Transforming growth factor-β enhances secretory component and major histocompatibility complex class I antigen expression on rat IEC-6 intestinal epithelial cells

Transforming growth factor-β (TGF-β) has been implicated as having a role in inflammatory responses by inducing cellular infiltration and the release of inflammatory cytokines. In this study, the IEC-6 rat intestinal epithelial cell line was used as a model to assess the effect of TGF-β₁ on the expression of various plasma membrane determinants. TGF-β₁ induced a dose-dependent increase in the percentage of cells expressing surface secretory component (SC) and class I major histocompatibility (MHC) antigens. However, the expression of class II MHC was unaffected. In contrast, epidermal growth factor had no effect on any of the surface proteins studied. The TGF-β₁-enhanced expression of SC was accompanied by an enhanced binding of polymeric, but not monomeric, immunoglobulin A (IgA). Preincubation of the TGF-β₁-treated cells with an anti-human β-galactosyltransferase (β-GT) antiserum did not block the binding of the anti-SC antibody, indicating that the TGF-β-induced increase in SC staining was due to SC expression and not the polymeric immunoglobulin-binding enzyme, β-GT. These results indicate that TGF-β₁ may be important in immune functions involving intestinal epithelial cells by enhancing the expression of surface class I MHC antigens and SC, a protein responsible for the transport of polymeric IgA into the intestinal lumen.     

Analysis of familial hypoalphalipoproteinemia syndromes

Familial hypoalphalipoproteinemias (HA) are a heterogenous group of disorders characterized by various degrees of HDL deficiency. Differential diagnosis involves clinical and biochemical evaluation after intervention designed to correct known secondary causes of low HDL. Two specific HAs are discussed in this report: 1. primary isolated HA (PIHA) is a poorly characterized entity with an apparent autosomal dominant transmission and distinct abnormalities in the structure and function of HDL. 2. Lecithin: cholesterol acyltransferase (LCAT) deficiency syndromes are caused by a number of different genetic defects that lead to at least two distinct clinical presentations i.e. familial LCAT deficiency and fish eye disease. PIHA is an example of a genetic disorder whose diagnosis would greatly be improved by the availability of molecular diagnostic tests. Conversely, the effect of the genetic heterogeneity of LCAT deficiency syndromes on diagnosis is best overcome by utilizing existing biochemical measurement of LCAT activity and the plasma cholesterol esterification rate.     

No tree an island: the plant–caterpillar food web of a secondary rain forest in New Guinea

We characterized a plant–caterpillar food web from secondary vegetation in a New Guinean rain forest that included 63 plant species (87.5% of the total basal area), 546 Lepidoptera species and 1679 trophic links between them. The strongest 14 associations involved 50% of all individual caterpillars while some links were extremely rare. A caterpillar randomly picked from the vegetation will, with ≥ 50% probability, (1) feed on one to three host plants (of the 63 studied), (2) feed on < 20% of local plant biomass and (3) have ≥ 90% of population concentrated on a single host plant species. Generalist species were quantitatively unimportant. Caterpillar assemblages on locally monotypic plant genera were distinct, while sympatric congeneric hosts shared many caterpillar species. The partitioning of the plant–caterpillar food web thus depends on the composition of the vegetation. In secondary forest the predominant plant genera were locally monotypic and supported locally isolated caterpillar assemblages.     

Preparation and characterization of two LysB29 specifically labelled fluorescent derivatives of human insulin.

The preparation and characterization of two novel LysB29 selectively labelled fluorescent derivatives of human insulin are described. Two probes were chosen: 4-chloro-7-nitrobenz-2-oxa-1,3-diazole (NBD) and 7-methoxycoumarin-4-acetic acid (MCA), which have a relatively small, compact structure and are able to react with amino groups to form highly fluorescent derivatives. The combination of solid phase peptide synthesis and enzymatic semisynthesis was chosen for preparation of these fluorescent derivatives. Using two different protocols of solid-phase peptide synthesis, two fluorescent octapeptides were prepared corresponding to the position B23-B30 of human insulin, each with a different fluorescent label, NBD or MCA, on the epsilon-amino group of lysine. Then, the fluorescent octapeptides were coupled to desoctapeptide-(B23-B30)-insulin by a trypsin catalysed reaction. The receptor binding affinities of two novel fluorescent derivatives of human insulin with NBD and MCA (HI-NBD and HI-MCA) were determined on rat adipose tissue plasma membranes. Both fluorescent insulins, HI-NBD and HI-MCA, had only slightly reduced binding affinity and will be used for studying the interaction of insulin with its receptor.     

