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L D Wang

Publications and source records attributed to L D Wang.

At least 37 records · Page 2Linked to original sources
PubMed1998

Genomic cloning of 18 kDa oleosin and detection of triacylglycerols and oleosin isoforms in maturing rice and postgerminative seedlings.

Oleosins are hydrophobic proteins localized abundantly in the oil bodies of plant seeds. Two distinct oleosin isoforms of molecular masses 18 and 16 kDa are present in rice oil bodies. These isoforms were found in similar ratio in rice embryos and aleurone layers. To survey potential DNA sequences involved in the activation of oleosin genes, a genomic clone of rice 18 kDa oleosin was sequenced, and its 5'-flanking region was compared with that of the known rice 16 kDa oleosin gene. Corresponding mRNAs of the two rice oleosin isoforms appeared seven days after pollination and vanished in mature seeds. Triacylglycerols and oleosins were accumulated concomitantly in maturing rice reeds in accord with the active assembly of oil bodies, and partly mobilized in postgerminative seedlings. Approximately 60% of the stored triacylglycerols in rice were not utilized: while the majority of oil bodies in embryos were mobilized in five days after imbibition, those in aleurone layers remained intact in postgerminative seedlings.

Base Sequence↗
PubMed1998

Characterization of the histamine H2 receptor structural components involved in dual signaling.

We previously demonstrated that the histamine H2 receptor can activate both adenylate cyclase (AC) and phospholipase C (PLC) signaling pathways via separate GTP-dependent mechanisms. We examined whether H2 receptor-specific peptides corresponding to the amino (N) or carboxyl terminus (C) of the second (2i) or third (3i) intracytoplasmic loops or the carboxyl terminal tail (P4iN) could effect histamine- stimulated AC and PLC activity in cell membranes prepared from HEPA cells stably transfected to express the canine H2 histamine receptor cDNA. Tiotidine binding and basal signaling were not altered by the synthetic peptides. H2P2iN, H2P2iC, H2P3iN and H2P4iN did not effect histamine stimulated AC activity although H2P3iC (10(-4) M) significantly inhibited this parameter (65.6 +/- 7.2% of maximal stimulation) (n = 6). Combination of the five peptides (H2P2iN, H2P2iC, H2P3iN, H2P3iC and H2P4iN) abolished histamine stimulated AC activity. Although all of the peptides inhibited histamine-stimulated PLC activity to a moderate degree individually, H2P3iC (10(-4) M) had the greatest effect, decreasing PLC activation to 20.8 +/- 6.3% of maximal stimulation (IC50 = 7.5 X 10(-7) M) (n = 6). H2P3iC and the peptide combination did not alter, forskolin, GTP gamma s or epinephrine-stimulated AC activity nor GTP gamma s and vasopressin-stimulated PLC. These studies demonstrate that both the second and third intracytoplasmic loops of the histamine H2 receptor are linked to separate signaling pathways in a differential manner.

Adenylyl Cyclases↗
PubMed1997

Activation of the human histamine H2 receptor is linked to cell proliferation and c-fos gene transcription.

We examined whether histamine could regulate cell proliferation and expression of the early response gene c-fos in HEK-293 cells stably transfected with the human H2 receptor (HEK-H2). Histamine stimulated [3H]thymidine incorporation [50% effective concentration (EC50) = 3.6 x 10(-6) M] in HEK-H2 cells in a cimetidine-sensitive manner and increased c-fos mRNA in a time-dependent fashion, reaching maximal induction after 30 min. Histamine induced luciferase activity in HEK-H2 cells transiently transfected with a construct containing the luciferase reporter gene (Luc) coupled to the serum response element (SRE) of the c-fos gene promoter (EC50 = 1.5 x 10(-6) M) or a plasmid containing the SRE core fragment (bases -320 to -298). The protein kinase C (PKC) inhibitor staurosporine and long-term pretreatment of HEK cells with phorbol ester inhibited the effect of histamine on PKC activation, SRE-Luc activity, and [3H]thymidine incorporation. We have demonstrated that activation of the human H2 receptor can lead to induction of c-fos gene transcription and cell proliferation through a PKC-dependent mechanism.

