Zeeman spectroscopy is used to demonstrate that phenomenological crystal-field parameters determined for the two
C
1
point-group symmetry sites in Er
3+
:Y
2
SiO
5
may be transferred to other ions. ...The two crystallographic six-and seven-coordinate substitutional sites may be distinguished by comparing the spectra with crystal-field calculations.
Nonpeptide agonists of each of the five somatostatin receptors were identified in combinatorial libraries constructed on the basis of molecular modeling of known peptide agonists. In vitro ...experiments using these selective compounds demonstrated the role of the somatostatin subtype-2 receptor in inhibition of glucagon release from mouse pancreatic alpha cells and the somatostatin subtype-5 receptor as a mediator of insulin secretion from pancreatic beta cells. Both receptors regulated growth hormone release from the rat anterior pituitary gland. The availability of high-affinity, subtype-selective agonists for each of the somatostatin receptors provides a direct approach to defining their physiological functions.
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► T. circumcincta GDH cDNA (TcGDH) of 1614bp encoded a 538 amino acid protein. ► TcGDH protein had 96% and 93% similarity to H. contortus and C. elegans GDH. ► Kinetic properties were ...similar to GDH in homogenates of T. circumcincta. ► TcGDH was a dual cofactor enzyme. ► Both 1mM ADP and ATP increased deaminating activity, not in the reverse direction.
A full length cDNA encoding glutamate dehydrogenase was cloned from Teladorsagia circumcincta (TcGDH). The TcGDH cDNA (1614bp) encoded a 538 amino acid protein. The predicted amino acid sequence showed 96% and 93% similarity with Haemonchus contortus and Caenorhabditis elegans GDH, respectively. A soluble N-terminal 6xHis-tagged GDH protein was expressed in the recombinant Escherichia coli strain BL21 (DE3) pGroESL, purified and characterised. The recombinant TcGDH had similar kinetic properties to those of the enzyme in homogenates of T. circumcincta, including greater activity in the aminating than deaminating reaction. Addition of 1mM ADP and ATP increased activity about 3-fold in the deaminating reaction, but had no effect in the reverse direction. TcGDH was a dual co-factor enzyme that operated both with NAD+ and NADP+, GDH activity was greater in the deaminating reaction with NADP+ as co-factor and more with NADH in the aminating reaction.
Small synthetic molecules termed growth hormone secretagogues (GHSs) act on the pituitary gland and the hypothalamus to stimulate and amplify pulsatile growth hormone (GH) release. A heterotrimeric ...GTP-binding protein (G protein)-coupled receptor (GPC-R) of the pituitary and arcuate ventro-medial and infundibular hypothalamus of swine and humans was cloned and was shown to be the target of the GHSs. On the basis of its pharmacological and molecular characterization, this GPC-R defines a neuroendocrine pathway for the control of pulsatile GH release and supports the notion that the GHSs mimic an undiscovered hormone.
Germanium membranes and microstructures of 50–1000nm thickness have been fabricated by a combination of epitaxial growth on a Si substrate and simple etching processes. The strain in these structures ...has been measured by high-resolution micro-X-ray diffraction and micro-Raman spectroscopy. The strain in these membranes is extremely isotropic and the surface is observed to be very smooth, with an RMS roughness below 2nm. The process of membrane fabrication also serves to remove the misfit dislocation network that originally forms at the Si/Ge interface, with benefits for the mechanical, optical and electrical properties of the crystalline membranes.
