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Biomedical subjects

K Dietz

Publications and source records attributed to K Dietz.

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

Evaluation of the Murex CMV DNA Hybrid Capture assay (version 2.0) for early diagnosis of cytomegalovirus infection in recipients of an allogeneic stem cell transplant.

Early diagnosis of CMV infection based on sensitive diagnostic assays has helped to reduce CMV-related mortality after allogeneic stem cell transplantation (SCT). In this study, the commercialized Murex CMV DNA Hybrid Capture assay (version 2.0) (HCS) was prospectively compared to an in-house CMV-DNA PCR assay from whole blood in patients after allogeneic stem cell transplantation. Overall, a high concordance between HCS and PCR was documented (kappa = 0.686; n = 385). The HCS assay was found to be as sensitive as the PCR indicating active CMV infection at a median of 35 and 34 days after transplantation, respectively. None of the HCS-negative patients developed CMV-related symptoms (negative predictive value 100%). Declining CMV DNA load in the blood was found to be an indicator for effective antiviral therapy, whereas persistence of a high viral load was associated with fatal CMV disease. In conclusion, the Hybrid Capture CMV DNA assay (v 2.0) allows early diagnosis of CMV infection after allogeneic SCT and assessment of the efficacy of antiviral therapy.

Adolescent↗
PubMed2001

[Influence of experience on intra- and interindividual variability in assessing peripheral endothelial dysfunction with high resolution ultrasound].

UNLABELLED: The non-invasive evaluation of endothelial dysfunction with high-resolution ultrasound has become a widely accepted tool in determination of high-risk subjects for early atherosclerosis. Furthermore it is often used as intermediate outcome in intervention studies. AIM: We examined the influence of examiner experience on intra- and inter-individual variability in the measurement of flow-associated vasodilation (FAD) independent of automated analysis systems. METHOD: FAD was measured on two occasions in 7 and 8 subjects respectively (mean age 32 +/- 3 years) by two investigators after different prior training procedures with a 13 MHz linear transducer (LA14A, ESAOTE Biomedica). RESULTS: The intra-individual variability expressed as median absolute difference in the measurements of FAD was 1.1 % (range from 0.03 % to 3.2 %) for examiner one with an experience of more than 50 FAD measurements through former studies and 2.9 % (range from 1.6 % to 9.2 %) for examiner two with only 10 training examinations under supervision. By a further training period of two months, with an increase of examinations of additional 20 measurements by both examiners, the intra-observer variability could be dropped to 0.9 % (range from 0.03 % to 1.3 %) for examiner two (p = 0.0025) with no significant change for examiner one (median 0.6 % with a range from 0.14 % to 3.7 %). As expected, the inter-individual variability was not influenced by this further training (median 1.0 % with a range of 0.5 % to 3.6 % versus a median of 1.6 % with a range from 0.15 % to 7.5 %). CONCLUSION: 30 training measurements of FAD under supervision should be regarded as minimum requirement for valid determination of endothelial function. The reachable result for the intra-observer variability is thereby within the range of computed analysis systems.

Adult↗
PubMed2001

[Quantitative assessment of therapy related effects after breast conserving therapy with dynamic MRI of the breast].

