National long-term trends in health-related quality of life using EQ-5D-3L in South Korea, 2008-2021, including the COVID-19 pandemic: a representative serial study of 2.8 million people.

OBJECTIVE: There is a scarcity of literature investigating the impact of the coronavirus disease 2019 (COVID-19) pandemic on long-term trends in health-related quality of life (HrQoL) using large-scale and representative data. Thus, we aimed to investigate the nationwide and long-term trends in quality of life (QoL) using the European Quality of Life- 5 dimensions, 3-level version (EQ-5D-3L) from a Korean representative serial study of 2.8 million people, 2008-2021. SUBJECTS AND METHODS: This Korean study used data on adults between 2008 and 2021 who participated in the Community Health Survey. Timeframes were categorized as COVID-19 mid-pandemic (2021) and pre-pandemic (2008-2019). The mean EQ-5D-3L index for the whole population and subgroups stratified by demographic characters was evaluated for each timeframe, and differences between before and during the COVID-19 pandemic were also analyzed. RESULTS: 2,827,240 adults who responded to the survey, 2008-2021, were eligible for this study. Overall EQ-5D index persistently decreased from 2008-2016, then minimally decreased during the pandemic, still being much higher than forecasted before the COVID-19 pandemic. The reduction in the rate of decline in QoL after the COVID-19 outbreak was especially marked in white-collared, young adults, people with 'good' or 'very good' subjective health, and college-educated or above group. On the other hand, the previously increasing trend of QoL in the elderly group has decelerated during the pandemic, and QoL of the 'very bad' subjective health group recorded the lowest in the whole study period. CONCLUSIONS: The present study investigated the long-term trend of QoL in Korean adults using serial data over the past 14 years, with a special emphasis on comparing the pre- and mid-COVID-19 pandemic periods.

National prevalence and socioeconomic factors associated with the acceptance of COVID-19 vaccines in South Korea: a large-scale representative study in 2021.

OBJECTIVE: Among the global efforts toward preventing the COVID-19 pandemic, vaccines are a pivotal factor in ending the pandemic. Thus, through a large-scale population-based study, we investigated the individual-, social-, and family-associated factors affecting the acceptance of COVID-19 vaccines in South Korea. PATIENTS AND METHODS: Data were obtained from a nationwide representative study (Korea Community Health) conducted in 2021. To determine the individual-, social-, and family-associated variables for COVID-19 vaccination acceptance, we investigated data from 225,319 individuals. RESULTS: In the total sample (n=225,319), 184,529 COVID-19-vaccinated people and 40,790 non-vaccinated people were evaluated. The factors related to the acceptance of COVID-19 vaccination were significantly associated with the demographic factors, namely, older age group, female sex, and a history of influenza vaccination, as well as medical conditions such as diabetes, hypertension, and depression. Socioeconomic conditions influencing the acceptance of COVID-19 vaccination were significantly associated with low-income families and blue-collar workers. Health-related risk factors were high in the obese group. However, a noteworthy negative association was found between the acceptance of vaccination and smoking habits and alcohol consumption. Conversely, a positive association was observed between academic level and vaccination acceptance. CONCLUSIONS: Our findings suggest that old age, female sex, a history of influenza vaccination, medical conditions, such as diabetes, hypertension, and depression, low-income families, blue-collar workers, and health-related risk factors, such as obesity, were associated with the acceptance of COVID-19 vaccination. Additionally, a high academic level, absence of smoking habits, and non-current alcohol use were positively associated with vaccine acceptance.

17-year trends of body mass index, overweight, and obesity among adolescents from 2005 to 2021, including the COVID-19 pandemic: a Korean national representative study.

