Prevalence of diabetes and impaired fasting glucose in the Chinese adult population: International Collaborative Study of Cardiovascular Disease in Asia (InterASIA)

AIMS/HYPOTHESIS

To estimate the prevalence of diagnosed and undiagnosed diabetes and impaired fasting glucose in the general adult population of China.

METHODS

The International Collaborative Study of Cardiovascular Disease in ASIA, conducted from 2000 to 2001, included a nationally representative sample of 15 540 adults, aged 35 to 74 years. An overnight fasting blood specimen was collected to measure serum glucose and information on history of diabetes and use of hypoglycaemic medications was obtained by a standard questionnaire. Undiagnosed diabetes (fasting glucose > or =7.0 mmol/l) and impaired fasting glucose (6.1-6.9 mmol/l) were defined using the American Diabetes Association criteria.

RESULTS

Prevalence of self-reported diagnosed diabetes, undiagnosed diabetes, and impaired fasting glucose in Chinese adults were 1.3%, 4.2%, and 7.3%, respectively. Overall, 5.2% or 12.7 million men and 5.8% or 13.3 million women in China aged 35 to 74 years had diabetes (self-reported diagnosis plus undiagnosed diabetes). The age-standardized prevalence of diabetes was higher in residents of northern compared to southern China (7.4% vs 5.4%, p<0.001) and in those living in urban compared to rural areas (7.8% vs 5.1%, p<0.001).

CONCLUSIONS/INTERPRETATION

Our results show that the prevalence of diabetes in the adult population in China is much higher than previously reported. Three out of every four diabetes patients are undiagnosed, indicative of a lack of population-based screening programmmes and a relatively rapid and recent increase in incidence of diabetes. These results indicate that diabetes has become a major public health problem in China and underscore the need for national strategies aimed at prevention and treatment of diabetes.

Depth-resolved model-based reconstruction of attenuation coefficients in optical coherence tomography

We present a method, based on a single scattering model, to calculate the attenuation coefficient of each pixel in optical coherence tomography (OCT) depth profiles. Numerical simulations were used to determine the model's response to different depths and attenuation coefficients. Experiments were performed on uniform and layered phantoms with varying attenuation coefficients. They were measured by a 1300 nm OCT system and their attenuation coefficients were evaluated by our proposed method and by fitting the OCT slope as the gold standard. Both methods showed largely consistent results for the uniform phantoms. On the layered phantom, only our proposed method accurately estimated the attenuation coefficients. For all phantoms, the proposed method largely reduced the variability of the estimated attenuation coefficients. The method was illustrated on an in-vivo retinal OCT scan, effectively removing common imaging artifacts such as shadowing. By providing localized, per-pixel attenuation coefficients, this method enables tissue characterization based on attenuation coefficient estimates from OCT data.

Headache, cerebrovascular symptoms, and stroke: the Atherosclerosis Risk in Communities Study

OBJECTIVE

To evaluate the occurrence of stroke/TIA symptoms and ischemic stroke events among those with a lifetime history of migraine or other headaches with some migraine features in a biracial cohort of older adults.

METHODS

Participants were 12,750 African-American and white men and women from the Atherosclerosis Risk in Communities Study (1993 to 1995). The participants were queried about their lifetime headache history and characterized using modified International Headache Society diagnostic criteria. Stroke/TIA symptoms were classified using a computerized diagnostic algorithm, and ischemic stroke events were identified and validated using medical records. Multivariate logistic regression was used to assess the relationship between headache types and stroke/TIA symptoms and ischemic stroke events.

RESULTS

Migraine with aura was strongly associated with stroke symptoms (odds ratio [OR] 5.46, 95% CI: 3.64 to 8.18), TIA symptoms (OR 4.28, 95% CI: 3.02 to 6.08), and verified ischemic stroke events (OR 2.81, 95% CI: 1.60 to 4.92). Similarly, other headaches with aura were significantly associated with stroke symptoms (OR 3.68, 95% CI: 2.26 to 5.99) and TIA symptoms (OR 4.53, 95% CI: 3.08 to 6.67). In contrast, the associations for migraine without aura and other headaches without aura were not as consistent or robust.

