Immunocytochemical study of cells in the vitreous of proliferative vitreoretretinopathy

PURPOSE

To identify the cellular components of vitreous samples obtained during vitrectomy for proliferative vitreoretinopathy (PVR).

METHODS

With the use of three intermediate filament (IF) proteins, vimentin, glial fibrillary acidic protein (GFAP), and cytokeratin (CK), cytocentrifuge slides of 14 fresh vitreous aspirates were detected with immunohistochemical technique.

RESULTS

All the specimens contained epithelial-like proliferative cells with or without pigment and some membrane-like pieces. Immunocytochemical staining showed that 76.0-90.0% cells stained for CK, 17.4-29.6% cells expressed GFAP, and 80.1-91.0% cells were positive for vimentin.

CONCLUSIONS

Majority of cells in the vitreous samples originated from retinal pigment epithelial cells (RPE) and glial cells in PVR. Expression of IF proteins may be determined by tissue of origin and local microenvironment.

[The design of an ultrasonics Doppler spectrum analysis system for fetal umbilical blood flow monitoring]

This paper explains the design of an Ultrasonics Doppler Spectrum Analysis System for fetal umbilical blood flow monitoring. The gist of discussion includes the sampling method of the Doppler signals and the algorithm of the blood flow parameters. Because the DSP chip is not used in the AD cardboard, the hardware design is simplified and the system works steadily. In the process of computing the blood flow paramenters, an autochange method of the amplitude threshold and a timeout control technology are used, so the algorithm has good adaptability and works very stable.

[Chemical constituents of Cichorium intybus L]

OBJECTIVE

To investigate the chemical constituents of Cichorium intybus.

METHOD

Constituents were separated by means of solvent extraction and chromatography on silical gel. The structures were established by spectral analysis and chemical evidence.

RESULT

Seven compounds were isolated from the roots of C. intybus and four of them were identified as alpha-amyrin, taraxerone, baurenyl acetate and beta-sitosterol.

CONCLUSION

All the four compounds were obtained from the plant for the first time.

Targeted disruption of the mouse lysosomal acid lipase gene: long-term survival with massive cholesteryl ester and triglyceride storage

Lysosomal acid lipase (LAL) is essential for the hydrolysis of the triglycerides and cholesteryl esters in lysosomes. Its deficiency produces two phenotypes, a severe infantile-onset variant, Wolman disease (WD), and a later onset variant, cholesteryl ester storage disease (CESD). A mouse model with a LAL null mutation was produced by targeting disruption of the mouse gene. Homozygote knockout mice (lal -/lal-) produce no LAL mRNA, protein or enzyme activity. The lal-/lal- mice are born in Mendelian ratios, are normal appearing at birth, and follow normal development into adulthood. However, massive accumulation of triglycerides and cholesteryl esters occurs in several organs. By 21 days, the liver develops a yellow-orange color and is approximately 1.5-2.0x larger than normal. The accumulated cholesteryl esters and triglycerides are approximately 30-fold greater than normal. The lal+/lal- mice have approximately 50% of normal LAL activity and do not show lipid accumulation. Male and female lal-/lal- mice are fertile and can be bred to produce progeny. This mouse model is a phenotypic model of human CESD, and a biochemical and histopathologic mimic of human WD. The lal-/lal- mice provide a model to determine the role of LAL in lipid metabolism and the pathogenesis of its deficiency states.

trp RNA-binding attenuation protein-mediated long distance RNA refolding regulates translation of trpE in Bacillus subtilis

