Postsettlement survival linked to larval life in a marine fish

There is a growing realization that the scale and degree of population connectivity are crucial to the dynamics and persistence of spatially structured populations. For marine organisms with complex life cycles, experiences during larval life may influence phenotypic traits, performance, and the probability of postsettlement survival. For a Caribbean reef fish (Thalassoma bifasciatum) on an oceanic island, we used otolith (ear stone) elemental profiles of lead (Pb) to assign recent settlers to a group that developed in waters elevated in Pb concentrations throughout larval life (i.e., nearshore signature) and a group that developed in waters depleted in Pb (i.e., offshore signature), potentially dispersing from upstream sources across oceanic waters. Larval history influenced early life history traits: offshore developers initially grew slowly but compensated with fast growth upon entering nearshore waters and metamorphosed in better condition with higher energy reserves. As shown in previous studies, local production contributed heavily to settlement: at least 45% of settlers developed nearshore. However, only 23% of survivors after the first month displayed a nearshore otolith profile. Therefore, settlers with different larval histories suffered differential mortality. Importantly, selective mortality was mediated by larval history, in that the postsettlement intensity of selection was much greater for fish that developed nearshore, potentially because they had developed in a less selectively intense larval environment. Given the potential for asymmetrical postsettlement source-based survival, successful spatial management of marine populations may require knowledge of "realized connectivity" on ecological scales, which takes into account the postsettlement fitness of individuals from different sources.     

The hummingbird tongue is a fluid trap, not a capillary tube

Hummingbird tongues pick up a liquid, calorie-dense food that cannot be grasped, a physical challenge that has long inspired the study of nectar-transport mechanics. Existing biophysical models predict optimal hummingbird foraging on the basis of equations that assume that fluid rises through the tongue in the same way as through capillary tubes. We demonstrate that the hummingbird tongue does not function like a pair of tiny, static tubes drawing up floral nectar via capillary action. Instead, we show that the tongue tip is a dynamic liquid-trapping device that changes configuration and shape dramatically as it moves in and out of fluids. We also show that the tongue-fluid interactions are identical in both living and dead birds, demonstrating that this mechanism is a function of the tongue structure itself, and therefore highly efficient because no energy expenditure by the bird is required to drive the opening and closing of the trap. Our results rule out previous conclusions from capillarity-based models of nectar feeding and highlight the necessity of developing a new biophysical model for nectar intake in hummingbirds. Our findings have ramifications for the study of feeding mechanics in other nectarivorous birds, and for the understanding of the evolution of nectarivory in general. We propose a conceptual mechanical explanation for this unique fluid-trapping capacity, with far-reaching practical applications (e.g., biomimetics).     

Surfactant degradation activity in bronchoalveolar lavage fluid from guinea pigs challenged with antigen

BACKGROUND AND OBJECTIVE: Surfactant dysfunction is a characteristic of bronchial asthma, but mechanisms of dysfunction following antigen exposure are not understood. The aim of this study was to examine whether bronchoalveolar lavage fluid (BALF) has surfactant degradation activity after antigen challenge, using an animal model of asthma. METHODS: BALF was collected 24 h after a challenge with aerosolized antigen solution in actively sensitized guinea pigs and from non-sensitized control guinea pigs. The surface tension of BALF was measured by pulsating bubble surfactometer. Surfactant activity was expressed as the minimum surface tension of BALF after 5 min of pulsation. BALF was separated into a cellular phospholipid fraction and supernatant, and reconstituted into 'pellet + supernatant' and 'pellet + saline' fractions. RESULTS: Surfactant activity of BALF from sensitized antigen-challenged animals was reduced after 4 h of incubation at 37 degrees C but a decrease was not observed in BALF from non-sensitized control animals. The decrease of surfactant activity in BALF from challenged animals was prevented by incubation at 4 degrees C. Disappearance of surfactant activity after incubation at 37 degrees C was observed in the 'pellet + supernatant', but not in the 'pellet + saline' fraction. The decrease of surfactant activity in BALF was also partially suppressed by the secretory phospholipase A2 inhibitor, indoxam, and by a cocktail of protease inhibitors. CONCLUSION: Surfactant-degrading activity was present in the supernatant of BALF from antigen-challenged guinea pigs. This activity may be attributed to secretory phospholipase A2 and to proteases present in the antigen-challenged airway.     

