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Research describing esterase gene amplification in an organophosphate resistant mosquito is presented. In particular the possibility of allele recombination is investigated.

Objective To investigate the impact of demographic factors and develop normative data for two verbal fluency tests in a sample of Spanish-Speakers living in the U.S./Mexico border region. Participants and Method The sample consisted of 252 adults (Age: M = 37.3, SD = 10.2, range 19-60; Education: M = 10.7, SD = 4.37, range 0-20, 59% female), living in the US-Mexico border region of Arizona and California. Participants completed the letter (letters P, M, and R) and semantic (Animal Naming) fluency tests as part of a larger neuropsychological test norming study. Normative T-scores were computed with fractional polynomial equations controlling for age, education, and sex. We also calculated the rates of impairment (T < 40) that would be obtained by applying the newly developed norms and available test norms for non-Hispanic English-speakers. Results Higher education was significantly associated with better raw scores on both verbal fluency tests (letter: r = 0.41, semantic: r = 0.36, ps <.001), and older age was significantly associated with higher raw scores on letter fluency (r = 0.14, p <.05). There were no other significant effects of demographic factors. The normalized distribution of T-scores with the new norms showed the expected impairment rate (16% letter and 15% semantic fluency). However, application of existing non-Hispanic White norms resulted in 23% impairment for letter fluency and 24% in semantic fluency. Using non-Hispanic Black norms resulted in 9% impairment in letter fluency and 2% in semantic fluency. Conclusions We provide norms for Spanish speakers living along the U.S-Mexico border region for two verbal fluency tests that are co-normed with a more extensive neuropsychological battery. We demonstrate that application of existing norms derived from English speaking samples yield inaccurate estimates of impairment. As such, these regional norms will improve the interpretation of verbal fluency performance in Spanish-speakers living in the US-Mexico borderland. [ABSTRACT FROM AUTHOR]

Objective To provide norms applicable to Spanish-speakers living in the US- Mexico border region for the Halstead Category Test, a test of executive function. Participants and Method Healthy Spanish-speakers (n = 252) were recruited from the US–Mexico border regions (Age: M = 37.3, SD = 10.2, range 19-60; Education: M = 10.7, SD = 4.3, range 0-20; 58% female). Participants completed the Category Test as part of a larger neuropsychological test battery. Relationships between demographic variables and raw error scores were assessed using Spearman and Wilcoxon Rank-sum tests. Demographically corrected T-scores for the Category Test were normed using fractional polynomial equations accounting for age, education, and sex. For comparison, T-scores were also computed for the Spanish-speaking normative sample using published norms for English-speaking non-Hispanic Whites and African Americans, which were also adjusted for age, education and sex. Impairment rates based on -1SD (T < 40) were calculated using both, published and current, norms. Results Older age was significantly associated with higher number of errors (Spearman ρ = 0.32, p <.001) and higher education was associated with lower number of errors (Spearman ρ = -0.52, p <.001), with no other significant demographic effects. Applying non-Hispanic norms resulted in overestimation of impairment rates in the Spanish-speaking sample (impairment rate: 48% with White norms and 27% with African American norms). This pattern was evident across levels of education except in participants with 13+ years of education, where rates of impairment using African American norms were comparable to those based on the newly developed norms. Conclusions The present study is the first to develop norms for the Category test in a sample of Spanish-speakers in the US-Mexico border region. These norms will provide tools for the assessment of executive function in this population. Research concerning generalizability of norms to other Spanish-speaking populations is needed. [ABSTRACT FROM AUTHOR]

