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At least 19 recordsLinked to original sources
PubMed1977

Glycogen deposits in the pyloric gland of the ascidian Styela clava (Urochordata).

The pyloric gland of Styela clava contains large glycogen deposits that are digested by treatment with alpha amylase and depleted by 15 days starvation. The deposits are surrounded by cytoplasmic regions containing smooth endoplasmic reticulum and mitochondria. The cells also have rough endoplasmic reticulum, Golgi cisterns, lysosomes, microvilli, cilia, and lateral infoldings of the plasma membrane. The fine structure of the pyloric cells and the position of tubules between the absorptive epithelium and general circulation suggest that the gland functions as the vertebrate liver in carbohydrate metabolism. The pyloric cells of Styela do not appear to be excretory in a "renal" sense, since there is no infolding of the basal plasmalemma and mitochondria are usually associated only with the glycogen deposits. However, a hepatic-like excretory role is consistent with current findings. In light of the phylogenic affinities of vertebrates and ascidians, it is possible that the pyloric gland is homologous to the liver.

Animals↗
PubMed1978

Bioluminescence: dual mechanism in a planktonic tunicate produces brilliant surface display.

Luminescent flashes emanate spontaneously and on mechanical stimulation from the bodies of Oikopleura dioica (Urochordata, Larvacea); flashes also emanate, on mechanical stimulation only, from both their occupied and discarded mucous houses. The luminescence is intrinsic to the animals and their houses. Field observations suggest that, because of this dual method of light production, larvaceans may contribute substantially to surface coastal displays of marine bioluminescence.

Animals↗
PubMed1977

Gel filtration analysis of vanadium in Ascidia nigra blood cell lysate.

Fractions from a Sephadex gel filtration of homogenized Ascidia nigra blood cell lysate were analyzed for vanadium by atomic absorption spectroscopy. The results were unaffected by temperature from 4-21 degrees C, and by ionic strength in the range 0.09-1.0 M (NaCl). Appreciable loss of vanadium in the supernatant was experienced above pH 2.2. Experiments at pH 2.1 under anaerobic conditions show that the green chromogen and the vanadium-containing bands elute separately. Under these experimental conditions, the vanadium-containing species is of relatively low (congruent to 1,000) molecular weight.

Animals↗
PubMed1975

Comparative physiology and the challenge of design.

Analysis of the complexity of biological organization commonly takes us through an initial and necessary stage of over-simplification towards the ultimate goal of an appreciation of the subtle intricacy of nature. One example of this is that recent advances in studies of the phosphagens have failed to confirm earlier hopes that the distribution of these substances could be used to confirm phylogenetic relationships. It is now suggested that a previously unrecognized factor influencing this distribution may be competing demands for arginine in the development of the testes. Another illustration is the belief that the presence of iodine in ascidians may provide a clue to the origin of thyroidal biosynthesis. This belief is probably sound, but the presence of abundant iodine in the tunic may well be a false trail. More significant is the presence of much smaller amounts of bound iodine in the endostyle, where its presence is probably correlated with specialized protein metabolism associated with the ciliary feeding mechanism. A third illustration, discussed in more detail, is provided by recent recognition that the gut is a major component of the vertebrate endocrine system. This lays open attractive fields of research, ranging from problems of molecular and hormonal evolution to aspects of fish farming and the physiology of gut parasites. The need is thus plain for breadth of perspective in comparative physiological research, and for recognition that the ultimate concern of the biologist is with the life and relationships of the whole organism.

Animals↗
PubMed1977

Segregation during cleavage of a factor determining endodermal alkaline phosphatase development in ascidian embryos.

