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Biomedical subjects

M L Tsai

Publications and source records attributed to M L Tsai.

At least 19 recordsLinked to original sources
PubMed2003

The differential effects of tamoxifen and ICI 182,780 on the reduction of Na+/K+ ATPase activity and spontaneous oscillations by 17beta-estradiol.

A prolonged treatment with 17beta-estradiol reduces the frequency of spontaneous oscillations and the Na+/K+ ATPase activity in rat uteri. Acute inhibition of Na+/K+ ATPase activity by a Na+/K+ ATPase inhibitor, ouabain, decreases the frequency of oxytocin-induced oscillations in uteri. Therefore, the purpose of this study was to examine whether the prolonged inhibition of Na+/K+ ATPase activity by 17beta-estradiol was estrogen receptor (ER)-dependent. The uterine explants from ovariectomized rats were cultured in vitro as our experimental model to compare the effect of two antiestrogenic compounds (ICI 182,780 and tamoxifen) on the Na+/K+ ATPase activity and the frequency of spontaneous oscillations. ATPase assay and a standard muscle bath apparatus were to measure the activity and the contraction. When compared with the control, a 2-day treatment with 17beta-estradiol in vivo or in vitro decreased the activity and the frequency. ICI 182,780 lowered the activity but tamoxifen did not. ICI 182,780 did not decrease the frequency but tamoxifen did. Even the reversal effects of these antiestrogenic compounds on the reduced activity and the frequency by 17beta-estradiol were different. Tamoxifen elicited a greater reversal effect on the reduced activity but ICI 182,780 did not. In contrast, ICI 182,780 elicited a greater reversal effect on the reduced frequency but tamoxifen did not. Prolonged inhibition of Na+/K+ ATPase activity by K+-free solution suppressed the frequency with the elevation of basal tension. Addition of KCl at lower concentrations (0.3-1.2 mM) induced oscillatory contraction after reducing the basal tension. As our data suggest, the prolonged effect of 17beta-estradiol may decrease uterine the activity through ER dependent and independent pathways. The reduction of uterine Na+/K+ ATPase activity by estrogens may increase the basal tension after each oscillatory cycle, which, in part, contributes to the reduced frequency of spontaneous oscillations.

Animals↗
PubMed2001

The inhibitory effects of lead on steroidogenesis in MA-10 mouse Leydig tumor cells.

Lead is an environmental and occupational pollutant. It has been reported that lead affects the male reproductive system in humans and animals. However, the cellular mechanism of the adverse effect of lead on Leydig cell steroidogenesis remains unknown. To clarify whether lead has a direct effect on Leydig cells and how lead affects Leydig cells, MA-10 cells, a mouse Leydig tumor cell line, were exploited in this study. Lead acetate significantly inhibited hCG- and dbcAMP-stimulated progesterone production in MA-10 cells at 2 h. Steroid production stimulated by hCG or dbcAMP were reduced by lead. The mechanism of lead in reducing MA-10 cell steroidogenesis was further investigated. The expression of Steroidogenic Acute Regulatory (StAR) protein and the activities of P450 side-chain cleavage (P450scc) and 3beta-hydroxysteroid dehydrogenase (3beta-HSD) enzymes were detected. Cells were treated with dbcAMP, 22R-hydroxycholesterol or pregnenolone alone or in combination with lead acetate ranging from 10(-8) to 10(-5) M for 2 h. The expression of StAR protein stimulated by dbcAMP was suppressed by lead at about 50%. Progesterone productions treated with 22R-hydroxycholesterol or pregnenolone were reduced 30-40% in lead-treated MA-10 cells. These data suggest that lead directly inhibited steroidogenesis by decreasing StAR protein expression and the activities of P450scc and 3beta-HSD enzymes with a dose-response trend in MA-10 cells. Moreover, cadmium, a calcium channel blocker, abolished inhibitory effect of lead on MA-10 cell steroid production. This indicates that lead might act on calcium channel to regulate MA-10 cell steroidogenesis.

3-Hydroxysteroid Dehydrogenases↗
PubMed2001

The spectrum of postinfectious encephalomyelitis.

