Changes in methyl-sensitive restriction sites of liver DNA from hamsters chronically exposed to hydrazine sulfate.

Hydrazine sulfate is a genotoxic hepatocarcinogen for the hamster. A study was conducted to follow changes in DNA maintenance methylation in selected genes in liver DNA during the 21-month induction of liver adenomas and hepatocellular carcinomas by demonstrating changes in restriction fragment length polymorphism. Male Syrian golden hamsters were exposed to hydrazine sulfate in the drinking water at three concentrations (170, 340 and 510 mg/l) shown previously to result in a dose-dependent induction of liver tumors.

Methylation status of DNA cytosine during the course of induction of liver cancer in hamsters by hydrazine sulfate.

Hydrazine, which is toxic and carcinogenic to rodent liver, has been shown to react with endogenous formaldehyde in the liver to form formaldehyde hydrazone (CH2 = N-NH2), an alkylating intermediate that methylates DNA guanine at the N7- and O6-positions. Studies were conducted to investigate the role of chronic hydrazine-induced hepatotoxicity on DNA maintenance methylation (formation of 5-methyldeoxycytosine) and the development of liver cancer. Male Syrian golden hamsters were given hydrazine sulfate (0, 170, 340 and 510 mg/l) in drinking water for 21 months (average dose 0, 4.

Forskolin carbamates: binding and activation studies with type I adenylyl cyclase.

Three series of analogs were regioselectively prepared from a protected forskolin precursor to afford 7-carbamoyl-7-desacetylforskolins (series 1), 6-carbamoyl-7-desacetylforskolins (series 2), and 6-carbamoylforskolins (series 3). The analogs were pharmacologically evaluated for binding (IC50) to and activation (EC50) of type I adenylyl cyclase in membranes from stably transfected Sf9 cell lines expressing a single adenylate cyclase subtype. The following ranges were determined for the IC50's and EC50's of each individual series: series 1, IC50 = 43-1600 nM, EC50 = 0.

Anticonvulsant activity of topiramate and phenytoin in a rat model of ischemia-induced epilepsy.

Topiramate, a structurally novel anticonvulsant, and phenytoin were evaluated in a rat model of ischemia-induced epilepsy. In this model a transient global cerebral ischemia is induced by cardiac compression. By precisely controlling the experimental conditions the procedure causes reproducible neurological deficits that include audiogenic epileptic seizures.

Characterization of a benzodiazepine receptor site with exceptionally high affinity for Ro 15-4513 in the rat CNS.

The binding of [3H]Ro 15-4513, [3H]flunitrazepam and [3H]flumazenil to rat CNS membranes was studied at 2 degrees C, 22 degrees C and 37 degrees C using ligand concentrations ranging from approximately 0.06 nM to 10 microM. Analysis of the binding saturation data suggested the existence of high-affinity sites (Kd < 10 nM) and low-affinity sites (Kd > 100 nM) for each ligand.

Modulation of DNA adduct formation by successive exposures of DNA to small and bulky chemical carcinogens.

The effect of a carcinogen-DNA adduct on the formation of a second adduct upon subsequent exposure to a second carcinogen was studied using (i) a modified Maxam-Gilbert chemical sequencing reaction and (ii) a DNA synthesis termination analysis. A DNA fragment of known sequence was reacted with micromolar concentrations of N-methyl-N-nitrosourea (MNU), (+)-r-7,t-8-dihydroxy-t-9,10- epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE), N-acetoxy-2- acetylaminofluorene (N-acetoxy-AAF), or aflatoxin B1-8,9-epoxide (AFB1 epoxide) singly or in successive double reactions. N-Acetoxy-AAF adducts were sensitive to the Maxam-Gilbert sequencing reaction for guanine; these adducts significantly blocked the formation of BPDE-guanine adducts.

Serotonin and norepinephrine uptake inhibiting activity of centrally acting analgesics: structural determinants and role in antinociception.

