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Biomedical subjects

K Schenk

Publications and source records attributed to K Schenk.

18 recordsLinked to original sources
PubMed2002

Quantitative process evaluation of a community-based HIV/AIDS behavioural intervention in rural Uganda.

This paper describes the implementation of a large community-based HIV/AIDS behavioural intervention in rural Uganda and presents 4 years' worth of quantitative process data. The intervention involved 560 field-based workers (57% male, 76% subsistence farmers, mean age 35 years), supervised by six central staff. Intervention channels included drama and video shows, Community Educators (CEs), as well as leaflet and condom distribution. Activities focused on one or more of 16 key topics. In total, 392 000 attendances (51% female) were recorded--a mean of over 6 for each of the 64 000 target adults--at 81 000 activities, with CEs attracting 71% of the total attendance; 164 000 leaflets and 242 000 condoms were also distributed. The annual cost of the intervention per target individual was approximately US$1.76. Our voluntary workforce experienced an annual attrition rate of 11%, with 'stable' workers more likely to be older, married or opinion leaders in their community than those who dropped out. We calculate that even a significant increase in the proportion of female field workers would have made little difference either to the sex ratio of attendees or to overall attendance. In spite of some initial resistance to the intervention, particularly in relation to condoms, we have demonstrated that people in rural Africa can accept and actively participate in the dissemination of HIV/AIDS prevention messages throughout their own communities.

Adolescent↗
PubMed2001

Development of a new carbon-carbon bond forming reaction. new organic chemistry of sulfur dioxide. Asymmetric four-component synthesis of polyfunctional sulfones.

At low temperature 1-alkoxy-1,3-dienes add to sulfur dioxide activated by a Lewis or Brønstedt acid and generate zwitterionic intermediates that can be quenched by enoxysilanes. The resulting beta,gamma-unsaturated silyl sulfinates can be desilylated and reacted with methyl iodide to provide polyfunctional sulfones. Exploratory studies of this four-component synthesis of sulfones are reported. Enantiomerically pure derivatives containing up to three new stereogenic centers can be obtained using enantiomerically pure (E,E)-1-alkoxy-2-methylpenta-1,3-dienes derived from alpha-methyl benzyl alcohols, including the Greene's chiral auxiliary. The stereochemistry of the reactions is consistent with a mechanism involving the suprafacial hetero-Diels-Alder addition of sulfur dioxide to the 1-alkoxy-1,3-dienes that are rapidly ionized into zwitterionic intermediates.

Journal Article↗
PubMed2001

Synthesis and solution conformational analysis of 2,3-anhydro-3-C-[(1R)-2,6-anhydro-1-deoxy-1-fluoro-D-glycero-D-gulo-heptitol-1-C-yl]-beta-D-gulo-furanose: first example of a monofluoromethylene-linked C-disaccharide.

Condensation of 2,3,4,6-tetra-O-benzyl-beta-D-glucopyranosylcarbaldehyde with isolevoglucosenone induced by Et(2)AlI, followed by epoxidation, gave an aldol that was fluorinated into a monofluoromethylene C-glucopyranoside that was converted into the title C-disaccharide 1. Its conformational behavior in water has been studied by using a combination of NMR spectroscopy (J and NOE data) and molecular mechanics calculations.

Carbohydrate Conformation↗
PubMed2001

[Microbiological and immunological monitoring in polyarticular rheumatoid arthritis after total joint replacement].

