Temporal and local appearance of alkaline phosphatase activity in early stages of guided bone regeneration. A descriptive histochemical study in humans

Alkaline phosphatase (ALP) catalyzes the hydrolysis of phosphate esters and it seems to be a prerequisite for normal skeletal mineralization. Also, ALP is the most widely recognized marker of osteoblast phenotypes. By a tissue regenerative technique called Guided Bone Regeneration (GBR), it is possible nowadays to regenerate small bony defects. The aim of the present study was to investigate early events in bone healing and neogenesis by studying histochemically the temporal and local appearance of the marker Alkaline Phosphatase (ALP) in a GBR model system. Nine healthy volunteers (5 males, 4 females, mean age 31.7 years) participated in the experiment. After raising a mucoperiosteal flap from the mandibular second molar to the retromolar area in each volunteer, a hollow titanium test cylinder was placed into a congruent bony bed and the coronal end of the cylinder was closed with an ePTFE-membrane. Then the flap was adapted and sutured to obtain primary wound closure. After 2, 7 and 12 weeks, the regenerated tissue within the cylinders was harvested. Histologically, ALP activity was observed associated with the osteoid seams in the very basal part of the regenerate where new bone trabeculae were in the process of being formed. More coronally, large round cells seemed to secrete an ALP-positive substance since in the center of such cell clusters strong ALP activity located extracellularly was detected. In the present experiment, ALP seemed to have been an early sign of osteoblast secretion of a matrix which subsequently was determined to become osteoid. ALP activity was never seen isolated within connective tissue and away from bone. This is an indication that its source is linked to existing bone. The present study has documented for the first time the appearance of ALP activity in guided bone regenerations in humans. It has revealed that: 1) Osteogenesis in guided bone regeneration is preceded by localized, marked expression of ALP in an organized connective tissue environment. 2) Bone neogenesis is an early event in this experimental setup and may be detected already 2 weeks after wounding. 3) Expression of ALP and subsequent bone neogenesis is originating from and topographically linked to pre-existing bone structures.

Selective spinal anesthesia for outpatient laparoscopy. III: sufentanil vs lidocaine-sufentanil

PURPOSE

The efficacy of low dose intrathecal lidocaine-sufentanil was compared with intrathecal sufentanil for short duration outpatient gynecological laparoscopy.

METHODS

Thirteen ASA I and II patients undergoing gynecological laparoscopy were studied in a randomized double-blind trial. Patients received either intrathecal 10 mg lidocaine plus 10 microg sufentanil (Group LS) or intrathecal 20 microg sufentanil (Group S), each diluted to 3 mL with sterile water through a 27g Whitacre needle in the sitting position. Sensory and motor recovery were assessed with pinprick and a modified Bromage scale.

RESULTS

One of seven Group LS patients and two of five Group S patients required conversion to general anesthesia for failed skin test with forceps. Two of the remaining three Group S patients felt sharpness with skin incision. The study was terminated early because of inadequate anesthesia in Group S. The small sample size (n = 9) made statistical analysis uninformative.

CONCLUSION

Intrathecal 20 microg sufentanil is unsuitable as a sole agent for gynecological laparoscopy.

Simple and inexpensive but highly discriminating method for computer-assisted DNA fingerprinting of Pseudomonas aeruginosa

We describe here a method for computer-assisted fingerprinting of Pseudomonas aeruginosa. In this method, DNA is digested with SalI, and bands with molecular sizes of >/=9.7 kb are visually scored after electrophoresis on agarose gels. Pattern scores are entered into a Microsoft Excel database. In scoring, the number of bands within each of a set of molecular size ranges is scored, rather than the absolute molecular size of each band, substantially enhancing the speed and reproducibility of the method, while eliminating the need for using expensive gel scanning equipment and software. Pattern scores are used to generate matrices of genetic distance values, which can be visualized in neighbor-joining trees. The method reliably distinguishes two epidemiologically unrelated isolates in 99.3% of all comparisons. The genetic relationships between isolates observed with the method were consistent with those obtained by analysis of two P. aeruginosa genes, indicating that it provides valid estimates of genetic divergence between isolates. Using the method, respiratory tract isolates from cystic fibrosis patients in Green Lane Hospital in Auckland, New Zealand, were shown to be genetically less diverse than epidemiologically unrelated isolates from other patients. This finding was not due to the existence of clusters of related strains specialized toward colonization of the respiratory tract and thus was indicative of transmission between patients. Analysis of multiple isolates from individual cystic fibrosis patients suggested that up to five separate clusters of genetically related strains may simultaneously be present in a patient. The method described should significantly enhance our ability to investigate the epidemiology of P. aeruginosa.

