Optokinetic reflex in squirrel monkeys after long-term monocular deprivation

Horizontal optokinetic nystagmus (OKN) as well as neuronal response properties in the nucleus of the optic tract and the dorsal terminal nucleus of the accessory optic system (NOT-DTN) were investigated in three monocularly deprived squirrel monkeys. In two monkeys occlusion of one eye was performed at birth (early) and in the third after 7 weeks (late). In adulthood, in early deprived monkeys monocular horizontal OKN tested through the non-deprived eye was symmetrical and in no way different from normal, i.e. stimulation in the temporonasal and nasotemporal direction elicited equal and robust responses. OKN through the early occluded eye, however, was grossly abnormal with low gain and great variability in the consistency of nasotemporal and temporonasal slow phase eye movements. When in the late deprived monkey the non-deprived eye was occluded a strong spontaneous nystagmus developed despite the deprived eye viewing a stationary pattern. The slow phases were directed from nasal to temporal for the deprived eye. When tested through the non-deprived eye all neuronal responses of the NOT-DTN were normal. The deprived eye's influence on NOT-DTN neurons was extremely weak. No neuron with a moderate or even dominant input from the deprived eye was found after early deprivation. In the late deprived case the deficit was not as severe but still the non-deprived eye was clearly dominating the responses in all neurons tested. Velocity tuning of neurons tested through the non-deprived eye was normal and qualitatively corresponded well to slow phase eye velocity in response to equivalent retinal slip during OKN. Through the early deprived eye, however, velocity tuning was extremely poor. It was somewhat better through the late deprived eye. We suggest that the dramatic deterioration in the optokinetic reflex found after long-term monocular deprivation for the amblyopic eye is probably caused by the almost complete loss of retinal and cortical input driven by that eye to the NOT-DTN. These results are discussed in relation to our previous results in cats and reports in the literature for humans with occlusion amblyopia.     

Mercury accumulation in the squirrel monkey eye after mercury vapour exposure

Squirrel monkeys were exposed to mercury vapour at different concentrations and for different numbers of days. The calculated total mercury absorption ranged between 1.4-2.9 mg (range of daily absorption 0.02-0.04 mg). The monkeys were killed at different intervals after the end of exposure (range 1 month - 3 years) and the eyes were enucleated. Eyes from four un-exposed monkeys were used as control material. Mapping of the mercury distribution in the eye revealed that the non-myelin-containing portion of the optic disc was densely loaded with mercury deposits, which are mostly confined to the capillary walls and the glial columns. The white matter of the brain does not accumulate mercury at these exposure levels, which might suggest that the myelinization process inhibits the accumulation of mercury. The pigmented epithelium of the pars plicata of the ciliary body and of the retina contained a considerable amount of mercury. This finding indicates that mercury is trapped within the melanocytes, which keeps potentially dangerous material from reaching the neural retina. In addition, the retinal capillary walls were densely loaded with mercury deposits, even 3 years after exposure. It was also found that the inner layers of the retina accumulated mercury during a 3-year period. It is known that the biological half-time of mercury in the brain may exceed years. This seems also to be the case for the ocular tissue.     

Platelet serotonin and interleukin-1 beta after sleep deprivation and recovery sleep in humans

Sleep deprivation (SD) represents a well-established therapy for major depression. Recent findings suggest that the antidepressive effects of sleep deprivation are mediated at least in part by pro-serotoninergic mechanisms. Furthermore, SD has been demonstrated to modify different host defense activities. We therefore investigated the serotonin (5-HT) content in platelets, platelet density distribution and 5-HT-induced IL-1 beta release from platelets in 10 healthy men before and after total SD (TSD) as well as after recovery sleep. Blood samples were drawn on 3 consecutive days at 7.00 h, 13.00 h, and 19.00 h, respectively. In addition, the psychophysiological parameters tiredness and wakefulness were assessed. After TSD the normal daily variation of IL-1 beta release with high morning levels and low evening levels was found to be significantly inverted. The release of IL-1 beta corresponded positively to the subjectively experienced tiredness of the probands. Analysis of platelet density distribution indicated a significant daily variation of low density platelets with low levels in the morning and high levels in the evening, which was absent after TSD. Our findings favour an increased pro-serotoninergic effect after TSD, which comprises respective variations of the host defense system, but is abolished by consecutive recovery sleep.     

