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Biomedical subjects

P Simons

Publications and source records attributed to P Simons.

At least 19 recordsLinked to original sources
PubMed2001

Detection of epitope-tagged proteins in flow cytometry: fluorescence resonance energy transfer-based assays on beads with femtomole resolution.

Epitope tagging of expressed proteins is a versatile tool for the detection and purification of the proteins. This approach has been used in protein-protein interaction studies, protein localization, and immunoprecipitation. Among the most popular tag systems is the FLAG epitope tag, which is recognized by three monoclonal antibodies M1, M2, and M5. We describe novel approaches to the detection of epitope-tagged proteins via fluorescence resonance energy transfer on beads. We have synthesized and characterized biotinylated and fluorescein-labeled FLAG peptides and examined the binding of FLAG peptides to commercial streptavidin beads using flow cytometric analysis. A requirement of assay development is the elucidation of parameters that characterize the binding interactions between component systems. We have thus compiled a set of Kd values determined from a series of equilibrium binding experiments with beads, peptides, and antibodies. We have defined conditions for binding biotinylated and fluoresceinated FLAG peptides to beads. Site occupancies of the peptides were determined to be on the order of several million sites per bead and Kd values in the 0.3-2.0 nM range. The affinity for antibody attachment to peptides was determined to be in the low nanomolar range (less than 10 nM) for measurements on beads and solution. We demonstrate the applicability of this methodology to assay development, by detecting femtomole amounts of N-terminal FLAG-bacteria alkaline phosphatase fusion protein. These characterizations form the basis of generalizable and high throughput assays for proteins with known epitopes, for research, proteomic, or clinical applications.

Antibodies↗
PubMed2000

Baseline HIV type 1 genotypic resistance to a newly added nucleoside analog is predictive of virologic failure of the new therapy.

We evaluated the predictive value of baseline HIV-1 genotypic resistance mutations for failure of a nucleoside reverse transcriptase inhibitor (NRTI) containing therapy. The change in therapy of 88 HIV-1-infected patients was analyzed retrospectively, relating the genotypic resistance profile at baseline to the evolution of viral load and CD4+ T cell counts. Genotypic resistance at baseline and at 6 months was evaluated with the LiPA HIV-1 RT, which detects mutations at codons 41, 69, 70, 74, 184, and 215. At 1 to 3 months after change in therapy, patients without preexisting resistance mutations to the new drug (group S) had a significantly better evolution in viral load (reduction of 0.37 log(10)) compared with patients with known preexisting resistance mutation(s) (group R) (increase of 0.08 log(10)). This difference was particularly striking for patients with the baseline M184V mutation and whose treatment was modified by the addition of lamivudine. After 6 months the median difference in viral load evolution between the two groups increased to 0.61 log(10): the viral load of patients of group S was still 0.18 log(10) below baseline while patients of group R had an increase of 0.43 log(10) in viral load above baseline. Changes in CD4+ T cell counts were not significantly different. The evolution in viral load in HIV-1-infected patients with and without baseline resistance mutation(s) toward a newly added NRTI is significantly different at 1-3 months and at 6 months after changing or adding one NRTI.

CD4 Lymphocyte Count↗
PubMed2000

Patients with pulmonary fibrosis: cardiac function assessed with MR imaging.

PURPOSE: To detect abnormalities in cardiac function by using magnetic resonance (MR) imaging in patients with mild to moderate pulmonary fibrosis and to evaluate the relationship between pulmonary function and cardiac function. MATERIALS AND METHODS: Sixteen patients were compared with 16 sex- and age-matched healthy control subjects. Systolic function was assessed by using multisection multiphase cine MR imaging. Diastolic function was assessed with flow-sensitive MR imaging across the mitral and tricuspid valves. MR imaging results were compared with the severity of impairment in pulmonary function. RESULTS: Biventricular systolic function and left ventricular diastolic function were normal in patients, but right ventricular diastolic function was significantly impaired versus that of control subjects, with a ratio of peak flow during early diastolic (E) filling to peak flow during atrial contraction (A) of 0.85 +/- 0.40 versus 1.28 +/- 0.50 (P =.035). Biventricular E/A ratios were strongly correlated to age in patients and control subjects. The right ventricular E/A ratio in patients corresponded with values that are normally expected in people 20 years older. Diastolic left and right ventricular functions were significantly correlated with each other. There was no relationship between pulmonary function and cardiac function. CONCLUSION: Impairment of right ventricular diastolic function was found by using MR imaging in patients with mild to moderate pulmonary fibrosis, whereas left ventricular diastolic function and biventricular systolic function were preserved.

