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W Kamm

Publications and source records attributed to W Kamm.

17 recordsLinked to original sources
PubMed2001

Analysis of steryl esters in cocoa butter by on-line liquid chromatography-gas chromatography.

On-line liquid chromatography-gas chromatography (LC-GC) has been applied to the analysis of steryl esters in cocoa butter. Separation of the steryl esters was achieved after on-line transfer to capillary GC. HPLC removes the large amount of triglycerides and pre-separates the components of interest, thus avoiding time-consuming sample preparation prior to GC analysis. The identities of the compounds were confirmed by GC-MS investigation of the collected HPLC fraction and by comparison of the mass spectra (chemical ionization using ammonia as ionization gas) to those of synthesized reference compounds. Using cholesteryl laurate as internal standard, steryl esters were quantified in commercial cocoa butter samples, the detection limit being 3 mg/kg and the quantification limit 10 mg/kg, respectively. Only slight differences in percentage distributions of steryl esters depending on the geographical origin of the material were observed. The patterns were shown to remain unchanged after deodorization. The method described might be a valuable tool for authenticity assessment of cocoa butter.

Chromatography, Gas↗
PubMed2001

Transport of peptidomimetic thrombin inhibitors with a 3-amidino-phenylalanine structure: permeability and efflux mechanism in monolayers of a human intestinal cell line (Caco-2).

PURPOSE: Peptidomimetic thrombin inhibitors derived from Nalpha-(2-naphthylsulfonyl)-3-amidino-phenylalanine with different basic and acidic substituents were investigated with respect to their intestinal transport behavior. METHODS: Intestinal permeability coefficients were studied using Caco-2 monolayers and a reversed-phase HPLC method for quantitation. RESULTS: Apparent permeability coefficients Papp of compounds with a free amidino group were in general low (<10 x 10(-8) cm/s) and independent of the structure of the amide part (C-terminus). Polarized efflux, however, was strongly affected by substituents in the amide moiety yielding the following efflux ratios (ER): methylpiperidide (1) (ER 45) > piperidine carboxylic acid methylester (ER 6-11) > piperidine carboxylic acids (ER 1.9-2.9) > piperazide (ER -0.17). Efflux of (1) was temperature-dependent, but independent of the enantiomeric configuration, accompanied by an increase in transepithelial electrical resistance (TEER), and could be reduced by P-gp inhibitors (PSC 833, Cremophor EL) but not by indomethacin. Replacement of the amidine group of (1) by aminomethyl-, amino-, and oxamidine- moieties drastically increased absorptive permeability (46-68 fold) with ER < 3.4. In contrast, the oxamidine with a C-terminal nipecotic acid residue (8) displayed also a temperature dependent efflux- without altering TEER (ER 22). This efflux was sensitive to PSC833/Cremophor EL and indomethacin. CONCLUSIONS: Basic and acidic residues of amidino-phenylalanine-derived thrombin inhibitors mediate affinity to intestinal efflux pumps. presumably P-gp and MRP. P-gp mediated efflux was related to a net positive charge and accompanied by an increased TEER. Among the methylpiperide (1) promoieties studied the oxamidino group seems to be very promising in overcoming both transport and efflux problems frequently encountered with peptidomimetics containing amidines.

Amidines↗
PubMed2001

Tetanus toxoid loaded nanoparticles from sulfobutylated poly(vinyl alcohol)-graft-poly(lactide-co-glycolide): evaluation of antibody response after oral and nasal application in mice.

PURPOSE: Aim of the study was the evaluation of the potential of novel tetanus toxoid (TT) loaded nanoparticles (NP) for electing an immune response in mice against TT. METHODS: Six week-old female Balb/c mice were immunized by oral (p.o.), nasal (i.n.) and intraperitoneal (i.p.) application of TT NP loaded by adsorption. As polymer a novel polyester, sulfobutylated poly(vinyl alcohol)-graft-poly(lactide-co-glycolide), SB(43)-PVAL-g-PLGA was used. Blood samples were collected 4 and 6 weeks after immunization and assayed for serum IgG- as well as IgA antibody titers by ELISA. NP formulations varying in size and loading were compared to alum adsorbates as well as to TT solutions. RESULTS: Both, p.o. and i.n. administration of TT associated NP increased serum titers up to 3 x 10(3) (IgG) and 2 x 10(3) (IgA). While small NP induced significantly higher titers then larger ones after oral administration, intermediate NP induced antibodies after nasal application. Of the mucosal routes investigated, i.n. seems to be more promising compared to p.o. immunization. CONCLUSIONS: Antigen loaded NP prepared from surface modified polyesters combined with CT show considerable potential as a vaccine delivery system for mucosal immunization. The results warrant further experiments to explore in more detail the potential use of NP as mucosal vaccine delivery system.

