Biomedical subjects

H V Nguyen

Publications and source records attributed to H V Nguyen.

At least 55 records · Page 3Linked to original sources

PubMed1994

Endourological treatment of lumbar and iliac ureteral stones. A comparative study of 49 cases.

The efficacy of the Lithoclast has been described extensively in the recent literature. However, to our knowledge, few articles have dealt with the safety of this technique. We present a retrospective study of 49 patients with stones of the lumbar and iliac ureter treated between 1989 and 1992 either by means of the Lithoclast (17 patients), by electrohydraulic shock waves (16 patients), or by trapping the stones in a wire stone basket (16 patients). The success rates were 88% for the Lithoclast and wire stone baskets and 62% for electorhydraulic shock waves. The mean dimensions of the stones were 10 mm for the Lithoclast and electrohydraulic shock wave groups, and 7 mm for the wire stone basket group. Complications consisted of 7 ureteral lesions (2 cases with the Lithoclast, 4 cases with electrohydraulic shock waves and 1 case with the wire stone basket) and 1 stripping of the lower ureter following stone extraction with a wire stone basket, which required open reimplantation. This study demonstrates the efficacy and safety of the Lithoclast for the treatment of large stones of the lumbar and iliac ureter.

Adolescent↗

PubMed1993

A slow clearing, fibrin-specific, PAI-1 resistant variant of t-PA (T103N, KHRR 296-299 AAAA).

Site directed mutagenesis was used to construct a t-PA variant that contains an additional glycosylation site in the first kringle domain (T103N) combined with a tetra-alanine substitution in the protease domain (KHRR 296-299 AAAA). This combination variant has a plasma clearance rate that is 4.5-fold slower in rats and 5.4-fold slower in rabbits than t-PA. It is also less than one tenth as active as t-PA towards plasminogen in the presence of fibrinogen, and has approximately twice the normal activity in the presence of fibrin. It shows substantial resistance to the fast acting inhibitor, plasminogen activator inhibitor-1 (PAI-1), requiring a 10-fold greater molar excess of PAI-1 to reduce its activity by 50%, compared to t-PA. This is the result of a reduction of nearly 100-fold in the second order rate constant for PAI-1 inactivation. These results show that it is possible to combine mutations in different domains of t-PA to construct a variant which is simultaneously slower clearing, less reactive towards plasminogen in the absence of a fibrin clot, and resistant to inactivation by PAI-1.

Animals↗

PubMed1993

Enhanced response of muscle protein synthesis and plasma insulin to food intake in suckled rats.

To compare the sensitivity of muscle protein synthesis to food intake in neonatal and weaned rats, 5- and 16-day-old suckled rats and 28-day-old weaned rats were either fed, fasted for 8-10 h, or refed for 1-4 h after an 8-h fast. Protein synthesis was measured in vivo in soleus and plantaris muscles with a large dose of L-[4-3H]phenylalanine. In fed rats, fractional rates of protein synthesis (KS) decreased with age. Fasting decreased KS, and refeeding increased KS most in 5-day-old animals, less in 16-day-old rats, and least in 28-day-old rats. In 5-day-old rats, there were no differences in KS between soleus and plantaris muscles in the fed state and after fasting and refeeding; at 28 days, KS was higher in soleus than in plantaris in fed rats, and the soleus did not respond to fasting and refeeding. In rats at all three ages, the concentration of most plasma amino acids decreased during fasting; when 5-day-old rats were refed, plasma amino acid concentrations increased, but not to the levels in the fed state. Plasma insulin concentrations increased with age. Plasma insulin concentrations decreased more rapidly with fasting and increased more extensively with refeeding in 5-day-old rats than in older rats. These results suggest that muscle protein synthesis is more responsive to food intake in young suckled rats than in older suckled or weaned rats; this increased responsiveness is accompanied by greater changes in circulating insulin concentrations.

Aging↗

PubMed1992

Radioiodination of the active site of tissue plasminogen activator: a method for radiolabeling serine proteases with tyrosylprolylarginyl chloromethyl ketone.

