[A 5-year retrospective study of computer aided design and computer aided manufacturing ceramic endocrowns in endodontically treated posterior teeth]

Objective: To evaluate the clinical outcomes of computer aided design and computer aided manufacturing (CAD/CAM) ceramic endocrowns in endodontically treated posterior teeth after five years by a retrospective study. Methods: Patients who received CAD/CAM ceramic endocrowns after endodontically treatment in Department of Endodontics, School of Stomatology, The Fourth Military Medical University between January 2016 and June 2017 were invited for this clinical study. Clinical performance was evaluated in the aspect of color match, anatomic form,marginal adaptation, restoration integrity and secondary caries. Survival rate of the restorations was calculated by the use of Kaplan-Meier method. Log-rank test was applied as well for the sake of analyzing the effect of tooth position, sex and materials to the survival rate of the restorations. Results: Seventy-four patients, 25 men and 49 women with age of (38.8±10.2) years, participated in this study for a total of 101 CAD/CAM ceramic endocrowns after observation period of (62.8±12.0) months. There were 8 failed cases among 101 restorations, 5 were loss of retention, 2 were ceramic fracture and 1 was secondary caries respectively. In particular, 93% (89/96) restorations got score A on anatomic form and 95% (91/96) restorations got score A on marginal adaptation, while 38% (36/96) restorations showed the good color match compared with the abutment teeth. The estimated cumulative survival rate of CAD/CAM ceramic endocrowns in endodontically treated posterior teeth after 5 years was 93.0% (95%CI: 87.9%-98.1%). The single-factor Log-rank analysis demonstrated that there was no statistically significant difference in the survival rate of CAD/CAM ceramic endocrowns among men and women, premolars and molars, position in the dental arch, or different materials (χ²<0.01, P=0.957; χ²=0.64, P=0.422; χ²=0.69, P=0.407; χ²=0.88, P=0.349). Conclusions: Based on this clinical study, the clinical performance of CAD/CAM ceramic endocrowns in endodontically treated posterior teeth after five years is reliable, which could be a general option to restore nonvital teeth.

Nomogram to predict survival of patients with advanced and metastatic pancreatic Cancer

BACKGROUND

Nomograms are rarely employed to estimate the survival of patients with advanced and metastatic pancreatic cancer (PC). Herein, we developed a comprehensive approach to using a nomogram to predict survival probability in patients with advanced and metastatic PC.

METHODS

A total of 323 patients with advanced and metastatic PC were identified from the Chinese People's Liberation Army (PLA) General Hospital. A baseline nomogram was constructed using baseline variables of 323 patients. Additionally, 233 patients, whose tumors showed initial responses to first-line chemotherapy, were enrolled in the chemotherapy response-based model. 128 patients and 108 patients with advanced and metastatic PC from January 2019 to April 2021 were selected for external validating baseline model and chemotherapy response-based model. The 1-year and 2-year survival probability was evaluated using multivariate COX regression models. The discrimination and calibration capacity of the nomograms were assessed using C-statistic and calibration plots. The predictive accuracy and net benefit of the nomograms were evaluated using ROC curve and DCA, respectively.

RESULTS

In the baseline model, six variables (gender, KPS, baseline TB, baseline N, baseline WBC and baseline CA19-9) were used in the final model. In the chemotherapy response-based model, nine variables (KPS, gender, ascites, baseline N, baseline CA 19-9, baseline CEA, change in CA 19-9 level at week, change in CEA level at week and initial response to chemotherapy) were included in the final model. The C-statistics of the baseline nomogram and the chemotherapy response-based nomogram were 0.67 (95% CI, 0.62-0.71) and 0.74 (95% CI, 0.69-0.77), respectively.

CONCLUSION

These nomograms were constructed to predict the survival probability of patients of advanced and metastatic PC. The baseline model and chemotherapy response-based model performed well in survival prediction.

The germline-specific expression of Foxl3a and its paralogous Foxl3b are associated with male gonadal differentiation in the Japanese eel, Anguilla japonica

Unlike its paralog Foxl2, which is well known for its role in ovarian development in vertebrates, the function of Foxl3 is still unclear. Foxl3 is an ancient duplicated copy of Foxl2. It is present as a single copy in ray-finned fish. But, due to repeated losses, it is absent in most tetrapods. Our transcriptomic data, however, show that two Foxl3s (Foxl3a and its paralog Foxl3b) are present in Japanese eel. Foxl3a is predominantly expressed in the pituitary, and Foxl3b is predominantly expressed in the gills. Both Foxl3s show a sex-dimorphic expression, being higher expression in testes than in ovaries. Moreover, Foxl3a and Foxl3b were exclusively expressed during gonadal differentiation in control eels (100% male). Conversely, Foxl3a and Foxl3b significantly decreased after gonadal differentiation in E2-treated eels (100% female). Furthermore, in accordance the difference in adhesive ability between somatic cells and germline cells in testes, Foxl3s showed a high expression in suspension cells (putative germline cells) and low expression in adhesive cells (putative somatic cells). In situ hybridization further showed that Foxl3a and Foxl3b were expressed in the testicular germline cells. In addition, Foxl3s expression was not changed by sex steroids in in vitro testes culture. Taken together, our results suggest that the teleost-specific Foxl3 paralog was repeatedly lost in most fish after the third round of whole genome duplication. The two germline-expressed Foxl3s had higher expression levels in males than in females during gonadal differentiation in Japanese eel. These results demonstrated that Foxl3s might play an important role in germline sexual fate determination from ancient fish to modern fish.

Demonstration of a Functionally Active tPA-Like Plasminogen Activator in Human Platelets

The mechanism of platelet-enhanced fibrinolysis is unclear. We therefore investigated the fibrinolytic activity of human platelets and demonstrated that they contain a tissue plasminogen activator (tPA)- like plasminogen activator, abbreviated as tPA-like-PA. This activator was detected by ELISA in platelet incubation medium and in platelet Triton extracts. Plasminogen activation assays showed that this tPA- like-PA could induce plasminogen activation to form plasmin. Western blots of Triton extracts incubated with anti-tPA antibody demonstrated a major 64-kD protein band, compared to a 70-kD band for standard single chain tPA, plus a minor 118-kD band corresponding to a complex of tPA-like-PA and plasminogen activator inhibitor (PAI-1). Western blots of Triton extracts incubated with anti-PAI-1 antibody produced an approximately similar high-molecular-weight (118 kD) protein band. Fibrin zymographic analysis of affinity-purified tPA-like- PA demonstrated a major and a minor fibrin lysis zone, which approximately corresponded to the tPA-like-PA and its complex with PAI-1 observed by Western blots. Immunogold labelling and electron microscopy demonstrated that platelet activator, either as the free form or co-localized with PAI-1, was present in granules and in channels of the open canalicular system. We conclude that platelets contain a functionally active tPA-like-PA, whose low fibrinolytic activity might be due to its readily forming a complex with PAI-1. This functionally active tPA-like-PA might contribute to the enhanced fibrinolytic activity of platelets observed in platelet-rich thrombi.

[Investigation of the cognition and behavior on drug safety in Beijing middle school students]

OBJECTIVE

To understand the cognition and behavior of drug safety in Beijing middle school students and provide advice for relevant education.

METHODS

A cross-sectional survey using paper questionnaires was carried out on the student body of nine Beijing middle schools. Multi-stage proportionate stratified cluster sampling was adopted to enroll participants. In addition to demographic questions, the questionnaire included 17 questions assessing the cognition and behavior of safe drug use, prioritizing questions that aligned with the health education guideline for primary and secondary school students from Chinese Ministry of Education. Descriptive statistical methods were applied using the SAS 9.2 software.

RESULTS

Of the 4 220 students investigated, 2 097(49.7%) were males and 2 123(50.3%) were females. The average age was (14.3±1.7) years. 2 030(48.1%) students were from downtown areas, 1 511(35.8%) were from urban-rural linking areas and 679(16.1%) were from rural areas. Half (51.5%) of the respondents were junior high school students, and the others were from senior high schools (34.2%) and vocational high schools (14.3%). Most of the students (89.6%) lived off campus. The awareness rate of drug safety knowledge was 74.4%, the median score of drug safety behavior was 4 points (full score was 5 points) and there was a statistically positive correlation between the two (Spearman's correlation coefficient was 0.156, P<0.001). Both the awareness rates and the drug safety behavior scores were statistically different among the students in different regions, different school types and different residence types (P<0.001). Multiple factors analysis demonstrated the correlation between the cognition degrees of both drug safety knowledge, behavior and the above factors. Of all the students, 80.4% agreed that any drug could have adverse drug reactions; 40.5% were aware that antibiotics couldn't kill viruses; as many as 49.6% mistook aspirin as antibiotic; 97.4% would read drug instructions before taking them; Only 42.4% put expired drugs into special recycling bins; 49.8% would deviate from the suggested dosage and frequency of their medication when they were sick with common diseases.

