Dephosphorylation of autophosphorylated insulin and epidermal-growth-factor receptors by two major subtypes of protein-tyrosine-phosphatase from human placenta

The identity of protein-tyrosine-phosphatases (PTPases) active against autophosphorylated insulin receptor was probed by using an insulin-receptor-related peptide phosphorylated on tyrosine (peptide 1142-1153). Two major peaks of PTPase activity were resolved from the particulate (Triton X-100-soluble) fraction of human placenta by chromatography on DEAE-cellulose. The two peaks were purified 1300-2300-fold; other peaks of PTPase activity (greater than 15%) were not detected. Properties of the PTPases indicated that they corresponded to subtypes 1A and 1B. Both subtypes appeared capable of catalysing dephosphorylation of all autophosphorylation sites in three domains of the insulin receptor, with no appreciable difference in the pattern of dephosphorylation detected by two-dimensional tryptic-peptide mapping. The tyrosine-1150 domain of the insulin receptor in triply phosphorylated form was found to be highly sensitive to the action of both PTPases, and was dephosphorylated at least 4 times faster than the doubly and singly phosphorylated forms of the tyrosine-1150 domain or phosphorylation sites in other domains by either PTPase. This is significant, as the level of the triphosphotyrosine-1150 species has been shown to correlate well with the capacity of the insulin-receptor tyrosine kinase to phosphorylate other proteins. Both subtypes also dephosphorylated autophosphorylated epidermal-growth-factor (EGF) receptor by greater than 95%. Placental particulate (and cytosolic) PTPase activity against either receptor distributed approximately 2:1 between subtypes 1A and 1B as assayed in the presence of EDTA. In summary, PTPases within two major subtypes have been identified as phosphotyrosyl-insulin and -EGF-receptor phosphatases in vitro. The PTPases identified exhibit high affinities for substrates and high activities in cells, which is commensurate with the PTPases being important in vivo in controlling or reversing autophosphorylation-induced regulatory or signalling events.

Agrobacterium mediated genetic transformation of chickpea, Cicer arietinum L

In leaf and stem explants of chickpea, wild type strains of Agrobacteria were able to induce tumors. These tumors were capable of phytohormone independent growth. A supervirulent strain A281 was found to be most effective. Thus, using an agrobacterium R1601, which carries genes conferring supervirulent phenotype along with a plant selectable marker gene (npt II), transformed calli of chickpea were selected in the presence of 100 micrograms/ml level of kanamycin. Molecular analyses of genomic DNA from transformed calli confirmed the integration of the marker gene into chickpea genome.

Temporal distribution of retinoic acid and cellular retinoic acid-binding protein (CRABP) in the fetal hamster

The temporal relationship between the distribution of retinoic acid, a known human and rodent teratogen, and that of cellular retinoic acid-binding protein (CRABP) was investigated from Day 11 to Day 14 of hamster prenatal development. The 11,12-(3)H2 and 15(-14C) forms of all-trans-retinoic acid were used for quantitative distribution studies and autoradiography, respectively, and were evaluated 15 min after a single intravenous injection. Radioactivity was detected in all fetal tissues examined (brain, liver, heart, spinal cord, limb, and skin), and at Day 14, approximately 66% of the total radioactivity was present as parent all-trans-retinoic acid. High concentrations of total radioactivity were observed by autoradiography in the midbrain and hindbrain (mesencephalon, metencephalon, and myelencephalon) and spinal cord, but not in the forebrain. At the earliest time studied, limb buds showed relatively high concentrations of radioactivity. Levels of radioactivity were also high in portions of the developing face, nose, and tongue. Immunohistochemical analyses indicated that the amount of CRABP in Day 14 tissues was the highest in spinal cord followed by limb and skin; heart and liver contained only relatively small amounts of this protein. From Day 11 to Day 14, the amount of CRABP, as measured by high-performance size-exclusion liquid chromatography, in the whole body decreased as gestation progressed. Microscopic immunohistochemical localization of CRABP found the highest concentration in the ventral midbrain and in the ventral and lateral sides of the hindbrain and spinal cord; CRABP was also abundant in tongue, limb, and skin. The distribution of CRABP-positive cells in the central nervous system was similar to the distribution of retinoic acid. The data presented here indicate that fetal CRABP appears to play a role in differential accumulation of retinoic acid in certain structures of the developing hamster. The patterns of tissue retinoid and CRABP distribution observed here are consistent with the patterns of congenital malformations induced by prenatal retinoid exposure.

Pharmacokinetics of intratracheally administered aflatoxin B1

High concentrations of the carcinogen aflatoxin B1 (AFB1) are commonly found in respirable, airborne grain dusts, and inhaled AFB1 has been shown to be a risk factor for occupational pulmonary carcinogenesis. The fate of AFB1 exposure via the respiratory tract is therefore of interest in an evaluation of potential occupational risk. The pharmacokinetic disposition of intratracheally administered AFB1 was studied in male Sprague-Dawley rats. Blood and tissues were sampled at selected intervals for 3 weeks following administration of a single dose of grain dust-adsorbed or microcrystalline [3H]AFB1 (6 micro-Ci: microgramsg/kg). The blood concentration-time profiles from both groups best approximated a two-compartment open model with first-order absorption. The first-order absorption rate constant was significantly less in the animals given dust-adsorbed AFB1 than in those receiving microcrystalline AFB1 (0.083 vs -0.1060 min -1, respectively), although the first-order elimination rate constants for both groups were nearly identical (0.00928 and 0.00921 hr-1, respectively). Blood concentrations of the AFB1 metabolites AFM1, AFQ1, AFL, and AFP1 showed little differences among the two groups. The tissue concentrations of aflatoxins for the microcrystalline group were significantly greater at 3 hr in all tissues examined except for the trachea and lung in which those for the dust-adsorbed group were greater. At 3 days and 3 weeks, no significant differences between exposure groups were seen in any tissue except fat, where the amount of aflatoxins was greater for the dust-adsorbed group. AFB1 binding to DNA was significantly greater in the trachea and lung of the dust-adsorbed group compared to that in the microcrystalline group at 3 hr, whereas in the liver the AFB1-DNA binding in the microcrystalline group was significantly greater during this time. Thus, particle association of AFB1 increased the respiratory tract retention of this compound at early time intervals, which might be a factor in the reputed carcinogenic action of this compound in the respiratory tract. These findings may be useful as part of a comprehensive study to evaluate the disposition of AFB1 in individuals exposed to grain dusts laden with this carcinogen.