OBJECTIVE: There is a lack of pediatric studies that have analyzed trends in mean body mass index (BMI) and the prevalence of obesity and overweight over a period that includes the mid-stage of the COVID-19 pandemic. Thus, we aimed to investigate trends in BMI, overweight, and obesity among Korean adolescents from 2005 to 2021, including the COVID-19 pandemic. SUBJECTS AND METHODS: We used data from the Korea Youth Risk Behavior Web-based Survey (KYRBS), which is nationally representative of South Korea. The study included middle- and high-school students between the ages of 12 and 18. We examined trends in mean BMI and prevalence of obesity and/or overweight during the COVID-19 pandemic and compared these to those of pre-pandemic trends in each subgroup by gender, grade, and residential region. RESULTS: Data from 1,111,300 adolescents (mean age: 15.04 years) were analyzed. The estimated weighted mean BMI was 20.48 kg/m2 (95% CI, 20.46-20.51) between 2005 and 2007, and this was 21.61 kg/m2 (95% CI, 21.54-21.68) in 2021. The prevalence of overweight and obesity was 13.1% (95% CI, 12.9-13.3%) between 2005 and 2007 and 23.4% (95% CI, 22.8-24.0%) in 2021. The mean BMI and prevalence of obesity and overweight have gradually increased over the past 17 years; however, the extent of change in mean BMI and in the prevalence of obesity and overweight during the pandemic was distinctly less than before. The 17-year trends in the mean BMI, obesity, and overweight exhibited a considerable rise from 2005 to 2021; however, the slope during the COVID-19 pandemic (2020-2021) was significantly less prominent than in the pre-pandemic (2005-2019). CONCLUSIONS: These findings enable us to comprehend long-term trends in the mean BMI of Korean adolescents and further emphasize the need for practical prevention measures against youth obesity and overweight.

Ethnic and sex differences in the distributions of body mass index and waist circumference among adults: a binationally representative study in South Korea and the United States.

OBJECTIVE: The ethnic and sex differences in the distributions of body mass index (BMI) and waist circumference (WC) among adults are largely unknown. Therefore, we aimed to investigate the percentiles of BMI and WC in groups divided according to age, sex, and ethnicity. PATIENTS AND METHODS: We conducted a population-based binational study of adults aged ≥20 years based on data from two sources: US National Health and Nutrition Examination Survey (2015 to 2020) and Korea National Health and Nutrition Examination Survey (2016 to 2019). RESULTS: Weight, height, and WC were measured in 13,144 American adults and 30,191 Korean adults. Overall, BMI increased at younger ages and decreased at older ages, which indicates a reversed U-shaped relationship, and differed in terms of age, sex, and ethnicity. Women in the other Hispanic, non-Hispanic white, non-Hispanic black, and "other ethnic groups" showed a common BMI peak at ages 50-54 years. The patterns of WC distribution were similar to those of BMI distribution. CONCLUSIONS: In this binational representative study, we found varied distributions of ethnic and sex differences in BMI and WC. Considering the differences in these distributions may help improve individual and personalized treatment strategies.

National trends in suicide-related behaviors among youths between 2005-2020, including COVID-19: a Korean representative survey of one million adolescents.

OBJECTIVE: It is difficult to conclude that COVID-19 is associated with a decrease in the suicide attempts rate by comparing only a short-term period. Therefore, it is necessary to examine attempted suicide rates through a trend analysis over a longer period. This study aimed to investigate an estimated long-term trend regarding the prevalence of suicide-related behaviors among adolescents in South Korea from 2005 to 2020, including COVID-19. SUBJECTS AND METHODS: We sourced data from a national representative survey (Korea Youth Risk Behavior Survey) and analyzed one million Korean adolescents aged 13 to 18 years (n=1,057,885) from 2005 to 2020. The 16-year trends regarding the prevalence of sadness or despair and suicidal ideation and attempt and the trend changes before and during COVID-19. RESULTS: Data of 1,057,885 Korean adolescents was analyzed (weighted mean age, 15.03 years; males, 52.5%; females, 47.5%). Although the 16-year trend in the prevalence of sadness or despair and suicide ideation and attempt consistently decreased (prevalence of sadness or despair between 2005-2008, 38.0% with 95% confidence interval [CI], 37.7 to 38.4 vs. prevalence in 2020, 25.0% [24.5 to 25.6]; suicide ideation between 2005-2008, 21.9% [21.6 to 22.1] vs. prevalence in 2020, 10.7% [10.3 to 11.1]; and suicide attempt between 2005-2008, 5.0% [4.9 to 5.2] vs. prevalence in 2020, 1.9% [1.8 to 2.0]), the downward slope decreased during COVID-19 (ßdiff in sadness, 0.215 with 95% CI 0.206 to 0.224; ßdiff in suicidal ideation, 0.245 [0.234 to 0.256]; and ßdiff in suicide attempt, 0.219 [0.201 to 0.237]) compared with pre-pandemic period. CONCLUSIONS: This study found that the observed risk of suicide-related behaviors during the pandemic was higher than expected through long-term trend analysis of the prevalence of sadness/despair and suicidal ideation and attempts among South Korean adolescents. We need a profound epidemiologic study of the change in mental health due to the pandemic's impact and the establishment of prevention strategies for suicide ideation and attempt.

