A model for the pattern of deposition of microfibrils in the cell wall of Glaucocystis

Freeze-fracturing of Glaucocystis nostochinearum Itzigsohn cells during cell-wall microfibril deposition indicates that unidirectionally polarized microfibril ends are localized in a zone of synthesis covering about 30% of the sarface area of the plasma membrane. Within this zone there are about 6 microfibril ends/m² cell surface. It is proposed that microfibrils are generated by the passage of their tips over the cell surface and that the pattern of microfibril organization at the poles of the cells, in which microfibrils of alternate layers are interconnected at 3 rotation centres, results directly from the pattern of this translation of microfibril tips. In a model of the deposition pattern it is proposed that the zone of synthesis may split into 3 sub-zones as the poles are approached, each sub-zone being responsible for the generation of one rotation centre. It is demonstrated that the microfibrillar component of the entire wall could be generated by the steady translation of the microfibril tips (at which synthesis is presumed to occur) over the cell surface at a rate of 0.25–0.5 m min^-1. Microcinematography indicates that the protoplast rotates during cell-wall deposition, and it is proposed that this rotation may play a role in the generation of the microfibril deposition pattern.     

Molecular dynamics simulations of solvated crystal models of cellulose I(alpha) and III(I)

Swelling behaviors of cellulose I(alpha) and III(I) crystals have been studied using molecular dynamics simulations of the solvated finite-crystal models. The typical crystal models consisted of 48 x 10-mer chains. For the cellulose I(alpha) crystal, models consisting of different numbers of chains and chain lengths were also studied. The structural features of the swollen crystal models, including the cellulose I(beta) crystal model reported previously, were compared. A distinct right-handed twist was observed for models of the native cellulose crystals (cellulose I(alpha) and I(beta)), with a greater amount of twisting observed for the I(alpha) crystal model. Although the amount of twist decreased with increasing dimensions of the cellulose I(alpha) crystal model, the relative changes in twist angle suggest that considerable twist would arise in a crystal model of the actual dimensions. In contrast to the swelling behavior of crystal models of the native cellulose, the cellulose III(I) crystal model exhibited local, gradual disordering at the corner of the reducing end. Comparison of the lattice energies indicated that the cellulose chains of the I(beta) crystal were packed in the most stable fashion, whereas those of the I(alpha) and III(I) crystals were in a metastable state, which is consistent with the crystallization behaviors observed. Upon heating of the native cellulose crystal models, the chain sheets of the I(alpha) model showed a continuous increase in twist angle, suggesting weaker intersheet interactions in this model. The swollen crystal models of cellulose I(alpha) and III(I) reproduce well the representative structural features observed in the corresponding crystal structures. The crystal model twist thus characterizes the swelling behavior of the native cellulose crystal models, which seems to be related to the insolubility of the crystals.     

Structure of rigid-layer of Rhizobium cell wall. I. Purification on the peptidoglycan from the cellulose microfibrils

The bag shaped peptidoglycan layer of Rhizobium cell wall was isolated from intact cells after treatment with sodium dodecylsulfate and trypsin, chymotrypsin or pepsin digestion. Results of chemical analysis of acid hydrolyzed peptidoglycan revealed beside two amino sugars: glucosamine and muramic acid, three major amino acids; alanine, glutamic acid and 2,6-diaminopimelic acid and also significant amount of glucose. Evidence were provided that the polyglucose found in peptidoglycan preparations of three strains of Rhizobium trifolii, one of Rhizobium leguminosarum and one of Rhizobium meliloti consist of cellulose microfibrils. The content of cellulose present in Rhizobium peptidoglycans ranged from 60 to 80%. Methods of peptidoglycan purification from the cellulose microfibrils are described.     

