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B Ulbrich

Publications and source records attributed to B Ulbrich.

At least 19 recordsLinked to original sources
PubMed1996

Risk assessment for neurobehavioral toxicity: SGOMSEC joint report.

Behavioral end points for neurotoxicity risk assessment have been developed and examined over the past three decades. They are now ready to move from simple qualitative guidelines, such as exemplified by reference doses, to more quantitative models, such as benchmark doses, based on dose-response information. Risk assessors, confronted by a wider array of methodologies and data than in the past, should be offered guidance in interpretation because now they have to deal with unaccustomed questions and problems. These include reversibility, susceptible populations, multiple end points, and the details of dose-response and dose-effect distributions.

Animals↗
PubMed1996

Neurobehavioral aspects of developmental toxicity testing.

Tests for detection of neurobehavioral changes in the offspring have been a regulatory requirement in developmental toxicity testing of drugs for almost 20 years. Keeping their purpose of hazard identification and risk assessment for humans in mind, investigators and agency reviewers have become deeply ingrained with some stereotyped behaviors with respect to such relevant issues as choice of animal species and data evaluation. Other problematic areas of study design and conduct, selection of litter representatives for testing, what methods to combine in a testing battery, and statistical treatment of results and their interpretation, will need more research and discussion in the future.

Animals↗
PubMed1994

Peri- and postnatal exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin: effects on physiological development, reflexes, locomotor activity and learning behaviour in Wistar rats.

Effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on the development of rat offspring were studied after administration of a loading dose of 300 or 1000 ng TCDD/kg body wt on day 19 of pregnancy, followed by weekly maintenance doses of 120 or 400 ng TCDD/kg body wt. The dose regimens led to a fluctuation of average TCDD concentrations in the liver of the offspring of 4.9-14.9 ng/g (TCDD1000/400 group) or 1.4-6.3 ng/g (TCDD300/120 group) during the course of the experiment. In both TCDD-exposed groups the body weight of the offspring was significantly lower on postnatal day 7 (PND 7); in the high dose group from PND 7 to PND 31. Some landmarks of postnatal development were retarded in the exposed groups; in particular, the vaginal opening was delayed for several days in both TCDD-exposed groups. The TCDD-exposed animals revealed a reduced ability to remain on a rotating rod. During reflex testing, the rate of successfully responding animals was higher in the exposed groups. No statistically significant differences in the locomotor activity between controls and TCDD-exposed offspring were detectable under our experimental conditions. In a discrimination learning test no effects on the learning ability were found. However, TCDD-exposed offspring showed an increase in unanswered trials during critical phases of the task. They also exhibited increased locomotor activity in a novel environment; prior to an amphetamine challenge dose of 1 mg/kg body weight. Amphetamine-induced activity was decreased in a dose-dependent manner.

Animals↗
PubMed1990

Requirements of preclinical examinations.

The eye is an important and sensitive target organ not only for ophthalmic drugs but also generally for adverse drug effects and has to be taken into consideration accordingly when performing toxicological studies. Depending on the drug in question protocols for oculotoxicity studies have to be determined on a case by case basis. The test battery used to detect possible eye damage should be an intelligent combination of pharmacokinetic/metabolic studies, clinical examinations, pathomorphologic examinations, and biochemical tests. For special studies on oculotoxicity only pigmented animals should be used. The legal basis for the necessity to conduct oculotoxicity studies and ophthalmologic examinations in toxicity studies is given by national law (AMG) and guidelines and by EEC-Guidelines. Studies have to be performed according to the principles of Good Laboratory Praxis.

Animals↗
PubMed1980

Mammalian mitochondrial ribosomes. Studies on the exchangeability of polypeptide chain elongation factors from bacterial and mitochondrial systems.

Mammalian mitochondrial ribosomes from rat liver synthesised poly(phenylalanine) from [14C]-Phe-tRNA in the presence of a homologous 10(5) X gav supernatent fraction. The activity depended on the addition of synthetic template and was resistant to cycloheximide. The polyanion spermidine had a stimulatory effect on peptide synthesis in vitro. In contrast to Escherichia coli ribosomes, which also functioned with heterologous supernatant fractions, 55-S mitochondrial ribosomes were inactive when supplemented with heterologous supernatant fractions from E. coli or with purified bacterial elongation factors. EF-T slightly stimulated polyphenylalanine synthesis when added in combination with mitochondrial supernatant fractions. Two-dimensional electrophoretic analysis of the protein content of both supernatant fractions revealed considerable differences in the distribution of the species-specific proteins according to their isoelectric points. The mitochondrial supernatant proteins were in general more basic, and the few acidic proteins did not co-migrate with EF-Tu or EF-G from E. coli.

