Biochemistry and functional aspects of human glandular kallikreins

Human urinary kallikrein was purified by gel filtration on Sephacryl S-200 and affinity chromatography on aprotinin-Sepharose, followed by ion exchange chromatography on DEAE-Sepharose. In dodecylsulfate gel electrophoresis two protein bands with molecular weights of 41,000 and 34,000 were separated. The amino acid composition and the carbohydrate content of the kallikrein preparation were determined; isoleucine was identified as the only aminoterminal amino acid. The bimolecular velocity constant for the inhibition by diisopropyl fluorophosphate was determined as 9±2 l mol–1 min–1. The hydrolysis of a number of substrates was investigated and AcPheArgOEt was found to be the most sensitive substrate for human urinary kallikrein. Using this substrate an assay method for kallikrein in human urine was developed. It was shown by radioimmunoassay that pig pancreatic kallikrein can be absorbed in the rat intestinal tract. Furthermore, in dogs the renal excretion of glandular kallikrein from blood was demonstrated by radioimmunological methods

Specific CT 3D rendering of the treatment zone after Irreversible Electroporation (IRE) in a pig liver model: the “Chebyshev Center Concept” to define the maximum treatable tumor size

Background: Size and shape of the treatment zone after Irreversible electroporation (IRE) can be difficult to depict due to the use of multiple applicators with complex spatial configuration. Exact geometrical definition of the treatment zone, however, is mandatory for acute treatment control since incomplete tumor coverage results in limited oncological outcome. In this study, the “Chebyshev Center Concept” was introduced for CT 3d rendering to assess size and position of the maximum treatable tumor at a specific safety margin. Methods: In seven pig livers, three different IRE protocols were applied to create treatment zones of different size and shape: Protocol 1 (n = 5 IREs), Protocol 2 (n = 5 IREs), and Protocol 3 (n = 5 IREs). Contrast-enhanced CT was used to assess the treatment zones. Technique A consisted of a semi-automated software prototype for CT 3d rendering with the “Chebyshev Center Concept” implemented (the “Chebyshev Center” is the center of the largest inscribed sphere within the treatment zone) with automated definition of parameters for size, shape and position. Technique B consisted of standard CT 3d analysis with manual definition of the same parameters but position. Results: For Protocol 1 and 2, short diameter of the treatment zone and diameter of the largest inscribed sphere within the treatment zone were not significantly different between Technique A and B. For Protocol 3, short diameter of the treatment zone and diameter of the largest inscribed sphere within the treatment zone were significantly smaller for Technique A compared with Technique B (41.1 ± 13.1 mm versus 53.8 ± 1.1 mm and 39.0 ± 8.4 mm versus 53.8 ± 1.1 mm; p < 0.05 and p < 0.01). For Protocol 1, 2 and 3, sphericity of the treatment zone was significantly larger for Technique A compared with B. Conclusions: Regarding size and shape of the treatment zone after IRE, CT 3d rendering with the “Chebyshev Center Concept” implemented provides significantly different results compared with standard CT 3d analysis. Since the latter overestimates the size of the treatment zone, the “Chebyshev Center Concept” could be used for a more objective acute treatment control

Abstracts from the 8th International Conference on cGMP Generators, Effectors and Therapeutic Implications

This work was supported by a restricted research grant of Bayer AG

Inhibition of flucloxacillin tubular renal secretion by piperacillin

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECTMost β-lactams are excreted by filtration and to a greater extent by tubular secretion, which is a capacity-limited saturable pathway.Pharmacokinetic interactions between co-administered β-lactams have been frequently reported; however, their mechanism and possible clinical benefits are not well defined.We are not aware of the interaction between piperacillin and flucloxacillin being reported in the literature