PURPOSE: To quantify therapy related effects after breast conservation therapy (BCT) with dynamic MRI of the breast. METHODS: Twenty patients (median age 51 years) with breast conserving tumor excision were included. Contrast enhanced dynamic MRI was performed before and 3, 6 and 12 months after adjuvant radiation therapy (RT) with a total dose of 50.0 to 50.4 Gy. The following sequences were applied: axial fat-suppressed T(2)-weighted; coronal contrast enhanced 3D spoiled gradient-echo (first measurement prior to the administration of 0.16 mmol/kg Gd-DTPA, six repetitive measurements); sagittal T(1)-weighted Flash3D. Enhancement data were obtained using a computer software with automated segmentation of regions of interest (ROIs). After defining ROIs for skin, parenchyma and pectoral muscle of each breast the early enhancement after the first post contrast measurement (E(1)) and the slope of enhancement between the second and last postcontrast measurement (SE(2-L)) were calculated. The edema was quantified by assessing the signal intensities (SI) in the T(2)-weighted images. The thickness of the skin was measured in the sagittal T(1)-weighted images. RESULTS: Three months after RT statistically significant increases between 51 and 179 % of the SI and E(1) quotients were detected for all tissues compared to the examinations prior to RT. Six months after RT the skin still presented a by 102 % significantly higher E(1) quotient, and a by 140 % significantly increased SI quotient. No significant differences for SI and E(1) quotients could be observed 12 months after RT compared to the examinations prior to RT. A significant increase of the SE(2-L) difference for the skin from 0.0225 to 0.0691 and 0.0665 was found 3 and 6 months after RT, respectively. No significant differences between the initial MR examination and the follow-up examinations 3, 6 and 12 months could be detected for the SE(2-L) differences of the parenchyma. CONCLUSION: Early therapy related effects after BCT can be exactly quantified with dynamic MRI using an automated ROI-segmentation and whole breast analysis software. Both edema formation and early enhancement show peaks 3 months after RT, and after 12 months there is no statistically significant difference compared with baseline.

Adult↗
PubMed2001

Plasma clearance of iodine contrast media as a measure of glomerular filtration rate in critically ill patients.

OBJECTIVE: The selection of the optimal method for assessing renal function relies on the accuracy of the technique. Plasma clearance of nonradioactive iodine contrast media (i.e., iohexol or iopromide) has been suggested as a reliable alternative to the renal clearance of inulin for estimating glomerular filtration rate (GFR). The accuracy of this method when used with critically ill patients displaying different levels of renal function in an intensive care unit (ICU) has not, until now, been examined. DESIGN: The accuracy of double- and multiple-point iohexol or iopromide plasma clearances was compared with that of already established techniques for measuring GFR (creatinine clearance, formula clearance by Cockcroft and Gault) and with that of inulin clearance, which is regarded as the gold standard for the measurement of GFR. PATIENTS: Values were obtained from 31 ICU patients who exhibited a wide range of renal function (serum creatinine: 0.6-6.7 mg/dL). MEASUREMENTS: Inulin clearance was performed using the constant-infusion technique. Creatinine clearance was determined from 24-hr urine samples. The clearance formula was calculated according to Cockcroft and Gault's formula. Iohexol or iopromide were applied as a single intravenous dose, and blood samples were taken up to 6 hrs after the injection. Iodine concentrations were determined by radiographic fluorescence. RESULTS: Plasma clearance of iohexol/iopromide measured after the single injection of contrast media and that of the conventional inulin clearance was almost identical (y = 0.971x + 7.65, r2 =.96; n = 31). Two-point clearance of iohexol/iopromide (double sampling technique) was as reliable as the three-point clearance (three-slope-intercept method, y = 0.995x + 0.62, r2 =.999; n = 18). With respect to inulin clearance, GFR measurements determined by creatinine clearance or according to the formula given by Cockcroft and Gault revealed errors that increased proportionally (y = 1.03x, r2 =.88; n = 27; and y = 0.93x, r2 =.62; n = 31, respectively). It could also be shown that the accuracy of GFR measurements involving plasma clearance of iohexol was not greatly affected by the degree of renal insufficiency or the route by which contrast media were applied. CONCLUSION: These findings indicate that the determination of plasma clearance of iohexol/iopromide is a simple, rapid, and accurate method that can indeed be used for estimating GFR in ICU patients with normal renal function or even different degrees of renal insufficiency.

Adult↗
PubMed2001

Therapeutic drug monitoring of clozapine in relapse prevention: a five-year prospective study.

