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Biomedical subjects

L Lin

Publications and source records attributed to L Lin.

At least 415 records · Page 23Linked to original sources
PubMed1988

Specificity of tumor necrosis factor toxicity for human mammary carcinomas relative to normal mammary epithelium and correlation with response to doxorubicin.

By using a unique short-term culture system capable of growing both normal and malignant breast epithelial tissue, human recombinant tumor necrosis factor (TNF) showed preferential cytotoxicity to malignant cells as compared to the corresponding nonmalignant cells. Most of the malignant specimens were sensitive to TNF with 13 of 18 specimens showing 90% inhibition of clonal growth (ID90) by less than 500 units of TNF per ml of culture fluid. In contrast, all 13 nonmalignant specimens tested clustered at the resistant end of the TNF response spectrum, with ID90 values being greater than 5000 units of TNF per ml of culture fluid. This differential sensitivity to TNF was seen in three cases in which malignant and nonmalignant breast epithelial tissues from the same patient were studied. To investigate the mechanism of resistance to TNF by normal cells, the presence of receptors for TNF was determined. Five of six cultures showed specific binding of 125I-labeled TNF and there was no relationship between the degree of resistance and the degree of specific binding. Simultaneous comparison of tumor responsiveness to doxorubicin and TNF revealed a positive correlation in ID90 values; these results may have important implications for the clinical use of TNF in cancer patients heavily pretreated with doxorubicin.

Breast↗
PubMed1988

Coenzyme Q10 content in different parts of the normal human heart.

Coenzyme Q10 (CoQ10) and citrate synthase (CS) activities were analysed in the myocardium of brain-dead organ donors (14-40 years). Different parts of the heart were studied: right and left auricular appendage, right and left atrium, right ventricle (septum and free wall) and left ventricle (septum, free wall, and papillary muscle). Freeze-dried, dissected myocardial samples were analysed for CoQ10 content by HPLC and CS activity by fluorometric technique. CoQ10 content in the normal human myocardium was lowest in auricular appendages and atria (0.25 +/- 0.06 mg X g-1 dry muscle), intermediate in right ventricle (0.37 +/- 0.05 mg X g-1 dm) and highest in left ventricle (0.42 +/- 0.07 mg X g-1 dm). CS activity showed the same relationship between these locations as CoQ10. The results suggest that there exist differences in CoQ10 content between different parts of the normal human myocardium. These differences were closely related to the differences in CS activity between corresponding parts. The differences between different parts of the heart may be related to divergent work demand, and the constant relationship between CS and CoQ10 may be related to their coupling to the mitochondrial oxidative metabolism.

Adult↗
PubMed1988

A micromethod for measuring carbonic anhydrase activity using 18O exchange between CO2 and H2O.

We have developed a method of measuring the activity and characteristics of carbonic anhydrase (CA) using the disappearance of 18O from CO2 in 1 ml of gas contained in a glass chamber as it exchanges with H2O in 0.01 ml 0.25 M NaHCO3 solution in a thin (25 micron) porous membrane. Serial gas samples (approximately 0.02 ml) are analyzed in a mass spectrometer to obtain the rate of disappearance of the label. The enzyme activity can be measured inside intact cell or particle membranes. As little as 10(-15) mol of high-activity type CA can be detected at 25 degrees C, and the activity of 200 times this amount can be measured. The uncatalyzed hydration reaction velocity constant was 0.056 +/- 0.004 s-1, in agreement with published data.

Bicarbonates↗
PubMed1987

Significance of elevated MB isoenzyme with normal creatine kinase in acute myocardial infarction.

The significance of elevated levels of the MB isomer of creatine kinase (CK-MB) when creatine kinase (CK) level is normal was studied in 400 patients with suspected acute myocardial infarction (AMI). In 350 patients both CK and CK-MB were elevated (group 1), in 21 only CK-MB was elevated (group 2), in 24 neither enzyme was elevated (group 3) and in 5 only CK was elevated (group 4). In 57% of patients in group 2 the CK level was doubled, with a characteristic enzyme curve, within the normal range, suggesting that an increase in CK had been missed because arbitrary definitions of "normal" were used. The median CK increase (60 IU/liter) in group 2 was greater than that in group 3 (23 IU/liter) (p less than 0.001). Patients in group 1 with small AMIs had a relative increase in CK similar to that in group 2. However, patients in group 2 had a lower baseline CK level so that peak CK did not become abnormally high despite a 5-fold increase in some patients. In patients in group 1 with small AMIs, CK was elevated in fewer samples than CK-MB. If only 2 samples were obtained in all patients, elevation of CK levels would have been missed in 63 group 1 patients, erroneously increasing the number of patients in group 2 fourfold (to 84 of 400, or 21%, instead of 21 of 400, or only 5%). Conversely, if patients in group 2 with a doubling of CK are excluded, the prevalence of elevated CK-MB with normal CK would be only 9 of 400 (2%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Oxidation of 5-hydroxytryptamine and 5,7-dihydroxytryptamine. A new oxidation pathway and formation of a novel neurotoxin.

The electrochemical oxidation of 5-hydroxytryptamine (5-HT) in acidic solution proceeds through a minor route leading first to 5,7-dihydroxytryptamine (5,7-DHT) then to 4,5,7-trihydroxytryptamine and finally to 5-hydroxytryptamine-4,7-dione. The latter compound is a major electrochemical oxidation product of 5,7-DHT at pH 2 and 7 and a major autoxidation product at pH greater than or equal to 6. Preliminary biological results indicate that 5-hydroxytryptamine-4,7-dione is a more potent central nervous system toxin than 5,7-DHT. These results show for the first time a chemical pathway from 5-HT to 5,7-DHT and suggest possible minor metabolic oxidative pathways for the neurotransmitter 5-HT to at least two powerful neurotoxins.

5,6-Dihydroxytryptamine↗
PubMed1985

Rapid automated high-performance liquid chromatographic analysis of cyclic adenosine 3',5'-monophosphate. Synthesis in brain tissues.

A rapid and sensitive automated system for measuring cyclic adenosine 3',5'-monophosphate (cAMP) synthesized from either radiolabelled adenine or adenosine 5'-triphosphate (ATP) in intact and broken cell tissue preparations, respectively, is described. After incubation with radiolabelled precursor, tissue samples are deproteinized and then injected directly onto a reversed-phase high-performance liquid chromatographic column. The column effluent fraction which contains cAMP is collected into scintillation vials and assayed for tritium by liquid scintillation spectrometry. Since the high-performance liquid chromatographic and fraction collection procedures are automated, over fifty samples can be analyzed in duplicate in a single day. The utility of this assay is illustrated by investigations of the effects of beta-adrenergic receptor stimulation on cAMP synthesis in tissue slices prepared from rat cerebral cortex and dopamine on cAMP synthesis in striatal membrane preparations.

Adenine↗
PubMed1985

Evaluation of papain/chymopapain cross allergenicity.

Recent clinical evidence suggests that papain and chymopapain may share common allergenicity. Patients that become sensitized to papain may subsequently experience an allergic reaction when they are exposed to chymopapain. This study demonstrates a cross antigenicity between the proteolytic enzyme preparations papain and chymopapain. Serum samples from six patients who demonstrated 4+ skin reactions to papain also revealed positive RAST ratios to both papain and chymopapain. In addition, serum samples from 12 clinically nonreactive patients who had discolysis with chymopapain demonstrated positive RAST results to papain as well as to chymopapain.

Allergens↗