Vestibular bone thickness of the mandible in relation to the mandibular canal-a retrospective CBCT-based study

Background

The aim of this study was to assess vestibular bone thickness of the mandible in relation to the mandibular canal and position of the mental foramen in relation to the neighbouring teeth. Measurements were performed on radiographic cone-beam computed tomography (CBCT) images.

Methods

This retrospective study analysed 314 CBCTs, having been taken at the Clinic of Cranio-Maxillofacial and Oral Surgery, University of Zurich, Switzerland.

Results

CBCTs from 168 female and 146 male patients (median age 40.2 years) were analysed. Median bone thickness lateral to the nerve canal to the buccal mandibular cortical plate was ~ 4 mm immediately posterior to the mental foramen, increased to ≤ 6 mm over the next 30 mm, then decreased to ~ 3 mm at the level of the mandibular foramen. In two thirds of cases, both mental foramina were located near the second premolar (66.2% right, 67.7% left). Bone thickness and the position of the mental foramen showed marked intra- and interindividual variance.

Conclusions

A preoperative CBCT is recommended for detailed planning of surgical interventions that may reach the mandibular canal (e.g. wisdom teeth removal, root resection, implant placement, bone block harvesting).

Preoperative 3D imaging in maxillary sinus: brief review of the literature and case report

OBJECTIVE

The purpose of the present case report is to document the removal of a radix in antro without a hemorrhagic complication in presence of a posterior superior alveolar artery (PSAA) with a 2.8 mm diameter following a radiographic 3D planning by cone beam computed tomography (CBCT) scan. Furthermore, a brief literature overview on studies describing the existence and the variance of the PSAA is provided.

METHOD AND MATERIALS

A foreign body removal in the right maxillary sinus was performed on a 33-year-old healthy man by using the lateral window osteotomy. The preoperative CBCT scan showed three arteries in the lateral maxillary sinus wall at a distance of 24.6 mm, 19.5 mm, and 13.5 mm to the alveolar crest.

RESULTS

By removing a foreign body out of the maxillary sinus a vessel with a diameter of nearly 3 mm was exposed. Due to CBCT scan planning and the use of piezosurgery it was possible to avoid any damage to the vessel during the operation. The postoperative healing was uneventful and no complications occurred.

CONCLUSION

Although laceration of vessels with a large diameter during lateral window osteotomy is not life-threatening it may compromise visualization and reduces the surgical outcome. Therefore, 3D imaging is recommended for the minimization of intra- and postoperative complications and for the localization of any foreign body in relation to other anatomical structures. This is of special interest in case of anatomical variances of blood vessels.

A retrospective analysis of factors influencing the success of autotransplanted posterior teeth

Background

Survival and success rates of tooth transplantations even after long follow-up periods have been shown to be very high. Nevertheless, it is important to analyse factors potentially influencing these rates. The aim of this study was to assess the influence on success of potential factors.

Methods

The research was based on a retrospective analysis of clinical and radiological data from a sample of 59 subjects (75 transplanted teeth). The follow-up period varied from 0.44 to 12.28 years (mean 3.95 years). Success rates were calculated and depicted with Kaplan-Meier plots. Log-rank tests were used to analyse the effect of root development stage, apex width, the use of enamel matrix proteins or the surgeon on success of transplantations.

Results

Results for success of premolar transplantations were comparable with already published data, while molars performed worse than shown in other studies. The surgeon performing the transplantation (p = 0.001) and tooth type (p ≤ 0.001) were significantly associated with transplantation success. Use of enamel matrix proteins (p = 0.10), root development stage (p = 0.13), the recipient area (p = 0.48) and apex width (p = 0.59) were not significantly associated with success.

Conclusions

Molar transplantations were not as successful as premolar transplantations; however, success rates varied greatly depending on the surgeon’s experience. The use of enamel matrix proteins as well as root development stage, the recipient area and apex width did not show significant associations with success of tooth transplantations.

Frequency and anatomy of the retromolar canal - implications for the dental practice

The retromolar canal (RMC) is an anatomical variant of the mandibular canal. Apart from blood vessels it also contains accessory nerve fibers and is clinically important, because its presence can account for failures of mandibular block anesthesias and in rare cases, injuries of its neurovascular bundle can lead to complications such as hemorrhages and dysesthesias. The aim of this retrospective case study was to analyze the frequency and anatomy of the RMC using cone beam computed tomography (CBCT) in order to draw conclusions for the dental practice. A total of 680 CBCT scans comprising 1,340 mandibular sides were evaluated. A total of 216 RMCs (16.12%) were found. The most common appearance of the canal (39.82%) corresponded to type Al (vertical course), whereas type C (horizontal course) occurred least often (6.02%). Mean measured values were 1.03 mm (SD=0.27mm) regarding the RMC diameter, 10.19 mm (SD=2.64mm) regarding the RMC height and 15.10 mm (SD=2.83 mm) regarding the distance of the RMC to the second molar. Neither demographic factors nor the spatial resolution of the CBCT had a statistically significant impact on the frequency of the RMC. Since the present study revealed a frequency of RMCs amounting to 16.12% (corresponding approximately to every sixth retromolar area), we recommend to spare it during surgery or to consider an additional locoregional anesthesia in the retromolar region. For preoperative diagnosis the CBCT has proved suitable, offering the possibility to select the spatial resolution depending on the indication, so that radiation exposure is reduced without a decrease in validity.

