Natural peptides as building blocks for the synthesis of large protein-like molecules with hydrazone and oxime linkages

Methods are known for the production of synthetic protein-like molecules of nonlinear architecture with molecular masses in the 10-20 kDa range. To synthesize such compounds of higher molecular mass and complexity, chemoselective ligation of natural (as opposed to synthetic) peptide building blocks was studied. In preliminary experiments with model peptides, conditions for the formation of peptide oximes were investigated, and their stability at alkaline pH was examined, to resolve a literature controversy. It was found that low pH (down to 2.1) was suitable for polyoxime formation and that the oxime bond was stable for up to 65 h at pH 8 and for more than 2 h at pH 9. Then, using natural peptides, it was found to be possible to synthesize, and characterize by mass spectrometry, nine-component species with molecular masses > 48 kDa. This is about twice the size of homogeneous artificial proteins previously described. Such complex molecules of defined structure are beginning to find applications as vaccine candidates, as radioimmunodiagnostic agents, and as nonviral gene therapy delivery vehicles.

Identification of muscarinic receptor subtypes in mouse parotid gland

Immunoprecipitation of muscarinic receptors from mouse parotid membranes by specific subtype antisera showed that M3 and M1 receptors represented 75 and 15% of the total number of precipitable receptors, respectively. [N-methyl-3H]methylscopolamine (NMS) labeled a single class of high-affinity binding sites in membranes from parotid glands with a dissociation constant of 0.67 +/- 0.02 nM and a maximum binding capacity of 176 +/- 15 fmol/mg protein. Competition curves for NMS, atropine, 4-diphenylacetoxy-N-methylpiperidine methiodide (4-DAMP) and para-fluoro-hexahydro-sila-difenidol fit best to a one-site binding model, whereas pirenzepine and methoctramine fit best to a two-site binding model, indicating 76-90% M3 receptors. Results from the use of pirenzepine indicated that the second mouse parotid receptor subtype, unlike that of the submandibular gland, has atypical characteristics for an M1 receptor. The rank order of potency of muscarinic antagonists in inhibiting phosphoinositide turnover and biphasic effects of carbachol on isoproterenol-stimulated adenosine 3',5'-cyclic monophosphate (cAMP) accumulation was atropine > or = 4-DAMP >> pirenzepine > AF-DX 116. A specific M1 antagonist, m1-toxin, had no effect on carbachol augmentation or inhibition of isoproterenol responses. Results suggest that M3 receptors couple to both augmentation and inhibition of stimulated cAMP levels.

Gbetagamma transduces [Ca2+]i oscillations and Galphaq a sustained response during stimulation of pancreatic acinar cells with [Ca2+]i-mobilizing agonists

A central unresolved question in agonist-evoked [Ca2+]i signaling is the pathway by which [Ca2+]i oscillations and a sustained response are transduced. We show here that activation of Gbetagamma signal [Ca2+]i oscillations and activation of Galphaq signal a sustained response during stimulation by a number of Ca2+-mobilizing agonists. Thus, infusion of purified Gbetagamma into pancreatic acinar cells through a patch pipette evokes [Ca2+]i oscillations by Ca2+ release from internal stores, which were inhibited by two independent scavengers of Gbetagamma, the beta-adrenergic receptor kinase fragment, and a mutated Galphai1G203A. These proteins, as well as an inhibitory antibody against Galphaq/11, prevent [Ca2+]i oscillations and the sustained response when applied before cell stimulation, possibly by preventing the dissociation of Gq into its subunits. After cell stimulation and dissociation of Gq into Gbetagamma and Galphaq, scavenging Gbetagamma stabilized the sustained response and inhibited reassociation of the subunits on termination of cell stimulation with antagonist, whereas scavenging Galphaq inhibited the sustained response and uncovered the Gbetagamma-dependent oscillations. These findings provide a general mechanism by which Ca2+-mobilizing agonists can control the type of [Ca2+]i signal to be transduced to the cell interior.

[Effects on fetal and infant's development of intrauterine cytomegalovirus infection]

OBJECTIVE

To study the early effects of fetal development and remote sequalae of mental development of infants after intrauterine human cytomegalovirus (HCMV) infection.

