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Biomedical subjects

R Thomas

Publications and source records attributed to R Thomas.

At least 181 records · Page 10Linked to original sources
PubMed2000

Use of pattern standard deviation instead of corrected pattern standard deviation in Anderson's criteria.

PURPOSE: To determine whether the use of pattern standard deviation instead of corrected pattern standard deviation, as part of Anderson's criteria, makes a difference in categorizing a single field printout using the full threshold strategy on the Humphrey's Field Analyzer. MATERIALS AND METHODS: Forty-eight patients with glaucomatous field defects of varying severity underwent full threshold perimetry on the Humphrey's Field Analyzer. The third field of one eye was used for the study. The agreement between CPSD and PSD alone was determined. Each field was then categorized using Anderson's criteria first using CPSD and then PSD. The kappa statistic was used to determine agreement in both situations. RESULTS: The agreement between CPSD and PSD alone, as determined by kappa, was 0.77. The kappa statistic for categorization using Anderson's criteria was 0.82; the weighted kappa was 0.92. CONCLUSION: There was almost perfect agreement using the PSD instead of CPSD as part of Anderson's criteria. This substitution seems valid for the spectrum of field defects used in this series, at least for the full threshold programs.

Adult↗
PubMed2000

The clinical development of 9-aminocamptothecin.

9-Aminocamptothecin (9-AC) is a topoisomerase I-targeting agent first synthesized by Wani and Wall in 1986. Because of its potent in vitro effects and promising preclinical activity in colorectal cancer animal models, it was designated a high-priority compound for further drug development by the NCI. In 1993, 9-AC first entered clinical trials as a 72-hour intravenous (i.v.) infusion. Predictable myelosuppression was the major dose-limiting toxicity, and pharmacokinetic studies showed a relatively short plasma half-life and unstable lactone ring. Unfortunately, phase II studies using this schedule showed minimal or no activity in tumors such as colorectal and lung cancer. Modest activity was observed in ovarian cancer and in refractory lymphomas. Efforts to improve systemic drug exposure by utilizing alternative schedules of administration of 9-AC such as prolonged, continuous intravenous infusions have also been tested. However, phase II studies of 120-hour weekly infusions of 9-AC have not shown improved activity against solid tumors such as colorectal cancer. More recently, a daily times 5 days i.v. administration schedule has been tested. Currently, further development of intravenously administered 9-AC for the treatment of colorectal cancer is not promising. Thus, topotecan and irinotecan remain the only two successfully developed topoisomerase I-targeting drugs in the United States. This experience with 9-AC raises important questions regarding how to best select new topoisomerase I-targeting drugs for future clinical development.

Animals↗
PubMed2000

Who answers 'willingness to pay' questions?

OBJECTIVES: The objectives of this study were twofold. The first was to compare characteristics of responders and non-responders to a survey of women attending a bone mineral density screening service in Aberdeen concerned with the screening process which contained questions on attenders' willingness to pay (WTP) and willingness to wait (WTW) for screening. The second objective was to compare the characteristics of those responding to either the WTP or the WTW questions relative to those who responded to both. METHODS: After receiving a scan, women completed the questionnaire at the clinic or returned it by post. Logistic regression analysis was used to compare the characteristics of the responders and non-responders. RESULTS: Those who smoked were less likely to return the questionnaire, whilst those who drank alcohol were more likely to return it. The majority of respondents answered both WTP and WTW questions. The proportions responding to the WTW and WTP questions were 93.2% and 81.5% for the two questions, respectively (95% confidence interval of difference = 9.4% to 13.9%). The only result which was statistically significant at the 1% level showed that, relative to those who answered the WTW but not the WTP questions, those who answered both were more likely to be older when they left full-time education. A weaker statistical association (at the 5% level) revealed that those who were older when leaving full-time education were more likely to answer a WTP question than not. CONCLUSIONS: WTP questions seem to be less acceptable to those who leave full-time education earlier. Analysts may need to account for this in future studies. Whether such results can be replicated and reasons for non-response should be investigated.

Bone Density↗
PubMed2000

Human papillomavirus type, proliferative activity, and p53: potential markers of aggressive papillomatosis.

