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.     

Alzheimer's disease-like phosphorylation of the microtubule-associated protein tau by glycogen synthase kinase-3 in transfected mammalian cells

Background: Paired helical filaments (PHFs) are a characteristic pathological feature of Alzheimer's disease; their principal component is the microtubule-associated protein tau. The tau in PHFs (PHF-tau) is hyperphosphorylated, but the cellular mechanisms responsible for this hyperphosphorylation have yet to be elucidated. A number of kinases, including mitogen-activated protein (MAP) kinase, glycogen synthase kinase (GSK)-3α, GSK-3β and cyclin-dependent kinase-5, phosphorylate recombinant tau in vitro so that it resembles PHF-tau as judged by its reactivity with a panel of antibodies capable of discriminating between normal tau and PHF-tau, and by a reduced electrophoretic mobility that is characteristic of PHF-tau. To determine whether MAP kinase, GSK-3α and GSK-3β can also induce Alzheimer's disease-like phosphorylation of tau in mammalian cells, we studied the phosphorylation status of tau in primary neuronal cultures and transfected COS cells following changes in the activities of MAP kinase and GSK-3.Results Activating MAP kinase in cultures of primary neurons or transfected COS cells expressing tau isoforms did not increase the level of phosphorylation for any PHF-tau epitope investigated. But elevating GSK-3 activity in the COS cells by co-transfection with GSK-3α or GSK-3β decreased the electrophoretic mobility of tau so that it resembled that of PHF-tau, and induced reactivity with eight PHF-tau-selective monoclonal antibodies.Conclusion Our data indicate that GSK-3α and/or GSK-3β, but not MAP kinase, are good candidates for generating PHF-type phosphorylation of tau in Alzheimer's disease. The involvement of other kinases in the generation of PHFs cannot, however, be eliminated. Our results suggest that aberrant regulation of GSK-3 may be a pathogenic mechanism in Alzheimer's disease.     

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.     

Computer determination of perfusion patterns in pulmonary capillary networks

Hanger, Christopher C., Robert G. Presson, Jr., Osamu Okada,Steven J. Janke, John J. Watkins, Wiltz W. Wagner, Jr., and Ronald L. Capen. Computer determination of perfusion patterns in pulmonarycapillary networks. J. Appl. Physiol.82(4): 1283-1289, 1997.Individual pulmonary capillaries are notsteadily perfused. By using in vivo microscopy, it can readily bedemonstrated that perfusion continually switches between capillarysegments and between portions of the network within a single alveolarwall. These changes in capillary perfusion occur even when upstream pressure and flow are constant. Flow switching between capillary segments in the absence of hemodynamic changes in large upstream vessels suggests that capillary perfusion patterns could be random. Tocalculate the probability that perfusion patterns could occur bychance, it is necessary to know the total number of possible perfusionpatterns in a given capillary network. We developed a computer programthat can determine every possible perfusion pattern for any givencapillary network, and from that information we can calculate whetherperfusion of individual segments in the network is random. With theresults of the computer program, we have obtained statistical evidencethat some capillary segments in a network are nonrandomly perfused.

     

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.     

The growth of rhododendrons in containers in soil,treated with either CaCO3, Ca(OH)2 or CaSO4

Summary Rhododendrons were grown in containers for a period of six and a half years (six growth cycles) in soil mixes which contained liberal amounts of either CaCO₃, Ca(OH)₂ or CaSO₄.No evidence was obtained to suggest that the plants were sensitive to liming of the soil or to excessive applications of calcium. The only reaction observed was a leaf chlorosis and veinal necrosis which developed for a brief period following the heavy application of CaSO₄ in the fifth season. The application of Ca(OH)₂ raised the pH throughout the soil profile to over 7, and CaSO₄ induced a consistent increase in leaf calcium.     

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.     

Collapsin response mediator protein-2 hyperphosphorylation is an early event in Alzheimer's disease progression

Collapsin response mediator protein 2 (CRMP2) is an abundant brain-enriched protein that can regulate microtubule assembly in neurons. This function of CRMP2 is regulated by phosphorylation by glycogen synthase kinase 3 (GSK3) and cyclin-dependent kinase 5 (Cdk5). Here, using novel phosphospecific antibodies, we demonstrate that phosphorylation of CRMP2 at Ser522 (Cdk5-mediated) is increased in Alzheimer's disease (AD) brain, while CRMP2 expression and phosphorylation of the closely related isoform CRMP4 are not altered. In addition, CRMP2 phosphorylation at the Cdk5 and GSK3 sites is increased in cortex and hippocampus of the triple transgenic mouse [presenilin-1 (PS1)(M146V)KI; Thy1.2-amyloid precursor protein (APP)(swe); Thy1.2tau(P301L)] that develops AD-like plaques and tangles, as well as the double (PS1(M146V)KI; Thy1.2-APP(swe)) transgenic mouse. The hyperphosphorylation is similar in magnitude to that in human AD and is evident by 2 months of age, ahead of plaque or tangle formation. Meanwhile, there is no change in CRMP2 phosphorylation in two other transgenic mouse lines that display elevated amyloid beta peptide levels (Tg2576 and APP/amyloid beta-binding alcohol dehydrogenase). Similarly, CRMP2 phosphorylation is normal in hippocampus and cortex of Tau(P301L) mice that develop tangles but not plaques. These observations implicate hyperphosphorylation of CRMP2 as an early event in the development of AD and suggest that it can be induced by a severe APP over-expression and/or processing defect.     

Astrocytes are important mediators of A��-induced neurotoxicity and tau phosphorylation in primary culture

Alzheimer''s disease (AD) is pathologically characterised by the age-dependent deposition of β-amyloid (Aβ) in senile plaques, intraneuronal accumulation of tau as neurofibrillary tangles, synaptic dysfunction and neuronal death. Neuroinflammation, typified by the accumulation of activated microglia and reactive astrocytes, is believed to modulate the development and/or progression of AD. We have used primary rat neuronal, astrocytic and mixed cortical cultures to investigate the contribution of astrocyte-mediated inflammatory responses during Aβ-induced neuronal loss. We report that the presence of small numbers of astrocytes exacerbate Aβ-induced neuronal death, caspase-3 activation and the production of caspase-3-cleaved tau. Furthermore, we show that astrocytes are essential for the Aβ-induced tau phosphorylation observed in primary neurons. The release of soluble inflammatory factor(s) from astrocytes accompanies these events, and inhibition of astrocyte activation with the anti-inflammatory agent, minocycline, reduces astrocytic inflammatory responses and the associated neuronal loss. Aβ-induced increases in caspase-3 activation and the production of caspase-3-truncated tau species in neurons were reduced when the astrocytic response was attenuated with minocycline. Taken together, these results show that astrocytes are important mediators of the neurotoxic events downstream of elevated Aβ in models of AD, and suggest that mechanisms underlying pro-inflammatory cytokine release might be an important target for therapy.