Interactive effects of Louisiana Sweet Crude (LSC) thin oil sheens and ultraviolet light on mortality and swimming behavior of the larval Eastern oyster, Crassostrea virginica.

The Eastern oyster (Crassostrea virginica) is an important commercial bivalve species which also has numerous ecological roles including biogeochemical cycling, providing habitat for larval fish and crustaceans, and reducing the impacts of coastal storms. Oil may pose a threat to oyster larvae swimming in the water column, leading to potential negative effects on survival, growth, and development. Oil toxicity may be further enhanced by chemical changes in the presence of sunlight. This study determined the toxicity of thin oil sheens with and without ultraviolet (UV) light, then examined the latent effects of the short term exposure on longer term survival and swimming ability. Larval C. virginica were exposed to four different oil sheen thicknesses for 24 h with either no UV light or 2-h UV light. Following the exposure, larvae were transferred to clean seawater and no UV light for 96 h. The presence of a 2-h UV light exposure significantly increased oyster mortality, indicating photo-enhanced toxicity. The LC50 for a 24-h oil sheen exposure without UV was 7.26 µm (23 µg/L PAH50) while a 2 h-UV exposure lowered the sheen toxicity threshold to 2.67 µm (10 µg/L PAH50). A previous 24-h oil sheen exposure (≥0.5 µm) led to latent effects on larval oyster survival, regardless of previous UV exposure. Sublethal impacts to larval oyster swimming behavior were also observed from the previous oil sheen exposure combined with UV exposure. This study provides new data for the toxicity of thin oil sheens to a sensitive early life stage of estuarine bivalve.

Acute Polychlorinated Biphenyl Benthic Invertebrate Toxicity Testing to Support the 2017 Chronic Dose-Response Sediment Injury Model.

As managers and decision makers evaluate pollutant risk, it is critical that we are able to measure an assessment of the injury. Often, these estimates are difficult to determine for benthic organisms, so in 2017 a chronic polychlorinated biphenyl (PCB) sediment dose-response model to predict benthic invertebrate injury was proposed. Given both natural resource trustee and consultant questions following publication concerning that the aqueous chronic toxicity testing data used in the 2017 model development were primarily from the 1970s and 1980s, this follow-up short communication is meant to provide the user some additional data that are more recent. With the advances in analytical and quantitative environmental chemistry (i.e., better detection limits and congener separation), we chose to complete acute aquatic toxicity testing using 3 estuarine invertebrates and lethal endpoints (20 and 50% lethal concentrations). This acute testing was selected because chronic aquatic testing for PCBs outside of the data used in the 2017 study was not available to us. The aquatic results used in the present study were changed to sediment using equilibrium partitioning, as done in the 2017 chronic model, after using the same organic-carbon partition coefficient and total organic carbon for our equilibrium partitioning (EqP)-measured calculations. Based on these acute aquatic toxicity results and a general acute-to-chronic injury concentration ratio of approximately 10, we found that the 2017 model was valid and, hence, that a 1.0 µg/g chronic PCB sediment criterion is a reasonable estimation of potential benthic invertebrate injury. This was followed by spiked sediment tests where percent acute sediment injury was compared to the EqP-derived chronic value and the results from 2017; modest agreement is shown. Environ Toxicol Chem 2021;40:1188-1193. Published 2020. This article is a U.S. Government work and is in the public domain in the USA.

Homoclinic-doubling and homoclinic-gluing bifurcations in the Takens-Bogdanov normal form with D 4 symmetry.

In this paper, we investigate the dynamics of a fourth-order normal form near a double Takens-Bogdanov bifurcation. The reduced system of this normal form possesses eight pairs of homoclinic orbits for certain parameter values. The nonlinear time transformation method is applied to obtain an analytical approximation of the homoclinic orbit in the perturbed system and to construct the homoclinic bifurcation curve as well. Using numerical continuation, period-doubling and homoclinic-doubling cascades emanating from a codimension-2 bifurcation point are found. A codimension-2 homoclinic-gluing bifurcation point at which several homoclinic orbits concerning the origin glue together to form a new homoclinic orbit is also obtained. It is shown that in the vicinity of these bifurcation points, the system may exhibit chaos and chaotic attractors.

Comparative Toxicity of Two Chemical Dispersants and Dispersed Oil in Estuarine Organisms.

