Progesterone inhibits glucocorticoid-induced murine thymocyte apoptosis

Sex and sex hormones modulate immune development and responses. A primary target of their effects is the structure and cellularity of the thymus; therefore, we examined the effects of sex and sex steroids on thymocyte apoptosis. We demonstrate initially that male DBA mice have a significantly higher percentage of glucocorticoid-induced apoptotic thymocytes (46.1+/-3.8%) than their female counterparts (31.6+/-3.1%; P=0.012). We postulated that this gender difference was due to differential modulation of glucocorticoid-induced apoptosis by sex hormones such as estrogen, testosterone or progesterone. Both estrogen and testosterone increased in vitro thymocyte apoptosis. In contrast, progesterone not only inhibited spontaneous in vitro thymocyte apoptosis, but also prevented in vitro glucocorticoid-induced apoptosis. Progesterone administration also suppressed glucocorticoid-induced in vivo thymocyte apoptosis. These results suggest that anti-apoptotic effects of progesterone may influence T cell development and subsequent immune responses.

A regulatory cascade of the nuclear receptors FXR, SHP-1, and LRH-1 represses bile acid biosynthesis

Bile acids repress the transcription of cytochrome P450 7A1 (CYP7A1), which catalyzes the rate-limiting step in bile acid biosynthesis. Although bile acids activate the farnesoid X receptor (FXR), the mechanism underlying bile acid-mediated repression of CYP7A1 remained unclear. We have used a potent, nonsteroidal FXR ligand to show that FXR induces expression of small heterodimer partner 1 (SHP-1), an atypical member of the nuclear receptor family that lacks a DNA-binding domain. SHP-1 represses expression of CYP7A1 by inhibiting the activity of liver receptor homolog 1 (LRH-1), an orphan nuclear receptor that is known to regulate CYP7A1 expression positively. This bile acid-activated regulatory cascade provides a molecular basis for the coordinate suppression of CYP7A1 and other genes involved in bile acid biosynthesis.

Effect of buprenorphine on CYP3A activity in rat and human liver microsomes

Buprenorphine is a partial opioid agonist available in France as an alternative to methadone in the treatment of opiate-dependent individuals. Twenty deaths have been reported in patients who have ingested buprenorphine in combination with benzodiazepines. Since buprenorphine and many benzodiazepines are CYP3A substrates, the effect of buprenorphine on CYP3A activity was examined in order to assess the likelihood of a pharmacokinetic interaction. The formation of 6beta-hydroxytestosterone was measured in dexamethasone-induced rat liver microsomes and in human liver microsomes under control conditions and in the presence of buprenorphine. Buprenorphine was found to be a weak inhibitor of CYP3A with a 50% decrease in enzyme activity occurring at a concentration of 118 microM (IC50) in human liver microsomes. IC50 was 0.3 microM for ketoconazole in the same system. Since the IC50 for buprenorphine is roughly 2000 times higher than typical plasma concentrations, this drug is unlikely to cause clinically significant inhibition of CYP3A in patients. Excessive CNS depression due to the combination of buprenorphine and benzodiazepines is most likely due to additive or synergistic pharmacologic effect unrelated to a pharmacokinetic interaction between the drugs.

Quantitative alleles of CR1: coding sequence analysis and comparison of haplotypes in two ethnic groups

The quantitative expression of complement receptor type 1 (CR1) on erythrocytes is regulated by two CR1 alleles that differ in having genomic HindIII fragments of either 7.4 or 6.9 kb and that determine high (H allele) or low (L allele) CR1 expression, respectively, across a 10-fold range. To investigate whether the product of the L allele may contain amino acid substitutions that make it more susceptible to proteolysis, cDNA sequence spanning the CR1 coding region was analyzed in two donors who were homozygous for the H and L alleles and differed by 7-fold in their mean numbers of CR1 per erythrocyte. Sequence differences were detected at 10 nucleotide positions, including 6 that would cause amino acid substitutions. The HindIII RFLP and 3 of the latter 6 sites were analyzed in genomic DNA of 85 Caucasians and 75 African Americans; sites encoding the other amino acid substitutions were analyzed less extensively. Two major haplotypes defined prototypic H and L alleles in both ethnic groups, suggesting that these alleles existed before the African and European populations diverged. Decreased erythrocyte CR1 expression is associated with impaired clearance of immune complexes from blood. Persistence of the L allele in all populations that have been analyzed may suggest a compensatory survival advantage, perhaps related to malaria or another infectious disease.

Quantitative Alleles of CR1: Coding Sequence Analysis and Comparison of Haplotypes in Two Ethnic Groups

The quantitative expression of complement receptor type 1 (CR1) on erythrocytes is regulated by two CR1 alleles that differ in having genomic HindIII fragments of either 7.4 or 6.9 kb and that determine high (H allele) or low (L allele) CR1 expression, respectively, across a 10-fold range. To investigate whether the product of the L allele may contain amino acid substitutions that make it more susceptible to proteolysis, cDNA sequence spanning the CR1 coding region was analyzed in two donors who were homozygous for the H and L alleles and differed by 7-fold in their mean numbers of CR1 per erythrocyte. Sequence differences were detected at 10 nucleotide positions, including 6 that would cause amino acid substitutions. The HindIII RFLP and 3 of the latter 6 sites were analyzed in genomic DNA of 85 Caucasians and 75 African Americans; sites encoding the other amino acid substitutions were analyzed less extensively. Two major haplotypes defined prototypic H and L alleles in both ethnic groups, suggesting that these alleles existed before the African and European populations diverged. Decreased erythrocyte CR1 expression is associated with impaired clearance of immune complexes from blood. Persistence of the L allele in all populations that have been analyzed may suggest a compensatory survival advantage, perhaps related to malaria or another infectious disease.

Analysis of complement receptor type 1 (CR1) expression on erythrocytes and of CR1 allelic markers in Caucasian and African American populations

CR1 expression on erythrocytes (E) is regulated by an element that is tightly linked in Caucasians to the site of an RFLP of the CR1 gene. Genomic HindIII fragments of 7.4 and 6.9 kb identify alleles that are expressed in high (H allele) or low (L allele) amounts, respectively. When age-fractionated E of donors heterozygous for both the H and L alleles and for CR1 allotypes of differing molecular weights were analyzed in Western blots, the product of the L allele appeared to have an increased rate of loss during cell aging. A coding sequence polymorphism of CR1 predicted to cause a Pro-->Arg substitution in its proximal extramembranous region was tightly linked in Caucasians to the site of the HindIII RFLP. However, neither this polymorphism nor the HindIII RFLP correlated with CR1 expression among African Americans. Relative instability of CR1 encoded by the L allele thus may derive from another coding sequence polymorphism, or may require both the Pro-->Arg substitution and epistatic effects of another polymorphic gene.

