Biomedical subjects

S Adkins

Publications and source records attributed to S Adkins.

27 records · Page 2Linked to original sources

PubMed1993

Molecular basis for the polymorphic forms of human serum paraoxonase/arylesterase: glutamine or arginine at position 191, for the respective A or B allozymes.

The paraoxonase/arylesterase gene is located close to the cystic fibrosis gene on chromosome 7. Human serum contains two paraoxonase/arylesterase allozymes, A and B, which differ in their substrate specificities and kinetic properties. Purified A, AB, and B esterases were digested with trypsin, and the resultant peptides were compared by high-performance liquid chromatography. The elution profiles were very similar for all three samples, except for (1) one peptide (i.e., peptide A) seen only in the A and AB profiles and (2) another peptide (i.e., peptide B) seen only in the B and AB profiles. Sequencing revealed that peptide A had glutamine at amino acid position 191, whereas peptide B was generated by cleavage on the carboxy side of position 191, presumably because there was a basic (trypsin-specific) amino acid at that position. Working independently, our laboratory and one other laboratory have sequenced the coding region for paraoxonase from human liver cDNA libraries and have identified two polymorphic sites: Arg/Gln at position 191 and Leu/Met at position 54. Using PCR amplification and direct sequencing of nucleotides in both polymorphic regions with genomic DNA, we have estimated the allelic frequencies and have determined their concordance with the serum paraoxonase allozyme phenotypes in 27 unrelated adults and in 16 members of a three-generation pedigree. Among unrelated individuals, the Met/Leu polymorphism at position 54 did not correlate with the serum esterase phenotype. In contrast, the particular amino acid at position 191 correlated perfectly with serum phenotypes: A-type individuals had Gln at position 191, and B-type individuals had Arg at position 191; AB-type serum was found only with the heterozygous (Arg/Gln) combination. Pedigree analysis showed both polymorphisms to be inherited in the expected Mendelian manner and confirmed that only the 191 polymorphism showed concordance with the serum paraoxonase/arylesterase phenotypes.

Amino Acid Sequence↗

PubMed1992

Assessing work retention issues.

Within 6 months, a 10-member Nursing Services task force created and administered a literature-based retention survey. Tool development and administration is described. The 33-item tool was completed by 85% of the staff. Responses led to the formation of work groups, charged with addressing dissatisfiers and communicating implementation strategies to the hospital at large.

Adult↗

PubMed1992

Identification of two different point mutations associated with the fluoride-resistant phenotype for human butyrylcholinesterase.

The fluoride variant of human butyrylcholinesterase owes its name to the observation that it is resistant to inhibition by 0.050 mM sodium fluoride in the in vitro assay. Individuals who are heterozygous for the fluoride and atypical alleles experience about 30 min of apnea, rather than the usual 3-5 min, after receiving succinyldicholine. Earlier we reported that the atypical variant has a nucleotide substitution which changes Asp 70 to Gly. In the present work we have identified two different point mutations associated with the fluoride-resistant phenotype. Fluoride-1 has a nucleotide substitution which changes Thr 243 to Met (ACG to ATG). Fluoride-2 has a substitution which changes Gly 390 to Val (GGT to GTT). These results were obtained by DNA sequence analysis of the butyrylcholinesterase gene after amplification by PCR. The subjects for these analyses were 4 patients and 21 family members.

Amino Acid Sequence↗

PubMed1987

Location of disulfide bonds within the sequence of human serum cholinesterase.

Human serum cholinesterase was digested with pepsin under conditions which left disulfide bonds intact. Peptides were isolated by high pressure liquid chromatography, and those containing disulfide bonds were identified by a color assay. Peptides were characterized by amino acid sequencing and composition analysis. Human serum cholinesterase contains 8 half-cystines in each subunit of 574 amino acids. Six of these form three internal disulfide bridges: between Cys65-Cys92, Cys252-Cys263, and Cys400-Cys519. A disulfide bond with Cys65 rather than Cys66 was inferred by homology with Torpedo acetylcholinesterase. Cys571 forms a disulfide bridge with Cys571 of an identical subunit. This interchain disulfide bridge is four amino acids from the carboxyl terminus. A peptide containing the interchain disulfide is readily cleaved from cholinesterase by trypsin (Lockridge, O., and La Du, B. N. (1982) J. Biol. Chem. 257, 12012-12018), suggesting that the carboxyl terminus is near the surface of the globular tetrameric protein. The disulfide bridges in human cholinesterase have exactly the same location as in Torpedo californica acetylcholinesterase. There is one potential free sulfhydryl in human cholinesterase at Cys66, but this sulfhydryl could not be alkylated. Comparison of human cholinesterase, and Torpedo and Drosophila acetylcholinesterases to the serine proteases suggests that the cholinesterases constitute a separate family of serine esterases, distinct from the trypsin family and from subtilisin.

