Crystallization at low salt concentration and alkaline pH and preliminary crystallographic data for a monoclinic form of yeast enolase

Yeast enolase (2-phospho-D-glycerate hydrolyase, E.C. 4.2.1.11) has been crystallized by vapor diffusion from a solution containing 22% PEG 4000, 100 mM Tris buffer pH = 9.3, 200 mM Li(2)SO(4). The crystals are monoclinic with a = 122.5, b = 111.8, c = 63.7 A, beta = 95.6 degrees, space group P2(1) and two dimeric molecules are present in an asymmetric part of the unit cell. Crystals have been successfully transferred to an artificial mother liquor, pH = 7.8, 20 mM in Mg(2+) and 5 mM in 2-phospho-D-glycerate. We believe that under these lower salt concentration and more alkaline conditions we should be able to localize the two metal ions that participate in catalysis as well as examine binding of high-affinity inhibitors.

[Studies on the feasibility of detecting circulating antibodies in saliva of Schistosoma japonicum infected rabbits]

AIM

To investigate the feasibility of detecting anti-Schistosoma japonicum antibodies in saliva.

METHODS

Saliva and serum samples of 5 infected, 7 reinfected and 8 treated rabbits were collected at different times periods. The CAb in saliva and serum was detected by using ELISA.

RESULTS

The sensitivity of ELISA was 94.7% for saliva and 100% for serum. The specificity of ELISA was 100% for both saliva and serum.

CONCLUSION

Saliva can be used to detect circulating antibodies for the diagnosis of schistosomiasis japonica.

[Determination of circulating antigen in urine of rabbits infected with Schistosoma japonicum]

AIM

To develop an immunoassay for the detection of circulating schistosome antigen (CSA) in host urine.

METHODS

CSA extracted from the urine of the rabbits infected with Schistosoma japonicum was used for preparing and selecting specific monoclonal antibody. A one-step dot-ELISA using this specific McAb and a 2nd antibody was used for detection of circulating schistosome antigen in the urine of infected rabbits.

RESULTS

No CSA was detected in urine from all of 22 rabbits before infection. The positive rate of CSA in infected rabbits was correlated with the intensity of infection and the time of infection. No CSA was detected in the urine rabbits of 3 weeks after infection with 25 cercariae while the positive rate of CSA in the urine from rabbits infected with 200 cercariae was 40% and 100% after 3 and 6 weeks, respectively. A combination of CSA detection in both urine and serum may increase the detectability.

CONCLUSION

The specific McAb prepared by urine CSA of Schistosoma japonicum-infected rabbits can be used as a probe for detecting CSA in the urine of infected rabbits.

[Application of dot immunogold filtration assay for diagnosis of Schistosomiasis japonica]

AIM

To quest for a simple and convenient assay for the diagnosis of schistosomiasis.

METHODS

Three monoclonal antibodies against different epitopes of antigens of S. japonicum were used to develop a dot immunogold filtration assay for detection of schistosomal antigen-antibody reaction on the membrane during the filtration process. The results could be read with the naked eye within a few minutes.

RESULTS

The sensitivity of the SEA assay was 16 ng/ml. In 69 serum samples from patients with chronic schistosomiasis, the positive rate and specificity of this assay were 60.8% and 95.2%, respectively. Dot-ELISA was used in detecting 137 serum samples from patients with chronic schistosomiasis, the positive rate and specificity were 54.7% and 94.6%, respectively. When sandwich-ELISA was used in detecting 118 serum samples from patients with chronic schistosomiasis, the positive rate and specificity were 61.9% and 95.7%, respectively.

CONCLUSION

The sensitivity and specificity of DIFA were similar to those of ELISA, but DIFA required less time and no special equipment.

[Important prognostic factors in patients with skull base erosion from nasopharyngeal carcinoma after radiotherapy]

OBJECTIVE

To evaluate the long-term outcome and prognostic factors in patients with skull base erosion from nasopharyngeal carcinoma (NPC) after initial radiation therapy.

METHODS

From January 1985 to December 1986, 100 patients (71 male, 29 female) with the diagnosis of NPC were found to have skull base erosion from computed tomography (CT). The mean age was 41 (16-66) years. Ninety-six patients had World Health Organization (WHO) type III undifferentiated carcinoma while four had type I carcinomas. Metastatic workup including chest radiography, liver ultrasound and liver function test were negative. All patients underwent external beam radiotherapy alone to 66-80 Gy over 6-8 weeks. Daily fraction size of 2 Gy was delivered utilizing cobalt-60 or linear accelerator. No patient received chemotherapy. All patients were followed up at regular intervals after irradiation. Median follow-up was 22.3 months (2 months-174 months). Overall survival of the cohort was computed by the Kaplan-Meier method. Potential prognostic factors on survival were examined. Multivariate analyses was performed using Cox regression model.

