Trees adjust nutrient acquisition strategies across tropical forest secondary succession

Nutrient limitation may constrain the ability of recovering and mature tropical forests to serve as a carbon sink. However, it is unclear to what extent trees can utilize nutrient acquisition strategies - especially root phosphatase enzymes and mycorrhizal symbioses - to overcome low nutrient availability across secondary succession. Using a large-scale, full factorial nitrogen and phosphorus fertilization experiment of 76 plots along a secondary successional gradient in lowland wet tropical forests of Panama, we tested the extent to which root phosphatase enzyme activity and mycorrhizal colonization are flexible, and if investment shifts over succession, reflective of changing nutrient limitation. We also conducted a meta-analysis to test how tropical trees adjust these strategies in response to nutrient additions and across succession. We find that tropical trees are dynamic, adjusting investment in strategies - particularly root phosphatase - in response to changing nutrient conditions through succession. These changes reflect a shift from strong nitrogen to weak phosphorus limitation over succession. Our meta-analysis findings were consistent with our field study; we found more predictable responses of root phosphatase than mycorrhizal colonization to nutrient availability. Our findings suggest that nutrient acquisition strategies respond to nutrient availability and demand in tropical forests, likely critical for alleviating nutrient limitation.

Toward a coordinated understanding of hydro-biogeochemical root functions in tropical forests for application in vegetation models

Tropical forest root characteristics and resource acquisition strategies are underrepresented in vegetation and global models, hampering the prediction of forest-climate feedbacks for these carbon-rich ecosystems. Lowland tropical forests often have globally unique combinations of high taxonomic and functional biodiversity, rainfall seasonality, and strongly weathered infertile soils, giving rise to distinct patterns in root traits and functions compared with higher latitude ecosystems. We provide a roadmap for integrating recent advances in our understanding of tropical forest belowground function into vegetation models, focusing on water and nutrient acquisition. We offer comparisons of recent advances in empirical and model understanding of root characteristics that represent important functional processes in tropical forests. We focus on: (1) fine-root strategies for soil resource exploration, (2) coupling and trade-offs in fine-root water vs nutrient acquisition, and (3) aboveground-belowground linkages in plant resource acquisition and use. We suggest avenues for representing these extremely diverse plant communities in computationally manageable and ecologically meaningful groups in models for linked aboveground-belowground hydro-nutrient functions. Tropical forests are undergoing warming, shifting rainfall regimes, and exacerbation of soil nutrient scarcity caused by elevated atmospheric CO2. The accurate model representation of tropical forest functions is crucial for understanding the interactions of this biome with the climate.

Intraspecific trait variability facilitates tree species persistence along riparian forest edges in Southern Amazonia

Tropical forest fragmentation from agricultural expansion alters the microclimatic conditions of the remaining forests, with effects on vegetation structure and function. However, little is known about how the functional trait variability within and among tree species in fragmented landscapes influence and facilitate species' persistence in these new environmental conditions. Here, we assessed potential changes in tree species' functional traits in riparian forests within six riparian forests in cropland catchments (Cropland) and four riparian forests in forested catchments (Forest) in southern Amazonia. We sampled 12 common functional traits of 123 species across all sites: 64 common to both croplands and forests, 33 restricted to croplands, and 26 restricted to forests. We found that forest-restricted species had leaves that were thinner, larger, and with higher phosphorus (P) content, compared to cropland-restricted ones. Tree species common to both environments showed higher intraspecific variability in functional traits, with leaf thickness and leaf P concentration varying the most. Species turnover contributed more to differences between forest and cropland environments only for the stem-specific density trait. We conclude that the intraspecific variability of functional traits (leaf thickness, leaf P, and specific leaf area) facilitates species persistence in riparian forests occurring within catchments cleared for agricultural expansion in Amazonia.

Fire decreases soil enzyme activities and reorganizes microbially-mediated nutrient cycles: A meta-analysis

The biogeochemical signature of fire shapes the functioning of many ecosystems. Fire changes nutrient cycles not only by volatilizing plant material, but also by altering organic matter decomposition-a process regulated by soil extracellular enzyme activities (EEAs). However, our understanding of fire effects on EEAs and their feedbacks to nutrient cycles is incomplete. We conducted a meta-analysis with 301 field studies and found that fire significantly decreased EEAs by ~20-40%. Fire decreased EEAs by reducing soil microbial biomass and organic matter substrates. Soil nitrogen-acquiring EEA declined alongside decreasing available nitrogen, likely from fire-driven volatilization of nitrogen and decreased microbial activity. Fire decreased soil phosphorus-acquiring EEA but increased available phosphorus, likely from pyro-mineralization of organic phosphorus. These findings suggest that fire suppresses soil microbes and consumes their substrates, thereby slowing microbially-mediated nutrient cycles (especially phosphorus) via decreased EEAs. These changes can become increasingly important as fire frequency and severity in many ecosystems continue to shift in response to global change.

A review of carbon farming impacts on nitrogen cycling, retention, and loss

Soil carbon (C) sequestration in agricultural working lands via soil amendments and management practices is considered a relatively well-tested and affordable approach for removing CO₂ from the atmosphere. Carbon farming provides useful benefits for soil health, biomass production, and crop resilience, but the effects of different soil C sequestration approaches on the nitrogen (N) cycle remain controversial. While some C farming practices have been shown to reduce N fertilizer use in some cases, C farming could also impose an unwanted "N penalty" through which soil C gains can only be maintained with additional N inputs, thereby increasing N losses to the environment. We systematically reviewed meta-analysis studies on the impacts of C farming on N cycling in agroecosystems and estimated the cumulative effect of several C farming practices on N cycling. We found that, on average, combined C farming practices significantly reduced nitrous oxide emissions and nitrate leaching from soils, thus inferring both N cycling and climate change benefits. In addition to more widely studied C farming practices that generate organic C, we also discuss silicate rock additions, which offer a pathway to inorganic C sequestration that does not require additional N inputs, framing important questions for future research.

Molybdenum, phosphorus, and pH do not constrain nitrogen fixation in a tropical forest in the southeastern Amazon

High rates of biological nitrogen fixation (BNF) are commonly reported for tropical forests, but most studies have been conducted in regions that receive substantial inputs of molybdenum (Mo) from atmospheric dust and sea-salt aerosols. Even in these regions, the low availability of Mo can constrain free-living BNF catalyzed by heterotrophic bacteria and archaea. We hypothesized that in regions where atmospheric inputs of Mo are low and soils are highly weathered, such as the southeastern Amazon, Mo would constrain BNF. We also hypothesized that the high soil acidity, characteristic of the Amazon Basin, would further constrain Mo availability and therefore soil BNF. We conducted two field experiments across the wet and dry seasons, adding Mo, phosphorus (P), and lime alone and in combination to the forest floor in the southeastern Amazon. We sampled soils and litter immediately, and then weeks and months after the applications, and measured Mo and P availability through resin extractions and BNF with the acetylene reduction assay. The experimental additions of Mo and P increased their availability and the lime increased soil pH. While the combination of Mo and P increased BNF at some time points, BNF rates did not increase strongly or consistently across the study as a whole, suggesting that Mo, P, and soil pH are not the dominant controls over BNF. In a separate short-term laboratory experiment, BNF did not respond strongly to Mo and P even when labile carbon was added. We postulate that high nitrogen (N) availability in this area of the Amazon, as indicated by the stoichiometry of soils and vegetation and the high nitrate soil stocks, likely suppresses BNF at this site. These patterns may also extend across highly weathered soils with high N availability in other topographically stable regions of the tropics.

Looking back to look ahead: a vision for soil denitrification research

Denitrification plays a critical role in regulating ecosystem nutrient availability and anthropogenic reactive nitrogen (N) production. Its importance has inspired an increasing number of studies, yet it remains the most poorly constrained term in terrestrial ecosystem N budgets. We censused the peer-reviewed soil denitrification literature (1975-2015) to identify opportunities for future studies to advance our understanding despite the inherent challenges in studying the process. We found that only one-third of studies reported estimates of both nitrous oxide (N₂ O) and dinitrogen (N₂ ) production fluxes, often the dominant end products of denitrification, while the majority of studies reported only net N₂ O fluxes or denitrification potential. Of the 236 studies that measured complete denitrification to N₂ , 49% used the acetylene inhibition method, 84% were conducted in the laboratory, 81% were performed on surface soils (0-20 cm depth), 75% were located in North America and Europe, and 78% performed treatment manipulations, mostly of N, carbon, or water. To improve understanding of soil denitrification, we recommend broadening access to technologies for new methodologies to measure soil N₂ production rates, conducting more studies in the tropics and on subsoils, performing standardized experiments on unmanipulated soils, and using more precise terminology to refer to measured process rates (e.g., net N₂ O flux or denitrification potential). To overcome the greater challenges in studying soil denitrification, we envision coordinated research efforts based on standard reporting of metadata for all soil denitrification studies, standard protocols for studies contributing to a Global Denitrification Research Network, and a global consortium of denitrification researchers to facilitate sharing ideas, resources, and to provide mentorship for researchers new to the field.

