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Biomedical subjects

W J Shen

Publications and source records attributed to W J Shen.

At least 19 recordsLinked to original sources
PubMed2001

Characterization of the functional interaction of adipocyte lipid-binding protein with hormone-sensitive lipase.

Hormone-sensitive lipase (HSL) is an intracellular lipase that plays an important role in the hydrolysis of triacylglycerol in adipose tissue. HSL has been shown to interact with adipocyte lipid-binding protein (ALBP), a member of the family of intracellular lipid-binding proteins that bind fatty acids and other hydrophobic ligands. The current studies have addressed the functional significance of the association and mapped the site of interaction between HSL and ALBP. Incubation of homogeneous ALBP with purified, recombinant HSL in vitro resulted in a 2-fold increase in substrate hydrolysis. Moreover, the ability of oleate to inhibit HSL hydrolytic activity was attenuated by co-incubation with ALBP. Co-transfection of Chinese hamster ovary cells with HSL and ALBP resulted in greater hydrolytic activity than transfection of cells with HSL and vector alone. Deletional mutations of HSL localized the region of HSL that interacts with ALBP to amino acids 192-200, and site-directed mutagenesis of individual amino acids in this region identified His-194 and Glu-199 as critical for mediating the interaction of HSL with ALBP. Interestingly, HSL mutants H194L and E199A, each of which retained normal basal hydrolytic activity, failed to display an increase in hydrolytic activity when co-transfected with wild type ALBP. Therefore, ALBP increases the hydrolytic activity of HSL through its ability to bind and sequester fatty acids and via specific protein-protein interaction. Thus, HSL and ALBP constitute a functionally important lipolytic complex.

Animals↗
PubMed2001

Stimulation of lipolysis and hormone-sensitive lipase via the extracellular signal-regulated kinase pathway.

Hormonally stimulated lipolysis occurs by activation of cyclic AMP-dependent protein kinase (PKA) which phosphorylates hormone-sensitive lipase (HSL) and increases adipocyte lipolysis. Evidence suggests that catecholamines not only can activate PKA, but also the mitogen-activated protein kinase pathway and extracellular signal-regulated kinase (ERK). We now demonstrate that two different inhibitors of MEK, the upstream activator of ERK, block catecholamine- and beta(3)-stimulated lipolysis by approximately 30%. Furthermore, treatment of adipocytes with dioctanoylglycerol, which activates ERK, increases lipolysis, although MEK inhibitors decrease dioctanoylglycerol-stimulated activation of lipolysis. Using a tamoxifen regulatable Raf system expressed in 3T3-L1 preadipocytes, exposure to tamoxifen causes a 14-fold activation of ERK within 15-30 min and results in approximately 2-fold increase in HSL activity. In addition, when differentiated 3T3-L1 cells expressing the regulatable Raf were exposed to tamoxifen, a 2-fold increase in lipolysis is observed. HSL is a substrate of activated ERK and site-directed mutagenesis of putative ERK consensus phosphorylation sites in HSL identified Ser(600) as the site phosphorylated by active ERK. When S600A HSL was expressed in 3T3-L1 cells expressing the regulatable Raf, tamoxifen treatment fails to increase its activity. Thus, activation of the ERK pathway appears to be able to regulate adipocyte lipolysis by phosphorylating HSL on Ser(600) and increasing the activity of HSL.

3T3 Cells↗
PubMed2001

Nonoperative treatment versus posterior fixation for thoracolumbar junction burst fractures without neurologic deficit.

STUDY DESIGN: A prospective clinical trial was conducted. OBJECTIVE: To compare the results of nonoperative treatment versus short-segment posterior fixation using pedicle screws. SUMMARY OF BACKGROUND DATA: A previous study showed that nonoperative treatment with early mobilization produced good results, even when the posterior column was involved. METHODS: This study involved 80 patients. Inclusion criteria required the following: neurologically intact patient, single-level closed burst fracture involving T11-L2, no fracture dislocations or pedicle fractures, age of 18 to 65 years (nonpathologic adult), and no other major organ system or musculoskeletal injuries. Patients in the nonoperative group (n = 47) were allowed activity to the point of pain tolerance beginning on the day of injury using a hyperextension brace. Patients in the operative group (n = 33) underwent three-level, (one above, one at fracture level, and one below) fixation using VSP or TSRH instrumentation. The follow-up period was 2 years. RESULTS: The surgical group had less pain up to 3 months and a better Greenough Low Back Outcome Score up to 6 months, but the outcome was similar afterward. No neurologic deficit in any patient. In the nonoperative group, the kyphosis angle worsened by 4 degrees, and the retropulsion decreased from 34% to 15%. In the operative group, there was one case of superficial infection and two cases of broken screws. The kyphosis angle was improved initially by 17 degrees, but this was gradually lost. Hospital charges were four times higher in the operative group. CONCLUSIONS: Short-segment posterior fixation provides partial kyphosis correction and earlier pain relief, but the functional outcome at 2 years is similar. Early activity to the point of pain tolerance can be safely allowed.

