Biomedical subjects

J M Shen

Publications and source records attributed to J M Shen.

At least 19 recordsLinked to original sources

PubMed1995

Respiratory studies in SUNCT syndrome.

Seven SUNCT patients (six men, one woman) took part in this study. In four patients, respiratory variables were compared during and outside attacks. In five patients, peripheral chemosensitivity was tested and compared with a control group matched with respect to age, sex, and smoking habits. The results indicate that SUNCT patients hyperventilate during attacks. Moreover, they appear to hyperventilate slightly under basal conditions. The tests for peripheral chemoreceptor activity indicated no differences between the SUNCT and the control groups except for one variable, namely the mean ventilatory response to a single breath of 13% CO2. It is possible that this indicates a blunted response of the peripheral chemoreceptors. On the other hand, it may also represent a chance finding, since none of the other results presented suggested such a conclusion, and the size of the test group was very small. The results do not indicate that a reduction in oxygen saturation can trigger SUNCT since low levels of oxygen saturation were only rarely accompanied by SUNCT, whereas many attacks were not associated with any appreciable lowering in arterial oxygen saturation.

Aged↗

PubMed1994

SUNCT syndrome: estimation of cerebral blood flow velocity with transcranial Doppler ultrasonography.

Four patients with SUNCT syndrome (Short-lasting, Unilateral, Neuralgiform headache attacks with Conjunctival injection and Tearing) were investigated with Doppler ultrasonography. Blood flow velocity (V) was measured in all intracranial arteries during both normocapnia and voluntary hyperventilation in 4 patients outside attacks (2 during remission; 2 during bout, but outside attacks) and in 8 healthy individuals. Vasomotor reactivity (VMR) was calculated on the basis of the formula of percentage change in V divided by the reduction in end-tidal PCO2 (PETCO2). Under the basal condition, the patients had a slightly, but non-significantly higher V in the middle cerebral artery (MCA) (P > 0.1) and lower V in the basilar artery (P > 0.05) than controls. During hyperventilation, a significant reduction in V was observed in the anterior and posterior cerebral arteries, at a level 1.5-2 SD above that in controls (P < 0.05), but a non-significant difference in VMR in comparison with controls. VMCA was continuously insonated during spontaneous (n = 8) and precipitated (n = 4) attacks in one particular patient on different days. Prior to attack, VMCA was significantly lower on the symptomatic side than on the non-symptomatic side (P < 0.014). VMCA decreased significantly during spontaneous attacks on both sides (P < 0.01) in comparison with the pre-attack stage, and returned to baseline before the cessation of attack. Similar findings were made during precipitated attacks. PETCO2, was rather constant throughout the entire attack study. Our data suggest that abnormal cerebral circulation may be part of the SUNCT syndrome. The vascular changes may have underlying mechanisms differing from those of the pain.

Acute Disease↗

PubMed1994

Cluster headache: pulse rate changes evoked by hyperoxia and hypoxia.

To test the influence of arterial O2 saturation (SaO2) on heart rate in cluster headache, changes in pulse rate induced by hyperoxia and hypoxia were monitored in 11 cluster headache patients (6 during cluster period, and 5 during remission). The results were compared with those obtained in 11 age and sex matched healthy individuals. The subjects were administered 5 min each of 100% O2 and 12% O2 in nitrogen in sequence. The aim of the latter procedure was to reduce SaO2 to approximately 80%. Pulse rate was recorded every minute from a finger pulse oximeter during the whole procedure. Cluster headache patients, in particular during the bout, had a slightly lower basal pulse rate than controls (P > 0.5, Student's t-test). This tendency was maintained throughout the test. Hyperoxia and hypoxia resulted in a marked, significant decrease and increase, respectively, in pulse rate from baseline values within each group. However, the difference between groups was not significant at any stage. Cluster headache patients therefore seem to have the same heart rate response to changes in SaO2 as healthy individuals. The marked heart rate changes which sometimes accompany cluster headache are unlikely to be caused by SaO2 changes.

Adult↗

PubMed1994

Cluster headache: the peripheral chemosensitivity as indicated by the single-breath CO2 test.

