Conquering influenza: recent advances in anti-influenza drug discovery

Morbidity and mortality associated with influenza virus infection have cut a wide swathe through medical history. Even with the development of killed virus vaccines, illness due to influenza virus infection continues to be a major health problem throughout the world. This may change over the next few years with the development of a new class of antiviral agents targeting the catalytic site of the viral neuraminidase enzyme. These agents have been demonstrated to be both efficacious and clinically beneficial. In addition, investigation into alternative anti-influenza targets continues. These include inhibitors of hemagglutinin-mediated functions, the viral polymerase and new inhibitors of M2 ion channel activity.

Disruption of mRad50 causes embryonic stem cell lethality, abnormal embryonic development, and sensitivity to ionizing radiation

The Mre11/Rad50 protein complex functions in diverse aspects of the cellular response to double-strand breaks (DSBs), including the detection of DNA damage, the activation of cell cycle checkpoints, and DSB repair. Whereas genetic analyses in Saccharomyces cerevisiae have provided insight regarding DSB repair functions of this highly conserved complex, the implication of the human complex in Nijmegen breakage syndrome reveals its role in cell cycle checkpoint functions. We established mRad50 mutant mice to examine the role of the mammalian Mre11/Rad50 protein complex in the DNA damage response. Early embryonic cells deficient in mRad50 are hypersensitive to ionizing radiation, consistent with a role for this complex in the repair of ionizing radiation-induced DSBs. However, the null mrad50 mutation is lethal in cultured embryonic stem cells and in early developing embryos, indicating that the mammalian Mre11/Rad50 protein complex mediates functions in normally growing cells that are essential for viability.

Computational methods for ultrasonic bone assessment

Ultrasound has been proposed as a means to noninvasively assess bone and, particularly, bone strength and fracture risk. Although there has been some success in this application, there is still much that is unknown regarding the propagation of ultrasound through bone. Because strength and fracture risk are a function of both bone mineral density and architectural structure, this study was carried out to examine how architecture and density interact in ultrasound propagation. Due to the difficulties inherent in obtaining fresh bone specimens and associated architectural and density features, simulation methods were used to explore the interactions of ultrasound with bone. A sample of calcaneal trabecular bone was scanned with micro-CT and subjected to morphological image processing (erosions and dilations) operations to obtain a total of 15 three-dimensional (3-D) data sets. Fifteen two-dimensional (2-D) slices obtained from the 3-D data sets were then analyzed to evaluate their respective architectures and densities. The architecture was characterized through the fabric feature, and the density was represented in terms of the bone volume fraction. Computer simulations of ultrasonic propagation through each of the 15 2-D bone slices were carried out, and the ultrasonic velocity and mean frequency of the received waveforms were evaluated. Results demonstrate that ultrasound propagation is affected by both density and architecture, although there was not a simple linear correlation between the relative degree of structural anisotropy with the ultrasound measurements. This study elucidates further aspects of propagation of ultrasound through bone, and demonstrates as well as the power of computational methods for ultrasound research in general and tissue and bone characterization in particular.

Molecular interactions of N-RAP, a nebulin-related protein of striated muscle myotendon junctions and intercalated disks

N-RAP is a recently discovered muscle-specific protein that is concentrated at the myotendon junctions in skeletal muscle and at the intercalated disks in cardiac muscle. The C-terminal half of N-RAP contains a region with sequence homology to nebulin, while a LIM domain is found at its N-terminus. N-RAP is hypothesized to perform an anchoring function, linking the terminal actin filaments of myofibrils to protein complexes located beneath the sarcolemma. We used a solid-phase assay to screen myofibrillar and junctional proteins for binding to several recombinant fragments of N-RAP, including the nebulin-like super repeat region (N-RAP-SR), the N-terminal half including the LIM domain (N-RAP-NH), and the region of N-RAP between the super repeat region and the LIM domain (N-RAP-IB). Actin is the only myofibrillar protein tested that exhibits specific binding to N-RAP, with high-affinity binding to N-RAP super repeats, and 10-fold weaker binding to N-RAP-IB. In contrast, myosin, isolated myosin heads, tropomyosin, and troponin exhibited no specific interaction with N-RAP domains. A recombinant fragment corresponding to the C-terminal one-fourth of vinculin also binds specifically to N-RAP super repeats, while no specific N-RAP binding activity was observed for other regions of the vinculin molecule. Finally, talin binds with high affinity to the LIM domain of N-RAP. These results support our hypothesis that N-RAP is part of a complex of proteins that anchors the terminal actin filaments of the myofibril to the membrane, and functions in transmitting tension from the myofibrils to the extracellular matrix.

Expression of p16 and CDK4 in oral premalignant lesions and oral squamous cell carcinomas: a semi-quantitative immunohistochemical study

The protein, p16, the product of cyclin-dependent kinase number 2 (CDKN2) gene, is one of the negative regulators of the cell cycle. CDK4, encoded by CDK4 gene, is the substrate of p16. We investigated the expression of p16 and CDK4 and their role in the progression of oral premalignant lesions (OPLs) and oral squamous cell carcinomas (OSCCs) in a Chinese cohort. A total of 74 samples were obtained from patients with hyperkeratosis (10), OPLs [30; mild (10), moderate (10) and severe (10) dysplastic lesions], OSCCs (15; 8 non-metastatic, 7 metastatic), and normal oral tissues (10), together with local lymph nodes (9) of patients with metastatic OSCCs. A labelled streptavidin biotin (LSAB) immunohistochemistry assay was performed and a semi-quantitative method was used to evaluate the staining intensity. The staining patterns of p16 and CDK4 were similar in all tissues and were located in both the nuclei and the cytoplasm. However, the antigen distribution characteristics and the degree of expression of both p16 and CDK4 varied at different developmental stages of the lesions. Hyperkeratotic and dysplastic lesions tended to display a progressively increasing degree of p16- and CDK4-positive nuclei as compared with normal tissues. Also, positive staining cytoplasm was highly evident in OSCCs with a very low nuclear staining (P<0.05). Forty-six of 56-, p16-positive cases were CDK4-positive, while only 6 were CDK4-positive but p16-negative, implying a high correlation between these parameters (r=0.813, P<0.001). This study indicates that the expression of p16 and CDK4 is intimately involved in the development of OPLs and OSCCs and the likely existence of a positive feedback loop between p16 and CDK4.