Objective To examine neurocognitive impairment (NCI) in vulnerable HIV infected (HIV+) adults in Mexico. Participants and Method Twenty-eight adults (15 HIV+ and 13 HIV-) living in Tijuana (Mexico) participated in the study (Age: M = 40.5, SD = 11.1; 54% female; Education: M = 8.6, SD = 4.7). Participants with HIV were recruited from the board-and-care home "Las Memorias" (100% AIDS; 93% on ART; Years since HIV diagnosis: Median = 11, IQR = 5,16). Healthy controls, matched in age and education to HIV+ participants, were recruited from the same city. Participants completed a neuropsychological test battery which was comprised of the Modified Wisconsin Card Sorting Test, letter and animal fluency, Trail Making Test Parts A and B, Stroop Color-Word Test, and Symbol-Digit Test. Raw scores garnered from these tests were transformed to percentiles using norms for a Mexican population, and averaged to calculate scores on global cognition and on three cognitive domains (verbal fluency, processing speed and executive function). Wilcoxon rank sum tests were conducted to investigate group differences. NCI was defined as global percentile scores < 16. Results HIV+ participants showed significantly lower scores in global cognition (p =.04, Cohen's d = 0.86), as well as the domains of processing speed (p =.03, Cohen's d = 0.87) and executive function (p =.04, Cohen's d = 0.84), with no significant differences (but medium effect sizes) on verbal fluency (p =.10, Cohen's d = 0.60). NCI was evident in 53% of HIV+ persons and 15% of healthy controls. Conclusions Approximately half of the persons living with HIV showed notable NCI, which is consistent with findings of prior studies of Latinos in the US with HIV. This pattern of neurocognitive function was also similar to those of prior studies in HIV. Future studies might examine key predictors of HIV-associated NCI in this vulnerable Mexican population, including biological and culturally relevant factors: such as deportation, and discrimination for sexual preference or HIV status. [ABSTRACT FROM AUTHOR]

BackgroundAfrican Americans are disproportionally affected by HIV and have poorer rates of antiretroviral therapy (ART) adherence compared to other racial or ethnic groups in the United States. Factors associated with poor HIV disease outcomes are commonly associated with sociostructural barriers that prevent engagement with and retention in HIV care. SMS text messaging interventions to promote ART adherence among predominantly non-Hispanic White persons with HIV (PWH) have been shown to be efficacious; however, limited research has been devoted to culturally tailoring interventions for underrepresented racial/ethnic groups. Considering African Americans show poorer engagement along the HIV care continuum, we developed an individualized and culturally tailored two-way SMS text messaging intervention to improve ART adherence and associated virologic suppression among African American PWH. ObjectiveIn this paper we describe the protocol of a culturally tailored individualized Texting for Adherence Building (iTAB) intervention in a 24- to 48-week, single-arm study. MethodsWe developed a culturally tailored iTAB intervention, which we are implementing in a 24- to 48-week, single-arm study. Participants were recruited from the Family Health Centers of San Diego (FHCSD), a federally qualified health center. Patient inclusion criteria were (1) receiving care at the FHCSD, (2) living with HIV, (3) self-identification as Black, African American, or of African ancestry, (4) English speaking, (5) age 18 or older, (6) currently on ART, and (7) able to provide informed consent. Study enrollment began in November 2017 and closed in July 2019. A total of 90 participants from the FHCSD enrolled in the iTAB intervention, and we anticipate completing data collection in July 2020. Participants were assisted in individualizing and customizing their SMS text message preferences at the baseline study visit. Self-assessment measures are collected at baseline, interim, and final study visits. Problems related to sending/receiving SMS text messages and barriers to ART adherence are assessed at each interim study visit. The FHCSD staff monitors and tracks participants’ daily SMS text message responses to ART adherence reminders using a clinical dashboard. ResultsWe hypothesize that the proportion of individuals achieving HIV virologic suppression (viral load

Objective: To determine the reliability of teleneuropsychological (TNP) compared to in-person assessments (IPA) in people with HIV (PWH) and without HIV (HIV-)., Methods: Participants included 80 PWH (M age = 58.7, SD age = 11.0) and 23 HIV- (M age = 61.9, SD age = 16.7). Participants completed two comprehensive neuropsychological IPA before one TNP during the COVID-19 pandemic (March-December 2020). The neuropsychological tests included: Hopkins Verbal Learning Test-Revised (HVLT-R Total and Delayed Recall), Controlled Oral Word Association Test (COWAT; FAS-English or PMR-Spanish), Animal Fluency, Action (Verb) Fluency, Wechsler Adult Intelligence Scale 3 rd Edition (WAIS-III) Symbol Search and Letter Number Sequencing, Stroop Color and Word Test, Paced Auditory Serial Addition Test (Channel 1), and Boston Naming Test. Total raw scores and sub-scores were used in analyses. In the total sample and by HIV status, test-retest reliability and performance-level differences were evaluated between the two consecutive IPA (i.e., IPA1 and IPA2), and mean in-person scores (IPA-M), and TNP., Results: There were statistically significant test-retest correlations between IPA1 and IPA2 ( r or ρ = .603-.883, ps < .001), and between IPA-M and TNP ( r or ρ = .622-.958, ps < .001). In the total sample, significantly lower test-retest scores were found between IPA-M and TNP on the COWAT (PMR), Stroop Color and Word Test, WAIS-III Letter Number Sequencing, and HVLT-R Total Recall ( ps < .05). Results were similar in PWH only., Conclusions: This study demonstrates reliability of TNP in PWH and HIV-. TNP assessments are a promising way to improve access to traditional neuropsychological services and maintain ongoing clinical research studies during the COVID-19 pandemic.

