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Biomedical subjects

M Hsu

Publications and source records attributed to M Hsu.

72 records · Page 4Linked to original sources
PubMed1985

Human T cell clones express functional homing receptors required for normal lymphocyte trafficking.

To function efficiently in vivo, lymphocytes must circulate from the blood into lymphoid tissues and other sites of immune reaction. Herein, we show that human cytotoxic and helper T cell clones and lines, maintained in vitro with IL-2, express the functional capacity to recognize and bind to high endothelial venules (HEV), a capacity essential for lymphocyte exit from the blood, and hence for normal lymphocyte trafficking. The expression of functional homing receptors distinguishes human T cell clones from their murine counterparts, which uniformly lack receptors for HEV and are unable to migrate normally from the blood in vivo. The results raise the possibility that human T cell clones may be more effective in mediating in vivo immune responses than is suggested by murine models.

Appendix↗
PubMed1984

Analysis of Sendai virus mRNAs with cDNA clones of viral genes and sequences of biologically important regions of the fusion protein.

cDNA clones representing five of the genes of Sendai virus (P, HN, NP, F, and M) were isolated and used to identify the viral mRNAs by hybridization. Five mRNAs that were monocistronic transcripts of these genes were identified. A sixth transcript, which was identified on the basis of size and of hybridization to viral RNA but not to the cDNA of the other five genes, is thought to represent the message for the L protein. In addition, polycistronic transcripts of the NP and P genes and of the M and F genes were also found. The latter establishes the position of the F gene adjacent to the M gene; these results confirm and extend the previously reported partial gene order of the virus. Nucleotide sequences and derived amino acid sequences of two biologically important regions of the F protein--approximately 25% of F proximal to its COOH terminus and the region spanning the site of the proteolytic cleavage that activates the fusion activity of the protein--are presented. The F protein has an unusually large "cytoplasmic domain" of 42 amino acids beyond the hydrophobic region by which it is anchored in the viral membrane. A single possible trypsin cleavage site was found at the junction of the F1 and F2 polypeptides, and 26 hydrophobic amino acids extend from this cleavage site at the NH2 terminus of the F1 polypeptide.

Amino Acid Sequence↗
PubMed1981

Activation of the Sendai virus fusion protein (f) involves a conformational change with exposure of a new hydrophobic region.

The F protein of paramyxoviruses is actively involved in the induction of membrane fusion. This fusion may be between viral and cellular membranes, as in the initiation of infection or in virus-induced lysis of erythrocytes, or between the plasma membranes of different cells. The F protein is activated by proteolytic cleavage to yield two disulfide-linked polypeptides (F1 and F2); however, its mechanism of action is not clear. In the present study, the conformations of the inactive, uncleaved precursor of glycoprotein (F0), and the active, cleaved form (F1,2) have been compared. The UV circular dichroism spectra of the two forms of the F protein indicate that cleavage results in a conformational change. Detergent-binding studies by velocity sedimentation analysis of Triton X-100-protein complexes revealed an increase in exposed hydrophobic surface of the protein on cleavage. The inactive F0 bound an estimated 27 molecules of Triton X-100/F polypeptide; these molecules are presumably bound to the hydrophobic region of the glycoprotein that anchors the spike-like protein in the virus membrane and that is common to both forms of F. The active form, F1,2, bound 67 molecules of Triton X-100. This increase in the number of detergent binding sites upon F protein activation indicates the presence of a hydrophobic region that is peculiar to the active form, and that may be of functional significance in the membrane fusion reaction.

Centrifugation, Density Gradient↗
PubMed1981

The use of rotating gratings for the treatment of amblyopia: a clinical trial.

The use of rotating gratings for the treatment of amblyopia was subjected to a controlled clinical trial. A treatment group (N = 19) observed rotating gratings for 15 min per week for 10 weeks and a control group (N = 19) observed a blank rotating disk for the same period. Both groups of amblyopes performed visually guided tasks to maintain their interest during treatment. Data were acquired in a double-masked manner. A second control group (N = 4) underwent weekly acuity evaluation without any form of treatment. Visual acuity was evaluated before and after each session and analyzed with a linear regression fit to a probit transform by a minicomputer. By using a criterion change in acuity of 10% Snell Sterling, we found no significant change of acuity in any group or between groups. These results demonstrate that rotating gratings are an insignificant variable in the treatment of amblyopia.

