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Biomedical subjects

T Nguyen

Publications and source records attributed to T Nguyen.

At least 397 records · Page 22Linked to original sources
PubMed1988

High-performance liquid chromatography of amino acids, peptides and proteins. LXXXIV. Application of derivative spectroscopy to the study of column residency effects in the reversed-phase and size-exclusion liquid chromatographic separation of proteins.

The influence of column residency times on the reversed-phase gradient elution behaviour of human and bovine growth hormones has been investigated using on-line photodiode array spectroscopic detection. Stationary phase induced effects on protein conformation were monitored by changes in the maxima to minima ratio of the second derivative spectrum of the eluted protein. Significant changes in the second derivative ratio of the unmodified and the fully reduced and alkylated protein were observed following long incubation times, i.e. t(dwell) greater than 15 min, at the stationary phase surface in the presence of 0.1% trifluoroacetic acid before elution with a 0-75% aqueous acetonitrile gradient. The application of multi-wavelength detection in the study of equilibrium unfolding of growth hormones in urea by size-exclusion chromatography was also investigated. On-line photodiode array instrumentation and derivative spectra rationing was employed to monitor tertiary and quaternary structural changes associated with protein denaturation during a chromatographic separation. These studies clearly demonstrate the powerful detection capabilities of such instrumental approaches for the on-line evaluation of both stationary phase surface and/or mobile phase mediated changes in protein conformation.

Alkylation↗
PubMed1988

Hematologic changes occurring with cardiac catheterization.

The composition of the blood influences rheology and therefore might affect hemodynamics. During cardiac catheterization and angiography, blood is sampled and contrast media, fluid, and heparin are administered. To determine the effects of these perturbations on the blood cell count and coagulation, femoral vein samples were obtained at the beginning of cardiac catheterization, before heparin, 4,000 U; at the end, before protamine reversal; and after protamine, 40 mg, was administered. At the end of catheterization, 41 +/- 3 min after heparin administration, all cellular constituents were significantly lower than control: White (W) blood cells (BC) were 8.1 +/- 2.7% lower (P less than 0.05), red (R) BC, 10 +/- 1.8% (P less than 0.05), and platelets (P) 10.9 +/- 1.5% (P less than 0.05). Protamine lowered further WBC by 23 +/- 4% (P less than 0.05 and P) by 14 +/- 2% (P less than 0.05), but did not change RBC (4.13 +/- 0.20 x 10(6) to 4.25 +/- 0.23 x 10(6]. Before protamine administration, all patients had a partial thromboplastin time (PTT) 1.5 times the control value and ten of 13 patients had a value greater than 100 sec. Although four of 13 patients had an incomplete reversal of PTT after protamine, none suffered an untoward event. In conclusion, cardiac catheterization produces changes in the cellular composition of the blood, and such changes might influence hemodynamic measurements.

Adult↗
PubMed1988

Clinicopathologic studies in childhood pancreatitis.

In a review of pediatric autopsies from 1951 to 1985, we identified 40 cases in which pancreatitis was diagnosed pathologically. Twenty-six of these patients were under 4 years of age, and the male-to-female ratio was 1.5. Six groups of patients were identified: 10 with hepatobiliary disease, including 9 with biliary atresia; 7 with immunosuppressive therapy for tumors (n = 2), leukemia (n = 4) and aplastic anemia (n = 1); 6 with viral infections; 8 with congenital anomalies, including congenital heart disease (n = 3); and 9 with miscellaneous problems. Several patients had surgery and various intercurrent complications. Clinical features attributable to the pancreatitis included vomiting or excessive nasogastric drainage (60%), pleural effusions (40%), and abdominal pain (25%). However, the diagnosis was suspected clinically in only 5 of 40 patients. Our findings suggest several pathogenic mechanisms exist for childhood pancreatitis: biliary obstruction, infections, drug toxicity, immunosuppression (acting in synergy with drug toxicity, trauma, and low-flow states resulting from shock, heart failure, and vasculopathy.

Adolescent↗
PubMed1988

Effect of renal mass reduction on kidney tissue concentration of gentamycin following a single dose.

Controversy exists concerning the effect of pre-existing renal disease on aminoglycoside nephrotoxicity. Since nephrotoxicity appears to be related to gentamycin concentration in the renal tissue, we studied the effect of renal mass reduction on renal tissue gentamycin concentration. Four groups of male Sprague-Dawley rats, who had undergone progressive renal mass reduction, were studied after injection with a single dose of gentamycin. As expected, serum gentamycin concentration was increased in nephrectomized animals and showed significant inverse correlation with the weight of the residual renal tissue. However, urinary gentamycin secretion rate was proportional with the weight of the residual renal tissue. Renal tissue gentamycin concentrations in the nephrectomized animals were significantly higher than that found in the sham-operated controls. The data indicate that renal tissue gentamycin concentration attained after a single dose of the drug is higher in the presence of reduced renal mass.

Animals↗
PubMed1987

Lack of effect of chronic carbamazepine on brain somatostatin in the rat.

