Structural characterization of chemically derivatized oligosaccharides by nanoflow electrospray ionization mass spectrometry

Oligosaccharides released from several glycoproteins were derivatized with either 4-aminobenzoic acid 2-(diethylamino)ethyl ester (ABDEAE) (Yoshino, K.; et al. Anal. Chem. 1995, 67, 4028-4031) or 2-aminopyridine. The resulting derivatives were analyzed on a nanoflow electrospray ionization (ESI) quadrupole-inlet time-of-flight mass spectrometer using the low-energy collision-induced dissociation technique. In the MS/MS spectra, the oxonium (b or internal series) and y series ions, which are derived from the multiply charged precursor ions, were predominant and were used for the structural readout. Some oxonium ions that were observed in the low-mass region, but that were not found in the PSD analyses (Mo, W.; et al. Anal. Chem. 1998, 70, 4520-4526), rendered a more detailed structural insight. The oxonium ions at m/z 512.2, which are derived from the fucosylated oligosaccharides of immunoglobulin Y and thyroglobulin, were observed, suggesting that fucosylation had occurred proximal to the outer nonreducing terminus. In addition, the data herein show that structural elucidation can be routinely achieved at a low sample concentration. For the case of ABDEAE derivatives, this can be achieved at the 50 fmol/microL level and with the actual sample consumption at the attomole level using nanoflow ESI MS/MS.

Cocaine-induced hypertension: role of the peripheral sympathetic system

Cocaine causes hypertension at least in part by stimulating the sympathetic nervous system, but it is not clear if this effect is centrally or peripherally mediated. To address this issue we studied the vasoconstrictive effect of cocaine in vivo and in isolated artery segments. In vivo cocaine increased mean arterial blood pressure (MAP) by 40 mmHg within 1 min of administration. Pretreatment with prazosin blocked this response by 62%. With clonidine the pre-cocaine MAP was lower and the hypertensive effect of cocaine was blocked by 50%, indicating an important role for central alpha-adrenergic mechanisms. In isolated rat carotid arteries cocaine-induced vasoconstriction was completely blocked by prazosin, phentolamine, and 6-hydroxydopamine, indicating a clear role for a peripheral effect. However, the relative contribution of the central alpha-adrenergic mechanism to the total vasoconstrictive response of cocaine was not clarified. 1999 Academic Press.

Changes in collagenases and TGF-beta precede structural alterations in a model of chronic renal fibrosis

BACKGROUND

To study the role of collagenases and transforming growth factor-beta (TGF-beta) in the genesis of interstitial fibrosis, we used the model of bromoethylamine (BEA)-induced papillary necrosis, which is known to lead over a period of 1 to 12 months to interstitial fibrosis and renal insufficiency.

METHODS

Rats were injected with BEA, and urine and kidney tissue (cortex and medulla) were collected after 1, 2, 3, 7, and 30 days. One kidney was perfused and fixed for morphological studies and immunostained for collagen type I, III, and IV. The other kidney was used to prepare cortex and medulla extracts for gelatinases (by fluorometric and zymographic techniques), tissue inhibitors of metalloproteinase-1 (TIMP-1), and TIMP-2 (by enzyme-linked immunosorbent assay, ELISA) and TGF-beta1 (by ELISA).

RESULTS

Albuminuria and interstitial fibrosis were present in BEA rats by day 7, which continued until day 30. Immunocytochemical staining for collagen types showed that collagen III and IV increased in the interstitium by day 30, but collagen I remained unchanged. Gelatinase activity in the medulla decreased by 57% compared with control by day 2 and remained low until day 30. In the cortex, gelatinase activity remained unchanged between 0 and 7 days after BEA but decreased by 72% by day 30. TIMP-1 and TIMP-2 were decreased by 80% compared with day 0 in both the medulla (by day 1) and cortex (by day 2) and remained low up to day 30. TGF-beta1 immunoreactivity increased progressively until day 2 in the medulla (16-fold higher than control) and day 3 in the cortex (8-fold higher than control) and returned to control level by day 3 in the medulla and by day 30 in the cortex. Two days after BEA injection, the mRNA for TGF-beta1 was increased eightfold in the cortex and 12-fold in the medulla, and it remained high for up to 30 days.

