A rationally designed anticancer drug targeting a unique binding cavity of tubulin

A novel mono-THF containing synthetic anticancer drug (WHI-261) was designed for targeting a previously unrecognized unique narrow binding cavity on the surface of tubulin. The anti-cancer activity of WHI-261 was confirmed using MTT assays. The structure-based design, synthesis, and biological activity of WHI-261 are reported.

Estrogen receptor-KRAB chimeras are potent ligand-dependent repressors of estrogen-regulated gene expression

As an approach to targeted repression of genes of interest, we describe the development of human estrogen receptor (ER) alpha-KRAB repressor domain chimeras that are potent ligand-dependent repressors of the transcription of estrogen response element (ERE)-containing promoters and analyze their mechanisms of action. Repression by the KRAB domain was dominant over transactivation mediated by ER AF1 and AF2. An ERE and an ER ligand (estrogen or antiestrogen) were required for repression. Studies with several promoters and cell lines demonstrated that the presence of EREs, rather than the capacity for estrogen induction, determines the potential for repression of a gene by the KRAB-ERalpha-KRAB (KERK) chimera. A single consensus ERE was sufficient for repression, but the KERK chimera was unable to suppress transcription from the imperfect ERE in the native pS2 promoter. We recently reported mutations that enhance binding of a steroid receptor DNA-binding domain to the ERE. Introducing these mutations into wild-type ER enhanced transactivation from the pS2 ERE. Insertion of these mutations into KERK created the novel repressor KERK-3M, which is a potent repressor of both ER-induced and basal transcription on a promoter containing the pS2 ERE. These modified ER-KRAB chimeras should prove useful as new tools for the functional analysis and repression of ER-regulated genes.

Emx1-specific expression of foreign genes using "knock-in" approach

Emx1 is a mouse homologue of the Drosophila homeobox gene empty spiracles. Its expression is limited to the neurons in developing and adult cerebral cortex and hippocampus. Because of the highly restricted expression pattern of the Emx1 gene, it would be quite desirable to characterize the promoter of the Emx1 for directing foreign gene expression in the transgenic mouse. We report here that we have achieved the Emx1-specific expression in transgenic mice by inserting the lacZ reporter and cre genes directly into the exon 1 of the Emx1 gene using embryonic stem (ES) cell technology. The distribution of the beta-galactosidase activity in the transgenic mice was consistent with the published results obtained using in situ hybridization and immunohistochemistry. Furthermore, we have demonstrated that Cre protein was present in the cerebral cortex of the transgenic mice and was able to mediate loxP-specific recombination in vitro. The creation of this line of cre transgenic mice, and the demonstration that the insertion site located in the exon 1 of the Emx1 gene could render foreign genes a specific expression pattern restricted to the developing and adult cerebral cortex and hippocampus, should be conducive to further studies of the effect of a gene mutation or overexpression upon the development and plasticity of cerebral cortex and hippocampus.

[Studies on antiplatelet aggregation and anticoagulant action of Curcuma phaeocaulis]

OBJECTIVE

To study the effects of Curcuma phaeocaulis Valeton on platelet aggregation and anticoagulant action.

METHODS

Antiplatelet aggregation and anticoagulant action of Curcuma phaeocaulis Valeton of mice is observed in platelet aggregation and coagulant time.

RESULTS

The experimental results show that Curcuma phaeocaulis Valeton can inhibit platelet aggregation, prolong time of mice coagulation.

CONCLUSION

Antiplatelet aggregation and anticoagulant action of processed products with vinegar is the most powerful.

Structure-based design of a novel synthetic spiroketal pyran as a pharmacophore for the marine natural product spongistatin 1

SPIKET-P, a novel synthetic spiroketal pyran, was rationally designed as a pharmocophore for the tubulin depolymerizing marine natural product Spongistatin 1. SPIKET-P was prepared from the commercially available benzyl (R)-(-)-glycidyl ether using a versatile 11-step synthetic scheme in a stereocontrolled fashion. At nanomolar concentrations, SPIKET-P caused tubulin depolymerization in cell-free turbidity assays and exhibited potent cytotoxic activity against cancer cells as evidenced by destruction of microtubule organization, and prevention of mitotic spindle formation in human breast cancer cells.

