Analysis and origins of the human and mouse RNase L genes: mediators of interferon action

The 2',5'-oligoadenylate-activated enzyme, RNase L, is an endoribonuclease implicated in the antiviral and apoptotic activities of interferons. To probe the genetics of the 2-5A system, the human and mouse genes were cloned, characterized, and compared. The first coding exon of both genes encodes the regulatory regions of RNase L, 67-70% of the proteins including nine ankyrin repeats, the 2-5A binding domain, and several protein kinase homology motifs. In contrast, the coding sequence for the ribonuclease domain in the mouse and human gene is divided among three exons. The transcriptional start site of the human RNase L gene was located in noncoding exon I by primer extension analysis. A complete coding sequence of mouse RNase L was obtained revealing a 735-amino acid protein with 64% identity to human RNase L. A hypothesis is presented concerning the evolutionary relationship of RNase L to both an ankyrin repeat protein kinase and the kinase-endoribonuclease. IRE1, that mediates the unfolded protein response.

[Clinical analysis of 10 cases of true histiocytic lymphoma]

OBJECTIVE

To explore the clinical and pathological characteristics of true histiocytic lymphoma.

METHODS

The clinical and pathological data of 10 true histiocytic lymphoma patients admitted between 1986 and 1996 to our hospital was retrospectively reviewed.

RESULTS

True histiocytic lymphoma accounted for 0.6% of non-Hodgkin's lymphoma(NHL) admitted in this period to our hospital. Enzymes associated with true histiocytic lymphoma were detected in all the 10 cases. The tumor cells were excluded from T/B lymphoid origin in 6 cases by immunohistochemistry. Eight cases received chemotherapy + irradiation +/- excision of primary lesion, 1 simply received irradiation and 1 received bone marrow transplantation. The response rate was 100%, with a 1, 3 and 5 year survival rate of 100%, 90% and 70%, respectively. The expected 10 year disease free survival rate is 40%.

CONCLUSION

True histiocytic lymphoma is a rare subset of NHL. Those originated from lymph node are sensitive to chemotherapy and irradiation with a favorable prognosis.

Inhibition of formation of oxidative volatile components in fermented cucumbers by ascorbic acid and turmeric

Two naturally occurring antioxidants, ascorbic acid and turmeric, were effective in inhibiting formation of hexanal, (E)-2-penenal, (E)-2-hexenal, (E)-2-heptenal, and (E)-2-octenal when slurries of fermented cucumber tissue were exposed to oxygen. Added ascorbic acid prevented formation of most of these oxidative aldehydes at 175 ppm or greater. Turmeric, which is used commercially as a yellow coloring in cucumber pickle products, was found to almost completely prevent aldehyde formation at 40 ppm.

RNase L-independent specific 28S rRNA cleavage in murine coronavirus-infected cells

We characterized a novel 28S rRNA cleavage in cells infected with the murine coronavirus mouse hepatitis virus (MHV). The 28S rRNA cleavage occurred as early as 4 h postinfection (p.i.) in MHV-infected DBT cells, with the appearance of subsequent cleavage products and a decrease in the amount of intact 28S rRNA with increasing times of infection; almost all of the intact 28S rRNA disappeared by 24 h p.i. In contrast, no specific 18S rRNA cleavage was detected in infected cells. MHV-induced 28S rRNA cleavage was detected in all MHV-susceptible cell lines and all MHV strains tested. MHV replication was required for the 28S rRNA cleavage, and mature cytoplasmic 28S rRNA underwent cleavage. In certain combination of cells and viruses, pretreatment of virus-infected cells with interferon activates a cellular endoribonuclease, RNase L, that causes rRNA degradation. No interferon was detected in the inoculum used for MHV infection. Addition of anti-interferon antibody to MHV-infected cells did not inhibit 28S rRNA cleavage. Furthermore, 28S rRNA cleavage occurred in an MHV-infected mouse embryonic fibroblast cell line derived from RNase L knockout mice. Thus, MHV-induced 28S rRNA cleavage was independent of the activation of RNase L. MHV-induced 28S rRNA cleavage was also different from apoptosis-related rRNA degradation, which usually occurs concomitantly with DNA fragmentation. In MHV-infected 17Cl-1 cells, 28S rRNA cleavage preceded DNA fragmentation by at least 18 h. Blockage of apoptosis in MHV-infected 17Cl-1 cells by treatment with a caspase inhibitor did not block 28S rRNA cleavage. Furthermore, MHV-induced 28S rRNA cleavage occurred in MHV-infected DBT cells that do not show apoptotic signs, including activation of caspase-3 and DNA fragmentation. Thus, MHV-induced 28S rRNA cleavage appeared to differ from any rRNA degradation mechanism described previously.

