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Biomedical subjects

J L Ford

Publications and source records attributed to J L Ford.

At least 37 records · Page 2Linked to original sources
PubMed1999

Determination of the glass transition temperatures of some new methyl methacrylate copolymers using modulated temperature differential scanning calorimetry (MTDSC).

PURPOSE: The purpose of this study was to determine the glass transition temperatures of new graft copolymers using Modulated Temperature Differential Scanning Calorimetry (MTDSC), and to assess the differences between starch and cellulosic derivatives of methyl methacrylate and between two different drying methods used in their preparation. METHODS: Graft copolymers of methyl methacrylate were synthesized and dried by oven or freeze-drying. Surface area measurements and different thermal analysis techniques (Differential Scanning Calorimetry (DSC), Thermogravimetric analysis (TGA) and MTDSC) were used to characterize these copolymers. Results. DSC was not sensitive enough to identify the T(g)s of the copolymers, however they were clearly identifiable by MTDSC. T(g) values obtained may depend on the method of preparation that also altered their physical characteristics e.g. specific surface area. Cellulose derivatives showed lower T(g)s than starch derivatives. The results also depended on the drying method used, thus, freeze dried products had slightly lower T(g)s than oven dried products. CONCLUSIONS: MTDSC represents a useful thermal technique that allows the identification of glass transitions in these new copolymers with higher sensitivity and resolution than conventional DSC, separating the transition from overlapping phenomena such as decomposition or dehydration. The Tg of this new class of copolymers appeared to be dependent on polymer composition and drying method used.

Calorimetry, Differential Scanning↗
PubMed1999

Release of propranolol hydrochloride from matrix tablets containing sodium carboxymethylcellulose and hydroxypropylmethylcellulose.

Hydroxypropylmethylcellulose (HPMC) and three viscosity grades of sodium carboxymethylcellulose (NaCMC), namely NaCMC (Blanose 7H 4XF), NaCMC (Courlose P 800), and NaCMC (Courlose P 350), were investigated for their ability to provide a sustained release of propranolol hydrochloride from matrices. The rank order of release rate, in the absence of HPMC, was NaCMC (Blanose) < NaCMC P 800 < NaCMC P 350 for matrices containing 95-285 mg NaCMC, and was dependent on their viscosity grades. The effects of changing the ratio of HPMC to NaCMC (Blanose) and the drug/total polymer ratio were examined. The release rates decreased as the proportion of NaCMC in the matrices increased. Zero-order release of propranolol hydrochloride was obtained from matrices containing 285 mg 3:1 NaCMC (Blanose)/HPMC. Differential scanning calorimetry was used to quantify the moisture uptake by the polymers at 37 degrees C. Wafers containing NaCMC (Blanose) or 1:1 HPMC/NaCMC (Blanose) absorbed water similarly. A study of the erosion rates of matrices containing polymer only indicated that NaCMC (Blanose) eroded more quickly than HPMC. When propranolol hydrochloride was included in matrices containing NaCMC (Blanose), the erosion was reduced as a result of the insolubility of a complex formed between NaCMC and propranolol hydrochloride. The interaction between propranolol hydrochloride and NaCMC (Blanose) was confirmed by both dialysis and by monitoring the release of sodium ions from the matrices.

Adrenergic beta-Antagonists↗
PubMed1998

The effects of lag-time and dwell-time on the compaction properties of 1:1 paracetamol/microcrystalline cellulose tablets prepared by pre-compression and main compression.

The effects of lag-time and dwell-time on the compaction properties of tablets compressed from a 1:1 blend of paracetamol and microcrystalline cellulose have been examined using a compaction simulator. Increases in lag-times (from 0.06 to 0.53 s) resulted in small increases in the tensile strengths of the tablets when combinations of 80 and 160 MPa were used as the compression pressures. Further increases in lag-time did not alter the tablet strengths. When combinations of 240 and 320 MPa were used for pre-compression and main compression, the effects on the tensile strengths were more complex, partly because the high elastic recoveries of the tablets resulted in greater variability in the data. Increases in lag-times from 0.06 to 0.97 s resulted in an increase of between 12 and 28% in tensile strength. Longer lag-times (1.24 or 1.52 s) did not result in further increases in tensile strength. The application of a dwell-time of 0.26 s during pre-compression or main compression pressures of 80 and 160 MPa generally led to a decrease (14-22%) in tensile strength compared with tablets where no dwell-time was used. This was because of increases in both the elastic recoveries and elastic energies. Subsequent increases in dwell-time from 0.26 to 0.9 s resulted in increases in tablet strength compared with that obtained when no dwell-time was applied. The tensile strengths of tablets made with a pre-compression of 160 MPa then a main compression of 80 MPa were 11-33% higher than those of tablets made with a pre-compression of 80 MPa then a main compression of 160 MPa. This was because higher plastic energies and more plastic deformation occurred at the higher pre-compression. Generally, the application of dwell-time resulted in greater increases in tensile strengths than lag-time, which had less effect on the compaction properties.

