Noise-induced hearing loss and combined noise and vibration exposure.

BACKGROUND: While there is a wide body of literature addressing noise-induced hearing loss (NIHL) and hand-arm vibration syndrome (HAVS) independently, relatively few studies have considered the combined effects of noise and vibration. These studies have suggested an increased risk of NIHL in workers with vibration white finger (VWF), though the relationship remains poorly understood. AIMS: To determine whether hearing impairment is worse in noise-exposed workers with VWF than in workers with similar noise exposures but without VWF. METHODS: The Quebec National Institute of Public Health audiometric database was used in conjunction with work-related accident and occupational diseases data from the Quebec workers' compensation board to analyse differences in audiometry results between vibration-exposed workers in the mining and forestry industries and the overall source population, and between mining and forestry workers with documented VWF and those without VWF. The International Organization for Standardization (ISO) 7029 standards were used to calculate hearing loss not attributable to age. RESULTS: 15751 vibration-exposed workers were identified in an overall source population of 59339. Workers with VWF (n = 96) had significantly worse hearing at every frequency studied (500, 1000, 2000 4000 Hz) compared with other mining and forestry workers without VWF. CONCLUSIONS: This study confirms previous findings of greater hearing loss at higher frequencies in workers with VWF, but also found a significant difference in hearing loss at low frequencies. It therefore supports the association between combined noise and hand-arm vibration (HAV) exposure and NIHL.

Transcutaneous immunization with a Vibrio cholerae O1 Ogawa synthetic hexasaccharide conjugate following oral whole-cell cholera vaccination boosts vibriocidal responses and induces protective immunity in mice.

A shortcoming of currently available oral cholera vaccines is their induction of relatively short-term protection against cholera compared to that afforded by wild-type disease. We were interested in whether transcutaneous or subcutaneous boosting using a neoglycoconjugate vaccine made from a synthetic terminal hexasaccharide of the O-specific polysaccharide of Vibrio cholerae O1 (Ogawa) coupled to bovine serum albumin as a carrier (CHO-BSA) could boost lipopolysaccharide (LPS)-specific and vibriocidal antibody responses and result in protective immunity following oral priming immunization with whole-cell cholera vaccine. We found that boosting with CHO-BSA with immunoadjuvantative cholera toxin (CT) or Escherichia coli heat-labile toxin (LT) following oral priming with attenuated V. cholerae O1 vaccine strain O395-NT resulted in significant increases in serum anti-V. cholerae LPS IgG, IgM, and IgA (P < 0.01) responses as well as in anti-Ogawa (P < 0.01) and anti-Inaba (P < 0.05) vibriocidal titers in mice. The LPS-specific IgA responses in stool were induced by transcutaneous (P < 0.01) but not subcutaneous immunization. Immune responses following use of CT or LT as an adjuvant were comparable. In a neonatal mouse challenge assay, immune serum from boosted mice was associated with 79% protective efficacy against death. Our results suggest that transcutaneous and subcutaneous boosting with a neoglycoconjugate following oral cholera vaccination may be an effective strategy to prolong protective immune responses against V. cholerae.

A variant in long palate, lung and nasal epithelium clone 1 is associated with cholera in a Bangladeshi population.

Vibrio cholerae causes a dehydrating diarrheal illness that can be rapidly fatal in the absence of specific treatment. The organism is an historic scourge and, like similar infectious diseases, may have influenced the evolution of the human genome. We report here the results of the first candidate gene association study of cholera. In a family-based study of 76 pedigrees from Dhaka, Bangladesh, we evaluated the association between cholera and five candidate genes-the cystic fibrosis transmembrane receptor; lactoferrin; long palate, lung and nasal epithelium clone 1 (LPLUNC1); estrogen-related receptor alpha and calcium-activated chloride channel 1. We found a significant association with a marker in the promoter region of LPLUNC1 (rs11906665), a member of a family of evolutionarily conserved innate immunity proteins. An earlier microarray-based study of duodenal biopsies showed significantly increased expression of LPLUNC1 in cholera patients compared with healthy control subjects. Our results suggest that variation in host innate immune responses may influence the outcome of exposure to V. cholerae in an endemic setting.

Multiple work-related accidents: tracing the role of hearing status and noise exposure.

