Biomedical subjects

D T Chang

Publications and source records attributed to D T Chang.

At least 19 recordsLinked to original sources

PubMed2000

Reconstructive surgery for children with pelvic rhabdomyosarcoma.

Rhabdomyosarcoma is the most common soft-tissue sarcoma found in children and can arise almost anywhere skeletal muscle is found. It represents 4% to 8% of malignant solid tumors in children, ranking behind central nervous system tumors, lymphoma, neuroblastoma, and Wilms' tumor. Reconstructive surgery has become an integral part of the total plan in patients undergoing radical surgery for rhabdomyosarcoma. Advances in surgical techniques can often provide a reasonable lifestyle for patients.

Child↗

PubMed1999

Use of a laparoscopic insufflation port for ileal conduit endoscopy.

We present an effective and simple technique for performing endoscopy of an ileal conduit. With a laparoscopic insufflation port in the stoma, a flexible cystoscope or ureteroscope can be inserted. The one-way valve of the port prevents leakage of irrigation fluid and allows the conduit to distend for optimal visualization. This technique is particularly useful when access to the upper urinary tracts is needed.

Endoscopes, Gastrointestinal↗

PubMed1999

Vaginal reconstruction.

Absence of the vagina presents a challenging problem for the reconstructive urologist. This article reviews the pertinent diagnostic and pretreatment considerations and the surgical options, in particular, bowel vaginoplasty, for these patients.

Abnormalities, Multiple↗

PubMed1999

Declining sperm counts in the United States? A critical review.

PURPOSE: Recent reports suggest declining sperm counts in the United States. These reports did not include all available data and did not account for geographic variations noted in prior studies. We examined all available data on U.S. sperm counts and evaluated whether geographic variations account for the decline suggested. MATERIALS AND METHODS: We reviewed all 29 U.S. studies from 1938 to 1996 reporting manually counted semen analyses of 9,612 fertile or presumably fertile men. We determined mean sperm concentrations by geographic location with weighted analysis of variance, and assessed any changes with time by linear regression analysis. RESULTS: Mean sperm concentrations from New York were significantly higher than from all other U.S. cities (98.6 versus 71.6 x 10(6) sperm per cc, respectively, p = 0.006). There has been no statistically significant change with time for mean sperm concentrations reported from New York (p = 0.49) or from U.S. cities other than New York (p = 0.62). Analysis without separating by location revealed a decline (p = 0.047). CONCLUSIONS: Sperm concentrations are highest in New York compared to other U.S. cities. When accounting for this geographic difference and examining all available data, there appears to be no significant change in sperm counts in the U.S. during the last 60 years. Further studies addressing the causes of geographic variations are needed.

Humans↗

PubMed1998

Rapid reduction in blood flow to the rat ventral prostate gland after castration: preliminary evidence that androgens influence prostate size by regulating blood flow to the prostate gland and prostatic endothelial cell survival.

BACKGROUND: Androgenic steroids regulate the development and size of the mammalian prostate gland. The mechanism(s) for this growth control might involve a direct effect on prostate cell proliferation and survival as well as more complex effects on the tissue environment supporting nourishment and oxygenation. In this study, we evaluated an animal model of androgen action on the prostate, the rat ventral prostate gland, to determine whether acute androgen withdrawal, by means of castration, might alter the primary blood flow to the prostate gland and for the effects of castration on prostatic endothelial cell viability. METHODS: Groups of rats studied included intact control males, males that had been surgically castrated, or males that received a sham-surgical castration. Relative blood flow (RBF) to the rat ventral prostate glands and rat bladders were measured at 18 and 24 hr after castration or sham castration using a fluorescent microsphere infusion technique. Thin sections from fixed and embedded rat ventral prostate glands obtained from unoperated or 12-hr castrated rats were analyzed by the TUNEL immunostaining technique to microscopically identify and quantify apoptotic epithelial, stromal, and endothelial cells. RESULTS: RBF to the rat ventral prostate was reduced by 38%, at 18 hr after castration when compared with intact or sham-operated rats and by 45% at 24 hr after castration (P=0.038 unoperated/0.025 sham operated). In contrast, RBF to the bladder was not significantly different between any of the groups in the 24-hr castrate experiment. TUNEL staining analysis of ventral prostate tissues obtained from 12-hr castrated rats showed only rare TUNEL-positive epithelial cells similar to the control tissue but significantly increased TUNEL labeling for endothelial and other ventral prostate stromal cells. CONCLUSIONS: Castration resulted in a rapid and significant reduction of blood flow to the mature rat ventral prostate gland that was not seen in the bladder. This reduction precedes the appearance of apoptosis in the epithelial cells of the tissue but more coincided with the appearance of TUNEL-positive prostate vascular endothelial and stromal cells, suggesting that androgens support the survival of cells in the vascular and stromal compartment of the rat prostate as well as in the prostatic epithelium. These preliminary data support the concept that androgen action on the prostate might involve primary regulation of prostate blood flow and prostate vascular cell vitality.