Increment-threshold spectral sensitivity in the squirrel monkey.

Measured the spectral sensitivity of 5 adult squirrel monkeys and 2 human males in an increment-threshold context. Under conditions of dark adaptation the spectral sensitivity of the squirrel monkey was closely similar to that of man. For conditions of light adaptation, the squirrel monkey showed maximal sensitivity at 540 nm. with subsidiary peaks at 600 and 440 nm. Relative to man, the squirrel monkey was considerably less sensitive to wavelengths longer than 580 nm. For this species there are substantial differences between the spectral sensitivity functions determined by increment-threshold methods and those obtained using critical flicker frequency (CFF) techniques. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Behavioral thermoregulation in the squirrel monkey: Adaptation processes during prolonged microwave exposure.

Investigated exposure duration at power densities above and below the threshold of 6-8 mW/cm2 with 2 male monkeys. Ss were restrained in the far field of a horn antenna inside an anechoic chamber heated and cooled by forced convection. Ss learned to control the temperature of the circulating chamber air by selecting between cold and warm air sources. Ss were exposed to 12.4-cm (2450-MHz) continuous-wave microwaves for periods from 5 to 150 min. Microwave power densities explored were 4, 10, and 20 mW/cm2. The 4 mW/cm2 microwave exposure did not modify thermoregulatory behavior. The 10 and 20 mW/cm2 exposures stimulated the monkeys to select ambient temperatures 1.5 and 3.0°C cooler than control levels, respectively. Except during the early minutes of an exposure, duration had no significant effect on selection of air temperature or on the body temperatures thereby achieved. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of posterior parietal and frontal neocortical lesions in the squirrel monkey.

2 groups of squirrel monkeys with frontal or parietal cortical lesions and an unoperated control group (N = 12) received the following in the order mentioned: brightness discrimination; 3 forms of a spatial pattern discrimination in which the essential cue and site of reinforcement were separated (SSP); delayed response; form discrimination; and 3 forms of a spatial pattern discrimination in which the essential cue and site of reinforcement were identical. Ss with frontal lesions were impaired on delayed response, and those with parietal lesions were impaired on form and SSP discriminations. Neither group was impaired on brightness discrimination. Results confirm and extend previous findings that the posterior parietal cortex of nonhuman primates is critically involved in visually guided spatial discriminations when the primary cue and the site of reinforcement are separated. (46 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Behavioral thermoregulation in the squirrel monkey when response effort is varied.

Three adult male squirrel monkeys controlled the air temperature within their test chamber by pulling a chain to select between 2 preset air temperatures, 10 and 50Deg.C. When the force required to pull the chain was increased in steps from 2.94 to 6.86 N, interresponse interval increased, resulting in wider air temperature swings within the chamber. The average air temperature selected became progressively lower, producing a concomitant fall in skin temperature. However, internal body temperatures (rectal and brainstem) remained nearly constant due to a compensatory increase in metabolic heat production. By allowing a cooler, rather than warmer, environment to result from a decreased response rate, Ss guarded against hyperthermia, which they were ill equipped to handle autonomically. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of sleep deprivation on driving safety in housestaff

Sleep deprivation is known to affect driving safety. Housestaff (HS) are routinely sleep-deprived when on call. We hypothesized that this would affect their driving. We therefore administered questionnaires regarding driving to 70 pediatric HS, who were on call every fourth night, and to 85 faculty members (FAC), who were rarely disturbed at night. HS were questioned about events during their residency, and FAC were questioned about events during the preceding three years. There was an 87% response rate for each group. HS slept 2.7 +/- 0.9 (SD) hours when on call vs 7.2 +/- 0.8 hours when not on call (p < 0.001). 44% of HS had fallen asleep when stopped at a light, vs 12.5% FAC (p < 0.001). 23% of HS had fallen asleep while driving vs. 8% FAC (ns). A total of 49% of HS had fallen asleep at the wheel; 90% of these events occurred post-call. In contrast, only 13% of FAC had fallen asleep at the wheel (p < 0.001). HS had received a total of 25 traffic citations for moving violations vs. 15 for FAC and were involved in 20 motor vehicle accidents vs. 11 for FAC. One traffic citation clearly resulted from HS falling asleep at the wheel vs. none for FAC. We conclude that HS frequently fall asleep when driving post-call. We speculate that current HS work schedules may place some HS at risk for injury to themselves and others. Further study, using prospectively objective measures is indicated.     

