Development, validation, and interlaboratory comparison of an HMG-CoA reductase inhibition assay for quantitation of atorvastatin in plasma matrices

An HMG-CoA reductase inhibition assay was developed and validated for quantitation of atorvastatin in human, dog, rat, and mouse plasma. Atorvastatin was isolated from plasma by protein precipitation. Rat-liver microsomes were used to provide the reductase enzyme. The method was validated by assaying calibration standards and quality controls in triplicate on each of the 3 days. A customized computer program was used for data calculation. Quantitation of the assay ranged from 0.36 to 16 ng/ml of atorvastatin in different plasma matrices. Assay precision and accuracy, based on the coefficient of variation and percent relative error, respectively, of quality controls were 10.4% to 14.5% and within +/- 6.25% in human; 4.89% to 10.6% (+/- 8.13%) in dog; 2.68% to 8.62% (+/- 5.00%) in rat; and 3.68% to 8.96% (+/- 5.38%) in mouse plasma. The method has been applied to pharmacokinetic studies of atorvastatin in human and toxicokinetic studies in dog, rat, and mouse after atorvastatin administration. Atorvastatin equivalent concentrations in a set of plasma samples from subjects receiving single and multiple doses of atorvastatin were determined by validated HMG-CoA reductase inhibition assays at four different laboratories. Results were compared using linear regression and concordance correlation statistical procedures. Good agreements among these data indicated that results from different laboratories with the same validated method can be used interchangeably.

A prospective study of bone mineral density change in Taiwan

In 1989, a cross-sectional study was carried out in Lin-Kou Township, Taiwan, to determine the distribution of bone mineral density (BMD) in the lumbar spine of Chinese people. Lumbar spine BMD was measured using dual-photon absorptiometry in 404 healthy volunteers (266 women and 138 men, aged 15 to 83 years). In 1994-1995, 318 of the same volunteers were reexamined for the present study. Except for there being fewer males and smokers present, there were no significant differences between the second survey respondents and nonrespondents. Spine BMD decreased at over 1% per year in Chinese women over age 50, which was somewhat higher than reported for caucasian women. Since there was a loss of BMD in Chinese women after their 20s, a case can be made for starting preventive activities for female adolescents. There were no differences in the mean BMD change rates among the different age groups of Chinese men. Baseline BMD, menopause, and weight change were associated with the lumbar spine BMD change rates in Chinese women. Body mass index was the only variable significantly associated with BMD change in Chinese men. The rate of BMD change was not associated with diet.

Stimulation of endothelial cell production of vasoconstrictive substances by hypertensive sera

The endothelial cell regulates vessel tone by elaborating a number of vasoactive substances such as thromboxane and endothelin, both of which are highly vaosconstrictive, and prostacyclin and nitric oxide, both of which are vasodilatory. The current study examines the postulate that one of the mechanisms responsible for the increased vessel tone found in hypertension is the presence of substances in the sera of patients with this disorder that stimulates selectively the endothelial cell production of thromboxane and endothelin. Sera from ten patients with mild hypertension and from 11 age-matched controls were incubated with human umbilical arterial endothelial cells and the concentrations of endothelin, thromboxane, prostacyclin, and nitric oxide produced by the cells was measured in the supernatant. The results of the assays showed that the amounts of thromboxane and endothelin produced by endothelial cells in response to stimulation by hypertensive sera were significantly higher than the amounts produced in response to control sera; in comparison, the amounts of prostacyclin and nitric oxide produced by the cells in response to either hypertensive sera or control sera were not significantly different. The findings suggest that a mechanism that may be responsible for the increased vascular tone found in hypertension is the presence of substances in hypertensive sera that stimulate endothelial cells selectively to produce increased amounts of the vasoconstrictive hormones, endothelin and thromboxane.

Effects of N-methyl berbamine on delayed outward potassium current in isolated rat hepatocytes

AIM

To study the effects of N-methyl berbamine (NMB) on the delayed outward potassium currents (Ik) in isolated rat hepatocytes.

METHODS

With patch-clamp techniques and whole-cell recording method, holding potential -50 mV, command potential +30 to +140 mV, duration 900 ms.