The Lutetium–Hafnium radiogenic isotopic system is widely used as a chronometer and tracer of planetary evolution. In order for this isotopic system to fulfill its potential in planetary studies, the ...Lu–Hf system parameters need to be more tightly constrained, in particular the Lu–Hf isotopic composition of the chondritic uniform reservoir (CHUR) and, by extension, the bulk silicate Earth (BSE). We present new Lu–Hf and Sm–Nd isotopic compositions of unequilibrated carbonaceous, ordinary, and enstatite chondrites of petrologic types 1, 2, and 3 which define a narrow range of Lu/Hf ratios (3%) identical with that of Sm/Nd. This contrasts with previously published data from mostly equilibrated ordinary chondrites of petrologic types 4, 5, and 6 which have a much larger range in Lu/Hf (28%). This heterogeneity has hampered an unambiguous choice for the Lu–Hf isotopic composition of CHUR. Our new determinations of Lu–Hf CHUR parameters are 176Lu/177Hf=0.0336±1 and 176Hf/177Hf=0.282785±11 (2σm), which are higher than previous estimates and, together with average Sm–Nd chondrite compositions of unequilibrated chondrites of 147Sm/144Nd=0.1960±4 and 143Nd/144Nd=0.512630±11 (2σm), now provide firm constraints on the chondritic parameters for both Lu–Hf and Sm–Nd isotopic systems. A comparison of Lu–Hf and Sm–Nd data show that terrestrial planets, as well as early differentiated planetesimals, converge toward a common initial Hf and Nd isotope composition corresponding to the average of chondrites. Finally, a compilation of Lu–Hf isotopic data of unequilibrated and equilibrated chondrites demonstrates that the 176Lu decay decay-constant value cannot be resolved by age comparison on metamorphosed or shocked planetary materials which have a complex history.
Pectin is abundant in modern day diets, as it comprises the middle lamellae and one-third of the dry carbohydrate weight of fruit and vegetable cell walls. Currently there is no specialized model ...organism for studying pectin fermentation in the human colon, as our collective understanding is informed by versatile glycan-degrading bacteria rather than by specialist pectin degraders. Here we show that the genome of Monoglobus pectinilyticus possesses a highly specialized glycobiome for pectin degradation, unique amongst Firmicutes known to be in the human gut. Its genome encodes a simple set of metabolic pathways relevant to pectin sugar utilization, and its predicted glycobiome comprises an unusual distribution of carbohydrate-active enzymes (CAZymes) with numerous extracellular methyl/acetyl esterases and pectate lyases. We predict the M. pectinilyticus degradative process is facilitated by cell-surface S-layer homology (SLH) domain-containing proteins, which proteomics analysis shows are differentially expressed in response to pectin. Some of these abundant cell surface proteins of M. pectinilyticus share unique modular organizations rarely observed in human gut bacteria, featuring pectin-specific CAZyme domains and the cell wall-anchoring SLH motifs. We observed M. pectinilyticus degrades various pectins, RG-I, and galactan to produce polysaccharide degradation products (PDPs) which are presumably shared with other inhabitants of the human gut microbiome (HGM). This strain occupies a new ecological niche for a primary degrader specialized in foraging a habitually consumed plant glycan, thereby enriching our understanding of the diverse community profile of the HGM.
New efforts to link climate reconstructions from shoreline deposits and sediment cores yield an improved and more detailed lake history from the Bolivian Altiplano. On the Southern Altiplano, 10 lake ...oscillations have been identified from this new unified chronology, each coincident with North Atlantic cold events such as Heinrich Events H5, H2, H1, and the Younger Dryas. By coupling this new lake history to a hydrologic budget model we are able to evaluate precipitation variability on the Southern Bolivian Altiplano over the last 130ka. These modeling efforts underscore the relative aridity of the Altiplano during the rare and small lake cycles occurring between 80 and 20ka, when colder temperatures combined with little or no change in rainfall produced smaller paleolakes. Relative aridity between 80 and 20ka contrasts with the immense Tauca lake cycle (18.1–14.1ka), which was six times larger than modern Lake Titicaca and coincided with Heinrich Event 1. This improved paleolake record from the Southern Altiplano reveals a strong link between central Andean climate and Atlantic sea-surface temperature gradients during the late Pleistocene, even though today rainfall variability is driven mostly by Pacific sea-surface temperature anomalies associated with El Niño/Southern Oscillation. However, not all Heinrich Events appear to result in lake expansions, most conspicuously during the global cold interval between 80 and 20ka when the Altiplano and Amazon Basin were relatively arid.
► The timing of lake cycles on Bolivian Altiplano over the last 130,000yr is presented. ► Ten lake oscillations are identified in sediment cores and from shorelines. ► The precipitation change associated with each lake is modeled. ► Lakes are small or absent during a global cold interval. ► Big lakes coincided with North Atlantic cold events.
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