Structure of the Staphylococcus aureus cell wall determined by the freeze-substitution method.

The fine structure of the Staphylococcus aureus cell wall was determined by electron microscopy with the new technique of rapid freezing and substitution fixation. The surface of the cell wall was covered with a fuzzy coat which consisted of fine fibers or an electron-dense mass. Morphological examination of the cell wall, which was treated sequentially with sodium dodecyl sulfate, trypsin, and trichloroacetic acid, revealed that this coat was partially removed by trypsin digestion and was completely removed by trichloroacetic acid extraction but was not affected by sodium dodecyl sulfate treatment, suggesting that the fuzzy coat consists mostly of a complex of teichoic acids and proteins. This was confirmed by the application of the concanavalin A-ferritin technique for teichoic acid and antiferritin immunoglobulin G technique for protein A.     

Quantitative analysis of changes in cell shape of Amoeba proteus during locomotion and upon responses to salt stimuli

A new parameter expressing the complexity of cell shape defined as (periphery)²/(area) in 2D projection was found useful for a quantitative analysis of changes in the cell shape of Amoeba proteus and potentially of any amoeboid cells. During locomotion the complexity and the motive force of the protoplasmic streaming in amoeba varied periodically, and the Fourier analysis of the two showed a similar pattern in the power spectrum, giving a rather broad peak at about 2.5 × 10⁻³ Hz. The complexity increased mainly due to elongation of the cell as external Ca²⁺ increased. This effect was blocked by La³⁺, half the inhibition being attained at 1/200 amount of the coexisting Ca²⁺. On the other hand, the complexity decreased due to rounding up of the cell as the concentration of other cations, such as Sr²⁺, Mg²⁺, Co²⁺, Ni²⁺, Na⁺, K⁺ etc., increased. Irrespective of the opposite effects of Ca²⁺ and other cations on the cell shape, the ATP concentration in amoeba decreased in both cases with increase of all these cations. The irregularity in amoeboid motility is discussed in terms of a dynamic system theory.     

C3b and c3d receptor sites on human fibroblasts derived from several human tissues.

The C3b and C3d receptor sites on one cell line of human diploid fibroblasts (WI-38) were reported in previous papers [3, 4]. In this paper we describe that C3b and C3d receptor sites can also be detected in fibroblast cell lines derived from other human tissues. We consider that C3b and C3d receptors are normally found on the cell surfaces of all human fibroblasts.     

Impact of Pulsed Nd:YAG Laser Irradiation on the Growth and Mortality of the Biofilm Forming Marine Bacterium Pseudoalteromonas carrageenovora

The impact of pulsed laser irradiation on the marine biofilm forming bacterium Pseudoalteromonas carrageenovora was investigated in the laboratory by monitoring mortality and the post-irradiation growth pattern. The impact of laser irradiation on bacterial mortality increased with the duration of irradiation. Laser irradiation at 532 nm (0.1 J cm m 2 ) for 15 min resulted in a 53% cell mortality immediately after irradiation. However, the impact after a period of 5 h (delayed impact) was more severe. The growth pattern of irradiated samples showed a prolonged lag phase compared to the reference, due to a reduction in total viable counts (TVC) in the irradiated samples. Nucleic acid staining is suggested to be a promising technique for monitoring laser inflicted bacterial mortality. Thus, the results suggest that laser irradiation could be considered as an alternative technique to reduce the number of biofilm forming bacteria and thereby biofilm formation on hard surfaces.     

Hermaphroditism in fishes: an annotated list of species,phylogeny, and mating system

Fewer than 1% of vertebrate species are hermaphroditic, and essentially all of these are fishes. Four types of hermaphroditism are known in fishes: simultaneous (or synchronous) hermaphroditism (SH), protandry (male-to-female sex change; PA), protogyny (female-to-male sex change; PG), and bidirectional sex change (BS or reversed sex change in protogynous species). Here we present an annotated list of hermaphroditic fish species from a comprehensive review and careful re-examination of all primary literature. We confirmed functional hermaphroditism in more than 450 species in 41 families of 17 teleost orders. PG is the most abundant type (305 species of 20 families), and the others are much less abundant, BS in 66 species of seven families, SH in 55 species of 13 families, and PA in 54 species of 14 families. The recently proposed phylogenetic tree indicated that SH and PA have evolved several times in not-closely related lineages of Teleostei but that PG (and BS) has evolved only in four lineages of Percomorpha. Examination of the relation between hermaphroditism type and mating system in each species mostly supported the size-advantage model that predicts the evolution of sequential hermaphroditism. Finally, intraspecific variations in sexual pattern are discussed in relation to population density, which may cause variation in mating system.

     

α5β1 integrin induces the expression of noncartilaginous procollagen gene expression in articular chondrocytes cultured in monolayers

Introduction

Articular chondrocytes undergo an obvious phenotypic change when cultured in monolayers. During this change, or dedifferentiation, the expression of type I and type III procollagen is induced where normal chondrocytes express little type I and type III procollagen. In this study, we attempted to determine the mechanism(s) for the induction of such procollagen expression in dedifferentiating chondrocytes.

Methods

All experiments were performed using primary-cultured human articular chondrocytes under approval of institutional review boards. Integrin(s) responsible for the induction of type I and type III procollagen expression were specified by RNAi experiments. The signal pathway(s) involved in the induction were determined by specific inhibitors and RNAi experiments. Adenovirus-mediated experiments were performed to identify a small GTPase regulating the activity of integrins in dedifferentiating chondrocytes. The effect of inhibition of integrins on dedifferentiation was investigated by experiments using echistatin, a potent disintegrin. The effect of echistatin was investigated first with monolayer-cultured chondrocytes, and then with pellet-cultured chondrocytes.

Results

In dedifferentiating chondrocytes, α5β1 integrin was found to be involved in the induction of type I and type III procollagen expression. The induction was known to be mediated by v-akt murine thymoma viral oncogene homolog (AKT) signaling. Among the three AKT isoforms, AKT1 seemed to be most involved in the signaling. Elated RAS viral (r-ras) oncogene homolog (RRAS) was considered to regulate the progression of dedifferentiation by modulating the affinity and avidity of α5β1 integrin to ligands. Echistatin inhibited dedifferentiation of monolayer-cultured chondrocytes. Furthermore, the matrix formed by pellet-cultured chondrocytes more closely resembled that of normal cartilage compared with the controls.

Conclusions

The result of this study has shown, for the first time, that α5β1 integrin may be responsible for the induction of non-cartilaginous collagen expression in chondrocytes undergoing dedifferentiation. Again, this study has shown that the inhibition of ligand ligation to integrins may be an effective strategy to inhibit phenotypic change of cultured chondrocytes, and to improve the quality of matrix synthesized by primary cultured chondrocytes.     

Use of the 2-(2-Pyridyl)Ethyl Protecting Group in the Synthesis of DNA Fragments via Phosphoramidite Intermediates

Abstract

2-(2-Pyridyl)ethyl is a new protecting group for the internucleotidic linkages in the synthesis of oligodeoxyribo-nucleotides by the phosphoramidite method. This group is stable to alkali and acid, and can be removed by two step procedures under mild conditions. Furthermore, we have found that bis-(diiso-propylamino)chlorophosphine is much more effective for the preparation of bis-(diisopropylamino)alkoxyphosphine than various dichlorophosphines. The synthesis of oligodeoxyribonucleotides by using 2-(2-pyridyl)ethyl-deoxyribonucleoside-3′-0-N,N-diisopropyl-amidite units is also described.