Fatty acid synthesis suppresses dietary polyunsaturated fatty acid use

Dietary polyunsaturated fatty acids (PUFA) are increasingly recognized for their health benefits, whereas a high production of endogenous fatty acids - a process called de novo lipogenesis (DNL) - is closely linked to metabolic diseases. Determinants of PUFA incorporation into complex lipids are insufficiently understood and may influence the onset and progression of metabolic diseases. Here we show that fatty acid synthase (FASN), the key enzyme of DNL, critically determines the use of dietary PUFA in mice and humans. Moreover, the combination of FASN inhibition and PUFA-supplementation decreases liver triacylglycerols (TAG) in mice fed with high-fat diet. Mechanistically, FASN inhibition causes higher PUFA uptake via the lysophosphatidylcholine transporter MFSD2A, and a diacylglycerol O-acyltransferase 2 (DGAT2)-dependent incorporation of PUFA into TAG. Overall, the outcome of PUFA supplementation may depend on the degree of endogenous DNL and combining PUFA supplementation and FASN inhibition might be a promising approach to target metabolic disease.

Regulation of acetylation of plant cell wall components is complex and responds to external stimuli

Previously, we reported that the allelic de-etiolated by zinc (dez) and trichome birefringence (tbr) mutants exhibit photomorphogenic development in the dark, which is enhanced by high Zn. TRICHOME BIREFRINGENCE-LIKE proteins had been implicated in transferring acetyl groups to various hemicelluloses. Pectin O-acetylation levels were lower in dark-grown dez seedlings than in the wild type. We observed Zn-enhanced photomorphogenesis in the dark also in the reduced wall acetylation 2 (rwa2-3) mutant, which exhibits lowered O-acetylation levels of cell wall macromolecules including pectins and xyloglucans, supporting a role for cell wall macromolecule O-acetylation in the photomorphogenic phenotypes of rwa2-3 and dez. Application of very short oligogalacturonides (vsOGs) restored skotomorphogenesis in dark-grown dez and rwa2-3. Here we demonstrate that in dez, O-acetylation of non-pectin cell wall components, notably of xyloglucan, is enhanced. Our results highlight the complexity of cell wall homeostasis and indicate against an influence of xyloglucan O-acetylation on light-dependent seedling development.

Spray-assisted alignment of Layer-by-Layer assembled silver nanowires: a general approach for the preparation of highly anisotropic nano-composite films

The present article focuses on the build-up and the properties of oriented silver nanowire monolayer films and Layer-by-Layer assembled multilayer films. We describe the template-free oriented spray-assisted assembly of silver nanowires at solid/air-interfaces using Grazing Incidence Spraying, a simple and versatile approach that allows the formation of highly oriented thin films with a tunable density and in-plane orientation. Depending on the spraying conditions the nematic order parameter, which describes the angular spread of misaligned nanowires, can be as high as 0.98 (a value of 1.00 corresponding to a perfectly parallel alignment). The combination with the Layer-by-Layer assembly allows building multilayer thin films possessing in-plane anisotropy. In order to demonstrate that the local alignment does not cancel out on the macroscopic scale but leads to direction-dependent properties, we use linearly polarized UV-Vis-NIR spectroscopy to probe the selective excitation of the transverse and longitudinal localized plasmon resonances of the nanowires. The polarization efficiency of the thin films increases strongly with the in-plane density, the degree of orientation, and the number of silver nanowire layers. Multilayer films containing 4 layers of nanowires oriented in the same direction reach a polarization efficiency of up to 97% in the near-infrared region.

Comparison of environmental risk factors for esophageal atresia, anorectal malformations, and the combined phenotype in 263 German families

