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PubMed2003

Role of mast cells in gastrointestinal mucosal defense.

The purpose of this review, based on studies from our laboratory as well as from others, is to summarize salient features of mast cell immunobiology and to describe their associations with gastrointestinal mucosal defense. Gastrointestinal mast cells are involved in many pathologic effects, such as food hypersensitivity. On the other hand, they also play a protective role in defense against parasitic and microbial infections. Thus, they have both positive and negative effects, but presently the mechanisms that control the balance of these various effects are poorly known. It has been suggested that stabilization of mast cells may be a key mechanism to protect the gastrointestinal tract from injury. Few molecules are known to possess both mast cell stabilizing and gastrointestinal cytoprotective activity. These include zinc compounds, sodium cromoglycate, FPL 52694, ketotifen, aloe vera, certain flavonoids such as quercetin, some sulfated proteoglycans such as chondroitin sulfate and dehydroleucodine. Dehydroleucodine, a sesquiterpene lactone isolated from Artemisia douglasiana Besser, exhibits anti-inflammatory and gastrointestinal cytoprotective action. The lactone stimulates mucus production, and inhibits histamine and serotonin release from intestinal mast cells. The lactone could act as a selective mast cell stabilizer by releasing cytoprotective factors and inhibiting pro-inflammatory mast cell mediators.

Animals↗
PubMed2004

Update: Cutaneous leishmaniasis in U.S. military personnel--Southwest/Central Asia, 2002-2004.

Cutaneous leishmaniasis (CL) is a sand fly-borne parasitic infection. Preliminary data about cases of CL in military personnel deployed to three countries (Afghanistan, Iraq, and Kuwait) in Southwest/Central Asia have been published previously. During August 2002-February 2004, Department of Defense (DoD) staff identified 522 parasitologically confirmed cases of CL in military personnel. Leishmania major was the etiologic agent for all 176 cases for which species data, obtained by isoenzyme electrophoresis of cultured parasites, are available. This update focuses on the 361 cases (69% of 522) in patients whose demographic data were collected systematically under treatment protocols for therapy with the pentavalent antimonial compound sodium stibogluconate (Pentostam(R); GlaxoSmithKline, United Kingdom) at Walter Reed Army Medical Center, District of Columbia. U.S. health-care providers should consider CL in persons with persistent skin lesions who were deployed to Southwest/Central Asia or who were in other areas where leishmaniasis is endemic.

Adult↗
PubMed1991

[The role of guanyl cyclase in the regulation of aggregation of human thrombocytes].

Increased platelet aggregability is one of the etiological factors of vascular diseases. It is suggested that the cGMP system is involved in the negative regulation of platelet aggregation. The study of platelet guanylate cyclase (GC), a key enzyme of the cGMP system, permits a more thorough understanding of biochemical control of aggregation and opens a possibility of the development of specific action on platelets in pathological states of hemostasis. The authors have revealed a high linear correlation between the increase in aggregability and the decrease in GC activity and in its response to the NO-containing compound sodium nitroprusside (SNP). During ADP-induced aggregation, the state of GC activation by SNP increases (due to saturation of the enzyme by endogenous heme); the platelet cGMP content also rises. In platelets with prevented aggregation (SNP before ADP), GC parameters remain unchanged. NP caused disaggregation of irreversibly aggregated platelets and accelerated disaggregation in the case of reversible aggregation. NO is known to be an endogenous activator of GC and this circumstance gives an opportunity of direct action on platelets (with the help of NO-containing drugs) in order to diminish their hyperaggregability and to prevent spontaneous aggregation that takes place in vascular diseases.

Adenosine Diphosphate↗
PubMed1990

Mechanisms of resistance of confluent human and rat colon cancer cells to anthracyclines: alteration of drug passive diffusion.

