Epigenetic regulation by hypoxia, N-acetylcysteine and hydrogen sulphide of the fetal vasculature in growth restricted offspring: A study in humans and chicken embryos.

Fetal growth restriction (FGR) is a common outcome in human suboptimal gestation and is related to prenatal origins of cardiovascular dysfunction in offspring. Despite this, therapy of human translational potential has not been identified. Using human umbilical and placental vessels and the chicken embryo model, we combined cellular, molecular, and functional studies to determine whether N-acetylcysteine (NAC) and hydrogen sulphide (H2S) protect cardiovascular function in growth-restricted unborn offspring. In human umbilical and placental arteries from control or FGR pregnancy and in vessels from near-term chicken embryos incubated under normoxic or hypoxic conditions, we determined the expression of the H2S gene CTH (i.e. cystathionine γ-lyase) (via quantitative PCR), the production of H2S (enzymatic activity), the DNA methylation profile (pyrosequencing) and vasodilator reactivity (wire myography) in the presence and absence of NAC treatment. The data show that FGR and hypoxia increased CTH expression in the embryonic/fetal vasculature in both species. NAC treatment increased aortic CTH expression and H2S production and enhanced third-order femoral artery dilator responses to the H2S donor sodium hydrosulphide in chicken embryos. NAC treatment also restored impaired endothelial relaxation in human third-to-fourth order chorionic arteries from FGR pregnancies and in third-order femoral arteries from hypoxic chicken embryos. This NAC-induced protection against endothelial dysfunction in hypoxic chicken embryos was mediated via nitric oxide independent mechanisms. Both developmental hypoxia and NAC promoted vascular changes in CTH DNA and NOS3 methylation patterns in chicken embryos. Combined, therefore, the data support that the effects of NAC and H2S offer a powerful mechanism of human translational potential against fetal cardiovascular dysfunction in complicated pregnancy. KEY POINTS: Gestation complicated by chronic fetal hypoxia and fetal growth restriction (FGR) increases a prenatal origin of cardiovascular disease in offspring, increasing interest in antenatal therapy to prevent against a fetal origin of cardiovascular dysfunction. We investigated the effects between N-acetylcysteine (NAC) and hydrogen sulphide (H2S) in the vasculature in FGR human pregnancy and in chronically hypoxic chicken embryos. Combining cellular, molecular, epigenetic and functional studies, we show that the vascular expression and synthesis of H2S is enhanced in hypoxic and FGR unborn offspring in both species and this acts to protect their vasculature. Therefore, the NAC/H2S pathway offers a powerful therapeutic mechanism of human translational potential against fetal cardiovascular dysfunction in complicated pregnancy.

A Compilation of Drug Etiologies of Stevens-Johnson Syndrome and Toxic Epidermal Necrolysis.

Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are adverse reactions that affect the mucocutaneous surfaces by causing necrosis and detachment of the epidermis. The difference between SJS and TEN is in the percentage of the body surface area (BSA) affected. TEN is known to affect greater BSA than SJS. The pathogenesis of SJS/TEN is attributed to drug-specific cell-mediated cytotoxic reactions that directly and indirectly lead to keratinocyte apoptosis through mediators. Clinical presentation begins with influenza-like symptoms, with the disease affecting the skin, oral, ocular, and urogenital regions most frequently. Although SJS/TEN is mainly due to various drugs, infection and vaccination can also induce SJS/TEN. This review outlines a compilation of all drugs implicated in SJS/TEN cases based on studies, mainly in case reports and other study types. Drug classes implicated in SJS/TEN cases include antibiotics, anticonvulsants, antineoplastics, analgesics, and diuretics, among others. There is no fully established diagnostic modality for SJS/TEN; treatment is done mainly by withdrawing the offending agent. In addition to withdrawing the offending agent, a multidisciplinary care team is essential in managing these patients. Several pharmacologic modalities have also been proposed in treatment, but there is still insufficient evidence for the efficacy of one against the other.

MitoQ as an antenatal antioxidant treatment improves markers of lung maturation in healthy and hypoxic pregnancy.

