Effects of fetal bovine serum on ferrous ion-induced oxidative stress in pheochromocytoma (PC12) cells

Ferrous ion (Fe2+) has been considered to be a cause of neuronal oxidative injury. Since body fluids contain protein and serum is an essential component of tissue culture medium, we have examined the role of serum protein on Fe2+-mediated oxidative stress using PC12 cells and rat cerebral cortices. Fe2+ or the combination of ascorbate and Fe2+ increased concentrations of thiobarbituric acid reactive substances (TBARS) in PC12 cells and cerebrocortical homogenates in medium (RPMI 1640), but did not increase TBARS when the medium was supplemented with 10% fetal bovine serum. Treatment with ascorbate/Fe2+ in serum-free medium reduced endogenous glutathione (GSH) concentration in PC12 cells. However, the medium supplemented with serum did not reduce GSH concentrations. PC12 cell death induced by ascorbate/Fe2+ was alleviated by increasing serum or bovine albumin concentrations in the medium. These observations indicated that oxidative injury caused by the transition metal ion could be lessened by adding fetal bovine serum to culture medium.

Oxidative stress induced by ascorbate causes neuronal damage in an in vitro system

Of particular physiological interest, ascorbate, the ionized form of ascorbic acid, possesses strong reducing properties. However, it has been shown to induce oxidative stress and lead to apoptosis under certain experimental conditions. Ascorbate in the brain is released during hypoxia, including stroke, and is subsequently oxidized in plasma. The oxidized product (dehydroascorbate) is transported into neurons via a glucose transporter (GLUT) during a reperfusion period. The dehydroascorbate taken up by cells is reduced to ascorbate by both enzymatic and non-enzymatic processes, and the ascorbate is stored in cells. This reduction process causes an oxidative stress, due to coupling of redox reactions, which can induce cellular damage and trigger apoptosis. Ascorbate treatment decreased cellular glutathione (GSH) content, and increased the rates of lipid peroxide production in rat cortical slices. Wortmannin, a specific inhibitor of phosphatidylinositol (PI)-3-kinase (a key enzyme in GLUT translocation), prevented the ascorbate induced-decrease of GSH content, and suppressed ascorbate-induced lipid peroxide production. However, wortmannin was ineffective in reducing hydrogen peroxide (H(2)O(2))-induced oxidative stress. The oxidative stress caused ceramide accumulation, which was proportionally changed with lipid peroxides when the cortical slices were treated with ascorbate. These differential effects support the hypothesis that GLUT efficiently transports the dehydroascorbate into neurons, causing oxidative stress.

Pathogenesis of lumbosacral lipoma: a test of the "premature dysjunction" theory

Premature separation of the neuroectoderm from the ipsilateral surface ectoderm allowing mesenchymal tissue to invade into the central canal, or "premature dysjunction" theory, was proposed for the pathogenesis of dorsal type lumbosacral lipoma. To test this theory, the unilateral neural fold was incised using Hamburger and Hamilton stage 12 or 13 chick embryos. Among 35 embryos evaluated, 15 showed abnormal findings, and of these one showed findings which suggested lumbosacral lipoma: a back lump, blending of the neuroepithelium and mesenchyme through indistinct basement membrane and vertebral body abnormalities. The other 14 embryos showed abnormalities including blunt tails, open neural tube defects, incomplete closure of the dorsal neuroepithelium with intact skin, skin dimples, disorganized gray matter, scoliosis, ectopic neuroepithelium and an accessory spinal cord. The results revealed that the incision of the unilateral neural fold in the early chick embryo may produce a lesion suggestive of lumbosacral lipoma, a finding which supports the premature dysjunction theory. This method needs further refinement to overcome technical difficulties, high mortality, and a low yield before being adopted as an experimental model for lumbosacral lipoma.

A possible relation of the Helicobacter pylori pfr gene to iron deficiency anemia?

BACKGROUND

H. pylori infection is thought to contribute to iron-deficiency anemia, especially during puberty. The ferritin protein Pfr of H. pylori is homologous to eukaryotic and prokaryotic ferritins. The purpose of this study was to analyze the H. pylori pfr status in gastric biopsy specimens according to clinical data, including antral gastritis with or without iron-deficiency anemia.