Esophageal atresia with or without tracheoesophageal fistula (EA/TEF) and anorectal malformations (ARM) represent the severe ends of the fore- and hindgut malformation spectra. Previous research suggests that environmental factors are implicated in their etiology. These risk factors might indicate the influence of specific etiological mechanisms on distinct developmental processes (e.g. fore- vs. hindgut malformation). The present study compared environmental factors in patients with isolated EA/TEF, isolated ARM, and the combined phenotype during the periconceptional period and the first trimester of pregnancy in order to investigate the hypothesis that fore- and hindgut malformations involve differing environmental factors. Patients with isolated EA/TEF (n = 98), isolated ARM (n = 123), and the combined phenotype (n = 42) were included. Families were recruited within the context of two German multicenter studies of the genetic and environmental causes of EA/TEF (great consortium) and ARM (CURE-Net). Exposures of interest were ascertained using an epidemiological questionnaire. Chi-square, Fisher's exact, and Mann-Whitney U-tests were used to assess differences between the three phenotypes. Newborns with isolated EA/TEF and the combined phenotype had significantly lower birth weights than newborns with isolated ARM (P = 0.001 and P < 0.0001, respectively). Mothers of isolated EA/TEF consumed more alcohol periconceptional (80%) than mothers of isolated ARM or the combined phenotype (each 67%). Parental smoking (P = 0.003) and artificial reproductive techniques (P = 0.03) were associated with isolated ARM. Unexpectedly, maternal periconceptional multivitamin supplementation was most frequent among patients with the most severe form of disorder, i.e. the combined phenotype (19%). Significant differences in birth weight were apparent between the three phenotype groups. This might be attributable to the limited ability of EA/TEF fetuses to swallow amniotic fluid, thus depriving them of its nutritive properties. Furthermore, the present data suggest that fore- and hindgut malformations involve differing environmental factors. Maternal periconceptional multivitamin supplementation was highest among patients with the combined phenotype. This latter finding is contrary to expectation, and warrants further analysis in large prospective epidemiological studies.

Protective effect of myostatin gene deletion on aging-related muscle metabolic decline

While myostatin gene deletion is a promising therapy to fight muscle loss during aging, this approach induces also skeletal muscle metabolic changes such as mitochondrial deficits, redox alteration and increased fatigability. In the present study, we evaluated the effects of aging on these features in aged wild-type (WT) and mstn knockout (KO) mice. Moreover, to determine whether an enriched-antioxidant diet may be useful to prevent age-related disorders, we orally administered to the two genotypes a melon concentrate rich in superoxide dismutase for 12 weeks. We reported that mitochondrial functional abnormalities persisted (decreased state 3 and 4 of respiration; p<0.05) in skeletal muscle from aged KO mice; however, differences with WT mice were attenuated at old age in line with reduced difference on running endurance between the two genotypes. Interestingly, we showed an increase in glutathione levels, associated with lower lipid peroxidation levels in KO muscle. Enriched antioxidant diet reduced the aging-related negative effects on maximal aerobic velocity and running limit time (p<0.05) in both groups, with systemic adaptations on body weight. The redox status and the hypertrophic phenotype appeared to be beneficial to KO mice, mitigating the effect of aging on the skeletal muscle metabolic remodeling.

Anisotropic optical and conductive properties of oriented 1D-nanoparticle thin films made by spray-assisted self-assembly

We report on the fabrication of oriented anisotropic metal nanoparticle thin films made by Grazing Incidence Spraying (GIS) and on the anisotropic plasmonic properties of the resulting thin films. Gold nanorods of two different aspect ratios and silver nanowires were self-assembled as a uniaxially aligned monolayer with the GIS approach. In particular, we examine the influence of the nanowire/nanorod length and diameter on the degree of ordering determined by electron microscopy pictures. Furthermore, we show that the anisotropy of the optical properties (probed by polarized UV-visible-near infrared spectroscopy) strongly depend on the quality of alignment. The prepared monolayer thin films have an orientation order parameter of up to 0.83 for silver nanowires, which is reflected in an optical anisotropy of 0.57 in the UV-visible and 0.76 in the near infrared through the selective excitation of transverse and longitudinal surface plasmon resonance modes. The electronic transport in oriented silver nanowire monolayers is also shown to be highly directional, with the sheet resistance varying over almost an order of magnitude depending on the transport direction. Such anisotropic conductive plasmonic thin films may find applications in various fields like biochemical sensing, energy transport and harvesting or optoelectronic devices.

