Biomedical subjects

F S Lee

Publications and source records attributed to F S Lee.

At least 37 records · Page 2Linked to original sources

PubMed1998

[Influences of Freon-12 (CF2CCl2) on the electron number densities in an inductively coupled plasma (ICP) measured with Halpha line--the applications of ICP in the disposal of hazardous waste].

The inductively coupled plasma was applied to decompose Freon 12 (CF2CCl2). The efficiency of the decomposition was indirectly evaluated by comparing the electron number densities in the central channel of the ICP with the addition of different amounts of Freon-12. Halpha line (656.3nm) was used to measure the electron number density due to Hbeta line (486.1nm) is seriously interfered with the addition of Freon-12 under the selected operating conditions. The "thermal pinch" effect was found with the addition of Freon-12, which is beneficial to the complete decomposition of the compound.

English Abstract↗

PubMed1998

Biomechanical evaluation of the schuhli nut.

The schuhli out is a device designed to lock an AO 4.5-mm cortical screw to a 4.5-mm dynamic compression plate independent of bony contact with the plate. The nut engages the screw below the plate, elevating the plate, and locking the screw at a 90 degrees angle, thus preventing toggling. Photoelastic modeling and biomechanical testing on sheep tibias were done to determine the mechanical properties of constructs using schuhli nuts. Use of schuhli nuts was shown to decrease stress in the bone below the plate. The initial axial stiffness of a construct fixed with schuhli nuts is less than a construct with standard screws, but the rate of loss of stiffness with cyclic loading is similar. When a cortical defect is present at the near cortex and the screw engages the far cortex only, the use of a schuhli nut significantly improves the stability of the construct compared with a standard screw alone, and behaves mechanically the same as a standard construct with intact cortices. This indicates that the schuhli nut acts as a substitute for a deficient cortex. The schuhli nut can be useful in osteoporotic bone because it prevents the screw from stripping the threads in the bone as the screw is advanced. It also serves to lock the screw to help prevent the screw from backing out. The schuhli nut may be a useful tool to improve stability in the treatment of complex fractures, reconstructions, or in pathologic bone.

Animals↗

PubMed1998

Reconstruction of intrinsic hand deformities.

Intrinsic muscle contractures are a frequently overlooked cause of hand dysfunction. Tightness of these muscles may occur despite appropriate management. This article addresses the evaluation and treatment of these contractures.

Compartment Syndromes↗

PubMed1997

A protein factor that inhibits ATP-dependent glutamate and gamma-aminobutyric acid accumulation into synaptic vesicles: purification and initial characterization.

Glutamate, the major excitatory neurotransmitter in the mammalian central nervous system, is transported into and stored in synaptic vesicles. We have purified to apparent homogeneity a protein from brain cytosol that inhibits glutamate and gamma-aminobutyric acid uptake into synaptic vesicles and have termed this protein "inhibitory protein factor" (IPF). IPF refers to three distinct proteins with relative molecular weights of 138,000 (IPF alpha), 135,000 (IPF beta), and 132,000 (IPF gamma), respectively. Gel filtration and sedimentation data suggest that all three proteins share an elongated structure, identical Stokes radius (60 A), and identical sedimentation coefficient (4.3 S). Using these values and a partial specific volume of 0.716 ml/g, we determined the native molecular weight for IPF alpha to be 103,000. Partial sequence analysis shows that IPF alpha is derived from alpha fodrin, a protein implicated in several diverse cellular activities. IPF alpha inhibits ATP-dependent glutamate uptake into purified synaptic vesicles with an IC50 of approximately 26 nM, while showing no ability to inhibit ATP-independent uptake at concentrations up to 100 nM. Moreover, IPF alpha inhibited neither norepinephrine uptake into chromaffin vesicles nor Na+-dependent glutamate uptake into synaptosomes. However, IPF alpha inhibited uptake of gamma-aminobutyric acid into synaptic vesicles derived from spinal cord, suggesting that inhibition may not be limited to glutamatergic systems. We propose that IPF could be a novel component of a presynaptic regulatory system. Such a system might modulate neurotransmitter accumulation into synaptic vesicles and thus regulate the overall efficacy of neurotransmission.

Adenosine Triphosphate↗

PubMed1997

Activation of the IkappaB alpha kinase complex by MEKK1, a kinase of the JNK pathway.

