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Biomedical subjects

G Koch

Publications and source records attributed to G Koch.

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

Calibration and validation of an ASM3-based steady-state model for activated sludge systems--part I: Prediction of nitrogen removal and sludge production.

The steady-state model from Siegrist and Gujer (1994) which can be used for the design and optimisation of nitrogen-removing activated sludge plants is applied to the stoichiometrics and kinetics of a validated Activated Sludge Model No. 3. It considers the wastewater composition, the effect of the electron acceptor on the average sludge production, the oxygen input into anoxic volumes, denitrification in the secondary clarifier, the temperature and various operating conditions. The organic substrate for denitrification originates from readily degradable substrate from the influent, from the hydrolysis of slowly degradable particulate substrate along the activated sludge plant and from the endogenous respiration of the biomass. The model is calibrated and validated with data from long-term full-scale and pilot-plant experiments for Swiss municipal wastewater. The most sensitive parameters as well as the uncertainty of the model prognosis for various COD-to-nitrogen ratios from inlet water and anoxic volume fractions were calculated with the aid of sensitivity analyses and Monte-Carlo simulations. Excel spreadsheets of the model for different flow schemes are available from the corresponding author.

Biomass↗
PubMed2001

Calibration and validation of an ASM3-based steady-state model for activated sludge systems--part II: Prediction of phosphorus removal.

An ASM3-based steady-state model which can be used for estimating the average nitrogen-removal, sludge-production and phosphorus-removal rates of different biological phosphorus-removing systems (AAO, UCT, intermittent processes) is developed. It considers the wastewater composition, the oxygen and nitrate input in the anaerobic compartment and the interaction between biological phosphorus removal and denitrification for different operating conditions. The model is calibrated and validated with data from a number of long-term pilot and full-scale experiments for Swiss municipal wastewater. The steady-state model is adequate for a comparison of different BPR process configurations or for a first estimation of the nutrient-removal efficiency. It allows the plant performance and key parameters to be determined very quickly. Excel spreadsheets of the model for different flow schemes are available from the corresponding author.

Anaerobiosis↗
PubMed2001

The EAWAG Bio-P module for activated sludge model No. 3.

An additional module for the prediction of enhanced biological phosphorus removal is presented on the basis of a calibrated version of ASM3. The module uses modified processes from ASM2d but neglects the fermentation of readily degradable substrate. Biomass decay is modeled in the form of endogenous respiration as in ASM3. Moreover, an additional glycogen pool and biologically induced P-precipitation were not taken into account. The module was systematically calibrated with experimental data from various batch experiments, a full-scale WWTP and a pilot plant treating Swiss municipal waste water. A standard parameter set allowed all data to be simulated.

Biomass↗
PubMed2001

On the retention and effectiveness of fissure sealant in permanent molars after 15-20 years: a cohort study.

The aim of the present study was to clinically evaluate fissure sealants on the occlusal fissures and buccal pits of permanent first and second molars after 20 and 15 years, respectively. The population consisted of 72 children, each of whom had had their four first molars sealed between 1977 and 1980. At the annual examinations, all caries-free, newly erupted second molars were sealed. When sealant was applied to the second molars, the first molars were checked and sealant was reapplied to those that had deficient sealants. At the follow-up, when the subjects were 26-27 years of age, 27 in the original group had moved from the community. Thus, the present result is based on 45 subjects. One hundred and fifty-three sealed first molars and 161 sealed second molars were available for inspection. At the follow-up examination of the first molars 20 years after sealant had been applied, 65% showed complete retention, 22% partial retention without caries, and 13% caries or restoration in the occlusal fissures or buccal pits. At the 15-year follow-up of the second molars, the corresponding figures were 65%, 30%, and 5%, respectively. Of the restored or carious molars, significantly more were found in the mandible than in the maxilla (P<0.001). This longitudinal study showed that pit and fissure sealants--applied during childhood--have a longlasting, caries-preventive effect.

Adult↗
PubMed2001

Infantile presentation of the mtDNA A3243G tRNA(Leu (UUR)) mutation.

