Biomedical subjects

M Y Lee

Publications and source records attributed to M Y Lee.

At least 91 records · Page 5Linked to original sources

PubMed1999

Improvement of cerebral ATP and choline deficiencies by Shao-Yin-Ren Shi-Quang-Da-Bu-Tang in senescence-accelerated mouse prone 8.

Shao-Yin-Ren Shi-Quang-Da-Bu-Tang (SDT) has been used traditionally to improve the systemic blood circulation and biological energy production in the body. The object of this study is to determine the effect of SDT extract on the decline of cerebral adenosine triphosphate (ATP) and choline content associated with learning and memory impairments in senescence-accelerated mice prone 8 (SAM P8). Twenty-four-week old mice were orally treated with SDT at 400 mg/kg body weight per day, and continued for 12 consecutive weeks. At the termination of the treatment, the body weight of SAM P8 was markedly lower than that of the equal aged senescence-resistant prone 1 (SAM R1), but this was conspicuously recovered to the level of SAM R1 by SDT treatment. SDT also significantly reduced the decline of cerebral weight (P < 0.05). By comparison with normal mice, a spontaneous decrease of cerebral ATP was observed in the SAM P8. Two- and 6-fold increases of cerebral ATP content were found in SAM R1 and SAM P8 by SDT administration, respectively. The cerebral choline content was significantly different between SAM R1 and SAM P8 aged 36-week old (P < 0.01). SDT remarkably restored the decrease of cerebral choline content in SAM P8 (P < 0.01). Taken together, these results demonstrate that SDT can reduce the decrease of cerebral weight, and restore the decline of cerebral ATP and choline content associated with an alteration of neuronal metabolism in SAM P8 brain. This suggests that pharmacological properties of SDT may participate in improvement of declined cerebral energy production and cholinergic neurotransmitter synthesis in senile dementia.

Adenosine Triphosphate↗

PubMed1999

Expression of osteopontin mRNA in the adult rat brain.

Examining the distribution of osteopontin (OPN) in the rat brain using in situ hybridization, it was found that OPN mRNA was restricted to likely neurons in the olfactory bulb and the brain stem; it was not detected in the telencephalon and the diencephalon. In addition, Northern blot analysis showed a confined expression only in the brain stem with higher level in the pons and the medulla than in the midbrain. In the brain stem, it was found in functionally diverse areas including motor-related areas, sensory system and reticular formation. This specific but widespread distribution suggests that OPN may play an important role in the adult rat brain.

Animals↗

PubMed1999

Direct interaction of proliferating cell nuclear antigen with the p125 catalytic subunit of mammalian DNA polymerase delta.

The formation of a complex between DNA polymerase delta (pol delta) and its sliding clamp, proliferating cell nuclear antigen (PCNA), is responsible for the maintenance of processive DNA synthesis at the leading strand of the replication fork. In this study, the ability of the p125 catalytic subunit of DNA polymerase delta to engage in protein-protein interactions with PCNA was established by biochemical and genetic methods. p125 and PCNA were shown to co-immunoprecipitate from either calf thymus or HeLa extracts, or when they were ectopically co-expressed in Cos 7 cells. Because pol delta is a multimeric protein, this interaction could be indirect. Thus, rigorous evidence was sought for a direct interaction of the p125 catalytic subunit and PCNA. To do this, the ability of recombinant p125 to interact with PCNA was established by biochemical means. p125 co-expressed with PCNA in Sf9 cells was shown to form a physical complex that can be detected on gel filtration and that can be cross-linked with the bifunctional cross-linking agent Sulfo-EGS (ethylene glycol bis (sulfosuccinimidylsuccinate)). An interaction between p125 and PCNA could also be demonstrated in the yeast two hybrid system. Overlay experiments using biotinylated PCNA showed that the free p125 subunit interacts with PCNA. The PCNA overlay blotting method was also used to demonstrate the binding of synthetic peptides corresponding to the N2 region of pol delta and provides evidence for a site on pol delta that is involved in the protein-protein interactions between PCNA and pol delta. This region contains a sequence that is a potential member of the PCNA binding motif found in other PCNA-binding proteins. These studies provide an unequivocal demonstration that the p125 subunit of pol delta interacts with PCNA.

