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Biomedical subjects

F Peters

Publications and source records attributed to F Peters.

At least 19 recordsLinked to original sources
PubMed2006

A type II-collagen derived peptide and its nitrated form as new markers of inflammation and cartilage degradation in equine osteochondral lesions.

Markers of cartilage breakdown enable studying the degradation of cartilage matrix in equine joint pathologies. This study was designed to determine the levels of Coll2-1, a peptide of the triple helix of type II collagen, and Coll2-1NO(2), its nitrated form in the plasma of healthy horses (controls; n=37) and horses suffering from osteochondrosis (n=34). Clinical and arthroscopic scores were attributed reflecting the severity of lesions and were related to the plasma levels of Coll2-1 and Coll2-1NO(2). The median of Coll2-1 was significantly higher in the control group, whereas the mean of Coll2-1NO(2) showed significant elevation in the pathological group. However, the measurement means of scoring classes did not vary significantly. The markers were able to differentiate the group of horses suffering from osteochondrosis from the group of healthy horses. The elevation of Coll2-1NO(2) in the pathological group indicates an inflammation, mediated through reactive oxygen species and/or increased myeloperoxidase activity.

Animals↗
PubMed2005

Poor results of 5-aminolevulinic acid-photodynamic therapy for residual high-grade dysplasia and early cancer in barrett esophagus after endoscopic resection.

BACKGROUND AND STUDY AIMS: The aim of the study was to evaluate the efficacy of photodynamic therapy (PDT) in the treatment of residual high-grade dysplasia or early cancer (HGD/EC) after endoscopic resection in Barrett esophagus. PATIENTS AND METHODS: Study patients were separated into group A, with proven residual HGD/EC, and group B with possible HGD/EC (positive lateral margins in the endoscopic resection specimen, without HGD/EC in the remaining Barrett esophagus). PDT treatment consisted of 5-aminolevulinic (5-ALA) photosensitization (40 mg/kg) followed by illumination of the Barrett esophagus with a total light dose of 100 J/cm (2). Complete remission was defined as the absence of HGD/EC in biopsies taken in two consecutive follow-up endoscopies. The percentage regression of Barrett esophagus, as well as the recurrence rate of HGD/EC, was calculated. RESULTS: 20 patients underwent PDT (group A, 11; group B, 9). Mild complications were seen in 4/26 procedures. The overall success rate was 15/20 (75 %). There was a significant difference in success rate between group A (55 %) and group B (100 %); P = 0.03. All patients had residual Barrett esophagus after PDT; the median regression percentage was 50 % (IQR 25 - 70 %). Recurrence of HGD/EC occurred in four patients (two each in groups A and B) after a median follow up of 30 months. CONCLUSIONS: In this selected group of patients, the addition of 5-ALA-PDT after endoscopic resection for HGD/EC had a disappointing success rate in patients who had residual HGD/EC after endoscopic resection. Most patients undergoing 5-ALA-PDT have residual Barrett mucosa after PDT and 5-ALA-PDT does not seem to prevent recurrences during follow-up.

Aged↗
PubMed2005

Development of an enzyme-linked immunosorbent assay for specific equine neutrophil myeloperoxidase measurement in blood.

Equine inflammatory disease is accompanied by a neutrophil activation resulting in the release of granulocytic enzyme myeloperoxidase (MPO). To measure MPO in horse plasma as marker of neutrophil activation, the authors purified equine neutrophil MPO and developed a specific enzyme immunoassay using 2 specific polyclonal antibodies obtained from rabbit (primary antibody) and guinea pig (secondary antibody). The sandwich complex "primary antibody-MPO-secondary antibody" was detected using a goat anti-guinea pig immunoglobulin antibody conjugated to alkaline phosphatase. The enzyme-linked immunosorbent assay (ELISA) showed good precision and accuracy, with intra- and interassay coefficients of variation below 10% for MPO concentrations ranging from 0.78 to 50 ng/ml. A stable plasma MPO value, unaffected by time elapsed between blood collection and centrifugation, was obtained with plasma from EDTA anticoagulated blood. The mean MPO value measured in 38 healthy horses was 181.80 +/- 64.74 ng/ml. In 20 horses suffering from obstruction of the large or small intestine, MPO concentrations measured at the time of arrival at the intensive care unit were significantly higher than mean normal value, ranging from 477.88 to 2,748.13 ng/ml. Work is in progress to apply this MPO ELISA technique to other biological fluids and other equine diseases.

Animals↗
PubMed2004

Effects of small-scale turbulence on bacteria: a matter of size.

