Direct spectroscopic detection of a zwitterionic excited state.

Two electrons in two weakly coupled orbitals give rise to two states (diradical) with electrons residing in separate orbitals and two states (zwitterionic) with both electrons paired in one orbital or the other. This two-electron, two-orbital state manifold has eluded experimental confirmation because the zwitterionic states have been difficult to locate. Two-photon excitation of fluorescence from Mo(2)CI(4)(PMe(3))(4) (D2d) has been measured with linearly and circularly polarized light. From the polarization ratio and the energy of the observed transition, the 2(1)A(1) (delta*delta*) excited state has been located and characterized. In conjunction with the one-photon allowed (1)B(2) (deltadelta*) excited state, the zwitterionic state manifold for the quadruply bonded metal-metal class of compounds is thus established.

Conjugation of benzo(a)pyrene 7,8-dihydrodiol-9,10-epoxide in infant Swiss-Webster mice.

Benzo(a)pyrene 7,8-dihydrodiol-9,10-epoxide (BPDE), accepted as the ultimate carcinogen of benzo(a)pyrene, has a very short half-life in aqueous solutions yet induces lung tumors when injected into infant mice. To evaluate the possibility that metabolites of BPDE, principally in the form of stable conjugates, contribute to binding to DNA in peripheral tissues, infant mice were injected i.p. with 39 nmol (+/- ) anti-BPDE. One h after injection, 5% of the dose was recovered in serum and appeared mostly as conjugated metabolites (54% as glucuronides and 16% as glutathione conjugates). Amounts of direct acting electrophiles in serum estimated by trapping with DNA comprised less than 0.02% of the injected dose. No more than 10% of the radioactivity in extracts of liver, lung, and kidney was recovered as BPDE. Glutathione conjugates predominated in the liver and lung, whereas glucuronides were the major metabolites in kidney. Radioactivity bound to DNA in liver, lung, and kidney was 21.5, 42.7, and 7.8 pmol/mg, respectively. Despite the rapid conversion of BPDE to stable conjugates, 32P-postlabeling profiles of DNA adducts in lung closely resembled that noted after addition of BPDE directly to lung homogenate. Thus, the reactive intermediate as well as stable conjugates of BPDE may be transported to target tissues where they initiate tumors.

Reciprocal effects of energy utilization on palmitate oxidation and esterification in hepatocytes of fed rats.

The effects of the energy-dependent process of urea synthesis from NH4Cl on the partition of [1-14C]palmitate between oxidation and esterification were examined in hepatocytes of fed rats. A high rate of urea formation from NH4Cl resulted in stimulation of total palmitate oxidation by 25 and 15% at 0.2 and 1 mM fatty acid, respectively. The stimulation of palmitate oxidation was reciprocally correlated with diminished palmitate incorporation into lipids, mainly triacylglycerols. This relationship was almost stoichiometric. NH4Cl increased the palmitate oxidation/esterification ratio from 0.72 to 1.13 and from 0.94 to 1.36 in the presence of 0.2 mM and 1 mM palmitate, respectively. The transaminase inhibitor, aminooxyacetate, strongly inhibited urea synthesis from NH4Cl, had little effect on the low beta-hydroxybutyrate/acetoacetate ratio in the presence of NH4Cl, completely reversed the changes in palmitate metabolism caused by NH4Cl and did not affect palmitate metabolism in the absence of NH4Cl. Therefore, the increased utilization of energy for urea synthesis was the causative factor by which NH4Cl stimulated total palmitate oxidation and led in consequence to its decreased esterification into lipids. Accordingly, these observations indicate that in liver cells the rate of ATP utilization is one of the determinants of triacylglycerol synthesis.

Preservation of the rate and profile of xenobiotic metabolism in rat hepatocytes stored in liquid nitrogen.

