Chemical modification of isoflavones in soyfoods during cooking and processing

The principal chemical forms of isoflavones in soybean are their 6''-O-malonyl-beta-glucoside (6OMalGlc) conjugates. Experiments were carried out to determine the best conditions for extraction of isoflavones from soyfoods and the effects of commercial processing procedures and of cooking on isoflavone concentrations and composition. Hot alcohol extraction of ground soybeans deesterified 6OMalGlc conjugates. Although room temperature extraction slowed the conversion, extraction at 4 degrees C for 2-4 h led to the highest yield of 6OMalGlc conjugates and the lowest proportion of beta-glucoside conjugates. Analysis of soyfood products by reversed-phase HPLC-mass spectrometry revealed that defatted soy flour that had not been heat treated consisted mostly of 6OMalGlc conjugates; in contrast, toasted soy flour contained large amounts of 6''-O-acetyl-beta-glucoside conjugates, formed by heat-induced decarboxylation of the malonate group to acetate. Soymilk and tofu consisted almost entirely of beta-glucoside conjugates; low-fat versions of these products were markedly depleted in isoflavones. Alcohol-washed soy-protein concentrates contained few isoflavones. Isolated soy protein and textured vegetable protein consisted of a mixture of all 3 types of isoflavone conjugates. Baking or frying of textured vegetable protein at 190 degrees C and baking of soy flour in cookies did not alter total isoflavone content, but there was a steady increase in beta-glucoside conjugates at the expense of 6OMalGlc conjugates. The chemical form of isoflavones in foods should be taken into consideration when evaluating their availability for absorption from the diet.

Phytoestrogens and breast cancer

Phytoestrogens are paradoxical. Because of their structural similarity to the physiological oestrogens, they have been assumed to increase the risk of breast cancer. However, nations where the largest amounts of phytoestrogens are consumed in the diet have the lowest incidence of and rate of death from breast cancer. Although these epidemiological observations do not prove that phytoestrogens have anti-cancer properties, many preclinical experiments support this concept. Some indicate that early life exposure to phytoestrogens may be critical for breast cancer prevention. Clinical studies to define the effect of phytoestrogens on breast cancer recurrence are underway. The recent discovery of a second class of oestrogen receptors, with a differential distribution among the tissues, may enable an explanation of the phytoestrogen paradox. These receptors have opened a way of utilizing phytoestrogens in the treatment of oestrogen-sensitive chronic diseases such as atherosclerosis and osteoporosis.

Tyrosine kinase inhibitor effects on avian osteoclastic acid transport

We found that tyrosine kinase pp60(c-src) coisolates with acid-transporting osteoclast membranes and hypothesized that this kinase regulates hydrochloric acid transport. We assayed the membrane acid transport and bone degradation effects of tyrosine kinase inhibitors in avian osteoclasts. Isoflavone, tyrphostin, and benzoquinonoid inhibitors were compared with inactive analogues to determine nonspecific effects. Acid-secreting membranes, isolated by nitrogen cavitation, were assayed as reconstituted vesicles by using acridine orange to indicate ATP-dependent hydrogen ion transport. The soy isoflavone genistein and the benzoquinonoid antibiotic herbimycin inhibited hydrochloric acid transport with 50% inhibition at approximately 10 and approximately 2 micromol/L, respectively; effects appeared in <2 min and were reversible. In membrane incubated with inhibitors, the herbimycin effect also inhibited Cl- transport by variable amounts, suggesting that this compound affects Cl- channel activity. However, genistein and tyrphostins did not produce chloride dependent effects. After 30 min with ATP, tyrphostin A47 irreversibly inhibited hydrochloric acid transport with 50% inhibition at approximately 10 micromol/L. Tyrphostin A25 and controls, tyrphostin A1 and daidzein (a genistein congener), were inactive despite preincubation. Osteoclastic bone resorption was more sensitive to the inhibitors over 3-5-d assays than was membrane acid transport, except for tyrphostins. Herbimycin and genistein inhibited bone resorption with half maximal effects at 0.5 and 10 micromol/L and complete inhibition at 3 d in 1 and 20 micromol/L, respectively. None of the tyrphostins, including A47, nor daidzein inhibited resorption to >20 micromol/L. We conclude that tyrosine kinase inhibition directly inhibits osteoclast membrane hydrochloric acid transport; differences among inhibitors may reflect chemical reactivity and permeability.