National trends in the prevalence of hepatitis B and C in South Korea, before and during the COVID-19 pandemic (2007-2021) - a nationwide representative study.

OBJECTIVE: Due to the various changes caused by the COVID-19 pandemic, some infectious diseases showed different epidemiology and prevalence during the pandemic. However, there is a lack of comprehensive studies on trends in the prevalence of hepatitis B and C related to the pandemic. Thus, we compared the prevalence of hepatitis B and C before and during the COVID-19 pandemic in South Korea. SUBJECTS AND METHODS: We conducted a comprehensive trend analysis with a nationwide serial cross-sectional survey from 2007 to 2021 (n=86,931) using the Korea National Health and Nutrition Examination Survey (KNHANES). The changes in the prevalence of hepatitis B and C were evaluated using a weighted regression model to assess the impact of the COVID-19 pandemic. RESULTS: From 2007 to 2021, 86,931 Korean adults aged 19 or older were included in the KNHANES data. The prevalence of hepatitis B showed a declining trend until the onset of the pandemic (1.80% in 2007-2009; 1.08% in 2016-2019; and 1.01% in 2020), at which point this trend reversed (1.39% in 2021). The prevalence of hepatitis C remained stable (0.14% in 2007-2009 and 0.18% in 2016-2019), with no particular surge related to the COVID-19 pandemic (ßdiff, -0.002; 95% CI, -0.761 to 0.756). For hepatitis B, old age was identified as a pandemic-related vulnerable factor (ratio of odds ratio, 1.68; 95% CI, 1.05-2.70). CONCLUSIONS: In this study, unlike other infectious diseases, hepatitis B and C did not show a decreasing trend during the pandemic. In particular, hepatitis B showed a rebound trend during the pandemic, which was noticeable in those aged 60 or older. Further studies are needed to support these findings.

Trends in body mass index changes among Korean adolescents between 2005-2020, including the COVID-19 pandemic period: a national representative survey of one million adolescents.

OBJECTIVE: The impact of the coronavirus disease 2019 (COVID-19) pandemic on weight gain in children and adolescents remains unknown. We aimed to identify an estimated 15-year trend in mean body mass index (BMI) changes and prevalence of obesity and overweight among Korean adolescents from 2005 to 2020, including the period of the COVID-19 pandemic. PATIENTS AND METHODS: We analyzed data taken from a nationwide survey (Korea Youth Risk Behavior Survey), between 2005 and 2020. Representative samples of one million Korean adolescents aged 13-18 years (n=1,057,885) were examined. The 15-year trends in mean BMI and proportion of obesity or overweight, and the changes due to the COVID-19 pandemic were analyzed. RESULTS: The data of 1,057,885 Korean adolescents were analyzed (mean age: 14.98 years; females, 48.4%). The estimated weighted mean BMI was 20.5 kg/m2 [95% confidence interval (CI), 20.4-20.5] from 2005 to 2008 and 21.5 kg/m2 (95% CI, 21.4-21.6) in 2020 (during the COVID-19 pandemic). Although the 15-year trend of mean BMI gradually increased, the change in mean BMI before and during the pandemic significantly lessened (ßdiff, -0.027; 95% CI, -0.028 to -0.026). The 15-year (2005-2020) trend changes in the prevalence of obesity and overweight were similar (obesity prevalence from 2005-2008, 3.2%; 95% CI, 3.1-3.3 vs. obesity prevalence in 2020, 8.6%; 95% CI, 8.2-9.0; ßdiff, -0.309; 95% CI, -0.330 to -0.288). CONCLUSIONS: The 15-year trend of overall mean BMI and obesity and overweight prevalence demonstrated a significant increase; however, its slope decreased during the pandemic. These landmark results suggest the need for the development of precise strategies to prevent pediatric obesity and overweight during the COVID-19 pandemic.

