Direct inhibition of cyclooxygenase-1 and -2 by the kinase inhibitors SB 203580 and PD 98059. SB 203580 also inhibits thromboxane synthase

The kinase inhibitors SB 203580 and PD 98059 have been reported to be specific inhibitors of the 38- and 42/44-kDa mitogen-activated protein kinase (MAPK) pathways, respectively. In this study, the two inhibitors were found to decrease platelet aggregation induced by low concentrations of arachidonic acid, suggesting that they also interfere with the metabolism of arachidonic acid to thromboxane A2. In support of this, SB 203580 and PD 98059 inhibited the conversion of exogenous [3H]arachidonic acid to [3H]thromboxane in intact platelets. Measurement of platelet cyclooxygenase-1 activity following immunoprecipitation revealed that SB 203580 and PD 98059 are direct inhibitors of this enzyme. Both compounds were shown to inhibit purified cyclooxygenase-1 and -2 by a reversible mechanism. In addition, SB 203580 (but not PD 98059) inhibited platelet aggregation induced by prostaglandin H2 and the conversion of prostaglandin H2 to thromboxane A2 in intact platelets. SB 203580 also inhibited this pathway in platelet microsome preparations, suggesting a direct inhibitory effect on thromboxane synthase. These results demonstrate that direct effects of the two kinase inhibitors on active arachidonic acid metabolites have to be excluded before using these compounds for the investigation of MAPKs in signal transduction pathways. This is of particular relevance to studies on the regulation of cytosolic phospholipase A2 as these two MAPKs are capable of phosphorylating cytosolic phospholipase A2, thereby increasing its intrinsic activity.     

The antitumour activity of the prodrug N-L-leucyl-doxorubicin and its parent compound doxorubicin in human tumour xenografts

The antitumour activity of the investigational agent N-L-leucyl-doxorubicin (Leu-DOX) was compared with that of doxorubicin (DOX) in human tumour xenografts growing subcutaneously in athymic nude mice. Leu-DOX was developed as a prodrug of DOX, and may be converted into the clinically active parent compound by hydrolytic enzymes present in or on tumour cells. It has been suggested that a better therapeutic index with a reduced cardiac toxicity and higher efficacy might be obtained. Both compounds were administered intravenously weekly for 2 weeks, each at maximum tolerated doses of 8 mg/kg and 28 mg/kg for DOX and Leu-DOX, respectively. The panel of xenografts represented three different tumour types. Leu-DOX showed antitumour activity, defined as tumour growth inhibition > 50% and specific growth delay > 1.0, in 10 of the 16 tumours, including two of five breast, five of seven small cell and three of four non-small cell lung carcinomas. In comparison, DOX was active in one breast, four small cell lung and two lung adenocarcinoma xenografts. In all the DOX sensitive lung tumours, Leu-DOX showed higher efficacy than the parent compound. Based on the results of the present study, and since phase I clinical trials with Leu-DOX have already been performed, phase II clinical evaluation of Leu-DOX in patients with breast and lung cancer is recommended.     

Efficient random subcloning of DNA sheared in a recirculating point-sink flow system

Based on a high-performance liquid chromatographic pump, we have built a device that allows recirculation of DNA through a 63-microm orifice with ensuing fractionation to a minimum fragment size of approximately 300 base pairs. Residence time of the DNA fragments in the converging flow created by a sudden contraction was found to be sufficiently long to allow extension of the DNA molecules into a highly extended conformation and, hence, breakage to occur at midpoint. In most instances, 30 passages sufficed to obtain a narrow size distribution, with >90% of the fragments lying within a 2-fold size distribution. The shear rate required to achieve breakage was found to be inversely proportional to the 1.0 power of the molecular weight. Compared with a restriction digest, up to 40% of all fragments could be cloned directly, with only marginal improvements in cloning efficiency having been observed upon prior end repair with Klenow, T4 polymerase or T4 polynucleotide kinase. Sequencing revealed a fairly random distribution of the fragments.     

