[Protective effects of sodium selenite and selenomethionine on genotoxicity to human peripheral lymphocytes induced by arsenic]

Inhibition bioassay of sister chromatid exchanges (SCE) and DNA synthesis was carried out to study the mechanism that selenium, as a chemical agent for intervention, could antagonize the effects of arsenic on body damage and lower incidence of tumor. Results demonstrated that SCE frequency in peripheral lymphocytes induced by As2O3 could be significantly reduced by preincubation with 5 x 10(-7), 1 x 10(-6) mol/L Na2SeO3 and co-exposure of 1 x 10(-6) mol/L selenomethionine. Inhibition of DNA synthesis could be antagonized by preincubation in with 5 x 10(-6) mol/L Na2SeO3 and co-exposure of 1 x 10(-6), 5 x 10(-6) mol/L selenomethionine. But, the mechanism that protective effects of selenium on the damage to cell genetic material induced by arsenic should be studied further.

Analysis of disparity gradient based cooperative stereo

This paper argues that the disparity gradient subsumes various constraints for stereo matching, and can thus be used as the basis of a unified cooperative stereo algorithm. Traditionally, selection of the neighborhood support function (NSF) in cooperative stereo was left as a heuristic exercise. We present an analysis and evaluation of three families of NSFs based on the disparity gradient. It is shown that an exponential decay function with a conveniently selectable parameter is well behaved in that it yields the least error, converges steadily, and produces correctly located weak-winners. The discovery of the well-behaved function facilitates the success of the disparity gradient based approach. It is suggested that this function will help a two-pass algorithm in resolving the dilemma of surface continuity and discontinuity/occlusion. In our experiments, the unified cooperative stereo-matching algorithm is tested on random-dot stereograms containing opaque and transparent surfaces. It is also shown to be applicable to both area matching and contour matching in real-world images.

Changes in sodium intake and blood pressure in a community-based intervention project in China

A sodium intervention project was carried out in Tianjin, China, as part of the Tianjin Project, which is a national pilot, community-based intervention programme to reduce non-communicable diseases. The aim of this 3 year sodium project was to evaluate the feasibility and effects of sodium reduction in the population. The evaluation of the programme was based on examinations of independent cross-sectional population samples in 1989 (1719 persons) and in 1992 (2304 persons) in the intervention and matched reference areas. Food weighing and consecutive 3 day food records were used to measure dietary intake. The mean sodium intake fell 22 mmol/day in men and 11 mmol/day in women in the intervention area from 1989 to 1992. The reduction was significant in men (P = 0.001) and near significance in women (P = 0.05). The sodium intake increased significantly in men in the reference area. There was a significant net reduction in sodium intake in men in the intervention area. This reduction was similar in different educational and occupational groups suggesting that the intervention had reached the whole community. The mean systolic blood pressure (SBP) decreased 3 mm Hg for the total population and 2 mm Hg for normotensives in the intervention area. There was a significant net reduction in SBP both in all or in normotensive subjects. These results support the conclusion that community-based sodium intervention is feasible for hypertension prevention. However, the sodium intake is still very high in this population, which warrants further effective intervention.

Endoplasmic reticulum protein Hsp47 binds specifically to the N-terminal globular domain of the amino-propeptide of the procollagen I alpha 1 (I)-chain

Hsp47, an endoplasmic reticulum-resident heat shock protein in fibroblasts, has gelatin-binding properties. It had been hypothesized that it functions as a chaperone regulating procollagen chain folding and/or assembly, but the mechanism of the hsp47-procollagen I interaction was not clear. Hsp47 could bind to both denatured and native procollagen I. A series of competition studies were carried out in which various collagens and collagen domain peptides were incubated with 35[S]-methionine-labeled murine 3T6 cell lysates prior to mixing with gelatin-Sepharose 4B beads. The gelatin-bound proteins were collected and analyzed by gel electrophoresis and autoradiography. Collagenase digested procollagen I had the same effect as denatured intact procollagen, indicating that the propeptides were the major interaction sites. The addition of intact pro alpha 1(I)-N-propeptide at 25 micrograms/ml completely inhibited hsp47 binding to the gelatin-Sepharose. Even the pentapeptide VPTDE, residues 86-90 of the pro alpha 1(I)-N-propeptide, inhibits hsp47-gelatin binding. These data implicating the pro alpha 1(I)-N-propeptide domain were confirmed by examination of polysome-associated pro alpha chains. The nascent pro alpha 1(I)-chains with intact N-propeptide regions could be precipitated by monoclonal hsp47 antibody 11D10, but could not be precipitated by monoclonal anti-pro alpha 1 (I)-N-propeptide antibody SP1.D8 unless dissociated from the hsp47. GST-fusion protein constructs of residues 23-108 (NP1), 23-151 (NP2), and 23-178 (NP3) within the pro alpha 1 (I)- N-propeptide were coupled to Sepharose 4B and used as affinity beads for collection of hsp47 from 3T6 cell lysates. NP1 and NP2 both showed strong specific binding for lysate hsp47. Finally, the interaction was studied in membrane-free in vitro cotranslation systems in which the complete pro alpha 1(I)- and pro alpha 2(I)-chain RNAs were translated alone and in mixtures with each other and with hsp47 RNA. There was no interaction evident between pro alpha 2(I)-chains and hsp47, whereas there was strong interaction between pro alpha 1(I)-chains and nascent hsp47. SP1.D8 could not precipitate pro alpha 1(I)-chains from the translation mix if nascent hsp47 was present. These data all suggest that if hsp47 has a "chaperone" role during procollagen chain processing and folding it performs this specific role via its preferential interaction with the pro alpha 1 (I) chain, and the pro alpha 1(I) amino-propeptide region in particular.