Site-specific dephosphorylation and deactivation of the human insulin receptor tyrosine kinase by particulate and soluble phosphotyrosyl protein phosphatases

Insulin receptor tyrosine kinase activation, induced by insulin-stimulated autophosphorylation, was measured using a synthetic peptide containing residues 1142-1153 of the insulin receptor and shown to be reversed by both particulate and soluble phosphotyrosyl protein phosphatases from rat liver. Deactivation of the tyrosine kinase was highly sensitive to phosphatase action and was correlated best with disappearance of insulin receptors triphosphorylated in the tyrosine-1150 domain. Dephosphorylation of the di- and mono-phosphorylated forms of the tyrosine-1150 domain generated during dephosphorylation or of phosphorylation sites in the C-terminal or putative juxta-membrane domains occurred 3- greater than 10-fold more slowly than deactivation of the tyrosine kinase, and these phosphorylated species did not appear to appreciably (less than 20%) contribute to tyrosine kinase activation. These results indicate that the transition from the triply to the doubly phosphorylated form of the tyrosine-1150 domain acts as an important switch for deactivation of the insulin receptor tyrosine kinase during dephosphorylation. The exquisite sensitivity of this dephosphorylation/deactivation event to phosphotyrosyl protein phosphatase action, combined with the high affinities of this phosphatases for substrates and the high activities of the phosphatases in cells, suggests that the tyrosine kinase activity expressed by insulin-stimulated insulin receptors is likely to be stringently regulated.

Hypothalamic-pituitary-adrenocortical axis activity and immune function after oral exposure to benzene and toluene

Benzene and toluene, commonly used solvents, possess neurotoxic and immunotoxic effects. Male CD-1 mice were continuously fed drinking water containing 0, 31, 166 and 790 mg/l benzene and 0, 17, 80 and 405 mg/l toluene, respectively. The concentrations of hypothalamic norepinephrine (NE) and its metabolite vanillylmandelic acid (VMA), circulating corticosterone and adrenocorticotropic hormone (ACTH), and lymphocyte-derived interleukin-2 (IL-2) activity were evaluated after 28 days of exposure to each solvent. Serum corticosterone was also measured at pretreatment, 2, 7, and 14 days of exposure. The concentrations of NE, VMA, ACTH and corticosterone were increased following exposure to these solvents. Benzene increased corticosterone levels in mice after 7 days (166 and 790 mg/l) and at 28 days (790 mg/l). Toluene elevated corticosterone levels at 14 and 28 days at the 405 mg/l exposure. IL-2 production by mouse T-lymphocytes was suppressed in the two higher benzene-treated groups, while toluene decreased IL-2 synthesis at the highest level only. Both benzene and toluene exposures stimulated hypothalamic-pituitary-adrenocortical (HPA) activity. Elevated corticosterone has been reported to inhibit IL-2 production and impair immunocompetence. Organic solvents may have, at least partially, an additive adverse effect on immune function via activated HPA status.

Effects of repeated intermittent exposures to nitrous oxide on central neurotransmitters and hepatic methionine synthetase activity in CD-1 mice

The central neurotransmitters and hepatic methionine synthetase (MS) appear to play an important role in mediating the side effects associated with N2O exposure. Male CD-1 mice were exposed to 0, 50, 500, and 5,000 ppm of N2O 6 hr per day, 5 days a week for 2 or 13 weeks. One day after the last day of exposure, the animals were decapitated and steady state concentrations of norepinephrine (NE), dopamine (DA), serotonin (5-HT), 3-methoxy-4-hydroxy-mandelic acid (VMA), 3-methoxy-4-hydroxyphenyl glycol (MOPEG), dihydroxphenylacetic acid (DOPAC), and 5-hydroxyindoleacetic acid (5-HIAA) were determined in six discreet brain regions using electrochemical high-performance liquid chromatography. Hepatic MS activity was measured using a newly developed non-isotopic method. After a 2-week exposure to 5,000 ppm N2O, levels of NE and DA in some brain regions were significantly increased and were accompanied by significant decreases in the levels of their major metabolites. Serotonin levels were significantly decreased in certain brain regions. After the 13-week exposure to 5,000 ppm N2O, levels of NE, DA, and 5-HT significantly increased in the hypothalamus. Hepatic MS activity was not affected at any dose level of N2O used. The alterations in neurotransmitter levels may be related to the reported clinical and behavioral effects associated with N2O misuse or occupational exposures.

Transmembranous organization of (Ca2(+)-Mg2+)-ATPase from sarcoplasmic reticulum. Evidence for lumenal location of residues 877-888

An antipeptide antibody was produced against a peptide corresponding to residues 877-888 of fast twitch rabbit sarcoplasmic reticulum ATPase. This antipeptide antibody bound strongly to the ATPase in sarcoplasmic reticulum vesicles only after the vesicles had been solubilized with the detergent C12E8 indicating that its epitope was located in the lumen of the sarcoplasmic reticulum. Digestion of sarcoplasmic reticulum or purified (Ca2(+)-MG2+)-ATPase by proteinase K for up to 1 h resulted in a stable ATPase fragment of 30 kDa containing the epitope for the above antibody and the epitope for an antibody directed against the C terminus. Further proteolysis revealed smaller fragments (Mr 19,000 and 13,000) containing both epitopes. By contrast, small fragments of the ATPase (less than 29 kDa) containing the N-terminal epitope were not observed even after short exposures to proteinase K. These data support the view that the (Ca2(+)-MG2+)-ATPase has 10 transmembranous helices.