CONCLUSIONS

Migraines and other headaches, particularly those accompanied by aura, were associated with an increased occurrence of stroke/TIA symptoms and ischemic stroke events.

DNA damage in the nucleosome core is refractory to repair by human excision nuclease

To investigate the effect of nucleosomes on nucleotide excision repair in humans, we prepared a mononucleosome containing a (6-4) photoproduct in the nucleosome core and examined its repair with the reconstituted human excision nuclease system and with cell extracts. Nucleosomal DNA is repaired at a rate of about 10% of that for naked DNA in both systems. These results are in agreement with in vivo data showing a considerably slower rate of repair of overall genomic DNA relative to that for transcriptionally active DNA. Furthermore, our results indicate that the first-order packing of DNA in nucleosomes is a primary determinant of slow repair of DNA in chromatin.

Two-kidney, two clip renovascular hypertensive rats can be used as stroke-prone rats

BACKGROUND AND PURPOSE

The cerebrovascular lesions in stroke-prone spontaneously hypertensive rats are not only dependent on high blood pressure but partly related to pressure-independent genetic factors. The aim of the present study was to observe whether spontaneous stroke occurred in renovascular hypertensive rats without a genetic deficiency.

METHODS

The 1-kidney, 1 clip (1k1c); 2-kidney, 1 clip (2k1c); and 2-kidney, 2 clip (2k2c) methods were used to induce hypertension in male Sprague-Dawley rats with a ring-shaped silver clip. Sham-operated rats were used as controls. Blood pressure and neurological symptoms were observed in the rats without any artificial inducement. Brain sections stained with hematoxylin-eosin and phosphotungstic acid-hematoxylin were examined under a microscope to determine stroke foci.

RESULTS

The attack rate of stable hypertension was 100% (55/55) in the 2k2c group, which was significantly higher than that in the 1k1c (23/30, 76.7%) and 2k1c (21/30, 70%) groups (P<0.01). None of the rats in the 2k2c group died of acute renal failure or suffered from diffuse cerebral lesions postoperatively. Forty weeks after renal artery constriction, the incidence of spontaneous stroke in the 2k2c group was 61.8% (34/55), which was significant higher than that in the 1k1c (7/30, 23.3%) and 2k1c (5/30,16.7%) groups (P<0.01). Stroke foci were not observed in normotensive controls.

CONCLUSIONS

We conclude that 2k2c renovascular hypertensive rats with proper renal artery constriction can be used as stroke-prone renovascular hypertensive rats independent of a genetic deficiency.

Collagen induced arthritis as an experimental model for rheumatoid arthritis. Immunogenetics, pathogenesis and autoimmunity

The type II collagen (CII) induced arthritis animal model (CIA) provides opportunities to study the nature of autoimmune reactions leading to arthritis and may be used as a model for rheumatoid arthritis (RA). Thus, in similarity with RA, the CIA model, when induced with autologous CII, shows a chronic and progressive disease course. The susceptibility to both RA and CIA are correlated to the expression of certain MHC class II allotype genes. In both diseases are autoantibodies to CII and rheumatoid factors produced. Immunohistopathology of affected joints show in both diseases a dominance of activated macrophages/fibroblasts with a significant infiltration of activated T cells and an infiltration of granulocytes. We do here suggest that both RA and CIA are dependent on a synergy between delayed type hypersensitivity and immune complex mediated inflammatory mechanisms and that CIA provides opportunities for studies of immunospecific reactions leading to arthritis.