Twenty-three outpatients with schizophrenia (ICD-10 F20.xx) treated with clozapine (CZ) as monotherapy entered a prospective study on relapse prevention. Every 4 weeks, psychopathology was assessed by the Brief Psychiatric Rating Scale (BPRS), and plasma CZ and norclozapine levels were measured. Patients were enrolled after complete remission of positive symptoms for at least 4 months according to the psychosis cluster of the BPRS and at a mean of 3.3 years after their last hospitalization. At the time of enrollment, the median BPRS total score was 29 points (range, 19-48). Within 4 months, the baseline CZ plasma level was established as the mean of CZ levels from at least four subsequent measurements. These baseline plasma levels were considered as the optimal relapse-preventing plasma CZ levels in the individual patients. When the patients were enrolled, they were considered to be prone to relapse. Relapse was defined as clinical deterioration, hospitalization, or both. Plasma levels were considered a prognostic factor, and patients were defined as at increased risk if plasma levels decreased by more than 40% from baseline CZ plasma level. The effect of plasma CZ levels on clinical outcome was evaluated by a Cox regression with plasma level as a time-dependent covariate. Within 46 months of enrollment, 32 episodes of relapse events in 10 patients were available for evaluation. Seventeen patients had a plasma level decrease of more than 40% at some point. In 12 of these, the decrease was present for more than 12% of the observation period. Eight patients of this group relapsed, and three of these had to be rehospitalized. Two patients relapsed, although their plasma levels decreased by more than 40% for less than 12% of the observation period. Within the first 2 years, relapse-free survival curves illustrate that both groups (episodes under elevated risk and episodes not under elevated risk) had identical relapse patterns, but from then on the relapse risk increased rapidly in the group with longer exposure to elevated risk. In a Cox model with a 40% decrease of plasma CZ levels as a dichotomous time-varying explanatory covariate, the risk ratio is 6 (95% confidence interval = 2-19, p = 0.003). The 10 patients who relapsed exhibited safe plasma levels (less than a 40% decrease from their baseline levels) for only 210 months, and 13 nonrelapsing patients had plasma levels defined as safe for 426 months.

Antipsychotic Agents↗
PubMed2001

Efficacy and safety of contact transscleral diode laser cyclophotocoagulation for advanced glaucoma.

BACKGROUND: This prospective study was conducted to evaluate the efficacy and safety of transscleral diode laser cyclophotocoagulation in refractory, advanced glaucoma. PATIENTS AND METHODS: One hundred eyes of 100 patients with advanced glaucoma refractory to medical treatment were consecutively treated by transscleral diode laser cyclophotocoagulation. Success was defined as a final intraocular pressure between 5 and 21 mm Hg in eyes with a visual acuity of more than hard movements, relief of pain in eyes with a visual acuity of hand movements or less including blind eyes, and reduction of carbonic anhydrase inhibitor use in all eyes. RESULTS: Ninety-three patients were followed up for 1 year after initial treatment. The overall success rate was 74.2%. Of 60 eyes with a visual acuity of more than hand movements, intraocular pressure between 5 and 21 mm Hg was achieved in 41 (68.3%) eyes. Relief of pain was achieved in 28 (84.8%) of 33 eyes. Reduction of systemic carbonic anhydrase inhibitor use was highly significant (P < 0.0001). Within 1 year, 173 laser procedures (mean, 1.9 per patient) were performed. The probability of success increased significantly (P = 0.004) with the age of the patients, from 55% for patients younger than the age of 50 years to 83% for patients older than the age of 50 years. Previous ocular surgery decreased the success probability from 95% to 68% (P = 0.02). A high success rate was achieved in inflammatory glaucoma (75%), primary open-angle glaucoma (89.5%), and neovascular glaucoma (86.7%). The results were relatively poor in traumatic glaucoma (57.1%), aphakic glaucoma (57.1%), and congenital or juvenile glaucoma (62.5%). No significant relationship between loss of visual acuity and failure of treatment (P = 0.3) could be detected. No phthisis bulbi or persistent hypotonia developed. CONCLUSIONS: Transscleral diode laser cyclophotocoagulation is an effective and safe method for the treatment of advanced, refractory glaucoma. However, repeated treatments are often necessary. Success of treatment depends on the age of patients, previous surgery, and the type of glaucoma.