Daily energy expenditure of the grey mouse lemur (Microcebus murinus): a small primate that uses torpor

We aimed to investigate the pattern of utilisation of torpor and its impact on energy budgets in free-living grey mouse lemurs (Microcebus murinus), a small nocturnal primate endemic to Madagascar. We measured daily energy expenditure (DEE) and water turnover using doubly labelled water, and we used temperature-sensitive radio collars to measure skin temperature (Tsk) and home range. Our results showed that male and female mouse lemurs in the wild enter torpor spontaneously over a wide range of ambient temperatures (Ta) during the dry season, but not during the rainy season. Mouse lemurs remained torpid between 1.7-8.9 h with a daily mean of 3.4 h, and their Tsk s fell to a minimum of 18.8 degrees C. Mean home ranges of mouse lemurs which remained normothermic were similar in the rainy and dry season. During the dry season, the mean home range of mouse lemurs showing daily torpor was significantly smaller than that of animals remaining normothermic. The DEE of M. murinus remaining normothermic in the rainy season (122 +/- 65.4 kJ x day(-1)) was about the same of that of normothermic mouse lemurs in the dry season (115.5 +/- 27.3 kJ x day(-1)). During the dry season, the mean DEE of M. murinus that utilised daily torpor was 103.4 +/- 32.7 kJ x day(-1) which is not significantly different from the mean DEE of animals remaining normothermic. We found that the DEE of mouse lemurs using daily torpor was significantly correlated with the mean temperature difference between Tsk and Ta (r2 = 0.37) and with torpor bout length (r2 = 0.46), while none of these factors explained significant amounts of variation in the DEE of the mouse lemurs remaining normothermic. The mean water flux rate of mouse lemurs using daily torpor (13.0 +/- 4.1 ml x day(-1)) was significantly lower than that of mouse lemurs remaining normothermic (19.4 +/- 3.8 ml x day(-1)), suggesting the lemurs conserve water by entering torpor. Thus, this first study on the energy budget of free-ranging M. murinus demonstrates that torpor may not only reflect its impact on the daily energy demands, but involve wider adaptive implications such as water requirements.

The transcriptome of Arabidopsis thaliana during systemic acquired resistance

Infected plants undergo transcriptional reprogramming during initiation of both local defence and systemic acquired resistance (SAR). We monitored gene-expression changes in Arabidopsis thaliana under 14 different SAR-inducing or SAR-repressing conditions using a DNA microarray representing approximately 25-30% of all A. thaliana genes. We derived groups of genes with common regulation patterns, or regulons. The regulon containing PR-1, a reliable marker gene for SAR in A. thaliana, contains known PR genes and novel genes likely to function during SAR and disease resistance. We identified a common promoter element in genes of this regulon that binds members of a plant-specific transcription factor family. Our results extend expression profiling to definition of regulatory networks and gene discovery in plants.

