From the Cover: Echolocating bats rely on an innate speed-of-sound reference

Animals must encode fundamental physical relationships in their brains. A heron plunging its head underwater to skewer a fish must correct for light refraction, an archerfish shooting down an insect must “consider” gravity, and an echolocating bat that is attacking prey must account for the speed of sound in order to assess its distance. Do animals learn these relations or are they encoded innately and can they adjust them as adults are all open questions. We addressed this question by shifting the speed of sound and assessing the sensory behavior of a bat species that naturally experiences different speeds of sound. We found that both newborn pups and adults are unable to adjust to this shift, suggesting that the speed of sound is innately encoded in the bat brain. Moreover, our results suggest that bats encode the world in terms of time and do not translate time into distance. Our results shed light on the evolution of innate and flexible sensory perception.

Every organism must reliably sense its environment in order to survive and reproduce (1). Some sensory systems are innate and unalterable (2), allowing for efficient use even by naïve newborn animals (3–5). Others require learning or experience-dependent development—usually during a critical period during ontogeny (6, 7), though sometimes retained through adulthood (8), allowing for adapting sensing to changing environments (9, 10). The ability to accurately estimate distances with sub-centimeter accuracy is a hallmark of bat echolocation (11–13). Bats achieve this accuracy by means of delay-tuned neurons—neurons that are activated by specific call–echo time delays, supposedly encoding target distance (14–19), although it should be noted that some work suggests that the tuning width of delay-tuned neurons might not allow the accuracy that bats exhibit in delay perception (20). Though delay tuning has been shown to be (at least partially) innate at the neural level (21), this has never been tested behaviorally. Namely, when a newborn bat takes off for the first time, does its brain correctly translate time delays into distance?Translating time into distance relies on a reference of the speed of sound (SOS). This physical characteristic of the environment is not as stable as it may seem. The SOS may change considerably due to various environmental factors such as humidity, altitude, and temperature (22). Bats (Chiroptera) are a specious and widely distributed order of highly mobile and long-lived animals. They therefore experience a range of SOSs (with more than 5% variation, see below) between species, among species, and even within the life of a single individual. We therefore speculated that the reference of the SOS may not be innate to allow for the environmentally dependent SOS experienced by each animal.To test this, we examined the acquisition of the SOS reference by exposing neonatal bats to an increased SOS environment from birth (Materials and Methods). We reared two groups of bats from birth to independent flight in two flight chambers: six bats in normal air (henceforth: “air pups”) and five bats in a helium-enriched air environment (Heliox), where the speed of sound was 15% higher (henceforth: “Heliox pups”). Notably, Heliox pups were never active and did not echolocate in non-Heliox environment (Materials and Methods). This 15% shift is higher than the ecological range and was chosen because it is high enough to enable us to document behavioral changes but low enough so as to allow the bats to function (that is, to fly despite the change in air density). In order to feed, the bats had to fly to a target positioned 1.3 m away from their wooden slit roost. Once the bats learned to fly to the target independently (after ca. 9 wk), we first documented their echolocation in the environment where they were brought up, and we then moved them to the other treatment for testing (Materials and Methods). Because bats adjust their echolocation parameters to the distance of the target, before and during flight (23), we used their echolocation to assess the bats’ target range estimates. If the SOS reference is learned based on experience, the bats raised in Heliox should have learned a faster reference, so that when they flew in normal air, they would have perceived the target as farther than it really was. We also ran the same experiments on adult bats to test adult plasticity.     

Touching the Other's Suffering: Cross‐Cultural Challenges in Palliative Treatment Along Geopolitical Crossroads

The authors describe the cross-cultural considerations in caring for a Palestinian breast cancer patient by an Israeli heath care team. The processes that facilitated a metamorphosis from possible hostility to receptiveness based on historical cultural conflicts were rooted in professionalism, patient-centered care, and cross-cultural sensitivity, woven into the patient’s own health beliefs and affinity to traditional Islamic medicine.     