Cellular proteins bind to the poly(U) tract of the 3' untranslated region of hepatitis C virus RNA genome

UV cross-linking analyses were performed in an attempt to determine cellular protein-viral RNA interactions with the 3' untranslated region (3' UTR) of the hepatitis C virus RNA genome. Two cellular proteins, with estimated molecular masses of 58 kDa (p58) and 35 kDa (p35), respectively, were found to specifically bind to the 3' UTR. The p58 protein was determined to be the polypyrimidine tract-binding protein. In addition to binding to the conserved 98 nucleotides (nt) of the 3' UTR, p58 also binds to the poly(U) tract of the 3' UTR. The p35 protein was found to interact only with the poly(U) tract of the 3' UTR. These conclusions are supported by the following findings: (1) p58, and not p35, binds to the 3' end conserved 98 nt, (2) both p58 and p35 bind to a 3' UTR RNA with a deletion of the conserved 98 nt, (3) the 98-nt deletion mutant 3' UTR competed out both p58 and p35 binding, (4) a poly(U) homopolymer competed out both p58 and p35 binding, (5) a 3' UTR RNA with deletion of the poly(U) tract competed out only p58 binding but not p35 binding, and (6) an RNA containing the variable region of the 3' UTR with a deletion of both poly(U) tract and 98 nt failed to compete for binding of either p58 or p35. Interaction of these cellular proteins with the HCV 3' UTR is probably involved in regulation of translation and/or replication of the HCV RNA genome.

The effect of surface roughness on the stress adaptation of trabecular architecture around a cylindrical implant

The effect of implant-bone bonding and the effect of implant surface roughness on bone remodeling near the bone-implant interface were studied by using a surface remodeling theory and the boundary element method. The study has shown that implant attachment plays an important role in bone remodeling near the implant. It has been observed in animal experiments and in clinical situations that the remodeled trabecular bone architecture around a cylindrical implant could vary, on one hand, from a hub surrounding the implant with a set of external spokes to, on the other hand, a hubless situation in which a set of spokes attach directly to the implant. It is shown here that the difference in these structures may be attributed to differences in implant attachment. The results show that the bone with perfect bonding or roller boundary condition without a gap remodeled to a hubless spoke trabecular bone architecture. On the other hand, the roller boundary condition with a specified gap yielded a spoke trabecular architecture with a hub or ring surrounding the implant. These quantitative results mirror the experimental and clinical observations. It is concluded that the hub is a consequence of the gap and not a consequence of the lack of friction between the implant and the bone.

pH-dependent changes in photoaffinity labeling patterns of the H1 influenza virus hemagglutinin by using an inhibitor of viral fusion

The hemagglutinin (HA) protein undergoes a low-pH-induced conformational change in the acidic milieu of the endosome, resulting in fusion of viral and cellular membranes. A class of compounds that specifically interact with the HA protein of H1 and H2 subtype viruses and inhibit this conformational change was recently described (G. X. Luo et al., Virology 226:66-76, 1996, and J. Virol. 71:4062-4070, 1997). In this study, purified HA trimers (bromelain-cleaved HA [BHA]) are used to examine the properties and binding characteristics of these inhibitors. Compounds were able to inhibit the low-pH-induced change of isolated trimers, as detected by resistance to digestion with trypsin. Protection from digestion was extremely stable, as BHA-inhibitor complexes could be incubated for 24 h in low pH with almost no change in BHA structure. One inhibitor was prepared as a radiolabeled photoaffinity analog and used to probe for specific drug interactions with the HA protein. Analysis of BHA after photoaffinity analog binding and UV cross-linking revealed that the HA2 subunit of the HA was specifically radiolabeled. Cross-linking of the photoaffinity analog to BHA under neutral (native) pH conditions identified a stretch of amino acids within the alpha-helix of HA2 that interact with the inhibitor. Interestingly, cross-linking of the analog under acidic conditions identified a different region within the HA2 N terminus which interacts with the photoaffinity compound. These attachment sites help to delineate a potential binding pocket and suggest a model whereby the BHA is able to undergo a partial, reversible structural change in the presence of inhibitor compound.

A functional DNA binding domain is required for growth hormone-induced nuclear accumulation of Stat5B

The mechanisms regulating the cellular distribution of STAT family transcription factors remain poorly understood. To identify regions of Stat5B required for ligand-induced nuclear accumulation, we constructed a cDNA encoding green fluorescent protein (GFP) fused to the N terminus of Stat5B and performed site-directed mutagenesis. When co-expressed with growth hormone (GH) receptor in COS-7 cells, GFP-Stat5B is tyrosyl-phosphorylated, forms dimers, and binds DNA in response to GH in a manner indistinguishable from untagged Stat5B. In multiple cell types, laser scanning confocal imaging of GFP-Stat5B co-expressed with GH receptor shows that GFP-Stat5B undergoes a rapid, dramatic accumulation in the nucleus upon GH stimulation. We introduced alanine substitutions in several regions of Stat5B and assayed for GH-dependent nuclear localization. Only the mutation that prevented binding to DNA (466VVVI469) abrogated GH-stimulated nuclear localization. This mutant fusion protein is tyrosyl-phosphorylated and dimerizes in response to GH. These results suggest that either high affinity binding to DNA contributes to nuclear accumulation of Stat5B or that this region is crucial for two functions, namely accumulation of Stat5B in the nucleus and DNA binding. Thus, we have identified a mutant Stat5 defective in nuclear localization despite its ability to be tyrosyl-phosphorylated and to dimerize.

[Expression of CDK4 protein in oral carcinogenesis]

OBJECTIVE

To study the expression of cyclin dependent kinase 4(CDK4) protein in oral carcinogenesis.

METHODS

An LSAB immunohistochemistry method was applied to 80 cases of paraffine-fixed tissues to study the expression and distribution of CDK4 in normal oral mucosa, oral premalignant lesion (OPL) and oral squamous cell carcinoma.

RESULTS

The overexpression of CDK4 protein was observed in the progression of OPL. Meanwhile, a correlation analysis was applied to investigate the relationship between P16 and CDK4 expression, and the result showed that the coefficient of correlation was 0.813, which was statistically significant.

CONCLUSION

The overexpression of CDK4 is involved in the progression of OPL, and there is a positive feedback loop between CDK4 and P16.

[Analysis of rice leaf proteins induced by Magnaporthe grisae with capillary zone electrophoresis]

Intercellular and intracellular proteins which were extracted from rice seedling leaves induced by Magnaporthe grisae, as well as those of control, were analysed by capillary zone electrophoresis. Intercellular proteins were extracted with sterilized water, while intracellular proteins were extracted with acidic protein extraction buffer. Protein adsorption to capillary wall was suppressed by using linear polyacrylamide coated capillary (75 microns x 57 cm) instead of uncoated capillary. Separations were performed at 25 degrees C with a positive voltage of 20 kV. Samples were injected into the capillary by applying pressure (3.0 kPa) for 5 s. The running buffer consisted of 50 mmol/L phosphoric acid (pH 2.0), and detection was achieved at 200 nm with a diode array detector. Being compared with a control, a new kind of protein induced by Magnaporthe grisae was identified in rice leaf intracellular proteins with Grubbs method which is used to test outliers in mathematical statistics.

