Cyclooxygenase-2 expression in human thyroid disease

OBJECTIVES

Cyclooxygenase (COX)-2, which is the inducible form of the COX enzyme for prostaglandin synthesis and a key mediator of epithelial cell growth, has been shown to be up-regulated in gastrointestinal cancers. Additionally, regular intake of other non-steroidal anti-inflammatory drugs (NSAID) is known to decrease the incidence of these cancers. Therefore, the goals of the present study were to determine the possible involvement of COX-2 in human thyroid diseases.

METHODS

We used immunohistochemical staining and Western blot analysis to characterize the expression of COX-2 proteins in thyroid tissues from 64 patients with thyroiditis, benign tumors, and malignant tumors with or without metastasis. Immunoreactivity scores were calculated by multiplication of the determined grades.

RESULTS

COX-2 proteins were not expressed in normal thyroid tissues. However, each type of tumor tissue showed intense bands of COX-2 protein expression in Western blot analyses, and the immunoreactivity scores were 7.67+/-1.17 (SD) for thyroiditis, 7.87+/-0.9 for benign tumors, 7.53+/-1.53 for follicular cancer, 7.63+/-1.11 for papillary cancer without metastasis, and 7.17+/-1.55 for papillary cancer with metastasis. No significant differences were found in the levels of COX-2 expression between different tumor tissue types.

CONCLUSION

No significant correlations were observed between clinical and/or pathological characteristics of thyroid tumors and the intensity of COX-2 protein expression. In addition, we found no difference in COX-2 protein expression between thyroiditis and thyroid tumors. Thus, up-regulation of COX-2 protein synthesis in human thyroid diseases does not appear to be of clinical significance.

[Synthesis of reactivators of phosphorylated acetylcholinesterase of bis-pyridiniumdialdoxime type with a 3-oxapentane connecting chain and their testing in vitro on a model of the enzyme inhibited by chlorpyrifos and methylchlorpyrifos]

Insecticides (e.g., parathion, chlorpyrifos, methylchlorpyrifos) and nerve agents (e.g.. soman, sarin, tabun, VX) belong to the group of organophosphates. They are able to irreversibly inhibit the enzyme acetylcholinesterase (AChE). Three new reactivators with a 3-oxapentane connecting chain were prepared. The ability of the new compounds to reactivate AChE inhibited by pesticides was tested in vitro and compared to known oxime 10(-3) M which is unfortunately not applicable to in vivo experiments. All tested compounds are practically ineffective for methylchlorpyrifos-inhibited AChE at the physiological concentration (10(-5) M). On the other hand, the known reactivators surpass new substances in the case of chlorpyrifos-inhibited AChE at both concentrations.

Inhibitory effect of select nitrocompounds on growth and survivability of Listeria monocytogenes in vitro

We report the effects of 2-nitro-1-propanol (2NPOH), 2-nitroethanol (2NEOH), and nitroethane (NE) on growth and survivability of Listeria monocytogenes. In all cases, inhibition was greatest with 2NPOH and least with NE. For example, specific growth rates of L. monocytogenes strain 18 declined (P < 0.05) 76, 60, and 29% from controls during aerobic culture at 37 degrees C in brain heart infusion broth containing 10 mM 2NPOH, 2NEOH, or NE, respectively. Mean specific growth rate for the controls incubated likewise without added nitrocompound was 0.62 +/- 0.02 h(-1). Specific growth rates of L. monocytogenes Scott A decreased (P < 0.05) 67, 45, and 11%, respectively, from controls (0.67 +/- 0.02 h(-1)) when cultured similarly. Specific growth rates for L. monocytogenes strain 18 incubated similarly except at 30 degrees C were reduced (P < 0.05) 76, 60, and 30%, respectively, and were reduced (P < 0.05) 78, 23, and 23% during anaerobic culture at 30 degrees C in brain heart infusion broth containing 15 mM 2NPOH, 2NEOH, or NE (control rates ranged from 0.37 +/- 0.07 to 0.74 +/- 0.05 h(-1)). Survivability of L. monocytogenes strain 18 was reduced (P < 0.05) during aerobic storage (4 months at 4 degrees C) in brain heart infusion broth containing 2NPOH or 2NEOH (by 7.8 and 1.9 log units, respectively) but not NE. The inhibitory effect of 2NPOH was approximately 20% greater during growth at pH 7.0 than at pH 5.6 or 8.0. These results demonstrate the differential inhibitory activity of 2NPOH, 2NEOH, and NE against L. monocytogenes in vitro.

