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PubMed1996

Concurrent reflectance imaging and microdialysis in the freely behaving cat.

We present a method to perform simultaneous microdialysis with light reflectance imaging of neural activity in a discrete brain region of the freely behaving animal. We applied this method to the dorsal hippocampus of freely behaving cats to (1) measure extracellular glutamate and reflectance variations across a sleep-waking cycle, (2) assess spatially coherent neural activity changes accompanying local perfusion of cocaine and (3) measure local changes in cell volume induced by infusion of hyper- and hypo-osmotic solutions. Higher extracellular glutamate concentrations corresponded to higher imaged neural activity. Sequential images showed that cocaine perfusion elicited a propagating reflectance change as cocaine reached the tissue. Microperfusion of hypo-osmotic solution ( - 100 mOsm), which increases cell volume, decreased reflectance. Microperfusion of hyperosmotic sucrose solutions, which reduce cell volume, increased reflectance in a dose-dependent manner. The data indicate that reflectance imaging can measure changes in cell volume, and could, thus, measure neural activity through activity/cell volume corollaries. Combining microdialysis and optical imaging enables investigation of the neurochemical bases of spontaneous neural activity patterns within discrete brain nuclei.

Animals↗

PubMed1988

Reflected reentry in depolarized foci with variable conduction impairment in 1 day old infarcted canine cardiac tissue.

A recent study in 1 day old infarcted canine cardiac tissue demonstrated that variations in entrance and exit characteristics of depolarized spontaneous foci could profoundly affect their expression, resulting in behaviors such as modulated parasystole and entrainment, second and third degree exit block "autoentrainment" and annihilation (abrupt termination) of spontaneous activity. Foci with exit and entrance delay should also allow the occurrence of reflected reentry. To test this, the left circumflex coronary artery was ligated and, after 1 day, simultaneous microelectrode impalements were made in infarcted and uninfarcted portions of isolated ventricular preparations. Preparations were stimulated from the uninfarcted portions. Reflected reentry was demonstrated in 5 of 11 preparations. It occurred when exit conduction delay resulted in reexcitation of the focus or, alternatively, when entrance conduction delay resulted in reexcitation of extrafocal tissue. Reflection occurred in which the action potentials were reexcited during phase 2 or 3, resulting in prolongation of action potential duration (type I), and in which reexcitation occurred after full or nearly full repolarization, resulting in a closely coupled extrasystole (type II). Electrotonic modulation and reflection could coexist, the type of behavior depending on the phase relation between focal and extra-focal action potentials. An example is illustrated in which type I reflection occurred only when preceding driven activity induced overdrive suppression of exit conduction from the focus. The results suggest that, in infarcted tissue, entrance and exit conduction delays to depolarized foci may form the basis for the occurrence of reflected reentry.

Action Potentials↗

PubMed1992

Dynamic optical property changes: implications for reflectance feedback control of photocoagulation.

During laser treatment, coagulation affects the optical properties of the tissue. In particular, the formation of a white lesion significantly increases the scattering coefficient. This change in the optical properties in turn affects the laser light distribution in the tissue. The white lesion formed during photocoagulation of the retina has a dynamic effect upon reflection and fluence rate. This problem has been simulated on a model medium consisting of a thin absorbing layer covered with a 1 cm thick layer of albumin. The albumin layer is subdivided into coagulated (white) and uncoagulated (clear) layers. The optical properties of each layer have been determined and these values have been used to model light distribution in the medium. One-dimensional adding-doubling and three-dimensional Monte Carlo methods have provided light distributions in the medium for varying thicknesses of the coagulated albumin. Computed fluence reaching the absorbing layer decreased in the presence of a 275 microns or thicker coagulated layer. The coagulated layer attenuates light because it is highly scattering; however, this scattering also leads to a sub-surface peak in fluence rate at a level higher than the incident fluence. The latter effect outweighed the former for coagulated layer thicknesses less than 275 microns. Computed reflectance of argon laser light from a semi-infinite coagulated region initially increased linearly as a function of thickness. As the coagulation thickness increased beyond 4-5 optical depths, the reflectance approached a constant value, R infinity, at 9 optical depths (2 mm). Experimentally measured total reflectance is shown to be an inadequate indicator of the thickness of a lesion (finite coagulated volume); however, central reflectance from a lesion measured with a CCD camera confirmed the computed trends. These results provide a theoretical foundation for control of lesion thickness using reflectance images.

