Neuroendocrine cell type-specific and inducible expression of the chromogranin B gene: crucial role of the proximal promoter

Chromogranin B, a soluble acidic secretory protein, is widely distributed in neuroendocrine and neuronal cells, although not in other cell types. To identify the elements governing such widespread, yet selective, expression of the gene, we characterized the isolated mouse chromogranin B promoter. 5'-Promoter deletions localized neuroendocrine cell type-specific expression to the proximal chromogranin B promoter (from -216 to -91 bp); this region contains an E box (at [-206 bp]CACCTG[-201 bp]), four G/C-rich regions (at [-196 bp]CCCCGC[-191 bp], [-134 bp]CCGCCCGC[-127 bp], [-125 bp]GGCGCCGCC[-117 bp], and [-115 bp]CGGGGC[-110 bp]), and a cAMP response element (CRE; at [-102 bp]TGACGTCA[-95 bp]). A 60-bp core promoter region, defined by an internal deletion from - 134 to -74 bp upstream of the cap site and spanning the CRE and three G/C-rich regions, directed tissue-specific expression of the gene. The CRE motif directed cell type-specific expression of the chromogranin B gene in neurons, whereas three of the G/C-rich regions played a crucial role in neuroendocrine cells. Both the endogenous chromogranin B gene and the transfected chromogranin B promoter were induced by preganglionic secretory stimuli (pituitary adenylyl cyclase-activating polypeptide, vasoactive intestinal peptide, or a nicotinic cholinergic agonist), establishing stimulus-transcription coupling for this promoter. The adenylyl cyclase activator forskolin, nerve growth factor, and retinoic acid also activated the chromogranin B gene. Secretagogue-inducible expression of chromogranin B also mapped onto the proximal promoter; inducible expression was entirely lost upon internal deletion of the 60-bp core (from 134 to -74 bp). We conclude that CRE and G/C-rich domains are crucial determinants of both cell type-specific and secretagogue-inducible expression of the chromogranin B gene.

Chemoenzymatic synthesis and fluorescent visualization of cell-surface selectin-bound sialyl Lewis x derivatives

Sialyl Lewis x (sLe(x)) derivatives conjugated to readily visualized molecular labels are useful chemical probes to study selectin-carbohydrate interactions. Localization of the selectins on the surface of leukocytes and activated endothelial cells can be detected through fluorescence of bound selectin ligands. Herein we present a short chemoenzymatic synthesis of a fluorescently labeled bivalent sLe(x) conjugate. The use of an amino-substituted monovalent sLe(x) to obtain fluorescent- and biotin-labeled sLe(x) derivatives is also described. The cell-staining utility of the fluorescent sLe(x) conjugates is demonstrated for a HUVEC cell line expressing E-selectin and for CHO-K1 cells expressing either L- or E-selectin.

Coupled electromagnetic and thermal modeling of microwave oven heating of foods

Temperature distributions from heating in a domestic microwave oven were studied by considering the coupling between the electromagnetics and heat transfer through changes in dielectric properties during heating. Maxwell's equations for electromagnetics and the thermal energy equations are solved numerically using two separate finite-element softwares. The coupling between the softwares was developed by writing special modules that interfaced these softwares at the system level. Experimentally measured temperature profiles were compared with the numerical predictions. The importance of coupling was evident when the properties changed significantly with temperature for low and high dielectric loss materials and more so for the high loss materials. For moderate loss materials, when the properties do not change as much with temperature, coupled solutions lead to results very close to the results for the uncoupled solution.

Chemical and immunochemical studies of the O-antigen from enteropathogenic Escherichia coli O158 lipopolysaccharide

The O-specific polysaccharide isolated from Escherichia coli O158 smooth lipopolysaccharide contains L-rhamnose, D-glucose and 2-acetamido-2-deoxy-D-galactose in the molar ratios 1:2:2. Studies on composition, methylation analysis and specific degradations together with a 1H and 13C NMR spectral study established that the O-antigen is built up from a pentasaccharide repeating unit having the following structure: [formula: see text] The most effective inhibitory part of the oligosaccharide from E. coli O158 lipopolysaccharide has been serologically characterized by an ELISA-inhibition study using different sugars. The results showed that methyl alpha- and beta-D-GalpNAc are the most effective inhibitors among the monosaccharides tested, while the main antibody specificity lies on the main-chain trisaccharide repeating unit.