OBJECTIVES: Our main purpose was to investigate any relationship between noise exposure levels in the workplace, degree of hearing loss (HL), and the relative risk of accident (OR of single or multiple events). METHODS: We conducted a retrospective study of 52 982 male workers aged 16-64 years with long-standing exposures to occupational noise over a 5-year period, using "hearing status" and "noise exposure" from the registry held by the Quebec National Institute of Public Health. Information on work-related accidents was obtained from the Quebec Workers' Compensation Board. Hearing threshold level measurements and noise exposures were regressed on the numbers of accidents after adjusting for age. RESULTS: Exposure to extremely noisy environments (L(eq8h) (equivalent noise level for 8 h exposure) > or =90 dBA) is associated with a higher relative risk of accident. The severity of hearing impairment (average bilateral hearing threshold levels at 3, 4 and 6 kHz) increases the relative risk of single and multiple events when threshold levels exceed 15 dB of hearing loss. The relative risk of multiple events (four or more) is approximately three times higher among severely hearing-impaired workers who are exposed to L(eq8h) > or =90 dBA. CONCLUSION: Single and multiple events are associated with high noise exposure and hearing status. This suggests that reducing noise exposure contributes to increased safety in noisy industries and prevents hearing loss. Hearing-impaired workers assigned to noisy workstations should be provided with assistive listening devices and efficient communication strategies should be implemented.

Conocimientos, actitudes y prácticas de las mujeres embarazadas en Iquitos, Perú, acerca de la anemia, la uncinariasis y el uso de antihelmínticos / Knowledge, attitudes and practices of the women embarrassed in Iquitos, Peru, about the anemia, the uncinariasis and the use of antihelmintics

Un estudio sobre conocimientos, actitudes y prácticas (CAP) fue desarrollado en julio de 2001, acerca de 99 gestantes atendidas por la clínica prenatal del Hospital Apoyo de Iquitos, Perú, la anemia, la uncinariasis y el uso de antihelmínticos. 55 por ciento sabían lo que la anemia era. Aunque el 53 por ciento sabían lo que eran parásitos, solo el 21 por ciento podían identificar un parásito por algún nombre. El 60 por ciento de la mujeres creían que tomar medicamentos durante el embarazo podría causar daños al bebé; sin embargo, de estas mujeres el 70 por ciento reportaron que quisieran ser tratadas contra parásitos mientras que están embarazadas si estuvieran infectadas. Está claro que el conocimiento de parásitos y la anemia en la población estudiada estaba limitada. Los resultados de este estudio necesitan ser combinados con evidencia en la prevalencia y la severidad de la anemia e infecciones parasitarias junto con la información sobre la dieta y los factores de riesgos con el objetivo de desarrollar un efectivo programa prenatal de salud y nutrición.

Oral immunization of BALB/c mice with Giardia duodenalis recombinant cyst wall protein inhibits shedding of cysts.

The process of encystation is a key step in the Giardia duodenalis life cycle that allows this intestinal protozoan to survive between hosts during person-to-person, animal-to-person, waterborne, or food-borne transmission. The release of cysts from infected persons and animals is the main contributing factor to contamination of the environment. Genes coding for cyst wall proteins (CWPs), which could be used for developing a transmission-blocking vaccine, have been cloned. Since the immunogenicity of recombinant Giardia CWP is unknown, we have investigated the immunogenicity of recombinant CWP2 (rCWP2) and its efficacy in interfering with the phenomenon of encystation taking place in the small bowels of BALB/c mice vaccinated with the recombinant protein. Here we report that the immunization of BALB/c mice with rCWP2 stimulated the immune system in a manner comparable to that for a live infection with Giardia muris cysts. Fecal and serum anti-rCWP2 immunoglobulin A (IgA) antibodies were detected in the immunized mice. In addition, anti-rCWP2 IgG1 and IgG2a antibodies were detected in the serum. mRNAs coding for Th1 and Th2 types of cytokines were detected in spleen and Peyer's patch cells from immunized mice. When the vaccinated mice were challenged with live cysts, the animals shed fewer cysts. We conclude that rCWP2 is a possible candidate antigen for the development of a transmission-blocking vaccine.

Crystal structure of histidinol phosphate aminotransferase (HisC) from Escherichia coli, and its covalent complex with pyridoxal-5'-phosphate and l-histidinol phosphate.

