Historical aspects of glutathione and cancer chemotherapy

This presentation sets in historical context the impact of glutathione and its metabolism upon the efficacy of several anticancer drugs. The basic biochemistry of the tripeptide is reviewed briefly, highlighting its role in oxido-reduction and in the gamma-glutamyl cycle. The ability of selective modulators of glutathione metabolism, such as buthionine sulfoximine, as adjuncts to chemotherapy is also discussed.

The absorption of bismuth and salicylate from oral doses of Pepto-Bismol (bismuth salicylate)

Plasma bismuth and plasma salicylate concentrations were measured before and after three 30-ml oral doses of bismuth salicylate (Pepto-Bismol liquid) in 10 fasting healthy subjects. From 0 to 120 min following the first dose of bismuth salicylate, the plasma bismuth concentration was less than 1 ng/ml. The peak median plasma bismuth concentration was at +240 min (1.7 ng/ml; range 0.8-5.3 ng/ml). Salicylate appeared in the plasma of all subjects at +30 min, and it reached a peak at +120 min (median 61 mg/L; range 46-104 mg/L). The study demonstrates that, despite rapid and substantial absorption of salicylate, there is negligible absorption of bismuth into the bloodstream from standard oral doses of bismuth salicylate.

Intravenous albumin infusion is an effective therapy for hyponatraemia in cirrhotic patients with ascites

The treatment of moderate to severe hyponatraemia in patients with decompensated liver disease is unsatisfactory. We report our preliminary experience using intravenous infusion of albumin to treat this condition. Three patients with cirrhosis, ascites, and hyponatraemia responded satisfactorily to treatment; one patient with fulminant hepatitis B did not respond. Intravenous albumin infusion is a safe and effective therapy for patients with cirrhosis complicated by hyponatraemia. Its main role may be in preparing patients for surgery, particularly liver transplantation.

Plasma fibrinogen levels in stroke

Plasma fibrinogen levels were estimated in 56 patients of stroke, admitted in the hospital within 24 hours of symptoms. The levels were found to be raised significantly (531.73 +/- 74 mg%) compared to those of the age and sex matched control group (445.78 +/- 92.28 mg%). When the levels in stroke group with one risk factor were compared to those of individuals with comparable control group with same risk factor, a significant difference was observed in hypertensive, smokers, alcoholics and atherosclerotic stroke groups, which indicates that the observed rise is related to phenomenon of stroke rather than the associated risk factors. However, the rise observed in hypertensive stroke group (554.26 +/- 47.08 mg%) is significantly more (p. less than 0.01) than that occurring for nonhypertensive stroke group (497.82 +/- 93.12 mg%) indicating that the presence of hypertension does contribute to the rise.

Effect of device length and background doping on the relative magnitudes of phase and amplitude modulation in GaAs/AIGaAs PIN multiple quantum well waveguide optical modulators: erratum

This erratum Letter points out an error in the caption of Fig. 4 of this paper.

Intracellular metabolites of cisplatin in the rat kidney

The appearance of low-molecular-weight metabolites of cisplatin in the cytosol of cells from the cortex and outer medulla of the rat kidney has been examined using HPLC up to 24 h following cisplatin administration. Comparison was made between these metabolites and those present in plasma, urine and liver. The effect of sodium chloride (NaCl) pretreatment, which is known to reduce cisplatin-induced nephrotoxicity, on these metabolites was also investigated. Platinum levels in the kidney cortex and medulla and the cytosol reached maximal levels within 1 h of i.p. injection of 5 mg/kg cisplatin. At least six platinum species, including cisplatin, were present 1 h post-dosing, with the principal species being the parent drug; all of these species were either neutral or negatively charged. Although the concentration of most of the platinum species fell with time, that of one species eluting before cisplatin rose, and by 24 h it was the major metabolite. Cisplatin and two other major cytosolic platinum species were also present in urine and plasma, both of which also contained a number of charged species that were absent from the cytosol. The liver cytosol contained at least five metabolites 1 h post-dosing, but, in contrast to the kidney cytosol at the same time, the predominant species was that eluting before cisplatin and not cisplatin itself. One of the metabolites in the cytosol and urine had the same retention time as an adduct of cisplatin with glutathione and with cysteine. Urinary samples also contained a metabolite coeluting with aquated cisplatin. Pretreatment of animals with NaCl significantly reduced the platinum concentration in the kidney, with a corresponding decrease in the cytosolic metabolites; this may have contributed significantly to the reduction in cisplatin-induced nephrotoxicity after NaCl pretreatment. NaCl also significantly reduced a possible aquated species present in the urine, which may also have contributed to the reduction in nephrotoxicity. The data suggest that cisplatin itself may be the nephrotoxic species, since it is the intracellular platinum compound present in highest concentration during the early critical period after its administration.

