[Epidemiological characteristics of reinfection of 2019-nCoV and influencing factors in Ningbo].

Objective: To analyze the epidemiological characteristics of reinfection of 2019-nCoV and influencing factors, and provide evidence for effective prevention and control of COVID-19 epidemic. Methods: The incidence data of COVID-19 in Ningbo from January 1, 2020 to November 30, 2022 were collected from the infectious disease surveillance system of Chinese information system for disease control and prevention. The incidence of reinfection of 2019-nCoV was investigated by using questionnaire. logistic regression analysis was used to analyze the influences of gender, age, time interval from the first infection, history of underlying disease, 2019-nCoV vaccination dose and disease severity on the reinfection. Results: A total of 897 previous 2019-nCoV infection cases were investigated, of which 115 experienced the reinfection of 2019-nCoV, the reinfection rate was 12.82%. The interval between the two infections M(Q1, Q3) was 1 052 (504, 1 056) days. Univariate analysis showed that age, 2019-nCoV vaccination dose, history of underlying disease, type of 2019-nCoV variant causing the first infection, time interval from the first infection and severity of the first infection were associated with the reinfection rate (all P<0.05). Multivariate logistic regression analysis showed that the risk for reinfection in age group 30- years was higher than that in age group ≥60 years (OR=2.10, 95%CI: 1.11-3.97). No reinfection occurred in those with time interval from the first infection of <6 months, and the risk for reinfection was higher in those with the time interval of ≥12 months than in those with the time interval of 6- months (OR=6.68, 95%CI: 3.46-12.90). The risk for reinfection was higher in the common or mild cases than in the asymptomatic cases (OR=2.64, 95%CI: 1.18-5.88; OR=2.79, 95%CI: 1.27-6.11). Conclusion: The time interval from the first infection was an important influencing factor for the reinfection of 2019-nCoV, and the probability of the reinfection within 6 months was low.

[Clinical diagnosis and treatment of optic nerve glioma: a review].

Optic nerve glioma (ONG) is a relatively rare central nervous system tumor that mainly affects children and adolescents. It can be classified into sporadic and neurofibromatosis type 1 (NF1)-associated types. The histological type is mainly a low-grade pilocytic astrocytoma. The typical clinical manifestations are visual impairment and painless eye protrusion, and the imaging features mainly present as fusiform swelling or irregular masses. Chemotherapy is still the first-line treatment for ONG, and other treatment options include radiotherapy, surgical resection, and molecular targeted therapy. Screening and monitoring of NF1 patients are also crucial. The prognosis of ONG is difficult to predict, and close monitoring and timely effective intervention are necessary.

[Research advances on the application of carbon dots in wound treatment].

Chronic and infectious wound healing has always been an issue of concern in clinical and scientific research, in which bacterial infection and oxidative damage are the key factors hindering wound healing. Carbon dots, as a new material, has attracted much attention because of its unique physical and chemical properties and good biological safety. In recent years, the researches on the antibacterial property, antioxidant, and photoluminescence properties of carbon dots are more and more extensive and carbon dots have great potential in the treatment of chronic and infectious wounds. This paper reviews the research progress of carbon dots in three aspects: antibacterial, anti-oxidation and monitoring of wound infection are reviewed, and further discusses its specific mechanism, potential research direction, and application prospect.

A high-speed radiation imaging system based on liquid scintillator filled capillary arrays.

A high-speed radiation imaging system based on an image converter of liquid scintillator filled capillary arrays has been developed, which is sensitive to x rays, gamma rays, and neutrons. This imaging system has advantages of both high spatial resolution and high sensitivity because increasing the thickness of the image converter only leads to little deterioration on imaging resolution. The capillary arrays have dimensions of 150 mm diameter and 50 mm thickness, with 100 µm diameter of each capillary. The fluorescence decay time of the filled liquid scintillator based on the mixture of p-xylene and 2,5-diphenyloxazole has been evaluated to be ∼3 ns with the single photon method under the gamma ray excitation. The spatial resolution has been experimentally evaluated to be about 1.15 and 0.6 mm, under excitation of x rays and neutrons, respectively. The imaging system has been applied for diagnosing the dynamic x-ray spot generated by the rod pinch. Two frames in single shot with 15 ns temporal resolution and 20 ns inter-frame separation time have been obtained, which show the spatiotemporal distribution of the electrons bombarding the tungsten rod, indicating the ability of this imaging system in diagnosing dynamic radiation objects. In addition, the technique of capillary arrays provides a promising path for applications of advanced liquid scintillators in the field of radiation imaging.

