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Biomedical subjects

C H Lin

Publications and source records attributed to C H Lin.

At least 361 records · Page 20Linked to original sources
PubMed1986

Normal and dystrophic hamster myoblast and fibroblast growth in culture.

Normal and dystrophic hamster myoblasts and fibroblasts were compared for characteristic indicators of growth and differentiation. Clonal analysis of myoblast cultures indicated that 80% of colonies judged to be fusion-competent had differentiated. Dystrophic myoblasts were identical to normal in terms of their morphology, fusion potential (81.4%), and myokinase activity (59.6-49.1 mU/mg at 2-7 days), but displayed a significantly higher plating efficiency (normal: 52.6%; dystrophic: 82.1%), a longer doubling time (normal: 21.7 hours; dystrophic: 33.3 hours), and a lower day-7 creatine kinase activity (normal: 60.7 mU/mg; dystrophic: 41.3 mU/mg). Dystrophic fibroblasts were indistinguishable from normal ones in terms of their morphology, plating efficiency (90.4%), and doubling time (32.5 hours), but displayed a significantly lower day-2 creatine kinase activity (normal 58.3 mU/mg; dystrophic: 35.8 mU/mg) and day-7 myokinase activity (normal: 52.7 mU/mg; dystrophic: 39.9 mU/mg). The results are suggestive of an early and differential expression of the primary defect in dystrophic hamster myoblasts and fibroblasts in culture.

Adenylate Kinase↗
PubMed1986

Properties of diacylglycerol kinase purified from bovine brain.

A nearly homogeneous but somewhat unstable diacylglycerol kinase (ca. MW 72,000 daltons) was purified from bovine brain by modification of the procedure of Kanoh et al. (Kanoh, H., Kondoh, H., and Ono, T. [1983] J. Biol. Chem. 258, 1767-1774). The purification consisted of four steps (brain cytosol isolation and successive chromatography on DEAE-cellulose, Sephadex G-25 for desalting and ATP-agarose) carried out in buffers stabilized with EDTA, ATP and dithiothreitol (DTT). Specific activities, determined within 4 hr of purification, ranged from 908-1857 nmol ATP incorporated/min/mg protein, with the variation reflecting the instability. Optimal activities required deoxycholate (0.1%), one of the phosphoglycerides [phosphatidylcholine (PC), phosphatidylethanolamine (PE) or phosphatidylserine (PS)] (0.025-0.25 mM), ATP (5 mM, apparent Km = 0.57 mM), 1,2-dioleoyl-rac-glycerol (5 mM, apparent Km = 1 mM) and Mg2+ (10 mM, apparent Km = 2.2 mM). Phosphatidylinositol (PI) was slightly less effective than PC, PE or PS and noninhibitory in combination with PC, PE or PS. Relative to PC phosphatidic acid (PA) (52%), sphingomyelin (48%), lyso-PC (1.5%) and lyso-PI (28.6%) were less effective activators. The sulfhydryl reagents, p-chloromercuribenzoic acid (PCMB) (1.0 mM), N-ethylmaleimide (NEM) (1.0 and 2.0 mM) and 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB) (1.0 mM), showed strong inhibition of activity which was prevented by 0.5 mM DTT. In contrast to other reports, this purified enzyme showed no monoacylglycerol kinase activity. Comparison of diacylglycerols of varying fatty acid composition indicated that the enzyme showed a preference for substrates with at least one unsaturated fatty acid, particularly in the 2-position.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

The synthesis of benzindene prostacyclin analogs as potential antiulcer agents.

Two new diastereomeric benzindene prostacyclin analogs (U-72,382 and U-72,383) related to the potent antiulcer agent U-68,215 have been synthesized. These cyclohexyl ring modified analogs of U-68,215 were prepared to determine how the gastrointestinal and hypotensive endpoints observed for U-68,215 would be affected.

Animals↗
PubMed1986

Kinetic studies and structure-activity relationships of bispyridinium oximes as reactivators of acetylcholinesterase inhibited by organophosphorus compounds.

The kinetics of the reactivation of acetylcholinesterase inhibited by isopropyl methylphosphonofluoridate was studied. The reactivators used include nine bispyridinium monooximes and three bispyridinium dioximes. The dissociation constant (Kd) and the rate constant (k2) of dephosphorylation of the complex formed from the organophosphorus acetylcholinesterase (OP-AChE) and the oxime were measured. The reactivation parameters obtained from the in vitro kinetic studies were used to elucidate the structure-activity relationships. The hydrophobic property of a nonoxime substituent at the 3-position on the pyridinium ring can exert a positive effect on their binding affinity to OP-AChE. However, the rate constants (k2) of the nucleophilic displacement of OP-AChE by oximes depend negatively on these physical and structural factors of the oximes. The correlations of the in vivo antidotal efficacy (ED50) of these bispyridinium oximes have been analyzed with their pharmacological properties, e.g., reactivation potency, antimuscarinic activities, and antinicotinic activities. However, no satisfactory correlations were observed. It may be concluded that the detoxication mechanism of poisoning by isopropyl methylphosphonofluoridate is different from those of pinacolyl methylphosphonofluoridate and paraoxon.