Cell Division↗
PubMed1997

Esophageal and gastric cardia epithelial cell proliferation in northern Chinese subjects living in a high-incidence area.

Linxian and the nearby county Huixian, in the Henan province in Northern China, have a very high incidence of esophageal squamous cell carcinoma (SCC). Previous studies from these counties have suggested that increased proliferation of esophageal epithelial cells, morphologically manifested as basal cell hyperplasia (BCH) and dysplasia (DYS), is an early indicator of abnormality in persons predisposed to SCC. A high incidence of gastric cardia adenocarcinoma (AC) was also found in these areas. To determine proliferation patterns of esophageal and gastric cardia epithelia with normal and different severities of precancerous lesions, we measured proliferating cell nuclear antigen (PCNA), Ki-67, and bromodeoxyuridine (BrdU) incorporation and compared the results. Esophageal biopsies (175) and gastric cardia biopsies (41) were collected from symptom-free subjects in Huixian. Of these, 23 esophageal biopsies were incubated with BrdU. The avidin-biotin-peroxidase complex (ABC) method was used to detect PCNA, Ki-67, and BrdU. The number of immunostain-positive cells was counted manually. Intense immunostaining for PCNA, Ki-67, and BrdU was observed in the cell nuclei of tissues with normal and different severities of precancerous lesions. With esophageal biopsies, both PCNA and Ki-67 increased significantly as the epithelia progressed from normal to BCH and to DYS. The number of PCNA- and Ki-67-positive cells was three times higher than that of BrdU incorporation in the same category of BCH. With cardia biopsies, the number of Ki-67 positive cells was lower in normal tissue and increased significantly from chronic superficial gastritis to chronic atrophic gastritis to DYS. Staining patterns for PCNA and Ki-67 were correlated with the histopathology of the esophagus. The correlation was not as clear with gastric cardia. BrdU studies appear to be more complicated. The PCNA and Ki-67 methods may be useful for screening high-risk esophageal and gastric cardia cancer subjects, and for monitoring chemoprevention effects.

Adenocarcinoma↗
PubMed1996

p53 protein accumulation and gene mutations in multifocal esophageal precancerous lesions from symptom free subjects in a high incidence area for esophageal carcinoma in Henan, China.

BACKGROUND: Multifocal occurrence of precancerous lesions of the esophagus has been observed among individuals in a high incidence area for esophageal carcinoma in Henan Province, China. Results from recent studies suggest that p53 protein accumulation and mutation occur early in the pathogenesis of esophageal carcinoma. Discordant p53 gene mutations have been observed in invasive carcinoma and preinvasive lesions from a patient with esophageal carcinoma. The p53 alterations in the multifocal precancerous lesions from symptom-free subjects, however, have not been investigated. METHOD: Two biopsy samples, one each from the middle-third and the lower-third of the esophagus, from each subject, were taken from 55 symptom-free subjects in a high incidence area for esophageal cancer in Huixian, Henan Province, China. p53 protein accumulation and p53 gene mutation were analyzed in the multifocal esophageal precancerous lesions from these subjects. RESULTS: Histopathologic examination showed that among the 110 biopsies, 20 had dysplasia, 72 had basal cell hyperplasia, and 18 had normal epithelia. Concurrent lesions at the middle- and lower-third biopsy occurred in 2 subjects with dysplasia (2 of 55 subjects, 4%) and 26 subjects with basal cell hyperplasia (26 of 55 subjects, 47%). Analysis by immunohistochemistry showed high concurrent rates of p53 protein accumulation (51 of 55 subjects, 93%). p53 sequence analysis of 32 samples from 16 subjects identified missense mutations in 5. In one subject, there were three different mutations in the middle-third biopsy (codon 161, GCC-->GAC) and the lower-third biopsy (codon 159, GCC-->CCC). A single mutation was detected in the other four subjects in either the middle- or lower-third biopsy. CONCLUSIONS: The present findings indicate that p53 protein accumulation and mutations occur in the early stages of human esophageal carcinogenesis. Independent somatic mutations of the p53 tumor suppressor gene and protein accumulation in different regions of the esophageal "field" might be key molecular events in multifocal esophageal carcinogenesis.

