Cytochrome P450 2E1 is the primary enzyme responsible for low-dose carbon tetrachloride metabolism in human liver microsomes.

We examined which human CYP450 forms contribute to carbon tetrachloride (CCl(4)) bioactivation using hepatic microsomes, heterologously expressed enzymes, inhibitory antibodies and selective chemical inhibitors. CCl(4) metabolism was determined by measuring chloroform formation under anaerobic conditions. Pooled human microsomes metabolized CCl(4) with a K(m) of 57 microM and a V(max) of 2.

Ultraviolet damage and nucleosome folding of the 5S ribosomal RNA gene.

The Xenopus borealis somatic 5S ribosomal RNA gene was used as a model system to determine the mutual effects of nucleosome folding and formation of ultraviolet (UV) photoproducts (primarily cis-syn cyclobutane pyrimidine dimers, or CPDs) in chromatin. We analyzed the preferred rotational and translational settings of 5S rDNA on the histone octamer surface after induction of up to 0.8 CPD/nucleosome core (2.

Effect of calcium channel antagonists nifedipine and nicardipine on rat cytochrome P-450 2B and 3A forms.

Calcium channel antagonists are widely prescribed for treatment of hypertension. In this study, we examined whether treatment with the calcium channel antagonists, nicardipine, nifedipine or diltiazem, alters cytochrome P-450 2B or 3A (CYP2B or CYP3A, respectively) expression in rat liver. Western blot analyses were undertaken using antibodies specific for one or several members of these cytochrome P-450 subfamilies.

Enterohepatic recirculation of trichloroethanol glucuronide as a significant source of trichloroacetic acid. Metabolites of trichloroethylene.

Trichloroacetic acid (TCA) is a metabolite of trichloroethylene (TRI) thought to contribute to its hepatocarcinogenic effects in mice. Recent studies have shown that peak blood concentrations of TCA do not occur until approximately 12 hr after an oral dose of TRI; however, blood concentrations of TRI reach a maximum within 1 hr and is nondetectable after 2 hr. The objective of this study was to examine quantitatively enterohepatic recirculation of trichloroethanol (TCEOH) and TCA as a possible mechanism responsible for the delayed production of TCA.

DNA damage can alter the stability of nucleosomes: effects are dependent on damage type.

We have investigated the effects of DNA damage by (+/-)-anti-benzo[a]pyrene diol epoxide (BPDE) and UV light on the formation of a positioned nucleosome in the Xenopus borealis 5S rRNA gene. Gel-shift analysis of the reconstituted products indicates that BPDE damage facilitates the formation of a nucleosome onto this sequence. Competitive reconstitution experiments show that average levels of 0.

Analysis of radiation induced nucleobase-peptide crosslinks by electrospray ionization mass spectrometry.

Upon exposure to ionizing radiation, DNA undergoes a variety of modifications including the production of a covalent bond between the nucleobase thymine and the amino acid tyrosine. These crosslinked lesions, produced in cells exposed to ionizing radiation, if unrepaired are thought to result in cell death. We have used electrospray ionization mass spectrometry (ESI-MS) to study a model system consisting of the peptide angiotensin, a 10 amino acid peptide containing only one tyrosine residue, irradiated in the presence of the nucleobase thymine.

Molecular weight determination of plasmid DNA using electrospray ionization mass spectrometry.

Ionization and molecular weight (MW) determination of megadalton size plasmid DNA has been achieved using electrospray ionization (ESI) with Fourier transform ion cyclotron resonance (FTICR) mass spectrometry. DNA molecules were shown to remain intact through electrospray ionization by collection on a specially prepared surface, followed by agarose gel electrophoresis. Individual highly charged ions of plasmid DNA produced by ESI were trapped in an FTICR cell for up to several hours and reacted with acetic acid to induce charge state shifts.

Characterization of radiation-induced thymine-tyrosine crosslinks by electrospray ionization mass spectrometry.

Exposure to ionizing radiation leads to formation of covalent crosslinks between DNA and proteins. The nature, extent and site of the modifications are not well understood due to the difficulty in assessing free radical-induced damage in biopolymers. Electrospray ionization mass spectrometry (ESI-MS) permits direct analyses of intact oligopeptides, permitting characterization of the radiation-induced DNA-protein covalently crosslinked constituents.

Neonatal exposure to xenobiotics alters adult hepatic protein kinase C alpha levels and testosterone metabolism: differential effects by diethylstilbestrol and phenobarbital.

