High-resolution structure of hair-cell tip links

Transduction-channel gating by hair cells apparently requires a gating spring, an elastic element that transmits force to the channels. To determine whether the gating spring is the tip link, a filament interconnecting two stereocilia along the axis of mechanical sensitivity, we examined the tip link's structure at high resolution by using rapid-freeze, deep-etch electron microscopy. We found that the tip link is a right-handed, coiled double filament that usually forks into two branches before contacting a taller stereocilium; at the other end, several short filaments extend to the tip link from the shorter stereocilium. The structure of the tip link suggests that it is either a helical polymer or a braided pair of filamentous macromolecules and is thus likely to be relatively stiff and inextensible. Such behavior is incompatible with the measured elasticity of the gating spring, suggesting that the gating spring instead lies in series with the helical segment of the tip link.

A Calcium-Selective Channel from Root-Tip Endomembranes of Garden Cress1

A Ca2+ channel from root-tip endomembranes of garden cress (Lepidium sativum L.) (LCC1) was characterized using the planar lipid-bilayer technique. Investigation of single-channel recordings revealed that LCC1 is voltage gated and strongly rectifying. In symmetrical 50 mm CaCl2 solutions, the single-channel conductance was 24 picosiemens. LCC1 showed a moderate selectivity for Ca2+ over K+ (9.4:1) and was permeable for a range of divalent cations (Ca2+, Ba2+, and Sr2+). In contrast to Bryonia dioica Ca2+ channel 1, a Ca2+-selective channel from the endoplasmic reticulum of touch-sensitive tendrils, LCC1 showed no bursting channel activity and had a low open probability and mean open time (2.83 ms at 50 mV). Inhibitor studies demonstrated that LCC1 is blocked by micromolar concentrations of erythrosin B (inhibitor concentration for 50% inhibition [IC50] = 1.8 μm) and the trivalent cations La3+ (IC50 = 5 μm) and Gd3+ (IC50 = 10 μm), whereas verapamil showed no blocking effect. LCC1 may play an important role in the regulation of the cytoplasmic free Ca2+ concentration in root-tip and/or root-cap cells. The question of whether this ion channel is part of the gravitropic signal transduction pathway deserves further investigation.

The mammalian fauna on the islands at the northern tip of Sabah, Borneo / Shukor Md. Nor.

n.s. no.83(1996)

TTIP and Public Procurement: Going beyond the tip of the iceberg. CEPS Policy Brief No. 339, March 2016

Trade negotiations involving international public procurement rules are on the rise, stimulating a growing interest in having a clear picture of the economic stakes involved, including the current level of international openness. A recent paper published by the European Centre for International Political Economy (Messerlin, 2016) made an attempt to provide a range of estimates for the EU and the US and found relatively low rates of import penetration. This analytical approach, however, looked only at the ‘tip of the procurement iceberg’, as the data used covered primarily only one modality of international procurement (direct cross-border), which is not the main avenue for international government procurement. Other modalities, such as procurement from foreign subsidiaries established in Europe, account for much more. Such an approach therefore ignores the main modalities through which foreign firms win EU contracts. Once these other main procurement modalities are taken into account, EU openness in procurement is much higher. Comparable data across all modalities do not yet exist for the US, but we do have clear evidence that the US has introduced the largest number of protectionist procurement measures since 2008 affecting all modalities for international procurement. Against this background, this Policy Brief makes four basic points: i. Public procurement is a key area of trade negotiations, and TTIP is no exception to this rule. ii. The existing levels of openness in procurement markets need to be assessed across all three main procurement modalities and not based only on direct cross-border procurement, which is not the main procurement avenue. According to this comprehensive metric, the EU market already has a high foreign participation rate, including by US companies. iii. Unfortunately, similar data do not exist for the US market. But there is growing evidence of discriminatory measures introduced in recent years, which impede the ability of EU firms to compete on a level-playing field in US procurement markets. iv. The importance of procurement as a key negotiating area requires better data and a greater analytical engagement.

