Intraoperative monitoring of corticospinal function.
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Electroencephalography↗
Biomedical subjects
R Hicks
Publications and source records attributed to R Hicks.
Trial-to-trial variability of corticospinal volleys in human subjects.
The trial-to-trial variability of the different components of corticospinal volleys evoked by transcranial electrical stimulation of the motor cortex using a constant stimulus intensity was measured from epidural recordings during surgery to correct scoliosis. The recordings were made when there was no operative interference, and blood pressure, temperature, ventilation and anaesthetic regimen were stable. A simple D wave with a single negative peak of 10-30 microV amplitude was recorded in 4 patients. It varied little in amplitude (S.D.s < 8% for 100 consecutive single responses). In 4 patients the stimulus was adjusted to produce a complex D wave with 3 components, the earliest 2 of which arise from subcortical/brain-stem sites. The variability of amplitude of these components was high (S.D.s of 13-50%), but the variability of latency was low (S.D.s of 2-3%). Eighteen I waves were recorded in 6 of the subjects. Their variability from trial to trial was similar to that of the components of the complex D wave. It is argued that there would be greater trial-to-trial variability of the corticospinal volley in the awake state, particularly when the stimulus was magnetic rather than electrical. Explanations for changes in the compound muscle action potential produced by transcranial stimulation, electrical or magnetic, must take into account that a constant stimulus does not evoke an identical descending volley.
Adolescent↗
Transcranial electrical stimulation of the motor cortex in man: further evidence for the site of activation.
1. The motor cortex was stimulated electrically (vertex anode; cathode 6 cm lateral) in neurologically normal subjects undergoing surgery for scoliosis, and the evoked corticospinal volleys were recorded from the spinal cord using epidural electrodes. 2. Stimuli > 330 V produced a complex D-wave volley containing three separate peaks, with high-threshold components, 0.8 ms (D2) and 1.6 ms (D3), in advance of the lowest-threshold component (D1). As stimuli increased up to 1500 V, D3 replaced the later components completely, but there was no further latency 'jump'. 3. Brainstem stimulation using electrodes over each mastoid process produced a descending volley that had the same latencies as D3. At threshold, stimulation of the brainstem or spinal cord attenuated the D wave evoked by simultaneous cortical stimulation. 4. It is concluded that transcranial electrical stimulation of the motor cortex at high intensities can access corticospinal neurones at the pyramidal decussation, and that stimulation of the brainstem (and the spinal cord) preferentially accesses corticospinal axons. At threshold, motor cortex stimulation probably activates corticospinal neurones at or near the cerebral cortex.
Adolescent↗
Hospital vocational training. New post addresses deficiencies.
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Family Practice↗
v-mos-transformed cells fail to enter quiescence but growth arrest in G1 following serum withdrawal.
The product of the mos protooncogene normally functions in the induction of meiosis and regulation of cell-cycle progression in oocytes. Here we have investigated the cell-cycle progression of NIH3T3 cells transformed by the v-mos gene. Flow cytometric analysis showed that logarithmically growing v-mos-transformed cells do not differ from their nontransformed counterparts in the distribution of cells in the G1, S, and G2/M phases. Likewise, after serum withdrawal for 48 h, both normal and v-mos-transformed NIH3T3 cells have essentially ceased proliferation, as analyzed by flow cytometry, [3H]thymidine and BrdU incorporation into newly synthesized DNA, and mitotic indexes. However, while the normal NIH3T3 cells are arrested in a quiescent state, the v-mos-transformed cells are arrested in early to mid G1, prior to the point where cells require certain amino acids for proliferation (V point). In agreement with these different arrest points, the v-mos-transformed cells enter S phase following serum stimulation within about 8 h, without the additional 4- to 6-h lag period characteristically displayed by the parental NIH3T3 cells. In addition, we show a lack of expression of a growth arrest-specific gene product, gas1, in the serum-arrested v-mos-transformed cells. These data demonstrated that v-mos-transformed cells display growth characteristics that differ fundamentally from those of normal cells or cells transformed by overexpression of myc [1]. Our results suggest that the v-mos oncoprotein transforms cells, at least in part, by preventing exit from the cell cycle into quiescence.
3T3 Cells↗
The selection of antibodies for targeted therapy of small-cell lung cancer (SCLC) using a human tumour spheroid model to compare the uptake of cluster 1 and cluster w4 antibodies.
