Increasing growth and yield by altering carbon metabolism in a transgenic leaf oil crop

Engineering high biomass plants that produce oil (triacylglycerol or TAG) in vegetative rather than seed-related tissues could help meet our growing demand for plant oil. Several studies have already demonstrated the potential of this approach by creating transgenic crop and model plants that accumulate TAG in their leaves and stems. However, TAG synthesis may compete with other important carbon and energy reserves, including carbohydrate production, and thereby limit plant growth. The aims of this study were thus: first, to investigate the effect of TAG accumulation on growth and development of previously generated high leaf oil tobacco plants; and second, to increase plant growth and/or oil yields by further altering carbon fixation and partitioning. This study showed that TAG accumulation varied with leaf and plant developmental stage, affected leaf carbon and nitrogen partitioning and reduced the relative growth rate and final biomass of high leaf oil plants. To overcome these growth limitations, four genes related to carbon fixation (encoding CBB cycle enzymes SBPase and chloroplast-targeted FBPase) or carbon partitioning (encoding sucrose biosynthetic enzyme cytosolic FBPase and lipid-related transcription factor DOF4) were overexpressed in high leaf oil plants. In glasshouse conditions, all four constructs increased early growth without affecting TAG accumulation while chloroplast-targeted FBPase and DOF4 also increased final biomass and oil yields. These results highlight the reliance of plant growth on carbon partitioning, in addition to carbon supply, and will guide future attempts to improve biomass and TAG accumulation in transgenic leaf oil crops.

Pyrenoid loss impairs carbon-concentrating mechanism induction and alters primary metabolism in Chlamydomonas reinhardtii

Carbon-concentrating mechanisms (CCMs) enable efficient photosynthesis and growth in CO2-limiting environments, and in eukaryotic microalgae localisation of Rubisco to a microcompartment called the pyrenoid is key. In the model green alga Chlamydomonas reinhardtii, Rubisco preferentially relocalises to the pyrenoid during CCM induction and pyrenoid-less mutants lack a functioning CCM and grow very poorly at low CO2. The aim of this study was to investigate the CO2 response of pyrenoid-positive (pyr+) and pyrenoid-negative (pyr-) mutant strains to determine the effect of pyrenoid absence on CCM induction and gene expression. Shotgun proteomic analysis of low-CO2-adapted strains showed reduced accumulation of some CCM-related proteins, suggesting that pyr- has limited capacity to respond to low-CO2 conditions. Comparisons between gene transcription and protein expression revealed potential regulatory interactions, since Rubisco protein linker (EPYC1) protein did not accumulate in pyr- despite increased transcription, while elements of the LCIB/LCIC complex were also differentially expressed. Furthermore, pyr- showed altered abundance of a number of proteins involved in primary metabolism, perhaps due to the failure to adapt to low CO2. This work highlights two-way regulation between CCM induction and pyrenoid formation, and provides novel candidates for future studies of pyrenoid assembly and CCM function.

Dynamics of carbon-concentrating mechanism induction and protein relocalization during the dark-to-light transition in synchronized Chlamydomonas reinhardtii

In the model green alga Chlamydomonas reinhardtii, a carbon-concentrating mechanism (CCM) is induced under low CO2 in the light and comprises active inorganic carbon transport components, carbonic anhydrases, and aggregation of Rubisco in the chloroplast pyrenoid. Previous studies have focused predominantly on asynchronous cultures of cells grown under low versus high CO2. Here, we have investigated the dynamics of CCM activation in synchronized cells grown in dark/light cycles compared with induction under low CO2. The specific focus was to undertake detailed time course experiments comparing physiology and gene expression during the dark-to-light transition. First, the CCM could be fully induced 1 h before dawn, as measured by the photosynthetic affinity for inorganic carbon. This occurred in advance of maximum gene transcription and protein accumulation and contrasted with the coordinated induction observed under low CO2. Between 2 and 1 h before dawn, the proportion of Rubisco and the thylakoid lumen carbonic anhydrase in the pyrenoid rose substantially, coincident with increased CCM activity. Thus, other mechanisms are likely to activate the CCM before dawn, independent of gene transcription of known CCM components. Furthermore, this study highlights the value of using synchronized cells during the dark-to-light transition as an alternative means of investigating CCM induction.

Isolation of intact sub-dermal secretory cavities from Eucalyptus

BACKGROUND

The biosynthesis of plant natural products in sub-dermal secretory cavities is poorly understood at the molecular level, largely due to the difficulty of physically isolating these structures for study. Our aim was to develop a protocol for isolating live and intact sub-dermal secretory cavities, and to do this, we used leaves from three species of Eucalyptus with cavities that are relatively large and rich in essential oils.

RESULTS

Leaves were digested using a variety of commercially available enzymes. A pectinase from Aspergillus niger was found to allow isolation of intact cavities after a relatively short incubation (12 h), with no visible artifacts from digestion and no loss of cellular integrity or cavity contents. Several measurements indicated the potential of the isolated cavities for further functional studies. First, the cavities were found to consume oxygen at a rate that is comparable to that estimated from leaf respiratory rates. Second, mRNA was extracted from cavities, and it was used to amplify a cDNA fragment with high similarity to that of a monoterpene synthase. Third, the contents of the cavity lumen were extracted, showing an unexpectedly low abundance of volatile essential oils and a sizeable amount of non-volatile material, which is contrary to the widely accepted role of secretory cavities as predominantly essential oil repositories.

CONCLUSIONS

The protocol described herein is likely to be adaptable to a range of Eucalyptus species with sub-dermal secretory cavities, and should find wide application in studies of the developmental and functional biology of these structures, and the biosynthesis of the plant natural products they contain.

Microchip-based synthesis and analysis: control of multicomponent reaction products and intermediates

A miniaturised-SYNthesis and Total Analysis System (mu SYNTAS) was used for the solution-phase synthesis and on-line analysis (TOF-MS) of Ugi multicomponent reaction (MCR) products. This approach provides an unusually high degree of control of the MCR and delivers detailed, novel information on reaction intermediates in real-time. Specifically, the Ugi 4 component condensation (4CC) involving the reaction of an amine, acid, aldehyde and isocyanide species was performed at room temperature in a controllable fashion. Furthermore, observation of the nitrilium intermediate, cyclohexyl(2-piperidin-1-ylethylidyne)ammonium chloride, is presented for the first time.

