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C Y Chai

Publications and source records attributed to C Y Chai.

At least 73 records · Page 4Linked to original sources
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

Propofol inhibits medullary pressor mechanisms in cats.

PURPOSE: Propofol may cause hypotension and the mechanism is complex. The present study was designed to determine the direct actions of propofol in medulla of cats. METHODS: Mean systematic arterial pressure (MSAP), heart rate (HR) and cardiac contractility (dp/dt) were compared before and after administration of propofol the femoral vein (2, 3, or 4 mg.kg-1), vertebral artery (1 mg.kg-1) or the lateral cerebral ventricle (0.5 mg.kg-1) in eight anaesthetized cats. To study the direct effect of propofol in medulla, pressor areas of the dorsomedial medulla (DM) and rostral ventrolateral medulla (RVLM), or the depressor area of the caudal ventrolateral medulla (CVLM) were first identified with electrical stimuli and then confirmed by pressure microinjection of glutamate (Glu, 0.25M, 30 nl) via a multibarrel-micropipette in 28 cats. One hour later, propofol (0.001%, 50 nl) was microinjected at the same site. Electrical stimulation and Glu were applied again to compare changes of SAP, HR and dp/dt with that of the control. RESULTS: Propofol dose-dependently decreased SAP, HR and cardiac contractility. The percent increase of MSAP induced by Glu were reduced by propofol in DM (59 +/- 3% vs 13 +/- 2%, n = 11, P < 0.01) or in RVLM (56 +/- 4% vs 18 +/- 2%, n = 9, P < 0.01). In CVLM, propofol slightly but not significantly increased depressor responses elicited by Glu (-27 +/- 2% vs -33 +/- 3%, n = 5, P > 0.05). CONCLUSION: Our results show that propofol principally inhibits the vasomotor mechanism in the dorsomedial and ventrolateral medulla to effect its hypotensive actions.

Anesthetics, Intravenous↗
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↗
PubMed1997

Elevated basic fibroblast growth factor levels in stroke-prone spontaneously hypertensive rats.

Basic fibroblast growth factor is a biologically active polypeptide with mitogenic, angiogenic and neurotrophic properties. In the present study, the temporal and spatial expressions of basic fibroblast growth factor in stroke-prone spontaneously hypertensive rats were compared to two related strains of rat: spontaneously hypertensive rats and normotensive Wistar Kyoto rats. Higher levels of total RNA concentration were found in cerebral cortex of four-week-old stroke-prone rats compared to spontaneously hypertensive rats and Wistar Kyoto rats. Northern blot analysis showed no changes in levels of basic fibroblast growth factor messenger RNA with increasing age in cerebral cortex of Wistar Kyoto and spontaneously hypertensive rats. However, significant increases were found in 26- and 38-week-old stroke-prone rats compared to four-week-old stroke-prone rats. Although messenger RNA increases were also found in subcortical and cerebellar regions, a significant difference in levels of basic fibroblast growth factor messenger RNA was observed only in cerebral cortices among these three strains. This age-related increase in basic fibroblast growth factor messenger RNA correlated with the increase incidence of stroke in stroke-prone rats. Immunohistochemical study further revealed a dramatic increase in levels of basic fibroblast growth factor immunoreactivity in cerebral cortex of 30-week-old stroke-prone rats as compared to young stroke-prone rats, as well as age-matched Wistar Kyoto and spontaneously hypertensive rats. This increase in basic fibroblast growth factor immunoreactivity therefore appears very specific to aged stroke-prone rats. However, immunoreactivity decreased once severe tissue damages were observed in the cerebral cortex. Basic fibroblast growth factor-positive cells were diffusely expressed in cerebral cortex; double staining with glial fibrillary acidic protein showed the majority of these basic fibroblast growth factor-positive cells to be astrocytes. In summary, although young stroke-prone spontaneously hypertensive rats showed significantly higher RNA concentration, significant increases in levels of basic fibroblast growth factor, including both messenger RNA and protein expression, were observed in aged stroke-prone rats with a high incidence of stroke. These findings suggest the possibility that basic fibroblast growth factor may play a role in the developmental sequelae of cerebral lesions in stroke-prone spontaneously hypertensive rats.

Animals↗
PubMed1997

Evidence of a direct projection from the cardiovascular-reactive dorsal medulla to the intermediolateral cell column of the spinal cord in cats as revealed by light and electron microscopy.

