ABSTRACT
Global obesity as a major public health problem has increased at pandemic rate, with men often outpacing women. Survey data show that the overall prevalence of obesity is higher among women than men, yet in high-income developed countries, the prevalence of overweight is higher among men than women. The differential impact of different economic stages has prompted research in transition economies such as China. Using an instrumental variable approach based on a sample of 13,574 individuals from nine provinces in the Chinese Household Income Project (CHIP), we find a 7% excess-weight premium in wages for overweight men and a 4.6% penalty for overweight women, compared to their healthy-weight peers. We also find an inverse u-shaped association between the body mass index (BMI) and logarithm of monthly income for men, with an implied optimum above the threshold of obesity, while women are better off the slimmer they are. The excess-weight premium in wages for Chinese urban men might be associated with entrenched business practices of excessive dining and drinking associated with senior positions. Policies aimed at reducing obesity in China must be adapted to its unique sociocultural context in order to have gender-differentiated effects.
Subject(s)
Obesity , Overweight , Salaries and Fringe Benefits , Adult , Body Mass Index , China/epidemiology , Female , Humans , Male , Middle Aged , Obesity/epidemiology , Overweight/epidemiology , Prevalence , Sex Factors , Socioeconomic FactorsABSTRACT
Ejaculated mammalian sperm must acquire fertilization capacity after residing into the female reproductive tract, a process collectively known as capacitation. Cholesterol efflux was required for sperm maturation. Different from flagellated sperm, C. elegans sperm are crawling cells. C. elegans sperm are highly enriched with cholesterol though this animal species lacks biosynthetic pathway for cholesterol and its survival requires an exogenous cholesterol supply. The low abundance of cholesterol in C. elegans lipid extract is thought insufficient to form lipid microdomains ubiquitously in this organism. We present evidence that cholesterol is enriched in the plasma membrane of C. elegans spermatids and that cholesterol- and glycosphingolipids (GSLs)-enriched membrane microdomains (lipid microdomains) mediate sperm activation. Disruption of sperm lipid microdomains by acute manipulation of cholesterol in vitro blocks the sperm activation. Restriction of cholesterol uptake also results in the abnormal sperm activation in both males and hermaphrodites. Manipulation of the integrity of lipid microdomains by targeting the biosynthesis of GSLs inhibits sperm activation and the inhibition can be rescued by the addition of exogenous GSLs. The cleavage of glycosylphosphatidylinositol (GPI)-anchored proteins, which are exclusively found in lipid microdomains, also affects sperm activation. We conclude that localized signaling mediated by lipid microdomains is critical for worm sperm activation. Lipid microdomains composed of cholesterol and GSLs have been observed in flagellated sperm of several animal species, thus cholesterol, before its efflux from the plasma membrane, might be needed to assemble into a platform for some more important upstream signal sorting during spermatogenesis than was previously thought.
Subject(s)
Caenorhabditis elegans/physiology , Cholesterol/metabolism , Glycosphingolipids/biosynthesis , Spermatozoa/physiology , Animals , Caenorhabditis elegans/metabolism , Caenorhabditis elegans Proteins/metabolism , Cell Fusion , Cell Membrane/metabolism , Female , Fertilization/drug effects , Filipin/pharmacology , Glucosyltransferases/metabolism , Glycosphingolipids/pharmacology , Hermaphroditic Organisms , Male , Membrane Microdomains/metabolism , Microscopy, Confocal , Microscopy, Electron, Transmission , Microscopy, Immunoelectron , Monensin/pharmacology , Proton Ionophores/pharmacology , Sperm Motility/drug effects , Sperm Motility/physiology , Spermatids/metabolism , Spermatids/physiology , Spermatids/ultrastructure , Spermatozoa/metabolism , Spermatozoa/ultrastructureABSTRACT
A lectin, Craniella australiensis (CAL), was isolated from sponge C. australiensis by ion-exchange on DEAE-Sephacel and purified by gel filtration on Sephadex G-150 and HPLC on DEAE-5PW. The purified lectin was a trimeric protein as revealed by SDS-PAGE and MALDI-TOF analysis. SDS-PAGE showed that the CAL protein had a molecular mass of 54 kDa, and consisted of three 18 kDa subunits. Gel filtration of purified lectin on Sephadex G-200 indicates that it exists as a 54 kDa protein in its native state. The amino acid composition was rich in Thr and Glx. CAL was found to agglutinate native and trypsinized human A, B erythrocytes, and agglutinate native erythrocytes of mouse, sheep, rabbit and chicken, and trypsinized erythrocytes of sheep and rabbit. The hemagglutination activity was inhibited by glycoproteins such as PSM and asialo-PSM, but not by any of the monosaccharides tested. The activity was stable between 20 and 70 degrees C. Significant CAL activity was observed between pH 5 and 8. The lectin reaction is independent of the presence of divalent cations Ca2+ and Mg2+. The sequence of N-terminal residues of CAL was determined as TSSCQSIVVE. The lectin showed a potent mitogenic response towards BALB/c splenocytes.