RESULTS

One, three, five, and ten year overall survival rates for the cohort were 79%, 38%, 27% and 13%, respectively. However, in the sub-group of patients with both anterior cranial nerves (I-VIII) and posterior cranial nerve (IX-XII) involvement had a five-year survival of only 7.7%. Causes of death included local recurrence (59 patients), distant metastases (21 patients), both local recurrence and distant metastases (1 patient) and unrelated causes (5 patients). After multivariate analysis, complete recovery of cranial nerve involvement, cranial nerves palsy and recovery of headache after irradiation were found to be independent prognostic factors in this cohort.

CONCLUSION

This report presents one of the longest follow-ups of patients with nasopharyngeal carcinoma invading skill base. It demonstrates the importance of cranial nerves involvement as well as recovery of headache and cranial nerve palsy. These factors should be evaluated carefully from history and physical examination as well as imaging studies. Currently available magnetic resonance imaging (MRI) is highly recommended as an additional test. A subgroup of patients with skull base involvement had long-term survival after radiotherapy alone. More aggressive strategy such as combined chemo-radiotherapy and altered fractionation radiotherapy may improve outcome in patients with poor prognostic factors.

[The complexity measure and its application to EEG analysis]

In this paper are reviewed the conceptions, characteristics and application of the complexity measure in studying EEG. The reviewers expound the advantages and problems of using complexity measure in the analysis of EEG in different physiological states and deem it a new way to study and understand the human brain function.

[The resource conservation and utilization of wild Sika deer in China]

There had once been six subspecies of Sika deer (Cervus nippon) in China, but now only three subspecies in wild, i.e. Northeast China, Sichuan and South China subspecies, and all the three subspecies lie in the endangered status. Most of population are very small, and their distribution ranges have already been broken up into many isolated patches, furthermore, their habitats have been deteriorating. So it is very necessary to enhance the protecting of wild sika deer. Some endangered and small populations of wild deer can be saved by inflows of domestic health deer. Wild deer can help farm deer to acquire some good characters again by interbreeding between them. So we think that the purposes of protecting wild population and developing domestic population can be achieved by cooperating between reserves and deer farms.

Angiogenic growth factor messenger ribonucleic acids in uterine natural killer cells

Angiogenesis is essential for endometrial growth and repair, and disruption of this process may lead to common disorders of women, including menorrhagia and endometriosis. In pregnancy, failure of the endometrial spiral arterioles to undergo remodeling leads to preeclampsia. Here we report that in addition to vascular endothelial growth factor A (VEGF-A), human endometrium expresses messenger ribonucleic acids (mRNAs) encoding VEGF-C, placenta growth factor (PlGF), the angiopoietins, angiopoietin 1 (Ang1) and Ang2, and the receptors VEGFR-3 (Flt-4), Tie 1, and Tie 2. Levels of VEGF-C, PlGF, and Tie 2 changed during the menstrual cycle. Intense hybridization for VEGF-C and PlGF mRNAs was found in uterine nature killer cells in secretory phase endometrium and for Ang2 mRNA in the same cells in the late secretory phase. Interleukin-2 (IL-2) and IL-15 up-regulated VEGF-C, but not PlGF or Ang2, mRNA levels in isolated NK cells. Conditioned medium from decidual NK cells did not induce human umbilical vein endothelial cell apoptosis. These results indicate that human endometrium expresses a wide range of angiogenic growth factors and that uterine nature killer cells may play an important role in the abnormal endometrial angiogenesis that underlies a range of disorders affecting women.

Pyrido[2,3-d]pyrimidin-7-one inhibitors of cyclin-dependent kinases

The identification of 8-ethyl-2-phenylamino-8H-pyrido[2, 3-d]pyrimidin-7-one (1) as an inhibitor of Cdk4 led to the initiation of a program to evaluate related pyrido[2, 3-d]pyrimidin-7-ones for inhibition of cyclin-dependent kinases (Cdks). Analysis of more than 60 analogues has identified some clear SAR trends that may be exploited in the design of more potent Cdk inhibitors. The most potent Cdk4 inhibitors reported in this study inhibit Cdk4 with IC(50) = 0.004 microM ([ATP] = 25 microM). X-ray crystallographic analysis of representative compounds bound to the related kinase, Cdk2, reveals that they occupy the ATP binding site. Modest selectivity between Cdks is exhibited by some compounds, and Cdk4-selective inhibitors block pRb(+) cells in the G(1)-phase of the cell division cycle.