The biosynthesis of histidine is a central metabolic process in organisms ranging from bacteria to yeast and plants. The seventh step in the synthesis of histidine within eubacteria is carried out by a pyridoxal-5'-phosphate (PLP)-dependent l-histidinol phosphate aminotransferase (HisC, EC 2.6.1.9). Here, we report the crystal structure of l-histidinol phosphate aminotransferase from Escherichia coli, as a complex with pyridoxamine-5'-phosphate (PMP) at 1.5 A resolution, as the internal aldimine with PLP, and in a covalent, tetrahedral complex consisting of PLP and l-histidinol phosphate attached to Lys214, both at 2.2 A resolution. This covalent complex resembles, in structural terms, the gem-diamine intermediate that is formed transiently during conversion of the internal to external aldimine.HisC is a dimeric enzyme with a mass of approximately 80 kDa. Like most PLP-dependent enzymes, each HisC monomer consists of two domains, a larger PLP-binding domain having an alpha/beta/alpha topology, and a smaller domain. An N-terminal arm contributes to the dimerization of the two monomers. The PLP-binding domain of HisC shows weak sequence similarity, but significant structural similarity with the PLP-binding domains of a number of PLP-dependent enzymes. Residues that interact with the PLP cofactor, including Tyr55, Asn157, Asp184, Tyr187, Ser213, Lys214 and Arg222, are conserved in the family of aspartate, tyrosine and histidinol phosphate aminotransferases. The imidazole ring of l-histidinol phosphate is bound, in part, through a hydrogen bond with Tyr110, a residue that is substituted by Phe in the broad substrate specific HisC enzymes from Zymomonas mobilis and Bacillus subtilis. Comparison of the structures of the HisC internal aldimine, the PMP complex and the HisC l-histidinol phosphate complex reveal minimal changes in protein or ligand structure. Proton transfer, required for conversion of the gem-diamine to the external aldimine, does not appear to be limited by the distance between substrate and lysine amino groups. We propose that the tetrahedral complex has resulted from non-productive binding of l-histidinol phosphate soaked into the HisC crystals, resulting in its inability to be converted to the external aldimine at the HisC active site.

The crystal structure of Escherichia coli MoeA, a protein from the molybdopterin synthesis pathway.

MoeA is involved in synthesis of the molybdopterin cofactor, although its function is not yet clearly defined. The three-dimensional structure of the Escherichia coli protein was solved at 2.2 A resolution. The locations of highly conserved residues among the prokaryotic and eukaryotic MoeA homologs identifies a cleft in the dimer interface as the likely functional site. Of the four domains of MoeA, domain 2 displays a novel fold and domains 1 and 4 each have only one known structural homolog. Domain 3, in contrast, is structurally similar to many other proteins. The protein that resembles domain 3 most closely is MogA, another protein required for molybdopterin cofactor synthesis. The overall similarity between MoeA and MogA, and the similarities in a constellation of residues that are strongly conserved in MoeA, suggests that these proteins bind similar ligands or substrates and may have similar functions.

Three-dimensional structure of 2-amino-3-ketobutyrate CoA ligase from Escherichia coli complexed with a PLP-substrate intermediate: inferred reaction mechanism.

2-Amino-3-ketobutyrate CoA ligase (KBL, EC 2.3.1.29) is a pyridoxal phosphate (PLP) dependent enzyme, which catalyzes the second reaction step on the main metabolic degradation pathway for threonine. It acts in concert with threonine dehydrogenase and converts 2-amino-3-ketobutyrate, the product of threonine dehydrogenation by the latter enzyme, with the participation of cofactor CoA, to glycine and acetyl-CoA. The enzyme has been well conserved during evolution, with 54% amino acid sequence identity between the Escherichia coli and human enzymes. We present the three-dimensional structure of E. coli KBL determined at 2.0 A resolution. KBL belongs to the alpha family of PLP-dependent enzymes, for which the prototypic member is aspartate aminotransferase. Its closest structural homologue is E. coli 8-amino-7-oxononanoate synthase. Like many other members of the alpha family, the functional form of KBL is a dimer, and one such dimer is found in the asymmetric unit in the crystal. There are two active sites per dimer, located at the dimer interface. Both monomers contribute side chains to each active/substrate binding site. Electron density maps indicated the presence in the crystal of the Schiff base intermediate of 2-amino-3-ketobutyrate and PLP, an external aldimine, which remained bound to KBL throughout the protein purification procedure. The observed interactions between the aldimine and the side chains in the substrate binding site explain the specificity for the substrate and provide the basis for a detailed proposal of the reaction mechanism of KBL. A putative binding site of the CoA cofactor was assigned, and implications for the cooperation with threonine dehydrogenase were considered.

Analysis of the relative abundance of different types of bacteria capable of toluene degradation in a compost biofilter.