Expression of the trpEDCFBA operon is regulated at both the transcriptional and translational levels by the trp RNA-binding attenuation protein (TRAP) of Bacillus subtilis. When cells contain sufficient levels of tryptophan to activate TRAP, the protein binds to trp operon transcripts as they are being synthesized, most often causing transcription termination. However, termination is never 100% efficient, and transcripts that escape termination are subject to translational control. We determined that TRAP-mediated translational control of trpE can occur via a novel RNA conformational switch mechanism. When TRAP binds to the 5'-untranslated leader segment of a trp operon read-through transcript, it can disrupt a large secondary structure containing a portion of the TRAP binding target. This promotes refolding of the RNA such that the trpE Shine-Dalgarno sequence, located more than 100 nucleotides downstream from the TRAP binding site, becomes sequestered in a stable RNA hairpin. Results from cell-free translation, ribosome toeprint, and RNA structure mapping experiments demonstrate that formation of this structure reduces TrpE synthesis by blocking ribosome access to the trpE ribosome binding site. The role of the Shine-Dalgarno blocking hairpin in controlling translation of trpE was confirmed by examining the effect of multiple nucleotide substitutions that abolish the structure without altering the Shine-Dalgarno sequence itself. The possibility of protein-mediated RNA refolding as a general mechanism in controlling gene expression is discussed.

Molecular and enzymatic analyses of lysosomal acid lipase in cholesteryl ester storage disease

Human lysosomal acid lipase (hLAL) is essential for the hydrolysis of cholesteryl esters and triglycerides in the lysosome. Defective hLAL activity leads to two autosomal recessive traits, Wolman disease (WD) or cholesteryl ester storage disease (CESD). Phenotypically, WD has accumulation of both triglycerides and cholesteryl esters, while CESD has mainly elevated cholesteryl esters. We characterized mutations in the hLAL gene from two CESD siblings. By reverse transcriptase-PCR (RT-PCR) and cDNA cloning and sequencing, we identified homozygous deletion mutations of nucleotides 863 to 934, in the hLAL transcript. Normal levels of LAL mRNA were detected. The deletion in mRNA is due to a G to A transition in the last nucleotide of exon 8 of the hLAL gene, a splice junction mutation (E8SJM) that resulted in exon skipping, and a predicted in-frame deletion of the 24 amino acids. [35S]Met metabolic labeling studies in fibroblasts showed a low level of E8SJM LAL ( approximately 38%) that was highly unstable. Heterologous expression of E8SJM LAL in insect cells gave an LAL with low catalytic activity toward cholesteryl oleate and triolein. The effects of this mutation are complex with the production of decreased amounts of an unstable LAL that is catalytically defective. The results suggest that E8SJM leads to essentially a null allele and that the differences in WD and CESD phenotype involve other factors.

[The design of the ultrasonic Doppler spectrum analyze system for the naval blood stream of fetus]

The design of the Ultrasonic Doppler Specturm Analyze System for the naval blood stream of the fetus is discussed, mainly on the sampling method of the Doppler signals and the algorithm of the blood stream parameters. Because the DSP chip is not used in the AD cardboard, the hardware design is not only simplified, but also works more steady. In the process of the blood stream parameters, an autochange method of the amplitude threshold and a time-out control technology are used, so the algorithm has good adaptation and works very stable.

Activation of the tobacco SIP kinase by both a cell wall-derived carbohydrate elicitor and purified proteinaceous elicitins from Phytophthora spp

Two purified proteinaceous fungal elicitors, parasiticein (an alpha elicitin) and cryptogein (a beta elicitin), as well as a fungal cell wall-derived carbohydrate elicitor all rapidly activated a 48-kD kinase in tobacco suspension cells. The maximum activation of this kinase paralleled or preceded medium alkalization and activation of the defense gene phenylalanine ammonia-lyase (PAL). In addition, the two elicitins, which also induced hypersensitive cell death, activated a 44- and a 40-kD kinase with delayed kinetics. By contrast, the cell wall-derived elicitor only weakly activated the 44-kD kinase and failed to activate the 40-kD kinase. The size and substrate preference of the 48-kD kinase are reminiscent of the recently purified and cloned salicylic acid-induced protein (SIP) kinase, which is a member of the mitogen-activated protein kinase family. Antibodies raised against a peptide corresponding to the unique N terminus of SIP kinase immunoreacted with the 48-kD kinase activated by all three elicitors from Phytophthora spp. In addition, the cell wall elicitor and the salicylic acid-activated 48-kD kinase copurified through several chromatography steps and comigrated on two-dimensional gels. Based on these results, all three fungal elicitors appear to activate the SIP kinase. In addition, inhibition of SIP kinase activation by kinase inhibitors correlated with the suppression of cell wall elicitor-induced medium alkalization and PAL gene activation, suggesting a regulatory function for the SIP kinase in these defense responses.

