Possible Effects Of Environmental Factors Research Articles

Environmental Factors Affecting the Concentration of DNA in Blood and Saliva Stains: A Review

DNA evidence has now become an essential part of forensic investigations since it offers vital information for person identification and crime resolution. However, the biological material is affected by some environmental factors which may impact the DNA in biological samples. This may affect the correctness and reliability of forensic DNA analysis. This review is related to the influence of various environmental conditions on the stability and degradation of DNA in biological stains including blood and saliva stains. The common factors that affect DNA are temperature, humidity, exposure to sunlight, and type of substrate. The information is crucial to improve forensic DNA analysis and forensic protocol optimization. The DNA stability and integrity in biological materials, such as blood and saliva stains, are indispensable for forensic DNA analysis. Environmental influences, however, significantly affect DNA concentration and may jeopardize forensic analysis. The present review explores various environmental factors for their effect on DNA stability in blood and saliva stains. While DNA degradation is slowed but not completely prevented by low temperatures, it is accelerated by high temperatures. Risks of contamination arise from the promotion of microbial growth and DNA breakdown by humidity. DNA photodamage brought on by sunlight exposure results in strand breakage and cross-linking. DNA stability is also influenced by the type of substrate used; porous surfaces, such as cloth, are better at keeping fluids than non-porous ones, such as glass. Maintaining the integrity of DNA evidence requires an understanding of these variables. The present studies will help to create sophisticated DNA preservation methods for use in forensic DNA examination. The study emphasizes the requirement of improvement in forensic DNA analysis skills, related to the preservation of DNA pieces of evidence and the possible effect of environmental factors.

Trailing the heat: Eurasian tealAnas creccaschedule their spring migration basing on the increase in soil temperatures along the route

Migratory behaviour allows individuals to inhabit areas with optimal environmental conditions throughout the year. To reduce energy expenditure and the risk of mortality while migrating, birds may schedule their departures basing on environmental cues that provide seasonal and/or local information. In this study, we aimed to identify the possible effect of environmental factors on the spring migration of 30 Eurasian tealAnas creccatracked between 2014 and 2018 from Italian wintering areas. We used Cox proportional hazard and generalized estimating equation models to evaluate the environmental cues that affect teal's decision to start migratory movements from the wintering grounds and continue migration from stopover sites. Apart from the anticipated effect of photoperiod, the onset of spring migration was not substantially influenced by environmental variables, whereas the speed of migration seemed to be influenced by both seasonal (increased ground temperature, an indicator of spring advancement) and local (low cloud cover and northward blowing winds, which support migratory flight) environmental cues. The slow migration observed in teal may favour a strategy in which migratory timing is modulated mainly by the conditions encountered during the journey rather than at the start of the migration. This suggested low impact of local environmental variables on the onset of spring migration could have important consequences both for the management of this species for hunting purposes and for the way the species might respond to the ongoing climatic change.

Evaluation of the effects of environmental factors and eating habits on exfoliation syndrome and glaucoma in a Turkish population.

This study aimed to assess the possible effect of environmental factors and eating habits on patients with the exfoliation syndrome (XFS) and exfoliative glaucoma (XFG) in a Turkish population. A questionnaire was applied to 1,000 individuals, including 290 patients with XFS, 210 patients with XFG, and 500 age- and sex-matched healthy control participants. Sociodemographic characteristics, home type and warming methods, living and working conditions (indoor-outdoor), dietary habits based on the the guidance of Turkey Dietary Guidelines, (Determination of Nutritional Status Report and Turkey National Nutrition and Health Survey) and using sunglasses were evaluated. The chi-square test, Student t test, and analysis of variance were used for the statistical analysis with SPSS v. 23.0 software. The case-control groups were matched during data collection, and age and sex distribution in groups was analyzed; however, no difference was found. The average years and hours spent outdoor were statistically different between case and control groups (P < 0.05). The disease risk among individuals wearing sunglasses was 2.74 times less than that among those who did not wear sunglasses. Individuals born in the city had 1.46 times lower risk. Also, living out of the city until the age of 12 years increased the risk of getting the disease 1.36 times. In addition, while living in an apartment decreased the risk of disease, using a stove increased. The control groups had more healthy eating habits than the case groups. This case-control study showed that time spent outdoors, wearing sunglasses, home type, heating method, and eating habits might be associated with XFS and XFG.