Multi-copy nuclear pseudogenes of mitochondrial DNA reveal recent acute genetic changes in the human genome

Four nuclear pseudogenes homologous to the 10031-10195-bp region of the human mitochondrial genome were detected by constant denaturant capillary electrophoresis. Among them, one pseudogene is present as at least five copies in each cell, in accordance with our previous observations of multi-copy mitochondrial DNA pseudogenes. The presence of multiple identical copies of pseudogenes suggests that the human genome underwent a series of genetic changes, including gene amplifications, very recently in evolutionary history, i.e., within the last 390000 years.

Relationships between translation of pro alpha1(I) and pro alpha2(I) mRNAs during synthesis of the type I procollagen heterotrimer

Final assembly of the procollagen I heterotrimeric molecule is initiated by interactions between the carboxyl propeptide domains of completed, or nearly completed nascent pro alpha chains. These interactions register the chains for triple helix folding. Prior to these events, however, the appropriate nascent chains must be brought within the same compartments of the endoplasmic reticulum (ER). We hypothesize that the co-localization of the synthesis of the nascent pro alpha1(I) and pro alpha2(I) chains results from an interaction between their translational complexes during chain synthesis. This has been investigated by studying the polyribosomal loading of the pro alpha-chain messages during in vitro translation in the presence and absence of microsomal membranes, and in cells which have the ability to synthesize the pro alpha1 homotrimer or the normal heterotrimer. Recombinant human pro alpha1(I) and pro alpha2(I) cDNAs were inserted into plasmids and then transcribed in vitro. The resulting RNAs were translated separately and in mixture in a cell-free rabbit reticulocyte lysate +/- canine pancreatic microsomes. Cycloheximide (100 mu g/ml) was added and the polysomes were collected and fractionated on a 15-50% sucrose gradient. The RNA was extracted from each fraction and the level of each chain message was determined by RT-PCR. Polysomes from K16 (heterotrimer-producing), W8 (pro alpha1(I) homotrimer), and A2' (heterotrimer + homotrimer) cells were similarly analyzed. Translations of the pro alpha1(I) and pro alpha2(I) messages proceeded independently in the cell-free, membrane-free systems, but were coordinately altered in the presence of membrane. The cell-free + membrane translation systems mimicked the behavior of the comparable cell polysome mRNA loading distributions. These data all suggest that there is an interaction between the pro alpha chain translational complexes at the ER membrane surface which temporally and spatially localize the nascent chains for efficient heteromeric selection and folding.

Relationship between muscarinic receptor subtypes and cyclic nucleotides in pons-medulla oblongata

AIM

To study the relationship between muscarinic receptor (M-R) subtypes and cyclic nucleotides in pons-medulla oblongata (MeOb).

METHODS

The contents of cGMP and cAMP in Sprague-Dawley rat pons-MeOb, cerebellum and cerebral cortex were assayed by radioimmunoassay and competitive protein-binding assay, respectively, after ip injections of drugs. Control rats were given ip normal saline.

RESULTS

M1-R agonist pilocarpine (6, 15 mg kg-1, ip) increased the content of cGMP in the pons-MeOb and cerebral cortex, but did not bring about any noticeable change in the cAMP content. The increase of cGMP was antagonized by ip pirenzepine or scopolamine. On the other hand, ip M2-R agonist 6 beta-acetoxy nortropane (6 beta-AN) 25 micrograms kg-1 reduced not only cAMP contents in the pons-MeOb and cerebellum but also cGMP contents in the pons-MeOb and cerebral cortex, while 6 beta-AN 12 micrograms kg-1 only lowered cAMP content. The decreases of cGMP and cAMP induced by 6 beta-AN were antagonized by ip AF-DX 116 or atropine, respectively.

CONCLUSION

Stimulation of M1-R causes the increase of cGMP and that of M2-R induces the decreases of both cGMP and cAMP in the pons-MeOb.

Modulation of cell spreading and migration by pp125FAK phosphorylation

We provide evidence for both matrix-dependent and pp60v-src tyrosine kinase-dependent modulation of cell migration via tyrosine phosphorylation of pp125FAK, a focal adhesion kinase, thought to be involved in integrin-mediated signaling. Enhanced pp125FAK tyrosine phosphorylation and cell spreading was associated with decreased migration. Cells plated on type I collagen were less spread and exhibited lower levels of pp125FAK tyrosine phosphorylation and faster migration rates compared with cells on fibronectin that were well spread, which exhibited enhanced levels of pp125FAK tyrosine phosphorylation and slower migration rates. Inside-out signaling via expression of pp60v-src or its kinase-negative mutant caused a decrease in cell migration by changing the extent of pp125FAK tyrosine phosphorylation to above or below the levels obtained with control cells plated on fibronectin. Hence, pp125FAK tyrosine phosphorylation appears to play a role in the signaling cascade pathway involved in regulation of extracellular matrix-modulated, integrin-mediated cell migration.

