Large trans-ethnic meta-analysis identifies AKR1C4 as a novel gene associated with age at menarche.

STUDY QUESTION: Does the expansion of genome-wide association studies (GWAS) to a broader range of ancestries improve the ability to identify and generalise variants associated with age at menarche (AAM) in European populations to a wider range of world populations? SUMMARY ANSWER: By including women with diverse and predominantly non-European ancestry in a large-scale meta-analysis of AAM with half of the women being of African ancestry, we identified a new locus associated with AAM in African-ancestry participants, and generalised loci from GWAS of European ancestry individuals. WHAT IS KNOWN ALREADY: AAM is a highly polygenic puberty trait associated with various diseases later in life. Both AAM and diseases associated with puberty timing vary by race or ethnicity. The majority of GWAS of AAM have been performed in European ancestry women. STUDY DESIGN, SIZE, DURATION: We analysed a total of 38 546 women who did not have predominantly European ancestry backgrounds: 25 149 women from seven studies from the ReproGen Consortium and 13 397 women from the UK Biobank. In addition, we used an independent sample of 5148 African-ancestry women from the Southern Community Cohort Study (SCCS) for replication. PARTICIPANTS/MATERIALS, SETTING, METHODS: Each AAM GWAS was performed by study and ancestry or ethnic group using linear regression models adjusted for birth year and study-specific covariates. ReproGen and UK Biobank results were meta-analysed using an inverse variance-weighted average method. A trans-ethnic meta-analysis was also carried out to assess heterogeneity due to different ancestry. MAIN RESULTS AND THE ROLE OF CHANCE: We observed consistent direction and effect sizes between our meta-analysis and the largest GWAS conducted in European or Asian ancestry women. We validated four AAM loci (1p31, 6q16, 6q22 and 9q31) with common genetic variants at P < 5 × 10-7. We detected one new association (10p15) at P < 5 × 10-8 with a low-frequency genetic variant lying in AKR1C4, which was replicated in an independent sample. This gene belongs to a family of enzymes that regulate the metabolism of steroid hormones and have been implicated in the pathophysiology of uterine diseases. The genetic variant in the new locus is more frequent in African-ancestry participants, and has a very low frequency in Asian or European-ancestry individuals. LARGE SCALE DATA: N/A. LIMITATIONS, REASONS FOR CAUTION: Extreme AAM (<9 years or >18 years) were excluded from analysis. Women may not fully recall their AAM as most of the studies were conducted many years later. Further studies in women with diverse and predominantly non-European ancestry are needed to confirm and extend these findings, but the availability of such replication samples is limited. WIDER IMPLICATIONS OF THE FINDINGS: Expanding association studies to a broader range of ancestries or ethnicities may improve the identification of new genetic variants associated with complex diseases or traits and the generalisation of variants from European-ancestry studies to a wider range of world populations. STUDY FUNDING/COMPETING INTEREST(S): Funding was provided by CHARGE Consortium grant R01HL105756-07: Gene Discovery For CVD and Aging Phenotypes and by the NIH grant U24AG051129 awarded by the National Institute on Aging (NIA). The authors have no conflict of interest to declare.

Cadmium body burden and increased blood pressure in middle-aged American Indians: the Strong Heart Study.

