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Biomedical subjects

L T Nguyen

Publications and source records attributed to L T Nguyen.

At least 55 records · Page 3Linked to original sources
PubMed2000

Normocalcemic hyperparathyroidism in Vietnamese immigrants living in southern California.

OBJECTIVE: To characterize the normocalcemic hyperparathyroidism in Vietnamese immigrants living in southern California. METHODS: Of 14 Vietnamese patients with primary hyperparathyroidism who were observed between 1991 and 1996, 50% (7 patients; 2 men and 5 women) had normal and/or fluctuating levels of serum total calcium. When the serum calcium was corrected for the albumin, the "corrected" calcium was lower than the measured serum total calcium. Their mean age was 56.4 +/- 11.4 years. All patients had normal serum levels of albumin and serum phosphate. RESULTS: Women were affected more often than men by a ratio of 5:2. The serum-ionized calcium as well as intact PTH were increased in all patients. Five patients underwent surgery with confirmation of parathyroid adenomas. Two patients refused surgery. They did not have osteitis fibrosa cystica by radiological examination. One patient had low plasma levels of 25-hydroxyvitamin D. Five of 7 normocalcemic patients (70%) were born in the month of December compared with 2 of seven hypercalcemic patients (30%). CONCLUSION: The blood ionized calcium and intact parathyroid hormone are necessary for confirmation of normocalcemic hyperparathyroidism. Most of our normocalcemic hyperparathyroid patients (70%) were born in the month of December. We postulate that a combination of exposure to solar ultraviolet light during the formation of the fetal parathyroid glands and stimulation from low vitamin D levels in the wintertime may be related to the development of hyperparathyroidism. However, it is difficult to prove a definite correlation between normocalcemic hyperparathyroidism and their month of birth (December), especially when these observations were seen in a small group of patients.

Adult↗
PubMed2000

Hyperthyroidism and asthma.

Two patients presented with new onset of thyrotoxicosis and they then developed episodic wheezing a few months afterward. The asthmatic attacks improved when the patients were rendered in a euthyroid state with treatment. The present paper discusses the relationship between two diseases, hyperthyroidism and asthma, and the underlying factors potentially contributing to their conditions. The present findings suggest that asthma may develop in a susceptible individual with hyperthyroidism and it is possible that the reactive oxygen species may be a contributory factor in exacerbating wheezing in our hyperthyroid patients.

Adult↗
PubMed2000

Folate and vitamin B12-deficiency anemias in Vietnamese immigrants living in Southern California.

BACKGROUND: Although the occurrence of iron deficiency anemia and hemoglobinopathies in Vietnamese immigrants has been reported, folate and vitamin B12 deficiencies have not. Proper diagnosis and effective treatment is necessary to achieve a complete correction of anemia. METHODS: We retrospectively analyzed the records of Vietnamese immigrants seen in our medical clinic from 1991 to 1993. Fifty-nine anemic patients (48 females and 11 males) had low levels of red blood cell (RBC) folate and/or serum vitamin B12. RESULTS: The patients' mean age was 37.7+/-17 years. Mean hemoglobin and hematocrit values were 11.4+/-0.7 g/dL and 34.4%+/-2.2%, respectively. Mean corpuscular volume (MCV) was normal in 40 patients (68%) (mean, 89.1+/-5 fL) and low in 19 patients (32%) (mean, 69.7+/-6 fL). Forty-four patients had low RBC folate levels (mean, 157.7+/-41.7 ng/mL). Twenty patients had low serum vitamin B12 levels (mean, 165.6+/-47 pg/mL). Fourteen patients had ferritin levels of <20%. CONCLUSIONS: Concomitant folate, vitamin B12, and iron deficiencies or hemoglobinopathies might have been responsible for either normal or low MCV in some of our anemic patients. In this ethnic group, RBC folate and serum vitamin B12 levels should be determined in all anemic patients.

Adolescent↗
PubMed2000

Detection of cytochrome P450 and other drug-metabolizing enzyme mRNAs in peripheral blood mononuclear cells using DNA arrays.