CONCLUSIONS

The fibrosis that follows papillary necrosis is associated with both high TGF-beta1 expression and depressed gelatinolytic activity.

Carbamylated proteins activate glomerular mesangial cells and stimulate collagen deposition

Carbamylated proteins formed in renal insufficiency from the spontaneous decomposition of urea exert a variety of metabolic effects. Here we examined the effects of carbamylated proteins on glomerular mesangial cells to determine whether urea retention in early renal insufficiency may itself promote glomerular sclerosis and hasten the progression to kidney failure. To this effect we carbamylated fetal bovine serum proteins in vitro and tested their effect on mesangial cell proliferation (by tritiated thymidine uptake), de novo protein synthesis (by tritiated leucine uptake), collagen I and collagen IV accumulation (by avidin-biotin enzyme immunoassay), and gelatinase levels in the medium (by zymography and quantitative fluorescence assay). Carbamylated fetal bovine serum at concentrations present in uremia increased tritiated thymidine incorporation by 50% without altering tritiated leucine incorporation, and it increased collagens I and IV in the monolayer by 150% to 300%. Gelatinase activity was unchanged. We conclude that carbamylated proteins can activate mesangial cells to a profibrogenic phenotype. From a clinical perspective, the carbamylation of proteins by elevated urea levels may accelerate the progression to kidney failure and thus set up a vicious cycle in which the nitrogen retention itself would cause further progression of fibrosis and deterioration of kidney function.

Structural analysis of oligosaccharides derivatized with 4-aminobenzoic acid 2-(diethylamino)ethyl ester by matrix-assisted laser desorption/ionization mass spectrometry

Oligosaccharides derivatized with 4-aminobenzoic acid 2-(diethylamino) ethyl ester (ABDEAE) can be analyzed by ESI (Yoshino, K.; et al. Anal. Chem. 1995, 67, 4028-4031) and MALDI (Takao, T.; et al. Rapid Commun. Mass Spectrom. 1996, 10, 637-640) mass spectrometry. In this study, oligosaccharides derived from the enzymatic cleavage of the sugar chains of glycoproteins ribonuclease B, erythropoietin, and transferrin were subjected to ABDEAE derivatization, prior to analysis on a matrix-assisted laser desorption/ionization time-of-flight mass spectrometer (MALDI-TOF MS) for high-resolution mass measurement and a postsource decay (PSD) experiment. In the mass measurement of ABDEAE derivatives, quasi-molecular ion species have been observed in monoisotopic resolution using 2,5-dihydroxybenzoic acid as the matrix from spots that contain 50-200 fmol of sample; in the PSD analyses from the spots contained 500 fmol-1 pmol of sample, the predominant backbone ion series which covers the entire mass range for all the derivatives, the internal ion series which reflect the branched trimannosyl core structure of N-glycans, and the low m/z fingerprint ion of ABDEAE were consecutively observed, permitting structure elucidation of the oligosaccharides. Given the effectiveness of this derivatization in terms of its high sensitivity and resolution with respect to MALDI-TOF MS, current methodology is clearly applicable to the sensitive detection and accurate structural analysis of N-glycans.

