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Biomedical subjects

C Y Chai

Publications and source records attributed to C Y Chai.

At least 91 records · Page 5Linked to original sources
PubMed1996

Angiotensin II activates pressor and depressor sites of the pontomedulla that react to glutamate.

1. In cats anaesthetized with a mixture of alpha-chloralose (40 mg/kg) and urethane (400 mg/kg) and in rats anaesthetized with a mixture of alpha-chloralose (60 mg/kg) and urethane (800 mg/kg), changes in systemic arterial pressure (SAP), heart rate (HR) and sympathetic activities of vertebral (VNA) and renal (RNA) nerves were determined following the microinjection of angiotensin II (AngII; 0.16 mmol/L; 50 nL) into the pressor and depressor sites of the pontomedulla previously reacted to a microinjection of monosodium L-glutamate (Glu; 0.1 mol/L; 50 nL). Pressor sites included gigantocellular tegmental field (FTG) and dorsal medulla (DM) and rostral ventrolateral medulla (VLM). The depressor site was the caudal VLM (CVLM). The effects of losartan (1 mmol/L; 50 nL), a specific AT1 receptor non-peptide antagonist for AngII, on responses induced by AngII in the VLM, DM and CVLM were also determined. 2. In 30% of pressor sites in the FTG, 55% in the VLM and 67% in the DM and in 76% of depressor sites in the CVLM previously exposed to Glu, microinjection of AngII to the same site produced pressor or depressor responses similar to that of Glu, but smaller in magnitude, particularly in the pressor VLM. Changes in both VNA and RNA induced by AngII were also smaller than those induced by Glu, particularly RNA from DM activation. 3. In the dorsal motor nucleus of the vagus, AngII, as Glu, produced marked bradycardia, but again this was smaller in magnitude than the bradycardia produced by Glu. 4. In rats, in the DM near or around the nucleus of the solitary tract where Glu increased SAP, microinjection of AngII (0.8 mmol/L; 60 nL) produced a depressor response, while the microinjection of 1.6 mmol/L (60 nL) AngII produced a pressor response. 5. Losartan blocked the increase in SAP induced by AngII in the VLM and DM. Decreases in SAP induced by AngII in the CVLM, however, were only slightly decreased by losartan. 6. Our data suggest that a significant portion of pressor and depressor sites of the pontomedulla contain neurons responsive to both AngII and Glu. In neurons in the VLM and DM, AngII produced pressor responses that were primarily mediated through AT1 receptors, while the depressor actions of AngII in the CVLM were not mediated by AT1 receptors.

Angiotensin II↗
PubMed1996

Immunohistochemical pattern of P53 protein in human astrocytic tumors.

P53 immunohistochemistry in astrocytic tumors has usually been evaluated by the percentage of positive cells. However, in this study we analyzed the P53 immunopositive cells by their patterns of distribution. Formalin-fixed and paraffin-embedded sections from 38 patients with astrocytic tumors were examined. The distribution pattern of P53 immunostaining cells was divided into 3 types: negative, locally scattered, and diffuse clustering. There were 2 positive stains in 5 astrocytomas (40%), 12 positive in 24 anaplastic astrocytomas (50%), and 7 positive in 9 glioblastoma multiformes (78%). In astrocytomas, the positive cells were locally scattered. In anaplastic astrocytoma and GBM, the positive cells appeared locally scattered or as diffuse clustering. For the variant immunoreactive expression, the mean ages for patients with negative, locally scattered and diffusely clustered P53 immunostaining were as follows: 51.4, 52.6, and 28.4 years (P < 0.01), respectively. In anaplastic astrocytoma and GBM, the diffusely clustered pattern was more common in younger patients, whereas elderly patients in same groups tended to have few or no P53 immunopositive cells. Thus, our results implicate that clonal expansion of P53 immunopositive cells is associated with brain tumor progression.

Adolescent↗
PubMed1996

Descending pressor pathways from the dorsomedial and ventrolateral medulla of cats.