New approaches to obtaining individual peak height velocity and age at peak height velocity from the SITAR model

OBJECTIVE

We compared three methods for estimating the individual peak height velocity (PHV) and age at peak height velocity (APHV) from the SuperImposition by Translation and Rotation (SITAR) model.

METHODS

We fitted the SITAR model using simulated data and heights of 12 girls from the Chard Growth Study and obtained individual PHVs and APHVs from three methods: the model method, the quadratic function method and the numerical method, which are available in our newly developed R package"iapvbs". The mean, interquartile range, range of biases in estimated APHV and PHV as well as the rates of warning and unreasonable cases, i.e. estimated APHVs being outside the range of age measurements, from the three methods were presented and compared.

RESULTS

When the growth curves of all individuals were well fitted by the SITAR model, all three methods estimated individual APHVs with similarly small biases, with a few unreasonable cases (0.16%) observed when the model method was used while more computation time required for the numerical method. When the growth curves of some individuals were not very well fitted, the model method generated more unreasonable individual APHV (8.15%) and more bias in PHV and APHV, compared to those estimated by the numerical method and quadratic function method. In line with the observations from the simulated data, the real data analysis demonstrated that the numerical method generated more reliable PHV and APHV for individuals with growth curve not well fitted by the SITAR model.

CONCLUSION

The performance of different methods estimating individual APHV depends largely on how well the growth curves are fitted by the SITAR model. The quadratic function method is more superior when growth curves of all individuals are well fitted by the SITAR model; otherwise, the numerical method should be adopted for getting most robust estimates of PHV and APHV. The model method generates unreasonable APHV estimates, particularly when the growth curves are not well fitted.

Collaborative Study of a Proposed International Standard for Plasma Fibrinogen Measurement

There is increased interest in the relationship between plasma fibrinogen levels and the incidence of coronary artery disease. The National Institute for Biological Standards and Control (UK) has completed a study to establish an International Standard for plasma fibrinogen. This study was conducted using a recommended assay procedure to measure the clottable material present in the proposed lyophilised Standard (coded 89/644). Twenty-two laboratories from nine countries took part in the study and analysis of the data allowed the calibration of 89/644 at 2.4 mg/ml clottable protein. Agreement with this figure was established in two laboratories using three or more different assays for plasma fibrinogen. Degradation studies of the proposed plasma fibrinogen Standard suggested that no loss of clottable protein was observed when the lyophilised material was stored at 20° C for 1 year.

The Fibrinogen Sub-Committee of the ISTH (Amsterdam, The Netherlands, June 1991) supported the establishment of 89/644 as an International Standard. This collaborative study will be presented to the Expert Committee on Biological Standardisation of the World Health Organisation at their 1992 session. In the meantime 89/644 will be distributed as the proposed International Standard for plasma fibrinogen measurement containing 2.4 mg/ ml clottable protein.

The Association of Intergenerational Mismatch With Adiposity and Blood Pressure in Childhood and Adolescence

PURPOSE

An intergenerational "mismatch," a transition from limited to plentiful living conditions over generations, may increase cardiovascular disease risks. In a migrant population within a homogenous culture, we tested the hypothesis that an intergenerational mismatch in childhood living condition is associated with higher body mass index (BMI) and blood pressure in childhood and adolescence.

METHODS

We used data from 6,965 native born Chinese in Hong Kong (participated in "Children of 1997" birth cohort) and migrant Chinese born elsewhere in China in 1997 (N = 9,845). We classified children into those with intergenerational mismatch (child migrants or first-generation migrants) or those without (second+-generation migrants). Generalized estimating equations were used to examine the associations of migration status (child migrants, first-generation migrants or second+-generation migrants) with age- and sex-specific BMI z-score at 8-15 years and age-, sex-, and height-specific blood pressure z-score at 11-13 years, adjusted for sex, month of birth, and age.

RESULTS

Compared with second+-generation migrants, first-generation migrants had higher diastolic blood pressure z-score (.04, 95% confidence interval (CI) .02, .06) and BMI z-score (.12, 95% CI .06, .18), whereas child migrants had higher diastolic blood pressure z-score (.03, 95% CI .01, .05) regardless of age at migration and higher BMI z-score if they had migrated in infancy (.17, 95% CI .11, .23).

CONCLUSION

Different relations for blood pressure and BMI suggest that intergenerational mismatch and proximal exposures may have different impacts on adiposity and blood pressure.

The Efficacy of Emergency Medicine Ward for the Management of Patients with Mental Disorders

Objective

Patients with mental disorders are one of the target groups selected for management in the Emergency Medicine Ward (EMW) with the enrolment of psychiatric advanced practice nurses. This study aimed to determine whether the EMW can be efficiently used for the management of patients with mental disorders in terms of length of stay (LOS), admission rate, and re-attendance rate when compared with the medical ward.

Methods

This was a retrospective descriptive study. Patients with mental disorders were defined and recruited from the Princess Margaret Hospital during two selected study periods: pre-opening (pre-EMW) and post-opening (post-EMW) of the EMW. All emergency department records of patients with mental disorders within these two periods were reviewed and data of the selected samples were retrieved from different computer databases.

Results

The total number of patients with mental disorders was 565 in the pre-EMW period and 404 in the post-EMW period; 214 (37.9%) cases were admitted into the medical ward in the pre-EMW period while only 62 (15.3%) were admitted into the medical ward in the post-EMW period. The mean LOS in the pre-EMW period was 67.7 hours. For the post-EMW period, the mean LOS was 32.3 hours. The reduction in mean LOS was 35.4 hours, and 82% of the study patients treated in the EMW were discharged within 48 hours. Notably, 23.3% of the cases re-attended the emergency department after discharge from the medical ward, whereas only 8.8% of cases re-attended after discharge from the EMW.

Conclusion

Patients with mental disorders or related problems can be efficaciously managed in the EMW, as evidenced by a decrease in the length of stay, admission rate, and re-attendance rate.

Aetiological bases of 46,XY disorders of sex development in the Hong Kong Chinese population

OBJECTIVE

Disorders of sex development are due to congenital defects in chromosomal, gonadal, or anatomical sex development. The objective of this study was to determine the aetiology of this group of disorders in the Hong Kong Chinese population.

SETTING

Five public hospitals in Hong Kong.

PATIENTS

Patients with 46,XY disorders of sex development under the care of paediatric endocrinologists between July 2009 and June 2011.

MAIN OUTCOME MEASURES

Measurement of serum gonadotropins, adrenal and testicular hormones, and urinary steroid profiling. Mutational analysis of genes involved in sexual differentiation by direct DNA sequencing and multiplex ligation-dependent probe amplification.

RESULTS

Overall, 64 patients were recruited for the study. Their age at presentation ranged from birth to 17 years. The majority presented with ambiguous external genitalia including micropenis and severe hypospadias. A few presented with delayed puberty and primary amenorrhea. Baseline and post-human chorionic gonadotropin-stimulated testosterone and dihydrotestosterone levels were not discriminatory in patients with or without AR gene mutations. Of the patients, 22 had a confirmed genetic disease, with 11 having 5α-reductase 2 deficiency, seven with androgen insensitivity syndrome, one each with cholesterol side-chain cleavage enzyme deficiency, Frasier syndrome, NR5A1-related sex reversal, and persistent Müllerian duct syndrome.

CONCLUSIONS

Our findings suggest that 5α-reductase 2 deficiency and androgen insensitivity syndrome are possibly the two most common causes of 46,XY disorders of sex development in the Hong Kong Chinese population. Since hormonal findings can be unreliable, mutational analysis of the SRD5A2 and AR genes should be considered the first-line tests for these patients.

The Association of Infant Growth Patterns with Adiposity in Adolescence: Prospective Observations from Hong Kong's 'Children of 1997' Birth Cohort

BACKGROUND

The role of infant growth in adiposity remains unclear.

METHODS

We used multivariable linear regression, with inverse probability weighting and multiple imputation to account for loss to follow-up, in a population-representative Chinese birth cohort, 'Children of 1997' in Hong Kong, to examine, in terms births, the adjusted association of infant (birth to 12 months) weight growth trajectories with body mass index (BMI) (n = 6861, 88% follow-up), waist-to-height ratio (WHtR), and waist-to-hip ratio (WHR) (n = 5398, 69% follow-up) at ∼ 14 years.

