SI Response Research Articles

Contribution of somatosensory cortex to responses in the rat cerebellar granule cell layer following peripheral tactile stimulation.

The spatial coincidence of somatosensory cerebral cortex (SI) and trigeminal projections to the cerebellar hemisphere has been previously demonstrated. In this paper we describe the temporal relationship between tactilely-evoked responses in SI and in the granule cell layer of the cerebellar hemisphere, in anesthetized rats. We simultaneously recorded field potentials in areas of common receptive fields of SI and of the cerebellar folium crus IIa after peripheral tactile stimulation of the corresponding facial area. Response of the cerebellar granule cell layer to a brief tactile stimulation consisted of two components at different latencies. We found a strong correlation between the latency of the SI response and that of the second (long-latency) cerebellar component following facial stimulation. No such relationship was found between the latency of the SI response and that of the first (short-latency) cerebellar component, originating from a direct trigeminocerebellar pathway. In addition, lidocaine pressure injection in SI, cortical ablation, and decerebration all significantly affected the second cerebellar peak but not the first. Further, when tactile stimuli were presented 75 ms apart, the response in SI failed, as did the second cerebellar peak, while the short-latency cerebellar response still occurred. We found a wide spatial distribution of the upper lip response beyond the upper lip area in crus IIa for the long-latency component of the cerebellar response. Our results demonstrate that SI is the primary contributor to the cerebellar long-latency response to peripheral tactile stimulation. These results are discussed in the context of Purkinje cell responses to tactile input.

Resuscitation of the critically III in the ED: Responses of blood pressure, heart rate, shock index, central venous oxygen saturation, and lactate

To describe the simultaneous responses of systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial blood pressure (MAP), heart rate (HR), shock index ( SI = HR SBP ), central venous oxyhemoglobin saturation (ScvO 2), and arterial blood lactate concentration (Lact) to resuscitation of critically ill patients in the emergency department (ED), an observational descriptive study was conducted in the ED of an urban teaching hospital. Thirty-six patients admitted from the ED to the medical intensive care unit were studied. Vital signs were measured immediately on arrival to the ED (phase 1). After initial resuscitation and stabilization, ie, HR between 50 and 120 beats/min and MAP between 70 and 110 mm Hg (phase 2), ScvO 2 and Lact were measured and additional therapy was given in the ED to increase ScvO 2 to >65% and decrease Lact to <2 mmol/L, if needed (phase 3). SBP, DBP, MAP, HR, SI, ScvO 2, and Lact were measured. Initial resuscitation increased SBP from 103 ± 39 to 118 ± 29 mm Hg ( P < .05) and MAP from 67 ± 35 to 82 ± 22 mm Hg ( P < .05) but did not affect DBP (53 ± 35 to 63 ± 22 mm Hg, P = NS), HR (110 ± 26 to 110 ± 22 beats/min, P = NS) or SI (from 1.3 ± 0.7 to 1.0 ± 0.3, P = NS) from phase 1 to phase 2. ScvO 2 remained <65% and/or Lact >2.0 mmol/L in 31 of 36 patients at phase 2, and additional therapy was required. Lact was decreased (from 4.6 ± 3.8 to 2.6 ± 2.5 mmol/L, P < .05) and ScvO 2 was increased (from 52 ± 18 to 65 ± 13%, P < .05) without significant additional changes in SBP, DBP, MAP, HR, or SI at phase 3. The in-hospital mortality was 14% for this group of patients. It was concluded that additional therapy is required in the majority of critically ill patients to restore adequate systemic oxygenation after initial resuscitation and hemodynamic stabilization in the ED. Additional therapy to increase ScvO 2 and decrease Lact may not produce substantial responses in SBP, DBP, MAP, HR, and SI. The measurement of ScvO 2 and Lact can be utilized to guide this phase of additional therapy in the ED.

