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Biomedical subjects

P Lewis

Publications and source records attributed to P Lewis.

At least 109 records · Page 6Linked to original sources
PubMed1994

Whole-body 18F-fluorodeoxyglucose positron emission tomography in preoperative evaluation of lung cancer.

Despite use of computed tomography, some lung cancer patients are found to have unresectable disease at surgery, or they present early with metastases. We studied whether whole-body positron emission tomography (PET) with 18F-fluorodeoxyglucose (18FDG) would improve the preoperative detection of metastases. We retrospectively analysed 34 patients with "operable" non-small-cell lung cancer who underwent 18FDG PET after routine assessment. Management changes produced by the PET scan and confirmatory tests were reviewed. PET identified unsuspected malignant lesions in 10 (29%) patients. Management changes occurred in 14 (41%), including 6 (18%) patients who were changed to non-surgical therapy. These data suggest that whole-body 18FDG PET improves preoperative assessment of lung cancer patients.

Aged↗
PubMed1994

Transient epileptic amnesia differentiated from psychogenic "fugue": neuropsychological, EEG, and PET findings.

A patient had repeated episodes of transient loss of memory, which had been attributed to psychogenic causes. Preservation of his sense of personal identity and the presence of repetitive questioning indicated an organic basis, however, and the multiplicity of the attacks and their brief duration suggested an epileptic aetiology. Although three standard EEGs, CT and MRI were all normal, two sleep EEGs confirmed bilateral foci in the temporal lobes. The attacks responded to an anticonvulsant. A fluoro-deoxyglucose PET scan, performed a few months after the most recent attack, was normal. The patient also had impaired anterograde memory that persisted six months after recovery from the acute attacks.

Amnesia↗
PubMed1994

Testing the limits of freedom of contract: the commercialization of reproductive materials and services.

This article examines the cases for and against commercializing, or "commodifying," reproductive materials and services. Using a supply/demand third-party framework, three basic scenarios in which commercial-exchange relationships may be possible--exchange of gametes and zygotes, exchange of gestational services, and exchange of fetal material--and the major parties of interest, or stakeholders, are identified. The study sketches the liberal, essentialist, and radical contingency theories that shape the debate over the commercialization of reproductive materials and services. The article then attempts to derive some basic governing principles that reflect as much common ground as possible amongst these various normative perspectives, while recognizing that complete reconciliation is impossible. Taken together, these principles are designed to reflect a strategy of "constrained commodification," where commercialization or commodification, that is, financial remuneration, plays a relatively neutral role in the utilization of reproductive materials and services. In light of these principles, the article concludes by sketching legal and regulatory regimes with respect to the exchange of gametes and zygotes, gestational services, and fetal tissue.

Aborted Fetus↗
PubMed1994

Posteromedial tibial polyethylene failure in total knee replacements.

This report details 16 cases of focal posteromedial tibial polyethylene wear and failure after total knee arthroplasty. This wear phenomenon was associated with an external rotatory subluxation of the tibial component relative to the femoral component. Failure occurred in ten Miller Galante 1, three Porous Coated Anatomic, two Kinematic, and one Press-Fit Condylar knee designs at a mean time of 45 months from their implantation. With this type of failure, there did not seem to be a relationship with metal type, fixation, polyethylene manufacturing method, or polyethylene thickness. A relatively flat design of the tibial articular surface was common to all of these components. In certain patients this articular design may allow excessive component translation, which leads to polyethylene deformity, wear, and subluxation. Some methods for preventing this failure mode are reported here.

Aged↗
PubMed1993

A nuclear localization signal within HIV-1 matrix protein that governs infection of non-dividing cells.

Permissiveness of the host cell to productive infection by oncoretroviruses is cell-cycle dependent, and nuclear localization of viral nucleoprotein preintegration complexes will occur only after cells have passed through mitosis. In contrast, establishment of an integrated provirus after infection by the lentivirus HIV-1 is independent of host cell proliferation. The ability of HIV-1 to replicate in non-dividing cells is partly accounted for by the karyophilic properties of the viral preintegration complex which, after virus infection, is actively transported to the host cell nucleus. Here we report that the gag matrix protein of HIV-1 contains a nuclear localization sequence which, when conjugated to a heterologous protein, directs its nuclear import. In addition, HIV-1 mutants containing amino-acid substitutions in this nuclear localization signal integrate and replicate within dividing but not growth-arrested cells, and thus display a phenotype more representative of an oncoretrovirus.

Amino Acid Sequence↗
PubMed1993

Temozolomide: a new oral cytotoxic chemotherapeutic agent with promising activity against primary brain tumours.

