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Biomedical subjects

E Y Cheng

Publications and source records attributed to E Y Cheng.

At least 55 records · Page 3Linked to original sources

Modeling the future workforce of obstetrics and gynecology.

OBJECTIVE: To examine the current supply and distribution of obstetrician-gynecologists and project future supply under various scenarios. METHODS: A discrete actuarial supply model was developed, and practice patterns were analyzed. Supply projections under different scenarios, distributions, and practice profiles were examined. RESULTS: Women are expected to become the majority of practitioners by 2014. Continuation of current residency output will result in slow to no growth in obstetrician-gynecologist-to-female population ratios over the next 20 years. A minor (10%) reduction in specialty training would slow specialty growth over the next decade, followed by a slight reduction in supply. Services provided chiefly involve ambulatory reproductive health care, pregnancy, and surgical correction of conditions specific to the female genitourinary system. Even though the proportion of deliveries performed by midwives has increased and family practitioners have maintained their share, obstetrician-gynecologists provide the vast majority of obstetric care and virtually all services for perinatal complications. Generalist services represent relatively minor aspects of their practices. Care of the aged female population is highly fragmented among specialties; more than 50% of all aged Medicare beneficiaries who saw an obstetrician-gynecologist at least once failed to receive a majority of services from any one physician specialty. CONCLUSION: On the basis of trends in patient demographics and care patterns, obstetrician-gynecologists must resolve whether to provide more generalist office-based care, especially to the rapidly growing older female population, or to invest more intensively in surgical specialty care. The specialty's unique contributions to women's health should influence this decision.

Forecasting↗

Myofascial wrap to treat intractable urinary incontinence in children.

OBJECTIVES: The management of intractable urinary incontinence in the patient with cloacal or bladder exstrophy/epispadias, failed bladder neck plasty, or failed augmentation cystoplasty remains a surgical challenge. The myofascial wrap, a modification of the rectus fascial wrap, was developed to treat intractable urinary incontinence due to sphincteric incompetence in these problematic cases. A full-thickness, vascularized pedicle of anterior rectus sheath, rectus abdominis muscle, and posterior rector sheath is incorporated into a bladder neck wrap to provide support, mucosal coaptation, and active muscular tone. METHODS: Eight patients (5 females and 3 males) with total urinary incontinence due to sphincteric incompetence underwent the myofascial wrap. Urinary tract pathology included cloacal exstrophy (2), female epispadias (2), classic bladder exstrophy (1), male epispadias (1), myelomeningocele (1), and a pelvic tumor (1). The procedure is performed by harvesting a full-thickness strip of pedicled rectus muscle along with the anterior and posterior fascial sheaths. The strip is passed underneath and then over the bladder neck in a near 360 degrees wrap. The free end of the wrap is anchored into the pubic bone in an ipsilateral subperiosteal pouch. RESULTS: Six of the 8 patients are completely continent, and 2 patients void spontaneously without the need for catheterization. CONCLUSIONS: The myofascial wrap provides support, mucosal coaptation, and muscular tone to an incompetent sphincter and bladder neck. Favorable results in a very difficult population of pediatric patients warrant its continued use.

Adolescent↗

Multi-institutional study of testicular microlithiasis in childhood: a benign or premalignant condition?