Identification of a fourth subunit of mammalian DNA polymerase delta

A 12-kDa and two 25-kDa polypeptides were isolated with highly purified calf thymus DNA polymerase delta by conventional chromatography. A 16-mer peptide sequence was obtained from the 12-kDa polypeptide which matched a new open reading frame from a human EST () encoding a hypothetical protein of unknown function. The protein was designated as p12. Human EST was identified as the putative human homologue of Schizosaccharomyces pombe Cdm1 by a tBlastn search of the EST data base using S. pombe Cdm1. The open reading frame of human EST encoded a polypeptide of 107 amino acids with a predicted molecular mass of 12.4 kDa, consistent with the experimental findings. p12 is 25% identical to S pombe Cdm1. Both of the 25-kDa polypeptide sequences matched the hypothetical KIAA0039 protein sequence, recently identified as the third subunit of pol delta. Western blotting of immunoaffinity purified calf thymus pol delta revealed the presence of p125, p50, p68 (the KIAA0039 product), and p12. With the identification of p12 mammalian pol delta can now be shown to consist of four subunits. These studies pave the way for more detailed analysis of the possible functions of the mammalian subunits of pol delta.

Metabolic syndrome, its preeminent clusters, incident coronary heart disease and all-cause mortality--results of prospective analysis for the Atherosclerosis Risk in Communities study

OBJECTIVE

To investigate the prospective association between Metabolic Syndrome (MetS) and coronary heart disease (CHD) and all-cause mortality.

SUBJECTS AND DESIGN

A bi-racial cohort of 14 699 middle-aged Americans from the Atherosclerosis Risk in Communities study were followed for the development of new CHD and death over a period of 9 years. MetS, using the original ATP-III criteria, was defined as having at least three of the following components: elevated blood pressure (BP), elevated plasma glucose, elevated blood triglyceride (TG), increased waist circumference, and low HDL cholesterol (HDL-c). Incident CHD cases included hospitalized myocardial infarction (MI), fatal CHD, revascularization procedures, and silent MI as detected by EKG.

RESULTS

The prevalence of the MetS at baseline was 29%, 30%, 40% and 26% among CHD-free white women, white men, black women, and black men, respectively. There were 1018 incident CHD cases and 1039 deaths. The relative risk (RR) and 95% confidence interval (CI) of incident CHD associated with MetS was 2.46 (1.99, 3.03) for women and 1.86 (1.59, 2.18) for men. Clear dose-response relationship between the number of MetS components and incidence of CHD was found (P for linear trend <0.001). The following three clusters of MetS components posed the highest risk for CHD: (i) the elevated BP and glucose and low HDL-c group [RR = 5.68 (3.44, 9.37)]; (ii) the elevated BP and glucose and TG group [RR = 5.08 (2.96, 8.70)]; and (iii) the elevated BP and TG and low HDL-c group [RR = 3.98 (2.75, 5.77)]. When all five components co-existed, the risk was the highest [RR = 6.24 (4.65, 8.36)]. Similar results with attenuated RR were found for all-cause mortality.

CONCLUSIONS

Individuals, especially women, with the MetS have significantly higher risk of developing CHD. The riskiest combination is high-BP and glucose clustered with low HDL-c or high TG. These data highlight the importance of targeting MetS in the prevention of CHD and premature death.

Modification of an effector strain for replacement therapy of dental caries to enable clinical safety trials

AIMS

To construct a genetically modified strain of Streptococcus mutans for dental caries prevention. The strain has significantly reduced cariogenicity owing to a deletion of the entire open reading frame for lactate dehydrogenase, and has excellent colonization potential through the production of a natural antibiotic called mutacin 1140. For use in human clinical trials, additional mutations were introduced to enable rapid elimination of the strain in case of adverse side effects and to increase genetic stability.

METHODS

Deletion mutations were introduced into the dal gene for d-alanine biosynthesis and the comE gene for genetic transformation. The resulting strain, A2JM, was tested for dependence on exogenous d-alanine and its ability to be eradicated from colonized rats. The strain was also tested for its ability to exchange DNA with another strain of S. mutans in in vitro and in vivo models.

CONCLUSIONS

A2JM was completely dependent on exogenous d-alanine, but could colonize the oral cavity of rats in low numbers in the absence of dietary d-alanine. Results indicated that A2JM can scavenge d-alanine from other plaque bacteria. Lowering of the total oral bacterial load through daily application of chlorhexidine enabled virtually complete eradication of A2JM. The introduction of the comE gene did not significantly decrease the transformability of A2JM in in vitro or in vivo models. The addition of a deletion in the comE gene does, nonetheless, provide additional safety as it has a very low reversion frequency.

