Specificity of Glossopharyngeal Nerve Responses to Astringent Compounds in Xenopus

Astringent compounds were applied to oral epithelium of theclawed toad, Xenopus laevis, and rapidly rising and highly sensitiveresponses could be recorded from the whole glossopharyngealnerve, but not at all from the trigeminal nerve. The responseto 10 mM tannic acid decreased progressively with repetitiveapplication. These responses to tannic acid, however, recoveredcompletely by treating with chemicals capable of forming stronghydrogen and hydrophobic bonds. These chemical bondings aregenerally recognized as a model for polyphenol (tannin)-proteininteractions based on physico-chemical measurements in vitro.The high affinities of these chemicals for tannic acid may beeffective in releasing both bonds in the interaction of tannicacid with the receptor molecules. Our results provide in vivoevidence for this model. Chem. Senses 21: 459–465, 1996.     

Gustatory Responsiveness to food-associated acids in the spider monkey (Ateles geoffroyi)

The gustatory responsiveness of four adult spider monkeys to five food-associated acids was assessed in two-bottle preference tests of brief duration (3 min). The animals were given the choice between a 30 mM sucrose solution and defined concentrations of citric acid, ascorbic acid, malic acid, acetic acid, or tannic acid dissolved in a 30 mM sucrose solution. With this procedure,Ateles geoffroyi was found to significantly discriminate concentrations as low as 5 mM ascorbic acid, citric acid, and acetic acid, 10 mM malic acid, and 0.1 mM tannic acid from the alternative stimulus. With the latter two substances, the monkeys rejected all suprathreshold concentrations tested, whereas with the former three substances, the animals showed an inverted U-shaped function of preference, i.e. they rejected high concentrations, but significantly preferred low but detectable concentrations of these acidic tastants over the alternative sweet stimulus. The results showed (1) the spider monkey to respond to the same range of acid concentrations as other nonhuman primate species; (2) thatAteles geoffroyi, is able to detect food-associated acids at concentrations well below those present in most fruits; and (3) that unlike most other primate species tested so far, spider monkeys do not generally reject acidic tastants but show a substanceand concentration-dependent change in responsiveness that may range from rejection to preference. The results support the assumptions that spider monkeys may use sourness and/or astringency of food-associated acids as a criterion for food selection, and that the gustatory responsiveness ofAteles geoffroyi to acidic tastants might reflect an evolutionary adaptation to frugivory.     

A comparison of taste thresholds for sweet and astringent-tasting compounds in great apes

Taste responses to fructose and tannic acid were compared between great apes using the 'two-bottle test' with tests of brief duration. The taste thresholds for fructose were [10-20] mM in Pongo pygmaeus, [40-50] mM in Pan troglodytes, and [70-80] mM in Gorilla gorilla. Inhibition thresholds for tannic acid were [2.9-3.5] mM in Pongo and [2.9-5.9] mM in Pan. Gorillas apparently significantly preferred tannins at low concentrations ([0.59-5.9] mM) but rejected concentrations above [8.8-14.7] mM. These results are discussed in relation to the effects of phylogenetic inertia and biological adaptation.     

Tannic Acid-Dependent Modulation of Selected Lactobacillus plantarum Traits Linked to Gastrointestinal Survival

Background

Owing to its antimicrobial properties dietary tannins may alter the functional efficacy of probiotic lactobacilli in the gastrointestinal (GI)-tract influencing their growth, viability and molecular adaptation to the intestinal environment.

Methods and Findings

The effects of tannic acid on Lactobacillus plantarum WCFS1 were studied by in vitro growth monitoring and visualizing the morphological alteration on the cell wall using transmission electron microscopy. Growth upon tannic acid was characterized by dose-dependent reductions of initial viable counts and extended lag phases. Lag phase-cells growing upon 0.5 mM tannic acid were abnormally shaped and experienced disturbance on the cell wall such as roughness, occasional leakage and release of cell debris, but resumed growth later at tannic acid concentrations high as 2.5 mM. To gain insight on how the response to tannic acid influenced the molecular adaptation of L. plantarum to the GI-tract conditions, gene expression of selected biomarkers for GI-survival was assessed by RT-qPCR on cDNA templates synthetized from mRNA samples obtained from cells treated with 0.5 or 2 mM tannic acid. Tannic acid-dependent gene induction was confirmed for selected genes highly expressed in the gut or with confirmed roles in GI-survival. No differential expression was observed for the pbp2A gene, a biomarker negatively related with GI-survival. However PBP2A was not labeled by Bocillin FL, a fluorescent dye-labeled penicillin V derivative, in the presence of tannic acid which suggests for enhanced GI-survival reportedly associated with the inactivation of this function.

