Evaluation of tussilagone: a cardiovascular-respiratory stimulant isolated from Chinese herbal medicine

1. Traditional Chinese herbal medicine has long used Kuandong Hua (Tussilago farfara L.) in the treatment of various respiratory conditions. 2. Recently, it has been found that an extract of this plant (7R,14R)-14-acetoxy-7-[(2'E)-3'-methylpent-2'-enoyloxy ]-oplopanone, is a potent cardiovascular and respiratory stimulant. 3. This compound has been named Tussilagone (TUS) and when administered intravenously, has been shown to produce an instant and dose dependent pressor effect in anesthetized dogs (0.02-0.3 mg/kg), cats (0.02-0.5 mg/kg), and rats (0.4-4 mg/kg). 4. This pressor effect is similar to that of dopamine; however, no tachyphylaxis has been observed. 5. In addition to its cardiovascular effects TUS produced a significant stimulation of respiration in experimental animals. 6. The acute intravenous LD50 in mice of this compound was 28.9 mg/kg.

Enhanced cardiotoxicity in rabbits treated with verapamil and adriamycin

Verapamil, a calcium channel blocker, reduces resistance of some tumors to Adriamycin by inhibiting Adriamycin efflux from resistant cells. This study shows that rabbits given 7 mg/kg of Adriamycin and 0.8 mg/kg of verapamil died earlier with functional and morphological cardiac abnormalities than rabbits given Adriamycin alone. Rabbits that were given verapamil and died peracutely had higher concentrations of Adriamycin in the myocardium. The relatively high dose of Adriamycin was expected to produce cardiotoxicity in rabbits within a matter of days. However, peracute death (within hours) in rabbits given the same dose of Adriamycin but with verapamil treatment was unexpected. These results suggest that combining Adriamycin with verapamil increases early cardiac toxicity. Therefore, clinical use of this combination should be approached cautiously until the interactions, including the possibility for enhanced normal tissue damage, are fully understood.

Daunorubicin-induced DNA lesions in isolated rat hepatocytes and mammary epithelial cells

Daunorubicin, an anticancer drug, induces primarily mammary adenocarcinoma in Sprague-Dawley rats. We investigated daunorubicin-induced DNA lesions in enzymatically isolated mammary epithelial cells and hepatocytes from 7-8-week-old female Sprague-Dawley rats. Differences were observed in the type and quantity of DNA lesions in mammary epithelial cells and hepatocytes as determined by alkaline elution analysis. DNA single-strand breaks and proteinase-K-sensitive cross-linking lesions were observed in mammary epithelial cells. Hepatocytes appeared to have significantly lower relative frequencies of single-strand breaks than mammary epithelial cells when treated with daunorubicin (1.5-10.0 micrograms/10(6) cells). Hepatocytes displayed two types of cross-link. One form was sensitive to proteinase-K digestion, whereas the other form was insensitive. The metabolism of daunorubicin to the aglycone metabolites was substantially lower in mammary cells than in hepatocytes. However, the total uptake of the drug was similar in these two cell types. A metabolite, 7-deoxydaunorubicinol aglycone, was unable to induce single-strand breaks or cross-linking lesions in mammary epithelial cells. Both cell types exhibited a similar ability to repair radiation-induced single-strand breaks of DNA. However, the mammary cells may be less able to repair daunorubicin-mediated DNA damage. These results revealed that mammary epithelial cells are less able to metabolize the active mutagen/carcinogen, daunorubicin, than are hepatocytes. This, coupled with the observations of greater apparent DNA damage in mammary cells, may be of primary importance in the drug-induced carcinogenicity in the rat mammary tissue.

Enzyme-linked immunosorbent assay using Mycobacterium tuberculosis antigen 5 for the diagnosis of pulmonary tuberculosis in China

Measurement of serum IgG antibody to Mycobacterium tuberculosis antigen 5 by enzyme-linked immunosorbent assay was evaluated as a serodiagnostic test for pulmonary tuberculosis in China. The test was 89% sensitive and 94 to 100% specific with high accuracies of prediction. Among 82 tuberculous patients, antibody titer was related to the extent of pulmonary disease. Among control subjects, false positive tests were encountered among 5 of 52 persons with other pulmonary disease and not among 30 healthy subjects. The characteristics of this test compare favorably with those reported for sputum smear examination.

