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Biomedical subjects

L T Nguyen

Publications and source records attributed to L T Nguyen.

At least 91 records · Page 5Linked to original sources
PubMed1994

Aortoesophageal fistula: congenital and acquired causes.

Aortoesophageal fistula (AEF) is a rare but frequently lethal cause of upper gastrointestinal bleeding. This is a report of the authors' experience with four cases--two from congenital and two from acquired causes. A review of the pediatric cases reported in the literature is included. The mortality from AEF is high, and can be decreased in two ways. AEF can be prevented by avoiding prolonged nasogastric intubation in patients with known vascular rings, and by promptly removing esophageal foreign bodies and promptly treating periesophageal abscesses. Once an AEF occurs, it presents with typical large-herald upper gastrointestinal bleeding of bright red blood, and cardiovascular collapse. Recognition of this pattern, with vigorous resuscitation and aggressive surgical management, will improve the survival rate.

Aortic Diseases↗
PubMed1994

Gastroesophageal reflux associated with large diaphragmatic hernias.

Extracorporeal membrane oxygenation (ECMO) support has improved the outlook for some infants who have large diaphragmatic hernias (CDH). This has resulted in a subset of survivors of CDH with typically larger defects, more severe pulmonary hypoplasia, and more associated pathologies. This report describes the authors' experience with gastroesophageal reflux in patients with large diaphragmatic hernias who require ECMO. Contrary to previous reports, this reflux was severe and intractable. There appears to be a component of associated gastric dysmotility. In treating this reflux, medical therapy and anterior fundoplication were not successful, and Nissen fundoplication combined with pyloroplasty was required to control reflux and to allow gastric feeding. On the basis of the authors' experience, it is recommended that patients who have gastroesophageal reflux after CDH repair, for whom medical management has failed, be managed aggressively by surgery, with early Nissen fundoplication, and pyloroplasty and insertion of a gastric feeding tube.

Animals↗
PubMed1992

The major form of protein tyrosine kinase in the dog prostate is expressed by a 50 kDa polypeptide.

We have already reported that the protein tyrosine kinase (PTK) activity in the dog prostate is distributed in cytosolic (75%) and particulate (Triton X-100-solubilized) fractions and that upon gel filtration, both PTKs migrate as entities of Mr 44,000 [(1991) Biochem. Cell. Biol. 69, 146-153]. Herein we demonstrate by immunoprecipitation with anti-phosphotyrosine antibodies that the soluble PTK has the ability to undergo self-phosphorylation. In addition, the polypeptide responsible for that enzymatic activity has been identified by 2 approaches: (1) a two-dimensional electrophoresis, in which the first dimension performed in non-denaturing conditions allowed the localization of the native enzyme, while the second dimension (SDS-PAGE) permitted the analysis of alkali-resistant phosphoproteins corresponding to the activity; (2) protein renaturation after SDS-PAGE followed by in situ phosphorylation (with [gamma-32P]ATP) of polyGT electrophoresed together with the enzyme preparation; the exclusive presence of the radiolabeled phosphotyrosine in the renatured protein confirmed its enzymatic nature. Using these methods, the major form of PTK in the dog prostate was shown to be expressed by a 50 kDa polypeptide which possesses autophosphorylation sites and which is present in the cytosol as an active monomer.

Animals↗
PubMed1992

Congenital urethral fistula with normal anus: a report of two cases.

Congenital rectourethral or anourethral fistulae without imperforate anus in males are rare, representing less than 1% of anorectal malformations. We report our experience with two males with "N type" urethral fistulae. One, a 5-year-old boy, presented with recurrent urinary tract infections (UTIs) and passage of urine per anus. Investigations included a voiding cystourethrogram (VCUG), which demonstrated a fistula from the urethra to the anus. On physical examination, a small perianal opening was noted just outside the anus, which drained a small amount of urine after voiding. The fistula was excised via a perineal approach. The second patient is a 5-year-old boy with a long history of recurrent UTI requiring multiple hospitalizations since the newborn period. Chronic renal failure developed as a complication of repeated urinary tract infections. Investigations showed a single hydronephrotic pelvic kidney and a small bladder. He underwent numerous diagnostic and reconstructive procedures including cystoscopy and augmentation cystoplasty. Recurrent infections continued and an N type anourethral fistula was eventually diagnosed. The fistula was located between the anal canal and the membranous urethra. An anterior perineal approach was also used. Both fistulae were easily located, and reconstructive surgery of the urethra was not required. Postoperative VCUGs in both patients were normal. They have been free of infection with normal urinary continence since resection of the fistula. Congenital N type anourethral fistulae are rare, but should be considered in cases of recurrent urinary tract infections. The diagnosis may be missed by endoscopic procedures, but VCUG should demonstrate the fistulous tract.

