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Biomedical subjects

L S Wan

Publications and source records attributed to L S Wan.

At least 19 recordsLinked to original sources
PubMed2001

Endometrial brush biopsy for the diagnosis of endometrial cancer.

OBJECTIVE: To evaluate a new technique for processing endometrial cytology for the diagnosis and exclusion of endometrial cancer. STUDY DESIGN: All women at risk for endometrial cancer with clinical indications for endometrial biopsy were evaluated by endometrial brush biopsy (Tao Brush, Cook OB-GYN, Bloomington, Indiana) and Pipelle (Cooper Surgical, Shelton, Connecticut) endometrial biopsies during one office visit. Patients were followed longitudinally for the development of endometrial cancer or until undergoing dilatation and curettage or hysterectomy. All comparisons were analyzed using the chi 2 or t test. RESULTS: One hundred one women (mean age, 58; range, 35-86) had endometrial biopsies performed. Median follow-up was > 21 months (range, 3-29). Twenty-two had cancer or atypia, while the remaining had benign diagnoses. When correlated with the final diagnosis, the Tao Brush had 95.5% sensitivity and the Pipelle, 86% sensitivity. Both devices had 100% specificity, positive predictive value of 100% and negative predictive value of 98%. When the results of the two biopsy devices are considered together, the positive and negative predictive value for detecting or excluding endometrial cancer was 100%. Based on 1998 Medicare reimbursements, a simultaneous second office biopsy using the Tao brush could save approximately $67 per case as compared to a sonohistogram and much more when compared to dilatation and curettage. CONCLUSION: Endometrial cancer can be reliably detected and excluded using these two distinct office biopsy devices simultaneously during one office visit. In patients with an indication for endometrial biopsy, no further diagnostic test may be necessary to exclude or diagnose endometrial cancer or atypia.

Adult↗
PubMed2000

Role of base plate rotational speed in controlling spheroid size distribution and minimizing oversize particle formation during spheroid production by rotary processing.

The occurrence of material adhesion and formation of oversize particles in the product yield during one-pot spheroid production by rotary processing leads to a less predictable process and a decrease in the usable portion of the total product yield obtained from each production run. The use of variable speeds of the rotating frictional base plate during the spheronization run was investigated for achieving optimal spheroid production. When the base plate speed was increased during liquid addition, the greater centrifugal forces generated improved liquid distribution and the mixing of the moist powder mass, resulting in a decrease in the amount of oversize particles formed. When the base plate was maintained at a high speed throughout the run, the amount of oversize particles and mean spheroid size increased, and a greater "between batch" mean spheroid size variability was also observed. The findings showed that, when higher speeds were used, the residence time must be adjusted accordingly to avoid excessive coalescence and growth while maintaining even liquid distribution. A "low-high-low" speed variation during rotary processing may be used to produce spheroids with a narrow size distribution and with a minimal amount of oversize particles in the total product yield.

Adsorption↗
PubMed2000

Endometrial biopsy using the Tao Brush method. A study of 50 women in a general gynecologic practice.

OBJECTIVE: To test whether the Tao Brush can retrieve sufficient endometrium for diagnosis and also to observe patients' tolerance of its use. STUDY DESIGN: Fifty women underwent Tao Brush sampling: 25 were sampled by Tao Brush alone, and the remainder were sampled by Pipelle immediately following. Patients' reactions to each method were observed. RESULTS: Pipelle currettes larger pieces of endometrium; the Tao Brush obtains smaller pieces. There was no discrepancy between Tao Brush and Pipelle except that Pipelle sampled two of five endometrial polyps, while the Tao Brush sampled none. There was less tissue insufficient for diagnosis with the Tao Brush (2%) than Pipelle (12%). Most patients did not show signs of distress during Tao Brush sampling but grimaced during Pipelle suction curettage. For each of the 16 patients in the second group, the Tao Brush was significantly less painful than Pipelle (P < .01). CONCLUSION: Our data suggest that the Tao Brush is an effective alternative endometrial sampler, causes less pain and produces less tissue insufficient for diagnosis than does the Pipelle. The CPT billing codes (58100) are the same for both the Pipelle and Tao Brush.

