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Biomedical subjects

T Nguyen

Publications and source records attributed to T Nguyen.

At least 307 records · Page 17Linked to original sources
PubMed1994

Symptomatic fracture incidence in elderly men and women: the Dubbo Osteoporosis Epidemiology Study (DOES).

This longitudinal population-based study documents the incidence of all symptomatic fractures from 1989 to 1992 in an elderly, predominantly Caucasian population of males and females (> or = 60 years as at 1 January 1989) living in the geographically isolated region of the city of Dubbo, NSW, Australia. Fractures were ascertained by reviewing reports from all radiology services in the region. There were 306 fractures in 271 patients during the study period representing 11,401 person-years of observation. In the 60-80 year age group only 10% of fractures involved the hip, while in the over-80 age group this proportion rose to 41%. Incidence of distal forearm, hip and total fractures increased exponentially in both sexes with increasing age. Rib fractures were relatively common, with incidence rates for rib fractures similar to those for humeral fractures. Overall fracture incidence was 2685 per 100,000 person-years (males 1940 per 100,000 and females 3250 per 100,000). Residual lifetime fracture risk in a person aged 60 years with average life expectancy was 29% for males and 56% for females. Symptomatic fracture rates with the improved methodology in this study were higher than previously reported in both elderly males and females, with a marked preponderance of non-hip fractures in the 60-80 year age group. These symptomatic fractures have previously been underestimated, if not largely ignored, in public health approaches including cost-benefit analyses of osteoporosis prevention and treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1994

Charged-particle mutagenesis II. Mutagenic effects of high energy charged particles in normal human fibroblasts.

The biological effects of high LET charged particles are a subject of great concern with regard to the prediction of radiation risk in space. In this report, mutagenic effects of high LET charged particles are quantitatively measured using primary cultures of human skin fibroblasts, and the spectrum of induced mutations are analyzed. The LET of the charged particles ranged from 25 KeV/micrometer to 975 KeV/micrometer with particle energy (on the cells) between 94-603 MeV/u. The X-chromosome linked hypoxanthine guanine phosphoribosyl transferase (hprt) locus was used as the target gene. Exposure to these high LET charged particles resulted in exponential survival curves; whereas, mutation induction was fitted by a linear model. The Relative Biological Effect (RBE) for cell-killing ranged from 3.73 to 1.25, while that for mutant induction ranged from 5.74 to 0.48. Maximum RBE values were obtained at the LET of 150 keV/micrometer. The inactivation cross-section (alpha i) and the action cross-section for mutant induction (alpha m) ranged from 2.2 to 92.0 micrometer2 and 0.09 to 5.56 x 10(-3) micrometer2, respectively. The maximum values were obtained by 56Fe with an LET of 200 keV/micrometer. The mutagenicity (alpha m/alpha i) ranged from 2.05 to 7.99 x 10(-5) with the maximum value at 150 keV/micrometer. Furthermore, molecular analysis of mutants induced by charged particles indicates that higher LET beams are more likely to cause larger deletions in the hprt locus.

Cell Death↗
PubMed1994

Ileal patch ureteroplasty for repair of ureteral strictures: clinical application and results in 4 patients.

Four patients with severe ureteral strictures recovered adequate renal and ureteral function after application of an ileal patch graft to the area of stenosis. No metabolic abnormalities resulted from use of the ileal patch graft. Candidates for this type of repair have severe ureteral strictures after prior attempts at repair. They have ureters encased in scar but lumens are maintained. Ileal patch graft construction is depicted graphically.

Adult↗
PubMed1994

Cloning, characterization, and distribution of a mu-opioid receptor in rat brain.

We report the isolation and characterization of a rat cDNA clone encoding a mu-opioid receptor. This receptor, a 398 amino acid protein, shares 59% overall identity with the mouse delta- and kappa-opioid receptors. Transient expression of the receptor in COS cells revealed high-affinity binding of mu-selective opioid antagonists and agonists, with a KD for naloxone approximately 1.5 nM, and for [D-Ala2,N-Me-Phe4,Gly5-ol]-enkephalin (DAMGO) and morphine at the high-affinity site of 2-4 nM, confirming a mu-opioid pharmacological profile. Northern blotting and in situ hybridization histochemistry revealed that the mu-opioid receptor mRNA was expressed in many brain regions, including cerebral cortex, caudate putamen, nucleus accumbens, olfactory tubercle, septal nuclei, thalamus, hippocampus, and medial habenular nucleus, in keeping with the known distribution of the mu-opioid receptor.