RESULTS

Infant weight growth trajectories had graded associations with adolescent BMI and WHtR but not with WHR, such that compared with adolescents born light with slow infant growth, adolescents born heavy with fast infant growth had higher BMI z-score [0.60, 95% confidence interval (CI) 0.49, 0.70], higher WHtR z-score (0.17, 95% CI 0.08, 0.26) but similar WHR z-score (-0.02, 95% CI -0.11, 0.08), adjusted for sex, gestational age, parental education, parental BMI, parental height, and parental place of birth.

CONCLUSIONS

Varying associations of infant growth with different adiposity measures suggest a complex role of infant growth in long-term health, perhaps because infant growth, or its underlying drivers, influences build and body composition as well as adiposity.

Dopamine-dependent corticostriatal synaptic filtering regulates sensorimotor behavior

Modulation of corticostriatal synaptic activity by dopamine is required for normal sensorimotor behaviors. After loss of nigrostriatal dopamine axons in Parkinson's disease, l-3,4-dihydroxyphenlalanine (l-DOPA) and dopamine D2-like receptor agonists are used as replacement therapy, although these drugs also trigger sensitized sensorimotor responses including dyskinesias and impulse control disorders. In mice, we lesioned dopamine projections to the left dorsal striatum and assayed unilateral sensorimotor deficits with the corridor test as well as presynaptic corticostriatal activity with the synaptic vesicle probe, FM1-43. Sham-lesioned mice acquired food equivalently on both sides, while D2 receptor activation filtered the less active corticostriatal terminals, a response that required coincident co-activation of mGlu-R5 metabotropic glutamate and CB1 endocannabinoid receptors. Lesioned mice did not acquire food from their right, but overused that side following treatment with l-DOPA. Synaptic filtering on the lesioned side was abolished by either l-DOPA or a D2 receptor agonist, but when combined with a CB1 receptor antagonist, l-DOPA or D2 agonists normalized both synaptic filtering and behavior. Thus, high-pass filtering of corticostriatal synapses by the coordinated activation of D2, mGlu-R5, and CB1 receptors is required for normal sensorimotor response to environmental cues.

Improving the mapping of condition-specific health-related quality of life onto SF-6D score

BACKGROUND

This study sought to improve the predicative performance and goodness-of-fit of mapping models, as part of indirect valuation, by introducing cubic spline smoothing to map a group of health-related quality of life (HRQOL) measures onto a preference-based measure.

METHODS

This study was a secondary analysis of a cross-sectional health survey data assessing the HRQOL for patients with colorectal neoplasms. Mapping functions of condition-specific functional assessment of cancer therapy-colorectal (FACT-C) onto preference-based SF-6D measure were developed using a dataset of 553 Chinese subjects with different stages of colorectal neoplasm. The missing values of FACT-C were imputed using multiple imputation. Then three widely applicable models (ordinary least square (OLS), Tobit and two-part models) were employed for the mapping function after applying the cubic spline smoothing on the data. For the evaluation of the effectiveness of cubic spline smoothing and multiple imputation, the goodness-of-fit and prediction performance of each model were compared.

RESULTS

Analyses showed that the models fitted with transformed data from cubic spline smoothing offered better performance in goodness-of-fit and prediction than the models fitted with the original data. The values of [Formula: see text] were improved by over 10%, and the root mean square error and the mean absolute error were both reduced. The best goodness-of-fit and performance were achieved by OLS model using transformed data from cubic spline smoothing.

CONCLUSIONS

Cubic spline smoothing and multiple imputation were recommended for the mapping of HRQOL measures onto the preference-based measure. Among the three mapping models, the simple-to-use OLS model had the best performance.

First Report of Anthracnose Caused by Colletotrichum gloeosporioides on Soybean (Glycine max) in Malaysia

Soybean (Glycine max L.) is one of the most economically important crops in the world, and anthracnose is known to infect soybean in most countries. Colletotrichum truncatum is the common pathogen causing anthracnose of soybean. However, at least five species of Colletotrichum have been reported on soybean worldwide (2). In July 2010, anthracnose symptoms were observed on soybean in the experimental fields of the agriculture station in Ladang Dua, University Putra Malaysia located in Selangor state of Malaysia. Symptoms were initially observed on a few plants randomly within one field, but after 4 weeks, the disease was found in two additional fields scattered across an area of 1 km². Pinkish-brown lesions were observed on the pods, and the formation of dark lesions on the leaves and stems was sometimes followed by stem girdling, dieback, and distorted growth. At later stages, numerous epidermal acervuli developed in the lesions, and mucilaginous conidial masses appeared during periods of high relative humidity. Conidia produced in acervuli were straight, cylindric, hyaline, and aseptate, with both ends rounded. Conidia measured (mean ± SD) 14.2 ± 0.6 × 3.6 ± 0.7 μm, and the L/W ratio was 3.95 μm. Six isolates of the fungus were obtained and identified as C. gloeosporioides on the basis of morphological characterization (3). The isolates were deposited in the University Putra of Malaysia Culture Collection (UPMCC). PDA cultures were white at first and subsequently became grayish to pink to reddish-brown. Amplification and sequence analysis of coding and none-coding regions of the ITS-rDNA (GenBank JX669450), actin (JX827430), β-tubulin (JX827454), histone (JX827448), chitin synthase (JX827436), and glyceraldehyde-3-phosphate dehydrogenase (JX827442) obtained from the representative isolate, CGM50, aligned with deposited sequences from GenBank and revealed 99 to 100% sequence identity with C. gloeosporioides strains (JX258757, JX009790, GQ849434, HM575301, JQ005413, and JX00948 from GenBank). One representative isolate, CGM50, was used for pathogenicity testing. Four non-infected detached leaves and pods of 24-day-old G. max var. Palmetto were surface-sterilized and inoculated by placing 10 μl of a conidial suspension (10⁶ conidia ml^-1) using either the wound/drop or non-wound/drop method (4), with 10 μl distilled water as a negative control. Leaves and pods were incubated at 25°C, 98% RH. The experiment was repeated twice. Five days after inoculation, the development of typical field symptoms, including acervuli formation, occurred on the leaves and pods of inoculated plants, but not on the negative controls. A fungus with the same colony and conidial morphology as CGM50 was recovered from the lesions on the inoculated leaves and pods. Anthracnose caused by C. gloeosporioides on soybean plants has been reported previously in different countries, but not in Malaysia (3). Geographically, the climate of Malaysia is highly conducive to maintain and cause outbreaks of anthracnose all year round; thus, the development of management recommendations will be inevitable for anthracnose control. To our knowledge, this is the first report of C. gloeosporioides causing anthracnose on soybean in Malaysia. References: (1) U. Damm et al. Fungal Diversity 39:45, 2009. (2) S. L. Chen et al. J. Phytopathol. 154:654, 2006. (3) B. C. Sutton. The Genus Glomerella and its Anamorph Colletotrichum. CAB International, Wallingford, UK, 1992. (4) P. P. Than et al. Plant Pathol. 57:562, 2008. ERRATUM: A correction was made to this Disease Note on May 19, 2014. The author N. Soleimani was added.

First Report of Anthracnose Caused by Colletotrichum capsici on Bok Choy (Brassica chinensis) in Malaysia