Amino Acid Sequence↗

PubMed1999

Advantages of calcium green-1 over other fluorescent dyes in measuring cytosolic calcium in platelets.

Fluorescent indicators are widely used in the measurements of cytosolic calcium in many cell types for many purposes because they are relatively easy to use. Notwithstanding, they have some defects to prevent accurate measurements under certain conditions, such as significant dye leakage and UV-quenching effect. Menadione, a representative quinone derivative with antiaggregating effect, is also UV-absorbent. To investigate whether menadione can affect the change of cytosolic calcium in platelets by agonist, we measured the change of cytosolic calcium level using calcium green-1. Since this dye has not been used previously in platelets, we determined that the optimal loading of calcium green-1 to platelets was achieved using 3 microM dye incubated for 60 min at 37 degrees C. Our study compared the use of calcium green-1 with fura-2 and fluo-3 (two widely used dyes) in measurements of cytosolic calcium. Fura-2 is UV-excited, so when menadione was treated in fura-2-loaded cells, it had a quenching effect. Fluo-3, the other visible fluorescent indicator, leaked from platelets very rapidly and required the use of anion channel blockers which are known to affect physiological response of platelets. Our study demonstrated that changes in cytosolic calcium levels can be accurately measured without these problems by using calcium green-1. We therefore were able to demonstrate that menadione inhibited calcium increase by thrombin in a dose-dependent manner similar to menadione's antiaggregating effect in platelets.

Aniline Compounds↗

PubMed1999

Transient upregulation of osteopontin mRNA in hippocampus and striatum following global forebrain ischemia in rats.

We investigated the spatial and temporal expression of osteopontin (OPN) mRNA following transient forebrain ischemia in rats. Experiments were carried out using a four-vessel occlusion model for forebrain ischemia. The transient induction of OPN mRNA after global ischemia occurred earlier in the striatum than in the hippocampus. It was pronounced in the dorsomedial striatum close to the lateral ventricle and in the CA1 subfield and the subiculum of the hippocampus before microglial cells became more reactive. It also could be detected in the dentate hilus and to a marginal extent in the CA3. Our results suggest that the hippocampus and the striatum following global forebrain ischemia upregulate OPN mRNA in different spatiotemporal profiles.

Animals↗

PubMed1999

Synthesis of recombinant blood coagulation factor VIII (FVIII) heavy and light chains and reconstitution of active form of FVIII.

FVIII is synthesized as a single chain precursor of approximately 280 kD with the domain structure of A1-A2-B-A3-C1-C2 and it circulates as a series of metal ion-linked heterodimers that result from cleavages at B-A3 junction as well as additional cleavages within B domain. Factor VIII is converted to its active form, factor VIIIa, upon proteolytic cleavages by thrombin and is a heterotrimer composed of the A1, A2, and A3-C1-C2 subunits. A1 subunits of factor VIIIa terminates with 36 residue segment (Met337-Arg372) rich in acidic residues. This segment is removed after cleavages at Arg336 by activated protein C, which results in inactivation of the cofactor. In the present study, site-directed mutagenesis of FVIII at Arg336 to Gln336 was performed in order to produce an inactivation resistant mutant rFVIII (rFVIIIm) with an extended physiological stability. A recombinant mutant heavy chain of FVIII (rFVIII-Hm; Arg336 to Gln336) and wild-type light chain of FVIII (rFVIII-L) were expressed in Baculovirus-insect cell (Sf9) system, and a biologically active recombinant mutant FVIII (rFVIIIm) was reconstituted from rFVIII-Hm and rFVIII-L in the FVIII-depleted human plasma containing 40 mM CaCl2. The rFVIIIm exhibited cofactor activity of FVIIIa (2.85 x 10(-2) units/mg protein) that sustained the high level activity during in vitro incubation at 37 degrees C for 24 h, while the cofactor activity of normal plasma was declined steadily for the period. These results indicate that rFVIIIm (Arg336 to Gln336) expressed in Baculovirus-insect cell system is inactivation resistant in the plasma coagulation milieu and may be useful for the treatment of hemophilia A.

