Stem cell factor retards differentiation of normal human erythroid progenitor cells while stimulating proliferation

Stem cell factor (SCF), the ligand for the c-kit tyrosine kinase receptor, markedly stimulates the accumulation of erythroid progenitor cells in vitro. We now report that SCF delays erythroid differentiation among the progeny of individual erythroid progenitors while greatly increasing the proliferation of these progeny. These effects appear to be independent of an effect on maintenance of cell viability. Highly purified day-6 erythroid colony-forming cells (ECFC), consisting mainly of colony-forming units-erythroid (CFU-E), were generated from human peripheral blood burst-forming units-erythroid (BFU-E). Addition of SCF to the ECFC in serum-free liquid culture, together with erythropoietin (EP) and insulin-like growth factor 1 (IGF-1), resulted in a marked increase in DNA synthesis, associated with a delayed peak in cellular benzidine positivity and a delayed incorporation of 59Fe into hemoglobin compared with cultures without SCF. In the presence of SCF, the number of ECFC was greatly expanded during this culture period, and total production of benzidine-positive cells plus hemoglobin synthesis were ultimately increased. To determine the effect of SCF on individual ECFC, single-cell cultures were performed in both semisolid and liquid media. These cultures demonstrated that SCF, in the presence of EP and IGF-1, acted on single cells and their descendants to delay erythroid differentiation while substantially stimulating cellular proliferation, without an enhancement of viability of the initial cells. This was also evident when the effect of SCF was determined using clones of ECFC derived from single BFU-E. Our experiments demonstrate that SCF acts on individual day-6 ECFC to retard erythroid differentiation while simultaneously providing enhanced proliferation by a process apparently independent of an effect on cell viability or programmed cell death.     

Inaccuracies associated with the automated measurement of mean cell hemoglobin concentration in dehydrated cells

Because of discrepancies between electronically and manually measured values of mean cell hemoglobin concentration (MCHC) encountered in studies of pathologic red cells, we studied the effect of cell water content on MCHC measurements by both methods. A series of red cell samples with varying water contents (54%-164% normal) were prepared from normal cells using the antibiotic nystatin. MCHC was then measured, using the microhematocrit centrifuge and three different electronic cell counters in common laboratory use. For MCHC values above 36 g/dl as measured by the spun hematocrit method, all three electronic counters under estimmated the MCHC, with increasing error as the true MCHC increased. For MCHC values below 30 g/dl, the values from two conductivity based instruments agreed with those from the spun hematocrit method, whereas one instrument based on light scattering overestimated the MCHC. These results indicate that inaccuracies in the measured mean cell volume (MCV) of dehydrated or otherwise undeformable cells may lead to spurious values for MCHC when electronic cell counters are used.     

人脂肪干细胞复合脱细胞软骨基质支架在生物反应器中构建组织工程软骨

目的:观察人脂肪干细胞复合脱细胞软骨基质支架在生物反应器中初步构建组织工程软骨的可行性。方法:实验于2005-04/2006-05在解放军总医院骨科研究所完成。脂肪组织和关节软骨均来自膝关节置换术中切除的组织,并经患者知情同意。关节软骨冻干后经粉碎机粉碎,过筛,选取25～38μm大小的软骨微粒。在样品中先加入2.5g/L胰蛋白酶,37℃消化24h,再加入1%Triton X-100震荡72h。将软骨微粒和蒸馏水按1∶3的比例混合后滴加在模板中,置入冷冻干燥机冻干后行紫外线交联。紫外线照射8h完成。最后经25kGy 60Co辐照灭菌完成支架制备。取膝关节置换术中切除的髌下脂肪垫,酶消法获得脂肪干细胞,扩增后复合于脱细胞软骨基质制成圆柱状三维支架上(细胞密度5×1010L-1),置于生物反应器中进行诱导培养,同时设静态培养组作为对照,3周后观测大体形态和组织学形态变化,同时进行组织化学(包括番红花O,阿利新蓝染色)和Ⅱ型胶原免疫组织化学分析。结果:生物反应器组诱导培养3周苏木精-伊红染色显示支架结构消失,只有中心区域残存少量支架结构;静态培养组支架结构尚存在,有少量基质分泌。番红花O染色显示生物反应器组细胞外有大量蛋白聚糖沉积,阿利新蓝染色表明有软骨特异性蛋白多糖的聚集;而静态培养组只有部分区域染色且淡于生物反应器组。Ⅰ型胶原免疫组化的结果显示,在生物反应器组细胞能够合成大量软骨细胞特异性胶原成分,而静态培养组呈弱阳性。结论:生物反应器培养明显促进了脂肪干细胞的增殖与软骨分化,是体外构建组织工程软骨的良好方法。     

