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Biomedical subjects

M Berna

Publications and source records attributed to M Berna.

10 recordsLinked to original sources
PubMed2004

Slow release of two antibiotics of veterinary interest from PVA hydrogels.

Two antibiotics, tylosin tartrate and oxytetracycline hydrochloride, were entrapped in poly(vinyl alcohol) (PVA) hydrogels (MW 31,000-50,000) by a cryogen procedure obtaining a controlled release system suitable for veterinary application. It was found that at a low drug matrix loading (10 mg/ml), the in vitro release rate of both antibiotics could be reduced by a previous freeze drying of the gel, while no reduction in drug rate took place in heavily loaded matrices (300 mg/ml). When PVA hydrogels containing tylosin were administered to rats per os the drug could not be detected in the blood, but it was found in organs,: liver, kidneys, and muscles, for up to 120 h. On the other hand, when the same amount of drug was administered orally as powder, no appreciable organ accumulation was detected, while the drug was found in faeces and urine. These data show that PVA hydrogels can be a suitable slow release system for tylosin administration. Oxytetracycline could also be quantitatively entrapped and released from PVA hydrogels, but once administered per os to rats, it was not detected in blood or organs.

Administration, Oral↗
PubMed2002

Collection, storage, and filtration of in vivo study samples using 96-well filter plates to facilitate automated sample preparation and LC/MS/MS analysis.

The benefits of high-throughput bioanalysis within the pharmaceutical industry are well established. One of the most significant bottlenecks in bioanalysis is transferring in vivo-generated study samples from their collection tubes during sample preparation and extraction. In most cases, the plasma samples must be stored frozen prior to analysis, and the freeze/thaw (F/T) process introduces thrombin clots that are capable of plugging pipets and automated liquid-transfer systems. A new approach to dealing with this problem involves the use of Ansys Captiva 96-well 20-microm polypropylene filter plates to collect, store frozen, and filter plasma samples prior to bioanalysis. The samples are collected from the test subjects, and the corresponding plasma samples are placed directly into the wells of the filter plate. Two Duoseal (patent pending) covers are used to seal the top and bottom of the plate, and the plate is stored at down to -70 degrees C. Prior to sample analysis, the seals are removed and the plate is placed in a 96-well SPE manifold. As the plasma thaws, it passes (by gravity or mild vacuum) through the polypropylene filter into a 96-well collection plate. A multichannel pipet or automated liquid-transfer system is used to transfer sample aliquots without fear of plugging. A significant advantage of this approach is that, unlike other methods, issues related to incomplete pipetting are virtually eliminated. The entire process is rapid since thawing and filtering take place simultaneously, and if a second F/T cycle is required for reanalysis, it is not necessary to refilter the samples (additional clotting was not observed after three F/T cycles). This technique was tested using monkey, rat, and dog plasma and sodium heparin and EDTA anticoagulants. To assess the possibility of nonspecific binding to the polypropylene filter, a variety of drug candidates from diverse drug classes were studied. Validation data generated for two Lilly compounds from distinct classes, before and after filtering, are presented in this paper as practical examples of this technique. While LC/MS/MS is the primary method of bioanalysis in our laboratory, the technique presented in this paper is applicable to other forms of detection as well.

Autoanalysis↗
PubMed2002

Determination of olanzapine in human blood by liquid chromatography-tandem mass spectrometry.

A liquid chromatographic-tandem mass spectrometric (LC-MS-MS) assay was developed and validated to quantitatively determine olanzapine (OLZ) concentrations in human blood. Liquid-liquid extraction, using n-butanol:cyclohexane (3:47, v/v), was used to isolate OLZ and its internal standard, LY170158, from the biological matrix. Chromatographic resolution of OLZ from endogenous interferences and known metabolites was accomplished with a MetaChem Monochrom HPLC column (4.6 x 150 mm, d(p) 5 microm). Detection occurred using a Perkin-Elmer Sciex API III Plus triple quadrupole mass spectrometer using positive ion APCI and multiple reaction monitoring (MRM). The linear dynamic range was from 5 to 500 ng ml(-1) based on a 0.25-ml aliquot of human blood. The inter-day precision (%RSD) and accuracy (%RE) ranged from 3.65 to 10.64 and from -2.14 to 3.07, respectively. Modifications to an existing assay for the determination of OLZ in human plasma were necessary. A different structural analog was used as the internal standard due to instability observed for the original analog when using human blood as the matrix. A second modification was the addition of the anti-oxidant sodium ascorbate to inhibit degradation of OLZ in human blood, as has been noted by other investigators. Upon fortification of human blood with sodium ascorbate (final concentration, 0.33 mM), OLZ was found to be stable for at least 1 week at -70 degrees C as well as through two freeze-thaw cycles. This assay, which will be used to investigate the distribution of OLZ in human blood, grants insight into the proper sample handling conditions needed to perform valid determinations of OLZ in human blood.

