Comparative effects of trichothecene mycotoxins on bovine platelet function: Acetyl T-2 toxin,a more potent inhibitor than T-2 toxin

The effects of the trichothecene mycotoxins (acetyl T-2 toxin, T-2 toxin, HT-2 toxin, palmityl T-2 toxin, diacetoxyscirpenol (DAS), deoxynivalenol (DON), and T-2 tetraol) on bovine platelet function were examined in homologous plasma stimulated with platelet activating factor (PAF). The mycotoxins inhibited platelet function with the following order of potency: acetyl T-2 toxin > palmityl T-2 toxin = DAS > HT-2 toxin = T-2 toxin. While T-2 tetraol was completely ineffective as an inhibitor, DON exhibited minimal inhibitory activity at concentrations above 10×10^?4M. The stability of the platelet aggregates formed was significantly reduced in all mycotoxin treated platelets compared to that of the untreated PAF controls. It is suggested that the increased sensitivity of PAF stimulated bovine platelets to the more lipophilic mycotoxins may be related to their more efficient partitioning into the platelet membrane compared to the more hydrophilic compounds.     

An extensive review on antifungal approaches in the treatment of mucormycosis

During the period of COVID-19, the occurrences of mucormycosis in immunocompromised patients have increased significantly. Mucormycosis (black fungus) is a rare and rapidly progressing fungal infection associated with high mortality and morbidity in India as well as globally. The causative agents for this infection are collectively called mucoromycetes which are the members of the order Mucorales. The diagnosis of the infection needs to be performed as soon as the occurrence of clinical symptoms which differs with types of Mucorales infection. Imaging techniques magnetic resonance imaging or computed tomography scan, culture testing, and microscopy are the approaches for the diagnosis. After the diagnosis of the infection is confirmed, rapid action is needed for the treatment in the form of antifungal therapy or surgery depending upon the severity of the infection. Delaying in treatment declines the chances of survival. In antifungal therapy, there are two approaches first-line therapy (monotherapy) and combination therapy. Amphotericin B ( 1 ) and isavuconazole ( 2 ) are the drugs of choice for first-line therapy in the treatment of mucormycosis. Salvage therapy with posaconazole ( 3 ) and deferasirox ( 4 ) is another approach for patients who are not responsible for any other therapy. Adjunctive therapy is also used in the treatment of mucormycosis along with first-line therapy, which involves hyperbaric oxygen and cytokine therapy. There are some drugs like VT-1161 ( 5 ) and APX001A ( 6 ), Colistin, SCH 42427, and PC1244 that are under clinical trials. Despite all these approaches, none can be 100% successful in giving results. Therefore, new medications with favorable or little side effects are required for the treatment of mucormycosis.     

Monoclonal antibodies to rabbit liver cytochrome P-448

Cytochrome P-448 (mol wt 55,000 Daltons) from rabbit liver was purified to a specific content of 16.6 nmol/mg. Mice were immunised with this preparation, their spleens removed and dissociated lymphocytes hybridised with myeloma cells. Four monoclonal antibodies against cytochrome P-448 were raised and partially characterised. All four antibodies interacted with cytochrome P-448 in intact microsomal fractions and selectively immunoadsorbed cytochrome P-448 from solubilised microsomal preparations. One of the antibodies inhibited benzo[a] pyrene hydroxylase activity in a reconstituted system, one had no effect on activity and two increased activity. The possible applications of such antibodies are discussed.     

Saikosaponin-d,a novel SERCA inhibitor,induces autophagic cell death in apoptosis-defective cells

Autophagy is an important cellular process that controls cells in a normal homeostatic state by recycling nutrients to maintain cellular energy levels for cell survival via the turnover of proteins and damaged organelles. However, persistent activation of autophagy can lead to excessive depletion of cellular organelles and essential proteins, leading to caspase-independent autophagic cell death. As such, inducing cell death through this autophagic mechanism could be an alternative approach to the treatment of cancers. Recently, we have identified a novel autophagic inducer, saikosaponin-d (Ssd), from a medicinal plant that induces autophagy in various types of cancer cells through the formation of autophagosomes as measured by GFP-LC3 puncta formation. By computational virtual docking analysis, biochemical assays and advanced live-cell imaging techniques, Ssd was shown to increase cytosolic calcium level via direct inhibition of sarcoplasmic/endoplasmic reticulum Ca²⁺ ATPase pump, leading to autophagy induction through the activation of the Ca²⁺/calmodulin-dependent kinase kinase–AMP-activated protein kinase–mammalian target of rapamycin pathway. In addition, Ssd treatment causes the disruption of calcium homeostasis, which induces endoplasmic reticulum stress as well as the unfolded protein responses pathway. Ssd also proved to be a potent cytotoxic agent in apoptosis-defective or apoptosis-resistant mouse embryonic fibroblast cells, which either lack caspases 3, 7 or 8 or had the Bax-Bak double knockout. These results provide a detailed understanding of the mechanism of action of Ssd, as a novel autophagic inducer, which has the potential of being developed into an anti-cancer agent for targeting apoptosis-resistant cancer cells.     

