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PubMed2005

Modeling high-frequency electromotility of cochlear outer hair cell in microchamber experiment.

Cochlear outer hair cells (OHC) are critically important for the amplification and sharp frequency selectivity of the mammalian ear. The microchamber experiment has been an effective tool to analyze the OHC high-frequency performance. In this study, the OHC electrical stimulation in the microchamber is simulated. The model takes into account the inertial and viscous properties of fluids inside and outside the cell as well as the viscoelastic and piezoelectric properties of the cell composite membrane (wall). The closed ends of the cylindrical cell were considered as oscillatory rigid plates. The final solution was obtained in terms of Fourier series, and it was checked against the available results of the microchamber experiment. The conditions of the interaction between the cell and pipette was analyzed, and it was found that the amount of slip along the contact surface has a significant effect on the cell electromotile response. The cell's length changes were computed as a function of frequency, and their dependence on the viscosities of both fluids and the cell wall was analyzed. The distribution of the viscous losses inside the fluids was also estimated. The proposed approach can help in a better understanding of the high-frequency OHC electromotility under experimental and physiological conditions.

Cell Movement↗
PubMed1977

Ultrastructure of Nocardia-like variants of Mycobacterium smegmatis and chemical composition of the basal cell wall layer.

Mycobacterium smegmatis, its orange-red--pigmented (OR) variants, and back mutant strains were examined by electron microscopy using ultrathin sectioning, negative or positive staining, and freeze-fracture-etching methods. The parental and back mutant strains showed almost identical ultrastructures. Specifically, thick ramified fibers measuring about 15 nm in diameter were always visible in the positively stained cell wall, although they were not readily visualized with negative staining or freeze-fracture-etching. In contrast, the cell walls of OR variants contained fibrous networks measuring about 11 nm in diameter, which could be observed by positive and negative staining as well as freeze-fracture-etching. Although cytoplasmic structures appeared similar among the four strains examined, mesosomes were significantly more abundant in the OR variants. The basal layer of the cell wall obtained as a phenol residue consisted of a dense membranous matrix containing scattered fibrous structures in the parental and back mutant strains, and fibrous networks in the OR variants. Chemical analyses showed that the basal layers of all four strains contained the same neutral sugars, amino sugars, and amino acids, i.e., arabinose, galactose, muramic acid, glucosamine, alanine, glutamic acid, and diaminopimelic acid. The alpha-branched, beta-hydroxylated fatty acids contained in the basal layers differ among the four strains, however, with nocardomycolic acids being present in the OR variants and mycolic acids in the parental and back mutant strains. Our previous conclusion that OR variants of M. smegmatis have characteristics similar to those of nocardia is supported by the present study.

Amino Acids↗
PubMed2007

Substitution F659G in the Irr1p/Scc3p cohesin influences the cell wall of Saccharomyces cerevisiae.

The sister chromatid cohesion complex of Saccharomyces cerevisiae is composed of proteins termed cohesins. The complex forms a ring structure that entraps sister DNAs, probably following replication. The mechanism of cohesion is universal and the proteins participating in this process are evolutionarily highly conserved. We investigated the Irr1p/Scc3p cohesin subunit, an under-studied protein. We show that the presence of a mutated copy of IRR1 gene, encoding the F658G substitution in Irr1p, changes the sensitivity of the heterozygous irr1-1/IRR1 diploid to cell wall-affecting compounds. Microscopic images indicate that chitin distribution in the mutant cell wall is affected, although the biochemical composition of the cell wall is not drastically changed. This observation suggests that irr1-1 mutation in heterozygous state may influence the cell wall integrity and indicates a possible link between mechanisms regulating the cell wall biosynthesis, nuclear migration and chromosome segregation.

Cell Cycle Proteins↗
PubMed1993

Cell Wall Metabolism in Ripening Fruit (VI. Effect of the Antisense Polygalacturonase Gene on Cell Wall Changes Accompanying Ripening in Transgenic Tomatoes).

