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Biomedical subjects

M Nguyen

Publications and source records attributed to M Nguyen.

At least 145 records · Page 8Linked to original sources
PubMed1996

Forceful epidural injections for the treatment of lumbosciatic pain with post-operative lumbar spinal fibrosis.

OBJECTIVE: To evaluate the efficacy of forceful epidural corticosteroid injections in lumbosciatic pain ascribed to post-operative lumbar spinal fibrosis. METHOD: Randomized controlled study comparing forceful injections via the sacral hiatus of 125 mg prednisolone acetate + 40 ml saline (treatment group) and injections via the same route of 125 mg prednisolone acetate alone (control group). Results were compared after six and 18 months. The main evaluation criterion was a subjective assessment of overall efficacy done by the patient using a seven-level scale. RESULTS: After six months, the proportion of patients who were relieved of their sciatica was significantly higher in the forceful injection group (n = 29; 45%) than in the control group (n = 31; 19%) (p = 0.03). Success rates for low back pain were 29% and 6% in the forceful injection and control groups, respectively. Among secondary efficacy criteria, nerve root pain evaluated on a visual analog scale and by Schöber's index showed significantly greater improvement in the forceful injection group than in the control group. After 18 months, results were still in favor of the forceful injection group, with success rates of 39% for the sciatica and 31% for the low back pain. The proportion of patients who returned to work was similar in the two groups. CONCLUSION: Although mediocre overall, the results of forceful epidural corticosteroid injections are better than those of simple epidural injections of a corticosteroid alone. Given the paucity of effective treatments for lumbosciatic pain apparently due to postoperative fibrosis, forceful injections should be given a place in the treatment of this condition.

Adult↗
PubMed1995

Peripheral blood harvest of unaffected CD34+ CD38- hematopoietic precursors in paroxysmal nocturnal hemoglobinuria.

Paroxysmal nocturnal hemoglobinuria (PNH) arises from somatic mutation of a bone marrow progenitor that disrupts glycosylinositol phospholipid (GPI) anchoring of cell surface proteins. We recently characterized the expression of GPI-anchored decay acclerating factor (DAF) and CD59 during hematopoietic development in PNH marrow. We found that, although a subset of early hematopoietic precursors identified by the CD34+CD38- phenotype exhibits normal DAF and CD59 expression, DAF and CD59 are absent on the majority of CD34+CD38- cells. Pluripotent CD34+CD38- hematopoietic stem cells normally circulate in the peripheral blood and can be collected by apheresis, cryopreserved, and later used for reconstitution of hematopoiesis. In this study, we examined the phenotypes of CD34+ cells that are released into the blood of PNH patients. Analyses of apheresis samples from three affected individuals showed discrete populations of circulating DAF+CD59+CD34+ and DAF-CD59-CD34+ cells. Variable proportions of CD34+CD38- cells were present within the peripheral blood CD34+ cells of each patient, but in all three cases the DAF+CD59+CD34+CD38- cell subset subset. Because CD34+ cells lacking CD38 antigen are highly enriched for self-renewing hematopoietic stem cells, these findings indicate that apheresis samples can serve as a source of unaffected stem cells for autologous marrow transplantation of PNH patients.

ADP-ribosyl Cyclase↗
PubMed1995

A gene-type-specific enhancer regulates the carbamyl phosphate synthetase I promoter by cooperating with the proximal GAG activating element.

The rat carbamyl phosphate synthetase I gene is expressed in two cell types: hepatocytes and epithelial cells of the intestinal mucosa. The proximal promoter contains a single activating element, GAG, two repressor elements (sites I and III) and an anti-repressor element (site II). Although these elements together exhibit the potential for complex regulation, they are unable to confer tissue-specific promoter activity. Here we have identified a cell-type-specific enhancer that lies 10 kilobases upstream of the promoter. Unexpectedly, the enhancer also functioned in a gene-type-specific manner. The enhancer stimulated promoter activity exclusively through the proximal GAG element. Abrogation of GAG, either directly by mutation of GAG or indirectly by sites I and III repressors, abolished enhancer activation. Conversely, activation of the heterologous thymidine kinase promoter by the enhancer required the introduction of GAG. The requirement for GAG, therefore, functions to constrain the enhancer to a specific target promoter.

