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Biomedical subjects

S A Lee

Publications and source records attributed to S A Lee.

At least 37 records · Page 2Linked to original sources
PubMed2000

Complications and results of subdural grid electrode implantation in epilepsy surgery.

BACKGROUND: We assessed the risk of delayed subdural hematoma and other complications associated with subdural grid implantation. METHODS: Forty-nine patients underwent subdural grid implantation with/without subdural strips or depth electrodes from January 1994 to August 1998. To identify the risk associated with subdural grid implantation, a retrospective review of all patients' medical records and radiological studies was performed. RESULTS: The major complications of 50 subdural grid electrode implantations were as follows: four cases (7.8%) of delayed subdural hematoma at the site of the subdural grid, requiring emergency operation; two cases (3.9%) of infection; one case (2.0%) of epidural hematoma; and one case (2.0%) of brain swelling. After subdural hematoma removal, the electrodes were left in place. CCTV monitoring and cortical stimulation studies were continued thereafter. No delayed subdural hematoma has occurred since routine placement of subdural drains was begun. CONCLUSIONS: In our experience the worst complication of subdural grid implantation has been delayed subdural hematoma. Placement of subdural drains and close observation may be helpful to prevent this serious complication.

Adolescent↗
PubMed2000

CD8(+) cell noncytotoxic anti-human immunodeficiency virus response inhibits expression of viral RNA but not reverse transcription or provirus integration.

CD8(+) T cells from human immunodeficiency virus (HIV)-infected individuals can suppress HIV replication in CD4(+) cells by a noncytotoxic mechanism that inhibits the expression of viral RNA. The present study examined whether other step(s) in the virus replicative cycle could be affected by the CD8(+) cells. Culturing HIV-infected CD4(+) T cells with antiviral CD8(+) T cells did not significantly reduce the amounts of (i) early HIV DNA reverse transcripts (detected by LTR-U3/R), (ii) total nuclear HIV gag DNA, or (iii) integrated proviral DNA. However, exposure to the CD8(+) T cells did cause a reduction in the amount of multiply spliced tat and full-length gag mRNA expressed by the infected CD4(+) T cells, confirming previous observations. The levels of glyceraldehyde-3-phosphate dehydrogenase and interleukin-2 receptor-alpha mRNA were not affected. The results support the conclusion that the noncytotoxic anti-HIV response of CD8(+) T cells, demonstrable in vitro, does not affect any of the virus replication steps leading to the integration of proviral HIV, but specifically interrupts the expression of viral RNA.

CD4-Positive T-Lymphocytes↗
PubMed2000

NaDNA-bipyridyl-(ethylenediamine)platinum (II) complex: structure in oriented wet-spun films and fibers.

Complexes of NaDNA with bipyridyl-(ethylenediamine)platinum(II) (abbreviated [(bipy)Pt(en)](2+)) in solid, oriented films, prepared with a wet-spinning method, have been studied using x-ray diffraction, elastic neutron scattering, two-dimensional magic-angle-spinning nuclear magnetic resonance (NMR), infrared (IR) linear dichroism, and IR absorption. All of these experiments indicate that the DNA in this complex is in the B conformation. The neutron diffraction experiments reveal that the rise per residue is 3.31 A, indicating that the [(bipy)Pt(en)](2+) molecular ion causes a small distortion of the B conformation. The neutron data in the direction perpendicular to the helical axis are consistent with a centered orthorhombic unit cell with a=22.65 A and b=32.2 A. The NMR and IR experiments show that the orientation of phosphate groups in the DNA small middle dot[(bipy)Pt(en)](2+) complex is the same as that observed for pure DNA in the B conformation. The IR experiments also show that the [(bipy)Pt(en)](2+) molecular ion stabilizes the B conformation of DNA down to 59% relative humidity, a low water activity. Mechanochemical experiments on wet-spun NaDNA fibers in 68% ethanol with and without [(bipy)Pt(en)](2+) reveal a 9% elongation of the DNA fibers as the complex is formed.

2,2'-Dipyridyl↗
PubMed2000

Intracranial EEG seizure-onset patterns in neocortical epilepsy.