Acetylcholinesterase↗
PubMed1986

Monkey erythropoietin gene: cloning, expression and comparison with the human erythropoietin gene.

The erythropoietin (Epo) gene from Cynomolgus monkeys has been isolated from a kidney cDNA library using mixed 20-mer oligodeoxynucleotide probes. The gene encodes a 168 amino acid (aa) mature protein with a calculated Mr of 18,490 and a presumptive signal peptide of 24 aa. The Epo gene, when transfected into Chinese hamster ovary (CHO) cells, produces a glycosylated protein with an apparent Mr of 34,000. The expressed product is biologically active in vivo. The monkey gene exhibits 92% and 94% homology to the human gene at the aa and nucleotide sequence levels, respectively. When compared with the human Epo, monkey Epo has an additional 3-aa residue at the N terminus of the mature protein and a deletion of an internal lysine residue.

Amino Acid Sequence↗
PubMed1986

Chromosomal assignment of the human erythropoietin gene and its DNA polymorphism.

Erythropoietin (EPO), a glycoprotein hormone, is the major physiological regulator of erythrocyte production in mammals. A cDNA clone containing the entire human EPO-coding region was used for Southern blot analysis of a series of human-Chinese hamster somatic cell hybrids containing different combinations of human chromosomes. Synteny analysis revealed 100% concordance between the EPO gene and human chromosome 7. Further localization to the region q11-q22 was accomplished by in situ hybridization of 3H-labeled human EPO cDNA to metaphase chromosomes prepared from both human lymphocytes and the cell hybrid 879-2a that contained human chromosomes 5, 7, 9, 12, and 21. In addition, restriction fragment length polymorphisms were detected at a frequency of approximately 20% in a Chinese population using restriction enzymes either HindIII or HinfI. These polymorphisms were inherited in a Mendelian fashion. Thus, the EPO marker is reasonably polymorphic and should be useful in linkage analysis with other genetic markers on chromosome 7, including the locus for cystic fibrosis.

Chromosome Mapping↗
PubMed1986

Calcium buffering capacity of human seminal plasma: the role of EGTA in stimulating sperm motility.

The role of EGTA in stimulating human sperm motility (reported in Lancet i: 460-461, 1984) was investigated by measuring the calcium buffering capacity of human seminal plasma. Human seminal plasma contains 9.5 +/- 1.1 mM (mean +/- SE) calcium of which 0.16 +/- 0.01 mM only exists as free Ca2+. The free Ca2+ concentration was not changed by the addition of either 1 mM CaCl2 or 1 mM EGTA. The ability of seminal plasma to bind calcium ions was determined by adding varying amounts of CaCl2. Scatchard analysis of the results indicates the presence of high amounts of high-affinity (Kd1 = 3.4 +/- 0.2 microM, Bm1 = 11.5 +/- 1.5 mM) and low-affinity (Kd2 = 0.55 +/- 0.04 mM, Bm2 = 30.4 +/- 1.7 mM) Ca2+-complexing agents. The low-affinity Ca2+-binding substance may be citrate. These results seem to suggest that human seminal plasma has a high Ca2+ buffering capacity and the stimulation of sperm motility by EGTA ought to be mediated via a mechanism other than the reduction of the free calcium concentration in semen.

Calcium↗
PubMed1985

Lysosomal triacylglycerol lipase activity in L6 myoblasts and its changes on differentiation.

L6 myoblasts, before fusion, accumulate large stores of neutral lipid when cultured in medium supplemented with fatty acid. Upon fusion to terminally differentiated myotubes, a noticeable decrease in these neutral-lipid stores was observed. Triacylglycerol lipase activity was examined in L6 myoblasts at various stages of cell differentiation to assess a possible role for this enzyme in the above phenomenon. In this first study to demonstrate lipolytic activity in cultured muscle cells, the activity was found to be totally dependent on the presence of a detergent, either Cutscum or Triton X-100, during homogenization. The inhibition by many thiol-specific reagents [N-ethylmaleimide, p-chloromercuribenzoate, iodoacetate, 5,5'-dithiobis-(2-nitrobenzoic acid)] suggest that a thiol group is at or near the active site. The observed acidic pH optimum (5.5-6.0), the acute inhibition by chlorpromazine (a lysosomal lipase inhibitor) and the distribution of lipolytic activity upon cell fractionation (which co-sediments with acid phosphatase, a lysosomal marker enzyme) suggest that the lipase may be of lysosomal origin. Under the optimal conditions described, the triacylglycerol lipase activity of L6 myoblasts was determined to be 2.9 +/- 0.4 nmol of oleic acid released/min per mg of DNA. This activity increased 3-fold, to 9.0 +/- 1.6 nmol/min per mg, in the myotube phase. This increase in lipolytic activity may be responsible for the observed decrease in neutral-lipid stores of differentiating myoblasts.

Acid Phosphatase↗
PubMed1985

Cloning and expression of the human erythropoietin gene.