Cadmium (Cd) is an environmental pollutant that has been associated with cardiovascular disease in populations, but the relationship of Cd with hypertension has been inconsistent. We studied the association between urinary Cd concentrations, a measure of total body burden, and blood pressure in American Indians, a US population with above national average Cd burden. Urinary Cd was measured using inductively coupled plasma mass spectrometry, and adjusted for urinary creatinine concentration. Among 3714 middle-aged American Indian participants of the Strong Heart Study (mean age 56 years, 41% male, 67% ever-smokers, 23% taking antihypertensive medications), urinary Cd ranged from 0.01 to 78.48 µg g-1 creatinine (geometric mean=0.94 µg g-1) and it was correlated with smoking pack-year among ever-smokers (r2=0.16, P<0.0001). Participants who were smokers were on average light-smokers (mean 10.8 pack-years), and urinary Cd was similarly elevated in light- and never-smokers (geometric means of 0.88 µg g-1 creatinine for both categories). Log-transformed urinary Cd was significantly associated with higher systolic blood pressure in models adjusted for age, sex, geographic area, body mass index, smoking (ever vs never, and cumulative pack-years) and kidney function (mean blood pressure difference by lnCd concentration (ß)=1.64, P=0.002). These associations were present among light- and never-smokers (ß=2.03, P=0.002, n=2627), although not significant among never-smokers (ß=1.22, P=0.18, n=1260). Cd was also associated with diastolic blood pressure among light- and never-smokers (ß=0.94, P=0.004). These findings suggest that there is a relationship between Cd body burden and increased blood pressure in American Indians, a population with increased cardiovascular disease risk.

Gestational weight gain in women with systemic lupus erythematosus.

Objective The objective of this study was to estimate the proportion of pregnant women with systemic lupus erythematosus meeting Institute of Medicine guidelines for gestational weight gain and determine correlates of adherence to guidelines. Methods Singleton, live births in the Hopkins Lupus Pregnancy Cohort 1987-2015 were included. Pre-pregnancy weight was the weight recorded 12 months prior to pregnancy/first trimester. Final weight was the last weight recorded in the third trimester. Adherence to Institute of Medicine guidelines (inadequate, adequate, or excessive) was based on pre-pregnancy body mass index. Fisher's exact test and analysis of variance determined factors associated with not meeting guidelines. Stepwise selection estimated predictors of gestational weight gain. Results Of the 211 pregnancies, 34%, 24% and 42% had inadequate, adequate and excessive gestational weight gain, respectively. In exploratory analyses, differences in Institute of Medicine adherence were observed by pre-pregnancy body mass index, race, elevated creatinine during pregnancy and pre-pregnancy blood pressure. Odds of inadequate and excessive gestational weight gain increased 12% with each 1 kg/m2 increase in pre-pregnancy body mass index. Lower maternal education was associated with increased odds of inadequate and excessive gestational weight gain. Conclusions As in the general population, most women with systemic lupus erythematosus did not meet Institute of Medicine guidelines. Our results identified predictors of gestational weight gain to aid in targeted interventions to improve guideline adherence in this population.

Rare, low frequency and common coding variants in CHRNA5 and their contribution to nicotine dependence in European and African Americans.

The common nonsynonymous variant rs16969968 in the α5 nicotinic receptor subunit gene (CHRNA5) is the strongest genetic risk factor for nicotine dependence in European Americans and contributes to risk in African Americans. To comprehensively examine whether other CHRNA5 coding variation influences nicotine dependence risk, we performed targeted sequencing on 1582 nicotine-dependent cases (Fagerström Test for Nicotine Dependence score⩾4) and 1238 non-dependent controls, with independent replication of common and low frequency variants using 12 studies with exome chip data. Nicotine dependence was examined using logistic regression with individual common variants (minor allele frequency (MAF)⩾0.05), aggregate low frequency variants (0.05>MAF⩾0.005) and aggregate rare variants (MAF<0.005). Meta-analysis of primary results was performed with replication studies containing 12 174 heavy and 11 290 light smokers. Next-generation sequencing with 180 × coverage identified 24 nonsynonymous variants and 2 frameshift deletions in CHRNA5, including 9 novel variants in the 2820 subjects. Meta-analysis confirmed the risk effect of the only common variant (rs16969968, European ancestry: odds ratio (OR)=1.3, P=3.5 × 10(-11); African ancestry: OR=1.3, P=0.01) and demonstrated that three low frequency variants contributed an independent risk (aggregate term, European ancestry: OR=1.3, P=0.005; African ancestry: OR=1.4, P=0.0006). The remaining 22 rare coding variants were associated with increased risk of nicotine dependence in the European American primary sample (OR=12.9, P=0.01) and in the same risk direction in African Americans (OR=1.5, P=0.37). Our results indicate that common, low frequency and rare CHRNA5 coding variants are independently associated with nicotine dependence risk. These newly identified variants likely influence the risk for smoking-related diseases such as lung cancer.

