The absence of electrically demonstrable polarizing factors in Hydra

Various investigators have shown that in the marine hydroids, Tubularia, Obelia, Eudendrium, and Pennaria, regeneration and polarity is affected by an electrical field applied parallel to the regenerate. Using electrical currents up to the physiological limits for Hydra, no relation between electrical current and regeneration rate or polarity could be demonstrated. This is in spite of the fact that adult Hydra are normally electrically polarized with the distal end approximately–18 mV relative to the proximal end of the animal. When the electrophoretic mobility and isoelectric point of cells from distal, central and proximal thirds of Hydra were measured, a significant difference was found between cells of the two cell layers but not between cells of the three body thirds. These results are discussed in relation to Hydra growth factors described by various other authors.     

Three digestive movements in<Emphasis Type="Italic"> Hydra</Emphasis> regulated by the diffuse nerve net in the body column

The mammalian digestive tract undergoes various digestive movements such as peristalsis and segmentation movement. How those digestive movements and the underlying mechanisms appeared in evolution remains unraveled. A widely accepted view has been that, early in evolution, the digestive process was static based upon diffusion, and later it became dynamic involving digestive movements. Here, we report digestive movements which occur in Hydra, a member of the phylum Cnidaria. We find that the body column of Hydra undergoes a series of movements when fed with Artemia. Comparison of the movements to those in mammals showed similarities in appearance to esophageal reflex, segmentation movement, and defecation reflex. When nerve cells were eliminated, polyps showed only a weak segmentation movement, demonstrating that the diffuse nerve net in the body column of Hydra primarily regulates the movements just as the netlike enteric nervous system does in mammals. Elimination of both secretory gland cells and nerve cells resulted in the complete loss of movement, suggesting that the gland cells are involved in the weak movement. Overall, these observations suggest that the digestive process in Hydra is dynamic and that the diffuse nerve net regulates the digestive movements as a primitive form of enteric nervous system.     

The general occurrence of intramitochondrial crystals in Hydra cells

Summary Intramitochondrial crystals are found in normal Hydra as well as in animals undergoing various conditions (budding, regenerating, eserinetreated, and sexual). They appear in all regions of the animal, but seem to be more prevalent at or near the extremities: hypostome, tentacles and basal disk. They are found in all of the seven basic cell types: interstitial, cnidocyte, nerve, epithelio-muscular, gland, mucous and digestive cells. The chemical nature of the intramitochondrial crystals is unknown and their significance remains speculative.This investigation was supported by the National Science Foundation, Grant Number Gb-27395     

Identification and linkage relationships of three hexokinase genes in Aedes aegypti

Four regions of hexokinase activity are detected by starch gel electrophoresis of adult Aedes aegypti. Three of the regions, Hk-2, Hk-3, and Hk-4, are produced by three tightly linked loci, located on the third chromosome 7.25 map units from the locus fuzzy. The three loci show developmental differences as well as differences in substrate specificity.This work was supported by grants from the National Institutes of Health, AI 05118-02 and AI 12016.     

Effects of Altered Light and Feeding Regimes on the Zooplankton Feeding Capability of Hydra viridis

The effects of light regime, feeding regime and tentacle number on the zooplankton feeding capability of Hydra viridis were tested in the laboratory. Feeding was measured by exposing Hydra to a known volume of Artemia salina nauplii and recording the number captured and ingested. In all cases there was a correlation between the number of Artemia captured and the number ingested. H. viridis with 7 tentacles captured and ingested more Artemia than Hydra with 6 tentacles. However, changes in light and/or feeding regimes did not alter the number of tentacles/Hydra. Varying light and feeding regimes altered the number of Zoochlorellae/cell and Hydra growth rate. There was no effect on the number of Artemia captured or ingested and no effect on the percent ingestion of captured Artemia. These data suggest that, under these conditions, zooplankton feeding by H. viridis is independent of nutritional history.     