Competitive Inhibition of Renal Tubular Secretion of Gemifloxacin by Probenecid▿

Probenecid interacts with transport processes of drugs at several sites in the body. For most quinolones, renal clearance is reduced by concomitant administration of probenecid. The interaction between gemifloxacin and probenecid has not yet been studied. We studied the extent, time course, site(s), and mechanism of this interaction. Seventeen healthy volunteers participated in a randomized, two-way crossover study. Subjects received 320 mg gemifloxacin as an oral tablet without and with 4.5 g probenecid divided in eight oral doses. Drug concentrations in plasma and urine were analyzed by liquid chromatography-tandem mass spectrometry. WinNonlin was used for noncompartmental analysis, compartmental modeling, and statistics, and NONMEM was used for visual predictive checks. Concomitant administration of probenecid increased plasma gemifloxacin concentrations and amounts excreted in urine compared to baseline amounts. Data are average estimates (percent coefficients of variation). Modeling showed a competitive inhibition of the renal tubular secretion of gemifloxacin by probenecid as the most likely mechanism of the interaction. The estimated Km and Vmax for the saturable part of renal elimination were 9.16 mg/liter (20%) and 113 mg/h (21%), respectively. Based on the molar ratio, the affinity for the renal transporter was 10-fold higher for gemifloxacin than for probenecid. Since probenecid reached an ∼200-times-higher area under the molar concentration-time curve from 0 to 24 h than gemifloxacin, probenecid inhibited the active tubular secretion of gemifloxacin. Probenecid also reduced the nonrenal clearance of gemifloxacin from 25.2 (26%) to 21.0 (23%) liters/h. Probenecid inhibited the renal tubular secretion of gemifloxacin, most likely by a competitive mechanism, and slightly decreased nonrenal clearance of gemifloxacin

Prevalence of vitamin D insufficiency in radiologists: a cross-sectional study

OBJECTIVE To compare the prevalence of vitamin D insufficiency between radiologists and a control group of non-radiologists. MATERIALS AND METHODS This prospective cross-sectional study was conducted at the Swiss Congress of Radiology in May of 2016. Attendees (radiologists and non-radiologists) were asked to give a venous blood sample to measure vitamin D (25-hydroxyvitamin D) blood serum level. Vitamin D insufficiency was defined as < 50 nmol/l (30 ng/ml). We collected information on profession, age, gender, vitamin D supplements, recent sunny vacation, and eating fish. We compared vitamin D between radiologists and non-radiologists. RESULTS A total of 137 radiologists (mean age, 38 ± 10 years) and 164 non-radiologists (mean age, 40 ± 12 years) participated in the study. Prevalence of vitamin D insufficiency in both groups was similar (58.4% (80/137) vs. 53.7% (88/164); p = 0.240). Forty-three participants were under vitamin D supplementation. In those without supplementation, we found no difference in vitamin D between groups (44.0 ± 16.2 nmol/l (17.6 ± 6.5 ng/ml) vs. 44.4 ± 16.9 nmol/l (17.8 ± 6.8 ng/ml); p = 0.757). Average vitamin D levels for radiologists were slightly lower (-0.98 nmol/l (0.39 ng/ml), 95% confidence interval - 5.96 to 4.00 (- 2.38 to 1.6 ng/ml); p = 0.699), when adjusting for the potential confounders, but not statistically significant. The odds ratio of vitamin D insufficiency for radiologists versus non-radiologists was 1.7 (95% CI = 0.94-3.06; p = 0.078) after adjusting for the other independent variables. CONCLUSIONS The prevalence of vitamin D insufficiency in radiologists was high (58.4%), but not substantially higher than in non-radiologists

Penetration of Moxifloxacin into Bone Evaluated by Monte Carlo Simulation▿

Moxifloxacin is a fluoroquinolone with a broad spectrum of activity and good penetration into many tissues, including bone. Penetration of moxifloxacin into bone has not yet been studied using compartmental modeling techniques. Therefore, we determined the rate and extent of bone penetration by moxifloxacin and evaluated its pharmacodynamic profile in bone via Monte Carlo simulation. Twenty-four patients (10 males, 14 females) undergoing total hip replacement received 400 mg moxifloxacin orally 2 to 7 h prior to surgery. Blood and bone specimens were collected. Bone samples were pulverized under liquid nitrogen by a cryogenic mill, including an internal standard. Drug concentrations were analyzed by high-performance liquid chromatography. We used ADAPT II (results reported), NONMEM, and WinBUGS for pharmacokinetic analysis. Monte Carlo simulation was performed to reverse engineer the necessary area under the free concentration-time curve fAUCSERUM/MIC in serum and total AUCBONE/MIC in bone for a successful clinical or microbiological outcome. The median (10% to 90% percentile for between-subject variability) of the AUC in bone divided by the AUC in serum (AUCBONE/AUCSERUM) was 80% (51 to 126%) for cortical bone and 78% (42 to 144%) for cancellous bone. Equilibration between serum and bone was rapid. Moxifloxacin achieved robust (≥90%) probabilities of target attainment (PTAs) in serum, cortical bone, and cancellous bone up to MICs of ≤0.375 mg/liter based on the targets fAUCSERUM/MIC ≥ 40 and AUCBONE/MIC ≥ 33. Moxifloxacin showed high bone concentrations and a rapid equilibrium between bone and serum. The favorable PTAs compared to the 90%-inhibitory MIC of Staphylococcus aureus warrant future clinical trials on the effectiveness of moxifloxacin in the treatment of bone infections