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Biomedical subjects

D Peña

Publications and source records attributed to D Peña.

7 recordsLinked to original sources
PubMed2001

Remote C-H activation of phenyl-substituted alkenes by BH(3).THF: mechanism and applications.

[reaction: see text] The hydroboration of tetrasubstituted alkenes and, in particular, bicyclic alkenes with BH(3).THF at 50 degrees C provides, via a highly stereoselective 1,2-rearrangement and a remote C-H activation, a diol in which the relative stereochemistry of three centers has been controlled. A mechanistic study provides general rules for remote C-H activation and leads to new synthetic applications.

Journal Article↗
PubMed2001

Pneumoencephalomeningitis secondary to infected lumbar arthrodesis with a fistula: a case report.

Pneumocephalus associated with spinal problems is very rare. Association with encephalomeningitis secondary to a fistula after an infected elective lumbar spine fusion has not been previously reported. The authors report a case in which the clinical onset of pneumoencephalomeningitis occurred after an airplane flight. CT-scan and lumbar puncture were used to make diagnosis; the treatment was based on parenteral antibiotics. The symptoms and signs of infection and neurological deficit resolved but the fistula remained. Diagnosis in such cases must be based upon CT-scan and lumbar puncture. Treatment should consist of systemic antibiotic therapy. Surgical management of infection and fistula is desirable, should the status of the patient allow such a treatment. In any case, as airplane flights in such cases may predispose to pneumocephalus, patients with an infected CSF fistula should avoid airplane flights until the problem is solved.

Aircraft↗
PubMed1995

Activation of progelatinase B (MMP-9) by gelatinase A (MMP-2).

The M(r) 72,000 (MMP-2; gelatinase A) and M(r) 92,000 (MMP-9; gelatinase B) gelatinases are two members of the family of matrix metalloproteinases (MMPs). These proteinases are thought to play a critical role in tumor cell invasion and are frequently coexpressed in human cancers. Gelatinases are secreted in a latent inactive form, and their conversion to the active species can be accomplished by other proteolytic enzymes, including other MMPs. We report herein that organomercurial or plasma membrane-activated M(r) 72,000 gelatinase A activates progelatinase B to an M(r) 82,000 active form in a process inhibited by tissue inhibitor of metalloproteinase (TIMP)-1 and TIMP-2. Progelatinase B activation was accomplished by the two active species of gelatinase A, the M(r) 62,000 and M(r) 45,000 forms, generated after plasma membrane or organomercurial activation of TIMP-2-free progelatinase A. The M(r) 45,000 species of gelatinase A lacks both the NH2-terminal profragment and the COOH-terminal domain known to play a role in plasma membrane activation and the regulation of TIMP-2 inhibition. These results suggest a novel mechanism of activation of progelatinase B mediated by gelatinase A species that may be localized in the surface of tumor cells and enhance matrix degradation during cancer metastasis.

Amino Acid Sequence↗
PubMedDate not supplied

Ulcer recurrence among Filipino patients: clinical profile and risk factors.

Patients with endoscopic diagnosis of gastric and/or duodenal ulcers who eventually had endoscopic confirmation of ulcer healing after any anti-ulcer medication were entered in a 3 year study to determine ulcer recurrence rate, onset of ulcer recurrence and factors associated with ulcer recurrence. Patients from two participating centres who are not on any maintenance treatment had endoscopic examinations at 3, 6 and 12 months after ulcer healing or at any time of symptom recurrence. There were 144 patients entered into the study. The 1 year recurrence rate observed among 125 Filipino patients who completed the study was 73% wherein 71% occurred within the first six months. This was comparable with those reported in the world literature. Thirty-three per cent of those with recurrent ulcers were asymptomatic. The difference in the recurrence rate between gastric and duodenal ulcers was not statistically significant. The only risk factors found to be associated with ulcer relapse were history of smoking and alcohol intake. CLO test for Helicobacter pylori done in 45 patients with recurrent ulcers were all positive, suggesting a strong association between H. pylori and ulcer recurrence.

Anti-Ulcer Agents↗