Studies on thymocyte subpopulations in guinea pigs. VI. Differentiation of precursor cells in vivo and in vitro

The relation between six subpopulations of guinea pig thymocytes, separated on the basis of PNA binding and buoyant density, was studied. Incubation in vitro of either unseparated thymocytes or isolated large, low density cells, caused a shift towards smaller cells with high buoyant density. In order to determine whether these changes reflect a normal differentiation we pulsed labelled thymocytes with 3H-Thymidine and traced the labelling in the separate subpopulations after different intervals by autoradiography. Both in vivo and in vitro, the thymidine was initially incorporated mainly into PNA+ cells (85% of all labelled cells), particularly into PNA+ low-density cells (called PNA+Ia), which constitute 14% of all thymus cells (1). Correlation with autoradiographic sections of the thymus indicated that these cells were mainly located in the subcapsular and juxtamedullary cortex. At 24 h after labelling in vivo, more than 95% of the labelled cells were smaller, high density cells, both PNA+ and PNA-. At this time, labelled cells were present throughout the thymus with no preferential localization. Labelling and incubation in vitro were accompanied by similar changes after a 24-h time period when cells were cultured in the presence of serum. We conclude that the labelled PNA+Ia cells represent precursor cells, located in the subcapsular and juxtamedullary parts of the cortex. Within 24 h these cells differentiate into high density cells, some of which are PNA-. The corresponding results obtained in vitro indicate that these differentiation steps may also occur in the absence of a thymic microenvironment, and the study of histological sections indicate that these steps were not associated with any major relocalization within the thymus.     

ED chest radiography for children with asthma exacerbation is infrequently associated with change of management

Background

Acute asthma exacerbations (AAE) account for many Pediatric Emergency Department (PED) visits. Chest radiography (CXR) is often performed in these patients to identify practice-changing findings such as pneumonia (PNA). Limited knowledge exists to balance the cost and radiation dose of CXR with expected yield of clinically meaningful information.

Antigenic properties of Schistosoma mansoni aminopeptidases: Evolution during the development in mammalian hosts

The involvement in the immunity to schistosomiasis of an aminopeptidase activity of schistosomula, 20-day-old and adult worms of Schistosoma mansoni has been studied. This activity, hydrolysing leucine-p-nitroanilide and alanine-p-nitroanilide at pH 7.4 was immunoprecipitated by various infected rat and human sera. These antigenic enzymes were expressed at day 28 after infection in the rat and seemed to be specific for the Schistosoma species. Several aminopeptidase activities were found after analysis by isoelectric focusing of the adult extract but only the pI 8.3 peak was antigenic. Three antigenic peaks were demonstrated after AcA 34 Ultrogel filtration. The biological relevance of these antigenic enzymes in schistosomiasis is discussed.     

The thymus in "bare lymphocyte" syndrome: significance of expression of major histocompatibility complex antigens on thymic epithelial cells in intrathymic T-cell maturation

Thymic biopsies from two patients with combined immunodeficiency and defective expression of HLA class I and class II antigens on blood mononuclear cells ("bare lymphocyte" syndrome) were investigated. This made possible an evaluation of the significance of HLA antigen expression in a detailed (immuno)histologic study. Both thymuses showed a normal lobular architecture with distinct cortex-medulla areas, well-differentiated epithelium, including ultrastructurally defined subtypes, and Hassall's corpuscles. Normal numbers of lymphoid cells were present and normal T-cell phenotype was found. Using anti-HLA-A,B,C antisera, confluent staining of the medulla (stroma and lymphocytes) was observed. One of the thymuses was found to be negative for HLA class II antigen expression: the other revealed only HLA-DR positivity of nonlymphoid cells in the medulla. These cells were not of epithelial nature as judged from double staining with anti-keratin antibody. There was no expression of HLA-DC/DS. These observations differ from findings in the normal thymus, wherein epithelial cells in the cortex carry HLA class I and class II antigens, and epithelial cells in the medulla express HLA class I, and for a minor part class II antigens. The results indicate a normal sequential acquisition of T-cell differentiation antigens in the thymus of both cases. It is suggested that the expression of HLA class I and class II antigens on epithelial cells in the normal thymus cortex does not play a significant role in the sequential acquisition of differentiation antigens on T lymphocytes.     

PMA及PNA在预测2型糖尿病并发肾病变中的实用价值

目的探讨血小板-中性粒细胞聚集体(PNA)、血小板-单核细胞聚集体(PMA)检测在预测2型糖尿病并发症中的实用价值。方法应用流式细胞仪检测2型糖尿病并发肾病变患者血浆的PMA、PNA,并以无并发症的2型糖尿病患者和健康人作为对照,比较上述三组PMA、PNA的水平,用ROC曲线评价此试验的临床应用价值。结果 2型糖尿病并发肾病变组PMA、PNA水平显著高于无并发症组,而后者又显著高于健康对照。ROC曲线显示,PMA对2型糖尿病患者并发肾病变诊断临界值灵敏度为96.7%,特异性为100.0%,截断点为40.12%;PNA灵敏度为96.7%,特异性为88.3%,截断点为26.98%,可见PMA优于PNA。曲线下面积分别为0.986和0.963。结论 PMA、PNA可以预测2型糖尿病肾病变,应用流式细胞法检测其灵敏度和特异性均较满意,PMA特异性优于PNA。     

Expression of lectin-specific cellular glycoconjugates during oral carcinogenesis

The binding pattern of two lectins, concanavalin A (ConA) and peanut agglutin (PNA), in various phases of tumour progression in the oral epithelium was studied. These included non-dysplastic, dysplastic and neoplastic lesions as well as normal tissue. ConA and PNA showed intense staining in the basement membrane of all types of lesions. Little difference was observed in the staining patterns between different stages of oral carcinogenesis, either with ConA or PNA. ConA showed mild cytoplasmic and membrane staining in all types of lesions while PNA showed moderate to intense staining in both the cytoplasm and membrane of lower-layer cells in all histological groups. The present study therefore shows that these lectins have limited value in the elucidation of oral carcinogenesis and are of insignificant diagnostic value.Abbreviations ConA concanavalin A - PNA peanut agglutinin S. Kannan was supported by a research fellowship from the Council for Scientific and Industrial Research, India.