Mechanisms of action of the soy isoflavone genistein: emerging role for its effects via transforming growth factor beta signaling pathways

The soy isoflavone genistein attenuates growth factor- and cytokine-stimulated proliferation of both normal and cancer cells. This article reviews our current understanding of the potential mechanisms of action of genistein. In membrane preparations from mammalian cells, genistein is a potent and specific inhibitor of tyrosine autophosphorylation of the epidermal growth factor (EGF) receptor. However, in several cell systems in which it inhibits growth, genistein does not alter tyrosine phosphorylation of the EGF receptor or other tyrosine kinase substrates thought to be involved in signal transduction pathways, suggesting that other mechanisms may be responsible for its action. Alternatives include inhibition of DNA topoisomerase II activity, regulation of cell cycle checkpoints, and antiangiogenic and antioxidant activity. Experiments in our laboratory suggest a new concept, that genistein may inhibit cell growth by modulating transforming growth factor (TGF) beta1 signaling pathways. Such a link between genistein action and TGFbeta1 function is supported by preliminary results of studies in patients with hereditary hemorrhagic telangiectasia (a genetic disorder involving mutations in proteins that regulate TGFbeta receptor complex formation and signaling) in which several patients had dramatic attenuation of their symptoms after 1 wk of ingesting soy-based beverages. These preclinical studies in combination with our cell culture data suggest that the mechanism of genistein involves, if not requires, TGFbeta1-signaling.

Metabolism of the isoflavones genistein and biochanin A in human breast cancer cell lines

There is substantial variation in the growth inhibition of different human breast cancer cell lines by the isoflavones genistein and biochanin A. ZR-75-1 and BT-20 cells are > or = 2- to 4-fold less sensitive to these isoflavones than are MCF-7 cells, whereas T47D cells have a sensitivity similar to that of MCF-7 cells. To determine whether these differences are related to isoflavone metabolism by these cancer cells, each of the cell lines was incubated with [4-(14)C]genistein and [4-(14)C]biochanin A. Metabolites in the cell culture media were identified by radio-HPLC electrospray ionization mass spectrometry. One metabolite of genistein (genistein 7-sulfate) and 2 metabolites of biochanin A (genistein and genistein 7-sulfate) were detected by radio-HPLC. Further analysis by mass spectrometry identified 3 other metabolites, a hydroxylated methylated form of each isoflavone and a biochanin A sulfate. IC50 (the concentration at which the growth rate was halved) values of the breast cancer cell lines did not correlate well with production of genistein 7-sulfate from genistein or with biochanin A sulfate, genistein 7-sulfate, or genistein from biochanin A. However, IC50 values correlated with the production of the hydroxylated and methylated forms of the isoflavones. Only T47D cells produced these metabolites in this study, and only T47D cells had IC50 values similar to those of MCF-7 cells, which also produced the hydroxylated and methylated metabolites. These data suggest that the hydroxylated and methylated metabolites may be the active forms of genistein in human breast cancer cells and emphasize the importance of isoflavone metabolism in the mechanism of action of isoflavones.

Nitrosation of uric acid by peroxynitrite. Formation of a vasoactive nitric oxide donor

Peroxynitrite (ONOO-), formed by the reaction between nitric oxide (. NO) and superoxide, has been implicated in the etiology of numerous disease processes. Low molecular weight antioxidants, including uric acid, may minimize ONOO---mediated damage to tissues. The tissue-sparing effects of uric acid are typically attributed to oxidant scavenging; however, little attention has been paid to the biology of the reaction products. In this study, a previously unidentified uric acid derivative was detected in ONOO--treated human plasma. The product of the uric acid/ONOO- reaction resulted in endothelium-independent vasorelaxation of rat thoracic aorta, with an EC50 value in the range of 0.03-0.3 microM. Oxyhemoglobin, a .NO scavenger, completely attenuated detectable .NO release and vascular relaxation. Uric acid plus decomposed ONOO- neither released .NO nor altered vascular reactivity. Electrochemical quantification of .NO confirmed that the uric acid/ONOO- reaction resulted in spontaneous (thiol-independent) and protracted (t1/2 approximately 125 min) release of .NO. Mass spectroscopic analysis indicated that the product was a nitrated uric acid derivative. The uric acid nitration/nitrosation product may play a pivotal role in human pathophysiology by releasing .NO, which could decrease vascular tone, increase tissue blood flow, and thereby constitute a role for uric acid not previously described.