Descending pathways of the pressor areas in dorsomedial (DM) and ventrolateral (VLM) medulla were studied physiologically and anatomically. The electrically induced pressor response from either DM or VLM that previously responded to glutamate (Glu) was slightly but not significantly decreased after splitting the medulla at midline. After electrolytic lesion in the ipsilateral lateral tegmental field (LTF) of caudal medulla, 4 mm caudal to the obex, electrically induced pressor responses from DM and VLM previously responded to Glu decreased significantly from 71% to 20% and from 57% to 7%, respectively. The dorsomedial LTF was found to be responsible for the DM responses, while the ventrolateral LTF for the VLM responses. Following electrolytic lesion in the ipsilateral dorsolateral funiculus (DLF) between C4 and C5, the magnitude of DM-induced pressor responses decreased significantly from 74% to 37% and that of the VLM from 75% to 14%. After electrolytic lesion at the ipsilateral intermediolateral cell column (IML) of T2 spinal cord, the pressor responses on DM and VLM stimulations also decreased significantly. Lesioning the remaining IML almost completely abolished the induced pressor responses. Seven to ten days following kainic acid injections into DM or VLM to destroy neurons therein, degenerative fibers (silver impregnation) were found to descend from the medulla to thoracic spinal cord, principally ipsilaterally, but with some fibers crossing to the controlateral medulla. Data from both physiological and anatomical studies suggest that fibers from DM and VLM descend ipsilaterally through different pathways and converge at LTF 4 min caudal to the obex, and then further descend to DLF before reaching the thoracic IML.

Animals↗
PubMed1996

Effects of precollicular decerebration on the vasomotor and sympathetic nerve responses to locus coeruleus stimulation.

In 25 cats under intraperitoneal alpha-chloralose (40 mg/kg) and urethane (400 mg/kg) anesthesia, cardiovascular reactive sites of locus coeruleus (L.C) were stimulated by rectangular pulses (0.5 ms, 80 Hz, 100 to 200 microA) and/or by microinjection of sodium glutamate (Glu, 0.25 M, 70-150 nl). Changes of systemic arterial blood pressure (SAP) and sympathetic vertebral (VNA) and renal (RNA) nerve activities following stimulations were analyzed and, furthermore, SAP responses were compared before and after precollicular decerebration (PD). Microinjection of Glu in this region often produced a moderate increase and less often decrease in SAP. Depressor points were located dorsal to the sites eliciting pressor responses. In the majority of LC stimulations (69%) VNA increased along with the increase of SAP, while the RNA decreased. In a few stimulations marked increase in VNA and decrease in RNA occurred with little change in SAP. PD itself produced various degrees of a temporary (lasted for 5 to 15 min) decrease in SAP from 40 to 100 mmHg. Following PD, three types of change in the LC induced SAP responses were observed in a decreasing order, i.e., the responses were slightly reduced or slightly augmented, or the LC induced depressor responses were converted to a pressor one. Findings of the present study showed that neural mechanism in LC responsible for the changes of SAP and sympathetic nerve activities may exist in a topographic organization. LC is different from the gigantocellular tegmental field (FTG) located in the same rostral pons. The marked pressor responses elicited by activation of the FTG depend entirely on the rostral brain structure, while LC is not. Some brain structures rostral to superior colliculi may exert both inhibitory and excitatory influences over LC in cardiovascular integration.

Animals↗
PubMed1995

Vasodilatation produced by stimulation of parvocellular reticular formation in the medulla of anesthetized-decerebrate cats.

