PubMed Health⌕ Search

Biomedical subjects

L H Tang

Publications and source records attributed to L H Tang.

At least 19 recordsLinked to original sources

A phase II trial of neoadjuvant cisplatin-fluorouracil followed by postoperative intraperitoneal floxuridine-leucovorin in patients with locally advanced gastric cancer.

BACKGROUND: The aim of the study was to evaluate the efficacy and toxicity of neoadjuvant chemotherapy with intravenous (i.v.) cisplatin and fluorouracil (5-FU), surgery and postoperative intraperitoneal (i.p.) floxuridine (FUdR) and leucovorin (LV) in patients with locally advanced gastric cancer. PATIENTS AND METHODS: Preoperative staging was confirmed by laparoscopy (LAP). Two cycles of i.v. cisplatin (20 mg/m(2)/day, rapid infusion) and 5-FU (1000 mg/m(2), continuous 24-h infusion), given on days 1-5 and 29-34, were followed by a radical gastrectomy and a D2 lymphadenectomy. Patients having R0 resections were to receive three cycles of i.p. FUdR (1000 mg/m(2)) and LV (240 mg/m(2)), given on days 1-3, 15-17 and 29-31. Intraperitoneal chemotherapy was begun 5-10 days from surgery. RESULTS: Thirty-eight patients were treated. Both preoperative and postoperative chemotherapy were well tolerated. T stage downstaging (pretreatment LAP versus surgical pathological stage) was seen in 23% of patients. The R0 resection rate was 84%. Neither an increase in postoperative morbidity nor operative mortality was noted. With a median follow-up of 43.0 months, 15 patients (39.5%) are still alive (median survival 30.3 months). Good pathologic response, seen in five patients (15%), was associated with better survival (P = 0.053). Peritoneal and hepatic failures were found in 22% and 9% of patients, respectively. Quality of life seemed to be preserved. CONCLUSIONS: Neoadjuvant cisplatin/5-FU followed by postoperative i.p. FUdR/LV can be safely delivered to patients undergoing radical gastrectomy and D2 lymphadenectomy. The R0 resection and the survival rates are encouraging. An association between pathologic response and patient outcome was suggested.

Adenocarcinoma↗

Molecular evidence supports that Anopheles anthropophagus from China and Anopheles lesteri from Japan are the same species.

The Hyrcanus group of Anopheles consists of many related species, of which An. sinensis, An. lesteri, and An. anthropophagus are known as malaria vector species. It is not possible to identify these species morphologically in the adult and larval stages. Nucleotide sequence alignment of 2nd internal transcribed spacer (ITS2) regions from 4 specimens of An. lesteri collected in Japan, 2 specimens of An. anthropophagus collected in China, and 1 specimen of An. sinensis collected in Korea were sequenced and compared. Sequences of ITS2 regions varied only at 4 sites between An. lesteri and An. anthropophagus, and individual variations among each An. lesteri and An. anthropophagus were found at 5 and 7 sites, respectively, whereas sequences varied at 161 sites between An. lesteri and An. sinensis. This molecular evidence strongly supports that An. lesteri from Japan and An. anthropophagus from China are the same species.

Animals↗

PACAP mediates the neural proliferative pathway of Mastomys enterochromaffin-like cell transformation.