PURPOSE: Testicular microlithiasis, a rare ultrasonographic diagnosis in children, has been shown to coexist in benign and malignant conditions. The natural history of incidentally discovered testicular microlithiasis has not been well defined in the pediatric population. The concern that testicular microlithiasis may be a premalignant condition has been raised. Reports indicate as much as a 45% association of germ cell tumors with testicular microlithiasis at the time of tumor diagnosis and there have been 4 cases of interval testicular tumor development associated with preexisting testicular microlithiasis. To address this issue we performed a multi-institutional study to evaluate children with incidentally diagnosed testicular microlithiasis. MATERIALS AND METHODS: Data on 26 patients with a mean age of 12.3 years at presentation with incidentally discovered testicular microlithiasis were collected from 7 institutions. Presenting scrotal conditions were reviewed. Two children with a previous testicular malignancy were excluded from study. RESULTS: Followup ranged from 1 month to 7 years (mean 27.6 months). Testicular biopsy and tumor marker (alpha-fetoprotein and beta-human chorionic gonadotropin) determinations were performed in 9 and 15 patients, respectively. To date no testicular tumor has developed during clinical followup. CONCLUSIONS: Our multi-institutional study has not yet shown a trend toward the malignant degeneration of incidentally diagnosed testicular microlithiasis in children. However, we still advocate close surveillance of patients with testicular microlithiasis, such as yearly testicular ultrasound, physical examination, and judicious tumor marker determinations. We propose that a registry be started to follow prospectively patients with testicular microlithiasis to define its significance better.

Adolescent↗

Frontal lobe shortening in second-trimester fetuses with trisomy 21: usefulness as a US marker.

PURPOSE: To determine whether the frontal lobe is disproportionately smaller than normal in second-trimester fetuses with Down syndrome by using prenatal ultrasonographic (US) measurements of the frontothalamic distance (FTD). MATERIALS AND METHODS: The FTD, measured from the inner table of the frontal bone to the posterior margin of the thalamus, was measured in 43 fetuses (mean gestational age, 17.2 weeks +/- 1.3 [standard deviation]; range, 15.0-20.4 weeks) with chromosomally proved trisomy 21 and in 160 chromosomally normal fetuses (mean gestational age, 17.1 weeks +/- 1.5; range, 14.5-22.5 weeks). Other cranial biometric ratios also were calculated. RESULTS: The FTD was best predicted from the estimated gestational age (EGA) in the euploid population with the quadratic equation FTD = -0.0120 x EGA2 + 0.6917 x EGA - 5.2349 (R2 = .731) or from the biparietal diameter (BPD) with the linear equation FTD = 0.6837 x BPD + 0.5525 (R2 = .731). If an observed-to-expected ratio of 0.84 is used as a cutoff sign to screen for trisomy 21, a sensitivity of 16%, specificity of 97%, odds ratio of 6.03 (95% confidence interval, 1.81, 20.1), and relative risk of 5.98 are achieved. CONCLUSION: The frontal lobe is statistically significantly smaller in fetuses with trisomy 21. US measurement of the FTD may prove to be a useful adjunctive screening tool if used with other markers for Down syndrome.

Down Syndrome↗

An analysis of meiotic pairing in trisomy 21 oocytes using fluorescent in situ hybridization.

We report the use of chromosome 21-specific painting probes to analyze early stages of oogenesis in nine trisomy 21 fetuses. The proportion of cells in zygotene and pachytene in the trisomic ovaries ranged from 8 to 70% with a mean of 42% +/- 19 while the comparable values of euploid specimens ranged from 34 to 90% with a mean of 65% +/- 19. The low proportion of pairing cells may be the basis for the ovarian dysgenesis observed in some trisomy infants. Five percent of trisomic pachytene cells exhibited complete asynapsis which is an order of magnitude higher than that observed in euploid cells. A large fraction of the asynaptic cells were atretic which is consistent with the hypothesis of meiotic pairing as a signal for atresia. In addition, the asynaptic cells exhibited asynapsis of chromosomes other than 21, which we interpret as an interchromosomal effect of trisomy 21.

Chromosomes, Human, Pair 21↗

The prune-belly syndrome: a new and simplified technique of abdominal wall reconstruction.

