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J T Bernert

Publications and source records attributed to J T Bernert.

46 records · Page 3Linked to original sources
PubMed1979

Factors regulating the elongation of palmitic and stearic acid by rat liver microsomes.

Analysis of the rates of overall chain elongation and condensation of malonyl-CoA with palmitoyl-CoA and stearoyl-CoA as primers demonstrated that for each primer, the rate of the overall metabolic process was similar to the initial condensation. The specific activity for condensation with palmitoyl-CoA was eleven times greater than for stearoyl-CoA. The specific activities of both the beta-hydroxyacyl-CoA dehydrase and 2-trans-enoyl-CoA reductase reactions were much higher than for either condensation or chain elongation, although these rates were somewhat greater with the intermediates required in chain elongating palmitoyl-CoA than for stearoyl-CoA. Both substrates were incorporated into phospholipids at low rates and there was a time-dependent hydrolytic cleavage of the acyl-CoA primers which was partially prevented by bovine serum albumin. These findings demonstrate that there was no selective removal of either primer which could result in specific substrate depletion and an apparent reduction in the rate of condensation. These combined results firmly establish the rate-limiting nature and high degree of substrate specificity exhibited during the initial condensation step in fatty acid elongation.

Animals↗
PubMed1979

The isolation of acyl-CoA derivatives as products of partial reactions in the microsomal chain elongation of fatty acids.

An analysis of overall chain elongation, condensation, beta-hydroxyacyl-CoA dehydrase and 2-trans enoyl-CoA reductase reactions, using the appropriate CoA derivatives as substrates which are required in the microsomal chain elongation of both palmitoyl-CoA and 6,9-octadecadienoyl-CoA, demonstrated that in each instance, the products of these reactions were the CoA derivatives. Reverse dehydrase reactions run with 2-trans enoyl-CoA derivatives as substrates, in the absence of NADPH, revealed that the product was the beta-hydroxyacyl-Coa. In the presence of NADPH, incubations with beta-hydroxyacyl-CoA demonstrated that both the 2-trans derivatives and the alpha, beta-saturated product were recovered as their CoA derivatives. These latter findings are more consistent with the involvement of discrete dehydrase and 2-trans-enoyl-CoA reductase enzymes rather than a single protein catalyzing two reactions.

Acyl Coenzyme A↗
PubMed1978

The effect of bovine serum albumin on partial reactions of palmitoyl-CoA chain elongation by rat liver microsomes.

In the absence of albumin, v/s curves for both condensation and overall chain elongation demonstrated that the specific activity for overall chain elongation was 3.7 times that of condensation. When the molar ratio of palmitoyl-CoA to albumin was greater than 2 : 1, the specific activity of chain elongation exceeded that of condensation. At these low albumin concentrations, in the absence of NADPH, the beta-ketostearoyl-coA was converted back to palmitate. This cleavage reaction is inhibited by albumin in a concentration-dependent manner. When the palmitoyl-CoA to albumin molar ratio was less than 2 : 1, the specific activity for condensation exceeded that for overall chain elongation and some beta-ketostearate was shown to accumulate under chain elongation conditions. The specific activity for dehydration of beta-hydroxystearoyl-CoA was maximal when the acyl-CoA to albumin molar ratio was between 10 : 1 and 4 : 1 but the rate of this reaction was not markedly influenced by variations in albumin concentration. The specific activity for the NADPH-dependent reduction of 2-trans-octa-decenoyl-CoA was 18 nmol . min(-1) . mg(-1) in the absence of albumin and increased to a maximum of 112 when the substrate to albumin molar ratio was 2 : 1. At higher albumin concentrations the reductase reaction was inhibited. Conversely, the specific activity for the reverse dehydrase was maximal at low albumin concentrations and the rate of this reaction declined as the albumin concentration increased. Our results demonstrate that albumin not only alleviates a substrate induced inhibition but also regulates the metabolic fate of 2-trans-octadecenoyl-CoA and in this regard may possibly substitute for acyl-CoA binding proteins.

Acyl Coenzyme A↗
PubMed1975

Studies to determine the role rates of chain elongation and desaturation play in regulating the unsaturated fatty acid composition of rat liver lipids.

Rat liver microsomes were used to measure the rates of chain elongation and desaturation of acids in the linoleate, oleate and palmitoleate biosynthetic pathways. These studies were designed to determine whether there is a relationship between rates of conversion and the types of unsaturated fatty acids found in rat liver lipids. In some cases rates of conversion correlate well with the types of unsaturated fatty acid found inrat liver lipids. In other cases, rates of conversion must be correlated with other controls such as competitive interactions, retroconversion, and specificities for incorporating given acids into lipids in order to explain the unsaturated fatty acid composition of rat liver lipids. The roles and interrelationships of these various metabolic processes are discussed relative to the control of polyunsaturated fatty acid biosynthesis.

Animals↗
PubMedDate not supplied

Chlorinated hydrocarbon levels in human serum: effects of fasting and feeding.