Subclinical effects of groundwater contaminants. IV. Effects of repeated oral exposure to combinations of benzene and toluene on regional brain monoamine metabolism in mice

Benzene and toluene are known neurotoxicants that may interact in vivo. The effect of combined treatment with benzene and toluene on the endogenous concentrations of the catecholamines norepinephrine (NE) and dopamine (DA), the catecholamine metabolites vanillylmandelic acid (VMA), 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), and the indoleamine serotonin (5-HT) and its metabolite 5-hydroxy-indoleacetic acid (5-HIAA), were investigated in six discrete brain regions of CD-1 mice. Groups of male, adult mice were continuously exposed to benzene (166 mg/l), toluene (80 and 325 mg/l), and combinations of benzene + toluene (80 or 325 mg/l) in drinking water for 4 weeks. Benzene produced increases of NE in the hypothalamus, cortex, midbrain and medulla oblongata, DA in the hypothalamus and corpus striatum, and 5-HT in all dissected brain regions except cerebellum. Elevated levels of various monoamine metabolites were also observed in these brain areas. Toluene ingestion alone also significantly increased the concentrations of NE, DA, 5-HT, and their metabolites in several brain regions. Mice given the combined treatments exhibited raised regional neurochemical levels when compared to the untreated controls. Increased concentrations of biogenic amine metabolites in several brain regions were greater in the combined exposures of benzene and toluene than when either chemical was used alone. The findings were different from those observed on immune parameters using similar treatment protocols, where simultaneous exposure to toluene prevented the immunotoxic effects of benzene.

Percutaneous retinoid absorption and embryotoxicity

A single application of 17 micrograms/kg or 8.7 mg/kg all-trans-[10,11-3H2]-retinoic acid dissolved in acetone to shaved dorsal hamster skin resulted in rapid absorption and dose-dependent rates of elimination. An equation describing a two-compartment open model with a very brief lag time and first-order uptake and elimination was used to describe the central plasma compartment kinetics. Unchanged all-trans-retinoic acid represented less than or equal to 4% of the total circulating radio-activity. Peak circulating concentrations of parent all-trans-retinoic acid were less than those observed after an equivalent oral dose, but prolonged absorption from the skin appears to contribute to high total bioavailability of topical retinoid. Topical administration to intact skin of up to three consecutive doses of 10.5 mg/kg/d all-trans-retinoic acid or a single 5 mg/kg dose of etretinate (Ro 10-9359) during a critical stage of embryogenesis in hamsters caused erythema and/or dose-dependent epidermal hyperplasia at the site of application, but failed to induce a significant teratogenic response. Topical application of 0.01-1.0 mg/kg arotinoid Ro 13-6298 resulted in dose-dependent mucocutaneous toxicity and an increase in the numbers of dead embryos and malformed offspring. The marked skin toxicity and attenuated concentrations in maternal blood, compared to the oral route, limit the amounts of retinoid that can reach the hamster embryo. It is thus more important to compare the retinoid systemic values (absorbed dose) than it is to compare the oral or topical (applied) dose, when interpreting the results of conventional teratogenicity bioassays. The data suggest that in the human it is skin toxicity that limits the amounts of retinoid that can be applied and subsequently reach the embryo. In the rodent, overt skin toxicity under continued dosing could increase the amounts of retinoid penetrating the skin and reaching the embryo.

Platelet MAO inhibition, urinary MHPG, and leukocyte beta-adrenergic receptors in depressed patients treated with phenelzine

The authors investigated three biochemical indices of peripheral catecholamine activity in 36 depressed inpatients treated with the monoamine oxidase (MAO) inhibitor phenelzine. Platelet MAO activity, urinary excretion of 3-methoxy-4-hydroxyphenylglycol (MHPG), and leukocyte beta-adrenergic receptor functions were measured before and during the 4th week of phenelzine treatment. There were significant reductions in platelet MAO activity, urinary MHPG excretion, and depressive symptoms in all of the patients. Responders had the same decrease in MHPG as nonresponders. There were no changes in leukocyte beta-receptor function in a small subgroup of the patients.

Dithiocarbamates and prevention of cadmium teratogenesis in the hamster

Certain dithiocarbamates (DTC) have been reported to protect against cadmium (Cd)-induced lethality and to decrease Cd body burden. The present study evaluated the influence of sodium N-benzyl-D-glucamine dithiocarbamate, sodium N-di(hydroxyethyl)amine dithiocarbamate, sodium 4-carboxyamidopiperidine-N-dithiocarbamate, and sodium N-methyl-D-glucamine dithiocarbamate on Cd-induced teratogenesis in the hamster. When given as a single ip injection at 2.2 mmol/kg 15 min prior to iv CdCl2 (2 mg/kg), all of the DTC afforded significant protection against Cd-induced developmental toxicity and reduced kidney [Cd] in the dam. Maternal liver [Cd] was reduced with the glucamine and dihydroxyethyl amine analogs, but treatment with the piperidine failed to influence hepatic [Cd]. Pretreatment of the dams with DTC 24 hr prior to Cd challenge failed to protect against Cd-induced embryotoxicity, and provided minimal, if any, reduction in renal or hepatic [Cd]. Pretreatment with the N-methyl-D-glucamine congener 24 hr prior to Cd exposure increased embryolethality. The dose-time relationships found here suggest that pharmacologically effective levels of these DTC decline within 24 hr of treatment and that induction of metallothionein does not play a major role in DTC antagonism of Cd poisoning.

Separation of a ruptured angioplasty balloon with successful percutaneous retrieval--a case report

A case of ruptured angioplasty balloon with complete separation from the catheter is presented. Successful percutaneous retrieval of the balloon with endoscopic biopsy forceps was performed.

