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PubMed1983

Hydra transplantation phenomena and the mechanism of Hydra head regeneration. II. Properties of the head activation.

Measurements were made of the "head activation" in transplanted fragments of Hydra tissue. The measurements confirm that head activation is graded in the body and that activation increases during head regeneration. Experiments of two different sorts show that regeneration-specific activation increase is confined to the presumptive head zone. When head formation is initiated and subsequently blocked, the activation decays back to its original level in about 12 hr; this is three times faster than the activation decay observed in body tissue moved to a more basal position. Experiments on foot formation phenomena show a similar lability difference. It thus appears that regeneration-specific activation increase involves a mechanism different from the one responsible for the gradient of activation in the body. Cutting produces a local increase of the head and/or foot activation level; this increase decays in about 12 hr. These results and those of the preceding paper are consistent with a version of the Gierer-Meinhardt model which also accounts for the regulation of the head/body proportion in Hydra.

Animals↗
PubMed1991

Cell lineages in Hydra: isolation and characterization of an interstitial stem cell restricted to egg production in Hydra oligactis.

In an attempt to isolate unipotent stem cells (progenitors to the nerve cells, nematocytes, gland cells, and gametes) from Hydra oligactis females, animals were treated with a drug (hydroxyurea, HU) that preferentially lowers or eliminates the interstitial stem cells, leaving the epithelial tissue intact. In this epithelial environment, interstitial cells remaining after treatment will proliferate and differentiate, permitting a long-term analysis of their developmental capabilities. Following treatment of females with HU, animals were isolated that contained interstitial cells that gave rise to eggs only. Two clones of animals containing these cells were propagated for several years and the growth and differentiation behavior of the interstitial cells examined in their asexually produced offspring. During this time, the cells displayed an extensive proliferative capacity (classifying them as stem cells) and remained restricted to egg differentiation. It is proposed that both the sperm- and the egg-restricted stem cells arise from a multipotent stem cell, which also gives rise to the somatic cells (see above), and that, in hydra, sex is ultimately determined by interactions between cells of the two germ cell lineages.

Animals↗
PubMed1964

BEHAVIOR IN HYDRA PIRARDI: INHIBITION OF THE CONTRACTION RESPONSES OF HYDRA PIRARDI.

Hydra pirardi contracts spontaneously and in response to external stimuli of light and mechanical agitation. Inhibition of these contractions occurs when the animal feeds on Artemia salina or when reduced glutathione is present in the environment. Such inhibition demonstrates the control of one receptor-effector system by another in hydra.

Animals↗
PubMed1978

Genetic analysis of developmental mechanisms in hydra. V. Cell lineage and development of chimera hydra.

Chimeric hydra were produced by making use of a strain (nf-1) which lacks interstitial cells, nerve cells and nematocytes. This strain arises by spontaneous loss of interstitial cells from its parental strain (sf-1) (Sugiyama & Fujisawa, 1978). Reintroduction of interstitial cells from other strains into nf-1 leads to the creation of chimeric strains that consisted of epithelial cells derived from strain sf-1 and interstitial cells and their derivatives (nerves and nematocytes) from other strains. In chimeras, interstitial or epithelial cells apparently maintain very stable cell lineages; no indication was obtained that suggested interstitial cell differentiation into epithelial cells or dedifferentiation in the opposite direction during the long courses of chimera cultures (up to one year). Developmental characters of chimeras were examined and compared to those of the epithelial cell (sf-1) and the interstitial cell donors. Almost all of the chimera's characters examined (growth rate, budding rate, tentacle numbers, polyp size, regenerative capacity, etc.) closely resembled those of the epithelial cell donor, but not of the interstitial cell donors. This suggests that epithelial cells, rather than interstitial or nerve cells, are the primary determinant of most, if not all, of hydra developmental characters.

Animals↗
PubMed1991

Effect of insecticides (Dimiline WP 25, Torak EC 24 and Gamacide 20) on hydra (Hydra vulgaris Pallas).

Investigations showed that the three insecticides used had the most damaging effect upon hydra immediately after treatment. The tentacles and the hypostome are the parts most often damaged. Inse the affected cells, lesions appear in the intracellular membranes, the nucleus shell and the membranes of the mitochondria, Golgi complex and the endoplasmic reticulum, while the cell membrane is preserved. The damaged parts of the body regenerate within three days. Zymogen cells play a significant role in the course of regeneration. They dedifferentiate into gastrodermal interstitial cells and later into other types of cells of the ectoderm and the gastroderm. Apart from their intense participation in regeneration, these totipotent cells also invariably participate in the formation of new hydra buds. It was observed that Dimiline WP 25 and Torak EC 24 in the concentrations used stimulate asexual reproduction of this animal.