Plant Material as a Novel Tool in Designing and Formulating Modern Biostimulants—Analysis of Botanical Extract from Linum usitatissimum L.

Nowadays, researchers are looking into next-generation biostimulants that can be designed as a dedicated agronomic tool based on plant materials. The aim of the present study was to develop a novel biostimulating product, based on plant material in the form of linseed aqueous extracts. The scope of the research included the physicochemical characterization of the product and identification of its biostimulating potential. The study has confirmed that the plant biostimulant derived from L. usitatissimum can be used as a viable agronomic tool for growing soybean. The designed and produced biostimulant is rich in bioactive compounds, including amino acids, free fatty acids, carbohydrates, and micro- and macroelements. The tested biostimulant showed significantly lower values of surface tension in relation to water and a commercial biostimulant. The soybean crops responded to the application of the preparation by improvements in agronomic and morphological levels. The linseed macerates were effective in terms of soybean yields and profitability. Our findings serve as preliminary evidence for the viability of designing and developing novel biostimulants derived from plant materials. This comprehensive approach to designing and formulating novel bioproducts necessitates more extensive and targeted research to fully explain the mechanisms behind the improvements observed in the soybean cultivation.     

Uric acid enhances T cell immune responses to hepatitis B surface antigen-pulsed-dendritic cells in mice

AIMTo study the induction of T cellular immune responses in BALB/c mice immunized with uric acid and dendritic cells(DCs)pulsed with hepatitis B virus surface antigen(HBsAg).METHODSDCs were generated from bone-marrow cells of BABL/c mice,and then pulsed or unpulsed with HBsAg protein(HBsAg-pulsed-DCs or unpulsed-DCs)in vitro.BABL/c mice were immunized with HBsAg-pulsed-DCs(1×106)and uric acid,injected through the tail vein of each mouse.The mice in control groups were immunized with HBsAg-pulsed-DCs alone,unpulsed-DCs alone or 200 μg uric acid alone or PBS alone.The immunization was repeated 7 d later.Cytotoxic T lymphocytes(CTLs)/n vivo were determined by the CFSE labeled spleen lysis assay.Spleen cells or spleen T cells were isolated,and re-stimulated in vitro with HBsAg for 120 h or 72 h.Production of IFN-γ and IL-4 secreted by spleen cells were determined by ELISA method;proliferation of spleen T cells were detected by flow cytometry.RESULTSThe cytotoxicities of HBsAg-specific-CTLs,generated after immunization of HBsAg-pulsed-DCs and uric acid,were 68.63% ± 11.32% and significantly stronger than that in the control groups(P ＜ 0.01).Compared with control groups,in mice treated with uric acid and HBsAg-pulsed-DCs,the spleen T cell proliferation to HBsAg re-stimulation was stronger(1.34 ± 0.093 vs 1.081 ± 0.028,P ＜ 0.01),the level of IFN-γsecreted by splenocytes was higher(266.575 ± 51.323 vs 135.223 ± 32.563,P ＜ 0.01),and IL-4 level was lower(22.385 ± 2.252 vs 40.598 ± 4.218,P ＜ 0.01).CONCLUSIONUric acid can strongly enhance T cell immune responses induced by HBsAg-pulsed-DCs vaccine.Uric acid may serve as an effective adjuvant of DC vaccine against HBV infection.     

