[Significance of pathological type in cervical lymph metastasis of laryngeal cancer]

To research significance of pathological type in cervical lymph metastasis of laryngeal cancer. Observing metastasis lymph nodes in serial sections of 55 cases neck dissection specimens with microscope. Single type 21 cases, 90% of them were occult metastasis, three-year survival rate was 90%. Multiple types 10 cases, 70% of them were occult metastasis, three-year survival rate was 70%. Gathering type 24 cases, 92% of them can be palpated by physician, three-year survival rate was 54%. It is suitable that cervical metastasis lymph nodes of laryngeal cancer were divided into three types in pathology. It is significance for treatment and prognosis.

Characterization and functional analysis of the cis-autoproteolysis active center of glycosylasparaginase

Glycosylasparaginase is an N-terminal nucleophile hydrolase and is activated by intramolecular autoproteolytic processing. This cis-autoproteolysis possesses unique kinetics characterized by a reversible N-O acyl rearrangement step in the processing. Arg-180 and Asp-183, involved in binding of the substrate in the mature enzyme, are also involved in binding of free amino acids in the partially formed substrate pocket on certain mutant precursors. This binding site is sequestered in the wild-type precursor. Binding of free amino acids on mutant precursors can either inhibit or accelerate their processing, depending on the individual mutants and amino acids. The polypeptide sequence at the processing site, which is highly conserved, adopts a special conformation. Asp-151 is essential for maintaining this conformation, possibly by anchoring its side chain into the partially formed substrate pocket through interaction with Arg-180. The reactive nucleophile Thr-152 is activated not only by deprotonation by His-150 but also by interaction with Thr-170, suggesting a His-Thr-Thr active triad for the autoproteolysis.

Site-directed mutagenesis of essential residues involved in the mechanism of bacterial glycosylasparaginase

Flavobacterium glycosylasparaginase was cloned in an Escherichia coli expression system. Site-directed mutagenesis was performed at residues suggested to be important in the catalytic mechanism based on the crystal structure of the human enzyme and other biochemical studies. In vitro autoproteolysis allowed the mutant enzymes to be activated, including those that were slow to self-cleave. Based on the activity of the mutant enzymes, six catalytically essential amino acids were identified: Trp-11, Asp-66, Thr-152, Thr-170, Arg-180, and Asp-183. Kinetic analysis of each mutant further defined the function of these residues in substrate specificity and reaction rate. Mutagenesis of the N-terminal nucleophile residue Thr-152 confirmed the key function of its side-chain hydroxyl group. Partial activities of mutants T152S/C were in agreement with the general mechanism of N-terminal nucleophile (Ntn)-amidohydrolases. The side-chain hydroxyl of Thr-170 contributes to the reaction rate based on studies of mutants T170S/C/A. Residues Asp-183 and Arg-180 were found to H-bond, respectively, with the charged alpha-amino and alpha-carboxyl group of the substrate (Asn-GlcNAc). Mutants R180Q/L and D183E/N had greatly decreased substrate affinity and reduced reaction rates. Kinetic studies also showed that Trp-11 is involved in regulation of the enzyme reaction rate, contradictory to a previous suggestion that this residue is involved in substrate binding. Asp-66 is a new residue found to be important in enzyme activity. The overall active site structure involving these catalytic residues resembles the glutaminase domain of glucosamine 6-phosphate synthase, another member of the Ntn-amidohydrolase family of enzymes.

Crystal structure of glycosylasparaginase from Flavobacterium meningosepticum

The crystal structure of recombinant glycosylasparaginase from Flavobacterium meningosepticum has been determined at 2.32 angstroms resolution. This enzyme is a glycoamidase that cleaves the link between the asparagine and the N-acetylglucosamine of N-linked oligosaccharides and plays a major role in the degradation of glycoproteins. The three-dimensional structure of the bacterial enzyme is very similar to that of the human enzyme, although it lacks the four disulfide bridges found in the human enzyme. The main difference is the absence of a small random coil domain at the end of the alpha-chain that forms part of the substrate binding cleft and that has a role in the stabilization of the tetramer of the human enzyme. The bacterial glycosylasparaginase is observed as an (alphabeta)2-tetramer in the crystal, despite being a dimer in solution. The study of the structure of the bacterial enzyme allows further evaluation of the effects of disease-causing mutations in the human enzyme and confirms the suitability of the bacterial enzyme as a model for functional analysis.