Hepatic enzymes that metabolize endogenous and xenobiotic compounds have been shown to be altered in adult rats that had been exposed to xenobiotics as neonates. Protein kinase C (PKC) is important in intracellular signaling and has been implicated in the regulation of hepatic monooxygenases. Therefore, we examined the effects of neonatal exposure to diethylstilbestrol (DES) and phenobarbital (PB) on hepatic microsomal testosterone metabolism and on the alpha form of protein kinase C (PKC alpha) in adult rats.

The laryngeal mask airway. Safety, efficacy, and current use.

In 1983, the laryngeal mask airway (LMA) was introduced as a new airway device. It can be inserted without the aid of a laryngoscope or neuromuscular blockade. Compared with the face mask, the LMA allows for a more "hands-free approach" to airway management providing the anesthesiologist the freedom of not holding a mask.

Nucleosome structure modulates benzo[a]pyrenediol epoxide adduct formation.

We have studied the binding of a chemical carcinogen to DNA reconstituted with histone octamers to determine the effect that nucleosome structure has on covalent adduct formation. Reconstitution of a plasmid containing the somatic 5S rRNA gene from Xenopus borealis resulted in characteristic nucleosome structure, as determined by micrococcal nuclease digestion, shifted migration in agarose gels, and hydroxyl radical footprinting. Formation of covalent adducts by benzo[a]pyrenediol epoxide (BPDE) occurred initially at a slower rate in reconstituted DNA than in naked plasmid, but after 2 h the total adduction levels (adducts/plasmid) were equal in both samples.

Radiologic regression of primary sclerosing cholangitis following combination therapy with an endoprosthesis and ursodeoxycholic acid.

Bile duct strictures seen in patients with primary sclerosing cholangitis are generally considered irreversible. Oral ursodeoxycholic acid therapy has been shown to improve symptoms and biochemical abnormalities, as well as reverse intrahepatic alterations in patients with biliary strictures. Endoscopic therapy also has been effective in relieving symptoms, improving biochemical and radiologic abnormalities, and preventing recurrent cholangitis in patients with primary sclerosing cholangitis.

Electrospray ionization mass spectrometric characterization of acrylamide adducts to hemoglobin.

The most common procedure to identify hemoglobin adducts has been to cleave the adducts from the protein and characterize the adducting species, by, for example, derivatization and gas chromatography/mass spectrometry. To extend these approaches we used electrospray ionization mass spectrometry (ESI-MS) to characterize adducted hemoglobin. For this we incubated [14C]acrylamide with the purified human hemoglobin (type A0) under conditions that yielded high adduct levels.

The effect of wrist rest, caffeine, and oral timolol on the hand steadiness of ophthalmologists.

Because hand steadiness is an important aspect of microsurgical technique, hand movement, amplified by a hand-held laser pointer, was measured in 14 ophthalmology trainees on four separate mornings when each had ingested (1) 200mg of caffeine, (2) 12.5mg of timolol (2.5mL of timolol 0.

Alterations in cytochrome P-450 levels in adult rats following neonatal exposure to xenobiotics.

Neonatal exposure to certain xenobiotics has been shown to alter hepatic metabolism in adult rats in a manner that indicates long-term changes in enzyme regulation. Previously, we have observed changes in adult testosterone metabolism and in cytochrome P-450 (P-450) mRNA levels in animals neonatally exposed to phenobarbital (PB) or diethylstilbestrol (DES). In order to test for other enzyme alterations, we used Western blot procedures for specific P-450s to analyze hepatic microsomes from adult rats (24 wk old) that had been exposed neonatally to DES, PB, 7,12-dimethylbenz[a]anthracene (DMBA), or pregnenolone 16 alpha-carbonitrile (PCN).

Changes in adult metabolism of aflatoxin B1 in rats neonatally exposed to diethylstilbestrol. Alterations in alpha-class glutathione S-transferases.

Neonatal exposure of rats to xenobiotics has been shown to produce long-term alterations in hepatic enzyme activities and in levels of DNA adducts following carcinogen exposure. We exposed newborn male rats to diethylstilbestrol (DES), pregnenolone-16 alpha-carbonitrile, 7,12-dimethylbenz[a]anthracene or phenobarbital on days 1, 3 and 5 of age. At five months of age, males were injected with 1 mg/kg of [3H]aflatoxin B1 (AFB1), killed after 2 h and examined for AF-DNA adduction in the liver.

Tubular adenoma of the main pancreatic duct.

We report a case of tubular adenoma of the duct of Wirsung with focal villous changes. To our knowledge, this is the 13th reported case of this uncommon neoplasm and the first with a primarily tubular histologic pattern. The patient presented with abdominal pain and diarrhea and was found on endoscopic retrograde cholangiopancreaticography to have a mass in the head of the pancreas, which was confirmed by endoscopic ultrasound.