Cloning of an alkaline ceramidase from Saccharomyces cerevisiae. An enzyme with reverse (CoA-independent) ceramide synthase activity

Ceramide is not only a core intermediate of sphingolipids but also an important modulator of many cellular events including apoptosis, cell cycle arrest, senescence, differentiation, and stress responses. Its turnover may be tightly regulated. However, little is known about the regulation of its metabolism because most enzymes responsible for its synthesis and breakdown have yet to be cloned. Here we report the cloning and characterization of the yeast gene YPC1 (YBR183w) by screening Saccharomyces cerevisiae genes whose overexpression bestows resistance to fumonisin B1. We demonstrate that the yeast gene YPC1 encodes an alkaline ceramidase activity responsible for the breakdown of dihydroceramide and phytoceramide but not unsaturated ceramide. YPC1 ceramidase activity was confirmed by in vitro studies using an Escherichia coli expression system. Importantly, YPC1p also has reverse activity, catalyzing synthesis of phytoceramide from palmitic acid and phytosphingosine. This ceramide synthase activity is CoA-independent and is resistant to fumonisin B1, thus explaining why YPC1 was cloned as a fumonisin B1-resistant gene.

Cre-mediated cerebellum- and hippocampus-restricted gene mutation in mouse brain

Using the phage P1-derived Cre/loxP recombination system, we have created a line of cre-transgenic mice in which the Cre-mediated gene deletion is restricted to granule cells of cerebellum and dentate gyrus of hippocampus. Low levels of deletion were also present in pyramidal cells of hippocampal CA1 and CA3 fields. The Cre/loxP recombination occurred prenatally. The recombination efficiencies in the granular layer of the cerebellum, the granular layer of the dentate gyrus, and the CA1 and CA3 pyramidal cells of the hippocampus were 34.0%, 23.1%, 3.0%, and 9.8%, respectively. This line of cre-transgenic mice should be conducive to studies of the effect of a gene mutation upon brain development and plasticity.

N-[2-(4-methylphenyl)ethyl]-N'-[2-(5-bromopyridyl)]-thiourea as a potent inhibitor of NNRTI-resistant and multidrug-resistant human immunodeficiency virus type 1

The composite non-nucleoside reverse transcriptase inhibitor (NNRTI) binding pocket model was used to study a number of thiourea analogues with different substitutions at the 4-phenyl position including N-[2-(4-methylphenyl)ethyl]-N'-[2-(5-bromopyridyl)]-thiourea (compound HI-244), which inhibited recombinant RT better than trovirdine or compound HI-275 with an unsubstituted phenyl ring. HI-244 effectively inhibited the replication of HIV-1 strain HTLV(IIIB) in human peripheral blood mononuclear cells with an IC50 value of 0.007 microM, which is equal to the IC50 value of trovirdine. Notably, HI-244 was 20 times more effective than trovirdine against the multidrug-resistant HIV-1 strain RT-MDR with a V106A mutation (as well as additional mutations involving the RT residues 74V, 41L and 215Y) and seven times more potent than trovirdine against the NNRTI-resistant HIV-1 strain A17 with a Y181C mutation.

A retrospective study of bilateral alveolar bone grafting

OBJECTIVE

To evaluate the treatment results of bilateral alveolar bone grafting (BABG) in patients with bilateral complete clefts of lip and palate.

METHODS

A retrospective study was performed in 66 bilateral complete cleft lip and palate patients who received the procedure of BABG, among them 15 were primary BABG and 51 were secondary BABG. The patients were further divided into three groups according to age and eruption stage of the canine at the time of surgery. The result of BABG was evaluated on the radiographs.