The purpose of this study was to determine whether the expression of cytochrome P450 (CYP) enzyme mRNAs, other drug-metabolizing enzyme mRNAs, and transporter mRNAs can be detected using DNA arrays. Total RNA was isolated from peripheral blood mononuclear cells of 10 multiple sclerosis patients and 10 age- and sex-matched controls. The mRNA was reverse transcribed to radiolabeled cDNA, and the resultant cDNA was used to probe a DNA array containing several thousand known human genes. The signals corresponding to several CYPs, drug-metabolizing, and transporter mRNAs was substantially above background. The results demonstrate that the DNA array technique has the sensitivity and the selectivity for applications in the pharmaceutical sciences. The mean values for mRNAs of specific CYPs and drug-metabolizing enzymes in peripheral blood cells were compared with reported values for liver. The capabilities of DNA arrays may prove useful for characterizing CYP expression in a variety of clinical samples.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1999

Activated T cells regulate bone loss and joint destruction in adjuvant arthritis through osteoprotegerin ligand.

Bone remodelling and bone loss are controlled by a balance between the tumour necrosis factor family molecule osteoprotegerin ligand (OPGL) and its decoy receptor osteoprotegerin (OPG). In addition, OPGL regulates lymph node organogenesis, lymphocyte development and interactions between T cells and dendritic cells in the immune system. The OPGL receptor, RANK, is expressed on chondrocytes, osteoclast precursors and mature osteoclasts. OPGL expression in T cells is induced by antigen receptor engagement, which suggests that activated T cells may influence bone metabolism through OPGL and RANK. Here we report that activated T cells can directly trigger osteoclastogenesis through OPGL. Systemic activation of T cells in vivo leads to an OPGL-mediated increase in osteoclastogenesis and bone loss. In a T-cell-dependent model of rat adjuvant arthritis characterized by severe joint inflammation, bone and cartilage destruction and crippling, blocking of OPGL through osteoprotegerin treatment at the onset of disease prevents bone and cartilage destruction but not inflammation. These results show that both systemic and local T-cell activation can lead to OPGL production and subsequent bone loss, and they provide a novel paradigm for T cells as regulators of bone physiology.

Animals↗
PubMed1999

Abducens internuclear and ascending tract of Deiters inputs to medial rectus motoneurons in the cat oculomotor nucleus: neurotransmitters.

The abducens internuclear and ascending tract of Deiters (ATD) pathways are the principal excitatory inputs to medial rectus motoneurons in the oculomotor nucleus and are related to the control of conjugate horizontal eye movements. Differences in the morphology and soma-dendritic distribution of abducens internuclear and ATD synaptic endings are correlated with known differences in the physiological properties of these independent inputs. The present study extends these observations to the ultrastructural localization of the excitatory amino acid neurotransmitters, glutamate and aspartate, using a postembedding immunogold procedure combined with the pre-embedding immunoperoxidase localization of anterogradely transported biocytin from the abducens nucleus and the ventral lateral vestibular nucleus. Consistent with their spheroidal synaptic vesicle content and the asymmetric pre/postsynaptic membrane profile, both the abducens internuclear and ATD synaptic endings are labeled with glutamate and aspartate. However, quantitative analysis of the density of colloidal gold particles associated with mitochondria versus synaptic vesicles/axoplasmic matrix reveals significant differences in the metabolic versus neurotransmitter pools of the amino acids in the two populations of synaptic endings. The findings indicate that both aspartate and glutamate, possibly co-localized, are the excitatory neurotransmitters utilized by abducens internuclear synaptic endings whose burst-tonic physiological activity conveys information related to eye position to medial rectus motoneurons. By contrast, glutamate is the excitatory neurotransmitter associated with ATD synaptic endings whose high frequency burst activity is related to head velocity.

Abducens Nerve↗
PubMed1999

Glycogen content and excitation-contraction coupling in mechanically skinned muscle fibres of the cane toad.

1. Mechanically skinned skeletal muscle fibres from the twitch region of the iliofibularis muscle of cane toads were used to investigate the relationship between fibre glycogen content and fibre capacity to respond to transverse tubular (T-) system depolarization. 2. A large proportion of total fibre glycogen remained in mechanically skinned muscle fibres exposed to aqueous solutions. This glycogen pool (about 80% of total fibre glycogen) was very stable when the preparation was incubated in a rigor solution (pH 7.0) but decreased gradually at a rate of 0.59+/-0.20% min-1 in a relaxing solution (200 nM [Ca2+]). The rate was considerably higher (2.66+/-0.38% min(-1)) when the preparations were exposed to 30 microM [Ca2+]. An even greater rate of glycogen loss was found after T-system depolarization-induced contractions. The Ca2+-dependent loss of fibre glycogen was caused by endogenous glycogenolytic processes. 3. Silver stained SDS gels of components eluted into relaxing solution from single skinned fibres revealed a rapid (2 min) loss of parvalbumin and at least 10 other proteins varying in molecular mass between 10 and 80 kDa but there was essentially no loss of myosin heavy and light chains and actin. Subsequent elution for a further 30 min in either relaxing or maximally Ca2+-activating solution did not result in additional, appreciable detectable loss of fibre protein. 4. Depletion of fibre glycogen was associated with loss of fibre ability to respond to T-system depolarization even though the bathing solutions contained high levels of ATP (8 mM) and creatine phosphate (10 mM). 5. The capacity of mechanically skinned fibres to respond to T-system depolarization was highly positively correlated (P<0.0001) with initial fibre glycogen concentration. 6. In conclusion, the results show that (i) the capacity of skeletal muscle to respond to T-system depolarization is related directly or indirectly to the non-washable glycogen pool in fibres, (ii) this relationship holds for conditions where glycogen is not required as a source of energy and (iii) the mechanically skinned fibre preparation is well suited to study the regulation of endogenous glycogenolytic enzymes.

