Stable and metastable states of human amylin in solution

Patients with type II diabetes exhibit fibrillar deposits of human amylin protein in the pancreas. It has been proposed that amylin oligomers arising along the aggregation or fibril-formation pathways are important in the genesis of the disease. In a step toward understanding these aggregation pathways, in this work we report the conformational preferences of human amylin monomer in solution using molecular simulations and infrared experiments. In particular, we identify a stable conformer that could play a key role in aggregation. We find that amylin adopts three stable conformations: one with an α-helical segment comprising residues 9-17 and a short antiparallel β-sheet comprising residues 24-28 and 31-35; one with an extended antiparallel β-hairpin with the turn region comprising residues 20-23; and one with no particular structure. Using detailed calculations, we determine the relative stability of these various conformations, finding that the β-hairpin conformation is the most stable, followed by the α-helical conformation, and then the unstructured coil. To test our predicted structure, we calculate its infrared spectrum in the amide I stretch regime, which is sensitive to secondary structure through vibrational couplings and linewidths, and compare it to experiment. We find that theoretically predicted spectra are in good agreement with the experimental line shapes presented herein. The implications of the monomer secondary structures on its aggregation pathway and on its interaction with cell membranes are discussed.     

Deleterious effects of potassium bromate administration on renal and hepatic tissues of Swiss mice

Potassium bromate (KBrO₃) is widely used as a food additive and is a major water disinfection by-product. The present study reports the side effects of KBrO₃ administration in Swiss mice. Animals were randomly divided into three groups: control, low dose KBrO₃ (100 mg/kg/day) and high dose KBrO₃ (200 mg/kg/day) groups. Administration of KBrO₃ led to decreased white blood corpuscles (WBCs), red blood corpuscles (RBCs) and platelets count in the animals of both the high and the low dose groups. Altered lipid profile represented as low density lipoprotein (LDL), high density lipoprotein (HDL) and cholesterol levels were observed in plasma samples of both KBrO₃ treated groups of mice. Also, an increased plasma level of LDH was detected in both KBrO₃ treated groups. Histological investigations showed impaired renal and hepatic histology that was concomitant with increased plasma Creatinine level in both of KBrO₃-treated groups. Nevertheless, decreased glutathione (GSH) level in both renal and hepatic tissue of mice after KBrO₃ intake was detected. These results show that KBrO₃ has serious damaging effects and therefore, its use should be avoided.     

Solution Structures of Rat Amylin Peptide: Simulation, Theory, and Experiment

Amyloid deposits of amylin in the pancreas are an important characteristic feature found in patients with Type-2 diabetes. The aggregate has been considered important in the disease pathology and has been studied extensively. However, the secondary structures of the individual peptide have not been clearly identified. In this work, we present detailed solution structures of rat amylin using a combination of Monte Carlo and molecular dynamics simulations. A new Monte Carlo method is presented to determine the free energy of distinct biomolecular conformations. Both folded and random-coil conformations of rat amylin are observed in water and their relative stability is examined in detail. The former contains an α-helical segment comprised of residues 7-17. We find that at room temperature the folded structure is more stable, whereas at higher temperatures the random-coil structure predominates. From the configurations and weights we calculate the α-carbon NMR chemical shifts, with results that are in reasonable agreement with experiments of others. We also calculate the infrared spectrum in the amide I stretch regime, and the results are in fair agreement with the experimental line shape presented herein.     

Warming and hypoxia reduce the performance and survival of northern bay scallops (Argopecten irradians irradians) amid a fishery collapse

Warming temperatures and diminishing dissolved oxygen (DO) concentrations are among the most pervasive drivers of global coastal change. While regions of the Northwest Atlantic Ocean are experiencing greater than average warming, the combined effects of thermal and hypoxic stress on marine life in this region are poorly understood. Populations of the northern bay scallop, Argopecten irradians irradians across the northeast United States have experienced severe declines in recent decades. This study used a combination of high-resolution (~1 km) satellite-based temperature records, long-term temperature and DO records, field and laboratory experiments, and high-frequency measures of scallop cardiac activity in an ecosystem setting to quantify decadal summer warming and assess the vulnerability of northern bay scallops to thermal and hypoxic stress across their geographic distribution. From 2003 to 2020, significant summer warming (up to ~0.2°C year⁻¹) occurred across most of the bay scallop range. At a New York field site in 2020, all individuals perished during an 8-day estuarine heatwave that coincided with severe diel-cycling hypoxia. Yet at a Massachusetts site with comparable DO levels but lower daily mean temperatures, mortality was not observed. A 96-h laboratory experiment recreating observed daily temperatures of 25 or 29°C, and normoxia or hypoxia (22.2% air saturation), revealed a 120-fold increased likelihood of mortality in the 29°C-hypoxic treatment compared with control conditions, with scallop clearance rates also reduced by 97%. Cardiac activity measurements during a field deployment indicated that low DO and elevated daily temperatures modulate oxygen consumption rates and likely impact aerobic scope. Collectively, these findings suggest that concomitant thermal and hypoxic stress can have detrimental effects on scallop physiology and survival and potentially disrupt entire fisheries. Recovery of hypoxic systems may benefit vulnerable fisheries under continued warming.     

