336 research outputs found
A second species of the genus Sturmius BRETFELD, 1994: Sturmius truncivivus n.sp. from Brazil (Insecta, Collembola, Symphypleona)
From Manaus, Brazil, AM, Sturmius truncivivus n.sp. is described. It is the second species of this remarkable genus, which is known from Colombia and shows an unusual combination of characteristics. This new species lives on trees, as does the type species, but has not been collected from epiphytes but by trunk traps
Shell structure and electron-electron interaction in self-assembled InAs quantum dots
Using far-infrared spectroscopy, we investigate the excitations of
self-organized InAs quantum dots as a function of the electron number per dot,
1<n<6, which is monitored in situ by capacitance spectroscopy. Whereas the
well-known two-mode spectrum is observed when the lowest s - states are filled,
we find a rich excitation spectrum for n=3, which reflects the importance of
electron-electron interaction in the present, strongly non-parabolic confining
potential. From capacitance spectroscopy we find that the electronic shell
structure in our dots gives rise to a distinct pattern in the charging energies
which strongly deviates from the monotonic behavior of the Coulomb blockade
found in mesoscopic or metallic structures.Comment: 4 pages, 3 PostScript figure
Fibrinogen αCâregions are not directly involved in fibrin polymerization as evidenced by a "DoubleâDetroit" recombinant fibrinogen mutant and knobsâmimic peptides
Background:
Fibrin polymerization, following fibrinopeptides A and B (FpA, FpB) cleavage, relies on newly exposed αâ and ÎČâchains Nâtermini (GPR, GHR; Aâ, Bâknobs, respectively) engaging preâexistent a and b pockets in other fibrin(ogen) molecules' Îłâ and (B)ÎČâchains Câterminal regions. A role for mostly disordered (A)αâchains Câterminal regions "bridging" between fibrin molecules/fibrils has been proposed.
Objectives:
Fibrinogen Detroit is a clinically observed mutation (AαR19âS) with nonâengaging GPS Aâknobs. By analogy, a similar BÎČâchain mutation, BÎČR17âS, should produce nonâengaging GHS Bâknobs. A homozygous âDoubleâDetroitâ mutant (AαR19âS, BÎČR17âS; DDâFG) was developed: with Aâa and Bâb engagements endogenously blocked, other interactions would become apparent.
Methods:
DDâFG, wildâtype recombinant (WTâFG), and human plasma (hpâFG) fibrinogen selfâassociation was studied by turbidimetry coupled with fibrinopeptides release HPLC/mass spectrometry analyses, and by lightâscattering following sizeâexclusion chromatography (SEâHPLC).
Results:
In contrast to WTâFG and hpâFG, DDâFG produced no turbidity increase, irrespective of thrombin concentration. The SEâHPLC profile of concentrated DDâFG was unaffected by thrombin treatment, and lightâscattering, at lower concentration, showed no intensity and hydrodynamic radius changes. Compared with hpâFG, both WTâFG and DDâFG showed no FpA cleavage difference, while ~50% FpB was not recovered. Correspondingly, SDSâPAGE/Westernâblots revealed partial BÎČâchain Nâterminal and Aαâchain Câterminal degradation. Nevertheless, ~70% DDâFG molecules bearing (A)αCâregions potentially able to associate were available. Higherâconcentration, nearlyâintact hpâFG with 500âfold molar excess GPRPâNH2/GHRPâNH2 knobsâmimics experiments confirmed these noâassociations findings.
Conclusions:
(A)αCâregions interactions appear too weak to assist native fibrin polymerization, at least without knobs engagement. Their role in all stages should be carefully reconsidered
El estilo de comunicación del entrenador y la percepción del clima motivacional generado por los entrenadores y compañeros
El presente estudio se propuso evaluar las relaciones entre el estilode comunicaciĂłn del entrenador y el clima motivacional generado por Ă©l ypor los compañeros de equipo. Se observĂł a tres entrenadores de fĂștbol conel Sistema de EvaluaciĂłn de las Conductas del Entrenador (CBAS) en tres partidoscada uno. TambiĂ©n participaron 39 jugadores de los mismos equiposque los entrenadores, en la franja de edad de 12 a 14 años, que contestaronlos cuestionarios: a) cuestionario de percepciĂłn de los comportamientos delentrenador (CBAS-PBS); b) clima motivacional generado por el entrenador(PMCSQ-2); c) cuestionario del clima motivacional de los iguales en eldeporte (PeerMCYSQ). A partir de los resultados obtenidos, se evidenciauna correlaciĂłn entre conductas positivas que perciben que emiten los entrenadoresy la percepciĂłn de un clima de implicaciĂłn a la tarea. AdemĂĄs,de una correlaciĂłn entre el clima de implicaciĂłn a la tarea generado por elentrenador y el generado por los compañeros. TambiĂ©n se encontrĂł unacorrelaciĂłn positiva entre las percepciones de comportamientos punitivosdel entrenador y la generaciĂłn de un clima motivacional de implicaciĂłnal ego. El clima de implicaciĂłn al ego generado por el entrenador tambiĂ©nse correlaciona con los dos factores del clima de implicaciĂłn al ego de loscompañeros, la competencia y el conflicto intra-equipo
Zero-field spin splitting in InAs-AlSb quantum wells revisited
We present magnetotransport experiments on high-quality InAs-AlSb quantum
wells that show a perfectly clean single-period Shubnikov-de Haas oscillation
down to very low magnetic fields. In contrast to theoretical expectations based
on an asymmetry induced zero-field spin splitting, no beating effect is
observed. The carrier density has been changed by the persistent photo
conductivity effect as well as via the application of hydrostatic pressure in
order to influence the electric field at the interface of the electron gas.