To ascertain whether the dorsal medulla, a well-established vasopressor structure, would project directly to the sympathetic intermediolateral cell column of the spinal cord, we have carried out both anterograde and retrograde tracing studies in cats. For anterograde tracing, biotin-dextran was iontophoretically delivered into the cardiovascular-reactive dorsal medulla following its functional identification by electrical stimulation. The anterogradely transported biotin-dextran was then visualized using the avidin-biotin-horseradish peroxidase complex method. By light microscopy, dextran-labelled varicose axons were observed bilaterally in the intermediolateral nucleus extending from segments T1 to L3, but concentrated in segments T1-T5, notably at levels T2-T4. Electron microscopic examination revealed the localization of biotin-dextran reaction product in some small myelinated axons and axon terminals in the intermediolateral cell column. The majority of tracer-labelled axonal boutons contained spherical synaptic vesicles and made asymmetric synaptic contacts primarily with small dendrites. A few boutons contained polymorphic synaptic vesicles and tended to form symmetric axodendritic synapses. Spinally projecting neurons of the dorsal medulla were identified using the retrograde transport of horseradish peroxidase injected into the electrically cardiovascular-reactive intermediolateral nucleus. The labelled neurons were localized in the medullary dorsomedial reticular formation ventromedial to the nucleus of the solitary tract, approximately 0.5-5 mm rostral to the obex. The projection was bilateral, but was relatively denser in the rostral portion of the contralateral dorsal medulla. The present findings support the hypothesis that the dorsal medulla, through its direct pathway innervating the intermediolateral nucleus, may serve as a sympathetic premotor structure for regulation of arterial pressure.

Animals↗
PubMed1997

Involvement of non-NMDA and NMDA receptors in glutamate-induced pressor or depressor responses of the pons and medulla.

1. Fifty-five intact and six baroreceptor denervated and vagotomized cats of either sex were anaesthetized intraperitoneally with urethane (400 mg/kg) and alpha-chloralose (40 mg/kg). Responses of the systemic arterial pressure (SAP), mean SAP (MSAP) and sympathetic vertebral nerve (VNA) and renal nerve activities (RNA) were recorded. 2. In intact animals, monosodium L-glutamate (Glu, 0.1 mol/L, 50 nL) was microinjected into pressor areas of the locus coeruleus (LC), gigantocellular tegmental field (GTF), rostral ventrolateral medulla (RVLM) and dorsomedial medulla (DM), and the depressor areas of caudal ventrolateral medulla (CVLM). The induced actions were compared before and after microinjection of either glutamate antagonists, glutamate diethylester (GDEE, 0.5 mol/L, 50-100 nL), a competitive AMPA receptor blocker, or 2-amino-5-phosphonovaleric acid (D-AP5, 0.025 mol/L, 50-100 nL), a competitive N-methyl-D-aspartate (NMDA) receptor blocker. GDEE completely blocked the increases of SAP and VNA elicited from all pressor areas. D-AP5 only partially blocked the pressor but slightly blocked VNA and RNA responses from LC, GTF and DM, particularly those from RVLM. Neither GDEE nor D-AP5 blocked the depressor responses of SAP and two nerve activities elicited from CVLM. 3. In baroreceptor denervated animals, NMDA (2 mmol/L, 50-100 nL) and AMPA (0.2 mmol/L, 50-100 nL) were micro-injected into the same pressor areas of GTF, RVLM and DM and the depressor area of CVLM responsive to Glu activation (0.1 mol/L, 30 nL). In RVLM, DM and CVLM, the results of either NMDA or AMPA were similar to those induced by Glu. However, in GTF, microinjection of either NMDA or AMPA did not induce similar responses to Glu. This suggests that the nature of GTF may differ from RVLM and DM. 4. The above results suggest that the Glu-induced pressor responses from LC, GTF, DM and especially RVLM, are primarily mediated through AMPA receptors. The Glu-induced depressor responses from CVLM may not be predominantly mediated by either AMPA or NMDA receptors. 5. In both baroreceptor-intact and -denervated cats stimulation of the pressor areas often produced an increase of VNA and a decrease of RNA, while in the depressor CVLM decreased both VNA and RNA. The VNA, but not RNA were positively correlated with the pressor responses, while both VNA and RNA were positively correlated with the depressor responses. This may suggest that neurons of the sympathetic vertebral and renal nerves are topographically organized in the brain.

2-Amino-5-phosphonovalerate↗
PubMed1997

The inhibitory effect of UVB irradiation on the expression of p53 and Ki-67 proteins in arsenic-induced Bowen's disease.