Novel preharvest strategies involving the use of experimental chlorate preparations and nitro-based compounds to prevent colonization of food-producing animals by foodborne pathogens

Foodborne diseases caused by enterohemorrhagic Escherichia coli, Salmonella, and Campylobacter species are of public health and economic significance. Shedding of these pathogens during production and slaughter are risks for contamination of products for human consumption. Consequently, strategies are sought to prevent or reduce the carriage of these pathogens in food animals before slaughter. Experimental products containing chlorate salts have been proven efficacious in reducing concentrations of E. coli and Salmonella Typhimurium in the gut of cattle, sheep, swine, and poultry when administered as feed or water additives. Mechanistically, chlorate selectively targets bacteria expressing respiratory nitrate reductase activity, such as most members of the family Enterobacteriaceae, as this enzyme catalyzes the reduction of chlorate to lethal chlorite. Most beneficial gut bacteria lack respiratory nitrate reductase activity, and thus the technology appears compatible with many bacteria exhibiting competitive exclusion capabilities. More recently, select nitrocompounds have been investigated as potential feed additives, and although these nitrocompounds significantly reduce pathogens on their own, evidence indicates that they may most effectively be used to complement the bactericidal activity of chlorate. A particularly attractive aspect of the nitrocompound technology is that, as potent inhibitors of ruminal methanogenesis, they may allow producers the opportunity to recoup costs associated with their use. At present, neither chlorate nor the nitrocompounds have been approved as feed additives by the US Food and Drug Administration, and consequently they are not yet available for commercial use.

Inhibitory activity of 2-nitropropanol against select food-borne pathogens in vitro*

AIMS

To test the inhibitory activity of 2-nitro-1-propanol (2NPOH) against Salmonella Typhimurium, Escherichia coli O157:H7 and Enterococcus faecalis.

METHODS AND RESULTS

Specific growth rates (h(-1)) of S. Typhimurium, E. coli O157:H7 and Ent. faecalis were determined during culture in tryptic soya broth (TSB) supplemented with 0-10 mm 2NPOH. Growth rates were inhibited by 2NPOH, with nearly complete inhibition observed with 10 mm. Studies with S. Typhimurium revealed that its survivability during culture in TSB containing 5 or 10 mm 2NPOH was lower (P < 0.05) under aerobic than anaerobic conditions. The survivability of Salmonella during anaerobic culture in TSB containing 2.5 mm 2NPOH was less at pH 5.6 than at pH 7.0 and 8.0. No Salmonella survived anaerobic incubation in TSB supplemented with 10 mm 2NPOH regardless of pH. When incubated in suspensions of freshly collected populations of ruminal and faecal bacteria, Salmonella concentrations were lower (P < 0.05) in suspensions containing 10 mm 2NPOH than in suspensions containing no 2NPOH.

CONCLUSIONS

2NPOH inhibited S. Typhimurium, E. coli O157:H7 and Ent. faecalis.

SIGNIFICANCE AND IMPACT OF THE STUDY

Results suggest that 2NPOH may be a useful antimicrobial supplement to reduce carriage of certain food-borne pathogens in food animals.

Effect of Drinking-Water Administration of Experimental Chlorate Ion Preparations on Salmonella enterica serovar Typhimurium Colonization in Weaned and Finished Pigs

Foodborne disease caused by Salmonella is of public health and economic significance. In order to assess the practical effectiveness of a new intervention strategy, experimental chlorate preparations (ECP) were administered via the drinking water to weaned and finished pigs that had been orally challenged the previous day with 10(9)-10(10) colony-forming units of Salmonella serovar Typhimurium. After 24 or 36 h ad libitum access to 0X, 1X or 2X ECP treatment (where X is the concentration estimated to deliver a minimal daily effective dose), the pigs were euthanized and gut contents and lymph tissue collected at necropsy were cultured for the challenge Salmonella. Drinking water administration of ECP effectively reduced (p < 0.05) caecal Salmonella concentrations and, with the weaned pigs, tended (p < or = 0.10) to reduce rectal Salmonella concentrations. No negative effects of ECP treatment on water intake and animal wellbeing were observed and only marginal effects on gut fermentation characteristics occurred. The bactericidal effect of administering ECP in drinking water was relatively rapid, with reductions in caecal Salmonella concentrations occurring within 24 h. These results suggest that ECP administered to pigs just days before slaughter may reduce gut concentrations of Salmonella; however, the impacts of such reductions on slaughter hygiene have yet to be determined.

