Stem cell factor enhances the survival but not the self-renewal of murine hematopoietic long-term repopulating cells

The effects of stem cell factor (SCF) have been tested on a murine bone marrow subpopulation (RH123lo, Lin-, Ly6A/E+) that is highly enriched for long-term hematopoietic repopulating cells. SCF maintained cells from this population with long-term repopulating ability for up to 10 days in vitro. However, compared with freshly isolated cells, the level of engraftment in vivo by the cultured cells declined during the in vitro culture period, suggesting that SCF alone was unable to stimulate the self-renewal of long-term repopulating cells. By direct visualization of cultures, only small numbers of cells survived and rarely underwent cell division. However, SCF did directly stimulate proliferation of a population (Rh123med/hi,Lin-,Ly6A/E+) enriched for short-term repopulating cells. These data suggest that stem cell differentiation is associated with the development of mitogenic activity by SCF at least in some progenitor cell populations.     

The detection and use of hemoglobin mutants in the direct analysis of human globin genes

Many human globin-chain mutants contain amino acid replacements that result from single base changes in the corresponding globin gene. Using recombinants, the coding sequences of each of the alpha-, beta-, Ggamma- , and Agamma-globin genes have now been determined. Those sequences of DNA that are cleaved by a number of specific restriction endonucleases have been identified and accurately positioned. Mutations at these sequences abolish the restriction site, and therefore, the pattern of DNA fragments containing hybridizing globin-gene sequences is altered compared to DNA from normal persons. This allows the identification of one of a pair of cross-hybridizing human globin-gene sequences, as is shown here for the two alpha-globin, the two gamma-globin, and the delta- and beta-globin genes.     

Heterogeneity in human neutrophil, macrophage and eosinophil progenitor cells demonstrated by velocity sedimentation separation

Progenitor cells of neutrophils, monocyte-macrophages, and eosinophils in human marrow were enumerated in agar cultures stimulated by placental conditioned medium or white cell underlayers. Fractionation of marrow populations by velocity sedimentation showed that the profiles of neutrophil and macrophage colony-forming cells shifted from a peak of 8-9 mm/hr in 7-day cultures to a peak of 6-7 mm/hr in 14-day cultures. This shift was due to degeneration of some early colonies formed by rapidly sedimenting cells and the delayed formation of colonies by slowly sedimenting cells. Eosinophil colony formation was delayed until the second week of incubation. Further evidence of heterogeneity was the observation that rapidly sedimenting colony forming cells were more responsive to stimulation than more slowly sedimenting cells. In the macrophage and eosinophil populations, cluster-forming cells were partially segregatable form colony-forming cells. The observed heterogeneity was similar to the described previously in the mouse and suggests that separate subpopulations of progenitor cells may exist within each hemopoietic family that could possibly give rise to functionally different progeny.     

Clinical inertia contributes to poor diabetes control in a primary care setting

PURPOSE: The purpose of this study was to determine whether "clinical inertia"-inadequate intensification of therapy by the provider-could contribute to high A1C levels in patients with type 2 diabetes managed in a primary care site. METHODS: In a prospective observational study, management was compared in the Medical Clinic, a primary care site supervised by general internal medicine faculty, and the Diabetes Clinic, a specialty site supervised by endocrinologists. These municipal hospital clinics serve a common population that is largely African American, poor, and uninsured. RESULTS: Four hundred thirty-eight African American patients in the Medical Clinic and 2157 in the Diabetes Clinic were similar in average age, diabetes duration, body mass index, and gender, but A1C averaged 8.6% in the Medical Clinic versus 7.7% in the Diabetes Clinic (P < .0001). Use of pharmacotherapy was less intensive in the Medical Clinic (less use of insulin), and when patients had elevated glucose levels during clinic visits, therapy was less than half as likely to be advanced in the Medical Clinic compared to the Diabetes Clinic (P < .0001). Intensification rates were lower in the Medical Clinic regardless of type of therapy (P < .0001), and intensification of therapy was independently associated with improvement in A1C (P < .001). CONCLUSIONS: Medical Clinic patients had worse glycemic control, were less likely to be treated with insulin, and were less likely to have their therapy intensified if glucose levels were elevated. To improve diabetes management and glycemic control nationwide, physicians in training and generalists must learn to overcome clinical inertia, to intensify therapy when appropriate, and to use insulin when clinically indicated.     