Adult↗
PubMed1996

Immunohistoselective sequencing (IHSS) of p53 tumor suppressor gene in human oesophageal precancerous lesions.

Accumulation of p53 protein occurs in human oesophageal precancerous lesions and even in near-normal oesophageal epithelium. In some instances, p53 gene mutations have been detected. In many of the cases of p53 protein accumulation in early lesions, however, p53 mutations were not detected due to either the lack of mutation or the low abundance of cells with a mutation. In order to enrich p53 immunostain-positive cells for single strand conformation polymorphism (SSCP) analysis and DNA sequencing, an immunohisto-selective sequencing (IHSS) method was developed. Anti-p53 antibody-peroxidase stained oesophageal tissue sections were subjected to ultraviolet (UV) irradiation to damage the DNA in p53 immunostain-negative cells. The immunostain protected p53 immunostain-positive cells from the UV light and thus preserved the DNA in those cells for PCR amplification. Comparison of the SSCP results from sections with and without UV treatment showed that the IHSS method selectively enriched p53 immunostain-positive cells. With this method, we could analyse mutations in samples with as few as 30 p53 immunostain-positive cells per tissue section. Analysis was carried out on tissues with precancerous lesions from six surgically-resected oesophageal specimens and 13 oesophageal biopsies from symptom-free subjects. The results of mutation analysis for some of the samples were confirmed by microdissection to enrich the p53-positive cells. The mutations in tissues with precancerous lesions were compared with those in the corresponding squamous cell carcinomas. The IHSS method is shown to be a simple and effective way to analyse mutations in p53 immunostain-positive cells. IHSS may also be a general method for molecular analysis of biological specimens after immunohistochemical staining.

DNA↗
PubMed1996

Radon measurements in underground dwellings from two prefectures in China.

Radon, an established lung carcinogen, remains the single most important environmental radiation exposure. Yet, an excess of lung cancer from breathing radon in homes has not been consistently demonstrated in studies conducted to date. To address several major problems that have hindered previous studies of lung cancer and radon in homes, we have embarked upon a lung cancer case-control study in Gansu Province, China, where a substantial proportion of the population live in underground dwellings. In this paper, we report on results of a pilot study in which radon measurements were made for 3 days in the summer in 40 homes under normal occupancy conditions using short-term E-PERM detectors and for 6 months from February through August in 49 homes using long-term alpha-track detectors. Useable E-PERM data were obtained from 38 homes and useable alpha-track data from 47 homes. For both types of detectors, measurements were approximately log-normally distributed. Arithmetic and geometric means were 233 and 185 Bq m-3 (range 74-1,590 Bq m-3) for E-PERM measurements and 165 and 158 Bq m-3 (range 74-592 Bq m-3) for alpha-track measurements, respectively; 68% of E-PERM measured homes and 55% of alpha-track measured homes exceeded 148 Bq m-3. Alpha-track measurements made at the entry, middle, and rear areas of the underground dwellings did not differ significantly (arithmetic means of 168, 162, and 165 Bq m-3 with standard deviations 63, 73, and 48, respectively), which suggests that air circulation may be minimal. The underground dwellings measured in the pilot study had high radon levels and the underground dwellers may provide an excellent population for studying indoor radon and risk of lung cancer.

Air Pollution, Indoor↗
PubMed1996

Reproducibility of an esophageal biopsy sampling procedure in a high-incidence area for esophageal cancer in northern China.

