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Biomedical subjects

S F Yang

Publications and source records attributed to S F Yang.

At least 55 records · Page 3Linked to original sources
PubMed1992

Purification and characterization of 1-aminocyclopropane-1-carboxylate oxidase from apple fruit.

1-Aminocyclopropane-1-carboxylate (ACC) oxidase catalyzes the oxidation of ACC to ethylene. Following conventional column fractionation, the enzyme was purified 180-fold to near homogeneity with a specific activity of 20 nmol/(mg.min). This purified enzyme preparation migrated as a single protein band with an apparent molecular mass of 35 kDa on SDS/PAGE and 39 kDa on gel filtration. As in vivo, the purified enzyme required CO2 for activity. Removal of CO2 from the reaction mixture completely abolished the enzyme activity, while 0.5% atmospheric CO2 (0.15 mM in the medium) gave half-maximal activity. The purified enzyme displayed an absolute requirement for Fe2+ and ascorbate. The stoichiometry of the enzymatic reaction was determined: ACC + ascorbate + O2-->C2H4 + HCN + CO2 + dehydroascorbate + 2 H2O. A polyclonal antibody was raised against a synthetic tridecapeptide (PDLEEEYRKTMKE) whose sequence was deduced from the apple pAE12 cDNA [Dong, J. G., Olson, D., Silverstone, A. & Yang, S. F. (1992) Plant Physiol. 98, 1530-1531], which is homologous to tomato cDNAs encoding ACC oxidase. On a Western blot, this antibody specifically recognized the purified ACC oxidase protein. The amino acid composition of the purified enzyme agreed well with that deduced from the pAE12 sequence. When the protein was cleaved with CNBr and one of the peptide fragments was isolated and sequenced for 20 cycles, its sequence (KEFAVELEKLAEKLLDLLCE) precisely matched that predicted from pAE12 (residues 115-134). When preclimacteric apple fruit was treated with ethylene, a parallel increase in in vivo and in vitro ACC oxidase activities was observed, and this increase was accompanied by a concomitant increase in the level of pAE12 transcript. These observations support the conclusion that the isolated ACC oxidase protein is encoded by pAE12.

Amino Acid Oxidoreductases↗
PubMed1992

Differential accumulation of transcripts for four tomato 1-aminocyclopropane-1-carboxylate synthase homologs under various conditions.

Degenerate oligonucleotide primers corresponding to conserved regions flanking the active-site domain of 1-aminocyclopropane-1-carboxylate (ACC) synthase (EC 4.4.1.14) were used for the polymerase chain reaction (PCR) to amplify DNA fragments from mRNA isolated from tomato fruit and tomato suspension cell culture. Antibodies raised against two conserved peptide sequences (TNPSNPLGTT and SLSKDLGLPGFRVG) were used to screen for positive colonies, after the PCR products were cloned into a Bluescript plasmid and expressed in Escherichia coli. Four distinct cDNA fragments encoding ACC synthase homologs were isolated. While pBTAS1 and pBTAS4 were obtained from fruit mRNA, cell culture mRNA yielded three sequences, pBTAS1, pBTAS2, and pBTAS3. Sequencing of these gene fragments revealed that pBTAS1 and pBTAS4 were identical to those full-length sequences previously reported by Van Der Straeten et al. [Van Der Straeten, D., Van Wiemeersch, L., Goodman, H. & Van Montague, M. (1990) Proc. Natl. Acad. Sci. USA 87, 4859-4863] and Olson et al. [Olson, D. C., White, J. A., Edelman, J., Harkin, R. N. & Kende, H. (1991) Proc. Natl. Acad. Sci. USA 88, 5340-5344] from tomato fruit, whereas pBTAS2 and pBTAS3 represent new sequences. Ribonuclease protection assays were used to examine the expression of these transcripts under three different conditions of enhanced ethylene production--namely, during fruit ripening, in response to mechanical wounding in fruit tissue, and auxin stimulation in vegetative tissue. Transcripts of pBTAS1 accumulated massively during ripening and wounding but only slightly in response to auxin treatment. Although pBTAS4 was associated with fruit ripening, it was unresponsive to auxin treatment in vegetative tissue. In contrast, the expression of pBTAS2 and pBTAS3 was greatly promoted in auxin-treated vegetative tissue but was absent from fruit tissue. While the expression of pBTAS2 was moderately dependent on wounding, pBTAS3 was unresponsive to wounding. These data support the view that ACC synthase is encoded by a multigene family and that the members are differentially expressed in response to developmental, environmental, and hormonal factors.

