Of tunicate

Hirose, E., Aoki, M., and Chiba, K. (1996). Fine structures of tunic cells and distribution of bacteria in the tunic of the luminescent ascidian Clavelina miniate. Zool. Sci. 13 519-523. 

Lissoclinum species of tunicates produce a range of cyclic peptides, which contain thiazole, thiazoline and oxazoline rings. Most belong to the general families patellamides (octapeptides), lissoclinamides (heptapeptides) or bistratamides (hexapeptides) [22],... 

The antineoplastic, cyclic peptide dolastatin 3 (197) was isolated from the sea hare Dolabella auricularia in small quantities [187]. It bears much structural resemblance to the cyclic peptides of tunicates. Synthetic attempts indicated that the original published structure was incorrect [188]. Three reports of research directed towards synthesis of possible components of dolastatin 3 (197) failed to help with the correct structure [189-191]. Reisolation of 197 allowed the determination of the correct sequence of amino acids in this cyclic pentapeptide and the new structure was confirmed by synthesis [192]. Synthesis of dolastatin 3 (197) and the corresponding 12R diastereoisomer permitted study of the solution... 

The sea squirts or tunicates are fascinating marine creatures, their name being derived from the tunic made of cellulosic material that surrounds the body of the animal. In 1911, Henze discovered vanadium in the blood of Phallusia mammillata C.343 He later found the same with other ascidians (a class of tunicates). In vanadium-accumulating species, most vanadium is located in the vacuoles—vanadophores—of certain types of blood cells—the vanadocytes. The concentration in the vanadophore can be as high as 1M and this value must be compared with concentrations of the order of 2 x 10-8 M for vanadium in sea water.344 Kustin et al. have reviewed the work done to understand the efficient accumulation and the possible biological roles of the metal.345... 

The first suggestion of a possible biochemical function for vanadium came from the discovery that vanadocytes, the green blood cells of tunicates (sea squirts), contain 1.0 M V(III) and 1.5-2 M H2S04. 613 It was proposed that a V-containing protein is an oxygen carrier. However, the V3+ appears not to be associated with proteins612 and it does not carry 02. 

Natural History of Tunicates—Our Closest Marine Invertebrate Relations... 

In the external environment of tunicates, most metal ions are cationic, few are anionic. Vanadium is one of the anions, as it is present predominantly as HzVOj at the pH of sea water. Only chromate, among the metal-containing anions, is significant in sea water and it is present at a fiftieth the concentration of vanadium8. Other anions to consider are sulfate and phosphate, present as SO4 and HPO4" in sea water. 

It is known that vanadium in extremely small amounts is a nutritional requirement for many types of organism, including higher animals. Among marine organisms which accumulate vanadium are members of an order of tunicates, the Asddiacea (sea squirts). Some lichens and a toadstool are also known to contain vanadium in the active sites of some enzymes. The high abundance of vanadium in fossil matter of animal and plant origin (for example, the crude oil from Venezuela) seems to indicate that this element was perhaps more prevalent in early life. 

Classification schemes have been devised that take into account the lability of tunicate blood cells (137,138). In one scheme (138) four main categories of tunicate blood cell are recognized stem cells, amoebocytes, vacuolated cells, and pigment cells (Fig. 4). Main categories are further subdivided in Ciona intestinalis, for example, hyaline amoebocytes are numerous and comprise 30% of the total blood cell population (139). 

The issue of whether tunicate blood cells are involved in oxygen uptake and transport could, of course, be settled by experimentation. This challenge was met for tunicate specimens collected from both Atlantic " ] and Pacific ocean waters, " ] using an oxygen electrode to measure dissolved dioxygen concentrations. It was found that the oxygenbinding capacity of tunicate blood cells was indistinguishable from that of sea water. 

The meaning of each experimental parameter is now clear 02 (h 1) is the apparent rate constant p3 = ya>> where yx is relative radioactivity at infinite time and iSi = 1 — y - The apparent rate constant obtained from these data shows a variation reflecting the different masses of tunicates used in the experiments. This difference from experiment to experiment results in a variation of the ratio of absorption sites to volume of sea water. Constancy is exhibited when 02 is divided by a... 

Addition of tunicates to a closed sea water system represents addition of a stock solution of binding sites with concentration [L]0. The actual concentration of binding sites available, [L], can be thought of as a dilution of the total number of binding sites, [L]0mt (mt is the tunicate mass) by the mass of sea water, ms, in the experiment ie., [L] = [L]0/nt/ms, where both mt and ms are in kg units. Substitution into Eq. (3) yields. 

Raftos D, Hutchinson A. 1997. Effects of common estuarine pollutants on the immune reactions of tunicates. Biol Bull 192 62-72. 

It is important at this point to address the need for a new paradigm that was not recognized in the early work of Atalla and VanderHart. The title of the early articles was still defined in terms of the classical approach to cellulose structure in that the two forms of cellulose, and 1,3, were referred to as two distinct crystalline forms. Note was not taken at that point of the rapidly developing evidence that the lateral dimensions of most native cellulose fibrils were very limited and that cellulose nanofibrils have an inherent tendency to develop a right-handed twist when cellulose chain molecules aggregate. While this important development had shed some light on the controversies associated with many of the prior interpretations of diffractometric characterizations of native celluloses, it had not yet provided conclusive evidence that the interpretations based on the symmetry of the P2i space group for crystalline cellulose cannot be valid for native celluloses. It was the acquisition of the Raman spectra of Tunicate and Valonia celluloses that provided the conclusive evidence. 

Figure 9 Raman spectra of tunicate (Halocynthia roretzi) and Valonia macrophysa celluloses in the Raman active regions.

Once an absorbent has been selected, the design of the absorber will require the procurement of tunic physical property data on the absoibenl-absotbale system. In addition to the standard physical properties such as density, viscosity, surface tension, and heal capacity, specific data will be required on vapor-liquid equilibrium and the hent of solution or reaction. 

Tunicates, the only animals known to produce cellulose, are a family of sea animals that have a mantle consisting of cellulose microfibrils embedded in a protein matrix [Fig. 13.2). The thick leathery mantle in their mature phase is used as a new source of cellulose. Most research has used a class of tunicates that are commonly known as "sea squirts" [Ascldlacea), marine invertebrate filter feeders [9]. The structure and properties of tunicate cellulose [TC) are expected to be comparable between species, but there may be small differences in the cellulose microfibril formation process [10]. 

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