HISTORY AND ADMISSION FINDINGS: A 51-year-old man with polyarticular rheumatoid arthritis since the age of 10 years, which had required three total joint replacements, presented in a generally good condition for replacement of the left elbow joint, which was swollen and had reduced movement. TREATMENT AND COURSE: The postoperative condition was without complication until the 7th day when arthritic signs set in, interpreted as part of the underlying disease, and cortisone was administered. After microbiological tests had been done and the patient's general state had deteriorated, antibiotic treatment with flucloxacillin and gentamycin as well as local irrigation and suction-drainage of all involved joints was started. Granulocyte and monocyte functions were analysed. Staphylococcal isolates from the patient induced reduced "respiratory burst" activity of the neutrophil granulocytes, apparently the cause of the septic dissemination. He was discharged on the 32. postoperative day, to be followed-up as an out-patient. CONCLUSION: Both adequate antibiotic administration and, especially, thorough local reduction of pathogens are needed for efficacious treatment. Rapid restoration of granulocyte function and of the "immunocompetence" of monocytes within normal limits are part of the reason for a good therapeutic response. This indicates the need for up-to-date preoperative immunological diagnosis in patients with suppressed immunity to assess the risk of infection and thus plan elective intervention.

Anti-Bacterial Agents↗
PubMed2001

Rapid activation of Na+/H+-exchange in MDCK cells by aldosterone involves MAP-kinase ERK1/2.

The mineralocorticoid aldosterone is essential for the adequate regulation of electrolyte homeostasis, extracellular volume and blood pressure. As a steroid hormone it influences cellular functions by genomic actions. Previously it has been shown that aldosterone can activate Na+/H+-exchange (NHE) by a rapid, nongenomic mechanism. Because (1) NHE can be regulated by ERK1/2 (extracellular signal-regulated kinase) and (2) steroids have been reported to rapidly activate ERK1/2, we tested the hypothesis that activation of NHE by aldosterone involves ERK1/2, using MDCK-C11 cells. We show that nanomolar concentrations of aldosterone induce a rapid, non-genomic activation of NHE, which is characterized by an increased affinity for H+ with minor changes in the maximum transport rate. Accordingly, aldosterone led to an increase of cytosolic steady-state pH. The aldosterone-induced activation of NHE was prevented by the two specific inhibitors of ERK1/2 activation, PD 98059 (2.5 x 10(-5) mol/l) and U0126 (10(-5) mol/l). Furthermore, in the presence of U0126 there was no aldosterone-induced increase of steady-state pH. Finally, aldosterone induced a rapid phosphorylation of ERK1/2, indicating its ability to activate ERK1/2. The data presented here support the hypothesis that the rapid activation of NHE by aldosterone at nanomolar concentrations involves ERK1/2. Thus, in certain cell types, the MAPK cascade may represent an additional pathway mediating rapid aldosterone effects.

Acid-Base Equilibrium↗
PubMed2000

17O NMR spectroscopy of sulfolenes (2,5-dihydrothiophene-1,1-dioxides) and sultines (3,6-dihydro-1,2-oxathiin-2-oxides)--experiment and quantum calculations: synthesis of 4,9-dioxo-1,2-oxathiacyclodecane-2-oxide, a new heterocycle

The products of hetero-Diels-Alder reactions (sultines) and cheletropic addition reactions (sulfolenes) between 1,3-dienes and sulfur dioxide can be distinguished by their 17O NMR shifts. Experimental data have been collected for derivatives of 3,6-dihydro-1,2-oxathiin-2-oxide and of 2,5-dihydrothiophene-1,1-dioxide. This data was then compared with that calculated by the gauge independent atomic orbital (GIAO) method at the HF/6-31 + G(d,p) and HF/6-311 + G(3df, 2p) levels of theory with geometries optimized by MP2/6-31G(d) calculations. GIAO-MBPT(2) calculations were also performed with the 6-31 + G(d,p) basis set. The adduct between (E)-1-methoxybutadiene and SO2 is sulfolene 3, the ozonolysis of which in SO2 followed by work-up with ethanol provided (2RS,3SR,6SR)-(31), (2RS,3RS,6SR)-(32), and (2RS,3RS, 6RS)-2,6-diethoxy-3-methoxy-1,4-oxathiane-4,4-dioxide (33). Single-crystal X-ray diffraction studies are reported for 32 and 33. Ozonolysis of the hetero-Diels-Alder adduct of SO2 with 1,2-dimethylidenecyclohexane produced 4,9-dioxo-1,2-oxathiacyclodecane-2-oxide (34), the first member of a new class of sulfur heterocycles.