Animals↗
PubMed1995

The "common stem cell" hypothesis reevaluated: human fetal bone marrow contains separate populations of hematopoietic and stromal progenitors.

There is a long-standing controversy as to whether a single bone marrow (BM)-derived cell can differentiate along both hematopoietic and stromal lineages. Both primitive hematopoietic and stromal progenitor cells in human BM express the CD34 antigen but lack expression of other surface markers, such as CD38. In this study we examined the CD34+, CD38- fraction of human fetal BM by multiparameter fluorescence-activated cell sorting (FACS) analysis and single-cell sorting. CD34+, C38- cells could be divided into HLA-DR+ and HLA-DR- fractions. After single-cell sorting, 59% of the HLA-DR+ cells formed hematopoietic colonies. In contrast, the CD34+, CD38-, HLA-DR- cells were much more heterogeneous with respect to their light scatter properties, expression of other hematopoietic markers (CD10, CD36, CD43, CD49b, CD49d, CD49e, CD50, CD62E, CD90w, CD105, and CD106), and growth properties. Single CD34+, CD38-, HLA-DR- cells sorted into individual culture wells formed either hematopoietic or stromal colonies. The presence or absence of CD50 (ICAM-3) expression distinguished hematopoietic from stromal progenitors within the CD34+, CD38-, HLA-DR- population. The CD50+ fraction had light scatter characteristics and growth properties of hematopoietic progenitor cells. In contrast, the CD50- fraction lacked hematopoietic progenitor activity but contained clonogenic stromal progenitors at a mean frequency of 5%. We tested the hypothesis that cultures derived from single cells with the CD34+, CD38-, HLA-DR- phenotype could differentiate along both a hematopoietic and stromal lineage. The cultures contained a variety of mesenchymal cell types and mononuclear cells that had the morphologic appearance of histiocytes. Immunophenotyping of cells from these cultures indicated a stromal rather than a hematopoietic origin. In addition, the growth of the histiocytic cells was independent of the presence or the absence of hematopoietic growth factors. Based on sorting more than 30,000 single cells with the CD34+, CD38-, HLA-DR- phenotype into individual culture wells, and an analysis of 864 stromal cultures initiated by single CD34+ BM cells, this study does not support the hypothesis of a single common progenitor for both hematopoietic and stromal lineages within human fetal BM.

Antigens, CD↗
PubMed1995

Import and insertion of proteins into the mitochondrial outer membrane.

Nuclear-encoded proteins destined for insertion into the mitochondrial outer membrane, follow the same general pathway for import as proteins that are translocated to interior compartments within the organelle. This observation is true both for beta-barrel-type proteins and for proteins that contain hydrophobic alpha-helical transmembrane segments. In this review, we describe what is known about the various steps leading to protein insertion into the outer membrane, and discuss the energetics that favor vectorial translocation into and across this membrane. The selection of the outer membrane during import may involve a lateral release of the translocating polypeptide from the import machinery so that the appropriate domains of the protein become embedded in the lipid bilayer. One type of topogenic domain that can guarantee such selection of the outer membrane is a signal-anchor sequence of the type characterized for the bitopic protein Mas70p. It is suggested that a signal-anchor sequence selective for the mitochondrial outer membrane causes abrogation of polypeptide translocation and triggers the release of the transmembrane segment into the surrounding lipid bilayer, prior to any possibility for the commitment of translocation to the interior of the organelle. Specific structural features of the signal-anchor sequence specify its orientation in the membrane, and can confer on this sequence the ability to form homo-oligomers and hetero-oligomers. Strategies other than a signal-anchor sequence may be employed by other classes of proteins for selection of the outer-membrane. Of note is the ability of the outer-membrane import machinery to catalyze integration of the correct set of proteins into the outer-membrane bilayer, while allowing proteins that are destined for integration into the bilayer of the inner membrane to pass through unimpeded. Again, however, different proteins may employ different strategies. One model proposes that this can be accomplished by a combination of a matrix-targeting signal and a distal stop-transfer sequence. In this model, the formation of contact sites, which is triggered when the matrix-targeting signal engages the import machinery of the inner membrane, may prevent the outer-membrane translocon from recognizing and responding to the downstream stop-transfer domain. This allows the transmembrane segment to pass across the outer-membrane, and subsequently integrate into the inner membrane.

