Diet of oceanic loggerhead sea turtles (Caretta caretta) in the central North Pacific

Diet analysis of 52 loggerhead sea turtles (Caretta caretta) collected as bycatch from 1990 to 1992 in the high-seas driftnet fishery operating between lat. 29.5°N and 43°N and between long. 150°E and 154°W demonstrated that these turtles fed predominately at the surface; few deeper water prey items were present in their stomachs. The turtles ranged in size from 13.5 to 74.0 cm curved carapace length. Whole turtles (n =10) and excised stomachs (n= 42) were frozen and transported to a laboratory for analysis of major faunal components. Neustonic species accounted for four of the five most common prey taxa. The most common prey items were Janthina spp. (Gastropoda); Carinaria cithara Benson 1835 (Heteropoda); a chondrophore, Velella velella (Hydrodia); Lepas spp. (Cirripedia), Planes spp. (Decapoda: Grapsidae), and pyrosomas (Pyrosoma spp.)

Influence of Decompression Rate on Hemodynamic Compensation to Continuous Lower Body Negative Pressure

We applied lower body negative pressure (LBNP) continuously, at three decompression rates, in an attempt to simulate uncontrolled hemorrhage as might be experienced by victims of traumatic injury. The purpose of our study was to determine whether hemodynamic compensations to simulated hemorrhage depend more on the magnitude, or the rate of change in pressure applied. Forty five (45) young, healthy subjects participated. We recorded the electrocardiogram, beat-to-beat arterial pressure (finger photoplethysmography), and measured cardiac output (inert gas rebreathing to calculate stroke volume) during continuous LBNP applied at three different decompression rates (n = 15 subjects for each rate; slow = 3 mm Hg∙min-1; medium = 6 mm Hg∙min-1; and fast = 12 mm Hg∙min-1) to an ending pressure of -60 mmHg. Slopes relating changes of dependent variable responses to the magnitude of decompression were calculated with linear regression, and group results were compared with ANOVA. LBNP increased (pooled across groups from 0 to -60 mmHg) heart rates (+28%; p ≤ .05 ), and decreased mean arterial pressures (-10%; p ≤ .05) and stroke volumes (-66%; p ≤ .05). The magnitude of changes induced by LBNP were not different between groups (p ≥ .4). Slopes (pooled across groups) relating heart rate (.3 bpm/mmHg ), mean arterial pressure (-.16 mmHg/mmHg), and stroke volume (-1.3 ml/mmHg) to the level of LBNP applied were not dependent on decompression rate (all ANOVA comparisons, p ≥ .3). We conclude that hemodynamic changes during continuous LBNP are associated directly with the magnitude of pressure applied, irrespective of the rate of decompression. Our results suggest that hemodynamic compensations to simulated uncontrolled hemorrhage are robust, and are not compromised by increasing the speed of decompression to simulate a greater rate of blood loss

Avian GIS models signal human risk for West Nile virus in Mississippi

BACKGROUND: West Nile virus (WNV) poses a significant health risk for residents of Mississippi. Physicians and state health officials are interested in new and efficient methods for monitoring disease spread and predicting future outbreaks. Geographic Information Systems (GIS) models have the potential to support these efforts. Environmental conditions favorable for mosquito habitat were modeled using GIS to derive WNV risk maps for Mississippi. Variables important to WNV dissemination were selected and classified as static and dynamic. The static variables included road density, stream density, slope, and vegetation. The dynamic variable represented seasonal water budget and was calculated using precipitation and evaporation estimates. Significance tests provided deterministic evidence of variable importance to the models. RESULTS: Several models were developed to estimate WNV risk including a landscape-base model and seasonal climatic sub-models. P-values from t-tests guided variable importance ranking. Variables were ranked and weights assigned as follows: road density (0.4), stream density (0.3), slope (0.2) and vegetation (0.1). This landscape-base model was modified by climatic conditions to assess the importance of climate to WNV risk. Human case data at the zip code level were used to validate modeling results. All models were summarized by zip codes for interpretation and model validation. For all models, estimated risk was higher for zip codes with at least one human case than for zip codes where no human cases were recorded. Overall median measure of risk by zip code indicated that 67% of human cases occurred in the high-risk category. CONCLUSION: Modeling results indicated that dead bird occurrences are correlated with human WNV risk and can facilitate the assessment of environmental variables that contribute to that risk. Each variable's importance in GIS-based risk predictions was assigned deterministically. Our models indicated non-uniform distribution of risk across the state and showed elevated risk in urban and as well as rural areas. Model limitations include resolution of human data, zip code aggregation issues, and quality/availability of vegetation and stream density layers. Our approach verified that WNV risk can be modeled at the state level and can be modified for risk predictions of other vector-borne diseases in varied ecological regions

Effects of Hypovolemia on Cerebral Blood Velocity and Autoregulation During Upright Tilt: Implications for Post-Spaceflight Orthostasis