The effects of atrazine on female wistar rats: an evaluation of the protocol for assessing pubertal development and thyroid function

The effects of atrazine (ATR), a chlorotriazine herbicide, on the onset of puberty were evaluated in Wistar rats. Female rats were dosed by oral gavage from postnatal day(s) (PND) 22 through PND 41 with 0, 12.5, 25, 50, 100, or 200 mg ATR/kg. Vaginal opening (VO) was significantly delayed 3.4, 4.5, or greater than 6.8 days by 50, 100, and 200 mg/kg, respectively. VO had not occurred in 4 of 15 females in the 200 mg/kg group by the time of necropsies (PND 41). Body weight (bw) at necropsy was reduced in the 200 mg/kg group by 11.6%, but was not different from the control (0) in the 50 and 100 mg/kg groups. To examine the influence of reduced bw on pubertal development, a group of pair-fed controls was included whose daily food intake was dependent upon the amount consumed by their counterpart in the 200 mg/kg group. Although necropsy bw was reduced to the same extent as the ATR females, VO in the pair-fed controls was not significantly delayed. Adrenal, kidney, pituitary, ovary, and uterine weights were reduced by 200 mg/kg ATR. Serum T(3), T(4), and TSH were unaltered by ATR, which was consistent with no histopathologic/morphologic changes in the thyroid. Estrous cyclicity was monitored in a second group of females from VO to PND 149. The number of females displaying regular 4- or 5-day estrous cycles during the first 15-day interval after VO was lower in the 100 and 200 mg/kg ATR and pair-fed controls. Irregular cycles were characterized by extended periods of diestrus. By the end of the second 15-day interval (PND 57-71), no effects on estrous cyclicity were observed. These data show that ATR can delay the onset of puberty and alter estrous cyclicity in the female Wistar rat ( NOAEL of 25 mg/kg). Reduced food consumption and bw did not account for the delay in VO, because this effect was not observed in the pair-fed controls. In addition, the effect on estrous cyclicity was observed in the 100 mg/kg ATR group where no significant reduction in bw was observed.

Absorption, metabolism, and excretion of intravenously and orally administered [14C]telmisartan in healthy volunteers

The study was conducted in healthy male volunteers to evaluate the absorption, metabolic pattern, and mode of elimination of telmisartan, a nonpeptide angiotensin II receptor antagonist. [14C]telmisartan was administered orally in solution as a single 40 mg dose to 5 subjects. A further 5 subjects received short-term intravenous infusion of [14C]telmisartan 40 mg. Measurement of total 14C radioactivity in plasma showed that about 50% was absorbed following oral administration, with maximum plasma concentration observed after 0.5 to 1 hour. Absolute bioavailability was 43%. On average, 84% of total radioactivity in plasma reflected the parent compound. The remainder of total radioactivity could be ascribed to the glucuronide conjugate of telmisartan, which represented the only metabolite in man. About 99.5% of telmisartan was bound to plasma protein, mainly to albumin and alpha-1-acid glycoprotein. Telmisartan was reversibly distributed into erythrocytes. More than 90% of administered dose was excreted within 120 hours, and the excretion balance was complete 144 hours after dosing. Radioactivity was almost exclusively (> 98%) excreted via the feces; urinary excretion accounted for < 1% of the dose, irrespective of the route of administration. In the small fraction excreted into urine, the glucuronide conjugate of telmisartan was predominant. Although some telmisartan glucuronide was detected in plasma, only unchanged drug was identified in the feces. No changes in vital signs, electrocardiogram, or clinical laboratory tests were detected following telmisartan administration, and adverse events, predominantly unrelated to treatment and of mild intensity, were infrequent. One subject fainted and, on another occasion, reported faintness; these events were probably due to the antihypertensive action of the intravenous study medication.

Liquid chromatographic-tandem mass spectrometric method for the analysis of a neurokinin-1 antagonist and its metabolite using automated solid-phase sample preparation and automated data handling and reporting

Pharmacokinetic studies play a vital role during the development of new pharmaceutical substances. Data presented demonstrate an accurate, precise and robust assay for a neurokinin-1 receptor antagonist and its metabolite with HPLC-MS-MS. Sample preparation is performed by solid-phase extraction (SPE) in the 96-well plate format. This process is fully automated with a Tecan Genesis pipetting system using its standard robotic manipulator arm (ROMA). All instruments are fully integrated in a study oriented laboratory information system (LIMS) with an Oracle database that communicates bi-directional with the analytical equipment. Finally, the results are reported by push button operation.