Gamete plasticity in a broadcast spawning marine invertebrate

Sperm competition has classically been thought to maintain anisogamy (large eggs and smaller sperm) because males are thought to maximize their chance of winning fertilizations by trading sperm size for number. More recently it has been recognized that sperm quality (e.g., size, velocity) can also influence sperm competition, although studies have yielded conflicting results. Because sex evolved in the sea, debate has continued over the role of sperm competition and sperm environment in determining both sperm and egg size in externally fertilizing broadcast spawners. Remarkably, however, there have been no direct tests of whether broadcast spawners change the traits of their gametes depending on the likelihood of sperm competition. We manipulated the density (and thus, sperm environment) of a broadcast spawning ascidian (Styela plicata) in the field and then determined whether the phenotype of eggs and sperm changed. We found that sperm from adults kept at high density were larger and more motile than sperm from low-density adults. In vitro fertilizations revealed that sperm from high-density adults also lived longer and induced less polyspermy. Adult density also affected egg traits: eggs from high-density adults were smaller targets for sperm overall but produced larger ovicells than eggs from low-density adults. This suggests that broadcast spawning mothers balance (potentially conflicting) pre- and postzygotic selection pressures on egg size. Overall, our results suggest that sperm competition does not represent a strong force maintaining anisogamy in broadcast spawners. Instead, sperm limitation seems to select for large eggs and smaller, more numerous sperm.     

TRPA1 acts as a cold sensor in vitro and in vivo

TRPA1 functions as an excitatory ionotropic receptor in sensory neurons. It was originally described as a noxious cold-activated channel, but its cold sensitivity has been disputed in later studies, and the contribution of TRPA1 to thermosensing is currently a matter of strong debate. Here, we provide several lines of evidence to establish that TRPA1 acts as a cold sensor in vitro and in vivo. First, we demonstrate that heterologously expressed TRPA1 is activated by cold in a Ca²⁺-independent and Ca²⁺ store-independent manner; temperature-dependent gating of TRPA1 is mechanistically analogous to that of other temperature-sensitive TRP channels, and it is preserved after treatment with the TRPA1 agonist mustard oil. Second, we identify and characterize a specific subset of cold-sensitive trigeminal ganglion neurons that is absent in TRPA1-deficient mice. Finally, cold plate and tail-flick experiments reveal TRPA1-dependent, cold-induced nociceptive behavior in mice. We conclude that TRPA1 acts as a major sensor for noxious cold.     

Subunit stoichiometry and arrangement in a heteromeric glutamate-gated chloride channel

