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Biomedical subjects

P Chang

Publications and source records attributed to P Chang.

At least 145 records · Page 8Linked to original sources
PubMed1997

Requirements for both Rac1 and Cdc42 in membrane ruffling and phagocytosis in leukocytes.

Specific pathways linking heterotrimeric G proteins and Fcgamma receptors to the actin-based cytoskeleton are poorly understood. To test a requirement for Rho family members in cytoskeletal events mediated by structurally diverse receptors in leukocytes, we transfected the full-length human chemotactic peptide receptor in RAW 264.7 cells and examined cytoskeletal alterations in response to the chemotactic peptide formyl-methionyl-leucyl-phenylalanine (FMLP), colony stimulating factor-1 (CSF-1), IgG-coated particles, and phorbol 12-myristate 13-acetate (PMA). Expression of Rac1 N17, Cdc42 N17, or the GAP domain of n-chimaerin inhibited cytoskeletal responses to FMLP and CSF-1, and blocked phagocytosis. Accumulation of F-actin- rich "phagocytic cups" was partially inhibited by expression of Rac1 N17 or Cdc42 N17. In contrast, PMA-induced ruffling was not inhibited by expression of Rac1 N17, but was blocked by expression of Cdc42 N17, indicating that cytoskeletal inhibition by these constructs was nonoverlapping. These results demonstrate differential requirements for Rho family GTPases in leukocyte motility, and indicate that both Rac1 and Cdc42 are required for Fcgamma receptor- mediated phagocytosis and for membrane ruffling mediated by structurally distinct receptors in macrophages.

Animals↗
PubMed1997

Transduction of murine and human tumors using recombinant adenovirus vectors.

BACKGROUND: Most cytokine-based cancer gene therapy clinical trials have used labor-intensive, retrovirus-mediated strategies resulting in unpredictable gene expression. Recombinant AdV vectors were evaluated for easier, more reproducible gene transfer into 12 human melanoma, 2 murine fibrosarcomas, and 8 other tumor cell lines. METHODS: AdV vectors contained a reporter (Escherichia coli beta-galactosidase or firefly luciferase) or cytokine gene (human interleukin-2 [IL-2] or IL-7). Transduction efficiencies and expression levels were assessed by histochemical staining, flow cytometry, polymerase chain reaction, fluorometry, and enzyme-linked immunosorbent assay. Tumorigenicity was determined by subcutaneous injection of cells into syngeneic mice. RESULTS: All cell lines studied were transduced with AdV. Most cell lines exhibited 100% transduction efficiencies (by flow cytometry) at multiplicities of infection (MOI) epsilon 10. Gene expression correlated linearly with MOI, but a cytopathic effect was observed at MOI > 100 with all vectors. Nanogram gene expression levels were routinely achieved. Irradiation (30 Gy) minimally affected expression levels. Tumorigenicity of AdV-IL-2-transduced fibrosarcoma cells in mice was inversely related to IL-2 production. A majority of mice that rejected their tumor challenge were immune to tumor rechallenge. CONCLUSIONS: E1-deleted AdV vectors may prove useful in generating tumor vaccines ex vivo with high, transient cytokine expression levels.

Adenoviridae↗
PubMed1997

Mutation detection in the repeated part of the PKD1 gene.

The principle cause of one of the most prevalent genetic disorders, autosomal dominant polycystic kidney disease, involves mutations in the PKD1 gene. However, since its identification in 1994, only 27 mutations have been published. Detection of mutations has been complicated because the greater part of the gene lies within a genomic region that is reiterated several times at another locus on chromosome 16. Amplification of DNA fragments in the repeated part of the PKD1 gene will lead to coamplification of highly homologous fragments derived from this other locus. These additional fragments severely hamper point-mutation detection. None of the point mutations published to date are located in the repeated part of the PKD1 gene. However, we have reduced the problems posed by the strong homology, by using the protein-truncation test, and we have identified eight novel mutations, seven of which are located in the repeated part of the PKD1 gene.

Chromosomes, Human, Pair 16↗
PubMed1997

Fecal incontinence in scleroderma. Clinical features, anorectal manometric findings, and their therapeutic implications.

