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Biomedical subjects

R Chung

Publications and source records attributed to R Chung.

At least 19 recordsLinked to original sources

The laparoscopic experience of surgical graduates in the United States.

BACKGROUND: Although laparoscopic surgery has become widespread during the past decade, no systematic study of the training needs exists. To obtain guidance for planning, we analyzed the national resident operative experience during the past 8 years. METHODS: The laparoscopic experiences of all surgical residents graduating between 1994 and 2001 were subjected to regression analysis. The laparoscopic volume of each trainee and change in ratio of laparoscopic/open operation over time were used to estimate the growth of individual laparoscopic operations in training programs. RESULTS: Laparoscopic surgery constituted only 5.7% of a trainee's total surgical experience in 1994, but comprised 13% by 2001. A resident completing training in 1994 performed 53 laparoscopic operations, of which 79% (42) were cholecystectomies. By 2001, a graduate performed 126 laparoscopic operations, of which 68% (86) were cholecystectomies. During the interim, most laparoscopic operations exhibited growth. Trainee experience in some newer operations has also increased steadily but at a much slower rate. CONCLUSIONS: This descriptive statistical survey of training experience yields a comprehensive picture of the laparoscopic capability of the young surgeon. The growth potential of some newer operations has also been measured. Using these data, guidelines can be drawn as to which operation programs should focus resources on training residents. Since competence depends on exposure, residency training alone may not provide sufficient depth to allow recent graduates to perform the newer operations independently.

Adult↗

Murine leukemia virus in organs of senescence-prone and -resistant mouse strains.

A series of inbred strains of mice have been developed that are either prone (SAMP) or resistant (SAMR) to accelerated senescence. All of these strains originated from an inadvertent cross or crosses between the AKR/J mouse strain and an unknown strain(s). The characteristics of the nine senescence-prone lines differ, with all strains showing generalized aspects of accelerated aging but with each line having a specific aging-related change that is emphasized, e.g. learning and memory deficits, osteoporosis and senile amyloidosis. The senescence-resistant strains have normal patterns of aging and do not show the specific aging-related changes seen in SAMP strains. The fact that AKR mice have high levels of endogenous, ecotropic murine leukemia virus (MuLV) prompted an examination of the expression levels of MuLV in SAM strains. Analysis of brain, spleen and thymus samples revealed that seven of nine SAMP strains had high levels of MuLV and contained the Emv11 provirus (previously termed Akv1) that encodes the predominant MuLV found in AKR mice. In contrast, none of the SAMR strains had Emv11 or significant amounts of virus. The current findings represent an initial step in determining the role of MuLV in the accelerated senescence seen in SAMP strains.

Aging↗

Hemivertebra in monozygotic twins.

STUDY DESIGN: A case report. OBJECTIVES: To report and discuss a case of thoracic hemivertebra in monozygotic twins. SUMMARY OF BACKGROUND DATA: The etiology of congenital scoliosis remains unclear. Both a genetic basis and environmental influences have been postulated. A few isolated reports of discordant spinal anomalies in twins exist. METHODS: Clinical examination and plain radiograph evaluation were performed on female monozygotic twins with congenital scoliosis secondary to thoracic hemivertebra. RESULTS: Congenital thoracic scoliosis was documented in both of a set of monozygotic twins. CONCLUSIONS: To the authors' knowledge, this is the first report of similar congenital vertebral abnormalities in identical twins in the English literature.

Diseases in Twins↗

Spinal ropivacaine for cesarean section: a dose-finding study.