Acetylcholinesterase↗

PubMed1987

Mitochondrial hydrogen peroxide generation and activities of glutathione peroxidase and superoxide dismutase following global ischemia.

We used isolated, buffer-perfused rabbit hearts to evaluate whether global, normothermic ischemia altered mitochondrial hydrogen peroxide (H2O2) generation and mitochondrial activities of the major enzymes responsible for degrading H2O2 and superoxide anion (O2-.): glutathione peroxidase (GPD) and superoxide dismutase (SOD), respectively. This preparation lacks exogenous neutrophils and endogenous xanthine oxidase, which are other potential sources of oxygen metabolites. Ischemia depressed mitochondrial oxidative phosphorylation parameters, State 4 succinate-supported H2O2 generation rates, and the relative flux of State 4 oxygen consumption that was diverted to H2O2 formation. The production of H2O2 was not abolished. Ischemia and reperfusion significantly reduced the activities of SOD (by 43%) and GPD (by 39%) in the mitochondrial fraction. Cytosolic GPD activity was also depressed. The results suggest that the myocardial cell's ability to enzymatically degrade H2O2 and O2-. is compromised, particularly in the mitochondrion. Although mitochondrial H2O2 production is decreased, the mitochondria may persist as a source of this oxygen metabolite following ischemia. Collectively, the data may help explain why mitochondria are vulnerable targets of free radical-mediated damage due to ischemia.

Animals↗

PubMed1987

Brain cDNA clone for human cholinesterase.

A cDNA library from human basal ganglia was screened with oligonucleotide probes corresponding to portions of the amino acid sequence of human serum cholinesterase (EC 3.1.1.8). Five overlapping clones, representing 2.4 kilobases, were isolated. The sequenced cDNA contained 207 base pairs of coding sequence 5' to the amino terminus of the mature protein in which there were four ATG translation start sites in the same reading frame as the protein. Only the ATG coding for Met-(-28) lay within a favorable consensus sequence for functional initiators. There were 1722 base pairs of coding sequence corresponding to the protein found circulating in human serum. The amino acid sequence deduced from the cDNA exactly matched the 574 amino acid sequence of human serum cholinesterase, as previously determined by Edman degradation. Therefore, our clones represented cholinesterase (EC 3.1.1.8) rather than acetylcholinesterase (EC 3.1.1.7). It was concluded that the amino acid sequences of cholinesterase from two different tissues, human brain and human serum, were identical. Hybridization of genomic DNA blots suggested that a single gene, or very few genes, coded for cholinesterase.

Amino Acid Sequence↗

PubMed1986

Analysis of the serum paraoxonase/arylesterase polymorphism in some Sudanese families.

The combination of several qualitative tests of paraoxonase and arylesterase activity of human serum permits a clear, unequivical designation of phenotype for nearly every individual. The qualitative tests appear to be applicable for further studies of sample populations from Africa, the near East, and the Orient. These tests should facilitate the estimation of the respective gene frequencies in various ethnic groups. It is probable that the same two major alleles determining the isozymes of paraoxonase/arylesterase of human serum are present in the European, North American and African populations. However, there appears to be a higher frequency of B alleles among African and Oriental people. Further surveys should provide more details of the ethnic differences and the extent of variation in gene frequencies in selected populations for this interesting polymorphic protein.

Alleles↗

PubMedDate not supplied

Hydrogen peroxide generation by mitochondria isolated from regionally ischemic and nonischemic dog myocardium.

