Replisome structure suggests mechanism for continuous fork progression and post-replication repair.

What happens to DNA replication when it encounters a damaged or nicked DNA template has been under investigation for five decades. Initially it was thought that DNA polymerase, and thus the replication-fork progression, would stall at road blocks. After the discovery of replication-fork helicase and replication re-initiation factors by the 1990s, it became clear that the replisome can "skip" impasses and finish replication with single-stranded gaps and double-strand breaks in the product DNA. But the mechanism for continuous fork progression after encountering roadblocks is entangled with translesion synthesis, replication fork reversal and recombination repair. The recently determined structure of the bacteriophage T7 replisome offers the first glimpse of how helicase, primase, leading-and lagging-strand DNA polymerases are organized around a DNA replication fork. The tightly coupled leading-strand polymerase and lagging-strand helicase provides a scaffold to consolidate data accumulated over the past five decades and offers a fresh perspective on how the replisome may skip lesions and complete discontinuous DNA synthesis. Comparison of the independently evolved bacterial and eukaryotic replisomes suggests that repair of discontinuous DNA synthesis occurs post replication in both.

Early days of DNA repair: discovery of nucleotide excision repair and homology-dependent recombinational repair.

The discovery of nucleotide excision repair in 1964 showed that DNA could be repaired by a mechanism that removed the damaged section of a strand and replaced it accurately by using the remaining intact strand as the template. This result showed that DNA could be actively metabolized in a process that had no precedent. In 1968, experiments describing postreplication repair, a process dependent on homologous recombination, were reported. The authors of these papers were either at Yale University or had prior Yale connections. Here we recount some of the events leading to these discoveries and consider the impact on further research at Yale and elsewhere.

Dewatering behavior of sewage screenings.

Screenings from municipal sewage treatment plants have increased in importance in recent years, particularly in Germany, where laws prohibit depositing of screenings in landfill. This paper presents basic investigations of sewage screenings, especially the structure and dewatering behavior. Two standard experiments are conducted. First, the relationship between pressure and water content is determined. Secondly the flow resistance as a function of pressure is evaluated. The results help to derive simulation models in order to understand how the material behaves inside a wash press.

Hybrid approach combining off-pump CABG with transapical aortic valve implantation via median sternotomy.

We report the case of a 75-year-old patient diagnosed with severe aortic stenosis and two-vessel coronary artery disease. Due to multiple comorbidities including chronic renal insufficiency, stroke and pulmonary hypertension (EuroSCORE: 34%; STS mortality risk: 14.9%), he was not a candidate for conventional aortic valve surgery. He underwent a novel hybrid treatment approach combining off-pump CABG and transapical aortic valve implantation via a median sternotomy. Extracorporeal circulation could be entirely avoided.

Contact shot with unusual soot pattern.

In a suicidal shot to the temple two roundish zones of powder soot blackening were found above the entrance wound. The paired zones of powder soot blackening were caused by two gas outlets located on the upper side of the muzzle end of the weapon used (converted blank cartridge pistol of make Rhöner). The conclusions that can be drawn from this particular soot pattern with regard to the type of the weapon, the muzzle-to-target distance, the direction of fire and the way of holding the weapon are discussed.

[Early post-mortem animal bites after suicidal gunshot wound to the head of a police dog handler]. / Frühpostmortaler Tierfrass nach suizidalem Kopfschuss eines polizeilichen Hundeführers.

A 41-year-old police officer committed suicide in his office by firing a contact shot to the left temple. When the body was found 12 hours later, the German shepherd dog the officer had been in charge of had caused considerable damage on the lower half of the face and the adjacent parts of the neck. The clothing of the suicide was undamaged. Blood traces in the shape of paws were found at the place of death. The wound margins of the postmortem animal injury were nicked and jagged by the canine teeth. The entrance and exit wounds were not affected by the soft tissue defect. The findings gathered are discussed in reference to the relevant literature.

[Alcohol stove as a source of CO poisoning in a camper]. / Spirituskocher als Quelle einer CO-Vergiftung im Wohnmobil.

Although the number of deaths from fatal CO poisoning has strongly declined since the change from coal gas to natural gas, accidental and suicidal carbon monoxide intoxications still have to be expected. In motor vehicles the exhaust gases from the engine and a stationary heating are the major sources of intoxication. In closed campers and caravans the operation of gas and spirit cooking stoves etc. may also lead to an accumulation of carbon monoxide due to incomplete combustion.

The Ross operation: do native aortic, native pulmonary, and homograft pulmonary valve size and form differences influence results?