Effects of insulin and LongR(3) on serum-free Chinese hamster ovary cell cultures expressing two recombinant proteins

Insulin is the most commonly used growth factor for sustaining cell growth and viability in serum-free Chinese hamster ovary (CHO) cell cultures. In the present study insulin and IGF-1 analogue (LongR(3)) were compared for their ability to support growth, viability, and production of two serum-free CHO cell lines expressing recombinant protein. The first cell line, VA12, expresses protein B, and the second cell line, CL23, expresses protein C. Both molecules are recombinant cytokine receptors. VA12 will grow in serum-free media lacking growth factor, while CL23 requires either insulin or LongR(3) for cell growth. Both cell lines, however, require a growth factor for optimal performance under production conditions. In this study, LongR(3) was better able to sustain the viability of both cell lines under production conditions than insulin. These data indicate that while insulin and LongR(3) can both serve as growth and viability factors for CHO cells, LongR(3) is the preferred growth factor for cell lines VA12 and CL23.

The validity of telepathological frozen section diagnosis with ISDN-mediated remote microscopy

We investigated 109 randomly selected frozen section specimens from lung surgery patients in a retrospective blind mode using telepathology equipment. The telepathology system applied (HISTKOM) used one ISDN B-channel and telemicroscopy with a remotely operated robotic microscope. The performance of telepathological frozen section diagnosis was compared with that of conventional frozen section diagnosis. The false-positive rate achieved was identical for both methods. The sensitivity (P=0.03), but not the specificity, was significantly lower for the telepathological method. The time needed to establish a diagnosis with the remote microscope was too high; therefore, upgrading to multichannel technology is recommended. The quality of the images transmitted was judged to be sufficient by the pathologists involved in the study. In conclusion, with further technical improvements in telemicroscopy and additional experience in telepathology, remote diagnosis seems to be feasible.

Absence of odd-even parity behavior for Kondo resonances in quantum dots

Zero-bias anomalies in the conductance through quantum dots have recently been identified as Kondo resonances and explained in terms of the Anderson impurity model. The effect requires a degeneracy and it has been proposed that this should occur for odd electron numbers on the dot. In this paper we present data, obtained on a split-gate quantum dot with a small number of electrons, which are in disagreement with this expectation. The mapping of the Anderson model on the quantum dot is discussed in terms of an interacting N electron system demonstrating why this expectation can fail.

[Lassa fever]

A 22-year-old female German student was admitted with fever of unknown origin for 5 days to the hospital of her hometown immediately after returning from a 7-week journey under simple conditions through 4 West African countries. After exclusion of malaria and typhoid and nonrespondence to antibiosis, she was transferred on the 4th day to the Department of Tropical Medicine in Würzburg. After the clinical assumption of Lassa fever, the virus was confirmed by PCR within 3 hours (Bernhard Nocht Institute, Hamburg) on the 10th day of her illness. The assumption was based on travel history, continuous fever, cough, pharyngitis, thoracic pain, and exclusion of other acute infections. From the beginning, the patient was cared for with barrier nursing and after diagnosis under strict isolation in an intensive care unit reserved for her alone by a team of doctors and nurses specialized in tropical medicine and intensive care. The staff was protected through isolation suits with filters. Monitoring and therapy entailed all methods of intensive care and intravenous administration of ribavirin 16 mg/kg body weight = 900 mg every 6 hours. The patient died on the 14th day of her illness in a volume deficiency shock due to uncontrollable heavy hemorrhage from all organs including the skin, a so-called "leakage syndrome".

CONCLUSION

Conclusions are drawn regarding training in tropical medicine, diagnostics of highly contagious infections, intensive care of patients affected with them under isolation, contact tracing, psychological crisis intervention for personnel, media information, care of the infectious corpse and disposal of infectious waste.

