Identification of the sex-determining region in flathead grey mullet (Mugil cephalus).

Elucidation of the sex-determination mechanism in flathead grey mullet (Mugil cephalus) is required to exploit its economic potential by production of genetically determined monosex populations and application of hormonal treatment to parents rather than to the marketed progeny. Our objective was to construct a first-generation linkage map of the M. cephalus in order to identify the sex-determining region and sex-determination system. Deep-sequencing data of a single male was assembled and aligned to the genome of Nile tilapia (Oreochromis niloticus). A total 245 M. cephalus microsatellite markers were designed, spanning the syntenic tilapia genome assembly at intervals of 10 Mb. In the mapping family of full-sib progeny, 156 segregating markers were used to construct a first-generation linkage map of 24 linkage groups (LGs), corresponding to the number of chromosomes. The linkage map spanned approximately 1200 cM with an average inter-marker distance of 10.6 cM. Markers segregating on LG9 in two independent mapping families showed nearly complete concordance with gender (R2  = 0.95). The sex determining locus was fine mapped within an interval of 8.6 cM on LG9. The sex of offspring was determined only by the alleles transmitted from the father, thus indicating an XY sex-determination system.

Gaseous ammonia pretreatment lowers the required energy input for fine milling-enhanced enzymatic saccharification of switchgrass.

BACKGROUND: Fine milling of dry lignocellulosic biomass, without prior chemical pretreatment, can produce a high percent theoretical yield of sugars during subsequent enzymatic saccharification. However, the high sugar yields, necessary for a commercial biofuels process, are costly, with the milling energy input, necessary to achieve such yields even exceeding the energy content of the biomass. In this study, we show that low moisture gaseous ammonia pretreatment of switchgrass, in advance of the milling step, significantly reduces the milling energy required to give high sugar titers. RESULTS: We have found that the increase in monomeric sugar yields upon enzymatic saccharification of ball-milled, but not chemically treated switchgrass, is more closely tied to the formation of crystallites of cellulose with a negative linear dependence on the coherent domain size than to a decrease in particle size or to an increase in surface area of the biomass. The milling energy required to reach ~80 % of theoretical yield of glucose under these conditions is intolerably high, however, approximating two times the energy content of the biomass. Two different low moisture content ammonia pretreatments, prior to milling, significantly reduce the required milling energy (four to eightfold, depending on the pretreatment). These involve either heating the biomass at 150-160 °C for 1 h at 10 wt% gaseous ammonia or incubating at room temperature for 9 days at 20 wt% gaseous ammonia, the latter mimicking potential treatment during biomass storage. We have tested this combination of pretreatment and milling on switchgrass using a variety of milling methods, but mostly using ball and attritor milling. In the case of the high-temperature gaseous ammonia treatment followed by attritor milling, the increase in the monomeric sugar yield upon saccharification shows a negative linear dependence on the second or third power of the cellulose crystalline coherent domain size, implying that the surfaces as well as the ends of the cellulose fibrils are accessible to cellulolytic enzymes. CONCLUSIONS: The combination of knife milling, low moisture gaseous ammonia pretreatment followed by attritor milling that costs only ~5 % of the energy content of the biomass for a total energy input of ~11 % of the biomass energy content, is capable of delivering high sugar titers upon enzymatic saccharification. These results show, therefore, how to better integrate a mechanochemical step into the pretreatment of switchgrass in a commercial biomass to biofuels conversion process.

In vitro effect of cortisol and urotensin I on arginine vasotocin and isotocin secretion from pituitary cells of gilthead sea bream Sparus aurata.