Quantitative analysis for the cellulose I alpha crystalline phase in developing wood cell walls

FT-IR and X-ray analyses were employed to determine the relative ratio of cellulose Ialpha and Ibeta crystalline phases present in each developmental stage of coniferous tracheid cell wall formation. The IR spectra showed that initially the Ialpha phase occupies 50% of the crystalline regions in the primary cell wall cellulose and this value drops to 20% after ceasing of the cell enlarging growth for the formation of the secondary wall cellulose (the remaining regions are composed of the Ibeta phase). Although it is reasonable that the content for Ibeta, which is stress-reduced crystalline form, was higher in the secondary wall formation (Kataoka Y, and Kondo T. Macromolecules 1996;29:6356 6358) it is more interesting that during the crystallization of stress-induced Ialpha cellulose for the primary wall the stress-reduced Ibeta, is also possible to be crystallized in an alternative way. This means that throughout the period the Ialpha-causing stress may not be necessarily kept loaded. In light of our previously reported hypothesis (Kataoka Y. and Kondo T. Macromolecules 1998;31:760-764) for the formation of Ialpha phase due to cellular growing stresses in the primary wall cellulose, such an alternating on-off stress effect to account for the occurrence of both Ialpha and Ibeta phases might be related to a biological growth system in coniferous wood cells.     

Complete primary structure of rainbow trout type I collagen consisting of alpha1(I)alpha2(I)alpha3(I) heterotrimers.

The subunit compositions of skin and muscle type I collagens from rainbow trout were found to be alpha1(I)alpha2(I)alpha3(I) and [alpha1(I)](2)alpha2(I), respectively. The occurrence of alpha3(I) has been observed only for bonyfish. The skin collagen exhibited more susceptibility to both heat denaturation and MMP-13 digestion than the muscle counterpart; the former had a lower denaturation temperature by about 0.5 degrees C than the latter. The lower stability of skin collagen, however, is not due to the low levels of imino acids because the contents of Pro and Hyp were almost constant in both collagens. On the other hand, some cDNAs coding for the N-terminal and/or a part of triple-helical domains of proalpha(I) chains were cloned from the cDNA library of rainbow trout fibroblasts. These cDNAs together with the previously cloned collagen cDNAs gave information about the complete primary structure of type I procollagen. The main triple-helical domain of each proalpha(I) chain had 338 uninterrupted Gly-X-Y triplets consisting of 1014 amino acids and was unique in its high content of Gly-Gly doublets. In particular, the bonyfish-specific alpha(I) chain, proalpha3(I) was characterized by the small number of Gly-Pro-Pro triplets, 19, and the large number of Gly-Gly doublets, 38, in the triple-helical domain, compared to 23 and 22, respectively, for proalpha1(I). The small number of Gly-Pro-Pro and the large number of Gly-Gly in proalpha3(I) was assumed to partially loosen the triple-helical structure of skin collagen, leading to the lower stability of skin collagen mentioned above. Finally, phylogenetic analyses revealed that proalpha3(I) had diverged from proalpha1(I). This study is the first report of the complete primary structure of fish type I procollagen.     

Effect of rumen ciliates on the digestion of different carbohydrates in sheep. I.--Utilization of cell wall carbohydrates (cellulose and hemicellulose) and of starch

Two diets rich in cell-wall carbohydrates or starch were given to 10 rumen-fistulated sheep; two sheep were defaunated and the others were inoculated with Polyplastron multivesiculatum (P) or Entodinium sp. (E), or both (P + E), or with conventional fauna. Ciliate biomass was greater when the animals were fed a high starch diet than when the diet was rich in cell-wall carbohydrates (table 2). With both diets, the Entodinium genus in the mixed fauna sampling predominated. We showed that Polyplastron was directly involved in cell-wall carbohydrate breakdown, while Entodinium capacity to digest cellulose remained low. We noted that with a diet rich in cellulose and hemicellulose, bacterial cellulolytic activity was improved by the presence of ciliates in the rumen but was decreased with the "starch" diet (table 3). The greater VFA concentration observed in the faunated animals expressed ciliate effect on the fermentations as well as activation of bacterial metabolism. With a high starch diet, the Entodinium sp. ciliates may have a buffering effect on the pH values in the rumen by limiting bacterial fermentation after food intake and by prolonging starch digestion during the day (table 4). The composition of the VFA mixture was modified by ciliate inoculation. The molar proportion of butyric acid always increased, while that of acetic and propionic acids evolved differently according to the diets and the ciliates (table 4). The higher ammonia concentration in the rumen liquor observed in faunated animals (table 4) could be explained either by the breakdown of both feed and bacterial proteins ingested by ciliates or by a lower ammonia nitrogen incorporation by fewer bacteria. Statistical analyses were used to explain the specific effect of P and E and also the interactions between them and between each of them and the diets.     