Adhesive interactions in hemopoiesis

Blood cells developing in the bone marrow exhibit adhesive interactions with stromal reticular cells and specialized macrophages, and with several defined components of the extracellular matrix. Receptors that are known to participate in these interactions include certain integrins, selectins, members of the immunoglobulin superfamily, and CD44, and this list may be expected to grow. Specific inhibitors of some integrins and of CD44 have been shown to disrupt hemopoiesis in vitro; thus the function of adhesive receptors appears critical to blood cell development. The capacity of such receptors to transmit signals through the plasma membrane suggests that they regulate not just the physical interactions of hemopoietic cells, but also the responses of the cells to their environment.

Iron chelates bind nitric oxide and decrease mortality in an experimental model of septic shock

The hydroxamic acid siderophore ferrioxamine B [FeIII(HDFB)+] and the iron complex of diethylenetri-aminepentaacetic acid [FeIII(DTPA)2-] protected mice against death by septic shock induced by Corynebacterium parvum + lipopolysaccharide. Although FeIII(DTPA)2- was somewhat more effective than FeIII(HDFB)+, the iron-free ligand H4DFB+ was significantly more effective than DTPA. The hydroxamic acid chelator has a much higher iron affinity than the amine carboxylate, allowing for more efficient formation of the FeIII(HDFB)+ complex upon administration of the iron-free ligand. Electrochemical studies show that FeIII(DTPA)2- binds NO stoichiometrically upon reduction to iron(II) at biologically relevant potentials to form a stable NO adduct. In contrast, FeIII(HDFB)+ is a stable and efficient electrocatalyst for the reduction of NO to N2O at biologically relevant potentials. These results suggest that the mechanism of protection against death by septic shock involves NO scavenging and that particularly effective drugs that operate a low dosages may be designed based on the principle of redox catalysis. These complexes constitute a new family of drugs that rely on the special ability of transition metals to activate small molecules. In addition, the wealth of information available on siderophore chemistry and biology provides an intellectual platform for further development.

Adult respiratory distress syndrome induced by a Chinese medicine, Kamisyoyo-san

We report the first case of Kamisyoyo-san-induced adult respiratory distress syndrome (ARDS). A 59-year-old female was given Kamisyoyo-san for treatment of seborrheic dermatitis. She then presented with a respiratory illness having clinical, radiologic and functional characteristics of ARDS. Bronchoalveolar lavage fluid showed an increased number of lymphocytes, neutrophils and eosinophils. The lymphocyte stimulation test with Kamisyoyo-san was positive.

Xenogeneic ICAM-1 gene transfer suppresses tumorigenicity and generates protective antitumor immunity

Tumorigenicity in Fischer rats was not significantly reduced when the rat ICAM-1 gene was overexpressed in the rat tumor cell lines, JM-1 and SST-2. When these rat tumor cell lines were genetically modified with a gene encoding human ICAM-1, tumorigenicity was dramatically reduced. Expression of xenogeneic ICAM-1 did not alter the growth rate, expression of the major histocompatibility complex, nor morphological appearance of the cells. However, it did facilitate a tumor-specific immunological recognition and rejection of the genetically modified tumor cells. This effect resulted in a tumor-specific, long-term protective immunity directed against genetically unmodified tumor cells. Most importantly, administration of tumor cells genetically modified with genes encoding xenogeneic ICAM-1 can facilitate an immunological response to genetically unaltered pre-existing tumors. Transferring splenocytes from animals 'vaccinated' with the xenogeneic ICAM-1 gene altered tumor cells was able to transfer the antitumor response into recipient animals. Furthermore, transfer of CD8+ T lymphocytes produced the same result. These results suggested that tumors specific CD8+ T lymphocytes were activated by the xenogeneic altered tumor cells. THis activation generated the long-term, tumor-specific immunity.

Soluble intercellular adhesion molecule 1 (ICAM-1) antigen in sera of bronchial asthmatics

Previous studies have suggested that intercellular adhesion molecule 1 (ICAM-1, CD54) may be involved in the pathogenesis of asthma. In addition, a soluble form of ICAM-1 (sICAM-1) has been detected in increased concentrations in the sera of patients with certain inflammatory conditions. To determine whether bronchial asthma is associated with increased levels of sICAM-1 in serum and to assess the effects of therapy on these levels, the concentrations of sICAM-1 were measured in sera of healthy donors and asthmatic patients. The mean (+/- SD) level of serum sICAM-1 for 60 asthmatic patients (304.0 +/- 82.5 ng/mL) was significantly higher than that for 39 healthy volunteers (260.9 +/- 67.2 ng/mL; p = 0.004). Twenty-two patients considered to have atopic asthma and 24 patients with nonatopic asthma did not differ in their levels of sICAM-1. In 14 patients, serum concentrations of sICAM-1 were higher during asthma attacks than in the same patients during remission (p = 0.035). Serum sICAM-1 levels were lower in nine patients during treatment with oral prednisolone (2.5 to 40 mg/d) than during periods without systemic corticosteroid therapy (p = 0.002). Thus, active bronchial asthma is associated with the presence of increased levels of sICAM-1 in serum, and these levels may be modulated by corticosteroid therapy.

2-Amino-6-methoxypurine arabinoside: an agent for T-cell malignancies

Earlier studies have shown guanine arabinoside (ara-G) is an effective agent against growth of T-cell lines and freshly isolated human T-leukemic cells. However, poor water solubility of ara-G limits clinical use. 2-Amino-6-methoxypurine arabinoside (506U) is a water-soluble prodrug converted to ara-G by adenosine deaminase. 506U is not a substrate for deoxycytidine kinase, adenosine kinase, or purine nucleoside phosphorylase and is phosphorylated by mitochondrial deoxyguanosine kinase at a rate 4% that of ara-G phosphorylation. Mitochondrial DNA polymerase was the least sensitive to ara-GTP inhibition of the five human DNA polymerases tested. [3H]506U was anabolized to ara-G 5'-phosphates in CEM cells but not to phosphorylated metabolites of 506U. 506U was selective for transformed T over B cells and also inhibited growth in two of three monocytic lines tested. 506U given i.v. to cynomolgus monkeys was rapidly converted to ara-G; the ara-G had a half-life of approximately 2 h. 506U had in vivo dose-dependent efficacy against human T-cell tumors in immunodeficient mice. A Phase 1 trial of 506U against refractory hematological malignancies is now in progress at two study sites.

