[Analysis of cinnamic acid in storax and its original plant by HPLC]

The contents of free and hydrolytic cinnamic acid in storax and its original plant (Liquidambar orientalis) were determined by high performance liquid chromatography, and the chromatographic behaviors were studied. In styrax gummi, the contents of free and hydrolytic cinnamic acid were 7.03% and 25.26% respectively; and in its original plant, they were 0.3% evenly.

A functional chimeric modular polyketide synthase generated via domain replacement

BACKGROUND

Modular polyketide synthases (PKSs), such as 6-deoxyerythronolide B synthase (DEBS), are large multifunctional enzymes that catalyze the biosynthesis of structurally complex and medically important natural products. Active sites within these assemblies are organized into 'modules', such that each module catalyzes the stereospecific addition of a new monomer onto a growing polyketide chain and also sets the reduction level of the beta-carbon atom of the resulting intermediate. The core of each module is made up of a 'reductive segment', which includes all, some, or none of a set of ketoreductase (KR), dehydratase, and enoylreductase domains, in addition to a large interdomain region which lacks overt function but may contribute to structural stability and inter-domain dynamics within modules. The highly conserved organization of reductive segments within modules suggests that they might be able to function in unnatural contexts to generate novel organic molecules.

RESULTS

To investigate domain substitution as a method for altering PKS function, a chimeric enzyme was engineered. Using a bimodular derivative of DEBS (DEBS1+TE), the reductive segment of module 2, which includes a functional KR, was replaced with its homolog from module 3 of DEBS, which contains a (naturally occurring) nonfunctional KR. A recombinant strain expressing the chimeric gene produced the predicted ketolactone with a yield (35 %) comparable to that of a control strain in which the KR2 domain was retained but mutationally inactivated.

CONCLUSIONS

These results demonstrate considerable structural tolerance within an important segment found in virtually every PKS module. The domain boundaries defined here could be exploited for the construction of numerous loss-of-function and possibly even gain-of-function mutants within this remarkable family of multifunctional enzymes.

Covalent binding to DNA in vitro of 2',3'-oxides derived from allylbenzene analogs

Epoxidation at the allylic side chain is a major metabolic pathway for allylbenzene and its naturally occurring analogs safrole, estragole, and eugenol. We demonstrate herein that the epoxide metabolites of allylbenzene, estragole, and safrole can form covalent adducts with DNA in vitro, binding primarily to guanine, but also to the other three DNA bases. Epoxide hydrolases can prevent the binding of allylbenzene 2',3'-oxide to DNA in vitro. Four distinct adducts were detected by analytical TLC after the reaction of 2'-deoxyguanosine with allylbenzene 2',3'-oxide. One unstable adduct was formed rapidly, but gradually disappeared, whereas the other three adducts were formed more slowly but persisted. The major persistent adduct, which was isolated by preparative chromatography, was examined by MS and NMR. The structure of this adduct is 3'-N1-deoxyguanosyl-(2'-hydroxypropylbenzene). In addition, a generally applicable paradigm for the identification of deoxyguanosine or guanosine adducts by 13C and 1H NMR spectroscopy is presented.

DNA fragmentation during bone formation in neonatal rodents assessed by transferase-mediated end labeling

To study the fate of bone cells, we used the transferase-mediated, biotin-dUTP nick end-labeling (TUNEL) assay to detect DNA fragmentation during the formation of intramembranous and endochondral bone in newly born hamsters, mice, and rats. In alveolar bone forming around the developing tooth crowns, DNA fragmentation was found in three cell types: TRAP-negative mononuclear cells at the bone surface, osteocytes, and some but not all nuclei of TRAP-positive osteoclasts. Osteoblasts did not undergo DNA fragmentation. A strong positive correlation was found between contacts of TUNEL-positive osteocytes and osteoclasts. Extracellular bone matrix also stained occasionally for the presence of DNA fragments. During endochondral bone formation, TUNEL staining was detected in late hypertrophic chondrocytes of the epiphyseal growth plate. During rapid longitudinal growth of long bones, TUNEL-positive hypertrophic chondrocytes were found coincident with or slightly after invasion of blood vessels from the diaphysis. However, during slow longitudinal growth and in secondary ossification centers, DNA fragmentation was seen in hypertrophic chondrocytes still located within their lacunae. We conclude that some of the osteocytes in deeper layers of bone die within their lacuna and disperse nuclear fragments over the extracellular matrix, that a majority of the osteocytes are phagocytosed and degraded by osteoclasts at sites of intense bone resorption, and that during endochondral ossification, substantial numbers of late hypertrophic chondrocyte cells undergo cell death.

ABT-299, a novel PAF antagonist, attenuates multiple effects of endotoxemia in conscious rats

ABT-299, a highly potent and selective platelet activating factor (PAF) antagonist, was found to be effective in rat models of endotoxic shock. ABT-299 inhibited and reversed LPS-induced hypotension (ED50 of .008 mg/kg, intraarterially). When given prior to LPS challenge, ABT-299 (.1 mg/kg, intravenously) completely inhibited LPS-induced intestinal damage for as long as 8 h after the administration of the antagonist. Pretreatment of rats with ABT-299 (5 mg/kg, intravenously over 4 h) prevented by 85-95% symptoms of disseminated intravascular coagulation (DIC) induced by LPS, including thrombocytopenia, prolongation of prothrombin and partial thromboplastin time, decreased serum fibrinogen, and elevation of serum fibrinogen/fibrin degradation products. A .1 mg/kg dose of ABT-299 administered orally or intravenously improved long-term survival to 80% and 90%, respectively, following a lethal dose (LD65) of LPS. ABT-299 (.1 mg/kg) was also effective in preventing hypotension and gastrointestinal damage induced by lipoteichoic acid (LTA), a putative causative agent of shock in Gram-positive infections. These results illustrate the impressive potency and duration of action of ABT-299 and support the putative role of PAF in acute models of endotoxic shock.

cDNA cloning of mouse nebulin. Evidence that the nebulin-coding sequence is highly conserved among vertebrates

Nebulin is a family of giant myofibrillar proteins with molecular masses ranging over 700-900 kDa. Using a human nebulin cDNA probe, we isolated three nebulin cDNA clones from a mouse skeletal muscle cDNA library. These three clones, labeled 8c. 7a and 4b. carry inserts of 2.0, 3.0 and 3.5 kb, respectively. In Northern blots, each insert detected the same approximately = 25 kb message from skeletal muscle as the human nebulin probe, while detecting no messages from cardiac muscle. Sequence data in combination with reverse-transcriptase PCR indicates that clones 7a and 8c overlap to form 4076 bp contiguous sequence. Alignment with the published full-length human nebulin sequence indicates that clone 4b overlaps with clone 7a over 1596 bp. However, after the first 798-bp overlap, the sequence of these two mouse nebulin clones diverge, suggesting that they derive from distinct transcripts encoding isoforms of mouse nebulin. The mouse nebulin clones encode a series of = 245-residue super repeats, each of which can be subdivided into seven = 35-residue, weakly repeating modules centered around a conserved tyrosine residue, consistent with the human nebulin sequence. The mouse nebulin clones align along the central third of the full-length human sequence, corresponding to super repeats 8-16 of the 22 super repeats found in human nebulin. The translated sequence is greater than 90% identical to the human sequence, with the exception of a 200-amino-acid region at the C-terminus of clone 4b, which is less than 60% identical. In genomic Southern blots, a mouse nebulin probe detected a homologous sequence in a wide variety of vertebrate species under stringent conditions. However, no significant hybridization was observed to genomic DNA from invertebrates and microorganisms, even under very low stringency. The sequence and Southern-blot data suggest that the nebulin sequence is highly conserved among vertebrate species.