Adolescent↗
PubMed1980

Role of paramyxovirus glycoproteins in the interactions between viral and cell membranes.

Interactions of paramyxoviruses with cell membranes are mediated by two virus-coded glycoproteins of the virus membrane: HN and F. The HN protein is responsible for the attachment of virions to the membrane of the target cell. The F protein mediates fusion between the virus membrane and the cell membrane, and this step is essential for the infection process as well as for the expression of other biological activities of paramyxoviruses, i.e., cell fusion and hemolysis. The activity of F is dependent on the proteolytic processing of a precursor (F0) to yield two disulfide-linked subunits (F1 and F2), and unless this cleavage occurs, the virions are inactive and not infectious. Viruses differ in their susceptibility to specific proteases, as demonstrated with Sendai virus and its protease activation (pa) mutants. Findings with these viruses indicate that the host range, tissue tropism, and the ability of paramyxoviruses to spread within a host and to cause disease are dependent on the availability of an appropriate protease capable of cleaving the viral glycoprotein. Experiments with reconstituted particles that contain purified F protein and phosphatidylcholine indicate that to be active the F protein must be inserted in a lipid bilayer, and that no other viral function is needed for the membrane fusion process. Attachment of the F-protein-containing particles to the target membrane is a prerequisite for fusion; however, this function can be supplied by wheat germ agglutinin as well as by the virus protein responsible for attachment of intact virus, i.e., HN. Studies on the structure of the paramyxovirus glycoproteins indicate that they are inserted with a hydrophobic region of the molecule in the lipid bilayer of the virus membrane. Analysis of the primary structure of the F protein at the cleavage site revealed striking sequence homology among three paramyxoviruses, indicating a requirement for cleavage at a sharply defined site and the importance of a specific primary sequence for biological activity. This region is highly hydrophobic, suggesting that it may interact with the lipid biylayer of the target cell membrane during virus penetration, cell fusion, or hemolysis. Further studies of this system should provide knowledge regarding the mechanisms involved in viral penetration and in membrane fusion in general.

Amino Acid Sequence↗
PubMed1978

Altering the specificity of restriction endonuclease: effect of replacing Mg2+ with Mn2+.

In the presence of 100 mM Tris buffer (pH 7.5) and 1-10 mM Mg2+ EcoRI endonuclease cleaves DNA at a specific nucleotide sequence and in a characteristic way: -GAATTC-. But if Mg2+ is replaced by Mn2+, the specificity of the cleavage is relaxed and cleavages occur at many other sites; moreover, there appears to be a hierarchy of cleavage rates at the pseudo-EcoRI restriction sites. For example, SV40 DNA is cleaved only once in the usual digestion conditions, but with Mn2+ more than ten cleavages are made; the five most rapidly cleaved SV40 DNA map locations are 0/1.0 larger than 0.93 larger than 0.33 approximately equal to 0.42 larger than 0.29 approximately equal to 0.40 larger than 0.25. Mn2+ also alters the restriction specificity of HindIII but not HpaII endonuclease.

DNA Restriction Enzymes↗
PubMed1977

Prognosis of nasopharyngeal carcinoma by Epstein-Barr virus antibody titer.

A total of 433 samples of serum were collected from 305 patients with histopathologically proved anaplastic nasopharyngeal carcinoma (NPC). Antibodies against viral capsid antigens (VCA) of Epstein-Barr (EB) virus were titrated by means of indirect fluorescent antibody technique, using P3HR-1 cells as the target. High anti-VCA antibody titer in patients with NPC was found beginning to decline at the end of radiotherapy. Most (66.7%) of the patients were found to have a detectable reduction in antibody titer within six months after radiotherapy. Persistent high antibody titer after treatment correlates to high risk of the recurrence of the disease. This prognostic importance of anti-VCA titer becomes apparent at the end of radiotherapy, significant (P less than .05) within one year after treatment, and highly significant (P less than .0005) over one year after treatment.

Antibodies, Viral↗
PubMedDate not supplied

A comparison of the composition of silk proteins produced by spiders and insects.