Midodrine treatment for patients with hemodialysis hypotension

Hypotension is the principal complication of chronic hemodialysis. Autonomic insufficiency is thought to be a primary contributing cause of hemodialysis hypotension. We treated patients who experience hemodialysis hypotension with midodrine, a selective alpha-1 adrenergic pressor agent in an initial effort to assess potential efficacy. Twenty-one patients who experienced severe hypotension during hemodialysis participated in this study. To qualify, patients had to exhibit a fall of > or = 30 mmHg in systolic blood pressure with associated clinical symptoms during hemodialysis. The lowest intra- and post-dialysis blood pressures were monitored for five consecutive hemodialysis treatment periods before receiving midodrine, as a baseline. After the patients were titrated to a maintenance midodrine dose, the lowest intra- and post-dialysis blood pressure data were again collected for five consecutive dialysis treatments. Hemodialysis blood pressures on midodrine treatment were compared to baseline to evaluate the effect of midodrine. Midodrine given at a mean treatment dose of 8 mg (range 2.5-25) significantly increased the mean (+ or - SE) minimal systolic pressure from 93.1 "+ or - " 3.8 to 107.1 + or - 3.2 mmHg (p <0.01) and elevated the mean diastolic pressure from 52.3 + or - 2.9 to 57.9 + or - 2.3 mmHg during hemodialysis. Also, the post-dialysis blood pressures (systolic/diastolic) were significantly increased from 115.6 + or - 3.1/62.3 + or - 2.1 to 129.9 + or - 3.9/68.1 + or - 1.7 mmHg (p <0.01 and 0.05, respectively). No apparent clinical or laboratory abnormalities were observed. Oral midodrine appears to be a safe and effective therapy for the treatment of hemodialysis hypotension.

Progressive hemochromatotic cardiomyopathy despite reversal of iron deposition after liver transplantation

Dilated cardiomyopathy is a frequent and serious complication of idiopathic hemochromatosis. The mechanism by which disordered iron metabolism induces heart failure is not entirely understood, but myocardial dysfunction appears to be intimately related to the deposition of iron in myocytes. Cardiac function characteristically worsens or improves in proportion to the degree of iron accumulation in cardiac myocytes. The authors report the case of a 47-year-old man with idiopathic hemochromatosis and cirrhosis who developed symptoms of congestive heart failure and was found to have dilated cardiomyopathy 7 months after receiving a liver transplant. An initial endomyocardial heart biopsy demonstrated severe iron deposition in myocytes. The patient's heart failure worsened in the next 3 years and he eventually required a heart transplant. Examination of the explanted heart revealed dilated cardiomyopathy, but the previously demonstrated iron deposits in the cardiac myocytes were depleted. This "uncoupling" of cardiac function and cardiac iron load suggests that a threshold may be reached at which point the metabolic and ultrastructural derangements of iron deposition are no longer reversible, even with the removal of the inciting agent. Furthermore, displacement of myocyte iron stores after liver transplantation implicates altered hepatic iron metabolism as a primary or contributing mechanism in the pathophysiology of idiopathic hemochromatosis.

Comparison of determinants of frame size in older adults

Accurate designations of body frame size can enhance the interpretation of height-weight tables. Determinants of frame size should be quantifiable, reflective of skeletal dimensions, and not influenced by adiposity. Visual assessment, the height:wrist circumference ratio, elbow breadth by 1983 and 1984 standards, and Frame Index 2 were studied in 300 healthy adults over 64 years of age. Distribution of frame size across small, medium, and large categories revealed that visual assessment and height:wrist circumference ratio agreed with designations of elbow breadth measurements for less than 50% of the population. Highest levels of agreement occurred between elbow breadth (1984) and Frame Index 2. For men, high partial correlations between height:wrist circumference ratio and subscapular fatfold measurements corrected for age and arm muscle area indicated that measurement may be affected by body fat. Lowest correlations with subscapular fatfolds were for wrist and ankle breadths for women and ankle breadth for men. Elbow breadth and Frame Index 2 had low negative correlations with subscapular skinfold for men but much higher values for women. Elbow breadth measurements are widely used as frame size determinants, but for women, at least, ankle and wrist breadths meet the criterion of low associations with body fatness.

Effects of chronic ethanol exposure on cardiac receptor-adenylyl cyclase coupling: studies in cultured embryonic chick myocytes and ethanol fed rats

Ethanol effects in the brain appear to be mediated at least in part by an alteration in receptor-effector coupling via guanine nucleotide-binding regulatory proteins (G proteins). To test the hypothesis that a similar pathway participates in the cardiotoxic effects of ethanol, we assessed the effects of chronic ethanol on two commonly used experimental models: embryonic chick myocytes in culture and ventricular myocardium from chronically fed rats. Ethanol had no effect on either the function or quantity of G proteins as assessed by effector-stimulated adenylyl cyclase activity and the levels of ADP-ribosylation substrates. In contrast, effector-stimulated adenylyl cyclase activity was significantly altered in the liver of ethanol-fed rats. These results suggest that receptor-effector coupling via G proteins in our two cardiac models is insensitive to ethanol and that ethanol effects may be species or organ specific.