Chemical dispersants can be a useful tool to mitigate oil spills. This study examined potential risks to sensitive estuarine species by comparing the toxicity of two dispersants (Corexit® EC9500A and Finasol® OSR 52) individually and in chemically enhanced water-accommodated fractions (CEWAFs) of Louisiana Sweet Crude oil. Acute toxicity thresholds and sublethal biomarker responses were determined in seven species (sheepshead minnow, grass shrimp, mysid, amphipod, polychaete, hard clam, mud snail). Comparing median lethal (LC50) values for the dispersants, Finasol was generally more toxic than Corexit and had greater sublethal toxicity (impaired embryonic hatching, increased lipid peroxidation, decreased acetylcholinesterase activity). The nominal concentration-based mean LC50 for all species tested with Corexit was 150.31 mg/L compared with 43.27 mg/L with Finasol. Comparing the toxicity of the CEWAFs using the nominal concentrations (% CEWAF), Corexit-CEWAFs appeared more toxic than Finasol-CEWAFs; however, when LC50 values were calculated using measured hydrocarbon concentrations, the Finasol-CEWAFs were more toxic. There was greater dispersion efficiency leading to greater hydrocarbon concentrations measured in the Corexit-CEWAF solutions than in equivalent Finasol-CEWAF solutions. The measured concentration-based mean LC50 values for all species tested with Corexit-CEWAF were 261.96 mg/L total extractable hydrocarbons (TEH) and 2.95 mg/L total polycyclic aromatic hydrocarbons (PAH), whereas the mean LC50 values for all species tested with Finasol-CEWAF were 23.19 mg/L TEH and 0.49 mg/L total PAH. Larval life stages were generally more sensitive to dispersants and dispersed oil than adult life stages within a species. These results will help to inform management decisions regarding the use of oil-spill dispersants.

Effects of salinity on oil dispersant toxicity in the grass shrimp, Palaemonetes pugio.

Chemical dispersants can be a useful tool to mitigate oil spills, but the potential risks to sensitive estuarine species should be carefully considered. To improve the decision making process, more information is needed regarding the effects of oil spill dispersants on the health of coastal ecosystems under variable environmental conditions such as salinity. The effects of salinity on the toxicity of two oil dispersants, Corexit® 9500 and Finasol® OSR 52, were examined in this study. Corexit® 9500 was the primary dispersant used during the 2010 Deepwater Horizon oil spill event, while Finasol® OSR 52 is another dispersant approved for oil spill response in the U.S., yet considerably less is known regarding its toxicity to estuarine species. The grass shrimp, Palaemonetes pugio, was used as a model estuarine species. It is a euryhaline species that tolerates salinities from brackish to full strength seawater. Adult and larval life stages were tested with each dispersant at three salinities, 5, 20, and 30 ppt. Median acute lethal toxicity thresholds and oxidative stress responses were determined. The toxicity of both dispersants was significantly influenced by salinity, with greatest toxicity observed at the lowest salinity tested. Larval shrimp were significantly more sensitive than adult shrimp to both dispersants, and both life stages were significantly more sensitive to Finasol than to Corexit. Oxidative stress in adult shrimp, as measured by increased lipid peroxidation activity, occurred with exposure to both dispersants. These data will assist environmental managers in making informed decisions regarding dispersant use in future oil spills.

Dynamics of two-strain influenza model with cross-immunity and no quarantine class.

The question about whether a periodic solution can exists for a given epidemiological model is a complicated one and has a long history (Hethcote and Levin, Applied math. ecology, biomathematics, vol 18. Springer, Berlin, pp 193-211, 1989). For influenza models, it is well known that a periodic solution can exists for a single-strain model with periodic contact rate (Aron and Schwartz, J Math Biol 110:665-679, 1984; Kuznetsov and Piccardi, J Math Biol 32:109-121, 1994), or a multiple-strain model with cross-immunity and quarantine class or age-structure (Nuño et al., Mathematical epidemiology. Lecture notes in mathematics, vol 1945. Springer, Berlin, 2008, chapter 13). In this paper, we prove the local asymptotic stability of the interior steady-state of a two-strain influenza model with sufficiently close cross-immunity and no quarantine class or age-structure. We also show that if the cross-immunity between two strains are far apart; then it is possible for the interior steady-state to lose its stability and bifurcation of periodic solutions can occur. Our results extend those obtained by Nuño et.al. (SIAM J Appl Math 65:964-982, 2005). This problem is important because understanding the reasons behind periodic outbreaks of seasonal flu is an important issue in public health.

Risk factors for recurrence in patients with papillary thyroid carcinoma undergoing modified radical neck dissection.