CONCLUSION

Overall, the cognition of drug safety in Beijing middle school students is good, but problems still exist in medication adherence, the management of expired drugs and the antibiotics cognition, which need to be fixed through specific, pointed way of education. And more efforts should be made to improve the cognition in rural regions, vocational high schools and on campus students.

[Association between statins use and liver injury based on prescription sequence symmetry analysis]

OBJECTIVE

To study the association between statins use and liver-injury through prescription sequence symmetry analysis(PSSA)and evaluate the feasibility of the method to be used in Chinese Medical Insurance Database.

METHODS

The data of the patients who prescribed both statins and liver-proactive drugs in Chinese Basic Medical Insurance Database in 2013 were selected as study subjects to calculate the adjusted sequence ratio(ASR)with signal detection methods to determine the study parameters and investigate the potential association between statins use and liver-injury.

RESULTS

In 5 649 individuals which met the inclusion criteria, the washout period was set as one month and interval period was set as 60 days. The overall ASR of statins was 1.471(95%CI: 1.395-1.550), the ASR of atorvastatin was 1.419(95% CI: 1.335-1.508), the ASR of simvastatin was 1.307(95%CI: 1.164-1.467). The positive signal was strong in 30 days interval period.

CONCLUSIONS

PSSA indicated that there might be potential association between statins use and liver-injury, especially the uses of atorvastatin and simvastatin. This signal detection method may be a fast and effective method in drug safety evaluation and can be used in Chinese Medical Insurance Database.

Therapeutic effect of Pleurotus eryngii cellulose on experimental fatty liver in rats

The aim of this study was to explore the therapeutic effect of Pleurotus eryngii cellulose on experimental fatty liver in rats. Rats were fed high-fat fodder to establish a rat fatty liver model, and were then fed different concentrations of Pleurotus eryngii cellulose for six weeks. Lipitor was used as a positive control. Measured levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), total cholesterol (TC), and total triglyceride (TG); the activity of malondialdehyde (MDA), superoxide dismutase (SOD), hepatic lipase (HL), and lipoprotein lipase; and liver histopathological changes. Successfully established rat fatty liver model after feeding high-fat fodder for one week. A diet of P. eryngii cellulose for six weeks significantly reduced ALT, AST, TC, and TG levels in rat serum (P < 0.01); TC and AST levels in P. eryngii cellulose high-dose group and Lipitor group were not significantly different from those of the control (P > 0.05). SOD activity increased significantly, while MDA and HL activity decreased (P < 0.05); fatty degeneration and fat accumulation both decreased in hepatic tissue. Hepatic protection of P. eryngii cellulose showed dose-related effect. P. eryngii cellulose can affect lipid metabolism, having therapeutic effects on fatty liver in rats.

Screening of differentially expressed genes between multiple trauma patients with and without sepsis

The purpose of this study was to identify critical genes associated with septic multiple trauma by comparing peripheral whole blood samples from multiple trauma patients with and without sepsis. A microarray data set was downloaded from the Gene Expression Omnibus (GEO) database. This data set included 70 samples, 36 from multiple trauma patients with sepsis and 34 from multiple trauma patients without sepsis (as a control set). The data were preprocessed, and differentially expressed genes (DEGs) were then screened for using packages of the R language. Functional analysis of DEGs was performed with DAVID. Interaction networks were then established for the most up- and down-regulated genes using HitPredict. Pathway-enrichment analysis was conducted for genes in the networks using WebGestalt. Fifty-eight DEGs were identified. The expression levels of PLAU (down-regulated) and MMP8 (up-regulated) presented the largest fold-changes, and interaction networks were established for these genes. Further analysis revealed that PLAT (plasminogen activator, tissue) and SERPINF2 (serpin peptidase inhibitor, clade F, member 2), which interact with PLAU, play important roles in the pathway of the component and coagulation cascade. We hypothesize that PLAU is a major regulator of the component and coagulation cascade, and down-regulation of PLAU results in dysfunction of the pathway, causing sepsis.

Effect of inhibitors on glycoprotein biosynthesis and bacterial adhesion

Group B streptococci adhere to influenza-virus infected canine kidney epithelial cells but not to uninfected cells. For studies of the molecular nature of this interaction the bacteria were radiolabelled and a quantitative binding assay was developed with which the following properties of the system were observed. (1) Adhesion was specific for group B streptococci (GBS); streptococci from other serological groups did not bind and did not inhibit adhesion of radioactive GBS. (2) Binding of GBS to infected kidney cells was inhibited by the addition of cell walls from GBS to the kidney cell monolayers. (3) Preincubation of GBS with free influenza virus prevented their attachment to infected kidney cell monolayers. With a centrifugation type of assay, labelled influenza virus bound to GBS. This binding could be inhibited by several glycoproteins after removal of the terminal sialic acid. Asialo-glycopeptides of the complex type, isolated from these inhibitory glycoproteins, also bound to GBS. The influenza viral glycoproteins have been partially characterized and shown to contain a glycosylamine type of complex oligosaccharide. This type of oligosaccharide is biosynthesized by means of lipid-linked saccharide intermediates. Several antibiotics such as tunicamycin and streptovirudin, and other inhibitors such as 2-deoxyglucose and glucosamine, inhibit this lipid-linked pathway. These inhibitors also prevent the formation of mature influenza virus as well as the adherence of group B streptococci. Other inhibitors of protein glycosylation should be valuable as tools for improving further our understanding of the mechanism of cell adhesion.

Optical coherence tomography for noninvasive diagnosis of epithelial cancers

We summarize our recent progress in the development of the optical coherence tomography (OCT) systems suitable for clinical diagnosis and the preliminary results for in vivo diagnosis of epithelial cancers (e.g., bladder cancers). The endoscopic spectral-domain OCT system allows simultaneous, real-time, cross-sectional OCT images of tissue structure and functions (i.e., local Doppler blood flow) of biological tissue for enhanced diagnosis. A new approach to use spectral demodulation of elastic scattering is discussed for potential cancer grading. The transverse and axial resolutions of the OCT scopes are 12 microm and 10 microm, respectively. Results of the preliminary clinical studies show that unlike animal carcinogenesis models, bladder cancers in humans are more complicated in terms of epithelial backscattering changes: some lesions exhibit enhanced backscattering; some show reduced scattering owing to complex surface condition changes such as asperities or invaginations induced by tumorigenesis (e.g., papillary transitional cell cancers). Nevertheless, promising results can be provided by incorporating other diagnostic parameters such as changes in local vasculature and urothelial heterogeneity.

FLUORESCENCE GUIDED OPTICAL COHERENCE TOMOGRAPHY FOR THE DIAGNOSIS OF EARLY BLADDER CANCER IN A RAT MODEL

PURPOSE

We describe the technique of fluorescence image guided optical coherence tomography (FG-OCT). We examined its ability to enhance specificity and sensitivity for the noninvasive diagnosis of early bladder cancer.

MATERIALS AND METHODS

Transitional cell carcinoma was developed in 54 Fisher 344 female rats by intravesical methyl-nitroso-urea instillations. Two or three rats were diagnosed sequentially by 5-ALA (5-aminolevulinic acid hydrochloride) induced fluorescence imaging, cross-sectional OCT and histological microscopy weekly during weeks 11 to 33 following initial methyl-nitroso-urea instillation to track the course of carcinogenesis.

RESULTS

The specificity of fluorescence detection was significantly enhanced by FG-OCT (53% and 93%, respectively, p <0.0001). The sensitivity of fluorescence detection and FG-OCT was 79% and 100%, respectively.

CONCLUSIONS

FG-OCT cystoscopy has the potential to diagnose early bladder cancer with high sensitivity and specificity with drastically decreased imaging time compared to that of white light guided OCT cystoscopy.

High-resolution imaging characterization of bladder dynamic morphophysiology by time-lapse optical coherence tomography

We report an experimental study of the possibility of high-speed optical coherence tomography (OCT) for high-resolution imaging characterization of detrusor dynamic morphophysiology and analysis of the mechanisms that lead to geriatric incontinence (GI). The spontaneous contractility of intact fresh rabbit bladders was imaged with two-dimensional (2D) OCT ex vivo at up to 8 frames/s. The time-lapse 2D OCT images were postprocessed by image segmentation and fast-Fourier-transform analysis to characterize the dynamic morphological changes of the bladder contractility. In addition, we studied young and aging rat bladders to analyze the differences in dynamics. Preliminary results of our ex vivo study reveal that time-lapse OCT can track the contractile waves of bladders at high spatial resolution and characterize their dynamic morphophysiology in terms of amplitude, phase, and frequency. The results suggest that time-lapse OCT has the potential to act as a detrusor optical biopsy to enhance the diagnosis of detrusor dysfunction and thus of the mechanisms that lead to GI.