Argon↗

PubMed1990

Hazards of laser beam reflections in eyes containing gas.

Three patients suffered photic or thermal laser injuries at unintended sites because of reflection from gas-fluid interfaces in eyes containing gas. Fresnel's equations predict the amount of light transmitted or reflected at optical interfaces. Application of Fresnel's equations demonstrate that significant laser reflection occurs at gas-fluid or fluid-gas interfaces, especially at high angles of incidence. Photocoagulation across gas-fluid or fluid-gas interfaces should be avoided to reduce the risk of unintended damage from reflected light. If photocoagulation must be performed across an interface, the surgeon should minimize the angle of incidence of the treatment laser beam, use a divergent beam, and consider the location and intensity of the reflected beam. Because of the higher phototoxicity of blue light, photocoagulation with blue-green lasers across gas-fluid or fluid-gas interfaces is undesirable. Proper polarization of the treatment laser beam may significantly reduce laser reflectance.

Aged↗

PubMed1995

Developing and maintaining reflection in clinical journals.

There is a pressing need in today's world for nurses who are willing and able to transform health care. Teaching strategies that foster reflection are in order. The use of dialogue journals has been widely reported in the nursing literature as an effective strategy for assisting students to reflect about learning experiences in the clinical area. Despite the promise that journal writing will enhance students' ability to reflect on their clinical learning experiences, not all students respond positively to journal writing as a learning tool. The paper is a discussion of some of the common difficulties that arise in the use of clinical journals as a reflective strategy in nursing education. Common problems in the use of clinical journals include procrastination; superficial, nonreflective entries; waning enthusiasm about the activity; and unwillingness or inability to reflect. The possible etiologies for these problems will be explored. Specifically, the paper will focus on ways to prevent or minimize these concerns by maintaining and enhancing the factors required for students to reflect in clinical journals.

Autobiographies as Topic↗

PubMed1996

Student reflective groups at a Scottish College of Nursing.

In this paper student views on reflective groups, set up as an important element of the new Project 2000 course in a Scottish College of Nursing, are reported. A random sample of 19 students were interviewed. While the reflective groups were very popular with students because they provided support, there was little evidence of a linkage between theory and practice. It was clear that the ambitious objective of stimulating reflection-on-action was not attained. Practice certainly was discussed, but it tended to be dominated by dramatic and emotionally charged aspects of care rather than the more frequent routine concerns. There were, however, indications that the original aim of the reflective groups could be achieved if tutors could establish a common understanding of the purpose of the groups and of reflection, and if the practices on which students reflected consisted less of single day visits where the students saw themselves as nonparticipant outsiders.

Education, Nursing, Baccalaureate↗

PubMed1997

Using patients: exploring the ethical dimension of reflective practice in nurse education.

Within nurse education there is a growing interest in the use of reflective practice as a vehicle for professional development. Additionally, clinically reflective practice is seen as an ideal way of improving performance and patient care. In this paper it will be argued that whilst this development is potentially valuable to both professionals and clients, there are major ethical issues which need to be addressed. The "how to' literature appears to focus predominately on the practitioners subjective description and interpretation of events. It is usual for these events to include details of clients: but not usual for clients to be aware that information about them is being used in this way. Within a deontological ethical framework the use of people as means rather than ends is considered to be morally wrong. However, clients have probably always been used by professionals to some extent: Things such as case conferences and clinical trials are legitimated by the intention to improve training and practice, and are regulated by various professional codes and committees. It would appear, however, that reflective practice is quantitatively and qualitatively different from the above, and thus may cross a moral boundary. Reflective practice is not simply re-examining someone's case: it involves personal interpretation and judgement. The reflector may be recording incidents, verbally or in written form, which would not otherwise be recorded, and may be controversial. This raises questions about the nature and ownership of knowledge, and the responsibilities of people who have such knowledge. Systematic and continued reflection may be akin to action research and, as such, considerations of rigour, authenticity and informed consent need to be addressed. Thus whilst reflective practice may prove to be a good thing, it cannot be seen in isolation from wider ethical concerns.

Education, Nursing↗

PubMed1992

Comparison of reflection and transmission pulse oximetry after open-heart surgery.