Acetaminophen↗
PubMed1997

Local and systemic eosinophil activation in allergic fungal sinusitis.

BACKGROUND: In allergic fungal sinusitis diagnostic and monitoring criteria are not firmly established, and the role of eosinophils in pathogenesis is not clear. OBJECTIVE: To determine whether assessment of eosinophil activation by measurement of eosinophil cationic protein in serum or allergic mucin would be useful in distinguishing patients with allergic fungal sinusitis from patients with chronic sinusitis of other etiologies. METHODS: Thirteen patients referred for possible allergic fungal sinusitis were evaluated and given a definite allergic fungal sinusitis diagnosis if they met five of the following six criteria: (1) history and physical not suggesting another etiology, (2) sinus computed tomography consistent with allergic fungal sinusitis, (3) typical allergic mucin, (4) fungus isolated from allergic mucin, (5) presence of fungal-specific IgE, and (6) elevated total IgE. Eosinophil cationic protein, a marker of eosinophil activation, was measured in serum and allergic mucin. RESULTS: Nine patients met criteria for allergic fungal sinusitis. All patients had nasal polyps and were atopic. Eight of the patients had allergic rhinitis and three had asthma. Mean total IgE at surgery was 1,385 IU/mL. A fungus was isolated from allergic mucin of eight patients. All patients demonstrated fungal-specific IgE. Mean allergic mucin eosinophil cationic protein levels obtained at surgery were significantly higher in patients with allergic fungal sinusitis than in four patients not meeting strict diagnostic criteria, and in 16 control patients having sinus surgery for other indications. There was no significant difference in serum eosinophil cationic protein levels between the three groups. Serial allergic mucin eosinophil cationic protein levels appeared to correspond with disease activity in some allergic fungal sinusitis patients. CONCLUSIONS: Eosinophils in allergic mucin are activated. Measuring eosinophil cationic protein may be useful in diagnosis of allergic fungal sinusitis and in monitoring response to therapy.

Adolescent↗
PubMed1997

Studies on the interaction between water and (hydroxypropyl)methylcellulose.

The moisture sorption and desorption profiles of four different viscosity grades of (hydroxypropyl)methylcellulose (HPMC) 2208 (HPMC K100, HPMC K4M, HPMC K15M, and HPMC K100M) of different particle size fractions were analyzed according to the Young and Nelson equations. These equations describe three locations of the sorbed moisture: monolayer adsorption, externally adsorbed moisture, and internally absorbed moisture. The effects of particle size and viscosity grade of HPMC on the three locations of moisture showed that an increase in particle size generally resulted in a reduction in the amount of internal absorption and an increase in the amount of external adsorption. These changes were more apparent for HPMC K100 and HPMC K4M than for the higher viscosity grades. The lowest values of internally absorbed moisture were obtained for HPMC K100M. Changes in tensile strengths, mean yield pressures, and elastic recoveries of HPMC K4M tablets were explained in terms of the changes produced in the internally absorbed moisture and the externally adsorbed moisture. The amounts of nonfreezing and freezing water in samples exposed to moisture were determined from melting endotherms obtained by differential scanning calorimetry. Increases in the water:HPMC ratio resulted in increases in the enthalpies of water melting for the four viscosity grades of HPMC for the < 45 and 250-350 microns particle size fractions. The amount of nonfreezable water was unaffected by change in viscosity grade or particle size.

Calorimetry, Differential Scanning↗
PubMed1997

Examination of the compaction properties of a 1:1 acetaminophen:microcrystalline cellulose mixture using precompression and main compression.

