Kidneys extract BNP and NT-proBNP in healthy young men.

Renal metabolism of the cardiac marker NH2-terminal-pro-brain natriuretic peptide (NT-proBNP) has been suggested. Therefore, we determined the renal extraction ratios of NT-proBNP and its bioactive coproduct brain natriuretic peptide (BNP) at rest and during exercise. In addition, the cerebral ratios were evaluated. Ten young healthy men were investigated at baseline, during moderate cycle exercise (heart rate: 140, Borg scale: 14-15), and in the recovery with BNP and NT-proBNP measured from the brachial artery and the jugular and renal veins, and the renal and cerebral extraction ratios (Ext-Ren and Ext-Cer, respectively) were calculated. Cardiac output, stroke volume, heart rate, mean arterial pressures, and estimated glomerular filtration were determined. BNP and NT-proBNP were extracted by the kidneys but not by the brain. We observed no effect of exercise. The mean values (+/- SE) of Ext-Ren of NT-proBNP were similar (0.19 +/- 0.05, 0.21 +/- 0.06, and 0.12 +/- 0.03, respectively) during the three sessions (P > 0.05). Also the Ext-Ren of BNP were similar (0.18 +/- 0.07, 0.15 +/- 0.11, and 0.14 +/- 0.06, respectively; P > 0.05). There were no significant differences between Ext-Ren of BNP and NT-proBNP during the three sessions (P > 0.05). The Ext-Cer of both peptides varied insignificantly between -0.21 +/- 0.15 and 0.11 +/- 0.08. The renal extraction ratio of both BNP and NT-proBNP is approximately 0.15-0.20. There is no cerebral extraction, and short-term moderate exercise does not affect these values. Our findings suggest that the kidneys extract BNP and NT-proBNP to a similar extent in healthy young men.     

Two differing salmon GnRH precursor mRNAs are co-expressed in the brain of sockeye salmon (Oncorhynchus nerka)

The localization of two salmon-type gonadotropin-releasing hormone (sGnRH) precursors, pro-sGnRH-I (short type) and pro-sGnRH-II (long type), was investigated by using in situ hybridization techniques in the brain of the landlocked sockeye salmon, Oncorhynchus nerka. We used 30-mer oligonucleotide probes complementary to pro-sGnRH-I and pro-sGnRH-II cDNA. No significant differences were observed in the localization of sGnRH neurons expressing pro-sGnRH-I and pro-sGnRH-II mRNAs; both were expressed in the olfactory nerve, the olfactory bulbs, the regions between the olfactory bulb and telencephalon, the ventral telencephalon, the preoptic area, and the hypothalamus. Almost all sGnRH neurons examined co-expressed both precursors. The expression of two sGnRH precursors in the same neuron and the wide distribution of such neurons in the brain suggest that there are no functional differences between the two precursors.     

Autophagy is important in islet homeostasis and compensatory increase of beta cell mass in response to high-fat diet

Autophagy is an evolutionarily conserved machinery for bulk degradation of cytoplasmic components. Here, we report upregulation of autophagosome formation in pancreatic beta cells in diabetic db/db and in nondiabetic high-fat-fed C57BL/6 mice. Free fatty acids (FFAs), which can cause peripheral insulin resistance associated with diabetes, induced autophagy in beta cells. Genetic ablation of atg7 in beta cells resulted in degeneration of islets and impaired glucose tolerance with reduced insulin secretion. While high-fat diet stimulated beta cell autophagy in control mice, it induced profound deterioration of glucose tolerance in autophagy-deficient mutants, partly because of the lack of compensatory increase in beta cell mass. These findings suggest that basal autophagy is important for maintenance of normal islet architecture and function. The results also identified a unique role for inductive autophagy as an adaptive response of beta cells in the presence of insulin resistance induced by high-fat diet.     

Thermodynamic and kinetic determinants of Thermotoga maritima cold shock protein stability: a structural and dynamic analysis

The cold shock protein (CSP) from hyperthermophile Thermotoga maritima (TmCSP) is only marginally stable (DeltaG(T(opt)) = 0.3 kcal/mol) at 353 K, the optimum environmental temperature (T(opt)) for T. maritima. In comparison, homologous CSPs from E. coli (DeltaG(T(opt)) = 2.2 kcal/mol) and B. subtilis (DeltaG(T(opt)) = 1.5 kcal/mol) are at least five times more stable at 310 K, the T(opt) for the mesophiles. Yet at the room temperature, TmCSP is more stable (DeltaG(T(R)) = 4.7 kcal/mol) than its homologues (DeltaG(T(R)) = 3.0 kcal/mol for E. coli CSP and DeltaG(T(R)) = 2.1 kcal/mol for B. subtilis CSP). This unique observation suggests that kinetic, rather than thermodynamic, barriers toward unfolding might help TmCSP native structure at high temperatures. Consistently, the unfolding rate of TmCSP is considerably slower than its homologues. High temperature (600 K) complete unfolding molecular dynamics (MD) simulations of TmCSP support our hypothesis and reveal an unfolding scheme unique to TmCSP. For all the studied homologues of TmCSP, the unfolding process first starts at the C-terminal region and N-terminal region unfolds in the end. But for TmCSP, both the terminals resist unfolding for consistently longer simulation times and, in the end, unfold simultaneously. In TmCSP, the C-terminal region is better fortified and has better interactions with the N-terminal region due to the charged residues, R2, E47, E49, H61, K63, and E66, being in spatial vicinity. The electrostatic interactions among these residues are unique to TmCSP. Consistently, the room temperature MD simulations show that TmCSP is more rigid at its N- and C-termini as compared to its homologues from E. coli, B. subtilis, and B. caldolyticus.     

