Chemical Intolerance among Hairdressers in Denmark

Objectives

To investigate the prevalence and the severity of fragrance-related symptoms among hairdressers in Denmark compared with the Danish general population. Further, to characterize former hairdressers who are severely chemically intolerant to fragranced products in relation to sex, age and health- and work-related reasons for leaving the hairdressing profession.

Methods

The study population consisted of all hairdressers who graduated from the public vocational schools in Denmark during 1985 and 2007 (n = 7840) and a random sample of individuals from the Danish general population (n = 6000). Both populations received a postal questionnaire on symptoms from inhalation of fragranced products and the resultant behavioural consequences. All former hairdressers also answered additional questions on health- and work-related reasons for leaving the profession.

Results

No differences were found in the prevalence (OR = 1.0, CI = 0.89–1.14) or the severity (OR = 1.1, CI = 0.80–1.51) of symptoms from inhalation of fragranced products in hairdressers compared with the general population. Among hairdressers, however, experience of fragrance-related symptoms (OR = 1.2, CI = 1.01–1.31) and adjustments of social (OR = 1.8, CI = 1.12–2.80) and occupational conditions (OR = 2.8, CI = 1.84–4.25) were reported significantly more often by former hairdressers than current hairdressers.

Conclusions

The prevalence and the severity of fragrance-related symptoms were similar in hairdressers and the general population. Former hairdressers were more affected by fragranced products than current hairdressers were. Although fragrance-related symptoms did not seem to be more frequent among hairdressers, the hairdressing profession might pose a problem for those who are chemically intolerant.     

The functional half-life of an mRNA depends on the ribosome spacing in an early coding region

Bacterial mRNAs are translated by closely spaced ribosomes and degraded from the 5′-end, with half-lives of around 2 min at 37 °C in most cases. Ribosome-free or “naked” mRNA is known to be readily degraded, but the initial event that inactivates the mRNA functionally has not been fully described. Here, we characterize a determinant of the functional stability of an mRNA, which is located in the early coding region. Using literature values for the mRNA half-lives of variant lacZ mRNAs in Escherichia coli, we modeled how the ribosome spacing is affected by the translation rate of the individual codons. When comparing the ribosome spacing at various segments of the mRNA to its functional half-life, we found a clear correlation between the functional mRNA half-life and the ribosome spacing in the mRNA region approximately between codon 20 and codon 45. From this finding, we predicted that inserts of slowly translated codons before codon 20 or after codon 45 should shorten or prolong, respectively, the functional mRNA half-life by altering the ribosome density in the important region. These predictions were tested on eight new lacZ variants, and their experimentally determined mRNA half-lives all supported the model. We thus suggest that translation-rate-mediated differences in the spacing between ribosomes in this early coding region is a parameter that determines the mRNAs functional half-life. We present a model that is in accordance with many earlier observations and that allows a prediction of the functional half-life of a given mRNA sequence.     

Design of thermostable rhamnogalacturonan lyase mutants from Bacillus licheniformis by combination of targeted single point mutations

Rhamnogalacturonan I lyases (RGI lyases) (EC 4.2.2.-) catalyze cleavage of α-1,4 bonds between rhamnose and galacturonic acid in the backbone of pectins by β-elimination. In the present study, targeted improvement of the thermostability of a PL family 11 RGI lyase from Bacillus licheniformis (DSM 13/ATCC14580) was examined by using a combinatorial protein engineering approach exploring additive effects of single amino acid substitutions. These were selected by using a consensus approach together with assessing protein stability changes (PoPMuSiC) and B-factor iterative test (B-FIT). The second-generation mutants involved combinations of two to seven individually favorable single mutations. Thermal stability was examined as half-life at 60 °C and by recording of thermal transitions by circular dichroism. Surprisingly, the biggest increment in thermal stability was achieved by producing the wild-type RGI lyase in Bacillus subtilis as opposed to in Pichia pastoris; this effect is suggested to be a negative result of glycosylation of the P. pastoris expressed enzyme. A ~ twofold improvement in thermal stability at 60 °C, accompanied by less significant increases in T _m of the enzyme mutants, were obtained due to additive stabilizing effects of single amino acid mutations (E434L, G55V, and G326E) compared to the wild type. The crystal structure of the B. licheniformis wild-type RGI lyase was also determined; the structural analysis corroborated that especially mutation of charged amino acids to hydrophobic ones in surface-exposed loops produced favorable thermal stability effects.     

