Elizabeth McKenzie

Trace metal chemistry and silicification of microorganisms in geothermal sinter, Taupo Volcanic Zone, New Zealand

Abstract As part of a pilot study investigating the role of microorganisms in the immobilisation of As, Sb, B, Tl and Hg, the inorganic geochemistry of seven different active sinter deposits and their contact fluids were characterised. A comprehensive series of sequential extractions for a suite of trace elements was carried out on siliceous sinter and a mixed silica-carbonate sinter. The extractions showed whether metals were loosely exchangeable or bound to carbonate, oxide, organic or crystalline fractions. Hyperthermophilic microbial communities associated with sinters deposited from high temperature (92–94°C) fluids at a variety of geothermal sources were investigated using SEM. The rapidity and style of silicification of the hyperthermophiles can be correlated with the dissolved silica content of the fluid. Although high concentrations of Hg and Tl were found associated with the organic fraction of the sinters, there was no evidence to suggest that any of the heavy metals were associated preferentially with the hyperthermophiles at the high temperature (92–94°C) ends of the terrestrial thermal spring ecosystems studied.

Maternal Dietary Patterns and Gestational Diabetes Mellitus in a Multi-Ethnic Asian Cohort: The GUSTO Study

Gestational Diabetes Mellitus (GDM) is associated with an increased risk of perinatal morbidity and long term health issues for both the mother and offspring. Previous research has demonstrated associations between maternal diet and GDM development, but evidence in Asian populations is limited. The objective of our study was to examine the cross-sectional relationship between maternal dietary patterns during pregnancy and the risk of GDM in a multi-ethnic Asian cohort. Maternal diet was ascertained using 24-h dietary recalls from participants in the Growing up in Singapore towards healthy outcomes (GUSTO) study—a prospective mother-offspring cohort, and GDM was diagnosed according to 1999 World Health Organisation guidelines. Dietary patterns were identified using factor analysis, and multivariate regression analyses performed to assess the association with GDM. Of 909 participants, 17.6% were diagnosed with GDM. Three dietary patterns were identified: a vegetable-fruit-rice-based-diet, a seafood-noodle-based-diet and a pasta-cheese-processed-meat-diet. After adjusting for confounding variables, the seafood-noodle-based-diet was associated with a lower likelihood of GDM (Odds Ratio (95% Confidence Interval)) = 0.74 (0.59, 0.93). The dietary pattern found to be associated with GDM in our study was substantially different to those reported previously in Western populations.

Detection of methamphetamine in indoor air using dynamic solid phase microextraction: a supplementary method to surface wipe sampling

Surface wipe sampling for methamphetamine is a standard protocol in many jurisdictions for sampling at suspected or known former clandestine methamphetamine laboratories, but this method relies on samples being taken from representatively contaminated surfaces. We have investigated whether a rapid sampling method for airborne methamphetamine can be used to supplement surface sampling. A dynamic solid phase microextraction (SPME) field sampler was constructed and tested in the field and in the laboratory. This device enabled large volumes of air to be passed over SPME fibres exposed during the comparatively short time (<2 h) that a testing company might be present at a former clandestine laboratory. The collected samples were then analyzed by gas chromatography-mass spectrometry. Airborne methamphetamine was detected with this method at former clandestine methamphetamine laboratory sites where surface wipe sampling showed surface methamphetamine concentrations greater than 40 μg/100 cm2.

Metabolite Profile of Cervicovaginal Fluids from Early Pregnancy Is Not Predictive of Spontaneous Preterm Birth

In our study, we used a mass spectrometry-based metabolomic approach to search for biomarkers that may act as early indicators of spontaneous preterm birth (sPTB). Samples were selected as a nested case-control study from the Screening for Pregnancy Endpoints (SCOPE) biobank in Auckland, New Zealand. Cervicovaginal swabs were collected at 20 weeks from women who were originally assessed as being at low risk of sPTB. Samples were analysed using gas chromatography-mass spectrometry (GC-MS). Despite the low amount of biomass (16–23 mg), 112 compounds were detected. Statistical analysis showed no significant correlations with sPTB. Comparison of reported infection and plasma inflammatory markers from early pregnancy showed two inflammatory markers were correlated with reported infection, but no correlation with any compounds in the metabolite profile was observed. We hypothesise that the lack of biomarkers of sPTB in the cervicovaginal fluid metabolome is simply because it lacks such markers in early pregnancy. We propose alternative biofluids be investigated for markers of sPTB. Our results lead us to call for greater scrutiny of previously published metabolomic data relating to biomarkers of sPTB in cervicovaginal fluids, as the use of small, high risk, or late pregnancy cohorts may identify metabolite biomarkers that are irrelevant for predicting risk in normal populations.