Fecal incontinence is an under-reported complication of scleroderma. Ten incontinent patients with scleroderma were evaluated through anorectal manometry and compared with 20 incontinent patients without scleroderma who were matched for age and sex as controls. The scleroderma patients had a higher voluntary external anal squeeze pressure, whereas the resting internal anal sphincter pressure was similar to that of the control group. The threshold for rectal sensation in the scleroderma group was significantly less than that in controls. Episodes of fecal incontinence, anal canal length, and maximal tolerable volume were not significantly different between the study groups. The rectoanal inhibitory response was abnormal in 80% of patients with systemic sclerosis but was normal in 70% of the controls. Stool consistency was significantly looser in the scleroderma patients. Treatment of fecal incontinence in scleroderma patients may be successful in many patients using a combination of dietary and pharmacologic manipulation because diarrhea is an important etiologic cofactor superimposed on reduced internal anal sphincter pressure.

Adult↗
PubMed1997

The effect of the delay phenomenon on the vascularity of rabbit abdominal cutaneous island flaps.

The beneficial effects of the delay phenomenon have been evaluated extensively and are widely known. However, no study has quantified the vascular changes seen in an abdominal cutaneous island flap following a surgical delay by vascular pedicle ligation. We evaluated the effect of unilateral superficial inferior epigastric and deep inferior epigastric pedicle ligation on the vascularity of a rabbit abdominal cutaneous island flap. Thirty rabbits underwent a left superficial inferior epigastric and deep inferior epigastric pedicle ligation as a delay procedure. A 19 x 15 cm abdominal cutaneous island flap was elevated at the time of sacrifice, based solely on the right superficial inferior epigastric pedicle. The flap vasculature was then evaluated by methylene blue injection and lead oxide microangiography at 0, 5, 10, 15, 21, and 27 days following the delay procedure. Methylene blue studies revealed perfusion of only the right (nonligated) side of the flap on day 0 and perfusion of the entire flap by day 15. This "capture" of the left (ligated) superficial inferior epigastric artery angiosome by day 15 could only have been achieved through enhanced cross-midline perfusion. Lead oxide microangiography revealed an increase in the number of vessels from day 0 to day 27 on both the ligated and nonligated sides in all the following: the number of large "choke" vessels (> 0.5 mm) crossing the flap midline, total number of vessels (all sizes) crossing the flap midline, and total number of vessels (all sizes) at the medial aspect of the right and left superficial inferior epigastric artery angiosomes. A statistically significant increase in these vessels was not seen until day 21. The effect of the delay phenomenon was significantly greater on the ligated side compared with the nonligated side. The areas of the flap that were relatively more ischemic following left superficial inferior epigastric pedicle ligation (medial aspect of the caudad half of the left superficial inferior epigastric artery angiosome) showed greater increases in vascularity with the delay procedure than did areas of lesser ischemia (medial aspect of the cephalad half of the right superficial inferior epigastric artery angiosome).

Abdominal Muscles↗
PubMed1997

The effect of the delay phenomenon on the vascularity of rabbit rectus abdominis muscles.

The transverse rectus abdominis muscle (TRAM) flap has become the "gold standard" for autogenous breast tissue reconstruction. Complications are reported in 10 to 40 percent of patients undergoing this procedure, and many are related to soft-tissue necrosis secondary to ischemia. Various methods have been proposed to improve TRAM flap survival, including surgical delay of the flap. The beneficial effects of the delay phenomenon have been well established in laboratory studies and clinical evaluations. Many investigators agree that the delay phenomenon will enhance arterial inflow and venous outflow from the TRAM flap. No study has quantified the changes seen in the rectus abdominis muscle following a delay procedure. In this prospective, controlled, and blinded experiment, we evaluate the effect of a unilateral superficial inferior epigastric and deep inferior epigastric artery and vein ligation on the vascularity of the rectus abdominis muscles in rabbits. Thirty-eight rabbits underwent a left superficial inferior epigastric and deep inferior epigastric pedicle ligation as a delay procedure. The rectus abdominis muscle vasculature was then evaluated by lead oxide microangiography at 0, 5, 10, 15, 21, and 27 days following the delay procedure. Magnification (x 2) was used to count the number of vessels at the periphery of the deep inferior epigastric artery angiosomes in the microangiograms. An increase in the number of vessels from day 0 to day 27 was seen on both the ligated and nonligated sides in all the following: the number of large (> 0.5 mm) "choke" vessels and total number of vessels (all sizes) crossing the abdominal wall midline and the total number of vessels (all sizes) at the medial, superior, and lateral aspects of the right and left deep inferior epigastric artery angiosomes. A statistically significant increase in these vessels was not seen until day 21. The effect of the delay phenomenon was significantly greater on the ligated side compared with the nonligated side. The areas of the rectus abdominis muscles that were relatively more ischemic following left deep inferior epigastric pedicle ligation (medial aspect of the left deep inferior epigastric artery angiosome) showed greater increases in vascularity with the delay procedure than did areas of lesser ischemia (lateral aspect of the right deep inferior epigastric artery angiosome).