Recognition of pertussis toxin by antibodies to synthetic peptides

Eight synthetic peptides, selected from the amino acid sequence of pertussis toxin (PT) subunits S1, S2, S3 and S4, were assessed for their ability to induce protein-recognizing and neutralizing antibodies. Seven of these peptides, prepared as conjugates of either keyhole limpet haemocyanin or tetanus toxoid, induced significant levels of antibody, all of which reacted with SDS-denatured PT on Western blots. Six of the antibodies bound to PT-coated ELISA plates; this binding was inhibited by homologous peptide antigen. However, none of the antibodies, including those directed against the N-terminus of subunit S1, were able to attenuate in vivo or in vitro toxin-dependent activity. Further investigation revealed that only one antibody, specific for the C-terminus of S1 (peptide Slc, 237-255), could recognize the conformation of native PT in solution. The other five antipeptide antibodies which reacted with PT-coated ELISA plates did not recognize PT when captured onto ELISA plates via either a monoclonal antibody or fetuin, unless the conformation of the toxin had been relaxed by reduction with dithiothreitol. Conversely, the native PT-recognizing response of peptide Slc did not bind the conformationally relaxed PT molecule. From this study, it appears likely that a peptide capable of inducing PT-neutralizing antibody must closely resemble the conformation of the cognate sequence in the native protein.

Subclinical effects of groundwater contaminants. III. Effects of repeated oral exposure to combinations of benzene and toluene on immunologic responses in mice

Toxicity of environmental pollutants may be expressed as combined effects of a chemicals. Benzene, a proven hematotoxic agent, frequently occurs with toluene in cocontaminated groundwater. Groups of CD-1 male mice were exposed continuously for 4 weeks to benzene (166 mg/l), toluene (80 and 325 mg/l), and combinations of benzene (166 mg/l) + toluene (80 mg/l or 325 mg/l) in drinking water. Benzene-induced anemia was alleviated by simultaneous toluene treatment. Leukopenia and lymphopenia were observed in the case of benzene only and benzene + toluene (80 mg/l)-treated mice. The cytopenia, however, was less severe in the benzene + toluene (325 mg/l)-treated group. Immunotoxicity induced by benzene treatment alone was characterized by involution of thymic mass and suppressions of both B- and T-cell mitogeneses, mixed lymphocyte culture response to alloantigens, the tumor lytic ability of cytotoxic T-lymphocytes as determined by 51Cr-release assay, and antibody production response to T-dependent antigen (sheep red blood cells). IL-2 secretion by Con A-stimulated mouse T-cells was decreased in the benzene-treated group. Toluene (325 mg/l) completely inhibited these adverse effects when it was coadministered with benzene, while the low dose of toluene (80 mg/l) did not protect against benzene-induced depressions of immune functions. Toluene administered alone at levels up to 325 mg/l showed no obvious immunotoxic effects. Results of this study demonstrated that toluene, in sufficient amounts, has an antagonistic effect on benzene immunotoxicity.

Pharmacological effects of methylphenidate on plasma homovanillic acid and growth hormone

The acute pharmacological actions of methylphenidate, a potent psychotogenic stimulant, were studied by measuring plasma homovanillic acid (HVA) and serum growth hormone (GH) as indices of presynaptic and postsynaptic functions, respectively. Twenty psychiatric inpatients participated in a double-blind, placebo-randomized study of methylphenidate infusion. Multiple samples of plasma HVA and GH were measured before and up to 24 hours after both methylphenidate and placebo infusions. There was a robust and significant GH response during the 2-hour postmethylphenidate period when compared to placebo. The peak response was significantly greater in male patients than in female patients. Although there were no changes in plasma HVA during the 2 hours following the infusion, there was a significant decrease in HVA 24 hours after methylphenidate as compared to preinfusion baseline values. Plasma HVA values also tended to be lower 24 hours after methylphenidate when compared to the corresponding postplacebo value. Schizophrenic patients did not differ significantly from nonschizophrenic patients in their physiological or biochemical responses.

Serum iron and total iron binding capacity in leprosy patients

Serum Iron and total Iron binding capacity was estimated by Ramsay's Method in 40 leprosy patients having different types of leprosy and 20 normal subjects serving as controls. Significantly low serum Iron and total Iron binding capacity were observed in lepromatous leprosy patients.

Short term toxicity of nitrous oxide on the immune, hemopoietic, and endocrine systems in CD-1 mice

Occupational exposures to subanesthetic levels of N2O have been documented to result in suppressed proliferative cell activities. Male CD-1 mice were exposed to 0, 50, 500, and 5000 ppm of N2O for 6 hr/day, 5 days/week for 2 or 13 weeks. Tritiated-thymidine ([3H]-TdR) uptake was measured in CD-1 splenic lymphocytes cultured with and without mitogens and in a mixed lymphocyte culture (MLC). Antibody-mediated immunocompetency was determined for sheep red blood cell (SRBC)-sensitized animals by plaque forming cell (PFC) assay and serum anti-SRBC antibody (Ab) titer. Deoxyuridine suppression tests (dUrdST) were performed on bone marrow cells. There was significantly decreased splenic lymphocyte uptake of [3H]-TdR by cells cultured with mitogenic substances and in MLC following 2-week exposures to 5000 ppm. After 13-week exposures the animals' splenic lymphocytes showed increased [3H]-TdR uptake following high N2O dosing in both the mitogen-induced blastogenesis and MLC assays. Compared to control animals, the 5000 ppm exposure group had significantly depressed PFC activity and circulating anti-SRBC Ab levels following the 13-week N2O exposures, and all 13-week exposure groups demonstrated decreased liver weights and leukopenia. Bone marrow activity at these dosing levels was depressed in a dose-dependent fashion following 13-week gas exposures.