METHODS

A total of 26 H. pylori-positive patients aged from 10-18 years were categorized into subgroups based on the presence or absence of iron-deficiency anemia. All of them had antral gastritis. Sixteen patients were proved to have iron-deficiency anemia by hematological study, two of which had a duodenal ulcer. The other 10 patients showed normal hematological findings. DNA isolation was performed from each of the gastric biopsy specimens. PCR amplification of the pfr gene coding was done using two sets of primers. The pfr region, 501 bp, was generated by linking the sequences of the two PCR products. The nucleotide and protein sequences were compared between the pfr regions from Korean H. pylori strains and the NCTC 11638 strain, which was obtained from the Genbank. Sequence comparisons were also performed for the pfr regions between the iron-deficiency anemia (+) and (-) groups.

RESULTS

Analysis of the complete coding region of the pfr gene revealed three sites of mutation. The Ser39Ala mutation was found in 100% (26/26), Gly111Asn in 26.9% (7/26), and Gly82Ser in 11.5% (3/26). There were no significant differences in the mutations of the pfr regions between the iron deficiency anemia (+) and (-) groups.

CONCLUSION

The mutation in the pfr gene did not relate with the clinical phenotype, iron deficiency anemia. Further studies are needed on the aspects of host side or other complex factors to elucidate the mechanisms by which the H. pylori infection might lead to iron deficiency anemia.

CAS agar diffusion assay for the measurement of siderophores in biological fluids

We developed a simple and universal method, by modifying the universal CAS (Chrome azurol S) assay, measuring siderophores in various biological fluids. We named the assay as CAS agar diffusion (CASAD) assay. CAS plate devoid of nutrients was prepared by using Bacto-agar (1.5%, w/v) as a matrix. Holes with 5-mm-diameter were punched on the CAS agar plate. Each hole was added by 35 microl of the test fluids containing Desferal that was twofold serially diluted. After incubating at 37 degrees C or room temperature for 4-8 h, the size of orange haloes formed around the holes was measured. The size of orange haloes correlated well with the concentration of Desferal in all the biological fluids tested in this study. CASAD assay showed consistent results in wide pH range from 5 to 9. Addition of iron to the test fluids containing Desferal decreased the size of orange haloes in a dose-dependent manner, which suggests that the CASAD assay detects only iron non-bound siderophore. These results suggest that CASAD assay would serve as a simple, stable, and highly reproducible test for screening and quantitative siderophore analysis in biological fluids.

Expression of MAGE-1, -2, and -3 genes in gastric carcinomas and cancer cell lines derived from Korean patients

We investigated the expression of MAGE-1, -2, and -3 genes in tissues of 51 gastric carcinomas from Korean patients and in 11 gastric cancer cell lines established in Korea using reverse transcriptase-polymerase chain reaction along with immunohistochemical analyses and DNA sequencing. Among the 51 gastric carcinomas, MAGE-1, -2, and -3 genes were expressed in 16 (31%), 22 (43%), and 17 (33%), respectively, and 31 (60%) expressed at least one of the three genes. In contrast, none of the three MAGE genes were expressed in normal sites of gastric tissue from each cancer patient. Out of 11 gastric cancer cell lines, MAGE-1, -2, and -3 genes were expressed in two (18%), five (46%), and four (36%), respectively. According to the clinicopathological analysis, the expression of any of the three MAGE genes was not significantly correlated with several clinicopathological factors except histologic types (p= 0.067). Immunohistochemical analyses identified positive staining with monoclonal antibodies 77B and 57B specifically against MAGE-1 and -3 proteins, respectively, in nuclei and cytoplasms of cells in mRNA-positive tumor tissue. These findings suggest the possibility as a target for tumor-specific immunotherapy for Korean patients.

Synthesis of phosphatidylserine in carrot cells cultured under carbon-source starvation

When carrot suspension cells were cultured on medium containing no carbon source (starvation), the levels of phosphatidylserine (PS) increased transiently 3-4 d after the initiation of starvation while levels of most other phospholipid (PL) species decreased. We previously reported that fatty acids of these PLs served as an alternative carbon source during starvation. The present study showed that cells possess two different biosynthetic pathways involving phosphatidylcholine (PC)/phosphatidylethanolamine (PE) exchange enzymes and PS synthase to synthesize PS. These activities peaked similarly 4 d after the initiation of starvation and coincided with the peak of PS level. The synthesis of serine was also significantly activated during starvation. The activity of phosphoserine aminotransferase (PSAT) which is involved in serine synthesis increased with a time course similar to that of the increase in the PS level. These observations suggest that the increase in PS level plays an important role in membranes which are degraded during starvation.