Expression of alpha2,8/2,9-polysialyltransferase from Escherichia coli K92. Characterization of the enzyme and its reaction products

The capsular polysaccharide of Escherichia coli K92 contains alternating -8-NeuAcalpha2- and -9-NeuAcalpha2- linkages. The enzyme catalyzing this polymerizing reaction has been cloned from the genomic DNA of E. coli K92. The 1.2-kilobase polymerase chain reaction fragment was subcloned in pRSET vector and the protein was expressed in the BL21(DE3) strain of E. coli with a hexameric histidine at its N-terminal end. The enzyme was isolated in the supernatant after lysis of the cells and fractionated by ultracentrifugation. Western blotting using anti-histidine antibody showed the presence of a band that migrated at about 47.5 kDa on both reducing and nonreducing SDS-polyacrylamide gel electrophoresis, indicating a monomeric enzyme. Among the carbohydrate acceptors tested, N-acetylneuraminic acid and the gangliosides G(D3) and G(Q1b) were preferred substrates. The cell-free enzyme reaction products obtained were characterized by NMR and mass spectrometry, which indicated the presence of both alpha2,9- and alpha2,8-linked polysialyl structure. The K92 neuS gene was used to transform the K1 strain of E. coli, the capsule of which contains only -8-NeuAcalpha2- linkages. Analysis of the polysaccharides isolated from these transformed cells is consistent with the presence of both -8-NeuAcalpha2- and -9-NeuAcalpha2- linkages. Our results suggest that the neuS gene product of E. coli K92 catalyzes the synthesis of polysialic acid with alpha2,9- and alpha2,8-linkages in vitro and in vivo.

Molecular cloning and expression of adenosine kinase from Leishmania donovani: identification of unconventional P-loop motif

The unique catalytic characteristics of adenosine kinase (Adk) and its stage-specific differential activity pattern have made this enzyme a prospective target for chemotherapeutic manipulation in the purine-auxotrophic parasitic protozoan Leishmania donovani. However, nothing is known about the structure of the parasite Adk. We report here the cloning of its gene and the characterization of the gene product. The encoded protein, consisting of 345 amino acid residues with a calculated molecular mass of 37173 Da, shares limited but significant similarity with sugar kinases and inosine-guanosine kinase of microbial origin, supporting the notion that these enzymes might have the same ancestral origin. The identity of the parasite enzyme with the corresponding enzyme from two other sources so far described was only 40%. Furthermore, 5' RNA mapping studies indicated that the Adk gene transcript is matured post-transcriptionally with the trans-splicing of the mini-exon (spliced leader) occurring at nt -160 from the predicted translation initiation site. The biochemical properties of the recombinant enzyme were similar to those of the enzyme isolated from leishmanial cells. The intrinsic tryptophan fluorescence of the enzyme was substrate-sensitive. On the basis of a multiple protein-alignment sequence comparison and ATP-induced fluorescence quenching in the presence or the absence of KI and acrylamide, the docking site for ATP has been provisionally identified and shown to have marked divergence from the consensus P-loop motif reported for ATP- or GTP-binding proteins from other sources.

Measuring brain tissue oxygenation compared with jugular venous oxygen saturation for monitoring cerebral oxygenation after traumatic brain injury

