Biomedical subjects

C Y Chai

Publications and source records attributed to C Y Chai.

At least 19 recordsLinked to original sources

PubMed1992

Presence of neuronal cell bodies in the sympathetic pressor areas of dorsal and ventrolateral medulla inhibiting phrenic nerve discharge in cats.

To examine whether neuronal cell bodies (perikarya) in the pressor areas of dorsal medulla or ventrolateral medulla also modulate respiratory function, phrenic nerve activity was monitored and correlated with the pressor response in chloralose-urethane anaesthetized cats. The animals were paralyzed and artificially ventilated maintaining the end-tidal fractional concentration of CO2 at 0.04-0.05. The same pressor point in the dorsal or ventrolateral medulla was stimulated electrically (rectangular pulse of 20-200 microA, 80 Hz and 0.5 ms) and then chemically (0.25-0.5 M sodium glutamate, 80-200 nl). Areas producing pressor effects in either the dorsal or ventrolateral medulla produced a current-dependent decrease of phrenic discharge. The decrease in Pna was significant when the electrical current reached 50 microA or above. It occurred immediately before the onset of increase in blood pressure. Injection of glutamate to the same pressor point in either the dorsal or ventrolateral medulla produced a similar decrease in phrenic nerve activity. The results suggest that in the pressor areas of dorsal and ventrolateral medulla there are neuronal perikarya that can increase systemic arterial pressure and inhibit phrenic nerve activity. Whether the same or separate neurones are responsible for these responses is to be determined.

Animals↗

PubMed1992

Differential effects on sympathetic nerve activities elicited by activation of neurons in the pressor areas of dorsal and rostral ventrolateral medulla in cats.

Changes of the nerve activity of the sympathetic renal and vertebral nerves were elicited by microinjection of sodium glutamate (50 nmol/100 nl) into the pressor areas of the dorsal (DM) and rostral ventrolateral medulla (RVLM) in cats under urethane-chloralose anesthesia. Animals were bilaterally vagotomized, artificially ventilated, and paralyzed with gallamine triethiodide. The vertebral nerve activity always increased when pressor responses were induced by DM or RVLM stimulation. However, the effects of medullary stimulation on the renal nerve activity were variable. Three types of renal nerve responses concomitant with the pressor responses were observed in either baroreceptor-intact or baroreceptor-denervated cats. They were: (1) augmentation (type I); (2) attenuation (type II); and (3) insignificant change (type III). Type I responses were often elicited by RVLM stimulation whereas type II responses were often elicited by DM stimulation. Findings suggested that neurons integrating these sympathetic nerve activities were not equally distributed in the pressor areas of DM and RVLM. This result supports the notion that neurons located in different pressor areas of the brainstem exert differential effects over different sympathetic nerve activities.

Animals↗

PubMed1992

Coexistence of autonomic and somatic mechanisms in the pressor areas of medulla in cats.

The effects of electrical stimulation and microinjection of sodium glutamate (0.5 M) in the sympathetic pressor areas of the dorsal medulla (DM), ventrolateral medulla (VLM), and parvocellular nucleus (PVC) on the knee jerk, crossed extension, and evoked potential of the L5 ventral root produced by intermittent electrical stimulation were studied in 98 adult cats anesthetized with chloralose and urethane. During electrical and glutamate stimulation of these pressor areas, in addition to the rise of systemic arterial blood pressure marked inhibition of the spinal reflex was produced, indicating presence of neuronal perikarya responsible for these actions. Mild to moderate augmentation of spinal reflexes was also observed during brain stimulation but only in a few cases. The magnitude of the somatic effects among the pressor areas of the VLM, DM, and PVC subsequent to glutamate activation was about the same. Induced spinal reflex inhibition, independent from the baroreceptor and vagal influence, remained essentially unaltered after acute midcollicular decerebration. The inhibition was also observed in cats decerebellated 8-10 days in advance. The inhibition was not affected after bilateral electrolytic- or kainic-acid-induced lesions in the paramedian reticular nucleus (PRN). On the contrary, PRN-induced spinal reflex inhibition was attenuated after bilateral lesions in the DM or VLM. Data suggest that there coexists neuronal subpopulations in the VLM, DM, and PVC that can affect both the sympathetic pressor systems and spinal reflexes.