A case of epidermoid cyst of the intrapancreatic accessory spleen

A 54-year-old woman presented with a huge palpable mass on left upper quadrant of the abdomen. After preoperative work-up, a cystic disease of pancreatic tail or accessory spleen was initially suspected. We performed exploratory laparotomy and resected both the spleen and a 15 x 11 cm-sized huge cystic mass containing a part of solid component which extended continuously to the pancreatic tail. The solid component, comprising the upper portion of the resected cyst, was reddish brown and granular like as normal splenic tissue. The inner surface of the cyst was smooth and was filled with yellowish white material. Histologic examination showed an epidermoid cyst originating in the accessory spleen of the pancreatic tail lacking hair or skin appendages.

Quantitative analysis of eotaxin and RANTES messenger RNA in nasal polyps: association of tissue and nasal eosinophils

OBJECTIVES/HYPOTHESIS

Nasal polyps develop in the ethmoidal and middle turbinate area, often in relation to inflammatory conditions. Their exact etiology and pathogenesis are still under debate. Histologically, the polyps are infiltrated by a number of inflammatory cells, with eosinophil predominating in most specimens. This finding suggests that the nasal polyp is an inflammatory growth that is controlled by the local environment. The chemokines eotaxin and RANTES (regulated on activation normal T cell expressed and secreted) have been postulated to be involved in the recruitment and activation of eosinophils to certain inflamed tissues. The purpose of this study was to investigate eotaxin and RANTES mRNA expression in nasal polyps and its effect on tissue and nasal eosinophils.

METHODS

Nasal polyps (917 allergic and 30 nonallergic cases) were obtained from endoscopic sinus surgery, and 15 normal inferior turbinates also were taken. Immunohistochemical staining for eosinophils and quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) tests for eotaxin and RANTES mRNA expression were performed, and the concentration of nasal eosinophil cationic protein (ECP) was measured.

RESULTS

The amounts of eotaxin mRNA in the allergic nasal polyps were 11.4 times higher and the levels in the nonallergic polyps were 6.4 times higher than in the normal inferior turbinate. However, the RANTES mRNA expression did not show any differences among the three groups. Tissue eosinophilia and nasal ECP levels were significantly correlated with eotaxin mRNA level but not with RANTES mRNA expression.

CONCLUSION

Nasal polyp eosinophilic infiltration and activation correlate mainly with increased eotaxin gene expression rather than with RANTES expression.

Pneumatic colonic rupture accompanied by tension pneumoperitoneum

Rupture of the colon caused by high pressure compressed air is a rare, unique and traumatic intra-abdominal injury. As the use of compressed air in industrial work has increased, so has the risk of associated pneumatic injuries from its improper use. Recently we experienced a case of pneumatic rupture of the sigmoid colon accompanied by tension pneumoperitoneum, which caused respiratory distress. The patient's respiration was very rapid with the rate of 44 breaths per minute. On arterial blood gas analysis, pH was 7.40, pO2 68 mmHg, pCO2 44 mmHg, and SaO2 90%. Chest X-ray film showed marked pneumoperitoneum and an elevated diaphragm. The respiratory distress was severe and required immediate relief by emergency decompression peritoneocentesis before surgical intervention consisting of the serosal tear repair, colonic rupture colostomy and abdominal cavity irrigation. A follow up operation 2 months later for colostomy repair completed the patient's recovery.

Vibrio vulnificus has the transmembrane transcription activator ToxRS stimulating the expression of the hemolysin gene vvhA