Enhancing early bladder cancer detection with fluorescence-guided endoscopic optical coherence tomography

We report an experimental study of the possibility of enhancing early bladder cancer diagnosis with fluorescence-image-guided endoscopic optical coherence tomography (OCT). After the intravesical instillation of a 10% solution of 5-aminolevulinic acid, simultaneous fluorescence imaging (excitation of 380-420 nm, emission of 620-700 nm) and OCT are performed on rat bladders to identify the photochemical and morphological changes associated with uroepithelial tumorigenesis. The preliminary results of our ex vivo study reveal that both fluorescence and OCT can identify early uroepithelial cancers, and OCT can detect precancerous lesions (e.g., hyperplasia) that fluorescence may miss. This suggests that a cystoscope combining 5-aminolevulinic acid fluorescence and OCT imaging has the potential to enhance the efficiency and sensitivity of early bladder cancer diagnosis.

New insights on trehalose: a multifunctional molecule

Trehalose is a nonreducing disaccharide in which the two glucose units are linked in an alpha,alpha-1,1-glycosidic linkage. This sugar is present in a wide variety of organisms, including bacteria, yeast, fungi, insects, invertebrates, and lower and higher plants, where it may serve as a source of energy and carbon. In yeast and plants, it may also serve as a signaling molecule to direct or control certain metabolic pathways or even to affect growth. In addition, it has been shown that trehalose can protect proteins and cellular membranes from inactivation or denaturation caused by a variety of stress conditions, including desiccation, dehydration, heat, cold, and oxidation. Finally, in mycobacteria and corynebacteria, trehalose is an integral component of various glycolipids that are important cell wall structures. There are now at least three different pathways described for the biosynthesis of trehalose. The best known and most widely distributed pathway involves the transfer of glucose from UDP-glucose (or GDP-glucose in some cases) to glucose 6-phosphate to form trehalose-6-phosphate and UDP. This reaction is catalyzed by the trehalose-P synthase (TPS here, or OtsA in Escherichia coli ). Organisms that use this pathway usually also have a trehalose-P phosphatase (TPP here, or OtsB in E. coli) that converts the trehalose-P to free trehalose. A second pathway that has been reported in a few unusual bacteria involves the intramolecular rearrangement of maltose (glucosyl-alpha1,4-glucopyranoside) to convert the 1,4-linkage to the 1,1-bond of trehalose. This reaction is catalyzed by the enzyme called trehalose synthase and gives rise to free trehalose as the initial product. A third pathway involves several different enzymes, the first of which rearranges the glucose at the reducing end of a glycogen chain to convert the alpha1,4-linkage to an alpha,alpha1,1-bond. A second enzyme then releases the trehalose disaccharide from the reducing end of the glycogen molecule. Finally, in mushrooms there is a trehalose phosphorylase that catalyzes the phosphorolysis of trehalose to produce glucose-1-phosphate and glucose. This reaction is reversible in vitro and could theoretically give rise to trehalose from glucose-1-P and glucose. Another important enzyme in trehalose metabolism is trehalase (T), which may be involved in energy metabolism and also have a regulatory role in controlling the levels of trehalose in cells. This enzyme may be important in lowering trehalose concentrations once the stress is alleviated. Recent studies in yeast indicate that the enzymes involved in trehalose synthesis (TPS, TPP) exist together in a complex that is highly regulated at the activity level as well as at the genetic level.

Trehalose-phosphate synthase of Mycobacterium tuberculosis. Cloning, expression and properties of the recombinant enzyme

The trehalose-phosphate synthase (TPS) of Mycobacterium smegmatis was previously purified to apparent homogeneity and several peptides from the 58 kDa protein were sequenced. Based on that sequence information, the gene for TPS was identified in the Mycobacterium tuberculosis genome, and the gene was cloned and expressed in Escherichia coli with a (His)6 tag at the amino terminus. The TPS was expressed in good yield and as active enzyme, and was purified on a metal ion column to give a single band of approximately 58 kDa on SDS/PAGE. Approximately 1.3 mg of purified TPS were obtained from a 1-L culture of E. coli ( approximately 2.3 g cell paste). The purified recombinant enzyme showed a single band of approximately 58 kDa on SDS/PAGE, but a molecular mass of approximately 220 kDa by gel filtration, indicating that the active TPS is probably a tetrameric protein. Like the enzyme originally purified from M. smegmatis, the recombinant enzyme is an unusual glycosyltransferase as it can utilize any of the nucleoside diphosphate glucose derivatives as glucosyl donors, i.e. ADP-glucose, CDP-glucose, GDP-glucose, TDP-glucose and UDP-glucose, with ADP-glucose, GDP-glucose and UDP-glucose being the preferred substrates. These studies prove conclusively that the mycobacterial TPS is indeed responsible for catalyzing the synthesis of trehalose-P from any of the nucleoside diphosphate glucose derivatives. Although the original enzyme from M. smegmatis was greatly stimulated in its utilization of UDP-glucose by polyanions such as heparin, the recombinant enzyme was stimulated only modestly by heparin. The Km for UDP-glucose as the glucosyl donor was approximately 18 mm, and that for GDP-glucose was approximately 16 mm. The enzyme was specific for glucose-6-P as the glucosyl acceptor, and the Km for this substrate was approximately 7 mm when UDP-glucose was the glucosyl donor and approximately 4 mm with GDP-glucose. TPS did not show an absolute requirement for divalent cations, but activity was increased about twofold by 10 mm Mn2+. This recombinant system will be useful for obtaining sufficient amounts of protein for structural studies. TPS should be a valuable target site for chemotherapeutic intervention in tuberculosis.

Trehalose-based oligosaccharides isolated from the cytoplasm of Mycobacterium smegmatis. Relation to trehalose-based oligosaccharides attached to lipid

A series of trehalose-based oligosaccharides were isolated from the cytoplasmic fraction of Mycobacterium smegmatis and purified by gel-filtration and paper chromatography and TLC. Their structures were determined by HPLC and GLC to determine sugar composition and ratios, MALDI-TOF MS to measure molecular mass, methylation analysis to determine linkages, (1)H-NMR to obtain anomeric configurations of glycosidic linkages, and exoglycosidase digestions followed by TLC to determine sequences and anomeric configurations of the monosaccharides. Six different oligosaccharides were identified all with trehalose as the basic structure and additional glucose or galactose residues attached in various linkages. One of these oligosaccharides is the disaccharide trehalose (Glcalpha1-1alphaGlc), which is present in substantial amounts in these cells and also in other mycobacteria. Two other oligosaccharides, the tetrasaccharides Glcalpha1-4Glcalpha1-1alphaGlc6-1alphaGal and Galalpha1-6Galalpha1-6Glcalpha1-1alphaGlc, have not previously been isolated from natural sources or synthesized chemically. The fourth oligosaccharide, Glcbeta1-6Glcbeta1-6Glcalpha1-1alphaGlc, has been isolated from corynebacteria, but not reported in other organisms. Two other oligosaccharides, Glcalpha1-4Glcalpha1-1alphaGlc, which has been synthesized chemically and isolated from insects but not previously reported in mycobacteria, and Glcbeta1-6Glcalpha1-1alphaGlc, which was previously isolated from Mycobacterium fortuitum and yeast, were also characterized. Another trisaccharide found in the cytosol has been partially characterized as arabinosyl-1-4trehalose, but neither the anomeric configuration nor the D or L configuration of the arabinose is known. In analogy with sucrose and its higher homologs, raffinose and stachyose, which may act as protective agents during maturation drying in plants, these trehalose homologs may also have a protective role in mycobacteria, perhaps during latency.