The compaction properties of a 1:1 acetaminophen and microcrystalline cellulose (MCC) mixture have been studied using a compaction simulator to make tablets by single compression and by a combination of precompression and main compression. The tensile strengths of the tablets and the energies involved in the compressions were determined. The tensile strengths of the tablets increased with increases in single compression pressure from 80 to 400 MPa and as the total applied pressure increased from 80 MPa up to around 400 MPa when combinations of precompression and main compression pressures were used. The tablet porosity decreased with increase in main compression pressure while the tablet tensile strengths increased. At minimum tablet porosity, further increase in main compression pressure could no longer result in increase in tablet strengths. Tablets compressed with combinations of precompression and main compression were stronger (2.15 +/- 0.02 to 3.99 +/- 0.1 MPa) than those produced with single compression (0.73 +/- 0.01 to 3.09 +/- 0.05 MPa). The total gross energies of compression increased with an increase in pressure of both the precompression and main compression. The elastic energies during main compression increased with an increase in precompression pressure as the tablet exhibited greater elastic deformation and reduced plasticity on second compression. The increase in elastic energies during main compression may also be because elastic energy is recoverable and is independent of precompression. As the precompression pressure increased, the minimum tablet porosity was attained; hence, the plastic energy during main compression became smaller while the elastic energy increased. Thus, a combination of low precompression and main compression pressures of 160/80 MPa or 80/160 MPa are more advantageous in the tableting of the 1:1 acetaminophen:MCC than a high single compression pressure of 320 or 400 MPa.

Acetaminophen↗
PubMed1997

Effect of medium composition, agitation and the presence of EDTA on the antimicrobial activity of cryptolepine.

The antimicrobial activity of cryptolepine is influenced by the type of medium employed, agitation and the presence of non-inhibitory concentrations of EDTA. The use of Mueller-Hinton broth (MHB), iso-sensitest broth and tryptone soya broth (TSB) produced lower minimum inhibitory concentrations (MICs) for some of the test organisms compared with nutrient broth or yeast dextrose broth (YDB). For example, a fourfold drop in MIC was recorded for Saccharomyces cerevisiae in MHB compared with the same organism tested in YDB. Agitation of the broths during incubation nearly always produced lower MICs for the bacteria, an eightfold decrease in MIC being recorded for Escherichia coli cultured in nutrient broth with agitation compared with a statically maintained culture. A non-inhibitory concentration (10(-3) mol l-1) of disodium EDTA enhanced the antimicrobial activity of cryptolepine. Against E. coli NCTC 11,560, an eightfold decrease in MIC and minimum bactericidal concentration (MBC) was recorded when tested in the presence of EDTA.

Alkaloids↗
PubMed1997

Physical stability of solid dispersions containing triamterene or temazepam in polyethylene glycols.

The effect of storage on the physical stability of solid dispersions of triamterene or temazepam in polyethylene glycols was studied using differential scanning calorimetry (DSC), particle-size analysis and dissolution methods. The enthalpies of fusion of the carriers, without included drug and previously fused and crystallized, increased on storage. Analysis of similarly treated solid dispersions, containing either 10% temazepam or 10% triamterene, showed that each drug influenced the morphology of the polyethylene glycol (PEG). The enthalpies and melting points of the solidus components of the dispersions' carriers were initially reduced after preparation, but on storage these increased. The particle sizes of the drugs dispersed in the PEGs increased on storage. The changes in dissolution after storage of triamterene or temazepam dispersions were smaller for dispersions in PEG 1500 than for dispersions in PEGs of higher molecular weight (PEG 2000, PEG 4000 or PEG 6000) in which the reduction in dissolution was particularly marked during the first month of storage. The rank order of changes in dissolution were PEG 1500 < < PEG 2000 < PEG 4000 approximately PEG 6000.

Anti-Anxiety Agents↗
PubMed1996

Influence of pH on the release of propranolol hydrochloride from matrices containing hydroxypropylmethylcellulose K4M and carbopol 974.

The dissolution of propranolol hydrochloride from matrices containing hydroxypropylmethylcellulose K4M (HPMC K4M) and carbopol 974 has been investigated using 0.1 M hydrochloric acid or phosphate buffer at pH 4.5 or pH 7.5. In 0.1 M hydrochloric acid, HPMC K4M predominantly controlled release since carbopol has a low solubility at this pH. As the pH increased, the carbopol became increasingly ionized and interacted with propranolol hydrochloride to form an insoluble complex which retarded the release of the drug. In addition, the nature of the interaction between carbopol 974 and HPMC K4M altered. DSC and viscometric studies indicated that the two polymers contributed synergistically to the gel network at pH 7.5. Thus at pH 7.5 polymers contributed to matrix integrity and to the control of drug release.