Erythromycin biosynthesis: exploiting the catalytic versatility of the modular polyketide synthase

DEBS 1 + TE is a recombinant modular polyketide synthase (PKS) in which the first two biosynthetic modules of the 6-deoxyerythronolide B synthase are linked to the thioesterase domain normally found at the C-terminus of DEBS 3. Incubation of DEBS 1 + TE with propionyl-CoA, methylamalonyl-CoA, and NADPH gives the triketide lactone (2R,3S,4S,5R)-2,4-dimethyl-3, 5-dihydroxy-n-heptanoic acid delta-lactone (2), the cyclized form of the normal triketide chain elongation product of DEBS 1. In order to probe the molecular recognition features of the PKS and to explore its synthetic versatility, [2,3-13C2]-(2S,3R)-2-methyl-3-hydroxypentanoyl-NAC thioester (3), an analogue of the normal diketide chain elongation intermediate, and (2RS)-methyl-malonyl-CoA were incubated with DEBS 1 + TE, leading to the formation of the predicted labeled triketide ketolactone [4,5-13C2]-8, as established by 13C NMR analysis and comparison with spectra of synthetic 8. This stereoselective conversion illustrates the potential of using modular PKSs as multifunctional catalysts for the enzymatic synthesis of novel polyketides.

Characterization of inhibition of M2 ion channel activity by BL-1743, an inhibitor of influenza A virus

The influenza A virus M2 integral membrane protein has ion channel activity that can be inhibited by the antiviral drug amantadine. Recently, a spirene-containing compound, BL-1743 (2-[3-azaspiro (5,5)undecanol]-2-imidazoline), that inhibits influenza virus growth was identified (S. Kurtz, G. Lao, K. M. Hahnenberger, C. Brooks, O. Gecha, K. Ingalls, K.-I. Numata, and M. Krystal, Antimicrob. Agents Chemother. 39:2204-2209, 1995). We have examined the ability of BL-1743 to inhibit the M2 ion channel when expressed in oocytes of Xenopus laevis. BL-1743 inhibition is complete as far as can be measured by electrophysiological methods and is reversible, with a reverse reaction rate constant of 4.0 x 10(-3) s(-1). In contrast, amantadine inhibition is irreversible within the time frame of the experiment. However, BL-1743 inhibition and amantadine inhibition have similar properties. The majority of isolated influenza viruses resistant to BL-1743 are also amantadine resistant. In addition, all known amino acid changes which result in amantadine resistance also confer BL-1743 resistance. However, one BL-1743-resistant virus isolated, designated M2-I35T, contained the change Ile-35-->Thr. This virus is >70-fold more resistant to BL-1743 and only 10-fold more resistant to amantadine than the wild-type virus. When the ion channel activity of M2-I35T was examined in oocytes, it was found that M2-I35T is BL-1743 resistant but is reversibly inhibited by amantadine. These findings suggest that these two drugs interact differently with the M2 protein transmembrane pore region.

[The role of thermal injury on nitric oxide (NO) production by mouse macrophages and its possible mechanism]

To study the production NO by macrophages (M phi) after burn injury and the possible mechanism, we determined the NO production and the iNOS (inducible NO synthase) activity of peritoneal M phi (PM phi) in scald mouse, and the effect of iNOS specific blocker NMMA. Actinomycin D (AD) and protein tyrosine kinase (PTK), special inhibitor Genisteinon them in vitro. It was found that PM phi produced excessive NO in the early postburn phase and the iNOS activity was increased significantly, and there was a positive correlation between them. NMMA, AD as well as Genistein could inhibit the NO production, the activity of iNOS was decreased by both AD and Genistein. The results suggested that M phi was activated after thermal injury and it could produce NO excessively through initiating iNOS synthesis. PTK signal system was involved in the NO production by M phi via affecting the iNOS synthesis after burn injury.

BMP 7 is required for nephrogenesis, eye development, and skeletal patterning

In summary, the generation of BMP-7-deficient mice has provided additional evidence that this family of growth factors regulate many morphogenetic processes including but not limited to skeletal development. In particular our experiments demonstrate that BMP 7 acts as an early inducer of glomeruli formation, and that it is required for skeletal patterning and lens formation. Our results not only demonstrate that BMP 7 is involved in the differentiation of several organs during development, but also raise the hypothesis that mutations in the Bmp 7 gene itself or in the genetic pathway could be responsible for several human genetic diseases in which glomerulus formation is impaired.

Properties of ABT-299, a prodrug of A-85783, a highly potent platelet activating factor receptor antagonist

ABT-299 is an aqueous soluble prodrug that is converted rapidly in vivo to A-85783, a novel, highly potent, specific platelet activating factor (PAF) antagonist. The K, for inhibiting PAF binding to rabbit platelet membranes is 3.9 and 0.3 nM for human platelets. Inhibition is selective and reversible and is correlated with functional antagonism of PAF-mediated cellular responses (calcium mobilization, priming of superoxide generation, aggregation and degranulation). The in vivo generation of A-85783 from ABT-299 leads to potent inhibition of PAF-induced inflammatory responses (increased vascular permeability, hypotension and edema) and PAF-induced lethality. When administered i.v., the potency (ED50) of ABT-299 for inhibiting PAF responses was between 6 to 10 micrograms/kg in the rat and mouse and 100 micrograms/kg in the guinea pig. A dose of 100 micrograms/kg in the rat provided greater than 60% protection for 8 to 16 hr against cutaneous and systemic PAF challenge. This duration was also evidenced by ex vivo inhibition of platelet aggregation in guinea pig and sheep. In addition to being active parenterally, ABT-299 exhibited p.o. activity in the rat and mouse (ED50 = 100 micrograms/kg in both species). Pharmacokinetic studies in the rat revealed that ABT-299 was converted rapidly to A-85783 and, in turn, metabolized to the corresponding pyridine-N-oxide and sulfoxide metabolites. These metabolites exhibited significant potency in vitro and in vivo and thus may contribute to the activity observed after administration of ABT-299.

[The study of local electroretinogram in age-related macular degeneration]

PURPOSE

Observing the features of electro-activities at macular region in age-related macular degeneration (AMD), and evaluating the sensitivities of local electroretinogram (LERG).

