Review: Hydrogels for cell immobilization

Hydrogels are being investigated for mammalian cell immobilization. Their material properties can be engineered for biocompatibility, selective permeability, mechanical and chemical stability, and other requirements as specified by the application including uniform cell distribution and a given membrane thickness or mechanical strength. These aqueous gels are attractive for analytical and tissue engineering applications and can be used with immobilization in therapies for various diseases as well as to generate bioartificial organs. Recent advances have broadened the use of hydrogel cell immobilization in biomedical fields. To provide an overview of available technology, this review surveys the current developments in immobilization of mammalian cells in hydrogels. Discussions cover hydrogel requirements for use in adhesion, matrix entrapment, and microencapsulation, the respective processing methods, as well as current applications. (c) 1996 John Wiley & Sons, Inc.     

Reaction mechanism of isomaltooligosaccharides synthesis by α-glucosidase fromAspergillus carbonarious

Summary An -glucosidase fromAspergillus carbonarious CCRC 30414 was employed for investigating the enzymatic synthesis of isomaltooligosaccharides from maltose. The enzyme transferred a glucose unit from the nonreducing end of maltose and other -linked glucosyl oligosaccharides to glucose and other glucosyl oligosaccharides which function as accepting co-substrates. The transfer of a glucose unit occurs most frequently to the 6-OH position of the nonreducing end of acceptor, but transfer to 4-OH position also occurs. Treatment of 30 % (w/v) maltose with the enzyme under optimum conditions afforded more than 50% isomaltooligosaccharides.     

Behavioral responses of the whitebacked planthopperSogatella furcifera (Homoptera: Delphacidae) on rice plants whose odors have been masked

In a two-choice test, moreS. furcifera females settled more often on exposed plants than on parafilm-masked ones, regardless of the susceptibility of rice varieties. This indicates that rice volatiles play an important role in the insect's short-range orientation to its host. The fact that more insects settled on exposed resistant Rathu Heenati (RHT) than to masked susceptible Taichung Native 1 (TN1) suggests that there must be certain common volatiles released by both varieties. Few females landed on masked plants of either RHT or TN1. This implies that the insect could not recognize at a distance that a plant was resistant or susceptible without olfactory stimuli.S. furcifera excreted less honeydew on masked plants than on exposed ones for both varieties and more on masked TN1 than on exposed RHT. The electronic monitoring of feeding behavior demonstrates that the insect made more frequent probes and had shorter phloem ingestion durations on exposed RHT than on exposed TN1 and on masked RHT than on masked TN1. Moreover, the insect had longer phloem ingestion durations on masked TN1 than on exposed RHT. These results suggest that volatile chemicals given off by resistant RHT plants have a negative effect on feeding.     

Clonal growth in woody plants: A review

Bulkiness, longevity and solidity of the body in woody plants enable the successive development of accessory shoots and adventitious roots in (1) both proximal and distal positions on organs, (2) both the above-ground and below-ground space, (3) both the aerial and soil environments. In monocotyledons, woody rhizomes play an essential role in the basic growth habit and architectural models. In dicotyledonous and a few gymnospermous trees, attached and successively disconnected ramets play a multilateral role in the pertinent life strategies. The majority of sprouts, coppice shoots and root suckers behave as opportunistic organs (a) serving as means of vegetative reproduction, (b) securing colonization of unoccupied ground, (c) increasing competitive power of the species within the community, (d) increasing survival rate of the stressed/disturbed genet in marginal habitats, (e) forming replacement for ageing or damaged organs, and (f) enabling reiteration of the genet's entire architectural model.     

