Does incubation period of COVID-19 vary with age? A study of epidemiologically linked cases in Singapore.

This study estimates the incubation period of COVID-19 among locally transmitted cases, and its association with age to better inform public health measures in containing COVID-19. Epidemiological data of all PCR-confirmed COVID-19 cases from all restructured hospitals in Singapore were collected between 23 January 2020 and 2 April 2020. Activity mapping and detailed epidemiological investigation were conducted by trained personnel. Positive cases without clear exposure to another positive case were excluded from the analysis. One hundred and sixty-four cases (15.6% of patients) met the inclusion criteria during the defined period. The crude median incubation period was 5 days (range 1-12 days) and median age was 42 years (range 5-79 years). The median incubation period among those 70 years and older was significantly longer than those younger than 70 years (8 vis-à-vis 5 days, P = 0.040). Incubation period was negatively correlated with day of illness in both groups. These findings support current policies of 14-day quarantine periods for close contacts of confirmed cases and 28 days for monitoring infections in known clusters. An elderly person who may have a longer incubation period than a younger counterpart may benefit from earlier and proactive testing, especially after exposure to a positive case.

Projecting the Burden of Chronic Kidney Disease in a Developed Country and Its Implications on Public Health.

BACKGROUND: Chronic Kidney Disease (CKD) is a major public health problem worldwide. There is limited literature on a model to project the number of people with CKD. This study projects the number of residents with CKD in Singapore by 2035 using a Markov model. METHODS: A Markov model with nine mutually exclusive health states was developed according to the clinical course of CKD, based on a discrete time interval of 1 year. The model simulated the transition of cohorts across different health states from 2007 to 2035 using prevalence, incidence, mortality, disease transition, and disease detection rates. RESULTS: From 2007 to 2035, the number of residents with CKD is projected to increase from 316,521 to 887,870 and the prevalence from 12.2% to 24.3%. Patients with CKD stages 1-2 constituted the largest proportion. The proportion of undiagnosed cases will decline from 72.1% to 56.4%, resulting from faster progression to higher CKD stages and its eventual detection. CONCLUSION: By 2035, about one-quarter of the Singapore residents are expected to have CKD. National policies need to focus on primary disease prevention and early disease detection to avoid delayed treatment of CKD which eventually leads to end-stage renal disease.

Impact of coculturing Bifidobacterium animalis subsp. lactis HN019 with yeasts on microbial viability and metabolite formation.

AIMS: To evaluate the impact of coculturing Bifidobacterium animalis subsp. lactis HN019 with yeasts on microbial viability and metabolite production. METHODS AND RESULTS: Monocultures and bacteria-yeast cocultures of B. lactis HN019 and 10 different yeast strains belonging to different species in skim milk media were fermented at 37°C. The presence of yeasts enhanced the growth rate and metabolic activities of B. lactis HN019, which might be attributed to their antioxidative properties. The viability of yeasts, when cocultured with bifidobacteria, was either unaffected or suppressed, depending on the strain. When the B. lactis HN019 monoculture and cocultures with Saccharomyces cerevisiae EC-1118, Pichia kluyveri FrootZen and Kluyveromyces lactis KL71 were fermented to pH 4·7, there were no significant differences in their organic acid composition. On the other hand, cocultures produced significantly higher quantities of alcohols and/or esters than the monoculture. Coculturing B. lactis HN019 with yeasts did not improve the viability of the probiotic during storage at 10°C for 8 weeks, as the bifidobacteria itself demonstrated satisfactory survival in the fermented SMM. CONCLUSIONS: Coculturing B. lactis HN019 with yeasts accelerated the growth of the bifidobacteria and increased the production aroma-active volatile metabolites. SIGNIFICANCE AND IMPACT OF THE STUDY: This study demonstrates the potential of utilizing specific yeast species as starter or adjunct cultures to simultaneously improve the growth of fastidious bifidobacteria and modulate the organoleptic properties of fermented food products.

Molecular characterization of glycation-associated skin ageing: an alternative skin model to study in vitro antiglycation activity of topical cosmeceutical and pharmaceutical formulations.

