Socioeconomic inequalities in psychosocial well-being among adolescents under the COVID-19 pandemic: a cross-regional comparative analysis in Hong Kong, mainland China, and the Netherlands.

BACKGROUND: Despite evidence on socioeconomic inequalities in psychosocial well-being of adolescents under the COVID-19 pandemic, the explanatory factors and their potential variations across contexts remained understudied. Hence, this cross-regional study compared the extent of inequalities and the mediating pathways across Hong Kong, Mainland China, and the Netherlands. METHODS: Between July 2021 and January 2022, 25 secondary schools from diverse socioeconomic background were purposively sampled from Hong Kong, Zhejiang (Mainland China), and Limburg (the Netherlands). 3595 junior students completed an online survey during class about their socioeconomic position, psychosocial factors, and well-being. Socioeconomic inequalities were assessed by multiple linear regressions using the Slope Index of Inequality (SII), whereas the mediating pathways through learning difficulty, overall worry about COVID-19, impact on family' financial status, resilience, trust in government regarding pandemic management, and adaptation to social distancing were examined by mediation analyses moderated by regions. RESULTS: The adverse psychosocial impact of COVID-19 was stronger in the Netherlands and Hong Kong compared with Mainland China. The greatest extent of socioeconomic inequalities in the change in psychosocial well-being was observed among students in the Netherlands (SII = 0.59 [95% CI = 0.38-0.80]), followed by Hong Kong (SII = 0.37 [0.21-0.52]) and Mainland China (SII = 0.12 [0.00-0.23]). Learning difficulty and resilience were the major mediators in Mainland China and Hong Kong, but to a lesser extent in the Netherlands. CONCLUSION: Socioeconomic inequalities in psychosocial well-being were evident among adolescents under the pandemic, with learning difficulty and resilience of students as the key mediators. Differences in the social contexts should be considered to better understand the variations in inequalities and mediating pathways across regions.

Experience of South and Southeast Asian minority women in Hong Kong during COVID-19 pandemic: a qualitative study.

BACKGROUND: Hong Kong has a relatively low incidence rate of COVID-19 across the globe. Nevertheless, ethnic minorities in Hong Kong, especially South Asians (SAs) and Southeast Asians (SEAs), face numerous physical, mental, social, economic, cultural and religious challenges during the pandemic. This study explores the experiences of SA and SEA women in a predominantly Chinese metropolitan city. METHODS: Ten SA and SEA women were recruited and face-to-face interviews were conducted. Questions about participants' daily life experience, physical and mental health conditions, economic situation and social interaction amid COVID-19 pandemic were asked to assess the impact of COVID-19. RESULTS: SAs and SEAs have a distinctive family culture, and women experienced significant physical and mental impact of COVID-19 due to their unique gender role in the family. In addition to taking care of their family in Hong Kong, SA and SEA women also had to mentally and financially support family members residing in their home countries. Access to COVID-related information was restricted due to language barrier. Public health measures including social distancing imposed extra burden on ethnic minorities with limited social and religious support. CONCLUSIONS: Even when COVID-19 incidence rate is relatively low in Hong Kong, the pandemic made life even more challenging for SAs and SEAs, which is a community already struggling with language barriers, financial woes, and discrimination. This in turn could have led to greater health inequalities. Government and civil organizations should take the social determinants of health inequalities into account when implementing COVID-19-related public health policies and strategies.

The mediating role of individual-level social capital among worries, mental health and subjective well-being among adults in Hong Kong during the COVID-19 pandemic.

The COVID-19 pandemic has substantially induced worries and affected individual mental health and subjective well-being. Nonetheless, a high level of social capital could potentially protect individuals who suffer from mental health problems and thus promote their subjective well-being, especially under the social distancing policies during the pandemic. To this end, based on a random sample of 1053 Hong Kong adults, structural equation modeling was applied to study the path relationships between the worries of COVID-19, social capital, mental health problems, and subjective well-being. The study found that worries during the pandemic were associated with mental health and subjective well-being, through social capital as a mediator. Moreover, social capital exhibited a stronger influence on mental health and subjective well-being in the economically inactive group than in the economically active group. This study highlights the important role of social capital during the COVID-19 pandemic. While Hong Kong's COVID-19 response has primarily focused on disease prevention, it must be noted that social services and mutual-help activities are also crucial for people to withstand the crisis.