Both NF-kappaB and c-Jun are activated by cytokines such as TNF-alpha and by stresses such as UV irradiation. A key step in the activation of NF-kappaB is the phosphorylation of its inhibitor, IkappaB alpha, by a ubiquitination-inducible multiprotein kinase complex (IkappaB alpha kinase). A central kinase in the c-Jun activation pathway is mitogen-activated protein kinase/ERK kinase kinase-1 (MEKK1). Here, we show that MEKK1 induces the site-specific phosphorylation of IkappaB alpha in vivo and, most strikingly, can directly activate the IkappaB alpha kinase complex in vitro. Thus, MEKK1 is a critical component of both the c-Jun and NF-kappaB stress response pathways. Since the IkappaB alpha kinase complex can be independently activated by ubiquitination or MEKK1-dependent phosphorylation, it may be an integrator of multiple signal transduction pathways leading to the activation of NF-kappaB.

Animals↗

PubMed1997

Synaptic vesicle glutamate uptake in epileptic (EL) mice.

The ATP-dependent glutamate uptake system of synaptic vesicles was investigated in epileptic (EL) mice to determine whether glutamate uptake activity correlates with seizure susceptibility or development. Given the focal seizure onset, glutamate uptake activity was measured in four separate brain regions: cerebrum (minus hippocampus), hippocampus, cerebellum, and brain stem. The EL values were compared to those of age-matched controls; DDY and ABP/LeJ (ABP) mice. The glutamate uptake specific activity for EL cerebrum was significantly higher than that for the control mice (approx. 400 days old), but was not elevated prior to seizure onset (46 days old). No difference in glutamate uptake was observed between the strains in the other brain regions. We conclude that increased synaptic vesicle glutamate uptake is brain-region specific (cerebrum) and is associated with the development or maintenance, rather than the initial cause, of seizures in the EL model of epilepsy.

Adenosine Triphosphate↗

PubMed1997

Extended high-frequency thresholds in older adults.

Most measures of auditory sensitivity at extended high frequencies (frequencies greater than 8 kHz) have been obtained from listeners with normal hearing less than 40 years of age. The purpose of this study was (a) to measure thresholds at frequencies above 8 kHz in older listeners who, as a group, have elevated thresholds at lower frequencies, and (b) to assess test-retest reliability, age and gender effects, and the influence of thresholds below 8 kHz. Extended high-frequency (EHF) thresholds were measured for 162 older listeners (60-79 years) using a commercially available high-frequency audiometer, with a frequency range of 8 to 18 kHz and an intensity range of 0 to 110 dB SPL. Thresholds were measured once at the beginning of a 1- to 2-hour test session and then remeasured at the end of the test session. EHF thresholds of older listeners with normal hearing at conventional audiometric frequencies were substantially higher than the thresholds reported for younger listeners, with normal hearing by Dreschler and van der Hulst (1987). EHF thresholds of older listeners with hearing loss at conventional audiometric frequencies were further elevated as compared to older listeners with normal hearing. Differences in EHF thresholds between females and males were either not present or were reduced when gender differences in conventional audiometric thresholds were taken into account. No significant differences were seen in thresholds at 8 kHz and higher between the 60- to 69-and 70- to 79-year-old age groups. Results also indicated that thresholds above 8 kHz can be measured in older listeners within a clinically acceptable +/- 10 dB test-retest range.

Age Factors↗

PubMed1997

Age-related and gender-related changes in monaural speech recognition.

Previous studies of older listeners suggest age-related declines in speech recognition. However, the interpretation of these results is not straightforward because auditory thresholds, which account for the largest proportion of the variance in speech-recognition scores, also vary considerably with age. Here, effects of age, gender, and auditory thresholds on several measures of speech recognition were assessed for a large sample of individuals enrolled in a longitudinal study of age-related hearing loss. Participants ranged in age from 55-84 years. They were evaluated with a battery of conventional audiometric measures and speech-recognition materials, including NU-6 monosyllabic words, Synthetic Sentence Identification sentences, and high-context and low-context sentences from the Speech Perception in Noise test. Two analyses were conducted to assure that changes in speech-recognition scores with age were examined independently of age-related changes in auditory thresholds. In the first analysis, no significant differences in speech recognition were observed for individuals in three age groups (55-64, 65-74, 75-84 years) who were selected so that average puretone thresholds for the groups were within 5 dB. In the second analysis, using partial correlations to adjust both score and age for their association with average thresholds, significant declines with age were observed for males in maximum word recognition, maximum synthetic sentence identification, and keyword recognition in high-context sentences. For females, no significant changes in speech recognition with age were observed for any test.