Androgens↗

PubMed1998

Transurethral cystotomy repair.

We present a novel transurethral technique for cystotomy repair. This method can be used for immediate bladder repair following limited bladder injury and avoids the morbidity associated with laparotomy.

Humans↗

PubMed1998

The Malone antegrade continence enema procedure in the management of patients with spina bifida.

BACKGROUND: In patients with spina bifida, traditional bowel management programs such as suppositories, retrograde enemas, and manual disimpaction have been largely unsatisfactory. The Malone antegrade continence enema (ACE) procedure has largely changed our approach to bowel management in this patient group. STUDY DESIGN: Over a 3-year period between January 1994 and January 1997, 27 patients with spina bifida underwent the Malone ACE procedure at our institutions. At the time of their ACE procedure, four patients underwent simultaneous continent urinary diversion and three had simultaneous small-bowel bladder augmentation. All the patients were evaluated for 9 months or more after their procedure, and 10 of the patients have been followed for more than 2 years. RESULTS: Postoperatively, predictable bowel control and continence were achieved in 19 of the 27 patients, but 6 had some rectal soiling requiring a sanitary pad. All patients were out of diapers and none reported stomal leakage. Eighteen of the 27 patients were able to manage independently and 9 required assistance. Two patients had stopped using their ACE stoma despite good technical results. The appendix was used as a catheterizable stoma in 15 of the 27 patients. The appendix was not available in 12 patients, so a tubularized cecal flap was used in 9 and a small-bowel neoappendix was created in 3. Complications included stomal stenosis in 5 patients, cecal-flap necrosis in 1, and stomal granulations in 3. CONCLUSIONS: We believe that the ACE procedure provides reliable colonic emptying and avoids fecal soiling in the majority of individuals, and we find it widely and enthusiastically accepted by patients with spina bifida.

Adolescent↗

PubMed1996

Overexpression of a Rrp1 transgene reduces the somatic mutation and recombination frequency induced by oxidative DNA damage in Drosophila melanogaster.

Recombination repair protein 1 (Rrp1) includes a C-terminal region homologous to several DNA repair proteins, including Escherichia coli exonuclease III and human APE, that repair oxidative and alkylation damage to DNA. The nuclease activities of Rrp1 include apurinic/apyrimidinic endonuclease, 3'-phosphodiesterase, 3'-phosphatase, and 3'-exonuclease. As shown previously, the C-terminal nuclease region of Rrp1 is sufficient to repair oxidative- and alkylation-induced DNA damage in repair-deficient E. coli mutants. DNA strand-transfer and single-stranded DNA renaturation activities are associated with the unique N-terminal region of Rrp1, which suggests possible additional functions that include recombinational repair or homologous recombination. By using the Drosophila w/w+ mosaic eye system, which detects loss of heterozygosity as changes in eye pigmentation, somatic mutation and recombination frequencies were determined in transgenic flies overexpressing wild-type Rrp1 protein from a heat-shock-inducible transgene. A large decrease in mosaic clone frequency is observed when Rrp1 overexpression precedes treatment with gamma-rays, bleomycin, or paraquat. In contrast, Rrp1 overexpression does not alter the spot frequency after treatment with the alkylating agents methyl methanesulfonate or methyl nitrosourea. A reduction in mosaic clone frequency depends on the expression of the Rrp1 transgene and on the nature of the induced DNA damage. These data suggest a lesion-specific involvement of Rrp1 in the repair of oxidative DNA damage.

Alkylating Agents↗

PubMed1996

Effects of diode laser welding with dye-enhanced glue on tensile strength of sutures commonly used in urology.