Fine structure of the pterin layer in the dermis of Rana pipiens

Summary The fine structure of the pterin layer was investigated in both wild type Rana pipiens and Rana pipiens homozygous for the speckle mutant gene. No difference in morphology of the layer was noted between the wild type and mutant. The layer lines the outer surface of the stratum compactum of the dermis and separates this stratum from the stratum spongiosum. The pterin layer consists of extra-cellular material and contains membrane-bounded granules filled with fine spicules. Many of the spicules are somewhat similar in appearance to the initial calcification loci present in developing membrane bone. The layer first appears in the tadpole at approximately stage 14 (Taylor and Kollros, 1946); subsequent developmental stages are described.This work was supported by United States Public Health Service Fellowships (to G.E.W.) 1-FO2-CA32869-01 and 5-FO2-CA32869-02; (to L.W.B.) 1-FO2-GM-32, 906-01 and 1-FO2-GM-32-906-02; by funds from an Institutional Grant to the University of Colorado from the American Cancer Society (L.W.B.); by National Research Council (Canada) Grant # A6209 (L.W.B.); by Program Project HD-02282 of the National Institutes of Health; and by Health Sciences Advancement Award FR-02084 from the National Institutes of Health.     

Genetic linkage relationships between two enzyme loci,Est-2 and acph,in the mosquito Aedes (Finlaya) togoi

An esterase locus (Est-2), coding for carboxylesterase, and an acid phosphatase locus (Acph) were genetically studied by agar gel electrophoresis in the mosquito Aedes (Finlaya) togoi. The Est-2 and Acph variants occur as a monomer and a dimer, respectively. Both enzyme loci are linked to the sex locus (M) and s (straw-colored larva); the gene arrangement and recombination distances were Est-2—12.6%—s—31.7%—M—2.9%—Acph—3.2%—Est-3. The Est-3 locus was previously shown to code for carboxylesterase.This work was supported by Grant AI 16983-02 from the National Institutes of Health, Bethesda, Md.     

Histological and ultrastructural studies of the basal disk of Hydra

Summary The gastrodermis and mesoglea of the basal disk of Hydra were investigated to conclude a three-part series of papers. The gastrodermis is composed of digestive cells (most predominant cell type), mucous and nerve cells (both immature and fully differentiated). The principal function of the digestive cells appears to be storage of protein, lipid and glycogen reserves which are utilized by neighboring cells. Mucous cells apparently use some of the reserves to synthesize their secretions which lubricate cells and prevent cell damage during egestion of waste through the aboral pore. The function of the gastrodermal nerve cells is uncertain.The mesoglea of the basal disk, contains the same structural components as seen in other regions of the polyp. It is reasonable to assume that it maintains the same function of cell adhesion and migration. As the mesoglea converges on the aboral pore, it loses its structural integrity and cells are sloughed off the column.This investigation was supported by The National Science Foundation, Grant Number GB-27395.     

The Hydra small ubiquitin‐like modifier

SUMO is a protein posttranslational modifier. SUMO cycle components are believed to be conserved in all eukaryotes. Proteomic analyses have lead to the identification a wealth of SUMO targets that are involved in almost every cellular function in eukaryotes. In this article, we describe the characterization of SUMO Cycle components in Hydra, a Cnidarian with an ability to regenerate body parts. In cells, the translated SUMO polypeptide cannot conjugate to a substrate protein unless the C‐terminal tail is cleaved, exposing the di‐Glycine motif. This critical task is done by SUMO proteases that in addition to SUMO maturation are also involved in deconjugating SUMO from its substrate. We describe the identification, bioinformatics analysis, cloning, and biochemical characterization of Hydra SUMO cycle components, with a focus on SUMO and SUMO proteases. We demonstrate that the ability of SUMO proteases to process immature SUMO is conserved from Hydra to flies. A transgenic Hydra, expressing a SUMO‐GFP fusion protein under a constitutive actin promoter, is generated in an attempt to monitor the SUMO Cycle in vivo as also to purify and identify SUMO targets in Hydra. genesis 51:619–629. © 2013 Wiley Periodicals, Inc.     

Is homarine a morphogen in the marine hydroid Hydractinia?

Summary Homogenate of coelenterate tissue interferes with metamorphosis in Hydractinia and pattern formation in both Hydractinia, and Hydra. From the extracts two fractions comprising low-molecular-weight compounds with strong metamorphosis-inhibiting activity were separated. One of these contains, as the active compound, homarine (N-methyl picolinic acid). Homarine concentrations down to 10^–6 mol/l stop or retard metamorphosis. High concentrations block the continuation of metamorphosis as long as they are maintained in the culture medium and treatment with homarine during metamorphosis influences the proportioning of the future polyp's body pattern. Most of the homarine found in Hydra tissue derives from Artemia given as food. It is not identical with inhibitor I, an activity partially purified from Hydra tissue, which prevents head and foot formation in Hydra.     

