Enhanced proliferation of WI38 cells in the presence of glucocorticoid-conditioned medium

The addition of hydrocortisone (HC) or dexamethasone (DEX) to WI38 cells at subcultivation is known to result in increased saturation densities (20-40%). We report that maximal increases in saturation density are, however, only observed if HC is added to the culture shortly after subcultivation. We have found that the proliferative response of WI38 cells to glucocorticoids is mediated by a secondary stimulatory factor(s) present in medium-conditioned by cells in the presence of the hormone. Control cultures refed with medium conditioned in the presence of HC for the first 24 h after seeding (24 h HC-CM) achieve saturation densities 20-40% higher than cultures refed with either medium conditioned in the absence of the hormone (24 h CM) or 24 h CM supplemented with fresh HC. Furthermore, WI38 cultures remain responsive to the stimulatory activity present in 24 h HC-CM throughout the growth cycle. The stimulatory effects of 24 h HC-CM are enhanced by repeatedly refeeding cultures; WI38 cells refed every 2 days with 24 h HC-CM demonstrate an extended period of logarithmic growth and achieve densities 2-3 times higher than controls. A preliminary characterization of this activity shows it to be of low molecular weight (MW) (dialyzable using 12 000 MW cut-off tubing) and heat-stable (75 degrees C).     

DNA assessment in thin sections of lymphomas by densitometric and stereological methods: comparison with imprint and flow cytometric results

The nuclear DNA content was estimated in 2 microns sections of 18 lymphoma cases by two methods: (1) Feulgen densitometry using QTM 900 with correction by Bins' procedure which allows size-independent DNA distributions; (2) stereological unfolding as proposed by Cruz-Orive giving sphere-size distributions. A general correlation was found between results and DNA measurements obtained by imprint and flow cytometric techniques in the same specimens. When histologic DNA profiles were compared to cytologic histograms, a high correlation was found between the distribution of ploidy classes by correspondence analysis. However two highly proliferating lymphomas were erroneously classified as aneuploid. Conversely, sphere-size distributions allowed the identification of the majority of aneuploid lymphomas but failed to recognize proliferating ones. It appears that when cytologic specimens are not available, densitometric studies on sections may provide valuable information on DNA content, with complementary data obtained from stereological procedures.     

Enhanced rates of enzymatic saccharification and catalytic synthesis of biofuel substrates in gelatinized cellulose generated by trifluoroacetic acid

Background

The crystallinity of cellulose is a principal factor limiting the efficient hydrolysis of biomass to fermentable sugars or direct catalytic conversion to biofuel components. We evaluated the impact of TFA-induced gelatinization of crystalline cellulose on enhancement of enzymatic digestion and catalytic conversion to biofuel substrates.

Results

Low-temperature swelling of cotton linter cellulose in TFA at subzero temperatures followed by gentle heating to 55 °C dissolves the microfibril structure and forms composites of crystalline and amorphous gels upon addition of ethanol. The extent of gelatinization of crystalline cellulose was determined by reduction of birefringence in darkfield microscopy, loss of X-ray diffractability, and loss of resistance to acid hydrolysis. Upon freeze-drying, an additional degree of crystallinity returned as mostly cellulose II. Both enzymatic digestion with a commercial cellulase cocktail and maleic acid/AlCl₃-catalyzed conversion to 5-hydroxymethylfurfural and levulinic acid were markedly enhanced with the low-temperature swollen cellulose. Only small improvements in rates and extent of hydrolysis and catalytic conversion were achieved upon heating to fully dissolve cellulose.

Conclusions

Low-temperature swelling of cellulose in TFA substantially reduces recalcitrance of crystalline cellulose to both enzymatic digestion and catalytic conversion. In a closed system to prevent loss of fluorohydrocarbons, the relative ease of recovery and regeneration of TFA by distillation makes it a potentially useful agent in large-scale deconstruction of biomass, not only for enzymatic depolymerization but also for enhancing rates of catalytic conversion to biofuel components and useful bio-products.