METHODS

The LERG of 2.5, 5, 7.5 degrees at macula had been recorded in 99 eyes (68 dry form, 31 wet form) of 80 AMD patients. The contrast study had also been carried out with visual acuities and lesion areas at the corresponding region.

RESULTS

The results showed that there were no significant differences between the decreased amplitudes of a and b waves of LERG in dry form AMD with normal controls (P > 0. 05). While significant differences existed in wet form AMD (P < 0.01). The changes of LERG at 2.5 degrees were greater than those of the other two regions. The correlation study on b wave amplitude and visual acuity of AMD patients showed that there was a positive correlation existed between them only in wet form AMD at 2.5 degrees region (r = 0.516, P < 0.05). The negative correlations were observed between amplitudes of b wave and lesion areas in wet form AMD at the three macular regions. Drusen of dry form AMD had no effects on the amplitudes of LERG.

CONCLUSIONS

The impairments on macular function from two types of AMD are different. This study reveals that the LERG is a sensitive method of visual electrophysiology for measuring macular function. The smaller the testing area, the higher the sensitivity.

Nuclear DNA fragmentation during postnatal tooth development of mouse and hamster and during dentin repair in the rat

The TUNEL (transferase-mediated, dUTP-biotin nick end labeling) method for in situ labeling of DNA strands was utilized to localize DNA fragmentation in cells involved in tooth formation in the neonatal mouse and hamster. Positive reactions for the presence of DNA fragments were obtained in some epithelial cells of the cervical loop region of incisors, late secretory, transitional and early maturation stage ameloblasts, stratum intermedium cells and in shortened ameloblasts just before eruption. Also, cells of the periodontal ligament of the continuously erupting incisors stained positive shortly before eruption. Odontoblasts were negative but became strongly positive during the formation of physiological osteodentin at the tip of developing incisors. Osteodentin matrix and the surfaces of unerupted enamel and cementum just prior to eruption stained for DNA fragments as well. DNA fragmentation could be elicited in odontoblasts and underlying pulpal tissues of mature erupted molars after mechanical injury to the odontoblast processes during cavity preparation. We conclude that, in rodents, DNA fragmentation and cell death are biological processes which take place in a variety of cells involved in formation of teeth. The TUNEL staining technique is a simple but powerful tool to examine the fate of cells and tissues undergoing either programmed cell death (apoptosis) or fragmentation of nuclear DNA induced by external factors leading to pathological changes.

Local electroretinogram and pattern visual evoked potential in maculopathies

PURPOSES

To observe the characteristics of local electroretinogram (LERG) in normal subjects and patients with maculopathies, and to evaluate the applied worth of LERG and pattern visual evoked potential (PVEP) in maculopathies.

METHODS

LERGs at 5 degrees and 15 degrees macular regions were recorded from 27 normal subjects (54 eyes). The factors of age, different eyes and stimulate areas for LERG influence were observed. Meanwhile, the LERG and PVEP were recorded from 25 patients (35 eyes) with maculopathies for making contrast study.

RESULTS

In normal subjects, there was no significant influence of age to LERG. As the stimulated areas increased, the a- and b-wave amplitudes of LERG increased. In the patients with maculopathies, the a- and b-wave amplitudes of LERG at 5 degrees, 10 degrees and 15 degrees macular regions were significantly lowered and the mean values of P1 latency were prolonged and N1-P1 amplitudes of VEP were lowered, comparing with the control group. In the nearing stimulated area (5 degrees LERG and 14.9 x 19 degrees PVEP), there were no significant differences of the abnormal rates of both LERG and PVEP.

CONCLUSION

There are close sensitivities of testing the function of macular region with LERG and PVEP in maculopathies. However, LERG is not influenced by the visual path diseases and visual acuity, it is a more effective and direct way than PVEP in measuring macular function.

Development of an in situ toxicity assay system using recombinant baculoviruses

A new method for experimentally analyzing the role of enzymes involved in metabolizing mutagenic, carcinogenic, or cytotoxic chemicals is described. Spodoptera fugiperda (SF-21) cells infected with recombinant baculoviruses are used for high level expression of one or more cloned enzymes. The ability of these enzymes to prevent or enhance the toxicity of drugs and xenobiotics is then measured in situ. Initial parameters for the system were developed and optimized using baculoviruses engineered for expression of the mouse soluble epoxide hydrolase (msEH, EC 3.3.2.3) or the rat cytochrome P4501A1. SF-21 cells expressing msEH were resistant to trans-stilbene oxide toxicity as well as several other toxic epoxides including: cis-stilbene oxide, 1,2,7,8-diepoxyoctane, allylbenzene oxide, and estragole oxide. The msEH markedly reduced DNA and protein adduct formation in SF-21 cells exposed to [3H]allylbenzene oxide or [3H]estragole oxide. On the other hand, 9,10-epoxyoctadecanoic acid and methyl 9,10-epoxyoctadecanoate were toxic only to cells expressing sEH, suggesting that the corresponding fatty acid diols were cytotoxic. This was confirmed by showing that chemically synthesized diols of these fatty acid epoxides were toxic to control SF-21 cells at the same concentration as were the epoxides to cells expressing sEH. A recombinant baculovirus containing a chimeric cDNA formed between the rat P4501A1 and the yeast NADPH-P450 reductase was also constructed and expressed in this system. A model compound, naphthalene, was toxic to SF-21 infected with the rat P4501A1/reductase chimeric co-infecting SF-21 cells with either a human or a rat microsomal EH virus along with P4501A1/reductase virus. These results demonstrate the usefulness of this new system for experimentally analyzing the role of enzymes hypothesized to metabolize endogenous and exogenous chemicals of human health concern.

Analysis of limb patterning in BMP-7-deficient mice

Bone morphogenetic proteins (BMPs) are polypeptide signaling molecules, belonging to the TGF-beta superfamily. They were originally identified by their ability to induce ectopic bone formation, but their expression patterns in embryos suggest multiple functions. BMP-7-deficient mice show among other mesodermal and skeletal patterning defects, polydactyly in the hindlimbs [Luo G, Hofmann C, Bronckers ALJJ, Sohocki M, Bradley A, Karsenty G (1995): Genes Dev 9:2808-2820; Dudley AT, Lyons KM, Robertson EJ (1995): Genes Dev 9:2795-2807]. Here we report a more detailed analysis of the limb phenotype in BMP-7-deficient mice using in situ hybridization to monitor expression of molecules implicated in patterning processes of the developing vertebrate limb. In previous studies we showed that Sonic hedgehog (Shh) was expressed normally, but Hoxd-13 expression in limb mesenchyme was lower in BMP-7 mutant limbs. Here we show that Hoxd-11 expression domains are also contracted and decreased in intensity in mutant limbs, suggesting that 5' genes of the Hoxd cluster are coordinately downregulated, while another Bmp, Bmp-2, which can be activated by Shh, is similarly expressed. The mutant limb buds are broader than normal buds, and fibroblast growth factor Fgf-8 is expressed throughout the extended ridge. However, expression of the homeobox gene Msx-1, which has been shown to be involved in epithelial-mesenchymal interactions during limb development, was decreased in the mesenchyme of BMP-7 mutant limbs. Taken together, our data suggest that BMP-7 is involved in regulating proliferation and/or epithelial-mesenchymal interactions in the developing limb.