Animals↗
PubMed1984

Genetic analysis of developmental mechanisms in hydra. XII. Analysis of chimaeric hydra produced from a normal and a slow-budding strain (L4).

Chimaeric hydra strains were produced from a normal strain (105) and a naturally-occurring mutant strain (L4) which has a large polyp size, a low budding rate and a high head-inhibition potential. Various properties of the chimaeras were then examined and compared to those of the two parental strains. Hydra tissue consists of three cell lineages: the ectodermal epithelial, the endodermal epithelial and the interstitial cell lineages. Using the methods recently developed by Marcum & Campbell (1978b) and by Wanek & Campbell (1982), six chimaeric strains were produced which contained six different combinations of the three cell lineages from 105 and L4. Evidence obtained from the comparison of the chimaeras and their parental strains indicates that the ectodermal epithelial cell lineage in L4 is primarily responsible for the large polyp size and the low budding rate of this strain, whereas the endodermal epithelial cell lineage is largely, and the interstitial cell lineage is also partially, responsible for the high head-inhibition potential in L4. This suggests that the mechanisms determining the occurrence and location of bud formation and the mechanisms determining the inhibition potential levels are not related to each other (cf. Takano & Sugiyama, 1983; Bode & Bode, 1983). Evidence was also obtained which suggests that the levels of the head-activation and head-inhibition potentials in the chimaeras are determined independent of each other, apparently without the cross-catalytic relationship between them assumed in the Gierer-Meinhardt model (Gierer & Meinhardt, 1972; Meinhardt & Gierer, 1974).

Animals↗
PubMed1986

Sex determination in hydra: control by a subpopulation of interstitial cells in Hydra oligactis males.

The stability of sexual phenotype was examined in a single clone of Hydra oligactis males maintained at two culture temperatures, 18 and 22 degrees C. At these temperatures animals of this species do not reproduce sexually, but reproduce asexually by budding, and males and females are morphologically indistinguishable. When the temperature is lowered to 10 degrees C gametogenesis is induced and sexual phenotype can be assayed. Males cultured for several years at 18 degrees C expressed a stable sexual phenotype when induced to undergo gametogenesis; males remained male. Those cultured at 22 degrees C for 1 year, however, expressed a low frequency of sex reversal from male to female; males ceased sperm differentiation and began producing eggs. Male sex reversal in cultures maintained at the higher temperature was correlated with the loss of a specific subpopulation of interstitial cells, those that bind the monoclonal antibody, AC2, which labels cells specific to the spermatogenic pathway in H. oligactis males. When interstitial cells restricted to this pathway were reintroduced into sex-reversed males (phenotypic females), the male phenotype was reestablished and animals reverted to sperm production. To further investigate the role of AC2+ cells in the masculinization of females, normal males (containing AC2+ cells) and sex-reversed males (lacking AC2+ cells) were grafted to females. In grafts between normal males and females, egg production ceased and sperm differentiation ensued, whereas those between sex-reversed males and females continued to produce eggs. Thus, the presence of AC2+ interstitial cells is strictly correlated with male sexual phenotypes and it is only in their absence that the female phenotype is expressed.

Animals↗
PubMed1991

Simultaneous effects of head activator on the dynamics of apical and basal regeneration in Hydra vulgaris (formerly Hydra attenuata).

Previous studies have demonstrated that head activator (HA), an 11 amino acid peptide, stimulates head-specific differentiation processes in hydra. Additionally, HA enhances the differentiation of interstitial cells into nerve cells. This study investigated the effects of exogenous synthetic HA on the dynamics of both apical and basal regeneration in a piece of tissue excised from the body column of treated animals which comprised one-eighth of the original animal. The dynamics of apical and basal regeneration were monitored using the monoclonal antibody TS19. This antibody binds to apical and basal ectodermal tissue very early in the process of regeneration, before morphological structures are evident. Labeling is ultimately localized to the tentacles of the head and a ring above the basal disc. Thus, TS19 is a useful tool for analyzing the dynamics of both apical and basal patterning processes in the same regenerate simultaneously. Quantification of TS19 positive areas on regenerates over a time course of 72 hr revealed that HA treatment accelerated and amplified the dynamics of both apical and basal TS19 labeling. The specific basal effect was novel and was demonstrated to occur in the absence of a determined head independently of new nerve cell differentiation. It is proposed that the basal effect was the result of growth factor-like activity of HA.

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