In cats activation of the dorsal facial area (DFA) in the medulla produced an increase of blood flow in the common carotid artery (CCA). This involves flow increases in both intra- and extra-cranial vessels via cranial parasympathetic nerves. In this study, we attempted to explore transmitter mechanisms involved in vasodilatation in extracranial vascular beds due to DFA activation. Cats were anesthetized with intraperitoneal urethane (350 mg/kg) and chloralose (35 mg/kg). Electrical stimulation (100 microA, 20 Hz, 0.5 ms for 5 s) or microinjection of sodium glutamate (Glu, 0.25 M, 50 nl) in DFA increased the velocity of flow in CCA ipsilateral to the stimulation. After control values were obtained, the animals were subjected to decerebration with transection level just rostral to superior colliculi (precollicular decerebration). The increased CCA flow velocity induced by DFA activation was not altered before and after decerebration. Atropine (muscarinic blocker, 0.5-2.0 mg/kg, i.v.) alone only partially attenuated the increase, but the increase was totally blocked by additional N(omega)-L-arginine methyl ester (nitric oxide synthase inhibitor) in 7 out of 9 cats. These findings suggest that extracranial vasodilatation induced by DFA activation does not depend on the sympathetic nervous system, but involves the muscarinic- and nitric-oxide-mediated systems.

Animals↗
PubMed1995

Dynamic analysis of ethanol effects on NMDA-evoked dopamine overflow in rat striatum.

This study was undertaken to dynamically examine the effects of ethanol on the striatal dopaminergic transmission, in terms of N-methyl-D-aspartate (NMDA)-evoked dopamine release and dopamine uptake. In the striatum of urethane-anesthetized Sprague-Dawley rats, extracellular dopamine was measured using in vivo electrochemical detection coupled with a nafion-coated carbon fiber working electrode. Micro-ejection of NMDA evoked a transient dopamine release from the dopamine-containing nerve terminals in striatum. Local application of ethanol by pressure ejection did not elicit significant changes in spontaneous dopamine release. However, with ethanol pretreatment, the time course of NMDA-induced dopamine release was markedly prolonged while the magnitude and the rate of clearance were significantly reduced. These effects were compared to those of nomifensine, a dopamine uptake blocker. Nominfensine pretreatment was found to augment the time course of NMDA-evoked dopamine release analogous to those by ethanol pretreatment. Furthermore, pretreatment with ethanol did not increase the time course parameters of dopamine signals if dopamine releases were induced by co-application of NMDA and nominfensine. These data suggest that in addition to the attenuation of NMDA-evoked dopamine release, ethanol inhibits dopamine uptake in a similar fashion to that observed with nomifensine in situ in the striatum. Indeed, ethanol altered the uptake of exogenous dopamine from the extracellular space of striatal cortex. The time course of dopamine signals was prolonged and the rate of clearance was reduced after ethanol treatment. Taken together, our data demonstrate that ethanol simultaneously inhibits NMDA-evoked dopamine release and dopamine uptake in the striatum, suggesting the importance of the interplay between release and uptake in ethanol effects on striatal dopaminergic transmission.

Animals↗
PubMed1995

Screening of lead exposure among workers in Selangor and Federal Territory in Malaysia.

The study of lead exposure among workers in Selangor and the Federal Territory was carried out based on the delta-aminolevulinic acid (ALA) level in urine. Occupations which are expected to have higher lead exposure were chosen in this research. The ALA level in the workers' urine was linked to a few variables which may contribute to the lead level in the body. The result of this study showed that the ALA level of the urine of university students (0.352 +/- 0.038 mg/100 ml) < clerical staff (0.560 +/- 0.043 mg/100 ml) < traffic police (0.612 +/- 0.064 mg/100 ml) < vehicle workshop workers (0.673 +/- 0.099 mg/100 ml) < petrol kiosk workers (0.717 +/- 0.069 mg/100 ml) < bus drivers/conductors (0.850 +/- 0.055 mg/100 ml) which was similar to workers in the printing industry (0.852 +/- 0.110 mg/100 ml). The ALA levels in the urine of the exposed workers were significantly different from the control group (university students). However, results obtained from clerical staff revealed that they were also in the exposed group category. Analysis of variance showed that the exposed groups are in a population which is different from the control population. Correlation tests suggest that there is no significant connection between the ALA level in the urine and the variables tested. Furthermore, Duncan's Multiple Range Test showed no significant differences between the smoking/non smoking group, alcoholic/non-alcoholic group, race and sex (p > 0.05).

Journal Article↗
PubMed1995

Involvement of nitric oxide in dopaminergic transmission in rat striatum: an in vivo electrochemical study.