Evaluation of alternative methods for the detection of bovine leukaemia virus in cattle

AIM

To evaluate commercially available enzyme-linked immunosorbent assays (ELISAs) and the polymerase chain reaction (PCR) for their ability to detect antibodies against or nucleic acid of the bovine leukaemia virus (BLV), the causal agent of enzootic bovine leukosis (EBL), and to assess their usefulness in a national eradication programme.

METHODS

Eighty-two well-defined sera (including 18 from an OIE reference laboratory) and 399 field sera from New Zealand cattle were tested in five ELISAs and the results compared with the agar gel immunodiffusion (AGID) test and electrophoretic immunoblotting (EIB) results. A polymerase chain reaction-based technique, which could detect BLV-RNA and proviral-DNA, was also evaluated on a subsample of the field cases.

RESULTS

Two commercial ELISAs classified 99% of the defined sera correctly, with the other three ranging in their correct classification between 88% and 95%. The ELISAs agreed in their general classification on the majority of the 399 blood samples (91.7%), and with the AGID for more than 95 % of the sera. In a dilution series of the international reference serum E4, the highest dilution with a positive (or suspicious) result ranged from 1:80 to 1:5120. A dilution series of 202 field positive samples tested in the preferred ELISA detected 98% of positive sera at a 15 and 1: 10 dilution, reducing to 78% at a 1:80 dilution of the sera. Agreement between serological tests and PCR was poor, mainly due to failure of the PCR to detect a number of serologically positive animals.

CONCLUSION

ELISA tests detected about 10% more reactors than the AGID and the EIB combined. Some ELISA-positive animals were not detected by PCR, raising doubts about the usefulness of PCR-based technology in EBL eradication programmes.

Structure-activity study of the lantibiotic mutacin II from Streptococcus mutans T8 by a gene replacement strategy

Mutacin II, elaborated by group II Streptococcus mutans, is a ribosomally synthesized and posttranslationally modified polypeptide antibiotic containing unusual thioether and didehydro amino acids. To ascertain the role of specific amino acid residues in mutacin II antimicrobial activity, we developed a streptococcal expression system that facilitates the replacement of the mutA gene with a single copy of a mutated variant gene. As a result, variants of mutacin II can be designed and expressed. The system was tested by constructing the following mutant peptides: delta N1, V7A, P9A, T10A, T10S, C15A, C26A, and C27A. All of these mutacin II variants except delta N1 and T10A, which were not secreted, were isolated, and their identities were verified by mass spectrometry. Variants P9A, C15A, C26A, and C27A failed to exert antimicrobial activity. Because the P9A and T10A variants comprise the "hinge" region of mutacin II, these observations suggest that in addition to the thioether and didehydro amino acids, the hinge region is essential for biological activity and biosynthesis or export of the peptide. Tandem mass spectrometry of the N-terminal part of the wild-type molecule and its C15A variant confirmed that the threonine at position 10 is dehydrated and present as a didehydrobutyrine residue. This analysis of the active T10S variant further suggested that a didehydro amino acid at this position is specific for antimicrobial activity and that the biosynthetic machinery does not discriminate between threonine and serine. In contrast, the lack of production of mutacin variants with alanine substituted for threonine at position 10, as well as the deletion of asparagine at the N terminus (delta N1), indicates that specific residues in the propeptide may be crucial for certain steps in the biosynthetic pathway of this lantibiotic.

