Structure of the green heme in myeloperoxidase

A 3-A-resolution X-ray crystal structure of canine myeloperoxidase has previously revealed the overall structure of the molecule, including the polypeptide backbone conformation, but did not provide an unambiguous structure for the covalently bound heme. A higher resolution (2.28 A) X-ray crystal structure of human myeloperoxidase has now shown that the heme is a novel derivative of protoporphyrin IX in which three ring substituents form covalent bonds with amino acid side chains in the protein. Modified methyl groups on pyrrole rings A and C form ester linkages with glutamate 242 and aspartate 94, while a covalent bond between the vinyl group on ring A and the sulfur atom of methionine 243 results in a sulfonium ion linkage. The heme tetrapyrrole ring also shows considerable distortion from the planar conformation seen in most heme-containing proteins. The observed bending appears to result from these covalent bonds between diametrically opposed pyrrole rings A and C and the protein. Sequence comparisons suggest that the two ester linkages to the heme may also occur in other homologous mammalian peroxidases, but that the sulfonium ion linkage may be a unique feature of myeloperoxidase.

Chinese character operating system of traditional Chinese medicine and pharmacology (TCMP)

With the development in research, teaching and literature work in traditional Chinese medicine and pharmacology (TCMP) by means of computers, it has been found that the existing Chinese character operative systems cannot meet the need of carrying out information processing and software development in this field, since these systems do not include many of the common and special terms in TCMP. This makes it inconvenient to exchange academic thoughts in information processing in this field with our colleagues at home and abroad and greatly affects the sharing of the literature data in TCMP. It is therefore necessary to develop a Chinese character operating system applicable to the use of computers in the research of TCMP. Recently, we have developed jointly a Chinese character operating system of TCMP. This system is based on the original GB2312-80 Chinese character international code, to which are added 1,150 Chinese characters commonly used in TCMP. The five-stroke code, which make input possible according to word forms, are used for the input of expanded words. Besides, the system also provides the codes of a number of common names of Chinese materia medica, acupoint names, common terms in traditional Chinese medicine (TCM), TCM disease names, names of classic TCM works, etc. It also provides a convenient character-creating software. We hope that our work will lead to discussions concerning the difficult problems in computer processing of TCMP literature, i.e. the Chinese character.

Oligosaccharides from human milk as revealed by matrix-assisted laser desorption/ionization mass spectrometry

In this study neutral and acidic oligosaccharide fractions prepared from human milk have been investigated using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). The fraction of neutral oligosaccharides was separated by gel permeation chromatography (GPC) and the resulting subfractions were analyzed by MALDI-MS using the positive ion mode. Several low-molecular-weight glycans (degree of polymerization up to 13) were observed whose structures have already been elucidated. In addition, a variety of so far unknown large-sized carbohydrates was detected whose molecular weights range from M(r) 2242 to 8000. The large-sized glycans which possess a low abundance appear to be composed of both lactosamine and fucose residues attached to the lactose unit at the reducing end of the sugar chains with a highly variable stochiometry. Following subfractionation by GPC, acidic (i.e., containing sialic acid) glycans were analyzed by MALDI-MS using both positive and negative ion mode. Because of the inferior stability of acidic glycans, various matrices were applied and compared with respect to signal intensity, resolution, and analyte stability.

Differential cDNA cloning by enzymatic degrading subtraction (EDS)

We describe a new method, called enzymatic degrading subtraction (EDS), for the construction of subtractive libraries from PCR amplified cDNA. The novel features of this method are that i) the tester DNA is blocked by thionucleotide incorporation; ii) the rate of hybridization is accelerated by phenol-emulsion reassociation; and iii) the driver cDNA and hybrid molecules are enzymatically removed by digestion with exonucleases III and VII rather than by physical partitioning. We demonstrate the utility of EDS by constructing a subtractive library enriched for cDNAs expressed in adult but not in embryonic rat brains.

