Detailed studies on substrate structure requirements of glycoamidases A and F

Glycoamidases (peptide-N4-(N-acetyl-beta-glucosaminyl)asparagine amidase, EC 3.5.1.52; also known as peptide: N-glycanases (PNGases) release N-linked oligosaccharides from glycopeptides and/or glycoproteins by hydrolyzing the glycosylated beta-amide bond of the asparagine side chain. The most widely used glycoamidases are those from Flavobacterium meningosepticum (glycoamidase F or PNGase F) and almond emulsin (glycoamidase A or PNGase A). To study the substrate structure requirement of these enzymes systematically, we synthesized >30 glycopeptides containing cellobiose, lactose, GlcNAc, and di-N,N'-acetylchitobiose (CTB). The length of the peptide was varied from one to five amino acids, and glycosylamines were linked to either Asn or Gln located at different positions in the peptide, including NH2 and COOH termini. Neither enzyme could cleave cellobiose and lactose glycopeptides, indicating that the 2-acetamido group on the Asn-linked GlcNAc is important in the recognition by both glycoamidases A and F. GlcNAc peptides could be cleaved by both enzymes, albeit not as effectively as CTB glycopeptides. Neither enzyme requires the Asn-Xaa-(Ser/Thr) sequence (required for N-glycosylation) for activity. Glycoamidase A could even hydrolyze a Gln-bound CTB glycopeptide, whereas the action of glycoamidase F on this substrate is minimal. While glycoamidase A could act on CTB dipeptides, glycoamidase F preferred a tripeptide or longer. The Km and Vmax values of glycoamidase A for t-butoxycarbonyl-(CTB)-Asn-Ala-Ser-OMe were 2.1 mM and 0.66 micromol/min/mg, respectively. A natural glycodipeptide, Man9-GlcNAc2-Asn-Phe, was also completely hydrolyzed by glycoamidase A.

alpha-KDOase activity in oyster and synthesis of alpha- and beta-4-methylumbelliferyl ketosides of 3-deoxy-D-manno-octulosonic acid

Although alpha- and beta-linked 3-deoxy-D-manno-octulosonic acid (KDO) is found in lipopolysaccharides (LPSs) of Gram-negative bacteria, capsular polysaccharides of microorganisms, and plants, very little is known about its degradation. Using both thin-layer chromatography and the periodate-thiobarbituric acid reaction, we found that the hepatopancreas of oyster (Crassostrea virginica) contained an enzyme (alpha-KDOase) capable of releasing alpha-linked KDO from LPSs. To facilitate the studies of alpha-KDOase, we have carried out the synthesis of 4-methylumbelliferyl-alpha-KDO (alpha-KDO-MU) by conjugating the glycosyl chloride of the per-O-acetylated methylester of KDO with methylumbelliferone by the SN2 type reaction and the catalyzed phase-transfer. In both cases, the beta-anomer was obtained as the major product with a yield of about 80%, whereas the yield of alpha-anomer was only about 7%. Attempts to increase the yield of alpha-anomer were not successful. alpha-KDO-MU was used as substrate to follow the purification of alpha-KDOase from oyster hepatopancreas. The pH optimum for oyster alpha-KDOase was determined to be 4.5 using Re-LPS as substrate and 3.0 using alpha-KDO-MU as substrate. The enzyme was found to be stable in the pH range of 3-8. This enzyme released KDO from different LPSs, including Re-LPS from Escherichia coli and Salmonella minnesota, Rd-LPS from S. minnesota, and de-O-acyl-Re-LPS (Kiang, J., Szu, S. C., Wang, L.X., Tang, M., and Lee, Y. C. (1997) Anal. Biochem. 245, 97-101).