Relationship between plain radiographic patterns and three- dimensional trabecular architecture in the human calcaneus

The purpose of this study was to determine the relationship between three-dimensional (3D) trabecular structure and two-dimensional plain radiographic patterns. An in vitro cylinder of human calcaneal trabecular bone was three-dimensionally imaged by micro-CT using synchrotron radiation, at 33.4 micrometer resolution. The original 3D image was processed using 14 distinct sequences of morphologic operations, i.e., of dilations and erosions, to obtain a total of 15 3D models or images of calcaneal trabecular bone. These 15 models had distinct densities (volume fractions) and architectures. The 3D structure of each calcaneal model was assessed using mean intercept length (fabric), by averaging individual fabric measurements associated with each medial-lateral image slice, and determining the relative anisotropy, R(3D), of the structure. A summated pattern or plain radiograph was also computed from the 3D image data for each calcaneal model. Each summated pattern was then locally thresholded, and the resulting two-dimensional (2D) binary image analyzed using the same fabric analysis as used for the 3D data. The anisotropy of the 2D summated pattern was denoted by R(x-ray). The volume fractions of the 15 models ranged from 0.08 to 0.19 with a mean of 0. 14. The medial-lateral anisotropies, R(3D), ranged from 1.38 to 2.54 with a mean of 1.88. The anisotropy of the 2D summated patterns, R(x-ray), ranged from 1.35 to 2.18 with a mean of 1.71. The linear correlation of the 3D trabecular architecture, R(3D), with the radiographic trabecular architecture, R(x-ray), was 0.99 (p<0.0001). This study shows that the plain radiograph contains architectural information directly related to the underlying 3D structure. A well-controlled sequential reproducible plain radiograph may prove useful for monitoring changes in trabecular architecture in vivo and in identifying those individuals at increased risk of osteoporotic fracture.

A selenium-containing abzyme, the activity of which surpassed the level of native glutathione peroxidase

Using two different glutathione derivatives as hapten, we have prepared two abzymes, which display glutathione peroxidase (GPX) activity. Their GPX activities are 0.2 and 1.6 times that of natural GPX from rabbit liver, respectively. Selenium content analysis indicates that the activity difference between the two abzymes is possibly attributed to the conformation difference of the abzymes.

A General Formulation for Unidimensional Unfolding and Pairwise Preference Models: Making Explicit the Latitude of Acceptance

Probabilistic unfolding models for direct responses of persons to statements are characterised by single peaked response functions. The range in which a positive response is most likely is termed the latitude of acceptance, a well known but little researched concept in the modelling of attitude measurement. This paper derives a general form for probabilistic unfolding models in which a natural parameter characterises the latitude of acceptance. It is shown that a number of already known models for unfolding can be reexpressed in this general form with different operational functions and that, in doing so, the implied latitude of acceptance for these models is identified. It is also shown that other unfolding models can be generated readily by specifying the operational function of the general form. A general form for pairwise preference models is also presented. A discussion on the latitude of acceptance parameter as a scale parameter is also provided. Copyright 1998 Academic Press.

[The inhibitory effect of wild-type p53 gene on the growth and proliferation of lingual squamous cell carcinoma cell line Tca8113 in nude mice]

The aim of this study was to observe the growth and proliferation of the Tca8113 cell line in nude mice after the wild-type p53 gene has been transfered by electroporation. The experiment consisted of four groups: the wild-type p53 gene, blank control plasmid, the mutant p53 gene, and blank control into which no gene was transfered. After the gene was transfected, the cells were planted into 16 nude mice respectively. When the tumor formed, the nude mice were killed and the tumors were studied by regular pathology, stereology and immunohistochemistry. The results showed that in the wild-type p53 gene group, the tumors weighed less heavy, the pathological mitosis decreased markedly, and stereologically, the ratio of the area of necrosis to the total tumorous area was smaller. Similarly, the count of the proliferation cell nuclear antigen in non-necrotic area went down. The above findings were statistically significant (P < 0.05). These indicate that when the tumor cells re-obtain the well functional exogenic wild-type p53 gene, the gene expresses and produces new negative cell-growth regulator to replace the abnormal regulation system partially, then the growth and proliferation of the tumors can be inhibited; therefore, it is suggested that the p53 tumor suppressor gene may possibly be used as a gene therapy agent to treat oral squamous cell carcinoma.

[Studies on the biological and clinical characteristics of acquired pneumonia caused by K. planticola]

OBJECTIVE

To investigate the characteristics of biological, and clinical epidemiology of acquired pneumonia caused by a new type of Klebsiella, K. planticola.

METHOD

9 strains of K. planticola were isolated from respiratory samples of patients, in vitro, biological and serologic identification were done, in vivo, infected animal models were also evaluated. Clinical epidemiological inquiries were also performed.

RESULT

9 strains' biological features were different from those of the other Klebsiella. The 9 patients' ages were over forty and the primary disease was the third type tuberculosis of lungs. Using of antituberculosis drugs for long term as well as penicillins might be the predisposing factors, corticosteroids were used in 3 of the 9 patients, Combined infection with other pathogens in addition to K. planticola occurred in 8 patients, in 7/8, Candida albicans was identified. Drug sensitive tests show that all of them were resistant to penicillins and sensitive to the second and third generation cephalosporins.

CONCLUSION

The new strain of Klebsiella was studied and this information will be useful for diagnosing and treating K. platicola.

Prolactin and growth hormone signal transduction in lymphohaemopoietic cells

The peptide hormones, prolactin (PRL) and growth hormone (GH), are known to regulate numerous target tissues. Among such targets are cells of the immune system, including T cells, B cells, macrophages and natural killer cells. We have cloned a panel of PRL- and GH-inducible T cell genes for use in studies to understand how these hormones through the expression of these genes modulate the biology of immune function cells. This article focuses on the signalling pathways emanating from the PRL receptor (PRL-R) and GH receptor (GH-R), and the expression of PRL-inducible target genes.

Chromosomal transposition of a Tc1/mariner-like element in mouse embryonic stem cells

Mouse has become an increasingly important organism for modeling human diseases and for determining gene function in a mammalian context. Unfortunately, transposon-tagged mutagenesis, one of the most valuable tools for functional genomics, still is not available in this organism. On the other hand, it has long been speculated that members of the Tc1/mariner-like elements may be less dependent on host factors and, hence, can be introduced into heterologous organisms. However, this prediction has not been realized in mice. We report here the chromosomal transposition of the Sleeping Beauty (SB) element in mouse embryonic stem cells, providing evidence that it can be used as an in vivo mutagen in mice.