Association between maternal exposure to phthalates and lower language ability in offspring derived from hair metabolome analysis

The fetus undergoes a crucial period of neurodevelopment in utero. The maternal hair metabolome provides an integrated record of the metabolic state of the mother prior to, and during pregnancy. We investigated whether variation in the maternal hair metabolome was associated with neurodevelopmental differences across infants. Maternal hair samples and infant neurocognitive assessments (using the Bayley III Scales of Infant Development at 24 months) were obtained for 373 infant-mother dyads between 26–28 weeks’ gestation from the Growing Up in Singapore Towards Healthy Outcomes cohort. The hair metabolome was analysed using gas chromatography-mass spectrometry. Intensity measurements were obtained for 276 compounds. After controlling for maternal education, ethnicity, and infant sex, associations between metabolites and expressive language skills were detected, but not for receptive language, cognitive or motor skills. The results confirm previous research associating higher levels of phthalates with lower language ability. In addition, scores were positively associated with a cluster of compounds, including adipic acid and medium-chain fatty acids. The data support associations between the maternal hair metabolome and neurodevelopmental processes of the fetus. The association between phthalates and lower language ability highlights a modifiable risk factor that warrants further investigation.

Dynamic solid phase microextraction analysis for airborne methamphetamine: quantitation using isotopically substituted methamphetamine

A vapour dosing system was developed that gave constant concentrations of methamphetamine in the range 1 to 10 μg m−3. This was used to calibrate the response of solid phase microextraction (SPME) fibres in passive and dynamic sampling modes. Exposure of 100 μm polydimethylsiloxane SPME fibres to a constant concentration of 1–5 μg m−3 methamphetamine over 1–70 min followed by GC-MS analysis produced a curvilinear pre-steady state sorption curve sufficiently reproducible to enable calibration of the SPME absorption. There was no evidence for loss of methamphetamine from the polydimethylsiloxane fibre under static ambient conditions for 5 h or during exposure to 1 L min−1 airflow in a dynamic SPME sampler for 90 min at room temperature. Sequential exposure of SPME fibres to methamphetamine and d9-methamphetamine showed that both analytes were retained. These results demonstrate that solid phase microextraction can be used with pre-loaded isotopically substituted methamphetamine as an internal standard for accurate quantitation of airborne methamphetamine. The isotopic labeling experiments also showed that the dosing system had a small but significant reservoir of methamphetamine, even though it was constructed from mainly inert materials and much of it was at elevated temperature. We therefore recommend that separate vapour dosing units be used for labeled and unlabeled methamphetamine.

Maternal circulating vitamin status and colostrum vitamin composition in healthy lactating women—A systematic approach

Colostrum is the first ingested sole nutritional source for the newborn infant. The vitamin profile of colostrum depends on the maternal vitamin status, which in turn is influenced by diet and lifestyle. Yet, the relationship between maternal vitamin status and colostrum vitamin composition has not been systematically reviewed. This review was conducted with the aim to generate a comprehensive overview on the relationship between maternal serum (plasma) vitamin concentration and corresponding colostrum composition. Three electronic databases, Embase (Ovid), Medline (Ovid), and Cochrane, were systematically searched based on predefined inclusion and exclusion criteria. Finally, a total of 11 eligible publications were included that examined the vitamins A, C, D, E, and K in both biological fluids. Maternal vitamin A, D, E, and K blood levels were unrelated to colostrum content of the respective vitamins, and serum vitamin A was inversely correlated with colostrum vitamin E. Colostrum versus maternal serum vitamins were higher for vitamins A, C, and K, lower for vitamin D, and divergent results were reported for vitamin E levels. Colostrum appears typically enriched in vitamin A, C, and K compared to maternal serum, possibly indicative of active mammary gland transport mechanisms. Inter-individual and inter-study high variability in colostrum’s vitamin content endorses its sensitivity to external factors.

Using the Food Metabolome to Understand the Relationship Between Maternal Diet and Gestational Diabetes

Maternal diet has been associated with the development and progression of GDM and as a result, provides a great avenue for exploring prevention strategies. However, the current state of the literature investigating maternal diet and GDM relies heavily on observational studies and, as a whole, is inconclusive and in some instances, conflicting. To better understand the relationship between maternal diet and GDM, a less subjective measure needs to be established. Metabolomics, the study of low-weight organic molecules, is an analytical approach that can be used to objectively identify diet-related biomarkers of GDM. The identification of diet-related biomarkers of GDM could lead to the development of personalised nutrition strategies for the prevention of GDM and its associated consequences. This chapter outlines the growing problem of GDM, and proposes the analysis of the food metabolome (the sum of the detectable metabolites found in the human system as a result of the ingestion and digestion of food components) for identifying dietary biomarkers of GDM, as well as elucidating the mechanisms underlying the relationship between maternal diet and GDM. This chapter also discusses the analytical considerations, and sampling methodology required to reproducibly analyse the food metabolome for linking the maternal diet with GDM. Biological samples to consider for analysis include blood, urine, amniotic fluid, saliva, hair and breath. Different analytical platforms can be used to analyse the food metabolome [e.g. nuclear magnetic resonance, mass spectrometry coupled to chromatographic separation (gas chromatography, liquid chromatography)], each has its own strengths. Using a combination of different platforms and extraction techniques will provide a more comprehensive view of the metabolome.