Animals↗

PubMed1992

Reduction of blood PO2 decrease and PCO2 increase during asphyxia by paramedian reticular nucleus in cats.

Effects of activation of paramedian reticular nucleus (PRN) on the systemic arterial blood pressure (SAP), heart rate, renal nerve activity (RNA), and changes of the partial pressure of the arterial blood oxygen (PO2) and carbon dioxide (PCO2) during asphyxia were studied in cats anesthetized with chloralose (40 mg/kg) and urethane (400 mg/kg). During a 35-s period of asphyxial anoxia, SAP and RNA increased while heart rate decreased significantly. The arterial blood PO2 decreased by 64.6 +/- 4.7% while the PCO2 increased by 54.6 +/- 6.3%. Electrical stimulation of PRN produced a mild to moderate decrease of the SAP, heart rate, and RNA, but arterial PO2 and PCO2 did not change significantly. When PRN was stimulated simultaneously with asphyxia, increases of SAP and RNA and changes of blood gases subsequent to asphyxia reduced significantly. Arterial PO2 decreased only 54.0 +/- 4.9% while the PCO2 increased 39.4 +/- 10.5% (p < 0.01). Similar effects were observed in the venous blood from inferior vena cava. In addition, when the arteriovenous difference of PO2 and PCO2 was compared, simultaneous PRN stimulation during asphyxia produced a higher PO2 reserve (66.3%) and less PCO2 production (-7%) than without PRN stimulation; PO2 54.2%, PCO2 (-2.9%). The results suggest that PRN is a structure that can exert inhibition over a wide spectrum of body functions; not only autonomic system but probably also metabolism.

Animals↗

PubMed1992

Consequences of opiate agonist and antagonist in myocardial ischaemia suggest a role of endogenous opioid peptides in ischaemic heart disease.

OBJECTIVE: The aim was to evaluate the effects of an opiate agonist (U50,488H) and an opiate antagonist (naloxone) in myocardial ischaemia. METHODS: A left thoracotomy was performed and the left coronary artery was ligated in adult Sprague-Dawley rats of either sex (350-400 g). Blood pressure, heart rate and electrocardiogram were measured before and after injections of U50,488H or naloxone and throughout the 30 min postligation period. RESULTS: Following coronary artery occlusion, all rats in the control group developed arrhythmias, bradycardia, and hypotension. U50,488H potentiated and naloxone attenuated the ischaemia induced arrhythmias, bradycardia, and hypotension. CONCLUSIONS: The potentiating and blocking effects of U50,488H and naloxone, respectively, suggest that endogenous opioid peptides are involved in the pathophysiology of myocardial ischaemia and play an important role in ischaemic heart disease.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗

PubMed1992

Pneumatosis cystoides intestinalis arising in jejunal diverticular disease: report of a case and a suggestion to its pathogenesis.

The occurrence of pneumatosis cystoides intestinalis (PCI) in the gastrointestinal tract is rare. Among the cases already documented in the English language literature, the association of PCI with jejunal diverticulosis has only been mentioned once or twice. We herein report a case of a 63-year-old woman who had both entities concurrently in a segment of the jejunum. What is important to note is the relationship of PCI to the diverticulosis and its possible pathogenesis. Through histological examination and review of related articles, we are convinced that a mechanical theory plays a pivotal role when both diseases occur in the same segment of intestine and are compounded by obstruction or impaired peristalsis. This finding, when properly applied to PCI in other settings, helps to resolve the pathogenesis of PCI and other related gas-filled cysts.

Diverticulum↗

PubMed1992

Internal jugular phlebectasia.