BACKGROUND: This study evaluated the impact of lymph node-related factors on the risk of and site of recurrence in patients who had papillary thyroid carcinoma with lymph node metastasis in the lateral compartment (classified as pN1b). METHODS: Patients underwent total thyroidectomy with unilateral modified radical neck dissection for classical papillary thyroid carcinoma. Risk factors for recurrence were evaluated according to the pattern of recurrence. RESULTS: A total of 324 patients were included in the study. The median follow-up was 63 (range 14-181) months. Recurrence was detected in 47 patients (14·5 per cent). In the multivariable analysis, a maximum diameter of metastatic lymph nodes larger than 2·0 cm (hazard ratio (HR) 1·15, 95 per cent c.i. 1·06 to 1·25; P = 0·033) and a central compartment metastatic lymph node ratio of more than 0·42 (HR 3·35, 1·65 to 6·79; P < 0·001) were identified as independent risk factors for locoregional recurrence. Age 45 years or older (HR 5·69, 1·24 to 26·12; P = 0·025) and extranodal extension of metastasis (HR 12·71, 1·64 to 98·25; P = 0·015) were risk factors for distant metastasis. In subgroup analysis of locoregional recurrence, several lymph node-related factors affected the risk of recurrence according to the specific site of metastasis. CONCLUSION: Lymph node-related factors are of importance for the risk of recurrence in patients with classical papillary thyroid carcinoma classified as pN1b.

Application of whole-exome sequencing for detecting copy number variants in CMT1A/HNPP.

Large insertions and deletions (indels), including copy number variations (CNVs), are commonly seen in many diseases. Standard approaches for indel detection rely on well-established methods such as qPCR or short tandem repeat (STR) markers. Recently, a number of tools for CNV detection based on next-generation sequencing (NGS) data have also been developed; however, use of these methods is limited. Here, we used whole-exome sequencing (WES) in patients previously diagnosed with CMT1A or HNPP using STR markers to evaluate the ability of WES to improve the clinical diagnosis. Patients were evaluated utilizing three CNV detection tools including CONIFER, ExomeCNV and CEQer, and array comparative genomic hybridization (aCGH). We identified a breakpoint region at 17p11.2-p12 in patients with CMT1A and HNPP. CNV detection levels were similar in both 6 Gb (mean read depth = 80×) and 17 Gb (mean read depth = 190×) data. Taken together, these data suggest that 6 Gb WES data are sufficient to reveal the genetic causes of various diseases and can be used to estimate single mutations, indels, and CNVs simultaneously. Furthermore, our data strongly indicate that CNV detection by NGS is a rapid and cost-effective method for clinical diagnosis of genetically heterogeneous disorders such as CMT neuropathy.

Exposure of the grass shrimp, Palaemonetes pugio, to antimicrobial compounds affects associated Vibrio bacterial density and development of antibiotic resistance.

Antimicrobial compounds are widespread, emerging contaminants in the aquatic environment and may threaten ecosystem and human health. This study characterized effects of antimicrobial compounds common to human and veterinary medicine, aquaculture, and consumer personal care products [erythromycin (ERY), sulfamethoxazole (SMX), oxytetracycline (OTC), and triclosan (TCS)] in the grass shrimp Palaemonetes pugio. The effects of antimicrobial treatments on grass shrimp mortality and lipid peroxidation activity were measured. The effects of antimicrobial treatments on the bacterial community of the shrimp were then assessed by measuring Vibrio density and testing bacterial isolates for antibiotic resistance. TCS (0.33 mg/L) increased shrimp mortality by 37% and increased lipid peroxidation activity by 63%. A mixture of 0.33 mg/L TCS and 60 mg/L SMX caused a 47% increase in shrimp mortality and an 88% increase in lipid peroxidation activity. Exposure to SMX (30 mg/L or 60 mg/L) alone and to a mixture of SMX/ERY/OTC did not significantly affect shrimp survival or lipid peroxidation activity. Shrimp exposure to 0.33 mg/L TCS increased Vibrio density 350% as compared to the control whereas SMX, the SMX/TCS mixture, and the mixture of SMX/ERY/OTC decreased Vibrio density 78-94%. Increased Vibrio antibiotic resistance was observed for all shrimp antimicrobial treatments except for the mixture of SMX/ERY/OTC. Approximately 87% of grass shrimp Vibrio isolates displayed resistance to TCS in the control treatment suggesting a high level of TCS resistance in environmental Vibrio populations. The presence of TCS in coastal waters may preferentially increase the resistance and abundance of pathogenic bacteria. These results indicate the need for further study into the potential interactions between antimicrobials, aquatic organisms, and associated bacterial communities.