Animals↗
PubMed1995

Primary structure and sequence analysis of RNA2 of a mechanically transmitted barley mild mosaic virus isolate: an evolutionary relationship between bymo- and furoviruses.

The RNA2 nucleotide sequence of a mechanically transmitted isolate of barley mild mosaic virus (BaMMV) has been determined. A combination of Northern blot and sequence analysis indicates that this RNA2 lacks approximately 1000 nucleotides of its C-terminal protein (P2) gene, with respect to Polymyxa graminis transmitted BaMMV. This is confirmed by sequence comparison with RNA2 of a fungus transmitted BaMMV isolate, which reveals the presence of a single deletion located in the 3'-terminal part of the P2 gene. As a consequence, this RNA2 codes for a P2 protein of only 34 K. Sequence homology between the bymovirus P2 protein and the capsid readthrough protein of beet necrotic yellow vein virus and soil-borne wheat mosaic virus suggests an evolutionary relationship between bymo- and furoviruses.

Amino Acid Sequence↗
PubMed1995

Changes observed in Doppler studies of the fetal circulation in pregnancies complicated by pre-eclampsia or the delivery of a small-for-gestational-age baby. I. Cross-sectional analysis.

The aim of this study was to compare changes in Doppler ultrasound studies of the fetal circulation in normal pregnancies with a group of pregnancies complicated by proteinuric pregnancy-induced hypertension (PPIH), delivery of a small-for-gestational-age (SGA) baby, or both. A total of 167 uncomplicated pregnancies with a term delivery of an appropriately grown baby (AGA) were used to define the normal range. Altogether, 123 high-risk pregnancies with a known outcome constituted the study group. A color duplex ultrasound machine was used to perform biometry and fetal Doppler studies. Measurements obtained from the fetal circulation included the umbilical artery (UA) pulsatility index (PI), the middle cerebral artery (MCA) PI and time-averaged velocity (TAV), the thoracic aorta (AO) PI and TAV. In addition, the ratio between the MCA PI and UA PI, the MCA PI and the AO PI, and the product of the MCA PI and AO TAV were used in the analysis. A total of 105 pregnancies had a complicated outcome. They were divided into three categories: PPIH only (pregnancies complicated by PPIH with the delivery of an AGA fetus, n = 17), SGA only (delivery of an SGA baby, with no evidence of PPIH, n = 55), and PPIH + SGA (pregnancies complicated by pre-eclampsia and delivery of an SGA baby, n = 37). The PPIH + SGA group represented true clinical intrauterine growth retardation. Cross-sectional reference ranges were created using the observations from the normal group. z-scores (standard deviation from the mean of the normal range) of the last observations made before delivery were calculated for each of the vessel velocimetry measurements and ratios. The statistical significance of z-score values was calculated using analysis of variance. The MCA and UA PI values showed the greatest deviation for any single-vessel parameter. The ratios of fetal Doppler indices (MCA/UA PI ratio, MCA/AO PI ratio and the MCA PI/AO TAV index) demonstrated greater deviation from normal than any individual vessel. The UA PI z-score for PPIH+SGA delivering < 34 weeks gestation (2.92) was significantly greater than the z-score for PPIH+SGA delivering > or = 34 weeks (1.20, p < 0.05). Fetal Doppler indices, in particular ratios that include measurements obtained from the cerebral circulation, help in the recognition of the small fetus that is growth-retarded. At term, evidence of fetal hemodynamic redistribution may exist in the presence of a normal umbilical artery PI. Fetal Doppler indices provide information that is not readily obtained from more conventional tests of fetal well-being.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1995

Caenorhabditis elegans mutants resistant to inhibitors of acetylcholinesterase.