In an attempt to dissect the virulence regulatory mechanism in Vibrio vulnificus, we tried to identify the V. cholerae transmembrane virulence regulator toxRS (toxRS(Vc)) homologs in V. vulnificus. By comparing the sequences of toxRS of V. cholerae and V. parahaemolyticus (toxRS(Vp)), we designed a degenerate primer set targeting well-conserved sequences. Using the PCR product as an authentic probe for Southern blot hybridization, a 1.6-kb BglII-HindIII fragment and a 1.2-kb HindIII fragment containing two complete open reading frames and one partial open reading frame attributable to toxR(Vv), toxS(Vv), and htpG(Vv) were cloned. ToxR(Vv) shared 55.0 and 63.0% sequence homology with ToxR(Vc) and ToxR(Vp), respectively. ToxS(Vv) was 71.5 and 65.7% homologous to ToxS(Vc) and ToxS(Vp), respectively. The amino acid sequences of ToxRS(Vv) showed transmembrane and activity domains similar to those observed in ToxRS(Vc) and ToxRS(Vp). Western blot analysis proved the expression of ToxR(Vv) in V. vulnificus. ToxRS(Vv) enhanced, in an Escherichia coli background, the expression of the V. vulnificus hemolysin gene (vvhA) fivefold. ToxRS(Vv) also activated the ToxR(Vc)-regulated ctx promoter incorporated into an E. coli chromosome. A toxR(Vv) null mutation decreased hemolysin production. The defect in hemolysin production could be complemented by a plasmid harboring the wild-type gene. The toxR(Vv) mutation also showed a reversed outer membrane protein expression profile in comparison to the isogenic wild-type strain. These results demonstrate that ToxR(Vv) may regulate the virulence expression of V. vulnificus.

Recombinant kringle 1-3 of plasminogen inhibits rabbit corneal angiogenesis induced by angiogenin

PURPOSE

Angiostatin is a potent angiogenesis inhibitor that has been identified as a cryptic fragment of plasminogen molecule containing the first four kringle domain. Angiogenin, a 14-kDa monomeric protein, a potent blood vessel inducer, is expressed in tumors and present in mammalian plasma. The purpose of this study was to determine whether recombinant kringle 1-3 (rKI-3) of human plasminogen could interfere with angiogenesis induced by angiogenin and to evaluate the role of angiogenin in corneal angiogenesis in rabbit.

METHODS

A Hydron polymer pellet containing 2.0 microg of angiogenin was implanted intrastromally into the superior cornea of each of 44 rabbit eyes. All eyes received an intrastromal pellet and were randomized into either one group treated with 12.5 microg of rKI-3 (n = 25) or the other group treated with phosphate-buffered saline (PBS; n = 19). Both pellets were positioned in parallel at the site 1.2 mm from the superior limbus. Two masked observers kept the angiogenesis score daily, based on the number and the length of new vessels. The corneas with induced angiogenesis also were examined histologically.

RESULTS

On the third day of the angiogenin pellets implantation, the eye treated with rKI-3 had less angiogenesis (mean score, 4.2 +/- 6.6) than eye treated with PBS (mean score, 16.1 +/- 17.1; p < 0.05, Mann-Whitney U test). The cornea treated with PBS also showed much more leukocyte adhesion than the cornea treated with rKI-3.

CONCLUSION

Recombinant kringle 1-3 appears to inhibit angiogenin-induced angiogenesis in a rabbit corneal pocket assay. Recombinant kringle 1-3 may have therapeutic potential as an antiangiogenic agent.

The inhibitory effects of recombinant plasminogen kringle 1-3 on the neovascularization of rabbit cornea induced by angiogenin, bFGF, and VEGF

Angiostatin is a potent angiogenesis inhibitor that is composed of the first four kringles of plasminogen fragment. Angiostatin with one less kringle molecule (kringle 1 to 3) was recently demonstrated to be an effective angiogenic inhibitor. To determine whether recombinant plasminogen kringle 1-3 (rPK1-3) can inhibit the corneal neovascularization induced by potent angiogenic factors; angiogenin, bFGF, or VEGF, hydron polymer discs each containing 2.0 microg of angiogenin, 500 ng of bFGF, or 500 ng of VEGF respectively were implanted into the corneal stroma of 138 rabbit eyes, and then discs each containing 10 microg, 12.5 microg, 20 microg or 30 microg of rPK1-3 were implanted randomly. Discs containing phosphate buffered saline were also implanted as a control. The angiogenesis score on number and length of newly formed vessels on the each of the rabbit's cornea were recorded daily by two observers (blinded). The treated corneas were also examined histologically. Recombinant PK1-3 treated corneas showed less neovascularization induced by all angiogenic factors (p < 0.05). and the extent of inhibition of neovascularization was proportional to the concentration of rPK1-3 (p < 0.05). Histologic examination showed leukocyte infiltration into the corneal stroma on the PBS treated eyes whereas rPK1-3 treated eyes showed only traces of leukocytes. These results of the effective rPK1-3 inhibition of corneal neovascularization induced by angiogenin, bFGF, or VEGF suggest that this angiostatin related fragment, rPK1-3, may be useful in the treatment of various neovascular diseases.