[Clinical and pathological study on cervical lymph node metastasis of supraglottic cancer]

AIM

To study pathological features of cervical lymph node metastasis and the relationship between supraglottic cancer and cervical lymph node metastasis.

METHOD

Observation of 100 whole-organ serial sections of the larynges and 170 sides of the radical neck dissection specimens.

RESULTS

1. Cervical lymph node metastasis 55 cases, metastatic rate 55%; 2. Four series of cervical metastasis: clinico-pathologic metastases (29 cases), pathologic metastases (26 cases), clinical metastases (5 cases), no metastasis (40 cases). 3. Four stages of metastatic lymphnode: early stage, growth stage, fullness stage and capsular perforative stage; 4. Three types of metastases: single type (21 cases), multiple type (10 cases) and aggregated (24 cases) type. 5. Metastatic rates of supraglottic cancer of different regions: aryepiglottic fold 85.7%, arytenoid cartilage area 66.6%, epiglotto-ventricular fold 56.8%, epiglottic 46.4%, ventricular fold 45.4%. 6. When the tumour spread to the perilaryngeal region, the metastatic rate was 80% to 84%.

CONCLUSION

Metastatic rate of cervical lymph node is higher in supraglottic cancers, the aggregated type and capsular perforative stage are more in metastasis lymph nodes. Analysis the original sites of supraglottic cancer is conductive to the prediction of the cervical lymph node metastasis.

Cloning and biochemical characterization of an anionic peroxidase from Zea mays

We have isolated, cloned and characterized a cDNA from Zea mays L., denoted ZmAP1, coding for an anionic peroxidase. The open reading frame of ZmAP1 starting 72 residues from the 5' end of the cDNA predicts a 37,778 dalton protein of 356 amino acid residues. The protein has high similarity to other peroxidases and contains two peroxidase motifs that carry two highly conserved histidines in the active center. We expressed recombinant ZmAP1 protein in E. coli as a fusion with maltose-binding protein. The fusion protein was biochemically active after addition of hemin to the apoprotein. The maize peroxidase ZmAP1 has a pH optimum at pH 4.0 and a Km of 0.2 mM for the substrate 2,2'-azino-bis-(3-ethyl-benzothiazolin-6-sulfonic acid) at this pH. In maize seedlings the ZmAP1 gene is expressed predominantly in roots, the mesocotyl, the coleoptile and to a lower extent in the node, whereas no expression in the primary leaf was found. In situ hybridization shows that the expression of ZmAP1 in the young maize root is confined to the epidermis, hypodermis and the pericycle.

A nodule-specific gene family from Alnus glutinosa encodes glycine- and histidine-rich proteins expressed in the early stages of actinorhizal nodule development

Two cDNAs representing different members (agNt84 and ag164) of a gene family encoding glycine- and histidine-rich proteins have been isolated from cDNA libraries from Alnus glutinosa root nodules. Expression of the corresponding genes could only be detected in nodules. With in situ hybridization, the expression in nodules was found to occur in young, infected cells of the prefixation zone (zone 2). The encoded proteins contain putative signal peptides for targeting to the endomembrane system, sharing sequence similarity with signal peptides from plant glycine-rich proteins, among them nodulin 24, a nodule-specific protein from soybean. This similarity suggests that, analogous to nodulin-24, proteins encoded by agNt84/ag164 may be located at the interface between the host plant membrane and the matrix surrounding the endosymbiont. The 3' untranslated regions of the cDNAs contain unusual poly(AT)n stretches that may play a role in the regulation of RNA stability. The protein encoded by agNt84 cDNA was expressed in Escherichia coli as a fusion with maltose-binding protein, and was shown to have the ability to bind to a nickel-chelating resin, indicating that it may function as a metal-binding protein.

Nitrogen metabolism in actinorhizal nodules of Alnus glutinosa: expression of glutamine synthetase and acetylornithine transaminase

Two nodule cDNA clones representing genes involved in Alnus glutinosa nitrogen metabolism were analysed. ag11 encoded glutamine synthetase (GS), the enzyme responsible for ammonium assimilation, while ag118 encoded acetylornithine transaminase (AOTA), an enzyme involved in the biosynthesis of citrulline, the nitrogen transport form in Alnus. GS mRNA was found at highest levels in root nodules, where it was present in the infected cells as well as in the cells of the pericycle of the vascular system. AOTA transcripts were found at high levels in nodules, confined to the infected cells, suggesting that in nodules of A. glutinosa, citrulline biosynthesis takes place mainly in the infected cells.