(-)-Stepholidine antagonizes the inhibition by D2 receptor agonists on synaptosomal tyrosine hydroylase in rat corpus striatum

AIM

To evaluate the action of (-)-stepholidine (SPD), a novel dopamine (DA) receptor antagonist, on inhibition by presynaptic D2 receptor agonists on the activity of synaptosomal tyrosine hydroxylase (TH) in the striatum.

METHOD

The TH activity was measured by HPLC-ECD.

RESULTS

The mixed DA receptor agonist apomorphine (Apo 10.4 nmol L-1) and selective D2 receptor agonists N-0437 (0.4 pmol L-1) and quinpirole (0.8 mumol L-1) inhibited the activity of TH, while selective D1 receptor agonist SKF 38393 (0.001-10 mumol L-1) and SPD (1-100 mumol L-1) failed to inhibit the TH activity. The inhibition of N-0437 and quinpirole were antagonized by D2 receptor antagonist spiperone and SPD.

CONCLUSION

The negative feedback regulation of presynaptic DA receptors is mediated via D2 receptors and SPD is an antagonist on presynaptic D2 DA receptors.

Assessment of sodium and potassium in processed foods in an urban area in China

OBJECTIVE

To identify commonly consumed processed foods with high sodium (Na) content and sodium to potassium (Na:K) ratio for the purpose of using this information in a community-based nutrition education programme.

DESIGN

Calculations of Na and K intake were based on the data of a dietary survey carried out in Tianjin in 1992. All processed foods were randomly sampled based on manufacturers and market survey.

SETTING

The survey was conducted in the urban area in Tianjin, China.

PARTICIPANTS

2317 subjects aged 15-64 years old were included in the dietary survey. The response rate was 95%.

MAIN RESULTS

The mean sodium intake was 6517 mg in men and 5708 mg in women. 38% of the total Na intake came from processed foods and condiments in both of the urban men and women in Tianjin. 122 processed foods with sales volumes were identified. Most of the processed foods had high Na content and high Na:K ratio, especially Na-rich condiments, salted vegetables, fried dough cake and sausages. The Na content of most processed foods in Tianjin was higher than the mean value reported in the Chinese Food Composition Table.

CONCLUSION

Processed foods contribute an important part of dietary Na in the urban diet in Tianjin. It is necessary to initiate nutrition intervention activities aiming at regulations on the Na content of processed foods and to advise the people to reduce consumption of salty foods.

Suppression of tumorigenesis by transcription units expressing the antisense E6 and E7 messenger RNA (mRNA) for the transforming proteins of the human papilloma virus and the sense mRNA for the retinoblastoma gene in cervical carcinoma cells

Human cervical carcinoma cell lines that harbor human papilloma virus (HPV) have been reported to express HPV E6 and E7 proteins at least in the beginning stages if not at all stages of the disease. The HPV E6 and E7 proteins bind to and inactivate the products of the p53 and retinoblastoma (Rb) tumor suppressor genes, which thereby allow the cervical carcinoma cells to circumvent the action of these tumor suppressor genes. We observed that the introduction of the antisense HPV 18 E6 and E7 sequences, as well as a sense cDNA for the human wild-type Rb gene into a human cervical carcinoma cell line (HeLa), which is positive for the HPV 18 provirus, decreased the in vitro and in vivo growth rate of the transfected cells if both antisense transcripts for the HPV 18 E6 and E7 and sense transcripts for human Rb were expressed. In addition, overexpression of a complementary DNA (cDNA) for the Rb messenger RNA was sufficient to slow the proliferation of HeLa cells, and the level of Rb cDNA expression was correlated with the degree to which the rate of growth of the tumor was slowed. The results of our experiments show that the presence of HPV E6 and E7 proteins and the resultant inactivation of Rb in cervical carcinoma cells contributes to the neoplastic phenotype even in highly evolved cervical carcinoma cell lines such as HeLa, which have been derived from a cervical carcinoma patient at an advanced stage of the disease process. These data suggest that the HPV proteins play a role not only at the beginning of cervical cancer, but also at advanced stages of this disease. These experiments may lead to genetic approaches to the control of this disease that involve antisense sequences that downregulate the E6 and E7 genes or lead to expression of the Rb gene.