Human Immunodeficiency Virus-1 Viral Load Is Elevated in Individuals With Reverse-Transcriptase Mutation M184V/I During Virological Failure of First-Line Antiretroviral Therapy and Is Associated With Compensatory Mutation L74I.

BACKGROUND: M184V/I cause high-level lamivudine (3TC) and emtricitabine (FTC) resistance and increased tenofovir disoproxil fumarate (TDF) susceptibility. Nonetheless, 3TC and FTC (collectively referred to as XTC) appear to retain modest activity against human immunodeficiency virus-1 with these mutations possibly as a result of reduced replication capacity. In this study, we determined how M184V/I impacts virus load (VL) in patients failing therapy on a TDF/XTC plus nonnucleoside reverse-transcriptase inhibitor (NNRTI)-containing regimen. METHODS: We compared VL in the absence and presence of M184V/I across studies using random effects meta-analysis. The effect of mutations on virus reverse-transcriptase activity and infectiousness was analyzed in vitro. RESULTS: M184I/V was present in 817 (56.5%) of 1445 individuals with virologic failure (VF). Virus load was similar in individuals with or without M184I/V (difference in log10 VL, 0.18; 95% confidence interval, .05-.31). CD4 count was lower both at initiation of antiretroviral therapy and at VF in participants who went on to develop M184V/I. L74I was present in 10.2% of persons with M184V/I but absent in persons without M184V/I (P < .0001). In vitro, L74I compensated for defective replication of M184V-mutated virus. CONCLUSIONS: Virus loads were similar in persons with and without M184V/I during VF on a TDF/XTC/NNRTI-containing regimen. Therefore, we did not find evidence for a benefit of XTC in the context of first-line failure on this combination.

Single Nucleotide Polymorphism of Interleukin-18 and Interleukin-18 Receptor and the Risk of Papillary Thyroid Cancer.

PURPOSE: Growing evidence suggests that interleukin-18 (IL-18) levels may affect neoplasia and that single nucleotide polymorphisms (SNPs) within IL-18 gene may influence its production. In this study, we evaluated whether IL-18 and IL-18 receptor (IL-18R) polymorphisms are associated with the development and clinicopathological features of papillary thyroid carcinoma (PTC). MATERIALS AND METHODS: Using direct sequencing, we investigated the association between functional polymorphisms of IL-18 and IL-18R genes and susceptibility to PTC in 94 PTC patients and 260 healthy controls. Genetic data were analyzed using commercially available software. Multiple logistic regression models were used to calculate odds ratios, 95% confidence intervals, and P-values for the association between the genotypes and risk of PTC. The PTC patients were further subgrouped and compared with respect to their clinicopathological characteristics. RESULTS: 3 SNPs of IL-18 (rs549908, rs360717, and rs187238) and one of IL-18R (rs1420106) examined in this study were significantly associated with the development of PTC. The allelic frequencies of the 3 SNPs of IL-18 also showed significant association with lymph node metastasis. CONCLUSION: IL-18 and IL-18R polymorphisms may contribute to the development and lymph node metastasis of PTC.

Predicted residual activity of rilpivirine in HIV-1 infected patients failing therapy including NNRTIs efavirenz or nevirapine.

