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At least 19 recordsLinked to original sources
PubMed1999

Expression and developmental regulation of the Hydra-RFamide and Hydra-LWamide preprohormone genes in Hydra: evidence for transient phases of head formation.

Hydra magnipapillata has three distinct genes coding for preprohormones A, B, and C, each yielding a characteristic set of Hydra-RFamide (Arg-Phe-NH2) neuropeptides, and a fourth gene coding for a preprohormone that yields various Hydra-LWamide (Leu-Trp-NH2) neuropeptides. Using a whole-mount double-labeling in situ hybridization technique, we found that each of the four genes is specifically expressed in a different subset of neurons in the ectoderm of adult Hydra. The preprohormone A gene is expressed in neurons of the tentacles, hypostome (a region between tentacles and mouth opening), upper gastric region, and peduncle (an area just above the foot). The preprohormone B gene is exclusively expressed in neurons of the hypostome, whereas the preprohormone C gene is exclusively expressed in neurons of the tentacles. The Hydra-LWamide preprohormone gene is expressed in neurons located in all parts of Hydra with maxima in tentacles, hypostome, and basal disk (foot). Studies on animals regenerating a head showed that the prepro-Hydra-LWamide gene is expressed first, followed by the preprohormone A and subsequently the preprohormone C and the preprohormone B genes. This sequence of events could be explained by a model based on positional values in a morphogen gradient. Our head-regeneration experiments also give support for transient phases of head formation: first tentacle-specific preprohormone C neurons (frequently associated with a small tentacle bud) appear at the center of the regenerating tip, which they are then replaced by hypostome-specific preprohormone B neurons. Thus, the regenerating tip first attains a tentacle-like appearance and only later this tip develops into a hypostome. In a developing bud of Hydra, tentacle-specific preprohormone C neurons and hypostome-specific preprohormone B neurons appear about simultaneously in their correct positions, but during a later phase of head development, additional tentacle-specific preprohormone C neurons appear as a ring at the center of the hypostome and then disappear again. Nerve-free Hydra consisting of only epithelial cells do not express the preprohormone A, B, or C or the LWamide preprohormone genes. These animals, however, have a normal phenotype, showing that the preprohormone A, B, and C and the LWamide genes are not essential for the basic pattern formation of Hydra.

Animals↗
PubMed2000

Two-color double-labeling in situ hybridization of whole-mount Hydra using RNA probes for five different Hydra neuropeptide preprohormones: evidence for colocalization.

The freshwater polyp Hydra magnipapillata has a primitive nervous system that produces at least three distinct classes of neuropeptides: various peptides having the C-terminal sequence Arg-Phe-NH2 (the Hydra-RFamide family), Leu-Trp-NH2 (the Hydra-LWamide family), and a single peptide having the C-terminal sequence Lys-Val-NH2 (Hydra-KVamide). The various Hydra-RFamides are synthesized by three different preprohormones: preprohormone-A, -B, and -C. The various Hydra-LWamides are synthesized by a single preprohormone (prepro-Hydra-LWamide), as is Hydra-KVamide (prepro-Hydra-KVamide). Using a wholemount double-labeling two-color in situ hybridization technique and RNA probes specific for each of these five Hydra preprohormone mRNAs, we found that specific sets of neurons express each of the five preprohormones, except for the peduncle region of Hydra (an area just above the basal disk), where a population of neurons exists that expresses both preprohormones-A and preproHydra-KVamide mRNAs. The functional significance of this coexpression is unclear. This is the first report on the coexpression of two well-characterized preprohormones (yielding two well-characterized neurohormone families) in cnidarians. This report also shows that there are at least six neurochemically different populations of neurons in Hydra.

Animals↗
PubMed1993

Extracellular matrix (mesoglea) of Hydra vulgaris III. Formation and function during morphogenesis of hydra cell aggregates.