Adolescent↗
PubMed2001

Diagnosis and monitoring of murine histoplasmosis by a nested PCR assay.

A newly developed nested PCR assay was applied to murine models of histoplasmosis. ICR and BALB/c mice were intravenously infected with Histoplasma capsulatum and sacrificed up to 29 days later. Samples of blood, spleen, and lung homogenates were cultured and examined by the PCR assay. In the ICR mouse model, 265 of 319 organ samples showed concordant results. With 7 samples, the culture was positive and the PCR assay was negative whereas a positive PCR but a negative culture were obtained with 47 samples (P < 0.0001 according to McNemar's test). Organ homogenates and blood samples of either spontaneously cured or treated BALB/c mice were PCR negative. The nested PCR assay performs excellently in the monitoring of spontaneously and treatment-cured murine histoplasmosis. It limits the infection risks of the laboratory staff and might be of diagnostic value for humans.

Animals↗
PubMed2001

Peripheral artery occlusion: treatment with abciximab plus urokinase versus with urokinase alone--a randomized pilot trial (the PROMPT Study). Platelet Receptor Antibodies in Order to Manage Peripheral Artery Thrombosis.

PURPOSE: To evaluate the combination of a platelet glycoprotein IIb/IIIa complex receptor inhibitor and urokinase for treatment of recent (<or=6 weeks) arterial occlusion of the legs. MATERIALS AND METHODS: Seventy patients with lower extremity arterial occlusion of less than 6 weeks duration were randomly separated into two treatment groups: urokinase plus abciximab or urokinase plus placebo. Primary end points were the rate of major complications at 30 days after randomization and the rates of amputation-free survival and survival without open surgery or major amputation at follow-up of 90 days. Two readers unaware of the patients' treatment group assignments analyzed digital subtraction angiograms as they related to the study end points, with a final consensus reading. RESULTS: Thrombolysis relative to clot length was faster in the urokinase-plus-abciximab group (odds ratio, 0.52; 95% CI: 0.35, 0.76; P < .001). There were no procedure-related deaths or intracranial hemorrhages, but the rate of nonfatal major bleeding was higher with urokinase plus abciximab (four of 50 patients) than with urokinase alone (none of 20 patients; P = .32). At 90 days, amputation-free survival was 96% (48 of 50 patients) in the urokinase-plus-abciximab group compared with 80% (16 of 20 patients) in the urokinase alone group. The hazard ratio for the two Kaplan-Meier curves was 0.42 (95% CI: 0.16, 0.96; P = .04). CONCLUSION: In patients with lower extremity arterial occlusion who were undergoing urokinase thrombolysis, adjunctive abciximab treatment resulted in faster thrombus dissolution and improved amputation-free survival, despite an increase in major bleeding.

Abciximab↗
PubMed2001

Methods of experimental and clinical assessment of the relative measurement accuracy of an intracranial pressure transducer. Technical note.

The assessment of the actual measurement accuracy of an intracranial pressure (ICP) transducer is imperative but still very difficult in practice. The authors tested the Codman MicroSensor ICP transducer experimentally. Additionally, a bedside test for assessment of measurement accuracy was used before and after clinical monitoring. For laboratory testing, seven new transducers were examined for measurement accuracy at increasing pressures ranging from 0 to 75 mm Hg. Drift was evaluated for 10 days at six different pressure levels ranging from 0 to 50 mm Hg. Temperature drift was assessed over a temperature range from 20 to 45 degrees C. The percentage absolute difference was used in the assessment of measurement accuracy. For clinical testing, measurement accuracy was assessed intraoperatively just before the insertion of the transducer and in an open water bath after its explantation, at 10 cm H2O both times. The maximum percentage absolute difference was 9% at a pressure of 10 mm Hg, and declined toward 2.3% at a pressure of 75 mm Hg. The maximum drift over 10 days was -4 mm Hg. Within the range of 30 to 40 degrees C, temperature drift was negligible. Over a period of 2 years, between June 1997 and June 1999, 40 ICP transducers were implanted in 35 patients by one surgeon. Of these devices, a malfunction was detected in two of them by testing them in a water bath before insertion. Experimental and clinical results indicate that this miniature strain-gauge transducer measures accurately; however, control readings for the probe by means of measurement in an open water bath just before insertion are strongly recommended.