We investigated the effects of chronic carbamazepine treatment in rats on brain somatostatin. Following 12 days of carbamazepine treatment, no changes in somatostatin levels were found in any of the brain areas examined which included: amygdala, hippocampus, caudate-putamen, median eminence, arcuate nucleus, nucleus accumbens, nucleus interstitialis of the stria terminalis, nucleus periventricularis, parietal cortex, and occipital cortex. Thus, carbamazepine in low doses does not affect basal levels of brain somatostatin in the rat, in contrast to the previous reports of decreased somatostatin in the cerebrospinal fluid of affectively ill patients.

Animals↗
PubMed1987

Urinary digoxin-like immunoreactive substance in pregnancy. Relation to urinary electrolytes.

High concentrations of digoxin-like immunoreactive substance (DLIS) have been identified in amniotic fluid and in blood during pregnancy. In this study, urine from healthy women was analyzed for DLIS during pregnancy and following delivery, and levels were related to various clinical and urinary findings. Urinary DLIS increased progressively during pregnancy, having a linear relation to gestational week (DLIS = 0.032 week + 0.46, Syx = 0.52, r = 0.46, p less than 0.01), and fell to nonpregnant values during the first postpartum day. The urinary DLIS level correlated with urinary creatinine (r = 0.50, p less than 0.01) and urinary calcium (r = 0.56, p less than 0.01) levels. When adjusted for the gestational week, the urinary DLIS level also correlated with urinary potassium (r = 0.48, p less than 0.01), creatinine (r = 0.55, p less than 0.01), and magnesium (r = 0.55, p less than 0.01) levels. After adjustment for the urinary creatinine level, only the relation of urinary DLIS and urinary calcium levels remained significant (r = 0.44, p less than 0.05). The urinary DLIS level was not found to be related to systemic blood pressure. The ratios of sodium to potassium (r = -0.43, p less than 0.05) and calcium to magnesium (r = 0.37, p less than 0.05) were also related to gestational week but were independent of the urinary DLIS level. Thus, urinary DLIS increases progressively during pregnancy and falls to nonpregnant values on the first postpartum day, the urinary DLIS level can be related to urinary creatinine, urinary potassium, and urinary magnesium levels, and when adjusted for the urinary creatinine level, the urinary calcium level relates independently to the urinary DLIS level.

Blood Pressure↗
PubMed1986

[Surgical treatment of hepatoma on a cirrhotic liver].

From January 1, 1975 to July 1, 1984, 37 patients with a tentative diagnosis of hepatocarcinoma on cirrhosis were operated upon. There were 34 men and 3 women, aged from 32 to 82 years (mean: 60 years). The diagnosis of cirrhosis rested either on a history of liver failure associated with clinical and biochemical signs of hepatocellular dysfunction (4 cases), or on a positive liver biopsy (5 cases). In 20 cases the diagnosis was suspected on account of abnormal liver function tests, but in 8 patients it was revealed by macroscopic examination of the liver during surgery. Cirrhosis was attributed to chronic alcoholism in 25 cases, haemochromatosis in 11 cases and positive HBs antigen in 7 cases. The diagnosis of hepatocarcinoma, suggested by altered general condition or recent pain, rested on the finding of a tumoral image at scintigraphy (16 cases), ultrasonography (19 cases), computed tomography (7 cases), arteriography (17 cases) or laparoscopy (7 cases). In only 7/32 patients was the alpha-foetoprotein level higher than 500 ng/l. Surgery confirmed the diagnosis of hepatocarcinoma in every case but that of cirrhosis in only 14/37 cases; 10 patients had lesion of hepatic fibrosis and 1 had regenerative nodular hyperplasia. In 10 cases no accurate histological diagnosis could be made since the liver tissue sample had been taken too close to the tumour. The finding of normal liver tissue shows that one should not refrain from operating merely because the diagnosis of cirrhosis rests on clinical grounds. Since 1979, surgical treatment consists in an attempt to excise the tumour. Per-operative mortality is the same with excision surgery (21%) as with exploratory or palliative surgery (17%). Fourteen excisions were performed (i.e. aresectability rate of 38% for the series): 2 liver transplantations, 2 right hepatectomies, 2 left hepatectomies, 2 left lobectomies, 2 bisegmentectomies and 3 tumorectomies. The survival rate of 2 years was 27%, as opposed to 5% with exploratory or palliative surgery. Systematic monitoring of cirrhosis with ultrasonography should result in early diagnosis of hepatocarcinoma at a stage where limited hepatic excision is possible and the chances of surviving are highest.

Adult↗
PubMed1986

Use of an antibody to characterize and determine the role of the major Met-tRNAf deacylase from rabbit reticulocyte ribosomes.