Child, Preschool↗
PubMed1992

Effect of tray space on the accuracy of monophasic polyvinylsiloxane impressions.

The effect of tray space on the dimensional accuracy and stability of impressions made from four brands of monophasic polyvinyl siloxane material was assessed on the recovered stone casts by quantitative and qualitative methods. In general, both evaluation methods agreed that tray space and repeat pour did not affect the accuracy of the dies for individual castings. But disagreement was observed in the findings for fixed partial dentures (FPDs). Quantitative measurement of the interpreparation (IP) dimensions did suggest the possibility of a potential problem when a FPD is cast in one piece because of a significantly reduced distance between the two abutments. However, from the findings of this study it can be concluded that a rigid stock tray can be used with a monophasic polyvinyl siloxane impression material.

Analysis of Variance↗
PubMed1992

The design of a rule-based clinical event monitor in a multi-vendor hospital computing environment.

The Clinical Event Monitor (CEM) described here is a prototype system designed to explore the issues involved in building an institutional CEM that permits rapid, automated evaluation of clinical transactions and notification to clinicians of exceptional events in a multi-vendor computing environment. The CEM uses expert systems, database, and systems integration techniques. Ancillary (departmental) applications, including as Patient Registration, Laboratories, and Pharmacy have been licensed from commercial vendors. Application-to-application and application-to-database interfaces were built to mirror subsets of the ancillary patient databases into an institutional relational database (Oracle). The CEM receives registration updates via an HL7 message and evaluates data dependencies in rules via an interface to the relational database. The CEM engine was built using Nexpert, a commercially available expert system shell. Our short term goals were to: (1) build and maintain a patient census within the expert system environment via net based HL7 update broadcasts; (2) explore the data-driven features of Nexpert, (3) deliver prototype exception reports. This paper describes in general terms the design features of the CEM and in detail the features of a patient registry to NEXPERT bridge (from Oracle via HL7 structured transactions to NEXPERT) and the delivery of exception reports.

Databases, Factual↗
PubMed1991

Prostatic epithelial cells in culture: phosphorylation of protein tyrosyl residues and tyrosine protein kinase activity.

The ability of dividing canine prostatic epithelial cells in primary monolayers to phosphorylate protein tyrosyl residues was evaluated by metabolic studies performed through incorporation of [32P]-phosphate into alkali-resistant phosphoproteins and by the assay of their tyrosine protein kinase activity. The presence of sodium orthovanadate during cell incubation with [32P]-phosphate greatly enhanced the relative labelling intensity of a 44 kDa alkali-resistant phosphoprotein and the total cellular content of phosphotyrosine in proteins; in this respect, growth factors such as epidermal growth factor, insulin, and insulin-like growth factor I, and the steroids dihydrotestosterone and estradiol were inactive. When the cells were solubilized, sodium orthovanadate stimulated their tyrosine protein kinase activity and inhibited their phosphotyrosine phosphatase activity. To characterize the tyrosine protein kinase of these cultured cells, conditions for optimal activity were established using the substrate poly [Glu80Na, Tyr20]. The subcellular localization of the enzyme was determined upon cell fractionation: 88% of the kinase activity was associated with the particulate fraction and 30% of this activity was partially solubilized with 0.5% Triton X-100; this solubilization was improved to 83% in the presence of 0.25 M KCI. The enzyme directly solubilized from prostatic cells with Triton X-100 (38% of activity) mainly catalyzed the alkali-resistant phosphorylation of pp63, pp59, and pp44, which contained phosphotyrosine. These proteins were also phosphorylated by the major peak of kinase activity which was eluted at an apparent molecular weight of 300-350 kDa upon gel filtration.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Loosening of cementless femoral stems: a biomechanical analysis of immediate fixation with loading vertical, femur horizontal.

