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R Nguyen

Publications and source records attributed to R Nguyen.

14 recordsLinked to original sources
PubMed2001

Quantification of sodium dodecyl sulfate in microliter-volume biochemical samples by visible light spectroscopy.

A method for sodium dodecyl sulfate (SDS) quantitation in microliter-volume complex biochemical samples is described. The quantitation is based on the use of a dye, stains-all, the color of which changes from intense fuchsia to yellow upon addition of SDS. We show that this color change is gradual and proportional to the amount of SDS added to the stains-all solution, thus allowing its use to reliably quantitate SDS in biochemical samples by means of a visible light spectrophotometer. A large number of compounds widely used in biochemistry are herein shown not to interfere with the SDS measurement when they are present in the sample at usual biochemical concentrations. Furthermore, linearity between the color change and the amount of SDS present in the sample is never impaired when huge amounts of these compounds are also present, thus making this quantitation method highly reliable with use of a calibration curve. The method allows easy and reliable quantitation of microgram amounts of SDS in microliter-volume biochemical samples.

Animals↗
PubMed2001

Dynamic combinatorial chemistry.

Dynamic combinatorial chemistry is based on the reversible combination of initial building blocks to form dynamic combinatorial libraries. It has recently emerged as an efficient strategy to detect and to evaluate affinity between the library products and a target molecule. In this review, examples from various fields of chemistry and biochemistry are presented and extensively discussed. The last section deals with the practical aspects for implementing this approach.

Combinatorial Chemistry Techniques↗
PubMed2000

Gahat: a Napalese cure for urolithiasis?

OBJECTIVES: Gahat (Vigna unguiculata) is a legume used for centuries in Nepal and Pakistan to treat the symptoms associated with urinary calculi. We prospectively evaluated the effect of Gahat consumption on 24-hour urine parameters in an attempt to assess its in vivo effect in normal volunteers. METHODS: Eight non-stone-forming volunteers collected 24-hour urine specimens while on their routine diets for baseline data. Urine was analyzed for pH, volume, calcium, citrate, phosphate, sodium, magnesium, uric acid, and oxalate. The Gahat was prepared according to local custom. No additives were used to enhance flavor. The pureed mixture (8 ounces) was ingested three times daily for 2 days. Subjects were instructed to maintain their normal diet, including fluid intake and activity during the study period. Twenty-four hours after the start of Gahat intake, a second 24-hour urine collection was initiated while volunteers continued the Gahat. Results of the urine samples before and after Gahat intake were analyzed, using the paired Student t test. RESULTS: There were no significant differences in urinary electrolytes between the urine samples before and after Gahat intake. Magnesium, urine volume, and uric acid differences approached clinical significance. CONCLUSIONS: Gahat increased urinary magnesium through an unknown mechanism and had no effect on other routine 24-hour urine electrolytes. The increase in urinary volume is attributed to the increase in fluid consumption by the subjects. If this legume is effective in preventing or dissolving urinary calculi, it may act through mechanisms not identified in 24-hour urine electrolytes.

Citrates↗
PubMed2000

Hierarchy of merlin and ezrin N- and C-terminal domain interactions in homo- and heterotypic associations and their relationship to binding of scaffolding proteins EBP50 and E3KARP.

The neurofibromatosis 2 tumor suppressor gene product merlin has strong sequence identity to the ezrin-radixin-moesin (ERM) family over its approximately 300-residue N-terminal domain. ERM proteins are membrane cytoskeletal linkers that are negatively regulated by an intramolecular association between domains known as NH(2)- and COOH-ERM association domains (N- and C-ERMADs) that mask sites for binding membrane-associated proteins, such as EBP50 and E3KARP, and F-actin. Here we show that merlin has self-association regions analogous to the N- and C-ERMADs. Moreover, the N-/C-ERMAD interaction in merlin is relatively weak and dynamic, and this property is reflected by the ability of full-length recombinant merlin to form homo-oligomers. Remarkably, the merlin C-ERMAD has a higher affinity for the N-ERMAD of ezrin than the N-ERMAD of merlin. Both the ezrin and merlin N-ERMAD bind EBP50. This interaction with the ezrin N-ERMAD can be inhibited by the presence of the ezrin C-ERMAD, whereas interaction with the merlin N-ERMAD is not inhibited by either C-ERMAD. E3KARP binds tightly to the ezrin N-ERMAD but has little affinity for the merlin N-ERMAD. The implications of these associations and the hierarchies of binding for the function and regulation of merlin and ERM proteins are discussed.

Blotting, Western↗
PubMed2000

ERM-Merlin and EBP50 protein families in plasma membrane organization and function.