BACKGROUND: The dose-response relation for spinal ropivacaine is undetermined, and there are few data available for obstetric patients. METHODS: In a prospective, randomized, double-blind investigation, the authors studied 72 patients undergoing elective cesarean delivery. An epidural catheter was placed at the L2-L3 vertebral interspace. Lumbar puncture was then performed at the L3-L4 vertebral interspace, and patients were randomized to receive a dose of spinal ropivacaine diluted to 3 ml with normal saline: 10 mg (n = 12), 15 mg (n = 20), 20 mg (n = 20), or 25 mg (n = 20). Sensory changes assessed by ice and pin prick and motor changes assessed by modified Bromage score were recorded at timed intervals. A dose was considered effective if an upper sensory level to pin prick of T7 or above was achieved and epidural supplementation was not required intraoperatively. RESULTS: Anesthesia was successful in 8.3, 45, 70, and 90% of the 10-, 15-, 20-, and 25-mg groups, respectively. A sigmoid dose-response curve and a probit log dose-response plot were obtained, and the authors determined the ED50 (95% confidence interval) to be 16.7 (14.1-18.8) mg and the ED95 (95% confidence interval) to be 26.8 (23.6-34.1) mg. Duration of sensory and motor block and degree of motor block, but not onset of anesthesia, were positively related to dose. CONCLUSIONS: The ED50 and estimated ED95 for spinal ropivacaine were 16.7 and 26.8 mg, respectively. Ropivacaine is a suitable agent for spinal anesthesia for cesarean delivery.

Adult↗

3-D reconstruction from tomographic data using 2-D active contours.

Reconstructing three-dimensional (3-D) shapes of structures like internal organs from tomographic data is an important problem in medical imaging. Various forms of the deformable surface model have been proposed to tackle it, but they are either computationally expensive or limited to tubular shapes. In this paper a 3-D reconstruction mechanism that requires only 2-D deformations is proposed. Advantages of the proposed model include that it is conformable to any 3-D shape, efficient, and highly parallelizable. Most importantly, it requires from the user an initial 2-D contour on only one of the tomograph slices to start with. Experimental results are shown to illustrate the performance of the model.

Computers↗

A case controlled study of laparoscopic incisional hernia repair.

BACKGROUND: Although the feasibility of laparoscopic incisional herniorrhaphy has been demonstrated, its advantages over the open technique are still unproven. METHODS: Fourteen consecutive laparoscopic incisional hernia repairs were compared with 14 matched controls of the open repair done by the same surgeon at the same institution. The controls were selected by a medical record technician not connected with the study. The cases were selected to match diagnoses, ASA status, and body weight as closely as possible. The outcome data for operating time, blood loss, hospitalization, resumption of oral intake, and postoperative complications were analyzed for statistically significant differences. RESULTS: There was no statistical difference between the two groups in the parameters of blood loss, hospital days, or days to oral intake. The laparoscopic operation took 40% longer. Similar complications were seen in both groups. No mortality or early recurrences occurred in either group. CONCLUSION: Laparoscopic incisional hernia repair of at least moderate complexity had no demonstrable advantage over the open repair in the present study.

Aged↗

Lack of serological evidence for Mycoplasma fermentans infection in army Gulf War veterans: a large scale case-control study.

Mycoplasma firmentans is suspected in the development of 'Gulf War illness' in veterans of Operation Desert Storm. We conducted a matched case-control study for the prevalence of M. firmentans-specific antibodies before and after the operation, as well as seroconversion rates in veterans with and without complaints of 'Gulf War illness'. Cases consisted of Gulf War veterans, who complained of various illnesses and were enrolled in the second phase of the health evaluation by the Army Comprehensive Clinical Examination Program (CCEP). Controls were selected from Gulf War veterans who did not participate in the registry and did not request a health evaluation by the CCEP. Before operation deployment, 34 out of 718 of the cases (48%) and 116 out of 2233 of the controls (5.2%) tested positive for M. fermentans-specific antibodies. There was no difference in rates of seroconversion between cases and controls (1.1 vs. 1.2%) to M. fermentans during Operation Desert Storm. Thus, there is no serological evidence that suggests infectionby M. fermentans is associated with development of 'Gulf War illness'.

Adolescent↗

A method of teaching clinical research in a community hospital residency program.