Alterations in hepatic metabolism of sulfur-containing amino acids induced by ethanol in rats

Alterations in hepatic metabolism of S-amino acids were monitored over one week in male rats treated with a single dose of ethanol (3 g/kg, ip). Methionine and S-adenosylhomocysteine concentrations were increased rapidly, but S-adenosylmethionine, cysteine, and glutathione (GSH) decreased following ethanol administration. Activities of methionine adenosyltransferase, cystathionine gamma-lyase and cystathionine beta-synthase were all inhibited. gamma-Glutamylcysteine synthetase activity was increased from t = 8 hr, but GSH level did not return to control for 24 hr. Hepatic hypotaurine and taurine levels were elevated immediately, but reduced below control in 18 hr. Changes in serum and urinary taurine levels were consistent with results observed in liver. Cysteine dioxygenase activity was increased rapidly, but declined from t = 24 hr. The results show that a single dose of ethanol induces profound changes in hepatic S-amino acid metabolism, some of which persist for several days. Ethanol not only inhibits the cysteine synthesis but suppresses the cysteine availability further by enhancing its irreversible catabolism to taurine, which would play a significant role in the depletion of hepatic GSH.

Effects of sodium chlorate on toxin production by Escherichia coli O157:H7

Chlorate kills E. coli O157:H7 and has been proposed as a feed additive to be included in cattle rations immediately prior to slaughter to reduce E. coli O157: H7 populations in the gut. Antibiotic usage is not recommended in cases of E. coil O157:H7-induced hemorrhagic colitis because some antibiotics stimulate increased toxin production. This study was undertaken to determine if chlorate treatment affected toxin production. Pure cultures of E. coil O157:H7 were treated with 1/4 MIC of antibiotics (ampicillin, tetracycline, ceftiofur, gentamicin, monensin, tylosin, penicillin, ciprofloxacin, and novobiocin); toxin production was significantly increased by some antibiotics, but not by chlorate. Studies with mixed fecal bacteria demonstrated that chlorate killed E. coli O157:H7, but again did not stimulate toxin production. Chlorate appears to be an effective method to reduce shiga toxin-producing E. coil (STEC) populations in food animals, but additional studies are warranted before it is used to control infections.

Antimicrobial Resistance and Serotype Prevalence of Salmonella Isolated from Dairy Cattle in the Southwestern United States

Mature dairy cattle were sampled over a 2-year period (2001-2002) on six farms in New Mexico and Texas. Fecal samples (n = 1560) were collected via rectal palpation and cultured for Salmonella, and one isolate from each positive sample was serotyped. Three isolates of each serotype, with the exception of Salmonella Newport (n = 12), were examined for susceptibility to 17 antimicrobial agents. Twenty-two different serotypes were identified from a total of 393 Salmonella isolates. Montevideo was the predominant serotype (27%) followed by Mbandaka (15%), Senftenberg (11.4%), Newport (6.4%), Anatum (4.8%), and Give (4.8%). Salmonella Typhimurium and Dublin, two frequently reported serotypes, accounted for only 1% of the observed serotypes in this study. Sixty-four percent of the serotypes were susceptible to all 17 antimicrobials, 14% were resistant to a single agent, and 22% were multiresistant (2-11 types of resistance). All isolates tested were susceptible to amikacin, apramycin, imipenem, ceftriaxone, nalidixic acid, and ciprofloxacin. The most frequent types of resistance were to sulfamethoxazole, tetracycline, streptomycin, kanamycin, chloramphenicol, and ampicillin (ranging from 8.9 to 22.4%). Serotypes demonstrating multiple resistance included Dublin and Give (resistant to three or more antibiotics), Typhimurium (resistant to five antibiotics), and Newport (four and two isolates resistant to six and nine antibiotics, respectively). Class 1 integrons were present in only two Salmonella Dublin isolates and one Salmonella Newport isolate. The most prevalent resistance patterns observed in this study were toward antimicrobial agents commonly used in cattle, while all Salmonella isolates were susceptible to ceftriaxone and ciprofloxacin, antibiotics used in human medicine.

