Effect of chemistry and morphology on the biofunctionality of self-assembling diblock copolypeptide hydrogels

Amphiphilic, diblock copolypeptides of hydrophilic lysine or glutamic acid and hydrophobic leucine or valine have been observed to self-assemble into rigid hydrogels in aqueous solution at neutral pH and very low volume fraction of polymer, > or =0.5 wt % polypeptide. Laser scanning confocal microscopy and ultra small angle neutron scattering revealed a heterogeneous microstructure with distinct domains of hydrogel matrix and pure water pores. In situ nanoscale characterization, using cryogenic transmission electron microscopy, revealed a porous, interconnected membranous network of assembled polypeptides. At concentrations of polypeptide below gelation, diblocks containing lysine were cytotoxic to cells, whereas those containing glutamic acid were noncytotoxic. At higher polypeptide concentrations, within rigid gel scaffolds, both lysine and glutamic acid based diblocks were noncytotoxic but did not support cell attachment/proliferation. The cationic chemistry observed as cytotoxic in the fluid state was essentially inert in the intact, rigid hydrogel state.     

Relationship between histology,development and tumorigenesis of mammary gland in female rat

The mammary gland is a dynamic organ that undergoes structural and functional changes associated with growth, reproduction, and post-menopausal regression. The postnatal transformations of the epithelium and stromal cells of the mammary gland may contribute to its susceptibility to carcinogenesis. The increased cancer incidence in mammary glands of humans and similarly of rodents in association with their development is believed to be partly explained by proliferative activity together with lesser degree of differentiation, but it is not completely understood how the virgin gland retains its higher susceptibility to carcinogenesis. During its developmental cycle, the mammary gland displays many of the properties associated with breast cancer. An early first full-term pregnancy may have a protective effect. Rodent models are useful for investigating potential breast carcinogens. The purpose of this review is to help recognizing histological appearance of the epithelium and the stroma of the normal mammary gland in rats, and throughout its development in relation to tumorigenic potential.     

Probing the importance of lateral hydrophobic association in self-assembling peptide hydrogelators

A class of peptides has been designed whose ability to self-assemble into hydrogel is dependent on their conformationally folded state. Under unfolding conditions aqueous peptide solutions are freely flowing having the viscosity of water. When folding is triggered by external stimuli, peptides adopt a β-hairpin conformation that self-assembles into a highly crosslinked network of fibrils affording mechanically rigid hydrogels. MAX 1, a 20 residue, amphiphilic hairpin self-assembles via a mechanism which entails both lateral and facial self-assembly events to form a network of fibrils whose local structure consists of a bilayer of hairpins hydrogen bonded in the direction of fibril growth. Lateral self-assembly along the long axis of the fibril is mainly facilitated by intermolecular hydrogen bonding between the strands of distinct hairpins and the formation of hydrophobic contacts between residue side chains of laterally associating hairpins. Facial assembly is driven by the hydrophobic collapse of the valine-rich faces of the amphiphilic hairpins affording a bilayer laminate. The importance of forming lateral hydrophobic contacts during hairpin self-assembly and the relative contribution these interactions have towards nano-scale morphology and material rigidity is probed via the study of: MAX1, a hairpin designed to exploit lateral hydrophobic interactions; MAX 4, a peptide with reduced ability to form these interactions; and MAX5, a control peptide. CD spectroscopy and rheological experiments suggest that the formation of lateral hydrophobic interactions aids the kinetics of assembly and contributes to the mechanical rigidity of the hydrogel. Transmission electron microscopy (TEM) shows that these interactions play an essential role in the self-assembly process leading to distinct nano-scale morphologies. Electronic Supplementary Material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

