Role of the cystine-knot motif at the C-terminus of rat mucin protein Muc2 in dimer formation and secretion

DNA constructs based on the 534-amino-acid C-terminus of rat mucin protein Muc2 (RMC), were transfected into COS cells and the resultant (35)S-labelled dimers and monomers were detected by SDS/PAGE of immunoprecipitates. The cystine-knot construct, encoding the C-terminal 115 amino acids, appeared in cell lysates as a 45 kDa dimer, but was not secreted. A construct, devoid of the cystine knot, failed to form dimers. Site-specific mutagenesis within the cystine knot was performed on a conserved unpaired cysteine (designated Cys-X), which has been implicated in some cystine-knot-containing growth factors as being important for intermolecular disulphide-bond formation. Dimerization of RMC was effectively abolished. Each cysteine (Cys-1-Cys-6) comprising the three intramolecular disulphide bonds of the cystine knot was then mutated. Dimer formation was impaired in each case, although much less so for the Cys-3 mutant than the others. Abnormal high-molecular-mass, disulphide-dependent aggregates formed with mutations Cys-1, Cys-2, Cys-4 and Cys-5(,) and were poorly secreted. It is concluded that the intact cystine-knot domain is essential for dimerization of the C-terminal domain of rat Muc2, and that residue Cys-X in the knot plays a key role. The structural integrity of the cystine knot, maintained by intramolecular bonds Cys-1-Cys-4, Cys-2-Cys-5 and Cys-3-Cys-6, also appears to be important for dimerization, probably by allowing correct positioning of the unpaired Cys-X residue for stable intermolecular cystine-bond formation.

[Antioxidation of flavones of wheat germ on mammary tumor of rats]

The effect of flavonoids of wheat germ on mammary tumor of rats induced by 7,12-dimethylben(a) anthracene (DMBA) was investigated. Sprague-Dawley female rats (50 day-old, weighted around 176 g) were randomly divided into 4 groups. The negative and positive control group were fed on stoke diet. The high and low dose test groups were fed on diets with wheat germ flavonoids 10 and 2 g/kg respectively. Except rats in the negative control group, each rat was given DMBA 15 mg dissolved in 1.5 ml vegetable oil by tube feeding. After the administration of DMBA for 24 weeks, the incidence of tumor in the high dose test group was lower than that in the positive control group. The activity of blood and liver glutathione peroxidase (GSH-Px) and peroxidase dismutase(SOD) in the test groups was significantly higher than those in the positive control group, while the MDA level was significantly lower. The results suggested that the effect of flavonoids on inducing peroxidase might be one of the chemical prevention mechanisms on mammary tumors.

Regulation of alpha-smooth muscle actin and CRBP-1 expression by retinoic acid and TGF-beta in cultured fibroblasts

We have reported that Cellular Retinol Binding Protein-1 (CRBP-1) is expressed de novo during skin wound healing by a proportion of fibroblastic cells which then differentiate into myofibroblasts and express alpha-smooth muscle actin. In fibroblasts cultured from different tissues we have shown that alpha-smooth muscle actin expression, mainly controlled by Transforming Growth Factor-beta (TGF-beta), is also regulated by retinoic acid and that CRBP-1, known to be a retinoic acid-responsive gene, is modulated by TGF-beta. The aim of the present study has been to investigate the relationships between retinoic acid and TGF-beta in regulating the expression of CRBP-1 and alpha-smooth muscle actin in cultured rat subcutaneous tissue fibroblasts. We have observed that the TGF-beta-induced, but not the retinoic acid-induced, alpha-smooth muscle actin expression is associated with a modulation of endogenous TGF-beta and TGF-beta receptors, suggesting that the action of retinoic acid on alpha-smooth muscle actin expression is not mediated by TGF-beta. The expression of CRBP-1 is regulated at the transcriptional level by TGF-beta and retinoic acid but not synergistically, suggesting a possible common pathway. However, retinoic acid, but not TGF-beta, increases the transcription of a transiently transfected chimeric construct containing the retinoic acid response element of the CRBP-1 promoter, indicating that TGF-beta does not influence CRBP-1 through the retinoic acid pathway. Our results indicate that distinct pathways regulate the genes involved in the appearance and evolution of the myofibroblastic cells. The characterization of these pathways will be helpful for the design of drugs influencing wound healing.