Mitochondrial DNA (mtDNA) disorders are clinically very heterogeneous, ranging from single organ involvement to severe multisystem disease. One of the most frequently observed mtDNA mutations is the A-to-G transition at position 3243 of the tRNA(Leu (UUR)) gene. This mutation is often related to MELAS syndrome. However, not all patients with the A3243G mutation share the same clinical disease expression and, on the contrary, patients clinically exhibiting MELAS syndrome may have other mtDNA mutations. Here we describe two patients with a very early infantile presentation of disease associated with the A3243G mutation. Patient 1 presented with hypotonia, feeding difficulties and failure to thrive (FTT) at the age of 3 months. Laboratory investigations showed persistent hyperlactic acidemia, elevated lactate/pyruvate ratios and elevated alanine concentrations in blood. Developmental delay was progressive and he developed cardiomyopathy and seizures. Death occurred at the age of 3.5 years. Patient 2 was born prematurely and had persistent, severe lactic acidosis from birth on. Moderate biventricular hypertrophy was seen on ultrasound studies of the heart and, suffering from progressive lactic acidosis, he died at the age of 13 days. Because of the rarity of this very early presentation, we searched the literature for other infantile cases associated with the A3243G mutation and found 8 additional ones. In infants presenting with lactic acidosis/hyperlactic acidemia, failure to thrive, hypotonia, seizures and/or cardiomyopathy, mtDNA mutational analysis, also for the disease entities, usually only observed in juveniles or adults is warranted.

Acidosis, Lactic↗
PubMed2001

Endovascular stent-graft repair of acute thoracic aortic dissection--early clinical experiences.

BACKGROUND: Standard treatment of acute thoracic aortic dissection type B is the medical therapy used for most patients, according to Stanford. Surgical therapy involves a high mortality rate and is reserved for patients with complicated dissections. We report from four patients with acute thoracic aortic dissection, treated endoluminally by stent-graft implantation. METHODS: Four patients with complicated acute thoracic aortic dissections type B were treated endoluminally by transfemoral stent-graft implantation. Preoperative evaluation was performed with spiral-computed tomography and calibrated aortography. The Talent stent-graft system (Metronic) was used in all patients. RESULTS: The primary entry tear could be sealed successfully and complete thrombosis of the false thoracic aortic lumen was obtained in all cases. In one patient, transposition of the left subclavian artery was performed, in two patients the stent-grafts had to be placed across the origin of the left subclavian artery. No severe intra- or postoperative complications occurred. CONCLUSION: Endoluminal treatment of acute thoracic aortic dissection seems to be a less invasive and effective therapy. Long-term results for this method are necessary.

Acute Disease↗
PubMed2001

Parieto-frontal interactions in visual-object and visual-spatial working memory: evidence from transcranial magnetic stimulation.

This study aimed to investigate whether transcranial magnetic stimulation (TMS) can induce selective working memory (WM) deficits of visual-object versus visual-spatial information in normal humans. Thirty-five healthy subjects performed two computerized visual n-back tasks, in which they were required to memorize spatial locations or abstract patterns. In a first series of experiments, unilateral or bilateral TMS was delivered on posterior parietal and middle temporal regions of both hemispheres after various delays during the WM task. Bilateral temporal TMS increased reaction times (RTs) in the visual-object, whereas bilateral parietal TMS selectively increased RTs in the visual-spatial WM task. These effects were evident at a delay of 300 ms. Response accuracy was not affected by bilateral or unilateral TMS of either cortical region. In a second group of experiments, bilateral TMS was applied over the superior frontal gyrus (SFG) or the dorsolateral prefrontal cortex (DLPFC). TMS of the SFG selectively increased RTs in the visual-spatial WM task, whereas TMS of the DLPFC interfered with both WM tasks, in terms of both accuracy and RTs. These effects were evident when TMS was applied after a delay of 600 ms, but not one of 300 ms. These findings confirm the segregation of WM buffers for object and spatial information in the posterior cortical regions. In the frontal cortex, the DLPFC appears to be necessary for WM computations regardless of the stimulus material.

Adult↗
PubMed2001

Campomelic dysplasia without sex reversal in a Turkish patient is due to mutation Ala119Val within the SOX9 gene.

