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Biomedical subjects

T P Lin

Publications and source records attributed to T P Lin.

At least 55 records · Page 3Linked to original sources
PubMed1991

Mutants of Arabidopsis with altered regulation of starch degradation.

Mutants of Arabidopsis thaliana (L.) Heynh. with altered regulation of starch degradation were identified by screening for plants that retained high levels of leaf starch after a period of extended darkness. The mutant phenotype was also expressed in seeds, flowers, and roots, indicating that the same pathway of starch degradation is used in these tissues. In many respects, the physiological consequences of the mutations were equivalent to the effects observed in previously characterized mutants of Arabidopsis that are unable to synthesize starch. One mutant line, which was characterized in detail, had normal levels of activity of the starch degradative enzymes alpha-amylase, beta-amylase, phosphorylase, D-enzyme, and debranching enzyme. Thus, it was not possible to establish a biochemical basis for the phenotype, which was due to a recessive mutation at a locus designated sex1 at position 12.2 on chromosome 1. This raises the possibility that hitherto unidentified factors, altered by the mutation, play a key role in regulating or catalyzing starch degradation.

Journal Article↗
PubMed1989

Altered regulation of beta-amylase activity in mutants of Arabidopsis with lesions in starch metabolism.

Three classes of mutants of Arabidopsis thaliana (L.) Heynhold with alterations in starch metabolism were found to have higher levels of leaf amylase activity than the wild type when grown in a 12-hr photoperiod. This effect was dependent upon the developmental stage of the plants and was largely suppressed during growth in continuous light. The various amylolytic activities in crude extracts were separated by electrophoresis in nondenaturing polyacrylamide gels and visualized by activity staining. The increased amylase activity in the mutants was due to an up to 40-fold increase in the activity of an extrachloroplast beta-amylase (EC 3.2.1.2). These observations indicate the existence of a regulatory mechanism that controls the amount of beta-amylase activity in response to fluctuations in photosynthetic carbohydrate metabolism. It is paradoxical that beta-amylase appears to be a highly regulated enzyme, but as yet no physiologically relevant function can be assigned to this enzyme due to the absence of starch in the cytoplasmic compartment of leaf cells.

Journal Article↗
PubMed1989

Purification and Characterization of Pectinmethylesterase from Ficus awkeotsang Makino Achenes.

Pectinmethylesterase from the pericarp of jelly fig (Ficus awkeotsang) achenes was extracted and purified to a specific activity of 289 micromole proton produced per minute per milligram protein. Pectinmethylesterase, a major protein with high specific activity in the crude extract, was monomeric with a molecular weight of 38,000. The enzyme preparation was stable in distilled water at 4 degrees C for at least 6 months, and at 60 degrees C for at least 10 minutes. This enzyme functioned optimally at pH 6.5 to 7.5 when the assay mixture contained no NaCl or at low NaCl concentration. The pH optimum shifted to lower pH as the NaCl concentration was increased. The K(m) value for pectin was 0.75 milligram per milliliter pectin, corresponding to a V(max) value of 310 micromoles per minute per milligram protein. Inhibition studies with antibodies indicated that jelly fig achene pectinmethylesterase and the two other pectinmethylesterases from orange and tomato were similar in their active site conformation; however, the surface determinants may be very different because no precipitation between anti-jelly fig pectinmethylesterase immune serum and the pectin methylesterase from orange and tomato could be observed in the double immunodiffusion analysis. Specific antisera raised against jelly fig achene pectinmethylesterase in a Western blot experiment also showed low similarity between jelly fig pectinmethylesterase with that from orange and tomato. This observation was also supported by the very low isoelectric point (pH 3.5) of jelly fig pectinmethylesterase, compared with high isoelectric points reported for most of the pectinmethylesterases. Amino acid composition and N-terminal sequence have been obtained. High homology of the N-terminal amino acid residues between jelly fig and tomato pectinmethylesterase (O Markovic, H Jornvall [1986] Eur J Biochem 158: 455-462) was observed. Pectinmethylesterase activity causes the release of protons from the deesterification of pectin such that a low pH environment is created, and this may be related to the cell growth. Pectinmethylesterase is not needed for jelly fig seed germination, however the gel formed from pectin and pectinmethylesterase may insure a water source for the germinating jelly fig seeds.

Journal Article↗
PubMed1989

Enzyme-linked immunosorbent assay with BCG sonicate antigen for diagnostic potential of mycobacterial infection in Taiwan.