RESULTS

NMB reduced Ik in a concentration-dependent manner. When the concentrations of NMB were 20, 50, 400 nmol.L-1 and 50 mumol.L-1, the amplitude values of Ik were decreased to 3.6 +/- 0.4 (P > 0.05), 2.1 +/- 1.6 (P > 0.05), 3.7 +/- 1.6 (P < 0.05), 2.3 +/- 1.3 nA (P < 0.01) from 4.4 +/- 1.0 (n = 4), 2.5 +/- 1.8 (n = 4), 5.8 +/- 2.1 (n = 5), 4.6 +/- 1.3 (n = 6) nA of control, respectively. The inhibitory rates were 10%, 15%, 37%, and 51%, respectively.

CONCLUSION

NMB was a K+ channel inhibitor.

The human papillomavirus-16 E6 oncoprotein decreases the vigilance of mitotic checkpoints

The E6 and E7 proteins of the high risk human papillomaviruses (HPVs) are consistently expressed in HPV-positive cervical carcinomas. We investigated the ability of HPV-16 E6 and E7 to disrupt mitotic checkpoints in normal diploid human cells. Acute expression of HPV-16 E6, but not HPV-16 E7, decreased the fidelity of multiple checkpoints controlling entry into and exit from mitosis. After irradiation, nearly 50% of cells containing HPV-16 E6 readily entered mitosis as opposed to less than 10% of control cells. Consistent with this, asynchronous populations of cells expressing HPV-16 E6 had increased cdc2-associated histone H1 kinase activity relative to control populations. In addition, HPV-16 E6 increased sensitivity to chemically-induced S-phase premature mitosis and decreased mitotic spindle assembly checkpoint function relative to control populations. HPV-16 E6 mutants with a reduced ability to target p53 for degradation were unable to abrogate mitotic checkpoints, suggesting a possible mechanism by which HPV-16 E6 disrupts mitotic checkpoints. Expression of a mutant p53 gene yielded an intermediate phenotype relative to HPV-16 E6, generating moderate increases in sensitivity to chemically-induced S-phase PCC and mitotic spindle disruption and a heightened propensity to enter mitosis after irradiation.

Genetic interactions of conserved regions in the DEAD-box protein Prp28p

The yeast PRP28 g ene has been implicated in nuclear precursor messenger RNA (pre-mRNA) splicing, a two-step reaction involved in a multitude of RNA structural alterations. Prp28p, the gene product of PRP28 , is a member of the evolutionarily conserved DEAD-box proteins (DBPs). Members of DBPs are involved in a variety of RNA-related biochemical processes, presumably by their putative RNA helicase activities. Prp28p has been speculated to play a role in melting the duplex between U4 and U6 small nuclear RNAs (snRNAs), leading to the formation of an active spliceosome. To study the function of Prp28p and its interactions with other components of the splicing machinery, we have isolated and characterized a large number of prp28 conditional mutants. Strikingly, many of these prp28 mutations are localized in the highly conserved motifs found in all the DBPs. Intragenic reversion analysis suggests that regions of motifs II, III and V, as well as of motifs I and IV, in Prp28p are likely to be in close proximity to each other. Our results thus provide the first hint of the local structural arrangement for Prp28p, and perhaps for other DBPs as well.

Radiologic placement of subcutaneous infusion chest ports for long-term central venous access

OBJECTIVE

The technical success and complications associated with radiologic placement of subcutaneous implantable chest ports for long-term central venous access were evaluated.

MATERIALS AND METHODS

Between May 1, 1996, and December 31, 1996, 80 chest ports were placed in 80 consecutive patients using the right internal jugular vein as the preferred access route. All procedures occurred in interventional radiology suites with patients receiving conscious sedation. Both sonography and fluoroscopy were used for venipuncture and to guide port insertion. Follow-up was obtained by the clinical service and by performing chart reviews electronically.

RESULTS

Technical success was 100%, and follow-up was obtained in all patients. One procedural complication occurred that was unrelated to actual catheter placement. Mean catheter use was 155 days (total, 12,168 days; range, 18-303 days). Confirmed catheter-related infection rate was 3%, or 0.016 per 100 access days; symptomatic catheter-related central venous thrombosis rate was 1%, or 0.008 per 100 access days; and 5% of catheters were removed prematurely. No instances of hematoma formation, catheter tip migration or malposition, symptomatic air embolism, spontaneous catheter fracture, or pneumothorax were found.

CONCLUSION

With the benefit of both sonographic and fluoroscopic guidance, subcutaneous implantable chest ports can be inserted by radiologists with equal or lower complication rates than those reported in surgical series. Image-guided insertion of chest ports should replace rather than supplement unguided placement.