Targets of nitric oxide in a mouse model of liver inflammation by Corynebacterium parvum

Treatment of mice with Corynebacterium parvum induces chronic inflammation. This treatment followed by an injection of lipopolysaccharide (LPS) produces hepatic necrosis and death. We examined liver tissue by using electron paramagnetic resonance (EPR) spectroscopy and found that, in addition to the previously reported nonheme nitrosyl complexes, heme nitrosyl complexes were also formed. Hemoglobin nitrosyl complexes measured in the whole blood of mice treated with C. parvum were not increased after additional LPS treatment. However, this treatment significantly increased the heme nitrosyl complexes in the liver, whereas the nonheme nitrosyl complex concentration was unaffected. EPR signals from whole blood and liver tissues from mice treated with C. parvum and C. parvum + LPS were inhibited by prolonged treatment with NG-monomethyl-L-arginine (L-NMA). Nitric oxide (.NO) is known to bind to cytochrome P450 heme, and we consistently found a suppression of EPR signals attributable to ferric low-spin cytochrome P450/P420 peaks in the livers of mice treated with C. parvum and C. parvum + LPS. By performing analyses of EPR spectra obtained from hepatocytes exposed to .NO, we were able to unambiguously identify EPR signals attributable to cytochrome P420 and nonheme nitrosyl complexes in the livers of both treatments. Deconvolution of the composite in vivo EPR spectra indicated that hemoglobin nitrosyl complexes contributed weakly in the C. parvum livers, but threefold more in the C. parvum + LPS livers, suggesting that hemorrhage may have occurred. Experiments with L-NMA treatment revealed that this additional .NO production did not correlate with hepatic necrosis and onset of death. Immunoprecipitation of liver cytosols from C. parvum- and (C. parvum + LPS)-treated mice using an antibody against mouse inducible nitric oxide synthase showed that this enzyme was indeed present in the cytosolic fractions and was absent in those from control livers. Our novel detection of cytochrome P420 nitrosyl complex in vivo may be linked to any role of hepatic P450's functions during liver inflammation.

Microenvironmental factors involved in the establishment of erythropoiesis in bone marrow

Human erythropoiesis is focused near the venous sinuses of the bone marrow in EBI that are comprised of erythroblasts in intimate contact with supportive CM. The surface molecules and secreted products of fibroblastic reticular cells support the adhesion of erythroblasts and CM, and sequester growth factors near their surfaces. Cohesiveness within the EBI decreases as its associated erythroid cells mature, and the erythroblasts cease to express certain cytoadhesive molecules. Finally, the erythroblasts enucleate and separate from the EBI. Transiently motile reticulocytes enter the circulation through intracellular pores of venous sinus endothelial cells, and their nuclear remnants are ingested by CM or perisinal macrophages.

A novel 37-Kd adhesive membrane protein from cloned murine bone marrow stromal cells and cloned murine hematopoietic progenitor cells

The adhesion of hematopoietic progenitor cells to bone marrow stromal cells is critical to hematopoiesis and involves multiple effector molecules. Stromal cell molecules that participate in this interaction were sought by analyzing the detergent-soluble membrane proteins of GBI/6 stromal cells that could be adsorbed by intact FDCP-1 progenitor cells. A single-chain protein from GBI/6 cells having an apparent molecular weight of 37 Kd was selectively adsorbed by FDCP-1 cells. This protein, designated p37, could be surface-radiolabeled and thus appeared to be exposed on the cell membrane. An apparently identical 37-Kd protein was expressed by three stromal cell lines, by Swiss 3T3 fibroblastic cells, and by FDCP-1 and FDCP-2 progenitor cells. p37 was selectively adsorbed from membrane lysates by a variety of murine hematopoietic cells, including erythrocytes, but not by human erythrocytes. Binding of p37 to cells was calcium-dependent, and was not affected by inhibitors of the hematopoietic homing receptor or the cell-binding or heparin-binding functions of fibronectin. It is proposed that p37 may be a novel adhesive molecule expressed on the surface of a variety of hematopoietic cells that could participate in both homotypic and heterotypic interactions of stromal and progenitor cells.

Potentiation by thiopurines and sulfhydryl-reactive agents of the inhibition by 3-deazaadenosine of mononuclear phagocytes

Combination effects of 3-deazaadenosine (c3Ado) on antibody-dependent phagocytosis in mouse resident peritoneal cells and human peripheral blood monocytes precultured with cytotoxic thiols, azathioprine (AZA) or 6-mercaptopurine (6-MP), and thiol-reactive agents, 2-cyclohexene-1-one (2-CH) or ethacrynic acid (ETA), are described. In the mouse cell preparations, a non-inhibitory concentration of 10 microM AZA or 6-MP potentiated the inhibition by 5 and 10 microM c3Ado of phagocytosis. Higher concentrations of AZA or 6-MP (50, 100 microM) and c3Ado (40, 50 microM) were needed to achieve similar effects in human monocytes. Both 2-CH (50 microM) and ETA (25 microM) inhibited mouse cell phagocytosis and acted synergistically with c3Ado. Precultivation of mouse cells with an inhibitor of glutathione synthesis, buthionine sulfoximine (BSO, 50 microM) caused no inhibition of phagocytosis and no potentiation of the inhibition by c3Ado, although BSO potentiated the inhibition by 2-CH (50 microM). In human monocytes, non-inhibitory concentrations (10 and 25 microM) of gold sodium thiomalate (GST), AZA, and c3Ado, but not 6-MP, potentiated the inhibition by 2-CH (25-37.5 microM) of phagocytosis. Results are discussed in connection with the possible modulation by endogenous sulfhydryl-reactive metabolites of phospholipid turnover of the effects of c3Ado.

