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Biomedical subjects

S Schell

Publications and source records attributed to S Schell.

11 recordsLinked to original sources
PubMed1999

The pain-related negative difference potential: a direct measure of central pain pathway activity or of interactions between the innocuous somatosensory and pain pathways?

Negative difference potential (NDP) is a sural nerve-evoked scalp potential derived by subtracting potentials elicited at the pain threshold level from those elicited at supra-pain threshold levels. Our recent work examined the possibility that the NDP reflects a pain-related inhibition of neurons in the innocuous somatosensory pathways. Although failing to find any evidence for this inhibition, these studies do present the possibility that the NDP reflects an attention- and/or task-related decrease in the innocuous somatosensory activity that is elicited by the noxious electrical stimulus. To test this hypothesis, 35 healthy subjects were given three attention/task relevance conditions presented in counterbalanced order: rate the subjective magnitude of the painful aspects of the noxious electrical stimulus; rate the subjective magnitude of the non-painful aspects of the noxious electrical stimulus; and, ignore the stimulus. Neither changes in attention nor the task relevance of the non-painful aspects of the stimulus had any effect on NDP amplitude. These data demonstrate that the NDP does not reflect an attention- or task-related modulation of innocuous somatosensory activity. Rather, our evidence to date suggests that the NDP is generated by activity in the central pain pathways.

Adult↗
PubMed1999

Evidence that the anterior cingulate and supplementary somatosensory cortices generate the pain-related negative difference potential.

OBJECTIVE: The pain-related negative difference potential (NDP) is derived by subtracting sural nerve-evoked somatosensory evoked potentials elicited at the pain threshold level from those elicited at supra-pain threshold levels. This experiment evaluated a hypothesis derived from our earlier work, namely that the NDP is generated by pain-related activity in the primary somatosensory (SI) cortex. METHODS: The dipole source localization method was applied to NDPs evoked by electrical stimulation of the finger and of the sural nerve in 20 subjects. RESULTS: Comparison of several one-, two- and three-source configurations demonstrated that both the finger-evoked NDP and the sural nerve-evoked NDP are best-fit by two sources, with one located in or near the anterior cingulate cortex and the other in or near the supplementary somatosensory area. CONCLUSIONS: Both the anterior cingulate cortex and the supplementary somatosensory area receive afferent projections from medial thalamic nuclei that receive nociceptive inputs, and both have been shown to respond to noxious stimulation. Hence, although the results of this experiment did not confirm our hypothesis that the NDP is generated in SI, they are consistent with the hypothesis that the NDP is generated in the supraspinal pain pathways.

Brain Mapping↗
PubMed1999

Innocuous-related sural nerve-evoked and finger-evoked potentials generated in the primary somatosensory and supplementary motor cortices.

OBJECTIVE: Our earlier work revealed two components of the somatosensory evoked potential, which we have labeled SP1 and SP4a, that appear to be generated by neurons involved in the innocuous aspects of somatosensation. The objective of the present study was to examine a hypothesis developed in our earlier work, namely that SP1 and SP4a are generated in the primary somatosensory cortex. METHODS: The dipole source localization method was applied to SP1 and SP4a evoked by electrical stimulation of the fingers and of the sural nerve in 20 subjects. The subjects rated the subjective magnitude of each stimulus on a 9 point scale. RESULTS: The finger-evoked and sural nerve-evoked SP1 were best-fit by single sources located in the primary somatosensory cortex (SI) hand and foot areas, respectively. Both the finger-evoked and the sural nerve-evoked SP4a, on the other hand, were best-fit by a single source located in the supplementary motor area (SMA). CONCLUSIONS: These results are consistent with our hypothesis that SP1 reflects the activity of SI neurons that are involved in innocuous somatosensation. SP4a is not generated in SI as we originally hypothesized, but rather in the SMA. The SP4a amplitude-stimulus intensity function and the dependence of the SP4a source location on the evoking stimulus site and not the hand registering the magnitude rating suggests that SP4a reflects the response of SMA neurons to afferent input from the innocuous somatosensory pathways. Hence, SP4a may be generated by SMA activity involved in the sensory-guided selection and/or generation of motor responses.

Adolescent↗
PubMed1988

Nakahara memorial lecture. Regulation of T lymphocyte responses: interactions among receptors.