[Carcinoembryonic antigen and immunoglobin in gastric juice in the diagnosis of gastric cancer]

Levels of carcinoembryonic antigen (CEA) and immunoglobin (Ig) in gastric juice of 93 patients with benign and malignant gastric diseases were assayed. The CEA level in gastric cancer patients (55.73 +/- 38.26 ng/ml) was obviously higher than that in peptic ulcer (15.51 +/- 12.09 ng/ml) and superficial gastritis (26.96 +/- 20.17 ng/ml). But no significant difference was found between the CEA levels of gastric cancer and chronic atrophic gastritis (48.66 +/- 31.87 ng/ml). Also, elevated CEA was closely correlated to intestinal metaplasia. The positive rate of Ig was significantly higher in gastric cancer (IgG greater than or equal to 185 ug/ml, IgA greater than or equal to 100 ug/ml) than in benign gastric diseases. Although no correlation is present in the CEA and Ig in gastric juice, the combination of these two methods could improve the diagnostic accuracy. We believe that the two assays are worthy for screening gastric cancer from patients with high risk, and for identifying precancerous lesions.

[Circulating immune complex and cancer in the digestive system]

The zone electrophoresis on agarose was used to determine the incidence of circulating immune complex (CIC) in blood of 60 patients with cancer in the digestive system and 42 healthy donors. The correlation between cancer and CIC was investigated. The positive results is 75% in patients and 14.2% in the control. There is a significant correlation between the CIC and the stage of lesion. Higher incidence was observed in patients with stage I and II lesions (100% and 85%) than those with stage III lesions (40%). Among 13 positive patients, 5 with stage I lesion became negative and 8 with stage II or III lesions were still positive after operation. These data suggest that the zone electrophoresis be a reliable assay for the diagnosis and prognosis of patients with digestive system cancer. To measure the CIC periodically may be useful for the follow up of the tumor condition before and after treatment.

Comparison of intra-arterial cis-diamminedichloroplatinum II with high-dose methotrexate and citrovorum factor rescue in the treatment of primary osteosarcoma

A randomized two-arm study was undertaken to determine relative tumoricidal effects of intra-arterial cis-diamminedichloroplatinum II (I/A-CDP) and high-dose methotrexate with citrovorum factor rescue (MTX-CF) in the treatment of the primary tumor in patients with osteosarcoma. Responses were evaluated by clinical, radiographic, angiographic, and pathologic parameters. Fifteen patients were randomized to receive MTX-CF and 15 to I/A-CDP. In the MTX-CF arm there were four responses (three complete responses, one partial response) whereas in the I/A CDP arm there were nine responses (seven complete responses, two partial responses). Two patients who failed MTX-CF and requested alternative treatment with I/A-CDP also responded. The total I/A-CDP response was 11/17.

Altered fucosylation of membrane glycoproteins from cystic fibrosis fibroblasts

Peripheral membrane glycopeptides isolated from skin fibroblasts of patients with cystic fibrosis (CF) had an altered fucosylation when compared to age, race, and sex-matched controls. Glycopeptides obtained by trypsin treatment of cultured cells, metabolically labeled with L-[3H]fucose, were purified on a Sephadex G-50 column. The neutral monosaccharide composition of the glycopeptides was determined by gas-liquid chromatography of the alditol acetate derivatives. The fucose content of the CF membrane glycopeptides and the molar ratio of fucose to the other monosaccharides were increased when compared with those of controls. The mean fucose content was 2.3 +/- 1.7 (SD) and 0.3 +/- 0.05 (SD) nmol per 10(6) cells for CF control glycopeptides, respectively. Moreover, the specific activity of incorporated L-[3H]fucose was markedly decreased in the CF glycopeptides, 355 +/- 183 (SD) and 2707 +/- 839 (SD) cpm per nmol of fucose for the CF and controls, respectively. The membrane glycopeptides were further purified and characterized by affinity chromatography on immobilized lectins. The decreased specific activity of incorporated fucose was present in CF glycopeptides which bound to immobilized lentil lectin before and after Pronase degradation. Moreover, the CF glycopeptides bound more tightly to lentil lectin. Several classes of glycopeptides bind to lentil lectin and all contain Fuc alpha 1----6GlcNAc at the core. The binding characteristics of the Pronase-digested membrane glycopeptides for immobilized concanavalin A, lentil leukoagglutinating phytohemagglutinin, erythroagglutinating phytohemagglutinin, and serotonin provided information on the structure of the altered CF glycopeptides. Most of these radioactive glycopeptides were of the biantennary type containing at least one sialic acid residue and all containing fucosyl residues at the asparagine core.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of nutritional depletion and repletion on plasma methotrexate pharmacokinetics