Conclusions

Probiotic L. plantarum WCFS1 is able to overcome the toxic effects of tannic acid. This dietary constituent modulates molecular traits linked to the adaptation to intestinal environment in ways previously shown to enhance GI-survival.     

Elution of dissolved Fe from mangrove soil by tannin solution

To reveal the role of tannins in mangroves, tannins in mangrove leaves and the Fe eluted from mangrove soil by adding tannin solutions of different salinity levels was investigated. Leaves of six mangrove and 16 non-mangrove species, and samples of a mangrove floor, Andosol and dark red soil were collected. Results were: (1) Increasing tannic acid concentration to ~50 mM, increased the Fe eluted from mangrove soil to ~20 μgg^?1. (2) When a 100 mM tannic acid solution was added, the Fe eluted from mangrove soil was 5.5 times higher than dark red soil. (3) Although elution of Fe from mangrove soil was higher than in Andosol one day after submersion in a 10 mM tannic acid solution, the difference was stable after 2 days. (4) The elution of Fe from all soils significantly decreased with increasing salinity of a 10 mM tannic acid solution. However, the amount from mangrove soil was 6.1 times higher than dark red soil even with 35 ‰ salinity. (5) The tannin content in the mangrove leaves was 99 ± 16 mgg^?1 and non-mangrove leaves was 76 ± 19 mgg^?1. (6) The Fe eluted from mangrove soil had a positive correlation with the tannin concentrations in the added leaf solution. Tannins in mangrove species promote the elution of Fe from mangrove floor soil even in saline water. Fe complexes were formed when mangrove soil was mixed with leaf tannins suggesting that Fe produced by tannins in mangrove leaves growing in land/sea interfaces likely plays a direct role in marine ecosystems.     

Tyrosinase inhibitors from galls of Rhus javanica leaves and their effects on insects

As a defense mechanism of the leaves of Rhus javanica (Anacardiaceae) against the aphid Melaphis chinensis (Aphididae) attack, tannic acid is rapidly accumulated and forms galls along the midrib of the leaves resulting in a unique natural medicine Gallae Rhois. Tannic acid was found to inhibit the oxidation of L-3,4-dihydroxyphenylalanine (L-DOPA) catalyzed by tyrosinase (EC 1.14.18.1) with an IC50 of 22 microM. The aphid would detoxify the ingested toxic tannic acid to relatively nontoxic gallic acid, whereas the non-adapted pink bollworm Pectinophora gossypiella larvae are sensitive to the ingested tannic acid.     

Does acclimation reduce the negative effects of acorn tannins in the wood mouse<Emphasis Type="Italic">Apodemus speciosus</Emphasis>?

Acclimation as a mechanism of mitigating the damaging effects of acorn tannins was examined in the Japanese wood mouseApodemus speciosus Temminck, 1844. Mice were fed the two types of diet: a control diet (laboratory chow for mice), and acorns ofQuercus serrata (QS), which differ in tannin contents (control=0%, QS=2.7% tannic acid equivalent). Body weight changes and digestive abilities were compared between the first stage (Days 1 to 5; Day 0 was defined as the first day of acorn feeding) and the second stage (Days 6 to 10). The amount of salivary proline-rich proteins (PRPs), which are thought to be defensive products to tannins, was measured before and after the experiment. The responses of the wood mice to QS acorns differed between stages: decreases in body weight during the second stage were less than half those that occurred during the first stage; digestive abilities tended to improve; and the relative amount of PRPs after the experiment increased by a factor of five compared with the value recorded before the experiment in the QS-feeding mice. These results suggest that the negative effects of ingesting acorn tannins may be reduced by acclimation, which may result primarily from the induction of PRP production.     

