Vestibular-somatosensory convergence in head movement control during locomotion after long-duration space flight.

Space flight causes astronauts to be exposed to adaptation in both the vestibular and body load-sensing somatosensory systems. The goal of these studies was to examine the contributions of vestibular and body load-sensing somatosensory influences on vestibular mediated head movement control during locomotion after long-duration space flight. Subjects walked on a motor driven treadmill while performing a gaze stabilization task. Data were collected from three independent subject groups that included bilateral labyrinthine deficient (LD) patients, normal subjects before and after 30 minutes of 40% bodyweight unloaded treadmill walking, and astronauts before and after long-duration space flight. Motion data from the head and trunk segments were used to calculate the amplitude of angular head pitch and trunk vertical translation movement while subjects performed a gaze stabilization task, to estimate the contributions of vestibular reflexive mechanisms in head pitch movements. Exposure to unloaded locomotion caused a significant increase in head pitch movements in normal subjects, whereas the head pitch movements of LD patients were significantly decreased. This is the first evidence of adaptation of vestibular mediated head movement responses to unloaded treadmill walking. Astronaut subjects showed a heterogeneous response of both increases and decreases in the amplitude of head pitch movement. We infer that body load-sensing somatosensory input centrally modulates vestibular input and can adaptively modify vestibularly mediated head-movement control during locomotion. Thus, space flight may cause central adaptation of the converging vestibular and body load-sensing somatosensory systems leading to alterations in head movement control.

Efficient resonantly pumped tape cast composite ceramic Er:YAG laser at 1645 nm.

Laser operation of a composite ceramic Er:YAG rod is demonstrated at 1645 nm with a slope efficiency of 56.9% under resonant pumping at 1532.3 nm. This is believed to be the first reported composite ceramic Er:YAG laser and also the first reported use of a tape cast technique for producing laser ceramics.

Effects of adaptation of vestibulo-ocular reflex function on manual target localization.

The goal of the present study was to determine if adaptive modulation of vestibulo-ocular reflex (VOR) function is associated with commensurate alterations in manual target localization. To measure the effects of adapted VOR on manual responses we developed the Vestibular-Contingent Pointing Test (VCP). In the VCP test, subjects pointed to a remembered target following passive whole body rotation in the dark. In the first experiment, subjects performed VCP before and after wearing 0.5X minifying lenses that adaptively attenuate horizontal VOR gain. Results showed that adaptive reduction in horizontal VOR gain was accompanied by a commensurate change in VCP performance. In the second experiment, bilaterally labyrinthine deficient (LD) subjects were tested to confirm that vestibular cues were central to the spatial coding of both eye and hand movements during VCP. LD subjects performed significantly worse than normal subjects. These results demonstrate that adaptive change in VOR can lead to alterations in manual target localization.

Using factor analysis to identify neuromuscular synergies during treadmill walking.

Neuroscientists are often interested in grouping variables to facilitate understanding of a particular phenomenon. Factor analysis is a powerful statistical technique that groups variables into conceptually meaningful clusters, but remains underutilized by neuroscience researchers presumably due to its complicated concepts and procedures. This paper illustrates an application of factor analysis to identify coordinated patterns of whole-body muscle activation during treadmill walking. Ten male subjects walked on a treadmill (6.4 km/h) for 20 s during which surface electromyographic (EMG) activity was obtained from the left side sternocleidomastoid, neck extensors, erector spinae, and right side biceps femoris, rectus femoris, tibialis anterior, and medial gastrocnemius. Factor analysis revealed 65% of the variance of seven muscles sampled aligned with two orthogonal factors, labeled 'transition control' and 'loading'. These two factors describe coordinated patterns of muscular activity across body segments that would not be evident by evaluating individual muscle patterns. The results show that factor analysis can be effectively used to explore relationships among muscle patterns across all body segments to increase understanding of the complex coordination necessary for smooth and efficient locomotion. We encourage neuroscientists to consider using factor analysis to identify coordinated patterns of neuromuscular activation that would be obscured using more traditional EMG analyses.

Adaptation of neuromuscular activation patterns during treadmill walking after long-duration space flight.