Jugular bulb oximetry is the most widely used method of monitoring cerebral oxygenation. More recently, measurement of brain tissue oxygenation has been reported in head-injured patients. We compared the changes in brain tissue oxygen partial pressure (PbO2) with changes in jugular venous oxygen saturation (SjVO2) in response to hyperventilation in areas of brain with and without focal pathology. Thirteen patients with severe head injuries were studied. A multiparameter sensor was inserted into areas of brain with focal pathology in five patients and outside areas of focal pathology in eight patients. A fiberoptic catheter was inserted into the right jugular bulb. Patients were hyperventilated in a stepwise manner from a PaCO2 of approximately 35 mm Hg to a PaCO2 of 22 mm Hg. There was no significant change in cerebral perfusion pressure or arterial partial pressure of oxygen with hyperventilation. In areas without focal pathology, there was a good correlation between changes in SjVO2 and PbO2 (deltaSjVO2 and deltaPbO2; r2 = 0.69, P < 0.0001). In areas with focal pathology, there was no correlation between deltaSjVO, and APbO2 (r2 =0.07, P = 0.23). In this study, we demonstrated that measurement of local tissue oxygenation can highlight focal differences in regional cerebral oxygenation that are disguised when measuring SjVO2. Thus, monitoring of PbO2 is a useful addition to multimodal monitoring of patients with traumatic head injury.

IMPLICATIONS

Brain oxygenation is currently monitored by using jugular bulb oximetry, which attracts a number of potential artifacts and may not reflect regional changes in oxygenation. We compared this method with measurement of brain tissue oxygenation using a multiparameter sensor inserted into brain tissue. The brain tissue monitor seemed to reflect regional brain oxygenation better than jugular bulb oximetry.

Chemical characterization of the lipopolysaccharides from enteropathogenic Escherichia coli O142 and O158

Lipopolysaccharides (LPS) from two enteropathogenic strains of E. coli O142 and O158 were isolated by hot phenol-water extraction procedure. Polyacrylamide gel electrophoretic pattern of the LPS showed the typical ladder like pattern of smooth type of LPS. The LPS of E. coli O158 was found to contain L-rhamnose, D-glucose and N-acetyl-D-galactosamine as major constituents together with D-galactose, N-acetyl-D-glucosamine, L-glycero-D-manno-heptose and 2-keto-3-deoxy-D-manno-octulosonic acid (KDO) whereas LPS from E. coli O142 contained L-rhamnose, N-acetyl-D-glucosamine and N-acetyl-D-galactosamine as major constituents together with D-glucose, D-galactose, N-acetyl-D-glucosamine, L-glycero-D-mannoheptose and 2-keto-3-deoxy-D-manno-octulosonic acid (KDO). LPS was degraded by mild acid hydrolysis to yield a degraded polysaccharide fraction and an insoluble lipid-A fraction. The main fatty acids of the lipid-A fraction of the LPS were C12:O, C14:O, and 3-OH C14:O for O158 strain whereas E. coli O142 lipid-A consisted of C12:O, C14:O, 3-OH C14:O, and C16:O. The degraded polysaccharide fraction on gel permeation chromatography gave a high moleculer weight O-chain fraction and a core oligosaccharide and a fraction containing degraded sugars. The chemical composition of LPS and its fragmented products are reported in this communication.

Thawing of foods in a microwave oven: I. Effect of power levels and power cycling

Microwave thawing is faster than other methods, but it can produce significant non-uniformity of heating. The objective of this study was to perform comprehensive experimentation and heat transfer modeling to relate the time to thaw and the non-uniformity of thawing to power cycling, power level and the surface heat transfer coefficient. The governing energy equation was formulated with an exponential decay of the microwave flux from the surface. Surface microwave flux was obtained from the measured temperature rise using inverse heat transfer analysis. Gradual phase change was formulated as an apparent specific heat, and was obtained for the experimental material tylose from differential scanning calorimetry (DSC) measurements. The temperatures were measured immediately following heating with a fast response thermocouple. Dielectric properties were measured above freezing. Results show that the microwave flux at the surface and its decay are affected by the changes in the power level. Power cycling has an almost identical effect as continuous power at the reduced level of the average cycled power. As power level increases, the surface flux increases by the same fraction. At higher power levels, however, the outside thaws relatively faster. A "shield" develops due to a much reduced microwave penetration depth at the surface. This thawing time at higher power levels is reduced considerably. Temperature increases initially are non-uniform since the surface is heated at a faster rate than the interior. In keeping with the assumption that once the temperature reaches 100 degrees C, all energy absorbed goes into evaporation, and subsequent temperature is maintained at 100 degrees C. Thus, eventually, non-uniformity starts to decrease.

