The factor V B-domain provides two functions to facilitate thrombin cleavage and release of the light chain

Blood coagulation factors V and VIII are homologous proteins that have the domain organization A1-A2-B-A3-C1-C2. Upon thrombin activation, the B-domains of both molecules are released. Previous studies on factor VIII showed that the B-domain was not required for thrombin cleavage or activity. In contrast, deletion of the factor V B-domain (residues 709 to 1545) yielded a molecule with sevenfold reduced procoagulant activity that was not cleaved by thrombin. However, this factor V B- domain deletion molecule was activated by factor Xa, although the fold- activation was 85% that of wild-type factor V. Thrombin cleavage of factor V occurs initially after residue 709 and subsequently after residues 1018 and 1545. The requirement for thrombin cleavage within the B-domain at residue 1018 was evaluated by mutagenesis of Arg1018 to Ile. In the resultant R1018I mutant, the rate of thrombin activation and appearance of maximal cofactor activity was delayed and was consistent with delayed cleavage of the light chain at residue 1545. In contrast, the rate of factor Xa activation in the R1018I mutant was not altered. This finding suggests that thrombin cleavage at 1018 facilitates subsequent thrombin cleavage at 1545. Further mutagenesis was used to study the requirement for sequences within the factor V B- domain for thrombin cleavage at residue 1545. Whereas the factor V deletion molecule removing residues 709 to 1545 was not cleaved by thrombin, a smaller B-domain deletion molecule (residues 709 to 1476) containing an acidic amino acid-rich region (residues 1490 to 1520) was effectively cleaved by thrombin. These results show that residues 1476 to 1545, which contain an acidic amino acid-rich region, were required for thrombin cleavage of the light chain. Introduction of an acidic amino acid-rich region from factor VIII (residues 337 to 372) into the factor V 709 to 1545 deletion also restored thrombin cleavage of the light chain. In contrast, similar replacement with the acidic region from the factor VIII light chain (residues 1649 to 1689) was significantly less effective in promoting thrombin cleavage of the light chain. This finding suggests that the different acidic regions in factors V and VIII are not functionally equivalent in their interaction with thrombin.(ABSTRACT TRUNCATED AT 400 WORDS)     

Vasodilator agents and supracollicular transection fail to inhibit cortical spreading depression in the cat

It remains an open question as to whether cortical spreading depression (CSD) is the pathophysiological correlate of the neurological symptoms in migraine with aura. In the experimental animal, CSD is an electrophysiological phenomenon mainly mediated via NMDA receptors. However, according to case reports in humans, visual aura in migraine can be alleviated by vasodilator substances, such as amyl nitrite and isoprenaline. There is also circumstantial evidence that brainstem nuclei (dorsal raphe nucleus and locus coeruleus) may play a pivotal role in the initiation of aura. In this study, CSD was elicited in alpha-chloralose anesthetized cats by cortical needle stab injury and monitored by means of laser Doppler flowmetry. Topical application of isoprenaline (0.1-1%) and amyl nitrite (0.05%) onto the exposed cortex had no effect on the elicitation or propagation of CSD. Also, after supracollicular transection, subsequent CSDs showed no differences in the speed of propagation and associated flow changes. We conclude from these data that--given CSD probably exists in humans during migraine--spreading neurological deficits during migraine aura are independent of brainstem influence and have a primarily neuronal rather than vascular mechanism of generation.     

铁皮石斛试管苗快速繁殖的研究

兰科植物铁皮石斛(Dendrobium candidum Wall.ex Lind1.)的茎为常用名贵中药。多年来,主要依靠采收野生品种供药用和出口,致使野生资源枯竭,现已成为日益稀少的濒危植物。兰属种子和石斛属种子试管繁殖已积累不少资料,但是有关铁皮石斛种子试管繁殖的研究只有少量简单的报道,对其种子在试管繁殖过程中,所需外界条件的研究也不够     

荧光原位杂交技术分析人结肠菌群方法研究

建立荧光原位杂交技术分析人体内结肠菌群的方法。取受试者新鲜粪便 ,选用 5种特异性的 16SrRNA寡核苷酸探针 ,检测粪便样本收集后的保存时间、温度 ,离心条件及样本固定液存放时间对杂交计数结果的影响。结果建立最佳实验条件为 :粪便样本收集后应尽快在 4℃下保存 ,放置时间不要超过 12小时即作处理 ;样本的适宜离心条件为 70 0g 2分钟 ;样本用多聚甲醛固定后在 - 80℃下存放时间不要超过 5个月。该方法具有较好的稳定性 ,可以有效地检出个体之间结肠菌群的差异。     