BACKGROUND AND OBJECTIVE: Tissue welding using laser-activated protein solders may soon become an alternative to sutured tissue approximation. In most cases, approximating sutures are used both to align tissue edges and provide added tensile strength. Collateral thermal injury, however, may cause disruption of tissue alignment and weaken the tensile strength of sutures. The objective of this study was to evaluate the effect of laser welding on the tensile strength of suture materials used in urologic surgery. STUDY DESIGN/MATERIAL AND METHODS: Eleven types of sutures were exposed to diode laser energy (power density = 15.9 W/cm2) for 10, 30, and 60 seconds. Each suture was compared with and without the addition of dye-enhanced albumin-based solder. After exposure, each suture material was strained (2"/min) until ultimate breakage on a tensometer and compared to untreated sutures using ANOVA. RESULTS: The strength of undyed sutures were not significantly affected; however, violet and green-dyed sutures were in general weakened by laser exposure in the presence of dye-enhanced glue. Laser activation of the smallest caliber, dyed sutures (7-0) in the presence of glue caused the most significant loss of tensile strength of all sutures tested. CONCLUSION: These results indicate that the thermal effects of laser welding using our technique decrease the tensile strength of dyed sutures. A thermally resistant suture material (undyed or clear) may prevent disruption of wounds closed by laser welding techniques.

Adhesives↗

PubMed1996

Laser welding with albumin-based solder: experimental full-tubed skin graft urethroplasty.

BACKGROUND AND OBJECTIVES: Fistula and stricture formation at the site of sutured anastomoses are frequent complications of major urethroplasty. We performed urethroplasty using laser-welded skin tube grafts in the hope that in addition to being free of suture holes, grafts would be as strong as or stronger than sutured controls. STUDY DESIGN/MATERIAL AND METHODS: Scrotal skin was harvested from each of 11 rabbits and fashioned into tubes 3-4 cm in length using either conventional suture techniques or laser welding. Welding was performed using an 808-nm diode laser and a dye-enhanced solder composed of albumin and sodium hyaluronate. Laser power density was 15.9 watts/cm2. For each graft, leak pressure, and urethroplasty time (tube creation and anastomosis to native urethra) were measured. RESULTS: Urethroplasty time was significantly shorter and initial leak pressures were seven times greater in the laser-welded group. CONCLUSIONS: The near-uniform occurrence of strictures in both groups suggests that the rabbit is not an ideal model for free tube graft urethroplasty. However, our data indicate that laser welding with albumin-based solder, when used in the appropriate setting, may offer the potential for the rapid creation of watertight grafts in reconstructive urology.

Aluminum↗

PubMed1996

Hypospadias repair by laser tissue soldering: intraoperative results and follow-up in 30 children.

OBJECTIVES: We examined the use of laser tissue soldering (LTS) as an adjunct to suturing of, as well as a primary means of, tissue closure in urethral reconstruction. METHODS: Since June 1994, 26 boys ranging in age from 3 months to 14 years (mean 3.0 years) underwent hypospadias repair using LTS techniques. The classification of hypospadias was subcoronal in 13, midpenile in 5, penoscrotal in 7, and scrotal in 1. Laser tissue soldering was used in an additional 4 patients: tunica vaginalis patch graft corporoplasty in 2 (scrotal hypospadias), epispadias fistulae in 1, and urethral diverticulum in 1. Of these cases, 3 hypospadias repairs were completely sutureless. An intraoperative comparision was made between suturing and LTS with respect to operative time and degree of difficulty in performing LTS. Postoperatively, patients were examined to determine complications, including stricture, fistula, or impaired wound healing. An unselected group of 25 consecutive boys undergoing hypospadias repair between 1991 and 1992 served as a historical control group. RESULTS: No intraoperative complications resulted from laser activation. In 5 of the 30 procedures (16.6%), suture disruption was noted to occur, with a higher incidence seen with finer, dyed suture material. For hypospadias repair, the average time to suture was 6.7 min/cm (n = 23), whereas it was 3.1 min/cm for adjunctive LTS (n = 23) and 1.4 min/cm for sutureless urethroplasty (n = 3). Follow-up ranged from 3 to 22 months (average 9.6). Four fistulae were noted (1 onlay, 2 skin tube grafts, 1 Thiersch tube) each following penoscrotal or scrotal hypospadias repair; a fifth fistula developed following a traumatic catheterization in a sutureless repair. The overall complication rate in the LTS group was 19% (5 of 26) versus 24% (6 of 25) for controls, whereas that for the distal forms of hypospadias was 11% (2 of 18) and 13.6% (3 of 22), respectively. CONCLUSIONS: Tissue soldering with laser and chromophore-doped solder is feasible, safe, and easy to perform. Laser tissue soldering may be an alternative to standard microsuture technique for hypospadias repair.

Adolescent↗

PubMed1995

Limb-patterning activity and restricted posterior localization of the amino-terminal product of Sonic hedgehog cleavage.