Two colon cancer cell lines, HT-29 (human) and DHD/K12/TRb (rat), were grown as monolayer cultures to various confluence degrees. The cytotoxic efficacies of doxorubicin and 4'-deoxydoxorubicin, evaluated by a survival assay, and the nuclear drug concentrations, measured by microspectrofluorometry, were shown to progressively decrease with the augmentation of confluence. This confluence dependent resistance (CDR) to anthracyclines was demonstrated independent of the multidrug resistance drug efflux mechanism. The cellular uptake of three compounds (sodium [51Cr]chromate, D-[14C]alanine, L-[14C]glucose) known to passively diffuse across the cell membrane as anthracyclines do was also reduced in confluent cells. After trypsin cell detachment, the kinetics of reversion of the sodium [51Cr]chromate uptake decrease and that of CDR were similar. Therefore, CDR may be attributed to a reduction of anthracycline cell intake due to a general alteration of passive diffusion across the cell membrane. However, CDR is only partly explained by this phenomenon since a reduced sensitivity of confluent cells was observed compared with nonconfluent cells for a similar amount of drug in their nuclei. CDR could explain the high resistance to anthracyclines of some solid tumors, such as colon tumors, in which cancer cells are tightly aggregated.

Animals↗
PubMed1989

Selenium-induced protection against cis-diamminedichloroplatinum(II) nephrotoxicity in mice and rats.

The influence of selenium on cis-diamminedichloroplatinum(II) (c-DDP) nephrotoxicity in mice and rats was assessed, using single doses of both compounds. Sodium selenite, 2 mg of selenium per kg, given 1 h before c-DDP, greatly reduced blood urea nitrogen and creatinine levels and morphological kidney damage in both BALB/c mice and Wistar rats, while administration 1 h after c-DDP did not. Liver toxicity of selenium was evaluated by measuring serum glutamic pyruvate transaminase and serum glutamic oxalate transaminase and by routine histology. No liver damage was observed in animals treated with sodium selenite, 2 mg of selenium per kg, and physiological saline or c-DDP. Pretreatment with sodium selenite did not reduce the antitumor activity of c-DDP against MPC 11 plasmacytoma or Prima breast tumor in BALB/c mice. The present results indicate that sodium selenite may provide protection against c-DDP nephrotoxicity, when it is given before c-DDP. Moreover, selenium has an antineoplastic activity against several tumors. The combination of these qualities may open new perspectives in cancer chemotherapy.

Animals↗
PubMedDate not supplied

[Mechanisms of the action of hypertonic solutions on the ionic permeability of human skin].

For human skin transcutaneous transport of I ions in vitro depends on sodium chloride-iodide concentration relations in mineral water, whereas such transport for Br ions in mainly determined by absolute concentration of sodium chloride. Optimal proportions of the salts have been specified for I and Br ions transcutaneous transport in definite concentration range. An unknown feature of the mechanism of action of hypertonic salt solutions on ionic skin permeability has been identified. The results are analyzed from the point of view of the ion pairs conception.

Bromides↗
PubMed1988

The potentiation of arsenicals with difluoromethylornithine (DFMO): experimental studies in murine trypanosomiasis.

The efficacy of melarsoprol in the treatment of chronic T. b. brucei infections in mice can be increased approximately 5 times if DL-a-difluoromethylornithine (DFMO) is given in the drinking water at the same time. A more detailed study substantiated the concept that a reduction in both the size and the rate of replacement of the trypanothione pool are the key factors in the efficiency of melarsoprol chemotherapy. It was therefore best to give the melarsoprol towards the end of the DFMO regimen, and as a guanylhydrazone (TBG) also blocks trypanothione (polyamine) biosynthesis, if TBG/DFMO are given together the treatment period can be reduced to 8 days. The antimony compound, sodium stibogluconate (Pentostam), used in combination with DFMO can also cure these infections and demonstrates that arsenic could be substituted by antimony in the treatment of CNS infections.

Animals↗
PubMed1979

Isotopically labelled compounds in the study of extracellular fluid space in dog bone.

The extracellular fluid space in dog bone has been examined using a series of isotopically labelled compounds. Sodium-77 bromide and indium-113m ethylenediaminetetracetic acid were used as extracellular fluid space markers, radioactive water as a total fluid space marker, and potassium-43 chloride to examine the existence of a bone membrane. The clearance of each tracer from bone was monitored for a period of 2h post-injection. Graphical analysis of the clearance curves shows that the number of exponential functions vary depending on the type of tracer used. The fact that a sum of three exponential terms can completely describe each curve indicates that a simple model consisting of three compartments is sufficient to approximate the clearance of these tracers from bone and its associated fluid space. It is concluded that bone consists of an extracellular fluid space, and that this space may well play an important part in the transference of solutes and the mechanisms involved in their localization on the hydroxyapatite crystals of bone.

