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Biomedical subjects

D Mayer

Publications and source records attributed to D Mayer.

At least 181 records · Page 10Linked to original sources
PubMed1986

Loss of adenylate cyclase activity in preneoplastic and neoplastic lesions induced in rat liver by N-nitrosomorpholine.

Adenylate cyclase (AC) activity was demonstrated histochemically using adenylate-(beta,gamma-methylene)diphosphate as substrate in cryostat sections of livers from 45 rats treated for 7-10 weeks with N-nitrosomorpholine (NNM) (120 mg/l drinking water) and from nine untreated control rats. The enzyme patterns of normal tissue, preneoplastic and neoplastic lesions were characterized and correlated with the morphologically defined stages of tumour development in the liver. Light microscopically, the enzyme activity of normal tissue was restricted to the plasma membrane, and was most pronounced along the bile canaliculi of the hepatocytes. In glycogen storage foci and mixed cell foci induced by NNM no, or only very weak, AC activity was visible. In the cells of neoplastic nodules and hepatocellular carcinomas AC activity was also clearly reduced. However, in small parts of the plasma membrane which lined lumina resembling normal bile canaliculi and in cytoplasmic vesicles closely associated with these structures, some AC activity was occasionally detected by light and electron microscopy. Whereas the tissue of normal appearance surrounding the lesions showed a marked increase in AC activity in the presence of glucagon, forskolin and cholera toxin. AC activity in the preneoplastic and neoplastic liver lesions could not, or could only weakly, be stimulated by this treatment. As demonstrated in serial sections of the foci, the reduction in AC activity corresponded to changes in the activity of other enzymes studied earlier in the same model. Thus the reduction in AC activity was accompanied by a decrease in the activity of glucose-6-phosphatase and glycogen phosphorylase, and by an increase in the activity of glucose-6-phosphate dehydrogenase. The results support the concept that the focal changes in the activity of many enzymes (including those of carbohydrate metabolism) during hepatocarcinogenesis are the consequence of aberrations in superordinate regulatory mechanisms of cell metabolism.

Adenylyl Cyclase Inhibitors↗
PubMed1985

Investigation of the carbohydrate metabolism of normal and neoplastic hepatocytes using 2,6-dichlorophenolindophenol as a probe for NAD(P)H production measured by voltammetry.

An electrochemical technique is described for measurement of intracellular NAD(P)H production. This technique involves an auxiliary redox system taken up by the cells which is then measured voltammetrically after reduction by NAD(P)H. The redox system used was 2, 6-dichlorophenolindophenol (DCPIP). It was shown to undergo a quasi-reversible two-electron transfer at the rotating gold disc electrode serving as an indicator electrode. The anodic wave of the reduced form of DCPIP was taken to indicate the amount of NAD(P)H produced by metabolic processes with glucose as substrate for a given number of cells. The following types of cell were investigated in suspension: Morris hepatoma 3924, a hepatocyte-derived cell line, and normal hepatocytes. Marked differences between normal and transformed cells were found under aerobic compared to anaerobic conditions. These were explained in terms of alterations in carbohydrate metabolism, e.g., Pasteur effect occurring on cell transformation.

2,6-Dichloroindophenol↗
PubMed1985

Voltammetric measurements of the kinetics of enzymatic reduction of 2, 6-dichlorophenolindophenol in normal and neoplastic hepatocytes using glucose as substrate.

Amperometric methods were used to study reaction kinetics of 2, 6-dichlorophenolindophenol (DCPIP) with NADH in the homogeneous phase. The second-order rate constant of the reaction was calculated to be 2.4 M-1 . s-1 at 37 degrees C. The reoxidation of the reduced form of DCPIP in air-saturated phosphate-buffered saline was found to follow pseudo-first-order reaction kinetics with rate constant of 5.9 X 10(-4) s-1. These data were compared to the reduction of DCPIP in suspensions of normal and neoplastic hepatocytes, in the absence and presence of oxygen. The reduction of DCPIP by intracellular NAD(P)H was shown to follow mixed-type reaction kinetics different from those of the homogeneous phase. From this, the conclusion was drawn that complexes of enzymes transferring electrons to and from NAD(P)H are involved in intracellular reduction of DCPIP.

