Behavior of supercoiled DNA

We study DNA supercoiling in a quantitative fashion by micromanipulating single linear DNA molecules with a magnetic field gradient. By anchoring one end of the DNA to multiple sites on a magnetic bead and the other end to multiple sites on a glass surface, we were able to exert torsional control on the DNA. A rotating magnetic field was used to induce rotation of the magnetic bead, and reversibly over- and underwind the molecule. The magnetic field was also used to increase or decrease the stretching force exerted by the magnetic bead on the DNA. The molecule's degree of supercoiling could therefore be quantitatively controlled and monitored, and tethered-particle motion analysis allowed us to measure the stretching force acting on the DNA. Experimental results indicate that this is a very powerful technique for measuring forces at the picoscale. We studied the effect of stretching forces ranging from 0.01 pN to 100 pN on supercoiled DNA (-0.1 < sigma < 0.2) in a variety of ionic conditions. Other effects, such as stretching-relaxing hysteresis and the braiding of two DNA molecules, are discussed.     

Advances in multimodality therapy for laryngeal cancer

Combined induction chemotherapy and external beam radiation therapy is an effective treatment for selected patients with advanced-stage laryngeal cancer. The larynx can be preserved in two-thirds of patients receiving this treatment. Investigations continue to evaluate the ideal treatment regimen, the delivery of chemotherapy, patient selection, biologic markers predicting response, functional outcome, and the effectiveness of this treatment at other sites.     

Percutaneous therapy of structural heart disease: pediatric disease

Interventional therapy of congenital heart lesions at cardiac catheterization has greatly increased during the past decade. At the authors' institution, the frequency of such procedures among catheterizations has increased from 5% to more than 60%. The variety of lesions so treated continues to expand and equipment continues to improve. These procedures may be divided into 2 groups, namely (1) those involving balloon dilation of stenotic valves and vessel obstructions with stent placement being increasingly used in the latter and (2) those involving occlusion of lesions with (a) coils, such as aortopulmonary collaterals, patent ductus arteriosi and coronary artery fistulae and (b) umbrella devices, such as atrial and ventricular septal defects. These have replaced surgery as the initial procedure of choice in many lesions including valvar pulmonary and aortic stenoses, and postoperative aortic coarctation in young patients. In addition, use of the double-umbrella device even in noncongenital lesions appears promising.     

MR arthrography of the shoulder

Although conventional MR imaging allows direct visualization of major anatomic structures, smaller intraarticular structures, including the glenoid labrum, glenohumeral ligaments, and articular surface of the rotator cuff tendon can be difficult to evaluate in the absence of a joint effusion. The authors review the techniques employed in performing MR arthrography, imaging characteristics of MR arthrography, and diagnostic utilization of the technique. Suggested indications are provided.     

Search for DNA repair inhibitors: selective binding of nucleic bases-acridine conjugates to a DNA duplex containing an abasic site

The abasic site is one of the most frequent DNA lesions generated by spontaneous or enzymatic cleavage of the N-glycosidic bond. The abasic site is also an intermediate in the nucleotide and base excision DNA repair. We examined molecules which recognize and cleave DNA at the abasic site with high efficiency. These molecules incorporate in their structure a nucleic base for abasic site recognition, an intercalator for DNA binding, and a polyamino linker for ionic interaction and DNA cleavage. Such compounds, by interfering with abasic sites in DNA, are also inhibitors of DNA repair. In order to better understand the parameters of the interaction, we carried out a UV thermal denaturation study of synthetic oligonucleotides containing the lesion both in the absence and in the presence of the drugs. A similar study was also carried out using the corresponding nonmodified oligonucleotide. The results indicate selective binding of the base-chain-intercalator conjugates to the abasic site containing oligonucleotides.     

Simultaneous determination of aortic valve area by the Gorlin formula and by transesophageal echocardiography under different transvalvular flow conditions. Evidence that anatomic aortic valve area does not change with variations in flow in aortic stenosis