Activation of the tobacco SIP kinase by both a cell wall-derived carbohydrate elicitor and purified proteinaceous elicitins from Phytophthora spp

Two purified proteinaceous fungal elicitors, parasiticein (an alpha elicitin) and cryptogein (a beta elicitin), as well as a fungal cell wall-derived carbohydrate elicitor all rapidly activated a 48-kD kinase in tobacco suspension cells. The maximum activation of this kinase paralleled or preceded medium alkalization and activation of the defense gene phenylalanine ammonia-lyase (PAL). In addition, the two elicitins, which also induced hypersensitive cell death, activated a 44- and a 40-kD kinase with delayed kinetics. By contrast, the cell wall-derived elicitor only weakly activated the 44-kD kinase and failed to activate the 40-kD kinase. The size and substrate preference of the 48-kD kinase are reminiscent of the recently purified and cloned salicylic acid-induced protein (SIP) kinase, which is a member of the mitogen-activated protein kinase family. Antibodies raised against a peptide corresponding to the unique N terminus of SIP kinase immunoreacted with the 48-kD kinase activated by all three elicitors from Phytophthora spp. In addition, the cell wall elicitor and the salicylic acid-activated 48-kD kinase copurified through several chromatography steps and comigrated on two-dimensional gels. Based on these results, all three fungal elicitors appear to activate the SIP kinase. In addition, inhibition of SIP kinase activation by kinase inhibitors correlated with the suppression of cell wall elicitor-induced medium alkalization and PAL gene activation, suggesting a regulatory function for the SIP kinase in these defense responses.

EMG study in the diagnosis and differential diagnosis of lipid storage myopathy

Clinical, electromyographic and pathological features were studied in 18 patients with lipid storage myopathy (group I) and 18 patients with polymyositis and dermatomyositis (group II). The results showed a remarkable lower spontaneous activity(SA) incidence (14%) in group I than that (55%) in group II; 46% and 34% short-duration motor unit potentials(MUAPs) with polyphasic potentials and 74% and 71% short-duration MUAPs without polyphasic potentials respectively; the percentages of increased polyphasic MUAPs were same in the two groups. The reduced or pathologic interference patterns accounted for 61% in the group I and 50% in group II. Increased CPK, LDH and HBD were also found in both of them. It is suggested that the lipid storage myopathy may be diagnosed when patients have muscle weakness and myalgia with short-duration and low-amplitude and polyphasic MUAPs without or with occasional spontaneous activities, and increased CPK, LDH and HBD.

The epidemiology study of hyperuricemia and gout in a community population of Huangpu District in Shanghai

OBJECTIVE

To investigate the prevalence of hyperuricemia and gout in a community population of Huangpu District in Shanghai.

METHODS

In the target community, 2037 dwellers were interviewed with relevan questionnares from house to house. According to even house number 1017 blood samples were taken for serum uric acid (SUA) levels measured with the uricase-peroxidase enzymatic method.

RESULTS

The prevalence of hyperuricemia was 14.2% in men (SUA > 70 mg/L, 62 cases), 7.1% in women (SUA > 60 mg/L, 41 cases), 10.1% in both sexes. Seven gout patients were all men. The prevalence of gout in 2037 dwellers in Huangpu District was 0.77% in men and 0.34% in both sexes.

CONCLUSIONS

The mean SUA level in each age group in this survey was much higher than that of a previous study 1 carried out in Shanghai, Beijing and Guangzhou in 1980 (P < 0.05). And the prevalence of hyperuricemia was increased rapidly (in men: from 1.4% in the survey of 1980 to 14.2% in our survey; in women: from 1.3% in the survey of 1980 to 7.1% in our survey). Compared with Idonesia data in 1992, the prevalence of hyperuricemia and gout in our survey was lower than that in Indonesia (P < 0.05), which suggests that racial and genetic predispositions are key causative factors.