The aim of this study is to evaluate the effect of ultraviolet B (UVB) on arsenic-induced Bowen's disease. Four patients were irradiated with 750 mJ/cm2 of UVB and biopsies were performed before treatment and 2 weeks later. Immunohistochemical stains of p53 and Ki-67 were compared by the labelled-streptavidin method before and after the UVB treatment. We found that the number of p53 and Ki-67 positive cells after the UVB treatment were significantly fewer than those of non-UVB-treated specimens. These results suggest that the UVB inhibitory effect in Bowen's disease needs further studies to clarify its value in potentially retarding the progression of the hyperproliferative status in overt skin cancer on a molecular basis.

Arsenic↗
PubMed1997

Detrusor-sphincter dyssynergia induced by cold stimulation of the urinary bladder of rats.

Instillation of cold water into the urinary bladder has been used as a diagnostic test to evaluate neurogenic dysfunctions of the lower urinary tract (LUT). This study examined the effects of cold stimulation on the LUT of urethan-anesthetized rats. Urinary bladder pressure and external urethral sphincter (EUS) electromyogram (EMG) were recorded during cystometrograms in which body- or room-temperature saline was infused continuously into the bladder and voided through the urethra. Subsequent infusion of cold saline (6-8 degrees C) into the bladder increased by approximately 100% the duration and amplitude of supraspinal reflex bladder contractions, increased baseline bladder pressure, increased the pressure threshold for inducing micturition, and increased EUS EMG activity. Blocking EUS activity by transecting the pudendal nerves or by administering a neuromuscular blocking agent markedly reduced or eliminated the effect of cold stimulation. Capsaicin pretreatment suppressed the effect of cold stimulation. It is concluded that cold temperatures stimulate capsaicin-sensitive C fiber bladder afferents that reflexly activate the EUS, producing detrusor and sphincter dyssynergia and increasing urethral outlet resistance. This in turn increases the amplitude and duration of bladder contractions during voiding.

Acclimatization↗
PubMed1997

Depletion of stratum corneum intercellular lipid lamellae and barrier function abnormalities after long-term topical corticosteroids.

The intercellular lipid lamellae of the stratum corneum (SC) is believed to provide the permeability barrier of the epidermis. Previous functional studies have demonstrated an increase in the transepidermal water loss (TEWL) after long-term use of topical corticosteroids (TCS): however, direct morphological confirmation of this barrier abnormality is still lacking. The aim of this study was to determine whether any abnormality could be detected in the structure of the SC intercellular lipid lamellae in patients after long-term TCS. Atrophic skin and untreated normal skin of 10 patients after long-term TCS were examined by transmission electron microscopy using ruthenium tetroxide-fixed tissue for the multilamellar lipid sheets of SC, and oil red O stain for neutral lipids of the SC. Layers of the SC were evaluated by 0.1% methylene blue stain after alkaline expansion, and TEWL was measured by Evaporimeter EP1. The TCS-treated atrophic skin had fewer layers of horny cells, mean 9.4 layers, than the normal control skin, 18 layers (P < 0.001) and increased TEWL of 21.3 g/m2 compared with the control skin TEWL of 6.7 g/m2 (P < 0.01). The mean neutral lipid content of the SC was also significantly lower (P < 0.001). Moreover, ultrastructural studies revealed a marked decrease in both the numbers of intercellular lipid lamellae of SC and membrane-coating granules of stratum granulosum in the atrophic skin. These results suggest that the diminution in the SC intercellular lipid lamellae and SC cell layers play an important part in the pathogenesis of barrier dysfunction after long-term use of TCS.

Administration, Topical↗
PubMed1997

A mixture of allogeneic dermal tissue and autologous microskin grafting of rabbit skin wound.

In a rabbit model, transplantation of largely expanded microskin grafts (expansion ratio 25 X) were studied. In Group I, the autologous microskin grafts were transplanted onto the full-thickness skin defect on the back of a rabbit and were overlaid with Biobrane. In Group II, the autologous microskin grafts were mixed with allogeneic microdermal substance (expansion ratio 25 X) before the transplantation. The percentage of re-epithelialized area to the total grafted wound was analyzed by means of computerized planimetric analyses of photographs of the grafted wounds on days 11 and 13. Biopsies of the grafted wounds were done. On day 11, the mean percentage of Group I was 72.4% and that of Group II was 82.7%. On day 13, they were 82.3% in Group I and 92.3% in Group II. In Group II, the allogeneic dermal tissue did not cause obvious rejection in the neoepithelium. Histological features showed the existence of allogeneic dermal tissue in the grafted wound. The adding of largely expanded allogeneic dermal substance to autologous microskin grafts in Group II provided better circumstances than that in Group I for re-epithelialization of autologous mciroskin grafts.

Animals↗
PubMed1997

Expression of epidermal growth factor receptors and c-erbB-2 proteins in human astrocytic tumors.