We characterized 18 genes from Caenorhabditis elegans that, when mutated, confer recessive resistance to inhibitors of acetylcholinesterase. These include previously described genes as well as newly identified genes; they encode essential as well as nonessential functions. In the absence of acetylcholinesterase inhibitors, the different mutants display a wide range of behavioral deficits, from mild uncoordination to almost complete paralysis. Measurements of acetylcholine levels in these mutants suggest that some of the genes are involved in presynaptic functions.

Acetylcholine↗
PubMed1995

[Hypercalcemia and squamous cell carcinoma of the upper respiratory-digestive tracts. Incidence and prognosis].

We performed a retrospective analysis on all head and neck cancers with hypercalcemia seen between January 1988 and June 1993 at the Centre Oscar-Lambret, cancer center of northern France. Hypercalcemia, non albumin-corrected, higher than 2.60 mmol/l was observed in 173 of 3,394 consecutive patients (5%). Median age of patients with hypercalcemia was 53 years and 97% of these patients were males. All patients with hypercalcemia had advanced or recurrent and/or metastatic squamous cell carcinoma of head and neck (SCCHN); 31 of them were not pretreated. There was no significant difference in histology between patients with or without hypercalcemia, but hypercalcemia was most commonly associated with lesions of the oropharynx (p = 0.00001). The median of calcemia was of 2.83 mmol/l (2.61-4.70). Gastrointestinal and neurologic symptoms respectively occurred in 24% and in 14% of patients and bone metastases in 25% of patients. Median survival after the first determination of hypercalcemia was of 7 weeks (0-128) for the overall group of 173 patients and of 12 weeks (1-128) for those 31 patients with hypercalcemia at initial diagnosis. Prognosis associated factors were: efficacy of antitumour treatment, performance status and hypercalcemia superior or not to 3 mmol/l. We concluded that hypercalcemia in head and neck cancer is usually a late manifestation associated with advanced, recurrent and/or metastatic disease and carries a poor prognosis. The prolongation of survival can be obtained in some patients if an effective antitumour treatment is feasible.

Adult↗
PubMed1994

The cloning and expression of a human creatine transporter.

A human creatine transporter (hCRT-BS2M) cDNA clone was isolated from a human brainstem/spinal cord using a PCR and phage plaque hybridization based technique. This clone included an open reading frame of 1,905 base pairs(bp) within a 2,283bp cDNA. Northern blot hybridization detected the expression of corresponding mRNAs most prominently in the skeletal muscle, heart and kidney. Peptide sequence analysis of the hCRT-BS2M protein product revealed 12 putative transmembrane domains. The predicted protein sequence further demonstrates that the hCRT-BS2M has highly conserved amino acid identity with the other members of the sodium dependent plasma membrane transporter family. Transient expression of the hCRT-BS2M in COS-7 cells demonstrates sodium dependent [14C]creatine uptake with a KM value of 14.9 +/- 3.0 microM (n = 5) that is attenuated by creatine and selective structural analogues of creatine.

Amino Acid Sequence↗
PubMed1994

Role of membrane anchor domain of Bcl-2 in suppression of apoptosis caused by E1B-defective adenovirus.