A nonlinear compartmental model of Sr metabolism. I. Non-steady-state kinetics and model building

A model of Sr metabolism was developed by using plasma and urinary Sr kinetic data obtained in groups of postmenopausal women who received four different oral doses of Sr and collected during the Sr administration period (25 days) and for 28 days after cessation of treatment. A nonlinear compartmental formalism that is appropriate for study of non-steady-state kinetics and allows dissociation of variables pertaining to Sr metabolism (system 1) from those indirectly operating on it (system 2) was used. At each stage of model development, the dose-dependent model response was fitted to the four sets of data considered simultaneously (1 set per dose). A seven-compartment model with internal Sr distribution and intestinal, urinary, and bone metabolic pathways was selected. It includes two kinds of nonlinearities: those accounting for saturable intestinal and bone processes, which behave as intrinsic nonlinearities because they are directly dependent on Sr, and extrinsic nonlinearities (dependent on system 2), which suggest the cooperative involvement of plasma Sr changes in modulating some intestinal and bone mineral metabolic pathways. With the set of identified parameter values, the initial steady-state model predictions are relevant to known physiology, and some peculiarities of model behavior for long-term Sr administration were simulated.     

A nonlinear compartmental model of Sr metabolism. II. Its physiological relevance for Ca metabolism

We have studied the peculiarities of the nonlinear compartmental model for human Sr metabolism (Staub JF, Foos E, Courtin B, Jochemsen R, and Perault-Staub AM. Am J Physiol Regul Integr Comp Physiol 284: R819-R834, 2003), including its physiological reliability in the context of Sr-Ca similarity-dissimilarity. We found it to be relevant to Ca metabolism, except for discrimination against Sr relative to Ca at urinary and intestinal levels. The main findings are as follows: 1) the saturable part of intestinal absorption, shared by Sr and Ca, does not seem to be responsible for the discrimination of the transcellular pathway; 2) although there is little discrimination in bone, the physicochemical behaviors of Sr and Ca at the bone surface differ, at least quantitatively; and 3) Sr behaves as a "tracer" for Ca metabolic pathways and, under non-steady-state conditions, can also reveal self-regulatory processes. It is suggested that they depend on Ca2+ (cationic)-sensing receptors that are apparently more sensitive to Sr than to Ca. Acting on gastrointestinal and osteoblast lineage cells, these slow processes might contribute to adaptive, rather than homeostatic, regulation of Ca metabolism. Understanding these features could help clarify the pharmacological and therapeutic effects of oral Sr.     

A novel method for expression and large-scale production of human brain l-glutamate decarboxylase

l-Glutamate decarboxylase (GAD; EC 4.1.1.15) is the rate-limiting enzyme involved in the synthesis of gamma-aminobutyric acid (GABA), the major inhibitory neurotransmitter in the mammalian brain. Imbalance in the conversion of glutamate to GABA has been implicated in a host of human diseases. Studies on the structure, function, and therapeutic use of GAD have been precluded by insufficient quantities of purified active enzyme. Here we report a novel methodology for the expression and large-scale production of enzymatically active, pure, recombinant human GAD65 and GAD67. This method circumvents the sequestering of expressed protein into insoluble inclusion bodies and reduces production of truncated proteins. The availability of sufficient quantities of purified HGAD65 and HGAD67 has allowed for the production of specific polyclonal antibodies that discriminate between the two isoforms. This methodology, in addition to providing key human brain enzymes, may be generally applicable to other systems.     

The EphB4 receptor suppresses breast cancer cell tumorigenicity through an Abl-Crk pathway

Recent evidence supports a role for EphB receptor tyrosine kinases as tumour suppressors in colorectal and prostate cancer. However, it is unclear how these receptors inhibit cancer cell tumorigenicity - an activity that is highly unusual for a family of receptor tyrosine kinases. Here, we report that the EphB4 receptor can behave as a tumour suppressor in a mouse xenograft model of breast cancer when stimulated by its ligand, ephrin-B2. In breast cancer cells, EphB4 activates an antioncogenic pathway involving Abl family tyrosine kinases and the Crk adaptor protein. This Abl-Crk pathway inhibits breast cancer cell viability and proliferation in addition to motility and invasion, and also downregulates the pro-invasive matrix metalloprotease, MMP-2. Consistent with these effects, EphB4 and the Abl-Crk pathway are constitutively active in non-transformed mammary epithelial cells. These findings identify a novel Eph receptor signalling pathway with tumour-suppressor activity and predict that therapeutic intervention to activate EphB4 signalling will inhibit tumour progression.