Ionophores: their use as ruminant growth promotants and impact on food safety

Ionophores (such as monensin, lasalocid, laidlomycin, salinomycin and narasin) are antimicrobial compounds that are commonly fed to ruminant animals to improve feed efficiency. These antimicrobials specifically target the ruminal bacterial population and alter the microbial ecology of the intestinal microbial consortium, resulting in increased carbon and nitrogen retention by the animal, increasing production efficiency. Ionophores transport ions across cell membranes of susceptible bacteria, dissipating ion gradients and uncoupling energy expenditures from growth, killing these bacteria. Not all bacteria are susceptible to ionophores, and several species have been shown to develop several mechanisms of ionophore resistance. The prophylactic use of antimicrobials as growth promotants in food animals has fallen under greater scrutiny due to fears of the spread of antibiotic resistance. Because of the complexity and high degree of specificity of ionophore resistance, it appears that ionophores do not contribute to the development of antibiotic resistance to important human drugs. Therefore it appears that ionophores will continue to play a significant role in improving the efficiency of animal production in the future.

Effects of the antibiotic ionophores monensin, lasalocid, laidlomycin propionate and bambermycin on Salmonella and E. coli O157:H7 in vitro

AIMS

To examine the effects of ionophores on Salmonella and Escherichia coli O157:H7 in pure and mixed ruminal fluid cultures.

METHODS AND RESULTS

Four Salmonella serotypes (Dublin, Derby, Typhimurium, and Enteriditis) and two strains of E. coli O157:H7 (ATCC 43895 and FDIU 6058) were cultured in the presence of varying concentrations of ionophores (monensin, lasalocid, laidlomycin propionate, and bambermycin) in pure and mixed ruminal fluid cultures. Bacterial growth rates in pure culture were not affected (P > 0.10) by ionophores at concentrations up to 10 times the approximate rumen ionophore concentration under normal feeding regimens. Likewise, ionophores had no effect (P > 0.10) on Salmonella or E. coli CFU plated from 24-h ruminal fluid incubations. Ionophore treatment decreased (P < 0.01) the acetate : propionate ratio in ruminal fluid cultures as expected.

CONCLUSIONS

Ionophores had no effect on the foodborne pathogens Salmonella and E. coli O157:H7 in vitro.

SIGNIFICANCE AND IMPACT OF THE STUDY

The results suggest that ionophore feeding would have little or no effect on Salmonella or E. coli populations in the ruminant.

Identification of structural domains affecting transactivation potential of Nm23

The strong transactivation activity of the C-terminal half (amino acids 76-152) of Nm23 was reported previously. Here we examined a structural domain preventing or necessary to its transactivation activity. The C-terminal 1/4 (amino acids 109-152) was sufficient for transactivation, but the C-terminal half with a longer N-terminal extension (amino acids 58-152) caused the loss of the transactivation ability. Furthermore, coexpression of the N-terminal half with the C-terminus of Nm23-H1 blocked the transactivation activity of the C-terminal half, where direct interaction of both truncated proteins was demonstrated in vitro. Transactivation activities in the C-terminal halves of the known mutants (P96S, H118F, S120G, and S120A) exhibiting differential antimetastasis effects were also tested. Significant reduction of transactivation activity was observed only in H118F, indicating that NPD kinase active-site histidine is required. This suggests that transactivation potential of Nm23 is related to NDP kinase activity but not to metastasis suppressor activity.