Calcium-sensitive calcium influx in photoreceptor inner segments

The effect of external calcium concentration ([Ca2+]o) on membrane potential-dependent calcium signals in isolated tiger salamander rod and cone photoreceptor inner segments was investigated with patch-clamp and calcium imaging techniques. Mild depolarizations led to increases in intracellular Ca2+ levels ([Ca2+]i) that were smaller when [Ca2+]o was elevated to 10 mM than when it was 3 mM, even though maximum Ca2+ conductance increased 30% with the increase in [Ca2+]o. When external calcium was lowered to 1 mM [Ca2+]o, maximum Ca2+ conductance was reduced, as expected, but the mild depolarization-induced increase in [Ca2+]i was larger than in 3 mM [Ca2+]o. In contrast, when photoreceptors were strongly depolarized, the increase in [Ca2+]i was less when [Ca2+]o was reduced. An explanation for these observations comes from an assessment of Ca2+ channel gating in voltage-clamped photoreceptors under changing conditions of [Ca2+]o. Although Ca2+ conductance increased with increasing [Ca2+]o, surface charge effects dictated large shifts in the voltage dependence of Ca2+ channel gating. Relative to the control condition (3 mM [Ca2+]o), 10 mM [Ca2+]o shifted Ca2+ channel activation 8 mV positive, reducing channel open probability over a broad range of potentials. Reducing [Ca2+]o to 1 mM reduced Ca2+ conductance but shifted Ca2+ channel activation negative by 6 mV. Thus the intracellular calcium signals reflect a balance between competing changes in gating and permeation of Ca2+ channels mediated by [Ca2+]o. In mildly depolarized cells, the [Ca2+]o-induced changes in Ca2+ channel activation proved stronger than the [Ca2+]o-induced changes in conductance. In response to the larger depolarizations caused by 80 mM [K+]o, the opposite is true, with conductance changes dominating the effects on channel activation.

HPLC-mass spectrometry analysis of isoflavones

The current interest in the role of dietary isoflavonoids, particularly the soy isoflavone genistein, in lowering the risk of several chronic diseases, has led to the need for rapid, sensitive and precise assays for isoflavones and their metabolites in food matrices and in various physiological fluids and tissues. HPLC has the advantage over GC-based methods in that all the conjugated and unconjugated isoflavonoids and their metabolites can be separated and analyzed without the need for derivatization. An important advance in mass spectrometry has been the introduction of effective interfaces between the HPLC and the mass spectrometer, namely the electrospray ionization (ESI) and the heated nebulizer-atmospheric pressure chemical ionization (HN-APCI) interfaces. Because of the isoflavonoid concentrations in fluids such as bile or urine, preliminary extraction, so essential for GC-MS and many other analytical methods, is not necessary. This immediately overcomes the thorny issue of finding an effective solid-phase extraction procedure. Using reversed-phase HPLC-ESI-MS, it is possible to obtain a mass/intensity map of all isoflavonoid metabolites in a single 20 min analysis. Analysis of isoflavonoid conjugates in serum/plasma samples requires initial extraction, but the conjugates can be measured intact either by capillary reversed-phase HPLC-ESI-MS or on regular reversed-phase columns by HPLC-HN-APCI-MS. In both cases, specificity is obtained by causing the parent isoflavonoid molecular ions to undergo collision-induced dissociation to form specific daughter ions in a triple quadrupole MS instrument. When it is only necessary to measure the total isoflavonoids and their metabolites in blood, hydrolysis can be performed directly in serum/plasma samples and isoflavonoids recovered by ether or ethyl acetate solvent extraction. The isoflavone aglucones can be analyzed by HPLC-MS under isocratic solvent conditions, thereby drastically shortening analysis time and opening up prospects for automation. Therefore, HPLC-MS is a technique that is broadly applicable to the major issues in phytoestrogen research.

Evolution of the health benefits of soy isoflavones

Soy is a unique dietary source of the isoflavones, genistein and daidzein. It has been part of the Southeast Asian diet for nearly five millenia, whereas consumption of soy in the United States and Western Europe has been limited to the 20th century. Heavy consumption of soy in Southeast Asian populations is associated with reduction in the rates of certain cancers and cardiovascular disease. Recent experimental evidence suggests that phytochemicals in soy are responsible for its beneficial effects, which may also include prevention of osteoporosis, a hereditary chronic nose bleed syndrome, and autoimmune diseases. Exposure of soy formula-fed infants to the potential estrogenizing effects of the isoflavones is limited by the first pass effect of the liver following the uptake of isoflavones from the gut. Several mechanisms of action of isoflavones have been proposed-both through estrogen-dependent and estrogen-independent pathways.