Resilience and coping strategies of older adults in Hong Kong during COVID-19 pandemic: a mixed methods study.

BACKGROUND: Despite the adverse physical health impact of COVID-19 on older adults, whether they are psychosocially vulnerable under the pandemic remains debatable. In this mixed methods study, we examined the psychosocial vulnerability of older adults relative to their younger counterparts and explored how they coped with the pandemic. METHODS: From September to October 2020, 1067 adults in Hong Kong were randomly sampled and completed a telephone survey, whereas 10 older adults were recruited for individual interviews between September 2020 and April 2021. Quantitative measurements included subjective well-being, worries about COVID-19, and changes in social capital and social interaction since the pandemic. The transcribed qualitative data were closely read and summarized using thematic analyses. RESULTS: Compared with younger adults, older adults tended to be less worried about COVID-19 infection and economic activity/livelihood, despite being slightly more worried about supplies of personal protective equipment. They also had better subjective well-being in terms of happiness and life satisfaction, with their social capital and social interaction less affected. In addition, five themes emerged from the qualitative interviews: (1) life philosophy; (2) economic security; (3) telecommunication; (4) role of community organizations and social workers; and (5) positive coping strategies. CONCLUSIONS: Older adults in this study showed better psychosocial well-being than their younger counterparts under the COVID-19 pandemic, which challenged the deeply rooted societal stereotype about the vulnerability of older adults. The stronger resilience for positive coping, technological assistance, and targeted government and community support may have protected older adults from distress during the pandemic.

Socioeconomic Patterns of COVID-19 Clusters in Low-Incidence City, Hong Kong.

Although coronavirus disease (COVID-19) outbreaks have been relatively well controlled in Hong Kong, containment remains challenging among socioeconomically disadvantaged persons. They are at higher risk for widespread COVID-19 transmission through sizable clustering, probably because of exposure to social settings in which existing mitigation policies had differential socioeconomic effects.

Long Working Hours, Precarious Employment and Anxiety Symptoms Among Working Chinese Population in Hong Kong.

This study aimed to examine the association between working hours and anxiety of a working population in Hong Kong. We used a cross sectional data from a population-based household survey of Hong Kong Chinese adults. Key measures included employment status, skill level, working hours, length of stay at current job and anxiety level. Symptoms of anxiety were assessed using the Depression Anxiety Stress Scale (DASS-21). The data were analysed using logistic regression. Chinese adults who had long working hours (≥ 72 h per week) had higher odds of developing symptoms of anxiety than those who worked for ≤ 36 h per week (odds ratio [OR] 5.94, 95% confidence interval [CI]: 1.82‒19.41). Compared with short period (< 1 year), long period of stay at current job (≥ 5 years) was found as a protective factor from anxiety (OR 0.38, 95% CI: 0.20‒0.73). We found that a working period of 72 h per week was a significant threshold to cause anxiety to workers. Stable job arrangement was a protective factor to workers from anxiety. Implementation of labour market regulations, such as standard working hour policy and stable job arrangement, was also significant to mitigate risk of anxiety for working people in Hong Kong.

cDNA cloning and mRNA expression of retinoid-X-receptor in the ovary of the shrimp Metapenaeus ensis.