SIGNIFICANCE AND IMPACT OF THE STUDY

Based on the safety and efficacy profiles established in vitro and in animal models, A2JM appears suitable for safe use in human clinical trials.

Temporal synchronization in the primary auditory response in the pigeon

Spike potentials were recorded from single fibres in the auditory nerve of the pigeon. In responses elicited by tonal stimuli, the timing of each spike relative to stimulus waveform was measured and period histograms were constructed. Phase locking of spikes was estimated in terms of a synchronicity index obtained by vector addition within the period histogram. A second measure of synchrony in the spike responses was obtained, that of temporal dispersion. For a population of fibres, vector strength of phase locking decreased for frequencies above 1 kHz, as reported for several other species. Temporal dispersion, however, also decreased with frequency, indicating enhanced temporal synchrony as frequency increased within the bandwidth of phase locking. The upper frequency limit of phase locking appears to depend on irreducible jitter of biological origin in the timing of spikes. For individual fibres, the bandwidth of synchronization of spikes consistently exceeds the response area, covering in addition the areas of suppression adjacent to the response area. Spike trains suppressed by a tonal stimulus become synchronized to that stimulus. Phase angles of synchronized responses systematically change as a function of tone level, when tone frequency is above or below CF, as reported for other avian species. Synchronicity and phase angle intensity functions are quite independent of spike rate intensity functions.

Evidence that DNA polymerase delta isolated by immunoaffinity chromatography exhibits high-molecular weight characteristics and is associated with the KIAA0039 protein and RPA

DNA polymerase delta, the key enzyme for eukaryotic chromosomal replication, has been well characterized as consisting of a core enzyme of a 125 kDa catalytic subunit and a smaller 50 kDa subunit. However, less is known about the other proteins that may comprise additional subunits or participate in the macromolecular protein complex that is involved in chromosomal DNA replication. In this study, the properties of calf thymus pol delta preparations isolated by immunoaffinity chromatography were investigated. It is demonstrated for the first time using highly purified preparations that the pol delta heterodimer is associated with other polypeptides in high-molecular weight species that range from 260000 to >500000 in size, as determined by FPLC gel filtration. These preparations are associated with polypeptides of ca. 68-70, 34, 32, and 25 kDa. Similar findings were revealed with glycerol gradient ultracentrifugation. The p68 polypeptide was shown to be a PCNA binding protein by overlay methods with biotinylated PCNA. Protein sequencing of the p68, p34, and p25 polypeptide bands revealed sequences that correspond to the hypothetical protein KIAA0039. KIAA0039 displays a small but significant degree of homology to Schizosaccharomyces pombe Cdc27, which, like Saccharomyces cerevisiae Pol32p, has been described as the third subunit of yeast pol delta. These studies provide evidence that p68 is a subunit of pol delta. In addition, the p68-70 and p32 polypeptides were found to be derived from the 70 and 32 kDa subunits of RPA, respectively.

Fine mapping of 10q and 18q for familial Alzheimer's disease in Caribbean Hispanics

Familial Alzheimer's disease (AD [MIM 104300]) has been a focus of intense investigation, primarily in Caucasian families from Europe and North America families. Although the late-onset form of familial AD, beginning after age 65 years, has been linked to regions on chromosomes 10q and 12p, the specific genetic variants have not yet been consistently identified. Using a unique cohort of families of Caribbean Hispanics ancestry, we screened the genome using 340 markers on 490 family members from 96 families with predominantly late-onset AD. We observed the strongest support for linkage on 18q (LOD=3.14). However, 17 additional markers (chromosomes 1-6, 8, 10, 12, and 14) exceeded a two-point LOD score of 1.0 under the affecteds-only autosomal dominant model or affected sibpair model. As we previously reported the fine-mapping effort on 12p showing modest evidence of linkage, we focused our fine-mapping efforts on two other candidate regions in the current report, namely 10q and 18q. We added 31 family members and eight additional Caribbean Hispanic families to fine map 10q and 18q. With additional microsatellite markers, the evidence for linkage for 18q strengthened near 112 cM, where the two-point LOD score for D18S541 was 3.37 and the highest NPL score in that region was 3.65 (P=0.000177). This narrow region contains a small number of genes expressed in the brain. However, at 10q (134-138 cM), the NPL score decreased from 3.15 (P=0.000486) to 2.1 (P=0.0218), but two broad peaks remained overlapping with previously reported peaks. Our results provide modest support for linkage on 10q and 12p in this cohort of Caribbean Hispanic families with familial Alzheimer's disease, and strong evidence for a new locus on 18q.