The invertebrate glutamate-gated chloride-selective receptors (GluClRs) are ion channels serving as targets for ivermectin (IVM), a broad-spectrum anthelmintic drug used to treat human parasitic diseases like river blindness and lymphatic filariasis. The native GluClR is a heteropentamer consisting of α and β subunit types, with yet unknown subunit stoichiometry and arrangement. Based on the recent crystal structure of a homomeric GluClαR, we introduced mutations at the intersubunit interfaces where Glu (the neurotransmitter) binds. By electrophysiological characterization of these mutants, we found heteromeric assemblies with two equivalent Glu-binding sites at β/α intersubunit interfaces, where the GluClβ and GluClα subunits, respectively, contribute the “principal” and “complementary” components of the putative Glu-binding pockets. We identified a mutation in the IVM-binding site (far away from the Glu-binding sites), which significantly increased the sensitivity of the heteromeric mutant receptor to both Glu and IVM, and improved the receptor subunits’ cooperativity. We further characterized this heteromeric GluClR mutant as a receptor having a third Glu-binding site at an α/α intersubunit interface. Altogether, our data unveil heteromeric GluClR assemblies having three α and two β subunits arranged in a counterclockwise β-α-β-α-α fashion, as viewed from the extracellular side, with either two or three Glu-binding site interfaces.Glutamate-gated chloride-selective receptors (GluClRs) are pentameric glutamate-gated chloride channels unique to invertebrates. They belong to the Cys-loop receptor superfamily of transmembrane oligomers that open an intrinsic cationic or anionic channel pore upon binding of neurotransmitters, such as ACh, serotonin, GABA, Gly, histamine, or Glu (1–9). GluClRs are specific targets for ivermectin (IVM), a broad-spectrum anthelmintic drug used to treat filarial diseases like onchocerciasis (river blindness) and elephantiasis (lymphatic filariasis) that afflict hundreds of millions of people worldwide (10, 11). IVM is also broadly used in cattle, swine, and pets to kill gastrointestinal roundworms, lungworms, grubs, sucking lice, and mange mites (12). The high efficiency of IVM stems from its capacity to act as an agonist that keeps the receptor’s ion channel continuously open (13–18). Because the GluClR is chloride-selective, IVM causes sustained hyperpolarization across postsynaptic membranes in the parasitic nematodes. This long-term hyperpolarization leads to suppression of excitation in motor neurons and inhibition of locomotion (19); inhibition of the pharyngeal muscle activity, which interrupts with feeding behavior (20); and interruption of secretion processes that are crucial for evading the host immune system (21).Genes encoding two GluClR homologous subunits, GluClα and GluClβ (glc-1 and glc-2, respectively), were first cloned from Caenorhabditis elegans (13). When expressed in Xenopus oocytes, homomeric GluClαRs respond to IVM but not to Glu and, in contrast, homomeric GluClβRs respond to Glu but not to IVM (13, 16, 17, 22). A recent 3D crystal structure of a truncated homomeric GluClαR (GluClα_crystR; Protein Data Bank ID code 3RIF) shows that when IVM is bound at the five α/α intersubunit interfaces in the ion-channel pore periphery, Glu is lodged at the five α/α intersubunit interfaces in the ligand-binding domain (LigBD) (23) (Fig. 1A). These Glu-binding sites are homologous to the neurotransmitter/agonist-binding sites of other Cys-loop receptors (1, 2, 24), bacterial homologs of Cys-loop receptors (25–30), and ACh-binding proteins (31–34).Open in a separate windowFig. 1.Structural characteristics of GluClRs. (A) Two neighboring subunits of the homopentameric GluClα_crystR [Protein Data Bank (PDB) ID code 3RIF] are shown from the side in light and dark gray colors. Wide gray horizontal lines mark the putative membrane borders. The four coupling loops are colored as shown in C and the upper row of D. Glu and IVM are shown as space-filling models with carbon, oxygen, and nitrogen atoms colored in yellow, red, and blue, respectively. They are bound at the α(+)/α(−) intersubunit interface far away from each other: Glu in the extracellular LigBD and IVM in the upper part of the pore-domain periphery, between M1 (of the light gray subunit) and M3 (of the dark gray subunit). Note that in Cys-loop receptors, the principal and complementary faces of a neurotransmitter-binding pocket are formed by the (+) and (−) sides of two adjacent subunits, respectively. (B) Top view of the GluClα_cryst pentamer showing five identical subunits, which are colored differently to highlight the intersubunit interfaces located between the (+) and (−) sides. (C) Space-filling models of residues belonging to the coupling loops, which create an extensive bond network at the interface between the LigBD and the ion-channel pore domain. (D) Schemes of GluClR subunits used in this study. The M1–M4 transmembrane segments are numbered 1–4. Different colors reflect differences in amino acid sequences (Fig. S1).Importantly, the naturally occurring GluClR robustly responds to both Glu and IVM independently; therefore, it is considered to consist of both GluClα and GluClβ subunit types (13–18). However, little is known about the stoichiometry and molecular arrangement of the subunits in heteromeric GluClRs. Furthermore, the aforementioned crystallographic observations (23) are consistent with earlier studies showing that Glu elicits current responses in homomeric GluClαRs only when applied after activation by IVM (14), which gives rise to the following question: Could an α/α intersubunit interface be formed in a heteromeric assembly, bind Glu, and functionally participate in the activation process even without IVM preassociation? To resolve this question, we clarified here the stoichiometry and positions of the α and β subunits in GluClα/βR heteromeric assemblies that carry mutations in both the putative Glu- and IVM-binding pockets.     