METHODS

Enzyme-linked immunoabsorbant assay (ELISA) were used for screening HCMV antibodies in the serum of 1419 pregnant women. HCMV DNA were examined by PCR in maternal blood, amniotic fluid and/ or umbilical blood for those with serum HCMV-IgM positive and some with HCMV negative. According to the results, group A (n = 53) included women with positive serum HCMV-IgM and HCMV DNA, and also positive HCMV DNA in amniotic fluid and/or umbilical blood: group B (n = 87) were women with positive serum HCMV-IgM and HCMV DNA but negative HCMV DNA in amniotic fluid and/or umbilical blood: group C (n = 34) served as control with all negative. The above 174 cases were carefully monitored for fetal development. Baley scales of infant development (BSID) were used to test both mental development index (MDI) and psychomotor development index (PDI) at 2-30 months after birth for babies in group A and C.

RESULTS

The occurrences of fetal intrauterine death, congenital malformation, fetal growth retardation and neonatal asphyxia were significantly higher in group A than that in group B and C (P < 0.05) and the average birth weight and height were also significantly lower in group A (P < 0.05). The mental development of infants in group A were remarkably slower than that of group C (P < 0.01).

CONCLUSION

Active HCMV intrauterine infection may cause congential infection, birth defects and mental retardation in childhood.

Regulation of the inositol 1,4,5-trisphosphate-activated Ca2+ channel by activation of G proteins

Streptolysin O-permeable pancreatic acini were used to study the regulation of the inositol 1,4,5-trisphosphate (IP3)-activated Ca2+ channel (IPACC) by agonists and antagonists. Measurements of the apparent affinity for IP3 (KappIP3) showed that the IPACC is dynamically controlled during cell stimulation and inhibition, i.e. agonists decreased and antagonists increased KappIP3. KappIP3 was also independently regulated by thimerosal, Ca2+ content of the stores, the incubation temperature, activation of protein kinases, and inhibition of protein phosphatases, but none of these mechanisms contributed to the regulation by agonists and antagonists. Incubating the cells with low concentration of GTPgammaS or AIF3 reproduced the effect of the agonist on KappIP3. Moreover, low [GTPgammaS] allowed activation of the IPACC by agonists at basal levels of IP3 and markedly impaired channel inactivation by antagonists. Channel sensitization by GTPgammaS also restored the ability of thimerosal to mobilize Ca2+ from internal stores with no change in cellular IP3 levels. The combination of low [GTPgammaS] and thimerosal locked the channel in an open, antagonist-insensitive state. All modulatory effects of GTPgammaS are independent of phospholipase C activation and IP3 production. We propose that the dynamic regulation of the IPACC by a G protein-dependent mechanism can play a major role in triggering and maintaining Ca2+ oscillations at low agonist concentrations when minimal or no changes in IP3 level take place.

[Pharmacological action of siwei shaoyao decoction]

The Siwei Shaoyao Decoction possesses a marked effect on the alleviation of trigeminal neuralgia in rats caused by penicillin G potassium injection. As shown from the hot-plate test, it also has an obvious analgesic effect on mice. To some extent, the decoction has a significant anti-inflammatory effect on the acute edema in hind paws of rats and the effect is believed to be related to the reduction of capillary permeability.

Engineered GFP as a vital reporter in plants

BACKGROUND

The green-fluorescent protein (GFP) of the jellyfish Aequorea victoria has recently been used as a universal reporter in a broad range of heterologous living cells and organisms. Although successful in some plant transient expression assays based on strong promoters or high copy number viral vectors, further improvement of expression efficiency and fluorescent intensity are required for GFP to be useful as a marker in intact plants. Here, we report that an extensively modified GFP is a versatile and sensitive reporter in a variety of living plant cells and in transgenic plants.

RESULTS

We show that a re-engineered GFP gene sequence, with the favored codons of highly expressed human proteins, gives 20-fold higher GFP expression in maize leaf cells than the original jellyfish GFP sequence. When combined with a mutation in the chromophore, the replacement of the serine at position 65 with a threonine, the new GFP sequence gives more than 100-fold brighter fluorescent signals upon excitation with 490 nm (blue) light, and swifter chromophore formation. We also show that this modified GFP has a broad use in various transient expression systems, and allows the easy detection of weak promoter activity, visualization of protein targeting into the nucleus and various plastids, and analysis of signal transduction pathways in living single cells and in transgenic plants.

