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Biomedical subjects

J Keller

Publications and source records attributed to J Keller.

At least 55 records · Page 3Linked to original sources
PubMed2003

Cellulosic waste degradation by rumen-enhanced anaerobic digestion.

Anaerobic digestion of lignocellulosic material is carried out effectively in many natural microbial ecosystems including the rumen. A rumen-enhanced anaerobic sequencing batch reactor was used to investigate cellulose degradation to give analysis of overall process stoichiometry and rates of hydrolysis. The reactor achieved VFA production rates of 207-236 mg COD/L/h at a loading rate of 10 g/L/d. Overloading of the reactor resulted in elevated production of propionic acid, and on occasion, the presence of succinic acid. With improvements in mixing and solids wasting, the anaerobic sequencing batch reactor system could enable full-scale application of the process for treatment of cellulosic waste material.

Animals↗
PubMed2003

Integrated control of nitrate recirculation and external carbon addition in a predenitrification system.

The integrated control of nitrate recirculation and external carbon addition in a predenitrification biological wastewater treatment system is studied. The proposed control structure consists of four feedback control loops, which manipulate the nitrate recirculation and the carbon dosage flows in a highly coordinated manner such that the consumption of external carbon is minimised while the nitrate discharge limits (based on both grab and composite samples) are met. The control system requires the measurement of the nitrate concentrations at the end of both the anoxic and the aerobic zones. Distinct from ordinary control systems, which typically minimise the variation in the controlled variables, the proposed control system essentially maximises the diurnal variation of the effluent nitrate concentration and through this maximises the use of influent COD for denitrification, thus minimising the requirement for external carbon source. Simulation studies using a commonly accepted simulation benchmark show that the controlled system consistently achieves the designated effluent quality with minimum costs.

Bioreactors↗
PubMed2002

[How extensively should irritable bowel syndrome be investigated? Expensive bowel sounds in the abdomen].

Its high prevalence, chronic course, sometimes very troubling symptoms and rather limited therapeutic options, make the irritable bowel syndrome (IBS) one of the most common conditions seen by the family doctor, internist and gastroenterologist. IBS is characterized by abdominal pain accompanied by altered bowel movements and a facultative association with abdominal distension. IBS runs a chronic recurrent course punctuated by relatively symptom-free phases, and an overall good prognosis for survival (quoad vitam). Visceral hypersensitivity, altered gastrointestinal motility, psychosocial factors, and neurotransmitter imbalance are under discussion as underlying pathophysiology. An orienting medical history, clinical examination and exclusion of such alarm symptoms as weight loss, general debility and rectal bleeding, must be followed by a rational choice of further diagnostic measures.

Colonic Diseases, Functional↗
PubMed2002

[Proper patient counseling, recommended nutrition, specific medication. The basics of irritable bowel syndrome therapy].

In the treatment of the irritable bowel syndrome, it is important to qualify unrealistic expectations with regard to treatment, at an early stage. The therapeutic spectrum encompasses establishment of good rapport between physician and patient, modification of life style, provision of good patient information, reassurance, coping strategies, and temporal restraints on medication. Depending on the leading symptoms, the latter may range from laxatives to probiotics, anticholinergics or spasmolytics, prokinetic and anti-diarrheal agents, to 5-HT3/HT4 receptor antagonists. In individual patients with frequently recurrent or permanent pain, the use of tricyclic antidepressants may be considered. Painkillers should be reserved for patients in whom other therapeutic strategies have failed.

Abdominal Pain↗
PubMed2002

[Autoimmune pancreatitis].

Over the last years several case reports and articles have been published suggesting that a new form of chronic pancreatitis has been diagnosed and named autoimmune pancreatitis. The present overview scrutinizes the proposed evidence in the light of the current literature and aims to prove whether autoimmune pancreatitis is a special entity of chronic pancreatitis.

Autoantigens↗
PubMed2002

[Chronic intestinal pseudo-obstruction: pathogenesis, diagnosis and therapy].

Chronic intestinal pseudo-obstruction (CIPO) is a rare disease in which a severe intestinal motility disorder impairs transit of chyme so that patients suffer from symptoms of a mechanical ileus without mechanical obstruction. CIPO may be a primary or secondary disorder due to muscular, neurologic, metabolic or endocrine disorders, but may also occur postinfectiously, postoperatively, following abdominal radiation or be caused by drugs or noxae. In severe cases, the typical history of (repeated) symptoms of mechanical obstruction leading to unsuccessful laparotomies will give key clues for diagnosis. If CIPO is suspected, mechanical obstruction must be searched for carefully by radiologic and endoscopic examinations. Histologic diagnosis usually demands full thickness biopsies of the intestinal wall. Small intestinal manometry allows diagnosis of CIPO even during oligosymptomatic intervals as well as differentiation between neuropathic and myopathic forms of the disease. The main therapeutic goals consist in: 1. Maintenance of an adequate nutritional state by oral and/or enteral nutrition; in severe cases home-parenteral nutrition may be required and particularly in children intestinal transplantation may be the ultima ratio. 2. Reconstitution of intestinal propulsion by prokinetic drugs. 3. Therapy of complications such as bacterial overgrowth and severe pain by antibiotics and specific surgical procedures. Unnecessary laparotomies should be strictly avoided because they may lead to adhesions and markedly complicate the clinical course.