Adenosine Triphosphate↗
PubMed1999

Abducens internuclear and ascending tract of deiters inputs to medial rectus motoneurons in the cat oculomotor nucleus: synaptic organization.

Abducens internuclear and ascending tract of Deiters (ATD) inputs to medial rectus motoneurons in the oculomotor nucleus are important for conjugate horizontal movements. In the present study, the organization of these separate populations of neurons and their synaptic connections with medial rectus motoneurons in the cat oculomotor nucleus have been examined by light and electron microscopy by using retrograde and anterograde axonal tracers. Consistent with the patterns of retrograde horseradish peroxidase labeling, the abducens internuclear projection is predominantly, if not exclusively, contralateral, whereas the ATD projection is exclusively ipsilateral, as demonstrated by anterograde autoradiographic and biocytin labeling. Both populations of synaptic endings contain spheroidal synaptic vesicles and establish synaptic contacts with modest postsynaptic densifications. In addition, ATD synaptic endings frequently are associated with subjunctional dense bodies and subsurface cisternae. The two populations of excitatory inputs differ, however, in their soma-dendritic distribution. The majority of abducens internuclear synaptic endings contact distal dendrites, whereas the majority of ATD synaptic endings contact proximal dendrites or somata. Abducens internuclear synaptic endings furthermore have a higher density of mitochondria than ATD synaptic endings. The more proximal location of ATD synaptic endings is consistent with the faster rise time and earlier reversal to polarizing currents of ATD excitatory postsynaptic potentials in comparison to those evoked by the abducens internuclear pathway as determined electrophysiologically. Given the differences in the physiologic signals conveyed by the abducens internuclear (eye velocity and eye position) and ATD (head velocity) pathways, the findings in this study suggest that the soma-dendritic stratification of the two inputs to medial rectus motoneurons may provide a means for the separate control of visuomotor and vestibular functions, respectively.

Abducens Nerve↗
PubMed1999

25 years' experience with lymphangiomas in children.

BACKGROUND/PURPOSE: The management of lymphangioma in children is challenging because complete resection is difficult to achieve in some cases, and recurrences are common. The authors reviewed their experience to assess the risk factors for recurrence and the role of nonoperative treatment. METHODS: A retrospective study over a period of 25 years was carried out. One hundred eighty-six patients with 191 lesions (five patients with de novo lesions in different sites) were treated. There were 98 boys and 88 girls. The average age at diagnosis was 3.3 years (range, fetal life to 17 years) and the average size 8 cm in diameter. Histocytological confirmation was obtained in all patients. The involved sites were head and neck, 89 patients (48%); trunk and extremities, 78 patients (42%); internal or visceral locations (eg, abdominal and thorax), 19 patients (10%). The treatment consisted of macroscopically complete excision in 145 patients (150 lesions, of which five were recurrences in different sites), partial excision in 10 patients, aspiration in five patients, laser excision in 10 patients, biopsy only in four patients, drainage and biopsy in two patients, and injection of sclerosing agents in 10 patients. RESULTS: There were 54 recurrences; 44 underwent excision (five of them more than once), and five regressed spontaneously on follow-up. Five other recurrences were stable and not progressing. Recurrences, (defined as clinically obvious disease), were found to be 100% after aspiration, 100% after injection, 40% after incomplete excision, 40% after laser excision, and 17% after macroscopically complete excision. The recurrence rate in the last group was the highest in the head (33%), the least in the internal locations (0%), and intermediate for the cervical location (13%). There were no significant differences, in terms of outcome, between those who had their surgery immediately at the time of diagnosis (n = 101) and those who had delayed surgery (n = 85). CONCLUSIONS: There were fewer recurrences after macroscopically complete excision. Aspiration and injection had the highest recurrence rate. Risk factors for recurrence included location, size, and complexity of lesions. A period of observation may be useful for infants to facilitate complete excision. In the present series, spontaneous regression was infrequent and was seen more often with recurrent lesions.