We occluded the left anterior descending coronary artery of anesthetized, open-chest dogs, for 1 or 2 h. Some hearts were reperfused for 1 h after 1 h of ischemia. We isolated mitochondria from the central ischemic zone (CIZ) and a surrounding nonischemic zone (NIZ) of the left ventricle, and assayed H2O2 production using a horseradish peroxidase-dual wavelength spectrophotometric technique. Mitochondria, studied in the absence of exogenous respiratory chain inhibitors, generated H2O2 during State 4 respiration with succinate as the substrate. NIZ mitochondria in all groups produced ca. 1.5 nmols H2O2/min/mg protein (no significant differences between groups). The State 4 O2 consumption rates of NIZ mitochondria from hearts subjected to 1 h ischemia plus reperfusion, or 2 h of ischemia (ca. 30 nmols/min/mg) were significantly higher than that of NIZ mitochondria of hearts subjected to only 1 h of ischemia (23 nmols/min/mg). Thus, the ratio between H2O2 produced and State 4 O2 consumption fell from 6.5% to 5%. Mitochondria from all CIZ samples had State 4 O2 consumption rates that were not different from corresponding NIZ values. However CIZ mitochondria of hearts subjected to 1 h ischemia without reperfusion produced less H2O2 (1.1 +/- 0.1 nmols/min/mg), and had a slightly reduced H2O2/O2 ratio (4.4 +/- 0.7%), compared with their NIZ samples (1.5 +/- 0.1 nmols/min/mg; 5.3%). Reperfusion after 1 h of ischemia abolished these regional differences. The CIZ mitochondria from hearts subjected to 2 h ischemia produced only 0.75 +/- 0.22 nmols H2O2/min/mg (2.5% of State 4 O2 consumption). These values were 50% of corresponding NIZ values, and were significantly less than for any other group or tissue region. If similar phenomena occur in conscious animals subjected to incomplete regional ischemia, especially of relatively brief duration or if accompanied by reduced intracellular defenses against oxidants such as H2O2, they suggest that mitochondria persist as H2O2 sources and so may contribute to the oxidant load and myocardial dysfunction.

Adenosine Diphosphate↗

PubMedDate not supplied

Perception of chemotherapy side effects cancer versus noncancer patients.

PURPOSE: This study was conducted to identify and compare perceptions regarding the disruption in quality of life caused by chemotherapy side effects in patients with cancer receiving chemotherapy and in noncancer, chemotherapy-naive patients. DESCRIPTION OF STUDY: One hundred forty-six patients with cancer and 224 patients without cancer completed two instruments to assess the perceived magnitude of 41 physical and psychosocial chemotherapy side effects. Instrument 1 used a 5-point Likert scale (1 = not at all; 2 = a little bit; 3 = somewhat; 4 = quite a bit; and 5 = very much) to summarize patient responses to the question, "How much did or would each of the following side effects of chemotherapy bother you?" Instrument 2 was a serial ranking questionnaire that asked patients to select the 10 most bothersome side effects to numerically rank the top five. An index of the relative magnitude of chemotherapy side effects was calculated for each instrument. RESULTS: For patients with cancer, loss of hair 50%), changes in taste (46%), constantly being tired (42%), affects work duties (39%), changes in smell perception (35%) were most frequently perceived as bothering them "quite a bit" or "very much." Nausea and vomiting were ranked 11th and 22nd, respectively. With instrument 2, the five side effects perceived as most troublesome were, in decreasing order: nausea, loss of hair, constantly tired, vomiting, and changes in the way things taste. For noncancer patients, those factors potentially bothersome "quite a bit" or "very much" were: financial hardship (82%), hardship on family (78%), vomiting (73%), shortness of breath (70%), and ability to perform work duties (69%). Via instrument 2, the top five side effects, in decreasing order were: vomiting, hardship on family, loss of hair, financial hardship, nausea, having to move close to a treatment center. CLINICAL IMPLICATIONS: Noncancer, chemotherapy-naive patients perceived most chemotherapy-associated side effects as having greater impact on the quality of life than did cancer patients who had received chemotherapy. These findings can be used to direct patient education, education of the public, specific materials concerning cancer chemotherapy. The expertise of various members of the healthcare team can maximize the patient's comprehension of the adverse effects of the treatment options. The physician's knowledge of the overall treatment plan can assist in patient understanding; oncology pharmacists nurses are in a unique position to educate patients their families regarding potential chemotherapy side effects.

Adult↗