Ethanol ablation of predominantly cystic thyroid nodules: evaluation of recurrence rate and factors related to recurrence.

AIM: To evaluate recurrence rate and associated risk factors for recurrence after ethanol ablation (EA) in patients with predominantly cystic thyroid nodules. MATERIALS AND METHODS: This observational study was approved by the Ethics Committee of the Institutional Review Board and informed consent for procedures was obtained. From April 2009 to April 2013, 107 consecutive patients with predominantly cystic nodules were treated using EA. Recurrence was defined as nodules showing a residual solid portion with internal vascularity, cosmetic problems remaining, or persistent symptoms, and patients who requested additional therapy to resolve their symptomatic or cosmetic problems. Delayed recurrence was defined as treated nodules that showed no recurrent features at 1 month, but showed newly developed recurrent features during the longer follow-up period. Multivariate analysis was used for variables to demonstrate the independent factors related to volume reduction. RESULTS: One month after EA, 18.7% of patients (20/107) showed recurrence. Among 87 patients with non-recurrence, 24.1% (21/87) showed delayed recurrence. The total recurrence rate was 38.3% (41/107). Patients with recurrence (n = 41) were treated using radiofrequency ablation (n = 28), second EA (n = 4), and refused further treatment (n = 9). These patients responded well to repeat EA and radiofrequency ablation. Multivariate analysis demonstrated that the initial nodule volume (>20 ml; p < 0.036) and vascularity (grade >1; p < 0.049) were independent predictors of volume reduction at last follow-up. CONCLUSIONS: The results revealed that although EA seemed to be effective during the initial period, delayed recurrence should be considered during longer-term follow-up. The independent predictors of recurrence were initial volume (>20 ml) and vascularity.

A cohort study of MFN2 mutations and phenotypic spectrums in Charcot-Marie-Tooth disease 2A patients.

Charcot-Marie-Tooth disease 2A (CMT2A) is the most common axonal form of peripheral neuropathy caused by a defect in the mitofusin 2 (MFN2) gene, which encodes an outer mitochondrial membrane GTPase. MFN2 mutations result in a large range of phenotypes. This study analyzed the prevalence of MFN2 mutation in Korean families with their assorted phenotypes (607 CMT families and 160 CMT2 families). Direct sequencing of the MFN2 coding exons or whole-exome sequencing has been applied to identify causative mutations. A total of 21 mutations were found in 36 CMT2 families. Comparative genotype-phenotype correlations impacting severity, onset age, and specific symptoms were assessed. Most mutations were seen in the GTPase domain (∼86%). A deletion mutation found in the transmembrane helices is reported for the first time, as well as five novel mutations at other domains. MFN2 mutations made up 5.9% of total CMT families, whereas 22.9% in CMT2 families, of which 27.8% occurred de novo. Interestingly, patient phenotypes ranged from mild to severe even for the same mutation, suggesting other factors influenced phenotype and penetrance. This CMT2A cohort study will be useful for molecular diagnosis and treatment of axonal neuropathy.

Interactive effects of mosquito control insecticide toxicity, hypoxia, and increased carbon dioxide on larval and juvenile eastern oysters and hard clams.

Mosquito control insecticide use in the coastal zone coincides with the habitat and mariculture operations of commercially and ecologically important shellfish species. Few data are available regarding insecticide toxicity to shellfish early life stages, and potential interactions with abiotic stressors, such as low oxygen and increased CO2 (low pH), are less understood. Toxicity was assessed at 4 and 21 days for larval and juvenile stages of the Eastern oyster, Crassostrea virginica, and the hard clam, Mercenaria mercenaria, using two pyrethroids (resmethrin and permethrin), an organophosphate (naled), and a juvenile growth hormone mimic (methoprene). Acute toxicity (4-day LC50) values ranged from 1.59 to >10 mg/L. Overall, clams were more susceptible to mosquito control insecticides than oysters. Naled was the most toxic compound in oyster larvae, whereas resmethrin was the most toxic compound in clam larvae. Mortality for both species generally increased with chronic insecticide exposure (21-day LC50 values ranged from 0.60 to 9.49 mg/L). Insecticide exposure also caused sublethal effects, including decreased swimming activity after 4 days in larval oysters (4-day EC50 values of 0.60 to 2.33 mg/L) and decreased growth (shell area and weight) in juvenile clams and oysters after 21 days (detected at concentrations ranging from 0.625 to 10 mg/L). Hypoxia, hypercapnia, and a combination of hypoxia and hypercapnia caused mortality in larval clams and increased resmethrin toxicity. These data will benefit both shellfish mariculture operations and environmental resource agencies as they manage the use of mosquito control insecticides near coastal ecosystems.

