Biomedical subjects

L Lai

Publications and source records attributed to L Lai.

At least 19 recordsLinked to original sources

PubMed1996

Epileptiform activity and hippocampal damage produced by intrahippocampal injection of guanidinosuccinic acid in rat.

Guanidinosuccinic acid (GSA) is a guanidino compound found in mammalian central nervous system and physiological fluids. Its level has been found to be greatly increased in serum and cerebrospinal fluid of patients with renal failure, and the compound is suggested to play a role in uremic encephalopathy. In this report we examined the behavioral, electrographic and morphological effects of intrahippocampal GSA injection in unanesthetized rats. Intrahippocampal administration of 2 microliters GSA solution (3.5 nM) was followed by behavior observation, and electrohippocampographic and electrocorticographic recording. GSA-injected animals showed partial clonic seizures leading to generalized clonic seizures, and eventually status epilepticus. These were accompanied by epileptiform electrographic discharges. During generalized clonic seizures, the electrohippocampogram showed arythmic bursting spikes. Epileptiform electric activity persisted even after the generalized clonic convulsions had stopped, and lasted until the animals were killed, 5 days following injection. Microscopic examination of brain slices of these rats revealed severe neural damage in CA1 area of hippocampus. Treatment of rats with the non-competitive NMDA receptor antagonist ketamine prevented both partial and generalized clonic seizures, epileptiform electrographic discharges, and GSA-induced hippocampal damage.

Animals↗

PubMed1996

Conformational analysis of two glycoproteins: a Monte Carlo simulated annealing approach using a soft-sphere potential.

The Monte Carlo simulated annealing method was effectively used to predict the three-dimensional structure of the carbohydrate part of two glycoproteins: 1 vsg and 2 fbj from a protein data bank, utilizing a soft-sphere potential. The result was compared both to the crystal structure and to the structure of the corresponding isolated oligosaccharide structure simulated using an ECEPP/2 force field. A good agreement with crystal structure was reached. The interaction with the protein environment was found to significantly influence the structure of the carbohydrate moiety.

Carbohydrate Conformation↗

PubMed1996

NMR determination of the structure of Julibroside J1.

Julibroside J1 is a new triterpenoid saponin which contains one triterpene, two monoterpenes and nine sugar residues. The structure has been determined almost exclusively by high-resolution NMR methods. The 1H and 13C NMR spectra of Julibroside J1 C5D5N have been assigned by homonuclear and heteronuclear correlation experiments, such as COSY, CH-COSY, TOCSY, HMBC, HMQC-COSY, HMQC-TOCSY and NOESY. Anomeric configurations were obtained by combined use of 1JCH and 3JH1,H2 and NOESY data. The particular sugar residues were identified by utilizing 3JHH values obtained from TOCSY cross-peaks, NOE difference spectra, and several 1D-TOCSY spectra, and three-bond intra-ring cross-peaks from a HMBC spectrum. Linkage assignments were made using the HMBC spectrum, and supplemented by NOE data from the NOESY spectrum. The structure of Julibroside J1 was characterized as 3-O-[beta-D-xylopyranosyl-(1-->2)-alpha-L-arabinopyranosyl-(1-->6) -beta-D- glucopyranosyl]-21-O-((6S)-2-trans-2-hydroxymethyl-6-methyl-6-O-[4-O-((6 S)- 2-trans-2,6-dimethyl-6-O-(6-deoxy-beta-D-glucopyranosyl)-2,7-octadien oyl)-6- deoxy-beta-D-glucopyranosyl]-2,7-octadienoyl)-acacic acid 28-O-(beta-D-glucopyranosyl-(1-->3)-[alpha-L-arabinofuranosyl-(1-->4)]- alpha-L-rhamnopyranosyl-(1-->2))-beta-D-glucopyranosyl ester.

Carbohydrate Conformation↗

PubMed1996

Comparison of three different hybridization assays in the quantitative measurement of serum hepatitis B virus DNA.