Variations in the anatomical positioning of impacted mandibular wisdom teeth and their practical implications

Surgical removal of impacted third molars is one of the most frequent procedures in oral surgery. Here, three-dimensional (3D) imaging is often used, yet its necessity is still being heavily debated. The aim of the study was to describe the variation in the anatomical positioning of third mandibular molars, and, by doing so, examine the necessity of 3D imaging. A retrospective case study was performed with the patients from an oral surgery department from January 2009 to February 2013. The primary focus of the study was on the spatial relationship to the mandibular canal, as well as angulation, root configuration, and developmental stage of the wisdom tooth. Descriptive statistics were calculated for these variables. A total of 1197 wisdom teeth in 699 patients were evaluated. 46.7% exhibited direct contact to the mandibular canal, another 28.7% showed close proximity and 24.6% a measurable distance. In 29.0%, the mandibular canal was vestibular and in 23.8% lingual to the wisdom tooth. In 7.4%, it was interradicular and in 0.6% intraradicular. Most teeth had one (21.3%) or two (55.3%) roots. Others had three (17.6%), four (2.0%) or five (0.2%) roots. In 31.4% of the teeth, the root perforated the lingual compact bone, and in 4.3% the vestibular compact bone. 44.4% of the teeth had mesial angulation, 9.7% distal angulation, 35.3% lingual and 2.9% buccal angulation. Due to the anatomical variety, the use of 3D imaging is recommended before surgical removal of mandibular third molars if conventional imaging cannot exclude complicated conditions.

[An atypical Stafne cavity-multi-chamber bone lesion with bucal expansion. A case report]

In the literature Stafne bone cavities are mostly described for male patients in their fifth and sixth decade. Usually the lingual cavities appear as ovoid lesions located unilateral in the molar region of the lower jaw underneath the inferior alveolar nerve. Classically they contain parts of the submandibular gland. This case study describes a patient who was referred to the authors’ clinic with a cavity in the right lower jaw extending over a mesio-distal diameter of 24 mm. Its appearance on panoramic x‑ray and cone beam computer tomography (CTBT) was inconclusive. The diagnosis could finally be made after magnetic resonance imaging (MRI). It was based on the content of gland, fat and lymphatic tissue in a lingual open cavity, which is a characteristic feature of Stafne bone cavities. Assumed aetiology and differential diagnosis are discussed.

Pregnancy and Birth After a Two-Step PGD: Polar Body Diagnosis for Hemophilia A and Array CGH on Trophectoderm Cells for Chromosomal Aberrations

Objective: To demonstrate that a PGD program can be successfully established after the 2011 verdict of the German Bundestag concerning PGD. Material and Method: Eight years previously, the couple had had a daughter who suffered from clinically manifest hemophilia A due to an unbalanced X-inactivation, as well as microdeletion syndrome resulting in severe physical and mental disability. The couple wished to have a second child but refused the idea of a "trial" pregnancy. Given the indications for both, it was necessary to carry out polar body diagnosis (PBD) to rule out hemophilia A and, during the same cycle, a subsequent PGD on the blastocysts to rule out genetic aberrations. The PBD and PGD (trophectoderm biopsy, TEB) were performed after high-dosage ovarian stimulation and ICSI fertilization of the oocytes. A blastocyst was successfully transferred on day 6. Results: The patient conceived immediately. The pregnancy developed normally and the patient gave birth to a girl in the 40th week of pregnancy. Post-natal examinations showed that the baby is free from hemophilia A and is developing normally both physically and mentally. Conclusion: Establishment of a PGD program is now possible after legalization of PGD in Germany. It is possible to apply two investigative techniques in a single treatment cycle if multifactorial diagnosis is required.

[Risk assessment in patients undergoing osseous antiresorptive therapy in dentistry. An update]

Antiresorptive therapy is prescribed in particular for the treatment of osteoporosis as well as for the treatment of tumor-induced hypercalcemia and metastatic bone disease. As a consequence, osteopathologies such as bisphosphonate-related osteonecrosis of the jaws (BRONJ) may occur. In 2008, our department reported on BRONJ in a paper that provided dental clinicians with information on diagnostics, therapy, and prevention (Dannemann et al., Schweizer Monatsschrift für Zahnmedizin, Vol. 118, 2/2008). During the last 8 years, new findings have emerged concerning potential etiologies, modes of therapy, and the use of additional antiresorptive therapies. For example, an important point for colleagues in dental practice is the now common intravenous administration of bisphosphonates in osteoporosis patients, which may lead to uncertainty when assessing risk in these patients. For this reason, this article provides an update of the above mentioned publication and gives dental clinicians an updated guideline concerning risk assessment in patients undergoing antiresorptive therapy. In this context, a risk assessment algorithm is presented. The pathogenesis, diagnosis, therapy, and prevention of BRONJ and oral implantation in patients receiving antiresorptive therapy are addressed with regard to the current literature. Finally, we present two example cases.

Tongue cancer in young patients: case report of a 26-year-old patient

Introduction

This article presents the case of a 26-year-old woman with tongue cancer. The median age at the diagnosis of the tongue’s cancer is 61 years. Only approximately 2% of patients are diagnosed before the age of 35.