Bok choy (Brassica chinensis L.) is a temperate vegetable grown in the cool highland areas of Malaysia. In June 2010, vegetable growing areas of the Cameron Highlands, located in Pahang State, Malaysia, were surveyed for the prevalence of anthracnose disease caused by Colletotrichum species. Diseased samples were randomly collected from 12 infested fields. Anthracnose incidence on bok choy varied from 8 to 36% in different nursery fields. Disease symptoms initially appeared as small water-soaked spots scattered on the leaf petioles of young plants. As these spots increased in size, they developed irregular round spots that turned to sunken grayish brown lesions surrounded by brownish borders. When the lesions were numerous, leaves collapsed. Pale buff to salmon conidial mass and acervuli were observed on well-developed lesions. The acervuli diameter varied in size from 198 to 486 μm, averaging 278.5 μm. Morphological and cultural characteristics of the fungus were examined on potato dextrose agar incubated for 7 days at 25 ± 2°C under constant fluorescent light. Vegetative mycelia were hyaline, septate, branched, and 2 to 7 μm in diameter. The color of the fungal colonies was grayish brown. Conidia were hyaline, aseptate, falcate, apices acute, and 21.8 to 28.5 × 2.6 to 3.4 mm. Setae were pale brown to dark brown, 75 to 155 μm long, base cylindrical, and tapering towards the acute tip. Appressoria were solitary or in dense groups, light to dark brown, entire edge to lobed, roundish to clavate, 6.5 to 14 × 5.8 to 8.6 μm, averaging 9.2 × 6.8 μm, and had a L/W ratio of 1.35. Based on the keys outlined by Mordue 1971 (2) and Sutton 1980 (3), the characteristics of this fungus corresponded to Colletotrichum capsici. Sequence analysis of the ITS-rDNA obtained from the Malaysian strain CCM3 (GenBank Accession No. JQ685746) using primers ITS5 and ITS4 (1) when aligned with deposited sequences from GenBank revealed 99 to 100% sequence identity with C. capsici strains (DQ286158, JQ685754, DQ286156, GQ936210, and GQ369594). A representative strain CCM3 was used for pathogenicity testing. Four non-infected detached leaves of 2-week-old B. chinensis were surface-sterilized and inoculated by placing 10 μl of conidial suspension (10⁶ conidia ml^-1) using either the wound/drop or non-wound/drop method, and distilled water was used as a control (1). Leaves were incubated at 25°C, 98% RH. The experiment was repeated twice. Five days after inoculation, typical anthracnose symptoms with acervuli formation appeared on the surface of tissues inoculated with the spore suspension, but not on the water controls. A fungus with the characteristics of C. capsici was recovered from the lesions on the inoculated leaves. Anthracnose caused by C. capsici has been reported on different vegetable crops, but not on bok choy (3). To the best of our knowledge, this is the first report of C. capsici causing anthracnose on bok choy in Malaysia. References: (1) R. Ford et al. Aust. Plant Pathol. 33:559, 2004. (2) J. E. M. Mordue. CMI Description of Pathogenic Fungi and Bacteria. Commonwealth Mycol. Inst., Kew, UK. 1971. (3) B. C. Sutton. The Genus Glomerella and its anamorph Colletotrichum. CAB International, Wallingford, UK, 1992. (4) P. P. Than et al. Plant Pathol. 57:562, 2008.

First Report of Pod and Stem Blight of Lima Bean Caused by Diaporthe phaseolorum var. sojae in Malaysia

In July 2011, a severe outbreak of pod and stem blight was observed on lima bean (Phaseolus lunatus L.) plants grown in the Cameron Highlands, located in Pahang State, Malaysia. Disease incidence varied from 33 to 75% in different fields. Pods and stems exhibited withered, light brown to reddish brown necrotic areas. Sub-circular and brown lesions were produced on the leaves. These lesions varied in size, often reaching a diameter of 1 to 2 cm. After tissue death, numerous pycnidia were observed on the surface of the pod or stem. The pycnidia diameter varied from 155 to 495 μm, averaging 265.45 μm, and on the surface of the pod or stem, pycnidia were often arranged concentrically or linearly, respectively. Pycnidiospores were hyaline, 1-celled, usually straight, and rarely, slightly curved. The α-spores varied from 5.5 to 9.0 × 2.5 to 4.0 μm; averaging 7.3 × 3.5 μm. The β-spores found either alone or with pycnidiospores in pycnidia were slender, hyaline, nonseptate, and straight or curved. Size varied from 15.8 to 38.0 × 1.3 to 2.1 μm; averaging 25.86 × 1.8 μm. The colony characteristics were recorded from pure cultures grown on potato dextrose agar plates, and incubated in darkness for 7 days at 25 °C, then exposed to 16/8 h light and dark periods at 25°C for a further 14 to 21 days. Morphological characteristics of the colonies and spores on PDA matched those described for P. phaseolorum var. sojae (2). Colonies were white, compact, with wavy mycelium and stromata with pycnidia that contained abundant β-spores. Sequence analysis of the ribosomal DNA internal transcribed spacer obtained from the Malaysian isolate FM1 (GenBank Accession No. JQ514150) using primers ITS5 and ITS4 (1) aligned with deposited sequences from GenBank confirmed identity and revealed 99% to 100% DNA similarity with P. phaseolorum strains (AY577815, AF001020, HM012819, JQ936148). The isolate FM1 was used for pathogenicity testing. Five non-infected detached leaves and pods of 4-week-old lima bean were surface sterilized and inoculated by placing 10 μl of conidial suspension (10⁶ conidia ml^-1) on the surface of leaves and pods using either the wound/drop or non-wound/drop method and distilled water used as control (3). The inoculated leaves and pods were incubated at 25 °C and 98% RH, and the experiment was performed twice. Disease reactions and symptoms were evaluated after inoculation. After one week, typical symptoms of pod and stem blight appeared with formation of pycnidia on the surface of the tissues, but not on non-inoculated controls. P. phaseolorum var. sojae was consistently reisolated from symptoms. To our knowledge, this is the first report of P. phaseolorum var. sojae causing pod and stem blight of lima bean in Malaysia. References: (1) R. Ford et al. Aust. Plant Pathol. 33:559, 2004. (2) G. L. Hartman et al. Compendium of Soybean Diseases. 4th ed. American Phytopathological Society, St. Paul, MN, 1999. (3) P. P. Than et al. Plant Pathol. 57:562, 2008.

First Report of Marasmiellus palmivorus Causing Post-Emergence Damping Off on Coconut Seedlings in Malaysia

In April and June 2010, coconut seedlings with symptoms of very slow growth, yellowing of leaves, and general abnormal leaf growth were observed in germination beds in Teluk Intan, Perak, Malaysia. The roots were soft, rotten, and brown, extending upward and downward from these lesions. Rhizomorphs and basidiocarps were produced on coconut seeds near the germination eye and identified as Marasmiellus palmivorus according description by Turner (2). Three isolates were obtained by plating surface sterilized symptomatic roots and basidiocarp on malt extract agar (MEA) amended with 85% lactic acid (1 ml added to 11 of the medium). To confirm the identity of the fungus, genomic DNA was extracted from mycelia and basidiocarps of isolates and the large subunit (LSU) region was amplified and sequenced using LR0R/LR7 primers (3). All isolates had identical LSU sequences (GenBank Accession No. JQ654233 to JQ654235). Sequences were identical to each other and 99% similar to a M. palmivorus sequence deposited in the NCBI database (Accession No. AY639434).To confirm pathogenicity, three isolates of M. palmivorus that were obtained from symptomatic plant tissue was inoculated onto seeds of Malaysian Red Dwarf variety. Each isolate was grown in 100 ml of malt extract broth in 250 ml Erlenmeyer flasks and incubated at 27 ± 2°C for 5 days on an orbital shaker (125 rpm). The resulting culture was passed through two layers of sterile cloth. Mycelial suspension was obtained by blending mycelia in 100 ml of sterile water. Seeds were sterilized by soaking in 10% v/v sodium hypochlorite in distilled water for 3 min. The seeds were then rinsed three times over running tap water. The calyx portion of the seed was removed and five holes were made around the germination eye. The seeds were inoculated by injecting 2 ml of suspension into each hole. The control seeds were inoculated with sterile distilled water only. The seeds were transferred to 40-cm diameter plastic pots containing a mixture of sand, soil, and peat in the ratio of 3:2:1, respectively, and steam treated at 100°C for 1.5 h. Pots were placed in the glasshouse with normal exposures to day-night cycles, temperatures of 29 ± 4°C, and high relative humidity (85 to 95%) achieved by spraying water twice daily. After 2 months, 75% of the inoculated seeds failed to germinate. It was speculated that the artificial inoculum was higher than under germination bed conditions. Rhizomorphs and basidiocarps were produced on husk seeds near the germination eye. Seedlings that emerged successfully developed symptoms similar to those observed in the germination bed. No symptoms developed in the noninoculated seeds and seedlings. At 80 days post inoculation, basidiocarps were observed emerging from three diseased seedlings near the germination eye. Three reisolations were made on MEA from root lesions surface sterilized. Pathogenicity tests and LSU sequence analyses indicated that M. palmivorus is the causal agent of the symptoms observed on coconut seedlings. M. palmivorus was first recorded on coconuts and oil palm in the 1920s (1) and attacks the fruit and the petiole on oil palm (2). To our knowledge, this is the first report of M. palmivorus causing post-emergence damping off on coconut seedlings. References: (1) K. G. Singh. A check-list of host and diseases in Malaysia. Ministry of Agriculture and Fisheries, Malaysia, 1973. (2) P. D. Turner. Oil palm diseases and disorders. Oxford University Press. 1981. (3) R. Vilgalys et al. J. Bacteriol. 172:4238, 1990.

Meat consumption and risk of lung cancer: evidence from observational studies

BACKGROUND

A number of epidemiological studies have reported inconsistent findings on the association between meat consumption and lung cancer.

DESIGN

We therefore conducted a systematic review and meta-analysis to investigate the relationship between meat consumption and lung cancer risk in epidemiological studies.