Role of nitric oxide in penile erection

The present study was undertaken to investigate the role of nitric oxide (NO) in erectile physiology by correlating its action with the existence and activity of nitric oxide synthase (NOS), which produces NO. We applied Western blot analysis in both human and rat penile tissue. In the rat, reduced nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase staining and spectrophotometric assay were also performed, in addition to in vivo electroerection study with pharmacological manipulation. Western blot analysis identified a protein of 155 KDa identical to the neural form of NOS in the human and rat penis. The NOS blot densities in the two species were similar, and both were lower than that in the rat cerebellum. Histochemical staining localized NOS to neurons innervating the corpora cavernosa, including the pelvic plexus, the cavernosal nerves and their terminal fibers within the corporeal erectile tissue, and dorsal penile nerves. NOS activity was also found in the cerebellum, urethra, penis, and urinary bladder, in decreasing order of intensity. Intracavernous injections of NOS inhibitor (L-NOARG or L-NAME in concentrations from 10(-6) M to 10(-3) M suppressed electrostimulation-induced erection in a concentration-dependent manner. Subsequent intracavernous injection of L-Arginine (10(-2) M) partially restored the erection. The neural form of constitutive NOS in the corpora cavernosa synthesizes NO, which mediates penile erection. Determination of cavernosal NOS expression or activity may permit characterization of certain pathological conditions that cause impotence.

Surgical treatment for pulmonary aspergilloma: a 28 year experience

BACKGROUND

Pulmonary aspergilloma has been treated surgically for many years but the mortality rates of larger surgical series, varying from 7% to 23%, is not considered acceptable by today's standards. The authors report their experience in the surgical treatment of pulmonary aspergilloma and present a review of the literature.

METHODS

Sixty seven patients who underwent thoracotomy for pulmonary aspergilloma from 1968 to 1995 were studied retrospectively by reviewing their medical records.

RESULTS

The most common clinical presentation of pulmonary aspergilloma was haemoptysis which occurred in 61 patients (91.0%). Tuberculosis was the most common pre-existing disease, occurring in 54 patients (80.6%). The plain chest radiograph showed the typical "air-crescent" sign in 36 patients (53.7%). Systemic antifungal therapy neither palliated the clinical symptoms nor eradicated the aspergilloma, and transarterial embolisation was also unsuccessful. Surgery offered the only chance of cure for both unilateral and bilateral disease. Procedures varied from segmentectomy to pneumonectomy with most (61.4%) undergoing lobectomy. There was one death following surgery from pneumonia and 15 postoperative complications occurred in 12 patients-empyema (7), massive bleeding (3), bronchopleural fistula (2), wound infection (2), and Horner's syndrome (1). Postoperatively, most of the patients were symptom-free.

CONCLUSIONS

With appropriate preoperative evaluation and judicious surgical technique, surgery is the preferred treatment for pulmonary aspergilloma, both for eradicating the tumour and for curing the underlying disease.

Facile synthesis of a high-affinity ligand for mammalian hepatic lectin containing three terminal N-acetylgalactosamine residues

A simple cluster glycoside containing three residues of N-acetylgalactosamine with proper inter-residual distances can be a high-affinity ligand for asialoglycoprotein receptor of mammalian liver. YEE(ah-GalNAc)3 [Lee, R. T., and Lee, Y. C. (1987) Glycoconjugate J, 4, 317-328] is such a ligand having a Kd in the subnanomolar range, and this high-affinity ligand has been successfully utilized in the delivery of gene to the parenchymal cells of the liver [Merwin, J. R., Noell, G. S., Thomas, W. L., Chiou, H. C., DeRome, M. E., McKee, T. D., Spitalny, G. L., and Findeis, M. A. (1994) Bioconjugate Chem. 5, 612-620; Hangeland, J. J., Levis, J. T., Lee, Y. C., and Ts'o, P. O. P. (1995) Bioconjugate Chem. 6, 695-701]. Reported here is a synthetic procedure for an equally effective, homologous trivalent ligand, YDD(G-ah-GalNAc)3. The advantage offered by this new cluster glycoside is that the synthetic scheme accomplishes purification of reaction intermediates and the product without chromatographic separations. This greatly simplifies the procedure and allows scale-up of the operation at reduced cost of production.