Case presentation

Our patient survived acute myeloid leukemia (AML) before her second year. She had been having recurrent, poorly healing aphtae on the right side of the tongue for a period of months before the symptoms of the tongue cancer appeared. As a treatment a partial glossectomy was conducted on the right side and a neck dissection of levels I-III. Than a reconstruction of the tongue with a radialis free vascularised flap from left side was performed.

Discussion

It should be always looked for the causal factor in young patients with a neoplasm. There is strong evidence for second malignant neoplasms in survivors of childhood cancer.

Risk-adapted dental care prior to intensity-modulated radiotherapy (IMRT)

BACKGROUND

At the Clinic for Radiation Oncology at the Zurich University Hospital (UniversitätsSpital Zürich [USZ]), head-and-neck tumor (HNT) patients have been treated with intensity-modulated radiotherapy (IMRT) since 01/2002 (n 〉 800). This method causes less damage to normal tissues adjacent to the tumor, and thus it was possible in the head/neck region to markedly reduce the rate of osteoradionecrosis (ORN), in addition to reducing the rate of severe xerostomia. Based on these results, risk-adapted dental care (RaDC) was adopted by our clinic as the standard mode of pre-IMRT dental treatment. The guidelines as formulated by Grötz et al. were respected. ORN prophylaxis is one of the most important goals of pre-radiotherapy dental care, and the ORN rate is a measurable parameter for the efficacy of dental care, given a certain radiation technique. The aim of the present study was therefore to evaluate the efficacy of RaDC as reflected by the ORN rate of our IMRT patients.

MATERIALS AND METHODS

IN August 2006, RaDC was clinically implemented and has been used for all HNT patients prior to IMRT since then. Before that (01/2002-07/2006), dental restorations were performed according to the usual procedure.

RESULTS

The rate of grade-2 ORN was similar in the conventionally treated and RaDC groups (2% and 1%, resp.); grade-3 ORN had not occurred by the time the analysis was conducted. As expected, fewer extractions were performed in the RaDC cohort (no extractions in 47% of the RaDC/IMRT cohort vs. 27% in the IMRT cohort receiving conventional dental care).

CONCLUSION

After considerably less invasive dental treatment, no higher-grade ORN occurred and no ORN-related jaw resections were required. Based on the present data, risk-adapted minimally invasive dental care is recommended before IMRT.

The human alpha(2)-plasmin inhibitor: functional characterization of the unique plasmin(ogen)-binding region

The human alpha(2)-plasmin inhibitor (A2PI) possesses unique N- and C-terminal extensions that significantly influence its biological activities. The C-terminal segment, A2PIC (Asn(398)-Lys(452)), contains six lysines thought to be involved in the binding to lysine-binding sites in the kringle domains of human plasminogen, of which four (Lys(422), Lys(429), Lys(436), Lys(452)) are completely and two (Lys(406), Lys(415)) are partially conserved. Multiple Lys to Ala mutants of A2PIC were expressed in Escherichia coli and used in intrinsic fluorescence titrations with kringle domains K1, K4, K4 + 5, and K1 + 2 + 3 of human plasminogen. We were able to identify the C-terminal Lys(452) as the main binding partner in recombinant A2PIC (rA2PIC) constructs with isolated kringles. We could show a cooperative, zipper-like enhancement of the interaction between C-terminal Lys(452) and internal Lys(436) of rA2PIC and isolated K1 + 2 + 3, whereas the other internal lysine residues contribute only to a minor extent to the binding process. Sulfated Tyr(445) in the unique C-terminal segment revealed no influence on the binding affinity to kringle domains.

[Intraosseous anesthesia X-tip system in tooth extraction]

The purpose of this study was to determine the anesthetic efficacy of a intraosseous anesthesia (IOA) as an alternative to the infra alveolar nerve block (IANB) or the maxillary anesthesia. 55 subjects who underwent a tooth extraction received a primary X-tip intraosseous injection (LLC Lakewood, New Jersey, U.S.A.) of Ubistesin forte (articaini hydrochloridum 40 mg, adrenalinum 10 pg ut adrenalini hydrochloridum 1:100000, median 1.5 ml). A pulse oximeter measured the heart rate and the oxygen saturation. The results demonstrated, that the maximum heart rate was higher with the intraosseous injection (average 14.6 beats/min increase) during 1.5-2 minutes, but there was no depression of the oxygen saturation. The wound healing was uneventful. We registered five non-responders which were treated additionally with 1.3 ml of Ubistesin forte terminal anesthesia. For all patients the IOA was unpleasant similar to a "normal" anesthesia. Success of the intraosseous injection was 91%, comparable to the study of Turner et al. (2002) (or the clinical experience after an IANB). For non-responders to an IANB the IOA seems to be a good alternative method.