Apoptosis-linked gene 2 binds to the death domain of Fas and dissociates from Fas during Fas-mediated apoptosis in Jurkat cells

Apoptosis-linked gene 2 (ALG-2) is a member of the family of Ca(2+)-binding proteins with penta-EF-hand and is essential for the execution of apoptosis by various signals including Fas activation. We studied the regulation of ALG-2 during Fas-mediated apoptosis in Jurkat cells. The 22-kDa ALG-2 protein is cleaved and becomes a 19-kDa protein after Fas activation. The appearance of 19-kDa ALG-2 protein increases for 4 h after treatment with 200 ng/ml of anti-Fas Ab treatment and gradually degrades afterward. Confocal microscopic analysis showed that ALG-2 translocated from the plasma membrane to the cytosol during Fas-mediated apoptosis. Therefore, we examined if ALG-2 interacts with Fas. The protein-protein interaction of ALG-2 with Fas was demonstrated using yeast two-hybrid assays as well as in vitro GST pull-down assay. Endogenous ALG-2 was immunoprecipitated with anti-Fas Ab in Jurkat cells without Fas activation. However, the endogenous ALG-2 was no longer immunoprecipitated with anti-Fas Ab 2 h after anti-Fas Ab treatment. This study, for the first time, presents a direct molecular connection of ALG-2 to apoptosis by its direct interaction with Fas, and enlists ALG-2 as a new member of posttranslationally modified proteins during Fas-mediated apoptotic process.

Rutaecarpine, a quinazolinocarboline alkaloid, inhibits prostaglandin production in RAW264.7 macrophages

In order to delineate the mechanism involved in the anti-inflammatory activity of rutaecarpine, its effects on the production of prostaglandin (PG) and therein involved enzymes were examined. Rutaecarpine reduced the production of PGE(2) in RAW264.7 cells treated with lipopolysaccharide (LPS) in a dose dependent manner when added to the culture media at the time of stimulation. However, the inhibition of total cellular cyclooxygenase (COX) activity under the same experimental condition was observed only at high concentrations of rutaecarpine. Rutaecarpine did not affected the levels of COX-2 mRNA and protein in macrophages stimulated with LPS. Calcium ionophore A23187 induced-PG production and [(3)H]-arachidonic acid release were significantly decreased by the pretreatment of rutaecarpine for 30 minutes. With the same treatment schedule, however, rutaecarpine failed to alter the activities of cellular COX-1 and COX-2. Collectively, our data suggest that anti-inflammatory effect of rutaecarpine is, at least in part, ascribed to the diminution of PG production through inhibition of arachidonic acid release albeit the nature of its effects on PLA(2) activity remains to be elaborated.

Behavior of murine renal carcinoma cells grown in ectopic or orthotopic sites in syngeneic mice

We examined whether the organ microenvironment modulates the metastatic behavior and the response to doxorubicin (DXR) in murine renal carcinoma (RENCA) cells. Tumor cells were injected into kidney (orthotopic) and subcutis (ectopic) of syngeneic mice. Lung metastases developed in up to 57% (17/30) of animals having kidney tumors but not in those with skin tumors. Tumors growing in the kidney were more resistant to DXR than tumors growing in the subcutis when mice were given intravenous injections of DXR (8 mg/kg) on days 8 and 15 after implantation. In addition, tumor cells cultured from kidney tumors were initially more resistant to DXR than tumor cells cultured from subcutis tumors. After tumor cells were passaged in vitro, all cells exhibited a similar sensitivity to DXR. Additionally, we examined the expression levels of mdr1, EGFR and type IV collagenase by an in situ mRNA hybridization technique. A higher mRNA expression for type IV collagenase and EGFR was found in kidney tumors than in subcutis tumors. These results demonstrate that the organ environment influences the drug responsiveness and the expression of metastasis-related genes in murine renal carcinoma cells.

Effect of endoscopic sinus surgery on asthmatic patients with chronic rhinosinusitis

There have been several reports on the effectiveness of endoscopic sinus surgery (ESS) in asthmatic patients with chronic rhinosinusitis. Whether ESS has a positive effect on the clinical course of asthma still remains controversial. There have been several subjective evaluations but few objective results. We performed a study to evaluate the effectiveness of ESS in 19 patients with asthma who underwent ESS for rhinosinusitis. The use of antiasthma medication and postoperative asthma symptoms was analyzed. Objective changes of pulmonary function tests were evaluated. There was a significant improvement in diurnal and nocturnal asthma symptoms. Improvements in asthma medication scores were also confirmed, and individual asthma symptoms (dyspnea, cough, wheezing, and sputum production) improved significantly. Despite a reduction in use of antiasthma medication after ESS, the parameters of the pulmonary function tests did not change. Both subjectively and objectively, it seems that ESS, when used to treat asthmatic patients with chronic rhinosinusitis, can play a significant role in the clinical improvement of asthma.