A simple procedure for cryopreservation of rat hepatocytes that allows recovery of viable cells retaining activities of phase I and phase II drug metabolism equivalent to freshly isolated cells is described. The cooling process was initiated 30 min after incubation of freshly isolated hepatocytes at 37 degrees in Krebs-Ringer bicarbonate buffer containing 15 mM glucose to allow for metabolic equilibration. At the end of this period, hepatocyte suspensions were supplemented with 1.7% albumin, 13.3% dimethyl sulfoxide, and the synthetic buffers, 3-[N-morpholino]propanesulfonic acid (MOPS) and N-[2-hydroxyethyl]piperazine-N'-[2-ethanesulfonic acid] (HEPES). Hepatocytes were cooled in a stepwise manner to -196 degrees by holding the cells for 1 hr at -20 degrees and then for 1 hr at -70 degrees before transfer into liquid nitrogen. After thawing and removal of damaged cells by centrifugation in Percoll, the total recovery of viable hepatocytes subjected to freezing was about 42%. The contents of ATP, ADP, and AMP were not altered significantly in cells stored in liquid nitrogen. The metabolic competence of cryopreserved hepatocytes was further confirmed by their ability to synthesize urea from NH4Cl and ornithine at the same high rate that was observed in freshly isolated cells (693 +/- 68 and 740 +/- 68 nmol.mg dry wt-1 x hr-1, respectively). Similarly, cryopreservation did not affect drug-metabolizing systems as indicated by the metabolism of benzo[a]pyrene and 7-ethoxycoumarin, two model substrates. In both freshly isolated and cryopreserved hepatocytes, 7-ethoxycoumarin was O-deethylated to 7-hydroxycoumarin at essentially the same rates (8.66 +/- 0.75 and 8.25 +/- 0.53 nmol.mg dry wt-1.hr-1, respectively) and 7-hydroxycoumarin accumulated in hepatocyte suspensions almost exclusively in the conjugated form. The storage of hepatocytes in liquid nitrogen also did not affect the complex metabolism of benzo[a]pyrene to total oxygenated metabolites and, more importantly, to metabolites conjugated with glutathione, glucuronic acid, and sulfuric acid. Thus, cryopreserved hepatocytes represent a valid and convenient model to study drug biotransformation in intact cells.

Metabolism of benzo[a]pyrene and (-)-trans-benzo[a]pyrene-7,8-dihydrodiol by freshly isolated hepatocytes of brown bullheads.

The metabolism of [3H]benzo[a]pyrene (BP) and (-)-trans-[14C]7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene (BP-7,8-diol) was studied in freshly isolated hepatocytes of the wild benthic fish, brown bullhead (Ictalurus nebulosus). Bullhead hepatocytes incubated with 40 microM [3H]BP for 1 h metabolized BP to water soluble metabolites which were separated on silica gel t.l.c. plates to reveal conjugates with glucuronic acid, glutathione, and sulfate (51%, 14% and 4% of total metabolites, respectively). Additional metabolites that were extractable with ethyl acetate were separated by reversed phase HPLC to reveal only two major metabolites: BP-9,10-dihydrodiol and BP-7,8-diol (13% and 2.6% of total metabolites, respectively). Hepatocytes isolated from individual fish displayed an 11-fold variability in the rates at which they metabolized BP (756 +/- 167 pmol x mg dry wt-1 x h-1), which correlated negatively (r = -0.7, P less than 0.01) with an 18-fold variability in the glycogen content of the cells. Hepatocytes isolated from the same fish, in parallel incubations under the same optimum conditions, metabolized BP-7,8-diol 4.5-fold faster than they metabolized BP. The variability in the rate of BP-7,8-diol metabolism was about 7-fold. Major metabolites included glutathione conjugates, glucuronides and sulfates (35%, 25% and 30% of total metabolites, respectively). These conjugates, like those formed from BP, were degradable with gamma-glutamyltransferase, beta-glucuronidase and arylsulfatase, respectively. Ethyl acetate extractable metabolites were predominantly isomeric benzo-ring tetrahydrotetrols (9% of total metabolites). In summary, this study indicates that during short-term incubations bull-head hepatocytes metabolize BP and BP-7,8-diol primarily to conjugated derivatives. The usefulness of thin-layer chromatography for the convenient determination of the rate of BP-7,8-diol metabolism is demonstrated.

Predominance of glucuronidation over sulfation in metabolism of 1-hydroxybenzo[a]pyrene by isolated rat hepatocytes.