Animals↗
PubMed1994

Nitric oxide inhibits indoleamine 2,3-dioxygenase activity in interferon-gamma primed mononuclear phagocytes.

Indoleamine 2,3-dioxygenase (IDO) and nitric oxide synthase are part of the anti-tumor and antimicrobial activities of mononuclear phagocytes induced by interferon-gamma (IFN gamma). As IDO is a heme-containing enzyme and NO, the product of nitric oxide synthase-initiated arginine degradation, is a regulator of heme enzymes, we investigated whether NO is capable of modulating IDO activity in IFN gamma-primed mononuclear phagocytes. Authentic NO gas or the NO-generating compound, diethylamine dinitric oxide adduct, dose-dependently inhibited IDO activity in cell lysates prepared from IFN gamma-primed human peripheral blood mononuclear cells, as assessed by the ascorbate/methylene blue assay for IDO. In contrast, neither nitrite nor nitrate affected IDO activity. Exposure of intact IFN gamma-primed human peripheral blood mononuclear cells or monocyte-derived macrophages to any of the NO-generating compounds, sodium nitroprusside, glyceryl trinitrate, S-nitroso-N-acetylpenicillamine, or diethylamine dinitric oxide adduct, resulted in inhibition of both the consumption of tryptophan from and formation of its metabolite, kynurenine, in the culture medium. The observed inhibition of IDO activity was not due to toxicity of the NO generators and was abrogated by the co-addition of oxyhemoglobin, an antagonist of NO function. Comparable concentrations of nitrite or nitrate did not inhibit IDO activity in intact cells. In contrast to human cells, addition of IFN gamma to murine macrophages, cultured in complete RPMI 1640 medium, readily induced nitric oxide synthase. Others have reported that such treatment does not induce IDO activity in these cells. However, induction of IDO activity was observed in murine macrophages when the synthesis of reactive nitrogen species was inhibited, by using arginine-free medium and/or the nitric oxide synthesis inhibitor, NG-monomethyl-L-arginine. Together, these results demonstrate that both exogenous and endogenous NO inhibit IDO activity and that oxidative arginine and tryptophan metabolism in IFN gamma-primed mononuclear phagocytes are functionally related. Our study thereby provides an insight into how these cells may regulate some of their antimicrobial and anti-tumor activities.

Amino Acid Oxidoreductases↗
PubMed1995

Nitric oxide-induced apoptosis in RAW 264.7 macrophages is antagonized by protein kinase C- and protein kinase A-activating compounds.

Endogenously generated or exogenously applied nitric oxide (NO) redox species induce apoptotic cell death in murine RAW 264.7 macrophages. Activation of the inducible NO synthase by incubation of cells with a combination of lipopolysaccharide and interferon-gamma produced internucleosomal DNA fragmentation and morphological alterations, i.e., chromatin condensation, indicative of apoptotic cell death. These alterations, reflecting the production of NO, were prevented by an inhibitor of NO synthase, NG-monomethyl-L-arginine. Moreover, NO derived from endogenous or exogenous sources caused accumulation of the tumor suppressor gene p53. Proposing a link between NO generation and DNA fragmentation, we investigated interfering biochemical signaling pathways. Therefore, we tested the ability of four NO-releasing compounds [sodium nitroprusside (SNP), 3-morpholinosydnonimine (SIN-1), S-nitroso-N-acetylpenicillamine (SNAP), and S-nitrosoglutathione (GSNO)] to cause specific DNA fragmentation. All NO donors induced DNA fragmentation in a time- and concentration-dependent manner. However, substance-specific differences became obvious. After an 8-hr incubation period, GSNO proved to be the strongest apoptotic inducer, whereas SIN-1 was much less active. Apoptosis was rapid with GSNO and SNP, yielding specific DNA fragments after 4 hr and 5 hr, respectively. In contrast, SNAP and SIN-1 produced DNA fragmentation after considerable lag times of 9 hr and 14 hr, respectively. Furthermore, an inhibitory effect of protein kinase C (PKC) and cAMP-dependent protein kinase became apparent. 12-O-Tetradecanoylphorbol-13-acetate, an activator of PKC, inhibited DNA fragmentation by all four NO donors, whereas PKC inhibitors such as staurosporine and calphostin C sensitized macrophages to apoptosis induced by SNP and GSNO. Lipophilic cAMP analogues suppressed SNP-, SIN-1, and SNAP-induced DNA fragmentation. Thus, our study suggests the existence of specific down-modulatory mechanisms related to NO-induced apoptotic DNA fragmentation.