Serum uric acid does not predict incident metabolic syndrome in a population with high prevalence of obesity.

AIM: To evaluate whether uric acid (UA) predicts 4-yr incidence of metabolic syndrome (MetS) in non-diabetic participants of the Strong Heart Study (SHS) cohort. METHODS AND RESULTS: In this population-based prospective study we analyzed 1499 American Indians (890 women), without diabetes or MetS, controlled during the 4th SHS exam and re-examined 4 years later during the 5th SHS exam. Participants were divided into sex-specific tertiles of UA and the first two tertiles (group N) were compared with the third tertile (group H). Body mass index (BMI = 28.3 ± 7 vs. 31.1 ± 7 kg/m(2)), fat-free mass (FFM = 52.0 ± 14 vs. 54.9 ± 11 kg), waist-to-hip ratio, HOMA-IR (3.66 vs. 4.26), BP and indices of inflammation were significantly higher in group H than in group N (all p < 0.001). Incident MetS at the time of the 5th exam was more frequent in group H than group N (35 vs. 28%, OR 1.44 (95% CI = 1.10-1.91; p < 0.01). This association was still significant (OR = 1.13, p = 0.04) independently of family relatedness, sex, history of hypertension, HOMA-IR, central adiposity and renal function, but disappeared when fat-free mass was included in the model. CONCLUSIONS: In the SHS, UA levels are associated to parameters of insulin resistance and to indices of inflammation. UA levels, however, do not predict incident MetS independently of the initial obesity-related increased FFM.

Epidemiology and genetic determinants of progressive deterioration of glycaemia in American Indians: the Strong Heart Family Study.

AIMS/HYPOTHESIS: Type 2 diabetes is a chronic, heterogeneous disease and a major risk factor for cardiovascular diseases. The underlying mechanisms leading to progression to type 2 diabetes are not fully understood and genetic tools may help to identify important pathways of glycaemic deterioration. METHODS: Using prospective data on American Indians from the Strong Heart Family Study, we identified 373 individuals defined as progressors (diabetes incident cases), 566 individuals with transitory impaired fasting glucose (IFG) and 1,011 controls (normal fasting glycaemia at all visits). We estimated the heritability (h(2)) of the traits and the evidence for association with 16 known variants identified in type 2 diabetes genome-wide association studies. RESULTS: We noted high h(2) for diabetes progression (h(2) = 0.65 ± 0.16, p = 2.7 × 10(-6)) but little contribution of genetic factors to transitory IFG (h(2) = 0.09 ± 0.10, p = 0.19) for models adjusted for multiple risk factors. At least three variants (in WFS1, TSPAN8 and THADA) were nominally associated with diabetes progression in age- and sex-adjusted analyses with estimates showing the same direction of effects as reported in the discovery European ancestry studies. CONCLUSIONS/INTERPRETATION: Our findings do not exclude these loci for diabetes susceptibility in American Indians and suggest phenotypic heterogeneity of the IFG trait, which may have implications for genetic studies when diagnosis is based on a single time-point measure.

Replication of genetic loci for ages at menarche and menopause in the multi-ethnic Population Architecture using Genomics and Epidemiology (PAGE) study.

