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Biomedical subjects

K R Robinson

Publications and source records attributed to K R Robinson.

At least 73 records · Page 4Linked to original sources
PubMed1981

The direction of growth of differentiating neurones and myoblasts from frog embryos in an applied electric field.

1. Disaggregated single neurones and myoblasts obtained from the neural tube and somites of Xenopus laevis embryos (stages 17-21) were cultured in the presence of steady small electric fields. 2. Neurites grew preferentially towards the negative pole, or cathode, in field strengths of 7-190 mV/mm. Many turned through considerable angles to do so. This effect disappeared below a threshold level of about 7 mV/mm. 3. Greater numbers of neurones sprouted neurites in cultures exposed to an electric field compared to control cultures. The difference could be as much as tenfold. The threshold level of this phenomenon was about 6-8 mV/mm. Other cell types such as pigment cells and fibroblasts were also stimulated to differentiate in culture by an electric field, although to a lesser extent than neurones. 4. Applied electric fields had no effect on the location of the origin of neurites on the cell body. 5. Spherical myoblasts cultured in applied electric fields (36-170 mV/mm) elongated with a bipolar axis of growth which was perpendicular to the electric field. The response was graded and disappeared at field strengths below 36 mV/mm. 6. It is suggested that in vivo, the direction of neural outgrowth from the neural tube and the strict spatial organization of somites might be under the control, in part, of endogenous electric fields. Possible sources of these are discussed.

Animals↗
PubMed1980

Endogenous electric field around muscle fibres depends on the Na+-K+ pump.

We describe here experiments which reveal a new physiological specialization in the endplate (synaptic) region of skeletal muscle fibres. Using a vibrating microelectrode which can detect small currents flowing in extracellular fluid, we have found that the membrane in the endplate region behaves as though a steady positive current is generated in this location. Current re-enters the fibre in the extrajunctional region. Further experiments show that this current is dependent on the activity of the sodium pump. The electric field created by this current may be important for long-term interactions between muscle and nerve.

Animals↗
PubMed1980

Endogenous electrical currents in the water mold Blastocladiella emersonii during growth and sporulation.

We have explored the pattern of electrical currents generated by single cells of the water mold Blastocladiella emersonii at several stages of its life cycle. Extracellular currents were measured with a vibrating probe constructed after the design of Jaffe and Nuccitelli [Jaffe, L. F. & Nuccitelli, R. (1974) J. Cell Biol. 63, 614-628]. In growing cells positive current, of the order of 1 microA/cm2, enters the rhizoid and leaves from the thallus; circumstantial evidence suggests that protons carry much of the current. Sporulation is associated with reversal of the current pattern, such that positive current enters the thallus and leaves from the rhizoidal region; the ions that carry the current have not been identified. These current patterns appear to play a role in the spatial localization of fungal growth and development.

Blastocladiella↗
PubMed1979

Electrical currents through full-grown and maturing Xenopus oocytes.

An extracellular vibrating electrode was used to map the current pattern around Xenopus laevis oocytes. Current was found to enter the animal hemisphere and leave the vegetal hemisphere; in fully grown oocytes from which the follicle cells had been removed, the maximal current density was about 1 microamperemeter/cm2. This current decreased to nearly zero in response to progesterone and several other maturation-producing agents. In the case of progesterone, the decline began within a few minutes of the addition of the hormone and proceeded with a half-time of about 20 min. An analysis of the effects on the current of the removal or addition of various ions and drugs led to the inference that the major current-carrying ion was chloride and that the chloride permeability was controlled by calcium.

Animals↗
PubMed1977

Electrophoresis of concanavalin A receptors along embryonic muscle cell membrane.

Fluorescent concanavalin A (con A)-labelling showed that an electric field of 4 V cm-1 grossly redistributed con A receptors alone the plasma membranes of living muscle cells within 4 h. This field produced a voltage drop of 12 mV across these 30 micronm-wide cells. The movement of receptors was independent of cell metabolism and seemed to be electrophoretic in nature.

Animals↗
PubMed1975

Polarizing fucoid eggs drive a calcium current through themselves.

Calcium ions enter the prospective growth pole of polarizing Pelvetia eggs faster than the opposite pole and leave this antipode faster than the growth pole. The calcium current is greatest when first measured at 6 hours after fertilization and decreases as the time of final commitment to growth in a particular direction approaches.

Biological Transport, Active↗
PubMedDate not supplied

Localization of steady currents in the lens.

Steady currents around the rat lens were measured with a vibrating probe. Inward currents were found at the anterior pole and to a lesser degree at the posterior pole. Outward currents were localized at the equator. These currents were inhibited and even reversed by high concentrations of potassium. Ouabain blocked currents after 24 hrs but not after 6 hrs of exposure. The composition of the medium was not critical. For example, currents were observed in NaCl and in MgSO4 solutions.

Animals↗
PubMedDate not supplied

Developing a scale to measure denial levels of clients with actual or potential myocardial infarctions.

OBJECTIVE: To refine and test the Robinson Self-Appraisal Inventory-Form D (RSAI-Form D), a self-administered scale designed to measure denial in coronary clients. DESIGN: Exploratory research. SETTING: Two midwestern medical centers. SAMPLE: The sample was composed of 130 patients 75 years of age and younger with actual or potential myocardial infarction. MEASURES: Two instruments, the Demographic Data Form and the RSAI-Form D, were completed by the participants. RESULTS: Cronbach's coefficient alpha, factor analysis, t test, and stepwise multiple regression were used in the data analysis. A coefficient alpha for the 20-item scale was 0.80 for both Day 2 and Day 4. Day 2 and Day 4 oblique rotations revealed that items loaded on four factors but did not load on the same factors for both days: therefore, factors were identified for each day. There was a significant decrease in RSAI-Form D scores from the second to fourth hospitalized day (t = 5.83, p = 0.001). Two predictors, number of prior hospitalizations of chest pain, and whether or not the individual had sustained a myocardial infarction this admission (identified by stepwise multiple regression) explained 9.4% of the variance in the change in RSAI-Form D scores from Day 2 to Day 4 (F[2, 127] = 6.55, p = 0.001). CONCLUSIONS: Findings of the study did provide preliminary evidence that the RSAI-Form D is a reliable and valid inventory. Four aspects of denial were extracted, thus providing supportive evidence to the nurse that the use of single specific or global criteria does not provide sufficient data for assessing denial.

Denial, Psychological↗