Chronic fetal hypoxaemia is a common pregnancy complication that increases the risk of infants experiencing respiratory complications at birth. In turn, chronic fetal hypoxaemia promotes oxidative stress, and maternal antioxidant therapy in animal models of hypoxic pregnancy has proven to be protective with regards to fetal growth and cardiovascular development. However, whether antenatal antioxidant therapy confers any benefit on lung development in complicated pregnancies has not yet been investigated. Here, we tested the hypothesis that maternal antenatal treatment with MitoQ will protect the developing lung in hypoxic pregnancy in sheep, a species with similar fetal lung developmental milestones as humans. Maternal treatment with MitoQ during late gestation promoted fetal pulmonary surfactant maturation and an increase in the expression of lung mitochondrial complexes III and V independent of oxygenation. Maternal treatment with MitoQ in hypoxic pregnancy also increased the expression of genes regulating liquid reabsorption in the fetal lung. These data support the hypothesis tested and suggest that MitoQ as an antenatal targeted antioxidant treatment may improve lung maturation in the late gestation fetus. KEY POINTS: Chronic fetal hypoxaemia promotes oxidative stress, and maternal antioxidant therapy in hypoxic pregnancy has proven to be protective with regards to fetal growth and cardiovascular development. MitoQ is a targeted antioxidant that uses the cell and the mitochondrial membrane potential to accumulate within the mitochondria. Treatment of healthy or hypoxic pregnancy with MitoQ, increases the expression of key molecules involved in surfactant maturation, lung liquid reabsorption and in mitochondrial proteins driving ATP synthesis in the fetal sheep lung. There were no detrimental effects of MitoQ treatment alone on the molecular components measured in the present study, suggesting that maternal antioxidant treatment has no effect on other components of normal maturation of the surfactant system.

Chronic Hypoxia in Ovine Pregnancy Recapitulates Physiological and Molecular Markers of Preeclampsia in the Mother, Placenta, and Offspring.

BACKGROUND: Preeclampsia continues to be a prevalent pregnancy complication and underlying mechanisms remain controversial. A common feature of preeclampsia is utero-placenta hypoxia. In contrast to the impact of hypoxia on the placenta and fetus, comparatively little is known about the maternal physiology. METHODS: We adopted an integrative approach to investigate the inter-relationship between chronic hypoxia during pregnancy with maternal, placental, and fetal outcomes, common in preeclampsia. We exploited a novel technique using isobaric hypoxic chambers and in vivo continuous cardiovascular recording technology for measurement of blood pressure in sheep and studied the placental stress in response to hypoxia at cellular and subcellular levels. RESULTS: Chronic hypoxia in ovine pregnancy promoted fetal growth restriction (FGR) with evidence of fetal brain-sparing, increased placental hypoxia-mediated oxidative damage, and activated placental stress response pathways. These changes were linked with dilation of the placental endoplasmic reticulum (ER) cisternae and increased placental expression of the antiangiogenic factors sFlt-1 (soluble fms-like tyrosine kinase 1) and sEng (soluble endoglin), combined with a shift towards an angiogenic imbalance in the maternal circulation. Chronic hypoxia further led to an increase in uteroplacental vascular resistance and the fall in maternal blood pressure with advancing gestation measured in normoxic pregnancy did not occur in hypoxic pregnancy. CONCLUSIONS: Therefore, we show in an ovine model of sea-level adverse pregnancy that chronic hypoxia recapitulates physiological and molecular features of preeclampsia in the mother, placenta, and offspring.

Embryonic cardioprotection by hydrogen sulphide: studies of isolated cardiac function and ischaemia-reperfusion injury in the chicken embryo.