Chronic Disease↗
PubMed2002

Combined hydraulic and biological modelling and full-scale validation of SBR process.

The biological reactions during the settling and decant periods of Sequencing Batch Reactors (SBRs) are generally ignored as they are not easily measured or described by modelling approaches. However, important processes are taking place, and in particular when the influent is fed into the bottom of the reactor at the same time (one of the main features of the UniFed process), the inclusion of these stages is crucial for accurate process predictions. Due to the vertical stratification of both liquid and solid components, a one-dimensional hydraulic model is combined with a modified ASM 2d biological model to allow the prediction of settling velocity, sludge concentration, soluble components and biological processes during the non-mixed periods of the SBR. The model is calibrated on a full-scale UniFed SBR system with tracer breakthrough tests, depth profiles of particulate and soluble compounds and measurements of the key components during the mixed aerobic period. This model is then validated against results from an independent experimental period with considerably different operating parameters. In both cases, the model is able to accurately predict the stratification and most of the biological reactions occurring in the sludge blanket and the supernatant during the non-mixed periods. Together with a correct description of the mixed aerobic period, a good prediction of the overall SBR performance can be achieved.

Bioreactors↗
PubMed2002

The influence of calcium on granular sludge in a full-scale UASB treating paper mill wastewater.

Calcium precipitation can have a number of effects on the performance of high-rate anaerobic performance including cementing of the sludge bed, limiting diffusion, and diluting the active biomass. The aim of this study was to observe the influence of precipitation in a stable full-scale system fed with high-calcium paper factory wastewater. Granules were examined from an upflow anaerobic sludge blanket reactor (volume 1,805 m3) at a recycled paper mill with a loading rate of 5.7-6.6 kgCOD.m(-3).d(-1) and influent calcium concentration of 400-700 gCa m(-3). The granules were relatively small (1 mm), with a 200-400 microm core of calcium precipitate as observed with energy dispersive X-ray spectroscopy. Compared to other granules, Methanomicrobiales not Methanobacteriales were the dominant hydrogen or formate utilisers, and putative acidogens were filamentous. The strength of the paper mill fed granules was very high when compared to granules from other full-scale reactors, and a partial linear correlation between granule strength and calcium concentration was identified.

Biomass↗
PubMed2002

The IWA Anaerobic Digestion Model No 1 (ADM1).

The IWA Anaerobic Digestion Modelling Task Group was established in 1997 at the 8th World Congress on Anaerobic Digestion (Sendai, Japan) with the goal of developing a generalised anaerobic digestion model. The structured model includes multiple steps describing biochemical as well as physicochemical processes. The biochemical steps include disintegration from homogeneous particulates to carbohydrates, proteins and lipids; extracellular hydrolysis of these particulate substrates to sugars, amino acids, and long chain fatty acids (LCFA), respectively; acidogenesis from sugars and amino acids to volatile fatty acids (VFAs) and hydrogen; acetogenesis of LCFA and VFAs to acetate; and separate methanogenesis steps from acetate and hydrogen/CO2. The physico-chemical equations describe ion association and dissociation, and gas-liquid transfer. Implemented as a differential and algebraic equation (DAE) set, there are 26 dynamic state concentration variables, and 8 implicit algebraic variables per reactor vessel or element. Implemented as differential equations (DE) only, there are 32 dynamic concentration state variables.

Bioreactors↗
PubMed2002

The development and use of real-time PCR for the quantification of nitrifiers in activated sludge.

Chemical analytical data has long been used to monitor the performance of activated sludge plants even though the process relies on the performance of microorganisms. It is now evident that a rapid and reliable quantitative method is required, to be able to monitor the organisms responsible for nutrient transformation and their activities, allowing avenues for more efficient nutrient removal. The development of real-time or quantitative polymerase chain reaction (PCR) also known as TaqMan or 5'-nuclease assay has allowed the rapid, quantitative analysis of DNA templates, eliminating some of the variability traditionally associated with other quantitative techniques. In this study analysis of Nitrospira spp., one of the key organisms in nitrite oxidation in wastewater treatment, was used to validate real-time PCR for the their quantification in activated sludge. A probe and primer set, targeting the 16S rRNA gene of Nitrospira spp. was designed according to the constraints of the TaqMan specifications. Samples used to evaluate the method included DNA from the sludge from full-scale wastewater treatment plants and laboratory scale systems. The reproducibility, quantitative efficiency and specificity were assessed in the evaluation. It was concluded that the method is sensitive and reproducible but has some constraints on the quantitative efficiency. A survey of full-scale systems for Nitrospira spp. was carried out and the results are presented here.