[Inhibition of growth and metastasis of human giant cell carcinoma of the lung by transfection of antisense VEGF121 cDNA]

OBJECTIVE

To explore the effects of blocking the VEGF/VEGF receptor paracrine pathway on growth and metastasis of human lung carcinoma cell line PG and to evaluate its potential application in gene therapy of cancer.

METHODS

The eukaryotic expression vectors bearing either sense-VEGF121 cDNA or antisense-VEGF121 cDNA was constructed and transfected into PG cells. In vitro and in vivo tests such as Northern blotting hybridization, Western blotting immunochemistry analysis, as well as xenografting in nude mice were used to analyze the effect of antisense-VEGF.

RESULTS

The transfectants stably expressing antisense VEGF121 were observed to produce markedly reduced 3.3 kb VEGF mRNA and 45 KD, 41 KD, 32KD VEGF proteins. When xenografted s.c. into nude mice, growth and metastasis of the antisense-VEGF transfected cell lines were greatly inhibited when compared with control cells.

CONCLUSION

Antisense VEGF gene significantly inhibited tumor growth and metastasis and may provide an experimental example for the development of antiangiogenic gene therapy.

Detection and analysis of Bacillus subtilis growth with piezoelectric quartz crystal impedance based on starch hydrolysis

A piezoelectric quartz crystal (PQC) impedance method based on the alpha-amylase-catalyzed hydrolysis of starch present in a culture medium has been developed for in situ monitoring of the whole growth process of Bacillus subtilis and the variation in the activity of alpha-amylase during bacterial growth. An S-shaped response behavior was observed for Deltaf(0), and simultaneously inverse S-shaped responses were found for DeltaR(1) and DeltaL(1). The ratio of DeltaR(1) to Deltaf(0) or DeltaL(1) coincided well with that calculated from Martin's equations reflecting the solution density-viscosity effect, suggesting that the continuing change in liquid loading onto the PQC surface causes significant variation in Deltaf(0), DeltaR(1), and DeltaL(1). Bacterial growth equations were derived from the kinetics of the enzyme-catalyzed hydrolysis of starch, which fit well with the experimental responses of Deltaf(0), DeltaR(1), and DeltaL(1). Kinetic parameters of bacterial growth, including the asymptote (A), the maximum specific growth rate (microm), and the lag time (lambda), were obtained and were in good agreement with those obtained from the pour plate count method. The variation in the activity of alpha-amylase exhibited peak-type behavior with its maximum value at the later stage of the log phase. In addition, the influence of initial bacterial concentration was also investigated.

Study of the Adsorption of Glutathione on a Gold Electrode by Using Electrochemical Quartz Crystal Impedance, Electrochemical Impedance Spectroscopy, and Cyclic Voltammetry

Adsorption of a biological peptide, glutathione, on a gold electrode was studied by using electrochemical quartz crystal impedance (EQCI), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV) techniques. The time courses of responses of piezoelectric and electrochemical impedance parameters were simultaneously obtained during the adsorption processes of the two forms of peptide, oxidized and reduced glutathione. It was found that the frequency curve due to the oxidized glutathione (GSSG) adsorption exhibited a character of a sum of two exponential functions. For reduced glutathione (GSH), the frequency adsorption curve could be expressed by a first-order reaction kinetic model and the corresponding kinetic parameters at different amounts of GSH were obtained. The heterogeneous charge-transfer rate constants of ferricyanide/ferrocyanide before and after the peptide adsorption were determined by CV and EIS methods, respectively. According to the simple equivalent electric network of the electrochemical interface, the electrochemical impedance parameters were also obtained. The results showed that the proposed method should be found in wider applications in interfacial biochemistry studies since these combined techniques have advantages in real time multidimensional information including electrochemical and electrochemical impedance parameters. Copyright 2000 Academic Press.