Purification and characterization of a 94 KD high molecular weight allergen from house dust mite, Dermatophagoides pteronyssinus

House dust mite allergens from Dermatophagoides pteronyssinus is an important cause of severe allergic asthma and rhinitis in many countries. Although several low to medium molecular weight allergens had been well characterized, limited studies on the high molecular weight IgE-binding components were reported. In this study, a 94 kD high molecular weight allergen from crude mite body extract of D. pteronyssinus was purified and characterized. Monoclonal antibody (mAb) affinity chromatography and high performance liquid chromatography were used to purify 94 kD allergen. Its antigenicity and allergenicity were confirmed by in vitro and in vivo studies. Two mAbs 2205-3.45 and 2220-7.25 specific to 94 kD high molecular weight component of D. pteronyssinus were generated. The epitopes recognized by these mAbs were species-specific. Enzyme-linked immunosorbent assay (ELISA) of IgE reactivity in the sera from 40 asthmatic children allergic to D. pteronyssinus showed that 37.5% of them had significantly higher optical density values (range 0.011 to 0.452) than normal (range 0.013 to 0.035). In in vivo skin test showed that 9 out of 20 (45%) asthmatic children were positive to 94 kD allergen. The results demonstrate that 94 kD high molecular weight component is an important allergen existing in house dust mite in Taiwan.

Wound fluids from saline solution- and Staphylococcus aureus peptidoglycan-inoculated sponges induce expression of matrix metalloproteinase 13 messenger ribonucleic acid by cultured rat fibroblasts

Polyvinyl alcohol sponges inoculated with Staphylococcus aureus peptidoglycan induce an accelerated wound healing response when implanted subcutaneously in rats. S. aureus peptidoglycan leads to a marked increase (50%) in reparative tissue collagen (as measured by hydroxyproline) by 4 days. However, this effect drops by 7 days and by 14 days; hydroxyproline levels are similar in sponges inoculated with S. aureus peptidoglycan or saline solution. These data suggest a very active early remodeling process in S. aureus peptidoglycan sponge reparative tissue. Consistent with this observation, we had found that steady-state levels of matrix metalloproteinase-13 mRNA were higher and persisted longer in S. aureus peptidoglycan sponge reparative tissue than in controls. We hypothesized that S. aureus peptidoglycan might induce a change in reparative tissue fibroblast phenotype or modify the character of the wound fluid. Fibroblasts obtained from saline solution- and S. aureus peptidoglycan-inoculated sponges 4 days after subcutaneous implantation and cultured in Eagle's minimal essential medium supplemented with 10% fetal calf serum were similar with respect to morphologic features, proliferation, and expression of pro alpha1 (I) and alpha1 (III) collagens and tissue inhibitor of metalloproteinase-1 mRNA by Northern blot analysis. Neither cell type expressed matrix metalloproteinase-13 mRNA. No changes in the above parameters were detected when such fibroblasts were cultured for 24 hours in the presence of 0.5 mg of S. aureus peptidoglycan per 10 ml of medium or with fluid obtained from control sponges cultured for 12 hours with phosphate-buffered saline solution. Wound fluids extracted with Eagle's minimal essential medium by homogenization of saline solution- and S. aureus peptidoglycan-inoculated sponges implanted subcutaneously for 12 hours did not affect the proliferation of the fibroblasts. However, the extracts had a profound effect on the cellular expression of tissue inhibitor of metalloproteinase-1, matrix metalloproteinase-13, and pro alpha1 (I) collagen mRNA. Specifically, expression of matrix metalloproteinase-13 mRNA was induced, expression of pro alpha1 (I) collagen mRNA was reduced by 70%, and expression of tissue inhibitor of metalloproteinase-1 mRNA was increased by 150%. These changes were the same irrespective of whether the wound fluid was obtained from saline solution- or S. aureus peptidoglycan-inoculated sponges. Fluid obtained from S. aureus peptidoglycan-inoculated sponges, which contain a greater inflammatory exudate than saline solution-inoculated sponges do, is enriched in matrix metalloproteinase-13 mRNA-inducing activity. The nature of the factor(s) that induces matrix metalloproteinase-13 mRNA expression is not known. However, preliminary data suggest that the matrix metalloproteinase-13-inducing factor(s) is heterogeneous with regard to size and is temperature sensitive and trypsin resistant.