KEY POINTS: In mammals, pregnancy complications can trigger an embryonic or fetal origin of cardiac dysfunction. However, underlying mechanisms remain uncertain because the partial contributions of the challenge on the mother, placenta or offspring are difficult to disentangle. The avian embryo permits isolation of the direct effects of suboptimal conditions during development on the cardiac function of the offspring, independent of additional effects on the mother and/or the placenta. Therefore, the objectives of this work were to adapt the isolated Langendorff technique using the chicken embryo to study the physiology of the developing heart. Here, we introduce a novel technique and show the utility of the technique for exploring cardioprotective roles of H2 S in the chicken embryo heart. This work lays the foundation for studying the direct effects of H2 S therapy on the embryonic heart independent of effects on the mother and the placenta in adverse development. ABSTRACT: This study adapted the isolated Langendorff preparation to study the chicken embryo heart in response to ischaemia-reperfusion (IR) injury. The utility of the technique was tested by investigating cardioprotective effects of hydrogen sulphide (H2 S) and underlying mechanisms. Embryonic hearts (19 out of 21 days of incubation) mounted on a Langendorff preparation were exposed to IR (30 min ischaemia) after 4 treatments administered randomly, all as a 1 mm bolus, into the perfusate: saline vehicle (control); sodium hydrogen sulphide (NaHS); NaHS plus glibenclamide, an antagonist of KATP opening (NaHS Glib), and Glib alone (Glib). Relative to controls, NaHS treatment improved cardiac function after ischaemia (mean ± SD for area under the curve, AUC, for left ventricular developed pressure, LVDP: 1767.3 ± 929.5 vs. 492.7 ± 308.1; myocardial contractility, dP/dtmax : 2748.9 ± 1514.9 vs. 763.7 ± 433.1) and decreased infarct size (22.7 ± 8.0 vs. 43.9 ± 4.2%) and cardiac damage (% change in creatinine kinase, 49.3 ± 41.3 vs. 214.6 ± 155.1; all P < 0.05). Beneficial effects of NaHS were blocked by Glib. Glib alone had no effects. NaHS increased coronary flow rate (CFR) during baseline (mean ± SD for AUC: 134.3 ± 91.6 vs. 92.2 ± 35.8) and post IR (1467 ± 529.5 vs. 748.0 ± 222.1; both P < 0.05). However, this effect was not prevented by Glib. Therefore, the chicken embryo heart is amenable for study via the Langendorff preparation under basal conditions and during IR. The data show that H2 S confers embryonic cardiac protection via opening of myocardial KATP channels and not via increasing CFR. H2 S may prove a useful therapeutic agent to protect the human fetal heart against IR injury, as may occur in complicated labour.

Genetic assessment of the effects of streamscape succession on coho salmon Oncorhynchus kisutch colonization in recently deglaciated streams.

Measures of genetic diversity within and among populations and historical geomorphological data on stream landscapes were used in model simulations based on approximate Bayesian computation (ABC) to examine hypotheses of the relative importance of stream features (geomorphology and age) associated with colonization events and gene flow for coho salmon Oncorhynchus kisutch breeding in recently deglaciated streams (50-240 years b.p.) in Glacier Bay National Park (GBNP), Alaska. Population estimates of genetic diversity including heterozygosity and allelic richness declined significantly and monotonically from the oldest and largest to youngest and smallest GBNP streams. Interpopulation variance in allele frequency increased with increasing distance between streams (r = 0·435, P < 0·01) and was inversely related to stream age (r = -0·281, P < 0·01). The most supported model of colonization involved ongoing or recent (<10 generations before sampling) colonization originating from large populations outside Glacier Bay proper into all other GBNP streams sampled. Results here show that sustained gene flow from large source populations is important to recently established O. kisutch metapopulations. Studies that document how genetic and demographic characteristics of newly founded populations vary associated with successional changes in stream habitat are of particular importance to and have significant implications for, restoration of declining or repatriation of extirpated populations in other regions of the species' native range.

Colonizing the world in spite of reduced MHC variation.

The major histocompatibility complex (MHC), which harbours the most polymorphic vertebrate genes, plays a critical role in the host-pathogen coevolutionary arms race. However, the extent to which MHC diversity determines disease susceptibility and long-term persistence of populations is currently under debate, as recent studies have demonstrated that low MHC variability does not necessarily hamper population viability. However, these studies typically assayed small and decimated populations in species with restricted distribution, thereby making inferences about the evolutionary potential of these populations difficult. Here, we show that MHC impoverishment has not constrained the ecological radiation and flourishing of falcons (Aves: Falconidae) worldwide. We found two remarkably different patterns of MHC variation within the genus Falco. Whereas MHC variation in kestrels (the basal group within the genus) is very high, falcons exhibit ancestrally low intra- and interspecific MHC variability. This pattern is not due to the inadvertent survey of paralogous genes or pseudogenes. Further, patterns of variation in mitochondrial or other nuclear genes do not indicate a generalized low level of genome-wide variability among falcons. Although a relative contribution of genetic drift cannot be completely ruled out, we propose the falcons went through an evolutionary transition, driven and maintained by natural selection, from primarily highly variable towards low polymorphic and slow-evolving MHC genes with a very specific immune function. This study highlights that the importance of MHC diversity cannot be generalized among vertebrates, and hints at the evolution of compensatory immune mechanisms in falcons to cope with emerging and continuously evolving pathogens.