In vivo electrochemical detection with a Nafion-coated carbon fiber working electrode, which provides information on the spatial and temporal dynamics of dopamine overflow, was used to investigate the involvement of nitric oxide (NO) in the dopaminergic transmission in the striatum of urethane-anesthetized Sprague-Dawley rats. A mixture of N-methyl-D-aspartate (NMDA) and nomifensine, a dopamine uptake blocker, was locally pressure-ejected to elicit a transient dopamine overflow from the dopamine-containing nerve terminals in the striatum. Local application of N omega-nitro-L-arginine methyl ester (L-NAME), which blocks endogenous NO formation, increased the magnitude of dopamine/release evoked by a subsequent NMDA and nomifensine application but resulted in no significant alteration in the time course. Furthermore, microejection of L-arginine, an NO precursor, or sodium nitroprusside (SNP), an NO generator, did not cause detectable changes in dopamine level in the striatal extracellular space. However, NMDA-induced dopamine release was profoundly inhibited with L-arginine or SNP pretreatment. In addition, NO affects dopamine uptake in rat striatum. Exogenous dopamine applied through a micropipette, reversibly and reproducibly, elicited an electrochemical signal. The time course of these signals was significantly prolonged by L-NAME treatment. These data suggest that NO is diversely involved in regulating dopaminergic transmission in rat striatum.

Animals↗
PubMed1995

Animal study of skin resurfacing using the ultrapulse carbon dioxide laser.

Ultrapulse carbon dioxide laser ablation of rabbit skin was investigated. Macroscopic and microscopic appearance of the ablation site was evaluated for 1 month. The Ultrapulse carbon dioxide laser was set in the ultrapulse mode and the parameters selected were 250 mJ of energy per pulse and 2 W average power with the 3-mm spot size collimated handpiece. Macroscopic investigation showed that ultrapulse carbon dioxide laser ablation removed rabbit skin precisely and bloodlessly without char formation. Skin re-epithelialization without scarring and perfect hair growth restoration within 3 weeks were impressive. Microscopic investigation demonstrated a layer of tissue thermal necrosis measured as 70 +/- 10 microns. During the first 2 weeks, laser ablation wound re-epithelialization begins with multiplying epidermal layers (from 2-3 cell layers to about 13 to 15 cell layers). There were marked fibroblastic reactions and capillary congestion within papillary dermis. By the end of 4 weeks, the thickened epidermal layer appeared normal. The repaired papillary dermal collagen showed a relative compact configuration and greater cellularity in Masson stain was found 2 to 3 weeks later and also was near normal 4 weeks after laser treatment. These findings suggest that Ultrapulse's delivery of short-duration, high-energy pulses may provide a new approach (laser dermal ablation) to damage selectively the epidermis and papillary dermis of rabbit skin in one single-pulse impaction with uneventful wound healing within 1 month.

Animals↗
PubMed1995

Changes in intra- and extracranial tissue blood flow upon stimulation of a reticular area dorsal to the facial nucleus in cats.

1. A small area in the dorsal part of the lateral tegmental field specifically responsible for the increase of blood flow in the common carotid artery (CCA) without accompanying change in the resting blood pressure was first identified in our laboratory. Since the area is located just dorsal to the facial nucleus, we named it the dorsal facial area (DFA; Kuo et al. 1987). 2. The purpose of this study was to clarify whether an increase of blood flow in intra- and/or extracranial tissues was responsible for the increase in CCA blood flow upon DFA stimulation, and to determine the role of cholinergic transmission in this response. 3. In 20 cats under chloralose and urethane anaesthesia, microsphere reference flow technique was used to measure the regional blood flow of intra- and extracranial tissues. 4. Electrical stimulation of the DFA appeared to increase the regional blood flow of both cerebral hemispheres (intracranial tissues) and to increase predominantly the regional blood flow of extracranial tissues on the side ipsilateral to stimulation. Increases in the regional blood flow of intracranial tissues were enhanced after i.v. administration of atropine but reduced with physostigmine. In contrast, increases in the regional blood flow of extracranial tissues were reduced after i.v. atropine but enhanced after physostigmine. 5. These findings suggest that DFA stimulation may promote the release of ACh in intra- and extracranial vessels. The muscarinic action may restrict the DFA-induced increase in blood flow of intracranial tissues, but enhance that of extracranial tissues.