Protein kinase C inhibitors attenuate protective effect of high glucose against hypoxic injury in H9c2 cardiac cells

In this study, we demonstrated that PKC inhibitors significantly attenuated the cardioprotective effect produced by high-glucose (22 mM) treatment for 48 h against hypoxic injury in H9c2 cardiac cells. PKC activators mimicked the cardioprotective effect of high glucose. These results suggest a possible role of PKC activation in high-glucose--induced protection.

Structure of C42D Azotobacter vinelandii FdI. A Cys-X-X-Asp-X-X-Cys motif ligates an air-stable [4Fe-4S]2+/+ cluster

All naturally occurring ferredoxins that have Cys-X-X-Asp-X-X-Cys motifs contain [4Fe-4S](2+/+) clusters that can be easily and reversibly converted to [3Fe-4S](+/0) clusters. In contrast, ferredoxins with unmodified Cys-X-X-Cys-X-X-Cys motifs assemble [4Fe-4S](2+/+) clusters that cannot be easily interconverted with [3Fe-4S](+/0) clusters. In this study we changed the central cysteine of the Cys(39)-X-X-Cys(42)-X-X-Cys(45) of Azotobacter vinelandii FdI, which coordinates its [4Fe-4S](2+/+) cluster, into an aspartate. UV-visible, EPR, and CD spectroscopies, metal analysis, and x-ray crystallography show that, like native FdI, aerobically purified C42D FdI is a seven-iron protein retaining its [4Fe-4S](2+/+) cluster with monodentate aspartate ligation to one iron. Unlike known clusters of this type the reduced [4Fe-4S](+) cluster of C42D FdI exhibits only an S = 1/2 EPR with no higher spin signals detected. The cluster shows only a minor change in reduction potential relative to the native protein. All attempts to convert the cluster to a 3Fe cluster using conventional methods of oxygen or ferricyanide oxidation or thiol exchange were not successful. The cluster conversion was ultimately accomplished using a new electrochemical method. Hydrophobic and electrostatic interaction and the lack of Gly residues adjacent to the Asp ligand explain the remarkable stability of this cluster.

Mechanism for antiplatelet effect of onion: AA release inhibition, thromboxane A(2)synthase inhibition and TXA(2)/PGH(2)receptor blockade

Antiplatelet actions of aqueous extract of onion were investigated in rat and human platelet. IC(50)values of onion extract for collagen-, thrombin-, arachidonic acid (AA)-induced aggregations and collagen-induced thromboxane A(2)(TXA(2)) formation were 0.17 +/- 0. 01, 0.23 + 0.03, 0.34 +/- 0.02 and 0.12 +/- 0.01 g/ml, respectively. [(3)H]-AA release induced by collagen (10 microg/ml) in rat platelet was decreased by onion compared to control (22.1 +/- 2.13 and 5.2 +/- 0.82% of total [(3)H]-AA incorporated, respectively). In fura-2 loaded platelets, the elevation of intracellular Ca(2+)concentration stimulated by collagen was inhibited by onion. Onion had no cytotoxic effect in platelet. Onion significantly inhibited TXA(2)synthase activity without influence on COX activity. Platelet aggregation induced by U46619, a stable TXA(2)mimetic, was inhibited by onion, indicating its antagonism for TXA(2)/PGH(2)receptor. These results suggest that the mechanism for antiplatelet effect of onion may, at least partly, involve AA release diminution, TXA(2)synthase inhibition and TXA(2)/PGH(2)receptor blockade.