BACKGROUND: To provide clinical research experience in community hospital programs, we integrated research training with the daily work of surgical residency. METHODS: Teaching conferences and daily care of patients served as a source of projects. Emphasizing team work, high-yield projects are assigned to principal resident investigators, who lead a project team. Regular meetings with the faculty provides guidance and supervision, working to meet an abstract deadline. RESULTS: Over a 3-year period, 10 of 16 trainees participated in at least one project. Thirteen projects were presented at national meetings and 13 articles (including 6 from presentations) were published. Three projects were abandoned for lack of progress, and 5 manuscripts have been rejected. CONCLUSION: The integrated program trains multiple residents/projects with low requirements in space and funding, but high demands of organization and faculty time.

Curriculum↗

Febrile response after knee and hip arthroplasty.

Documentation of the normal fever response after total knee and hip replacement is important to avoid an unnecessary workup for sepsis, and to provide justification for early discharge (dictated by the current medical reimbursement climate) despite persistent postoperative fever. One hundred patients who underwent total knee arthroplasty and 100 patients who underwent total hip arthroplasty were reviewed, several of whom had extensive sepsis workups for evaluation of postoperative fever. No patient in this series had a documented joint infection. All patients were treated with warfarin for deep vein thombrosis prophylaxis. All patients used incentive spirometry and were started on ambulation training on postoperative Day 1. All were given antibiotic prophylaxis for 48 hours. The maximum daily postoperative temperature occurred in most patients on postoperative Day 1 and gradually leveled off toward normal by postoperative Day 5. Only one patient had a maximum temperature on postoperative Day 4 that was greater than that on postoperative Day 3. Patients undergoing revision procedures tended to have a more pronounced febrile response, but the differences were not statistically significant. No significant differences were seen between patients who had epidural anesthesia and patients who had general anesthesia. Seventeen patients had postoperative chest radiographs for evaluation of fever. None had significant atelectasis. The presence of a positive urine culture had no effect on the fever response, with most positive results being identified after the fever had returned toward normal. Postoperative fever after total joint arthroplasty is a normal inflammatory response. A workup for sepsis is not indicated in the perioperative period unless corroborating signs or symptoms are present. Early discharge is appropriate if the febrile response is decreasing progressively.

Anesthesia, Epidural↗

Ultrasound characterization by stable statistical patterns.

It is shown that automated characterization of ultrasound images can be achieved effectively if the images are confined to single internal organs. The ultrasound image of a particular organ gives statistical textures of its structures, which are consistent with stable patterns. Analysis of these patterns leads to the construction, from a few statistical parameters, of a fast and effective algorithm to characterize these ultrasound images. A small training set is adequate. A similar approach may be used to detect tumour sites from liver ultrasonograms. The algorithms are implemented on an IBM-compatible personal computer for future incorporation into existing ultrasound machines.

Algorithms↗

Once weekly azithromycin therapy for prevention of Mycobacterium avium complex infection in patients with AIDS: a randomized, double-blind, placebo-controlled multicenter trial.

We conducted a randomized, double-blind, placebo-controlled multicenter trial of azithromycin (1,200 mg once weekly) for the prevention of Mycobacterium avium complex (MAC) infection in patients with AIDS and a CD4 cell count of < 100/mm3. In an intent-to-treat analysis through the end of therapy plus 30 days, nine (10.6%) of 85 azithromycin recipients and 22 (24.7%) of 89 placebo recipients developed MAC infection (hazard ratio, 0.34; P = .004). There was no difference in the ranges of minimal inhibitory concentrations of either clarithromycin or azithromycin for the five breakthrough (first) MAC isolates from the azithromycin group and the 18 breakthrough MAC isolates from the placebo group. Of the 76 patients who died during the study, four (10.5%) of 38 azithromycin recipients and 12 (31.6%) of 38 placebo recipients had a MAC infection followed by death (P = .025). For deaths due to all causes, there was no difference in time to death or number of deaths between the two groups. Episodes of non-MAC bacterial infection per 100 patient years occurred in 43 azithromycin recipients and 88 placebo recipients (relative risk, 0.49; 95% confidence interval, 0.33-0.73). The most common toxic effect noted during the study was gastrointestinal, reported by 78.9% of azithromycin recipients and 27.5% of placebo recipients. Azithromycin given once weekly is safe and effective in preventing disseminated MAC infection, death due to MAC infection, and respiratory tract infections in patients with AIDS and CD4 cell counts of < 100/mm3.