Cell walls of tomato (Lycopersicon esculentum Mill.) fruit, prepared so as to minimize residual hydrolytic activity and autolysis, exhibit increasing solubilization of pectins as ripening proceeds, and this process is not evident in fruit from transgenic plants with the antisense gene for polygalacturonase (PG). A comparison of activities of a number of possible cell wall hydrolases indicated that antisense fruit differ from control fruit specifically in their low PG activity. The composition of cell wall fractions of mature green fruit from transgenic and control (wild-type) plants were indistinguishable except for trans-1,2-diaminocyclohexane-N,N,N[prime],N[prime]-tetraacetic acid (CDTA)-soluble pectins of transgenic fruit, which had elevated levels of arabinose and galactose. Neutral polysaccharides and polyuronides increased in the water-soluble fraction of wild-type fruit during ripening, and this was matched by a decline in Na2CO3-soluble pectins, equal in magnitude and timing. This, together with compositional analysis showing increasing galactose, arabinose, and rhamnose in the water-soluble fraction, mirrored by a decline of these same residues in the Na2CO3-soluble pectins, suggests that the polyuronides and neutral polysaccharides solubilized by PG come from the Na2CO3-soluble fraction of the tomato cell wall. In addition to the loss of galactose from the cell wall as a result of PG activity, both antisense and control fruit exhibit an independent decline in galactose in both the CDTA-soluble and Na2CO3-soluble fractions, which may play a role in fruit softening.

Journal Article↗
PubMed1973

Chemical analysis of cell walls and autolytic digests of Bacillus psychrophilus.

The amino acid composition of isolated cell walls of Bacillus psychrophilus has been determined before and after extraction of protein with ethylenediamine-tetraacetic acid at 45 C. This revealed that the peptidoglycan consists of Ala, Lys, and Glu in a molar ratio of 3:1:2. By using autolytic digests of log-phase cell walls, it was possible to detect 14 ninhydrin-positive degradation products. Chemical analyses of the seven major bands from these digests indicated that the amino acid sequence of the peptide subunit in the murein of this organism consists of muramyl-l-alanyl-gamma-d-glutamyl-l-lysyl- d-alanine, and the linkage between adjacent peptides is supplied by a second d-glutamic acid which is bound to the sigma-amino group of lysine and the carboxyl group of the d-alanine through its amino group. The nature of the solubilized wall fragments indicates that each of the peptide bonds in the murein is hydrolyzed by autolysins except the l-alanyl-gamma-d-glutamyl linkage.

Alanine↗
PubMed1975

[Dependence of various antigen formation of Proteus mirabilis strain 1095/67 growing on minimal nutrient media].

Proteus mirabilis strain 1095/67 has been cultivated in surface culture on different minimal media, which were composed either of single amino acids or combinations of several amino acids without or with stepwise addition of other C-sources up to the complete medium. We found a direct dependence of the formation of the various antigens (moving to the cathode, to the anode, or not moving) on the composition of the medium. Certain amino acids (Ala, Glu, Asp. Ser) elicit only parts of the antigenic spectrum formed in complete medium, but enrich special antigens. With only 2 amino acids (Ala and Glu) and the vitamins thiamine, pyridoxal, and niacine in the anorganic basic medium the complete antigenic spectrum can be formed. We have shown that the composition of the cell wall varies with the composition of the culture medium. In shaked cultures we found serine to be essential for the production of the antigen moving to the cathode and the thermolabile antigene moving to the anode (ATA), niacine to be of fundamental importance in the biosynthesis of all antigens. Already under very limited supply of nutrients ATA, common to all gram-negative bacteria, is formed and, therefore, it seems to be a very basic cell wall component.

Amino Acids↗
PubMed1966

Chemical composition and serological analysis of the cell wall of Peptostreptococcus.