Phlebectasia, defined as abnormal venous dilation, may occur in a number of different sites. Two cases with definite diagnosis of internal jugular phlebectasia were reported. The first case was a 6-year-old girl with a bulging mass on right neck for 3 years. Angiography and CT scan showed definite diagnosis, and the bulging mass was resected from the internal jugular vein (IJV). The second case was a 66-year-old female patient, also complained of a bulging mass on her right neck. Sonogram and CT scan also showed the same diagnosis. Because it did not bother the patient, she was just under close observation. From the three kinds of diagnostic modalities, we found sonography is an effective technique because of its clarity, safety and low cost.

Aged↗

PubMed1992

[Ileal inflammatory fibroid polyp: case report].

The inflammatory fibroid polyp is a rare, polypoid lesion in the gastrointestinal tract. It occurs in the stomach, small intestine, and large intestine in descending order of frequency. This case report shows an ileal inflammatory fibroid polyp that causes ileoileal intussusception. So far, the histogenesis and pathogenesis of these kinds of polyps are still uncertain. Under the microscopic examination, the lesion appears to be made up of spindle-shaped or stellate cells that are morphologically identical to proliferating fibroblasts. Immunostaining results are strongly positive for vimentin and focally positive for S100 protein. However, epithelial membrane antigen, factor VIII R Ag, smooth muscle actin, and lysozyme test are all negative. This favors the view that the inflammatory fibroid polyp is fibroblastic in origin.

Aged↗

PubMed1992

Afferent and efferent connections of the paramedian reticular nucleus in the brain stem of cats.

Anatomical connections of the paramedian reticular nucleus (PRN) of the caudal medulla were investigated using a bi-directional tracer, horseradish peroxidase (HRP). The followings were observed when the tracer was microinjected to PRN: A. Both labelled neurons and terminals were found in the areas of the mesencephalic cardioinhibitory mechanism (CIM), the gigantocellular reticular nucleus (GRN), the ambiguus nucleus (AN) and the contralateral PRN. B. Only labelled terminals were demonstrated in the area of the nucleus of solitary tract (NTS) and the intermedial lateral cell column (IML) of the spinal cord. C. Only retrogradely labelled neurons were observed in the areas of the dorsal and dorsomedial medulla (DM) and ventrolateral medulla (VLM). A few labelled neurons were observed in the periaqueductal gray, the cuneiform nucleus and superior colliculus of the mesencephalon as well as the alamina spinal trigeminal nucleus. When HRP was applied to the CIM, GRN or AN structures, respectively, both labelled cells and terminals were found in the PRN area. HRP injection in the VLM showed only labelled terminals in the PRN. However, injection of HRP to DM showed neither labelling neurons nor terminals in PRN. Results suggest that PRN projects to the pressor area of DM/NTS and IML through which PRN could exert its inhibitory functions on the sympathetic pressor actions. In addition, PRN may suppress the vagal bradycardiac action through its reciprocal connections with CIM, GRN and AN. No lateralization in the PRN pathway was evident.

Afferent Pathways↗

PubMed1992

Correlation of cardiovascular and respiratory responses to glutamate excitation of pressor areas of the medulla in cats.

Cardiorespiratory responses, including changes of systemic arterial pressure (SAP), renal or splanchnic sympathetic nerve activity (SNA) and phrenic nerve activity (PNA), were elicited by microinjection of monosodium glutamate solution (0.5 M, 100 nl) into the dorsal (DM) and rostral ventrolateral medulla (RVLM) in 15 vagotomized cats anesthetized by urethane-chloralose and paralyzed by gallamine triethiodide. Artificial ventilation was adjusted to keep the end-tidal CO2 concentration at 4.0-0.5%. Sixty two pressor and 17 non-pressor sites were stimulated. Most of the stimulations inhibited the PNA. The responses of SNA was variable, showing increases, decreases or no change. Inhibition of SNA during SAP increase was not secondary to baroreceptor activation as the inhibition persisted in carotid sinus/aortic denervated animals. Although various combinations of changes of SNA and PNA were observed, their temporal courses were similar in many instances. Attenuation of SNA and PNA was synchronized, suggesting that these changes are coupled in the stimulating sites. The findings suggest that some neurons in DM and RVLM act as a functional unit to modulate cardiorespiratory functions whereas others simply coexist in the same area independent from each other.