Spheroids of a small-cell lung cancer (SCLC) cell line POC were used to evaluate the uptake and penetration of two antibodies recognising different SCLC antigens. Spheroids approximately 300-400 microns in diameter were incubated with 1 microgram ml-1 125I-labelled NY.3D11, an antibody which reacts with the cluster 1 group antigen (neural cell adhesion molecule; NCAM) and [125I]SWA11, which binds to the cluster w4 antigen. The rate of uptake of both antibodies was similar; an initially rapid phase was seen during the first 8 h and maximum uptake occurred by 24 h. The mean uptake per spheroid at 24 h was 0.97 ng for [125I]NY.3D11 and 0.45 ng for [125I]SWA11. An objective measurement of antibody penetration into spheroids was developed using a computerised image analysis of immunostained sections of spheroids. The concentration of antibody and incubation times were varied. Both antibodies penetrated the spheroids to a depth of 50 microns after 30 min. This increased to about 100 microns after 4 h incubation with 1 or 100 micrograms ml-1 SWA11. The results with 1 microgram ml-1 NY.3D11 were similar, but in the presence of 100 micrograms ml-1 NY.3D11 penetration into the spheroid was deep and diffuse. These results demonstrate a major concentration-dependent difference in the uptake and penetration of cluster 1 and cluster w4 antibodies in this spheroid model and they have implications for the selection of antibodies for targeted therapy of SCLC.
Antibodies, Monoclonal↗
Spontaneous oesophageal haematoma: a review of the difficult diagnosis.
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Diagnosis, Differential↗
A simple method for the evaluation of receptor binding capacity of modified cytokines.
We have developed a flow cytometric method to evaluate the binding of interleukin-2 analogues to receptors. The method relies on competition for binding between a fluorescein-conjugated monoclonal antibody (MoAb) directed against the human interleukin-2 receptor alpha chain (fluorescein isothiocyanate (FITC) anti-IL-2R) and the test protein. IL-2R positive cells are incubated with FITC-anti-IL-2R MoAb in the presence of native IL-2 or IL-2 iodinated by either the chloramine-T or the lactoperoxidase-glucose-oxidase method. The binding of IL-2 is indicated by decreased fluorescence. This method is suitable for measuring the binding capacity of modified IL-2 molecules and avoids the need for radioactive tracers. It provides a simple and reproducible technique, which can be extended readily to the study of the receptor binding capacity of cytokines conjugated with toxins, drugs or other molecules.
Antibodies, Monoclonal↗
Captopril inhibits the 72 kDa and 92 kDa matrix metalloproteinases.
Gelatinases are metalloproteinases in the kidney which can cleave type IV collagen as well as gelatin. We partially purified the 72 kDa and 92 kDa gelatinases. The gelatinolytic activity was measured by zymography and a quantitative biotin-avidin assay. By zymography, captopril in concentrations of 20 mM and 40 mM added to the incubation buffer reduced the gelatinolytic activity in a dose-dependent manner. The addition of zinc in a concentration of 50 to 100 microM reversed most of the inhibitory effect of captopril. By the biotin-avidin assay, captopril in a concentration of 30 to 50 nM reduced half of either the 72 kDa or 92 kDa gelatinolytic activity. Zinc in a concentration of 50 microM completely reversed the inhibitory effect of 1 microM captopril on both gelatinases. Lisinopril, a non-sulfhydryl ACE inhibitor, similarly inhibited the gelatinases, but a 100-fold higher concentration of the drug was needed. These findings suggest that captopril reversibly inhibits the 72 kDa and 92 kDa metalloproteinases by interacting with the zinc ion at their active sites. This inhibitory effect is observed with captopril levels comparable to the concentrations needed to inhibit the angiotensin converting enzyme in vivo and may at least partially explain some of the renoprotective effects seen with this drug.
Animals↗
Direct comparison of corticospinal volleys in human subjects to transcranial magnetic and electrical stimulation.