Animals↗
PubMed1995

Enhanced sympathetic reactivity to glutamate stimulation in medulla oblongata of spontaneously hypertensive rats.

The distribution and reactivity of vasomotor sites in the ventrolateral (VLM) and dorsomedial medulla (DMM) of stroke-prone spontaneously hypertensive rats (SHRSP), spontaneously hypertensive rats (SHR), and Wistar-Kyoto rats (WKY) were compared. Rats were anesthetized with alpha-chloralose and urethan. Baroreceptor denervation and vagotomy were performed. L-Glutamate (Glu, 10 mM, 30 nl) was microinjected into the DMM or VLM to identify vasoactive sites. The extent and the patterns of distribution of these sites in the three strains of rats were similar. The dose-response curve of the vasoactive site was studied with 1-500 pmol of Glu. The maximum responses of blood pressure and renal sympathetic activity were larger and threshold doses of Glu were lower in hypertensive rats. The significance of the differences among the strains was analyzed before and after adjustment for baseline pressure or activity. Most of the differences were statistically significant before baseline adjustment. After baseline adjustment, many differences between the SHRSP and the WKY remained significant. However, the only significant difference detected between the SHR and the WKY was the threshold dose for eliciting renal sympathetic change in the caudal VLM. These results suggest that there may be a general increase in excitability of the vasomotor neurons in the medulla of the hypertensive rats.

Animals↗
PubMed1995

Histopathologic studies of gastric mucosa following gastric substitution in benign and malignant esophageal disease.

Gastric interposition was performed and prospectively studied in 9 patients with esophageal cancer, 1 patient with esophageal neurofibroma and 5 with corrosive esophageal stricture. The postoperative follow-up periods were between 6 to 68 months with a mean of 28.6 months. The subjects were then endoscopically reviewed. Twelve of them were macroscopically normal. The others exhibited signs of inflammation and hyperemia. Mucosal biopsies were obtained at the upper and lower third of the graft. The histologic findings were compared with those of the preoperative specimens. Among the 15 post-operative specimens, only minute histologic changes were seen. Three patients whose proximal grafts showed inflammatory signs revealed congestion. Another 2 patients exhibited granulocyte infiltration in the mucosa of the distal third. The mucosal structure of the remaining 10 patients was similar to that of the preoperative graft. In conclusion, the macroscopic and microscopic changes were few and minimal although there were alterations in function, physiology and location of the stomach.

Adult↗
PubMed1995

[Secretory carcinoma of the breast--a case report].

Secretory breast carcinoma is a very rare tumor of the breast and has distinctive pathological characteristics such as (1) the presence of large amounts of intracellular and extracellular secretion and (2) granular eosinophilic cytoplasma of the cells. It usually occurs in children or adolescents and is known to have a better prognosis than the usual ductal carcinoma. The preoperative aspiration cytology is also distinctive and it could permit planning the optimal surgical therapy such as breast conservation surgery for young patients. We report a case of secretory breast carcinoma in a 35 year-old female and her preoperative aspiration cytology in Liu's stain. To our knowledge, Secretory breast carcinoma has not been reported previously in Taiwan.

Adult↗
PubMed1995

Frozen section of diagnosis of breast lesions.