RESULTS

Twenty-three case-control and 11 cohort studies were included. All studies adjusted for smoking or conducted in never smokers. The summary relative risks (RRs) of lung cancer for the highest versus lowest intake categories were 1.35 (95% confidence interval (CI) 1.08-1.69) for total meat, 1.34 (95% CI 1.18-1.52) for red meat, and 1.06 (95% CI 0.90-1.25) for processed meat. An inverse association was found between poultry intake and lung cancer (RR = 0.91, 95% CI 0.85-0.97), but not for total white meat (RR = 1.06, 95% CI 0.82-1.37) or fish (RR = 1.01, 95% CI 0.96-1.07).

CONCLUSIONS

The relationship between meat intake and lung cancer risk appears to depend on the types of meat consumed. A high intake of red meat may increase the risk of lung cancer by about 35%, while a high intake of poultry decreases the risk by about 10%. More well-designed cohort studies on meat mutagens or heme iron, meat cooking preferences, and doneness level are needed to fully characterize this meat-lung cancer association.

First Report of Alternaria tenuissima Causing Leaf Spot on Eggplant in Malaysia

A leaf spot on eggplant (Solanum melongena) was observed in major eggplant growing regions in Malaysia, including the Cameron Highlands and Johor State, during 2011. Disease incidence averaged approximately 30% in severely infected regions in about 150 ha of eggplant fields and greenhouses examined. Early symptoms consisted of small, circular, brown, necrotic spots uniformly distributed on leaves. The spots gradually enlarged and developed concentric rings. Eventually, the spots coalesced and caused extensive leaf senescence. A fungus was recovered consistently by plating surface-sterilized (1% NaOCl) sections of symptomatic leaf tissue onto potato dextrose agar (PDA). For conidial production, the fungus was grown on potato carrot agar (PCA) and V8 agar media under a 16-h/8-h dark/light photoperiod at 25°C (4). Fungal colonies were a dark olive color with loose, cottony mycelium. Simple conidiophores were ≤120 μm long and produced numerous conidia in long chains. Conidia averaged 20.0 × 7.5 μm and contained two to five transverse septa and the occasional longitudinal septum. Twelve isolates of the fungus were identified as Alternaria tenuissima on the basis of morphological characterization (4). Confirmation of the species identification was obtained by molecular characterization of the internal transcribed spacer (ITS) region of rDNA amplified from DNA extracted from a representative isolate using universal primers ITS4 and ITS5 (2). The 558 bp DNA band amplified was sent for direct sequencing. The sequence (GenBank Accession No. JQ736021) was subjected to BLAST analysis (1) and was 99% identical to published ITS rDNA sequences of isolates of A. tenuissima (GenBank Accession Nos. DQ323692 and AY154712). Pathogenicity tests were performed by inoculating four detached leaves from 45-day-old plants of the eggplant cv. 125066x with 20 μl drops (three drops/leaf) of a conidial suspension containing 10⁵ conidia/ml in sterile distilled water. Four control leaves were inoculated with sterile water. Leaves inoculated with the fungus and those treated with sterile water were incubated in chambers at 25°C and 95% RH with a 12-h photoperiod/day (2). Leaf spot symptoms typical of those caused by A. tenuissima developed on leaves inoculated with the fungus 7 days after inoculation, and the fungus was consistently reisolated from these leaves. The control leaves remained asymptomatic and the pathogen was not reisolated from the leaves. The pathogenicity test was repeated with similar results. To our knowledge, this is the first report of A. tenuissima causing a leaf spot on eggplant in Malaysia. A. tenuissima has been reported to cause leaf spot and fruit rot on eggplant in India (3). References: (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997. (2) B. M. Pryor and T. J. Michailides. Phytopathology 92:406, 2002. (3) P. Raja et al. New Disease Rep. 12:31, 2005. (4) E. G. Simmons. Page 1 in: Alternaria Biology, Plant Diseases and Metabolites. J. Chelchowski and A. Visconti, eds. Elsevier, Amsterdam, 1992.

First Report of Tomato Gray Leaf Spot Disease Caused by Stemphylium solani in Malaysia

In June 2011, tomatoes (Solanum lycopersicum) in major growing areas of the Cameron Highlands and the Johor state in Malaysia were affected by a leaf spot disease. Disease incidence exceeded 80% in some severely infected regions. Symptoms on 50 observed plants initially appeared on leaves as small, brownish black specks, which later became grayish brown, angular lesions surrounded by a yellow border. As the lesions matured, the affected leaves dried up and became brittle and later developed cracks in the center of the lesions. A survey was performed in these growing areas and 27 isolates of the pathogen were isolated from the tomato leaves on potato carrot agar (PCA). The isolates were purified by the single spore technique and were transferred onto PCA and V8 agar media for conidiophore and conidia production under alternating light (8 hours per day) and darkness (16 hours per day) (4). Colonies on PCA and V8 agar exhibited grey mycelium and numerous conidia were formed at the terminal end of conidiophores. The conidiophores were up to 240 μm long. Conidia were oblong with 2 to 11 transverse and 1 to 6 longitudinal septa and were 24 to 69.6 μm long × 9.6 to 14.4 μm wide. The pathogen was identified as Stemphylium solani on the basis of morphological criteria (2). In addition, DNA was extracted and the internal transcribed spacer region (ITS) was amplified by universal primers ITS5 and ITS4 (1). The PCR product was purified by the commercial PCR purification kit and the purified PCR product sequenced. The resulting sequences were 100% identical to published S. solani sequences (GenBank Accestion Nos. AF203451 and HQ840713). The amplified ITS region was deposited with NCBI GenBank under Accession No. JQ657726. A representative isolate of the pathogen was inoculated on detached 45-day-old tomato leaves of Malaysian cultivar 152177-A for pathogenicity testing. One wounded and two nonwounded leaflets per leaf were used in this experiment. The leaves were wounded by applying pressure to leaf blades with the serrated edge of a forceps. A 20-μl drop of conidial suspension containing 10⁵ conidia/ml was used to inoculate these leaves (3). The inoculated leaves were placed on moist filter paper in petri dishes and incubated for 48 h at 25°C. Control leaves were inoculated with sterilized distilled water. After 7 days, typical symptoms for S. solani similar to those observed in the farmers' fields developed on both wounded and nonwounded inoculated leaves, but not on noninoculated controls, and S. solani was consistently reisolated. To our knowledge, this is the first report of S. solani causing gray leaf spot of tomato in Malaysia. References: (1) M. P. S. Camara et al. Mycologia 94:660, 2002. (2) B. S. Kim et al. Plant Pathol. J. 15:348, 1999. (3) B. M. Pryor and T. J. Michailides. Phytopathology 92:406, 2002. (4) E. G. Simmons. CBS Biodiversity Series 6:775, 2007.

First Report of Gray Leaf Spot on Pepper Caused by Stemphylium solani in Malaysia

Symptoms of gray leaf spot were first observed in June 2011 on pepper (Capsicum annuum) plants cultivated in the Cameron Highlands and Johor State, the two main regions of pepper production in Malaysia (about 1,000 ha). Disease incidence exceeded 70% in severely infected fields and greenhouses. Symptoms initially appeared as tiny (average 1.3 mm in diameter), round, orange-brown spots on the leaves, with the center of each spot turning gray to white as the disease developed, and the margin of each spot remaining dark brown. A fungus was isolated consistently from the lesions using sections of symptomatic leaf tissue surface-sterilized in 1% NaOCl for 2 min, rinsed in sterile water, dried, and plated onto PDA and V8 agar media (3). After 7 days, the fungal colonies were gray, dematiaceous conidia had formed at the end of long conidiophores (19.2 to 33.6 × 12.0 to 21.6 μm), and the conidia typically had two to six transverse and one to four longitudinal septa. Fifteen isolates were identified as Stemphylium solani on the basis of morphological criteria described by Kim et al. (3). The universal primers ITS5 and ITS4 were used to amplify the internal transcribed spacer region (ITS1, 5.8, and ITS2) of ribosomal DNA (rDNA) of a representative isolate (2). A 570 bp fragment was amplified, purified, sequenced, and identified as S. solani using a BLAST search with 100% identity to the published ITS sequence of an S. solani isolate in GenBank (1). The sequence was deposited in GenBank (Accession No. JQ736024). Pathogenicity of the fungal isolate was tested by inoculating healthy pepper leaves of cv. 152177-A. A 20-μl drop of conidial suspension (10⁵ spores/ml) was used to inoculate each of four detached, 45-day-old pepper leaves placed on moist filter papers in petri dishes (4). Four control leaves were inoculated similarly with sterilized, distilled water. The leaves were incubated at 25°C at 95% relative humidity for 7 days. Gray leaf spot symptoms similar to those observed on the original pepper plants began to develop on leaves inoculated with the fungus after 3 days, and S. solani was consistently reisolated from the leaves. Control leaves did not develop symptoms and the fungus was not reisolated from these leaves. Pathogenicity testing was repeated with the same results. To our knowledge, this is the first report of S. solani causing gray leaf spot on pepper in Malaysia. References: (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997. (2) M. P. S. Camara et al. Mycologia 94:660, 2002. (3) B. S. Kim et al. Plant Pathol. J. 15:348, 1999. (4) B. M. Pryor and T. J. Michailides. Phytopathology 92:406, 2002.