OBJECTIVES: The purpose of this study was to determine the impact of changes in flow on aortic valve area (AVA) as measured by the Gorlin formula and transesophageal echocardiographic (TEE) planimetry. BACKGROUND: The meaning of flow-related changes in AVA calculations using the Gorlin formula in patients with aortic stenosis remains controversial. It has been suggested that flow dependence of the calculated area could be due to a true widening of the orifice as flow increases or to a disproportionate flow dependence of the formula itself. Alternatively, anatomic AVA can be measured by direct planimetry of the valve orifice with TEE. METHODS: Simultaneous measurement of the planimetered and Gorlin valve area was performed intraoperatively under different hemodynamic conditions in 11 patients. Left ventricular and ascending aortic pressures were measured simultaneously after transventricular and aortic punctures. Changes in flow were induced by dobutamine infusion. Using multiplane TEE, AVA was planimetered at the level of the leaflet tips in the short-axis view. RESULTS: Overall, cardiac output, stroke volume and transvalvular volume flow rate ranged from 2.5 to 7.3 liters/min, from 43 to 86 ml and from 102 to 306 ml/min, respectively. During dobutamine infusion, cardiac-output increased by 42% and mean aortic valve gradient by 54%. When minimal flow was compared with maximal flow, the Gorlin area varied from (mean +/- SD) 0.44 +/- 0.12 to 0.60 +/- 0.14 cm2 (p < 0.005). The mean change in Gorlin area under different flow rates was 36 +/- 32%. Despite these changes, there was no significant change in the planimetered area when minimal flow was compared with maximal flow. The mean difference in planimetered area under different flow rates was 0.002 +/- 0.01 cm2 (p = 0.86). CONCLUSIONS: By simultaneous determination of Gorlin formula and TEE planimetry valve areas, we showed that acute changes in transvalvular volume flow substantially altered valve area calculated by the Gorlin formula but did not result in significant alterations of the anatomic valve area in aortic stenosis. These results suggest that the flow-related variation in the Gorlin AVA is due to a disproportionate flow dependence of the formula itself and not a true change in valve area.     

Percutaneous angioplasty for infrainguinal graft-related stenoses

OBJECTIVE: To assess the success of percutaneous transluminal angioplasty (PTA) in treating infrainguinal graft-related stenoses. DESIGN: Retrospective analysis of stenoses undergoing PTA over 6 years. MATERIALS: Fifty-seven stenoses in 42 grafts. METHODS: Site, length and type of stenoses recorded. Follow-up till discharge, graft occlusion or death. RESULTS: PTA was successful in 48/57 stenoses in 36 grafts (G), with a poor result in seven. Further PTA was required in seven stenoses (7 G). One graft occluded at PTA and one stenosis was inaccessible. Overall graft (G) patency (median 13 months) was 82% (1 year patency 84%). Of 48 successful PTAs (37 G), 36 remained patent (28 G), eight (4 G) occluded and four were lost to follow-up (4 G). Fourteen of thirty-six stenoses which remained patent required further intervention (seven PTA, six jump grafts, one vein patch). The four occlusions were associated with small veins (two), multiple stenoses (one) and a PTFE graft which occluded 10 days following PTA. Of the seven PTAs with a poor angiographic result, five remained patent, three after further intervention. CONCLUSION: PTA is the best treatment for localised stenoses. Stenoses > 2 cm or multiple (three or more) stenoses are best treated surgically. Follow-up is essential, as 20% require further intervention.     

An experimental study on inhibitory effect of Chinese medicine tai-bao on antisperm antibody

OBJECTIVE: To investigate whether Chinese medicine Tai-bao could inhibit antisperm antibody in experimental mice. METHODS: The experimental immunoinfertility mice were due to antisperm antibody induced by injection of human sperm membrane antigens. The experimental immuno-infertile mice used in the present study were divided into four groups including Tai-bao high dose group (46.8 g.kg-1.d-1), Tai-bao low dose group (31.2 g.kg-1.d-1), prednisone group and normal saline group. The enzyme linked immune sorbent assay (ELISA) and microcytotoxic assay were used for detection of antisperm antibody. The change of levels of antisperm antibody before and after treatment, pregnant rate, and the number of implantation were investigated in tested mice. RESULTS: The pregnant rates in normal saline group, prednisone group, Tai-bao high dose group and low dose were 38.89%, 47.06%, 70.00% and 75.00% respectively. The rate of pregnancy in Tai-bao low dose group was significantly higher as compared with normal saline group (P < 0.05). The rate of implantation in Tai-bao low dose group was significantly higher than that in prednisone group (P < 0.05). The results of detection of the cytotoxic antibody to sperm showed that cytotoxic percentages in Tai-bao high dose group (63.0 +/- 10.3%) and prednisone group (56.3 +/- 13.7%) were significantly lower (P < 0.05 and P < 0.01) than that in normal saline group (72.84 +/- 5.05%). CONCLUSION: Chinese medicine Tai-bao possesses regulatory effect on reproductive immune function, inhibitory effect on antisperm cytotoxic antibody, and promoting effect on pregnancy.     

Structural adaptations in the specialized bacteriophage T4 co-chaperonin Gp31 expand the size of the Anfinsen cage

The Gp31 protein from bacteriophage T4 functionally substitutes for the bacterial co-chaperonin GroES in assisted protein folding reactions both in vitro and in vivo. But Gp31 is required for the folding and/or assembly of the T4 major capsid protein Gp23, and this requirement cannot be satisfied by GroES. The 2.3 A crystal structure of Gp31 shows that its tertiary and quaternary structures are similar to those of GroES despite the existence of only 14% sequence identity between the two proteins. However, Gp31 shows a series of structural adaptations which will increase the size and the hydrophilicity of the "Anfinsen cage," the enclosed cavity within the GroEL/GroES complex that is the location of the chaperonin-assisted protein folding reaction.