RESULTS

(1) The overall success rate of BABG was 75.0%, with 83.3% and 72.5% for primary and secondary BABG respectively; (2) The marginal bone level was found to be significantly higher in the youngest age group than in the other groups both for primary and secondary BABG; (3) For both primary and secondary BABG, Group C (patients' age more than 16 years) had the least optimal success rate, with 66.7% and 65.1% respectively.

CONCLUSION

Simultaneous primary palate repair and BABG is safe and feasible procedure for treating unoperated bilateral complete cleft lip and cleft palate patients. For both primary and secondary BABG, significantly better results can be achieved if the operation is performed before eruption of the canine.

Proteinase inhibitor 9, an inhibitor of granzyme B-mediated apoptosis, is a primary estrogen-inducible gene in human liver cells

Although liver is an estrogen target tissue, the number of hepatic genes known to be directly induced by estrogen is very small. We identified proteinase inhibitor 9, or PI-9, as being rapidly and strongly induced by estrogen in an estrogen receptor-positive human liver cell line (HepG2-ER7). Since PI-9 mRNA was also induced by estrogen in a human liver biopsy sample, PI-9 is a genuine estrogen-regulated human gene. PI-9 is a potent inhibitor of granzyme B and of granzyme B-mediated apoptosis. Estrogens induced PI-9 mRNA within 2 h, PI-9 mRNA levels reached a plateau of 30-40-fold induction in 4 h, and induction was not blocked by cycloheximide, indicating that induction of PI-9 mRNA is a primary response. The antiestrogen trans-hydroxytamoxifen was a partial agonist for PI-9 mRNA induction, whereas the antiestrogen ICI 182, 780 was a pure antagonist. Western blot analysis showed that estrogen strongly increases PI-9 protein levels. Inhibition of transcription with actinomycin D resulted in identical rates of PI-9 mRNA decay in the presence and absence of estrogen. We isolated genomic clones containing the PI-9 promoter region, identified a putative transcription start site, and carried out transient transfections of PI-9-luciferase reporter gene constructs. The estrogen, moxestrol, elicited a robust induction from the PI-9-luciferase reporter. Mutational inactivation of three potential imperfect estrogen response elements in the PI-9 5'-flanking region had no effect on moxestrol estrogen receptor induction.

Differential expression of rat frizzled-related frzb-1 and frizzled receptor fz1 and fz2 genes in the rat aorta after balloon injury

Frzb-1 is a secreted protein, presenting similarity with the Wnt-binding domain of the frizzled family of receptors, which acts as an antagonist of Wnt signaling. Using mRNA differential display in the rat aorta balloon injury model, we identified overexpression of Frzb-1 mRNA and determined its cDNA sequence. By quantitative reverse transcription-polymerase chain reaction and RNase protection assay, a biphasic upregulation of rFrzb-1 expression was observed, with significant peaks of a 1.7-fold increase at 4 days and a 1. 5-fold increase at 3 weeks after aortic injury in vivo. In contrast, expression of the rat frizzled receptor genes rfz1 and rfz2 were transiently downregulated at 1 and 4 hours after balloon injury. rFrzb-1 was expressed predominantly in rat aortic smooth muscle cells (RASMCs) and barely in aortic fibroblasts and endothelial cells (RAECs), whereas rfz1 and rfz2 were expressed in all of these cells when stimulated with serum. Transient downregulation of rfz1 and rfz2 expression was reproduced by stimulation of quiescent RASMCs with serum, platelet-derived growth factor-BB, or fibroblast growth factor-2. In contrast, rFrzb-1 expression diminished slowly, to reach a 2-fold decrease 24 hours after growth factor stimulation, implying that quiescent RASMCs expressed higher levels of rFrzb-1 mRNA than did proliferative ones. Overexpression of rFrzb-1 in the aorta seemed to coincide with the arrest of RASMC proliferation occurring in the media 4 days and in the neointima 3 weeks after balloon injury. Our results demonstrate that rfrzb-1, rfz1, and rfz2 are differentially regulated in response to arterial injury and that this modulation seems to follow the proliferative state of RASMCs, suggesting that these Wnt-signaling components may be involved in intimal vascular disease.