A single-breath CO2 test was carried out in cluster headache patients both during bout and remission, and in matched healthy individuals (n = 10 for each group) to assess peripheral chemosensitivity. The test subjects inhaled one tidal breath of 13% CO2 in air. The response was expressed as the maximal increase in inspiratory minute ventilation (Vi) within 20 seconds from the exposure to CO2, divided by the increase in end-tidal PCO2 (PETCO2) (the difference in PCO2 between the test breath and the preceding control breaths): delta Vi/delta PETCO2. Under the initial resting condition, cluster headache patients within the bout showed a slight hyperventilation in that there was a significantly reduced PETCO2 (P < 0.05, Student's paired t-test), and during remission, higher Vi, and a lower PETCO2 (P < 0.05, Wilcoxon signed rank test), in comparison with the controls. There was no statistically significant difference as regards the peripheral chemosensitivity between cluster headache and control groups. These results indicate that cluster headache patients have an intact and properly-functioning carotid body.

Administration, Inhalation↗

PubMed1993

Increased release of immunoreactive CCK-8 by electroacupuncture and enhancement of electroacupuncture analgesia by CCK-B antagonist in rat spinal cord.

Cholecystokinin octapeptide (CCK-8) in CNS has been shown to function as a neuropeptide with potent anti-opioid activity. It hinders opioid analgesia and facilitates opioid tolerance. The present study showed that electroacupuncture (EA) stimulation produced a marked increase of the CCK-8 immunoreactivity (ir) in the perfusate of the rat spinal cord. The increase of CCK-8-ir was most marked in response to EA of 100 Hz and 15 Hz, and less marked in response to EA of 2 Hz. Since CCK-8 has been shown to possess potent anti-opioid activity at the spinal level, blockade of the spinal CCK effect would be expected to potentiate EA-induced analgesia which is known to be opioid-mediated. Intrathecal (i.t.) administration of CCK-B antagonist L-365,260 per se did not affect tail flick latency (TFL) to any significant extent, yet it potentiated EA induced analgesia in a dose- and frequency-dependent manner. The potentiation was most marked at a dose range of 2.5-5.0 ng (i.t.) and at a frequency rank order of 100 Hz > 15 Hz > 2 Hz. The results suggest that an increased release of CCK-8 following EA may limit the effect of opioid peptides, and that the CCK-B receptor mediates the anti-opioid effect of CCK-8 in rat spinal cord.

Acupuncture Analgesia↗

PubMed1993

SUNCT syndrome: forehead sweating pattern.

The forehead sweating function has been assessed in SUNCT syndrome--a short-lasting, unilateral, neuralgiform headache syndrome with autonomic phenomena on the symptomatic side (conjunctival injection, lacrimation, etc.). In the three patients (of a total of six) who could be studied during paroxysms, increased evaporation was present on the symptomatic side of the forehead compared to the non-symptomatic side during attacks or to the symptomatic side between attacks. Basal sweating was generally within control limits, so long as the attack frequency was not so high as to influence the interictal level. During attacks precipitated by eating chocolate or sour apple (in the case of one of the patients), forehead sweating was also increased on the symptomatic side. The forehead sweating responses to heating and pilocarpine were without any notable or systematic asymmetries. The forehead sweating pattern in SUNCT syndrome may differ from the patterns in unilateral headaches like cluster headache, on the one hand (in which there is generally an asymmetry during heating and pilocarpine tests), and chronic paroxysmal hemicrania (CPH) and cervicogenic headache, on the other (where there is no systematic increase during attacks.

Aged↗

PubMed1993

Cluster headache in identical twins.

Twin brothers with cluster headache are described. Monozygosity was demonstrated by conventional genetic markers and DNA-typing. Both had "mini-bouts" in the early stages. In the one, attacks were always excruciatingly severe; in the other, they started out as "mild", eventually becoming more severe. Both brothers also suffered from paroxysmal tachycardia. The connection between attacks of tachycardia and cluster headache remains enigmatic. The observation of cluster headache in monozygotic twins underscores the importance of genetic factors in the etiology. The ratio between cluster headache prevalence in close family members vs. prevalence in the general population may be higher in cluster headache than in migraine.

Cluster Headache↗

PubMed1993

Cluster headache: the ventilatory response to transient hypoxia with pure nitrogen.

To determine whether the carotid body plays a pathogenetic role in cluster headache, 20 cluster headache patients have been studied. Of these, 11 patients were in the interparoxysmal cluster phase, and 9 were in remission. Comparison was made with healthy subjects matched for sex, age, and smoking habits. Transient hypoxia was induced by inhalation of 1-8 breaths of 100% nitrogen (N2), until the arterial oxygen saturation (SaO2) decreased to around 80%. Changes in ventilation (tidal volume, inspiratory minute ventilation (VI), and end-tidal PCO2 (PETCO2)), were analyzed breath-by-breath. Under basal conditions, cluster headache patients had a slightly higher SaO2 and VI when compared to controls. PETCO2 was significantly lower (P < 0.05) during the cluster period as measured by Wilcoxon signed rank test for paired data, and during remission, according to the Student's paired t-test, in comparison with controls. After exposure to N2, no significant difference was found in the rate of reduction of SaO2 between any of the groups. A higher absolute increase in VI, but a relative (%) decrease in VI at moderate hypoxia were measured, the differences between patients and controls being on the border of the level of significance. Chemoreceptor sensitivity of the carotid body, expressed as the slope of a regression curve obtained by plotting the increase in VI against the reduction in SaO2, showed no statistical difference between the groups. The results do not support the hypothesis of a pathogenetic role for the carotid body in cluster headache.