BACKGROUND: Glycation is a nonenzymatic reaction that cross-links a sugar molecule and protein macromolecule to form advanced glycation products (AGEs) that are associated with various age-related disorders; thus glycation plays an important role in skin chronological ageing. OBJECTIVES: To develop a novel in vitro skin glycation model as a screening tool for topical formulations with antiglycation properties and to further characterize, at the molecular level, the glycation stress-driven skin ageing mechanism. METHODS: The glycation model was developed using human reconstituted full-thickness skin; the presence of Nε -(carboxymethyl) lysine (CML) was used as evidence of the degree of glycation. Topical application of emulsion containing a well-known antiglycation compound (aminoguanidine) was used to verify the sensitivity and robustness of the model. Cytokine immunoassay, quantitative real-time polymerase chain reaction and histological analysis were further implemented to characterize the molecular mechanisms of skin ageing in the skin glycation model. RESULTS: Transcriptomic and cytokine profiling analyses in the skin glycation model demonstrated multiple biological changes, including extracellular matrix catabolism, skin barrier function impairment, oxidative stress and subsequently the inflammatory response. Darkness and yellowness of skin tone observed in the in vitro skin glycation model correlated well with the degree of glycation stress. CONCLUSIONS: The newly developed skin glycation model in this study has provided a new technological dimension in screening antiglycation properties of topical pharmaceutical or cosmeceutical formulations. This study concomitantly provides insights into skin ageing mechanisms driven by glycation stress, which could be useful in formulating skin antiageing therapy in future studies.

Enhancement of bifidobacteria survival by Williopsis saturnus var. saturnus in milk.

The viability of three strains of probiotic Bifidobacterium lactis that were inoculated into UHT milk was examined with and without the presence of the yeast, Williopsis saturnus var. saturnus NCYC 22, in polypropylene tubes at 30 °C. The B. lactis viable cell count for strains HN019 and BB-12 remained above 6.0 Log cfu/ml, while strain B94 had 5.7 Log cfu/ml after six weeks of incubation in the presence of the co-inoculated yeast. Incubating the bifidus milk without added yeast under anaerobic condition did not improve the survival of B. lactis HN019, indicating that oxygen removal may not be responsible for W. saturnus NCYC 22's viability enhancing property. The addition of yeast supernatant or non-viable yeast also did not show any stabilising effects, suggesting that physical contact and/or interaction between viable W. saturnus and B. lactis plays an important role in sustaining the viability of the probiotic. W. saturnus NCYC 22 could increase the survival of B. lactis in bifidus milk under ambient temperature regardless of the initial concentration of yeast cells inoculated due to yeast growth. This study demonstrated the viability enhancing effect of viable W. saturnus NCYC 22 on B. lactis HN019, which could help towards extending the shelf-life of dairy beverages containing probiotic bifidobacteria.

Cannulated versus non-cannulated cancellous screw fixation for femoral neck fractures: a synthetic bone biomechanical study.

PURPOSE: To compare the compressive strength of cannulated versus non-cannulated cancellous screws for undisplaced femoral neck fractures in synthetic bones. METHODS: 18 synthetic proximal femurs simulating an AO B1 valgus impacted femoral neck fracture in osteoporotic bone were used. The fracture angles were between 55º and 63º (Pauwels grade 2). Fixation was made using 6.5-mm non-cannulated screws (n=6), 6.5-mm cannulated screws (n=6), or 7.3-mm cannulated screws (n=6). A custom-built jig was designed to guide the insertion of the screws in an identical triangular configuration. Screws were tightened by a single operator using a torque-measuring screwdriver. The femoral head was subjected to progressive axial loading at 5 mm/min. The load to failure and displacement were recorded. RESULTS: The 3 groups did not differ significantly except that the load to failure was higher in the construct with 6.5-mm non-cannulated screws than that with 6.5-mm cannulated screws (1222 N vs 1008 N, p=0.003). CONCLUSION: The compressive strength of a synthetic bone hip fracture model fixed with non-cannulated screws was higher than that of cannulated screws of the same diameter.

