Judith Tamburlin

The effect of proteasome inhibitors on mammalian erythroid terminal differentiation

OBJECTIVES Murine erythroblasts infected with the anemia-inducing strain of Friend virus (FVA cells) terminally differentiate to the reticulocyte stage after 48 hours of culture in vitro in response to erythropoietin (EPO). The objective of this study was to determine the possible role of proteasome-mediated proteolysis during the terminal differentiation of FVA cells. MATERIALS AND METHODS The proteasome inhibitors MG132 and lactacystin were used to perturb the normal function of proteasomes during terminal differentiation. Effects of proteasome inhibitors on terminal differentiation were quantitated by evaluation of cellular morphology after benzidine staining and by Western blot analyses. RESULTS Treatment of EPO-stimulated FVA cells with lactacystin or MG132 at later periods of culture increased accumulations of nuclear and cytosolic ubiquitinated proteins and decreased nuclear extrusion to less than 40% of controls. CONCLUSIONS Our results suggest that the proteasomal degradation of ubiquitinated proteins plays an important role in the enucleation of mammalian erythroblasts.

A Confirmatory Analysis of the Organ Donation Readiness Index: Measuring the Potential for Organ Donations Among African Americans

The need for transplant exceeds the number of available organs. Antigen compatible organs are particularly scarce for African Americans because of their proportionately lower rate of donations. This study presents a measure of organ donation readiness. Examination of the factor structure and a test of weak invariance were conducted on cross-sectional (n = 2,662) and longitudinal data (n = 1,316) in a community-based sample of African Americans. A second-order structural equation was used to model the relationship between three latent factors. The results corroborate earlier research and confirm a second-order model structure consisting of 3 factors (Fear, Knowledge, and Action) in a set of 9 self-report items. The second-order model specification provided a good fit to the data. Social workers involved in organ procurement efforts and counseling of family members may find the instrument a useful tool for identifying readiness for organ donation among African Americans.

Exploring the use of the stages of change model to increase organ donations among African Americans

Abstract The success of organ transplants is affected by the degree of antigen match between donor and recipient. With organ transplants among African Americans, finding a good antigen match is difficult. While the consent rate for organ donations among Caucasians is 50%, this rate among African Americans is only 12%. The resulting ratio of donors to “recipients” is 1 to 9 in African Americans. The majority of organs received by African Americans come from Caucasian donors, thereby reducing the probability of an antigen match and increasing the probability of organ rejection. These circumstances could be improved if the organ donation rate eamong African Americans was increased. There is some empirical support for the theory that behavior change occurs through identifiable stages. This paper presents evidence for the construct validity of a stage of change measure suitable for use in designing and evaluating attempts to promote organ donations in the African American community. Use of this measure also permits clinicians to assess how receptive a client will be to organ donation promotional material. Use of this measure offers the possibility of refining approaches to organ donations among African Americans. Increases in the donor rate will result in a larger pool of antigen compatible organs in this subpopulation.

Folate exacerbates the effects of ethanol on peripubertal mouse mammary gland development

Alcohol consumption is linked with increased breast cancer risk in women, even at low levels of ingestion. The proposed mechanisms whereby ethanol exerts its effects include decreased folate levels resulting in diminished DNA synthesis and repair, and/or acetaldehyde-generated DNA damage. Based on these proposed mechanisms, we hypothesized that ethanol would have increased deleterious effects during periods of rapid mammary gland epithelial proliferation, such as peripuberty, and that folate deficiency alone might mimic and/or exacerbate the effects of ethanol. To test this hypothesis, weight-matched 28-35 day old CD2F1 female mice were pair-fed liquid diets ±3.2% ethanol, ±0.1% folate for 4 weeks. Folate status was confirmed by assay of liver and kidney tissues. In folate deficient mice, no significant ethanol-induced changes to the mammary gland were observed. Folate replete mice fed ethanol had an increased number of ducts per section, due to an increased number of terminal short branches. Serum estrogen levels were increased by ethanol, but only in folate replete mice. These results demonstrate that folate deficiency alone does not mimic the effects of ethanol, and that folate deficiency in the presence of ethanol blocks proliferative effects of ethanol on the mammary ductal tree.

Formation of intracellular vesicles in neonatal and adult erythrocytes: evidence against the concept of neonatal hyposplenism

ABSTRACT: Intraerythrocytic vesicles accumulate in the peripheral blood as a result of impaired clearance of these intracellular inclusions by the spleen. The observation that neonates demonstrate an increased percentage of erythrocytes containing these vesicles constitutes the primary evidence supporting the concept that the newborn is functionally hyposplenic. Neonatal erythrocytes also demonstrate an increased propensity to undergo a variety of endocytic processes. We therefore questioned whether the increase in red cell vesicles in the neonate might be the result of increased vesicle formation as opposed to impaired splenic clearance. Newborn and adult erythrocytes were incubated in vitro in synthetic medium at 37° C. Several parameters confirmed the maintenance of physiologic conditions, including levels of erythrocyte phosphate metabolites monitored by nuclear magnetic resonance. The acquisition of intraerythrocytic vesicles during the course of these incubations was compared. Over a period of 144 h, 19.2% of neonatal erythrocytes acquired vesicles compared to 3.7% of the adult cells (p < 0.001). The increase in vesicles was greater in younger density-separated erythrocytes in both the neonate (37.6%, p < 0.0005) and the adult (10.3%, p < 0.002), but persisted even in the oldest erythrocytes (12.2% and 2.4%, respectively). We conclude that the increase in erythrocytic vesicles in the neonate may not simply be an indication of hyposplenism, but a reflection of increased vesicle formation which overwhelms the clearance capability of the spleen.