The crystal structure and amino acid sequence of dehaloperoxidase from Amphitrite ornata indicate common ancestry with globins

The full-length, protein coding sequence for dehaloperoxidase was obtained using a reverse genetic approach and a cDNA library from marine worm Amphitrite ornata. The crystal structure of the dehaloperoxidase (DHP) was determined by the multiple isomorphous replacement method and was refined at 1.8-A resolution. The enzyme fold is that of the globin family and, together with the amino acid sequence information, indicates that the enzyme evolved from an ancient oxygen carrier. The peroxidase activity of DHP arose mainly through changes in the positions of the proximal and distal histidines relative to those seen in globins. The structure of a complex of DHP with 4-iodophenol is also reported, and it shows that in contrast to larger heme peroxidases DHP binds organic substrates in the distal cavity. The binding is facilitated by the histidine swinging in and out of the cavity. The modeled position of the oxygen atom bound to the heme suggests that the enzymatic reaction proceeds via direct attack of the oxygen atom on the carbon atom bound to the halogen atom.

[Modification of surface of Dacron materials by UV irradiation for prevention of microbial adhesion]

UV irradiation grafting method was used to modify the surface of Prosthetic Valve materials (Dacron) for prevention of bacteria-adhesion, and PEG was introduced to the surface of Dacron by this method. The result showed that the chemical magnifying effect of PEG improved the grafting of heparin on the material surface. This method can obviously reduce the number of adherent bacteria.

[Effect of fish oil supplementation on fatty acid composition and neurotransmitters of growing rats]

In order to observe the change of brain fatty acid composition and neurotransmitter by DHA supplementation during the development stage of young rats, pregnant rats were randomly divided into four groups: normal control group (O), low (L), medium (M) and high (H) dose-DHA supplemented groups. The fatty acids composition, the levels of 5-hydroxy-tryptamine (5-HT), dopamine (DA), norepinephrine (NE) and somatostatin (SS) in ceretral cortex and hippocampus of offsprings were measured. The body weight of pregnant rats and offsprings were also observed. The results showed that DHA content of brain homogenate and the levels of 5-HT, DA and SS in hippocampus of experimental young rats were significantly higher than those of the control group. And the body weight of young rats in the three DHA-supplemented groups were retarded in different degree. It was concluded that DHA supplementation changed the fatty acid composition and increased the levels of 5-HT, DA and SS in hippocampus. Proper ratio of n-3 and n-6 fatty acids in dietary supplementation should be considered.

[Study of bacterial adhesion to prosthetic valve materials in vitro]

This article reports a study of the bacterial adhesion to prosthetic valve materials in vitro. The method for assessing the degree of bacterial adhesion to prosthetic valve materials was established primarily. The capacities of staphylococcus aureus(SA), staphylococcus epidermidis(SE), Escherichia Coli(EC) and Pseudomonas aeruginosa(PA) for adhesion to Dacron, Pyrolytic carbon and polytetrofluoroethylene (PTFE) were quantitatively determined by the plate counting and Gamma-ray counting of 125I radiolabeled bacteria in vitro. The results showed that the capacities of four types of bacteria for adhesion to Dacron, Pyrolytic carbon and PTFE coincided with the bacterial-growth curve. The capacities of four bacteria for adhering to Dacron were stronger. The adhesion of SE to Pyrolytic carbon was the strongest. The adhesion of PA Kept up a high level. The capacities of EC and PA for adhering to PTFE were the strongest. The results indicate that the capacities of different types of bacteria for adhesion to the same prosthetic valve material are different, and the capacities of one type of bacteria for adhesion to different materials are also different.

[Modification of the surface of prosthetic valve material by LGDP for protection against microbial adhesion]

This study aimed at the surface modification of prosthetic valve materials by means of cold glow discharge plasma. Orthogonal design was adopted to select the optimal scheme by the experiments of the singular factor, such as output power, gas flow rate, treatment time etc. The PEG-200 was introducted to the surface. Grafting a layer of heparin onto the surface; coating a layer of PEG-like onto the surface first, and then the grafting heparin. Comparing the adhesive amounts of staphylococcus epidermidis (SE), the adhesive curves for Dacron, which was treated by the above methods; the last one is the best.

