In vivo release and turnover of secreted platelet antiheparin proteins in rhesus monkey (Macaca mulatta)

Human and rhesus monkey platelets secrete at least two antiheparin proteins: platelet factor 4 (PF4) and low affinity platelet factor 4 (LA-PF4). Neither of these proteins showed species-related antigenic differences. As determined by radioimmunoassay, the levels of PF4 and LA-PF4 antigen per 10(9) monkey platelets amounted to 10.7 and 20.3 microgram, respectively. One milliliter of monkey plasma prepared from blood collected into an anticoagulant composed of EDTA, prostaglandin E1, and theophylline solution contained 22.4 ng LA-PF4 and 8.0 ng PF4. Concentrations of these two platelet-specific proteins in monkeys closely resembled levels found in human platelets and plasma. Infusion of prostacyclin (PGI2) (100 or 300 ng/kg/min) into monkeys for 15 min resulted in a significant decrease of plasma levels of LA-PF4 antigen and of PF4 by 40%--60% (p < 0.0001). This decrease was related to the inhibitory effect of PGI2 on the secretion of platelets stimulated by a catheter or by venipuncture. Longer infusion of PGI2 did not produce further significant change. The supernate obtained after aggregation of human platelets stimulated by thrombin was injected into monkeys receiving PGI2 infusion. The disappearance of LA-PF4 antigen in monkey plasma followed a biphasic exponential curve with half-lives for the fast and slow components of 8.4 and 63 min. PF4 disappeared faster but followed the same pattern (half-lives for the fast and slow component of 2.1 and 70 min). Analysis of the experimental data suggests that the low levels of secreted platelet proteins in monkey plasma are related to their minimal in vivo release and to their rapid clearance.     

Prediction of response to antiretroviral therapy by human experts and by the EuResist data‐driven expert system (the EVE study)

Objectives

The EuResist expert system is a novel data‐driven online system for computing the probability of 8‐week success for any given pair of HIV‐1 genotype and combination antiretroviral therapy regimen plus optional patient information. The objective of this study was to compare the EuResist system vs. human experts (EVE) for the ability to predict response to treatment.

Methods

The EuResist system was compared with 10 HIV‐1 drug resistance experts for the ability to predict 8‐week response to 25 treatment cases derived from the EuResist database validation data set. All current and past patient data were made available to simulate clinical practice. The experts were asked to provide a qualitative and quantitative estimate of the probability of treatment success.

Results

There were 15 treatment successes and 10 treatment failures. In the classification task, the number of mislabelled cases was six for EuResist and 6–13 for the human experts [mean±standard deviation (SD) 9.1±1.9]. The accuracy of EuResist was higher than the average for the experts (0.76 vs. 0.64, respectively). The quantitative estimates computed by EuResist were significantly correlated (Pearson r=0.695, P<0.0001) with the mean quantitative estimates provided by the experts. However, the agreement among experts was only moderate (for the classification task, inter‐rater κ=0.355; for the quantitative estimation, mean±SD coefficient of variation=55.9±22.4%).

Conclusions

With this limited data set, the EuResist engine performed comparably to or better than human experts. The system warrants further investigation as a treatment‐decision support tool in clinical practice.     

Factors influencing the acceleration of human factor XIa inactivation by antithrombin III

Controversy exists in the literature concerning the potentiating effect of heparin on the inactivation rate of factor XIa by antithrombin III (AT III) in both purified systems and in plasma. We have analyzed the factors that could influence this reaction and found that ionic strength of the medium, as well as the type and concentration of the heparin preparations accounted for the major discrepancies in the literature. At I = 0.43 N, a preparation of bovine lung heparin at 1 U/mL did not augment the inactivation rate of factor XIa by inhibitors in plasma or by purified AT III. However, when ionic strength was decreased, a progressive increase in the potentiating effect was observed, reaching 6.5-fold at I = 0.15 N. At saturating concentrations of heparin, which results in the formation of 100% AT III-heparin complex, (greater than ten-fold molar excess over AT III) in purified systems, all heparin preparations (porcine, bovine, low molecular weight [LMW], and high affinity) yielded an approximately 30-fold augmentation of the factor XIa inactivation rate. However, when heparin was less than saturating, we observed that various heparin preparations affected the AT III-induced inactivation of factor XIa to different degrees even though they exhibited the same inhibitory activity (1 U/mL) against thrombin. This variation resulted from differences in the number of AT III binding sites in each heparin preparation, despite a similar Kd for each. Addition of high molecular weight kininogen (HK) to AT III-heparin complexes did not enhance their ability to inhibit factor XIa, and high concentrations of HK decreased the inactivation rate. A high therapeutic dose of heparin only permits the formation of 2.5% to 16.5% of the AT III-heparin complexes that can be achieved at saturation. We observed that 1 U/mL heparin (bovine lung heparin) (high therapeutic concentration) in virtually undiluted plasma only accelerated the inactivation rate of factor XIa (in the absence of other active enzymes) less than two-fold. These new observations further support our previous conclusion that therapeutic levels of heparin have little to no influence on the inactivation rate of factor XIa in plasma.     

