl jasmonate. The PAL inhibitor, 2-aminoindan-2-phosphonic acid (AIP) completely inhibits both the touch- and methyl jasmonate-induced deposition of lignin-like material in the Bianconi plate, but has no effect on coiling. From these results, it can be concluded that the cessation of growth at the ventral side of a free-coiling tendril is not due to induced lignification but rather, lignification seems to serve the function of increasing the mechanical strength of the coiled tendril.     

外源乙酰胆碱在丝瓜卷须弯曲中起“神经递质”的作用

用乙酰胆碱（ＡＣｈ）或毒扁豆碱处理离体丝瓜卷须不仅能增强机械刺激引发的卷曲程度,甚至可以直接引发卷须的弯曲运动。用阿托品预处理卷须可以抑制由机械刺激引发的电化学波传递,减弱ＡＣｈ对卷须弯曲运动的效应;而Ｄ－管箭毒预处理卷须则无此效应。说明在丝瓜卷须中ＡＣｈ是通过毒蕈碱型受体传递电化波并引起原生质收缩和快速弯曲运动,这与动物神经－平滑肌突触传递兴奋的机制很相似。     

Topographic mapping of the axons of the femoral chordotonal organ neurons in the cricket Gryllus bimaculatus

Central projections of the femoral chordotonal organ (FCO) neurons in the cricket Gryllus bimaculatus were investigated by selectively staining small numbers of axons. The FCOs in all legs consist of partly fused ventral and dorsal scoloparia in the proximal femur. The ventral scoloparium neurons can be reliably divided into two groups: the ventral group neurons (VG), which are arranged in a sequentially smaller manner distally, and dorsal group neurons (DG), which simply aggregate in the proximal region near the dorsal scoloparium. All axons of the FCO projected to the ipsilateral half of the respective thoracic ganglion. The VG axons possessed dorso-lateral branches in the motor association neuropile and antero-ventral branches dorso-lateral to the anterior ventral association centre. However, the more proximally the somata were situated, the more medially the main neurites terminated. The DG axons showed some variations: some axons of the distally located neurons possessed dorso-lateral branches and terminated on the boundary region of the mVAC, while the other axons terminated exclusively in the medical ventral association centre (mVAC), including the ventral part, which receives auditory sensory neuron projections. All axons of the dorsal scoloparium neurons projected exclusively into the dorsal part of the mVAC; however, the ventrally located neurons projected more ventrally than did the dorsally located neurons. The above characteristics were nearly identical in the pro- and metathoracic FCOs. These results suggest that the cricket FCO axons are roughly organized in a somatotopic map and are broadly differentiated in their function.     

Biochemical investigations of retinotectal adhesive specificity

The preferential adhesion of chick neural retina cells to surfaces of intact optic tecta has been investigated biochemically. The study uses a collection assay in which single cells from either dorsal or ventral halves of neural retain adhere preferentially to ventral or dorsal halves of optic tecta respectively. The data presented support the following conclusions: (a) The adhesion of ventral retina to dorsal tecta seems to depend on proteins located on ventral retina and on terminal β-N-acetylgalactosamine residues on dorsal tecta. (b) The adhesion of dorsal retina to ventral tecta seems to depend on proteins located on ventral tecta and on terminal β- N-acetylgalactosamine residues on dorsal retina. (c) A double gradient model for retinotectal adhesion along the dorsoventral axis is consistent with the data presented. The model utilizes only two complementary molecules. The molecule suggested to be concentrated dorsally in both retina and tectum seems to require terminal β-N-acetylgalactosamine residues for adhesion. Its activity is not affected by protease. A molecule fitting these qualifications, the ganglioside GM(2), could not be detected in a gradient, but lecithin vesicles containing GM(2) adhered preferentially to ventral tectal surfaces. The second molecule, concentrated ventrally in both retina and tectum, is a protein and seems capable of binding terminal β-N- acetylgalactosamine residues. One enzyme, UDP-galactose:GM(2) galactosyltransferase, has been found to be more concentrated in ventral retina than dorsal, but only by 30 percent.     