Automation↗
PubMed2002

Nitrogen removal in a SBR using the OGAR process control system.

OGAR is an industrial process control system that utilises on-line redox measurements to control the aeration sequence in an activated sludge process. Compared to conventional process control systems that use dissolved oxygen, OGAR makes use of redox as a control parameter during both aerobic and anoxic conditions. This paper reports on its first application in a sequencing batch reactor. The principal aim of this project is to demonstrate the capability of OGAR to achieve concentrations of total nitrogen in the treated effluent of less than 10 mg/L, which are typically stipulated by Queensland's Environmental Protection Agency (EPA). In this study the use of the control system resulted in the following SBR performance: consistent effluent total nitrogen less than 5.0 mg/L; ammonia concentration reduced from 31.6 mg/L to 0.32 mg/L, effluent nitrate 2.8 mg/L; DO setpoint 1.5 mg/L had 10% higher effluent total nitrogen compared to DO setpoint 4.0 mg/L and redox end-points for nitrification 400 mV, denitrification 150 mV.

Ammonia↗
PubMed2001

Spectral and magnetic properties of alpha- and gamma-Ce from dynamical mean-field theory and local density approximation.

We present excitation spectra for Ce metal obtained with an ab initio scheme combining local density approximation and dynamical mean-field theory including itinerant spd and correlated f states. The local interactions among the f electrons lead to typical many-body resonances in the f density of states (DOS), such as lower and upper Hubbard bands and the Kondo resonance. The spd DOS show weak renormalization effects due to hybridization. We observe different Kondo temperatures for alpha- and gamma-Ce due to strong volume dependence of the effective hybridization strength for the localized f electrons. Finally we compare our results with a variety of experimental data.

Journal Article↗
PubMed2001

Childhood morbidity and air pollution in the Teplice program.

BACKGROUND: A study of morbidity of children aged 0 to 3 years was conducted in two districts in the Czech Republic. Comparisons were made between children living in Teplice district, known for its high air pollution, and children living in Practice, a district with consistently lower particulate and SO2 exposures. METHODS AND RESULTS: The children were selected for the follow up based on deliveries from May 1994 to December 1966. Childhood morbidity during the first three years of life of 452 children was extracted from their pediatric records. Diagnoses were coded using the International Classification of Diseases--10th edition, and categorized into broad groupings. Children born in Teplice experienced a significantly higher rate of otitis media and otalgia, gastrointestinal infections, upper respiratory infections, and pneumonia, but did not differ in their risk for bronchitis or for viral infections such as varicella. These findings remained after multiple linear regression models adjusted for education, maternal age, maternal smoking, and other smokers in the household, breastfeeding, and attendance at day care. CONCLUSIONS: Air pollution may alter early childhood susceptibility to infection, but other differences between the districts must be considered: systematic diagnostic differences for several health outcomes comparing pediatricians in Teplice vs. Practice, differences in health-care seeking behavior by the parents, and inadequate control for confounding.

Air Pollution↗
PubMed2001

Analysis of toxicity of Merkel cell carcinoma of the skin treated with synchronous carboplatin/etoposide and radiation: a Trans-Tasman Radiation Oncology Group study.