Retinoid-X-receptor (RXR) plays an essential role in the molting process of decapod crustaceans, by forming a heterodimeric complex with the ecdysteroid receptor. However, its role during female reproduction, especially in the process of ovarian maturation, has not been characterized. To get an insight into the molecular events governing the process of ovarian maturation in shrimps, the full-length cDNA of RXR from Metapenaeus ensis was cloned by extension of truncated cDNA by using the RACE technique. The open reading frame of MeRXR encodes a 410 amino acid protein with a deduced molecular weight of 44.8 kDa, and putative pI of 6.64, which roughly matched our observation from 2DE gel. Phylogenetic analysis showed that MeRXR has high similarity to RXR of Penaeus chinensis and P. japonicus. RT-PCR revealed that MeRXR was universally expressed in all tissues investigated. The variation in MeRXR mRNA expression pattern during ovarian maturation was further analyzed by real-time PCR. In contrast to the decrease in MeRXR at protein level with ovarian maturation, MeRXR mRNA level was low in pre-vitellogenic and mid-vitellogenic ovaries, and increased significantly from mid-vitellogenic to late-vitellogenic stages. This result suggests that MeRXR transcripts in the mature ovary probably act as maternal messages for regulating early molting events during embryonic development.

Determinants of depression and anxiety in homeless people: A population survey of homeless people in Hong Kong.

BACKGROUND: There are growing concerns about the homeless and mental health issues globally. This study aims to examine the mental health situation of homelessness and the determinants of anxiety and depression of them in Hong Kong. METHOD: The data from the largest territory-wide study of the homeless population in 2021 was analyzed. Descriptive statistics and logistic regressions were used to investigate the association between mental health and socioeconomic variables, including demographic background, economic indicators, COVID-19 worries, government measures, and respect by others. The symptoms of depression and anxiety were assessed using Patient Health Questionnaire (PHQ) and General Anxiety Disorder (GAD). RESULTS: The results showed that being female, food insecurity, and chronic diseases were the risk factors for anxiety and depression. A high level of respect by others was the protective factor for depression (adjusted OR 0.37, 95% CI [0.23, 0.61]) and anxiety (adjusted OR 0.40, 95% CI [0.24, 0.68]), compared to a low level of respect in the multivariate model. CONCLUSIONS: Providing medical outreach services, additional resources for social services, implementation of homeless-friendly policies, and a progressive supply of public and transitional housing would help enhance the well-being of the homeless population.

Secular trends of life expectancy and disability-free life expectancy at age 65 and associated gender and area-level socioeconomic inequalities in Hong Kong: a serial cross-sectional study between 2007 and 2020.

Background: Despite Hong Kong's world leading longevity, little is known about its associated disability burden and social patterning. Hence, this study assessed the gender-specific secular trends and area-level inequalities in life expectancy (LE) and disability-free life expectancy (DFLE) at age 65 in Hong Kong. Methods: Population structure, death records, and disability data in 2007, 2013, and 2020 were retrieved from the Census and Statistics Department to estimate LE and DFLE using the Sullivan Method. District-based sociodemographic indicators were used to compare LE and DFLE across 18 districts of Hong Kong in 2013. Findings: Between 2007 and 2020, LE at age 65 increased by 3.7 years (from 18.3 to 22.0) in men and by 2.1 years (from 22.7 to 24.8) in women. By contrast, DFLE increased more slowly, by 1.8 years (from 14.6 to 16.3) in men and by only 0.1 year (from 16.4 to 16.5) in women, leading to a substantial increase in proportion of life spent with disability. Results from multiple linear regression using district-based data in 2013 showed a similar extent of associations of education with LE and DFLE (mean year difference: 0.81 [95% CI: 0.14, 1.48] and 0.68 [0.10, 1.27], respectively, per 10% increase in average education level), while female gender was more strongly associated with LE (4.44 [3.56, 5.31]) than with DFLE (2.00 [1.18, 2.82]). Interpretation: Expansion of disability burden and male-female health-survival paradox hold true in Hong Kong. Unlike Western countries with a stronger socioeconomic patterning of DFLE, the extent of area-level socioeconomic inequalities in LE and DFLE appears to be more comparable in Hong Kong. Funding: Health and Medical Research Fund (Ref. no.: 19202031) by the Health Bureau of Hong Kong.

Socioeconomic inequality in the worsening of psychosocial wellbeing via disrupted social conditions during COVID-19 among adolescents in Hong Kong: self-resilience matters.

