Microstructure and mechanical properties of forged and rolled rings made from X20Cr13 steel

The article describes the results of microstructure and mechanical properties tests (according to PN-EN ISO 6892- 1:2016-09 and PN-EN ISO 6507-1:2007), which were obtained on specimens taken from a fragment of a ring rolled in the temperature range from 1220 °C to 950 °C, with dimensions ø965/803 x 164 mm, annealed and heat-treated: quenching at the temperature of 1 030 ± 10 °C in oil and tempering at a temperature of 650 °C. The starting material for rolling was a forging with an opening of ø560/230 x 180 mm. Comparative hardness tests were also performed on specimens taken from the ring after rolling and softening annealing. The Rm>/sub>, Rp0.2 and A indices of the ring fragment after heat treatment, as assumed, were respectively: 942 MPa, 763 MPa and 17 %

Microstructure and mechanical properties of forged and rolled rings made from X20Cr13 steel

The article describes the results of microstructure and mechanical properties tests (according to PN-EN ISO 6892- 1:2016-09 and PN-EN ISO 6507-1:2007), which were obtained on specimens taken from a fragment of a ring rolled in the temperature range from 1220 °C to 950 °C, with dimensions ø965/803 x 164 mm, annealed and heat-treated: quenching at the temperature of 1 030 ± 10 °C in oil and tempering at a temperature of 650 °C. The starting material for rolling was a forging with an opening of ø560/230 x 180 mm. Comparative hardness tests were also performed on specimens taken from the ring after rolling and softening annealing. The Rm>/sub>, Rp0.2 and A indices of the ring fragment after heat treatment, as assumed, were respectively: 942 MPa, 763 MPa and 17 %

Ewaluation and analysis of the large-size forged and rolled en AW – 7057 alumminum alloy ring structure

The article presents the results of tests on the structure and hardness of a large-size ring made of EN AW - 7075 aluminium alloy produced under industrial conditions at the Zarmen FPA forge according to the developed technology - a combined forging and rolling method. Studies of the ring were carried out in order to assess its structure and hardness after the forming processes. The scope of the study included microscopic observations (microstructure and EDS), X-ray phase analysis and hardness distribution measurements

Ewaluation and analysis of the large-size forged and rolled en AW – 7057 alumminum alloy ring structure

The article presents the results of tests on the structure and hardness of a large-size ring made of EN AW - 7075 aluminium alloy produced under industrial conditions at the Zarmen FPA forge according to the developed technology - a combined forging and rolling method. Studies of the ring were carried out in order to assess its structure and hardness after the forming processes. The scope of the study included microscopic observations (microstructure and EDS), X-ray phase analysis and hardness distribution measurements

Reduction in podocyte density as a pathologic feature in early diabetic nephropathy in rodents: Prevention by lipoic acid treatment

BACKGROUND: A reduction in the number of podocytes and podocyte density has been documented in the kidneys of patients with diabetes mellitus. Additional studies have shown that podocyte injury and loss occurs in both diabetic animals and humans. However, most studies in animals have examined relatively long-term changes in podocyte number and density and have not examined effects early after initiation of diabetes. We hypothesized that streptozotocin diabetes in rats and mice would result in an early reduction in podocyte density and that this reduction would be prevented by antioxidants. METHODS: The number of podocytes per glomerular section and the podocyte density in glomeruli from rats and mice with streptozotocin (STZ)-diabetes mellitus was determined at several time points based on detection of the glomerular podocyte specific antigens, WT-1 and GLEPP1. The effect of insulin administration or treatment with the antioxidant, α-lipoic acid, on podocyte number was assessed. RESULTS: Experimental diabetes resulted in a rapid decline in apparent podocyte number and podocyte density. A significant reduction in podocytes/glomerular cross-section was found in STZ diabetes in rats at 2 weeks (14%), 6 weeks (18%) and 8 weeks (34%) following STZ injection. Similar declines in apparent podocyte number were found in STZ diabetes in C57BL/6 mice at 2 weeks, but not at 3 days after injection. Treatment with α-lipoic acid substantially prevented podocyte loss in diabetic rats but treatment with insulin had only a modest effect. CONCLUSION: STZ diabetes results in reduction in apparent podocyte number and in podocyte density within 2 weeks after onset of hyperglycemia. Prevention of these effects with antioxidant therapy suggests that this early reduction in podocyte density is due in part to increased levels of reactive oxygen species as well as hyperglycemia