Effects of tryptophan supplementation on plasma tryptophan and related hormone levels in heifers and dairy cows

This study was conducted to investigate the effects of rumen-protected tryptophan (125 g tryptophan per day) in heifers and dairy cows. Blood samples from dairy cows and heifers were collected for 24h in 3-h intervals on the day before tryptophan supplementation, on day 2, 5 and 7 of tryptophan supplementation, and in heifers additionally on d 14 after tryptophan supplementation was ceased. Plasma tryptophan, melatonin, serotonin, and prolactin concentrations were determined. Tryptophan plasma concentrations on d 5 were augmented at day (11:00 h) and nighttime (02:00 h), (P<0.05) in response to tryptophan supplementation in heifers by 119% and in dairy cows by 47%, respectively, as compared with d 0. Melatonin increased (P<0.05) in response to tryptophan supplementation in heifers, but not in cows. The effect of tryptophan supplementation on plasma tryptophan and melatonin was reversible as demonstrated in heifers on d 14 after cessation of tryptophan supplementation. Serotonin and prolactin in plasma did not respond to tryptophan supplementation. However, milk yield during morning milking increased significantly in tryptophan supplemented cows on d 1, 3 and 4 as compared to the day before tryptophan supplementation. Additional blood samples were taken during afternoon milking in cows at 1-min intervals for the analyses of oxytocin and prolactin on the day before the start and on d 7 of tryptophan supplementation. Milk flow curves were recorded during milking. No effect of tryptophan supplementation on the milking related release of oxytocin and prolactin and on any characteristic of milk flow was observed. In conclusion, tryptophan supplementation caused increased plasma tryptophan in cows and heifers and plasma melatonin in heifers. However, plasma serotonin, prolactin and oxytocin release in cows remained unchanged by tryptophan supplementation. Milk yield at morning milking increased slightly and transiently in response to tryptophan supplementation.

Structural/functional characterization of the alpha 2-plasmin inhibitor C-terminal peptide

The alpha(2)-plasmin inhibitor (A2PI) is a main physiological regulator of the trypsin-like serine proteinase plasmin. It is composed of an N-terminal 15 amino acid fibrin cross-linking polypeptide, a 382-residue serpin domain, and a flexible C-terminal segment. The latter, peptide Asn(398)-Lys(452), and its Lys452Ala mutant were expressed as recombinant proteins in Escherichia coli (r-A2PIC and r-A2PICmut, respectively). CD and NMR analyses indicate that r-A2PIC is flexible, loosely folded, and with low content of regular secondary structure. Functional characterization via intrinsic fluorescence ligand titrations shows that r-A2PIC interacts with the isolated plasminogen kringle 1 (r-K1) (K(a) approximately 69.9 mM(-)(1)), K4 (K(a) approximately 45.7 mM(-)(1)), K5 (K(a) approximately 4.3 mM(-)(1)), and r-K2 (K(a) approximately 3.2 mM(-)(1)), all of which are known to exhibit lysine-binding capability. The affinities of these kringles for r-A2PIC are consistently larger than those reported for the ligand N(alpha)-acetyllysine, a mimic of a C-terminal Lys residue. The r-A2PICmut, with a C-terminal Ala residue, also interacts with r-K1 and K4, although with approximately 5-fold lesser affinities relative to r-A2PIC, demonstrating that while Lys(452) plays a major role in the binding, internal residues in r-A2PIC tether the kringles. (1)H NMR spectroscopy shows that key aromatic residues within the K4 lysine-binding site (LBS), namely, Trp(25), Trp(62), Phe(64), Trp(72), and Tyr(74), selectively respond to the addition of r-A2PIC and r-A2PICmut, indicating that these interactions proceed via the kringles' canonical LBS. We conclude that r-A2PIC docks to kringles primarily through lysine side chains and that Lys(452) most definitely enhances the binding. This suggests that multiple Lys residues within A2PI could contribute, perhaps in a zipper-like fashion, to its binding to the in-tandem, multikringle array that configures the plasmin heavy chain.

A conserved ubiquitin ligase of the nuclear envelope/endoplasmic reticulum that functions in both ER-associated and Matalpha2 repressor degradation

Substrate discrimination in the ubiquitin-proteasome system is believed to be dictated by specific combinations of ubiquitin-protein ligases (E3s) and ubiquitin-conjugating enzymes (E2s). Here we identify Doa10/Ssm4 as a yeast E3 that is embedded in the endoplasmic reticulum (ER)/nuclear envelope yet can target the soluble transcription factor Matalpha2. Doa10 contains an unusual RING finger, which has ubiquitin-ligase activity in vitro and is essential in vivo for degradation of alpha2 via its Deg1 degradation signal. Doa10 functions with two E2s, Ubc6 and Ubc7, to ubiquitinate Deg1-bearing substrates, and it is also required for the degradation of at least one ER membrane protein. Interestingly, different short-lived ER proteins show distinct requirements for Doa10 and another ER-localized E3, Hrd1. Nevertheless, the two E3s overlap in function: A doa10Delta hrd1Delta mutant is far more sensitive to cadmium relative to either single mutant and displays strong constitutive induction of the unfolded protein response; this suggests a role for both E3s in eliminating aberrant ER proteins. The likely human ortholog of DOA10 is in the cri-du-chat syndrome critical region on chromosome 5p, suggesting that defective ubiquitin ligation might contribute to this common genetic disorder.