Mouse lysosomal acid lipase: characterization of the gene and analysis of promoter activity

Lysosomal acid lipase (LAL) is required for the hydrolysis of intracellular cholesteryl esters and triglycerides that are delivered to lysosomes by low density lipoprotein (LDL) receptor-mediated endocytosis. To understand that the expression of LAL mRNA and protein is tissue and cell specifically regulated in mice, genomic clones for the mouse lysosomal acid lipase (mLAL) gene were isolated and characterized. The 6.8 kb of the mLAL gene 5'-flanking region was sequenced. Comparisons of mouse and human LAL genes organization revealed identical intron/exon boundaries, except for intron 1 of the mouse gene, and identical exonic length of exons 3-9. The transcription start sites and exon 1 of mLAL were characterized by 5'-RACE-PCR and S1 nuclease mapping. Transfection of 5' flanking deletions of mLAL luciferase reporter gene construct identified positive and negative regulatory elements that varied with cell type. Transfection of three progressively smaller pieces of intron 1 inserted into an SV40 promoter and luciferase reporter gene revealed an enhancer-like activity in intron 1 that is also cell type specific. These studies provide insight into the basis for regulation of this critical enzyme in lipid metabolism.

[The analysis of donkey-hide glue, antler glue and tortoise shell glue by means of circular dichroism]

Donkey-hide glue, antler glue, tortoise shell glue and their forgeries were identified by the analysis method of circular dichroism(CD) in this paper. The standard spectra and data were set up. The method is simple, fast and accurate.

Cloning of an inr- and E-box-binding protein, TFII-I, that interacts physically and functionally with USF1

The transcription factor TFII-I has been shown to bind independently to two distinct promoter elements, a pyrimidine-rich initiator (Inr) and a recognition site (E-box) for upstream stimulatory factor 1 (USF1), and to stimulate USF1 binding to both of these sites. Here we describe the isolation of a cDNA encoding TFII-I and demonstrate that the corresponding 120 kDa polypeptide, when expressed ectopically, is capable of binding to both Inr and E-box elements. The primary structure of TFII-I reveals novel features that include six directly repeated 90 residue motifs that each possess a potential helix-loop/span-helix homology. These unique structural features suggest that TFII-I may have the capacity for multiple protein-protein and, potentially, multiple protein-DNA interactions. Consistent with this hypothesis and with previous in vitro studies, we further demonstrate that ectopic TFII-I and USF1 can act synergistically, and in some cases independently, to activate transcription in vivo through both Inr and the E-box elements of the adenovirus major late promoter. We also describe domains of USF1 that are necessary for its independent and synergistic activation functions.

Cloning, chromosome localization, expression, and characterization of an Src homology 2 and pleckstrin homology domain-containing insulin receptor binding protein hGrb10gamma

hGrb10alpha (previously named Grb-IR) is a Src-homology 2 domain-containing protein that binds with high affinity to the tyrosine-phosphorylated insulin receptor and insulin-like growth factor-1 receptor. At least two isoforms of human Grb10, (hGrb10alpha and hGrb10beta), which differ in the pleckstrin homology (PH) domain and the N-terminal sequence, have previously been identified in insulin target tissues such as human skeletal muscle and fat cells. Here we report the cloning of the third isoform of the hGrb10 family (hGrb10gamma) from human skeletal muscle and its localization to human chromosome 7. We have also determined the human chromosome localization of Grb7 to 17q21-q22 and Grb14 to chromosome 2. hGrb10gamma contains an intact PH domain and an N-terminal sequence that is present in hGrb10alpha but absent in hGrb10beta. RNase protection assays and Western blot analysis showed that hGrb10alpha and hGrb10gamma are differentially expressed in insulin target cells including skeletal muscle, liver, and adipocyte cells. hGrb10gamma is also expressed in HeLa cells and various breast cancer cell lines. The protein bound with high affinity to the insulin receptor in cells, and the interaction was dependent on the tyrosine phosphorylation of the receptor. hGrb10gamma also underwent insulin-stimulated membrane translocation and serine phosphorylation. hGrb10gamma phosphorylation was inhibited by PD98059, a specific inhibitor of mitogen-activated protein kinase kinase, and wortmannin, a specific inhibitor of phosphatidylinositol 3-kinase. Taken together, our data suggest that hGrb10 isoforms are potential downstream signaling components of the insulin receptor tyrosine kinase and that the PH domain may play an important role in the involvement of these isoforms in signal transduction pathways initiated by insulin and other growth factors.