Thawing of foods in a microwave oven: II. Effect of load geometry and dielectric properties

Non-uniformity of temperatures in thawing of food and biological materials inside a microwave oven is affected by size, shape, and dielectric properties of the load (food). The objective of this study was to relate the time to thaw and the non-uniformity of heating to the shape, size, and the dielectric properties of the load. The details of the heat transfer analysis, experimental measurement of thermal and dielectric properties, and temperature measurements are described in a companion paper. Results show that both the aspect ratio and the volume have a significant effect on the heating rates, time to thaw and the non-uniformity of temperatures during thawing. A "shield" develops from surface thawing and leads to reduced microwave penetration. This "shield" develops more readily at higher dielectric loss, thereby effectively increasing the thawing time even more for a lossy material at higher power levels. Thawing time increases linearly with volume. As the load aspect ratio decreases (it is made flatter), it thaws faster since the energy decays relatively less in a thinner material. These new results could provide a more rational and quantitative approach to development of frozen food products to be heated in a microwave oven.

Thermal stresses from large volumetric expansion during freezing of biomaterials

Thermal stresses were studied in freezing of biomaterials containing significant amounts of water. An apparent specific heat formulation of the energy equation and a viscoelastic model for the mechanics problem were used to analyze the transient axi-symmetric freezing of a long cylinder. Viscoelastic properties were measured in an Instron machine. Results show that, before phase change occurs at any location, both radial and circumferential stresses are tensile and keep increasing until phase change begins. The maximum principal tensile stress during phase change increases with a decrease in boundary temperature (faster cooling). This is consistent with experimentally observed fractures at a lower boundary temperature. Large volumetric expansion during water to ice transformation was shown to be the primary contributor to large stress development. For very rapid freezing, relaxation may not be significant, and an elastic model may be sufficient.

A study of the effects of pulsed electromagnetic field therapy with respect to serological grouping in rheumatoid arthritis

The positive role of pulsed electromagnetic field (PEMF) therapy in rheumatoid arthritis (RA) is known. The differential role of serological status of patients in RA is also well known. This paper presents a study of the differential effects of PEMF therapy on the two serological groups of patients. The responses of the seropositive patients are found to be more subdued. Varying effects of the therapy in alleviating the different symptomatologies indicate that the rheumatoid factor (RF) is more resistant to PEMF.

Mutation of the sialyltransferase S-sialylmotif alters the kinetics of the donor and acceptor substrates

Protein sequence analysis of the cloned sialyltransferase gene family has revealed the presence of two conserved protein motifs in the middle of the lumenal catalytic domain, termed L-sialylmotif and S-sialylmotif. In our previous study (Datta, A. K., and Paulson, J. C. (1995) J. Biol. Chem. 270, 1497-1500) the larger L-sialylmotif of ST6Gal I was analyzed by site-directed mutagenesis, which provided evidence that it participates in the binding of the CMP-NeuAc, a common donor substrate for all the sialyltransferases. However, none of the mutants tested in this motif had any significant effect on their binding affinities toward the acceptor substrate asialo alpha1-acid glycoprotein. In this study, we have investigated the role of the S-sialylmotif of the same enzyme ST6Gal I. In total, nine mutants have been constructed by changing the conserved amino acids of this motif to mostly alanine by site-directed mutagenesis. Kinetic analysis for the mutants which retained sialyltransferase activity showed that the mutations in the S-sialylmotif caused a change of Km values for both the donor and the acceptor substrates. Our results indicated that this motif participates in the binding of both the substrates. A sequence homology search also supported this finding, which showed that the downstream amino acid sequence of the S-sialylmotif is conserved for each subgroup of this enzyme family, indicating its association with the acceptor substrate.

Circadian rhythm of cutaneous hypersensitivity reactions in nocturnal asthma

BACKGROUND

Diurnal variation in mast cell discharge may play a central role in the early morning fall in peak expiratory flow rate (PEFR) in nocturnal asthmatic patients.