CONCLUSIONS

The modified GFP is a simple and economical new tool for the direct visualization of promoter activities with a broad range of strength and cell specificity. It can be used to measure dynamic responses of signal transduction pathways, transfection efficiency, and subcellular localization of chimeric proteins, and should be suitable for many other applications in genetically modified living cells and tissues of higher plants. The data also suggest that the codon usage effect might be universal, allowing the design of recombinant proteins with high expression efficiency in evolutionarily distant species such as humans and maize.

[Prevention of endotoxic shock in rats with hepatic stimulating substance]

In order to understand the mechanism of prevention of endotoxic shock and evaluate the pathological changes taking place, an animal model of endotoxic shock was established by intravenous injection of endotoxin into rats, which were then treated with a hepatic stimulating substance, hepatopoietin (HPN). The results were as follows; (1) There was coincidence of low blood pressure and high serum level of tumor necrosis factor (TNF) in the experimental rats. (2) Simultaneous intravenous injection of endotoxin and introperitoneal injection of HPN showed that HPN can prevent the drop of blood pressure, lower the TNF level and ameliorate the tissure injury in lungs and kidneys induced by endotoxin. If HPN was given 15 minutes ofter injection of endotoxin, the drop of blood pressure could not be prevented and the TNF level remained high. It is suggested that TNF is an important mediator for endotoxic shock and treatment of endotoxic shock might be effective, if it is intituted early.

13C-methacetin breath test parameter S for liver diseases diagnosis

The mechanism of 13C-methacetin breath test is set forth clearly with the analysis of pharmacokinetics mode, and the measuring method of 13C-methacetin breath test and its clinical applications in the diagnosis of liver diseases are reported in detail. On the basis of comprehensive analysis of the clinical test data, the advanced diagnostic parameter S is of important significance for the application and development of breath test.

1H NMR structural study of free and template-linked antigenic peptide representing the C-terminal region of the heavy chain of influenza virus hemagglutinin

A 12 kDa template-assembled molecule, incorporating four oxime-linked synthetic peptides representing residues 306-328 of influenza virus hemagglutinin (HA), has been analysed by 1H NMR spectroscopy. The molecule (referred to as the 'tetraoxime') is of interest because it has been shown to elicit a better immune response than the free, monomeric peptide not only in the production of antibodies crossreactive with HA but also in its ability to elicit CD4+ T helper cells. We describe here an NMR structural analysis of (i) the unlinked template molecule and (ii) the free peptide and show that their conformations are not affected upon assembly of the tetraoxime. Our results suggest that the increased immune response observed for the tetraoxime may be due to its greater size and valency compared to that of the free peptide rather than being due to any induced structural effects.

Synthesis of a new template with a built-in adjuvant and its use in constructing peptide vaccine candidates through polyoxime chemistry

Synthetic lipopeptides are showing promise as vaccine candidates, but until now it has been very difficult to prepare them in homogeneous form. We describe the synthesis and characterization of a new water-soluble, four-branched template with a built-in lipophilic adjuvant (Pam3Cys). Through the use of oxime chemistry, we attached four copies of an unprotected influenza virus peptide and characterized the product (13 kDa) by reversed-phase HPLC and electrospray ionization mass spectrometry. Several other such constructions were made using the new template and different peptides. We seem to have a general method for making synthetic lipopeptides in homogeneous form.

Identification of two epitopes on the dengue 4 virus capsid protein recognized by a serotype-specific and a panel of serotype-cross-reactive human CD4+ cytotoxic T-lymphocyte clones