The human erythropoietin gene has been isolated from a genomic phage library by using mixed 20-mer and 17-mer oligonucleotide probes. The entire coding region of the gene is contained in a 5.4-kilobase HindIII-BamHI fragment. The gene contains four intervening sequences (1562 base pairs) and five exons (582 base pairs). It encodes a 27-amino acid signal peptide and a 166-amino acid mature protein with a calculated Mr of 18,399. The erythropoietin gene, when introduced into Chinese hamster ovary cells, produces erythropoietin that is biologically active in vitro and in vivo.

Amino Acid Sequence↗
PubMed1985

Molecular epidemiology of cytomegalovirus infections associated with bone marrow transplantation.

Restriction endonuclease analysis of purified viral DNA was used to study the molecular epidemiologic characteristics of cytomegalovirus infection in 18 patients having bone marrow transplantation. Four patients who had had asymptomatic excretion of cytomegalovirus in urine before transplantation subsequently developed a cytomegalovirus infection after transplantation (pneumonia in 2 patients, fever and viremia in 1 patient, and asymptomatic viruria in 1 patient). In each patient, the infection that developed after transplantation was caused by a cytomegalovirus strain genetically identical to the isolate detected in urine before transplantation. Cytomegalovirus isolates from different sites (buffy coat, lung, and urine) of the same patient were also identical, but cytomegalovirus isolates from different patients were never identical. Our results suggest that some cytomegalovirus infections after bone marrow transplantation may be caused by strains present before transplantation. The great structural and genetic variability of cytomegalovirus isolates must be considered in the development of effective diagnostic and immunoprophylactic measures for infection after marrow transplantation.

Adolescent↗
PubMed1984

Intravenous immunoglobulin for modification of cytomegalovirus infections associated with bone marrow transplantation. Preliminary results of a controlled trial.

The effects of immune globulin intravenous, 5 percent in 10 percent maltose, on cytomegalovirus infection and interstitial pneumonia in bone marrow transplants were evaluated in a randomized controlled trial. Eighteen patients were given weekly doses (20 cc/kg) of intravenous immunoglobulin before and after transplantation, and 18 patients were controls. The incidence of cytomegalovirus infection was similar in the control and intravenous immunoglobulin-treated groups, but symptomatic cytomegalovirus infection (eight of 18 versus three of 18, p = 0.14) and interstitial pneumonia (10 of 18 versus four of 18, p = 0.08) occurred less frequently in the group receiving intravenous immunoglobulin. Cytomegalovirus pneumonia developed in eight control patients and in three patients receiving intravenous immunoglobulin (p = 0.14), whereas two control patients and one patient receiving intravenous immunoglobulin experienced idiopathic interstitial pneumonia. These preliminary results suggest that intravenous immunoglobulin can modify the severity of cytomegalovirus infection and prevent interstitial pneumonia in bone marrow transplant recipients.

Adolescent↗
PubMed1984

Characterization of an isozyme of S-adenosylmethionine synthetase from rat liver.

An isozyme of S-adenosylmethionine synthetase has been purified to homogeneity by ammonium sulfate fractionation, DEAE-cellulose column chromatography, and gel filtration on a Sephadex G-200 column. The purified enzyme is very unstable and has a molecular weight of 120 000 consisting of two identical subunits. Amino acid analysis on the purified enzyme showed glycine, glutamate, and aspartate to be the most abundant and the aromatic amino acids to be the least abundant. It possesses tripolyphosphatase activity which can be stimulated five to six times by S-adenosylmethionine (20-40 microM). The findings support the conclusion that an enzyme-bound tripolyphosphate is an obligatory intermediate in the enzymatic synthesis of S-adenosyl-methionine from ATP and methionine.

Amino Acids↗
PubMed1984

Adverse behavioral effects of the anticholinesterase poisoning protector pralidoxime methanesulfonate.

Pralidoxime methanesulfonate (P2S) has anticholinesterase protective properties, but it also has an array of gastrointestinal (GI) symptoms. Because such a symptom would be disadvantageous to occupational workers who handled and used organophosphorus anticholinesterase continuously, and to soldiers who have had oral pretreatment in a situation where anticholinesterase agent poisoning is a possibility, this question was investigated in rats using three behavioral paradigms to evaluate the feasibility of the oral prophylactic regimen. These are: (1) conditioned taste aversion (CTA), (2) operant behavior and (3) spontaneous locomotor activity (SMA); these three behavioral parameters are analogous to toxicant-induced gastrointestinal (GI) disturbances, performance of learned tasks and behavioral arousal, respectively. Dose-response studies of P2S in dose levels of 0.2, 0.4, 0.8 and 1.6 gm/kg (P.O.) were evaluated. The results consistently demonstrated that only the highest dose significantly produced marked decreases in consumption of flavored solution associated with its ingestion, suppressed keypress response maintained under a 20-response fixed-ratio schedule of water presentation, and inhibited SMA. By inference, if CTA, operant behavior and SMA are appropriate paradigms, P2S, on an acute single oral high dose level, would cause GI disturbances, impair task performance and induce sedation in man.

Animals↗