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Biomedical subjects

L Copeland

Publications and source records attributed to L Copeland.

At least 37 records · Page 2Linked to original sources
PubMed1990

Children's perceptions of AIDS.

Knowledge and attitudes about AIDS were surveyed in 147 children between the ages of 6 and 12. Awareness of and accurate information about AIDS increased steadily through the early school years. From third grade on, over 90% of children had heard of AIDS, with the majority capable of providing additional accurate information. Significant misconceptions were also identified in all age groups. Television was found to be the major source of information about AIDS for most children.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Palliative radiotherapy for ovarian cancer.

Large single-fraction irradiation is effective palliation for advanced ovarian cancer. It has an acceptable complication rate and requires only a limited number of visits (i.e., one treatment per 4-week course) to administer. Forty-two patients received single or multiple fractions of (three maximum) 10 Gray (Gy) to the pelvis. Most patients had advanced disease, 71.4% had Stage III or IV and 90.5% Grade 2 or 3 at the time of diagnosis. Forty patients had received preirradiation chemotherapy. Tumor size before and after radiotherapy was evaluable in 34 patients and decreased in 25. Bleeding decreased or stopped in 15 of 21 patients, and pain lessened or ceased in 11 of 20 patients. Thirteen patients had surgical procedures performed after irradiation therapy. Ten had gastrointestinal procedures, and in six radiation injury was believed to be the main contributor to complication. Hemorrhagic cystitis or proctitis occurred 6 to 18 months after irradiation in four patients. Three of these four patients received three 10 Gy fractions. The safest and most efficient dose may be one or two fractions, since three 10 Gy fractions may not increase palliation.

Carcinoma↗
PubMed1987

Combination chemotherapy for metastatic or recurrent adenocarcinoma of the cervix.

Twenty-four patients with recurrent or widespread adenocarcinoma of the cervix were treated with combination chemotherapy. The drugs used were 5-fluorouracil (5-FU) (500 to 800 mg/m2), doxorubicin (40 to 50 mg/m2), and cisplatin (50 to 60 mg/m2). The chemotherapy was administered as a 76-hour continuous infusion via a silastic central venous catheter and repeated every 28 days. The total response rate was 42% (25% complete and 17% partial). Median duration of response was 7 months. Areas of response were usually lung and lymph node metastases. Toxicity, mainly neutropenia, was acceptable. All patients relapsed. This combination chemotherapy results in a modest response rate for a malignancy about which there is little information regarding the treatment of disseminated disease. Future studies should determine the activity of this combination administered in a bolus fashion.

Adenocarcinoma↗
PubMed1987

Pediatricians' reported practices in the assessment and treatment of attention deficit disorders.

This study examined, in a national survey, the assessment and treatment practices of pediatricians who care for children with attention deficit disorders (ADD). A questionnaire was sent to randomly selected members of the American Academy of Pediatrics (AAP), stratified by state. Of 417 (52%) responses returned, there were 290 (38%) completed questionnaires. It was found that most pediatricians did not utilize specific DSM-III criteria for ADD; however, they do rely on symptoms of distractibility, overactivity, and impulsivity, which are the behaviors central to the DSM-III diagnosis. In addition, learning difficulties were felt to be contributory. Parents were the most frequently reported sources of information about a child's behavior, but the histories provided by teachers, and psychoeducational reports, also were sought frequently. Many pediatricians still use diagnostic procedures that have recently come under question, such as soft neurologic signs, activity level in the office, and response to stimulant medication. Methylphenidate and behavior modification were the most frequent therapies employed. Over half of the respondents use periodic reevaluation with rating scales to determine medication efficacy, but very few use placebo trials. More recently trained pediatricians tended to rely more on behavioral treatments than did earlier trained physicians.

Attention Deficit Disorder with Hyperactivity↗
PubMed1985

Sucrose synthase of soybean nodules.