BACKGROUND: Sonic hedgehog (Shh), a vertebrate homolog of the Drosophila segment polarity gene hedgehog (hh), has been implicated in patterning of the developing chick limb. Such a role is suggested by the restricted expression of Shh along the posterior limb bud margin, and by the observation that heterologous cells expressing Shh have limb-polarizing activity resembling that of cells from the polarizing region of the posterior limb bud margin. It has not been demonstrated, however, that the Sonic hedgehog protein (SHH) alone is sufficient for limb patterning. SHH has been shown to undergo autoproteolytic cleavage in vitro, yielding two smaller products. It is of interest, therefore, to determine whether processing of SHH occurs in the developing limb and how such processing influences the function of SHH. RESULTS: We demonstrate that SHH is proteolytically processed in developing chick limbs. Grafts of cells expressing SHH protein variants that correspond to individual cleavage products demonstrate that the ability to induce patterned gene expression and to impose morphological pattern upon the limb bud is limited to the amino-terminal product (SHH-N) of SHH proteolytic cleavage. We also demonstrate that bacterially synthesized and purified SHH-N, released from implanted beads, is sufficient for limb-patterning activity. Finally, we show that the endogenous amino-terminal cleavage product is tightly localized to the posterior margin of the limb bud. CONCLUSIONS: Our data show that, of the two cleavage products resulting from SHH autoproteolysis, SHH-N expressed in grafted heterologous cells or supplied in purified form is sufficient to impose pattern upon the developing limb. Moreover, the restricted localization of the endogenous amino-terminal SHH cleavage product to the posterior border of the chick limb bud makes it unlikely that its patterning activity results from it being distributed in a broad gradient across the antero-posterior axis. More consistent with the observed localization is a model in which the amino-terminal SHH cleavage product exerts its patterning effects by local induction in or near the polarizing region, initiating a cascade of gene expression that ultimately extends across the developing limb.

Animals↗

PubMed1995

Floor plate and motor neuron induction by different concentrations of the amino-terminal cleavage product of sonic hedgehog autoproteolysis.

The differentiation of floor plate cells and motor neurons can be induced by Sonic hedgehog (SHH), a secreted signaling protein that undergoes autoproteolytic cleavage to generate amino- and carboxy-terminal products. We have found that both floor plate cells and motor neurons are induced by the amino-terminal cleavage product of SHH (SHH-N). The threshold concentration of SHH-N required for motor neuron induction is about 5-fold lower than that required for floor plate induction. Higher concentrations of SHH-N can induce floor plate cells at the expense of motor neuron differentiation. Our results suggest that the induction of floor plate cells and motor neurons by the notochord in vivo is mediated by exposure of neural plate cells to different concentrations of the amino-terminal product of SHH autoproteolytic cleavage.

Animals↗

PubMed1995

Long-range sclerotome induction by sonic hedgehog: direct role of the amino-terminal cleavage product and modulation by the cyclic AMP signaling pathway.

A long-range signal encoded by the Sonic hedgehog (Shh) gene has been implicated as the ventral patterning influence from the notochord that induces sclerotome and represses dermomyotome in somite differentiation. Long-range effects of hedgehog (hh) signaling have been suggested to result either from local induction of a secondary diffusible signal or from the direct action of the highly diffusible carboxy-terminal product of HH autoproteolytic cleavage. Here we provide evidence that the long-range somite patterning effects of SHH are instead mediated by a direct action of the amino-terminal cleavage product. We also show that pharmacological manipulations to increase the activity of cyclic AMP-dependent protein kinase A can selectively antagonize the effects of the amino-terminal cleavage product. Our results support the operation of a single evolutionarily conserved signaling pathway for both local and direct long-range inductive actions of HH family members.

Animals↗

PubMed1995

Laser tissue soldering in urinary tract reconstruction: first human experience.

OBJECTIVES: Laser tissue soldering (LTS) in the urinary tract provides an immediate leak-free seal and may avoid complications seen with conventional repair (such as fistula and stricture). We have begun a Phase I clinical trial investigating the use of LTS in performing urologic reconstructive surgery. METHODS: Ten patients (aged 3 months to 38 years) underwent urologic reconstruction using LTS with a protein solder composed of human albumin (42%) and indocyanine green dye. In each case standard microsuture repair preceded laser-soldered suture line reinforcement. Anastomotic closure time and immediate leak pressure were measured. Postoperatively, all patients were evaluated for evidence of complications, including stricture, fistula formation, or impaired healing. RESULTS: Using LTS as an adjunct to suturing added an average of 7.9 +/- 3.0 minutes (28%) to the overall mean anastomotic time of 28.3 +/- 9.4 minutes. Intraoperative leak pressure measurements for laser-soldered anastomoses (> or = 94.2 +/- 24.2 mm Hg) were significantly higher (P < 0.001) than primarily sutured anastomoses (20 +/- 2.9 mm Hg). Two instances of suture disruption (20%) occurred during laser activation, neither of which were repaired with sutures. Average follow-up for all patients was 7.1 + - 2.2 months. There were no intraoperative or postoperative complications, including the 2 patients with suture disruption. CONCLUSIONS: These initial clinical results indicate that LTS is safe, easy to perform, and, contrary to conventional suturing, provides an immediate leak-free closure. Follow-up in these and other patients, as well as those undergoing sutureless and stent-free procedures, will determine whether our method of LTS benefits patients undergoing urologic reconstruction.