Hydra, as a member of the phylum Cnidaria, is characterized by a body lining organized as an epithelial bilayer with an intervening extracellular matrix (ECM) termed the mesoglea. Previous studies have established that the mesoglea has components indicative of mammalian ECM such as type IV collagen, laminin, fibronectin, and heparan sulfate proteoglycan, and these components appear to play a critical role in hydra head regeneration. A remarkable feature of hydra is its ability to reorganize into its adult structure within 96 hr to 7 days from pellets formed from dissociated hydra cells. This regenerative model has been termed the hydra cell aggregate system. The present study has been designed to characterize the biogenesis of mesoglea in hydra cell aggregates and to determine its role in morphogenesis of aggregates. We find that hydra cell aggregates first form an epithelial bilayer by 12 hr of development and then subsequently develop a mesoglea. Morphogenesis of hydra structure then follows formation of the mesoglea. Immunofluorescence studies indicate that mesoglea components are first deposited between the epithelial bilayer by about 12-17 hr of pellet formation, and pulse-labeling studies indicate that the translation rate of matrix components peaks by 48-72 hr of development. Ultrastructural studies indicate that a mature mesoglea is formed by 48-96 hr of pellet formation. Drugs such as beta-aminoproprionitrile and 2,2'-dipydridyl, which interfere with the cross-linking of collagens, and p-nitrophenyl-beta-D-xylopyranoside, which interferes with the addition of GAG moieties to proteoglycan core molecules, were found to reversibly block development of hydra cell aggregates. Transmission electron microscopy studies indicate that these drugs affect the ultrastructure of the mesoglea. In addition, both polyclonal and monoclonal antibodies raised to isolated mesoglea were found to block development of hydra cell aggregates. These studies indicate that (1) mesoglea formation is rapid and precedes morphogenetic processes during aggregate development, and (2) formation of mesoglea is essential for normal morphogenesis of hydra cell aggregates.

2,2'-Dipyridyl↗
PubMed1998

Three different prohormones yield a variety of Hydra-RFamide (Arg-Phe-NH2) neuropeptides in Hydra magnipapillata.

The freshwater polyp Hydra is the most frequently used model for the study of development in cnidarians. Recently we isolated four novel Arg-Phe-NH2 (RFamide) neuropeptides, the Hydra-RFamides I-IV, from Hydra magnipapillata. Here we describe the molecular cloning of three different preprohormones from H. magnipapillata, each of which gives rise to a variety of RFamide neuropeptides. Preprohormone A contains one copy of unprocessed Hydra-RFamide I (QWLGGRFG), II (QWFNGRFG), III/IV [(KP)HLRGRFG] and two putative neuropeptide sequences (QLMSGRFG and QLMRGRFG). Preprohormone B has the same general organization as preprohormone A, but instead of unprocessed Hydra-RFamide III/IV it contains a slightly different neuropeptide sequence [(KP)HYRGRFG]. Preprohormone C contains one copy of unprocessed Hydra-RFamide I and seven additional putative neuropeptide sequences (with the common N-terminal sequence QWF/LSGRFGL). The two Hydra-RFamide II copies (in preprohormones A and B) are preceded by Thr residues, and the single Hydra-RFamide III/IV copy (in preprohormone A) is preceded by an Asn residue, confirming that cnidarians use unconventional processing signals to generate neuropeptides from their precursor proteins. Southern blot analyses suggest that preprohormones A and B are each coded for by a single gene, whereas one or possibly two closely related genes code for preprohormone C. Northern blot analyses and in situ hybridizations show that the gene coding for preprohormone A is expressed in neurons of both the head and foot regions of Hydra, whereas the genes coding for preprohormones B and C are specifically expressed in neurons of different regions of the head. All of this shows that neuropeptide biosynthesis in the primitive metazoan Hydra is already rather complex.

Amino Acid Sequence↗
PubMed1993

Genetic analysis of developmental mechanisms in hydra. XX. Cloning of interstitial stem cells restricted to the sperm differentiation pathway in Hydra magnipapillata.