Physiological modeling of disposition of potential tumor-imaging radiopharmaceuticals in tumor-bearing mice

Radiopharmaceuticals have great potential in the early detection of human tumors. Three potential 99mTc-labeled platinum compounds based on cisplatin have been synthesized and tested in tumored mice. This report presents the analysis of the disposition data obtained after a single intravenous injection with an empirical, physiologically based pharmacokinetic model. The radioactivity of each radiopharmaceutical after administration was measured in blood, urine, and 15 tissues, including tumor. Parameters included in the model were tissue volumes (experimentally determined), tissue blood flows (determined from literature values), tissue:blood extraction ratios (determined by nonlinear least-squares regression with MULTI-FORTE), and clearance terms (also determined by nonlinear least-squares regression). Data were weighted by the reciprocal of the square of the observed values. Good fits to the experimental data were obtained. As expected, the compound producing the best tumor:blood profile (3) also had the highest tumor extraction ratio (6.2 versus 2.0 and 1.3 for 1 and 2, respectively). Total body clearance values for the radioactivity associated with the three compounds 1-3 were calculated to be 0.09, 0.04, and 0.016 mL/min, respectively. Analysis of data with such an empirical, physiologically based model may assist future development of suitable tumor-imaging agents.

Genotoxicity and cell cycle effects of platinum-based imaging agents in cisplatin-resistant human tumour cells

A series of cis-dichloroplatinum(II) 2,3-diaminopropionamide complexes synthesised as potential imaging agents was tested for activity against a human ovarian tumour cell line (CI-80-13S) with high natural resistance to cisplatin and carboplatin as compared with other human cells. The most potent compound, the dimethyl ester of dichloro-[4-(methyleneiminodiacetic acid)phenyl (2',3'-diamino-propionamide)]platinum(II) (complex III), exhibited toxicity towards CI-80-13S cells similar to that observed in other cell lines, an effect that was not shown by the ligand alone or by cis-dichloroplatinum(II) 2,3-diaminopropionamide. However, complex III ester reproduced the genotoxic effects of cisplatin as judged by differential inactivation of two strains of adenovirus and by inhibition of cellular DNA and RNA synthesis; no major differences in these properties were observed between CI-80-13S and cisplatin-sensitive cells. Substantial inhibition of DNA and RNA synthesis was found within 2 h of treatment, much earlier than the effect of cisplatin. Complex III ester, which was 30- to 100-fold less potent than cisplatin, inhibited cell cycle progression in a similar way to equitoxic cisplatin, with cells accumulating in G2 at a dose of low toxicity and being arrested in all stages at higher levels. The latter in combination with colcemid caused extensive fragmentation of CI-80-13S cells. These results suggest that the mechanism of toxicity of such complexes involves factors, in addition to DNA damage, which rapidly inhibit nucleic acid synthesis and overcome natural resistance to cisplatin in the CI-80-13S cell line.

Phenolic Analogs of Amino Carboxylic Acid Ligands for 99mTc. 4. N-(2-Hydroxybenzyl)glycines (hbg)

Ten tridentate ligands , N-(2-hydroxybenzyl) glycines ( hbg ) (5), were prepared by the Mannich reaction of a phenol with formaldehyde and glycine and/or by the reduction of the Schiff base of a substituted salicylaldehyde and glycine. In three instances the bis compounds (6b,c,i) were also formed by the first method.

Biological evaluation of 99mTc labelled cis-platinum containing benzyliminodiacetic acids as potential tumour imaging agents

The synthesis of three new potential tumour-imaging radiopharmaceuticals in which a cis-platin derivative is attached to benzyl iminodiacetic acid, a ligand capable of forming a stable complex with 99mTc, has previously been reported by us [Awaluddin et al. Appl. Radiat. Isot. 38, 671-674 (1987)]. We have now carried out extensive biodistribution studies on these compounds as well as on two fragments of their structures which do not contain platinum. The results suggest that the presence of platinum is not essential for the tumour-localizing properties of the radiopharmaceuticals.

Synthetic approaches to a carboranyl thiouracil

Thiouracil is selectively incorporated into melanotic murine melanomas during melanin synthesis. This selectivity makes thiouracil a likely vehicle for boron in the diagnosis and therapy of melanoma. Several synthetic routes to thiouracils bearing an alkyl decacarboranyl group attached to various positions on the ring have been investigated. The successful syntheses of three new alkynyl thiouracils and the conversion of one of them into a carboranyl thiouracil are described.

Structure of the human CR1 gene. Molecular basis of the structural and quantitative polymorphisms and identification of a new CR1-like allele

Structural and quantitative polymorphisms have been described in human CR1. In the former, the S allotype is larger than the F allotype by 40-50 kD, the size of a long homologous repeat (LHR). In the latter, homozygotes for a 7.4-kb Hind III fragment express fourfold more CR1 per erythrocyte than do homozygotes for the allelic 6.9-kb restriction fragment. The basis for these genomic polymorphisms has been determined by restriction mapping the entire S allele and part of the F allele. The S allele is 158 kb and contains 5 LHRs of 20-30 kb, designated -A, -B/A, -B, -C, and -D, respectively, 5' to 3'. Extensive homology was found among the LHRs in their restriction maps, exon organization, and the coding and noncoding sequences. The presence of LHR-B/A in the S allele but not in the F allele accounts for the longer transcripts and polypeptide associated with the former allotype. At least 42 exons are present in the S allele, with distinct exons for the leader sequence, the transmembrane and cytoplasmic regions and most of the SCRs comprising the extracellular portion of CR1. Consistent with the mapping of the ligand binding site to the first two SCRs in each LHR, the second SCRs in LHR-A, -B/A, -B, and -C are encoded by two exons, reflecting a specialized function for this unit. The allelic 7.4/6.9-kb Hind III fragments extend from the 3' region of LHR-C to LHR-D. The 6.9-kb restriction fragment is the result of a new Hind III site generated by a single base change in the intron between the exons encoding the second SCR of LHR-D. A second cluster of genomic clones has been identified by hybridization to CR1 probes. Although they contain regions of hybridization to the cDNA and genomic probes derived from CR1, these cannot be overlapped with the structural gene owing to their distinct restriction maps. Three genomic polymorphisms previously identified by CR1 cDNA probes map to this region. These additional clones may represent part of a duplicated allele located nearby within the CR1 locus.

Phenolic Analogs of Amino Carboxylic Acid Ligands for 99mTc. II. Synthesis and Characterization of N,N'-Ethylenebis[N-(o-Hydroxybenzyl)-glycines] (ehbg)

Ten N,N,- ethylenebis [N-(o- hydroxybenzyl ) glycines ] ( ehbg ), eight of them new, have been synthesized and characterized by their i.r ., 1H n.m.r . and f.a.b, mass spectra and by conversion of their dimethyl ester dihydrochlorides.