The medical records of 52 consecutive patients diagnosed with postinfectious encephalitis/encephalomyelitis during the period from 1980 to 1998, including 29 males and 23 females, were reviewed. These patients were divided into three groups according to their clinical and neurodiagnostic characteristics: (1) group I: postinfectious encephalitis, 38 patients; (2) group II: acute disseminated encephalomyelitis (ADEM), 13 patients; (3) group III: multiphasic disseminated encephalomyelitis (MDEM), one patient. Fever, headache/vomiting, seizure and disturbance of consciousness were common clinical features in all patients, while pictures of pyramidal, extrapyramidal, brainstem, and spinal cord lesions were more often found in the group II and group III patients than in the group I patients. Magnetic resonance imaging (MRI) revealed abnormal lesions in six (60%) of ten group I patients, but all group II (n=7) and group III (n=1) patients who received MRI study showed abnormal signals in various regions of the brain including the cerebral hemisphere, basal ganglia, brainstem and cerebellum. Patients with ADEM and MDEM had a longer clinical course and more neurological sequelae than group I patients. This study demonstrates the breadth of the clinical spectrum of postinfectious encephalomyelitis. Thorough clinical observations and appropriate neurodiagnostic studies such as MRI are crucial for the diagnosis.

Brain↗
PubMed2001

Clinical and electroencephalographic findings in early and late onset benign childhood epilepsy with occipital paroxysms.

Twenty-six patients were studied who had the clinical and electroencephalographic features of benign childhood epilepsy with occipital paroxysms (BCEOP) as defined by the Commission of the International League Against Epilepsy (ILAE). Twelve patients were characterized as having early-onset benign childhood occipital seizures (EBOS) susceptible syndrome, as described by Panayiotopoulos, and 14 patients had late onset childhood idiopathic occipital seizures (LOS). Patients with symptomatic epilepsy and whose EEGs exhibited occipital spikes were excluded. The age of onset of the EBOS group ranged from 2.6 to 9.4 years (mean: 4.9+/-1.7 years), which was significantly younger than the LOS group (range: 4-12 years, mean:8.4+/-2.5 years). Both sexes were equally affected. The patients in the EBOS group had less frequent and longer seizures, ictal vomiting, more frequent deviation of the eyes, adversive seizures and more frequent nocturnal and secondary generalized seizures (P<0.05). By comparison, patients in the LOS group had a higher incidence of seizures, shorter duration of seizures and more frequent diurnal onset (P<0.01); also, although not statistically significant, the LOS group had more frequent visual hallucinations and headaches. The EEG topography in both groups showed at either side of occipital area typical paroxysms that were unilateral or bilaterally synchronous. Neither group had dipoles according to scalp voltage mapping. The clinical prognoses were favorable for both groups. To distinguish EBOS from LOS, detailed description of the age of onset, motor symptoms, visual symptoms, presence of eye deviation and diurnal or nocturnal occurrence are essential.

Age of Onset↗
PubMed2001

Effect of antenatal dexamethasone on the expression of endothelial nitric oxide synthase in the lungs of postnatal pups.

Activities of endothelial nitric oxide synthase (eNOS) are developmentally regulated and its presence at birth may play a role in the transition of cardiopulmonary circulation. Antenatal dexamethasone (Dex) therapy accelerates fetal lung maturation. We speculate that Dex therapy may enhance pulmonary eNOS protein expression in the newborn. This article examines whether antenatal Dex therapy affected the expression of eNOS in the lungs of rat pups in the postnatal period. Time-dated pregnant Wistar rats were subjected to 2 doses of Dex (0.8 mg/kg, intramuscularly, daily) or equivalent volume of normal saline at the 18th and 19th gestational day and delivered naturally. The newborn pups were randomly assigned to 4 groups by age: days 1, 3, 5, and 7. After homogenization, abundance of eNOS protein in lungs was determined by Western blot analysis. There were 7 dams in each group. Mean body weights of the pups in the Dex group were lighter than those in the control at birth and remained stunted up to day 7 (5.68+/-0.47 g v 6.34+/-0.47 g, P <.01). However, there were no differences in wet lung weights and lung/body weight ratios between both groups in the study period. Abundance of eNOS protein expression decreased in both the control and Dex groups (P < .01). Pups that received antenatal Dex had 39% more in abundance of eNOS protein expression in lungs when compared to the control on day 1 (P < .05) but there were no differences between both groups from day 3 to 7. We conclude that antenatal Dex therapy enhances the abundance of eNOS protein expression in the lung at birth and could be a factor in improving respiratory functions in infants who received antenatal steroid therapy.