Hydra magnipapillata polyps containing a subpopulation of interstitial stem cells restricted to the germline differentiation pathway were obtained. Chim-C1 is a chimeric strain produced by combining wild-type epithelial cell lineages with a temperature-sensitive interstitial cell lineage. It grows normally at 18 degrees C. When cultured at 25 degrees C, many polyps lost interstitial cells and their differentiation products (nerve cells and nematocytes), and subsequently turned into epithelial hydra unable to move or feed. Some polyps, however, turned into an unexpected type, termed "pseudo-epithelial hydra." These polyps resembled epithelial hydra in the absence of nerve cells or nematocytes in the tissue and in their inability to move or feed. In contrast to epithelial hydra, however, their tissue contained proliferating interstitial cells. Similar pseudo-epithelial hydra were also produced from another strain, nem-1, by means of hydroxyurea treatment. Clones of pseudo-epithelial hydra were maintained through force-feeding over 130 days for chim-C1 and over 2 years for nem-1. In both cases, interstitial cells proliferated throughout the period without producing any nerve cells or nematocytes. These interstitial cells, however, differentiated into sperm. Thus, the interstitial cells present in pseudo-epithelial hydra were able to differentiate into gametic cells but not into somatic cells (nerve cells and nematocytes). These observations suggest that, as Littlefield (1985, Dev. Biol. 112, 185-193) has shown for H. oligactis, the interstitial stem cell population in H. magnipapillata includes a subpopulation which can differentiate only into gametic cells.

Animals↗
PubMed1981

Hydra viridis: transfer of metabolites between Hydra and symbiotic algae.

"Back transfer" of metabolites from food to endosymbiotic algae in the digestive cells of Hydra viridis was demonstrated. Brine shrimp nauplii labeled with tritiated precursors of protein and nucleic acids (DNA and RNA) were fed to light and dark grown hydras. The fate of the label after a single feeding with radioactive material in hydra and algal fractions was followed by scintillation counting and autoradiographic techniques. Labeled thymidine was incorporated into DNA in both light- and dark-grown hydras. Although the symbiosis persists indefinitely in hydras in darkness (7-10 days) the number of algae per cell is reduced. Tritiated orotic acid and tritiated uridine, RNA precursors, were incorporated into peptides and proteins, and to a lesser extent into simple sugars, oligosaccharides, and oligonucleotides in hydra and algal fractions. Thus the metabolites of the brine shrimp food are available to both partners. A decrease over time in label introduced as 3H-orotic acid and 3H-uridine and incorporated into hydra RNA is compensated for by an increase in label in the algae, implying competition for constant quantities of metabolites from the single feeding. Although food availability, light, number of algae per cell, and other factors influence the quantity and rate of nutrient transfer between the partners, in both light and dark grown hydras the amount of "back transfer" of metabolites to the symbiotic algae is impressive.

Animals↗
PubMed1997

Molecular cloning of a preprohormone from Hydra magnipapillata containing multiple copies of Hydra-L Wamide (Leu-Trp-NH2) neuropeptides: evidence for processing at Ser and Asn residues.

The simple, freshwater polyp Hydra is often used as a model to study development in cnidarians. Recently, a neuropeptide, < Glu-Gln-Pro-Gly-Leu-Trp-NH2, has been isolated from sea anemones that induces metamorphosis in a hydroid planula larva to become a polyp. Here, we have cloned a preprohormone from Hydra magnipapillata containing 11 (eight different) immature neuropeptide sequences that are structurally related to the metamorphosis-inducing neuropeptide from sea anermones. During the final phase of our cloning experiments, another research team independently isolated and sequenced five of the neuropeptides originally found on the preprohormone. Comparison of these mature neuropeptide structures with the immature neuropeptide sequences on the preprohormone shows that most immature neuropeptide sequences are preceded by Ser or Asn residues, indicating that these residues must be novel processing sites. Thus, the structure of the Hydra preprohormone confirms our earlier findings that cnidarian preprohormones contain unusual or novel processing sites. Nearly all neuropeptide copies located on the Hydra preprohormone will give rise to mature neuropeptides with a C-terminal Gly-Leu-Trp-NH2 sequence (the most frequent one being Gly-Pro-Pro-Pro-Gly-Leu-Trp-NH2; Hydra-LWamide l; three copies). Based on their structural similarities with the metamorphosis-inducing neuropeptide from sea anemones, the mature peptides derived from the Hydra-LWamide preprohormone are potential candidates for being developmentally active neurohormones in Hydra.