Adult↗
PubMed2000

MR arthrography of the rotator cuff and capsulolabral complex.

MR arthrography of the shoulder has reached maturity in recent years. As opposed to conventional MRI of the shoulder it is less prone to artefacts frequently leading to equivocal interpretation. The spectrum of pathology in which MR arthrography has significant advantages is reviewed, with emphasis on the rotator cuff and the capsulolabral complex.

Joint Capsule↗
PubMed1998

Posterior labrocapsular periosteal sleeve avulsion complicating locked posterior shoulder dislocation.

This case presents the imaging features of a posterior shoulder dislocation complicated by a rare but surgically relevant lesion of the posterior labrum. Due to the attachment of the posterior capsule to the posterior portion of the labrum, which in itself is attached to the posterior scapular periosteum, stripping of the labrum by the posterior capsule resulted in a posterior labrocapsular periosteal sleeve avulsion.

Adult↗
PubMed1996

Venous pumps of the hand. Their clinical importance.

Oedema remains one of the most common causes of hand stiffness. Local venous return is intimately associated with oedema formation and management. To elucidate the underlying mechanisms of venous return, the venous pumping systems in the hand were objectively and quantitatively investigated using Doppler ultrasound, cadaveric dissection and venography. It was demonstrated that functionally there are three independent venous systems: the superficial palmar, deep palmar and dorsal veins, which are activated by palm compression, isometric intrinsic muscle contraction, and dorsum compression, respectively. Each system was investigated independently and found to increase venous blood velocity in both the cephalic and ulnar veins. These systems were also shown to act in synergy, producing the greatest velocity increase when concurrently activated during fist-clenching. The volume of blood pumped during fist-clenching could also be potentiated by preloading by digit abduction. The clinical applications of these findings are discussed.

Blood Flow Velocity↗
PubMed1996

Xeroderma pigmentosum--Cockayne syndrome complex: a further case.

We report on a male patient born to healthy, first cousin, Moroccan parents. During the pregnancy growth retardation was observed. Birth weight, length, and OFC were all well below the 3rd centile. Facial anomalies, microphthalmia, cleft palate, small penis, and flexion contractures of large joints were noted. Cerebral MRI showed dysmyelination. The clinical course was characterised by feeding difficulties, growth failure, lack of development, photosensitivity, and death at 7 months. The main differential diagnoses were COFS syndrome and early onset Cockayne syndrome (CS). UV exposure of cultured fibroblasts showed inhibition of nucleic acids synthesis. Further DNA repair studies showed extreme cellular sensitivity to UV and xeroderma pigmentosum (XP)-like defective nucleotide excision repair (NER), which in combination with the clinical symptoms indicated the very rare XP-CS complex. Complementation analysis showed that the XPG gene is affected in this patient. In cases suspected of having COFS syndrome and early onset CS, extensive DNA repair studies are needed to reach the definitive diagnosis, thereby allowing reliable genetic counselling and prenatal diagnosis.

Cell Survival↗
PubMed1994

Myth of substituted judgment. Surrogate decision making regarding life support is unreliable.

OBJECTIVE: To identify factors predicting the accuracy of surrogate decision making in life support decisions. DESIGN: Questionnaire. SETTING: Urban Veterans Affairs hospital. PATIENTS AND DESIGN: Fifty hospitalized patients and their chosen surrogates were given questionnaires describing life support modalities and four common medical scenarios in which life support would be contemplated. An additional 50 patients also completed the questionnaire. Patients gave their choices of life support in the different scenarios. Surrogates guessed the patients' answers (substituted judgment). Details of the patient-surrogate relationship were asked. Patients completed a depression inventory. MAIN RESULTS: Surrogates correctly guessed patients' wishes about life support overall on 59.3% of the questions, not better than random chance (kappa = .09). The only predictor of accurate surrogate decision making was specific discussion between patient and surrogate about life support. SECONDARY RESULTS: Patients had an overall low desire for life support (35%), and a majority favored euthanasia under some circumstances (62%). There was no relationship between depression score and desire for life support. CONCLUSIONS: Substituted judgment by surrogates is not more accurate than random chance. Discussion between patient and surrogate about life support correlated with more accurate substituted judgment.