An Arabidopsis gene regulatory network for secondary cell wall synthesis

The plant cell wall is an important factor for determining cell shape, function and response to the environment. Secondary cell walls, such as those found in xylem, are composed of cellulose, hemicelluloses and lignin and account for the bulk of plant biomass. The coordination between transcriptional regulation of synthesis for each polymer is complex and vital to cell function. A regulatory hierarchy of developmental switches has been proposed, although the full complement of regulators remains unknown. Here, we present a protein-DNA network between Arabidopsis transcription factors and secondary cell wall metabolic genes with gene expression regulated by a series of feed-forward loops. This model allowed us to develop and validate new hypotheses about secondary wall gene regulation under abiotic stress. Distinct stresses are able to perturb targeted genes to potentially promote functional adaptation. These interactions will serve as a foundation for understanding the regulation of a complex, integral plant component.

Prevention and treatment of Clostridium perfringens epsilon toxin intoxication in mice with a neutralizing monoclonal antibody (c4D7) produced in Nicotiana benthamiana

Epsilon toxin (ETX), produced by Clostridium perfringens types B and D, is among the most lethal toxins known. ETX is a potential bioterrorism threat that was listed as a Category B agent by the U.S. Centers for Disease Control until 2012 and it still remains a toxin of interest for several government agencies. We produced a monoclonal antibody (MAb) against ETX (ETX MAb c4D7) in Nicotiana benthamiana and characterized its preventive and therapeutic efficacy in mice. The ETX preparation used was highly lethal for mice (LD50 = 1.6 μg/kg) and resulted in a mean time from inoculation to death of 18 and 180 min when administered intravenously or intraperitoneally, respectively. High lethal challenge resulted in dramatic increases of a variety of pro-inflammatory cytokines in serum, while lower, but still lethal doses, did not elicit such responses. ETX MAb c4D7 was highly effective prophylactically (ED50 = 0.3 mg/kg; ED100 = 0.8 mg/kg) and also provided protection when delivered 15-30 min post-ETX intoxication. These data suggest that ETX MAb c4D7 may have use as a pre- and post-exposure treatment for ETX intoxication.

Nanotrench for nano and microparticle electrical interconnects

We present a simple and versatile patterning procedure for the reliable and reproducible fabrication of high aspect ratio (10(4)) electrical interconnects that have separation distances down to 20 nm and lengths of several hundreds of microns. The process uses standard optical lithography techniques and allows parallel processing of many junctions, making it easily scalable and industrially relevant. We demonstrate the suitability of these nanotrenches as electrical interconnects for addressing micro and nanoparticles by realizing several circuits with integrated species. Furthermore, low impedance metal-metal low contacts are shown to be obtained when trapping a single metal-coated microsphere in the gap, emphasizing the intrinsic good electrical conductivity of the interconnects, even though a wet process is used. Highly resistive magnetite-based nanoparticles networks also demonstrate the advantage of the high aspect ratio of the nanotrenches for providing access to electrical properties of highly resistive materials, with leakage current levels below 1 pA.

Effects of the mur1 mutation on xyloglucans produced by suspension-cultured Arabidopsis thaliana cells

Mutation of the Arabidopsis thaliana (L.) Heynh. gene MUR1, which encodes an isoform of GDP-D-mannose-4,6-dehydratase, affects the biosynthetic conversion of GDP-mannose to GDP-fucose. Cell walls in the aerial tissues of mur1 plants are almost devoid of alpha-L-fucosyl residues, which are partially replaced by closely related alpha-L-galactosyl residues. A line of suspension-cultured A. thaliana cells was generated from leaves of mur1 plants and the structure of the xyloglucan in the walls of these cells was structurally characterized. Xyloglucan fractions were prepared from the walls of both wild-type (WT) and mur1 cells by sequential extraction with a xyloglucan-specific endoglucanase (XEG) and aqueous KOH. Structural analysis of these fractions revealed that xyloglucan produced by cultured mur1 cells is similar, but not identical to that isolated from leaves of mur1 plants. As previously reported for mur1 leaves, the xyloglucan from cultured mur1 cells contains less than 5% of the fucose present in the xyloglucan from WT cells. Fucosylation of the xyloglucan is substantially restored when mur1 cells are grown in medium supplemented with L-fucose. Xyloglucan isolated from leaves contains more oligosaccharide subunits in which the central sidechain is terminated with a beta-D-galactosyl residue than does xyloglucan prepared from cultured cells. This was observed for both mur1 and WT plants, indicating that this correlation is independent of the mur1 mutation and that it is possible to distinguish changes due to genetic mutation from those due to the physiological state of the cells in culture. Suspension-cultured cells thus provide a convenient source of genetically altered cell wall material, facilitating the biochemical characterization of mutations that affect cell wall structure.