This study aimed at determining whether in vitro secretion of two neuropeptides, arginine vasotocin (AVT) and isotocin (IT), from pituitary cells of gilthead sea bream Sparus aurata was affected by cortisol and urotensin (UI). Pituitary cells were exposed to 1·4 × 10(-8) , 1·4 × 10(-7) and 0·4 × 10(-6) M cortisol and 10(-12) , 10(-10) and 10(-8) M UI for 6, 24 and 48 h, respectively. AVT and IT contents were determined in the culture media by high-performance liquid chromatography (HPLC). An increase in AVT secretion and a decrease in IT secretion were observed at all cortisol doses. UI increased AVT secretion after 6 h of incubation at all doses. After 24 h, however, only the highest dose of UI still displayed an effect. IT secretion was not influenced by UI. It was thus demonstrated that cortisol does influence AVT and IT secretion from S. aurata pituitary cells, while UI regulates AVT secretion, as a component of hypothalamic-pituitary-interrenal (HPI) axis in this species.

Enzyme replacement therapy for mucopolysaccharidosis VI: long-term cardiac effects of galsulfase (Naglazyme®) therapy.

Characteristic cardiac valve abnormalities and left ventricular hypertrophy are present in untreated patients with mucopolysaccharidosis type VI (MPS VI). Cardiac ultrasound was performed to investigate these findings in subjects during long-term enzyme replacement therapy (ERT) with recombinant human arylsulfatase B (rhASB, rhN-acetylgalactosamine 4-sulfatase, galsulfase, Naglazyme®). Studies were conducted in 54 subjects before ERT was begun and at specific intervals for up to 96 weeks of weekly infusions of rhASB at 1 mg/kg during phase 1/2, phase 2, and phase 3 trials of rhASB. At baseline, mitral and aortic valve obstruction was present and was significantly greater in those ≥12 years of age. Mild mitral and trace aortic regurgitation were present, the former being significantly greater in those <12 years. Left ventricular hypertrophy, with averaged z-scores ranging from 1.6-1.9 SD greater than normal, was present for ages both <12 and ≥12 years. After 96 weeks of ERT, ventricular septal hypertrophy regressed in those <12 years. For those ≥12 years, septal hypertrophy was unchanged, and aortic regurgitation increased statistically but not physiologically. Obstructive gradients across mitral and aortic valves remained unchanged. The results suggest that long-term ERT is effective in reducing intraventricular septal hypertrophy and preventing progression of cardiac valve abnormalities when administered to those <12 years of age.

High-efficiency solution-processed Cu2ZnSn(S,Se)4 thin-film solar cells prepared from binary and ternary nanoparticles.

A new solution-based method to fabricate Cu(2)ZnSn(S,Se)(4) (CZTSSe) thin films is presented. Binary and ternary chalcogenide nanoparticles were synthesized and used as precursors to form CZTSSe thin films. The composition of the CZTSSe films can be easily controlled by adjusting the ratio of the nanoparticles used. The effect of compositional adjustment on device performance is illustrated. Laboratory-scale photovoltaic cells with 8.5% total-area efficiency (or 9.6% active-area efficiency) were demonstrated without anti-reflective coatings. Material characterization data revealed the formation of a bilayer microstructure during thermal processing and suggested a path forward on device improvement.

GnRHa-mediated stimulation of the reproductive endocrine axis in captive Atlantic bluefin tuna, Thunnus thynnus.

