Biomedical subjects

S H Liu

Publications and source records attributed to S H Liu.

At least 145 records · Page 8Linked to original sources

PubMed1994

Anterior cruciate ligament tear. A new diagnostic index on magnetic resonance imaging.

An objective index of anterior cruciate ligament (ACL) tears based on posterior cruciate ligament (PCL) shape has been introduced. The PCL shapes on magnetic resonance imaging (MRI) were measured in 67 patients (31 normal ACL, 31 torn ACL, and five partial ACL tears, all confirmed by arthroscopy). All of the measurements were performed in a blinded manner, without previous knowledge of the MRI or arthroscopy diagnosis. The index consisted of the ratio B/A, with B equaling the length of the line between the posterior inferior tibial and the superior anterior femoral attachment of the PCL, and A equaling the maximum perpendicular distance from this line to the PCL. All measurements were performed twice, and the mean was used for statistical significance. The average index ratio was 5.4 and 3.9 for normal ACL and torn ACL, respectively. Using a cutoff value of 4.75, the sensitivity of the index was 87% and the specificity was 84%. An objective and reproducible index measurement of PCL shape for normal and injured ACL has been established. It provides additional information for both orthopaedic surgeons and radiologists in the diagnosis of ACL injury.

Adolescent↗

PubMed1994

Comparison of functional knee braces for control of anterior tibial displacement.

Using a surrogate knee model, the ten custom functional knee braces that previous studies had shown to be most effective were tested for restraint to anterior tibial displacement. Testing was performed at 20 degrees knee flexion with applied forces ranging from 50 to 400 N. All braces reduced anterior tibial displacement. Resistance to anterior tibial displacement depends directly on the brace design and is inversely related to the applied force. Post-bilateral hinge shell braces exhibited the most resistance to anterior tibial displacement. Few braces were effective in controlling anterior tibial displacement comparable with a normal knee at low forces. Most of the braces were less effective at controlling anterior tibial displacement at high forces.

Adult↗

PubMed1993

Characterization of the 5' end of the mouse Ent gene encoding the basement membrane protein, entactin.

Entactin (Ent) is a 150-kDa basement membrane glycoprotein that forms a complex with laminin and also binds to type-IV collagen. For the initial characterization of the 5' end of the mouse Ent gene, we isolated genomic clones that encompass the first three exons of the gene. A 3.5-kb EcoRI fragment at the 5' end of the gene was sequenced and shown to contain 1226 bp of the 5'-flanking DNA, the 260-bp first exon, and 2060 bp of the first intron. The second exon is separated from the first exon by an intron that spans greater than 18 kb. The major transcription start point (tsp) was mapped to 35 nucleotides upstream from the translation start codon. The 5'-flanking DNA contains a putative TATA box, two CAAT boxes and two GC boxes. Nine potential AP-2- and two potential AP-1-binding sites were found in the upstream region and the first intron. The first 248 bp of the promoter region are G+C rich, and they are 65% identical to the promoter of human Ent. Fragments of the 5'-flanking DNA linked to a reporter gene were shown to have promoter activity in transient transfection assays.

Amino Acid Sequence↗

PubMed1993

The carboxyl-terminal transactivation domain of human serum response factor contains DNA-activated protein kinase phosphorylation sites.

The serum response factor (SRF) is a 67-kDa phosphoprotein that, together with auxiliary factors, modulates transcription of immediate early genes containing serum response elements in their promoters. Here we show that the carboxyl-terminal domain of human SRF is phosphorylated in vivo and is recognized in vitro by the double-stranded DNA-activated serine/threonine-specific protein kinase, DNA-PK. SRF phosphorylation by DNA-PK was stimulated by its cognate binding site. Protein microsequence analysis of a 22-amino acid synthetic SRF peptide and phosphopeptide analysis of genetically altered glutathione S-transferase-SRF fusion proteins identified Ser-435 and Ser-446 of human SRF as sites phosphorylated by DNA-PK. Both serines are followed by glutamine. Changing Gln-436 and Gln-447 to other residues reduced or eliminated phosphorylation by DNA-PK, confirming that these glutamines are important determinants for kinase recognition. The carboxyl-terminal transcription activation domain was mapped within a 71-amino acid region that contains both DNA-PK phosphorylation sites. Amino acid substitutions that interfered with phosphorylation by DNA-PK at Ser-435/446 in GAL4-SRF fusion proteins were reduced in transactivation potency. From these data we suggest that DNA-PK phosphorylation may modulate SRF activity in vivo.

