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Biomedical subjects

R Simon

Publications and source records attributed to R Simon.

At least 55 records · Page 3Linked to original sources
PubMed2001

[Actinomycosis of the small intestine--an unusual cause of acute abdomen].

Actinomycosis is subacute or chronic disease manifested by a defined granulomatous inflammation with the development of infiltrates, abscesses and fistulae. A 35-year-old female patient was admitted and operated at the Second Surgical Clinic because of symptoms of diffuse peritonitis. Laparotomy revealed a duplicit tumour of the small intestine, an abscess of the abdominal wall in the left mesogastrium and pyoovarium bilaterale. 70 cm of the small intestine were resected, incision of the abscess and bilateral adnexotomy were performed. Histological examination revealed a suppurative, partly fibroproductive inflammation with an actinomycotic etiopathology. After antibiotic treatment the patient was discharged home, the gynaecologist removed an intrauterine device. Three months after the first operation the patient in a serious septic condition was readmitted to the clinic with signs of diffuse peritonitis. A double perforation of the small intestine was found and an end-to-end anastomosis was made after resection of the small intestine. The postoperative course was complicated by respiratory failure and failure of the circulation associated with septic shock and subsequent death. In the conclusion the authors emphasize the problem of preoperative diagnosis of the abdominal form of actinomycosis, its possible development in relation to intrauterine contraceptive devices and its clinical manifestation as acute abdomen.

Abdomen, Acute↗
PubMed2000

Chromosome abnormalities in malignant melanoma: clinical significance of nonrandom chromosome abnormalities in 206 cases.

We report the cytogenetic abnormalities from a series of 206 primary malignant melanoma specimens referred to a single institution. A total of 169 out of 206 unique cases had chromosome breakpoints. A previously described statistical method was used to detect nonrandom distribution of chromosome breakpoints at the level of chromosome regions. Nonrandom occurrence of chromosome breakpoints (indicating that the observed number of breaks significantly exceeded the expected number of breaks) was detected in 28 regions, suggesting a hierarchy of genetic abnormalities in melanoma. Clinical variables and tumor characteristics were analyzed for associations with the presence of any nonrandom chromosome breakpoints; with individual, nonrandomly involved chromosome regions; and with paired, nonrandomly involved chromosome regions. No nonrandomly involved chromosome regions or pairs of regions appeared to significantly affect survival. These results identify recurring, nonrandom chromosome abnormalities in malignant melanoma. These results suggest that recurring, nonrandom chromosome alterations play a key role in the etiology and/or progression of malignant melanoma and identify targets within the genome for molecular genetic studies.

Chromosome Aberrations↗
PubMed2000

A model to select chemotherapy regimens for phase III trials for extensive-stage small-cell lung cancer.

BACKGROUND: Many more phase II studies have favorable outcomes than the subsequent phase III trials. We used historical data from phase II and phase III studies for patients with extensive-stage small-cell lung cancer (SCLC) to generate a statistical model to provide assistance in selecting chemotherapy regimens from phase II studies for subsequent use in phase III randomized studies. METHODS: Information from 21 phase III trials for patients with extensive-stage SCLC initiated during the period from 1972 through 1990 was reviewed to identify those that were preceded by phase II studies of the same regimen. We used data from all the trial pairs to develop a statistical model in which the number of patients, the median survival of patients, and the number of deaths observed in the phase II trial are used to estimate the statistical power of the subsequent phase III trial. All statistical tests were two-sided. RESULTS: Nine phase II studies were identified that preceded phase III trials of the same regimen. The regimens from two phase II studies with the greatest expected power in the phase III trial (0. 62 and 0.58) both demonstrated significantly prolonged survival when compared with standard treatment in subsequent phase III trials (P<. 001 and P =.002, respectively). The regimens from six of the other phase II studies, for which the median power expected in the phase III trial was 0.28 (range, 0.19-0.52), showed no difference when compared with standard treatment in a phase III trial. CONCLUSIONS: Phase II studies for particular regimens that have an expected power of greater than 0.55 provide a reasonable basis for proceeding with a phase III trial.

Antineoplastic Agents↗
PubMed2000

Molecular classification of cutaneous malignant melanoma by gene expression profiling.

The most common human cancers are malignant neoplasms of the skin. Incidence of cutaneous melanoma is rising especially steeply, with minimal progress in non-surgical treatment of advanced disease. Despite significant effort to identify independent predictors of melanoma outcome, no accepted histopathological, molecular or immunohistochemical marker defines subsets of this neoplasm. Accordingly, though melanoma is thought to present with different 'taxonomic' forms, these are considered part of a continuous spectrum rather than discrete entities. Here we report the discovery of a subset of melanomas identified by mathematical analysis of gene expression in a series of samples. Remarkably, many genes underlying the classification of this subset are differentially regulated in invasive melanomas that form primitive tubular networks in vitro, a feature of some highly aggressive metastatic melanomas. Global transcript analysis can identify unrecognized subtypes of cutaneous melanoma and predict experimentally verifiable phenotypic characteristics that may be of importance to disease progression.

