Biomedical subjects

D T Chang

Publications and source records attributed to D T Chang.

28 records · Page 2Linked to original sources

PubMed1995

Sutureless rabbit bladder mucosa patch graft urethroplasty using diode laser and solder.

Fistula and strictures at the site of sutured anastomoses are frequent complications of major urethroplasty. We harvested bladder mucosa in 26 rabbits to repair large defects in the proximal urethra using laser-activated solder in the hope that such a repair would be stronger, faster to create and avoid common complications seen with conventional repair. Large oval defects were created in the proximal urethra in all animals undergoing urethroplasty. Twelve animals underwent bladder mucosa graft closure via diode (808 nm.) laser activation of an albumin-based solder (50% were suture-free). Fourteen additional animals underwent closure with 7-zero polydiaxanone suture (controls). Leak pressure and time of repair were recorded for each graft. Additional sections of bladder mucosa were harvested, transected and repaired by laser welding to determine tensile strength. In both groups, radiography, urethroscopy and clinical course were evaluated for as much as 6 weeks postoperatively. Urethroplasty time was significantly (p < 0.01) shorter for the laser group (13.8 +/- 2.5 minutes) than for the sutured repair group (24.0 +/- 5.3 minutes). Initial leak pressures for the lasered grafts averaged at least 4 times those of sutured grafts (p < 0.01). The tensile strength for lasered bladder mucosa was 3.16 +/- 1.12 kg./cm.2 Early retrograde urethrograms (RUG) performed at 7 days (n = 5) revealed urinary extravasation and fistula formation in 2 control animals compared with a normal urethral appearance in 3 lasered repairs. Early retrograde urethrograms performed at 21 days (n = 21) demonstrated smooth-walled urethras with no evidence of fistula, stricture, or urinary extravasation in the lasered group; varying degrees of reactive mucosal proliferation were seen in the controls. Urethroscopy confirmed these observations. At 6 weeks, histologic examination confirmed the presence of viable graft in all animals. We conclude that bladder mucosa patch graft urethroplasty using diode laser welding and albumin-based solder is an attractive alternative to conventional methods.

Animals↗

PubMed1994

Renal effects of CO2 insufflation: oliguria and acute renal dysfunction in a rat pneumoperitoneum model.

OBJECTIVE: To determine the mechanism by which oliguria develops during raised intra-abdominal pressure secondary to CO2 insufflation, we created a rat pneumoperitoneum model. METHODS: Male Sprague-Dawley rats (n = 67) were organized into three groups. Each group was subjected to abdominal pressures of 0 (control), 5, or 10 mm Hg, over one, two, and four hours. Fourteen additional rats underwent a two-hour period of 10 mm Hg insufflation pressure followed by desufflation to 0 mm Hg. Urine output (UO) and serum creatinine levels were measured both during insufflation at one, two, and four hours, and two, four, ten, and twenty-two hours following its release. These measurements were compared to control values at each time point. Ultrasonic flow probes placed around both the inferior vena cava (IVC) and abdominal aorta during insufflation characterized the effects of increased abdominal pressure on blood flow. The flow rate was determined at insufflation pressures of 0 (control, 100% flow) to 25 mm Hg. RESULTS: Rats subjected to 10 mm Hg pressure had significant decreases in UO (oliguria) compared to controls for up to four hours (P < 0.01). There were no significant differences in UO in the control or 5 mm Hg groups over each time interval. While a reduction in UO was observed at two, four, and ten hours postrelease, significance was achieved only at ten hours (P < 0.006). By twenty-two hours postrelease, no differences in UO were observed. Serum creatinine elevations declined two hours postdesufflation. IVC flow was reduced by 92.9 percent at 10 mm Hg, while arterial flow decreased by 46.4 percent. Flow was restored to preinsufflation levels after release of pneumoperitoneum. CONCLUSIONS: Oliguria can be produced in rats undergoing pneumoperitoneum. The renal effects of pneumoperitoneum are most likely related to renal vascular insufficiency from central venous compression.

Acute Disease↗

PubMed1994

Incidence of external spermatic veins in patients undergoing inguinal varicocelectomy.