[Expression of human chorionic gonadotropin, human placental lactogen and pregnancy-specific 1-glycoprotein in malignant trophoblastic neoplasms]

The expression of placental hormones in 91 malignant trophoblastic neoplasms was studied immunohistochemically using a panel of antibodies against hCG, human placental lactogen (hPL) and pregnancy-specific 1-glycoprotein (SP). The results indicated that the expression of hCG in invasive moles was weaker than that in choriocarcinoma, but the expression of hPL and SP1 was stronger than those in choriocarcinoma. The expression of hPL and SP1 in the metastatic tumors of invasive moles was weaker than the expression at in the primary tumors, but the secretory capacity of hCG in metastatic choriocarcinomas was stronger than that in the primary neoplasms. In this study, the qualities of expression of the placental hormones in invasive moles and choriocarcinomas corresponded to the degree of tumor malignancy, the biological behaviour and the grading of trophoblastic cell differentiation. We believe that the detection of hCG, hPL and SP1, in malignant trophoblastic neoplasms was of value for establishing tumor diagnosis and typing and for judgement on prognosis.

Identification and zinc dependence of the bovine herpesvirus 1 transactivator protein BICP0

Bovine herpesvirus 1 (BHV-1) specifies and unspliced early 2.6-kb RNA (ER2.6) which is 3' coterminal with exon 2 of the 2.9-kb immediate-early (IE) RNA. The two transcripts have a common open reading frame (676 codons). The predicted protein, designated BHV-1 infected cell protein 0 (BICP0), contains a zinc finger domain with homology to ICP0 of herpes simplex virus type 1 and protein 61 of varicella-zoster virus, and depending on the promoter, it acts as a strong activator or as a repressor in transient expression assays. In situ immunoadsorbent assays using antisera against synthetic oligopeptides demonstrated that BICP0 accumulates in nuclei of BHV-1-infected cells, as expected for an IE gene product involved in gene regulation. Western blots (immunoblots) revealed a BHV-1-specific 97-kDa protein which was detectable during the IE phase and also at later periods of infection, indicating that the kinetics of BICP0 synthesis is consistent with the switch from IER2.9 to ER2.6. To confirm that ER2.6 encoded the 97-kDa BICP0 protein, a DNA fragment containing BICP0-coding sequences was inserted into the Autographa californica baculovirus genome. A recombinant protein, identified by its reactivity with antipeptide sera, exhibited the same electrophoretic mobility as BICP0 specified by BHV-1. We microinjected Xenopus oocytes with a BICP0 effector plasmid and a promoter-chloramphenicol acetyltransferase plasmid. BICP0-induced stimulation of this promoter was strongly reduced when intracellular zinc was chelated by thionein, indicating that the effect of BICP0 is zinc dependent.

[Determination of ceftizoxime in serum by high performance liquid chromatography]

This paper reports the determination of ceftizoxime, a new cephalosporin antibiotic, in serum by RP-HPLC. The technique for serum protein precipitation by adding perchloric acid is adapted for sample preparations. After centrifugation, a 100 microliters portion of aqueous phase is injected into chromatographic column of ultrasphere CN, the mobile phase being a mixture of methanol and 1% acetic acid (15:85). The standard curve is linear within the range of 2.5-120 mg/L in serum. The detection limit of ceftizoxime in serum stands at 0.1 mg/L. The recoveries from serum samples after protein precipitation reach 95.4-96.3%. The within day CVs and interday CVs are 2.7-3.3% and 4.8-7.6%, respectively. This method is rapid, reliable and reproducible. It has been utilized to measure the concentration of ceftizoxime in patient serum for clinical research and pharmacokinetic studies.

Effects of alcohol-induced lipid interdigitation on proton permeability in L-alpha-dipalmitoylphosphatidylcholine vesicles