What benefit specialists think about medical savings account options for large firms

Currently, tax-preferred medical savings accounts (MSAs) are being offered on a trial basis to employees of small companies. This article reports results of a survey investigating the potential impact of adding an MSA to a medium- or large-sized firm's employee benefit offerings. The variables examined fall into the categories of attitudes toward views on employee benefits in general, the MSA option and issues associated with risk segmentation.

Kirsten ras mutations in patients with colorectal cancer: the 'RASCAL II' study

Researchers worldwide with information about the Kirsten ras (Ki-ras) tumour genotype and outcome of patients with colorectal cancer were invited to provide that data in a schematized format for inclusion in a collaborative database called RASCAL (The Kirsten ras in-colorectal-cancer collaborative group). Our results from 2721 such patients have been presented previously and for the first time in any common cancer, showed conclusively that different gene mutations have different impacts on outcome, even when the mutations occur at the same site on the genome. To explore the effect of Ki-ras mutations at different stages of colorectal cancer, more patients were recruited to the database, which was reanalysed when information on 4268 patients from 42 centres in 21 countries had been entered. After predetermined exclusion criteria were applied, data on 3439 patients were entered into a multivariate analysis. This found that of the 12 possible mutations on codons 12 and 13 of Kirsten ras, only one mutation on codon 12, glycine to valine, found in 8.6% of all patients, had a statistically significant impact on failure-free survival (P = 0.004, HR 1.3) and overall survival (P = 0.008, HR 1.29). This mutation appeared to have a greater impact on outcome in Dukes' C cancers (failure-free survival, P = 0.008, HR 1.5; overall survival P = 0.02, HR 1.45) than in Dukes' B tumours (failure-free survival, P = 0.46, HR 1.12; overall survival P = 0.36, HR 1.15). Ki-ras mutations may occur early in the development of pre-cancerous adenomas in the colon and rectum. However, this collaborative study suggests that not only is the presence of a codon 12 glycine to valine mutation important for cancer progression but also that it may predispose to more aggressive biological behaviour in patients with advanced colorectal cancer.

Functional cloning of an endo-arabinanase from Aspergillus aculeatus and its heterologous expression in A. or oryzae and tobacco

Functional cloning in yeast has been used to isolate full-length cDNAs encoding an endo-alpha-1,5-L-arabinanase from the filamentous fungus Aspergillus aculeatus. Screening of a cDNA library constructed in a yeast expression vector for transformants that hydrolysed AZCL-arabinan identified 44 Saccharomyces cerevisiae clones all harbouring the same arabinanase-encoding cDNA. The cloned cDNA was expressed in A. oryzae and the recombinant enzyme was purified and characterized. The mode of action of the enzyme was studied by analysis of the digestion pattern towards debranched arabinan. The digestion profile obtained strongly suggests that the enzyme is an endo-arabinanase. In addition, the feasibility using Nicotiana tabacum as an alternative host for arabinanase expression was investigated.

Changes in the structure of xyloglucan during cell elongation

Xyloglucans were isolated by sequential extraction of the cell walls of pea (Pisum sativum L. cv. Alaska) with a xyloglucan-specific endoglucanase and KOH. The xyloglucan content and xyloglucan-oligosaccharide composition were determined for fractions obtained from the elongating and non-elongating segments of pea stems grown in the light and in darkness. The results were consistent with the hypothesis that regulated growth of the cell wall depends on xyloglucan metabolism. Furthermore, the characterization of xyloglucan extracted from leaves of light-grown pea plants indicates that xyloglucan metabolism is tissue specific. Changes in xyloglucan subunit structure observed in elongating stems are consistent with the in muro realization of a metabolic pathway that was previously proposed solely on the basis of the in vitro activities of plant glycosyl hydrolases.

