Effect of non-tumor cell contamination on detection of p53 gene mutations in human gastric cancer cells by polymerase chain reaction single-strand conformation polymorphism analysis

BACKGROUND

We have previously studied p53 gene mutations in 25 primary gastric cancer tissues by polymerase chain reaction single-strand conformation polymorphism (PCR-SSCP) analysis for exon 4-8 and immunohistochemical staining with anti-p53 antibody. In four cases, the discrepancy of the results was observed between the two methods. In one case positive by PCR-SSCP but negative by immunohistochemical staining, the mutation was silent. In three cases, the p53 gene mutations were detected only by immunohistochemical staining. This discrepancy may be due to the contamination of the samples by cells without p53 gene mutation, such as non-tumor cells. This study was conducted to investigate the sensitivity of PCR-SSCP analysis to p53 gene mutations when the sample was contaminated with non-tumor cells.

METHODS

Genomic DNA was extracted by the digestion with proteinase K and phenol-chloroform-ethanol method from two human gastric adenocarcinoma cell lines, MKN-45 and KATO III. To investigate the sensitivity of PCR-SSCP, DNA extracted from cancer cells was mixed with DNA obtained from normal gastric mucosal cells at various ratios. PCR-SSCP analysis for exon 4-8 of the p53 gene was performed with the mixed DNA samples.

RESULTS

In KATO III, no PCR products were generated in exon 4-8 of the p53 gene by PCR, suggesting that both alleles from exon 4-8 of the p53 gene were deleted. In MKN-45, the mobility shift was observed in exon 4. Therefore, the effect of non-tumor cell contamination on the detection of p53 gene mutations was conducted using MKN-45 and normal gastric mucosal cells. In the mixed DNA samples of MKN-45 and normal gastric mucosal cells, an extra band with the migration similar to that of MKN-45 was found in the samples of 1:8 dilution or less, while no extra band was grossly detectable in DNA of normal gastric mucosal cells and in the samples of more than 1:16 dilution.

CONCLUSIONS

These results suggest that the detection of p53 mutations by PCR-SSCP analysis may be underestimated in samples contaminated by a large number of non-tumor cells.

Cloning and sequence analysis of a murine cDNA encoding glutamate decarboxylase (GAD65)

We report the cloning and cDNA sequence of murine GAD65. Murine GAD65 is comprised of 585 amino acids and shares a high degree of homology with human and rat GAD65, with most divergences occurring near their amino-termini. The murine GAD65 sequence will allow evaluation of the role of this gene in murine neurogenetic and autoimmune diseases.

Purification and biochemical properties of an alkaline pullulanase from alkalophilic Bacillus sp. S-1

A novel extracellular pullulanase (PUL-E, pullulan 6-glucanohydrolase, EC 3.2.1.41) has been purified from the alkalophilic Bacillus sp. S-1. The purified enzyme had a molecular mass of about 140 kDa on denaturated and natural conditions. The pI was 5.5. The pullulanase, when resolved by SDS-PAGE, was negative for Schiff staining, suggesting that the enzyme is not a glycoprotein. The N-terminal amino acid sequence of the enzyme was Phe-Leu-Asn-Met-Ser-(Trp-Phe). The enzyme displayed a temperature optimum of around 60 degrees C and a pH optimum of around pH 9.0. The enzyme was stable to incubation from pH 4.0 to pH 11.0 at 4 degrees C for 24 h. The presence of pullulan protected the enzyme from heat inactivation, the extent depending upon the substrate concentration. The activity of the enzyme was stimulated by Mn2+ ions. Ca2+ ions and EDTA did not inhibit the enzyme activity. The enzyme hydrolyzed the alpha-1,6-linkages of amylopectin, glycogens, alpha,beta-limited dextrin, and pullulan. The enzyme had an apparent Km of 7.92 mg/ml for pullulan, a Km of 1.63 mg/ml for amylopectin, and a Km of 3.1 mg/ml for alpha,beta-limited dextrin, when measured at pH 9.0 and 50 degrees C. The enzyme caused the complete hydrolysis of pullulan to maltotriose. The activity was not inhibited by alpha, beta, or gamma-cyclodextrins. The western blotting analysis with mouse anti-serum against PUL-E showed that PUL-E is produced as a single enzyme form during bacterial cultivation.