Amino Acid Sequence↗
PubMed1992

Turnover of 1-aminocyclopropane-1-carboxylic Acid synthase protein in wounded tomato fruit tissue.

Ethylene production in plant tissues declines rapidly following induction, and this decline is due to a rapid decrease in the activity of 1-aminocyclopropane-1-carboxylic acid (ACC) synthase, a key enzyme in ethylene biosynthesis. To study the nature of the rapid turnover of ACC synthase in vivo, proteins in wounded ripening tomato (Lycopersicon esculentum) fruit discs were radiolabeled with [(35)S]methionine, followed by a chase with nonradioactive methionine. Periodically, the radioactive ACC synthase was isolated with an immunoaffinity gel and analyzed. ACC synthase protein decayed rapidly in vivo with an apparent half-life of about 58 min. This value for protein turnover in vivo is similar to that previously reported for activity half-life in vivo and substrate-dependent enzyme inactivation in vitro. Carbonylcyanide-m-chlorophenylhydrazone and 2,4-dinitrophenol, potent uncouplers of oxidative phosphorylation, strongly inhibited the rapid decay of ACC synthase protein in the tissue. Degradation of this enzyme protein was moderately inhibited by the administration of aminooxyacetic acid, a competitive inhibitor of ACC synthase with respect to its substrate S-adenosyl-l-methionine, alpha,alpha'-dipyridyl, and phenylmethanesulfonyl fluoride or leupeptin, serine protease inhibitors. These results support the notion that the substrate S-adenosyl-l-methionine participates in the rapid inactivation of the enzyme in vivo and suggest that some ATP-dependent processes, such as the ubiquitin-requiring pathway, are involved in the degradation of ACC synthase proteins.

Journal Article↗
PubMed1992

Induction of 1-aminocyclopropane-1-carboxylate synthase mRNA by auxin in mung bean hypocotyls and cultured apple shoots.

Auxin is known to promote ethylene production in vegetative tissues by increasing the activity of 1-aminocyclopropane-1-carboxylate (ACC) synthase; therefore, we have studied the effect of auxins on ACC synthase mRNA expression. Total RNA was isolated from auxin-incubated cultured apple (Malus sylvestris Mill.) shoots or mung bean (Vigna radiata L.) hypocotyls. These RNAs and a set of oligonucleotide primers corresponding to two conserved amino acid sequences (SNPLGTT and MSSFGLV) found in ACC synthases isolated from other species were used for polymerase chain reaction-based amplification of DNA fragments encoding the ACC synthase-active site domain. We obtained and sequenced a 290-base pair cDNA fragment (pAA1) from cultured apple shoots and a 328-base pair cDNA clone (pMBA1) from mung bean hypocotyls. Comparisons of their deduced amino acid sequences with those of previously characterized ACC synthase cDNAs indicate that both fragments are, indeed, closely related to ACC synthase cDNA. Northern blot analyses further showed that the expression of these transcripts is regulated by auxin treatment. These data indicate that auxin induces ethylene production transcriptionally by increasing the ACC synthase transcripts. The pAA1 shares 46% amino acid sequence homology with ripening-regulated apple fruit ACC synthase, indicating that ripening-regulated and auxin-regulated ACC synthases are encoded by different genes. In mung bean hypocotyls, aminooxyacetic acid, a potent inhibitor of ACC synthase activity, promoted the expression of auxin-induced ACC synthase mRNA, but cycloheximide inhibited this induction.

Journal Article↗
PubMed1992

Extraction and partial characterization of the ethylene-forming enzyme from apple fruit.

Ethylene-forming enzyme (EFE) was isolated from apple (Malus domestica Borkh. cv Golden Delicious) fruit tissue. The enzyme activity in the homogenate is associated with the pellet fraction and can be solubilized with Triton X-100 or polyvinylpolypyrrolidone. The solubilized enzyme system resembles the in vivo system in that it exhibits a low K(m) (17 micromolar) for its substrate 1-aminocyclopropane-1-carboxylic acid (ACC), is stereospecific toward 2-ethyl-ACC stereoisomers for 1-butene production, and is inhibited by cobalt ions and alpha-aminoisobutyric acid. Intact preclimacteric fruits treated with exogenous ethylene showed a marked increase in in vivo EFE activity and this increase was accompanied by a parallel increase in in vitro EFE activity. These results support the notion that the isolated EFE represents the authentic in vivo activity.