On the polarity of cellulose in the cell wall of Valonia

The orientation of the triclinic phase of cellulose in the cell wall of Valonia ventricosa J. Agardh was investigated by X-ray- and electron-diffraction analysis. In addition to the well-documented uniplanar-axial organization of the cell wall which requires that the a ^* axis should be always perpendicular to the wall surface, the direction of this axis was also found to be pointing outward from the plasma membrane side of the wall. This unidirectionality was persistent throughout the various layers that constitute the cell wall and also for the three microfibrillar orientations that occur in Valonia cell walls. The unidirectionality of the a ^* axis indicates, in particular, that the Valonia cellulose microfibrils are not twisted along their axis. These observations are consistent with a cellulose biosynthetic scheme where a close association exists between terminal-complex orientations and those of the cellulose microfibrils. In this context, the unidirectionality of the a ^* axis of cellulose seems to be related to the restricted mobility of the terminal complexes which are able to slide in the plasma membrane but not to rotate along their long axis.Abbreviations TC terminal complex This work was initiated during a visit of J.F.R at Grenoble in the framework of a France-Québec exchange program. J.S. was recipient of a CNRS fellowship. The diagram in Fig. 8 was kindly drawn for us by Miss Yukie Saito from the Department of Forest Products, the University of Tokyo.     

Cell-specific in vivo DNA-protein interactions at the proximal promoters of the pro alpha 1(I) and the pro alpha2(I) collagen genes.

We performed in vivo dimethylsulfate footprinting of the 220 bp mouse proximal proalpha1(I) collagen promoter and the 350 bp mouse proximal proalpha2(I) collagen promoter in BALB/3T3 fibroblasts, primary mouse skin fibroblasts, S-194 B cells, NMuLi liver epithelial cells and RAG renal adenocarcinoma cells and in vitro DNase I footprinting of these promoters using nuclear extracts of these different cell types. Whereas proalpha1(I) and proalpha2(I) collagen RNAs were present in BALB/3T3 fibroblasts and primary fibroblasts, these RNAs could not be detected in the three other cell lines. Comparison of in vitro DNase I footprints for each of the two proximal collagen promoters indicated that the patterns of protection were very similar with the different nuclear extracts, suggesting that the DNA binding proteins binding to these promoters were present in all cell types tested. In contrast, in vivo footprints over these proximal promoters were cell-specific, occurring only in fibroblast cells and not in the other three cell types. The in vivo footprints were generally located within the in vitro footprinted regions. Our results suggest that although all cell types tested contained nuclear proteins that can bind to the proximal proalpha1(I) and proalpha2(I) collagen promoters in vitro , it is only in fibroblasts that these proteins bind to their cognate sites in vivo . We discuss possible regulatory mechanisms in type I collagen genes that can contribute to the cell-specific in vivo protein-DNA interactions at the proximal promoters.     