The biosynthetic gene cluster for the microtubule-stabilizing agents epothilones A and B from Sorangium cellulosum So ce90

BACKGROUND

Epothilones are produced by the myxobacterium Sorangium cellulosum So ce90, and, like paclitaxel (Taxol((R))), they inhibit microtubule depolymerisation and arrest the cell cycle at the G2-M phase. They are effective against P-glycoprotein-expressing multiple-drug-resistant tumor cell lines and are more water soluble than paclitaxel. The total synthesis of epothilones has been achieved, but has not provided an economically viable alternative to fermentation. We set out to clone, sequence and analyze the gene cluster responsible for the biosynthesis of the epothilones in S. cellulosum So ce90.

RESULTS

A cluster of 22 open reading frames spanning 68,750 base pairs of the S. cellulosum So ce90 genome has been sequenced and found to encode nine modules of a polyketide synthase (PKS), one module of a nonribosomal peptide synthetase (NRPS), a cytochrome P450, and two putative antibiotic transport proteins. Disruptions in the genes encoding the PKS abolished epothilone production. The first PKS module and the NRPS module are proposed to co-operate in forming the thiazole heterocycle of epothilone from an acetate and a cysteine by condensation, cyclodehydration and subsequent dehydrogenation. The remaining eight PKS modules are responsible for the elaboration of the rest of the epothilone carbon skeleton.

CONCLUSIONS

The overall architecture of the gene cluster responsible for epothilone biosynthesis has been determined. The availability of the cluster should facilitate the generation of designer epothilones by combinatorial biosynthesis approaches, and the heterologous expression of epothilones in surrogate microbial hosts.

Metabolism and temperature regulation during daily torpor in the smallest primate, the pygmy mouse lemur (Microcebus myoxinus) in Madagascar

Thermoregulation, energetics and patterns of torpor in the pygmy mouse lemur, Microcebus myoxinus, were investigated under natural conditions of photoperiod and temperature in the Kirindy/CFPF Forest in western Madagascar. M. myoxinus entered torpor spontaneously during the cool dry season. Torpor only occurred on a daily basis and torpor bout duration was on average 9.6 h, and ranged from 4.6 h to 19.2 h. Metabolic rates during torpor were reduced to about 86% of the normothermic value. Minimum body temperature during daily torpor was 6.8 degrees C at an ambient temperature of 6.3 degrees C. Entry into torpor occurred randomly between 2000 and 0620 hours, whereas arousals from torpor were clustered around 1300 hours within a narrow time window of less than 4 h. Arousal from torpor was a two-step process with a first passive climb of body temperature to a mean of 27 degrees C, carried by the daily increase of ambient temperature when oxygen consumption remained more or less constant, followed by a second active increase of oxygen consumption to further raise the body temperature to normothermic values. In conclusion, daily body temperature rhythms in M. myoxinus further reduce the energetic costs of daily torpor seen in other species: they extend to unusually low body temperatures and consequently low metabolic rates in torpor, and they employ passive warming to reduce the energetic costs of arousal. Thus, these energy-conserving adaptations may represent an important energetic aid to the pygmy mouse lemur and help to promote their individual fitness.

A simple method for extraction of fungal genomic DNA

We have developed a new, simple and effective method for extraction of fungal genomic DNA. The initial steps involved suspension of freeze-dried mycelium in buffer containing sodium dodecyl sulphate, detachment of DNA from polysaccharides by mild shearing, NaCl precipitation of polysaccharides and protein, chloroform extraction and ethanol precipitation. The ethanol precipitate was then subjected to a second round of mild shearing, NaCl precipitation, chloroform extraction and ethanol precipitation. The procedure required approximately 1 h to perform. The method yielded 8-32 microg of high molecular weight DNA per 30 mg of freeze-dried mycelium when tested on six fungal species: Aspergillus niger, A. flavus, Fusarium graminarum, Neotyphodium lolii, Penicillium citrinum and Rhizopus nigricanes. The DNA was digestible with EcoRI, HindIII, SalI and BamHI. For the slow-growing N. lolii, a modification of the method was developed that removed the agar residue from colonies grown on agar plates by centrifugation at 13 000 rev min(-1) in the presence of CsCl. The modified method yielded 1.5-2 microg of high molecular weight DNA per colony.

