Normal Room Light Research Articles

The Stability of Amikacin, Gentamicin, and Tobramycin in Total Nutrient Admixtures

Amikacin (A), gentamicin (G), and tobramycin (T) were added to eight different total nutrient admixtures (TNA) with varying concentrations of dextrose, amino acid, and fat emulsion to determine drug and emulsion stability. All TNA were prepared aseptically and stored at room temperature under normal room lighting for 12 hr before drug addition. One volume of each drug was added to an equal volume of each of the eight TNAs to simulate 1:1 piggyback contact volumes. Samples were left at room temperature for 6 hr. Drug concentrations were analyzed by fluorescence polarization immunoassay. TNA/drug admixtures were pH tested and visually inspected before and after centrifugation in microhematocrit tubes, noting signs of emulsion stability at 1 and 6 hr. Emulsion particle size was determined at 1 and 6 hr using interference contrast microscopy. All three drugs retained their immunoreactivity in all TNAs for at least 6 hr. G and T were stable in all eight TNAs for at least 6 hr with no significant effect on emulsion particle size or stability after centrifugation. A was incompatible with all eight TNAs, resulting in visual breaking of all emulsions within 1 hr. Therefore, G and T, but not A, can be administered via piggyback method with the eight TNAs tested if the infusion is completed within 6 hr.

Anatomical plasticity of synapses in the lamina of the optic lobe of the fly

Insects are frequently assumed to have hard-wired nervous systems that fail to demonstrate functional plasticity. We have produced changes in synaptic frequency, and analysed their developmental time course, dynamics and reversibility, in the lamina underlying the compound eye of the fly, by exposing young adults to different visual stimuli. The class of synapse examined feeds back from L2, one of the monopolar cells found in each lamina cartridge, to photoreceptor terminals; each site is a synaptic dyad marked by the presence of a few, round vesicles surrounding a T-shaped presynaptic ribbon and, in the photoreceptor, by a subsynaptic vacuole. In control adult flies reared in normal room lighting, the frequency of synaptic profiles scored in micrographs of single sections initially increased until one day post-eclosion (E + 1), but declined thereafter. Frequencies measured in left and right eyes of the same control animals were closely matched. Experimental flies were put for one to two days into an integrating sphere illuminated continuously with square-wave, 25 Hz green light. They had one eye occluded, so providing control comparisons between flicker-reared (FR) and occluded (dark-reared, DR) eyes within the same animal. The DR eyes invariably (n greater than 22) had higher frequencies of synaptic profiles than those seeing light, regardless of age or the period of light exposure, although the detailed relative effects of FR and DR depend upon the age of the animal. The evidence suggests that exposure to light actively depresses synaptic frequency and increases its variability. The greatest difference (30%) achieved was at two to four days after eclosion and there was no difference beyond six days, so demarcating a prospective sensitive period. Rearing in DC light was equally effective as FR, so visual contrasts per se are apparently inessential. Frequency values can change rapidly. During the first 24 h post-eclosion, DR resulted in new synapses adding to L2's complement of 25-35 at a maximum rate of 4 per 6 h, whereas light exposure caused a frequency decrease after as little as 6 h. Alternating 24 h periods of light and dark during the first two days produced reversible synaptic frequency changes. Individual synaptic contacts enlarge with age but not significantly with different visual experiences. The decrease in frequency of synaptic profiles with age thus actually underestimates the true decrease in synaptic number, whereas the altered synaptic frequencies seen after differential exposure represent true differences in synaptic number.(ABSTRACT TRUNCATED AT 400 WORDS)

A hand optometer for measuring dark focus

To measure the accommodative state of the eye in a stimulus free condition, the so called dark focus, a simple optometer was constructed based on the principle of the polarized vernier optometer originally proposed by Moses (1971). Data obtained with this hand optometer were compared with those of two other subjective techniques, the polarized vernier optometer and the laser optometer, and were found to be similar. The advantage of this hand optometer is that it is a convenient device that allows one to measure the dark focus within minutes, under normal room lighting.

Sex differences in investigatory and grooming behaviors of laboratory rats (Rattus norvegicus) following exposure to novelty.