PURPOSE: We investigated neocortical seizure-onset patterns recorded by intracranial EEG with regard to anatomic location, pathologic substrate, and prognostic value for surgical outcome. METHODS: Seizure onset was analyzed in 53 neocortical resective epilepsy surgery patients. Anatomic location was divided into temporal and extratemporal. Pathologic substrate was classified as developmental, mature, and negative or non-specific gliosis. Onset frequency was categorized by visual analysis into tradition EEG frequency bands. Spatial extent was divided into focal (fewer than four contacts) and regional (more than five contacts). Waveform at seizure onset was divided into several types based on their morphology. Onset features were examined with respect to anatomic location, pathologic substrate, and surgical outcome. RESULTS: Seizure-onset frequency was significantly related to spatial distribution and to anatomic location. Extratemporal and regional onset were more commonly in the gamma range, and temporal and focal onset in the beta frequency range or slower. Waveform could be categorized into five different patterns, of which low voltage fast activity (LVFA) was the most common form (57%). LVFA and rhythmic alpha-theta spike activity were more common in developmental than in mature pathology, whereas rhythmic sinusoidal waves at onset were found in only mature substrates. Waveform pattern showed a possible correlation with surgical outcome (p = 0.097): LVFA and rhythmic sinusoidal waves onset patterns were associated with favorable outcome more often (40.4%) than the other three patterns (6.3%). Slow onset suggested poor outcome in the subgroup of developmental pathology (p = 0.062). CONCLUSIONS: Certain electrographic seizure-onset features are associated with specific substrates and outcomes, whereas others reflect the anatomic location and its connections independent of the pathology.

Adolescent↗
PubMed1999

Raman and infrared studies of nucleosides at high pressures: I. Adenosine.

Room temperature Raman and infrared (IR) spectra of crystalline adenosine at pressures between 1 atm and 10 GPa are reported. Vibrational modes were identified through assignments in the literature. Many modes were found to increase in frequency with pressure; however, some irregularities were observed. Discontinuities were observed in numerous Raman and IR modes near 2.5 GPa, indicating a phase transition. The modes associated with the glycosidic bond shift significantly down in frequency near this pressure, suggesting a weakening of the associated bond. The IR modes associated with hydrogen-stretching motions were found to decrease in frequency with pressure.

Adenosine↗
PubMed1999

Mediation of a phase transition in hyaluronate films by the counterions Li, Cs, Mg and Ca as observed by infrared spectroscopy, optical microscopy and optical birefringence.

Infrared (IR) spectroscopy and optical microscopy have been performed as a function of relative humidity (rh) on wet-spun oriented films of hyaluronate (HA) prepared with various counterions. Complete swelling measurements have been obtained through optical microscopy for films of Cs-, Mg-, and CaHA. IR spectroscopy of Cs-, Mg-, Ca-, and LiHA films was performed for skeletal vibrations (800-1000 cm(-1)) and for vibrational modes (1150-1300 cm(-1)) attributed to C-C and C-O stretching modes and C-C-H and C-O-H bending modes. These techniques reveal evidence of a counterion-dependent phase transition occuring at high relative humidities. Optical birefringence measurements on the polycrystalline samples showed order before and disorder after the transition from lower to higher humidity.

Birefringence↗
PubMed1999

Clinical analysis of 12 Korean Lambert-Eaton myasthenic syndrome (LEMS) patients.

The Lambert-Eaton myasthenic syndrome (LEMS) heralds the occurrence of malignancy, especially small-cell lung cancer (SCLC), but it can also occur in the absence of cancer. Twelve patients were diagnosed as LEMS by clinical features and the classical electrophysiological triad, which includes a low amplitude of compound muscle action potentials (CMAP), decremental responses on low-rate stimulation, and incremental responses on high-rate stimulation on the repetitive nerve stimulation (RNS) test. There were 6 male and 6 female patients, ranging in age from 49 to 66 years. Malignancy(all were SCLC) was found in 7 patients. Males predominantly expressed the paraneoplastic form; whereas the primary autoimmune form was found only in women, who showed a good response to corticosteroid treatment. The neurological features were similar in both groups: proximal lower limb weakness, depressed muscle stretch reflexes, and dryness of mouth in nearly all patients. Bulbar dysfunction and limb paresthesia were a little more frequent in the paraneoplastic form. In RNS tests, the characteristic electrophysiological abnormalities were found in all patients and were more profound in the paraneoplastic form. We concluded that LEMS is commonly associated with malignancy, especially SCLC, but it should also be stressed that there are many female LEMS patients who do not harbor any malignancy at all, and that other treatment strategies such as immunotherapy should be considered for these patients.