Androstanediol and 5-androstenediol profiling for detecting exogenously administered dihydrotestosterone, epitestosterone, and dehydroepiandrosterone: potential use in gas chromatography isotope ratio mass spectrometry

The basis of a potential method for confirming intake of four natural androgens (testosterone, epitestosterone, dihydrotestosterone, and dehydroepiandrosterone is presented. The method relies on isolating from urine a steroid fraction containing androstenediol and androstanediol metabolites of these natural steroids and analyzing their 13C content by gas chromatography, combustion, isotope ratio mass spectrometry. The steroids were recovered from urine by conjugate hydrolysis with a Helix pomatia preparation (sulfatase and beta-glucuronidase), Girard T reagent separation to obtain a nonketonic fraction, and Sephadex LH-20 chromatography for purification. Metabolites appropriate for all of the natural steroids could be separated (as diacetates) by gas chromatography on a DB-17 capillary column viz.: 5 alpha (and beta)-androstane-3 alpha,17 alpha-diol (epitestosterone as precursor); 5 alpha (and beta)-androstane-3 alpha,17 beta-diol (testosterone as precursor); 5-androstene-3 beta,17 beta-diol (dehydroepiandrosterone precursor); and 5 alpha-androstane-3 alpha,17 beta- (and 17 alpha-) diol (dihydrotestosterone precursor). Measurement of the 13C content of the specific analytes after ingestion of the androgen precursors demonstrated a lowering of delta 13C/1000 value compared to normal values. Typically, in the male individual studied, delta 13C/1000 values for all components were -26 to -27 before drug administration and -29 to -30 at 6 h after, the latter values reflecting those obtaining for commercial synthetic steroid compared to in vivo synthesized steroid. While generally the metabolism of the steroids was as expected, this was not the case for 5 alpha-dihydrotestosterone. A major metabolite was 5 alpha-androstane-3 alpha,17 alpha-diol, which had presumably been formed by 17 beta/17 alpha isomerization, a process previously known for unnatural anabolics but not for natural hormones. The isolation, purification, and isotope ratio mass spectrometry techniques described may form the basis of a general method for confirming natural steroid misuse by sports participants.

The benefits of laparoscopic antireflux surgery for the treatment of gastroesophageal reflux disease

In the U.S., more then 10% of adults have symptoms of gastroesophageal reflux disease (GERD), which is caused by the combination of incompetent lower esophageal sphincter and sliding hiatal hernia. Most symptoms of this disease are mild and they do not require treatment. However, severe conditions such as esophageal erosion, ulceration, stricture, asthma due to aspiration and chronic respiratory infections require medical or surgical managements. Most patients can be effectively treated with traditional medical management utilizing dietary modification, weight loss, raising the head of the bed, antacids, H2 antagonists and proton pump inhibitors. Recently, though, it has been proven that long-term relief may be achieved more efficiently with antireflux surgery or Laparoscopic Nissen fundoplication. Since 1993, a total of 80 patients with advanced GERD have undergone laparoscopic nissen fundoplication at the United Hospital Center in Clarksburg, W.Va., and the results have been excellent. In addition, the hospital charges for patients having laparoscopic Nissen fundoplication are much less than for those who undergo open procedure and the recuperation time is much shorter.

Intracranial ganglioglioma: CT and MRI findings

Thirteen cases of pathologically proved intracranial gangliogliomas were reviewed in order to define the characteristic computed tomography (CT) and magnetic resonance image (MRI)-features. All patients were evaluated with CT and four of them were studied by MRI. Six tumors were cystic dominant mixed masses with remarkable focal contrast enhancement (6/13, 46%); and seven were solid in nature with variable contrast enhancement (7/13, 54%). Nine of them contained calcification (9/13, 69%). The temporal lobe was affected in six patients (6/13, 46%); the posterior fossa in four patients; the frontal lobe in two; the remaining huge one in the frontal, temporal and basal ganglion. On MRI, the findings were similar to those of the CT. Gangliogliomas do not have a characteristic CT and MRI features. They may appear as pure cystlike tumors, cystic dominant mixed tumors with remarkable focal contrast enhancement, solid tumors with variable contrast enhancement or diffuse involving the brain parenchyma and/or subarachnoid spaces. However, radiologists should include ganglioglioma in the differential diagnosis when we find patient has a long-standing process as well as a calcified tumor in the temporal lobe with following characteristic; cystic dominant mixed tumor with remarkable focal contrast enhancement, or a solid mass without hemorrhage or significant surrounding edema.