Structure-distribution studies on some 99mTc-o-hydroxybenzyliminodiacetic acid complexes

Biodistributions of a series of thirteen 99mTc-o-hydroxy-benzyliminodiacetic acid complexes were carried out in rats and their hepatobiliary and urinary outputs correlated with lipophilicity, molecular weight, influence of substituent and plasma protein binding. Hepatobiliary output was moderate for those ligands with large alkyl substituents [t-butyl (36%), and iso-octyl (42%)] but compared to HIDA compounds was relatively low, indicating that they would not be suitable for clinical use. Halogen substituents had only a small effect on increasing hepatobiliary output but a large effect on reducing the urinary clearance.

Deficiency of the C3b/C4b receptor (CR1) of erythrocytes in systemic lupus erythematosus: analysis of the stability of the defect and of a restriction fragment length polymorphism of the CR1 gene

The role of genetic factors in controlling CR1 quantitative expression on erythrocytes (E) of patients with systemic lupus erythematosus (SLE) was reexamined by determining the temporal stability of CR1 numbers and the frequency of a CR1 genomic restriction fragment length polymorphism (RFLP). The mean number of binding sites/(E) for Yz-1 monoclonal anti-CR1 correlated with the number of sites for polyclonal anti-CR1 that had been determined 2 to 4 yr previously in 18 normal persons (p less than 0.001), 18 patients (p less than 0.001), and 28 relatives (p less than 0.001), indicating that CR1 sites/E was a stable characteristic in all three groups. The mean number of Yz-1 sites/E was 281 +/- 34 (+/- SEM) in 28 probands with SLE and 457 +/- 21 in 93 relatives, both determinations being less than that for 100 normal persons, 553 +/- 21 (p less than 0.002). Thirty-six patients and 51 normal individuals were also assessed for the presence of the 7.4 kb and 6.9 kb HindIII CR1 allelic restriction fragments that correlate with high and low expression, respectively, of CR1 on E. The distribution of patients differed from normal (p less than 0.05), with a smaller proportion being homozygous for the 7.4 kb allele. In addition, the mean numbers of Yz-1 sites/E for patients and relatives who were homozygous (p less than 0.02) and heterozygous (p less than 0.05) for the 7.4 kb allele were significantly lower than those for normal persons matched for the HindIII RFLP, suggesting the existence of additional heritable factors that decrease CR1 expression. The stability over time of the CR1 deficiency among patients, the finding of decreased CR1 number among an expanded group of relatives, the altered frequency among patients of CR1 alleles defined by the HindIII RFLP, and the decreased expression of CR1 on E among patients and relatives compared with normal individuals having the same HindIII RFLP indicate a role for genetic factors in CR1 deficiency in SLE.

Deficiency of the C3b/C4b receptor (CR1) of erythrocytes in systemic lupus erythematosus: analysis of the stability of the defect and of a restriction fragment length polymorphism of the CR1 gene

The role of genetic factors in controlling CR1 quantitative expression on erythrocytes (E) of patients with systemic lupus erythematosus (SLE) was reexamined by determining the temporal stability of CR1 numbers and the frequency of a CR1 genomic restriction fragment length polymorphism (RFLP). The mean number of binding sites/(E) for Yz-1 monoclonal anti-CR1 correlated with the number of sites for polyclonal anti-CR1 that had been determined 2 to 4 yr previously in 18 normal persons (p less than 0.001), 18 patients (p less than 0.001), and 28 relatives (p less than 0.001), indicating that CR1 sites/E was a stable characteristic in all three groups. The mean number of Yz-1 sites/E was 281 +/- 34 (+/- SEM) in 28 probands with SLE and 457 +/- 21 in 93 relatives, both determinations being less than that for 100 normal persons, 553 +/- 21 (p less than 0.002). Thirty-six patients and 51 normal individuals were also assessed for the presence of the 7.4 kb and 6.9 kb HindIII CR1 allelic restriction fragments that correlate with high and low expression, respectively, of CR1 on E. The distribution of patients differed from normal (p less than 0.05), with a smaller proportion being homozygous for the 7.4 kb allele. In addition, the mean numbers of Yz-1 sites/E for patients and relatives who were homozygous (p less than 0.02) and heterozygous (p less than 0.05) for the 7.4 kb allele were significantly lower than those for normal persons matched for the HindIII RFLP, suggesting the existence of additional heritable factors that decrease CR1 expression. The stability over time of the CR1 deficiency among patients, the finding of decreased CR1 number among an expanded group of relatives, the altered frequency among patients of CR1 alleles defined by the HindIII RFLP, and the decreased expression of CR1 on E among patients and relatives compared with normal individuals having the same HindIII RFLP indicate a role for genetic factors in CR1 deficiency in SLE.

Human C3b/C4b receptor (CR1). Demonstration of long homologous repeating domains that are composed of the short consensus repeats characteristics of C3/C4 binding proteins

10 overlapping CR1 cDNA clones that span 5.5 kb were isolated from a tonsillar library and sequenced in whole or in part. A single long open reading frame beginning at the 5' end of the clones and extending 4.7 kb downstream to a stop codon was identified. This sequence represents approximately 80% of the estimated 6 kb of coding sequence for the F allotype of CR1. Three tandem, direct, long homologous repeats (LHRs) of 450 amino acids were identified. Analysis of the sequences of tryptic peptides provided evidence for a fourth LHR in the F allotype of CR1. Amino acid identity between the LHRs ranged from 70% between the first and third repeats to 99% between the NH2-terminal 250 amino acids of the first and second repeats. Each LHR comprises seven short consensus repeats (SCRs) of 60-70 amino acids that resemble the SCRs of other C3/C4 binding proteins, such as complement receptor type 2, factors B and H, C4 binding protein, and C2. Two additional SCRs join the LHRs to a single membrane-spanning domain of 25 amino acids; thus, the F allotype of CR1 probably contains at least 30 SCRs, 23 of which have been sequenced. Each SCR is predicted to form a triple loop structure in which the four conserved half-cystines form disulfide linkages. The linear alignment of 30 SCRs as a semi-rigid structure would extend 1,140A from the plasma membrane and might facilitate the interaction of CR1 with C3b and C4b located within the interstices of immune complexes and microbial cell walls. The COOH-terminal cytoplasmic domain of 43 residues contains a six-amino-acid sequence that is homologous to the sequence in the epidermal growth factor receptor that is phosphorylated by protein kinase C.