PURPOSE: Various techniques of reconstruction have been developed to improve the cosmetic and functional status of the abdominal wall in the prune-belly syndrome. We describe a new extraperitoneal plication technique of abdominoplasty that is simplified in comparison to other established procedures in that it obviates the need for a fascial incision and/or entrance into the peritoneal cavity in patients who do not require a concurrent intra-abdominal procedure. MATERIALS AND METHODS: Since 1980 this technique of abdominoplasty has been performed in 13 patients 9 months to 11 years old (mean age 3.8) at 2 institutions. Seven patients underwent surgery before age 2.5 years. Abdominal wall reconstruction was performed as an isolated extraperitoneal procedure in 5 patients, while 8 had concomitant procedures performed with the abdominoplasty, including bilateral Fowler-Stephens orchiopexy in 7, ureteral reconstruction/reimplantation in 5, excision of urachal diverticulum or cyst in 2, reduction cystoplasty in 1 and Tenckhoff catheter placement in 1. RESULTS: In all cases the cosmetic result was excellent and satisfactory to patients, parents and surgeons. Since the first procedure was performed 17 years ago, only 1 patient has returned with abdominal wall laxity or bulging in the area of repair. CONCLUSIONS: Our method of abdominal wall reconstruction in the prune-belly syndrome produces a cosmetically excellent and durable result. In contrast to other techniques of abdominoplasty, the need for a fascial incision and/or entrance into the peritoneal cavity is avoided. We believe that this modified procedure offers distinct technical and anatomical advantages over other existing techniques.

Abdominal Muscles↗

Captopril (an inhibitor of angiotensin converting enzyme) inhibits obstructive changes in the neonatal rabbit bladder.

OBJECTIVES: To investigate whether angiotensin II has a role in the regulation of bladder smooth muscle growth and function, we developed a model of bladder neck obstruction (BNO) in the neonatal rabbit and investigated the effect of captopril (angiotensin converting enzyme inhibitor) on the obstructive changes in the developing bladder. METHODS: Partial BNO was induced in a group of 2-day-old rabbits (n = 8) by placing a loose 2-0 silk ligature around the vesicourethral junction. A second group of rabbits subjected to the identical partial BNO procedure (n = 8) was given captopril (1 mg/kg/day). Twelve days postobstruction, bladders from these animals, along with paired controls (n = 8), were harvested and assayed for total protein, DNA, and collagen content. RESULTS: Partial BNO resulted in a 170% increase in wet weight (P < 0.05), 132% increase in protein/deoxyribonucleic acid (DNA) ratio (P < 0.05), 75% increase in total DNA (P < 0.05), and 115% increase in total collagen (P < 0.05). When compared with obstructed animals, captopril administration significantly inhibited the increase in total DNA (P < 0.05) and reduced the amount of total collagen (P = 0.054). Examination of histology specimens demonstrated that captopril inhibited the serosal hyperplasia and collagen deposition associated with obstruction. CONCLUSIONS: These data demonstrate that captopril partially inhibits the changes in the neonatal rabbit bladder associated with obstruction, supporting the hypothesis that angiotensin II is involved in the regulation of bladder smooth muscle growth and collagen production.

Angiotensin-Converting Enzyme Inhibitors↗

Urine levels of transforming growth factor-beta 1 in children with ureteropelvic junction obstruction.

OBJECTIVES: To determine if there are measurable quantities of transforming growth factor-beta 1 (TGF-beta 1) in the urine of children with either normal or pathologic conditions of the urinary tract, specifically vesicoureteral reflux (VUR) and ureteropelvic junction obstruction (UPJO). We also sought to determine if the urine TGF-beta level could distinguish between renal obstruction and no obstruction. METHODS: Preoperative bladder urine from consecutive patients undergoing pyeloplasty (UPJO group; n = 13), ureteral reimplantation (VUR group; n = 11), or circumcision/orchiopexy (control group; n = 19) as well as urine from the renal pelvis of the UPJO group was collected. The urine level of TGF-beta 1 was measured using a quantitative sandwich enzyme immunoassay technique. RESULTS: Urine level of TGF-beta 1 was detected in each group: control (26.6 +/- 6.3 pg/mL), reflux (22.1 +/- 9.6), UPJO-pelvic urine (82.4 +/- 19.3), UPJO-bladder urine (31.2 +/- 8.2). The urine TGF-beta 1 concentration in pelvic urine in the UPJO group was significantly higher than that in bladder urine in children in the UPJO group (p = 0.03). TGF-beta 1 concentrations were similar from the bladder of children in all three study groups (p = NS). CONCLUSIONS: Urine TGF-beta 1 is detectable in children with normal and pathologic urinary tracts. The level of this urine marker is elevated in the renal pelvis of children with UPJO compared to the level in the bladder of either obstructed or nonobstructed upper urinary tracts.