Human neoplasms elicit multiple specific immune responses in the autologous host

Expression of cDNA libraries from human melanoma, renal cancer, astrocytoma, and Hodgkin disease in Escherichia coli and screening for clones reactive with high-titer IgG antibodies in autologous patient serum lead to the discovery of at least four antigens with a restricted expression pattern in each tumor. Besides antigens known to elicit T-cell responses, such as MAGE-1 and tyrosinase, numerous additional antigens that were overexpressed or specifically expressed in tumors of the same type were identified. Sequence analyses suggest that many of these molecules, besides being the target of a specific immune response, might be of relevance for tumor growth. Antibodies to a given antigen were usually confined to patients with the same tumor type. The unexpected frequency of human tumor antigens, which can be readily defined at the molecular level by the serological analysis of autologous tumor cDNA expression cloning, indicates that human neoplasms elicit multiple specific immune responses in the autologous host and provides diagnostic and therapeutic approaches to human cancer.

Cell-free synthesis of polyketides by recombinant erythromycin polyketide synthases

Modular polyketide synthases (PKSs) are complex multi-enzyme proteins that catalyse the bacterial biosynthesis of many pharmaceutically useful polyketides. The PKSs are organized into a series of modules, each containing the active catalytic sites required for one step in the synthesis process. Here we report a method for cell-free enzymatic synthesis of 6-deoxyerythronolide B (6-dEB), the parent molecule of the antibiotic erythromycin A, using recombinant 6-deoxyerythronolide B synthase (DEBS), a modular PKS with at least 28 distinct active sites. We have also synthesized in vitro a triketide lactone by using a truncated mutant of DEBS. The availability of such cell-free synthetic routes will allow direct investigation of the structural and mechanistic basis for the unusual combination of high substrate specificity and tolerance to genetic reprogramming found in this enzyme family.

BMP-7 is an inducer of nephrogenesis, and is also required for eye development and skeletal patterning

Bone morphogenetic proteins (BMPs) are multifunctional growth factors originally identified by their ability to induce ectopic bone formation. To investigate the function of one of the BMPs, BMP-7, we have generated BMP-7-deficient mice using embryonic stem cell technology. BMP-7-deficient mice die shortly after birth because of poor kidney development. Histological analysis of mutant embryos at several stages of development revealed that metanephric mesenchymal cells fail to differentiate, resulting in a virtual absence of glomerulus in newborn kidneys. In situ hybridization analysis showed that the absence of BMP-7 affects the expression of molecular markers of nephrogenesis, such as Pax-2 and Wnt-4 between 12.5 and 14.5 days postcoitum (dpc). This identifies BMP-7 as an inducer of nephrogenesis. In addition, BMP-7-deficient mice have eye defects that appear to originate during lens induction. Finally, BMP-7-deficient mice also have skeletal patterning defects restricted to the rib cage, the skull, and the hindlimbs.

Observation and quantitation of exocytosis from the cell body of a fully developed neuron in Planorbis corneus

We have discovered a neuronal system that releases neurotransmitter via exocytosis from the cell body. In the large dopamine cell of the pond snail Planorbis corneus, depolarization induces rhythmic release of dopamine from the cell body. When a stimulant is applied extracellularly or intracellularly in situ to the cell body, transient dopamine concentration packets that appear in a bursting pattern are observed. Dopamine release is calcium dependent and release is on the time scale expected for exocytosis (2 to 4 msec rise times). Quantitation of individual events reveals an average of 818,000 molecules per exocytotic event. As many as 89,000 individual exocytotic events have been observed following a single stimulation of one cell. Neurotransmitter exocytosis from the neuronal cell body appears to represent an alternative form of neurocommunication to synaptic transmission.

[The change of filtration-index of erythrocyte malonyldialdehyde and superoxide dismutase in patients with pregnancy induced hypertension]

OBJECTIVE

To observe the relationship between the filtration-index of erythrocytes and concentration of erythrocytic superoxide dismutase (SOD), plasma malonyldialdehyde (MDA) in cases of pregnancy induced hypertension (PIH).

METHODS

We have measured the level of MDA and filtration-index, SOD content of erythrocytes in maternal and cord blood of 31 cases with PIH (group A) and 25 cases of normal pregnancy (group B) using TBA method, nucleopore membraned cell deformability meter and pyrogallol self-oxidizing method.

RESULTS

The mean filtration-index level and erythrocytic SOD were significantly higher in group A than those of group B (P < 0.01 and P < 0.05). The mean content of plasmatic MDA in group A increased markedly (P < 0.01) compared to that of group B. There was no difference of these parameters in cord blood between group A and group B.

CONCLUSION

The decrease of red cell deformability due to the increase of plasma MDA level may be the underlying mechanism of PIH.

[Experimental study of implantation of autologous vascular endothelial cells on dacron grafts]

Ten mongrel dogs underwent carotid artery bypass 17 times with dacron grafts, 4mm in inner diameter and 5cm in length. The grafts in experimental group A were immediately seeded with autologous endothelial cells harvested by 0.25% trypsin solution (n = 7). The grafts in experimental group B were seeded with autologous endothelial cells cryopreserved in liquid nitrogen for 1 week (n = 3). The grafts in contrast group was not seeded with any endothelial cells implanted in the contralateral carotid arteries in group A (n = 7). The number of endothelial cells harvested in the two groups was 0.9 +/- 0.3 x 10. Factor VIII related antigen stain method confirmed the cells harvested by 0.25% trypsin solution to be endothelial cells. The grafts were removed and studied at the end of 2, 4, and 6 week after implantation. The total patency rate of group A was 85.7% (6/7), and that of the contrast group 57% (4/7). The weight of thrombus in group A was 40.6 +/- 36.9mg and the contrast group 85.9 +/- 26.3mg (P < 0.01). Scanning electron microscopy revealed that the cells at the middle segment of the grafts in the group A and B had the characteristics of ellipse, and tight intercellular junction, while the middle segment grafts in contrast group were covered by platelets, erythrocytes, leukocytes and fibrin. Transmission electron microscopy, factor VIII related antigen stain method, and vimentin stain method demonstrated that the cells in the group A and B showed characteristics of endothelial cells. It was concluded that endothelialization of the dacron grafts could be accelerated and the quality could be improved by immediate seeding with endothelial cells or by seeding with endothelial cells cryopreserved in liquid nitrogen for 1 week.