Orthostatic stability depends on maintenance of adequate cerebral blood flow. Orthostatic instability experienced by returning astronauts is associated with microgravity-induced hypovolemia, suggesting that hypovolemia may disrupt the ability of the cerebral vasculature to regulate blood flow. PURPOSE: To test the hypothesis that hypovolemia reduces cerebral blood velocity and impairs cerebral autoregulation (CA) during upright tilt. METHODS: Nine males (age 23 ± .5 yrs; height 172 ± 2 cm; weight 87 ± 3 kg; mean ± SE) were tilted head-up to 70° on two occasions separated by at least 5 days under euhydration (EUH) and dehydration (DEH) conditions. Dehydration was induced with 40 mg Furosemide and 8 h water restriction. Plasma volumes (PV) and blood volumes (BV) were estimated from venous hemoglobin and hematocrit. ECG, beat-by-beat finger arterial pressures, and cerebral blood velocity (CBV) were measured during a five min supine baseline, and during the first (T1) and last (T2) five min of upright tilt. Dynamic CA was assessed in the frequency domain with cross-spectral analysis of mean arterial pressure (MAP) and mean CBV within the frequency range of 0.07-0.2 Hz. RESULTS: Furosemide reduced PV by 10 ± 2 % and BV by 6 ± 2 % (P = .005 and P = .07). MAP decreased during tilt (P \u3c .007), but the reduction was similar between hydration conditions. CBV during DEH was lower during the entire 10-min tilt by about 7 cm/s (P \u3c .004) compared with EUH. Low frequency coherence was higher during DEH T1 compared with EUH T1 (.67 ± .04 vs .51 ± .04; P = .02), but coherence decreased as tilt continued, and was similar to EUH during T2 (P = 0.7). CONCLUSIONS: Increased coherence during the first 5 min of tilt suggests that reductions of CBV with hypovolemia might be explained by a reduced autoregulatory capacity. However, maintenance of lower CBV despite reduced coherence during the second 5 min of tilt suggests that disruptions of autoregulatory capacity with hypovolemia are transient. Our results provide evidence that hypovolemic astronauts may be at greatest risk for orthostatic intolerance immediately upon assumption of upright posture

Influence of Controlled Breathing on Cerebrovascular Control During Upright Tilt

Arterial pressures oscillate with the frequency of respiration, and these oscillations are translated directly to the cerebrovasculature. For this reason, intrinsic cerebrovascular control is assessed at the low frequency (LF; .07-.2 Hz). When humans breathe spontaneously, it is possible that breathing frequency encroaches on these non-respiratory rhythms, thereby confounding the interpretation of intrinsic cerebrovascular control. PURPOSE: To test the hypothesis that controlled breathing (CB) decreases, and spontaneous breathing (SB) increases the reliance of cerebral blood velocity on arterial pressure within the LF range in both the supine and upright postures. METHODS: We recorded ECG, finger arterial pressure (Finometer), transcranial Doppler ultrasound of the middle cerebral artery, and end-tidal CO₂ in 20 healthy male volunteers (24±2 yrs). Ten subjects breathed in time to a metronome set at a pace of 15 breaths/min (CB), and ten subjects breathed spontaneously (SB). Both groups were studied in the supine and head-up tilt (HUT) positions for 5-min. Reliance of mean cerebral blood velocity (CBVmean) on mean arterial pressure (MAP) was assessed over the LF with cross-spectral coherence analysis (COH). RESULTS: Respiratory rates were not different between CB and SB during supine (p=.86), but were lower for SB compared with CB during HUT (11.7±.7 vs. 14.8±.1; p\u3c.001). End-tidal CO₂ was decreased by CB during both supine and HUT (p\u3c.05). CBVmean was decreased with CB during supine (p=.04), but was similar between CB and SB during HUT (p=.14). Neither LFMAP nor LFCBVmean oscillations were different in the supine position (p\u3e.6), but were increased (with a trend for LFMAP) with SB during HUT (p=.003 for LF CBVmean and p=.09 for LFMAP). COH was not different in the supine position between CB and SB (.42±.05 for CB and .61±.06 SB; p=.13), but was lower for CB in the HUT position (.55±.05 for CB and .78±.08 for SB; p=.02). CONCLUSION: Reliance of CBVmean on MAP is increased in the LF range when subjects breathe spontaneously during HUT. We attribute changes in COH during HUT to entrainment of respiratory-mediated arterial pressure fluctuations on the cerebrovasculature. However, the potential confounding influence of hypocapnia warrants further investigation

Cardiorespiratory Responses during 2-Person CPR using Two Assisted CPR Devices Versus Manual CPR