STUDY QUESTION: Do genetic associations identified in genome-wide association studies (GWAS) of age at menarche (AM) and age at natural menopause (ANM) replicate in women of diverse race/ancestry from the Population Architecture using Genomics and Epidemiology (PAGE) Study? SUMMARY ANSWER: We replicated GWAS reproductive trait single nucleotide polymorphisms (SNPs) in our European descent population and found that many SNPs were also associated with AM and ANM in populations of diverse ancestry. WHAT IS KNOWN ALREADY: Menarche and menopause mark the reproductive lifespan in women and are important risk factors for chronic diseases including obesity, cardiovascular disease and cancer. Both events are believed to be influenced by environmental and genetic factors, and vary in populations differing by genetic ancestry and geography. Most genetic variants associated with these traits have been identified in GWAS of European-descent populations. STUDY DESIGN, SIZE, DURATION: A total of 42 251 women of diverse ancestry from PAGE were included in cross-sectional analyses of AM and ANM. MATERIALS, SETTING, METHODS: SNPs previously associated with ANM (n = 5 SNPs) and AM (n = 3 SNPs) in GWAS were genotyped in American Indians, African Americans, Asians, European Americans, Hispanics and Native Hawaiians. To test SNP associations with ANM or AM, we used linear regression models stratified by race/ethnicity and PAGE sub-study. Results were then combined in race-specific fixed effect meta-analyses for each outcome. For replication and generalization analyses, significance was defined at P < 0.01 for ANM analyses and P < 0.017 for AM analyses. MAIN RESULTS AND THE ROLE OF CHANCE: We replicated findings for AM SNPs in the LIN28B locus and an intergenic region on 9q31 in European Americans. The LIN28B SNPs (rs314277 and rs314280) were also significantly associated with AM in Asians, but not in other race/ethnicity groups. Linkage disequilibrium (LD) patterns at this locus varied widely among the ancestral groups. With the exception of an intergenic SNP at 13q34, all ANM SNPs replicated in European Americans. Three were significantly associated with ANM in other race/ethnicity populations: rs2153157 (6p24.2/SYCP2L), rs365132 (5q35/UIMC1) and rs16991615 (20p12.3/MCM8). While rs1172822 (19q13/BRSK1) was not significant in the populations of non-European descent, effect sizes showed similar trends. LIMITATIONS, REASONS FOR CAUTION: Lack of association for the GWAS SNPs in the non-European American groups may be due to differences in locus LD patterns between these groups and the European-descent populations included in the GWAS discovery studies; and in some cases, lower power may also contribute to non-significant findings. WIDER IMPLICATIONS OF THE FINDINGS: The discovery of genetic variants associated with the reproductive traits provides an important opportunity to elucidate the biological mechanisms involved with normal variation and disorders of menarche and menopause. In this study we replicated most, but not all reported SNPs in European descent populations and examined the epidemiologic architecture of these early reported variants, describing their generalizability and effect size across differing ancestral populations. Such data will be increasingly important for prioritizing GWAS SNPs for follow-up in fine-mapping and resequencing studies, as well as in translational research.

Association of heat shock proteins with all-cause mortality.

Experimental mild heat shock is widely known as an intervention that results in extended longevity in various models along the evolutionary lineage. Heat shock proteins (HSPs) are highly upregulated immediately after a heat shock. The elevation in HSP levels was shown to inhibit stress-mediated cell death, and recent experiments indicate a highly versatile role for these proteins as inhibitors of programmed cell death. In this study, we examined common genetic variations in 31 genes encoding all members of the HSP70, small HSP, and heat shock factor (HSF) families for their association with all-cause mortality. Our discovery cohort was the Rotterdam study (RS1) containing 5,974 participants aged 55 years and older (3,174 deaths). We assessed 4,430 single nucleotide polymorphisms (SNPs) using the HumanHap550K Genotyping BeadChip from Illumina. After adjusting for multiple testing by permutation analysis, three SNPs showed evidence for association with all-cause mortality in RS1. These findings were followed in eight independent population-based cohorts, leading to a total of 25,007 participants (8,444 deaths). In the replication phase, only HSF2 (rs1416733) remained significantly associated with all-cause mortality. Rs1416733 is a known cis-eQTL for HSF2. Our findings suggest a role of HSF2 in all-cause mortality.

PNPLA3 gene-by-visceral adipose tissue volume interaction and the pathogenesis of fatty liver disease: the NHLBI family heart study.