BACKGROUND: The pulmonary autograft approaches the ideal aortic valve substitute but numerous technical modifications are debated. The valves involved often differ in diameter and shape of the recipient annulus. We previously reported simplified surgical rules and early results of 52 patients and here we extend the report to 76 patients and analyze the mid-term results with respect to valve mismatch. METHODS: We studied the influence of geometric discrepancies. Valve regurgitation and gradient are compared for size discrepancies up to or more than 3 mm between recipient annulus and pulmonary autograft. The normal tricuspid recipient aortic annulus is compared with the flat circular redo-prosthetic or bicuspid annulus. Patients with plication of the aortic annulus and remodeling of the distal aorta are reviewed, and lastly donor homograft to pulmonary autograft discrepancies up to and more than 3 mm are compared. RESULTS: The results were comparable in all groups and no significant differences were observed. CONCLUSION: The pulmonary autograft operation may be simplified, with good results at the least in the first year despite operative tailoring due to valve discrepancies.

A specific 3' exonuclease activity of UvrABC.

Specific cutting of undamaged DNA by UvrABC nuclease is observed. It occurs seven nucleotides (nt) from the 3' terminus of oligonucleotides annealed to single-stranded M13 DNA circles. Although the location of the UvrABC cut on undamaged DNA is similar to that of the cut on the 5' side of a damaged DNA site during the dual incision reaction, the cut of undamaged DNA is not an intermediate in the dual incision step. On DNA duplexes with a single AAF adduct, the anticipated cut at the eighth phosphodiester bond 5' of the lesion is present, but extra cuts at 7-nt increments are observed at the 15th and 22nd phosphodiester bonds. We suggest that these additional cuts are made by the UvrABC activity observed on undamaged DNA; such activity is referred to as ABC 3' exonuclease and may play a significant role by providing a suitable gap for RecA-mediated recombinational exchanges during repair of interstrand crosslinks and closely opposed lesions. This ABC 3' exonuclease activity depends on higher concentrations of Uvr proteins as compared with dual incision and may be relevant to reactions that occur when UvrA and UvrB are increased during SOS induction.

The influence of geometric mismatch between the native aortic, native pulmonary and homograft pulmonary valve on the results of the pulmonary autograft operation.

BACKGROUND: The pulmonary autograft operation has achieved broad acceptance and may be the ideal aortic valve substitute. Both the pulmonary autograft and the aortic homograft are more complicated procedures than prosthetic valve replacement. The trend to insert the pulmonary autograft as a root replacement rather than in the subcoronary position has achieved greater uniformity in the results, but there is still confusing diversity in opinions on technical details and anatomical dimensions. The importance of both size and shape mismatches between the three valves involved has received little attention. The valves often differ in diameter and in the shape of the recipient aortic annulus. This uncertainty and the diversity of opinions on essential technical details was disconcerting when we proceeded from aortic homograft-to-pulmonary autograft operations, this was compounded by only a single homograft being available for every operation as we have no homograft bank. METHODS: We compared the hemodynamic results regarding various geometric mismatches. All operative details were the same and patients were studied at regular intervals. Comparisons were made in patients with mismatch between recipient aortic annulus and pulmonary autograft. Patients with a normal tricuspid aortic annulus were compared to those with either a circular redo prosthetic valve annulus or a bicuspid recipient annulus. Thirdly we compared the patients with plication of the aortic annulus to those with remodeling of the distal aorta. Lastly we compared mismatch between donor homograft and pulmonary autograft. RESULTS: No influence of geometric mismatch between the three valves could be found on the results of the pulmonary autograft operation. CONCLUSIONS: Good results are obtainable without a painful learning curve if one keeps to certain surgical principles. It need not be a complicated operation and geometric mismatches between the three valves involved may be compensated for adequately.

Endaortitis of coarctation of the aorta after invasive diagnostics.

We report the case of a young woman in whom endaortitis developed at the site of a coarctation of the aorta after the invasive investigation of right fossa iliac pain. The organism responsible suggests a causal relationship to the investigations without antibiotic prophylaxis, and we emphasize the need for antibiotic prophylaxis in these cases. Invasive investigation of isolated coarctation in a young adult or adolescent is probably superfluous.

UvrAB activity at a damaged DNA site: is unpaired DNA present?

To study the activity of the Escherichia coli UvrA and UvrB nucleotide excision repair proteins during the formation of the pre-incision complex at a damaged DNA site, we used substrates with modifications around a single 2-(acetylamino)fluorene (AAF) lesion. Based on the release of AAF-containing oligonucleotides from a single-stranded DNA circle, we conclude that during interaction with our substrates UvrAB introduces changes in DNA which are localized at the lesion and are limited to 1-3 bp. Since these changes might include a denaturation of DNA at the lesion site and, consequently, a bubble structure might be present in a pre-incision complex, we studied incision activity of UvrABC excinuclease on substrates with 1-4 unpaired bases next to an AAF adduct. Opening more than one base on either or both sides of the lesion caused a significant decrease in the incision activity of UvrABC, but did not change the position of the incision sites. We conclude that the UvrAB action leading to a pre-incision complex does not include the formation of a bubble intermediate generated by extensive denaturation of base pairs.