3T3 Cells↗

PubMed1993

Streptolysin O-permeabilized cell system for studying trans-acting activities of exogenous nuclear proteins.

Efficient transfer of exogenous proteins into culture animal cells can be achieved by Streptolysin O (SLO) permeabilization of plasma membranes. We used this method to establish an in vitro transcription system for early response genes. The promoters of many early response genes contain an essential DNA motif known as the Serum Response Element (SRE). Recent data has shown that this DNA sequence is recognized by Serum Response Factor (SRF) and its associated proteins. Our initial experiments showed that HeLa nuclear extracts induced the transcription of the c-fos gene in serum-starved murine fibroblasts which were permeabilized by either physical method (glass beads) or cytolytic pore-forming protein (SLO). Plasma membrane permeabilization presumably permits passive diffusion of macromolecules into target cells and we showed that a truncated SRF expressed in bacteria was translocated into the nucleus within 30 minutes after SLO permeabilization. HeLa crude extracts were fractionated in order to identify the active nuclear factors. SRF was purified by binding to Wheat Germ Agglutinin (WGA)-agarose but the active factors remained in the WGA-unbound fractions. Our results demonstrate that this permeabilized cell in vitro transcription system is simple, efficient and can be used to test crude nuclear fractions as well as purified proteins expressed in bacteria; it will be an useful tool for the reproduction of transcriptional regulation on chromatin templates in vitro as well as the investigation of the biochemical functions of specific transcription factors or signal transduction effectors.

3T3 Cells↗

PubMed1993

Studies on the inhibition by chlorpromazine of myotonia induced by ion channel modulators in mouse skeletal muscle.

The myotonic activity of mouse soleus and extensor digitorum longus muscles induced by either a combination of K+ channel blockers (4-aminopyridine) and a Cl- channel blocker (9-anthracene carboxylic acid) or a Cl- channel blocker in low Ca2+ (0.25 mM) Krebs or a Na+ channel activator (veratridine) was characterized in this paper. Myotonic activity was characterized by an increase in both the contraction amplitude and contraction duration accompanied by stimulus-related repeated action potentials. The slow soleus and fast extensor digitorum longus muscles appeared to differ in their responses to these ion channel modifiers. Nevertheless, chlorpromazine at a low concentration of 1 microM significantly inhibited all kinds of myotonic activity; it reduced the prolonged contraction duration and attenuated the stimulus-related repeated action potential firing. This depressant action of chlorpromazine was apparently not correlated with inhibition of either calmodulin or phospholipase A2 activity, since the myotonic depressant action of calmodulin inhibitors, such as dibucaine, flunarizine, chlorpromazine, trifluoperazine and diltiazem, was unrelated to their potency in inhibiting the activity of calmodulin or phospholipase A2. However, phosphatidylcholine was found to inhibit the myotonic depressant action of chlorpromazine. It is therefore, tentatively concluded that chlorpromazine interacted with membrane phospholipids, thereby changing membrane ion channel activity and depressing myotonic activity. These findings indicate that chlorpromazine might be useful in the management of clinical myotonia.

4-Aminopyridine↗

PubMed1993

Adoptive transfer of experimental autoimmune dacryoadenitis in susceptible and resistant mice.

Strains of mice with diverse genetic backgrounds were compared for their ability to develop experimental autoimmune dacryoadenitis (EAD) after immunization with a purified lacrimal gland antigen (LG-Ag) in complete Freund's adjuvant. Susceptibility to the induction of EAD was linked to the murine H-2 histocompatibility background. SJL/J mice with the H-2s haplotype were the most susceptible to EAD, developing extensive cellular infiltration of the lacrimal gland, but those with the H-2d haplotype (BALB/c mice) or H-2q haplotype (DBA/J mice) were resistant to EAD, having little or no infiltration of the lacrimal gland. There was no correlation between the development of EAD and either the antibody response or the in vitro lymphocyte proliferative response to LG-Ag. The differences in the induction of EAD observed between susceptible and resistant strains resided in the different capacity of their lymphocytes to transfer disease. Splenocytes from susceptible SJL/J mice sensitized with LG-Ag in CFA could be activated in vitro with LG-Ag to transfer disease to normal syngeneic recipients. The capacity for adoptive transfer was abrogated by treatment with anti-Thy 1.2 antibody plus complement, an indication that T cells are responsible for the transfer of EAD. However, EAD cannot be transferred with the donor cells from resistant mice even after they have been cultured in vitro with LG-Ag. These results suggest that T cells play a major role in the induction of EAD and that variations in susceptibility are under the control of distinct genetically inherited mechanisms that may include active suppression.

