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Biomedical subjects

K T Nguyen

Publications and source records attributed to K T Nguyen.

At least 55 records · Page 3Linked to original sources
PubMed1995

Spontaneous and evoked dysesthesias observed in the rat after spinal cordotomies.

Thirty-six rats have received surgical spinal cord lesions, 7 at a thoracic and 29 at a cervical level. More than 70% of rats with lesions which involved the lateral column (spinothalamic tract) developed spontaneous dysesthesias in the contralateral limb. Only high cervical (C1-C2) lateral column lesions were followed frequently by forelimb signs. Lesions restricted to the dorsal columns were not followed by dysesthesias.

Animals↗
PubMed1994

[Cholesteatoma in children. Apropos of 104 cases].

Between 1988 and 1993, 94 children from 3 to 15 years of age underwent one or more surgical procedures for cholesteatoma or epithelization of the middle ear space. Ten children had bilateral disease. 94 ears were operated for the first time and 10 ears had had previous surgery at other institutions. A total of 204 procedures were performed: 190 for cholesteatoma and 14 for epithelization of the middle ear space. Preoperative audiometry showed a mean air-bone gap of 30 decibels. 69% of the ears had ossicular osteolysis. The surgical technique was decided at the time of surgery. This was most often a canal-wall-up procedure which was almost routinely followed by surgical revision (92%). Pearl-like masses or recurrent cholesteatoma were frequently found at the second or third operation (73%) but most could ultimately be controlled with a canal-wall-up procedure. A canal-wall-up down procedure was necessary in 20% of the ears at either the second or third operation because of important residual or recurrent cholesteatoma. Post-operative audiometry showed a mean air-bone gap of 30 decibels.

Age Factors↗
PubMed1994

[Section of the facial nerve. Apropos of 40 cases].

From January, 1985 through December, 1992, 40 patients were referred to the Department of Otoneurology of the Lille University Hospital for traumatic facial nerve injury. The injury was located in the intracranial, intratemporal, or extracranial segments of the nerve in 19, 15 and 6 patients, respectively. The trauma was iatrogenic in 30 patients. It was the result of surgery for a tumor of the posterior fossa, of the temporal bone or of the parotid in 19, 2 and 3 patients, respectively. Nerve injury had occurred during surgery for chronic otitis or a parotid fistula in 5 and 1 patients, respectively. Finally, it was the result of temporal bone fracture in 7 patients. We used various techniques for repair of the nerve. Anastomosis, whether end to end or with an interposition graph and with or without rerouting, was accomplished in 17 patients, as often as possible during the first month following injury (12/17 patients). Hypoglossofacial crossovers were used in 23 patients. Evaluation of the results may vary according to the choice and interpretation of an international facial nerve grading system. We define 4 categories of results: satisfactory, moderate poor and no improvement. The results of anastomosis were best when the repair with or without rerouting was undertaken as soon after injury as possible (7 satisfactory results for 16 patients evaluated). Hypoglossofacial anastomosis gave 5 satisfactory results for 17 patients evaluated. Following this operation a spastic tendency is frequent and seems more important in patients operated during the two months following nerve injury.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Transactivation of the human multidrug resistance (MDR1) gene promoter by p53 mutants.

Multidrug resistance in human cancer is associated with overexpression of the MDR1 gene, which encodes a plasma membrane energy-dependent efflux pump termed P-glycoprotein (or the multidrug transporter), which confers cross-resistance to multiple hydrophobic natural product cytotoxic drugs. We have previously shown in cotransfection experiments that activity of the human MDR1 gene promoter is modulated by Ras and p53, suggesting that expression of the MDR1 gene may be associated with the activation of oncogenes and/or functional loss of tumor suppressor genes during oncogenesis. To further characterize the effects of p53 on the MDR1 promoter, we have shown in the current study that the region of the promoter that is required for transactivation by p53 mutants overlaps with the region that is essential for basal promoter activity. In addition, we also have shown that several different p53 mutants transactivate the MDR1 promoter in several different cell types, including embryo fibroblasts derived from the p53-deficient (p53-l-) mice generated by gene targeting.