The measurement of hepatitis B virus (HBV) DNA, is important for monitoring and evaluating the efficacy of anti-viral agents in the treatment of patients with chronic hepatitis B. Three different hybridization assays for quantitative measurement of HBV DNA: direct membrane (dot-blot) hybridization, liquid hybridization (Abbott HBV DNA assay) and branched DNA signal amplification assay (Quantiplex, Chiron), were applied to 114 serial serum samples obtained from 13 patients with chronic active hepatitis B who had received ribavirin 600 mg daily for four weeks. Among the three assays, the correlation was found to be highest between Quantiplex and Abbott HBV DNA assay (r = 0.71, p < 0.01), moderate between Quantiplex and dot-blot hybridization (r = 0.58, p < 0.01) and lowest between dot-blot hybridization and Abbott HBV DNA assay (r = 0.27, p < 0.01). Quantiplex detected 107 (94%) of 114 specimens and was the most sensitive assay. All specimens positive by dot-blot hybridization and Abbott HBV DNA assays were detected positive by Quantiplex. The Dot-blot hybridization assay detected all 89 (100%) specimens with a high HBV DNA level (> or = 10 million genome equivalent (Meq)/ml by Quantiplex), but detected only 7 (50%) of 14 specimens with a low HBV DNA level (< 10 Meq/ml). The Abbott HBV DNA assay detected 85 (95%) of 89 specimens with a high HBV DNA level, but detected only 3 (17%) of 18 specimens with a low HBV DNA level. Among 7 negative specimens in the Quantiplex assay, 2 were detected positive by polymerase chain reaction. In conclusion, Quantiplex assay was more sensitive than Abbott HBV DNA assay and dot-blot hybridization assay for quantitative measurement of serum HBV DNA and can be used in the evaluation of the therapeutic drug effect on chronic hepatitis B patients.

Alanine Transaminase↗

PubMed1996

Prevalence of Helicobacter pylori infection in elderly inpatients and in institutionalized old people: correlation with nutritional status.

Helicobater pylori plays an important role in the aetiology and development of peptic ulcer disease. The prevalence of H. pylori infection increases with age, and is influenced by low socioeconomic status and poor hygiene owing to person-to-person transmission of the organism by the oral-faecal route. The aim of this study was to investigate the prevalence of H. pylori infection, detected serologically, in elderly patients admitted to a geriatric rehabilitation ward and in a sample of institutionalized old subjects. Nutritional status was also evaluated in order to examine its relation to H. pylori infection. The overall prevalence of H. pylori infection was 70.8%, the prevalence in hospitalized patients being 72.9% and in institutionalized subjects 68.7%. No significant correlation was observed between anti-H. pylori IgG levels and either age or length of stay in the institution. We found no difference between H. pylori positive and negative patients as regards their self-sufficiency and cognitive functions. The prevalence of anti-H. pylori antibodies in the serum was not related to blood variables (including nutritional indices), history of drug consumption (in particular nonsteroidal anti-inflammatory drugs), dyspeptic symptoms, or alcohol and smoking habits.

Aged↗

PubMed1996

Solid-phase synthesis, metal binding and folding properties of caulimovirus-related 'zinc finger'.

A 17-residue peptide containing the caulimovirus-related "zinc finger' was prepared by solid-phase peptide synthesis. Fluorescence measurements showed that the tryptophan quantum yield was Zn(2+)-dependent, allowing a 1:1 a stoichiometry for the complex to be determined. The structure of the peptide was characterized using circular dichroic spectroscopy, which indicates that the peptide exhibits a random coiled conformation in the absence of zinc but appears to form an ordered structure in the presence of zinc.

Amino Acid Sequence↗

PubMed1996

Tempol prevents impairment of the endothelial cell wound healing response caused by ionising radiation.

