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Biomedical subjects

S C Liu

Publications and source records attributed to S C Liu.

At least 19 recordsLinked to original sources
PubMed1995

Molecular basis of altered red blood cell membrane properties in Southeast Asian ovalocytosis: role of the mutant band 3 protein in band 3 oligomerization and retention by the membrane skeleton.

Southeast Asian ovalocytosis (SAO) is an asymptomatic trait characterized by rigid, poorly deformable red cells that resist invasion by several strains of malaria parasites. The underlying molecular genetic defect involves simple heterozygous state for a mutant band 3 protein, which contains a deletion of amino acids 400 through 408, linked with a Lys 56-to-Glu substitution (band 3-Memphis polymorphism). To elucidate the contribution of the mutant SAO band 3 protein to increased SAO red blood cell (RBC) rigidity, we examined the participation of the mutant SAO band 3 protein in increased band 3 attachment to the skeleton and band 3 oligomerization. We found first that SAO RBC skeletons retained more band 3 than normal cells and that this increased retention preferentially involved the mutant SAO band 3 protein. Second, SAO RBCs contained a higher percentage of band 3 oligomer-ankyrin complexes than normal cells, and these oligomers were preferentially enriched by the mutant SAO protein. At the ultrastructural level, the increased oligomer formation of SAO RBCs was reflected by stacking of band 3-containing intramembrane particles (IMP) into longitudinal strands. The IMP stacking was not reversed by treating SAO RBCs in alkaline pH (pH 11), which is known to weaken ankyrin-band 3 interactions, or by removing the cytoplasmic domain of band 3 from SAO membranes with trypsin. Finally, we found that band 3 protein in intact SAO RBCs exhibited a markedly decreased rotational mobility, presumably reflecting the increased oligomerization and the membrane skeletal association of the SAO band 3 protein. We propose that the mutant SAO band 3 has an increased propensity to form oligomers, which appear as longitudinal strands of IMP and exhibit increased association with membrane skeleton. This band 3 oligomerization underlies the increase in membrane rigidity by precluding membrane skeletal extension, which is necessary for membrane deformation.

Anion Exchange Protein 1, Erythrocyte↗
PubMed1995

Portal vein embolization with lipiodol for treatment of HCC--an experimental study.

A suspension of iodized oil and anticancer agent was injected into the portal veins of 20 rats with hepatic carcinoma. Oil drops were seen in tumor cell lines, small blood vessels inside the cancer nest, the sinusoid, and the central veins. After injection of oil suspension through the portal vein the distal small vessels were embolized and necrotic changes of tumor cells and their subordinate normal liver cells were observed. The results obtained in this experiment provided a good anatomical and pathological basis for treating liver cancers with the portal vein embolization with chemotherapeutic agents.

Animals↗
PubMed1995

Craniofacial injuries in unhelmeted riders of motorbikes.

We studied 1160 consecutive craniofacial injuries sustained by unhelmeted motorbike riders in Taipei, Taiwan, between 1990 and 1993, in order to investigate the distribution, type and severity of these injuries. The average age of the victims was 31 years (SD 13.2), with 84 per cent of them being between ages 16 and 45. The facial and cranial areas were defined as being separated by the line between eyebrows and ears. The incidence of facial injuries was the same as that of cranial injuries (both 68 per cent). While facial injuries occurred most often in the cheek and chin, most cranial injuries occurred in the forehead and parietal region. Although the majority of facial injuries resulted in mild brain injuries, they may also cause serious cosmetic problems, and some were associated with serious brain damage. Motorbike riders need good face protection. Since most motorbikes in Taipei travel relatively slowly, these results may also apply to bicyclists; in other words, cyclists may also need good face protection.

Accidents, Traffic↗
PubMed1995

Oral transforming growth factor-alpha enhances jejunal mucosal recovery and electrical resistance in piglet rotavirus enteritis.