Journal Article↗
PubMed1992

[The efficacy of intravenous fentanyl patient-controlled analgesia for postoperative pain relief].

The safety and efficacy of patient-controlled analgesia used for postoperative pain relief were evaluated. Cumulative 24-hour requirements were analyzed for possible correlation with patient characteristics. All patients who used a patient-controlled analgesia device for postoperative pain relief were reviewed from June to October 1991. The device Baxter's basal/bolus infusor with patient control module, was used to deliver fentanyl in 379 patients. The fentanyl requirement, verbal analog pain score, first passage of flatus, side effects, sedative score, and degree of satisfaction were examined. The fentanyl requirement during the first 24 hours after operation was analyzed with regard to age, body weight, and sex. The daily fentanyl consumption in the first three postoperative days was 928 +/- 352 micrograms (n = 338), 553 +/- 259 micrograms (n = 220), and 490 +/- 222 micrograms (n = 71), respectively. The requirement for fentanyl during the first 24 hours after surgery was significantly higher than for the next two days (p-value < 0.001). Fentanyl consumption correlated well with body weight, and inversely with age. No difference was found between fentanyl consumption and sex (p-value = 0.4687). The mean time to the first passage of flatus in patients with abdominal surgery was 54.6 +/- 26.4 hours. The incidence of nausea, vomiting, and dizziness was similar, about 20% of patients. Itching was noted in 7% of patients. Oversedation (class 4) was found in three patients during the first operative day, the sedative score for other patients were around class 1-3. No patient exhibited signs of respiratory depression or withdrawal syndrome.(ABSTRACT TRUNCATED AT 250 WORDS)

Abdomen↗
PubMed1991

Purification and characterization of 1-aminocyclopropane-1-carboxylate synthase from apple fruits.

1-Aminocyclopropane-1-carboxylate (ACC) synthase, a key enzyme in ethylene biosynthesis, was isolated and partially purified from apple (Malus sylvestris Mill.) fruits. Unlike ACC synthase isolated from other sources, apple ACC synthase is associated with the pellet fraction and can be solubilized in active form with Triton X-100. Following five purification steps, the solubilized enzyme was purified over 5000-fold to a specific activity of 100 micromoles per milligram protein per hour, and its purity was estimated to be 20 to 30%. Using this preparation, specific monoclonal antibodies were raised. Monoclonal antibodies against ACC synthase immunoglobulin were coupled to protein-A agarose to make an immunoaffinity column, which effectively purified the enzyme from a relatively crude enzyme preparation (100 units per milligram protein). As with the tomato enzyme, apple ACC synthase was inactivated and radiolabeled by its substrate S-adenosyl-l-methionine. Apple ACC synthase was identified to be a 48-kilodalton protein based on the observation that it was specifically bound to immunoaffinity column and it was specifically radiolabeled by its substrate S-adenosyl-l-methionine.

Journal Article↗
PubMed1991

Acute poisoning with a glyphosate-surfactant herbicide ('Roundup'): a review of 93 cases.

Between 1 January 1980, and 30 September 1989, 93 cases of exposure to herbicides containing glyphosphate and surfactant ('Roundup') were treated at Changhua Christian Hospital. The average amount of the 41% solution of glyphosate herbicide ingested by non-survivors was 184 +/- 70 ml (range 85-200 ml), but much larger amounts (500 ml) were reported to have been ingested by some patients and only resulted in mild to moderate symptomatology. Accidental exposure was asymptomatic after dermal contact with spray (six cases), while mild oral discomfort occurred after accidental ingestion (13 cases). Intentional ingestion (80 cases) resulted in erosion of the gastrointestinal tract (66%), seen as sore throat (43%), dysphagia (31%), and gastrointestinal haemorrhage (8%). Other organs were affected less often (non-specific leucocytosis 65%, lung 23%, liver 19%, cardiovascular 18%, kidney 14%, and CNS 12%). There were seven deaths, all of which occurred within hours of ingestion, two before the patient arrived at the hospital. Deaths following ingestion of 'Roundup' alone were due to a syndrome that involved hypotension, unresponsive to intravenous fluids or vasopressor drugs, and sometimes pulmonary oedema, in the presence of normal central venous pressure.