[A study of the relevant factors of removal of common bile duct stones with endoscopic mechanical lithotripsy]

Endoscopic mechanical lithotripsy (EML) was attempted in 41 patients with common bile duct stones unable to be removed by endoscopic sphincterotomy. These patients had altogether 89 stones with stone size ranged from 5 to 30 mm (mean transverse diameter 16.6 +/- 6.0 mm and mean longitudinal diameter 20.0 +/- 7.1 mm). 31 patients had 34 stones greater than or equal to 20 mm in transverse diameter. The overall stone removal rate was 97.6%. The rate of complete removal of the stone fragments with EML at one time was 78.6% (11/14) for large, 58.8% (10/17) for middle and 0 (0/5) for small incision of the sphincter. In patients with diameter of the distal common bile duct greater than or equal to 14 mm and less than 9 mm the rate was 83.3% and 30.8% respectively and the difference was of significance (P < 0.05). The rate of complete removal for using basket and balloon catheter was 6/10 and 4/9 separately and that for combined used of these two methods 83.3% (10/12). The rate of spontaneous passage of the stone (within one week) was 1/5. It is concluded that complete removal of the stone fragments was related mainly to the length of the incision, diameter of distal common bile duct and methods of removing stone fragments after the crush with lithotripsy basket; when the stone is large and there is the no space around the stone for lithotripsy basket manipulation, a large amount of diluted contrast material is injected into the bile duct so as to increase the space and facilitate the ensonaring of the stone with lithotripsy basket. Hard stones can not be crushed easily, so they constitute one of the reasons of failure.

[Preparation of galactosyl-cytochrome C and studies on its hepatic targeting property]

This paper reports the preparation of the coupling compound between thiogalactose and cytochrome C(Cyt-C). The binding tests of this compound to asialoglycoprotein receptor have also been carried out in vivo. The results show that the pharmacokinetics of this compound is in accordance with the basic characteristic of receptor induced binding. The highest uptake of liver reaches to 32.9% and at the same time the conjugate remains 78.6% the biological activity of Cyt-C. It is possibly a hepatic targeting drug or a hepatic targeting carrier.

[The preparation of hepatic receptor imaging agent 99mTc-DTPA-NGA]

The method of preparation and the character of the hepatic receptor imaging agent 99mTc-DTPA-NGA have been presented. The radio-chemical purity of the imaging agent is higher than 95% and the stability of the imaging agent is more than 6 hours in vitro and in human blood. The agent is able to tend to liver and has the character of receptor-intervene-conduct binding. Our comparative study of 99mTc-DTPA-NGA versus 99mTc-NGA reveals, the stability of the former in vitro and in human blood is better than that of the latter. The imaging in rabbits shows that the imaging quality of the former is higher than that of the latter. The radioactive metabolites in urine have been examined. The former does not fall off 99mTc in vivo, but the latter falls off 99mTc clearly. 10 clinical hepatic imagings have had satisfactory results.

Activation of glycosylasparaginase. Formation of active N-terminal threonine by intramolecular autoproteolysis

The activation mechanism of glycosylasparaginase of Flavobacterium meningosepticum has been analyzed by site-directed mutagenesis and activation of purified precursors in vitro. Mutation of Thr-152 to Ser or Cys leads to gene products that are not activated in vivo but are activated in vitro because processing of the mutant precursors is inhibited by certain amino acids in the cell. Kinetic studies reveal that activation is an intramolecular autoproteolytic process. The involvement of His-150 and Thr/Ser/Cys-152 in activation suggests that autoproteolysis resembles proteolysis by serine/cysteine proteases. Multiple functions of the highly conserved active threonine residue are implicated.

