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R Thomas

Publications and source records attributed to R Thomas.

At least 109 records · Page 6Linked to original sources
PubMed2001

Role of frequency doubling perimetry in detecting neuro-ophthalmic visual field defects.

PURPOSE: To report the ability of frequency doubling perimetry to detect "neuro-ophthalmic" field defects, characterize them as hemianopic or quadrantanopic, and differentiate glaucomatous from "other" neuro-ophthalmic field defects. METHODS: Sixty eyes of 30 normal subjects, 50 eyes of 29 patients with glaucomatous defects, and 138 eyes of 103 patients with "typical" neuro-ophthalmic field defects underwent automated perimetry using the Swedish Interactive Threshold Algorithm and frequency doubling perimetry. The sensitivity and specificity for identification of a field defect (frequency doubling perimetry 20-5 and 20-1 screening tests), or to characterize hemianopia/quadrantanopia (full threshold test) were determined. Ability to discriminate glaucomatous defects was determined by comparing frequency doubling perimetry full threshold test in glaucoma to pooled results of normal and neuro-ophthalmic groups. RESULTS: On frequency doubling perimetry, a single point depressed to less than 1% probability had a sensitivity of 97.1% (20-5 test) and 95.7% (20-1 test) for detecting a neuro-ophthalmic visual field defect. The corresponding specificities were 95% using pooled results in normal subjects and patients with glaucoma and "other" neuro-ophthalmic field defects. In 20-5 screening a single abnormal point depressed to less than 2% probability level had a sensitivity of 98.6% (specificity 85%). Two abnormal points in the 20-1 screening depressed to less than 1% probability level had a specificity of 100% (sensitivity 84.8%). In frequency doubling perimetry full threshold, sensitivity and specificity for detection of hemianopia were 86.8% and 83.2%; for quadrantanopia they were 79.2% and 38.6%. The sensitivity and specificity for categorizing a defect as glaucomatous were 86% and 74.7%. CONCLUSIONS: Frequency doubling perimetry is a sensitive and specific test for detecting "neuro-ophthalmic" field defects. The presence of two abnormal points (20-1 screening program) "rules in" the presence of a field defect. A normal 20-5 program (absence of a single abnormal point) almost "rules out" a defect. Frequency doubling perimetry could not accurately categorize hemianopic, quadrantanopic, or glaucomatous defects.

Child↗
PubMed2001

Effect of extracorporeal membrane oxygenation on left ventricular function of swine.

BACKGROUND: Previous clinical and experimental investigations have produced inconsistent data describing the effects of veno-arterial extracorporeal membrane oxygenation (VA ECMO) on intrinsic left ventricular (LV) function. We report an animal model that allows investigation of the effects of VA ECMO on the mechanics of the LV using two load-insensitive indices: end-systolic pressure-minor axis dimension relationship (ESPDR) and preload recruitable dimensional stroke work (PRDSW). METHODS: Eight piglets (5 to 11 kg) were anesthetized, instrumented, and placed on VA ECMO. Throughout the experiment, systemic and left atrial partial pressure of oxygen were maintained between 100 to 200 mm Hg. At ECMO flow rate of 50% of baseline cardiac output, data were collected prior to ECMO, at 4 and 6 hours during ECMO, and after weaning from ECMO. Data measured or calculated for each time point included heart rate, LV pressures and minor axis dimensions at different pre-loads, first derivative of LV pressure with respect to time, velocity of circumferential fiber length shortening (VCF), LV shortening fraction (LVSF), ESPDR, and PRDSW. RESULTS: A significant (p < 0.05) decrease in LVSF and VCF was seen at 4 and 6 hours during ECMO when compared to baseline, but the ESPDR and PRDSW did not change during ECMO. CONCLUSIONS: VA ECMO alone changes some of the load-dependent parameters of contractility, but intrinsic function of the heart is not significantly affected as measured by load-insensitive indices of LV performance.

Animals↗
PubMed2001

Outpatient radical prostatectomy: impact of standard perineal approach on patient outcome.