Ultralow emittance, multi-MeV proton beams from a laser virtual-cathode plasma accelerator.

The laminarity of high-current multi-MeV proton beams produced by irradiating thin metallic foils with ultraintense lasers has been measured. For proton energies >10 MeV, the transverse and longitudinal emittance are, respectively, <0.004 mm mrad and <10(-4) eV s, i.e., at least 100-fold and may be as much as 10(4)-fold better than conventional accelerator beams. The fast acceleration being electrostatic from an initially cold surface, only collisions with the accelerating fast electrons appear to limit the beam laminarity. The ion beam source size is measured to be <15 microm (FWHM) for proton energies >10 MeV.

Founding events influence genetic population structure of sockeye salmon (Oncorhynchus nerka) in Lake Clark, Alaska.

Bottlenecks can have lasting effects on genetic population structure that obscure patterns of contemporary gene flow and drift. Sockeye salmon are vulnerable to bottleneck effects because they are a highly structured species with excellent colonizing abilities and often occupy geologically young habitats. We describe genetic divergence among and genetic variation within spawning populations of sockeye salmon throughout the Lake Clark area of Alaska. Fin tissue was collected from sockeye salmon representing 15 spawning populations of Lake Clark, Six-mile Lake, and Lake Iliamna. Allele frequencies differed significantly at 11 microsatellite loci in 96 of 105 pairwise population comparisons. Pairwise estimates of FST ranged from zero to 0.089. Six-mile Lake and Lake Clark populations have historically been grouped together for management purposes and are geographically proximate. However, Six-mile Lake populations are genetically similar to Lake Iliamna populations and are divergent from Lake Clark populations. The reduced allelic diversity and strong divergence of Lake Clark populations relative to Six-mile Lake and Lake Iliamna populations suggest a bottleneck associated with the colonization of Lake Clark by sockeye salmon. Geographic distance and spawning habitat differences apparently do not contribute to isolation and divergence among populations. However, temporal isolation based on spawning time and founder effects associated with ongoing glacial retreat and colonization of new spawning habitats contribute to the genetic population structure of Lake Clark sockeye salmon. Nonequilibrium conditions and the strong influence of genetic drift caution against using estimates of divergence to estimate gene flow among populations of Lake Clark sockeye salmon.

Properties of the ultrashort gain length, self-amplified spontaneous emission free-electron laser in the linear regime and saturation.

VISA (Visible to Infrared SASE Amplifier) is a high-gain self-amplified spontaneous emission (SASE) free-electron laser (FEL), which achieved saturation at 840 nm within a single-pass 4-m undulator. The experiment was performed at the Accelerator Test Facility at BNL, using a high brightness 70-MeV electron beam. A gain length shorter than 18 cm has been obtained, yielding a total gain of 2 x 10(8) at saturation. The FEL performance, including the spectral, angular, and statistical properties of SASE radiation, has been characterized for different electron beam conditions. Results are compared to the three-dimensional SASE FEL theory and start-to-end numerical simulations of the entire injector, transport, and FEL systems. An agreement between simulations and experimental results has been obtained at an unprecedented level of detail.

Alfa and beta estrogen receptors and the biliary tree.