Acrylic Resins↗
PubMed1996

The influence of moisture content on the consolidation properties of hydroxypropylmethylcellulose K4M (HPMC 2208).

The effect of moisture content, compression speed and compression force on the compaction properties of HPMC K4M has been evaluated. As the moisture content increased from 0 to 14.9% w/w, the thickness of HPMC K4M compacts increased at constant compression force and speed. This increase in moisture content also resulted in a marked increase in the tensile strength of the tablets. At a speed of 15 mm s-1 and force of 10 kN, as the moisture content increased from 0 to 14.9% w/w, the tensile strengths increased from 1.34 to 8.54 Mpa. Equivalent tensile strengths could be obtained with less compression force as the moisture content in the polymer was increased. Increasing the compression speed generally decreased the tensile strength of HPMC K4M tablets. The dependence of tablet porosity and tensile strength on compression speeds showed that HPMC K4M is consolidated by plastic deformation. At all compression speeds, an increase in moisture content reduced the percentage elastic recovery of HPMC compacts due to greater tablet consolidation. The lowest elastic recovery (1.18%) was found for tablets made at 15 mm s-1 and 5 kN, containing 14.9% w/w moisture content.

Analysis of Variance↗
PubMed1996

The effect of moisture on the heckel and energy analysis of hydroxypropylmethylcellulose 2208 (HPMC K4M).

The influence of moisture content on the Heckel analysis, energy analysis and strain-rate sensitivity of hydroxyproplymethylcellulose 2208 (HPMC K4M) has been evaluated. An increase in moisture content from 0 to 14.9% w/w decreased the mean yield pressure, probably due to a plasticizing effect of moisture which reduced the resistance of particles to deformation. For each moisture content (0, 2.2, 3.8, 5.9, 9.6 and 14.9% w/w), the initial relative density and the extrapolated density from the linear portion of the Heckel plot, tended to decrease with increasing compression speed. Minor changes were observed in the initial relative density due to changes in the moisture content. The strain-rate sensitivity increased from 21.6 to 50.7% as the moisture content increased from 0 to 14.9% w/w, indicating that the plasticity of HPMC increased with increase in moisture content, whereas increase in moisture content from 0 to 14.9% w/w decreased the plastic energy. Increase in compression force or speed of compaction increased both the plastic and elastic energies. An increase in moisture content from 0 to 5.9% w/w slightly reduced the elastic energy but above 5.9% moisture content the elastic energy was unaffected by the moisture content.

Analysis of Variance↗
PubMed1996

Solidification studies of polyethylene glycols, gelucire 44/14 or their dispersions with triamterene or temazepam.

The solidification of polyethylene glycols (PEG 1500, PEG 2000, PEG 4000, PEG 6000), gelucire 44/14 or their dispersions containing triamterene or temazepam were studied to assess the feasibility of using these dispersions to liquid-fill hard gelatin capsules. Solidification from melts, investigated by differential scanning calorimetry using cooling cycles, showed a tendency of the drugs, carriers or their dispersions to supercool. The degree of supercooling depended on the rate of cooling, the drug content and, for the PEGs, on the molecular weight. PEG 1500 and PEG 2000 gave one morphological form, irrespective of cooling rate; PEG 4000 and PEG 6000 solidified into at least two forms, depending on the cooling rate. Incorporation of drugs affected the morphology of the PEGs during solidification. The rate of crystal growth was, furthermore, influenced by the fusion temperature, molecular weight and the degree of supercooling. The degree of crystallinity, as measured by the enthalpies of solidification, decreased with increasing cooling rate. The results show that reducing the rate of solidification could lead to incomplete solidification, giving products that are liable to change on storage.

Calorimetry, Differential Scanning↗
PubMed1996

Poly-(D,L-lactic acid) microspheres incorporating histological dyes for intra-pulmonary histopathological investigations.

Polylactic acid (PLA) microspheres incorporating fluorescein as a histological marker have been prepared and used as a model for the testing of inhaled PLA microspheres (2-5 microns) in the lung. PLA microspheres (20 mg) were delivered to rabbits in the form of a saline nebulization. The distribution pattern within the pulmonary system showed that the fluorescein-labelled microspheres were distributed about the four lobes in discrete groups. The comparative numbers of these groups showed a trend towards a reduced concentration in the lower lobes. Subsequent histological examination revealed that the microsphere-treated lungs had been significantly damaged after 24 h. Histological damage was assessed in terms of pulmonary haemorrhage, eosinophilia and neutrophil infiltration.