Urine biomarker concentrations reflecting kidney tubule injury and dysfunction were not associated with brain MRI measures.Higher eGFR was associated with lower total brain cerebral blood flow.This is the first evaluation of the relationship of kidney tubule biomarkers with brain imaging by MRI in patients with CKD., Competing Interests: D. Rifkin reports being a scientific advisor or member of American Journal of Kidney Diseases Editorial Board (feature editor), American Board of Internal Medicine Nephrology Exam Committee; and reports having other interests/relationships as Co-investigator, US site, Empagliflozin-KIDNEY study (pending). D.E. Weiner reports having consultancy agreements by participating in Medical Advisory Boards for Akebia (2020, 2021), Cara Therapeutics (2020), Janssen Biopharmaceuticals (2019), and Tricida (2019); reports receiving honoraria for Akebia, paid to DCI; reports receiving research funding from all compensation paid to AstraZeneca (site Principal Investigator (PI), completed 2020), CSL Behring (site PI, ongoing), Goldfinch Bio (site PI, ongoing), Janssen Biopharmaceuticals (site PI, completed 2019), Tufts MC, Dialysis Clinic, Inc. (site PI for trials contracted with Dialysis Clinic, Inc. [DCI] including Ardelyx, ongoing, and Cara Therapeutics, completed); reports receiving honoraria from the National Kidney Foundation for editorial positions at American Journal of Kidney Diseases and Kidney Medicine, Elsevier for royalties from the National Kidney Foundation's (NKF) Primer on Kidney Diseases; reports being a scientific advisor or member as Co-Editor-in-Chief, NKF Primer on Kidney Diseases, 8th Edition, Editor-in-Chief, Kidney Medicine, Medical Director of Clinical Research, Dialysis Clinic Inc., Member, American Society of Nephrology Quality and Policy Committees and American Society of Nephrology representative to Kidney Care Partners, Scientific Advisory Board, National Kidney Foundation; and reports having other interests/relationships as Chair, adjudications committee, Evaluation of Effect of TRC101 in Progression of CKD in Subjects with Metabolic Acidosis (VALOR-CKD Trial, George Institute, Clinical Research Organization [CRO], sponsored by Tricida), Member of the Data Monitoring Committee, “Feasibility of Hemodialysis with GARNET? In Chronic Hemodialysis Patients with a Bloodstream Infection” Trial (Avania CRO). J.H. Ix reports having consultancy agreements with Ardelyx, AstraZeneca, Bayer, Jnana, and Sanifit; reports receiving research funding from Baxter International; and reports being a scientific advisor or member of AlphaYoung. M. Marquine reports research funding from the National Institutes of Health. M.G. Shlipak reports having consultancy agreements with Cricket Health, Intercept Pharmaceuticals, University of Washington Cardiovascular Health Study, and Veterans Medical; reports receiving research funding from Bayer Pharmaceuticals; reports receiving honoraria from AstraZeneca, Bayer, and Boehringer Ingelheim; reports being a scientific advisor or member of American Journal of Kidney Disease, Journal of the American Society of Nephrology, and Circulation; and reports having other interests/relationships as Board Member, Northern California Institute for Research and Education. M. Kurella Tamura reports receiving honoraria from the American Federation for Aging Research; and reports being a scientific advisor or member of the Beeson External Advisory Committee, CJASN Editorial Board, and the Clin-Star Advisory Board. N.M. Pajewski reports having an ownership interest in Eyenovia and Ocuphire Pharma; and reports being a scientific advisor or member of Journal of the American Geriatrics Society. All remaining authors have nothing to disclose., (Copyright © 2022 by the American Society of Nephrology.)