Campomelic dysplasia is a rare neonatal skeletal malformation syndrome mainly characterized by congenital bowing and angulation of long bones in combination with other skeletal and extraskeletal defects. Two thirds of karyotypic males exhibit male-to-female sex reversal. Point mutations within SOX9 in 17q24-25 or rearrangements upstream to SOX9 as well as a deletion of a complete gene, causing haploinsufficiency of the gene product, have been detected in some patients. Recurrent mutations appear to be rare and most mutations detected in campomelic dysplasia are family specific. Here, we report on a Turkish patient with a 46,XY karyotype affected by campomelic dysplasia without sex reversal. Sequencing the SOX9 gene revealed a heterozygous Ala119Val mutation in exon 1, coding for the highly conserved HMG-box of the gene. This mutation is not present in the parents' lymphocyte DNAs. The same mutation was recently reported in a patient with 46,XX karyotype. Additionally, our patient is homozygous for the common polymorphism c507C-->T, while both parents are heterozygous.

Child, Preschool↗
PubMed2001

Long-term evaluation of a fissure sealing programme in Public Dental Service clinics in Sweden.

The aim of the present study was to evaluate the long-term results of a systematic fissure sealing programme of the occlusal surfaces of newly erupted permanent first molars. All 15-year-olds (n=815) who had been regularly treated at seven Public Dental Service clinics in Jönköping County, Sweden, since the eruption of their permanent first molars participated in the study. Data on fissure sealing and restorative treatment were extracted from the dental records of the patients. When the patients were 15 years of age, it was found that 6% of the original 2456 sealed occlusal permanent first molars had received Class II restorations. Seventy-eight per cent of the remaining 2322 sealed occlusal surfaces were judged to be caries-free by the child's ordinary dentist. This long-term retrospective study indicates that a structured fissure sealing programme is of great benefit for oral health.

Adolescent↗
PubMed2000

Discoloration of ceramic hydroxyapatite used for protein chromatography.

Hydroxyapatite chromatography was used to purify a recombinant human protein at preparative (400 g) scale. The hydroxyapatite column became progressively discolored as the number of chromatographic cycles increased. Elemental analysis showed that Mn, Fe, Al, Cd, Ba, Cr and Sn were found in used, discolored hydroxyapatite but were below the detection limit (1 ppm) in new hydroxyapatite. Metal ions were not removed from the discolored hydroxyapatite by regeneration with 0.5 M sodium phosphate followed by 0.5 M sodium hydroxide. Chromatographic performance was not affected by the accumulation of metal ions for at least 8 cycles on the preparative column (media volume 56 l) and for at least 12 cycles on the laboratory-scale column (media volume 3.7 ml).

Ceramics↗
PubMed2000

Movement cueing and motor execution in patients with dystonia: a kinematic study.

To investigate whether the type of movement cueing influences motor performance in patients with dystonia, we studied externally triggered (ET) and self-initiated (SI) sequential rapid arm movements in patients with generalized or focal dystonia and healthy control subjects. The ET task required subjects to initiate movements in response to consecutive visual cues; the SI task allowed them to start at will. To determine whether patients found sequential motor tasks more difficult than single tasks, we also analyzed single ET movements. Control subjects performed the SI task significantly faster than the ET task. Their single ET movements and first ET sequential submovements had similar speeds. Patients with generalized dystonia were slow in performing the single movement, the ET and the SI sequential tasks, and they executed the SI sequence more slowly than the ET. They made long pauses between SI sequential submovements, had longer reaction times during the ET sequences, and performed the first ET submovement more slowly than the single ET movement. Patients with focal dystonia had normal reaction times but they performed single and sequential tasks slowly, made long pauses during SI tasks, and also executed the first ET submovement more slowly than the single ET movement. Our findings indicate that patients with dystonia have a general impairment of sequential movements. The more marked slowness in executing SI than ET movements observed in patients with generalized dystonia shows that dystonia impairs internal cueing more than external cueing mechanisms. Overall, these findings imply abnormal activation of primary and nonprimary motor areas during movement in dystonia. The greater impairment of SI tasks as well as the delayed motor responses during ET task suggest predominant underactivity of the supplementary motor area.

Adolescent↗
PubMed2000

Large-scale purification of recombinant human angiostatin.