PERICLINAL CHIMERAS COMPOSED OF LYCOPERSICON PERUVIANUM AND L. ESCULENTUM DEMONSTRATE THAT S-LOCUS ASSOCIATED PROTEINS AND SELF-INCOMPATIBILITY CAN BE UNCOUPLED

Lycopersicon peruvianum is a wild species of tomato that exhibits gametophytic self-incompatibility (S), wherein the SI response is controlled by the genotype of the pollen. Cultivated tomato (L. esculentum) is a self-compatible species. Assisted by phenotypic markers, periclinal graft chimeras between these two species have been obtained. Fruit set analysis following breeding demonstrated that the available five chimeras (PPE, PEE, PEP, EPP, and EEP) are able to accept pollen from L. peruvianum, suggesting that there is a failure of the SI response. SI response is known to be dependent on S-locus associated proteins. These proteins are present in the style, which is mainly derived from the L1 and L2 layers of meristem. RNA analysis of the style tissue using a cloned S-locus cDNA as a probe showed that, except for EEP, all chimeras expressed the S-allele. This was also confirmed by SDS-PAGE analysis of stylar proteins that were present in variable amounts depending on the periclinal combination. Thus, the breakdown of SI is not associated with the lack of expression of the S-locus. Further work is being conducted to understand the nature of this breakdown.

Parallel processing of tactile information in cat cerebral cortex: effect of reversible inactivation of SII on SI responses

1. Responsiveness of neurons in the distal forelimb region of primary somatosensory cortex (SI) was examined in cat in association with the cooling-induced, reversible inactivation of the corresponding region of the second somatosensory area (SII). The aim was to test whether a component of the stimulus-generated tactile input to SI came via an indirect, intracortical path from the thalamus through SII, or whether, when SI responsiveness fell in association with SII inactivation, the effect could be explained by a disfacilitation of the SI neuron; that is, a removal of a tonic facilitatory influence on the SI neuron that arises from within SII. 2. The responses of 33 SI neurons to controlled tactile stimuli, usually 1-s long trains of vibration or rectangular pulses delivered to the skin of the distal forelimb, were examined quantitatively before, during, and after the rapid, reversible inactivation of the SII area. 3. Nineteen of the 33 neurons (approximately 60%) were unaffected in their response level by SII inactivation. These included neurons of several functional classes whose input came from different classes of tactile afferent fibers, including the Pacinian corpuscle (PC) associated fibers, other rapidly adapting (RA) afferents from glabrous skin, and presumed hair follicle afferent (HFA) fibers. The remaining 14 neurons (approximately 40%), which also included different functional classes, displayed a reduction in response level with SII inactivation. Because this was not accompanied by significant prolongation of the SI spike waveforms, it is not attributable to direct spread of cooling from SII to SI. Construction of stimulus-response relations demonstrated that any effect of SII inactivation on individual SI neurons was consistent over the whole response range. 4. The fall in responsiveness for some SI neurons in association with SII inactivation may be attributable to disfacilitation, that is, a loss of tonic facilitation arising in SII, rather than to a block of peripherally generated inputs that traverse an indirect path from the skin to SI, via SII. There are three reasons for suggesting this. First, in the course of SII cooling, the latency and time course of SI evoked potentials were not delayed in a way that might be expected if part of the SI response had come via SII. Second, the SII inactivation could reduce the SI spontaneous activity (as well as the stimulus-related responsiveness). The facilitation from SII is therefore not necessarily dependent on overt tactile stimulation, and its source may therefore be endogenous to SII.(ABSTRACT TRUNCATED AT 400 WORDS)

How Does Posture Influence the Haemodynamic Assessment of a Cardiovascular Drug? Experience with Nicardipine

The extent to which posture altered the haemodynamic response to slow calcium channel blocker nicardipine was evaluated in 22 male patients with angiographically confirmed coronary artery disease. Patients were randomly allocated to supine or upright posture and an otherwise identical protocol performed in each group. At rest, following a control saline period, four doses of the drug (log cumulative dosage: 1.25, 2.5, 5.0, and 10.0 mg) were administered by i.v. infusion over a total period of 40 min; haemodynamic indices were recorded during the 3-5 min following each 5 min infusion. The exercise effects of the drug, in each posture, were determined by comparison of a control predrug exercise with observations at the same workload following the maximal cumulative dose. Nicardipine reduced resting mean blood pressure (MBP) and systemic vascular resistance index (SVRI) in both postures, the decrease being more pronounced when upright (MBP, -12%, -18%; p less than 0.01: SVRI, -30%, -46%; p less than 0.01). The increases in cardiac index (CI) and stroke volume index (SVI) were higher when upright (29 and 54% vs. 10 and 27%; p less than 0.01). Pulmonary artery occluded pressure (PAOP) increased by 29% when upright, without change when supine. On exercise, the effects for HR, MBP, CI, SI, and SVRI responses were independent of posture; however, a qualitative difference was apparent for PAOP (-17% vs. +14%; p less than 0.05). Thus, although the actions of nicardipine were qualitatively similar, quantitative differences related to posture were confirmed. These differences appeared to relate to posture-related baseline haemodynamic differences between the groups but with similar postnicardipine absolute values.

