In the nervous system, NMDA receptors (NMDARs) participate in neurotransmission and modulate the viability of neurons. In contrast, little is known about the role of NMDARs in pancreatic islets and ...the insulin-secreting beta cells whose functional impairment contributes to diabetes mellitus. Here we found that inhibition of NMDARs in mouse and human islets enhanced their glucose-stimulated insulin secretion (GSIS) and survival of islet cells. Further, NMDAR inhibition prolonged the amount of time that glucose-stimulated beta cells spent in a depolarized state with high cytosolic Ca(2+) concentrations. We also noticed that, in vivo, the NMDAR antagonist dextromethorphan (DXM) enhanced glucose tolerance in mice, and that in vitro dextrorphan, the main metabolite of DXM, amplified the stimulatory effect of exendin-4 on GSIS. In a mouse model of type 2 diabetes mellitus (T2DM), long-term treatment with DXM improved islet insulin content, islet cell mass and blood glucose control. Further, in a small clinical trial we found that individuals with T2DM treated with DXM showed enhanced serum insulin concentrations and glucose tolerance. Our data highlight the possibility that antagonists of NMDARs may provide a useful adjunct treatment for diabetes.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SBMB, UILJ, UKNU, UL, UM, UPUK
Self-monitoring of blood glucose using capillary glucose testing (C) has a number of shortcomings compared to continuous glucose monitoring (CGM). We aimed to compare these two methods and used blood ...glucose measurements in venous blood (IV) as a reference. Postprandial blood glucose levels were measured after 50 g oral glucose load and after the consumption of a portion of different foods containing 50 g of carbohydrates. We also evaluated the associations between postprandial glucose responses and the clinical characteristics of the participants at the beginning of the study.
12 healthy volunteers (age: 36 ± 17 years, BMI: 24.9 ± 3.5 kg/m²) ate white bread (WB) and whole grain (WG) bread and drank a 50 g glucose drink as reference. Postprandial glucose responses were evaluated by CGM, IV and C blood glucose measurements. Incremental area under the curve (AUC
) of postprandial blood glucose was calculated for 1 h (AUC
) and 2 h (AUC
).
After the consumption of white bread and whole grain bread, the AUC
did not differ between CGM and IV or C. AUC
of CGM showed no difference compared to C. Correlation analyses revealed a positive association of age with glucose AUC
(
= 0.768;
= 0.004) and WG AUC
(
= 0.758;
= 0.004); fasting blood glucose correlated with WG AUC
(
= 0.838;
< 0.001).
Despite considerable inter-individual variability of postprandial glycemic responses, CGM evaluated postprandial glycemic excursions which had comparable results compared to standard blood glucose measurements under real-life conditions. Associations of AUC
and AUC
postprandial glucose response with age or fasting blood glucose could be shown.
Mushroom tyrosinase diversity – six precursor isoforms, all capable of being activated and generating protein purification interfering compounds – is taking one step further to reconnaissance. This ...innovative method for protein purification provides access to latent tyrosinase from natural sources and enabled experiments revealing insights in a hitherto uncharacterized isoform. Display omitted
•An innovative method for protein purification from natural sources.•Indications that full length PPO4 has in vivo a membrane orientated origin.•Mass spectrometric measurements provide exact cleavage sites for maturation.•Revealing PTMs in the protein backbone and strain specific sequence heterogeneity.
Tyrosinases catalyze two initial reaction steps in the formation of melanin. Purification of tyrosinases had always been a process accompanied with various problems caused by enzymatic browning processes. Here, an approach is presented for the purification of the latent enzyme from mushrooms which averts and removes interfering compounds (e.g. polyphenols) in advance to the extraction process. The described method is supposed being well suitable as a general protein purification protocol from natural sources like fungi and plants.
The purified enzyme was investigated in detail by means of mass spectrometry: its intact protein mass was determined as 64,247.3Da and it was identified as number four of in total six isoforms (PPO1–6) by means of sequence analysis. Some PTMs, strain specific sequence disparities and several cleavage sites including the one causing enzyme-activation (Ser383) were determined, thus, providing insights on the maturation process of this latent tyrosinase zymogen. Based on these sequence data it can be concluded that the polypeptide backbone of the latent form of the tyrosinase PPO4 ranges from Ser2 to Thr565, missing when compared to the gene-derived sequence a small part (46 amino acids) of the C-terminal tail. The high content on hydrophobic amino acids within this missing tail gives rise to speculations whether this part might have a function as a membrane anchor.
Tail regeneration in urodeles requires the coordinated growth and patterning of the regenerating tissues types, including the spinal cord, cartilage and muscle. The dorsoventral (DV) orientation of ...the spinal cord at the amputation plane determines the DV patterning of the regenerating spinal cord as well as the patterning of surrounding tissues such as cartilage. We investigated this phenomenon on a molecular level. Both the mature and regenerating axolotl spinal cord express molecular markers of DV progenitor cell domains found during embryonic neural tube development, including Pax6 , Pax7 and Msx1 . Furthermore, the expression of Sonic hedgehog ( Shh ) is localized to the ventral floor plate domain in both mature and regenerating spinal cord. Patched1 receptor expression indicated that hedgehog signaling occurs not only within the spinal cord but is also transmitted to the surrounding blastema. Cyclopamine treatment revealed that hedgehog signaling is not only required for DV patterning of the regenerating spinal cord but also had profound effects on the regeneration of surrounding, mesodermal tissues. Proliferation of tail blastema cells was severely impaired, resulting in an overall cessation of tail regeneration, and blastema cells no longer expressed the early cartilage marker Sox9 . Spinal cord removal experiments revealed that hedgehog signaling, while required for blastema growth is not sufficient for tail regeneration in the absence of the spinal cord. By contrast to the cyclopamine effect on tail regeneration, cyclopamine-treated regenerating limbs achieve a normal length and contain cartilage. This study represents the first molecular localization of DV patterning information in mature tissue that controls regeneration. Interestingly, although tail regeneration does not occur through the formation of somites, the Shh-dependent pathways that control embryonic somite patterning and proliferation may be utilized within the blastema, albeit with a different topography to mediate growth and patterning of tail tissues during regeneration.