Adolescent↗
PubMed1991

[A comparison of patient-controlled analgesia with traditional intramuscular administration for postoperative pain relief].

The use of a disposable non-electronic patient-controlled analgesia (PCA) device (Baxter) was evaluated in this study. Every patient under trial was instructed thoroughly how to use the PCA device before operation. The PCA device delivers a 25 mg IV injection of pethidine upon patient demand with a delay of 15 min between allowable administrations. The degree of patient satisfaction, the drug consumption, and the duration of using analgesia were compared with those in IM pethidine group. The results showed that, in the PCA group, the duration of using analgesic was longer; the drug consumption was greater (especially during the first 20 h after operation); and the degree of patient satisfaction was higher. The series comprised a total of 54 patients, 14 of whom complained of mild dizziness or nausea which did not require specific treatment. In sum, giving analgesic by the Baxter PCA device was a safe and effective alternative for IM analgesic in postoperative pain control.

Analgesia, Patient-Controlled↗
PubMed1990

Characterization and sequencing of the active site of 1-aminocyclopropane-1-carboxylate synthase.

The pyridoxal phosphate (PLP)-dependent 1-aminocyclopropane-1-carboxylic acid (ACC) synthase (S-adenosyl-L-methionine methylthioadenosine-lyase, EC 4.4.1.14), the key enzyme in ethylene biosynthesis, is inactivated by its substrate S-adenosylmethionine (AdoMet). Apple ACC synthase was purified with an immunoaffinity gel, and its active site was probed with NaB3H4 or Ado[14C]Met. HPLC separation of the trypsin digest yielded a single radioactive peptide. Peptide sequencing of both 3H- and 14C-labeled peptides revealed a common dodecapeptide of Ser-Leu-Ser-Xaa-Asp-Leu-Gly-Leu-Pro-Gly-Phe-Arg, where Xaa was the modified, radioactive residue in each case. Acid hydrolysis of the 3H-labeled enzyme released radioactive N-pyridoxyllysine, indicating that the active-site peptide contained lysine at position 4. Mass spectrometry of the 14C-labeled peptide indicated a protonated molecular ion at m/z 1390.6, from which the mass of Xaa was calculated to be 229, a number that is equivalent to the mass of a lysine residue alkylated by the 2-aminobutyrate portion of AdoMet, as we previously proposed. These results indicate that the same active-site lysine binds the PLP and convalently links to the 2-aminobutyrate portion of AdoMet during inactivation. The active site of tomato ACC synthase was probed in the same manner with Ado[14C]Met. Sequencing of the tomato active-site peptide revealed two highly conserved dodecapeptides; the minor peptide possessed a sequence identical to that of the apple enzyme, whereas the major peptide differed from the minor peptide in that methionine replaced leucine at position 6.

Amino Acid Sequence↗
PubMed1990

Characterization of abscisic Acid-induced ethylene production in citrus leaf and tomato fruit tissues.

Abscisic acid (ABA) significantly stimulated ethylene production in citrus (Citrus sinensis [L.] Osbeck, cv Shamouti orange) leaf discs. The extent of stimulation was dependent upon the concentration of ABA (0.1-1 milimolar) and the duration of treatment (15-300 minutes). Aging the discs before applying ABA increased ABA-induced ethylene production due to enhancement of both ethylene-forming enzyme activity and the responsiveness of ABA. Discs excised from mature leaves were much more responsive to ABA than discs excised from young or senescing leaves. ABA stimulated ethylene production shortly after application, suggesting that ABA does not enhance ethylene production via the acceleration of senescence. The stimulating effect of ABA on ethylene production resulted mainly from the enhancement of 1-aminocylopropane-1-carboxylic acid synthesis. Stimulation of ethylene production by ABA in intact citrus leaves and tomato (Lycopersicon esculentum Mill., cv Castlemart) fruit was small but could be increased by various forms of wounding.

Journal Article↗
PubMed1990

Continuing root formation following apexification treatment.

A case report is presented in which continuing root formation occurred in an immature mandibular second premolar after calcium hydroxide apexification treatment. An apical hard tissue barrier was accompanied by a separate disto-apically growing root 18 months posttreatment. Histologic evaluation of the root revealed immature hard tissue mixed with calcium hydroxide, connective tissue and bone, apically in the original root canal. In the separate new formed part of the root, pulp tissue, odontoblasts, predentin, cementum and an apical foreman could be identified.

