The aging analysis of natural rubber-Copaifera oblongifolia extract membranes.

Natural rubber (NR), derived from Hevea brasiliensis, has properties for biomedical applications. Several studies indicate that these properties can be amplified when we associate another bioproduct. However, there are no studies of aging aspects of this biomaterial regarding changes in functionality, structure and composition. The objective was to evaluate the aging process of natural rubber membranes - copaiba (NRC) subjected to controlled conditions of time, light and presence of oxygen. The NRC was prepared and stored in the presence or absence of light and vacuum, for periods of 30, 60 and 90 days. Subsequently, the membranes were characterized through the techniques of wettability, infrared spectroscopy, thermal analysis, scanning microscopy and antioxidant activity. The wettability analysis, showed that NRC membranes both in the zero time and in the aging time were hydrophilic. Through thermogravimetric analysis and differential exploratory analysis the membranes remained thermally stable. The scanning electronic microscopy, indicated no morphological alterations during the observed period. After 90 days, the packaged membranes showed satisfactory antioxidant activity. Our results suggest that the membranes were resistant to the storage period, since they maintained their chemical, thermal, morphological and antioxidant characteristics. Hence, it corroborates to use of membranes as a possible curative for biomedical applications.

Reversal of mitochondrial malate dehydrogenase 2 enables anaplerosis via redox rescue in respiration-deficient cells.

Inhibition of the electron transport chain (ETC) prevents the regeneration of mitochondrial NAD+, resulting in cessation of the oxidative tricarboxylic acid (TCA) cycle and a consequent dependence upon reductive carboxylation for aspartate synthesis. NAD+ regeneration alone in the cytosol can rescue the viability of ETC-deficient cells. Yet, how this occurs and whether transfer of oxidative equivalents to the mitochondrion is required remain unknown. Here, we show that inhibition of the ETC drives reversal of the mitochondrial aspartate transaminase (GOT2) as well as malate and succinate dehydrogenases (MDH2 and SDH) to transfer oxidative NAD+ equivalents into the mitochondrion. This supports the NAD+-dependent activity of the mitochondrial glutamate dehydrogenase (GDH) and thereby enables anaplerosis-the entry of glutamine-derived carbon into the TCA cycle and connected biosynthetic pathways. Thus, under impaired ETC function, the cytosolic redox state is communicated into the mitochondrion and acts as a rheostat to support GDH activity and cell viability.