The ezrin-radixin-moesin (ERM) family of proteins have emerged as key regulatory molecules in linking F-actin to specific membrane proteins, especially in cell surface structures. Merlin, the product of the NF2 tumor suppressor gene, has sequence similarity to ERM proteins and binds to some of the same membrane proteins, but lacks a C-terminal F-actin binding site. In this review we discuss how ERM proteins and merlin are negatively regulated by an intramolecular association between their N- and C-terminal domains. Activation of at least ERM proteins can be accomplished by C-terminal phosphorylation in the presence of PIP2. We also discuss membrane proteins to which ERM and merlin bind, including those making an indirect linkage through the PDZ-containing adaptor molecules EBP50 and E3KARP. Finally, the function of these proteins in cortical structure, endocytic traffic, signal transduction, and growth control is discussed.

Animals↗
PubMed2000

Endoscopic thoracic sympathectomy for treatment of essential hyperhidrosis syndrome: experience with 650 patients.

Patients with essential hyperhidrosis (EH) syndrome may experience subjective suffering and social/occupational challenges. We examined the safety and efficacy of minimally invasive endoscopic surgery for treating EH. Single bilateral incisions, followed by endoscopic thoracic sympathectomy (ETS)-mediated bilateral ablation of the T2 sympathetic ganglia, were used to treat 650 patients with a primary diagnosis of palmar (90%) or facial hyperhidrosis (10%). Palmar and facial hyperhidrosis were resolved in 584 of 585 (>99%) and 62 of 65 (95%) patients, respectively. Surgery required less than 1 hour, and no patient experienced a life-threatening adverse event. Compensatory sweating was observed in 83% of patients and was considered mild or moderate in approximately 67% of those patients. Innovations in ETS have resulted in minimally invasive, highly efficient, safe treatment of EH. Surgery is minimally intrusive to patients, who were usually discharged within 2 hours after surgery and able to resume normal activities within 1 week.

Adolescent↗
PubMed1999

Clinical study of combined penetrating keratoplasty, pars plana vitrectomy with temporary keratoprosthesis, and pars plana seton implant.

PURPOSE: To assess the effectiveness of a combined procedure (pars plana vitrectomy with temporary keratoprosthesis, penetrating keratoplasty, and pars plana seton implant) in preserving vision and controlling intraocular pressure (IOP). METHODS: We reviewed the course of visual acuity, IOP, graft clarity, retinal status, and complications in 18 patients who underwent the above procedure during one operating sitting. RESULTS: Preoperative diagnoses were varied. The majority of patients had pseudophakic bullous keratopathy and failed corneal transplants with glaucoma. Preoperative mean visual acuity was hand motions. Preoperative mean IOP was 27+/-13 mm Hg. Initially, all patients had attached retina. With a mean follow-up of 17+/-9 months, six patients had improved vision greater than 2 lines and 10 had unchanged vision. Only two patients lost vision greater than 2 lines. The final average IOP was 16+/-6 mm Hg and only one eye had a pressure above 22 mm Hg. Three eyes were classified as complete failures; two of the three became phthisical. Two patients developed rhegmatogenous detachments requiring further surgery. CONCLUSION: The combined procedure offers reasonable improvement in vision, good pressure control, and a tolerable number of complications. It is a useful procedure in eyes that probably would not have been treatable otherwise.

Adolescent↗
PubMed1998

Long- and short-term variability of automated perimetry results in patients with optic neuritis and healthy subjects.

OBJECTIVE: To measure the short- and long-term variability of automated perimetry in patients with optic neuritis and normal subjects. DESIGN: Prospective case-control design of patients with recovered optic neuritis with intraday and interday repetitions to obtain robust variability measurements. Entry criteria included a corrected pattern SD that was worse than the normal 5% probability level and a mean deviation worse than -3 dB but better than -20 dB. Five Humphrey 30-2 full threshold tests were administered during a 7-hour period (1 test every 2 hours) on the same day and at the same periods on 5 separate days. SUBJECTS: Seventeen patients with recovered optic neuritis and 10 healthy subjects of similar age. MAIN OUTCOME MEASURES: Short-term variability and long-term variability for global visual field data. RESULTS: Patients with optic neuritis demonstrated variations in visual field sensitivity that were outside the entire range of variability for normal controls. These variations occurred for multiple tests performed on the same day at specific times and for tests performed at specific times on different days. There were no consistent patterns of sensitivity changes that could be attributed to time of day. The most dramatic fluctuations occurred in a patient whose visual fields varied from normal to a hemianopic defect from one week to another and from a partial quadrant loss to a hemianopic defect at different times on the same day. Seven of the patients with optic neuritis also demonstrated intermittent vertical step defects. CONCLUSIONS: Patients with resolved optic neuritis can have large variations in visual field results on different days and at different times on the same day. The variations affect both the severity and the pattern of visual field loss and do not appear to be consistent across patients. These data indicate that care must be taken when automated visual field results in patients with optic neuritis are interpreted. Distinguishing systematic changes in sensitivity from variability requires more than a comparison of the current visual field with the most recent previous visual field.