Breakdown of self-incompatibility during pistil development in Lycopersicon peruvianum by modified bud pollination

Stylar self-incompatibility barriers in L. peruvianum can be avoided if pollen germination and growth through immature pistils is promoted under specific environmental conditions approximately 2–3 days before the initiation of anthesis. Since immature stigmas lack sufficient exudate for pollen germination, the sandwiching of a thin layer of pollen germination medium between the stigma and a mineral oil layer containing pollen allows precocious pollen germination and some compatible pollen tube growth through the style. This procedure is rapid, inexpensive, applicable in the field, and makes efficient use of pollen. Consistent though low seed yields have been obtained. A high proportion of aborted seed, seedling lethals, and aberrant seedling phenotypes in selfed progeny indicate the presence of strong post-zygotic barriers to such selfing. No evidence for a reduction in the strength of the SI response with increasing pistil age was observed.

Mapping human somatosensory cortex with positron emission tomography.

Positron emission tomography measurements of regional cerebral blood flow were used to detect focal neuronal activation in the first somatosensory cortex (SI) of humans induced by cutaneous vibratory stimulation. Intravenously administered water labeled with oxygen-15 (H2(15)O) was used as a blood flow tracer to obtain five stimulated-state and two resting-state blood flow images in each of eight normal volunteers. Three cutaneous surfaces were tested: lips, fingers, and toes. Intense, highly focal SI responses were seen during all 39 stimulated-state trials. The SI responses from the three stimulation sites were anatomically distinct and formed a medial-to-lateral homonculus in every subject. Response magnitudes (increase in local blood flow) and response locales (expressed as proportionately measured bicommissural stereotaxic coordinates) were highly consistent among subjects and on repeated trials for each subject. These findings suggest that eliciting cerebral blood flow responses by cutaneous vibration provides a safe, rapid, and reproducible tool for locating and assessing the functional status of somatosensory cortex, and offers potential clinical and research utility. This study has established normative values for future applications of this experimental paradigm.

An investigation of the possible interaction mechanisms for Si(Li) and Ge detector response functions by Monte Carlo simulation

Simple physical mechanisms implemented by either analog Monte Carlo simulations or analytical models have been used to investigate the Si(Li) and Ge detector response functions for X- and gamma rays, respectively. The mechanisms investigated include the various possible combinations of partial losses of photoelectric and Auger electrons from the detector surfaces and complete losses of the various photons involved such as the Si K X-ray, the 0.511 MeV annihilation photons, and single or multiple Compton scattered photons. The most probable interaction mechanisms for each detector response function feature are identified and the simple analytical functions that have been used in the past are justified.

Induction of functional retinal projections to the somatosensory system.

Optic axons can be induced to form permanent, retinotopic connections in the auditory (medial geniculate, MG) and somatosensory (ventrobasal, VB) nuclei of the Syrian hamster thalamus; this occurs when the principal targets of retinofugal axons are ablated in newborn hamsters and alternative terminal space is created by partial deafferentation of MG or VB. The experimentally induced retinal projection to the somatosensory nucleus occurs by the stabilization of an early, normally transient projection. The present study was undertaken to determine whether the anomalous, stabilized retino-VB projection is functional. Newborn hamsters were operated on to produce permanent retino-VB projections and when the animals were mature, neurophysiological recordings were made in the cortical targets of VB, the first and second somatosensory cortices (SI and SII, respectively). Visual stimulation within well-defined receptive fields reliably evoked multi-unit responses in SI and SII of operated, but not normal hamsters. The representations of the visual field in SI and SII showed a partially retinotopic organization. These results demonstrate that optic tract axons can form functional synapses in the thalamic somatosensory nucleus, and suggest that neural structures which normally process information specific to one sensory modality have the potential to mediate function for other modalities.