Background: Adolescents, especially the socioeconomically disadvantaged, are facing devastating psychosocial impact of the COVID-19 pandemic during their critical developmental period. This study aims to (i) examine the socioeconomic patterning of the worsening of psychosocial wellbeing, (ii) delineate the underlying mediating factors (i.e., overall worry about COVID-19, family's financial difficulty, learning problems, and loneliness), and (iii) explore the moderating effect of resilience in the inter-relationship among adolescents under COVID-19. Methods: Based on maximum variation sampling of 12 secondary schools of diverse socioeconomic background in Hong Kong, 1018 students aged 14-16 years were recruited and completed the online survey between September and October 2021. Multi-group structural equation modeling (SEM) by resilience levels was employed to delineate the pathways between socioeconomic position and the worsening of psychosocial wellbeing. Results: SEM analysis showed a significant total effect of socioeconomic ladder with the worsening of psychosocial wellbeing during the pandemic in the overall sample (ß = -0.149 [95% CI = -0.217 - -0.081], p < 0.001), which operated indirectly through learning problems and loneliness (both p < 0.001 for their indirect effects). Consistent pattern with stronger effect size was observed in the lower resilience group; nonetheless, the associations were substantially mitigated in the higher resilience group. Conclusion: In addition to facilitating self-directed learning and easing loneliness during the pandemic, evidence-based strategies to build up resilience among adolescents are critical to buffer against the adverse socioeconomic and psychosocial impacts of the pandemic or other potential catastrophic events in the future.

Mitigating inequalities in community care needs of older adults with dementia: a qualitative case study of an integrated model of community care operated under the proportionate universalism principle.

BACKGROUND: Population ageing and community care on older adults, as well as the marked social inequalities in health, have received growing concern by the government and the community. This study evaluated the medico-social integrated day care model of the Cadenza Hub for older adults with dementia. We also examined whether services subsidized by the publicly funded graded financial support of the Community Care Service Voucher for the Elderly (CCSV) could mitigate social inequalities in community care needs, from the perspective of the caregivers. METHODS: In this qualitative case study, we adopted purposeful sampling strategy to recruit 14 caregivers of active day care service users with dementia, with different socioeconomic background and duration of service use, for face-to-face semi-structured in-depth interviews between June and August 2021. The transcribed data were closely read to capture key themes using thematic analyses. RESULTS: Caregivers faced tremendous caregiving burden in the absence of community care support and struggled in choosing care services. Most informants benefited from the day care service, whereas the financial support of CCSV was crucial to ensure equitable access to community care. Non-governmental organizations and social workers were the key to bridging the information gap. CONCLUSION: The integrated day care of the Cadenza Hub appeared to have addressed the unmet needs of older adults with dementia and their caregivers, including the socioeconomically disadvantaged with the CCSV support. The community care service delivery model might be applicable to address other health inequalities problems.

The impact of trust in government on pandemic management on the compliance with voluntary COVID-19 vaccination policy among adolescents after social unrest in Hong Kong.

Background: The launch of COVID-19 vaccines among students provides an opportunity to re-open schools safely. Nonetheless, under the voluntary vaccination policy, the lack of trust in government since the unprecedented massive social unrest in Hong Kong may hinder the vaccination progress. This study aims to assess the impact of trust in government regarding pandemic management on the willingness, uptake, and intention of COVID-19 vaccination among students in Hong Kong. Methods: Based on maximum variation sampling of 12 secondary schools of diverse socioeconomic background, 1,020 students aged 14-16 years completed an online survey between September and October 2021. Results: 59.2% of the sample received at least one dose of the COVID-19 vaccine, 25.2% showed willingness of vaccination, 44.7% of the unvaccinated intended to receive the vaccine, whereas 13.4% were trustful to the government regarding pandemic management. Results from multivariable logistic regressions showed independent associations of trust with greater vaccination uptake [aOR = 1.63 (95% CI = 1.06-2.52), compared to distrust], willingness [aOR = 12.40 (7.72-19.93)], and intention [aOR = 4.49 (2.06-9.75)]. However, the impact of trust on vaccine uptake reversed [aOR = 0.53 (0.32-0.87)] after additional adjustment for the willingness of vaccination. Conclusion: Students with higher trust in government regarding pandemic management tended to have greater vaccination willingness and hence uptake; nonetheless, given the same level of willingness, distrust might have facilitated a faster adoption of vaccination as a self-initiated protective behavior. As the level of trust is generally low among secondary school students in Hong Kong, rebuilding trust during adolescence is of importance for better preparedness of the next pandemic.

