Using ferritin-labeled protein A and colloidal gold-labeled anti-rabbit IgG, the fate of the sheep transferrin receptor has been followed microscopically during reticulocyte maturation in vitro. After a few minutes of incubation at 37°C, the receptor is found on the cell surface or in simple vesicles of 100-200 nm, in which the receptor appears to line the limiting membrane of the vesicles. With time (60 min or longer), large multivesicular elements (MVEs) appear whose diameter may reach 1-1.5/~m. Inside these large MVEs are round bodies of ~50-nm diam that bear the receptor at their external surfaces. The limiting membrane of the large MVEs is relatively free from receptor. When the large MVEs fuse with the plasma membrane, their contents, the 50-nm bodies, are released into the medium. The 50-nrn bodies appear to arise by budding from the limiting membrane of the intracellular vesicles. Removal of surface receptor with pronase does not prevent exocytosis of internalized receptor. It is proposed that the exocytosis of the ~50-nm bodies represents the mechanism by which the transferrin receptor is shed during reticulocyte maturation.It is well known that the transferrin receptor is lost during the maturation of the reticulocyte into the erythrocyte (1-4). Recent studies have shown that the maturation process can be followed in vitro (4, 5-7). The loss of the transferrin receptor can be used as a marker of maturation (4-6), the transferrin receptor being released, undegraded, to the medium in vesicular form (6, 7). The transferrin receptor is known to recycle many times during the course of Fe 3÷ delivery without degradation of either the receptor or the natural ligand, transferrin (8-l 1). It has been shown in several systems (8,(12)(13)(14)(15)(16)(17)(18)(19)(20), using either labeled transferrin or antibody against the transferrin receptor, that the ligand and the receptor are internalized into vesicles (endosomes) during incubation at temperatures above 10*C and that this internalization may constitute part of the iron delivery mechanism.Since the transferrin receptor is largely lost from sheep reticulocytes during 24 h of incubation in vitro (5-7), intermediate stages associated with vesicle externalization during receptor elimination might become apparent during the longterm incubation of reticulocytes. No studies to date have addressed the question of the processing that may occur to prepare the receptor for externalization during reticulocyte maturation. We have previously shown (6) that a polyclonal 942 antibody against the transferrin receptor is internalized (as judged by resistance to acid treatment), and that during the course of long-term incubation (several hours at 37"C), this internalized antibody and the surface-bound antibody are lost from the cells along with the antibody-binding capacity of the cells. Since no degraded antibody was found, both internal and surface antibody appear to be eliminated from the cells without degradation.The rate of loss of internalized 125I-antibody as we...

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MyoD is a master regulatory gene for myogenesis. Under the control of a retroviral long terminal repeat, MyoD was expressed in a variety of differentiated cell types by using either a DNA transfection vector or a retrovirus. Expression of muscle-specific proteins was observed in chicken, human, and rat primary fibroblasts and in differentiated melanoma, neuroblastoma, liver, and adipocyte lines. The ability of MyoD to activate muscle genes in a variety of differentiated cell lines suggests that no additional tissuespecific factors other than MyoD are needed to activate the downstream program for terminal muscle differentiation or that, if such factors exist, they are themselves activated by MyoD expression.

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The genetics of Wilms' tumour (WT), a paediatric malignancy of the kidney, is complex. Inactivation of the tumour suppressor gene, WT1, is associated with tumour aetiology in approximately 10-15% of WTs. Chromosome 17p changes have been noted in cytogenetic studies of WTs, prompting us to screen 140 WTs for p53 mutations. When histopathology reports were available, p53 mutations were present in eight of eleven anaplastic WTs, a tumour subtype associated with poor prognosis. Amplification of MDM2, a gene whose product binds and sequesters p53, was excluded. Our results indicate that p53 alterations provide a molecular marker for anaplastic WTs.

Summary Background 80% of individuals with cancer will require a surgical procedure, yet little comparative data exist on early outcomes in low-income and middle-income countries (LMICs). We compared postoperative outcomes in breast, colorectal, and gastric cancer surgery in hospitals worldwide, focusing on the effect of disease stage and complications on postoperative mortality. Methods This was a multicentre, international prospective cohort study of consecutive adult patients undergoing surgery for primary breast, colorectal, or gastric cancer requiring a skin incision done under general or neuraxial anaesthesia. The primary outcome was death or major complication within 30 days of surgery. Multilevel logistic regression determined relationships within three-level nested models of patients within hospitals and countries. Hospital-level infrastructure effects were explored with three-way mediation analyses. This study was registered with ClinicalTrials.gov , NCT03471494 . Findings Between April 1, 2018, and Jan 31, 2019, we enrolled 15 958 patients from 428 hospitals in 82 countries (high income 9106 patients, 31 countries; upper-middle income 2721 patients, 23 countries; or lower-middle income 4131 patients, 28 countries). Patients in LMICs presented with more advanced disease compared with patients in high-income countries. 30-day mortality was higher for gastric cancer in low-income or lower-middle-income countries (adjusted odds ratio 3·72, 95% CI 1·70–8·16) and for colorectal cancer in low-income or lower-middle-income countries (4·59, 2·39–8·80) and upper-middle-income countries (2·06, 1·11–3·83). No difference in 30-day mortality was seen in breast cancer. The proportion of patients who died after a major complication was greatest in low-income or lower-middle-income countries (6·15, 3·26–11·59) and upper-middle-income countries (3·89, 2·08–7·29). Postoperative death after complications was partly explained by patient factors (60%) and partly by hospital or country (40%). The absence of consistently available postoperative care facilities was associated with seven to 10 more deaths per 100 major complications in LMICs. Cancer stage alone explained little of the early variation in mortality or postoperative complications. Interpretation Higher levels of mortality after cancer surgery in LMICs was not fully explained by later presentation of disease. The capacity to rescue patients from surgical complications is a tangible opportunity for meaningful intervention. Early death after cancer surgery might be reduced by policies focusing on strengthening perioperative care systems to detect and intervene in common complications. Funding National Institute for Health Research Global Health Research Unit.

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