Angiography↗
PubMed1997

[Detection of hepatitis A virus in environmental samples by coupled reverse transcription and polymerase chain reaction].

A direct reverse transcription coupled with polymerase chain reaction (RT-PCR) was used to detect HAV-seeded sea water, coastal sediment and Arca subcrenata, HAV strain treated by different kind of disinfection, and naturally occurring HAV in Arca subcrenata. The results showed that HAV could be detected in HAV-seeded sea water, coastal sediment and Arca subcrenata. HAV could also be detected in HAV strain disinfected by phenol, suggesting that inactive HAV could also show positive PCR. Only Arca subcrenata collected from Shanghai in 1988 showed positive result by RCR, but negative by immunofluorescence at the same time. This result demonstrated that HAV was not infectious owing to long time storage. The author's method has the advantage of involving fewer manipulations.

China↗
PubMed1997

Plasma derived von Willebrand factor preparations: collagen binding and ristocetin cofactor activities.

Five plasma preparations (11 lots) used in the treatment of von Willebrand's disease (vWD) were evaluated. The collagen binding function of von Willebrand factor (vWF) containing preparations was compared with the ristocetin cofactor activity and the vWF antigen. Some preparations have higher ratio of functional activity (ristocetin cofactor and collagen binding) relative to the antigen than is found in normal plasma. The ristocetin cofactor activity and the collagen binding activity are tightly correlated (r = .95). Ultracentrifugal (UCF) analysis was used to compare the size distribution of vWf antigen, ristocetin cofactor and collagen binding activity. The sedimentation of all of the vWF parameters in the plasma products was slower than in plasma. In plasma products the ristocetin cofactor activity sediments the most rapidly, the collagen binding activity is slower and the antigen the slowest. The collagen/antigen ratio decreases with decreasing vWF size. Assignment of potency to vWF containing preparations utilizing the collagen binding activity may be more precise and as accurate as with the traditional ristocetin cofactor assay.

Biological Assay↗
PubMed1996

Rationale, background, and design of the randomized angiotensin receptor antagonist--angiotensin-converting enzyme inhibitor study (RAAS).

The randomized angiotensin receptor antagonist--angiotensin converting enzyme (ACE)--Inhibitor Study (RAAS) was designed to test the hypothesis that the addition of an angiotensin II type 1 receptor blocking agent, losartan 50 mg/day, to an ACE-inhibitor, enalapril 10 mg twice a day (group 1), will be more effective than standard-dose enalapril 10 mg twice a day (group 2) or high-dose enalapril alone 20 mg twice a day (group 3), in blocking the activation of the renin angiotensin aldosterone system in patients with heart failure and left ventricular systolic dysfunction. The addition of an angiotensin II type 1 receptor blocking agent to an ACE inhibitor would theoretically block ACE as well as non-ACE-dependent angiotensin II formation while maintaining the potential beneficial effect of ACE inhibitor-induced bradykinin formation. One hundred twenty patients with left ventricular systolic dysfunction and moderate to severe heart failure despite treatment with an ACE inhibitor will be randomized to 1 of the 3 groups and followed for 6 weeks, with an optional long-term week extension to determine the safety and tolerability of the combination of losaratan and enalapril, its effectiveness in preventing rest and exercise-induced neurohumoral activation (plasma norepinephrine, N-terminal proatrial natriuretic factor, angiotensin II, and aldosterone), as well as quality of life and exercise performance (6-minute walk test).