Plasminogen activator inhibitor-1 fused with erythropoietin (EPO) mimetic peptide (EMP) enhances the EPO activity of EMP

Erythropoietin (EPO) mimetic peptide (EMP) encoding sequence was inserted into the gene of plasminogen activator inhibitor-1 (PAI-1) between Ala348 and Pro349 (P2'-P3'), generating a novel gene, PAI-1/EMP (PMP). This was cloned into pET32a expression vector, fused with TrxA peptide in the vector, and a 63-kDa protein was expressed in inclusion bodies with an expression level >50%. The TrxA/PMP protein was purified by Ni-NTA-agarose metal-ligand affinity chromatography to a purity >90%, showing a single, silver-stained band on SDS-PAGE. Using a reticulocyte counting assay, the EPO activity of PMP was determined to be 5,000 IU/mg, 2,500-fold that of EMP.

Renal protective effects of blocking the intrarenal renin-angiotensin system: angiotensin II type I receptor antagonist compared with angiotensin-converting enzyme inhibitor

The present study compared renoprotective effects of angiotensin II type I receptor antagonist (AT1RA) with angiotensin converting enzyme inhibitor (ACEI), and their influence on the renin-angiotensin-system (RAS). Experimental nephrotic syndrome was induced in SD rats by repeated peritoneal injections of puromycin. Twenty-eight rats were randomly divided into four groups: normal control, nephrotic control, ACEI-treated, and AT1RA-treated groups. Serum, urine, and renal tissue were collected for study at the end of 12 weeks. Compared with those of the nephrotic control group, urinary protein was less and renal function was better in both treated groups. The glomerular and interstitial damage indexes of both ACEI- and AT1RA-treated rats were lower than those of nephrotic control rats, with no significant difference observed between the two treated groups. Local renal ACE activity and angiotensin II concentration were elevated in nephrotic rats (p< 0.01). However, there is no significant difference in circulating RAS, renal tissue renin, and aldosterone between the normal control and nephrotic control rats. As expected, enalapril inhibited the local renal ACE activity and significantly decreased angiotensin II (p< 0.01). Intrarenal ACE activity and angiotensin concentration returned to normal levels after treatment with irbesartan (p< 0.01). In conclusion, AT1RA and ACEI have comparable renal protective effects, and these protective effects were associated with the inhibition of intrarenal ANG II.

Effect of deficiency of the double-stranded RNA-dependent protein kinase, PKR, on antiviral resistance in the presence or absence of ribonuclease L: HSV-1 replication is particularly sensitive to deficiency of the major IFN-mediated enzymes

Control of viral replication by interferon (IFN) is thought to be principally mediated by the 2',5'-oligoadenylate synthetase (OAS)/RNAse L, double-stranded dependent protein kinase (PKR), and myxovirus resistance protein (Mx) pathways. In this study, we monitored the constitutive and IFN-induced antiviral activity in mouse embryo fibroblasts lines derived from mice with targeted disruption of either PKR or PKR/RNAse L genes. At high multiplicity of infection (moi = 10), the absence of PKR had no effect on replication of vesicular stomatitis virus (VSV) but moderately enhanced encephalomyocarditis virus (EMCV) growth and greatly increased replication of herpes simplex virus-1 (HSV-1). Replication of EMCV, HSV-1, and VSV was modestly higher in PKR-/- RNAse L-/- fibroblasts when compared with control cells. Although the antiviral action of IFN-alpha was unaffected by the absence of PKR, IFN action was significantly impaired in the double knockout cells but was dependent on the stage of the virus cycle. At early stages, it appeared that anti-EMCV and anti-HSV-1 action of IFN-alpha was significantly compromised, although weak residual antiviral activity was seen. The action of IFN-alpha against VSV was specifically compromised at a late stage of virus replication. The results showed that PKR is an important mediator in constitutive resistance against HSV-1 and that RNAse L is also necessary for the full antiviral activity of IFN against a variety of viruses. These results supported the existence of novel pathways aimed toward specific stages of the virus life cycle.