6-Carboxyfluorescein was employed to examine the effect of alcohol-induced lipid interdigitation on proton permeability in L-alpha-dipalmitoylphosphatidylcholine (DPPC) large unilamellar vesicles. Proton permeability was measured by monitoring the decrease of 6-carboxyfluorescein fluorescence after a pH gradient from 3.5 (outside the vesicle) to 8.0 (inside the vesicle) was established. At 20 degrees C and below 1.2 M ethanol, the fluorescence decrease is best described by a single exponential function. Above 1.2 M ethanol, the intensity decrease is better described by a two-exponential decay law. Using the fitted rate constants and the vesicle radii determined from light-scattering measurements, the proton permeability coefficient, P, in DPPC vesicles was calculated as a function of ethanol concentration. At 20 degrees C, P increases monotonically with increasing ethanol content up to 1.0 M, followed by an abrupt increase at 1.2 M. The vesicle size also exhibits a sudden increase at around 1.2 M ethanol, which has been shown to result from vesicle aggregation rather than vesicle fusion. The abrupt increases in P and in vesicle size occur at the concentration region close to the critical ethanol concentration for the formation of the fully interdigitated gel state of DPPC. At 14 degrees C, the abrupt change in P shifts to 1.9-2.0 M ethanol, completely in accordance with the ethanol-temperature phase diagram of interdigitated DPPC. Effects of methanol and benzyl alcohol on lipid interdigitation have also been examined. At 20 degrees C, DPPC large unilamellar vesicles exhibit a dramatic change in P at 3 M methanol and at 40 mM benzyl alcohol. These concentrations come close to the critical methanol and benzyl alcohol concentrations for the formation of fully interdigitated DPPC structures determined previously by others. It can be concluded that proton permeability increases dramatically as DPPC is transformed from the noninterdigitated gel to the fully interdigitated gel state by high concentrations of alcohol. This marked increase in proton permeability can be attributed to the combined effect of the changes in membrane thickness and surface charge density, due to the ethanol-induced lipid interdigitation. The possible effects of the increased proton permeability caused by ingested ethanol on gastric mucosal membranes are discussed.

Influence of thymosin on the level of cyclic nucleotides in rats with experimental varicocele

Experimental varicocele was induced by partial ligation of the left renal vein in rats, and the effect of thymosin (fraction 5), a hormone secreted by the thymus, on the level of cyclic nucleotides was investigated. The levels of cAMP and cGMP in plasma and testicular tissue were estimated using radioimmunoassay techniques. The results showed that the level of cAMP in bilateral testicular tissues in rats with experimental varicocele decreased considerably, especially in the left testicular tissue as compared with that in the control group (P < 0.05). 4 weeks after thymosin administration (0.5 mg/rat, twice a week), the level of cAMP in bilateral testicular tissues rose significantly, as compared with that in the experimental varicocele group (P < 0.01). These findings indicate that there exists imbalance in the metabolism of cyclic nucleotides in rats with experimental varicocele. This suggests that the abnormal level of cyclic nucleotides is one of the causes of infertility with varicocele. Since thymosin participates in the metabolism and regulation of cyclic nucleotides, it may have a direct or an indirect effect on the growth and function of reproductive cells.

Effects of thymosin on the secretion of the sexual hormone in rats with experimental varicocele

Hormonal abnormality in experimental varicocele induced by partial ligation of left renal vein and the effect of thymosin (fraction 5) on the secretion of the sexual hormone were studied in rats. Serum testosterone level was lowered after varicocele formation, but could be reversed or increased by intraperitoneal administration of thymosin 5 mg/rat twice a week for 4 weeks with concomitant increase of testicular testosterone content. Changes in FSH and LH both in serum and testis, determined with immunoassay method as that of testosterone, were insignificant as compared with control or thymosin treated groups.

[The use of domestic viscoelastic substances in IOL implantation and their toxicity to endothelial cells in vitro]

34 senile cataract patients were randomly divided into groups of 1% sodium hyaluronate (Healon) 14 patients, 2% hydroxypropylmethylcellulose (HPMC) 10 patients and Viscose 10 patients for extracapsular cataract extraction with IOL implantation. The rate of endothelial cell loss, the corneal thickness, the intraocular pressure, and the anterior chamber reactions were investigated; the toxicity of the viscoelastic substances on human corneal endothelial cells was studied in vitro for comparative evaluation.

