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Biomedical subjects

L Hsu

Publications and source records attributed to L Hsu.

At least 145 records · Page 8Linked to original sources
PubMed1989

Uptake and acylation of 2-acyl-lysophospholipids by Escherichia coli.

The efficiency of extracellular 2-acyl-lysophospholipid incorporation into Escherichia coli membranes and the acyl donor utilized to acylate the 2-acyl-lysophospholipid was determined. Exogenous 2-acyl-lysophospholipids were acylated via the acyl-acyl carrier protein synthetase/2-acylglycerophosphoethanolamine acyltransferase pathway. The maximum extent of 2-acyl-lysophospholipid incorporation into the membrane was approximately 2.5% of the normal phospholipid biosynthetic rate.

Acylation↗
PubMed1989

[Expression of exogenous platelet-derived growth factor B chain gene in CHO cells].

CHO cells were transfected with plasmid pSM-1 (containing human c-sis cDNA) singly or co-transfected with pSV 2 neo DNA by calcium phosphate method. After low serum or G418 selection several cell lines with expression of platelet-derived growth factor (PDGF) were obtained. One among them, FB5, was of the highest PDGF expression and showed the following biological characteristics when compared with CHO cells: (1) a prominent change in morphology from spindle to round in shape: (2) increase of growth rate; (3) growth in low serum (2%) medium as a semisuspension culture; (4) growth on soft agar to larger colonies; (5) synthesis of PDGF in cytoplasm identified by immunofluorescent method; (6) the conditioned medium stimulated DNA synthesis of NRK cells; (7) RNA dot hybridization showing high transcription of PDGF mRNA; (8) southern blot showing integration of human c-sis gene was still stable after 7 months. These results indicated that intergration of exogenous c-sis gene and its high expression might cause CHO cells to high growth rate and even transformation. The establishment of this stable transformed cell line, FB5 is thought to be a good model for further study on the function of PDGF in cell growth control and cell transformation.

Animals↗
PubMed1988

Ca2+-mediated catabolism of human erythrocyte band 3 protein.

Catabolism of human erythrocyte membrane band 3 protein in the presence of Ca2+ was studied. An increase in the amount of a 30 kDa amino terminal fragment of band 3 was observed when erythrocyte membranes were incubated for 30 min with 1 mM Ca2+ in the presence of whole erythrosol. Incubation of the membranes with Ca2+ alone did not result in band 3 breakdown. Generation of the 30 kDa fragment from band 3 was related to the action of a leupeptin-sensitive Ca2+-dependent proteinase in the cytosol. This proteinase was also responsible for the increased production of a 52 kDa and a 70 kDa transmembrane carboxyl terminal fragment of band 3. From the size of the generated fragments, it is deduced that in the presence of Ca2+ and Ca2+-dependent proteinase, band 3 protein is cleaved at the cytoplasm/membrane interface and along its cytoplasmic domain.

Anion Exchange Protein 1, Erythrocyte↗
PubMed1988

Evolution of the responses to exercise in left ventricular aneurysms after anterior wall acute myocardial infarction.

The evolution of the heart rate, blood pressure and electrocardiographic responses to exercise in 20 patients (group A) who exhibited echocardiographic evidence of left ventricular (LV) aneurysms after acute myocardial infarction (AMI) were examined. The responses were compared with those seen in 19 patients without LV aneurysms who were matched for age, gender and location of infarct (group B). Patients taking beta blockers were excluded from the study. It was found that the heart rate response to exercise was accentuated in group A at the time of discharge from hospital and that it became attenuated over 9 to 12 months. The blood pressure response was significantly increased over 9 to 12 months in group B. Persistence of ST elevation during exercise, 10 to 12 weeks after AMI, was diagnostic of an LV aneurysm. One year after AMI the sensitivity of ST elevation was 90%, specificity was 95% and the negative predictive value 90%.

Blood Pressure↗
PubMed1988

Equilibrium dialysis studies of plasma binding of thyroxine, triiodothyronine and their glucuronide and sulfate conjugates in human and cat plasma.

Binding of thyroxine (T4), triiodothyronine (T3) and their glucuronide and sulfate conjugates, T4G, T3G, T4S and T3S, was assessed by equilibrium dialysis in plasma from 6 euthyroid humans and 5 euthyroid cats. In humans, the dialyzable percentages of T4, T4G and T4S were 0.029 +/- 0.003 (mean +/- S.D.), 0.14 +/- 0.04 and 0.08 +/- 0.02 respectively. For T3, T3G and T3S they were 0.31 +/- 0.04, 0.33 +/- 0.07 and 0.22 +/- 0.02. In cats, the corresponding values for T4, T4G and T4S were 0.057 +/- 0.009, 0.20 +/- 0.10 and 0.53 +/- 0.04; for T3, T3G and T3S they were 0.47 +/- 0.08, 0.51 +/- 0.11, and 0.53 +/- 0.11. We conclude that glucuronide conjugation has little or no inhibiting effect on the plasma binding of T3, and that T3S is actually more tightly bound than T3 in human (but not feline) plasma. On the other hand, conjugation to either the glucuronide or the sulfate markedly reduced T4 binding in plasma from both species.