Effect of device length and background doping on the relative magnitudes of phase and amplitude modulation in GaAs/AIGaAs PIN multiple quantum well waveguide optical modulators

In this paper we present a model for the behavior of a PIN waveguide optical modulator utilizing the quantum confined Stark effect. The model uses experimental data to determine the electric field dependence of absorption coefficient and refractive index changes in 100-A GaAs/100-A Al(0.3)Ga(0.7)As quantum wells, and then uses these data to model a symmetric waveguide structure with a core full of quantum wells. We have determined general design rules for the background doping and length of low chirp amplitude modulators and phase modulators with low amplitude modulation. The chief results are that the doping should be high for an amplitude modulator and low for a phase modulator, and in both cases the device should be kept short.

Inhibition of platelet aggregation by abnormal high density lipoprotein particles in plasma from patients with hepatic cirrhosis

ADP-induced aggregation of normal washed platelets was measured by nephelometry in the presence of plasma high density lipoprotein (HDL) from normal subjects and from 30 patients with hepatic cirrhosis. HDL, at one-eighth of its plasma concentration, inhibited platelet aggregation; the effect of cirrhotic HDL (40% [SD 29%] inhibition) was significantly greater than that of normal HDL (16% [11%]). The mean apolipoprotein E content of cirrhotic HDL was significantly higher than that of normal HDL, and strongly inhibitory HDL contained twice as many apolipoprotein-E-rich particles as weakly inhibitory HDL. Inhibition of platelet aggregation was correlated with the apolipoprotein E content of HDL from patients with cirrhosis.

Implementing RECONSIDER, a diagnostic prompting computer system, at the Georgetown University Medical Center

RECONSIDER, a computer program for diagnostic prompting developed at the University of California, San Francisco, has been implemented at the Georgetown University Medical Center as part of the Integrated Academic Information Management System Model Development grant project supported by the National Library of Medicine. The system is available for student use in the Biomedical Information Resources Center of the Dahlgren Memorial Library. Instruction on use of the computer system is provided by the library and instruction on medical use of the knowledge base is directed by the faculty. The implementation, capabilities, enhancements such as the addition of Current Medical Information and Terminology (5th ed.), and evaluation of the system are reported.

Three-terminal noninverting optoelectronic logic device

A novel noninverting optoelectronic logic device using a GaAs/AlGaAs multiple-quantum-well modulator is demonstrated that combines electronic nonlinearity with optical input and output and is bistable. The device is bistable but displays hard limiting and an optical gain of 12.

Optical properties of (Al,Ga)As/GaAs multiple quantum well planar waveguides and the fabrication of single-mode rib waveguides and directional couplers by reactive ion etching

An anisotropic absorption edge was observed in an (Al,Ga)As/GaAs multiple quantum well double-heterostructure (MQW-DH) single-mode planar optical waveguide. Single-mode rib waveguides and directional couplers were fabricated by SiCl(4) reactive ion etching. The results were found to be consistent with the assumption that the refractive index of the MQW structure for TE propagation is given by the weighted rms average value of the refractive indices of the constituent layers.