Active site and oligosaccharide recognition residues of peptide-N4-(N-acetyl-beta-D-glucosaminyl)asparagine amidase F

Crystallographic analysis and site-directed mutagenesis have been used to identify the catalytic and oligosaccharide recognition residues of peptide-N4-(N-acetyl-beta-D-glucosaminyl)asparagine amidase F (PNGase F), an amidohydrolase that removes intact asparagine-linked oligosaccharide chains from glycoproteins and glycopeptides. Mutagenesis has shown that three acidic residues, Asp-60, Glu-206, and Glu-118, that are located in a cleft at the interface between the two domains of the protein are essential for activity. The D60N mutant has no detectable activity, while E206Q and E118Q have less than 0.01 and 0.1% of the wild-type activity, respectively. Crystallographic analysis, at 2.0-A resolution, of the complex of the wild-type enzyme with the product, N,N'-diacetylchitobiose, shows that Asp-60 is in direct contact with the substrate at the cleavage site, while Glu-206 makes contact through a bridging water molecule. This indicates that Asp-60 is the primary catalytic residue, while Glu-206 probably is important for stabilization of reaction intermediates. Glu-118 forms a hydrogen bond with O6 of the second N-acetylglucosamine residue of the substrate and the low activity of the E118Q mutant results from its reduced ability to bind the oligosaccharide. This analysis also suggests that the mechanism of action of PNGase F differs from those of L-asparaginase and glycosylasparaginase, which involve a threonine residue as the nucleophile.

Crystal structure of endo-beta-N-acetylglucosaminidase H at 1.9 A resolution: active-site geometry and substrate recognition

BACKGROUND

Endo-beta-N-acetylglucosaminidase H (Endo H), an endoglycosidase secreted by Streptomyces plicatus, hydrolyzes the glycosidic bond between the core N-acetyglucosamine residues of asparagine-linked high-mannose oligosaccharides. Endo H is a commonly used reagent in glycobiology research, including the characterization of oligosaccharides in glycoproteins. On-going crystallographic studies of Endo H and related endoglycosidases are aimed at identifying the molecular features that determine the different substrate specificities of these enzymes.

RESULTS

The three-dimensional structure of Endo H has been determined to 1.9 A resolution. The overall fold of the enzyme is that of an irregular (alpha/beta)8-barrel comprising eight beta-strand/loop/alpha-helix units. Units 5 and 6 have very short loop sections at the top of the molecule and their alpha-helices are replaced by sections of extended geometry. The loop of unit 2 includes a small two-stranded antiparallel beta-sheet. A shallow curved cleft runs across the surface of the molecule from the area of units 5 and 6, over the core of the beta-barrel to the area of the beta-sheet of loop 2. This cleft contains the putative catalytic residues Asp130 and Glu132 above the core of the beta-barrel. These residues are surrounded by several aromatic residues. The loop 2 area of the cleft is formed by neutral polar residues, mostly asparagines.

CONCLUSIONS

The structure of Endo H is very similar to that of Endo F1, a closely related endoglycosidase secreted by Flavobacterium meningosepticum. Detailed comparison of the structures of Endo H and Endo F1 supports the model previously proposed for substate binding and recognition, in which the area of loop 2 determines the substrate specificity and the alpha-helices of units 5 and 6 are missing to accommodate the protein moiety of the substrate.

[Single high-dose and fractionated low dose cisplatin in the EP protocol for advanced NSCLC--a prospective randomized trial on 72 patients]

A prospective randomized trial on 72 patients (12 cases in stage III and 60 cases in stage IV) suffering from non-small cell lung cancer (NSCLC) was carried out from January 1993 to March 1994 to assess the immediate results of single high dose DDP and fractionated low doses DDP in the EP (Etoposide and Cisplatin, DDP) protocol. The response rate to the former regimen was 47.1% (16/34) as compared with 39.5% (15/38) of the latter. The difference between these two regimens were not statistically significant (P > 0.10). The former regimen had higher incedence of delayed vomiting (P < 0.01), but the latter had more severe bone marrow suppression (P < 0.05). Without significant difference in renal toxicity (P > 0.10). The authors suggest that, the EP protocol consisting of fractionated doses of DDP, may be more preferrable due to its mild gastro-intestinal toxic reaction and less expensive in the treatment of advanced NSCLC patients. Yet, it is necessary to guard against its renal toxicity and myelosuppression.

[Analysis of 100 cases of precancerous laryngeal lesions]

Hundred cases of precancerous laryngeal lesions were analysed on the basis of clinical pathology. The results showed that there was close relationship between the precancerous laryngeal lesions and voice abuse and long-term heavy smoking. The pathology showed epithelial hyperplasis and mild to severe atypical hyperplasia (heterotype). Scanning electronmicroscopy revealed that the more severe the degree of the epithelial heterotype, the more pleomorphic the shape of cell morphology, margin. Twenty cases had malignant changes later, and the rate of malignant change was high in those with atypical hyperplasia. Some lesions which were taken for polyps clinically and pathologycally could also have malignant changes, so more attention should be paid to these lesions during clinical management.