Growth impairment resulting from expression of influenza virus M2 protein in Saccharomyces cerevisiae: identification of a novel inhibitor of influenza virus

The gene encoding M2, the ion channel-forming protein of influenza virus A, was expressed under the control of an inducible promoter in Saccharomyces cerevisiae. By using single and multicopy plasmids containing GAL promoter-M2 fusions, a correlation was observed between plasmid copy number and growth in medium inducing M2 expression. Cells expressing M2 from multicopy plasmids have reduced growth rates, suggesting that high levels of M2 are toxic to growth. The addition of amantadine, a compound known to block the ion channel activity of certain M2 alleles, restores the growth rates to wild-type levels in cells expressing an amantadine-susceptible allele of M2 but not an amantadine-resistant allele of M2, suggesting that M2 expression in S. cerevisiae results in the formation of functional M2 ion channels. Measurements of extracellular acidification by microphysiometry suggest that proton efflux in M2-expressing cells is altered and that the addition of amantadine permits the reestablishment of the proton gradient. The growth impairment phenotype resulting from M2 expression was used to develop a high-capacity screening assay which identified a novel inhibitor possessing an antiviral profile similar to that of amantadine.

Implementation of strain rate as a bone remodeling stimulus

Strain rate is implemented as a stimulus for surface bone remodeling. Using idealized models for trabecular bone structures, the surface remodeling predictions using the strain rate as the stimulus are compared with the predictions using the peak strain magnitude as the stimulus. For a uniaxially loaded cruciform shape, the comparison shows that the two surface remodeling stimuli predict the same final shape under a periodic compressive load, but the two evolutionary paths to final shapes are different. Two biaxially loaded regular grid models of trabecular structure were considered, one a grid of square diamond shaped elements and the other a brick wall patterned grid. For both of these idealized trabecular structures, the comparison shows that the two surface remodeling stimuli predict the same final shape under a periodic compressive load, even from these distinctly different initial grid patterns, and the evolutionary paths to final shapes are quite different. In general the two stimuli do not predict the same remodeling and the conditions under which they do are derived. The models developed are also applied to the data from the animal experiments reported in Goldstein et al. (1991), and it is shown that the strain rate stimulus predicts bone remodeling similar to what was experimentally observed.

Erythromycin biosynthesis. Highly efficient incorporation of polyketide chain elongation intermediates into 6-deoxyerythronolide B in an engineered Streptomyces host

Feeding of (2S,3R)-[2,3-13C2]-2-methyl-3-hydroxypentanoyl NAC thioester (1a) to the recombinant organism Streptomyces coelicolor CH999/pCK7 harboring the complete set of eryA genes from Saccharopolyspora erythraea encoding the 6-deoxyerythronolide B synthase (DEBS) resulted in the formation of 6-deoxyerythronolide B (2a) labeled with 13C at C-12 and C-13, as evidenced by the appearance of a pair of enhanced and coupled doublets in the 13C NMR spectrum. The level of 13C enrichment was 15-20 atom% 13C, as much as 100 times higher than the usually observed efficiency of incorporation of NAC thioesters into polyketide metabolites. Similar incorporation of (2S,3R)-[3-2H,3-13C]-2-methyl-3-hydroxypentanoyl NAC thioester (1b) gave 6-deoxyerythronolide B (2b) labeled with both 13C and deuterium at C-13. The intact incorporation of both precursors confirms the normal functioning of the recombinant DEBS proteins in the heterologous host.

[Determinate titer of tuberculosis antibody with cytomembrane antigen]

Using tuberculous cytomembrane antibody and titer determining methodology, serum specimens from 165 pulmonary tuberculosis patients were analysed. The results showed: 75.7% of specimen is in high level, titer > or = 1:400.20% in low level, titer 1:100-1:200.4. 42% negative. This method is more sensitive than usually used PPD and polymeric OT antigen. At the same time, sputum specimens from 406 TB patients were examined for TB bacilli, the result demonstrated that the positive rate of sputum smear in the patients with titer > or = 800 is up to 95.71%-100%.1:400 is 69.86%, 1:100-1:200 is 14%-22.09%, < 1:100 is 10%.

The matrix Gla protein gene is a marker of the chondrogenesis cell lineage during mouse development

Matrix Gla protein (MGP) is, along with osteocalcin, a skeletal member of the family of extracellular mineral-binding Gla proteins. Although the precise function of these proteins remains obscure, circumstantial evidence suggests that they play a role in endochondral ossification. As a first step toward understanding MGP function we have performed a preliminary characterization of its promoter element and studied the developmental pattern of expression of this gene. DNA transfection experiments indicate that the mouse MGP promoter functions better in cells expressing the MGP gene than in cells that do not express the gene. During mouse development, MGP gene expression is detectable as early as day 10.5 of embryonic development (E10.5), before any skeletal structures are identifiable. In situ hybridization analysis shows that MGP mRNA is initially present at the mesenchymal epithelial interphase in lung and limb buds. As development proceeds, MGP gene is predominantly expressed in cells of the chondrocytic lineage in areas that will undergo endochondral ossification as well as in areas that will remain cartilaginous, such as the trachea and bronchi. In growth plate cartilage, MGP mRNA is present in resting, proliferative, and late hypertrophic chondrocytes. Surprisingly, MGP mRNA is absent from the early hypertrophic chondrocytes and from the osteoblasts. Finally, the MGP gene is expressed at a lower level in kidney medulla and uterus smooth muscle but not in brain, spleen, or heart during development. This study demonstrates that during development MGP gene expression occurs early and is predominant at the epithelial mesenchymal interfaces, principally of lung and limb buds, and in cells of the chondrocytic lineage. This finding raises the intriguing possibility that MGP may play distinct roles during embryogenesis and in the adult organism.

Metabolism of allylbenzene 2',3'-oxide and estragole 2',3'-oxide in the isolated perfused rat liver

The metabolism of allylbenzene 2',3'-oxide, estragole 2',3'-oxide, allylbenzene and estragole was studied in the isolated perfused rat liver. Formation of dihydrodiol and glutathione conjugate metabolites was detected for both epoxides and the presence of dihydrodiol metabolites after perfusion of allylbenzene or estragole indicated the formation of allylic epoxide intermediates in the intact liver. A comparison of elimination kinetics for parent compounds and epoxides indicated that epoxides were relatively rapidly detoxified and probably do not accumulate on formation in vivo. Acute toxicity of epoxides, measured as the release of alanine aminotransferase activity into the perfusate, or genetic toxicity, determined as covalent binding of radiolabeled epoxide to DNA, were not observed. It was concluded that both epoxide hydrolases and glutathione S-transferases can effectively detoxify the allylic epoxides derived from either allylbenzene or estragole and effectively prevent cellular or genetic toxicity of these reactive intermediates. Epoxide hydrolases appear to play the major role in the detoxication of these epoxides in vivo.

Amperometric monitoring of stimulated catecholamine release from rat pheochromocytoma (PC12) cells at the zeptomole level

Catecholamine release from rat pheochromocytoma (PC12) cells has been observed at zeptomole levels using dc-amperometric detection with carbon fiber microelectrodes. Time-resolved individual exocytic events from PC12 cells have been recorded and analyzed with 1.2 ms time resolution. The average area under 1912 current transients from 13 PC12 cells corresponds to 190 zmol (114,300 molecules per release event). The average width at half-height of these current transients is 9.3 ms, in agreement with the time frame of exocytosis. The detection limit of the method reported here is as low as 31 zmol. This is the first report of direct electrochemical observation of quantal release from PC12 cells. The successful application of this electrochemical scheme to monitor catecholamines released from small vesicles also suggests that it may be possible to apply this technique to monitor quantal release from synaptic vesicles.