The objective of this study was to evaluate the reproducibility of the biopsy sampling procedure in research on esophageal lesions. Biopsies were taken from the middle and lower thirds of the esophagus, one from each site, from 25 subjects in a high-incidence area for esophageal cancer in Xinye County of Henan Province, China. The biopsy sampling procedure was repeated on the same subjects 10 days later. When the biopsies were analyzed together and those with worse pathologies were used for diagnosis, 52% of the subjects had the same grade of lesions in the second biopsy examination, 32% had lower-grade lesions, and 16% had higher-grade lesions.

Adult↗
PubMed1995

Inhibition of N-nitrosomethylbenzylamine-induced esophageal tumorigenesis in rats by green and black tea.

In this study, we investigated the effects of green tea and black tea, when given either during or after carcinogen treatment, on esophageal tumorigenesis in male Sprague-Dawley rats. Rats were treated with N-nitrosomethylbenzylamine (NMBzA) (2.5 mg/kg, s.c., twice weekly) for 5 weeks; 39 weeks after the initial dose of NMBzA, 65% of the rats had esophageal tumors with an average of 1.4 +/- 0.3 tumors per rat. In the groups of rats receiving 0.6% of decaffeinated green tea (DGT) or decaffeinated black tea (DBT) (6 mg tea solids/ml) as the sole source of drinking fluid during the NMBzA-treatment period, esophageal tumor incidence and multiplicity were reduced by approximately 70%. When the tea preparations were given after the NMBzA treatment period, the esophageal papilloma incidence and multiplicity were reduced by approximately 50%. The volume per tumor was much smaller in rats that received black tea after the carcinogen treatment period. In a second experiment, NMBzA was given to rats at a dose of 3.5 mg/kg (s.c., twice weekly) for 5 weeks; after 16 weeks, the tumor incidence was 82% and tumor multiplicity was 6.7 +/- 1.2 tumors per rat. In the groups of rats receiving 0.9% regular green tea (RGT) or DGT after the NMBzA treatment period, tumor multiplicity was decreased by > 55%. The volume per tumor was reduced by approximately 60% in the rats receiving 0.9% RGT. Histological analysis indicated that both the incidence and multiplicity of esophageal carcinoma was decreased by either RGT or DGT. The blood and urine levels of green tea polyphenols due to tea administration were determined in rats, and the levels were comparable to those in humans after tea ingestion. The above results indicate that both green tea and black tea can inhibit the tumorigenic action of NMBzA during the period of carcinogen treatment and the subsequent molecular events important for esophageal tumorigenesis.

Animals↗
PubMed1994

Changes in p53 and cyclin D1 protein levels and cell proliferation in different stages of human esophageal and gastric-cardia carcinogenesis.

The objective of this study was to quantify the changes in p53 and cyclin D1 protein levels in different stages of human esophageal and gastric cardia carcinogenesis in a high-risk population in Henan, China. Immunoreactivity of p53, cyclin D1 and proliferating-cell nuclear antigen (PCNA) was observed in the cell nuclei of esophageal and gastric cardia biopsies. The number of p53-immunostaining-positive cells was low in normal epithelia, slightly increased in basal-cell hyperplasia (BCH), markedly increased in dysplasia (DYS) (10-fold), and further increased in squamous-cell carcinoma (SCC) (40-fold). This pattern of change was similar to that of cell proliferation as indicated by PCNA immunostaining. On the other hand, the number of cyclin D1-immunostaining-positive cells did not increase from BCH to DYS, although a slight increase from DYS to SCC was noted. In the gastric cardia, again, the pattern of change of p53-positive cells in different stages of lesions paralleled the pattern of cell proliferation. The number of p53-positive cells was very low, much lower than that of PCNA-positive cells, in normal, chronic superficial gastritis (CSG) and chronic atrophic gastritis (CAG); therefore, the increase of p53-positive cells from CAG to DYS was more dramatic (100-fold). From DYS to adenocarcinoma (AC), the p53-positive and the PCNA-positive cells increased 4-fold. On the other hand, the number of cyclin D1-positive cells did not increase in pre-cancerous lesions, but increased slightly in AC. This study demonstrates that p53 protein accumulation increased with the progression of pre-cancerous lesions, especially in the genesis of dysplasia, both in the esophagus and in the gastric cardia. Our approach of quantitative immunohistochemistry sheds light on the mechanisms of genesis of esophageal and gastric-cardia cancers, which frequently occur together in many high-incidence areas.