OmpF changes and the complexity of Escherichia coli adaptation to prolonged lactose limitation

The disaccharide lactose has no specific diffusion pathway across the outer membrane of Escherichia coli. At least three classes of spontaneous mutation affecting outer membrane permeability arose with each of three independent E. coli populations adapting to prolonged lactose limitation in chemostats. Both structural and regulatory mutations affecting OmpF porin predominated in isolates after 210-280 generations of culture. Six types of ompF mutation were found, including in-frame deletions and substitutions at Arg82 and Asp113, all affecting the channel constriction residues of OmpF. Isolates had increased susceptibility to antibiotics and were affected in the quantity of OmpF, LamB and OmpA proteins. A minimum of three or four mutations was evident in all isolates after 280 generations in a lactose-limited environment, in addition to lac mutations defined in previous studies.

Bound structures of novel P3-P1' beta-strand mimetic inhibitors of thrombin

The X-ray crystal structures of four beta-strand-templated active site inhibitors of thrombin containing P1' groups have been determined and refined at about 2.1-A resolution to crystallographic R-values between 0.148 and 0.164. Two of the inhibitors have an alpha-ketoamide functionality at the scissile bond; the other two have a nonhydrolyzable electrophilic group at the P1' position. The binding of lysine is compared with that of arginine at the S1 specificity site, while that of D,L-phenylalanine enantiomorphs is compared in the S3 region of thrombin. Four different P1' moieties bind at the S1' subsite in three different ways. The binding constants vary between 2.0 microM and 70 pM. The bound structures are used to intercorrelate the various binding constants and also lead to insightful inferences concerning binding at the S1' site of thrombin.

Mechanism of triclosan inhibition of bacterial fatty acid synthesis

Triclosan is a broad-spectrum antibacterial agent that inhibits bacterial fatty acid synthesis at the enoyl-acyl carrier protein reductase (FabI) step. Resistance to triclosan in Escherichia coli is acquired through a missense mutation in the fabI gene that leads to the expression of FabI[G93V]. The specific activity and substrate affinities of FabI[G93V] are similar to FabI. Two different binding assays establish that triclosan dramatically increases the affinity of FabI for NAD+. In contrast, triclosan does not increase the binding of NAD+ to FabI[G93V]. The x-ray crystal structure of the FabI-NAD+-triclosan complex confirms that hydrogen bonds and hydrophobic interactions between triclosan and both the protein and the NAD+ cofactor contribute to the formation of a stable ternary complex, with the drug binding at the enoyl substrate site. These data show that the formation of a noncovalent "bi-substrate" complex accounts for the effectiveness of triclosan as a FabI inhibitor and illustrates that mutations in the FabI active site that interfere with the formation of a stable FabI-NAD+-triclosan ternary complex acquire resistance to the drug.

Structure of extracellular tissue factor complexed with factor VIIa inhibited with a BPTI mutant

The event that initiates the extrinsic pathway of blood coagulation is the association of coagulation factor VIIa (VIIa) with its cell-bound receptor, tissue factor (TF), exposed to blood circulation following tissue injury and/or vascular damage. The natural inhibitor of the TF.VIIa complex is the first Kunitz domain of tissue factor pathway inhibitor (TFPI-K1). The structure of TF. VIIa reversibly inhibited with a potent (Ki=0.4 nM) bovine pancreatic trypsin inhibitor (BPTI) mutant (5L15), a homolog of TFPI-K1, has been determined at 2.1 A resolution. When bound to TF, the four domain VIIa molecule assumes an extended conformation with its light chain wrapping around the framework of the two domain TF cofactor. The 5L15 inhibitor associates with the active site of VIIa similar to trypsin-bound BPTI, but makes several unique interactions near the perimeter of the site that are not observed in the latter. Most of the interactions are polar and involve mutated positions of 5L15. Of the eight rationally engineered mutations distinguishing 5L15 from BPTI, seven are involved in productive interactions stabilizing the enzyme-inhibitor association with four contributing contacts unique to the VIIa.5L15 complex. Two additional unique interactions are due to distinguishing residues in the VIIa sequence: a salt bridge between Arg20 of 5L15 and Asp60 of an insertion loop of VIIa, and a hydrogen bond between Tyr34O of the inhibitor and Lys192NZ of the enzyme. These interactions were used further to model binding of TFPI-K1 to VIIa and TFPI-K2 to factor Xa, the principal activation product of TF.VIIa. The structure of the ternary protein complex identifies the determinants important for binding within and near the active site of VIIa, and provides cogent information for addressing the manner in which substrates of VIIa are bound and hydrolyzed in blood coagulation. It should also provide guidance in structure-aided drug design for the discovery of potent and selective small molecule VIIa inhibitors.