N'-[2-(2-thiophene)ethyl]-N'-[2-(5-bromopyridyl)] thiourea as a potent inhibitor of NNI-resistant and multidrug-resistant human immunodeficiency virus-1

The thiophene-ethyl thiourea (TET) compound N'-[2-(2-thiophene)ethyl]-N'-[2-(5-bromopyridyl)]-thiourea (compound HI-443) was five times more potent than trovirdine, 1250 times more potent than nevirapine, 100 times more potent than delavirdine, 75 times more potent than MKC-442, and 50 times more potent than AZT against the multidrug resistant HIV-1 strain RT-MDR with a V106A mutation. HI-443 was almost as potent against the NNI-resistant HIV-1 strain A17 with a Y181C mutation as it was against HTLV(IIIB). The activity of HI-443 against A17 was ten times more potent than that of trovirdine, 2083 times more potent than that of nevirapine, and 1042 times more potent than that of delavirdine. HI-443 inhibited the replication of the NNI-resistant HIV-1 strain A17 variant with Y181C plus K103N mutations in RT with an IC50 value of 3.3 microM, whereas the IC50 values of trovirdine, nevirapine, and delavirdine were all >100 microM. These findings establish the novel thiophene containing thiourea compound HI-443 as a novel NNI with potent antiviral activity against NNI-sensitive, NNI-resistant and multidrug-resistant strains of HIV-1.

No braiding of Holliday junctions in positively supercoiled DNA molecules

The Holliday junction is a prominent intermediate in genetic recombination that consists of four double helical arms of DNA flanking a branch point. Under many conditions, the Holliday junction arranges its arms into two stacked domains that can be oriented so that genetic markers are parallel or antiparallel. In this arrangement, two strands retain a helical conformation, and the other two strands effect the crossover between helical domains. The products of recombination are altered by a crossover isomerization event, which switches the strands fulfilling these two roles. It appears that effecting this switch from the parallel conformation by the simplest mechanism results in braiding the crossover strands at the branch point. In previous work we showed by topological means that a short, parallel, DNA double crossover molecule with closed ends did not braid its branch point; however, that molecule was too short to adopt the necessary positively supercoiled topology. Here, we have addressed the same problem using a larger molecule of the same type. We have constructed a parallel DNA double crossover molecule with closed ends, containing 14 double helical turns in each helix between its crossover points. We have prepared this molecule in a relaxed form by simple ligation and in a positively supercoiled form by ligation in the presence of netropsin. The positively supercoiled molecule is of the right topology to accommodate braiding. We have compared the relaxed and supercoiled versions for their responses to probes that include hydroxyl radicals, KMnO4, the junction resolvases endonuclease VII and RuvC, and RuvC activation of KMNO4 sensitivity. In no case did we find evidence for a braid at the crossover point. We conclude that Holliday junctions do not braid at their branch points, and that the topological problem created by crossover isomerization in the parallel conformation is likely to be solved by distributing the stress over the helices that flank the branch point.

A quantitative assessment of how Canadian intensivists believe they utilize oxygen in the intensive care unit

OBJECTIVES

To investigate attitudes and practices regarding oxygen therapy in intensive care units (ICUs) and to devise quantitative descriptive indices.

SETTING

Canadian university-affiliated adult ICUs.

PARTICIPANTS

Fifty-two medical directors of ICUs in 48 institutions.

INTERVENTION

Structured postal questionnaire returned by 48 participants.