Administration, Intranasal↗
PubMed2000

Evaluation of absorption enhancement for a potent cyclopeptidic alpha(nu)beta(3)-antagonist in a human intestinal cell line (Caco-2).

Different absorption enhancing principles for a potent cyclopeptidic alpha(nu)beta(3)-antagonist (EMD 121974) were investigated in monolayers of a human intestinal cell line (Caco-2). Transepithelial transport was quantitated by reversed-phase high-performance liquid chromatography. Cytotoxic effects were characterized by determination of transepithelial electrical resistances (TEERs), propidium iodide (PI)-influx, FITC-phalloidin staining and the release of cytosolic lactate dehydrogenase (LDH). Medium chain fatty acids (MCFAs, NaC10, NaC12) and taurocholate (NaTC) were the most efficient enhancers of cyclopeptide and FITC-dextran 4400 permeability coefficients, displaying different time profiles of activity. Whereas NaTC (15 mM) showed almost a constant permeation enhancing effect from 20 min up to 120 min (ca. 12-fold), MCFA absorption enhancement was markedly dependent on incubation time (NaC10, 20 min: 1.2-fold, 120 min: 17-fold; NaC12, 20 min: 4.3-fold, 120 min: 13-fold). All cytotoxicity assays demonstrated that MCFAs were significantly more cytotoxic than NaTC. Ion pairing with hydrophobic amino acids and heptane sulfonate distinctly increased octanol-buffer partition coefficients of the cationic cyclopeptide but did not enhance its transepithelial permeability. Nanoparticles as well as beta-cyclodextrin neither affected integrity of the cells nor transport properties of the cyclopeptide. In summary, significant absorption enhancement was only observed with NaTC or MCFAs. Increase in permeability coefficients using NaTC occurred rapidly with acceptable cytotoxicities and merits further investigations.

Biological Transport↗
PubMed2000

Biodegradable nanoparticles for oral delivery of peptides: is there a role for polymers to affect mucosal uptake?

Numerous authors have demonstrated uptake of micro- and nanospheres, consisting of natural or synthetic polymeric materials from the gastrointestinal tract over the past two decades. The exploitation of particulate carrier systems for the delivery of peptides and other hydrophilic macromolecules via the oral route remains a challenging task due to morphological and physiological absorption barriers in the gastrointestinal tract. This review examines recent progress in the field of nanoparticle uptake from this site of administration. Since most studies have been performed with poly(styrene) particles of different sizes relatively little is known about both the effect of physicochemical particle properties critical for absorption after peroral application, and the mechanisms of gastrointestinal particle uptake. Apart from particle size, type and composition of the polymers used for micro- or nanoencapsulation are crucial for an uptake and transport across mucosal barriers. Factors such as particle surface charge and hydrophilic/hydrophobic balance of these polymeric materials have not been investigated systematically since adjustment of these particle properties is almost impossible without synthetic modification of the polymers. The current findings will be reviewed and compared to those obtained with nanoparticles consisting of a novel class of charged comb polyesters, poly(2-sulfobutyl-vinyl alcohol)-graft-poly(D,L-lactic-co-glycolic acid), SB-PVAL-g-PLGA, allowing adjustment of physicochemical nanoparticle properties with a single class of polymers.

Administration, Oral↗
PubMed1999

Prodrug approach for alphaIIbbeta3-peptidomimetic antagonists to enhance their transport in monolayers of a human intestinal cell line (Caco-2): comparison of in vitro and in vivo data.