BACKGROUND: Fatty liver disease (FLD) is characterized by increased intrahepatic triglyceride content with or without inflammation and is associated with obesity, and features of the metabolic syndrome. Several recent genome-wide association studies have reported an association between single-nucleotide polymorphism rs738409 in the (patatin-like phospholipase domain-containing protein 3) PNPLA3 gene and FLD. Liver attenuation (LA; hounsfield units, HU) by computed tomography is a non-invasive measure of liver fat, with lower values of HU indicating higher liver fat content. Clinically, a LA value of 40 HU indicates moderate-to-severe hepatic steatosis. OBJECTIVE: We investigated whether missense rs738409 PNPLA3 interacted with abdominal visceral adipose tissue (VAT) volume (cm) to reduce LA (that is, increased liver fat) in 1019 European American men and 1238 European American women from the Family Heart Study. METHODS: We used linear regression to test the additive effect of genotype, abdominal VAT, and their multiplicative interaction on LA adjusted for age, body mass index, high-density lipoprotein-cholesterol, insulin resistance, serum triglycerides, abdominal subcutaneous adipose tissue and alcohol intake. RESULTS: In men and women combined, the interaction between each copy of the rs738409 variant allele (minor allele frequency 0.23) and 100 cm/150 mm slice VAT decreased LA by 2.68±0.35 HU (P<0.01). The interaction of 100 cm VAT and the variant allele was associated with a greater decrease in LA in women than men (-4.8±0.6 and -2.2±0.5 HU, respectively). CONCLUSIONS: The interaction between genotype and VAT volume suggest key differences in the role of PNPLA3 genotype in conjunction with abdominal VAT in liver fat accrual. The stronger association of the PNPLA3 genotype and liver fat in women suggests that women may be more sensitive to liver fat accumulation in the setting of increased visceral fat, compared with men. The presence of the PNPLA3 variant genotype, particularly in the context of high VAT content may have an important role in FLD.

Genome-wide meta-analyses of smoking behaviors in African Americans.

The identification and exploration of genetic loci that influence smoking behaviors have been conducted primarily in populations of the European ancestry. Here we report results of the first genome-wide association study meta-analysis of smoking behavior in African Americans in the Study of Tobacco in Minority Populations Genetics Consortium (n = 32,389). We identified one non-coding single-nucleotide polymorphism (SNP; rs2036527[A]) on chromosome 15q25.1 associated with smoking quantity (cigarettes per day), which exceeded genome-wide significance (ß = 0.040, s.e. = 0.007, P = 1.84 × 10(-8)). This variant is present in the 5'-distal enhancer region of the CHRNA5 gene and defines the primary index signal reported in studies of the European ancestry. No other SNP reached genome-wide significance for smoking initiation (SI, ever vs never smoking), age of SI, or smoking cessation (SC, former vs current smoking). Informative associations that approached genome-wide significance included three modestly correlated variants, at 15q25.1 within PSMA4, CHRNA5 and CHRNA3 for smoking quantity, which are associated with a second signal previously reported in studies in European ancestry populations, and a signal represented by three SNPs in the SPOCK2 gene on chr10q22.1. The association at 15q25.1 confirms this region as an important susceptibility locus for smoking quantity in men and women of African ancestry. Larger studies will be needed to validate the suggestive loci that did not reach genome-wide significance and further elucidate the contribution of genetic variation to disparities in cigarette consumption, SC and smoking-attributable disease between African Americans and European Americans.

Age at menarche and risk of type 2 diabetes among African-American and white women in the Atherosclerosis Risk in Communities (ARIC) study.