It is known that radiation therapy results in some form of damage to the microcirculation. In support of this view, we found that capillary endothelial cells (EC) treated with X-rays (8 Gy) were defective in their ability to recover a denuded area. A scrape wound of 2 mm width was produced in monolayers 30 min after X-ray or sham treatment. After 48 h, the number of cells migrating into each of five successive 125 microns zones from both sides of the original wound were determined. Greater numbers of sham-treated EC entered zones 3 and 4, compared with irradiated cultures, and only sham-treated EC entered the most distant zone 5. We examined actin fibre orientation within migrating irradiated and sham-treated EC using 2-(D-2-aminobutanoic acid)-7-(N6-((((3,6-bis(dimethylamino)xanthylium-9-yl) carboxyphenyl) amino)thioxomethyl)-L-lysine), chloride (NBD)-phalloidin, immunofluorescent microscopy and computer image analysis. After 48 h, sham-treated, but not irradiated EC, contained actin which was orientated perpendicular to the original wound edge. After 6-9 days, only sham-treated EC closed the wounds. Tempol (4 hydroxy-2,2,6,6-tetra methylpiperidine-1-oxyl)(0.5 or 2 mM)), included in the media during irradiation, prevented this wound healing delay, when measured within the first 24 h. In conclusion, radiation treatment of capillary EC results in a wound healing defect. This defect appears to be related to the EC's inability to realign actin. Tempol protects EC from exhibiting a wound healing delay.

Animals↗

PubMed1996

Cross reactive anti-tetanus and anti-melittin Fab fragments by phage display after tetanus toxoid immunisation.

Amino acid sequence homology between tetanus toxoid, a common vaccine and melittin, a bee venom allergen provided us with two antigen models for studying the production of cross reactive antibodies after immunisation. Analysis of the serum of an atopic patient recently boosted with tetanus toxoid revealed the presence of anti-melittin and anti-tetanus antibodies. From this donor a phage display Fab library was constructed five days after vaccination. Screening of this library either with melittin alone or with tetanus toxoid followed by melittin allowed the isolation of Fab fragments specific to melittin but also Fab fragments which cross react with melittin and tetanus toxoid. Amino acid analysis revealed diversity in the heavy and the light Ig chains of the melittin specific and of the cross reactive clones. Interestingly we found that the light chain recognised melittin whereas the heavy chain preferentially bound to tetanus toxoid suggesting that cross reactivity may be due to the different binding specificities of the individual Ig chains.

Amino Acid Sequence↗

PubMed1995

Analysis of thymic subpopulations expressing the activation antigen GL7. Expression, genetics, and function.

Previously, we reported an mAb, GL7, that defines an activation Ag expressed by in vitro-stimulated B and T cells as well as by a subpopulation of thymocytes. The current study analyzes the GL7-expressing populations of adult and fetal thymus and demonstrates that: 1) The majority of GL7+ adult thymocytes are CD4+CD8- cells that are CD3 epsilon high, TCR-alpha beta high, HSAlow, and bimodal for CD69 expression. The 3G11-6C10- subset of CD4+CD8- thymocytes is enriched in GL7-expressing cells. 2) Strain differences exist in the expression of GL7 on adult CD4+CD8- thymocytes; 21.9 +/- 5.9% of BALB/c CD4+CD8- thymocytes are GL7+, whereas 4.4 +/- 1.7% of C57BL/6 CD4+CD8- thymocytes are GL7+. The low GL7 expression phenotype is dominant in CB6F1 thymocytes (7.0 +/- 2.0%), and analysis of BALB/c x CB6F1 mice suggests that low GL7 expression is determined by multiple genes. 3) CD4+CD8- GL7+ thymocytes from BALB/c mice, but not C57BL/6 mice, are skewed toward a high proportion of V beta 8+ cells. 4) Adult GL7+ CD4+CD8- thymocytes can be activated by TCR-specific stimuli to proliferate and to secrete high amounts of IL-4. 5) Fetal thymocytes contain GL7+ cells, which are predominantly CD4-CD8-, HSAlow, CD69-, and bimodal for TCR-gamma delta. Thus, GL7 expression defines a subpopulation of functionally competent TCR-alpha beta+ CD4+CD8- thymocytes as well as TCR-gamma delta+ and TCR- subpopulations of fetal CD4-CD8- thymocytes.

Animals↗

PubMed1995

Potentiation of apoptosis by treatment with the protein kinase C-specific inhibitor safingol in mitomycin C-treated gastric cancer cells.