Expanding coverage via tax credits: trade-offs and outcomes

In this paper we discuss various options for using refundable tax credits to reduce the number of uninsured persons. The effect of tax credits on the number of uninsured depends on the form of the credit scheme adopted. Moreover, since large subsidies for private insurance directed to low-income persons have never been implemented, there is considerable uncertainty about the effect of various tax credit proposals. We find that small credits will do little to reduce the number of uninsured but that credits covering about half of the premium for a benchmark policy might have a significant effect, especially if they take a fixed-dollar form and can be used for policies with few restrictions. Finally, we discuss the normative issues surrounding the "costs" of these credits schemes, and the policy issues raised by the uncertainty of the effects.

Alternative valuations of work loss and productivity

In this article, we examine the indirect costs (i.e., work loss and productivity costs) of employee illness from the employer's perspective. We provide a conceptual framework to help employers consider alternative views with regard to assessing indirect costs and valuing the health care they purchase. First, we discuss the matter of perspective and how an employer should view and assess indirect costs. We briefly review current models of measuring indirect costs, and we critique these models. Then we introduce a simple, conceptual framework based on the ideas of health capital and labor productivity, and we lay out the effects of health investment on indirect costs while considering what employees desire and employers can provide. Finally, we offer an agenda for further research.

Preservation of the delayed-type hypersensitivity response to alloantigen by xyloglucans or oligogalacturonide does not correlate with the capacity to reject ultraviolet-induced skin tumors in mice

Chronic exposure to ultraviolet radiation suppresses T cell-mediated immune responses and induces the formation of suppressor T lymphocytes that prevent the rejection of highly antigenic ultraviolet-induced skin cancers in mice. Tamarind seed xyloglucans and pectinic oligogalacturonides prevent suppression of delayed-type hypersensitivity immune responses in mice to Candida albicans and alloantigen caused by a single exposure of ultraviolet radiation. We therefore investigated the ability of these poly/oligosaccharides to prevent suppression of T cell-mediated immune responses and suppressor cell induction during chronic ultraviolet irradiation and to preserve the capacity of ultraviolet-irradiated mice to reject a transplanted, highly antigenic, ultraviolet-induced tumor. C3H/HeN mice were treated 3x per week for 12 wk with 15 kJ per m2 ultraviolet B radiation followed by application of the polysaccharides/ oligosaccharides. The delayed-type hypersensitivity responses to C. albicans and alloantigen were measured after 1, 6, and 12 wk of treatment. Following the 12th wk of treatment the remaining mice were injected with the highly antigenic ultraviolet-induced, syngeneic tumor cell line UV5497-5. The polysaccharides/oligosaccharides protected delayed-type hypersensitivity responses to C. albicans but not contact hypersensitivity responses to dinitrofluorobenzene for up to 6 wk of ultraviolet radiation after which protection declined and suppressor cells were observed. In contrast, the delayed-type hypersensitivity response to alloantigen was preserved for the entire 12 wk of ultraviolet irradiation. Despite protection of immunity to alloantigen, the transplanted tumor cells grew equally well in all ultraviolet-irradiated animals. These results indicate that delayed-type hypersensitivity responses are heterogeneous and that delayed-type hypersensitivity to alloantigen is not a surrogate marker for rejection of ultraviolet-induced skin tumors.

Pectin engineering: modification of potato pectin by in vivo expression of an endo-1,4-beta-D-galactanase

Potato tuber pectin is rich in galactan (oligomer of beta-1,4-linked galactosyl residues). We have expressed a fungal endo-galactanase cDNA in potato under control of the granule bound starch synthase promoter to obtain expression of the enzyme in tubers during growth. The transgenic plants displayed no altered phenotype compared with the wild type. Fungal endo-galactanase activity was quantified in the transgenic tubers, and its expression was verified by Western blot analysis. The effect of the endo-galactanase activity on potato tuber pectin was studied by Fourier transform infrared microspectroscopy, immuno-gold labeling, and sugar analysis. All analyses revealed alterations in pectin composition. Monosaccharide composition of total cell walls and isolated rhamnogalacturonan I fragments showed a reduction in galactosyl content to 30% in the transformants compared with the wild type. Increased solubility of pectin from transgenic cell walls by endo-polygalacturonase/pectin methylesterase digestion points to other changes in wall architecture.

What would happen if large firms offered MSAs?