Animals↗

PubMed1999

Expression of vascular endothelial growth factor mRNA following transient forebrain ischemia in rats.

Using a reproducible two-vessel occlusion model for forebrain ischemia in rats, we investigated the temporal and spatial changes of vascular endothelial growth factor (VEGF) expression after transient forebrain ischemia with Northern blot analysis and in situ hybridization. Northern blot analysis revealed that VEGF mRNA of the hippocampus was increased from 12 h after reperfusion, with a peak at 1 day. In situ hybridization and double labeling for VEGF mRNA and glial fibrillary acidic protein showed a transient induction of VEGF mRNA in the neurons of the hippocampus from 12 h of reperfusion with a peak at 1 day, and in the astrocytes of the hippocampus, caudoputamen, thalamus and cortical regions at 1 day. After 3 days, no more VEGF signal was detected. Our results demonstrate that astrocytes and neurons each upregulate VEGF mRNA in different temporal and spatial patterns after transient forebrain ischemia in the rat, and these patterns appear to be different from those in transient focal cerebral ischemia.

Animals↗

PubMed1999

Anemic hypoxia in moderate intracerebral hemorrhage: the alterations of cerebral hemodynamics and brain metabolism.

To determine the influence of anemic hypoxia on cerebral hemodynamics and brain metabolism during pathological conditions of the brain, moderate-sized intracerebral hemorrhage (ICH) was created in canines with and without preoperatively inducing chronic anemia. The changes in cerebral perfusion pressure (CPP) and cerebral blood flow velocities (CBFv) were evaluated as well as the determinations for cerebral extraction fraction of oxygen (CEO2), arteriovenous oxygen content difference (AVDO2) and lactate (Lac) concentrations through the arterial and superior sagittal sinus (SSS) samples. Before ICH production, anemic animals (n = 8) showed a significant reduction in cerebral AVDO2 and arteriovenous Lac difference (AVDLac) but had higher CBFv as well as CEO2 than did nonanemic animals (n = 8). The CBFv began to decrease within 30 min after ICH in anemic but not in nonanemic animals, and the difference between the two groups was found to be significant at 2 h (P<0.05). Following ICH, anemic group also showed coupling reductions in CEO2 and AVDO2, indicating a decreased cerebral metabolic rate for oxygen (CMRO2) relative to the baseline data, compared with a constant CMRO2 in nonanemic group in which the CEO2, AVDO2, and CBFv remained relatively normal. Moreover, compared to the baseline data, a significant increase of the AVDLac was found in anemic but not in nonanemic group, although the former had lower Lac concentrations of the SSS than did the latter group throughout the whole observation period. We conclude that, in cases with chronically reduced Hct, cerebral hemodynamics and oxygenation remain in favorable conditions, thus decreasing Lac production of the brain. The findings suggest a lowered metabolic demand of the brain tissue due to reduced cerebral O2-carrying capacity. During the early phase of moderate ICH, the regulation capacity in cerebral hemodynamics and brain oxygenation tend to deteriorate in profound anemic hypoxia, which consequently leads to enhancing at least modest anaerobic glycolysis.

Anemia↗

PubMed1999

Inward and outward rectifying potassium currents set membrane potentials in activated rat microglia.