Abdominal Neoplasms↗
PubMed1999

Increased resting energy expenditure is related to plasma TNF-alpha concentration in stable COPD patients.

UNLABELLED: The objective of this study was to test whether increased resting energy expenditure (REE) in chronic obstructive pulmonary disease (COPD) patients is related to increased cost of breathing and/or to increased cytokine production. In 36 non-inflammatory (CRP: 17.6 +/- 13.1 mg.l(-1), mean +/- SD; orosomucoid: 0.71 +/- 0.18 g.l(-1)), non-malnourished (BMI: 23.6 +/- 4.3 kg.m(-2)), clinically stable, non severely hypoxic COPD patients (60.5 +/- 8.9 years) we measured REE, pulmonary function and plasma cytokine concentrations (TNF-alpha, IL1 and IL6). REE was increased by 10 +/- 11% (P< 0.001) above predicted values. Plasma TNF-alpha concentration was increased in all patients (mean value 26.3 +/- 14.3 pg.ml(-1)). Excess REE (with respect to values predicted by Harris-Benedict equations) was correlated with plasma TNF-alpha concentration (P< 0.005), but not with the degree of airway obstruction, lung overinflation, or with oxygen cost of breathing. Theophylline treatment resulted in a significant increase in REE by 15%. IN CONCLUSION: non-malnourished, clinically stable, non-severely hypoxic COPD patients display an increased REE that is related with plasma TNF-alpha concentration (without apparent systemic inflammation) and to theophylline treatment, but that is independent of parameters of respiratory function.

Basal Metabolism↗
PubMed1999

TRAF2 deficiency results in hyperactivity of certain TNFR1 signals and impairment of CD40-mediated responses.

Tumor necrosis factor (TNF) receptor-associated factor 2 (TRAF2) can interact with various members of the TNF receptor family. Previously, we reported that TRAF2-deficient mice die prematurely and have elevated serum TNF levels. In this study, we demonstrate that TRAF2-deficient macrophages produce increased amounts of nitric oxide (NO) and TNF in response to TNF stimulation. Furthermore, we could enhance the survival of TRAF2-deficient mice by eliminating either TNF or TNFR1. Using these double-knockout mice, we show that in the absence of TRAF2, the T helper-dependent antibody response, CD40-mediated proliferation, and NF-kappaB activation are defective. These data demonstrate two important roles of TRAF2, one as a negative regulator of certain TNFR1 signals and the other as a positive mediator of CD40 signaling.

Animals↗
PubMed1999

An electrophoretic study of myosin heavy chain expression in skeletal muscles of the toad Bufo marinus.

In this study we developed an SDS-PAGE protocol which for the first time separates effectively all myosin heavy chain (MHC) isoforms expected to be expressed in iliofibularis (IF), pyriformis (PYR), cruralis (CRU) and sartorius (SAR) muscles of the toad Bufo marinus on the basis of previously reported fibre type composition. The main feature of the method is the use of alanine instead of glycine both in the separating gel and in the running buffer. The correlation between the MHC isoform composition of IF, SAR and PYR muscles determined in this study and the previously reported fibre type composition of IF and SAR muscles in the toad and of PYR muscle in the frog was used to tentatively identify the MHC isoforms expressed by twitch fibre types 1, 2 and 3 and by tonic fibres. The alanine-SDS electrophoretic method was employed to examine changes in the MHC composition of IF, PYR, CRU and SAR muscles with the ontogenetic growth of the toad from post-natal life (body weight < 1 g) to late adulthood (body weight 200-450 g). The developmental changes in the MHC isoform composition of the toad IF muscle observed in this study are in very good agreement with those in the fibre type composition of the developing IF muscle reported in the literature.

Animals↗
PubMed1999

Flow cytometric analysis of in vitro proinflammatory cytokine secretion in peripheral blood from multiple sclerosis patients.