A controlled-release implant loaded with GnRH agonist (GnRHa) was used to induce spawning in Atlantic bluefin tuna (Thunnus thynnus) during two consecutive reproductive seasons. The fish were implanted underwater and sampled between days 2 and 8 after treatment. At the time of GnRHa treatment, females were in full vitellogenesis and males in spermiation. There was a rapid burst of pituitary luteinizing hormone (LH) release at day 2 after treatment in GnRHa-treated fish, and circulating LH remained elevated up to day 8 after treatment. In contrast, control fish had significantly lower levels in the plasma, but higher LH content in the pituitary, as observed in many other cultured fishes that fail to undergo oocyte maturation, ovulation and spawning unless induced by an exogenous GnRHa. Plasma testosterone (T) and 17ß-estradiol (E(2)) were elevated in response to the GnRHa treatment in females, while 11-ketotestosterone (11-KT) but not T was elevated in males. Even though oocyte maturation and ovulation did occur in GnRHa-induced fish, no significant elevations in 17,20ß-dihydroxy-4-pregnen-3-one (17,20ß-P) or 17,20ß,21-trihydroxy-4-pregnen-3-one (20ß-S), in either the free, conjugated or 5ß-reduced,3α-hydroxylated forms was observed in fish sampled within 6 days after treatment. Interestingly, a significant peak in plasma free 17,20ß-P levels occurred in both males and females at day 8 after treatment. Histological sections of the ovaries in these females contained oocytes at the migrating germinal vesicle stage, suggesting the role of this hormone as a maturation-inducing steroid in Atlantic bluefin tuna. In conclusion, the GnRHa implants activated effectively the reproductive endocrine axis in captive Atlantic bluefin tuna broodstocks, through stimulation of sustained elevations in plasma LH, which in turn evoked the synthesis and secretion of the relevant sex steroids leading to gamete maturation and release.

Glycolipids from a colloid chemical point of view.

Glycolipids are a group of compounds with a broad range of applications. Two types of glycolipids (alkylpolyglycosides and gangliosides) were examined with regard to their physicochemical properties. Despite their structural differences, they have in common that they are amphiphilic molecules and able to aggregate to form monolayers, bilayers, micelles, lyothropic mesophases or vesicles. The structures of glycolipid micelles were investigated by different experimental techniques in addition to molecular dynamic simulations. The knowledge of the physicochemical properties of gangliosides enables a better understanding of their biological functions. Structural features were obtained for the monosialogangliosides GM1, GM2 and GT1b from bovine brain by means of mass spectrometry. Further the aggregation behaviour was determined by small-angle neutron and dynamic light scattering experiments. Interaction studies of these compounds were carried out by means of surface plasmon resonance using gangliosides incorporated liposomes. They were used as model membranes that interact with the lectins WGA, RCA and HPA. The interaction of lectins immobilized to a modified silicon surface was investigated by in-situ ellipsometry.

In-situ X-ray absorption spectroscopy study of Pt and Ru chemistry during methanol electrooxidation.

Methanol electrooxidation in a 0.5 M sulfuric acid electrolyte containing 1.0 M CH3OH was studied on 30% Pt/carbon and 30% PtRu/carbon (Pt/Ru = 1:1) catalysts using X-ray absorption spectroscopy (XAS). Absorption by Pt and Ru was measured at constant photon energy in the near edge region during linear potential sweeps of 10-50 mV/s between 0.01 and 1.36 V vs rhe. The absorption results were used to follow Pt and Ru oxidation and reduction under transient conditions as well as to monitor Ru dissolution. Both catalysts exhibited higher activity for methanol oxidation at high potential following multiple potential cycles. Correlation of XAS data with the potential sweeps indicates that Pt catalysts lose activity at high potentials due to Pt oxidation. The addition of Ru to Pt accelerates the rate of methanol oxidation at all potentials. Ru is more readily oxidized than Pt, but unlike Pt, its oxidation does not result in a decrease in catalytic activity. PtRu/carbon catalysts underwent significant changes during potential cycling due to Ru loss. Similar current density vs potential results were obtained using the same PtRu/carbon catalyst at the same loading in a membrane electrode assembly half cell with only a Nafion (DuPont) solid electrolyte. The results are interpreted in terms of a bifunctional catalyst mechanism in which Pt surface sites serve to chemisorb and dissociate methanol to protons and carbon monoxide, while Ru surface sites activate water and accelerate the oxidation of the chemisorbed CO intermediate. PtRu/carbon catalysts maintain their activity at very high potentials, which is attributed to the ability of the added Ru to keep Pt present in a reduced state, a necessary requirement for methanol chemisorption and dissociation.