This paper reports the results of a survey of more than 500 health benefit specialists about the advice they would give to medium-size and large employers on offering a tax-advantaged medical savings account (MSA). About 42 percent of respondents would recommend an MSA combined with a catastrophic health plan, while a third would advise against such a plan. When presented with a specific example of an MSA package that would be attractive to a large fraction of workers, the percentage of benefit specialists favoring adding an MSA option rose to 74 percent. However, respondents generally did not believe that most workers would choose the MSA, especially if the alternative were a health maintenance organization (HMO).

LST1: a gene with extensive alternative splicing and immunomodulatory function

The gene of the leukocyte-specific transcript (LST1) is encoded within the TNF region of the human MHC. The LST1 gene is constitutively expressed in leukocytes and dendritic cells, and it is characterized by extensive alternative splicing. We identified 7 different LST1 splice variants in PBMC; thus, 14 LST1 splice variants (LST1/A-LST1/N) have been detected in various cell types. These isoforms code for transmembrane as well as soluble LST1 proteins characterized by two alternative open reading frames at their 3' end. We demonstrate the presence of the transmembrane variant LST1/C on the cell surface of the monocytic cell lines U937 and THP1. Recombinant expression of LST1/C permitted its profound inhibitory effect on lymphocyte proliferation to be observed. In contrast, the alternative transmembrane variant LST1/A, the extracellular domain of which shows no amino acid sequence homology to LST1/C exerted a weaker but similar inhibitory effect on PBMC. These data demonstrate the protein expression of LST1 on the cell surface of mononuclear cells, and they show an inhibitory effect on lymphocyte proliferation of two LST1 proteins although they have only a very short amino acid homology.

O-Acetylation of plant cell wall polysaccharides: identification and partial characterization of a rhamnogalacturonan O-acetyl-transferase from potato suspension-cultured cells

A microsomal preparation from suspension-cultured potato stem cells (Solanum tuberosum L. cv. AZY) was incubated with [14C]acetyl-CoA resulting in a precipitable radiolabeled product. Analysis of the product revealed that it consisted mostly of acetylated proteins and cell wall polysaccharides, including xyloglucan, homogalacturonan and rhamnogalacturonan I. Thus, acetyl-CoA is a donor-substrate for the O-acetylation of wall polysaccharides. A rhamnogalacturonan acetylesterase was used to develop an assay to measure and characterize rhamnogalacturonan O-acetyl transferase activity in the microsomal preparation. Using this assay, it was shown that the transferase activity was highest during the linear growth phase of the cells, had a pH-optimum at pH 7.0, a temperature optimum at 30 degrees C, an apparent Km of 35 microM and an apparent Vmax of 0.9 pkat per mg protein. Further analysis of the radiolabeled acetylated product revealed that it had a molecular mass > 500 kDa.

Enzymatic synthesis and purification of uridine diphospho-beta-l-arabinopyranose, a substrate for the biosynthesis of plant polysaccharides

Many plant cell wall components such as the polysaccharides xylans and pectins or the glycoproteins arabinogalactan proteins and extensins contain arabinosyl residues. The arabinosyl substituents are thought to be incorporated into these wall polymers by the action of arabinosyltransferases using UDP-l-arabinose as the precursor. UDP-l-arabinose is not commercially available and therefore a procedure for generating UDP-l-arabinose was developed for use in studies on the biosynthesis of the arabinose-containing polymers. In this procedure UDP-d-xylose is incubated with an enzyme preparation from wheat germ and the nucleotide sugars in the reaction mixture are extracted. High-performance anion-exchange chromatography of the extract resolves two major UV-absorbing components: one corresponding to UDP-xylose and a second that elutes earlier. TLC analysis of collected and hydrolyzed fractions demonstrated the presence of l-arabinose in the early eluting fraction. Further analysis by NMR identified the compound as UDP-beta-l-arabinopyranose. The procedure reported here provides an efficient method for preparing either radioactive UDP-l-[(14)C]arabinose or nonradioactive UDP-l-arabinose and can also be used as an assay for UDP-xylose-4-epimerase activity.

