Inventing Engineered Organoids for end-stage liver failure patients

Journal of Molecular Histology - End-stage liver disease (ESLD) is a term used clinically in reference to a group of liver diseases with liver transplantation as the choice of treatment. Due to the...     

Cytoskeletal disruption induces T cell apoptosis by a caspase-3 mediated mechanism

T cell apoptosis can be triggered by different mechanisms that lead to distinctive features such as cell shrinkage, membrane blebbing, phosphatidylserine externalization, and internucleosomal DNA fragmentation. Prevailing models for the induction of apoptosis place the cytoskeleton as a distal target of the death effector molecules ('executioners'). However, the cytoskeleton can also play a role in the induction of apoptosis as suggested by the finding that cytoskeletal disruption can induce apoptosis. The mechanism by which this occurs is unknown. Here, we report that T cell apoptosis by cytoskeletal disruption involves a protein synthesis-independent mechanism leading to up-regulation of caspase-3 protease activity and increased accessibility of active caspase-3 to its substrate. Thus, cytoskeleton integrity may regulate the subcellular compartmentalization of death effector molecules.     

Effects of thiol agents on the accumulation of cadmium by rat liver parenchymal and Kupffer cells

The rate of Cd accumulation by adult rat liver parenchymal cells in serum free primary culture in the presence of 100 μM CdCl₂ was 10 times greater than that by non-parenchymal Kupffer cells. Addition of the monothiol chelating agents, cysteine and penicillamine, decreased Cd uptake in both cell types, the effect becoming more pronounced as the monothiol concentration was increased from 0.1 to 1.0 mM. These monothiols thus appear to reduce the availability of Cd for transport across the cell membrane. In contrast 1–10 molar excesses of the dithiol agents 2,3-dimercaptopropanol (BAL) or dithiothreitol (DTT) stimulated to variable extents the rate of Cd accumulation 2–10-fold in parenchymal cells and by over 100-fold in Kupffer cells. Supplementation of the media with 3% serum had little effect on the Cd accumulation in the presence of monothiols but substantially depressed Cd uptake in the presence of dithiols. Intravenous injection of Cd (0.05 mg/kg CdCl₂) with up to a 10-fold molar excess of cysteine or penicillamine had little effect on the hepatocellular Cd distribution. However Cd uptake by non-parenchymal cells was increased markedly by the simultaneous administration of BAL or DTT in 2 or 10 molar excess. Evidence is provided that these results may be partially explained by the endocytosis, particularly in Kupffer cells, of colloidal complexes of Cd which are formed with the dithiols but not the monothiols. These observations demonstrate that the physicochemical form of Cd determines its hepatocellular distribution which may be an important factor in the manifestation of Cd toxicity after thiol treatment.     

Integrated system approach to dark fermentative biohydrogen production for enhanced yield,energy efficiency and substrate recovery

The challenges of climate change, dwindling fossil reserves, and environmental pollution have fuelled the need to search for clean and sustainable energy resources. The process of biohydrogen has been highlighted as a propitious alternative energy of the future because it has many socio-economic benefits such as non-polluting features, the ability to use diverse feedstocks including waste materials, the process uses various microorganisms, and it is the simplest method of producing hydrogen. However, the establishment of a biohydrogen driven economy has been hindered by low process yields due to the accumulation of inhibitory products. Over the past few years, various optimization methods have been used in literature. Among these, integration of bioprocesses is gaining increasing prominence as an effective approach that could be used to achieve a theoretical yield of 4 mol H₂ mol^?1 glucose. In batch integrated systems, dark fermentation is used as a primary process for conversion of substrates into biohydrogen, carbon dioxide, and volatile fatty acids. This is followed by a secondary anaerobic process for further biohydrogen conversion efficiency. This review discusses the current challenges facing scale-up studies in dark fermentation process. It elucidates the potential of batch integrated systems in biohydrogen process development. Furthermore, it explores the various integrated fermentation techniques that are employed in biohydrogen process development. Finally, the review concludes with recommendations on improvement of these integrated processes for enhanced biohydrogen yields which could pave a way for the establishment of a large-scale biohydrogen production process.     

p34cdc2 is physically associated with and phosphorylated by a cdc2-specific tyrosine kinase.