An isolated left common carotid artery from the main pulmonary artery: possible malseptation of the truncoaortic sac.

An isolated left common carotid artery (LCA) is an extremely rare condition with only four reported cases. In each case, the isolated carotid artery connects to the right or left pulmonary artery via the ductus arteriosus and the embryologic basis for the abnormalities is believed to reflect an error in the development of the branchial arches. We present a case of an isolated LCA connecting to the main pulmonary artery in association with a right aortic arch and an anomalous origin of the left subclavian artery from the descending aorta. The left ligamentus arteriosus was identified separately. This may represent a disturbance in the septation of the truncoaortic sac secondary to abnormal migration of neural crest cells rather than a pure developmental anomaly of the branchial arches.

Tilapia glycoprotein hormone alpha subunit: cDNA cloning and hypothalamic regulation.

The cDNA encoding the glycoprotein alpha (GPalpha) subunit of tilapia (Oreochromis mossambicus) was partially cloned using RACE-polymerase chain reaction (PCR) technique. The amplified cDNA was found to be 583 bases long, and to consist of a portion of the signal peptide, the full sequence encoding the mature peptide (94 amino acids) and the 3' untranslated region. Northern blot analysis revealed a single band of approximately 600 bp. Alignment of the deduced amino acids of the mature protein showed that the tilapia GPalpha subunit shares more than 80% identity with that of other perciform fish (i.e. striped bass, sea bream and yellowfin porgy) and less than 70% with that of more taxonomically remote fish and other vertebrates. Exposure of dispersed tilapia pituitary cells to salmon gonadotropin-releasing hormone (sGnRH) elevated GPalpha mRNA levels via both PKC and cAMP-protein kinase A (PKA) pathways. The transcript levels were also regulated by pituitary adenylate cyclase activating polypeptide (PACAP) and neuropeptide Y (NPY), both acting through PKC and PKA pathways. Moreover, a combined treatment of PACAP or NPY with GnRH seems to have an additive effect on the GPalpha subunit gene transcription. These results suggest that in tilapia the expression of GPalpha subunit is regulated by GnRH mainly via PKC and PKA pathways. Furthermore, PACAP and NPY can elevate the GnRH-stimulated GPalpha subunit transcription and can directly affect the subunit mRNA levels, via the same transduction pathways.

Characterization of tilapia FSHbeta gene and analysis of its 5' flanking region.

The objective of the current study was to unveil molecular mechanisms underlying transcriptional regulation of the FSHbeta gene expression in the pituitary of tilapia (Oreochromis mossambicus). The full-length sequence of tilapia FSHbeta (tFSHbeta) gene was determined. Its transcriptional unit (2.7 kb) exhibits the conserved genomic organization, i.e. three exons and two introns. Primer extension and RT-PCR analysis revealed heterogeneity of the tFSHbeta transcripts, due to alternate mRNA splicing and multiple initiation sites for transcription. Examination of the 5' flanking region (5'FR) of the tFSHbeta gene identified potential CAAT and TATA promoter proximal elements as well as several sequences of cis-acting motifs known to dictate inducible and tissue-specific transcriptional regulation in other gonadotropin genes. Chimeric constructs containing 1.7 kb of the tFSHbeta 5'FR fused to a luciferase (LUC) reporter gene were transiently transfected into primary culture of tilapia pituitary cells. The tFSHbeta-LUC construct was efficiently expressed under basal conditions and was rapidly induced by GnRH stimulation. Our data indicate that the 5'FR contains a functional promoter, which is responsive to GnRH treatment. In addition, 5' deletion analysis showed that the 1.7 kb, DNA sequence of the FSHbeta 5'FR encompasses both positive and negative regulatory elements.

Regulation of gonadotropin subunit genes in tilapia.