Determination of retigabine and its acetyl metabolite in biological matrices by on-line solid-phase extraction (column switching) liquid chromatography with tandem mass spectrometry

A HPLC assay with tandem mass spectrometric detection in the positive-ion atmospheric pressure chemical ionisation (APCI) mode for the sensitive determination of retigabine [(I), D-23129] and its acetyl metabolite [(II), ADW 21-360] in plasma was developed, utilising the structural analogue (D-10328), (III), as internal standard. Automated on-line solid-phase extraction of diluted plasma samples, based on 200-microl plasma aliquots, at pH 6.5, allowed a reliable quantification of retigabine and the acetyl metabolite down to 1 ng/ml. Injection of 500 microl of diluted plasma onto a C2 stationary phase-based column switching system in combination with a 75 mm x 4 mm reversed-phase analytical column at a flow-rate of 0.5 ml/min provided cycle times of 4 min per sample. The standard curves were linear from 1 to 1000 ng/ml using weighted linear regression analysis (1/x2). The method is accurate (mean accuracy < or = +/- 10%), precise (RSD < +/- 15%) and sensitive, providing lower limits of quantification in plasma of 1 ng/ml for retigabine (I), and 2.5 ng/ml for the metabolite (II) with limits of detection of 0.5 ng/ml for both analytes. Up to 200 unknowns may be analysed each 24 h per analyst.

Theory of controlling stochastic resonance

The concept of controlling stochastic resonance has been recently introduced [L. Gammaitoni et al., Phys. Rev. Lett. 82, 4574 (1999)] to enhance or suppress the spectral response to threshold-crossing events triggered by a time-periodic signal in background noise. Here, we develop a general theoretical framework, based on a rate equation approach. This generic two-state theory captures the essential features observed in our experiments and numerical simulations.

Enantioselective high-performance liquid chromatography assay of (+)R- and (-)S-alpha-lipoic acid in human plasma

A specific plasma level assay for the enantiomers of alpha-lipoic acid is described. It makes use of liquid-liquid extraction, chemical reduction to the dithiol enantiomers, and their precolumn chiral derivatisation with o-phthalaldehyde in the presence of D-phenylalanine. The two diastereomeric derivatives are separated by reversed-phase HPLC with fluorescence detection. The working range of the assay is between 15 ng/ml (lower limit of quantitation) and 1,000 ng/ml for either enantiomer.

Noise sustained propagation: local versus global noise

We expand on prior results on noise supported signal propagation in arrays of coupled bistable elements. We present and compare experimental and numerical results for kink propagation under the influence of local and global fluctuations. As demonstrated previously for local noise, an optimum range of global noise power exists for which the medium acts as a reliable transmission "channel." We discuss implications for propagation failure in a model of cardiac tissue, and present a general theoretical framework based on discrete kink statistics. Valid for generic bistable chains, the theory captures the essential features observed in our experiments and numerical simulations.

Pharmacokinetic-pharmacodynamic modeling of testosterone and luteinizing hormone suppression by cetrorelix in healthy volunteers

Cetrorelix (CET), a potent luteinizing hormone-releasing hormone (LH-RH) antagonist, was recently approved for the prevention of premature ovulation in patients undergoing a controlled ovarian stimulation (COS), followed by oocyte pickup and assisted reproductive techniques (ART), and is currently under clinical trials for benign prostate hyperplasia, endometriosis, and tumors sensitive to sex hormones. CET suppresses luteinizing hormone (LH), follicle-stimulating hormone (FSH), and testosterone (T) in men. The purpose of this study was to evaluate the pharmacokinetics and absolute bioavailability of 3 mg intravenously and subcutaneously administered CET in healthy male and female volunteers and to develop a pharmacokinetic-pharmacodynamic (PK-PD) model to link the plasma concentrations of CET to the T and LH suppression in males. Following intravenous (IV) (n = 5) and subcutaneous (SC) (n = 6) administration of CET acetate, CET and hormone plasma levels were measured by radioimmunoassay (RIA) and enzyme immunoassay (EIA) methods, respectively. Pharmacokinetics of CET was explained by a three-compartment model for the IV route and by a two-compartment model with first-order absorption for the SC route. Average absolute bioavailability after SC administration was 85%. There were no differences in the pharmacokinetics between male and female subjects (ANOVA, p > 0.05). Single IV and SC doses of CET caused immediate and distinct suppression of LH, FSH, and T levels by 80%, 45% and 95% of their baseline levels, respectively. The duration of hormone suppression was longer for the SC route. An indirect-response PK-PD Emax model was developed to link the measured CET plasma concentrations with the respective T or LH levels. In addition, the circadian rhythm of T levels was accounted by including a cosine function in a second separate PD model. The PD model with cosine function was applied to T baseline levels as well as to the suppressed concentrations after CET dosing. The two models adequately described the PK-PD relationship between plasma levels of CET and T suppression following IV and SC dosing. The EC50 values (mean +/- SD) for the suppression of T were similar (p > 0.05) between the two routes of administration and the two models.