Animals↗
PubMed1985

Specificity of cytochemical demonstration of adenylate cyclase in liver using adenylate-(beta, gamma-methylene) diphosphate as substrate.

Adenylate cyclase activity was demonstrated cytochemically in rat liver for the first time under the light microscope using cryostat sections mounted on glass cover slips and fixed with 1% glutaraldehyde for 1 min. Adenylate-(beta, gamma-methylene)diphosphate (AMP-P(CH2)P) was introduced as a new substrate for adenylate cyclase. It was found that adenylate cyclase was distributed heterogenously within the liver lobule. The enzyme activity was stronger in the area surrounding the central vein. A more specific localization at the plasma membrane and less unspecific background was obtained with AMP-P(CH2)P as compared to adenylylimidodiphosphate (AMP-P(NH)P). The specificity of the enzyme reaction using AMP-P(CH2)P was proved by increased formation of reaction product in the presence of 0.05 mg/ml glucagon and 0.125 mg/ml cholera toxin, as well as by inhibition of the reaction with 0.05 mg/ml alloxan. These effects were also observed at the electron microscopic level. On the other hand, no increase in reaction was observed in the presence of glucagon with AMP-P(NH)P as a substrate for adenylate cyclase, and only a weak activation was observed after adding cholera toxin; alloxan-inhibition was not complete. These effects may be due to the presence of enzymes which hydrolyze AMP-P(NH)P nonspecifically, superimposing on the product of adenylate cyclase activity. We therefore suggest the use of AMP-P(CH2)P as substrate for histochemical adenylate cyclase demonstration in the liver.

Adenosine Triphosphate↗
PubMed1985

Study of carbohydrate metabolism in glycogen storing cell lines derived from cultured rat hepatocytes.

Some aspects of carbohydrate metabolism were investigated in three non-malignant, glycogen storing, cell lines derived from a primary culture of rat hepatocytes, and in the Morris hepatoma 3924 cells. The three cell lines show biochemical alterations which are, to a large extent, similar to those found in the hepatoma cells: increased activity of glycolytic enzymes and decreased activity of gluconeogenetic enzymes. An increase of glucose-6-phosphate dehydrogenase activity is also found. The three cell lines, as the Morris hepatoma cells, actively convert glucose into lactate under the in vitro conditions of culture. Fructose is not taken up as quickly as glucose and galactose is not metabolized. As compared with normal hepatocytes, the three cell lines have altered metabolism and growth behaviour. They largely resemble the preneoplastic cells appearing in rat liver at the early stages of experimental carcinogenesis.

Animals↗
PubMed1985

Investigations on the carcinogenicity of dipyrone in rats.

A carcinogenicity study with dipyrone (metamizol methanesulfonate) was conducted in male and female Wistar rats. The compound was administered with the feed for a period of 24 months in doses of 0, 1000, or 3000 ppm, followed by a 6-month recovery period (without compound administration). The rats in the high-dose group, especially the females, showed a statistically significant body weight gain retardation which was not correlated with reduced feed consumption. The chronic administration of dipyrone did not influence the survival of the rats. No treatment-related changes in clinical signs and hematological parameters occurred. The absolute and relative weights of thyroids and pituitaries in the high-dose males were increased statistically significantly but were still within the normal range of the rat strain used. Histological examination of the animals which died intercurrently or were killed in extremis or at the end of the recovery period did not reveal any nonneoplastic or neoplastic changes which were compound related under the test conditions used. All of the tumors in all groups of animals were considered spontaneous in nature. Dipyrone did not show carcinogenic potential in rats in this study.

Administration, Oral↗
PubMed1985

Study of beta-adrenoceptors and beta-adrenergic responsiveness in cultured "preneoplastic-like" and neoplastic rat hepatocytes.