Amino Acid Sequence↗
PubMed1995

A 25.7 x 10(3) M(r) hydra metalloproteinase (HMP1), a member of the astacin family, localizes to the extracellular matrix of Hydra vulgaris in a head-specific manner and has a developmental function.

Hydra extracellular matrix (ECM) is composed of a number of components seen in vertebrate ECM such as laminin, type IV collagen, fibronectin, and heparan sulfate proteoglycan. A number of functional studies have shown that hydra ECM plays an important role in pattern formation and morphogenesis of this simple metazoan. The present study was designed to identify matrix degrading proteinases in hydra and determine their potential function in hydra morphogenesis. Using SDS-PAGE gelatin-zymography, five gelatinolytic bands were identified with relative molecular masses of 67 x 10(3), 51-58 x 10(3) (a triplet) and 25-29 x 10(3), respectively. Inhibition studies indicated that all of these gelatinases were metalloproteinases. Gelatin-zymography indicated that there was a differential distribution of these gelatinases along the longitudinal axis of hydra, with the 67 x 10(3) M(r) gelatinase being concentrated in the body column, while the 51-58 x 10(3) M(r) gelatinase triplet and the 25-29 x 10(3) M(r) gelatinase concentrated in the head region. Purification procedures were successfully developed for the 25-29 x 10(3) M(r) metalloproteinase which has been termed hydra metalloproteinase 1 (HMP1) and which appeared as a single band with a SDS-PAGE mobility of 25.7 x 10(3) M(r). The N-terminal sequence of purified HMP1 indicated that it has structural homology with metalloproteinases that belong to the astacin family. Subsequent cloning and sequencing of cDNA clones confirmed the identification of HMP1 as an astacin-like metalloproteinase. Immunocytochemical studies with antibodies generated against the purified enzyme and to a synthetic peptide indicated that HMP1 was localized to the ECM of tentacles. Functional studies were performed in which purified HMP1, anti-HMP1 IgG, or suspected substrates of HMP1 (e.g. growth factors such as TGF-beta 1) were introduced into the interepithelial compartment of hydra using a 'DMSO loading' procedure. These studies indicated that HMP1 has a functional role during a number of developmental processes such as head regeneration and cell differentiation/transdifferentiation of tentacle battery cells.

Amino Acid Sequence↗
PubMed2001

Hydra and Niccolo Paganini (1782-1840)--two peas in a pod? The molecular basis of extracellular matrix structure in the invertebrate, Hydra.

The body wall of Hydra is organized as an epithelial bilayer with an intervening extracellular matrix (ECM). Molecular and biochemical analyses of Hydra ECM have established that it contains components similar to those seen in more complicated vertebrates such as human. In terms of biophysical parameters, Hydra ECM is highly flexible; a property that facilitates continuous movements along the organism's longitudinal and radial axis. A more rigid ECM, as in vertebrates, would not be compatible with this degree of movement. The flexible nature of Hydra ECM can now be explained in part by the unique structure of the organism's collagens. Interestingly, some aspects of the structural features of Hydra collagens mimic what is seen in Ehlers-Danlos syndrome, an inherited condition in humans that results in an abnormally flexible ECM that can be debilitating in extreme cases. This review will focus on structure-function relationships of the ECM of Hydra.

Animals↗
PubMed1996

Isolation of four novel neuropeptides, the hydra-RFamides I-IV, from Hydra magnipapillata.

Using a radioimmunoassay for the sequence Arg-Phe-NH2 (RFamide), we have isolated four novel peptides from extracts of Hydra magnipapillata: <Glu-Trp-Leu-Gly-Gly-Arg-Phe-NH2 (Hydra-RFamide I), <Glu-Trp-Phe-Asn-Gly-Arg-Phe-NH2 (Hydra-RFamide II), Lys-Pro-His-Leu-Arg-Gly-Arg-Phe-NH2 (Hydra-RFamide III) and His-Leu-Arg-Gly-Arg-Phe-NH2 (Hydra-RFamide IV). The Hydra-RFamides I-IV are neuropeptides. They form a peptide family with other known neuropeptides from hydromedusae, sea anemones and sea pansies.