Disposition and metabolism of cetrorelix, a potent luteinizing hormone-releasing hormone antagonist, in rats and dogs

Disposition and metabolism of cetrorelix was studied in intact and bile duct-cannulated rats and dogs after s.c. injection. An s.c. dose of 0.1 mg/kg [(14)C]cetrorelix was rapidly and completely absorbed in rats. T(max) in plasma and most tissues was at 2 h. Radioactivity at the injection site in rats declined to 10% by 24 h. The extent of (14)C absorption in rats calculated from excretion until 264 h was 94%. Exposure of the target organ pituitary gland was demonstrated with a time course similar to plasma but on a higher level. Rats excreted 69.6% of radioactivity via feces and 24. 3% into urine. Excretion was nearly complete within 48 h. No enteral reabsorption was detected. In dogs t(max) in plasma was 1.3 h. (14)C- and cetrorelix-plasma levels were similar until 24 h, indicating a negligible amount of metabolites. A dose of 1 mg/kg in dogs showed an increasing influence of a slow absorption phase (flip-flop). In dogs equal amounts of the (14)C dose were found within 192 h in feces and urine, 46 and 48%, respectively. In urine of both species, only intact cetrorelix was detected. In bile and feces of both species qualitatively the same metabolites were found, characterized as truncated peptides of the parent decapeptide. The major metabolite occurring in bile of both species was the (1-7)heptapeptide. The amounts of the (1-4)tetrapeptide in feces of rats but not in that of dogs increase with time, suggesting additional degradation of the peptide in the gastrointestinal tract of rats by enteric metabolization.

Quantification of perifosine, an alkylphosphocholine anti-tumour agent, in plasma by pneumatically assisted electrospray tandem mass spectrometry coupled with high-performance liquid chromatography

An HPLC assay with tandem mass spectrometric detection in the positive-ion Turbo-Ion-Spray (TISP) mode for the fast and sensitive determination of perifosine ((I), D-21266) in human plasma was developed, utilising the structural analogue, miltefosine ((II), D-18506), as internal standard. Automated solid-phase extraction of diluted plasma samples, based on 250-microl plasma aliquots, at pH 6.5, allowed a reliable quantification of perifosine down to 4 ng/ml. Injection of 200 microl of plasma extracts onto a 100x3 mm normal-phase analytical column at a flow-rate of 0.5 ml/min provided retention-times of 2.4 and 2.1 min for perifosine (I) and the internal standard (II), respectively. The standard curves were linear from 4 to 2000 ng/ml using weighted linear regression analysis (1/Y2). The inter-assay and intra-assay accuracies for the calibration standards were within +0.9% and -0.2%, exhibiting precisions (C.V.) of +/-6.5 and +/-7.3%, respectively. Up to 100 unknowns may be analysed each 24 h per analyst.

Stochastic resonance in coupled nonlinear dynamic elements

We investigate the response of a linear chain of diffusively coupled diode resonators under the influence of thermal noise. We also examine the connection between spatiotemporal stochastic resonance and the presence of kink-antikink pairs in the array. The interplay of nucleation rates and kink speeds is briefly addressed. The experimental results are supplemented with simulations on a coupled map lattice. We furthermore present analytical results for the synchronization and signal processing properties of a Phi(4) field theory and explore the effects of various forms of nonlinear coupling. (c) 1998 American Institute of Physics.

Stability analysis of fixed points via chaos control

This paper reviews recent advances in the application of chaos control techniques to the stability analysis of two-dimensional dynamical systems. We demonstrate how the system's response to one or multiple feedback controllers can be utilized to calculate the characteristic multipliers associated with an unstable periodic orbit. The experimental results, obtained for a single and two coupled diode resonators, agree well with the presented theory. (c) 1997 American Institute of Physics.

Investigation of the stereoselective in vitro metabolism of the chiral antiasthmatic/antiallergic drug flezelastine by high-performance liquid chromatography and capillary zone electrophoresis

An achiral HPLC method using a silica gel column as well as two independent chiral analytical methods by HPLC and capillary zone electrophoresis (CZE) were developed in order to investigate the in vitro metabolism of the racemic antiasthmatic/antiallergic drug flezelastine. The chiral HPLC analysis was performed on a Chiralpak AD column, which also allowed the simultaneous separation of the N-dephenethyl metabolite. The chiral separation by CZE was achieved by the addition of beta-cyclodextrin to the run buffer. The stereoselectivity of the in vitro biotransformation of flezelastine was investigated using liver homogenates of different species. Depending on the species, diverse stereoselective aspects were demonstrated. The determination of the enantiomeric ratios of flezelastine and of N-dephenethylflezelastine after incubations of racemic flezelastine with liver microsomes revealed that porcine liver microsomes showed the greatest enantioselectivity of the biotransformation. (-)-Flezelastine was preferentially metabolized. After incubations with bovine liver microsomes the enantiomer of N-dephenethylflezelastine formed from (+)-flezelastine dominated. Incubations of the pure enantiomers of flezelastine with induced rat liver microsomes resulted in the stereoselective formation of a hitherto unknown metabolite, which was only detected in samples of (+)-flezelastine. Initial structure elucidation of the compound indicated that the new metabolite was most likely an aromatically hydroxylated derivative of the N-dephenethylflezelastine.