Animals↗
PubMed1994

Primary left atrial leiomyosarcoma simulating pulmonary thromboembolism.

The authors describe a patient with primary left atrial leiomyosarcoma extending into the right pulmonary veins. The initial presentation and ventilation-perfusion scanning suggested pulmonary thromboembolism. The results of transthoracic echocardiography were nondiagnostic, and the diagnosis was eventually made on the basis of computed tomography (CT) and transesophageal echocardiography findings. The diagnosis was confirmed at surgery. This case demonstrates the complementary roles of CT and transesophageal echocardiography in the evaluation of intracardiac masses when transthoracic echocardiography is nondiagnostic. It also illustrates that cardiac tumours may present with nonspecific symptoms that mimic those of other disease.

Diagnosis, Differential↗
PubMed1993

Plasma factor V activation is prevented by activated protein C in the presence of phospholipid vesicles, not platelets.

Activated protein C (APC) is a vitamin K dependent anticoagulant which catalyzes the inactivation of factor V a and VIII a, in a reaction modulated by phospholipid membrane surface, or blood platelets. APC prevents thrombin generation at a much lower concentration when added to recalcified plasma and phospholipid vesicles, than recalcified plasma and platelets. This observation was attributed to a platelet associated APC inhibitor. We have performed serial thrombin, factor V one stage and two stage assays and Western blotting of dilute recalcified plasma containing either phospholipid vesicles or platelets and APC. More thrombin was formed at a given APC concentration with platelets than phospholipid. One stage factor V values increased to higher levels with platelets and APC than phospholipid and APC. Two stage factor V values decreased substantially with platelets and 5 nM APC but remained unchanged with phospholipid and 5 nM APC. Western blotting of plasma factor V confirmed factor V activation in the presence of platelets and APC, but lack of factor V activation with phospholipid and APC. Inclusion of platelets or platelet membrane with phospholipid enhanced rather than inhibited APC catalyzed plasma factor V inactivation. Platelet activation further enhanced factor V activation and inactivation at any given APC concentration. Plasma thrombin generation in the presence of platelets and APC is related to ongoing factor V activation. No inhibition of APC inactivation of FVa occurs in the presence of platelets.

Blood Coagulation↗
PubMed1992

A new class of bradykinin antagonists: synthesis and in vitro activity of bissuccinimidoalkane peptide dimers.

A systematic study on the dimerization of the bradykinin (BK) antagonist D-Arg0-Arg1-Pro2-Hyp3-Gly4-Phe5-Ser6-D-Phe 7-Leu8-Arg9 has been performed. The first part of this study involved compounds wherein dimerization was carried out by sequentially replacing each amino acid with cysteine and cross-linking with bismaleimidohexane. The second part of this study utilized a series of bissuccinimidoalkane dimers wherein the intervening methylene chain was varied systematically from n = 2 to n = 12 while the point of dimerization was held constant at position 6. The biological activities of these dimers were then evaluated on BK-induced smooth muscle contraction in two different isolated tissue preparations: guinea pig ileum (GPI) and rat uterus (RU). Several of the dimeric BK antagonists displayed remarkable activities and long durations of action. In addition, dimerization at position 4, 7, 8, or 9 produced dimeric analogues with markedly reduced potency. Rank order of antagonist potency as a function of dimerization position is as follows: rat uterus, 6 greater than 5 greater than 0 greater than 2 greater than 1 greater than 3 much greater than 4, 7, 8, 9; guinea pig ileum, 6 greater than 5 greater than 3 greater than 2 greater than 1 greater than 0 much greater than 4, 7, 8, 9. Evaluation of the linker length as represented by the number of methylene units indicated an optimal distance between the two monomeric peptides of six to eight methylene moieties. These studies also revealed that the carbon-chain length significantly affected the duration of action in vitro and resulted in partial agonism effects when n greater than 8. The optimum activity in vitro was achieved with dimerization at position 6 and n = 6 (designated herein as compound 25; alternatively, CP-0127). Similar effects in potency were also seen when the monomeric antagonist D-Arg0-Arg1-Pro2-Hyp3-Gly4-Phe5-Ser6-D-Phe 7-Phe8-Arg9 (NPC-567) was dimerized using similar chemistry. These results suggest that the development of BK antagonists of significant therapeutic potential may be possible using a dimerization strategy that can overcome the heretofore limiting problems of potency and in vivo duration of action found with many of the BK antagonists in the literature.