Rilpivirine is a second-generation nonnucleoside reverse-transcriptase inhibitor (NNRTI) currently indicated for first-line therapy, but its clinical benefit for HIV-1 infected patients failing first-generation NNRTIs is largely undefined. This study quantified the extent of genotypic rilpivirine resistance in viral isolates from 1212 patients upon failure of efavirenz- or nevirapine-containing antiretroviral treatment, of whom more than respectively 80% and 90% showed high-level genotypic resistance to the failing NNRTI. Of all study patients, 47% showed a rilpivirine resistance-associated mutation (RPV-RAM), whereas preserved residual rilpivirine activity was predicted in half of the patients by three genotypic drug resistance interpretation algorithms. An NNRTI-dependent impact on rilpivirine resistance was detected. Compared with the use of nevirapine, the use of efavirenz was associated with a 32% lower risk of having a RPV-RAM and a 50% lower risk of predicted reduced rilpivirine susceptibility. Most prevalent RPV-RAMs after nevirapine experience were Y181C and H221Y, whereas L100I+K103N, Y188L and K101E occurred most in efavirenz-experienced patients. Predicted rilpivirine activity was not affected by HIV-1 subtype, although frequency of individual mutations differed across subtypes. In conclusion, this genotypic resistance analysis strongly suggests that the latest NNRTI, rilpivirine, may retain activity in a large proportion of HIV-1 patients in whom resistance failed while they were on an efavirenz- or nevirapine-containing regimen, and may present an attractive option for second-line treatment given its good safety profile and dosing convenience. However, prospective clinical studies assessing the effectiveness of rilpivirine for NNRTI-experienced patients are warranted to validate knowledge derived from genotypic and phenotypic drug resistance studies.

Sciadopitysin alleviates methylglyoxal-mediated glycation in osteoblastic MC3T3-E1 cells by enhancing glyoxalase system and mitochondrial biogenesis.

Methylglyoxal (MG) is a precursor of advanced glycation end products, which contribute to diabetic complications, including bone defects. In the present study, the effect of sciadopitysin on MG-induced cytotoxicity was investigated using osteoblastic MC3T3-E1 cells. Pretreatment of MC3T3-E1 cells with sciadopitysin prevented the MG-induced cell death and protein adducts formation. Sciadopitysin restored the MG-induced change in glyoxalase activity almost to the control level and increased glutathione levels. In addition, sciadopitysin decreased MG-induced formation of intracellular reactive oxygen species (ROS), mitochondrial superoxide, and cardiolipin peroxidation. These findings suggest that sciadopitysin provides a protective action against MG-induced glycation by increasing MG detoxification system and by reducing oxidative stress. Pretreatment with sciadopitysin prior to MG exposure reduced MG-induced mitochondrial dysfunction by preventing mitochondrial membrane potential (MMP) dissipation and adenosine triphosphate (ATP) loss. The nitric oxide (NO) level was decreased by MG treatment, but it was significantly increased by sciadopitysin, suggesting that sciadopitysin may induce NO-dependent mitochondrial biogenesis. Furthermore, sciadopitysin treatment increased the levels of sirtuin 1 (SIRT1), peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1α), nuclear respiratory factor 1 (NRF-1), and mitochondrial transcription factor A (TFAM). These findings indicate that sciadopitysin might exert its therapeutic effects via upregulation of mitochondrial biogenesis. Therefore, sciadopitysin may prevent the development of diabetic osteopathy.

Methylglyoxal induces oxidative stress and mitochondrial dysfunction in osteoblastic MC3T3-E1 cells.