In vivo incorporation of lipoic acid enantiomers and homologues in the pyruvate dehydrogenase complex from Escherichia coli

The strain Escherichia coli JRG26, which has a defect in the lipoic acid biosynthesis, was cultivated in the presence of R-lipoic acid, S-lipoic acid, RS-dithiolane-3-caproic acid, RS-bisnorlipoic acid, and RS-tetranorlipoic acid, respectively. With the exception of the last compound the strain was able to grow with all these substances. R-lipoic acid was the most efficient factor, concentrations of 10 ng/l were sufficient to support growth of the cells, while 10(4)-fold to 10(7)-fold higher concentrations were necessary for the other compounds. The specific catalytic activity of the pyruvate dehydrogenase complex isolated from the cells grown on RS-dithiolane-3-caproic acid was only slightly lower than from cells grown on R-lipoic acid. With RS bisnorlipoic acid the specific activity was one third compared to that of the native enzyme complex. The incorporation of the RS-bisnorlipoic acid into the pyruvate dehydrogenase could directly be demonstrated by polyclonal antibodies directed against R-lipoic acid and RS-bisnorlipoic acid, both conjugated to BSA. Western blot analysis showed that the antibodies against the R-lipoic acid reacted specifically with the E2 component of pyruvate dehydrogenase complex purified from cells grown on this factor, while antibodies against RS-bisnorlipoic acid reacted with the enzyme complex isolated from cells grown in the presence of this compound.

Interaction of alpha-lipoic acid enantiomers and homologues with the enzyme components of the mammalian pyruvate dehydrogenase complex

Lipoic acid (alpha-lipoic acid, thioctic acid) is applied as a therapeutic agent in various diseases accompanied by polyneuropathia such as diabetes mellitus. The stereoselectivity and specificity of lipoic acid for the pyruvate dehydrogenase complex and its component enzymes from different sources has been studied. The dihydrolipoamide dehydrogenase component from pig heart has a clear preference for R-lipoic acid, a substrate which reacts 24 times faster than the S-enantiomer. Selectivity is more at the stage of the catalytic reaction than of binding. The Michaelis constants of both enantiomers are comparable (Km = 3.7 and 5.5 mM for R- and S-lipoic acid, respectively) and the S-enantiomer inhibits the R-lipoic acid dependent reaction with an inhibition constant similar to its Michaelis constant. When three lipoic acid homologues were tested, RS-1,2-dithiolane-3-caproic acid was one carbon atom longer than lipoic acid, while RS-bisnorlipoic acid and RS-tetranorlipoic acid were two and four carbon atoms shorter, respectively. All are poor substrates but bind to and inhibit the enzyme with an affinity similar to that of S-lipoic acid. No essential differences with respect to its reaction with lipoic acid enantiomers and homologues exist between free and complex-bound dihydrolipoamide dehydrogenase. Dihydrolipoamide dehydrogenase from human renal carcinoma has a higher Michaelis constant for R-lipoic acid (Km = 18 mM) and does not accept the S-enantiomer as a substrate. Both enantiomers of lipoic acid are inhibitors of the overall reaction of the bovine pyruvate dehydrogenase complex, but stimulate the respective enzyme complexes from rat as well as from Escherichia coli. The S-enantiomer is the stronger inhibitor, the R-enantiomer the better activator. The two enantiomers have no influence on the partial reaction of the bovine pyruvate dehydrogenase component, but do inhibit this enzyme component from rat kidney. The implications of these results are discussed.

High-performance liquid chromatographic assay for the determination of the decapeptide cetrorelix, a novel luteinizing hormone-releasing hormone antagonist, in human plasma

This is the first paper which describes a HPLC method for the determination of the decapeptide cetrorelix, a potent luteinizing hormone-releasing hormone (LH-RH) antagonist, in human plasma by liquid-liquid extraction, concentration by back-extraction with diluted acid into a smaller volume, and fluorescence detection, using the decapeptide D-21740 as internal standard. The excitation (227 nm) and emission wavelengths (340 nm) for cetrorelix and the internal standard are identical. The extraction yield for both peptides is ca. 50% and the assay is linear over the concentration range 2-20 ng/ml in plasma. The mobile phase components are ammonium acetate buffer (0.05 mol/l, pH 4) as solvent A and methanol-acetonitrile (1:1, v/v) as solvent B. The elution condition for the peptides from the column (Lichrospher 60 RP-Select B 5 microns, 250 x 4 mm I.D.) is isocratic with a 49:51 mixture of solvent A-solvent B. The lower limit of quantitation for cetrorelix is 2 ng/ml human plasma.

Metabolic fate of the novel antihypertensive drug naftopidil

The metabolism of 14C-naftopidil ((R,S)-1-(2-methoxyphenyl)-1-piperazinyl-3- (1-naphthyl-oxy-2-propanol, CAS 57149-07-2) and the pharmacodynamic action of the metabolites was investigated. The metabolic pathway in rat, dog, mouse and man was qualitatively similar, with preference for the hydroxylation of the phenyl or naphthyl moiety of naftopidil [phenyl)hydroxy-metabolite, (naphthyl)hydroxy-metabolite). Cleavage of the parent compound and production of the propylene glycol metabolite was a further important reaction especially for rat and man. In all species investigated, demethylation of naftopidil occurs to a minor extent. O-desmethyl-naftopidil, (phenyl)hydroxy-naftopidil and (naphthyl)hydroxy-naftopidil were found to have similar affinities for the alpha 1-adrenoceptors as the parent compound (IC50)nmol/l): 433.0; 585.0; 52.7; respectively; naftopidil: 235.0). The naftopidil metabolites, like the parent compound showed no alpha 2- or beta-adrenoceptor affinity.