Adult↗
PubMed2001

Human BMP-7/OP-1 induces the growth and differentiation of adipocytes and osteoblasts in bone marrow stromal cell cultures.

We studied the effects of BMP-7/OP-1 on growth and differentiation of bone marrow stromal cells. BMS2, a mouse bone marrow stromal cell line capable of differentiating into adipocytes and osteoblasts, were treated in a serum-free medium containing differentiation agents that favor the expression of both lineages. BMP-7/OP-1 stimulated cell proliferation and differentiation concomitantly. These effects were dose- and growth phase-dependent. Cells were more sensitive to the treatment early in the culture (30-40% confluence) with a significant increase in cell proliferation and markers of differentiation at low concentrations. When treated later in the growth phase (90-100% confluence), no significant increase in cell proliferation was seen. The concentration requirement for cells later in the culture to reach an equivalent degree of differentiation was 3-10- fold higher than for cells treated early. In both cases, the effects on adipocyte differentiation were biphasic; low concentrations stimulated adipocyte differentiation which was inhibited at higher concentrations where stimulation of osteoblast markers were observed. We conclude that cell proliferation and cell differentiation into adipocyte/osteoblast can occur simultaneously under BMP-7/OP-1 treatment.

Adipocytes↗
PubMed2001

Absence of cardiac lipid accumulation in transgenic mice with heart-specific HSL overexpression.

Hormone-sensitive lipase (HSL) hydrolyzes triglyceride (TG) in adipose tissue. HSL is also expressed in heart. To explore the actions of cardiac HSL, heart-specific, tetracycline (Tc)-controlled HSL-overexpressing mice were generated. Tc-responsive element-HSL transgenic (Tg) mice were generated and crossed with myosin heavy chain (MHC)alpha-tTA Tg mice, which express the Tc-responsive transactivator (tTA) in the heart. The double-Tg mice (MHC-HSL) were maintained with doxycycline (Dox) to suppress Tg HSL. Upon removal of Dox, cardiac HSL activity and protein increased 12- and 8-fold, respectively, and the expression was heart specific. Although cardiac TG content increased twofold in control mice after an overnight fast, it did not increase in HSL-induced mice. Electron microscopy showed numerous lipid droplets in the myocardium of fasted control mice, whereas fasted HSL-induced mice showed virtually no droplets. Microarray analysis showed altered expression of cardiac genes for fatty acid oxidation, transcription factors, signaling molecules, cytoskeletal proteins, and histocompatibility antigens in HSL-induced mice. Thus cardiac HSL plays a role in controlling accumulation of triglyceride droplets and can affect the expression of a number of cardiac genes.

Animals↗
PubMed2001

[The clinical and pathologic study of embeded supernumerary teeth].

OBJECTIVE: To analyse the clinic and pathologic features of 100 embedded supernumerary teeth, to find out the rule of cystic change of supernumerary teeth and its relationship to malocclusion, and to present the methods of therapy. METHODS: Analysis of clinical data, X-ray manifestation,comparison of the findings on operation and pathological changes demonstrated the correct diagnosis of supernumerary teeth. RESULTS: On statistics and analysis,66% of the crowns of the supernumerary teeth were showed different sizes of circular photic shades,but only 35% were proved to be cystic change by biopsies. CONCLUSION: This study showed that 35% had cystic change among 100 cases,so if the diagnosis can be made in these cases with indication of operation the extraction of the supernumerary teeth must be done as soon as possible.

English Abstract↗
PubMed2000

Hormone-sensitive lipase functions as an oligomer.