Biosynthesis of d-arabinose in Mycobacterium smegmatis: specific labeling from d-glucose

d-Arabinose is a major sugar in the cell wall polysaccharides of Mycobacterium tuberculosis and other mycobacterial species. The reactions involved in the biosynthesis and activation of d-arabinose represent excellent potential sites for drug intervention since d-arabinose is not found in mammalian cells, and the cell wall arabinomannan and/or arabinogalactan appear to be essential for cell survival. Since the pathway involved in conversion of d-glucose to d-arabinose is unknown, we incubated cells of Mycobacterium smegmatis individually with [1-(14)C]glucose, [3,4-(14)C]glucose, and [6-(14)C]glucose and compared the specific activities of the cell wall-bound arabinose. Although the specific activity of the arabinose was about 25% lower with [6-(14)C]glucose than with other labels, there did not appear to be selective loss of either carbon 1 or carbon 6, suggesting that arabinose was not formed by loss of carbon 1 of glucose via the oxidative step of the pentose phosphate pathway, or by loss of carbon 6 in the uronic acid pathway. Similar labeling patterns were observed with ribose isolated from the nucleic acid fraction. Since these results suggested an unusual pathway of pentose formation, labeling studies were also done with [1-(13)C]glucose, [2-(13)C]glucose, and [6-(13)C]glucose and the cell wall arabinose was examined by NMR analysis. This method allows one to determine the relative (13)C content in each carbon of the arabinose. The labeling patterns suggested that the most likely pathway was condensation of carbons 1 and 2 of fructose 6-phosphate produced by the transaldolase reaction with carbons 4, 5, and 6 (i.e., glyceraldehyde 3-phosphate) formed by fructose-1,6 bisphosphate aldolase. Cell-free enzyme extracts of M. smegmatis were incubated with ribose 5-phosphate, xylulose 5-phosphate, and d-arabinose 5-phosphate under a variety of experimental conditions. Although the ribose 5-phosphate and xylulose 5-phosphate were converted to other pentoses and hexoses, no arabinose 5-phosphate (or free arabinose) was detected in any of these reactions. In addition, these enzyme extracts did not convert arabinose 5-phosphate to any other pentose or hexose. In addition, incubation of [(14)C]glucose 6-phosphate and various nucleoside triphosphates (ATP, CTP, GTP, TTP, and UTP) with cytosolic or membrane fractions from the mycobacterial cells did not result in formation of a nucleotide form of arabinose, although other radioactive sugars including rhamnose and galactose were found in the nucleotide fraction. Furthermore, no radioactive arabinose was found in the nucleotide fraction isolated from M. smegmatis cells grown in [(3)H]glucose, nor was arabinose detected in a large-scale extraction of the sugar nucleotide fraction from 300 g of cells. The logical conclusion from these studies is that d-arabinose is probably produced from d-ribose by epimerization of carbon 2 of the ribose moiety of polyprenylphosphate-ribose to form polyprenylphosphate-arabinose, which is then used as the precursor for formation of arabinosyl polymers.

Specificity of the high-mannose recognition site between Enterobacter cloacae pili adhesin and HT-29 cell membranes

Enterobacter cloacae has been implicated as one of the causative agents in neonatal infection and causes a septicemia thought to be initiated via the gastrointestinal tract. The adhesion of radiolabeled E. cloacae to HT-29 cells was concentration and temperature dependent and was effectively blocked by unlabeled bacteria or by millimolar concentrations of alpha-mannosides and micromolar concentrations of high-mannose oligosaccharides. A variety of well-characterized mannose oligosaccharides were tested as inhibitors of adhesion. The best inhibitor was the Man9(GlcNAc)2-tyrosinamide, which was considerably better than other tyrosinamide-linked oligosaccharides such as Man7(GlcNAc)2, Man6(GlcNAc)2 or Man5(GlcNAc)2. Further evidence that the bacteria preferred Man9(GlcNAc)2 structures was obtained by growing HT-29 cells in the presence of glycoprotein processing inhibitors that block mannosidase I and increase the amount of protein-bound Man9(GlcNAc)2 at the cell surface. Such cells bound 1.5- to 2-fold more bacteria than did control cells. The adhesin involved in binding to high-mannose structures was purified from isolated pili. On sodium dodecyl sulfate-gels, a 35-kDa protein was identified by its specific binding to a mannose-containing biotinylated albumin. The amino acid sequences of several peptides from the 35-kDa subunit showed over 85% identity to FimH, the mannose-specific adhesin of Salmonella typhimurium. Pili were labeled with 125I and examined for the ability to bind to HT-29 cells. Binding showed saturation kinetics and was inhibited by the addition of Man9(GlcNAc)2-tyrosinamide but not by oligosaccharides with fewer mannose residues. Polyclonal antibody against this 35-kDa protein also effectively blocked adhesion of pili or E. cloacae, but no effect was observed with nonspecific antibody. These studies demonstrate that the 35-kDa pilus subunit is a lectin whose specificity is directed toward Man, (GlcNAc)2 oligosaccharides.

Homonojirimycin and N-methyl-homonojirimycin inhibit N-linked oligosaccharide processing

Homonojirimycin (HNJ) and N-methylhomonojirimycin (MHNJ) were tested as inhibitors of the purified glycoprotein processing enzymes, glucosidase I and glucosidase II. MHNJ was a reasonably good inhibitor of glucosidase I (Ki = 1 x 10(-6) M) and was about three times as effective on this enzyme as was HNJ. On the other hand, HNJ inhibited glucosidase II with a Ki of about 1 x 10(-6) M, whereas MHNJ was three times less effective (Ki = 3 x 10(-5) M). However, the butyl derivative of HNJ had very low activity toward these two processing glucosidases. HNJ and its methyl derivative were also tested in vivo using influenza virus-infected MDCK cells, and measuring the inhibition of N-linked oligosaccharide processing of the viral envelope glycoproteins. With 100 micrograms/ml of MHNJ in the medium, essentially all of the N-linked oligosaccharide chains of the virus were of the "high-mannose" type with the major structure being characterized as Glc3Man9(GlcNAc)2. Similar results were obtained with HNJ although this compound was less effective in vivo as well as in vitro. These results are in keeping with these inhibitors being effective at the glucosidase I step. Both inhibitors were also tested in MDCK cell cultures to determine whether they affected the in vivo synthesis of proteins, or of lipid-linked saccharides. In contrast to deoxynojirimycin, which has been reported to inhibit the formation of lipid-linked saccharides, no effects were seen on either the incorporation of mannose into lipid-linked saccharides or the incorporation of leucine into protein.

Biological activities of the nortropane alkaloid, calystegine B2, and analogs: structure-function relationships

Calystegines, polyhydroxy nortropane alkaloids, are a recently discovered group of plant secondary metabolites believed to influence rhizosphere ecology as nutritional sources for soil microorganisms and as glycosidase inhibitors. Evidence is presented that calystegines mediate nutritional relationships under natural conditions and that their biological activities are closely correlated with their chemical structures and stereochemistry. Assays using synthetic (+)- and (-)-enantiomers of calystegine B2 established that catabolism by Rhizobium meliloti, glycosidase inhibition, and allelopathic activities were uniquely associated with the natural, (+)-enantiomer. Furthermore, the N-methyl derivative of calystegine B2 was not catabolized by R. meliloti, and it inhibited alpha-galactosidase, but not beta-glucosidase, whereas the parent alkaloid inhibits both enzymes. This N-methyl analog therefore could serve to construct a cellular or animal model for Fabry's disease, which is caused by a lack of alpha-galactosidase activity.

Inhibition of glycoprotein processing by L-fructose and L-xylulose

A number of unusual and rare carbohydrates were tested as potential inhibitors of various glycosidases, as well as inhibitors of N-linked oligosaccharide processing. The best inhibitors of several arylglycosidases and of glucosidase I were L-xylulose and L-fructose. Both of these sugars showed some inhibitory activity towards yeast alpha-glucosidase but were inactive against beta-glucosidase and other arylglycosidases. The inhibition of yeast alpha-glucosidase by L-xylulose was of a competitive nature and required a concentration of 1 x 10(-5) M for 50% inhibition. Both L-xylulose and L-fructose also inhibited the purified soybean glucosidase I, with 50% inhibition occurring at about 1 x 10(-4) M, but showed no inhibitory activity against soybean glucosidase II. When influenza virus-infected MDCK cells were raised in the presence of L-xylulose, there was a dose-dependent inhibition in the formation of complex types of oligosaccharides on the viral glycoproteins consistent with the inhibition of the processing glucosidase I. This inhibition resulted in the occurrence of oligosaccharides on the viral glycoproteins that were characterized as Glc3Man9(GlcNAc)2 structures. L-Fructose also inhibited glycoprotein processing in cell culture, and the inhibition resulted in the formation of similar oligosaccharides to those seen with L-xylulose. However, L-fructose was a poorer inhibitor than L-xylulose and required much higher concentrations for the same degree of inhibition. Neither of these compounds inhibited protein synthesis or the formation of lipid-linked saccharides in culture MDCK cells, even when tested at concentrations of 5 mg/ml (about 30 mM) of culture media.