Temozolomide, a new oral cytotoxic agent, has been given to 28 patients with primary brain tumours. Treatment was given at a dose of 150 mg/m2/day for 5 days (i.e. total dose 750 mg/m2) escalating, if no significant myelosuppression was noted on day 22, to 200 mg/m2/day for 5 days (i.e. total dose 1000 mg/m2) for subsequent courses at 4 week intervals. A major improvement in computer tomography (CT) scan was noted in 5/10 patients with astrocytomas recurrent after radiotherapy, with a major clinical improvement but minor improvement on CT scan in one further patient. Reduction in the size of the CT lesion was also observed in 4/7 patients with newly diagnosed high grade astrocytomas given 2-3 courses of temozolomide prior to irradiation. 1 patient with recurrent medulloblastoma had a clinical response in bone metastases. Temozolomide was well tolerated with little subjective toxicity and usually predictable myelosuppression and is a promising new drug in the treatment of primary brain tumours.

Administration, Oral↗
PubMed1993

A combined urodynamic and continence unit--a review of the first 19 years.

We have completed a 19-year audit of all patients referred to the urodynamic/continence unit since its inception in 1972 and their subsequent clinical management; a total of 20,437 patients were referred, increasing from 51 in the first year to 1564 in 1990. Although the annual number of referrals has remained constant for the last 8 years, the need for more complex urodynamic assessment such as video-cystourethrography has increased from 5% (56/1164) in 1981 to 25% (385/1564) in 1990. The number of out-patient attendances to medical, physiotherapy and continence clinics has also increased over that period. We conclude that the number of referrals represents increasing recognition of the value of urodynamic assessment. Accurate diagnosis leads to more effective treatment, whether surgical, medical or conservative. Some methods of diagnosis are complex and suitable only for a tertiary referral centre.

Ambulatory Care↗
PubMed1993

Generalization of a tactile stimulus in horses.

Using horses, we investigated the control of operant behavior by a tactile stimulus (the training stimulus) and the generalization of behavior to six other similar test stimuli. In a stall, the experimenters mounted a response panel in the doorway. Located on this panel were a response lever and a grain dispenser. The experimenters secured a tactile-stimulus belt to the horse's back. The stimulus belt was constructed by mounting seven solenoids along a piece of burlap in a manner that allowed each to provide the delivery of a tactile stimulus, a repetitive light tapping, at different locations (spaced 10.0 cm apart) along the horse's back. Two preliminary steps were necessary before generalization testing: training a measurable response (lip pressing) and training on several reinforcement schedules in the presence of a training stimulus (tapping by one of the solenoids). We then gave each horse two generalization test sessions. Results indicated that the horses' behavior was effectively controlled by the training stimulus. Horses made the greatest number of responses to the training stimulus, and the tendency to respond to the other test stimuli diminished as the stimuli became farther away from the training stimulus. These findings are discussed in the context of behavioral principles and their relevance to the training of horses.

Animals↗
PubMed1992

Human immunodeficiency virus infection of cells arrested in the cell cycle.

Cell proliferation is necessary for proviral integration and productive infection of most retroviruses. Nevertheless, the human immunodeficiency virus (HIV) can infect non-dividing macrophages. This ability to grow in non-dividing cells is not specific to macrophages because, as we show here, CD4+ HeLa cells arrested at stage G2 of the cell cycle can be infected by HIV-1. Proliferation is necessary for these same cells to be infected by a murine retrovirus, MuLV. HIV-1 integrates into the arrested cell DNA and produces viral RNA and protein in a pattern similar to that in normal cells. In addition, our data suggest that the ability to infect non-dividing cells is due to one of the HIV-1 core virion proteins. HIV infection of non-dividing cells distinguishes lentiviruses from other retroviruses and is likely to be important in the natural history of HIV infection.

Base Sequence↗
PubMed1992

Comparison of plain with pH-adjusted bupivacaine with hyaluronidase for peribulbar block.

Fifty patients scheduled for cataract surgery under peribulbar block were randomised to receive either plain (pH 5.4) or pH-adjusted (pH 6.8 range 6.7-6.9) 0.75% bupivacaine. Hyaluronidase was added to both solutions prior to peribulbar block. The time of onset of akinesia of the globe and the need for supplementary injections were recorded by an independent observer. Patients who returned for surgery to the second eye received the alternative local anaesthetic solution for the second peribulbar block. The relative efficacy of the different anaesthetic solutions was compared in patients who underwent unilateral surgery (Group A, n = 50). In 12 patients (Group B) who underwent bilateral surgery, direct comparisons between eyes in the same patient were possible. In both groups of patients, eyes receiving peribulbar block with the pH-adjusted solution showed a shorter time to partial akinesia of the globe (P less than 0.05). However, there was no difference between the solutions in the time to complete akinesia of the globe, but the number of supplementary injections required for an effective block with the pH-adjusted solution was increased. Onset time to akinesia of the lateral and superior rectus muscles was shortened in patients receiving the pH-adjusted solution but there were minimal effects on the medial and inferior recti.

Anesthesia, Local↗