Angiotensin Receptor Antagonists↗
PubMed1996

Syk tyrosine kinase is required for immunoreceptor tyrosine activation motif-dependent actin assembly.

Clustering of several multisubunit receptors on hematopoetic cells results in a signaling cascade involving the phosphorylation of immunoreceptor tyrosine activation motifs, or "ITAMs," and actin polymerization. Recent experiments indicate that direct clustering of the ITAM-binding protein, p72(syk) (Syk), is capable of transmitting a phagocytic signal in COS cells (Greenberg, S., Chang, P., Wang, D., Xavier, R., and Seed, B.(1996) Proc. Natl. Acad. Sci. U. S. A. 93, 1103-1107). However, the possibility of redundant signaling pathways makes it difficult to test the requirement for Syk in ITAM-dependent actin polymerization in hematopoetic cells. We developed a model system to study ITAM-dependent actin assembly. DT40 lymphocytes were transfected with fusion proteins encoding the transmembrane and cytosolic domains of the ITAM-containing gamma subunit of Fc receptors. Clustering the gamma-containing fusion proteins with IgG-coated erythrocytes triggered submembranous actin assembly. This response depended on an intact ITAM, was absent in cell lines that had been engineered to lack Syk, and was augmented in cell lines that stably overexpressed Syk. These experiments demonstrate an absolute requirement for Syk tyrosine kinase in ITAM-dependent actin assembly in transfected lymphocytes.

Actins↗
PubMed1996

Clustered syk tyrosine kinase domains trigger phagocytosis.

Phagocytosis is a phylogenetically primitive mechanism adapted by specialized cells of the immune system to ingest particulate pathogens. Recent evidence suggests that the program of specific cytoskeletal rearrangements that underlies phagocytosis may share elements with the antigen receptor signaling pathway in lymphocytes. Tyrosine phosphorylation, necessary for both lymphocyte effector function and phagocytosis, is thought to allow cytoskeletal elements to couple to the intracellular domains of antigen and Fc receptor subunits. We show here that the intracellular domains of the receptors are not inherently required for cytoskeletal coupling. Chimeric transmembrane proteins bearing syk but not src family tyrosine kinase domains are capable of autonomously triggering phagocytosis and redistribution of filamentous actin in COS cells. These responses cannot be initiated by a receptor chimera bearing a point mutation in the syk catalytic domain, and the kinase domain alone is sufficient for initiating cytoskeletal coupling.

Actins↗
PubMed1996

A technique for laparoscopic completion of vaginal hysterectomy.

Recently, the use of laparoscopic assistance in vaginal hysterectomy has become popular, although its role in gynecologic surgery has not been well established. A way to define this role is to start the hysterectomy vaginally and use laparoscopic assistance only if it becomes necessary. We present a new technique in which vaginal hysterectomy proceeds to the opening of the peritoneal reflections and ligature of uterine vessels and uterosacral ligaments. If laparoscopic assistance becomes necessary at this point, a uterine manipulator with an adapted inflatable balloon is inserted vaginally, allowing completion of the procedure laparoscopically while maintaining a pneumoperitoneum. Eight operations were performed successfully in our institution using this new technique. Operative time was less than with conventional laparoscopically assisted vaginal hysterectomy. The technique also simplified the management of the uterine vessels and detachment of the bladder.

Female↗
PubMed1996

Preservation of endothelium-dependent vasodilation with low-potassium University of Wisconsin solution.

