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Biomedical subjects

Y L Ma

Publications and source records attributed to Y L Ma.

At least 37 records · Page 2Linked to original sources
PubMed1998

Enhanced glial cell line-derived neurotrophic factor mRNA expression upon (-)-deprenyl and melatonin treatments.

Glial cell line-derived neurotrophic factor (GDNF) has been shown to be a preferentially selective neurotrophic factor for dopamine (DA) neurons. In the present study, we have examined the distribution of GDNF mRNA expression in several major DA-containing cell body and terminal areas and the regulation of GDNF mRNA expression upon various pharmacological treatments. Results indicated that there is a relatively higher GDNF mRNA level in neurons of the nigrostriatal and mesolimbic dopaminergic pathways. Upon chronic 1-methyl-4-phenyl1,2,3,6-tetrahydropyridine (MPTP) treatment (30 mg/ kg, i.p., for 7 days), DA level was decreased, whereas GDNF mRNA expression was increased in the striatum, suggesting that more GDNF is synthesized and expressed to cope with the neurotoxin insult. Furthermore, among several DA neuron protective and/or therapeutic agents examined, both intrastriatal injections of (-)-deprenyl (1.25 microg and 2.5 microg) and melatonin (30 microg, 60 microg, and 120 microg) significantly enhanced GDNF mRNA expression in the striatum, whereas the same concentrations of (-)-deprenyl did not affect monoamine oxidase B (MAOB) activity, although it increased glutathione peroxidase (GPx) and/or superoxide dismutase (SOD) activities. Similarly, the same concentrations of melatonin did not alter SOD or GPx activities, except that the highest dose of melatonin (120 microg) increased lipid peroxidation in the striatum. Conversely, GM1 ganglioside injection (45 microg) lacked of an effect on GDNF mRNA expression. Together, these results suggest that both (-)-deprenyl and melatonin up-regulate GDNF gene expression at threshold doses lower than that needed for altering MAOB activity and/or the antioxidant enzyme systems, respectively. These results provide new information on the neuroprotective and therapeutic mechanisms of (-)-deprenyl and melatonin on DA neurons.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1998

Interaction of methylprednisolone and transient asphyxia on the inner ear of the adrenalectomized rat.

Methylprednisolone has been shown clinically to have beneficial effects on certain types of hearing loss. In the current study, compound action potential (CAP) thresholds, endocochlear potentials (EPs), and potassium concentration (CK+) values in the endolymph were determined under conditions of transient asphyxia (45 seconds) and methylprednisolone treatment (24 hours) in bilateral adrenalectomized rats. Treatment with methylprednisolone significantly reduced the effect of transient asphyxia on CAP thresholds as compared with nontreated animals. Methylprednisolone did not alter the dramatic short-term reduction in the EPs produced by anoxia. Potassium concentrations in treated adrenalectomized rats were significantly lower before transient asphyxia than in nontreated adrenalectomized rats. In the nontreated rats, transient asphyxia induced a reduction in CK+ levels that was not seen in the methylprednisolone-treated animals. The data support the clinical application of methylprednisolone for certain forms of hearing loss and for potassium imbalance in the endolymph.

Adrenalectomy↗
PubMed1998

Brain-derived neurotrophic factor antisense oligonucleotide impairs memory retention and inhibits long-term potentiation in rats.

We have examined the relationship between brain-derived neurotrophic factor gene expression in the hippocampus and memory retention as well as long-term potentiation of rats. One-way inhibitory avoidance learning was adopted as the behavioural paradigm. Results revealed that brain-derived neurotrophic factor messenger RNA levels in the dentate gyrus of the hippocampus were markedly increased at 1 h, 3 h and 6 h post-training in rats showing good retention performance when compared with the poor retention controls. Direct injection of brain-derived neurotrophic factor antisense oligonucleotide into the dentate gyrus of the hippocampus before memory consolidation takes place markedly impaired retention performance in rats. It also significantly decreased brain-derived neurotrophic factor messenger RNA level in the dentate gyrus. The same antisense treatment also markedly reduced the amplitude and slope of excitatory postsynaptic potential as well as the brain-derived neurotrophic factor messenger RNA level in the dentate gyrus. These results suggest that hippocampal brain-derived neurotrophic factor gene expression plays an important role in the memory consolidation process and in the expression of long-term potentiation in rats. These results provide the first evidence to relate brain-derived neurotrophic factor gene expression and memory function in vertebrates. It further suggests that brain-derived neurotrophic factor gene expression is involved in behavioural plasticity.

Animals↗
PubMed1997

Altered calcium homeostasis in the rat cochlear duct and endogenous corticosteroid insufficiency.