Activation of phosphodiesterase IV during desensitization of the A2A adenosine receptor-mediated cyclic AMP response in rat pheochromocytoma (PC12) cells

Prolonged activation of an A2A adenosine receptor significantly inhibits the cellular response to subsequent stimulation (A2A desensitization). We have reported previously that activation of phosphodiesterase (PDE) contributes to A2A desensitization in PC12 cells. In the present study, we show that a type IV PDE (PDE4)-selective inhibitor (Ro 20-1724) effectively blocks the increase in PDE activity in desensitized cells. Thus, PDE4 appears to be the PDE specifically activated during A2A desensitization in PC12 cells. Prolonged treatment of PC12 cells with an A2A-selective agonist (CGS21680) leads to increased PDE4 activity in a dose-dependent manner, which can be blocked by an A2A-selective antagonist [8-(3-chlorostyryl)caffeine]. Using two PDE4 antibodies, we were able to demonstrate that the levels of two PDE4-immunoreactive bands (72 and 79 kDa) were increased significantly during A2A desensitization. Prolonged treatment with forskolin to elevate intracellular cyclic AMP contents also resulted in increased PDE4 activity. In addition, activation of PDE4 activity during A2A desensitization could be blocked by a protein kinase A (PKA)-selective inhibitor (H89) and was not observed in a PKA-deficient PC12 cell line (A123). Taken together, activation of PDE4 via a cyclic AMP/PKA-dependent pathway plays a critical role in dampening the signal of the A2A receptor.

4-Methylumbelliferyl glycosides of N-acetyl 4-thiochito-oligosaccharides as fluorogenic substrates for chitodextrinase from Vibrio furnissii

The degradation of chitin involves a diverse array of enzymes, some with overlapping substrate specificities. In order to distinguish between different types of enzymes, specific substrates are needed. Toward this end, two new fluorogenic substrates containing thio-glycosidic linkages, 4-methylumbelliferyl N,N'-diacetyl-4-thio-beta-chitobioside (Mu-TCB) and N,N',N"-triacetyl-4,4'-dithio-beta-chitotrioside (Mu-TCT) are described. The substitution of the glycosidic oxygens (except the one that links oligosaccharide with the fluorogenic aglycon) with a sulfur atom resulted in resistance of these compounds to N-acetyl-beta-hexosaminidases while they were specific substrates for the newly discovered chitodextrinase from Vibrio furnissii (Keyhani,N.O. and Roseman,S. (1996) J. Biol. Chem., 271, 33414-33424) and some bacterial chitinases. The enzyme kinetics of these 4-S-linked substrates, Mu-TCB and Mu-TCT, as well as the O-linked 4-methylumbelliferyl N,N'-diacetyl-beta-chitobioside (Mu-CB) and N,N',N"-triacetyl-beta-chitotrioside (Mu-CT) with the chitodextrinase were studied and compared. The usefulness of the substrates for screening for chitodextrinase and/or chitinase activity was demonstrated.

Major depressive disorder with delusion of having AIDS: a case report

Acquired immune deficiency syndrome (AIDS) has become a topic of increasing public concern. Several conditions have been described in patients who are afraid that they have acquired AIDS, including depression, somatization disorders, hypochondriasis, adjustment disorders and various psychoses. This paper presents a case study of a young man with persistent fear of having AIDS. In spite of negative HIV test results, the patient still insisted that he suffered from AIDS. The psychiatric diagnosis was major depressive disorder with delusion of having AIDS. The patient was treated with fluoxetine 40 mg qd and sulpiride 400 mg qn. After two weeks on medication, his fear of AIDS subsided and he improved remarkably. The most important intervention in patients with delusion of having AIDS is to identify and treat the underlying psychopathology. The following case is representative of our experience.

A transcriptional mediator protein that is required for activation of many RNA polymerase II promoters and is conserved from yeast to humans

A temperature-sensitive mutation was obtained in Med6p, a component of the mediator complex from the yeast Saccharomyces cerevisiae. The mediator complex has been shown to enable transcriptional activation in vitro. This mutation in Med6p abolished activation of transcription from four of five inducible promoters tested in vivo. There was no effect, however, on uninduced transcription, transcription of constitutively expressed genes, or transcription by RNA polymerases I and III. Mediator-RNA polymerase II complex isolated from the mutant yeast strain was temperature sensitive for transcriptional activation in a reconstituted in vitro system due to a defect in initiation complex formation. A database search revealed the existence of MED6-related genes in humans and Caenorhabditis elegans, suggesting that the role of mediator in transcriptional activation is conserved throughout the evolution.