Effects of macrocyclic trichothecene congeners on the viability and mitogenesis of murine splenic lymphocytes

The effects of several congeners of the macrocyclic class of trichothecene mycotoxins on murine splenic cells in vitro were investigated. The mycotoxins were roritoxin B, myrotoxin B, roridins A, D and E, baccharinoids B4, B5 and B12, 16-hydroxyverrucarin A, and verrucarins A and J. Lymphocytes from CD-1 mice were cultured with each of the mycotoxins for 48 h to assess cytotoxicity. The maximum effect of various trichothecenes produced on cells occurred at concentrations ranging from 10(-6) to 10(-4) M. Mycotoxins had no effect at concentrations ranging from 10(-12) to 10(-7) M. The mitogenic stimulants concanavalin A, lipopolysaccharide, phytohemagglutinin, and pokeweed mitogen were added to splenic lymphocyte cultures along with varying concentrations of selected mycotoxins. Blastogenesis was inhibited at concentrations 2-5 orders of magnitude lower than those which produced lethality on resting lymphocytes.

Trifluoperazine plasma levels and clinical response

The authors studied 36 acutely psychotic inpatients who were diagnosed as having either a schizophrenic (N = 30) or other psychotic (N = 6) disorder. After a washout phase averaging 18 days, all patients were placed on trifluoperazine 5 mg orally twice a day. Plasma levels of trifluoperazine were obtained on days 11 and 15 of treatment and then compared with clinical response. After 2 weeks of treatment an inverted U-shaped relationship was found between change scores on the Brief Psychiatric Rating Scale and trifluoperazine plasma levels.

Construction of chickpea genomic library

For construction of chickpea genomic library, DNA was isolated, purified on CsCl gradient and size fractionated into 15-20 Kb fragments after restriction with Sau 3A. These fragments were ligated to phage lambda (EMBL-3) vector and the recombinant molecules packaged in vitro into viable phage particles. The recombinant phages were obtained as phages on a P2 lysogen of E. coli (Spi- selection) and amplified to establish a permanent library. This is the first report of the construction of chickpea genomic library.

Immunotoxic potential of N-ethyl, N-nitrosourea (ENU) in CD1 mice

The immunotoxic potential of ENU, a potent and transplacental neurocarcinogen, was evaluated in male CD1 mice. The animals received i.p. injections of ENU--0, 2, 8 or 32 mg/kg body weight, in citrate-phosphate buffer, twice weekly for three weeks. Splenic lymphocytes were cultured in the presence of mitogens, lipopolysaccharide, pokeweed mitogen, concanavalin A and phytohaemagglutinin. Mixed lymphocyte cultures in the presence of allogeneic cells were also tested. Blastogenic response decreased in a dose-dependent manner, as measured by the 3H-thymidine uptake by splenocytes. Primary antibody production by splenic lymphocytes from animals challenged with a T-dependent antigen (sheep red blood cells) was stimulated at low doses but depressed at the highest dose group compared with the controls, whereas T-independent cell response showed no significant change. Our results suggest that exposure to repeated, low levels of ENU significantly alters the immune status of CD1 mice. The effects appear to be somewhat selective to T cell processes, based on in vivo responses to T-dependent and T-independent antigens.

Evidence for the cytoplasmic location of the N- and C-terminal segments of sarcoplasmic reticulum (Ca2+-Mg2+)-ATPase

Antibodies were produced against 5 peptides corresponding to segments of the (Ca2+-Mg2+)-ATPase of fast-twitch rabbit skeletal muscle sarcoplasmic reticulum (SR) including the N- and C-terminal regions. With the exception of antibodies directed against the peptide corresponding to residues 567-582 all antibodies bound strongly to the ATPase in intact SR vesicles, indicating that the epitopes were located on the cytoplasmic face of the SR. When the vesicles were disrupted, by solubilisation in SDS, binding of these antibodies was unchanged, further supporting the idea that these epitopes were located on the cytoplasmic face of SR. This is the first demonstration of the location of the N- and C-terminal regions of SR (Ca2+-Mg2+)-ATPase. These observations are discussed in the light of current structural models of the ATPase.

Relationship of the hypothalamic-pituitary-adrenal axis with chemically induced immunomodulation. I. Stress-like response after exposure to T-2 toxin

T-2 toxin (T-2), a trichothecene mycotoxin, produced by several members of the genus Fusarium is a cytotoxic feed contaminant and has been shown to by immunomodulatory. It is suspected that T-2 associated immunomodulation is mediated partly through the hypothalamic-pituitary-adrenal (HPA) axis. T-2, prepared in 4% ethanol/corn oil, was administered orally to male CD-1 mice. Endotoxemia was evident 24 h after a single, oral exposure to T-2. Blood levels of corticosterone, indicative of the stress-response, increased 24 h after T-2 exposure. Hypothalamic norepinephrine and serum corticosterone levels increased in a dose-related manner after 2 weeks of T-2 exposure. Endotoxin, detected in the serum of animals exposed to 2.5 mg/kg T-2 for 1 week, was not associated with bacteremia. Neither endotoxin nor bacteremia were detectable after 2 or 4 weeks of T-2 exposure. Exposure to 2.5 mg/kg T-2 also affected several organs. The forestomach was ulcerated, with lymphocytic infiltration, epithelial proliferation, and hyperkeratinization. Increased spleen weight was associated with a proliferative red pulp. No histological changes were observed in the enlarged liver. Gastritis has been associated with increased corticosteroid production; cortical depletion and reduced mass of the thymus are phenomena attributable to increased corticosteroid levels. An increased corticosteroid level has been associated with thymic involution leading potentially to decreased T-dependent antibody response, a known effect of T-2.