Inhibition of the trehalose-P synthase of mycobacteria by various antibiotics

A number of antibiotics were tested as potential inhibitors of the purified trehalose-P synthase of Mycobacterium smegmatis. Of about 30 compounds tested, 4 (cathomycin, circulin, diumycin, and moenomycin) were active against this enzyme. Thus each of these compounds inhibited the formation of trehalose-P by the purified trehalose-P synthase when either UDP-glucose or GDP-glucose was used as the glucosyl donor. However, preincubation of the synthase with heparin, a polyanion activator of the enzyme when UDP-glucose is used as the substrate, prevented the inhibition by these various antibiotics. Fifty percent inhibition by diumycin and moenomycin occurred at a concentration of about 50 microg/ml (Ki of about 1 x 10(-5) M), but 50% inhibition by cathomycin and circulin required substantially higher concentrations (about 50 to 200 microg/ml). The inhibition by cathomycin, diumycin, and moenomycin was of the competitive type, whereas that by circulin was noncompetitive in nature. However, the inhibition was of a complex nature and the data suggest two different binding sites for these inhibitors. Photoaffinity labeling of the synthase with an azido-UDP-[32P]glucose probe was effectively blocked by diumycin, moenomycin, or cathomycin indicating that these inhibitors do interact at the substrate binding site. These antibiotics also inhibited the growth of M. smegmatis when added to cells innoculated into trypticase soy broth. The inhibition of growth was concentration-dependent and directly proportional to the size of the bacterial innoculum. These antibiotics, however, did not inhibit protein synthesis nor did they inhibit the incorporation of mannose into lipid-linked saccharides.

Trehalose-P synthase of mycobacteria: its substrate specificity is affected by polyanions

The trehalose-P synthase was purified to near homogeneity from the cytoplasmic fraction of Mycobacterium smegmatis. At the final stage of purification, the enzyme preparation showed one major band of 59 kDa on SDS gels. The 59 kDa band became labeled with N3-UDP[32P]-glucose, and this labeling was inhibited in a concentration-dependent manner by either unlabeled UDP-glucose or GDP-glucose. The native enzyme also had a molecular weight of about 60 kDa by gel filtration, indicating that the active enzyme is a monomer. The 59 kDa protein was subjected to endoproteinase Lys-C digestion, and three peptides isolated by HPLC were sequenced. The sequences of 56 amino acids in these three peptides showed 60% identity to the trehalose-P synthases of Saccharomyces cerevesiae and Schizosaccharomyces pombe. The purified mycobacterial enzyme catalyzed the synthesis of trehalose-P from glucose-6-P and a variety of nucleoside diphosphate glucose derivatives, depending on whether a polyanion was absent or present. Thus, UDP-glucose and GDP-glucose were the best glucosyl donors, but maximum activity with UDP-glucose required the presence of a polyanion such as heparin, whereas activity with GDP-glucose was relatively independent of polyanion. The presence of heparin in the incubation mixture increased the affinity of the enzyme for UDP-glucose by a factor of 100, or more. However, the affinity for GDP-glucose was only twofold better in the presence of heparin. The purified synthase also utilized ADP-glucose and CDP-glucose, but the K(m) for these glucosyl donors was quite high even in the presence of polyanion. The effect of heparin on UDP-glucose activity was dose-dependent and maximum at about 1-2 micrograms of heparin/incubation. However, the size of the heparin molecule (i.e., the number of monosaccharide residues) was critical for activation, and only those heparins with 18 or more monosaccharide units were effective in stimulating activity.

The complete nucleotide sequence of the mouse thyroid-specific enhancer-binding protein (T/EBP) gene: extensive identity of the deduced amino acid sequence with the human protein

A mouse thyroid-specific enhancer-binding protein (T/EBP) gene and its flanking regions have been cloned and completely sequenced. The gene consists of 2 exons and exhibits high similarity (83-97%) to the rat sequence throughout the coding region and including an intron and up to 1.3 kbp upstream to the ATG initiation codon. A cDNA clone encoding human T/EBP has been also isolated and sequenced. Comparison of the deduced amino acid sequence of T/EBP revealed an extensive identity of 98% between mouse and the human protein.

Demonstration of a functionally active tPA-like plasminogen activator in human platelets

The mechanism of platelet-enhanced fibrinolysis is unclear. We therefore investigated the fibrinolytic activity of human platelets and demonstrated that they contain a tissue plasminogen activator (tPA)-like plasminogen activator, abbreviated as tPA-like-PA. This activator was detected by ELISA in platelet incubation medium and in platelet Triton extracts. Plasminogen activation assays showed that this tPA-like-PA could induce plasminogen activation to form plasmin. Western blots of Triton extracts incubated with anti-tPA antibody demonstrated a major 64-kD protein band, compared to a 70-kD band for standard single chain tPA, plus a minor 118-kD band corresponding to a complex of tPA-like-PA and plasminogen activator inhibitor (PAI-1). Western blots of Triton extracts incubated with anti-PAI-1 antibody produced an approximately similar high-molecular-weight (118 kD) protein band. Fibrin zymographic analysis of affinity-purified tPA-like-PA demonstrated a major and a minor fibrin lysis zone, which approximately corresponded to the tPA-like-PA and its complex with PAI-1 observed by Western blots. Immunogold labelling and electron microscopy demonstrated that platelet activator, either as the free form or co-localized with PAI-1, was present in granules and in channels of the open canalicular system. We conclude that platelets contain a functionally active tPA-like-PA, whose low fibrinolytic activity might be due to its readily forming a complex with PAI-1. This functionally active tPA-like-PA might contribute to the enhanced fibrinolytic activity of platelets observed in platelet-rich thrombi.

2-Hydroxymethyl-3,4-dihydroxy-6-methyl-pyrrolidine (6-deoxy-DMDP), an alkaloid beta-mannosidase inhibitor from seeds of Angylocalyx pynaertii

A polyhydroxy alkaloid has been isolated from the seeds of the African legume Angylocalyx pynaertii and identified as a 2-hydroxymethyl-3,4-dihydroxy-5-methylpyrrolidine by ms and 1H- and 13C-nmr spectroscopy. The absolute stereochemistry was established, by a stereochemically unambiguous synthesis from diacetone glucose, as 2,5-imino-1,2,5-trideoxy-D-mannitol, which may also be regarded as 2R,5R-dihydroxymethyl-3R,4R-dihydroxypyrrolidine (DMDP) [2] in which a hydroxymethyl group is deoxygenated, i.e., 6-deoxy-DMDP [1]. Whereas the structurally related polyhydroxypyrrolidine alkaloids which have previously been discovered are inhibitors of alpha- and beta-glucosidase, 6-deoxy-DMDP is unique in inhibiting beta-mannosidase. In addition to this novel alkaloid and 2-hydroxymethyl-3,4-dihydroxypyrrolidine [3], previously shown to be present in several Angylocalyx species, the known piperidine alkaloids deoxymannojirimycin [4] and fagomine [5] were identified for the first time as constituents of An. pynaertii seeds.

Calystegins, a novel class of alkaloid glycosidase inhibitors

The alkaloid extract from roots of naturally growing Convolvulus arvensis, purified by ion-exchange chromatography, showed significant inhibitory activity toward beta-glucosidase and alpha-galactosidase. The demonstrated occurrence of polyhydroxy-nortropane alkaloids, the calystegins, in C. arvensis and their structural similarity to known polyhydroxy alkaloid glycosidase inhibitors, suggested that these might be responsible for the observed activity. Pure calystegins, isolated from transformed root cultures of the related plant species Calystegia sepium, were tested for glycosidase inhibitory activity. The purity of the alkaloids was established by gas chromatography and their identity confirmed by their mass spectrometric fragmentation patterns. The trihydroxy alkaloid, calystegin A3, was a moderately good inhibitor of beta-glucosidase (Ki = 4.3 x 10(-5) M) and a weak inhibitor of alpha-galactosidase (Ki = 1.9 x 10(-4) M). An increased level of hydroxylation, as in the tetrahydroxy calystegins B, consisting of 27% calystegin B1 and 73% calystegin B2, resulted in greatly enhanced inhibitory activity. The calystegins B were potent inhibitors of beta-glucosidase (Ki = 3 x 10(-6) M) and alpha-galactosidase (Ki = 7 x 10(-6) M). These levels of activity are comparable with those of the polyhydroxy indolizidine alkaloids castanospermine and swainsonine toward alpha-glucosidase and alpha-mannosidase, respectively, and of the polyhydroxy pyrrolizidine alkaloid australine toward alpha-glucosidase. The calystegins therefore compose a new structural class of polyhydroxy alkaloids, the nortropanes, possessing potent glycosidase inhibitory properties.

The effects of castanospermine and swainsonine on the activity and synthesis of intestinal sucrase

Castanospermine is an indolizidine alkaloid that is found in the seeds of the Australian tree Castanospermum australe. These seeds have been reported to be toxic to animals and to cause severe gastrointestinal upset. In order to determine whether castanospermine is responsible for this toxicity, the alkaloid was injected into young mice or rats, and its effects on various intestinal disaccharidases were determined. Another indolizidine alkaloid, the alpha-mannosidase inhibitor swainsonine, was also tested to compare its effects to those of castanospermine. Castanospermine strongly and rapidly inhibited the activity of the disaccharidases, sucrase, maltase, and trehalase, with sucrase being the most sensitive to inhibition. The loss of activity of these enzymes, especially sucrase, in injected animals appeared to be due to a direct inhibition of enzyme activity, rather than to a change in the structure of the glycan chains of the enzyme, since only minor alterations in carbohydrates were observed. On the other hand, swainsonine, when injected into animals, also profoundly decreased the activity of the sucrase, but this alkaloid had no direct effect on sucrase activity although it did markedly alter the carbohydrate nature of this glycoprotein. This change in oligosaccharide structure may affect protein conformation, stability, or targeting, any or all of which may in turn affect activity. In in vitro studies with the purified enzyme, castanospermine was found to be a competitive inhibitor of intestinal sucrase, but it was a noncompetitive inhibitor of intestinal maltase. A number of other glucosidase inhibitors that inhibit sucrase activity in vitro are also described.