Response of Bacterial Communities to Heavy Metal Contamination in an Abandoned Chromate Factory

The chromium slags left by industry emission has caused serious damage to the local ecological environment, and microorganisms were sensitive to the variation in the surrounding environmental factors. In this work, 14 soil samples around an abandoned chromate factory were collected. We utilized the 16S rRNA regions from soil DNA to explore the possible effects of environmental factors on soil bacterial communities. High-throughput DNA sequencing results suggested that bacterial communities varied greatly from different soil samples, but Actinobacteria and Proteobacteria were predominant in all samples in the phylum level. In addition, Pseudarthrobacter, Thiobacillus, Paenisporosarcina, Sphingomonas, and Bacillus were abundant at a more refined species level. Based on redundancy analysis (RDA) and variation partitioning analysis (VPA), the results revealed that pH value, soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), chromium (Cr) and lead (Pb) could obviously affect the bacterial community structure. Heavy metals, soil nutrients, and pH could explain 37.69%, 13.61%, and 31.41% of bacterial community variation, respectively. This study would provide a theoretical basis for future remediation of local Cr-contaminated soil.

Deletion of UCP1 in Tg2576 Mice Increases Body Temperature and Exacerbates Alzheimer's Disease-Related Pathologies.

We previously demonstrated that the Alzheimer's disease (AD)-like model mice, Tg2576, housed at a high ambient temperature of 30 °C for 13 months, exhibited increased body temperature, which increased amyloid-β (Aβ) levels and tau stability, leading to tau phosphorylation and ultimately inducing memory impairment. Here, we aimed to exclude the possible effect of environmental factors associated with the difference in ambient temperature (23 °C vs. 30 °C) and to further clarify the effects of elevated body temperature on AD-like pathologies. We generated uncoupling protein 1 (UCP1) deletion in Tg2576 mice, Tg2576/UCP1-/-, because UCP1 deletion mice show a sustained rise in body temperature at normal room temperature. As expected, the body temperature in Tg2576/UCP1-/- mice was higher than that in Tg2576/ UCP1+/+ mice at 23 °C, which was accompanied by upregulated Aβ levels due to increased β-secretase (BACE1) and decreased neprilysin (NEP) protein levels in the brains of Tg2576/UCP1-/- mice compared with those in the Tg2576/ UCP1+/+ mice. Elevated body temperature also increased total tau levels, leading to enhanced phosphorylation, heat shock protein induction, and activated tau kinases. Furthermore, elevated body temperature enhanced glial activation and decreased synaptic protein levels in the brain. Taken together, these findings demonstrate that elevated body temperatures exacerbate AD-like pathologies.

Multiple environmental exposures in early-life and allergy-related outcomes in childhood

IntroductionEarly onset and high prevalence of allergic diseases result in high individual and socio-economic burdens. Several studies provide evidence for possible effects of environmental factors on allergic diseases, but these are mainly single-exposure studies. The exposome provides a novel holistic approach by simultaneously studying a large set of exposures. The aim of the study was to evaluate the association between a broad range of prenatal and childhood environmental exposures and allergy-related outcomes in children. Material and MethodsAnalyses of associations between 90 prenatal and 107 childhood exposures and allergy-related outcomes (last 12 months: rhinitis and itchy rash; ever: doctor-diagnosed eczema and food allergy) in 6–11 years old children (n = 1270) from the European Human Early-Life Exposome cohort were performed. Initially, we used an exposome-wide association study (ExWAS) considering the exposures independently, followed by a deletion-substitution-addition selection (DSA) algorithm considering all exposures simultaneously. All the exposure variables selected in the DSA were included in a final multi-exposure model using binomial general linear model (GLM). ResultsIn ExWAS, no exposures were associated with the outcomes after correction for multiple comparison. In multi-exposure models for prenatal exposures, lower distance of residence to nearest road and higher di-iso-nonyl phthalate level were associated with increased risk of rhinitis, and particulate matter absorbance (PMabs) was associated with a decreased risk. Furthermore, traffic density on nearest road was associated with increased risk of itchy rash and diethyl phthalate with a reduced risk. DSA selected no associations of childhood exposures, or between prenatal exposures and eczema or food allergy. DiscussionThis first comprehensive and systematic analysis of many environmental exposures suggests that prenatal exposure to traffic-related variables, PMabs and phthalates are associated with rhinitis and itchy rash.