Clinically, a relationship exists among nutritional status, drug responsiveness, and host toxicity, but the effects of nutrition on chemotherapy drug metabolism are relatively unknown. This article evaluates the effect of malnutrition and nutritional repletion on plasma methotrexate (MTX) pharmacokinetics. In Study I, 55 non-tumor-bearing rats were fed regular diet (RD) (N = 27) or protein-free diet (PFD) (N = 28) for 10 days. On day 10, MTX 20 mg/kg was injected intraperitoneally and four to six animals in each group were killed at 30 minutes, 1, 2, 6, 24, and 48 hours following MTX administration. Plasma MTX was measured by dihydrofolate reductase enzyme inhibition assay and was found to be significantly elevated (P less than 0.01) in PFD animals as compared with RD animals at 1 and 2 hours following MTX injection. In Study II, 87 tumor-bearing rats were fed RD (N = 29) or PFD (N = 58) for 10 days. At this time, 27 PFD rats were switched to RD (PFD----RD), while 31 rats remained on PFD. MTX 20 mg/kg was injected intraperitoneally and six to eight rats in each group were killed at 1, 2, 6, and 24 hours post-MTX injection. Mean levels were found to be significantly elevated at 2, 6, and 24 hours in PFD (P less than 0.01) and PFD----RD (P less than 0.05) compared with RD rats. Several investigators have shown that increased plasma MTX levels at 24 and 48 hours after drug administration correlates with host toxicity in patients receiving chemotherapy. In this experimental study, malnutrition delayed plasma MTX clearance, and nutritional repletion for 2 days was insufficient to return MTX pharmacokinetics to normal. These results in experimental animals suggest an explanation for increased MTX toxicity in malnourished individuals.

Systemic thermochemotherapy: toxicity and plasma pharmacokinetics of methotrexate and doxorubicin

Chemotherapy administered during systemic hyperthermia is more tumoricidal than either modality used alone. The purpose of this study was to evaluate plasma drug pharmacokinetics and host toxicity when methotrexate (MTX) or doxorubicin (adriamycin--ADR) was given at 37 or 43 degrees C. Eight dogs were heated to 43 degrees C for 1 hr without chemotherapy; eight dogs received MTX (5 mg/kg) and four dogs received ADR (2 mg/kg) intravenously as a constant infusion at 43 or 37 degrees C. Blood samples were obtained at 0, 1, 2, 24, and 48 hr. Mean plasma MTX levels were not significantly different at 1, 2, and 6 hours in 43 and 37 degrees C dogs, but at 24 and 48 hr mean plasma MTX levels were significantly elevated in heated (43 degrees C) dogs compared with sham-heated (37 degrees C) dogs. Plasma MTX concentration multiplied by time (area under curve) was 131 g . hr/liter in 43 degrees C dogs compared with 73 g . hr/liter in 37 degrees C dogs (P less than 0.001). Vomiting and bloody diarrhea lasted an average of 4 days in heated control dogs (no drugs) 4 days in 37 degrees C dogs, and 5 to 7 days in 43 degrees C MTX dogs. Mean plasma ADR levels were similar in 37 and 43 degrees C dogs at all time intervals. Vomiting and bloody diarrhea lasted at least 7 days in 43 degrees C dogs compared with only 1 day in 37 degrees C dogs treated with ADR.(ABSTRACT TRUNCATED AT 250 WORDS)