Animals↗
PubMed2000

Preferential reduction of Na+/K+ ATPase alpha3 by 17beta-estradiol influences contraction frequency in rat uteri.

One beta1 and two alpha (alpha1 and alpha3) isoforms of Na+/K+-ATPase exist in rat uteri. Previous immunocytochemistry studies have suggested that the alpha3 isoform may be involved in calcium regulation indirectly. Estrogens are known to both modulate Na+/K+-ATPase activities in non-uterine tissues and suppress spontaneous uterine contractions in rats. Thus the purpose of this study was to examine the correlation between estrogens-modulated uterine contraction and the expression of Na+/K+-ATPase alpha3 isoform in rats. After 1-, 2-, and 4- day treatments with 17beta-estradiol (E2, 5 microg/ml/kg, s.c., daily), the diameter of uterine horn was measured. The contraction force of uterine strips was measured by standard muscle bath apparatus. The protein abundance and enzyme activity of Na+/K+-ATPase in rat uteri were measured by Western blot analysis and ATPase assay, respectively. One day of E2 decreased both contraction frequency and alpha3-protein expression without the change in uterine diameter, enzyme activity or other isoforms. Two days of E2 reduced contraction frequency, the enzyme activity, as well as alpha3- and beta1- protein abundance but increased alpha1-protein and uterine diameter. Four days of E2 elicited similar effects as two days of E2, but did not affect alpha1-protein abundance. In conclusion, E2 elicits differential effects on isoform expression. After 1-day treatment with 17beta-estradiol, the decrease in the expression of alpha3 and beta1 without a change in Na+/K+-ATPase activity suggests that some isoform other than beta1 exist in rat uteri. The positive correlation between the reduction of alpha3-and the decrease of contraction frequency suggests the involvement of alpha3 isoform in uterine oscillation.

Animals↗
PubMed2000

In vivo exposure to carbon disulfide increases the contraction frequency of pregnant rat uteri through an indirect pathway.

Exposure to CS2, an organic solvent, is associated with an increased rate of abnormal labor or dysmenorrhea. Contraction of quiescent uteri during pregnancy can cause preterm labor. We wish to know the effects of in vivo and in vitro exposures to CS2 on uterine contractions of mid-gestation rats. After 10-d exposure to 300 or 600 mg/kg CS2, uteri of pregnant rats were measured for contractile responses to various stimuli, such as KCl, oxytocin, carbachol or A23187, a calcium ionophore, using standard muscle bath apparatus. CS2 treatment significantly increased the contractile response to KCl, carbachol, and A23187. The increase to A23187 was the greatest. In contrast, in vitro exposure to CS2 immediately suppressed carbachol-induced contraction but did not affect spontaneous and KCl-induced contractions. Results showed the pregnant uterus of the rat is susceptible to CS2. The influence of in vivo exposure to CS2 on uterine contraction was opposite to that in vitro. The increased response of CS2-treated uteri to A23187 suggests that in vivo exposure to CS2 may sensitize contraction machinery to calcium through indirect pathways.

Animals↗
PubMed2000

Postinfectious encephalomyelitis: etiologic and diagnostic trends.