Study on three dimensional reconstruction of transesophageal echocardiographic images

Using biplane transesophageal echocardiography and the concept of three dimensional transthoracic echocardiography, we performed three dimensional reconstruction of transesophageal images of various clinicopathologic cases, including atrial septal defect, mitral stenosis, mitral valve prolapse and pulmonary stenosis. The hardware equipment and image processing flow chart of three dimensional reconstruction of transesophageal echocardiographic images are described. Our present study indicates that three dimensional reconstruction of transesophageal echocardiographic images could display multi-regional three dimensional structures of heart and great vessels, including superior vena cava, ascending aorta, right ventricular outflow tract, pulmonary artery and left heart, with clear, visual and stereoscopic imaging. The regional structures could be displayed at different levels of stereo-anatomic-sections and in different orientations of rotating stereo-images, which could provide accurate three dimensional anatomical information for cardiac stereo-morphological study and definition of spatial location and size of cardiac abnormalities.

Inhibition of oncogene expression by green tea and (-)-epigallocatechin gallate in mice

The effects of tea drinking on the tobacco-specific nitrosamine 4-(methylnitrosamine)-1-(3-pyridyl)-1-butanone (NNK)-induced mouse lung oncogene expression and the effect of topical application of the tea polyphenol component (-)-epigallocatechin-3-gallate (EGCG) on 12-O-tedradecanoylphorbol-13-acetate (TPA)-induced mouse skin oncogene expression were investigated. In the first experiment, mice were treated with NNK (1.3 mg/kg body wt ip) once a day for three days and were given 2% tea in drinking water during the whole experimental period. After four or eight weeks, the lung tissue of the mice treated with NNK displayed a significantly high level of expression in c-myc, c-raf, and c-H-ras oncogenes, and they were all inhibited by tea drinking with inhibitory rates of 50%, 20%, and 50%, respectively. In the second experiment, a single application of 10 nmol of TPA to mouse skin led to a marked increase in the transcripts' level of ornithine decarboxylase (ODC) gene, protein kinase C (PKC) gene, and c-myc oncogene at four hours after TPA administration. Topical application of EGCG (1 or 5 mumol) one hour before the application of TPA inhibited all TPA-induced gene expression in a dose-dependent fashion. These results confirm the anticarcinogenic effects of tea and suggest that a possible mechanism is the effect of tea on carcinogen-induced oncogene expression.

Dietary survey in a Chinese population

OBJECTIVES

To assess food pattern and nutrition profile aiming at planning population-based nutrition intervention for chronic diseases control.

DESIGN

A randomized survey.

SETTING

The survey was carried out in Tianjin, one of the three largest cities in China.

SUBJECTS

3683 subjects aged 15-64 years old were selected by a random stratified multilevel cluster sampling.

INTERVENTION

The diet was assessed by food weighing plus consecutive individual 3 day food records.

RESULTS

Distinct differences in dietary pattern and nutrient intakes were found between subjects living in urban and rural areas. The diet of urban people was richer in fat and high quality protein compared with the diet of rural people. Low intakes of vitamin A, calcium, riboflavin, and zinc were found in both areas, the situation being worse in the rural areas. The sodium intake and sodium:potassium ratio was very high in both areas. Cholesterol intake was much higher among the urban people.

CONCLUSION

The study suggests that integrated nutrition intervention is needed to prevent insufficient intake of some nutrients and control dietary risk factors related to chronic diseases.

Associations between blood pressure and dietary intake and urinary excretion of electrolytes in a Chinese population

OBJECTIVE

To examine the associations between blood pressure and sodium, potassium, calcium and magnesium in a cross-sectional study by 24-h urine collections and food weighing with 3-day food records in 328 males and 335 females in Tianjin, People's Republic of China.

RESULTS

A very high sodium intake and sodium:potassium ratio was confirmed in the study population. After adjusting for confounding variables, both dietary and urinary sodium and sodium:potassium ratio were significantly and positively correlated with blood pressure. Although a negative correlation was found between potassium and blood pressure, the association was significant only between urinary potassium and systolic blood pressure in females and in both sexes combined. No significant associations were found between blood pressure and either intake of or urinary excretion of calcium and magnesium. The dietary intake correlated highly with urinary excretion of electrolytes. In both sexes a strong positive association was found between blood pressure and age, and between blood pressure and body mass index. Higher blood pressure was shown in subjects with higher sodium and alcohol intake, higher body mass index and lower potassium intake.

CONCLUSION

The present results indicate that factors contributing to high blood pressure in Tianjin, People's Republic of China, are related to age, body mass index, high sodium intake and sodium:potassium ratio.

Angiogenin promotes invasiveness of cultured endothelial cells by stimulation of cell-associated proteolytic activities

Angiogenin, a potent inducer of neovascularization in the chicken chorioallantoic membrane and rabbit cornea, promotes endothelial cell invasion of Matrigel basement membrane. A transformed bovine aortic endothelial cell line, GM 7373, is 5 times more invasive when cultured in the presence of 1 microgram of bovine angiogenin per ml than in its absence. A polyclonal anti-angiogenin antibody and alpha 2-antiplasmin neutralize the effect of angiogenin, but an angiogenin-binding protein (actin) does not. Further, this concentration of angiogenin induces a 14-fold increase in the cell-associated proteolytic activity of cultured endothelial cells, determined with a tissue-type plasminogen activator-specific peptide as the substrate. In addition, cells cultured on a three-dimensional fibrin gel in the presence of angiogenin are 3 times more capable of dissolving the gel and forming focal defects in the underlying matrix. The results indicate that angiogenin can enhance the ability of endothelial cells to digest extracellular matrix components and degrade basement membrane, thereby facilitating cell invasion and migration. Binding of angiogenin to its cell-surface binding protein (actin) followed by dissociation of the angiogenin-actin complex from the cell surface and subsequent activation of tissue-type plasminogen activator/plasmin are likely steps involved in the processes of endothelial cell invasion and angiogenesis.