Prior research suggested that during exposure to novel stimuli, rodent investigation and self-grooming behaviors may be sexually dimorphic and interact with ambient illumination. To test this notion we compared the behavior of adult male and female groups of Long-Evans hooded rats in normal room lighting (860 lx) and in very dim, red light (0.2 lx) following exposure to a novel juvenile conspecific. Illuminance level had little or no effect, but investigatory and subsequent self-grooming behaviors of males were substantially greater than those of females, and females engaged in greater ambulatory activity than did males. In a second experiment adult males and females were exposed to a novel inanimate object. No reliable sex differences were observed. We conclude that social novelty, as provided by exposure to a juvenile conspecific, stimulates greater investigation and postinvestigatory self-grooming than exposure to a novel inanimate object and that exposure to novel conspecifics presents a useful method for the investigation of sex differences, gonadal hormone effects, and interactions of hormones with neurotransmitter systems governing motor control systems.

Assessing Optimal Illumination for Visual Response Accuracy in Visually Impaired Adults

The currently accepted position concerning recommended lighting for visually impaired individuals is that individually identified and specified lighting is required for these persons to attain optimal visual performance. However, there is presently no formula for predicting the placement or intensity of a light source needed for any given patient, nor are there any specific rules for determining optimal illumination for visually impaired individuals. The purpose of the present study was to determine (a) if individual levels of optimal illumination could be reliably determined for visually impaired adults, and (b) if the level identified in assessment had validity in relation to a practical reading task. Visual response accuracy was assessed across 10 levels of illumination which were all greater than normal room lighting. Each level was presented 4 times for a total of 40 experimental trials.

Movement under emergency lighting: the effects of changeover from normal lighting

This paper considers how people's ability to move over an escape route is affected by different procedures for changing from normal room lighting to emergency lighting. The experiment took place in a large open plan office at two emergency lighting illuminances, 0.16 lx and 0.012 lx. The changeover to emergency lighting was either instantaneous or involved a 5 second period of darkness before the emergency lighting came on, as is allowed by BS 5266. The subjects were instructed either to move as soon as the emergency lighting came on or to wait until they felt able to move unhesitatingly over the escape route. The time taken to leave the office, the manner of movement and subjects' opinions of the conditions were all recorded. They showed that movement was faster, smoother and easier at 0.16 lx than at 0.012 lx, for all conditions. When the subjects moved immediately the emergency lighting came on, having a 5 second period of darkness allowed more rapid, steadier movement with fewer collisions once movement started. However, the total time taken to leave the room was slightly longer than if the subjects moved immediately following an instantaneous changeover. Allowing the subjects to wait until they felt able to move unhesitatingly, ensured smooth steady movement but the total time taken at 0.012 lx was much longer than if the subjects started to move immediately after the changeover. Estimates of the state of adaptation of the visual system following a step change in luminance provide a plausible explanation of all these results.

Biochemical studies on the effects of continuous light on the albino rat retina

The causal mechanism of light damage in the albino rat retina has been investigated. Male and female albino Wistar rats weighing 200–300 g and previously maintained in normal room lighting of approximately 15 hr light (0·85±0·05 × 10 −4 W cm −2) per 9 hr dark cycle were simultaneously exposed continuously to uniform fluorescent light flux of 3·01±0·5 × 10 −3 W cm −2 for a period of 6–18 hr. The animals were killed immediately after exposure and the retinas analysed for their contents of DNA, protein and lipids. There were significant losses of retinal DNA, protein, total lipid and polyunsaturated fatty acids, particularly docosahexaenoic acid. The losses were progressive with duration of exposure. There were also changes in phospholipid subclasses. These results could indicate altered photoreceptor-membrane viability secondary to continuous illumination. The ultimate effect would be the loss of photoreceptor cells with a concomitant loss of normal physiological function. Generally, gender was found to play no significant role, thus excluding possible endocrine interference. It is suggested that lipoperoxidative reactions could account for the observations made in this study. The danger of over-exposure to radiant flux in the tropics is inferred from these observations.

Movement under emergency lighting: the effect of illuminance

This paper describes an investigation carried out in a large open plan office with the aim of identifying the illuminance necessary for rapid, safe movement under emergency lighting conditions. In the experiment, the times taken for each subject to cover an escape route were measured. The manner in which the subjects moved was observed and their opinions of the conditions were noted. This data was collected from sixty subjects in all, twelve at each illuminance condition. The subjects were not familiar with the office and were of working age. From the data collected it is concluded that at a mean illuminance of 0.2 lx, people experience some difficulty in moving quickly and unhesitatingly over the escape route. At a mean illuminance of 1 Ix there is no difficulty in moving smoothly and steadily over the escape route at a speed similar to that achieved under the normal room lighting. These results suggest that the present emergency lighting criterion of a minimum illuminance of 0.2 Ix is only reasonable if it is indeed treated as an absolute minimum. They also indicate that it would be useful to adopt a mean illuminance of 1 Ix on the escape route as an additional emergency lighting criterion. Three subsidiary experiments were carried out to explore the effects of age, familiarity with the office and group movement rather than individual movement. These subsidiary experiments showed that these factors made little difference to the subject's ability to move under the emergency lighting. Therefore the conclusions reached for the main experiment also apply to older people of working age, to those who are familiar with the space and to people moving in small groups.