This study shows that 1-hydroxybenzo[a]pyrene glucuronide and 1-hydroxybenzo[a]pyrene sulfate are formed in isolated rat hepatocytes. Formation of these conjugates by hepatocytes incubated with 1-acetoxy-[G-3H]benzo[a]pyrene (100 microM) as a source of intracellular 1-hydroxy-[G-3H]benzo[a]pyrene was documented by comparison of the spectra of metabolites separated by HPLC with the spectra of 1-hydroxybenzo[a]pyrene glucuronide and 1-hydroxybenzo[a]pyrene sulfate standards. The rates of 1-hydroxybenzo[a]pyrene glucuronidation and sulfation were 7.72 +/- 1.03 and 0.68 +/- 0.02 nmol x mg dry wt.-1 x 30 min-1, respectively. The rate of 1-hydroxybenzo[a]pyrene glucuronide production by intact cells corresponded well with the total activity of UDP-glucuronosyltransferase(s) determined in permeabilized hepatocytes. Cryopreserved hepatocytes fully retained a high capacity to glucuronidate the benzo[a]pyrene phenol.

Modeling spontaneous minute volume in coronary artery bypass graft patients.

This article presented a mathematical method by which the future trajectory of patient SMV may be predicted in the postoperative weaning period. The method outlined enables critical-care staff to predict the SMV trajectory up to 30 minutes into the future. Having this capability enables physicians, respiratory therapists, and nurses to more efficiently guide patient treatment and schedule rounds within the ICU.

Variables and designs in psychiatric/mental health nursing research articles published from 1982 to 1992.

Research designs and variables of interest were classified in 194 mental health psychiatric articles published between 1982 and 1992. Common variables only could be identified in 100 articles and independent and dependent variables were identified in the remaining 94 articles. The majority of research designs were descriptive. The variables pertained to diverse interests from nurse and patient perspectives, specifically including patients' behavioural responses to illness, care and caregivers. These variables were then compared by the writers to the current research foci as identified in the recent literature. As listed, these are: biological psychiatry; working with the chronically and persistently mentally ill; shifting of care to the community; working with consumers; and outcome research. There is some link between research published between 1982 and 1992 and current trends in design and a few variables of interest. However, current researchers in mental health psychiatric nursing need to change foci and their relationships with other disciplines to ensure relevancy in their research programmes.

A systematic review of the psychiatric/mental health nursing research literature 1982-1992.

The purpose of this study was to assess the quality of quantitative psychiatric/mental health nursing research articles published in English between 1982 and 1992, worldwide. Criteria for selection of articles included nurse authorship or co-authorship, use of a quantitative design and pertinence to an aspect of the nursing process with psychiatric/mental health patients. One hundred and ninety-four articles met these criteria. The quality of each article was assessed by two nurse experts using Duffy's Research Appraisal Checklist (RAC). Forty-six point nine per cent of the articles were rated as superior, 50% as average and 3.1% as below average. Other findings identified journals that published research articles, countries in which research was completed, applicability of funding and qualifications of the authors. The major implications of this study are that nurses can be directed to superior articles; more publication of research by nurse authors is warranted, research is being completed with little financial support, highly rated research publications tend to get funding and editorial policies affect the quality of publication.

[Familial occurrence of Crouzon's disease]. / Rodzinne wystepowanie choroby Crouzona

The authors report a family of 8 subjects in which 6 members demonstrate significant abnormalities in the development of the facial skeleton and the skull in the form of craniofacial dysostosis (Crouzon's disease) with complications including optic nerve atrophy, divergent squint in 4 children and borderline mental retardation in 3 of these children.

Re-investigation of the presence of UDP-glucuronosyltransferase in rat liver mitochondria.

Specific activities of UDP-glucuronosyltransferase and glucose-6-phosphatase, a marker enzyme of endoplasmic reticulum, were measured in mitochondria and microsomes. In mitochondria the specific activity of UDP-glucuronosyltransferase represented only 7-11% of that found in microsomes, when measured in the presence of various aglycone substrates, including 4-nitrophenol, 4-methylumbelliferone, 1-naphthol, phenolphthalein, testosterone and 17 beta-estradiol. Similarly, the specific activity of glucose-6-phosphatase in mitochondrial preparations was about 80% of that found in microsomes. In conclusion, it seems that in rat liver the UDP-glucuronosyltransferase activity associated with mitochondrial fractions reflects the presence of membrane fragments derived from endoplasmic reticulum, rather than mitochondrial location of this enzyme.

