Cytotoxic effect of plant polyphenols and fat-soluble vitamins on malignant human cultured cells

In vitro studies showed that several flavonoids, tannic acid, gallic acid and fat-soluble vitamins inhibited HeLa and Raji lymphoma cell growth. The inhibition trend exhibited by these compounds was similar for both cell lines, and their growth was inhibited dose dependently. Butein, (10 microM), the most potent anti-proliferative agent, exerted 30% growth inhibition and was more effective on HeLa cells. Retinol (100 microM) inhibited cell proliferation completely. Tannic acid was twice as potent as its monomer gallic acid. From structure-activity consideration, the C2,3-double bond of the flavonoid molecule was important for activity. Flavonoid aglycones were more effective than their corresponding glycosides in suppressing cell growth.

Physiological pharmacokinetic modeling of inhaled trichloroethylene in rats

The pharmacokinetics of trichloroethylene (TCE) was characterized during and following inhalation exposures of male Sprague-Dawley rats. The blood and exhaled breath TCE time-course data were used to formulate and assess the accuracy of predictions of a physiologically based pharmacokinetic (PB-PK) model for TCE inhalation. Fifty or 500 ppm of TCE was inhaled by unanesthetized rats of 325-375 g for 2 hr through a miniaturized one-way breathing valve. Repetitive samples of the inhaled and exhaled breath streams, as well as arterial blood, were collected concurrently during and for 3 hr following the exposures and analyzed for TCE by headspace gas chromatography. Respiratory rates and volumes were continuously monitored and used in conjunction with the pharmacokinetic data to delineate uptake and elimination profiles. Levels of TCE in the exhaled breath attained near steady-state soon after the beginning of exposures, and were then directly proportional to the inhaled concentration. Exhaled breath levels of TCE in rats were similar in magnitude to values previously published for TCE inhalation exposures of humans. Levels of TCE in the blood of the 50 ppm-exposed animals also rapidly approached near steady-state, but blood levels in the 500 ppm-exposed animals rose progressively, reaching concentrations 25- to 30-fold higher than in the 50 ppm group during the second hour of exposure. The 10-fold increase in inhaled concentration resulted in an 8.7-fold increase in cumulative uptake, or total absorbed dose. These findings of nonlinearity indicate that metabolic saturation ensued during the 500 ppm exposure. The PB-PK model was characterized as blood flow-limited with TCE eliminated unchanged in the exhaled breath and by saturable liver metabolism. The uptake and elimination profiles were accurately simulated by the PB-PK model for both the 50 and 500 ppm TCE exposure levels. Such a model may be quite useful in risk assessments in predicting internal (i.e., systemically absorbed) doses of TCE and other volatile organics under a variety of exposure scenarios.

Effect of mechanical ventilation and barotrauma on pulmonary clearance of 99mtechnetium diethylenetriamine pentaacetate in lambs

We studied the effect of positive pressure mechanical ventilation on the pulmonary clearance (k) of 99mtechnetium diethylenetriamine pentaacetate (99mTc-DTPA) in lambs. Twelve lambs were anesthetized and ventilated with air at 25 breaths/min and with end expiratory airway pressure at 2 cm H2O for a minimum period of 8 h. Four lambs received normal pressure ventilation with peak airway pressure at 17 +/- 3 cm H2O and eight received high pressure ventilation with peak airway pressure at 41 +/- 2 cm H2O. Three 99mTc-DTPA clearance studies were done in each lamb; at the start and after 4 and 8 h of mechanical ventilation. All clearance measurements were made at normal peak airway pressure 16 +/- 3 cm H2O. Baseline clearance rate, k, (n = 12) was 1.2 +/- 0.5% (SD). During normal pressure ventilation, k increased from 1.0 +/- 0.5 to 2.2 +/- 0.8% after 4 h and to 2.7 +/- 0.8% after 8 h. During high pressure ventilation, k increased from 1.4 +/- 0.4 to 3.6 +/- 1.3% after 4 h and to 4.8 +/- 1.2% after 8 h. To see if 8 h of mechanical ventilation was associated with other evidence of lung epithelial injury, we determined the movement of I125 labeled albumin from the interstitium into the airspace, lung water content, lung histology, and lung lavage constituents in the lambs at the end of the study. All variables were similar between ventilated and four unventilated lambs, except the percentage of alveolar macrophages recovered by lavage, which was more in the ventilated lambs.(ABSTRACT TRUNCATED AT 250 WORDS)