[Detection of interleukin-8 and nitric oxide in chronic prostatitis]

We detected levels of interleukin-8(IL-8) and nitric oxide(NO) in 62 prostatic fluids. The results were that microbiologic exam, IL-8 content, and NO level in control group were all negative; there was not significant difference on the microbiologic exam and NO level between the chronic prostatitis group and non-prostatitis group; there was significant difference between two groups of IL-8 positive ratio. These results suggest that the IL-8 detected in the prostatic fluid of patients with prostatitis may be a diagnostic indicator of prostatic infection.

[Clinical evaluation of cardiac troponin I in ischemic heart diseases]

The detection of cardiac troponin I(cTnI), including serum or plasma, was evaluated in 114 patients with ischemic heart diseases or other heart diseases. The results were that the sensitivity of cTnI detection(qualitative analysis, cutoff is 0.2 ng.ml-1) was higher than that of creatine kinase(CK), creatine kinase-MB(CK-MB), alpha-hydroxybutyrate dehydrogenase(alpha-HBD), lactic dehydrogenase(LDH), and aspartic transaminase(AST) for diagnosing acute myocardial infarction (AMI) (93.2% vs 68.2%, 68.2%, 65.9%, 65.9%, and 75.0%; P < 0.05; respectively). The specificity of cTnI detection was higher than that of alpha-HBD, LDH, and AST(95.2% vs 81.0%, 73.8%, and 54.0%; P < 0.05; respectively) and similar to CK and CK-MB(95.2% vs 83.3% and 83.3%; P > 0.05; respectively). On the other hand, the sensitivity of cTnI in patients with unstable angina pectoris was 45.5%. It was higher than stable angina pectoris and lower than AMI. The results suggest that the cardiac troponin I is a better cardiac injury marker than other cardiac markers for diagnosing AMI.

Determination of the binding parameters of drug to protein by equilibrium dialysis/piezoelectric quartz crystal sensor

A novel method, equilibrium dialysis/piezoelectric quartz crystal sensor, applied to determine the binding parameters of diethyldithiocarbamate to human plasma protein is proposed. Based on the investigation of the equilibrium reaction for the binding of drug to protein, the related theoretical equations for this binding were derived. By monitoring the frequency responses of a copper-plated piezoelectric quartz crystal sensor to drug in and out of a dialysis membrane after equilibrium, the binding parameters were determined, i.e., 0.375 micromol g(-1) for beta(p), 6.496 microM for K(dp), 141.99 L mmol(-1) for K(p), and 0.043 for N. These values were in good agreement with reference values. It was found that this method may have application for studying the characteristics of the interaction between other drugs and proteins.

Thyroid organoid formation in simulated microgravity: influence of keratinocyte growth factor

The generation of artificial human thyroid tissues in suspension (low-shear environment, present in simulated microgravity [MG] and generated by a rotary cell culture system [RCCS]), was enhanced by increasing medium kinematic viscosity with a (3% v/v) suspension of extracellular matrix (basement membrane extract [BME]) in serum-free medium to generate artificial human thyroid organoids. Recombinant human keratinocyte growth factor (KGF, 7 ng/mL) facilitated human thyrocyte aggregation and three-dimensional (3-D) differentiation. There was an MG-associated decrease in extractable DNA that was reversed after addition of keratinocyte growth factor (KGF). In simulated MG, the increase in extractable DNA after KGF addition was up to 170% over non-KGF control cultures. In contrast, monolayer cultures in unit gravity showed a maximum DNA increase of 39% after KGF addition. Morphologically, differentiated thyroid neofollicles displayed polarization and were located in close proximity after 2 weeks of culture. Immunogold labeling with antibody to human thyroglobulin (Tg) revealed staining of follicular lumina and secretory vesicles, and a time-dependent increase in human Tg was detected in the culture media. Culture under simulated MG thus allowed direct visualization of KGF-facilitated thyrocyte/extracellular matrix interaction. Such artificial human thyroid organoids-generated in MG and in the presence of KGF-structurally resembled natural thyroid tissue. The above findings may have implications for autoimmune thyroid disease where KGF (if, for example, secreted locally by intraepithelial gammadelta T cells among other cells) may contribute to thyroid cell growth.