MEASUREMENTS AND MAIN RESULTS

Attitudes, beliefs, and stated practices relating to oxygen use in ICUs were determined. Novel descriptors S-50min (minutes of oxygen saturation [Sao2] acceptable to >50% of respondents), F-50max (maximum F(IO)2 above which <50% of respondents would increase F(IO)2), and F-50min (minimum F(IO)2 below which <50% of respondents would decrease F(IO)2) were determined. All respondents believed that oxygen toxicity was a concern. Twenty-nine percent of respondents indicated that they did not always assess tissue oxygenation in critical cases. A stepwise reduction in acceptance of progressive desaturation and increasing duration of hypoxemia was found. Presented with a stable patient with Sao2 of 98%, the maximum level of F(IO)2 above which respondents stated that they would not increase the F(IO)2 was 0.41+/-0.17 (mean +/- SD). For stable patients with Sao2 of 85%, the minimum F(IO)2 below which respondents would not reduce F(IO)2 was 0.59+/-0.23 (mean +/- SD). F-50max was 0.8 vs. 0.5 for Sao2 of 80%-85% vs. 85%-90%, respectively; F-50min was 0.6 vs. 0.21 for Sao2 of 90%-95% vs. 95%-100%, respectively.

CONCLUSIONS

Considerable variation exists in the attitudes, beliefs, and stated practices relating to the management of oxygen therapy in the ICU. These data are amenable to quantitative description and illustrate the necessity for documentation of actual practice and development of support systems for decision-making in this and similar areas.

Therapeutic effect of abstinence capsule on withdrawal symptoms of heroin addicts

435 heroin addicts were treated for 10 days to evaluate the therapeutic effectiveness of abstinence capsule on heroin withdrawal symptoms and its main adverse actions. Lofexidine was applied in a control group of 48 addicts. The single blind method and some determination methods used internationally were employed to evaluate the therapeutic effectiveness and adverse actions of the drugs. The results showed that the abstinence capsule has better therapeutic effectiveness, with less adverse actions, wider safety range, longer time of action and less cost than lofexidine.

Specificity of alpha-cyano-beta-hydroxy-beta-methyl-n-[4-(trifluoromethoxy)phe nyl]-propenamide as an inhibitor of the epidermal growth factor receptor tyrosine kinase

The epidermal growth factor receptor (EGFR) tyrosine kinase has an essential function for the survival of human breast cancer cells. In a systematic effort to design potent and specific inhibitors of this receptor family protein tyrosine kinase (PTK) as antibreast cancer agents, we recently reported the construction of a three-dimensional homology model of the EGFR kinase domain. In this model, the catalytic site is defined by two beta-sheets that form an interface at the cleft between the NH2-terminal and COOH-terminal lobes of the kinase domain. Our modeling studies revealed a distinct, remarkably planar triangular binding pocket within the kinase domain with approximate dimensions of 15 A x 12 A x 12 A, and the thickness of the binding pocket is approximately 7 A with an estimated volume of approximately 600 A3 available for inhibitor binding. Molecular docking studies had identified alpha-cyano-beta-hydroxy-beta-methyl-N-[4-(trifluoromethoxy)phenyl]-p ropenamide (LFM-A12) as our lead inhibitor, with an estimated binding constant of 13 microM, which subsequently inhibited EGFR kinase in vitro with an IC50 value of 1.7 microM. LFM-A12 was also discovered to be a highly specific inhibitor of the EGFR. Even at very high concentrations ranging from 175-350 microM, this inhibitor did not affect the enzymatic activity of other PTKs, including the Janus kinases JAK1 and JAK3, the Src family kinase HCK, the Tec family member Bruton's tyrosine kinase, SYK kinase, and the receptor family PTK insulin receptor kinase. This observation is in contrast to the activity of a quinazoline inhibitor tested as a control, 4-(3-bromo, 4-hydroxyanilino)-6,7-dimethoxyquinazoline, which was shown to inhibit EGFR and other tyrosine kinases such as HCK, JAK3, and SYK.