Endogenous C19-steroids and oestradiol levels in human primary breast tumour tissues and their correlation with androgen and oestrogen receptors

Endogenous levels of testosterone, 5 alpha-dihydrotestosterone (5 alpha-DHT), androstenedione and oestradiol as well as levels of androgen (AR) and oestrogen (ER) receptors were measured in human primary breast tumour samples. The purification procedure developed allowed simultaneous quantitation of the four steroids, by radioimmunoassay, in small samples with adequate precision, sensitivity and accuracy. The majority of the tumours analysed contained detectable levels of the four steroids in the homogenate or cytosol fractions. There was no significant correlation between steroid content of the tissue and the age of the patient for any of the four steroids. A positive correlation (r = 0.71) was found between the levels of 5 alpha-DHT and testosterone in tumours. In general, tissue steroid concentrations decreased with an increase in dedifferentiation. Fifty-two per cent of the tumours analysed for receptor content were found to be ER positive, and a similar proportion were AR positive. No relationship was observed between AR status and age although receptor concentration was significantly (P = 0.004) higher in post-menopausal women when only receptor positive tumours were evaluated. The mean values for AR and ER were higher in tumours containing both receptors than in tumours showing either receptor alone; there was, however, no significant relationship between concentrations of the two receptors. No correlation was observed between tumour AR or ER status and any of the four steroids measured in either fraction. In addition, the ratio between the combined levels of 5 alpha-DHT and testosterone compared to oestradiol in the same tumour, only showed a maximum value of 40. Thus, in vivo these two androgens are unlikely to influence oestrogen action in human primary breast tumours by interfering with the association of oestradiol with its receptor.

A low molecular weight lead-binding protein in brain attenuates lead inhibition of delta-aminolevulinic acid dehydratase: comparison with a renal lead-binding protein

A low molecular weight high-affinity lead-binding protein (PbBP) in kidney appears to account, at least in part, for the relative insensitivity of renal delta-aminolevulinic acid dehydratase (ALAD) to Pb inhibition. A PbBP is also known to exist in brain cytosol but is not a major Pb-binding constituent in liver. This study was undertaken to examine the relative sensitivity of brain and liver ALAD to Pb inhibition in vitro and to determine if inhibition of hepatic ALAD by Pb could be reversed by addition of partially purified brain PbBP to liver cytosol. This effect was also compared with that of a previously described renal PbBP. Finally, the mechanism(s) of reversal of Pb inhibition of ALAD by these tissue-specific PbBPs were studied. A concentration-dependent reversal of Pb-induced inhibition of hepatic ALAD activity was observed for both brain and kidney PbBPs. Inhibition of hepatic ALAD activity by 0.1 to 1.6 microM Pb was partially reversed by a single concentration of brain PbBP. No differences in sensitivity of ALAD to Pb inhibition in various brain regions were observed. Kinetic analysis of both brain and liver ALAD activity at an IC50 Pb showed a "mixed" or noncompetitive inhibition pattern. Addition of brain PbBP reduced markedly the inhibitory effects of Pb on the Vmax of the liver enzyme. Incubation of 65Zn-labeled PbBP fractions from brain and kidney with purified bovine liver ALAD demonstrated that the PbBPs donate Zn to ALAD.(ABSTRACT TRUNCATED AT 250 WORDS)

In vivo oestrogenicity and binding characteristics of alpha-zearalanol (P-1496) to different classes of oestrogen binding proteins in rat liver

It is now well established that the mycotoxin zearalenone and some of its derivatives possess oestrogenic activity. In the present study, the binding characteristics of [3H]zearalanol (P-1496) to different classes of sites including [1] the oestrogen receptor, [2] the higher capacity lower affinity (HCLA) sites, [3] the antioestrogen sites and [4] a new class of binding sites apparently specific for P-1496 were examined in rat liver. Analysis of the binding by sucrose density gradient centrifugation confirmed that P-1496 binds to the oestrogen receptor but not to the higher capacity lower affinity sites for oestradiol-17 beta. Furthermore, saturation experiments using partially-purified fractions showed that P-1496 binds to the oestrogen receptor with an affinity very similar to that of oestradiol-17 beta (apparent dissociation constants ranged from 0.1-0.3 nM). Competition studies using partially purified cytosolic oestrogen receptor suggested that P-1496 binds to a second high affinity site distinct from the oestrogen receptor. This binding site was further characterized as selective for P-1496 by saturation analysis following the complete occupancy of oestrogen receptor by oestradiol-17 beta. The in vitro binding characteristics of P-1496 were then compared with in vivo effects on concentrations of serum triglycerides. Treatment of ovariectomized female rats daily with 1.5 or 2 mg P-1496/kg body weight resulted in marked increases in the concentrations of serum triglycerides associated with the very low density lipoprotein (VLDL) fraction. Dose-response studies indicated that there was no sex difference with respect to the dose necessary to produce significant increases in serum triglycerides. The present study shows striking similarities between the binding of P-1496 and oestradiol-17 beta to liver oestrogen receptor in vitro. However, differences are observed with respect to their binding to other cytoplasmic components of liver. In addition, although P-1496 is capable of eliciting in vivo oestrogenic effects in liver, it is much less potent than oestradiol-17 beta.