1. The effects of graded transcranial magnetic and anodal electrical stimulation of the human motor cortex were compared in human subjects undergoing orthopaedic operations on the spine, before and after withdrawal of volatile anaesthesia. Corticospinal volleys were recorded from the spinal cord in the low-cervical and low-thoracic regions (six subjects) or the mid-thoracic region (two subjects) using bipolar electrodes inserted into the epidural space. 2. Electrical stimuli were delivered using anode at the vertex and cathode 7 cm laterally. The corticospinal volley at threshold consisted of a single deflection with a mean latency to peak of 4.17 ms at the rostral recording site. With further increases in stimulus strength the latency of this D wave shortened in two steps, first by 0.89 ms (seven subjects) and then by a further 0.8 ms (two subjects), indicating that the site of activation of some corticospinal neurones had shifted to deep subcortical sites. 3. When volatile anaesthetics were given, a corticospinal volley could not be defined in three subjects with magnetic stimuli of 70, 80 and 100% maximal stimulator output with the coil at the vertex (Novametrix Magstim 200, round coil, external diameter 14 cm). In the remaining five subjects, the component of lowest threshold was a D wave recorded at the rostral site at 4.0 ms when stimulus intensity was, on average, 70%. With stimuli of 90-100% a total of five small I waves could be defined in the five subjects (i.e. on average one I wave per subject). 4. After cessation of volatile anaesthetics in seven subjects, the thresholds for D and I waves were lower and their amplitudes were greater. The D wave remained the component of lowest threshold in all subjects, appearing at the low-cervical level with magnetic stimuli of 50%. However, in three subjects I waves also appeared at D wave threshold, and the D wave was smaller than with electrical stimulation at I wave threshold. There was no consistent change in latency of the magnetic D wave as stimulus intensity was increased to 100%. 5. These findings suggest that the previously reported difference in latency of the EMG potentials produced in upper-limb muscles by anodal stimulation and magnetic stimulation of the human motor cortex is not because the corticospinal volley induced by magnetic stimulation lacks a D wave.(ABSTRACT TRUNCATED AT 400 WORDS)
Adolescent↗
Human papillomavirus type 16 E7 associates with a histone H1 kinase and with p107 through sequences necessary for transformation.
The transforming function of human papillomavirus type 16 (HPV16) E7 has been shown to depend on activities additional to the ability to bind RB. In this paper we describe two further properties of E7 which may also contribute to transformation, an association with a histone H1 kinase at the G2/M phase of the cell cycle and an ability to bind the RB-related protein p107. The region of E7 identified previously as important for RB binding was found to be involved in the association with the kinase and complex formation with p107, although analysis of E7 point mutants within this region revealed a difference in the precise sequence requirement for RB and p107 binding. Association with the kinase activity correlated with the ability to bind RB, but the restriction of the kinase association to the G2/M phase of the cell cycle implies that this activity might not be directly mediated by RB binding. Since kinase-binding-deficient E7 mutants are also transformation defective, this may represent an independent function of E7 which plays a role in the G2/M phase of the cell cycle.
Cell Line↗
Potentiation of etoposide-induced cytotoxicity and DNA damage in CCRF-CEM cells by pretreatment with non-cytotoxic concentrations of arabinosyl cytosine.
Pretreatment of the human lymphoblastoid cell line CCRF-CEM with 0.02 microM arabinosyl cytosine (ara C) enhances both the cytotoxic and the DNA-damaging effects of etoposide. This concentration of ara C is itself non-cytotoxic and results in no detectable DNA damage as measured by alkaline elution. Ara C pretreatment results in the synchronisation of cells, a 24-h pretreatment resulting in the accumulation of cells in the early S phase. The sensitivity of cells to etoposide-induced cytotoxicity was increased 2.5 times and DNA damage was enhanced 1.66 times by this pretreatment. Maximal potentiation of etoposide-induced DNA damage (2.06-fold increase) was observed after 48 h continuous treatment with ara C, but no further enhancement of cytotoxicity occurred. Cell-cycle analysis demonstrated that 48 h ara C treatment resulted in the accumulation of cells in the late S/G2M phase. Cells returned to a normal cell-cycle distribution within 24 h of the removal of ara C, and the potentiation of etoposide activity was then reduced to a 1.3- to 1.4-fold level. DNA damage induced by etoposide following ara C pretreatment was qualitatively identical to that produced by etoposide alone, suggesting a mechanism involving topoisomerase II. To investigate this possibility, we measured topoisomerase II protein levels by immunoblotting. Measurement of topoisomerase II levels in whole-cell lysates of ara C-pretreated cells showed a 3- to 5-fold increase in topoisomerase levels relative to total protein content. This suggests that elevated enzyme levels may be responsible for the increased sensitivity of ara C-pretreated cells to etoposide.
Cell Cycle↗
Assessment of corticospinal and somatosensory conduction simultaneously during scoliosis surgery.
The function of descending motor pathways and that of ascending sensory pathways in the spinal cord were monitored at the same time in 120 patients undergoing surgery for scoliosis. Transcranial electrical stimulation of the motor cortex was performed simultaneously with stimulation of the tibial nerves in the popliteal fossae, and the descending and ascending volleys were recorded from the spinal cord at two levels using epidural electrodes. Stable recordings of both volleys have been obtained in all neurologically normal patients and in many with pre-existing neurological deficits. The experimental conditions which resulted in reliable recordings were explored in select patients and include: a vertex-anode/lateral cathode montage for transcranial stimulation, epidural recording of evoked corticospinal and somatosensory volleys at two spinal levels, a high-pass filter of 500 Hz, and stable anaesthesia. The epidural recording allows full muscle relaxation and the use of volatile anaesthetics; recording at two levels allows a deterioration in function to be identified quickly and distinguished from an artifactual change.