Animals↗

PubMed1993

Treatment of experimental autoimmune dacryoadenitis with cyclosporin A.

Experimental autoimmune dacryoadenitis (EAD) was induced in SJL/J mice by a single injection of purified lacrimal gland antigen (LG-Ag) in complete Freund's adjuvant. The disease is characterized by lymphocytic infiltration of the lacrimal gland and production of lacrimal gland-specific antibodies. We examined the effects of cyclosporin A (CsA) on the development and progression of this inflammatory disease. CsA (100 mg/kg/day), given from the time of immunization for 14 days, completely blocked the development of EAD in all treated mice. Both cellular and humoral immune responses to LG-Ag were markedly reduced by the administration of CsA as evidenced by the near absence of lymphocyte proliferative response and the reduced production of circulating anti-LG-Ag antibodies. Delayed CsA treatment beginning on Day 7 after immunization totally abrogated the development of lacrimal histological lesions and lymphocyte proliferative response to LG-Ag. However, serum anti-LG-Ag titers were only marginally decreased in CsA-treated animals. Treatment with CsA was found effective even when daily injections were started 14 days after immunization with LG-Ag. CsA prevented the inflammatory cell response in 5 of 10 mice when the disease was established. The lymphocyte proliferative response to LG-Ag was moderately depressed in CsA-treated animals, but antibody titers were the same as those in the oil-treated control. These studies demonstrate that CsA has a therapeutic effect in this murine model of dacryoadenitis and suggest a critical role for T lymphocytes in the pathogenesis of EAD.

Animals↗

PubMed1993

Use of ion channel blockers in the exploration of possible mechanisms involved in the myopathy of diabetic mice.

Changes in the muscle contractions of the phrenic nerve-diaphragm preparation from the diabetic mouse were investigated by means of K(+)- and Cl(-)-channel blockers and the Ca(2+)-mobilizing agent, selenite. The K(+)-channel blockers (UO2(2+) and 4-aminopyridine) cooperated synergistically with the Cl(-)-channel blockers (Cd2+ and 9-anthracenecarboxylic acid) in increasing normal muscle contraction as described previously, but failed to induce this effect in the diaphragm of the diabetic mouse. Treatment with a Cl(-)-channel blocker alone in 0.25 mmol/l Ca2+ Krebs solution induced a myotonic activity accompanied by stimulus-bound repetitive action potential firings. This effect was also diminished in the diaphragm from diabetic mice. The membrane potential of the muscle cells in the diaphragm of the diabetic mouse was slightly but significantly decreased. The membrane input resistance was also increased and was refractory to being further increased by either a Cl(-)-channel blocker or a low Cl(-)-medium. Furthermore, the membrane chloride conductance was found to be decreased, but the membrane K+ conductance remained unchanged in the muscle from diabetic mice. These changes of membrane properties in the muscles from diabetic mice were shown to be similar to those induced by either Cl(-)-channel blockers or a low Cl(-)-medium. In addition, the combined treatment of the diaphragm from diabetic mice with Cd2+ plus UO2(2+) in 0.25 mmol/l Ca2+ Krebs solution and then stepwise replenishment of Ca2+ led to a greater restoration of muscle contractions at a lower cumulative Ca2+ concentration than that was found with the normal diaphragm.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗

PubMed1993

Posterior superior impingement of the rotator cuff on the glenoid rim as a cause of shoulder pain in the overhead athlete.

A case of impingement of the deep surface of the supraspinatus tendon on the posterior superior rim of the glenoid and mild anterior laxity has been presented. The partial-thickness tear of the undersurface rotator cuff tendon, degenerative tear of the posterior superior labrum, and osteochondral impression fracture of the humeral head have been documented. The purpose of this case report is to present the pathological findings associated with posterior superior glenoid rim impingement and emphasize its role as a cause of shoulder pain in the overhead athlete. In addition it is important to stress the fact that shoulder pain in the overhead athlete may be multifactorial.