A steroidogenic tilapia gonadotropin (taGtH=LH) was purified from pituitaries of hybrid tilapia (Oreochromis niloticus x O. aureus) and a homologous RIA was established. This RIA enabled the study of the endocrine regulation of GtH release, the transduction pathways involved in its secretion and its profile during the spawning cycle. Discrepancies between steroid and taGtH peaks during the cycle led to the conclusion that an additional gonadotropin similar to salmonid FSH operates early in the cycle. In order to identify this hormone and to study the endocrine control of synthesis of all gonadotropin (GtH) subunits, a molecular approach was taken. The cDNA sequences and the entire gene sequences encoding the FSHbeta and LHbeta subunits, as well as an incomplete sequence of the glycoprotein hormone alpha subunit (GPalpha), were cloned. Salmon gonadotropin-releasing hormone (sGnRH) elevated mRNA steady-state levels of all three GtH subunits in cultured pituitary cells. Pituitary adenylate cyclase-activating polypeptide (PACAP) and neuropeptide Y (NPY) also stimulated the expression of these subunits and potentiated the effect of GnRH, except that NPY did not affect FSHbeta. The GnRH and NPY effects were found to be mediated mainly through protein kinase C (PKC), while protein kinase A (PKA) cascade was involved to a lesser extent. Mitogen-activated protein kinase (MAPK) cascade takes part in mediating GnRH effects, possibly via PKC. Testosterone (T) and estradiol (E2), but not 11-ketotestosterone (KT), are able to elevate GPalpha and LHbeta mRNAs in pituitary cells of early maturing or regressing males. Low levels of T exposure are associated with elevated FSHbeta mRNA in cells of mature fish, while higher levels suppress it, but elevate LHbeta mRNA. In vivo observations also showed the association of low T levels with increased FSHbeta mRNA and high T levels with elevated LHbeta mRNA. In accordance with these findings, analysis of LHbeta and FSHbeta 5' gene-flanking regions revealed on both gene promoters a GtH-specific element (GSE), half site estrogen response elements (ERE), cAMP response element (CRE) and AP1. In vitro experiments showed that recombinant human activin-A leads to higher levels of GPalpha, FSHbeta and LHbeta mRNAs in pituitary cell culture. Porcine inhibin marginally decreased the mRNA levels of GPalpha and FSHbeta, but at a low level (1 ng/ml) it stimulated that of LHbeta. These results shed some light on certain hypothalamic and gonadal hormones regulating the expression of GtH subunit genes in tilapia. In addition, they provide evidence for their differential regulation, and insight into their mode of action.

Pulmonary artery translocation: a surgical option for complex anomalous coronary artery anatomy.

Rather than perform a difficult and potentially high risk coronary reimplantation in a patient with an aberrant right coronary artery coursing between the aorta and pulmonary artery, the main pulmonary artery was translocated toward the left pulmonary hilum to create additional space between the aortic and pulmonic trunks.

Aortic laceration secondary to palmaz stent placement for treatment of superior vena cava syndrome.

Aortic laceration secondary to Palmaz Stent placement for treatment of superior vena cava syndrome is reported. This potentially life-threatening complication should be considered when rigid balloon expandable stents are used to treat superior vena cava syndrome of benign origin. Cathet. Cardiovasc. Intervent. 49:160-162, 2000.

Reproductive development of male and female tilapia hybrids (Oreochromis niloticus x O. aureus) and changes in mRNA levels of gonadotropin (GtH) Ibeta and IIbeta subunits.