Adult↗
PubMed1999

Effect of off-bottom clearance on properties of pellets produced by melt pelletization.

This study examines the influence of off-bottom clearance on size and size distribution of pellets produced during melt pelletization at different postmelt impeller speeds and binder concentrations using lactose and polyethylene glycol. Melt pelletization of lactose powder 450 M in an 8-liter highshear mixer, the floor of which was made of polytetrafluoroethylene (PTFE), was carried out with polyethylene glycol 3000 as the meltable binder. Erosion of the PTFE floor of the mixer occurred with time of use and this caused a change in the off-bottom clearance. The findings showed that with a wider clearance, the size distribution of pellets was wider and pellets were much larger. These changes were the results of changes in the mixing intensity and impact frequency of the mass in relation to the eddies formed within the off-bottom clearance. The changes were not associated with the reduction in the circulating material load by entrapment into the off-bottom clearance. In the melt pelletization process, the quality of product was higher if the clearance was kept to a minimum. The off-bottom clearance was best measured at the beginning of each pelletization run because the PTFE floor of the mixer was prone to erosion.

Drug Compounding↗
PubMed1999

Effects of physical properties of PEG 6000 on pellets produced by melt pelletization.

This study examined the effects of polyethylene glycol (PEG) binders of different physical forms and from different commercial sources on size and size distribution of pellets produced. The meltable binders used were PEG 6000 in the form of flakes, and coarse and fine powders, and melt pelletization using lactose 450 M was carried out in an 8-liter high-shear mixer. Binder particle size, molecular weight, tack, and viscosity were determined. The results showed that the size and size distribution of the pellets obtained could not be explained by the binder particle size. The size and size distribution of the pellets were related to the tack and viscosity of the molten binders. PEGs used were labeled as the same nominal molecular weight grade, although their determined molecular weights could be quite different. Differences in tack and viscosity of the molten binders were associated with determined molecular weight of the binders. The melt pelletization process is sensitive to tack and viscosity of the molten binders. When different PEG brands of the same nominal molecular weight or different batches of the same brand are used in melt pelletization, it is important to characterize the tack and viscosity of the binders used. The effects of the physical form of binders on the pellet quality appear to be less important when compared to the influences of tack and viscosity of the molten binder.

Drug Compounding↗
PubMed1999

Mixed polymer coating for modified release from coated spheroids.

Modified-release drug spheroids coated with an aqueous mixture of high-viscosity hydroxypropylmethylcellulose (HPMC) and sodium carboxymethylcellulose (NaCMC) were formulated. The preparation of core drug spheroids and the coating procedures were performed using the rotary processor and a bottom-spray fluidized bed, respectively. Dissolution studies indicated that incorporation of suitable additives, such as poly(vinylpyrrolidone) (PVP) and poly(ethylene glycol) 400 (PEG) improved the flexibility and integrity of the coat layer by retarding the drug release. An increase in coating levels applied generally retarded the release rate of the drug. However, the ratio of HPMC to NaCMC in the mixed, plasticized polymeric coat played a more dominant role in determining the dissolution T50% values. The optimal ratio of HPMC to NaCMC for prolonged drug release was found to be 3:1, whereas an increase in the amount of NaCMC in the mixed polymer coat only increased drug release. The synergistic viscosity effect of HPMC and NaCMC in retarding drug release rate was greater in distilled water than in dissolution media of pH 1 and 7.2. Cross-sectional view of the scanning electron micrograph showed that all of the coated spheroids exhibited a well-fused, continuous, and distinct layer of coating film. The drug release kinetics followed a biexponential first-order kinetic model.