[Subtotal laryngectomy reconstructed by platysma myocutaneous flaps]

OBJECTIVE

To study the feasibility, surgical techniques and the results of laryngeal function preservation during subtotal laryngectomy in laryngeal carcinoma.

METHODS

A retrospective review was made of 13 patients treated by subtotal laryngectomy and laryngeal reconstruction from 1991 to 1996. Eleven patients were male and 2 were female. The age ranged from 46 to 72 years, with a mean of 53.25. All cases were of stage IV. The essence of this operation is to reconstruct the new larynx with two platysma myocutaneous flaps following subtotal laryngectomy.

RESULTS

The success rate of voice rehabilitation was 100%. Among them, the acceptability rating scores in 11 cases were 7 and the intelligibility scores ranged from 95% to 98%. The other two cases had acceptability 5 and intelligibility form 90% to 94%. The three-year survival rate was 84.6% (11/13), 5-year survival rate was 76.9% (10/13).

CONCLUSION

This form of laryngeal reconstruction in subtotal laryngectomy is helpful to restore laryngeal function and decrease the rate of total laryngectomy. The procedure is easy, safe and applicable to patients treated by subtotal laryngectomy.

[Observation on the kinetic process in replantation of the recurrent laryngeal nerve of the dog]

OBJECTIVE

In order to provide experimental foundation for replantation in the recurrent laryngeal nerve(RLM) of the laryngeal reconstruction and laryngeal transplantation.

METHOD

The left RLN of ten caine dogs were cut. The histopathology of the cut RLN were observed under the microscope after operation (two dogs) and 3.5 hours later (two dogs). Meanwhile the RLN were sewed up under the microscope at once. The kinetic process in regeneration of the RLN were observeded 1 week (two dogs), 2 week (two dogs) and 4 week (two dogs) after the replantation.

RESULT

The replantation of RLN of six dogs succeeded.

CONCLUSION

The results confirmed that sewing up the cut RLN at once is helpful to get normal regeneration in the replantation.

[Composition and structure of bioflocculant BP25]

A strain of Bacillus megaterium screened from activated sludge could produce exocellular flocculant. The flocculant was purified through ethanol precipitation and Sephadex S-500 column chromatography. The purified flocculant BP25 was assayed by Bradford reaction, agarose gel electrophoresis and Sulfate-phenol method. The results showed that BP25 was a kind of polysaccharide which contains 36.97% O, 6.28% H, 47.00% C, 0% No NMR assay showed BP-25 contains no uronic acid. Gas-chromatography assay combined with thin-layer chromatography of acid hydralate revealed that BP25 contains Glucose and Mannose with the mole ratio of 4:1. Methylation analysis revealed the polysaccharide contains alpha-1, 6 glycosidicbond and alpha-1, 3 glycosidicbond. The main chains are comprised of Glucose and all the Mannose are in the side chains. Possible repeating unit structure was deduced.

[Prognostic influence of parapharyngeal space involvement in nasopharyngeal carcinoma]

OBJECTIVE

To explore the prognostic influence of parapharyngeal space involvement in nasopharyngeal carcinoma (NPC).

METHODS

From Jan. 1987 to Dec. 1994, 197 previously untreated NPC patients were examined by CT scan. The prognostic factors ware evaluated by univariate and multivariate analyses on SPSS 8.0 software.

RESULTS

The actual survival rate, disease-free survival rate and local failure-free rate were negatively affected by the presence of parapharyngeal space involvement (P = 0.0115, P = 0.0035, P = 0.0367). The 5-year actual survival rate, disease-free survival rate and local failure-free rate in patients without tumor invasion to parapharyngeal space was 87.9%, 88.0% and 96.9%, respectively. The survival rate in patients with tumor invasion to prestyloid space was 75.0%, 71.2% and 93.7%, respectively. That in patients with tumor invasion to poststyloid space was 60.5%, 57.7% and 86.8%, respectively. The 5-year distant metastasis-free survival rate was 88.1% in patients without poststyloid involvement as compared to 73.8% in those with poststyloid involvement.

CONCLUSION

The survival and local tumor control are affected by parapharyngeal space involvement. Distant metastasis is more likely to occur when the tumor growth involves poststyloid space.