Generation of expressed sequence tags of random root cDNA clones of Brassica napus by single-run partial sequencing

Two hundred thirty-seven expressed sequence tags (ESTs) of Brassica napus were generated by single-run partial sequencing of 197 random root cDNA clones. A computer search of these root ESTs revealed that 21 ESTs show significant similarity to the protein-coding sequences in the existing data bases, including five stress- or defense-related genes and four clones related to the genes from other kingdoms. Northern blot analysis of the 10 data base-matched cDNA clones revealed that many of the clones are expressed most abundantly in root but less abundantly in other organs. However, two clones were highly root specific. The results show that generation of the root ESTs by partial sequencing of random cDNA clones along with the expression analysis is an efficient approach to isolate genes that are functional in plant root in a large scale. We also discuss the results of the examination of cDNA libraries and sequencing methods suitable for this approach.

Chicxulub Multiring Impact Basin: Size and Other Characteristics Derived from Gravity Analysis

The buried Chicxulub impact structure in Mexico, which is linked to the Cretaceous- Tertiary (K-T) boundary layer, may be significantly larger than previously suspected. Reprocessed gravity data over Northern Yucatan reveal three major rings and parts of a fourth ring, spaced similarly to those observed at multiring impact basins on other planets. The outer ring, probably corresponding to the basin's topographic rim, is almost 300 kilometers in diameter, indicating that Chicxulub may be one of the largest impact structures produced in the inner solar system since the period of early bombardment ended nearly 4 billion years ago.

Effect of the myotonic dystrophy (DM) mutation on mRNA levels of the DM gene

Myotonic dystrophy (DM) results from the amplification of an unstable CTG repeat in the 3' untranslated region of a transcript encoding a putative serine/threonine kinase. We have analysed the amplification of the repeat and the steady state levels of the DM kinase (DMK) mRNA in tissues and cell lines from normal and congenital DM individuals. Southern blot analysis of DNA samples from a severely affected neonate shows somatic heterogeneity of the repeat in all tissues studied. RNA analyses on these tissues show a marked increase in DMK steady state mRNA levels. We demonstrate that the mutant DMK allele is expressed regardless of the number of CTG repeats and that the increase in DMK mRNA levels is due to elevated mutant mRNA levels. We postulate that elevated DMK levels explains the dominant inheritance pattern of DM.

Purification and characterization of Thermus caldophilus GK24 DNA polymerase

A thermostable DNA polymerase from Thermus caldophilus GK24 was purified to near homogeneity by chromatographic methods, including ion-exchange, gel-filtration and affinity chromatography. The purified enzyme had a specific activity of 8400 U/mg at 75 degrees C and a molecular mass of 95 kDa, estimated by SDS/PAGE and Superose-12 gel filtration. Reaction conditions were investigated in terms of pH, metal-ion concentration and temperature. Experimental results showed that T. caldophilus (Tca) DNA polymerase had a maximum activity near pH 8.7 at 75 degrees C. The N-terminal sequence of the enzyme was highly similar to that of Thermus aquaticus (Taq) DNA polymerase, which was consistent with the fact that the enzyme had 5'-to-3' exonuclease activity and no 3'-to-5' exonuclease activity. Gene amplification using Tca DNA polymerase resulted in longer products than amplification using Taq DNA polymerase.

Biology and neurobiology of Borna disease viruses (BDV), defined by antibodies, neutralizability and their pathogenic potential

Borna disease viruses (BDV) isolated from more than 20 naturally infected horses, 2 sheep and a possible feline isolate were included in these studies. Most of these wild-type viruses were grown in rabbit cells. Specifically rabbit-adapted viruses establish persistent infection in immortalized cell lines of various animal species. Brain-, tissue culture-, and cell-free released viruses could all be neutralized with antibodies from naturally and experimentally infected animals (horse; hamster, rat, rabbit, mouse, and chicken), with highest titres in birds. Splenectomized rabbits, which were subsequently infected with BDV, efficiently produced high titres of neutralizing antibodies. All of the neutralizing sera and cerebrospinal fluids from infected animals inhibited tissue culture spread of BDV. Experimental infection and hyperimmunization induced antibodies directed against the major components of the soluble antigen (60, 40/38, 25 and 14.5 kD proteins). Analysis of the s-antigen complex with these sera and 6 stable monoclonal antibodies revealed that it consists of 40/38 and 25 kD proteins. Although each of these antibodies detected intracellular virus-specific structures they did not recognize outer plasma membrane antigens, showed no cross-reactivity, and had no neutralizing capacity. Unifying pathogenetic concepts of this neurotropic virus and its structural elements are discussed.