Transcriptional control of the human plasma membrane phospholipid scramblase 1 gene is mediated by interferon-alpha

Interferons (IFNs) mediate their diverse biologic activities through induction of the expression of multiple genes. Whereas the mode of action of certain of these IFN-regulated genes has been well characterized, most of the molecular and cellular events underlying the constellation of biologic responses to the IFNs remain unresolved. This study showed that the newly identified PLSCR1 gene for phospholipid scramblase, previously implicated in remodeling of plasma membrane phospholipids, is regulated at the transcriptional level by IFN-alpha. Analysis of 5' flanking genomic sequence in reporter constructs showed that transcriptional control of PLSCR1 was entirely regulated by a single IFN-stimulated response element located in the first exon. A similar induction of PLSCR1 by IFN-alpha2a was also observed in a variety of other human tumor cell lines as well as in human umbilical vein endothelial cells. In these cell lines, the marked IFN-alpha2a-induced increase in PLSCR1 protein expression, ranging as high as 10-fold above basal levels, was not accompanied by increased cell surface exposure of phosphatidylserine, suggesting that remodeling of the cell surface requires both exposure to IFN and a second yet-to-be identified event to stimulate plasma membrane phospholipid scramblase activity and to mobilize phosphatidylserine to the cell surface. (Blood. 2000;95:2593-2599)

[The hereditary liability of otosclerosis and the strategies for treatment and prevention]

OBJECTIVE

Otosclerosis is a disease of hereditary liability. It might be related to an autosomal dominant inheritance. The genetic penetrance is determined by multifactorial influences. This paper was designed to study the reasonable strategies for prevention and treatment of this disease.

METHODS

A retrospective review derived from data of the management and follow-up of 14 cases in 6 families. According to the special pathological features of active phase of the otospongiosis, the suitable strategies for prevention and treatment of this disease were suggested.

RESULTS

Diagnosis of 14 cases were confirmed by audiological, operative and/or pathological examinations. Eleven of fourteen cases underwent stapedectomy, in which 10 cases had the surgery on the ear with severer hearing loss, and one case on both sides. In all of the surgical cases, hearing levels improved significantly. Three cases have not yet received the stapedectomy, in which two cases scheduled for the surgery are currently treated by chondroitin sulfate and one case refused the surgical treatment due to financial shortage.

CONCLUSION

Examination of the ear function at regular intervals (6-12 months) is recommended for the adults among the family members with high-incidence of otosclerosis. Audiological and radiological examination play an important role in early diagnosis and treatment. Attention should be paid to the medicine for management and prevention of this disease. Stapedectomy is an optimal choice for clinical otosclerosis not only due to its capacity to improve the hearing level but also to prevent the advance of hearing loss. Hearing aid is the suitable choice if stapedectomy is contraindicated.

[The effects of electroporation-mediated erythropoietin (EPO) gene transfer into skeleton muscle on renal anemia]

OBJECTIVE

To investigate the effects of erythropoietin (EPO) gene transfer into skeleton muscle mediated by electroporation on renal anemia.