AIDS-Related Opportunistic Infections↗

Amino-terminal charge affects the periplasmic accumulation of recombinant heregulin/EGF hybrids exported using the Escherichia coli alkaline phosphatase signal sequence.

An Escherichia coli expression system that exploits the bacterial alkaline phosphatase (PhoA) signal sequence to translocate recombinant human epidermal growth factor (hEGF) to the periplasm was used to evaluate how changes in the composition and sequence of amino acids near the PhoA-hEGF junction influence the periplasmic accumulation of recombinant protein. A series of chimeric structural genes was generated by in vitro replacement of hEGF sequence with analogous segments from the EGF-like domain of human heregulin (HRG), significantly altering the electrostatic character of the amino-terminal region of the mature protein. Quantitation of HRG/EGF protein in E. coli periplasmic extracts, by RP-HPLC, showed a fourfold decrease after one of two acidic residues located in the amino-terminal region of the mature hEGF, near the PhoA junction, was replaced. An additional threefold decrease was observed when the second acidic residue was replaced with a positively charged lysine. Further extension of the amino-terminal HRG sequence, beyond the first six residues, resulted in net neutralization of a more distant EGF acidic residue with no additional effect on protein yield. The importance of having a negatively charged group in the amino-terminal region of the mature protein was confirmed when insertion of an aspartic acid near the amino-terminus of two poorly expressed hybrid protein sequences resulted in a five- to eightfold increase in their recovery from the periplasm. This study demonstrates the importance of having negatively charged residues near the fusion junction of recombinant proteins expressed in E. coli using the PhoA signal sequence for protein export.

Alkaline Phosphatase↗

A case-controlled study of laparoscopic splenectomy.

BACKGROUND: The utility of laparoscopic splenectomy (LS) has not been tested in general surgical practice. This is a case controlled study comparing the clinical results and economics of L.S. and open splenectomy (OS) in a community hospital. METHODS: The outcome of a series of 15 patients undergoing LS were compared to 15 patients undergoing OS matched for diagnosis, splenic weight, age, and main co-morbidites, selected by a person independent of the project. RESULTS: In both series, the indications were immune thrombocytopenic purpura, hemolytic anemias, hairy cell leukemia and, staging for Hodgkin's disease. LS resulted in shorter hospitalization (2.3 vs 8.8 days) with fewer postoperative complications. However, the operation was 1.7 times as long, and the operating room charge 2.9 times as high, so that the total cost of LS ($18,015) was greater than that for OS ($14,524). If the cost of treatment of complications is included, then the total is the same for both at our institutions. CONCLUSION: Except for a few indications not addressed in this study, LS can be used in lieu of OS.

Case-Control Studies↗

Second-look laparoscopy for visceral ischemia facilitated by preinstalled ports.

Much of the information of a second-look laparotomy can be obtained by a second-look laparoscopy. We describe the strategy and technique of installing laparoscopy ports at the end of the primary laparotomy for visceral ischemia to facilitate a second-look laparoscopy in the ensuing 72 hours. The advantages and limitations are illustrated by three cases. The primary advantage appears to be that when second-look laparoscopy can be accomplished at a minimal cost, much of the inhibition to use it is removed. However, more experience is necessary before the procedure can be used to replace laparotomy.

Abdominal Pain↗

Modulation of the function of human MDR1 P-glycoprotein by the antimalarial drug mefloquine.