Inhibition of glycosylphosphatidylinositol anchor formation by mannosamine

Many eucaryotic cell surface proteins are anchored to the plasma membrane via a glycosylphosphatidylinositol (GPI), of which the core region is highly conserved from protozoa to mammalian cells. Previous studies (Lisanti, M. P., Field, M. C., Caras, I. W., Menon, A. K., and Rodiguez-Boulan, E. (1991) EMBO J. 10, 1969-1977) showed that mannosamine blocked the expression of a recombinant GPI-anchored protein in Madin-Darby canine kidney cells and converted this protein to an unpolarized secretory product. In the present study, we examined the effect of mannosamine on the formation of the glycan portion of the GPI anchor precursors. This amino sugar inhibited the incorporation of mannose into the glycan portion, and the inhibition was dose-dependent. Mannosamine was shown to be incorporated into the glycan as mannosamine, probably mostly in the second mannose position and thereby to block the further addition of mannose and other anchor components. The products formed in the presence of this drug were characterized by gel filtration and high resolution TLC both before and after deamination with nitrous acid and dephosphorylation by HF. Galactosamine and trehalosamine were inactive in this system, whereas glucosamine also inhibited mannose incorporation into GPI intermediates.

Formation of unusual mannosamine-containing lipid-linked oligosaccharides in Madin-Darby canine kidney cell cultures

Glc3Man9(GlcNAc)2-pyrophosphoryl-dolichol is the major lipid-linked oligosaccharide (LLO) produced by Madin-Darby canine kidney cells in culture. However, when these cells are incubated in the presence of millimolar concentrations of mannosamine and labeled with [2-3H]mannose, they accumulate various LLO that have smaller-sized oligosaccharides with unusual structures and the Glc3Man9(GlcNAc)2-pyrophosphoryl-dolichol is not detected. Thus in the presence of 10 mM mannosamine, more than 80% of the oligosaccharides are eluted from concanavalin A-Sepharose with 10 mM alpha-methylglucoside, indicating that they no longer have the tight-binding characteristics of control oligosaccharides. In addition, 20-40% of these oligosaccharides bind to Dowex 50-H+, indicating the presence of mannosamine in these structures. Interestingly enough, these abnormal oligosaccharides are still transferred to protein. The mannosamine-induced oligosaccharides were separated into neutral and basic fractions on a cation exchange resin. The neutral oligosaccharides ranged in size from hexose3(GlcNAc)2 to hexose10(GlcNAc)2 with the major species being Man5(GlcNAc)2 to Man7(GlcNAc)2. These oligosaccharides were almost completely susceptible to digestion by alpha-mannosidase and by endoglucosaminidase H. The basic oligosaccharides showed anomolous behavior on the Bio-Gel P-4 columns and appeared to be of small size on the standard columns, ranging from hexose2 to hexose4. However, most of these oligosaccharides were susceptible to digestion by endoglucosaminidase H as well as by alpha-mannosidase, suggesting that they were of different size and structure than would be predicted from the gel filtration patterns. Significantly, when the basic oligosaccharides were subjected to chemical N-acetylation, or when the gel filtration columns were run at high pH rather than at the usual pH of 3.0, the basic oligosaccharides migrated like much larger oligosaccharides. These data provide strong evidence to indicate that some mannosamine can be incorporated into the LLO, and that these mannosamine-containing oligosaccharides exhibit unusual properties. Preliminary studies indicated that Madin-Darby canine kidney cells do incorporate label from [3H]mannosamine into the LLO.

D-mannonolactam amidrazone. A new mannosidase inhibitor that also inhibits the endoplasmic reticulum or cytoplasmic alpha-mannosidase

The amidrazone of D-mannonolactam (see compound 5, Fig. 1) was synthesized chemically as a mimic of the mannopyranosyl cation and tested as a potential inhibitor of mannosidases. In this study compound 5 is shown to be a more general mannosidase inhibitor than other currently known compounds and exhibits properties not previously observed with any other mannosidase inhibitors. Thus D-mannonolactam amidrazone not only inhibits the Golgi mannosidase I (IC50 = 4 microM) and mannosidase II (IC50 = 90-100 nM), but it is the first inhibitor that has been shown to be a potent inhibitor of the soluble or endoplasmic reticulum alpha-mannosidase (IC50 = 1 microM). This compound also inhibited the aryl-mannosidases regardless of anomeric configuration although it was much more effective on enzymes recognizing alpha-linked mannose, i.e. jack bean and mung bean alpha-mannosidases (IC50 = 400 nM) as compared with fungal beta-mannosidase (IC50 = 150 microM). Mannonoamidrazone was tested in animal cell cultures using influenza virus-infected Madin-Darby canine kidney cells as a model system, and was found to prevent almost completely the formation of complex types of N-linked oligosaccharides with the formation of about equal amounts of Man9(GlcNAc)2 and Man8(GlcNAc)2 structures. Thus D-mannonolactam amidrazone is a potent but broad spectrum mannosidase inhibitor whose structure and properties should provide valuable insight into the design of other useful glycosidase inhibitors.

6,7-Diepicastanospermine, a tetrahydroxyindolizidine alkaloid inhibitor of amyloglucosidase

A tetrahydroxyindolizidine alkaloid, 6,7-diepicastanospermine, was isolated from the seeds of Castanospermum australe by extraction with methanol and purified to homogeneity using ion-exchange, preparative thin-layer, and radial chromatography. A very low yield of a pyrrolidine alkaloid, N-(hydroxyethyl)-2-(hydroxymethyl)-3-hydroxypyrrolidine, was also obtained by analogous methods. The purity of both alkaloids was established by gas chromatography of their trimethylsilyl (TMS) derivatives as better than 99%. The molecular weight of each alkaloid was established as 189 and 161, respectively, by mass spectrometry, and the structure of each was deduced from their 1H and 13C NMR spectra. The structure of the pyrrolidine alkaloid is suggestive of a possible biosynthetic route to the polyhydroxyindolizidine and polyhydroxypyrrolizidine alkaloids which co-occur in C. australe. 6,7-Diepicastanospermine was found to be a moderately good inhibitor of the fungal alpha-glucosidase, amyloglucosidase (Ki = 8.4 x 10(-5) M) and a relatively weak inhibitor of beta-glucosidase. It failed to inhibit alpha- or beta-galactosidase, alpha- or beta-mannosidase, or alpha-L-fucosidase. Comparison of its inhibitory activity toward amyloglucosidase with those of its isomers, castanospermine and 6-epicastanospermine, demonstrated that epimerization of a single hydroxyl group can produce significant alteration of such inhibitory properties.

Purification and characterization of dolichyl-P-mannose:Man5(GlcNAc)2-PP-dolichol mannosyltransferase

The dolichyl-P-mannose:dolichyl-PP-heptasaccharide alpha-mannosyltransferase (2.4.1.130), which catalyzes the transfer of mannose from dolichyl-P-mannose to the Man5(GlcNAc)2-PP-dolichol acceptor glycolipid, was solubilized from pig aorta microsomes with 0.5% NP-40 and purified 985-fold by a variety of conventional methods. The partially purified enzyme had a pH optimum of 6.5 and required Ca2+, at an optimum concentration of 8-10 mM, for activity. Mn2+ was only 20% as effective as Ca2+, and Mg2+ was inhibitory. The mannosyltransferase activity was also inhibited by the addition of EDTA to the enzyme, but this inhibition was fully reversible by the addition of Ca2+. The enzyme was quite specific for dolichyl-P-mannose as the mannosyl donor and Man5(GlcNAc)2-PP-dolichol as the mannosyl acceptor. The Km values for dolichyl-P-mannose and the acceptor lipid Man5(GlcNAc)2-PP-dolichol were 1.8 and 1.6 microM. On Bio-Gel P-4 columns and by HPLC, the radiolabeled oligosaccharide formed during incubation of dolichyl-P-[14C]mannose and unlabeled Man5(GlcNAc)2-PP-dolichol with the purified enzyme behaved like Man6(GlcNAc)2. This octasaccharide was susceptible to digestion by endoglucosaminidase H, indicating that the newly added mannose was attached to the 6-linked mannose in an alpha 1,3-linkage. This linkage was further confirmed by acetolysis of the oligosaccharide product [i.e., Man6(GlcNAc)2], which gave a labeled disaccharide as the major product (greater than 90%).