OBJECTIVE: To determine if there was a difference between reflection and transmission pulse oximeters in their ability to regain data display after hypothermia in patients recovering from open-heart surgery. DESIGN: Prospective, randomized, controlled study. PATIENTS: Nineteen adult patients scheduled for open-heart surgery were studied immediately after surgery in the ICU. INTERVENTIONS: Transmission and reflection sensors were used in random order in two simultaneously monitoring identical oximeters and probes. The time difference at the start of display between the oximeters was measured and the skin temperatures in the region of the probes, cardiac index, systolic BP, pulse pressure, and systemic vascular resistance index were recorded. RESULTS: The mean skin temperatures at the probe sites differed significantly (p = .001) at the moment of data acquisition. The mean forehead, ear lobe, and fingertip temperatures (simultaneously measured) were 33.9 degrees C, 31.8 degrees C, and 28.8 degrees C, respectively. The hemodynamic variables were comparable at the moment when the oximeters resumed display. The reflection probe was the first to resume function in 12 patients and the transmission probe was the first to resume function in four patients (p less than .02). The bias of the reflection probe was 1.4% (SD 2.2) and that of the transmission probe was -0.4% (SD 2.7). All the patients were normoxic throughout the study. CONCLUSION: The forehead reflection probe regained signal detection earlier than the transmission probe on the ear lobe in patients with compromised peripheral blood flow and cool periphery. This finding may be due to higher skin temperature at the reflection probe site, since the systemic hemodynamic conditions were equal at the time of the data acquisition of both sensors.

Adult↗

PubMed1979

Resentful and reflective coping with arbitrary authority and blood pressure: Detroit.

Two hypotheses about coping with an arbitrary authority, an angry boss, were tested: (1) styles of handling anger vary with social status, and (2) these styles are in turn related to blood pressure levels. Two styles of coping were tested: model R-R, Resentful vs. Reflective, and model I/O/R, Anger-In, Anger-Out, and Reflective. Handling an angry boss by Reflection is reported by more women than men, by those in middle-class areas rather than lower class, and does not vary by race. Working class report more use of Anger-Out than middle class who in turn report more use of Reflection. In general, the Anger-In response did not vary by race, sex, or area of residence (12-18%). For model R-R, Reflection of boss's anger was related to lower blood pressure when compared to Resentful responses, within sex, race, and residence groups. For model I/O/R, working-class, high stress persons who expressed Anger-Out showed the highest mean levels. Reflection is an appraisal response related to vascular and neural deceleration in stress experiments. This mode can be learned, and may aid in handling daily emotional-loaded stimuli to control blood pressure, along with learning a relaxation response.

Adaptation, Psychological↗

PubMed1992

Anxiety, accuracy and reflection: the limits of professional development.

Reflection is a key concept in the development and maintenance of nursing expertise in theory and practice, yet commentators have rarely examined difficulties associated with it. This paper describes the role of reflection in nursing and relates it to information-processing accounts of human memory. The issues raised by the role of memory in mediating reflection are discussed, in the context of an examination of the importance of accuracy in reflection-on-practice. It is argued that anxiety is of particular importance in mediating accurate reflection. Whilst it is concluded that reflection is inherently flawed, a range of tactics to enhance it are explored, with particular emphasis on anxiety reduction and reduction of the burden of the memory task.

Anxiety↗

PubMed1984

Surface reflection interference microscopy: a new method for visualizing cytoskeletal components by light microscopy.

Surface reflection interference microscopy of detergent resistant residues of cultured cells stained with protein dyes can be used to obtain high resolution images of the cytoskeleton. We have compared the images obtained using different dyes and have examined the effect of four of these dyes on the visualization of different parts of the cytoskeleton in detail. The dependence of contrast of the images obtained on the illuminating numerical aperture and the wavelength of incident light was determined. Staining with Acid Yellow 36, Guinea Green B and Naphtol Blue Black produces images from the entire cytoskeleton and contrast in these images is relatively insensitive to changes in the incident wavelength. Coomassie Brilliant Blue R250 images, on the other hand, result primarily from reflection from the lower surface of the cytoskeleton and the contrast of these images is sensitive to changes in incident wavelength dropping abruptly in the region of the transmission peak of the stain. From the different spectral sensitivities of the reflection images obtained and from differential interference effects at low and high illuminating numerical apertures, we conclude that the reflection images obtained using the first three stains result from modulation of the reflection by interference effects. In contrast, in the case of Coomassie Brilliant Blue R250 the resulting image originates mainly from selective reflection of wavelength near the absorption range of the dye.