Adult↗
PubMed2000

Dependence of stem cell fate in Arabidopsis on a feedback loop regulated by CLV3 activity.

The fate of stem cells in plant meristems is governed by directional signaling systems that are regulated by negative feedback. In Arabidopsis thaliana, the CLAVATA (CLV) genes encode the essential components of a negative, stem cell-restricting pathway. We used transgenic plants overexpressing CLV3 to show that meristem cell accumulation and fate depends directly on the level of CLV3 activity and that CLV3 signaling occurs exclusively through a CLV1/CLV2 receptor kinase complex. We also demonstrate that the CLV pathway acts by repressing the activity of the transcription factor WUSCHEL, an element of the positive, stem cell-promoting pathway.

Arabidopsis↗
PubMed2000

Carvedilol for prevention of restenosis after directional coronary atherectomy : final results of the European carvedilol atherectomy restenosis (EUROCARE) trial.

BACKGROUND: In addition to its known properties as a competitive, nonselective beta and alpha-1 receptor blocker, carvedilol directly inhibits vascular myocyte migration and proliferation and exerts antioxidant effects that are considerably greater than those of vitamin E or probucol. This provides the basis for an evaluation of carvedilol for the prevention of coronary restenosis. METHODS AND RESULTS: In a prospective, double-blind, randomized, placebo-controlled trial, 25 mg of carvedilol was given twice daily, starting 24 hours before scheduled directional coronary atherectomy and continuing for 5 months after a successful procedure. The primary end point was the minimal luminal diameter as determined during follow-up angiography 26+/-2 weeks after the procedure. Of 406 randomized patients, 377 underwent attempted atherectomy, and in 324 (88.9%), a </=50% diameter stenosis was achieved without the use of a stent. Evaluable follow-up angiography was available in 292 eligible patients (90%). No differences in minimal luminal diameter (1.99+/-0.73 mm versus 2.00+/-0.74 mm), angiographic restenosis rate (23.4% versus 23.9%), target lesion revascularization (16.2 versus 14.5), or event-free survival (79.2% versus 79.7%) between the placebo and carvedilol groups were observed at 7 months. CONCLUSIONS: The maximum recommended daily dose of the antioxidant and beta-blocker carvedilol failed to reduce restenosis after successful atherectomy. These findings are in contrast to those of the Multivitamins and Probucol Trial, which raises doubts regarding the validity of the interpretation that restenosis reduction by probucol was via antioxidant effects. The relationship between antioxidant agents and restenosis remains to be elucidated.

Adrenergic Antagonists↗
PubMed2000

Peres-horodecki separability criterion for continuous variable systems

The Peres-Horodecki criterion of positivity under partial transpose is studied in the context of separability of bipartite continuous variable states. The partial transpose operation admits, in the continuous case, a geometric interpretation as mirror reflection in phase space. This recognition leads to uncertainty principles, stronger than the traditional ones, to be obeyed by all separable states. For all bipartite Gaussian states, the Peres-Horodecki criterion turns out to be a necessary and sufficient condition for separability.

Journal Article↗
PubMed2000

Length and loss of heterozygosity of an intron 1 polymorphic sequence of egfr is related to cytogenetic alterations and epithelial growth factor receptor expression.

Overexpression of epithelial growth factor receptor (EGFR) is correlated with a poor prognosis and reduced steroid receptor expression. Recently, it was demonstrated that the length of a CA repeat in the intron 1 of EGFR correlated with the expression of EGFR in vitro. We investigated 112 cases of cancerous and noncancerous breast tumor samples for loss of heterozygosity (LOH) in intron 1 of the egfr gene and determined the intratumoral EGFR content and genetic alterations by comparative genomic hybridization. Heterozygous tumors with short CA repeats showed elevated EGFR expression in contrast to tumors with longer CA repeats. Tumors with LOH in intron 1 of egfr revealed higher EGFR expression when the longer allele was lost compared with loss of the shorter allele. Additionally, tumors with a loss of the long allele showed more chromosomal alterations, especially a higher frequency of amplifications. We conclude that the CA repeat status in intron 1 of the egfr gene also modulates the intratumoral EGFR content in vivo. Furthermore, LOH at the CA repeat is associated with genetically advanced tumors. Therefore, allele-specific gene expression due to LOH of the CA repeat could be assumed to be an important event in invasive breast cancer development.

Alleles↗
PubMed2000

Estimation of tamoxifen's efficacy for preventing the formation and growth of breast tumors.