Central nervous system pharmacology of Baker's antifolate (NSC139105) in man

Radiolabelled Baker's Antifolate (BAF) was administered to 6 patients undergoing surgical resection of intracerebral tumors. Levels of radioactivity in resected tumor and edematous brain adjacent to tumor were generally higher than levels in concurrent plasma samples and were generally comparable to levels in temporalis muscle. Levels in tumor cyst fluid were far lower than concurrent plasma levels and levels in surrounding tumor. Chromatography was performed on tumor from 2 patients and revealed that only a small proportion of the radioactivity represented unchanged BAF. The major metabolite present in tissues was 1 000 times less potent as an inhibitor of dihydrofolate reductase than was BAF. Five patients had cerebrospinal fluid (CSF) sampled following administration of tracer doses of radiolabelled BAF. Radioactivity levels were far lower in CSF than in plasma. Levels of radioactivity in the CSF were also far lower than levels in tumor and brain samples from other patients and were slightly lower than tumor cyst fluid levels. Two patients had CSF collected after they received therapeutic doses of BAF. In these patients, both CSF and plasma were assayed using a dihydrofolate reductase inhibition assay. As with tracer dose studies, CSF concentrations of BAF were substantially lower than were concurrent plasma concentrations. Thus it appears that only very low concentrations of BAF are attainable in human CSF and intracerebral tumor, although a metabolite which is a very weak inhibitor of dihydrofolate reductase attains high concentrations in tumor.

A simplified new method for the identification of arboviruses: virus detection using enzyme immunoassay on cultured cells

A simple new method is reported for the identification of arbovirus isolates and the titration of arboviruses. Horseradish peroxidase conjugated Staphylococcus aureus protein A was used for the indirect staining of virus antigens grown in an Aedes albopictus cell line, C6/36 cells. Thirty-five isolates from Culex tritaeniorhynchus mosquitoes were examined by this method and 20 of these were identified as Japanese encephalitis virus (JEV). These results were confirmed by immunofluorescent assay and plaque neutralization test. Comparative titration of JEV, Murray Valley encephalitis (MVE) and Kunjin viruses showed that this method was as sensitive as the chick embryo plaque assay. Specific enzymatic reactions on these virus-infected cells began to appear before day 3 and reached the end-point on day 5 post-infection of C6/36 cells, whereas the cytopathic effect (CPE) appeared about 2 days later than the positive enzymatic reactions. Fixation with 10% formalin for 0.5-8 h did not damage the positive reaction in infected cells and did not increase the background colour of uninfected cells.

Clinical pharmacokinetics of methotrexate in children

Among the few antineoplastic agents investigated pharmacologically in children and adults, methotrexate has been clearly demonstrated to be handled differently in the two age groups. Age has in fact proved to be a major determinant, exerting an effect on both the pharmacokinetics and pharmacodynamics of methotrexate. Its pharmacokinetics, in turn, determine the drug toxicity. The beta-phase of methotrexate clearance, represented by the plasma drug concentration 48 hours from the start of a 6-hour infusion in a high dose treatment regimen, appears to be constant with age. In children, an increasing plasma drug concentration is apparent with increasing age, but whether this trend reflects a potential increase in the area under the plasma concentration-time curve of methotrexate has yet to be defined. Recent investigations have suggested that the drug is more completely distributed in the tissues of children than adults at the same infused dosage. This may explain the increased tissue toxicity caused by methotrexate. However, other observations suggest a faster drug turnover rate in the tissues of children. This may prevent the drug from concentrating in vital organs. Whether the metabolism of methotrexate, particularly the biosynthesis of methotrexate polyglutamates, plays a role in the biological effect of the drug is worthy of further investigation. The high brain tissue concentration after systemic methotrexate infusion and the slower efflux of methotrexate from brain tissues and cerebrospinal fluid make these tissues vulnerable to methotrexate toxicity.