Validity and reliability of a self-reported measure of medication adherence in patients with Type 2 diabetes mellitus in Singapore.

AIMS: A reliable and valid measure is essential for the assessment of medication adherence. Until now, no patient-reported medication adherence measure has been validated in Singapore. The aim of this study was to validate a modified 4-item Morisky-Green-Levine Medication Adherence Scale in patients with Type 2 diabetes in Singapore. METHODS: A cross-sectional survey was conducted in a sample of outpatients with Type 2 diabetes in Singapore from September to December in 2009. Respondents completed either an English or Chinese version of the modified 4-item Morisky-Green-Levine Medication Adherence Scale. The scale scores ranged from 0 to 4, with higher scores indicating better medication adherence. Reliability was assessed using Cronbach's alpha. Content validity was assessed by expert review. Construct validity was examined using factor analysis and hypothesis testing. RESULTS: Of the 294 respondents who completed the modified Morisky-Green-Levine Medication Adherence Scale, 13.3, 21.4, 35.7 and 29.6% had a score of 0-1, 2, 3 and 4, respectively. The internal consistency of the scale was moderate (Cronbach's alpha = 0.62). Principal component analysis showed that the four items loaded onto one factor (eigenvalue = 1.95). Respondents with higher scores were older (P < 0.001), had lower HbA(1c) levels (P < 0.001) and had better adherence to physician-recommended diet (P < 0.001) and physical exercise (P = 0.02). CONCLUSIONS: The psychometric properties of the modified Morisky-Green-Levine Medication Adherence Scale were less than satisfactory. A ceiling effect was observed. The scale may not be an adequate measure to assess medication adherence in patients with Type 2 diabetes in Singapore. Future research could target refining the scale and investigating its use in other patient populations.

Stratifying healthcare costs using the Diabetes Complication Severity Index.

OBJECTIVE: We aim to determine whether healthcare costs for patients diagnosed with Type 2 Diabetes Mellitus (T2DM) are associated with the severity of diabetes complications as measured by the Diabetes Complication Severity Index (DCSI). METHODS: Retrospective cohort analysis was performed on a 2007 primary care cohort of T2DM patients. The DCSI is a 13-point scale, which comprises 7 categories of complications and their severity levels. Healthcare cost data from 2008 and 2009 were used as primary outcome. Inpatient and outpatient costs incurred for services consumed by patients within the provider network were included. Generalized linear model with log-link and gamma distribution was used to predict healthcare costs. RESULTS: Of the 59,767 T2DM patients, 2977 (5.0%) deaths occurred and 1336 (2.2%) were lost to follow up. Healthcare cost was strongly associated with increase in DCSI score. Compared to patients without complications, those with more complications (higher DCSI score) had an increased risk of higher healthcare costs. Risk ratio (RR) increased from 1.25 (95%CI: 1.19-1.32) for DCSI=1 to 1.61 (1.51-1.72) for DCSI=2; 2.10 (1.91-2.31) for DCSI=3; 2.52 (2.21-2.87) for DCSI=4 and 3.62 (3.09-4.25) for DCSI≥5. As a continuous score, a one-point increase in the DCSI was associated with a cost increase of 27% (95%CI: 1.25-1.29). CONCLUSION: The DCSI score is a useful tool for predicting direct healthcare costs. The DCSI can be used to triage high-risk patients for more focused secondary prevention interventions at primary care level, in a bid to lower overall healthcare costs.

Health-related quality of life and glycaemic control in patients with Type 2 diabetes mellitus in Singapore.

