Dimer packings with gaps and electrostatics

Fisher and Stephenson conjectured in 1963 that the correlation function (defined by dimer packings) of two unit holes on the square lattice is rotationally invariant in the limit of large separation between the holes. We consider the same problem on the hexagonal lattice, extend it to an arbitrary finite collection of holes, and present an explicit conjectural answer. In recent work we managed to prove this conjecture in two fairly general cases. The quantity giving the answer can be regarded as the exponential of the negative of the two-dimensional electrostatic energy of a system of charges naturally associated with the holes. We further develop this analogy to electrostatics by presenting two different natural ways to define a field in our setup, and showing that both lead to the electric field, in the limit of large separations between the holes. For one of the fields, this is also stated as a limit shape theorem for random surfaces, with the continuum limit being a sum of helicoids. We conclude by explaining the relationship of our results to previous results in the physics literature on spin correlations in the Ising model.     

肾病综合征患者D-二聚体的检测

目的 探讨肾病综合征患者D-二聚体的检测及临床意义.方法 将笔者所在医院2009年2～6月收治的32例肾病综合征患者的D-二聚体检测资料作为观察组,同期健康者的D-二聚体检测资料作为对照组,对两组进行比较分析.结果 肾病综合征患者的D-二聚体水平明显高于对照组,随着尿蛋白量的增加而增加.结论 D-二聚体检测可以反映肾病综合征患者体内的血凝状态,有利于预防深静脉血栓等并发症的发生.     

Preparation and activity of nitrated insulin dimer

Nitration of insulin using tetranitromethane causes polymerisation involving cross-linked tyrosyl residues. By performing this reaction with insulin crystals, in which it is known that B16 tyrosine of one monomer is closely associated with B26 of the neighbouring monomer within the dimer, it has been possible to isolate a covalent dimer of insulin cross-linked between these two tyrosines. It was, however, first necessary to block the reactive A14 tyrosine. Both rhombo-hedral (hexameric) and cubic (dimeric) pig insulin crystals were used, the latter proving successful in yielding a pure dimeric product as shown by oxidative sulphitolysis and HPLC. The purified nitrated dimer was biologically active (ca. 10% potency compared to monomeric insulin in a lipogenesis assay) suggesting that the residues responsible for insulin's action are present on the surface of the dimer and not buried in the interface.     

Non-invasive diagnostic work-up of patients with clinically suspected pulmonary embolism; results of a management study.

BACKGROUND: Clinicians often deviate from the recommended algorithm for the diagnosis of pulmonary embolism consisting of ventilation-perfusion scintigraphy and pulmonary angiography. OBJECTIVES: To assess the safety and feasibility of a diagnostic algorithm which reduces the need for lung scintigraphy and avoids the use of angiography. PATIENTS AND METHODS: Consecutive patients with a clinical suspicion of pulmonary embolism were prospectively investigated according to an algorithm in which the diagnosis of pulmonary embolism was excluded after a low clinical probability estimate and a normal d-dimer test result, a normal perfusion scintigraphy result, or a non-high probability scintigraphy result in combination with normal serial ultrasonography of the legs. In these patients anticoagulant treatment was withheld and they were followed up for 3 months to record possible thromboembolic events. During the study period, 923 consecutive patients were seen, of whom 292 were excluded because of predefined criteria. RESULTS: Of the 631 included patients, the diagnosis was refuted on the basis of a low clinical probability estimate and a normal d-dimer test result (95 patients), normal perfusion scintigraphy (161 patients) and non-high probability lung scintigraphy followed by normal serial ultrasonography (210 patients). Of these 466 patients, venous thromboembolic complications during follow-up occurred in six (complication rate 1.3%, 95% confidence interval 0.5, 2.8). The diagnostic protocol was completed in 92% of all included patients. CONCLUSION: The diagnosis of pulmonary embolism can be safely ruled out by a non-invasive algorithm consisting of d-dimer testing combined with a clinical probability estimate, lung scintigraphy, or serial ultrasonography of the legs (in case of non-diagnostic lung scintigraphy).     