Effect of infants on adult social relations in the squirrel monkey (Saimiri Sciureus)

7 groups of squirrel monkeys were observed to assess the effect of infants on social interactions and interanimal distances among adult members of their natal groups. Each group contained one or two infants, 5 to 7 months of age at the start of the study. Infants initiated affiliative and playful interactions with all adults, whereas adults directed few mostly antagonistic, interactions toward infants. Following the removal of infants from groups, distances between adults decreased and adult affiliative interactions increased more than 100%. The results indicate that infants within the age range examined can have a pervasive, primarily inhibitory, influence on adult social relationships.     

Extraocular motor unit and whole-muscle responses in the lateral rectus muscle of the squirrel monkey

Because primate studies provide data for the current experimental models of the human oculomotor system, we investigated the relationship of lateral rectus muscle motoneuron firing to muscle unit contractile characteristics in the squirrel monkey. Also examined was the correlation of whole-muscle contractile force with the degree of evoked eye displacement. A force transducer was used to record lateral rectus whole-muscle or muscle unit contraction in response to abducens whole-nerve stimulation or stimulation of single abducens motoneurons or axons. Horizontal eye displacement was recorded using a magnetic search coil. (1) Motor units could be categorized based on contraction speed (fusion frequency) and fatigue. (2) The kt value (change in motoneuronal firing necessary to increase motor unit force by 1.0 mg) of the units correlated with maximum tetanic tension. (3) There was some tendency for maximum tetanic tension of this unit population to separate into three groups. (4) At a constant frequency of 100 Hz, 95% of the motor units demonstrated significantly different force levels dependent on immediately previous stimulation history (hysteresis). (5) A mean force change of 0.32 gm/ degrees and a mean frequency change of 4.7 Hz/ degrees of eye displacement were observed in response to whole-nerve stimulation. These quantitative data provide the first contractile measures of primate extraocular motor units. Models of eye movement dynamics may need to consider the nonlinear transformations observed between stimulation rate and muscle tension as well as the probability that as few as two to three motor units can deviate the eye 1 degrees.     

Conflict and repression during sleep deprivation.

"A series of three TAT cards representing a continuum of low, medium, and high sleep suggestions was selected on the basis of rankings by 10 psychologists and 10 lay people. These three cards were administered… to 24 experimental Ss after about 86 hours of sleep deprivation, as well as to 24 control subjects… . [On these TAT cards] the sleep-deprived group gave fewer sleep themes than did the control group… . The results… were interpreted as indicating that the subjects were avoiding thoughts or verbal responses which might arouse overpowering sleepiness… . An analysis of these phenomena in terms of the Dollard-Miller theory of repression was made." 23 refs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Salivary cortisol: a non-invasive measure of hypothalamo-pituitary-adrenocortical activity in the squirrel monkey, Saimiri sciureus

STUDY OBJECTIVES: To study the in vitro effects of the serotonin2 (5-HT2) receptor agonist 1-(2.5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) in skeletal muscle specimens from malignant hyperthermia-susceptible (MHS) and normal (MHN) patients following pretreatment with the 5-HT2 receptor antagonist ritanserin. DESIGN: Prospective study. SETTING: Malignant hyperthermia (MH) laboratory at a university hospital. PATIENTS: 41 patients undergoing in vitro contracture test for diagnosis of MH susceptibility. INTERVENTIONS: Skeletal muscle biopsies in adult patients were performed with a 3-in-1 nerve block with 40 ml prilocaine 1%. In children, general anesthesia was induced with 50 micrograms/kg alfentanil intravenously (i.v.) and 2 to 2.5 micrograms/kg propofol i.v. and maintained with a continuous infusion of propofol (< or = 150 micrograms/kg/min) and nitrous oxide (66%) in oxygen. MEASUREMENTS AND MAIN RESULTS: Patients were first classified as MHS or MHN by the in vitro contracture test according to the European MH protocol. Surplus muscle specimens of 21 MHS and 20 MHN patients were used in this study. At first, DOI was added to the organ bath at a concentration of 0.02 mM. In the second part of the study, muscle specimens were preincubated with ritanserin 0.01 mM for 10 minutes before DOI 0.02 mM was added to the bath. Muscle specimens from all patients developed contractures after administration of DOI. The onset of contractures was significantly faster in MHS muscles, and the magnitude of contracture was significantly greater than in MHN. The muscle twitch decreased significantly in both groups after DOI. After pretreatment with ritanserin, start of contracture was significantly delayed in MHS muscles. MHN muscles failed to develop contractures. The maximum level of contracture was significantly reduced in MHS. Muscle twitch decreased also in both MHS and MHN groups. CONCLUSIONS: The findings may indicate that stimulation of 5-HT2 receptors is involved in MH induction. Furthermore, 5-HT2 receptor antagonists could possibly be effective in preventing MH. Additional studies are required to determine if administration of 5-HT2 receptor antagonists could be of additional value in the treatment or prevention of anesthetic-induced MH.     