Taste Responses to Fructose and Tannic Acid Among Gorillas (Gorilla gorilla gorilla)

We investigated the taste responses to fructose and tannic acid compounds among 6 western gorillas (Gorilla gorilla gorilla) at the San Francisco Zoo. We presented the subjects with 12 reference concentrations of 3–300 mM fructose, paired with tap water in paired-choice experimental trials. We subsequently presented them with tap water paired with 8 dilute concentrations of tannic acid (0.25–6 mM) dissolved in 100 mM fructose solutions and 8 concentrations (0.25–6 mM) dissolved in 300 mM fructose solutions. The gorillas exhibited a broadly similar preference threshold for fructose (50 mM) to those of other nonhuman primate and human samples. The gorillas tolerated moderate levels of tanninc acid, especially when presented in a very sweet package. The depressing effect of tannic acid on the ingestion of fructose solutions appeared to increase progressively with tannin concentration and was lower as fructose concentration increased. The inhibition threshold for tannic acid solutions was reached at 4 mM tannic acid in 100 mM fructose solution, and at 6 mM tannic acid in 300 mM fructose solutions. These results suggest that gorillas use sweetness as a criterion for food selection and regard those with moderate levels of tannins as palatable. Our findings corroberate food preference studies and nutritional analyses of wild gorilla foods indicating that they prefer sugary foods and readily consume ones containing moderate levels of tannins. Taste responses may facilitate a flexible frugivorous/folivorous diet among gorillas.     

Initial licking responses of mice to sweeteners: effects of tas1r3 polymorphisms

Recent studies have established that the T1R3 receptor plays a central role in the taste-mediated ingestive response to sweeteners by mice. First, transgenic mice lacking the gene for T1R3, Tas1r3, show dramatically reduced lick responsiveness to most sweeteners. Second, strains with the taster allele of Tas1r3 (T strains) are more sensitive to low sweetener concentrations than strains with the nontaster allele (NT strains) and consume greater quantities of low- to midrange concentrations of sweeteners during 24-h tests. We asked how Tas1r3 polymorphisms influence the initial licking responses of four T strains (FVB/NJ, SWR/J, SM/J, and C57BL/6J) and four NT strains (BALB/cJ, 129P3/J, DBA/2J, and C3H/HeJ) to two sweeteners (sucrose and SC-45647, an artificial sweetener). We used the initial licking response as a measure of the taste-mediated ingestive response because its brief duration minimizes the potential contribution of nontaste factors (e.g., negative and positive postingestive feedback). Further, we used two complimentary short-term intake tests (the brief-access taste test and a novel 1-min preference test) to reduce the possibility that our findings were an epiphenomenon of a specific testing procedure. In both tests, the T strains were more responsive than the NT strains to low concentrations of each sweetener. At higher concentrations, however, there was considerable overlap between the T and NT strains. In fact, the initial licking response of several NT strains was more vigorous than (or equivalent to) that of several T strains. There was also considerable variation among strains with the same Tas1r3 allele. We conclude that Tas1r3 polymorphisms contribute to strain differences in initial lick responsiveness to low but not high concentrations of sweeteners.     

Interaction of the salivary low-molecular-weight mucin (MG2) with Actinobacillus actinomycetemcomitans

Periodontitis is associated with the presence of certain Gram-negative bacteria in the oral cavity, among these Actinobacillus actinomycetemcomitans. In order to determine which types of salivary components interact with A. actinomycetemcomitans two strains (HG 1175 and FDC Y4) were incubated with whole saliva and individual glandular secretions, viz. parotid, submandibular, and sublingual saliva. Immunochemical analysis by immunoblotting of bacteria-bound salivary proteins showed that IgA, the low-molecular mucin MG2, parotid agglutinin, and a 300 kDa sublingual and submandibular glycoprotein, were bound to the bacterial strains tested. In addition, adherence of A. actinomycetemcomitans to salivary proteins in a solid-phase was studied. After electrophoresis and transfer of salivary proteins to nitrocellulose membranes A. actinomycetemcomitans adhered only to MG2. In this assay periodate treatment, mild acid hydrolysis or neuraminidase digestion of the saliva glycoproteins abolished binding of two clinical isolates (HG 1175 and NY 664), suggesting that sialic acid residues on MG2 are involved in the binding. In contrast, adherence of the smooth laboratory strain Y4 was not affected by removal of sialic acid residues or even periodate treatment of MG2.Abbreviations S-IgA Secretory IgA - MG1 high-molecular-weight mucin - MG2 low-molecular-weight mucin - EP-GP extra parotid-glycoprotein - PRPs proline-rich proteins - SNA Sambucus nigra agglutinin - MAA Maackia amurensis agglutinin - PNA peanut agglutinin - UEA Ulex europaeus agglutinin     