Electrophysiological forms of Guillain-Barre syndrome in Beijing suburb

OBJECTIVE

To recognize different forms of Guillain-Barre syndrome (GBS) in northern China.

METHODS

Twenty-one cases were found in two counties of Beijing suburb from January 1993, to December, 1994. Multiple electrophysiological studies including magnetic motor evoked potential, F-wave, motor and sensory conduction velocity, blink reflex and needle electromyography were conducted on nineteen cases of them. Twelve cases accepted electrophysiological follow-up study.

RESULTS

Altogether 17 cases showed demyelination features in multiple electrodiagnosis. Ten cases of them were accompanied by different extent of axonal lesion. Only one case showed main or primary axonal lesion.

CONCLUSIONS

Demyelination is the main type of pathophysiological lesion of GBS in Beijing suburb. Different extent of axonal lesion can appear in some cases, but primary and main axonal type is rare in this area.

A clinical study on compound da huang (radix et Rhizoma rhei) preparations for improvement of senile persons' memory ability

By comparison of the effects of the Compound Tong Jiang Oral Liquid with Da Huang added (TJ [symbol: see text]) and Qi Yin Oral Liquid (QY [symbol: see text]) without Da Huang on senile persons' memory ability, it is discovered that the effects of TJ on shortening the interval between defecations and the duration of defecation, and on improving senile persons' memory ability are significantly better than that of QY (P < 0.05). In addition, TJ can also decrease the serum content of lipid peroxidase and increase the superoxide dismutase activity in red blood cells (RBC). Thus, it is demonstrated that Dahuang and its agents possess the action of anti-senility and can improve mentality.

Liver-directed gene transfer in non-human primates

To develop a primate model for liver-directed gene therapy, we studied several gene transfer vehicles and routes in eight rhesus monkeys (Macaca mulatta). For this purpose, we used first-generation, replication-deficient adenoviral vectors carrying the Escherichia coli lacZ gene (Ad.CMVlacZ) or a lacZ-containing plasmid (pCMV beta) with lipofectamine for transfection. The reporter gene construct was infused into either the portal vasculature, common bile duct, or saphenous vein. Adenovirus-mediated gene transfer via the portal vein resulted in expression of lacZ in over 70% of hepatocytes by days 3-7, but was accompanied by acute hepatitis. Adenovirus-mediated gene transfer via the common bile duct resulted in lacZ expression in less than 10% of hepatocytes and was accompanied by portal inflammation. The animals mounted a significant immune response, as demonstrated by adenoviral antigen-induced T-cell proliferation and production of neutralizing anti-adenovirus antibodies and antibodies to E. coli beta-galactosidase (beta-Gal). Activation of the immune response was associated with rapid decrease of the reporter gene by days 13-21. Lipofectamine-mediated gene transfer was inefficient, and no lacZ expression in the liver was detected. To limit the host immune response, 4 animals were immunosuppressed by cyclophosphamide/prednisone and then infused with the Ad.CMVlacZ via the portal vein or the saphenous vein. The monkeys showed sustained expression of lacZ for up to 35 days with no evidence of inflammation. The primates transduced via the saphenous vein showed a level of beta-Gal expression in the liver similar to that of the portal vein-infused animals. In conclusion, adenovirus-mediated gene transfer to non-human primate livers via the portal vein or saphenous vein is efficient, but it results in transient expression and is accompanied by an immune response to both vector and transgene products and acute hepatitis, whereas lipofectamine-mediated transfer is inefficient. Manipulation of the host immune response may expand potential applications of adenoviral vectors for liver-directed gene transfer.