The precise neuromuscular control needed for optimal locomotion, particularly around heel strike and toe off, is known to he compromised after short duration (8- to 15-day) space flight. We hypothesized here that longer exposure to weightlessness would result in maladaptive neuromuscular activation during postflight treadmill walking. We also hypothesized that space flight would affect the ability of the sensory-motor control system to generate adaptive neuromuscular activation patterns in response to changes in visual target distance during postflight treadmill walking. Seven crewmembers, who completed 3- to 6-month missions, walked on a motorized treadmill while visually fixating on a target placed 30 cm (NEAR) or 2 m (FAR) from the subject's eyes. Electronic foot switch data and surface electromyography were collected from selected muscles of the right lower limb. Results indicate that the phasic features of neuromuscular activation were moderately affected and the relative amplitude of activity in the tibialis anterior and rectus femoris around toe off changed after space flight. Changes also were evident after space flight in how these muscles adapted to the shift in visual target distance.

Sertraline-associated syndrome of inappropriate antidiuretic hormone: case report and review of the literature.

Selective serotonin reuptake inhibitors have gained widespread use in the treatment of depression. A 78-year-old woman became hyponatremic 3 days after being treated with sertraline and was subsequently diagnosed with the syndrome of inappropriate antidiuretic hormone (SIADH). She became symptomatic, but experienced rapid resolution of the laboratory and clinical abnormalities associated with SIADH on discontinuing sertraline and receiving fluid restriction, hypertonic saline, and demeclocycline. Several mechanisms may relate SIADH and vasopressin release to serotonin.

Frasier syndrome.

OBJECTIVE: To present the case of a 17-year-old girl with primary amenorrhea and a history of hypertension since age 13 years. METHODS: The patient's clinical, laboratory, and radiologic data were summarized, and features of Frasier syndrome and Drash syndrome were compared. RESULTS: The patient's weight was 126 kg, height was 185 cm, and blood pressure was 150/100 mm Hg. She had minimal breast budding and scant pubic hair. Laboratory data were compatible with hypergonadotropic hypogonadism. An ultrasound study of the pelvis revealed an infantile uterus and a questionable right gonad. The patient also had nephrotic-range proteinuria in conjunction with decreased creatinine clearance and normal findings on ultrasonography of the kidneys. A karyotype photomicrograph showed a male 46,XY chromosomal pattern. Although the patient's chronologic age was 17 years, her bone age was 12 1/2 years. CONCLUSION: The patient was diagnosed as having Frasier syndrome. She underwent removal of a left-sided ovary and a right adnexal mass, and her condition is well controlled with lisinopril (10 mg daily) and estrogen therapy.

The demographics of labour turnover: a comparison of ordinal probit and censored count data models.

The authors use date collected in 1977 on unemployed residents of West Germany aged 15-54 years old to compare two statistical models used to analyze labor market mobility. "Two classes of statistical models seem appropriate for this type of analysis, the ordinal probit model assuming a latent continuous variable behind the observables, and the count data approach with prominent members as the Poisson and the negative binomial model.... The first point of interest is to explore whether both approaches lead to similar findings.... We outline some approaches...that enable a...researcher to judge the quality of the estimated model....[Then] we compare the performance of the ordinal probit and count data models. Section 2 presents data and hypotheses. Section 3 discusses the econometric methodology. Section 4 contains the empirical results and the model comparisons." (SUMMARY IN FRE)

Savings, remittances, and return migration.

"We use a data set of immigrants to West Germany to simultaneously study both savings and remittances which we relate to individual characteristics, economic variables, migration experiences and remigration plans. Section 2 discusses the basic hypotheses and explains the data. Section 3 presents the empirical study and Section 4 summarizes." The results suggest that "savings and remittances of migrants can be well explained by remigration plans and economic as well as demographic variables. However, the planned future duration of residence in Germany has a negative and significant effect only on remittances."

Multiple pulse laser-induced damage phenomena in silicates.

Multiple pulse laser-induced bulk damage has been studied in fused silica and borosilicate glass. The fluence dependence and pulse repetition frequency dependence of the damage make it clear that laser irradiation promotes damage on subsequent pulses, and the evidence favors attribution of the effect to transient entities such as point defects rather than larger imperfections such as inclusions. However, the influence of preirradiation defects on damage thresholds is small, and a luminescence experiment places low limits on the possible concentration of conduction band electrons prior to damage. The constraints these results place on possible mechanisms of multiple damage are briefly discussed.

Hypoglycemia in a diabetes nurse care coordinator.

A 26-yr-old registered nurse who is employed as a diabetes nurse care coordinator had episodes of symptomatic fasting hypoglycemia associated with hyperinsulinemia and a relatively suppressed plasma C-peptide concentration, arousing the suspicion of self-induced illness. However, using a species-specific radioimmunoassay, the species of insulin during an episode of hypoglycemia was determined to be human in origin. Once the patient's illness was attributed to endogenous insulin hypersecretion, prompt surgical intervention and the diagnosis of nesidioblastosis in an adult was made.