Adenocarcinoma↗
PubMed1994

p53 tumor suppressor gene mutation in early esophageal precancerous lesions and carcinoma among high-risk populations in Henan, China.

To understand whether p53 gene mutation is an early or late event in esophageal carcinogenesis, biopsy samples of esophageal epithelium from symptom-free subjects in a high incidence area, Huixian county of Henan Province, China, were analyzed. Mutations in exons 5, 6, 7, and 8 of p53 were analyzed by single-strand conformation polymorphism analysis and DNA sequencing. Among the 37 biopsy samples showing accumulation of p53 protein in immunohistochemical staining, missense mutations of p53 gene were detected in 1 of 3 samples with normal epithelia, 3 of 23 samples with basal cell hyperplasia, and 4 of 11 samples with dysplasia. All mutations occurred at exon 5 with 3 at codon 175, 2 at codon 176, and 1 each at codons 159, 135, and codon 132. Of the 8 mutations, there were 3 G to A transitions and 3 G to T transversions. To understand the mutation spectrum and possible causative factors of esophageal cancer in this area, surgically resected human primary esophageal carcinomas from Linxian county were analyzed for p53 gene mutations in exons 5, 6, 7, and 8. Mutations were detected in 16 of 29 samples (55%). Twelve samples contained different missense point mutations, with 75% transitions (7 G to A and 2 A to G) and 25% transversions (2 G to T and 1 G to C). Most of the mutations were located at either exon 5 or exon 7. A deletion and an insertion of nucleotides leading to frame-shift mutations were detected in each of two other samples. The results demonstrate that p53 protein accumulation and gene mutation may occur at very early stages of esophageal carcinogenesis. In carcinomas, there was a higher frequency of p53 gene mutations, which accounts for most of the cases with p53 protein accumulation.

Adult↗
PubMed1993

Accumulation of p53 protein in human esophageal precancerous lesions: a possible early biomarker for carcinogenesis.

The level of p53 protein was determined immunohistochemically in normal tissues and tissues with different severities of lesions (basal cell hyperplasia, dysplasia, carcinoma in situ, and carcinoma) from surgically resected human esophagi and esophageal biopsies of symptom-free subjects. The samples were from an area with high esophageal cancer incidence in northern China (Linxian and Huixian in the Henan province). Tissue sections were incubated with p53 antibodies for immunostaining. Conventional hematoxylin and eosin stain was also used. In surgically resected esophageal specimens, elevated p53 protein levels were found in the cell nuclei in tissues with precancerous and cancerous lesions. From basal cell hyperplasia to dysplasia to carcinoma in situ, the p53 immunostain-positive cells increased in number, and their distribution had roughly the same pattern as that of the proliferating cells. However, positive stain was not observed in the dividing basal cells of the normal epithelium of the surgically resected tissues. A similar pattern of immunostaining was observed in the abnormal tissues of the biopsy samples from the symptom-free subjects. An intriguing observation is that some p53 immunostain-positive cells were observed in 3 of 6 cases of histologically normal epithelia of biopsy samples. Only the papillary immunostaining pattern was observed in these three "normal" cases. Although the molecular basis for such positive stain remains to be investigated, it is possible that p53 protein accumulation occurs early in the pathogenesis of esophageal cancer and that p53 mutation is closely associated with the initiation of this cancer. The accumulation of p53 protein may be a promising early biomarker for identifying high-risk subjects for esophageal cancer.

Adult↗
PubMed1992

Molecular basis for the interaction of histamine with the histamine H2 receptor.