Biomarkers↗

The effect of angiotensin converting enzyme inhibition and angiotensin II receptor antagonism on obstructed rat bladder.

PURPOSE: Others have demonstrated that inhibition of angiotensin II production partially ameliorates obstructive changes in the neonatal rabbit bladder. We examined the effect of angiotensin II converting enzyme inhibition and receptor antagonism on the obstructed rat bladder. MATERIALS AND METHODS: Three groups of animals were investigated. Partial bladder neck obstruction was created in 23 rats by placing a 2-zero silk ligature around the vesicourethral junction. Eight rats were given untreated tap water, 9 were given water supplemented with 50 mg./kg. of the angiotensin-converting enzyme inhibitor captopril and 6 were given water with 30 mg./kg. of the angiotensin II subtype AT1 receptor antagonist losartan potassium. Eight unobstructed rats served as controls. After 2 weeks of partial outlet obstruction the animals were sacrificed and bladders were harvested. Routine histological evaluation and assays for total protein, deoxyribonucleic acid and collagen content were performed. RESULTS: Histological evaluation revealed that administration of captopril or losartan potassium resulted in a mild decrease in the degree of obstructive bladder changes. Biochemically neither captopril nor losartan potassium caused a significant decrease in the amount of total deoxyribonucleic acid, protein or collagen content per bladder compared to untreated obstructed bladders. CONCLUSIONS: In contrast to previous studies in neonatal rabbits, neither captopril nor losartan potassium significantly ameliorated the histological or biochemical features of partial bladder outlet obstruction in the rat. Further investigation is necessary into species specific differences to understand better the role that angiotensin II may have in mediating the bladder changes of experimentally induced obstruction.

Angiotensin Receptor Antagonists↗

Surgical versus endoscopic correction of vesicoureteral reflux in children with neurogenic bladder dysfunction.

PURPOSE: We attempted to compare the efficacy of subureteral polytetrafluoroethylene injection and ureteral reimplantation for treating vesicoureteral reflux in children with neurogenic bladder dysfunction. MATERIALS AND METHODS: We retrospectively studied the records of all children with neurogenic bladder dysfunction and reflux into single collecting systems treated with cross-trigonal ureteroneocystostomy or subureteral polytetrafluoroethylene injection. Followup cystography was performed 2 months postoperatively and ultrasound was done twice yearly thereafter. Urodynamic data were evaluated when available. Success was defined as complete eradication of reflux. Data were stratified by procedure, patient sex, grade and laterality of reflux, and the presence of unilateral or bilateral reflux, and then compared using chi-square analysis. RESULTS: Of 85 patients (118 ureters) identified followup data were available in 95%. Subureteral polytetrafluoroethylene injection and ureteroneocystostomy were done on 60 and 47 ureters, respectively. Both groups were similar in mean patient age, followup and preoperative degree of reflux. Success rates after ureteroneocystostomy and a single injection were 84.3 versus 56.7%. The cumulative success rate of subureteral polytetrafluoroethylene injection was 61% after a second injection. The success rate of ureteroneocystostomy was significantly greater than that of injection (p = 0.02). Reflux resolved in all patients in whom injection failed and who underwent secondary reimplantation. Successful ureteroneocystostomy was unrelated to patient sex, reflux grade or laterality, or bilateral versus unilateral reflux. Subureteral polytetrafluoroethylene injection was more likely to fail in higher grades of reflux (p = 0.03) but success was otherwise unrelated to other parameters. Failure to correct reflux was unrelated to urodynamic findings. CONCLUSIONS: Primary open ureteral reimplantation is more effective than subureteral polytetrafluoroethylene injection for correcting reflux in children with neurogenic bladder dysfunction. Despite controversy related to the appropriate injectable substance, the relative technical simplicity, outpatient nature, rapid recovery and potential for successful secondary reimplantation support a role for subureteral polytetrafluoroethylene injection in managing reflux in these difficult cases.