Low- and high-density lipoprotein cholesterol and ischemic cerebrovascular disease: the bezafibrate infarction prevention registry

BACKGROUND: Despite increasing evidence that beta-hydroxy-beta-methyglutaryl coenzyme A reductase inhibitors reduce the incidence of stroke in patients with coronary heart disease (CHD), the associations between blood lipid levels and cerebrovascular disease (CVD) are not clear. OBJECTIVE: To evaluate whether blood cholesterol level and its fractions are risk factors for stroke in a large group of patients with CHD. METHODS: We followed up 11 177 patients with documented CHD who were screened for but not included in the Bezafibrate Infarction Prevention study, a secondary prevention randomized clinical trial of lipid modification, and had no history of stroke for subsequent CVD. During a 6- to 8-year follow-up period, 941 patients were identified as having nonhemorrhagic CVD, of whom 487 had verified ischemic stroke or transient ischemic attack (TIA). RESULTS: Increases in age-adjusted rates of both nonhemorrhagic CVD and verified ischemic stroke or TIA were identified with increasing cholesterol and low-density lipoprotein cholesterol levels, decreasing high-density lipoprotein cholesterol levels, and decreasing percentage of total serum cholesterol contained in the HDL moiety. In logistic regression models, adjusting for clinical covariates, the following odds ratios (95% confidence intervals) were identified for lipid values in the upper vs lower tertile for the end point of nonhemorrhagic CVD: total cholesterol, 1.43 (1.20-1.70); low-density lipoprotein cholesterol, 1.52 (1.27-1.81), high-density lipoprotein cholesterol, 0.84 (0.70-1.00); and percentage of serum cholesterol contained in HDL, 0.69 (0.58-0.83). Similar trends appeared for the end point of verified ischemic stroke or TIA. CONCLUSION: These findings clearly support the role of total cholesterol and its fractions in prediction of ischemic CVD among patients with established CHD.     

Selective degradation of cyclin B1 mRNA in rat oocytes by RNA interference (RNAi)

Cyclic adenosine monophosphate (cAMP) keeps oocytes in meiotic arrest, thereby preventing activation of the key regulators of meiosis, p34cdc2/cyclin B1, (known as maturation-promoting factor (MPF)) and Erk 1 and 2, members of the mitogen-activated protein kinase (MAPK) family. The activity of MAPK in oocytes is upregulated by Mos. We previously demonstrated that Mos translation in rat oocytes is negatively regulated by a PKA-mediated cAMP action, which inhibits c-mos mRNA polyadenylation and is associated with the suppression of p34 cdc2 kinase. The goal of the present study was to provide definitive evidence that Mos translation is subjected to MPF regulation. In order to inhibit MPF activity, we employed the double-stranded (ds) RNA interference (RNAi) of gene expression. We demonstrated that the introduction of cyclin B1 dsRNA into rat oocytes selectively depleted the corresponding mRNA, further ablating its protein product. These oocytes, which exhibit low MPF activity, failed to elongate the c-mos mRNA poly(A) tail, did not accumulate Mos and were unable to activate MAPK. We conclude that an active MPF in rat oocytes is necessary for c-mos mRNA polyadenylation and Mos translation.     

Does the level of amniotic fluid have an effect on the accuracy of sonographic estimated fetal weight at term?

Objective: Controversy exists concerning the impact of amniotic fluid index (AFI) on the accuracy of sonographic estimation of fetal weight (EFW). Thus, we aimed to evaluate whether differences in AFI has an influence on the accuracy of sonographic EFW.

Methods: All term, singleton pregnancies which underwent a sonographic EFW and measurement of AFI within a week from delivery were included. Cases were stratified into three categories according to AFI: (1) Normal AFI (51–249?mm), (2) Oligohydramnios (AFI?≤?50?mm) and (3) Polyhydramnios (AFI?≥?250?mm). Inaccurate EFW was defined if there was more than 15% difference between sonographic EFW and actual birthweight.

Results: Overall, 1746 pregnancies were identified (1096 with normal AFI, 455 with oligohydramnios and 195 with polyhydramnios). Mean AFI was 115.8?±?60?mm, 28.1?±?13?mm and 293?±?35?mm, p?<?0.001, and mean sonographic EFW was 3182.5?±?573?g, 3118.8?±?517?g and 3713.2?±?461?g, p?<?0.001, respectively. Demographic data and gestational age at delivery were similar. Mean birthweight was 3221.7?±?535?g, 3132.5?±?505?g and 3654.1?±?480?g, p?<?0.001, respectively. The rate of inaccurate EFW was similar between the groups (8.4%, 8.7% and 9.7%, p?=?0.19, respectively). On multivariate analysis, AFI was not associated with EFW inaccuracy (OR 1.01, 95% C.I 0.67–1.54, p?=?0.93).

Conclusion: AFI has limited impact on the percentage of errors in sonographic fetal weight estimation a week prior delivery.