Purification and biophysical characterization of a new [2Fe-2S] ferredoxin from Azotobacter vinelandii, a putative [Fe-S] cluster assembly/repair protein

During the purification of site-directed mutant variants of Azotobacter vinelandii ferredoxin I (FdI), a pink protein, which was not observed in native FdI preparations, appeared to associate specifically with variants that had mutations in ligands to FdI [Fe-S] clusters. That protein, which we designate FdIV, has now been purified. NH(2)-terminal sequence analysis revealed that the protein is the product of a previously described gene, herein designated fdxD, that is in the A. vinelandii iscSUA operon that encodes proteins involved in iron-sulfur cluster assembly or repair. An apoprotein molecular mass of 12,434.03 +/- 0.21 Da was determined by mass spectrometry consistent with the known gene sequence. The monomeric protein was shown to contain a single [2Fe-2S](2+/+) cluster by UV/visible, CD, and EPR spectroscopies with a reduction potential of -344 mV versus the standard hydrogen electrode. When overexpressed in Escherichia coli, recombinant FdIV holoprotein was successfully assembled. However, the polypeptide of the recombinant protein was modified in some way such that the apoprotein molecular mass increased by 52 Da. Antibodies raised against FdIV and EPR spectroscopy were used to examine the relative levels of FdIV and FdI in various A. vinelandii strains leading to the conclusion that FdIV levels appear to be specifically increased under conditions where another protein, NADPH:ferredoxin reductase is also up-regulated. In that case, the fpr gene is known to be activated in response to oxidative stress. This suggests that the fdxD gene and other genes in the iron-sulfur cluster assembly or repair operon might be similarly up-regulated in response to oxidative stress.

Location of the iron-sulfur clusters FA and FB in photosystem I: an electron paramagnetic resonance study of spin relaxation enhancement of P700+

Photosystem I (PS I) mediates electron-transfer from plastocyanin to ferredoxin via a photochemically active chlorophyll dimer (P700), a monomeric chlorophyll electron acceptor (A0), a phylloquinone (A1), and three [4Fe-4S] clusters (FX/A/B). The sequence of electron-transfer events between the iron-sulfur cluster, FX, and ferredoxin is presently unclear. Owing to the presence of a 2-fold symmetry in the PsaC protein to which the iron-sulfur clusters F(A) and F(B) are bound, the spatial arrangement of these cofactors with respect to the C2-axis of symmetry in PS I is uncertain as well. An unequivocal determination of the spatial arrangement of the iron-sulfur clusters FA and FB within the protein is necessary to unravel the complete electron-transport chain in PS I. In the present study, we generate EPR signals from charge-separated spin pairs (P700+-FredX/A/B) in PS I and characterize them by progressive microwave power saturation measurements to determine the arrangement of the iron-sulfur clusters FX/A/B relative to P700. The microwave power at half saturation (P1/2) of P700+ is greater when both FA and FB are reduced in untreated PS I than when only FA is reduced in mercury-treated PS I. The experimental P1/2 values are compared to values calculated by using P700-FA/B crystallographic distances and assuming that either FA or FB is closer to P700+. On the basis of this comparison of experimental and theoretical values of spin relaxation enhancement effects on P700+ in P700+ [4Fe-4S]- charge-separated pairs, we find that iron-sulfur cluster FA is in closer proximity to P700 than the FB cluster.

Protein kinase C inhibitors abolish the increased resistance of diabetic rat heart to ischemia-reperfusion injury

Protein kinase C (PKC) has been implicated in ischemic preconditioning, but whether it plays a role in the cardioprotection observed in the diabetic heart is not known. We assessed the possible role of PKC by investigating whether the inhibition of PKC with staurosporine (Stau, 0.01 microM) or chelerythrine (Chel, 1 microM) can abolish the increased resistance to ischemia (25 min)-reperfusion (30 min) injury in Langendorff perfused hearts from streptozotocin-induced 4-week diabetic rats. In the diabetic heart, pre-ischemic left ventricular developed pressure (LVDP), double product (DP: LVDPxheart rate/1,000), +/- dP/dt(max) and coronary flow rate (CFR) were all reduced compared to the control. The pretreatment with Stau or Chel significantly improved these parameters. The post-ischemic contractile function was recovered to a greater extent in the diabetic heart (116.9 +/- 20.5% of pre-ischemic DP) than in the control (23.3 +/- 2.3% of pre-ischemic DP), indicating the increased resistance of the diabetic heart to ischemia-reperfusion injury. The treatment with Stau or Chel abolished the enhanced recovery in the diabetic heart (36.0 +/- 14.6 and 54.1 +/- 12.8% of pre-ischemic DP, respectively). The reduction in post-ischemic end diastolic pressure (EDP) and lactate dehydrogenase (LDH) release in diabetes (13.5 +/- 2.5 mmHg and 27.2 +/- 6.2 U/g heart) compared to the control (55.8 +/- 2.9 mmHg and 60. 3 +/- 5.7 U/g heart) was significantly (p<0.05) increased by pretreatment with Stau (39.0 +/- 4.9 mmHg and 53.1 +/- 7.6 U/g heart) or Chel (36.2 +/- 3.0 mmHg and 48.8 +/- 4.3 U/g heart). Neither Stau nor Chel had any influence on the post-ischemic values of LVDP, DP, +/- dP/dt(max), EDP and LDH release in the control heart. In the conclusion, the present results suggest that PKC activation may, at least in part, contribute to the increased resistance of the diabetic heart to ischemia-reperfusion injury.