Neuromagnetic determinations of evoked responses in human SI and SII associated with mechanical stimulation of the index finger

Neuromagnetic determinations of evoked responses in human SI and SII associated with mechanical stimulation of the index finger

Shear punch and ball microhardness measurements of 14 MeV neutron irradiation hardening in five metals

The irradiation hardening response of five metals irradiated in RTNS-II was investigated using a combination of ball microhardness and shear punch test techniques. The specimens were transmission electron microscopy disks of pure nickel, Ni-5wt%Si, pure iron, solution annealed prime candidate alloy (PCA) for Path A, and 40% cold worked MFE 316 stainless steel. Specimens were irradiated in RTNS-II to fluences in the range 6 × 10 16 to 6 × 10 17 n/cm 2 . Only limited ball microhardness data could be obtained because of disk thickness. However, the ball microhardness data obtained were in good agreement with shear punch data. It was found that the pure metals exhibited little hardening after exposure to fluences of ~1 × 10 17 n/cm 2 , but Ni-5 Si exhibited significant hardening after 6 × 10 17 n/cm 2 . Hardening in PCA was similar to that observed in solution annealed 316 stainless steel; and hardening in 40% cold worked MFE 316 was relatively small after 6 × 10 17 n/cm 2 . The Ni-5 Si response may be due to irradiation induced precipitation.

Analysis of porous silicon

Porous silicon, suitable after oxidation for dielectric isolation, has been produced successfully by anodizing silicon in strong HF. The oxidized layer has been shown to have promise in device manufacture, providing high packing densities and radiation hardness. Anodizing has been carried out using both single and double cells, following the effects of current density. HF concentration and silicon resistivity. The resultant porous layers have been characterised with respect to composition and structure. The materials produced differ considerably in lattice strain, composition and reactivities. Prompt radiation analyses 19F(p,αγ), 16O(d,α), 12C(d,p), are useful for monitoring the anodizing procedures and subsequent oxidation: currently, interest centres on the mechanistic information obtained. RBS analysis using α-particles gives a much lower Si response from porous than from bulk silicon. Glancing angle proton recoil analyses reveal considerable quantities of hydrogen in the porous layers. These mutually consistent findings have considerable mechanistic significance; extensive Si-H bonding occurs following a 2 equivalent Faradaic process.

Reticular influences on primary and augmenting responses in the somatosensory cortex

The effects of brief, conditioning trains of high-frequency pulses to the midbrain reticular formation (RF) on primary and augmenting responses of somatosensory (SI) cortex were investigated. Testing stimulation was applied to the ventrobasal (VB) thalamus or to the white matter (WM) beneath SI in VB-lesioned animals. The RF-elicited EEG activation was associated with increased firing rates of SI neurons, enhanced probability of early synaptic discharges to VB or WM stimuli, and significantly reduced duration of the suppressed firing period following an afferent VB or WM volley. The diminished latency of the postinhibitory rebound under RF stimulation had the consequence that, within 10/sec shock-train, the second stimulus was delivered following completion of the rebound component and, instead of an augmented potential, generated a field response of primary-type. The dependence of the RF-induced change in augmenting potentials upon the sharpening effect exerted on the preceding inhibitory-rebound sequence was corroborated by analyzing the RF influence on neurons with different time-course of recovery from inhibition. The replacement of augmenting potentials by primary responses under RF stimulation is advanced as the mechanism behind the obliteration of spontaneously developing ‘type I’ spindle-waves during EEG arousal. The demonstration of RF influences on SI responses to WM stimulation in VB-lesioned animals points out the cortical level of the effects. The reticulo-thalamo-cortical pathways underlying these influences are discussed.

Synchronization of the electrocorticogram by visceral and somatic bradykinin stimulation in anesthetized cats

The cortical response to visceral and somatic bradykinin stimulation was studied in cats under light to moderate pentobarbital anesthesia. Following the injection of bradykinin into arteries supplying visceral organs and somatic structures, a marked cortical synchronization was recorded. The bilateral, rhythmic discharge in the theta to alpha range was best seen on SI; occasionally the contralateral SI response was more prominent. The cortical synchronization and its distribution were the same for visceral and somatic stimulation. There was only minimal response desensitization to multiple injections of bradykinin in rapid succession. Following transection of the thoracolumbar spinal cord, synchronization failed to develop after hindlimb injections but continued to be seen after forelimb stimulation; similarly, partial denervation of a limb blocked the bradykinin response. No synchronization or desynchronization could be produced by epinephrine and nitroglycerine which caused phasic changes in systemic blood pressure equal to or greater than those seen with bradykinin. The results are discussed in terms of possible pathways and receptors. It is suggested that bradykinin acts primarily on free nerve endings common to visceral and deep somatic tissue with convergence of impulses occurring at spinal and higher levels. The preferential response of SI may reflect afferent activity generated by natural, painful stimulation of deep somatic and visceral organs. Normally, this component would be masked by the concomitant non-specific arousal response of the medial reticulo-thalamic system which was depressed by the anesthetic.