Oral toxicity of 1,2-dichloropropane: acute, short-term, and long-term studies in rats

The objective of this investigation was to characterize the acute and short- and long-term toxic potency of orally administered 1,2-dichloropropane (DCP). In the acute and short-term studies, male rats of 250-300 g were gavaged with 0, 100, 250, 500, or 1000 mg DCP/kg in corn oil once daily for up to 10 consecutive days. Although ingestion of DCP caused body weight loss and CNS depression, few other toxic effects were manifest 24 hr after a single dose of the chemical. Morphological changes were limited to liver centrilobular cells in 500 and 1000 mg/kg rats. Similarly, elevated activity of some serum enzymes occurred only at these two highest dose levels. Hepatic nonprotein sulfhydryl (NPS) levels were decreased and renal NPS levels increased at 24 hr. In the short-term study resistance developed to DCP hepatotoxicity over the 10 consecutive days of exposure, as reflected by progressively lower serum enzyme levels and by decreases in the severity and incidence of toxic hepatitis and periportal vacuolization. Nucleolar enlargement in hepatocytes, however, was observed at all dosage levels at 5 and 10 days. There were a number of manifestations of hemolytic anemia, including erythrophagocytosis in the liver, splenic hemosiderosis and hyperplasia of erythropoietic elements of the red pulp, renal tubular cell hemosiderosis, and hyperbilirubinemia. Urinalyses and histopathology revealed no evidence of nephrotoxicity. In the long-term study, male rats initially weighing 180-200 g were gavaged five times weekly for up to 13 weeks with 0, 100, 250, 500, or 750 mg DCP/kg. As over one-half the 750 mg/kg group died within 10 days, the survivors were sacrificed. Histopathological changes in the 750 mg/kg animals included mild hepatitis and splenic hemosiderosis, as well as adrenal medullary vacuolization and cortical lipidosis, testicular degeneration and a reduction in sperm, and increased number of degenerate spermatogonia in the epididymis in some members of the group. Similar testicular and epididymal degenerative change also were observed in some 500 mg/kg animals after 13 weeks of dosing. There was a progressive increase in the number of deaths in the 500 mg/kg group, such that more than 50% were dead by 13 weeks. No deaths occurred in the 100 or 250 mg/kg groups. The DCP dosage regimen also produced a dose-dependent decrease in body weight gain. DCP exhibited very limited hepatotoxic potential and no apparent nephrotoxic potential in the long-term study. Slight elevations in serum ornithine-carbamyltransferase activity, periportal vacuolization, and active fibroplasia in the liver were seen in the 500 mg/kg animals.

The uptake and elimination of 1,1,1-trichloroethane during and following inhalation exposures in rats

