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Biomedical subjects

R Pentz

Publications and source records attributed to R Pentz.

At least 19 recordsLinked to original sources
PubMed2007

The return of research results to participants: pilot questionnaire of adolescents and parents of children with cancer.

PURPOSE: The offer to return research results to participants is increasingly recognized as an ethical obligation, although few researchers routinely return results. We examined the needs and attitudes of parents of children with cancer and of adolescents with cancer to the return of research results. METHODS: Seven experts in research ethics scored content validity on parent and adolescent questionnaires previously developed through focus group and phone interviews. The questionnaires were revised and provided to 30 parents and 10 adolescents in a tertiary care oncology setting. RESULTS: The content validity index for individual questions and the overall questionnaires scored as 0.86 for both questionnaires. All 30 parents and 10 adolescents who agreed to participate returned questionnaires. The majority (>95%) indicated that they had a strong or very strong right to receive results. Letter or e-mail was a satisfactory means to return results described as good or neutral (66% parents, 100% adolescents) but more participants wished face-to-face disclosure of results with negative implications (50% parents, 60% adolescents). Very few wanted results disseminated through a Web site. The majority acknowledged the need for peer-review before disclosure (60% of adolescents and parents) but did not want "to be the last to know." CONCLUSIONS: Our data suggest that pediatric oncology patients and parents of children with cancer strongly feel that they have a right to research results, and that they wish to receive these in a timely manner.

Adolescent↗
PubMed2005

Troxerutin protects the isolated perfused rat liver from a possible lipid peroxidation by coumarin.

For more than 40 years coumarin has been successfully used in the therapy of chronic venous insufficiency (CVI). The occurrence of liver injuries is rather rare and happens predominantly when doses are administered which are significantly higher than necessary for therapeutical use. Such effects caused by high coumarin concentrations are reproducible in in vivo experiments in mice or rats and HepG2-cells. In order to characterize the mechanism of liver injuries, the isolated perfused rat liver has been chosen as model. Since liver injuries are quite rare, if coumarin is used in co-medication with troxerutin, a possible protective influence of this flavonoid has been investigated. In concentrations higher than 4 mmol/l, coumarin alone is effective in the isolated perfused rat liver. Then the release of the enzymes alanine aminotransferase (ALT) and lactate dehydrogenase (LDH) increases and there is a measurable reduction of perfusion flow, oxygen consumption and rate of bile secretion. Additionally, the concentrations of hepatic adenosine triphosphate (ATP) and oxidized and total glutathione (GSSG/GSH) decrease. In the livers of fasting animals, coumarin doubles the concentration of hepatic malondialdehyde (MDA). This effect cannot be detected if troxerutin is added. In general, troxerutin reduces the concentration of all coumarin-metabolites in the perfusate and bile and changes the ratio of the main metabolites, coumarin: 3-hydroxycoumarin: 7-hydroxycoumarin. An analysis of the metabolic steps also shows that the amount of coumarin eliminated via faeces does not stem from absorbed coumarin, because the amount of orally applied coumarin detectable in the bile is less than 1%. The study demonstrates that troxerutin has hepatoprotective properties and thus protects the liver from a possible lipid peroxidation caused by coumarin. However, it is necessary to point out that these adverse effects caused by coumarin can be detected only in very high concentrations considerably above the regular therapeutical dosage. This allows the conclusion that troxerutin is a beneficial cofactor in coumarin preparations used for the therapy of chronic venous insufficiency.

Alanine Transaminase↗
PubMed2001

Informed consent for pediatric leukemia research: clinician perspectives.

BACKGROUND: Good, fully informed consent is critical to the ethical conduct of clinical cancer research. The authors examined clinician perspectives on informed consent for pediatric research by surveying clinicians at five major medical centers that routinely enroll patients in Children's Cancer Group studies. METHODS: Building on a pilot study, a questionnaire was designed to elicit clinicians' general opinions, approaches, and suggestions related to informed consent in pediatric leukemia trials. Questionnaires were mailed to 132 clinicians. Eighty-nine questionnaires were returned, along with 13 nonparticipant forms notifying us of the clinician's inability to participate because of a lack of experience in pediatric informed consent. The response rate was 75%. RESULTS: Providing information so that families can decide about study entry was ranked as the most important goal of the informed consent process, whereas parents' state of shock was rated the most significant obstacle to good informed consent. Clinicians cited high levels of parental comprehension of key aspects of clinical research studies and reported information overload and increased anxiety as effects of the informed consent process on parents. Several key items were associated with clinicians' gender, race, and professional experience. Finally, one open-ended question yielded 126 suggestions for how to improve the informed consent process that were grouped into 10 meaningful categories. CONCLUSIONS: Clinicians report a range of approaches, opinions, concerns, and suggestions for improving the informed consent process. The article proposes that their views and suggestions be integrated with those of parents and patients in attempts to survey and improve informed consent in pediatric oncology.