[A study on inhibitory effect of plant growth retardants on earlier bolting of Chinese Angelica]

OBJECTIVE

Seeking chemical ways of controlling the earlier bolting of Chinese Angelica (CA).

METHOD

PP333, B9 and MH in different concentrations and combinations were sprayed into the CA leaves in different periods.

RESULTS

In leaf proliferating period the spray could inkibit the earlier bolting, shortening the length of the stem foot, increasing the stem diameter and enhancing the leaf chlorophy 11 contents. The quality of CA production was increased as a result of greater root weight and main root volume. In leaf luxuriatino period the spray showed no marked effect. The growth of the plant would be inhibited by any spray in excessive concentrations.

CONCLUSION

Leaf spray could control the earlier bolting of CA.

Human immunodeficiency virus type 1 subtypes differ in disease progression

At least 10 different genetic human immunodeficiency virus type 1 (HIV-1) subtypes (A-J) are responsible for the AIDS pandemic. Much of the understanding of HIV-1 disease progression derives from studies in the developed world where HIV infection is almost exclusively subtype B. This has led many to question whether the properties and consequences of HIV-1 infection can be generalized across subtypes that afflict the majority of infected persons in the developing world. From 1985 to 1997, a prospective study of registered female sex workers in Senegal tracked the introduction and spread of HIV-1 subtypes A, C, D, and G. In clinical follow-up, the AIDS-free survival curves differed by HIV-1 subtype. Women infected with a non-A subtype were 8 times more likely to develop AIDS than were those infected with subtype A (hazard ratio=8.23; P=. 009), the predominant subtype in the study. These data suggest that HIV-1 subtypes may differ in rates of progression to AIDS.

[A preliminary investigation on causes of failure of vitreoretinal surgery for complicated rhegmatogenic retinal detachments]

OBJECTIVE

To evaluate the failure causes of vitreoretinal surgery for complicated rhegmatogenic retinal detachment.

METHODS

Vitreoretinal (VR) surgery was performed on 477 cases (479 eyes) with complicated rhegmatogenic retinal detachment, the operative procedures including vitrectomy, peeling of pre-retinal membrane, fluid-air exchange, inert gas (SF(6) or C(3)F(8)) or silicone tamponade.

RESULTS

On discharge, the operation was effective in 349 eyes (72.87%) and failed in 130 (27.13%) eyes.

CONCLUSION

The multiple stepwise multivariate regression shows that the factors significantly influencing VR surgery are silicone tamponade, giant retinal tears, SF(6) tamponade, iatrogenic tear, anterior proliferative vitreoretinopathy (PVR), subretinal proliferation, PVR, C(3)F(8) tamponade, operative frequency and choroidal detachments.

Highly selective mechanism-based thrombin inhibitors: structures of thrombin and trypsin inhibited with rigid peptidyl aldehydes

The crystal structures of three highly potent and selective low-molecular weight rigid peptidyl aldehyde inhibitors complexed with thrombin have been determined and refined to R values 0.152-0. 170 at 1.8-2.1 A resolution. Since the selectivity of two of the inhibitors was >1600 with respect to trypsin, the structures of trypsin-inhibited complexes of these inhibitors were also determined (R = 0.142-0.157 at 1.9-2.1 A resolution). The selectivity appears to reside in the inability of a benzenesulfonamide group to bind at the equivalent of the D-enantiomorphic S3 site of thrombin, which may be related to the lack of a 60-insertion loop in trypsin. All the inhibitors have a novel lactam moiety at the P3 position, while the two with greatest trypsin selectivity have a guanidinopiperidyl group at the P1 position that binds in the S1 specificity site. Differences in the binding constants of these inhibitors are correlated with their interactions with thrombin and trypsin. The kinetics of inhibition vary from slow to fast with thrombin and are fast in all cases with trypsin. The kinetics are examined in terms of the slow formation of a stable transition-state complex in a two-step mechanism. The structures of both thrombin and trypsin complexes show similar well-defined transition states in the S1 site and at the electrophilic carbon atom and Ser195OG. The trypsin structures, however, suggest that the first step in a two-step kinetic mechanism may involve formation of a weak transition-state complex, rather than binding dominated by the P2-P4 positions.