Aged↗
PubMed1998

Impaired ionizing radiation-induced activation of a nuclear signal essential for phosphorylation of c-Jun by dually phosphorylated c-Jun amino-terminal kinases in ataxia telangiectasia fibroblasts.

The c-Jun amino-terminal kinases (JNKs) participate in intracellular signaling in response to cytokines and cellular stresses. JNKs are activated by phosphorylation on two critical residues, the threonine 183 and tyrosine 185, within the TPY motif. The activated JNKs, in turn, phosphorylate the nuclear protein c-Jun, a major component of the transcription factor AP1. In vitro studies have revealed a defect in ionizing radiation-induced activation of the JNK signaling pathway in lymphoblastoid cells from individuals with ataxia telangiectasia (AT). However, the biochemical basis for this signaling defect is not clear. Here, we show that ionizing radiation induces the phosphorylation of endogenous c-Jun in normal fibroblasts but not in AT fibroblasts. The p46 isoforms of dually phosphorylated JNKs were detected in the nuclei of both normal and AT fibroblasts following exposure to ionizing radiation or sham radiation. However, c-Jun kinase activity was detected in normal cells but not in AT cells. Furthermore, an exogenous purified active JNK protein was able to phosphorylate endogenous c-Jun in nuclear extracts only of normal cells and only after the cells were irradiated. Electrophoretic mobility shift assays also showed that the ionizing radiation-induced increase in the DNA binding activity of AP1 observed in normal cells was absent or markedly reduced in AT cell lines. These data suggest that the defect in ionizing radiation-induced signaling through c-Jun in AT cells is the result of impaired function of an unknown nuclear protein or proteins that negatively regulate both JNK and c-Jun.

Ataxia Telangiectasia↗
PubMed1998

Simultaneous determination of benzene, toluene, ethylbenzene, and xylenes in urine by thermal desorption-gas chromatography.

The determination of metabolites of benzene, toluene, ethylbenzene, and xylenes in urine has been used to assess human exposure to these compounds. The analyses of urine samples for these metabolites are tedious and time consuming. The determination of unmetabolized individual compounds in urine has been studied previously with some success. A simultaneous determination of several unmetabolized VOC compounds in urine by thermal desorption-gas chromatography was conducted to assess the exposure of smokers and nonsmokers to these compounds. The method of thermal desorption-GC was sensitive enough to detect a significant difference in exposure levels due to the contribution of light smoking in the environmentally-exposed group.

Adult↗
PubMed1997

Regulation of p53 in response to ionizing radiation in ataxia telangiectasia fibroblasts.

PURPOSE: An analysis of the structure and expression of p53 in fibroblasts from patients with ataxia telangiectasia (AT) is presented. METHODS AND MATERIALS: p53 status in primary and SV40 T antigen-transformed AT cell lines was analyzed using immunocytochemistry and by sequencing with the dideoxynucleotide termination method. The expression of p53 transcript was measured by Northern analysis. The kinetics of p53 protein expression and DNA-binding activity were measured at various intervals following irradiation. RESULTS: No mutation of p53 sequences was found in AT cells. Decreased levels of p53 mRNA and protein were observed in AT5BIVA cells compared to other SV40 T antigen-immortalized fibroblasts. Furthermore, DNA-protein binding analysis shows that a fraction of p53 in the nuclear extracts from AT5BIVA is regulated and binds to specific DNA sequence following irradiation. CONCLUSION: These data provide evidence for a heterogeneity of the p53 function in SV40-transformed AT cells. It also supports the hypothesis that a regulatory mechanism of p53 activity remains in T antigen-expressing cells in response to ionizing radiation damage.

Ataxia Telangiectasia↗
PubMed1997

ATM gene product phosphorylates I kappa B-alpha.

The recently cloned ATM gene is mutated in patients with ataxia telangiectasia, but its biological functions remain to be experimentally determined. Structural analysis has revealed ATM sequence similarities to the catalytic domains of phosphatidyl-3 kinase and other members of this family of yeast and mammalian proteins. Rabbit polyclonal antibodies raised against polypeptide regions unique to the COOH terminus and to the NH2 terminus of the published ATM sequence confirm ATM as M(r) approximately 350,000 protein in normal cells, which is missing in AT cells. Immunoprecipitated protein(s) is capable of phosphorylating I kappa B-alpha in an in vitro kinase assay. However, we did not observe a phosphatidyl-3 kinase or a DNA-dependent protein kinase function by ATM immunoprecipitates. These data support a protein kinase activity for ATM and suggest a role in NF-kappa B activation.