PURPOSE: As managed care becomes more prevalent, urologists must critically evaluate the economic aspect of and patient satisfaction with urological practice patterns. We have previously reported the advantages of radical perineal prostatectomy, which decreases hospitalization and morbidity, and provides a more rapid return to normal activity, translating into cost savings. We have since evaluated the satisfaction of patients who underwent outpatient radical prostatectomy with and without laparoscopic pelvic lymph node dissection. MATERIALS AND METHODS: We evaluated the charts of 250 consecutive patients who underwent outpatient radical perineal prostatectomy with less than 24 hours of hospitalization from 1992 to 1997. Complications, pain management, blood transfusion, and bowel and urinary dysfunction were assessed. Validated quality of life questionnaires were mailed to 200 patients several months postoperatively and a 62% response rate was achieved. RESULTS: Mean followup in the series was 30 months. In the perioperative period there were rectal perforation in less than 2% of patients, anastomotic stricture in 3%, perineal fistula in 0.4% and blood transfusion in 11%. Some problems with bowel movements immediately after the procedure, such as diarrhea, constipation or soiled underwear, developed in 17% of patients, of whom up to 20% had had some bowel dysfunction before surgery. In the majority bowel problems resolved in an average of 7.3 weeks. Persistent new onset bowel trouble developed in 9 of the 124 patients (7%). The questionnaire demonstrated persistent significant urinary incontinence in 8 cases (7%). Nerve sparing was attempted in 54 patients, including 22 (41%) who achieve erection sufficient for vaginal penetration and are satisfied with sexual function. Of the patients 17% reported problems after hospital discharge that were mostly related to Foley catheter management. Overall 94.8% of patients were satisfied with treatment. Physical and social/family well-being appeared to be excellent according to the questionnaire. Only 12% of patients would have preferred longer hospitalization. The preferred method of pain control was nonsteroidal anti-inflammatory drugs. CONCLUSIONS: Radical perineal prostatectomy is a low morbidity alternative for localized prostate cancer. Outpatient radical perineal prostatectomy may be performed with good patient satisfaction and safety. There appear to be few bowel problems after long-term followup.

Aged↗
PubMed2001

An algorithm for targeted convergence of Euler or Newton iterations.

The concept of multistationarity has become essential for understanding cell differentiation. For this reason theoretical biologists have more and more frequently to determine the steady values, often multiple, of systems of non-linear differential equations. It is well known that iteration processes of current use converge or not towards a fixed point depending on the absolute value of the slope of the iteration function in the vicinity of the considered fixed point. A number of methods have been developed to obtain or accelerate convergence. As biologists, we do not pretend to review these works. Rather, we propose here a simple algorithm which permits to converge at will towards a chosen type of steady state. Others and we have used this procedure extensively for years for the analysis of complex biological systems. A compact program (using Mathematica) is available.

Algorithms↗
PubMed2001

Molecular cytogenetic analysis of a novel high-grade canine T-lymphoblastic lymphoma demonstrating co-expression of CD3 and CD79a cell markers.

We present the molecular cytogenetic analysis of a novel case of canine lymphoma, in a nine-year-old entire male collie cross retriever dog that presented with an enlarged prescapular lymph node. A diagnosis of high-grade lymphoblastic lymphoma was made by histological evaluation of fixed lymph node biopsy sections, whilst immunohistochemical analyses demonstrated co-expression of B- and T-cell antigens (CD79a and CD3) by 95% of lymphomatous cells. Comparative genomic hybridisation (CGH) analysis detected loss of dog chromosomes 11, 30 and 38 and gain of chromosome 36 within the lymphoma biopsy specimen. These findings correlated with direct cytogenetic analysis of tumour metaphases using whole chromosome paint probes representing each of these four chromosomes. This study represents the first report of the combined application of both direct and indirect cytogenetic techniques for the analysis of recurrent chromosome aberrations in canine cancer.

Animals↗
PubMed2001

Interruption of coding sequences by heterologous introns can enhance the functional expression of recombinant genes.

Sustained expression of recombinant proteins is a critical factor for the effectiveness of numerous applications in the biomedical sciences including the treatment of human disease by gene therapy, the large scale production of therapeutic proteins, as well as the investigation of gene function by transgenesis or cell type specific mutagenesis. Although much attention has been paid to the optimisation of regulatory sequences such as promoters, untranslated regions and polyadenylation signals, effective and sustained expression of recombinant genes in vivo is often difficult to achieve. Here we report that the creation of artificial exons, by insertion of two short heterologous introns into open reading frames, is not only compatible with functional expression, but also leads to a 30-fold enhancement of mRNA production for both green fluorescent protein and the bacteriophage P1-derived Cre recombinase. The levels of green fluorescence were increased five-fold in cell lines and sustained long-term expression at increased levels was observed in rat brain after transduction with a herpes simplex virus-based vector. The data presented identify a means by which the expression of recombinant genes can be enhanced considerably, in addition to and independently from the surrounding regulatory sequences. The method should help obtain sustained and effective expression of recombinant proteins in vivo.