Murine hematopoietic stem and progenitor cells: I. Enrichment and biologic characterization

Murine bone marrow cells were fractionated by fluorescence-activated cell sorting into Rh123lo Lin- c-kit+ Ly6A+, Rh123hi Lin-c-kit+ Ly6A+, and Lin- c-kit+ Ly6A- populations within which most, if not all, of the hematopoietic activities of the marrow resided. The Rh123lo Lin- c- kit+Ly6A+ cells, which consist exclusively of small- or medium-sized lymphocyte-like cells, are highly enriched for long-term hematopoietic in vivo repopulating cells. The enrichment factor for these cells from the marrow was estimated as 2,000-fold. The Rh123hi Lin- c-kit+ Ly6A+ cells, although also highly enriched for day-12 spleen colony-forming units, were relatively depleted of long-term in vivo repopulation capacity. Most, if not all Lin- c-kit+ Ly6A- cells were Rb123hi. In contrast to both Rh123lo and Rh123hi Lin- c-kit+ Ly6A+ stem cell populations, the Lin- c-kit+ Ly6A- cells can be stimulated to proliferate in vitro in the presence of single cytokines, which is a characteristic of committed progenitor cells. No marked synergistic interactions between individual cytokines were observed with this cell population. Both Rh123hi Lin- c-kit+ Ly6A+ mature stem cell and Lin- c- kit+ Ly6A- progenitor cell populations displayed in vivo repopulation kinetics resembling those of the putative short-term hematopoietic repopulating cells.     

Left atrial volume as a morphophysiologic expression of left ventricular diastolic dysfunction and relation to cardiovascular risk burden

Left ventricular (LV) diastolic dysfunction is prevalent in the community. Current assessment of diastolic function can be complex, involving Doppler evaluation of an array of hemodynamic data. The relation between left atrial (LA) volume and diastolic function, and between LA volume and cardiovascular risk and disease burden are not well known. In the present prospective study of 140 adults, mean age 58 ± 19 years, referred for a clinically-indicated echocardiogram and in sinus rhythm, with no history of atrial arrhythmias or valvular heart disease, we determined the LA volume, LV diastolic function status, cardiovascular risk score (based on age, gender, history of systemic hypertension, diabetes mellitus, hyperlipidemia, and smoking), and cardiovascular disease burden (based on confirmed vascular disease, congestive heart failure, and transient ischemic attack or stroke). LA volume was found to correlate positively with age, body surface area, cardiovascular risk score, LV end-diastolic and end-systolic dimensions, LV mass, diastolic function grade, tissue Doppler E/E′, tricuspid regurgitation velocity, and negatively with LV ejection fraction (all p <0.006). In a multivariate clinical model, LA volume indexed to body surface area (indexed LA volume) was independently associated with cardiovascular risk score (p <0.001), congestive heart failure (p = 0.014), vascular disease (p = 0.012), transient ischemic attack or stroke (p = 0.021), and history of smoking (p = 0.008). In a clinical and echocardiographic model, indexed LA volume was strongly associated with diastolic function grade (p <0.001), independent of LV ejection fraction, age, gender, and cardiovascular risk score. In patients without a history of atrial arrhythmias or valvular heart disease, LA volume expressed the severity of diastolic dysfunction and provided an index of cardiovascular risk and disease burden.     

Lipid mediators in cystic fibrosis and chronic obstructive pulmonary disease

In order to investigate the possible role of arachidonic acid metabolites as lipid mediators in cystic fibrosis and chronic obstructive pulmonary disease (COPD), sputum from patients with cystic fibrosis, chronic bronchitis, or bronchiectasis was analyzed for various eicosanoids using a combination of radioimmunoassay and bioassay. Leukotriene (LT) B4, cysteinyl-containing LTs, and prostaglandins (PGs) E2, F2 alpha, 6-oxo-PGF1 alpha, and thromboxane B2 were found in all sputum samples. Saliva, which can contaminate sputum, contained low concentrations of prostanoids but not LTs. Inflammatory cells, including polymorphonuclear leukocytes (PMNs) are present in sputum. Because LTB4 generated by these cells is chemotactic for PMNs, it is suggested that this dihydroxy acid contributes to the inflammation of cystic fibrosis and other diseases characterized by airway obstruction. The source of the cysteinyl-containing LTs is less clear; these LTs may constrict respiratory smooth muscle and/or stimulate mucus formation.