Timothy E Hopkins | PubMed Health

PubMed2006

Functionality dependent olefin activity in acyclic diene metathesis polymerization: mass spectrometry characterization of amino acid functionalized olefins.

Mass spectrometry has become an essential tool in delineating the structural properties of a new series of amino acid functionalized acyclic diene metathesis (ADMET) polymers known as bioolefins. These measurements, coupled with the measurement of the polymers chemical and physical properties, assist in the determination of their utility as biomaterials. In the present study, a set of five polymers with different bulk size and electronic properties were chosen for structural analyses by MALDI-TOF, MALDI-FTICR, and DIOS-TOF. The obtained data show that due to the competing metathesis and isomerization during ADMET, depending on their structural properties, the olefins display different selectivity toward main metathesis or isomerized products.

Acids, Acyclic↗

PubMed2003

Rapid development of Chiari I malformation in an infant with Seckel syndrome and craniosynostosis. Case report and review of the literature.

To illustrate the rapidity with which a child can develop a severe, symptomatic Chiari I malformation, the authors present the case of a 3-month-old infant with Seckel syndrome (microcephaly, micrognathia, craniosynostosis, and multiple other abnormalities) and posterior sagittal and bilateral lambdoid synostosis. The infant underwent magnetic resonance (MR) imaging shortly after birth; the initial image demonstrated the cerebellar tonsils in the posterior fossa, with no herniation. He subsequently developed severe apneic episodes and bradycardia; repeated MR imaging at 3 months demonstrated severe tonsillar herniation with compression of the brainstem. The child underwent posterior fossa remodeling surgery, including release of the posterior sagittal and lambdoid sutures and decompression of the Chiari I malformation. The patient's apnea gradually improved; however, he died of complications of pneumonia and sepsis several weeks later. The authors identified from the literature 21 patients in whom there was a documented MR image or other neuroimage that did not reveal evidence of a Chiari I malformation, followed by a subsequent study with clear documentation of the presence of Chiari I malformation. The interval between the initial study and the development of the tonsillar herniation ranged from 11 days to 18.5 years. In most cases, a lumbar cerebrospinal fluid (CSF) diversion had been performed. This patient developed a severely symptomatic Chiari I malformation during a 3-month period. These reports illustrate that the Chiari I malformation can develop rapidly in the face of increased intracranial pressure, craniosynostosis, and spinal CSF diversion.

Abnormalities, Multiple↗