Molecular Architecture of a Complex between an Adhesion Protein from the Malaria Parasite and Intracellular Adhesion Molecule 1

The adhesion of Plasmodium falciparum-infected erythrocytes to human tissues or endothelium is central to the pathology caused by the parasite during malaria. It contributes to the avoidance of parasite clearance by the spleen and to the specific pathologies of cerebral and placental malaria. The PfEMP1 family of adhesive proteins is responsible for this sequestration by mediating interactions with diverse human ligands. In addition, as the primary targets of acquired, protective immunity, the PfEMP1s are potential vaccine candidates. PfEMP1s contain large extracellular ectodomains made from CIDR (cysteine-rich interdomain regions) and DBL (Duffy-binding-like) domains and show extensive variation in sequence, size, and domain organization. Here we use biophysical methods to characterize the entire ∼300-kDa ectodomain from IT4VAR13, a protein that interacts with the host receptor, intercellular adhesion molecule-1 (ICAM-1). We show through small angle x-ray scattering that IT4VAR13 is rigid, elongated, and monomeric. We also show that it interacts with ICAM-1 through the DBLβ domain alone, forming a 1:1 complex. These studies provide a first low resolution structural view of a PfEMP1 ectodomain in complex with its ligand. They show that it combines a modular domain arrangement consisting of individual ligand binding domains, with a defined higher order architecture that exposes the ICAM-1 binding surface to allow adhesion.     

Regulation of dCTP deaminase from Escherichia coli by nonallosteric dTTP binding to an inactive form of the enzyme

The trimeric dCTP deaminase produces dUTP that is hydrolysed to dUMP by the structurally closely related dUTPase. This pathway provides 70-80% of the total dUMP as a precursor for dTTP. Accordingly, dCTP deaminase is regulated by dTTP, which increases the substrate concentration for half-maximal activity and the cooperativity of dCTP saturation. Likewise, increasing concentrations of dCTP increase the cooperativity of dTTP inhibition. Previous structural studies showed that the complexes of inactive mutant protein, E138A, with dUTP or dCTP bound, and wild-type enzyme with dUTP bound were all highly similar and characterized by having an ordered C-terminal. When comparing with a new structure in which dTTP is bound to the active site of E138A, the region between Val120 and His125 was found to be in a new conformation. This and the previous conformation were mutually exclusive within the trimer. Also, the dCTP complex of the inactive H121A was found to have residues 120-125 in this new conformation, indicating that it renders the enzyme inactive. The C-terminal fold was found to be disordered for both new complexes. We suggest that the cooperative kinetics are imposed by a dTTP-dependent lag of product formation observed in presteady-state kinetics. This lag may be derived from a slow equilibration between an inactive and an active conformation of dCTP deaminase represented by the dTTP complex and the dUTP/dCTP complex, respectively. The dCTP deaminase then resembles a simple concerted system subjected to effector binding, but without the use of an allosteric site.     

Ribonucleic acid is a component of the oligomeric, transformed mouse AtT-20 cell glucocorticoid receptor