[High performance liquid chromatographic determination of hydroxyphenytoin in human urine]

A high-performance liquid chromatographic method for the determination of p-hydroxyphenytoin (p-HDPH) in human urine was reported. Following acid hydrolysis of urine sample at 90 degrees C for 1 h, an internal standard, nitrophenol, was added. The sample was extracted with n-hexane-ethyl acetate (50:50), and organic layer was evaporated. The residue was dissolved in methanol and chromatographed on an Ultrasphere-ODS column, using a mobile phase of phosphate buffer (0.03 mol/L, pH 6.0): methanol (65:35) at a flow rate of 0.8 ml/min. The eluent was monitored at 240 nm. The standard curve was linear within the range 5.0-200 micrograms/ml (r = 0.9998). Analytical recovery rates were 102.8 +/- 7.3% (p-HDPH 9.70 micrograms/ml, n = 5) and 104.9 +/- 6.4% (p-HDPH 54.70 micrograms/ml, n = 5). The cumulative recovery of p-HDPH in 0-12 h volunteers' urine samples accounted for 20% of the oral dose of 100 mg phenytoin sodium.

X-ray crystal structure of canine myeloperoxidase at 3 A resolution

The three-dimensional structure of the enzyme myeloperoxidase has been determined by X-ray crystallography to 3 A resolution. Two heavy atom derivatives were used to phase an initial multiple isomorphous replacement map that was subsequently improved by solvent flattening and non-crystallographic symmetry averaging. Crystallographic refinement gave a final model with an R-factor of 0.257. The root-mean-square deviations from ideality for bond lengths and angles were 0.011 A and 3.8 degrees. Two, apparently identical, halves of the molecule are related by local dyad and covalently linked by a single disulfide bridge. Each half-molecule consists of two polypeptide chains of 108 and 466 amino acid residues, a heme prosthetic group, a bound calcium ion and at least three sites of asparagine-linked glycosylation. There are six additional intra-chain disulfide bonds, five in the large polypeptide and one in the small. A central core region that includes the heme binding site is composed of five alpha-helices. Regions of the larger polypeptide surrounding this core are organized into locally folded domains in which the secondary structure is predominantly alpha-helical with very little organized beta-sheet. A proximal ligand to the heme iron atom has been identified as histidine 336, which is in turn hydrogen-bonded to asparagine 421. On the distal side of the heme, histidine 95 and arginine 239 are likely to participate directly in the catalytic mechanism, in a manner analogous to the distal histidine and arginine of the non-homologous enzyme cytochrome c peroxidase. The site of the covalent linkage to the heme has been tentatively identified as glutamate 242, although the chemical nature of the link remains uncertain. The calcium binding site has been located in a loop comprising residues 168 to 174 together with aspartate 96. Myeloperoxidase is a member of a family of homologous mammalian peroxidases that includes thyroid peroxidase, eosinophil peroxidase and lactoperoxidase. The heme environment, defined by our model for myeloperoxidase, appears to be highly conserved in these four mammalian peroxidases. Furthermore, the conservation of all 12 cysteine residues involved in the six intra-chain disulfide bonds and the calcium binding loop suggests that the three-dimensional structures of members of this gene family are likely to be quite similar.

Conformational analysis of the anomeric forms of kojibiose, nigerose, and maltose using MM3

Energy surfaces were computed for relative orientations of the relaxed pyranosyl rings of the two anomeric forms of kojibiose, nigerose, and maltose, the (1----2)-alpha, (1----3)-alpha, and (1----4)-alpha-linked D-glucosyl disaccharides, respectively. Twenty-four combinations of starting conformations of the rotatable side-groups were considered for each disaccharide. Optimized structures were calculated using MM3 on a 20 degree grid spacing of the torsional angles about the glycosidic bonds. The energy surfaces of the six disaccharides were similar in many respects but differed in detail within the low-energy regions. The maps also illustrate the importance of the exo-anomeric effect and linkage type in determining the conformational flexibility of disaccharides. Torsional conformations of known crystal structures of maltosyl-containing molecules lie in a lower MM3 energy range than previously reported.

Composition of human islet cell preparations for transplantation

To study the cellular composition of human islet cell isolates for transplantation, formalin-fixed and paraffin-embedded cell pellets were stained by the immunoperoxidase method with a panel of antibodies characterising endocrine, epithelial, soft tissue and haematolymphoid components. Immediately after separation, the isolates contained 30-80% islet cells, differing mainly in the content of islet and acinar cells, whereas the soft tissue, ductal/ductular and haematolymphoid elements comprised a relatively constant 10-20%. After 1 week in culture the islet cell content of less highly purified isolates (30-40% islets) dropped dramatically to 5%. The highly purified isolates (70-80% islets) showed only a minimal change in cellular composition; however, approximately two-thirds of islet cells were degranulated and did not stain for insulin. Haematolymphoid components were still present in all cultured isolates. We conclude that primarily mechanical purification methods and short-term culture are not sufficient to eliminate highly immunogenic cells. In addition, short-term culture is deleterious to the isolate if a significant number of acinar cells is still present after enrichment.