Amino Acid Sequence↗
PubMed1994

Cellular accumulation and DNA damage induced by liposomal cis-bis-neodecanoato-trans-R,R-1,2-diaminocyclohexaneplatinum+ ++(II) in LoVo and LoVo/PDD cells.

Liposomal cis-bis-neodecanato-trans-R,R-1,2-diaminocyclohexaneplatinum (11) (L-NDDP) is a liposome-entrapped platinum complex that has shown partial lack of cross-resistance with cisplatin in human colon carcinoma LoVo cells. We studied the drug accumulation and DNA damage induced by L-NDDP and cisplatin in LoVo and LoVo/PDD cells. Our results indicate that the accumulation of L-NDDP in LoVo cells is several-fold higher than that of cisplatin; that the accumulation of L-NDDP is similar in both cell lines, whereas that of cisplatin is reduced by 2- to 3-fold in LoVo/PDD cells; and that the transmembrane transport of cisplatin is highly dependent on temperature while that of L-NDDP is not. We also found that the cytotoxicity of both agents correlates with the extent of DNA-protein cross-link formation, and that DNA interstrand cross-linking does not appear to play a role in the cytotoxicity of L-NDDP, whereas it correlates with cisplatin cytotoxicity.

Antineoplastic Agents↗
PubMed1994

Evaluation of new transport medium for detection of herpes simplex virus by culture and direct enzyme-linked immunosorbent assay.

The transport medium Multi-Microbe Media (M4) was evaluated prospectively by culture and direct enzyme-linked immunosorbent assay (ELISA) for detection of herpes simplex virus from 473 specimens. In addition, 377 specimens in Bartels Viral Transport Medium were evaluated. By using culture as a "gold standard," the ELISA sensitivity was approximately 85%, while the specificities exceeded 96% for both media.

Antigens, Viral↗
PubMed1994

Transcription of brain natriuretic peptide and atrial natriuretic peptide genes in human tissues.

We have compared the expression of atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) genes in various human tissues using a quantitative polymerase chain reaction technique. Tissues of three human subjects, obtained at autopsy, were analyzed. BNP transcripts could be detected in the central nervous system, lung, thyroid, adrenal, kidney, spleen, small intestine, ovary, uterus, and striated muscle. ANP transcripts could also be demonstrated in various human extracardiac tissues including several endocrine organs. In all peripheral tissues, the level of both natriuretic peptide transcripts was approximately 1-2 orders of magnitude lower than in cardiac ventricular tissues. This distribution is in marked contrast to the much lower level of ANP and BNP transcripts present in extracardiac rat tissues (generally less than 1/1000 of ventricles). These data suggest differential expression of the two natriuretic peptide genes in cardiac and extracardiac tissues in man. Furthermore, the presence of local synthesis of ANP and BNP in various peripheral organs suggests paracrine and/or autocrine function of these natriuretic peptides.

Animals↗
PubMed1994

Hypertonic saline dextran prime reduces increased intracranial pressure during cardiopulmonary bypass in pigs.

Children and adults who develop neurologic deficits after cardiac surgery may experience cerebral ischemia during cardiopulmonary bypass. Increased intracranial pressure (ICP) may contribute to cerebral ischemia during bypass. Hypertonic saline dextran (HSD), a hyperosmotic, hyperoncotic resuscitation solution, decreases ICP in trauma resuscitation. We hypothesized that HSD would decrease ICP, reduce brain water, and reduce intravascular fluid requirements during bypass. Twelve swine were divided into two bypass groups: Group 1 (ISO = isotonic) received as prime 1 L of lactated Ringer's solution and 500 mL of 6% hydroxyethyl starch. Group 2 (HSD = hypertonic saline/dextran) received as prime 1 L of lactated Ringer's solution, 500 mL of 6% hydroxyethyl starch, and 1 mL/kg of 24% hypertonic saline/25% dextran. Normothermic bypass was instituted at 100 mL.kg-1.min-1. ICP increased significantly during bypass with ISO prime but not with HSD. Brain water in the cerebrum did not differ between groups but was reduced in the cerebellum to 75.9% +/- 1.4%. We conclude that HSD prevented any significant increase in ICP during normothermic bypass, and substantially improved fluid balance during bypass. In cardiac surgery patients in whom maintaining decreased ICP and reducing isotonic fluid administration is important, HSD may be a useful addition to the bypass prime solution.

Animals↗
PubMed1994

[Late recurrence of melanoma beyond 10 years].