Activation of pyramidal neurons by intrinsic longitudinal connections in the hippocampus

In the guinea pig, EPSPs and population spikes were found to be generated in the apical dendrites of pyramidal neurons of middle and ventral hippocampus, in response to dorsal hippocampal commissure (PSD) stimulation, without any involvement of dentate gyrus granule cells of corresponding segments. These long-latency synaptic effects were evoked only by repetitive (0.2-2.0 c/sec) PSD stimulation and showed increasing latency in ventral direction. A cross section between dorsal and middle hippocampus was followed by the disappearance of the responses ventrally to the section. The results show that the postsynaptic discharge of dorsal pyramidal neurons is transferred to more ventral hippocampal segments by an intrahippocampal longitudinal association system.     

A Motorneurone Cell Body Located Either Dorsally or Ventrally within a Crustacean Abdominal Ganglion

In the last abdominal ganglion of the squat lobster Galathea strigosa (Decapoda, Anomura) a unique pair of flexor motorneurones exist whose medial cell bodies occur paired either on the ventral or the dorsal surface of the ganglion or else are located separately, one dorsal and the other ventral. In 60 squat lobsters (30 ♂ 30 ♀), this pair of medial dorsal/ventral (MDV) cell bodies was found in 4 distinct cell pair configurations: ventral/ventral, 24; dorsal/dorsal, 5; right ventral/left dorsal, 14; right dorsal/left ventral, 17. MDV cell bodies were never found lying midway between the dorsal and ventral surfaces. The distribution of configurations was approximately the same for both sides of the ganglion and for both sexes, and whether a cell occurred ventrally or dorsally was found to be independent of the position of its partner. The determination of cell body location appears not to be influenced by any cell-cell interaction, despite an apparent ‘point of close association’ between the two soma neurites and a strong bias overall towards the ventral location (dorsal 1/3, ventral 2/3).     

Patterning of angiogenesis in the zebrafish embryo

Little is known about how vascular patterns are generated in the embryo. The vasculature of the zebrafish trunk has an extremely regular pattern. One intersegmental vessel (ISV) sprouts from the aorta, runs between each pair of somites, and connects to the dorsal longitudinal anastomotic vessel (DLAV). We now define the cellular origins, migratory paths and cell fates that generate these metameric vessels of the trunk. Additionally, by a genetic screen we define one gene, out of bounds (obd), that constrains this angiogenic growth to a specific path. We have performed lineage analysis, using laser activation of a caged dye and mosaic construction to determine the origin of cells that constitute the ISV. Individual angioblasts destined for the ISVs arise from the lateral posterior mesoderm (LPM), and migrate to the dorsal aorta, from where they migrate between somites to their final position in the ISVs and dorsal longitudinal anastomotic vessel (DLAV). Cells of each ISV leave the aorta only between the ventral regions of two adjacent somites, and migrate dorsally to assume one of three ISV cell fates. Most dorsal is a T-shaped cell, based in the DLAV and branching ventrally; the second constitutes a connecting cell; and the third an inverted T-shaped cell, based in the aorta and branching dorsally. The ISV remains between somites during its ventral course, but changes to run mid-somite dorsally. This suggests that the pattern of ISV growth ventrally and dorsally is guided by different cues. We have also performed an ENU mutagenesis screen of 750 mutagenized genomes and identified one mutation, obd that disrupts this pattern. In obd mutant embryos, ISVs sprout precociously at abnormal sites and migrate anomalously in the vicinity of ventral somite. The dorsal extent of the ISV is less perturbed. Precocious sprouting can be inhibited in a VEGF morphant, but the anomalous site of origin of obd ISVs remains. In mosaic embryos, obd somite causes adjacent wild-type endothelial cells to assume the anomalous ISV pattern of obd embryos. Thus, the launching position of the new sprout and its initial trajectory are directed by inhibitory signals from ventral somites. Zebrafish ISVs are a tractable system for defining the origins and fates of vessels, and for dissecting elements that govern patterns of vessel growth.     