Genistein alters the ontogeny of mammary gland development and protects against chemically-induced mammary cancer in rats

Breast cancer is the most common cancer in US females and is the second leading cause of cancer death among women. By contrast, Asian women consuming a traditional diet high in soy products have a relatively low incidence of breast cancer. Asians who emigrate to the United States and adopt a Western diet lose this protection. Soy-based diets are high in phytoestrogens, and one of these components is genistein. Using the dimethylbenz(a)anthracene (DMBA) mammary cancer rodent model, we have investigated the breast cancer protective potential of genistein. Our results demonstrate that neonatal and prepubertal genistein treatments altered the ontogeny of the mammary gland and rendered the adult animals less susceptible to chemically-induced mammary cancer. Neonatal genistein treatment did not significantly alter the rate of formation and persistence of DMBA-DNA adducts in the mammary gland. While high concentrations of genistein during the neonatal period caused adverse effects on ovarian follicular development, prepubertal genistein treatment did not appear to be toxic in either the female reproductive tract or the endocrine system.

Immunodetection of manganese superoxide dismutase in cultured human retroocular fibroblasts using sera directed against the thyrotropin receptor

The identification of antigenic targets in the retroocular autoimmune response of Graves' ophthalmopathy is likely to increase our understanding of mechanisms underlying this disorder. While a number of putative autoantigens have been identified on the basis of molecular weight or cell of origin, a determination of the significance of these antigens is contingent upon an identification of the amino acid sequence. Our group has previously identified immunoreactive retroocular fibroblast (ROF) proteins recognized by thyrotropin receptor (hTSH-R) antisera (anti-p1), at molecular weights of 95, 71, 41, and 14-25 kDa. In the present study, proteins detected by anti-p1 and visualized by Ponceau staining were isolated and processed for microsequencing. Ponceau staining revealed dense bands at molecular weights of 14 and 23 kDa, and a weak band at 41 kDa. N-terminal sequencing was performed on the prominent band at approximately 23 kDa, showing it to be manganese superoxide dismutase (MnSOD), a mitochondrial enzyme responsible for protection against oxygen free radical-associated cellular damage. Sequence comparison of MnSOD to the hTSH-R peptide, p1, revealed a linear segment of amino acid homology. Preincubation of anti-p1 with p1 blocked immunodetection of the 23 kDa band corresponding to MnSOD, and immunoprecipitation of ROF protein using anti-pi yielded protein recognized by anti-MnSOD. Autoimmunity against human recombinant MnSOD was further assessed by ELISA. Patients with Graves' disease (n = 53) had significantly higher ELISA indices than normal control subjects (n = 29), while patients with Hashimoto's thyroiditis had intermediate values. These results document MnSOD autoantibodies in patients with Graves' disease and suggest that this may result from an immune cross-reactivity between MnSOD and the TSH-receptor.

Cyclic-nucleotide-gated channels mediate synaptic feedback by nitric oxide

Cyclic-nucleotide-gated (CNG) channels in outer segments of vertebrate photoreceptors generate electrical signals in response to changes in cyclic GMP concentration during phototransduction. CNG channels also allow the influx of Ca2+, which is essential for photoreceptor adaptation. In cone photoreceptors, cGMP triggers an increase in membrane capacitance indicative of exocytosis, suggesting that CNG channels are also involved in synaptic function. Here we examine whether CNG channels reside in cone terminals and whether they regulate neurotransmitter release, specifically in response to nitric oxide (NO), a retrograde transmitter that increases cGMP synthesis and potentiates synaptic transmission in the brain. Using intact retina, we show that endogenous NO modulates synapses between cones and horizontal cells. In experiments on isolated cones, we show directly that CNG channels occur in clusters and are indirectly activated by S-nitrosocysteine (SNC), an NO donor. Furthermore, both SNC and pCPT-cGMP, a membrane-permeant analogue of cGMP, trigger the release of transmitter from the cone terminals. The NO-induced transmitter release is suppressed by guanylate cyclase inhibitors and prevented by direct activation of CNG channels, indicating that their activation is required for NO to elicit release. These results expand our view of CNG channel function to include the regulation of synaptic transmission and mediation of the presynaptic effects of NO.