This manuscript summarizes recent data showing that estrogens and their receptors play an important role in modulating cholangiocyte proliferation. We have recently demonstrated that rat cholangiocytes express both estrogen receptors (ER)-alpha and -beta subtypes, while hepatocytes only express ER-alpha. ER and especially the ER-beta subtype, are overexpressed in cholangiocytes proliferating after bile duct ligation (BDL) in the rat, in association with enlarged bile duct mass and with enhanced estradiol serum levels. Cholangiocyte proliferation, during BDL, is impaired by estrogen antagonists (tamoxifen, ICI 182,780) which furthermore, induce the overexpression of Fas antigen and activate apoptosis of proliferating cholangiocytes. 17beta-estradiol stimulates, in vitro cholangiocyte proliferation, and this effect is individually blocked by tamoxifen or ICI 182,780. Cholangiocyte proliferation during BDL was associated with an enhanced protein expression of phosphorylated extracellular regulated kinases (ERK)1/2 which is, in contrast, negatively modulated by tamoxifen in association with its antiproliferative effect. This indicates a major involvement of the ERK system in the estrogen modulation of cholangiocyte proliferation.

Microsatellite analyses of the trout of northwest Mexico.

The trout of northwest Mexico represent an undescribed group of fish considered part of the Oncorhynchus mykiss (Pacific trout) complex of species and subspecies. Recent genetic studies have shown these fish to have important genetic diversity and a unique evolutionary history when compared to coastal rainbow trout. Increased levels of allelic diversity have been found in this species at the southern extent of its range. In this study we describe the trout in the Sierra Madre Occidental from the rios Yaqui, Mayo, Casas Grandes and de Bavispe, and their relationship to the more southern distribution of Mexican golden trout (O. chrysogaster) using 11 microsatellite loci. Microsatellite allelic diversity in Mexican trout was high with a mean of 6.6 alleles/locus, average heterozygosity = 0.35, and a mean Fst = 0.43 for all loci combined. Microsatellite data were congruent with previously published mtDNA results showing unique panmictic population structure in the Rio Yaqui trout that differs from Pacific coastal trout and Mexican golden trout. These data also add support for the theory of headwaters transfer of trout across the Continental Divide from tributaries of the Rio de Bavispe into the Rio Casas Grandes. Rio Mayo trout share a close genetic relationship to trout in Rio Yaqui, but sample sizes from the Rio Mayo prevent significant comparisons in this study. Microsatellite analyses show significant allelic frequency differences between Rio Yaqui trout and O. chrysogaster in Sinaloa and Durango Mexico, adding further support for a unique evolutionary status for this group of northwestern Mexican trout.

Estrogens stimulate proliferation of intrahepatic biliary epithelium in rats.

BACKGROUND & AIMS: We investigated the expression of estrogen receptor (ER) alpha and beta subtypes in cholangiocytes of normal and bile duct-ligated (BDL) rats and evaluated the role and mechanisms of estrogens in the modulation of cholangiocyte proliferation. METHODS: ER-alpha and ER-beta were analyzed by immunohistochemistry, reverse-transcription polymerase chain reaction, and Western blotting in normal and BDL rats. The effects of the ER antagonists tamoxifen and ICI 182,780 on cholangiocyte proliferation were evaluated. RESULTS: Cholangiocytes expressed both ER-alpha and ER-beta subtypes, whereas hepatocytes expressed only ER-alpha. In association with a marked cholangiocyte proliferation and with enhanced estradiol serum levels, the immunoreactivity for ER-alpha involved a 3-fold higher percentage of cholangiocytes in 3-week BDL than in normal rats; immunoreactivity for ER-beta showed a 30-fold increase. Western blot analysis showed that during BDL, the total amount of ER-beta in cholangiocytes was markedly increased (5-fold), whereas that of ER-alpha decreased slightly (-25%). Treatment with tamoxifen or ICI 182,780 of 3-week BDL rats inhibited cholangiocyte proliferation and induced overexpression of Fas antigen and apoptosis in cholangiocytes. In vitro, 17 beta estradiol stimulated proliferation of cholangiocyte, an effect blocked to the same extent by tamoxifen or ICI 182,780. CONCLUSIONS: This study suggests that estrogens and their receptors play a role in the modulation of cholangiocyte proliferation.

The function of alkaline phosphatase in the liver: regulation of intrahepatic biliary epithelium secretory activities in the rat.