Electrical fixing of 1000 angle-multiplexed holograms in SBN:75

We have demonstrated electrical fixing of 1000 angle-multiplexed holograms in a 1-cm(3)volume Ce-doped SBN:75 crystal. A revealing procedure yielded an average diffraction efficiency of 0.005% for each hologram, with approximately 20% variation. The erasure resistance of the fixed gratings was verified.

Structural studies of receptor binding by cholera toxin mutants

The wide range of receptor binding affinities reported to result from mutations at residue Gly 33 of the cholera toxin B-pentamer (CTB) has been most puzzling. For instance, introduction of an aspartate at this position abolishes receptor binding, whereas substitution by arginine retains receptor affinity despite the larger side chain. We now report the structure determination and 2.3-A refinement of the CTB mutant Gly 33-->Arg complexed with the GM1 oligosaccharide, as well as the 2.2-A refinement of a Gly 33-->Asp mutant of the closely related Escherichia coli heat-labile enterotoxin B-pentamer (LTB). Two of the five receptor binding sites in the Gly 33-->Arg CTB mutant are occupied by bound GM1 oligosaccharide; two other sites are involved in a reciprocal toxin:toxin interaction; one site is unoccupied. We further report a higher resolution (2.0 A) determination and refinement of the wild-type CTB:GM1 oligosaccharide complex in which all five oligosaccharides are seen to be bound in essentially identical conformations. Saccharide conformation and binding interactions are very similar in both the CTB wild-type and Gly 33-->Arg mutant complexes. The protein conformation observed for the binding-deficient Gly 33-->Asp mutant of LTB does not differ substantially from that seen in the toxin:saccharide complexes. The critical nature of the side chain of residue 33 is apparently due to a limited range of subtle rearrangements available to both the toxin and the saccharide to accommodate receptor binding. The intermolecular interactions seen in the CTB (Gly 33-->Arg) complex with oligosaccharide suggest that the affinity of this mutant for the receptor is close to the self-affinity corresponding to the toxin:toxin binding interaction that has now been observed in crystal structures of three CTB mutants.

Pharmacokinetics of pirmenol enantiomers and pharmacodynamics of pirmenol racemate in patients with premature ventricular contractions

The pharmacokinetics and pharmacodynamics of pirmenol were investigated in 12 patients with premature ventricular contractions (PVCs) after oral administration of racemic pirmenol, 100 mg and 200 mg every 12 hours. Holter monitoring was performed and serial blood samples were collected after the seventh doses. Plasma concentrations of pirmenol enantiomer were determined using a stereospecific liquid chromatographic assay. Clearance of total (-)-pirmenol was 20% higher than that of total (+)-pirmenol, and the difference in unbound clearance was 45% between enantiomers. Total pirmenol showed a smaller difference because of stereoselective protein binding, with 25% (100-mg dose) or 27% (200-mg dose) higher fraction unbound for (+)-pirmenol than for (-)-pirmenol. Distribution volume was similar for both enantiomers. Dose-dependent clearance was observed for unbound pirmenol enantiomers, as both enantiomers showed 20% lower unbound clearance at the higher dose. Antiarrhythmic effect (% reduction in PVCs from baseline) was correlated with plasma concentrations of pirmenol using a sigmoid maximum drug effect model, and patients showed a large variability in their antiarrhythmic response to plasma concentrations of pirmenol. The median value for minimum effective plasma concentration of racemic pirmenol was 1.5 micrograms/mL.

Cloning of anti-Gal Fabs from combinatorial phage display libraries: structural analysis and comparison of Fab expression in pComb3H and pComb8 phage

Anti-Gal is the most abundant natural antibody in humans. It interacts specifically with the carbohydrate epitope Gal alpha1-3Galbeta1-4GlcNAc-R (termed the alpha-galactosyl epitope). In an attempt to characterize the Ig genes encoding anti-Gal, two combinatorial phage display libraries in phagemid pComb3H were screened for anti-Gal Fabs. For this purpose, phages were incubated with biotinylated BSA coupled with alpha-galactosyl epitopes (designated alpha-Gal-BSA). Subsequently, phages complexed with alpha-Gal-BSA were isolated by streptavidin-coupled magnetic beads. Because of the low affinity of this antibody, a characteristic shared with other anti-carbohydrate antibodies, only two clones displaying anti-Gal activity were isolated. Clone G9 contained the VH gene V3-43 and VL gene DPK15, whereas clone P19 contained the VH gene V3-15 and VL gene DPL16. Both clones contained between five and 14 mutations in their H and L chain V genes. The affinity of clone G9 was found to be higher than that of clone P19, as only the former could bind to solid-phase alpha-galactosyl epitopes in an enzyme-linked immunosorbent assay. This interaction could be increased by expressing Fabs in phagemid pComb8 grown in the presence of IPTG. Under such conditions, the IPTG-activated Lac-Z promoter induces an increased expression of Fabs that are linked to phage envelope protein VIII, resulting in multiple Fab display on the phage. The data suggest that screening combinatorial phage display libraries for anti-carbohydrate antibodies may be more effective with pComb8 phage grown in the presence of IPTG.