Localized alkaline phosphatase activity (EC 3.1.3.1) develops progressively in endodermal tissues of the presumptive digestive system in Ciona intestinalis embryos. It was first detected histochemically at late gastrulation, and a puromycin sensitivity period coincident with this time suggests that new alkaline phosphatase is synthesized. Embryos in which cell division was blocked with cytochalasin B at early cleavage stages up to the 64-cell stage, eventually differentiated strong alkaline phosphatase activity in certain cells at each cleavage-arrested stage. The maximum cell numbers and their positions were identical to those of the previously known endodermal cell lineage. Actinomycin D did not prevent development of endodermal alkaline phosphatase when administered from fertilization onwards, nor did other inhibitors of RNA synthesis (chromomycin A3, cordycepin, and daunomycin). There is probably a preformed maternal mRNA for endodermal alkaline phosphatase present in the unfertilizec Ciona egg. Either this RNA itself, or some related translation factor, is localized in the egg cytoplasm and segregated during early cleavages into the endodermal cell lineage of the embryo.

Acetylcholinesterase↗
PubMed1979

Development of acetylchilinesterase during embryogenesis of the ascidian Ciona intestinalis.

We have characterized the embryonic muscle cell cholinesterase of the solitary ascidian, Ciona intestinalis (L.). The effects of selective enzyme inhibitors and the inhibition of enzyme activity at high concentrations of substrate suggest that the muscle cell enzyme is an acetylcholinesterase (E.C. 3.1.1.7). After gastrulation and before hatching, acetylcholinesterase activity increased 35- to 40-fold; after hatching (18 hours postfertilization) this activity continued to increase, leveling off at about 36 hours of development. Histochemical observations showed that before hatching acetylcholinesterase was located principally in the muscle cells of the tail and, after hatching, it began to develop in cells of the adult musculature and brain. Inhibition of protein syntnesis by puromycin and of RNA synthesis by actinomycin D, suggest that both protein and RNA synthesis were required for the increase in acetylcholinesterase activity observed in unhatched embryos. Although the continued increase in enzyme activity duirng embryonic development was sensitive to puromycin at all times tested, the actinomycin D sensitivity of this increase was restricted to a discrete time that was completed by about 11 hours of development.

Acetylcholinesterase↗
PubMed1977

Comparative studies on the structure of reproductive organs of four botryllid ascidians.

Reproductive organs of four botryllid ascidians, Botryllus primigenus, Botryllus schlosseri, Botrylloides violaceus and Botrylloides leachi, were studied histologically. In every species, the egg follicle consisting of an egg and its inner and outer follicles, is attached to the follicle stalk, the vesicle being composed of a flat epithelium, which in its turn is connected to the atrial epithelium or to the brood pouch specialized from it. In B. schlosseri, the egg is ovulated into the atrial cavity and remains there held by the brood cup, of which the inner epithelium is derived from the follicle stalk and the outer one from the atrial epithelium. In B. primigenus, the brood pouch develops as a diverticulum of the atrial cavity, around the entrance of which a fold differentiates from the atrial epithelium and closes the pouch during embryogenesis. In both species of Botrylloides, the brood pouch is formed by the outgrowth of the thickened atrial epithelium into the blood space, the entrance of which is closed during embryogenesis. The discarded outer follicle completely disintegrates soon after ovulation in B. schlosseri, but part of it remains throughout embryogenesis in the blood space in B. primigenus or projecting into the interior of the brood pouch in Botrylloides. In primigenus, the testis, when it accompanies the egg follicle, is placed at the bottom of the brood pouch and the sperm is shed through the pouch prior to ovulation. In B. schlosseri and the Botrylloides species, the testis is located independently from the egg follicle and the sperm matures after ovulation.

Animals↗
PubMed1977

Fine structure of the gap junction in the tunicate heart.

The plasma membranes of the tunicate heart exhibit an abundance of macular gap junctions distributed widely over the membrane surface. A study of these junctions by the freeze-etch technique was undertaken in an effort to elucidate the fine structure of this important membrane modification in a primitive heart. In cross or near-cross fractured junctions the junctional particles in contiguous membranes appear to be paired in register and to meet in the midline. In favorable face views, the junctional particles are seen to be disposed in hexagonal array. The individual particles display a distinct rosette-like substructure consistent with a six-membered ring of globular protein molecules clustered around a central channel. Similar junctional-type particles can be found in nonjunctional areas of membrane suggesting that the transport mechanism which they may represent is not restricted to the gap junction.

