Photostimulation Research Articles

Influence of ovariectomy and photostimulation on luteinizing hormone in the domestic turkey: evidence for differential regulation of gene expression and hormone secretion.

We have investigated the effects of ovariectomy (OVX) and photostimulation (PS) on anterior pituitary LH beta mRNA abundance and circulating levels of LH in the domestic turkey. The birds were divided into the following four treatment groups: non-PS SHAM, PS SHAM, non-PS OVX, and PS OVX. Photostimulation was initiated 7 days after OVX. Anterior pituitaries and blood samples were collected on Days 0, 1, 3, 7, 14, and 26 after PS. The experiment was terminated when the PS SHAM birds were laying eggs regularly. Photostimulation of intact birds induced an increase in both LH beta mRNA levels (Days 3, 14, and 26 of PS) and serum LH (Days 14 and 26 of PS; p < 0.05), while OVX of non-PS birds significantly elevated LH on Days 7, 10, 21, and 33 and LH beta mRNA levels on Days 7, 8, 10, 14, and 33 post-OVX. Circulating LH titers in the PS OVX birds were well above the levels in the non-PS OVX group (p < 0.005); however, LH beta mRNA abundance was not significantly greater (p > 0.05). Our results indicate that OVX and PS appear to be additive in stimulating LH secretion but do not have this effect on LH beta mRNA levels. We have hypothesized that gonadectomy induces near-maximal accumulation of LH beta mRNA and that therefore the subsequent stimulus of a long photoperiod has no additional effect. We suggest that increases in serum LH levels, beyond those of the OVX bird, may be controlled post-transcriptionally.

Visual evoked potential monitoring of optic nerve function during surgery.

A study was made with intra-operative flash--visual evoked potentials (VEP) monitored using a fibre-optic/contact lens photo stimulator in 57 patients undergoing intra-orbital surgical procedures with potential risk to the optic nerve. The VEPs recorded under enflurane and nitrous oxide anaesthesia did not differ significantly in latency or amplitude from the pre-operative recordings. Transient abolition of the VEP was seen under many circumstances and did not correlate with the outcome of surgery, but absence of a previously normal VEP for more than four minutes during surgical manipulation within the orbit did show a correlation with post operative impairment of vision. The technique provides early warning to the surgeon of threats to the integrity of the optic nerve.

Photostimulation studies in pure and Li-doped alkali halides

Room temperature X-rayed single crystals of KCl and KCl:Li are subjected to photostimulation (PS) at liquid nitrogen temperature (LNT) with light corresponding to their F-band (F-light). Out of the six and seven monochromatic thermoluminescence (MTL) glow peaks of X-rayed KCl and KCl:Li crystals, only four and six glow peaks, respectively, are found to be stimulable with F-light. A similar experiment is made with pure and Li-doped KBr crystals, X-rayed at −50 °C and F-stimulated at LNT for 15 s. Out of six MTL glow peaks both in KBr and KBr:Li, two and four MTL glow peaks, respectively, are found to be stimulated with F-light at LNT. The different photostimulated MTL peaks are attributed to shallow F- and F'-centre traps filled either by the capture of photo-electrons from the conduction band or through electron tunneling from an excited state F-centre to a neighbouring F-centre. The apparent differences in pure and doped system with regard to photostimulation are attributed to the incorporation of Li-ions in the lattice. KCl- und KCl: Li-Einkristalle, die bei Raumtemperatur rontgenbestrahlt werden, werden einer Photostimulation (PS) bei der Temperatur des flussigen Stickstoff (LNT) mit Licht entsprechend ihrer F-Bande (F-Licht) ausgesetzt. Von den sechs und sieben monochromatischen Thermolumineszenz-Glowmaxima von rontgenbestrahlten KCl- und KCl:Li-Kristallen werden nur vier bzw. sechs Glowmaxima gefunden, die mit F-Licht stimulierbar sind. Ein ahnliches Experiment mit reinen und Li-dotierten KBr-Kristallen wird an Kristallen durchgefuhrt, die bei LNT 15s mit F-Licht stimuliert werden. Von den sechs MTL-Glowmaxima in KBr und KBr:Li werden zwei bzw. vier Glowmaxima gefunden, die mit F-Licht bei LNT stimuliert werden. Die verschiedenen photostimulierten MTL-Glowmaxima werden den flachen F- und F'-Haftstellen zugeordnet, die entweder durch Einfang von Photoelektronen aus dem Leitungsband oder durch Elektronentunnelung aus angeregten F-Zentren-Zustanden zu einem benachbarten F-Zentrum gefullt werden. Die auftretenden Differenzen fur reine und dotierte Systeme bezuglich einer Photostimulierung werden dem Einbau von Li-Ionen in das Gitter zugeschrieben.