Mutations at palmitylation sites of the influenza virus hemagglutinin affect virus formation

The carboxy terminus of the hemagglutinin (HA) of influenza A viruses contains three cysteine residues which are highly conserved among HA subtypes. It has previously been shown for the H2, H3, and H7 subtypes of HA that these cysteine residues are modified by the covalent attachment of palmitic acid. In order to study the role of the acylated cysteines in the formation of infectious influenza viruses, we introduced mutations into the HA of influenza A/WSN/33 virus (H1 subtype) by reverse-genetics techniques. We found that the cysteine at position 563 of the cytoplasmic tail is required for infectious-particle formation. The cysteine at position 560 can be changed to alanine or tyrosine to yield virus strains that are attenuated in cell cultures. The change from cysteine at position 553 to serine or alanine does not significantly alter the phenotype of the virus. The requirement for a cysteine at position 563 suggests a functional role for palmitylation of the cytoplasmic tail. This interpretation is further supported by experiments in which two or more of the cysteine residues were mutated, eliminating potential palmitylation sites. None of these double or triple mutations resulted in infectious virus. Selection of revertants of the attenuated cysteine-to-tyrosine mutant (mutation at position 560) always resulted in reversion to cysteine rather than to other amino acids. Although our data indicate a biological role for the conserved cysteine residues in the cytoplasmic tail of the HA of influenza viruses, we cannot exclude the possibility that structural constraints in the cytoplasmic tail of the HA--rather than altered palmitylation--are the determining factors for infectious-particle formation.

Detoxication of the 2',3'-epoxide metabolites of allylbenzene and estragole. Conjugation with glutathione

The enzymatic detoxication in vitro of the 2',3'-epoxide derivatives of allylbenzene and estragole was examined, and the relative rates of enzymatic glutathione conjugation and epoxide hydrolysis were compared with those for styrene 1',2'-oxide. HPLC was used to determine the amounts of dihydrodiol and glutathione conjugate metabolites formed by cell extracts from several sources. Although some differences among species were observed, in general, the rates of epoxide inactivation by both pathways are similar. We conclude that one explanation for the apparent lack of genotoxicity of these allylic epoxides in vivo may be their rapid metabolic inactivation by both glutathione S-transferases and epoxide hydrolases, which occur to approximately equal degrees in vitro.

A simple procedure for the expression of genes in transgenic soybean callus tissue

Cotyledons from germinating seeds of the soybean cultivar Peking were inoculated with virulent Agrobacterium tumefaciens strain A281:pZA-7 which carries a wild type Ti plasmid pTiBo542 and a disarmed Ti plasmid (a binary vector)pZA-7 which contains the βglucuronidase (uidA) and neomycin phosphotransferase (nptII) genes. Tumors were produced on all inoculated explants and 82% of these tumor lines were cotransformed by the nptII gene from the binary vector pZA-7 as shown by PCR analysis (18 of 22 lines tested). Eleven of these 18 lines were also resistant to kanamycin. Eleven lines expressed β-glucuronidase activity (GUS), six of which were also kanamycin resistant. Since there is a high rate of coexpression of genes carried by the binary vector, this system provides a simple and rapid method for the expression of genes of interest in transformed soybean tissue which has been used successfully to test constructs designed for soybean transformation.

Expression of MUC2 gene is down-regulated by vitamin A at the transcriptional level in vitro in tracheobronchial epithelial cells

The functional role of airway mucin in the respiratory system is well recognized. The isolation of mucin cDNA clones, MUC genes, introduces new information regarding the structure of the mucin core protein; however, the nature of the authentic core protein of airway mucin is still unresolved. In this communication, the effects of vitamin A on the regulation of MUC2 gene expression in primary tracheobronchial epithelial (TBE) cells of human and nonhuman primates were examined. Vitamin A has been recognized as one of the most important nutrients in the regulation of airway mucous cell differentiation. The expression of the MUC2 gene has been demonstrated in both rat and human tracheal tissues. The monkey cDNA clone MT80 was isolated from a cDNA library derived from vitamin A-depleted cultures of monkey TBE cells using a synthetic oligonucleotide probe corresponding to the 69 nucleotides of a tandemly repeated sequence in human MUC2 cDNA. DNA sequencing revealed a similar tandemly repeated sequence, except that 72 oligonucleotide repeats were observed in the monkey cDNA clone. Using the MT80 cDNA as a probe, the expression of the MUC2 gene was studied in vitro. The corresponding MUC2 message level in primary cultures of monkey TBE cells was down-regulated by vitamin A. This result was consistently demonstrated in primary human and hamster TBE cultures. The down-regulation was both time- and dosage-dependent on vitamin A. A nuclear run-on assay demonstrated a decrease in the transcriptional rate of the MUC2 gene in nuclei isolated from vitamin A-treated cultures. These results suggest that MUC2 gene expression in TBE cells is transcriptionally down-regulated by vitamin A.

A PCR differential screening method for rapid isolation of clones from a cDNA library

We have developed a new two-step differential screening method that allows the rapid isolation of induced or suppressed pure gene clones from a lambda phage cDNA library. This method involves a primary differential screening step and a PCR differential screening step. From the primary screening step, impure pools of positive cDNA clones are obtained. Each pool of clones is then amplified directly by PCR using two primers flanking the cloning site in the vector. The PCR products are run on two duplicate agarose gels and blotted onto two filter strips. These two filters are then subjected to differential Southern hybridization with different cDNA probes. Each pure positive cDNA band on the gel is identified and selected for further subcloning. This method has three advantages over the traditional differential screening method. First, several rounds of plaque rescreening are replaced by a single PCR screening. Second, plaque hybridization is replaced by a more reliable and accurate PCR DNA Southern hybridization. Third, the time-consuming and tedious phage DNA isolation step is eliminated, and subcloning is facilitated by direct cloning of the pure PCR product to a plasmid vector. We have successfully used this method to isolate ozone-responsive genes from a cDNA library of monkey respiratory airways.

Direct observation of the effect of autoreceptors on stimulated release of catecholamines from adrenal cells

The direct effect of alpha 2-autoreceptors was studied by measuring the effects of piperoxan, an alpha 2-autoreceptor antagonist, and clonidine, an agonist on catecholamine exocytosis, from single bovine chromaffin cells in culture. Catecholamine release was elicited by stimulation with 100 microM nicotine and was monitored electrochemically with a carbon-fiber microelectrode placed adjacent to the cell. These electrodes allowed the number of exocytotic release events to be monitored and reported as total charge for release following a specific stimulus. Repeated stimulation with 100 microM nicotine showed that total release caused by the second exposure to nicotine was 32% of the first, and release caused by the third exposure to nicotine was 80% of the second. Total release of catecholamine increased significantly after application of 20 microM piperoxan relative to a control application of balanced salt solution. Application of 20 microM piperoxan alone did not cause release. After the cells were incubated in culture medium containing 20 microM clonidine, a significant decrease in nicotine-stimulated catecholamine release was observed. These results confirm that there are autoreceptors on chromaffin cells and, when relatively high levels of catecholamine are released, the catecholamine stimulates the alpha 2-autoreceptors, which inhibits subsequent release through a negative feedback mechanism. In addition to piperoxan, the sympathomimetic drug amphetamine also increases quantal release after application of nicotine. Amphetamine increases the extracellular concentration of catecholamine, and these data appear to indicate that at least part of the pharmacology of amphetamine might involve blocking catecholamine autoreceptors.