CONTEXT: The predictive value of nuclear proliferation antigen (Ki-67), tumor suppressor gene product p53, and human papillomavirus type has not been evaluated for outcome of laryngeal papilloma. OBJECTIVE: This study was designed to determine whether immunohistochemical analysis of Ki-67 and p53 and human papillomavirus typing by polymerase chain reaction are able to identify patients with a more aggressive course of laryngeal papillomatosis. DESIGN: Immunohistochemistry and polymerase chain reaction were performed on archival, paraffin-embedded, laryngeal papillomatosis biopsy specimens at the time of diagnosis, at an intermediate time during treatment, and at the last procedure available. Staining indexes for Ki-67 and p53 were determined, and human papillomavirus type was analyzed for all biopsies. PATIENTS: Twelve patients with recurrent laryngeal papillomatosis for at least 5 years were selected from patients treated at our institution during the last 20 years. MAIN OUTCOME MEASURES: Separate analyses were conducted comparing average Ki-67 and p53 indexes against disease outcome, viral type, or average number of procedures per year. Associations were analyzed between virus type, average number of procedures per year, outcome, and histology. RESULTS: No statistically significant associations were noted in Ki-67 or p53 indexes and outcome. Weak associations were noted for p53 indexes and procedures per year and virus type. Weak associations also were noted between virus type and development of neoplasia. CONCLUSIONS: Our observations suggest that human papillomavirus typing may be helpful in identifying patients with aggressive recurrent laryngeal papillomatosis. The weak association between p53 indexes and procedures per year and virus type may have some predictive value in identifying aggressive lesions.

Biomarkers, Tumor↗
PubMed2000

Percutaneous ablation of caliceal diverticulum: long-term followup.

PURPOSE: A caliceal diverticulum is a nonsecretory cavity that serves as a conduit for urinary stasis and its ensuing complications. Indications for intervention and modes of therapy are controversial. We report a series of patients treated with a percutaneous endourological approach to ablation of the diverticular cavity. MATERIALS AND METHODS: A total of 14 patients underwent percutaneous ablation of a caliceal diverticulum for flank pain a mean of 15.5 months in duration. These caliceal diverticula were associated with urinary tract infection in 43% of cases and/or renal calculi in 78%. Mean calculus diameter was 10.2 mm. and mean diverticular diameter was 10.9 mm. An open ended ureteral catheter was placed into the renal pelvis via cystoscopy. Retrograde instillation of radiopaque contrast medium facilitated the localization of a percutaneous renal puncture made directly into the caliceal diverticulum. A flexible tip guide wire was coiled in the diverticulum, and no effort was made to traverse the infundibulum and establish continuity with the remainder of the collecting system. Tract dilation into the caliceal diverticulum was performed, and percutaneous stone fragmentation and extraction were accomplished. The lining of the caliceal diverticulum was electrocauterized using a roller ball electrode. A balloon nephrostomy tube consisting of a Foley catheter with the tip cut off was positioned into the diverticulum. An indwelling ureteral stent was placed and a Foley catheter provided bladder drainage for 48 hours to maintain a low pressure system. The nephrostomy tube was removed after 24 to 48 hours and the ureteral stent was removed after 2 to 4 weeks. RESULTS: Mean operative time was 162 minutes and mean hospital stay was 2.3 days. Obliteration of the diverticular infundibulum and cavity was documented by contrast radiography (excretory urography or retrograde pyelography), and noncontrast and contrast enhanced computerized tomography, respectively, in all 14 patients. No patients have had recurrent symptoms, calculi or urinary tract infection at a mean 38-month followup. CONCLUSIONS: Percutaneous electrocautery ablation of caliceal diverticula without cannulation or dilation of the diverticular infundibulum represents a safe and effective mode of therapy. Careful patient selection and preparation optimize the efficacy of this technique.

Adolescent↗
PubMed2000

Differential expression of osteonectin/SPARC during human prostate cancer progression.

The precise mechanism(s) involved in invasion and metastasis of prostate cancer (CaP) is poorly understood. Osteonectin [ON (also known as SPARC or BM-40)] is an antiadhesive protein known to be involved in cell-matrix interactions, migration, and angiogenesis. In this report, we studied the expression of ON in human prostate cell lines, primary tumors, and metastatic foci of CaP. Reverse transcription-PCR and nonradioactive in situ hybridization (ISH) techniques were used to determine ON gene expression. Immunohistochemistry was carried out using the polyclonal antibody LF37 and/or the monoclonal antibody ON-mAb. Low to moderate levels of ON mRNA and protein were observed in glandular epithelial cells of normal tissue as well as a few primary CaPs. However, high levels of ON mRNA and protein were observed in most of the CaP metastatic foci, both osseous and nonosseous. This correlated well with our findings that multiple different CaP cell lines including four CaP cell lines derived from metastases show high levels of ON gene expression. Furthermore, ISH analyses and cell-specific reverse transcription-PCR evaluation showed that both the luminal and basal cells express the ON gene. We conclude that the differential pattern of ON expression suggests that it may play an important role in the progression of CaP.

Antibodies, Monoclonal↗
PubMed2000

1999 American Urological Association Gallup Survey: changes in physician practice patterns, treatment of incontinence and bladder cancer, and impact of managed care.