Adult↗
PubMed1999

The effects of garlic preparations against human tumor cell proliferation.

Epidemiological studies in China provide reason to suspect that a rich garlic content in the diet might reduce the proliferation of tumors in humans. We conducted experiments on human tumor cell lines and determined the influence of a garlic powder preparation, a garlic extract (reported as 8-10% L(+)-alliin enriched), and a combination thereof, on cellular proliferation in cell cultures, employing the widely used indirect neutral red procedure. Garlic powder failed to inhibit the growth of human hepatoma HepG2 or human colorectal carcinoma Caco2 cells at concentrations of up to 1000 micrograms/ml. Garlic extract, in which the alliin content was highly enriched was also unable to inhibit the growth of these cells. However, when the garlic extract was supplemented with garlic powder (to 10% final concentration) there was a concentration-dependent clear inhibition of tumor cell growth (IC50 values of 330 micrograms/ml for HepG2 and 480 micrograms/ml for Caco-2 cells). The growth of the human lymphatic leukemia cell line CCRF CEM was significantly inhibited in a dose-dependent manner by both garlic powder and garlic extract at concentrations as low as 30 micrograms/ml. However, no potentiation of this effect occurred upon mixing of the two preparations. Our results suggest that the antiproliferative effects of garlic may be due to breakdown products of alliin, such as allicin or polysulfides, rather than alliin itself, since the addition of an alliinase system (garlic powder) to an alliin enriched preparation without alliinase (garlic extract) potentiated the effects observed with the two preparations alone.

Animals↗
PubMed1999

Effects of garlic preparations on superoxide production by phorbol ester activated granulocytes.

Sulfur containing constituents of garlic are considered responsible for conveying the antioxidative properties of garlic preparations. The radical scavenging properties of garlic preparations against oxygen radicals, specifically their ability to inhibit the formation of superoxide anions, were investigated using human granulocytes activated with 10 nM phorbol myristyl acetate (PMA). A garlic powder preparation inhibited the production of superoxide with a calculated IC50 of 390 micrograms/ml. An 8-10% alliin enriched garlic extract (alliinase inactivated) did not inhibit superoxide production even at concentrations as high as 1000 micrograms/ml. When the extract was mixed with garlic powder (90% garlic powder, 10% garlic extract), there was a clear inhibition of superoxide production with an IC50 value of 295 micrograms/ml. An even stronger inhibitory effect could be achieved when garlic powder was added to garlic extract (10% garlic powder, 90% extract, IC50 = 160 micrograms/ml). These experimental results suggest that the alliin metabolite allicin may be responsible for the oxygen radical scavenging properties of garlic.

Carcinogens↗
PubMed1999

The toxic and metabolic effects of 23 aliphatic alcohols in the isolated perfused rat liver.

We investigated the acute toxic and metabolic effects of 23-aliphatic alcohols (16 saturated and 7 unsaturated) in the isolated perfused rat liver at a concentration of 65.1 mmol/l (approximately 0.3% ethanol). The capacity of the straight chain primary alcohols (methanol, ethanol, 1-propanol, 1-butanol and 1-pentanol) to release the enzymes glutamate-pyruvate transaminase (GPT), lactate dehydrogenase (LDH) and glutamate dehydrogenase (GLDH) into the perfusate was strongly correlated with their carbon chain length. The secondary alcohols were less active in this respect whereas branching of the carbon chain did not consistently change alcohol toxicity. Unsaturation in the straight chain but not in the branched chain alcohols was accompanied by an increase in toxicity. An increased enzyme release was in general accompanied by, and correlated to, reductions in oxygen consumption, bile secretion, and perfusion flow of the isolated livers. Statistically significant correlations exist between parameters of alcohol-induced hepatotoxicity and the membrane/buffer partition coefficents of the alcohols. With the exception of methanol, all alcohols tested increased the lactate/pyruvate ratio of the perfusate, although this effect was not correlated to the degree of hepatic injury. Hepatic ATP concentrations decreased in most cases in line with hepatic injury and were particularly correlated with changes in oxygen consumption. Hepatic concentrations of reduced glutathione (GSH) were only diminished by the unsaturated alcohols, whereas an increase in hepatic oxidized glutathione (GSSG) occurred only with some of the saturated alcohols. Hepatic concentrations of malondialdehyde (MDA) increased after two saturated and three unsaturated alcohols but did not correlate with other parameters of hepatotoxicity. In conclusion, alcohol-induced hepatotoxicity is primarily due to membrane damage induced by the direct solvent properties of the alcohols. The consequences and relative contributions of alcohol metabolization to the overall hepatotoxicity of higher alcohols requires further study.