Antipsychotic Agents↗
PubMed2001

Clinical characteristics and outcome of a cohort of 101 patients with hepatocellular carcinoma.

AIM: To conduct a cohort study of 101 patients with hepatocellular carcinoma (HCC) presenting to a tertiary care medical referral center in Germany between 1997 and 1999. METHODS AND RESULTS: Data were retrospectively analyzed by chart review. In 95 cases (72 males and 23 females) sufficient data were available for analysis. Twenty five (29%) of 85 patients were HBsAg or anti HBc positive, 21/85 (25%) were anti HCV positive, and 6/85 (7%) were positive for both HBV and HCV-markers. Age was significantly lower in HBV positive patients than in the other two groups. Thirty one (34%) of 90 patients had histories of alcohol abuse. In 79/94 (84%) patients, cirrhosis was diagnosed. Of these cirrhotic patients, 29/79 (37%) belonged to Child Pugh's group (CHILD) A, 32/79 (40%) to CHILD B, and 18/79 (23%) to CHILD C. AFP was elevated in 61/91 (67%) patients. A single tumor nodule was found in 38/94 (40%), more than one nodule in 31/94 (34%), and 25/94 (26%) had a diffusely infiltrating tumor, i.e. the tumor margins could not be seen on imaging procedures. Portal vein thrombosis was present in 19/94 (20%). Imaging data consistent with lymph node metastases were found in 10/92 (11%), while distant metastases were found in 8/93 (9%). According to Okuda 28/94 (30%) were grouped to stage I, 53/94 (56%) were grouped to stage II, and 13/94 (14%) were grouped to stage II. Survival data were available for 83 patients. The Kaplan-Meier estimate for median survival was 8 4 months. Factors influencing survival were the Okuda score, the presence of portal vein thrombosis, and the presence of ascites. The presence of non complicated liver cirrhosis by itself, distant metastases, or infection with hepatitis viruses did not influence survival. AFP positivity by itself did not influence survival, though patients with an AFP value greater than 100 microg/L did experience shortened survival. Treatment besides tamoxifen or supportive care was associated with prolonged survival. The influence of therapy on survival was most pronounced in Okuda stage II patients. There was longer survival in those Okuda stage II patients who were treated with percutaneous ethanol injection. CONCLUSION: Even in a low incidence area such as Germany, the majority of HCC is caused by viral hepatitis and therefore potentially preventable. Reflecting the high proportion of advanced stage tumors in our patients, the median survival was poor. Patients who received active therapy had a longer survival.

Adult↗
PubMed1999

Determination of LY295501 in human plasma by reverse phase HPLC with UV detection.

A high performance liquid chromatographic (HPLC) assay was developed and validated for the quantitative determination of LY295501 in human plasma. A structural analog, LY186641, was selected as the internal standard. The samples were processed by protein precipitation with acetonitrile followed by concentration of the supernatants and reconstitution. Chromatographic resolution of LY295501 from endogenous plasma components was accomplished with a Waters Novapak C18 HPLC column (3.9 x 150 mm, d(p) 4 mm). Detection was by absorbance at 260 nm. The linear dynamic range was from 5 to 400 microg ml(-1) of human plasma using a 0.25 ml aliquot. The inter-day precision (%RSD) and accuracy (%RE) in plasma ranged from 2.4 to 4.7, and -4.9 to 1.4, respectively. This assay is both simple and rapid, and has been used to successfully analyze over 1500 samples from human clinical trials.

Antineoplastic Agents↗
PubMed1998

Determination of LY355703 in dog and mouse plasma by positive ion liquid chromatography/tandem mass spectrometry with atmospheric pressure chemical ionization.