[A case of communicating oncocytic carcinoma of the naso-orbit].

A patient with a left eyelid mass for more than 1 year was admitted. One year ago, the patient underwent left sinus mass resection in another hospital, and the postoperative histopathology showed oncocytic carcinoma. Imaging examination in our hospital revealed lesions in the left eyelid and inner canthus, involving the canalis nasolacrimalis and orbit. The orbital mass was removed under general anesthesia. The histopathological diagnosis was oncocytic carcinoma.

[Research progress on primary orbital melanoma].

Primary orbital melanoma (POM) is a sort of extremely rare orbital malignancy. It often associates with melanin lesion such as congenital ocular melanocytosis and blue nevus. The most common clinical manifestation of POM is progressive painless proptosis. There are some difficulties in diagnosing this disease. MRI shows characteristic expression of this disease as an important way to diagnose POM, while pathology is the gold standard. Surgery is the mainstay of treatment in patients with POM. In addition, adjuvant radiotherapy and chemotherapy should be considered. This article systematically reviews the research progress of pathogenesis, clinical manifestation, auxiliary examination, differential diagnosis and treatment of POM, in order to provide some thoughts for the future study of the rare malignancy. (Chin J Ophthalmol, 2021, 57: 861-864).

[Effects of sural nerve nutrition vess els-supported flap for reconstruction of distal lower leg and ankle soft tissue defects].

Objective: To observe the effects of sural nerve nutrition vessels-supported flap for reconstruction of distal lower leg and ankle soft tissue defects. Methods: From June 2014 to June 2017, 37 patients with calf distal and ankle soft tissue defect were repaired with sural nerve nutrition vessels-supported flap, of them 12 cases with calf distal soft tissue defect wounds and 25 cases with ankle soft tissue defect wounds.The scope of flaps was 9 cm×4 cm to 18 cm×9 cm, anti-infection, anti-freezing and dressing treatments were carried out after operation.The results of two-point discrimination among reexamination were recorded. Results: All the flaps survived without ulcer and effusion, only 1 flap for reconstruction of medial malleolus swelled and deactivated at the beginning while it recovered with proper dressings.During the follow-up periods, all the flaps kept favorable feelings, aspects and functions, and the two-point discrimination was 5 to 15 mm [averaged (11.2±1.7) mm]. Conclusion: Sural nerve nutrition vessels-supported flap brings significant effects with excellent safety and reliability in repairing calf and ankle soft tissue defects.

[Progression of the pathogenesis of thyroid associated ophthalmopathy].

Thyroid associated ophthalmopathy (TAO) is a common complication of Graves' disease (GD). The clinical manifestations are mainly swelling and retracted eyelid, protopsis and limited eye movements, and optic neuropathy can be seen in severe cases. The mechanism of TAO is not yet clear. A large number of studies have found that the disorders of autoimmunity play an important role in TAO, while genetic factors, oxidative stress, and environmental factors such as smoking participate in it. Therefore, we consult a large number of studies and expound the pathogenesis from the aspects of genetic susceptibility, immune mechanism, oxidative stress, and the effects of smoking to provide referrences for clinical associated studies. (Chin J Ophthalmol, 2017, 53: 474-480).

Investigation of an InP-based image converter with optical excitation.

An image converter based on an indium phosphide has been developed to measure the two-dimensional spatial profile of the incident photon flux by probing the rapid change of the refractive index in the semiconductor. The spatial resolution, dynamic range, and temporal response of this image converter have been investigated with optical methods. The results show that the spatial resolution is ∼15 cycles/mm at the percent modulation transfer function of 0.5, the dynamic range is about 100, and the time response is in the order of 600 ps. This scheme can provide an alternative choice as an imaging diagnostic for experiments in the area of high-energy density physics.

[Research on the correlation and regulation of bone metabolism related biochemical indexes in different gestational ages].