Cellular mechanisms of stimulation of bud production in Hydra by low levels of inorganic lead compounds

Summary Treatment of Hydra with subtoxic levels of inorganic lead compounds (lead nitrate and lead chloride) for periods ranging from 5 min to one hour causes a temporary increase in bud production as compared to untreated control animals. This effect can be inhibited by the addition of large amounts of calcium chloride to the culture medium.The increased rate of budding is preceded by a dramatic increase in the number of nerve cells per animal, which is first observed within six hours after lead treatment. This appears to be the result of an increased rate of mitosis in the undifferentiated interstitial cells and their subsequent differentiation into nerve cells. The total number of cells per animal also increases after exposure to lead compounds, suggesting that lead may act as a general mitotic stimulator of all dividing cell types in Hydra.This investigation was supported by the National Science Foundation, Grant GB-27395     

Perioral synaptic connections and their possible role in the feeding behavior of Hydra

Electron microscopic observations of serially sectioned perioral neurons revealed a complex synaptic organization in which reciprocal synapses were observed for the first time in Hydra. Sensory cells had reciprocal synapses with each other and with ganglion cells, which in turn had reciprocal synapses with each other. A two-way chemical synapse with vesicles on both sides of the paramembranous densities was observed between ganglion cells; none was found between sensory cells. Ganglion cell axons participated in serial axo-axo-epitheliomuscular synapses. Two-cell pathways formed by direct sensory cell-nematocyte or neuromuscular synapses and three-cell pathways forming indirect sensory cell-ganglion cell-nematocyte or neuromuscular synaptic interconnections were found. It is possible that either simple direct changes in or direct effects on threshold stimuli could trigger both nematocyst discharge and/or muscular contraction and effect more complex intermediate pathways modulating feeding behavior. Each large epitheliomuscular cell enveloped from one to four sensory cells in the perioral region. The concentration of sensory cells around the mouth and their complex synaptic connections with each other and with ganglion and effector cells support our hypothesis for neural control of feeding behavior in Hydra.     

The Application of Autoradiography to Developmental Studies in the Hydrozoa

The uptake of isotopically labelled nucleotides and amino acidshas been studied in five species of hydrozoans. In three speciesthe label was introduced both through immersion in a mediumcontaining the labeled compound and by injecting the labeledcompound into the gastrovascular cavity. In the remaining twospecies the label was introduced by immersion only. The comparisonof soaked and injected specimens clearly indicates that injectionis the method of choice whenever the injection of compoundsinto the gastrovascular cavity is possible. The relative easewith which labeled compounds were absorbed can be correlatedwith the ultrastructure of the epidermal and gastrodermal cellsurfaces and their associated extracellular coats. The use ofthese autoradiographic techniques is illustrated by the useof injected tritiated thymidine and tritiated uiidine to followthe replacement cycle of the zymogenic secretory cell in Hydra,and the use of immersion to introduce tritiated thymidine intothe planula larva of Pennaria.     

Control of metamorphosis and pattern formation in Hydratinia (hydrozoa,cnidaria)

Hydractinia echinata is a marine colonial hydroid, a relative of the more widely known Hydra. In contrast to Hydra, embryogenesis, metamorphosis and colony growth in Hydractinia are experimentally accessible and therefore, provide an ideal model system for investigating the biochemical basis of pattern formation. In particular, the processes involved in the transformation of the drop-shaped freely swimming larva into a sessile tube-shaped polyp are easily monitored, because this transfomation can be induced by application of various substances. Our results indicate that the internal level of S-adenosylmethionine (SAM), potentially the most important methyl donor in transmethylation processes, plays a key role in the onset of metamorphosis. It is also proposed that the internal level of SAM plays a pivotal role in the proportioning and spacing of polyps within the colony.     

Inhibitory effects of organic sulfur compounds on Histoplasma capsulatum

Summary Eight classes of organic sulfur compounds, comprising 42 substances, were tested in vitro for activity against the yeast phase ofHistoplasma capsulatum Darling. Activity was found in the classes of thiols, thio acids, disulfides, and thiolsulfonates. The classes of sulfinates, sulfenamides, penicillamine analogs, and reaction products of thiols with aldehydes or ketones were unpromising. Tentative conclusions are drawn of structure-activity relations within classes as a guide to coupling of classes to form disulfides.This investigation was supported by Biomedical Science Support Grant, National Institutes of Health Grant FR-07089-02 to Vanderbilt University (Ilda McVeigh) and by PHS Research Grant AM-11685 from the National Institute of Arthritis and Metabolic Diseases (Lamar Field).     