Control of N-linked oligosaccharide synthesis: cellular levels of dolichyl phosphate are not the only regulatory factor

When MDCK cells were incubated in the presence of the protein synthesis inhibitor puromycin or cycloheximide, there was a rapid and concentration-dependent inhibition in the incorporation of [2-3H]mannose into lipid-linked oligosaccharide and into protein. However, mannose incorporation into dolichyl-P-mannose was not affected. Interestingly, these inhibitors did block [6-3H]glucosamine incorporation into dolichyl-PP-GlcNAc as well as into lipid-linked oligosaccharides. Similar results were obtained when other cell lines were used and also when inhibitors of protein glycosylation such as beta-hydroxynorvaline and beta-fluoroasparagine were used. Cells incubated in puromycin did not show any changes in the levels of sugar nucleotides, GDP-mannose or UDP-GlcNAc, or in the in vitro activities of the glycosyltransferases that add mannose to the lipid-linked oligosaccharides. The inhibition of mannose incorporation into lipid-linked oligosaccharides could not be overcome by addition of dolichyl-P to the inhibited cells, even though the addition of dolichyl-P to control cells stimulated mannose incorporation into dolichyl-P-mannose, lipid-linked oligosaccharides, and protein from 3- to 5-fold. Thus, limitations in the levels of dolichyl-P do not appear to be a major factor in this inhibition. On the other hand, addition of the tripeptide acceptor N-acyl-Asn-Try-Thr did overcome the puromycin inhibition to some extent, suggesting that accumulation of some intermediate such as lipid-linked oligosaccharides might be involved in the inhibition.

Purification and properties of arylmannosidases from mung bean seedlings and soybean cells

Two arylmannosidases (signified as A and B) were purified to homogeneity from soluble and microsomal fractions of mung bean seedlings. Arylmannosidase A from the microsomes appeared the same on native gels and on SDS gels as soluble arylmannosidase A, the same was true for arylmannosidase B. Sedimentation velocity studies indicated that both enzymes were homogeneous, and that arylmannosidase A had a molecular mass of 237 kd while B had a molecular mass of 243 kd. Arylmannosidase A showed two major protein bands on SDS gels with molecular masses of 60 and 55 kd, and minor bands of 79, 39 and 35 kd. All of these bands were N-linked since they were susceptible to digestion by endoglucosaminidase H. In addition, at least the major bands could be detected by Western blots with antibody raised against the xylose moiety of N-linked plant oligosaccharides, and they could also be labeled in soybean suspension cells with [2-3H]mannose. Arylmannosidase B showed three major bands with molecular masses of 72, 55 and 45 kd, and minor bands of 42 and 39 kd. With the possible exception of the 45 and 42 kd bands, all of these bands are glycoproteins. Arylmannosidases A and B showed somewhat different kinetics in terms of mannose release from high-mannose oligosaccharides, but they were equally susceptible to inhibition by swainsonine and mannostatin A. Polyclonal antibody raised against the arylmannosidase B cross-reacted equally well with arylmannosidase A from mung bean seedlings and with arylmannosidase from soybean cells. However, monoclonal antibody against mung bean arylmannosidase A was much less effective against arylmannosidase B. Antibody was used to examine the biosynthesis and structure of the carbohydrate chains of arylmannosidase in soybean cells grown in [2-3H]mannose. Treatment of the purified enzyme with Endo H released approximately 50% of the radioactivity, and these labeled oligosaccharides were of the high-mannose type, i.e. mostly Man9GlcNAc. The precipitated protein isolated from the Endo H treatment still contained 50% of the radioactivity, and this was present in modified structures that probably contain xylose residues.

Australine, a pyrrolizidine alkaloid that inhibits amyloglucosidase and glycoprotein processing

Australine [(1R,2R,3R,7S,7aR)-3-(hydroxymethyl)-1,2,7-trihydroxypyrrolizid ine] is a polyhydroxylated pyrrolizidine alkaloid that was isolated from the seeds of the Australian tree Castanospermum australe and characterized by NMR and X-ray diffraction analysis [Molyneux et al. (1988) J. Nat. Prod. (in press)]. Since swainsonine and catanospermine are polyhydroxylated indolizidine alkaloids that inhibit specific glycosidases, we tested australine against a variety of exoglycosidases to determine whether it would inhibit any of these enzymes. This alkaloid proved to be a good inhibitor of the alpha-glucosidase amyloglucosidase (50% inhibition at 5.8 microM), but it did not inhibit beta-glucosidase, alpha- or beta-mannosidase, or alpha- or beta-galactosidase. The inhibition of amyloglucosidase was of a competitive nature. Australine also inhibited the glycoprotein processing enzyme glucosidase I, but had only slight activity toward glucosidase II. When incubated with cultured cells, this alkaloid inhibited glycoprotein processing at the glucosidase I step and caused the accumulation of glycoproteins with Glc3Man7-9(GlcNAc)2-oligosaccharides.

Selective inhibition of glycoprotein-processing enzymes. Differential inhibition of glucosidases I and II in cell culture

In this study, we compared the effects of 2,6-dideoxy-2,6-imino-7-O-(beta-D-glucopyranosyl)-D-glycero-L-gulohep titol (MDL) to those of the glucosidase I inhibitor, castanospermine, on the purified processing enzymes glucosidases I and II. WE also compared the effects of these two inhibitors on glycoprotein processing in cell culture using influenza virus-infected Madin-Darby canine kidney cells as a model system. With the purified processing enzymes, castanospermine was a better inhibitor of glucosidase I than of glucosidase II, whereas MDL is more effective against glucosidase II than glucosidase I. In cell culture at the appropriate dose, MDL also preferentially affected glucosidase II. Thus, at 250 micrograms/ml MDL, the major [3H]glucose-labeled (or [3H]mannose-labeled) glycopeptide from the viral hemagglutinin was susceptible to endoglucosaminidase H, and the oligosaccharide liberated by this treatment was characterized as a Glc2Man7-9GlcNAc on the basis of size, resistance to digestion by glucosidase I (but sensitivity to glucosidase II), methylation analysis, and Smith degradation studies. These data indicate that at appropriate concentrations of MDL (250 micrograms/ml), one can selectively inhibit glucosidase II in Madin-Darby canine kidney cells. However, at higher concentrations of inhibitor (500 micrograms/ml), both enzymes are apparently affected. Since MDL did not greatly inhibit the synthesis of lipid-linked saccharides or the synthesis of protein or RNA, it should be a useful tool for studies on the biosynthesis and role of N-linked oligosaccharides in glycoprotein function.

Preparation and characterization of radioactive castanospermine

A procedure for the preparation of tritiated castanospermine is described. The tritiated alkaloid was shown to be chromatographically identical to the native material and exhibited the same inhibitory properties. Radiolabeled castanospermine tightly bound to purified intestinal sucrase. Following gel chromatography, each mole of enzyme was shown to have bound 1 mol of the radioactive alkaloid. Cultured MDCK cells were also shown to take up the labeled castanospermine. This compound should be a useful tool in the investigation of enzymes that are responsible for the processing of glycoprotein oligosaccharides.

The effect of glycoprotein-processing inhibitors on the secretion of glycoproteins by Madin-Darby canine kidney cells

The effects of various glycoprotein-processing inhibitors on the biosynthesis and secretion of N-linked glycoproteins was examined in cultured Madin-Darby canine kidney (MDCK) cells. Since incorporation of [2-3H]mannose into lipid-linked saccharides and into glycoproteins was much greater in phosphate-buffered saline (PBS) than in serum-supplemented basal medium (BME), most experiments were done in PBS. Castanospermine, an inhibitor of glucosidase I, caused the formation of glycoproteins having mostly Glc3Man7-9(GlcNAc)2 structures; deoxymannojirimycin, an inhibitor of mannosidase I, gave mostly glycoproteins with Man9(GlcNAc)2 structures; swainsonine, an inhibitor of mannosidase II, caused the accumulation of hybrid types of oligosaccharides. Castanospermine and swainsonine, either in PBS or in BME medium, had no effect on the incorporation of [2-3H]mannose or [5,6-3H]leucine into the secreted glycoproteins and, in fact, there was some increase in mannose incorporation in their presence. These inhibitors also did not affect mannose incorporation into cellular glycoproteins nor did they affect the biosynthesis as measured by mannose incorporation into lipid-linked saccharides. On the other hand in PBS medium, deoxymannojirimycin, at 25 micrograms/mL, caused a 75% inhibition in mannose incorporation into secreted glycoproteins, but had no effect on the incorporation of [3H]leucine into the secreted glycoproteins. Since deoxymannojirimycin also strongly inhibited mannose incorporation into lipid-linked oligosaccharides in PBS, the decreased amount of radioactivity in the secreted and cellular glycoproteins may reflect the formation of glycoproteins with fewer than normal numbers of oligosaccharide chains, owing to the low levels of oligosaccharide donor. However, in BME medium, there was only slight inhibition of mannose incorporation into lipid-linked saccharides and into cellular and secreted glycoproteins.