Decreased oral warfarin clearance after ranitidine and cimetidine

Oxidative metabolism inhibition of a number of drugs by cimetidine has been attributed to its imidazole ring, a hypothesis that has been supported by reports that ranitidine does not affect drug metabolism despite being five times as potent as cimetidine as an H2-receptor antagonist. In five healthy subjects ranitidine at 150 mg twice daily induced a 27% fall in apparent oral warfarin clearance. In the same subjects cimetidine at 1 gm/day induced a 36% decrease in warfarin clearance. In two of the subjects the experiment was repeated after giving 750 mg ranitidine per day and in two other subjects after 200 mg cimetidine twice daily. In both instances there was a stepwise fall in warfarin clearance with increasing doses. The data indicate that interference with drug metabolism by H2-receptor antagonists is not confined to cimetidine but that on a molar basis ranitidine and cimetidine are roughly equivalent in inhibiting warfarin clearance and that the effects are related to dose.

High-dose methotrexate as part of remission maintenance therapy for childhood acute lymphocytic leukemia: a Pediatric Oncology Group pilot study

Seventeen children with acute lymphocytic leukemia (ALL) in remission were treated with parenteral high-dose methotrexate (HDM) pulses every eight weeks during standard 6-mercaptopurine and methotrexate (MTX) oral maintenance therapy. MTX (1,000 mg/m2) was infused over one hour followed by one hour of intravenous hydration for the purpose of achieving plasma and cerebrospinal fluid (CSF) levels greater than 10(-6) M for a period of 24 hours. Leucovorin (15 mg/m2) was administered orally six, 12, and 18 hours after completion of the HDM. Plasma and CSF concentrations of MTX were evaluated serially in the first 48 hours. During the first 24 hours, the plasma MTX level was maintained at greater than 10(-6) M. The patients receiving intrathecal MTX at a dose of 15 mg/m2 had an adequate, sustained MTX level in the CSF, but when no intrathecal MTX was administered, the CSF levels were less than 10(-6) M. For that reason, intrathecal MTX in a low dose (6 mg/m2) was injected intrathecally one hour after the HDM infusion, allowing the MTX level in CSF to approximate 10(-6) M over the 24 hours. The toxicity of this therapy was minimal. Due to the facts that the plasma and CSF MTX levels could be sustained above the desired concentrations and this regimen could be given in the outpatient clinic, this program has been incorporated into an ongoing study in an effort to prolong complete remissions.

Treatment of primary osteosarcoma with intra-arterial and intravenous high-dose methotrexate

In an effort to achieve high concentrations and prolonged exposure times, high-dose methotrexate (MTX) was administered by the intra-arterial route over 6 hours at a dose of 12.5 g/m2 to nine patients with osteosarcoma. This was followed by citrovorum factor (CF) rescue, which was initiated 12 hours after completion of the infusion (MTX-CF). The regimen achieved high local concentrations over a finite period. No toxicity was encountered. Treatment was administered at weekly intervals, during which intravenous MTX-CF was interposed if facilities for intra-arterial administration were not available. However, despite increases in local venous concentrations and exposure times, only four of nine patients (44%) responded. This is similar to responses achieved with 7.5 g/m2 (48%) with CF initiated 2 hours after completion of the infusion. Higher MTX doses, intra-arterial administration, and prolongation of cytotoxic exposure time did not confer a therapeutic advantage as opposed to "conventional" intravenous high doses.

Modulation of polymorphonuclear leukocyte function by doxorubicin (Adriamycin) and alpha tocopherol (vitamin E)

The effect of various concentrations of Adriamycin alone and Adriamycin plus vitamin E on human polymorphonuclear leukocyte (PMNL) function was determined. Aliquots of PMNLs were incubated at 37 degrees C with saline or vitamin E and then exposed to Adriamycin. A significant decrease in 1-14C glucose utilization and oxygen consumption by zymosan stimulated PMNLs occurred when PMNLs were incubated with 1, 10, 20, 1000 and 200 micrograms/ml concentrations of Adriamycin. Preincubation of the PMNLs with vitamin E afforded partial protection at lower concentrations. The total uptake at 3, 10 and 20 min of methyl 3H thymidine labeled S. aureus by control PMNL was significantly greater than by PMNLs exposed for 60 min to 100 micrograms/ml of Adriamycin. Intracellular Adriamycin concentrations increased in a dose dependent fashion. Viability of cells before and after incubation was 95%. Adriamycin inhibited oxidative metabolic and functional activity of PMNLs in a dose related manner. Preincubation of PMNLs with vitamin E partially protected them from the effects of Adriamycin.