A randomized, investigator-masked trial determined the effects of oral recombinant human transforming growth factor-alpha (TGF alpha) on jejunal mucosal recovery in 75 piglets with rotavirus diarrhea. Rotavirus inoculation of artificially reared piglets induced subtotal (approximately 50%) villus atrophy and watery diarrhea. Dietary TGF alpha was associated with significant restoration of villus surface area by 4 d postinoculation (p.i.) and complete restoration by 8 d p.i., whereas saline-treated animals required 12 d for recovery. Jejunal segments from clinically recovered TGF alpha-treated piglets showed an increase in electrical resistance across the epithelial barrier in vitro which was proportional to villus height. TGF alpha treatment for 12 d also produced a 30-50% increase in jejunal mucosal mass (protein content and wet weight), compared with the corresponding values in saline-treated piglets and in uninfected controls. However, oral TGF alpha did not hasten the resolution of diarrhea, enhance the specific activities of jejunal mucosal digestive enzymes, or increase jejunal glucose-stimulated Na+ absorption in vitro. We conclude that dietary TGF alpha stimulates jejunal mucosal hypertrophy, improves barrier function, and enhances regrowth of villi in rotavirus enteritis; however, it does not facilitate the restoration of functional activity or mucosal digestive enzymes. Oral TGF alpha can facilitate intestinal epithelial recovery in diseases associated with mucosal damage.

Administration, Oral↗
PubMed1994

Sequence of the region downstream of the Vitreoscilla hemoglobin gene: vgb is not part of a multigene operon.

The 1668 base pairs (bp) downstream of the Vitreoscilla hemoglobin gene were sequenced in the hope of finding related genes that might be part of an operon. Instead, a sequence was found that constituted an open reading frame (ORF) of 569 amino acids (apparently the carboxy-terminal part of a larger ORF), in the direction opposite to the hemoglobin gene. This sequence was found to have 64% similarity with the 1685 bp at the 3' end of the Escherichia coli uvrA gene. The inferred amino acid sequence of the Vitreoscilla DNA has 69% similarity with the corresponding sequence of the E. coli uvrA protein, with similarities of 90, 100, and 85% in the helix-turn-helix, C-terminal ATP binding, and C-terminal zinc finger domains, respectively. The distance between the 3' ends of the Vitreoscilla hemoglobin and uvrA genes is 63 bp.

Adenosine Triphosphatases↗
PubMed1992

Band 3 Memphis: a widespread polymorphism with abnormal electrophoretic mobility of erythrocyte band 3 protein caused by substitution AAG----GAG (Lys----Glu) in codon 56.

Band 3 Memphis (b3M) is a variant of the erythrocyte band 3 protein detected in individuals of virtually all ethnic groups and characterized by a reduced mobility of proteolytic fragments derived from the N-terminus of the cytoplasmic domain of band 3 (cdb3). We have sequenced band 3 cDNA corresponding to cdb3 in 12 heterozygotes for the b3M polymorphism including one white, one black, one Chinese, one Philippino, one Malay, and seven Melanesian subjects. In all individuals, we found a single-base substitution in codon 56 of one band 3 allele changing lysine to glutamic acid (AAG----GAG) which, in some of them, was linked with an additional mutation in cdb3. Since the change of codon 56 from AAG to GAG was the only mutation in the studied individuals found within the cDNA segment coding for the abnormally migrating fragment of cdb3, we conclude that it represents the underlying molecular basis of the b3M polymorphism. We further support this conclusion by showing that electrophoresis in the presence of 4 mol/L urea abolished the difference in migration between proteolytic products of b3M and normal band 3, and that a fusion protein prepared from cDNA coding for the b3M allele again exhibits reduced electrophoretic mobility compared with the normal fusion protein. Finally, since most of the previously cloned mouse, rat, and chicken band 3 and band 3-related proteins contain glutamic acid in the position corresponding to amino acid 56 in the human band 3, we propose that the Memphis variant is the evolutionarily older form of band 3.

Anion Exchange Protein 1, Erythrocyte↗
PubMed1992

Asynchronous synthesis of membrane skeletal proteins during terminal maturation of murine erythroblasts.