Animals↗

PubMed1994

VDT screen reflections and accommodation response.

Reflections in computer screens are imaged behind the screen and therefore potentially create a conflicting cue to appropriate accommodation response to the plane of screen. We investigated the effect of screen reflections on accommodation response by producing reflections (1.33 D accommodation demand) surrounding and overlying the fixation point (2 D accommodation demand) in the screen. We have found little evidence that reflections in visual display terminal screens can influence the accuracy of the users' accommodation responses under normal binocular viewing conditions. The accuracy of the accommodation response was not significantly influenced by the position of the reflections, the presence of surrounding text (peripheral cues), or the subjects' dark focus level. The variability of accommodation response did not significantly change under the various test conditions. However, accommodation errors were apparent to a small degree (< 0.25 D) under some monocular viewing conditions in the presence of screen reflections.

Accommodation, Ocular↗

PubMed1984

Prediction versus reflection in therapist demonstrations of understanding: three analogue experiments.

Many forms of therapy deem it important for therapists to demonstrate to their clients that they understand the particular client's dilemma. The most common approach to therapists' demonstrations of understanding is the Rogerian method of reflection. Another approach to demonstrating understanding is to make accurate predictions of the client's behaviour. The purpose of the present experiments was to test the hypothesis that therapist predictions (predictive interactions) would be viewed by observers as more demonstrative of understanding the client than therapist reflections (reflective interactions) and therapist admissions of not understanding the client's problem (naive interactions). In each experiment, subjects were randomly assigned to conditions, read excerpts from an interview transcript, and then rated therapist understanding of the client's problems and therapist demonstrations of understanding. The results of all three experiments were consistent and indicated that: predictive interactions were judged as superior to reflective interactions and naive interactions on ratings of demonstrated understanding; reflective and naive interactions did not differ on any measure. These results question the utility of reflective interactions in clinical practice for communicating understanding to clients and support the notion that accurate therapist predictions of client behaviour may be more useful in demonstrating understanding. The results also indicate the need to study these phenomena more thoroughly in clinical settings.

Adult↗

PubMed1989

Reflected reentry, delayed conduction, and electrotonic inhibition in segmentally depressed atrial tissues.

Reflection is a subclass of reentrant cardiac arrhythmias in which reexcitation of the heart occurs as a result of to and fro electrotonically mediated transmission of impulses across a narrow zone of impaired conductivity. Although relatively well characterized in ventricular tissues, the reflection mechanism has not been studied in atrial tissues. In this study we examine the possibility of reflected reentry in segmentally depressed atrial tissues and evaluate conduction characteristics in these preparations. Narrow strips of atrial pectinate muscle or crista terminalis (canine and calf) were placed in a three-chambered bath and the central segment was superfused with an isotonic sucrose solution or an "ischemic" Tyrode's solution. Proximal to distal conduction across the 1.0- to 1.2-mm wide ischemic gap showed step delays as long as 210 ms. Reflected reentry was readily demonstrable when prominent step delays occurred during anterograde conduction of the impulse across the gap. Progressive acceleration of the stimulation rate resulted in progressively greater impairment of anterograde conduction until complete block occurred. The incidence and patterns of reflected reentry were therefore a sensitive function of the stimulation rate. Other features exhibited by these preparations include a slow recovery of excitability following the action potential, postrepolarization refractoriness, and electrotonic inhibition and summation. Our data suggest that the characteristics of conduction and reflection in segmentally depressed atrial tissues are qualitatively similar to those in ventricular tissues. The presence of electrotonic inhibition in atrial may also help to explain the functionally inexcitable zone seen in the vortex of the leading circle model of atrial flutter.

Action Potentials↗

PubMed1993

Gestational age correlates with skin reflectance in newborn infants of 24-42 weeks gestation.

