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Biomedical subjects

J R Nixon

Publications and source records attributed to J R Nixon.

At least 19 recordsLinked to original sources
PubMed1991

Synovial sarcoma: a clinicopathological review.

We have reviewed 20 cases of synovial sarcoma. The main clinical and pathological features of these cases are outlined. Typically these tumours arise in the leg in young adults with a long history before presentation and diagnosis. Clinical and radiological findings are unhelpful in making an early diagnosis. The five year survival rate in this series was 43%. The best guide to prognosis was assessment of mitotic activity. A high index of suspicion is required if the diagnosis is not to be missed. Adequate wide excision of the tumour is the mainstay of treatment.

Adolescent↗
PubMed1991

Survivorship analysis of the Ring hip arthroplasty.

Two hundred fifty-three Ring mark 2 metal-on-metal hip arthroplasties performed between 1968 and 1974 were evaluated using survivorship analysis. Using revision as the criterion for failure, the authors found a cumulative survival rate of 60.4% after 21 years. The results are compared with data from previous studies that used survivorship analysis for metal-on-metal hip arthroplasties, and it is shown that the Ring hip arthroplasty performed as well as the McKee-Farrar prosthesis and better than the Stanmore prosthesis.

Aged↗
PubMed1991

A review of 100 consecutive Richard's total knee replacements.

One hundred consecutive Richard's Maximum Contact (RMC) knee replacements were performed in Belfast between 1978 and 1982. Most of the 100 knees (86 patients) involved had been in severe pain, had marked stiffness or gross knee deformity, or were chairbound because of the knee. They were reviewed between five and eight and a half years (mean five years and eleven months) after operation. Thirteen patients (13 knees) died before review leaving eighty seven knees in 73 patients available for study. Using a modification of the British Orthopaedic Association knee function assessment chart, 26 knees (30%) were graded as excellent, 22 (25%) as good, 19 (22%) as fair and nine (10%) as poor. There were five implant failures, four the result of deep infection, one due to loosening. Six patients were chairbound at review and were also graded as failures. These results support the view that total knee replacement approaches the predictability and success of arthroplasty of the hip.

Adult↗
PubMed1991

A prosthesis augmentation device for the prevention of recurrent hip dislocation. A preliminary report.

At present, revision is the only standard option for cases of recurrent hip prosthesis dislocation. A device is described that contains the head of the femoral component, preventing dislocation, while only slightly restricting external rotation of the affected leg. The device can be inserted through a small incision, minimizing operation time. This device differs from others, e.g., the reversed acetabular cup, by being predrilled (with drill guide supplied), modular in design, and tailored to the dimensions of the cup site.

Aged↗
PubMed1989

Cerebral tuberous sclerosis: postmortem magnetic resonance imaging and pathologic anatomy.

We conducted postmortem magnetic resonance imaging (MRI) studies of five brains from patients with a clinical and pathologic diagnosis of tuberous sclerosis. Areas of prolonged T1 and T2 relaxation could easily be identified within the white matter subjacent to the cortical tubers despite formalin fixation and storage. The signal changes were identical to those reported in living patients with the disease. The detection of cortical tubers by MRI in two patients who were 34 and 35 years of age, respectively, at the time of death suggests that the signal changes on MRI are less affected by aging than are the low-attenuation changes on computed tomography, which are rarely identified in patients older than 27 years of age. Once the changes caused by fixation of tissues are considered, postmortem MRI is a viable investigative tool in studying tuberous sclerosis and other diseases, and it seems to correlate well with the MRI findings in living patients, as well as the gross and histopathologic changes seen at autopsy.

Adolescent↗
PubMed1989

Cerebral tuberous sclerosis: MR imaging.

Nineteen patients with a clinical diagnosis of tuberous sclerosis were examined with high-field-strength magnetic resonance (MR) imaging. Their ages ranged from 6 months to 12 years. In 17 cases, the MR examinations showed both subependymal nodules and multiple peripheral gyral lesions consistent with cortical tubers. Cortical tubers were more frequently demonstrated on spin-echo images obtained with a long repetition time (TR). Because the signal abnormality was located predominantly in the subcortical portion of the tubers, the terms "gyral core" and "sulcal island" were used to describe the patterns noted at MR imaging. Subependymal nodules were best seen on inversion-recovery or short TR spin-echo images, although hypointensity within the nodules consistent with calcification was present in 14 patients and was most evident on long TR spin-echo images. Computed tomographic (CT) scans that had been obtained within 3 years of MR images were available for 13 patients. Intracranial calcification was more accurately diagnosed with CT. However, MR imaging is more sensitive than CT in the detection of gyral tubers and, thus, may be better for screening family members and others in whom tuberous sclerosis is a possibility.

Brain↗
PubMed1987

Trapping of chemical carcinogens with magnetic polyethyleneimine microcapsules: II. Effect of membrane and reactant structures.