Bahn, Arthur N. (Northwestern University, Chicago, Ill.), Patrick C. Y. Kung, and James A. Hayashi. Chemical composition and serological analysis of the cell wall of Peptostreptococcus. J. Bacteriol. 91:1672-1676. 1966.-Chemical and serological analyses were made of the cell wall of Peptostreptococcus to characterize taxonomically this genus of anaerobic streptococci. Cell wall hydrolysates of P. putridus strains 06 and 85, P. intermedius strains 11 and 87, and P. elsdenii strain B-159 were prepared, and the cell wall sugars were measured quantitatively by paper chromatography. Strain 85 contained only glucose, whereas strain 06 contained 93% glucose and 7% mannose. Strain 87 contained only rhamnose, and strain 11 contained approximately equal amounts of glucose and rhamnose. Strain B-159 differed from all the other strains in having a low (3.1%) content of total carbohydrate, consisting of rhamnose, galactose, and glucose. Quantitative amino acid analyses showed that the major amino compounds present in the cell wall were glutamic and aspartic acids, alanine, lysine, muramic acid, glucosamine, and galactosamine. Strains 06 and 85 possessed this complement of amino compounds, but strains 11 and 87 had relatively little aspartic acid. Strain B-159 was markedly different in having a high content of glycine and diaminopimelic acid, with only traces of lysine; it was the only strain in which teichoic acid was found. Serological analyses were made with the use of cell wall extracts as antigenic material and with homologous antisera, as well as streptococcal group antisera for groups A through S. The only strong agglutination was obtained between strain 87 antigen and group C antisera; weak agglutination was obtained with 87 against N, O, and K, and between strain 11 and groups E and F. All other antisera gave negative reactions. It is concluded that strain B-159 does not belong to the genus Peptostreptococcus, that strains 06 and 85 are members of P. putridus, and that strains 11 and 87 may be members of two different genera.

Agglutination Tests↗
PubMed1980

Composition and properties of the cell wall of Methanospirillum hungatii.

Dithiothreitol reacted, at pH 9.0, with the isolated cell walls of Methanospirillum hungatii, to release about 23% of the cell wall dry weight as a high molecular weight fraction (> 0.5 million daltons). Untreated walls consisted of 70% amino acids, 11% lipid, and 6.6% carbohydrate. Sugars were identified as rhamnose, ribose, glucose, galactose, and mannose. The wall material that was released contained only 47% amino acids and was enriched in lipid, glucose, and phosphate. These results support data from electron micrographs, showing the localized release of cell wall material by the disulfide bond-breaking reagent at alkaline pH. In amino acid composition the untreated walls did not differ greatly from the material released by dithiothreitol, but differed considerably from the walls of another strain of M. hungatii. The ratios of the amino acids found in the cell wall proteins of several archaebacteria and of Bacillus cereus spore coats were similar.

Amino Acids↗
PubMed2001

Ion-exchange properties of cell walls isolated from lupine roots.

Acid-base properties of cell walls isolated from various root tissues of 7-day-old lupine seedlings and 14-day-old lupine plants grown in various media were studied. The ion-exchange capacity of root cell walls was estimated at various pH values (from 2 to 12) and constant ionic strength (10 mM). The parameters determining the qualitative and quantitative composition of cell wall ionogenic groups along the root length and in its radial direction were estimated using Gregor's model. This model fits the experimental data reasonably well. Four types of ionogenic groups were found in the cell walls: an amino group (pKa approximately 3), two types of carboxylic groups (pKa approximately 5 and 7.3, the first being the carboxylic group of galacturonic acid), and a phenolic group (pKa approximately 10). The number of functional groups of each type was estimated, and the corresponding ionization constant values were calculated. It is shown that the chemical composition of the ionogenic groups was constant along the root length as well as in its radial direction and did not depend on either physiological state or root nutrition, while the number of different groups varied. The content of carboxylic groups of alpha-D-polygalacturonic acid in the root cell walls of 14-day-old plants was shown to depend on the distance from the root tip, being maximal in the zone of lateral roots. The number of these groups was 10- and 2-fold less in the central cylinder compared to that of cortex for 14-day-old plants and 7-day-old seedlings, respectively.

Amino Acids↗
PubMed1987

Relationship of cell surface morphology and composition of Streptococcus salivarius K+ to adherence and hydrophobicity.

The cell surfaces of a range of variants of Streptococcus salivarius HB, altered in cell wall antigen composition, were compared with those of the parent with respect to adherence, ability to adsorb to hexadecane, morphology, and exposure of lipoteichoic acid (LTA). Adherence to host surfaces was measured by using both saliva-coated hydroxyapatite beads and tissue-cultured HeLa cells, and interbacterial adherence was measured by using Veillonella alcalescens V1 cells. Progressive loss of the protease-sensitive fibril classes was generally associated with decreasing ability to adsorb to hexadecane. However, increased exposure of protein antigen C (AgC) increased the apparent hydrophobicity of the cell. This correlated with the finding that AgC was the most hydrophobic of the solubilized fibrillar cell wall antigens. Collectively, this demonstrates that adsorption to hydrophobic ligands is directly related to the density of the fibrillar layer on the cells and the properties and surface exposure of specific fibril classes. The involvement of hydrophobic interactions in AgC-associated attachment was suggested by its sensitivity to low levels of the hydrophobic bond-breaking agent tetramethyl urea, although the reduction was not to the level of adherence observed with strains lacking AgC. However, hydrophobicity was less essential to other adherence reactions. Circumstantial evidence, including immunoelectron microscopy, showing that LTA was virtually absent from the fibrillar layer, whole-cell enzyme-linked immunosorbent assay, suggesting that surface exposure of LTA related inversely to the density of the fibrillar layer, and agarose gel electrophoresis, showing that LTA was not specifically associated with protein fibrillar antigens, strongly suggested that LTA does not confer hydrophobic properties to these cells and is not involved in adherence reactions associated with the cell wall protein antigens.