ラット歯髄から視床・大脳皮質への投射路の解析および歯髄電気刺激による皮質誘発電位に対するMorphineとBarbiturateの影響について

Pain pathways from the tooth pulp to the somatosensory cortex and the effects of morphine and barbiturate on the cortical responses evoked by the stimulation of the pulp were investigated electrophysiologically in rats. 1) Responses to the tooth pulp stimulation (contra- and ipsilateral) were recorded from the somatosensory face area I (SI) and II (SID. Latency of the response in SII was longer than that in SI. The latencies of the ipsilateral responses in SII were 2.5-3.0 msec longer than those of the contralateral responses and the ipsilateral responses were eliminated by acute ablation of the opposite cortex including SI and SII. 2) Although the contralateral responses in SI were significantly depressed by morphine (2.5, 5 and 10 mg/kg i. p.), the depression did not depend on the dose of morphine. The ipsilateral responses were significantly emphanced by morphine (5 and 10 mg/kg). 3) The contra- and ipsilateral responses in SII were significantly depressed by morphine and these depression depended on the dose of morphine. 4) The contra- and ipsilateral responses in SI and SII were essentially unchanged by pentobarbital sodium (4, 8 and 16 mg/kg), but the ipsilateral responses were enhanced. 5) All responses except the ipsilateral surface positive response in SI were significantly depressed by a high dose of pentobarbital sodium (32 mg/kg). The results obtained suggest that this somatosensory face area II and the pathway to this area from the tooth pulp may play an important role in the mechanism of pain.

Cerebral somatosensory responses evoked during sleep in the cat

The effects of sleep on somatic evoked responses were studied in cats prepared with implanted ulnar nerve stimulating electrodes and cortical and subcortical recording electrodes. 1. 1. Short-latency (less than 15 msec) responses in the thalamic relay nucleus (VPL) and in somatosensory cortex (SI) were modified as follows: the VPL response was smallest during “slow wave” sleep (SS) and largest during “rapid” sleep (RS). Primary positive and negative responses in SI were small during waking (W) and largest during RS. 2. 2. A 25–40 msec peak latency, positive response in n. centre médian (CM) was largest during RS. 3. 3. Long-latency (75–300 msec) responses were recorded maximally during SS from VPL, SI, midline cortex, CM, mesencephalic reticular formation, and basal forebrain. These responses were uniformly suppressed or abolished during W and RS. 4. 4. Changes in evoked responses between waking and sleep were compared for cat and man and found to be similar. However, a consistent interspecies difference is that the primary positive response in cat is largest during RS whereas in man it is smallest during RS.

Cortical and subcortical evoked responses to central stimuli during wakefulness and sleep

In cats with chronically implanted electrodes, “lemniscal” pathway and “extra-lemniscal” evoked responses were studied during wakefulness (W), “slow” sleep (SS), and “rapid” sleep (RS). 1. 1. The amplitude of post-synaptic components of the cortical (SI) response to stimulation of ventrobasal complex (VB) or the somatic radiation increased progressively from W to SS to RS. 2. 2. The recovery cycle of the SI response showed less depression during RS than during W, and less depression during SS than during RS. 3. 3. It is suggested that cortical responsiveness is enhanced during RS compared with W. Judging by SI response amplitudfe, cortical responsiveness may be enhanced during RS compared with SS. However, the increased depression of the recovery cycle during RS suggests an increase of some inhibitory influence. 4. 4. The short latency response in VB to stimulation of medial lemniscus was smallest during SS and largest during RS. “Secondary” and recruiting responses to stimulation of mesencephalic reticular formation and centre médian were largest during SS. 5. 5. In RS all these evoked responses showed further changes of amplitude during bursts of rapid eye movements (REM). The possibility is discussed that the correlation of neural activity and REM is due to activity of the pontine reticular formation.