The pharmacokinetics of 1,1,1-trichloroethane (TRI) was studied in male Sprague-Dawley rats in order to characterize and quantify TRI uptake and elimination oby direct measurements of the inhaled and exhaled compound. Fifty or 500 ppm TRI was inhaled for 2 hr through a one-way breathing valve by unanesthetized rats of 325-375 g. Repetitive samples of the separate inhaled and exhaled breath streams, as well as arterial blood, were collected concurrently both during and following TRI inhalation and analyzed for TRI by gas chromatography. Respiratory rates and volumes were continuously monitored during and following exposure and were used in conjunction with the pharmacokinetic data to characterize profiles of uptake and elimination. TRI was very rapidly absorbed from the lung, in that substantial levels were present in arterial blood at the first sampling time (i.e., 2 min). Blood and exhaled breath concentrations of TRI increased rapidly after the initiation of exposure, approaching but not reaching steady state during the 2-hr exposures. The blood and exhaled breath concentrations were directly proportional to the exposure concentration during the exposures. Percentage uptake of TRI decreased 30-35% during the first hour of inhalation, diminishing to approximately 45-50% by the end of the exposure. Total cumulative uptake in the 50 and 500 ppm groups over the 2-hr inhalation exposures was determined to be 6 and 48 mg/kg body wt, respectively. By the end of the exposure period, 2.1 and 20.8 mg, respectively, of inhaled TRI was eliminated from rats inhaling 50 and 500 ppm TRI. A physiological pharmacokinetic model for TRI inhalation was utilized to predict blood and exhaled breath concentrations for comparison with observed experimental values. Overall, values predicted by the physiological pharmacokinetic model for TRI levels in the blood and exhaled breath were in close agreement with measured values both during and following TRI inhalation.

Effect of hematocrit on microvascular pressures in 3- to 5-wk-old rabbit lungs

To examine the effects of blood hematocrit (Hct) and apparent viscosity on the pulmonary microcirculation, we studied 30 isolated, perfused 3- to 5-wk-old rabbits with varying perfusate Hct. We partitioned total vascular resistance by measuring pulmonary artery and left atrial pressures and by micropuncture the pressures in the subpleural microcirculation in 20-40 microns diameter arterioles, 20-40 microns venules, and 250-300 microns venules. To prevent active vasomotion and changes in vessel geometry, we paralyzed the vasculature with papaverine hydrochloride. We studied four groups of lungs: group I (n = 7) with low Hct (17.8 +/- 2.4%); group II (n = 9) with medium Hct (46.8 +/- 8.2%); group III (n = 6) with high Hct (74.4 +/- 5.8%); and group IV (n = 8) with both low and high Hct perfusates. Lungs were perfused at constant flow (80 +/- 4 ml.kg body wt-1.min-1) in zone 3, airway and venous pressures being 6 and 8 cmH2O, respectively. We found that in lungs perfused with low Hct, approximately 52% of the total resistance was in arteries, approximately 25% in microvessels, and approximately 21% in small veins, with very little resistance in large veins. With an increase in perfusate hematocrit and apparent viscosity, total pulmonary vascular resistance increased mainly because of an increase in resistance in arteries and small veins, with little change in resistance in microvessels and large veins.

Effect of cell substrate on antioxidant enzyme activities in cultured renal glomerular epithelium

The activities of three antioxidant enzymes, superoxide dismutase, catalase, and glutathione peroxidase, were monitored in isolated guinea pig glomeruli and primary or subcultured glomerular epithelial cells. Cell injury was assessed by morphologic studies and by measurement of cellular lipid peroxidation (levels of malondialdehyde). Antioxidant enzyme activities were very different in cultured cells than in parent glomeruli. The possible effect of culture substrates (tissue culture plastic, bovine corneal endothelial [BCE] cell basement membrane, and PF-HR-9 endodermal cell basement membrane) on antioxidant enzyme status, cell morphology, and lipid peroxidation was also assessed. Glomerular epithelial cells cultured on the BCE cell basement membrane substrate survived longer and showed less lipid peroxidation than cells cultured on plastic or the HR-9 substrate. Cells cultured on a plastic substrate had substantially less glutathione peroxidase activity than cells cultured on either BCE or HR-9 basement membranes.

Blood cultures in neonates with percutaneous central venous catheters

We compared the results of 74 pairs of blood cultures obtained simultaneously every two weeks from a peripheral vein and a percutaneously inserted central venous catheter in 38 newborns. Three babies (7.9%) had bacteraemia. In two of these the central catheter was colonised 48 hours beforehand.

