Chronic headaches due to occult hydrocephalus.
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Adult↗
Biomedical subjects
Richard J Edwards
Publications and source records attributed to Richard J Edwards.
Death and third ventriculostomy.
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Adolescent↗
A simple method for genome-wide screening for advantageous insertions of mobile DNAs in Escherichia coli.
Laboratory evolution in Escherichia coli has revealed that fitness typically increases in experimental populations. These changes are sometimes associated with changes in insertion sequence positions, some of which may themselves cause advantageous phenotypes. We have a novel and general method for identifying genes in Escherichia coli, whose knockout by mobile DNA insertions is beneficial in experimental evolution. Insertion sites in favored clones can be identified by reference to genomic information. We have implemented the method using modified Tn10 transposons bearing kanamycin and chloramphenicol resistance cassettes. Results are consistent across replicated experiments, demonstrating that the insertions are themselves creating selective advantages, rather than hitch-hiking with favorable base substitutions. The successful clones have subsequently been confirmed to have a fitness advantage relative to the progenitor strain. In experiments in shaking culture, we find that advantageous insertions usually fall in operons required in the pathways creating flagella. The method allows a rapid genome-wide screening for advantageous insertions in arbitrary environmental conditions. It allows investigation of the extent to which transient mutations generating environment-dependent selective advantages may help to explain the persistence of mobile DNAs in primarily clonal organisms, such as E. coli.
Chloramphenicol Resistance↗
Side-effects of risperidone therapy mimicking cerebrospinal fluid shunt malfunction: implications for clinical monitoring and management.
Risperidone is an atypical antipsychotic used in the treatment of several psychiatric disorders in both children and adults. We present two patients with hydrocephalus and learning difficulties who were admitted to the neurosurgical unit with a suspected cerebrospinal fluid shunt malfunction and raised intracranial pressure. They had both been commenced on risperidone for the treatment of aggressive outbursts. Twelve days after commencing risperidone, the first patient developed symptoms of headache, nausea, vomiting, drowsiness, lethargy and two episodes of collapse. The second patient presented with similar symptoms 4 days after his risperidone dose was increased. An unnecessary shunt exploration was averted in both cases when it was noted that the side-effect profile of risperidone mimicked exactly those of shunt malfunction. Discontinuation of the drug resulted in complete resolution of all symptoms within 72 h. Many patients with shunted hydrocephalus have associated developmental disorders that may warrant treatment with risperidone. Clinicians should be aware of the potential symptom overlap between shunt malfunction and risperidone side-effects in these patients.
Adult↗
Trigeminal neuralgia caused by microarteriovenous malformations of the trigeminal nerve root entry zone: symptomatic relief following complete excision of the lesion with nerve root preservation.
OBJECT: Within a series of 341 consecutive patients who underwent posterior fossa surgery for trigeminal neuralgia (TN), in five the cause was found to be a microarteriovenous malformation (micro-AVM) located in the region of the trigeminal nerve root entry zone (REZ). The surgical management and clinical outcomes of these cases are presented. METHODS: Patients were identified from a prospectively collected database of all cases of TN treated at one institution between 1980 and 2000. Presentation was clinically indistinguishable from TN caused by vascular compression. Preoperative imaging, including computerized tomography scanning (two cases) and magnetic resonance (MR) imaging and MR angiography (three cases), failed to demonstrate an AVM except for one case in which multiple abnormal vessels were identified in the trigeminal REZ on an MR image obtained using a 1.5-tesla magnet. All patients underwent a standard retromastoid craniotomy. In all cases a small AVM embedded in the trigeminal REZ was identified and completely excised, with preservation of the trigeminal nerve. All patients experienced immediate relief of pain following surgery. Postoperatively, in one patient a small pontine hematoma developed, resulting in permanent trigeminal nerve anesthesia in the V2 and V3 divisions. All patients were free from pain at a mean follow-up period of 30 months. CONCLUSIONS: These rare lesions are usually angiographically occult, but may sometimes be identifiable on high-resolution MR images. Total microsurgical resection with nerve preservation is possible, although operative complications are relatively common, reflecting the intimate association between these lesions and the pons. Complete resection is advised not only for symptom relief, but also to eliminate the theoretical risk of pontine hemorrhage.
Adult↗
Absolute net charge and the biological activity of oligopeptides.
Sequences of human proteins are frequently prepared as synthetic oligopeptides to assess their functional ability to act as compounds modulating pathways involving the parent protein. Our objective was to analyze a set of oligopeptides, to determine if their solubility or activity correlated with features of their primary sequence, or with features of properties inferred from three-dimensional structural models derived by conformational searches. We generated a conformational database for a set of 78 oligopeptides, derived from human proteins, and correlated their 3D structures with solubility and biological assay activity (as measured by platelet activation and inhibition). Parameters of these conformers (frequency of coil, frequency of turns, the degree of packing, and the energy) did not correlate with solubility, which was instead partly predicted by two measures obtained from primary sequence analysis, that is, the hydrophobic moment and the number of charges. The platelet activity of peptides was correlated with a parameter derived from the structural modeling; this was the second virial coefficient (a measure of the tendency for a structure to autoaggregate). This could be explained by an excess among the active peptides of those which had either a large number of positive charges or in some cases a large number of negative charges, with a corresponding deficit of peptides with a mixture of negative and positive charges. We subsequently determined that a panel of 523 commercially available (and biologically active) peptides shared this elevation of absolute net charge: there were significantly lower frequencies of peptides of mixed charges compared to expectations. We conclude that the design of biologically active peptides should consider favoring those with a higher absolute net charge.
Amino Acid Sequence↗