Adolescent↗

Soft tissue sarcomas: preoperative versus postoperative radiotherapy.

External beam radiation may be given either before or after excision of a primary soft tissue sarcoma. This study was undertaken to determine whether or not the timing of radiotherapy was associated with any difference in either local control, survival, or incidence of complications. The files of 112 patients with a primary, nonmetastatic, extremity soft tissue sarcoma, treated with limb salvage surgery and irradiation were evaluated. Data regarding tumor stage, grade, site, surgical margin, dosage and timing of radiotherapy, treatment complications, disease relapse, and relapse-free survival (RFS) were analyzed. Kaplan-Meier lifetable analysis was used to determine survival estimates. There was no significant difference in the 5-year RFS between patients receiving radiotherapy (RT) preoperatively versus postoperatively; 56 +/- 15% and 67 +/- 12% (P = 0.12, Mantel-Cox), respectively. There was no significant difference in the overall survival between patients receiving RT preoperatively versus postoperatively; 75 +/- 15% and 79 +/- 11% (P = 0.94), respectively. Actuarial local control at 5 years for preoperative versus postoperative RT patients was not statistically different; 83 +/- 12% versus 91 +/- 8% (P = 0.41), respectively. Wound complications were more frequent in preoperative RT patients (31%) compared to postoperative RT patients (8%) (P = 0.0014, chi-square). Preoperative irradiation was not associated with any benefit in terms of relapse-free survival, overall survival or actuarial local control in this series. A higher incidence of major wound complications was found among patients treated with preoperative irradiation. We recommend that patients with a resectable extremity soft tissue sarcoma be treated with postoperative irradiation, reserving preoperative irradiation for those situations in which either the tumor is initially thought to be unresectable or the original tumor boundaries are obscured.

Adolescent↗

Recall in the sedated ICU patient.

The effect of sedation on ICU patient recall is uncertain. Ensuring suppression of awareness and, particularly, recall, may prevent post-ICU psychological problems. Development of ICU sedation pathways and improved neurophysiologic monitoring techniques may help clinicians provide good levels of recall suppression and sedation when they are most needed by ICU patients.

Anxiety↗

Differential effects of desflurane and halothane on peripheral airway smooth muscle.

Volatile anaesthetics have been shown to have direct relaxant effects on airway smooth muscle. We have examined the effects of 0.9, 1.9, and 2.8 dog MAC of desflurane and halothane on isolated proximal and distal canine airways precontracted with acetylcholine. The proximal and distal airway smooth muscle relaxed with increasing concentration of each anaesthetic in a dose-related manner. Desflurane had a greater relaxant effect than halothane on the proximal airway only at 2.8 MAC. Desflurane relaxed the distal airway to a greater extent than halothane at 1.9 and 2.8 MAC. The distal airway smooth muscle was more sensitive to volatile anaesthetics than the proximal airway smooth muscle with either halothane or desflurane at all concentrations tested. This effect may be a result of differences in cartilage content, myosin content, epithelium-dependent effects, receptor density, myofilament sensitivity to Ca2+, sarcoplasmic reticulum Ca2+ control, or ionic fluxes in the proximal airway compared with the distal airway. The increased sensitivity of airway smooth muscle to desflurane compared with halothane is not known but may be related to possible differences in the effects of Ca2+ homeostasis.

Acetylcholine↗

Direct relaxant effects of intravenous anesthetics on airway smooth muscle.