Antigens, Bacterial↗
PubMed1995

Morphogenesis and cell wall changes in maize shoots under simulated microgravity conditions.

Various plant organs show a spontaneous curvature on a three-dimensional clinostat. Changes in the cell wall metabolism underlying the curvature were examined in maize shoots. In coleoptile nodes, no differences were detected in either the level or the composition of cell wall polysaccharides between the convex and the concave halves. However, the convex side showed a higher activity of (1 --> 3),(l --> 4)-beta-glucan breakdown, which appears to be associated with the curvature. In the elongating region of coleoptiles, the accumulation of wall polysaccharides occurred in the convex side. There was no significant difference in the glucanase activity between both sides. Thus, the spontaneous curvature in different regions of maize shoots may be brought about through different mechanisms under simulated microgravity conditions.

Cell Wall↗
PubMed1991

[The modification of the cell wall proteins in group A streptococci type M 29 under the influence of spermidine contained in the culture medium].

The addition of spermidine into growth medium used for the cultivation of group A streptococci, type M 29, leads to changes in the amino acid composition of cell walls and surface proteins isolated by the method of E. H. Beachey et al. The separation of surface proteins into fibrinogen-binding proteins and fibrinogen receptors by affinity chromatography techniques on cellulose with covalently bound fibrinogen indicates that the proportion of these proteins in pepsin extracts obtained from different strains varies. Both spermidine and avirulent strains have similar content of fibrinogen-binding proteins, although these proteins are absent in virulent strains. Different amounts of fibrinogen receptors are extracted from all strains. As shown in the enzyme immunoassay, fibrinogen receptors contain no group-specific polysaccharide A, Fc-receptors and interact with total antiserum to group A streptococci, type M 29 [correction of 28]. Fibrinogen receptors isolated from the strains under study have been found to have similar amino acid composition. On the basis of these results we believe that neither receptor capacity to fibrinogen nor amino acid composition is indicative of the protective properties of protein M.

Amino Acids↗
PubMed2000

Physicochemical characteristics of onion (Allium cepa L.) tissues.

The structure and mechanical properties of onions are important factors affecting their textural quality. The onion bulb consists of several layers of pigmented, papery scales surrounding fleshy storage scales that comprise an upper epidermis, an intermediate parenchyma tissue, and a lower epidermis. The purpose of this study was to examine the chemical composition of cell walls from the papery scales and outer fleshy scales of onion (Allium cepa L. cv. Sturon) in relation to their mechanical properties. Cell-wall material (CWM) was prepared from the component tissues and analyzed for its carbohydrate and phenolic composition. The CWMs were rich in uronic acid and glucose, with smaller quantities of arabinose, galactose, and xylose. In the fleshy scales, the lower epidermis contained relatively more galactose-rich pectic polysaccharides, whereas the upper epidermis and the papery scales contained virtually no galactose. Analysis of mechanical properties showed that the order of strength of the tissues was papery scales > fleshy scales, which were in the order lower epidermis > upper epidermis > intermediate parenchyma. The upper epidermis of fleshy scales was stronger in the vertical than the horizontal direction, and both orientations showed negligible notch sensitivity. Cyclohexane-trans-1,2-diaminetetraacetate-induced vortex-induced cell separation of the intermediate layer of fleshy scales indicated that calcium cross-linking may play an important role in cell-cell adhesion. A small but significant amount of ferulic acid was found in the walls, predominantly in the thick cuticle of the lower epidermis of fleshy scales. Alkali-labile wall-bound flavonoids were also detected.

Carboxylic Acids↗