Enzyme replacement therapy for mucopolysaccharidosis VI (Maroteaux-Lamy syndrome): experience in Hong Kong

Mucopolysaccharidosis VI (Maroteaux-Lamy syndrome) is a very rare inherited lysosomal storage disease. We evaluated the efficacy and safety of weekly infusions of recombinant human arylsulfatase B as enzyme replacement therapy for two patients in whom this condition was advanced. The primary outcome variables were the distance walked in a 6-minute walk test, forced vital capacity, and ejection fraction. The secondary outcome variables were the number of stairs climbed in a 3-minute stair climbing test, joint mobility, urinary glycosaminoglycan excretion, auto-continuous positive airway pressure study and liver size. After 24 weeks of treatment, patient A walked 40 m (36%) and patient B walked 66 m (58%) more in the walk test than at baseline. After 48 weeks, in patient A the corresponding improvements were 142 m (129%) in the walk test and 33 stairs (60%) in the 3-minute stair climbing test, and in patient B the respective improvements were 198 m (174%) and 77 stairs (140%). There was a significant decline in urinary glycosaminoglycan excretion and improvement in range of motion of joints in both patients. The auto-continuous positive airway pressure study revealed improvements in patient A, while other efficacy variables remained static. There were no drug-related adverse events or allergic reactions reported during and after the infusions of recombinant human arylsulfatase B. Recombinant human arylsulfatase B significantly improves endurance and reduces urinary glycosaminoglycan excretion. The drug is generally safe and well tolerated.

First Report of Pseudoperonospora cubensis Causing Downy Mildew of Trichosanthes cucumerina in Malaysia

In December 2008, infected leaves of Trichosanthes cucumerina were observed on commercial cucurbit farms located in Pontian, Johor (south of West Malaysia). Bright yellow and small necrotic lesions were observed on the adaxial surface of the leaves, whereas sporangiophores were observed on pale yellowish brown-to-brown lesions on the abaxial surface. The length and width of the sporangia ranged from 19 to 36 μm (28.6) and 11 to 23 μm (17.6), respectively. The length of the sporangiophores ranged from 310 to 450 μm, with an average length of 380 μm. The pathogen was identified as Pseudoperonospora cubensis on the basis of the morphological criteria described by Palti and Cohen (2). To confirm the morphological findings, DNA was extracted from symptomatic tissue and the internal transcribed spacer (ITS) region was PCR amplified using primers ITS5-P2 and ITS4 (3). The appropriate-sized amplicon was gel excised and column purified and then submitted for direct sequencing. The resulting 802 bp amplified ITS region was 100% identical to published P. cubensis sequences (GenBank Accession Nos. EU876603, EU876584, and AY198306). This sequence was deposited with NCBI GenBank under the Accession No. GU233293. In this study, pathogenicity tests were conducted using detached leaf disc assays (1) and a P. cubensis isolate obtained from T. cucumerina. For this purpose, leaf discs were excised from 6- to 8-week-old leaves of T. cucumerina using a 20-mm cork borer. Five leaf discs were placed with their abaxial surface facing upward on moist filter paper in petri dishes. Each of four leaf discs was inoculated with four 10-μl droplets of a 1 × 10⁵ per ml sporangial suspension, whereas the fifth disc was inoculated with water droplets and served as a control. Three replications were completed. The leaf discs were placed in darkness at 14 ± 2°C for 24 h and subsequently incubated with a 12-h photoperiod. After 10 days, sporulation was observed on the sporangia-inoculated leaf discs with similar morphological features to the initial field samples. To our knowledge, this is the first report of P. cubensis causing downy mildew of T. cucumerina in Malaysia. References: (1) A. Lebeda and M. P. Widrlechner. J. Plant Dis. Prot. 110:337, 2003. (2) J. Palti and Y. Cohen. Phytoparasitica 8:109, 1980. (3) H. Voglmayr and O. Constantinescu. Mycol. Res. 112:487, 2008.

Newer fluoroquinolones for treating respiratory infection: do they mask tuberculosis?

Possible masking of tuberculosis (TB) in treatment of community-acquired respiratory infection by newer fluoroquinolones has not been examined in randomised controlled trials. We undertook a randomised, open-label controlled trial involving adults with community-acquired pneumonia or infective exacerbation of bronchiectasis encountered in government chest clinics in Hong Kong. 427 participants were assigned by random permutated blocks of 20 to receive either amoxicillin clavulanate (n = 212) or moxifloxacin (n = 215). Participants were followed for 1 yr for active pulmonary TB. Excluding three participants with positive baseline culture, 13 developed active pulmonary TB: 10 (4.8%) out of 210 were given amoxicillin clavulanate, and three (1.4%) out of 214 were given moxifloxacin. The difference was significant by both proportion and time-to-event analysis. Post hoc analysis showed a significant decrease in the proportion with active pulmonary TB from 4.8% to 2.4% and 0% among participants given amoxicillin clavulanate (n = 210), moxifloxacin for predominantly 5 days (n = 127) and 10 days (n = 87), respectively. The log rank test for trend also showed a significant difference between the three subgroups. Regression models reaffirmed the linear effect; the adjusted odds ratio (95% confidence interval) of active pulmonary TB after moxifloxacin exposure up to predominantly 10 days was 0.3 (0.1-0.9). Newer fluoroquinolones appear to mask active pulmonary TB.

Role of Mycoplasma genitalium and Ureaplasma urealyticum in non-gonococcal urethritis in Hong Kong

OBJECTIVE

To determine the association of Mycoplasma genitalium and Ureaplasma urealyticum in symptomatic male patients presenting with non-gonococcal urethritis in a sexually transmitted infection clinic in Hong Kong.

DESIGN

Cross-sectional study.

SETTING

A sexually transmitted infection clinic, Department of Health, Centre for Health Protection, Hong Kong.

PATIENTS

A cohort of consecutive new male patients attending the government sexually transmitted infection clinic.

MAIN OUTCOME MEASURES

Prevalence of Mycoplasma genitalium and Ureaplasma urealyticum among symptomatic male patients with non-gonococcal urethritis and asymptomatic patients without non-gonococcal urethritis.

RESULTS

Specimens of 22 and 10 patients tested positive by polymerase chain reaction for Ureaplasma urealyticum and Mycoplasma genitalium respectively, among the symptomatic non-gonococcal urethritis group (n=98). In the asymptomatic control group (n=236), corresponding patient numbers whose specimens tested positive were 47 and 5. There was no statistically significant difference between the two groups, in terms of the proportion of patients infected with Mycoplasma genitalium (P=0.799) or Ureaplasma urealyticum (P=0.535).

CONCLUSIONS

In our study, demonstration of Mycoplasma genitalium and Ureaplasma urealyticum by polymerase chain reaction was not associated with symptomatic non-gonococcal urethritis in male patients attending a Hong Kong government clinic for sexually transmitted infections.

TB surveillance in correctional institutions in Hong Kong, 1999-2005

OBJECTIVE

To understand the epidemiology of tuberculosis (TB) inside the prison system of Hong Kong.

METHOD

Prospective territory-wide TB surveillance was conducted among prisoners in 24 correctional institutions.

RESULTS

From 1999 to 2005, 622 prevalent TB cases diagnosed before or within 3 months of incarceration and 214 incident cases diagnosed after 3 months were reported by prison staff to a paper-based central prison TB registry. Both crude prevalence and incidence were falling (chi(2) for trend, both P < 0.001), despite a higher sex- and age-adjusted prison TB incidence as compared to the general population (indirectly standardised rate [ISR] 280.6 vs. 108.0/100000, P < 0.001). Illegal immigrants (odds ratio [OR] 3.6, 95% confidence interval [CI] 1.8-7.4) and drug addicts (OR 2.04, 95%CI 1.13-3.7) were two major risk groups. The TB incident risk disappeared after their exclusion (ISR 117.1 vs. 108.0/100000, P = 0.52). No significant difference in the multidrug-resistant rate was found when comparing the group with the general population (3.5% vs. 1.0%, OR 3.6, 95%CI 0.5-28.4). No extensively drug-resistant (XDR) cases were identified.