Role of nitric oxide in cocaine-induced acute hypertension

Cocaine causes acute hypertension by blocking catecholamine reuptake. There is evidence that it also impairs the peripheral endothelial nitric oxide system, which is normally vasodilatory. We further explored the role of nitric oxide in cocaine-induced vasoconstriction in anesthetized rats, and in vitro by using isolated carotid artery segments. Cocaine administered intravenously in rats increased mean arterial pressure by 30 to 40 mm Hg within 1 min. This effect was dose dependent and the maximum effect was observed at a dose of 1.25 mg/kg. The prototype catecholamine norepinephrine induced a similar increase in blood pressure. When rats were pretreated with NG-monomethyl-L-arginine (L-NMMA, a blocker of nitric oxide) and challenged with cocaine, the increase in blood pressure was blocked by 80%, whereas pretreatment with L-NMMA did not block norepinephrine-induced vasoconstriction. Both cocaine and norepinephrine also induced an immediate vasoconstriction in isolated carotid artery preparations. The in vitro vasoconstriction induced by cocaine was blocked by pretreatment with L-NMMA, whereas L-NMMA did not block the norepinephrine-induced vasoconstriction in vitro. Furthermore, carotid artery stripped of endothelium responded to norepinephrine but failed to respond to L-NMMA or cocaine. S-nitroso-N-acetyl-D,L-penicillamine (SNAP)-a precursor of nitric oxide- stimulated nitric oxide production in control coronary artery fragments. When these fragments were incubated with cocaine there was a 20% reduction in the production of nitrite oxide. These results suggest that cocaine exerts its peripheral vasoconstriction at least in part by inhibiting local vasodilator nitric oxide.

Effect of glycated proteins on the matrix of glomerular epithelial cells

In this study, cultured glomerular epithelial cells (GEC) were exposed to a diabetic milieu containing glycated proteins to determine whether such proteins cause metabolic alterations that may lead to defects seen in the extracellular matrix in diabetic nephropathy. Cultured glomerular epithelial cells were cloned and maintained in RPMI media containing 10% fetal bovine serum (FBS). The medium was changed to RPMI-1% glycated FBS (experimental) or RPMI-1% control FBS, and cells were incubated for 1 or 4 d. Mitogenicity was tested by 3H-thymidine uptake. The media were collected and analyzed for collagenase activity by a quantitative fluorescence assay and by zymography. The cell layers were processed for matrix antigen (collagen I, glomerular basement membrane antigens, laminin, and fibronectin) and for the proteins of the tight junction (cadherin, desmosomal protein) by quantitative immunoperoxidase and immunofluorescence. Cell lysates were tested for cadherin and desmosomal protein by immunoblotting. Cells were also grown on 0.2-microM filter membranes to test for permeability to 3H-inulin and 125I-albumin. Glycated FBS resulted in a 1.8-fold increase in 3H-thymidine uptake in subconfluent layers accompanied by an increase in cell number. The treatment caused accumulation of laminin (18% above control, P < 0.05) and basement membrane antigens (33% above control, P < 0.05). Collagen I and fibronectin were unchanged. Exposing cells to glycated FBS changed the distribution of cadherin from a linear to a diffuse pattern associated with a decrease in cadherin observed on immunoblots. The media of glycated FBS-treated cells contained 45% lower collagenase activity (72-, 92-, and 150-kD species). Permeability to inulin increased by 550% and to albumin by 320% in glycated FBS-treated monolayers compared with controls. It is concluded that glycated proteins increased the accumulation of matrix proteins in the GEC, associated with a concomitant depression in collagenase activity. There were qualitative and quantitative changes in the tight junction protein cadherin. These matrix changes resulted in a functional defect in the permselective properties of the GEC tight junctions and manifested as increased leakage of inulin and albumin. Thus, the GEC are metabolically sensitive to the presence of glycated proteins, and this could play a role in the pathogenesis of diabetic nephropathy.

Accurate peptide sequencing by post-source decay matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Partial 18O-labeling of peptides has been applied to post-source decay experiments in a matrix-assisted laser desorption/ionization time-of-flight mass spectrometer. The ions which originate from the carboxyl terminus of a peptide partially retain 18O atoms which have readily been incorporated into the C-terminal carboxyl groups during enzymatic hydrolysis in a buffer containing 40 atom percent H218O. The isotopic resolution of singly charged precursor ions and their product ions obtained for peptides up to ca. 2800 Da has been achieved using the delayed extraction method, which permits the rapid identification and assignment of the 18O-labeled and non-labeled ion species in the PSD spectra. The results obtained from several 18O-labeled peptides, derived from an enzymatic digest, demonstrate the accuracy and reproducibility of the present method, which will be in widespread use for protein identification via database searching or for investigations of totally unknown proteins.