Evolutionary trail of the mitochondrial genome as based on human 16S rDNA pseudogenes

In the course of studies on mutations in human mitochondrial (mt) DNA, we have uncovered and sequenced four new nuclear pseudogenes corresponding to bp 2457-2657 of the mt 16S rDNA. The four genes and their homologies with human mtDNA are E2 (62.4%), K10 (74.4%), E1 (84.6%) and LE6 (93.2%). When these five pseudogene sequences and another previously reported pseudogene sequence are compared with each other, they display what appears to be an ordered series of steps from a hypothetical common ancestor. The sequence of the hypothetical ancestor closely resembles that found in a wide variety of present-day mammalian mt genomes. The pseudogene sequences suggest an evolutionary trail of mt mutation dominated by base pair transitions punctuated by integration into the nuclear genome. Once integrated into the nuclear genome, the pseudogenes appear to follow the distinctive nuclear mutational pathway in which GC to AT transitions predominate and CpG sequences are preferentially eliminated.

Expression and alternative splicing of the deleted in colorectal cancer (DCC) gene in normal and malignant tissues

The DCC (deleted in colorectal cancer) gene was identified because it is affected by somatic mutations in colorectal tumors, including allelic losses in greater than 70% of cancers and localized mutations in a subset of cases. The DCC gene also may be inactivated in other tumor types, including cancers of the pancreas, stomach, breast, prostate, and brain, as well as some leukemias. We have characterized DCC complementary DNAs obtained from human fetal brain tissues and IMR32 human neuroblastoma cells. Based on the fetal brain complementary DNA sequence, the predicted transmembrane DCC protein product has 1447 amino acids. The extracellular domain of about 1100 amino acids has four immunoglobulin-like domains and six fibronectin type III-like domains; the 325-amino acid cytoplasmic domain does not show similarity to previously characterized proteins. Comparison of DCC complementary DNAs from IMR32 cells to those from fetal brain identified two potential alternative splice sites. Studies of adult mouse tissues revealed that DCC transcripts were present at very low levels in all tissues studied, and alternative splicing of DCC transcripts was seen in some tissues. Immunoblotting and immunoprecipitation studies with DCC-specific antisera identified protein species with molecular weights of approximately 175,000-190,000 in some rodent tissues and human tumor cell lines. DCC protein expression was highest in brain tissues and neural crest-derived cell lines and markedly reduced or absent in the majority of cancer cell lines studied. Treatment of DCC-expressing cells with tunicamycin decreased the apparent molecular weight of the immunoreactive proteins, establishing that DCC is a glycoprotein. The studies presented here demonstrate that the DCC gene encodes several related glycoprotein species that are likely to be expressed at very low levels in many normal adult tissues. Furthermore, the absence of DCC expression in some of the cancer cell lines studied may result from genetic inactivation of DCC.

Clinical application of three-dimensional transesophageal echocardiography

Three-dimensional transesophageal echocardiography is a new and evolving cardiac imaging technique. We reported our experiences of its clinical applications in 59 patients. A series of special temporal longitudinal views were selected by the frame grabber. Then the computer connected each digitized endocardial surface of the longitudinal views according to their spatial position and reconstructed the three-dimensional, cardiac shaded picture with gray scale. The three-dimensional transesophageal echocardiographic images were divided into three areas. The right area was right anterior to the esophagus and included such structures as the superior vena cava, right atrium, interatrial septum, and left atrium; the size, shape, and location of an atrial septal defect could be clearly shown. In the middle area the origin and the course of the two great arteries could be visualized, thus facilitating the diagnosis of transposition of the great arteries; in patients with obstruction of the right ventricular outflow tract, the circular ridgelike narrowing in the right ventricle was clearly visualized. In the left area the contour and size of the left ventricle and left atrium and the shape and point of coaptation of the mitral valve could be demonstrated; in patients with mitral valve prolapse, part of either leaflet protruded into the left atrium and appeared as a spoonlike depression in the mitral valve. Other entities subjected to three-dimensional transesophageal echocardiographic reconstruction included cor triatriatum, left atrial myxoma, aneurysm of sinus of Valsalva, dissecting aortic aneurysm, mitral stenosis, mitral regurgitation, and mitral valve prolapse.(ABSTRACT TRUNCATED AT 250 WORDS)

[The physiological function of plasma apoA-I--the anti-viral effects of apoA-I and its fragments]

Apolipoprotein A-I (apoA-I), the major protein of plasma high density lipoproteins, was found to inhibit herpes simplex virus type I (HSV-I) induced cell fusion at physiological concentrations (mumol/L). Plasma apoA-I from three different species was used to study the anti-viral effects by microneutralization test. Marked inhibition of virus-induced cell fusion was observed when the virus or the cells were pretreated with apoA-I, suggesting that apoA-I may have a direct effect on the virus and the cells. This function may be related to the structure of apoA-I.