We examined the influence of small-scale turbulence and its associated shear on bacterioplankton abundance and cell size. We incubated natural microbial assemblages and bacteria-only fractions and subjected them to treatments with turbulence and additions of mineral nutrients and/or organic carbon. Bacterial abundance was not affected directly by turbulence in bacteria-only incubations. In natural microbial assemblage incubations, bacterial concentrations were higher under turbulence than in still-water controls when nutrients were added. In general, in the turbulence treatments bacteria increased significantly in size, mainly due to elongation of cells. The addition of inorganic nutrients had a negative effect on bacterial size, but a significantly positive effect on abundance independently of other factors such as turbulence and the presence of predators. Flagellate grazing did not trigger an increase in bacterial size as a grazing resistance response in unmixed containers. With the addition of organic carbon, bacteria elongated and partly settled to the bottom of the containers, in both the turbulent and still treatment, but bacterial abundance did not further increase. Furthermore, bacteria aggregated in the turbulence treatments after the second day of incubation even in the absence of other components of the microbial community. We found that turbulence and the associated shear increase bacterial size and change bacterial morphology, at least under certain nutrient conditions. This might be due to a physiological response (enhanced growth rate and/or unbalanced growth) or due to the selection of opportunistic strains when organic carbon is in excess compared to mineral nutrients. We suggest that shear associated with turbulent flow enhances the DOM flux to bacteria directly as well as indirectly through enhanced grazing activity and photosynthetic release. The formation of bacterial aggregates and filaments under turbulence might give selective advantage to bacteria in terms of nutrient uptake and grazing resistance.

Bacteria↗
PubMed2004

Cohesion induced by a rotating magnetic field in a granular material.

We report experiments on a magnetic cohesive granular material made of steel spheres in the millimeter range. A magnetic field magnetizes the spheres, so that an interaction force between grains appears. A rotating magnetic field is applied parallel to plane of the quasi-two-dimensional cell containing the spheres so that only the time averaged force between two particles will be considered. Both maximum angle of stability and angles of repose are measured. The maximum angle of stability is found to depend linearly on the interaction force. Another noticeable feature is the lack of dependence of the maximum angle of stability on the initial height of the heap. We show that the angle of repose is less sensitive to the magnetic interaction force than the maximum of stability. At last, we discuss the importance of using a rotating field rather than a constant one. In particular, we report some measurements of both the maximum angle of stability and the angle of repose in constant field, which show a strong dependence of the angles of avalanche on the direction of the field.

Journal Article↗
PubMed2004

Fatal pulmonary embolism in hospitalised patients: a necropsy review.

AIMS: To carry out a retrospective review of all postmortem reports during the period 1991 to 2000 at King's College Hospital, London, as an extension of a previous analysis performed for the period 1965 to 1990. METHODS: The number of deaths resulting from necropsy confirmed fatal pulmonary embolism in hospitalised patients was determined, and a limited analysis of the clinical characteristics of those patients who died was performed. RESULTS: During the 10 year period, 16 104 deaths occurred and 6833 (42.4%) necropsies were performed. The outcome measure, fatal pulmonary embolism, was recorded as cause of death in 265 cases (3.9% of all necropsies; 5.2% of adult cases). No deaths from pulmonary embolism occurred in patients under 18 years of age; 80.0% occurred in patients older than 60 years. Of the fatal emboli, 214 of 265 (80.8%) occurred in patients who had not undergone recent surgery. Of these patients, 110 (51.4%) had suffered an acute medical illness in the six weeks before death, most often an acute infectious episode (26 cases). CONCLUSIONS: Thromboembolic events remain a relatively common cause of death in hospitalised patients and appear to occur more frequently in non-surgical than in surgical patients.

Adolescent↗
PubMed2003

[Preoperative risk assessment and ambulatory management].

Evidence and practical approach of Coronary Risk Assessment in noncardiac surgery are reviewed. Growing literature suggests a benefit of perioperative b-blockade. Therefore, risk stratification and management are described in algorithms in order to provide a useful tool for practitioners both in the hospital and ambulatory setting.

Adrenergic beta-Agonists↗
PubMed2003

Simultaneous bilateral spontaneous pneumothorax in a patient with recurrent, extraosseous multiple myeloma.

