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Biomedical subjects

K Walter

Publications and source records attributed to K Walter.

At least 19 recordsLinked to original sources
PubMed2001

Gestational regulation of the gene expression of C-type natriuretic peptide in mouse reproductive and embryonic tissue.

C-Type natriuretic peptide (CNP) is a vasoactive hormone and the endothelial component of the natriuretic peptide system. We examined the expression of CNP in mouse reproductive organs and embryos at different stages of gestation. Pregnant mice were killed and embryos were dissected on gestational days 9.5, 12.5, 15.5, 18.5 postconceptionem (pc) and at term. Nonpregnant mice were used as controls. Total RNA was isolated from placenta, ovaries, myometrium and from head and trunk of embryos and neonates. CNP-mRNA was quantified by ribonuclease-protection assay (RPA). Uterine CNP-mRNA concentrations increase during pregnancy up to the sevenfold concentration, whereas in the ovaries these levels decrease to 10% compared to nonpregnant controls. In the placenta, a peak of CNP expression has been observed around day 15.5 pc, whereby placenta showed the strongest CNP signals. CNP-mRNA concentrations in embryos are gestational age-dependent with a high level at day 9.5 pc in head and trunk. These results indicate that CNP has a regulatory function in pregnancy and embryonic development.

Animals↗
PubMed2001

Nontruncating APC germ-line mutations and mismatch repair deficiency play a minor role in APC mutation-negative polyposis.

Familial adenomatous polyposis, an autosomal-dominantly inherited colorectal cancer predisposition syndrome, is caused by germ-line mutations in the adenomatous polyposis coli (APC) gene. Despite the use of different screening methods, studies worldwide fail to identify APC mutations in 20-50% of all familial adenomatous polyposis patients (APC mutation-negatives). In this study, missense mutations in the coding region of the APC gene, which would have been missed by the protein truncation test, as well as mutations in the APC promoter and the 3' untranslated region, were determined by the single nucleotide polymorphism discovery assay and direct DNA sequencing in 31 mutation-negative polyposis patients. Seventeen gene alterations were identified, whereof four (12.9%) represent possibly pathogenic germ-line mutations: silent A290T (promoter) and A8822G (3' untranslated region) as well as missense R99W and E1317Q (coding region). The 27 remaining, truly APC mutation-negative polyposis patients displayed a significantly later age at diagnosis compared with APC mutation carriers (46.1 versus 35.2 years; P < 0.01). APC mutation-negative individuals with >100 colonic polyps were more likely to present with extracolonic disease (P < 0.05) than those with <100. Assessment of microsatellite instability (MSI), a hallmark of mismatch repair deficiency, in 68 tumors from 21 truly APC mutation-negative patients, identified 4 (5.9%) unstable tubulo-villous adenomas (3 MSI-High and 1 MSI-Low), stemming from 4 (19%) unrelated individuals and likely to be caused by hMLH1 promoter hypermethylation. In conclusion, only a small proportion of APC germ-line mutation carriers is missed by the protein truncation test, and mismatch repair deficiency does not seem to substantially contribute to tumor development in APC mutation-negative polyposis patients.

3' Untranslated Regions↗
PubMed2001

[Relative bioavailability of diclofenac after a single administration of a new multiple-unit formulation of enteric-coated pellets].

