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Biomedical subjects

S Lin

Publications and source records attributed to S Lin.

At least 577 records · Page 32Linked to original sources
PubMed1984

Lateral diffusion of human histocompatibility antigens in isolated plasma membranes.

We have prepared large (5-10 microns) plasma membrane fragments by lysis of VA-2, human, cells adherent to Sephadex beads. The membrane fragments may be removed from beads by sonication and stained with fluorescent antibodies to human histocompatibility antigens, HLA antigens. Lateral diffusion of labelled antigens is followed by the method of fluorescence photobleaching recovery (FPR). HLA antigens of isolated membranes diffuse at the same rate, approx. (2-4) X 10(-10) cm2 X s-1 as they do in intact cells. This rate may be modified by incubating membranes in a variety of media. Buffers of slightly acid pH (6.5 or less) enhance lateral diffusion, while the presence of divalent ions slightly reduces diffusion rates. Our major finding is that incubation of 37 degrees in 0.10 M phosphate buffer increases lateral diffusion 3-5-fold.

Buffers↗
PubMed1984

Brevin and vitamin D binding protein: comparison of the effects of two serum proteins on actin assembly and disassembly.

Actin depolymerizing activity in serum can be attributed to the two proteins brevin and vitamin D binding protein (DBP). To investigate their mechanisms of action, we used a number of techniques, including procedures involving the fluorescent pyrene-labeled actin probe, to compare the interaction of the two proteins with G- and F-actin in vitro. With a fluorescence enhancement assay, we determined that brevin forms a 1:2 complex and DBP forms a 1:1 complex with pyrene-G-actin. We also found that both proteins reduce the viscosity of F-actin measured with high-shear and low-shear viscometers, with brevin effective at much lower concentrations than DBP. In polymerization experiments, brevin inhibits filament elongation at substoichiometric levels by inhibiting monomer addition at the barbed end but can also accelerate polymerization by nucleating assembly of filaments which grow from the pointed end. DBP does not nucleate filament assembly and inhibits filament elongation at either end only at near-stoichiometric levels. Brevin, but not DBP, accelerates disassembly of filaments diluted into a depolymerizing medium. This is consistent with the capability of brevin to sever preformed filaments associated with erythrocyte membranes and to increase the number of filament ends as estimated by a cytochalasin binding assay. In steady-state experiments involving the use of pyrene-actin, brevin produces only a small increase in the apparent monomer concentration when the critical concentrations at the two ends of the filaments are the same (i.e., in 0.1 M KCl). However, when the critical concentration at the pointed end is higher than that at the barbed end (i.e., in 2 mM MgCl2), low molar ratios of brevin sharply increase the monomer concentration to the critical concentration of the pointed end. This allows substoichiometric amounts of brevin to completely depolymerize filaments when the total actin concentration is at or below that of the pointed end. In contrast to brevin, DBP increases the amount of nonfilamentous actin in a stoichiometric and dose-dependent manner regardless of the nature of the salt in the medium. We conclude from this study that brevin is similar in its mechanism of action to other proteins known to bind to the barbed end of filaments and that DBP is related in its action to proteins that complex monomers and prevent them from participating in the polymerization process.

Actins↗
PubMed1984

Ammonia, postsynaptic inhibition and CNS-energy state.

Ammonia intoxication decreases the hyperpolarizing action of postsynaptic inhibition. This study examines the metabolic state of the spinal cord during this effect of ammonia intoxication on spinal motoneurons. ATP, ADP, AMP, the adenylate energy charge, glucose, PCr, pyruvate, alpha-ketoglutarate and glutamate were unchanged during the effect of ammonia on the hyperpolarizing action of postsynaptic inhibition. NH4+, glutamine and lactate were increased. Ammonia intoxication affected postsynaptic inhibition without changes of the resting membrane potential, the neuron input resistance, the action potential and EPSPs. The encephalopathy caused by ammonia intoxication is known to occur without an alteration of the tissue energy state. The effect of ammonia intoxication on postsynaptic inhibition can be considered as a cause of the encephalopathy because postsynaptic inhibition is altered without a change of the tissue energy state, the resting membrane potential, the whole neuron resistance, the action potential and EPSPs.