Objective: To investigate the correlation and metabolic characteristics of the growth hormone (GH) and other bone metabolism related biochemical markers in pregnancy women serum. Methods: Determination of GH, 25 hydroxy vitamin D(25(OH)D), osteocalcin n-terminal fragments (N-MID), total propeptide of type 1 procollagen (TP1NP) and alkaline phosphatase (ALP) levels in different gestation women serum, the experimental group involving 75 cases of early pregnancy women(11-14 weeks), 135 cases of pregnancy women(15-21 weeks), 62 cases of late pregnancy women(31-40 weeks) and 28 cases of postpartum women(1-3 days). All cases were selected from prenatal screening patients in hospital from February 2016 to February 2017. The control group involving 55 cases of physically healthy nulliparous. The indicators of GH, 25(OH)D, TPINP and N-MID were detected by electrochemiluminescence and ALP were detected by rate method. All data were processed by SPSS. Variance analysis and Pearson correlation analysis were employed. Results: Serum GH level in early pregnancy, pregnancy, late pregnancy and control group were (4.54±2.26), (9.04±3.23), (20.16±4.89), (0.55±0.49)µg/L, respectively. The difference was statistically significant (F=270.037, P<0.01). Serum GH in each group of pregnant women were more higher than those in control group (all P<0.01), and there was statistical difference in different gestational stages(all P<0.01). Serum 25 (OH)D expression in early pregnancy, pregnancy and late pregnancy were (25.60±14.48), (27.10±12.05), (25.45±9.85)nmol/L. Compared with the control group(39.93±14.88)nmol/L, the difference was statistically significant (all P<0.01). Serum TP1NP level in early pregnancy, pregnancy, late pregnancy and control group were (44.44±11.80), (48.41±20.87), (102.63±41.73), (54.73±24.07)µg/L, respectively. The difference was significantly significant (F=54.027, P<0.01) and TP1NP in late pregnancy group was obvious higher than in early pregnancy group, pregnancy group and control group apart(all P<0.01). Serum N-MID level in early pregnancy, pregnancy, late pregnancy and control group were (5.91±2.64), (7.45±2.27), (17.24±6.47), (18.52±6.95)µg/L, and the difference was significantly significant(F=55.699, P<0.01). N-MID in early and middle pregnancy group were apparent lower than that in late pregnancy and control group (all P<0.01). Serum ALP level in early pregnancy, pregnancy, late pregnancy and control group were (49.74±10.14), (77.76±26.90), (168.34±45.15), (52.81±10.33) U/L, and the difference was significantly significant(F=180.349, P<0.01). However, there was noticeable difference in ALP level between late pregnancy and other pregnant group(P<0.01 or P<0.05). The serum GH, TP1NP and N-MID in postpartum women (1-3 days) were (1.44±0.99), (73.41±34.27), (12.10±5.64) µg/L, respectively. Compare with late pregnancy groups, the difference was significantly significant(all P<0.01). The content of GH in serum of 272 cases pregnant women was positively correlated with the concentration of TP1NP, N-MID and ALP, the gestational age and body weight of pregnant women(r=0.509, 0.720, 0.862, 0.827, 0.324, all P<0.01). The content of TP1NP, N-MID and ALP were positively correlated with gestational age, respectively(r=0.603, 0.722, 0.901, all P<0.01). Moreover, TP1NP expression was positively correlated with N-MID (r=0.849, P<0.01), and there was no correlation between other indexes. Conclusions: These findings have revealed that there are different metabolic character of the GH and bone metabolism related biochemical indexes during different pregnancy period. And there is a positive correlation between gestational age and the index of GH, N-MID, TP1NP, ALP, respectively. Finally, the bone metabolism is more active and Vitamin D deficiency is severe throughout pregnancy.

[Treatment and prognostic analysis of retinoblastoma patients with choroid invasion].

Objective: To observe the treatment and prognosis of choroid invasion of retinoblastoma (RB) in children. Method: A total of 149 children who had been diagnosed with unilateral RB and received enucleation disclosing tumor invasion to choroid from January 2006 to December 2013 in Beijing Tongren Hospital were recruited in this study. Choroid involvement was classified as massive choroid invasion and focal choroid invasion. Massive choroid invasion was defined as a maximum diameter of invasive tumor focus of 3 mm or more in diameter that might reach the scleral tissue. Focal choroid invasion was defined as a tumor focus of less than 3 mm in diameter without involvement of sclera. The treatment was delivered according to the invasive status of tumor with combination of histopathological high risk factors. The prognosis of different degrees of choroid invasion was observed. They were divided into two groups according to whether the merger of other high histopathologic risk factors, the survival situation was compared. The subjects were followed up for 1 to 9 years (the median follow-up time: 4 years and 1 month). Result: Among the 149 subjects, 90 were boys and 59 were girls. The right eye was affected in 81 patients and the left eye in 68 patients. Sixteen patients died, resulting in an overall survival rate of 89.3%. Among massive choroid invasion in 47 cases, 9 patients experienced disease recurrence and death resulting in a survival rate of 80.9%. While the focal choroid invasion was found in 102 cases, only 7 children had disease relapsed and died resulting in a survival rate of 93.1% which was statistically significant (χ2=5.067, P=0.024). Among 8 patients with massive choroid invasion without pathological high-risk factors, no death occurred, while in other 39 patients with high-risk factors, 9 died with a mortality rate of 23.1%, however, the difference was not statistically significant (Fisher's exact probability method, P=0.323). Among 60 patients with focal choroid invasion without pathological high-risk factors, no death was observed, while among the other 42 patients presenting high-risk factors, 7 of them died with a mortality rate of 16.7% (Fisher's exact probability method, P=0.003). Cox multivariate analysis showed that massive choroid invasion and surgical margin of the optic nerve were influential factors of prognosis. Conclusion: Patients with focal choroid invasion have a low disease recurrence and may not receive adjuvant chemotherapy. Patients with massive choroid invasion without presenting pathological high-risk factors warrant further prospective study to assess whether adjuvant chemotherapy is needed. However chemotherapy is recommended for those with massive choroid invasion presenting with risk factors to avoid the high disease recurrence in such patients.