Purification and characterization of Yersinia enterocolitica envelope proteins which induce antibodies that react with human thyrotropin receptor

Graves' disease is an autoimmune disease mediated by autoantibodies to the thyrotropin receptor (TSHR). Several studies have suggested that the development of Graves' disease may be linked to infection with the enteric pathogen Yersinia enterocolitica. Using the purified recombinant extracellular domain of human TSHR (ETSHR), we have recently shown that immunization of mice with Y. enterocolitica results in the production of antibodies capable of reacting with the ETSHR. In this study, we identify two low molecular weight (5.5 kDa and 8 kDa) envelope proteins of Yersinia containing epitopes that are crossreactive with the TSHR. Identification of these crossreactive envelope proteins was achieved by Western blotting using affinity-purified anti-Y. enterocolitica antibodies that specifically react with the TSHR and, conversely, for envelope proteins of Yersinia. Confirmation that these Yersinia proteins contained crossreactive epitopes with the ETSHR was obtained by immunizing mice with partially purified envelope proteins, which resulted in the production of Abs that recognized the ETSHR. Further, some of the cross-reactive envelope proteins were purified with SDS-PAGE and HPLC. The crossreactive envelope proteins were shown to be chromosomally encoded, exposed on the surface of bacteria, and produced by virulent as well as avirulent strains of Yersinia (Y. pestis, Y. pseudotuberculosis, Y. enterocolitica VW+, and Y. enterocolitica VW-). These results identify for the first time the Yersinia envelope proteins that are crossreactive with the ETSHR. Availability of these proteins will allow future studies to determine whether patients with Graves' disease have a unique immune response against these proteins when compared with healthy individuals.

Purification and characterization of Yersinia enterocolitica envelope proteins which induce antibodies that react with human thyrotropin receptor

Graves' disease is an autoimmune disease mediated by autoantibodies to the thyrotropin receptor (TSHR). Several studies have suggested that the development of Graves' disease may be linked to infection with the enteric pathogen Yersinia enterocolitica. Using the purified recombinant extracellular domain of human TSHR (ETSHR), we have recently shown that immunization of mice with Y. enterocolitica results in the production of antibodies capable of reacting with the ETSHR. In this study, we identify two low molecular weight (5.5 kDa and 8 kDa) envelope proteins of Yersinia containing epitopes that are crossreactive with the TSHR. Identification of these crossreactive envelope proteins was achieved by Western blotting using affinity-purified anti-Y. enterocolitica antibodies that specifically react with the TSHR and, conversely, for envelope proteins of Yersinia. Confirmation that these Yersinia proteins contained crossreactive epitopes with the ETSHR was obtained by immunizing mice with partially purified envelope proteins, which resulted in the production of Abs that recognized the ETSHR. Further, some of the cross-reactive envelope proteins were purified with SDS-PAGE and HPLC. The crossreactive envelope proteins were shown to be chromosomally encoded, exposed on the surface of bacteria, and produced by virulent as well as avirulent strains of Yersinia (Y. pestis, Y. pseudotuberculosis, Y. enterocolitica VW+, and Y. enterocolitica VW-). These results identify for the first time the Yersinia envelope proteins that are crossreactive with the ETSHR. Availability of these proteins will allow future studies to determine whether patients with Graves' disease have a unique immune response against these proteins when compared with healthy individuals.

Continuous electrophoretic separations in narrow channels coupled to small-bore capillaries

Continuous zone electrophoretic separations in channels have been demonstrated. This new technique has the potential to continuously sample and separate analytes from volume-limited microenvironments. A small-bore capillary is used to electrophoretically sample, but not separate, a mixture of dansylated amino acids. The capillary is coupled to a quartz channel structure in a manner which allows continuous injection of the sampled material into the channel. The channel functions to continuously separate the sampled material via electrophoresis. A laser-induced fluorescence detection scheme, which involves two fiber optic arrays situated at the channel exit, monitors eluting analytes. A continuous separation of dansylated amino acids on the time scale of a few minutes demonstrates the utility of the technique. Sampling has been performed continuously up to 400 s, and initial detection limits are approximately 30 microM.

Alterations of the stalk of the influenza virus neuraminidase: deletions and insertions

The neuraminidase (NA) of influenza viruses cleaves sialic acids from receptors, prevents self-aggregation and facilitates release of virus during budding from host cells. Although the structure and function of the globular head of the influenza virus NA has been well studied, much less is known about the stalk of the NA, the region between the viral membrane and the globular head. Applying a reverse genetics system, we altered the stalk of the influenza A/WSN/33 virus NA by making deletions, insertions and mutations in this region of the gene. Our data show that the length of the NA stalk can be variable. Deletions of up to 28 amino acids and insertions of up to 41 amino acids in the stalk region did not abolish formation of infectious progeny virus. The data also indicate that the cysteine at position 76 is essential for formation of infectious virus, and that deletions beyond the cysteine did not result in infectious virus. Interestingly, shortening of the length of the stalk region by 28 amino acids resulted in a virus with a markedly reduced growth rate in MDCK cells as compared to that in MDBK cells. An insertion of 41 extra amino acids into the stalk did not significantly interfere with viral growth in MDCK or MDBK cells, which suggests that the stalk region would tolerate the introduction of long foreign sequences.

Immunization of mice with Yersinia enterocolitica leads to the induction of antithyrotropin receptor antibodies

It is well established that autoimmune Graves' disease, which is characterized by hyperthyroidism, is mediated by autoantibodies to the thyrotropin receptor (TSHr). Although what initially triggers this autoantibody response is not known, a number of studies have suggested that Yersinia enterocolitica, an enterobacteria, could initiate the immune response against the TSHr. In this study, we produced antibodies against purified extracellular domain of human TSHr (ETSHr) and showed that anti-ETSHr antibodies reacted with envelope preparations from Y. enterocolitica. This reactivity was specifically blocked by preincubating sera with purified ETSHr. Moreover, antibodies reactive with ETSHr were induced by immunizing mice with Y. enterocolitica but not with Shigella flexneri SA100, Salmonella typhimurium TML, and Listeria monocytogenes. Anti-Y. enterocolitica antisera specifically reacted with the ETSHr protein and the reactivity could be blocked both by ETSHr and Y. enterocolitica envelope proteins. Our studies provide the first direct evidence that immunization with Y. enterocolitica can lead to the production of antibodies capable of reacting with TSHr and might provide the initial stimulus necessary for breakdown of self-tolerance to TSHr, eventually leading to the development of autoimmunity to TSHr.