Free calcium concentration (CCa2+) profiles were evaluated in perilymph, endolymph, marginal cells, spiral ligament and blood serum of adrenalectomized (ADX) rats. Free CCa2+ was significantly greater in perilymph and significantly reduced in the serum of the ADX animals as compared to sham-operated animals. In addition, higher levels of free CCa2+ were found in the spiral ligament in ADX animals. Free CCa2+ did not appear to be affected by ADX in marginal cells and endolymph. These data suggest that marked reductions in endogenous levels of corticosteroids may have a systematic effect on free CCa2+ that is detectable in blood serum as well as cochlear fluids and tissues.

Adrenal Cortex Hormones↗
PubMed1997

Reconstruction of prostatic acinus-like structure from ventral and dorsolateral prostatic epithelial cells of the rat in three-dimensional collagen gel matrix culture.

PURPOSE: The study was carried out to reconstruct a prostatic acinus-like structure from prostatic epithelial cells in a new culture system which can provide a more physiological condition than conventional cell culture methods. MATERIALS AND METHODS: Prostatic epithelial cells were isolated from ventral and dorsolateral prostates of the rat and were separately cultured in three-dimensional collagen gel matrix. The cultured cells were observed by photo-microscopy and transmission electron microscopy. Differentiation and proliferation of the cultured cells were examined by immunohistochemistry using PAP and PSA kits and a bromodeoxy-uridine (BrdU) kit. The cell area of acinus-like structures in the transverse sections was measured by computer with the Interaktive Bild-Analyse System. RESULTS: Dissociated prostatic epithelial cells were organized into three-dimensional spherical or branching cellular aggregates in collagen gel matrix. Through cell proliferation and differentiation, the cellular aggregates formed prostatic acinus-like structures, which consisted of a small intercellular lumen enclosed by one layer of cuboidal epithelial cells. The epithelial cells were connected together by junctional complexes, had microvilli at the luminal surface, and the basal side was surrounded by a distinct basal lamina. In the lumina of acinus-like structures, secretory products were often found. CONCLUSIONS: Prostatic acinus-like structures were reconstructed from dissociated prostatic epithelial cells in three-dimensional collagen gel matrix culture. The reconstructed acinus-like structures are similar to prostatic acini in vivo in structure and function. This three-dimensional collagen gel matrix culture model may provide a useful means for investigating prostatic diseases and influences that hormones and growth factors exert on prostatic epithelial cells.

Acid Phosphatase↗
PubMed1996

Correlative evidence of hypertension and altered cochlear microhomeostasis: electrophysiological changes in the spontaneously hypertensive rat.

The spontaneously hypertensive rat model has been used to show that hypertension is an important pathophysiological risk factor in age-related hearing loss. In the present study, compound action potential (CAP), electrochemical potential (ECP), and potassium concentration (CK+) measurements were taken from the cochlea of genetically predisposed, spontaneously hypertensive rats (SHR) and from normotensive Wistar-Kyoto (WKY) rats. In the SHR model, as the duration of hypertension increased with the animal's age (from 3 to 8 months), CAP thresholds increased, ECP increased in marginal cells only, and CK+ increased in both endolymph and marginal cells. Collectively, the data suggest that ionic alternations of cellular potentials are involved in hearing changes in the hypertensive state. Ultimately, such data may assist in understanding hearing loss in individuals who are diagnosed with hypertension.

Action Potentials↗
PubMed1996

In situ real-time sequential potentiometric determinations of potassium concentrations from three cochlear regions in noise-exposed rats.

Double-barrelled potassium selective microelectrodes (K-ISME) were used in situ for real-time sequential determinations of potassium concentrations (CK+) in endolymph, marginal cells and the spiral ligaments of rats exposed to moderate noise at 100 dB for 30 min (NE) and control (CTL) animals. CK+ in NE animals at these sites did not differ significantly when compared to CK+ in CTL animals. However, there was a slight decrease in CK+ in marginal cells in the noise-exposed animals.

Animals↗
PubMed1996

Electrochemical potentials and potassium concentration profiles recorded from perilymph, endolymph and associated inner ear tissues in adrenalectomized rats.

This study evaluated the electrochemical potentials and potassium concentration (Ck+) profiles in the perilymph, endolymph, marginal cells, and spiral ligament of adrenalectomized rats in which endogenous corticosteroids had been removed. Electrochemical potentials recorded at the four cochlear sites were not affected by adrenalectomy (ADX). Ck+ was greater in the endolymph of the ADX animals as compared to control animals. Additionally, there was an increase of Ck+ in the marginal cells, perilymph, and spiral ligament tissues of the ADX animals as compared to control animals, although the observed increases were not statistically significant. In a previous study (Ma et al., 1995a), it was found that potassium levels in the blood plasma of ADX animals were higher than those identified in normal rats; thus, ADX may have a systemic effect on Ck+ that is detectable in both tissues and fluids within the cochlea. Even though Ck+ was elevated within the cochlea in the ADX model, the functional response of the inner ear, as assessed electrophysiologically, was not altered.