METHODS

We tested the hypothesis that there is a circadian rhythm in mast cell response to allergen in 15 patients with nocturnal asthma by measuring the magnitude of cutaneous hypersensitivity reactions at 0600, 1200, 1800, and 2400 hours. Pre-admission, prick skin testing on the ventral aspect of the forearm to various allergens was performed. The allergen producing the largest wheal was tested at six sites on one forearm. Response was quantified after 20 minutes by measuring the area of the wheal produced using planimetry. Every six hours the skin testing was repeated at six new sites on alternating forearms. The average area of the six wheals was calculated and recorded at each time. The prick skin technique was used at all times.

RESULTS

Maximal reactions occurred in 10 of the 15 patients at noon (P = .031, Friedman's two way analysis of variance). In these 10 patients wheal area at the time of maximum reactivity was on average 3.3-fold higher than at the time of minimum reactivity. The mean wheal areas for all 15 patients at 0600, 1200, 1800, and 2400 hours were 34 mm2, 42 mm2, 34 mm2, and 35 mm2 respectively.

CONCLUSIONS

These observations support the concept of a circadian rhythm in mast cell activity in patients with severe nocturnal asthma.

Biodegradation of lantadene A, the pentacyclic triterpenoid hepatotoxin by Pseudomonas pickettii

A bacterial strain capable of biodegradation of lantadene A (22 beta-angeloyloxy-3-oxoolean-12-en-28-oic acid) has been isolated from soil using lantadene A as the sole carbon source. The organism is rod shaped, Gram negative, motile and has been identified as Pseudomonas pickettii. This is the first report of the biodegradation of a pentacyclic triterpenoid.

Sialylmotifs of sialyltransferases

The sialyl moiety of sialylated glycoconjugates expressed on the cell surface are increasingly recognized as the key determinants of various biological recognition events. The transfer of sialic acid to these glycoconjugates are catalyzed by sialyltransferases, a group of 15 or more Golgi enzymes. Cloning of three sialyltransferases from this laboratory, indicated for the first time, that these enzymes are type II membrane proteins and share the topological features common to other glycosyltransferases. However, unlike the other members of the glycosyltransferase family, these enzymes showed the presence of two conserve protein domains, termed 'sialylmotifs'. This unique feature was subsequently found to be present in all the sialyltransferases cloned to-date. The larger 'L-sialylmotif' consisting of 48-49 amino acids is present in the middle of the luminal catalytic domain and has, eight invariant residues, while the 'S-sialylmotif' present closer to the C-terminal end of the enzyme has two invariants among a stretch of 23 amino acids. The other not-so-invariant amino acids are also conserved and their replacement is limited. The functional role of these two sialylmotifs were investigated by single-point site-directed mutagenesis using Gal beta 1, 4GlcNAc alpha 2,6-sialyltransferase (ST6Gal I) as a model. Detailed kinetic analysis of the mutants indicated that the 'L-sialylmotif' contributes to the binding of the common donor substrate CMP-NeuAc, while the 'S-sialylmotif' contributes to the binding of both the donor and acceptor substrates.

Differential depletion of human respiratory tract antioxidants in response to ozone challenge

The toxicity of ozone, the major component of photochemical smog, is related to its powerful oxidising ability, and many of its deleterious effects are mediated through free radical reactions. As the majority of ozone oxidation events are thought to be confined to the pulmonary epithelial lining fluid, we studied the interaction of ozone with a range of small molecular weight antioxidants found within this compartment: ascorbic acid (AH2), uric acid (UA), and reduced glutathione (GSH). Epithelial lining fluid obtained as bronchoalveolar lavage (BAL) fluid, was taken from 16 male subjects and the antioxidant concentrations determined for each subject. BAL fluid samples from nine of these subjects were then exposed, using an interfacial exposure system, to a range (50-1000 ppb) of ozone concentrations. Both AH2 and UA were consumed by ozone in a time and ozone concentration dependent manner, with mean consumption rates of 1.7 +/- 0.8 and 1.0 +/- 0.5 pmol L-1 s-1 ppb-1, respectively. Considerable intersubject variation was however observed. The individual rates of consumption for each antioxidant were significantly correlated with the respective initial antioxidant concentration. In contrast, although GSH was consumed at 50 ppb ozone, the rate of consumption did not change with increasing ozone concentration. We conclude that there is differential depletion of BAL fluid antioxidants, suggesting a reactivity hierarchy toward ozone in human ELF of AH2 > UA > > GSH.