SUCROSE SYNTHASE (UDPGLUCOSE: d-fructose 2-alpha-d-glucosyl transferase, EC 2.4.1.13) has been purified from the plant cytosolic fraction of soybean (Glycine max L. Merr cv Williams) nodules. The native enzyme had a molecular weight of 400,000. The subunit molecular weight was 90,000 and a tetrameric structure is proposed for soybean nodule sucrose synthase. Optimum activity in the sucrose cleavage and synthesis directions was at pH 6 and pH 9.5 respectively, and the enzyme displayed typical Michaelis-Menten kinetics. Soybean nodule sucrose synthase had a high affinity for UDP (K(m), 5 micromolar) and a relatively low affinity for ADP (apparent K(m), 0.13 millimolar) and CDP (apparent K(m), 1.1 millimolar). The K(m) for sucrose was 31 millimolar. In the synthesis direction, UDPglucose (K(m), 0.012 millimolar) was a more effective glucosyl donor than ADPglucose (K(m), 1.6 millimolar) and the K(m) for fructose was 3.7 millimolar. Divalent cations stimulated activity in both the cleavage and synthesis directions and the enzyme was very sensitive to inhibition by heavy metals.

Journal Article↗
PubMed1985

Hexose kinases from the plant cytosolic fraction of soybean nodules.

The enzymes responsible for the phosphorylation of hexoses in the plant cytosolic fraction of soybean (Glycine max L. Merr cv Williams) nodules have been studied and a hexokinase (ATP:d-hexose 6-phosphotransferase EC 2.7.1.1) and fructokinase (ATP:d-fructose 6-phosphotransferase EC 2.7.1.4) shown to be involved. The plant cytosolic hexokinase had optimum activity from pH 8.2 to 8.9 and the enzyme displayed typical Michaelis-Menten kinetics. Hexokinase had a higher affinity for glucose (K(m) 0.075 millimolar) than fructose (K(m) 2.5 millimolar) and is likely to phosphorylate mainly glucose in vivo. The plant cytosolic fructokinase had a pH optimum of 8.2 and required K(+) ions for maximum activity. The enzyme was specific for fructose (apparent K(m) 0.077 millimolar) but concentrations of fructose greater than 0.4 millimolar were inhibitory. The native molecular weight of fructokinase was 84,000 +/- 5,000. The roles of these enzymes in the metabolism of glucose and fructose in the host cytoplasm of soybean nodules are discussed.

Journal Article↗
PubMed1984

Kinetic studies of fructokinase I of pea seeds.

Fructokinase I of pea seeds has been purified to homogeneity and the enzyme shown to be monomeric, with a molecular weight of 72,000 +/- 4000. The reaction mechanism was investigated by means of initial velocity studies. Both substrates inhibited the enzyme; the inhibition caused by MgATP was linear-uncompetitive with respect to fructose whereas that caused by D-fructose was hyperbolic-noncompetitive against MgATP. The product D-fructose 6-phosphate caused hyperbolic-noncompetitive inhibition with respect to both substrates. MgADP caused noncompetitive inhibition, which gave intercept and slope replots that were linear with D-fructose but hyperbolic with MgATP. Free Mg2+ caused linear-uncompetitive inhibition when either substrate was varied. L-Sorbose and beta, gamma-methyleneadenosine 5'-triphosphate were used as analogs of D-fructose and MgATP, respectively. Inhibition experiments using these compounds indicated that substrate addition was steady-state ordered, with MgATP adding first. The product inhibition experiments were found to be consistent with a steady-state random release of products. The substrate inhibition caused by MgATP was most likely due to the formation of an enzyme-MgATP-product dead-end complex, whereas that caused by D-fructose was due to alternative pathways in the reaction mechanism. The inhibition caused by Mg2+ can be explained in terms of a dead-end complex with either a central complex or an enzyme-product complex.

Adenosine Diphosphate↗
PubMed1984

Enzymes of sucrose breakdown in soybean nodules: alkaline invertase.

The specific activities of acid and alkaline invertases (beta-d-fructofuranoside fructohydrolase, EC 3.2.1.26), sucrose synthase (UDPglucose: d-fructose 2-alpha-d-glucosyltransferase, EC 2.4.1.13), hexokinase (ATP: d-hexose 6-phosphotransferase, EC 2.7.1.1), and fructokinase (ATP: d-fructose 6-phosphotransferase, EC 2.7.1.4) were determined in soybean (Glycine max L. Merr cv Williams) nodules at different stages of development and, for comparison, in roots of nonnodulated soybeans. Alkaline invertase and sucrose synthase were both involved in sucrose metabolism in the nodules, but there was only a small amount of acid invertase present. The nodules contained more phosphorylating activity with fructose than glucose. Essentially all of the alkaline invertase, sucrose synthase, and fructokinase were in the soluble fraction of nodule extracts whereas hexokinase was in the bacteroid, plant particulate, and soluble fractions.Soybean nodule alkaline invertase was partially purified and shown to be a beta-d-fructofuranosidase which was specific for sucrose. The pH optimum was 7.6 and the K(m) for sucrose was 10 millimolar. Fructose was a competitive inhibitor. Tris was a noncompetitive inhibitor and the enzyme was very sensitive to inhibition by heavy metals.