Estimates of emissions of SO2, NOx, HCl and NH3 from a densely populated region of the UK

Estimates of emissions of SO2, NOx, HCl and NH3 have been made for a densely populated region of the UK, the North-West of England, using data on power generation, incinerator plant capacity, fuel usage and animal and human population statistics. The spatial distributions of SO2 and NOx emissions are quite different, reflecting their different source strengths. The emissions from motor vehicles make up 52% of the NOx emissions from the North-West of England, whilst those from fossil-fuel-fired power stations make up 20%. The emissions of fossil-fuel-fired power stations make up 58% of SO2 emissions from the North-West. A large fossil-fuel-fired power station is the largest known point source for emissions of SO2, NOx and HCl. The largest contribution to NH3 emissions in the North-West is from cattle. Humans may contribute some NH3 to overall emissions but there is considerable uncertainty as to how much is emitted and what fraction of this is deposited within buildings. The uncertainties in the methodologies used are high-lighted and, where possible, recommendations are made as to how future emissions estimates might be improved. Potential reductions in emissions of SO2, NOx and HCl are discussed under basic scenarios of planned power station closures in the area and the compliance of the electricity generation industry with the European Community Directive on Large Combustion Plants.

Catalytic properties of the cloned amylase from Bacillus licheniformis

A gene encoding a new amylolytic enzyme of Bacillus licheniformis (BLMA) has been cloned, and we characterized the enzyme expressed in Escherichia coli. The genomic DNA of B. licheniformis was double-digested with EcoRI and BamHI and ligated the pBR322. The transformed E. coli was selected by its amylolytic activity, which carries the recombinant plasmid pIJ322 containing a 3.5-kilobase fragment of B. licheniformis DNA. The purified enzyme encoded by pIJ322 was capable of hydrolyzing pullulan and cyclodextrin as well as starch. It was active over a pH range of 6-8 and its optimum temperature was 50 degrees C. The molecular weight of the enzyme was 64,000, and the isoelectric point was 5.4. It degraded soluble starch by cleaving maltose units preferentially but did not attack alpha-1,6-linkage. The enzyme also hydrolyzed pullulan to panose units exclusively. In the presence of glucose, however, it transferred the panosyl moiety to glucose with the formation of alpha-1,6-linkage. The specificity of transferring activity is evident from the result of the maltosyl-transferring reaction which produces isopanose from maltotriose and glucose. The molecular structure of the enzyme deduced from the nucleotide sequence of the clone maintains limited similarity in the conserved regions to the other amylolytic enzymes.

Proteolytic modification of raw-starch-digesting amylase from Bacillus circulans F-2 with subtilisin: separation of the substrate-hydrolytic domain and the raw substrate-adsorbable domain

Raw starch-digesting amylase (BF-2A, 93,000 Da) from Bacillus circulans F-2 was converted into two components during digestion with subtilisin. The two components were separated and designated BF-2A' (63 kDa) and BF-2B (30 kDa), respectively. BF-2A' exhibited the same hydrolysis curve for soluble starch as the original amylase (BF-2A). Moreover, the catalytic activities of original and modified enzymes were indistinguishable in Km, Vmax and in their specific activity for soluble starch hydrolysis. However, its absorbability and digestibility on raw starch was greatly decreased. Furthermore, the enzymatic action pattern on soluble starch was differed greatly from that of BF-2A. The stability of the enzymes decreased below pH 5.5 and at 50 degrees C, while it was quite stable even at pH 12. On the other hand, the smaller peptide (BF-2B) could be adsorbed onto raw starch. From these results, it is suggested that the larger peptide (BF-2A') has a region responsible for the expression of the enzyme activity to hydrolyze soluble substrate, and the smaller peptide (BF-2B) plays a role on raw starch adsorption and also contributes to the original enzyme-to-enzyme stabilization. A proposed model of the raw-starch-digesting enzyme from this strain is extensively discussed.

Absent or faint renal uptake on bone scan. Etiology and significance in metastatic bone disease

A review of 14,296 unselected bone scans identified 889 scans showing absent or faint renal uptake. The majority of cases were associated with renal insufficiency (816/889; 91.8%), while widespread metastatic bone disease was the most common cause in a group of patients without renal disease (53/889; 6.0%). Of the 140 patients with prostate cancer, 108 (77.1%) had evidence of bone metastasis, 19 of whom (17.6%) revealed absent or faint renal uptake, demonstrating that poor renal uptake is more frequently associated with prostate cancer than with any other malignancy. Of note was that 162 out of 328 (49.4%) patients with stomach cancer at varying stages showed evidence of bone metastasis, and 14 of them (8.6%) showed poor renal images on bone scan. Interestingly, ankylosing spondylitis and rheumatoid arthritis were occasional causes of lack of renal activity (4 and 3 cases, respectively). A case of adult-form osteopetrosis, showing strikingly increased uptake mainly in the long bones with markedly diminished renal uptake, was also included in this study. Of the 53 bone scans with metastatic disease showing poor renal uptake, 44 (83.0%) revealed evidence of diffuse or multiple metastases in both spine and ribs, while 49 (92.5%) showed malignant involvement in three or more regions and 35 (66.0%) in four or more regions, suggesting widespread bone involvement in most cases.