Prooxidant effects of ascorbate in rat brain slices

Ascorbate is a well-known reducing agent, but it can generate oxidative potential under appropriate condition. In rat cerebral cortex homogenate, 1 mM ascorbate decreased thiobarbituric acid-reactive substances (TBARS) content to 86% +/- 4% of control values, confirming that ascorbate is a reducing agent. However, ascorbate increased TBARS, in a dose-related manner, in slices prepared from cerebral cortex. Ferrous ion (Fe2+) had little effect on ascorbate-induced lipid oxidation in cortical slices, and EDTA did not have an influence on the ascorbate-induced oxidative action. Conversely, ascorbate plus Fe2+ elevated TBARS content to more than threefold over ascorbate alone in tissue homogenates. In summary, ascorbate is a reducing agent in the brain tissue homogenate but has an oxidizing effect in brain slices. A hypothesis is proposed to explain the oxidative effects of ascorbate in cortical slices, wherein extracellular ascorbate is oxidized to dehydroascorbate, which is rapidly carried into the cells via a glucose transporter (GLUT). The dehydroascorbate in cytosol is then reduced back to ascorbate, and, during the reduction process, cellular components are oxidized.

Dopamine agonists both stimulate and inhibit prolactin release in GH4ZR7 cells

Prolactin secretion from the anterior pituitary gland is regulated by multiple factors including prolactin-release inhibiting factors (PIFs) and prolactin releasing factors. PIFs, however, usually dominate to exert a tonic inhibition in the biological system, and the physiological PIF is believed to be dopamine. However, there is accumulating evidence that dopamine can not only inhibit but also stimulate prolactin release. Many investigators believe that this is achieved by activating inhibitory and stimulatory subtypes of dopamine receptors. We tried to demonstrate that one subtype of dopamine receptors is capable of both inhibiting or stimulating prolactin release using GH(4)ZR(7) cells. GH(4)ZR(7) cells express only a short form of dopamine D(2) receptors (D(2s)). Low concentrations of three well-established D(2) receptor agonists (dopamine, apomorphine and bromocriptine) stimulated prolactin release from GH(4)ZR(7) cells while high concentrations inhibited the release. Haloperidol, a D(2) receptor antagonist, blocked the inhibitory action, but was unable to block the dopamine-induced stimulatory action. Pretreatment of cells with phenoxybenzamine, a receptor alkylating agent, abolished both the dopamine-induced stimulatory and inhibitory actions. Our results support the thesis that the stimulation of prolactin release induced by dopamine is mediated through dopamine D(2s) receptors since the GH(4)ZR(7) cells have only D(2s) receptors among dopamine receptors. We have concluded that the D(2s) receptor is capable of both stimulating and inhibiting prolactin release, probably via the activation of a G(s) protein by low concentrations and a G(i) protein by high concentrations of dopaminergic agents.

Effective immunotherapy of cancer by DNA vaccination

Direct injection of naked plasmid DNA either intramuscularly or intradermally induces strong, long-lived cell-mediated and humoral immune responses to the antigen encoded by the gene vaccine. In the present study, we used gene vaccination with naked plasmid DNA to induce prophylactic immune responses to tumor associated antigens. MAGE-1 (melanoma antigen 1) is an ideal candidate for cancer vaccines because it belongs to a family of genes that are expressed in a number of human tumors of various histological types but not in normal adult tissues except for the testis, and because both humoral and cell-mediated immune responses against MAGE-1 antigen were detected in tumor patients. Intradermal administration of plasmid DNA encoding MAGE-1 (pcMAGE1) induced anti-MAGE-1-specific antibody in BALB/c mice. In contrast, no detectable level of anti-MAGE-1 antibody was induced by intramuscular injection of pcMAGE1. Also, intradermal injection of pcMAGE1 was capable of generating CTLs reactive with MAGE-1-transfected murine tumor cells, M-MSV-MAGE1. Most of the mice (8 out of 10) immunized with pcMAGE1 rejected the challenge of M-MSV-MAGE1 tumor cells, compared with control animals most of which developed tumors. This suggests that intradermal DNA vaccination could provide a novel immunotherapy of cancer.