Disregulation of mitotic checkpoints and regulatory proteins following acute expression of SV40 large T antigen in diploid human cells

SV40 large T antigen (T) inactivates the tumor suppressor proteins p53 and pRb, and can induce cells to enter DNA replication at inappropriate times. We show here that T also compromises three cell cycle checkpoints that regulate the entry into and exit from mitosis. Human diploid fibroblasts infected with a retrovirus expressing T displayed an attenuated radiation-induced mitotic delay, were more susceptible to chemical-induced uncoupling of mitosis from the completion of DNA replication, and were more likely to exit mitosis and rereplicate their DNA when mitotic spindle assembly was inhibited. Consistent with altered mitotic checkpoint control, cells expressing T displayed elevated protein levels and/or associated activities of the mitotic regulatory proteins cyclin A, cyclin B, Cdc25C and p34(cdc2). These changes in mitotic control were evident within 5-10 population doublings after retroviral infection, indicating a direct effect of T expression. Cells acutely infected with the T-expressing retrovirus suffered numerical and structural chromosome aberrations, including increases in aneuploidy, dicentric chromosomes, chromatid exchanges and chromosome breaks and gaps. These findings indicate that T rapidly disrupts mitotic checkpoints that help maintain genomic stability, and suggest mechanisms by which T induces chromosome aberrations and promotes the immortalization and neoplastic transformation of human cells.

Serum responses to the combination of Epstein-Barr virus antigens from both latent and acute phases in nasopharyngeal carcinoma: complementary test of EBNA-1 with EA-D

Elevated serum IgA to antigens of EBV is associated with nasopharyngeal carcinoma (NPC). We have tested 620 NPC sera by ELISA for the presence of antibodies to EBV-encoded DNA binding protein, EBV-specific DNA polymerase, early antigen-diffused (EA-D), EBV nuclear antigen 1 (EBNA-1), EBV-specific thymidine kinase, and BamHI Z fragment EBV replication antigen. Sensitivity of these proteins was in the range of 51.5-79.5% for IgA and 69.4-82.8% for IgG. The complementary use of EBNA-1 with EA-D, however, could increase the sensitivity significantly to 98.1%. Western blot analysis further showed that the combination of EBNA-1 and EA-D is most useful for the detection of NPC. This is the first report of using double biomarkers including EBV gene products from both latent and active infections. The results of this study suggest that EBV in NPC may not be latent alone and that the method may be valuable for the early detection, early treatment, and better survival rate of patients with NPC. Because the application of recombinant EBV protein in ELISA is cost-effective and feasible for mass screening, the method may be of worth for further clinical investigation.

A mitosis-specific phosphorylation of the gap junction protein connexin43 in human vascular cells: biochemical characterization and localization

Western blotting studies revealed that connexin43 (Cx43), one of the major gap junction proteins in human vascular endothelial cells, is posttranslationally modified during mitosis. This mitosis-specific modification results in a Cx43 species that migrates as a single protein band and was designated Cx43(m). Cx43(m) was shown to be the result of additional Ser/Thr phosphorylation as indicated by: (a) the increased gel mobility induced by both alkaline phosphatase and the Ser/ Thr-specific protein phosphatase-2A (PP2A) and (b) the removal of virtually all (32)P(i) from Cx43(m) by PP2A. Immunofluorescent confocal microscopy of mitotic cells revealed that Cx43 is intracellularly located, while in nonmitotic cells Cx43 is located at regions of cell-cell contact. Dye coupling studies revealed that mitotic endothelial cells were uncoupled from each other and from nonmitotic cells. After cytokinesis, sister cells resumed cell coupling independent of de novo protein synthesis. The mitosis-specific phosphorylation of Cx43 correlates with the transient loss of gap junction intercellular communication and redistribution of Cx43, suggesting that a protein kinase that regulates gap junctions is active in M-phase.