Effects of the pathogenic Vibrio tapetis on defence factors of susceptible and non-susceptible bivalve species: II. Cellular and biochemical changes following in vivo challenge

This work compared the effect of challenge with Vibrio tapetis, the etiologic agent of brown ring disease (BRD) in clams, and other bacterial strains on defence-related factors in four bivalve species: Ruditapes philippinarum (highly susceptible to BRD), R. decussatus (slightly susceptible to BRD), Mercenaria mercenaria and Crassostrea virginica (both non-susceptible to BRD). Results show that bacterial challenge modulated defence-related factors, namely total and differential haemocyte counts, percentage of viable haemocytes, and lysozyme activity, both in haemolymph and extrapallial fluid. Injection with bacteria induced a response that was dependent upon the bacterial and bivalve species investigated, and upon the site of inoculation: external (pallial cavity), pseudo-internal (extrapallial space), or internal compartment (adductor muscle). The most conspicuous changes were systematically measured in R. philippinarum injected with V. tapetis, indicating a bacterial pathogenicity particular to the host in which it causes a specific disease syndrome. Alterations of defence-related factors were maximal in haemolymph of clams injected with V. tapetis in the muscle, and in the extrapallial fluid when the bacteria were injected into the pallial or the extrapallial cavity. Resistance to the development of the BRD symptom was not related to the extent of the haemocyte reaction measured following in vivo challenge.     

Context-Specific Mechanisms of Cell Polarity Regulation

Cell polarity is an essential process shared by almost all animal tissues. Moreover, cell polarity enables cells to sense and respond to the cues provided by the neighboring cells and the surrounding microenvironment. These responses play a critical role in regulating key physiological processes, including cell migration, proliferation, differentiation, vesicle trafficking and immune responses. The polarity protein complexes regulating these interactions are highly evolutionarily conserved between vertebrates and invertebrates. Interestingly, these polarity complexes interact with each other and key signaling pathways in a cell-polarity context-dependent manner. However, the exact mechanisms by which these interactions take place are poorly understood. In this review, we will focus on the roles of the key polarity complexes SCRIB, PAR and Crumbs in regulating different forms of cell polarity, including epithelial cell polarity, cell migration, asymmetric cell division and the T-cell immunological synapse assembly and signaling.     

Role of serum Metadherin mRNA expression in the diagnosis and prediction of survival in patients with colorectal cancer

Molecular Biology Reports - Early diagnosis and treatment of colorectal cancer (CRC) are important for improving patients’ survival. Metadherin is an oncogene that plays a pivotal role in...     

A rapid improved method for sexing embryo of water buffalo

The objective of the experiment of this paper is to develop and improve in the sexing method for preimplantation embryos of water buffalo (Bubalus bubalis) using loop-mediated isothermal amplification (LAMP) reaction. Embryo sexing has been recognized to control effectively the sex of offspring in the embryo transfer industry. A rapid and simple detection system was established by adding ethidium bromide (EB) or 5μl of CuSO4 (3M) to the product of LAMP reaction. The result of these additions after 2 min was a color change and a precipitate. It could be employed as an alternative method in the detection of the reaction products in place of the time consuming electrophoresis or the turbidity meter. The in vitro produced buffalo embryos were divided into one to eight pieces using a microblade attached to a micromanipulator. The cell number in each piece was counted before sexing. Sexing of DNA samples extracted from one to five biopsies cells was performed by LAMP. After biopsy, the remaining part of the embryos was used to confirm the sex by polymerase chain reaction (PCR). Fifty buffalo embryos were used and the accuracy of sex prediction was 100% when the blastomeres dissociated from a morula exceeds three. In conclusion, the present procedure without turbidity meter and electrophoresis was reliable and applicable for sexing the water buffalo embryos.