BACKGROUND AND AIM: Pituitary adenylate-cyclase activating peptide (PACAP) is a more potent proliferative agent than gastrin for rat enterochromaffin-like (ECL) cell proliferation in vitro. The role of this neurotransmitter during gastrin-mediated ECL cell tumor formation and gastrin-autonomous ECL cell neoplasia is unknown. METHODS AND RESULTS: ECL cell transformation was induced in the Mastomys using 16 wk H2 receptor blockade of acid inhibition. Examination of the epithelial fundic mucosa demonstrated that PACAP-immunoreactivity significantly increased in the tumor mucosa compared to the naïve stomach, and was associated with ECL cells. Naïve and tumor ECL cells were then purified (approximately 95%) from Mastomys and the presence of all three PACAP/VPAC receptor subtypes was demonstrated by polymerase chain-reaction amplification. Thereafter, cells were maintained in short-term (48 h) primary cultures. PACAP significantly (p<0.05) increased 24 h bromo-deoxyuridine uptake (approximately 4-fold) in both cell types with estimated EC(50) values of approximately 4x10(-16) M and approximately 2x10(-16) M, respectively. Specific receptor antagonists (PAC1/VPAC1) of PACAP competitively inhibited these proliferative effects in naïve cells. Oligonucleotide antisense directed against PAC1 significantly inhibited PACAP-stimulated DNA synthesis by approximately 85% (p<0.05) in tumor cells. CONCLUSION: PACAP is a potent and effective modulator of ECL cell proliferation. The expression of this neuropeptide and its receptors, particularly PAC1, suggest the existence of a neural regulatory pathway of ECL cell proliferation and transformation.

Animals↗

Anomalous finite-size effect in superconducting Josephson junction arrays.

We show that a previously reported discrepancy between simulations of superconducting Josephson junction arrays and the theoretical analysis of Ambegaokar, Halperin, Nelson, and Siggia (AHNS) [Phys. Rev. Lett. 40, 783 (1978)] is rooted in a peculiar finite-size effect under periodic boundary conditions. Our simulation results for the largest array support the power-law I-V curves predicted by AHNS. Analysis of the vortex dynamics reveals two intrinsic length scales set by the applied current, which define three size regimes with distinctive I-V characteristics.

Journal Article↗

Rare-event induced binding transition of heteropolymers.

Sequence heterogeneity broadens the binding transition of a polymer onto a linear or planar substrate. This effect is analyzed in a real-space renormalization group scheme designed to capture the statistics of rare events. In the strongly disordered regime, binding initiates at an exponentially rare set of "good contacts." Renormalization of the contact potential yields a Kosterlitz--Thouless-type transition in any dimension. This and other predictions are confirmed by extensive numerical simulations of a directed polymer interacting with a columnar defect.

Journal Article↗

[The role of Anopheles anthropophagus in malaria transmission in in Xinyang City of Henan Province].

OBJECTIVE: To study the role of Anopheles anthropophagus in malaria transmission and transmission threshold so as to provide basis for vector surveillance and malaria control strategy. METHODS: Parasitological and entomological methods were used in the investigation at 5 villages of Xinyang City, Henan Province. RESULTS: From July to August, 1999, 74 febrile cases (10.9% of the total population) were examined. Among them 50 were infected, the incidence in the population of surveyed spots was 7.4%. Active detection was made in another randomly selected two villages and found that the parasite rate in the inhabitants was 2.0%, and the positive rate of IFA was 8.4%. Only vivax malaria was detected. An. anthropophagus and An. sinensis were collected, with An. anthropophagus as the predominant one in human dwellings. The estimated man-biting rate and the human blood index were 4.9388 and 0.7858 respectively. The vectorial capacity of An. anthropophagus was 5.5296. The critical man-biting rate of An. anthropophagus was 0.2407 as calculated by the formula (ma = -rlnP/abPh) according to Macdonald's model. The local man-biting rate was 20 times higher than that of the critical man-biting rate. CONCLUSION: The results demonstrated that An. anthropophagus is the principal vector in malaria transmission in the area. The findings imply that the critical man-biting rate is of practicable importance in vector surveillance.

Animals↗

Helicobacter pylori alters gastric epithelial cell cycle events and gastrin secretion in Mongolian gerbils.