Molecular weight of gastric mucus glycoprotein is a determinant of the degree of subsequent aspirin induced chronic gastric ulceration in the rat

Mucus was sampled from the gastric mucosal surface of anaesthetised rats. Three weeks later these rats were orally dosed each day with aspirin (375 mg/kg) for six months. Then the number and size of the aspirin induced chronic gastric ulcers were assessed. Gel filtration chromatography of the mucus samples showed that mucus glycoprotein was present in both high and low molecular weight forms. There was a natural variation between individual rats in the percentage of glycoprotein in the high molecular weight form (mean = 58.9%; SD = 9.6%; n = 23). This variation correlated strongly with the degree of subsequent aspirin induced chronic gastric ulceration (r = -0.85, p less than 0.001). This is the first time that a pre-existent variability in a mucosal defence factor has been shown to predict susceptibility of the stomach to chronic ulceration.

Human diseases associated with C3 receptor deficiencies

Genetic deficiencies of complement receptors have recently been described. CR1 expression is reduced on erythrocytes, leucocytes and podocytes of many patients with systemic lupus erythematosus because of both genetic and acquired mechanisms. CR1 deficiency is also found in AIDS and AIDS-related syndromes and correlates with clinical subpopulations of HIV-infected patients. The pathogenic significance of CR1 deficiency relates to the functions of CR1 in clearance of immune complexes, phagocytosis and immune regulation. CR3 deficiency occurs as an autosomal recessive inherited disease characterized by the lack of or severe reduction in expression of the leucocyte antigens CR3, LFA1, p150,95 and their common chain. The disease is associated with severe defects in neutrophil and lymphocyte functions and recurrent bacterial infections. The in vivo effects of C3 receptor deficiencies emphasize the critical role of these membrane molecules in immunity.

Phenolic Analogs of Amino Carboxylic-Acid Ligands for Tc-99m. 1. Synthesis and Characterization of N,N'-Ethylenebis[2-(-O-Hydroxyphenyl)Glycines] (Ehpg)

Nine N,N'- ethylenebis [2-(o- hydroxyphenyl ) glycines ] ( ehpg ) have been prepared and characterized by conversion into their dimethyl ester dihydrochlorides. Their i.r ., 1H n.m.r. and f.a.b. mass spectral data are presented and discussed.

Synthesis and characterization of potential tumor scintigraphic agents

Potential tumor imaging radiopharmaceutical agents have been prepared by attaching a cisplatin derivative to a ligand capable of forming a stable complex with 99mTc. Three new organometallic compounds, with iminodiacetic acid as the 99mTc chelating group and 2,3-diaminopropionamide as the platinum complexing group, have been prepared and characterized. Preliminary biodistribution studies in tumor bearing mice support the utility of this approach.

Peptic erosion of gastric mucus in the rat

1. The effect of pepsin on the loss of mucus glycoprotein from the gastric epithelial mucus layer was studied in the rat. 2. Pepsin was instilled into the gastric lumen, and luminal contents were subsequently assayed. 3. Glycoprotein loss increased with luminal pepsin, up to a concentration of 1 mg pepsin/ml. 4. Luminal glycoprotein had a molecular size distribution intermediate between subunit, and native mucus glycoprotein of the epithelial mucus layer. 5. Incubation of gastric epithelial scrapings with pepsin demonstrated that insoluble, native mucus glycoprotein was rapidly degraded to soluble glycoprotein of similar molecular size distribution to that found in vivo in the lumen.

Phenyl Tetraacetic Acid Ligands for Gadolinium: Potential Magnetic-Resonance Image Enhancing Agents

Three new ligands suitable for chelation to gadolinium have been synthesized. N,N'- (1,2-Phenylenebis[imino(2-oxoethane-2,l-diyl)])bis[N-(carboxymethyl)glycine] and N,N'-(1,3-phenylenebis[imino(2-oxoethane-2,l-diyl)])bis[N-(carboxymethyl)glycine] were prepared from the corresponding phenylenediamines and N,N'-[1-(4-methylpheny1)ethane-1,2-diyl]bis[N-(carboxymethyl)glycine] from 4-methylbenzaldehyde. Attempted syntheses of other para derivatives of the latter compound produced only oxopiperazinediacetic acids.

Analysis of multiple restriction fragment length polymorphisms of the gene for the human complement receptor type I. Duplication of genomic sequences occurs in association with a high molecular mass receptor allotype

Human CR1 exhibits an unusual form of polymorphism in which allotypic variants differ in the molecular weight of their respective polypeptide chains. To address mechanisms involved in the generation of the CR1 allotypes, DNA from individuals having the F allotype (250,000 Mr), the S allotype (290,000 Mr), and the F' allotype (210,000 Mr) was digested by restriction enzymes, and Southern blots were hybridized with CR1 cDNA and genomic probes. With the use of Bam HI and Sac I, an additional restriction fragment was observed in 20 of 21 individuals having the S allotype with no associated loss of other restriction fragments. Southern blot analysis with a noncoding genomic probe derived from the S allotype-specific Bam HI fragment showed hybridization to this fragment and to two other fragments that were also present in FF individuals. Thus, an intervening sequence may be repeated twice in the F allele and three times in the S allele. A restriction fragment length polymorphism (RFLP) unique to two individuals expressing the F' allotype was seen with Eco RV, but the absence of persons homozygous for this rare allotype prevented further comparisons with the F and S allotypes. Analysis of the CR1 transcripts associated with the three CR1 allotypes indicated that these differed by 1.3-1.5 kb and had the same rank order as the corresponding allotypes. Taken together, these findings suggest that the S allele was generated from the F allele by the acquisition of additional sequences, the coding portion of which may correspond to a long homologous repeat of approximately 1.4 kb that has been identified in CR1 cDNA. We saw two other RFLPs with Hind III and Pvu II that were in linkage dysequilibrium with the Bam HI-Sac I RFLPs associated with the S allotype, and a third polymorphism was seen with Eco RI that was not in linkage dysequilibrium with the other polymorphisms. Thus, 10 commonly occurring CR1 alleles can be defined, making this locus a useful marker for the long arm of chromosome 1 to which the CR1 gene maps.