Reverse LISS plating for intertrochanteric Hip Fractures in elderly patients

Background  

Fractures of the intertrochanteric hip are common and the treatment of unstable fractures generally requires an operative approach. In elderly patients, osteoporosis makes internal fixation problematic and frequently contributes to failed fixation and poor clinical results. We have attempted to apply the Less Invasive Stabilization System (LISS) in reverse position for the repair of intertrochanteric hip fractures in elderly patients with osteoporotic bones. A retrospective review is presented of the cases of 28 elderly patients with stable and unstable fractures of the intertrochanteric hip treated using the reverse LISS.     

The Malawi National Tuberculosis Programme: an equity analysis

Background  

Until 2005, the Malawi National Tuberculosis Control Programme had been implemented as a vertical programme. Working within the Sector Wide Approach (SWAp) provides a new environment and new opportunities for monitoring the equity performance of the programme. This paper synthesizes what is known on equity and TB in Malawi and highlights areas for further action and advocacy.     

The Growth Factor Midkine Antagonizes VEGF Signaling In Vitro and In Vivo

Midkine (MDK) is a heparin-binding growth factor involved in growth, survival, migration, and differentiation of various target cells and dysregulation of MDK signaling is implicated in a variety of inflammatory diseases and cancers. Although MDK has been reported to act on endothelial cells and to have proangiogenic effects, the exact role of MDK in angiogenesis is poorly defined. Here, we report that MDK is actually a modulator of angiogenesis and that it can abrogate the vascular endothelial growth factor A (VEGF-A)-induced proliferation of human microvascular endothelial cells in vitro through the downregulation of proangiogenic cytokines and through the upregulation of the antiangiogenic factor, tissue inhibitor of metalloproteinase 2. Phosphorylation of vascular endothelial growth factor receptor 2 (VEGFR-2) and of downstream signaling molecules, such as phosphatidylinositol-3-kinase and mitogen-activated protein kinases, is also impaired. Moreover, MDK downregulates VEGF-A-induced neovascularization and vascular permeability in vivo. We propose a model in which MDK is a new modulator of the VEGF-A-VEGFR-2 axis.     

Long-bone growth in fetuses with Down syndrome

Short stature is a well-recognized component of Down syndrome. The femur lengths of affected fetuses have been observed to be shorter than normal, with a ratio of actual to expected femur length of less than 0.91 indicating a high risk of trisomy. To further evaluate this finding we have determined the relationship between limb lengths and gestational age in 37 postmortem fetal specimens with trisomy 21. Control values were obtained from 174 normal fetuses. Measurements of the femur, tibia, fibula, humerus, radius, and ulna were made from roentgenograms or by direct measurement of the bone. Most measurements for each bone of the affected fetuses fell below the normal regression line for that bone, but only 3/37 femurs, 4/32 tibias, 5/32 fibulas, 9/32 humeri, 10/32 radii, and 7/32 ulnas fell more than 2 SDs below the mean. The ratios of actual to expected femur lengths were computed and six fetuses with Down syndrome (16.2%) had ratios less than 0.91. The bones of the extremities of fetuses with trisomy 21 are shorter than normal, but the differences are relatively small. The ratio of actual/expected femur lengths was a less efficient predictor of Down syndrome than were either maternal age or maternal serum alpha-fetoprotein tests. The upper extremity bones were shorter than normal more often than were the bones of the lower extremity, and this finding should be explored further in a prospective study.     