BACKGROUND & AIMS: Human colonization with Helicobacter pylori increases the risk for distal gastric adenocarcinoma, possibly by altering gastric epithelial cell cycle events and/or gastrin secretion. This study aimed to determine whether H. pylori virulence-related characteristics affect apoptosis, proliferation, and gastrin levels in a rodent model of gastric adenocarcinoma. METHODS: Mongolian gerbils were challenged with H. pylori wild-type or isogenic cagA(-) and vacA(-) mutants, and apoptotic and proliferating cells were identified by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling and proliferating cell nuclear antigen immunohistochemistry, respectively. Serum gastrin levels were determined by radioimmunoassay. RESULTS: Gastric epithelial cell turnover was no different after infection with the wild-type, cagA(-), or vacA(-) strains. H. pylori infection significantly increased antral apoptosis 2-4 weeks after challenge, before apoptotic indices decreased to baseline. In contrast, antral proliferation rates were significantly higher 16-20 weeks after inoculation, but then decreased by 40 weeks. Antral proliferation was significantly related to serum gastrin levels, whereas antral apoptosis was inversely related to acute inflammation and lymphoid follicles. CONCLUSIONS: In H. pylori-infected gerbils, enhanced antral apoptosis is an early and transient cell cycle event. Epithelial cell proliferation peaks later and is significantly related to increased gastrin levels, suggesting that epithelial cell growth in H. pylori-colonized mucosa may be mediated by gastrin-dependent mechanisms.

Animals↗

Gastrin-mediated alterations in gastric epithelial apoptosis and proliferation in a mastomys rodent model of gastric neoplasia.

BACKGROUND/AIMS: Hypergastrinemia secondary to low acid secretion is associated with gastric carcinoid formation in Mastomys. We investigated the effect of gastrin on oxyntic epithelial apoptosis and proliferation in this model. METHODS: Hypergastrinemia and mucosal hyperplasia were induced by irreversible H(2) receptor blockade with loxtidine. Gastrin levels were normalised in some animals by 10 days' loxtidine withdrawal. Serum gastrin was determined by radioimmunoassay, proliferative, enterochromaffin-like cells and Bcl-2 protein family expression by immunohistochemistry, and apoptotic cells by terminal deoxyuridine nucleotide nick end labeling (TUNEL). RESULTS: Proliferating cells were increased 4-fold in loxtidine-treated animals, and returned to normal upon loxtidine withdrawal. Enterochromaffin-like cell number increased 2-fold with loxtidine, and did not decrease after withdrawal. Apoptotic epithelial cells were located at the luminal surface and increased 1.8-fold with loxtidine, returning to control levels upon withdrawal. The ratio of proliferative to apoptotic cells was lower in the control and withdrawn groups than in the loxtidine group (0.26+/-0.05 and 0.26+/-0.08 vs. 0.77+/-0.12). With hypergastrinemia, the expression of Bcl-2 and Bak was increased and Bax decreased in the middle of the gland. CONCLUSION: Hypergastrinemia is associated with alterations in both proliferation and apoptosis in Mastomys gastric mucosa. This may contribute to the pathogenesis of mucosal hyperplasia in this model.

Animals↗

Helicobacter pylori lipopolysaccharide alters ECL cell DNA synthesis via a CD14 receptor and polyamine pathway in mastomys.

Chronic Helicobacter pylori infection is associated with alterations in gastric mucosal cell proliferation. Despite the recognition that bacterial lipopolysaccharide (LPS) is present in biologically active quantities in the gastric mucosa, the mechanisms by which it stimulates cells are largely unknown. We have previously established a gastric enterochromaffin-like (ECL) cell neoplasia model in the African rodent species Mastomys and identified that tumor ECL cell proliferation is associated with polyamine biosynthesis and ornithine decarboxylase (ODC) activity. In addition, we have shown that H. pylori LPS exhibits a specific mitogenic effect on naive ECL cells in vitro. The aim of this study was to evaluate whether H. pylori has a direct effect on tumor ECL cell proliferation in vitro and further to evaluate the possible molecular mechanisms for this effect. ECL cell neoplasia was generated in Mastomys by endogenous hypergastrinemia induced by H(2) blockade (loxtidine 1 g/kg/day) and tumor ECL cells prepared. The DNA synthesis in 24-hour cultured tumor cells was measured by bromodeoxyuridine uptake and ODC activity by (14)CO(2) formation from (14)C-ornithine. The putative LPS receptor, CD14, was evaluated by reverse-transcription polymerase chain reaction. Our results demonstrated: (1) H. pylori LPS (10(-12) to 10(-7) M) stimulated basal DNA synthesis (2.2-fold) with an estimated EC(50) of 10(-10) M; (2) this proliferative response correlated with an increase in ODC activity (1.4-fold, EC(50) approximately 10(-10) M) which could be inhibited by a specific ODC inhibitor, difluoromethyl ornithine, at 10(-9) M; (3) the CD14 receptor was identified in both naive and transformed ECL cells by reverse-transcription polymerase chain reaction, and (4) the effects of LPS were inhibited by blocking the CD14 receptor with its specific monoclonal antibody (1:100). Thus, H. pylori LPS appears to influence tumor ECL cell proliferation by activation of the intracellular polyamine pathway and ODC activity via a CD14 receptor on the ECL cell.