Journal Article↗
PubMed1999

[Experiences with the GSB (Geschwend-Scheier-Bähler) III total endoprosthesis in the elbow joint].

Studies on the results with elbow prostheses published in the seventies reported on marked problems such as high loosening rates and instabilities of the joints. However, enormous progresses in elbow replacements have been made in the meantime. Therefore, we analyzed the results of the GSB III-elbow-prostheses that were implanted in our department for 9 years. Between January 1, 1987 and April 1995 at our department 34 total elbow replacements were performed in 32 patients. In this study, we reviewed 25 patients with elbow replacements both clinically and radiologically. The clinical outcome was rated according to the score of INGLIS and PELLICI. The mean follow-up time was 3.7 years. Our follow up examination revealed a total complication rate of 22%. Septic prosthesis loosening with explantation of the prostheses occurred in 3 patients resulting in a prosthesis survival-rate of 88%. However, clinical assessment revealed 80% excellent or good results. While the range of motion could only be improved to a small degree, a marked reduction of the preoperative pain could be achieved. Patients were satisfied with the outcome of the operation in 97%. Although the results of total elbow arthroplasties cannot be compared with those of hip or knee arthroplasties, in selected patients with rheumatoid arthritis and osteoathrosis the use of elbow replacements proved to be a successful procedure with satisfactory results. The implantation of elbow prostheses should mainly be considered when debilitating pain, strongly limited range of motion and instability of the joint are the main problems.

Arthritis, Rheumatoid↗
PubMed1998

[Covering extensive soft tissue defects in infected knee endoprostheses by gastrocnemius flap].

Total knee arthroplasty has become a routine procedure in surgery. Deep infections have an incidence of 2-5%. Major risk factors are large prostheses, rheumatoid arthritis, diabetes mellitus and postoperative wound-healing complications. In large soft-tissue defects with skin necrosis, local wound care shows poor results, especially if loosening of the prosthesis and necrosis of the patellar ligament are evident. In these cases, no standard surgical therapy has been developed yet. Thus, we consider meticulous débridement with synovialectomy to be mandatory. Exchange of the prosthesis may be necessary. Soft-tissue coverage ought to be performed with a gastrocnemius muscle flap covered with a split-thickness skin graft. In the last three years, 11 patients with large soft-tissue defects and necrosis of the ligament were treated according to this concept. In all cases the muscle flap healed primarily and soft tissue coverage was excellent. Two patients who underwent single-stage removal and reimplantation of the prosthesis showed reinfections of the prosthesis. Reconstruction of the ligament was performed with the flap tendon. The patients with two-stage removal and reimplantation of the prosthesis and those who retained their implants had a good functional outcome. The gastrocnemius muscle flap provides easy and reliable soft-tissue reconstruction in large defects. In our patients a two-stage operation for reimplantation of the prosthesis was superior to a single-stage procedure. The reconstructed ligament should be reinforced with autologous material to prevent a secondary rupture. Early reconstruction with sufficient soft-tissue coverage and reconstruction of the ligament offers the patient the best chances of obtaining a good functional result and prevents arthrodesis or amputation. In addition, reconstructive surgery reduces the length of hospital stay and costs.

Aged↗
PubMed1989

Mutation induction in haploid yeast after split-dose radiation-exposure. I. Fractionated UV-irradiation.

Mutation induction was investigated in wild-type haploid yeast Saccharomyces cerevisiae after split-dose UV-irradiation. Cells were exposed to fractionated 254 nm-UV-doses separated by intervals from 0 to 6 h with incubation either on non-nutrient or nutrient agar between. The test parameter was resistance to canavanine. If modifications of sensitivity due to incubation are appropriately taken into account there is no change of mutation frequency.

Culture Media↗