AIMS: To investigate the health-related quality of life of patients with diabetes mellitus in Singapore and its associations with diabetes-related characteristics and glycaemic control. METHODS: An interviewer-administered, cross-sectional survey was conducted in a sample of 301 adult diabetes patients under primary care. The survey questionnaire included both a generic health-related quality of life measure, the Euroqol 5-D and a diabetes-specific instrument, the Audit of Diabetes-dependent Quality of Life. Patients' most recent HbA(1c) values were extracted from their medical records. RESULTS: After excluding patients who lacked the 90-day HbA(1c) test result, the final number of responses analysed was 282. Pain/discomfort was the most common complaint among the five Euroqol 5-D domains (by 28.0% of the respondents). Lack of freedom to eat was the Audit of Diabetes-dependent Quality of Life domain with the greatest negative average weighted impact (= -3.8, on a scale of -9 to 3). A significant association was observed between Audit of Diabetes-dependent Quality of Life average weighted impact and both duration of diabetes and use of insulin. A negative correlation was found between health-related quality of life and HbA(1c) values in both health-related quality of life measures (both r=-0.2, P=0.001). CONCLUSIONS: Patients with diabetes in primary-care settings frequently reported problems with pain/discomfort and restrictions in diet. Poorer health-related quality of life was found to be associated with higher HbA(1c) values. The chronicity of diabetes and insulin therapy may have a negative impact on patients' diabetes-related health-related quality of life. This study indicates the importance of achieving better disease management to improve the health-related quality of life of patients with diabetes.

Biological characterization of non-steroidal progestins from botanicals used for women's health.

Progesterone plays a central role in women's reproductive health. Synthetic progestins, such as medroxyprogesterone acetate (MPA) are often used in hormone replacement therapy (HRT), oral contraceptives, and for the treatment of endometriosis and infertility. Although MPA is clinically effective, it also promiscuously binds to androgen and glucocorticoid receptors (AR/GR) leading to many undesirable side effects including cardiovascular diseases and breast cancers. Therefore, identifying alternative progestins is clinically significant. The purpose of this study was to biologically characterize non-steroidal progestins from botanicals by investigating theirinteraction and activation of progesterone receptor (PR). Eight botanicals commonly used to alleviate menopausal symptoms were investigated to determine if they contain progestins using a progesterone responsive element (PRE) luciferase reporter assay and a PR polarization competitive binding assay. Red clover extract stimulated PRE-luciferase and bound to PR. A library of purified compounds previously isolated from red clover was screened using the luciferase reporter assay. Kaempferol identified in red clover and a structurally similar flavonoid, apigenin, bound to PR and induced progestegenic activity and P4 regulated genes in breast epithelial cells and human endometrial stromal cells (HESC). Kaempferol and apigenin demonstrated higher progestegenic potency in the HESC compared to breast epithelial cells. Furthermore, phytoprogestins were able to activate P4 signaling in breast epithelial cells without downregulating PR expression. These data suggest that botanical extracts used for women's health may contain compounds capable of activating progesterone receptor signaling.

Effect of rifampin on the pharmacokinetics of Axitinib (AG-013736) in Japanese and Caucasian healthy volunteers.

PURPOSE: Axitinib, a potent and selective inhibitor of vascular endothelial growth factor receptors 1, 2, 3, is metabolized by cytochrome P450 3A4 and glucuronidation. This study evaluated the effect of rifampin, a potent inducer of drug-metabolizing enzymes, on axitinib plasma pharmacokinetics. Equal numbers of Japanese and Caucasian subjects were enrolled to assess the potential differences in axitinib pharmacokinetics between the two ethnicities. METHODS: Forty healthy volunteers were randomized to receive 5 mg axitinib alone and with 600 mg rifampin. RESULTS: Rifampin expectedly decreased AUCinf and Cmax of axitinib (geometric mean reduced by 79 and 71%, respectively). However, differences in axitinib pharmacokinetics were not observed between Japanese and Caucasian subjects (geometric mean ratios for axitinib treatment alone for AUCinf and Cmax were 103 and 96%). CONCLUSIONS: The results support a common axitinib starting dose in both populations. Potent inducers of drug-metabolizing enzymes reduce axitinib exposure and dose adjustments may be needed for optimal efficacy.

Cereulide, the emetic toxin of Bacillus cereus, is putatively a product of nonribosomal peptide synthesis.