Yeast sphingosine-1-phosphate phosphatases: assay, expression, deletion, purification, and cellular localization by GFP tagging

DHS-1-P phosphatases cloned from yeast represent novel lipid phosphatases, which were not thought to exist in yeast. Identification and characterization of YSR2 and YSR3 have demonstrated that the DHS-1-P phosphatase is an important mediator in the biosynthesis of sphingolipids and in the maintenance of the balance of signaling lipid molecules ceramide, sphingosine, and sphingosine-1-P. Methods introduced here for purification, activity assay, in vivo labeling, and cellular localization using GFP tagging are expected to facilitate our understanding of this enzyme.

Structure-based design of potent inhibitors of EGF-receptor tyrosine kinase as anti-cancer agents

In a systematic effort to design inhibitors of the epidermal growth factor receptor (EGFR) family protein tyrosine kinases (PTK) as anti-cancer agents, we have constructed a three-dimensional homology model of the EGFR kinase domain and used molecular modeling methods for the structure-based design of analogs of the active metabolite of leflunomide (LFM) with potent and specific inhibitory activity against EGFR. These docking studies identified alpha-cyano-beta-hydroxy-beta-methyl-N-[4-(trifluoromethoxy)phenyl]-p ropenamide (LFM-A12) as our lead compound, which was predicted to bind to the EGFR catalytic site in a planar conformation. LFM-A12 inhibited the proliferation (IC50 = 26.3 microM) and in vitro invasiveness (IC50 = 28.4 microM) of EGFR positive human breast cancer cells in a concentration-dependent fashion. Similarly, the model of the EGFR binding pocket was used in combination with docking procedures to predict the favorable placement of chemical groups with defined sizes at multiple modification sites on another class of EGFR inhibitors, the 4-anilinoquinazoline. This approach has led to the successful design of a dibromo quinazoline derivative, WHI-P97, which had an estimated Ki value of 0.09 microM from modeling studies and a measured IC50 value of 2.5 microM in EGFR kinase inhibition assays. WHI-P97 effectively inhibited the in vitro invasiveness of EGFR-positive human cancer cells in a concentration-dependent manner. However, unlike LFM-A12, the quinazoline compounds are not specific for EGFR.

A disrupted homologue of the human CLN3 or juvenile neuronal ceroid lipofuscinosis gene in Saccharomyces cerevisiae: a model to study Batten disease

1. In order to investigate the biological function of the human CLN3 gene that is defective in Batten disease, we created a yeast strain by PCR-targeted disruption of the yeast gene (YHC3), which is a homologue of the human CLN3 gene. 2. The phenotypic characterization revealed that the yhc3 delta mutants are more sensitive to combined heat and alkaline stress than the wild-type strains as determined by inhibition of cell proliferation. 3. This suggests that the yhc3 delta mutant is a good model to investigate the biological function of human CLN3 gene in mammalian cells and to understand the pathophysiology of juvenile Batten disease.

N-[2-(1-cyclohexenyl)ethyl]-N'-[2-(5-bromopyridyl)]-thiourea and N'-[2-(1-cyclohexenyl)ethyl]-N'-[2-(5-chloropyridyl)]-thiourea as potent inhibitors of multidrug-resistant human immunodeficiency virus-1