The diagnostic potential of enzyme-linked immunosorbent assay (ELISA) with Bacillus Calmette-Guerin (BCG) sonicate antigen for detection of mycobacterial infections, including pulmonary tuberculosis and leprosy, has been evaluated in Taiwan area. One hundred blood samples were collected from 74 active and 26 inactive pulmonary tuberculosis patients of the Taiwan Provincial Tuberculosis Control Bureau. Another 50 samples were collected from 24 lepromatous, 23 tuberculoid and 3 borderline leprosy patients at the Taiwan Provincial Lo-Sheng Leprosarium. The IgG anti-BCG sonicate levels were compared among patients with tuberculosis, active or inactive, patients with leprosy, and healthy individuals. Patients with tuberculosis, both active and inactive, and those with leprosy had higher BCG sonicate antibody levels and frequencies above cutoff value than healthy subjects (for BCG-sonicate antibody, p less than 0.05 for inactive tuberculosis, p less than 0.0001 for others; for frequency above cutoff, p less than 0.001 for inactive tuberculosis, p less than 0.0001 for others). Among the three groups of patients, significant differences were noted in anti-BCG sonicate antibody level, and there was no difference of frequency above the cutoff value (i.e. inactive tuberculosis had lower level than active tuberculosis and leprosy, p less than 0.005). In conclusion, ELISA with BCG sonicate antigen could serve as a diagnostic aid for mycobacterial infection in Taiwan. However, it was not possible to differentiate disease activity in tuberculosis, or to discriminate infectious species of mycobacteria. Purified mycobacterial antigens should be tried in further research to improve the specificity and sensitivity in serodiagnosis with ELISA.

Antibodies, Bacterial↗
PubMed1988

Subcellular localization and characterization of amylases in Arabidopsis leaf.

Amylolytic enzymes of Arabidopsis leaf tissue were partially purified and characterized. Endoamylase, starch phosphorylase, d-enzyme (transglycosylase), and possibly exoamylase were found in the chloroplasts. Endoamylase, fraction A2, found only in the chloroplast, was resolved from the exoamylases by chromatography on a Mono Q column and migrated with an R(F) of 0.44 on 7% polyacrylamide gel electrophoresis. Exoamylase fraction, A1, has an R(F) of 0.23 on the polyacrylamide gel. Viscometric analysis showed that A1 has a slope of 0.013, which is same as that of A3, the extrachloroplastic amylase. A1, however, can be distinguished from A3 by having much higher amylolytic activity in succinate buffer than acetate buffer, and having much less reactivity with amylose. A1 probably is also localized in the chloroplast, and contributes to the 30 to 40% higher amylolytic activity of the chloroplast preparation in succinate than acetate buffer at pH 6.0. The high activity of d-enzyme compared to the amylolytic activity in the chloroplast suggests that transglycosylation probably has an important role during starch degradation in Arabidopsis leaf. Extrachloroplastic amylase, A3, has an R(F) of 0.55 on 7% electrophoretic gel and constitutes 80% of the total leaf amylolytic activity. The results of substrate specificity studies, action pattern and viscometric analyses indicate that the extrachloroplastic amylases are exolytic.

Journal Article↗
PubMed1988

Characterization of d-Enzyme (4-alpha-Glucanotransferase) in Arabidopsis Leaf.

Two major forms of d-enzyme (4-alpha-glucanotransferase, EC 2.4.1.25) were successfully separated from most of the amylase activity using FPLC-Mono Q column chromatography. Transfer of a maltosyl group was observed upon the incubation of d-enzyme with maltotriose and d-[U-(14) C]glucose. About 4.5% of the radioactivity was transferred to maltotriose in 2 hours. End product analysis showed the accumulation of glucose and maltopentaose from maltotriose within the first 10 minutes of the reaction. Several other maltodextrins were also observed with longer incubation times, although maltose was never produced. A quantitative measurement of maltodextrin production from the reaction of [(14) C]maltotriose with d-enzyme showed that the quantity of maltotriose decreased from 100% to 31% after 3 hours incubation, while glucose, maltotetraose, maltopentaose, maltohexaose, maltoheptaose, maltooctaose, and higher maltodextrins increased in amount. Glucose is the major product throughout the course of the reaction of d-enzyme with maltotriose. Maltotriose, in addition to glucose, are the major products in the reaction of d-enzyme with maltodextrins with a chain length greater than maltotriose. This study confirms the existence of a transglycosylase that disproportionates maltotriose and higher maltodextrins by transferring maltosyl or maltodextrinyl groups between maltodextrins resulting in the production of glucose and different maltodextrins, but not maltose, in leaf tissue with enzymic properties very similar to the previously reported d-enzyme in potato.

Journal Article↗
PubMed1988

Isolation and Characterization of a Starchless Mutant of Arabidopsis thaliana (L.) Heynh Lacking ADPglucose Pyrophosphorylase Activity.