The cytokines, interferon-gamma (IFN-gamma), tumor necrosis factor-alpha (TNF-alpha), and interleukin-2 (IL-2) are important endogenous proinflammatory proteins and have been linked to disease activity in multiple sclerosis. In this study, we use flow cytometric methodology to compare the secretion of IFN-gamma, IL-2, and TNF-alpha from peripheral blood-derived T cells of multiple sclerosis patients to the secretion in healthy controls. The percentages of IFN-gamma, IL-2, and TNF-alpha secreting cells are not significantly different between multiple sclerosis patients and controls. However, the TNF-alpha secreting CD3 cell percentage is correlated with the IFN-gamma and IL-2 secreting CD3 cell percentages in multiple sclerosis patients. In the controls, only the TNF-alpha secreting CD3 cell percentage is correlated with IFN-gamma. These findings show that correlated secretion of cytokines occurs in multiple sclerosis and suggest that concerted intercytokine interactions may play an important role in the disease.

Adolescent↗
PubMed1999

Organic arsenic intoxication from bird's nest soup.

OBJECTIVE: To present a case of organic arsenic intoxication after consumption of bird's nest soup in a Vietnamese patient. METHOD: We have described the clinical picture of a patient with organic arsenic intoxication, and high levels of urine arsenic after consumption of bird's nest soup. RESULT: Withdrawal of bird's nest soup coincided with a decrease in urinary arsenic levels and the disappearance of peripheral neuropathy. CONCLUSION: This case illustrates the environmental contamination of bird's nest soup with organic arsenic. A prompt removal of the source from the diet resulted in clinical improvement.

Arsenic Poisoning↗
PubMed1999

Evaluation of pulmonary function in workers exposed to hexamethylene diisocyanate.

Production of hexamethylene diisocyanate (HDI) biuret and trimer from HDI monomer was started in 1988 at the plant under study. Pulmonary function tests were included as part of the annual evaluation of the workers in that unit. HDI is expected to have toxic properties similar to those of toluene diisocyanate. The latter has caused accelerated declines in pulmonary function in exposed workers. In 1991, an initial longitudinal evaluation of those pulmonary function tests was performed, comparing annual declines in forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1). The purpose of the study was to evaluate whether or not exposures to HDI at the unit had caused any accelerated decline in FVC or FEV1. No significant differences were seen in that evaluation, but it was decided that the study be continued in a prospective fashion. The study has been continued through 1997. The slope of the annual change in FVC and FEV1 were calculated for a group of workers and a matched control group. The average annual decline in FVC for the exposed group (cases) was 0.026 L, compared with 0.025 L for the control group. For the decline in FEV1, the results were 0.044 L, compared with 0.041 L (P = 0.79). These results are virtually identical and support a conclusion that exposures within this unit to HDI have not caused an accelerated decline in FVC or FEV1. Exposures to HDI were measured during this period. The time-weighted average exposure to HDI during work not requiring respiratory protection in the unit (approximately 2 hours per day) was 0.5 parts per billion. The average daily high peak exposure was 2.9 parts per billion. Exposure to these levels appear to pose no risk of accelerated decline in pulmonary function.

Adult↗
PubMed1998

Expression of the human histocompatibility leukocyte antigen DR3 transgene reduces the severity of demyelination in a murine model of multiple sclerosis.

The role of various MHC genes in determining the progression of multiple sclerosis (MS) remains controversial. The HLA-DR3 gene has been associated with benign relapsing MS in some genetic epidemiologic studies, but with disease progression in others. We induced demyelination in highly susceptible B10.M and B10.Q mice expressing the DR3 (HLA-DRB1*0301) transgene to determine directly the effects of a human transgene by infecting them with Theiler's murine encephalomyelitis virus (TMEV). DR3+ mice experienced a dramatic reduction in the extent and severity of demyelination compared with DR3- littermate controls, whereas anti-TMEV antibody titers, delayed-type hypersensitivity responses, and levels of infectious virus, virus antigen, and virus RNA were similar in both groups. To address a possible mechanism of how the human transgene is reducing virus-induced demyelination, we analyzed cytokine expression in the lesions and also determined whether B10.M mice can respond to peptides derived from the DR3 molecule. Intense staining for IFN-gamma and IL-4, T helper (TH) 1 and TH2 cytokines, respectively, was found in the lesions of TMEV-infected DR3- mice but not in the DR3+ transgenic mice at day 21 after infection. DR3 peptides elicited strong proliferative responses in B10.M mice but not in B10.M (DR3+) mice. These experiments are the first to demonstrate that a human class II DR gene can alter the severity of demyelination in an animal model of MS without influencing viral load. These experiments are consistent with a mechanism by which DR3 reduces demyelination by altering the cytokine expression in the lesions, possibly by deleting T cells involved in virus-induced pathology.

Animals↗