Animals↗
PubMed1995

Genetic analysis of developmental mechanisms in Hydra. XXII. Two types of female germ stem cells are present in a male strain of Hydra magnipapillata.

Three types of interstitial stem cell subpopulation were isolated from Hydra magnipapillata, and their roles in sex determination were examined. A subpopulation of interstitial stem cells restricted to the sperm differentiation pathway was isolated previously from strain nem-1 (male). Another subpopulation restricted to the egg differentiation pathway was also isolated from the same strain. Hydroxyurea treatment was used for isolation in both cases. "Pseudoepithelial hydra" containing only sperm- or egg-restricted stem cell but no other interstitial stem cell types were maintained by force-feeding for 2 years. Sex reversal from egg- to sperm-restricted stem cells occurred three times during this period. Both of these two stem cell types are numerous in the central gastric region of the pseudoepithelial hydra, but absent in the foot region below the budding zone. Foot tissue was cut out from normal nem-1 polyps (male) and allowed to regenerate. The regenerates produced eggs but no sperm upon sex induction. These and other results suggest that the foot tissue contains multipotent stem cells capable of differentiating into eggs during sexual differentiation. These observations suggest that strain nem-1 (male) contains three types of interstitial stem cell subpopulations: (1) sperm-restricted stem cells, (2) egg-restricted stem cells, and (3) multipotent stem cells capable of differentiating into nerve cells, nematocytes, and eggs. Upon sex induction, however, differentiation of eggs by the latter two types is suppressed, and only sperm are produced by the sperm-restricted stem cells. Evidence is presented which suggests that similar "phenotypic males," which normally only produce sperm but contain the stem cell types capable of differentiating into eggs, occur widely in Hydra magnipapillata. A possible relationship between phenotypic male hydra and hermaphroditic hydra is discussed.

Animals↗
PubMed1982

Cultivation of bacteria-free Hydra viridis: missing budding factor in nonsymbiotic hydra.

Bacteria-free hydra, cultured in sterile media, were fed bacteria-free larvae of Artemia salina. Normal growth and budding were obtained in symbiotic and aposymbiotic Hydra viridis. Two nonsymbiotic hydra species did not form buds under bacteria-free conditions. When these hydra were fed nonsterile Artemia, or if the medium was reinoculated with bacteria isolated from budding stock cultures, normal budding was resumed. An exogenous budding factor, which can be provided by nonsterile Artemia larvae, or even by some bacteria, appears to be required by these nonsymbiotic hydra. This factor is endogenous in Hydra viridis.

Animals↗
PubMed1988

Thermotolerance and synthesis of heat shock proteins: these responses are present in Hydra attenuata but absent in Hydra oligactis.

Organisms respond to environmental stress by synthesizing a small number of highly conserved heat shock proteins. In organisms as diverse as bacteria, plants, invertebrates, and vertebrates, synthesis of these proteins is directly correlated with the acquisition of thermotolerance. While studying the freshwater coelenterate hydra, we observed that Hydra oligactis was extremely sensitive to thermal stress. In contrast, the related species Hydra attenuata survives short-term exposure to high temperatures. Furthermore, after incubation at an elevated but nonlethal temperature, H. oligactis did not become thermotolerant. H. attenuata, however, acquired thermotolerance after such a preincubation. In H. attenuata the major heat shock protein was found to be 60 kDa in size. H. oligactis did not synthesize detectable levels of this protein or any new species of proteins in response to stress. Several other species of hydra were found to behave like H. oligactis in response to stress. Thus, these findings provide direct support for the hypothesis that heat shock proteins are required for stress tolerance and that the major heat shock protein in hydra does not have any effects on normal growth or physiology. The findings also indicate that the presence of a heat shock response might be related to the natural environment in which an organism lives.