We analyzed the CD4+ T-lymphocyte response of a donor who had received an experimental live-attenuated dengue 4 virus (D4V) vaccine. Bulk culture proliferative responses of peripheral blood mononuclear cells (PBMC) to noninfectious dengue virus (DV) antigens showed the highest proliferation to D4V antigen, with lesser, cross-reactive proliferation to D2V antigen. We established CD4+ cytotoxic T-lymphocyte clones (CTL) by stimulation with D4 antigen. Using recombinant baculovirus antigens, we identified seven CTL clones that recognized D4V capsid protein. Six of these CTL clones were cross-reactive between D2 and D4, and one clone was specific for D4. Using synthetic peptides, we found that the D4V-specific CTL clone recognized an epitope between amino acids (aa) 47 and 55 of the capsid protein, while the cross-reactive CTL clones each recognized epitopes in a separate location, between aa 83 and 92, which is conserved between D2V and D4V. This region of the capsid protein induced a variety of CD4+ T-cell responses, as indicated by the fact that six clones which recognized a peptide spanning this region showed heterogeneity in their recognition of truncations of this same peptide. The bulk culture response of the donor's PBMC to the epitope peptide spanning aa 84 to 92 was also examined. Peptides containing this epitope induced proliferation of the donor's PBMC in bulk culture, but peptides not containing the entire epitope did not induce proliferation. Also, PBMC stimulated in bulk culture with noninfectious D4V antigen lysed autologous target cells pulsed with peptides containing aa 84 to 92. These results indicate that this donor exhibits memory CD4+ T-cell responses directed against the DV capsid protein and suggest that the response to the capsid protein is dominant not only in vitro at the clonal level but in bulk culture responses as well. Since previous studies have indicated that the CTL responses to DV infection seem to be directed mainly against the envelope (E) and NS3 proteins, these results are the first to indicate that the DV capsid protein is also a target of the antiviral T-cell response.

A synthetic peptide-based polyoxime vaccine construct of high purity and activity

An artificial protein containing four copies of a peptide comprising the C-terminal 23 residues of influenza virus hemagglutinin was constructed using oxime chemistry and compared with two tetrameric multiple antigenic peptide (MAP) constructions of the same peptide displayed either radially or linearly which were made by conventional techniques. The tetra-oxime was much more homogeneous yielding a single peak on reversed phase HLPC and the correct mass spectrum. In addition, the tetra-oxime was found to be recognized by anti-peptide antibodies, to stimulate at low concentrations a T-cell clone and also to elicit in mice high titres of antibodies which were able to recognize native virus. The modular polyoxime approach, which permits artificial proteins to be assembled rapidly, in high yield and in high purity, is expected to lead to an increase in the use of artificial proteins in vaccine technology.

[The role of ondansetron (Qilu) in the prevention of non-cisplatin-induced vomiting--a randomized clinical trial]

The antiemetic effect of ondansetron (supplied by Qilu Pharmaceutical Company) in patients receiving non-cisplatin chemotherapy (containing CTX and/or ADM) was studied in a multiple centre, randomized cross-over trial. The patients who had vomiting in the first turn of chemotherapy entered the trial. The patients received randomly ondansetron or control drugs-metoclopramide or Zofran (Glaxo) in the second turn of chemotherapy. In the third, the patients were cross-over to use the other antiemetic drug. A total of 155 patients were enrolled into the study. The results showed, the effective control rate (0-2 emetic episodes) on the first day were 87.7% of patients treated with ondansetron and 61.6% treated with metoclopramide. The mean frequency of vomiting was 0.8 times in ondansetron and 2.7 times in metoclopramide (P < 0.01). Ondansetron was superior to metoclopramide for the control of emesis. The antiemetic effects of ondansetron (Qilu) and Zofran (Glaxo) were very similar. The side-effects of ondansetron were mild.

[The role of ondansetron (qi lu) in the prevention of cisplatin-induced vomiting--a randomized clinical trial]

The antiemetic effect of ondansetron (Supplied by Qi Lu Pharmaceutical Company) in cisplatin-induced nausea and vomiting was studied in a randomized cross-over trial in 167 patients. The daily dose of cisplatin was 30mg for 5 days, 50mg for 3 days or 50mg/m2 for 1-2 days. The patients received randomly ondansetron, metoclopramide or Zofran (Glaxo) in the first cycle of the treatment and received the other antiemetic drug in the second cycle. The effective control rate of acute emesis (0-2 emetic episodes) was 86.6% in patients treated with ondansetron and 35.4% in those treated with metoclopramide. The mean frequency of vomiting was 1.1 times in ondansetron and 5.7 times in metoclopramide (P < 0.01). The results show that ondansetron (Qi Lu) is superior to metoclopramide for the control of acute or delayed emesis. The antiemetic effects of ondansetron (Qi Lu) and Zofram (Glaxo) are similar. The side-effects of ondansetron are mild.