The relative bioavailability of diclofenac (CAS 15307-86-5) was investigated after a single administration of a multiple-unit formulation containing 75 mg diclofenac sodium in enteric-coated pellets (A) in comparison to an enteric-coated tablet with 50 mg diclofenac sodium (B), a capsule containing 140 mg diclofenac resinate (C) and a dispersible tablet containing 46.5 mg diclofenac acid (D). The study was carried out in a four-way crossover design in 16 healthy male volunteers. Serum concentrations of diclofenac were determined with a validated and specific HPLC-method. After dose normalisation, a mean relative bioavailability of 99% (B), 142% (C) and 116% (D) was determined for the pellet formulation. According to the corresponding 90%-confidence interval, bioequivalence for the extent of bioavailability of the test formulation can be concluded compared to the enteric-coated tablet. In comparison to the formulations C and D, the test formulation showed an increased extent of bioavailability. Further differences in pharmacokinetics were observed for the rate-dependent parameters. For the test formulation, the highest mean maximum serum concentration (1595 ng/ml) was measured with a corresponding tmax of 0.8 h. For the reference formulations, mean peak serum concentrations of 1285 ng/ml after 2.0 h (B), 370 ng/ml after 1.8 h (C) and 735 ng/ml after 1.9 h (D) were observed. Despite the enteric-coating of the pellets, a short lagtime of 0.4 h was determined for the test formulation. For the other rapid-release formulation (D), the lagtime was of a similar magnitude (0.3 h), while drug release and absorption from the enteric-coated tablet and the diclofenac resinate capsule were delayed (1.8 and 0.7 h, respectively). Due to the rapid and high bioavailability of diclofenac, the multiple-unit formulation fulfills the prerequisites for the oral treatment of acute painful conditions when prompt analgesic and anti-inflammatory efficacy is desired.

Adult↗
PubMed2001

Left ventricular function in mice lacking the AT2 receptor.

OBJECTIVES: The role of the AT2 receptor in the heart is incompletely understood. We investigated left ventricular performance in AT2 receptor knockout mice, with and without deoxycorticosterone acetate (DOCA)-salt treatment. Given the putative opposing functions of the AT1 and AT2 receptor, we also analysed AT1 receptor expression in the left ventricle. METHODS: We used a miniaturized conductance-manometer system to measure pressure-volume loops for analysing left ventricular performance under baseline conditions and after increasing peripheral vascular resistance. We determined left ventricular AT1-receptor expression by RNase-protection assays. RESULTS: In AT2 receptor knockout mice, end-systolic and end-diastolic volumes were lower than in wild-type mice, so that pressure-volume loops were shifted leftward. Left ventricular systolic and diastolic kinetics were not different between the groups. AT2 receptor knockout mice and wild-type mice both stabilized their reduced stroke volume after laparatomy as peripheral resistance was increased. DOCA-salt treatment increased elastance in AT2 receptor knockout mice, compared to controls. Furthermore, AT2 receptor knockout mice had a steeper increase in dP/dtmax. Left ventricular AT1 receptor gene expression was increased in AT2 receptor knockout mice and was not down-regulated in response to DOCA-salt treatment. Finally, the hearts of AT2 receptor knockout mice were smaller than controls, but increased in size in response to DOCA-salt treatment. CONCLUSIONS: AT2 receptor knockout mice displayed no major changes in left ventricular function at baseline or in response to DOCA-salt treatment, compared to wild-type mice. The AT2 receptor may be important to AT1 receptor expression in response to DOCA-salt challenge and may have some influence on cardiac growth responses.

Animals↗
PubMed2000

Design of adenosine kinase inhibitors from the NMR-based screening of fragments.

A strategy is described for designing high-affinity ligands using information derived from the NMR-based screening of fragments. The method involves the fragmentation of an existing lead molecule, identification of suitable replacements for the fragments, and incorporation of the newly identified fragments into the original scaffold. Using this technique, novel substituents were rapidly identified and incorporated into lead inhibitors of adenosine kinase that exhibited potent in vitro and in vivo activities. This approach is a valuable strategy for modifying existing leads to improve their potency, bioavailability, or toxicity profile and thus represents a useful technique for lead optimization.

Adenosine Kinase↗
PubMed2000

On a new artificial mediator accepting NADP(H) oxidoreductase from Clostridium thermoaceticum.