Large joint implants must have immediate fixation to be successful. Unfortunately, the magnitude and consistency of achieving this remains largely unknown. For cementless femoral components it is being increasingly appreciated that torsional loading as occurs during stair climbing or rising from a chair leads to loosening and thigh pain in some cases. A biomechanical test was developed to evaluate fixation in this position. Twelve pairs of human cadaveric femora were press-fit with an AML stem. Each femur was secured in a horizontal position, and the prosthetic head cyclically loaded in a vertically downward direction. The offset of the prosthetic head resulted in a combined torsional and compressive load being applied to the stem within the proximal femur. Loosening was found to consistently occur and rapidly accelerate when the head subsided more than 0.2 mm during 100 cycles. For the AML stem, loosening developed at loads from 62 to 171% of body weight and after as few as 800 cycles. This is within the physiologic range of normal daily activities as measured by others with instrumented prostheses. This poses a challenge to the ability of press-fit stems to tolerate torsional loads in vivo. Patients with a cementless prosthesis should be protected from torsional loading until porous ingrowth and/or bone remodelling have had time to occur. Testing the same stem in paired femora demonstrated no right vs left difference (p greater than 0.6).

Biomechanical Phenomena↗
PubMed1991

Laparoscopic cholecystectomy: a treatment option for gallbladder disease in children.

Laparoscopic cholecystectomy was performed safely in two children ages 7 and 15 years. Special considerations were required in the younger child because of the discrepancy between the length of the instruments and the size of the peritoneal cavity. Both children remained in hospital less than 24 hours and were able to resume normal diet and activity quickly. Pediatric surgeons with special training in laparoscopic surgery may want to use this treatment modality for children with biliary tract disease.

Adolescent↗
PubMed1991

Congenital adenomatoid malformation of the lung: current management and prognosis.

A retrospective 10-year review of congenital adenomatoid malformation (CAM) included 10 cases diagnosed in utero by ultrasound and 13 cases that presented postnatally. Two prenatally diagnosed cases were aborted because of associated lethal anomalies. All remaining patients underwent resection. Up to one third of all cases, whether diagnosed prenatally or postnatally, were asymptomatic. Resection is recommended to avoid respiratory distress, infection, or associated malignancy. There were 5 nonsurvivors, including 2 therapeutic abortions and 3 who died postoperatively. All had either polyhydramnios or ascites. All patients who died postoperatively had a respiratory arrest at birth and underwent immediate lobectomy. All died on the first day of life after a brief period and were found to have associated pulmonary hypoplasia. One had undergone a prenatal transthoracic cyst aspiration at 34 weeks gestation in an attempt to allow lung growth and prevent premature labor. Prenatal ultrasound findings suggestive of poor prognosis included polyhydramnios, ascites, mediastinal shift, and noncystic type III CAM. However, there is a spectrum of severity of CAM. The lesion can either regress and be asymptomatic at birth, or it can progress to cause either fetal death from hydrops or neonatal death caused by associated pulmonary hypoplasia. These findings should be considered in prenatal counseling for CAM.

Cystic Adenomatoid Malformation of Lung, Congenita↗
PubMed1991

A more than 25-year experience with end-to-end versus end-to-side repair for esophageal atresia.

End-to-end anastomosis has become the standard technique for repair of esophageal atresia with distal tracheoesophageal fistula. End-to-side anastomosis with ligation of the fistula in continuity has also been advocated. For over 25 years both methods have been used in this hospital. The purpose of this report is to compare retrospectively the results obtained with these two techniques. Between 1962 and 1988, 111 neonates underwent repair of esophageal atresia and distal tracheoesophageal fistula. 74 patients had an end-to-end repair and 37 had end-to-side anastomosis with fistula ligation, according to the surgeons' preference. There were no significant differences between the two groups with respect to preoperative variables and Waterston classification. There was a significantly increased incidence of fistula recanalization (22% v 3%, P = .003) and mortality directly related to the esophageal atresia (16% v 3%, P = .03) in the end-to-side group versus the end-to-end group. The end-to-end group had a significantly higher incidence of gastroesophageal reflux. Logistic regression analysis showed that the end-to-side repair was associated with a greater overall mortality. We conclude that the end-to-end repair appears to be a safer procedure than the end-to-side technique.

Analysis of Variance↗
PubMed1990

Mutagenesis of the a subunit of the F1F0-ATP synthase from Escherichia coli in the region of Asn-192.