Effect of parenteral amino acid supplementation on short-term and long-term outcomes in severe alcoholic hepatitis: a randomized controlled trial

The effect of parenteral amino acid administration on nutritional state, liver function and mortality was assessed in patients with severe alcoholic hepatitis. Twenty-eight patients received 2 l/day of a solution of dextrose (65 gm/L) and amino acids (25.8 gm/L) for 1 mo, whereas 26 received only the dextrose solution. All patients were allowed to eat a standard hospital diet. During the month in the hospital, there were six deaths in the treatment group and five deaths in the control group. Nitrogen balance improved in the treated group, but not in the control group. Creatinine-height index, triceps skin fold measurement and levels of serum albumin and prealbumin increased similarly in both groups. Serum retinol binding protein increased more in the treatment group than it did in the control group, and transferrin was increased only in the treatment group. Serum bilirubin, type III amino-terminal procollagen peptide and aminopyrine clearance improved more in the treatment group than in the control group, whereas serum AST and prothrombin time improved in the treatment group but not in the control group. Cumulative 2-yr survival rates from the day of entry into the study were 42% and 38% in the treatment and control groups, respectively. Patients who survived 2 yr and patients in the treatment group who died during the 2-yr follow-up had continued improvement in serum retinol binding protein, transferrin, bilirubin and prothrombin time. These parameters were unchanged in patients in the control group who died during follow-up.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of vasopressor hormones and modulators of protein kinase C on glutathione efflux from perfused rat liver

Vasopressor hormones alter efflux of glutathione (GSH) and increase permeability of tight junctions in perfused rat liver. Infusions of 10 nM angiotensin II, 10 microM phenylephrine, and 10 nM vasopressin significantly increased efflux of GSH into perfusate by 32-41% and decreased biliary efflux by 31-57%. Direct modulation of protein kinase C (PKC) activity by 600 nM phorbol 12,13-dibutyrate (PDB), 5 microM 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (H-7), 5 microM sphingosine, or 10 nM staurosporine altered the pattern of efflux of GSH but not biliary oxidized glutathione disulfide (GSSG)-GSH ratios. Phorbol dibutyrate mimicked the vasopressor-mediated effects, increasing perfusate efflux by 31% and decreasing biliary efflux by 45%. Inhibitors of PKC caused qualitatively opposite responses, changing perfusate GSH by -37 to 18% and increasing biliary efflux by 22-161%. Whereas vasopressin increased penetration of [14C]sucrose into bile, modulation of PKC activity by PDB and H-7 did not affect the permeability of tight junctions to [14C]sucrose. Although pretreatment with H-7 blocked vasopressin-mediated changes in efflux of GSH, it did not prevent the increase in [14C]sucrose penetrance. We conclude that alterations in sinusoidal and biliary efflux of GSH can occur independent of changes in permeability of hepatocellular tight junctions. These findings suggest a role for protein kinase C in modulating the hepatic efflux of GSH.

Energy state and vasomotor tone in hypoxic pig lungs

To evaluate the role of energy state in pulmonary vascular responses to hypoxia, we exposed isolated pig lungs to decreases in inspired PO2 or increases in perfusate NaCN concentration. Lung energy state was assessed by 31P nuclear magnetic resonance spectroscopy or measurement of adenine nucleotides by high-pressure liquid chromatography in freeze-clamped biopsies. In ventilated lungs, inspired PO2 of 200 (normoxia), 50 (hypoxia), and 0 Torr (anoxia) did not change adenine nucleotides but resulted in steady-state pulmonary arterial pressure (Ppa) values of 15.5 +/- 1.4, 30.3 +/- 1.8, and 17.2 +/- 1.9 mmHg, respectively, indicating vasoconstriction during hypoxia and reversal of vasoconstriction during anoxia. In degassed lungs, similar changes in Ppa were observed; however, energy state deteriorated during anoxia. An increase in perfusate NaCN concentration from 0 to 0.1 mM progressively increased Ppa and did not alter adenine nucleotides, whereas 1 mM reversed this vasoconstriction and caused deterioration of energy state. These results suggest that 1) pulmonary vasoconstrictor responses to hypoxia or cyanide occurred independently of whole lung energy state, 2) the inability of the pulmonary vasculature to sustain hypoxic vasoconstriction during anoxia might be associated with decreased energy state in some lung compartment, and 3) atelectasis was detrimental to whole lung energy state.

Cephalosporin-induced alteration in hepatic glutathione redox state. A potential mechanism for inhibition of hepatic reduction of vitamin K1,2,3-epoxide in the rat

Hypoprothrombinemia is a serious adverse effect of antimicrobial therapy that occurs after administration of some second- and third-generation cephalosporins which contain the methyltetrazole-thiol (MTT) group. Previous studies have shown that in vitro MTT directly inhibits microsomal gamma-carboxylation of a synthetic pentapeptide. Since MTT is a thiocarbamide, a type of compound that can increase oxidation of glutathione, the present studies were carried out to determine whether alterations in hepatic glutathione redox state might interfere with vitamin K metabolism. Dose-related increases in biliary efflux and hepatic concentration of oxidized glutathione (GSSG) occurred after intravenous administration of MTT or MTT-containing antibiotics to rats. This finding suggested that these compounds could alter the hepatic glutathione redox state in vivo. Microsomal reduction of vitamin K epoxide occurred in the presence of 100 microM dithiothreitol (DTT), but was inhibited by preincubation with GSSG at concentrations as low as 10 microM. At higher concentrations of DTT (1.0 mM) inhibition by GSSG persisted, but higher concentrations were required, suggesting that the thiol/disulfide ratio, rather than the absolute concentration of GSSG was important. By contrast, GSSG did not effect microsomal gamma-carboxylation of a pentapeptide, using either vitamin K1 or its hydroquinone as a cofactor. These findings suggest a novel mechanism for the hypoprothrombinemia occurring after administration of MTT-containing antibiotics.

Plasma tumor necrosis factor alpha predicts decreased long-term survival in severe alcoholic hepatitis

Plasma tumor necrosis factor alpha (TNF alpha), interleukin 1 alpha (IL-1 alpha), and interleukin 1 beta (IL-1 beta) were measured in plasma samples obtained from 23 patients with severe alcoholic hepatitis on admission and after 30 days of hospitalization. Over a 2-year follow-up period, 14 patients died at a mean time of 8 months following discharge. The presence of elevated plasma TNF alpha either at admission or discharge from the hospital was associated with death in 82% (14/17) of patients. By contrast absence of elevated plasma TNF alpha was associated with survival in 100% (6/6). The difference in survival with and without detectable plasma TNF alpha was significant at p = 0.0022. Plasma TNF alpha was not elevated in alcoholic patients without clinically apparent liver disease, with alcoholic cirrhosis, or in nonalcoholic healthy controls. Plasma IL-1 alpha was also significantly increased in alcoholic hepatitis whereas IL-1 beta was not. Neither IL-1 alpha nor beta was correlated with outcome in the alcoholic hepatitis group. It is concluded that the presence of elevated plasma TNF alpha is a significant predictor of decreased long-term survival in patients with severe alcoholic hepatitis.