Effects of the membrane structure and reactant type on the trapping of carcinogens and other reactive species by semipermeable magnetic polyethyleneimine (PEI) microcapsules are investigated. A series of these microcapsules with poly(hexamethyleneterephthalamide) membranes was prepared by interfacial polymerization with an 8-fold variation of hexamethylenediamine concentration in the aqueous emulsion phase. Although little change was found in the encapsulation of PEI (within the microcapsule core) and magnetite, the microcapsule membrane showed a 6-fold alteration in regard to mass and associated PEI. All the microcapsule types tested were capable of trapping N-methyl-N-nitrosourea and fluorescein isothiocyanate as covalent-binding probes, and eosin and tetrasodium copper phthalocyanine tetrasulfonic acid (CPTS) as ionic-binding probes. Very rapid penetration and reaction of eosin and CPTS with the membranes was demonstrated, with apparent saturation of membrane binding affecting the overall trapping. Differences in the site and quantity of binding were ascribed to the following factors: the core:membrane distribution of incorporated PEI; the probe molecular weight; the reaction or adsorption of the probes with the microcapsule membrane; the probe stability in aqueous solution; and the amount of probe used. These probes represent the chemical-physical features of many known carcinogens or metabolites; together with previous data, these results indicate the potential usefulness of this type of microcapsule for trapping carcinogens (and their metabolites) as covalently or ionically bound products.

Capsules↗
PubMed1987

Trapping of chemical carcinogens with magnetic polyethyleneimine microcapsules: III. In vivo trapping of electrophiles from N-methyl-N-nitrosourea and recovery from feces.

The use of semipermeable magnetic polyethyleneimine (PEI) microcapsules for trapping carcinogens in vivo is described. After intragastric administration to rodents, up to 40% of the microcapsules were extracted magnetically from fecal suspensions, with most recovered in the first 24 h after administration. The mean diameter of the recovered microcapsule population was in some cases larger than that administered. The changes in size distribution and incomplete recovery could be ascribed to the magnetic extraction technique rather than loss or destruction of microcapsules in vivo. By contrast, magnetic hemoglobin microcapsules were not stable in vivo and were recovered in very low yields. An important factor determining the recovery of administered PEI microcapsules was the amount of encapsulated magnetite. Microcapsules administered intragastrically to rodents trapped up to 0.02% of an intragastric dose of N-[methyl-14C]-N-nitrosourea (1). Binding was dose dependent with the limiting factor being the number of available binding sites; increasing the number of administered microcapsules accordingly increased the total amount of 1 bound by them. After administration of [14C--CH3]-derivatized microcapsules, the recovery from feces of microcapsule-associated radioactivity was 48-74%, up to twice the numerical recovery. Although this indicates that microencapsulated labeled core PEI was recovered, it could not be released upon sonication. This was due in part to an increased resistance of the microcapsules to sonication caused by GI tract transit that was probably due to nonspecific absorption of substances. Subsequent acid treatment released some radiolabeled core PEI, as indicated by precipitation with polyacrylic acid. Excreted microcapsules were found to have material adsorbed both on the outer membrane surface and also throughout the membrane.

Animals↗
PubMed1986

Trapping of chemical carcinogens with magnetic polyethyleneimine microcapsules: I. Microcapsule preparation and in vitro reactivity of encapsulated nucleophiles.

In this paper we describe the synthesis and characterization of magnetic microcapsules, intended for use in vivo, and which contain polyethyleneimine nucleophilic targets capable of trapping electrophilic carcinogens. The microcapsules, 15-50 microns in diameter, consist of a semipermeable cross-linked nylon membrane surrounding core polyethyleneimine and magnetite. These microcapsules can be readily manipulated and extracted from aqueous suspensions by magnetic fields. Core polyethyleneimine was released after membrane rupture by sonication. Magnetic hemoglobin microcapsules were also prepared but were unsuitable due to precipitation of hemoglobin within the core. Treatment by proteolytic enzymes that are present in the gastrointestinal tract caused microcapsule damage resulting in protein release, whereas polyethyleneimine microcapsules remained unaffected. After incubation with N-[methyl-14C]-N-nitrosourea, (1) the microcapsules retained covalently bound radiolabel, both in core polyethyleneimine and the microcapsule membrane. The efficiency of the binding of 1 was investigated by varying the polymer concentration during microcapsule manufacture. These type of microcapsules appear to have the desired properties for investigating carcinogen exposure in the mammalian gastrointestinal tract. They can be prepared easily and reproducibly, contain sufficient magnetite to allow their facile recovery from aqueous suspensions, are easily broken to release soluble core polyethyleneimine, and are stable to hydrolytic enzymes (trypsin) in vitro.

Carcinogens↗
PubMed1985

The effect of sodium lauryl sulphate, cetrimide and polysorbate 20 surfactants on complex coacervate volume and droplet size.

The effects of sodium lauryl sulphate (SLS), cetrimide and polysorbate 20 surfactants at concentrations below, at and above their critical micelle concentration (CMC) on the complex coacervation of varying concentrations of gelatin and acacia have been described. The overall effect of increasing concentration of SLS was to reduce the weight of coacervate formed. The addition of increasing concentrations of cetrimide produced an increase in the weight of coacervate. The two lowest concentrations of polysorbate 20 produced an increase in coacervate weight while the highest concentration, above the CMC, reduced the coacervate weight. These effects have been explained in terms of shielding of electrostatic attractions between gelatin and acacia polyions by adsorption of ionic and non-ionic surfactant molecules onto the polyions. The addition of surfactants influenced the size distribution of the coacervate droplets that were produced. It is believed that the reduction in interfacial tension by the aggregation of surfactant molecules at the coacervate-equilibrium liquid interface permitted the formation of smaller coacervate droplets.

Capsules↗
PubMed1980

Sustained-release dosage forms of microencapsulated isoniazid.

The preparation and release characteristics of microcapsules of isoniazid have been studied. The differing techniques of microencapsulation are assessed and the dissolution of drug from suspended and tableted microcapsules prepared using the chosen technique has been monitored for in vitro release.

Capsules↗