Covalent crosslinking of myosin subfragment-1 and heavy meromyosin to actin at various molar ratios: Different correlations between ATPase activity and crosslinking extent

Summary This paper describes a systematic study of crosslinking of skeletal muscle myosin subfragment-1 (S1) and heavy meromyosin (HMM) to F-actin in the rigor state with 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide (EDC). We followed the time courses of S1 or HMM head crosslinking at various actin:S1 or actin:HMM head molar ratios and the resulting superactivation of ATPase activity. The ATPase activity of the covalent complexes was measured at 0.5 M KCl, where the covalent complexes retain superactivated ATPase activity but the activity of uncrosslinked myosin heads is not activated by actin. S1 crosslinking was slowest at the actin:S1 molar ratio of 11, but faster at larger molar ratios, where more than 80% of added S1 could be crosslinked to actin. In spite of the dependence of crosslinking rate on actinS1 ratio, there were two linear correlations between ATPase activity and the extent of S1 crosslinking to actin: one for S1 crosslinked to actin at actinS1 molar ratios more than 2.71 and the other for S1 crosslinked at a molar ratio of 11. Extrapolation of the former correlation line to 100% crosslinked S1 gave an ATPase activity of 39 s^–1 for actin-S1 covalent complex at 25 °C, whereas that of the other correlation line gave 21 s^–1. The latter smaller activity suggests that the interface between actin and S1 in their rigor complexes at a molar ratio of 11 is different from that at molar ratios of more than 2.71. The acto-HMM crosslinking rate depended on the ratio of actin to HMM head, like that of S1 crosslinking to actin. The ATPase activity of crosslinked actin-HMM was, unlike that of actin-S1 covalent complexes, bell-shaped as a function of the crosslinked heads, but chymotryptic conversion of HMM to S1 in the covalent complexes made the bell-shaped characteristics disappear and increased the activity close to that of actin-Sl covalent complexes. These results indicate that some physical constraint imposed on myosin heads suppresses the actin-activated ATPase activity of HMM crosslinked to actin.     

Effect of impression holding time and tray removal speed on the dimensional accuracy of impressions for artificial abutment tooth inclined

Odontology - Oral scanners allow dental impressions to be taken in a short time without the use of an impression material. However, it has been noted that high impression accuracy cannot be...     

Efficacy of Granulocyte and Monocyte Adsorption Apheresis for Treatment of Palmoplantar Pustulosis

Palmoplantar pustulosis (PPP) is characterized by neutrophilic pustules with erythema, which are limited to the hands and feet. Although granulocyte and monocyte adsorption apheresis (GMA) has shown remarkable effects on generalized pustular psoriasis, there are few reports of PPP treated with GMA. We treated three refractory PPP patients using GMA weekly for 5 weeks. The skin eruptions were assessed by a 5‐grade score for scales, pustules, and erythema. GMA decreased the total grade from 9 to 2 in patients 1 and 2, and from 7 to 3 in patient 3. The GMA effects were estimated to be excellent in all three patients. Pustule formation and pain disappeared in all cases. The treatment effect lasted for at least 5 months after GMA. GMA was also effective for relieving the arthralgia in one patient, but it recurred at 6 weeks. Based on these findings, GMA could be an effective therapy for refractory PPP.     

Current and future directions for treating hepatitis B virus infection

Hepatitis B virus(HBV) persistently infects approximately 350 million people, and approximately 600000 liverrelated deaths are observed per year worldwide. HBV infection is also one of the major risk factors for hepatocellular carcinoma(HCC). The persistence of serum hepatitis B e antigen(HBe Ag) and high level of serum HBV DNA are thought to reflect a high HBV replication status in hepatocytes, causing cirrhosis, HCC and liver-related deaths. It has been reported that antiviral therapy, such as peginterferon and nucleos(t)ide analogues(NUCs), could suppress liver-related death by inhibiting the HBV DNA levels and inducing seroconversion from HBe Ag to antibody to HBe antigen. Currently, peginterferon is widely used, but there are also several disadvantages in the use of peginterferon, such as various adverse events, the administration route and duration. It is difficult to predict the effects of treatment and interferon is contraindicated for the patients with advanced fibrosis of the liver and cirrhosis. With respect to NUCs, entecavir and tenofovir disoproxil fumarate are current the first-choice drugs. NUCs can be administered orally, and their anti-viral effects are stronger than that of peginterferon. However, because cessation of NUC administration leads to high levels of viral replication and causes severe hepatitis, they must be administered for a long time. On the other hand, the use of both interferon and NUCs cannot eliminate covalently closed circular DNA of HBV. In this review, we evaluate the natural course of chronic HBV infection and then provide an outline of these representative drugs, such as peginterferon, entecavir and tenofovir disoproxil fumarate.     

The Stent-Eluting Drugs Sirolimus and Paclitaxel Suppress Healing of the Endothelium by Induction of Autophagy

Clinical studies have indicated that the stent-eluting drugs sirolimus and paclitaxel impact restenosis; however, it is still elusive how these drugs affect the vascular endothelium at the molecular and cellular levels. The purpose of this study was to determine whether sirolimus and paclitaxel induce molecular and cellular alterations in the vascular endothelium. Endothelial regrowth was assessed in human aortic endothelial cells and rat aortic endothelium. Molecular and cellular alterations were analyzed in human aortic endothelial cells by Western blot analysis, transmission electron microscopy, and immunofluorescence staining. Green fluorescent protein-LC3 mice were used to analyze autophagic endothelium. Here, we show that sirolimus and paclitaxel differentially induce self-digesting autophagy in vascular endothelial cells with changes in expression of LC3B, p53, and Bcl-2, considerably suppressing re-endothelialization and revascularization. These results suggest that phenotypic alteration in the endothelium by sirolimus or paclitaxel might affect the rates of late stent thrombosis, myocardial infarction, and mortality.Sirolimus and paclitaxel, which were originally used for immunosuppression or cancer treatment, have been shown to have a new therapeutic application in preventing restenosis after angioplasty.^1,2 Angioplasty induces target vascular injury that often accelerates mitogen-mediated vascular smooth muscle proliferation and formation of neointimal hyperplasia. In this situation, both sirolimus and paclitaxel have been shown to inhibit cell cycle proliferation and migration of vascular smooth muscle cells.³ On the basis of these findings, drug-eluting stents (DES), including a sirolimus-eluting stent, and a paclitaxel-eluting stent, have been implanted in millions of patients with coronary artery disease undergoing percutaneous coronary intervention, and their efficacy and safety relative to bare-metal stents have been investigated in randomized clinical trials worldwide.⁴While enthusiasm for DES use with this technology has been increasing, recent reports have sounded an alarm that patients with DES may encounter life threatening complications such as late stent thrombosis, in-stent thrombosis, and myocardial infarction.^5,6 These clinical data, together with the effects of sirolimus and paclitaxel on cell cycle inhibition,³ indicate that endothelial dysfunction may exist. However, presently, little information is available regarding the direct effects of sirolimus and paclitaxel on the vascular endothelium. Here, we hypothesized that sirolimus and paclitaxel would have undefined effects on the vascular endothelium, which correlate with unfavorable outcomes after DES use.