A comparison of pregnancy outcome in overweight and normal weight women

From a population of singleton pregnancies, 152 overweight women (greater than 110% of standard) were matched with normal weight women (95-110%) for age, height, parity, race, and smoking habits. Comparisons were made of initial weight (weight at the first prenatal visit) and gestational weight gain and pregnancy outcome. Mean birth weights and gestational ages of infants of normal and overweight women were not significantly different. For normal weight women birth weight increased significantly as height, initial weight, and body mas index increased (p less than 0.01), but no such relationship existed for overweight women. The lack of effect of initial weight on birth weight in overweight women is attributable, in part, to the significantly less gestational weight gains of these mothers (6.3 kg vs 8.2 kg). When normal and overweight gravida had gestational weight gains of less than 7 kg, offspring of overweight mothers were significantly heavier. Gestational weight gain was positively correlated with birth weight for both normal (p less than 0.0001) and overweight women (p less than 0.001). Within the overweight and normal weight groups, smokers had lower initial weights and gestational weight gains than nonsmokers. Offspring of normal weight smokers had a mean birth weight 232 g less than that of nonsmokers (p less than 0.01). The difference in birth weight between overweight smokers and nonsmokers (135 g) was not statistically significant. While there is substantial data to support a weight gain of 10-12 kg in normal weight gravida, it would appear that a gain of approximately 7 kg in overweight middle class women does not impair fetal growth as measured by birth weight.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of pyridine dinucleotides in cultured rat hepatocytes by high-performance liquid chromatography

An isocratic reverse-phase high-performance liquid chromatography method for the separation and quantitation of total pyridine dinucleotides in hepatocyte cultures is described. Cells are extracted with cold 3 M perchloric acid or 0.5 N sodium hydroxide containing 50% (v/v) ethanol and 35% cesium chloride for the determination of the oxidized or reduced pyridine dinucleotides, respectively. Pyridine dinucleotides in the neutralized extracts were separated on an Excellopak ODS C18 (4.6 X 150 mm) column with 0.1 M potassium phosphate, pH 6.0, containing 3.75% methanol as the mobile phase. NAD+ and NADP+ were detected spectrophotometrically at 254 nm. The response was linear from 5 to 4000 pmol with recoveries of NAD+ and NADP+ of 98 and 101.1%, respectively. NADH and NADPH were monitored fluorometrically by activation at 370 nm and emission in the 400-700 nm range. The reduced pyridine dinucleotides had a linear response from 7.5 to 60 pmol with recoveries of NADH and NADPH of 99.4 and 101.3%, respectively. The coefficients of variation for all of the pyridine dinucleotide standards were less than 3.5%.

Impaired hepatic elimination of paranitrophenol and its metabolites in the rat following chronic ethanol pretreatment

Chronic ethanol feeding has been shown to enhance hepatic microsomal drug oxidation in humans and in laboratory animals. However, the effects of chronic ethanol administration on drug conjugation are less conclusive. We have studied the effects of chronic ethanol feeding on (a) the conjugation and elimination of p-nitrophenol (PNP) by the isolated perfused rat liver, (b) the formation of PNP glucuronide by hepatic microsomal PNP-glucuronyltransferase in vitro and (c) the hepatic content of UDP-glucuronic acid (UDPGA). PNP elimination from the isolated perfused rat liver was best described as a combination of parallel saturable and first-order processes. Ethanol pretreatment did not influence the former but resulted in a 48% reduction in the rate of elimination by the latter. This was associated with a significant reduction in recovery of PNP-glucuronide from bile, but no change in concentrations of PNP glucuronide or sulfate in perfusate. Michaelis constants and Vmax for PNP-glucuronyltransferase in native and solubilized microsomes and UDPGA concentrations in liver were not influenced by ethanol pretreatment. These results suggest that chronic ethanol treatment reduces PNP elimination in the intact liver primarily via a reduction in the biliary excretion of PNP glucuronide without altering glucuronidation per se.

Zonal distribution of paracetamol glucuronidation in the isolated perfused rat liver

1. The lobular distribution of paracetamol conjugation was studied using antegrade and retrograde perfusion of isolated rat liver. After addition of 25 mg of paracetamol, recovery of sulphate from antegrade perfusions was greater than from retrograde perfusions indicating periportal predominance of this metabolic pathway. 2. Recovery of sulphate was greater than recovery of glucuronide after addition of 25 mg of paracetamol during both antegrade and retrograde perfusions. Recovery of sulphate was similar after addition of 25 or 100 mg of paracetamol, whereas recovery of the glucuronide was increased at the higher dose, indicating a higher capacity for glucuronidation than for sulphation, but a higher affinity for sulphation. 3. Recovery of glucuronide from antegrade and retrograde perfusions was similar after addition of 25 mg of paracetamol, but was greater from antegrade perfusions after addition of 100 mg. This indicates that drug concentration may be an important determinant of the zonal distribution of drug metabolism. Factors other than localization of drug-metabolizing enzymes, such as competition with other metabolic pathways or availability of cofactors, may also influence the apparent zonal distribution of drug metabolism.

Role of prostacyclin in the splanchnic hyperemia contributing to portal hypertension

To determine the possible role of prostacyclin (PGI2) as a mediator of the splanchnic hyperemia seen with portal hypertension, the portal and mesenteric hemodynamics in normal and portal hypertensive rabbits were studied before and after cyclo-oxygenase blockade. Three weeks after partial portal vein ligation, splenic pulp pressure was elevated from 4.3 +/- 0.9 to 9.8 +/- 0.8 mmHg (p less than 0.01). Mesenteric blood flow increased from 77.0 +/- 4.7 ml.min-1.100 g-1 to 99.1 +/- 5.19 ml/min-1/100 g-1. Mesenteric vascular resistance fell from 0.82 +/- 0.6 mmHg/ml-1/min-1 to 0.49 +/- 0.07 mmHg/ml-1/min-1 (p less than 0.01). These hemodynamic changes were associated with a 27.3 +/- 0.2% rise in systemic arterial levels of PGI2 (p less than 0.01) and were substantially ameliorated by cyclo-oxygenase blockade with indomethacin. The effects of indomethacin blockade were reversed by exogenous PGI2. Moreover, in normotensive rabbits, infusion of PGI2 reproduced the splanchnic hyperemia and caused a very small but significant increase in portosystemic shunting. These findings support the previously proposed concept that splanchnic hyperemia may contribute to the maintenance of chronic portal hypertension. Furthermore, they suggest that this effect may be partially mediated by splanchnic PGI2 production.