3,4-Methylenedioxyamphetamine↗
PubMed1996

Comparative studies on the toxicity of mercury, cadmium, and copper toward the isolated perfused rat liver.

The toxic effects of cadmium, mercury, and copper were compared over the over range 0.01, 0.03, and 0.1 mM using the isolated perfused rat liver preparation. All metals caused similar changes in various parameters used to describe general toxicity. Thus reductions in oxygen consumption, perfusion flow, and biliary secretion were found, while lactate dehydrogenase release into the perfusate, as well as liver weight, increased also in a dose-dependent fashion. Each metal caused similar magnitudes of changes and exerted similar potency. Measurement of other parameters indicating more specific injury revealed a number of differences. Although all metals reduced hepatic ATP concentration, mercury and cadmium were more potent than copper in this respect. Cadmium was the most potent at decreasing reduced glutathione levels. Mercury was most effective at increasing tissue calcium content, while copper was less so, and cadmium ineffective. Only copper significantly increased tissue malondialdehyde (MDA) content, while all metals increased its release into perfusate. Furthermore, whereas cadmium seemed the most potent metal in increasing MDA release, it was least efficacious, while copper was the most. Antioxidants such as superoxide dismutase, catalase, and Trolox C only reduced cadmium's influence on MDA in perfusate; however, they did not affect cadmium's ability to alter most other parameters of vitality. Albumin reversed the toxic effects of copper and mercury, but not cadmium. While metal-induced reductions in perfusion flow accounted for some of the toxic effects of the metals investigated, the results as a whole supported the suggestion that all metals exerted toxicity at the mitochondria, since ATP levels were reduced in a manner that could not be reproduced by perfusion flow reduction alone. Lipid peroxidation appears to play little role in determining toxicity induced by any of these metals. Furthermore, albumin may play an important physiological role in preventing hepatic injury that might otherwise be induced through acute metal intoxication.

Adenosine Triphosphate↗
PubMed1996

Use of minors as bone marrow donors: current attitude and management. A survey of 56 pediatric transplantation centers.

OBJECTIVE: To determine the current attitude about the use of minors as bone marrow donors in pediatric bone marrow transplantation (BMT) centers in North America. STUDY DESIGN: A questionnaire was mailed to 70 North American BMT centers. The questionnaire asked for opinions on a number of ethical and clinical issues pertaining to the use of minors as marrow donors. A case history was included and respondents were asked to check all appropriate answers listed in the survey. RESULTS: Fifty-six (80%) of 70 centers responded. There was general consensus on many issues. Pediatricians endorse the validity of parental consent, even in potentially controversial situations. Most are prepared to extract marrow from young (about 6 months of age) infants and are willing to use the same donor more than once. There is general approval of performing BMT with experimental protocols, and the projected outcome of BMT does not affect the decision to use a minor as a marrow donor. There is less consensus regarding the optimal management of minors donating a large volume of bone marrow. CONCLUSION: This survey shows a fairly consistent attitude among pediatric BMT centers about the use of minors as marrow donors. The actual management of such donors was not evaluated in detail and requires further study.

Adolescent↗
PubMed1995

Elimination of amrinone during continuous veno-venous haemofiltration after cardiac surgery.

We studied the elimination of amrinone during continuous veno-venous haemofiltration (CVVHF) in three anuric patients after cardiac surgery. The patients had developed low cardiac output followed by acute prerenal failure. Plasma amrinone levels measured by HPLC were fitted to a two-compartment model. We found significant amrinone clearance, with a mean sieving coefficient (S) of 0.44%, which correlates with the protein-unbound, pharmacologically effective fraction of amrinone. The AUC of the arterial plasma concentration-time curve was decreased by 49.8%. All pharmacokinetic parameters showed wide interindividual variation. To ensure the therapeutic effect of amrinone and to avoid toxic adverse effects monitoring of plasma amrinone levels is necessary.

