Clonal variation in cell surface display of an H-2 protein lacking a cytoplasmic tail

Truncated variants of the gene encoding H-2Ld, an integral membrane protein encoded by the major histocompatibility complex, were constructed by in vitro mutagenesis to elucidate the function of charged amino acids found on the cytoplasmic side of the transmembrane (TM) region. Analysis of cloned L cells transfected with these genes shows that the seven amino acids following the TM segment, four of which are basic, enhance the cell surface expression of H-2Ld protein but are not required for it. However, some clones do not express a tailless H-2Ld protein on the cell surface but express it intracellularly where it has a long half-life. Turnover measurements on cell surface H-2Ld proteins suggest that the basic residues following the TM segment are not a "stop transfer" sequence (Blobel, G., 1980, Proc. Natl. Acad. Sci. USA., 77:1496-1500) which anchors the H-2Ld protein in the membrane. Pulse-chase and endoglycosidase H sensitivity studies show that H-2Ld proteins lacking some or all of the basic residues and H-2Ld proteins which have a full-length cytoplasmic tail are processed with different kinetics. These results suggest an involvement of the membrane-proximal region of the cytoplasmic tail in the intracellular transport of H-2Ld. We further suggest that the L cell clones which do and do not express a tailless H-2Ld protein on the cell surface differ in the ability to transport a tailless integral membrane protein to the cell surface

Tectonic DSAEK for the Management of Impending Corneal Perforation

Purpose. To report a case of severe corneal thinning secondary to dry eye treated with a tectonic Descemet stripping automated lamellar keratoplasty (DSAEK) and amniotic membrane graft. Methods. A 72-year-old man with a history of long standing diabetes mellitus type 2 and dry eye presented with 80% corneal thinning and edema on the right eye and no signs of infectious disease, initially managed with topical unpreserved lubrication and 20% autologous serum drops. Eight weeks after, the defect advanced in size and depth until Descemetocele was formed. Thereafter, he underwent DSAEK for tectonic purposes. One month after the procedure, the posterior lamellar graft was well adhered but a 4 mm epithelial defect was still present. A multilayered amniotic membrane graft was then performed. Results. Ocular surface healed quickly and reepithelization occurred over a 2-week period. Eight months after, the ocular surface remained stable and structurally adequate. Conclusion. Tectonic DSAEK in conjunction with multilayered amniotic graft may not only provide structural support and avoid corneal perforation, but may also promote reepithelization and ocular surface healing and decrease concomitant inflammation

Diminishing benefits of urban living for children and adolescents’ growth and development

Optimal growth and development in childhood and adolescence is crucial for lifelong health and well-being1–6. Here we used data from 2,325 population-based studies, with measurements of height and weight from 71 million participants, to report the height and body-mass index (BMI) of children and adolescents aged 5–19 years on the basis of rural and urban place of residence in 200 countries and territories from 1990 to 2020. In 1990, children and adolescents residing in cities were taller than their rural counterparts in all but a few high-income countries. By 2020, the urban height advantage became smaller in most countries, and in many high-income western countries it reversed into a small urban-based disadvantage. The exception was for boys in most countries in sub-Saharan Africa and in some countries in Oceania, south Asia and the region of central Asia, Middle East and north Africa. In these countries, successive cohorts of boys from rural places either did not gain height or possibly became shorter, and hence fell further behind their urban peers. The difference between the age-standardized mean BMI of children in urban and rural areas was <1.1 kg m–2 in the vast majority of countries. Within this small range, BMI increased slightly more in cities than in rural areas, except in south Asia, sub-Saharan Africa and some countries in central and eastern Europe. Our results show that in much of the world, the growth and developmental advantages of living in cities have diminished in the twenty-first century, whereas in much of sub-Saharan Africa they have amplified