[Is glaucoma a mitochondrial neurodegenerative disease].

The retinal ganglion cell, due to peculiar structural and energetic constraints, appears acutely susceptible to mitochondrial dysfunction. Emerging evidence suggests that changes in the mitochondrial DNA(mtDNA)and in nuclear DNA genes that encode mitochondrial proteins may influence mitochondrial structure and function and, therefore, contribute to the pathogenesis of primary open angle glaucoma. As the main glaucoma risk factors are elevated intraocular pressure and older age, we discuss their relationship with mitochondrial dysfunction. If the contribution of mitochondrial dysfunction to glaucoma pathogenesis is further established, emerging therapies aiming to optimize mitochondrial function represent potential clinical treatments. (Chin J Ophthalmol, 2016, 52: 714-717).

Protective effect of ginsenoside against acute renal failure via reduction of renal oxidative stress and enhanced expression of ChAT in the proximal convoluted tubule and ERK1/2 in the paraventricular nuclei.

Generation of reactive oxygen species significantly contributes to the pathogenesis of acute renal failure (ARF) induced by myoglobin release. Ginsenosides (GS), the principal active ingredients of ginseng, is considered as an extremely good antioxidative composition of Chinese traditional and herbal drugs. The purpose of the present study was to investigate the protective effect of ginsenoside in rats with ARF on the changes of cholinergic nervous system in the kidney as well as on the involvement of mitogen-activated protein kinases (MAPK) in the hypothalamic paraventricular nuclei (PVN). In our assay, glycerol-induced acute renal failure in rats was employed to study the protective effects of ginsenoside. Our results indicated that the treatment of ARF rats with ginsenosides for 48 h significantly reduced lipid peroxidation, restored the superoxide dismutase (SOD) level. Meanwhile, the obvious increase of choline acetyltransferase-immunoreactivity (ChAT-IR) in the proximal convoluted tubular cells (PCT) was observed by immunohistochemistry in ARF+GS group. The same effect was also observed in the changes of p-ERK1/2-IR in the hypothalamic paraventricular nuclei. Our results suggest that ginsenoside administered orally may have a strong renal protective effect against glycerol-induced ARF, reduce the renal oxidative stress, and ginsenoside can also activate the cholinergic system in PCT, simultaneously MAPK signal pathway in the PVN was also activated.

Design of a highly sensitive ethanol sensor using a nano-coaxial p-Co3O4/n-TiO2 heterojunction synthesized at low temperature.

In this paper, we describe the design, fabrication and gas-sensing tests of nano-coaxial p-Co3O4/n-TiO2 heterojunction. Specifically, uniform TiO2 nanotubular arrays have been assembled by anodization and used as templates for generation of the Co3O4 one-dimensional nanorods. The structure morphology and composition of as-prepared products have been characterized by SEM, XRD, TEM, and XPS. A possible growth mechanism governing the formation of such nano-coaxial heterojunctions is proposed. The TiO2 nanotube sensor shows a normal n-type response to reducing ethanol gas, whereas TiO2-Co3O4 exhibits p-type response with excellent sensing performances. This conversion of sensing behavior can be explained by the formation of p-n heterojunction structures. A possible sensing mechanism is also illustrated, which can provide theoretical guidance for the further development of advanced gas-sensitive materials with p-n heterojunction.