Stimulation of prostaglandin synthesis by hyperoxia in perinatal rat lung cells

Prostaglandins (PGs) have been implicated in the development of pulmonary oxygen toxicity. We tested the hypothesis that hyperoxia modulates PG synthesis in a differentiation-arrested primary lung cell culture model in the rat at three developmental ages: day-20 gestation (term = 22 days), days 1 and 3 after birth. The time courses of the response to hyperoxia were defined in preconfluent lung cells as well as in growth-arrested, confluent cells. From days 4-8 after plating in growth medium containing 10% carbonstripped fetal bovine serum, exposure to 95% O2, in contrast to 1% O2, inhibited cell proliferation but significantly enhanced the production of PGI2 and, to a lesser extent, PGE2 at all three ages. The capacity to metabolize exogenous arachidonic acid (AA) to PGI2 was also increased two-to threefold (P less than 0.01). Cellular release of lactate dehydrogenase, a measure of O2 toxicity, remained unchanged during exposure to 1% O2 but increased fivefold between 48 and 96 h after exposure to hyperoxia (from 2% total to 10.5%, P less than 0.01). In confluent, growtharrested cells, under serum-free conditions, exposure to hyperoxia for 24-48 h resulted in a similar induction of PG synthesis. Our results suggest that hyperoxia stimulates PG synthesis in the perinatal rat lung and that this effect is independent of cell growth or the presence of serum. We speculate that this hyperoxia-induced PG synthesis is a relatively early response to oxidant stress and may serve as an useful early marker for O2 toxicity in perinatal lung cells.

Localization of In-111 antimyosin Fab and 99mTc-pyrophosphate in reperfusion myocardial infarction model

The myocardial uptake of In-111 antimyosin Fab and Tc-99m pyrophosphate was studied in dogs undergoing coronary artery occlusion for 90 minutes followed by reperfusion. The regional myocardial blood flow was determined by injecting Sc-46 labeled microsphere and was related to the relative concentrations of In-111 antimyosin and Tc-99m pyrophosphate. There was an inverse linear correlation between In-111 antimyosin Fab localization and the regional blood flow in both the subendocardial (r = 0.81) and subepicardial myocardium (r = -0.80). The greatest uptake of antimyosin was observed in areas of severe blood flow reduction (0-10% of normal). On the other hand, there was no correlation between the Tc-99m pyrophosphate uptake and the degree of blood flow reduction. Maximal subendocardial localization of Tc-99m degree of blood flow reduction. Maximal subendocardial localization of Tc-99m pyrophosphate was observed in areas where the blood flow was reduced to 31-50% of the normal. In the case of the subepicardium, the greatest uptake was localized to areas of 0 to 10% of the normal flow. In addition, there was significant myocardial uptake in regions where the blood flow was minimally reduced (greater than 81%). This study suggests that In-111 antimyosin Fab is a specific and quantitative tool in the evaluation of myocardial necrosis.

Effects of reactive oxygen species on prostacyclin production in perinatal rat lung cells

A differentiation-arrested primary cell culture model was used to examine the role of reactive oxygen species in the control of prostacyclin (PGI2) production in the perinatal rat lung. Coincubation of the lung cells with arachidonic acid (AA) and xanthine (X, 0.25 mM) plus xanthine oxidase (XO, 10 mU/ml) or with AA and glucose (25 mM) plus glucose oxidase (25 mU/ml) augmented the AA-induced PGI2 output. Superoxide dismutase (10 U/ml) did not alter the X + XO effect, whereas catalase (10 U/ml) eliminated both X + XO and glucose plus glucose oxidase effects. H2O2 (1-200 microM) showed a dose-related biphasic augmentation with peak stimulation at 20 microM. Catalase again blocked this effect, but dimethylthiourea, a hydroxyl radical scavenger, did not. A 20-min pretreatment of the cells with X + XO, glucose plus glucose oxidase, or H2O2, however, diminished the capacity of the cells to convert exogenous AA to PGI2. This pretreatment effect was also blocked by catalase. The responses were similar in lung cells obtained from day 20 rat fetuses (term = 22 days) and 1-day-old newborn rats. Lactate dehydrogenase release was not detected during treatment periods but increased significantly after exposure to reactive oxygen species.(ABSTRACT TRUNCATED AT 250 WORDS)