Clinical and histopathological study of Charcot-Marie-Tooth neuropathy with a novel S90W mutation in BSCL2.

The objective of the study was to investigate the disease-causing mutation in an autosomal dominant Charcot-Marie-Tooth disease type 2 family and examine the clinical and histopathological evaluation. We enrolled a family of Korean origin with axonal Charcot-Marie-Tooth disease neuropathy (FC305; 13 males, six females) and applied genome-wide linkage analysis. Whole exome sequencing was performed for two patients. In addition, sural nerve biopsies were obtained from two patients. Through whole exome sequencing, we identified an average of 20,336 coding variants from two patients. We also found evidence of linkage mapped to chromosome 11p11-11q13.3 (LOD score of 3.6). Among these variants in the linkage region, we detected a novel p.S90W mutation in the Berardinelli-Seip congenital lipodystrophy 2 (BSCL2) gene, after filtering 31 Korean control exomes. Our p.S90W patients had frequent sensory disturbances, pyramidal tract signs, and predominant right thenar muscle atrophy in comparison with reported p.S90L patients. The phenotypic spectra were wide and demonstrated intrafamilial variability. Two patients with different clinical features underwent sural nerve biopsies; the myelinated fiber densities were increased slightly in both patients, which differed from two previous case reports of BSCL2 mutations (p.S90L and p.N88S). This report expands the variability of the clinical spectrum associated with the BSCL2 gene and describes the first family with the p.S90W mutation.

Recent advances in calorie restriction research on aging.

The extension of both median and maximum lifespan and the suppression of age-related diseases in laboratory animals by reduced food intake, i.e., calorie restriction (CR) are regarded as hallmarks of CR's anti-aging action. The diverse efficacy of CR to counteract aging effects and its experimental reproducibility has made it the gold standard of many aging intervention studies of recent years. Although CR originally was used as a tool to perturb the aging process of laboratory animals as to uncover clues of underlying mechanisms of aging processes, current CR research interests have shifted to the retardation of aging-related functional decline and the prevention of age-related diseases. Advances in CR research on non-human primates and recent endeavors using human subjects offer a promising outlook for CR's beneficial effects in healthy human aging. In this review, several major issues related to CR's anti-aging mechanisms are discussed by highlighting the importance of modulating deleterious chronic inflammation at molecular levels and the impact of epigenetic chromatin and histone modifications by CR at the ultimate control sites of gene expression. The recent research on rapamycin as a CR mimetic is summarized and a brief description of intermittent feeding patterns is reviewed in comparison to the CR effect.

Pretreatment HBeAg level and an early decrease in HBeAg level predict virologic response to entecavir treatment for HBeAg-positive chronic hepatitis B.

There are few reports on hepatitis B e antigen (HBeAg) titres during nucleos(t)ide analogues treatment. We investigated the changes in HBeAg levels in patients treated with entecavir and the usefulness of HBeAg quantification for predicting antiviral response. Ninety-five consecutive HBeAg-positive patients treated with entecavir for more than 48 weeks were enrolled. Serum levels of hepatitis B surface antigen (HBsAg), HBeAg and HBV DNA were assessed at 4-week intervals to week 24 and thereafter at 12-week intervals. Virologic response (Y1VR) was defined as an undetectable HBV DNA level at week 48 of therapy. During 48 weeks, HBeAg and HBV DNA level decreased significantly in a biphasic manner and HBsAg level tended to decease. Fifty-three patients (55.8%) attained Y1VR. Pretreatment HBeAg levels were significantly lower in the Y1VR group than in no Y1VR group. At week 4 and 12 of therapy, 25% and 41.4% of patients showed a decrease of HBeAg levels with >0.5 log(10) and >1.0 log(10) from baseline, respectively. These patients achieved more Y1VR than those with less decrease of HBeAg levels (97.7%vs 22.2% and 86.2%vs 29.3%, respectively). HBeAg level at week 12 had higher predictive values for Y1VR than HBV DNA level. Multivariate analysis revealed that a pretreatment HBeAg level of <360 PEIU/mL and the reduction in HBeAg level >1.0 log(10) at week 12 were associated with Y1VR. These results suggest that pretreatment HBeAg level and an early decrease in HBeAg level are useful measurements for predicting one-year virologic response during entecavir treatment.