Prophylactic thyroidectomy for MEN 2-related medullary thyroid carcinoma based on predictive testing for RET proto-oncogene mutation and basal serum calcitonin in China.

INTRODUCTION: Early and normative surgery is the only curative method for multiple endocrine neoplasia type 2 (MEN 2)-related medullary thyroid carcinoma (MTC). AIMS: To study the timing of prophylactic total thyroidectomy (TT) for MEN 2-related MTC with different RET mutations in a Chinese population, and to compare the sensitivity and accuracy of fully-automated chemiluminescence immunoassay (FACLIA) and radioimmunoassay (RIA) for serum calcitonin (Ct). METHODS: We collected 24 asymptomatic individuals from 8 unrelated Chinese families with MEN 2, and analyzed RET mutation and Ct levels. Then we performed TT on 17 of the 24 individuals, including TT (2/17), TT with bilateral level VI lymph-node dissection (B-LND(VI); 12/17) and TT with B-LND(VI) + modified unilateral/bilateral/local neck dissection (3/17). RESULTS: Histopathology revealed bilateral/unilateral MTC in 15/17 (88.2%; median diameter, 1.0 cm) and bilateral C-cell hyperplasia in 2/17 (11.8%; p.V292M/R67H/R982C and p.C618Y). Lymph-node metastasis/fibro-adipose tissue invasion (p.C634R) or solely fibro-adipose tissue invasion (p.C634Y) were found in 2/17 (11.8%). Elevated pre-surgical Ct (pre-Ct) was identified by FACLIA in 17/17 (median age, 24.0), while pre-Ct by RIA was found in only 6/15 (P < 0.001). The median follow-up was 22.0 months, during which 16/17 had no abnormality (one p.C634R individual had elevated Ct), and another 7 carriers still had consistently undetectable Ct by FACLIA. CONCLUSIONS: Our study highlights the importance and feasibility of individualized prophylactic TT for MEN 2-related MTC, based on predictive integrated screening of RET and pre-Ct levels. Besides, we recommend FACLIA to measure Ct for earlier diagnosis, treatment and follow-up monitoring of MTC.

Case report: a p.C618S RET proto-oncogene germline mutation in a large Chinese pedigree with familial medullary thyroid carcinoma.

We report a Chinese pedigree with familial medullary thyroid carcinoma. Direct sequencing of the entire coding sequences of Rearranged during Transfection (RET) identified a recurrent c.T1852A (p.C618S) mutation in 13 of 23 members. The polymorphisms c.A135G (p.A45A), c.A1296G (p.A432A), c.T2307G (p.L769L) and IVS19 + 15T > C were also found in 13 carriers, and c.G2073A (p.G691S) was found in 1 carrier. Of the 13 carriers, seven (mean age: 42.6 years, range: 27-64) presented MTC as the isolated clinical phenotype, with elevated basal serum calcitonin (average: 1077.9 ng/L, range: 504-2,652) and a mean diameter of thyroid nodules of 2.97 cm (range: 1.6-4.3); they underwent a total thyroidectomy with modified bilateral/unilateral neck dissection and/or level VI lymph node dissection. The other 6 carriers did not accept surgery (4 rejected, 2 awaited). These were 2 older patients (63 and 32 years) with elevated calcitonin (1359 and 41.4 ng/L) and multi-centric hypoechoic nodules (1.5 and 0.6 cm) with calcifications in both/left thyroid lobes; and Doppler ultrasound showed normal bilateral thyroids in 4 younger carriers (median age: 8.3 years, range: 4-12) but with increased calcitonin (average: 9.7 ng/L, range: 7.87-12.2) in 3 of them. The phenotype here is consistent with the clinical symptoms reported worldwide. We recommend that screening of hotspot regions of RET should be preferentially carried out, while whole-exon sequencing should be performed when clinical signs fail to reveal hotspot mutations or different phenotype discrepancies. Moreover, we strongly suggest prophylactic thyroidectomy should be performed before age 5 in carriers with p.C618S to prevent the occurrence and metastasis of MTC.

The influence of corticosterone on antizyme gene expression in early regenerating rat liver.