Conformation and activity ofPhaseolus coccineus var. rubronanus lectin

The conformation of native and denaturedPhaseolus coccineus var. rubronanus lectin was studied by circular dichroism (CD) and correlated to the hemagglutinating activity. The far-UV CD spectrum at 25°C showed a broad, negative band around 223 nm and a positive one at 196 nm. CD data analysis of the lectin indicated a -sheet-rich protein. At high temperatures, the spectrum was blue-shifted with increasing magnitude; these changes correlated well with the loss of the activity. The conformation of lectin betweenpH 2 and 10 remained essentially unchanged. AtpH 13 the CD spectrum resembled that of unordered form with a negative band near 200 nm and the activity was completely lost. The denatured lectin in 6 M guanidine hydrochloride would be renatured upon diluting the denaturant to 0.75 M; the changes in CD spectrum again correlated well with the loss of the activity. The effect of sodium dodecyl sulfate on the lectin was drastic; it sharply increased thea-helix at the expense of the -sheet and reduced the activity; the changes reached a plateau above 20 mM surfactant.     

Alkalinity Tolerance of Woody Species Used in Bauxite Waste Rehabilitation, Western Australia

Glasshouse trials, using trickle irrigation and increasing levels of NaOH-induced alkalinity, identified species that could be expected to tolerate the high-pH conditions of bauxite processing waste residue sites. Of 29 taxa tested, the most tolerant were Casuarina obesa, Melaleuca lanceolata, M. armillaris, M. nesophila, Eucalyptus loxophleba, E. halophila, E. platypus, Tamarix aphylla, and a particular clone of E. camaldulensis; E. spathulata, E. tetragona, E. preissiana, E. gomphocephala, E. diptera, and E. occidentalis proved to be relatively sensitive to severe alkaline conditions. Tolerance appeared to relate to an ability to maintain root membrane function, nutrient uptake balance, and ultimately root tissue structure while under increasing levels of alkalinity stress. Species normally inhabiting alkaline soils tended to have increased growth rates in nutrient irrigation conditions between pH 8 and 10 compared with control plants irrigated with nutrient solutions of pH values near 7.4. However, once the irrigation solutions reached pH 12 and the buffering capacity of the soil appeared to be exceeded, the condition of susceptible plants rapidly declined and death followed. Sensitive plants initially showed symptoms related to nutrient deficiency, followed by wilting and death as the root systems failed. Field trial conditions in the bauxite residue impoundments at Kwinana, Western Australia, include soils with pH values as high as 11.00. In general, the relative survival and growth of seedlings after eight months were predicted by the response under glasshouse trial conditions. Appropriately designed stress trials can be important ecological techniques in choosing species most capable of surviving difficult environmental conditions in the rehabilitation of damaged landscapes.     

A study of intermediates involved in the folding pathway for recombinant human macrophage colony-stimulating factor (M-CSF): evidence for two distinct folding pathways.

The folding pathway for a 150-amino acid recombinant form of the dimeric cytokine human macrophage colony-stimulating factor (M-CSF) has been studied. All 14 cysteine residues in the biologically active homodimer are involved in disulfide linkages. The structural characteristics of folding intermediates blocked with iodoacetamide reveal a rapid formation of a small amount of a non-native dimeric intermediate species followed by a slow progression via both monomeric and dimeric intermediates to the native dimer. The transition from monomer to fully folded dimer is complete within 25 h at room temperature at pH 9.0. The blocked intermediates are stable under conditions of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and thus represent various dimeric and folded monomeric species of the protein with different numbers of disulfide bridges. Peptide mapping and electrospray ionization mass spectrometry revealed that a folded monomeric species of M-CSF contained three of the four native disulfide bridges, and this folded monomer also showed some biological activity in a cell-based assay. The results presented here strongly suggest that M-CSF can fold via two different pathways, one involving monomeric intermediates and another involving only dimeric intermediates.     

The distribution of colony-forming cells in the kidney

Abstract. A method is described for producing outgrowths of small nephron segments (average 24 cells) in culture. The method was used to estimate an overall colony-forming efficiency of 4.6% for cells constituting the segments. Efficiency was found to be lower for thick segments (1%) than for thin segments (6%) from Henle's loop. The latter higher level indicates that precursor cells are concentrated near the middle of the nephron. For comparison, a two-dose irradiation technique was used to calculate a mean number of 5 ± 2 (SE) clonogens per segment producing outgrowths. This tended to be higher than the value of about 1 calculated from the 65% of segments producing outgrowths, as expected if the remaining segments contained no clonogens.