Journal Article↗
PubMed1984

Uterine endolymphatic stromal myosis: a collaborative study.

Fifty-two cases of the rare entity, uterine endolymphatic stromal myosis, were evaluated in a collaborative study by gynecologic oncologists trained at the M. D. Anderson Tumor Institute. Fifty percent developed recurrent disease subsequent to initial surgical therapy. Of the surgical stage I cases, 47% developed pelvic recurrences, and 9% developed distant recurrences only after initial therapy. The five- and ten-year life-table survival of surgical stages I to IV were 88% for stage I, 66% for stage II, 100% for stage III, and 75% for stage IV. These long-term survival rates were due in part to the hormonal sensitivity of the recurrent tumors. Because of the high recurrence rate after initial therapy, a suggested plan of therapy is presented for patients with uterine endolymphatic stromal myosis.

Adult↗
PubMed1983

Subcellular localization of hexose kinases in pea stems: mitochondrial hexokinase.

The subcellular localization of hexose phosphorylating activity in extracts of pea stems has been studied by differential centrifugation and sucrose density gradient centrifugation. The hexokinase (EC 2.7.1.1) was associated with the mitochondria, whereas fructokinase (EC 2.7.1.4) was in the cytosolic fraction. Some properties of the mitochondrial hexokinase were studied. The enzyme had a high affinity for glucose (K(m) 76 micromolar) and mannose (K(m) 71 micromolar) and a relatively low affinity for fructose (K(m) 15.7 millimolar). The K(m) for MgATP was 180 micromolar. The addition of salts stimulated the activity of the hexokinase. Al(3+) was a strong inhibitor at pH 7 but not at the optimum pH (8.2). The enzyme was not readily solubilized but, in experiments with intact mitochondria, was susceptible to proteolysis. A location on the outer mitochondrial membrane is suggested for the hexokinase of pea stems.

Journal Article↗
PubMed1981

Hexokinase II of Pea Seeds.

A second hexokinase (EC 2.7.1.1) was obtained from pea seed (Pisum sativum L. var. Progress No. 9) extracts. The enzyme, termed hexokinase II, had a high affinity (K(m), 48 micromolar) for glucose and a relatively low affinity (K(m), 10 millimolar) for fructose. The K(m) for MgATP was 86 micromolar. Mg(2+) was required for activity, but excess Mg(2+) was inhibitory. MgADP inhibited hexokinase II. The addition of salts of monovalent cations increased hexokinase II activity. Al(3+) was a strong inhibitor of the enzyme at pH 6.6 but not at the optimum pH (8.2). Citrate and 3-phosphoglycerate activated pea seed hexokinase II at pH 6.6, probably by coordinating with aluminum present as a contaminant in commercial ATP. The properties of hexokinase II are compared with those of the other three hexose kinases obtained from pea seed extracts. The possible role of these enzymes in plant carbohydrate metabolism is discussed.

Journal Article↗
PubMed1981

Purification of Spinach Leaf ADPglucose Pyrophosphorylase.

ADPglucose pyrophosphorylase from spinach leaves has been purified to homogeneity by hydrophobic chromatography carried out in 1 molar phosphate buffer. After polyacrylamide gel electrophoresis, the preparation showed only one protein staining band that coincided with a single activity stain. The enzyme appears to be composed of two subunits with molecular weights of 44,000 and 48,000, respectively, as determined by SDS polyacrylamide gel electrophoresis. Thus ADPglucose pyrophosphorylase of spinach appears to be comprised of subunits which are similar in size to the subunits of ADPglucose pyrophosphorylase isolated from bacterial sources. In contrast, a subunit molecular weight of 96,000 has been reported for the maize endosperm ADPglucose pyrophosphorylase (Fuchs RL and JO Smith 1979 Biochim Biophys Acta 556: 40-48). The purified enzyme retains similar allosteric and catalytic properties as reported previously and is more sensitive to phosphate inhibition under "dark"-simulated conditions than under "light"-simulated conditions.

Journal Article↗