Amrinone↗
PubMed1994

Bioethics reformation style.

The Hippocratic model is inadequate because it is too paternalistic, argues Rebecca D. Pentz in her response to Cameron. Instead, we would do well to think of the patient/doctor relationship in Reformation terms, using the pastor/congregation relationship as a model. Rejecting Hippocratic paternalism is not tantamount to an assertion of absolute autonomy; it entails patient responsibility, shared with the physician.

Bioethics↗
PubMed1990

Experimental studies on the acute cardiovascular toxicity of formalin and its antidotal treatment.

Rats anesthetized with pentobarbital and ventilated artificially were infused with 0.01 ml formalin (= 0.12 mmol formaldehyde)/kg.min. They exhibited a sharp decline of arterial blood pressure, heart rate and peripheral resistance and a slower one of cardiac output and died after 59.9 +/- 6.0 min of infusion. Sinus bradycardia and, in some cases, AV-arrhythmia occurred in the ECG. The additional infusion with cysteine attenuated the cardiovascular failure and more than doubled the survival time of formalin-infused rats. Infusion of N-acetylcysteine or correction of formalin-induced metabolic acidosis with sodium bicarbonate, on the other hand, did not exert antidotal activity. On isolated rat atria in vitro, formalin decreased the rate and the contractility and cysteine antagonized these effects of formalin. In conclusion, the severe and often lethal incidents observed following the therapeutic administration of formalin are due to the cardiovascular-depressive activity of formaldehyde and may be antagonized by cysteine.

Acetylcysteine↗
PubMed1990

[Effects of amalgam fillings on the mercury concentrations in amniotic fluid and breast milk].

Human amniotic fluid was gained from 95 pregnant women by amniocentesis (group 1) and from 20 women during delivery (group 2). The concentrations of inorganic mercury in amniotic fluid as assessed directly by cold-vapor atomic absorption spectrophotometry (CV-AAS) averaged 0.29 +/- 0.1 microgram/l in group 1 and 0.86 +/- 0.25 microgram/l in group 2. Surface areas of dental amalgam fillings were also estimated in these women and ranged between 0 and 930 mm2. There was no correlation between the surface area of maternal amalgam fillings and the concentrations of inorganic mercury in amniotic fluid (r = -0.122 and -0.069, respectively). Furthermore, no positive correlation existed between amalgam fillings and the concentration of total mercury in maternal blood (4.48 +/- 2.33 micrograms/l) and in neonatal blood (3.28 +/- 1.57 micrograms/l) as measured by CV-AAS in group 2 (r = -0.4 and -0.12, respectively). Concentrations of total mercury were also measured by CV-AAS in the breast milk of 86 women, five to ten days after delivery. These concentrations averaged 1.9 +/- 1.6 micrograms/l and were also not significantly correlated to the maternal amalgam surface areas (r = 0.188). In conclusion, maternal amalgam fillings are of no importance for the mercury load of the fetus and the neonate.

Adolescent↗
PubMed1989

Mechanistic study on formaldehyde-induced hepatotoxicity.

In isolated, hemoglobin-free perfused livers of fasted rats, formaldehyde at an initial concentration of 10 mmol/l produced toxicity as evidenced by a release of enzymes (GPT, SDH) and of glutathione (mainly GSSG) into the perfusate, an accumulation of calcium in the liver, and a depletion of hepatic glutathione. Formaldehyde also led to an enhanced release of malondialdehyde into the perfusate, indicating peroxidative processes and decreased hepatic oxygen consumption by about 50-70%. The electron microscopic investigation of formaldehyde-exposed livers showed a destruction of the mitochondria (ruptured membranes, loss of the cristae) and some damage of the rough endoplasmic reticulum. Feeding the rats prior to surgery attenuated the hepatotoxic effects of 10 mmol/l formaldehyde. At an initial concentration of 3 mmol/l, formaldehyde did not release enzymes from livers of fed or fasted rats but only from those whose glutathione content had been depleted by treatment with phorone (250 mg/kg ip 2 h earlier). Formaldehyde liberated glucose and lactate from the livers of fed but not from those of fasted rats, indicating anaerobic energy supply in the fed state. The hepatotoxic action of formaldehyde is not due to its metabolism to formate or to the 10% methanol added as a stabilizing agent to the commercially available 37% solution named formalin. In conclusion, by destruction of mitochondria, formaldehyde inhibits aerobic energy supply and thereby presumably produces hepatocellular damage.