Ultrastructure of the hypodermis during cuticle formation in the third molt of the nematode Nippostrongylus brasiliensis

Summary The fine structure of the hypodermis of Nippostrongylus brasiliensis, a parasitic nematode of the rat, was studied in free-living third-stage filariform (infective) larvae, and in parasitic forms undergoing the third molt. In filariform larvae the hypodermis displayed a comparatively poorly developed RER, and few Golgi complexes, mitochondria, and vesicles. Nuclei contained large amounts of heterochromatin and no nucleoli. After worms reached the lungs and the third molt began, the RER, Golgi complexes, mitochondria, multivesicular bodies, and coated vesicles greatly increased in amounts. Nuclei displayed less heterochromatin and contained prominent nucleoli. These morphological changes were associated with transition from the free-living to the parasitic mode in life. The results were correlated with the fact that the hypodermis in N. brasiliensis is actively synthesizing culticular collagen during the third molt.This investigation was supported, in part, by awards 1-F02-AI3750-02 and AI-09625 from the National Institutes of Health, United States Public Health Service.We are grateful to Lida Petruniak and Dora Lou for technical assistance.     

The chromosomal complement of blastomeres in Arbacia punctulata

The diploid chromosomal complement of blastomeres of Arbacia punctulata is composed of 44 units. It includes two chromosomal pairs with distinctive structural features: the Nos. 1 which are long and subacrocentric, and the Nos. 2, somewhat shorter and submediocentric. The remaining short chromosomes, although structurally similar to each other, may be divided into three recognizable groups.This research was supported in part by National Institutes of Health Grant HD 00635-02.     

A Catecholamine storage in the pancreatic A2-cells of owl monkey (Aotes trivirgatus)

Summary The fluorescence method ofFalck andHillarp was used to study the occurrence of biogenic monoamines in the islets of Langerhans of monkeys. A storage of a catecholamine was demonstrated in the A₂-cells of owl monkey, whereas no histochemically demonstrable amount of monoamines could be seen in the islet cells of marmoset,Rhesus monkey, squirrel monkey, andCebus monkey.Supported by grants from the Swedish Medical Research Council (No. B69-14x-712-04C) and by the National Institutes of Health (No. 06701-02).     

Early postmortem changes in the Organ of Corti (guinea pig)

Summary Early post mortem changes in the Organ of Corti are described. 15 minutes after death, when kept at room temperature, 20° C (63° F), an oedematous swelling is observed within the cytoplasm of hair cells and nerve endings, the latter being more severe affected. After 30 minutes post mortem the mitochondria of the hair cells have also become significantly swollen. Three hours post mortem the general character of the hair cells is still recognizable, but most of the nerve endings have been completely destroyed. Acknowledgement. We wish to express our appreciation of the skilful technical assistance of Mrs. B. Flock, Miss A.-M. Lundberg, Miss Sonja Löfvenius, Mr. G. Bornholm and Mr. Rune Ragnefjell.This work was supported by grants from the Swedish Medical Research Council, the National Institute of Health grant (no NB 03956-02), the Therese and Johan Anderssons minne, the Gustav and Tyra Svenssons fund and the King Gustav V Research Fund.     

Endosymbiosis in Hydra and the Evolution of Internal Defense System

Certain species of Chlorella have exploited an intracellularhabitat and occur naturally as cytobionts in Hydra viridissima.The algae evoke phagocytosis by Hydra digestive cells and aresequestered in individual phagosomes that migrate to the baseof the host cells and resist fusion with lysosomes. The abilityto resist digestion is closely correlated with release of extracellularcarbohydrate (maltose) by the algae. The established populationof algae grows at an average rate equal to or greater than thatof the host and a constant population density is maintained.The host regulates algal population density by expelling ordigesting excess algae, or by controlling algal cell division.The control mechanism is unknown but can be breached by additionof inorganic ions to the Hydra culture medium with the resultthat the algae overgrow the Hydra. The Hydra-Chlorella symbiosis is probably mutually beneficial,but conditions such as prolonged darkness (with or without feeding)can reduce the competitive fitness of the host since this conditionresults in heterotrophy by the algae at the expense of selectedhost substrates. The evolution of selective permeability toorganic substrates is a major feature of the successful colonizationof the intracellular habitat by symbiotic Chlorella.