An important question is how growing tissues establish a blood vessel network. Here we study vascular network formation in pancreatic islets, endocrine tissues derived from pancreatic epithelium. We ...find that depletion of integrin-linked kinase (ILK) in the pancreatic epithelial cells of mice results in glucose intolerance due to a loss of the intra-islet vasculature. In turn, blood vessels accumulate at the islet periphery. Neither alterations in endothelial cell proliferation, apoptosis, morphology, Vegfa expression and VEGF-A secretion nor 'empty sleeves' of vascular basement membrane are found. Instead, biophysical experiments reveal that the biomechanical properties of pancreatic islet cells, such as their actomyosin-mediated cortex tension and adhesive forces to endothelial cells, are significantly changed. These results suggest that a sorting event is driving the segregation of endothelial and epithelial cells and indicate that the epithelial biomechanical properties determine whether the blood vasculature invades or envelops a growing epithelial tissue.
Limb regeneration involves re-establishing a limb development program from cells within adult tissues. Identifying molecular handles that provide insight into the relationship between cell ...differentiation status and cell lineage is an important step to study limb blastema cell formation. Here, using single cell PCR, focusing on newly isolated Twist1 sequences, we molecularly profile axolotl limb blastema cells using several progenitor cell markers. We link their molecular expression profile to their embryonic lineage via cell tracking experiments. We use in situ hybridization to determine the spatial localization and extent of overlap of different markers and cell types. Finally, we show by single cell PCR that the mature axolotl limb harbors a small but significant population of Twist1+ cells.
► Single cell PCR molecular profiling of blastema subtypes. ► Isolation of Twist1 and Twist3 orthologs from axolotl. ► Twist1 and Twist3 expressed in lateral plate mesoderm derived blastema cells. ► Chondrogenic blastema cells co-express Twist1 and Sox9. ► Dermal blastema cells co-express Twist1 and Twist3.
During limb regeneration adult tissue is converted into a zone of undifferentiated progenitors called the blastema that reforms the diverse tissues of the limb. Previous experiments have led to wide ...acceptance that limb tissues dedifferentiate to form pluripotent cells. Here we have reexamined this question using an integrated GFP transgene to track the major limb tissues during limb regeneration in the salamander Ambystoma mexicanum (the axolotl). Surprisingly, we find that each tissue produces progenitor cells with restricted potential. Therefore, the blastema is a heterogeneous collection of restricted progenitor cells. On the basis of these findings, we further demonstrate that positional identity is a cell-type-specific property of blastema cells, in which cartilage-derived blastema cells harbour positional identity but Schwann-derived cells do not. Our results show that the complex phenomenon of limb regeneration can be achieved without complete dedifferentiation to a pluripotent state, a conclusion with important implications for regenerative medicine.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The β-cells of the islets of Langerhans are embedded in a dense capillary network. The blood vessels supply the islet cells with nutrients and oxygen, and in turn take up the secreted islet hormones ...to deliver them to target tissues. In addition, vessels provide a basement membrane, which optimizes islet function. In this review we focus on the dynamic interactions between blood vessels and β-cells, which are pivotal for enhancing insulin expression and β-cell proliferation in response to increased insulin demand during body growth, pregnancy, and virtually all conditions associated with insulin resistance. Importantly, a failure in this adaptive response might contribute to the onset of type 2 diabetes mellitus.
Clinical treatment of diabetic patients by islet transplantation faces various complications. At present, in vitro expansion of islets occurs at the cost of their essential features, which are ...insulin production and release. However, the recent discovery of blood vessel/β-cell interactions as an important aspect of insulin transcription, secretion, and proliferation might point us to ways of how this problem could be overcome.
The correct function of β-cells depends on the presence of a basement membrane, a specialized extracellular matrix located around the blood vessel wall in mouse and human pancreatic islets. In this chapter, we summarize how the vascular basement membrane influences insulin transcription, insulin secretion, and β-cell proliferation. In addition, a brief overview about basement membrane components and their interactions with cell surface receptors is given.
Vitamin B2 (Riboflavin) acts as a strong radiation protecting agent in Escherichia coli bacteria (AB1157) in aerated media.
This ability is reinforced by the addition of vitamin C. Under the ...influence of gamma-radiation, vitamin B2 completely suppresses
the cytostatic activity of mitomycin C (MMC). In the presence of both vitamins, B2 and C, MMC is converted from an efficient
cytostatic to a rather strong radiation protecting agent. This effect opens a new pathway for specific protection of normal
mammalian cells (with a high O 2 -content) under treatment with ionizing radiation.
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