Role of hypo-osmotic sperm swelling test in assisted reproduction

Hypo-osmotic sperm swelling (HOS) profile is found to be a better predictor of the fertilisability in those husbands possessing subnormal semen parameters. The group where husband's HOS gradings were less than 60%, no one could conceive his fertile wife even after intra-uterine insemination (IUI) for 8 times. However, in the other group where the HOS values were greater than 60%, conception were registered in 6 oligospermic and 2 asthenospermic husbands after 2 to 8 IUI amongst 22 married couples. No conception occurred in any normal coital cycle. All the pregnancies were delivered by elective caesarean section (4 females and 3 males), their birth weights were 2.705 +/- 0.425 kg. One aborted spontaneously at 10 weeks' gestation. The emerging fact in this study is where the HOS values are below 60% the male fertility is reduced, the chances of conception are trivial but fecundity is relatively fair where HOS reading is greater than 60%. It is also a no risk and high benefit method to pick and choose subfertile husbands who are likely to conceive their fertile wives by assisted reproductive techniques.

Characterization of pNiXa, a serpin of Xenopus laevis oocytes and embryos, and its histidine-rich, Ni(II)-binding domain

A Ni(II)-binding serpin, pNiXa, is abundant in Xenopus oocytes and embryos. Kinetic assays show that purified pNiXa strongly inhibits bovine alpha-chymotrypsin (Ki = 3 mM), weakly inhibits porcine elastase (K1 = 0.5 microM), and does not inhibit bovine trypsin. The reversible, slow-binding inhibition of alpha-chymotrypsin by pNiXa is unaffected by Ni(II). Ovochymase in egg exudates is inhibited by pNiXa, but to a limited extent, even at high pNiXa concentrations. An octadecapeptide that models the His-rich domain (-HRHRHEQQGHHDSAKHGH-) of pNiXa forms six-coordinate, octahedral Ni(II)-complexes when the N-terminus is acetylated, and a square-planar Ni(II)-complex when the N-terminus is unblocked. Spectroscopy reveals two distinct types of octahedral Ni(II)-coordination to the N-acetylated octadecapeptide, involving, respectively, 3-4 and 5-6 imidazole nitrogens; the octadecapeptide undergoes partial, reversible precipitation in pH- and Ni(II)-dependent fashion, suggesting an insoluble, Ni(II)-coupled (Hx)n-dimer. Such (Hx)n-peptide interaction is confirmed by an enzyme-linked biotinavidin assay with N-biotin-KHRHRHE-amide and N-acetyl-KHRHRHE-resin beads, which become coupled after adding Ni(II) or Zn(II). H2O2 oxidation of 2'-deoxyguanosine to mutagenic 8-hydroxy-2'-deoxyguanosine is enhanced by the octahedral Ni(II)-octadecapeptide complex, although the effect is more intense with the square-planar Ni(II)-octadecapeptide complex. Immunoperoxidase staining of whole mounts with pNiXa antibody shows that pNiXa is distributed throughout gastrula-stage embryos and is localized during organogenesis in the brain, eye, spinal cord, myotomes, craniofacial tissues, and other sites of Ni(II)-induced anomalies. Patterns of pNiXa staining are similar in controls and Ni(II)-exposed embryos. Binding of Ni(II) to pNiXa may cause embryotoxicity by enhancing oxidative reactions that produce tissue injury and genotoxicity. Although the natural target proteinases for pNiXa inhibition have not been established, pNiXa may be an important regulator of proteolysis during embryonic development.