Voriconazole and squamous cell carcinoma after lung transplantation: A multicenter study

This study evaluated the independent contribution of voriconazole to the development of squamous cell carcinoma (SCC) in lung transplant recipients, by attempting to account for important confounding factors, particularly immunosuppression. This international, multicenter, retrospective, cohort study included adult patients who underwent lung transplantation during 2005-2008. Cox regression analysis was used to assess the effects of voriconazole and other azoles, analyzed as time-dependent variables, on the risk of developing biopsy-confirmed SCC. Nine hundred lung transplant recipients were included. Median follow-up time from transplantation to end of follow-up was 3.51 years. In a Cox regression model, exposure to voriconazole alone (adjusted hazard ratio 2.39, 95% confidence interval 1.31-4.37) and exposure to voriconazole and other azole(s) (adjusted hazard ratio 3.45, 95% confidence interval 1.07-11.06) were associated with SCC compared with those unexposed after controlling for important confounders including immunosuppressants. Exposure to voriconazole was associated with increased risk of SCC of the skin in lung transplant recipients. Residual confounding could not be ruled out because of the use of proxy variables to control for some confounders. Benefits of voriconazole use when prescribed to lung transplant recipients should be carefully weighed versus the potential risk of SCC. EU PAS registration number: EUPAS5269.

Excitation and suppression of primary auditory fibres in the pigeon

Spike potentials were recorded from single fibres in the auditory nerve of the pigeon. In fibres with recognizable responses to sound, spontaneous activity and properties of responses to tonal stimuli were studied in quiet background conditions. Mean spontaneous rate in the sample of fibres was 35 spikes/s. Tuning of spike response to tones was manifest as a single peak in rate at each sound pressure level (SPL) in the frequency-intensity plane. The majority of fibres showed only excitation of spike rate above spontaneous rate. Post stimulus time histograms (PSTs) in such cases were typical of excitatory responses, previously described in birds and mammals showing pronounced adaptation and post-stimulus suppression of spike rate. In most cases of excitation-only responses, however, slopes of rate functions depended on stimulus frequency. Close to characteristic frequency (CF), slopes tended to decrease with increasing SPL, whereas away from CF, slopes tended to increase with SPL. In a minority of excitation-only responses, slopes of rate functions were parallel. In some fibres, tones adjacent to the response area caused overt suppression of spontaneous firing. For these fibres, the slopes of rate functions were more-strongly frequency-dependent, being negative at low SPL when rate suppression occurred. Suppression of spontaneous activity at low SPL was non-monotonic and quite different from suppression of spike rate at stimulus intensities above rat saturation. In PSTs of suppressed spontaneous activity, rebound occurred at the termination of the tone. The results clarify previous observations of suppression of primary auditory responses in birds. We conclude that responses in the majority of auditory fibres in the pigeon are the product of opposing excitatory and suppressive influences in the cochlea, generated by single tones in quite.