Pulse oximetry in very low birth weight infants with acute and chronic lung disease

With improved survival of very low birth weight infants, the incidence of bronchopulmonary dysplasia has significantly increased. Pulse oximetry appears to be an adequate alternative to transcutaneous PO2, for continuous arterial oxygen saturation (SaO2) monitoring in neonates; however, its usefulness has not been very well documented in very low birth weight infants. We studied 68 patients with birth weight less than 1,250 g; 44 neonates had respiratory distress syndrome and 24 had bronchopulmonary dysplasia. Using a Nellcor N-100 pulse oximeter, we compared transcutaneous oxygen saturation with simultaneous arterial samples analyzed for SaO2 (range 78% to 100%) using an IL 282 co-oximeter. Fetal hemoglobin was measured in 66 patients. We also evaluated the accuracy of transcutaneous PO2 in reflecting arterial PO2 in patients with bronchopulmonary dysplasia. Over a wide range of PO2, PCO2, pH, heart rate, BP, hematocrit, and fetal hemoglobin, linear regression analysis revealed a close correlation between pulse oximeter values and co-oximeter measured SaO2 in patients with acute (r = .88, Y = 19.41 + 0.79X) and chronic (r = .90, Y = 9.72 + 0.92X) disease. Regression analysis of transcutaneous v arterial PO2 in infants with bronchopulmonary dysplasia showed an r value of .78. In addition, in these patients with chronic disease, the mean difference between pulse oximeter SaO2 and co-oximeter measured SaO2 was 2.7 +/- 1.9% (SD); whereas the mean difference between transcutaneous and arterial PO2 was -14 +/- 10.7 mm Hg. Our findings indicate that pulse oximetry can be used reliably in very low birth weight infants with acute and chronic lung disease, for SaO2 values greater than 78%.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of metaproterenol on pulmonary mechanics, oxygenation, and ventilation in infants with chronic lung disease

Changes in pulmonary resistance, dynamic compliance, tidal volume, and transcutaneous PO2 and PCO2 after nebulized administration of metaproterenol were evaluated in eight newborn infants (birth weight 650 to 1060 g, gestational age 25 to 28 weeks) with chronic lung disease receiving mechanical ventilation. The infants were monitored continuously before and for 15 minutes after nebulization of metaproterenol during 3 consecutive days at mean age 34 days. There were significant increases in compliance, tidal volume, and tcPO2, and significant decreases in pulmonary resistance and tcPCO2. These data show that bronchospasm contributes significantly to the high pulmonary resistance in preterm infants with chronic lung disease and that metaproterenol is beneficial in the therapy of infants with chronic lung disease requiring mechanical ventilation.

Pulse oximetry for continuous oxygen monitoring in sick newborn infants

We studied 54 neonates with acute cardiorespiratory illness and 21 infants with bronchopulmonary dysplasia, to evaluate the accuracy of a nonheated pulse oximeter in predicting arterial oxygen saturation (SaO2). We also studied the accuracy of transcutaneous oxygen tension (tcPO2) in estimating arterial oxygen tension (PaO2) in infants with bronchopulmonary dysplasia. We compared pulse oximeter SaO2 with simultaneously measured SaO2 (range 78% to 100%) using a co-oximeter. Over a wide range of values for heart rate, blood pressure, hematocrit, PO2, PCO2, and pH, linear regression analysis revealed a close correlation between in vivo pulse oximeter readings and in vitro SaO2 measurements in patients with acute (r = 0.86, Y = 29.64 + 0.68X) and chronic (r = 0.91, Y = 6.29 + 0.96X) disease. Regression analysis of tcPO2 versus PaO2 showed an r value of 0.76 in infants with bronchopulmonary dysplasia. In these patients the mean difference between pulse oximeter SaO2 and in vitro SaO2 was 2.9% +/- 1.8% (SD), whereas the mean difference between tcPO2 and PaO2 was -14.5 +/- 11.1 mm Hg. Fetal hemoglobin ranged from 4.3% to 95%. We conclude that pulse oximetry is an appropriate alternative to tcPO2 for continuous oxygen monitoring in newborn infants with acute cardiorespiratory illnesses and chronic lung disease.