BACKGROUND: Protein kinase C (PKC) is a family of enzymes that function in processes relevant to carcinogenesis, tumor cell metastasis, and apoptosis. Safingol, an optical isomer (the L-threo enantiomer) of dihydrosphingosine, is a specific inhibitor of PKC and might represent a novel agent for anticancer therapy. Preclinical animal studies show that safingol alone has a minimal effect on tumor cell growth, but combining this compound with conventional chemotherapy agents dramatically potentiates their antitumor effects. It has been suggested that many chemotherapeutic agents exert their antitumor effects by inducing apoptosis. PURPOSE: We wanted to determine the extent to which safingol, alone or in combination with a standard chemotherapeutic agent (mitomycin C [MMC]), would promote apoptosis in gastric cancer cells in vitro. Furthermore, we investigated whether the induction of apoptosis in the treated cells was affected by their p53 tumor suppressor status or their drug-resistance status. METHODS: SK-GT-5 (p53-deficient and MMC-resistant) and MKN-74 (p53 wild-type and MMC-sensitive) gastric cancer cells were exposed to either no drug, safingol (50 microM) alone, MMC (5 micrograms/mL) alone, or a combination of safingol (50 microM) and MMC (5 micrograms/mL). In some experiments, cells were exposed simultaneously to safingol and the PKC activator, 3-phorbol 12-myristate 13-acetate (PMA), prior to treatment with MMC. Apoptosis was measured by two methods: 1) quantitative fluorescence microscopy of nuclear chromatin condensation in cells stained with the dye, bisbenzamide trihydrochloride (Hoechst-33258), and 2) terminal deoxynucleotidyl transferase (TdT) labeling of the 3'-OH ends of DNA fragments produced in apoptotic cells. RESULTS: As determined by quantitative fluorescence microscopy, exposure of SK-GT-5 cells to safingol alone induced apoptosis in 2% +/- 1% (mean +/- SD) of the cells, and MMC alone increased that level to 18% +/- 1%. However, the combination of safingol and MMC induced apoptosis in 39% +/- 1% of the cells (P < .001, for the drug combination versus MMC alone). With MKN-74 cells, safingol alone induced apoptosis in 8% +/- 3% of the cells, whereas MMC alone induced apoptosis in 40% +/- 4% of treated cells and the combination of safingol and MMC induced apoptosis in 83% +/- 4% of the cells. Similar results were obtained with the TdT assay. Simultaneous exposure of cells to safingol and PMA abrogated the safingol-mediated enhancement of MMC-induced apoptosis. CONCLUSIONS: The PKC inhibitor safingol enhances the cytotoxic effect of the chemotherapeutic agent MMC in gastric cancer cells by promoting drug-induced apoptosis. The induction of apoptosis occurs regardless of the p53 status or the drug-resistance status of the cells.

Apoptosis↗

PubMed1995

The mutational status of p53 protein in gastric and esophageal adenocarcinoma cell lines predicts sensitivity to chemotherapeutic agents.

Resistance to chemotherapy remains a serious problem in the successful treatment of gastric and esophageal cancers. DNA-damaging agents alter levels of p53 protein in several cell types and it has been speculated that regulation of p53 can be involved in the resistance or sensitivity of cancer cells to some chemotherapeutic drugs, depending on whether cells have mutant or wild-type p53; however, little is known about the relationship of p53 to drug sensitivity in gastric/esophageal cancers. Here we have examined human gastric/esophageal adenocarcinoma cell lines for p53 mutational status, chemosensitivity to 5-fluorouracil, mitomycin C, and cis-dichlorodiammineplatinum(II), alteration in p53 levels following exposure of cells to these drugs, and the mechanisms involved in regulating p53 levels. Our results indicate that wild-type p53 protein levels increase after treatment with each of these drugs via either post-translational and/or translational mechanisms and that this increase in wild-type p53 appears to be required for effective chemotherapeutic growth control of gastric/esophageal adenocarcinoma cells. In contrast, gastric/esophageal cancer cells expressing either mutated p53 protein or no p53 protein are more resistant to the growth-inhibitory effects of these drugs, despite the fact that drug exposure can also increase mutant p53 levels by a translational mechanism. Thus, these data indicate that the mutational status of p53 is predictive of chemosensitivity of gastric and esophageal adenocarcinomas, and suggest a mechanism in which p53 protein contributes to the cellular response to chemotherapy.