Separation of oligo/polymers of 5-N-acetylneuraminic acid, 5-N-glycolylneuraminic acid, and 2-keto-3-deoxy-D-glycero-D-galacto-nononic acid by high-performance anion-exchange chromatography with pulsed amperometric detector

A sensitive and efficient method to analyze oligo/ poly-sialic acids containing alpha2-8-linked 5-N-acetylneuraminic acid (Neu5Ac), 5-N-glycolylneuraminic acid (Neu5Gc), and deaminated neuraminic acid (KDN) using high-performance anion-exchange chromatography (HPAEC) with a pulsed amperometric detector (PAD-2) has been developed. Using a CarboPac PA-100 column and sodium nitrate as the pushing agent, polymers in colominic acid with degree of polymerization (DP) up to 80 were separated in 68 min. A similar DP-based resolution was also obtained on a CarboPac PA-1 column. The elution ladders of the Neu5Ac, Neu5Gc, and KDN series were sufficiently different to be used as diagnostic indices. This technique was applied to identification of the sialic acid components in a polysialoglycoprotein (PSGP) sample as well as monitoring the oligo/poly-KDN-containing fractions during the purification of KDN-containing glycoprotein (KDN-gp). The maximum DPs of oligo-Neu5Gc and oligo-KDN that can be detected in PSGP and KDN-gp hydrolysates were 11 and 8, respectively. The high sensitivity of this method was demonstrated by the quantification of Neu5Ac oligomers. Distributions of the monomer and oligo/polymers in the acid and enzymatic hydrolysates of colominic acid and PSGP under different conditions were also studied.

Foreign body aspiration into the lower airway in Chinese adults

OBJECTIVES

Foreign body aspiration into the lower airway in adults is uncommon. We designed this study to investigate the clinical presentations, precipitating factors, management choice, and complications of foreign body aspiration in Chinese adults.

PATIENTS AND METHODS

We analyzed 43 consecutive adult patients with foreign body aspiration between February 1980 and December 1995 from the medical record registry and cross index system of a tertiary medical center.

RESULTS

The most common symptoms are chronic cough, hemoptsis, fever, and dyspnea. Only three patients (7%) presented with choking. Chest radiograph demonstrated the foreign body in nine cases (21%). The most common foreign body was bone fragments (21/43, 49%). Lodgment is more common in the right, especially the right intermediate bronchus and basal bronchus. Three patients were also diagnosed as having lung cancers. Precipitating factors include CNS dysfunction, facial trauma, intubation, dental procedure, and underlying pulmonary diseases. Flexible fiberoptic bronchoscopy removed the foreign body in 25 cases (58%) during the first attempt and 32 cases (74%) in total. Complications include obstructive pneumonitis (including one case of actinomycosis infection), atelectasis, bronchiectasis, lung abscess, and lung torsion (two cases).

CONCLUSION

The nature of foreign body in Chinese adults was different from the Western adults. The initial clues to foreign body aspiration in adults are usually obscure or indirect. We suggest flexible fiberoptic bronchoscopy as the first-line approach. Follow-up bronchoscopy and chest radiograph are recommended to detect chronic complications or coexisting lung cancer.

Adrenal hormone regulation of fibronectin synthesis by type II pulmonary epithelial cells

Previous work suggested an association between changes in the alveolar extracellular matrix and epithelial cell growth in lungs of adrenalectomized rats in vivo. Other studies demonstrated that adrenal hormones modulate extracellular matrix synthesis by type II pulmonary epithelial cells in vitro. Adrenal hormone regulation of type II cell fibronectin synthesis was thus examined. Fibronectin synthesis was quantitated by immunoprecipitation of the metabolically labeled molecule from cells, extracellular matrix, and culture medium. On day 1 of primary culture, synthesis of matrix fibronectin by type II cells isolated from the lungs of adrenalectomized animals was more than twice that by cells isolated from control rats. Adrenalectomy elevated steady-state fibronectin mRNA levels in primary isolates of type II cells cultured for 1 or 3 days. These results suggest that altered fibronectin synthesis and deposition into the extracellular matrix accompany changes in type II cell phenotype that occur after adrenalectomy.