Crystallization and preliminary crystallographic analysis of two endo-beta-N-acetylglucosaminidases, endo H and endo F1

Endo H and F1 are endoglycosidases that cleave the oligosaccharide moiety of asparagine-linked glycoproteins by hydrolysis of the glycosidic bond in the N,N'-diacetylchitobiose core. The two enzymes are specific for high-mannose oligosaccharides. Here, we report the crystallization and preliminary crystallographic analysis of Endo H and Endo F1. Crystals were grown by hanging drop vapor diffusion methods. Both proteins crystallize from crystallization buffers containing polyethyleneglycol 8000 and zinc acetate as precipitating agents in cacodylate buffer. The crystals of Endo H belong to the tetragonal space group P4(1)2(1)2 (or P4(3)2(1)2) with cell dimensions: a = 85.22 A, c = 89.41 A. The crystals of Endo F1 belong to the hexagonal space group P6(1) (or P6(5)) with cell dimensions: a = 70.61 A, c = 100.32 A. Crystals of both proteins diffract to at least 1.8 A resolution.

[Characterization of receptor-mediated binding of 99mTc-NGA in vitro]

This paper reports results of an assay of the binding of 99mTc-galactosylneoglycoalbumin (NGA) and plasma membranes of the rat liver in vitro. The data showed that 99mTc-NGA could be bound to the membrane receptor with high affinity. Specificity and saturability, and that the amount of membrane-bound 99mTc-NGA varied linearly with the amount of membrane within each reaction tube. The biphasic curve of scatchard plot revealed that 99mTc-NGA was bound to two sites of the receptor with different affinity and concentration (K1 8.4089 x 10(9) L/mol, R1 1.7350 x 10(-12) mol/mg); K2 2.0827 x 10(8) L/mol, R2 6.9530 x 10(-12) mol/mg). Therefore, the authors consider that 99mTc-NGA is a promising hepatic receptor agent for imaging.

One-step rainbow holography using a dual lens with no slit

In this paper one-step rainbow holography that uses a dual lens for recording a three-dimensional diffuse object is discussed. During the exposure process, only one of the lenses is moved so that a synthetic slit formed at the observation position. Both of the lenses can have a shorter focal length, which has the effect of expanding the visual field and narrowing the synthetic slit. This method simplifies the experimental technique needed for synthetic-slit holography.

[The preparation of 99mTc-NGA instant lyophilized kit for hepatic imaging]

The preparation of one-step kit for the 99mTc labelled galactosyl-neo-glycoalbumin (NGA) using SnCl2 reduced method was reported in this paper. We developed a method of quality control and established the optimum scheme of technetium labelling on the basis of exploring the effects of varied labelled conditions on radiochemical purity. Our data indicates : (a) the kit is sterile, pyrogen-free and no toxic effects; (b) the operation is simple and fast; (c) its period of validity lasts no less than 3 months; (d) the radiochemical purity > 95%; (e) the stability of 99mTc-NGA in vitro > 4 hours; (f) the results of animal imaging and clinical probation are satisfactory.

[Pharmacokinetic studies on 99mTc-NGA in human]

Two normal subjects and three patients with hepatic disease were intravenously injected each with a single dose of 99mTc-NGA (galactosyl-neoglycoalbumin), a liver receptor imaging agent. The results showed that pharmacokinetics of 99mTc-NGA accorded with the two compartment open model. In the normal subjects, T1/2 alpha and T1/2 beta averaged 1.65 and 19.39 min respectively, indicating a rapid distribution process and a slow elimination process. There were significant differences in pharmacokinetics of 99mTc-NGA between the normal subjects and the patients with hepatic disease, and therefore the relevant parameters are of importance for the evaluation of hepatic function.

Rainbow holography using a large aperture lens for a full object beam

A method of making rainbow holograms by using a full object beam is described. In this technique we simultaneously use a moving object and a moving imaging lens, instead of using a slit during the exposure process. The position of the synthetic slit is independent of the position of the imaging lens and its focal length. Using this method, a one-step rainbow holographic image with a large visual field and high resolution can be obtained. A theoretical analysis and some experimental results are presented.