METHODS

Renal failure models were created by adenine-excessive diet (150 mg per day). Plasmid vectors encoding EPO were transferred by electroporation after 80 days when mean blood urea nitrogen level (BUN) had increased from 3.4 mmol/L +/- 1.3 mmol/L to 18.1 mmol/L +/- 4.1 mmol/L and the hematocrit had decreased from 45.6% +/- 2.1% to 25.4% +/- 3.7%. During the process of treatment, adenine-excessive diet was given. Hb, HCT, BUN and Cre in blood were tested by automatic analyzer; EPO level in the serum was tested by EPO ELISA kit, EPO gene expression was proved by RT/PCR. The survival rate was calculated.

RESULTS

Hematocrit increased to 34.4% +/- 7.5% only 7 days after the treatment and reached 91.4% of normal level (46% +/- 2%) after 5 weeks. The survival rate of test models after 9 weeks was 77.8%, which was remarkably higher than that of controls (16.7%). mRNA level of EPO gene expression was indicated by RT/PCR.

CONCLUSION

Electroporation can increase the efficiency of EPO gene transfer and thus greatly improve hematocrit in mice and prolong the life-span of chronic renal anemia models. This method can provide a new way for treatment of EPO-responsive anemias.

[The inhibition of prourokinase gene transfer on deposition of platelets on rabbit carotid artery intima]

OBJECTIVE

To observe the expression of pro-urokinase (proUK) gene in rabbit carotid artery transfected with replication-deficient adenovirus vector containing proUK gene (Ad/prouk) and the deposition of platelet on the same injured vessel.

METHODS

Ad/proUK (Ad/proUK, 3 x 10(10) pfu/ml) was injected into the right carotid artery locally. Wild type adenovirus (Ad) was locally injected into the left carotid artery as self-control. The expression of proUK gene was investigated by immunohistochemistry assay. After injury of the gene-transfected vessel by electric stimulation, the deposition of (111) In-labeled platelet was quantitatively observed. The thrombosis was observed with HE-stained vessel section.

RESULTS

There were lots of proUK granules in the endothelium of Ad/proUK gene-transfected vessel. The differences in (111) In-platelets deposition per gram dry weight vessel segment were significant between Ad/proUK and Ad transfected control vessels [(4.60 +/- 0.93) x 10(7)/g vs control (27.95 +/- 4.93) x 10(7)/g, P < 0.01)]. The HE-stained vessel section showed that there were only small thrombi in proUK gene-transfected vessel but massive thrombi almost blocked up the whole vessel in control vessel.

CONCLUSION

The proUK gene-transfected vessel can obviously inhibit (111) In-labeled platelet deposition on injured vessel and thus thrombosis.

Development of oxidized odor and volatile aldehydes in fermented cucumber tissue exposed to oxygen

Changes in volatile compounds in fermented cucumber tissue during exposure to oxygen were investigated by purge and trap sampling, followed by GC-MS. Hexanal and a series of trans unsaturated aldehydes, (E)-2-pentenal, (E)-2-hexenal, (E)-2-heptenal, and (E)-2-octenal, increased in fermented cucumber slurries exposed to oxygen. Sensory evaluation of oxidized odor was correlated with the increase in aldehyde concentrations. Other identified volatile components present after fermentation did not show major changes during exposure to oxygen. There was no decrease in the formation of aldehydes in fermented cucumber samples that were heated to inactivate enzymes before exposure to oxygen. These results indicated that the formation of aldehydes in oxygen was due to nonenzymatic reactions.

Activation of p38 mitogen-activated protein kinase and c-Jun NH(2)-terminal kinase by double-stranded RNA and encephalomyocarditis virus: involvement of RNase L, protein kinase R, and alternative pathways