PURPOSE: The Health Policy Survey and Research Committee of the American Urological Association and the Gallup Organization have performed a yearly survey of American urologists since 1992 to assess practice patterns. The results of the 1999 survey are presented. MATERIALS AND METHODS: A random sample of 503 urologists was interviewed in February and March 1999. Major content areas were physician practice patterns, the impact of managed care, and the treatment of pediatric patients, prostate cancer and benign prostatic hyperplasia, female incontinence and bladder cancer. RESULTS: The average urologist is 46.8 years old, certified by the American Board of Urology, sees 78 patients and performs 3.1 major surgical procedures weekly, refers moderate and complex pediatric procedures to specialists, and receives 40.6% of practice income from managed care. CONCLUSIONS: In an era when large group practices seem to be the norm remarkably 32% of urologists remain in solo practice. There has been a shift in where urologists spend their time, that is more in the office and less in the operating room. Minor and major open surgical procedures increased from 12.4 weekly to 16.4 and 2.9 to 3.1 in 1995 and 1999, respectively. Most urologists are comfortable treating straightforward pediatric problems such as cryptorchidism but refer more complex problems to pediatric urologists. Managed care represents an ever increasing proportion of urologist practice income, while office expenses continue to increase.

Adult↗
PubMed2000

The role of central corneal thickness in the diagnosis of glaucoma.

PURPOSE: To determine the effect of central corneal thickness (CCT) on applanation tonometry and any resultant misclassification of normals as ocular hypertension. METHOD: The central corneal thickness was measured using the ultrasound pachometer in 50 normals, 25 glaucoma and 23 ocular hypertensive patients. The student's "t" test was used to determine any significant difference in CCT between the three groups. RESULTS: There was a statistically significant difference in the mean CCT of the ocular hypertensives (0.574 +/- 0.033 mm) as compared to the glaucomas (0.534 +/- 0.030 mm) and normals (0.537 +/- 0.034 mm). Applying the described correction factor for corneal thickness, 39% of eyes with ocular hypertension were found to have a corrected IOP of 21 mmHg or less. CONCLUSIONS: Increased corneal thickness in ocular hypertension may lead to an overestimation of IOP in 39% of cases. Measurement of central corneal thickness is advisable when the clinical findings do not correlate with the applanation IOP.

Adult↗
PubMed2000

Towards achieving small-incision cataract surgery 99.8% of the time.

A surgical approach designed to reliably attain the modern goal of small incision cataract surgery 99.8% of the time is described. Phacoemulsification as well as a manual small incision technique is utilised to achieve the desired outcome as often as possible and for all types of cataracts. The logic, and required surgical steps are described and illustrated. This surgical technique allows the advantages of small incision surgery to be reliably achieved. The method is flexible and allows decisions and steps to be modified depending on the skill and comfort zone of the individual surgeon.

Anterior Chamber↗
PubMed2000

Comparison of optical and ultrasound pachometry.

PURPOSE: (1) To determine the agreement between optical and ultrasound pachometry for central corneal thickness measurements used to "correct" applanation intraocular pressure (IOP) readings. (2) To determine the inter- and intra-observer variability of optical and ultrasound pachometry. METHOD: Central corneal thickness (CCT) was measured in a masked manner using optical and ultrasound pachometry in 50 normal eyes. To assess intra- and inter-observer variability, multiple masked measurements were obtained in 51 eyes (optical pachometry) and 34 eyes (ultrasound pachometry). Agreement was determined by a published technique that uses the mean of the differences, standard error (SE) and standard deviation (SD). RESULTS: The mean difference in CCT between optical and ultrasound pachometry was 0.001 mm (SD 0.031 mm; SE 0.00439 mm). The mean inter-observer difference for the optical pachometer was 0.019 mm (SD 0.049 mm; SE 0.0069); the mean intra-observer difference was 0.003 mm (SD 0.017; SE 0.0.0024). The mean inter-observer difference for ultrasound pachometry was 0.001 mm (SD 0.009; SE 0.0015) and the mean intra-observer difference was 0.002 mm (SD 0.011; SE 0.0019). CONCLUSIONS: Ultrasound pachometry is the more reliable method for the measurement of central corneal thickness used to correct applanation IOP values. Optical pachometry had good intra-observer variability. The range of error in IOP correction for corneal thickness (inter-observer) that can occur using the ultrasound pachometer is -1.2 mmHg to +1.4 mmHg as compared to -5.6 mmHg to +8.5 mmHg with the optical pachometer.

Cornea↗
PubMed1999

Acute toxicity assessment of Polish (waste) water with a microplate-based Hydra attenuata assay: a comparison with the Microtox test.