Induction of Salivary Proteins Modifies Measures of Both Orosensory and Postingestive Feedback during Exposure to a Tannic Acid Diet

There are hundreds of proteins in saliva. Although it has long been hypothesized that these proteins modulate taste by interacting with taste receptors or taste stimuli, the functional impact of these proteins on feeding remains relatively unexplored. We have developed a new technique for saliva collection that does not interfere with daily behavioral testing and allows us to explore the relationship between feeding behavior and salivary protein expression. First, we monitored the alterations in salivary protein expression while simultaneously monitoring the animals'' feeding behavior and meal patterns on a custom control diet or on the same diet mixed with 3% tannic acid. We demonstrated that six protein bands increased in density with dietary tannic acid exposure. Several of these bands were significantly correlated with behaviors thought to represent both orosensory and postingestive signaling. In a follow-up experiment, unconditioned licking to 0.01–3% tannic acid solutions was measured during a brief-access taste test before and after exposure to the tannic acid diet. In this experiment, rats with salivary proteins upregulated found the tannin solution less aversive (i.e., licked more) than those in the control condition. These data suggest a role for salivary proteins in mediating changes in both orosensory and postingestive feedback.     

Amino acid sequence of a proline-rich phosphoglycoprotein from parotid secretion of the subhuman primate Macaca fascicularis

The complete amino acid sequence of the macaque proline-rich phosphoglycoprotein (MPRP) was determined by automated Edman degradation of the protein, fragments F-1 and F-2 derived from the protein by an intrinsic salivary protease, and chymotryptic, tryptic, Staphylococcus aureus V8 protease, and endoproteinase lysine-C peptides. MPRP contains 115 amino acid residues including phosphorylated serine at residues 1, 2, 6, 12, and 15, and 6 O-glycosidic carbohydrate units at residues 69, 75, 87 (threonine) and 96, 103, and 106 (serine). The Mr of the polypeptide moiety of the protein is 12,656. The amino-terminal domain contains all 5 phosphoserine residues and most of the other negatively charged and hydrophilic residues, whereas the carboxyl-terminal domain contains 24 of 25 proline residues, and 6 O-glycosidic oligosaccharides. Comparison of MPRP with the four major anionic proline-rich proteins (PRPs) from human glandular secretion shows that 57% of the amino acid residues are identical if gaps are introduced to maximize homology, suggesting that these proteins are phylogenetically related. Significant structural and functional differences occur between the macaque and human proteins. MPRP has 5 phosphoserines, PRPs have 2. MPRP is a glycoprotein, PRPs are not. MPRP inhibits the spontaneous precipitation (primary precipitation) of calcium phosphate salts from supersaturated solutions in addition to inhibiting seeded crystal growth (secondary precipitation) (Oppenheim, F. G., Offner, G. D., and Troxler, R. F. (1982) J. Biol. Chem. 257, 9271-9282), whereas PRPs inhibit only secondary precipitation. MPRP is the only major anionic proline-rich protein in macaque glandular secretion; in contrast, there are four major anionic PRPs and these display a genetic polymorphism. The significance of these structural differences with respect to biological function and the possible relationship of MPRP to salivary mucins are discussed.     

Proline-rich proteins and glycoproteins: expression of salivary gland multigene families

Our recent research interests have focused on a group of unusual proteins and glycoproteins high in proline content, or the so-called proline-rich proteins (PRPs). The PRPs are tissue-specific expressions of salivary gland multigene families. Normally PRPs are not detected or are present in very low amounts in rat, mouse and hamster salivary glands, but these unusual proteins are dramatically induced by treatment with the catecholamine isoproterenol. The structures and organizations of several PRP mRNAs and PRP genes have been determined. The amino acid sequences of all PRPs show 4 distinct regions, namely, a signal peptide, a transition region, a repeat region and a carboxyl-terminal region. Glycoproteins induced by isoproterenol treatment may be N-glycosylated or O-glycosylated. The N-glycosylated glycoprotein GP-158 from rat submandibular glands has a 12 amino acid glycopeptide which repeats possibly 49 times. Proline-rich proteins of the parotid glands of rats and mice are also greatly induced by dietary tannins. The apparent unique occurrence of PRPs in saliva suggests that one biological role is to neutralize the detrimental effects of dietary tannins and other polyphenols. The upstream regions of the mouse and hamster PRP genes contain cyclic AMP-regulated sequences as demonstrated by deletions and transient transfections. The PRP multigene family members of mouse are all located on chromosome 8.     