Physiological Studies on Pea Tendrils VIII. The Relationship of Circumnutation to Contact Coiling. — With a Description of a Laboratory Intervalometer Using Integrated Digital Circuits

The average rate of rotation of circumnutating tendrils of Pisum sativum L. ev. Alaska, was 1.57 ± 0.29 mm/min. 53% of the tendrils rotated clockwise and 47% counterclockwise. Circumnutation is apparently dependent on the maintenance of sufficient turgor as it stopped when either the roots or all the shoot appendages except the terminal tendril were excised, but resumed when the aerial wounds were covered with petroleum jelly. Both circumnutation and contact coiling were similarly retarded when the plant was cut in the middle of the top inter-node, or by the use of either juvenile or senescent organs. As the tendril circumnutated rapidly during the sweeping portion of its circuit, it was capable of coiling at only about 57% of the rate of which it could coil if stimulated during the relatively slow moving turn, Conversely, when the tendril was mechanically stimulated to coil, its rate of circumnutation decreased markedly and remained retarded as long as the tendril continued to coil. On the basis of these observations, it is concluded that contact coiling does not seem to be simply a modified form of circumnutation, but the two modes of movement might be related through a negative feedback system.     

INTERSEXUAL COMPARISON OF MIMETIC PROTECTION IN THE BLACK SWALLOWTAIL BUTTERFLY,PAPILIO POLYXENES: EXPERIMENTS WITH CAPTIVE BLUE JAY PREDATORS

The black swallowtail butterfly (Papilio polyxenes asterius Stoll), is commonly assumed to exhibit female-limited Batesian mimicry of the aposematic pipevine swallowtail (Battus philenor [L.]), since the dorsal wing surfaces of P. polyxenes females, but not males, resemble those of the model. However, the ventral wing surface is monomorphic and closely resembles that of the model in both sexes. Thus both sexes of P. polyxenes should benefit from mimicry during periods of ventral surface exposure, such as during overnight roosting and other times of high predatory risk. Eight blue jays (Cyanocitta cristata L.) were offered ventrally and dorsally exposed butterfly prey items in an outdoor aviary. Model-conditioned birds refused male and female P. polyxenes equally when the butterflies were presented ventrally. However, significantly more males than females were attacked when the dimorphic dorsum was visible. Both sexes are thus similarly protected when the ventral wing surface is displayed during roosting. The high degree of bird-to-bird variability in response to P. polyxenes mimics suggests that there is a spectrum in ability or willingness of predators to discriminate among mimics of varying similarity to the model. Sexual dimorphism of the dorsal surface of P. polyxenes wings may reflect sexual selection favoring males that are recognizable as satisfactory mates or intrasexual competitors.     

The tegumental surface of Phyllodistomum conostomum (Olsson, 1876) (Digenea), revealed by scanning electron microscopy

The external surface of P. conostomum is characterized by relatively large ridges encircling the anterior part of the worm at regular intervals. On the posterior part depressions on the ventral side at regular intervals and relatively small ridges on the dorsal side are present. Ventroposteriorally cobblestone-like protuberances observed are arranged in longitudinal rows. No corresponding arrangement was found dorsally. Only domed papillae (with and without a central knob) were observed, tentatively identified as sensory organs. The regular pattern of these papillae on the ventral and oral sucker is described, in addition to their arrangement ventrally and at the anterior end. A frontal pit anterior of oral suckers and a notch at the posterior end are figured and briefly described. No spines were observed on the body tegument.     

SDQR migrations in Caenorhabditis elegans are controlled by multiple guidance cues and changing responses to netrin UNC-6.