PURPOSE: Different lipophilic derivatives of a potent alphaIIbbeta3-antagonist with benzamidino-oxazolidinone structure were investigated with respect to transport and metabolism properties to evaluate their potential as prodrugs with improved absorption behavior. METHODS: Intestinal transport and metabolism of the compounds were studied in Caco-2 monolayers under in vitro conditions and quantitated by a reversed-phase HPLC- method. Peroral bioavailability in cynomolgus monkeys and inhibition of platelet aggregation (guinea pig) were compared to in vitro permeability coefficients. RESULTS: N-alkoxycarbonyl- and N-benzoyl-derivatization of the benzamidine-parent drug increased the apparent permeabilities across Caco-2 monolayers by a factor of 25-100 fold. Most prodrugs were transported mainly by passive diffusion, whereas the methoxycarbonyl-derivative EMD 122347 displayed directional transport from basolateral (BL) to apical (AP). This polarized efflux was concentration dependent (saturable kinetics with Km = 207 microM, Vmax = 0.275 nmol cm(-2) min(-1)) and could be reduced in the presence of verapamil (300 microM), an inhibitor of p-glycoprotein. Cell mediated cleavage of the prodrugs was low and showed only slight differences to hydrolysis in buffer solution, indicating a predominantly non enzymatic cleavage. Both peroral bioavailability (monkey) and the inhibition of ex-vivo platelet aggregation (guinea pig) gave the same rank order as the permeability coefficients obtained in Caco-2 monolayers. CONCLUSIONS: Alkoxycarbonylamidine- and benzoylamidine promoieties of a RGD mimetic alphaIIbbeta3-antagonist considerably increased both effect bioavailabilities in animal experiments as well as in-vitro permeability in cell monolayers, demonstrating the potential of this approach to enhance transport of peptidomimetic drugs.

Animals↗
PubMed1994

[Antibiotic sensitivity of gram-negative bacteria in intensive care units in Switzerland].

The sensitivity to the major antimicrobial agents of consecutively isolated gram-negative rods in intensive care units in Switzerland was investigated. A majority of strains originated from clinical specimens where infection or colonization could not be distinguished from each other. A total of 1024 isolates from 482 patients were tested by a standardized microtiter method. Of the beta-lactam antibiotics, imipenem (92% of bacteria sensitive), ceftazidime (90%), and aztreonam (85%) showed the greatest activity. 94% of the isolates were sensitive to ciprofloxacin, and 93% and 91% to amikacin and tobramycin respectively. There where considerable differences locally and in time, probably reflecting small outbreaks due to resistant bacteria and because selective pressure is locally dependent on the antimicrobial agents used. 122 patients were observed for an extended period. In 67 (55%) the same gram-negative rods persisted for up to 42 days without development of resistance. In 41 patients (34%) there was a change to other more resistant bacteria, especially to multi-resistant Pseudomonas aeruginosa, Flavobacterium meningo-septicum, Xanthomonas maltophilia or Enterobacter cloacae. In 12 patients (10%) bacteria of the same species with resistance to additional antimicrobial agents were observed.

Anti-Bacterial Agents↗
PubMed1989

Evaluation of the Cobas-Bact system for direct and rapid identification and antimicrobial susceptibility testing of Enterobacteriaceae from positive urine specimens.

A direct antimicrobial susceptibility test and a direct identification of Gram-stained urine specimens positive for Enterobacteriaceae using a new instrument (Cobas-Bact) were compared by means of the conventional Kirby-Bauer agar diffusion disk method and the spot indole test, an in-house set of identification tests or API 20E. Bacteria from 191 cases of monomicrobial bacteriuria due to members of the family Enterobacteriaceae were tested. Direct susceptibility testing was performed in 180 cases (94%), providing 1649 antibiotic-microorganism combinations. A complete agreement was reached in 82% and essential agreement in 92% of cases. Minor discrepancies were found in 163 (9.9%) major ones in 125 (7.6%) and very major ones in 10 (0.6%) of examinations. 72% of all minor and 71% of all major discrepancies were caused by two antibiotics: cephalothin and nitrofurantoin. Of the very major discrepancies, 50% were due to amoxicillin. Of 171 direct identifications obtained, 130 (76%) were "high-confidence" correct identifications (percentage of likelihood p greater than or equal to 80%), 25 (14.6%) "low-confidence" identifications (percentage of likelihood p less than 80%) and 16 (9.4%) misidentifications. On the whole, this direct and rapid Cobas-Bact identification and susceptibility testing procedure provided satisfying information within 5-6 h after collection of urine specimens positive for members of the Enterobacteriaceae family.