Adult↗
PubMed1998

A third locus (GLC1D) for adult-onset primary open-angle glaucoma maps to the 8q23 region.

PURPOSE: Two genes for adult-onset primary open-angle glaucoma have been mapped to chromosomes 2cen-q13 and 3q21-q24. We studied a family with adult-onset primary open-angle glaucoma in which the disease did not map to these two chromosomal regions. METHODS: We ascertained a four-generation family with adult-onset primary open-angle glaucoma in which the disease status of individuals was objectively assigned using defined criteria. Complete ophthalmologic examinations, visual field testing, optic nerve head photographs, and venous blood samples were obtained. Family members were genotyped using polymerase chain reaction amplification of microsatellite polymorphic markers. Linkage analysis was performed and lod scores were calculated. Haplotype transmission data were analyzed. RESULTS: A total of 20 subjects in three successive generations agreed to participate in the study. This included samples from eight affected subjects, one glaucoma suspect, one normal individual, and two spouses in generations II and III, and an additional eight individuals in generation IV. The phenotype in this family appears to be variable, with onset of visual field loss in middle age, followed by modest elevation of intraocular pressure and progression of the disease in older individuals. Linkage was established with a group of DNA markers located in the 8q23 region. A lod score value of 3.61 was obtained using marker D8S1471. Three other markers from the same region gave lod score values of over 3.0. Haplotype transmission data identified two recombination events that placed the gene in a 6.3-cM region flanked by D8S1830 and D8S592. The disease-bearing haplotype was inherited by eight affected subjects and three glaucoma suspects. CONCLUSION: We present evidence for a third adult-onset primary open-angle glaucoma locus (GLC1D) on chromosome 8q23. The genetic heterogeneity of adult-onset glaucoma is evident from the multiplicity of chromosomal loci associated with this disease.

Aged↗
PubMed1997

Surgical treatment of breast cancer in New South Wales 1991, 1992.

BACKGROUND: The purpose of this study was to examine existing data on women diagnosed with breast cancer in New South Wales in 1991 and 1992 and to describe surgical treatments received on an inpatient basis. METHODS: Analyses were based on the linkage of two databases: the New South Wales Central Cancer Registry and the New South Wales Health Department's Inpatient Statistics Collection. Data were limited to women who were resident and treated in New South Wales. Main analyses were restricted to definitive surgical procedures. RESULTS: Thirty-six per cent of women treated surgically for breast cancer in 1991 had breast-conserving therapy. This had increased to 39% in 1992. There were substantial geographical variations in the use of breast-conserving therapy in New South Wales which could not be explained by patient characteristics. Age, degree of spread at diagnosis, and area health service/ health region were all found to have an independent association with the probability of having a mastectomy. CONCLUSIONS: Women with a localized degree of spread living in non-metropolitan areas (Health Regions) were almost twice as likely to have a mastectomy as compared with similar women who were resident in metropolitan areas (Area Health Services). The concentration of radiotherapy services may have contributed to the urban/rural variation in breast-conserving therapy in New South Wales, but it is also likely that some of the variations that were observed may be a reflection of the failure of clinicians to use best current practice.

Adult↗
PubMed1995

Self-reported signs and symptoms in breast implant patients with novel antibodies to silicone surface associated antigens [anti-SSAA(x)].

In research animals, the immune adjuvant activity of silicone in eliciting antibodies to associated protein antigens is now well established. In humans, the immune adjuvant activity of silicone remains controversial. Clusters of data from various research groups are beginning to define the boundary conditions for future large epidemiological studies. In that spirit, this manuscript reports pilot clinical data from a serological study conducted 3 years ago and reported previously in this journal. Sera from a self-selected symptomatic population of patients with breast implants were assayed for elevated concentrations of antibodies showing binding avidity to silicone surface associated antigens [anti-SSAA(x)]. In that study of 249 patients, two distinct statistically significant subgroups were identified on the basis of the serological assay alone: patients without any elevated anti-SSAA(x) (negative) and patients with elevated anti-SSAA(x) (positive) (p < 0.001). In this study, a clinical survey returned by 226 of those patients was correlated with the previously acquired serological findings. The 11 most common clinical complaints reported by the 199 anti-SSAA(x) negative patients and by the 27 anti-SSAA(x) positive were compared and their frequencies analyzed. The 199 anti-SSAA(x) negative patients, as a group, showed a lower frequency of a variety of signs and symptoms compared to the 27 anti-SSAA(x) positive patients. Statistically significant differences were seen in three of the symptoms: fever, foot pain, and sleep disturbance (p < 0.05). In addition, the syndrome of fever in the absence of local chest pain was a significantly associated with anti-SSAA(x) positivity (p < 0.001).

Antibodies↗