Novel<Emphasis Type="Italic"> eceriferum</Emphasis> mutants in<Emphasis Type="Italic"> Arabidopsis thaliana</Emphasis>

We conducted a novel non-visual screen for cuticular wax mutants in Arabidopsis thaliana (L.) Heynh. Using gas chromatography we screened over 1,200 ethyl methane sulfonate (EMS)-mutagenized lines for alterations in the major A. thaliana wild-type stem cuticular chemicals. Five lines showed distinct differences from the wild type and were further analyzed by gas chromatography and scanning electron microscopy. The five mutants were mapped to specific chromosome locations and tested for allelism with other wax mutant loci mapping to the same region. Toward this end, the mapping of the cuticular wax (cer) mutants cer10 to cer20 was conducted to allow more efficient allelism tests with newly identified lines. From these five lines, we have identified three mutants defining novel genes that have been designated CER22, CER23, and CER24. Detailed stem and leaf chemistry has allowed us to place these novel mutants in specific steps of the cuticular wax biosynthetic pathway and to make hypotheses about the function of their gene products.Abbreviations EMS Ethyl methane sulfonate - SEM Scanning electron microscopy - SSLP Simple sequence length polymorphism - WT Wild type     

Racemic and chiral lactams as potent, selective and functionally active CCR4 antagonists

A series of racemic and chiral, nonracemic lactams that display high binding affinities, functional chemotaxis antagonism, and selectivity toward CCR4 are described. Compound 41, which provides reasonably high blood levels in mice when dosed intraperitoneally, was identified as a useful pharmacological tool to explore the role of CCR4 antagonism in animal models of allergic disease.     

Exploration of the P1 SAR of aldehyde cathepsin K inhibitors

The synthesis and biological activity of a series of aldehyde inhibitors of cathepsin K are reported. Exploration of the properties of the S(1) subsite with a series of alpha-amino aldehyde derivatives substituted at the P(1) position afforded compounds with cathepsin K IC(50)s between 52 microM and 15 nM.     

Requirement for the Rac GTPase in Chlamydia trachomatis invasion of non-phagocytic cells

Chlamydiae are gram-negative obligate intracellular pathogens to which access to an intracellular environment is paramount to their survival and replication. To this end, chlamydiae have evolved extremely efficient means of invading nonphagocytic cells. To elucidate the host cell machinery utilized by Chlamydia trachomatis in invasion, we examined the roles of the Rho GTPase family members in the internalization of chlamydial elementary bodies. Upon binding of elementary bodies on the cell surface, actin is rapidly recruited to the sites of internalization. Members of the Rho GTPase family are frequently involved in localized recruitment of actin. Clostridial Toxin B, which is a known enzymatic inhibitor of Rac, Cdc42 and Rho GTPases, significantly reduced chlamydial invasion of HeLa cells. Expression of dominant negative constructs in HeLa cells revealed that chlamydial uptake was dependent on Rac, but not on Cdc42 or RhoA. Rac but not Cdc42 was found to be activated by chlamydial attachment. The effect of dominant negative Rac expression on chlamydial uptake is manifested through the inhibition of actin recruitment to the sites of chlamydial entry. Studies utilizing Green Fluorescent Protein fusion constructs of Rac, Cdc42 and RhoA, showed Rac to be the sole member of the Rho GTPase family recruited to the site of chlamydial entry.     

Biochemical characterization of the ataxia-telangiectasia mutated (ATM) protein from human cells

Ataxia-telangiectasia mutated (ATM) is a serine/threonine protein kinase that plays a central role in controlling the cellular response to ionizing radiation and other DNA-damaging agents. ATM is a 3056 amino acid polypeptide that is present in low abundance in the nucleus of human cells. Here, we describe the purification and characterization of ATM from the nuclear fraction of HeLa cells. Microgram quantities of highly stable, kinase-active ATM were prepared. Purified ATM was phosphorylated on serine 1981 and was active towards a variety of known ATM substrates, including p53 and the Bloom Syndrome helicase, BLM. The protein kinase activity of ATM was selectively inhibited by wortmannin, caffeine and LY294002 and was stimulated by charged biological polymers, including single-stranded M13 DNA (ssDNA), sheared double-stranded calf thymus DNA, heparin sulfate and poly ADP-ribose (PAR), raising the possibility that charged structures may contribute to regulation of ATM activity. However, chemical inhibition of the formation of poly ADP-ribose in cells had no effect on the activation of ATM-dependent pathways by ionizing radiation. Using gel filtration chromatography, we also show that purified ATM, as well as ATM in crude nuclear extracts from unirradiated and irradiated cells elutes with an estimated native molecular weight of approximately 600 kDa. Moreover, dephosphorylation of serine 1981 did not affect the apparent molecular weight of ATM in irradiated extracts. Our results suggest that phosphorylation of serine 1981 alone may not directly regulate the subunit composition of ATM.     