Administration, Inhalation↗

PubMed1993

Cluster headache: transcranial Doppler assessment of dynamic cerebral circulatory changes during hypocapnia and attack.

Transcranial Doppler ultrasound (TCD) investigations have been carried out in cluster headache patients (8 during remission and 6 during bout) and 14 healthy subjects, to assess cerebral vasomotor reactivity (VMR) to hypocapnia induced by voluntary hyperventilation. VMR was expressed as the relative change in blood flow velocity (V) (%) as a function of the reduction in end-tidal PCO2 (PETCO2) (kPa), i.e. V/P ETCO2. TCD with simultaneous PETCO2 monitoring, was also performed in 5 patients during spontaneous attacks. Prior to hyperventilation, there was bilaterally lower anterior cerebral artery velocity (VACA) during the bout than during remission (P < 0.05 on the symptomatic side), and also lower than in the controls. During remission, VACA was higher on the symptomatic side than on the other side (P < 0.05). ACA also showed a lower VMR during the bout than during remission, and it was also lower than in controls (bout vs. remission on the non-symptomatic side, P < 0.01; on the symptomatic side, P > 0.1). Approximately 30 minutes after the onset of attack, PETCO2 started to decrease gradually from 4.65 to 4.10 kPa in one patient with severe attack. The VACA decreased markedly and bilaterally already at an early stage of the attack, i.e. prior to the hyperventilation. Middle cerebral artery velocity tended to decrease 30 minutes after the onset of attack on the symptomatic side, and 50 minutes after onset on the non-symptomatic side. It is concluded that the vascular changes observed most likely are secondary phenomena during the cluster headache attack.

Adult↗

PubMed1993

Transcranial Doppler sonography in chronic paroxysmal hemicrania.

Three patients with chronic paroxysmal hemicrania (CPH) (1 M, 2 F) and 9 healthy controls (8 M 1 F) were studied with transcranial Doppler (TCD) sonography. One patient who was studied during the spontaneous attacks hyperventilated markedly. Middle cerebral artery velocity (VMCA) was measured in the first attack, and anterior cerebral artery velocity (VACA) in the second attack, respectively. VMCA and VACA decreased bilaterally during attack. VMCA started to decrease at an early stage of the attack, i.e. prior to the major hyperventilation that was observed during the attack. VACA on the symptomatic side decreased less than that on the other side (P < 0.05). Cerebral vasomotor reactivity (VMR) was expressed as the percentage change in mean blood flow velocity as a function of end-tidal PCO2 (PETCO2) reduction induced by voluntary hyperventilation (delta V/delta PETCO2). In the 3 patients, a slightly lowered VMR was observed in the MCA and posterior cerebral artery on both sides, and in the ACA on the symptomatic side (P > 0.05) in comparison with controls. These observations may imply an abnormal vascular reactivity in CPH.

Adult↗

PubMed1992

Short-lasting, unilateral, neuralgiform headache attacks with conjunctival injection and tearing (SUNCT syndrome): IV. Respiratory sinus arrhythmia during and outside paroxysms.

SUNCT is a headache syndrome characterized by short-lasting (usually 15-120 sec), unilateral head pain paroxysms localized in the peri-ocular area, accompanied by conjunctival injection, lacrimation, nasal stuffiness, rhinorrhea, and subclinical forehead sweating, all on the symptomatic side. A relative bradycardia seems to be an integral part of the paroxysm; a parasympathetic stimulation could theoretically be the causative factor for the bradycardia. In 3 SUNCT patients, vagal nerve function (E:I ratio) has been monitored outside and during pain paroxysms, while 3 other patients could be studied in the attack-free period only. E:I ratio is obtainable in the course of a maximally deep breath and represents the ratio of the longest R-R interval during a 5 sec long expiration to the shortest R-R interval during a 5 sec long expiration. The mean E:I ratio of SUNCT patients outside paroxysms was significantly higher than the mean E:I ratio in an aged-matched control group. The E:I ratio was, however, significantly decreased during paroxysms in comparison with ratios obtained outside the pain paroxysms. After 0.6 mg atropine administration s.c. to one of the patients in the symptomatic phase, the heart rate increased, and the relative bradycardia during headache paroxysm was diminished (but not completely abolished). The E:I ratio was lowered but it was still slightly larger outside than during attacks. The reason for the abrupt and seemingly clear attack-related decrement in E:I ratio together with the previously described relative bradycardia remains enigmatic, however the possibility of increased parasympathetic tone cannot be excluded.