Adult↗

PubMed1993

Posteromedial ankle impingement.

We present a case of soft tissue impingement in the posteromedial ankle, which has not been previously reported. When a patient presents with chronic posteromedial ankle pain and swelling, clinicians should be suspicious of soft tissue impingement in the posteromedial ankle. Pertinent history and physical examinations are most helpful in the diagnosis of this lesion. Arthroscopic debridement of the hypertrophic soft tissue is successful in returning the patient to his or her previous activities.

Adult↗

PubMed1993

Neurovascular injuries to the shoulder.

The throwing athlete is at risk for neurovascular injuries of the shoulder because of the excessive demands placed upon the shoulder by repetitive throwing motions. The most commonly recognized neurovascular compression syndromes are axillary artery occlusion, effort thrombosis, quadrilateral space syndrome, and thoracic outlet syndrome. Diagnosis is aided by the use of the Adson's test, costoclavicular maneuver, and hyperabduction maneuver. Initial treatment usually is nonoperative. Anticoagulation or thrombolytic therapy can be used for vascular occlusion. Surgery usually is reserved for patients suffering acute or chronic symptoms despite nonoperative treatment. With proper treatment, most patients are able to resume their previous athletic activities in a timely manner with minimal disability.

Athletic Injuries↗

PubMed1993

[Change of beta tubulin gene expression in the motoneurons of spinal cord during nerve regeneration].

After crushing the right sciatic nerve of rat, the contents of both tubulin and beta tubulin mRNA increased significantly in the ventral horns of spinal cord. Analysis of tubulin in bilateral ventral horns by SDS-PAGE showed that tubulin in the injured side increased by 17%-121% of the control side. The results of in situ hybridization indicated with the signals of hybridization with beta tubulin cDNA probes were 27%-70% higher in motoneurons of the ventral horns in the injury side than the control. Northern blotting analysis of tubulin mRNA in ventral horns also revealed an increase of tubulin gene expression.

Animals↗

PubMed1993

Lacrimal gland-derived lymphocyte proliferation potentiating factor.

PURPOSE: To determine whether lacrimal gland acinar cells are involved in modulating local immune response; to isolate and characterize a lacrimal gland factor that exerts biological activities on T lymphocytes. METHODS: A protein factor has been purified from lacrimal gland extracts by a combination of ion exchange and gel-filtration chromatography. This factor has the capacity to enhance proliferation of T lymphocytes upon stimulation with a mitogen or an antigen. We have, therefore, called this substance lacrimal gland-derived lymphocyte proliferation potentiating factor (LG-F). RESULTS: Lacrimal gland-derived lymphocyte proliferation potentiating factor has a molecular weight of approximately 65,000 daltons as determined by gel-filtration and by polyacrylamide gel electrophoresis in sodium dodecyl sulfate. T cells demonstrate greater proliferation when cultured with high concentrations of concanavalin A (Con A) in the presence of LG-F, as compared with culture without addition of LG-F. This enhancing effect of LG-F may be mediated by IL-2, because the final cell count correlates with the levels of IL-2 secreted by LG-F-activated cells. Lacrimal gland-derived lymphocyte proliferation potentiating factor is nonmitogenic for T cells, but its potentiating effect is antigen-dependent. Dual stimulation of OA-primed T cells with both OA and LG-F results in greater proliferative activity, in contrast to culture with OA alone. CONCLUSIONS: The results suggest that lacrimal gland cells may interact with the immune system by elaborating nonspecific factors that modulate lymphocyte proliferation and augment lymphokine production. The presence of such a factor in the lacrimal gland may prove to be of importance in the generation of local immune responses.

Animals↗

PubMed1992

Mooren's ulcer and evidence of stromal graft rejection after penetrating keratoplasty.

A Mooren's ulcer developed in a 6-year-old girl after a penetrating keratoplasty for Peters' anomaly. A destructive, circumferential, and centripetal stromal ulceration recurred despite conjunctival resection, corneal gluing, topical and systemic administration of corticosteroids, and repeat graftings. Results of a systemic and a rheumatologic examination were unremarkable. Histopathologic evaluations of donor grafts consistently disclosed a lymphocytic and a plasma cell infiltrate. Indirect immunofluorescent staining using a normal donor cornea substrate was positive at the level of Bowman's membrane and stroma. The patient's lymphocytes were stimulated by a partially purified bovine corneal antigen and a positive antibody titer was found in the patient's sera to the same corneal antigen. These results suggest humoral and cell-mediated immune mechanisms can be involved in the initiation and perpetuation of a stromal rejection process after penetrating keratoplasty.

