VCP/p97 Extracts Sterically Trapped Ku70/80 Rings from DNA in Double-Strand Break Repair

During DNA double-strand break (DSB) repair, the ring-shaped Ku70/80 complex becomes trapped on DNA and needs to be actively extracted, but it has remained unclear what provides the required energy. By means of reconstitution of DSB repair on beads, we demonstrate here that DNA-locked Ku rings are released by the AAA-ATPase p97. To achieve this, p97 requires ATP hydrolysis, cooperates with the Ufd1-Npl4 ubiquitin-adaptor complex, and specifically targets Ku80 that is modified by K48-linked ubiquitin chains. In U2OS cells, chemical inhibition of p97 or siRNA-mediated depletion of p97 or its adapters impairs Ku80 removal after non-homologous end joining of DSBs. Moreover, this inhibition attenuates early steps in homologous recombination, consistent with p97-driven Ku release also affecting repair pathway choice. Thus, our data answer a central question regarding regulation of Ku in DSB repair and illustrate the ability of p97 to segregate even tightly bound protein complexes for release from DNA.

The p97-Ufd1-Npl4 ATPase complex ensures robustness of the G2/M checkpoint by facilitating CDC25A degradation

The p97-Ufd1-Npl4 ATPase complex is associated with the response to DNA damage and replication stress, but how its inactivation leads to manifestation of chromosome instability is unclear. Here, we show that p97-Ufd1-Npl4 has an additional direct role in the G2/M checkpoint. Upon DNA damage, p97-Ufd1-Npl4 binds CDC25A downstream of ubiquitination by the SCF-βTrCP ligase and facilitates its proteasomal degradation. Depletion of Ufd1-Npl4 leads to G2/M checkpoint failure due to persistent CDC25 activity and propagation of DNA damage into mitosis with deleterious effects on chromosome segregation. Thus, p97-Ufd1-Npl4 is an integral part of G2/M checkpoint signaling and thereby suppresses chromosome instability.

[Single injuries to distal leg arteries]

The appropriate treatment of an injury to a single arterial vessel of the calf is still a matter of discussion. Isolated injury of one of the calf arteries is generally not considered to cause severe ischemia of the leg. Other factors such as the degree of concomitant trauma to bones, nerves, veins and soft tissue, which may impair collateral circulation, seem to represent the real threat for the survival of the extremity. On the other hand, high numbers of amputations were reported after the Second World War following ligation of an injured single vessel of the calf. Concomitant injuries are poorly documented in these reports. Consequently a good physical examination as well as arteriography, duplex ultrasound scan and a high index of suspicion are mandatory to evaluate the impaired circulation of the calf and to prevent hasty ligation of a single vessel.

[Ruptured aneurysm of the pancreaticoduodenal artery. A rare etiology of acute abdomen]

Even among the uncommon aneurysms of the visceral arteries the aneurysm of the pancreaticoduodenalis artery is considered a rarity. Etiologically, numerous factors must be taken into account, the most significant one being arteriosclerosis. The clinical presentation is unspecific and ambiguous. CT and, above all, intra-arterial DSA allow for a diagnosis. A generous consideration of indicating operative intervention, even in asymptomatic patients, is especially justified because of the imminent risk of rupture. The preferable therapy consists of elimination of the aneurysm either conventionally by proximal and distal ligature of the pancreaticoduodenalis artery or endovascularly by embolization. In the future a treatment with coated stents (TPEG) would also seem possible. Special attention must be paid to concomitant occlusive disease in other visceral arteries since measures for vessel reconstruction may be required because of intraoperative impairment of the collateral circulation. We report on the rupture of an aneurysm of the pancreaticoduodenal inferior artery in association with celiac axis occlusion.

Characteristics of nasal airflow and the effect of a nasal dilator in normal human subjects

Nasal resistance contributes to negative airway pressure during breathing. We sought to define normal patterns of nasal flow and the effects of mechanical dilatation and splinting of the nares on flow during forced inspiration and expiration. Maximal inspiratory and expiratory flow volume loops (FVL) were determined in 17 normal subjects. Oral FVL were obtained with nares clamped and nasal FVL through a mask with and without dilatation of nares using a plastic splint (Nozovent). Oral FVL were normal in all. Two patterns of nasal FVL were observed: one indicating 'variable' extrathoracic obstruction, the other indicating 'fixed' extrathoracic obstruction. Maximal inspiratory flow at 50% of vital capacity (FiF50) was improved by the Nozovent only in those with a 'variable' pattern (FIF50 (L/sec): 1.54 +/- 0.3 to 2.86 +/- 0.5; P < 0.05, versus 1.92 +/- 0.3 to 2.21 +/- 0.3: P = 0.5). In subjects with a fixed pattern, failure of dilatation of the nares to increase flow suggests that the site of inspiratory flow limitation is within the bony nostril.

Failure of physician documentation of sleep complaints in hospitalized patients

Sleep disorders are acknowledged to be common but remain underrecognized by the medical community, often attributed to the failure to question patients about their sleep quality. We examined the prevalence of sleep complaints (insomnia or excessive daytime sleepiness) in a group of general medical patients by administering a questionnaire to hospitalized patients in a Veterans Affairs tertiary care medical center. A total of 222 consecutive adults (215 men, 60 +/- 14 years; body mass index, 24.8 +/- 5.6) completed the questionnaire. Of these, 105 patients (47%) had either insomnia, excessive daytime somnolence, or both; 63 (28%) had excessive daytime somnolence, which was severe in 27 (12%). Of 75 patients (34%) who had insomnia, a third were taking hypnotic medication. Forty patients (18%) had snoring, which was associated with excessive daytime somnolence in 36, whereas 46 patients (21%) had either restless legs or a combination of leg jerks and leg kicking or twitching during sleep, associated with a sleep complaint (insomnia in 32). The medical records were subsequently reviewed to assess the admitting physicians' recognition of these symptoms. No record included mention of any patient symptom related to sleep. We conclude that symptoms related to sleep, some of which may be clinically important, are common, and that none of these complaints appear to be recognized by the physicians of record.