Tyrosylprolylarginyl chloromethyl ketone (YPRck) is a radioiodinatable inhibitor that irreversibly binds the active site of tissue plasminogen activator (tPA). A two-step reaction is employed where (1) the YPRck reagent is iodinated and (2) the 125I-YPRck is reacted with the tPA sample; therefore the oxidative effects of conventional protein iodination are avoided. Using fibrin binding as a probe of native tPA binding function, YPRck labeling was shown to be superior to other types of surface iodination. 125I-YPRck was prepared at a high specific radioactivity; i.e., one 125I per 3.5 molecules of peptidyl chloromethyl ketone. Labeled YPRck formed a one to one covalent, sodium dodecyl sulfate stable, complex with tPA resulting in a preparation of 10 mCi per milligram protein, which corresponded to an incorporation ratio of 1:3.5 (125I-YPRck:tPA). Both one-chain and two-chain forms of tPA reacted with YPRck. Radiolabeling tPA with 125I-YPRck occurred in a time-dependent manner with half-maximal incorporation at approximately 30 min under the conditions employed in these studies. The pH optimum for the reaction of tPA with 125I-YPRck was 7.4. Solutions of tPA at less than 1 microgram/ml were efficiently labeled with 125I-YPRck, thus allowing the quantitation of functional protease by incorporation of radiolabel. Significantly, 125I-YPRck specifically labeled tPA in cell culture supernatants after transient transfection of cells with plasmid DNA containing the gene for tPA. Other serine proteases were tested for their relative reactivity with 125I-YPRck. Thrombin and Factor Xa incorporated 125I-YPRck to higher levels than two-chain tPA; whereas plasmin, urokinase, and other plasma proteases were not as efficiently radiolabeled. The use of 125I-YPRck allows rapid and specific radiolabeling of a large number of tPA samples in a nondenaturing environment with a known localization of the radiolabeling reagent.

Amino Acid Chloromethyl Ketones↗

PubMed1992

Involvement of residues 296-299 in the enzymatic activity of tissue-type plasminogen activator.

The tetra-alanine substitution variant KHRR 296-299 AAAA of tissue-type plasminogen activator (t-PA) was previously shown to have enhanced fibrin specificity and enhanced activity in the presence of fibrin compared with the wild-type form of the molecule. The structural requirements for these alterations in enzymatic activity were investigated by constructing several amino acid substitution variants at each of the positions from 296 to 299 and evaluating their activities under a variety of conditions. Effects on plasminogen activator activity were common among the point mutants at positions 296-299; nearly all had a phenotype similar to the KHRR 296-299 AAAA variant. The greatest effects on enzymatic function were found with multiple substitution variants, but some single charge reversals and proline substitutions had substantial effects. The enhanced fibrin specificity of KHRR 296-299 AAAA t-PA results in less fibrinogenolysis than seen with wild-type t-PA. Approximately four times greater concentration of KHRR 296-299 AAAA compared with wild-type t-PA was required to consume 50% of the fibrinogen in human plasma.

Alanine↗

PubMed1991

Response of muscle protein synthesis to fasting in suckling and weaned rats.

Protein synthetic efficiency (KRNA) is low in immature skeletal muscle of suckling rats and increases toward the end of the suckling period. To determine whether immature skeletal muscle is able to further reduce KRNA in response to fasting, suckling (5, 10, and 16 days of age) and weaned (28 days of age) rats were fed, fasted for 10 h, or fasted for 18 h and injected with a flooding dose of L-[4-3H]phenylalanine for measurement of muscle protein synthesis in vivo. In fed rats, fractional rates of protein synthesis (KS) and protein synthetic capacity decreased during the suckling period. KRNA increased toward the end of the suckling period. In 5-day-old rats, fasting for 10 h produced a 50% decline in KS of extensor digitorum longus and plantaris muscles, but KS did not change further after 18 h of fasting. In older suckled and weaned rats, 10 h of fasting decreased KS of extensor digitorum longus and plantaris muscles 30%; after 18 h of fasting, values had declined to 50% of those in fed animals. The reductions in KS in soleus muscles with 10 and 18 h of fasting were similar to those in other muscles at 5 and 10 days but were less than those in other muscles at 16 and 28 days. Changes in KRNA were similar to those for KS in all muscles from all age groups fasted for 10 and 18 h. Protein synthetic capacity decreased approximately 12% after 18 h of fasting, but this effect did not differ between age groups or muscle types.(ABSTRACT TRUNCATED AT 250 WORDS)

3-Hydroxybutyric Acid↗

PubMed1991

[Biological glue and obstruction of bronchial stumps. Experimental study. Sutureless bronchial closure of lobectomies in dogs].