Animals↗
PubMed1993

Effects of L-NG-nitro arginine on cholinergic transmission in the gastric muscle of the rabbit.

In the circular muscle of the rabbit gastric corpus, the nitric oxide-synthesis inhibitor L-NG-nitro arginine (L-NOARG), enhanced the neurally-induced cholinergic responses evoked by electrical field stimulation (EFS) and ganglionic stimulating agents (nicotine, dimethylphenyl piperazinium iodide). The muscular contractions caused by acetylcholine (Ach) and methacholine were not influenced by the nitric oxide-synthesis inhibitor. The nitric oxide-releasing compound sodium nitroprusside (SNP) did not affect the Ach-induced muscular responses. Our results suggest that L-NOARG enhances gastric cholinergic responses by removing an inhibitory influence exerted at the prejunctional level in the nerve-muscle pathway.

Acetylcholine↗
PubMed1993

Characterization of the bifunctional cytochrome c reductase-processing peptidase complex from potato mitochondria.

In potato, cytochrome c reductase, a protein complex of the respiratory chain, exhibits processing activity toward mitochondrial precursor proteins. One of the two cooperating components of the processing peptidase was shown to be identical with subunit III of the complex. Here we report that two additional proteins of the complex (subunit I and II) share 40-50% sequence identity with the processing enhancing protein, the other component of the processing enzyme from fungi and mammals. Thus the composition and structure of the complex integrated processing peptidase seems to be different from its fungal and mammalian counterparts. Cytochrome c reductase from potato is extraordinarily stable, and separation of subunit III from the complex leads to aggregation of the remaining subcomplex and irreversible loss of processing activity. Expression of the three high molecular weight subunits of the complex allowed purification of each individual protein. Neither the individual subunits nor their combinations are active in in vitro processing assays suggesting that they may need the structural support of the complex for activity. In contrast to mitochondrial processing peptidases from other organisms, the purified potato enzyme is active in the presence of high salt (above 1 M NaCl) and works efficiently without addition of metal ions. These data indicate that potato cytochrome c reductase is a bifunctional protein complex with unique features. Possibly, there is a more general evolutionary relationship between cytochrome c reductases and mitochondrial processing peptidases than hitherto assumed.

Amino Acid Sequence↗
PubMed1995

Clinical anticaries efficacy of NaF and SMFP dentifrices: overview and resolution of the scientific controversy.

Since the introduction of commercially marketed fluoride-containing dentifrices in the 1950s, the evolution of these products has seen a number of formulation changes, particularly with regard to the specific types of active fluoride agents they contain. Most currently marketed dentifrices contain one of two major fluoride compounds--sodium fluoride (NaF), or sodium monofluorophosphate (SMFP)--and much research effort has gone into continued investigations geared toward determining which, if either, of these two agents provides dentifrices with greater levels of anticaries efficacy. Historically, among clinical studies, most single-investigation attempts to resolve this issue have yielded equivocal results. During the past two years, however, renewed attempts on a larger scale have been made, including scientific symposia in Toronto, London, and Stockholm sponsored by major manufacturers of dentifrices. The conflicting conclusions derived from these undertakings have resulted in a scientific controversy as to which represents the most accurate resolution to the fluoride-comparison issue. The present paper considers processes for addressing this controversy, and identifies the key points of difference among those processes by which the three symposia arrived at their respective conclusions. An objective procedure for addressing the fluoride-comparison issue is offered, and applied to the clinical data which is currently available in the literature. The results of this analysis indicate that: 1) There is no statistically significant difference between the anticaries effectiveness of dentifrices containing fluoride as SMFP, and those containing fluoride as NaF; and 2) There is no clinically meaningful difference between the anticaries effectiveness of dentifrices containing fluoride as SMFP, and those containing fluoride as NaF.

Cariostatic Agents↗
PubMed1996

Effect of endotoxin on permeability of bovine cerebral endothelial cell layers in vitro.