[Experiences in the diagnosis and therapy of so-called thrombus in transit]

With the increasing use of cross-sectional echocardiography in patients with overt or suspected pulmonary thromboembolism in the emergency rooms, more and more right atrial thrombi are detected. These are so-called "transitthrombi" from the venous system on their way to the pulmonary arteries and they are a severe presentation of thromboembolic disease. They appear as an imminent pulmonary embolism and usually coexists with an already massive embolism. In patients were a right atrial thrombus is associated with a patent foramen ovale, paradoxical arterial embolism has been observed. Right sided heart thrombi have a high mortality rate and need immediate treatment. In our hospital we have seen 14 patients with right atrial thrombi and pulmonary embolism in a period of 6 years. Three patients had cardiac arrest with a massive pulmonary embolism, seven patients presented with a submassive embolism. All patients were treated immediately after echocardiographic diagnosis without pulmonary angiography. In about half of the cases transesophageal echocardiography was done additionally for diagnosis and monitoring. Therapeutic options were thrombectomy, fibrinolysis or anticoagulants. We treated one of our patients with thrombectomy, eleven patients with fibrinolysis and two patients with anticoagulants.

[Reduction of spastic increased muscle tone in multiple sclerosis by the nonopioid analgesic flupirtine]

OBJECTIVES

A reduction of muscle tone in rats can be found after intraperitoneal or intrathecal injection of flupirtine in analgetic doses. However, a muscle-relaxing effect in patients with spasticity has not yet been shown. In this study we investigated whether flupirtine can reduce the increased muscle tone in patients with spasticity.

METHODS

The muscle-relaxing effect of flupirtine was compared to that of tetrazepam and of placebo in a randomised, double-blind, cross-over design. Altogether 9 patients with spastically increased muscle tone of the lower limbs were investigated. The EMG activity integral of the rectus femoris muscle was chosen as quantitative parameter for degree and change of muscle tone. The EMG activity integral was measured using a dynamic bicycle ergometer 60, 120 and 180 min after administration of the tested drugs. The degree of spasticity was measured as the quotient of the EMG activity integral of the active and passive rotation phase. This quotient is inversely proportional to the spastic muscle activity.

RESULTS

With flupirtine a significant increase in the EMG activity integral was found after 60 min (maximum effect). From 120 min it showed a slow decline. With tetrazepam the maximal effect was reached after 180 min. Placebo did not change the EMG activity integral during the experiment.

CONCLUSION

These results support the thesis that flupirtine has a muscle-relaxing effect in patients with pathologically increased muscle tone.

Activation of human cytochrome P-450 3A4-catalyzed meloxicam 5'-methylhydroxylation by quinidine and hydroquinidine in vitro

In humans, meloxicam is metabolized mainly by cytochrome P-450 (CYP)-dependent hydroxylation of the 5'-methyl group. The predominant P-450 enzyme involved in meloxicam metabolism is CYP 2C9, with a minor contribution of CYP 3A4. Quinidine, a CYP 3A4 substrate commonly used as a selective in vitro inhibitor of CYP 2D6, was found to markedly increase the rate of meloxicam hydroxylation during in vitro experiments with human liver microsomes. A similar activation was observed with other compounds that are structurally related to quinidine. Besides quinidine, quinine and hydroquinidine were the most potent activators of meloxicam hydroxylation. Using expressed cytochrome P-450 enzymes and selective chemical inhibitors of CYP 2C9 and CYP 3A4, it was found that quinidine markedly increased the rate of CYP 3A4-mediated meloxicam hydroxylation but was virtually without effect on CYP 2C9. Kinetic analysis was performed to obtain insight into the possible mechanism of activation of CYP 3A4 and into the mutual interaction of quinidine/hydroquinidine and meloxicam. Quinidine and hydroquinidine decreased Km and increased Vmax of meloxicam hydroxylation, which was consistent with a mixed-type nonessential activation. Meloxicam, in turn, decreased both Km and Vmax of quinidine metabolism by CYP 3A4, indicating an uncompetitive inhibition mechanism. These results support the assumption that CYP 3A4 possesses at least two different substrate-binding sites. A clinically relevant effect on meloxicam drug therapy is not expected, because the most likely outcome in practice is moderately decreased meloxicam plasma concentrations.