Double-stranded RNA (dsRNA) accumulates in virus-infected mammalian cells and signals the activation of host defense pathways of the interferon system. We describe here a novel form of dsRNA-triggered signaling that leads to the stimulation of the p38 mitogen-activated protein kinase (p38 MAPK) and the c-Jun NH(2)-terminal kinase (JNK) and of their respective activators MKK3/6 and SEK1/MKK4. The dsRNA-dependent signaling to p38 MAPK was largely intact in cells lacking both RNase L and the dsRNA-activated protein kinase (PKR), i. e., the two best-characterized mediators of dsRNA-triggered antiviral responses. In contrast, activation of both MKK4 and JNK by dsRNA was greatly reduced in cells lacking RNase L (or lacking both RNase L and PKR) but was restored in these cells when introduction of dsRNA was followed by inhibition of ongoing protein synthesis or transcription. These results are consistent with the notion that the role of RNase L and PKR in the activation of MKK4 and JNK is the elimination, via inhibition of protein synthesis, of a labile negative regulator(s) of the signaling to JNK acting upstream of SEK1/MKK4. In the course of these studies, we identified a long-sought site of RNase L-mediated cleavage in the 28S rRNA, which could cause inhibition of translation, thus allowing the activation of JNK by dsRNA. We propose that p38 MAPK is a general participant in dsRNA-triggered cellular responses, whereas the activation of JNK might be restricted to cells with reduced rates of protein synthesis. Our studies demonstrate the existence of alternative (RNase L- and PKR-independent) dsRNA-triggered signaling pathways that lead to the stimulation of stress-activated MAPKs. Activation of p38 MAPK (but not of JNK) was demonstrated in mouse fibroblasts in response to infection with encephalomyocarditis virus (ECMV), a picornavirus that replicates through a dsRNA intermediate. Fibroblasts infected with EMCV (or treated with dsRNA) produced interleukin-6, an inflammatory and pyrogenic cytokine, in a p38 MAPK-dependent fashion. These findings suggest that stress-activated MAPKs participate in mediating inflammatory and febrile responses to viral infections.

Investigation of Electrosorption of Organic Molecules onto Gold and Nickel Electrodes Using an Electrochemical Quartz Crystal Microbalance

The adsorption behaviors of two organic molecules, benzoic acid (BA) and 2-butyne-1,4-diol (BD), on metal electrodes have been studied using an electrochemical quartz crystal microbalance (EQCM) combined with the cyclic voltammetry technique. In the range of potentials studied, BA molecules were adsorbed onto an electrodeposited gold electrode with a saturation concentration of 5.0 x 10(14) molecules/cm(2). It was found that the Frumkin isotherm model was most suitable to depict the electrosorption behavior. The isotherm parameters by nonlinear fitting, which agreed with the literature values, implied BA was chemisorbed on the gold surface. For BD on an electrodeposited nickel electrode, the equivalent molar mass of the reaction species was calculated on the basis of the voltammetry curve and mass curve, which were obtained simultaneously during the potential scan. The analysis of EQCM data for the electrosorption of BD on gold and nickel electrodes showed an irreversible characteristic; the latter effectively inhibited the hydrogen evolution reaction. Copyright 1999 Academic Press.

Formation of the antithrombin heterodimer in vivo and the onset of thrombosis

Antithrombin is shown to undergo a slow spontaneous conversion to its inactive latent conformation with readily discernible amounts present in plasma on incubation at 37 degrees C for 72 hours. More rapid conversion occurs on incubation of isolated antithrombin at 41 degrees C or 50 degrees C, but the appearance on electrophoresis of free latent antithrombin is preceded by the formation, in reciprocal proportions, of a new slow band. This slow component is shown to be a heterodimer of active and latent antithrombin. It can be isolated as a single stable band either by incubation of antithrombin or by mixing equimolar proportions of active and latent antithrombin under the same conditions that give overnight crystallization of the active/latent antithrombin heterodimer. Similarly, equimolar addition of latent antithrombin to plasma results electrophoretically in a quantitative shift to the slower heterodimer mobility. Clinically, the presence of latent antithrombin is potentially deleterious, because its linkage to form the heterodimer results in inactivation of the otherwise normal molecule linked to the latent antithrombin. In the case of alpha-antithrombin, because the dimer readily dissociates, there is only a 11% additive loss of activity, but with beta-antithrombin the dimer appears more stable, with the additive loss of activity from the normal beta component being 21%, increasing to 33% on stabilization of the dimer with heparin. This linked and selective loss of activity of beta-antithrombin provides an explanation for the unexpected severity of thrombotic episodes in heterozygotes with conformationally unstable antithrombins.