Objective: The Paced Auditory Serial Addition Test (PASAT) and Wechsler Adult Intelligence Scale Letter Number Sequencing subtest (LNS) are two commonly used measures of working memory. Demographic variables (age, education, ethnicity, etc.) can impact performance on these measures, underscoring the need for demographically adjusted norms. We aimed to develop normative data for the PASAT and LNS for Spanish-speaking adults living in the U.S.-Mexico border region as part of a larger normative effort., Method: Participants were native Spanish-speakers from the Neuropsychological Norms for the U.S. Mexico Border Region in Spanish (NP-NUMBRS) project. Two hundred and forty-nine participants completed the PASAT and 202 participants completed LNS. Ages ranged from 19 to 60 and education from 0 to 20 years., Results: Older age was associated with lower scores on LNS ( p < .01) but not PASAT. Lower education was associated with lower scores on both tests ( p s < .001). Women obtained lower raw scores than men on PASAT ( p s < .003), and there were no significant main effects of gender on LNS raw scores. Raw-to-scaled score conversions were calculated, and fractional polynomial equations were developed to calculate demographically-adjusted T-scores accounting for age, education, and gender. Published norms for English-speaking non-Hispanic Whites substantially overestimated rates of impairment (defined as T-score < 40) on both the PASAT and LNS., Conclusions: The use of the population-specific normative data may improve detection of working memory dysfunction in U.S. Spanish-speaking adults and contribute to improved diagnostic accuracy and treatment planning in this population. Whether the norms generalize to U.S. Spanish-speakers from other countries remains to be determined.

The aggregation of Latino subgroups in national studies creates an overly simplistic narrative that Latinos are at lower risk of mental illness and that foreign nativity seems protective against mental illness (i.e., immigrant paradox). This broad generalization does not hold up as the Latino population ages. Given that social inequalities for risk appear to widen with age, the social disadvantages of being Latino in the United States increase the risk for mental illness across the life span. This review focuses on the mental health of older Latinos, specifically the 3 subgroups with the longest residential history in the United States-Mexicans, Puerto Ricans, and Cubans. We examine relevant epidemiological and clinical psychopathology studies on aging in these Latino populations and present evidence of the heterogeneity of the older Latino population living in the United States, thus illustrating a limitation in this field-combining Latino subgroups despite their diversity because of small sample sizes. We address the migration experience-how intraethnic differences and age of migration affect mental health-and discuss social support and discrimination as key risk and protective factors. We conclude with a discussion on meeting the mental health needs of older Latinos with a focus on prevention, a promising approach to addressing mental illness in older Latinos, and future directions for mental health research in this population. Success in this endeavor would yield a substantial reduction in the burden of late-life depression and anxiety and a positive public health impact., (© The Author(s) 2020. Published by Oxford University Press on behalf of The Gerontological Society of America.)

Purpose of Review: This article critically reviews the utility of "phenotypes" as behavioral descriptors in aging/HIV research that inform biological underpinnings and treatment development. We adopt a phenotypic redefinition of aging conceptualized within a broader context of HIV infection and of aging. Phenotypes are defined as dimensions of behavior, closely related to fundamental mechanisms, and, thus, may be more informative than chronological age. Primary emphasis in this review is given to comorbid aging and cognitive aging, though other phenotypes (i.e., disability, frailty, accelerated aging, successful aging) are also discussed in relation to comorbid aging and cognitive aging., Recent Findings: The main findings that emerged from this review are as follows: (1) the phenotypes, comorbid aging and cognitive aging, are distinct from each other, yet overlapping; (2) associative relationships are the rule in HIV for comorbid and cognitive aging phenotypes; and (3) HIV behavioral interventions for both comorbid aging and cognitive aging have been limited. Three paths for research progress are identified for phenotype-defined aging/HIV research (i.e., clinical and behavioral specification, biological mechanisms, intervention targets), and some important research questions are suggested within each of these research paths.

Objectives: A variety of specific cultural adaptations have been proposed for older adult and minority mental health interventions. The objective of this study was to determine whether the BRIGHTEN Program, an individually tailored, interdisciplinary "virtual" team intervention, would equally meet the needs of a highly diverse sample of older adults with depression., Methods: Older adults who screened positive for depression were recruited from primary and specialty care settings to participate in the BRIGHTEN program. A secondary data analysis of 131 older adults (37.4% African-American, 29.0% Hispanic, 29.8% Non-Hispanic White) was conducted to explore the effects of demographic variables (race/ethnicity, income and education) on treatment outcome., Results: Compared to baseline, participants demonstrated significant improvements on the SF-12 Mental Health Composite and depression (GDS-15) scores at 6-month follow-up. There were no differences on outcome measures based on race/ethnicity, income or education with one exception-a difference between 12th grade and graduate degree education on SF-12 Mental Health Composite scores., Conclusions: While not explicitly tailored for specific ethnic groups, the BRIGHTEN program may be equally effective in reducing depression symptoms and improving mental health functioning in a highly socioeconomically and ethnically diverse, community-dwelling older adult population., Clinical Implications: Implications for behavioral health integration in primary care are discussed.