Active Compression-decompression-CPR (ACD-CPR) requires rescuers to perform work during both phases of CPR. ACD-CPR provides active pre-loading of a patient’s heart with venous return as well as enhanced stroke volume during resuscitation. Prolonged, one-person CPR is exhausting and associated with decayed CPR quality over time. Active compression-decompression-CPR (ACD-CPR) requires the rescuer to actively work during both phases of CPR. We evaluated the metabolic cost of manual CPR (M-CPR), ACD-CPR1, and ACD-CPR2 (with adhesive pad) during a 10-min resuscitation period. We hypothesized that the metabolic cost for the devices would be similar to M-CPR. Twenty (10 female) participants (23.5±3.5y, 165.8±25.6cm, 72.5±12.2kg) completed 3 randomized trials with performance feedback by investigators. Expired air was analyzed for estimations of metabolic cost via indirect calorimetry. Participants rested for 10 minutes before the baseline data collection followed by 10 min of CPR to simulate one-person CPR. Treatment effects were observed for VO2, METS, VCO2, RR, RQ, blood lactate, SBP, and RPE. No such effects were observed with HR and DBP as the observed condition differences for HR and DBP were not significantly different from each other. Blood lactate and SBP were significantly higher using ACD-CPR1 compared to MCPR and ACD-CPR2. Although a trend for elevated DBP was observed with ACD-CPR1, this was not significantly different. RQ values for the ACD-CPR1 device (1.0 ± 0.0) were significantly higher than the RQ values for M-CPR (0.9 ± 0.0) and ACD-CPR2 (0.9 ± 0.0). Assisted CPR using the ACD-CPR1 device is more stressful to the cardiorespiratory system as reflected by the higher SBP compared to the ACD-CPR1 or standard MCPR. Metabolically, the ACD-CPR1 required more VO2 and elicited higher RQ, RPE, and lactate values during 10-min simulated one-person resuscitation compared to M-CPR and ACD-CPR1. However, the ACD-CPR2 cardiorespiratory results were similar to that of M-CPR, despite the latter method’s higher rate of compressions (110/min) and passive decompressions

Effects of Acute Vaporized Nicotine in Non-tobacco Users at Rest and During Exercise

Smokers, and even non-smokers, may utilize vaporized nicotine delivered by electronic cigarette (EC) due to the perception that EC are “healthier” than traditional tobacco cigarettes. The effects of vaporized nicotine delivered by EC on resting blood pressure (BP) and metabolic rate (RMR), or BP and aerobic power during exercise have not been studied. This investigation tested the effects of acute vaporized nicotine inhalation by EC on resting BP and RMR and cycle exercise BP, metabolic responses, and aerobic power in young, normotensive non-smokers. Using a double-blind design, 20 subjects (10 female; 23.1±2.5 years, 1.69±0.1 m, 70.6±14.9 kg; 22.1±11.0% body fat) self-reporting as healthy and non-smoking participated. All subjects participated in two randomized trials: placebo (0 mg nicotine) or nicotine (18 mg nicotine). Participants inhaled from EC once every 30 s for 10 min (20 inhalations total) during each trial. RMR was assessed 40 min later by indirect calorimetry followed by an incremental cycle test. Participants’ pre-inhalation SBP, DBP, and HR were also not significantly different between conditions or from those averaged over the last 5 min of the indirect calorimetry protocol. Cotinine, a stable nicotine metabolite, was assessed on post-inhalation (i.e., 10 min) urine samples. The cotinine concentration ranges, as scored using the semi-quantitative urine analysis kit strips, were significantly higher (p-1) compared to placebo (0-10 ng•ml-1). RMR was assessed ~40 min after the last EC inhalation. RMR (p=0.39), VO2 (p=0.5), RQ (p=0.15), and HR (p=0.47) were not significantly different between the placebo and nicotine trials. Compared to the placebo trial, nicotine use resulted in a 3.7 mmHg lower resting SBP (p=0.04) but a 3.0 mmHg higher DBP (p=0.04). VO2peak was not different between the nicotine trial (2.3±0.8 L•min-1) and placebo trial (2.3±0.7 L•min-1) trials (p=0.77). No statistically distinguishable difference was observed for Wpeak between nicotine (201.0±53.8 W) and placebo (204.8±57.8 W) (p=0.29). There was a main effect of time over the cycle test for VO2 , energy expenditure, RQ, and HR but no between treatment effects. A main treatment effect was identified for DBP, which was higher following nicotine compared to placebo at all time points during the test (p=0.05). No time by treatment interaction was identified for any variable during exercise. Exercise DBPpeak after nicotine (79.4±7.6) was significantly higher (p=0.02) than placebo (74.9±8.3 mmHg). Peak SBP was not different between trials (p=0.14). Our results show that acute vaporized nicotine inhalation via EC increases resting and exercise DBP but does not affect RMR or cycle aerobic power in young, normotensive non-smokers

IDE spatio-temporal impact fluxes and high time-resolution studies of multi-impact events and long-lived debris clouds

The purpose of the Interplanetary Dust Experiment (IDE) on the Long Duration Exposure Facility (LDEF) was to sample the cosmic dust environment and to use the spatio-temporal aspect of the experiment to distinguish between the various components of the environment: zodiacal cloud, beta meteoroids, meteor streams, interstellar dust, and orbital debris. It was found that the introduction of precise time and even rudimentary directionality as co-lateral observables in sampling the particulate environment in near-Earth space produces an enormous qualitative improvement in the information content of the impact data. The orbital debris population is extremely clumpy, being dominated by persistent clouds in which the fluxes may rise orders of magnitude above the background. The IDE data suggest a strategy to minimize the damage to sensitive spacecraft components, using the observed characteristics of cloud encounters