Distinctive genetic variation of long‐segment Hirschsprung's disease in Taiwan

Hirschsprung's disease (HSCR) is a congenital disorder with the absence of myenteric and submucosal ganglion cells within distal gut. Due to multigenic inheritance and interactions, we employed next-generation sequencing (NGS) to investigate genetic backgrounds of long-segment HSCR (L-HSCR) in Taiwan. Genomic DNA extracted from peripheral blood of L-HSCR patients was subjected to capture-based NGS, based on a 31-gene panel. The variants with allele frequency <0.05 and predicted by computational methods as deleterious were further validated by Sanger sequencing in patients and their family as well to tell de novo from inherited variants. Between 2015/04 and 2018/05, this study enrolled 23 L-HSCR patients, including 15 (65.2%) sporadic cases and 8 (34.8%) familial patients in 4 different families. Six sporadic and seven familial cases showed possible harmful variants across eight different genes, accounting for an overall detection rate of 56.5%. These variants mainly resided in SEMA3C, followed by RET, NRG1, and NTRK1. Three sporadic and 2 familial cases exhibited strong pathogenic variants as a deletional frameshift or stop codon in RET, L1CAM or NRG1. In a HSCR family, the father passed on a pathogenic RET frameshift to two daughters; however, only one developed HSCR. Using NGS, we disclosed deleterious mutations such as a frameshift or stop codon in either familial or sporadic patients. Our cases with isolated L-HSCR or even total colonic aganglionosis appeared to exhibit complex patterns of inheritance and incomplete penetrance even in families with the same genetic variants, reflecting the possible effects of environmental factors and genetic modifiers.

Early-life exposome and lung function in children in Europe: an analysis of data from the longitudinal, population-based HELIX cohort

Several single-exposure studies have documented possible effects of environmental factors on lung function, but none has relied on an exposome approach. We aimed to evaluate the association between a broad range of prenatal and postnatal lifestyle and environmental exposures and lung function in children. In this analysis, we used data from 1033 mother-child pairs from the European Human Early-Life Exposome (HELIX) cohort (consisting of six existing longitudinal birth cohorts in France, Greece, Lithuania, Norway, Spain, and the UK of children born between 2003 and 2009) for whom a valid spirometry test was recorded for the child. 85 prenatal and 125 postnatal exposures relating to outdoor, indoor, chemical, and lifestyle factors were assessed, and lung function was measured by spirometry in children at age 6-12 years. Two agnostic linear regression methods, a deletion-substitution-addition (DSA) algorithm considering all exposures simultaneously, and an exposome-wide association study (ExWAS) considering exposures independently, were applied to test the association with forced expiratory volume in 1 s percent predicted values (FEV1%). We tested for two-way interaction between exposures and corrected for confounding by co-exposures. In the 1033 children (median age 8·1 years, IQR 6·5-9·0), mean FEV1% was 98·8% (SD 13·2). In the ExWAS, prenatal perfluorononanoate (p=0·034) and perfluorooctanoate (p=0·030) exposures were associated with lower FEV1%, and inverse distance to nearest road during pregnancy (p=0·030) was associated with higher FEV1%. Nine postnatal exposures were associated with lower FEV1%: copper (p=0·041), ethyl-paraben (p=0·029), five phthalate metabolites (mono-2-ethyl 5-carboxypentyl phthalate [p=0·016], mono-2-ethyl-5-hydroxyhexyl phthalate [p=0·023], mono-2-ethyl-5-oxohexyl phthalate [p=0·0085], mono-4-methyl-7-oxooctyl phthalate [p=0·040], and the sum of di-ethylhexyl phthalate metabolites [p=0·014]), house crowding (p=0·015), and facility density around schools (p=0·027). However, no exposure passed the significance threshold when corrected for multiple testing in ExWAS, and none was selected with the DSA algorithm, including when testing for exposure interactions. Our systematic exposome approach identified several environmental exposures, mainly chemicals, that might be associated with lung function. Reducing exposure to these ubiquitous chemicals could help to prevent the development of chronic respiratory disease. European Community's Seventh Framework Programme (HELIX project).