Cloning and expression of murine CYP2Cs and their ability to metabolize arachidonic acid

Five murine cytochrome P450 (CYP) 2C cDNAs were cloned and characterized, including four new members of this subfamily: CYP2C37, CYP2C38, CYP2C39, and CYP2C40. The cDNAs ranged from 1716 to 1812 bp in length and encoded polypeptides of 490 amino acid residues except for CYP2C40, which contained an additional glutamic acid residue at the carboxyl terminus. The amino acid identity of the murine CYP2Cs ranged from 69 to 92%, while the overall amino acid identity was 60%; however, within the six putative substrate recognition sites the identity was only 25 to 41%, suggesting possible differences in substrate specificity and product profiles. The CYP2C cDNAs were expressed in Escherichia coli following modification of the N-terminus. All five recombinant CYP2Cs metabolized arachidonic acid, but with different metabolic profiles and catalytic rates. Based on coelution with authentic standards on reverse-phase HPLC, themajor metabolites were tentatively identified asfollows: CYP2C29 and CYP2C39 produced 14, 15-cis-epoxyeicosatrienoic acid (EET); CYP2C37 produced 12-hydroxyeicosatetraenoic acid (HETE); CYP2C38 produced 11,12-EET; and CYP2C40 produced an unidentified metabolite that coeluted with 16-,17-, and 18-HETEs. The turnover numbers for CYP2C29, CYP2C37, CYP2C38, CYP2C39, and CYP2C40 were 0.34, 1.12, 5.15, 0.51, and 0.15 nmol/nmol/min, respectively. Reverse transcriptase-polymerase chain reaction demonstrated the presence of CYP2C29 mRNA in liver as well as in extrahepatic tissues including brain, kidney, lung, heart, and intestine. CYP2C38 and CYP2C40 were found in liver, brain, kidney, and intestine, with trace amounts in lung and heart, while CYP2C37 and CYP2C39 appeared to be liver specific.

[TLC identification of Flos Carthami]

In 137 kinds of medicinal meterials included 21 kinds of traditional Chinese patent medicines in Pharmacopoeia such as Qili Powder, character identified constituent of Flos Carthami was found by TLC, and was successful to be used to identification of Flos Carthami in 9 kinds of traditional Chinese patent meicines such as Qili Powder.

Effects of vitamin C on myocardial mitochondrial function and ATP content in hypoxic rats

AIM

To observe the effects of large dose of vitamin C (Vc) on myocardial mitochondrial function, ATP content, and myocardial structure in acute and chronic hypoxic rats.

METHODS

Rats were exposed to a simulated altitude 4000 m (barometric pressure = 43 kPa) for 3 and 30 d. Vc (0.75 g.kg-1.d-1) was injected i.p. The heart mitochondrial respiratory function were determined by Clark-type O2 electrode; mitochondrial membrane fluidity (MMF) were assayed through fluorescence polarizative method; the contents of ATP, ADP, and AMP in myocardial tissue were measured with HPLC.

RESULTS

After administration of Vc, the ATP content was increased from 35 +/- 3 mg.g-1 to 53 +/- 3 mg.g-1 in acute hypoxic rats (P < 0.01), from 42 +/- 4 mg.g-1 to 48 +/- 3 mg.g-1 in chronic hypoxic rats (P < 0.01); Pa, O2 was increased from 7.2 +/- 1.4 kPa to 9.5 +/- 1.2 kPa in acute hypoxic rats (P < 0.01); mitochondrial respiratory control rate (RCR) was increased from 2.1 +/- 0.6 to 4.7 +/- 0.5 in acute hypoxic rats (P < 0.01), and from 3.3 +/- 0.7 to 4.5 +/- 0.6 in chronic hypoxic rats (P < 0.01); MMF was increased in acute and chronic hypoxic rats (P < 0.05); the degree of myocardial necrosis in vitamin C preventive rats was attenuated as compared with those of acute hypoxic rats.

CONCLUSION

Vc is effective on improving myocardial energy metabolism and protecting against myocardial structural injury in hypoxic rats.

Biochemical characterization of selenium-containing catalytic antibody as a cytosolic glutathione peroxidase mimic

A selenium-containing catalytic antibody (Se-4A4), prepared by converting reactive serine residues of a monoclonal antibody (4A4) raised against a GSH derivative into selenocysteines, acts as a mimic of cytosolic glutathione peroxidase (cGPX). To clarify the mechanism of action of this catalytic antibody, detailed studies on kinetic behaviour and biological activity were carried out. A rate of acceleration (kcat/Km/kuncat) 10(7)-fold that of the uncatalytic reaction is observed. Under similar conditions, the turnover number (kcat) of Se-4A4 is 42% of that of the natural rabbit liver cGPX. The Se-4A4 reaction involves a Ping Pong mechanism, which is the same as that of the natural cGPX. The selenocysteine residue is located in the binding site of the antibody and is shown to be crucial for this activity. Of the thiol compounds tested, only GSH is able to serve as substrate for Se-4A4. It was demonstrated, using the free-radical-damage system (hypoxanthine/xanthine oxidase) of cardiac mitochondria, that Se-4A4 can protect mitochondria from free-radical damage at least 10(4)-fold more effectively than the natural cGPX.

The study of local electrophysiology in macular diseases

PURPOSES

To observe the features and clinical utility values of local electroretinogram (LERG) and local visual evoked potentials (LVEP) in macular diseases.

METHODS

The spot stimuli were obtained by changing the shutters with different sizes of hole at the posterior of Ganzfeld ball. The recording electrode for LERG was made with the filament of platinum as blepharophthalmostat like. The LERG and LVEP were simultaneously recorded in macular diseases.

RESULTS

The exudative AMD, Stargardt's disease, central serous chorioretinopathy and idiopathic macular hole had seriously decreased amplitudes of LERG and higher abnormal rates, comparing with atrophic AMD and idiopathic preretinal membranes in the region of 2.5 degrees and 5 degrees at macula. The abnormal rates in these diseases were higher for LERG than for LVEP.

CONCLUSION

The LERG can objectively measure the variation of macular function in maculopathies. The sensitivities of LVEP are lower than those of LERG for macular diseases.

Lactogenic hormone signal transduction

The peptide hormone prolactin (PRL) is known to regulate numerous target tissues. Among the less well-known targets are cells of the immune system, including T cells, B cells, and macrophages. Our laboratory has cloned a panel of PRL-inducible T-cell activation genes for use in studies investigating how PRL modulates the biology of cells of the immune system. This article focuses on two such PRL-inducible genes. One is a transcription factor called interferon regulatory factor-1, whose expression is regulated by signaling molecules along the PRL-inducible JAK/Stat signaling pathway. These signaling molecules include Stat1 and CBP as positive mediators and, unexpectedly, Stat5b as a negative mediator. A second PRL-inducible gene is c15/RNUDC, a novel nuclear movement protein, which may provide a link between PRL signaling and signaling via the lipid second messenger, platelet activating factor.

