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L Olavarrieta

Publications and source records attributed to L Olavarrieta.

8 recordsLinked to original sources
PubMed2002

DNA knotting caused by head-on collision of transcription and replication.

Collision of transcription and replication is uncommon, but the reason for nature to avoid this type of collision is still poorly understood. In Escherichia coli pBR322 is unstable and rapidly lost without selective pressure. Stability can be rescued if transcription of the tetracycline-resistance gene (Tet(R)), progressing against replication, is avoided. We investigated the topological consequences of the collision of transcription and replication in pBR322-derived plasmids where head-on collision between the replication fork and the RNA polymerase transcribing the Tet(R) gene was allowed or avoided. The results obtained indicate that this type of collision triggers knotting of the daughter duplexes behind the fork. We propose this deleterious topological consequence could explain the instability of pBR322 and could be also one of the reasons for nature to avoid head-on collision of transcription and replication.

Autoradiography↗
PubMed2002

Supercoiling, knotting and replication fork reversal in partially replicated plasmids.

To study the structure of partially replicated plasmids, we cloned the Escherichia coli polar replication terminator TerE in its active orientation at different locations in the ColE1 vector pBR18. The resulting plasmids, pBR18-TerE@StyI and pBR18-TerE@EcoRI, were analyzed by neutral/neutral two-dimensional agarose gel electrophoresis and electron microscopy. Replication forks stop at the Ter-TUS complex, leading to the accumulation of specific replication intermediates with a mass 1.26 times the mass of non-replicating plasmids for pBR18-TerE@StyI and 1.57 times for pBR18-TerE@EcoRI. The number of knotted bubbles detected after digestion with ScaI and the number and electrophoretic mobility of undigested partially replicated topoisomers reflect the changes in plasmid topology that occur in DNA molecules replicated to different extents. Exposure to increasing concentrations of chloroquine or ethidium bromide revealed that partially replicated topoisomers (CCCRIs) do not sustain positive supercoiling as efficiently as their non-replicating counterparts. It was suggested that this occurs because in partially replicated plasmids a positive DeltaLk is absorbed by regression of the replication fork. Indeed, we showed by electron microscopy that, at least in the presence of chloroquine, some of the CCCRIs of pBR18-Ter@StyI formed Holliday-like junction structures characteristic of reversed forks. However, not all the positive supercoiling was absorbed by fork reversal in the presence of high concentrations of ethidium bromide.

Blotting, Southern↗
PubMed2002

Knotting dynamics during DNA replication.

The topology of plasmid DNA changes continuously as replication progresses. But the dynamics of the process remains to be fully understood. Knotted bubbles form when topo IV knots the daughter duplexes behind the fork in response to their degree of intertwining. Here, we show that knotted bubbles can form during unimpaired DNA replication, but they become more evident in partially replicated intermediates containing a stalled fork. To learn more about the dynamics of knot formation as replication advances, we used two-dimensional agarose gel electrophoresis to identify knotted bubbles in partially replicated molecules in which the replication fork stalled at different stages of the process. The number and complexity of knotted bubbles rose as a function of bubble size, suggesting that knotting is affected by both precatenane density and bubble size.

DNA Replication↗
PubMed2001

Giant inguino-scrotal bladder hernia. Report of a case.

Bladder hernia is very uncommon. It tends to affect patients over the age of 50 and is predisposed by cervico-urethral obstruction. The condition is often diagnosed during inguinal hernia surgery. The authors report a case of massive inguino-scrotal bladder herniation. The different types of bladder hernia are described, and the clinical-radiological findings and surgical management are discussed.

Journal Article↗
PubMed1990

[Treatment of gastroesophageal reflux by pexis to the round ligament. Report of 100 operated patients followed-up for 16 to 23 years].

In a study of 1,491 patients operated with ligament cardiopexy from 1,694 onwards, which we published in 1986, we reviewed 100 consecutive cases operated 15 years earlier or more. The review was based on a radioclinical (100), fiberscopic (53) and manometric (71) study, as well as on a measurement of the pH in doubtful cases (22). The results were distributed into categories A (normal), B (occasional disorders), C (functional disorders without recurrence) and R (recurrence), as follows: A + B 81%, C 12% and R 6%. This recent study confirms the conclusions we drew in 1981: a 15-minute operation that cures 94% of the patients without recurrence after 15 years and more is an appropriate procedure.

Female↗
PubMed1989

[Hernial strangulation of Meckel's diverticulum: Littre's hernia. Apropos of 4 cases].

Hernial strangulation of Meckel's diverticulum (Littre's hernia) is a rare anatomoclinical form. It represents 10% of all complications of Meckel's diverticulum (8.8% of our cases), and complications like hemorrhage, perforation and diverticulitis are fairly frequent. Four cases of Littre's hernia are presented: two males and two females, with an average age of 67 years (range 50-83 years), representing 0.08% of all the inguinal-crural hernias operated in the department. The clinical manifestations were those of intestinal obstruction because a mixed type Littre's hernia was involved, with compromise of the diverticulum and its intestinal loop. Preoperative diagnosis is unlikely in strangulation without disturbances in the intestinal transit and, in fact, is even less likely if it is accompanied by obstruction. The diagnosis is thus almost always intraoperative. The correct treatment is surgery after restoring the patient's hemodynamic equilibrium. Simple and/or loop diverticulectomy via herniotomy, herniolaparotomy or laparotomy are debated. We think that this disorder can generally be resolved using the inguinal approach, as in any strangled hernia, with the technical option of using a larger, more comfortable and safer approach in cases of important obesity and/or deterioration of the loop (necrosis, perforation). In elderly patients with uncomplicated Littre's hernia and Meckel's diverticulum, abstention from diverticular exeresis may be justifiable. Of the four patients, the first two died from cardiogenic shock and pulmonary embolism, respectively; the last two evolved well (except for a wound abscess).

Aged↗