OBJECTIVES: To determine the incidence of external spermatic veins at inguinal varicocelectomy. METHODS: A prospective study was performed by making intraoperative observations on 78 varicocelectomies (47 patients) performed by a single surgeon. All patients were referred for evaluation of male infertility and had a palpable varicocele present when examined while performing a Valsalva maneuver in the upright position. Varicocelectomies were performed via the inguinal approach using x 2.5 loupe magnification. Presence of external spermatic veins was defined as visualization (with x 2.5 loupe magnification) of veins on the floor of the inguinal canal traveling posterolateral to the spermatic cord that then subsequently exited the spermatic cord before passing through the internal inguinal ring. Age, anesthetic technique, and need for incision of the external inguinal ring were also recorded for each patient. RESULTS: One third of patients had undergone left-sided varicocelectomies, while two thirds had undergone bilateral procedures. External spermatic veins were identified in 15% of left-sided varicoceles and 19% of right-sided ones. Of 31 patients undergoing bilateral varicocelectomies, 19% had at least 1 external spermatic vein. Of these patients, only 2 (7%) had a unilateral right external spermatic vein, none had a unilateral left external spermatic vein, and 4 (13%) had bilateral external spermatic veins. Overall, of all patients studied, 16% had at least 1 external spermatic vein. Follow-up at 1 year showed no evidence of clinical recurrence in any patient. CONCLUSIONS: These results emphasize the importance of distal gonadal venous anatomy in the surgeon's choice of the proper approach to varicocele repair, since external spermatic veins are only accessible via an inguinal approach.

Collateral Circulation↗

PubMed1994

Oliguria during laparoscopic surgery.

Oliguria is infrequently viewed as a complication of laparoscopic surgery. The rate of urine output in six healthy patients undergoing laparoscopic surgery was measured during the period of CO2 pneumoperitoneum and for several hours after desufflation. The average hourly urine output during insufflation was 0.30 +/- 0.14 mL/kg despite an average hourly intravenous infusion rate of lactated Ringer's solution of 13.0 +/- 4.0 mL/kg. After release of pneumoperitoneum, urine output increased 467% to 1.7 +/- 1.1 mL/kg per hour. Patients remained hemodynamically unchanged perioperatively. Preoperative and postoperative blood urea nitrogen and creatinine concentrations did not significantly differ. We discuss the potential etiologic factors in the development of oliguria in the setting of the increased intra-abdominal pressure of pneumoperitoneum and the implications of this acute but reversible renal dysfunction.

Abdomen↗

PubMed1994

Products, genetic linkage and limb patterning activity of a murine hedgehog gene.

The hedgehog (hh) segmentation gene of Drosophila melanogaster encodes a secreted signaling protein that functions in the patterning of larval and adult structures. Using low stringency hybridization and degenerate PCR primers, we have isolated complete or partial hh-like sequences from a range of invertebrate species including other insects, leech and sea urchin. We have also isolated three mouse and two human DNA fragments encoding distinct hh-like sequences. Our studies have focused upon Hhg-1, a mouse gene encoding a protein with 46% amino acid identity to hh. The Hhg-1 gene, which corresponds to the previously described vhh-1 or sonic class, is expressed in the notochord, ventral neural tube, lung bud, hindgut and posterior margin of the limb bud in developing mouse embryos. By segregation analysis the Hhg-1 gene has been localized to a region in proximal chromosome 5, where two mutations affecting mouse limb development previously have been mapped. In Drosophila embryos, ubiquitous expression of the Hhg-1 gene yields effects upon gene expression and cuticle pattern similar to those observed for the Drosophila hh gene. We also find that cultured quail cells transfected with a Hhg-1 expression construct can induce digit duplications when grafted to anterior or mid-distal but not posterior borders within the developing chick limb; more proximal limb element duplications are induced exclusively by mid-distal grafts. Both in transgenic Drosophila embryos and in transfected quail cells, the Hhg-1 protein product is cleaved to yield two stable fragments from a single larger precursor. The significance of Hhg-1 genetic linkage, patterning activity and proteolytic processing in Drosophila and chick embryos is discussed.

Animals↗

PubMed1989

Effects of platelet-derived growth factor and fibroblast growth factor on free intracellular calcium and mitogenesis.