Studies of the deleted in colorectal cancer gene in normal and neoplastic tissues

Chromosome 18q is among the chromosomal regions thought to harbor a tumor suppressor gene(s) that is frequently inactivated during the development of several cancer types, particularly those of the gastrointestinal tract. Moreover, preliminary data suggest that colorectal cancers with 18q LOH have a more aggressive clinical behavior than those cancers without 18q LOH. A candidate tumor suppressor gene from 18q, termed DCC for deleted in colorectal cancer, has been identified. The DCC gene is contained within the common region of LOH on 18q, its expression is markedly decreased or absent in colorectal cancers and cell lines, and a subset of colorectal cancers have been shown to have somatic mutations within the DCC gene. Thus, DCC represents the most promising candidate tumor suppressor gene from 18q. At present, however, many questions remain regarding the mechanisms underlying the inactivation of DCC in the majority of colorectal cancers. In addition, although studies of 18q LOH and DCC gene expression in other cancer types suggest that DCC inactivation may contribute to the pathogenesis of other tumor types, few studies have provided definitive data to demonstrate that DCC inactivation is a critical genetic event in these tumors. Moreover, little is known about the function of DCC in the regulation of normal cell growth and tumor suppression. The predicted structural similarity of DCC to the N-CAM family of cell-surface proteins suggests that it may function through cell-cell and/or cell-extracellular matrix interactions.(ABSTRACT TRUNCATED AT 250 WORDS)

Ethanol increases delta-opioid receptor gene expression in neuronal cell lines

Long-term treatment with ethanol increases delta-opioid receptor (DOR) expression in the NG108-15 neuroblastoma x glioma hybrid cell line. To determine the underlying mechanism, we studied the effects of ethanol on [3H]diprenorphine binding to intact cells and DOR gene expression in four related clonal neural cell lines. Incubation with 200 mM ethanol for 48 hr increased [3H]diprenorphine binding by 1.4- (N18TG2), 1.8- (NG108-15), 1.9- (N4TG1), and 3.0-fold (N1E-115). Treatment with 25, 50, or 100 mM ethanol for 1 week caused a dose-dependent increase in receptor expression. Receptor up-regulation was associated with an increase in the potency of etorphine for inhibiting prostaglandin E1-stimulated cAMP accumulation. Constitutive DOR expression differed more than 3-fold among the different cell lines and correlated positively with basal cAMP levels. Long-term ethanol treatment increased basal cAMP levels in three of the four cell lines, but did not induce cellular differentiation. Northern blot analysis demonstrated an identical pattern of multiple transcripts in the four cell lines. Ethanol increased the abundance of DOR mRNA by approximately 3-fold in N18TG2 cells and by approximately 5-fold in the remaining cell lines. These findings indicate that clinically relevant concentrations of ethanol regulate DOR expression by increasing the abundance of DOR mRNA. The disparity between the increase in gene expression and ligand binding suggests that ethanol may also modify mRNA translation or receptor processing.

Osteogenic protein-1 regulates L1 and neural cell adhesion molecule gene expression in neural cells

Osteogenic protein-1 (OP-1) is a member of the TGF-beta superfamily that is expressed in the nervous system. We recently showed that human recombinant osteogenic protein-1 (hOP-1) strongly promotes the aggregation of dividing neuroblastoma x glioma hybrid NG108-15 cells, in part by inducing the major isoforms of the neural cell adhesion molecule (N-CAM) (Perides, G., Safran, R. M., Rueger, D. C., and Charness, M. E. (1992) Proc. Natl. Acad. Sci. U. S. A. 89, 10326-10330). Here we show that hOP-1 induces L1 expression approximately 6-fold in NG108-15 cells without changing the levels of N-cadherin, neurofilament 200, Thy-1, tau, and G alpha s. OP-1 induction of L1 and N-CAM was unassociated with changes in cell proliferation and was not reproduced by cellular differentiation. The increased adhesiveness of hOP-1-treated NG108-15 cells could be inhibited in part by Fab fragments of an anti-L1 polyclonal antiserum. L1 and N-CAM expression first increased 12-18 h after hOP-1 treatment, reached a maximum after 2-3 days, persisted for up to 5 days, and returned to control levels 3 days after hOP-1 withdrawal. The increases in L1 and N-CAM protein levels were preceded or accompanied by large increases in the abundance of L1 and all detectable N-CAM mRNAs. Actinomycin D prevented the induction by hOP-1 of L1 and N-CAM mRNAs, suggesting that hOP-1 regulates immunoglobulin CAM gene transcription. OP-1 is the first described growth factor that regulates both N-CAM and L1 gene expression.