Identification of a restriction fragment length polymorphism by a CR1 cDNA that correlates with the number of CR1 on erythrocytes

A genetic basis for the regulation of the number of CR1 on E of different normal individuals was investigated by probing Southern blots of their genomic DNA with a 0.75-kb fragment of CR1 cDNA. Using Hind III, we observed a RFLP involving fragments of 7.4 kb and 6.9 kb that correlated with the number of CR1 on E. 32 individuals having only the 7.4-kb restriction fragment had a mean of 661 +/- 33 (SEM) CR1/E, 11 donors having both restriction fragments had a mean of 455 +/- 52 CR1/E, and 7 individuals having only the 6.9-kb fragment had a mean of 156 +/- 13 CR1/E, all means being significantly different (p less than 0.005). Cosegregation in a normal family of the Hind III restriction fragments with the S, F, and F' structural allotypes of CR1 confirmed that the regulatory element identified by these fragments is linked to the CR1 gene. Moreover, an analysis of the relative expression on E of these structural allotypes in association with either the 7.4-kb Hind III fragment or the 6.9-kb fragment showed that this regulatory element is cis-acting. In contrast, quantitation of CR1 of B lymphocytes and neutrophils revealed no differences in total CR1 expression between individuals homozygous for the 7.4-kb and 6.9-kb Hind III fragments. Thus, we have identified a genomic polymorphism that is linked to the CR1 gene and is associated with a cis-acting regulatory element for the expression of CR1 on E.

Decreased expression of the C3b/C4b receptor (CR1) and the C3d receptor (CR2) on B lymphocytes and of CR1 on neutrophils of patients with systemic lupus erythematosus

Decreased numbers of complement receptor type 1 (CR1) have been observed on erythrocytes of patients with systemic lupus erythematosus (SLE) and on glomerular podocytes of patients having proliferative nephritis of SLE. In the present study, the analysis of the cellular expression of CR1 has been extended to include leukocytes. In addition, expression by B lymphocytes of the C3d receptor (CR2), which also serves as the receptor for the Epstein-Barr virus, was assessed. Receptor expression was measured by 2-color fluorescent flow cytometry of peripheral blood B cells, identified by the presence of the B1 antigen, that had also been stained with anti-CR1 or anti-CR2. B cells from 17 patients with SLE exhibited a mean relative fluorescence for CR1 that was 61% of that found in 17 normal individuals (P less than 0.001). The expression of CR2 by the patients' B cells (n = 14) was 62% of that of the B cells from normal subjects (n = 17) (P less than 0.001). The expression of CR1 correlated with that of CR2 among patients (r = 0.63; P less than 0.01) but not with the expression of CR2 among normal individuals (r = 0.36; P greater than 0.1). The mean CR1 content of the patients' neutrophils was only 59% of the normal mean (P less than 0.001). Thus, abnormalities of complement receptor expression occur on the leukocytes of patients with SLE. These deficiencies may be secondary to interaction of the cells with the products of complement activation, or, in some individuals, the deficiencies may be familial.

Decreased expression of C3b receptor (CR1) on erythrocytes of patients with systemic lupus erythematosus contrasts with its normal expression in other systemic diseases and does not correlate with the occurrence or severity of SLE nephritis

Expression of the C3b/C4b receptor (CR1) on erythrocytes is decreased in patients with systemic lupus erythematosus (SLE) compared to normal individuals, and the CR1 antigen is absent from podocytes in severe diffuse proliferate nephritis of SLE. In the present study, we examined the relationship between the number of CR1 on erythrocytes and the occurrence and severity of SLE nephritis, and assessed the expression of CR1 on erythrocytes and the occurrence and severity of SLE nephritis, and assessed the expression of CR1 on erythrocytes in non-SLE nephritis and other systemic inflammatory diseases by measuring the binding of 125I-labeled rabbit F(ab')2 and murine monoclonal IgG anti-CR1 antibodies to erythrocytes of normal individuals and patients in a French population. The number of binding sites for monoclonal anti-CR1 antibody on erythrocytes of 116 normal individuals was 743 +/- 22 (mean +/- SEM) with a range of 169-1,333, and the frequency distribution of this number in the population was bimodal. In 112 patients with SLE, the mean number of CR1 sites on erythrocytes was decreased to 62% of the mean for normal individuals (p less than 0.001). No correlation was found between CR1 expression on erythrocytes and the presence or immunohistopathological type of glomerulonephritis in biopsy specimens from these patients. The mean number of CR1 on erythrocytes of 29 patients with non-SLE glomerulonephritis was slightly decreased to 89% of the normal mean (p greater than 0.05), which could not be attributed to glomerular immune complex disease or vasculitis.(ABSTRACT TRUNCATED AT 250 WORDS)

Phenolic aminocarboxylate chelates of 99mTc as hepatobiliary agents

A series of alkyl- and halogen-substituted derivatives of ethylenediamine di[o-hydroxyphenylacetic acid] (EDDHA) and N,N'-bis[2-hydroxybenzyl] ethylenediamine N,N'-diacetic acid (HBED) were complexed with 99mTc and their biodistribution was determined in rats. All complexes displayed substantial hepatobiliary excretion; of each series, 99mTc-Br-EDDHA and 99mTc-di-Cl-HBED had the maximum amount in the gastrointestinal tract. Scintigraphic studies of 99mTc-Cl-EDDHA in dogs revealed prompt imaging of the liver followed by imaging of the gall bladder as the complex was excreted into the bile.

Autoantibody to the C3b/C4b receptor and absence of this receptor from erythrocytes of a patient with systemic lupus erythematosus