Effect of alloxan-diabetes on gluconeogenesis and ureogenesis in isolated rabbit liver cells.

1. Neither alloxan-diabetes nor starvation affected the rate of glucose production in hepatocytes incubated with lactate, pyruvate, propionate or fructose as substrates. In contrast, glucose synthesis with either alanine or glutamine was increased nearly 3- and 12-fold respectively, in comparison with that in fed rabbits. 2. The addition of amino-oxyacetate resulted in about a 50% decrease in glucose formation from lactate in hepatocytes isolated from fed, alloxan-diabetic and starved rats, suggesting that both mitochondrial and cytosolic forms of rabbit phosphoenolpyruvate carboxykinase function actively during gluconeogenesis. 3. Alloxan-diabetes resulted in about 2-3-fold stimulation of urea production from either amino acid studied or NH4Cl as NH3 donor, whereas starvation caused a significant increase in the rate of ureogenesis only in the presence of alanine as the source of NH3. 4. As concluded from changes in the [3-hydroxybutyrate]/[acetoacetate] ratio, in hepatocytes from diabetic animals the mitochondrial redox state was shifted toward oxidation in comparison with that observed in liver cells isolated from fed rabbits.

Receptor mechanism of thrombin-induced endothelium-dependent and endothelium-independent coronary vascular effects in dogs.

We previously reported that thrombin produces endothelium-dependent relaxation and endothelium-independent constrictions in canine coronary arteries. To determine whether these opposing vascular effects of thrombin are mediated by the same receptor mechanism, but at different cell types, we investigated the effects of thrombin receptor agonist peptide (TRAP) on isolated canine coronary arteries with and without intact endothelium. In coronary arteries with intact endothelium, addition of 0.01-3.0 microM TRAP, a 14-amino acid residue peptide (SFLLRNPNDKYEPF) homologous to the newly exposed N-terminus after cleavage of the cloned human thrombin receptor, produced rapid, dose-dependent relaxation (Emax = -89.6 +/- 2.3%, n = 26). Threshold concentration was 0.03 microM, and IC50 value was 0.3 microM. Mechanical disruption of the endothelium completely abolished the TRAP-induced relaxation; instead a dose-dependent contraction was observed. Expressed as a percentage of the maximum 70 mM KCl-induced contraction, the maximum contraction observed with 3 microM TRAP was 62.0 +/- 4.1% (n = 32). Pretreatment of endothelium-intact coronary arteries with either 3 microM hemoglobin or 0.25 mM NG-monomethyl-L-arginine (L-NMMA), specific inhibitors of endothelium-derived relaxing factor or nitric oxide (EDRF/NO), also inhibited the relaxation and unmasked the constrictor effect. The pharmacokinetic characteristics of the opposing coronary vascular effects of TRAP are similar to those observed with thrombin, but specific thrombin inhibitors, such as hirudin and D-phenylalanyl-prolyl-L-arginine chloromethyl ketone (PPACK), which inhibit both thrombin relaxant and constrictor effects, had no effect on TRAP-induced responses.(ABSTRACT TRUNCATED AT 250 WORDS)

2,3-Dihydro-3-methyl-2-nitrimino-1,3-thiazole.

The title compound ¿alternatively, 3-methyl-2-[oxido(oxo)hydrazono]-2,3-dihydro-1,3-thiazole¿, C(4)H(5)N(3)O(2)S, was obtained by methylation of N-(2-thiazolyl)nitramine. The molecule lies on a mirror plane and the thiazole ring is planar, regular in shape and aromatic. The S atom participates in the aromatic sextet via an electron pair on the 3p(z) orbital. In the crystal, the molecules are arranged in parallel layers, bound to each other by weak C-H.O and C-H.N hydrogen bonds and by S.O dipolar interactions, with an interlayer separation of 3.23 A.