Search for the optimal sequence of the ribosome binding site by random oligonucleotide-directed mutagenesis

Synthetic DNA duplexes corresponding to the ribosome binding site (RBS) were synthesized through the phosphite method on solid support. The synthetic RBS DNA with partial random sequences was inserted into an appropriate site between the lpp-lac promoter and the beta-galactosidase structural gene in plasmid pMKT2. The level of beta-galactosidase expression was correlated with the color intensity of the recombinant colonies on X-gal plates. The bluest colonies were isolated and characterized with respect to beta-galactosidase enzyme activity and RBS sequence. There was good correlation between color intensity and the level of the enzyme activity, and this provided a reliable phenotypic screening method in the search for the optimal regulatory sequences. Novel RBS sequences obtained here show not only the unique nucleotide distribution, but also strong complemetarity to the 3' end region of 16S rRNA, from which could be deduced a generalized RBS sequence, the position of the SD region, and the 16S rRNA position mediated during translation initiation.

Ventilatory response to hypoxia in unanesthetized newborn kittens

We studied the ventilatory response to hypoxia in 11 unanesthetized newborn kittens (n = 54) between 2 and 36 days of age by use of a flow-through system. During quiet sleep, with a decrease in inspired O2 fraction from 21 to 10%, minute ventilation increased from 0.828 +/- 0.029 to 1.166 +/- 0.047 l.min-1.kg-1 (P less than 0.001) and then decreased to 0.929 +/- 0.043 by 10 min of hypoxia. The late decrease in ventilation during hypoxia was related to a decrease in tidal volume (P less than 0.001). Respiratory frequency increased from 47 +/- 1 to 56 +/- 2 breaths/min, and integrated diaphragmatic activity increased from 14.9 +/- 0.9 to 20.2 +/- 1.4 arbitrary units; both remained elevated during hypoxia (P less than 0.001). Younger kittens (less than 10 days) had a greater decrease in ventilation than older kittens. These results suggest that the late decrease in ventilation during hypoxia in the newborn kitten is not central but is due to a peripheral mechanism located in the lungs or respiratory pump and affecting tidal volume primarily. We speculate that either pulmonary bronchoconstriction or mechanical uncoupling of diaphragm and chest wall may be involved.

Effect of morphine on breathing and behavior in fetal sheep

To define the dose response of apnea and breathing to morphine we studied 12 fetuses at 116-141 days of gestation using our window technique. We instrumented the fetus to record electrocortical activity (ECoG), eye movements (EOG), diaphragmatic activity (integral of EMGdi), heart rate, carotid blood pressure, and amniotic pressure. Saline and morphine in doses of 0.03, 0.1, 0.5, 1, and 3 mg/kg were injected in random order in the jugular vein of the fetus during low-voltage ECoG. Fetuses were videotaped for evaluation of fetal behavior. We found 1) that saline did not elicit a response; 2) apnea, associated with a change from low- to high-voltage ECoG, increased from 2.2 +/- 1.5 (SE) min in two fetuses at a dose of 0.03 mg to 20 +/- 6.3 min in seven fetuses at 3 mg/kg (P less than 0.005); 3) the length of the breathing responses, associated with a change from high- to low-voltage ECoG, were 15 +/- 1.8 and 135.9 +/- 18.1 min (P less than 0.0005); 4) integral of EMGdi X frequency, an index equivalent to minute ventilation, increased from 1,763 +/- 317 arbitrary units to 10,658 +/- 1,843 at 1.0 mg/kg and then decreased to 7,997 +/- 1,335 at 3.0 mg/kg. These changes were related to a steady increase in integral of EMGdi, whereas frequency decreased at 3 mg/kg. There was an increase in breathing response to morphine plasma concentrations or morphine doses.(ABSTRACT TRUNCATED AT 250 WORDS)

Shivering following retrobulbar block

A case of a severe but brief period of shivering following a retrobulbar block (RBB) is presented. The shivering occurred within two minutes after completion of the RBB and subsided gradually within five minutes, without specific treatment. The patient remained conscious during the episode of shivering. The shivering was so abrupt and severe as to be misjudged as a seizure, but its onset appeared to be slower than a seizure. The mechanism of shivering appeared to be the central spread of local anaesthetic solution into the brain stem, along the optic nerve. Shivering may be a warning sign of brain stem anaesthesia and demands special care to anticipate life-threatening complications.