Molecular domains of the cellulose/xyloglucan network in the cell walls of higher plants

Cellulose and xyloglucan (XG) assemble to form the cellulose/XG network, which is considered to be the dominant load-bearing structure in the growing cell walls of non-graminaceous land plants. We have extended the most commonly accepted model for the macromolecular organization of XG in this network, based on the structural and quantitative analysis of three distinct XG fractions that can be differentially extracted from the cell walls isolated from etiolated pea stems. Approximately 8% of the dry weight of these cell walls consists of XG that can be solubilized by treatment of the walls with a XG-specific endoglucanase (XEG). This material corresponds to an enzyme-susceptible XG domain, proposed to form the cross-links between cellulose microfibrils. Another 10% of the cell wall consists of XG that can be solubilized by concentrated KOH after XEG treatment. This material constitutes another XG domain, proposed to be closely associated with the surface of the cellulose microfibrils. An additional 3% of the cell wall consists of XG that can be solubilized only when the XEG- and KOH-treated cell walls are treated with cellulase. This material constitutes a third XG domain, proposed to be entrapped within or between cellulose microfibrils. Analysis of the three fractions indicates that metabolism is essentially limited to the enzyme-susceptible domain. These results support the hypothesis that enzyme-catalyzed modification of XG cross-links in the cellulose/XG network is required for the growth and development of the primary plant cell wall, and demonstrate that the structural consequences of these metabolic events can be analyzed in detail.

Individual versus job-based health insurance: weighing the pros and cons

Although the majority of insured Americans receive their health insurance through their employers, some depend on the individual health insurance market. However, with increased criticism of the lack of choice in group coverage and various proposals including subsidies or tax credits to decrease the number of uninsured, the individual market may start to play a larger role. In this paper we conclude that although efficient large-group insurance will appropriately continue to exist, the individual market appears to be improving, in both administrative cost and protection against high premiums associated with high risk. For diverse workers now in small groups with little plan choice, the individual market might become a reasonable alternative.

Inhibition of UV-induced immune suppression and interleukin-10 production by plant oligosaccharides and polysaccharides

Application of Aloe barbadensis poly/oligosaccharides to UV-irradiated skin prevents photosuppression of delayed-type hypersensitivity (DTH) responses in mice. We tested the hypothesis that these carbohydrates belong to a family of biologically active, plant-derived polysaccharides that can regulate responses to injury in animal tissues. C3H mice were exposed to 5 kJ/m2 UVB from unfiltered FS40 sunlamps and treated with between 1 pg and 10 micrograms tamarind xyloglucans or control polysaccharides methylcellulose or dextran in saline. The mice were sensitized 3 days later with Candida albicans. Tamarind xyloglucans and purified Aloe poly/oligosaccharides prevented suppression of DTH responses in vivo and reduced the amount of interleukin (IL)-10 observed in UV-irradiated murine epidermis. Tamarind xyloglucans were immunoprotective at low picogram doses. In contrast, the control polysaccharides methylcellulose and dextran had no effect on immune suppression or cutaneous IL-10 at any dose. Tamarind xyloglucans and Aloe poly/oligosaccharides also prevented suppression of immune responses to alloantigen in mice exposed to 30 kJ/m2 UVB radiation. To assess the effect of the carbohydrates on keratinocytes, murine Pam212 cells were exposed to 300 J/m2 UVB radiation and treated for 1 h with tamarind xyloglucans or Aloe poly/oligosaccharides. Treatment of keratinocytes with immunoprotective carbohydrates reduced IL-10 production by approximately 50% compared with the cells treated with UV radiation alone and completely blocked suppressive activity of the culture supernatants in vivo. The tamarind xyloglucans also blocked UV-activated phosphorylation of SAPK/JNK protein but had no effect on p38 phosphorylation. These results indicate that animals, like plants, may use carbohydrates to regulate responses to environmental stimuli.