Oxidation of NADH by vanadium compounds in the presence of thiols

The nonenzymatic oxidation of NADH was studied spectrophotometrically in the presence of two vanadium compounds, sodium orthovanadate and vanadyl sulfate. At physiological pH 7.4, in 25 mM sodium phosphate buffer, addition of the synthetic thiol, dithioerythritol (DTE) results in a marked increase of NADH oxidation in the presence of sodium orthovanadate, but not in the presence of vanadyl sulfate. Other reductants, such as dithiothreitol and cysteine, can also increase NADH oxidation, whereas glutathione and ascorbate cannot. In all reactions, superoxide dismutase and catalase completely inhibit the vanadium-stimulated oxidation of NADH. Inhibition occurs in a concentration-dependent manner, and the boiled enzymes do not inhibit the thiol reaction. The hydroxyl radical scavenger, thiourea, inhibits the reaction, whereas urea cannot. ESR studies show that the ability of the thiol to reduce vanadate can be correlated with the degree of NADH oxidation. Using spin trapping techniques, hydroxyl radicals are detected during the course of the reaction. Addition of hydrogen peroxide to vanadyl in the presence of DTE greatly increases NADH oxidation; however, no NADH oxidation occurs when hydrogen peroxide is added to vanadyl and ascorbic acid. These results provide a partial explanation for the ability of vanadium compounds to both decrease cellular reducing equivalents and promote lipid peroxidation.

Pharmacokinetics, tissue distribution, and placental permeability of all-trans- and 13-cis-N-ethyl retinamides in pregnant hamsters

Retinamides have clinical applications in therapy of dermatologic disease, have cancer chemopreventive/chemotherapeutic activities, and possess larger therapeutic ratios than their acidic congeners. The N-ethyl-all-trans-retinamide (NERA) and its 13-cis congener (CNERA) failed to induce terata in hamsters, but an equivalent oral dose of all-trans- or 13-cis-retinoic acid was associated with a significant teratogenic response. Following intubation of 11.4 mg/kg of [3H]NERA or [3H]CNERA to pregnant hamsters during a sensitive stage of development, radioactivity accumulated in maternal bladder and liver. Although plasma concentrations of the parent retinamides declined to nondetectable levels within 12 hr of dosing, near-peak concentrations of retinamide metabolites persisted in maternal plasma until termination of the study (96 hr). Cis/trans isomerization of each retinamide at C13 occurred, but only 15-20% of the total dose could be accounted for as parent retinamide and its C13 isomer. The retinamides were not metabolized to detectable concentrations of circulating all-trans- or 13-cis-retinoic acid. Although the label associated with the retinamides and their biotransformation products crossed the placenta, there was no evidence for preferential accumulation in embryonic or fetal tissues. The results presented here show that the reduced teratogenic potency of retinamides compared to acidic retinoids cannot be ascribed to reduce placental transfer.

Pharmacokinetics, tissue distribution and placental permeability of tetrahydro-tetramethyl-naphthalenyl-propenyl benzoic acid (a retinoidal benzoic acid derivative) in hamsters

Tritiated tetrahydro-tetramethyl-naphthalenyl-propenyl benzoic acid (TTNPB; Ro 13-7410) was administered as a single oral bolus to pregnant hamsters (day 8) to determine the maternal plasma pharmacokinetic profile and peripheral tissue distribution patterns. Blood and tissue, including embryo or fetus, were collected at specific time intervals to 96 h and assayed for total radioactive compounds and/or parent retinoid. No lag time was required to describe retinoid absorption (t 1/2 pi = 1.2 h) with peak plasma levels at 2.4 h; the concentrations then declined with exponential elimination from the central compartment (t 1/2 e = 3 h). The maximum concentrations of circulating radioactive compound or metabolites after 100 micrograms/kg [3H]2-TTNPB occurred in liver greater than fetus greater than adrenal greater than lung approximately equal to kidney greater than plasma; after 1000 micrograms/kg, maternal liver accumulated the highest concentration followed by plasma greater than fetus = placenta = uterus. An unidentified, polar metabolite was detected in plasma at 0.5 h and by 12 h constituted greater than 90% of the total circulating radioactivity. TTNPB was absorbed and cleared more slowly, concentrated in the conceptus to a higher degree and possessed greater intrinsic activity than the naturally-occurring tetraene retinoids. These properties contribute to the marked teratogenic activity of TTNPB as compared to the tetraene retinoids.

Comparative distribution, pharmacokinetics and placental permeabilities of all-trans-retinoic acid, 13-cis-retinoic acid, all-trans-4-oxo-retinoic acid, retinyl acetate and 9-cis-retinal in hamsters

Pregnant hamsters were given a single oral dose (35 mumol/kg) of all-trans-retinoic acid, 13-cis-retinoic acid, all-trans-4-oxo-retinoic acid, 9-cis-retinal or all-trans-retinyl acetate during the early primitive streak stage of development. The radioactivity associated with the acidic retinoids was distributed to all tissues sampled (including placenta and fetus), with the largest accumulation in the liver and the least accumulation in fat. Radioactivity from 9-cis-retinal or retinyl acetate concentrated in the liver and lung. The all-trans-retinoic acid was oxidized in vivo to all-trans-4-oxo-retinoic acid and isomerized to 13-cis-retinoic acid: 13-cis-retinoic acid was oxidized to 13-cis-4-oxo-retinoic acid and isomerized to all-trans-retinoic acid. No parent 9-cis-retinal or retinyl acetate could be detected in maternal plasma. Plasma concentrations of the parent acidic retinoids reached their maxima within 60 min and then followed exponential decay. Of all the retinoids examined here, 13-cis-retinoic acid showed the largest area under the plasma curve, the slowest clearance and the longest elimination t1/2. Total plasma radioactivity, consisting of unidentified metabolites, remained elevated at 4 days after dosing. Maternal peak circulating concentrations of the parent retinoids, total radioactivity, plasma pharmacokinetic parameters or the total concentrations of residual radioactivity in fetal tissues could not be correlated with the differential teratogenic potencies of these retinoids.