[Lecture of principles and applications of capillary electrophoresis (VI) Applications of CE in DNA analysis, carbohydrate analysis and capillary ion analysis]

A review with 87 references on the application and new development of CE in DNA analysis, carbohydrate analysis and capillary ion analysis is presented. The DNA analysis included determinations of nucleotide, nucleoside and bases by CZE and MECC. It also includes dsDNA, PCR products analysis, purity control of oligonucleotide and DNA sequencing by CGE. Sometimes LIF detector needs to be introduced into DNA analysis. The carbohydrate analysis includes the methods for chemical derivatization and direct determination of carbohydrates by different CE modes. The capillary ion analysis includes the principle and determination of anions and cations.

[Simultaneous analysis of organic acids and inorganic anions in alcoholic drink (dongjiu) by ion chromatography]

An ion chromatographic method for the simultaneous analysis of organic acids and inorganic anions in Dongjiu (alcoholic drink) was developed. An anion exchange column Shim-pack IC-A1(100 mm x 4.6 mm) was used. In non-suppressed anion exchange chromatography, potassium hydrogen phthalate (KHPh) is used as eluent most widely. However, there are several problems in this eluent for the analysis of Dongjiu (alcoholic drink) sample, such as the influence of a negative peak to the determination of acetic acid, ascorbic acid and lactic acid, the non-resolution of ascorbic acid, and lactic acid, and part overlapping of the peak of acetic acid with water peak. In order to solve these problems, a mixed eluent of 0.50 mmol/L KHPh and 0.25 mmol/L phthalic acid(H2Ph) was used in this work. The main organic acids and inorganic anions in Dongjiu were separated without interference peaks. The detection limits obtained by using the mixed eluent were 0.05-0.13 mg/L, several times lower than those obtained by using single KHPh eluent. This method, being without pretreatment, is simple to operate.

[The testing of local electroretinogram in macular diseases]

OBJECTIVES

To record the local electroretinogram (LERG) in macular diseases, and define the using value of LERG in macular diseases.

METHODS

The LERGs of five kinds of maculopathies were recorded with a spot light stimulator at 2.5, 5.0, 7.5 degrees of macular region.

RESULTS

(1) The amplitudes of LERG at the three regions in Stargardt's disease, wet form age-related macular degeneration (AMD), central serous chorioretinopathy, and idiopathic macular hole were significantly lowered in comparison with the controls (P < 0.01). In the meanwhile, these diseases also showed high abnormal rates. While in dry form AMD and epiretinal membrane, the amplitudes of LERG had no significant changes (P > 0.05). (2) The abnormal rates of LERG were related to the stimulated area. In the three tested areas, the highest abnormal rates occurred at 2.5 degrees.

CONCLUSIONS

There are mean differences in macular electrical activities in these maculopathies. LERG is an effective method of electrophysiology for testing macular function.

Discovery and evaluation of a series of 3-acylindole imidazopyridine platelet-activating factor antagonists

Studies conducted with the goal of discovering a second-generation platelet-activating factor (PAF) antagonist have identified a novel class of potent and orally active antagonists which have high aqueous solubility and long duration of action in animal models. The compounds arose from the combination of the lipophilic indole portion of Abbott's first-generation PAF antagonist ABT-299 (2) with the methylimidazopyridine heterocycle moiety of British Biotechnology's BB-882 (1) and possess the positive attributes of both of these clinical candidates. Structure-activity relationship (SAR) studies indicated that modification of the indole and benzoyl spacer of lead compound 7b gave analogues that were more potent, longer-lived, and bioavailable and resulted in the identification of 1-(N, N-dimethylcarbamoyl)-4-ethynyl-3-[3-fluoro-4-[(1H-2-methylimidazo[4,5-c] pyrid-1-yl)methyl]benzoyl]indole hydrochloride (ABT-491, 22 m.HCl) which has been evaluated extensively and is currently in clinical development.

[Effect of interleukin-1, interleukin-6 on the intercellular communication of rat thyroid FRTL-5 cells]

We observed the effects of thyrotropin (TSH), interleukin (IL)-1 beta and IL-6 on the intercellular communication of FRTL-5 cells with fluorenscence redistribution after photobleaching (FRAP) analysis. FRTL-5 cells were cultured and exposed to the different concentrations of TSH, IL-1 beta and IL-6 for 12 hours. The mean fluorescence recovery rate (MFRR, %/min) of the cells labelled with carboxyfluocein diacetate (CFDA) after photobleaching was measured with laser scanning cytometry. The MFRR (%/min) of the cells after exposure to TSH was 0.445 +/- 0.033 at the control group, 0.679 +/- 0.054 at the group of 0.1 U/L, 0.950 +/- 0.073 at the group of 1 U/L, and 0.799 +/- 0.082 at the group of 5 U/L, respectively (F = 11.44, P < 0.01). The indicated that TSH could enhance the intercellular communication of FRTL-5 cells. The MFRR after exposure to IL-1 beta was 0.564 +/- 0.032 at the control group, 0.485 +/- 0.042 at the group of 10(3) U/L, 0.445 +/- 0.043 at the group of 10(4) U/L and 0.405 +/- 0.029 at the group of 10(5) U/L, respectively (F = 3.58, P < 0.01). The suggested that IL-1 beta could inhibite the intercellular communication of FRTL-5 cells. IL-6 had no obvious effect on the intercellular communication of FRTL-5 cells.

[Effect of hypoxia on maximal myocardial blood flow in right ventricle]

In order to study the changes of coronary reserve capacity, the effects of hypoxia on hemodynamics and maximal myocardial blood flow in right ventricle were observed. Rats wre divided into 3 groups:normoxic group (control), acute hypoxic group and chronic hypoxic group. Maxmimal myocardial blood flow in the right ventricle was measured with 99 m Tc radiolabelled from RBC during adenosine infusion. The results showed that cardiac output, PaO2 and oxygen delivery were decreased during acute hypoxia, but myocardial blood flow in right ventricle was increased, as compared with the control group. There were no significant change of maximal myocardial blood flow in the right ventricle in acute hypoxic rats. Hematocrit and blood viscosity at different shear rate and RV weight index were augmented, whereas oxygen delivery and myocardial blood flow became normal during chronic hypoxia. Maximal blood flow in RV was significantly decreased whereas arterial wall thickness and collagen in arterial adventitia were increased in chronic hypoxic rats. The above results suggest that the decreased coronary reserve might beresulted from the increasedblood viscosity, arterial wall thickness and collagen in arterial adventitia and right ventricular hypertrophy.

[Lecture of principles and applications of capillary electrophoresis (V) Applications of capillary electrophoresis in pharmaceutical analysis and clinical chemistry]

A review with 68 references is presented on the application and new developments of CE in pharmaceutical analysis, clinical chemistry and single cell analysis etc. The pharmaceutical analysis includes main component assay, determination of drug-related impurities, stoichiometric determination and quantitative determinations. The Chinese herb analysis includes determinations of main components and prescriptions of Chinese herb. The chiral separation includes separation mechanism and some new chiral selectors. The application of CE in clinical chemistry includes determinations of serum and protein, monitoring of drug metabolism, etc. Single cell analysis includes determinations of component in neurocells and human erythrocyte.