Adult↗
PubMed1987

Preparation and separation of the glucuronide and sulfate conjugates of thyroxine and triiodothyronine.

An enzymatic method for synthesis of labelled thyroxine glucuronide (T4G) and triiodothyronine glucuronide (T3G) from labelled thyroxine (T4) and triiodothyronine (T3) is presented. The synthetic glucuronides are completely digested by beta-glucuronidase, with recovery of the parent T4 or T3. They have distinctive elution patterns on HPLC and on Sephadex G25 chromatography, and can be clearly separated from T4 and T3 as well as from synthetic T4 sulfate (T4S) and T3 sulfate (T3S). On LH 20 chromatography, elution of T4G and T3G is intermediate between that of T4 and T3 and that of T4S and T3S. T3G can be well separated from other thyronines by HPLC alone, but T4G coelutes with rT3 on HPLC; these are then separated by adding a Sephadex G25 chromatography step. Biosynthetic 131I-T3G and 125I-T4G from the bile of a cat given 131I-T3 and 125I-T4 had similar HPLC chromatographic patterns to those of synthetic T3G and T4G. That the identified peaks from analysis of the bile were indeed T3G and T4G was confirmed by recovery of the parent T3 and T4 after beta-glucuronidase digestion.

Animals↗
PubMed1987

Are the red cell proteases a clock mechanism which turns on a signal of senescence?

The mammalian erythrocyte has a finite life span. In order to study the mechanism involved, a well-defined age group of erythrocytes must be obtained. Such cells are produced by a hypertransfusion system in mice. With this system, it was possible to show that the very oldest population of erythrocytes bind autoantibodies. This binding of the autoantibodies is not a gradual accumulation, but occurs primarily in the oldest red cells. The immunoglobulins bound are not isotype specific but reflect the isotype in the serum. The red cells with the oldest mean age are recognized and phagocytized most readily by peritoneal exudate macrophage in vitro. Earlier studies suggest that protein 3 may be involved in autoantibody binding. An investigation of protein 3 indicates that the human red cells contain well-defined catabolic products of this protein and there is little variation of these catabolic products among individuals both quantitatively and qualitatively. This suggests that there is a well-regulated catabolic system in the red cell. A study of the calcium-activated proteases, the only neutral proteases in the red cell, show that they do not directly generate the amino terminal catabolic fragments of protein 3 found in the erythrocyte.

Animals↗
PubMed1986

Prediction of coronary events following myocardial infarction using a discriminant function analysis.

This study was undertaken to derive an index for predicting coronary events in the first year after a myocardial infarction in "low-risk" patients enrolling in a Cardiac Rehabilitation Program. Data from 145 consecutive patients were analysed. The events were classified as follows: angina requiring further therapy, re-infarction and coronary death. Seventy patients had events: Angina--52, Re-infarction--8, Coronary Death--10. A discriminant function analysis was performed to predict such events using data available at the time of discharge from hospital. The following were significant predictors: (1) previous infarction/angina, (2) radiological evidence of cardiomegaly or lung congestion in the Coronary Care Unit, (3) Non-Q wave infarction and (4, 5 and 6) angina, atrial arrhythmias and a decrease in R wave amplitude in V5 during a pre-discharge exercise test. The jack-knife method classified correctly 71.2% of those with events and 72.6% of those without events. In patients with discriminant scores greater than +0.2, 82% developed events.

Adult↗
PubMed1985

Neurite-promoting effects of 12-O-tetradecanoylphorbol-13-acetate on chick embryo neurons.

The addition of the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) to defined growth medium enhanced the survival of ciliary neurons in dissociated cultures and promoted the rapid development of neurites from sympathetic and parasympathetic ganglion explants. Explants of the central nervous system including the cerebral cortex and spinal cord of chick embryos were, however, unresponsive to either 10 or 100 ng/ml of TPA.

Animals↗
PubMed1985

Catabolism of the anion transport protein in human erythrocytes.