Age Factors↗

PubMed1996

Topical tetracaine attenuates the pain of infiltration of buffered lidocaine.

OBJECTIVE: To determine whether topical tetracaine attenuates the pain of buffered lidocaine infiltration. METHODS: A prospective, randomized, double-blind trial was conducted involving adults with lacerations being repaired following local anesthesia. Two 0.5-mL injections of buffered lidocaine were given in a standardized manner. Injection 1 was given prior to application of topical study solution. Injection 2 was given on the opposite side of the laceration after topical application of a study solution that was 4 mL of either tetracaine or normal saline. Pain of each infiltration was measured using a visual analog pain scale. Pain score differences (injection 1 - injection 2) were compared for the 2 study solutions using a Wilcoxon 2-sample signed-rank test. RESULTS: Of 57 subjects studied, 29 received tetracaine and 28 received saline. The groups were similar in age, gender, wound length, wound location, and initial pain score. Pain scores decreased significantly in the tetracaine group as compared with the saline group. The median pain score difference for tetracaine was 12.0 mm, with an interquartile range (IQR) of 2 to 43 mm, as compared with 2 mm, with an IQR of - 17 to 21 mm for saline (p = 0.048). CONCLUSION: Topical tetracaine attenuates the pain of infiltration of buffered lidocaine.

Administration, Topical↗

PubMed1995

Insertional mutagenesis identifies a member of the Wnt gene family as a candidate oncogene in the mammary epithelium of int-2/Fgf-3 transgenic mice.

Transgenic mice harboring the int-2/Fgf-3 protooncogene under transcriptional control of the mouse mammary tumor virus (MMTV) promoter/enhancer exhibit a dramatic, benign hyperplasia of the mammary gland. In one int-2 transgenic line (TG.NX), this growth disturbance is evoked by pregnancy and regresses after parturition. Regression of hyperplastic mammary epithelium is less complete after successive pregnancies, and, within 10 months, most TG.NX mice stochastically develop mammary carcinomas that are transplantable in virgin, syngeneic mice. To identify genes that cooperate with int-2 in cell transformation, we infected TG.NX transgenic mice with MMTV. In a cohort of 14 animals, most mammary tumors represented clonal or oligoclonal outgrowths harboring one to five proviral MMTV integrants. Eight of 35 (23%) MMTV+ tumors exhibited proviral insertion at the Wnt-1 locus. No provirus was detected at the int-2, int-3, or Wnt-3 loci. By Southern analysis, two tumors had proviral insertions at the same genomic location, which was mapped to chromosome 15. Cloning of this int locus identified an additional member of the Wnt gene family. The predicted 389-amino acid protein is most closely related to zebrafish Wnt-10a (58% amino acid identity over 362 residues) and, based on homology analysis, was designated Wnt-10b. This newly discovered Wnt family member was expressed in the embryo and mammary gland of virgin but not pregnant mice and represents a candidate collaborating oncogene of int-2/Fgf-3 in the mammary epithelium.

Amino Acid Sequence↗

PubMed1995

Confidence limits for maximum word-recognition scores.

Clinical judgments are often made regarding whether maximum word-recognition scores (PBmax) are appropriate in relation to degree of sensorineural hearing loss. In order to determine if word recognition is significantly poorer than expected, it is necessary to consider the lower boundary of PBmax associated with a particular degree of hearing loss for speech materials commonly used to measure word recognition. The purpose of this experiment was to define a confidence limit for PBmax from Northwestern University Test #6 (NU-6) word-recognition scores obtained from a large group of young and aged subjects with confirmed cochlear hearing loss. Word-recognition scores at several speech levels were obtained from 407 ears with a wide range of pure-tone averages. Because the characteristics of the distribution of maximum scores are not known, a procedure was developed using computer simulations to approximate the distribution of word-recognition scores corresponding to PBmax and determine the 95% confidence limit (CL). Results of the simulation were confirmed by comparing means and standard deviations of PBmax derived from experimental and simulation data. Percentages of young and aged subjects with scores outside the 95% CL are equal to their proportions in the entire subject sample. If PBmax determined from a score-level psychometric function is poorer than the 95% CL, PBmax may be considered "disproportionately" poor in relation to the degree of hearing loss. One score measured at a single arbitrary suprathreshold level that is poorer than the 95% CL suggests that the score may underestimate PBmax and that word recognition should be measured at additional levels to obtain a more reasonable estimate of the listener's maximum word-recognition score.

Adult↗

PubMed1995