The effect of lipopolysaccharide (LPS) on cultured cerebral endothelial cells was investigated to assess the changes in the trans endothelial electrical resistance (TEER) across the blood-brain barrier that may occur during inflammatory diseases of the central nervous system. Primary cultures of bovine cerebral endothelial cells were cultured to tight monolayers with a TEER of 250 to 300 omega.cm2 on polycarbonate Transwell filters. LPS induced a time- and dose-dependent decline in TEER. Transport of the hydrophilic model compounds sodium fluorescein and fluorescein dextran (MR, 4 kDa) across monolayers of bovine cerebral endothelial cells increased more than 3-fold after treatment of the cells with LPS (50 ng/ml). Treatment of the monolayers with various concentrations of LPS caused a 3-to 4-fold increase in the permeability of bovine cerebral endothelial cells for [125I]bovine serum albumin, which was also preceded by a decrease in TEER. The reduction of TEER by LPS could be inhibited completely by indomethacin (10(-6)M for 30 min), a cyclooxygenase inhibitor, but not by dexamethasone, a glucocorticoid (10(-7) M for 16 hr). In conclusion, LPS administration to blood-brain barrier endothelial cells causes a decrease in TEER which leads to enhanced transport of low and high molecular weight molecules. During this process the production of eicosanoids by the endothelial cells seem to play a key role.

Animals↗
PubMed1996

Dose-response effects of radiation on the permeability of endothelial cells in culture.

Increased permeability is an early and universal response of the vasculature to radiation injury, yet the biological basis of this reaction is poorly understood. The present study determined the time course and the dose-response relationship of radiation-induced hyperpermeability in cultured bovine pulmonary artery endothelial (BPAE) cells. BPAE cells were grown to a confluent monolayer on microcarrier beads, and column chromatography methods were used to evaluate permeability to two low molecular weight compounds: sodium fluorescein (NaFlsc, mol. wt. = 342) and cyanocobalamin (B12, mol. wt. = 1355). This is a novel in vitro model to study mechanisms and modifiers of radiation-induced permeability of endothelial cells under flow conditions using nonradioactive tracers. Cell-covered beads were exposed to a single dose of 10 Gy Of 137Cs gamma rays and placed in the column, and permeability was measured every 30 min for 3 h. There was a time-dependent increase in permeability to both tracers, reaching significance by 2 h. Increased permeability was accompanied by perturbations in F-actin distribution in the BPAE cells as determined by rhodamine-phalloidin fluorescence microscopy. Neither catalase nor captopril ameliorated this hyperpermeability, but dibutyryl cAMP partially prevented it. At 3 h after 0, 1, 2, 5 and 10 Gy irradiation, permeability values of 11.8 +/- 2.1, 13.9 +/- 2.2, 20.9 +/- 3.6, 24.8 +/- 2.8 and 27.2 +/- 3.3 (10(-5) cm/s, +/- SEM), respectively, were observed using NaFlsc. The increase was significant (P < 0.05) at 2 Gy or higher. Permeability to B12 was significantly elevated after 5 or 10 Gy. These results suggest that permeability of endothelial cells to low molecular weight solutes increases within 3 h after therapeutic doses of radiation, and that cAMP ameliorates this response.

Actins↗
PubMedDate not supplied

Use of urease-bromothymol blue-agar method for large-scale testing of urine on grain and seeds.

The current AOAC method (963.28) for large-scale (50 g) testing of urine on grain is based on the reaction of sodium in urine with magnesium uranyl acetate. Detection of sodium suggests that urine is present and that a test for urea is appropriate. Urea is detected with urease-bromothymol blue-paper and is confirmed through its reaction with xanthydrol to form dixanthylurea crystals, which are detected microscopically. The initial nonspecific test for sodium can be influenced by the presence of salt or other sodium compounds. Furthermore, the magnesium uranyl acetate spray used in Method 963.28 potentially exposes the analyst to the aerosol of a volatile, toxic uranium compound. Excess reagents and analyzed test portions must be disposed of as radioactive waste. In addition, Method 963.28 requires several steps to determine the presence of urea. The alternative AOAC method (972.41) tests for the presence of urea from urine on individual seeds. Urea is enzymatically decomposed to ammonia and carbon dioxide by urease. Liberated ammonia shifts the pH, changing the color of the indicator in the agar from yellow to blue. This study adapts Method 972.41 to larger test samples. Up to 25 g grains and seeds are sprayed with urease test agar instead of being individually immersed in the urease test agar. The modified method was used to analyze urea on seeds and grains of 24 plants from 4 families. The method has a limit of detection of one seed contaminated with 1 microgram urea.

Aerosols↗