A microbial community of a compost biofilter treating toluene vapors was investigated using serum-bottle assays and mineral-agar plates. Toluene was not consumed in the absence of oxygen. However, filter-bed extracts exposed to toluene vapor as the only carbon source produced distinct colony types (phenotypic groups) that were counted separately. Strains from each group were isolated and checked for toluene-degradation activity in serum bottles. Only 15% of colonies were true toluene degraders. This population was divided into 11 genotypic groups based on DNA fingerprints. Identification of a member of each group using 16S rRNA gene-sequence comparison showed that they belonged to seven genera: Acinetobacter, Azoarcus, Mycobacterium, Nevskia, Pseudomonas, Pseudonocardia and Rhodococcus. Together, members of the genera Pseudonocardia and Rhodococcus were 34 times more numerous than all the others. We hypothesized that these two organisms are K-strategists (adapted to a resource-restricted and crowded environment) and that the compost biofilter is a K-environment. This would explain why they are not outnumbered by faster growers like Pseudomonas or Acinetobacter species, which would be r-strategists (adapted to a resource-abundant and uncrowded environment).

[Deaths at an early age in the city of Quebec, 17th-19th centuries]. / La mortalité en bas âge dans la ville de Québec, XVIIe-XIXe siècles.

Archaeological excavations carried out in two ancient cemeteries (1657-1844) of Notre-Dame-de-Québec Basilica in old Québec City allowed us to analyze the skeletal remains of more than 175 children who died before they were 10 years old. The proportion of infants is higher than expected according to the parish registers presumably because archaeologists recovered the remains of infants whose death had not been recorded in the registers. Two peaks of mortality have been noted: among the newborns and between one and two years old. The observed bone lesions lead us to believe that prenatal stress and rickets might be responsible for these high mortality rates. Although the samples from the two cemeteries were contemporaneous and drawn from the same community, there are some significant differences from the morbidity and mortality standpoint, tentatively attributed to the fact that most of the children recovered from one of the cemeteries were the victims of an epidemic while those from the other cemetery died in normal circumstances. This study shows how the analysis of skeletal remains can shed light on pathological conditions which otherwise would remain undocumented and how paleoanthropology opens new perspectives of research on diseases and death in the past.

Constitutive activation of the Saccharomyces cerevisiae mating response pathway by a MAP kinase kinase from Candida albicans.

The HST7 gene of Candida albicans encodes a protein with structural similarity to MAP kinase kinases. Expression of this gene in Saccharomyces cerevisiae complements disruption of the Ste7 MAP kinase kinase required for both mating in haploid cells and pseudohyphal growth in diploids. However, Hst7 expression does not complement loss of either the Pbs2 (Hog4) MAP kinase kinase required for response to high osmolarity, or loss of the Mkk1 and Mkk2 MAP kinase kinases required for proper cell wall biosynthesis. Intriguingly, HST7 acts as a hyperactive allele of STE7; expression of Hst7 activates the mating pathway even in the absence of upstream signaling components including the Ste7 regulator Ste11, elevates the basal level of the pheromone-inducible FUS1 gene, and amplifies the pseudohyphal growth response in diploid cells. Thus Hst7 appears to be at least partially independent of upstream activators or regulators, but selective in its activity on downstream target MAP kinases. Creation of Hst7/Ste7 hybrid proteins revealed that the C-terminal two-thirds of Hst7, which contains the protein kinase domain, is sufficient to confer this partial independence of upstream activators.

Uptake and metabolism of sphingolipids in isolated intestinal loops of mice.

Sphingolipids are found in all eukaryotic organisms. However, little is known about the digestion, uptake and subsequent metabolism of these constituents of food. In this study, radiolabeled sphingolipids were placed in isolated intestinal segments of female CF1 mice, and the metabolism and distribution of the radiolabel were followed. Most of the sphingomyelin was degraded to ceramide and other products in all regions of the intestine, and increasing amounts of several [3H]-labeled sphingolipids appeared in the tissues. Small amounts of the radiolabel disappeared from the intestinal loops and appeared in liver within the first 30 to 60 min implying that neither intact sphingomyelin nor its metabolites are transported very efficiently from the intestine to other organs. There were different degrees of uptake and metabolism of sphingomyelin, [4,5-3H-sphinganyl]ceramide, and [3H]sphingosine. The [3H]sphingomyelin was also administered by gavage and the appearance along the intestine measured. After 90 min, 12% was found in the cecum and colon. These results establish that some of the sphingomyelin that enters the gastrointestinal tract is hydrolyzed and taken up by the intestine, with the lipid backbone being degraded or reutilized for complex sphingolipid synthesis; however, at least a portion passes into the large intestine. The appearance of bioactive compounds throughout the gastrointestinal tract may alter the behavior of intestinal cells.