Although increased free intracellular calcium (Cai) may be one of the main regulators of cell growth and differentiation, studies in cell populations have implied that not all growth factors produce Cai increases. In order to examine in more detail whether Cai increases were related to mitogenesis, we used digital image analysis of intracellular Fura-2 fluorescence to measure Cai in individual BALB/c 3T3 cells stimulated with either platelet-derived growth factor (PDGF) or fibroblast growth factor (FGF). We found that PDGF induced larger and more prolonged Cai increases than FGF did, but that both growth factors induced an initial rapid increase in Cai (less than 2 min) followed by a later sustained increase (greater than 20 min). Only the prolonged Cai increase required extracellular calcium. Following PDGF treatment (1-8 units/ml), the percentage of cells with a large peak Cai increase (greater than twofold) correlated with the percentage of cells made competent (subsequent growth in 1% platelet-poor-plasma). In contrast, purified bovine basic FGF (200-800 pg/ml) and recombinant human acidic FGF (10-300 ng/ml) produced peak Cai increases that were not directly correlated with mitogenesis. In addition, concentrations of intracellular Quin 2 that inhibited Cai transients also inhibited PDGF stimulation but not FGF stimulation of mitogenesis. Thus, Cai increases are necessary for mitogenesis in BALB/c 3T3 cells stimulated by PDGF, but not that stimulated by FGF.

Aminoquinolines↗

PubMed1976

Computed tomography in a community hospital.

Computed tomography may be effectively utilized in the radiology department of a community hospital. An ideal program features regional services, 7-day, 24-hour coverage, immediate response to emergencies, prompt reporting, and availability of ancillary hospital services. Experience indicates that early scanning may eliminate the need for invasive diagnostic procedures, prevent or shorten hospital stay, and minimize the morbidity and expense of neuroradiological diagnosis.

Adult↗

PubMed1975

Insulin effect on creatine transport in skelatal muscle (38464).

Isulin is shown to directly enhance both the rate of transport and the uptake of cretine in vitro in isolated rat skeletal muscle. This action of the hormone on creatine transport is similar to that reported for the transport of some amino acids and sugars.

Animals↗

PubMed1969

Initial ATP Formation, NADP Reduction, CO(2) Fixation, and Chloroplast Flattening Upon Illuminating Pea Leaves.

Chloroplasts in living cells of detached and sectioned leaves of Pisum sativum had a thickness of 2.68 +/- 0.04 mu in the dark as determined from photographs made using a phase contrast microscope. Upon illumination with 4000 lux for 10 min, the chloroplasts flattened to 2.15 +/- 0.04 mu. There was a short lag period of about 11 sec at 1000 lux and 2 sec at 4000 lux before appreciable light-induced flattening occurred. Both ATP and reduced nicotinamide adenine dinucleotide phosphate (NADPH) in detached pea leaves increased upon illumination and then fell during the initial 60 sec. The maximum ATP level was attained in 16 sec at 1000 lux and 10 sec at 4000 lux, while NADPH required about twice as long to reach a maximum. A sustained rate of carbon dioxide fixation occurred after a lag period coinciding in time with the drop in the NADPH level. ATP appeared to be involved not only with carbon dioxide fixation, but also with some reaction beginning sooner, perhaps the light-induced chloroplast flattening. Considering the initial photophosphorylation and the sustained CO(2) fixation rates, the ATP formation rate in vivo apparently increased after the leaves had been in the light for a few min.

Journal Article↗

PubMedDate not supplied

Nonobstetrical abdominal surgery during pregnancy in Women's Hospital.

OBJECTIVE: To determine if nonobstetrical abdominal surgery during pregnancy in Women's Hospital at the University of Southern California School of Medicine was associated with increased rates of preterm delivery or spontaneous loss. Preoperative diagnostic accuracy was also evaluated. METHODS: We performed a retrospective review of all cases of nonobstetrical abdominal surgery in our institution during a 7-year period from November 1991 to November 1998. RESULTS: One hundred-six cases of nonobstetrical abdominal surgery were identified. Eighty-eight women underwent laparotomy and 18 had laparoscopic abdominal surgery. Seventy-three women had emergent surgery and 31 had elective surgery. Seventy-six percent (80/106) of subjects had the same preoperative and postoperative diagnoses. We obtained delivery data for 62 of 106 (59%) subjects. Eleven of 62 (18%) subjects who had nonobstetrical abdominal surgery during pregnancy delivered preterm (<37 weeks' gestation). This was not significantly different from the institutional preterm delivery rate of Women's Hospital (8999/56305 [16%]) (P = 0.84). Two of 106 (2%) women experienced spontaneous pregnancy loss following surgery; both occurred in the second trimester. CONCLUSIONS: Nonobstetrical abdominal surgery during pregnancy in Women's Hospital was not associated with higher frequencies of preterm deliveries or spontaneous losses than our institutional rates.

Abdomen↗