Exaggerated pulmonary hypertension with monocrotaline in rats susceptible to chronic mountain sickness

Hilltop (H) strain Sprague-Dawley rats are more susceptible to chronic mountain sickness than are the Madison (M) strain rats. It is unclear what role pulmonary vascular remodeling, polycythemia, and hypoxia-induced vasoconstriction play in mediating the more severe pulmonary hypertension that develops in the H rats during chronic hypoxia. It is also unclear whether the increased sensitivity of the H rats to chronic mountain sickness is specific for a hypoxia effect or, instead, reflects a general propensity toward the development of pulmonary hypertension. Monocrotaline (MCT) causes pulmonary vascular remodeling and pulmonary hypertension. We hypothesized that the difference in the pulmonary vascular response to chronic hypoxia between H and M rats reflects an increased sensitivity of the H rats to any pulmonary hypertensive stimuli. Consequently, we expected the two strains to also differ in their susceptibility to MCT-induced pulmonary hypertension. Pulmonary arterial pressures in conscious H and M rats were measured 3 wk after a single dose of MCT, exposure to a simulated high altitude of 18,000 ft (barometric pressure = 380 mmHg), and administration of a single dose of saline as a placebo. The H rats had significantly higher pulmonary arterial pressures and right ventricular weights after MCT and chronic hypoxia than did the M rats. The H rats also had more pulmonary vascular remodeling, i.e., greater wall thickness as a percentage of vessel diameter, after MCT and chronic hypoxia than did the M rats. The H rats had significantly lower arterial PO2 than did the M rats after MCT, but the degree of hypoxemia was mild [arterial PO2 of 72.5 +/- 0.8 (SE) Torr for H rats vs. 77.4 +/- 0.8 Torr for M rats after MCT]. The H rats had lower arterial PCO2 and larger minute ventilation values than did the M rats after MCT. These ventilatory differences suggest that MCT caused more severe pulmonary vascular damage in the H rats than in the M rats. These data support the hypothesis that the H rats have a general propensity to develop pulmonary hypertension and suggest that differences in pulmonary vascular remodeling account for the increased susceptibility of H rats, compared with M rats, to both MCT and chronic hypoxia-induced pulmonary hypertension.

Grafted poly-(ethylene glycol) on lipid surfaces inhibits protein adsorption and cell adhesion

Monolayers of dipalmitoyl-phosphatidylethanolamine (DPPE) mixing with various mole percentages of distearoyl-phosphatidylethanolamine (DSPE)-conjugated poly-(ethylene glycol) (PEG m.w. 750-5000) were deposited on DPPE-coated glass surfaces by the Langmuir-Blodgett method. Increasing percentages of grafted PEG in these supported lipid surfaces increasingly inhibit the adsorption of bovine serum albumin (BSA), laminin, and fibronectin. Increasing percentages of grafted PEG also inhibit the adhesion of erythrocytes, lymphocytes, and macrophages to these supported lipid surfaces. The adsorption of proteins on lipid coated glass surfaces were assayed by the fluorescence of FITC-labelled proteins. Cell adhesion was measured mainly by microscopic counting. The concentration of PEG-grafted lipids required for the inhibition of erythrocyte adhesion decreases with increasing molecular weight of the grafted PEG. The inhibitory effects are strongly dependent on the graft density of PEG at low concentrations, but weakly dependent on graft density at higher concentrations. For DSPE-PEG5000, the change of graft density dependency occurs approximately at the complete coverage of the lipid surface by the grafted polymer in the mushroom conformation (0.7 mol%), and the transition to partial brush conformation. The change-overs become less distinctive for grafted PEG of lower molecular weights, probably due to the failure of strictly mushroom and brush models of the polymer. The relative inhibitory efficiency is protein or cell dependent. The implication on the function of stealth liposomes is discussed.