Initial processing of human proenkephalin in bovine chromaffin cells

The opioid peptide precursor preproenkephalin (PPE) contains seven enkephalin sequences and is synthesized by epinephrine-producing adrenal chromaffin cells and various peripheral and central neurons. After removal of its signal peptide, PPE undergoes processing at dibasic amino acid sites to yield its final opioid products-Met-enkephalin, Leu-enkephalin, and various larger, enkephalin-containing peptides. Processing of PPE was examined in bovine chromaffin cells using a plasmid containing the human PPE (hPPE) cDNA under the control of the cytomegalovirus immediate early enhancer/promoter. Following transfection of this hPPE-containing plasmid into bovine chromaffin cells, several proenkephalin-immunoreactive bands were observed on western blots with monoclonal antibodies that recognize human, but not bovine, proenkephalin sequences. The pattern of hPPE-derived peptides observed was similar to that of bovine PPE processing products. A series of recombinant plasmids containing mutations in the hPPE sequence at putative processing sites was then constructed. Conversion of Lys-Lys and Lys-Arg sequences to Lys-Gln and of Arg-Arg to Arg-Gln altered initial hPPE processing at only three of the putative processing sites. When hPPE cDNA containing mutations at all of these initially processed sites was expressed, one or more alternative processing sites were revealed. These data suggest the importance of structural features in addition to the dibasic sequences that limit the processing of proenkephalin.     

A high-resolution map of genes, microsatellite markers, and new dinucleotide repeats from UBE1 to the GATA locus in the region Xp11.23

Several new genes and markers have recently been identified on the proximal short arm of the human X chromosome in the area of Xp11.23. We had previously generated a YAC contig in this region extending from UBE1 to the OATL1 locus. In this report two polymorphic dinucleotide repeats, DXS6949 and DXS6950, were isolated and characterized from the OATL1 locus. A panel of YAC deletion derivatives from the distal portion of the contig was used in conjunction with the rest of the YAC map to position the new microsatellites and order other markers localizing to this interval. The marker order was determined to be DXS1367-ZNF81-DXS6849-ZNF21-DXS6616-DXS 6950-DXS6949. In the proximal region below OATL1, we have isolated a pair of YACs from the GATA locus, B1026 and C01160. Mapping within these YACs indicates the orientation of DXS1126 and DXS1240, while a cosmid near the OATL1 region reveals the overlap between the YAC contigs from the two loci. This cosmid contains the gene responsible for Wiskott-Aldrich syndrome (WAS) and localizes the disease gene between OATL1 and GATA. These data enable the expansion of the present physical map of the X chromosome from UBE1 to the GATA locus, covering a large portion of the Xp11.23 region. Genetic cross-overs in Xp11.23 support the marker orientation and the position of WAS, contrary to previous reports. With the integration of both physical and genetic maps we have predicted the following marker order: Xpter-UBE1-SYN1/ARAF1/ TIMP1-DXS1367-ZNF81-DXS.6849-ZNF21-DXSy6616++ +-(OATL1, DXS6950-DXS6949)- WAS-(GATA, DXS1126)-DXS1240-Xcen.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of various lipid-bile salt mixed micelles on the intestinal absorption of amphotericin-B in rat

We investigated the effect of the somatosensory functions to the outcomes of motor functions in 28 patients with thalamic hemorrhage. The disturbance of the pyramidal tracts was assessed by the destruction of the internal capsule found in computed tomography (CT). The disturbance of the somatosensory function was analyzed by the N20 component of short-latency somatosensory evoked potentials (SSEP). The outcomes of motor function was evaluated after 3 months of ictus. Correlations between the outcomes of motor function, disturbance of the pyramidal tract, and disturbance of the somatosensory function were discussed. The result indicated that functional outcomes statistically correlated with neither disturbance of the internal capsule alone nor disturbance of N20 alone. But, there was statistically significant between functional outcomes and the combination of disturbance of the internal capsule with disturbance of N20 (p < 0.05, Wilcoxon signed-rank). There was not statistical difference in hematoma volume or consciousness. The implications of these results suggest that somatosensory function may affect the recovery of motor functions.