AIMS: To determine if cereulide, the emetic toxin produced by Bacillus cereus, is produced by a nonribosomal peptide synthetase (NRPS). METHODS AND RESULTS: NC Y, an emetic strain of Bacillus cereus, was examined for a NRPS gene using PCR with primers recognizing a fragment of a NRPS gene from the cyanobacterium Microcystis. The amplicon was sequenced and compared with other gene sequences using BLAST analysis, which showed that the amplicon from strain NC Y was similar in sequence to peptide synthetase genes in other micro-organisms, including Bacillus subtilis and B. brevis, while no such sequence was found in the complete genome sequence of a nonemetic strain of B. cereus. Specific PCR primers were then designed and used to screen 40 B. cereus isolates previously implicated in outbreaks of foodborne illness. The isolates were also screened for toxin production using the MTT cell cytotoxicity assay. PCR and MTT assay screening of the B. cereus isolates revealed a high correlation between the presence of the NRPS gene and cereulide production. CONCLUSIONS: The results indicate that cereulide is produced by a NRPS complex. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first study to provide evidence identifying the mechanism of production of cereulide, the emetic toxin of B. cereus. The PCR primers developed in the study allow determination of the potential for cereulide production among isolates of B. cereus.

A preliminary evaluation of a disease management programme for patients with diabetes mellitus and hypertension in a primary healthcare setting.

INTRODUCTION: The Comprehensive Chronic Care Programme (CCCP) is an intensified programme designed to provide comprehensive care for the management of diabetes mellitus, hypertension and hyperlipidaemia at a primary healthcare setting. A formative study was done to evaluate the effectiveness of the CCCP compared to the normal polyclinic management of diabetes mellitus. MATERIALS AND METHODS: Control of diabetes (HbA1c) and hypertension (blood pressure) in 63 diabetic patients of a pilot CCCP was compared with 100 diabetic patients not on the programme (non-CCCP) after a 6-month follow-up. Paired t-tests were conducted for differences in mean HbA1c values between baseline and after 6 months. The H-rank test was applied to check for significant differences in change categories of hypertension control between CCCP and non-CCCP cases. RESULTS: In the CCCP group, there was a two-point decrease in HbA1c after 6 months and 65.1% of the patients showed improvement. The proportion of patients achieving optimal diabetic control increased from 9.5% to 36.5%. Conversely, there was deterioration in the non-CCCP group with decrease in the proportion of patients achieving optimal diabetic control from 31% to 21%. Of the hypertensive patients in the CCCP group, 54.5% showed an improvement in blood pressure (BP) control while 44% of the non-CCCP group showed improvement at 6 months. CONCLUSIONS: CCCP, a comprehensive chronic disease management programme, is effective for good diabetic control of patients with diabetes mellitus.

Fuzzylot: a novel self-organising fuzzy-neural rule-based pilot system for automated vehicles.

This paper presents part of our research work concerned with the realisation of an Intelligent Vehicle and the technologies required for its routing, navigation, and control. An automated driver prototype has been developed using a self-organising fuzzy rule-based system (POPFNN-CRI(S)) to model and subsequently emulate human driving expertise. The ability of fuzzy logic to represent vague information using linguistic variables makes it a powerful tool to develop rule-based control systems when an exact working model is not available, as is the case of any vehicle-driving task. Designing a fuzzy system, however, is a complex endeavour, due to the need to define the variables and their associated fuzzy sets, and determine a suitable rule base. Many efforts have thus been devoted to automating this process, yielding the development of learning and optimisation techniques. One of them is the family of POP-FNNs, or Pseudo-Outer Product Fuzzy Neural Networks (TVR, AARS(S), AARS(NS), CRI, Yager). These generic self-organising neural networks developed at the Intelligent Systems Laboratory (ISL/NTU) are based on formal fuzzy mathematical theory and are able to objectively extract a fuzzy rule base from training data. In this application, a driving simulator has been developed, that integrates a detailed model of the car dynamics, complete with engine characteristics and environmental parameters, and an OpenGL-based 3D-simulation interface coupled with driving wheel and accelerator/ brake pedals. The simulator has been used on various road scenarios to record from a human pilot driving data consisting of steering and speed control actions associated to road features. Specifically, the POPFNN-CRI(S) system is used to cluster the data and extract a fuzzy rule base modelling the human driving behaviour. Finally, the effectiveness of the generated rule base has been validated using the simulator in autopilot mode.