A process for the purification of recombinant human angiostatin (rhAngiostatin), produced by Pichia pastoris fermentation operated at the 2000-L scale, is reported. rhAngiostatin was recovered and purified directly from crude fermentation broth by cation exchange expanded bed adsorption chromatography. Anion exchange chromatography, hydroxyapatite chromatography, and hydrophobic interaction chromatography were used for further purification. Full-length rhAngiostatin was separated from rhAngiostatin molecules fragmented by endoproteolysis. On average, 140 g of rhAngiostatin was produced per batch, with an overall yield of 59% (n = 9). The purification process was completed in approximately 48 h and used only inexpensive and nontoxic raw materials. Methods development, process synthesis, and process scale-up data are presented and discussed.

Ammonium Sulfate↗
PubMed2000

[How much pain is tolerable? Target expectations of surgical patients for pain therapy].

INTRODUCTION: Sufficient pain treatment is part of surgical therapy. One popular method of pain control is patient-controlled analgesia (PCA), which allows the patients to apply small doses of analgesics intravenously via a pump. Patient involvement in PCA requires an exact assessment of the patient's expectations as to the treatment of pain. METHODS: In a prospective study the patient's expectations of pain therapy were observed with respect to their disease and the actual intensity of pain during activities measured with a visual analogue scale (VAS). Fifty-three patients were involved, using a pain questionnaire. Healthy nursing staff (n = 44) served as a control group. RESULTS: Patients with benign (n = 29) or malignant (n = 24) disease showed no significant difference in the VAS scores accepted from patients as aim of successful pain therapy (25 points in the conservatively treated group and 27 points in the group of the operatively treated patients with malignant disease, 21 points in the operatively treated group with benign disease, and 18 points in the group suffering from chronic pain of benign causes). The aims for pain therapy showed no correlation with the actually felt pain intensity during movement. The control group of healthy nursing staff felt less actual pain during movement, but their expectations for sufficient pain treatment were not significantly different from the study patients (VAS 25.4 points).

Adult↗
PubMed2000

[Transposition of the subclavian artery with endovascular stent graft implantation for therapy of acute type B aortic dissection].

We report about a patient with a thoracic aneurysm caused by an acute type-B dissection. Due to the concomitant affections the risk of surgery was distinctly increased, the reconstruction was performed endo vascular by stentgraft implantation (Talent, World Medical Systems, Sunrise FL) after transposition of the left subclavian artery to create a sufficient neck for the proximal stent placement. Endoluminal treatment seems to be a promising, less invasive alternative method in the treatment of acute aortic dissections.

Acute Disease↗
PubMed2000

Endovascular stentgraft infection--a life-threatening complication.

The implantation of covered stents or stentgrafts has increased greatly in the last few years for the endovascular reconstruction of arterial aneurysms. We report of three patients experiencing severe septic complications after stentgraft implantation. Endovascular stentgraft infection is a serious complication with high morbidity and mortality. General antibiotic prophylaxis seems to be indicated when implanting stentgrafts.

Aged↗
PubMed2000

Caries prevalence and distribution in 3-20-year-olds in Jönköping, Sweden, in 1973, 1978, 1983, and 1993.

Four cross-sectional studies were carried out in 1973, 1978, 1983, and 1993 to collect clinical and radiographic epidemiological data on the dental health status of the inhabitants of Jönköping, Sweden. The aim of the present paper was to use these data to analyze trends in the development of caries among children and adolescents between 1973 and 1993. Approximately 500 randomly selected individuals evenly distributed among the age groups 3, 5, 10, 15, and 20 years participated in each study. The main results show that the numbers of caries-free individuals increased in all age groups. In 1993, the mean number of decayed and filled tooth surfaces in the primary (dfs) and the permanent (DFS) dentition in all age groups was less than half of that found in 1973. Most of this decrease took place during the first 5 years, i.e., between 1973 and 1978. Between 1978 and 1983, only minor changes were observed. There was a further reduction of approximately 30%-50% in dfs/DFS between 1983 and 1993 in 3-, 5-, 10-, and 20-year-olds. The frequency distributions of dfs/DFS for 5- and 15-year-olds revealed an increasing skewness over time: in 1993, a large majority of the children and adolescents had a low or moderate caries severity while only a small group had high scores of dfs/DFS.

Adolescent↗