CONCLUSION

TB remains a significant disease in local prisons. Further strengthening of TB control programmes in prisons, especially targeting the higher risk groups, is recommended.

Directly observed treatment of tuberculosis in Hong Kong

OBJECTIVE

To evaluate the local use of out-patient directly observed treatment (DOT) for tuberculosis (TB) control.

SETTING

Seventeen government chest clinics managing around 80% of TB patients in Hong Kong.

METHOD

A retrospective cohort. TB patients registered for treatment from 1 July to 31 August 2000 were followed up for 2 years. Baseline socio-demographic and clinical characteristics were correlated with adherence to DOT, mode of treatment and treatment outcomes.

RESULTS

Of 988 patients, respectively 142, 140 and 21 switched to non-DOT within 2 months, 2-6 months and after 6 months. More Chinese patients than ethnic minorities switched to non-DOT within the first 2 months (15.2% vs. 0%, P = 0.001). Geographical inconvenience (31.7%) was the primary reason for switching initially, with increasing proportions giving no specific reason after the second month. Patients staying on DOT in the first 2 months had a significantly higher cure rate than those not on DOT, in both univariate (92.7% vs. 83.9%, P = 0.002) and multivariate analysis (OR = 2.5, P = 0.001). Subsequent switching, intermittent or daily regimen did not appear to affect the outcome.

CONCLUSION

Significant numbers of patients failed to stay on DOT, and those staying initially had a better outcome.

Tuberculin response in BCG vaccinated schoolchildren and the estimation of annual risk of infection in Hong Kong

BACKGROUND

In Hong Kong there has been nearly universal neonatal BCG vaccination coverage since 1980.

METHOD

21 113 schoolchildren aged 6-9 years were skin tested with one unit of tuberculin (PPD RT-23) using the intradermal technique during a routine BCG revaccination programme. Information on sex, date of birth, date of tuberculin testing, and tuberculin reaction size at 72 hours was retrieved. The annual risk of tuberculous infection (ARTI) was estimated by three different approaches.

RESULTS

Significantly higher tuberculin positive rates were found in girls and with increasing age at all commonly used cut-off points (5, 10, and 15 mm). Using a cut-off point of > or =10 mm and the formula 1- (1 - tuberculin positive rate)(1/age), the ARTI was estimated to be 1.93% (95% CI 1.84 to 2.03) for girls and 1.41% (95% CI 1.33 to 1.50) for boys. Using the differences in the tuberculin positive rate between the 6-7 year and 8-9 year age groups, the ARTI became 1.90% (95% CI 1.09 to 2.70) and 1.84% (95% CI 1.15 to 2.54) for girls and boys, respectively. When the prevalence of infection was estimated by locating a secondary peak of the tuberculin reaction distribution curve at 15 mm and assuming a symmetrical distribution of reaction sizes among those infected around this peak, the corresponding ARTI was much lower at 0.52% (95% CI 0.46 to 0.59) and 0.43% (95% CI 0.37 to 0.49) for girls and boys, similar to that estimated indirectly from the prevalence of disease.

CONCLUSION

The ARTI as estimated by conventional methods was unexpectedly high among BCG vaccinated children and did not agree with that anticipated from the annual incidence of active disease. Further studies are needed to address the discrepancies, including the possible interaction between BCG and other environmental stimuli.

Correlated measurement error--implications for nutritional epidemiology

BACKGROUND

In nutritional epidemiology, it is common to fit models in which several dietary variables are included. However, with standard instruments for dietary assessment, not only are the intakes of many nutrients often highly correlated, but the errors in the estimation of the intake of different nutrients are also correlated. The effect of this error correlation on the results of observational studies has been little investigated. This paper describes the effect on multivariate regression coefficients of different levels of correlation, both between the variables themselves and between the errors of estimation of these variables.

METHODS

Using a simple model for the multivariate error structure, we examine the effect on the estimates of bivariate linear regression coefficients of (1) differential precision of measurement of the two independent variables, (2) differing levels of correlation between the true values of the two variables, and (3) differing levels of correlation between the errors of measurement of the two variables. As an example, the prediction of plasma vitamin C levels by dietary intake variables is considered, using data from the European Prospective Investigation of Cancer (EPIC) Norfolk study in which dietary intake was estimated using both a food frequency questionnaire (FFQ) and a 7-day diary (7DD). The dietary variables considered are vitamin C, fat, and energy, with different approaches taken to energy adjustment.

RESULTS

When the error correlation is zero, the estimates of the bivariate regression coefficients reflect the precision of measurement of the two variables and mutual confounding. The sum of the observed regression coefficients is biased towards the null as in univariate regression. When the error correlation is non-zero but below about 0.7, the effect is minor. However, as the error correlation increases beyond 0.8 the effect becomes large and highly dependent on the relative precision with which the two variables are measured. At the extreme, the bivariate estimates can become indefinitely large. In the example, the error correlation between fat and energy using the FFQ appears to be over 0.9, the corresponding value for the 7DD being approximately 0.85. The error correlation between vitamin C and fat, and vitamin C and energy, appears to be below 0.5 and smaller for the 7DD than for the FFQ. The impact of these error correlations on bivariate regression coefficients is large. The effect of energy adjustment differs widely between vitamin C and fat.

CONCLUSION

High levels of error correlation can have a large effect on bivariate regression estimates, varying widely depending on which two variables are considered. In particular, the effect of energy adjustment will vary widely. For vitamin C, the effect of energy adjustment appears negligible, whereas for fat the effect is large indicating that error correlation close to one can partially remove regression dilution due to measurement error. If, for fat intake, energy adjustment is performed by using energy density, the partial removal of regression dilution is achieved at the expense of substantial reduction in the true variance.

Transurethral resection of prostate (TURP) through the decades--a comparison of results over the last thirty years in a single institution in Asia

INTRODUCTION

This study was conducted to evaluate the results and complications of transurethral resection of prostate (TURP) over the last 30 years in our institution.

MATERIALS AND METHODS

This retrospective study encompasses 3 different eras: 168 patients in the late 70s, 175 patients in the late 80s and 283 patients in the late 90s. All the patients had at least 18 months of follow-up.

RESULTS

The mean age from the 1970s, the 1980s and 1999 were 68.8 years, 69.2 years and 69.4 years respectively. The proportion of patients operated on for acute retention fell from 78.6% (132) in the 1970s, to 54% (96) in the 1980s, and 43% (122) in 1999. The mean resection time was 44.8 minutes in 1989 and 41.8 minutes in 1999. The mean weight of prostate resected was 22.1 g in the 1970s, 24.2 g in 1989 and 22.2 g in 1999. 44% (74) required blood transfusion in the 1970s, with 11% (19) in 1989 and 4% (11) in 1999. There were 2 deaths (acute myocardial infarction and pneumonia) in the 1970s, 1 (pneumonia) in 1989 and no mortality in 1999. There were 4 patients with TURP syndrome in the 1970s, 3 in 1989 and 1 in 1999. The incidence of postoperative urinary tract infection (UTI) was 25% (42) in the 1970s, 16% (29) in 1989 and 6% (17) in 1999.

CONCLUSIONS

As expertise and experience in TURP progress, the complication rates fall, as evidenced by the lower rates of transfusion, TURP syndrome and postoperative UTI in the later series.

Socio-economic factors and tuberculosis: a district-based ecological analysis in Hong Kong

BACKGROUND

Relatively little is known about the impact of socio-economic factors on tuberculosis in a metropolitan city with high disease incidence.

METHOD

District-specific tuberculosis notification rates for 1995--1997 and 2000--2002 were indirectly sex- and age-adjusted and compared with the socio-economic characteristics in the 1996 by-census and 2001 census.

RESULTS

The differences between the 18 districts persisted after 3-year averaging and indirect standardisation. Only the percentage of population born locally, the percentage of the population widowed or divorced and the percentage of households residing in rooms or bedsits were consistently associated with the standardised notification ratios (SNR) for both periods, the first being negatively so (all P < 0.05). In a combined analysis with a general linear model for both periods, birth in China, residence <7 years, speaking other Asian languages, being married and in a single household were also significantly associated with the SNR (all P < 0.05). Using a backward conditional approach, only local birth, being married, and residing in rooms or bedsits were independent predictors of SNR (all P < 0.05). There was no significant association between SNR and socio-economic indices on education, occupation, unemployment and income.

CONCLUSION

Socio-economic factors other than simple poverty are affecting the district-specific tuberculosis rates in Hong Kong.

Wireless capsule endoscopy in Chinese patients with suspected small bowel diseases

OBJECTIVE

To evaluate the use of wireless capsule endoscopy in Chinese patients.