胚胎嗅鞘细胞移植治疗脑性瘫痪：4例术后4周结果报告

目的:观察胚胎嗅鞘细胞移植治疗脑性瘫痪的有效性和安全性。方法:①病例资料:4例因出生时缺血缺氧确诊为脑性瘫痪的患者,男2例,女2例,年龄分别为14岁、岁、个月、岁。嗅92817鞘细胞由北京市虹天济神经科学研究院细胞中心提供,实验经医学伦理委员会批准,4例脑性瘫痪患者均签署知情同意书。②实验方法:根据术前MRI或CT片,患者均在局麻下行微创立体定向嗅鞘细胞移植术,选取双额放射冠为注射靶点,每侧注射1.0×106个细胞。术后给予止血、抗感染、康复等常规处理。③实验评估:分别于嗅鞘细胞移植前、移植后4周采用脑瘫综合功能评定量表、脑瘫日常生活能力量表评价患者神经功能及生活质量的改善。结果:①嗅鞘细胞移植术后4周,4例患者较术前均有不同程度的神经功能改善,未出现手术并发症。②脑瘫综合功能评定总分:病例1由92.5分增至94分,病例2由55分增至56分,病例3由10.5分增至11.5分,病例4由9.5分增至13分。③脑性瘫痪日常生活能力量表总分:病例1由82.0分增至83.5分,病例2无变化,为16.5分,病例3由5.0分增至7.5分,病例4由5.0分增至8分。结论:嗅鞘细胞移植治疗脑性瘫痪患者近期评价安全可行,可部分改善神经功能与生活质量,长期效果有待进一步随访。     

Interleukin-3 treatment of rhesus monkeys leads to increased production of histamine-releasing cells that express interleukin-3 receptors at high levels

To understand the hematopoietic and nonhematopoietic responses to interleukin-3 (IL-3), expression of cell-surface IL-3 receptors (IL-3R) was examined on bone marrow (BM) cells and peripheral blood (PB) cells of rhesus monkeys during the course of in vivo IL-3 treatment. Whereas IL-3R expression is low in untreated monkeys, IL-3 administration led to a gradual increase in both low- and high-affinity binding sites for IL-3. This increase reflected the total number of cells expressing IL- 3Rs, as detected by flow cytometry using biotinylated IL-3. Most of these IL-3R+ cells in both BM and PB could be characterized as basophilic granulocytes that contained high levels of histamine. In contrast to the effect on these differentiated cells, IL-3 administration did not significantly alter the low level IL-3R expression on immature, CD34+ cells. Further flow cytometric analysis using biotinylated growth factors showed that the IL-3R+ basophils also expressed receptors for granulocyte-macrophage colony-stimulating factor (GM-CSF), but not for IL-6 or Kit ligand. These findings indicated that the IL-3R+ cells included neither monocytes, which express GM-CSFRs and IL-6Rs abundantly, nor mast cells, which express c- kit. By combining flow cytometric and Scatchard data, it was calculated that the basophils contain as many as 1 to 2 x 10(3) high-affinity IL- 3Rs and 15 to 30 x 10(3) low-affinity sites. The finding that in vivo IL-3 treatment leads to the production of large numbers of cells that express high levels of IL-3R and are capable of producing histamine provides an explanation for the often severe allergic reactions that occur during prolonged IL-3 administration. It also indicates that IL- 3, in addition to its direct effects on hematopoietic cells, may also stimulate hematopoiesis through the release of secondary mediators such as histamine by IL-3-responsive mature cells.     

Toxic epidermal necrolysis; 15 years'' experience in a Dutch burns centre

BACKGROUND: Toxic epidermal necrolysis (TEN) is a severe and potentially fatal drug reaction characterized by an extensive skin rash with blisters and exfoliation, frequently accompanied by mucositis. The wounds caused by TEN are similar to second-degree burns and severe cases may involve large areas of skin loss. OBJECTIVES: Analysis of our results in patients with TEN and evaluation of the variety of therapeutic interventions that has been studied and suggested in TEN. PATIENTS/METHODS: Retrospective analysis of 19 consecutive patients with TEN treated in our burns centre between 1989 and 2004. RESULTS: Immediate withdrawal of any potentially fatal drug, maximum supportive care, and a restricted and tailored antibiotic, medical and surgical treatment regimen confined mortality to 21%, whereas prognosis scores like APACHE II and SCORTEN predicted mortality of 22 and 30%, respectively. A positive contribution of selective digestive decontamination is suggested but has yet to be established. CONCLUSIONS: Because of a potentially fatal outcome, fast referral of a patient suspected of TEN to a specialized centre (mostly a burns unit or specialized dermatology centre) for expert wound management and tailored comprehensive care is strongly advised and contributes to survival.     

Comment on ‘Predicting recurrence in axillary node negative breast cancer patients’, by Rosner and Lane

on behalf of the Nottingham Breast Unit