The netrin guidance cue, UNC-6, and the netrin receptors, UNC-5 and UNC-40, guide SDQR cell and axon migrations in C. elegans. In wild-type larvae, SDQR migrations are away from ventral UNC-6-expressing cells, suggesting that UNC-6 repels SDQR. In unc-6 null larvae, SDQR migrations are towards the ventral midline, indicating a response to other guidance cues that directs the migrations ventrally. Although ectopic UNC-6 expression dorsal to the SDQR cell body would be predicted to cause ventral SDQR migrations in unc-6 null larvae, in fact, more migrations are directed dorsally, suggesting that SDQR is not always repelled from the dorsal source of UNC-6. UNC-5 is required for dorsal SDQR migrations, but not for the ventral migrations in unc-6 null larvae. UNC-40 appears to moderate both the response to UNC-6 and to the other cues. Our results show that SDQR responds to multiple guidance cues and they suggest that, besides UNC-6, other factors influence whether an UNC-6 responsive cell migrates toward or away from an UNC-6 source in vivo. We propose that multiple signals elicited by the guidance cues are integrated and interpreted by SDQR and that the response to UNC-6 can change depending on the combination of cues encountered during migration. These responses determine the final dorsoventral position of the SDQR cell and axon.     

Zebrafish topped is required for ventral motor axon guidance

Zebrafish primary motor axons extend along stereotyped pathways innervating distinct regions of the developing myotome. During development, these axons make stereotyped projections to ventral and dorsal myotome regions. Caudal primary motoneurons, CaPs, pioneer axon outgrowth along ventral myotomes; whereas, middle primary motoneurons, MiPs, extend axons along dorsal myotomes. Although the development and axon outgrowth of these motoneurons has been characterized, cues that determine whether axons will grow dorsally or ventrally have not been identified. The topped mutant was previously isolated in a genetic screen designed to uncover mutations that disrupt primary motor axon guidance. CaP axons in topped mutants fail to enter the ventral myotome at the proper time, stalling at the nascent horizontal myoseptum, which demarcates dorsal from ventral axial muscle. Later developing secondary motor nerves are also delayed in entering the ventral myotome whereas all other axons examined, including dorsally projecting MiP motor axons, are unaffected in topped mutants. Genetic mosaic analysis indicates that Topped function is non-cell autonomous for motoneurons, and when wild-type cells are transplanted into topped mutant embryos, ventromedial fast muscle are the only cell type able to rescue the CaP axon defect. These data suggest that Topped functions in the ventromedial fast muscle and is essential for motor axon outgrowth into the ventral myotome.     

Onychiurid species from Wanda Mountains in China,with descriptions of two new species (Collembola,Onychiuridae)

A checklist of onychiurid species from the Wanda Mountains in China is presented. Eighteen species belonging to twelve genera have been found, including two new species. Bionychiurus qinglongensis sp. n. can be easily distinguished from other known species of the genus by the absence of pseudocelli on Th. I tergum and fewer number of vesicles in postantennal organ. Onychiurus heilongjiangensis sp. n. is diagnosed by pseudocellar formulae as 32/133/33352 dorsally and 3/011/31120 ventrally, parapseudocellar formula as 0/000/111001+1^m, ratio of anal spine/unguis as 0.6, unguiculus without inner basal lamella, and male ventral organ absent.     

THE DYNAMICS OF WOUND CLOSURE AND ITS ROLE IN THE PROGRAMMING OF PLANARIAN REGENERATION. II — DISTALIZATION

When the dorsal and ventral epidermal layers join by first intention during the closure of the wound, the cells of their borders (M-cells) do not meet in the same manner in all sections. In anterior sections the dorsal M-cells attach themselves to the ventral basement membrane, so that only the dorsal epidermis is stretched. In posterior sections the dorsal and the ventral M-cells join by their apical edges without being closely apposed to the wound surface. Only the ventral cells are stretched because of their specific motility. In longitudinal sections the dorsal and the ventral M-cells also join by their apical edges, but since they are closely apposed to the wound surface both epidermal layers are stretched. The stretching is a process equivalent to distalization. The junction between the dorsal and the ventral epidermis is shifted ventrally in the anterior wounds (as in the intact heads) and dorsally in the posterior wounds (as in the intact tails). Some abnormalities of wound closure have been observed at levels where heteromorphic regeneration frequently occurs. These findings are consistent with the hypothesis previously advanced (3) that the modalities of wound closure establish the programme for regeneration.     