Methylglyoxal is a reactive dicarbonyl compound produced by glycolytic processing and identified as a precursor of advanced glycation end products. The elevated methylglyoxal levels in patients with diabetes are believed to contribute to diabetic complications, including bone defects. The objective of this study was to evaluate the effect of methylglyoxal on the function of osteoblastic MC3T3-E1 cells. The data indicated that methylglyoxal decreased osteoblast differentiation and induced osteoblast cytotoxicity. Pretreatment of MC3T3-E1 cells with aminoguanidine (a carbonyl scavenger), Trolox (an antioxidant), and cyclosporin A (a blocker of the mitochondrial permeability transition pore) prevented methylglyoxal-induced cytotoxicity in MC3T3-E1 cells. However, BAPTA/AM (an intracellular Ca(2+) chelator) and dantrolene (an inhibitor of endoplasmic reticulum Ca(2+) release) did not reverse the cytotoxic effect of methylglyoxal. Methylglyoxal increased the formation of intracellular reactive oxygen species, mitochondrial superoxide, and cardiolipin peroxidation in osteoblastic MC3T3-E1 cells. Methylglyoxal also decreased the mitochondrial membrane potential and intracellular ATP and nitric oxide levels, suggesting that carbonyl stress-induced loss of mitochondrial integrity contributes to the cytotoxicity of methylglyoxal. Furthermore, the results demonstrated that methylglyoxal induced protein adduct formation, inactivation of glyoxalase I, and activation of glyoxalase II. Aminoguanidine reversed all aforementioned effects of methylglyoxal. Taken together, these data support the notion that high methylglyoxal concentrations have detrimental effects on osteoblasts through a mechanism involving oxidative stress and mitochondrial dysfunction.

Vitamin D and diabetes in Koreans: analyses based on the Fourth Korea National Health and Nutrition Examination Survey (KNHANES), 2008-2009.

AIMS: A causal relationship between vitamin D deficiency and the incidence of diabetes mellitus has been suggested, but little research has been conducted on the Korean population. METHODS: We analysed the glucose tolerance status and serum 25-hydroxyvitamin D concentrations in 12263 subjects >19 years old who were registered for the Korea National Health and Nutrition Examination Survey, 2008-2009. RESULTS: Various demographic variables such as gender, age, season, resident area, physical activity, smoking, alcohol, marital status, education and occupation were associated with serum 25-hydroxyvitamin D concentrations. After adjusting for these variables as confounders, 25-hydroxyvitamin D concentrations in subjects with diabetes were significantly lower than those in subjects with normal glucose tolerance and those with impaired fasting glucose (P=0.005). Compared with the ≥ 75 nmol/l subgroup of serum 25-hydroxyvitamin D concentration, the odds ratios and 95% confidence intervals for diabetes mellitus were 1.206 (95%CI 0.948-1.534) in the 50- to 74-nmol/l subgroup, 1.339 (1.051-1.707) in the 25-to 49-nmol/l subgroup and 1.759 (1.267-2.443) in the <25-nmol/l subgroup. Compared with the serum ≥ 75-nmol/l 25-hydroxyvitamin D subgroup, serum insulin and homeostasis model assessment 2%B, a marker of insulin secretory capacity, were significantly higher, and homeostasis model assessment 2%S, a marker of insulin sensitivity, was significantly lower in the <25- and 25- to 49-nmol/l serum 25-hydroxyvitamin D subgroups than those in the other subgroups (P<0.001). CONCLUSIONS: The findings suggest that vitamin D deficiency, possibly involving altered insulin sensitivity, is associated with an increased risk for diabetes mellitus in the Korean population.

A novel PRKAR1A mutation in Korean Carney complex family.

Carney complex (CNC) is an autosomal dominant hereditary or sporadic multiple neoplastic syndrome that shows variable clinical symptoms. Generally, CNC appears as skin pigmentation, cardiac or cutaneous myxomas, and multiple endocrine tumours. We performed an extensive evaluation of 9 individuals within 1 family in whom CNC was suspected. Among them, 5 had CNC with various clinical manifestations. We also performed mutational analysis of suspected genes in these patients. Although all patients were members of the same family, variable CNC-related manifestations were observed in each patient. An analysis showed a novel deletion mutation (c.537delA) in exon 6 of the PRKAR1A gene in the patients. Based on our results, the patients were determined to have CNC type I. This is the first such mutational report in Korea.