A study was carried out in tilapia in order to see whether the gonadotropin (GtH) beta subunits show distinct patterns of expression at different stages of their reproductive development. Male and female tilapia hybrids (Oreochromis niloticus x O. aureus) were collected at various times of the year, and a number of parameters were measured in order to establish the reproductive state of the fish. Circulating testosterone (T), estradiol (E(2)) and 11 ketotestosterone (11KT) levels were assayed, gonads were removed for calculation of gonadosomatic index (GSI) values and histological studies, and RNA was extracted from the pituitaries for measurement of GtH Ibeta and IIbeta mRNA levels. In maturing fish of both sexes, the circulating steroid levels were positively correlated with each other (r(2) = 0.66-0.91) and in males, also with the GSI values (r(2) = 0.68). A positive correlation was also seen in these fish between GSI values and the prevalence of spermatocytes and spermatids (r(2) = 0.54). In maturing females, the maximal oocyte diameter was positively correlated with circulating E(2) levels (r(2) = 0.63), while GSI values showed no correlation; this presumably relates to the cycling nature of this asynchronous spawner. In regressing fish of both sexes, no clear correlation between these reproductive parameters was seen. In all fish, the GtH Ibeta mRNA levels were highest in fish with steroids ranging 1-10 ng T or E(2)/ml for males or females, respectively, and were lower in fish with steroids at higher or lower levels. In fish with high steroid levels, the IIbeta mRNA levels were also high, and in regressed males the increases were positively correlated. Exposure of cultured pituitary cells to either steroid (T at >10 nM, or E(2) at >1 nM) was followed by a decrease in the steady-state levels of the Ibeta transcript, while those of IIbeta were left unaltered. In situ hybridization studies revealed that in pituitaries of both sexes, the cells producing each of these mRNAs are located in a distinct location. These results suggest that gonadal steroids may exert differential feedback mechanisms at the level of the pituitary to control transcription of each GtH beta subunit in distinct cell types specific for each hormone.

Possible interactions between gonadotrophs and somatotrophs in the pituitary of tilapia: apparent roles for insulin-like growth factor I and estradiol.

The unique organization of the teleost pituitary, in which cells are grouped according to their characteristic hormone, makes this a suitable model for studying pituitary paracrine interactions. In a number of fish, including tilapia, there are variations in the circulating levels of the gonadotropins and GH, which are elevated during the reproductive season, suggesting interactions between the reproductive and growth axes. The aim of this study was to investigate paracrine interactions between the gonadotrophs and somatotrophs in the tilapia pituitary. Initially, dispersed pituitary cells were separated on a density gradient in which the gonadotrophs were found in the least dense fractions, and the somatotrophs were concentrated in the densest fraction. After 4 days in culture, cells in the least dense fractions showed characteristic cytoplasmic extensions not seen in the somatotrophs, which appeared small and failed to form aggregates; somatotrophs were found, however, attached to other non-GH cells. Staining of the nuclei with 4,6-diaminidino-2-phenyl-dihydrochloride revealed that the isolated somatotrophs had undergone nuclear condensation and fragmentation typical of apoptosis. Addition of either estradiol or human recombinant insulin-like growth factor I (IGF-I; 10 nM) to the somatotroph cultures increased the number of cell aggregates and reduced the number of condensed or fragmented nuclei. Immunocytochemical studies on pituitary sections revealed IGF-I immunoreactivity in regions of the proximal pars distalis that stain with gonadotropin IIbeta antisera and also in regions of the rostral pars distalis characteristic of corticotrophs; immunoreactive IGF-I was never seen in the region of the somatotrophs. Incubation of cells from the different fractions with testosterone (10 nM; 24 h) revealed that cells of the least dense fractions, which were rich in gonadotrophs, possessed aromatizing ability, which was absent in the somatotroph-enriched fraction. These results suggest that estradiol and IGF-I, both generated from cells other than the somatotrophs, may exert antiapoptotic effects and thus possibly control the size of this population of cells.

Endocrine regulation of gonadotropin and growth hormone gene transcription in fish.