[Evaluation on the cytotoxicity of Gallium alloy by MTT-assay]

OBJECTIVE

To test the cytotoxicity of Gallium alloy, a new mercury-free dental restorative material.

METHODS

L-929 mouse fibroblasts were used to detect the cell relative proliferation rate of Gallium alloy and high-copper amalgam by MTT-assay.

RESULTS

The results indecated that the relative growth rate induced by Gallium alloy was high (93.0% +/- 4.9% 2ds, 102.0% +/- 3.5% 4ds, 107.2% +/- 4.2% 7ds), and the cytotoxicity of Gallium alloy was 0 grade according to the Test Standard of Shanghai Medical Biomaterial, meaning Gallium alloy had no significant cytotoxicity and the relative growth rate of Gallium alloy was higher than that of high-copper amalgam. The high-copper amalgam showed medium cytotoxicity.

CONCLUSION

Gallium alloy has no significant cytotoxicity.

Mechanisms of wood degradation by brown-rot fungi: chelator-mediated cellulose degradation and binding of iron by cellulose

Iron, hydrogen peroxide, biochelators and oxalate are believed to play important roles in cellulose degradation by brown-rot fungi. The effect of these compounds in an 'enhanced' Fenton system on alpha-cellulose degradation was investigated specifically in regard to molecular weight distribution and cellulose-iron affinity. This study shows that the degradative ability of an ultrafiltered low molecular weight preparation of chelating compounds isolated from the brown-rot fungus Gloeophyllum trabeum (termed 'Gt chelator') increased with increasing Gt chelator concentration when the FeIII to Gt chelator ratio was greater than about 30:1. When this ratio was less than 30:1, increasing Gt chelator concentration did not accelerate cellulose degradation. In excess hydrogen peroxide, cellulose degradation increased and then decreased with increasing iron concentration when FeIII was present in excess of the Gt chelator. The critical ratio of FeIII to Gt chelator varied depending on the concentration of hydrogen peroxide in the system. Increasing iron concentration above a critical iron:chelator ratio inhibited cellulose degradation. The optimum pH for cellulose degradation mediated by Gt chelator was around 4.0. A comparison of the effects of 2,3-DHBA (a chelator that reduces iron similarly to Gt chelator) and Gt chelator with respect to cellulose degradation demonstrated the same pattern of cellulose degradation. Cellulose-iron affinity studies were conducted at three pH levels (3.6, 3.8, 4.1), and the binding constants for cellulose-FeIII, cellulose-FeII and cellulose-FeIII in the presence of Gt chelator were calculated. The binding constants for cellulose-FeIII at all three pH levels were much higher than those for cellulose-FeII, and the binding constants for cellulose-FeIII in the presence of Gt chelator were very close to those for cellulose-FeII. This is probably the result of FeIII reduction to FeII by Gt chelator and suggests that chelators from the fungus may be able to sequester iron from cellulose and reduce it in near proximity to the cellulose and thereby better promote depolymerization. The free radical generating system described has potential for use in a variety of industrial processing and pollution control applications.

Ultraviolet radiation-induced photoproducts in human skin DNA as biomarkers of damage and its repair

We have developed a 32P-postlabelling method for quantifying ultraviolet irradiation (UV)-induced cyclobutane dimers and 6-4 photoproducts in human skin in situ. We review the application of the method in studies with human volunteers, demonstrating dose-response relationships over a wide range of administered doses, repair kinetics of UV-damaged DNA among healthy individuals and melanoma patients, and modulation by sunscreens, tan and constitutive pigmentation of damage induction. A notable finding is the wide interindividual variation in DNA damage immediately after irradiation and in its repair. Moreover, the protective effects of sunscreens against erythema and DNA damage also show wide interindividual variation. These results cannot be explained by variation in the experimental methods used. The worst-case scenario is that the differences between individuals are multiplicative, resulting in 1000-fold differences in sensitivity in the population, which would be likely to translate into differences in risk of skin cancer.