Coagulation and inflammation biomarkers may help predict the severity of community‐acquired pneumonia

Background and objective: There are limited data on the relationship between the severity of community‐acquired pneumonia (CAP) and biomarkers of inflammation and coagulation. The aim of this study was to evaluate the association between the severity of CAP and serum levels of antithrombin III (AT‐III), protein C (P‐C), D‐dimers (D‐D) and CRP, at hospital admission. Methods: This was a prospective observational study in 77 adults (62.3% men), who were hospitalized for CAP. The severity of CAP was assessed using the confusion, uraemia, respiratory rate ≥30 breaths/min, low blood pressure, age ≥65 years (CURB‐65) score. Results: Forty patients (52%) had severe CAP (CURB‐65 score 3–5). Serum levels of AT‐III were lower and levels of D‐D and CRP were higher in patients with severe CAP than in patients with mild CAP (CURB‐65 score 0–2) (P < 0.001 for all comparisons). Levels of P‐C were lower in patients with severe CAP compared with those with mild CAP, but the difference was not significant (P = 0.459). At a cut‐off point of 85%, AT‐III showed a sensitivity of 80% and a specificity of 75%, as a determinant of the need for hospitalization. At a cut‐off point of 600 ng/mL, D‐D showed a sensitivity of 90% and a specificity of 75% and at a cut‐off point of 110 mg/L, CRP showed a sensitivity of 83% and a specificity of 79%, as determinants of the need for hospitalization. Conclusions: Serum levels of AT‐III, D‐D and CRP at admission appear to be useful biomarkers for assessing the severity of CAP.     

Pumping ions

1. This is a concise review of the field of ion pumping from the perspective of the authors. 2. The period covered spans the discovery of Na(+) and K(+) concentration gradients across animal cell membranes by Carl Schmidt in the 1850s, through the isolation of the Na(+) /K(+) -ATPase by Skou in 1957 (for which he was awarded the 1997 Nobel Prize in Chemistry), to the publication of the first crystal structure of the enzyme in 2007 and beyond. 3. Contributions of the authors' research group to the resolution of the questions of the mechanism of the allosteric role of ATP within the Na(+) /K(+) -ATPase reaction cycle and how protomeric versus diprotomeric states of the enzyme influence its kinetics are discussed within the context of the research field. 4. The results obtained indicate that the Na(+) /K(+) -ATPase has a single ATP binding site, which can be catalytic or allosteric in different parts of the enzyme's reaction cycle. 5. The long-running controversy over whether P-type ATPases function as protomers or diprotomers can be resolved in the case of the Na(+) /K(+) -ATPase by an ATP-induced dissociation of (αβ)(2) diprotomers into separate αβ protomers. 6. Kinetic data suggest that protein-protein interactions between the two αβ protomers within an (αβ)(2) diprotomer result in a much lower enzymatic turnover (i.e. a lower gear) when only one of the α-subunits of the diprotomer has bound ATP. The inactive αβ protomer within the diprotomer can be thought of as causing a drag on the active protomer.     

58例川崎病患儿出凝血四项和D-二聚体的检测及分析

目的探讨川崎病(KD)患儿治疗前后出凝血四项和D-二聚体的变化及其与冠状动脉损伤的关系。方法测定58例KD患儿出凝血四项,包括凝血酶原时间(PT)、部分凝血酶原活化时间(APTT)、凝血时间(TT)、纤维蛋白原定量(FIB)和D-二聚体(D-D),以及血小板计数(PLT),根据心脏彩超结果分为非冠状动脉损伤组(nCAL)和冠状动脉损伤组(CAL),并进行分析与评价。结果两组患儿治疗前PLT、FIB、D-D均高于正常,冠状动脉损伤组增高更明显,两组比较差异有统计学意义,治疗一周后PLT仍处于上升期,而FIB、D-D均较治疗前有所下降,但冠状动脉损伤组仍高于非冠状动脉损伤组,两组比较差异有统计学意义。结论 FIB、D-D是判断川崎病血液高凝状态及疗效的敏感指标。     

外伤性颅内血肿急性期血浆D-二聚体检测的临床价值

目的探讨外伤性颅内血肿急性期血浆D-二聚体(D-dimer)水平的动态变化与外伤性颅内血肿部位,治疗后转归的关系。方法采用透射免疫比浊法检测72例外伤性颅内血肿患者血浆D-dimer含量,并与62例高血压性脑出血患者和40例正常对照进行比较。结果外伤性颅内血肿患者血浆D-dimer致病后6 h、1周及2周血浆D-dimer水平显著升高,与高血压性脑出血患者组和正常对照组比较有显著牲差异(P<0.01),并以致病后6 h为最。同时,转归不良组血浆D-dimer水平显著升高,与转归良组比较有显著性差异(P<0.01)。结论外伤性颅内血肿急性期血浆D-dimer水平显著升高,揭示可能在该病急性期存在短暂的、纤溶活性增强的趋势。检测血浆D-dimer动态水平有助于判断抗纤溶治疗的效果及预测病情变化,并且血浆D-dimer水平的高低与出血部位、病人的转归密切相关。