Equipment Design↗
PubMed2000

Characterization of an extracellular chymostatin-sensitive serine protease preferentially expressed in young plant tissues.

Intercellular washing fluids from leaves of all tested higher plant species contained a serine-type protease which efficiently cleaved the artificial fluorogenic substrate MCA-Pro-Leu-Gly-Leu-Dnp-Ala-Arg (MCA). The activity varied between the species. The classification as serine protease was based on the sensitivity towards chymostatin and phenylmethylsulfonyl fluoride. MCA protease activity strongly declined with leaf age and was also detected in stems, roots and flower petals. In tobacco, specific activity of the chymostatin-sensitive MCA protease was about 40-fold higher in intercellular washing fluids than in whole leaf homogenate confirming the extracellular location of the MCA protease. The same enzyme activity was detected in developing tomato fruits; it showed a correlation with fruit growth and was not detectable in ripe fruits. The tobacco protease was sensitive to temperatures above 50 degrees C, had an isoelectric point of 5.8+/-0.1 and an apparent molecular mass of 68 kDa. Its pH optimum was very broad with little difference in activity between pH 5 and 9. Conversely, a casein-cleaving protease also present in intercellular washing fluids was insensitive towards chymostatin and revealed a pronounced pH optimum around 6.0. The data biochemically characterize a new type of extracellular proteolytic activity which may be particularly important during tissue expansion.

Amino Acid Sequence↗
PubMed2000

Modelling the transition of asexual blood stages of Plasmodium falciparum to gametocytes.

In this paper, we investigate the transition of asexual blood stages of P. falciparum to gametocytes. The study is based on daily data, collected from 262 individual courses of parasitaemia. We propose several mathematical models that follow biological reasoning. The models are fitted with maximum likelihood and are compared with each other. The models differ in the assumptions made about the mortality of circulating gametocytes and about the transition rate of the asexual parasites. Gametocyte mortality is modelled as being (i) constant over time, (ii) linearly increasing over time, (iii) linearly increasing over gametocyte age, and (iv) exponentially increasing over gametocyte age, respectively. The transition rate is either kept constant per patient or piecewise constant within intervals that correspond to waves of asexual parasitaemia which are assumed to be caused by different Pf(emp1)-variants. According to likelihood ratio tests, the models with age-dependent mortality rate and wave-dependent transition rates are superior to the models with constant transition rate and/or constant or time-dependent mortality rate. The best fits are reached for models with exponentially increasing (Gompertz-type) mortality. Furthermore, an impact of high asexual parasite densities on the survival of gametocytes, interpreted as a cytokine-mediated effect, is evident in some cases.

Animals↗
PubMed2000

Differential regulation of the monocytic calcium-binding peptides macrophage-inhibiting factor related protein-8 (MRP8/S100A8) and allograft inflammatory factor-1 (AIF-1) following human traumatic brain injury.