Inhibition of polypeptide chain initiation in rabbit reticulocyte lysate by phosphorylation of eukaryotic initiation factor-2(alpha) results, secondarily, in the enzymatic deacylation of Met-tRNAf on the 48 S initiation complexes that accumulate. We have prepared an antibody to a highly purified preparation of the major Met-tRNAf deacylase activity on rabbit reticulocyte ribosomes, termed deacylase II. Antibody, but not similarly purified normal IgG, completely neutralizes the activity of Met-tRNAf deacylase II and has no effect on Met-tRNAf deacylase I, a separate, minor, reticulocyte activity with the same substrate specificity but very different physical and enzymatic properties, strongly suggesting that deacylase I and II are distinct proteins. We partially purified Met-tRNAf deacylase activities from rabbit liver, myocardium and bone marrow ribosomes and found them to be similar to each other and to reticulocyte deacylase I in their enzymatic properties and insensitivity to anti-deacylase II, suggesting that deacylase I may be a general form of this enzyme, present in many cells, while deacylase II may be induced specifically during erythroid differentiation. Addition of the antibody to reticulocyte lysate incubated in the absence of hemin or presence of hemin plus 0.1 microgram/ml poly(I X C) did not reverse the inhibition of protein synthesis but did reduce the rate of turnover/utilization of Met-tRNAf and increase the level of Met-tRNAf bound to 48 S initiation complexes, demonstrating that the deacylase does not directly inhibit protein synthesis under these conditions but does mediate the deacylation, loss, and thus greater than expected turnover of Met-tRNAf in the 48 S complexes that accumulate.

Acyltransferases↗
PubMed1985

Primary structure of the soybean nodulin-23 gene and potential regulatory elements in the 5'-flanking regions of nodulin and leghemoglobin genes.

The nodulin-23 gene of soybean is one of the most abundantly transcribed genes induced during symbiosis with Rhizobium. Using a plasmid (pNod25) from a nodule cDNA library, we have isolated the nodulin-23 gene from a soybean genomic library. Nucleotide sequence analysis of the cDNA and of the genomic clone indicated that the coding region of this gene is 669 bp long and is interrupted by a single intron of about 530 bp. The deduced protein sequence suggests that nodulin-23 may have a signal sequence. The 5'-flanking sequence of two other nodulin genes, nodulin-24 encoding for a membrane polypeptide and one of the leghemoglobin genes (LbC3), were obtained. Comparison of these sequences revealed three conserved regions, one of which, an octanucleotide (GTTTCCCT), has 100% homology. The conserved sequences are arranged in a unique fashion and have a spatial organization with respect to order and position, which may suggest a potential regulatory role in controlling the expression of nodulin and leghemoglobin genes during symbiosis.

Amino Acid Sequence↗
PubMed1985

Primary structure of the soybean nodulin-35 gene encoding uricase II localized in the peroxisomes of uninfected cells of nodules.

Nodulin-35 (N-35), a subunit of nodule-specific uricase (uricase II) of soybean (Glycine max), is shown to be preferentially synthesized on free polysomes during nodule development and is localized in peroxisomes of the uninfected cells of this tissue. A cDNA clone, isolated by using mRNA from immunoprecipitated polysomes, revealed the primary structure of this protein with a molecular mass of 35,100. That this clone represents N-35 was confirmed by comparing the deduced amino acid sequence with the partial sequence of a CNBr-cleaved peptide of purified N-35. Southern blot hybridizations with genomic DNA suggest that there are several EcoRI fragments containing N-35 sequences. Three of these sequences were isolated from a genomic library of soybean. Nucleotide sequence analysis showed that the complete gene extends almost 5000 base pairs on two EcoRI fragments and the coding region (309 codons) is interrupted by seven introns ranging in size from 154 to 1341 base pairs. Lack of a signal sequence and its translation on free polysomes suggest that N-35 is posttranslationally transported to the peroxisomes. Furthermore, there is no cross-hybridization of N-35 cDNA with RNA from young (3- to 4-day) roots and leaves, indicating that the observed "uricase" activity in these tissues is due to the product of a different gene.

Journal Article↗
PubMed1985

Comparison of improved precipitation methods for quantification of high-density lipoprotein cholesterol.

We compared the standard Lipid Research Clinics heparin-Mn2+ (46 mmol/L) method and five improved precipitation methods for quantification of high-density lipoprotein (HDL) cholesterol. Three of these methods--a dextran sulfate-Mg2+ procedure, reported as a Selected Method, a modified heparin-Mn2+ (92 mmol/L) method, and a modified phosphotungstate-Mg2+ procedure--all gave similar results. Three other methods--the standard heparin-Mn2+ (46 mmol/L) method and two polyethylene glycol methods (75 g/L or pH 10 reagent at 100 g/L final concentrations)--gave slightly higher values for HDL cholesterol. Addition of NaCl or glucose to specimens did not significantly change protein precipitation. In terms of sedimentation effectiveness with hypertriglyceridemic specimens, the methods were ranked in the following order: polyethylene glycol (pH 10, 100 g/L) greater than dextran sulfate-Mg2+ greater than heparin-Mn2+ (92 mmol/L) = polyethylene glycol (75 g/L) greater than phosphotungstate-Mg2+ greater than heparin-Mn2+ (46 mmol/L).

Adolescent↗