Pharmacological characterization of KR-30988, a novel non-peptide AT1 receptor antagonist, in rat, rabbit and dog

The pharmacological profile of KR-30988, a non-peptide AT1-selective angiotensin receptor antagonist, has been investigated by use of a variety of experimental models in-vitro and in-vivo. KR-30988 inhibited the specific binding of [125I][Sar1, Ile8]-angiotensin II to the recombinant AT1 receptor from man with a potency similar to that of losartan (IC50 values, the concentrations of drugs displacing 50% of specific binding, 13.6 and 12.3 nM, respectively), but did not inhibit the binding of [125I]CGP 42112A to recombinant AT2 receptor from man (IC50 >10 microM for both drugs). Scatchard analysis showed that KR-30988 interacted competitively with recombinant AT1 receptor from man in the same manner as losartan. In functional studies with rat and rabbit aorta, KR-30988 noncompetitively inhibited the contractile response to angiotensin II (pD2, = -log EC50 (where EC50 is the dose resulting in 50% of a reference contraction), 8.64 and 7.73, respectively) with a 20-85% decrease in the maximum contractile responses, unlike losartan. In pithed rats intravenous KR-30988 resulted in a non-parallel shift to the right of the dose-pressor response curve to angiotensin II (ID50 value, the dose inhibiting the pressor response to angiotensin II by 50%, 0.09 mg kg(-1)) with a dose-dependent reduction in the maximum responses; in this antagonistic effect KR-30988 was 20 times (approx.) more potent than losartan (ID50 1-74 mg kg(-1)). In conscious renal hypertensive rats oral administration of KR-30988 produced a dose-dependent and long-lasting (>24 h) anti-hypertensive effect; the potency was six times that of losartan (ED30 values, the dose reducing mean arterial blood pressure by 30 mmHg, 0.48 and 2.97 mg kg(-1), respectively). In conscious furosemide-treated dogs oral administration of KR-30988 produced a dose-dependent and long-lasting (>8 h) hypotensive effect with a rapid onset of action (time to Emax, the maximum effect, 1-2 h); KR-30988 was eight times more potent than losartan (ED20, the dose reducing mean arterial blood pressure by 20 mm Hg, 1.04 and 7.96 mg kg(-1), respectively). These results suggest that KR-30988 is a potent, orally active selective AT1 receptor antagonist with a mode of insurmountable antagonism.

Tumor site-dependent differential modulation of systemic immunity in RENCA bearing mice

Renal cell carcinoma (RCC) is a highly metastatic cancer which is known to be immunogenic and responsive to immunotherapies using cytokines. The effect of tumor site (organ microenvironment) on the biologic behavior of murine RCC cell line (RENCA) was examined by observing systemic immunomodulations. Reduction of the spleen size observed in tumor bearing mice correlated with a significant decrease in splenic nucleated cell numbers. In the mice bearing RENCA cell tumors in the renal subcapsule, a significant increase of splenic T cell blastogenesis against Con-A (234% of naive control) was observed with reduction of NK activity (45% of naive control). The changes in T cell blastogenesis and NK activity observed in subcutis (s.c.) inoculated RENCA tumor bearers were less significant. However, macrophage functioning and proportions in the spleen were significantly increased only in s.c. tumor bearers. Data indicated tumor site-dependent differential modulation of systemic immunity in RENCA bearing mice which suggests that immunotherapy for RCC should consider not only the tumor but also the tumor's microenvironment.