Epicardial Radiofrequency Ablation Failure During Ablation Procedures for Ventricular Arrhythmias: Reasons and Implications for Outcomes.

BACKGROUND Radiofrequency ablation (RFA) from the epicardial space for ventricular arrhythmias is limited or impossible in some cases. Reasons for epicardial ablation failure and the effect on outcome have not been systematically analyzed. METHODS AND RESULTS We assessed reasons for epicardial RFA failure relative to the anatomic target area and the type of heart disease and assessed the effect of failed epicardial RFA on outcome after ablation procedures for ventricular arrhythmias in a large single-center cohort. Epicardial access was attempted during 309 ablation procedures in 277 patients and was achieved in 291 procedures (94%). Unlimited ablation in an identified target region could be performed in 181 cases (59%), limited ablation was possible in 22 cases (7%), and epicardial ablation was deemed not feasible in 88 cases (28%). Reasons for failed or limited ablation were unsuccessful epicardial access (6%), failure to identify an epicardial target (15%), proximity to a coronary artery (13%), proximity to the phrenic nerve (6%), and complications (<1%). Epicardial RFA was impeded in the majority of cases targeting the left ventricular summit region. Acute complications occurred in 9%. The risk for acute ablation failure was 8.3× higher (4.5-15.0; P<0.001) after no or limited epicardial RFA compared with unlimited RFA, and patients with unlimited epicardial RFA had better recurrence-free survival rates (P<0.001). CONCLUSIONS Epicardial RFA for ventricular arrhythmias is often limited even when pericardial access is successful. Variability of success is dependent on the target area, and the presence of factors limiting ablation is associated with worse outcomes.

Table 2.- Bryozoa collected during the LAMPOS expeditions between Punta Arenas and the northernmost tip of the Antarctic Peninsula

The 78 bryozoan species collected by the German R/V "Polarstern" during the LAMPOS cruise in April 2002, encompassing the Scotia Arc archipelagos between Tierra del Fuego and the Antarctic Peninsula, were studied to discern the biogeographical patterns of the Magellan region of South America, the Scotia Arc archipelagos and the Antarctic. The resulting dendrogram shows three clusters: an isolated one with the three easternmost archipelagos and the other two linking some of the northern and southern Scotia Arc archipelagos with Tierra del Fuego. A more comprehensive analysis using all the species previously recorded from the Scotia Arc archipelagos and adjacent areas (214 spp.) produced a clearer zoogeographical pattern without isolated clusters of localities. The Antarctic Peninsula plus the Scotia Arc archipelagos form a large cluster distinct from the Magellan-Falkland Subantarctic area. A third analysis making use of 78 genera present in the study area plus Australia and New Zealand reinforces this pattern, showing two clusters: one uniting South America and the Australian-New Zealand realm and the other linking the Scotia Arc archipelagos with the Antarctic Peninsula. These results indicate that the Scotia Arc archipelagos represent merely a very narrow bridge connecting two different bryozoan faunas with only a few bryozoan species in common between the study areas.

1st game at Crisler, Awaiting opening tip-off, UM Men's Basketball vs Kentucky, 1967

[President Hatcher is about to give ball to official]

Radiofrequency radiation levels and population exposure in urban areas of the Eastern United States /

Issued May 1978.

Phase of the low radiofrequency ground wave

Bibliography: p. 10.

The slag tip /

Mode of access: Internet.

Sochinenīi͡a. 1860-1886. Moskva, Tip. M. G. Volchaninova, 1886-1887.

Photocopy (on double leaves)

Tip cat /

Title vignette.

Goroda Moskovskogo gosudarstva v XVI [i.e. shestnadt︠s︡atom] vi︠e︡ki︠e︡. Izsli︠e︡dovanīe N. D. Chechulina. S.-Peterburg, Tip. I. N. Shorokhodova, 1889.

Includes bibliographical references.