Effects of ingested petroleum on the development of ovarian endocrine function in photostimulated mallard ducks (Anas platyrhynchos)

Female mallard ducks that had been raised to maturity on a non-stimulatory light regime were divided into two groups and abruptly exposed to a stimulatory regime of 18 hr light and 6 hr dark. At the same time, the experimental group was given food contaminated with petroleum while the control group continued to receive uncontaminated food. The plasma concentrations of estradiol, estrone, progesterone and luteinizing hormone (LH) in the control birds increased steadily during the first two weeks of photostimulation and by the 15th day they started to lay eggs. In contrast, the plasma concentrations of these hormones in the contaminated birds increased significantly more slowly than in the uncontaminated control birds, and none had started to lay on the 15th day of photostimulation. After 21 days, only 4 of the contaminated birds had started to lay, and in these the plasma concentrations of all the hormones had increased to levels found in the uncontaminated birds on the 15th day of photo stimulation. The plasma concentration of each of the hormones in the 4 other contaminated birds that had not started to lay on the 21st day, were still low and similar to the corresponding values recorded for them on the 15th day of photostimulation. The primary site at which these contaminants act to suppress the response is probably in the steroidogenic cells of the differentiating ovary; the resulting low plasma concentrations of estrogen may also exert an insufficient level of stimulatory feedback control over the adenohypophysis, and thus account for the abnormally low plasma LH concentrations found in the contaminated birds at this time. It is concluded that contaminants derived from ingested petroleum act quickly to interfere with photostimulated ovarian recrudescence, and the associated development of ovarian endocrine function.

The photo-gonadal response of a migratory bunting: evidence of an external coincidence system.

Male redheaded buntings (Emberiza bruniceps) were subjected to continuous darkness (DD) or short days (8L/16D) after photo-stimulation (15L/9D) for either 15 or 30 days. Two groups of birds (four each), after photo stimulation for 30 days, were continued on a regimen of 15L/9D. Another two groups (of four each) of photo-sensitive birds were also subjected to DD or 8L/16D; they served as controls. The effect of transfer to DD or 8L/16D on the size of testes was found not the be dependent upon the size attained at the time of transfer. The rate of testicular regression was nearly the same under both the treatments, i.e., in those birds transferred either to DD or to 8L/16D. The birds that were maintained on 15L/9D maintained enlarged testes; this excluded the possibility of the onset of photo-refractoriness during the treatment period. On the other hand, testes were not photo-stimulated in the photo-sensitive birds subjected to DD or 8L/16D. These results are consistent with the Bünning-Pittendrigh avian external coincidence model, but could be explained alternatively by a relatively simple internal coincidence model. Nevertheless, the application of the law of parsimony suggests the acceptance of the hypothesis of the external coincidence model.

Inferotemporal evoked potentials after visual discrimination training in squirrel monkey.

A squirrel monkey was trained to close a switch activating a photo stimulator set for a single flash. The color of the light signalled the availability or unavailability of a raisin reward. Evoked potentials were recorded across the inferotemporal cortex and adjacent white matter, after original training and after each of 3 reversals. In each case there was a greater negative deflection in response to the SD. The difference in potentials was much less for the last 2 reversals.

アセトンガス暴露の自律神経系機能に及ぼす影響に関する実験的研究

An experimental study was carried out to obtain physiological data substantiating the maximum allowable concentration of aceton gas in industrial hygiene. For this purpose it was intented to detect polygraphically the variations of physiological functions of the autonomic nervous system of man evoked by exposure to 250-270 ppm or 500-750 ppm concentration of aceton gas for 6 hours, with 1 hour free from aceton gas exposure in the middle, that is, from 9 : 00 to 12 : 00 a.m. and from 1 : 00 to 4 : 00 p.m. Subjects consisted of volunteers of 24 healthy male students (age; 18-28), which were devided into 3 groups (group of control of 8 students, group of low concentrations of 9 students, and group of high concentrations of 9 students, 2 of them being duplicated). They were individually examined while resting in bed for 6 hours (Tests for about 1 hour were repeated 6 times with pauses in between) a day for consecutive two days, and exposed to the aceton gas on the 2nd day except the control. Spontaneous variations and evoked variations in response to 1 second or 30 second auditory and visual incitements by “The Sound and Photo Stimulator for EEG” were observed throughout the experiment, but only the variations during the last 1 hour of both days were compared individually. On the other hand, the tendency of the variations and of the correlations between the phenomena in each group were compared between the 3 groups. The results thus obtained are as follows : 1) Galvanic skin reflexSpontaneous GSR after repeated stimuli decreased in the gas groups, while evoked GSR with repeated 30 sec. stimuli increased in the 250-270 ppm group. The latter phenomenon would probably be derived from both effects of the aceton gas and the high air temperature of the examination room. The evoked GSR with repeated 1 sec. stimuli and latent time of the reaction to 1 sec. stimuli showed no difference between three groups. Tendency of correlation between GSR and air temperature in the gas groups differed from that in the control group.2) Reflection photoelectric finger plethysmogramVasoconstrictive reaction and latent time of the reaction to stimuli and patterns of plethysmogram showed no difference between three groups. But, tendency of correlation between vasoconstrictive reaction to 30 sec. stimuli and air temperature in the gas groups differed from that in the control group.3) Period of heart beatPeriod of heart beat in the 500 ppm group shortened, while that in the control group lengthened. Tendency of correlation between the period and air temperature in the gas groups differed from that in the control group.4) Period of respirationPeriod of respiration showed no difference between the three groups. But, tendency of correlation between the period and air temperature in the gas groups differed from that in the control group.5) Cerebral activity from occipital electroencephalographCerebral activities in the gas groups rised in comparison with the control group. Tendency of correlation between the cerebral activity and air temperature in the gas groups differed from that in the control group.6) It was concluded that the aceton gas influenced not only the spontaneous GSR, the period of heart beat and the cerebral activity, but also the correlations between the physiological functions of the autonomic nervous system, air temperature and the cerebral activity.7) From these facts it is a matter of course that the MAC of aceton gas must be lowered to the level below 250 ppm.