Formation of the NO donors glyceryl mononitrate and glyceryl mononitrite from the reaction of peroxynitrite with glycerol

Peroxynitrite (ONOO-), formed from the rapid reaction of superoxide (O2-.) with NO, is known to generate stable compounds capable of donating NO on reaction with thiols and molecules containing hydroxy groups. Using glycerol as a model compound for the reactions of ONOO- with biomolecules containing hydroxy groups, we separated the products and identified them by HPLC/MS. It was shown that both glyceryl mononitrate and glyceryl mononitrite were formed and released NO on incubation with copper and l-cysteine. The compounds were stable over a period of 4h when shielded from light and kept on ice. Slow spontaneous decomposition occurred in the buffer used for the bioassay, but this was not sufficient to explain the vasorelaxing properties of these NO donors. It is concluded that the stable organic nitrate and nitrite have the capacity to be metabolized by vascular tissues, resulting in vasorelaxation.

Purification and characterization of a rat liver bile acid coenzyme A ligase from rat liver microsomes

In the present study, using the C24 bile acid chenodeoxycholic acid as substrate, rat liver bile acid CoA ligase activity (rBAL) was purified 200-fold from detergent-solubilized microsomes using a combination of Q-Sepharose anion exchange, hydroxyapatite, and CM-Sepharose chromatography. Purified rBAL had a molecular weight of 65 kDa by SDS-PAGE analysis. Gel filtration of purified rBAL indicated that rBAL activity forms a complex with other proteins with an apparent aggregate molecular weight of 243 kDa. A monoclonal antibody raised against the 65-kDa protein and covalently coupled to 6B-Sepharose completely absorbed rBAL activity from a semipurified preparation of rat liver microsomes. Western blot analysis confirmed the elution of the 65-kDa protein from the affinity phase at low pH. Optimum rBAL activity was found at pH 8.5, and activity was dependent on the divalent cation Mg2+. In the presence of 50 microM CoA and 2.5 mM MgCl2, kinetic analysis revealed that the apparent K(m)s of ATP and chenodeoxycholic acid of the purified enzyme were 548 +/- 247 and 18.0 +/- 6.2 microM, respectively, and the apparent Vmax was 9.53 +/- 2.0 nmol min-1 mg protein-1. The formation of chenodeoxycholyl-CoA by rBAL was strongly inhibited by hydrophobic bile acids (the C24 monohydroxy bile acid lithocholic acid and 3 alpha,7 alpha,12 alpha-trihydroxy-5 beta-cholestanoic acid, the C27 homolog of cholic acid), but only weakly by cholic acid. Chenodeoxycholyl-CoA and 3 alpha,7 alpha,12 alpha-trihydroxy-5 beta-cholestan-27-oyl-CoA were confirmed as reaction products of purified rBAL by HPLC-electrospray ionization mass spectrometry.

The chemopreventive properties of soy isoflavonoids in animal models of breast cancer

Genistein (5,7,4'-trihydroxyisoflavone), one of two major isoflavonoids in soy, has anti-proliferative effects on mitogen-stimulated cell growth of human breast cancer cells in culture and is a candidate for use in the prevention of breast cancer. Soy protein preparations containing isoflavonoid conjugates have chemopreventive activity in carcinogen-induced rat models of breast cancer. Recent experiments in these models with purified genistein have revealed that the timing of the exposure of rats to this isoflavonoid is critical. Rats treated neonatally or prepuberally with genistein have a longer latency before the appearance of 7,12-dimethylbenz[a]anthracene-induced mammary tumors and a marked reduction in tumor number. The mechanism of genistein's preventive action is in part dependent on its estrogenic activity, which causes a more rapid differentiation of the cells of the mammary gland, and analogous to the effects of an early pregnancy. Rats administered genistein after 35 days of age have smaller alterations in breast cancer risk, with a maximum reduction in mammary tumor number of 27%. In ovariectomized nude mice, dietary genistein increases cell proliferation of human breast cancer MCF-7 cell xenografts compared with a control diet. This estrogen-like effect of genistein is not observed in non-ovariectomized rats. Future studies on the anticancer potential of soy isoflavonoids should examine their interaction with other phytochemical components of soybeans and exploit newly developed animal models of breast cancer in which specific genes have been activated or inactivated.