Frozen section diagnosis rendered in 549 consecutive breast biopsies performed in 5 years in a single pathology laboratory was correlated with the final pathological diagnosis. There were no false positive reports among the 220 (40.1%) biopsies interpreted as benign lesions in paraffin sections. Among 329 (59.9%) malignant biopsies on paraffin sections, 3 cases were interpreted as benign lesions on frozen sections. Three false negatives included 2 ductal carcinoma in situ and one infiltrating ductal carcinoma associated with papillomatosis. The tumors were small and confined to the breast without any evidence of metastasis. There was a very good correspondence between the frozen section diagnosis and the paraffin section diagnosis (K = 0.98). The sensitivity of frozen section diagnosis was 99.1% and the clinical diagnostic specificity was 100%. Our results suggest that frozen section diagnosis is a highly reliable procedure, but small lesions (less than 1 cm in diameter, or non-palpable) should not be subjected to frozen section examination to avoid unnecessary loss of neoplastic tissue during the frozen section. The careful investigation of paraffin-embedded tissue is recommended for small breast lesions in breast conserving lumpectomy.

Breast Diseases↗
PubMed1995

[Metaplastic ossification in the breast--a case report].

Metaplastic calcification and ossification originating in the subcutaneous fat of the breast are rare and commonly included in the malignant tumor. We reported a 24-year-old female who developed a huge metaplastic ossification without neoplasm in her right breast. To the best of our knowledge, this is the second case in the world literature and the first case in Taiwan.

Adult↗
PubMed1995

Carbachol, glycine and gamma aminobutyric acid also activate cardiovascular neurons of pontomedulla responsive to glutamate.

Thirty-three cats under intraperitoneal chloralose (40 mg/kg) and urethane (400 mg/kg) anesthesia were used to explore the effect of microinjections (100 nl) of carbachol (CCh, 0.5 M), a cholinergic analogue, glycine (Gly, 1 M) and gamma aminobutyric acid (GABA, 0.4 M) on the cardiovascular-reactive sites in the pontomedulla that responded to microinjection of monosodium glutamate (Glu, 0.25 M, 100 nl) resulting in changes of systemic arterial pressure (SAP). Brain sites under exploration included gigantocellular tegmental field and lateral tegmental field (FTG-FTL), the dorsomedial (DM) and ventrolateral (VLM) medulla which produced pressor responses; caudal VLM (CVLM) and paramedian reticular nucleus (PRN) which produced depressor responses. It was found that CCh produced significant fall of SAP in DM and VLM while the rise of SAP in the same site by Glu. CCh produced SAP decrease in CVLM similar to Glu. GABA significantly caused a slight to moderate increase of SAP in FTG-FTL, DM and VLM, and decrease of SAP in CVLM, all in direction similar to that of Glu. Gly produced significant and marked increase of SAP in DM and VLM similar to Glu both in magnitude and duration. Gly produced increase of SAP in CVLM but the fall of SAP by Glu. PRN was relatively non-reactive except a few microinjections of CCh which produced hypotension. In conclusion, the cardiovascular-reactive sites in the pontomedulla that respond to Glu may also react to other chemicals or neurotransmitters. It is highly possible that multiple receptors of different nature co-exist in neurons of some cardiovascular regions in the pontomedulla.

Animals↗
PubMed1995

Evoked potential elicited by periaqueductal grey stimulation in the pressor sites of dorsal and ventrolateral medulla in cats.

Evoked potential methods were used to compare the patterns of responses to periaqueductal grey (PAG) stimulation in two major medullary sympathoexcitatory areas, namely, ventrolateral medulla (VLM) and dorsal medulla (DM). Adult cats were anesthestized with chloralose and urethane, paralyzed, ventilated and bilaterally vagotomized. Pressor points in the PAG were identified with rectangular pulses in 80 Hz, 200 microA, 0.1 ms and used as stimulation points. Pressor points in VLM and DM were identified by injection of 100 nl of 0.25 M glutamate solution. Adjacent points 1 mm away from these pressor points where injected the same amount of glutamate solution elicited very little blood pressure changes were used as control recording points. Stimulation of the PAG pressor points with rectangular pulse in 1 Hz, 0.1 ms, 200 microA elicited complex evoked field potentials in both VLM and DM. In 9 of the 13 pressor-control pairs tested, distinctive evoked potential of long latency were seen in the pressor point only. These evoked potentials, averaged 3.5 ms in the DM, and 5.6 ms in the VLM. Therefore, it was postulated that pressor points of PAG had separate and independent connections with DM and VLM.

Animals↗