Light Applied to Biology

Techniques of Photostimulation in Biology Edited by B. H. Crawford in association with G. W. Granger and R. A. Weale. Pp. 317. (North-Holland: Amsterdam; Wiley (Interscience): London and New York, 1968.) 117s.

Convulsive seizures in dieldrin exposed sheep during photic stimulation.

Dieldrin, a chlorinated hydrocarbon insecticide, causes hypersensitivity and muscular fasciculations which may be followed by clonic-tonic conv~~lsive seizures. There are changes in the cortical electroencephalogram (EEG) which occur prior to clinical toxicity. These changes consist of high amplitude (200 to 300 pv), slow wave (4 to 5 Hz) spindles of 1 to 3 sec. duration (Van Gelder, et al., 1968). As exposure continues, the slow wave activity occurs more frequently and is of greater duration. The signs of clinical toxicity described above are usually evident at this time. During convulsive seizures, the EEG consists of high-amplitude, fast waves with some spike-wave complexes similar to those seen in petit ma1 epileptic seizures. The EEG record gives an indication of the imminence of convulsive seizures. The presentation of a high intensity, variable-frequency light (Grass Model PS-2 Photo Stimulator) precipitated convulsive seizures in 3 exposed sheep prior to the occurrence of clinical toxicity. These same animals were unaffected by the photic stimulation prior to exposure. At approximately 11 to 14 Hz the animals began to convulse and continued convulsing as long as the photic stimulation was present. The convulsive seizure ended with the termination of the strobe. Unexposed control animals remained unaffected by this photic stimulation. It is not known whether the precipitation of convulsive seizures is unique to visual stimulation or is a more general response to massive sensory input. Further investigation with the use of repetitive auditory stimulation is underway. REFERENCE

THE ROLE OF THE PREPARATORY INTERVAL IN THE RELATIONSHIP BETWEEN EEG α‐BLOCKINGAND REACTION TIME

ABSTRACTThe association between α‐blocking and improved reaction times (RTs) has not been consistently demonstrated in past studies. The possible importance of the preparatory interval (PI) in this relationship has not been totally assessed, and it was felt that further exploration of this variable would help to explain the discrepancies. RTs were measured in two experiments, each using different types of stimuli and different PI durations. In the first, 4 PIs, 0.5‐, 3.0‐, 6.0‐, and 15.0‐sec, were used in a regular and irregular series. The warning signal was a 400‐cps tone; the stimulus, a 1000‐cps tone. In the second. PIs were 0.50‐, 0.75‐, 1.00‐, and 1.50‐sec; the stimulus was a single flash from a photo stimulator. EEGs were recorded simultaneously from the parieto‐occipital region. Both peak‐to‐peak amplitude measures and subjective ratings of α‐activity were made prior to the onset of the warning signal and the stimulus. The results did not support earlier findings of a relationship between α‐blocking and RT. However, RT and α‐blocking were each (independently) a function of the PI.

After-image fusion

A new aspect of the complex of after-image phenomena is described. It consists of the appearance of lines connecting initially separated after-images, if they are observed against a flickering background. These lines appear during the fading of the after-image. The after-images were produced by various configurations of Xenon flashes, the flickering background by a standard photo stimulator. The phenomena was called after-image fusion not to be confused with binocular fusion. The report is qualitative. The main conclusion reached is the actual existence of the fusion phenomenon. Possible influences of conditioning or suggesting were debated and thought of small importance. The phenomenon casts some doubts on the simple mechanistic retinal origin of the after-images.

Certain Chromatic and Brightness Changes Associated with Rate of Intermittency of Photo Stimulation

Certain Chromatic and Brightness Changes Associated with Rate of Intermittency of Photo Stimulation