Purification and characterization of PTP2C, a widely distributed protein tyrosine phosphatase containing two SH2 domains.

PTP2C, a widely distributed protein tyrosine phosphatase (PTP) containing two SH2 domains, was expressed as a recombinant enzyme in Escherichia coli and purified to near homogeneity. The purified enzyme and a truncated form lacking the SH2 domains (delta SH2-PTP2C) have been characterized with four commonly used substrates. Both forms showed pH optima of around neutrality for protein substrates but below 5.5 for a peptide substrate and para-nitrophenylphosphate. The dependence of the enzymes on ionic strength varied with the nature of the substrates involved. Like its analog PTP1C, PTP2C displayed a specific activity of less than 0.1% of that observed with other known PTPs toward protein substrates. Deletion of the SH2 domains increased its activity by 12-45-fold, depending on the substrates used. Limited trypsinolysis which cleaved about 4 kDa from the carboxyl terminus resulted in a 2-5-fold activation of the full-length enzyme but was essentially without effect on the truncated enzyme. Both forms showed similar responses to effectors including activators (e.g. anionic phospholipids) or inhibitors (e.g. vanadate, molybdate, or Zn2+). PTP2C and delta SH2-PTP2C were phosphorylated in vitro by mitogen-activated protein kinase, protein kinase C, and various protein tyrosine kinases; in the latter case, they underwent autodephosphorylation. No significant effect of the phosphorylation reactions on enzyme activity could be observed in vitro.

Molecular analysis of HEM6 (HEM12) in Saccharomyces cerevisiae, the gene for uroporphyrinogen decarboxylase.

HEM6 (HEM12) in Saccharomyces cerevisiae encodes uroporphyrinogen decarboxylase, the fifth enzyme in the heme biosynthetic pathway. The HEM6 (HEM12) gene was cloned by complementation of heme auxotrophy of a hem6 mutant. Sequence analysis revealed an open reading frame of 1086 nucleotides. The predicted amino acid sequence of HEM6 (HEM12) shows extensive homology to those reported for uroporphyrinogen decarboxylase from mammalian sources. Expression of HEM6 (HEM12) was investigated and was found to increase two-fold in a non-fermentable carbon source. However, HEM6 (HEM12) transcription was unaffected by heme or by intermediates in the heme biosynthetic pathway. In addition, HEM6 (HEM12) expression is not regulated by the transcriptional activator complex HAP2-3-4, as has been shown for some genes encoding heme biosynthetic enzymes.

Differences in glycogen, lipids, and enzymes in livers from rats flown on COSMOS 2044.

Livers from rats flown aboard COSMOS 2044 were analyzed for protein, carbohydrate (glycogen), and lipids as well as the activities of a number of key enzymes involved in metabolism of these compounds and xenobiotics. The major differences between the flight group and the synchronous control were elevations in microsomal protein, liver glycogen content, tyrosine aminotransferase, and tryptophan oxygenase and reductions in sphingolipids and the rate-limiting enzyme of heme biosynthesis, delta-aminolevulinic acid synthase. These results provide further evidence that spaceflight has pronounced and diverse effects on liver function; however, some of the results with samples from COSMOS 2044 differed notably from those from previous spaceflights. This may be due to conditions of spaceflight and/or the postflight recovery period for COSMOS 2044.

Structure and regulation of yeast HEM3, the gene for porphobilinogen deaminase.

Porphobilinogen deaminase is the third enzyme in the heme biosynthetic pathway. hem3 mutants in Saccharomyces cerevisiae are deficient in porphobilinogen deaminase activity. We have isolated the HEM3 gene by complementation of the heme auxotrophy of a hem3 mutant. Sequence analysis reveals an open reading frame of 981 nucleotides. The derived amino acid sequence of the protein encoded by HEM3 shows extensive homology to the reported sequences for porphobilinogen deaminase from a number of other sources, indicating that HEM3 is the structural gene for porphobilinogen deaminase. Earlier reports have suggested that expression of HEM3 is induced by porphobilinogen, the substrate of the encoded enzyme. We have investigated the transcription of HEM3 and have found that it is not affected by the ability of the cell to make porphobilinogen or heme. However, we have found that HAP2 and HAP3 gene products are involved in the expression of HEM3. An important element required for expression of HEM3 has been localized to a small region that contains a sequence homologous to the HAP2-3-4 binding sites of several genes including HEM1. These findings suggest that HEM3 expression is regulated in the same manner as that of HEM1 which encodes the first enzyme of the heme biosynthetic pathway.