Chloride is required for receptor-mediated divalent cation entry in mesangial cells

Agonists which stimulate the inositol 1,4,5 trisphosphate ([1,4,5]-IP3)-dependent mobilization of Ca2+ from intracellular stores also stimulate entry of divalent cations across the cell membrane. Under appropriate experimental conditions, divalent cation entry across the cell membrane can be monitored as the rate at which the intracellular fluorescence of divalent cation indicators is quenched by the addition of Mn2+ to the extracellular medium. We report that addition of vasopressin to fura-2-loaded glomerular mesangial cells in culture markedly accelerated the rate at which Mn2+ quenched fura-2 fluorescence at its Ca(2+)-insensitive wavelength in the presence of extracellular NaCl, but that this quench response was attenuated when Cl- was removed from the extracellular medium by equimolar substitution with impermeant anions (gluconate, methanesulfonate, acetate, lactate). Similarly, loss of agonist-induced quench also occurred when Cl- was substituted with gluconate in K(+)-containing media. Addition of the Cl- channel inhibitor, 5-nitro-2-(3-phenylpropylaminobenzoic acid) (NPPB), also inhibited Mn(2+)-induced quench of fura-2 fluorescence following vasopressin addition. In contrast, in the presence of gramicidin to provide an alternate conductance pathway to accompany divalent cation entry, agonist-dependent Mn2+ quench occurred even in the absence of extracellular Cl-, indicating that the requirement for Cl- was not the result of cotransport on a common transporter nor the result of Cl- serving as a necessary cofactor for divalent cation entry. A similar dependence on extracellular Cl- was observed for other Ca(2+)-mobilizing agonists such as endothelin, as well as the intracellular Ca2+ ATPase inhibitor, thapsigargin. Extracellular Cl- dependence for agonist-induced divalent cation entry was also reflected in a corresponding extracellular Cl- dependence for agonist-induced mesangial cell contraction. It has been previously shown by ourselves (Kremer et al., 1992a, Am. J. Physiol., 262:F668-F678) and others that agonist-stimulated calcium mobilization in mesangial cells is accompanied by inhibition of K+ conductance and increased Cl- conductance. Accordingly, we conclude that the current findings suggest that activation of Cl- conductance provides regulated charge compensation for receptor-mediated divalent cation entry in response to Ca(2+)-mobilizing vasoconstrictor agonists in mesangial cells.

[Development of a monoclonal antibody (AF9) to human breast carcinoma]

A monoclonal antibody AF9 (IgG1) was raised against human breast carcinoma by fusing murine myeloma SP2/0 cells with spleen cells from BALB/c mice immunized with cell membrane extracts from primary breast carcinoma. Immunohistochemical staining using the antibody showed reactivity in 19 out of 20 breast carcinoma tissues and in some nonbreast carcinomas such as hepatic, ovarian, lung, colon, and gastric carcinoma tissues. But no staining was observed in either normal tissues or other carcinomas. By immunological treatment, the antigen recognized by AF9 was referred to be glycoprotein with lipid component, and Western blotting revealed that its molecular weight is 51, 56, 67 and 73kd.

The synthesis and in vitro evaluation of a 99mtechnetium-nitroimidazole complex based on a bis(amine-phenol) ligand: comparison to BMS-181321

We have developed a 99mTechnetium complex for imaging of hypoxic tissue (BMS-181321). Recently, another nitroimidazole derivative, based upon a bis(amine-phenol) ligand, was described in the patent literature. To compare this compound to BMS-181321, we have synthesized the ligand, prepared its 99mTc complex, and evaluated its performance in two in vitro assays of bioefficacy: membrane permeability and uptake in normoxic and anoxic cardiocytes. In attempting to reproduce the synthesis of the ligand described in the patent application, we found that one intermediate could not be made by the method described, and alternative routes were investigated. Complexation of the bis(amine-phenol) nitroimidazole with 99mTc gave an apparent single complex; this appeared as a broad peak on HPLC analysis. Purification by a solid-phase method gave a complex with 95% radiochemical purity. This complex was not permeable to cultured bovine brain endothelial cells nor did it show preferential uptake in anoxic myocytes.