A mutant of Arabidopsis thaliana lacking ADPglucose pyrophosphorylase activity (EC 2.7.7.27) was isolated (from a mutagenized population of plants) by screening for the absence of leaf starch. The mutant grows as vigorously as the wild type in continuous light but more slowly than the wild type in a 12 hours light/12 hours dark photoperiod. Genetic analysis showed that the deficiency of both starch and ADPglucose pyrophosphorylase activity were attributable to a single, nuclear, recessive mutation at a locus designated adg1. The absence of starch in the mutant demonstrates that starch synthesis in the chloroplast is entirely dependent on a pathway involving ADPglucose pyrophosphorylase. Analysis of leaf extracts by two-dimensional polyacrylamide gel electrophoresis followed by Western blotting experiments using antibodies specific for spinach ADPglucose pyrophosphorylase showed that two proteins, present in the wild type, were absent from the mutant. The heterozygous F(1) progeny of a cross between the mutant and wild type had a specific activity of ADPglucose pyrophosphorylase indistinguishable from the wild type. These observations suggest that the mutation in the adg1 gene in TL25 might affect a regulatory locus.

Journal Article↗
PubMed1988

A Starch Deficient Mutant of Arabidopsis thaliana with Low ADPglucose Pyrophosphorylase Activity Lacks One of the Two Subunits of the Enzyme.

A starch deficient mutant of Arabidopsis thaliana (L.) Heynh. has been isolated in which leaf extracts contain only about 5% as much activity of ADPglucose pyrophosphorylase (EC 2.7.7.27) as the wild type. A single, nuclear mutation at a previously undescribed locus designated adg2 is responsible for the mutant phenotype. Although the mutant contained only 5% as much ADPglucose pyrophosphorylase activity as the wild type, it accumulated 40% as much starch when grown in a 12 hour photoperiod. The mutant also contained about 40% as much starch as the wild type when grown in continuous light, suggesting that the rate of synthesis regulates its steady state accumulation. Immunological analysis of leaf extracts using antibodies against the spinach 54 and 51 kilodalton (kD) ADPglucose pyrophosphorylase subunits indicated that the mutant is deficient in a cross-reactive 54 kD polypeptide and has only about 4% as much as the wild type of a cross-reactive 51 kD polypeptide. This result and genetic studies suggested that adg2 is a structural gene which codes for the 54 kD polypeptide, and provides the first functional evidence that the 54 kD polypeptide is a required component of the native ADPglucose pyrophosphorylase enzyme.

Journal Article↗
PubMed1988

Minimal inhibitory concentrations of isoniazid, rifampin, ethambutol, and streptomycin against Mycobacterium tuberculosis strains isolated before treatment of patients in Taiwan.

Minimal inhibitory concentrations (MICs) of isoniazid (INH), rifampin (RMP), ethambutol (EMB), and streptomycin (SM) for susceptible "wild" M. tuberculosis strains isolated from Taiwanese patients were within the limits previously reported for strains isolated in the United States. The highest agar-determined MICs (in 7H10 and 7H11 agar) corresponded well with the critical concentrations established for these media. The highest MICs found radiometrically in 7H12 broth were significantly lower than the critical concentrations proposed for this medium. On the basis of an evaluation of the highest broth-determined MICs found in this and in the previous study (1), we suggest that the following MICs, when determined radiometrically, should be used as breakpoints to classify the strain as "susceptible": for INH, 0.1 microgram/ml or less; for RMP, 0.5 microgram/ml or less; for EMB, 4.0 micrograms/ml or less; for SM, 2.0 micrograms/ml or less.

Antitubercular Agents↗
PubMed1987

An analysis of pulmonary tuberculosis data in Taiwan and Korea.

An analysis is carried out on pulmonary tuberculosis survey data from Taiwan and Korea. A mathematical model based on a Markov process is developed and used to estimate transition rates between various disease states, as well as certain 'infection parameters', which measure the strength of the relative contributions of different disease states and of endogenous reactivation to the incidence of tuberculosis in the population. It is found that endogenous reactivation plays a primary role in generating cases, followed by chronic sources of infection, particularly those with drug-sensitive organisms. Some recommendations are made with regard to optimizing treatment regimens. The methodology can easily be applied to other countries.

Adult↗
PubMed1987

Purification and properties of Acid phosphatase from plump and shriveled seeds of triticale.

A major triticale (X Triticosecale Wittmack) endosperm acid phosphatase (EC 3.1.2.2) (APase) from sib-lines producing plump and shriveled seed was purified 140- and 230-fold to a specific activity of 94 and 153 micromoles per minute per milligram protein respectively, by ammonium sulfate fractionation, ion-exchange chromatography, chromatofocusing, affinity column chromatography, and gel filtration. The purified enzyme from both materials is a monomeric glycoprotein with an apparent molecular weight of 45,700 +/- 500 containing 12% carbohydrate and an apparent isoelectric point of pH 5.9. It hydrolyzes tri- and di-phosphate of nucleosides as well as phosphate esters and exhibits characteristics of ATP-hydrolase and phosphatase. About 2-fold more of the APase was isolated from shriveled seeds, and the purified enzyme exhibited 3- and 5-fold higher V(max) for p-nitrophenyl phosphate and ATP, respectively, than that of plump seed. The I(50) for Pi concentration was 5.5-fold higher in APase of shriveled seed than the plump one. These varied quantitative and kinetic properties substantiate the role of APase in lines with shriveled seeds being reduction of starch accumulation by depleting substrates and energy supply in the cytosol.