Effects of ATP precursors on ATP and free ADP content and functional recovery of postischemic hearts

It has been proposed that administration of adenine nucleotide precursors might accelerate replenishment of myocardial ATP and "free" ADP, thus improving recovery of depressed contractility of postischemic hearts. To test this hypothesis, Langendorff-perfused rabbit hearts were subjected to 20 min of global ischemia and reperfused for 2 h with normal perfusate (n = 8) or perfusate containing 100 mumol/l of the ATP precursors adenosine (n = 8) or 5-amino-4-imidazolecarboxamide riboside (AICAriboside; n = 8). After reperfusion, developed pressure in untreated hearts averaged 70-80% of base line, whereas ATP content was reduced to approximately 70% of preischemic values. AICAriboside administration did not increase tissue ATP levels or contractility. However, in every heart that received adenosine during reperfusion, ATP content increased from a mean value of 65 +/- 4% of base line to 84 +/- 5% at the end of reperfusion (P less than 0.001). Free ADP also increased in adenosine-treated hearts from 40 to 50% of base line at the beginning of reperfusion, to normal levels by 60 min. However, no improvement in contractility was observed in the hearts that received adenosine. These results support the hypothesis that decreased availability of nucleotide precursors is responsible for depressed ATP levels in postischemic hearts; however, reduced ATP and free ADP levels may not be directly responsible for the depressed function of stunned myocardium.

Alcohol and dietary intake in the development of chronic pancreatitis and liver disease in alcoholism

Alcohol and dietary intake were determined in alcoholic patients with chronic pancreatitis and alcoholic liver disease. Patients with chronic pancreatitis, alcoholic hepatitis, and cirrhosis ingested approximately 50% of their calories as alcohol, and all had low mean intakes of protein, carbohydrate, and fat as compared with control subjects. Patients with severe alcoholic hepatitis had the lowest intake of nonalcohol calories and protein. Women with chronic pancreatitis had ingested alcohol for a shorter period of time than men whereas women with alcoholic hepatitis and cirrhosis had ingested less alcohol per kilogram body weight per day as compared with men. This study does not support the hypothesis that consumption of a high-protein and high-fat diet is a factor in the development of chronic pancreatitis in the alcoholic patient. The increased susceptibility of women as compared with men to alcoholic liver disease is established.

Factors that influence the outcome of pregnancy in middle-class women

A retrospective analysis was made of 1,080 singleton pregnancies of middle-class women to identify factors that influence outcome as measured by birth weight, gestational age, Apgar scores, and the incidence of complications. Increased birth weight was associated with increases in weight gain, maternal age, gestational age, maternal initial body weight, maternal hemoglobin and hematocrit values at 3 months, hemoglobin levels at 7 months, and socioeconomic status. For women whose initial weights were 90% to 135% of the standard, highest birth weights occurred when weight gains exceeded 29 lb. A 1 lb gain in maternal weight was associated with a 6 gm increase in birth weight. Birth weight was negatively correlated with a complicated obstetrical history and maternal cigarette smoking. Infants of heavy smokers weighed an average of 156 gm less than infants of nonsmokers. One-minute Apgar scores were significantly lower for infants of mothers who consumed alcohol and those who had had a complicated obstetrical history. Initial maternal weight and the husband's occupation positively influenced gestational age. There was no relationship between the incidence of maternal or infant complications and independent variables.

Effects of ethanol feeding and withdrawal on plasma glutathione elimination in the rat

Chronic ethanol feeding increases hepatic turnover and sinusoidal efflux of glutathione in rats. The present study was performed to determine whether the observed increase in glutathione efflux was due to increased extrahepatic requirements for glutathione. The concentration and disposition of plasma glutathione were determined in rats fed liquid diets containing 36% of calories as ethanol or pair-fed an isocaloric mixture with carbohydrate replacing ethanol calories for 5 to 8 weeks. The half-life and plasma clearance of [35S]glutathione were found to be similar in ethanol-fed and control rats and in rats withdrawn 24 hr from ethanol. Uptakes of the sulfur moiety of [35S]glutathione by kidney, jejunal mucosa, liver, lung, spleen, muscle and heart were also unchanged by ethanol feeding. The plasma glutathione concentration was significantly higher in ethanol-withdrawn rats 22.30 +/- 3.06 nmoles per ml (p less than 0.05) compared to pair-fed controls (13.51 +/- 2.04), while rats continuing to drink ethanol had intermediate levels (16.96 +/- 2.22). Plasma cysteine levels were slightly, but not significantly, higher in ethanol-fed rats. These findings suggest that increased sinusoidal efflux of glutathione in ethanol-fed rats is due to a direct effect of ethanol on hepatic glutathione transport and not due to an alteration in extrahepatic disposition of glutathione. In order to characterize further the effects of ethanol feeding on glutathione-dependent detoxification, activities of glutathione S-transferase, glutathione reductase and gamma-glutamyltransferase were determined.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in plasma amino acids during sobriety in alcoholic patients with and without liver disease

Plasma amino acid profiles of alcoholic subjects without clinically apparent liver disease, alcoholic patients with biopsy-proven alcoholic hepatitis, and nonalcoholic controls were compared. Differences in the plasma aminograms of alcoholic subjects with and without liver disease appear to be due predominantly to differences in liver function whereas differences in plasma amino acid levels between the alcoholic subjects and nonalcoholic controls may be related to inadequate dietary-protein intake and pyridoxine deficiency in the alcoholic groups.