To study the changes in the synthesis of the major membrane skeletal proteins, their assembly on the membrane, and their turnover during terminal red blood cell maturation in vivo, we have compared early proerythroblasts and late erythroblasts obtained from the spleens of mice at different times after infection with the anemia-inducing strain of Friend virus (FVA). Metabolic labeling of these cells indicates striking differences between early and late erythroblasts. In early erythroblasts, spectrin and ankyrin are synthesized in large amounts in the cytosol with proportionately high levels of spectrin and ankyrin messenger RNA (mRNA). In contrast, only small amounts of these polypeptides are incorporated into the skeleton, which is markedly unstable. In late erythroblasts, however, the synthesis of spectrin and ankyrin and their mRNA levels are substantially reduced, yet the net amounts of these polypeptides assembled in the membrane skeleton are markedly increased, and the membrane skeleton becomes stable with no detectable protein turnover. The mRNA levels and the synthesis of the band 3 and 4.1 proteins are increased considerably in terminally differentiated normoblasts with a concomitant increase in the net amount and the half-life of the newly assembled spectrin and ankyrin. Thus, the increased accumulation of spectrin and ankyrin at the late erythroblast stage is a consequence of an increased recruitment of these proteins on the membrane and an increase in their stability rather than a transcriptional upregulation. This is in contrast to band 3 and 4.1 proteins, which accumulate in direct proportion to their mRNA levels and rates of synthesis. These results suggest a key role for the band 3 and 4.1 proteins in conferring a long-term stability to the membrane skeleton during terminal red blood cell differentiation.

Anemia↗
PubMed1992

Selection and characterization of alpha-amylase-overproducing recombinant Escherichia coli containing the bacterial hemoglobin gene.

We previously reported that the presence of the bacterial (Vitreoscilla) hemoglobin gene enhances alpha-amylase production in recombinant Escherichia coli strain MK79. Using the growth of MK79 on starch as a selective method we have produced a mutant strain (BSC9) that produces up to four times as much alpha-amylase as MK79. Both MK79 and BSC9 produce the most alpha-amylase (per cell and per milliliter) in the stationary phase; almost all of the enzyme is intracellular in both strains. Modification of the standard alpha-amylase assay increases the amount of amylase detected about sixfold. BSC9 has about five to nine times as many copies per cell as MK79 of the recombinant plasmid, which carries both the amylase and hemoglobin genes, but both strains produce about the same amount of hemoglobin. While MK79 respiration decreases upon going from log to stationary phase, BSC9 respiration increases during the same period. The two latter results may be of particular importance in determining the way in which hemoglobin enhances the production of cloned protein products in recombinant bacteria.

Bacillus subtilis↗
PubMed1991

Deletion in erythrocyte band 3 gene in malaria-resistant Southeast Asian ovalocytosis.

Southeast Asian ovalocytosis (SAO) is a hereditary condition that is widespread in parts of Southeast Asia. The ovalocytic erythrocytes are rigid and resistant to invasion by various malarial parasites. We have previously found that the underlying defect in SAO involves band 3 protein, the major transmembrane protein, which has abnormal structure and function. We now report two linked mutations in the erythrocyte band 3 gene in SAO: (i) a deletion of codons 400-408 and (ii) a substitution, A----G, in the first base of codon 56 leading to substitution of Lys-56 by Glu-56. The first defect leads to a deletion of nine amino acids in the boundary of cytoplasmic and membrane domains of band 3. This defect has been detected in all 30 ovalocytic subjects from Malaysia, the Philippines, and two unrelated coastal regions of Papua New Guinea, whereas it was absent in all 30 controls from Southeast Asia and 20 subjects of different ethnic origin from the United States. The Lys-56----Glu substitution has likewise been found in all SAO subjects. However, it has also been detected in 5 of the 50 control subjects, suggesting that it represents a linked polymorphism. We conclude that the deletion of codons 400-408 in the band 3 gene constitutes the underlying molecular defect in SAO.

Anion Exchange Protein 1, Erythrocyte↗
PubMed1991

Uncoupling of the spectrin-based skeleton from the lipid bilayer in sickled red cells.

The distribution of spectrin and band 3 in deoxygenated reversibly sickled cells was visualized by immunofluorescence and immunoelectron microscopy. Antibodies against band 3, the major lipid-associated transmembrane protein, labeled the entire cell body, including the entire length of the long protruding spicule, whereas antibodies against spectrin labeled only the cell body and the base region of the spicules. The results suggest that the formation of long spicules during sickling is associated with a continuous polymerization of hemoglobin S polymers, presumably through gaps in the spectrin-actin meshwork, and a subsequent uncoupling of the lipid bilayer from the submembrane skeleton.