Aged↗

PubMed1991

Shortlasting, unilateral, neuralgiform headache attacks with conjunctival injection, tearing, and subclinical forehead sweating ("Sunct" syndrome): II. Changes in heart rate and arterial blood pressure during pain paroxysms.

The recently described "Sunct" syndrome is a rare picture of unilateral, shortlasting headache attacks accompanied by autonomic phenomena (conjunctival injection, tearing, etc.) on the symptomatic side. Heart rate and blood pressure were monitored in two elderly "Sunct" patients during and outside headache attacks. An ultrasound Doppler servo method was used for the non-invasive, continuous, beat-to-beat determination of instantaneous arterial blood pressure. In a third patient, systolic and diastolic blood pressure, both outside and during pain paroxysms, were assessed using the standard Korotkoff method. Heart rate was found to be significantly decreased during pain paroxysms. Systolic blood pressure was observed to be significantly increased during attacks, when compared with the inter-attack period, while a less consistent pattern was observed for diastolic blood pressure. Some of the changes in the cardiovascular system seemed to start prior to pain onset. Therefore, it seems unlikely that these changes were caused by pain activation of the sympathetic nervous system or the oculocardiac reflex.

Aged↗

PubMed1991

Cluster headache. Our current concepts.

Cluster headache and chronic paroxysmal hemicrania are assumed to be so closely related that they from a classification point of view have been grouped together under the superstructure: cluster headache syndrome. If this grouping will prove to stand the test of time, the pathogenesis of the two subgroups ought to be quite similar. CPH per se has two subgroups: those with and those without mechanical precipitation of attacks. If the aforementioned grouping of CPH is correct, then the CPH subdivision with mechanical precipitation of attacks should also be closely akin to cluster headache. Cluster headache, however, seems to lack the "nuchal" factor. It is felt that "midline structures", like the cavernous sinus, are of importance in cluster headache (cluster headache syndrome?) pathogenesis. In CPH with mechanical precipitation, attacks may be precipitated via "cervical volleys" a.m. Kerr, activating "midline" cavernous sinus structures, while the activation mechanisms in cluster headache is unknown.

Cavernous Sinus↗

PubMed1989

The development of bicuculline-induced epileptiform discharges in embryonic turtle cortex.

The appearance of bicuculline-induced epileptiform discharges was studied in embryonic turtle cortex using extracellular recording techniques. Drug-induced discharges occurred at an early stage of cortical plate formation, suggesting that mechanisms for synchronizing neuronal discharges are functional at this stage. Discharges originated in the medial cortex and increased in amplitude and decreased in frequency with development. gamma-Aminobutyric acid (GABA)-containing neurons and functional GABA receptors are present in advance of excitatory synchronizing mechanisms and may have a non-synaptic role in corticogenesis.

Animals↗

PubMed1988

Development of GABA responsiveness in embryonic turtle cortical neurons.

The whole-cell patch-clamp method was used to study the development of functional GABA receptors in cortical neurons dissociated from embryonic turtles. GABA elicited an increase in membrane conductance, even from cells obtained from the earliest stages of corticogenesis. The GABA-mediated conductance had a mean value 7.4 times greater than membrane 'leak' conductance and increased with developmental age. In all stages studied, the response inverted polarity at a value approximating ECl- and was blocked by applications of bicuculline, suggesting that it was mediated by GABAA receptors. GABA receptors are thus present and functional very early in corticogenesis, preceding electrogenesis, synaptogenesis, and full neuronal differentiation.

Animals↗

PubMed1987

Evidence for the inhibitory neurotransmitter gamma-aminobutyric acid in aspiny and sparsely spiny nonpyramidal neurons of the turtle dorsal cortex.