Nifedipine stability in cardioplegic solution

The stability of nifedipine in cardioplegic solution was studied. Cardioplegic solutions containing nifedipine at 275 and 500 micrograms/liter were stored in plastic bags covered in brown plastic wrappers (1) under normal room light at 25 degrees C and (2) in a dark refrigerator at 4 degrees C. Samples were removed periodically for 48 hours. Infusions of cardioplegic solution containing 275 micrograms/liter were simulated using tubing and flow rates of 100, 200, and 300 ml/min; bags were covered with aluminum foil, while tubing was exposed to normal room lighting or yellow lighting, which does not degrade nifedipine. Gas chromatography was used for nifedipine assays. Nifedipine degraded more rapidly at 25 degrees C than at 4 degrees C. However, even when protected from light and refrigerated, nifedipine concentrations declined to less than 90% of original potency by approximately six hours after preparation. There was no significant degradation during the simulated infusion regardless of light exposure or flow rate. Cardioplegic solutions containing nifedipine should be prepared immediately before the surgical procedure, refrigerated until use, and protected from light until administration.

Electrical conduction and low voltage blue electroluminescence in vacuum-deposited organic films

Bright blue (400–500 nm) recombination electroluminescence (EL) has often been observed from anthracene crystals with solid electrodes; external quantum efficiencies of 1%–8% have been seen and the theoretical efficiency is approximately 40%. The power efficiency has always been greatly degraded by the high voltages necessary to obtain reasonable currents through the comparatively thick crystals used. We report the preparation, and the structural, electrical and EL properties of approximately 0.6 μm vacuum-deposited anthracene films through which large steady state current densities can be passed at rather low applied voltages. The films showed the critical optimization effect, various structural and electrical properties exhibiting sharp singularities when the films were prepared at substrate temperatures within a narrow range near −60 °C. EL visible in normal room lighting was obtained at applied voltages of only about 30 V and up; in thinner films, EL could be seen in a darkened room at only about 12 V. This is apparently the first time that clearly visible EL has been reported from an organic material at voltages significantly less than 100 V. Broadly similar results were obtained for perylene and 1,12-benzperylene films; EL does not appear to have been observed before from these substances in any form. We discuss in some detail the prospects for practical EL devices based on organic films. In view of our results, and of the great improvements which are now probably feasible, we conclude that the prospects are promising; if these improvements can be realized, such devices could include high efficiency blue light-emitting diodes, and large-area broader wavelength systems for illumination applications.

The Baylor Video Acuity Tester.

A device has been developed that offers many advantages not available with traditional visual acuity testing methods. The Baylor Video Acuity Tester (BVAT) produces randomized targets, size selectable at electronic speeds for testing even in normal ambient room light. Comparisons of the BVAT with the Project-O-Chart (American Optical Corp, Southbridge, Mass) on 60 subjects yield correlations of .93 and .95. A test-retest correlation of the BVAT of .88 was found.

A 35 mm Hologram Camera

AbstractThe measurement facilities available from holographic interferometry are well known. It is, however, an inconvenient technique to operate and its use may be precluded when contemplating work outside the confines of a vibration isolated table located in a blacked out room.Based on a standard 35 mm rdlex camera the interference camera described here circumvents these difficulties. Using the principles of common path interferometry and white light holography, interferograms can be taken under normal room lighting conditions. Apart from the laser required to illuminate the object under study, operation of the camera is similar to ordinary photography there being no need for elaborate vibration isolation. An economic advantage is also realized by using acetate-based roll film in place of the usual glass backed plates.

The effect of long-term constant light on the frog pigment epithelium

Frogs exposed to constant normal room light (40 ft-c.) for 14 months were found to have a swollen pigment epithelium. The principal morphological feature seen in these swollen pigment epithelial cells was a vast array of smooth endoplasmic reticulum. and all of the normal cytoplasmic organelles were displaced to the apical margins of the cells. However, the underlying photoreceptors were undamaged and the outer segment showed no signs of swelling or vesiculation. When a dark/light period was used to induce rod shedding in these animals, shedding, ingestion, and phagocytosis occurred normally. The same general morphological changes, with an absence of swelling, could be induced in normal frogs using bright flashes of light followed by a period of darkness. Thus, the principal morphological effect of long-term constant light on the frog retina is on the pigment epithelium.