Fifty cases of postinfectious encephalomyelitis admitted to our Pediatric Department during the period 1980 to 1997 were consecutively collected and reviewed. There were 28 males and 22 females. The age of onset ranged from 9 months to 14 years. The antecedent infections included measles (6 cases), rubella (5 cases), mumps (4 cases), chicken pox (4 cases), Epstein-Barr virus infection (11 cases), mycoplasma infection (6 cases), and unknown etiology (14 cases). The cessation of measles, rubella, and mumps as causes for encephalomyelitis in our patients corresponds with the introduction of a measles-mumps-rubella nationwide vaccination program in Taiwan commencing in 1992. The main clinical symptoms were fever, headache, and/or vomiting, seizure, and motor weakness. The presenting signs included altered consciousness, meningeal signs, cranial nerve palsy, brainstem signs, involuntary movement, and cerebellar signs. Computed tomography scans were abnormal for 14 (56%) of 25 patients studied, whereas magnetic resonance imaging (MRI) disclosed lesions in 14 (82%) of 17 patients, with abnormal signals in various parts of the cerebral hemisphere, as well as in the basal ganglion, diencephalon, midbrain, brain stem, and cerebellum. Of the three patients with negative MRI findings, an abnormal finding on somatosensory evoked potential was noted for one patient, and a focal decrease in tracer uptake on single photon emission computed tomography (SPECT) was found for the other two patients. This study demonstrates that the causative agents of postinfectious encephalomyelitis in Taiwan have changed from those of traditional exanthematous diseases to nonspecific respiratory infections and suggests that this may also be the case in other parts of the world. MRI remains the imaging method of choice, whereas other neurofunctional studies such as evoked potentials and SPECT are complementary for the diagnosis.

Adolescent↗
PubMed1999

Quantitative relationship between fluctuations of blood pressure and sympathetic nerve activity in pentobarbital anesthetized rats.

Transfer function analysis was used to examine the coupling between the sympathetic nerve activity (SNA) and the blood pressure (BP) fluctuations. In pentobarbital anesthetized Wistar rats, linear regression of the relationship between frequency (X-axis) and the logarithmic transfer magnitude, i.e. log (BP power density/renal SNA power density) (Y-axis), in the low frequency range (0.016-0.85 Hz) revealed an excellent fit (r = 0.97-0.98). Comparing the regression lines, rats under large dose of pentobarbital anesthesia (40 mg/kg, i.v. single dose) had significantly smaller intercept and slope values compared to rats under small dose of pentobarbital anesthesia (12.5 mg/kg). When intercept and slope values were compared between intact and acutely sinoaortic denervated rats, no significant difference were found. The results suggest that sympathetic modulation of vasomotor tone may be a major factor in generating BP fluctuations between 0.016 and 0.85 Hz in rats. Furthermore, these results support the possibility of using low frequency spectral power of BP to quantitatively estimate the fluctuations of SNA for rats under pentobarbital anesthesia if anesthetic depth is controlled.

Anesthesia, Intravenous↗
PubMed1999

Effects of Fructus schizandrae on cycloheximide-induced amnesia in rats.

The effects of Fructus Schisandrae (Schizandra Chinensis, (FS) on cycloheximide (CXM)-induced amnesia by using a passive avoidance task were studied in rats. FS at 0.25 and 0.75 g/kg administered for 1 week significantly prolonged the CXM-shortened step-through latency (STL). Of the fractions (n-hexane, chloroform and water), only the water fraction at 25 mg/kg administered for 1 week prolonged the CXM-shortened STL. These results suggest that the water fraction is the main active fraction of FS.

Amnesia↗
PubMed1998

Attenuation of cardiac but not vascular component in baroreflex of spontaneously hypertensive rats.

The cardiac and vascular components of the baroreceptor reflex in spontaneously hypertensive rat (SHR) and stroke-prone spontaneously hypertensive rat (SHRSP) were compared against their counterparts in normotensive Wistar Kyoto rat (WKY). SHR, SHRSP and WKY of 12-16 weeks old were chronically instrumented for intra-arterial recording of blood pressure. Intravenous injections of phenylephrine and nitroprusside were used to challenge their baroreflex. The products of blood pressure change and the half time required for the pressure to return to the control value were used as the quantitative estimation of the blood pressure stabilizing capability. The cardiac component of the baroreflex was obtained from the change in the blood pressure stabilizing capability after blockade of beta and muscarinic receptors by atenolol and atropine, respectively. The vascular component was obtained by subtracting the cardiac component from the total stabilizing capability which was the difference after blockade with a ganglionic transmission blocker, hexamethonium. We found the cardiac component of the baroreflex of the hypertensive rats was significantly less sensitive than that of the WKY. In contrast, the vascular component of the baroreflex of the three strains did not differ significantly. Therefore, we concluded that the 12-16 week old SHRs were able to maintain a stable blood pressure due to the intact vascular component of the baroreflex.