AIMS/HYPOTHESIS: We examined race differences in the association between age at menarche and type 2 diabetes before and after adjustment for adiposity. METHODS: We analysed baseline and 9-year follow-up data from 8,491 women (n = 2,505 African-American, mean age 53.3 years; n = 5,986 white, mean age 54.0 years) in the Atherosclerosis Risk in Communities (ARIC) study. Stratifying by race, we used logistic regression to estimate the OR for prevalent diabetes at baseline, and Cox proportional hazard models to estimate the HR for incident diabetes over follow-up according to age at menarche category (8-11, 12, 13, 14 and 15-18 years). RESULTS: Adjusting for age and centre, we found that early age at menarche (8-11 vs 13 years) was associated with diabetes for white, but not African-American women in both the prevalent (white OR 1.72, 95% CI 1.32, 2.25; African-American OR 1.13, 95% CI 0.84, 1.51; interaction p = 0.043) and incident models (white HR 1.43, 95% CI 1.08, 1.89; African-American HR 1.20, 95% CI 0.87, 1.67; interaction p = 0.527). Adjustment for adiposity and lifestyle confounders attenuated associations for prevalent (white OR 1.41, 95% CI 1.05, 1.89; African-American OR 0.94, 95% CI 0.68, 1.30; interaction p = 0.093) and incident diabetes (white HR 1.22, 95% CI 0.92, 1.63; African-American HR 1.11, 95% CI 0.80, 1.56; interaction p = 0.554). CONCLUSIONS/INTERPRETATION: Early menarche was associated with type 2 diabetes in white women, and adulthood adiposity attenuated the relationship. We did not find a similar association in African-American women. Our findings suggest that there may be race/ethnic differences in the influence of developmental factors in the aetiology of type 2 diabetes, which merit further investigation.

Modelling honeybee visual guidance in a 3-D environment.

In view of the behavioral findings published on bees during the last two decades, it was proposed to decipher the principles underlying bees' autopilot system, focusing in particular on these insects' use of the optic flow (OF). Based on computer-simulated experiments, we developed a vision-based autopilot that enables a "simulated bee" to travel along a tunnel, controlling both its speed and its clearance from the right wall, left wall, ground, and roof. The flying agent thus equipped enjoys three translational degrees of freedom on the surge (x), sway (y), and heave (z) axes, which are uncoupled. This visuo-motor control system, which is called ALIS (AutopiLot using an Insect based vision System), is a dual OF regulator consisting of two interdependent feedback loops, each of which has its own OF set-point. The experiments presented here showed that the simulated bee was able to navigate safely along a straight or tapered tunnel and to react appropriately to any untoward OF perturbations, such as those resulting from the occasional lack of texture on one wall or the tapering of the tunnel. The minimalistic visual system used here (involving only eight pixels) suffices to jointly control both the clearance from the four walls and the forward speed, without having to measure any speeds or distances. The OF sensors and the simple visuo-motor control system we have developed account well for the results of ethological studies performed on honeybees flying freely along straight and tapered corridors.

Clinical and pathologic characteristics of focal segmental glomerulosclerosis pathologic variants.

Histologic variants of idiopathic focal segmental glomerulosclerosis (FSGS) may have prognostic value. A recent working classification system has distinguished five FSGS variants. We evaluated a cohort of adult patients with biopsy-proven FSGS diagnosed between March 1982 and July 2001 to determine if subtypes were associated with renal outcome. Renal biopsies were reviewed by two pathologists. Demographic and clinical data were obtained from charts. Outcomes were partial and complete remission of the nephrotic syndrome, and renal failure. The frequency of FSGS variants was: 3% cellular (N=6), 11% collapsing (N=22), 17% tip lesion (N=34), 26% perihilar (N=52), and 42% not otherwise specified (NOS) (N=83). Collapsing FSGS affected younger and more often black patients. Black race was uncommon in tip variant. Collapsing and tip variants had higher proteinuria and lower serum albumin than perihilar and NOS variants. Better renal function and less severe tubulointerstitial injury were observed in patients with tip variant. These patients were more likely to receive steroids and more often achieved complete remission (50%). After a median follow-up of 1.8 years, 23% of patients were on dialysis and 28% had renal failure. Collapsing FSGS had worse 1-year (74%) and 3-year (33%) renal survival compared to other variants (overall cohort renal survival at 1 and 3 years: 86 and 67%). Different histologic variants of FSGS have substantial differences in clinical features at the time of biopsy diagnosis and substantial differences in renal outcomes.