Animals↗

[Studies on lipase-catalyzed synthesis of L-ascorbyl palmitate in non-aqueous phase].

The investigation on the reaction media and lipases (NOVO435, MML, LIPOLASE, PPL) for enzymatic synthesis of L-ascorbyl palmitate as well as the factors effecting initial rate of synthesis reaction (rotation speed, temperature, water content, enzyme concentration, and substrate concentration) is presented. Among these investigated solvents and lipases, amyl alcohol and NOVO435 is the optimum pair. The reaction conditions have been optimized: 200 r/min, 55 degrees C, water content = 0, the amount of enzyme = 12.5% of the substrate's quantity.

Ascorbic Acid↗

A study of injectable tissue-engineered autologous cartilage.

OBJECTIVE: To test the effectiveness of the new techniques of tissue-engineered cartilage. METHODS: Chondrocytes were harvested through type II collagenase digestion from the auricle of New Zealand rabbits. The cells were mixed with alginate to generate chondrocytes/alginate composites with final cellular density of 50 x 10(6) per mL. Calcium chloride was used as the cross-linking agent to gel the aqueous alginate solution. The chondrocytes/alginate composites were injected into the dorsal subcutaneous tissue of New Zealand rabbits through autologous cells grafts. The specimens were observed during cartilage formation at 4, 8, and 12 weeks after injection. RESULTS: Prior to harvesting, chondrocytes/alginate composites were easily visualized under the dorsal skin of animals. The appearance of experimental specimens was similar to that of native cartilage in gross morphology. Using a standard hematoxylin and eosin stain, the histologic features of all experimental specimens demonstrated new cartilage formation. With a Masson's trichrome and safranin O stain, the presence of collagen and glycosaminoglycan (GAG) was observed at 8 and 12 weeks. CONCLUSION: This study demonstrated that polymerization of alginate hydrogel can be controlled to allow injection of chondrocytes that produce new autologous cartilage at subcutaneous dorsal site of rabbits. Injectable tissue-engineered autologous cartilage is promising for potential use in oral and maxillofacial surgery.

Alginates↗

[Practicability of IFAT using Plasmodium cynomolgi and Plasmodium falciparum antigens in different malarious areas].

OBJECTIVE: To compare the practicability of IFAT in different malarious areas using Plasmodium cynomolgi(P.c.) and Plasmodium falciparum(P.f.) antigens. METHODS: This survey was carried out in Yaliang Township of Sanya City, Hainan Province, where a mixed malaria is endemic, and in Tongbo County, Henan Province where only vivax malaria is endemic, and in Weihui City, Henan Province where vivax malaria has been under effective control since 1994-1998. RESULTS: In Yaliang Township, 310 blood samples were examined, the antibody positive rates with P.c. and P.f. were 37.4% and 31.3%, respectively, the rate of coincidence being 83.9%. In Tongbo County, 300 blood samples were examined. The antibody positive rates with P.c. and P.f. were 23.0% and 9.7%, respectively (P < 0.01). Another 245 blood samples from children were examined in Weihui City and the antibody positive rates were below 1% with two antigens, while the positive antibody rate was 3.3% with P.f. antigen. CONCLUSION: Both P.f. and P.c. antigens could be used in malaria antibody surveillance in mixted endemic areas, while in vivax malaria endemic areas, P.c. antigen was recommended.