Amino Acid Sequence↗
PubMed1992

Laparoscopic cholecystectomy in a patient with situs inversus viscerum: a case report.

A patient with known situs inversus viscerum of the abdomen and congenital heart disease presented with symptomatic cholelithiasis in a left-sided gallbladder. Laparoscopic cholecystectomy was carried out successfully, despite the reversed anatomic relationships, and the patient made a smooth recovery. This is the first case report of a successful laparoscopic cholecystectomy in a patient with a left-sided gallbladder.

Adult↗
PubMed1990

Plexiform neurofibroma: report of an unusual presentation.

We describe a plexiform neurofibroma discovered incidentally in a patient who was involved in a motor vehicle accident. The lesion simulated a subcapsular liver hematoma or diaphragmatic rupture on sonography, computed tomography and angiography.

Adult↗
PubMed1988

2D NMR studies of aminoglycoside antibiotics. Use of relayed coherence transfer for 1H resonance assignment and in situ structure elucidation of amikacin derivatives in reaction mixtures.

Phase-sensitive 2D 1H/1H COSY spectra can be used to identify the structures of individual pure specimens of the aminoglycoside antibiotic amikacin and its N-hemisuccinyl derivatives. However, even at 500 MHz the 2D chemical shift dispersion does not allow for unambiguous assignment of all cross-peaks. By use of 2D relayed coherence transfer experiments (RELAY) optimized to detect two-step 1H/1H scalar interactions in which one of the J-values is small, sufficient additional correlations can be obtained from the frequency-isolated resonances to allow facile tracing of all scalar connectivities. Complete assignments of the 1H NMR spectra of amikacin, its 6'-N-hemisuccinamide, and a novel bis(acylate) [gamma-N-(p-vinylbenzoyl)amikacin 6'-N-hemisuccinamide] were obtained for aqueous media. The NMR spectrum of amikacin free base was also assigned in dimethyl sulfoxide solution. The RELAY experiment can be extended to the analysis of reaction mixtures, which allows for the identification and resonance assignment of regioisomeric amikacin haptens in the mixture state. All of the N-monohemisuccinyl isomers of amikacin have been identified in reaction mixtures through the RELAY experiment. The relative reactivities of the amino functions of amikacin toward acylating agents were found to be 6'-N greater than 3-N equal to or greater than 3"-N equal to or greater than gamma-N. However, this reactivity order is altered after the initial acylation event.

Amikacin↗
PubMed1987

Two unusual causes of dysphagia: a pictorial essay.

Dysphagia was the presenting symptom in two adult patients. One had a mediastinal pancreatic pseudocyst, the other a pulmonary sling. The role of imaging methods in making the diagnoses is illustrated.

Adult↗
PubMed1986

Esophageal obstruction secondary to a mediastinal pancreatic pseudocyst.

The authors report a rare complication of pancreatic pseudocyst. A 47-year-old man suffered rapidly progressing dysphagia and complete esophageal obstruction secondary to extrinsic compression by mediastinal extension of a pancreatic pseudocyst. Ultrasonography and especially computerized tomography were instrumental in diagnosis and in the planning of the operation. A posterior cystogastrostomy successfully drained the pseudocyst and relieved the esophageal obstruction.

Deglutition Disorders↗