Prospective evaluation of percutaneous central venous silastic catheters in newborn infants with birth weights of 510 to 3,920 grams

With improved neonatal survival, especially of very low birth weight infants, our efforts should be directed toward reduction of morbidity. Sick preterm infants require total parenteral nutrition for prolonged periods of time due to extreme prematurity and feeding intolerance. However, the use of surgically placed Broviac catheters has been associated with a high complication rate. A prospective study of 53 percutaneous central venous Silastic catheterizations for administration of total parenteral nutrition was performed in 45 newborn infants. At the time of catheter insertion, 37 babies weighted less than 1,500 g and 19 weighed less than 1,000 g. Percutaneous central venous catheters were placed successfully the first time in 50 of 55 attempts. In three babies, insertion was successful on second attempt. The catheters remained in place for 25.4 +/- 16.7 days ([mean +/- SD] range two to 80 days). In babies weighing less than 1,000 g, the catheters remained in place for a longer period of time (34.0 +/- 18.0; range 12 to 80 days). Sixty-six percent of the catheters were removed electively. There were four cases of bacteremia (7.5%), and the overall incidence of mechanical complications was 26.4%. We conclude that percutaneous central venous catheters can be used safely and effectively in newborn infants for prolonged administration of total parenteral nutrition, especially in neonates weighing less than 1,000 g.

Effect of microsomal enzyme inducers on the urinary excretion pattern of mutagenic metabolites of the carcinogen 2,4-toluenediamine

2,4-Toluenediamine [(TDA) CAS: 95-80-7] was administered to rats pretreated with the microsomal enzyme inducers phenobarbital (PB), beta-naphthoflavone (beta NF), or 3-methylcholanthrene (MCA). The 24-hour urines of male F344 rats were examined for their mutagenic potency by means of the Salmonella assay, with the Aroclor 1254-pretreated rat liver S-9 fraction as an activating system. No revertants were found with TDA or its urinary metabolites in the absence of the S-9 fraction. In the presence of S-9, the number of revertants increased as the concentration of TDA or its urinary metabolites increased. The urinary metabolites, generated after the microsomal enzyme inducers (PB, beta NF, MCA), had increased mutagenic activity as compared with the controls (saline, corn oil). In the presence of beta-glucuronidase (beta G), increased numbers of TA98 revertants were noted in the urine of rats pretreated with PB, saline, or corn oil. Addition of sulfatase did not alter the number of TA98 revertants. Conversely, beta G treatment of urine from rats pretreated with MCA or beta NF led to a decrease in the number of TA98 revertants as compared to levels in urine without beta G. Addition of known urinary metabolites of TDA, such as 4-acetylamino-2-aminobenzoic acid or 2,4-diacetylaminobenzoic acid, to beta NF-pretreated rat urine had no inhibitory effect on the mutagenicity in the absence of beta G. However, in the presence of beta G, the inhibitory effect was similar to that noted with beta NF-pretreated rat urine. Upon separation of urinary metabolites (beta NF-pretreated rat urine) into free, conjugated, and water-soluble forms, the maximum number of TA98 revertants was associated with the free ethyl acetate-extractable fraction, which accounted for the total mutagenic activity associated with the original volume of urine. Conjugated metabolites showed much less mutagenic activity, and an inhibitory principle was associated with the water-soluble fraction.

In vitro activation and resultant binding of benzo[a]pyrene to DNA by microsomes from rats fed corn and menhaden oils