[Effect of Zn2+, Cd2+ and their combined on Ca, Fe and Mn uptake by wheat seedlings]

The effect of Zn, Cd and their combination on Ca, Fe and Mn uptake by wheat seedlings was studied with solution culture. The result shows the Zn and Cd contents of wheat increased with increasing concentrations of Zn2+ and Cd2+ in solution, while there was a difference between single and compound treatments. Zn affected Cd uptake by wheat, and Cd inhibited Zn uptake. The uptake of Ca and Mn reduced with the increase of Zn2+ and Cd2+ in solution. The uptake of Fe increased with increasing Zn2+ and Cd2+ concentrations in single treatment, while decreased in compound treatment. The interactive effect of Zn and Cd was also related to the parts of plants.

[Studies on the immobilized penicillin acylase on polymer beads]

The extracellular penicillin acylase from Bacillus megaterium was immobilized on oxirane group of Eupergit C beads. The apparent activity of the immobilized enzyme was about 1400 u.g-1 (dry weight). The optimal pH and temperature were 8.0 and 55 degrees C for hydrolytic reaction of penicillin G, respectively. The immobilized enzyme was stable in the pH range of 6.0-8.5 and at temperature below 45 degrees C. The apparent Michaelis constant for penicillin G was inhibition constant of phenylacetic acid as competitive 2 x 10(-2) mol.L-1 and Vm was 1.33 mmol.g-1 min-1 (dry weight) at 37 degrees C and PH8.0. The inhibitor and 6-APA as non-competitive inhibitor were 2.8 x 10(-2) mol.L-1 and 0.125 mol.L-1 for the immobilized enzyme at pH 8.0 and 37 degrees C, respectively. The remained activity of the immobilized enzyme was about 80% after operating 200 times for hydrolysis of penicillin G to 6-APA, and the average yield of 6-APA was 89.48%.

[Expressions of vascular endothelial growth factor and basic fibroblast growth factor in nasal polyp and its role]

OBJECTIVE

To evaluate the role of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor(bFGF) in the pathophysiology of nasal polyp.

METHODS

Thirty-nine patients with nasal polyp were divided into two groups: group A(representing type 1 and type 2 phase 1-2) and group B (representing type 2 phase 3 and type 3). The expression of VEGF and and bFGF in both groups were studied with immunohistochemical method.

RESULTS

VEGF and bFGF were not detected in norms. The detection rates of VEGF and bFGF were 59%, 41%, and 71%, 80% in group A and group B respectively. The positive rate and the number of positive cells were higher significantly in group B than that in group A. VEGF and bFGF were located mainly in the inflammatory cells and epithelial cells around the basilar membrane and inflammatory cells and endothelial cells around the vessel.

CONCLUSIONS

The overexpression of VEGF and bFGF in nasal polyp may contribute to the growth of vessels, accumulation of inflammatory cells, as a result, to enhance the development of nasal polyposis. This phenomenon maybe an important histological mark distinguishing ordinary polyp from polyposis.

Angiogenesis inhibition in the in vivo antineoplastic effect of manumycin and paclitaxel against anaplastic thyroid carcinoma

Our laboratory has investigated the anticancer effects of combined manumycin (a farnesyltransferase inhibitor) and paclitaxel (a microtubule inhibitor) against anaplastic thyroid carcinoma (ATC). In this study we reported the in vivo efficacy of this combination against ATC cells and the lack of toxicity of this treatment in mice. We observed that manumycin-treated tumors looked paler than both control and paclitaxel-treated tumors. We hypothesized that angiogenesis inhibition mediated part of the in vivo effect of manumycin. This hypothesis was supported by the findings that manumycin significantly inhibited angiogenesis (as directly demonstrated by measurement of hemoglobin content and vascular area) in Matrigel implanted into mice, that manumycin decreased the vascular endothelial growth factor in hypoxic ATC cells, and that both manumycin and paclitaxel inhibited endothelial cell proliferation. Interestingly, inhibition of endothelial tubule formation in Matrigel was enhanced by combining manumycin and paclitaxel. As angiogenesis and tumor growth are continuous processes, we investigated the effect of sustained delivery of manumycin and found that paclitaxel plus slow release manumycin (13.25 mg/kg x week) inhibited ATC xenografts more than paclitaxel plus intermittent manumycin (15 mg/kg x week). In conclusion, manumycin plus paclitaxel is an effective combination against ATC, and inhibition of angiogenesis plays a role in the antineoplastic effect of this combination.