Ethanol differentially increases alpha 2-adrenergic and muscarinic acetylcholine receptor gene expression in NG108-15 cells

Modulation of alpha 2-adrenergic and opioid neurotransmission may contribute to ethanol intoxication, tolerance, and physical dependence. We showed previously that ethanol increased the expression of functional delta-opioid receptors in NG108-15 cells (Charness, M. E., Querimit, L. A., and Diamond, I. (1986) J. Biol. Chem. 261, 3164-3169). Here we report that long-term (2 days) treatment of NG108-15 cells with ethanol increased the binding of the alpha 2-adrenergic receptor (alpha 2AR) antagonist [3H]rauwolscine and the muscarinic acetylcholine receptor (mAChR) antagonist [3H]quinuclidinyl benzilate by 2.8- and 1.4-fold, respectively. Increased receptor expression was associated with a proportionate increase in the potency of oxymetazoline and carbachol in inhibiting cAMP accumulation. Ethanol did not change the expression of G alpha i2 and reduced levels of G alpha s. Pertussis toxin pretreatment did not prevent the ethanol-induced increase in alpha 2AR, mAChR, and delta-opioid receptor expression. Ethanol caused a large (3.6-fold), dose-dependent increase in the abundance of alpha 2BAR mRNA (rat cDNA probe RNG, 4.1-kb transcript). Ethanol-induced increases in alpha 2BAR and alpha 2CAR (rat probe RG10, 2.5-kb transcript) mRNAs were first detected after 6 h of exposure to 100 mM ethanol, became maximal after 24 h, and persisted for up to 5 days. In contrast, ethanol caused only a small (1.3-fold) increase in the abundance of hm4 mAChR mRNA and did not change levels of G alpha i2 and G alpha s mRNAs. Our data indicate that clinically attainable concentrations of ethanol regulate alpha 2AR gene expression within the time frame of a single session of drinking.

DNA polymerase-catalyzed addition of nontemplated extra nucleotides to the 3' end of a DNA fragment

Some prokaryotic and eukaryotic DNA polymerases are capable of adding an additional nontemplated nucleotide residue at the 3' end of a DNA fragment (Clark et al., 1987; Clark, 1988). The extra nucleotide at the 3' end of the PCR product has been shown to be a critical factor determining the efficiency of cloning PCR products into plasmids and can affect mutation analyses with a PCR-denaturing gradient gel electrophoresis (DGGE) approach (Pfeiffer and Hu, 1993). In the present work, the ability of various DNA polymerases to add an extra nontemplated nucleotide at the 3' end of DNA was studied. The results show that out of the eight studied enzymes, five can add, with varying efficiencies, an extra nucleotide residue at the 3' end of DNA. Which extra nucleotide is added depends on the terminal residue and the DNA polymerase. Among the enzymes, thermostable Pfu DNA polymerase is found to be the best choice for PCR due to its relatively high fidelity (Scott et al., 1991; Coller, unpublished), and ability to produce blunt-ended DNA fragments. The relationship between the DNA polymerases' ability to add an extra nucleotide and their 3'-->5' exonuclease activity is also discussed.

Studies on antibiotic 230 as a molluscicide

In the course of studying molluscicidal effects of microorganisms, a microorganism belonging to Streptomycetaceae, Streptomyces griseolus (Strain 230) was isolated from soil and a certain microbial ingredient proved to have a molluscicidal activity. The effective substance was named antibiotic 230. As a result of several investigations on the antibiotic, the following chemical features were made clear. The chemical substance was an indol-carbazole-heterocyclic compound, the molecular weight 446 and the molecular formula C28H26N4O3. The antibiotic demonstrated a molluscicidal effect against Oncomelania snails and their eggs both in the laboratory and in the field. The compound had a wide bacteriostasis spectrum and a slight toxicity to fish in addition to the above, but it was non-toxic to plants.

A study on the clinical effect and immunological mechanism in the treatment of Hashimoto's thyroiditis by moxibustion

71 cases of Hashimoto's thyroiditis were treated by moxibustion and their immune function and thyroid function were observed. It was found that moxibustion was able to reduce the thyroid antibodies in the peripheral blood of the patients with hypothyroidism and to recover their thyroid function. It was also found that moxibustion could lower the thyroid antibody secretory levels and ADCC (antibody-dependent cell-mediated cytotoxicity) activities of the lymphocytes. In addition, the action of moxibustion in reducing the secretion of thyroid antibodies was related to its action of regulating the proportions of T lymphocyte subsets. The results indicate that the treatment of Hashimoto's thyroiditis by moxibustion is probably accomplished through its effect in regulating the relationship among the T lymphocyte subsets.

Polymorphism at codon 72 of the p53 gene in human acute myelogenous leukemia

A common polymorphism at codon 72 of the p53 gene in patients with acute myelogenous leukemia (AML) was analyzed by single-strand conformation polymorphism assay and sodium dodecyl sulfate polyacrylamide-gel electrophoresis of immunoprecipitated 35S-labeled P53 protein. No association between this polymorphism and a marked predisposition to AML was found. The half-lives of these two polymorphic forms of P53 were equivalent in normal phytohemagglutinin-stimulated lymphocytes, while the P53 Pro72 isoform was found to be twice as stable as the Arg72 isoform in Daudi cells.