[Detection of isoferritin level in breast cancer tissue and serum]

ELISA (double-determinant) was used to evaluate the isoferritin level in the breast cancer tissue. The isoferritin concentration was measured in cytosol extracts of 25 breast cancer tissues (BCT), 6 cancer surrounding tissues (CST) and 8 normal breast tissues (NBT). With the results of 16,023 +/- 15,732, 2467 +/- 1360 and 1382 +/- 647 ng/mcp (milligrams of ontosol protein), respectively. The isoferritin concentrations of BCT and CST were 11.6 and 1.8 times as much as that of NBT, and the differences were statistically significant (P < 0.001 and 0.05). The serum isoferritin level was also measured in 96 healthy persons and 68 breast cancer patients (mean 58.7 +/- 35.8 and 473.3 +/- 297.3 ng/ml) with the difference as big as 8.1 times. The results have demonstrated that the level of cytosol isoferritin in BCT is an important parameter of breast tissue malignance and may be also responsible for the serum isoferritin increase. Therefore we think that serum isoferritin may be used as a marker for early diagnosis of breast cancer.

[Biochemical effects of maternal intravenous and intra-amniotic infusion of amino-acids on fetal blood]

Before elective cesarean section, 58 normal term's pregnant women were randomly divided into three groups: intravenous (25 women), intra-amniotic (8 women) and control (25 women) groups. The first two groups received maternal intravenous and intra-amniotic infusion of amino acids respectively. The results showed that maternal intravenous administration of amino-acids led to increased levels of amino acids in maternal venous blood and fetal umbilical cord blood plasma (P < 0.05). There was no increase in fetal uptake of amino acids (P > 0.05). The levels of amino acids in fetal umbilical cord blood plasma of the intra-amniotic group were higher than those of the control group (P < 0.05) and intravenous group (P < 0.05). In the intra-amniotic group, the fetal uptake of amino acids increased (P < 0.05). There were no significant differences in fetal umbilical arterious pH, PO2 and PCO2 among the three groups (P > 0.2). Intra-amniotic infusion of 250ml amino-acids did not change the pressure of amniotic cavity (P > 0.2). The authors suggested that intra-amniotic infusion of amino acids, as a paraplacental nutritional route, should be more effective in the treatment for cases of intrauterine fetal growth retardation particularly for those accompanied by severe placental lesions.

Ionic mechanisms of electronic inhibition and concealed conduction in rabbit atrioventricular nodal myocytes

BACKGROUND

The term "concealed conduction" is used in electrocardiography when a proximal (atrial or ventricular) impulse penetrates the atrioventricular (AV) node but fails to traverse it completely. Its penetration into the node is inferred by its after effects on the propagation of succeeding impulses. Concealed AV nodal conduction is a well-established phenomenon, but its precise cellular and subcellular mechanisms are unknown. It has been suggested that concealed conduction results from a transient impairment of excitability caused by the subthreshold depolarization (ie, electrotonic inhibition) that is elicited downstream of the site of block.

METHODS AND RESULTS

We studied the ionic mechanism of electrotonic inhibition and concealed conduction in single myocytes isolated from the rabbit AV node. Cells were paced using just-threshold current pulses delivered at a constant (basic) cycle length of 1 second. Appropriately timed interpolation of a conditioning pulse of depolarizing but subthreshold current led to failure of the subsequent, previously successful activation. The ability of the subthreshold response to inhibit subsequent excitation was increased when the interval between the conditioning and succeeding pulses was shortened, when the amplitude of the conditioning pulse was increased, or when the inward sodium current was blocked by superfusion with tetrodotoxin (30 microM). Voltage clamp analysis demonstrated that electrotonic inhibition results from partial inactivation of the transient calcium current (ICa.T). Similar results were obtained using a mathematical model (Hodgkin-Huxley type) of the AV nodal myocyte. Additional simulations in a linear array of AV nodal cells showed that when a premature impulse fails to traverse the AV node, the subthreshold depolarization elicited downstream of the site of block may lead to a transient reduction of excitability with consequent delay or block of the succeeding impulse.

CONCLUSIONS

The overall data strongly suggest that some of the electrocardiographic manifestations of concealed AV conduction are the result of electrotonic inhibition of excitability secondary to a transient decrease in ICa.T.