Tracheal aspirate surface tension in babies with hyaline membrane disease: Effects of synthetic surfactant replacement

Our objective was to determine changes in surface tension of tracheal aspirate over the first 4–5 days of life in babies with hyaline membrane disease, with and without synthetic surfactant replacement. Tracheal aspirates were collected prior to and for 96–108 hr after initiation of a randomized double-blind trial of synthetic surfactant (EXOSURF® Neonatal) or air-treated control patients. Using the captive bubble technique, we measured minimum surface tension (initial adsorption, first quasi-static compression, dynamic cycling at 30 cpm, second quasi-static compression and 5 min after quasi-static compressions) in 39 surfactant-treated and 44 control babies. We also compared minimum surface tension with the respiratory support provided. Twelve hours after one dose of synthetic surfactant, minimum surface tension on first quasi-static compression decreased significantly from 20.9 ± 1.4 to 17.6 ± 1.3 mN/m compared to air-treated babies, who did not show any change. Reduction in minimum tracheal aspirate surface tension on first quasi-static compression and during dynamic cycling over 48–60 hr occurred more rapidly in surfactant-treated babies. Ventilator support did not correlate with minimum tracheal aspirate surface tension. We conclude that treatment of babies with synthetic surfactant improved tracheal aspirate minimum surface tension within 12 hr of the first dose and for the next 48–60 hr. Pediatr Pulmonol. 1998;26:173–182. © 1998 Wiley-Liss, Inc.     

Reversed voltage-dependent gating of a bacterial sodium channel with proline substitutions in the S6 transmembrane segment

Members of the voltage-gated-like ion channel superfamily have a conserved pore structure. Transmembrane helices that line the pore (M2 or S6) are thought to gate it at the cytoplasmic end by bending at a hinge glycine residue. Proline residues favor bending of alpha-helices, and substitution of proline for this glycine (G219) dramatically stabilizes the open state of a bacterial Na(+) channel NaChBac. Here we have probed S6 pore-lining residues of NaChBac by proline mutagenesis. Five of 15 proline-substitution mutants yielded depolarization-activated Na(+) channels, but only G219P channels have strongly negatively shifted voltage dependence of activation, demonstrating specificity for bending at G219 for depolarization-activated gating. Remarkably, three proline-substitution mutations on the same face of S6 as G219 yielded channels that activated upon hyperpolarization and inactivated very slowly. Studies of L226P showed that hyperpolarization to -147 mV gives half-maximal activation, 123 mV more negative than WT. Analysis of combination mutations and studies of block by the local anesthetic etidocaine favored the conclusion that hyperpolarization-activated gating results from opening of the cytoplasmic gate formed by S6 helices. Substitution of multiple amino acids for L226 indicated that hyperpolarization-activated gating was correlated with a high propensity for bending, whereas depolarization-activated gating was favored by a low propensity for bending. Our results further define the dominant role of bending of S6 in determining not only the voltage dependence but also the polarity of voltage-dependent gating. Native hyperpolarization-activated gating of hyperpolarization- and cyclic nucleotide-gated (HCN) channels in animals and KAT channels in plants may involve bending at analogous S6 amino acid residues.     

Glycine as a D-amino acid surrogate in the K(+)-selectivity filter

The K(+) channel-selectivity filter consists of two absolutely conserved glycine residues. Crystal structures show that the first glycine in the selectivity filter, Gly-77 in KcsA, is in a left-handed helical conformation. Although the left-handed helical conformation is not favorable for the naturally occurring L-amino acids, it is favorable for the chirally opposite D-amino acids. Here, we demonstrate that Gly-77 can be replaced by D-Ala with almost complete retention of function. In contrast, substitution with an L-amino acid results in a nonfunctional channel. This finding suggests that glycine is used as a surrogate D-amino acid in the selectivity filter. The absolute conservation of glycine in the K(+)-selectivity filter can be explained as a result of glycine being the only natural amino acid that can play this role.     