Still no indication of spin splitting at zero magnetic field was observed in
spite of highly resolved Shubnikov- de Haas oscillations up to filling factors
of 200. This surprising and unexpected result is discussed in view of other
recently published data.Comment: 4 pages, 3 figures, submitted to Phys. Rev.
Pomegranate juice, but not an extract, confers a lower glycemic response on a highâglycemic index food: randomized, crossover, controlled trials in healthy subjects
Background: Lowâglycemic index diets have demonstrated health benefits associated with a reduced risk of developing type 2 diabetes. Objectives: We tested whether pomegranate polyphenols could lower the glycemic response of a highâglycemic index food when consumed together and the mechanism by which this might occur. Design: We compared the acute effect of a pomegranate juice and a polyphenol-rich extract from pomegranate (supplement) on the bread-derived postprandial blood glucose concentration in 2 randomized, crossover, controlled studies (double-blinded for the supplements), each on 16 healthy volunteers. An additional randomized, crossover, controlled study on 16 volunteers consuming constituent fruit acids in a pH-balanced solution (same pH as pomegranate) and bread was conducted to determine any contributions to postprandial responses caused by acidic beverages. Results: As primary outcome, the incremental area under the curve for bread-derived blood glucose (â33.1% ± 18.1%, P = 0.000005) and peak blood glucose (25.4% ± 19.3%, P = 0.0004) were attenuated by pomegranate juice, compared with a control solution containing the equivalent amount of sugars. In contrast, the pomegranate supplement, or a solution containing the malic and citric acid components of the juice, was ineffective. The pomegranate polyphenol punicalagin was a very effective inhibitor of human α-amylase in vitro, comparable to the drug acarbose. Neither the pomegranate extract nor the individual component polyphenols inhibited 14C-D-glucose transport across differentiated Caco-2/TC7 cell monolayers, but they inhibited uptake of 14C-glucose into Xenopus oocytes expressing the human glucose transporter type 2. Further, some of the predicted pomegranate gut microbiota metabolites modulated 14C-D-glucose and 14C-deoxy-D-glucose uptake into hepatic HepG2 cells. Conclusions: These data indicate that pomegranate polyphenols, when present in a beverage but not in a supplement, can reduce the postprandial glycemic response of bread, whereas microbial metabolites from pomegranate polyphenols exhibit the potential to further modulate sugar metabolism much later in the postprandial period. This trial was registered at clinicaltrials.gov as NCT02486978, NCT02624609, and NCT03242876
Nutritional implications of olives and sugar: attenuation of post-prandial glucose spikes in healthy volunteers by inhibition of sucrose hydrolysis and glucose transport by oleuropein
Purpose: The secoiridoid oleuropein, as found in olives and olive leaves, modulates some biomarkers of diabetes risk in vivo. A possible mechanism may be to attenuate sugar digestion and absorption.
Methods: We explored the potential of oleuropein, prepared from olive leaves in a water soluble form (OLE), to inhibit digestive enzymes (α-amylase, maltase, sucrase), and lower [ÂčâŽC(U)]-glucose uptake in Xenopus oocytes expressing human GLUT2 and [ÂčâŽC(U)]-glucose transport across differentiated Caco-2 cell monolayers. We conducted 7 separate crossover, controlled, randomised intervention studies on healthy volunteers (double-blinded and placebo-controlled for the OLE supplement) to assess the effect of OLE on post-prandial blood glucose after consumption of bread, glucose or sucrose.
Results: OLE inhibited intestinal maltase, human sucrase, glucose transport across Caco-2 monolayers, and uptake of glucose by GLUT2 in Xenopus oocytes, but was a weak inhibitor of human α-amylase. OLE, in capsules, in solution or as naturally present in olives, did not affect post-prandial glucose derived from bread, while OLE in solution attenuated post-prandial blood glucose after consumption of 25 g sucrose, but had no effect when consumed with 50 g of sucrose or glucose.