Association between Helicobacter pylori gastritis and dental diseases: A cross-sectional, hospital-based study in Eastern Saudi Arabia.

There is inconsistent evidence about the association between Helicobacter pylori (H.pylori) and dental diseases with possible effect of environmental factors. The aims of the study were to assess (1) the association between gastric and oral H.pylori colonization and (2) the association between oral colonization of H.pylori and dental diseases. A cross-sectional study was conducted in King Fahad University hospital in Khobar, Eastern Saudi Arabia in 2017. Patients admitted to the Endoscopy Unit were recruited and clinically examined for plaque, decayed teeth (D), filled teeth (F), missing teeth (M), periodontal pocket depth (PPD), attachment loss (AL), and gingival bleeding in addition to assessing their age, gender, education, tooth brushing, flossing, and tobacco use with a questionnaire. Pooled dental plaque samples were collected and analyzed using nested polymerase chain reaction PCR to detect oral H.pylori. Gastroscopy was used to extract biopsies to assess gastritis and the presence of gastric H.pylori using Giemsa stain. Regression analysis was used to assess differences between patients with and without gastritis, oral H. pylori and gastric H. pylori in the percentage of sites with gingival bleeding, PPD, CAL, D, M, and F with adjustment for confounders. One hundred twenty patients were included. Most of them brushed daily (82.6%) and had university education (45.7%). Of these, 34.2% had gastric H.pylori and 5% had oral H.pylori. No significant association was observed between the percentage of sites with gingival bleeding, mean PPD, AL, F, and either gastritis, the presence of oral or gastric H.pylori. Patients with gastritis had significantly higher number of D and M than patients without gastritis (P= 0.03). In this study, the presence of gastric and oral H.pylori in patients with good oral hygiene and moderate socioeconomic status is not significantly associated with periodontal diseases. Patients with gastritis tend to have a higher number of decayed and missing teeth.

A Systematic Review of the Effects of Environmental Pollutants, Chemical Factors, and Climate Changes on Children’s Height

Objective: Height is a multifactorial characteristic affected by genetics, hormonal and environmental factors. The aim of this study was to systematically review the effects of environmental pollutants, chemical factors, and climate changes on children and adolescents’ height. Methods: This study searched scientific databases including PubMed, ISI Web of Science, and Scopus using key words such as “Environmental Pollution”, “Climate Change”, “Growth”, “Body Height”, “Child and adolescent development”, and their combination. By removing duplicates, relevant papers were selected in three phases. This review included studies that were conducted among children and adolescents up to the age of 18. After the quality assessment, data was extracted by a reviewer and rechecked by another one. The authors summarized information of 52 articles about the possible effects of environmental factors and climate change on height. Articles were divided to four categories, including air, soil, water pollutants, and climate changes. Results: The evidence indicates that exposure to environmental pollutants have different effects on height growth; some of them, such as air pollution with lead, arsenic, fossil fuels and smoking, as well as exposure to nuclear radiation among children is associated with shorter stature, while exposure to some soil pollutants and airport noise did not have any effect on children’s height growth. Conclusions: The current study proposes that exposure to some environmental pollutants and chemicals during childhood and puberty might have negative effects on height growth. Therefore, various interventions are necessary for reducing the production of these pollutants and the exposure of growing children to these environmental factors.

