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Biomedical subjects

S H Thompson

Publications and source records attributed to S H Thompson.

63 records · Page 4Linked to original sources
PubMed1977

Three pharmacologically distinct potassium channels in molluscan neurones.

1. Potassium currents were studied under voltage-clamp conditions in nerve cell bodies of the nudibranch Tritonia diomedia. 2. Potassium currents could be separated into three distinct components on the basis of their sensitivity to 4-aminopyridine (4-AP), tetraethyl-ammonium (TEA) and to Co2+ and Mn2+ ions. 3. A transient potassium current, similar to the fast outward current described by Connor & Stevens (1971b) and Neher (1971), was blocked by externally applied 4-AP but was much less sensitive to TEA or to Co2+ or Mn2+. A single 4-AP ion binds each receptor with an apparent dissociation constant of 1-5 X 10(-3) M. 4-AP decreases the rates of activation and inactivation and reduces the maximum conductance of transient current channels. 4. Delayed outward current was not effected by 4-AP at concentrations which blocked the transient current, but it could be divided into two components by external application of TEA and Co2+ or Mn2+. 5. A voltage-dependent component of delayed current, termed K-current, was blocked by TEA. Each K-current receptor binds a single TEA ion with an apparent dissociation constant of 8 X 10(-3) M. Co2+ and Mn2+ have little or no effect on K-current. 6. A second component of delayed outward current, termed C-current, depends on Ca2+ entry for its activation. It is similar to the Ca2+ dependent potassium current reported by Meech & Stranden (1975) in Helix cells. C-current is essentially blocked by 30 mM external Co2+ or Mn2+. It is little affected by TEA, however, being reduced by about 20% at a TEA concentration of 100 mM. 7. It is concluded that three sets of potassium selective channels contribute to the outward current and that these channels can be separated pharmacologically.

Animals↗
PubMed1976

Depolarizing afterpotentials and burst production in molluscan pacemaker neurons.

1. Spikes in molluscan bursting cells are followed by depolarizing afterpotentials (DAPs) which are not seen in nonbursting cells in the same ganglia. DAPs from successive spikes sum to provide a depolarizing drive capable of sustaining multiple discharge. 2. Subthreshold depolarization activates a DAP-like process in bursters. 3. DAP amplitude increases as the cell is hyperpolarized beyond the potassium equilibrium potential. The amplitude is not changed by intracellular iontophoresis of TEA-Cl. DAP amplitude is reduced by 39% after a 10-min exposure to CA++-free saline, and by 66% after 10 min in 4% Na+ (Tris substituted) saline. The amplitude is unchanged by exposure to K+-free saline. 4. During repetitive stimulation the amplitude of the summed DAP declines. 5. It is concluded that DAP results from a slowly decaying component of Ca++ and Na+ permeability.

Action Potentials↗
PubMedDate not supplied

Gigantiform cementoma of the jaws.

Fibro-osseous cemental lesions of the jaw remain a controversial area of bone/cementum pathology. This article describes the clinicopathological features of 28 lesions classified as gigantiform cementoma. Black women are affected more frequently than other race and sex groups, with a peak frequency of occurrence in the fourth and fifth decades. The posterior mandible is preferentially affected and unifocal lesions (67.9%) occur more frequently than multifocal lesions (32.1%). Dull pain and a centrifugal size increase are the most prevalent presenting symptoms. Of 28 cases with parental and sibling clinical information, there were no cases which exhibited an autosomal dominant genetic association. The pathogenesis of this lesion in relation to other cemental lesions of the jaws, as well as the clinical management of cemental jaw lesions, is discussed.

Adult↗
PubMedDate not supplied

Chondromyxoid fibroma of the jaws.

A new case of chondromyxoid fibroma of the jaws is reported, and the current world literature on chondromyxoid fibroma is reviewed. Chondromyxoid fibroma is a rare tumor arising from cartilage-forming mesenchymal tissue. In the long bones, it has frequently been confused with chondrosarcoma or benign chondroblastoma. When it occurs in the jaws, apparent confusion with myxomas of myxofibromas may result. In the jaws the neoplasm typically occurs in the mandible. Initial symptoms are pain or a slowly growing expansile mass. After evaluation of the natural history of these lesions, a conservative approach to surgical therapy is advocated.

Adult↗
PubMedDate not supplied

Model prenatal program of Rush Medical College at St. Basil's Free Peoples Clinic, Chicago.

The lack of adequate prenatal and gynecological care for indigent women has reached crisis proportions. The situation is aggravated by the diminishing supply of primary care physicians who are willing to practice obstetrics in community settings. Added to this condition is the rapidly declining number of medical students seeking careers in the primary care field. The Rush Prenatal Program at St. Basil's Free Peoples Clinic on Chicago's south side addresses these problems by (a) delivering comprehensive prenatal care to poor and disadvantaged women; (b) providing a learning environment in which medical students are taught to be humane, culturally sensitive, and competent physicians through active involvement in patient management; and (c) creating an experience that reinforces the student's self-motivation to practice community-oriented primary care. At the clinic 24 medical students, working in teams supervised by the three program physicians, maintain continuity of excellent prenatal care that follows the expectant mother from pregnancy through delivery and beyond. The Rush Prenatal Program, which has been initiated, organized, and managed by medical students, has evolved into a model of education and service that can be emulated at other institutions. All participants in the program--students, faculty, patients, and community representatives--are being followed longitudinally as a method of assessing program efficacy. This collaborative effort between an academic medical center and a neighborhood clinic demonstrates that such a partnership is not only feasible but potentially cost effective and socially responsible.

Chicago↗