Activation of cultured rat microglial cells with lipopolysaccharide (LPS), induced outward rectifying K+ (K(V)) current in addition to already existing inward rectifying K+ current (K(IR)). By measuring zero-current membrane-potentials using whole-cell patch-clamp method, we showed that K(V) current plays a direct role in setting membrane potential to near -45 mV. Since the membrane potentials of microglia show two prominent peaks at -45 and -70 mV, we hypothesize that K(IR) current might set the membrane potential to near -70 mV. We observed that cells with larger K(IR) current had a zero-current membrane-potential at around -70 mV, and that blocking of K(IR) current with Ba2+ depolarized membrane potentials to near -45 mV. These results indicate that the amounts of K(IR), and K(V) current determine the zero-current membrane-potentials in LPS-activated microglia.

Animals↗

PubMed1999

Expression of CNTF in Müller cells of the rat retina after pressure-induced ischemia.

We have investigated the expression and cellular localization of ciliary neurotrophic factor (CNTF) in the rat retina following ischemia induced by transiently increasing the intraocular pressure. In the normal retina, CNTF immunoreactivity was restricted to profiles in the ganglion cell layer. Following ischemia and reperfusion, immunoreactivity appeared in Müller cell somata and processes and its intensity increased between 1 day and 2 weeks post-lesion. Quantitative evaluation by immunoblotting confirmed that CNTF expression continuously increased up to 2 weeks after ischemic injury (to 600% of control levels), but had declined again to 250% of controls at 4 weeks post-lesion. Our findings suggest that CNTF supplied by Müller cells has a protective function for lesioned neurons following transient ischemia.

Animals↗

PubMed1999

Horizontal cells of the rat retina are resistant to degenerative processes induced by ischemia-reperfusion.

The fate of calbindin D28k (calbindin)-labeled horizontal cells in the ischemic rat retina induced by increasing intraocular pressure was investigated by immunocytochemistry using an antiserum against calbindin. In the normal retina, strong calbindin-like immunoreactivity was seen in the horizontal cells, and the density of the labelled horizontal cells was 815.3+/-15.2 per mm2. The thickness of the treated retina became progressively thinner with increasing reperfusion time after the ischemic insult due to a loss of retinal cells in the inner and outer nuclear layers. However, the densities of the horizontal cells per mm2 were 814.0+/-26.4 at 1 week, 813.3+/-20.8 at 2 weeks, and 812.6+/-11.5 at 4 weeks, indicating that horizontal cells did not degenerate during experimental periods. Thus, calbindin may have a protective role for horizontal cells to ischemic insult by its ability to buffer calcium influx in the rat retina.

Albinism↗

PubMed1999

Ethanol co-exposure increases lethality of allyl alcohol in male Sprague-Dawley rats.

Since allyl alcohol and ethanol are both metabolized by alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH), ethanol could affect allyl-alcohol induced toxicity under in vivo coexposure conditions. Male Sprague-Dawley rats were treated with ethanol (2 g/kg, i.p.) simultaneously or 2 h before with allyl alcohol (40 mg/kg, i.p.). Coexposure to allyl alcohol and ethanol resulted in neither enhancement nor protection in allyl alcohol-induced hepatotoxicity at 24 h. However, markedly increased lethality was observed under our coexposure conditions. Pretreatment with 4-methylpyrazole (4-MP) to inhibit ADH did not result in increased lethality to allyl alcohol or ethanol alone, but significantly reduced the lethality of the combined treatment. In contrast, ALDH inhibition increased the lethality of allyl alcohol alone as well as that of the combined allyl alcohol and ethanol treatment. Kinetic studies revealed that combined treatment with allyl alcohol and ethanol resulted in higher blood allyl alcohol levels compared to allyl alcohol alone, and these were accompanied by greater lethality. ADH inhibition increased allyl alcohol blood levels significantly when rats were treated with allyl alcohol alone or allyl alcohol plus ethanol, leading to protection against lethality. In contrast, ALDH inhibition did not affect blood allyl alcohol levels, but resulted in increased lethality. These data suggest a possible role for a metabolite of allyl alcohol, acrolein, in the increased lethality of allyl alcohol and ethanol coexposure in rats.