Anti-Bacterial Agents↗
PubMed1989

Evaluation of the Cobas-Bact system for direct and rapid identification and antimicrobial susceptibility testing of gram-negative rods from positive blood culture broths.

A direct antimicrobial susceptibility test and a direct identification of positive blood culture broths for gram-negative rods confirmed with Gram stain by using a new instrument, Cobas-Bact, were compared with the conventional Kirby-Bauer agar diffusion disk method and with the in-house set of identification or API 20E, respectively. The bacterial pellet of centrifuged positive blood culture broth was used to inoculate a Cobas-Bact susceptibility and identification rotor. Bacteria from 206 cases of monomicrobial septicemia due to members of the family Enterobacteriaceae were tested. In 198 episodes (96%), direct identification and antimicrobial susceptibility testing results were obtained for the same bacterial pathogen within 5 h of detection. Of 204 direct identifications obtained, 177 (86.6%) were "high-confidence" correct identifications (percentage of likelihood [P] greater than or equal to 80%) and 25 (12.5%) "low-confidence" correct identifications (P less than 80%), whereas only 2 misidentifications occurred (1 Escherichia coli and 1 Proteus mirabilis). Direct susceptibility testing was performed in 199 episodes (96%), providing 1,885 antibiotic-microorganism combinations. Full agreement reached 86.3%, and essential agreement reached 92.8%. Minor discrepancies were found in 120 (6.5%) of the tests, major discrepancies were found in 127 (6.8%) tests, and very major discrepancies were found in only 7 (0.4%) tests. Subsequent MIC determinations in cases of major or very major discrepancies reduced the number of major discrepancies involving cephalosporins from 60 to 16, whereas all those involving aminoglycosides remained. Overall, this direct and rapid Cobas-Bact identification and susceptibility testing procedure offered accurate information with 5 to 6 h after the laboratory detection of bacteremia and septicemia due to members of the Enterobacteriacease.

Bacteriological Techniques↗
PubMed1985

Evaluation of the Cobasbact system for rapid antimicrobial susceptibility testing of positive blood culture broths.

The automated Cobasbact system was adapted for direct antimicrobial susceptibility testing of positive blood culture broths and its performance compared with that of the conventional Kirby-Bauer agar disc diffusion method using 278 positive blood samples. Overall, 1746 antibiotic-organism combinations were tested. Full agreement was 86.9% and essential agreement (i.e. including minor discrepancies) was 91.8%. The system would seem to produce acceptable susceptibility results within five hours after detection of a positive blood culture broth.

Anti-Bacterial Agents↗
PubMedDate not supplied

Evaluation of a rapid latex agglutination test (Directigen) for the direct detection of group A streptococci from throat swabs.

A rapid group A beta-hemolytic streptococci (GAS) antigen detection test using latex agglutination (Directigen, Becton Dickinson) was compared with a conventional culture method for the direct detection of GAS from throat swabs. One throat specimen was collected from each of 229 patients. After standard inoculation onto sheep blood agar plates, all swabs were tested for GAS antigen. Of the 229 specimens tested, 46 (20%) were GAS-positive by culture. Direct latex agglutination agreed with culture in 222 of them (97%). The sensitivity of the test was 93% (43/46), the specificity 98% (179/183), the positive predictive value 91%, and the negative predictive value 98%. The detection of GAS antigen by coagglutination (Phadebact, Pharmacia) was also carried out. 81% (35/43) of the cultures and Directigen-positive specimens gave a positive coagglutination for GAS. 100% (179/179) of the cultures and Directigen-negative specimens were also negative by the coagglutination test. We conclude that the Directigen rapid latex agglutination test for the direct detection of GAS from throat swabs compares favorably with culture and has the advantage of providing same-day results.

Humans↗
PubMedDate not supplied

An industry view of compliance with European Community legislation.

This paper describes how from a situation within the European Community where each Member State had its own individual regulations for materials and articles in contact with food, the Community has developed a harmonized approach. The view is expressed that whilst this harmonization is desirable, the EC legislation as currently written is impractical. Flaws in the principles underlying EC controls are identified and whilst some parts of the harmonized regulations can form the basis for a workable scheme, substantial revision is needed. Proposals for improvement to the current Directives are suggested.

Animals↗