A liquid chromatographic/mass spectrometric assay was developed for the determination of LY355703, a potent anti-tumor drug, in mouse and dog plasma. Empore (3M) C18 solid-phase extraction cartridges were used for sample preparation in conjunction with a positive pressure manifold. Chromatographic separation was obtained with a cyano high-performance liquid chromatographic column and detection was conducted using atmospheric pressure chemical ionization tandem mass spectrometry in the selected reaction monitoring mode. A structural analog, compound LY354504, was used as the internal standard. The assay was validated for the determination of LY355703 in mouse (ICR and NuNu) and dog (beagle) plasma. The lower and upper limits of quantitation were 2.1 and 527 ng ml-1, respectively, using a 0.1 ml plasma aliquot. The signal-to-noise ratio of a typical 2.1 ng ml-1 standard was approximately 40:1. The inter-day precision (relative standard deviation) and accuracy (relative error) derived from the analysis of validation samples at five concentrations ranged from 2.7 to 7.6% and from 4.8 to 4.5%, respectively. Throughput is approximately one sample every 3 min. This assay is simple, sensitive, accurate, precise and is being used to support toxicokinetic studies in dog and mouse.

Animals↗
PubMed1998

Determination of olanzapine in human plasma and serum by liquid chromatography/tandem mass spectrometry.

A liquid chromatographic/tandem mass spectrometric (LC/MS/MS) assay was developed for the quantitative determination of olanzapine (LY170053, OLZ) in human plasma and serum. Bond Elut C2 solid-phase extraction cartridges (single cartridge or 96-well format), in conjunction with a positive pressure manifold, were used to extract OLZ and its internal standard, LY170222, from the biological matrix. Chromatographic resolution of OLZ from endogenous plasma interferences and its metabolites was accomplished with a MetaChem monochrom HPLC (4.6 x 150 mm, dp 5 microns). Detection was effected with a Perkin-Elmer SCIEX API III Plus mass spectrometer using positive ion atmospheric pressure chemical ionization and a multiple reaction monitoring protocol. The linear dynamic range was from 250 pg ml-1 to 50 ng ml-1 of human plasma/serum using a 0.5 ml aliquot. The inter-day precision (relative standard deviation) and accuracy (relative error) in plasma ranged from 6.26 to 7.66% and from -3.54 to 7.52%, respectively. The intra-day precision and accuracy in serum ranged from 3.46 to 8.76% and from -8.06 to 12.46%, respectively. This assay is sensitive and selective, and will be used to support both human clinical and toxicological analyses. Furthermore, using the 96-well solid-phase extraction format, sample preparation can be easily automated.

Antipsychotic Agents↗
PubMed1997

An automated multidimensional screening approach for rapid method development in high performance liquid chromatography.

Despite enormous advancements in the area of high performance liquid chromatography (HPLC) in recent years, method development remains a major challenge. This is primarily due to the unknown nature of the matrix material which sometimes is difficult to characterize (e.g. biological matrices). To improve the efficiency of method development a multidimensional screening approach was presented. This approach was based on two major steps: (1) a matrix spiked with drug was eluted from a large number of columns, each under different mobile phase compositions, to provide the preliminary selectivity-separation information; (2) this information was then used to compose column switching pairs (each pair consisted of a preparatory column followed by an analytical column) and the elution profile was evaluated to determine the suitable clean up and quantitation conditions. An example was provided using ethyl 3,5-bis(acetylamino)-2,4,6-triiodobenzoate (EEDA), an X-ray enhancement agent, in human plasma. Since the HPLC system was fully automated the data generation time, and consequently the method development time, can be significantly reduced.

Acetonitriles↗
PubMed1976

[Skin tests for 48/80 and histamine].

The variability in time of the cutaneous response, resulting from morbid and specially from therapeutic physiological interferences, restrains the credibility of cutaneous allergological investigations. The authors present the first results, established on control population considered as normal, of an approach to cutaneous reactivity by means of a non-specific histamine liberation, induced by a tween: 48/80 coupled with appreciation of the reactivity to histamine injected by the intra-dermal route. The study objectively demonstrates the variability in the response in terms of the doses injected, age, and especially in terms of drug interferences which usually, go in the direction of a hyporeactivity. On the contrary, hyper-reactivity is frequently observed in certain morbid conditions, in particular in spasmophilia. In conclusion, before including the 48/80 and histamine tests in the battery of allergological investigations, it seems indispensable to specify the limits in normal subjects and to better aprehend interferences which modify its expression.

Anaphylaxis↗