Animals↗

PubMed1991

NMDA antagonists attenuate hypertension induced by carotid clamping in the rostral ventrolateral medulla of rats.

The purpose of these experiments were to study the interactions of N-methyl-D-aspartate (NMDA) with baroreceptor reflexes induced by transient carotid clamping. Adult male Sprague-Dawley rats were anesthetized with urethane. Bilateral common carotid artery occlusion resulted in a reversible and reproducible hypertension in the vagotomized animals. This hypertensive reaction was blocked by intraventricular injection of NMDA antagonists, such as 2-amino-7-phosphono-heptaneoate (AP-7) and phencyclidine (PCP). We also found that blood pressure-sensitive neurons of the rostral ventrolateral medulla (RVLM) could be classified into two groups, on the basis of their responses to norepinephrine given intravenously. Using pressure microejection and single unit recording, we observed that clamping of the common carotids resulted in excitation of type I neurons. This evoked excitation, similar to that induced by NMDA, was blocked by locally applied AP-7. However, the carotid occlusion-induced responses of type II neurons were not blocked by AP-7. In conclusion, the present data suggest that NMDA receptors are involved in hypertensive responses during carotid occlusion, perhaps involving a site in the rostral ventrolateral medulla.

2-Amino-5-phosphonovalerate↗

PubMed1991

Sympathoadrenal excitation and inhibition by lower brainstem stimulation in cats.

Effects of stimulation of brainstem sites on hemodynamics and plasma catecholamine levels were assessed in cats under chloralose-urethane anesthesia. Pressor areas of the dorsal medulla (DM) and ventrolateral medulla (VLM) and the depressor area of the paramedian reticular nucleus (PRN) were stimulated electrically using a monopolar electrode, or chemically using sodium glutamate microinjection. Plasma levels of norepinephrine (NE) and epinephrine (EPI) were measured in caval blood above the adrenal veins. Electrical stimulation of the DM and VLM produced increases in blood pressure and in plasma NE and EPI levels that were enhanced after acute vagotomies. The NE and EPI responses were attenuated after acute, bilateral adrenalectomies, confirming augmented adrenomedullary secretion, whereas the pressor responses were intact. Injection of sodium glutamate into the same pressor regions of the DM or VLM also produced pressor responses and elevated plasma catecholamine levels, indicating that the responses resulted from activation of neuronal perikarya. Stimulation of the PRN attenuated pressor and catecholamine responses during stimulation of the DM and VLM. The results indicate that pressor responses during stimulation of the DM and VLM are due at least partly to activation of perikarya in these regions, are associated with but not dependent on adrenomedullary activation, and are enhanced after vagotomy; and that neurons of the PRN exert inhibitory modulation of the pressor and adrenomedullary responses during stimulation of VLM and DM.

Adrenal Glands↗

PubMed1991

Modulation of epidermal terminal differentiation in patients after long-term topical corticosteroids.

The expression of the various markers for terminal epidermal differentiation in atrophic skin of patients after long-term topical corticosteroids (TCS) was studied by electron microscopy, immunofluorescence using antibody to profilaggrin/filaggrin (PF/FG), immunoperoxidase staining using antibody to involucrin, and oil red O stain for neural lipids of the stratum corneum. Thirty-nine patients were subdivided into two groups: (A) 19 patients suffering from rebound phenomenon after stopping TCS and (B) 20 patients without rebound phenomenon. Biopsy specimens were taken before ending the use of TCS in both groups. In group A, both the morphological markers (including the different epidermal strata, keratohyalin granules, lamellar granules, and cornified cell envelopes) and the molecular markers (including involucrin, PF/FG, and neutral lipids) of terminal epidermal differentiation were significantly suppressed. On the other hand, the differentiational markers in the atrophic skin of patients without rebound phenomena were only slightly altered. These results suggest that potent TCS not only has antiproliferative actions but also inhibits the differentiation of epidermis, resulting in structural defects in the epidermis, especially the stratum corneum.