Adenocarcinoma↗

PubMed1995

Synthesis, conformation and opioid activity of deltorphins.

A series of deltorphin analogues was prepared by solid-phase peptide synthesis. Their opioid activity was evaluated in rat opiatic assay and their conformation was determined by two-dimension Nuclear Magnetic Resonance Spectroscopy. The analogues containing D-alanine acid at position 2 were much more potent in the assay than their corresponding isomers containing L-alanine acid at this position. The conformational analysis on NMR study in DMSO showed that C-terminal tetrapeptides of both deltorphin II and its L-alanine analog might form a 3(10) helix, which confirms that the substitution of D-amino acid at position 2 decreased the opioid activity.

Analgesics↗

PubMed1995

A new protein folding recognition potential function.

On the study of protein inverse folding problem, one goal is to find simple and efficient potential to evaluate the compatibility between structure and a given sequence. We present here a novo empirical mean force potential to address the importance of electrostatic interactions in protein inverse folding study. It is based on protein main chain polar fraction and constructed in a way similar with Sippl's from a database of 64 known independent three-dimensional protein structures. This potential was applied to recognize the protein native conformations among a conformation pool. Calculated results show that this potential is powerful in picking out native conformations, in addition it can also find structure similarity between proteins with low sequence similarity. The success of this new potential clearly shows the importance of electrostatic factors in protein inverse folding studies.

Electrochemistry↗

PubMed1995

A case of pneumatosis coli managed by restorative proctectomy and ileal pouch-anal anastomosis.

Pneumatosis coli is a rare condition in which gas filled cysts occur in the wall of the intestines. Most symptomatic patients can be managed conservatively but those who fail medical management or who develop bowel obstruction will require surgery. Surgery usually involves a limited colectomy with a potential for recurrence. We describe a case of pneumatosis coli managed successfully by restorative proctocolectomy and ileal pouch-anal anastomosis.

Anastomosis, Surgical↗

PubMed1995

The ASGE guidelines for the appropriate use of upper gastrointestinal endoscopy in an open access system.

AIMS: This multicenter and prospective study was aimed at examining the appropriate use of upper gastrointestinal endoscopy in an open access system (primary endoscopy) using the American Society for Gastrointestinal Endoscopy (ASGE) guidelines. We also wished to see whether these guidelines can be easily used in clinical practice. MATERIALS AND METHODS: Three thousand four hundred fourteen upper gastrointestinal endoscopies performed in seven endoscopy units of different size were studied prospectively. The real indication, to be with the guidelines, was determined by the endoscopist before performing the examination, based on a patient's history. RESULTS: Seven hundred eighty-one (23%) endoscopies were "generally not indicated," according to ASGE guidelines, and were distributed as follows: follow-up of duodenal ulcer healing (33%), follow-up of other healed benign diseases (24%), surveillance of gastric atrophy, pernicious anemia, metaplasia, treated achalasia, and prior gastric intervention (14%), diagnosis of dyspepsia considered functional in origin (13%), and uncomplicated heartburn responding to medical therapy (7%). Endoscopies "generally not indicated" accounted for 23% in the bigger endoscopy units, 24% in the average sized units, and 22% in the smaller ones. They accounted for 32% when the examination was prescribed by family doctors, 17% when prescribed by internists, 19% by surgeons, and 14% by gastroenterologists (p < 0.001). Eighty-six (2.5%) endoscopies were done for indications not provided in the guidelines. CONCLUSIONS: This study shows that ASGE guidelines are complete and easy to use and that the rate of inappropriate indications in an open access system can be considerable. They occurred mainly in the follow-up of healed benign disease and were more frequent when the examination was prescribed by the family doctor.

Endoscopy, Gastrointestinal↗

PubMed1994

CD18 integrin-dependent endothelial injury: effects of opsonized zymosan and phorbol ester activation.