We identified the catabolic products of protein 3 in human erythrocytes. Protein 3, the major protein of the erythrocyte membrane, functions in anion transport and reacts covalently with tritiated 4,4'-diisothiocyano-1,2-diphenylethane-2,2'-disulfonic acid ([3H]DIDS), a very selective inhibitor of anion transport. In this study, [3H]DIDS was used to label protein 3 in the membranes of normal cells and those from a donor heterozygous for a variant of protein 3, defined by its elongated amino-terminal end. Both types of cells contained [3H]DIDS-labeled peptides other than protein 3. A protein fragment of 60K molecular weight was found in normal cells, whereas both 60K and 63K fragments were identified in cells from the heterozygote. These peptides are identical with those generated by treatment of intact erythrocytes with Pronase or chymotrypsin. A polyclonal rabbit antibody specific for the purified 60K fragment of protein 3 was used to detect this protein and its products in the erythrocyte membrane. Autoradiographs of membrane peptides that were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, transferred to nitrocellulose, and allowed to react with the monospecific antibody showed, in addition to protein 3, a 60K fragment and fragments in the 40K region and in the 20-30K region. Cells containing the protein 3 variant yielded two fragments showing a 3K difference in molecular weight in all three regions, demonstrating that degradation of protein 3 is identical in normal erythrocytes and those heterozygous for the variant. This observation also confirms the common derivation of the fragments from protein 3.(ABSTRACT TRUNCATED AT 250 WORDS)

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1985

A new variant of the anion transport protein in human erythrocytes.

The major plasma membrane protein of human erythrocytes is the anion transport protein, termed protein 3. We previously reported a variant form of protein 3 that is elongated on the amino-terminal end of the molecule, which is exposed on the cytoplasmic side of the membrane, but otherwise its features are identical with those of the normal molecule. We have termed this molecule protein 3 variant 1. We now report a new variant form, protein 3 variant 2. The erythrocyte donor was a double heterozygote whose red cells possess a normal protein 3 and a protein 3 variant which is elongated and possesses a second variation at the 4,4'-diisothiocyano-2,2'-stilbenedisulfonic acid (DIDS) reactive site. Variant 2 reacts with 4,4'-diisothiocyano-1,2-diphenylethane-2,2'-disulfonic acid (H2DIDS) more readily than does the normal molecule. At high pH values, H2DIDS acts as a bifunctional cross-linking agent; it cross-links the proteolytic products generated by Pronase (or chymotrypsin) treatment of variant 2 less efficiently than noted for normal protein 3 or the first variant. Thus, the newly identified molecule has an alteration at the DIDS reactive site, which is near the outer surface of the membrane. The results can be interpreted as indicating that the DIDS binding site of variant 2 is more exposed than the normal molecule, but further removed from the site on the carboxyl-terminal fragment involved in cross-linking. Although there is a difference in the reactivity of the two protein 3 chains in variant 2, the reaction of variants 1 and 2 and normal cells with varying concentrations of [3H]H2DIDS results in the same amount of incorporation in all cells. Since protein 3 exists as a dimer or higher aggregate in the membrane, these results may indicate an interaction between monomers.(ABSTRACT TRUNCATED AT 250 WORDS)

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1985

Cardiovascular responses to early exercise in inferior wall ST acute myocardial infarction.

The heart rate and blood pressure responses to standardized exercise tests were studied in a group of patients with electrocardiographic evidence of inferior wall acute myocardial infarction (AMI). The tests were done on a bicycle ergometer at 8 to 10 days and 10 to 12 weeks after AMI. At 8 to 10 days after AMI, those with ST AMI (n = 12) had a significantly reduced heart rate response to exercise compared with patients with Q-wave AMI (n = 25). This difference was not evident at 10 to 12 weeks. The systolic blood pressure response in patients with ST AMI was lower than that of Q-wave AMI patients during the first exercise test, although the difference did not attain statistical significance but was significantly lower than the responses of both groups at the second test. The patients with ST AMI had smaller amounts of myocardial damage than those with Q-wave AMI as indicated by plasma creatine kinase values (p less than 0.01). These differences in the heart rate responses appeared to result from the preferential activation of nonmyelinated afferent fibers in the subepicardial region of the inferior wall of the myocardium.

Blood Pressure↗
PubMed1984

Effects of the tumor promoter 12-O-tetradecanoylphorbol-13-acetate on neurite outgrowth from chick embryo sensory ganglia.

The addition of the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) to defined growth medium stimulated an intense neurite outgrowth from chick sensory ganglia explants. The development of radial neurites was concentration dependent. At low concentrations of TPA (1.6 to 16 nM), neurites were long but moderate in numbers. At higher concentrations (160 to 480 nM), TPA produced dense, short neurites that formed thick fascicles. This reduced outgrowth in length was not related to cytotoxicity and was found to be reversible when the tumor-promoting agent was removed. Neurite outgrowth was also accompanied by an increase in proliferation of nonneuronal cells. Blocking the proliferation of nonneuronal components by the mitotic inhibitor 1-beta-D-arabinofuranosylcytosine did not inhibit neurite outgrowth, suggesting that the TPA-induced neurite differentiation was independent of nonneuronal cells. When TPA was tested in the presence of nerve growth factor, the induction of neurite differentiation was not affected. Other active tumor promoters including phorbol-12,13-didecanoate and mezerein also elicited neurite outgrowth, while nonpromoting agents such as phorbol and 4 alpha-phorbol-12,13-didecanoate were ineffective.