Animals↗
PubMed1979

Genetic analysis of developmental mechanisms in hydra. VI. Cellular composition of chimera hydra.

The homeostatic mechanisms that maintain constant cellular ratios in hydra tissue were studied using mutant and chimeric hydra strains. Mutants having abnormal cellular compositions are isolated through sexual inbreeding of wild hydra, as described in previous papers of this series. Chimeric hydra are produced by making use of a strain (nf-I) which lacks interstitial cells, nerve cells and nematocytes in its tissue. Reintroduction of interstitial cells from other strains (both normal and mutant) into nf-I leads to creation of chimeric strains having epithelial cell lineages from one strain (nf-I) and interstitial cell lineages from others. Analyses and comparisons of the cellular compositions of all these strains revealed that the numbers of nerve or interstitial cells in the chimeras were very similar to (statistically significantly correlated with) those in their interstitial cell donors. Since chimeras and their interstitial cell donors share the same interstitial cell lineages, this suggests that interstitial cells or their derivatives (nerves and nematocytes) play major roles in determining the nerve and interstitial cell levels in the hydra tissue. It is suggested that some form of homeostatic feedback mechanisms are probably involved in regulating the levels of these cell types.

Animals↗
PubMed1983

Hydra transplantation phenomena and the mechanism of hydra head regeneration. I. Properties of the head inhibition.

Measurements were made of the "head inhibition" and the "head inhibition gradient" in Hydra. Following decapitation, the head inhibition decays with a half-time of 2-3 hr. The slope of the inhibition gradient increases about twofold when the temperature is raised from 20 to 24 degrees C; the increase (at the higher temperature) occurs with a half-time of about 1.2 hr. These results are consistent with the idea that the head inhibition and the head inhibition gradient are due to a diffusing substance, made in the head and broken down in the body of Hydra, with a half-life of about 2 hr at 20 degrees C and about 1 hr at 24 degrees C. Calculations suggest a diffusion constant of 1-3 X 10(-6) cm2/sec and a gradient range (ratio of maximum to minimum concentration) of about 2. During head regeneration, the head inhibition returns much more slowly than one would expect if its production were switched on at the time of "head determination." The slow return of the inhibition can be explained if one assumes that determination is due to the "activation" of a few cells, while the restoration of inhibition depends on the lateral expansion of the activated region. This behavior is observed in a "proportion-regulating" diffusion-reaction model proposed by Gierer and Meinhardt, 1972, Kybernetik 12, 30-39. Transplants to beheaded animals demonstrate a substantial inhibition gradient even at 6 hr after decapitation, a time at which most of the inhibitor from the original head should have decayed and no substantial amount of inhibitor is expected from the regenerated head. Experiments in which parts of a hydra's body are removed suggest that this inhibition gradient is due to the production of some inhibitor in the body, with larger amounts produced in apical portions.

Animals↗
PubMedDate not supplied

The effects of dopamine synthesis inhibitors and dopamine antagonists on regeneration in the hydra Hydra attenuata.

The effects of catecholamine synthesis inhibitors (alpha-methyltyrosine, 3-iodotyrosine, and alpha-methyl-DOPA) and dopamine receptor blockers (haloperidol and spiperone) on the regeneration of apical, gastral, and basal fragments of the hydra Hydra attenuata were studied. These experiments showed that alpha-methyltyrosine and 3-iodotyrosine significantly inhibited regeneration but did not produce morphological anomalies. Alpha-Methyl-DOPA produce less inhibition of regeneration, but induced ectopic tentacles and outgrowths in gastral regenerates. Haloperidol and spiperone had no significant effect on the rate of regeneration but induced significant numbers of morphogenetic anomalies in gastral regenerates. Apical and basal regenerates, which retained their natural organizers (the head and base respectively) never yielded morphogenetic anomalies in the presence of either dopamine receptor blockers or dopamine synthesis inhibitors. The possible role of neurotransmitters. particularly dopamine, in morphogenesis in hydras is discussed.

Animals↗