Production of poly(3-hydroxybutyrate) and its copolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) by Erwinia sp. USMI-20.

A locally isolated soil microorganism identified as Erwinia sp. USMI-20 has been found to produce poly(3-hydroxybutyrate), P(3HB), from either palm oil or glucose and its copolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate), P(3HB-co-3HV), from a combination of palm oil and a second carbon source of either one of the following compounds: propionic acid, n-propanol, valeric acid and n-pentanol. It was found that Erwinia sp. USMI-20 could produce P(3HB) up to 69 wt.% polymer content with a dry cell weight of 4.4 g/l from an initial amount of 14.5 g/l of glucose followed by a feeding rate of glucose at 0.48 g/h glucose. On the other hand, the bacteria can achieve 46 wt.% of P(3HB) and a dry cell weight of 3.6 g/l from a batch fermentation in a 10-l fermentor from an initial concentration of 4.6 g/l of palm oil. Further characterisation of the polymer production was also carried out by using different types of palm oil. Among the different palm oils that were used, crude palm oil was the best lipid source for P(3HB) production as compared to palm olein and palm kernel oil. In the production of the copolymer, P(3HB-co-3HV), the highest mole fraction of 3-HV units could be as high as 47 mol% from a single feeding of valeric acid upon initial growth on palm oil.

Interactive brain atlas with the Visible Human Project data: development methods and techniques.

A prototype of an interactive digital brain atlas was developed by using the Visible Human Project data set of the National Library of Medicine. This data set provides corresponding axial magnetic resonance images, computed tomographic images, and cryosections of the brain. The prototype was developed to demonstrate the techniques and methods that will be used throughout the development process of the atlas. The atlas has a graphical user interface, supports user interaction with various representations of the brain (i.e., two-dimensional and three-dimensional [3D]), and displays multiple images simultaneously. Motion sequences of the 3D brain were incorporated in the atlas to provide an important link between two-dimensional brain slices and volume-rendered 3D anatomic structures. Volume visualization tools were used to interactively render, rotate, and reslice the volumetric brain data. The brain was segmented with manual tracing, thresholding, and morphologic algorithms and then rendered with volume-rendering tools.

Leukotrienes in bile during the early and the late airway responses after allergen challenge of sensitized rats.

The Brown Norway rat produces high levels of IgE in response to active immunization and develops both early and late airway constrictor responses after subsequent allergen challenge. We have used this model of allergic asthma to investigate the temporal relationship between the in vivo synthesis of peptidoleukotrienes (peptido-LTs) and the late response. Brown Norway rats that had been sensitized by injection of ovalbumin 2 to 3 wk prior to the commencement of the experiment were subjected to bile duct cannulation and tracheal intubation. The rats were challenged 2 h later by intratracheal instillation of ovalbumin. Lung resistance was measured before and at frequent intervals after antigen challenge. Biliary peptido-LTs (LTC4, LTD4, LTE4, and N-acetyl-LTE4) were measured by a combination of high pressure liquid chromatography and radioimmunoassay in bile samples collected for a period of 1 h before instillation of ovalbumin, and between zero and 1 h, 1 and 4 h, 4 and 6 h, and 6 and 8 h, subsequently. All of the 10 rats subjected to antigen challenge developed early responses. Of these, six also developed late responses, whereas two died about 1 h after challenge. The levels of peptido-LTs excreted in bile between 4 and 8 h after antigen challenge (corresponding in time to the late responses) were about four times higher in the ovalbumin-instilled rats that developed late responses (n = 6) than in the ovalbumin-sensitized control rats that had been subjected to instillation of saline (n = 6; p < 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)