Conclusion: The combined inhibition of sucrase activity and of glucose transport observed in vitro was sufficient to modify digestion of low doses of sucrose in healthy volunteers. In comparison, the weak inhibition of α-amylase by OLE was not enough to modify blood sugar when consumed with a starch-rich food, suggesting that a threshold potency is required for inhibition of digestive enzymes in order to translate into in vivo effects
Atrial natriuretic factor
The discovery of the first well-defined natriuretic hormone, the Atrial Natriuretic Factor (ANF), has prompted research on its impact on volume regulation in health and disease. The natriuretic, diuretic, and smooth muscle-relaxing properties suggest an important role of this novel hormone in pathophysiological states with sodium or volume retention, such as congestive heart failure or cirrhosis of the liver. Investigations on the implications of ANF in liver disease have been performed for little more than 1 year, and results are still controversial in many respects. At present, it seems very likely that there is no absolute deficiency of plasma ANF in patients with cirrhosis. Moreover, elevated plasma levels in cirrhotics with ascites have been reported by several groups. However, as yet, a molecular characterization of this increased immunoreactivity is still lacking. There is disagreement on the reduced release of and renal response to ANF in subgroups of cirrhotics; however, stimulus-response-coupling might be impaired. Further studies are needed to elucidate the pathophysiological implications and therapeutical potential of ANF in patients with chronic liver disease
Quantitative trait loci conferring grain mineral nutrient concentrations in durum wheat 3 wild emmer wheat RIL population
Mineral nutrient malnutrition, and particularly
deficiency in zinc and iron, afflicts over 3 billion people
worldwide. Wild emmer wheat, Triticum turgidum ssp.
dicoccoides, genepool harbors a rich allelic repertoire for
mineral nutrients in the grain. The genetic and physiological
basis of grain protein, micronutrients (zinc, iron,
copper and manganese) and macronutrients (calcium,
magnesium, potassium, phosphorus and sulfur) concentration
was studied in tetraploid wheat population of 152
recombinant inbred lines (RILs), derived from a cross
between durum wheat (cv. Langdon) and wild emmer
(accession G18-16). Wide genetic variation was found
among the RILs for all grain minerals, with considerable
transgressive effect. A total of 82 QTLs were mapped for
10 minerals with LOD score range of 3.2â16.7. Most QTLs
were in favor of the wild allele (50 QTLs). Fourteen pairs
of QTLs for the same trait were mapped to seemingly
homoeologous positions, reflecting synteny between the A
and B genomes. Significant positive correlation was found
between grain protein concentration (GPC), Zn, Fe and Cu,
which was supported by significant overlap between the
respective QTLs, suggesting common physiological and/or
genetic factors controlling the concentrations of these
mineral nutrients. Few genomic regions (chromosomes 2A,
5A, 6B and 7A) were found to harbor clusters of QTLs for
GPC and other nutrients. These identified QTLs may
facilitate the use of wild alleles for improving grain
nutritional quality of elite wheat cultivars, especially in
terms of protein, Zn and Fe
GPVI (Glycoprotein VI) Interaction With Fibrinogen Is Mediated by Avidity and the Fibrinogen αC-Region
Objective:
GPVI (glycoprotein VI) is a key molecular player in collagen-induced platelet signaling and aggregation. Recent evidence indicates that it also plays important role in platelet aggregation and thrombus growth through interaction with fibrin(ogen). However, there are discrepancies in the literature regarding whether the monomeric or dimeric form of GPVI binds to fibrinogen at high affinity. The mechanisms of interaction are also not clear, including which region of fibrinogen is responsible for GPVI binding. We aimed to gain further understanding of the mechanisms of interaction at molecular level and to identify the regions on fibrinogen important for GPVI binding.
Approach and Results:
Using multiple surface- and solution-based protein-protein interaction methods, we observe that dimeric GPVI binds to fibrinogen with much higher affinity and has a slower dissociation rate constant than the monomer due to avidity effects. Moreover, our data show that the highest affinity interaction of GPVI is with the αC-region of fibrinogen. We further show that GPVI interacts with immobilized fibrinogen and fibrin variants at a similar level, including a nonpolymerizing fibrin variant, suggesting that GPVI binding is independent of fibrin polymerization.
Conclusions:
Based on the above findings, we conclude that the higher affinity of dimeric GPVI over the monomer for fibrinogen interaction is achieved by avidity. The αC-region of fibrinogen appears essential for GPVI binding. We propose that fibrin polymerization into fibers during coagulation will cluster GPVI through its αC-region, leading to downstream signaling, further activation of platelets, and potentially stimulating clot growth
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