We studied the effects of alkaline phosphatase (AP) on the secretory processes of the rat intrahepatic biliary epithelium as well as the role of the intrahepatic biliary epithelium in the uptake and biliary secretion of exogenous AP. The effects of acute and chronic administration of AP on bile secretory parameters were investigated in vivo in normal and bile duct ligated (BDL) rats and in vitro in isolated rat bile duct units (IBDU). In vivo, acute AP administration decreased bile flow and biliary bicarbonate excretion and abolished secretin choleresis in BDL rats but not in normal rats. On the contrary, the AP inhibitor, levamisole, increased in BDL rat bile flow and biliary bicarbonate excretion. In vitro, basal and secretin-stimulated Cl(-)/HCO(3)(-) exchanger activity in IBDU was immediately inhibited by AP intraluminal microinjection (apical exposure) but only after a prolonged exposure to the basolateral pole. Levamisole increased the Cl(-)/HCO(3)(-) exchanger activity of IBDU. A significant basolateral uptake of AP occurs in IBDU with a progressive transport to the apical domain. AP chronic treatment increased AP and gamma-glutamyltranspeptidase (gamma-GT) activities in the intrahepatic bile ducts and hepatocyte canalicular pole, promoted enlargement of bile canaliculi, and decreased bile flow and biliary bicarbonate excretion. In conclusion, the intrahepatic biliary epithelium plays a role in the uptake and biliary secretion of serum AP. AP inhibits the secretory processes of the intrahepatic biliary epithelium and induces features of intrahepatic cholestasis after chronic administration. These findings indicate that AP plays an active role in down-regulating the secretory activities of the intrahepatic biliary epithelium.

Inheritance of nuclear DNA markers in gynogenetic haploid pink salmon.

We describe the inheritance of 460 PCR-based loci in the polyploid-derived pink salmon (Oncorhynchus gorbuscha) genome using gynogenetic haploid embryos. We detected a length polymorphism in a growth hormone gene (GH-2) intron that is caused by an 81 bp insertion homologous to the 3' end of the salmonid short interspersed repetitive element (SINE) SmaI. Such insertion polymorphisms within species bring into question the use of SINEs as phylogenetic markers. We confirmed that a microsatellite locus encodes a PCR-null allele that is responsible for an apparent deficit of heterozygotes in a population sample from Prince William Sound. Another set of microsatellite primers amplified alleles of the same molecular weight from both loci of a duplicated pair. In our analysis of several PCR-based multilocus techniques, we failed to detect evidence of comigrating fragments produced by duplicated loci. Segregation analysis of PCR-based markers using gynogenetic haploid embryos ensures that the interpretation of molecular variation is not complicated by heterozygosity, diploidy, or gene duplication. We urge investigators to test the inheritance of polymorphisms in salmonids prior to using them to measure genetic variation.

Role and mechanisms of action of acetylcholine in the regulation of rat cholangiocyte secretory functions.

UNLABELLED: We investigated, in isolated bile duct units (IBDU) and cholangiocytes isolated from normal rat liver, the occurrence of acetylcholine (ACh) receptors, and the role and mechanisms of ACh in the regulation of the Cl-/HCO3- exchanger activity. The Cl-/HCO3- exchanger activity was evaluated measuring changes in intracellular pH induced by acute Cl- removal/readmission. M3 subtype ACh receptors were detected in IBDU and isolated cholangiocytes by immunofluorescence, immunoelectron microscopy, and reverse transcriptase PCR. M1 subtype ACh receptor mRNA was not detected by reverse transcriptase PCR and M2 subtype was negative by immunofluorescence. ACh (10 microM) showed no effect on the basal activity of the Cl-/HCO3- exchanger. When IBDU were exposed to ACh plus secretin, ACh significantly (P < 0.03) increased the maximal rate of alkalinization after Cl- removal and the maximal rate of recovery after Cl- readmission compared with secretin alone (50 nM), indicating that ACh potentiates the stimulatory effect of secretin on the Cl-/HCO3- exchanger activity. This effect of ACh was blocked by the M3 ACh receptor antagonist, 4-diphenyl-acetoxy-N-(2-chloroethyl)-piperidine (40 nM), by the intracellular Ca2+ chelator, 1,2-bis (2-Aminophenoxy)- ethane-N,N,N', N'-tetraacetic acid acetoxymethylester (50 microM), but not by the protein kinase C antagonist, staurosporine (0.1 microM). Intracellular cAMP levels, in isolated rat cholangiocytes, were unaffected by ACh alone, but were markedly higher after exposure to secretin plus ACh compared with secretin alone (P < 0.01). The ACh-induced potentiation of the secretin effect on both intracellular cAMP levels and the Cl-/HCO3- exchanger activity was individually abolished by two calcineurin inhibitors, FK-506 and cyclosporin A (100 nM). CONCLUSIONS: M3 ACh receptors are markedly and diffusively represented in rat cholangiocytes. ACh did not influence the basal activity of the Cl-/HCO3- exchanger, but enhanced the stimulation by secretin of this anion exchanger by a Ca2+-dependent, protein kinase C-insensitive pathway that potentiates the secretin stimulation of adenylyl cyclase. Calcineurin most likely mediates the cross-talk between the calcium and adenylyl cyclase pathways. Since secretin targets cholangiocytes during parasympathetic predominance, coordinated regulation of Cl-/HCO3- exchanger by secretin (cAMP) and ACh (Ca2+) could play a major role in the regulation of ductal bicarbonate excretion in bile just when the bicarbonate requirement in the intestine is maximal.