[The development of a microcomputerized fetal electrocardiograph]

A new microcomputerized Fetal Electrocardiograph (FECG) is presented in this paper. A two-grade configuration (front-end & back-end) is designed for the instrument. The front-end processor is based on a Digital Signal Processor (DSP) TMS32010 and the Adaptive Noise Cancelling (ANC) algorithm to extract FECG with non-invasive method. The processed results are sent to the back-end personal computer for real time display, analysis and record. Clinical tests show the instrument is designed smartly and operated easily, and can be applied widely to many medical situations.

[Influence of bitumen on burn wounds and their surrounding skin in guinea-pigs]

This study assessed the topical effects of bitumen on burn wounds and their surrounding skin in guinea-pigs. It consisted of three different experiments. The bitumen used in this experiment was a soft tar produced by Daye Steel Plant. The first experiment showed that the skin of the bitumen group marked pathological changes under both light and electron microscopes. The second experiment suggested that healing of the burn wounds of bitumen group was delayed, and less hair follicle counts and a lower intradermal thickness were found as compared with the other groups. The third experiment indicated that the wound edges had been seriously destroyed by bitumen, leading to enlargement of the size of the ulcers, and hypertrophy of scar occurred after healing. It is concluded that bitumen, especially the soft coal tar, has more errosive, irritating and destructive effects, therefore in bitumen burns the bitumen must be immediately and entirely removed from burn wounds.

Epiglottic laryngoplasty after hemilaryngectomy for glottic cancer

Epiglottic laryngoplasty is technically feasible as a one-stage procedure with excellent functional results. Although the Kambic-Sedlacek-Tucker (K-S-T) technique of glottic reconstruction offers early extubation with an adequate airway, a subsequent wide neoglottis may increase the chance of aspiration and a poor voice. To better restore the laryngeal functions of closure and phonation, we made some modifications on the original K-S-T technique as follows: (1) One of the lateral margins of the epiglottis with the aryepiglottic fold is sutured to the arytenoid region of the cricoid rather than a thyroid cartilage remnant. A neo-arytenoid is formed. (2) The other lateral margin of the epiglottis with the aryepiglottic fold is sutured to the cut edge of the false and true cord instead of a thyroid ala remnant. Therefore both margins of the epiglottis with the aryepiglottic folds are lowered as much as possible to the level of the glottis. A new pseudocord is formed. (3) A cartilage cut is made at the anterior aspect of the epiglottis, leaving its laryngeal surface of mucoperichondrial intact. A new anterior commissure with a sharp angle is shaped by this maneuver. Nineteen hemilaryngectomies with modified epiglottic laryngoplasty have been performed by members of the Department of Otolaryngology of Guangxi Medical College since 1984. Results in this series are fairly good and indicate that the modified epiglottic laryngoplasty is effective in enhancing functional results in terms of respiration, deglutition, and phonation.

Epiglottic laryngoplasty after extended hemilaryngectomy for glottic cancer

This paper reports the experience in the application of modified epiglottic laryngoplasty in 20 extended hemilaryngectomies for glottic carcinoma. The Kambic-Sedlacek-Tucker (K-S-T) technique using the epiglottis in glottic reconstruction can lead to early decannulation with an excellent airway, but a wide glottis formed after operation will increase the chance of aspiration and poor voice. Sphincteric function preservation of the glottis is a key point to success in partial laryngectomy. In order to prevent aspiration and to improve the quality of voice, the reconstructive technique as modified as follows: (1) Lateral margin of the epiglottis was sutured to the cricoid. (2) The superior edge of the epiglottis was lowered to reconstruct the ventricular band. (3) A cut was made at the anterior aspect of the epiglottis to reconstruct the anterior commissure. It is the experience of the authors that modified epiglottic laryngoplasty is better than the K-S-T technique for preservation of laryngeal function after extended hemilaryngectomy.