A xyloglucan-specific endo-beta-1,4-glucanase from Aspergillus aculeatus: expression cloning in yeast, purification and characterization of the recombinant enzyme

A full-length c-DNA encoding a xyloglucan-specific endo -beta-1, 4-glucanase (XEG) has been isolated from the filamentous fungus Aspergillus aculeatus by expression cloning in yeast. The colonies expressing functional XEG were identified on agar plates containing azurine-dyed cross-linked xyloglucan. The cDNA encoding XEG was isolated, sequenced, cloned into an Aspergillus expression vector, and transformed into Aspergillus oryzae for heterologous expression. The recombinant enzyme was purified to apparent homogeneity by anion-exchange and gel permeation chromatography. The recombinant XEG has a molecular mass of 23,600, an isoelectric point of 3.4, and is optimally stable at a pH of 3.4 and temperature below 30 degreesC. The enzyme hydrolyzes structurally diverse xyloglucans from various sources, but hydrolyzes no other cell wall component and can therefore be considered a xyloglucan-specific endo -beta-1, 4-glucanohydrolase. XEG hydrolyzes its substrates with retention of the anomeric configuration. The Kmof the recombinant enzyme is 3.6 mg/ml, and its specific activity is 260 micromol/min per mg protein. The enzyme was tested for its ability to solubilize xyloglucan oligosaccharides from plant cell walls. It was shown that treatment of plant cell walls with XEG yields only xyloglucan oligosaccharides, indicating that this enzyme can be a powerful tool in the structural elucidation of xyloglucans.

Epidemiological study of p53 tumor suppressor gene mutations in patients from Luxembourg and the German Saar region with an advanced colorectal cancer using PCR-SSCP analysis

Mutations in the p53 tumor suppressor gene are usually associated with an advanced development of colorectal cancer characterized by the transition from the adenoma to the carcinoma stage. We used the polymerase chain reaction (PCR) followed by single-strand conformation polymorphism (SSCP) analysis to screen for the presence of mutations in the p53 gene of patients from Luxembourg and the German Saar region with colorectal cancers at various developmental stages. While we detected no mutations in 16 colic polypi at an early to intermediate stage (adenoma), we revealed seven (13.7%) non-silent point mutations (transitions) in exons 5 to 9 of the p53 gene in 51 colorectal tumors at a late stage (carcinoma). In addition to confirming previous observations, these results show that PCR-SSCP analysis can provide both a sensitive and rapid method for the genetic determination of the histopathological stage of colorectal samples.

Ki-ras oncogene and p53 tumour suppressor gene mutations in colorectal carcinomas from the European Saar-Luxembourg region are less frequent than predicted by the classic adenoma-carcinoma sequence model

Recent investigations of colorectal cancer (CRC) have suggested that the accumulation of specific alterations in cell-growth regulating genes trigger the stage-wise progression to malignancy and that at least some of them could be useful for prognosis. In this study, the frequency, location and type of mutations of the Ki-ras proto-oncogene exons 1-2 and p53 tumour-suppressor gene exons 5-9 were analysed in colorectal carcinomas of 72 patients from the European Saar-Luxembourg region using PCR-SSCP screening and direct sequencing. The incidences of Ki-ras activating and p53 inactivating point mutations in these European samples were much lower (Ki-ras: 5 (6.9%) and p53: 13 (18.1%)) than reported for both genes in American studies (40-50% at least) (P < 1 x 10(-3)). These results suggest that other genetic mechanisms than those proposed for the classic adenoma-carcinoma sequence model can frequently underlie CRC development and that Ki-ras and p53 mutations should not be considered as universal markers for CRC.

Structural characterization of novel L-galactose-containing oligosaccharide subunits of jojoba seed xyloglucans

Jojoba seed xyloglucan was shown to be a convenient source of biologically active xyloglucan oligosaccharides that contain both L- and D-galactosyl residues [E. Zablackis et al., Science, 272 (1996) 1808-1810]. Oligosaccharides were isolated by liquid chromatography of the mixture of oligosaccharides generated by treating jojoba seed xyloglucan with a beta-(1-->4)-endoglucanase. The purified oligosaccharides were reduced with NaBH4, converting them to oligoglycosyl alditol derivatives that were structurally characterized by a combination of mass spectrometry and 2-dimensional NMR spectroscopy. This analysis established that jojoba xyloglucan oligosaccharides contain the novel side-chain [alpha-L-Gal p-(1-->2)-beta-D-Galp-(1-->2)-alpha-D-Xyl p-(1-->6)-], which is structurally homologous to the fucose-containing side-chain [alpha-L-Fucp-(1-->2)-beta-D-Galp-(1-->2)-alpha-D-Xyl p-(1-->6)-] found in other biologically active xyloglucan oligosaccharides.