High-affinity lead binding proteins in rat kidney cytosol mediate cell-free nuclear translocation of lead

The PbII binding characteristics of the previously reported (Oskarsson et al., 1982) PbII binding proteins of rat kidney cytosol were investigated further. Saturation and Scatchard analysis of 203Pb binding in whole cytosol and in 40% saturated ammonium sulfate precipitated fractions disclosed a class of relatively high-affinity sites with an apparent Kd of approximately 50 nM and binding capacities of approximately 41 and 9 pmol/mg of protein, respectively. Two 203Pb binding proteins with approximate molecular masses of 63K and 11.5K daltons and a high molecular weight component (greater than 200K) were isolated by Sepharose-6B column chromatography. The time course of association of 203Pb with cytosol and the 63K protein showed maximum binding at 18 hr which was stable up to 25 hr at 4 degrees C. The approximate half-time dissociation rate (T 1/2) of specifically bound 203Pb to the 63K protein was 100 min at 4 degrees C whereas the 11.5K protein showed little dissociation of specifically bound ligand at this temperature. Saturation analysis of the three isolated proteins disclosed low capacity, high-affinity sites with similar apparent Kd values to the cytosol assay. Sucrose density gradient analysis of kidney cytosol showed approximate sedimentation coefficients of 2S, 4.6S and 7S for the 11.5K, 63K and the high molecular weight proteins, respectively. Competitive binding studies with cytosol demonstrated displacement of 203Pb by PbII, CdII and ZnII ions but not CaII ions.(ABSTRACT TRUNCATED AT 250 WORDS)

Abnormal high density lipoproteins from patients with liver disease regulate cholesterol metabolism in cultured human skin fibroblasts

Apolipoprotein B (apoB) of plasma low density lipoproteins (LDL) binds to high affinity receptors on many cell types. A minor subclass of high density lipoproteins (HDL), termed HDL1, which contains apoE but lacks apoB, binds to the same receptor. Bound lipoproteins are engulfed, degraded, and regulate intracellular cholesterol metabolism and receptor activity. The HDL of many patients with liver disease is rich in apoE. We tested the hypothesis that such patient HDL would reduce LDL binding and would themselves regulate cellular cholesterol metabolism. Normal HDL had little effect on binding, uptake, and degradation of 125I-labeled LDL by cultured human skin fibroblasts. Patient HDL (d 1.063-1.21 g/ml) inhibited these processes, and in 15 of the 25 samples studied there was more than 50% inhibition at 125I-labeled LDL and HDL protein concentrations of 10 micrograms/ml and 25 micrograms/ml, respectively. There was a significant negative correlation between the percentage of 125I-labeled LDL bound and the apoE content of the competing HDL (r = -0.54, P less than 0.01). Patient 125I-labeled HDL was also taken up and degraded by the fibroblasts, apparently through the LDL-receptor pathway, stimulated cellular cholesterol esterification, increased cell cholesteryl ester content, and suppressed cholesterol synthesis and receptor activity. We conclude that LDL catabolism by the receptor-mediated pathway may be impaired in liver disease and that patient HDL may deliver cholesterol to cells.