Effect of tannic acid on brush border disaccharidases in mammalian intestine

Tannic acid is a glucoside (penta-m-digallolyl-glucose), which exhibits a wide variety of physiological functions. Around neutral pH, 0.4 mM tannic acid produced 84% inhibition of rat brush border sucrase activity, but 35-40% enzyme inhibition was observed in the rabbit intestine at 0.08 mM concentration. In the mice, 74-77% enzyme inhibition was observed at 0.05 mM concentration of tannic acid. The observed inhibition was reversible in rat intestine. Tannic acid (0.2 mM) also inhibited lactase (18% in adult and 71% in suckling animals), maltase (76%) and trehalase (88%) activities in rat intestine. pH versus activity curves showed that 0.2 mM tannic acid inhibited enzyme activity in rat by 91% at pH 5.5 which was reduced to 14% at pH 8.5 compared to the respective controls. In the rabbit 18-60% enzyme inhibition was noticed below pH 7.0, however at pH 8.5, it was of the order of 38%. Kinetic analysis revealed that tannic acid is a competitive inhibitor of rat brush border sucrase at pH 6.8. Effect of tannic acid together with various -SH group reacting reagents revealed that the enzyme inhibition is additive in nature, suggesting the distinct nature of binding sites on the enzyme for these compounds. The results suggest that tannic acid is a potent inhibitor of intestinal brush border disaccharidases, and could modulate the intestinal functions.     

Isoproterenol increases sorting of parotid gland cargo proteins to the basolateral pathway

Exocrine cells have an essential function of sorting secreted proteins into the correct secretory pathway. A clear understanding of sorting in salivary glands would contribute to the correct targeting of therapeutic transgenes. The present work investigated whether there is a change in the relative proportions of basic proline-rich protein (PRP) and acidic PRPs in secretory granules in response to chronic isoproterenol treatment, and whether this alters the sorting of endogenous cargo proteins. Immunoblot analysis of secretory granules from rat parotids found a large increase of basic PRP over acidic PRPs in response to chronic isoproterenol treatment. Pulse chase experiments demonstrated that isoproterenol also decreased regulated secretion of newly synthesized secretory proteins, including PRPs, amylase and parotid secretory protein. This decreased efficiency of the apical regulated pathway may be mediated by alkalization of the secretory granules since it was reversed by treatment with mild acid. We also investigated changes in secretion through the basolateral (endocrine) pathways. A significant increase in parotid secretory protein and salivary amylase was detected in sera of isoproterenol-treated animals, suggesting increased routing of the regulated secretory proteins to the basolateral pathway. These studies demonstrate that shifts of endogenous proteins can modulate regulated secretion and sorting of cargo proteins. amylase; parotid secretory protein; polarized secretion     

Differential expression of proline-rich proteins in rabbit salivary glands.

Salivary glands synthesize and secrete an unusual family of proline-rich proteins (PRPs) that can be broadly divided into acidic and basic PRPs. We studied the tissue-specific expression of these proteins in rabbits, using antibodies to rabbit acidic and basic PRPs as well as antibodies and cDNA probes to human PRPs. By immunoblotting, in vitro translation, and Northern blotting, basic PRPs could be readily detected in the parotid gland but were absent in other salivary glands. In contrast, synthesis in vitro of acidic PRPs was detected in parotid, sublingual, and submandibular glands. Ultrastructural localization with immunogold showed heavy labeling with antibodies to acidic PRPs of secretory granules of parotid acinar cells and sublingual serous demilune cells. Less intense labeling occurred in the seromucous acinar cells of the submandibular gland. With antibodies to basic PRPs, the labeling of the parotid gland was similar to that observed with antibodies to acidic PRPs, but there was only weak labeling of granules of a few sublingual demilune cells, and no labeling of the submandibular gland. These results demonstrate a variable pattern of distribution of acidic and basic PRPs in rabbit salivary glands. These animals are therefore well suited for study of differential tissue expression of PRPs.     

