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Background There is a need to develop noninvasive methods to monitor intracranial pressure (ICP). Pupillary reactivity decreases in patients with elevated ICP with demonstrated cerebral edema. We sought to determine whether pupillary reactivity is affected when ICP is elevated in the absence of brain edema. Methods Healthy subjects and individuals with idiopathic intracranial hypertension (IIH) underwent pupillometry in different positions (upright, supine, and head-down tilt) and during different physiological maneuvers. A separate group of healthy subjects were tested in the upright resting position only. The pupillary dynamics were measured with a pupillometer. Results Healthy and IIH subjects were enrolled. In the healthy subjects the change from upright to head-down tilt led to a Neurological Pupil Index (NPI) decrease from 4.30 to 4.12, while maximum pupil size and minimum pupil size increased from 4.74 to 5.19 and 3.04 to 3.44, respectively. In the IIH group the maximum pupil size, minimum pupil size, and latency increased in magnitude with a decline in head tilt. The mean NPI of IIH subjects, 4.37, was greater than the healthy mean, 4.25. Also, the mean IIH Max and Min, 5.02 and 3.25, were greater than the healthy mean, 4.62 and 2.92. Discussion We observed changes in the pupillary reactivity in all subjects based on changes in position and task. There were also differences between the healthy and IIH subjects. This is consistent with our hypothesis that elevated intracranial pressure may result in decreased pupillary reactivity even in the absence of brain edema.Soeken TA, Alonso A, Grant A, Calvillo E, Gutierrez-Flores B, Clark J, Donoviel D, Bershad EM. Quantitative pupillometry for detection of intracranial pressure changes during head-down tilt. Aerosp Med Hum Perform. 2018; 89(8):717-723.

Astronauts aboard the International Space Station (ISS) have exhibited hyperopic shifts, posterior eye globe flattening, dilated optic nerve sheaths, and even optic disk swelling from spaceflight. Elevated intracranial pressure (ICP) consequent to cephalad fluid shifts is commonly hypothesized as contributing to these ocular changes. Head-down tilt (HDT) is frequently utilized as an Earth-based analog to study similar fluid shifts. Sealed environments like the ISS also exhibit elevated CO2, a potent arteriolar vasodilator that could further affect cerebral blood volume (CBV) and cerebral blood flow, intracranial compliance, and ICP. A collaborative pilot study between the National Space Biomedical Research Institute and the German Aerospace Center tested the hypotheses that 1) HDT and elevated CO2 physiologically interact and 2) cerebrovascular pulsatility is related to HDT and/or elevated CO2. In a double-blind crossover study ( n = 6), we measured CBV pulsatility via near-infrared spectroscopy, alongside noninvasive ICP and intraocular pressure (IOP) during 28-h −12° HDT at both nominal (0.04%) and elevated (0.5%) ambient CO2. In our cohort, CBV pulsatility increased significantly over time at cardiac frequencies (0.031 ± 0.009 μM/h increase in total hemoglobin concentration pulsatility amplitude) and Mayer wave frequencies (0.019 ± 0.005 μM/h increase). The HDT-CO2 interaction on pulsatility was not robust but rather driven by one individual. Significant differences between atmospheres were not detected in ICP or IOP. Further work is needed to determine whether individual differences in pulsatility responses to CO2 relate to visual changes in space. NEW & NOTEWORTHY Cerebral blood volume (CBV) pulsatility—as measured by near-infrared spectroscopy—increases over time during −12° head-down tilt at both cardiac and Mayer wave frequencies. CBV pulsatility appeared to increase more under elevated (0.5%) CO2 at Mayer wave frequencies in some individuals. If similar dynamic pulsatility increases occur in astronauts, there is the potential to initiate vascular and possibly other remodeling processes that lead to symptoms associated with sustained increases in intracranial pressure.

This study investigates the use of a mathematical model for thermoregulation as a tool in safety-of-flight issues and proposed solutions for mission operations of the Space Shuttle and the International Space Station. Specifically, this study assesses the effects of elevated cabin temperature and metabolic loads on astronauts wearing the Advanced Crew Escape Suit (ACES) and the Liquid Cooled Ventilation Garment (LCVG). The 225-node Wissler model is validated by comparison with two ground-based human subject tests, firefighters, and surrogate astronauts under anomalous conditions that show good agreement. Subsequent simulations indicate that the performance of the ACES/LCVG is marginal. Increases in either workload or cabin temperature from the nominal will increase rectal temperature, stored heat load, heart rate, and sweating leading to possible deficits in the ability of the astronauts to perform cognitive and motor tasks that could affect the safety of the mission, especially the safe landing of the Shuttle. Specific relationships are given between cabin temperature and metabolic rate that define the threshold for decreased manual dexterity and loss of tracking skills. Model results indicate that the most effective mitigation strategy would be to decrease the LCVG inlet temperature. Methods of accomplishing this are also proposed.