The presence of specific binding sites for tritiated CGP-12177, a beta-adrenergic antagonist, was investigated in the preneoplastic-like C1I cell-line and in Morris hepatoma MH3924 cells. It was found that C1I cells possess beta-adrenoceptors with the following characteristics: KD = 1.58 +/- 0.56 nM and Bmax = 4.41 +/- 0.88 fmol/10(6) cells. No specific binding sites could be found on MH3924 cells. Stimulation of the C1I cells beta-adrenoceptors by isoprenaline, salbutamol, adrenaline and noradrenaline induced cyclic AMP accumulation. Noradrenaline was, however, a hundred times less efficient than adrenaline, as is the case in normal rat hepatocytes. The order of potency of beta-antagonists either to displace the bound radioligand or to counteract isoprenaline induced cyclic AMP accumulation (IPS-339 greater than propranolol much greater than atenolol) indicates that the adrenoceptors present on the C1I cells are of the beta 2-subtype.

1-Methyl-3-isobutylxanthine↗
PubMed1984

Phalloidin depletes the mitochondrial Ca2+ compartment of hepatocytes.

In 3 h of incubation, primary cultures of rat hepatocytes attach to the substratum and exchange about 2.2 nmol 45Ca2+ per mg protein. In the presence of 1 microM phalloidin, the exchanged amount of 45Ca2+ was found to be decreased by about 30%. Using the uncoupling agent FCCP and the ionophore A23187 for further characterisation we determined that the 45Ca2+ deficit caused by phalloidin occurs in the FCCP-sensitive compartment, i.e., the mitochondria.

Animals↗
PubMed1984

Effects of intravenous versus intraatrial administration of doxorubicin on the function and structure of the heart.

To evaluate the relationship of toxicity of doxorubicin to route of administration, we studied 21 mongrel dogs which were randomly assigned to one of three groups: 1) a control group undergoing intraatrial indwelling catheter placement but no drug therapy; 2) an IV group receiving weekly doxorubicin by peripheral IV bolus administration; and 3) a catheter group receiving weekly doxorubicin through an indwelling intraatrial catheter. After 8 weeks all dogs were evaluated hemodynamically and then sacrificed. Sections of right ventricle were evaluated by light and electron microscopy. Although no hemodynamic alterations were found in any of the three groups, significant ultrastructural damage consistent with doxorubicin cardiac toxicity was demonstrable in four of the six evaluable catheter dogs receiving intraatrial doxorubicin, but in none of the other 13 dogs evaluated. This finding suggests that the intraatrial administration of doxorubicin may lead to cardiac toxicity at a lower cumulative dose than noted with peripheral IV administration.

Animals↗
PubMed1984

Hepatocellular glycogenosis and related pattern of enzymatic changes during hepatocarcinogenesis.

Systematic studies of the sequence of cellular changes during hepatocarcinogenesis induced predominantly in rats by stop experiments with N-nitrosomorpholine (NNM) led to the following main results and conclusions: The development of hepatocellular tumors is preceded by a multifocal hepatic glycogen storage disease (glycogenosis). Cytomorphological and cytochemical findings suggest a sequence of focal changes leading from clear and acidophilic glycogen storage foci through mixed cell foci and neoplastic nodules to hepatocellular carcinomas. The clear and acidophilic glycogen storage cells persisting after withdrawal of the carcinogen apparently represent a preneoplastic cell population, the neoplastic transformation of which is accompanied by a gradual reduction of glycogen and a concomitant increase in ribosomes (basophilia). The first appearance and frequency of the different liver lesions investigated was shown to depend on the dose of carcinogen administered. With increasing dose of NNM, the number of focal lesions considerably increased, and this was accompanied by an earlier development of mixed and basophilic cell populations. There was no indication of any reversibility of pronounced focal lesions under the experimental conditions chosen. On the contrary, the foci became larger and acquired phenotypic markers closer to neoplasia independent of further action of the carcinogen. Enzyme histochemically, the majority of the pronounced glycogen storage foci showed a reduction in the activities of glycogen phosphorylase and glucose-6-phosphatase while the activity of glucose-6-phosphate dehydrogenase, a key enzyme for the pentose phosphate pathway, was increased. The mixed cell foci, neoplastic nodules and carcinomas which emerged at later stages were characterized by a progressive shift away from glycogen metabolism towards glycolysis and the pentose phosphate pathway. as indicated by an increase in glyceraldehyde-3-phosphate dehydrogenase and glucose-6-phosphate dehydrogenase activities. These changes in enzyme pattern are in keeping with a developmental sequence leading from glycogen storage foci through mixed cell foci and neoplastic nodules to hepatocellular carcinomas. Biochemical microanalysis of dissected glycogen storage foci and mixed cell foci revealed that the foci composed exclusively of storage cells contained on an average 100% more glycogen than the normal liver tissue. The overall glycogen content of the mixed cell foci, which were composed of both glycogenotic and glycogen-poor basophilic cells, was not distinguishable from that of normal tissue.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1984