We examined the hypothesis that neutrophil (PMN)-mediated injury of the vascular endothelium is dependent on adhesion of PMNs to endothelial cells via the leukocyte adhesion glycoprotein CD11/CD18. We compared the PMN activation responses [i.e. adhesion to cultured endothelial cells, superoxide (O2-) production, degranulation, and cytosolic [Ca2+] ([Ca2+]i)] and endothelial injury elicited by opsonized zymosan (OZ, which is phagocytosed by PMNs) or phorbol 12-myristate 13-acetate (PMA, a protein kinase C activator). The basal adherence of nonstimulated PMNs to bovine pulmonary artery endothelial cells (BPAEC) was 9.0 +/- 1.1 PMN/field. PMA and OZ increased PMN adherence to BPAEC (to 31.1 +/- 1.4 and 39.8 +/- 3.8 PMN/field, respectively), which in both cases was inhibited by anti-CD18 monoclonal antibody (mAb) IB4. Stimulation of PMNs with PMA or OZ produced injury to 73% and 53% of BPAEC examined, respectively, which corresponded to 6.8-fold and 3.5-fold increases in transendothelial 125I-albumin permeability from baseline. Pretreatment of PMNs with mAb IB4 prevented endothelial injury in both cases. Both PMA and OZ increased the production of O2- (by 7.6-fold and 3.1-fold over control, respectively) and promoted the release of myeloperoxidase (5.2-fold and 9.1-fold over control, respectively) (P < .01). IB4 did not inhibit the PMA- or OZ-induced increases in O2-. IB4 did not inhibit the PMA-induced myeloperoxidase release but reduced by approximately 29% the OZ-induced myeloperoxidase release. Stimulation of PMNs layered on BPAEC with OZ (0.5 mg/ml) caused an approximately 7-fold increase in PMN [Ca2+]i over baseline, which decayed to a steady-state level above baseline at 10 min. IB4 (10 micrograms/ml) alone did not alter baseline [Ca2+]i and did not inhibit the OZ-induced increase in [Ca2+]i. In contrast to OZ, stimulation of PMNs with PMA did not increase [Ca2+]i. The results indicate that the protective effects of the anti-CD18 mAb IB4 were associated predominantly with its antiadherence property. Therefore, CD18 integrin-mediated PMN adhesion to the endothelium is a critical determinant of endothelial injury irrespective of the PMN-activating stimulus.

Animals↗

PubMed1994

Ocular manifestations of Sotos syndrome.

BACKGROUND: Sotos syndrome (cerebral gigantism) is a congenital syndrome characterized by large body size for patient age, advanced bone age, and unusual facial characteristics with varying levels of cognitive, developmental and perceptual deficits. While more than 150 cases have been reported, only a single case report has been published in the ophthalmic literature. This study briefly reviews the pertinent aspects of this syndrome and reports on the medical, physical, developmental and ocular manifestations of 32 subjects. METHODS: Our patient population was obtained from several schools and colleges of optometry and private offices and clinics of optometrists and ophthalmologists. The Sotos Syndrome Support Association assisted in obtaining patients for this study as well. All children had been previously diagnosed as having SS. Commonly accepted methods for evaluating young, non-verbal, and/or handicapped children were used. RESULTS: Our findings indicate that moderate to high refractive error (hyperopia), nystagmus, and strabismus (esotropia) are commonly associated conditions of this syndrome. CONCLUSIONS: Since many of our subjects exhibited these amblyogenic precursors, a routine optometric vision evaluation should be an essential part of the individual educational and habilitation plan for all children with Sotos syndrome.

Abnormalities, Multiple↗

PubMed1993

Defining topological equivalences in protein structures by means of a dynamic programming algorithm.

An automatic algorithm for defining topological equivalences in protein structures is presented. The algorithm is based on a dynamic programming technique and self-consistent scoring method. We have used it to align pairs of similar protein structures of several protein families and to identify recurrent structural domains in aspartic proteinase 2APR. Its ability to find suboptimal paths permits a thorough comparison of proteins at each level in the hierarchy of the protein structure: secondary structure, super-secondary structure, domain and entire globular structure. The algorithm has been extended to the structure alignment of ribonucleic acid and can be extended to the structure alignment of any linear polymer.

Algorithms↗