Adrenergic alpha-Agonists↗
PubMed1998

Evidence of independent origin of multiple tumors from patients with prostate cancer.

BACKGROUND: In men with prostate cancer, the gland usually contains two or more widely separate tumors. A critical issue of prostatic carcinogenesis is whether these multiple tumors are independent in origin. Molecular analysis of microsatellite (i.e., highly repeated, short nucleotide sequences) alterations in the DNA from separate tumors in the same prostate can be used to determine whether or not these separate tumors arise independently. METHODS: Four microsatellite polymorphic markers (D8S133, D8S136, and D8S137, for a putative tumor suppressor gene on chromosome 8p, and D17S855, for the BRCA1 gene on chromosome 17q) were used to examine the pattern of allelic loss in prostate cancer from 19 patients who had two or more distantly separate tumors (i.e., located on contralateral sides or separated by at least half the anterior-posterior diameter of the prostate). Forty distantly separate tumors were microdissected, DNA samples were prepared from formalin-fixed, paraffin-embedded wholemount prostate tissue section, and the overall frequencies of loss of heterozygosity at the four loci were determined. RESULTS: The pattern of allelic loss was compatible with independent tumor origin in 15 of 18 informative cases. A random discordant pattern of allelic deletion was observed in distantly separate tumors, whereas the same allele was consistently lost in cells from different regions of the same tumor. For three patients, the results were compatible with either intraglandular dissemination or independent origin of prostate cancer. CONCLUSIONS: Our data suggest that multiple tumors in some patients with prostate cancer have independent origin.

Chromosome Deletion↗
PubMed1998

Acute inhibition of spontaneous uterine contractions by an estrogenic polychlorinated biphenyl is associated with disruption of gap junctional communication.

An estrogenic polychlorinated biphenyl, 4-hydroxy-2',4', 6'-trichlorobiphenyl (4-OH-TCB), inhibits oscillatory uterine contractions immediately. Because increased gap junction formation is associated with the development of synchronized uterine contractions at term, we examined whether the inhibitory effect of 4-OH-TCB on spontaneous oscillatory contractions was due to the disruption of gap junctional communication. The effect of 4-OH-TCB on gap junctional communication was determined by intercellular Lucifer yellow dye transfer in primary cultures of myometrial myocytes isolated from midgestation rats. Intercellular dye transfer was inhibited by 4-OH-TCB or 17beta-estradiol in a concentration-dependent manner. The inhibitory effect of 4-OH-TCB on intercellular dye transfer was reversed by tetraethylammonium (TEA). To examine effects on uterine contraction, longitudinal uterine strips were excised from midgestation rats and placed in muscle baths for isometric force measurement. Spontaneous uterine oscillation was suppressed by 4-OH-TCB or 17beta-estradiol. The inhibitory effects of 4-OH-TCB and 17beta-estradiol on spontaneous oscillations were counteracted by TEA but were not affected by a calcium ionophore (A23187) or a calcium-dependent potassium channel blocker (apamin). These results suggest that the acute inhibition of spontaneous oscillatory contractions by an estrogenic polychlorinated biphenyl may result from the disruption of intercellular communication.

Animals↗
PubMed1998

Topographic mapping and clinical analysis of benign childhood epilepsy with centrotemporal spikes.