University of Wisconsin solution has provided excellent myocardial preservation. However, the high potassium content of the currently available University of Wisconsin solution has been implicated in coronary artery endothelial damage. We placed 16 neonatal (age 1 to 3 days) Duroc piglet hearts on an isolated nonworking perfusion circuit. Endothelium-dependent and endothelium-independent vasodilation were tested by measuring coronary blood flow after intracoronary infusion of bradykinin (10(-6) mol/L) and nitroprusside (10(-6) mol/L), respectively. In addition, nitric oxide levels were measured after bradykinin infusion. The hearts were then arrested blindly with either a modified University of Wisconsin solution (group 1; n = 8, K+ = 25 mEq/L) or standard University of Wisconsin solution (group 2; n = 8, K+ = 129 mEq/L) by infusion of cardioplegic solution every 20 minutes for a total of 2 hours. After bradykinin infusion, the mean coronary blood flow increased by 237.1% +/- 14.0% of baseline valves before arrest and by 232.8% +/- 16.0% after arrest in group 1 (p = not significant). As in the first group, the mean coronary blood flow in group 2 increased by 231.1% +/- 13.7% before arrest; however, the increase in mean coronary blood flow after arrest was significantly attenuated (163.3% +/- 12.8%, p < 0.01). The loss of endothelium-dependent coronary blood flow response in group 2 correlated with a decreased capacity to release nitric oxide after arrest (prearrest 8.25 +/- 2.30 nmol/min per gram versus postarrest -2.46 +/- 2.29 nmol/min per gram, p < 0.01). Endothelium-independent vasodilatory response revealed no significant difference between groups before and after arrest. These results suggest that the low-potassium University of Wisconsin solution provides superior protection of the endothelium by preserving the endothelium-dependent vasodilatory response to nitric oxide release.

Adenosine↗
PubMed1996

Cardiac gene transfer by intracoronary infusion of adenovirus vector-mediated reporter gene in the transplanted mouse heart.

This study introduces a model for intracoronary gene transfer in murine cardiac isografts using adenovirus vectors. This approach may offer an opportunity to modulate alloreactivity after cardiac transplantation. Donor hearts were infected via the coronary arteries with a volume of 10(9) plaque-forming units per milliliter of a recombinant adenovirus containing the beta-galactosidase-encoding gene (Ad.CMVLacZ). In a control group, 200 microliters of normal saline solution was infused. The grafts were stored in 4 degrees C cold saline solution for 15 minutes, then transplanted heterotopically into syngeneic hosts (B10.BR). The grafts were harvested at 3, 7, 15, or 30 days (n = 5 for each group) after transplantation, and beta-galactosidase activity was assessed by histochemical staining (X-gal). All grafts were functioning when harvested. X-gal staining pattern was nonuniform with positive staining appearing in epicardial, myocardial, and endocardial cells, as well as in the vessel walls. The cells permissive to infection consisted predominantly of myocardial cells. The mean total numbers of beta-gal-positive staining cells per slice were 68.7 +/- 27.3 in the 3-day group, 330.4 +/- 53.8 in the 7-day group, 151.3 +/- 48.0 in the 15-day group, and 39.9 +/- 10.8 in the 30-day group, thus peaking in the 7-day group (p < 0.05). Control isografts (n = 5), retrieved at day 30, revealed no staining activity. In conclusion, our model demonstrates that intracoronary gene transfer to the transplanted murine cardiac grafts is feasible at the time of harvest. Adenovirus-mediated gene transfer produces widespread gene expression which, though perhaps transient, does not adversely affect myocardial structure or function. This technology may allow modification of graft immunogenicity in the future through the production of therapeutic proteins sufficient to modulate local immune responses.

Adenoviridae↗
PubMed1996

Carpal tunnel release with and without epineurotomy: a comparative prospective trial.

A prospective, comparative study of epineurotomy as an adjunctive procedure to transverse carpal ligament release for the treatment of carpal tunnel syndrome was conducted. Eighty-six patients with 117 involved hands were entered into the study. After entry, all patients completed an extensive preoperative questionnaire, a detailed physical examination, and preoperative neurophysiologic testing. Seventy-five hands were followed for a minimum of 24 months. The operative findings were similar between the group of those undergoing epineurotomy and the group that did not undergo epineurotomy. Postoperatively the twopoint discrimination values for all fingers averaged 5.3 mm and 5.15 mm, respectively, for the epineurotomy and nonepineurotomy groups. The physical findings, neurophysiologic findings, and patient perceptions of outcome after surgery were similar. It was concluded that the study data do not support the use of epineurotomy as an adjunctive procedure during carpal tunnel release.

Adult↗