The purification and partial characterisation of an NADP(H) dependent artificial mediator accepting pyridine nucleotide oxidoreductase (AMAPOR) from the anaerobic Clostridium thermoaceticum is described. Depending on the redox potential of the artificial mediators the AMAPOR is able to regenerate NADP+ or NADPH rendering the enzyme useful for preparative work applying NADP(H) dependent oxidoreductases. At 37 degrees C crude extracts of C. thermoaceticum have an AMAPOR activity of 5-7 U mg(-1). This is 28 degrees under the optimal growth temperature of this microrganism. Out of apparently more than 10 AMAPOR active proteins in the crude cell extracts visible after electrophoresis and activity staining on the gel, two of these proteins were isolated. They seem to be two different oligomers. According to gel electrophoresis they show apparent molecular masses of about 200 and 400 kDa. These two forms showed after SDS gel electrophoresis two monomers with apparent molecular masses of 42 and 56 kDa which we call alpha and beta. The two oligomers may have the compositions alpha2beta2 and alpha4beta4. They contain Fe/S cluster and FAD. Various amounts of the FAD were lost during the purification procedure. This loss is partially reversible after addition of FAD. The AMAPOR reacts with rather different artificial mediators such as viologens, quinones e.g. 1,4-benzoquinone or anthraquinone-2,6-disulphonate, 2,6-dichloro-indophenol and clostridial rubredoxin. Two different ferredoxins from C. thermoaceticum, oxygen or lipoamide are no substrates indicating the here described AMAPOR is not a diaphorase in the usual sense.

Amino Acid Sequence↗
PubMed2000

A palliative accelerated irradiation regimen for advanced non-small-cell lung cancer vs. conventionally fractionated 60 GY: results of a randomized equivalence study.

PURPOSE: Radiation oncologists are often faced with patients with advanced non-small-cell lung cancer (NSCLC), who are not suitable candidates for state-of-the-art radical treatment, but who also are not judged to have a very short life expectancy. Some physicians treat these patients palliatively, whereas others advocate more intensive treatment. To find out if there is a substantial difference in outcome between these approaches, we performed a randomized prospective study. METHODS AND MATERIALS: Between 1994 and 1998, 152 eligible patients with advanced NSCLC Stage III (n = 121) or minimal Stage IV (n = 31) were randomized to receive conventionally fractionated (cf; A: 60 Gy, 6 weeks, n = 79) or short-term treatment (PAIR; B: 32 Gy, 2 Gy b.i.d.; n = 73) of tumor and mediastinum. RESULTS: One-year survival rate for all patients was 37% with no significant difference between the two treatment arms (A: 36%; B: 38%; p = 0.76). As far as can be judged from limited data available, palliation was adequate and similar for the two treatment arms. Apart from expected differences in the time course of esophagitis, acute side effects were moderate and equally distributed. No severe late effects were observed. CONCLUSIONS: In the present randomized trial, survival and available data on palliation were not different after cf to 60 Gy compared to the palliative PAIR regimen. Therefore, for patients who are not suitable for radical treatment approaches, the prescription of a palliative short-term irradiation appears preferable compared to cf over several weeks.

Adenocarcinoma↗
PubMed2000

Structure-directed discovery of potent non-peptidic inhibitors of human urokinase that access a novel binding subsite.

BACKGROUND: Human urokinase-type plasminogen activator has been implicated in the regulation and control of basement membrane and interstitial protein degradation. Because of its role in tissue remodeling, urokinase is a central player in the disease progression of cancer, making it an attractive target for design of an anticancer clinical agent: Few urokinase inhibitors have been described, which suggests that discovery of such a compound is in the early stages. Towards integrating structural data into this process, a new human urokinase crystal form amenable to structure-based drug design has been used to discover potent urokinase inhibitors. RESULTS: On the basis of crystallographic data, 2-naphthamidine was chosen as the lead scaffold for structure-directed optimization. This co-crystal structure shows the compound binding at the primary specificity pocket of the trypsin-like protease and at a novel binding subsite that is accessible from the 8-position of 2-napthamidine. This novel subsite was characterized and used to design two compounds with very different 8-substituents that inhibit urokinase with K(i) values of 30-40 nM. CONCLUSIONS: Utilization of a novel subsite yielded two potent urokinase inhibitors even though this site has not been widely used in inhibitor optimization with other trypsin-like proteases, such as those reported for thrombin or factor Xa. The extensive binding pockets present at the substrate-binding groove of these other proteins are blocked by unique insertion loops in urokinase, thus necessitating the utilization of additional binding subsites. Successful implementation of this strategy and characterization of the novel site provides a significant step towards the discovery of an anticancer clinical agent.

Binding Sites↗
PubMed2000

Prognostic factors in brain metastases: should patients be selected for aggressive treatment according to recursive partitioning analysis (RPA) classes?