Adult↗
PubMed1994

Percutaneous nucleus pulposus denaturation in treatment of lumbar disc protrusions--a prospective study of 50 neurosurgical patients.

In a prospective study on 50 patients, the 1064-nm Nd-YAG laser was used to denaturate protruding lumbar discs. The method of Ascher [1] was modified using a saline pressure infusion system. Early results show a very good decompressive effect with 48 out of 50 patients in the categories very good and good. At follow-up (mean 184 days postoperation) 31 out of 46 were in these categories, indicating a longer lasting retrieval of the protruded mass. A marked reduction of clinical nerve compression signs was noted. No severe complications occurred. Due to the irrigation system less low back pain was reported. The method seems promising in the standard neurosurgical setting.

Adult↗
PubMed1994

Lesbian (in)visibility in Italian Renaissance culture: Diana and other cases of donna con donna.

Current conceptualizations of sexual identity in the West are not necessarily useful to an historian investigating "lesbianism" in the social history and visual representations of different periods. After an overview of Renaissance documents treating donna con donna relations which examines the potentially positive effects of condemnation and silence, the paper focuses on Diana, the goddess of chastity, who bathed with her nymphs as an exemplar of female bodies preserved for heterosexual, reproductive pleasures. Yet the self-sufficiency and bodily contact sometimes represented in images of this secluded all-female gathering might suggest "deviant" responses from their viewers.

Art↗
PubMed1994

[Carcinoid tumor, a late diagnosis].

Carcinoid tumor is often a late diagnosis due to the unspecificity of symptoms leading the radiologist rely on different investigation procedures. We present a case illustrating the contribution of US by demonstrating the suggestive combination of radiating mesenteric densities with a mesenteric mass.

Aged↗
PubMed1992

Effect of pyritinol on EEG and SSEP in comatose patients in the acute phase of intensive care therapy.

The extent and duration of acute disturbances of consciousness depend on the severity and localization of the underlying cerebral dysfunction. The Glasgow Coma Scale (GCS) permits a relevant statement to be made on the course and recovery tendency of functional damage patterns in cerebral, mesencephalic, and brain stem structures. Therapy is directed at exerting a beneficial effect on the disturbed cerebral metabolism by administration of centrally active substances and at utilizing the available reserve plasticity of the brain for any possible recovery of mental performance. The bioavailability and profile of action of pyritinol have been well documented in animal experiments. We have studied the question as to the extent to which the substance influences the depth of coma in patients receiving acute intensive care therapy, and how this can be objectified electrophysiologically in the form of a specific central effect on basal brain structures. In a phase-II pilot study over five days the acute effect of intravenous 60-min. administration of 1,000 mg pyritinol on the depth of coma, the central conduction time (CCT) and the primary complex amplitude (N20/P25) of the SSEP, and on vigilance behavior (spectral edge frequencies and power) was investigated for 90 minutes in each case under intensive-medical steady-state conditions in 10 comatose patients. Because of the differences in the underlying brain damage, the primary depth of coma, age (30-89 years), sex (two female, eight male), as well as previous treatment (surgery, conservative), the significance of the results could not be evaluated by confirmatory statistical analysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

High level expression of active human alpha-1-antitrypsin in the milk of transgenic sheep.

We describe the generation of five sheep transgenic for a fusion of the ovine beta-lactoglobulin gene promotor to the human alpha 1-antitrypsin (h alpha 1AT) genomic sequences. Four of these animals are female and one male. Analysis of the expression of h alpha 1AT in the milk of three of these females shows that all express the human protein at levels greater than 1 gram per liter. In one case initial levels exceeded 60 grams per liter and stabilized at approximately 35 grams per liter as lactation progressed. Human alpha 1AT purified from the milk of these animals appears to be fully N-glycosylated and has a biological activity indistinguishable from human plasma-derived material.

Animals↗
PubMed1991

Commissioning new buildings: equipment.

Any new building will, with occasional exceptions, require new furnishings and equipment. In principle the organisation of this is straightforward. In practice it is a complicated exercise, full of snags. Phillip Simons discusses some of the problems.

Budgets↗