Self-assembled monolayers from a designed combinatorial library of de novo beta-sheet proteins

A variety of naturally occurring biomaterials owe their unusual structural and mechanical properties to layers of beta-sheet proteins laminated between layers of inorganic mineral. To explore the possibility of fabricating novel two-dimensional protein layers, we studied the self-assembly properties of de novo proteins from a designed combinatorial library. Each protein in the library has a distinct 63 amino acid sequence, yet they all share an identical binary pattern of polar and nonpolar residues, which was designed to favor the formation of six-stranded amphiphilic beta-sheets. Characterization of proteins isolated from the library demonstrates that (i) they self assemble into monolayers at an air/water interface; (ii) the monolayers are dominated by beta-sheet secondary structure, as shown by both circular dichroism and infrared spectroscopies; and (iii) the measured areas (500- 600 A(2)) of individual protein molecules in the monolayers match those expected for proteins folded into amphiphilic beta-sheets. The finding that similar structures are formed by distinctly different protein sequences suggests that assembly into beta-sheet monolayers can be encoded by binary patterning of polar and nonpolar amino acids. Moreover, because the designed binary pattern is compatible with a wide variety of different sequences, it may be possible to fabricate beta-sheet monolayers by using combinations of side chains that are explicitly designed to favor particular applications of novel biomaterials.

Covalent inhibition revealed by the crystal structure of the caspase-8/p35 complex

Apoptosis is a highly regulated process that is crucial for normal development and homeostasis of multicellular organisms. The p35 protein from baculoviruses effectively prevents apoptosis by its broad-spectrum caspase inhibition. Here we report the crystal structure of p35 in complex with human caspase-8 at 3.0 A resolution, and biochemical and mutagenesis studies based on the structural information. The structure reveals that the caspase is inhibited in the active site through a covalent thioester linkage to p35, which we confirmed by gel electrophoresis, hydroxylamine treatment and mass spectrometry experiments. The p35 protein undergoes dramatic conformational changes on cleavage by the caspase. The repositioning of the amino terminus of p35 into the active site of the caspase eliminates solvent accessibility of the catalytic dyad. This may be crucial for preventing hydrolysis of the thioester intermediate, which is supported by the abrogation of inhibitory activity through mutations at the N terminus of p35. The p35 protein also makes conserved contacts with the caspase outside the active-site region, providing the molecular basis for the broad-spectrum inhibitory activity of this protein. We demonstrate a new molecular mechanism of caspase inhibition, as well as protease inhibition in general.

Continuous crystalline carbonate apatite thin films. A biomimetic approach

In contrast to extensive studies on hydroxyapatite thin films, very little has been reported on the thin films of carbonated apatite (dahllite). In this report, we describe the synthesis and characterization of a highly crystalline dahllite thin film assembled via a biomimetic pathway. A free-standing continuous precursor film of carbonated calcium phosphate in an amorphous phase was first prepared by a solution-inhibited templating method (template-inhibition) at an air-water interface. A stearic acid surface monolayer acted as the template, while a carbonate-phosphate solution composed a binary inhibition system. The precursor film formed at the air/water interface was heated at 900 degrees C and transformed into a dense crystalline film that retained the overall shape of the precursor. The crystalline phase was characterized by XRD and IR to be a single-phase carbonate apatite, with carbonate substitutions in both type A (OH-) and type B (PO4(3-)) lattice positions.

Inhibition of corticotropin releasing hormone type-1 receptor translation by an upstream AUG triplet in the 5' untranslated region