Although it is well established that the analgesic effects of morphine are mediated by opioid receptors, previous studies have shown that some opioids additionally inhibit the uptake of serotonin and norepinephrine. The present investigation of a diverse group of opioids revealed that structurally identifiable subgroups inhibited the neuronal reuptake of these monoamines. Phenanthrene opioids with an oxygen bridge between C4 and C5, such as morphine and naloxone (group I), did not block norepinephrine or serotonin uptake, whereas phenanthrene opioids without the oxygen bridge and the C6-OH moiety, such as levorphanol and levomethorphan (group II), did inhibit uptake, as did nonphenanthrene opioids, such as d-propoxyphene and methadone (group III).

A distributed, scalable, community care network architecture for wide-area electronic patient records: modeling and simulation.

Principal systems issues relative to computerizing patient medical records that are yet to be addressed in the scientific literature include (1) the characteristics of networks, i.e. bandwidth and capacity, and their impact on the performance of the system, (2) the architecture and the underlying algorithm of the system, (3) the location and migration of medical records, (4) scalability of the system, and (5) the nature of the performance variation under heavy and light use of the network.

An overview of the CERC ARTEMIS project.

The basic premise of this effort is that health care can be made more effective and affordable by applying modern computer technology to improve collaboration among diverse and distributed health care providers. Information sharing, communication, and coordination are basic elements of any collaborative endeavor. In the health care domain, collaboration is characterized by cooperative activities by health care providers to deliver total and real-time care for their patients.

Interaction of abecarnil, bretazenil, and RO 19-8022 with diazepam-sensitive and -insensitive benzodiazepine sites in the rat cerebellum and cerebral cortex.

Abecarnil, bretazenil, and Ro 19-8022 inhibited the binding of [3H]Ro 15-4513 to diazepamsensitive and -insensitive sites in the rat cerebellum and cerebral cortex, but all three had a much higher affinity for the diazepam-sensitive sites in both tissues. The GABA-shift for bretazenil and Ro 19-8022 was low ( < 2) for all sites studied, consistent with their partial agonistic profile. The GABA-shift for abecarnil was appreciably higher for diazepam-sensitive binding in the cerebellum than in the cerebral cortex (1.

Hydralazine and other hydrazine derivatives and the formation of DNA adducts.

Previous work has demonstrated that hydrazine after formylation to its corresponding hydrazone may be activated both in vivo and in vitro to a methylating intermediate resulting in the formation of O6-methyl- and N7-methylguanines in DNA. Incubation of calf thymus DNA with the hydrazine derivative, hydralazine, and formaldehyde resulted in the production of N7-methylguanine and two aberrant bases in DNA. These bases were separated by strong cation-exchange high-performance liquid chromatographic fractionation of neutral thermal hydrolysates.

Hydrazine genotoxicity in the neonatal rat.

The neonatal rat, because of its relatively rapid rate of liver DNA replication without chemical or surgical induction, was used to assess the genotoxicity of the carcinogen hydrazine. Hydrazine is a more potent acute toxicant in the neonate than in the adult rat. Administration of hydrazine sc (1.

Topiramate: preclinical evaluation of structurally novel anticonvulsant.

Topiramate [TPM, 2,3:4,5-bis-O-(1-methylethylidene)-beta-D-fructopyranose sulfamate] (RWJ-17021-000, formerly McN-4853) is a structurally novel antiepileptic drug (AED). The preclinical anticonvulsant profile suggests that TPM acts primarily by blocking the spread of seizures. TPM was highly effective in the maximal electroshock (MES) seizure test in rats and mice.

Complementary and synergistic antinociceptive interaction between the enantiomers of tramadol.

The explanation for the co-existence of opioid and nonopioid components of tramadol-induced antinociception appears to be related to the different, but complementary and interactive, pharmacologies of its enantiomers. The (+) enantiomer had Ki values of only 1.33, 62.

Cerebral metabolic compartmentation as revealed by nuclear magnetic resonance analysis of D-[1-13C]glucose metabolism.

Nuclear magnetic resonance (NMR) was used to study the metabolic pathways involved in the conversion of glucose to glutamate, gamma-aminobutyrate (GABA), glutamine, and aspartate. D-[1-13C]Glucose was administered to rats intraperitoneally, and 6, 15, 30, or 45 min later the rats were killed and extracts from the forebrain were prepared for 13C-NMR analysis and amino acid analysis. The absolute amount of 13C present within each carbonatom pool was determined for C-2, C-3, and C-4 of glutamate, glutamine, and GABA, for C-2 and C-3 of aspartate, and for C-3 of lactate.