Formation and disposition of 7-hydroxymethotrexate in rabbits

The metabolism of methotrexate in rabbits was investigated following 6 hr of infusion with [3',5',7-(3)H]methotrexate (50 mg/kg). Methotrexate and its metabolites were analyzed by an enzyme kinetic method, reverse phase high-performance liquid chromatography, and scintillation counting of radioactivity. 7-Hydroxymethotrexate was found to be a major metabolite in plasma, urine, bile and various tissues of rabbits. Cumulative production of 7-hydroxymethotrexate during the first 6 hr was 31.8% of the total dose. The peak 7-hydroxymethotrexate concentration in plasma was reached at the end of the infusion, and this concentration was higher than the methotrexate concentration. The plasma clearance of 7-hydroxymethotrexate was biphasic in nature and slower than that of methotrexate. The highest methotrexate concentration was found in kidney after 6 hr. This concentration was found to be 7.2 times greater than that in plasma. A higher ratio of 7-hydroxymethotrexate/methotrexate was found in liver, small intestine, kidney and testis when compared to plasma. Lung and kidney showed significant conversion of methotrexate to 7-hydroxymethotrexate in vitro, as did the liver.

[Experimental study on pharmacokinetics of methotrexate and its metabolite (7-hydroxy-methotrexate) in tissue]

The metabolism of methotrexate was investigated in rabbits with six hours infusion of (3'5'7-3H) methotrexate (50mg/kg). Methotrexate and its metabolites were analyzed by reverse-phase high-pressure liquid chromatography and by counting of radioactivity. 7-Hydroxymethotrexate was found to be the major metabolite in the plasma, urine, bile and tissues of rabbits. Cumulative production of 7-Hydroxymethotrexate during the first six hours was 31.8% of the total dose. The 7-Hydroxymethotrexate concentration in plasma was reached to peak level in six hours after the initiation of the infusion, and was declined slower than that of methotrexate. The highest total radioactivity was found in the kidney after six hours, which was 7.24 times higher than that in plasma. Ratio of 7-Hydroxymethotrexate/methotrexate increased in the liver, small intestine, lung, kidney and testis. This data suggested that conversion of methotrexate to 7-hydroxymethotrexate took place in lung and kidney as well as in liver.

Clinical and pharmacologic investigation of the effects of alpha-tocopherol on adriamycin cardiotoxicity

Our data indicate that alpha-tocopherol used in an oral dose of 2 g/m2 daily results in a six- to eightfold increase of the vitamin E levels in serum. The occurrence of congestive heart failure in three patients and the observation of significant pathologic changes in endomyocardial biopsies in approximately half of the patients treated with a median cumulative adriamycin dose level of 550 mg/m2 indicate that alpha-tocopherol does not offer substantial protection against adriamycin-induced cardiac toxicity. The antitumor activity of the drug, however, is not compromised by the concomitant administration of the vitamin.

Effect of chronic irradiation of 60Co-gamma-ray at low dose rate on rhesus monkey - effect on peripheral blood and testis

The authors have demonstrated that after a long-term chronic irradiation of 2.17 rad/day for 2 months, the testis of the experimental monkey (Macaca mulatta) is extremely atrophied with a loss of reproductive ability. But the effect on peripheral blood is not apparent even after irradiation for 57 months. It should be noted that rhesus monkeys, being as sensitive to irradiation and similar in evolutionary steps as human beings, could be used as experimental animals to further study the dose rate for aspermatogenesis, the morphological injuring effect on the reproductive system and the cytogenetic effect of irradiation, and this is highly important to working out a standard of promised dose of irradiation for X-ray workers and an index or radiation protection monitoring.