PURPOSE: To determine whether or not Radiation Therapy Oncology Group (RTOG) recursive partitioning analysis (RPA) derived prognostic classes for patients with brain metastases are generally applicable and can be recommended as rational strategy for patient selection for future clinical trials. Inclusion of time to non-CNS death as additional endpoint besides death from any cause might result in further valuable information, as survival limitation due to uncontrolled extracranial disease can be explored. METHODS: We performed a retrospective analysis of prognostic factors for survival and time to non-CNS death in 528 patients treated at a single institution with radiotherapy or surgery plus radiotherapy for brain metastases. For this purpose, patients were divided into groups with Karnofsky performance status (KPS) <70% and KPS > or =70%, as proposed by the RTOG. RESULTS: Median overall survival was 2.9 months (2.0 months for patients with KPS <70% and 3.6 months for patients with KPS > or =70%, p < 0.001). We did not find other variables splitting patients with KPS <70% in different prognostic groups. However, advanced age, multiple brain metastases, presence of extracranial metastases, and uncontrolled primary tumor each predicted shorter survival in patients with KPS > or =70%. When grouped into the original RTOG RPA classes, our data set split into three subgroups with different prognosis and median survival times of 10.5, 3.5, and 2 months, respectively (p < 0.05). Only 3% of patients fell into the most favorable group. Median time to non-CNS death was 4.1 months (12.9 months in RPA class I, 4.9 months in RPA class II, and 3.8 months in RPA class III, respectively, p > 0.05 for RPA class II versus III). However, it was 8.5 months in RPA class II patients with controlled primary tumor, which was found to be the only prognostic factor for time to non-CNS death in patients with KPS > or =70%. In patients with KPS <70%, no statistically significant prognostic factors were identified for this endpoint. CONCLUSIONS: Despite some differences, this analysis essentially confirmed the value of RPA-derived prognostic classes, as published by the RTOG, when survival was chosen as endpoint. RPA class I patients seem to be most likely to profit from aggressive treatment strategies and should be included in appropriate clinical trials. However, their number appears to be very limited. Considering time to non-CNS death, our results suggest that certain patients in RPA class II also might benefit from increased local control of brain metastases.

Adult↗
PubMed2000

[Incidence of neurodermatitis (atopic dermatitis) in students starting school in Ostalbkreis in Baden-Württemberg].

The prevalence of atopic eczematous dermatitis differs considerably between countries. In a former study with preschool children the prevalence in Baden-Württemberg according to data from parent questionnaires was about 10 per cent. Taking into account the expected false positives and false negatives led to the approximated unbiased prevalence of 7 to 8 percent. To evaluate this estimate, the Health Department Ostalbkreis used the same questionnaire in a second study of the same age group. The questionnaires were self-administered by the parents during the medical examination before school entrance. The parents of positive administered cases (11.2 per cent) were asked for permission to contact the family doctor to have the diagnosis confirmed (or not). 75 per cent of the positive identified cases by questionnaires were confirmed by family doctors. Therefore, the prevalence of atopic eczematous dermatitis in preschool children aged six to seven years in the area of Ostalbkreis is about 8.5 per cent.

Child↗
PubMed2000

Dose-response relationships for radiotherapy of brain metastases: role of intermediate-dose stereotactic radiosurgery plus whole-brain radiotherapy.

The effects of intermediate-dose radiotherapy consisting of whole-brain radiotherapy (WBRT, 10 fractions of 3 Gy) plus stereotactic radiosurgery (SRS) were studied prospectively. Twenty-five adult patients with 31 brain metastases received WBRT plus linear accelerator (LINAC)-based single dose SRS with fixed treatment parameters (10 Gy at the isocenter, target volume enclosed by the 90% isodose). Median age was 63 years, median Karnofsky performance status 80%, and median diameter of brain metastases 2.4 cm. Fifteen patients had non-small-cell lung cancer. Because of some early deaths, only 26 lesions could be evaluated for response. We observed 1 complete and 15 partial remissions. Median time to progression inside or outside the SRS volume was 4.5 months. Actuarial local control of SRS-treated lesions was 61% at 1 year. At that time, only 37% of patients were free from new lesions outside the SRS volume. Median survival and cause-specific survival were 2.3 and 4.5 months, respectively (1-year survival rate 8% and 21%). Ten patients died of progressive brain metastases, 13 from extracranial disease progression (unknown cause of death in 2 cases). Comparable to SRS studies with higher doses, the majority of brain failures occurred outside the SRS volume and more patients died of extracranial progression than of uncontrolled brain metastases. Failure to improve survival can be explained by the high percentage of patients with extracranial metastases (52%). However, the present results appear less favorable than those of previous studies of SRS with 15 Gy to 16 Gy (1-year actuarial local control rates of 66-89%). Therefore, we recommend SRS with 15 Gy to 16 Gy for patients whose favorable prognostic factors justify a boost after WBRT.

