The Upper Tremadocian (Ordovician) graptolite Bryograptus: taxonomy, biostratigraphy and biogeography

Abstract:  The taxonomy, biostratigraphical and palaeogeographical distribution of the Lower Ordovician graptolite genus Bryograptus is evaluated. Bryograptus is recognized as a distinct triradiate anisograptid with a multiramous, pendent rhabdosome. The species of the genus Bryograptus can be interpreted as shallow water faunal elements with a strongly limited biogeographical distribution to the Atlantic Faunal Realm. Bryograptus is restricted to a narrow interval in the Upper Tremadocian, the Bryograptus Biozone of Scandinavia and South America (Argentina), making it a taxon with a high potential for precise biostratigraphical correlations. The proximal end development can be used to differentiate the genus Bryograptus from other pendent multiramous graptoloid genera with a homoplastic rhabdosome development. Characteristics of the proximal end development and structure easily differentiate these genera in relief specimens, but not in flattened material.     

Direct determination of the contractility of the guinea pig gallbladder: a new in vivo model

In vivo methods to study gallbladder contractility either equate gallbladder emptying with contraction or have relied on changes in gallbladder intravesicular pressure to reflect active transmural tension. We therefore devised an animal model in which the contractile force of the intact gallbladder is measured directly while the blood and neural supply remains uncompromised. Under general anesthesia one pole of the guinea pig gallbladder is anchored to the sternum and the other connected to a force displacement transducer. Any contraction--relaxation between these two points is recorded. This model was validated by measuring gallbladder response to both neuronal and humoral stimulation. Nerve stimulation was accomplished by means of two silver collar electrodes placed in contact with the cystic duct. With nerve stimulation, a frequency (0.5-10 Hz) or amplitude (1-10 V) dependent contraction occurred. Intravenous bethanechol (10 X 10(4) ng . kg-1 . h-1) and cholecystokinin (3 X 10(4) ng . kg-1 . h-1) both induced dose-dependent gallbladder contraction. This model should prove useful in assessing the physiologic control of gallbladder contraction.     

Wind,Waves, and Wing Loading: Morphological Specialization May Limit Range Expansion of Endangered Albatrosses

Among the varied adaptations for avian flight, the morphological traits allowing large-bodied albatrosses to capitalize on wind and wave energy for efficient long-distance flight are unparalleled. Consequently, the biogeographic distribution of most albatrosses is limited to the windiest oceanic regions on earth; however, exceptions exist. Species breeding in the North and Central Pacific Ocean (Phoebastria spp.) inhabit regions of lower wind speed and wave height than southern hemisphere genera, and have large intrageneric variation in body size and aerodynamic performance. Here, we test the hypothesis that regional wind and wave regimes explain observed differences in Phoebastria albatross morphology and we compare their aerodynamic performance to representatives from the other three genera of this globally distributed avian family. In the North and Central Pacific, two species (short-tailed P. albatrus and waved P. irrorata) are markedly larger, yet have the smallest breeding ranges near highly productive coastal upwelling systems. Short-tailed albatrosses, however, have 60% higher wing loading (weight per area of lift) compared to waved albatrosses. Indeed, calculated aerodynamic performance of waved albatrosses, the only tropical albatross species, is more similar to those of their smaller congeners (black-footed P. nigripes and Laysan P. immutabilis), which have relatively low wing loading and much larger foraging ranges that include central oceanic gyres of relatively low productivity. Globally, the aerodynamic performance of short-tailed and waved albatrosses are most anomalous for their body sizes, yet consistent with wind regimes within their breeding season foraging ranges. Our results are the first to integrate global wind and wave patterns with albatross aerodynamics, thereby identifying morphological specialization that may explain limited breeding ranges of two endangered albatross species. These results are further relevant to understanding past and potentially predicting future distributional limits of albatrosses globally, particularly with respect to climate change effects on basin-scale and regional wind fields.     