The effect of mannosamine on the formation of lipid-linked oligosaccharides and glycoproteins in canine kidney cells

Madin-Darby canine kidney (MDCK) cells normally form lipid-linked oligosaccharides having mostly the Glc3Man9GlcNAc2 oligosaccharide. However, when MDCK cells are incubated in 1 to 10 mM mannosamine and labeled with [2-3H]mannose, the major oligosaccharides associated with the dolichol were Man5GlcNAc2 and Man6GlcNAc2 structures. Since both of these oligosaccharides were susceptible to digestion by endo-beta-N-acetylglucosaminidase H, the Man5GlcNAc2 must be different in structure than the Man5GlcNAc2 usually found as a biosynthetic intermediate in the lipid-linked oligosaccharides. Methylation analysis also indicated that this Man5GlcNAc2 contained 1----3 linked mannose residues. Since pulse chase studies indicated that the lesion was in biosynthesis, it appears that mannosamine inhibits the in vivo formation of lipid-linked oligosaccharides perhaps by inhibiting the alpha-1,2-mannosyl transferases. Although the lipid-linked oligosaccharides produced in the presence of mannosamine were smaller in size than those of control cells and did not contain glucose, the oligosaccharides were still transferred in vivo to protein. Furthermore, the oligosaccharide portions of the glycoproteins were still processed as shown by the fact that the glycopeptides were of the complex and hybrid types and were labeled with [3H]mannose or [3H]galactose. In contrast, control cells produced complex and high-mannose structures but no hybrid oligosaccharides were detected. The inhibition by mannosamine could be overcome by adding high concentrations of glucose to the medium.

Inhibition of processing of plant N-linked oligosaccharides by castanospermine

Castanospermine (1,6,7,8-tetrahydroxyoctahydroindolizine) is a plant alkaloid that inhibits lysosomal alpha- and beta-glucosidase. It also inhibits processing of influenza viral glycoproteins by inhibiting glucosidase I and leads to altered glycoproteins with Glc3Man7GlcNAc2 structures. Castanospermine was tested as an inhibitor of glycoprotein processing in suspension-cultured soybean cells. Soybean cells were pulse-labeled with [2-3H]mannose and chased for varying periods in unlabeled medium. In normal cells, the initial glycopeptides contained oligosaccharides having Glc3Man9GlcNAc2 to Glc1Man9GlcNAc2 structures and these were trimmed during the chase to Man9GlcNac2 to Man7GlcNAc2 structures. In the presence of castanospermine, no trimming of glucose residues occurred although some mannose residues were apparently still removed. Thus, the major oligosaccharide in the glycopeptides of castanospermine-incubated cells after a 90-min chase was a Glc3Man7GlcNAc2 structure. Smaller amounts of Glc3Man6GlcNAc2 and Glc3Man5GlcNAc2 were also identified. Thus, in plant cells, castanospermine also prevents the removal of the outermost glucose residue.

Castanospermine inhibits the processing of the oligosaccharide portion of the influenza viral hemagglutinin

Castanospermine (1,6,7,8-tetrahydroxyoctahydroindolizine) is a plant alkaloid that inhibits alpha- and beta-glucosidase in fibroblast extracts [Saul, R., Chambers, J. P., Molyneux, R. J., & Elbein, A. D. (1983) Arch. Biochem. Biophys. 221, 593-597]. In the present study, castanospermine also proved to be a potent inhibitor of glycoprotein processing by virtue of the fact that it inhibits glucosidase I. Thus, when influenza virus was raised in the presence of castanospermine, at 10 micrograms/mL or higher, 80-90% of the viral glycopeptides were susceptible to the action of endoglucosaminidase H, whereas in the normal virus 70% of the glycopeptides are resistant to this enzyme. The major oligosaccharide released by endoglucosaminidase H from castanospermine-grown virus migrated like a hexose10GlcNac on a calibrated Bio-Gel P-4 column. This oligosaccharide was characterized as a Glc 3 Man 7 GlcNAc on the basis of various enzymatic treatments, as well as by methylation analysis of the [2-3H]-mannose-labeled or [6-3H]galactose-labeled oligosaccharide. The presence of three glucose residues in the oligosaccharide was also confirmed by periodate oxidation studies of the [6-3H]galactose-labeled hexose10GlcNAc. Castanospermine did not inhibit the incorporation of [3H]leucine or [14C]alanine into protein in MDCK cells at levels as high as 50 micrograms/mL. In addition, influenza virus produced in the presence of this alkaloid were fully infective and apparently produced in similar amounts to that of control cells, as determined by plaque counts. Castanospermine did, however, cause considerable changes in cell surface properties, since MDCK cells grown in 10 micrograms/mL castanospermine were able to bind twice as much [3H]concanavalin A as were control cells.

The formation of lipid-linked oligosaccharides in Madin-Darby canine kidney cells. Changes in oligosaccharide profiles induced by glucosamine

Glucosamine inhibits the incorporation of [2-3H]mannose into lipid-linked oligosaccharides and into glycoproteins in influenza virus-infected MDCK cells. Fifty per cent inhibition of these components requires about 2 mM glucosamine. The oligosaccharide portions of the lipid-linked oligosaccharides in cells inhibited with glucosamine were compared to that of normal cells by chromatography on Bio-Gel P-4 columns. In uninhibited cells, the major oligosaccharide formed from [2-3H]mannose was the Glc3Man9GlcNAc2 species as demonstrated by the products of endoglucosaminidase H and alpha-mannosidase digestion. At low concentrations of glucosamine (approximately 2 mM) or in short term incubations (1 to 2 h), the large oligosaccharide disappeared and was replaced by a Man7GlcNAc2 species. This was also characterized by various enzymatic treatments as well as its migration rate on Bio-Gel P-4 as compared to known oligosaccharides. At still higher glucosamine concentrations or longer incubation times, the Man7GlcNAc2 species also disappeared and was replaced by a Man3GlcNAc2 species. The effect of glucosamine was reversible such that when the cells were washed free of this inhibitor, they resumed the synthesis of the Glc3Man9GlcNAc2 species and the other two oligosaccharides disappeared. These smaller oligosaccharides were not observed when glucosamine was replaced by either 5 mM galactosamine or 5 mM N-acetylglucosamine.

Binding of [3H]heparin to human plasma low density lipoprotein

Computed tomography (CT) has made a profound impact on the diagnosis and treatment of neuroblastomas and ganglioneuromas. The size, location, calcification, composition, and contiguous spread of the tumors has been well demonstrated by CT. CT is essential for their staging, subsequent treatment, and follow-up. Seventy-seven children were reviewed, 67 with neuroblastoma and 10 with ganglioneuroma seen between 1976 and 1980. Fifty-eight had one or more body CT scans, 22 had metrizamide myelography and/or CT metrizamide myelography, and three patients had cranial CT. Intraspinal extension of tumor occurred in 11 instances, several requiring decompressive surgery. A workup plan for optimal use of CT and CT metrizamide myelography was developed from this experience.

Adherence of bacteria to mammalian cells: inhibition by tunicamycin and streptovirudin

Group B streptococci were labeled either by growing the cells in [14C]fructose or by using the surface label 4,4'-[3H]diisothiocyano-1,2-diphenylethane-2,2'-disulfonic acid, which reacts with amino groups. A quantitative assay was developed by using these labeled bacteria to study the adherence of streptococci to canine kidney epithelial cells. The bacteria adhered to kidney cells that had been infected with influenza A virus, but did not adhere to uninfected cells. The binding of 3H-labeled group B streptococci was proportional to the number of bacteria added and showed saturation kinetics. The binding was blocked by the addition of unlabeled group B streptococci but was not affected by addition of streptococci from other groups. It was also blocked by mixing the 3H-labeled streptococci with influenza A virus before adding the bacteria to the kidney cells. When the kidney cells were infected with influenza virus in the presence of either tunicamycin or streptovirudin, these antibiotics inhibited the appearance of viral hemagglutinin in the kidney cells and also prevented the release of mature virus. In these experiments, the adherence of 3h-labeled streptococci was also inhibited. Tunicamycin was shown to block the incorporation of [14C]mannose into lipid-linked oligosaccharides and glycoprotein in both normal and virus-infected kidney cells. These data give strong support to the notion that adherence of streptococci to mammalian cells involves recognition of viral hemagglutinin, a glycoprotein whose synthesis is blocked by certain antibiotics.