Effect of Environmental Factors on Knowledge Sharing in Construction Organization

The processes of environmental factors are milieu-focus, which can influence the knowledge sharing in construction organization. This study examines the possible effect of environmental factors in respect to managerial leadership, strategy/planning and culture on the relationship to the knowledge sharing. The study was carried out on project managers in construction organizations in Nigeria using a stratified random sample of 323 of different designations. A hypothesized model of knowledge sharing, and environmental factors was tested using structural equation modeling approach, and a proposed model was therefore developed. All the factor loadings were significant, leading to a prudent model achievement. The study serves as a guide to the construction managers for sharing knowledge in the construction organization. The finding indicated that environmental factors demonstrated significant influence on knowledge sharing.Â

Method of Housing and Transfer and Experimental Autoimmune Encephalomyelitis: An Experimental Study on C57BL/6

final outcome of EAE modeling. Some of these factors were observed and discussed in our experiment on C57BL/6 model. Objectives: The present research was carried out to find the possible effects of environmental factors, including transfer, handling, housing, and dark-light cycle on EAE modeling scoring. Materials and Methods: Twenty female mice (C57BL/6) were used that divided into two groups (n = 10) by random. The routine method of MS induction in mammals was used in both groups. Following induction, animals of group one were placed in a separated room with the least local translocation and handling, whereas animals of the second group were placed in the same room as the other animals with normal local allocation as others. The animals were observed and scored using routine clinical scoring for EAE. Results: Our data showed that the EAE induction in group one was significantly more successful than group two (with the mean score > 3). Conclusions: Although the EAE is still a scientific method to induce MS in rodents, it requires more attention to environmental factors that might influence the result. The mechanisms of these factors are unknown, but it seems that the role of housing environment should be taken into consideration.

Reproductive characteristics of citrus rootstocks grown under greenhouse and field environments

The aim of the present study was to evaluate the possible effect of environmental factors on meiosis, meiotic index, pollen viability and in vitro germination of pollen from stock plants of the rootstocks Trifoliate, 'Swingle', 'Troyer', 'Fepagro C13', 'Fepagro C37' and 'Fepagro C41' grown in a protected environment in comparison with stock plants grown in the field. The results showed that values for the characteristics analyzed in 2008, 2009 and 2010 were always higher in the field than in the greenhouse conditions. In the field, the average of normal meiotic cells was 60.05%, 44.44% and 60.12%, respectively, and in the greenhouse, 52.75%, 30.95% and 52.82%, respectively. Mean pollen viability in the field was 90.28%, 56.23% and 74.74%, and, in the greenhouse, 64.25%, 41.41% and 66.71%, respectively. As temperature oscillations were higher in the greenhouse than in the field, we suggest that this negatively affects the reproductive characteristics analyzed.

Epigenetic signature of panic disorder: A role of glutamate decarboxylase 1 (GAD1) DNA hypomethylation?

Glutamate decarboxylases (GAD67/65; GAD1/GAD2) are crucially involved in gamma-aminobutyric acid (GABA) synthesis and thus were repeatedly suggested to play an important role in the pathogenesis of anxiety disorders. In the present study, DNA methylation patterns in the GAD1 and GAD2 promoter and GAD1 intron 2 regions were investigated for association with panic disorder, with particular attention to possible effects of environmental factors. Sixty-five patients with panic disorder (f=44, m=21) and 65 matched healthy controls were analyzed for DNA methylation status at 38 GAD1 promoter/intron2 and 10 GAD2 promoter CpG sites via direct sequencing of sodium bisulfate treated DNA extracted from blood cells. Recent positive and negative life events were ascertained. Patients and controls were genotyped for GAD1 rs3762556, rs3791878 and rs3762555, all of which are located in the analyzed promoter region. Patients with panic disorder exhibited significantly lower average GAD1 methylation than healthy controls (p<0.001), particularly at three CpG sites in the promoter as well as in intron 2. The occurrence of negative life events was correlated with relatively decreased average methylation mainly in the female subsample (p=0.01). GAD1 SNP rs3762555 conferred a significantly lower methylation at three GAD1 intron 2 CpG sites (p<0.001). No differential methylation was observed in the GAD2 gene. The present pilot data suggest a potentially compensatory role of GAD1 gene hypomethylation in panic disorder possibly mediating the influence of negative life events and depending on genetic variation. Future studies are warranted to replicate the present finding in independent samples, preferably in a longitudinal design.