[Influence of HPD on immunological functions in patients with nasopharyngeal carcinoma treated by radiotherapy]

Seventy-eight patients with nasopharyngeal carcinoma were equally divided into two groups: 39 patients were treated by HPD plus radiation and 39 patients by radiation alone. Immunological functions were evaluated in each patient before and after radiation. The results showed that (1) in patients treated by RPD and radiation, no statistical difference was observed on immunological functions before and after treatment; (2) in patients treatd by radiation alone, the immunological functions, including OKT3, OKT4, OKT4/OKT8 ratio and lymphocyte transformation, were significantly decreased after treatment. These findings indicate that the immunological functions in patients with nasopharyngeal carcinoma could be protected by HPD during radiotherapy.

[Primary study of bacterial adhesion of prosthetic valve materials]

The adhesion of Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Pseudomonas aeruginosa and Candida albicans to Dacron and pyrolite carbon was measured in vitro with plate counting. The experimental result showed: the bacterials used in the experiment have adhesion to prosthetic valve materials; the bacterials have stronger adhesion to Dacron than to Pyrolite carbon; the bacterial adhesive capacity is significantly different and is affected by mechanical and chemical nature of biomaterials; Staphylococcur aureus has the strongest adhesion to Dacron, and Pseudomonas aeruginosa has the strongest adhesion to pyrolite carbon in all bacterials.

Mechanism of enolase: the crystal structure of asymmetric dimer enolase-2-phospho-D-glycerate/enolase-phosphoenolpyruvate at 2.0 A resolution

Enolase, a glycolytic enzyme that catalyzes the dehydration of 2-phospho-d-glycerate (PGA) to form phosphoenolpyruvate (PEP), is a homodimer in all eukaryotes and many prokaryotes. Here, we report the crystal structure of a complex between yeast enolase and an equilibrium mixture of PGA and PEP. The structure has been refined using 29 854 reflections with an F/sigma(F) of >/=3 to an R of 0.137 with average deviations of bond lengths and bond angles from ideal values of 0.013 A and 3.1 degrees , respectively. In this structure, the dimer constitutes the crystallographic asymmetric unit. The two subunits are similar, and their superposition gives a rms distance between Calpha atoms of 0.91 A. The exceptions to this are the catalytic loop Val153-Phe169 where the atomic positions in the two subunits differ by up to 4 A and the loop Ser250-Gln277, which follows the catalytic loop Val153-Phe169. In the first subunit, the imidazole side chain of His159 is in contact with the phosphate group of the substrate/product molecule; in the other it is separated by water molecules. A series of hydrogen bonds leading to a neighboring enolase dimer can be identified as being responsible for ordering and stabilization of the conformationally different subunits in the crystal lattice. The electron density present in the active site suggests that in the active site with the direct ligand-His159 hydrogen bond PGA is predominantly bound while in the active site where water molecules separate His159 from the ligand the binding of PEP dominates. The structure indicates that the water molecule hydrating carbon-3 of PEP in the PEP --> PGA reaction is activated by the carboxylates of Glu168 and Glu211. The crystals are unique because they have resolved two intermediates on the opposite sides of the transition state.

[Surgical management for giant retinal tear]

OBJECTIVE

To study the effect of surgical management for giant retinal tear (GRT).

METHODS

A standard three-point vitrectomy with silicone oil intraocular injection was performed on 41 cases. Of them, scleral buckling was also performed on 35 cases and lensectomy, on 17 cases. The basal vitreous gel and peri-retinal membranes were resected completely in all the cases. Air-fluid exchange, retinal tack or liquid perfluorocarbon were used to unroll and flatten the flap of the GRTs. Cryopexy or endophotocoagulation were applied to close the GRTs.

RESULTS

In the follow-up for 3-39 months (mean 11.6 months), total retinal attachment was achieved in 29 cases, macular retinal attachment in 7 cases, and no retinal attachment in 5 cases. The final visual acuities were 0.01-0.05 in 6 cases, 0.06-0.1 in 17 cases, 0.2-0.5 in 11 cases and 0.6-1.0 in 2 cases.

CONCLUSIONS

The key factor of successful operation is to unroll and flatten the flap of GRTs completely. Scleral buckling shows advantages and disadvantages, while appropriate scleral buckling is necessary in GRTs with proliferative vitreo-retinopathy. Postoperative further proliferation is the main factor affecting the long term effect of the treatment.