From April, 1989 to January, 1990, we have been "inducing bronchial fistulae" in dogs by performing 10 lobectomies, 5 middle and 5 caudal, in both the right and the left lung. The bronchial stump was not sutured but closed by a "Tissucol-vicryl mesk" implant, which can be adapted to the size of the stump and is fully absorbed in the long term and replaced by a natural fibrous plug. The results seem to be fairly satisfactory: no dog died; all stumps--followed up a D10, D12... up to the 11th month--were obturated without complications, at least in these animals whose bronchi were normal and not infected. Bronchial fistulae still are a serious complication of lung resections, and while the smaller fistulae (2-3 mm) can be managed with biological glue delivered by simple endoscopy, severe fistulae--especially after pneumonectomy, above all in the right lung--often demand difficult, high-risk surgery. This points out to the interest of this small experimental series. Two conditions are essential to successfully implement this alternative procedure: 1) perfect sterilization of the excision pocket; a window is often required, which in addition has the advantage of facilitating the insertion and observation of the implant; 2) a high concentration of aprotinin (10,000 units) delaying the dissolution of the glue plug, thus allowing it to be integrated by the natural healing process.

Adhesives↗

PubMed1990

[Should fragments of stone expelled after extracorporeal lithotripsy always be analyzed?].

The morphological and constitutional analysis of renal stone fragments expelled after extracorporeal shock wave lithotripsy enables the structure and morphological type of stones to be reconstructed in 92.8 per cent of the cases as regards surface and section and in 74.5 per cent of the cases down to the core. A study of the molecular and crystalline composition of such fragments demonstrated the preponderance of whewellite in both sexes (men 85.4 per cent; women 72.4 per cent). The frequency of weddellite was 1.6 times higher in men (73.8 per cent) than in women (44.8 per cent), and the frequencies of struvite and ammonium urate were 2.8 and 2.6 times respectively higher in women than in men, despite a significant fall in frequency as compared to a previous series. Correlations between morphological type of stone and biochemical data (when available) could be established in 84 per cent of the cases. This made it possible to initiate treatments aimed at preventing recurrences, the cost of these treatments in the long term being lower than that of the curative urological treatments, including extracorporeal shock wave lithotripsy.

Adult↗

PubMed1989

Protein turnover in skeletal muscle of suckling rats.

To determine the normal changes in protein turnover of skeletal muscle in vivo during the suckling period of rats, protein synthesis was measured in soleus, plantaris, anterior tibialis, and extensor digitorum longus (EDL) muscles of 1- to 28-day-old rats using a flooding dose of L-[4-3H]phenylalanine. Protein mass of hind-limb muscles increased nearly 100-fold, and RNA increased approximately 20-fold between 1 and 28 days of age. The total amount of protein synthesized per day increased 34-fold. Fractional protein synthesis rates (Ks) decreased two- to threefold between 1 and 28 days postpartum as a result of a decrease in protein synthetic capacity (RNA/protein). Protein synthetic efficiency (total protein synthesized/RNA) increased during this period. Ks were similar among the four muscles at 1-10 days. At 16 days, Ks increased in soleus and plantaris as a result of increases in protein synthetic efficiency; Ks did not increase in anterior tibialis and EDL. These data suggest that, during the suckling period, protein synthetic capacity in skeletal muscles of rats declines, while protein synthetic efficiency increases. The increase in translational efficiency occurred earlier in weight-bearing muscles (soleus, plantaris) than in non-weight-bearing muscles (anterior tibialis and EDL) and was associated with the appearance of mobility.

Aging↗

PubMed1988

Inhibition of macrophage activation by isoquinolinesulfonamides, phenothiazines, and a napthalenesulfonamide.

The influence of isoquinolinesulfonamides (H-7 and H-8), phenothiazines(trifluoperazine and fluphenazine), and a naphthalenesulfonamide (N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7) on stimulated superoxide anion production and phosphatidyl inositol (PI) cycle activity was investigated in the guinea pig alveolar macrophage. All five drugs were able to inhibit superoxide anion production stimulated by n-formyl-nel-leu-phe (FNLP), leukotriene B4 (LTB4), and phorbol-12,13-dibutyrate (PDB). The order of potency was trifluoperazine greater than or equal to fluphenazine greater than H-7 = W-7 greater than H-8. The dose response curves could be shifted to less efficacy by increasing extracellular calcium. By itself, W-7 markedly stimulated 45Ca+2 efflux, fluphenazine and trifluoperazine slightly stimulated 45Ca+2 efflux, while H-7 and H-8 had no effect on 45Ca+2 efflux from macrophages preloaded with 45Ca+2. Consistent with these results, W-7 markedly stimulated PI cycle activity, fluphenazine and trifluoperazine slightly stimulated PI cycle activity, while H-7 and H-8 had no significant effects on PI cycle activity. In addition, W-7 by itself was able to stimulate a weak and short-lived "burst" of superoxide anion production. In order to evaluate whether a site of action of the inhibitors was at protein kinase C and whether protein kinase C was involved in terminating the normally short-lived FNLP- and LTB4-stimulated macrophage activation, fluphenazine and H-7 were used to evaluate the duration of FNLP- and LTB4-stimulated PI cycle activity, at concentrations of the inhibitors that significantly blocked stimulated superoxide anion production. In all cases, FNLP and LTB4 still stimulated PI cycle activity, which still terminated even though protein kinase C was inhibited. These results suggest that all five drugs block protein kinase C, but H-7 was the most specific in its action at protein kinase C, while the phenothiazines and W-7 have multiple sites of action. In addition, these results suggest that protein kinase C may not function to cause the termination of FNLP- and LTB4-stimulated PI cycle activity and subsequent superoxide anion production.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗

PubMed1988

[13 cases of drug-induced calculi].

All urinary stones should undergo detailed studies to identify those related to drug therapy. Among 520 stones analyzed by infrared spectrophotometry, we found 13 drug-induced stones (13/520: 2.5%). Drug-induced stones were caused by glafenine in 7 cases, piridoxylate in 4 cases, triamterene in one case and an unknown organic compound in one case. Glafenine stones appear to develop more readily in infected urine. Triamterene stones are often associated with uric acid disorders. Piridoxylate induces the formation of glyoxylate which is responsible for hyperoxaluria and formation of oxalocalcium stones.

Aged↗

PubMed1987

Anatomical basis of modern thoracotomies: the latissimus dorsi and the "serratus anterior-rhomboid" complex.

The latissimus dorsi and the "serrato-rhomboid" complex are the muscles most often involved in present-day thoracotomies for lung surgery. The present anatomic study emphasizes: the continuity between the serratus anterior and the rhomboid levator scapulae mass as a wide muscular sheet with a deep common fascia, extending the serrato-thoracic space (of Gillis) to the vertebral column as the rhomboserrato-thoracic space (the levator scapulae is situated higher up, above the ordinary thoracotomy); the presence of a "composite fascia" in the posterior angle between the seratus anterior and the rhomboid; the long costal attachment area and the presence of two differently oriented layers for the muscular digitations of the middle and inferior parts of the serratus anterior. With a rich vascular supply from multiple sources, the serratus anterior and latissimus dorsi are two large flat muscles with a single longitudinal nervous pedicle proceeding from the brachial plexus. To avoid esthetic (winged scapula) and functional sequelae, it is imperative to safeguard this single innervation as far as possible : by halting division of the serratus anterior before reaching its neurovascular pedicle in lateral or anterolateral thoracotomy, and by transecting the latissimus dorsi very low down in standard postero-lateral thoracotomy. The other muscles are simply freed and retracted.

Humans↗

PubMed1987

[Absorbable synthetic clips and pulmonary excision. Our clinical experience].

Analysis of the first 50 clinical cases confirmed conclusions of experimental studies in large animals with respect to the use of absorbable synthetic clips formed of lactomer and polydioxanone. The advantages of clips when compared with ligatures include rapidity and simplicity of use and ease of insertion, even in regions difficult to approach surgically with the fingers. The advantages of clips of the absorbable synthetic type over conventional metallic material are: safety and reliability due to their locking system and the conservation of sufficient residual resistance, improved behavior in biologic media, radio-transparency and total inertia in magnetic fields compatible with postoperative radiation and modern medical imaging procedures (CT scan, IRM), and finally progressive resorption predictable by simple hydrolysis and then total disappearance after 6 to 7 months. With staplers of the TA and GIA type these clips make sutures and ligatures during lung resection surgery entirely automatic.

Absorption↗

PubMed1987

[Study of spontaneous crystalluria in patients with calcium oxalate calculi].