Alcohol Dehydrogenase↗

PubMed1999

Flavin-containing monooxygenase isoform 2: developmental expression in fetal and neonatal rabbit lung.

Mammalian flavin-containing monooxygenase functions in the oxygenation of numerous xenobiotics containing a soft nucleophile, usually a nitrogen or sulfur. A total of five distinct flavin monooxygenase (FMO) isoforms are expressed in mammals. Individual isoforms are expressed in a sex-, age-, and tissue-specific fashion. In this study, we document the early developmental appearance of the major isoform in rabbit lung, FMO2. FMO2 catalytic activity as well as protein and mRNA are not only present in fetal and neonatal lung but, in some instances, approach levels found in the adult. The expression pattern of FMO2 is similar to that of the two major constitutive cytochromes P450 found in rabbit lung, 2B4 and 4B1. The early developmental appearance of these monooxygenases indicate an important role in the protection of the fetus and neonate against toxic insult from foreign chemicals.

Animals↗

PubMed1999

The birthdates of GABA-immunoreactive amacrine cells in the rat retina.

The birthdates of GABAergic amacrine cells in the rat retina were investigated by immunocytochemistry using anti-GABA and anti-bromodeoxyuridine (BrdU) antisera. The ratio of co-localization of GABA to BrdU increased gradually from embryonic-day 13 (E13) and showed a peak value on E18 in the central retina and on E20 in the periphery. After birth, until postnatal-day 3 (P3), a few co-localized cells were observed in the inner nuclear layer (INL). However, in the peripheral retina, co-localized cells were observed in the INL and ganglion cell layer until P5. Our results suggest that the birthdates of GABA-immunoreactive cells vary, depending on cell-type and that there is a temporal lag in the GABA-immunoreactive cell production in the peripheral retina relative to the central retina.

Animals↗

PubMed1999

Comparison of the synergistic effects of tamsulosin versus phentolamine on penile erection: in vitro and in vivo studies.

In vitro and in vivo studies were performed to determine the potential use of tamsulosin (TAM) versus phentolamine (PHE) for intracavernosal injection (ICI) therapy when mixed with papaverine (PAP) and/or prostagladin E1 (PGE1) or with vasoactive intestinal polypeptide (VIP) for the treatment of erectile dysfunction. We performed isometric tension studies on rabbit (n = 15), dog (n = 5), and human (n = 10) cavernous smooth muscle strips with TAM, PAP, PHE, VIP, PGE1, and the combinations of PAP and PHE; PAP and TAM; VIP and PHE; VIP and TAM; PAP, PGE1 and PHE; and PAP, PGE1 and TAM. TAM-containing trimix (PAP 18.75 mg, PGE1 6.25 micromg, and TAM 0.875 mg per ml) or PHE-containing trimix (PAP, PGE1, and PHE 0.625 mg per ml) were also injected into the cavernous bodies of ten mongrel dogs. Among the single agents, TAM and PGE1 (only in human) had the strongest effect on the relaxation of cavernous muscles in rabbit, dog, and human strips (P<0.05). Relaxation responses to 2- or 3-drug mixtures containing tamsulosin were also significantly better (P<0.05) than PHE-containing ones in rabbit, dog, and human strips. The increase in intracavernosal pressure with a TAM-containing trimix was higher than with a PHE-containing one (0.03 ml; 81.2 vs. 75.8 mm Hg, 0.04 ml; 103.2 vs. 94.3 mm Hg), although not statistically different. The drop in systemic blood pressure was lower after injection of a TAM-containing trimix than a PHE-containing one, although not statistically different. In conclusion, tamsulosin might be a more efficacious and safer agent to use for ICI therapy than phentolamine.

Adrenergic alpha-Antagonists↗

PubMed1999

The application of transcranial Doppler sonography in patients with chronic subdural haematoma.