Tumorigenesis is the result of sequential or multiple genetic alterations. The overexpression or amplification of various oncogenes in diverse human brain tumors have been observed. While numerous studies on the immunohistochemical demonstration of EGFR-overexpression have been reported, little has been found in the literature about the c-erbB-2 protein in human astrocytic tumors. In the present study, we evaluated the expression of EGFR and c-erbB-2 protein in 33 astrocytic tumors with immunohistochemistry. According to the World Health Organization brain tumor classification, the study included 9 low-grade astrocytomas (grade 2), 15 anaplastic astrocytomas (grade 3), and 9 glioblastomas multiforme (grade 4). The positive EGFR immunoreactivity was detected in 28 (85%) of 33 tumors. The expression of EGFR increased with the grade of malignancy in low-grade astrocytomas (67%), anaplastic astrocytomas (87%), and glioblastomas (100%). For the expression of c-erbB-2 protein, 17 (51.5%) of 33 tumors were positive immunostain, including 3 low-grade astrocytomas (37.5%), 9 anaplastic astrocytomas (81.8%), and 5 glioblastomas (62.5%). Different degrees of immunoreactivity for c-erbB-2 protein were found in variant grades of astrocytomas. However, the positive immunostain of EGFR displayed moderate or strong reactivity. The coexpression of EGFR and c-erbB-2 protein was found in 17 (15.5%) of 33 tumors. The results emphasize that the overexpression of EGFR parallels astrocytoma progession and higher frequency of c-erbB-2 immunoreactivity was seen in snaplastic astrocytomas and glioblastomas than in low-grade astrocytomas.

Adolescent↗
PubMed1997

Effects of sonication on articular cartilage in experimental osteoarthritis.

OBJECTIVE: To investigate the histological effect of therapeutic ultrasound on arthritic cartilage of rats with various severities of induced osteoarthritis. METHODS: Twenty-seven rats with 3 different stages (Grade I, II, III) of papain induced knee arthritis received 7 min pulse sonication treatment, 3 times/week for 4 weeks. Another 27 rats with the same severity of induced arthritis were studied as controls. The severity of arthritis and related histopathological changes of articular cartilage were evaluated by bone scan and histological findings with hematoxylin and eosin stain. RESULTS: "Severity indexes" based on bone scan decreased after sonication treatment in each study group. Histopathological findings indicated marked cartilage repair in the early stage of induced arthritis (Grade I). However, progressive cartilage damage present in untreated Grade II, III induced arthritis was significantly reduced after sonication. CONCLUSION: Therapeutic ultrasound enhances cartilage repair in the early stage, and has the effect of arresting further deteriorative damage in the later stage of induced arthritis.

Animals↗
PubMed1997

The role of mucopolysaccharide induction in treatment of experimental osteoarthritis in rats by ultrasound.

Therapeutic ultrasound has been used in the treatment of osteoarthritis for the relief of symptom and improvement of functional status. In recent study, we found that ultrasound enhances cartilage repair in experimental early stage osteoarthritis, and prevents deteriorative changes in later stages. In the present study, we further investigate the bioeffects of ultrasound on cartilage matrix of experimental arthritis. Fifty-four rats with three different degrees of papain induced osteoarthritis classified by 99m-Tc pertechnetate bone scan were collected for ultrasound treatment. The changes in their arthritic severity after sonication treatment and two months after treatment were measured using 99m-Tc bone scan. The histopathological changes were evaluated through light microscope after disarticulation sections (H.E. stain), and the changes in mucopolysaccharide density in cartilage matrix were measured using a Optimas scanner analyzer after Alcian blue staining. The results showed that the density of mucopolysaccharide rose in the initial stage of induced arthritis, and decreased progressively in the later stage. The density of mucopolysaccharide increased upon complete sonication more for the treated rats than for the controls, and this was closely related with the improvement in histopathological findings, but inversely with the changes in arthritic severity. In conclusion, therapeutic ultrasound enhances mucopolysaccharide synthesis of arthritic cartilage, and results in the repair of arthritic cartilage in the early stage of induced arthritis and the prevention of deteriorative changes in later stages.

Animals↗
PubMed1996

Glycine produced pressor responses when microinjected in the pressor areas of pons and medulla in cats.