Development of necrosis and activation of disease resistance in transgenic tobacco plants with severely reduced catalase levels

Numerous studies argue that salicylic acid (SA) is an important component of the plant signal transduction pathway(s) leading to disease resistance. The discovery that the SA-binding protein is a catalase, whose activity is blocked by SA, led to the proposal that one of SA's modes of action is to inhibit this H2O2-degrading enzyme and thus elevate H2O2 levels. To test this model, an attempt was made to mimic the action of SA by reducing the synthesis of catalase using antisense RNA technology. Analyses of transgenic tobacco plants that expressed the tobacco catalase 1 (cat1) or catalase 2 (cat2) gene in an antisense orientation indicate that there is no correlation between modest to high levels of reduction in catalase activity and activation of plant defenses such as pathogenesis-related (PR)-1 protein synthesis. However, three independent antisense catalase transgenic plants (ASCAT1 Nos 16, 17, and 28), which exhibited the most severe reduction in catalase activity (approximately 90% or more), developed chlorosis or necrosis on some of their lower leaves. These same leaves accumulated very high levels of PR-1 proteins and showed enhanced resistance to tobacco mosaic virus. Necrosis and elevated SA, which appear to result from severe depression of catalase levels, may be responsible for the induction of these defense responses.

The trp RNA-binding attenuation protein regulates TrpG synthesis by binding to the trpG ribosome binding site of Bacillus subtilis

The trpG gene of Bacillus subtilis encodes a glutamine amidotransferase subunit which is involved in the biosynthesis of L-tryptophan and folic acid. The trp RNA-binding attenuation protein (TRAP) is involved in controlling expression of trpG at the level of translation in response to changes in the intracellular concentration of tryptophan. We performed in vitro experiments using purified TRAP to elucidate the mechanism of TRAP-dependent trpG regulation. A TRAP-trpG RNA footprint analysis showed that tryptophan-activated TRAP interacts with one UAG, one AAG, and seven GAG repeats present in the trpG transcript. Results from ribosome and TRAP toeprint experiments indicated that the ribosome and TRAP binding sites overlap. Experiments with a B. subtilis cell-free translation system demonstrated that TRAP inhibits TrpG synthesis. Thus, TRAP regulates translation of trpG by blocking ribosome access to the trpG ribosome binding site. Our results are consistent with a model in which each tryptophan-activated TRAP subunit interacts with one trinucleotide repeat in an RNA target, thereby wrapping the transcript around the periphery of the TRAP complex.

[Constuction of an improved system for the determination of fidelity of polymerase in PCR]

A system used for the determination of fidelity of DNA polymerase in PCR was developed in E.coli and was used to determine the fidelity of FD DNA polymerase in PCR amplication. Frame shift and base substitution mutations were created in vitro in the lacZ gene in pUC118 and pUC119. As a result, a set of six derived plasmids namely pFDFM118 and pFDFM119 (-1 frame shift), pFDFP118 and pFDFP119 (+1 frame shift), pFDFU118 and pFDFU119 (base substitution) were obtained. All of them failed to carry out lacZ alpha-complementation in E.coli MV1184 and the colonies appeared white on medium with X-Gal and IPTG consequently. PCR reaction was carried out using these derived plasmids as templates and the PCR products were ligated to specially constructed cloning vectors pFDFL118 or pFDFL119, and the ligated products were used to transform MV1184. If any back mutation happens to occur during PCR, the transformants would appear blue on medium with X-Gal and IPTG. By scoring the number of blue and white colonies, the fidelity of DNA polymerase can be calculated. With this system the error of replication of the FD DNA polymerase was found to be 10(-5)-10(-6).

Identification of a Soluble, High-Affinity Salicylic Acid-Binding Protein in Tobacco

Salicylic acid (SA) is a key component in the signal transduction pathway(s), leading to the activation of certain defense responses in plants after pathogen attack. Previous studies have identified several proteins, including catalase and ascorbate peroxidase, through which the SA signal might act. Here we describe a new SA-binding protein. This soluble protein is present in low abundance in tobacco (Nicotiana tabacum) leaves and has an apparent molecular weight of approximately 25,000. It reversibly binds SA with an apparent dissociation constant of 90 nM, an affinity that is 150-fold higher than that between SA and catalase. The ability of most analogs of SA to compete with labeled SA for binding to this protein correlated with their ability to induce defense gene expression and enhanced resistance. Strikingly, benzothiadiazole, a recently described chemical activator that induces plant defenses and disease resistance at very low rates of application, was the strongest competitor, being much more effective than unlabeled SA. The possible role of this SA-binding protein in defense signal transduction is discussed.