GLI3 mutations in human disorders mimic Drosophila cubitus interruptus protein functions and localization

Truncation mutations of the GLI3 zinc finger transcription factor can cause Greig cephalopolysyndactyly syndrome (GCPS), Pallister-Hall syndrome (PHS), and postaxial polydactyly type A (PAP-A). GLI3 is homologous to Drosophila Cubitus interruptus (Ci), which regulates the patched (ptc), gooseberry (gsb), and decapentaplegic (dpp) genes. Ci is sequestered in the cytoplasm and is subject to posttranslational processing whereby the full-length transcriptional activator form (Ci155) can be cleaved to a repressor form (Ci75). Under hedgehog signaling, the Ci155 form translocates to the nucleus whereas in the absence of hedgehog, the Ci75 form translocates to the nucleus. Based on the correlation of GLI3 truncation mutations and the human phenotypes, we hypothesized that GLI3 shows transcriptional activation or repression activity and subcellular localization similar to Ci. Here we show that full-length GLI3 localizes to the cytoplasm and activates PTCH1 expression, which is similar to full-length Ci155. PHS mutant protein (GLI3-PHS) localizes to the nucleus and represses GLI3-activated PTCH1 expression, which is similar to Ci75. The GCPS mutant protein has no effect on GLI3-activated PTCH1 transcription, consistent with the role of haploinsufficiency in this disorder. The PAP-A mutant protein (GLI3-PAP-A) showed less specific subcellular localization but still inhibited GLI3-activated PTCH1 transcription, suggesting it may be a weaker allele than the GLI3-PHS mutation. These data show that GLI3 mutations in humans mimic functional effects of the Drosophila ci gene and correlate with the distinct effects of these mutations on human development.

Zinc and copper inhibit nerve growth factor-mediated protection from oxidative stress-induced apoptosis

We have previously provided evidence that two transition metal cations, Zn2+ and Cu2+, can alter the conformation of nerve growth factor (NGF), rendering it unable to bind to its receptors or to activate signal transduction pathways. In the present study, we have assessed the influence of Zn2+ and Cu2+ on NGF-mediated protection from an oxidative insult. Exposure of rat pheochromocytoma (PC12) cells to hydrogen peroxide resulted in an increase in cell death via apoptosis, which was inhibited by NGF. Zn2+ and Cu2+, when added to cultures at a concentration of 100 microM, prevented NGF-mediated survival-promoting effects. Neither of these ions had an effect on basal cell viability (in the absence of NGF) after an oxidative insult. These results demonstrate that Zn2+ and Cu2+ can selectively inhibit NGF-mediated resistance to an oxidative stress, and have significant implications for neuronal function under both physiological and pathological (e.g. cerebral ischemia) conditions.

Clinical value of olfactory function tests after endoscopic sinus surgery: a short-term result

Functional endoscopic sinus surgery (FESS) is now the surgical procedure of choice for treating chronic sinusitis in patients of all ages. We performed the olfactory function test before and after FESS and assessed its clinical value. From February 1996 through July 1996, 50 bilateral sinusitis patients had received FESS, butanol threshold test, and odor identification test, performed preoperatively, at postoperative 1 month, and at postoperative 2 months. We analyzed preoperative computed tomography to determine the grade of sinusitis and status of the olfactory cleft. The status of the olfactory cleft significantly influenced the preoperative olfactory threshold score (p < 0.001). At 2 months postoperatively, the subjective symptoms of the patients were improved in 96% and objective olfactory threshold were improved in 68% of patients. There was no correlation between subjective symptoms and olfactory threshold improvement. Our study suggests that the olfactory threshold test may help predict the result of FESS, but for more accurate and reliable assessment, we should consider other objective methods like anterior rhinomanometry, acoustic rhinometry, ciliary beat frequency, and postoperative endoscopic findings.

Estimation of PC12 cell numbers with acid phosphatase assay and mitochondrial dehydrogenase assay: dopamine interferes with assay based on tetrazolium

Both the acid-phosphatase and mitochondrial dehydrogenase assay have been used to quantify cell numbers. The commonly used acid-phosphatase assay uses p-nitrophenyl phosphate as a substrate, while the mitochondrial dehydrogenase assay is based on the conversion of tetrazolium to formazan. Our experimental results showed that the former assay was more sensitive in detecting small numbers of PC12 cells (200-10,000 cells/well), whereas the latter was useful for larger numbers of cells (2000-40,000 cells/well). The number of PC12 cells decreased after dopamine treatment, according to the acid-phosphatase assay and by direct cell counts under a light microscope. However, the optical densities measured by the mitochondrial dehydrogenase assay increased after dopamine treatment. We tried to clarify discrepancies between the two assays, since dopamine is an important neurotransmitter and both assays are commonly used to estimate cell numbers. To elucidate the interference between dopamine and tetrazolium salt, cell-free control experiments were performed. Dopamine and other catecholamines (adrenaline and noradrenaline) reacted with tetrazolium and, thus, produced a false positive reaction in the assay. We therefore conclude that the tetrazolium assay is not a suitable method for evaluating the number of catecholamine-treated cells, while the acid-phosphatase assay is reliable and sensitive.