Imidazopyridine derivatives as potent and selective Polo-like kinase (PLK) inhibitors

A novel class of imidazopyridine derivatives was designed as PLK1 inhibitors. Extensive SAR studies supported by molecular modeling afforded a highly potent and selective compound 36. Compound 36 demonstrated good antitumor efficacy in xenograft nude rat model.     

High‐throughput screening of optimal solution conditions for structural biological studies by fluorescence correlation spectroscopy

Protein aggregation is an essential molecular event in a wide variety of biological situations, and is a causal factor in several degenerative diseases. The aggregation of proteins also frequently hampers structural biological analyses, such as solution NMR studies. Therefore, precise detection and characterization of protein aggregation are of crucial importance for various research fields. In this study, we demonstrate that fluorescence correlation spectroscopy (FCS) using a single‐molecule fluorescence detection system enables the detection of otherwise invisible aggregation of proteins at higher protein concentrations, which are suitable for structural biological experiments, and consumes relatively small amounts of protein over a short measurement time. Furthermore, utilizing FCS, we established a method for high‐throughput screening of protein aggregation and optimal solution conditions for structural biological experiments.     

Cochlear outer hair cell system is a logarithmic compressor

In general, sensors of the sensory organs are ultrasensitive, so that a gain control function would be essential to protect the sensors from high intensity stimuli. This holds for the cochlea, an acoustic sensor of high sensitivity. Above all, the cochlea has to be equipped with the organ mechanically protecting the vulnerable sensor from high amplitude sounds. In addition, to expand the apparent dynamic range of the cochlear sensor, the stimulus intensity i.e. amplitude, should be considerably compressed in the cochlea. Of course, the amplitude should be compressed logarithmically so as not to miss the low level signals as much as possible. Thus, it is very convenient if a logarithmic compressor (LC) exists in the cochlea. Then, we examined literatures on this subject, and finally we reached the conclusion that the outer hair cell (OHC) system is none other than the LC. Here we propose ‘the LC theory’ that the OHC system is the LC properly compressing the signal intensity together with the tectorial membrane. However, this theory is quite contradictory to the generally accepted theory that OHCs are selective amplifiers of the basilar membrane vibrations (CA theory). In our opinion, this contradiction is due to that the logic of the CA theory is not sound. If you enumerate all possible explanations of experimental data and examine them logically, you will never conclude to the CA theory. In a word, the CA theory confuses the effect of the LC with that of the selective amplifier. Certainly, they are very mistakable. On the other hand, because the LC theory is a logical result of the well-known experimental data, it is consistent with any of them. Moreover, the LC theory can easily explain the causes of such phenomena as otoacoustic emissions, two-tone suppression and loudness recruitment that have been difficult to be reasonably explained up to now. Needless to say, if the OHC system is the LC, you will have to re-create the auditory theory fundamentally. This means that every aspect of otology such as the clinical examination, the design of cochlear implant and the etiology of hearing impairments should be re-evaluated. The conclusion is that the CA theory should be corrected as quickly as possible.     

Inhibition of MEK/ERK signaling induces apoptosis of acute myelogenous leukemia cells via inhibition of eukaryotic initiation factor 4E-binding protein 1 and down-regulation of Mcl-1

We previously showed that the MEK inhibitor AZD6244 induced apoptosis in acute myelogenous leukemia (AML) HL60 cells. However, the mechanisms of AZD6244 to induce apoptosis remain to be fully elucidated. This study found that exposure of HL60 cells to AZD6244 down-regulated the levels of phosphor (p)-4E-binding protein 1 (4E-BP1), a substrate of mammalian target of rapamycin complex 1 (mTORC1), and anti-apoptotic protein Mcl-1. On the other hand, exposure of EOL-1 and MOLM13 cells to AZD6244 failed to induce apoptosis and levels of p-4E-BP1 and Mcl-1 were not down-regulated in these cells. These observations prompted us to hypothesize that down-regulation od 4E-BP1 and Mcl-1 might play an important role in AZD6244-mediated apoptosis. As expected, down-regulation of 4E-BP1 by an siRNA sensitized EOL-1 cells to AZD6244-mediated apoptosis in parallel with down-regulation of Mcl-1. Moreover, we found that blockade of mTORC1 by RAD001 synergistically enhanced the action of AZD6244 in leukemia cells.