[Selective extraction of organotin from biological sample by supercritical fluid extraction]

The preliminary separation and concentration of organotin compounds from the matrix of biological samples is necessary, due to the very low content of organotin and the fat included in samples will largely interfere the analysis of organotins. In this work, supercritical fluid extraction (SFE) for the preliminary separation and concentration of organotin has been studied. Pure CO2 was used as mobile phase. The extractives can be used to supercritical fluid chromatographic (SFC) analysis of organotins. The model sample was prepared by adding diphenyltin (DPT) to soya powder. The effects of the pressure and temperature on SFE were investigated. A small amount of fat was also extracted together with organotins. Extract was injected into SFC system, in which a Kapcell Pak ODS column was used for separation of organotin and fat. The effect of pressure on the extraction percentage of DPT and fat was investigated at 40 degrees C. At lower pressure (10-15 MPa), a maximum extraction efficiency (63%) was attained for DPT, while the fat is extracted only 28.3%. The increase in temperature is advantageous for the selective extraction of DPT. However, the extraction efficiency of DPT decreased as the extraction temperature was increased. When a lower pressure (10 MPa) and a higher temperature (50 degrees C) were used, the organotin (DPT) was extracted up to a maximum (59.9%) within 30 min, while fat was extracted only 4.9%.

Transcriptional inhibition by Stat5. Differential activities at growth-related versus differentiation-specific promoters

Prolactin (PRL) induces transcriptional activation of not only growth-related genes such as interferon regulatory factor-1 (IRF-1) but also differentiation-specific genes such as beta-casein through a signaling cascade consisting of Janus kinases and Stat (signal transducer and activator of transcription) factors. To understand better the role of Stats in PRL signaling, we cloned rat Stat5b from a PRL-responsive T cell line Nb2. A Stat5b-specific peptide antibody was generated. In PRL receptor reconstituted COS cells cotransfected with Stat5b or Stat5a, both Stat5 proteins become tyrosine phosphorylated and bind to the IRF-1 GAS (interferon-gamma activation sequence) element in a PRL-inducible manner. Unexpectedly, both Stat5b and Stat5a inhibit PRL induction of the IRF-1 promoter, but they mediate PRL stimulation of the beta-casein promoter. Stat5-mediated inhibition was observed only at the native IRF-1 promoter and not at the isolated IRF-1 GAS element linked to a heterologous thymidine kinase promoter. Mutational analyses showed that the DNA binding activity of Stat5b is not required, but the carboxyl-terminal transactivation domain is essential for Stat5b to inhibit PRL induction of the IRF-1 promoter. These results suggest that Stat5b mediates inhibition via protein-protein interactions. In contrast, both DNA binding and transactivation domains of Stat5b are required to mediate PRL induction of the beta-casein promoter. Furthermore, a carboxyl-terminal truncated dominant negative Stat5b can reverse Stat5b inhibition at the IRF-1 promoter. These studies suggest that Stat proteins can act as not only positive but also negative regulators of gene transcription. Further, Stat5 can modulate gene expression without binding to DNA but via protein-protein interactions.

Mapping of the gene (NRAP) encoding N-RAP in the mouse and human genomes

N-RAP is a nebulin-related actin-binding protein found at the myotendon junction in skeletal muscle and at the intercalated disks in cardiac muscle. We mapped the NRAP gene to mouse chromosome 19 using interspecific crosses and to human chromosome 10 using radiation hybrid panels. Comparative analysis of the mouse and human genomes indicates that the NRAP gene is located in regions of conserved synteny between the two species.

Inhibition of influenza viral polymerases by minimal viral RNA decoys

All gene segments of influenza virus share a common feature at their respective termini. Both the 5'- and 3'-terminal sequences are highly conserved and possess partial inverted complementarity. This allows for the formation of a double-stranded duplex, which plays a major role in transcription, replication and packaging of the viral genome. In vitro studies have shown that the viral polymerase binds to short RNA molecules containing these termini. In this study, attempts were made to test whether mini-RNA decoys containing either or both termini can inhibit the activity of the viral polymerase in vivo. RNA molecules containing either the 5' or the 3' noncoding sequences were unable to inhibit NS-CAT RNA replication, while mini-RNA decoys consisting of both the 5' and 3' noncoding sequences of vRNA or cRNA were able to efficiently inhibit the activity of the viral polymerases expressed from vaccinia virus vectors.

Growth hormone-induced tyrosyl phosphorylation and deoxyribonucleic acid binding activity of Stat5A and Stat5B

GH is known to activate JAK2 tyrosine kinase and members of the Stat family of transcription factors, including Stats 1, 3, and 5. The recent observation that at least two Stat5 proteins (Stat5A and Stat5B) exist in mouse and human, raises the question of whether GH activates both Stat5A and Stat5B and, if so, whether the requirements for activation are the same. An initial report investigating this issue demonstrated GH-dependent activation of Stat5A but not Stat5B. In this paper, we demonstrate (in COS cells expressing rat GH receptor (rGHR) and either Stat5A or Stat5B, 3T3-F442A fibroblasts, and CHO cells expressing rGHR) that GH induces tyrosyl phosphorylation of both Stat5A and Stat5B. Similar time courses of phosphorylation were observed for the two proteins. Interestingly, the pattern of observed bands differs for the two forms of Stat5. Two closely migrating Stat5A bands can be detected in cells treated with or without GH. Both of these bands become tyrosyl phosphorylated in response to GH. Three species of Stat5B are observed in untreated cells. An additional, more slowly migrating Stat5B band, appears upon treatment with GH. The three more slower migrating Stat5B bands observed in response to GH contain phosphorylated tyrosyl residues. We further demonstrate that GH induces binding of Stat5A and Stat5B, as well as Stat1, to the GAS-like element in the beta-casein promoter. We and others have demonstrated previously that specific regions of GHR are required for GH-dependent activation of what is here identified as Stat5B. To gain insight into the mechanism by which GH promotes tyrosyl phosphorylation of Stat5A, GH-dependent tyrosyl phosphorylation of Stat5A was examined in CHO cells expressing truncated and mutated rGHR. The results indicate that Stat5A and Stat5B require the same regions of rGHR for maximal activation by GH: the C-terminal half of the cytoplasmic domain; tyrosines 333 and/or 338 in the N-terminal half of the cytoplasmic domain; and the regions required for JAK2 activation. To dissect further the mechanism by which GH activates Stat5A and B, the requirement for JAK2 in GH-dependent Stat5 tyrosyl phosphorylation was assessed using JAK2-deficient cells expressing GHR (gamma2A-GHR) and the wild-type parental cell line expressing GHR (2C4-GHR). GH-induced tyrosyl phosphorylation of Stat5B in 2C4-GHR cells but not in the JAK2 deficient, gamma2A-GHR cells, indicating that JAK2 is required for GH-dependent tyrosyl phosphorylation of Stat5B. Western blotting revealed that Stat5A is not expressed in this cell type. Taken together, these findings suggest that: 1) GH activates both Stat5A and Stat5B in several cell types; 2) the pattern of bands observed differs for Stat5A and Stat5B; 3) GH-dependent tyrosyl phosphorylation of Stat5A requires specific regions of GHR, and these requirements are the same as for Stat5B; and 4) JAK2 kinase is required for GH-dependent tyrosyl phosphorylation of Stat5B and, most likely, Stat5A.