Molecular cloning and expression of human alpha2,8-sialyltransferase (hST8Sia V)

The cDNA encoding human alpha2,8-sialyltransferase (hST8Sia V) which exhibits activity toward gangliosides, GM1b, GD1a, GT1b, and GD3, was isolated by screening of human brain cDNA library with a DNA probe generated from the cDNA sequence of mouse ST8Sia V (mST8Sia V) and by 5'-RACE of mRNA from human brain tissue. Comparative analysis of this cDNA with mST8Sia V showed that each sequence of the predicted coding region contains 84% identity in both nucleotide and amino acid. Northern analysis of this cDNA indicated that, in contrast to mST8Sia V, two different sizes of transcripts corresponding to 11 and 2.5 kb were expressed in both human fetal and adult brain, while the transcript of 2.5 kb was detected only in adult heart and skeletal muscle. The enzyme expressed in COS cells showed a substrate specificity very similar to that of mST8Sia V.

Expression of functional gap junctions in cultured pulmonary alveolar epithelial cells

Recent observations suggest that cell-cell interactions may modulate the response of the alveolar epithelium to injury. Expression and function of gap junctions were thus evaluated in isolated alveolar type II cells. Freshly isolated (day 0) type II cells expressed mRNAs for gap junctional connexins 26, 32, and 43. Whereas connexin 26 mRNA declined approximately 40% in cultured cells, connexin 32 message decreased rapidly and was not detectable on day 1. In contrast, connexin 43 expression increased 10-fold by day 3 compared with day 0. Western blot confirmed a 30-fold elevation in connexin 43 protein. Connexin 45 mRNA was not detected. Functional gap junction-mediated calcium signal propagation was monitored using fura 2, a calcium-sensitive dye. Membrane deformation in a single type II cell increased intracellular calcium; the signal spread rapidly to neighboring cells by octanol-sensitive pathways. Transfer of Lucifer yellow between cells also was inhibited by octanol. These observations demonstrate functional gap junctions between cultured alveolar epithelial cells and suggest that gap junctional expression and gap junction-mediated cell-cell coupling are regulated with time in culture.

Usefulness of argyrophilic nucleolar organizer regions score to differentiate suspicious malignancy in pulmonary cytology

OBJECTIVE

Pulmonary cytologic specimens reported as "suspicious for malignancy" pose problems in clinical management. Silver staining for argyrophilic nucleolar organizer regions (AgNOR) has proved useful in making a cytopathologically differential diagnosis between benign and malignant cells. This study aimed to evaluate the usefulness of AgNOR score in the diagnosis of pulmonary cytologic specimens deemed inconclusive by conventional staining methods.

METHODS

Pulmonary cytologic specimens initially reported as suspicious for malignancy with Papanicolaou or May-Grünwald-Giemsa (MGG) staining obtained from 35 proved cases were destained then restained using the AgNOR technique. Another 35 cases with clear cytologic diagnosis were also examined for comparison. The median number of dots, defined as the AgNOR score, was used to differentiate malignant from benign specimens.

RESULTS

Malignant cases had significantly higher AgNOR scores than benign ones (p<0.001). There were no significant differences among smears previously stained with Papanicolaou or MGG method, among specimens obtained via bronchoscopic brushing, fine-needle aspiration of lung or pleural effusion, or among subgroups of malignant diseases. Based on the results of our previous study, the cutoff value of the AgNOR score to differentiate benignancy from malignancy was set at 6. At this setting, the sensitivity and specificity of AgNOR score were 88% and 80%, respectively, in aiding a differential diagnosis of pulmonary cytologic specimens initially classified as suspicious for malignancy. For those cases with a clear cytologic diagnosis, the sensitivity and specificity of AgNOR score were 92% and 100%, respectively. For all cases, the sensitivity of AgNOR score was 90% and the specificity was also 90%.