X-linked dominant Charcot-Marie-Tooth disease with connexin 32 (Cx32) mutations in Koreans.

X-linked dominant Charcot-Marie-Tooth disease (CMTX) is an inherited peripheral neuropathy, caused mainly by a mutation of connexin 32 (Cx32) gene. We performed a mutation analysis of Cx32 by direct sequencing of the coding sequence, then identified 23 mutations from 28 Korean CMTX families. Nine mutations were not reported previously: Gly5Ser, Ser26fs, Val37Leu, Thr86Ile, Val152fs, Phe153Cys, Asp178X, Ala197Val, and Ile214Asn. The extracellular 2 (EC2) domain of Cx32 protein was the hot spot mutation domain in 44% of Koreans. Transmembrane domain 4 was rarely affected in Koreans (4%), compared with 14% of Europeans. The EC1 and intracellular domain was not affected in Koreans, although they were frequently affected in Europeans. This study revealed that the frequencies of CMTX with Cx32 mutations are specific to different ethnic groups. The frequency of CMTX (5.3%) caused by Cx32 mutation in Koreans is similar to those in Asians but lower than those in Europeans. This study suggests differences between CMTX patients with Cx32 mutations and ethnic background.

The role of the nose and cranial base in profile assessment: a morphological comparison between native African and Caucasian samples.

OBJECTIVE: The purpose of this research was to evaluate the position of the nose and how it affects clinical judgment of the face in a native African sample. METHODS: We considered the anatomic location of the nose with respect to the anterior cranial base (ACB) as well as to the maxillary lip, based on guidelines set down by Holdaway but slightly modified for purposes of this research. RESULTS: A comparison of the Shona to a Caucasian sample using selected parameters devised by Holdaway (pronasale to labrale superius) indicated that the Shona had a nose and ACB that were shorter than those of the comparative group of Caucasians. The short anterior cranial base was associated with a short and retro-positioned nose which resulted in deceptively protrusive lips when assessed using Ricketts' profile line. Whilst there was no difference in nose depth between the groups, the nasal angle of the Shona was larger than that of Caucasians, indicating an up-tipped nose. CONCLUSION: The position of the nose has a bearing on orthodontic treatment planning. Understanding the facial morphology of the Shona led us to conclude that conventional soft tissue measurements may not be applicable to all patients who present for orthodontic treatment, and that it may be necessary to advise the patient to seek other avenues for satisfactory management, which, depending on the chief complaint, may include surgical augmentation of the nose and chin.

Serum hepatitis B surface antigen levels in the natural history of chronic hepatitis B infection.

BACKGROUND The production of hepatitis B surface antigen (HBsAg) may evolve during long-lasting virus-host interactions in chronic hepatitis B (CHB). The impact of age on HBsAg production remains unclear. AIM To determine the age-specific distribution patterns of HBsAg and related factors during the natural course of CHB infection. METHODS Seven hundred and sixty-eight untreated HBsAg carriers were enrolled in the study. The parameters and distribution patterns of HBsAg were evaluated in relation to age and immune phases. RESULTS The HBsAg levels were significantly lower in the HBeAg-negative stage, with the lowest levels in inactive carriers. The HBsAg tended to decrease from hepatitis to cirrhosis and to hepatocellular carcinoma, and from Child-Pugh class A to B and to C. Age and HBV DNA were independently associated with HBsAg levels. In HBeAg-positive patients, the HBsAg levels were distributed in a triphasic-like decline pattern by 2 logs across age strata. For HBeAg-negative patients, the titres in inactive carriers exhibited a 2-log reduction, but remained unchanged over age strata in patients with HBeAg-negative hepatitis. The ratios of HBsAg/HBV-DNA were highest, but steadily decreased with age in inactive carriers, whereas the levels remained largely unchanged over the entire age strata in patients with HBeAg-negative hepatitis. CONCLUSIONS Age and HBV DNA levels are independent parameters of HBsAg levels. During the natural course of CHB infection, HBsAg levels decrease with age and disease progression, but the patterns are significantly different between the immune phases of CHB. This information may contribute to our understanding of the immunopathogenesis of chronic hepatitis B and management involving HBsAg quantification.