Objectives The study goal was to determine whether a single Space Shuttle mission can induce decrements in astronaut hearing. Study design We retrospectively compared audiogram information obtained from Space Shuttle astronauts at 10 days preflight, day of return (R + 0), 3 days after landing return (R + 3), and at a mean delayed postflight follow-up of 8 months. Results Temporary threshold shift (mean, 4.6 dB) was noted in R + 0 versus preflight conditions (P < 0.01). Small permanent threshold shifts (mean, 0.83 dB) were found at R + 3 and postflight follow-up compared with preflight in the lower frequencies (500 to 2000 Hz), and corresponding pure tone average (P < 0.001). Conclusions and significance The data indicate that a single Shuttle flight can induce a substantial temporary threshold shift and a small but statistically significant permanent threshold shift, particularly in the frequencies involved in speech reception. Although single-mission effects are small, cumulative effects over several missions may ultimately produce clinically significant hearing loss.

Recent studies suggest that elevated intracranial pressure (ICP), created by hydrocephalus, can alter the lower limit of cerebrovascular autoregulation (LLA). Our objective in the present study was to determine if ICP elevation from cerebral venous outflow obstruction would result in comparable alterations in the LLA.Anesthetized juvenile pigs were assigned to one of two groups: naïve ICP (n = 15) or high ICP (20 mmHg; n = 20). To elevate ICP through venous obstruction, a modified 5F esophageal balloon catheter was inserted via the right external jugular vein into the superior vena cava (SVC) and inflated to maintain an ICP of20 mmHg. To calculate the LLA, gradual hypotension was induced by continuous hemorrhage from a catheter in the femoral vein. The LLA was determined by monitoring cortical laser Doppler flux (LDF).The naïve and high ICP groups had LLAs of 45 mmHg (95% CI: 41-49 mmHg) and 71 mmHg (95% CI: 66-77 mmHg) respectively by LDF. The LLA was significantly different between the two groups and correlated significantly with ICP.Elevated ICP from cephalic venous engorgement leads to an increase in the LLA. These findings suggest that pathologic processes resulting in cephalic venous outflow obstruction and intracranial venous congestion can acutely elevate ICP and may place the brain at risk for impaired cerebrovascular autoregulation.

Sequences homologous to the P transposable element have been identified in Musca domestica. Sequence analysis of a genomic clone (Md-P1) indicates that, although the house fly P element has lost its coding capacity, the basic general structure of drosophilid P elements is present. The house fly P element sequence shares a number of structural features with that from the blow fly, Lucilia cuprina, including a large intron separating exons 1 and 2, two additional introns interrupting exon 2 and the apparent absence of inverted repeat termini. Within a relatively well-conserved central region, the house fly sequence shows 59% similarity to the D. melanogaster P element, but distal regions are more diverged. Southern blot analysis of several strains indicated the presence of at least four P element copies.

Nucleotide sequences from two nuclear loci, alcohol dehydrogenase and internal transcribed spacer-1 of the nuclear ribosomal DNA repeats, and two mitochondrial genes, cytochrome oxidase I and cytochrome oxidase II, were determined from nine species in the Drosophila saltans species group. The partition homogeneity test and partitioned Bremer support were used to measure incongruence between phylogenetic hypotheses generated from individual partitions. Individual loci were generally congruent with each other and consistent with the previously proposed morphological hypothesis, although they differed in level of resolution. Since extreme conflict between partitions did not exist, the data were combined and analyzed simultaneously. The total evidence method gave a more resolved and highly supported phylogeny, as indicated by bootstrap proportions and decay indices, than did any of the individual analyses. The cordata and elliptica subgroups, considered to have diverged early in the history of the D. saltans group, were sister taxa to the remainder of the saltans group. The sturtevanti subgroup, represented by D. milleri and D. sturtevanti, occupies an intermediate position in this phylogeny. The saltans and parasaltans subgroups are sister clades and occupy the most recently derived portion of the phylogeny. As with previous morphological studies, phylogenetic relationships within the saltans subgroup were not satisfactorily resolved by the molecular data.

A patient with a fusiform aneurysm of the cervical vertebral artery at C-1 presenting with posterior circulation infarctions is reported. Exposure via the posterolateral approach, resection of the aneurysm, and end-to-end anastomosis are described. The authors emphasize the importance of the surgical approach and ability to expose and mobilize a generous portion of the cervical vertebral artery.