Administration, Inhalation↗
PubMed1995

Laboratory evaluation of a commercial immunoassay for fire ant allergen-specific IgE antibodies.

BACKGROUND: In vitro testing for fire ant sensitization would be useful for research purposes and in special clinical situations. METHODS: Laboratory performance of a commercial assay (Pharmacia CAP System, [PCS]), for specific IgE to Solenopsis invicta whole body extract was studied in 46 persons. Assay results were compared with those of venom skin testing, RAST, and ELISA. The manufacturer's global cutoffs were compared with cutoffs set by using methods derived from analytical detection limit theory. RESULTS: Thirty-two study subjects had positive skin test results, and 14 had negative results. Raw PCS data demonstrated a high level of correlation with RAST (rho = 0.941) and ELISA (rho = 0.931), and showed good correlation with skin testing (rho = -0.769). Analysis of binormal receiver operating characteristic curves, using skin test results as the reference standard, demonstrated no difference in performance among the three assays. The fixed global quantitative cutoff of 0.35 kUa/L was relatively insensitive. Use of the manufacturer's qualitative alternate scoring method cutoff substantially increased sensitivity without loss of specificity, as did lower limit of detection set by use of diluent. CONCLUSIONS: In situations in which skin testing for fire ant sensitization is not feasible, PCS appears to be an acceptable in vitro alternative method for determination of fire ant allergen-specific IgE.

Allergens↗
PubMed1995

The effect of cryptolepine on the morphology and survival of Escherichia coli, Candida albicans and Saccharomyces cerevisiae.

The antimicrobial activity of the indoloquinoline alkaloid, cryptolepine, isolated from Cryptolepis sanguinolenta (Fam. Periplocaceae) was determined against selected micro-organisms. The minimum inhibitory concentration (MIC) ranges obtained, expressed as microgram ml-1, were: 5-10 for Saccharomyces cerevisiae NCPF 3139; 10-20 for S. cerevisiae NCPF 3178; 20-40 for Escherichia coli NCTC 10418; 40-80 for E. coli NCTC 11560, Candida albicans ATCC 10231 and C. tropicalis NCPF; and 80-160 for C. albicans NCPF 3242 and NCPF 3262. Biocidal effects were noted at concentrations 2-4 times those of the MIC of the alkaloid following challenge with 10(6) cfu ml-1 of micro-organisms. Time-kill studies showed a reduction in viable count from 10(6) to < 10 cfu ml-1 in 4 h in C. albicans ATCC 10231 exposed to 320 micrograms ml-1 of the agent; 3 log cycle reductions were recorded for the 6 h counts of E. coli NCTC 10418 and S. cerevisiae NCPF 3139 exposed to 40 micrograms ml-1 and 160 micrograms ml-1 of the alkaloid respectively. These results were consistent with findings using scanning electron microscopy. Exposure of cells to biocidal concentrations of cryptolepine produced filamentation prior to lysis in E. coli NCTC 10418 and extreme disturbance of surface structure, including partial and total collapse, followed by lysis in C. albicans ATCC 10231 and S. cerevisiae NCPF 3139.

Alkaloids↗
PubMed1994

Development of an enzyme-linked immunosorbent assay for measurement of fire ant venom-specific IgE.

An enzyme-linked immunosorbent assay (ELISA) was developed for in vitro measurement of IgE specific for Solenopsis invicta venom. Enhanced binding microtiter plates were coated with S. invicta venom protein and incubated with sera from fire ant allergic patients and control subjects. Bound IgE was tagged with peroxidase-conjugated monoclonal anti-IgE and quantitated with the substrate/indicator system H2O2/tetramethylbenzidine. Absorbance (620 nm) represented venom-specific IgE values. The ELISA correlated well with the imported fire ant venom RAST (r = .87, P < .0001). Using skin test reactivity as the standard measure of venom-specific IgE, the venom ELISA appeared to be a sensitive in vitro assay comparable to venom RAST. ELISA is less expensive than RAST and does not require licensing or handling of radioisotopes.

Adult↗
PubMed1993

The homeless: help from hotels and restaurants.

Specific examples and information are given to service providers to address the needs of homeless people. Together nurses and restaurant and hotel managers combined their expertise to assist local agencies in their community kitchens and shelters.

Community Health Services↗