Murine helper T lymphocytes (HTL) have been categorized on the basis of the lymphokines they secrete. TH1 cells produce interleukin 2 (IL-2), interferon-gamma (IFN-gamma), and lymphotoxin, whereas TH2 cells produce IL-4 and IL-5 but not IL-2 or IFN-gamma. Both cell types apparently can produce IL-3, granulocyte-macrophage colony stimulating factor (GM-CSF), and tumor necrosis factor. We have found that there is at least one additional subset which secretes IL-4 and IFN-gamma. These helper T lymphocyte subsets also respond differently to immunoregulatory processes. T cell clones of all subtypes can proliferate in response to exogenous IL-2, but IL-4 apparently induces a proliferative response only in those subsets that produce IL-4. IFN-gamma inhibits the proliferation of TH2 clones, but does not affect the proliferation of TH1 clones, cytolytic T lymphocyte (CTL) clones, or cells that produce both IL-4 and IFN-gamma. TH1 cells pretreated with a saturating concentration of IL-2 do not proliferate when stimulated with anti-CD3 monoclonal antibody (mAb). However, proliferation of TH2 cells is enhanced by IL-2 pretreatment, while the TH1 clones or CTL clones through the T cell receptor (TCR) profoundly inhibits IL-2-induced proliferation of those cells, whereas such stimulation either has very little effect or augments the proliferation of IL-4-producing clones. Collectively, these data suggest that the combined influence of these cytokines and intensity of TCR stimulation may determine which cell types expand in number during a particular immunological situation.

Animals↗
PubMed1985

Allogeneic bone marrow transplantation for acute leukemia refractory to induction chemotherapy.

This article compares the outcome of 14 patients with primary refractory acute leukemia who underwent bone marrow transplantation from human leukocyte antigen (HLA)-identical donors with that of 18 age-matched control patients who received chemotherapy. Complete clearing of leukemia was seen in all 14 transplanted patients. Five of the transplanted patients are alive 98 to 1790 days posttransplant, and four are free of leukemia. Nine patients have died, eight with severe graft-versus-host disease associated with interstitial pneumonia or systemic infections and one with relapse from chemotherapy-associated infections. Engraftment was seen in all patients. Severe graft-versus-host disease (grades III and IV) was seen in ten patients and resolved in three patients following high-dose corticosteroid treatment. Three of the 18 control patients are alive, none of them in complete remission. It appears that the combination of piperazinedione and total-body irradiation followed by allogeneic transplant is effective induction treatment for primary refractory acute leukemia and will be considered in the future as first salvage treatment for patients failing induction treatment.

Acute Disease↗
PubMed1984

Obstructive lung disease after allogeneic bone marrow transplantation.

We report the cases of 3 patients with marked dyspnea and an obstructive ventilation disorder associated with chronic graft-versus-host disease after allogeneic bone marrow transplantation. This disorder was characterized by recurrent pulmonary infections and colonization of the lower respiratory tract by Pseudomonas aeruginosa. Two patients have shown rapidly progressive deterioration with death following due to respiratory failure. Intensive therapy with antibiotics, bronchodilators, high-dose steroids, and azathioprine was not effective in arresting the malignant course of this disorder.

Adult↗
PubMed1982

Results in patients with breast cancer treated by radical mastectomy and postoperative irradiation with no adjuvant chemotherapy.

In 1963 an electron beam became available, making irradiation of the chest wall technically easy. In addition to peripheral lymphatic irradiation in patients with positive axillary nodes and/or the tumor in the inner quadrants or centrally located, patients with tumor larger than 5 cm or with grave signs and/or a significant incidence of positive axillary nodes received chest wall irradiation. None of the patients has received elective chemotherapy. Disease-free survival rates at ten years are 54% for the overall group, 79% for the patients with negative nodes, 44% for patients with positive nodes, 61% for patients with 1-3 positive nodes, and 33% for patients with four or more positive nodes. The incidence of peripheral lymphatic failures is low as well as the incidence of failures on the chest wall in the patients having had chest wall irradiation. With the availability of electron beam and adjustments in doses, complications are nonexistent. The incidence of treatment failures, local-regional, or distant, that have appeared by ten years are compared with the incidence of failures that were experienced by the placebo patients in the clinical trial of the NSABP of thio-TEPA versus placebo. The clearly lesser incidence of treatment failures in the U.T.M.D. Anderson Hospital patients either suggests that postoperative irradiation may have survival benefits or that the data of the NSABP series are not representative of all series.

Breast Neoplasms↗
PubMed1978

Visceral Kaposi's sarcoma presenting as colitis.

An unusual example of Kaposi's sarcoma is reported in which the patient presented with a history of intractable diarrhea of 18 months duration. The roentgenographic and endoscopic findings were those of a segmental colitis. The diagnosis was established following the appearance of skin lesions and after a subtotal colectomy was performed. Kaposi's sarcoma was present in both the skin and colon.

Aged↗