Alanine Transaminase↗
PubMed1987

Enhancement by glutathione depletion of ethanol-induced acute hepatotoxicity in vitro and in vivo.

Ethanol at initial concentrations between 0.75 and 6 g/l produced a dose-dependent release of the enzymes glutamic-pyruvic-transaminase and sorbitol dehydrogenase (GPT, SDH) from the isolated perfused rat liver. At the concentration of 6 g/l, it also decreased the oxygen consumption and elevated the calcium content of the isolated livers. These toxic effects of ethanol were significantly enhanced in livers, the glutathione content of which had been depleted by pretreatment with phorone. Ethanol-induced toxicity in glutathione-depleted isolated livers could be prevented both by inhibition of alcohol dehydrogenase with 4-methylpyrazole and of xanthine oxidase with allopurinol. In rats, in vivo, 1.6 g/kg ethanol injected intravenously produced a small increase in serum GPT and SDH concentrations 4 h after its administration. This increase in enzyme activities was several-fold higher and longer lasting in rats pretreated with phorone. Glutathione depletion per se did not induce hepatotoxicity in vitro or in vivo. Since glutathione is involved in several lines of defense against oxidative damage, our results of an enhanced susceptibility of glutathione-depleted livers to ethanol toxicity favour the hypothesis that ethanol exerts its hepatotoxic action via an activation of molecular oxygen.

Alanine Transaminase↗
PubMed1987

Hepatotoxicity of acetaldehyde in rats.

The ability of acetaldehyde to initiate hepatotoxicity as evidenced by enzyme leakage, hepatic fat accumulation and histological alterations was studied in rats. Neither oral nor intraperitoneal treatment with acetaldehyde had any hepatotoxic effect, even following aldehyde dehydrogenase inhibition by disulfiram. This is probably due to the inability of exogenously added acetaldehyde to penetrate liver cell membranes. In contrast, acetaldehyde derived metabolically from ethanol was capable of inducing moderate hepatotoxicity when it accumulated upon pretreatment with disulfiram. Acetaldehyde may thus be partly responsible for alcohol-induced liver damage.

Acetaldehyde↗
PubMed1987

[Neonatal emergency: bupivacaine poisoning following maternal caudal anesthesia].

After maternal caudal anesthesia with bupivacaine life-threatening symptoms of bupivacaine intoxication occurred in the newborn. The local anesthetic had been injected directly into the fetal scalp. Cardiac shock caused by sinus bradycardia and impaired intracardial conduction (wide QRS-complex) was treated successfully. Seizures were absent. The bupivacain plasma level 90 min post partum was 3.6 mg/l, the elimination half-life 14 h. The symptoms presented in the newborn--especially the cardiovascular changes--coincide well with the results of animal experiments reported in the literature.

Anesthesia, Caudal↗
PubMed1986

Influence of extracellular calcium on allyl alcohol-induced hepatotoxicity.

The role of calcium in allyl alcohol-induced hepatotoxicity was investigated in the isolated haemoglobin-free perfused rat liver. At a Ca++ concentration of 2.5 mmol/l in the perfusate, allyl alcohol (initial concentration 1.17 mmol/l) produced an enhanced release of GPT and SDH from the liver, an increase in the lactate/pyruvate ratio of the perfusate, a decrease in hepatic oxygen consumption and an increase of both hepatic calcium and malondialdehyde content. In the absence of Ca++ in the perfusate, no hepatic calcium accumulation occurred with allyl alcohol, but all other signs of hepatic damage were as severe as with 2.5 mmol/l Ca++. On the other hand, high extracellular Ca++ (5 mmol/l) alone led to a threefold increase of liver calcium but produced only marginal hepatotoxicity and only slightly enhanced the hepatotoxic effects of allyl alcohol. The concentrations of allyl alcohol in the perfusate were not altered at different Ca++ concentrations. In conclusion, the primary allyl alcohol-induced hepatotoxic injury does not appear to depend upon an influx of extracellular calcium.

1-Propanol↗