A patient with simultaneous bilateral spontaneous pneumothorax (SBSP) due to pulmonary and pleural manifestations of recurrent multiple myeloma is presented. The patient died in shock of unknown cause. The diagnosis was suspected from pleural fluid examination showing an exudate with numerous plasmocytes. Macroscopically and histologically, the visceral organs and the bone marrow were infiltrated with multiple monoclonal proliferations of plasma cells staining positively for IgG and lambda chains. SBSP is a rare condition and may be caused by trauma, parenchymal lung disease, infections, or neoplasms. This is the first report of SBSP caused by pleuropulmonary infiltration of multiple myeloma.

Aged↗
PubMed2002

Generation of GW radiation pulses from a VUV free-electron laser operating in the femtosecond regime.

Experimental results are presented from vacuum-ultraviolet free-electron laser (FEL) operating in the self-amplified spontaneous emission (SASE) mode. The generation of ultrashort radiation pulses became possible due to specific tailoring of the bunch charge distribution. A complete characterization of the linear and nonlinear modes of the SASE FEL operation was performed. At saturation the FEL produces ultrashort pulses (30-100 fs FWHM) with a peak radiation power in the GW level and with full transverse coherence. The wavelength was tuned in the range of 95-105 nm.

Journal Article↗
PubMed2002

Continuous synthesis of amorphous carbonated apatites.

Amorphous carbonated hydroxyapatite was prepared by rapid mixing of aqueous solutions of a continuous computer-controlled reactor. The variation of the carbonate content in the solid product is possible by adjustment of the ratios of phosphate to carbonate in the initial solution. The principal reaction parameters (temperature, pH, stirrer speed, solution composition and supersaturation) are controlled and monitored. By controlling these processing parameters, a non-stoichiometric hydroxyapatite with fine-tuned crystallinity, morphology, and carbonate content can be reproducibly prepared. The higher solubility under the conditions of osteoclastic resorption was tested in vitro at constant pH (4.4).

Apatites↗
PubMed2002

Isolated erythema (cellulitis) of the breast.

This paper reports nine cases of breast cellulitis in women patients (four cases in pregnancy, four postmenopausal cases following hormone replacement therapy and one case of unilateral breast oedema following a mediastinal lymphoma). Biopsies were obtained from the erythematous area in one pregnant patient, one postmenopausal patient and the patient with breast oedema associated with the mediastinal lymphoma. Histology revealed unspecific dermatitis with extensive perivascular lymphoplasmocellular infiltrates. Histopathological examination of biopsies obtained from the underlying mammary tissue along with the corresponding mammographic data gave no evidence of mastitis or mammary carcinoma. The patients complained of sensitivity to touch, a feeling of local tightness or a burning sensation. These findings were reported in both breasts in the pregnant patients, but were unilateral in the others. The submammary fold was unremarkable, that is, no intertrigo was detected. The aetiology of the erthyema is probably associated with swelling of the breast tissue and a causal link with a specific endocrine constellation (pregnancy, postmenopausal HRT) can be postulated. A common factor in all cases presented here is the relatively long period of 4 to 13 weeks before healing of the lesion. Therapeutic intervention with antibiotics or dopamine agonists failed to influence the course. Similarly, steroid cream appeared to be of no value in these cases. Extensive erythema of the breast skin is a benign disease, for which there is still no known effective therapy. The lack of mammographic evidence and, especially, of positive palpatory findings make breast cancer highly improbable as the underlying cause.

Journal Article↗
PubMed2002

[Contraception in chronically ill adolescents].

Contraception in chronically ill adolescents has to consider side effects with regard to metabolic or hematological disease. Additionally the compliance of the patient has to be taken in account when consulting about contraceptives. In juvenile diabetics with good glycemic control and metabolic diseases of the amino acids oral contraceptives are justifiable. Adolescents with galactose-mia mostly suffer from premature ovarian failure and therefore have to be controlled wether they need contraception at all. Young women with sickle-cell anemia are at risk of thrombophilia. They should not be given hormonal contraceptives. In v. Willebrand-Jürgens-Syndrome oral contraceptives are favourable because it alleviates menorrhagia.

Adolescent↗
PubMed2001

Electronic communication in oligometallic complexes with ferrocene-based tris(1-pyrazolyl)borate ligands.