The Gene Ontology (GO) database and informatics resource.

The Gene Ontology (GO) project (http://www. geneontology.org/) provides structured, controlled vocabularies and classifications that cover several domains of molecular and cellular biology and are freely available for community use in the annotation of genes, gene products and sequences. Many model organism databases and genome annotation groups use the GO and contribute their annotation sets to the GO resource. The GO database integrates the vocabularies and contributed annotations and provides full access to this information in several formats. Members of the GO Consortium continually work collectively, involving outside experts as needed, to expand and update the GO vocabularies. The GO Web resource also provides access to extensive documentation about the GO project and links to applications that use GO data for functional analyses.

The Arabidopsis Information Resource (TAIR): a comprehensive database and web-based information retrieval, analysis, and visualization system for a model plant.

Arabidopsis thaliana, a small annual plant belonging to the mustard family, is the subject of study by an estimated 7000 researchers around the world. In addition to the large body of genetic, physiological and biochemical data gathered for this plant, it will be the first higher plant genome to be completely sequenced, with completion expected at the end of the year 2000. The sequencing effort has been coordinated by an international collaboration, the Arabidopsis Genome Initiative (AGI). The rationale for intensive investigation of Arabidopsis is that it is an excellent model for higher plants. In order to maximize use of the knowledge gained about this plant, there is a need for a comprehensive database and information retrieval and analysis system that will provide user-friendly access to Arabidopsis information. This paper describes the initial steps we have taken toward realizing these goals in a project called The Arabidopsis Information Resource (TAIR) (www.arabidopsis.org).

Unified display of Arabidopsis thaliana physical maps from AtDB, the A.thaliana database.

In the past several years, there has been a tremendous effort to construct physical maps and to sequence the genome of Arabidopsis thaliana. As a result, four of the five chromosomes are completely covered by overlapping clones except at the centromeric and nucleolus organizer regions (NOR). In addition, over 30% of the genome has been sequenced and completion is anticipated by the end of the year 2000. Despite these accomplishments, the physical maps are provided in many formats on laboratories' Web sites. These data are thus difficult to obtain in a coherent manner for researchers. To alleviate this problem, AtDB (Arabidopsis thaliana DataBase, URL: http://genome-www.stanford.edu/Arabidopsis/) has constructed a unified display of the physical maps where all publicly available physical-map data for all chromosomes are presented through the Web in a clickable, 'on-the-fly' graphic, created by CGI programs that directly consult our relational database.

Tetrad pollen formation in quartet mutants of Arabidopsis thaliana is associated with persistence of pectic polysaccharides of the pollen mother cell wall.

The quartet (qrt) mutants of Arabidopsis thaliana produce tetrad pollen in which microspores fail to separate during pollen development. Because the amount of callose deposition between microspores is correlated with tetrad pollen formation in other species, and because pectin is implicated as playing a role in cell adhesion, these cell-wall components in wild-type and mutant anthers were visualized by immunofluorescence microscopy at different stages of microsporogenesis. In wild-type, callose was detected around the pollen mother cell at the onset of meiosis and around the microspores during the tetrad stage. Microspores were released into the anther locule at the stage where callose was no longer detected. Deposition and degradation of callose during tetrad pollen formation in qrt1 and qrt2 mutants were indistinguishable from those in wild-type. Enzymatic removal of callose from wild-type microspores at the tetrad stage did not release the microspores, suggesting that callose removal is not sufficient to disperse the microspores in wild-type. Pectic components were detected in the primary wall of the pollen mother cell. This wall surrounded the callosic wall around the pollen mother cell and the microspores during the tetrad stage. In wild-type, pectic components of this wall were no longer detectable at the time of microspore release. However, in qrt1 and qrt2 mutants, pectic components of this wall persisted after callose degradation. This result suggests that failure of pectin degradation in the pollen mother cell wall is associated with tetrad pollen formation in qrt mutants, and indicates that QRT1 and QRT2 may be required for cell type-specific pectin degradation to separate microspores.