613 – Glutamate decarboxylase 1 dna hypomethylation - an epigenetic signature of panic disorder?

The glutamate decarboxylase (GAD67/65; GAD1/GAD2) as the rate-limiting enzyme in gamma-aminobutyric acid (GABA) synthesis has been suggested as a prime candidate in the pathogenesis of anxiety disorders. In the present study, DNA methylation of GAD1/2 gene regulatory regions was investigated for association with panic disorder with particular attention to possible effects of environmental factors. Sixty-five patients with panic disorder (f=44, m=21) and 65 matched healthy controls were analyzed for DNA methylation status at 40 GAD1 and 10 GAD2 CpG sites via direct sequencing of sodium bisulfate treated DNA extracted from blood cells. The occurrence of recent positive and negative life events was ascertained. Patients and controls were genotyped for GAD1 genetic variation. Patients with panic disorder exhibited significantly lower average GAD1 methylation than healthy controls. The occurrence of negative life events was correlated with relatively decreased average methylation mainly in the female subsample. GAD1 SNPs rs3749034 and rs3762555 conferred a significantly lower methylation at three GAD1 CpG sites. No differential methylation was observed in the GAD2 gene. The present pilot data suggest a - potentially compensatory - role of GAD1 gene hypomethylation in panic disorder possibly mediating the influence of negative life events and dependent on genetic variation. Future studies are warranted to replicate the present finding in independent samples, preferably applying a longitudinal design.

Sex discrimination of Buloke (Allocasuarina luehmannii) for selective revegetation

Allocasuarina luehmannii (Buloke) is a slow-growing dioecious species occurring primarily in south-eastern Australia. Larger seed-bearing female trees, at least 100 yrs old, are an essential food source for the threatened Calyptorhynchus banksii graptogyne (Karak). Sex-discrimination in Buloke was investigated utilising Random Amplified Polymorphic DNA (RAPD) and Inter-Simple Sequence Repeat (ISSR) techniques. While described as a dioecious species, 18% of the plants sampled were monoecious suggesting that this is in fact a subdioecious species. Stem material from 55 paddock trees was collected to identify genetic differences between female, male and monoecious plants. An initial screening of 56 primers, on a subset of five female, five male and five monoecious samples, identified 21 RAPD and 21 ISSR primers with clear scorable bands, but no unique female bands were amplified. Investigation into the sex determination mechanism of this species and the possible effect of environmental factors on sex expression is recommended before further sex-specific marker research is undertaken.

Childhood asthma and risk factors

This article summarizes the contribution of epidemiology to the understanding of childhood asthma. The first task in epidemiology is to determine prevalence and incidence of any disease. Epidemiological investigations are aimed at evaluating hypotheses about causes of disease by defining demographic characteristics of a certain population as well as by determining possible effects of environmental factors. In spite of some limitations, data obtained by epidemiological investigations have been valuable in confirming both the increasing incidence of asthma and the differences in prevalence in certain population groups. The observance of this phenomenon has led to much speculation and a lot of attempts to identify the reasons behind the rising prevalence. Epidemiological studies have identified risk factors for the development of childhood asthma and provided insight into natural history of disease and prognosis. Factors ranging from increased numbers of immunizations to increased air pollution have been suggested, but subsequent analysis has failed to provide the supporting evidence to implicate most of these possibilities. The concept known as the hygiene hypothesis has gained some support from epidemiological studies. The development of asthma as well as its severity are affected by numerous factors and their interactions can he explained by the heterogeneous nature of this disease.

The importance of making ends meet: Mutations in genes and altered expression of proteins of the MRN complex and cancer