Touch-Sensitive NADH Oxidase Activity of Pea and Cucumber Tendrils and Soybean Hypocotyl Sections

The cell surface reduced nicotinamide adenine dinucleotide (NADH) oxidase activity of soybean stems and of pea and cucumber tendrils responded to touch with a several-fold increase in activity. The increase in NADH oxidase persisted for 20 min or longer, and further touch stimulation during this period did not alter activity. With soybean sections, the specific activities in response to touch approximated those achieved maximally by auxin. Where the NADH oxidase was fully stimulated by 2,4-d, the NADH oxidase failed to respond further to touch. The findings indicate that the NADH oxidase of the plant cell surface is involved in the growth response to touch and in tendril coiling.     

Topographic mapping in dorsoventral axis of the Xenopus retinotectal system depends on signaling through ephrin-B ligands

Ephrin-B and EphB are distributed in matching dorsoventral gradients in the embryonic Xenopus visual system with retinal axons bearing high levels of ligand (dorsal) projecting to tectal regions with high receptor expression (ventral). In vitro stripe assays show that dorsal retinal axons prefer to grow on EphB receptor stripes supporting an attractive guidance mechanism. In vivo disruption of EphB/ephrin-B function by application of exogenous EphB or expression of dominant-negative ephrin-B ligand in dorsal retinal axons causes these axons to shift dorsally in the tectum, while misexpression of wild-type ephrin-B in ventral axons causes them to shift ventrally. These dorsoventral targeting errors are consistent with the hypothesis that an attractive mechanism that requires ephrin-B cytoplasmic domain is critical for retinotectal mapping in this axis.     

The oculomotor system of Daphnia magna

Summary The highly mobile cyclopic compound eye of Daphnia magna is rotated by six muscles arranged as three bilateral pairs. The three muscles on each side of the head share a common origin on the carapace and insert dorsally, laterally and ventrally on the eye. The dorsal and ventral muscles are each composed of two muscle fibers and the lateral muscle is composed of from two to five fibers, with three the most common number. Individual muscle fibers are spindle-shaped mononucleated cells with organized bundles of myofilaments. Lateral eye-muscle fibers are thinner than those of the other muscles but are otherwise similar in ultrastructure. Two motor neurons innervate each dorsal and each ventral muscle and one motor neuron innervates each lateral muscle. The cell bodies of the motor neurons are situated dorsally in the supraesophageal ganglion (SEG) and are ipsilateral to the muscles they innervate. The dendritic fields of the dorsal-muscle motor neurons are ipsilateral to their cell bodies; those of the ventral-muscle motor neurons are bilateral though predominantly contralateral. The central projections of the lateral-muscle motor neurons are unknown. In the dorsal and ventral muscles one motor axon synapses principally with one muscle fiber; in each lateral muscle the single motor axon branches to, and forms synapses with, all the fibers. The neuromuscular junctions, characterized by pre- and postsynaptic densities and clear vesicles, are similar in all the eye muscles.     

THE NERVOUS MECHANISM OF COORDINATION IN THE CRINOID,ANTEDON ROSACEUS

1. Stimulation causes Antedon to swim by means of alternate oral bending and dorsal stroke of the arms. Two arms of a given ray move alternately so that while one is executing the aboral stroke its mate is flexing ventrally. This implies reciprocal inhibition. 2. Recriprocal inhibition between the two arms of an isolated ray can be abolished by the use of either strychnine or nicotine. 3. Coordination between the rays is referable to the conducting properties of the nervous pentagon which connects the five rays. In this system an impulse loses in effectiveness as it passes from the point of origin. 4. When Antedon is made to rest oral face down on the floor of an aquarium, oral flexion of all the rays, swimming movements, and righting result. Antedon is therefore negatively stereotropic with reference to its ventral side. 5. Excitation of the dorsal cirri results in aboral bending of all the rays. Stimulation of the cirri inhibits ventral flexion to the extent of preventing righting movements while on the other hand stimulation of the ventral surface inhibits the grasp reflex of the cirri. Thus oral and aboral sides of Antedon exhibit dynamic symmetry although structurally dissimilar.