Ferrocene-based tris(1-pyrazolyl)borate ligands 1R-Li and 1R-Tl have been synthesized and used to generate a variety of heterotrinuclear transition metal complexes, 3R-M [R = H, SiMe(3), cyclohexyl, (cyclohexyl)methyl, phenyl; M(II) = Mn, Fe, Co, Ni, Cu, Zn]. The poor solubility of 3H-M is greatly enhanced by the introduction of large organic substituents into the 4-positions of all pyrazolyl rings. The unsubstituted ligand 1H-Li and the trinuclear complex 3Cym-Cu [Cym = (cyclohexyl)methyl] have been investigated by X-ray crystallography. 1H-Li, which represents the first example of a structurally characterized lithium tris(1-pyrazolyl)borate, forms centrosymmetric dimers in the solid state. A severe Jahn-Teller distortion was observed for the (Bpz(3))(2)Cu fragment in 3Cym-Cu. Compared to the parent compounds [(HBpz(3))(2)M], the presence of uncharged ferrocenyl substituents in 3R-M tends to shift the M(2+)/M(3+) redox potential to significantly more cathodic values. The opposite is true if the ferrocenyl fragments are in their cationic state, which results in an anodic shift of the M(2+)/M(3+) transition. Most interestingly, the two ferrocenyl fragments in 3R-Cu appear to be electronically communicating.

Journal Article↗
PubMed2001

Seawater-atmosphere O(2) exchange rates in open-top laboratory microcosms: application for continuous estimates of planktonic primary production and respiration.

Seawater-atmosphere O(2) exchange rates were experimentally measured in open-top laboratory microcosms. The objective was to establish the relationships between turbulence and oxygen transfer velocity, and thus correct continuously measured day-night changes in dissolved oxygen as estimates of planktonic primary production and respiration. After saturating 15-l sterile seawater microcosms with an oxygen-poor gas mix (4.9% O(2), 95.1% N(2)), the microcosms were left to equilibrate with the atmosphere under different turbulence conditions. The rate of increase in dissolved O(2) was measured at 15-min intervals with polarographic-pulsed electrodes and the corresponding values of the oxygen transfer velocity (the K(O(2)) constant for the different turbulence conditions) were determined. After pooling these and literature data obtained in similar experimental conditions, the relation between epsilon (turbulent kinetic energy dissipation rates) and K(O(2)) was determined. Theoretical K(O(2)) values were also calculated using semi-empirical models in which oxygen transfer velocity (K(O(2))) is related to wind velocity. Theoretical, wind related K(O(2)) values were significantly higher than the experimental ones, and as a consequence overestimate primary production and underestimate respiration rates, even resulting in nocturnal O(2) increase. The magnitude of the differences between experimentally derived and theoretically calculated oxygen transfer velocity, precludes the use of wind-derived equations to calculate K(O(2)) in meso- and microcosms experiments not affected by wind, while the equation obtained relating experimental epsilon and K(O(2)) provides statistically reliable estimations of primary production and respiration.

Journal Article↗
PubMed2001

Biologically and chemically optimized composites of carbonated apatite and polyglycolide as bone substitution materials.

We report on the development and characterization of a new composite material consisting of amorphous carbonated apatite, Ca(5)(PO(4), CO(3))(3)(OH), and microstructured poly(hydroxyacetic acid), polyglycolide (PGA). This material is able to keep the pH of a surrounding solution within the physiological range (7.2-7.6). This was achieved by chemical fine-tuning of the counterplay between the acidic degradation of the polyester and the basic dissolution of calcium phosphate. Microporous samples with pore sizes of <1 microm and compact samples were prepared. The biological behavior was assayed in vitro by long-term osteoblast culture. Morphological and biochemical analyses of cell differentiation revealed excellent biocompatibility, leading to cell attachment, collagen and osteocalcin expression, and mineral deposition. This material could be of use as a biodegradable bone substitution material and as a scaffold for tissue engineering.

Animals↗
PubMed2001

Simulating arterial wall calcification in vitro: biomimetic crystallization of calcium phosphates under controlled conditions.

OBJECTIVES: A method to simulate the biological and pathological crystallization of calcium phosphate in vitro is presented. BACKGROUND: The pathological crystallization of calcium phosphates during atherosclerosis is still poorly understood as it depends on a variety of external factors, e.g., the presence of biological molecules that act as crystallization promoters or inhibitors. METHODS: A computer-controlled double-diffusion device is presented that permits crystallization under constant external conditions (constant pH, constant concentrations of Ca2+ and PO4(3-)). RESULTS: The crystallization of hydroxyapatite occurs in a well-defined way. The presence of additives (cholesterol, magnesium) distinctively alters the morphology of the crystals. CONCLUSIONS: The simulation of pathological crystallization as in atherosclerosis is possible if the external conditions are kept strictly constant during the experiment. In order to obtain a meaningful insight into biological crystallization, this approach is essential as otherwise the external conditions change continuously during the experiment. The effect of additives can be conveniently studied.

Arteriosclerosis↗