Individual variation in the effects of dietary cholesterol on plasma lipoproteins and cellular cholesterol homeostasis in man. Studies of low density lipoprotein receptor activity and 3-hydroxy-3-methylglutaryl coenzyme A reductase activity in blood mononuclear cells

The effects of dietary cholesterol on plasma lipoproteins and cholesterol homeostasis in blood mononuclear cells have been examined in healthy adults. Addition of 1,500 mg of cholesterol to the daily diet of 37 subjects for 14 d was associated with a wide range of response of plasma total cholesterol concentration (from -6 to +75 mg/dl; mean change, +29 mg/dl; P < 0.001). Increases in plasma cholesterol reflected increased cholesterol concentrations in intermediate density lipoprotein (IDL; 1.006-1.019 g/ml), low density lipoprotein (LDL; 1.019-1.063 g/ml), and the HDL(2) subclass (1.063-1.125 g/ml) of high density lipoprotein, which on average accounted for 20, 58, and 22%, respectively, of the total increment. Similar responses occurred in 14 other subjects given 750 mg cholesterol per day for 28 d. Plasma apolipoprotein B concentrations in IDL and LDL also increased. THESE EFFECTS ON PLASMA LIPOPROTEINS WERE ACCOMPANIED BY THREE CHANGES IN FRESHLY ISOLATED BLOOD MONONUCLEAR CELLS: (a) an increase in cell cholesterol content (mean change, +17%; P < 0.01); (b) suppression of 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase activity (-32%; P < 0.001); and (c) reduction of LDL receptor activity (-74%; P < 0.01), quantified as the rate of degradation of (125)I-LDL to noniodide trichloroacetic acid-soluble material. These results provide the first direct evidence for the modulation of LDL receptor activity and HMG CoA reductase activity in a peripheral cell type in response to a dietary perturbation of human lipoprotein metabolism.The percentage increase in LDL cholesterol was negatively correlated with the percentage decrease in HMG CoA reductase activity (r = -0.49, P < 0.01). An additional negative correlation existed between the increment in plasma cholesterol concentration and the capacity of cells to degrade (125)I-LDL after derepression by preincubation for 72 h in lipoprotein-deficient medium (r = -0.74, P < 0.001). Thus, differences between individuals in the responses of the plasma lipoproteins to dietary cholesterol appear to be related in part to differences in the capacity of peripheral cells to catabolize LDL and to down-regulate cholesterol synthesis.

Splanchnic production of discoidal plasma high-density lipoprotein in man

The morphology of human plasma high-density lipoprotein (H.D.L.) subfractions in arterial and hepatic venous blood from seven human subjects was investigated by electron microscopy. The H.D.L.3 subclass from both sources and the H.D.L.2 subclass from arterial blood were composed of spherical particles, identical with normal human peripheral venous H.D.L. In contrast, H.D.L.2 isolated from hepatic venous blood was composed of a mixture of spherical and discoidal particles. The latter tended to form rouleaux, and had a diameter similar to that of nascent H.D.L. particles obtained from the peripheral venous blood of a patient with lecithin: cholesterol acyltransferase deficiency. This supports the view that nascent H.D.L. is secreted into the splanchnic bed in man.

The effects of cisplatin on the concentration of protein thiols and glutathione in the rat kidney

The effect of a nephrotoxic dose of cisplatin (5 mg/kg) on the concentrations in the rat kidney of both glutathione and protein-bound thiols was investigated. Total glutathione and oxidised glutathione were measured in the cortex and outer medulla using specific enzyme-based assays. The high-molecular-weight thiols were quantified in cells of the proximal tubule using a cyto-chemical technique. The concentration of total glutathione (oxidised and reduced) in the kidney cortex and outer medulla was significantly higher than that of controls at 1 h following cisplatin administration. The amount by which the concentration in treated animals exceeded that in controls increased to 50% at 72 h and remained significantly elevated for 120 h following treatment. This increase was mainly attributable to an increase in the concentration of reduced glutathione. In contrast, the concentration of protein thiols in the proximal tubules decreased significantly at 8 h after dosing, reaching a nadir 29% below that of controls at 120 h, thus coinciding with the maximal functional disturbance in the kidney as reflected by the concentration of blood urea. The decrease in protein thiols could not be correlated stoichiometrically with the platinum concentration in the cortex and outer medulla, which reached a peak of 16.3 +/- 0.3 micrograms/g wet tissue at 72 h after treatment. Evidently cisplatin perturbs the equilibrium that is said to exist between the concentration of reduced glutathione and that of protein thiols. This perturbation occurs well before the onset of overt functional disturbance of the kidney and is evident before the point at which the damage to the kidney caused by cisplatin becomes irreversible.