[Local electroretinogram and pattern visual evoked potential in maculopathies]

OBJECTIVES

To observe the changes of local electroretinogram (LERG) and pattern visual evoked potential (PVEP) in maculopathies and to evaluate the value of both LERG and PVEP in clinical application.

METHODS

LERGs at 5 degrees, 10 degrees and 15 degrees macular region were recorded from 27 normal subjects (54 eyes). The LERG and PVEP were recorded from 25 patients (35 eyes) with maculopathies.

RESULTS

In the patients with maculopathies, the amplitudes of LERG a wave and b wave at 5 degrees, 10 degrees and 15 degrees macular region were significantly lowered (P < 0.01), the mean value of P1 latency was prolonged and that of N1-P1 amplitude of VEP was lowered at 36.5', 73' and 146' in the comparison with the control group. In approximately the same stimulated area (15 degrees LERG and 14.8 degrees x 19.0 degrees PVEP), the abnormal rate of LERG was 62.2%, and the abnormal rates of PVEPs were 48.5% (146'), 54.5% (73') and 48.5% (36.5') respectively, no significant difference in the abnormal rate between LERG and each value of PVEP (P > 0.05) being found.

CONCLUSION

The abnormal rates of LERG and PVEP in maculopathies are close. Because LERG is not influenced by visual pathway diseases and visual acuity, LERG is more effective than PVEP and is a direct way in measuring macular function.

Molecular mechanism underlying the action of a novel fusion inhibitor of influenza A virus

In the initial stages of influenza virus infection, the hemagglutinin (HA) protein of influenza virus mediates both adsorption and penetration of the virus into the host cell. Recently, we identified and characterized BMY-27709 as an inhibitor of the H1 and H2 subtypes of influenza A virus that specifically inhibits the HA function necessary for virus-cell membrane fusion (G.-X. Luo, R. Colonno, and M. Krystal, Virology 226:66-76, 1996). Studies presented herein show that the inhibition is mediated through specific interaction with the HA protein. This binding represses the low-pH-induced conformational change of the HA protein which is a prerequisite for membrane fusion. In an attempt to define the binding pocket within the HA molecule, a number of drug-resistant viruses have been isolated and characterized. Sequence analyses of the HA gene of these drug-resistant viruses mapped amino acid changes responsible for drug resistance to a region located near the amino terminus of HA2. In addition, we have identified inactive analogs of BMY-27709 which are able to compete out the inhibitory activity of BMY-27709. This finding suggests that inhibition of the HA-mediated membrane fusion by this class of compounds is not solely the result of binding within the HA molecule but requires specific interactions.

[High performance liquid chromatographic analysis of organic acids in foods]

Because of the speed, selectivity, reliability, and simple sample preparation high performance liquid chromatography (HPLC) is the preferred method for simultaneous separation and determination of organic acids in foods. Ion exchange chromatography, ion exclusion chromtography and reversed phase HPLC are the most common chromatographic modes for analysis of organic acids in foods. The development and application of the three chromatographic modes are reviewed with 54 references. Ion exchange chromatography is most satisfactory for analysis of organic acids in foods, because organic acids are not interfered by other organic compounds, and inorganic anions in foods are determined simultaneously with organic acids.

Pharmacology of ABT-491, a highly potent platelet-activating factor receptor antagonist

ABT-491 (4-ethynyl-N, N-dimethyl-3-[3-fluoro-4-[(2-methyl-1H-imidazo-[4,5-c]pyridin-1-yl)methy l]benzoyl]-1H- indole-1-carboxamide hydrochloride) is a novel PAF (platelet-activating factor) receptor antagonist with a K(i) for inhibiting PAF binding to human platelets of 0.6 nM. Binding kinetics of ABT-491 to the PAF receptor is consistent with a relatively slow off-rate of the antagonist when compared to PAF. Inhibition of PAF binding is selective and is correlated with functional antagonism of PAF-mediated cellular responses (Ca2+ mobilization, priming, and degranulation). Administration of ABT-491 in vivo leads to potent inhibition of PAF-induced inflammatory responses (increased vascular permeability, hypotension, and edema) and PAF-induced lethality. Oral potency (ED50) was between 0.03 and 0.4 mg/kg in rat, mouse, and guinea-pig. When administered intravenously in these species, ABT-491 exhibited ED50 values between 0.005 and 0.016 mg/kg. An oral dose of 0.5 mg/kg in rat provided > 50% protection for 8 h against cutaneous PAF challenge. ABT-491 administered orally was also effective in inhibiting lipopolysaccharide-induced hypotension (ED50 = 0.04 mg/kg), gastrointestinal damage (0.05 mg/kg, 79% inhibition), and lethality (1 mg/kg, 85% vs. 57% survival). The potency of this novel antagonist suggests that ABT-491 will be useful in the treatment of PAF-mediated diseases.

Spontaneous calcification of arteries and cartilage in mice lacking matrix GLA protein

Calcification of the extracellular matrix (ECM) can be physiological or pathological. Physiological calcification occurs in bone when the soft ECM is converted into a rigid material capable of sustaining mechanical force; pathological calcification can occur in arteries and cartilage and other soft tissues. No molecular determinant regulating ECM calcification has yet been identified. A candidate molecule is matrix GLA protein (Mgp), a mineral-binding ECM protein synthesized by vascular smooth-muscle cells and chondrocytes, two cell types that produce an uncalcified ECM. Mice that lack Mgp develop to term but die within two months as a result of arterial calcification which leads to blood-vessel rupture. Chondrocytes that elaborate a typical cartilage matrix can be seen in the affected arteries. Mgp-deficient mice additionally exhibit inappropriate calcification of various cartilages, including the growth plate, which eventually leads to short stature, osteopenia and fractures. These results indicate that ECM calcification must be actively inhibited in soft tissues. To our knowledge, Mgp is the first inhibitor of calcification of arteries and cartilage to be characterized in vivo.