Total and partial sleep deprivation in the treatment of depression: preliminary communication]

Sleep deprivation (SD) has been proved to be an effective measure of antidepressive treatment (especially in endogenous depression). In a new study, 125 SD were examined on 93 depressed patients. The therapeutic benefit of SD on endogenous depression consists not only of the nightly clear up but also of provoking or improving a typical day wave the day after DS. A period of at least 36 h is necessary to survey the total effect of this method. The best results are achieved in patients with severe endogenous depression, especially in those with the typical day wave and distinct somatic symptoms. The effect of partial SD (for the second half of the night) is almost the same as that of total SD. The advantages of partial SD are: the patient can stand it easier, more often, and - in the company of a suited person - even at home. Finally, it is less complicate in clinical routine than selective REM-deprivation.     

Differences in sleep variables, blood adenosine, and body temperature between hypothyroid and euthyroid rats before and after REM sleep deprivation

Sleep deprivation causes an increase in energy expenditure in animals. Thyroid gland function has been related to metabolic function, and this may be compromised in sleep manipulations. The objectives of the present study were the following: 1) to develop a model of hypothyroid rats by surgical removal of thyroid glands without extirpation of the parathyroid; 2) to observe the sleep architecture in euthyroid (Etx) and hypothyroid (Htx) rats, both before and after rapid eye movement (REM) sleep deprivation (96 hours); 3) to challenge both groups (i.e. Etx and Htx) with REM sleep deprivation (96 hours) and then evaluate the effects on temperature; and 4) to measure the levels of adenosine and thyroid hormones in blood. One-month-old Wistar male rats (weight 90-100 g) were studied. The thyroid gland was removed, and the parathyroid glands were reimplanted within the neck muscle (Htx) under halothane anesthesia. A sham-operated group was also included (Etx). Four months later, the animals were studied according to the following protocols. Protocol 1: Animals of both groups (i.e. Etx and Htx) were implanted for sleep recordings. After a baseline polysomnography, these animals were REM sleep deprived by the platform method (96 hours). Protocol 2. An intraperitoneal temperature transducer was placed into animals of both groups under deep halothane anesthesia. They were studied at baseline, during 96 hours of REM sleep deprivation, and on the rebound period. Protocol 3: Plasma thyroid hormones [T3, T4, and thyroid-stimulating hormone (TSH)] and plasma adenosine were determined in both groups. Results of protocol 1 indicated that the main difference observed in Htx rats during the baseline sleep was an increase in delta sleep (slow-wave sleep 2) and a reduction in waking time compared with Etx animals. REM sleep rebound after 96 hours of REM sleep deprivation was similar in both groups. In protocol 2, the main finding was that Htx animals had reduced body temperature. A significant difference in body temperature between Etx and Htx animals was found mainly during lights-on period. REM sleep deprivation in the Etx group produced an increase in body temperature. Htx animals showed the opposite effect, with a reduction in body temperature during and after REM sleep deprivation. In protocol 3, the main findings were that Htx animals exhibited a significant reduction in blood thyroid hormones (T3, T4), and that they also had high levels of plasma adenosine. REM sleep deprivation produces changes in temperature regulation. The increase in body temperature during REM sleep deprivation may require thyroid integrity. Absence of the thyroid gland does not seem to influence REM sleep recovery after its deprivation. The high plasma adenosine levels found in the Htx group may explain the increase in delta sleep in this group.