The MRN protein complex, consisting of MRE1, RAD50 and NBS1, plays a crucial role in sensing DNA double-strand breaks (DSBs), and it is involved in cell cycle control. This makes the MRN complex an important guard of genome stability. Hypomorphic mutations in NBS1 result in the Nijmegen breakage syndrome (NBS), which is characterized by, among other things, an increased predisposition to malignancies, especially leukemia/lymphoma. Relatives of NBS patients carrying heterozygous mutations are also more prone to cancer development. This review summarizes several studies searching for associations between heterozygous mutations in NBS1, MRE11, and RAD50 and cancer and examining the levels of expression of proteins coded by these genes in tumor tissues. The results indicate that both decreased and increased expression of NBS1 may contribute to tumorigenesis, whereas overexpressed RAD50 has an anti-tumoric effect. MRE11 and RAD50 are also affected in tumors with microsatellite instability. However, the outcomes of association studies, which concerned primarily lymphomas/leukemias and breast cancer, were inconclusive. Heterozygous NBS1 mutations and molecular variants 657del5, I171V, R215W and E185Q were most commonly analyzed. Among these, an association with cancer was found most frequently for 657del5 (in leukemia/lymphoma and breast cancer) and I171V (in leukemia, breast, head and neck and colorectal cancers); however, other studies gave contradictory results. For other NBS1 as well as MRE11 and RAD50 variants, too little data were available to assess their role in cancer risk. Overall, the results suggest that heterozygous MRN complex mutations and molecular variants may contribute only to a limited fraction of tumors. This may be caused by several factors: various frequencies of the variants in specific populations, different criteria used for selection of control groups, possible effects of environmental factors, and potential interactions with variants of other low-risk genes. These issues, as well as the impact of the alterations on protein function, need to be addressed in future studies.

Temperature and relative humidity affect the selection of shelters by Triatoma infestans, vector of Chagas disease

The preference of Triatoma infestans for shelters at different temperatures or relative humidities (RH) was tested in laboratory assays. The insects preferred refuges at a temperature of 34°C rather than 26°C, and chose to stay in refuges with an RH of 20% rather than 80%. Temperature and RH records made inside and outside experimental chicken-houses under natural climatic conditions showed that such habitats tend to maintain an inner climate favourable to T. infestans. Typical refuges in adobe walls showed strongly damped fluctuations in minimum and maximum temperatures, and delayed changes in these parameters when compared with an external reference. Similarly, the jarilla ( Larrea sp .), a plant used for constructing roofing, damps fluctuations in minimum and maximum RH and delays these RH fluctuations when compared to an external reference. We discuss possible effects of environmental factors on the distribution of insects in human dwellings, and analyse the environmental characteristics of normally available refuges in materials used for house building in endemic zones.

Effects of rearing temperature on sex differentiation in the European sea bass (Dicentrarchus labrax L.)

Under culture conditions, sex ratios in the European sea bass (Dicentrarchus labrax L.) are consistently skewed in favor of males. Moreover, no heteromorphic sex chromosomes have been shown for this species. This bias towards males could be due to a possible effect of environmental factors on sex differentiation, as has already been described in other fish species. To test this hypothesis, sexually undifferentiated sea bass were reared under two different thermal regimes or two different photoperiodic regimes, resulting in four groups: Group SP = short photoperiod (9 hours light [L]:15 hours dark [D]), Group LP = long photoperiod (15 L:9 D), both reared under natural temperature (24°C, average); Group LT = low temperature (15°C), Group HT = high temperature (25°C), both reared under natural photoperiod (13.5 L:10.75 D, average). Treatments lasted 80 days, from 57 to 137 days post fertilization, coinciding with the time when gonads are more sensitive to the action of exogenous sex steroids. The resulting sex proportions were determined by periodic histological examinations of the gonads during the first 2 years of age. No females were found in group LT at any sampling, whereas in the other groups, female proportions never reached values higher than 27%. Moreover, sex differentiation in group LT was delayed with respect to the other groups, as no fish completed sex differentiation until 16.4 months of age, compared to the other groups in which some individuals completed sex differentiation at 9 months of age. In addition, growth was significantly (P > 0.05) delayed in group LT with respect to the other three experimental groups and especially marked during the first year of life. Furthermore, the low values for the gonadosomatic index (GSI), together with the decrease of the number of spermatogenic males, denote a delay in gonadal maturation with respect to the rest of the experimental groups. The results of this study suggest that temperature can play an important role in the process of sex differentiation and growth of the sea bass. However, the mechanism(s) underlying this sexual lability remain unknown. J. Exp. Zool. 281:207–216, 1998. © 1998 Wiley-Liss, Inc.