Interactions of dextransucrase purified from Streptococcus mutans 890 with plant polyphenols

Plant polyphenols have been extensively studied for their chemopreventive properties for human health. Dextransucrase plays an essential role in synthesizing exopolysaccharides from its exclusive substrate sucrose in Streptococcus mutans. In the present study, the effect of polyphenols gallic acid and tannic acid was investigated on the dextransucrase activity. The enzyme was purified by ethanol precipitation followed by column chromatography by Sephadex G-200 gel chromatography, followed by PEG-400 treatment. The purified enzyme exhibited 52 fold enrichment with 17.5% yield and specific activity of 3.54 Units/mg protein. On SDS-PAGE enzyme protein gave a single band with a molecular weight of 160 kDa. Dextransucrase activity was inhibited 80–90% by 0.04 mM tannic acid (TA) or 0.4 mM gallic acid (GA) suggesting that tannic acid has 10- fold more inhibitory potential than gallic acid on the activity of dextransucrase. CD/ORD studies revealed modifications in the tertiary structure of enzyme protein in presence of tannic acid and gallic acid, which were further confirmed by fluorescence spectra of the protein in presence of tannic acid. These results suggest that inhibition of dextransucrase activity in S. mutans by polyphenols may have potential applications in the prevention and control of dental caries.     

The Effect of Increased Internal Ion Concentration upon the Ion Uptake Isotherms of Excised Maize Root Segments

The influence of salt status of root tissue of Zea mays on influxof ⁸⁴Rb and ²²Na and net accumulation of K⁺ and Na⁺ was studied.Low-salt roots were grown in 0.5 mM CaCl₂, and high-salt rootsin 2.5 mM KC1 + 7.5 mM NaCl + 0.5 mM CaCl₂. High-salt statusgreatly reduced (approx. 90 per cent inhibition) both ²²Na and⁸⁶Rb influxes in the low concentration range isotherm (i.e.at external concentrations below 1 mM). A less marked inhibitionwas observed in the higher concentration range isotherm (1–30mM), indicating that the uptake in this range is less affectedby the salt status of the tissue. During transition from low- to high-salt status there was anet accumulation of K⁺ but not of Na⁺ despite the presence ofa measurable ²²Na⁺ influx at all times. The presence of a continuous²²Na influx but no net accumulation implies an Na⁺ efflux frommaize root tissue. The results differ significantly from thosepreviously published for barley and a possible explanation ofthese differences is discussed.     

Tannase activity from the marine cyanobacterium Phormidium valderianum BDU140441

The marine cyanobacterium Phormidium valderianum BDU 140441 exhibited the ability to grow at 0.25?mM tannic acid, a known hindering chemical for microbial growth. The tannic acid-degrading ability of the organism is evident from the UV–visible absorption spectrum. In addition, the existence of tannase has been localized by activity staining, and its induction in activity upon tannic acid exposure was confirmed in native gel. The critical tannic acid metabolization enzymes tested for are polyphenol oxidase and esterases; both are well known for tannic acid degradation. Upon tannic acid exposure, increased activity of polyphenol oxidase and expression of few new isoforms of esterase were identified by activity staining.     

Reactivation of Cytoplasmic Streaming in a Tonoplast-Permeabilized Cell Model of Acetabularia

To find whether cytoplasmic streaming in Acetabularia is controlledby Ca²⁺, a tonoplast-permeabilized cell model was prepared usinga vacuolar perfusion technique. The cytoplasmic streaming remainedalmost normal after perfusion with EGTA medium (10 mM EGTA,40 mM PIPES, 5mM MgCl₂ and 800 mM sorbitol, pH 6.9), but stoppedwithin 10 min when saponin medium (EGTA medium plus 50 µg/mlsaponin, 50 µg/ml hexokinase and 5 mM glucose) was perfused.This model system was reactivated with a solution containing0.5 mM ATP and different concentrations of Ca²⁺ (reactivationmedium). With the reactivation medium at pCa 6–5, theresumed streaming lasted for about 10 min before the cytoplasmaggregated. At pCa 4–3, the streaming was observed onlyfor a few minutes because the cytoplasm aggregated quickly.At pCa 7, no reactivated movement was observed. Reactivationwas not induced in an ATP- or Mg²⁺-deficient medium even inthe presence of an adequate concentration of Ca²⁺, and was inhibitedby 50 µg/ml cytochalasin B or 1 mM N-ethylmaleimide. We concluded from these observations that the cytoplasmic streamingin Acetabularia is very likely to be driven by the actomyosinsystem in the presence of Mg-ATP and Ca²⁺ at pCa 6–5. (Received October 31, 1984; Accepted April 1, 1985)