Zinc transfer from transcription factor IIIA fingers to thionein clusters

The rapid induction of thionein (apometallothionein) by many endogenous stimuli such as steroid hormones, cytokines, and second messengers suggests that this cysteine-rich, metal binding protein participates in an as yet undefined role in cellular regulatory processes. This study demonstrates with DNA and RNA binding assays and in vitro transcription measurements that thionein suppresses the binding of the Xenopus laevis zinc finger transcription factor IIIA (TFIIIA) to 5S RNA and to the 5S RNA gene and abrogates the capacity of TFIIIA to initiate the RNA polymerase III-catalyzed synthesis of 5S RNA. The effect is reversed by the addition of zinc and is not observed in the TFIIIA-independent transcription of a tRNA gene by the same RNA polymerase. In view of the strong tendency of thionein to complex posttransition metals such as zinc, one effect of its enhanced synthesis in vivo could be to reduce the intracellular disposability of zinc and thus modulate the actions of zinc-dependent enzymes and proteins, most notably those of the zinc finger transcription factors.

[Determination of hydrocortisone and methylprednisolone in plasma by reversed-phase HPLC]

A sensitive and rapid method for the simultaneous measurement of both hydrocortisone (HC) and methylprednisolone (MP) using dexamethasone (DX) as the internal standard was presented. High-performance liquid chromatograph Model 344 (Beckman, USA) with a 254 nm wavelength UV detector and reversed-phase Ultrasphere ODS (5 microns) column was used. Sample was extracted with ethyl acetate and the organic layer was evaporated to dryness under an air stream in a 37 degrees C water bath. The residue was dissolved in 30 microliters mobile phase and 20 microliters injected. The mobile phase of methanol and 0.01 mol/L acetate buffer (pH 3.0) (64:36) was pumped at 1.0 ml/min through the column. The detector was operated at 0.005 aufs. The retention time for HC, MP and DX was 5.43 min, 7.7 min and 11.5 min, respectively. Standard curve was linear in the concentration range of 0.02 to 1.28 mg/L for HC and 0.05 to 12.8 mg/L for MP. Sensitivity was 1 ng for HC and 1.5 ng for MP; extraction recovery 76-83%; within day CV less than 4%, and inter-day CV less than 6% for both steroids.

Thionein (apometallothionein) can modulate DNA binding and transcription activation by zinc finger containing factor Sp1

A number of transcription factors contain so-called zinc finger domains for the interaction with their cognate DNA sequence. It has been shown that removal of the zinc ions complexed in these zinc fingers abrogates DNA binding and transcription activation. Therefore we wanted to test the hypothesis that the activity of transcription factors could be regulated by physiological chelators of zinc. A prominent candidate for such a chelator is the Cys-rich protein thionein (apometallothionein) that is inducible by heavy metal loads, and by other environmental stimuli. Here we show with DNA binding and in vitro transcription assays that thionein indeed can inactivate the zinc finger-containing Sp1 in a reversible manner. By contrast, transcription factor Oct-1, which binds DNA via a homeo-domain, i.e. a helix-turn-helix motif not involving zinc ions, is refractory to thionein action. We propose that modulation of intracellular thionein concentration is used for the coordinated regulation of a large subset of genes whose transcription depends on zinc finger proteins.

Crystallization of a calcium-binding lysozyme from horse milk

Crystals of the calcium-containing lysozyme from horse milk have been grown by precipitation with sodium phosphate. The crystals are orthorhombic space group P2(1)2(1)2(1) with cell dimensions a = 53.2, b = 57.1, and c = 38.2 A and contain a single molecule in the asymmetric unit. The crystals are suitable for high resolution x-ray structural analysis.