Administration, Topical↗

PubMed1991

Differential actions of the medial region of caudal medulla on autonomic nerve activities.

1. The inhibitory effects produced by activation of the medial region of caudal medulla on activities of the left and right cardiac sympathetic, vagus and greater splanchnic nerves were studied in chloralose-urethane anaesthetized cats. 2. Electrical stimulation of the medial region produced an 80-92% inhibition of the sympathetic nerve activities, and a 45% and 58% inhibition of the left and right cardiac vagal nerve activities, respectively. There were no significant differences between effects elicited in the left and right autonomic nerves. Similar but smaller inhibitory effects were produced by micro-injection of sodium glutamate (0.5 mol/L) or DL-homocysteic acid (50 mmol/L) to the same medullary sites. 3. These data suggest that neurons residing in the medial medullary region exert strong inhibitory effects on autonomic nerve activities. Since the vasculature is principally innervated by sympathetic nerves, inhibition of sympathetic nerve activities might be the principal factor responsible for the depressor effects caused by activation of the medial region of caudal medulla. The heart is innervated both by sympathetic and parasympathetic nerves. Thus, their simultaneous inhibition during activation of the medial region elicits only a weak and variable inhibition of the heart.

Anesthesia↗

PubMed1991

Responses of neurons in paramedian reticular nucleus to chemical stimulations and alteration of blood pressure in rats.

Previous studies have shown that paramedian reticular nucleus (PRN) possessed sympathetic and parasympathetic inhibitions on autonomic nervous system. In the present study, the cardiovascular reactions of PRN by locally-applied DL-homocysteic acid (DLH), acetylcholine (ACh), monoamines and electrophysiological properties of PRN neurons responding to intravenous injection of ACh and NE were studied in adult Sprague-Dawley rats. In PRN, electrical stimulation caused hypotension and mild bradycardia while microinjection of DLH, which excites only cell body of the neurons but not passing fibers, evoked similar responses. Furthermore, direct application of ACh, norepinephrine (NE) or serotonin (5-HT) in PRN also produced hypotension, suggesting that these putative neurotransmitters may be involved in the cardiovascular responses in PRN. The electrophysiological properties of PRN neurons were studied: Neurons in PRN could be categorized into three types according to their neuronal activities in response to the changes of systemic arterial blood pressure (SAP) by ACh or NE given intravenously. Type I neurons (25/69) were activated in the same direction of SAP changes. Type II neurons (17/69) responded opposite to the direction of SAP changes. Type III neurons (27/69) responded inconsistently to the changes of SAP. All the three types of neurons were excited by locally-applied DLH and possessed a similar unfiltered action potential duration of greater than 0.5 msec.

Acetylcholine↗

PubMed1991

Neurons in the medullary gigantocellular reticular nucleus mediate cardioinhibition in cats.

The cardioinhibitory mechanisms (bradycardia) of the gigantocellular reticular nucleus (GRN) of medulla was studied in chloralose-urethane anesthetized cats by means of microinjection of sodium glutamate (0.5 M, 100 nl) and single neuron recording. Microinjection of glutamate excited the GRN neurons and produced the bradycardiac responses. The rostral GRN (rostral to the caudal superior olivary nucleus) had higher proportion of bradycardiac loci than the caudal GRN. This suggests that the density of cardioinhibitory neurons in GRN is higher in the rostral than the caudal level. Seventy-eight GRN neurons were recorded extracellularly. Activities of 60 neurons were tested if they were correlated with cardiac rhythm or systemic arterial blood pressure (SAP) changes following intravenous norepinephrine or nitroglycerin. Among these neurons 45% (27/60) exhibited changes related to SAP and 25% (15/60) related to cardiac rhythm. Sixty-one GRN neurons were tested by antidromic activation to determine whether they have axonal projection to the dorsal motor nucleus of vagus and nucleus tractus solitarius (DMN/NTS). Eighteen percent (11/61) of them had axonal projections to the DMN/NTS. These findings suggest that: (i) In GRN there are neurons which mediate cardioinhibition. (ii) These neurons may receive baroreceptor inputs. (iii) They may decrease heart rate through the DMN/NTX.