Development of a microscale cell culture analog to probe naphthalene toxicity

Prediction of human response to drugs or chemicals is difficult as a result of the complexity of living organisms. We describe an in vitro model that can realistically and inexpensively study the adsorption, distribution, metabolism, elimination, and potential toxicity (ADMET) of chemicals. A microscale cell culture analog (microCCA) is a physical replica of the physiologically based pharmacokinetics (PBPK) model. Such a microfabricated device consists of a fluidic network of channels to mimic the circulatory system and chambers containing cultured mammalian cells representing key functions of animal "organ" systems. This paper describes the application of a two-cell system, four-chamber microCCA ("lung"-"liver"-"other tissue"-"fat") device for proof-of-concept study using naphthalene as a model toxicant. Naphthalene is converted into reactive metabolites (i.e., 1,2-naphthalenediol and 1,2-naphthoquinone) in the "liver" compartment, which then circulate to the "lung" depleting glutathione (GSH) in lung cells. Such microfabricated in vitro devices are potential human surrogates for testing chemicals and pharmaceutics for toxicity and efficacy.     

Stent thrombosis in patients treated with thienopyridines: clinical description of 10 cases

Subacute stent thrombosis (SAST) is a major thrombotic complication of coronary stenting. Its occurrence has been substantially reduced by thienopyridine treatment. However, information on clinical profile of patients with SAST in clopidogrel era is limited. In order to define the incidence and factors predisposing to stent thrombosis, we analyzed the computerized angiographic database of three interventional cardiology centers. Out of a total number of 5903 percutaneous coronary interventions (PCIs) with stent implantation, we found 10 patients with SAST (0.17%). The indication for PCI was usually an early invasive approach (90%) during an acute coronary syndrome. All patients were treated with an apparently optimal antithrombotic regimen (90% received heparin or LMWH and 70% received IIb/IIIa receptor inhibitors and all given aspirin). In each of the patients, we could identify high-risk angiographic findings. SAST presentation was always clinically significant with definite myocardial infarction in 100% of cases. 80% of cases occurred during the first six days post PCI. Two patients had a recurrent event. Finally, despite earlier reports of atorvastatin-mediated inhibition of clopidogrel activation we did not find any patient with SAST taking both drugs. Thus, patients with stent thrombosis during thienopyridine treatment usually exhibit high-risk angiographic features. Prospective studies should be performed to elucidate drug interactions that may reduce clopidogrel efficacy and contribute to stent thrombosis.     

Multiple biomarker response in rainbow trout during exposure to hexavalent chromium

This research investigated hexavalent chromium toxicity in rainbow trout using a panel of biomarkers at different levels of biological organization. A time-course experiment in which rainbow trout were exposed in hard water (63.5 mg/L CaCO3) to a sublethal concentration of hexavalent chromium (10 mg/L) for a period of 28 days was conducted. The responses of multiple biomarkers were measured in gill and liver tissues at varying time points. Significant differences in metallothionein induction, superoxide dismutase activity, lipid peroxidation, cellular morphology, and growth were observed. Results indicated that gill tissues were more sensitive than hepatic tissues to chromium toxicity, yet hepatic tissues appeared to play a larger role in the organism's adaptive response to chromium compared to gill tissues. This study highlights the importance of using a set of integrated biomarkers to assess contaminant exposure and effects.     

XRHAMM functions in ran-dependent microtubule nucleation and pole formation during anastral spindle assembly

BACKGROUND: The regulated assembly of microtubules is essential for bipolar spindle formation. Depending on cell type, microtubules nucleate through two different pathways: centrosome-driven or chromatin-driven. The chromatin-driven pathway dominates in cells lacking centrosomes. RESULTS: Human RHAMM (receptor for hyaluronic-acid-mediated motility) was originally implicated in hyaluronic-acid-induced motility but has since been shown to associate with centrosomes and play a role in astral spindle pole integrity in mitotic systems. We have identified the Xenopus ortholog of human RHAMM as a microtubule-associated protein that plays a role in focusing spindle poles and is essential for efficient microtubule nucleation during spindle assembly without centrosomes. XRHAMM associates both with gamma-TuRC, a complex required for microtubule nucleation and with TPX2, a protein required for microtubule nucleation and spindle pole organization. CONCLUSIONS: XRHAMM facilitates Ran-dependent, chromatin-driven nucleation in a process that may require coordinate activation of TPX2 and gamma-TuRC.