Bcl-2 is an integral membrane protein that functions as a suppressor of programmed cell death. It contains a COOH-terminal signal anchor sequence that is selective for import and insertion of Bcl-2 into the mitochondrial outer membrane and, by a different mechanism, can also direct the protein to other membrane sites. Deletion of the signal anchor sequence rendered Bcl-2 cytosolic and impaired its ability to prevent apoptotic death of human KB cells infected with a mutant form of adenovirus type 5 that does not make E1B 19-kDa protein. When the predicted transmembrane domain of the Bcl-2 signal anchor was replaced with that of the signal anchor of the yeast outer mitochondrial membrane protein, Mas70p, the Bcl-2/Mas70p hybrid was found to be very similar to Bcl-2 in its distribution within transfected KB cells, in its ability to heterodimerize with Bax, and in its ability to suppress apoptosis. These results are consistent with a model in which the transmembrane segment contributes to the function of Bcl-2 by targeting and anchoring the protein to strategic membrane locations in the cell. Concentration of Bcl-2 at these sites may contribute to its proposed role as regulator, or component, of an antioxidant pathway.

Adenovirus E1B Proteins↗
PubMed1994

Elevated levels of an angiogenic peptide, basic fibroblast growth factor, in the urine of patients with a wide spectrum of cancers.

BACKGROUND: Experimental evidence supports the hypothesis that the development of blood vessels is fundamental to the growth and metastasis of solid tumors. Elevated levels of the angiogenic peptide basic fibroblast growth factor (bFGF) have been significantly correlated with the status and extent of disease in bladder cancer. PURPOSE: We measured the bFGF levels in patients with cancer in organs other than the bladder to determine whether elevated levels accompany these cancers. METHODS: Urine samples were collected from 950 patients having a wide variety of solid tumors, leukemia, or lymphoma and from a control group of 87 healthy volunteers and 198 patients with non-cancer-related diseases. Levels of bFGF in samples prepared from the urine were measured using an enzyme bioassay. RESULTS: Male control subjects had a median bFGF level of 151 pg/g and female control subjects a median of 237 pg/g, with a combined 90th percentile of 619 pg/g. An elevated level of bFGF was found in the urine of some of the patients with every type of tumor studied except cervical carcinoma. For example, patients with active local cancers had a median level of 312 pg/g. Those with active, metastatic cancers had a median level of 479 pg/g and a 90th percentile level of 14143 pg/g. After "elevated" was defined to mean higher than the 90th percentile level for controls, 31% of patients with local active and 47% of patients with metastatic active cancers showed elevated bFGF levels. Survival among cancer patients at the median follow-up time was 85%-88% for those with "normal" and 71%-72% for those with "elevated" urine bFGF levels. IMPLICATIONS: Our results suggest that bFGF in urine deserves further evaluation of its potential use as a monitor of therapy or as a predictor of outcome once a cancer has been diagnosed.

Analysis of Variance↗
PubMed1994

Diacerhein in the treatment of osteoarthritis of the hip.

OBJECTIVE: To determine the efficacy and safety of diacerhein, a potential new therapeutic agent with properties differing from those of existing nonsteroidal anti-inflammatory drugs (NSAIDs), and of a combination of diacerhein and an NSAID (tenoxicam) in the treatment of osteoarthritis (OA) of the hip. METHODS: Two hundred eighty-eight patients with painful OA of the hip were enrolled in an 8-week randomized, double-blind, placebo-controlled, 2 x 2 factorial design study. Four treatment groups were defined: 1) diacerhein placebo and tenoxicam placebo, 2) tenoxicam and diacerhein placebo, 3) diacerhein and tenoxicam placebo, and 4) diacerhein and tenoxicam. The daily dosages of diacerhein and tenoxicam were 100 mg and 20 mg, respectively. RESULTS: Analyses of efficacy showed no interaction between diacerhein and tenoxicam in terms of efficacy, a clinically significant rapid (< or = 2 weeks) and persisting effect of tenoxicam during the 8 weeks of the study, and a slow-acting (6 weeks) effect of diacerhein. Moderate, transient diarrhea was the most frequent side effect observed in the diacerhein group (37%) compared with the placebo group (4%). CONCLUSION: Both tenoxicam and diacerhein appear to be superior to placebo, and neither agent appears to significantly enhance or detract from the efficacy of the other when they are administered concomitantly. The onset of action of diacerhein appears to be delayed (> or = 4 weeks).