Action Potentials↗
PubMed1996

[Relaxation training on stress response to abdominal surgery].

In order to understand the effects of relaxation training on surgical stress response, a study was conducted among patients with abdominal surgery. Fifty-one patients were randomly divided into two groups. Experimental group (n = 25): patients received preoperative instruction and relaxation training, control group (n = 26): patients received only preoperative instruction. Anxiety state (state anxiety and physical symptoms of anxiety), blood pressure, heart rate, serum cortisone and postoperative pain of two groups were assessed and compared respectively on the third preoperative day, operation day, the first and the fourth postoperative day. Results showed that (1) there were significant differences between two groups (P < 0.05) in state anxiety scores on each day, physical symptoms on the first and fourth day after operation and severity of pain on the first postoperative day. (2) responses of systolic pressure, diastolic pressure and heart rate decreased in the experimental group. (3) Serum cortisone level decreased significantly in the experimental group on the first postoperative day (P < 0.05). This study shows that relaxation training has positive effects on surgical stress responses, especially in reducing the psychological anxiety response. Relaxation training can be served as an easy and effective method in nursing practice.

Humans↗
PubMed1996

Effects of daurisoline on intracellular Ca2+ activity in myocardium.

AIM: To explain the effect of daurisoline (DS) on delayed afterdepolarization (DAD). METHODS: Ca(2+)-sensitive microelectrode technic was used to record intracellular Ca2+ activity (alpha Cai) and triggered activity (TA) arising from DAD in myocardium. RESULTS: Strophantin G 3 mumol.L-1 yielded an increase in resting myocardial alpha Cai by 0.19 +/- 0.11 mumol.L-1 and transient elevations of alpha Cai by 1.48 +/- 0.55 and 4.96 +/- 1.81 mumol.L-1, respectively during the development of DAD and TA. By pretreatment with DS or verapamil, strophantin G-caused elevations of the alpha Cai in resting and provoked myocardia were eliminated and TA disappeared. DS 50 mumol.L-1 reduced Na(+)-free medium-induced elevation of dog Purkinje fibrous alpha Cai and abolished caffeine-induced increase of dog myocardial alpha Cai. CONCLUSIONS: DS inhibited DAD and TA by preventing an increase of alpha Cai via transmembrane Ca2+ entry and Ca2+ release from the reticulum.

Action Potentials↗
PubMed1995

Impaired retention by angiotensin II mediated by the AT1 receptor.

We demonstrated previously that hippocampal dentate gyrus neurons were sensitive to angiotensin II (AII) and recently discovered that AII applied directly to the dentate gyrus inhibited granule cell long-term potentiation induction and that the inhibition is mediated by the AT1 receptor and can be blocked by losartan, a specific AT1 antagonist. The purpose of the present study was to examine the effects of AII administered directly to the dentate gyrus, 1, 5, 50, 150, and 300 ng, on the retention of an inhibitory shock avoidance response and to determine if the resultant impairment of retention can be blocked by losartan. A total of 12 groups of rats in three experiments were studied. Three independent repetitions of 5 ng AII administered bilaterally to the dentate gyrus demonstrate a clear impairment of retention under these experimental conditions and that the impairment can be effectively prevented by pretreatment with 20 mg/kg of losartan IP.

Angiotensin II↗
PubMed1995

Amphetamine enhances memory retention and facilitates norepinephrine release from the hippocampus in rats.

The present study investigated the effects of intrahippocampal amphetamine on memory retention and the role of hippocampal norepinephrine (NE) in memory consolidation in rats. One-way inhibitory avoidance learning paradigm was adopted. Animals were trained to avoid the foot shock. The latency to step into the shock compartment was recorded as the retention measure. The ceiling score (full retention) was 600 s. Results indicated that intra-hippocampal injections of amphetamine produced a dose-dependent enhancement of memory retention with doses at 0.6 micrograms and 1.6 micrograms reaching a significant effect. The beta-adrenergic blocker propranolol, at a dose which did not affect retention alone (80 ng), antagonized the memory-enhancing effect of amphetamine. Along with this memory-enhancing effect, amphetamine also elevated the level of NE release, and this effect was significant in animals not showing a full retention score (nonresponders) than in animals showing a full retention score (responders), as assayed by in vivo microdialysis. Within the control group, the responders also had a higher level of NE than the nonresponders. All these results are probably due to the fact that responders have a higher level of NE release than nonresponders. The effect of amphetamine on NE release is, therefore, not as obvious in responders. These results together support our hypothesis that NE plays a facilitatory role in the memory process and amphetamine enhances retention performance, at least in part, through facilitation of hippocampal NE release.