We have replaced the pyridyl ring of trovirdine with an alicyclic cyclohexenyl, adamantyl or cis-myrtanyl ring. Only the cyclohexenyl-containing thiourea compound N-[2-(1-cyclohexenyl)ethyl]-N'-[2-(5-bromopyridyl)]- thiourea (HI-346) (as well as its chlorine-substituted derivative N-[2-(1-cyclohexenyl)ethyl]-N'-[2-(5-chloropyridyl)]- thiourea/HI-445) showed RT inhibitory activity. HI-346 and HI-445 effectively inhibited recombinant RT with better IC50 values than other anti-HIV agents tested. The ranking order of efficacy in cell-free RT inhibition assays was: HI-346 (IC50 = 0.4 microM) > HI-445 (IC50 = 0.5 microM) > trovirdine (IC50 = 0.8 microM) > MKC-442 (IC5 = 0.8 microM) = delavirdine (IC50 = 1.5 microM) > nevirapine (IC50 = 23 microM). In accord with this data, both compounds inhibited the replication of the drug-sensitive HIV-1 strain HTLV(IIIB) with better IC50 values than other anti-HIV agents tested. The ranking order of efficacy in cellular HIV-1 inhibition assays was: HI-445 = HI-346 (IC50 = 3 nM) > MKC-442 (IC50 = 4 nM) = AZT (IC50 = 4 nM) > trovirdine (IC50 = 7 nM) > delavirdine (IC50 = 9 nM) > nevirapine (IC50 = 34 nM). Surprisingly, the lead compounds HI-346 and HI-445 were 3-times more effective against the multidrug resistant HIV-1 strain RT-MDR with a V106A mutation (as well as additional mutations involving the RT residues 74V,41L, and 215Y) than they were against HTLV(IIIB) with wild-type RT. HI-346 and HI-445 were 20-times more potent than trovirdine, 200-times more potent than AZT, 300-times more potent than MKC-442, 400-times more potent than delavirdine, and 5000-times more potent than nevirapine against the multidrug resistant HIV-1 strain RT-MDR. HI-445 was also tested against the RT Y181C mutant A17 strain of HIV-1 and found to be >7-fold more effective than trovirdine and >1,400-fold more effective than nevirapine or delavirdine. Similarly, both HI-346 and HI-445 were more effective than trovirdine, nevirapine, and delavirdine against the problematic NNI-resistant HIV-1 strain A17-variant with both Y181C and K103N mutations in RT, although their activity was markedly reduced against this strain. Neither compound exhibited significant cytotoxicity at effective concentrations (CC50 >100 microM). These findings establish the lead compounds HI-346 and HI-445 as potent inhibitors of drug-sensitive as well as multidrug-resistant stains of HIV-1.

The dihydrosphingosine-1-phosphate phosphatases of Saccharomyces cerevisiae are important regulators of cell proliferation and heat stress responses

We have identified YSR2 and YSR3 of Saccharomyces cerevisiae as genes encoding dihydrosphingosine-1-phosphate phophatases which are involved in regulation of sphingolipid metabolism [Mao, Wadleigh, Jenkins, Hannun and Obeid (1997) J. Biol. Chem. 272, 28690-28694]. In this study, we explored the physiological roles that these enzymes may have in S. cerevisiae. Deletion of either YSR2, YSR3 or both did not affect viability or growth rate of yeast cells. However, overexpression of YSR2 significantly prolonged the doubling time of cell growth, whereas overexpression of YSR3 affected cell growth only slightly. Cell cycle analysis suggested that overexpression of either YSR2 or, to a lesser extent, YSR3 caused cell cycle arrest at the G1 phase. Disruption of YSR2, but not YSR3, conferred increased thermotolerance. On the other hand, overexpression of either YSR2 or YSR3 diminished thermotolerance. Using labelled dihydrosphingosine and dihydrosphingosine-1-P (DHS-1-P), we found that overexpression of YSR2 significantly increased ceramide formation, whereas deletion of YSR2, YSR3, or both, accumulated DHS-1-P, and deletion of YSR2 decreased ceramide formation. Together, these results show that the phenotypes of YSR2 are associated with changes in endogenous levels of the different sphingolipids. Green fluorescent protein tagging showed that in the exponentially growing cells, YSR2 and YSR3 had the same cellular localization to endoplasmic reticulum. However, YSR2 and YSR3 differ in mRNA levels: YSR2 had significantly higher mRNA levels than YSR3. This discrepancy might result in the functional differences that these proteins exhibited. In addition, this study implicates sphingolipids and their metabolism in the regulation of growth and heat stress responses of the yeast S. cerevisiae.