     

Burkitt's lymphoma. Distinction of subgroups by morphometric analysis of the characteristics of 55 cell lines

In an attempt to clarify the controversy about the distinction between Burkitt's and non-Burkitt's small noncleaved lymphomas, 55 cell lines derived from 48 Burkitt's lymphoma patients were characterized by morphometry on plastic-embedded sections. The results of the measurements permitted the identification of five main cytologic types, with regard to nuclear size, nuclear area dispersion and irregularity of nuclear profiles. The presence of the Epstein-Barr virus (EBV) and the geographic origin of the tumors seemed to play essential roles in the determination of nuclear size, with a significantly larger size seen in EBV-positive cell lines, and especially in the African lines among these. Immunoglobulin profile and monoclonal antibody expression also correlated with the nuclear size. Two conclusions may be drawn from this analysis. An in vivo transformation of the cells of Burkitt's lymphoma can be postulated to explain the wide morphologic spectrum of lymphomas presenting a rearrangement of chromosome 8. The fact that typical and atypical Burkitt's lymphomas cannot be differentiated by study of their derived cell lines raises the question as to the validity of the distinction between the two subtypes of small noncleaved lymphomas.     

The relation between Krogh and compartmental transport models

The meaning of compartmental concentration is intuitively simple in well-stirred compartment models with uniform concentration but not so in the general case. This meaning may be better understood by relating the general compartmental model to a spatially explicit one such as the Krogh cylinder model. We show that compartmental equations result directly by spatial averaging of the Krogh partial differential equations. Intercompartmental transport is usually stated as flux is proportional to the capillary-tissue concentration difference or $\text{J = ? (}\text{C}{}_{\mathrm{c}}\text{-}\text{C}{}_{\mathrm{T}}\text{)}$. We verify this simple equation by showing that flux in the Krogh model is also approximately first order and then derive the transport coefficient, ?, in terms of the geometry and diffusivity in the Krogh model. A relation between capillary and venous concentration or, for a gas, partial pressure is needed. For the highly diffusable, metabolic gas C0₂ this relation is $\text{P}{}_{\mathrm{c}}\text{= P}{}_{\mathrm{v}}\text{?}\text{M}\text{20K}{}_{\mathrm{c}}$ that is, capillary and venous partial pressures differ by one half the metabolic generation.     

Manipulation of Guaiacyl and Syringyl Monomer Biosynthesis in an Arabidopsis Cinnamyl Alcohol Dehydrogenase Mutant Results in Atypical Lignin Biosynthesis and Modified Cell Wall Structure

Modifying lignin composition and structure is a key strategy to increase plant cell wall digestibility for biofuel production. Disruption of the genes encoding both cinnamyl alcohol dehydrogenases (CADs), including CADC and CADD, in Arabidopsis thaliana results in the atypical incorporation of hydroxycinnamaldehydes into lignin. Another strategy to change lignin composition is downregulation or overexpression of ferulate 5-hydroxylase (F5H), which results in lignins enriched in guaiacyl or syringyl units, respectively. Here, we combined these approaches to generate plants enriched in coniferaldehyde-derived lignin units or lignins derived primarily from sinapaldehyde. The cadc cadd and ferulic acid hydroxylase1 (fah1) cadc cadd plants are similar in growth to wild-type plants even though their lignin compositions are drastically altered. In contrast, disruption of CAD in the F5H-overexpressing background results in dwarfism. The dwarfed phenotype observed in these plants does not appear to be related to collapsed xylem, a hallmark of many other lignin-deficient dwarf mutants. cadc cadd, fah1 cadc cadd, and cadd F5H-overexpressing plants have increased enzyme-catalyzed cell wall digestibility. Given that these CAD-deficient plants have similar total lignin contents and only differ in the amounts of hydroxycinnamaldehyde monomer incorporation, these results suggest that hydroxycinnamaldehyde content is a more important determinant of digestibility than lignin content.