BACKGROUND: Several randomized clinical trials have tested the hypothesis that tamoxifen is effective in preventing breast cancer. The largest such trial, the National Surgical Adjuvant Breast and Bowel Project's Breast Cancer Prevention Trial (BCPT), reported a 49% reduction in risk of invasive breast cancer for the tamoxifen group. However, it is unclear whether the effect of tamoxifen in this trial was mainly due to prevention of newly forming tumors or to treatment of occult disease. METHODS: We used various tumor growth models (i.e., exponential and Gompertzian [growth limited by tumor size]) and a computer simulation to approximate the percentage of detected tumors that were initiated after study entry. Maximum likelihood techniques were then used to estimate separately the efficacy of tamoxifen in treating occult disease and in preventing the formation and growth of new tumors. RESULTS: Under the assumptions of most of the growth models, the trial was sufficiently long for substantial numbers of new tumors to form, grow, and be detected during the trial. With the Gompertzian model and all available incidence data from the BCPT, it was estimated that 60% (95% confidence interval [CI] = 40%-80%) fewer new tumors were detected in the tamoxifen group than in the placebo group. Likewise, 35% (95% CI = 6%-63%) fewer occult tumors were detected in the tamoxifen group. With this model, the estimated incidence rate of invasive breast cancer among women in the placebo group of the BCPT was 7.7 (95% CI = 6.6-8.9) per 1000 women per year. Similar results were obtained with three exponential tumor growth models. CONCLUSIONS: These results support the concept that tamoxifen reduced cancer incidence in the BCPT through both treatment of occult disease and prevention of new tumor formation and growth. However, data from prevention trials may never be sufficient to completely distinguish prevention of new tumor formation from treatment of occult disease.

Adult↗
PubMed2000

Pericardiocentesis: differential aspects of a common procedure.

OBJECTIVE: To evaluate the risk and effectiveness of pericardiocentesis in primary and repeat cardiac tamponade. DESIGN: Retrospective analysis. SETTING: Intensive care unit in a medical university hospital. PATIENTS: Sixty-three consecutively admitted patients with cardiac tamponade. INTERVENTIONS: In all patients pericardiocentesis was performed via the subxiphoid pathway after echocardiographic detection of the pericardial effusion. MEASUREMENTS AND RESULTS: There was no adverse event in patients undergoing primary pericardiocentesis, which was sufficient to resolve pericardial effusion in 51 of 63 patients (81%). However, repeat pericardiocentesis necessitated by the recurrence of symptomatic pericardial effusion yielded suboptimal results in 10 of 12 patients (83%). CONCLUSION: Pericardiocentesis is the treatment of choice for primary symptomatic pericardial effusion. In recurrent pericardial effusion surgical approaches appear to be preferable.

Adult↗
PubMed2000

Reading and assessing reports of treatment studies in oncology.

Rapid advances in tumor biology, immunology, genomics, and technology give physicians great hopes for providing patients with better chances in the struggle against cancer. The pace of progress will be slowed, however, if we do not have clear answers regarding which treatments work and do not work. Such answers come from carefully designed, randomized, clinical trials. Such trials require infrastructure, commitment, cooperation, time, and money, and they provide little fame. They are, however, an invaluable contribution of the medical profession to their patients, to their next generation of colleagues, and to future patients. Randomized clinical trials that answer important medical questions definitively should be supported, participated in, and demanded by surgeons and oncologists.

Clinical Trials as Topic↗
PubMed2000

American College of Cardiology/European Society of Cardiology International Study of Angiographic Data Compression Phase I: The effect of lossy data compression on recognition of diagnostic features in digital coronary angiography.

OBJECTIVES: This study intended to determine the effect of varying degrees of lossy Joint Photographic Experts Group (JPEG) compression on detection of coronary angiographic features. BACKGROUND: Compression of digital coronary angiograms facilitates playback of images and decreases cost. There are little data on the effect of compression on the accuracy of coronary angiography. METHODS: At six centers, 71 angiographers each reviewed a set of 100 angiographic sequences. The 100 sequences were divided into four, 25-sequence subsets. Each subset of 25 was displayed either as original images or at one of three compression ratios (CRs) (6:1, 10:1 or 16:1). The effect of lossy compression on the sensitivity and specificity for detection of diagnostic features was determined. The effect of compression on subjective measures of image quality graded by the angiographers was also examined. RESULTS: Lossy compression at a ratio of 16:1 decreased the sensitivity for the detection of diagnostic features (76% vs. 80% p = 0.004). The largest effect was in the detection of calcification (52% vs. 63% at 16:1 compression vs. original images, p < 0.001). Subjective indicators of image quality indicated a reduction in confidence in interpretation at CRs of 10:1 and 16:1. CONCLUSIONS: With increased ratios of lossy compression, a degradation of digital coronary angiograms occurs that results in decreased diagnostic accuracy. The sensitivity for detection of common diagnostic features was decreased, and subjective assessment of image quality was impaired. Caution is warranted in the interpretation of coronary angiograms that have been subjected to lossy JPEG compression beyond a ratio of 6:1.

Adult↗