Role of Cys221 and Asn116 in the zinc-binding sites of the Aeromonas hydrophila metallo-beta-lactamase.

The CphA metallo-beta-lactamase produced by Aeromonas hydrophila exhibits two zinc-binding sites. Maximum activity is obtained upon binding of one zinc ion, whereas binding of the second zinc ion results in a drastic decrease in the hydrolytic activity. In this study, we analyzed the role of Asn116 and Cys221, two residues of the active site. These residues were replaced by site-directed mutagenesis and the different mutants were characterized. The C221S and C221A mutants were seriously impaired in their ability to bind the first, catalytic zinc ion and were nearly completely inactive, indicating a major role for Cys221 in the binding of the catalytic metal ion. By contrast, the binding of the second zinc ion was only slightly affected, at least for the C221S mutant. Mutation of Asn116 did not lead to a drastic decrease in the hydrolytic activity, indicating that this residue does not play a key role in the catalytic mechanism. However, the substitution of Asn116 by a Cys or His residue resulted in an approximately fivefold increase in the affinity for the second, inhibitory zinc ion. Together, these data suggested that the first zinc ion is located in the binding site involving the Cys221 and that the second zinc ion binds in the binding site involving Asn116 and, presumably, His118 and His196.

Meropenem stability to beta-lactamase hydrolysis and comparative in vitro activity against several beta-lactamase-producing Gram-negative strains.

The interaction between meropenem and class A, B, C and D beta-lactamases was studied by a spectrophotometric method. Class A, C and D beta-lactamases were unable to confer in vitro resistance to carbapenems. Surprisingly, several class B metallo-beta-lactamases expressed in Escherichia coli failed to confer resistance when a conventional inoculum (105 cfu/mL) was used.

Characterization of OXA-29 from Legionella (Fluoribacter) gormanii: molecular class D beta-lactamase with unusual properties.

A class D beta-lactamase determinant was isolated from the genome of Legionella (Fluoribacter) gormanii ATCC 33297(T). The enzyme, named OXA-29, is quite divergent from other class D beta-lactamases, being more similar (33 to 43% amino acid identity) to those of groups III (OXA-1) and IV (OXA-9, OXA-12, OXA-18, and OXA-22) than to other class D enzymes (21 to 24% sequence identity). Phylogenetic analysis confirmed the closer ancestry of OXA-29 with members of the former groups. The OXA-29 enzyme was purified from an Escherichia coli strain overexpressing the gene via a T7-based expression system by a single ion-exchange chromatography step on S-Sepharose. The mature enzyme consists of a 28.5-kDa polypeptide and exhibits an isoelectric pH of >9. Analysis of the kinetic parameters of OXA-29 revealed efficient activity (k(cat)/K(m) ratios of >10(5) M(-1) x s(-1)) for several penam compounds (oxacillin, methicillin, penicillin G, ampicillin, carbenicillin, and piperacillin) and also for cefazolin and nitrocefin. Oxyimino cephalosporins and aztreonam were also hydrolyzed, although less efficiently (k(cat)/K(m) ratios of around 10(3) M(-1) x s(-1)). Carbapenems were neither hydrolyzed nor inhibitory. OXA-29 was inhibited by BRL 42715 (50% inhibitory concentration [IC(50)], 0.44 microM) and by tazobactam (IC(50), 3.2 microM), but not by clavulanate. It was also unusually resistant to chloride ions (IC(50), >100 mM). Unlike OXA-10, OXA-29 was apparently found as a dimer both in diluted solutions and in the presence of EDTA. Its activity was either unaffected or inhibited by divalent cations. OXA-29 is a new class D beta-lactamase that exhibits some unusual properties likely reflecting original structural and mechanistic features.

Age differences and developmental trends in alarm peep responses by squirrel monkeys (Saimiri sciureus).