Animals↗

[Multi-bed & multi-parameter central monitoring system based on TCP/IP protocol].

Communication is one of the key problems to a central monitoring system. In this paper we put forward a central monitoring system using TCP/IP as the network protocol, Windows NT4.0 as the platform, forming a Intranet in a hospital. We also discussed the communication problem between the bed-side monitoring station and the central monitoring station in detail and then put forward a new protocol--Hospital Central Monitor Protocol (HCMP) based on TCP/IP to transfer monitoring data. It is easy to achieve tele-monitoring through the current communication subsystem.

Computer Communication Networks↗

Biological relevance of pituitary adenylate cyclase-activating polypeptide (PACAP) in the gastrointestinal tract.

Since its initial discovery in 1989, pituitary adenylate cyclase activating peptide (PACAP) has been noted to distribute widely in the brain, the respiratory and the gastrointestinal system. It occurs in two bioactive molecules, PACAP-27 and the C-terminally extended PACAP-38, which evoke activity by binding to three distinct types of high-affinity, G-protein coupled membrane receptors. It is present throughout the entirety of the gut but is rare in certain areas such as the intestinal mucosa and islets of Langerhans. PACAP-induced biological effects are protean and include alterations of motility in the bowel and the gallbladder, stimulation of gastric acid and intestinal secretion, hormone/enzyme release from the exocrine and endocrine pancreas, and the induction as well as inhibition of proliferation in neuroendocrine cells and tumors. Its hepatic activity has to date not been elucidated in detail. One of the interesting features of PACAP is the species and organ dependent variation of its biological effects. Of particular note is its superior potency when compared with other neuropeptides identified in the gut, and the involvement of a number of different second messenger systems upon PACAP receptor activation.

Animals↗

Pituitary adenylate cyclase-activating polypeptide modulates gastric enterochromaffin-like cell proliferation in rats.

BACKGROUND & AIMS: Gastric carcinoids (types I and II) involve the transformation of naive enterochromaffin-like (ECL) cells to the neoplastic state and are associated primarily with hypergastrinemia. In this study, we evaluated the effects of two related neuropeptides, pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal polypeptide (VIP), on ECL cell proliferation and characterized the receptor subtype(s) and signal transduction pathways that mediate this effect. METHODS: Purified rat ECL cells were analyzed in culture for DNA synthesis as measured by 24-hour 5-bromo-2-deoxyuridine (BrdU) uptake. Reverse-transcription polymerase chain reaction (RT-PCR) with gene-specific oligonucleotide primers was performed to characterize the PACAP/VIP receptor subtype(s). RESULTS: PACAP/VIP neuropeptide-stimulated BrdU uptake was significantly greater (3.4-3.8-fold greater than control) than that at the maximal dose of gastrin (2.2-fold greater than control). PACAP-stimulated ECL cell proliferation (EC50, approximately 3 x 10(-)14 mol/L) was approximately 100-fold more potent than VIP (EC50, approximately 3x 10(-)12 mol/L). The stimulated BrdU uptake by both PACAP and VIP was competitively inhibited by PACAP-receptor antagonist (IC50, 10(-)9 mol/L, 3 x 10(-)9 mol/L, respectively) and VIP-receptor antagonist (IC50, 3 x 10(-)7 mol/L, 5 x 10(-)7 mol/L, respectively). RT-PCR identified the presence of the PACAP-specific but not PACAP/VIP receptor subtypes. The PACAP-stimulated BrdU uptake was inhibited (70%-80%) by inhibitors of adenosine 3',5'-cyclic monophosphate, phosphatidylinositol 3 kinase, and protein tyrosine kinase as well as mitogen-activated protein kinase. CONCLUSIONS: PACAP/VIP-related peptides are more potent modulators of ECL cell proliferation than gastrin, and their effect is mediated by a PACAP-specific receptor whose activation is transduced by multiple intracellular messenger systems.

Androstadienes↗

Cell and tumour biology of the gastric enterochromaffin-like cell.