Anemia, Sickle Cell↗
PubMed1991

Cloning of the cDNA of alpha-momorcharin: a ribosome inactivating protein.

Using a lambda gt11 cDNA library constructed from the seeds of the bitter melon (Momordica charantia), we have obtained a full length cDNA containing the entire sequence of alpha-momorcharin by immunoscreening. The length of this cDNA is 1044 basepairs long and it consists of an open reading frame coding for a polypeptide of 286 amino acids. The first 23 residues of this polypeptide probably code for a signal sequence. The N-terminal sequence of the deduced protein is exactly identical to that determined by peptide sequencing. The sequence identity between alpha-momorcharin and other ribosome inactivating proteins, such as trichosanthin and ricin A chain, is high, i.e., 34-63%. Examination of the predicted secondary structure of alpha-momorcharin and trichosanthin indicates that these proteins have regions of high structural similarities and this may account for the common biological activities that they share, viz., abortificant, immunosuppressive, antitumor and inhibition of HIV-1.

Amino Acid Sequence↗
PubMed1991

Immunohistochemical detection of HBsAg and HBcAg in the liver of patients with schistosomiasis japonica complicated by hepatocellular carcinoma.

In liver biopsies from 21 patients with schistosomiasis japonica complicated by hepatocellular carcinoma (HCC), 69 patients with advanced schistosomiasis japonica, and 25 patients with HCC, HBsAg and HBcAg were investigated with peroxidase-antiperoxidase technique. The positive rate of HBAg (i.e. HBsAg and/or HBcAg) in the liver of patients with schistosomiasis japonica complicated by HCC was significantly higher than in the group of advanced schistosomiasis japonica, but similar to that in cases of HCC. The location of carcinoma cells in the liver was not related to the distribution of Schistosoma ova in patients with schistosomiasis japonica complicated by HCC. The results indicated that the complication with hepatitis B virus infection may be one of the major factors involved in the development of HCC in patients with schistosomiasis japonica.

Biopsy, Needle↗
PubMed1991

[Changes in T-lymphocyte subsets in patients with orthopedic trauma and effects of yipanzhu decoction on the impaired immune function].

The effects of yipanzhu decoction (YD) on immune function in 40 patients [2 groups, YD and normal saline (NS) group] with orthopedic trauma by taking T lymphocyte subsets as indexes were observed. The peripheral venous blood samples randomly taken from 30 healthy subjects served as control. The blood were collected within 24 hours after trauma. Then the YD and NS were respectively given to the patients in the 2 groups for 3 days, and the blood were taken 4th, 7th, 14th day after trauma for the observation of T subsets. The results revealed that before administration of YD the percentage of pan-T cells was reduced with an increased percentage of Ts cells and a decreased ratio between Th and Ts cells; 3 days after giving the drugs in YD group the percentage of pan-T cells was slightly increased, and the changed percentage of Ts cells and the ratio of Th/Ts cells mentioned above was recovered to normal, while in NS group all these indexes remained at abnormal range during the period we observed. The results suggested that YD could promote the recovery of abnormal T lymphocyte subsets in traumatized patients, and it possessed to some extent the function of immune regulation that was helpful to reduce the ratio of infection after trauma.

Adolescent↗
PubMed1991

Hepatic carcinoma. The possibility of transcatheter chemoembolization through the portal vein.

A suspension of iodized oil and anticancer agent was injected into the portal veins of 20 rats with hepatic carcinoma and of 20 normal rats to observe its distribution in the liver and the effect on cancer tissue and normal cells. Microscopic and transmission electron microscopic examinations were carried out. Oil drops were seen in tumor cell lines, small blood vessels inside the cancer nest, the sinusoids, and the central veins. More oil drops were found in the peripheral parts of the tumor than in the central part. The distal small vessels were embolized with necrotic change of tumor cells and their subordinate normal liver cells. We conclude that portal vein part takes in the blood supply of liver cancer and tumor cell necrosis can be achieved after administration of iodized oil and anticancer agent mixture through the portal vein. Hence transcatheter treatment through the portal vein may be helpful as a supplement to intraarterial treatment of primary liver cancer and transcatheter embolization via the portal vein to reinforce the intraarterial therapy may be recommended. This procedure may cause necrosis of normal liver cells and care must be taken in clinical application.

Animals↗