Alarm calls can code for different classes of predators or different types of predatory threat. Acoustic information can also encode the urgency of threat through variations in acoustic features within specific alarm call types. Squirrel monkeys (Saimiri sciureus) produce an alarm call, known as the alarm peep, in highly threatening situations. Infant squirrel monkeys appear to have an innate predisposition to respond to alarm peeps but require experience to associate alarm peeps with the appropriate type of predatory threat [Herzog & Hopf, American Journal of Primatology 7:99-106, 1984]. Little is known about age-related differences in the type or frequency of response to alarm peeps, or the development of alarm peep response in infants. The purpose of this study was to test experimentally the response strategies of different age classes of squirrel monkey to the playback of alarm peeps that were produced by infants, juveniles, or adults. Results suggest that infants, juveniles, and female subadults respond more frequently to alarm peeps than do adult females. Infant squirrel monkeys showed different behavioral strategies in response to alarm peeps as a function of age. Adult females differentiate between infant and adult alarm peeps by responding more frequently to the alarm peeps of adult females. These data demonstrate that squirrel monkeys use acoustic information to discern when to respond to the alarm peeps from conspecifics, and that infants gradually develop an adult-like response to alarm peeps over the first year of development.

Ceftibuten stability to active-site serine and metallo-beta-lactamases.

Ceftibuten is an oral third-generation cephalosporin active against a wide range of bacteria and shows an improved stability to hydrolysis by several beta-lactamases because of the carboxyethilidine moiety at position 7 of the ss-acyl side chain. The kinetic interactions between ceftibuten and active-site serine and metallo-ss-lactamases were investigated. The activity of several TEM-derived extended spectrum beta-lactamases (ESbetaLs) against ceftibuten, cefotaxime and ceftazidime was compared using K(m), K(cat) and K(cat)/K(m). Ceftibuten behaved as a poor substrate for class A and B beta-lactamases compared with cefotaxime. The chromosomal class C beta-lactamase from Enterobacter cloacae 908R gave a high K(cat) value (21 s(-1)), whereas there was poor activity with enzymes from Acinetobacter baumannii and Morganella morganii and ceftibuten. Ceftibuten resists hydrolysis in the presence of typical respiratory or urogenital-tract pathogens producing beta-lactamases.

Purification and biochemical characterization of the VIM-1 metallo-beta-lactamase.

VIM-1 is a new group 3 metallo-beta-lactamase recently detected in carbapenem-resistant nosocomial isolates of Pseudomonas aeruginosa from the Mediterranean area. In this work, VIM-1 was purified from an Escherichia coli strain carrying the cloned bla(VIM-1) gene by means of an anion-exchange chromatography step followed by a gel permeation chromatography step. The purified enzyme exhibited a molecular mass of 26 kDa in sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and an acidic pI of 5.1 in analytical isoelectric focusing. Amino-terminal sequencing showed that mature VIM-1 results from the removal of a 26-amino-acid signal peptide from the precursor. VIM-1 hydrolyzes a broad array of beta-lactam compounds, including penicillins, narrow- to expanded-spectrum cephalosporins, carbapenems, and mechanism-based serine-beta-lactamase inactivators. Only monobactams escape hydrolysis. The highest catalytic constant/K(m) ratios (>10(6) M(-1). s(-1)) were observed with carbenicillin, azlocillin, some cephalosporins (cephaloridine, cephalothin, cefuroxime, cefepime, and cefpirome), imipenem, and biapenem. Kinetic parameters showed remarkable variability with different beta-lactams and also within the various penam, cephem, and carbapenem compounds, resulting in no clear preference of the enzyme for any of these beta-lactam subfamilies. Significant differences were observed with some substrates between the kinetic parameters of VIM-1 and those of other metallo-beta-lactamases. Inactivation assays carried out with various chelating agents (EDTA, 1,10-o-phenanthroline, and pyridine-2,6-dicarboxylic acid) indicated that formation of a ternary enzyme-metal-chelator complex precedes metal removal from the zinc center of the protein and revealed notable differences in the inactivation parameters of VIM-1 with different agents.