A model proposing synaptic and extra-synaptic influences on the responses of cochlear nerve fibres

A unique property of sensory coding in the vertebrate auditory system is the existence of the classical form of excitatory centre-inhibitory surround in relative spike rate along the stimulus frequency dimension, in addition to a representation of temporal fine structure of high frequency periodic stimuli in the discharge pattern of primary afferent spike trains. We present a model which designates three factors that influence rate and temporal synchrony in spike responses; an excitatory factor, a suppressive factor and a synchronizing factor. The model proposes that an essential integration of bioelectric signals occurs in the primary afferent fibre. It is presumed that mean spike rate depends on mean level of membrane depolarization and synchronization depends on periodic modulation of membrane potential at the spike initiating zone. In the model, the excitatory factor is synaptically-mediated, excitatory post-synaptic potential (e.p.s.p.); the suppressive factor is negative DC polarization of the fibre membrane and the synchronizing factor is AC modulation of the fibre membrane potential. It is proposed that both the negatively-polarizing and high-frequency modulating signals are derived from extracellular current flow in the cochlea.

Characterization of the p125 subunit of human DNA polymerase delta and its deletion mutants. Interaction with cyclin-dependent kinase-cyclins

The catalytic subunit of human DNA polymerase (pol) delta was overexpressed in an active, soluble form by the use of a baculovirus system in insect cells. The recombinant enzyme was separated from endogenous DNA polymerases by phosphocellulose, Mono Q-Sepharose, and single-stranded DNA-cellulose chromatography. Recombinant DNA pol delta was also purified by immunoaffinity chromatography. The enzymatic properties of the purified catalytic subunit were characterized. The enzyme was active and possessed both DNA polymerase and associated 3' to 5' exonuclease activities. NH2-terminal deletion mutants retained polymerase activity, whereas the core and COOH-terminal deletion mutants were devoid of any measurable activities. Coinfection of Sf9 cells with recombinant baculovirus vectors for pol delta and cyclin-dependent kinase (cdk)-cyclins followed by metabolic labeling with 32Pi showed that the recombinant catalytic subunit of pol delta could be hyperphosphorylated by G1 phase-specific cdk-cyclins. When cdk2 was coexpressed with pol delta in Sf9 cells, pol delta was found to coimmunoprecipitate with antibodies against cdk2. Experiments with deletion mutants of pol delta showed that the NH2-terminal region was essential for this interaction. Coimmunoprecipitation and Western blot experiments in Molt 4 cells confirmed the interaction in vivo. Preliminary experiments showed that phosphorylation of the catalytic subunit of pol delta by cdk2-cyclins had little or no effect on the specific activity of the enzyme.

An in-situ thermally regenerated air purifier for indoor formaldehyde removal

Formaldehyde is a common indoor pollutant that is an irritant and has been classified as carcinogen to humans. Adsorption technology is safe and stable and removes formaldehyde efficiently, but its short life span and low adsorption capacity limit its indoor application. To overcome these limitations, we propose an in-situ thermally regenerated air purifier (TRAP) which self-regenerates as needed. This purifier has four working modes: cleaning mode, regeneration mode, exhaust mode, and outdoor air in-take mode, all of which are operated by valve switching. We developed a real-scale TRAP prototype with activated carbon as adsorbent. The experimental testing showed that the regeneration ratios for formaldehyde of TRAP were greater than 90% during 5 cycles of adsorption-regeneration and that through the 5 cycles, there was no damage to the adsorption material as confirmed by scanning electron microscope (SEM) and Brunauer-Emmett-Teller (BET) tests. The total energy consumption by the prototype for purifying 1000 m³ indoor air was 0.26 kWh. This in-situ thermal-regeneration method can recover the purifier's adsorption ability through at least five cycles.

Nesidioblastosis coexisting with islet cell tumor and intraductal papillary mucinous hyperplasia

A coexisting of intraductal papillary mucinous hyperplasia (IPMH) and islet cell tumor with nesidioblastosis of the pancreas in a 51-year-old man is reported. All of the clinical data indicated an insulinoma. A distal pancreatectomy was performed. A discrete mass measuring 1.9 x 2.0 cm was grossly identified in the tail of the pancreas. There were no other gross lesions. An islet cell tumor with nesidioblastosis was confirmed by immunostains and ultrastructural study. In addition, an IPMH was found that involved mainly branches of the pancreatic duct. The islet cell tumor and IPMH were topographically separated; however, there was a histologically intimate relationship between the nesidioblastosis and the IPMH. These findings indicate that the IPMH may have derived from autocrine and paracrine influences on the existing duct epithelial cells. To the best of our knowledge, this is the first report of nesidioblastosis coexisting with islet cell tumor and IPMH.