Accurate gestational age determination is limited in very low birthweight infants using neurological and physical assessments. As one of the markers of intrauterine development, skin maturation is assessed qualitatively by pediatricians. Based on this observation, we hypothesize that skin reflectance relates directly to gestational age. Light was delivered and collected from the skin through a topically placed optical patch. Reflected light was detected by the spectrophotometer and corrected by an adjacent laptop computer to yield the true total diffuse reflectance as a function of wavelength between 380-820 nm. The calculated reflectance at 837 nm (R837) where it is independent of melanin, was determined by extrapolation from the reflectance at 650 and 750 nm. Sixty-four neonates of different races with gestational ages of 24-42 weeks were studied at 2-151 h of age. R837 was related exponentially to gestational age (GA) by the equation R837 = Rmax(1-exp[-(GA-G0)/tau]), where Rmax is the maximal value of R837, G0 is an apparent delay time before dermal scattering increases rapidly, and tau is a time constant, r = 0.88, p < 0.001. In summary, the extrapolated skin reflectance offers a quantitative and objective assessment of gestational age which is independent of melanin and sex.

Black People↗

PubMed1981

Manipulation of ascending aortic pressure and flow wave reflections with the Valsalva maneuver: relationship to input impedance.

Dramatic changes in the shape of pulsatile ascending aortic pressure and flow wave forms occur during the Valsalva maneuver in man. To study these changes, aortic pressure and flow signals were recorded in eight patients using a multisensor catheter. Aortic input impedance was derived during the control, strain and postrelease phases of the Valsalva maneuver. During control, well-defined minima and maxima occurred in the spectral plots of impedance moduli. This pattern was accentuated during the postrelease phase. In contrast, input impedance during strain was almost equal to the characteristic impedance for all harmonics. These results imply that during the control and postrelease phases, strong reflections return to the ascending aorta, but during the strain phase, reflections are minimal, absent or more diffuse. From wave transmission theory, it also follows that pulsatile pressure and flow wave forms should be similar in shape in the absence of reflections and dissimilar in the presence of reflections. This was observed in all eight patients. By provoking changes in the arterial tree during the Valsalva maneuver, the magnitude and timing of wave reflections were significantly altered, resulting in marked changes in the shape of pulsatile aortic pressure and flow wave forms. This study demonstrates the importance of reflections in determining the shape of the arterial pulse.

Adult↗

PubMed1976

Skin reflectance in the newborn infant.

Skin reflectance in red, green, and blue light was measured at the sternum of 99 Caucasian infants ranging in gestational age from 26 to 44 weeks. Skin reflectance was consistently higher in female infants, but this difference was not statistically significant. Highly significant (P less than 0.001) increases in reflectance at all wave lengths were found when sternal reflectance during the first 48 hr of life was related to gestational age. The dispersion of data points about the regression line does not permit this method to be relied upon as the sole means of determining gestational age of infants. Serial studies indicate that reflectance increases in premature infants not given phototherapy, whereas premature infants receiving phototherapy show a fall in reflectance for the duration of therapy. This suggests that phototherapy may cause tanning of the skin.

Gestational Age↗

PubMed1997

Impulsive-reflective cognitive style, metacognition, and emotion in adolescence.

The study investigated the relationship between reflective or impulsive cognitive style, metacognitive functioning, and depression in young adolescents. Metacognitive functioning (metacognitive knowledge about reading and memory, monitoring of text comprehension) and self-reported depressive feelings were analyzed in a group of subjects who showed a Reflective or Impulsive cognitive style. The sample consisted of 56 junior high-school students (Grades 6, 7, and 8) selected from a larger original group of 61 subjects. We excluded from the original group those with an IQ below 75 on both the Verbal and Performance subscales on the short form of the WISC-R, those reported by teachers to have a severe learning disability, and those that did not complete the test battery due to long absences from school. The reflective-impulsive cognitive style was identified with the Matching Familiar Figures Test-20. Using the median of the distribution for both Latency (17 sec. per item) and Errors (9 errors) on this task, the sample was divided in four partially overlapping subgroups: 16 with Impulsive cognitive style (Latency below the median, Errors above the median), 13 with Reflective cognitive style (Latency above the median, Error below the median), 4 fast and accurate (both scores below the median), and 11 slow and inaccurate (both scores above the median). Twelve subjects with one or both scores coinciding with the critical value (median) were excluded. Analysis showed that subjects with Impulsive cognitive style had significantly lower scores than those with Reflective cognitive style in monitoring of comprehension of text. No differences were found on monitoring by eighth graders, irrespective of cognitive style. No differences between the two groups were found in metacognitive knowledge. Subjects with Impulsive cognitive style had significantly higher scores than subjects with Reflective cognitive style on a self-rating scale for childhood depression, the Children's Depression Inventory. The implications of these data are discussed.

Adolescent↗