A unique reaction in a common pathway: mechanism and function of chorismate synthase in the shikimate pathway

Chorismate synthase, the seventh enzyme in the shikimate pathway, catalyzes the transformation of 5-enolpyruvylshikimate 3-phosphate to chorismate which is the last common precursor in the biosynthesis of numerous aromatic compounds in bacteria, fungi and plants. The enzyme has an absolute requirement for reduced FMN as a cofactor, although the 1,4-anti elimination of phosphate and the C(6proR)-hydrogen does not involve a net redox change. The role of the reduced FMN in catalysis has long been elusive. However, recent detailed kinetic and bioorganic approaches have fundamentally advanced our understanding of the mechanism of action, suggesting an initial electron transfer from tightly bound reduced flavin to the substrate, a process which results in C-O bond cleavage. Studies on chorismate synthases from bacteria, fungi and plants revealed that in these organisms the reduced FMN cofactor is made available in different ways to chorismate synthase: chorismate synthases in fungi--in contrast to those in bacteria and plants--carry a second enzymatic activity which enables them to reduce FMN at the expense of NADPH. Yet, as shown by the analysis of the corresponding genes, all chorismate synthases are derived from a common ancestor. However, several issues revolving around the origin of reduced FMN, as well as the possible regulation of the enzyme activity by means of the availability of reduced FMN, remain poorly understood. This review summarizes recent developments in the biochemical and genetic arena and identifies future aims in this field.

AhR, ARNT, and CYP1A1 mRNA quantitation in cultured human embryonic palates exposed to TCDD and comparison with mouse palate in vivo and in culture

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is developmentally toxic in many species and induces cleft palate in the C57BL/6N mouse embryo. Palatogenesis in mouse and human embryos involves homologous processes at the morphological, cellular, and molecular levels. In organ culture, mouse and human palates respond similarly to TCDD. The present study quantitates the expression of AhR, ARNT, and CYP1A1 mRNA in human embryonic palates in organ culture. Palatal tissues were exposed to 1 x 10(-10), 1 x 10(-9), or 1 x 10(-8) M TCDD or control medium and sampled at 0, 2, 4, and 6 hours for quantitative RT-PCR using a synthetic RNA internal standard. Similar measurements of CYP1A1 gene expression were collected for mouse palates cultured in this model. In human palates, AhR expression correlated with ARNT and CYP1A1 mRNA expression. TCDD induction of CYP1A1 was time- and concentration-dependent. The expression of these genes presented a uniform and continuous distribution across the group of embryos, with no subset of either high or low expressors/responders. The ratio of AhR to ARNT was approximately 4:1. AhR mRNA increased during the culture period in both treated and control subjects; however, ARNT expression was relatively constant. TCDD did not alter either AhR or ARNT expression in a consistent dose- or time-related manner. Comparison of human and mouse data showed a high correlation across species for the induction of CYP1A1. Human embryos expressed approximately 350 times less AhR mRNA than the mouse, and in earlier studies it was shown that human palates required 200 times more TCDD to produce the same effects. When the morphological, cellular, and molecular responses to TCDD between mouse and human are compared, it seems highly unlikely that human embryos could be exposed to sufficient TCDD to achieve changes in palatal differentiation that would lead to cleft palate.

Metabolites of the angiotensin II antagonist tasosartan: the importance of a second acidic group

Described in this paper is the synthesis and pharmacological activity of five metabolites of the angiotensin II antagonist tasosartan (1). Of particular interest is the effect of the additional acidic group of the enol metabolite (8) on activity. As suggested by the structural-activity relationship of other angiotensin II antagonist series, a second acidic group can improve receptor binding activity but decrease in vivo activity after oral dosing. The metabolic introduction of a second acidic group in tasosartan bypasses this problem and contributes to the excellent profile of the compound. A molecular modeling study provides a rationale for the role of the enol group of 8 in AT1 receptor binding.