Cataract Extraction↗

PubMed1992

Experimental autoimmune dacryoadenitis: purification and characterization of a lacrimal gland antigen.

A soluble lacrimal gland antigen (LG-Ag) capable of inducing experimental autoimmune dacryoadenitis (EAD) in SJL/J mice has been purified from bovine lacrimal gland extracts by a combination of ion exchange and gel-filtration chromatography. Sodium dodecyl sulfate polyacrylamide gel electrophoresis showed a single band with a mobility corresponding to a molecular weight of 45,000 daltons. Antibodies raised in guinea pigs against purified LG-Ag were used to confirm the tissue-specificity and to assess the cellular localization of LG-Ag within tissues. Anti-LG-Ag serum reacted with the crude lacrimal gland extracts but not with the extracts of bovine submaxillary gland, parotid gland, or retina. As shown by immunofluorescent staining, LG-Ag appeared to be localized on the murine lacrimal ductal epithelial cells but was lacking in the salivary ducts. LG-Ag induced EAD that was characterized by infiltration of mononuclear cells around the ducts and associated vasculature, accompanied by extensive damage of the acinar cells. The lesions induced were tissue-specific, in that SJL/J mice immunized with LG-Ag had intense lymphocytic infiltrates in lacrimal gland, but had no significant lesions in their salivary and harderian glands. The availability of a purified LG antigen can facilitate the further analysis of pathogenetic mechanisms in EAD.

Animals↗

PubMed1992

Anterolateral impingement of the ankle.

Anterolateral impingement syndrome of the ankle is caused by entrapment of the hypertrophic soft tissue in the lateral gutter. The impingement process begins when an inversion sprain tears the anterior talofibular, and/or the calcaneofibular ligament. The ligamentous injury is not severe enough to cause chronic instability; however, inadequate immobilization and rehabilitation may lead to chronic inflammation in the ligament, resulting in formation of scar tissue. This tissue then becomes trapped between the talus and the lateral malleolus, causing irritation, pain, and further synovitis. The end result is chronic lateral ankle pain. Initial treatment involves physical therapy modalities and nonsteroidal anti-inflammatory medications. Those patients refractory to conservative treatment require arthroscopic debridement. A recent study has shown that arthroscopic debridement is successful in relieving pain and disability in high percentages of patients. Most patients were able to return to their previous levels of work and sports. Successful treatment of anterolateral impingement requires an accurate diagnosis with a clinical evaluation that excludes other causes of chronic ankle pain.

Ankle Injuries↗

PubMed1990

Neuromuscular actions of sodium selenite on chick biventer cervicis nerve-muscle preparation.

Sodium selenite was found to be toxic to chicks, with an LD50 of 8.5 micrograms/g, which was increased to 16.3 micrograms/g by NaCN. The major symptoms of chicks, treated with selenite, were sedation and then dyspnea and paralysis. The cause of death by selenite was apparently due to the respiratory failure. The possible mechanism of toxicity was explored in the isolated chick biventer cervicis nerve-muscle preparation. Selenite initially increased the amplitude of the twitch, reversed the suppression of the twitch caused by d-tubocurarine, Mg2+, Cd2+ or Mn2+ and significantly increased the quantal content and amplitude of endplate potentials. Subsequently, selenite depressed the amplitude of the twitch, blocked the axonal conduction and inhibited excitatory postsynaptic potentials. Both NH4+ and K+ enhanced the action of selenite in depressing the twitches. In addition, selenite induced a sustained contracture of the muscle, which was partially inhibited by removal of external Ca2+ and markedly blocked by EGTA. Entry of Ca2+ and release of the internal Ca2+ were considered to be responsible for inducing contracture by selenite. Pretreatment with trypsin, glutathione (GSH) and cyanide profoundly inhibited the effects of selenite, indicating that the site of action of selenite was on the outer membrane and the binding of selenite to the sulfhydryl groups of membrane proteins was proposed to be an essential step for selenite-induced contracture and neuromuscular action. These findings suggest that neuromuscular blockade and tetanic spasm, produced by selenite in chicks, may play a role in causing respiratory failure in vivo.

Animals↗