The use of Hydra attenuata in acute toxicity assessment is a potentially useful tool in (waste) water biomonitoring. The purpose of this study was to compare the sensitivity of H. attenuata with the extensively used Microtox test on 14 (waste) water samples from the Kraków region (South Poland). To this end, specific morphological changes displayed by the freshwater cnidarian Hydra attenuata (lethal LC50s and sublethal EC50s effects) and bioluminescence of the marine bacteria Vibrio fisheri (Microtox) were compared. Clearly, the Hydra assay was the more sensitive indicator of toxicity. No relationship was found among Hydra toxicological responses and water levels of As, Cd, Co, Cu, Pb and Zn. However, it appeared that toxicity to Hydra might be due to ammonia levels. Additional studies to better circumscribe the tolerance of H. attenuata to 'natural' water characteristics are needed.

Animals↗
PubMed1999

Silent functional magnetic resonance imaging demonstrates focal activation in rapid eye movement sleep.

Functional imaging of human sleep has been performed with nuclear medicine methods, but MRI has been difficult to implement, in part because of the noise associated with echo-planar imaging as well as the difficulty in reading physiologic signals in the MRI environment. We describe a silent MR sequence that can record brain activation over many hours with simultaneous acquisition of an EEG. This shows activation of occipital cortex and deactivation of frontal cortex during REM sleep, in agreement with previous studies using other techniques. MRI-Sleep-REM sleep.

Adult↗
PubMed1999

Resistance of rheumatoid synovial dendritic cells to the immunosuppressive effects of IL-10.

IL-10 down-regulates the APC function of many dendritic cells (DC), including human peripheral blood (PB) DC. In rheumatoid arthritis (RA), synovial fluid (SF) DC express markers of differentiation and are effective APC despite abundant synovial IL-10. The regulation of DC responsiveness to IL-10 was therefore examined by comparing the effect of IL-10 on normal PB and RA SF DC. Whereas IL-10 down-modulated APC function and MHC class II and B7 expression of PB DC, IL-10 had no such effect on SF DC. Since SF DC have differentiated in vivo in the presence of proinflammatory cytokines, PB DC were cocultured in the presence of IL-10 and either GM-CSF, IL-1beta, TNF-alpha, IL-6, or TGF-beta. GM-CSF, IL-1beta, and TNF-alpha were all able to restore APC function. Whereas the effects of IL-10 on PB DC were shown to be mediated by IL-10R1, neither PB nor RA SF DC constitutively expressed IL-10R1 mRNA or detectable surface protein. In contrast, IL-10R1 protein was demonstrated in PB and SF DC whole cell lysates, suggestive of predominant intracellular localization of the receptor. Thus, DC responsiveness to IL-10 may be regulated through modulation of cell surface IL-10R1 expression or signaling.

Antigen Presentation↗
PubMed1999

Reciprocal chromosome painting reveals detailed regions of conserved synteny between the karyotypes of the domestic dog (Canis familiaris) and human.

The domestic dog is increasingly being recognized as a useful model for human disease. The aim of this study was to conduct the first detailed whole-genome comparison of human and dog using bidirectional heterologous chromosome painting (reciprocal Zoo-FISH) analysis. We used whole-chromosome paint probes produced from degenerate oligonucleotide-primed PCR amplification of high-resolution bivariate flow-sorted human and dog chromosomes. No fewer than 68 evolutionarily conserved segments were identified between the dog and the human karyotypes. The use of elongated metaphase chromosomes for both species allowed the boundaries of each evolutionarily conserved segment to be determined to subband resolution. The distribution of conserved segments is discussed, as are the applications of these data in refining the current status of the dog genome map.

Animals↗
PubMed1999

Laparoscopic living donor nephrectomy: advantages of the hand-assisted method.

INTRODUCTION: The laparoscopic technique for living donor nephrectomy is a technically difficult procedure that has not yet gained widespread acceptance in the transplant community. The procedure may be more acceptable if alterations to the technique made it easier to perform and decreased operative times. METHODS: In August 1998, we altered the laparoscopic procedure to include the use of a device allowing hand assistance. Subsequently, all living donor nephrectomies have been done using the hand-assisted method. In this article, the results of 10 cases performed using the original laparoscopic technique are compared with the results of 12 cases using the hand-assisted technique, and a brief description of modifications to the original technique is given. RESULTS: No patients where turned down as living donors, and no contraindications to the pure or hand-assisted laparoscopic techniques where found. The hand-assisted technique significantly reduced the operative time (2.02+/-0.44 vs. 3.12+/-0.36 hr, P<0.05) and the warm ischemic time (1.23+/-0.54 vs. 3.91+/-0.53 min, P<0.05). The length of stay and recovery time to normal activities were not different between the pure laparoscopic and hand-assisted groups. CONCLUSION: The advantages of the hand-assisted technique include the ability to use tactile sense to facilitate dissection, retraction, and exposure. In addition, the final stages of vascular stapling and kidney removal are more sure and rapid. The modifications of the laparoscopic technique presented here provide measurable and subjective improvements to laparoscopic living donor nephrectomy. The hand-assisted method of laparoscopic nephrectomy may make the operation available to more transplant centers.

Adolescent↗