Animals↗
PubMed1975

Pools of ribosomal proteins in Escherichia coli. Studies on the exchange of proteins between pools and ribosomes.

A labelling technique in vivo has been introduced which allows the tritiation of cell components with high specific activity during growth in rich medium. By this technique the pool size of each protein can be measured directly in the supernatant from centrifugation at 150000 times g. A measurable pool was found for the proteins S1, S2, S10, L1, L4, L7, L8/9, L10, L12, L21, and L25. Experiments on migration of ribosomal proteins from the supernatant to ribosomes (i.e. association) and vice versa (dissociation) demonstrate a remarkable constancy in the composition of the ribosome. There is no significant difference between ribosomes engaged or not engaged in poly-(Phe) synthesis.

Escherichia coli↗
PubMedDate not supplied

Detection limits of different approaches in behavioral teratology, and correlation of effects with neurochemical parameters.

Five laboratories collaborated in the evaluation of detection limits of different testing concepts in behavioral teratology. In one laboratory, rat dams were treated by gavage with five doses of methylmercury (0.0, 0.25, 0.05, 0.5, and 5.0 mg/kg/day). The treatment period was restricted to days 6 to 9 of gestation. The usual reproduction parameters were assessed in the dams. The offspring (88-99 per group) were subjected to a routine developmental and behavioral testing battery. After completion of these tests, random samples of the animals were further investigated in four other laboratories using the following techniques: auditory startle habituation, visual discrimination and figure-8 activity monitor; wheel-shaped activity monitor and spatial alternation operant conditioning; two-compartment locomotor activity, passive avoidance and male ultrasonic vocalization during sexual behavior; assays of the weight of different brain areas, their glial fibrillary acidic (GFA) protein and S-100 protein concentration. The following dose-dependent effects were noted in ascending dose sensitivity order: delayed vaginal opening; increased and more variable passiveness in spatial alternation; impaired swimming behavior, increased GFA protein concentration in the cerebellar vermis; increased auditory startle amplitude, decreased intertrial interval pokes in the visual discrimination test, increased percentage of visits in passive area of figure-8 activity monitor, increased path iteration frequencies and decreased local activity in the wheel-shaped activity monitor, decreased locomotor activity in the two-compartment monitor, increased cerebellar vermis weight, and decreased S-100 protein in the hippocampus. Therefore, this study showed comparable sensitivities for the behavioral testing battery, for some automated multiparametric test systems and for the neurochemical assays.

Animals↗
PubMedDate not supplied

Specific toxicologic aspects of the quinolones.

Possible targets of quinolone toxicity include the juvenile joint, the kidney, the central nervous system (CNS), the eye, and the cardiovascular system. In immature animals all quinolones studied cause arthropathies of the major diarthrodial joints. Arthropathies have also developed in adult dogs after 12 months of pefloxacin treatment. At high doses the quinolones exert effects on renal function that are related to a foreign-body reaction caused by crystals; nephropathologic changes seem not to occur without crystalluria. In humans quinolones can have various CNS effects. The subcellular "substrate" for these effects is unknown. Further understanding of severe CNS reactions (confusion, hallucination, anxiety, agitation, nightmares, convulsive seizures, and depression) is needed. Pefloxacin causes cataracts in dogs after treatment for 8-12 months. Low-dose quinolones (administered as an intravenous bolus) cause pronounced but transient systolic hypotension in dogs and cats; cardiovascular effects may be mediated by histamine release. Quinolones inhibit the bacterial enzyme DNA gyrase. To exclude the possibility of damage to mammalian DNA, mutagenicity studies have been performed. Since all but two tests (which may give false-positive results) have been negative, quinolones appear to be nonmutagenic. Photosensitivity has occurred in humans given quinolones. Drug interactions can be clinically important.

Animals↗
PubMedDate not supplied

Testing strategies in behavioral teratology: II. Discrimination learning.

Male and female Wistar rats exposed to methylmercury chloride prenatally via drinking water (1.5 and 5.0 mg/l) were tested in a microcomputer-directed learning task (visual discrimination reversal) at the age of two months. Differences were observed between control and high dose group for several parameters, the most obvious being an increase in passiveness and in response latency, as well as a decrease in intertrial interval response rates in the methylmercury group. No effects were seen in the low dose group. Performances of male and female animals were quite similar. However, females showed longer response latencies and passiveness scores were somewhat higher than in males.

Amphetamine↗