PURPOSE: The acute and late toxicities of synchronous carboplatin, etoposide, and radiation therapy were prospectively assessed in a group of patients with high-risk Merkel cell carcinoma of the skin. PATIENTS AND METHODS: Forty patients from six different centers throughout Australia were entered into a Phase II study under the auspices of the Trans-Tasman Radiation Oncology Group. The trial was activated in 1996 and continues to accrue. Patients are eligible if they have disease localized to the primary site and nodes and are required to have at least one of the following high-risk features: recurrence after initial therapy, involved nodes, primary size greater than 1 cm, gross residual disease after surgery, or occult primary with nodes. Radiation was delivered to the primary site and nodes to a dose of 50 Gy in 25 fractions over 5 weeks, and synchronous carboplatin (area under curve [AUC] 4.5) and etoposide (80 mg/M(2) i.v.) were given on days 1-3 during weeks 1, 4, 7, and 10. The median age of the group was 67 years (43-78). RESULTS: The median duration of follow-up was 22 months (2-45). There were no treatment-related deaths. Grade 3 or 4 skin toxicity occurred in 63% of patients (95% CI 48, 78). The most serious acute effect was on neutrophils with Grade 3 or 4 (neutrophils < 1 x 10(9)/L), occurring in 60% (95% CI 45, 75) of cases. Complications from neutropenia (fever and sepsis) occurred in 16 patients (40% of cases). The median time for neutropenic complications was 27 days (9-35), and 10/16 (62%) cases of neutropenic fever occurred after the second cycle of chemotherapy. The probability of Grade 3 or 4 late effects on platelets (<50 x 10(9)/L) and hemoglobin (<8 g/dl) was 10% (95% CI 1, 20) and 6% (95% CI 2, 15), respectively. Of the 40 patients, 35 were able to complete 4 cycles of chemotherapy. There were no factors predictive for neutropenic toxicity at a p value < 0.05. CONCLUSIONS: The protocol has acceptable toxicity, and the treatment has been deliverable in a multi-institutional trial setting. Neutropenia is likely to occur with synchronous carboplatin/etoposide and radiation in this population of patients. The risk of a febrile neutropenia was greatest at the time of the second cycle of chemotherapy, when there was moist desquamation of skin or mucosal membranes that provided a portal for infection. This should be considered in the design of subsequent protocols with chemoradiotherapy.

Adult↗
PubMed2001

[Environmental pollution and childhood morbidity].

BACKGROUND: A study of morbidity of children aged 0 to 3 years was organized in two districts in the Czech Republic. Comparisons were drawn between children living in district Teplice, known for its high air pollution, and those living in Practice, the district with consistently lower particulate and SO2 exposures. METHODS AND RESULTS: 452 children of the follow up study were born between May 1994 and December 1996. Childhood morbidity during the first three years of life was obtained from their pediatric records. Diagnoses were coded using the International Classification of Diseases--the 10th edition, and categorized into broad groups. Children born in Teplice experienced a significantly higher rate of otitis media (and otalgia), gastrointestinal infections, upper respiratory infections, and pneumonia, but they did not differ in the risk of bronchitis or that of viral infections such as varicella. These findings remained valid after the multiple linear regression models were calculated and adjusted for education, maternal age, maternal smoking, and other smokers in the household, breastfeeding, and attendance at the day care. CONCLUSIONS: Air pollution may alter early childhood susceptibility to infection, but other differences between the districts have to be considered: systematic diagnostic differences for several health outcomes between pediatricians in Teplice and Practice, differences in health-care seeking approach of parents, and some hitherto unidentified factors.

Air Pollution↗
PubMed2001

Development of a novel molecular adapter for the optimization of immunotoxins.

Immunotoxins consisting of catalytic domains of natural toxins and tumor-specific ligands were modified by introducing a molecular adapter that is able to transport the toxic domain more efficiently into cells. The adapter is a three-component structure: its core is a membrane transfer sequence (MTS) flanked by two different cleavable sequences. The directed and irreversible cellular uptake of the construct is driven by either enzymatic or chemical cleavage of the two flanking sequences. In our studies, the purified A-chain of diphtheria toxin (DT) was coupled to two different MTSs via disulfide bonds. A cytotoxicity assay revealed that the constructs containing the MTSs were more potent than DT A-chain alone and that the disulfide bond was cleaved.

Diphtheria Toxin↗
PubMed2001

Hypoxia in human soft tissue sarcomas: adverse impact on survival and no association with p53 mutations.

Clinical and experimental studies have suggested that tumour hypoxia is associated with poor treatment outcome and that loss of apoptotic potential may play a role in malignant progression of neoplastic cells. The tumour suppressor gene p53 induces apoptosis under certain conditions and microenvironmental tumour hypoxia may select for mutant tumour cells with diminished apoptotic potential due to lack of p53 function. The aim of this study was to evaluate the prognostic relevance of oxygenation status for treatment outcome and to compare pre-treatment tumour oxygenation measurements were done in 31 of those by PCR using DNA extracted from paraffin-embaedded sections (n = 2) or frozen biopsies (n = 29). The overall median of the tumour median pO(2)was 19 mmHg (range 1-58 mmHg). Only 6 tumours had functional p53 mutations and no association was found between mutant p53 and tumour hypoxia. Five out of 6 STS with lower histopathological grade were well-oxygenated whereas high-grade STS were both hypoxic and well-oxygenated. At a median follow-up of 74 months, 16 patients were still alive among 28 available for survival analysis. When stratifying into hypoxic and well-oxygenated tumours patients with the most hypoxic tumours has a statistically poorer disease-specific and overall survival at 5 years. In conclusion hypoxia was an indicator for both a poorer disease specific and overall survival in human STS but hypoxic tumours were not characterized by mutations in the p53 gene.

Adult↗