Alcohol and nutrition: caloric value, bioenergetics, and relationship to liver damage

Alcoholic beverages contribute an appreciable percentage (4-6%) to the total caloric intake in Western societies. The caloric value of ethanol as fuel may be dose-related. Most evidence suggests that at moderate intake levels of less than 45 g/day (3 drinks) ethanol is efficiently utilized as a fuel by the liver. At high intakes, ethanol calories may not be utilized for cellular synthesis of ATP and maintenance of weight. The exact mechanism for this inefficient utilization remains unknown but may be related, in part, to metabolism of ethanol by the microsomal ethanol-oxidizing system, a reaction that does not contribute to generation of reducing equivalents for ATP synthesis. Although ethanol is utilized for ATP synthesis after single-dose administration, chronic consumption leads to morphological changes in hepatic mitochondria and to decreased ATP synthesis. Reductions in the activities of the enzymes of the mitochondrial electron transport chain have been reported after alcohol feeding and may help to explain decreases in hepatic ATP synthesis. There is some evidence that ATP degradation by "Na-K ATPase" is increased after ethanol feeding and that hepatic O2 consumption is likewise enhanced. However, other studies have failed to demonstrate enhanced O2 consumption. Current evidence suggests that malnutrition alone is not sufficient to explain the pathogenesis of chronic liver disease in alcoholics. Although the daily amount of alcohol consumed and the duration of excessive consumption are clearly important factors in the development of alcoholic hepatitis and cirrhosis, other factors, particularly nutritional deficiencies, may modulate the risk of developing alcohol-related liver damage. The prevalence of malnutrition is exceedingly high in alcoholics with clinically severe liver disease. Nutritional deficiencies are better correlated with a clinical index of severity than with histologic severity of alcoholic hepatitis. Prognosis and outcome of patients with alcoholic liver disease may be affected by nutritional deficiencies, which thus provides a rationale for aggressive nutritional management of these patients.

Increased hepatic efflux of glutathione after chronic ethanol feeding

Chronic ethanol feeding increases hepatotoxicity of drugs, such as acetaminophen, which form electrophilic metabolites. Availability of glutathione (GSH) is important in preventing liver damage from reactive metabolites. Chronic ethanol feeding has been reported to increase turnover of hepatic GSH in rats. The results of the present study show that the total hepatic efflux of GSH was increased from 5.95 +/- 0.42 nmoles/min/g liver (control) to 9.96 +/- 0.57 nmoles/min/g (P less than 0.001) in isolated perfused livers from rats 24 hr after withdrawal from chronic ethanol feeding. The increase in total efflux of GSH was due to a significant increase in sinusoidal GSH efflux from 4.76 +/- 0.49 nmoles/min/g liver in control rats to 9.07 +/- 0.47 nmoles/min/g (P less than 0.001) in ethanol-fed rats, while biliary efflux decreased slightly, 1.20 +/- 0.11 (control) vs 0.89 +/- 0.31 (ethanol). The increase in cellular efflux of GSH was similar in magnitude to the increase in hepatic GSH turnover that we reported previously. Biliary GSSG was similar in both groups of animals. Hepatic GGT activity was increased slightly, but not significantly, whereas renal GGT activity was similar in ethanol-fed rats. Hepatic GSH and GSSG levels were also similar. The increase in turnover of hepatic GSH in rats withdrawn from chronic ethanol feeding was most likely due to increased cellular efflux of GSH. This finding suggests that chronic ethanol feeding may increase cellular requirements for GSH, although the mechanism remains unknown. This alteration in GSH turnover may have important consequences for detoxification of xenobiotics or their metabolites by the liver.

Additive protection of cimetidine and N-acetylcysteine treatment against acetaminophen-induced hepatic necrosis in the rat

Cimetidine protects against acetaminophen hepatotoxicity in the rat as evidenced by improved survival, lower serum aminotransferases, improved liver histology, decreased in vivo and in vitro covalent binding of acetaminophen to liver protein and decreased rate of glutathione depletion. This protection is best explained by inhibition of acetaminophen oxidation by cimetidine. N-acetylcysteine, the accepted antidote, protects against acetaminophen hepatotoxicity primarily by enhancing glutathione synthesis. Inhibition of acetaminophen oxidation by cimetidine has been demonstrated directly in vitro with both rat and human liver microsomes. The aim of the present study was to determine whether cimetidine and N-acetylcysteine might be additive in their protection against acetaminophen hepatotoxicity as cimetidine and N-acetylcysteine have different mechanisms of protective action. Treatment with either cimetidine or N-acetylcysteine improved survival and serum transaminases in a dose-related manner but protection by the combination was additive when compared to each agent alone. Cimetidine decreased the rate of hepatic glutathione depletion and acetaminophen covalent binding in vivo in a dose-dependent manner whereas only a high dose of N-acetylcysteine decreased covalent binding. However, the combination of cimetidine and N-acetylcysteine more effectively prevented glutathione depletion and covalent binding in vivo than either agent used alone. We conclude that protection against acetaminophen hepatotoxicity using a combination of cimetidine and N-acetylcysteine is better than that found with either agent alone. Inasmuch as cimetidine does not increase hepatic glutathione per se, or does N-acetylcysteine inhibit acetaminophen oxidation, the additive protection against acetaminophen hepatotoxicity is best explained by the above mentioned mechanisms of action for each agent.

Alcohol-induced impairment of central nervous system function: behavioral skills involved in driving

Several points emerge from the large body of data on the effects of alcohol on CNS function. First, the degree of impairment is dose related, but not identical or strictly linear for all behaviors. Alcohol-related impairment of behavioral skills involved in driving is greatest for those tasks that require cognitive functioning; simple perception alone is least affected. Impairment of cognitive functioning, which includes information processing and decision making under conditions of divided attention, is evident at BALs above 50 mg/dl and is markedly affected above 100 mg/dl. Above a BAL of 100 mg/dl, almost all behavioral skills are impaired by alcohol. Most studies have employed only one or at most two doses of alcohol in testing for impairment. The limited range of BALs studied makes determination of the overall shape of the dose-response curve difficult. Second, alcohol-related impairment of CNS functions cannot be demonstrated at low BALs. There is no consistent evidence that BALs below 50 mg/dl impair any behavior in most individuals. Youth and the elderly, groups not typically studied in the laboratory, may represent exceptions to this general observation. Nonetheless, these findings are more consistent with a threshold effect for impairment than for impairment at all levels of BAL. Third, for most behavioral skills, the decrement in performance after alcohol is slight, rarely exceeding 35-50% of the control period. In many studies, changes of only 8-10% are reported to be statistically significant. Whether these small statistically significant decrements in performance are an explanation for increased crash risk remains uncertain.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of chronic ethanol feeding on glutathione turnover in the rat