Structure-based design of non-nucleoside reverse transcriptase inhibitors of drug-resistant human immunodeficiency virus

A computer model of reverse transcriptase (RT) from human immunodeficiency virus type 1 (HIV-1) was used to design thiourea compounds that were predicted to inhibit RT. The RT model was used to approximate how changes in binding pocket shape, volume and chemical properties resulting from residue mutations would affect inhibitor binding. Our lead compound, N-[2-(2,5-dimethoxyphenylethyl)]-N'-[2-(5-bromopyridyl)]-thi ourea (HI-236) was tested against clinically observed non-nucleoside inhibitor (NNI)-resistant mutated strains of HIV. HI-236 was more potent than trovirdine, MKC-442 and zidovudine against the drug-sensitive HIV-1 strain IIIB, 50-100 times more effective than delavirdine or nevirapine and twice as effective as our recently reported lead compound N-[2-(2-fluorophenethyl)]-N'-[2-(5-bromopyridyl)]-thiourea (HI-240) against the NNI-resistant Y181C mutant HIV-1 strain A17. HI-236 was highly effective against the multidrug-resistant HIV-1 strain RT-MDR containing multiple mutations involving the RT residues 74V, 41L, 106A and 215Y. In general, thiourea compounds such as HI-236 and HI-240 showed better inhibition of drug-resistant strains of HIV-1 than thioalkylbenzyl-pyrimidine compounds such as HI-280 and HI-281. The improved activity of thioureas against RT mutants is consistent with a structural analysis of the NNI binding pocket model of RT. The activity of HI-236 against RT-MDR was superior to that of other anti-HIV agents tested, in the following order, from high to low activity; HI-236 (IC50 5 nM), HI-240 (IC50 6 nM), trovirdine (IC50 20 nM), zidovudine (IC50 150 nM), MKC-442 (IC50 300 nM), delavirdine (IC50 400 nM) and nevirapine (IC50 5 microM).

[Selection of human phage antibodies against HAV and DNA sequence analysis]

OBJECTIVE

To obtain the anti-HAV antibodies.

METHODS

The antibody-capturing antigen strategy was used in panning antibody library with impure antigen. The HAV-binding activity and specificity of phage antibodies were assayed by sandwich ELISA and competitive inhibition ELISA.

RESULTS

Phage antibodies(Fab) against HAV were screened from a human immunoglobulin combinatorial library. Fd and light chain genes were sequenced. Comparison of the Fd gene and light chain gene with KABAT database showed that the heavy chain belonged to IgG1 subclass, and its variable region was derived from rearranged germ-line gene of DP88, D3-3 and JH5; while the light chain was a member of V kappa III family, the germ-line gene was DP kappa 22 and J kappa 4.

CONCLUSION

Phage antibodies against HAV were selected from the antibody library by using the antibody-capturing antigen strategy. The result also suggested that the antibody library was constructed successfully.

Intraventricular haemorrhage and its prognosis, prevention and treatment in term infants

The purpose of this study was to investigate the prognosis of intraventricular haemorrhage (IVH) in term infants and its prevention and treatment. The authors diagnosed IVH in full-term newborns by using computerized tomography (CT) or cranial ultrasonography (US). The results of CT or US were reviewed and the grade of haemorrhage was determined by an independent radiologist using Papile's criteria. All the infants were examined on the first day of their life by a paediatrician and judged to be full term. Survivors were examined between age 2 and 10 years at the Child Development Clinic by a Developmental Paediatrician using the Gesell scales and a standard neurologic examination. The results showed that three of 36 infants (8 per cent) died; complications of pregnancy were present in 17 mothers (47 per cent); nine women tested negative for platelet antigen 1 and their infants exhibited alloimmune thrombocytopenia. Age at diagnosis ranged from in utero to 28 days. Clinical presentation included feeding intolerance, irritability, jaundice, fever, and restlessness. Of the nine children with grade IV IVH, three died and six survivors were severely handicapped. Overall, 22 (67 per cent) of 33 survivors had no or mild handicap. The results of this study suggest that severity of haemorrhage was of prognostic value. Perinatal alloimmune thrombocytopenia turned out to be the single most important cause of severe haemorrhage and poor outcome. Identification and treatment of these infants must begin in utero if we are to prevent IVH and its complications in this group of patients.