The mammalian homologue of the yeast cdc2 gene encodes a 34-kilodalton serine/threonine kinase that is a subunit of M phase-promoting factor. Recent studies have shown that p34cdc2 is also a major tyrosine-phosphorylated protein in HeLa cells and that its phosphotyrosine content is cell cycle regulated and related to its kinase activity. Here, we show that cdc2 is physically associated with and phosphorylated in vitro by a highly specific tyrosine kinase. Tyrosine phosphorylation of cdc2 in vitro occurs at tyrosine 15, the same site that is phosphorylated in vivo. The association between the two kinases takes place in the cytosolic compartment and involves cyclin B-associated cdc2. Evidence is presented that a substantial fraction of cytosolic cdc2 is hypophosphorylated, whereas nuclear cdc2 is hyperphosphorylated. Finally, we show that the tyrosine kinase associated with cdc2 may be a 67-kilodalton protein and is distinct from src, abl, fms, and other previously reported tyrosine kinases.     

The role of oxidative stress in anxiety disorder: cause or consequence?

Anxiety disorders are the most common mental illness in the USA affecting 18% of the population. The cause(s) of anxiety disorders is/are not completely clear, and research in the neurobiology of anxiety at the molecular level is still rather limited. Although mounting clinical and preclinical evidence now indicates that oxidative stress may be a major component of anxiety pathology, whether oxidative stress is the cause or consequence remains elusive. Studies conducted over the past few years suggest that anxiety disorders may be characterised by lowered antioxidant defences and increased oxidative damage to proteins, lipids, and nucleic acids. In particular, oxidative modifications to proteins have actually been proposed as a potential factor in the onset and progression of several psychiatric disorders, including anxiety and depressive disorders. Oxidised proteins are normally degraded by the proteasome proteolytic complex in the cell cytoplasm, nucleus, and endoplasmic reticulum. The Lon protease performs a similar protective function inside mitochondria. Impairment of the proteasome and/or the Lon protease results in the accumulation of toxic oxidised proteins in the brain, which can cause severe neuronal trauma. Recent evidence points to possible proteolytic dysfunction and accumulation of damaged, oxidised proteins as factors that may determine the appearance and severity of psychotic symptoms in mood disorders. Thus, critical interactions between oxidative stress, proteasome, and the Lon protease may provide keys to the molecular mechanisms involved in emotional regulation, and may also be of great help in designing and screening novel anxiolytics and antidepressants.     

Purification and some catalytic properties of phosphoglucomutase from maize leaves

Phosphoglucomutase (EC 2.7.5.1, PGM) was purified to homogeneity from maize (Zea mays L.) leaves. The enzyme had specific activity 11. 7 U/mg protein and molecular mass (determined by gel-chromatography) of 133 +/- 4 kD. The molecular mass of PGM subunits determined by SDS-electrophoresis was 66 +/- 3 kD. The enzyme had Km for glucose-1-phosphate and glucose-1,6-diphosphate of 20.0 +/- 0.9 and 16.0 +/- 0.8 &mgr;M, respectively. Concentrations of glucose-1-phosphate and glucose-1,6-diphosphate above 3 and 0.4 mM, respectively, cause substrate inhibition. The enzyme activity was maximal at pH 8.0 and temperature 35 degreesC. Magnesium ions activate the enzyme and manganese ions inhibit it. 3-Phosphoglycerate is an uncompetitive inhibitor of the enzyme (Ki = 1.22 +/- 0.05 mM). Fructose-6-phosphate, 6-phosphogluconate, and ADP activate PGM, whereas ATP, UTP, and AMP inhibit the enzyme. Citrate was also a potent inhibitor, inhibitory effects of isocitrate and cis-aconitate being less pronounced.     

The many paths to frameshifting: kinetic modelling and analysis of the effects of different elongation steps on programmed –1 ribosomal frameshifting

Several important viruses including the human immunodeficiency virus type 1 (HIV-1) and the SARS-associated Coronavirus (SARS-CoV) employ programmed −1 ribosomal frameshifting (PRF) for their protein expression. Here, a kinetic framework is developed to describe −1 PRF. The model reveals three kinetic pathways to −1 PRF that yield two possible frameshift products: those incorporating zero frame encoded A-site tRNAs in the recoding site, and products incorporating −1 frame encoded A-site tRNAs. Using known kinetic rate constants, the individual contributions of different steps of the translation elongation cycle to −1 PRF and the ratio between two types of frameshift products were evaluated. A dual fluorescence reporter was employed in Escherichia coli to empirically test the model. Additionally, the study applied a novel mass spectrometry approach to quantify the ratios of the two frameshift products. A more detailed understanding of the mechanisms underlying −1 PRF may provide insight into developing antiviral therapeutics.