The limited strand-separating activity of the UvrAB protein complex and its role in the recognition of DNA damage.

The recognition by Escherichia coli Uvr nucleotide excision repair proteins of a variety of lesions with diverse chemical structures and the presence of helicase activity in the UvrAB complex which can displace short oligonucleotides annealed to single-stranded DNA led to a model in which this activity moves UvrAB along undamaged DNA to damaged sites where the lesion blocks further translocation and the protein-DNA pre-incision complex is formed. To evaluate this mechanism for damage recognition, we constructed substrates with oligonucleotides of different lengths annealed to single-stranded DNA circles and placed a single 2-(acetylamino)fluorene (AAF) lesion either on the oligonucleotide or on the circle. For the substrates with no lesion, the UvrAB complex effectively displaced a 22-mer but not a 27-mer or longer fragments. The presence of AAF on the oligonucleotide significantly increased the release of the 27-mer but oligomers of 30 or longer were not separated. Placing the lesion on the circular strand did not block the release of the fragments. Instead, the releasing activity of UvrAB was stimulated and also depended on the length of the annealed oligonucleotide. These observations do not agree with the predictions of a damage recognition mechanism that depends on helicase-driven translocation. Most likely, the strand-separating activity of UvrAB is a consequence of local changes occurring during the formation of a DNA-protein pre-incision complex at the damaged site and is not due to translocation of the protein along undamaged DNA to locate a lesion.

Sabia virus incident at Yale University.

An incident involving a human exposure to a newly isolated arenavirus, Sabia virus, in the Yale Arbovirus Research Unit occurred at Yale University on August 8, 1994. A senior-level visiting research scientist was exposed to Sabia virus while purifying the virus from a large volume of tissue culture fluid. The exposure resulted in development of a Sabia virus infection followed by recovery of the patient. The incident resulted in a comprehensive review by a Yale faculty committee and an external expert committee. As a result, a number of new practices and procedures were added to Yale's biosafety policy for investigating infectious agents in BL-3 facilities.

Spontaneous splenic rupture in a patient with multiloculated signet ring cell carcinoma of the urinary bladder.

We report a case of spontaneous splenic rupture caused by signet ring cell carcinoma of the urinary bladder. Rupture of the spleen usually stems from trauma and only rarely from solid tumor metastasis. Early diagnosis by ultrasound is essential since mortality is high without prompt splenectomy.

Vacuum activated polishing laps produce smooth aspheric surfaces.

A novel approach to computer controlled fabrication of aspheric optical surfaces utilizes semi-flexible vacuum activated polishing tools to produce high quality, smooth surface geometry on off-axis mirror components.

[Herpes simplex-associated exacerbation of Crohn's disease. Successful treatment with acyclovir]. / Herpes-simplex-assoziierte Exazerbation eines Morbus Crohn. Erfolgreiche Behandlung mit Aciclovir.

Seven years ago, a now 25-year-old man was found to have Crohn's disease of the terminal ileum as well as of the transverse and sigmoid colon. Despite treatment with both corticosteroids and mesalazine the disease progressed and led to almost complete stenosis of the lumen of the sigmoid colon so that surgical intervention was planned. But because immunohistological examination of the small and large intestinal mucosa had demonstrated herpes simplex virus (HSV I + II) DNA, additional treatment with acyclovir appeared worth-while. The morphological and clinical findings indeed changed decisively, obviating surgery. If a virus infection is found to be a pathogenetic co-factor in a case of Crohn's disease, a therapeutic trial with a suitable antiviral agent seems reasonable.

[Complete severance of the trunk in a pedestrian-automobile collision]. / Vollständige Rumpfdurchtrennung bei Fussgänger-PKW-Kollision.

A 70-year-old pedestrian was hit by a passenger car, when she crossed a road outside built-up areas; at the time of the collision the car drove at a speed of about 100 km/h and did not brake. In this lateral accident the trunk of the pedestrian was completely severed near the upper brim of the pelvis. The upper part of the body was flown into the interior of the car through the windscreen; the lower half of the body was found between the place of collision and the place, where the car came to a standstill. The body was not severed at the front edge of the roof, but in the region of the front edge of the engine hood. The abdominal skin and the inguinal region were marked by numerous transverse distension tears; these were indirect injuries of the collision caused by tensile strain due to inertia.