Late recurrence phenomenon in the course of melanoma (i.e. first recurrence after a 10 years or more disease free interval) is often ignored. Eleven cases and a literature review are presented. Main conclusions are: --lack of clinical or pathological criteria predicting the risk for a given patient, --possible underevaluation of the number of patients affected by these late recurrences, due to a premature follow up cessation, --advantages of prolonged clinical follow up over ten years aimed at early diagnosis of locoregional metastasis which may benefit from successful surgical treatment.

Adult↗
PubMed1994

Laparoscopic cholecystectomy: 563 cases at a community teaching hospital and a review of 12,201 cases in the literature. Monmouth Medical Center Laparoscopic Cholecystectomy Group.

Eleven surgeons attempted laparoscopic cholecystectomy in 563 patients over a 14-month period. Of these 563, 536 (95.3%) were performed successfully; the remaining patients required conversion to laparotomy, but only five because of complications. There were no mortalities associated with the procedure. Thirty-nine patients had complications, 14 surgical and related to the procedure itself. Weight was not considered a contraindication. The preoperative diagnosis in 83.6% patients with chronic cholecystitis, and in the remainder (16.4%) it was acute cholecystitis. Mean operative time was 86.4 min, and mean hospital stay for uncomplicated successful laparoscopic cholecystectomy was 1.9 days. An extensive review of the literature reveals an additional 9,792 laparoscopic cholecystectomies performed at the time of the writing of this paper. Our results compare favorably to these. A discussion of historical aspects of the procedure, contraindications to laparoscopic cholecystectomy, and the merits of selective intraoperative cholangiography are also presented.

Acute Disease↗
PubMed1994

[Cutaneous metastasis disclosing adrenal cortical carcinoma].

Metastases to the skin from internal malignant neoplasms are uncommon and often preterminal event. Cutaneous metastases from an adrenal cortical carcinoma have rarely been reported even in the advanced stages of the disease. A patient was initially seen with a small cutaneous lesion on the cheek and was found to have a large adrenal cortical tumor. Histologic comparison proved that the cutaneous lesion was a metastase from an adrenal cortical carcinoma.

Adrenal Cortex Neoplasms↗
PubMed1993

A human gene that shows identity with the gene encoding the angiotensin receptor is located on chromosome 11.

We report the cloning of a gene, intronless in its coding region, which we have named APJ. This gene was cloned using the polymerase chain reaction (PCR), with a set of primers designed on the basis of the conservation that members of G protein-coupled receptors (GPCR) have in their transmembrane (TM) regions. The putative receptor protein, APJ, shares closest identity to the angiotensin receptor (AT1) ranging from 40 to 50% in the hydrophobic TM regions of these receptors. The transcripts for this gene were detected in many regions of the brain. PCR analysis of somatic cell lines found APJ-related sequences to be only present on chromosome 11, and high-resolution mapping by fluorescence in situ hybridization (FISH) sublocalized APJ on band q12.

Amino Acid Sequence↗
PubMed1993

Prediction of osteoporotic fractures by postural instability and bone density.

OBJECTIVE: To investigate the utility of risk factors such as bone mineral density, lifestyle, and postural stability in the prediction of osteoporotic fractures. DESIGN: Longitudinal, epidemiological, and population based survey. SETTING: City of Dubbo, New South Wales. SUBJECTS: All residents of Dubbo aged > or = 60 on 1 January 1989. MAIN OUTCOME MEASURE: Incidence of fracture for individual subjects. RESULTS: The overall incidence of atraumatic fractures in men and women was 1.9% and 3.1% per annum respectively. The predominant sites of fracture were hip (18.9%), distal radius (18.5%), ribs and humerus (11.9% in each case), and ankle and foot (9.1% and 6.6% respectively). Major predictors of fractures in men and women were femoral neck bone mineral density, body sway, and quadriceps strength. Age, years since menopause, height, weight, and lifestyle factors were also correlated with bone mineral density and body sway and hence were indirect risk factors for fracture. Discriminant function analysis correctly identified 96% and 93% (sensitivities 88% and 81%) of men and women, respectively, who subsequently developed atraumatic fractures. Predictions based on this model indicated that a woman with a bone mineral density in the lowest quartile in the hip together with high body sway had a 8.4% probability of fracture per annum. This represented an almost 14-fold increase in risk of fracture compared with a woman in the highest bone mineral density quartile with low postural sway. An individual with all three predictors in the "highest risk" quartile had a 13.1% risk of fracture per annum. CONCLUSIONS: Bone mineral density, body sway, and muscle strength are independent and powerful synergistic predictors of fracture incidence.