Aged↗
PubMed1994

Quantitation of angiogenesis and antiangiogenesis in the chick embryo chorioallantoic membrane.

A novel method for quantitating angiogenesis and its inhibition has been developed for the chick embryo. The method is based on the vertical growth of new capillary blood vessels into a collagen gel through two parallel nylon meshes which align the capillaries for counting. Angiogenesis is induced by basic fibroblast growth factor contained within the gel and slowly released by aluminum sucrose octasulfate (sucralfate) or by tumor cells implanted on the gel. The potency of four different angiogenesis inhibitors was compared at concentrations of 0.6 to 600 nmole. This technique may facilitate the discovery and development of angiogenesis inhibitors for clinical application.

Allantois↗
PubMed1994

The neuropathology of intracerebroventricular t-butylhydroperoxide.

t-Butylhydroperoxide can be used as a model oxidative stress-inducing agent in the brain following intracerebroventricular administration. Mice were treated with saline, t-butanol, or t-butylhydroperoxide. t-Butanol is the major metabolite of t-butylhydroperoxide. t-Butylhydroperoxide had a number of effects, including that it damages dopaminergic, cholinergic, and GABAergic neurons as demonstrated immunohistochemically. Electron microscopic examination demonstrated that astrocytes, oligodendrocytes, endothelial cells, pericytes, and neurons are damaged by t-butylhydroperoxide. Dopamine and its metabolites were affected in a number of brain regions, as were serotonin and its metabolite. Choline acetyl transferase activity was decreased in the striatum. Edema was apparent as assessed by tissue protein levels. There was evidence of lipid peroxidation produced by t-butylhydroperoxide in the midbrain. t-Butylhydroperoxide is a neurotoxin that may be useful in understanding the unexpected ways the brain responds to oxidative stress.

Animals↗
PubMed1994

Identification of a human delta opioid receptor: cloning and expression.

The delta opioid receptor is an important target for analgesic drug development. This report describes the identification of delta opioid receptor clones from human cDNA libraries and the preparation of a human delta receptor cDNA in the pcDNA3 expression vector for transfection studies. The cDNA encodes a 372 amino acid protein that has 93% amino acid identity to mouse and rat delta receptors. COS-7 cells transfected with this clone express over 1.0 pmol receptor/mg protein when measured by saturation binding with [3H]naltrindole. The delta receptor selective ligands NTB, BNTX, [4'-Cl-Phe4]DPDPE and [D-Ala2,Glu4]deltorphin all have Ki values under 10 nM while the affinities of the mu and kappa opioid receptor ligands CTAP and U-69593, respectively, are over 4.0 microM. Agonists show binding to multiple affinity states of the receptor consistent with the presence of G-protein coupled and uncoupled forms of the expressed receptor. The 8-fold higher affinity of NTB relative to BNTX suggests that the human delta receptor is of the delta 2 subtype.

Amino Acid Sequence↗
PubMed1994

Evaluation of metastatic neck disease by computed tomography.

This study evaluated the accuracy of computed tomography (CT) scanning in the diagnosis of metastatic neck disease in primary squamous cell carcinoma of the oral cavity and oropharynx, and compared this modality with physical examination alone. The accuracy of the CT scan was found to be 62%, as compared with a 66% accuracy rate of physical examination. In cases of clinically enlarged lymph nodes, physical examination was found to be 71% accurate; the CT scan, 68% accurate. Both the sensitivity and the positive predictive value of the CT scan were lower than those of the physical examination in this patient population.

Carcinoma, Squamous Cell↗