MDR1 P-glycoprotein in membranes of human tumor cells of the CEM/VBL100 line was selectively labelled using photoreactive analogs of verapamil, N-(p-azido-3-[125I]salicyl)amino-verapamil ([125I]ASA-V) and prazosin, 2-[4-(4-azido-3-[125I]iodobenzoyl)piperazin-1-yl]4 -amino-6,7-dimethoxyyquinazoline ([125I]ASA-P). Mefloquine, a quinolinemethanol antimalarial drug, was shown to inhibit the labelling of P-glycoprotein with an efficiency similar to that for verapamil, a known chemosensitizer. By contrast, chloroquine competed poorly for the binding site on P-glycoprotein. Mefloquine also inhibited the functional activity of P-glycoprotein. It decreased the rates of extrusion of [3H]vinblastine and the fluorescent dyes, fluo-3 acetomethoxy ester and rhodamine 123, from drug-resistant cells and decreased the level of resistance of these cells to vinblastine. The ability of mefloquine to inhibit P-glycoprotein function may be involved in the neurotoxic side-effects occasionally associated with the use of mefloquine as an antimalarial drug.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

Increases in intra-abdominal pressure affect pulmonary compliance.

OBJECTIVES: To determine the effect of increased intra-abdominal pressure (IAP) on pulmonary compliance and to determine an effective means to measure IAP. DESIGN: A prospective study. SETTING: An urban tertiary care hospital. PATIENTS: Twenty-six adult patients undergoing laparoscopic cholecystectomy. INTERVENTIONS: Intra-operative management of laparoscopic cholecystectomy requiring endotracheal intubation with general anesthesia, nasogastric and urinary bladder catheters, and position changes. Additional interventions included use of a rectal manometer and a respiratory pressure module inserted within the ventilator circuit. MAIN OUTCOME MEASURES: Correlation of changes in IAP with changes in dynamic pulmonary compliance, measured as tidal volume/(end inspiratory pressure--end expiratory pressure) and comparison of three different measurement techniques (bladder, rectal, and gastric) with a standard technique (insufflation pressure) in three different positions (supine, Trendelenburg's, and reverse Trendelenburg's). RESULTS: Compliance was significantly related to insufflation pressure (P < .001) by analysis of variance. In the gas insufflation model, the mean increment in bladder pressure reflected most closely the IAP increment in the supine position (5.7 vs 6 mm Hg) but not in the Trendelenburg (2.1 vs 6 mm Hg) and reverse Trendelenburg positions (3.4 vs 6 mm Hg). Rectal and gastric pressures were also position dependent and technically less reliable. CONCLUSIONS: Increased IAP has a major influence on pulmonary compliance (50% decrease at 16 mm Hg). Measurements of IAP by intraorgan manometry are position dependent and may not accurately reflect the intraperitoneal pressure.

Abdomen↗

Reduction in tissue blood flow in J-shaped pelvic ileal reservoirs.

PURPOSE: This study sought to evaluate tissue blood flow during J-shaped ileal reservoir construction. METHODS: Using laser Doppler flowmetry, tissue blood flow was measured at various locations in J-shaped ileal reservoirs constructed in 10 dogs before pouch-anal anastomosis. For 12 weeks postoperatively, animals were assessed for clinical complications. In another five dogs, tissue blood flow was measured at various stages of J-pouch construction. RESULTS: Tissue blood flow in the reservoir was reduced and was lowest at the "apex" of the "J", the site of clinical stricture in one animal. During reservoir construction, longitudinal enterotomy was associated with the greatest reduction in tissue blood flow. Lowest blood flow in the reservoir was at the site of the intended pouch-anal anastomosis (11.5 +/- 1.6 ml/100 g/min vs. 43.4 +/- 3.4 ml/100 g/min (controls); P < 0.05). CONCLUSIONS: Operative maneuvers of J-shaped ileal reservoir construction, particularly longitudinal enterotomy, significantly reduce tissue perfusion in the involved bowel segment. Tissue blood flow in the pouch is lowest at the site of intended pouch-anal anastomosis, and this may contribute to development of complications seen clinically.

Anal Canal↗