CONCLUSIONS

The AgNOR score is of value in aiding a differential diagnosis between benign and malignant lesions in pulmonary specimens with equivocal cytologic features.

Mouse beta-galactoside alpha 2,3-sialyltransferases: comparison of in vitro substrate specificities and tissue specific expression

Four types of beta-galactoside alpha 2,3-sialyltransferase (ST3Gal I-IV) have been cloned from several animals, but some contradictory observations regarding their substrate specificities and expression have been reported. Therefore, it is necessary to concurrently analyze the substrate specificities of the four enzymes, of which the source should be one animal. Accordingly, the acceptor substrate specificities and gene expression of mST3Gal I-IV were analyzed. Since we had already cloned ST3Gal I and II, as previously reported (Lee, Y.-C. et al., Eur. J. Biochem., 216, 377-385 (1993); J. Biol. Chem., 269, 10028-10033 (1994)), the cDNAs of ST3Gal III and IV were cloned from mouse cDNA libraries. Each of the four enzymes was expressed in COS-7 cells as a recombinant enzyme fused with protein A, and applied on an IgG-Sepharose gel to eliminate endogenous sialyltransferase activity. ST3Gal I and II showed the highest activity toward Gal beta 1, 3 GalNAc (type III), very low activity toward Gal beta 1,3GlcNAc (type I), but none toward Gal beta 1,4GlcNAc (type II). ST3Gal III and IV exhibited high activity toward the type I and II disaccharides, but very low activity toward the type III one. On the other hand, asialo-GM1 (Gg4Cer) was as good a substrate for ST3Gal I and II as the type III disaccharide, though ST3Gal III and IV hardly utilized glycolipids as substrates, as indicated by in vitro experiments. Northern blot analysis revealed that enzymes of the ST3Gal-family are expressed mainly in a tissue-specific manner. The ST3Gal I gene was strongly expressed in spleen and salivary gland, and weakly in brain, liver, heart, kidney, and thymus. The ST3Gal II gene was strongly expressed in brain, and weakly in colon, thymus, salivary gland, and testis, and developmentally expressed in liver, heart, kidney, and spleen. The ST3Gal III and IV genes were expressed in a wide variety of tissues. These differences in tissue specific expression suggest the expression of each ST3Gal influences the distribution of sialyl-glycoconjugates in vivo.

AgNORs in lung cancer: correlation with DNA ploidy and degree of differentiation

OBJECTIVE

To assess the usefulness of enumerating argyrophilic nucleolar organizer regions (AgNORs) in assisting with the diagnosis, as well as its correlation with the degree of differentiation and DNA ploidy, in lung cancer.

STUDY DESIGN

The specimens, taken from 151 benign and malignant pulmonary tumors, were stained with silver nitrate before the number of AgNORs was counted. DNA ploidy was determined in 58 cases of lung cancers. All cases of adenocarcinoma and squamous cell carcinoma were histologically classified as well, moderately or poorly differentiated.

RESULTS

Lung cancers had more AgNORs than benign tumors, and small cell carcinomas had fewer AgNORs than non-NSCLC (P < .001). The mean AgNOR number in adenocarcinoma increased progressively in accordance with poorer differentiation (P < .001). There was no correlation between the number of AgNORs and DNA ploidy.

CONCLUSION

Counting AgNORs helps with the differential diagnosis of lung cancers. In adenocarcinoma of the lung, the AgNOR number increases as the degree of differentiation decreases.

Five years results of photorefractive keratectomy for myopia

PURPOSE

To evaluate the long-term stability, complications, and causative factors in eyes that had photorefractive keratectomy (PRK) for myopia.

SETTING

Kangnam St. Mary's Hospital, Seoul, Korea.

METHODS

This study evaluated the results of PRK in 201 myopic eyes with a consecutive 5 year follow-up. Preoperative myopia ranged from 2.25 to 12.50 diopters (D), with astigmatism of less than 1.50 D. The Excimer laser was set to a maximum correction of -6.50 D at a 5.0 mm diameter ablation zone. Patients with more than 7.00 D of myopia had double-pass PRK with two different ablation zone sizes (5.0 and 4.5 mm). The data were statistically analyzed using polynomial regression for evaluating long-term stability and myopic regression and Cox's proportional hazard model for evaluating causative factors.