Site-directed cassette mutagenesis was used to generate a series of amino acid substitutions in the a subunit of the Escherichia coli F1F0-ATP synthase. The following substitutions for Asn-192 were analyzed and shown to inhibit partially the ATP-dependent proton translocation without disrupting F1-F0 interactions: Leu, Val, Pro, Ser, Thr, and Arg. A group of multiple substitutions at residues Gln-181, Asn-184, and His-185 had no significant effect on ATP synthase function, as judged by growth yields, or by assays of ATP-dependent proton translocation, indicating that this region of the a subunit is not involved in function. Three double mutants were constructed in order to assess the independence of residues Asn-192, Glu-196, and Asn-214. Results of proton translocation assays of membranes from cells containing these double mutations are consistent with the interpretation that each of these residues is involved with proton movement, and that residues Asn-192 and Glu-196 may be coupled. Finally, the relationship between the mechanism of proton translocation by the E. coli ATP synthase and the chloroplast enzyme was probed by constructing variants of the E. coli a subunit containing several features of homologous chloroplast proteins. It was determined that these chloroplast features, in the region of Glu-196 of the E. coli a subunit,, were detrimental to ATP synthase function.

Amino Acid Sequence↗
PubMed1990

Appendicitis in children: current therapeutic recommendations.

Wound infection is the most common source of morbidity in appendicitis. Most recent pediatric series use protocols of preoperative antibiotics with aerobic and anaerobic coverage, intraoperative lavage, no peritoneal or wound drains, and continuation of antibiotics postoperatively with complicated appendicitis. There still remains controversy concerning skin closure and the duration of antibiotic therapy. We report the results of a prospective protocol followed over 2 years with 420 children. The protocol was designed to determine whether the skin could be closed primarily in all patients undergoing appendectomy. Preoperatively all patients received triple antibiotics (ampicillin, gentamicin, and clindamycin) that were continued postoperatively for two doses if there was a normal appendix or simple acute appendicitis, for at least 3 days with gangrenous appendicitis, and at least 5 days with perforated appendicitis. Antibiotics were continued if the patient remained febrile or had a white count greater than 10,000. No drains were used and the skin was closed primarily. The overall infectious complication rate was 1.0% (4/420). Among those with a normal appendix or simple acute appendicitis there were no infectious complications. Among those with gangrenous or perforated appendicitis there were 1.7% wound infections (2/117) and 1.7% intraabdominal abscesses (2/117). Duration of hospitalization was 2.1 days (range, 1 to 5 days) after simple acute appendicitis and 6.9 days (range, 3 to 40 days) after gangrenous or perforated appendicitis. These results set new standards in terms of wound management, infectious complications, and length of hospital stay.

Adolescent↗
PubMed1989

[Fixation anomaly of the duodenum. Apropos of 4 cases].

"Z"--shaped duodenum and "roller - coaster" duodenum are synonyms for malfixation of the duodenum. This rare malformation has been described recently. We report 4 cases (ages 3 months-9 years) with: --intermittent abdominal pain; --bilious vomiting; --failure to thrive. Radiologic examination of the upper gastrointestinal tract revealed a malformation of the distal duodenum (D2-D3) which presented a "Z" or "M" form and under fluoroscopy, this portion was very mobile, causing intermittent obstruction when it became kinked. All attempts of medical management have failed. At surgery, all the bands were cut, giving the duodenum a normal shape. The symptoms disappeared after surgery. Follow-up between 4 months and 3 years showed the patients were completely asymptomatic.

Child↗
PubMed1987

Bilateral Wilms' tumors: changing concepts in management.

Bilaterality is uncommon in Wilms' tumor, being present in 4% to 8% of the cases. We report the combined experience of two children's hospitals in one city over a 20-year period. We encountered nine cases of synchronous bilateral nephroblastoma (National Wilms' Tumor Study 3, stage V). Age at diagnosis ranged from 9 to 41 months (mean 23 months). There were five girls and four boys. Associated findings include nephroblastomatosis in three cases (33%), one of which also had a familial history; undescended testis in two cases; and minor anomalies in two other cases. Surgical treatment consisted of unilateral nephrectomy with contralateral partial nephrectomy or tumorectomy in six cases, nephrectomy with contralateral biopsy only in two cases, and the other patient had bilateral biopsies initially, followed at a later date by partial nephrectomy on one side. All patients received chemotherapy; actinomycin D (AMD) only was used in the oldest case, vincristine and AMD in five cases, to which was added cyclophosphamide in one case and adriamycin in two. Seven patients received radiation therapy. Seven out of the nine patients survived more than 2 years (77%); five are well, off chemotherapy, with no evidence of disease from 4 to 11 years after diagnosis. Two patients suffered from chronic renal failure and one died from complications after renal transplantation more than 19 years after diagnosis. The two patients who died from their disease presented with more advanced tumor. Therefore, the agressiveness of multimodal therapy can be tailored according to stage and histology, and effective chemotherapy allows maximal preservation of renal parenchyma in patients with stage I and II tumors.

Child, Preschool↗