Two conformationally vicinal thiols at the active site of Leishmania donovani adenosine kinase

Inactivation of adenosine kinase (Adk) from Leishmania donovani correlates with the modification of two conformationally vicinal cysteine residues. In contrast, Adk from hamster liver, despite being sensitive to monothiol-blocking reagents, was insensitive to dithiol modifiers. Inactivation kinetics and substrate-protection studies along with double-modification experiments successively with N-ethylmaleimide in the presence of Ado and sodium m-arsenite-2,3-dimercaptopropanol or diazenedicarboxylic acid bis-N,N'-dimethylamide supported assignment of the two thiols at the Ado-binding site. Cystine bridge formation impaired the ability of the modified enzyme to bind to the substrate. Tryptophan fluorescence of the enzyme was quenched after modification by dithiol-blocking reagents with concomitant loss of activity. However, treatment of the enzyme with methylmethanethiosulphonate (MMTS) led to complete inactivation without a marked change in protein fluorescence. Ado protected both fluorescence and catalytic activity against inactivation by both MMTS and dithiol-blocking reagents. Stern-Volmer quenching analysis of the native and Ado-complexed enzyme suggested that, of the four tryptophan residues, at least one is located at or near the active site. Furthermore quenching constants of native, Ado-complexed and dithiol-modified enzyme in the presence of either acrylamide or KI indicated spatial proximity of tryptophan and two cysteine residues within the hydrophobic domain of the Ado-binding site. Taken together the results suggest important function(s) for the cysteine residue(s). A schematic model is proposed to explain the inactivation of the enzyme by both monothiol- and dithiol-blocking reagents.

Large-scale expression of recombinant sialyltransferases and comparison of their kinetic properties with native enzymes

Values of Km were determined for three purified sialyltransferases and the corresponding recombinant enzymes. The enzymes were Gal beta 1-4GlcNAc alpha 2-6 sialyltransferase and Gal beta 1-3(4)GlcNAc alpha 2-3 sialyltransferase from rat liver; these enzymes are responsible for the attachment of sialic acid to N-linked oligosaccharide chains; and the Gal beta 1-3GalNAc alpha 2-3 sialyltransferase from porcine submaxillary gland that is responsible for the attachment of sialic acid to O-linked glycoproteins and glycolipids. A procedure for the large scale expression of active sialyltransferases from recombinant baculovirus-infected insect cells is described. For the liver enzymes values of Km were determined using rat and human asialo alpha 1 acid glycoprotein and N-acetyllactosamine as variable substrates; lacto-N-tetraose was also used with the Gal beta 1-3(4)GlcNAc alpha 2-3 sialyltransferases. Antifreeze glycoprotein was used as the macromolecular acceptor for the porcine enzyme. Values for Km were also determined using CMP-NeuAc as the variable substrate.

Efficient amplification using 'megaprimer' by asymmetric polymerase chain reaction

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Lipocortin-1 distribution in bronchoalveolar lavage from healthy human lung: effect of prednisolone

Lipocortin-1 (LC-1; annexin-1) may mediate some anti-inflammatory actions of the glucocorticoids, probably after binding to specific cell surface binding sites. We have quantified LC-1 levels in bronchoalveolar lavage (BAL) fluid and cells collected from seven healthy volunteers before and after 7 days of treatment with an oral glucocorticoid, prednisolone (30 mg/day). Extracellular BAL LC-1 was higher and cellular LC-1 was lower after prednisolone than before [extracellular: before, median 98 ng/mg albumin (range 48-350 ng/mg albumin); after, 236 ng/mg albumin (19-414 ng/mg albumin); P < 0.05. Cellular: before, 23.3 ng/10(6) cells (14.6-26.9 ng/10(6) cells); after, 18.0 ng/10(6) cells (122-268 ng/10(6) cells); P < 0.05]. The distribution of LC-1 within BAL cells ex vivo (cell surface = 25%, cytosol = 50%, membrane = 25%) was unaffected by prednisolone treatment. However, in adherent cells that had been cultured for 4 h, 70-80% of the LC-1 was on the cell surface. In summary, prednisolone appears to promote cellular release of LC-1. The difference in distribution of cellular LC-1 in BAL cells ex vivo and in vitro may reflect adherence and/or activation.