Xylitol mediated amelioration of acetylphenylhydrazine-induced hemolysis in rabbits

Xylitol was investigated for its ability to ameliorate hemolytic anemia induced by acetylphenylhydrazine in rabbits. Animal experiments were performed using two different concentrations of xylitol, a 5% and a 10% solution with a total dose of 2 g/kg body weight and infusion rates of 10 mg and 20 mg xylitol per kg body weight per minute respectively. Two doses of acetylphenylhydrazine (APH), 5 and 10 mg per kg, were injected intraperitoneally as hemolytic inducers in different groups of rabbits. All the rabbits infused with xylitol showed significantly less acute APH-induced hemolysis. The isotonic 5% xylitol solution was found to maintain and restore the hematological parameters (packed cell volume, hemoglobin concentration, reduced glutathione (GSH) content, and reticulocyte counts) better than the 10% xylitol solution. Increased 51CR-red cell survival confirmed the beneficial effect of xylitol. The survival of erythrocytes as represented by chromium-labeling in rabbits infused with 5% xylitol after treatment with 10 mg/kg APH increased from about 33% (the survival of red cells in rabbits injected with APH alone) to 67% of normal rabbits' red cell survival. Erythrocytes in APH-treated animals took up xylitol more readily than erythrocytes from control animals. Our results in rabbits suggest that (1) non-toxic dosage of xylitol is effective in ameliorating the hemolytic episode induced by APH, (2) there is a dose relationship between the hemolytic effect induced by APH and the preventive effect offered by xylitol, (3) drug-challenged cells effectively acquired two to three fold more xylitol to compensate for the cellular needs than that of the normal cells, and (4) sufficient xylitol (55 mg/dl) to act as substrate for xylitol dehydrogenase was recovered intracellularly in drug-challenged rabbit erythrocyte in vivo, in spite of a low plasma (less than 30 mg/dl) concentration of the substrate. This antihemolytic affect of xylitol is likely accomplished through NADPH generation, which maintains the level of GSH and protects the hemoglobin and other structural and functional proteins against peroxidative damage.

Metabolism of xylitol and glucose in rats bearing hepatocellular

The variation in metabolism of glucose and xylitol by diverse rat hepatocellular carcinomas and partially hepatectomized rat livers was studied. The AS-30D and FB56 tumors demonstrated a significantly different degree of utilization of glucose and xylitol in vitro. This correlated partially with the low activity of polyol dehydrogenase when xylitol was used as a substrate. The activity ofa nicotinamide adenine dinucleotide-dependent polyol dehydrogenase in various hepatomas ranged from nondetectable to 30 nmol/min/mg protein, with the lower activities in FB56 and AS-30D tumors at 0 and 0.22 nmol/min/mg, respectively; while nicotinamide adenine dinucleotide phosphate-dependent xylitol dehydrogenase activities ranged from 0 to FB56 to 3.31 nmol/min/mg protein in liver regenerated for 1 week. The activities of nicotinamide adenine dinucleotide phosphate-dependent enzyme for normal liver and AS-30D tumors measured 2.2 and 0.14 nmol/min/mg protein, respectively. Although only the 311C tumor had an activity equivalent to that of normal liver, the range of the nicotinamide adenine dinucleotide phosphate-dependent polyol dehydrogenase activities among the cell lines studies is narrow. The ratios of metabolites of [14C]glucose or [14C]xylitol were determined in rats bearing AS-30D tumors. Animals were given i.v. injections of a 10% solution of [14C]glucose or [14C]xylitol, 2 g/kg body weight. Assays of neutral sugar metabolites from each substrate in the acid-soluble fraction of liver or AS-30D tumor showed that xylitol in the liver was converted primarily into glucose while in the tumor 80 to 90% of the xylitol remained unchanged. This hepatocellular carcinoma is also markedly deficient in the ability to synthesize acid-insoluble glycogen and glycoprotein from xylitol as compared to the liver.