Induced suppression in spike responses to tone-on-noise stimuli in the auditory nerve of the pigeon

Spike potentials were recorded from single, afferent fibres in the pigeon auditory nerve. Pure-tone stimuli were presented in quiet and in combination with wide band noise. Presented alone, tones produced tuned response areas; noise generally drove spike rate to well above the spontaneous rate measured in quiet. When presented in combination with noise, tones up to 75 dB SPL at frequencies far from the fibre's response area had no effect on the noise-driven spike rate. As the tone frequency was shifted towards the response area, from above or below CF, suppression of the noise-driven spike rate became stronger until the tone reached the edge of the response area. Suppression of the noise-driven rate was directly proportional to the level of the tone. Within the area of response to the tone, tone-driven spike rates generally were unchanged or variably decreased (occasionally slightly increased) by tone-on-noise stimulation, depending on the relation of the tone frequency to CF and the level of the tone relative to that of the noise. Tuning properties were unaffected. It is suggested that in the pigeon, the suppression of driven spike rate during presentation of combination stimuli, which is common to all fibres, depends on the same mechanism as the suppression of spontaneous firing by tones that is observed in a proportion of fibres (Temchin, A.N. (1988), J. Comp. Physiol. A 163, 99-115; Hill et al., (1989) Hear. Res. 39, 37-48).

Novel insight into VOC removal performance of photocatalytic oxidation reactors

A general model has been developed for analyzing the removal of volatile organic compounds (VOCs) by photocatalytic oxidation (PCO) reactors, taking into consideration of the photocatalytic (surface) reaction and the convective mass transfer coefficients including allowance for their spatial dependence. On this basis, a novel insight into VOC removal performance of PCO reactors is presented. The key parameter for evaluating PCO reactor VOC removal performance is the number of the mass transfer unit (NTU(m)), which is shown to be a simple linear product of three dimensionless parameters: the ratio of the reaction area to the cross-sectional area of the flow channel (A*), the Stanton number of mass transfer (St(m)), and the reaction effectiveness (eta). The A* represents the geometric and structural characteristic of a PCO reactor. The St(m) shows the synergistic degree of alignment between the fluid and mass flow fields, and reflects the convective mass transfer rate of the reactor. The eta, describes the relative intensity between the PCO reaction rate and the mass transfer rate. By using the relationship and the parameters, the influence of various factors on the VOC removal performance, the bottleneck for improving the performance and design of a PCO reactor can be determined. Three examples are used to illustrate the application of our proposed model. It is found that the VOC removal bottleneck is the reaction rate for honeycomb type reactor, while mass transfer rate for light-in-tube type reactor. With six fins the fractional conversion of a light-in-tube reactor increases about 70% relative to the one without any fins.

PRACTICAL IMPLICATIONS

Indoor air quality problem caused by volatile organic compounds (VOCs) have annoyed people for many years. Photocatalytic oxidation (PCO) appears to be a promising technique for destroying VOCs in indoor air. With the model and the novel insight presented in this paper, the influence of various factors on the VOC removal performance can be determined. And the bottleneck for improving the performance of a PCO reactor can be easily identified. These are helpful for designing high performance PCO reactors and optimizing their operative performance.

Understanding and controlling airborne organic compounds in the indoor environment: mass transfer analysis and applications

Mass transfer is key to understanding and controlling indoor airborne organic chemical contaminants (e.g., VVOCs, VOCs, and SVOCs). In this study, we first introduce the fundamentals of mass transfer and then present a series of representative works from the past two decades, focusing on the most recent years. These works cover: (i) predicting and controlling emissions from indoor sources, (ii) determining concentrations of indoor air pollutants, (iii) estimating dermal exposure for some indoor gas-phase SVOCs, and (iv) optimizing air-purifying approaches. The mass transfer analysis spans the micro-, meso-, and macroscales and includes normal mass transfer modeling, inverse problem solving, and dimensionless analysis. These representative works have reported some novel approaches to mass transfer. Additionally, new dimensionless parameters such as the Little number and the normalized volume of clean air being completely cleaned in a given time period were proposed to better describe the general process characteristics in emissions and control of airborne organic compounds in the indoor environment. Finally, important problems that need further study are presented, reflecting the authors' perspective on the research opportunities in this area.