Dietary unsaturated fat is required for maximum induction of the hepatic mixed function oxidases (MFO) responsible for activating carcinogens to forms that may bind covalently to DNA. The aim of this study was to assess the influence of dietary fat type and content on the activities of some enzymes involved in activation and detoxification of the carcinogen benzo[a]pyrene (B[a]P). Modification of these changes by pretreatment with phenobarbital (PB) was also evaluated. Male rats were fed diet devoid of fat or containing 20% corn oil (CO) or 20% menhaden fish oil (MO) for 4 days. PB induced soluble glutathione S-transferase, a detoxifying enzyme, only in rats fed dietary fats. Microsomes from rats fed both types of dietary fat had increased levels of cytochrome P-450 (P-450) and PB induced P-450 only in rats fed these fats. Although ethoxycoumarin O-dealkylase was significantly elevated in the MO group, the induction by PB was not dependent on dietary fat type or level. Dietary fat increased microsome-catalyzed in vitro binding of [3H]-B[a]P to calf thymus DNA, especially in response to PB. Menhaden oil depressed B[a]P hydroxylation and PB treatment depressed this activity to the greatest extent in rats fed this diet. When calculated as B[a]P metabolized per unit of P-450, PB seems to induce a P-450 in fat fed animals having lower affinity and capacity for B[a]P hydroxylation and activation than in rats fed the fat-free diet.

Diagnostic value of cytology of voided urine

Cytologic examination of the sediment of voided urine is the only noninvasive method of detection, diagnosis and follow-up of tumors of the bladder and other anatomic components of the lower urinary tract. In order to assess the value of cytology of voided urine, we analyzed the diagnostic yield in 203 episodes, each composed of three sediments of voided urine obtained on consecutive days. For each one of these episodes, histologic material was available and was reviewed. Of special interest were 181 instances of primary or recurrent bladder tumors; in 37 of these patients, random biopsies of the bladder were also available for review. The concept of intraurothelial neoplasia (IUN), graded I, II or III, was introduced to describe degrees of atypia in flat urothelium, with IUN grade III corresponding to nonpapillary carcinoma in situ. The results documented that cytology of voided urine is highly reliable in the diagnosis of high-grade tumors, with a sensitivity of 94.2%. In primary flat carcinoma in situ (IUN III), the sensitivity was 100%. The method failed in the recognition of grade I papillary tumors and in about one-third of grade II tumors. There were no false-positive results in this study. In the 151 positive cases, the cytologic diagnosis was established on the first specimen in 79%, on the second specimen in an additional 14% and on the third specimen in 7% of cases. These results justify the use of three consecutive daily urine specimens for optimal diagnostic results. There is a remarkable similarity between the presence of cancer cells in voided urine and the DNA ploidy of bladder tumors, as established by Tribukait. The observations reported herein suggest that positive urine cytologies may correspond to aneuploid tumors and hence be not only of diagnostic but also of prognostic value. A direct proof of this hypothesis is under investigation; the results of this study justify the need for a field trial of an automated image analysis diagnostic system that was developed in this department.

Characterization and purification of a soluble protein controlling Ca-channel activity in paramecium

The analysis of the voltage-sensitive Ca++ channel of the unicellular eucaryote, Paramecium has been extended to a biochemical level based on recent observations that the transfer of cytoplasm from wild-type cells into mutants lacking Ca++-channel function ("pawn" in P. tetraurelia and "CNR" in P. caudatum) causes mutant cells to regain Ca++-channel function. We have microinjected various cytoplasmic fractions into mutant cells and measured the restored Ca++-channel function using a convenient behavioral assay. Following the "curing" activity, we characterized and purified the component from wild-type cytoplasm that can restore the function missing in cells carrying mutations in the cnrC gene. The curing factor is not an RNA, but a heat-labile, -SH-containing protein that appears to affect existing mutant channels on the ciliary membrane. We have purified this factor over 500-fold from the soluble cytoplasm using conventional techniques. The protein is of low apparent molecular weight (less than 30,000 daltons), acidic, soluble, and does not have the properties of calmodulin.