P53 gene mutations in acute myelogenous leukaemia

A polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) assay was used to identify the exons which contained point mutations in the conserved regions (exons 4-8) of the p53 gene in 49 acute myelogenous leukaemia (AML) patients. SSCP analysis in our study was consistent with the results of subsequent direct DNA sequencing in detecting point mutational change in exons 5 and 8 of one AML patient and in exons 7 and 8 of two additional AML patients. The mutations were located at codons 245 and 273, which have been found in many other tumours, and codons 178 and 290, which have not been reported previously. All of the p53 proteins in which we detected point mutations were immunoprecipitated by the p53 monoclonal antibody PAb 240, which has been shown to recognize a mutant conformation of p53 protein. Thus, our results indicate that functional inactivation of the p53 gene by point mutational change might be one of the mechanisms underlying disease progression of AML.

Altered conformation of the p53 protein in myeloid leukemia cells and mitogen-stimulated normal blood cells

Expression of the normal p53 gene promotes cell differentiation, maturation and apoptosis. The mutant p53 gene, which does not function normally, is frequently expressed at elevated levels in tumor cells [for review see Lane, D.P. & Benchimol, S. (1990). Genes Dev., 4, 1-8]. We have analysed the expression of and mutational change in the p53 gene in the peripheral blood cells of 49 primary acute myeloid leukemia (AML) patients. The p53 protein levels were elevated in 37 patients (75%) when measured by immunoprecipitation with antibodies PAb1801 and PAb421, which recognize both normal and mutant forms of the protein. The p53 protein from 32 of these 37 patients was immunoprecipitated by PAb240, which recognizes a conformation of p53 protein associated with point mutations. However, point mutations were detected by single-stranded conformation polymorphism (SSCP) assay and direct sequencing in only three patients at codons 178, 245, 273 and 290. Growth stimulation of normal lymphocytes also generated p53 which was immunoprecipitable by PAb240. Thus, alteration of p53 conformation, rather than acquisition of point mutations, could be the mechanism underlying the increased proliferation of myeloid cells in most AML patients.

Effects of l-stepholidine on synaptosomal Ca(2+)-ATPase and subcellular calmodulin in rat striatum

Our results showed that l-stepholidine (l-SPD) inhibited basal Ca(2+)-ATPase activity in rat striatal synaptosomes with an IC50 of 31.5 mumol.L-1, suggesting its interaction with Ca2+ transport. l-SPD inhibited also calmodulin (CaM)-activated basal Ca(2+)-ATPase in a concentration-dependent manner. A complete reversal of CaM activation of Ca(2+)-ATPase was observed with l-SPD 10 mumol.L-1. The activity of synaptosomal Ca(2+)-ATPase and membrane-bound CaM level were decreased in haloperidol (1 mg.kg-1.d-1, ip) and l-SPD (5, 10, and 30 mg.kg-1.d-1, ip) treated rats for 7 and 14 d, respectively. But the activity of Ca(2+)-ATPase and membrane CaM level were increased after treatment with the same of doses haloperidol and l-SPD for 21 d. During the treatments with haloperidol and l-SPD cytosolic and nuclear CaM levels were not altered. These results suggest that l-SPD may modulate the release and synthesis of dopamine (DA) and the negative feedback regulation of presynaptic DA receptors by altering Ca2+ and CaM regulating processes in the central dopaminergic nervous system.

Antagonism of l-stepholidine on D2 receptor-mediated inhibition of synaptosomal adenylate cyclase in rat corpus striatum

In the presence of Sch 23390 0.1 mumol.L-1, dopamine (DA) inhibited the activity of synaptosomal adenylate cyclase (AC) isolated from rat striatum in a concentration-dependent manner with IC50 value of 2.2 mumol.L-1. The maximal inhibition corresponded to a 51% decrease of basal enzyme activity and was obtained at DA 100 mumol.L-1. The inhibitory effect of DA was reversed by selective D2 receptor antagonist spiperone 10 mumol.L-1. N-0437, a selective D2 DA receptor agonist also inhibited the activity of AC in the manner similar to that of DA. Both the inhibitions induced by DA and N-0437 were antagonized by l-stepholidine (l-SPD). However, in the presence of Sch 23390, l-SPD alone also inhibited the activity of AC by 29% and 33% at the concentrations of 10 and 100 mumol.L-1, respectively. The inhibition of l-SPD on AC activity was significantly antagonized by spiperone. In the presence of Sch 23390, both DA and N-0437 increased the activity of high affinity GTP phosphohydrolase in striatal synaptosomes. The increases of GTP phosphohydrolase activity stimulated by DA and N-0437 were completely reversed by l-SPD 100 mumol.L-1. These results suggest that l-SPD antagonizes or reverses the D2 receptor-mediated inhibition of AC activity through affecting the regulation of Gi (inhibitory guanine nucleotide-dependent protein) on D2 receptor-coupled AC and therefore affects the negative feedback of presynaptic DA receptors. Moreover, the inhibition of AC activity induced by l-SPD alone may provide a useful biochemical index for dual action of l-SPD.