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Biomedical subjects

C F Bearer

Publications and source records attributed to C F Bearer.

29 records · Page 2Linked to original sources
PubMed1992

Fetal alcohol syndrome and fatty acid ethyl esters.

Fetal alcohol syndrome is the leading known cause of mental retardation. The syndrome, defined as growth retardation, midface hypoplasia, and neurologic dysfunction, represents only part of the spectrum of fetal alcohol effects. The biochemical mechanism of teratogenesis is unknown. In adults, metabolites of ethanol, FAEE, are known to accumulate in major organs. The formation of FAEE is catalyzed by a family of enzymes, FAEE synthases. Our hypothesis is that accumulation of FAEE in the embryo results in fetal alcohol syndrome. We have developed assays for FAEE and FAEE synthase activity using mg of tissue. Using these assays, we have shown the following: Human placenta, mouse placenta, heart, and liver are active in catalyzing the formation of FAEE. One h after maternal ethanol administration on gestational d 14, mouse placenta and fetuses accumulated significant quantities of FAEE. The fatty acid incorporated into FAEE was tissue dependent. Tissues from pregnant animals given ethanol on gestational d 7 showed persistence of FAEE on gestational d 14. We conclude that: 1) human and mouse placentas have significant FAEE synthase activity, 2) mouse heart, liver, placenta, and fetal tissues accumulate significant amounts of FAEE after maternal ethanol exposure, 3) there is tissue specificity for the fatty acid incorporated into FAEE, and 4) FAEE may persist for 7 d in placentas. These results provide a basis for further research into the role of FAEE in the development of fetal alcohol syndrome.

Acyltransferases↗
PubMed1991

The ubiquitin-activating enzyme, E1, is required for stress-induced lysosomal degradation of cellular proteins.

ts85, a cell line that harbors a mutant thermolabile ubiquitin-activating enzyme, E1, fails to degrade short lived proteins at the restrictive temperature (Ciechanover, A., Finley, D., and Varshavsky, A. (1984) Cell 37, 57-66). However, the involvement of the ubiquitin system in the degradation of long lived proteins (most cellular proteins fall in this category) has not been addressed. In the present study we show that upon shifting the mutant cells to the restrictive temperature, there is no change in the rate of degradation of long lived proteins. In contrast, shifting the wild-type cells (FM3A) to the high temperature is accompanied by a 2-fold increase in the rate of proteolysis of this group of proteins. This heat-induced accelerated degradation can be inhibited completely by NH4Cl and chloroquine. Similarly, exposure of the cells to starvation, a stimulus that activates the autophagic-lysosomal pathway, has no effect on the degradation of long lived proteins in the mutant cells after inactivation of E1. Under the same conditions, the degradation rate in the wild-type cells increases almost 4-fold. Analogous results were obtained using a different cell line that also harbors a thermolabile E1 (ts20 (Kulka, R. G., Raboy, B., Schuster, R., Parag, H. A., Diamond, G., Ciechanover, A., and Marcus, M. (1988) J. Biol. Chem. 263, 15726-15731)). Cycloheximide and 3-methyladenine, known inhibitors of formation of autophagic vacuoles, inhibit the heat-induced accelerated degradation of long lived proteins in wild-type cells. Taken together, the results suggest that 1) heat stress induces enhanced degradation of intracellular proteins; 2) the process occurs most probably in autophagic vacuoles; and 3) activation of ubiquitin is required for the formation of these vacuoles. As there is no change in the basal rate of degradation of intracellular proteins in the mutant cells at the restrictive temperature, it appears that the ubiquitin system is not involved in their breakdown.

Adenine↗
PubMed1978

Threonine inhibition of the aspartokinase--homoserine dehydrogenase I of Escherichia coli. Threonine binding studies.

Both activities of the aspartokinase--homoserine I (AK-HSD) of Escherichia coli are inhibited by threonine. Careful threonine binding studies have now been done which have allowed us to distinguish the various effects of threonine on the enzyme. The ultrafiltration technique of H. Paulus ((1969) Anal. Biochem. 32, 101) for measuring ligand binding was shown to be comparable with equilibrium dialysis techniques. Reduction in error by utilization of this procedure enabled us to obtain evidence for two different sets of threonine sites by direct binding studies. The binding data were mathematically consistent with two independent classes of threonine sites, each of which contained four sites per tetramer and had a Hill coefficient of about 2.3--2.5. KD for the second set of sites was five- to tenfold greater than the high affinity sites, depending upon conditions. The data now suggest that the sequential model for site--site interactions adequately describes the cooperativity of threonine binding to the high affinity set of sites.

Aspartokinase Homoserine Dehydrogenase↗
PubMedDate not supplied

Electromagnetic fields and infant incubators.

Two models of infant incubators were studied to determine the strength of the magnetic field generated by the heater and fan motors. Measurements were taken at intervals along the center line of the incubator. The results show that fields greater than 100 milligauss and 25 milligauss were measured in the C-86 and C-100 model Isolettes, respectively.

Electromagnetic Fields↗
PubMedDate not supplied

Environmental health hazards: how children are different from adults.

In policymaking on environmental health, it is often assumed that the entire population is exposed to and reacts to environmental contaminants in a similar manner. However, this assumption is misguided, especially where children are concerned. This article presents the scientific basis for the impacts of the environment on children, showing how children are different from adults in the ways in which they are exposed to environmental contamination and the ways in which they react to it when exposed. Specifically, the article examines the changing physical and biological environments of children. Children at different stages of development have unique physical risk factors for certain types of exposure because of changing location, levels of mobility, oxygen consumption, eating patterns, and behavior. When children are exposed to contaminants, their developing biological makeup--the way in which they absorb, distribute, and metabolize chemicals--will also affect how their bodies deal with the foreign substance. Each of these factors, along with the customs, laws, and regulations that affect the way in which children are exposed to the contaminants, had implications for the well-being of children in the years to come.

Adolescent↗