[Study on separating characteristics in capillary reversed-phase electrochromatography]

Capillary Electrochromatography (CEC) driven by electroosmotic flow is a new technique using fused silica capillaries packed with HPLC-type stationary phase. The analytes are separated by normal chromatographic partition between a mobile phase and a stationary phase. By using electroosmotic flow driving mobile phase, CEC promises theoretical plate efficiencies for HPLC. In this paper, some separating characteristics in capillary electrochromatography were studied by carrying out the separation of some neutral compounds on capillary column with 75microm i.d. x 30cm/37cm packed with ODS particles (3microm). The mobile phase was acetonitrile and water, which contains certain concentration of electrolyte. Samples were injected electrokinetically into the separating column. On-line UV detector was used. The Joule heating effect in packed CEC was lower than that in CZE, and a good linear relationship between the elecrtoosmotic flow (EOF) velocity and applied voltage was obtained as shown in Fig. 1. The influence of electrolyte and acetonitrile concentrations on the electroosmotic flow was studied, as shown in Fig. 2 and 5. The EOF was monitored by using thiourea as a marker. The EOF will decrease when the electrolyte concentration increases. The higher the acetonitrile concentration was, the lower the EOF was. The effect of linear velocity on column efficiencies was also investigated. The column effeciencies less than 2. 0 reduced plate height were obtained. The highest efficiency obtained in this work was 236000 plate per meter for a retained solute, benzene. It was found that the concentrations of acetonitrile and electrolyte were important experimental variables in performance of capillary electrochromatography.

Purification and characterization of bimodular and trimodular derivatives of the erythromycin polyketide synthase

Modular polyketide synthases (PKSs), such as the 6-deoxyerythronolide B synthase (DEBS), catalyze the biosynthesis of structurally complex and medicinally important natural products. DEBS is a dimeric protein complex that consists of three large multidomain polypeptide chains, DEBS 1, DEBS 2, and DEBS 3. In turn, each polypeptide includes two modules, where one module is responsible for a single round of condensation and associated reduction reactions. A hybrid protein comprised of the first two modules of DEBS fused to a thioesterase domain (DEBS 1 + TE) was purified to homogeneity in a fully active form (Kcat = 4.8 min-1). Synthesis of the anticipated triketide lactone required the presence of (2RS)-methylmalonyl-CoA and NADPH. When available, propionyl-CoA is the preferred source of primer units. However, in its absence the enzyme can derive primer units via decarboxylation of a methylmalonyl extender. The two subunits of an engineered trimodular derivative of DEBS, DEBS 1 and module 3 of DEBS 2 linked to the TE domain (module 3 + TE), were also individually purified and reconstituted to produce the expected tetraketide lactone in vitro (Kcat = 0.23 min-1). The considerably lower specific activity of this trimodular PKS relative to its bimodular counterpart presumably reflects inefficient association between DEBS 1 and module 3 + TE. As expected, module 3 + TE could be efficiently cross-linked as a homodimer. In contrast, no cross-links were detectable between modules 2 and 3, even though biosynthesis of the tetraketide requires transient interactions to occur between these two modules. Since module 3 only contains the minimal set of active sites required in a module (a ketosynthase, an acyltransferase, and an acyl carrier protein domain) and is the first active unimodular protein to be purified to homogeneity, it represents an attractive target for future biophysical and structural studies.

[Evaluation of capillary chromatographic columns packed by electrokinetic packing method]

In this paper, a method for electrokinetic packing capillary columns is reported. A higher column effeciency was obtained by performing electrochromatography on electrokinetic packing columns. The highest column efficiency in number of theoretical plate per meter was more than 200000, corresponding to reduced plate height less than 2. The reproducibilities of the same column in different intervals and different columns prepared from the same or different batches were compared. The relative standard deviations of the number of theoretical plate and retention time were less than 10% and 8%, respectively. The results indicated that high column efficiency and good reproducibility can be obtained on these new capillary packed columns.

6-deoxyerythronolide B synthase 1 is specifically acylated by a diketide intermediate at the beta-ketoacyl-acyl carrier protein synthase domain of module 2

We have used 6-deoxyerythronolide B synthase (DEBS) as a model system to investigate molecular recognition by a modular polyketide synthase (PKS). DEBS consists of three proteins (DEBS1, -2, and -3) that biosynthesize the polyketide skeleton of the antibiotic erythromycin from propionyl-CoA and methylmalonyl-CoA. Active sites within these multifunctional proteins are organized into biosynthetic "modules", each of which catalyzes a discrete round of polyketide chain elongation and adjusts the appropriate level of beta-ketoacylthioester reduction. Using DEBS1, we demonstrate that there is a substantial degree of molecular recognition in the processing of the natural diketide chain elongation intermediate. Exogenously added (2S,3R)-2-methyl-3-hydroxypentanoic acid N-acetylcysteamine thioester is exclusively recognized by its cognate beta-ketoacyl-acyl carrier protein synthase domain in module 2 (KS2). Labeled diketide specifically acylated DEBS1 in crude protein extracts and limited proteolysis localized the binding to module 2. The precise site of acylation in DEBS1 was established by the finding that a Cys2200 Ala mutant of DEBS1, lacking the KS2 active-site cysteine, did not undergo acylation by the diketide. Pretreatment of the wild-type protein with the beta-ketoacyl-ACP synthase inhibitor cerulenin also blocked acylation. These results indicate that in addition to the purely organizational consequences resulting from the order of active-site domains, the programming of polyketide biosynthesis by modular PKSs involves a substantial level of molecular recognition. This conclusion has important implications for the use of PKSs to rationally design novel polyketides.

Characterization of a hemagglutinin-specific inhibitor of influenza A virus

A novel inhibitor of influenza virus growth in tissue culture was identified and characterized. This compound (BMY-27709) has an IC50 of 3-8 microM for A/WSN/33 virus growth in a multicycle replication assay and is active against all H1 and H2 subtype viruses tested. However, BMY-27709 was found to be inactive against H3 subtype viruses, as well as influenza B/Lee/40 virus. BMY-27709 was also found to act against H1 and H2 viruses early in infection, suggesting that the target for inhibition is the hemagglutinin protein. This was confirmed through the use of reassortant viruses and the isolation of a virus resistant to BMY-27709. The resistant virus isolated contained a phenylalanine to serine change at amino acid 110 of the HA2 subunit. That this single mutation was responsible for the acquisition of resistance to BMY-27709 was proven through reverse genetics, as transfectant virus containing only this change was shown to be resistant to BMY-27709, while the control virus without this mutation remained sensitive. BMY-27709 is able to inhibit virus-induced red blood cell hemolysis, suggesting that it blocks the membrane fusion function of hemagglutinin. These experiments further illustrate that the hemagglutinin protein of influenza virus is a viable target for the discovery and development of small molecule inhibitors of virus growth.

Simultaneous formation of peptides and nucleotides from N-phosphothreonine

An intramolecular mutual activation between a phosphoryl group and carboxyl group results in the simultaneous formation of nucleotides and peptides by the reaction of nucleosides with N-(O,O-diisopropyl)phosphothreonine in anhydrous pyridine. These results suggest pathways for the simultaneous prebiotic synthesis of peptides and oligonucleotides.