Animals↗
PubMed1983

The interaction of human erythrocyte Band 3 with cytoskeletal components.

Band 3 of the human erythrocyte is involved in anion transport and binding of the cytoskeleton to the membrane bilayer. Human erythrocytes were treated to incorporate varying concentrations of DIDS (4,4'-diisothiocyanostilbene-2,2'-disulfonic acid) a non-penetrating, irreversible inhibitor of anion transport, and both functions of Band 3 were analyzed. The rate of efflux of 35SO2-4 was measured and the binding of cytoskeletal components to the membrane was evaluated by extracting the membranes with 0.1 N NaOH and analyzing for the peptides remaining with the membrane. It was found that 0.1 N NaOH extracts all the extrinsic proteins from membranes of untreated cells, while, in the case of the membranes from cells treated with DIDS, a portion of the cytoskeletal components, spectrin (Bands 1 and 2) and Band 2.1 (ankyrin, syndein) remain with the membrane. The amount of these cytoskeletal components remaining with the membrane depends on the concentrations of DIDS incorporated. The effect of DIDS on the extractability of the spectrin-Band 2.1 complex correlates well with DIDS inhibition of anion transport (r = 0.91). At DIDS concentrations which completely inhibit anion transport, about 10% of total spectrin-Band 2.1 complex remains unextracted. Another anion-transport inhibitor, pyridoxal phosphate, has no effect on binding of the cytoskeleton to the membrane. On the other hand, digestion of DIDS-pretreated intact erythrocytes with Pronase, chymotrypsin, or trypsin releases the tight binding of Band 3 to cytoskeleton on the inside of the membrane. Since trypsin does not hydrolyze Band 3 the data suggest that a second membrane protein which is trypsin sensitive may be involved with Band 3 in cytoskeletal binding.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1983

Comparison of steady and pulsatile flow in a double branching arterial model.

Data are presented to compare fluid flow parameters for steady flow with those for time-varying flow in a simplified two branch model which simulates the region of the abdominal aorta near the celiac and superior mesenteric branches of the dog. Measurements in the model included laser doppler anemometry velocity profiles during steady flow, sinusoidal flow with a superimposed mean flow (referred to as simple oscillatory flow) and arterial pulsatile flow. Shear rate measurements were made by an electrochemical technique during steady flow. Flow visualization studies were done during steady and pulsatile flow. Fluid flow effects in the simplified model during steady flow showed many similarities to the results from previous steady flow studies in a canine aortic cast. Shear rates in the region of the proximal (first, or celiac) branch were independent of flow rates in the distal (second, or mesenteric) branch, but the shear pattern within the proximal branch changed significantly as flow in the proximal branch increased. Shear rates on the proximal flow divider (leading edge into the distal branch) depended primarily on the flow rate to the proximal branch, but not on flow to the distal branch. At certain daughter branch flow ratios (approximately 2:1, proximal to distal), flow separation was promoted at the outer wall of the second branch, but flow separation did not occur in the first branch. In contrast to the canine aortic case results, flow separation was never detected on the distal (mesenteric) flow divider of the simplified model. This observation reflects the subtle effects of geometry on flow since the mesenteric flow divider in the canine cast protrudes into the main flow whereas the distal flow divider in the simplified model does not. There were distinct differences in the flow phenomena between steady, simple oscillatory and arterial pulsatile flow. Peak shear rates during pulsatile flow were as much as 10--100 times greater than steady flow shear rates at comparable mean flow rates. Particularly noteworthy for the pulsatile flow with a Womersley parameter of sixteen were very blunt velocity profiles throughout systole, and the absence of flow separation or reversal in those regions of the model that exhibited flow separation during steady flow. The shape of the waveform influences the nature of the flow during time-varying flows. Future studies of fluid dynamics in model systems must consider the pulsatile nature of the flow if a true interpretation of arterial flow phenomena is to be made.

Aorta, Abdominal↗
PubMed1982

Cholinesterase enzymes in the blood of patients with Alzheimer's disease.

Plasma pseudocholinesterase activity was about 100% higher in patients with Alzheimer's type dementia than in similar age controls. Red cell acetylcholinesterase activity tended to be lower in patients than controls. Administration of lecithin substantially increased plasma choline levels but did not alter activity of either of the cholinesterase enzymes.

Aged↗