Superoxide dismutase catalyzes nitration of tyrosines by peroxynitrite in the rod and head domains of neurofilament-L

Superoxide dismutase (SOD) catalyzes the nitration of specific tyrosine residues in proteins by peroxynitrite (ONOO-), which may be the damaging gain-of-function resulting from mutations to SOD associated with familial amyotrophic lateral sclerosis (ALS). We found that disassembled neurofilament-L (light subunit) was more susceptible to tyrosine nitration catalyzed by SOD in vitro. Neurofilament-L was selectively nitrated compared with the majority of other proteins present in brain homogenates. Assembled neurofilament-L was more resistant to nitration, suggesting that the susceptible tyrosine residues were protected by intersubunit contacts in assembled neurofilaments. Electrospray mass spectrometry of trypsin-digested neurofilament-L showed that tyrosine 17 in the head region and tyrosines 138, 177, and 265 in alpha-helical coil regions of the rod domain of neurofilament-L were particularly susceptible to SOD-catalyzed nitration. Nitrated neurofilament-L inhibited the assembly of unmodified neurofilament subunits, suggesting that the affected tyrosines are located in regions important for intersubunit contacts. Neurofilaments are major structural proteins expressed in motor neurons and known to be important for their survival in vivo. We suggest that SOD-catalyzed nitration of neurofilament-L may have a significant role in the pathogenesis of ALS.

Superoxide radical production stimulates retroocular fibroblast proliferation in Graves' ophthalmopathy

Retroocular fibroblast proliferation is believed to be a key component in the pathogenesis of Graves' ophthalmopathy. In the present study, we assessed the ability of superoxide radicals, generated using the xanthine oxidase/hypoxanthine system to induce cellular proliferation in cultured human retroocular fibroblasts obtained from two patients with severe Graves' ophthalmopathy and two control patients undergoing corrective eye surgery. In tissue obtained from patients with Graves' ophthalmopathy, fibroblast proliferation, as assessed by [3H]-thymidine incorporation, was induced by superoxide radicals in a dose-dependent manner. Xanthine oxidase or hypoxanthine alone had no proliferative effect, and control retroocular fibroblasts showed no proliferation in response to superoxide generation. Preincubation with the antithyroid drug methimazole, at concentrations ranging from 0-25 microM, prevented superoxide-induced fibroblast proliferation in a dose-response pattern. Preincubation with the xanthine oxidase inhibitor, allopurinol (1.0 mM) or the antioxidant nicotinamide (10 microM) also inhibited superoxide-induced fibroblast proliferation, whereas propylthiouracil (10 microM) had little effect. These studies suggest a pathway through which oxygen free radicals may contribute to the retroocular fibroblast proliferation observed in patients with Graves' ophthalmopathy.

Intravenous immunoglobulin in symptomatic and asymptomatic children with perinatal HIV infection

One hundred thirty-five children born to human immunodeficiency virus (HIV)-infected mothers were selected randomly to receive immunoglobulin (Gamimune-N, Miles Pharmaceutical Co) 200 mg/kg monthly for 1 year. All patients were seropositive by ELISA and Western blot at birth. At the time of the study, 15 symptomatic (P2) and 57 asymptomatic (P1) patients with evidence of viral infection (positive HIV culture or P24 antigen) received the immunoglobulin. Sixty-three indeterminate (PO) patients with no evidence of infection served as the control. Mean age for infants in group P2 was 32 months, 26 months for group P1, and 11 months for group PO. Significant reduction in the frequency of bacterial infections (ie, otitis media, upper respiratory tract infections, urinary tract infections, and acute gastroenteritis) was seen in the symptomatic group compared with both the asymptomatic and the control groups. Growth as measured by weight and height > 50th percentile was also markedly better in the symptomatic group than either asymptomatic or control patients. There was no significant difference in head circumference in all three groups. These results indicate that monthly intravenous immunoglobulin infusion (IVIG) appears to be beneficial to both symptomatic and asymptomatic HIV patients in reducing the frequency of bacterial infection and also enhancement of the immune response. However, symptomatic patients responded much better than the asymptomatic patients.