Carboxymethylcellulose Sodium↗
PubMed1992

Interaction of preservatives with macromolecules: Part I--Natural hydrocolloids.

Antibacterial activity of methyl-p-hydroxybenzoate against Ps. aeruginosa was evaluated in the presence of varying concentrations of acacia, tragacanth, sodium alginate, guar gum and carrageenin. All these hydrocolloids reduced the antibacterial activity to varying degrees. Tragacanth and guar gum inhibited the activity to a greater extent than acacia, sodium alginate and carrageenin. Hydrocolloids reduce the antibacterial activity of preservatives in two ways. Interaction of the preservative with hydrophilic macromolecules and subsequent reduction in the availability of preservative appears to be the predominant mechanism by which tragacanth and guar gum reduce the activity of methyl-p-hydroxybenzoate. Acacia, sodium alginate and carrageenin apparently act by offering physical protection to microbial cells from the action of the preservative. It is also probable that these hydrocolloids provide more favourable media for microbial growth thereby increasing the preservative requirement for adequate preservation.

Colloids↗
PubMed1991

Effect of surfactants on the antibacterial activity of preservatives.

Antibacterial activities of methyl-p-hydroxybenzoate, phenoxyethanol and chlorocresol against Pseudomonas aeruginosa were evaluated in the presence of varying concentrations of Tween 80. Below cmc level, the bactericidal activities increased with decrease in the surface tension values of Tween 80 solutions and with interfacial tension values of Tween 80 solution/liquid paraffin systems. Linear relationships were found to exist between the concentrations of each preservative required to reduce the microbial population by a factor 10(3) within 48 hours and the values of surface tension and interfacial tension respectively. Reduction in surface tension and interfacial tension would have increased the adsorption and uptake of preservatives by bacterial cells thereby killing the cells at a faster rate. Concentrations of Tween 80 above cmc also enhanced the antibacterial activities of these preservatives. This was attributed to the increase in the permeability of bacterial membranes to preservatives.

Microbial Sensitivity Tests↗
PubMed1991

Availability and activity of preservatives in emulsified systems.

Availability and activity of methyl-p-hydroxybenzoate, phenoxyethanol and chlorocresol in emulsions were studied by equilibrium dialysis and microbiological methods. Equation proposed by Bean and coworkers for calculating the availability of free preservatives in the aqueous phase of simple emulsion was also found to be applicable to modern emulsions composed of more than one oil and surfactant. The antimicrobial activity varied with the type of preservative and microorganism. Among the four test organisms, Pseudomonas aeruginosa and Staphylococcus aureus were more resistant to the various preservatives than Candida albicans and Aspergillus niger. The concentration of free preservative in the aqueous phase of the emulsion required to reduce the microbial population to the level specified in BP was found to be less than the concentration needed in distilled water indicating that the antimicrobial activity of the preservatives in emulsions is not entirely dependent on the concentration of their free form in the aqueous phase of emulsions.

Bacteria↗
PubMed1987

Measurement of the particle size of tablet excipients with the aid of video recording.

A method for the determination of the particle size of tablet excipients involving the use of video recording of microscopic examination of powders is described. The projected area of the particle profile was measured, and Feret's diameter and shape factors such as the elongation ratio, bulkiness factor, and surface factor were determined. Starch particles are the smallest among the excipients studied. Primojel particles are two to three times larger (Feret's diameter) and have up to 10 times greater projected areas. Particles of Avicel PH101, Ac-Di-Sol, Nymcel ZSD16 and ZSB10, and Polyplasdone XL have an irregular surface which results in large differences between the projected area diameter and the perimeter diameter. Particles of Nymcel and Ac-Di-Sol have the highest elongation ratio because of their cylindrical shape. Both Primojel and Starch have a low surface factor because of their spherical shape. This video-recording method is a simple system to observe, record, store, and retrieve particle-size data from microscopic examination of tablet excipients.

Excipients↗