Ammonia↗
PubMed1984

One base substitution in IVS-2 causes a beta +-thalassemia phenotype in a Chinese patient.

Two beta-globin genes derived from a Chinese patient with a beta +-thalassemia phenotype have been cloned and sequenced. A four-nucleotide deletion in codon 41 and 42 was found in one of the clones and a C to T substitution at position 654 of IVS-2 was detected in the other clone. The former change, which causes premature termination at codon 59, was found previously in another Chinese patient with homozygous beta 0-thalassemia. The latter change, which has not been reported so far, creates a sequence much like the consensus sequence of the 5' splice site. These results suggest that the new base change found in IVS-2 causes aberrant splicing of the beta-globin mRNA precursor. Thus, this patient is doubly heterozygous for beta 0- and beta +-thalassemia.

Base Sequence↗
PubMed1984

Isolation of surface membranes from neuronal and non-neuronal cell populations from embryonic chick brain. Opiate receptor activity of neuronal membranes.

Surface membranes were isolated from neuronal and non-neuronal cell populations prepared from embryonic chick brain. Sodium dodecyl sulfate gel electrophoresis showed that membranes from the two cell populations have distinctly different protein compositions. The neuronal cell membranes have opiate receptor activity with high- and low-affinity binding sites similar to those determined for intact neuronal cells.

Animals↗
PubMed1984

Transfer of language dominance.

It has been suggested that recovery from aphasia may depend on the ability of the nondominant hemisphere to subserve language functions. We describe a patient who illustrates a possible "transfer" of language dominance. The patients sustained two infarcts two years apart, one in each hemisphere, involving mirror image territories in the temporoparietal area. The clinical course of each infarct was almost identical, consisting of an initial Wernicke's aphasia which evolved into anomic aphasia during recovery.

Anomia↗
PubMed1984

Severe alcoholism in the mental health sector: II. Effects of service utilization on readmission.

A follow-up study of a cohort of suburban alcoholics who are comprehensively served by the public mental health sector used a Cox survival time analyses to examine the relationship of patient characteristics, receipt of outpatient services and readmission to inpatient care. Patients were followed up until their first readmission to inpatient care or for 2 yr subsequent to an inpatient episode. As expected, established chronicity was associated with short "survival" in the community, as were youth and living alone. For first admissions, the receipt of aftercare was associated with a decreased likelihood of readmission, especially in conjunction with inpatient stays of treatment that included rehabilitation services. Patients who had established a pattern of chronicity, however, appeared resistant to the effect of these services. The transition from inpatient to aftercare services was identified as a crucial point in treatment. Aftercare patients who did not receive services beyond 6 months in the community were likely to be readmitted, suggesting that this period is also an important focus for treatment planning.

Adult↗
PubMed1983

Detection of high molecular weight vinculin binding proteins in muscle and nonmuscle tissues with an electroblot-overlay technique.

In this study, we examined binding of radiolabelled vinculin to proteins separated on sodium dodecyl sulfate-polyacrylamide gels, and then electrophoretically transferred onto nitrocellulose sheets. We detected saturable binding of vinculin to polypeptides with apparent Mr's of 215,000, 205,000 and 185,000 in a low ionic strength extract from chicken gizzard membranes. Binding of vinculin to proteins with apparent Mr's of 205,000, 185,000, and 165,000 in human platelets was also detected. In addition, we found that [125I]vinculin binds to unlabelled vinculin and to alpha-actinin, although these interactions appear to be of lower affinity than those with the higher molecular weight proteins.

Animals↗
PubMed1983

Structural analysis of a beta-thalassemia gene found in Taiwan.

The beta-globin gene from a patient with homozygous beta-thalassemia in Taiwan was cloned and extensively sequenced. Four nucleotides in the codon for amino acids, 41 and 42, are deleted. This change generates a frame-shift mutation and a termination codon in the new 59th codon. Some changes in nucleotide sequence were also found in intervening sequences IVS1 and IVS2, and Exon3, and were considered to be sequence polymorphisms.

Amino Acid Sequence↗
PubMed1983

Identification of fibrinogen derivatives in the Triton-insoluble residue of human blood platelets.