Hormone-sensitive lipase (HSL) is a cytosolic neutral lipase whose activity is regulated by reversible phosphorylation and which is thought to be the rate-limiting enzyme for the mobilization of FFA from adipose tissue. In the current studies the subunit structure of HSL has been explored using sucrose gradient centrifugation and in vivo and in vitro protein-protein interactions. Evidence is provided to demonstrate that HSL exists as a functional dimer composed of homologous subunits. Dimeric HSL displayed approximately 40-fold greater activity against cholesteryl ester substrate when compared with monomeric HSL without any differences in affinity for the substrate. Truncations of HSL identified the importance of the N-terminal 300 amino acids, as well as other regions, in participating in the oligomerization of HSL. These studies support the notion that the N-terminal region of HSL represents a docking domain for protein-protein interactions and provide an additional mechanism for the posttranslational control of HSL activity in the cell via oligomerization.

Adipose Tissue↗
PubMed2000

Vastus lateralis fibrosis in habitual patella dislocation: an MRI study in 28 patients.

We studied 28 patients with habitual or recurrent dislocation of the patella with MRI of both thighs. Apart from the 2 patients whose dislocation could be related to trauma, we found signs of fibrosis of the vastus lateralis muscle in all the affected limbs of the 26 patients with an insidious onset of dislocation. This was seen as low signal intensity cords in the muscles in the T2 weighted image. Muscle degeneration was seen as high intensity signals in the T1 weighted image. In patients with unilateral disease, the vastus lateralis muscle of the affected side was hypotrophic, compared to that of the normal side. 2 patients underwent a biopsy of the affected muscle area. Histopathological examination revealed inflammatory cell infiltration, fibrosis, and muscle fiber degeneration. Fibrosis of the vastus lateralis muscle appears to be common in patients with habitual patella dislocation in our population, and may be the cause of the dislocation. Since release of such a contracture may be of value, MRI study of the thigh muscles is helpful in the evaluation of patients with this disorder.

Adolescent↗
PubMed1999

Interaction of rat hormone-sensitive lipase with adipocyte lipid-binding protein.

Hormone-sensitive lipase (HSL) is a cytosolic neutral lipase that functions as the rate-limiting enzyme for the mobilization of free fatty acids in adipose tissue. By using the yeast two-hybrid system to examine the potential interaction of HSL with other cellular proteins, evidence is provided to demonstrate a direct interaction of HSL with adipocyte lipid-binding protein (ALBP), a member of the family of intracellular lipid-binding proteins that binds fatty acids, retinoids, and other hydrophobic ligands. The interaction was demonstrated in vitro by the binding of ALBP to HSL translated in vitro, to HSL in extracts of HSL overexpressing Chinese hamster ovary (CHO) cells, and to HSL in extracts of rat adipose tissue. Finally, the presence of ALBP was documented in immune complexes from rat adipose tissue immunoprecipitated with anti-HSL antibodies. The HSL-ALBP interaction was mapped to an N-terminal 300-aa region of HSL that is distinct from the C-terminal catalytic domain. These results suggest that HSL-derived fatty acids are bound by ALBP to facilitate intracellular trafficking of hydrophobic lipids.

Amino Acid Sequence↗
PubMed1999

Nonsurgical treatment of three-column thoracolumbar junction burst fractures without neurologic deficit.

STUDY DESIGN: Retrospective review of the outcome of neurologically intact patients with three column thoracolumbar junction burst fractures that were treated nonsurgically. OBJECTIVE: To further define the parameters for nonsurgical management of thoracolumbar junction burst fractures. SUMMARY OF BACKGROUND DATA: Many texts list involvement of the posterior column as an indication for surgery and state that casting or bracing is mandatory. This has not been the authors' experience. METHODS: Thirty-eight patients with nonpathologic, single-level burst fractures of T11, T12, L1, or L2, and with posterior element fractures were studied retrospectively. The selection criteria required that the patient be neurologically intact, that the pedicles and facet joints not be fractured or dislocated, and that the angle of kyphosis be less than 35 degrees. The extent of retropulsion, loss of vertebral height, and presence of lamina or process fractures were not criteria. No attempt was made to reduce the fracture. Patients were allowed immediate ambulation as tolerated. Jewett braces were used in nine patients, but no bracing was used in the remainder. RESULTS: There were 22 males, 16 females. Median age 37 years (range, 16-65). Fracture involved both endplates in 16 patients (12 crush-cleavage type), the superior end-plate in 21, and the inferior endplate in 1. The hospital stay was from 2 to 18 days (median, 8 days). Follow-up averaged 4.1 years (range, 2.1-6.3). All patients remained neurologically intact. Eight patients had no pain, 24 had minimal pain, 4 had moderate pain, and 2 had moderate to severe pain. Twenty-nine of 38 patients (76%) were able to work at the same level. The initial kyphosis angle averaged 20 degrees (range 10-35 degrees). At follow-up it averaged 24 degrees (range 12-38 degrees). The maximum increase was 6 degrees. Some degree of retropulsed fragment resorption was noted in 35 cases. Complications were limited to transient urinary retention. There were no thromboembolisms, decubitus ulcers, or pulmonary complications. CONCLUSION: Despite the use of less restrictive criteria, no brace, and early activity as tolerated, the results are similar to those obtained with more restrictive protocols. The presence of vertical lamina fracture, spinous process fracture, and transverse process fracture are not contra--indications. Activity restriction and bracing may be important for pain control but probably does not change the long-term result.