A holographic interference camera

Describes a regular 35 mm reflex camera modified to incorporate the principles of the Lippmann-Bragg diffraction effect and focused image holography. This modification enables holographic interferometry to be executed in normal room lighting conditions without the need for elaborate vibration isolation.

Bilirubin Dynamics in the Gunn Rat during Phototherapy

Bilirubin dynamics were studied in homozygous Gunn rats under normal room lighting conditions and under conditions simulating phototherapy. A kinetic model was developed for the formation, distribution, and elimination of bilirubin. The decrease in plasma bilirubin concentration during illumination with low intensity [300 footcandles (fc)] and high intensity (1000–1100fc) light was studied. The plasma bilirubin concentration in the rats decreased under phototherapy until a new steady-state concentration was reached, the decline being more rapid under high intensity light conditions. Gunn rats were also injected with a tracer dose of 14C-bilirubin following a period during which the rats were illuminated with low or high intensity light. The distribution and elimination of the labeled bilirubin were followed under continuous illumination. The chosen kinetic model, when adapted to the set of data under investigation, fit all of the data concerning bilirubin kinetics in Gunn rats under continuous illumination.

The effect of ambient illumination on delayed-matching and delayed-response deficits from cooling dorsolateral prefrontal cortex

The possibility was examined that the delay-dependent increase in delayed matching-to-sample (DMS) and delayed-response (DR) errors induced by prefrontal cooling (FC) could be modified by changes in ambient illumination. Monkeys were tested in normal room lighting and in the dark with intratrial delays of 1–32 sec during FC and normal brain temperature (no cooling, NC). The results showed that FC increased errors and motor activity on trials with long intratrial intervals but had little effect with short delays. Ambient illumination had little effect during either FC or NC. The results are discussed in terms of relative differences in novelty of lighting or darkness with respect to the level of illumination during training.

The effect of visible light on the regeneration of rhodopsin

Both in vitro and in vivo , increased exposure to visible light decreases the regenerability of the visual pigment. Isolated opsin irradiated with increasing periods of white light decreased in pigment formation yields on combination with 9- or 11- cis retinal. The yield of regeneration of the visual pigment extracted from albino rats depended on the amount of light to which the animal had been exposed. Animals exposed to normal room light demonstrated lower regeneration yields than dark-reared animals, but these yields increased on dark adaption. Opsin from animals exposed to sunlamps did not regenerate any pigment. On dark adaption, the pigment yields increased but the opsin level remained below that for the control group.

A Small and Inexpensive Ultraviolet Dose-Rate Meter Useful in Biological Experiments

Although ultraviolet radiations are used extensively in biological experiments, the nonphysicist often finds their measurement tedious and expensive. This article describes a dose-rate meter of good accuracy and precision that is less expensive and more versatile than currently available devices. Because its output depends on wavelength, it is normally useful only where the spectral composition of the radiation is constant, as, for example, with low-pressure mercury arc "germicidal" lamps (emission chiefly at 2537 A) and fluorescent "black light" lamps (emission chiefly at 3000 to 4000 A).2 There are many ways of measuring ultraviolet radiations (1, 2). Some portable devices are described by Luckiesh (3) for use in various ultraviolet regions and fall into two categories, phototube types and photovoltaic-cell types. The phototube types are generally complex, requiring electronic circuits and batteries. A typical one is manufactured by General Electric (4) and is hereinafter referred to as the "GE meter." It consists of a battery-operated phototube with associated circuit and a direct-reading meter, all enclosed in a metal box about 11 x 15 x 16 cm. Its advantages are that it (1) is very sensitive and consequently has a very wide range, (2) comes ready to use, so that calibration is not necessary for the first few years of operation, and (3) has no response to normal room light. Unfortunately, it is expensive and too bulky for many experimental uses. Its complexity and requirement of batteries are further disadvantages. The photovoltaic-cell types are simpler, smaller, less expensive, and require no batteries, but they lack the very high sensitivity of the phototube types. Probably the simplest such device is a small General Electric light meter (photovoltaic cell attached directly to a meter) with an attachment consisting of a layer of zinc