Hispanics are the fastest growing ethnicity in the United States, yet there are limited well-validated neuropsychological tools in Spanish, and an even greater paucity of normative standards representing this population. The Spanish NIH Toolbox Cognition Battery (NIHTB-CB) is a novel neurocognitive screener; however, the original norms were developed combining Spanish- and English-versions of the battery. We developed normative standards for the Spanish NIHTB-CB, fully adjusting for demographic variables and based entirely on a Spanish-speaking sample. A total of 408 Spanish-speaking neurologically healthy adults (ages 18-85 years) and 496 children (ages 3-7 years) completed the NIH Toolbox norming project. We developed three types of scores: uncorrected based on the entire Spanish-speaking cohort, age-corrected, and fully demographically corrected (age, education, sex) scores for each of the seven NIHTB-CB tests and three composites (Fluid, Crystallized, Total Composites). Corrected scores were developed using polynomial regression models. Demographic factors demonstrated medium-to-large effects on uncorrected NIHTB-CB scores in a pattern that differed from that observed on the English NIHTB-CB. For example, in Spanish-speaking adults, education was more strongly associated with Fluid scores, but showed the strongest association with Crystallized scores among English-speaking adults. Demographic factors were no longer associated with fully corrected scores. The original norms were not successful in eliminating demographic effects, overestimating children's performances, and underestimating adults' performances on the Spanish NIHTB-CB. The disparate pattern of demographic associations on the Spanish versus English NIHTB-CB supports the need for distinct normative standards developed separately for each population. Fully adjusted scores presented here will aid in more accurately characterizing acquired brain dysfunction among U.S. Spanish-speakers.

Longitudinal cohort studies of HIV and substance use disorders play an important role in understanding these conditions, but high rates of attrition can threaten their integrity and generalizability. This study aimed to identify factors associated with attrition in a 5-year observational cohort study of 469 individuals with and without HIV infection and methamphetamine (MA) dependence. Rates of attrition in our four study groups were approximately 24% in HIV-MA-, 15% in HIV+MA-, 56% in HIV-MA+, and 47% in HIV+MA+ individuals. Predictors of attrition in the overall cohort included history of MA, alcohol, and other substance dependence, learning impairment, reduced cognitive reserve, and independence in activities of daily living (all p s < .05), but varied somewhat by clinical group. Of particular note, enrollment in a neuroimaging substudy was associated with significantly boosted rates of retention in the MA groups. Results from this investigation highlight the complexity of the clinical factors that influence retention in cohort studies of HIV-infected MA users and might guide the development and implementation of targeted retention efforts.

The population genetic structures of Culex pipiens Linnaeus were evaluated in China over a 2000 km transect that encompasses the two subspecies, C. p. pallens and C. p. quinquefasciatus. Four polymorphic allozyme loci were investigated in 1376 mosquitoes sampled from 20 populations across four provinces. These loci were not statistically dependent with no apparent heterozygote deficit or excess. On a regional scale (intra-province), a low (Fst=0.007-0.016) and significant genetic differentiation was found, with no clear geographical pattern. On a wider scale (inter-province), the genetic differentiation was higher (Fst=0.059), and an isolation by distance emerged. The results are compared with previous population genetic surveys of this mosquito species in different geographic areas over the world. The overall pattern suggests that Culex pipiens requires considerable distance (500-1000 km) to show isolation by distance, irrespective of the subspecies (C. p. pipiens, C. p. quinquefasciatus and C. p. pallens) or the geographic location.

Population surveys of Culex pipiens quinquefasciatus carried out in 1991 and 1999 were compared with data collected in 1990 before the beginning of the control program against this mosquito. Larval samples collected in 1999 displayed resistance to the four tested insecticides: permethrin, propoxur, temephos, and chlorpyrifos. Temephos resistance ratio at LC50 (RR50) ranged between 8.1- and 42-fold compared with 2.9- and 4.6-fold in 1990, and chlorpyrifos RR50 ranged between 8.6- and 123-fold compared with 6.4- and 19-fold in 1990. This increased resistance to organophosphorus insecticides was associated with a sharp decrease of susceptible genotypes at two loci (Ester and ace-1), as well as to an allele replacement at the Ester locus.