Aged↗
PubMed1993

Polymorphisms of the D4 dopamine receptor alleles in chronic alcoholism.

We have screened genomic DNA for the identification of D4 dopamine receptor polymorphisms. We show that the D4 dopamine receptor genotype in 72 severely affected chronic alcoholics is heterogeneous, with individuals homozygous and heterozygous for the various D4 receptor alleles. Alcoholics demonstrated a greater prevalence of the D4(3) (p < 0.005) and D4(6) (p < 0.005) alleles than has been reported in normals. There was a high prevalence of nicotine abuse among all D4 genotypes. The frequency of other drug abuse was higher in the D4(3,3) and the D4(4,7) groups, and the family history was strongly positive in the D4(2,4) group. The distribution of the D2 alleles showed equivalence in all D4 genotypes, except in D4(4,6) and D4(4,7) in whom the prevalence of the D2 A1A2 allele was 2-fold higher. The polymorphic variations of the D4 receptor genes should be among the factors considered in the assessment of individual differences in susceptibility to disorders such as alcohol abuse or drug addiction that may be mediated through central dopaminergic systems.

Adult↗
PubMed1993

Human immunodeficiency virus proteins induce the inhibitory cAMP/protein kinase A pathway in normal lymphocytes.

Proliferation of normal T lymphocytes is impaired by human immunodeficiency virus (HIV) proteins. In this paper, we demonstrate important parts of this mechanism. Initially, HIV-induced impairment of proliferation was shown to be an active process involving induction of protein tyrosine kinases in both CD4 and CD8 T cells. Furthermore, the impairment of cell proliferation was demonstrated to be linked to induction of the inhibitory protein kinase A (PKA) pathway by HIV proteins. This induction of PKA was accompanied by an increase in intracellular cAMP, which is necessary for the activation of PKA. Finally, increases in cAMP/PKA activity were shown to induce biochemical changes that impaired proliferation when cells were stimulated with phytohemagglutinin. This was demonstrated by showing that (i) agents, other than HIV proteins, that increase cAMP/PKA activity (cholera toxoid and 8-bromo-cAMP) also decreased T-lymphocyte proliferation; (ii) exposure of lymphocytes to HIV or cholera toxoid led to decreased membrane activity of the proliferation promoter protein kinase C upon stimulation; and (iii) agents that reduced cAMP generation neutralized the effect of HIV proteins and restored lymphocyte proliferation. These studies show that the HIV-induced augmentation of cAMP/PKA activity may be a key part of the mechanism responsible for all or part of the HIV-induced anergy of T lymphocytes.

Amino Acid Sequence↗
PubMed1993

Prevention of corticosteroid osteoporosis. A comparison of calcium, calcitriol, and calcitonin.

BACKGROUND: Prolonged corticosteroid therapy increases the risk of osteoporosis and fracture. We studied whether corticosteroid-induced osteoporosis could be prevented by treatment with calcium, calcitriol (1,25-dihydroxyvitamin D3), and calcitonin. METHODS: One hundred three patients starting long-term corticosteroid therapy were randomly assigned to receive 1000 mg of calcium per day orally and either calcitriol (0.5 to 1.0 microgram per day orally) plus salmon calcitonin (400 IU per day intranasally), calcitriol plus a placebo nasal spray, or double placebo for one year. Data on treatment efficacy were available for 92 of these patients. Bone density was measured every four months for two years by photon absorptiometry. There were no significant differences between groups with respect to age, underlying disease, initial bone density, or corticosteroid dose during the first year. RESULTS: Calcitriol (mean dose, 0.6 microgram per day), with or without calcitonin, prevented more bone loss from the lumbar spine (mean rates of change, -0.2 and -1.3 percent per year, respectively) than calcium alone (-4.3 percent per year, P = 0.0035). Bone loss at the femoral neck and distal radius was not significantly affected by any treatment. In the second year, lumbar bone loss did not occur in the group previously treated with calcitonin plus calcitriol (+0.7 percent per year), but it did occur in the group given calcium alone (-2.3 percent per year). The calcitriol group also lost lumbar bone (-3.6 percent per year) but received more corticosteroid in the second year than the other two groups. CONCLUSIONS: Calcitriol and calcium, used prophylactically with or without calcitonin, prevent corticosteroid-induced bone loss in the lumbar spine.

Adolescent↗