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Biomedical subjects

K R Robinson

Publications and source records attributed to K R Robinson.

At least 19 recordsLinked to original sources
PubMed1992

Electrical fields in the vicinity of epithelial wounds in the isolated bovine eye.

A lateral potential drop along the outer surface of the cornea could be measured at the edge of wounds made in the corneal epithelium of the isolated bovine eye when the cornea was covered by simulated tear film of modified Hanks' solution. These lateral fields (LFs) had an average magnitude of 42 +/- 1.4 mV mm-1 in the first 0.25 mm from the wound edge. The polarity of these surface LFs is more positive at the wound than in regions away from the wound. Very little if any lateral field could be measured at the edge of wounds along the inner surface of the corneal epithelium. The surface LFs depend on the cornea's transepithelial potential (TEP), which in this isolated bovine eye preparation we determined (with conventional microelectrode techniques) to have an average value of 24.7 +/- 2.2 mV, stroma-side positive. We found that this TEP drives a current from wounds in the epithelium with an average current density of 55 +/- 12 microA cm-2. We also have found that the average transcorneal potential (TCP) was 3.2 +/- 0.5 mV greater than the average TEP, confirming that the major contribution to the TCP comes from the corneal epithelium.

Animals↗
PubMed1992

A computerized 2-dimensional vibrating probe for mapping extracellular current patterns.

We describe a computer-assisted 2-dimensional vibrating probe system for mapping endogenous electric current patterns in biological preparations. This system overcomes some of the main limitations of the original 1-dimensional vibrating probe design and adds several new capabilities. Two piezo-electric bender elements mounted perpendicularly are used to vibrate the probe in a circle by applying 2 sine waves (1 to each element) that are 90 degrees out-of-phase with each other. The circular rotation of the probe allows it to detect simultaneously the 2 orthogonal components of a current in the horizontal plane. The voltages measured by the probe are digitized and analyzed by a computer and are used to calculate a current vector. A graphical representation of the current vector is then superimposed on a video image of the experimental preparation. This probe system responds to known currents in the expected manner and exhibits a low inherent noise level. Also included in this paper are some preliminary measurements made with this instrument on neurulating Xenopus embryos and on transected larval sea lamprey (Petromyzon marinus) spinal cords.

Animals↗
PubMed1992

Evidence of a role for endogenous electrical fields in chick embryo development.

We have tested directly the hypothesis that the endogenous electrical field in the chick embryo plays a causal role in development. Conductive implants, which shunt currents out of the embryo and thus alter the internal field, were placed under the dorsal skin at the mid-trunk level of stage 11-15 embryos. Currents leaving the posterior intestinal portal (p.i.p.) of these embryos were reduced by an average of 30%. Control embryos receiving non-conductive implants showed no change in p.i.p. currents. In the group receiving current shunts, 92% of the embryos exhibited some developmental abnormality. Only 11% of the control group displayed defects. The most common defect in the experimental group (81%) was in tail development. Tail defects ranged from complete absence to the formation of a normal length, but morphologically abnormal tail. Internally, tail structures (neural tube, notochord and somites) were frequently absent or aberrantly formed. In 33% of the experimental embryos, the notochord continued lengthening in the absence of any other tail development. This led to the formation of ourenteric outgrowths from the hindgut. Defects in limb bud and head development were also found in experimentally treated embryos, but at a much lower frequency than tail defects. The abnormalities observed in experimental embryos were very similar to those produced naturally in rumpless mutant chicks. A vibrating probe analysis of these mutants (from both dominant and recessive strains) showed that currents leaving the p.i.p. were significantly lower in phenotypically abnormal mutants than in wild-type and phenotypically normal mutant embryos from both strains. There was no apparent correlation between the average transepithelial potential (TEP) of these mutants and the development of tail abnormalities. The possible role of endogenous electrical fields in chick tail development is discussed.

Animals↗
PubMed1992

Survey of the degree to which critical care nurses are performing current procedural terminology-coded services.