RESULTS

An uncorrected visual acuity better than 20/25 was achieved in 62.4% of eyes. The main complication after PRK was myopic regression. Mean refractive error 5 years after PRK was -2.43 +/- 1.90 D. It was -1.49 +/- 0.60 D in moderately myopic eyes (less than 6.50 D) and -3.55 +/- 2.31 D in highly myopic eyes (over 7.00 D). According to our evaluation, the possible causative factors for myopic regression were pre-PRK refraction (P < .0001) and post-PRK corneal haze (P = .01); their relative risks were 3.33 and 1.93, respectively. Multivariate analysis eliminated the corneal haze factor.

CONCLUSION

Myopic regression occurred as long as 5 years after PRK, with the most important factor for myopic regression being pre-PRK refraction.

Tissue distribution and metabolism of the [32P]-labeled oligodeoxynucleoside methylphosphonate-neoglycopeptide conjugate, [YEE(ah-GalNAc)3]-SMCC-AET-pUmpT7, in the mouse

Development of oligodeoxynucleotides (oligo-dNs) and their analogs as therapeutic agents is complicated by their low rate of transport across cellular membranes, which is required for interaction with the intracellular complementary nucleic acid sequences, and the lack of tissue-specific delivery. To overcome these obstacles, bioconjugates between cell surface receptor ligands and oligodeoxynucleoside methylphosphonates (oligo-MPs) have been constructed containing homogeneous, chemically defined covalent linkages. We have previously established that a model conjugate, [32P]-labeled [YEE(ah-GalNAc)3]-SMCC-AET-pUmpT7 (1), is delivered to Hep G2 cells in a ligand-specific manner, reaching a peak value of 26 pmol per 10(6) cells after 24 hours incubation at 37 degrees C (Hangeland et al., 1995). In this work, the in vivo behavior of this conjugate is explored. Administration of this conjugate to mice via tail vein injection demonstrates rapid uptake in liver to the extent of 69.9 +/- 9.9% of the injected dose after 15 minutes. Thereafter, the conjugate and its metabolites are rapidly cleared via the kidney and urine. Polyacrylamide gel electrophoresis analysis of extracts of Hep G2 cells and mouse liver reveal the conjugate 1 to be extensively metabolized. In contrast, the conjugate found in mouse urine is largely intact. These data show that this novel, biodegradable delivery vehicle represents a viable approach for the delivery of antisense oligo-MPs and other oligo-dN analogs to the liver for therapeutic and diagnostic applications.

Fluorescence spectrometry in studies of carbohydrate-protein interactions

Fluorometric spectroscopy is a powerful tool for investigating the interaction between a carbohydrate ligand and binding proteins. The measurement is done in situ and thus circumventing the need for separation of bound ligand from the free ligand. The source of the fluorophore can be intrinsic, i.e., the tryptophan in the protein, or extrinsic (contained in the ligand). Techniques for assessing the affinity used are measurement on fluorescence intensity change, lifetime, polarization anisotropy, and energy transfer. The last technique can also be used to study conformational structures of glycopeptides. It is also useful in designing substrates for endo-type enzymes which allow continuous monitoring of the reaction.

Efficient immobilization of proteins by modification of plate surface with polystyrene derivatives

Immobilization of proteins on microplate wells by simple adsorption (e.g., for ELISA) is convenient, but it can be inefficient, especially if proteins are hydrophilic or small in size. This problem was alleviated by the use of polyvinylbenzyl lactonoylamide (PVLA). PVLA is strongly adsorbed to the hydrophobic well surface, and its lactonamide part can be oxidized with periodate to generate aldehydo groups. Proteins are then immobilized covalently to the aldehydo groups by reductive amination under mild conditions. Using this method, henceforth termed the PVLA method, alkaline phosphatase (AP) was immobilized to microplates six- to sevenfold greater than by simple adsorption (as measured by activity). Similarly, the activity of immobilized mannose-binding protein A (MBP-A) was 4- to 8-fold higher by the PVLA method than by simple adsorption. The PVLA-coated plates needed as little as 200 ng of MBP-A per well to have a sufficient amount of MBP-A immobilized for the measurement of binding of 125I-labeled mannosylated bovine serum albumin (125I-Man-BSA), but unmodified plates required as much as 20 micrograms/well MBP-A to obtain the same response. Recommended conditions for the PVLA method are 40 microliters of 2 mg/ml of PVLA for coating, 1 mM NaIO4 for the generation of the aldehydo groups, and a 2-h reductive amination at 37 degrees C between pH 8 and 9 for the protein ligation.