Calcium Hydroxide↗
PubMed1990

[Cerebral infarction after resection of epidermoid carcinoma of buccal mucosa under general anesthesia--report of one case].

A 60 year-old hypertensive male was operated with resection of epidermoid carcinoma of buccal mucosa. He was expired postoperation complicated with left middle cerebral artery infarction. The cerebral infarction may be induced by acute hypotension, improper position during operation and underlying disease associated with old age. Prevention methods included preoperative evaluation, immediately injection vasopressor when acute hypotension occurred during anesthesia, and avoidance of improper position to compress vertebral or carotid artery which may leading to cerebral perfusion insufficiency.

Anesthesia, General↗
PubMed1989

Specificity of S-adenosyl-L-methionine in the inactivation and the labeling of 1-aminocyclopropane-1-carboxylate synthase isolated from tomato fruits.

1-Aminocyclopropane-1-carboxylate (ACC) synthase, which catalyzes the conversion of S-adenosyl-L-methionine (AdoMet) to ACC, is irreversibly inactivated by its substrate AdoMet. AdoMet has two diastereomers with respect to its sulfonium center, (-)-AdoMet and (+)-AdoMet. We prepared (+)- and (-)-AdoMet from a commercial source, and compared their activities as a substrate and as an inactivator of ACC synthase isolated from tomato (Lycopersicon esculentum Mill). fruits. Only (-)-AdoMet produced ACC, whereas both (-)- and (+)-AdoMet inactivated ACC synthase; (+)-AdoMet inactivated the enzyme three times faster than (-)-AdoMet. We have previously shown that ACC synthase was specifically radiolabeled when the enzyme was incubated with S-adenosyl-L-[3,4-14C]methionine. The present results further indicate that S-adenosyl-L-[carboxyl-14C]methionine, but not S-adenosyl-L-[methyl-14C]methionine, radiolabeled the enzyme. These data suggest that the 2-aminobutyric acid portion of AdoMet is linked to ACC synthase during the autoinactivation process. A possible mechanism for ACC synthase inactivation by AdoMet is discussed.

Catalysis↗
PubMed1989

Ethylene-like activity of isocyanides.

Benzyl isocyanide, cyclohexyl isocyanide, benzyl isocyanate, methyl isocyanate, benzyl isothiocyanate, and methyl isothiocyanate were each tested for ethylene-like activity in a pea (Pisum sativum) growth assay. Only the isocyanides gave an ethylene-like response; the concentration that gave a half-maximal response was approximately 10 to 15 microliters per liter for each isocyanide, and this activity was inhibited by norbornadiene, a competitive inhibitor of ethylene action. Since the isocyanides did not promote endogenous ethylene production, it was concluded that the isocyanides acted directly to give an ethylene-like response. The isocyanides were further shown to elicit ethylene-like activity in a potato (Solanum tuberosum) tuber respiration assay, in a carnation (Dianthus caryophyllus) senescence assay and in a carrot (Daucus carota L.) isocoumarin formation assay. The feasibility of employing azido derivatives of benzyl isocyanide to photoaffinity label ethylene receptors in vivo is discussed.

Journal Article↗
PubMed1989

Inactivation of 1-Aminocyclopropane-1-Carboxylate Synthase by l-Vinylglycine as Related to the Mechanism-Based Inactivation of the Enzyme by S-Adenosyl-l-Methionine.

The pyridoxal phosphate-dependent 1-aminocyclopropane-1-carboxylate (ACC) synthase catalyzes the conversion of S-adenosyl-l-methionine (AdoMet) to ACC, and is inactivated by AdoMet during the reaction. l-Vinylglycine was found to be a competitive inhibitor of the enzyme, and to cause a time-dependent inactivation of the enzyme. The inactivation required the presence of pyridoxal phosphate and followed pseudo-first-order kinetics at various concentrations of l-vinylglycine. The Michaelis constant for l-vinylglycine in the inactivation reaction (K(inact)) was 3.3 millimolar and the maximum rate constant (k(max)) was 0.1 per minute. These findings, coupled with the previous observations that the suicidal action of AdoMet involved a covalent linkage of the aminobutyrate portion of AdoMet to the enzyme, support the view that the mechanism-based inactivation of ACC synthase by the substrate AdoMet proceeds through the formation of a vinylglycine-ACC synthase complex as an intermediate.

Journal Article↗