Several proteins (eg. actin, myosin, and actin-binding protein) in the Triton-insoluble residue of thrombin-stimulated platelets are important in the formation of cytoskeletal structures. Electrophoretic analyses have shown that unidentified protein bands of 68,000, 55,000, and 48-50,000 daltons are also present in larger amounts after thrombin stimulation. Since these molecular weights correspond roughly to those of the alpha, beta, and gamma chains of fibrin, and since fibrinogen is found in platelet alpha-granules, these bands were compared to those obtained when purified fibrinogen was treated with thrombin, exposed to 1% Triton X-100-5 mM EGTA, and the resultant Triton-insoluble residue sedimented. Identification of the 68,000-, 55,000-, and 48-50,000-dalton bands as fibrinogen derivatives was confirmed by identifying them in comigration studies and in autoradiographs of Triton-insoluble residues of platelets that were electrophoretically transferred to nitrocellulose paper and treated with antifibrinogen antibody and 125I-protein A. Furthermore, if the platelet suspension was treated with thrombin in the presence of calcium ions, protein bands characteristic of the action of Factor XIII on fibrin were observed, active platelet Factor XIII apparently having been made available by lysis of platelets during preparations. Making use of the electrophoretic properties of tubulin recently described by Best et al [1981], comigration studies using hog brain tubulin indicated that tubulin is not present in significant amounts in the Triton-insoluble residue of platelets as previously suggested. The identification of these proteins as fibrinogen derivatives does not demonstrate a physiological interaction between fibrin and the platelet cytoskeleton, since fibrin is Triton-insoluble and can be pelleted even in the absence of platelet cytoskeletons.

Blood Platelets↗
PubMed1983

Complexes containing actin and spectrin from erythrocyte and brain.

A complex of proteins with properties similar to those of erythrocyte spectrin-band 4.1-actin complex has been identified in a preparation derived from bovine brain. The complex has an apparent sedimentation coefficient of about 26S, and contains brain spectrin (also called fodrin) and actin as major components. The actin in the complex is in the oligomeric form, which nucleates assembly of actin filaments that grow from the "barbed" end. The complex cross-links actin filaments, resulting in an increase in low-shear viscosity. Whether the complex contains a protein analogous to erythrocyte band 4.1 is not known. However, it can be demonstrated that brain spectrin has the capability to interact with band 4.1 in a way which increases its ability to cross-link actin filaments.

Actins↗
PubMed1983

Ammonia intoxication and hyperpolarizing postsynaptic inhibition.

Systemic ammonia intoxication abolished the hyperpolarizing action of postsynaptic inhibition in the CNS at tissue concentrations of NH+4 which are sufficient to produce the earliest signs of encephalopathy. Therefore, the action of NH+4 on hyperpolarizing postsynaptic inhibition has to be considered as the cause, or as a contributing cause, of the encephalopathy due to systemic ammonia intoxication.

Ammonia↗
PubMed1983

Malignant fibrous histiocytoma of the heart.

A case of cardiac sarcoma was reported. The tumor, which arose from the posterior wall of the left atrium, was demonstrated by echocardiography, contrast-enhanced computed tomography and direct observation during surgery. The tumor was successfully excised under emergency operation and was diagnosed as malignant fibrous histiocytoma after histologic examination. The patient had been free of symptoms for several months, but died of rapidly progressive congestive heart failure 6 months after surgery.

Echocardiography↗
PubMed1982

The capactins, a class of proteins that cap the ends of actin filaments.

A number of proteins that bind specifically to the barbed ends of actin filaments in a cytochalasin-like manner have been purified to various degrees from a variety of muscle and non-muscle cells and tissues. Preliminary evidence also indicates that proteins that interact with the pointed ends of filaments are present in skeletal muscle. Because of their ability to cap one or the other end of an actin filament, we have designated this class of proteins as the 'capactins'. On the basis of their effect on actin filament assembly and interaction in vitro, we propose that the capactins play important roles in cellular regulation of actin-based cytoskeletal and contractile functions. Our finding that the disappearance of actin filament bundles in virally transformed fibroblasts can be correlated with an increase in capactin activity in the extracts of these cells is consistent with this hypothesis.

Actins↗