CpG methylation controls reactivation of HIV from latency

What are the purposes of prizes and recognitions? Are they lagging indicators of past achievements or leading indicators of things to come?     

Mislocalization of the MRN complex prevents ATR signaling during adenovirus infection

The protein kinases ataxia‐telangiectasia mutated (ATM) and ATM‐Rad3 related (ATR) are activated in response to DNA damage, genotoxic stress and virus infections. Here we show that during infection with wild‐type adenovirus, ATR and its cofactors RPA32, ATRIP and TopBP1 accumulate at viral replication centres, but there is minimal ATR activation. We show that the Mre11/Rad50/Nbs1 (MRN) complex is recruited to viral centres only during infection with adenoviruses lacking the early region E4 and ATR signaling is activated. This suggests a novel requirement for the MRN complex in ATR activation during virus infection, which is independent of Mre11 nuclease activity and recruitment of RPA/ATR/ATRIP/TopBP1. Unlike other damage scenarios, we found that ATM and ATR signaling are not dependent on each other during infection. We identify a region of the viral E4orf3 protein responsible for immobilization of the MRN complex and show that this prevents ATR signaling during adenovirus infection. We propose that immobilization of the MRN damage sensor by E4orf3 protein prevents recognition of viral genomes and blocks detrimental aspects of checkpoint signaling during virus infection.     

The effect of substituted amides of pyrazine-2-carboxylic acids on flavonolignan production in <Emphasis Type="Italic">Silybum marianum</Emphasis> culture <Emphasis Type="Italic">in vitro</Emphasis>

In vitro plant tissue and cell cultures were used to study herbicide effects on growth, selected metabolic activities and other phenomena. The effect of abiotic elicitors, two newly synthesized substituted amides of pyrazine-2-carboxylic acids (synthesized at the Department of Pharmaceutical Chemistry and Drug Control, School of Pharmacy in Hradec Kralove), on the flavonolignan accumulation in callus and suspension culture of Silybum marianum (L.) Gaertn. was investigated. The compounds markedly influenced production of flavonolignans in an in vitro culture. Particularly after the elicitation with a solution of compound 3-methylamide 5-tert-butylpyrazine-2-carboxylic acid at a concentration of 3.71×10⁻⁷ mol 1⁻¹ and within 72 h of elicitation, an increase in flavonolignan production by 893 % in suspension culture versus control took place. The flavonolignan accumulation in callus culture after the elicitation with a solution of 5-brom-2-hydroxyphenylamide of 5-tert-butyl-6-chloropyrazine-2-carboxylic acid was also increased by about 1039% (24 hour elicitation and concentration of 2.59×10⁻⁴ mol 1⁻¹).     

Diversity of Daphnia galeata life history traits in a vertically structured environment

We used laboratory experiments to investigate the life historytraits of clonal lineages of Daphnia galeata isolated from twovertically segregated subpopulations in a deep dimictic reservoir:one from the epilimnion and the other from the deep hypolimnion.We collected clones twice for the experiments, first at thebeginning of thermal stratification in May and then towardsthe end of the season in September. The results for May showedlonger postembryonic development (PED), bigger eggs in the firstclutch and slightly higher somatic increments in the hypolimneticclones. In addition, a remarkable tendency to produce ephippiawas recorded in the hypolimnetic clones, but not in the epilimneticclones. In September, the results were reversed—hypolimneticclones had shorter PED, lower somatic increments and a slightlyhigher number of eggs in the first clutch. Our results suggesta differentiation of life history traits in the two D. galeatapopulations inhabiting contrasting microhabitats of a reservoiras a result of (i) different depth preferences of certain clonesin the beginning of thermal stratification in spring and (ii)divergent selection processes due to segregation in differentenvironmental conditions. The ability of Daphnia to live indiverse environments, causing divergent selection processes,enhances the overall phenotypic and genotypic diversity of thewhole reservoir population.