Adolescent↗
PubMed1999

Plate fixation of fresh displaced midshaft clavicle fractures.

From 1992-1994, we operated on 251 fresh completely displaced mid-third clavicle fractures in adults; 232 were followed up. The fractures were plated with a Mizuho C-type plate or an AO/ASIF 3.5 mm reconstruction plate. Comminuted fragments were reduced and wired (133 cases). There were 150 men and 82 women; the median age was 37.3 years (range 18-79). The mean follow-up was 4.4 years (range 3.0-5.9). The mean time to radiographic union was 10 weeks. Seven patients (3%) developed nonunion. Healing with angulation occurred in 14 patients. Deep infection developed in one patient, and superficial infection in four cases; 21 patients reported soreness with changes in the weather and activity; 28 patients had residual skin numbness caudal to the incision. No patient had shoulder droop, and none had impairment of range of motion or shoulder strength. None developed new or late neurovascular impairment; 171 patients eventually had the hardware removed at an average 401 days post operatively. Overall, 94% were satisfied with the procedure. For completely displaced clavicle fractures in adults, plating is a reliable procedure.

Adolescent↗
PubMed1998

Mutational analysis of structural features of rat hormone-sensitive lipase.

Hormone-sensitive lipase (HSL) is a cytosolic neutral lipase that hydrolyzes intracellular stores of triacylglycerols and cholesteryl esters. HSL activity is regulated via phosphorylation-dephosphorylation, with cyclic AMP-dependent protein kinase increasing activity following phosphorylation of a single serine and Ca2+/calmodulin-dependent protein kinase II phosphorylating another serine at a basal site. The current studies used site-directed mutagenesis to show that Ser-563 of rat HSL is phosphorylated by cyclic AMP-dependent protein kinase and that Ser-565 is phosphorylated by Ca2+/calmodulin-dependent protein kinase II. Mutation of Ser-563-->Ala eliminated HSL hydrolytic activity against cholesteryl ester, triacylglycerol, and diacylglycerol substrates to the same extent as mutation of Ser-423-->Ala, the presumed catalytic site. Mutation of Ser-565-->Ala modestly decreased HSL activity. In contrast, mutation of Ser-563-->Asp preserved HSL hydrolytic activity and even increased activity 20% above the control wild-type enzyme. Molecular modeling of the catalytic pocket of HSL suggested the involvement of Val-710. Mutation of Val-710-->Ala resulted in an 85% loss of HSL hydrolytic activity. The results of these studies illustrate the importance of the presence of a hydroxyl group or negative charge at residue 563, either for proper conformation of rat HSL or for proper stabilization of substrate to allow maintenance of hydrolytic activity, as well as the importance of the involvement of additional amino acids in the catalytic pocket of the enzyme.

Alanine↗
PubMed1998

Arthrodesis with a short Huckstep nail as a salvage procedure for failed total knee arthroplasty.

Arthrodesis of the knee with use of a short Huckstep nail was performed in thirty-three patients (thirty-three knees) after failure of a non-constrained total knee arthroplasty. The indication for the arthrodesis was an infection in thirty-one knees and a Charcot joint in two. Three knees had had a failed attempt at arthrodesis with use of external fixation. The Huckstep nail was inserted through the knee, retrograde into the femur, and then antegrade into the tibia. The duration of the operation averaged 104 minutes (range, sixty-five to 155 minutes). Local bone graft was used in all knees. At the time of follow-up, at an average of forty-seven months (range, eighteen to ninety-four months), thirty knees (91 per cent) had radiographic evidence of union. The average time to union was 5.2 months (range, two to ten months) after the arthrodesis. Eight knees that had a grossly purulent infection were treated with debridement, which was followed by the arthrodesis as a second-stage procedure; the other knees had a one-stage arthrodesis. Only one of the thirty-one knees that had had an infection before the arthrodesis had a recurrence after it. Arthrodesis with a short Huckstep nail provides immediate axial and rotational stability and allows weight-bearing without use of external support as well as placement of the knee in a slightly flexed and valgus position. In addition, the nail does not migrate and it may be used even when there is a standard-size prosthesis in the ipsilateral hip.