Ketamine, at concentrations achieved with the usual clinical doses, has a direct relaxant effect on airway smooth muscle (ASM). This study investigates the dose-dependent direct relaxation effects of midazolam and propofol on both proximal and distal ASM compared with ketamine. The proximal and distal airways were dissected from eight mongrel dogs and cut into 2-mm rings. The rings were attached to pressure transducers and equilibrated in a Krebs-Ringer bicarbonate bath kept at 37 degrees C, pH 7.4, CO2 37 mm Hg, and PaO2 > 100 mm Hg. Optimal length was determined, a dose-response curve to acetylcholine was established, and the 50% effective dose (ED50) of acetylcholine was calculated. Ketamine, midazolam, or propofol were given in random order to each ring preconstricted with ED50 of acetylcholine in cumulative log incremental doses from 10(-6) to 10(-4) M. Relaxation response was the tension during anesthetic equilibrium, expressed as a percentage of the tension from ED50 of acetylcholine. The drug vehicles were tested for their effects on the ASM. No bronchorelaxation was seen with any of the intravenous anesthetics at 10(-6) M. Ketamine 10(-5) M produced at 17.9% +/- 2.1% relaxation in the distal ASM but had no effect on the proximal ASM. Neither propofol nor midazolam affected the ASM at 10(-5) M. The distal ASM was significantly (P < 0.005) more sensitive to 10(-4) M of all three drugs compared with the proximal ASM. In the proximal ASM, 10(-4) M of ketamine, midazolam and propofol reduced ASM tension by 14.9% +/- 4.4%, 19.0% +/-8.8%, and 14.7% +/- 5.5%, respectively, versus 36.4% +/- 3.2%, 58.6% +/- 6.1%, and 64.4% +/- 9.0% in the distal ASM. The drug vehicles had no effect on the ASM. We conclude that ketamine, midazolam, and propofol have direct relaxant effects on ASM. All three intravenous anesthetics have a greater direct relaxant effect on distal ASM than on proximal ASM. Only ketamine showed significant direct bronchorelaxing effects at concentrations that are likely to be achieved with the usual clinical dosing patterns.

Acetylcholine↗

Angiotensin II and basic fibroblast growth factor induce neonatal bladder stromal cell mitogenesis.

PURPOSE: Our aims were to establish primary stromal cell cultures from the neonatal rabbit bladder and investigate the potential mitogenic effects of angiotensin II and basic fibroblast growth factor on these cells. MATERIALS AND METHODS: Primary bladder stromal cell cultures were obtained from 3-day-old rabbits, plated at a density of 3 x 10(4) cells per ml. and allowed to grow for 24 hours. Subconfluent cells were growth arrested in serum deficient (0.25% newborn calf serum) or serum-free media for 24 hours and then stimulated with 10(-7) M. angiotensin II or 10 ng./ml. basic fibroblast growth factor for an additional 48 hours. Cell counts and [3H] thymidine incorporation were done to measure cellular proliferation and deoxyribonucleic acid synthesis. RESULTS: Angiotensin II and basic fibroblast growth factor each stimulated neonatal bladder stromal cell proliferation and [3H] thymidine incorporation under serum deficient conditions. Angiotensin II provoked an average 26% increase in cell number (p < 0.01) and 35% increase in [3H] thymidine incorporation (p < 0.01) compared to control values. Basic fibroblast growth factor was an even more potent mitogen with a 47% increase in cell number (p < 0.01) and 180% increase in [3H] thymidine incorporation (p < 0.01) compared to controls. In contrast, angiotensin II and basic fibroblast growth factor each failed to have significant stimulatory effects under serum-free conditions. CONCLUSIONS: Angiotensin II and basic fibroblast growth factor induce a mitogenic response to neonatal bladder stromal cells in vitro. These mitogenic effects require the presence of serum factors. Whether angiotensin II and basic fibroblast growth factor are involved in the in vivo regulation of bladder growth associated with obstructive uropathy requires further investigation.

Angiotensin II↗