Anastomosis, Surgical↗

PubMed1995

Testicular microlithiasis in a child with torsion of the appendix testis.

We report on an 8-year-old boy with a unilateral testicular mass and bilateral diffusely echogenic testes on sonography. At inguinal exploration torsion of an appendix testis with a reactive phlegmon was found and testis biopsy revealed significant testicular microlithiasis. To our knowledge our case demonstrates a previously undescribed presentation of testicular microlithiasis. The literature is reviewed and this disease entity is discussed.

Calculi↗

PubMed1995

Laser welding versus suturing in tunica vaginalis and venous patch graft corporoplasty.

Congenital penile curvature may result from corporeal disproportion in nearly 40% of cases, while in adults scarring of the corporeal bodies or periurethral fibrosis accounts for the majority of cases. Some surgeons advocate lengthening the fibrosed corporeal bodies by excising tunica albuginea and grafting such defects to straighten the penis. Tunica vaginalis, dermis, dorsal vein and lyophilized dura have been used for this purpose. Traditionally, these graft biomaterials have been sutured to the tunica albuginea. We assessed the feasibility, short-term safety and efficacy of diode laser tissue welding using albumin based solder and indocyanine green dye to perform patch graft corporoplasty in the dog. Ten animals were subjected to bilateral transverse excision of 1 x 2 cm. sections of tunica albuginea. Corporoplasty was performed using grafts composed of saphenous vein (5) or tunica vaginalis (5). Microsurgical repair with 7-zero polydioxanone suture (10) was compared to contralateral laser welded repair (10) by recording operative time, initial and short-term bursting pressures (mean plus or minus standard deviation) and histological analysis. Operative time on the laser side (9.8 +/- 2.3 minutes) was significantly shorter (p < 0.05) than on the suture side (17.1 +/- 5.1 minutes). Leak pressures, initially (laser 105.7 +/- 23.8 mm. Hg versus suture 35.3 +/- 8.0 mm. Hg), at 3 to 5 days (greater than 333.3 +/- 62.4 mm. Hg versus 136.6 +/- 39.4 mm. Hg) and at 7 to 10 days (greater than 397.8 +/- 39.8 mm. Hg versus 191.5 +/- 46.4 mm. Hg) were higher (p < 0.05) in the laser side compared to controls. Graft failure (necrosis) occurred in 3 repairs (2 laser on day 4 and 1 suture on day 10). Viable tissue with minimal differences in foreign body reaction between groups was observed in the remaining grafts. We conclude that laser welded patch graft corporoplasty using tunica vaginalis or vein is easy to perform, and provides excellent initial and short-term leak pressures. The use of laser welding in conjunction with suturing may be beneficial in corporoplasty for congenital or acquired penile curvature.

Animals↗

PubMed1995

Urodynamics and the etiology of post-prostatectomy urinary incontinence: the initial Columbia experience.

Post-prostatectomy incontinence is a disabling disorder. Urodynamic studies in 56 patients with post-prostatectomy incontinence were reviewed to determine its etiology. Of the patients 31 had undergone transurethral prostatectomy and 25 radical retropubic prostatectomy. After careful history and neurourological examination, uroflowmetry, post-void residual determination and synchronous multichannel video pressure/flow studies were done. The most common etiology for incontinence was detrusor instability alone, which was present in 34 patients (61%), including 24 (77%) after transurethral resection of the prostate and 10 (40%) after radical retropubic prostatectomy. Stress incontinence alone was present in only 3 patients (5%), including 1 (3%) after transurethral resection of the prostate and 2 (8%) after radical retropubic prostatectomy. Detrusor instability with stress incontinence was present in 19 patients (34%), including 6 (19%) after transurethral resection of the prostate and 13 (52%) after radical retropubic prostatectomy. Of these 19 patients 4 (21%) had poorly compliant bladders. This study demonstrates that stress incontinence alone is a relatively rare cause of post-prostatectomy incontinence, with detrusor instability present in more than 90% of the patients. Accurate diagnosis of post-prostatectomy incontinence etiology could ensure proper treatment for this disorder.

Aged↗