The aim of this study was to evaluate the haemodynamic changes of the middle cerebral artery (MCA) and their clinical significance before and after surgical aspiration in patients with chronic subdural haematoma (CSDH). Nineteen patients with CSDH (17 unilateral and 2 bilateral) received transcranial Doppler sonography (TCD) examinations for cerebral blood flow velocity (CBFv) of the MCA prior to and 5 days after neurosurgical treatment. A total of 21 lesion and 10 non-lesion hemispheres were included. Cranial computerized tomography (CT) and clinical assessments were performed before and 3 months following surgery. The preoperative TCD study revealed that the lesion hemisphere had a modest decrease in CBFv in the MCA as compared to the non-lesion hemisphere. Postoperatively, the CBFv significantly improved in the lesion hemisphere, but not in the non-lesion hemisphere, compared to the preoperative data (P < 0.005). The improvement in CBFv showed no significant correlation with brain shift and haematoma volume of the initial cranial CT. Additionally, two patients, who were proved to have a postoperative complication of subdural pneumocephalus, failed to attend follow-up examinations of TCD. Our results support TCD as an alternative follow-up examination for patients with CSDH, although it may not be sensitive enough as a preoperative screening tool. Postoperatively, improvements in the CBFv of the lesion hemisphere are characteristic. An unexplained difficulty of accessing cerebral basal arteries in follow-up TCD examinations should suggest pneumocephalus in the primary differential diagnosis.

Adult↗

PubMed1999

Effects of galvanic stimulation of the mastoid process on the gastric motility induced by caloric stimulation.

The effects of galvanic stimulation to the mastoid portion on the vestibuloautonomic symptoms induced by caloric stimulation, such as nausea, vomiting, and vertigo, were evaluated in this study. Gastric motility was measured by electrogastrography (EGG) in 20 healthy volunteers (11 male and nine female) aged 20-30 (average: 25.4) years. Electrical stimulation of the mastoid process with 1.0-3.0 mA, 1.0 ms, 100 Hz was applied using a bipolar-biaural method during caloric stimulation of the external auditory canal. The dominant frequency and power of EGG were determined using running spectral frequency analysis and the time-course of EGG was evaluated in a pseudo three dimensional graphic. Frequency of EGG was classified into normogastria with 3 cpm, bradygastria with lower than 3 cpm, and tachygastria with higher than 3 cpm. At quiescent period, normogastria was 78.7 +/- 3.7%, bradygastria 5.0 +/- 1.1%, and tachygastria 16.4 +/- 3.7%. Caloric stimulation with warm water in the unilateral ear and cold water in the contralateral ear elicited vestibuloautonomic symptoms, with accompanied decreases in normogastria (57.7 +/-4.6%, P < 0.01) and increases in tachygastria (34.8 +/- 4.8%, P < 0.01). Cathodal stimulation to the mastoid process ipsilateral to cold water irrigation during caloric stimulation restored normal pattern of gastric motility: normogastria in 77.1 + 5.3% and tachygastria in 19.3 +/- 4.7%, and relieved vestibuloautonomic symptoms. Cathodal stimulation to the inhibited vestibular system ameliorates the vestibular symptoms induced by caloric stimulation.

Adult↗

PubMed1999

Victim-blaming tendency toward people with AIDS among college students.

The victim-blaming tendency toward people with AIDS was examined in relation to gender, fraternity-sorority affiliation, classification (freshmen vs. others), religion (Catholic vs. others), and academic major (business college vs. others) in a survey of 818 students at a midwestern state university in the United States. Desired social distance from gay men and lesbians, the intervening variable in these relations, significantly mediated the indirect effect of fraternity-sorority affiliation, classification, and gender on the victim-blaming tendency. Gender and desired social distance were found to be significant direct determinants of the victim-blaming tendency toward people with AIDS. The study suggests that attitudes toward gay men and lesbians must change if attitudes toward people with AIDS are to change.

Acquired Immunodeficiency Syndrome↗