PURPOSE: To identify the degree to which current procedural terminology-coded services are provided by critical care nurses. Current procedural terminology codes are used by government and private insurers for reimbursement for office, home, hospital, nursing home and emergency department services. METHOD: Out of 100 randomly selected registered nurses invited to participate in this national survey, 43 completed the survey questionnaire. The majority of respondents were 18 to 40 years old, had a bachelor's degree, had practiced nursing between 5 and 10 years, and were employed as staff or charge nurses in an intensive care or emergency room setting. RESULTS: More than 70% of the group were found to perform 28 codes. The codes performed by the greatest number (42) were blood or blood component transfusion and cardiopulmonary resuscitation. One-way analysis of variance applied to the amount of supervision the nurses received while performing the codes and the educational level of the nurses revealed a significant difference between the groups. Post hoc analysis of all possible group comparisons showed that diploma-prepared nurses reported significantly more supervision than nurses having a bachelor's or master's degree. CONCLUSION: This exploratory study indicates that critical care nurses frequently perform selected codes with little or no supervision by a physician.

Abstracting and Indexing↗
PubMed1991

The neural tube of the Xenopus embryo maintains a potential difference across itself.

In Xenopus embryos, the ectodermal epithelium generates a substantial transepithelial potential (TEP) during certain periods of early development. In this study, we have found that the neural tube (which is derived from the embryonic ectodermal epithelium) of stage 21-25 Xenopus embryos also maintains a potential across itself, with the lumen being, on average, 18 +/- 1 mV negative relative to the interstitial spaces. This transneural tube potential (TNTP) declines gradually from a maximum of -21 +/- 2 mV at stage 23 to a minimum of -14 +/- 2 mV at stage 25. Vibrating probe measurements on transected embryos suggest that the neural tube is capable of driving a current. Large outward currents ranging from 10 to 26 microA/cm2 were detected just dorsal to the center of wounds in transected stage 21-24 embryos, but near the dorsal margin of the wound, in the region corresponding to the cut face of the neural tube, outward current densities were less than half the maximum, ranging from 3 to 9 microA/cm2. The reduced outward current near the dorsal margin suggests a locus of inward current in this region that is subtracted from the much larger outcurrents. Such greatly reduced outward currents were not detected near the ventral margin of the wound.

Animals↗
PubMed1991

A cytoplasmic gradient of Ca2+ is correlated with the growth of lily pollen tubes.

We have measured the distribution of cytoplasmic calcium in lily pollen tubes by microinjecting them with indo-1 and performing fluorescence ratio image analysis on them. All of the 16 tubes that were growing at the time of the calcium measurements showed a gradient of [Ca2+]i in the tip region, with Ca2+ being 1.25 to 3.32 times higher at the distal end in 15 cases and more than 5 times higher in one case. The extent of the gradient ranged from 22 to 65 microns. Most of the 15 nongrowing tubes either had no gradient or had lower Ca2+ in the tip region. While we have confirmed a previous report that lily pollen tubes can be loaded with the membrane-permeable acetoxymethyl ester forms of calcium indicators, the dyes loaded in this way are visibly partitioned into organelles and this method of loading is, therefore, not useful for the measurement of [Ca2+]i. Iontophoresis of the dye free acids into tubes produces a more uniform and diffuse fluorescence which does not appear to partition into organelles. Indo-1 remains in the pollen tubes longer than fura-2. The correlation between growth and the [Ca2+]i gradient in the apical portion of the pollen tube is discussed in relation to previous reports that have suggested that such a gradient should exist during polarized growth.

Calcium↗
PubMed1990

Endogenous electrical currents and the resultant voltage gradients in the chick embryo.

We have studied some of the electrophysiological properties of 2 1/2- to 4-day-old (stage 14-22) chick embryos. Using a recently developed two-dimensional vibrating probe, large currents were found to exit the posterior intestinal portal (p.i.p.) during the period of tail gut reduction. During this period, epithelial cells lining cloacal regions of the hindgut are dying, thus creating a low-resistance pathway for current flow out of the embryo. Currents entered the intact epithelium over other regions of the embryo. The outward currents at the p.i.p. were first detected at stage 15 and reached their average maximum current density of 112 +/- 10 microA/cm2 at stage 17. After stage 17, the magnitude of the currents decreased, dropping to 16 +/- 0.3 microA/cm2 by stage 22. The currents were reversibly reduced by about 50% when Na+ was replaced by choline in the bathing solution. The magnitude of the currents leaving the p.i.p. suggested the existence of a measurable intraembryonic voltage gradient. The transepithelial potential (TEP) of stage 14-21 embryos was measured lateral to the neural tube through the dorsal ectoderm. For all stages, the combined average TEP was 16 +/- 0.5 mV. Differences in the TEP between various regions of the embryo were used to calculate an intraembryonic voltage gradient. At stage 14, before outward current was found at the p.i.p., no significant intraembryonic voltage gradient was detected. At stage 17, when the outward current at the p.i.p. was maximum, a voltage gradient of 21 +/- 5 mV/mm (mean +/- SEM; N = 6) was measured in the caudal end of the embryo. This gradient in some cases was as steep as 33 mV/mm. This is well above the minimum level needed to affect the direction of embryonic cell migration in vitro. We hypothesize that this endogenous electrical field acts as a directional cue for neural crest cell movements in the developing chick embryo.