Amphetamine↗
PubMed1995

Combined effects of adrenalectomy and noise exposure on compound action potentials, endocochlear potentials and endolymphatic potassium concentrations.

The effects of removal of endogenous corticosteroids via bilateral adrenalectomy in combination with noise exposure (30 min at 100 dB) were determined by recording compound action potential (CAP) and endocochlear potentials (EP), and by measuring potassium concentrations (K+e) within the endolymph. Thirty-eight Long-Evans rats were divided into groups according to experimental treatments: adrenalectomy (ADX) or non-ADX and noise exposure or non-noise exposure. CAP thresholds, EP and K+e values were subjected to repeated-measures analysis of variance with group and time as factors classifying the measurements. Noise exposure resulted in significant elevations of CAP thresholds in both the ADX and non-ADX animals, but had no effect on either EP or endolymphatic K+e. Recovery was noted during all post-exposure measurement periods and was significantly faster for ADX animals. EP and K+e did not change during or after noise exposure. ADX animals showed a non-significant reduction of EP and a statistically significant increase of K+e during all measurement periods as compared to non-ADX animals.

Acoustic Stimulation↗
PubMed1994

[Discussion of the role of fiberoptic bronchoscopy examination in the choosing the type of operation for centre type lung cancer].

This paper summarized the clinical data of the 112 cases centre type lung cancer examined by the X-ray films or/and CT scan and fiberopiticbronchoscopy (FOB) from Oct. 1984 to Aug. 1993 and discussed the role of FOB examination playing in the surgical treatment of centre type lung cancer. The authors thinks the FOB examination should be one of the necessary means of routine pre-operation checking, because it takes an important part in finding area of bronchus infiltrated by the cancer and choosing the type of operation.

Adenocarcinoma↗
PubMed1994

[Measurement of cytoplasmic Ca2+ activity in myocardia with Ca(2+)-sensitive microelectrode].

The improved neutral ligand ETH1001 Ca(2+)-sensitive microelectrodes (Ca-ISE, tip diameter 0.4-0.8 mumol.L-1) are highly ion selective and sensitive and therefore can be reliably used to measure cytoplasmic Ca2+ activity (alpha iCa) in myocardia. The resting alpha iCa in guinea-pig ventricular trabecula, canine ventricular myocardia and Purkinje fibers were respectively 0.19 +/- 0.01, 0.20 +/- 0.02 and 0.46 +/- 0.07 mumol.L-1. Three mumol.L-1 strophantin G increased the resting and dynamic myocardial alpha iCa by 0.18 +/- 0.02 and 6.69 +/- 2.09 mumol.L-1 respectively, as well as engendered triggered activity (TA). When pretreated with 100 mumol.L-1 dauricine (Dau), strophantin G could no longer increase alpha iCa and TA disappeared. It is suggested thus the applicability of Ca-ISE for measurement of myocardia alpha iCa and TA is obvious.

Alkaloids↗
PubMed1993

[FeS2 changes in ignited pyritum].

FeS2 changes in Pyritum during igniting process were studied systematically by comparing Pyritum ignited under different conditions in terms of S content, Fe content, yielding ratio of ignited product and appearance features. Calcined Pyritum samples purchased from various parts of China were also compared in regard to their quality.

Hot Temperature↗
PubMed1993

[Effects of morphine on sensitivities of alpha-adrenoceptors in toad spinal ganglion neurons].

Intracellular recordings were performed on 35 neurons from 35 isolated toad spinal ganglia (SG) and the extracellular free calcium ion activities were measured in another 26 isolated toad SG by Ca(2+)-selective microelectrodes. The effects of morphine on the sensitivities of alpha-adrenoceptors were observed. It was found that depolarization of membrane potential induced by norepinephrine (NE 10-100 mumol.L-1) or alpha 1-adrenoceptor agonist phenylephrine (100 mumol.L-1) was depressed by morphine (27 mumol.L-1). Superfusing SG with opioid receptor antagonist naloxone (100 mumol.L-1) blocked the depressing effect of morphine on NE-induced depolarization. The depressing effect of morphine on NE-induced depolarization was not affected by superfusing SG with alpha 2-adrenoceptor antagonist yohimbine (5 mumol.L-1). NE (100 mumol.L-1) reduced the extracellular free calcium ion activity while morphine (27 mumol.L-1) increased the extracellular free calcium ion activity in SG. It is concluded that morphine down-regulates the sensitivity of alpha 1-adrenoceptor in toad SG neuron mediated by opioid receptor and the variation in Ca2+ activity may be involved in this effect.

Animals↗