We studied the topographic mapping of the electroencephalography (EEG) of 47 children whose clinical history and course were compatible with typical benign childhood epilepsy with centrotemporal spikes (BCECT). Twenty-nine (62%) patients showed typical dipole fields, with a negative potential field in the centrotemporal region and a positive field in the frontal region. Eighteen children did not demonstrate the typical dipole field. Their non-dipole rolandic discharges were localized in small fields of centrotemporal region. The patients with dipole fields in BCECT had significantly less frequent seizures than patients without dipole fields. Twelve of the 47 patients with BCECT (26%) had more than one EEG focus. The clinical courses of patients with multiple foci were not worse than those of patients with a single focus. We conclude that EEG topographic mapping is helpful in identifying typical or atypical EEG topographic patterns in patients with clinically diagnosed BCECT. We also conclude that the presence of dipole field usually indicates a better clinical course of epilepsy and multiple foci do not mean a poor clinical course.

Action Potentials↗
PubMed1998

Desiccation resistance of two semiterrestrial isopods, Ligia exotica and Ligia taiwanensis (Crustacea) in Taiwan.

The ability to resist desiccation stress was examined in two semiterrestrial Ligia species, Ligia exotica Roux and L. taiwanensis Lee, in Taiwan, under a certain desiccation condition. L. exotica exhibited the longer survival time, lower weight-specific rates of water loss, and the slightly higher ability of tolerance to water loss, compared to L. taiwanensis. In each species, the animal size displays a positive correlation to the survival time and total ability to resist desiccation, yet this size effects on the weight-specific water loss rate is negative. Neither water content nor maximum tolerance to water loss shows the association with the animal size in both species. The path ways and magnitudes of the interactions between these traits of desiccation resistance are analyzed and diagrammed using a stepwise regression model. In this model, the body sizes of animal can explain the most part of the variations in the survival time. The body size has a direct effect and an indirect effect, through the effect on water loss rate, on the time that the experimental animals can survival under this desiccated condition. These results suggest that L. exotica attains larger size than does L. taiwanensis, a lower transpiration rate and, consequently, a greater ability in desiccation resistance. The performances of these interactions in the desiccated resistance are more advantageous for L. exotica to migrate and colonize in variable land habitats within a certain limit, and as a result that L. exotica shows a broader distribution pattern than did L. taiwanensis in Taiwan.

Animals↗
PubMed1997

Frequency dependent sympathetic modulation of vasomotor tone in the anesthetized rat.

The hypothesis that sympathetic nerve system modulates a specific frequency range of blood pressure fluctuation was tested by electrical stimulation of the medullary sympathetic excitatory sites in anesthetized, paralyzed, vagotomized, cardiac sympathetic blocked, baroreceptor transected and angiotensin II converting enzyme inhibited rats. The frequency tested ranged from 0.02 to 1.7 Hz. For blood pressure fluctuation within this range there was no specific sympathetic reactive zone. Instead, low frequency fluctuation of sympathetic flow produced blood pressure fluctuation of the same frequency. Transfer magnitude of renal sympathetic activity to blood pressure decrease logarithmically with the increase of stimulation frequency. The relationship between the sympathetic spectral power (P(SND), (microV.s)2/Hz) and the blood pressure spectral power (P(BP), mmHg2/Hz) was found as P(BP)=10(1.3) x P(SND) x 10(-4.7x(frequency)). This transfer function demonstrates that when blood pressure fluctuation is used to estimate the sympathetic activity, it should be frequency weighted.

Anesthesia, General↗
PubMed1997

A simple method for the construction of a recording-injection microelectrode with glass-insulated microwire.

A rapid method for the production of a glass-insulated microwire electrode is described. A microwire was threaded into a glass capillary which was then pulled on a vertical pipette puller. A conical tip of the microwire was formed when the strongly heated glass capillary broke together with the wire in it. A tight seal of the glass-insulated microwire electrode between the glass and the metal was accomplished with silicone glue. The manufactured electrode performed consistently at different immersion depths, and yielded stable recordings of single units in the cerebral cortex and the medulla of rats. The strength and low impedance characteristics of the glass-insulated microwire electrode may make it useful for the recording of single units in deep brain structures. Furthermore, the electrode can be easily combined with another glass micropipette to form a dual recording-injection microelectrode unit.

Animals↗