Interrelationship between mitosis and endomitosis in cultures of human megakaryocyte progenitor cells [published erratum appears in Blood 1987 May;69(5):1547]

Sera from dogs rendered aplastic by total-body irradiation stimulate human bone marrow megakaryocyte progenitors to form megakaryocyte colonies in plasma clot cultures. In this investigation, we evaluated the effects of varying concentrations of such sera on both the mitotic and endomitotic phases of human megakaryocyte development in vitro. When low concentrations of aplastic canine sera (2.5% to 5.0% [vol/vol]) were added to cultures of human peripheral blood mononuclear cells in place of normal AB serum, megakaryocyte colony formation was augmented fivefold, cell numbers per colony increased approximately 2.5- fold, and the geometric mean megakaryocyte ploidy almost doubled. Further increasing the aplastic canine serum concentration from 10% to 30% (vol/vol) stimulated no additional colony formation. However, there was a further augmentation of cell numbers per colony associated with a progressive decrease in the mean megakaryocyte ploidy. Megakaryocyte cultures were harvested after 7, 12, 15, and 19 days of incubation, and these demonstrated that the lower mean ploidy values found at the higher concentrations of aplastic canine serum did not result from delayed endoreduplication. At all aplastic serum concentrations evaluated, there existed a strong correlation between nuclear ploidy and cell diameter. We conclude that both the mitotic and endomitotic events in human megakaryocytopoiesis may be influenced by a factor or factors present in aplastic canine serum. At lower in vitro concentrations, such sera stimulate both mitosis and endomitosis, which promotes the development of megakaryocyte colonies composed of larger cells with a higher mean ploidy. With increasing aplastic serum concentrations, colony formation plateaus and mitosis is favored over endomitosis. This results in colonies composed of more numerous but smaller megakaryocytes with a lower mean ploidy. Our data suggest that the size and extent of polyploidization that can be achieved by a developing megakaryocyte may be influenced by the mitotic prior history of its immediate precursor cell.     

Neighborhood Blight,Stress, and Health: A Walking Trial of Urban Greening and Ambulatory Heart Rate

We measured dynamic stress responses using ambulatory heart rate monitoring as participants in Philadelphia, Pennsylvania walked past vacant lots before and after a greening remediation treatment of randomly selected lots. Being in view of a greened vacant lot decreased heart rate significantly more than did being in view of a nongreened vacant lot or not in view of any vacant lot. Remediating neighborhood blight may reduce stress and improve health.Vacant lots are abandoned parcels of urban land that signal blight, with overgrown vegetation, trash dumping, and other illegal activities. Exposure to these lots is associated with negative health outcomes.1–7 Although complex social and economic factors broadly explain the relationship between neighborhood blight and health, limited experimentation with biological outcomes has been conducted in real-world settings.8The body’s stress response is a reasonable biological pathway for understanding the impact of neighborhood blight on health.9,10 Although this response is protective in acute situations, permanent downstream inflammatory changes and dysregulation of cardiovascular, neurological, and endocrine systems accumulate over a lifetime for persons repeatedly exposed to stressors in their neighborhood surroundings.11–16 Basic structural improvements to blighted neighborhood environments, such as “greening” vacant lots, offers a promising and sustainable, yet underused, solution to such stressors.5,17We examined the microspatial impact of neighborhood physical conditions during short neighborhood walks by experimentally testing a specific condition (the remediation of blighted vacant land) to a dynamic biological marker (heart rate).18–21 Using georeferenced heart rate monitoring in an experimental study of an individual’s native environment is a unique approach to field studies of neighborhood blight on acute stress.22     

Pancreatic and gastrointestinal hormones in chronic pancreatitis

Pancreatic and gut hormones have been measured in 39 patients with chronic pancreatitis, 16 of whom had severe pancreatic insufficiency. Patients with pancreatic insufficiency had significantly diminished fasting levels and postprandial rises of pancreatic polypeptide which were less than 20% of normal. Patients with chronic pancreatitis, with or without exocrine insufficiency, had two- to threefold higher plasma levels of motilin and enteroglucagon than controls. Plasma levels of insulin, pancreatic glucagon, gastric inhibitory polypeptide and gastrin were similar to normal in these patients. The pattern of response of these hormones to a test breakfast differs markedly from those seen in other gut disease states and may reflect pathophysiological mechanisms.     

Weaning from neonatal and pediatric ECMO with stand-by cannula

Journal of Artificial Organs - The precise moment for weaning a patient off extracorporeal membrane oxygenation (ECMO) is not always easy to establish. Also, mechanical causes may obligate to...