Long-term aminosalicylate therapy is under-used in patients with ulcerative colitis: a cross-sectional survey

BACKGROUND: There is evidence from case-control studies that aminosalicylate drugs can reduce colorectal cancer risk by 75-81% in patients with ulcerative colitis. Patients may fail to comply with long-term therapies, however, or may have been advised to discontinue treatment once in remission. AIM: To describe the usage of long-term aminosalicylate therapy in patients with ulcerative colitis. METHODS: A cross-sectional study was performed using data extracted from general practitioner clinical records on demographic features, extent and duration of disease, use of aminosalicylate therapy and specialist care. RESULTS: Three hundred and sixty-three people had ulcerative colitis and no history of colorectal surgery. Ninety-five of 175 (54%) patients with proctitis, 78 of 123 (63%) patients with left-sided colitis and 28 of 45 (62%) patients with extensive colitis were currently taking an aminosalicylate drug. Those doing so were more likely to be under specialist care than to be definitely or possibly discharged (odds ratio, 4.9; 95% confidence interval, 2.9-8.4). The likelihood of current aminosalicylate therapy was not related to gender or the extent of disease, but was negatively related to the duration of disease. CONCLUSIONS: A substantial minority of patients with ulcerative colitis does not take long-term aminosalicylate therapy. Those who do are more likely to be under specialist care, to be older or to have disease of shorter duration.     

Relation of bronchial responsiveness to body mass index in the ECRHS. European Community Respiratory Health Survey

BACKGROUND: There is substantial evidence for an association between symptoms of asthma and overweight or obesity. However, a study that reported no association between bronchial responsiveness (BHR) and body mass index (BMI) suggested that the relation of symptoms to obesity was due to increased diagnosis of asthma. The relation of BHR to BMI was therefore investigated in a large multicentre study. METHODS: Data were obtained for 11,277 participants in stage II of the European Community Respiratory Health Survey (ECRHS). BHR to methacholine was analysed in relation to BMI adjusted for a number of factors known to be associated with BHR, including baseline lung function and allergen sensitisation, and combined across 34 centres using random effects meta-analysis. RESULTS: BHR increased with increasing BMI in men (ECRHS slope changed by -0.027 for each unit increase in BMI, 95% confidence interval -0.044 to -0.010, p=0.002), but the relation in women was weak (-0.014, 95% CI -0.033 to 0.005, p=0.14). There was no evidence for an interaction of sex with BMI (p=0.41). CONCLUSIONS: BHR is related to BMI in the ECRHS. This suggests that the association is not due to greater diagnosis or perception of symptoms in obese people compared with those of normal weight. The data do not support the finding by some studies of a relation between asthma and obesity in women but not in men.     

Ultrasound and magnetic resonance imaging assessmentof active bowel segments in Crohn's disease

AIM: Determining bowel disease activity in Crohn's patients can be difficult on clinical and laboratory assessment. Endoscopy is invasive and barium studies use ionising radiation. The aim of this study was to compare ultrasound and magnetic resonance imaging (MRI) in detecting Crohn's disease activity in the small or large bowel. MATERIALS AND METHODS: Thirty patients, previously diagnosed with Crohn's disease, had bowel ultrasound and MR imaging, and were deemed active or inactive on each test. The 'gold standard' was based on clinical assessment and one or more of the following: endoscopy, barium studies or surgery. RESULTS: For determining Crohn's disease activity, the sensitivities and specificities of bowel ultrasound and MRI were 87 percent and 100 percent, and 87 percent and 71 percent, respectively. Significant parameters that defined disease activity were bowel wall thickening on ultrasound and MRI, and contrast enhancement of the bowel wall and mesenteric vascularity/stranding on MRI. CONCLUSION: Ultrasound and MRI were both sensitive for determining Crohn's disease activity in the bowel, but MRI with gadolinium enhancement was less specific.