Effects of Chronic Calorie Restriction or Dietary Resveratrol Supplementation on Insulin Sensitivity Markers in a Primate, Microcebus murinus

The prevalence of diabetes and hyperinsulinemia increases with age, inducing metabolic failure and limiting lifespan. Calorie restriction (CR) without malnutrition delays the aging process, but its long-term application to humans seems difficult. Resveratrol (RSV), a dietary polyphenol, appears to be a promising CR mimetic that can be easily administered in humans. In this work, we hypothesized that both CR and RSV impact insulin sensitivity in a non-human primate compared to standard-fed control (CTL) animals. Four- to five-year-old male grey mouse lemurs (Microcebus murinus) were assigned to three dietary groups: a CTL group, a CR group receiving 30% fewer calories than the CTL and a RSV group receiving the CTL diet supplemented with RSV (200 mg·day−1·kg−1). Insulin sensitivity and glycemia were assessed using an oral glucose tolerance test (OGTT) and the homeostasis model assessment of insulin resistance (HOMA-IR index) evaluation after 21 or 33 months of chronic treatment. Resting metabolic rate was also measured to assess the potential relationships between this energy expenditure parameter and insulin sensitivity markers. No differences were found after a 21-month period of treatment, except for lower glucose levels 30 min after glucose loading in CR animals. After 33 months, CR and RSV decreased glycemia after the oral glucose loading without decreasing fasting blood insulin. A general effect of treatment was observed on the HOMA-IR index, with an 81% reduction in CR animals and 53% in RSV animals after 33 months of treatment compared to CTL. Chronic CR and dietary supplementation with RSV affected insulin sensitivity by improving the glucose tolerance of animals without disturbing their baseline insulin secretion. These results suggest that both CR and RSV have beneficial effects on metabolic alterations, although these effects are different in amplitude between the two anti-aging treatments and potentially rely on different metabolic changes

Streptozotocin, Type I Diabetes Severity and Bone

As many as 50% of adults with type I (T1) diabetes exhibit bone loss and are at increased risk for fractures. Therapeutic development to prevent bone loss and/or restore lost bone in T1 diabetic patients requires knowledge of the molecular mechanisms accounting for the bone pathology. Because cell culture models alone cannot fully address the systemic/metabolic complexity of T1 diabetes, animal models are critical. A variety of models exist including spontaneous and pharmacologically induced T1 diabetic rodents. In this paper, we discuss the streptozotocin (STZ)-induced T1 diabetic mouse model and examine dose-dependent effects on disease severity and bone. Five daily injections of either 40 or 60 mg/kg STZ induce bone pathologies similar to spontaneously diabetic mouse and rat models and to human T1 diabetic bone pathology. Specifically, bone volume, mineral apposition rate, and osteocalcin serum and tibia messenger RNA levels are decreased. In contrast, bone marrow adiposity and aP2 expression are increased with either dose. However, high-dose STZ caused a more rapid elevation of blood glucose levels and a greater magnitude of change in body mass, fat pad mass, and bone gene expression (osteocalcin, aP2). An increase in cathepsin K and in the ratio of RANKL/OPG was noted in high-dose STZ mice, suggesting the possibility that severe diabetes could increase osteoclast activity, something not seen with lower doses. This may contribute to some of the disparity between existing studies regarding the role of osteoclasts in diabetic bone pathology. Examination of kidney and liver toxicity indicate that the high STZ dose causes some liver inflammation. In summary, the multiple low-dose STZ mouse model exhibits a similar bone phenotype to spontaneous models, has low toxicity, and serves as a useful tool for examining mechanisms of T1 diabetic bone loss

Assay for high glucose-mediated islet cell sensitization to apoptosis induced by streptozotocin and cytokines

Pancreatic β-cell apoptosis is known to participate in the β-cell destruction process that occurs in diabetes. It has been described that high glucose level induces a hyperfunctional status which could provoke apoptosis. This phenomenon is known as glucotoxicity and has been proposed that it can play a role in type 1 diabetes mellitus pathogenesis. In this study we develop an experimental design to sensitize pancreatic islet cells by high glucose to streptozotocin (STZ) and proinflammatory cytokines [interleukin (IL)-1β, tumor necrosis factor (TNF)-α and interferon (IFN)-γ]-induced apoptosis. This method is appropriate for subsequent quantification of apoptotic islet cells stained with Tdt-mediated dUTP Nick-End Labeling (TUNEL) and protein expression assays by Western Blotting (WB)