Glutathione protects PC12 cells from ascorbate- and dopamine-induced apoptosis

The role of reduced glutathione (GSH) on ascorbate- and dopamine-induced apoptosis in PC12 cells was investigated. Ascorbate is a potent reducing agent and is thus expected to protect against dopamine-induced apoptosis. However, we found that both ascorbate and dopamine killed PC12 cells and ascorbate enhanced dopamine-induced toxicity. The EC50 of cell toxicity induced by ascorbate, dopamine and dopamine plus 0.1 mM ascorbate during 24-h treatment were 0.93+/-0.15 mM, 0.18+/-0.05 mM and 0.13+/-0.04 mM, respectively. When the medium contained 10 mM GSH, the EC50 increased approximately three- and sevenfold for ascorbate and dopamine, respectively. With increased treatment duration, no further toxic effects of ascorbate or dopamine were observed. The GSH synthesis inhibitor, DL-buthionine-(S,R)-sulfoximine (BSO), induced cell toxicity and potentiated the toxic effects of ascorbate and dopamine, suggesting that endogenous GSH participates in protecting against basal oxidative stress. We conclude that both ascorbate and dopamine induce apoptosis in PC12 cells and further that GSH protects them from apoptosis. This study indicates that the toxic effects of ascorbate are potentially due to an oxidative mechanism, similar to that induced by dopamine.

Up-regulation of the expression of major histocompatibility complex class I antigens by plasmid DNA transfection in non-hematopoietic cells

The effect of DNA on the surface expression of major histocompatibility (MHC) class I antigens was examined in non-hematopoietic tumor cell lines. Transfection with plasmid DNA via liposome or electroporation significantly increased the surface expression of MHC class I molecules in a transient manner. Northern blot analysis showed that levels of MHC class I mRNA were increased by DNA transfection, probably via transcriptional activation. In contrast, the expression of the MHC class II and beta-actin genes was not affected, suggesting that the up-regulation of MHC class I expression by plasmid DNA works in a gene-specific manner.

A human transferrin-binding protein of Staphylococcus aureus is immunogenic in vivo and has an epitope in common with human transferrin receptor

To understand human immune responses against the human transferrin-binding protein of Staphylococcus aureus (SA-tbp), we examined cell wall proteins from S. aureus ATCC 6538 using human convalescent sera, and a monoclonal antibody specific for human transferrin receptor (McAb-HTR). The SA-tbp, detected by immunoblot assay, was iron-repressible, reacted with the convalescent sera, and cross-reacted with McAb-HTR. Immunoelectron microscopy probed with McAb-HTR showed a reaction zone around the test strain from the deferrated BHI. After being preincubated with an S. aureus-bacteremic serum, the electroblot of the SA-tbp still reacted with McAb-HTR, but not with human transferrin-horseradish peroxidase conjugate. We conclude, there are at least two kinds of epitopes in the SA-tbp; one able to bind to human transferrin is immunogenic in humans, but the other sharing epitopes common with human transferrin receptor is not immunogenic in humans.

Iron repressibility of siderophore and transferrin-binding protein in Staphylococcus aureus

In order to investigate whether the iron acquisition mechanisms of Staphylococcus aureus are induced by iron restriction in vitro, we examined S. aureus ATCC 6538 for production of siderophore and expression of transferrin-binding protein (SA-tbp) in normal or deferrated brain heart infusion broth (BHI). Siderophore production was earlier and greater in the deferrated BHI. The SA-tbp, detected by ligand blot assay, was expressed only in the deferrated BHI. When human transferrin was added to the deferrated BHI, siderophore production was later and lower than when transferrin was not present. In conclusion, both iron acquisition mechanisms of S. aureus were found to be iron-repressible and via both of them, human transferrin-bound iron was utilized for growth under iron-restricted condition.