Animals↗
PubMed1977

On the ultrastructure of polypeptide hormone-producing cells in the gut of the ascidian, Ciona intestinalis L. and the bivalve, Mytilus edulis L.

Ultrastructural evidence has been found for the presence of polypeptide hormone-producing cells in the gut of Ciona intestinalis L. and Mytilus edulis L. which do not appear to have been described before. Due to their localization and ultrastructural characteristics, it is suggested that the cells in Mytilus edulis probably produce an insulin-like substance and that some of these cells in Ciona interstinalis may produce 5-HT (5-Hydroxytryptamine). In each species only one granulated cell type can be observed; The granules, which are electron dense and membrane bound, also show a halo. The average diameter of the granules is 100-200 nm for Ciona and 200-400 nm for Mytilus.

Animals↗
PubMed1978

Endocrine cells in the oesophagus of the ascidian Styela clava, a cytochemical and immunofluorescence study.

Immunocytochemical studies have demonstrated the occurrence of an insulin-immunoreactive cell type in the oesophageal epithelium of the Ascidian Styela clava. Staining with aldehyde fuchsin has demonstrated a number of similar small, triangular, cells located on the basement membrane, which may have an endocrine function. Argyrophilic cells have also been found, suggesting the presence of a second endocrine cell type. The absence of argentaffin cells has led us to believe that the cells so far observed do not produce biogenic amines such as 5-HT (5-Hydroxytryptamine). The nature of these cells is discussed with reference to endocrine-like cells found in the digestive tracts of other protochordates.

Animals↗
PubMed1978

Endocrine cells in the gut of the ascidian Styela clava.

Ultrastructural studies have shown the presence of two types of granulated endocrine cell in the gut of Styela clava. Type I, which occurs in the stomach and intestine contains small irregular granules, each with a distinct halo. Type II, found only in the oesophagus contains larger rounded granules, often with little or no halo. The characteristics of these two cell types are compared with those of endocrine cells found in the digestive tracts of other protochordates and discussed with special reference to the evolution of gastrointestinal endocrine cells in vertebrates.

Animals↗
PubMed1977

Observations on the gastric epithelium of ascidians with special reference to Styela clava.

Transmission electron microscopy shows the gastric epithelium of Styela clava to comprise at least three distinct cell types. Ciliated mucous cells which form the crest of each stomach ridge produce mucus by an unexpected route. Vacuolated cells lining the ridge sides appear to be absorptive in function. Gastric enzymes are produced by typical protein secreting cells scattered amongst the vacuolated cells. Undifferentiated cells are found in the crypts between ridges. The structure and function of the gastric epithelium in Styela is discussed with special reference to the wider concepts of ascidian gut organization.

Animals↗
PubMed1978

The spermatozoon of Oikopleura dioica Fol (Larvacea, Tunicata).

The spermatozoon of Oikopleura dioica is about 30 micron long, with a spherical head, about 1 micron wide, a 3 micron long and 1 micron wide midpiece, and a 25 micron long tail with a tapered end piece. The head contains a nucleus with the chromatin volume limited to about 0.1 micron3. A small acrosome is found in an anterior inpocketing, and a flagellar basal body in a posterior inpocketing of the nucleus. The midpiece contains a single mitochondrion with the flagellar axoneme embedded in a grove along its medial surface. The flagellar axoneme has the typical 9 + 2 substructure, and the basal body the typical 9 + 0 substructure. A second centriole and special anchoring fibres are absent.

Acrosome↗
PubMed1979

Localization of somatostatin-, substance P- and calcitonin-like immunoreactivity in the neural ganglion of Ciona intestinalis L. (Ascidiaceae).

Indirect immunofluorescence studies using antisera to synthetic somatostatin, human calcitonin and substance P indicate, in the neural complex of the sea-squirt, Ciona intestinalis L., that these polypeptides are present in large perikarya situated at the periphery of the cerebral ganglion as well as in some smaller perikarya in the medulla. In the medullary and transitional zone, there are nerve fibres that cross-react positively with anti-calcitonin and anti-substance P.

Animals↗