The recent recognition of the nature of gastric carcinoids and the elucidation of the biological events associated with enterochromaffin-like cell transformation has provided an opportunity to advance the understanding of this particular type of neuroendocrine tumour. The relationship between hypergastrinaemia present in low acid disease states and the development of gastric carcinoids has led to an appreciation of the role of gastrin as a growth mediator in the evolution of this type of neoplasia. In addition, evidence exists to support a genetic predisposition to this tumour type in individuals with Multiple Endocrine Neoplasia type 1 syndrome, and in an experimental model--the African rodent species, Mastomys. The recent development of an isolated pure enterochromaffin-like cell preparation has facilitated the elucidation of the molecular physiology of the naive enterochromaffin-like cell and, in addition, allowed the evaluation of the cellular events associated with enterochromaffin-like cell transformation from the naive state to the neoplastic phenotype. This synopsis seeks to present information relevant to both the animal model and the human disease state. The aim is to facilitate an appreciation of the regulatory mechanisms of the enterochromaffin-like cell and delineate the changes consequent to the development of the neoplastic phenotype.

Animals↗

[Influence of Helicobacter pylori lipopolysaccharide on the function of enterochromaffin-like cells in vitro].

OBJECTIVE: To investigate the relationship between Helicobacter pylori (Hp) infection and pathophysiology of abnormal gastric acid secretion and mucosal proliferation by studying the effect of Hp lipopolysaccharide (LPS) on the function of enterochromaffin-like (ECL) cells in vitro. METHODS: Pure isolated ECL cell preparation with a purity of +/- 95% was developed by proteinase digestion, elutriation and density gradient centrifugation with viability of > 95% as determined by trypan blue exclusion. After a short duration of culture basal and stimulated histamine secretion and DNA synthesis of ECL cells were measured by enzyme immunoassay and bromodeoxyuridine (BrdU) uptake, respectively. RESULTS: Hp LPS stimulated basal and gastrin-stimulated histamine secretion (EC(50)4 x 10(-11) mol/L and EC(50) 10(-10) mol/L respectively). These effects were completely inhibited by somatostatin (10(-10) mol/L) but not by gastrin receptor antagonist L(365 260). Hp LPS did not stimulate basal DNA synthesis but significantly increased gastrin stimulated BrdU uptake with EC(50) of 10(-10) mol/L. Escherichia coil LPS had no significant effect on both histamine secretion and DNA synthesis. CONCLUSION: Hp stimulates both ECL cell proliferation and secretion in vitro. An interaction between Hp LPS and ECL cells may contribute to the reported abnormalities in acid secretion and gastric pathophysiology noted in Hp infection.

Animals↗

Gastrin-regulated expression of p53 in transformed enterochromaffin-like cells in the African rodent mastomys.

The tumor suppressor p53 functions at the G1/S-phase checkpoint of the cell cycle to direct cells that have accumulated somatic mutations toward apoptosis and away from mitosis. The p53 gene is commonly mutated in human cancers, but the molecular mechanisms regulating this event are not clear. The African rodent mastomys exhibits a genetic predisposition to develop gastric carcinoids derived from enterochromaffin-like (ECL) cells. The ECL cell transformation can be accelerated by acid inhibition-induced hypergastrinemia. This study evaluates the alteration of p53 during the rapid ECL cell transformation. Hypergastrinemia was generated by the irreversible histamine-2 receptor antagonist loxtidine for 8 weeks (hyperplasia) and 16 weeks (neoplasia). p53 expression was evaluated in fundic mucosa from different stages of transformation by Western blot analysis and immunohistochemistry using monoclonal antibodies against wild-type p53. RT-PCR and molecular sequence analysis of p53 were undertaken with mRNA isolated from purified ECL cells. Overproduction of the wild type of p53 was evident in ECL cells during hypergastrinemia, and the molecular characteristics of p53 were determined in naive and transformed ECL cells. p53 was mutated at the C-terminus in ECLoma induced by hypergastrinemia. Therefore, p53 is altered from overproduction to mutation during the development of hypergastrinemia-induced ECLoma and it may therefore play a role in the cell transformation.

Amino Acid Sequence↗