Biochemical microanalysis of glycogen content and glucose-6-phosphate dehydrogenase activity in focal lesions of the rat liver induced by N-nitrosomorpholine.

Persisting focal lesions, namely glycogen storage (glycogenotic) foci and mixed cell foci, were induced in liver by treatment of rats with the hepatocarcinogen N-nitrosomorpholine in a concentration of 200 mg/l drinking water for 7 weeks. Four and seven weeks after withdrawal of the carcinogen, the persisting foci were dissected from freeze-dried cryostat sections and their glycogen content and glucose-6-phosphate dehydrogenase activity were analyzed with highly sensitive luminometrical tests. The foci composed exclusively of storage cells contained on an average 100% more glycogen than the surrounding tissue of normal appearance or the liver parenchyma of untreated control animals. The overall glycogen content of the mixed cell foci, which were composed of both glycogenotic and glycogen-poor basophilic cells, was not distinguishable from that of the normal liver tissue. The activity of the G6PDH showed a clear tendency to higher values in the majority of the small glycogen storage foci (up to 100 ng dissected material). However, in larger glycogenotic foci and in particular in the mixed cell foci the activity of this enzyme was significantly higher (by a factor of approximately 3 and 6, respectively) than in the surrounding tissue of normal appearance and in the liver parenchyma of untreated controls. The data support the concept that hepatocarcinogens induce a focal hepatic glycogen storage disease of the liver which appears to elicit adaptive enzymatic changes gradually redirecting the disturbed carbohydrate metabolism towards other metabolic pathways, such as the pentose phosphate pathway.

Animals↗
PubMed1984

Response of infants to Haemophilus influenzae type b polysaccharide and diphtheria-tetanus-pertussis vaccines in combination.

In a multicenter study, responses to a combined vaccine containing standard diphtheria-tetanus-pertussis (DTP) and polyribosylribitol phosphate (PRP), the capsular polysaccharide of Haemophilus influenzae type b, were evaluated in 107 infants who received single doses at two, four, and six months of age and compared with those in 61 infants given single doses of DTP alone on the same schedule. Reaction rates were comparable in the two treatment groups. At seven months of age 61% of the subjects given the combined DTP-PRP vaccine and 8% and of those given DTP alone showed an antibody response to PRP, as defined as a twofold increase in titer over the lowest previous level. Among those given the DTP-PRP combined vaccine, 92% of the positive antibody responses occurred after the third dose. There was a variation in antibody response, possibly due to a difference in the vaccine lots administered.

Antibodies, Bacterial↗
PubMed1984

Effects of monoclonal antibody therapy in patients with chronic lymphocytic leukemia.