Twenty healthy adult humans had serum samples drawn on four occasions within a 24-hr period: after a 12 hr overnight fast, 4-5 hr after a high fat breakfast, at midafternoon, and the next morning after another 12 hr fast. Nonfasting samples had 22% to 29% higher mean concentrations (p less than 0.05) than did fasting samples for polychlorinated biphenyls (PCBs, 4.81 vs 3.74 ng/g serum wt), hexachlorobenzene (HCB, 0.163 vs 0.134 ng/g serum wt), and p,p'-dichlorodiphenyl-dichloroethylene (p,p'-DDE, 6.74 vs 5.37 ng/g serum wt) measured by electron capture gas liquid chromatography. Total serum lipids were estimated from measurements of total cholesterol, free cholesterol, triglycerides, and phospholipids and were 20% higher in nonfasting samples than in fasting samples (7.05 g/L vs 5.86 g/L). When PCBs, HCB, and p,p'-DDE concentrations were corrected by total serum lipids, results from fasting and non-fasting samples were not statistically different. Because of the differences in these chlorinated hydrocarbon concentrations observed with different sample collection regimens, meaningful comparison of analytical results requires standardizing collection procedures or correcting by total serum lipid levels.

Adult↗
PubMedDate not supplied

Analysis of benzoylecgonine in dried blood spots by liquid chromatography--atmospheric pressure chemical ionization tandem mass spectrometry.

Residual samples from blood spots (i.e., whole blood spotted onto filter paper) are a useful source for epidemiological screening studies involving newborns. However, the small volume of blood available from residual blood spots complicates the assay. A method for analyzing benzoylecgonine (BZE; the primary metabolite of cocaine) in blood spots, in which the blood spot is eluted with aqueous ammonium acetate-methanol containing N-methyl trideuterated-BZE as an internal standard, followed by high-performance liquid chromatography-atmospheric pressure chemical ionization tandem mass spectrometry using multiple reaction monitoring, has been developed. This approach provides a rapid, direct, sensitive (limit of detection, approximately 2 ng/mL, based on a 12-microL sample size), and highly specific means of determining BZE concentrations in blood spots. We have applied this method for confirmatory analyses in a large epidemiological study of the prevalence of cocaine use during late pregnancy.

Acetates↗
PubMedDate not supplied

Comparison of serum and salivary cotinine measurements by a sensitive high-performance liquid chromatography-tandem mass spectrometry method as an indicator of exposure to tobacco smoke among smokers and nonsmokers.

Exposure to tobacco smoke, both from active smoking and from passive exposure to environmental tobacco smoke, can be monitored by measuring cotinine, a metabolite of nicotine, in a variety of biological sources including blood, urine, and saliva. Previously, a sensitive atmospheric-pressure ionization, tandem mass spectrometric (LC-API-MS-MS) method for cotinine measurements in serum was developed in support of a large, recurrent national epidemiologic investigation. The current study examined the application of this LC-API-MS-MS method to both serum and saliva cotinine measurements in a group of 200 healthy adults, including both smokers and nonsmokers. The primary objective of this study was to evaluate the relationship between serum and saliva cotinine concentrations to facilitate the linking of results from epidemiologic studies using salivary cotinine measurements to existing national data based on serum cotinine analyses. The results indicate that a simple, linear relationship can be developed to describe serum and saliva cotinine concentrations in an individual, and the expression describing this relationship can be used to estimate with reasonable accuracy (approximately +/- 10%) the serum cotinine concentration in an individual given his or her salivary cotinine result. It was further confirmed that saliva cotinine samples are generally quite stable during storage after collection, even at ambient temperatures, and this sample matrix appears to be well-suited to the requirements of many epidemiologic investigations.

Adolescent↗
PubMedDate not supplied

Evaluation of four maternal smoking questions.

OBJECTIVE: The authors evaluated four questions about maternal smoking during pregnancy for use on birth certificates. METHODS: Question 1 (yes/no format) and Question 2 (trimester-specific design) were tested among 1171 women who delivered at two Kaiser Permanente medical centers in northern California. Responses to Questions 1 and 2 were compared with smoking information provided by participants in telephone interviews conducted during pregnancy. Question 3 (multiple choice format) and Question 4 (month- and grouped month-specific design) were tested among 900 women who enrolled in a statewide prenatal screening program and who delivered in 20 hospitals in four Central Valley counties. Responses to Questions 3 and 4 were compared with mid-pregnancy serum cotinine levels. The authors evaluated the four questions in terms of conciseness, response rate, data accuracy, and type of data requested. RESULTS: Questions 1 and 2 were the most concise. Response rates could not be calculated for Questions 1 and 2. Response rates were 86.0% for Question 3 and 74.2% for Question 4. Sensitivity was 47.3% for Question 1, 62.1% for Question 2, 83.8% for Question 3, and 86.7% for Question 4. The types of data requested by Questions 2 and 4 seem to best satisfy the needs of the broad audience of birth certificate users. CONCLUSIONS: No single question was clearly superior. The authors propose a combination of Questions 2 and 4, which asks about average number of cigarettes smoked per day in the three months before pregnancy and in each trimester of pregnancy.

Birth Certificates↗