Importance of hydroxyl radical in the vanadium-stimulated oxidation of NADH

Vanadium compounds are known to stimulate the oxidation of NAD(P)H, but the mechanism remains unclear. This reaction was studied spectrophotometrically and by electron spin resonance spectroscopy (ESR) using vanadium in the reduced state (+4, vanadyl) and the oxidized state (+5, vanadate). In 25 mM sodium phosphate buffer at pH 7.4, vanadyl was slightly more effective in stimulating NADH oxidation than was vanadate. Addition of a superoxide generating system, xanthine/xanthine oxidase, resulted in a marked increase in NADH oxidation by vanadyl, and to a lesser extent, by vanadate. Decreasing the pH with superoxide present increased NADH oxidation for both vanadate and vanadyl. Addition of hydrogen peroxide to the reaction mixture did not change the NADH oxidation by vanadate, regardless of concentration or pH. With vanadyl however, addition of hydrogen peroxide greatly enhanced NADH oxidation which further increased with lower pH. Use of the spin trap DMPO in reaction mixtures containing vanadyl and hydrogen peroxide or a superoxide generating system resulted in the detection by ESR of hydroxyl. In each case, the hydroxyl radical signal intensity increased with vanadium concentration. Catalase was able to inhibit the formation of the DMPO--OH adduct formed by vanadate plus superoxide. These results show that the ability of vanadium to act in a Fenton-type reaction is an important process in the vanadium-stimulated oxidation of NADH.

Effects of aflatoxin B1 on murine lymphocytic functions

We recently reported on the immunotoxic effects of Aflatoxin B1 (AFB1), a secondary fungal metabolite of Aspergillus flavus in mice. The present paper describes the effect of AFB1 on cellular functions in lymphocytes after in vivo or in vitro exposures. Male BALB/c mice received 0, 0.03, 0.145 or 0.7 mg/kg body weight of AFB1 for 4 weeks. A dose-related decrease in DNA synthesis in lymphocyte cultures with or without the mitogens (lipopolysaccharide, phytohemagglutinin, pokeweed mitogen and concanavalin A) was observed. No effects on protein or ribonucleic acid synthesis were observed. There were dose-dependent decreases in peripheral leucocyte counts and natural killer cell function. Splenic lymphocytes from normal mice cultured with 10(-6) to 10(-4) M AFB1 had decreased DNA synthesis at greater than 1 X 10(-5) M, a decreased protein synthesis at 10(-4) M and decreased RNA synthesis at greater than 2.5 X 10(-5) M. In vitro addition of AFB1 (greater than 50 microM) reduced generation of concanavalin A-induced suppressor cells. The results suggest that AFB1 had a direct and complex effect on lymphocytes and there is a differential sensitivity of various subpopulations.

Diurnal alterations of catecholamines, indoleamines and their metabolites in specific brain regions of the mouse

1. The diurnal variations of regional brain concentrations of dopamine (DA), norepinephrine (NE), serotonin (5-HT) and metabolites were determined in unperturbed male CD-1 mice. Determinations were made every 4 hr for 24 hr. 2. The most striking and significant variations in biogenic amines were seen in the hypothalamus, where concentrations of NE, DA and 5-HT varied in a rhythmic pattern and as much as two-fold during this period. 3. In some cases, daily alterations in parent biogenic amines were reflected by concurrent changes in their metabolites. 4. Since concentrations of neurotransmitters in the brain are often used as an indicator of stress and/or toxicity, these data should provide an accurate data base allowing for more accurate interpretation of results.

Study of serum zinc level in leprosy

Serum Zinc level was estimated in different types of leprosy by 'Dithiazone extraction' method in 75 leprosy patients comprising 15 each of Tuberculoid-Tuberculoid (TT); Borderline Tuberculoid (BT); Borderline Borderline (BB); Borderline Lepromatous (BL) and Lepromatous Lepromatous (LL). These findings were evaluated in comparison to 15 normal subjects serving as controls. Serum zinc level was observed to be significantly low in all types of leprosy except tuberculoid leprosy (TT). No significant difference was observed in serum zinc levels before and after 90 days of dapsone Therapy. The findings of our study are of considerable importance as zinc deficiency can be one of the factors involved in non-specific suppression of cell mediated Immunity (CMI) in lepromatous leprosy.

Effects of verrucarin A and roridin A, macrocyclic trichothecene mycotoxins, on the murine immune system

Verrucarin A (Ver A) and roridin A (Ror A), macrocyclic trichothecene mycotoxins, were examined for their immunomodulatory effects. Both mycotoxins were administered intraperitoneally at 0.35 mg/kg (1/2 the LD50) in CD-1 mice. Lymphocyte proliferation was studied on days 2, 4 and 7 after animals were dosed with Ver A. After day 2, no significant differences in [3H]thymidine (3H-TdR) incorporation were observed using concanavalin A (Con A), phytohemagglutinin (PHA), pokeweed mitogen (PWM) or lipopolysaccharide (LPS). On day 4 DNA synthesis induced by Con A, PHA and PWM was increased significantly. On day 7, PHA stimulation increased (p less than 0.001) above controls while Con A, PWM and LPS responses were not significantly different. The data indicated that Con A, PHA and PWM responses were time-dependent. Antibody production was evaluated by the hemolytic plaque assay; sheep red blood cells (SRBC) and Ver A were administered simultaneously, and Ver A was given 2 days after SRBC challenge. While spleen weights increased when Ver A was administered with SRBC or when the toxin was given 2 days after antigen, the antibody responses were not altered. In contrast, roridin A decreased PHA stimulation only on day 7 (p less than 0.05). There were no significant effects associated with the other mitogens. Antibody production did not differ significantly following administration of Ror A. Although Ver A and Ror A are equitoxic and structurally similar, their immunomodulatory properties for the given dose differ considerably. These different immunologic responses may be independent of other systemic toxic effects.

Evaluation of pesticide immunotoxicity

Immunotoxicologic effects have been reported for a number of pesticides. Since pesticides represent a large range of chemical classes, different types of chemicals may affect the complex immune system by a variety of mechanisms. A preliminary evaluation of pesticides for immunotoxicologic potential can best be incorporated in general subacute and chronic toxicity testing, with additional groups assigned for initial host-sensitivity assays. For chemicals that are possible candidates for immunotoxicity in preliminary assays, a comprehensive immunotoxicity screening has been suggested. Finally, emphasis should be given to mechanistic investigations to objectively assess the immunotoxicity of a new chemical and possible extrapolation to man. Animal models need to be developed for detecting the autoimmunologic potential of pesticides. This paper provides a brief listing of various approaches currently employed in the evaluation of immunotoxicity.