Inequalities in Psychiatric Morbidity in Hong Kong and Strategies for Mitigation.

This study explores the social gradient of psychiatric morbidity. The Hong Kong Mental Morbidity Survey (HKMMS), consisting of 5719 Chinese adults aged 16 to 75 years, was used. The Chinese version of the Revised Clinical Interview Schedule (CIS-R) was employed for psychiatric assessment of common mental disorders (CMD). People with a less advantaged socioeconomic position (lower education, lower household income, unemployment, small living area and public rental housing) had a higher prevalence of depression and anxiety disorder. People with lower incomes had worse physical health (OR 2.01, 95% CI 1.05-3.82) and greater odds of having CMD in the presence of a family history of psychiatric illnesses (OR 1.67, 95% CI 1.18-2.36). Unemployment also had a greater impact for those in lower-income groups (OR 2.67; 95% CI 1.85-3.85), whereas no significant association was observed in high-income groups (OR 0.56; 95% CI 0.14-2.17). Mitigating strategies in terms of services and social support should target socially disadvantaged groups with a high risk of psychiatric morbidity. Such strategies include collaboration among government, civil society and business sectors in harnessing community resources.

Association of living density with anxiety and stress: A cross-sectional population study in Hong Kong.

This study aims to enrich the comprehension of the effect of living density on anxiety and stress among adults in a global city. A random sample of 1,978 Hong Kong adults was interviewed in a cross-sectional population study in 2014-2015. Descriptive statistics and logistic regressions were used to investigate the association between housing variables and mental health indicators, namely, anxiety and stress. Logistic regression analysis results have shown that by controlling the confounding effect of demographic variables, income poverty, housing ownership and housing cost, the living density was significantly associated with anxiety and stress of residents. Compared with those living in high density of <7 m2 , living in medium density of ≥7 and <13 m2 was significantly associated with lower risk of anxiety (adjusted OR 0.52, 95% CI 0.30-0.88), and the risk was less for those living in low density of ≥13 m2 (adjusted OR 0.41, 95% CI 0.23-0.72). Meanwhile, living in low density of ≥13 m2 was significantly associated with a lower risk of stress (adjusted OR 0.44, 95% CI 0.20-0.97). These results highlighted the significant impact of living density on personal anxiety and stress. Moreover, female, younger adults or those living in income poverty were also at risk of anxiety and stress. In conclusion, our findings implied that improving housing policies, such as building public housing with adequate living areas and market regulation of living density of private housing, would help enhance the mental well-being of residents.

Socioeconomic inequality in mental well-being associated with COVID-19 containment measures in a low-incidence Asian globalized city.

The COVID-19 pandemic exposes and amplifies pre-existing inequalities even in places with relatively well-controlled outbreaks such as Hong Kong. This study aimed to explore whether the socioeconomically disadvantaged fare worse via various types of worry in terms of their mental health and well-being. Between September and October 2020, 1067 adults in Hong Kong were recruited via a cross-sectional population-wide telephone survey. The inter-relationship between deprivation, types of worry, mental health disorders, and subjective well-being was assessed using structural equation modelling. Results showed significant total effects of deprivation on worries about being infected (p = 0.002), economic activities and livelihood (p < 0.001), and personal savings (p < 0.001), as well as mental health disorders (p < 0.001) and subjective well-being (p < 0.001). Specifically, worry about economic activities and livelihood partly mediated the total effect of deprivation on mental health disorders (p = 0.004), whereas worry about personal savings and worry about economic activities and livelihood partially mediated the total effect of deprivation on subjective well-being (p = 0.007 and 0.002, respectively). Socioeconomic inequality, particularly in mental health and well-being, could be exacerbated via people's economic concerns during the pandemic, which was largely induced by the COVID-19 containment measures rather than the pandemic per se given the relatively low COVID-19 incidence in Hong Kong.