Differential N-glycan patterns of secreted and intracellular IgG produced in Trichoplusia ni cells

Structures of the N-linked oligosaccharide attached to the heavy chain of a heterologous murine IgG2a produced from Trichoplusia ni (TN-5B1-4, High Five) insect cells were characterized. Coexpression of the chaperone immunoglobulin heavy chain-binding protein (BiP) in the baculovirus-infected insect cells increased the soluble intracellular and secreted IgG level. This facilitated the detailed analysis of N-glycans from both intracellular and secreted IgG. Following purification of the immunoglobulins using Protein A-Sepharose, glycopeptides, prepared by trypsin-chymotrypsin digestion, were further digested with glycoamidase from sweet almond emulsin to obtain the oligosaccharide moieties. The resulting oligosaccharides were then reductively aminated with 2-aminopyridine and the structures identified by two-dimensional high performance liquid chromatography mapping (Tomiya, N., Awaya, J., Kurono, M., Endo, S., Arata, Y., and Takahashi, N. (1988) Anal. Biochem. 171, 73-90). The N-glycans obtained from the secreted IgG contain 35% complex type, some with terminal galactose residues at either alpha1, 3-Man or alpha1,6-Man branches of the Man3GlcNAc2 core. The remaining oligosaccharides detected in the secreted IgG were principally hybrid (30%) and paucimannosidic (35%) type N-glycans. Most (84%) of these secreted glycoforms contained fucose alpha1, 6-linked to the innermost GlcNAc residue and the presence of a potentially allergenic fucose alpha1,3-linked to the innermost GlcNAc residue was also detected. In contrast, the intracellular immunoglobulins included 50% high mannose-type N-glycans with lower levels of complex, hybrid, and paucimannosidic-type structures. Reverse phase one-dimensional high performance liquid chromatography analysis of the IgG N-glycans in the absence of heterologous BiP exhibited a similar distribution of intracellular and secreted glycoforms. These studies indicate that Trichoplusia ni TN-5B1-4 cells are capable of terminal galactosylation. However, the processing pathways in these cell lines appear to diverge from mammalian cells in the formation of paucimannosidic structures, in the presence of alpha1,3-fucose linkages, and in the absence of sialylation.

P53 overexpression in gastric adenocarcinoma with Helicobacter pylori infection

Gastric carcinogenesis has been studied in various aspects. Helicobacter pylori (Hp) infection and mutation of the p53 tumor suppressor gene have recently been argued to be important factors of gastric carcinogenesis. There have been many studies to determine the precise mechanism of how Hp is related to gastric cancer, but it is so far still unknown. We studied the relationship of Hp infection and p53 overexpression and tried to discover some significance in clinicopathologic factors such as age, sex, stage, site, differentiation and gross morphology. Ninety-six patients who were diagnosed with gastric cancer at Severance Hospital, Yonsei University Medical College from November 1995 to March 1996, and 96 control patients of non-ulcer dyspepsia (NUD) were studied by endoscopic biopsy of normal gastric tissue and cancer tissue. They also underwent the CLO (Delta West, Melbourne, Western Australia) test for Hp positivity and p53 immunohistochemical stain for p53 positivity. These data were analyzed for comparison with the clinicopathologic characteristics of gastric cancers. In conclusion, the differentiated group cancer had a significantly high Hp positivity and p53 positivity. There is a possibility that Hp infection and p53 tumor suppressor gene mutation might be significantly related in the gastric carcinogenic process of well- and moderately-differentiated adenocarcinomas, but further study is necessary to determine more direct clues on the carcinogenic roles of these factors.