Journal Article↗
PubMed1987

Short-course chemotherapy of pulmonary tuberculosis in pneumoconiotic patients.

This is the first prospective clinical trial recorded to date of short-course chemotherapy in pulmonary tuberculosis complicated by pneumoconiosis. Forty-eight anthrasillicotic and 11 silicotic patients with previously untreated pulmonary tuberculosis completed 9-month, short-course chemotherapy regimens: 2 months of daily streptomycin, isoniazid, rifampicin, and pyrazinamide followed by daily isoniazid and rifampicin for 7 months (2SHRZ/7HR). There were 3 treatment failures (5%). The remaining 56 patients (95%) all had their sputum converted within 4 months (mean, 1.5 months). Bacteriologic relapses were noted in 3 patients (5%) after 18 to 40 months of follow-up (mean, 28.4 months). The relapses occurred within 7 months after chemotherapy was stopped. There were 2 deaths from nontuberculosis causes during the follow-up period. Fifty-one patients (90%) remained bacteriologically sterile for 28.4 +/- 6.1 months. These results suggest that the 2SHRZ/7HR regimen is satisfactory in treating anthrasilicotic or silicotic patients with pulmonary tuberculosis, though antituberculosis chemotherapy seemed less effective in patients with pneumoconiosis than in those without pneumoconiosis.

Adult↗
PubMed1984

Effect of laser microbeam irradiation of the nucleus on the cleavage of mouse eggs in culture.

Two-cell mouse eggs were irradiated by a helium-cadmium laser on a spot of about 4 micron2 (d = 2.2 micron) in one or both nuclei either continuously or repeatedly at 0.36 erg micron-2 sec-1 and then cultured to observe cellular development. After exposing one nucleus to the microbeam to five or seven 1-sec pulses (1.80 or 2.52 ergs micron-2, respectively), about 45% developed to the 3-cell stage in 24 hr of culture. In overnight cultures of the 2-cell eggs in which both nuclei were irradiated for 9 or 20 sec continuously, 40 (9 sec) and 50% (20 sec) of the eggs remained at the 2-cell stage, while 45 (9 sec) and 25% (20 sec) developed to the 4-cell stage. Irradiating only one nucleus in a 2-cell egg by seven pulses in a spot of 4 micron2 amounting to 10 ergs reduced cleavage 45%. When both nuclei were each irradiated by a 9-sec continuous laser beam (totaling 13 ergs), about 40% of the embryos of the 2-cell stage did not divide. The effect of seven pulses on the blastomere cleavage of 2-cell mouse eggs appeared to be comparable to that of continuous 9-sec laser irradiation. Both pulse and continuous laser microirradiation methods may be developed for inactivation of the nucleus as a nonpipetting , less injurious method for enucleation of mammalian eggs.

Animals↗
PubMed1980

Entire litters developed from transferred eggs in whole body X-irradiated female mice.

The sensitivity of mouse eggs to sublethal X-irradiation was determined in vitro and in vivo with regard to the development of donor litters in foster mothers. One thousand seven hundred fifty-eight unfertilized eggs of agouti dark-eyed donor mice were transferred into 293 unirradiated or X-irradiated, mated female pink-eyed mice. Two hundred thirty-nine recipients became pregnant; of these 35 produced litters containing solely dark-eyed fetuses. Sublethal doses of X-radiation administered to donor eggs in vitro before transferring into unirradiated recipients did not influence significantly the number of litters of exclusively dark-eyed fetuses produced. However, recipients irradiated by 250 roentgens (r) produced more solely dark-eyed litters than did those irradiated with 100 r. In 21 pregnant females irradiated by 100 r, only 3 (14%) developed solely dark-eyed fetuses as compared to 22 pregnant females irradiated by 250 r, of which 13 (59%) developed solely dark-eyed fetuses, all from unirradiated, transferred eggs. Of another group of 22 pregnant females which received 250 r body irradiation and subsequently received eggs also irradiated by 250 r, only 7 (32%) produced litters of dark-eyed fetuses. No one female of these three groups carried native fetuses. Such radiation-induced infertility resulting from damage of native eggs rather than loss of mother's ability to carry a pregnancy, is frequently remedied by egg transfer.

Animals↗