In order to learn more about the anatomical substrate for gamma-aminobutyric acid (GABA)-mediated inhibition in cortical structures, the intrinsic neuronal organization of turtle dorsal cortex was studied by using Golgi impregnation, immunohistochemical localization of GABA and its synthetic enzyme glutamic acid decarboxylase (GAD), and histochemical localization of the presynaptic GABA-degrading enzyme GABA-transaminase (GABA-T). GABAergic markers are found in neurons identical in morphology and distribution to Golgi-impregnated aspiny and sparsely spiny nonpyramidal neurons with locally arborizing axons and appear to label most if not all of the nonpyramidal neurons. In addition, the GABAergic markers are found in punctate structures in a distribution characteristic of presumed inhibitory terminals. The spine-laden pyramidal neurons, the principal projecting cell type in the dorsal cortex, are devoid of labelling for GABAergic markers but are surrounded by presumed GABAergic terminals. The data complement previous physiological and ultrastructural studies that implicate aspiny and sparsely spiny nonpyramidal neurons as mediators of intrinsic inhibition of pyramidal neurons in turtle cortex. The results also suggest similarities in the functional organization of intrinsic inhibitory elements in turtle and mammalian cortex.

4-Aminobutyrate Transaminase↗

PubMed1986

Monoclonal antibodies to the turtle cortex reveal neuronal subsets, antigenic cross-reactivity with the mammalian neocortex, and forebrain structures sharing a pallial derivation.

The dorsal cortex of the pond turtle (Pseudemys scripta) is a relatively simple structure consisting of two principal classes of neurons that occupy three distinct layers. Morphological, pharmacological, and physiological data suggest many similarities to the mammalian neocortex, rendering it an interesting preparation for comparative studies. We prepared monoclonal antibodies to the turtle dorsal cortex by immunizing mice with cortical tissue from adult turtles. Twelve antibodies were generated that recognize specific components of the turtle cortex. Among these, eight antibodies label only neurons and four label only ependymal glial cells. Differences in tissue staining pattern and immunoglobulin class suggest a heterogeneity of antigenic specificity among the antibodies. The staining patterns of three of our antibodies are described. TC3, like all other neuron-marking antibodies generated, labels a subset of both pyramidal and stellate cell types. It also cross-reacts with a subset of mammalian cortical neurons and labels them with a pattern similar to that observed in the turtle cortex. TC5 stains ependymal cells and their glial processes in the turtle cortex, and cross-reacts with fibrous astrocytelike processes in mammalian neocortical white matter. TC9 appears to recognize antigens of neurons sharing a pallial derivation in turtle.

Animals↗

PubMed1986

Turtle hippocampal cortex contains distinct cell types, burst-firing neurons, and an epileptogenic subfield.

The dorsal and medial telencephalon of reptiles consists of a simple trilaminar cortex. The turtle dorsal cortex has been identified as a favorable physiological preparation that may bear a phylogenetic relationship to mammalian neocortex. While anatomical studies have likened the reptilian medial cortical region to mammalian hippocampus, its physiological properties have not been explored. We therefore used intracellular and extracellular recording techniques to examine the cellular and synaptic physiology of turtle "hippocampal" or medial cortex. Turtle medial cortex contains two principal classes of neurons, pyramidal cells and stellate neurons. Recordings with Lucifer yellow CH (LY)-filled microelectrodes allowed us to correlate the physiological properties of medial cortical neurons with their cellular morphology. Pyramidal neurons were situated in a single cellular layer and had spiny apical dendrites extending into the molecular layer. These cells fired relatively long-duration action potentials (APs) and showed frequency adaptation to suprathreshold current pulse injections. Stellate cells were usually found in the subcellular and molecular layers and had aspiny dendrites. In contrast to pyramidal cells, they fired brief APs and displayed no frequency adaptation. A discrete population of cells in the dorsal portion of medial cortex (DMC) was capable of bursting endogenously or in response to synaptic activation. Bursts usually contained an underlying slow depolarization and often occurred at regular intervals. Intracellular LY injections confirmed that these cells were pyramidal in morphology. Electrical stimulation of afferent fibers revealed that pyramidal cells and stellate neurons differed in their synaptic responses. In ventral medial cortex (VMC), afferent stimulation evoked a multiphasic response in most pyramidal cells, whereas stellate cells were synaptically excited. Orthodromic activation of DMC bursting cells resulted in a powerful excitation--often a short burst--and subsequent inhibition. Stellate neurons in DMC also had a biphasic synaptic response consisting of both an early excitation and a late inhibition. Experiments using intracellular chloride (Cl-) injection or focal bicuculline application suggested that part of the inhibitory component of the pyramidal cell synaptic response was dependent on a gamma-aminobutyric acid (GABA)-mediated increase in Cl- conductance. These results correlated with our immunohistochemical studies that revealed the presence of GABAergic neurons in medial cortex.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