2-Oxoglutarate transport: a potential mechanism for regulating glutamate and tricarboxylic acid cycle intermediates in neurons.

2-Oxoglutarate (alpha-ketoglutarate) is transported into synaptosomal and synaptoneurosomal preparations by a Na(+)-dependent, high-affinity process that exhibits complex kinetics, and is differentially modulated by glutamate, glutamine, aspartate, malate, and a soluble, heat-labile substance of high molecular weight present in rat brain extracts. Glutamate and aspartate generally inhibit 2-oxoglutarate uptake, but under certain conditions may increase uptake. Glutamine generally increases 2-oxoglutarate uptake, but under certain conditions may inhibit uptake.

Effect of 5-methylcytosine as a neighboring base on methylation of DNA guanine by N-methyl-N-nitrosourea.

Effects on N-methyl-N-nitrosourea (MNU) mediated methylation of the N7 position of guanine were compared in defined sequences of DNA containing cytosine or 5-methylcytosine (5mC) using a Maxam-Gilbert sequencing technique. Cytosine methylation in 5'-CpG-3' pairs within a subcloned fragment of the 5' region of the human HPRT gene was generated with SssI methylase and S-adenosylmethionine. Cytosine methylation was demonstrated by both the inhibition of DNA restriction by methylation sensitive endonucleases and the lack of cleavage at 5-methylcytosines by hydrazine.

Kinetics of 2-oxoglutarate uptake by synaptosomes from bovine and rat retina and cerebral cortex and regulation by glutamate and glutamine.

2-Oxoglutarate (2-OG) is a metabolic precursor of glutamate and may be utilized to replenish the neurotransmitter pool. 2-OG is rapidly transported into neurons by a high-affinity carrier that is particularly prevalent in glutamatergic terminals. Here we report the kinetics of [U-14C]2-OG uptake by crude synaptosomal preparations from bovine and rat retina and brain, and the modulatory effects of glutamate and glutamine.

Analysis of [1-13C]D-glucose metabolism in cultured astrocytes and neurons using nuclear magnetic resonance spectroscopy.

The metabolism of [1-13C]D-glucose by astrocytes, neurons and mixed astroglial/neuronal cultures derived from the striatum of fetal rats was studied using NMR. Metabolic activity was studied in resting and depolarized cells (55 mM K+), with dibutyryl cyclic-AMP added to the medium to promote cell differentiation, and with glutamate (0.1 mM) included in the medium.

1,3-Di(2-[5-3H]tolyl)guanidine labels more than one site in rat forebrain.

Studies of 1,3-di-(2-[5-3H]tolyl)guanidine ([3H]DTG) binding to rat brain membranes revealed that [3H]DTG binds to a high and a low affinity site with Kd values of 19.8 nM and 1.31 microM (corresponding Bmax values 291 fmol/mg protein and 8.

Adenosine 5'-monophosphate transport across the membrane of synaptosomes and myelin.

Synaptosome-enriched preparations from rat and guinea pig brain tissue vigorously accumulated [3H]-adenosine 5'-monophosphate ([3H]AMP). When the accumulation of [3H]AMP was determined using incubation periods of 30 s or less, high concentrations of adenosine, dipyridamole and soluflazine did not inhibit the accumulation of label appreciably. The accumulation of [3H]AMP was saturable, temperature-dependent, osmotic-sensitive and exhibited structural specificity.

Etoperidone, trazodone and MCPP: in vitro and in vivo identification of serotonin 5-HT1A (antagonistic) activity.

The Ki values for etoperidone, trazodone and MCPP (m-chlorophenylpiperazine dihydrochloride) at 5-HT1A sites (using rat cerebral cortical synaptosomes and [3H]8-OH-DPAT) were determined to be 20.2, 23.6 and 18.

Opioid and nonopioid components independently contribute to the mechanism of action of tramadol, an 'atypical' opioid analgesic.

Tramadol hydrochloride produced dose-related antinociception in mouse abdominal constriction [ED50 = 1.9 (1.2-2.