A phase I clinical trial was initiated to treat patients with stage IV B-derived chronic lymphocytic leukemia (CLL) with the IgG2a murine monoclonal antibody T101. This antibody binds to a 65,000-mol wt (T65) antigen found on normal T lymphocytes, malignant T lymphocytes, and B-derived CLL cells. All of the patients had a histologically confirmed diagnosis of advanced B-derived CLL and were refractory to standard therapy, and more than 50% of their leukemia cells reacted with the T101 antibody in vitro. The patients received T101 antibody two times per week, over two to 50 hours by intravenous administration in 100 mL of normal saline containing 5% human albumin. Twelve patients were treated with a fixed dosage of 1, 10, 50, or 100 mg, and one patient was treated with 140 mg of antibody. It was demonstrated that patients given two-hour infusions of 50 mg developed pulmonary toxicity, with shortness of breath and chest tightness. This toxicity was eliminated when infusions of 50 or 100 mg of T101 were prolonged to 50 hours. All dose levels caused a rapid but transient decrease in circulating leukemia cell counts. In vivo binding to circulating and bone marrow leukemia cells was demonstrated at all dose levels with increased binding at higher dosages. Antimurine antibody responses were not demonstrated in any patients at any time during treatment. Circulating free murine antibody was demonstrated in the serum of only the two patients treated with 100 mg of antibody as a 50-hour infusion and the patient treated with 140 mg of antibody over 30 hours. Antigenic modulation was demonstrated in patients treated at all dose levels but was particularly apparent in patients treated with prolonged infusions of 50 and 100 mg of antibody. We were also able to demonstrate antigenic modulation in lymph node cells, which strongly suggests in vivo labeling of these cells. Overall, T101 antibody alone appears to have a very limited therapeutic value for patients with CLL. The observations of in vivo labeling of tumor cells, antigenic modulation, antibody pharmacokinetics, toxicity, and antimurine antibody formation may be used in the future for more effective therapy when drugs or toxins are conjugated to the antibody.

Antibodies, Monoclonal↗
PubMed1984

[Bioequivalence of phenylbutazone preparations following a single intramuscular administration].

Bioequivalence was estimated in 6 resp. 7 male volunteers for two combination drugs of phenylbutazone (Neuro-Elmedal, Sigma Elmedal) after intramuscular administration using a monopreparation as a standard. Plasma levels of phenylbutazone were assayed by high pressure liquid chromatography. With respect to rate and extent both combination drugs were identical to the mono drug.

Absorption↗
PubMed1983

Endomyocardial fibrosis in rats treated with N-nitrosomorpholine.

Endomyocardial fibrosis was observed after long lag periods in male Sprague-Dawley rats treated for 1-14 weeks with the carcinogen N-nitrosomorpholine. The fibrosis developed predominantly in the left ventricle. It occurred during 29-78 weeks after withdrawal of the carcinogen in 5% and 79-108 weeks after withdrawal in 20% of the experimental animals, but was never observed in controls of the same age. We suggest that endomyocardial fibrosis was induced by a direct effect of the carcinogen on the fibroblasts of the endomyocardium.

Animals↗
PubMed1983

Preparation of tetramethylrhodaminyl-phalloidin and uptake of the toxin into short-term cultured hepatocytes by endocytosis.

A fluorescent phallotoxin with high photostability, tetramethylrhodaminyl-phalloidin (Rh-phalloidin), has been prepared. The affinity of this compound to rabbit muscle actin has been determined to be about 6 times lower than that of phalloidin. In freshly isolated hepatocytes the internalized fluorescent toxin stains the cellular actin. In contrary, there is no actin staining visible in cultured hepatocytes. Short-term cultured hepatocytes (5 h of culturing) incorporate the toxin by endocytosis; it is kept sealed in the endocytotic vesicles, which are usually found accumulated at the sites where cells touch after reaggregation.

Actins↗
PubMed1983

Influence of phenobarbital on glycogen metabolism of rat liver pretreated with N-nitrosomorpholine.

Sprague-Dawley rats were treated with N-nitrosomorpholine (NNM) alone (7 weeks, 120 mg/l in drinking water), with NNM followed by phenobarbital (PB) (750 mg/l for 6 weeks) or PB alone. The livers from these animals were investigated for glycogen content and activities of glucose-6-phosphatase, glucose-6-phosphate dehydrogenase, glycogen phosphorylase and glycogen synthetase. The following parameters proved to be significantly altered in the livers of rats treated with either NNM or PB or both compared with untreated controls: glycogen content was increased and the activities of glucose-6-phosphatase and glycogen synthetase were decreased. Although these data show some similarities in changes of glycogen metabolism of livers treated with NNM or PB, earlier histochemical investigations revealed important differences in the distribution of these alterations within the liver parenchyma.

Animals↗