How the deposition of cellulose microfibrils builds cell wall architecture

Cell walls, the extracytoplasmic matrices of plant cells, consist of an ordered array of cellulose microfibrils embedded in a matrix of polysaccharides and glycoproteins. This construction is reminiscent of steel rods in reinforced concrete. How a cell organizes these ordered textures around itself, creating its own desirable environment, is a fascinating question. We believe that nature adopted an economical solution to this design problem: it exploits the geometrical constraints imposed by the shape of the cell and the limited space in which microfibrils are deposited, enabling the wall textures essentially to 'build themselves'. This does not imply that the cell cannot control its wall texture. On the contrary, the cell has ample regulatory mechanisms to control wall texture formation by controlling the insertion of synthases and the distance between individual microfibrils within a wall lamella.     

Signal-induced degradation of I(kappa)B(alpha): association with NF-kappaB and the PEST sequence in I(kappa)B(alpha) are not required.

Signal-induced degradation of I(kappa)B(alpha) via the ubiquitin-proteasome pathway requires phosphorylation on residues serine 32 and serine 36 followed by ubiquitination on lysines 21 and 22. We investigated the role of other regions of I(kappa)B(alpha) which may be involved in its degradation. Here we report that the carboxy-terminal PEST sequence is not required for I(kappa)B(alpha) signal-induced degradation. However, removal of the PEST sequence stabilizes free I(kappa)B(alpha) in unstimulated cells. We further report that a PEST deletion mutant does not associate well with NF-(kappa)B proteins but is degraded in response to signal. Therefore, we conclude that both association with NF-(kappa)B and a PEST sequence are not required for signal-induced I(kappa)B(alpha) degradation. Additionally, the PEST sequence may be required for constitutive turnover of free I(kappa)B(alpha).     

Studies on the cell wall of Chlorella I. Quantitative changes in cell wall polysaccharides during the cell cycle of Chlorella ellipsoidea

1. 1. The cell wall of Chlorella ellipsoidea was fractionated intotwo components, alkali-soluble hemicellulose and alkali-insoluble"rigid wall". The former was composed of several neutral sugars,i.e. rhamnose, xylose, arabinose, mannose and galactose, andthe latter had glucosamine as a main constituent sugar.
2. 2.Quantitative changes in both hemicellulose and "rigid wall"contents during the cell cycle were followed using synchronouslygrown cells. The two cell wall components showed markedly differentchanges. Hemicellulose increased in proportion to the enlargementof the cell surface area in the growing phase, while the "rigidwall" remained almost constant in this phase. The "rigid wall"increased only in the reproduction phase—the time of autosporeformation.

(Received September 26, 1977; )     

Infection of Glaucocystis nostochinearum (Glaucophyta) by Lagenidium sp. (Oomycota) and its hyperparasite Pythiella sp. (Oomycota)

The glaucophyte Glaucocystis nostochinearum has to our knowledge been observed to be infected by a parasite for the first time. It was found in samples taken from the northernmost freshwater pond in Germany (on the island of Sylt). The fungal parasite was identified as the oomycete Lagenidium sp. which itself was parasitised by another oomycete, Pythiella sp.     

Triple alpha-genes (alpha alpha alpha anti3.7) in a patient with sickle cell anaemia.

This paper reports the case of a 17-year-old male student from the Jaizan area in south-western Saudi Arabia who had sickle cell anaemia and possessed three alpha-genes on one chromosome (alpha alpha alpha anti3.7) and two on the other. The clinical manifestations were severe, with frequent blood transfusion requirements and frequent episodes of painful crises, severe anaemia and tissue involvement. In comparison with age and sex-matched sickle cell anaemia patients with one alpha-gene deletion (-alpha/alpha alpha), or a normal alpha-gene arrangement (alpha alpha/alpha alpha), a more severe disease presentation was obvious in the propositus. It is suggested that with the surplus alpha-globin chains, more severe haematological and clinical abnormalities occur, these influence the phenotypic expression of sickle cell anaemia. However, more patients with this type of gene arrangement must be studied before a definite conclusion can be reached regarding the influence of excess alpha-globin chains on the presentation of sickle cell anaemia.