Vanadium and lipid peroxidation: evidence for involvement of vanadyl and hydroxyl radical

The present study was designed to determine which form of vanadium is involved in initiating conjugated diene formation in both purified and partially peroxidized fatty acids, and to determine if active oxygen radicals are involved in this process. We report that vanadyl is the active form of vanadium in initiating conjugated diene formation in micelles prepared from purified fatty acids or partially peroxidized fatty acids. Vanadate did not initiate conjugated diene formation in either case. Hydroxyl radicals were shown to be involved in the initiation of diene conjugation when vanadyl and hydrogen peroxide were added together in a reaction mixture. In this case, there was a rapid burst of conjugated diene formation which quickly leveled off. Using spin trapping techniques, hydroxyl radicals were shown to be generated in the vanadyl-catalyzed break-down of fatty acid hydroperoxides. A comparison was made between the ability of vanadyl or vanadyl chelates to decompose hydrogen peroxide and catalyze the decomposition of fatty acid hydroperoxides. It was found that strongly chelated vanadyl (vanadyl/EDTA) was much less effective in decomposing both hydrogen peroxide and fatty acid hydroperoxides than the weak vanadyl chelates (e.g., vanadyl/ADP). This study suggests a mechanism to explain the effects of vanadium on lipid peroxidation.

The effect of diagnosis and age on the DST: a metaanalytic approach

The authors present new data on the results of the pretreatment Dexamethasone Suppression Test (DST) in 164 drug-free inpatients, as well as on the effects of age on postdexamethasone cortisol values. Nonsuppression rates were 18% in schizophrenic patients (n = 44), versus 46% in patients with a major depression (n = 56). In addition, a significant correlation was found between age and the 4:00 PM postdexamethasone cortisol value among the depressed patients (r = 0.33). The authors then applied a metaanalysis to summarize 25 other studies that have addressed the schizophrenia/major depression dichotomy as it relates to the DST outcome. Nonsuppression rates were consistently different in schizophrenic patients (19%) when compared to patients with a major depression (51%) or normal controls (7%). These differences were highly significant as measured by the Mantel-Haenszel chi-square statistic. A metaanalysis applied to a series of correlations obtained from 14 other studies reporting an age/postdexamethasone cortisol relationship in affective patients indicated a modest, but significant correlation (r = 0.24) in a total of 1284 patients (p less than 1 x 10(-8)).

Self-limiting acrodermatitis enteropathica. A follow-up study of three interrelated families

A variant of acrodermatitis enteropathica is described that has its onset before weaning and clears when the child starts its normal solid diet. A pedigree with three interrelated families is reported where 10 children were afflicted with this variant. They had symptoms of hypozincemia for a brief period during infancy. At the time of this study, they were symptom-free and their serum zinc levels were found to be within normal limits. The term "self-limiting acrodermatitis enteropathica" is proposed for the variant. In one lactating mother, the mammary zinc secretion was determined and was found to be deficient and unresponsive to oral zinc supplements. The possible mode of inheritance is also discussed.

Structure-activity relationships of retinoids in developmental toxicology. III. Contribution of the vitamin A beta-cyclogeranylidene ring

The teratogenic potency of congeners of all-trans-retinoic acid (all-trans-RA) containing modifications or substitution of the naturally occurring beta-cyclogeranylidene ring was determined in Golden hamsters and compared to that of all-trans-RA. The following ring-modified retinoids were screened: phenyl (Ro 8-8717), furyl (Ro 8-9750), 4-methoxy-2,3,6-trimethylphenyl (Ro 21-6667), which also has a thiomethylene group in place of the trans-8,9 double bond of the etretin side chain, 4-hydroxy-2,3,6-trimethylphenyl (Ro 11-4768), 2-chloro-3,6-dimethyl-4-methoxyphenyl (Ro 12-0995), 2-(1-methoxyethyl)-5,5-dimethyl-1-cyclopentenyl (Ro 10-1770), 2-acetyl-5,5-dimethyl-1-cyclopentenyl (Ro 8-7699), and 10,11-epoxy-11,11-dimethyl (juvenile hormone III), which also has the bonds corresponding to the 7,8- and 11,12-double bond of the retinoid skeleton saturated. The retinoids Ro 12-4824, Ro 12-4825, and SRI2712-24 had C4-keto, C18-hydroxyl, and C18-methyl substituents, respectively. Motretinid (Ro 11-1430) had both 4-methoxy-2,3,6-trimethylphenyl ring and ethyl amide polar group modifications. Single oral retinoid doses administered to pregnant dams at 10:00 AM on Day 8 neither induced signs of hypervitaminosis A nor induced weight loss in any of the treated groups. Teratogenically active retinoids induced a malformation syndrome identical to that induced by all-trans-RA. At retinoid doses that were associated with malformations in all of the fetuses, embryolethality remained near that of vehicle-treated controls. The phenyl retinoid Ro 8-8717 was embryolethal but was not teratogenic. The ethyl amide derivative of the human and animal teratogen etretinate, motretinid, was teratogenic only at the highest dose administered, 350 mg/kg. The retinoids Ro 12-4824, Ro 12-4825, Ro 8-7699, and SRI 2712-24 were as potent as all-trans-RA. The chlorine substituted retinoid, Ro 12-0995, was sixfold more teratogenic than all-trans-RA, and the cyclopentene retinoid, Ro 10-1770, was 19 times more potent than all-trans-RA. The retinoids with furyl or epoxy group substitution for the cyclohexenyl ring were devoid of teratogenic activity up to equimolar doses of 75 mg/kg of all-trans-RA, and Ro 21-6667 was teratogenically inactive at a dose equivalent to 150 mg/kg of all-trans-RA. Major modifications of the beta-cyclogeranylidene ring can be made without altering teratogenic activity.(ABSTRACT TRUNCATED AT 400 WORDS)