The pituitary of a number of teleosts contains two gonadotropins (GtHs) which are produced in distinct populations of cells; the beta subunit of the GtH I being found in close proximity to the somatotrophs, while the II beta cells are more peripheral. In several species the GtH beta subunits are expressed at varying levels throughout the reproductive cycle, the I beta dominating in early maturing fish, after which the II beta becomes predominant. This suggests differential control of the beta subunit synthesis which may be regulated by both hypothalamic hormones and gonadal steroids. At ovulation and spawning, changes also occur in the somatotrophs, which become markedly more active, while plasma growth hormone (GH) levels increase. In a number of species, GnRH elevates either the I beta or the II beta mRNA levels, depending on the reproductive state of the fish. In tilapia, the GnRH effect on the II beta appears to be mediated through both cAMP-PKA and PKC pathways. GnRH also stimulates GH release in both goldfish and tilapia, but it increases the GH transcript levels only in goldfish; both GnRH and direct activation of PKC are ineffective in altering GH mRNA in tilapia pituitary cells. Dopamine (DA) does not alter II beta transcript levels in cultured tilapia pituitary cells, but increases GH mRNA levels in both rainbow trout and tilapia, in a PKA-dependent manner. This effect appears to be through interactions with Pit-1 and also by stabilizing the mRNA. Somatostatin (SRIF) does not alter GH transcript levels in either tilapia or rainbow trout, although it may alter GH synthesis by modulation of translation. Gonadal steroids appear to have differential effects on the transcription of the beta subunits. In tilapia, testosterone (T) elevates I beta mRNA levels in cells from immature or early maturing fish (in low doses), but depresses them in cells from late maturing fish and is ineffective in cells from regressed fish. Similar results were seen in early recrudescing male coho salmon injected with T or E2. T or E2 administered in vivo has dramatic stimulatory effects on the II beta transcript levels in immature fish of a number of species, while less powerful effects are seen in vitro. A response is also seen in cells from early maturing rainbow trout or tilapia, or regressed tilapia, but not in cells from late maturing or spawning fish. These results are substantiated by the finding that the promoter of the salmon II beta gene contains several estrogen responsive elements (EREs) which react and interact differently when exposed to varying levels of E2. In addition, activator protein-1 (AP-1) and steroidogenic factor-1 (SF-1) response elements are also found in the salmon II beta promoter; the AP-1 site is located close to a half ERE, while the SF-1 acts synergistically with the E2 receptor. The mRNA levels of both AP-1 and SP-1 are elevated, at least in mammals, by GnRH, suggesting possible sites for cross-talk between GnRH and steroid activated pathways. Reports of the effects of T or E2 on GH transcription differ. No effect is seen in vitro in pituitaries of tilapia, juvenile rainbow trout or common carp, but T does increase the transcript levels in pituitaries of both immature and mature goldfish. Reasons for these discrepancies are unclear, but other systemic hormones may be more instrumental than the gonadal steroids in regulating GH transcription. These include T3 which increases both GH mRNA levels and de novo synthesis (in tilapia and common carp) and insulin-like growth factor-I (IGF-I) which reduces GH transcript levels as well as inhibiting GH release.

Utility of intraoperative transesophageal echocardiography in the assessment of residual cardiac defects.

To investigate the accuracy of immediate postbypass transesophageal echocardiography in the assessment of residual cardiac defects, we compared intraoperative transesophageal echocardiograms with intra/postoperative data in 86 patients, aged 4 days to 30.7 years (median = 1.4 years), at risk for a total of 174 postoperative lesions: right (n = 55) or left (n = 26) ventricular outflow tract obstruction, ventricular septal defect (n = 65), aortic (n = 12) or mitral regurgitation (n = 8), or mitral stenosis (n = 8). Accuracy of intraoperative transesophageal echocardiography was evaluated based on comparison with (1) immediate post-bypass left (n = 4) or right (n = 9) ventricular outflow tract pressure gradients by pullback in the operating room, (2) direct surgical inspection of residual ventricular septal defects (n = 3), (3) pulmonary artery oxygen saturation (n = 49), (4) right ventricular outflow tract pullback gradient (n = 24), and (5) transthoracic echocardiogram (n = 51) performed within 40 days of surgery. The results indicate that intraoperative transesophageal echocardiography agreed with intra/postoperative data in 87% of patients at risk for right ventricular outflow tract obstruction, 96% at risk for left ventricular outflow tract obstruction, 97% at risk for ventricular septal defect, and 100% at risk for aortic regurgitation, mitral regurgitation, or mitral stenosis. Significant residual lesions led to immediate surgical revision in 11 cases: 3 ventricular septal defects, 6 right and 2 left ventricular outflow tract obstructions. Of these, intraoperative transesophageal echocardiography confirmed and quantified suspected residual lesions in 7 and identified unsuspected lesions in 4 cases. Immediate postbypass transesophageal echocardiography proved reliable for assessing residual ventricular septal defect, mitral stenosis, and mitral or aortic regurgitation. Although accurate for assessment of the left and right ventricular outflow tracts in most patients, transesophageal echocardiography may not reliably reflect the severity of obstruction in all cases.