We studied crystalluria in healthy subjects and in calcium oxalate stone formers using polarization microscopy and infrared spectroscopy, in freshly voided urine and after 48 h urine storage at +4 degrees C. 412 urine specimens from 39 normal subjects and from 172 stone formers were examined. In the latter, 90 voidings were obtained while on free diet, 61 on moderately calcium restricted diet, 34 in the fasting state and 136 while on thiazide therapy. In the normal subjects, all 91 voidings were obtained while on free diet. Crystalluria was more frequent in urine specimens collected on free diet in stone formers (48.9%) than in normal subjects (13.9%, p less than 0.001) and slightly decreased in patients on thiazide therapy (41.2%). Crystalluria increased following +4 degrees C urine storage in all groups. The most frequent crystalline phase was weddellite. Comparison of crystalline phases of calcium oxalate observed before and after +4 degrees C storage showed that crystallization spontaneously progressed to weddellite whatever the calcium oxalate phase initially present. On thiazide therapy we observed, in addition to lower calcium content, a decreased frequency of urate crystallization especially in +4 degrees C stored urine, in parallel with a decrease in urate concentration.

Calcium Oxalate↗

PubMed1986

[The 2 key muscles in thoracotomy for excision of the lung. The latissimus dorsi and the levator scapulae muscles].

Anatomical data related to the thoracotomies performed most frequently in lung surgery are described in some detail: continuity between serratus anterior and levator scapulae as a vide muscular sheet possessing a common deep aponeurosis (thoracolumbar fascia) extending Gilis' space to the vertebral column as the levator scapulae-thoraci space; presence of a "composite aponeurosis" in the posterior angle between serratus anterior and levator scapulae, covering the 8th rib triangle or triangle of auscultation; long costal insertion area and presence of two differently orientated muscle layers for the digitations, particularly of apical bundle. Supplied by a rich vascularization of multiple sources, the serratus anterior and latissimus dorsi are two muscles with single longitudinal nerve pedicles derived from brachial plexus. It is certainly the denervation which is responsible for the distal atrophy of these muscles "sectioned on the right of the selected ribs" following conventional thoracotomy. To avoid esthetic and functional sequelae this innervation must be preserved as far as possible by: interrupting division of serratus anterior anterior to long thoracic nerve and avoiding inclusion of axillary border of latissimus dorsi during lateral thoracotomy; sectioning the latissimus dorsi as low as possible--the other muscles being simply freed and inclined--during lateral thoracotomy.

Arteries↗

PubMed1986

[Retinal complications in diabetics with renal failure].

The following conclusion, are based on this series of 27 patients, all diabetics with end-stage renal failure: All, except one, with both diabetes and nephropathy exhibited retinopathy. Retinopathy, its severity and the prevalence of complications are primarily related to the evolution of diabetes, whatever the type and severity of the nephropathy, and independent of the presence or severity of hypertension. Good glycemia control did not induce efficient prevention of retinopathy. In insulin-dependent diabetic patients, the type of insulin used had no influence on the evolution or severity of the retinopathy. The duration of diabetes and the beginning in childhood are the major factors for complications risks.

Adult↗

PubMed1985

[Assessment of 7 years of automatic suturing in pulmonary surgery].

In 738 patients, the stapler-suturing methods were used in 2 main areas of concern: closure of the major hilar broncho-vascular structures (for smaller pulmonary vessels, we use absorbable ligating clips: Absolok from Ethicon and Polysurgiclip from USSC), suture of the lung parenchyma. Regarding pedicular sutures, our rate of bronchial fistula is 1,0% (or 4,4% if only pneumonectomies are taken into account: 1,4 on the left and 7,7 on the right). These rates are compared with those gathered from the literature, with emphasis on the right main bronchus. Regarding parenchymal sutures, we place TA and GIA on collapsed parenchyma for achieving a wide range of either intralobar or translobar procedures. We lay emphasis on: the conventional segmentectomies with stapling of the intersegmental surface, and the newer and more economical "non réglées" transsegmental resections in which the surgeon is anymore limited by segmental frontiers. The control of blood and air leakage from the cut surface is quite satisfactory, reducing significanthy the postoperative morbidity. For both major pedicular structures and fragile lung parenchyma, the stapler-suturing methods are very reliable and provide a quicker, simpler, safer, easier and more economical surgery in lung resections.

Bronchi↗

PubMed1984

Anatomical bases of transaxillary resection of the first rib.

Anatomical study of the costoclavicular space, with approach via inferolateral axillary route, allowing resection of the first rib. With the patient in the semisupine position, lifting the arm to the zenith allows the costoclavicular space to be opened widely and separation of the plane of the first rib from the neurovascular structures of the lateral wall of the axillary pyramid. In the first part of our work, we study successively the bony frame and its anatomical variations, the muscular frame and its anomalies, the cervical pleura and its associated fibromembranous complex. The second part is a succinct summary of the different stages of transaxillary resection of the first rib, with mention of the operative risks and landmarks in this approach.

Axilla↗