Immunization of mice with Yersinia enterocolitica leads to the induction of antithyrotropin receptor antibodies

It is well established that autoimmune Graves' disease, which is characterized by hyperthyroidism, is mediated by autoantibodies to the thyrotropin receptor (TSHr). Although what initially triggers this autoantibody response is not known, a number of studies have suggested that Yersinia enterocolitica, an enterobacteria, could initiate the immune response against the TSHr. In this study, we produced antibodies against purified extracellular domain of human TSHr (ETSHr) and showed that anti-ETSHr antibodies reacted with envelope preparations from Y. enterocolitica. This reactivity was specifically blocked by preincubating sera with purified ETSHr. Moreover, antibodies reactive with ETSHr were induced by immunizing mice with Y. enterocolitica but not with Shigella flexneri SA100, Salmonella typhimurium TML, and Listeria monocytogenes. Anti-Y. enterocolitica antisera specifically reacted with the ETSHr protein and the reactivity could be blocked both by ETSHr and Y. enterocolitica envelope proteins. Our studies provide the first direct evidence that immunization with Y. enterocolitica can lead to the production of antibodies capable of reacting with TSHr and might provide the initial stimulus necessary for breakdown of self-tolerance to TSHr, eventually leading to the development of autoimmunity to TSHr.

Tumor necrosis factor alpha binding to bacteria: evidence for a high-affinity receptor and alteration of bacterial virulence properties

Human and murine receptors for tumor necrosis factor alpha (TNF-alpha) are present on most somatic cells and have been characterized and cloned. In contrast, very little is currently known about whether TNF-alpha can bind to pathogens and whether such binding results in important biological consequences for the infected host. We now report that a number of gram-negative bacteria have receptors for TNF-alpha. Using 125I-labeled TNF-alpha, we show that Shigella flexneri has 276 receptors for TNF-alpha, with a Kd of 2.5 nM. The binding of labeled TNF-alpha to these bacterial receptors can be inhibited by cold TNF-alpha but not by cold TNF-beta. Binding of 125I-TNF-alpha to S. flexneri was inhibited by trypsin treatment of bacterial cells or incubation at 52 degrees C for 3 min. Monoclonal antibody to either the 55-kDa or the 75-kDa TNF-alpha receptor, which are present on different eukaryotic cells, had no effect on 125I-TNF-alpha binding to bacteria. A number of gram-negative bacteria were capable of binding 125I-TNF-alpha. Gram-positive bacteria bound significantly less 125I-TNF-alpha than gram-negative bacteria. Pretreatment of S. flexneri with TNF-alpha resulted in enhanced bacterial invasion of HeLa cells and enhanced uptake by human and murine macrophages. Pretreatment of HeLa cells with antibody to the 55-kDa TNF-alpha receptor abrogated enhanced invasion of HeLa cells by TNF-alpha-bacterium complexes. These results suggest that TNF-alpha-bacterium complexes can interact with TNF-alpha receptors present on eukaryotic cells. This report shows that gram-negative bacteria have receptors for TNF-alpha and that a virulence property of a bacterium is altered as a consequence of cytokine binding.

Inhibition of RNA polymerase by captan at both DNA and substrate binding sites

RNA synthesis carried out in vitro by Escherichia coli RNA polymerase was inhibited irreversibly by captan when T7 DNA was used as template. An earlier report and this one show that captan blocks the DNA binding site on the enzyme. Herein, it is also revealed that captan acts at the nucleoside triphosphate (NTP) binding site, and kinetic relationships of the action of captan at the two sites are detailed. The inhibition by captan via the DNA binding site of the enzyme was confirmed by kinetic studies and it was further shown that [14C]captan bound to the beta' subunit of RNA polymerase. This subunit contains the DNA binding site. Competitive-like inhibition by captan versus UTP led to the conclusion that captan also blocked the NTP binding site. In support of this conclusion, [14C]captan was observed to bind to the beta subunit which contains the NTP binding site. Whereas, preincubation of RNA polymerase with both DNA and NTPs prevented captan inhibition, preincubation with either DNA or NTPs alone was insufficient to protect the enzyme from the action of captan. Furthermore, the interaction of [14C]captan with the beta and beta' subunits was not prevented by a similar preincubation. Captan also bound, to a lesser extent, to the alpha and sigma subunits. Therefore, captan binding appears to involve interaction with RNA polymerase at sites in addition to those for DNA and NTP; however, this action does not inhibit the polymerase activity.

Mechanism of attenuation of a chimeric influenza A/B transfectant virus

The ribonucleoprotein transfection system for influenza virus allowed us to construct an influenza A virus containing a chimeric neuraminidase (NA) gene in which the noncoding sequence is derived from the NS gene of influenza B virus (T. Muster, E. K. Subbarao, M. Enami, B. P. Murphy, and P. Palese, Proc. Natl. Acad. Sci. USA 88:5177-5181, 1991). This transfectant virus is attenuated in mice and grows to lower titers in tissue culture than wild-type virus. Since such a virus has characteristics desirable for a live attenuated vaccine strain, attempts were made to characterize this virus at the molecular level. Our analysis suggests that the attenuation of the virus is due to changes in the cis signal sequences, which resulted in a reduction of transcription and replication of the chimeric NA gene. The major finding concerns a sixfold reduction in NA-specific viral RNA in the virion, causing a reduction in the ratio of infectious particles to physical particles compared with the ratio in wild-type virus. Although the NA-specific mRNA level is also reduced in transfectant virus-infected cells, it does not appear to contribute to the attenuation characteristics of the virus. The levels of the other RNAs and their expression appear to be unchanged for the transfectant virus. It is suggested that downregulation of the synthesis of one viral RNA segment leads to the generation of defective viruses during each replication cycle. We believe that this represents a general principle for attenuation which may be applied to other segmented viruses containing either single-stranded or double-stranded RNA.

Hydrolysis of the 2',3'-allylic epoxides of allylbenzene, estragole, eugenol, and safrole by both microsomal and cytosolic epoxide hydrolases

2',3'-Allylic epoxide derivatives of allylbenzene and its analogs estragole, eugenol, and safrole were synthesized, and their enzymatic conversion to dihydrodiols by cytosolic and microsomal epoxide hydrolases was examined. All four epoxides were good substrates for both epoxide hydrolases, with Michaelis constants in the low micromolar range. Two putatively selective inhibitors of cytosolic and microsomal epoxide hydrolases, trichloropropylene oxide and nordihydroguaiaretic acid, were used to inhibit the hydrolysis of these allylic epoxides. Minimal selectivity toward either hydrolase was seen with either inhibitor, suggesting that the "selectivity" of these inhibitors is highly substrate-dependent. The susceptibilities of these epoxides to rapid hydrolysis by both epoxide hydrolases may explain their low genotoxic potencies in vivo.