A 29-yr-old woman with systemic lupus erythematosus (SLE) was found to have no detectable C3b/C4b receptors (CR1) on her erythrocytes (E) when they were assayed by the binding of rabbit polyclonal and murine monoclonal (Yz-1) anti-CR1. Analysis by two-color fluorescent flow cytometry of CR1 expression on the patient's B lymphocytes that had been stained indirectly with monoclonal anti-B1 and rabbit F(ab')2 anti-CR1 also revealed a marked deficiency of CR1. Total cellular CR1 of neutrophils, assessed by a sandwich radioimmunoassay, was about half that of neutrophils from normal individuals. Because her E had expressed 173 sites/cell 2 yr before, the CR1 deficiency was considered to be acquired and a possible mechanism was sought. Autoantibody to CR1 was measured by a radioimmunoassay in which serum or its fractions were incubated in microtiter wells that had been coated with purified CR1, and binding of immunoglobulin to the wells was quantitated with 125I-labeled goat IgG antihuman F(ab')2. The CR1-specific binding of immunoglobulin from the patient's serum was 19.1 ng/well of the detecting antibody when her E had eight CR1 sites per cell; that of 28 healthy donors was 1.3 +/- 0.5 ng/well (mean +/- SEM), and that of 34 additional patients with SLE was 0.5 +/- 0.3 ng/well. The activity was present also in purified IgG and its F(ab')2 fragment, indicating that the binding of serum immunoglobulin to CR1 was not mediated by C3 fragments. The specificity of the patient's IgG for CR1 was confirmed when pretreatment of the CR1-coated wells with affinity-purified rabbit F(ab')2 anti-CR1 was shown to inhibit by 68% the binding of the IgG. The autoantibody also interacted with CR1 in cell membranes, as assessed by its capacity to inhibit the binding of indirectly fluoresceinated Yz-1 to neutrophils, and, when combined with goat IgG antihuman F(ab')2, to diminish the binding of dimeric C3b to normal E. During the period of the marked deficiency of CR1 the patient experienced an exacerbation of disease activity which was treated with prednisone. Clinical improvement was accompanied by a decrease in the serum concentration of anti-CR1 to levels present 2 yr earlier, and an increase of CR1 to 170 sites/E. The temporal association between high titers of an autoantibody to CR1, absence of CR1 from E, and heightened activity of SLE suggest that the former may have had a role in the other manifestations of the patient's disease.

Normal function of CR1 on affected erythrocytes of patients with paroxysmal nocturnal hemoglobinuria

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired hemolytic anemia in which affected erythrocytes (E) are abnormally sensitive to lysis by autologous complement. Affected E from patients with PNH (PNH-E) are deficient in an E membrane regulatory protein of complement, decay-accelerating factor (DAF). Because a functional defect in a second membrane regulatory protein of complement, CR1 (C3b receptor), has also been hypothesized, severely affected PNH-E (type III PNH-E) were tested for abnormalities in CR1 by four methods. E from two patients with 100% type III PNH-E had 3201 and 6783 sites per cell for binding of 125I-labeled rabbit polyclonal F(ab')2 anti-CR1. These values fall within the normal range of CR1 antigenic sites per cell (1267 to 7915, mean = 5,014 +/- 155 SEM) established by assaying the E from 113 healthy donors. The Ka of CR1 on type III PNH-E for 125I-labeled C3b dimer was 2.06 X 10(7) M-1, and the Ka values for the binding of the same ligand to the E from two healthy individuals were 2.45 X 10(7) M-1 and 1.58 X 10(7) M-1. In an assay designed to measure the capacity of human E (Eh) to accelerate the decay of the classical C3 convertase deposited on 1 X 10(7) bystander sheep E (EAC1gp,4bh,2agp), the half-life (t 1/2) of this convertase was diminished from 18.1 min (range 15.2 to 22.9) to 8.1 min (range 7.4 to 8.5) by the addition of 1 X 10(7) normal Eh, to 6.2 min by 100% type III PNH-E, and to 7.5 min by Eh pretreated with an IgG fraction of human antiserum directed against the D antigen of the Rh system. In contrast, Eh (t 1/2 = 7.4) pretreated with a saturating dose of F(ab')2 anti-CR1, and CR1-deficient Eh (less than 10 CR1 molecules/E) from a patient with systemic lupus erythematosus, showed a loss of convertase decay-accelerating capacity to t 1/2 = 11.6 and t 1/2 = 12.4, respectively. Type III PNH-E pretreated with anti-CR1 demonstrated a total loss of their decay-accelerating capacity (t 1/2 = 19.9). In an assay of I cofactor activity, soluble C3b was rapidly converted to iC3b by purified I plus Eh or type III PNH-E, whereas CR1-deficient Eh exhibited less than 5% the I cofactor activity of normal Eh.(ABSTRACT TRUNCATED AT 400 WORDS)

Normal function of CR1 on affected erythrocytes of patients with paroxysmal nocturnal hemoglobinuria

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired hemolytic anemia in which affected erythrocytes (E) are abnormally sensitive to lysis by autologous complement. Affected E from patients with PNH (PNH-E) are deficient in an E membrane regulatory protein of complement, decay-accelerating factor (DAF). Because a functional defect in a second membrane regulatory protein of complement, CR1 (C3b receptor), has also been hypothesized, severely affected PNH-E (type III PNH-E) were tested for abnormalities in CR1 by four methods. E from two patients with 100% type III PNH-E had 3201 and 6783 sites per cell for binding of 125I-labeled rabbit polyclonal F(ab')2 anti-CR1. These values fall within the normal range of CR1 antigenic sites per cell (1267 to 7915, mean = 5,014 +/- 155 SEM) established by assaying the E from 113 healthy donors. The Ka of CR1 on type III PNH-E for 125I-labeled C3b dimer was 2.06 X 10(7) M-1, and the Ka values for the binding of the same ligand to the E from two healthy individuals were 2.45 X 10(7) M-1 and 1.58 X 10(7) M-1. In an assay designed to measure the capacity of human E (Eh) to accelerate the decay of the classical C3 convertase deposited on 1 X 10(7) bystander sheep E (EAC1gp,4bh,2agp), the half-life (t 1/2) of this convertase was diminished from 18.1 min (range 15.2 to 22.9) to 8.1 min (range 7.4 to 8.5) by the addition of 1 X 10(7) normal Eh, to 6.2 min by 100% type III PNH-E, and to 7.5 min by Eh pretreated with an IgG fraction of human antiserum directed against the D antigen of the Rh system. In contrast, Eh (t 1/2 = 7.4) pretreated with a saturating dose of F(ab')2 anti-CR1, and CR1-deficient Eh (less than 10 CR1 molecules/E) from a patient with systemic lupus erythematosus, showed a loss of convertase decay-accelerating capacity to t 1/2 = 11.6 and t 1/2 = 12.4, respectively. Type III PNH-E pretreated with anti-CR1 demonstrated a total loss of their decay-accelerating capacity (t 1/2 = 19.9). In an assay of I cofactor activity, soluble C3b was rapidly converted to iC3b by purified I plus Eh or type III PNH-E, whereas CR1-deficient Eh exhibited less than 5% the I cofactor activity of normal Eh.(ABSTRACT TRUNCATED AT 400 WORDS)