Antibodies, Monoclonal↗
PubMed1997

Stabilization of the B conformation in unoriented films of calf thymus DNA by NaCl: a Raman and IR study.

Unoriented films of calf thymus NaDNA with either 3.0 or 5.0 NaCl per base pair were prepared by dehydrating unstressed gels. These films were studied by Raman and ir spectroscopy. The 5.0 samples showed very strong vibrational modes characteristic of the B conformation at relative humidities (RH) as low as 30%, indicating that those samples were entirely in the B conformation. The 3.0 samples showed weaker features: some of the DNA in these samples were in the B conformation at 80% RH while the DNA is essentially in a disordered phase at 30% RH.

Animals↗
PubMed1997

Vibrational analysis of phosphorothioate DNA: II. The POS group in the model compound dimethyl phosphorothioate [(CH3O)2(POS)]-.

The results of Raman and Infrared (IR) spectroscopic investigations on the vibrational modes of dimethyl phosphorothioate (DMPS) anion, [(CH3O)2(POS)]-, are reported. Ab initio calculations of the vibrational modes, the IR and Raman spectra and the interatomic force constants of DMPS were performed. A normal mode calculation was performed and the results were used to calculate the potential energy distribution for the vibrational modes. This analysis shows that in DMPS the P-S stretching mode has a frequency of about 630 cm-1 and an angle bending mode involving the sulfur atom has a frequency of about 440 cm-1. The proposed vibrational mode assignments will serve as marker bands in the conformational studies of phosphorothioate oligonucleotides which play a central role in the novel antisense therapeutic paradigm.

DNA↗
PubMed1997

Balo's concentric sclerosis: a clinical case study of brain MRI, biopsy, and proton magnetic resonance spectroscopic findings.

The antemortem diagnosis of Balo's concentric sclerosis was made in a 52 year old woman with subacute right hemiparesis on the basis of brain MRI and stereotactic brain biopsy, which showed multiple ring-like lesions of lamellated demyelination alternating with spared white matter. Proton magnetic resonance spectroscopy (1H-MRS) was carried out one and nine months after the onset of illness. The first 1H-MRS showed a decreased N-acetyl aspartate peak, an increased choline peak, presence of large lipid peaks, and high resonance at 1.4 ppm. The second 1H-MRS disclosed changes such as a decrease of lipid signal, a decrease of resonance at 1.4 ppm, and an increase in the myoinositol peak. These findings are similar to those reported for multiple sclerosis. It seems that this is the first report of 1H-MRS findings in Balo's concentric sclerosis.

Biopsy, Needle↗
PubMed1996

Differential scanning calorimetric and X-ray study of the binding of the water of primary hydration to calf-thymus DNA.

Differential scanning calorimetry has been used to study the thermal properties of hydrated films of calf-thymus Na-, K- and CsDNA between 20 and 320 degrees C. A broad endothermic transition near 75 degrees C and a sharp exothermic transition near 240 degrees C are observed. The broad transition is due to the dehydration of the DNA, while the exothermic transition is due to pyrolysis of the sample. the peak temperatures of both transitions increase as the scan rate is increased. Based on a Kissinger analysis, the net activation energy for the desorption of the primary water of hydration is about 0.6 eV while that for the pyrolysis is about 1.9 eV. X-ray diffraction patterns suggest that heating the DNA films to 180 degrees C once does not, but thrice does, destroy their structural ordering.

Calorimetry, Differential Scanning↗
PubMed1996

A Raman study of the time variability for the A-to-B transition in wet-spun films of calf-thymus DNA.

The time evolution of the A-to-B transition has been monitored by Raman spectroscopy and found to vary significantly for different samples. Though all samples were prepared in the identical fashion, some samples completed the transition on the time scale of several hours while other samples took days. The shortest time required for the A conformation to disappear was about 2 hours, as determined by the disappearance of the A-form Raman band at 807 cm-1. For these fastest transforming samples, the B-form Raman band at 835 cm-1 was clearly evident after about 5 hours. These data are consistent with the hypothesis that the A conformation of DNA is stabilized by intermolecular interactions.

Animals↗