The Impact of Bedbug (Cimex spp.) Bites on Self-Rated Health and Average Hours of Sleep per Day: A Cross-Sectional Study among Hong Kong Bedbug Victims.

Bedbugs (Cimex spp.) are a nuisance public-health pest that is on the rise globally, particularly in crowded cities such as Hong Kong. To investigate the health impacts of bedbug infestations among bedbug victims, online surveys were distributed in Hong Kong between June 2019 to July 2020. Data on sociodemographics, self-rated health, average hours of sleep per day, and details of bedbug infestation were collected. Bivariate and multivariable analysis were performed using logistic regression. The survey identified 422 bedbug victims; among them, 223 (52.9%) experienced ≥five bites in the past month; most bites occurred on the arms (n = 202, 47.8%) and legs (n = 215, 51%), and the most common reaction to bites were itchiness (n = 322, 76.3%), redness, and swelling of the skin (n = 246, 58.1%), and difficulties sleeping or restlessness (n = 125, 29.6%). Bites usually occurred during sleep (n = 230, 54.5%). For impact on daily life in the past month, most bedbug victims reported moderate to severe impact on mental and emotional health (n = 223, 52.8%) and sleeping quality (n = 239, 56.6%). Lower self-rated health (aOR < 1) was independently associated with impact on physical appearance (p = 0.008), spending money on medication or doctor consultation (p = 0.04), number of bites in the past month (p = 0.023), and irregular time of bites (p = 0.003). Lower average hours of sleep per day (aOR < 1) was independently associated with impact on mental and emotional health (p = 0.016). This study brings attention to the neglected issue of bedbug infestation by considering bedbugs as an infectious agent instead of a vector and providing empirical evidence describing its health impacts.

Differential Impacts of Multimorbidity on COVID-19 Severity across the Socioeconomic Ladder in Hong Kong: A Syndemic Perspective.

The severity of COVID-19 infections could be exacerbated by the epidemic of chronic diseases and underlying inequalities in social determinants of health. Nonetheless, there is scanty evidence in regions with a relatively well-controlled outbreak. This study examined the socioeconomic patterning of COVID-19 severity and its effect modification with multimorbidity in Hong Kong. 3074 local COVID-19 cases diagnosed from 5 July to 31 October 2020 were analyzed and followed up until 30 November 2020. Data on residential addresses, socio-demographic background, COVID-19 clinical conditions, and pre-existing chronic diseases of confirmed cases were retrieved from the Centre for Health Protection and the Hospital Authority. Results showed that, despite an independent adverse impact of multimorbidity on COVID-19 severity (aOR = 2.35 [95% CI = 1.72-3.19]), it varied across the socioeconomic ladder, with no significant risk among those living in the wealthiest areas (aOR = 0.80 [0.32-2.02]). Also, no significant association of the area-level income-poverty rate with severe COVID-19 was observed. In conclusion, the socioeconomic patterning of severe COVID-19 was mild in Hong Kong. Nonetheless, socioeconomic position interacted with multimorbidity to determine COVID-19 severity with a mitigated risk among the socioeconomically advantaged. Plausible explanations include the underlying socioeconomic inequalities in chronic disease management and the equity impact of the public-private dual-track healthcare system.

A novel C-type lectin from the shrimp Litopenaeus vannamei possesses anti-white spot syndrome virus activity.