Intracellular calcium (Ca2+) has been shown to function as second messenger and to be associated with activation of different cell types including microglia. Previously, in human focal cerebral infarctions an early expression of macrophage-related protein-8 (MRP8/ S100A8), a member of the Ca2+-binding S100-protein family, in microglia has been reported. On the other hand, a delayed activation of microglia was observed following traumatic brain injury (TBI). We therefore examined immunohistochemically microglial expression of MRP8 and allograft inflammatory factor-1 (AIF-1), identical to microglial response factor-1 (mrf-1) and ionized calcium binding adaptor molecule-1 (ibal) in human brains after TBI and in control brains. Both, MRP8 and AIF-1 are Ca2+-binding peptides which have been associated with microglial activation in experimental models and in human cerebral infarctions. Detection of AIF-1 in controls confirmed constitutive expression of this peptide in a subset of microglial cells. After TBI, the density of AIF-1+ microglia did not increase significantly. Lesional expression of AIF-1 did not significantly differ from other brain regions. Furthermore, following TBI, we found no significant differences in the density of AIF-1+ microglia as compared to controls. Microglial MRP8 expression was not detectable in controls and within the first 3 days post TBI, but increased rapidly after 3 days post TBI, suggesting a subpopulation of microglial cells to be AIF-1-/MRP8+. We conclude that the delayed expression of MRP8 and the lack of AIF-1 up-regulation in microglia after TBI is in contrast to ischemic brain lesions and might reflect different activation cascades of microglia.

Adolescent↗
PubMed2000

Stochastic models for aggregation processes.

Three models are presented, which describe the aggregation of objects into groups and the distributions of groups sizes and group numbers within habitats. The processes regarded are pure accumulation processes which involve only formation and invasion of groups. Invasion represents the special case of fusion when only single objects - and not groups - join a group of certain size. The basic model is derived by a single parameter, the formation probability q, which represents the probability of an object to form a new group. A novel, discrete and finite distribution that results for the group sizes is deduced from this aggregation process and it is shown that it converges to a geometric distribution if the number of objects tends to infinity. Two extensions of this model, which both converge to the Waring distribution, are added: the model can be extended either with a beta distributed formation probability or with the assumption that the invasion probability depends on the group size. Relationships between the limiting distributions involved are discussed.

Animals↗
PubMed2000

Contact tracing in stochastic and deterministic epidemic models.

We consider a simple unstructured individual based stochastic epidemic model with contact tracing. Even in the onset of the epidemic, contact tracing implies that infected individuals do not act independent of each other. Nevertheless, it is possible to analyze the embedded non-stationary Galton-Watson process. Based upon this analysis, threshold theorems and also the probability for major outbreaks can be derived. Furthermore, it is possible to obtain a deterministic model that approximates the stochastic process, and in this way, to determine the prevalence of disease in the quasi-stationary state and to investigate the dynamics of the epidemic.

Communicable Diseases↗
PubMed2000

Reduction of minimal erythema dose by sweating.

BACKGROUND/AIMS: Solar ultraviolet (UV) radiation is the most important environmental risk factor for melanoma and non-melanoma skin cancer. It is known that tap water and saltwater baths have a photosensitizing capacity in subsequent UV irradiation of the skin. The aim of the present study was to determine the influence of sweating from heat or from physical activity on the photosensitivity of the skin. METHODS: Minimal erythema dose to ultraviolet B (MED/UVB) was determined on the inner forearms of 22 healthy volunteers with a Saalmann Multi-tester. Sweating had been provoked by heat (sauna for 10 min) and, on another occasion, physical exercise (jogging for 15 min) followed by MED/UVB testing in a similar way. RESULTS: Compared to baseline MED/UVB there was a highly significant decrease in MED/UVB of up to 31.6% (median 15.8%, mean 15.9% +/- 10.0) after 10 min in the sauna and up to 40.9% (median 16.3%, mean 17.2% +/- 12.5) after 15 min jogging (P < 0.0001). CONCLUSION: Sweat influences the hydration of the horny layer of the skin, resulting in a decrease in reflection and dispersion of UV light. Moderate physical activities such as jogging and/or heat may facilitate erythema reaction. By sweating, outdoor workers and people practicing outdoor sports who are exposed to considerable amounts of solar UV radiation further increase their risk of sunburn.

Adult↗