Effects of azimilide, a new class III antiarrhythmic drug, on reentrant circuits causing ventricular tachycardia and fibrillation in a canine model of myocardial infarction

INTRODUCTION: Azimilide blocks the slow (I(Ks)) and fast (I(Kr)) components of the delayed rectifier potassium channel. It also has blocking effects on sodium (I(Na)) and calcium currents (I(CaL)). Its effects on reentrant circuits in infarct border zones causing ventricular tachyarrhythmias are unknown. METHODS AND RESULTS: Activation in reentrant circuits causing sustained ventricular tachycardia (SVT) and the initial polymorphic tachycardia that leads to ventricular fibrillation (VF) was mapped in the epicardial border zone (EBZ) of 4-day-old canine infarcts. Azimilide prolonged the effective refractory period (ERP) in both normal myocardium and EBZ, but reverse use-dependence in EBZ was prominent. Azimilide abolished SVT initiation by programmed electrical stimulation by prolonging the ERP at the site of stimulation either in normal or EBZ, preventing the occurrence of early premature impulses and the formation of lines of block in the EBZ necessary for formation of reentrant circuits. Azimilide prevented VF initiation by programmed electrical stimulation by causing conduction block of reentrant impulses in the EBZ during the initial beats of rapid polymorphic ventricular tachycardia, despite the reverse use-dependent effects on ERP. CONCLUSION: Azimilide has antiarrhythmic effects to prevent reentry causing SVT and VF in a canine infarct model.     

匹他伐他汀促进小鼠血管新生作用及其机制的研究

目的探讨匹他伐他汀对小鼠血管新生的促进作用及其可能的作用机制。方法建立野生型C3H／He小鼠下肢缺血模型并分为2组,缺血对照组,匹他伐他汀组。使用激光多普勒血流测定仪测定实验小鼠投药前、下肢缺血手术后双下肢血流。免疫荧光组化sP法计数缺血肢毛细血管数。免疫酶组化直接法计数缺血肢磷酸化蛋白激酶Akt（p-Akt）阳性细胞数。蛋白印迹杂交方法检测缺血肢血管内皮生长因子蛋白表达。镉还原Griess法测定实验结束后血清一氧化氮代谢产物含量。结果匹他伐他汀使实验小鼠术后缺血肢血流恢复明显,缺血肢与非缺血肢血流面积比明显增加;缺血肢毛细血管密度明显增加、p-Akt活性增加（p-Akt阳性细胞数明显增加）;血中一氧化氮代谢产物含量明显增高;缺血肢血管内皮生长因子蛋白表达增强。结论匹他伐他汀有促进小鼠血管新生的作用。     

Calpromotin,a cytoplasmic protein,is associated with the formation of dense cells in sickle cell anemia

We have tested the hypothesis that dense cell formation in sickle cell disease is associated with increased binding of calpromotin to the membrane, an event that occurs during the activation of calcium-dependent potassium transport. By SDS polyacrylamide gel electrophoresis, we found that sickle cell membranes contained more calpromotin than did normal membranes when stained with Coomassie brilliant blue or when transferred to nitrocellulose paper and immunostained with horseradish peroxidase. Also, the membranes from dense sickle cells contained significantly (P = 0.00055) higher levels of calpromotin, 2.62 ± 1.59 μg/mg membrane protein, compared to light sickle cells, 1.40 ± 0.70 μg/mg membrane protein, when measured by an enzyme-linked immunosorbent assay. The ratio of calpromotin associated with dense cell membranes to light cell membranes was significantly greater than 1.0 (P < 0.00005). Transmission electron micrographs of immunogold-labelled membranes supported the increase in calpromotin binding in dense sickle cell membranes. In addition, the immunogold probe demonstrated clustering, which was not observed in light sickle cell membranes nor in normal membranes. Finally, we incubated HbSS cells in vitro using a repetitive deoxygenation/reoxygenation procedure to produce dense cells and then measured the levels of calpromotin associated with their membranes. As expected, the levels of calpromotin bound to the membrane doubled during the procedure relative to the basal levels at the beginning of the incubation. The correlation coefficient, calculated between the increase in dense cell formation and the increase in calpromotin associated with the membrane, was statistically significant (P = 0.038). The results demonstrate that an increase in calpromotin binding to the membrane is associated with dense cell formation presumably through the activation of the calcium-dependent potassium channel. Am. J. Hematol. 56:100–106, 1997. © 1997 Wiley-Liss, Inc.     