Adult↗
PubMed2000

Pubertal alterations in growth and body composition. V. Energy expenditure, adiposity, and fat distribution.

We determined whether activity energy expenditure (AEE, from doubly labeled water and indirect calorimetry) or physical activity [7-day physical activity recall (PAR)] was more related to adiposity and the validity of PAR estimated total energy expenditure (TEE(PAR)) in prepubertal and pubertal boys (n = 14 and 15) and girls (n = 13 and 18). AEE, but not physical activity hours, was inversely related to fat mass (FM) after accounting for the fat-free mass, maturation, and age (partial r = -0.35, P < or = 0.01). From forward stepwise regression, pubertal maturation, AEE, and gender predicted FM (r(2) = 0.36). Abdominal visceral fat and subcutaneous fat were not related to AEE or activity hours after partial correlation with FM, maturation, and age. When assuming one metabolic equivalent (MET) equals 1 kcal. kg body wt(-1). h(-1), TEE(PAR) underestimated TEE from doubly labeled water (TEE bias) by 555 kcal/day +/- 2 SD limits of agreement of 913 kcal/day. The measured basal metabolic rate (BMR) was >1 kcal. kg body wt(-1). h(-1) and remained so until 16 yr of age. TEE bias was reduced when setting 1 MET equal to the measured (bias = 60 +/- 51 kcal/day) or predicted (bias = 53 +/- 50 kcal/day) BMR but was not consistent for an individual child (+/- 2 SD limits of agreement of 784 and 764 kcal/day, respectively) or across all maturation groups. After BMR was corrected, TEE bias remained greatest in the prepubertal girls. In conclusion, in children and adolescents, FM is more strongly related to AEE than activity time, and AEE, pubertal maturation, and gender explain 36% of the variance in FM. PAR should not be used to determine TEE of individual children and adolescents in a research setting but may have utility in large population-based pediatric studies, if an appropriate MET value is used to convert physical activity data to TEE data.

Adipose Tissue↗
PubMed1999

18F-deoxyglucose positron emission tomography (FDG-PET) for the planning of radiotherapy in lung cancer: high impact in patients with atelectasis.

PURPOSE: 18F-deoxyglucose positron emission tomography (FDG-PET) is increasingly applied in the staging of lung cancer (LC). This study analyzes the potential contribution of PET in radiotherapy planning for LC with special respect to tumor-associated atelectasis. METHODS AND MATERIALS: Thirty-four patients with histologically confirmed LC, who had been examined by PET during pretreatment staging, were included. All were irradiated after CT-based therapy planning with anterior/posterior (AP) portals encompassing the primary tumor and the mediastinum (CT portals, CP). The result of the PET examination was unknown in treatment planning. In retrospect, a PET portal (PP) was delineated and compared with the CP. RESULTS: In 12/34 cases, the shape and/or size of the portals were changed, primarily (n = 10) the size of the fields was reduced. The median area of CP was 182 cm2 versus 167 cm2 of PP. Seventeen of 34 patients had dys- or atelectasis caused by a central primary tumor. In these cases, differences between CP and PP were significantly more frequent than in the other patients (8/17 vs. 3/17, p = 0.03). CONCLUSION: In this retrospective analysis, the information provided by FDG-PET would have contributed to a substantial reduction of the size of radiotherapy portals. This applies particularly for patients with tumor-associated dys- or atelectasis.