The molecular environment of the Na+ binding site of thrombin

When Na+ binds to thrombin, a conformational change is induced that renders the enzyme kinetically faster and more specific in the activation of fibrinogen. Two Na+ binding sites have here been identified crystallographically by exchanging Na+ with Rb+. One is intermolecular, found on the surface between two symmetry-related thrombin molecules. Since it is not present in thrombin crystal structures having different crystal systems, the other Na+ site is the functionally relevant one. The second site has octahedral coordination with the carbonyl oxygen atoms of Arg221A and Lys224 and four conserved water molecules. It is located near Asp189 of the S1 specificity site in an elongated solvent channel (8 x 18 A) formed by four antiparallel beta-strands between Cys182-Cys191 and Val213-Tyr228. This channel, extending from the active site to the opposite surface of the enzyme, was first noted in the hirudin-thrombin structure and contains about 20 conserved water molecules linked together by a hydrogen bonding network that connects to the main chain of thrombin. Although the antiparallel beta-strand interactions of the functional Na+ binding site are the same in prethrombin2, the loops between the strands are very different, so that Asp189 and Arg221A are not positioned properly for either substrate or Na+ binding in prethrombin2. A water molecule with octahedral coordination has also been identified in factor Xa at the topologically equivalent Na+ site position of thrombin. Since activated protein C shows enhanced activity with monovalant cation binding, the same position is probably utilized by Na+. Since thrombin crystals could not be grown in the absence of Na+, the cation was leached from Na(+)-bound thrombin crystals by diffusion/exchange. Although both Na+ and their coordinating water molecules were removed from the Na+ binding sites, the remainder of the thrombin structure was, unexpectedly, the same. The lack of an allosteric change is most likely attributable to crystal packing effects. Thus, the structure of the slow form remains to be established crystallographically.

Crystallization and initial spectroscopic characterization of the heme-containing dehaloperoxidase from the marine polychaete Amphitrite ornata

The heme-containing dehaloperoxidase from Amphitrite ornata was crystallized from an unbuffered solution containing 30% PEG 8000 and 200 mM ammonium sulfate by the hanging-drop vapor-diffusion method. Dark-red bipyramidal crystals are orthorhombic in space group P2(1)2(1)2(1) with unit-cell dimensions a = 68.5, b = 68.4 and c = 61.1 A. The asymmetric unit contains two subunits related by a non-crystallographic twofold axis. The crystals scatter beyond 2 A resolution. The native data have been collected and one single-site mercury derivative has been found. SIRAS phasing was used to determine the positions of the heme Fe atoms and structure determination is in progress. A preliminary spectroscopic investigation indicates that the heme is protoporphyrin IX and its coordination sphere resembles that of a typical heme peroxidase, i.e. histidine ligated. Detailed spectroscopic and electrochemical studies are now under way.

K-ras mutation in sputum of patients with or without lung cancer

K-ras mutation appears in about 60% of patients with non-small-cell lung cancer (NSCLC). This frequency and its presence in normal appearing tissues point to the potential of ras oncogene mutation to serve as a good biomarker. Using enriched PCR (EPCR), which enables the detection of one mutant allele in the presence of 10,000 normal alleles, we have determined the frequency of mutant ras alleles in the sputum samples of patients with or without lung cancer. Samples were collected from 17 patients with NSCLC and from 40 controls who suffered from non-oncological lung diseases, including bronchitis, asthma, and pneumonia. Of the 37 samples obtained from patients with lung cancer, 18 were found to harbor ras oncogene mutations (48%). Of the 40 cases that were free of lung cancer, five were found to harbor this mutation (12.5%). The difference between the two frequencies was found to be significant (P < 0.01). These findings indicate that (a) K-ras oncogene mutation can be identified in routinely obtained sputum samples of patients who may be at risk of developing lung cancer and (b) the higher frequency of these mutations in samples of patients with lung cancer points to the potential use of the ras mutation as a biomarker for either exogenous or endogenous exposure to carcinogens. Thus, the ability to examine sputum provides a powerful and convenient source of sampling and may be adapted for future large-scale screening.

Gradual and random binarization of gray-scale holograms

A new method called gradual and random binarization to binarize gray-scale holograms, based on an iterative algorithm, is proposed. The binarization process is performed gradually, and the pixels to be binarized are chosen randomly. Errors caused by this operation are spatially diffused. A comparison with other established methods based on error diffusion, direct binary search, and iterative stepwise quantization shows that the gradual and random binarization method achieves a very good compromise between computational complexity and reconstruction quality. Optical reconstructions are presented.

A new staging system for nasopharyngeal carcinoma in China

PURPOSE

An accurate and rational nasopharyngeal carcinoma (NPC) stage based on images is proposed.