Two groups of Anopheles claviger sensu stricto Meigen (Diptera: Culicidae) were recently found in France, representing unclear genetic entities. To better understand this situation, sampling was extended to 13 European countries, and 47 samples were analyzed by investigating the polymorphism of 11 autosomal and 1 sex-linked allozyme loci. Genetic differentiation, as measured by F(st), between these two groups was confirmed, with no isolation by distance within each group. Among the twelve loci studied, none had diagnostic alleles. Group I is mainly located in western Europe (UK and south-west of France), and Group II covers eastern France and eastern and northern Europe. Intermediate populations, sampled at the overlapping range between them, do not display a heterozygote deficit, suggesting that these two groups are probably not genetically isolated. The origin of each group and its biological significance is discussed within the context of differentiation in refugia during recent glaciations.

In the mosquito Culex pipiens, various alleles at the Ester locus provide insecticide resistance. These resistance alleles display a heterogeneous geographical distribution, particularly in China, where they are highly diverse. A new resistance allele, Ester9, coding for the overproduced esterases A9 and B9, is characterized and compared to the known resistant allele Ester8 isolated from the same southern China sample (from Guangzhou). Both alleles provide low but significant resistance to chlorpyrifos (relative synergism ratio [RSR] > 3) and temephos (RSR = 1.4), which is consistent with the low level of gene amplification they display (15 copies for Ester9 and 4 copies for Ester8). The full genomic sequence of the allele coding A8 and A9 is presented, which allowed us to set up a polymerase chain reaction assay to specifically identify these alleles. The peculiar situation in southern China, where numerous resistance alleles coexist, is discussed in comparison with the Mediterranean situation, the only one with a similar diversity of overproduced esterases.

In several insects, there appears to be a high fitness cost associated with insecticide resistance genes during the overwintering period. In order to understand when and how this cost operates, all mosquitoes entering a natural cave for overwintering were regularly sampled, and their resistance genes at two loci (Ester and Ace.1) were individually identified. During the main period of entry (October and November), susceptible mosquitoes were first observed, followed by resistant ones, this trend being similar for both loci. This observation is best explained by a migration phenomenon, northern and more susceptible populations starting to overwinter first, followed by southern and more resistant ones. During the remaining part of the winter (December-March), mosquitoes entering the cave were still caught and they probably corresponded to individuals leaving a former overwintering site in search of a more suitable one. A lower overall frequency of resistant phenotypes was found in the second part of the winter at Ester, suggesting that a large fitness cost (42%) had operated. A decreasing frequency of resistant phenotypes was also found at Ace.1, indicating a large survival cost of resistant mosquitoes (7% for the homozygote Ace.1R) in their former overwintering site. These results are discussed in the light of the local evolution of these resistance genes in southern France.

In southern France, failure to control Culex pipiens L. with Bacillus sphaericus Neide toxin (Bs) was first detected in 1994, at the extreme east of the Languedoc-Roussillon coast. This failure was due to a single recessive mutant, sp-1R. Two complementary strategies were used to test whether sp-1R had invaded the Bs-controlled area by 1998. First, a strain (BP) was selected from resistant larvae sampled in the western part of the Bs-controlled area. In BP strain, resistance involved a single recessive gene, sp-2R, distinct from sp-1R, that conferred a similarly high resistance in the homozygous state (approximately 6,000-fold). Combining one copy of sp-1R and one of sp-2R conferred a > 100-fold resistance. Second, Bs-resistance was monitored among the offspring of field females crossed to sp-1RR homozygous males. Females were sampled in 20 localities of southern France and three localities of the Llobregat delta (Barcelona, Spain) where C. pipiens control is also intensive. The 537 females in the study produced enough larvae to infer their genotype: 462 progenies were susceptible and the survival rate of 51 others was explained by the presence of sp-1R and/or sp-2R. The remaining 24 cases indicated that other factors could confer resistance when combined with sp-1R. The current data showed that, even when recessive, resistant mutants can rapidly increase in frequency, providing some interactions that protect them from disappearance. We discuss the consequences of this finding on the current strategies aimed to avoid or delay resistance in the pests controlled with B. sphaericus or B. thuringiensis Berliner toxins.