Proteins that are highly expressed and composed of amino acids that are costly to synthesize are likely to place a greater drain on an organism's energy resources than proteins that are composed of ingested amino acids or ones that are metabolically simple to produce. Silks are highly expressed proteins produced by all spiders and many insects. We compared the metabolic costs of silks spun by arthropods by calculating the amount of ATP required to produce their component amino acids. Although a definitive conclusion requires detailed information on the dietary pools of amino acids available to arthropods, on the basis of the central metabolic pathways, silks spun by herbivorous, Lepidoptera larvae require significantly less ATP to synthesize than the dragline silks spun by predatory spiders. While not enough data are available to draw a statistically based conclusion, comparison of homologous silks across ancestral and derived taxa of the Araneoidea seems to suggest an evolutionary trend towards reduced silk costs. However, comparison of the synthetic costs of dragline silks across all araneomorph spiders suggests a complicated evolutionary pattern that cannot be attributed to phylogenetic position alone. We propose that the diverse silk-producing systems of the araneoid spiders (including three types of protein glues and three types of silk fibroin), evolved through intra-organ competition and that taxon-specific differences in the composition of silks drawn from homologous glands may reflect limited or fluctuating amino acid availability. The different functional properties of spider silks may be a secondary result of selection acting on different polypeptide templates.

Amino Acids↗
PubMedDate not supplied

Maximizing comfort and minimizing ischemia: a comparison of four methods of spinal immobilization.

OBJECTIVE: To determine which of four methods of spinal immobilization causes the least ischemic pain. METHODS: A prospective, nonblinded comparative trial was conducted at a statewide emergency medical services training facility using a convenience sample of emergency medical technician students. After lying motionless for 10 minutes, students evaluated each device using a 10-centimeter visual analog scale. Subjective comfort was used as a measure of ischemia. RESULTS: Comfort scores were significantly different for all methods (F = 101, p < 0.001). A backboard padded with a gurney mattress and eggcrate foam (the equivalent of a spinal rehabilitation bed) caused the least ischemic pain (9.6 cm, 95% CI, 8.9 to 9.8 cm). A backboard padded with a gurney mattress was the second most comfortable device (7.0 cm, 95%/CI, 6.4 to 7.4 cm). A backboard padded with a folded blanket was the third most comfortable (3.3 cm, 95% CI, 2.6 to 4.9 cm). The backboard alone caused the most pain (0.8 cm, 95% CI, 0.7 to 2.1 cm). CONCLUSION: Increasing the amount of padding on a backboard decreased the amount of ischemic pain caused by immobilization.

Analysis of Variance↗
PubMedDate not supplied

Expression of E-cadherin/catenin complex in nasopharyngeal carcinoma: correlation with clinicopathological parameters.

The E-cadherin/catenin complex plays an essential role in maintaining intimate intercellular associations and is considered to be involved in tumor metastasis and suppressing invasion by cancer cells. We have analyzed the expression of E-cadherin/catenin complex in a series of nasopharyngeal carcinoma (NPC) specimens using immunohistochemistry and immunoblotting. Data are correlated with the patients' clinicopathological parameters, including the clinical stage, presence of intracranial invasion, presence of lymph node or distant metastasis, and histological grading. The E-cadherin/catenin complex is down-expressed in most of the samples examined. Correlation with clinicopathological parameters shows that expression of alpha- and beta-catenin is associated with the occurrence of intracranial invasion.

Cadherins↗
PubMedDate not supplied

Interactions between human immunodeficiency virus type 1 reverse transcriptase, tRNA primer, and nucleocapsid protein during reverse transcription.

An early step in the life cycle of human immunodeficiency virus type 1 is the reverse transcription of the viral RNA genome into double-stranded DNA, which is subsequently translocated to the cell nucleus. It is then integrated into host DNA and serves as a template for viral gene expression. Reverse transcription is catalyzed by the viral enzyme reverse transcriptase and is a complex process comprising a series of RNA-dependent DNA polymerization, DNA-dependent DNA polymerization, and RNase H reactions. Strand transfer reactions are required to complete the process. Reverse transcription is initiated when a molecule of host cell tRNA(lys3), which serves as a primer, is bound to the primer binding site of viral genomic RNA. The viral nucleocapsid protein is involved in each of the initiation of reverse transcription and in subsequent strand transfer or template-switching events. We review the interactions among reverse transcriptase, viral genomic RNA, the tRNA primer of reverse transcription, and viral nucleocapsid protein in the various steps of reverse transcription, including primer placement, initiation, and processive synthesis.

Anti-HIV Agents↗