Confirming testosterone administration by isotope ratio mass spectrometric analysis of urinary androstanediols

A gas chromatographic combustion isotope ratio mass spectrometric (GC/C/IRMS) method was used for studying the incorporation of exogenous testosterone enanthate into excreted urinary 5 alpha- and 5 beta-androstane-3 alpha, 17 beta-diols. A multistep but straightforward work-up procedure produced a simple GC chromatogram of urinary steroid acetates composed principally of two androstanediols and pregnanediol. It is anticipated that such a method may form the basis of a doping control test for testosterone that could be used as a primary method during major sporting events or alternatively as a verification technique. Urine samples from five individuals were collected before and after administration of testosterone enanthate (250 mg). The delta 13C0/1000 value of andro-stanediols was around -26 to -28 during the baseline period and decreased to about -29 to -30 in the days following synthetic testosterone administration. One of the other major steroids in the chromatogram, pregnanediol, was utilized as the "internal standard," because its delta 13C0/1000 values did not markedly change following testosterone administration, remaining at -25 to -27. In all subjects studied, the delta 13C0/1000 values for androstanediols were reduced sufficiently over 8 days to confirm administration of synthetic testosterone. Although steroids isolated from urine of normal individuals from 12 different countries gave values between -24 and -28, this seemed not to be related to nationality or region. The most likely variable is the proportion of plants with low and high carbon 13 content in the diet. This variable is likely to be more affected by individual food preferences than broad ethnic food divisions. In this paper, we propose a ratio of delta 13C0/1000 for androstanediols to pregnanediol as a useful discriminant of testosterone misuse, a value above 1.1:1.0 being indicative of such misuse. The work-up procedure was designed for batch analysis and to use only simple techniques, rather than employ further instrumentation, such as high-performance liquid chromatography (HPLC), in purifying steroids for GC/C/IRMS.

Pharmacokinetics and pharmacodynamics of pirmenol enantiomers in coronary artery ligated dogs

The pharmacokinetics and pharmacodynamics of pirmenol enantiomers were investigated in coronary artery ligated mongrel dogs. Reduction in frequency of premature ventricular complexes (PVCs) was determined following intravenous administration of 5-mg/kg doses of racemic pirmenol (n = 5), (+)-pirmenol (n = 4), and (-)-pirmenol (n = 4), each given as a 5-min infusion. Electrocardiographic signals and blood samples were obtained serially over a 4-h period. Pirmenol enantiomer concentrations in plasma were determined by a stereospecific assay. Following the racemate dose, (-)-pirmenol had 47% lower clearance and 33% lower steady-state distribution volume than (+)-pirmenol. These differences could be mostly explained by stereoselective plasma protein binding, reflected in a 58% higher unbound fraction for (+)-pirmenol compared with (-)-pirmenol following racemate administration. Unbound pirmenol distribution volumes were nearly identical for both enantiomers, and unbound clearance was only 16% lower for (-)-pirmenol than (+)-pirmenol following administration of the racemate. Similar trends were observed for pirmenol enantiomers administered individually. Both pirmenol enantiomers were equally effective in arrhythmia suppression. The antiarrhythmic response of coronary artery ligated dogs to pirmenol was described by a sigmoid Emax model, and no statistically significant differences were observed in the pharmacodynamic parameters [i.e., EC50 (plasma concentration at 50% of maximum drug effect), S (constant that reflects the sigmoidal shape of the effect-concentration curve), and EC90 (plasma concentration at 90% of maximum drug effect)] for (+)-pirmenol, (-)-pirmenol, or pirmenol racemate.

Requirement of the DEAD-Box protein ded1p for messenger RNA translation

The DED1 gene, which encodes a putative RNA helicase, has been implicated in nuclear pre-messenger RNA splicing in the yeast Saccharomyces cerevisiae. It is shown here by genetic and biochemical analysis that translation, rather than splicing, is severely impaired in two newly isolated ded1 conditional mutants. Preliminary evidence suggests that the protein Ded1p may be required for the initiation step of translation, as is the distinct DEAD-box protein, eukaryotic initiation factor 4A (eIF4A). The DED1 gene could be functionally replaced by a mouse homolog, PL10, which suggests that the function of Ded1p in translation is evolutionarily conserved.