Aged↗
PubMed1996

Two-stage cementless revision THR after infection. 5 recurrences in 40 cases followed 2.5-7 years.

We revised 40 infected hip prostheses in 40 patients as a two-stage procedure, including intravenous and oral antibiotics, gentamicin beads, and delayed cementless implantation of porous-coated THR. The duration of antibiotic treatment was 8 weeks. The interval from resection to reimplantation was, on average, 48 (8-108) weeks. 39 patients were followed, on average, 4 (2.5-7) years. 5 patients had a recurrent infection. In patients who did not have a recurrent infection, the Harris hip score exceeded 80 in 32 patients. Radiographically, femoral component migration of 2-6 mm was noted in 3 cases. The recurrent infection rate, and the functional and radiographic results are comparable with those obtained using a two-stage procedure with antibiotic cement.

Adult↗
PubMed1995

Stimulation of human insulin receptor gene expression by retinoblastoma gene product.

Multiple cis-acting elements have been defined to be important for the transcriptional regulation of the human insulin receptor (hIR) gene expression. We report here that one of these elements also mediated the stimulation of hIR promoter activity by the retinoblastoma gene product (Rb). The cis-element responsible for Rb stimulation was localized to the GA and GC boxes situated between -643 to -607 of the hIR gene. We have previously demonstrated that these GA and GC boxes bind Sp1 with high affinity and are responsible for E1a activation of hIR promoter activity. Mutation of these sequences completely abolished Rb-dependent enhancement of hIR promoter activity. In addition, we localized three regions in the N-terminal domain of Rb to be involved in stimulation of hIR promoter activity. Our results represent one of the first studies to demonstrate a functional importance assigned to the multiple phosphorylation sites in the N terminus of Rb. Finally, the mechanism by which Rb activates the hIR promoter are presented.

Base Sequence↗
PubMed1995

Lipid clearing agents in steroid-induced osteoporosis.

Osteoporosis is a major complication of long-term steroid use. In this experimental study, the effect of lipid clearing agents on the preservation of bone mass was assessed. New Zealand white rabbits were divided into four groups: normal control, steroid only, steroid plus lovastatin and steroid plus bezafibrate. Treatments were continued for either 6 to 8 weeks or 13 to 15 weeks, after which the rabbits were sacrificed. Each rabbit's trabecular bone area from the central saggital sections of the femoral head was measured. At 6 to 8 weeks there was no significant difference between the steroid groups, but at 13 to 15 weeks the bone area in the steroid only group was significantly lower than in the groups that had also received lipid clearing agents. Histologic examination of livers from the normal control group showed significantly less degeneration than in all of the steroid groups. Lipid clearing agents appear to maintain bone mass in the femoral head, but do not avert fatty changes in the liver in steroid treated rabbits. Concomitant use of lipid clearing agents with steroids may have the potential to decrease the severity of steroid induced osteoporosis.

Animals↗
PubMed1994

Identification and partial sequence analysis of novel annexins in Lytechinus pictus oocytes.

The annexins are a major class of calcium-binding proteins with unknown functions. In an attempt to define novel model systems in which to study members of the annexin family, we have investigated the expression of annexins in eggs from the sea urchin Lytechinus pictus. Western blot analysis of L. pictus eggs using antisera raised against human annexins I, V and VI revealed the presence of immunoreactive proteins of approximately 34 kDa, 35 kDa and 68 kDa respectively. The sea urchin annexins behaved similarly to their mammalian counterparts, both during purification and in their ability to bind calcium-dependently to anionic phospholipids. Of the three sea urchin annexins, the 34 kDa form was most abundant, yielding sufficient quantities for peptide microsequencing. The amino acid sequences derived in this way showed the L. pictus annexin to be closely related both to mammalian annexin I and to annexins IX, X and XII from Drosophila and Hydra. However, N-terminal sequence from the L. pictus annexin showed it to be a novel member of the annexin super-gene family. The results are interesting in view of the complex evolution of the annexin gene family, and also point to the potential usefulness of echinoderm eggs as a model system in which to study annexin function.

Amino Acid Sequence↗