Immune response to rabies vaccine in Alaskan dogs: failure to achieve a consistently protective antibody response.

Previous studies in Thailand and Tunisia have shown that one injection of dog pre-exposure rabies vaccine does not produce a lasting antibody titre in a significant group of animals. We therefore duplicated the Thai study in a small North American community using healthy, owned dogs. A tissue culture vaccine of known high antigenicity was given intramuscularly as one primary injection and antibody titres were determined by the rapid fluorescent focus inhibition test on days 14, 30, 60, 180 and 360. Titres were less than 0.5 i.u./mL in 27% of dogs bled at 2 months, 24% at 6 months, and in 33% one year after the primary vaccination. In rabies endemic regions, it may be hazardous to rely on the previous vaccine history of a biting dog when making post-exposure management decisions. A retrospective study of antibody levels in previously vaccinated dogs in North America also indicated that a single injection of vaccine often failed to result in adequate titres.

Attributional antecedents of alcohol use in American Indian and Euroamerican adolescents.

American Indian and Euroamerican adolescents were compared in regard to the events that they saw as responsible for their alcohol use. American Indian males believed that heredity played a more important role in their use of alcohol than Euroamerican males. American Indian males also believed that fate was a more important influence on their use of alcohol than American Indian females and Euroamerican females and that environmental events (e.g., problems at home) were a less important influence than the three other groups. Euroamerican females saw distressing events as more responsible for their alcohol use than the American Indian females and Euroamerican males. Euroamerican females also saw themselves as more responsible for their alcohol use than the American Indian females and males and Euroamerican males. The treatment implications of these attributional differences in reasons for alcohol use are discussed, especially in regard to American Indian adolescent males.

Modulation of release of acetylcholine from the striatum by a proposed excitatory amino acid antagonist U-54494A: comparison with known antagonists, diazepam and phenytoin.

The effect of (U-54494A) cis-3,4-dichloro-N-methyl-N-[2-(1-Pyrrolidinyl)- cyclohexyl] benzamide monohydrochloride, an excitatory amino acid antagonist, on N-methyl-D-aspartic acid (NMDA)- and K(+)-evoked release of [3H]acetylcholine [( 3H]ACh) from slices of striatum was investigated. For the purpose of comparison, MK 801, PCP, CGP 37849, CPP, phenytoin and diazepam were investigated under identical conditions. Both U-54494A and the excitatory amino acid antagonists blocked NMDA-evoked release of [3H]ACh but these compounds failed to inhibit K(+)-evoked release of this neurotransmitter. Phenytoin blocked both NMDA and K(+)-evoked release of [3H]ACh, whereas diazepam was ineffective under similar conditions. These observations indicate that excitatory amino acid antagonists, including U-54494A, may mediate their anticonvulsant effect by blocking the activity of NMDA receptors, diazepam by activating the benzodiazepine receptors and phenytoin by inhibiting the activity of various depolarizing agents.