DESIGN

Retrospective analysis.

SETTING

University teaching hospital, Hong Kong.

PATIENTS

Twenty-eight patients who had undergone wireless capsule endoscopy between December 2002 and December 2003.

MAIN OUTCOME MEASURES

Diagnoses according to findings of capsule endoscopy and complications from the procedure.

RESULTS

The mean age of the 28 patients (15 men and 13 women) was 60.0 (standard deviation, 18.3) years. The indications for capsule endoscopy were obscure gastro-intestinal bleeding (n=16), unexplained iron-deficiency anaemia (n=9), and recurrent abdominal pain (n=3). Half of the patients had abnormal endoscopy findings that may account for their presenting symptoms. The most common abnormality was angioectasia of the small bowel. Small bowel ulcers and erosions were also noted in three patients with obscure bleeding. In contrast, none of the patients with recurrent abdominal pain had abnormal capsule endoscopy. No complications arose from the procedure.

CONCLUSIONS

Wireless capsule endoscopy is a safe and useful mode of investigation for the diagnosis of obscure gastro-intestinal bleeding in Chinese patients.

Estimation of magnitude in gene-environment interactions in the presence of measurement error

The design of studies aimed at identifying the interaction between genetic and environmental determinants in disease risk is attracting increased attention. In this paper, we study the effect of errors on measuring exposures and the effect of assessing genotype at one locus on the association of a continuous outcome measure with continuous exposures and genotype. The estimation of misclassification errors in assessing genotypes from a separate study is proposed. If the exposure measurement error is substantial, then even relatively small errors in genotyping within limits that are often quoted can have an appreciable effect on interaction estimates. We, thus, consider a method for correcting the measurement errors when the interaction between the exposures and the genetic factor is significant. Finally, we present an epidemiological example to demonstrate the importance of correcting measurement errors.

The detection of gene-environment interaction for continuous traits: should we deal with measurement error by bigger studies or better measurement?

BACKGROUND

The search for biologically relevant gene-environment interactions has been facilitated by technological advances in genotyping. The design of studies to detect interactions on continuous traits such as blood pressure and insulin sensitivity is attracting increasing attention. We have previously described power calculations for such studies, and this paper describes the extension of those calculations to take account of measurement error.

METHODS

The model considered in this paper is a simple linear regression relating a continuous outcome to a continuously distributed exposure variable in which the ratio of slopes for each genotype is considered as the interaction parameter. The classical measurement error model is used to describe the uncertainty in measurement in the outcome and the exposure. The sample size to detect differing magnitudes of interaction with varying frequencies of the minor allele are calculated for a given main effect observed with error both in the exposure and the outcome. The sample size to detect a given interaction for a given minor allele frequency is calculated for differing degrees of measurement error in the assessment of the exposure and the outcome.

RESULTS

The required sample size is dependent upon the magnitude of the interaction, the allele frequency and the strength of the association in those with the common allele. As an example, we take the situation in which the effect size in those with the common allele was a quarter of a standard deviation change in the outcome for a standard deviation change in the exposure. If a minor allele with a frequency of 20% leads to a doubling of that effect size, then the sample size is highly dependent upon the precision with which the exposure and outcome are measured. rho(Tx) and rho(Ty) are the correlation between the measured exposure and outcome, respectively and the true value. If poor measures of the exposure and outcome are used, (e.g. rho(Tx) = 0.3, rho(Ty) = 0.4), then a study size of 150 989 people would be required to detect the interaction with 95% power at a significance level of 10(-4). Such an interaction could be detected in study samples of under 10 000 people if more precise measurements of exposure and outcome were made (e.g. rho(Tx) = 0.7, rho(Ty) = 0.7), and possibly in samples of under 5000 if the precision of estimation were enhanced by taking repeated measurements.

CONCLUSIONS

The formulae for calculating the sample size required to study the interaction between a continuous exposure and a genetic factor on a continuous outcome variable in the face of measurement error will be of considerable utility in designing studies with appropriate power. These calculations suggest that smaller studies with repeated and more precise measurement of the exposure and outcome will be as powerful as studies even 20 times bigger, which necessarily employ less precise measures because of their size. Even though the cost of genotyping is falling, the magnitude of the effect of measurement error on the power to detect interaction on continuous traits suggests that investment in studies with better measurement may be a more appropriate strategy than attempting to deal with error by increasing sample sizes.

Clinics in diagnostic imaging (67). Hydronephrotic horseshoe kidneys with multiple calculi

Horseshoe kidney is the commonest congenital renal anomaly. Its inherently-poor drainage system renders the patient prone to stone formation. A 56-year-old man with bilateral renal stones in a horseshoe system associated with hydronephrosis is presented. He was treated successfully with bilateral CT-guided percutaneous nephrostomy and percutaneous nephrolithotripsy. Various treatment options, including ESWL, PCNL and open surgery, are discussed.

Childhood abuse and lifetime psychopathology in a community sample

OBJECTIVE

The authors assessed lifetime psychopathology in a general population sample and compared the rates of five psychiatric disorder categories between those who reported a childhood history of either physical or sexual abuse and those who did not.

METHOD

A modified version of the Composite International Diagnostic Interview and a self-completed questionnaire on child abuse were administered to a probability sample (N=7,016) of Ontario residents 15 to 64 years of age.

RESULTS

Those reporting a history of childhood physical abuse had significantly higher lifetime rates of anxiety disorders, alcohol abuse/dependence, and antisocial behavior and were more likely to have one or more disorders than were those without such a history. Women, but not men, with a history of physical abuse had significantly higher lifetime rates of major depression and illicit drug abuse/dependence than did women with no such history. A history of childhood sexual abuse was also associated with higher rates of all disorders considered in women. In men, the prevalence of disorders tended to be higher among those who reported exposure to sexual abuse, but only the associations with alcohol abuse/dependence and the category of one or more disorders reached statistical significance. The relationship between a childhood history of physical abuse and lifetime psychopathology varied significantly by gender for all categories except for anxiety disorders. Although not statistically significant, a similar relationship was seen between childhood history of sexual abuse and lifetime psychopathology.

CONCLUSIONS

A history of abuse in childhood increases the likelihood of lifetime psychopathology; this association appears stronger for women than men.

Sample size determination for studies of gene-environment interaction

BACKGROUND

The search for interaction effects is common in epidemiological studies, but the power of such studies is a major concern. This is a practical issue as many future studies will wish to investigate potential gene-gene and gene-environment interactions and therefore need to be planned on the basis of appropriate sample size calculations.

METHODS

The underlying model considered in this paper is a simple linear regression and relating a continuous outcome to a continuously distributed exposure variable.

RESULTS

The slope of the regression line is taken to be dependent on genotype, and the ratio of the slopes for each genotype is considered as the interaction parameter. Sample size is affected by the allele frequency and whether the genetic model is dominant or recessive. It is also critically dependent upon the size of the association between exposure and outcome, and the strength of the interaction term. The link between these determinants is graphically displayed to allow sample size and power to be estimated. An example of the analysis of the association between physical activity and glucose intolerance demonstrates how information from previous studies can be used to determine the sample size required to examine gene-environment interactions.

CONCLUSIONS

The formulae allowing the computation of the sample size required to study the interaction between a continuous environmental exposure and a genetic factor on a continuous outcome variable should have a practical utility in assisting the design of studies of appropriate power.

The Singapore General Hospital early clinical experience with the 7.5F flexible ureterorenoscope

INTRODUCTION

Reduced instrument size, increased flexibility, coupled with improved optics and larger working channels have enhanced the capabilities of the ureterorenoscope.

MATERIALS AND METHODS

We present our initial experience with the new 7.5F flexible ureterorenoscope. A total of 29 flexible ureterorenoscopies were performed from July 1995 to December 1997 by a single surgeon. The indications for flexible ureterorenoscopy was therapeutic in 10 (34.5%) patients (all had urolithiasis) whilst it was diagnostic in 19 patients (65.5%). For the diagnostic cohort, 9 (31.0%) patients had haematuria with radiological upper tract filling defect, 8 (27.6%) had radiological upper tract filling defect alone and 2 (6.9%) had ureteropelvic junction narrowing for evaluation.

RESULTS

Of the therapeutic cases, all 10 (100%) were stone free at 3 months. Of the diagnostic cases, 12 (63.2%) had normal findings, 4 (21.1%) had urolithiasis and 3 (15.8%) had transitional cell carcinoma (TCC). Of the 3 cases of TCC, one was managed endoscopically.

CONCLUSIONS

The smaller calibre and actively deflectable 7.5F flexible ureterorenoscopes facilitate various endoscopic procedures thus broadening the diagnostic and therapeutic scope of the ureterorenoscope.