The influence of an upstream open reading frame (ORF) in the 5'-untranslated region (UTR) of the mRNA on corticotropin-releasing hormone receptor type 1 (CRHR1) translation was studied in constructs containing the 5'-UTR of CRHR1, with or without an ATG-to-ATA mutation in the upstream ORF, and the main ORF of luciferase or CRHR1. Upstream mutation in luciferase constructs increased luciferase activity when transfected into COS-7 or AtT20 cells compared with the native 5'-UTR. Transfection of CRHR1 constructs containing the upstream mutation into AtT20 or LVIP2.0zc reporter cells, resulted in higher (125)I-Tyr-oCRH binding and corticotropin-releasing hormone-stimulated cAMP production, without changes in CRHR1 mRNA levels (measured by RNase protection assay). In vitro translation of luciferase or CRHR constructs with or without mutation of the upstream ATG, and Western blot analysis with anti-luciferase and anti-CRHR1 antibodies confirmed that mutation of the upstream ATG increases translation of the main ORF. The mechanism by which the upstream ORF inhibits translation may involve translation of the upstream peptide, because in vitro translation, or transfection into LVIP2.0zc cells of a fusion construct of the upstream ORF and green fluorescent protein (GFP) yielded a band consistent with the molecular size of GFP protein. The study shows that the upstream AUG in 5'-UTR of CRHR1 mRNA inhibits receptor expression by inhibiting mRNA translation and suggests the short open reading frame in the 5'-UTR plays a role in regulating translation of the CRH receptor.

[Change of inhabitant dietary pattern in Shandong province during 1988-1997]

Food consumption data of some bigger cities and towns of Shandong province during 1988-1997 had been collected and analyzed. The results showed that the consumption of cereals and vegetable in 1997 tended to be decreased and the consumption of meat, egg, fruit and milk in 1997 tended to be increased. The desirable dietary pattern (DDP) scores for cities and towns were 82.5, 78.7 in 1988, and 93.3, 88.4 in 1997 respectively. All these changes indicated that the dietary quality improved markedly but the consumption of bean and milk are not enough.

Novel 2,5-hexanedione analogues. Substituent-induced control of the protein cross-linking potential and oxidation susceptibility of the resulting primary amine-derived pyrroles

The neurotoxic gamma-diketone, 2,5-hexanedione (2,5-HD), induces neurofilamentous swellings at prenodal sites in proximal axons as a consequence of pyrrolation of lysine epsilon-amino groups on neurofilament proteins. However, there is disagreement as to whether pyrrole formation and the associated alteration of noncovalent interactions is sufficient to cause neurofilament accumulation, or whether pyrrole autoxidation and subsequent protein-protein cross-linking is an obligatory event. To investigate gamma-diketones that might form pyrroles inert to autoxidative-induced cross-linking, we synthesized 1,1,1-trifluoro-2,5-hexanedione, 3-(trifluoromethyl)-2,5-hexanedione (3-TFMHD), and two 3-(dialkylaminocarbonyl)-2,5-diketones and assessed their rates of pyrrole formation with amines, the oxidation susceptibility of the resulting pyrroles, and the protein cross-linking potential in vitro, relative to those of 3-methyl-2,5-hexanedione. 1,1,1-Trifluoro-2,5-hexanedione does not form pyrroles, but the three 2,5-HD analogues with an electron-withdrawing 3-substituent all rapidly formed pyrroles that were inert to autoxidation. Although 3-TMFHD nonetheless still induced cross-linking of ribonuclease A, by a nonoxidative mechanism independent of the pyrrole, the two 3-(dialkylaminocarbonyl)-2,5-diketones did not exhibit any protein cross-linking. As these two gamma-diketones possess aqueous-organic partitioning properties similar to those of 2,5-HD, they should serve as useful mechanistic probes in further studies.

[Research on fibrotic effect of Ni-Ti and 317L alloys in esophagus]

This study was conducted to examiune the fibrotic effect of Ni-Ti and 317L alloys in esophagus. The extract fluid from Ni-Ti, 317L alloys was made according to the ASTM standards of U.S.A. The Fb of esophageal scar was cultured primarily, then incubated with alloy abstract fluid. The proliferating activity of Fb was measured by MTT at 4, 24, 48, 72 hours in the course of culturing. The esophagus embedding test of Ni-Ti, 317L alloys was made according to ASTM standards of U.S.A. The tissue around the alloys was taken at weeks 2 and 12, and the pathologic changes were analysed. The results showed that Ni-Ti, 317L extract could depress the proliferating function of Fb gently, and the depressing action increased gradually with the culturing time. The result of embedding test was in accord with the ASTM standards of U.S.A. completely; the fibrotic membrane around the NiTi, 317L alloys became thinner with embedding time. These findings suggested that the scattering composition of Ni-Ti, 317L in body fluid might not activate the proliferating and secreting function of Fb, and the two alloys could not lead to fibrosis of esophagus aroun them.