Pharmacokinetic fate of the novel antihypertensive drug naftopidil

The pharmacokinetics of naftopidil (R,S)-1-[4-(2-methoxyphenyl)-1-piperazinyl]-3-(1-naphthyloxy)-2 propanol, CAS 57149-07-2) was studied in rats and dogs using 14C-labeled drug in pharmacodynamically effective doses (oral doses: 5/10 mg/kg and intravenous doses: 1/2.5 mg/kg in rats/dogs, respectively). Naftopidil (14C) was rapidly and in high extent absorbed in rats and dogs after oral administration. The absolute bioavailability of the parent compound amounted to 9% in rats and indicates a high first pass effect to in part pharmacodynamically effective metabolites, as was shown in a previous paper. The parent compound and its 14C-metabolites were widely distributed into the periphery, more pronounced in the rat than in the dog, as indicated from comparison of the volumes of distribution and dose corrected Cmax- and AUC0-infinity-values in plasma. Elimination of radioactivity from plasma occurred in rat and dog in a similar rate. Tissue distribution studies in the rat showed highest peak-concentrations in the gastrointestinal (GI) tract (evaluated with contents) due to the predominant biliary elimination, followed by liver, adrenals, pituitary and Harderian glands, lungs, pancreas, kidneys, adipose tissue, bone marrow, aorta, thyroid and lymph nodes. Radioactivity was eliminated from most of the tissues within the first 168 h. Highest fractions of the dose were detected--apart from the GI-tract--in liver, muscle, skin, blood, and kidneys. After repeated administration to rats, accumulation of radioactivity in the 28 tissues examined did not exceed factor 9 or factor 5 in most of the tissues.(ABSTRACT TRUNCATED AT 250 WORDS)

Arachidonic acid metabolism in isolated gastric mucous and parietal cells

Arachidonic acid metabolism was studied in isolated gastric mucous and parietal cells. During a 90 min incubation, mucous cells incorporated [1-14C]arachidonic acid (4.5 mumol/l) into triacylglycerols (500 pmol/mg protein), phosphatidylcholine (520), phosphatidylethanolamine (290) and phosphatidylinositol (100). 230 pmol/mg protein was recovered as 14CO2 and 130 pmol/mg protein in the form of unidentified water-soluble metabolites. The incorporation rates were linearly related with arachidonic acid concentration up to 10 mumol/l. Neither equimolar concentrations of oleic acid, palmitic acid and linoleic acid nor prostaglandin E2 (1 mumol/l) or indomethacin (10 mumol/l) affected incorporation. During prolonged incubation incorporated arachidonic acid was transferred from triacylglycerols and phosphatidylcholine to phosphatidylethanolamine. Upon subcellular fractionation most of the incorporated arachidonic acid was found in the microsomal fraction. Compared with mucous cells, parietal cells incorporated arachidonic acid less quickly into phospholipids, but utilized it more efficiently for energy metabolism. In conclusion gastric cells show a highly dynamic metabolism of arachidonic acid which is qualitatively similar but quantitatively different between cell types.

1-Naphthol conjugation in isolated cells from liver, jejunum, ileum, colon and kidney of the guinea pig

Cells from liver, jejunum, ileum, colon and kidney of the guinea pig were freshly prepared by standard isolation procedures. Cells were incubated in the presence of several concentrations of 1(14C)-naphthol, and formation of 1-naphthol glucuronide and 1-naphthol sulphate was assessed at various times by thin layer chromatography. Cells from all five tissues conjugated 1-naphthol. The velocity of conjugation was fastest in jejunals cells (2.9 nmole/mg prot X min) followed by cells from liver, ileum, colon and kidney (0.2 nmole/mg prot X min). The apparent Km-values for glucuronidation ranged from 17 microM to 32 microM, and those for sulphation from 15 microM to 35 microM. Each tissue had a specific conjugation pattern. The two extremes were kidney cells, which had a glucuronidation/sulphation ratio in excess of 10, and colon cells which had a ratio of 0.38. The data suggest that these tissues possess different levels of 1-naphthol-conjugating enzymes, which resemble with regard to their apparent substrate affinities.

[Evaluation of the aca lipase (DuPont) determination and of the lipase determination according to Myrick (Calbiochem-Behring) (author's transl)]

Two lipase methods, the method for the aca (DuPont) and the method according to Myrick (1976) Thesis, Birmingham Al.) (Calbiochem-Behring), were compared with the lipase method of Rick (1969) Z. Klin. Chem. Klin. Biochem. 7, 530--539) and with the amylase determination. The diagnostic value of the aca method, the amylase and the lipase method of Rick were in good agreement, whereas the method of Myrick gave conflicting results.

[Serum lipase and amylase activity after endoscopic retrograde pancreatography (author's transl)]

Serum activities of lipase and amylase were measured in 11 patients at short time intervals (-10 min; + 10, 30, 60 min; 2,3,4,6,8,24,48 hours) after an endoscopic retrograde pancreatography. Lipase activity increased rapidly in 9 patients in 10 min after the contrast instillation and obtained its maximum at the first hour of investigation. Amylase activity elevation occurred in 5 patients only and was significantly lower than that of lipase with a flat peak at 1-6 hours.