The electrophoretic polymorphism of loci encoding for 10 enzymes was studied in Culex p. quinquefasciatus Say from six localities of Vietnam. The analysis of 11 "neutral genes" showed that differentiation among samples was low, but significant (Fst = 0.06), and significantly related to geographic distance between sample sites. These results are similar to those observed in other countries (Europe and west Africa). A single type of overproduced esterases (A2-B2) was observed, and its frequency was high (60-100%) in all samples. This situation is in sharp contrast with that observed in other countries of South East Asia (China, South Korea and Japan), where two or more types of overproduced esterases have been reported. A map summarizing the geographic distribution of Asian Cr. p. quinquefasciatus with overproduced esterases is provided.

The cause of high resistance to chlorpyrifos observed in Tunisian Culex pipiens (L.) was investigated by comparing a Tunisian strain G (> 10,000-fold resistance), a French strain T (approximately 50-fold resistance), and a susceptible reference strain S. Strains G and T had the same level of propoxur resistance (approximately 1,000-fold) and were homozygous for an autosomal propoux-insensitive acetylcholinesterase (AChE-1). In G and T strains, as well as in the offspring of different F1s and backcrosses using these F1s and the S strain, the effect of DEF and Pb synergists on chlorpyrifos resistance was low or absent, indicating that increased detoxification by enzymes inhibited by these chemicals had a minor role. Chlorpyrifos resistance in the G strain was caused by a major gene (or group of genes) tightly linked to the Ace-1 gene (coding AChE-1 enzyme). The possibility of allelism between this gene and the Ace-1R allele present in the T strain was rejected by showing that AChE-1 inhibition by chlorpyrifos-oxon was not different between G and T mosquitoes.

To determine the outcome of the combined effects of gene flow, genetic drift, and selection on the evolution of insecticide-resistance genes in the mosquito Culex pipiens, samples were collected along three transects crossing treated and nontreated areas in northern Spain and southern France. Electrophoretic polymorphisms of five presumably neutral genes disclosed that differentiation among samples was low, and that both Wright F-statistics and Slatkin private-alleles methods provided a high estimate for Nm. In contrast, there was a strong differentiation in the distribution of resistance genes closely associated with insecticide treatments. These divergent situations are explained in relation to both the very recent origin of some resistance genes that are still localized geographically (A2-B2 and C1), and the high fitness cost of the older and ubiquitous ones in nontreated areas (A1, A4-B4, and Ace R )., (© 1995 The Society for the Study of Evolution.)

Before beginning a widespread control program against Culex pipiens quinquefasciatus in Martinique, resistance to temephos, chlorpyrifos, and two organophosphorous insecticides, was investigated at seven breeding sites. At LC95, populations exhibited resistance ratios between 6.9 and 11.6 for temephos and between 6.4 and 51.4 for chlorpyrifos. Overproduced esterases A2-B2 and B1, known to be involved in organophosphorous-resistance, were present at all breeding sites; esterases A2-B2 frequency was > 50% at all sites but one; and esterase B1 frequency was < 7%. Experimental treatment of three breeding sites with temephos induced no significant increase in resistance, but our esterase studies indicated a significant increase in the frequencies of esterase B1 and of a new highly active esterase C2. These results indicate that a large-scale C. p. quinquefasciatus control program with organophosphorous insecticides will induce a rapid increase of these resistance genes throughout Martinique. However, this may not necessarily result in high levels of resistance, because, at present, the level of gene amplification of esterase B still appears to be low.

Two highly active esterases, A2 and B2, were isolated in SeLax, a strain of Culex quinquefasciatus Say from California which demonstrated resistance levels of 19, 14, and 4.3 times to the organophosphate insecticides chlorpyrifos, temephos, and malathion, respectively. Selection of SeLax by temephos during 31 generations increased resistance to this insecticide to 65 times. This resistance was shown to be DEF-suppressible, monofactorial, and strongly associated with the presence of esterases A2 and B2. Although these two esterases are encoded by distinct structural genes, no disjunction was observed when SeLax was crossed to S-Lab, a susceptible strain, or to S54, a strain resistant to organophosphates by means of esterase A1. However, when SeLax was crossed to strain Tem-R, which is resistant to organophosphates because of a highly active esterase B1, all possible recombinants occurred. These results were discussed in relation to the recent discovery that increased activity of B esterases in the genus Culex is caused by gene amplification.