BACKGROUND AND STUDY AIMS: Antizyme 1, a specific inhibitor of Ornithine decarboxylase (ODC), plays a critical role in cell proliferation. Little is known about the impact of glucocorticoid on antizyme expression in the regenerating liver. In this paper, the effect of corticosterone on the gene expression of antizyme 1 in early regenerating rat liver induced by partial hepatectomy (PH) was investigated. MATERIALS AND METHODS: Bilateral adrenalectomies (ADX) were performed 3 days before PH. Corticosterone in sesame oil or sesame oil was injected sub-cutaneously to ADX rats. Antizyme 1 mRNA and protein levels as well as polyamine contents in the regenerating liver were determined by RT-PCR, Western blotting and HPLC, respectively. RESULTS: Antizyme 1 protein content in the oil-treated ADX group decreased significantly at 5, 7 and 9 h after PH compared to control. Following corticosterone administration the content rose dose-dependently during the whole experiment. At 5 h post-PH, the protein levels in 10 and 40 mg/kg corticosterone-treated ADX rats increased by 66% and 148%, respectively, when compared with the control group. However, no significant changes in antizyme 1 mRNA levels were observed in oil-treated ADX rats or corticosterone-treated groups compared to control. Polyamine contents in oil-treated ADX rats were the highest among all groups at 5 and 9 h. Corticosterone treatment resulted in a dramatic decrease of polyamine contents at most of the time points investigated when compared with those in control rats. CONCLUSIONS: Corticosterone treatment induces antizyme 1 protein synthesis in early regenerating rat liver. However, it has little effect on antizyme 1 gene transcription. (Acta gastroenterol. belg., 2011, 74, 289-294).

Protective effect of ginsenoside against acute renal failure and expression of tyrosine hydroxylase in the locus coeruleus.

Acute renal failure (ARF) is mainly characterized by acute tubular necrosis. No significant change was found for mortality rates over the past few decades despite significant advances in supportive care. In recent years, great effort has been focused on traditional and herbal medicine, which is much less toxic than those agents conventionally used and which is nowadays considered as a novel therapeutic agent for ARF. However, the effect of ginsenosides (GS) administered orally on ARF has not been reported yet and little is known about its cellular and molecular mechanism. The purpose of the study is to investigate the protective effect of ginsenoside in rats with ARF on the changes of tyrosine hydroxylase immunoreactivity (TH-IR) as well as on the involvement of mitogen-activated protein kinases (MAPK) in the locus coeruleus. In our assay, glycerol-induced acute renal failure in rats was employed to study the protective effects of ginsenoside. Our results indicated that the treatment of ARF rats with ginsenosides for 48 h significantly reduced the serum blood urea nitrogen, creatinine level, and lipid peroxidation, restored the GSH level and the normal renal morphology. Immunohistochemistry showed that an obvious increase of TH-IR was further enhanced in ARF+GS group. The same effect was also observed in the changes of p-ERK1/2-IR in the locus coeruleus. Our results suggest that ginsenoside administered orally may have a strong renal protective effect against glycerol-induced ARF, and ginsenoside can also activate the brain catecholaminergic neurons in the locus coeruleus. Our future attention will be focused to the question whether there is a correlation between the renal protective effect of ginsenosides against acute renal failure and the activation of tyrosine hydroxylase in the locus coeruleus.

Historical alpha-HCH budget in the Arctic Ocean: the Arctic Mass Balance Box Model (AMBBM).

An Arctic Mass Balance Box Model (AMBBM) has been developed to calculate a sequential historical alpha-hexachlorocyclohexane (alpha-HCH) budget in the Arctic Ocean from its introduction in the 1940s up to the present. The AMBBM is created in the context of the Arctic as a receptor, and has three major components: the air concentration module, the loading from Arctic river module and the transport/transformation module. The results of the model provide a more complete depiction of the behavior of alpha-HCH within the Arctic Ocean. Model output includes annual concentrations in Arctic air and water, annual alpha-HCH loading to, removal from the Arctic Ocean and annual cumulative burden of alpha-HCH in the Arctic waters from 1945 to 2000. Our model results compare well with published data in the 1980s and 1990s and show that the alpha-HCH burden in the Arctic Ocean started to accumulate in the early 1940s and reached the highest value of 6670 t in 1982, 1 year before China banned the use of technical HCH. Since then the burden of alpha-HCH in Arctic waters has decreased quickly by an average annual rate of approximately 270 ty(-1) during the 1990s, decreasing from 4220 t in 1990 to 1550 t in 2000. The complete elimination of alpha-HCH from Arctic waters would require another two decades. The total loading between 1945 and 2000 was 27700 t accounting for approximately 0.6% of total global alpha-HCH emission from agricultural land to the atmosphere. Differences in loadings of alpha-HCH to the North American Arctic Ocean and Eurasian Arctic Ocean are also discussed.