METHODS AND MATERIALS

Four hundred and twenty-one cases of NPC, treated in the Cancer Hospital, Sun Yat-sen University of Medical Sciences (SUMS), with computed tomography scanning before initial radiotherapy, are analyzed. Important prognostic factors that form the basis of the new staging system are screened out by means of Cox model and clinical experiences. Survival curves of various kinds of T and N stages are compared by computer simulation. A new staging system is proposed by studying the traditional staging systems such as the AJC, UICC, Ho's and Changsha systems.

RESULTS

According to the new staging criteria, the 5-year survival rates for Stages I-IV are 89.7%, 75.9%, 51.3%, and 22.2%, respectively.

CONCLUSION

This new clinical staging for NPC based on a large amount of cases multivariate analysis is satisfactory and widely used in China.

Catalytic metal ion binding in enolase: the crystal structure of an enolase-Mn2+-phosphonoacetohydroxamate complex at 2.4-A resolution

Enolase, a glycolytic enzyme that catalyzes the dehydration of 2-phospho-D-glycerate (PGA) to form phosphoenolpyruvate (PEP), requires two divalent metal ions per active site for activity. The first metal ion, traditionally referred to as "conformational", binds in a high-affinity site I. The second metal ion, "catalytic", binds in site II only in the presence of a substrate or substrate analogue and with much lower affinity for the physiological cofactor Mg2+. While the high-affinity site has been well characterized, the position of the lower affinity site has not been established so far. Here, we report the structure of the quaternary complex between enolase, the transition-state analogue phosphonoacetohydroxamate (PhAH), and two Mn2+ ions. The structure has been refined by using 16 561 reflections with F/sigma (F) > or = 3 to an R = 0.165 with average deviations of bond lengths and bond angles from ideal values of 0.013 A and 3.1 degrees, respectively. The "catalytic" metal ion is coordinated to two oxygen atoms of the phosphono moiety of PhAH and to the carbonyl oxygen of Gly37. Most likely, disordered water molecules complement its coordination sphere. The interaction with the site II metal ion must stabilize negative charge on the phosphate group and produce electron withdrawal from carbon 2 of the substrate, facilitating proton abstraction from carbon 2, the rate-limiting step in the catalytic process. The Gly37 residue is located in the flexible loop Ser36-His43, which assumes an "open" conformation in the absence of substrate and a "closed" conformation in the presence of a substrate.(ABSTRACT TRUNCATED AT 250 WORDS)

Fluoride inhibition of yeast enolase: crystal structure of the enolase-Mg(2+)-F(-)-Pi complex at 2.6 A resolution

Enolase in the presence of its physiological cofactor Mg2+ is inhibited by fluoride and phosphate ions in a strongly cooperative manner (Nowak, T, Maurer, P. Biochemistry 20:6901, 1981). The structure of the quaternary complex yeast enolase-Mg(2+)-F(-)-Pi has been determined by X-ray diffraction and refined to an R = 16.9% for those data with F/sigma (F) > or = 3 to 2.6 A resolution with a good geometry of the model. The movable loops of Pro-35-Ala-45, Val-153-Phe-169, and Asp-255-Asn-266 are in the closed conformation found previously in the precatalytic substrate-enzyme complex. Calculations of molecular electrostatic potential show that this conformation stabilizes binding of negatively charged ligands at the Mg2+ ion more strongly than the open conformation observed in the native enolase. This closed conformation is complementary to the transition state, which also has a negatively charged ion, hydroxide, at Mg2+. The synergism of inhibition by F- and Pi most probably is due to the requirement of Pi for the closed conformation. It is possible that other Mg(2+)-dependent enzymes that have OH- ions bound to the metal ion in the transition state also will be inhibited by fluoride ions.

[Application of ultrafiltration during cardiopulmonary bypass]

The ultrafiltration (UF) was employed in 20 patients undergoing open-heart operation with cardiopulmonary bypass (CPB). The number of controls was 10. The average UF duration was 24.7 +/- 9.6 min (12-49) and the average amount of ultrafiltrate was 1433.5 +/- 482.6 ml (650-2,350 ml). The volume load of UF group was similar with that of the control group. The output volume of UF group was greater than that of the control group (P less than 0.01). After UF, the degree of increase in hematocrit, plasma albumin and total plasma protein was 33.8%, 34.7%, and 26.0%, respectively. Moreover, we did not find any abnormal increase in blood viscosity. No additional adverse actions of UF were found.