Animals↗
PubMed2001

Chromosome assignment of six dog genes by FISH, and correlation with dog-human Zoo-FISH data.

Cross-species chromosome painting analyses have recently demonstrated the presence of regions of conserved synteny between the human and domestic dog genomes, aiding the search for candidate genes for inherited traits. Concerted efforts to subchromosomally assign substantial numbers of dog gene sequences are now needed in order to refine these comparative data, both in terms of marker density and resolution. We have developed novel PCR markers representing three dog genes (ALB, FOS, HNRPA2B1) for which no sequence or mapping data were previously available, to our knowledge. These, in addition to three gene markers previously described (ALDOA, RPE65, VCAM1), were used to isolate and chromosomally assign corresponding large insert genomic clones by fluorescence in situ hybridization (FISH). Chromosome assignments for these six dog genes are discussed in terms of those of the human orthologues, and correlated with existing comparative mapping information, identifying one apparent exception to existing Zoo-FISH data, and aiding refinement of the boundaries of conserved chromosome segments in both genomes.

Animals↗
PubMed2001

Improvement in quality of life for cancer patients treated with epoetin alfa.

Anaemia is a common complication of cancer and cancer therapies, and fatigue is one of the most common symptoms of anaemia, disrupting functional performance and reducing overall quality of life. The positive effects of treating renal patients with recombinant human erythropoietin are well documented. This case report series details the specific effects of fatigue on individual patients with cancer and their way of life, and describes their significant improvement in lifestyle following the reversal of anaemia using recombinant human erythropoietin, epoetin alfa.

Aged↗
PubMed2001

A study of four cases of extra-orbital giant cell angiofibroma with documentation of some unusual features.

AIMS: To document the clinical, light microscopic, immunohistochemical and ultrastructural features of four cases of extra-orbital giant cell angiofibromas. METHODS AND RESULTS: Sections of formalin-fixed paraffin-embedded specimens were studied by haematoxylin and eosin, reticulin and immunohistochemical stains. Electron microscopy was carried out in two cases on tissue fixed in formalin. The age of the patients ranged from 30 to 41 years. Two patients presented with a soft tissue swelling in the left groin, one patient had a left axillary soft tissue lump and one patient presented with a parotid lump. All lesions were well circumscribed and contained variably cellular and vascularized tissue composed of round to spindle cells with a patternless arrangement, scattered multinucleate giant cells and pseudovascular spaces conforming to the description of giant cell angiofibroma. Mononuclear and multinucleate tumour cells were both positive for vimentin and CD34; one tumour exhibited focal S100 protein and GFAP positivity. Both of the tumours examined by electron microscopy showed fibroblastic features, but in addition one contained cells having Schwannian features. All four patients were well without recurrent disease on follow-up (average 25 months). CONCLUSION: Giant cell angiofibroma shares many features with solitary fibrous tumour and giant cell fibroblastoma and shows a wider distribution than initially recognized. Rarely, Schwannian differentiation may be observed in these tumours.

Adult↗
PubMed2001

Ischemic colitis during treatment with alosetron.

Irritable bowel syndrome (IBS) is one of the most common entities observed by both primary care physicians and gastroenterologists. Alosetron is a potent and selective serotonin antagonist that recently became the first Food and Drug Administration-approved agent for diarrhea-predominant IBS. However, since approval, significant side effects have been noted with the use of alosetron including severe constipation, fecal impaction, and ischemic colitis. We describe a case of ischemic colitis in a male patient with IBS who was briefly treated with alosetron. Clinical, endoscopic, and pathologic features of the focal colitis strongly suggested ischemia. Symptoms correlated temporally with alosetron use, and symptoms abated with discontinuation of the drug. Endoscopic and pathologic resolution of the colitis were documented.

Carbolines↗