Animals↗

PubMed1991

Huge plexiform neurofibroma of the head and liver--case report.

Neurofibromatosis (NF) is a hereditary autosomal dominant disorder. Von Recklinghausen first described NF in 1882, which is now classified as Neurofibromatosis 1 (NF-1). NF-1 is the most commonly encountered NF which affects 1 in 4000 persons. Clinical manifestations of NF-1 include: generalized cutaneous neurofibroma, pigmented skin patches (cafe-au-lait spots), pigmented iris hamartoma (Lisch nodules), skeletal abnormally, CNS tumors, etc. The subject of this case study is a young adult male with a huge plexiform neurofibroma involving both the liver and head regions. The head tumor measured 10 x 8 x 3.5 cm3 in size, weighted approximately 180g with overlying hyperpigmented skin and an underlying congenital skull defect. A CT scan and MRI of the head and neck revealed a well defined lobulated tumor and deformed external ear. A abdominal sonogram, CT scan and MRI showed a huge plexiform neurofibroma with liver invasion. Lisch nodules and multiple cafe-au-lait spots were also found. Surgical removal of the head tumor along with an external ear reconstruction was performed. Satisfactory cosmetic results and improved hearing were achieved.

Adolescent↗

PubMed1991

Afferent and efferent connections of the mesencephalic cardioinhibitory area (CIM) in the cat.

The afferent and efferent connections between the cardioinhibitory area in the midbrain tegmental field (CIM) and brain stem structures related to cardiovascular integration in cats were investigated by horseradish peroxidase (HRP) for both cell origins and axonal terminations and by chemical (kainic acid) lesion for topographic pathways. Retrogradely labeled neurons were observed in the gigantocellular reticular nucleus (GRN), the pontine reticular nucleus of the pons (PON), the ambiguus nucleus (AN) and the paramedian reticular nucleus (PRN). A few neurons were also labeled in the following structures i.e., ventrolateral medulla (VLM), dorsomedial medulla (DMM), dorsomotor nucleus of the vagus nerve (DMV) and nucleus of solitary tract (NTS). Anterograde HRP labeled terminals were found surrounding the cell bodies of the aforementioned structures. They were most abundant in VLM, DMM, DMV, NTS, moderate in GRN, PRN and AN, but only scanty in hypothalamus. The fiber pathway of CIM neurons was also traced by degenerating fibers consequent to kainic acid lesion and by means of silver stain. Degenerating fiber bundle was found primarily projecting through the medial portion of the mesencephalic pontine structures. As the bundle reached the medulla oblongata, it bifurcated into a dorsal and a ventral tracts on its course. The dorsal tract was primarily coursing through the dorsomedial area, including DMM, NTS and DMV, and the ventral tract was mainly passing VLM, AN and inferior olivary nucleus (ION) areas. The present findings suggest that neurons in the CIM may receive inputs from various cardiovascular-related structures and make output bilaterally to some of pontine and medullary structures to modulate cardiovascular functions. Based on the anatomical findings, the profound bradycardia produced by CIM stimulation may be mediated through the following mechanisms: A. Direct activation of vagal preganglionic neurons in DMV, AN and ION. B. Indirect activation of neurons in GRN for vagal activation and of neurons in PRN for sympathetic inhibition.

Afferent Pathways↗