C-type lectins play key roles in pathogen recognition, innate immunity, and cell-cell interactions. Here, we report a new C-type lectin (C-type lectin 1) from the shrimp Litopenaeus vannamei (LvCTL1), which has activity against the white spot syndrome virus (WSSV). LvCTL1 is a 156-residue polypeptide containing a C-type carbohydrate recognition domain with an EPN (Glu(99)-Pro(100)-Asn(101)) motif that has a predicted ligand binding specificity for mannose. Reverse transcription-PCR analysis revealed that LvCTL1 mRNA was specifically expressed in the hepatopancreas of L. vannamei. Recombinant LvCTL1 (rLvCTL1) had hemagglutinating activity and ligand binding specificity for mannose and glucose. rLvCTL1 also had a strong affinity for WSSV and interacted with several envelope proteins of WSSV. Furthermore, we showed that the binding of rLvCTL1 to WSSV could protect shrimps from viral infection and prolong the survival of shrimps against WSSV infection. Our results suggest that LvCTL1 is a mannose-binding C-type lectin that binds to envelope proteins of WSSV to exert its antiviral activity. To our knowledge, this is the first report of a shrimp C-type lectin that has direct anti-WSSV activity.

The effects of farnesoic acid and 20-hydroxyecdysone on vitellogenin gene expression in the lobster, Homarus americanus, and possible roles in the reproductive process.

Reproduction in female lobster (Homarus americanus) is characterized by the maturation of the ovary, with a gradual increase in its size as a result of uptake of yolk protein precursor, vitellogenin (Vg) to the final product vitellin (Vn). Vn is formed by aggregation of several Vg subunits. In most decapods, the hepatopancreas is the major site of vitellogenin biosynthesis. The production of vitellogenin is controlled by endocrine factors. In this study, the effect of farnesoic acid (FA) and 20-hydroxyecdysone (20E) on production of vitellogenin by hepatopancreas (HaVg1) was investigated by in vitro organ explant HaVg1 gene expression was stimulated by FA or 20E in a dose-dependent manner. A 2-fold and 2.2-fold increase in HaVg1 gene expression was observed with 4.2 microM FA and 0.7 microM 20E, respectively. The stimulatory effect by either FA or 20E was observed principally during the first 90 min. Stimulation of HaVg1 gene expression by FA and 20E together is greater (3.3-fold increase) than that of either hormone alone. This stimulation was also observed within the first 90 min. To study the synergistic effect of these two hormones, FA and 20E were tested separately and together at low concentration (42.3 nM and 6.7 nM, respectively). Combined use of FA and 20E increased HaVg1 gene expression synergistically, but not additively. These findings should contribute to our understanding of lobster reproduction and provide insights into manipulation of lobster reproduction in aquaculture or under captive conditions.

Cloning and expression study of the lobster (Homarus americanus) vitellogenin: Conservation in gene structure among decapods.

This study reports the molecular characterization of the vitellogenin (Vg) of the lobster, Homarus americanus. Based on the annual collection of female lobsters, vitellogenesis commences in early March and continues through to September of each year. Using an antibody to vitellin of the lobster, H. americanus, several immunoreactive ovarian proteins were initially identified by Western blot analysis. The 80kDa protein contained the amino acid sequence APWGGNTPRC, identified subsequently by cDNA cloning to be identical to the lobster Vg. In common with the shrimp Metapenaeus ensis and crab Charybdis feriatus, the lobster HaVg1 gene comprises 14 introns and 15 exons. The deduced HaVg1 precursor is most similar to the Vg of the crayfish Cherax quadricarinatus (57%), followed by M. ensis (40-43% identity) and C. feriatus (38%). The results from genomic and RT-PCR cloning also confirmed the presence of multiple Vg genes in lobster. At early reproductive stages, the hepatopancreas HaVg1 transcript levels are low but increased to a maximum in animals with mature oocytes. The ovary, however, also expressed low levels of HaVg1. Using in vitro explant culture, treatment of hepatopancreas fragments with farnesoic acid or 20-hydroxyecdysone resulted in a significant stimulation in HaVg1 expression. From this study, it appears that Vg gene organization and expression pattern in decapods is highly conserved. Similar endocrine mechanisms may govern the process of vitellogenesis across the decapods.