Nutritional significance of fructose and sugar alcohols

Human metabolism of D-fructose, D-sorbitol, D-mannitol, and xylitol has been documented. In humans, sorbitol and xylitol at a single oral dose of 20 g or less and fructose at 70 g or less most likely can be fully absorbed. These there sugars can maintain, either independently or nearly independently, the integrity or the carbohydrate requirement for the growth of cells and animals. The absorption of D-mannitol is no more than 80% and is more laxative. In general, there is no adverse effect other than osmotic diarrhea after oral administration of these sugars. Transient hyperuricemia was seen in some humans. The chronic toxicity of life-long usage of these sugars in humans or other primates is not known. However, a 2-year Turku sugar studies suggested the safety of fructose and xylitol. Two-year feeding experiments in mice and rats indicated possible carcinogenicity of a high-percentage xylitol diet. Abnormalities of cellular growth were also documented in animals fed high percentages of sorbitol and sucrose. Long-term mannitol feeding experiments also revealed an increased incidence of benign thymic tumors in rats. Intravenous feeding of fructose, xylitol, and sorbitol causes major concern. The toxicity is total-dose and infusion-rate dependent. The physical toxicity induced by hyperosmolar effect of the concentrated infusion solutions can be lethal. The primary metabolic toxicities, mainly lactic acidosis and hypruricemia, are reversible. The suggested safe infusion rate of these sugars is 0.25 g/kg/h; sporadic toxic observations have been reported at this or lower doses (0.125 g/kg/h). The combination of glucose, fructose, xylitol, and sorbitol mixture intravenously is in use in Europe due to the critical threshold of each element. There are positive findings from the use of the combination in human illness (114). The beneficial effect of xylitol, mannitol, sorbitol, and fructose in decreasing order has been well documented in the prevention of dental caries in animals and in humans. Oral organisms do not appear to metabolically adapt to xylitol even after 4 years of in vivo exposure. This was based on the quantitation of xylitol dehydrogenase activity in saliva and oral organisms. In addition, a therapeutic and preventive effect for xylitol in human and animal dental caries has been demonstrated. There appears to be at least a theoretical edge in the dietary use of fructose, xylitol, and sorbitol in diabetics.(ABSTRACT TRUNCATED AT 400 WORDS)

Mass spectrometry of permethylated folic acid analogs

Folic acid and several analogs have been characterized as their permethylated derivatives. These derivatives are readily evaporated from the solid probe and provide spectra with abundant molecular ions and characteristic fragment ions. This method has been used to confirm the identities of the two methotrexate metabolites, 7-hydroxymethotrexate and 4-amino-4-deoxy-N(10)-methylpteroic acid, which have been isolated from human urine. The permethylation products of the folate cofactors, dihydrofolic acid, tetrahydrofolic acid and leucovorin, are also characterized.

Effect of ascorbic acid in vitro on lymphocyte reactivity to mitogens

The direct effects of ascorbic acid and dehydroascorbic acid in vitro on human lymphocyte proliferation to phytohemagglutinin (PHA) and concanavalin A (Con A) stimulation were determined. Cells exposed to physiologic and high concentrations of ascorbic acid and dehydroascorbic acid showed poorer tritiated thymidine ([3H]TdR) incorporation than controls without the vitamin. The inhibitory effect was dose-dependent, with the greatest inhibition occurring as the concentration of ascorbic acid and dehydroascorbic acid was increased. At supraoptimal concentrations of PHA and Con A, there was no recovery of the mitogen response, indicating that ascorbic acid did not inhibit the response by competition. Viability studies of cells in culture showed that concentrations of ascorbic acid and dehydroascorbic acid, which consistently inhibited mitogenic stimulation of lymphocytes, were noncytotoxic throughout the culture period. Timed addition of ascorbic acid to PHA-stimulated lymphocytes in culture demonstrated inhibition of [3H]TdR incorporation when ascorbic acid was added as late as 96 hours after initiation of culture. However, the greatest inhibitory effect was observed when ascorbic acid was added at initiation or early in culture. Inhibition was also evident when RNA and protein synthesis were determined. The results suggest that physiologic and high concentrations of ascorbic and dehydroascorbic acid affect early metabolic events in the process of mitogen-stimulated lymphocyte activation.