The inter‐rater reliability between nurse‐assessors clinically assessing infection of chronic wounds using the WUWHS criteria

The aim of this study was to determine the inter‐rater reliability between one expert‐nurse and four clinical‐nurses who were asked to clinically assess infection of chronic wounds by using the World Union of Wound Healing Societies (WUWHS) criteria. A quasi‐experimental design was used to collect the data. In comparison to phase 1 in which ‘open questions’ were asked, in phase 2 a pre‐printed form (checklist) was introduced. In both phases, 55 chronic wounds were clinically assessed. For each WUWHS criterion the inter‐rater reliability of signs and symptoms was expressed by Cohens Kappa (κ). A substantial agreement (κ ≥ 0·6) was considered as adequate. In both phases pocketing (p < 0·02), and erythema (p < 0·004) scored statistically significant results. Phase 2 showed higher inter‐rater agreements compared with phase 1 (three substantial agreements (easily bleeding/friable granulation tissue, delayed healing, increasing exudate), an almost perfect‐ and a perfect agreement for malodour and pain, respectively. According to the results it can be concluded that the clinical assessment of infection of chronic wounds may be better supported by a pre‐printed form than making use of an ‘open questions’ form. To provide this with a higher level of evidence, there is need for more well conducted studies.     

Are quality of family life and disease severity related in childhood atopic dermatitis?

BACKGROUND: Atopic dermatitis (AD) can be traumatizing to family life. Little is known about the relationship between quality of life in AD and disease severity. OBJECTIVE: To document family quality of life and relate this to severity of AD in children, for a 6-month period from a given point in time. STUDY DESIGN: These data are part of a longitudinal study conducted in two parts of the UK to investigate risk factors for AD severity and its impact on quality of life. SUBJECTS: and methods Thetargetedpopulation comprised children with AD aged 5-10 years in a primary-care setting. The general practitioners identified potential subjects and the UK diagnostic criteria for AD were used to verify the diagnosis. Both the children and their parents were interviewed. Eczema severity was assessed using a modified form of the SCORAD (SCORe Atopic Dermatitis) Index (SCORAD-D) from which parents' score of itching and sleep loss were excluded. The quality of family life was quantified by the Dermatitis Family Impact (DFI) questionnaire. These two parameters were evaluated on two occasions 6 months apart. ANALYSIS: Multiple regression analysis was used to investigate the relationship between the quality of family life and the severity of the AD in the children, at a specific point in time and over the following 6-month period. RESULTS: Of the 116 children attending the first visit, mean age 8 years, 106 attended the second visit (91%) and were included in the analysis. Quality of family life was shown to be significantly affected in 48 (45%) cases at the first visit and 38 (36%) cases at the second visit. The initial means of the DFI and SCORAD-D were 2.4 and 8.2, respectively. Six months later the mean final DFI and SCORAD-D were 1.9 and 7.7, respectively. Using multiple regression on the first and second visits, each unit increase in SCORAD-D was associated with 0.21 [95% confidence interval (CI) 0.06-0.37 P = 0.008] and 0.37 (95% CI 0.15-0.59, P = 0.001) units increase in quality of family life, respectively. This relationship remained significant even after adjustment for potential confounders (black skin, social class, sex, child's age, family size and location) each unit increase in SCORAD-D led to a 0.25 unit (95% CI 0.11-0.4, P = 0.001) and 0.23 unit (95% CI 0.05-0.42, P = 0.014) increase in DFI on the first and second visits, respectively. Changes in the DFI scores were significantly related to changes in the SCORAD-D scores (regression coefficient; 0.17 (95% CI 0.06-0.29, P = 0.002). CONCLUSIONS: We show that quality of family life is related to the severity of AD in children. This confirms the importance of parental assessment of the impact of the disease in the management of AD, because the disease affects the entire family. Also, these results show the response of DFI to change predictably with disease severity. This may imply that the DFI questionnaire could be used as an extra measure of outcome in everyday clinical practice as well as in research studies.