We undertook these studies to characterize the molecular basis of the interaction of histamine with the H2 receptor. Key areas of homology in the structures of the histamine H2 and beta 2 adrenergic receptor suggested specific transmembrane amino acids that might be important for binding of histamine. A third transmembrane aspartic acid of the histamine receptor (Asp98), thought to serve as a counter anion that interacts with the cationic amine moiety of histamine, was mutated to Asn98, and the mutated receptor was expressed in Hepa cells. Removal of the negatively charged amino acid abolished both binding of the H2 receptor antagonist [methyl-3H]tiotidine and histamine stimulated increases in cellular cAMP content. Mutation of a fifth transmembrane aspartic acid (Asp186) to Ala186 or Asn186 by itself or in conjunction with mutation of another fifth transmembrane amino acid (Thr190 to Ala190) resulted in a loss of [methyl-3H] tiotidine binding, although the generation of cAMP in response to histamine was maintained. The histamine receptor with only a Thr190 to Ala190 or Cys190 mutation retained the ability to bind [methyl-3H]tiotidine, but both the affinity and efficacy of binding were reduced. These data lead us to propose a model for histamine binding in which Asp98 is essential for histamine binding and action, Asp186 defines H2 selectivity, and Thr190 is important in establishing the kinetics of histamine binding, but is not essential for H2 selectivity.

Amino Acid Sequence↗
PubMed1992

[Preliminary study on nutrition and precancerous lesions of the esophagus in the adolescents].

This paper reports the prevalence of chronic esophagitis and nutritional status among 538 persons 15-26 years old in the high-risk area of esophageal cancer. 166 subjects were from households with history of esophageal cancer while 372 from households without. The frequency of chronic esophagitis among male and female adolescents in the high risk areas (37.6% and 36%) was significantly, higher than that in the low risk areas. Furthermore, the frequency of chronic esophagitis in the adolescents in households with history of esophageal cancer was also higher than that without history of this cancer. There was a positive correlation between avitaminosis C and chronic esophagitis. Suffering from avitaminosis C and B2, these people are prone to develop chronic esophagitis which, in turn, may serve as an early phase in the carcinogenesis of esophageal epithelium.

Adolescent↗
PubMed1991

Sucrose octasulfate stimulates gastric somatostatin release.

To explore the mechanisms of the effects of sucralfate on the stomach, we investigated the action of sucrose octasulfate (SOS), a constituent of sucralfate, on the function of canine gastric parietal cells and somatostatin cells and in the isolated perfused intact rat stomach. Somatostatin cells from the canine gastric fundus were isolated by EDTA-collagenase dispersion and counterflow elutriation, and somatostatin-like immunoreactivity (SLI) release in response to SOS was measured by radioimmunoassay. Similar methods were used to isolate gastric parietal cells, in which gastric acid secretion was measured by uptake of a radiolabeled weak base, [14C]aminopyrine. SLI release by the intact rat stomach was examined in an isolated vascularly perfused rat stomach model. SOS, either alone or co-administered with epinephrine or gastrin heptadecapeptide (G17), dose-dependently stimulated SLI release by isolated canine fundic D-cells. At the highest doses, SOS potentiated the effect of epinephrine but not G17. Similarly, SOS potentiated the stimulating effect of dibutyryl cyclic adenosine 3',5'-monophosphate (DBcAMP), but not 12-O-tetradecanoylphorbol 13-acetate (TPA). The effect of SOS on SLI release could be inhibited by octreotide, a somatostatin analogue. SOS did not alter acid secretion by cultured canine parietal cells either in the basal state or when coadministered with acid secretagogues. In isolated perfused rat stomach studies, SOS produced a significant (60% greater than basal) increase in SLI secretion. There was a similar effect when SOS was perfused against a background of isoproterenol. SOS stimulates SLI release from gastric somatostatin cells and from the isolated perfused stomach but has no direct effect on gastric parietal cells. These actions of SOS may mediate in part the apparent ability of sucralfate to enhance gastric mucosal defense.

Aminopyrine↗