Glutathione (GSH) is important in protection of cells against electrophilic drug injury and against reactive oxygen species. Both steady-state concentrations and turnover of GSH are important determinants of susceptibility of the hepatocyte to injury. Chronic ethanol administration is known to enhance susceptibility to electrophilic drug injury. We have examined the effects of chronic ethanol feeding on GSH turnover and the hepatic activities of GSH peroxidase and enzymes of the gamma-glutamyl cycle in the rat. Turnover of GSH was measured in individual animals by measuring the decrease in specific activity of GSH in bile over time after i.v. administration of [35S]cysteine. Rats fed ethanol had significantly increased rates of GSH turnover, 0.287 +/- 0.050 hr-1 vs 0.131 +/- 0.041 hr-1 (P less than 0.001), as well as steady-state GSH levels, 6.59 +/- 1.55 vs 4.30 +/- 1.28 mumoles/g liver (P less than 0.01). The activities of gamma-glutamyltransferase (GGT) and GSH-synthesizing enzymes were correspondingly increased significantly. By contrast, GSH peroxidase activity was decreased in ethanol-fed rats, 194 +/- 20.8 vs 311 +/- 89.9 nmoles NADPH oxidized/min/mg protein (P less than 0.001). Biliary output and concentrations of GSH and GSSG were similar in both groups. The increase in turnover of GSH was not due to an increase in oxidation of GSH. There was, however, an association between GSH turnover and the activity of hepatic GGT in ethanol-fed but not in control rats.

Selective inhibition of acetaminophen oxidation and toxicity by cimetidine and other histamine H2-receptor antagonists in vivo and in vitro in the rat and in man

Acetaminophen-induced hepatotoxicity results from hepatic enzymatic oxidation of acetaminophen to a toxic, electrophilic intermediate. Acetaminophen is ordinarily eliminated after conjugation with glucuronic acid and sulfate to nontoxic derivatives. Cimetidine has been shown to inhibit the hepatic oxidation of a number of drugs and to protect rats from acetaminophen-induced hepatic necrosis. The aim of this study was to define the mechanism by which cimetidine reduced acetaminophen-induced hepatic necrosis and to determine whether inhibition of formation of the reactive metabolite(s) of acetaminophen occurred also in man. In vivo cimetidine pretreatment decreased covalent binding of [3H]acetaminophen to the liver from 552 +/- 23.8 to 170 +/- 31.6 nmol/g protein 2 h after a toxic dose of acetaminophen in 3-methylcholanthrene pretreated rats (P less than 0.05). Cimetidine pretreatment also significantly reduced the rate of hepatic glutathione depletion. Both cimetidine and metiamide produced dose-dependent inhibition of acetaminophen oxidation in vitro, whereas inhibition by ranitidine and cimetidine sulfoxide was quantitatively less. Inhibition of acetaminophen oxidation by cimetidine and metiamide was primarily competitive with an inhibition constant (Ki) of 130 +/- 16 and 200 +/- 50 microM, respectively. By contrast, cimetidine inhibited acetaminophen glucuronidation minimally with a Ki of 1.39 +/- 0.23 mM. Similar results were obtained using human liver microsomes as a source of enzymes. In a dose-related fashion, cimetidine also reduced acetaminophen-induced toxicity to human lymphocytes when incubated with microsomes and NADPH. Pharmacokinetics of acetaminophen elimination were studied in normal volunteers with and without co-administration of cimetidine 300 mg every 6 h. In normal volunteers, cimetidine decreased the fractional clearance of the oxidized (potentially toxic) metabolites of acetaminophen more than the conjugated metabolites. This finding confirmed the hypothesis that cimetidine is a relatively selective inhibitor of the oxidation of acetaminophen to reactive metabolites in man as well as in animals. When considered together with the results of previous studies showing improved survival and decreased hepatoxicity in acetaminophen-poisoned animals, the present results provide a rational basis for assessing possible benefits of cimetidine treatment of acetaminophen overdoses in man.

Effects of oral contraceptive steroids on acetaminophen metabolism and elimination

Plasma acetaminophen elimination was examined in women taking low-dose estrogen oral contraceptive (OC) steroids and in age-matched control women. Fractional rates of elimination and fractional clearances were calculated for each of the metabolic pathways, including oxidation, sulfation, and glucuronidation. The cysteine adduct and mercapturic acid derivative of acetaminophen were used as an index of oxidative biotransformation, a potentially toxic route of metabolism for acetaminophen. Plasma acetaminophen clearance rose from 287 +/- 13 ml/min to 470 +/- 51 ml/min in women taking OC steroids, whereas elimination t1/2 decreased from 2.40 +/- 0.14 hr to 1.67 +/- 0.16 hr. The fractional clearance and rate of elimination of acetaminophen by glucuronidation increased in women taking OC steroids, whereas the clearance and elimination by sulfation did not differ significantly from values in control subjects. Fractional clearance of the cysteine adduct also increased significantly, but clearance of acetaminophen mercapturic acid did not change. These data suggest that the increased clearance of acetaminophen from plasma in women taking OC steroids results from increased glucuronidation of the drug, although the mechanism is not known.

Inhibition of caffeine elimination by short-term ethanol administration

Short-term ethanol ingestion has been shown to inhibit the metabolism of a number of drugs metabolized by cytochrome P-450 in both man and laboratory animals. However, the effects of short-term ethanol administration on the metabolism of cytochrome P-448-dependent drugs in man is unknown. Caffeine is a commonly used drug that is metabolized predominantly by a component of the hepatic microsomal mixed-function oxidase complex, known as cytochrome P-448. Therefore the elimination of caffeine given orally was studied in normal volunteers after receiving either orange juice or 0.8 gm/kg ethanol as a 25% solution in orange juice. Short-term administration of ethanol resulted in a significant decrease in the plasma clearance of caffeine from 96.6 +/- 13.4 ml/min to 60.7 +/- 10.5 (mean +/- S.E., p less than 0.05). There was also a corresponding significant increase in the elimination half-life of caffeine from 4.03 +/- 0.52 hr to 6.04 + 0.73 (mean + S.E., p less than 0.01). To determine whether the decrease in caffeine elimination was due to an inhibition of caffeine metabolism by ethanol or to an effect on caffeine absorption, caffeine disposition was studied in four healthy, mongrel dogs after intravenous administration. Each animal served as its own control. Caffeine clearance decreased significantly from a baseline value of 19.6 +/- 1.5 ml/min to 8.0 +/- 1.5 (mean +/- S.E., p less than 0.05) after administration of 3.0 gm/kg ethanol given orally 1 hr before intravenous caffeine injection. These results imply that short-term administration of ethanol inhibits the metabolism of caffeine, a predominantly cytochrome P-448-dependent substrate, in both man and dogs.