Characterization of the yeast flora present in some Turkish high-sugar products

In this study, 129 Turkish high-sugar products were examined in terms of their yeast flora and 73 representative strains were isolated. Yeast isolates were identified at species level by using Apilab Plus (bioMérieux, France), a specific computer program developed for ID 32C strips (bioMérieux, France). While one of the isolates could be identified at genus level as Aureobasidium, 66 of them were identified as 21 species belonging to 8 different genera. The distribution of these isolates were as follows: Candida (38), Rhodotorula (8), Zygosaccharomyces (7), Cryptococcus (6), Saccharomyces (3), Debaryomyces (2), Pichia (1) and Torulaspora (1). Approximately 70% of the isolates were found to have the ability to grow on media with 50% (w/w) glucose. Hence, they were characterized as xerotolerant strains. Although Zygosaccharomyces rouxii is known as the most xerotolerant yeast species, only two strains of Z. rouxii could be isolated from Turkish high-sugar foods. During identification studies, it was observed that ID 32C test strips should certainly be supported by morphological and physiological tests for obtaining more reliable identification results. If not, closely related yeast species such as anamorph and telemorph forms can not be distinguished.     

Seed characteristics and fatty acid composition of castor (<i>Ricinus communis</i> L.) varieties in Northeast China

Oil content and fatty acid composition were investigated on 12 castor varieties and strains by using the soxhlet extraction method and capillary gas chromatography. This was made to provide a reference and theoretical basis for castorbean breeding with high oil content, determine variability of seed compounds for breeding purposes, and broaden chemical material choices. Results revealed that crude fat percentage in seeds ranged from 18.91 to 35.84% with an average of 25.91%; the absolute content of ricinoleic acid varied between 171.65 g/kg and 314.03 g/kg with an average of 222.43 g/kg, and kernel crude fat percentage was between 24.28 and 46.97% with an average of 34.30%. All these study variables were highest in the 2129 strain. The percentage of ricinoleic acid in crude fat was between 83.85 to 87.62%, and the highest value was found in the zhebi4 accession. The other fatty acids appeared in small concentrations, and showed small amplitude: 1.12 to 1.61%, 1.21 to 1.61%, 3.53 to 4.80%, 5.35 to 6.38%, 0.52 to 0.79%, 0.05 to 0.08% and 0.43 to 0.55%, for palmitic, stearic, oleic, linolic, linolenic, arachidic, and arachidonic acids, respectively. One hundred seed weight was determined for each accession. One hundred seed weight ranged from 25.7 g to 34.0 g with an average of 29.9 g. There was a significant correlation between seed weight and oil content, but the correlation value was low (r=0.51). Cluster analysis by SSPS based on the content of fatty acid composition revealed that the accessions were divided into three independent clusters. These findings will clearly provide useful information for further research in breeding and utilization of castor oil.     

Tumor necrosis factor-alpha promotes survival in methotrexate-exposed macrophages by an NF-κB-dependent pathway

Introduction  

Methotrexate (MTX) induces macrophage apoptosis in vitro, but there is not much evidence for increased synovial macrophage apoptosis in MTX-treated patients. Macrophage apoptosis is reported, however, during clinical response to anti-tumor necrosis factor-alpha (TNF-α) treatments. This implies that TNF-α promotes macrophage survival and suggests that TNF-α may protect against MTX-induced apoptosis. We, therefore, investigated this proposal and the macrophage signaling pathways underlying it.     

The effect of some environmental parameters on the growth of yeasts originating from sugar containing foods

In this study, 65 yeast strains originating from sugar containing foods were tested for growth under different environmental conditions. In the experiments performed with glucose and NaCl, inhibition effect was observed at reduced a_w levels. Most of the strains were able to grow at both 4 and 37°C. Of the tested pH values, the most adverse effect on growth of the yeasts was observed at pH 2.5. All of the strains were able to grow at both 5 and 20% CO₂ levels. Acetic and propionic acids were found to be the most effective preservatives for inhibition of the strains. All of the yeasts, except aCandida glucosophila strain, failed to grow in the presence of 0.05% (w/v) sodium benzoate.