Amiloride↗
PubMed1990

Microinjected GTP-gamma-S inhibits progesterone-induced maturation of Xenopus oocytes.

GTP-gamma-S inhibits progesterone-induced maturation of Xenopus laevis oocytes and induces a rise in their cAMP levels. GTP-gamma-S does not inhibit MPF-induced maturation. Although GTP-gamma-S prevents the progesterone-induced increases in protein synthesis and phosphorylation, it has no effect on the basal rates of either. GTP-gamma-S also prevents the initial DAG drop induced by progesterone. GDP-beta-S effects are ambiguous, but it seems not to affect progesterone-induced maturation. These results suggest that although G-proteins are associated with the pathways affected by progesterone, the effects of progesterone are not mediated by a typical receptor/G-protein/effector interaction.

Animals↗
PubMed1990

H-ras(val12) induces cytoplasmic but not nuclear events of the cell cycle in small Xenopus oocytes.

Microinjection of H-ras(val12) protein into fully grown Xenopus oocytes has been shown to induce meiotic maturation. In the present study, mRNA encoding the mutant ras protein was injected into both fully grown (stage 6) and growing (stage 4) oocytes. The mRNA induced nuclear breakdown in stage 6 oocytes, as expected. However, the mRNA induced neither nuclear breakdown nor maturation promoting factor when injected into stage 4 oocytes. Instead, the response in stage 4 oocytes included an activation pulse of calcium, cortical granule breakdown, elevation of the vitelline envelope, and abortive cleavage furrows, all of which are characteristics of the activation response in mature eggs. In addition, the injected mRNA led to increased rates of endogenous protein synthesis and the migration of subcortical organelles into the oocyte interior. These observations are discussed relative to the suggestion that oncogenic ras protein leads to an increase in both diacylglycerol and inositol trisphosphate, which then regulate the various cytoplasmic events described.

Animals↗
PubMed1990

The role of nursing in the influenza epidemic of 1918-1919.

Just as the horrors of World War I were winding down, millions of people were stricken by an influenza epidemic that displaced war as the tragic focus of everyday life. The disease was known as the Spanish influenza and was pandemic in scope. Since the epidemic defied the capabilities of prevailing medicine, good nursing care was the best predictor of outcome. Nurses came to the rescue by working long, hard and tirelessly. One important outcome of the epidemic was a general recognition of the visiting nurse service and all nursing as a valuable and essential community service.

Disease Outbreaks↗
PubMed1990

The distribution of free calcium in transected spinal axons and its modulation by applied electrical fields.

Intracellular free-calcium concentration ([Ca2+]i) was measured in lamprey spinal axons using the fluorescent calcium indicator fura 2. We used both a photomultiplier tube and a video-image processing system to measure the temporal and spatial distributions of [Ca2+]i in the proximal segments of transected axons. Within 3 min following transection, a spatially graded increase in the [Ca2+]i was apparent in the last few millimeters of the axons. Superimposed on the initial gradient was a moving front of calcium that progressed up the axon, reaching 1.6 mm from the cut end in 3 hr. The [Ca2+]i behind the moving front exceeded 10 microM. This movement of Ca2+ was greatly reduced by an externally applied electrical field with the cathode distal to the lesion and was increased by an applied field of the opposite polarity. When axons were transected in Ca2(+)-free medium, no increases in [Ca2+]i occurred. One d after transection, [Ca2+]i was at or below the precut levels, except in the distal 250 microns, where it remained slightly elevated. Therefore, axons can survive the high levels of [Ca2+]i that occur after transection and can reestablish normal [Ca2+]i levels within 24 hr. Measurements of both the diffusion coefficient and the fluorescence polarization of fura 2 indicate that the dye is not significantly bound to axoplasmic components.