5-HT 3 receptors mediate the time-dependent vagal afferent modulation of nociception during chronic food allergen-sensitized visceral hyperalgesia in rats

Converging lines of evidence demonstrate a vagally mediated antinociceptive pathway in animals undergoing acute visceral insults, the contribution of this system to visceral pain following chronic noxious stimuli is unknown. 5-HT(3) receptor (5-HT(3)Rs) on spinal afferents are crucially involved in nociceptive processing, the role of 5-HT(3)Rs on vagal afferents is unclear. The aim of the present study was to determine the contribution of vagal afferents to visceral nociception in rats undergoing chronic luminal allergen stimulation and whether it involves vagal 5-HT(3)Rs. Sensitized rats received chicken egg albumin (EA, 1 mg mL(-1)) in drinking water for 2 weeks (day 1-14). Visceromotor response (VMR) to colorectal distension [colorectal distension (CRD), 60 mmHg] and the levels of mRNA encoding 5-HT(3)R (including 3A and 3B subunits) in the nodose ganglia (NG) were evaluated on day 2, 4, 8 and 15. Chronic EA challenge induced gradually increased visceral nociception, with a peak on day 15. Subdiaphragmatic vagotomy or functional deafferentation with capsaicin abolished this time-dependent manner, inducing hyperalgesia from day 2, lasting to day 15. Intraluminal infusion of a 5-HT(3)R antagonist (granisetron), whether alone or infused after local mucosa anaesthetic with 1% lidocaine, mimicked the effects of vagotomy. The mRNA levels for 5-HT(3B) or 5-HT(3A) subunit in the NG showed an opposite time-course to that of visceral pain, which increased from day 2, then decreased gradually to levels lower than those of controls. Our results demonstrate a time-dependent vagal afferent modulation of chronic allergen-sensitized visceral hyperalgesia, which may involve a 5-HT(3)R pathway.

Kinetics of folding and unfolding of alpha alpha-tropomyosin and of nonpolymerizable alpha alpha-tropomyosin

Stopped flow CD (SFCD) kinetic studies of self-assembly of coiled coils of rabbit alpha alpha-tropomyosin and of nonpolymerizable alpha alpha-tropomyosin (NPTm) are reported. The protein was denatured in 6 M urea buffer, then renatured by 10-fold dilution into benign saline buffer. Folding was monitored by SFCD in the backbone region (222 nm). Protein chains are shown to be totally unfolded (and separated in the reduced species) in the initial denaturing medium and fully folded as two-chain coiled coils in the final benign medium. In all cases of folding in benign buffer of totally unfolded chains, two phases were found in the folding process: a fast phase (less than 0.04 s, the SFCD dead time), in which an intermediate state with about 70% of the equilibrium ellipticity forms; followed by a slower, observable phase that completes the folding. The slow phase is first order (k-1 = 1.6 s at 20 degrees C), signifying that chain association for reduced samples occurs in the fast phase. In contrast, folding in benign buffer from an initial state with 70% of the equilibrium ellipticity is all fast, suggesting that the folding intermediate is not an equilibrium species. Cross-linking at Cys-190 increases the helix content of the fast-formed intermediate state to about 85% of the equilibrium value, but leaves the rate constant of the slow phase unchanged. In NPTm, which does not form high aggregates at low ionic strength, the rate of the observable phase is almost independent of ionic strength in the range of approximately 0.15-0.6 M, but is reduced one to two orders of magnitude by further reduction to 0.026 M. In folding from totally unfolded chains, the rate is reduced less than one order of magnitude by changing the final state to about 50% folded. In contrast to folding, unfolding of alpha alpha-tropomyosin from the native state is all fast.