The glucocorticoid receptor from mouse AtT-20 pituitary tumor cells exists in three forms. The largest form is an untransformed (non-DNA-binding), oligomeric species (9.1 S, 8.3 nm, Mr 319 000). Two transformed (DNA-binding) forms can be generated. One is an oligomeric protein (5.2 S, 6-8.3 nm, Mr 132 000-182 000), while the other is the monomeric, hormone-binding subunit (3.8 S, 6 nm, Mr 96 000). The composition of the oligomeric, transformed receptor and its relationship to the monomeric protein were examined. The 3.8S monomer can be isolated from DEAE-cellulose (0.12 M step elution) in a form that continues to sediment at about 3.8 S on molybdate-containing sucrose gradients and at about 4.2 S on molybdate-free gradients. Addition of a non-hormone-binding component isolated from the same DEAE-cellulose column (0.5 M KCl step) can apparently interact with the 3.8-4.2 S monomer, increasing its sedimentation coefficient to 5.2 S (on molybdate-containing gradients) or 6.6 S (on low-salt, molybdate-free gradients). This factor is a macromolecule (nondialyzable) and is heat-stable (100 degrees C, 20 min). A dose-dependent shift to the higher sedimentation coefficient is observed when increasing quantities of the 0.5 M step material are added to the receptor monomer. This activity is abolished when the 0.5 M step material is treated with ribonuclease A. Further, when RNA is purified from the 0.5 M step by phenol/chloroform extraction, its ability to increase the S value of the monomer is retained. Ribonuclease treatment of the untransformed, 9.1S, oligomeric complex does not cause a significant decrease in sedimentation rate, while the same treatment of the 5.2S, oligomeric, transformed receptor (obtained after Sephadex G-25 transformation) causes a decrease in sedimentation rate to about 3.8 S. The addition of bovine liver mRNA and rRNA does not cause a shift in sedimentation rate of the receptor monomer to a discrete, higher sedimenting receptor form. However, the addition of total rabbit liver tRNA or three distinct tRNA species causes a shift in sedimentation to a similar, but not identical, form as that with the 0.5 M step material. We propose that the 5.2S, oligomeric transformed glucocorticoid receptor is composed of one monomeric hormone-binding, protein subunit (Mr 96 000) and a low molecular weight RNA (Mr 36 000). This interaction may be important for the role of the receptor in regulating gene expression.     

Novel modulation of neuronal nicotinic acetylcholine receptors by association with the endogenous prototoxin lynx1

We previously identified lynx1 as a neuronal membrane molecule related to snake alpha-neurotoxins able to modulate nAChRs. Here, we show that lynx1 colocalizes with nAChRs on CNS neurons and physically associates with nAChRs. Single-channel recordings show that lynx1 promotes the largest of three current amplitudes elicited by ACh through alpha(4)beta(2) nAChRs and that lynx1 enhances desensitization. Macroscopic recordings quantify the enhancement of desensitization onset by lynx1 and further show that it slows recovery from desensitization and increases the EC(50). These experiments establish that direct interaction of lynx1 with nAChRs can result in a novel type of functional modulation and suggest that prototoxins may play important roles in vivo by modulating functional properties of their cognate CNS receptors.     

A search for growth related genes in Kalanchoë blossfeldiana

Differential display of mRNA from four sets of contrasting phenotypes were carried out in order to identify and isolate genes associated with elongating growth of Kalanchoë blossfeldiana. A total of 17 unique differential expressed cDNA fragments were sequenced and 12 showed homology to genes in other plant species. Three genes were subsequently tested for growth related activity by Virus Induced Gene Silencing (VIGS) in Nicotiana benthamiana. One gene fragment (13C) resulted in plants with significantly reduced growth (N = 20, P = 0.05, one-tailed students t-test) from day 25 after virus infection. Full-length cDNA and genomic DNA sequences were obtained by inverse PCR and thermal asymmetric interlaced (TAIL) PCR and the gene was named KbORF1. The predicted gene is 2244 bp long with three exons of 411 bp in total encoding a protein of 137 amino acid residues with homologs widespread among plants. The protein has no known function, but its expression has been confirmed in a proteomic study of Arabidopsis. Southern blot analysis shows two hybridizing fragments in agreement with the tetraploid nature of K. blossfeldiana. Fragment 13C comprises 446 bp of the gene, and the portion of 13C conferring growth retardation by VIGS is located 10 bp into the second intron indicating a regulatory function of this part of the KbORF1 mRNA. Differential display in combination with VIGS as a screening method proved to be a good functional approach not only to search for genes of interest, but also to isolate expressed genetic regulatory domains.