Anesthetics↗
Anodal and cathodal stimulation of the upper-limb area of the human motor cortex.
In 18 neurologically normal subjects the corticofugal volleys evoked by anodal and cathodal electrical stimulation of the motor cortex were recorded using epidural electrodes at the high-thoracic and low-thoracic regions of the spinal cord during surgery for scoliosis. At and just above threshold, anodal and cathodal stimulation of the upper-limb area and motor cortex produced a D wave that propagated to the low-thoracic region. The stimulus intensity required to produce D waves was significantly lower with anodal stimulation. I waves were recorded at higher stimulus intensities than the D wave but not more readily with cathodal stimulation. There was no significant difference in the extent to which stimulus intensity had to be increased above D-wave threshold to produce I waves with the two stimulus polarities, and the number of I waves was the same when the stimulus was increased by the same amount above D-wave threshold. After withdrawal of isoflurane, I waves could not be recorded when the stimulus intensity was below D-wave threshold with either stimulus polarity. Anodal stimulation over the upper-limb area remained more effective than cathodal stimulation in producing both D and I waves. These results indicate that, at threshold, regardless of anaesthesia, anodal and cathodal stimuli access upper-limb corticospinal neurons directly at a similar site, the anodal stimuli being more effective. In addition, the results suggest that some corticospinal neurons in the upper-limb area of motor cortex have projections to lumbar segments.
Adolescent↗
Corticospinal volleys evoked by electrical stimulation of human motor cortex after withdrawal of volatile anaesthetics.
1. In twenty-two neurologically normal patients undergoing surgery for scoliosis, corticospinal volleys to transcranial electrical stimulation of the motor cortex were recorded from the spinal cord using epidural electrodes. While anaesthesia was maintained by nitrous oxide and narcotics, volatile anaesthetics were withdrawn to determine whether such agents had a depressant effect on the evoked corticospinal volley. 2. Profound changes were documented in liminal D waves, there being an increase in amplitude averaging 392% following withdrawal of the volatile anaesthetic. There was a proportionately smaller increase (averaging 26%) in supraliminal D waves; these had a complex bifid or trifid shape indicating that some corticofugal axons were being activated deep to cortex. In general the effect on the D wave of withdrawing the anaesthetic agent was similar to that of increasing stimulus intensity. 3. Withdrawal of isoflurane dramatically increased the number of I waves and their mean amplitude. In the absence of isoflurane, I3 (mean latency 3.5 ms after the D wave) became the dominant I wave. The amplitude of I2 (mean latency 2.2 ms) became slightly smaller. The change in I waves could not be likened to an increase in stimulus intensity, because I waves invariably increase in, or remain of the same, amplitude as stimulus intensity is increased. 4. These findings indicate that changes in motor cortex excitability can result in major changes in the corticospinal volley produced by transcranial electrical stimulation, affecting both the D wave and I waves. They caution against identifying a cortical action solely on the basis of a change in the responses to magnetic stimulation of motor cortex but no such change to electrical stimulation.
Adolescent↗
'Tooth bleaching is vital'.
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Carbamide Peroxide↗
Identification of murine thymocyte populations capable of extensive proliferation in serially passaged thymic organ cultures.
Using the approach of titrating precursor cells into mouse thymus organ cultures and serial passage, we have sought to compare the proliferative capacities of cells derived from adult and embryonic thymus and related haemopoietic tissues. We find that cells derived from the liver and thymus of day 14 embryos are capable of extensive proliferation in such cultures (surviving for at least 12 weeks) whereas cells derived from adult sources (blood and thymus) display a much more restricted lifespan and potential for division. Analysis of sequentially passaged thymic lobes shows that cells lacking CD4 and CD8 (CD4- and CD8-) and a subset of single CD8 positives are selectively expanded in these cultures. A preliminary study of the CD4-CD8- populations in these lobes suggest that these include cells expressing surface CD3 (in association with either TCR alpha beta or TCR gamma delta) and a subset of CD4-CD8-CD3-. These findings suggest that sequential passage of thymocytes in organ culture may be a useful alternative strategy for characterising cells with high proliferative potential, resident in the thymus and also for probing their lineage relationships.
Animals↗