Differential effects of oral contraceptive steroids on the metabolism of benzodiazepines

The effects of oral contraceptive steroids (OCS) on the disposition and elimination of lorazepam, oxazepam, and chlordiazepoxide were examined. Lorazepam and oxazepam are metabolized via glucuronidation while chlordiazepoxide is metabolized by oxidation in the liver. The disposition and elimination of lorazepam, oxazepam, and chlordiazepoxide was studied in females not taking OCS and females taking OCS (norethindrone acetate, 1 mg; ethinyl estradiol, 50 micrograms) for 6 months or more. The t1/2 (beta) for lorazepam was significantly reduced in women taking OCS (6.0 +/- 3.1 vs. 14.0 +/- 6.2 hr) (p less than 0.005) as compared to controls, and the t1/2 (beta) for oxazepam was reduced in women taking OCS (7.71 +/- 3.23 vs. 12.09 +/- 5.08 hr) as compared to controls, but did not reach statistical significance. The plasma clearance of both lorazepam and oxazepam was significantly increased in women taking OCS [(288.9 +/- 165.9 vs. 77.5 +/- 3.29 ml per min) (p less than 0.01) and (251.2 +/- 106.9 vs. 97.86 +/- 69.4 ml per min) (p less than 0.01), respectively] as compared to controls. The volumes of distribution of lorazepam and oxazepam were significantly increased in women taking OCS (p less than 0.05) while plasma binding of these drugs was similar in both groups. In contrast, the t1/2 (beta) of chlordiazepoxide was significantly prolonged (20.58 +/- 8.08 vs. 11.63 +/- 5.91 hr) (p less than 0.05), and the plasma clearance was significantly reduced (13.41 +/- 4.69 vs. 33.22 +/- 12.37 ml per min) (p less than 0.05) in the OCS group as compared to controls. The volumes of distribution of chlordiazepoxide were similar in both groups, and the plasma binding of chlordiazepoxide tended to be lower in the OCS group but did not reach statistical significance. We conclude that OCS exert a differential effect on the elimination of benzodiazepines, whereby oxidation of chlordiazepoxide is impaired while the glucuronidation of lorazepam and oxazepam is enhanced by OCS.

Differential effects of chronic ethanol feeding on cytochrome P-448- and P-450-mediated drug metabolism in the rat

The effects of chronic ethanol feeding on cytochrome P-448- and P-450-mediated drug metabolism have been studied both in vivo and in vitro in the rat, using caffeine, phenacetin, antipyrine and aminopyrine as test substrates. N-Demethylation of aminopyrine (P-450 mediated) was increased both in vivo and in vitro in rats after chronic ethanol feeding (P less than 0.05) whereas in vivo N-demethylation of caffeine and O-dealkylation of phenacetin (P-448 mediated) were unchanged in the same animals. N-Demethylation of antipyrine was increased by both phenobarbital and 3-methylcholanthrene pretreatment and by chronic ethanol feeding (P less than 0.05), possibly due to cytochrome P-450 induction. Furthermore, the Michaelis affinity constants, Km, for hepatic microsomal aminopyrine N-demethylase and antipyrine N-demethylase were lower in chronic ethanol-fed animals (P less than 0.05), suggesting a qualitative change in the enzymes resulting in greater substrate affinity. These findings suggest a differential effect of chronic ethanol feeding on the induction of cytochrome P-450- and cytochrome P-448 mediated drug metabolism, with a greater effect on the former microsomal system.

Inhibition of microsomal drug metabolism by histamine H2-receptor antagonists studied in vivo and in vitro in rodents

Cimetidine has been demonstrated to impair microsomal oxidative drug metabolism in a dose-dependent manner in an animal model. The inhibition has also been shown to be rapid, occurring after a single dose. In the present study we demonstrate that recovery from inhibition after cimetidine withdrawal is also rapid, occurring within 24 h. Furthermore, chronic dosing with cimetidine does not result in tolerance to the inhibitory effect. Other H2-antihistamines have also been studied both in vivo and in vitro. Based on spectral binding changes, in vitro enzyme assays and in vivo aminopyrine breath tests, ICI 125,211, ranitidine, and cimetidine sulfoxide are much less inhibitory than cimetidine. The ability of cimetidine to impair the elimination of aminopyrine in the mouse after acute liver damage was greater than in the normal mouse.

The effects of variation in dietary protein and ethanol on hepatic microsomal drug metabolism in the rat

The effect of chronic ethanol consumption and variations in dietary protein content on microsomal drug metabolism were studied in rats pair-fed liquid diets containing 10, 20, ro 30% dietary protein with or without ethanol. In vitro drug metabolism was measured by aminopyrine breath tests and aminopyrine blood elimination kinetics. In vitro drug metabolism was assessed by measuring aminopyrine N-demethylase activity in the hepatic microsomal fraction. The rate of elimination of aminopyrine in vivo was increased in all ethanol-fed animals (p less than 0.05) regardless of the protein content of the diet. Animals receiving 10 or 20% protein diets with ethanol showed a 36% increase in drug elimination over pair-fed controls as compared to a 17% increase in drug elimination over controls in animals receiving 30% protein diets. Microsomal aminopyrine N-demethylase activities were similar in ethanol/fed animals and pair-fed controls. Cytochrome P-450 content was increased in all ethanol-fed animals (p less than 0.05) but the increase was not dependent on dietary protein content. These results indicate that the effect of chronic ethanol feeding in enhancing drug metabolism in vivo is influenced by the dietary protein content.