In 24 cats under chloralose/urethane anesthesia changes of systemic arterial pressure (SAP) and sympathetic vertebral nerve activities (VNA) were induced by microinjection of glycine (Gly, 1.0 M, 50 nl) into the pressor areas of the rostral pons, i.e., locus coeruleus-parabrachial nucleus (LC-PBN), nucleus of gigantocellular tegmental field-lateral tegmental field (FTG-FTL), and dorsomedial (DM) and ventrolateral (VLM) medulla. The effects were compared with those induced by microinjection of sodium glutamate (Glu, 0.25 M, 50 nl) into the same sites. In about 60% of the injections Gly produced increases in SAP and VNA similar to that of Glu. The increase in SAP was greater in VLM, while the increase in VNA was more marked in DM. In the rest of microinjections Gly and Glu produced changes of SAP and VNA in different combinations. The latency of Gly-induced increases in SAP and VNA was 1 to 3 s longer than that induced by Glu. Our findings show that although Gly is classified as an inhibitory transmitter, it often produced excitation of the pressor neurons in the pons and medulla similar to that of Glu. Whether Gly acts through the same cardiovascular neurons that respond to Glu or through activation of different kinds of neurons remains to be elucidated.

Animals↗
PubMed1996

The dorsal facial area of the medulla in cats: inhibitory action of serotonin on glutamate release in regulating common carotid blood flow.

Whether glutamate and serotonin would release and interact in the dorsal facial area (DFA) of cat medulla to regulate common carotid arterial (CCA) blood flow was explored by placing a microdialysis probe in DFA and employing high performance liquid chromatographic technique. Glutamate concentration was dose-dependently decreased by perfusion with serotonin, or alaproclate, a serotonin reuptake inhibitor. Serotonin and glutamate concentrations were increased by perfusion with KCl, a depolarizing agent. Furthermore, CCA blood flow was decreased when glutamate concentration was reduced by serotonin or alaproclate perfusion, and conversely increased when glutamate concentration was increased by KCl perfusion. In conclusion, glutamate and serotonin releases in DFA that involve regulation of CCA blood flow are tonically mediated by nerve terminals. The glutamate release is depressed by the serotonin release.

Alanine↗
PubMed1996

Expression of cyclin D1 and c-Ki-ras gene product in human epithelial ovarian tumors.

The expression of cyclin D1 gene product in human ovarian tumors was studied. We found that cyclin D1 is expressed at high levels in several ovarian cancer cell lines. Immunohistochemical study also showed that a significant proportion of primary ovarian tumor tissues overexpressed cyclin D1 gene product. Clear nuclear staining of cyclin D1 protein was detected in 28% of the cases. We also characterized the expression of c-Ki-ras gene product in ovarian cancer cell lines and tumor tissues. Amplification or overexpression of this proto-oncogene has been reported in ovarian tumors from Taiwan. These results show that c-Ki-ras is strongly expressed in PA-1 and NIH:OVCAR-3 cells in which cyclin D1 also expressed at high levels. Specific cytoplasmic staining of c-Ki-ras protein was detected in 11 tumors (52%). Statistical analyses show a strong positive correlation between cyclin D1 and c-Ki-ras immunoexpression. Thus, these data support the ideas that cyclin D1 may be involved in the pathogenesis of ovarian cancer, and coactivation of cyclin D1 and c-Ki-ras gene expression may represent one of the major pathways that lead to the development of ovarian cancer in Taiwan.

Carcinoma↗
PubMed1996

The early evaluation of induced osteoarthritis in rats with 99Tcm-pertechnetate scans.

Osteoarthritis was induced in 30 adult rats by serial injection of papain (3.5 mg kg-1) into the right knee on days 1, 4 and 7 of the study, with equal volumes of normal saline being injected into the left knee as a control. The severity of the induced arthritis was observed after the subcutaneous injection of 37 MBq kg-1 (1 mCi kg-1) 99Tcm-pertechnetate in the neck 24 h and 1, 2, 4, 6 and 8 weeks after the first intra-articular injection of papain. The ratio of radioactivity in the right compared with the left knee of each rat was measured as an index of the severity of osteoarthritis. After the scans, X-rays of both knees were obtained. At each state of progression, a rat was sacrificed and bilateral knee sections were performed for further pathological evaluation. The results were then compared with the changes in the radioactivity ratio and the X-rays. The radioactivity ratio of the knees reached a peak approximately 25 min after the subcutaneous injection of 99Tcm-pertechnetate and this value was chosen as the index of the severity of osteoarthritis. Marked differences in radioactivity in the left and right knees were observed as early as 24 h after the first intra-articular injection of papain. The radioactivity ratio increased with time, which correlated well with pathological changes. Joint space narrowing was not found on X-ray until 4 weeks post-injection. The results showed that the 99Tcm-pertechnetate scans correlated well with the pathological changes and that this method can detect osteoarthritis earlier than joint X-rays. It is suggested that a 99Tcm-pertechnetate scan is a useful means of evaluating early changes in induced osteoarthritis in rats.

Animals↗