Biochemical studies of the excitable membrane of paramecium tetraurelia. IX. Antibodies against ciliary membrane proteins

The excitable ciliary membrane of Paramecium regulates the direction of the ciliary beat, and thereby the swimming behavior of this organism. One approach to the problem of identifying the molecular components of the excitable membrane is to use antibodies as probes of function. We produced rabbit antisera against isolated ciliary membranes and against partially purified immobilization antigens derived from three serotypes (A, B, and H), and used these antisera as reagents to explore the role of specific membrane proteins in the immobilization reaction and in behavior. The immobilization characteristics and serotype cross-reactivities of the antisera were examined. We identified the antigens recognized by these sera using immunodiffusion and immunoprecipitation with 35S-labeled ciliary membranes. The major antigen recognized in homologous combinations of antigen-antiserum is the immobilization antigen (i-antigen), approximately 250,000 mol wt. Several secondary antigens, including a family of polypeptides of 42,000-45,000 mol wt, are common to the membranes of serotypes A, B, and H, and antibodies against these secondary antigens can apparently immobilize cells. This characterization of antiserum specificity has provided the basis for our studies on the effects of the antibodies on electrophysiological properties of cells and electron microscopic localization studies, which are reported in the accompanying paper. We have also used these antibodies to study the mechanism of cell immobilization by antibodies against the i-antigen. Monovalent fragments (Fab) against purified i-antigens bound to, but did not immobilize, living cells. Subsequent addition of goat anti-Fab antibodies caused immediate immobilization, presumably by cross-linking Fab fragments already bound to the surface. We conclude that antigen-antibody interaction per se is not sufficient for immobilization, and that antibody bivalency, which allows antigen cross-linking, is essential.

Antibodies to the ciliary membrane of Paramecium tetraurelia alter membrane excitability

Immobilization of Paramecium followed the binding of antibodies to the major proteins of the ciliary membrane (the immobilization antigens, i-antigens, approximately 250,000 mol wt). Immunoelectron microscopy showed this binding to be serotype-specific and to occur over the entire cell surface. Antibody binding also reduced the current through the Ca-channel of the excitable ciliary membrane as monitored using a voltage-clamp. The residual Ca-current appeared normal in its voltage sensitivity and kinetics. As a secondary consequence of antibody binding, the Ca-induced K-current was also reduced. The resting membrane characteristics and other activatable currents, however, were not significantly altered by the antibody treatment. Since monovalent fragments of the antibodies also reduced the current but did not immobilize the cell, the electrophysiological effects were not the secondary consequences of immobilization. Antibodies against the second most abundant family of proteins (42,000-45,000 mol wt) had similar electrophysiological effects as revealed by experiments in which the Paramecia and the serum were heterologous with respect to the i-antigen but homologous with respect to the 42,000-45,000-mol-wt proteins. Protease treatment, shown to remove the surface antigen, also caused a reduction of the Ca-inward current. The loss of the inward Ca-current does not seem to be due to a drop in the driving force for Ca++ entry since increasing the external Ca++ or reducing the internal Ca++ (through EGTA injection) did not restore the current. Here we discuss the possibilities that (a) the major proteins define the functional environment of the Ca-channel and that (b) the Ca-channel is more susceptible to certain general changes in the membrane.

Effects of dietary choline deficiency on the mutagenic activation of chemical carcinogens by rat liver fractions

Salmonella mutagenesis assays were used to evaluate the mutagenicity of several chemical carcinogens as mediated by liver S-9 fractions from rats fed a choline-supplemented (CS) or choline-devoid (CD) diet. The liver S-9 fraction from CD diet-fed rats was found to have a significantly decreased ability to activate 2-acetylaminofluorene (2-AAF), 2-aminoanthracene (2-AA) and 6-aminochrysene (6-AC), but not N-hydroxy-2-acetylaminofluorene (HO-N-2-AAF) and dimethylnitrosamine (DMN). The same liver S-9 fraction was also less effective in deactivating N-methyl-N1-nitro-N-nitrosoguanidine (MNNG) but not methylnitrosourea (MNU). A decrease (20%) in the cytochrome P-450 content was found in liver microsomes of CD diet-fed rats. Although it has been shown that feeding a CD diet to rats enhances chemical hepatocarcinogenesis, the data presented here suggest that CD diet does not increase the activation of the chemical procarcinogens tested.