Melatonin protects embryonic development and maintains sleep/wake behaviors from the deleterious effects of fluorene‐9‐bisphenol in zebrafish (Danio rerio)

Environmental endocrine chemicals have various adverse effects on the development of vertebrates. Fluorene‐9‐bisphenol (BHPF), a substitute of bisphenol A (BPA), is widely used in commercial production. The effects of BHPF on development and behavior are unclear. Melatonin plays a protective role under many unfavorable conditions. In this study, we investigated the effects of BHPF on the development and behaviors of zebrafish and whether melatonin reverses effects induced by BHPF. Zebrafish embryos were exposed to 0.1, 10, or 1000 nmol/L BHPF with or without 1 μmol/L melatonin from 2 hours postfertilization to 6 days postfertilization. The results showed that 0.1 and 10 nmol/L BHPF had little effect on development. High‐dose BHPF (1000 nmol/L) delayed the development, increased mortality and surface tension of embryonic chorions, caused aberrant expression of the key genes (ntl, shh, krox20, pax2, cmlc2) in early development detected by in situ hybridization, and damaged the CaP motor neurons, which were associated with locomotion ability detected by immunofluorescence. Melatonin addition reversed or weakened these adverse effects of BHPF on development, and melatonin alone increased surface tension as the effects of high‐dose BHPF. However, all groups of BHPF exposure triggered insomnia‐like behaviors, with increased waking activity and decreased rest behaviors. BHPF acted on the hypocretin (hcrt) system and upregulated the expression of sleep/wake regulators such as hcrt, hcrt receptor (hcrtr), arylalkylamine N‐acetyltransferase‐2 (aanat2). Melatonin recovered the alternation of sleep/wake behaviors induced by BHPF and restored abnormal gene expression to normal levels. This study showed that high‐dose BHPF had adverse effects on early development and induced behavioral alternations. However, melatonin prevented BHPF‐induced aberrant development and sleep/wake behaviors.     

Isotopic composition of atmospheric nitrate in a tropical marine boundary layer

Long-term observations of the reactive chemical composition of the tropical marine boundary layer (MBL) are rare, despite its crucial role for the chemical stability of the atmosphere. Recent observations of reactive bromine species in the tropical MBL showed unexpectedly high levels that could potentially have an impact on the ozone budget. Uncertainties in the ozone budget are amplified by our poor understanding of the fate of NO_x (= NO + NO₂), particularly the importance of nighttime chemical NO_x sinks. Here, we present year-round observations of the multiisotopic composition of atmospheric nitrate in the tropical MBL at the Cape Verde Atmospheric Observatory. We show that the observed oxygen isotope ratios of nitrate are compatible with nitrate formation chemistry, which includes the BrNO₃ sink at a level of ca. 20 ± 10% of nitrate formation pathways. The results also suggest that the N₂O₅ pathway is a negligible NO_x sink in this environment. Observations further indicate a possible link between the NO₂/NO_x ratio and the nitrogen isotopic content of nitrate in this low NO_x environment, possibly reflecting the seasonal change in the photochemical equilibrium among NO_x species. This study demonstrates the relevance of using the stable isotopes of oxygen and nitrogen of atmospheric nitrate in association with concentration measurements to identify and constrain chemical processes occurring in the MBL.