Molecular Convergence of Neurodevelopmental Disorders

Neurodevelopmental disorders (NDDs) are caused by mutations in diverse genes involved in different cellular functions, although there can be crosstalk, or convergence, between molecular pathways affected by different NDDs. To assess molecular convergence, we generated human neural progenitor cell models of 9q34 deletion syndrome, caused by haploinsufficiency of EHMT1, and 18q21 deletion syndrome, caused by haploinsufficiency of TCF4. Using next-generation RNA sequencing, methylation sequencing, chromatin immunoprecipitation sequencing, and whole-genome miRNA analysis, we identified several levels of convergence. We found mRNA and miRNA expression patterns that were more characteristic of differentiating cells than of proliferating cells, and we identified CpG clusters that had similar methylation states in both models of reduced gene dosage. There was significant overlap of gene targets of TCF4 and EHMT1, whereby 8.3% of TCF4 gene targets and 4.2% of EHMT1 gene targets were identical. These data suggest that 18q21 and 9q34 deletion syndromes show significant molecular convergence but distinct expression and methylation profiles. Common intersection points might highlight the most salient features of disease and provide avenues for similar treatments for NDDs caused by different genetic mutations.     

Determinants of biliary secretory pressure: the effects of two different bile acids

Biliary secretory pressure represents the force generated to deliver bile through the biliary system. Bile acid-induced toxicity may decrease canalicular bile formation and (or) induce back diffusion causing cholestasis. To determine if biliary secretory pressure is a sensitive indicator of bile toxicity, taurocholate was compared with a less cytotoxic bile acid, tauroursodeoxycholate. In fasted male Sprague-Dawley rats, the common bile duct was cannulated and the endogenous bile salt pool was removed by enteroclysis. Taurocholate (n = 35) or tauroursodeoxycholate (n = 35) in saline was infused for 1 h. Maximal biliary secretory pressure was then measured by attaching the biliary cannula to a column monometer and recording the maximum height to which bile rose. With taurocholate administration, bile flow and bile salt secretion linearly rose to a maximum infusion of 0.5 mumol/(min.g liver), above which hemolysis and death occurred. In contrast, tauroursodeoxycholate could be infused at higher rates with bile salt secretion plateauing at 1.25 mumol/(min.g liver] Both had similar choleretic potencies. Mean biliary secretory pressure at low (less than 0.15 mumol/(min.g liver] infusions was lower with taurocholate (22.5 cm bile) than tauroursodeoxycholate (25.2 cm). Further, increasing the taurocholate infusion decreased the biliary secretory pressure; yet for taurousodeoxycholate, pressure remained unchanged even at higher infusions. Thus, taurocholate but not tauroursodeoxycholate decreases biliary secretory pressure at high infusion rates, likely a reflection of its toxicity to the hepatobiliary epithelium.     

Hyperprolactinemia in hepatic encephalopathy may result from impaired central dopaminergic neurotransmission

Ten patients with liver disease and hepatic encephalopathy (HE) and eight normal controls were studied. Five of the 10 HE patients had hyperprolactinemia. The administration of L-dopa produced a decrease of serum prolactin in all. Prior administration of Carbidopa, a peripheral decarboxylase inhibitor, did not change the prolactin suppression by L-dopa in the normal controls or in the patients with normal baseline prolactin levels. In the hyperprolactinemic group, Carbidopa significantly inhibited the response to L-dopa. Impaired central neurotransmission, at least involving the hypothalamic-pituitary dopaminergic system, may underlie the hyperprolactinemia in HE.     

Cyclic AMP Phosphodiesterase in Leydig Cell Preparations of the Rat Testis

Enzymatic digestion of the interstitial tissue of early juvenile and adult rat testes resulted in an enrichment of the Leydig cell population. The cells of the intertubular preparation from adult testes were separated by centrifugal elutriation, according to differences in sedimentation velocity, a counter-flow centrifugation technique leading to 70% Leydig cell purity. Using this approach, it was possible to demonstrate that Leydig cells from adult testes contain only low affinity isoenzymes of cyclic AMP phosphodiesterase (PDE; E.C.: 3.1.4.17), an intracellular regulator of cAMP. Starch gel electrophoresis showed that the isozyme of cAMP PDE of Leydig cells is masked in crude testis homogenates due to the relatively low level of these cells in the total population. In Leydig cells, there are two different electrophoretic forms expressed which resemble two of eleven different molecular forms of cAMP PDE demonstrated for comparison in 21 different organs of the adult rat.
An interstitial cell preparation from early juvenile testes, with a Leydig cell content of up to 20%, was also investigated electrophoretically with regard to molecular forms of cAMP PDE, the properties of which were characterized by kinetic analysis of cAMP hydrolysis. The results presented are discussed in relation to the onset of testosterone synthesis in Leydig cells of prepubertal rats leading to the initiation of male puberty.