Carcinoma, Non-Small-Cell Lung↗
PubMed1999

Double-blind, randomized, placebo-controlled clinical trial on the efficacy and tolerability of a physostigmine patch in patients with senile dementia of the Alzheimer type.

Owing to the pharmacokinetic properties of physostigmine when administered by conventional routes, long-term cholinergic treatment of Alzheimer's disease is difficult to manage. In order to overcome the problems associated with the oral and intravenous application of physostigmine, and to improve patients' compliance, a transdermal therapeutic system was developed. The efficacy and tolerability of this system were evaluated in a double-blind, randomized, multicenter study comparing patches containing 30 mg and 60 mg physostigmine with a placebo patch. The clinical trial followed the basic principles of the various guidelines on the evaluation of anti-dementia drugs, and included patients with mild to moderate probable Alzheimer's disease. A total of 204 patients with probable Alzheimer's disease were included in the study. Of these, 136 patients were eligible for the according-to-protocol analysis of efficacy, 167 subjects for the intention-to-treat analysis of efficacy, and 181 patients were included in the safety analysis. In contrast to the hypothesis to be tested, the efficacy of physostigmine was not superior to that of placebo after a treatment period of 24 weeks. On the contrary, there was even a slight, but not statistically significant, trend toward a better outcome in the placebo group. Median physostigmine plasma concentrations of approximately 100 pg/ml were measured, showing a high degree of interindividual variability and no linear dose relationship between the 30 mg and 60 mg dosages. Plasma cholinesterase activity was not significantly affected by physostigmine. The physostigmine patch application in doses of 30 mg and 60 mg apparently did not lead to physostigmine plasma concentrations that were sufficient to compensate for cholinergic deficiencies in affected brain areas and produce clinical benefits. Both the drug and the transdermal system were generally well tolerated under the study conditions. Modifications of the patch system may perhaps make it possible to achieve higher physostigmine plasma concentrations, which seem to be required to induce the expected beneficial effects during long-term treatment of Alzheimer's disease.

Administration, Cutaneous↗
PubMed1999

The cystine knot of a squash-type protease inhibitor as a structural scaffold for Escherichia coli cell surface display of conformationally constrained peptides.

The Ecballium elaterium trypsin inhibitor II (EETI-II), a member of the squash family of protease inhibitors, is composed of 28 amino acid residues and is a potent inhibitor of trypsin. Its compact structure is defined by a triple-stranded antiparallel beta-sheet, which is held together by three intramolecular disulfide bonds forming a cystine knot. In order to explore the potential of the EETI-II peptide to serve as a structural scaffold for the presentation of randomized oligopeptides, we constructed two EETI-II derivatives, where the six-residue inhibitor loop was replaced by a 13-residue epitope of Sendai virus L-protein and by a 17-residue epitope from human bone Gla-protein. EETI-II and derived variants were produced via fusion to maltose binding protein MalE. By secretion of the fusion into the periplasmic space, fully oxidized and correctly folded EETI-II was obtained in high yield. EETI-II and derived variants could be presented on the Escherichia coli outer membrane by fusion to truncated Lpp'-OmpA', which comprises the first nine residues of mature lipoprotein plus the membrane spanning beta-strand from residues 46-66 of OmpA protein. Gene expression was under control of the strong and tightly regulated tetA promoter/operator. Cell viability was found to be drastically reduced by high level expression of Lpp'-OmpA'-EETI-II fusion protein. To restore cell viability, net accumulation of fusion protein in the outer membrane was reduced to a tolerable level by introduction of an amber codon at position 9 of the lpp' sequence and utilizing an amber suppressor strain as expression host. Cells expressing EETI-II variants containing an epitope were shown to be surface labeled with the respective monoclonal antibody by indirect immunofluorescence corroborating the cell surface exposure of the epitope sequences embedded in the EETI-II cystine knot scaffold. Cells displaying a particular epitope sequence could be enriched 10(7)-fold by combining magnetic cell sorting with fluorescence-activated cell sorting. These results demonstrate that E.coli cell surface display of conformationally constrained peptides tethered to the EETI-II cystine knot scaffold has the potential to become an effective technique for the rapid isolation of small peptide molecules from combinatorial libraries that bind with high affinity to acceptor molecules.

Amino Acid Sequence↗