Animals↗
PubMed1990

Denial in myocardial infarction patients.

Since nurses are the health professionals who have the closest and most frequent contact with patients, they are in the best position to assist the MI patient with management of denial. It is important for nurses to recognize the manifestations of denial and then be able to assess the amount that denial accelerates or impedes the patient's progress toward regained health. With this increased awareness, nurses become the major influence in helping the MI patient recover psychologically as well as physically.

Denial, Psychological↗
PubMed1989

The responses of pollen to applied electrical fields.

The growing pollen tubes of tomato and tobacco were exposed to electrical fields and the effect on the direction of growth was measured. They responded by turning toward the positive electrode (anode) and gave a detectable response in fields as small as 0.1 mV/tube diameter. The sites of germination of tobacco pollen grains were also affected by applied fields; the pollen tubes tended to emerge from the anodal side. This effect was detectable at a field of 0.4 mV/grain diameter.

Electricity↗
PubMed1988

An endogenous sodium current may mediate wound healing in Xenopus neurulae.

We have studied healing of Xenopus neurulae in order to investigate the role of endogenous sodium-carried electric currents in wound closure. Transected embryos healed completely within 7 hr in an artificial pond water medium. Wound closure was biphasic, with a rapid purse string-like contraction that was independent of sodium concentration followed by a slower sodium-dependent phase. The initial contraction was reversibly inhibited by cytochalasin B. Healing was prevented when neurulae were wounded and left to heal in sodium-free medium. Healing was also prevented in the presence of amiloride, benzamil, or ouabain, drugs that inhibit sodium flux through the epithelium. The transepithelial potential measured in intact neurulae fell rapidly and reversibly by 70% in response to 10 microM amiloride. Currents measured leaving the wound also decreased by 70% following amiloride addition. Our results indicate that at least one phase of wound healing in Xenopus neurulae is dependent upon an endogenous sodium-carried electric current. We hypothesize that the current may act by guiding epithelial cells to the wound site.

Amiloride↗
PubMed1987

A rise in cytosolic calcium is not necessary for maturation of Xenopus laevis oocytes.

Cytoplasmic free calcium levels during progesterone-induced meiotic maturation in Xenopus laevis oocytes were measured using the photoprotein aequorin. The resting level of [Ca2+]i was 92.6 +/- 30 nM. No significant changes were observed after progesterone addition, although a large pulse of [Ca2+]i was observed upon activation of matured oocytes. These findings are discussed in terms of the role of calcium in maturation and it is concluded that calcium is not the second messenger for progesterone. This conclusion is further supported by the finding that 100 microM TMB-8, a blocker of intracellular calcium release, had no effect on progesterone-induced maturation.

Aequorin↗
PubMed1987

Calcium does not act as a second messenger for adrenergic and cholinergic agonists in corneal epithelial cells.

The role of changes in intracellular [Ca2+]i as a second messenger in response to either adrenergic or cholinergic agonists was determined in isolated bovine corneal epithelial cells. [Ca2+]i was measured in suspensions of cells loaded with either of the fluorescent indicators quin2 or indo-1, as well as in single cells loaded with fura-2. Fluorescence from the cell suspensions was measured in a spectrofluorometer while single cell fluorescence was measured using a modified fluorescence microscope with a photon counting photometer. Cells were loaded with these dyes by incubation in Ringer's (pH 8.1) containing 2-50 microM of the acetoxymethyl ester of the indicator. Fluorescence was measured before and after exposure to either, one of the adrenergic agonists isoproterenol, phenylephrine or epinephrine, or the cholinergic agonist carbachol. The resting [Ca2+]i level from the quin2 experiments was 115 nM +/- 41 nM (SEM) (n = 23) whereas with fura-2 it was 71 +/- 10 nM (n = 30). In no case did we see any change in [Ca2+]i within 15 min after addition of any agonist but we were able to observe increased calcium when 0.5 microM ionomycin was added to either the same or untreated cells. The disparity in the resting levels determined by the two methods may result from various calibration problems. Our results indicate that changes in [Ca2+]i have no second messenger role in response to these agonists.

Aminoquinolines↗