Differential effects of gonadotropin-releasing hormone, dopamine and somatostatin and their second messengers on the mRNA levels of gonadotropin II beta subunit and growth hormone in the teleost fish, tilapia.

In cultured pituitary cells of tilapia, gonadotropin-releasing hormone (GnRH; 10 nM 4-24 h), elevation of cyclic AMP (by 10 microM forskolin or 0.2 mM 3-isobutyl-1-methylxanthine: IBMX 0.5-36 h) or activation of protein kinase C (PKC; by 12.5 nM tetradecanoyl phorbol-13-acetate: TPA, 0.5-24 h) all increased gonadotropin (GtH) II beta steady state mRNA levels by three to four-fold. The involvement of PKA and PKC in the GnRH stimulatory effect on both GtH release and GtH II beta mRNA levels was corroborated by use of the PKA and PKC inhibitors, H89 and GF109203X, respectively (100 nM) which attenuated the GnRH effect. Incubation with actinomycin D (8 microM, 4-21 h) after preexposure for 24 h to either forskolin (10 microM) or TPA (12.5 nM), revealed that rates of transcript degradation were slower in forskolin-treated cells (T 1/2 = 14.1 h) than in control or TPA-treated cells (T 1/2 = 8.47 or 8.38 h), suggesting a stabilizing effect on the mRNA. Dopamine (DA; 10 microM, 4-36 h) had no apparent effect on steady state mRNA levels of GtH II beta, but reduced GtH release by as much as 75%. Steady state levels of growth hormone (GH) mRNA were not affected by exposure to GnRH (10 nM, 4-24 h), although GH release was more than doubled. Similarly, activation of PKC (by TPA 12.5 nM, 1.5-36 h), which was shown to be essential for the GnRH-stimulatory effect on GH release, did not alter levels of the GH transcript, but increased GH release by more than fivefold. DA (10 microM, 4-24 h) moderately increased GH transcript levels (160%) with similar kinetics but lower potency than direct elevation of cAMP (by 10 microM forskolin or 0.2 mM IBMX, 0.5-36 h) which increased transcript levels by more than fourfold. The involvement of PKA in the DA effect was confirmed when the PKA inhibitor H89 (100 nM, 15 min prior to DA exposure) attenuated the DA effect on GH mRNA levels. Exposure of cells to actinomycin D (8 microM, 2-16 h) after treatment with forskolin (10 microM, 24 h) led to a slower rate of transcript degradation than in control cells (T 1/2 = 6.5 h vs. T 1/2 = 4.36 h), suggesting that cAMP also elicits a stabilizing effect on GH mRNA. Somatostatin (100 nM, 0.5-36 h) had no clear effect on GH transcript levels, but reduced GH release by as much as 90%. These results suggest that activation of either cAMP-PKA or PKC pathways can, possibly by different mechanisms, stimulate mRNA levels of the GtH II beta gene, but that only the cAMP-PKA pathway stimulates GH mRNA levels. It would appear therefore that GnRH, although stimulating GH release, does not regulate GH transcription in this fish.